Bibliography on CO2 Effects on Vegetation and Ecosystems: 1990-1999 Literature 

Michael H. Jones and Peter S. Curtis, editors

ORNL/CDIAC-129

July 2000

(http://cdiac.esd.ornl.gov/epubs/cdiac/cdiac129/cdiac129.html)


     1    
Abarzua, S., R. Altenburger, R. Callies, L.H. Grimme, A. Mayer, D. Leibfritz, and U.
Schiewer. 1993. Ammonium rhythm in cultures of the cyanobacterium microcystis- firma.
Physiologia Plantarum 89(3):659-663.

Over a period of several days, rhythmic changes in extracellular NH4+ concentration take place in
cultures of the cyanobacterium Microcystis firma (Breb et Lenorm.) Schmidle, strain Gromov/St.
Petersb. 398, under conditions of restricted CO2 supply and light/dark alternation. The changes are
enhanced by nitrate supply. Among the various processes generating intracellular NH4+ (NH4+
uptake, NO3- reduction, protein and amino acid degradation, photorespiration), NO3- reduction
appears as the one most important. This can be concluded from experiments with and without nitrate
and/or ammonium in the medium. In the presence of saturating CO2, continuous light, or continuous
darkness, rhythmic NH4+ oscillations are not induced. Studies of the incorporation of NH4+ nitrogen
by in vivo N-15-NMR show that if CO2 is supplied, N-15 is accumulated in several components with
the following time course: in the first hour in Gln (delta), in the second hour in the alpha- amino
groups of most nonbranched amino acids, in the third hour in gamma-aminobutyric acid (GABA), Orn
(delta) and Lys (epsilon), and in the sixth hour in Ala. Carbon limitation, however, results in
accumulation of label in the amide nitrogen of glutamine only.

KEYWORDS: METABOLISM, N-15, NMR-SPECTROSCOPY, NUCLEAR MAGNETIC-
RESONANCE


     2    
Abdin, O.A., X.M. Zhou, B.E. Coulman, D. Cloutier, M.A. Faris, and D.L. Smith. 1998. Effect
of sucrose supplementation by stem injection on the development of soybean plants. Journal of
Experimental Botany 49(329):2013-2018.

Over the past half decade several stem injection methods have been developed for cereal plants. These
methods allow researchers to administer solutions to cereal plants to study their effects on plant
physiology. However, little work has been done to extend this technique to non-cereals. An
experiment was conducted to test an injection technique that could be suitable for soybean plants
(Glycine max [L.] Merr.), and to study the effect of long-term injection of sucrose on the growth of
soybean plants. An injection setup comprising a supporting stand and a fluid injection system was
established. Pressure was applied to the plunger of a 5 ml syringe using ceramic bricks to force test
solutions into the plants. Solutions of 0, 150, and 300 g sucrose I-1 were injected into soybean plants
for 8 weeks starting at the seedling VC stage. Distilled water had the greatest uptake rate, followed
by the 150, and then the 300 g sucrose I-1 solutions. The overall average uptake during the injection
period was 77.3 ml. Average sucrose uptake values were 11.8 and 13.5 g per plant for the 150 and
300 g sucrose I-1 treatments. This represented approximately 65% of the total dry weight of the
plants. Sucrose injection increased leaf area and pod number relative to the control plants. Nodule
numbers were lower for sucrose injected treatments, but their dry weights were higher than the
control. Above-soil dry matter was higher for the plants injected with 300 g sucrose I-1 than those
injected with water. The injection system tested was able to administer concentrated solutions into
soybean plants for most of their period of growth and development. The sucrose supplementation had
positive effects on soybean growth but suppressed photosynthesis.

KEYWORDS: CARBON-DIOXIDE ENRICHMENT, ELEVATED CO2, GROWTH, LEAVES,
MAIZE, NITROGEN, PEDUNCLE PERFUSION, PHOTOSYNTHESIS, WHEAT, YIELD


     3    
Abdullaev, A.A., B.B. Dzhumaev, Z.N. Abdurakhmanova, V.L. Kaler, and I.M. Magmedov.
1992. Integral effect of environmental-factors on photosynthetic metabolism of carbon in cotton
leaves. Soviet Plant Physiology 39(2):140-144.

We used the method of mathematical experiment planning (a 2(3) scheme) to study the influence of
environmental factors separately or in combination on the photosynthetic rate and distribution of C-14
among products of photosynthetic carbon metabolism in the cotton (Gossypium hirsutum L.) leaf
Increase of light intensity during cultivation accelerated photosynthesis and stimulated incorporation
of C-14 into phosphoglyceric acid (PGA), sugar diphosphate (SDP), fructose monophosphate (FMP),
and malate, but suppressed incorporation of C-14 into sucrose, glucose monophosphate (GMP), and
glycerate. Temperature increase by itself and in any combination with other factors at the upper level
suppressed photosynthesis. Elevated temperature increased accumulation of the label in PGA,
sucrose, and malate, but lowered it in GMP, alanine, glycine, and serine. Growing plants at enhanced
CO2 concentration led to acceleration of photosynthesis and increase of the share of C-14 in SDP,
GMP, and malate, but decrease of it in sucrose, alanine, glycine, and serine. Very perceptible effects
of interaction are discernible in different combinations of factors. All three factors at the upper level
appreciably induced activity of phosphoenolpyruvate carboxylase (PEPCase) in cotton leaves.

KEYWORDS: PHYSIOLOGY


     4    
Aben, S.K., S.P. Seneweera, O. Ghannoum, and J.P. Conroy. 1999. Nitrogen requirements for
maximum growth and photosynthesis of rice, Oryza sativa L-cv. Jarrah grown at 36 And 70 Pa CO2.
Australian Journal of Plant Physiology 26(8):759-766.

The hypothesis that growth of rice (Oryza sativa L. cv. Jarrah) at elevated atmospheric CO2 partial
pressure alters leaf nitrogen (N) concentrations required to support maximum dry mass production
and photosynthetic rates during the period of rapid tiller initiation was tested by growing plants for
30 days in unstirred sand/hydroponic culture with N concentrations of 5, 20, 40, 60 and 100 mg N
L-1. Maximum growth and photosynthetic potential was greater at 70 than 36 Pa CO2 at all N
concentrations in the solution. Elevated CO2 reduced leaf N concentrations required to support 90%
of maximum growth and photosynthetic rates (critical concentration) from 40 to 27 g kg(-1) for
growth and from 45 to 30 g kg(-1) for photosynthesis. Morphological changes at elevated CO2
included increased tiller numbers and reduced leaf area ratio. The latter could be explained by lower
plant N concentrations which occurred at high CO2 at each N concentration in the solution, primarily
due to lower leaf blade and root N concentrations. Changes in tiller numbers at high CO2 were
unrelated to leaf or plant N but were strongly correlated with leaf soluble carbohydrate
concentrations. We conclude that elevated CO2 alters the nutritional physiology of rice during the
rapid tillering phase in a way that increases the efficiency of N utilisation for growth and
photosynthesis.

KEYWORDS: ACCLIMATION, CAPACITY, COTTON, ELEVATED CO2, LEAVES, NUTRITION,
PLANTS, RIBULOSE-1;5-BISPHOSPHATE CARBOXYLASE-OXYGENASE, WHEAT


     5    
Aber, J.D., S.V. Ollinger, C.A. Federer, P.B. Reich, M.L. Goulden, D.W. Kicklighter, J.M.
Melillo, and R.G. Lathrop. 1995. Predicting the effects of climate change on water yield and forest
production in the northeastern United States. Climate Research 5(3):207-222.

Rapid and simultaneous changes in temperature, precipitation and the atmospheric concentration of
CO2 are predicted to occur over the next century. Simple, well-validated models of ecosystem
function are required to predict the effects of these changes. This paper describes an improved version
of a forest carbon and water balance model (PnET-II) and the application of the model to predict
stand- and regional-level effects of changes in temperature, precipitation and atmospheric CO2
concentration. PnET-II is a simple, generalized, monthly time- step model of water and carbon
balances (gross and net) driven by nitrogen availability as expressed through foliar N concentration.
Improvements from the original model include a complete carbon balance and improvements in the
prediction of canopy phenology, as well as in the computation of canopy structure and
photosynthesis. The model was parameterized and run for 4 forest/site combinations and validated
against available data for water yield, gross and net carbon exchange and biomass production. The
validation exercise suggests that the determination of actual water availability to stands and the
occurrence or non-occurrence of soil-based water stress are critical to accurate modeling of forest
net primary production (NPP) and net ecosystem production (NEP). The model was then run for the
entire NewEngland/New York (USA) region using a 1 km resolution geographic information system.
predicted long- term NEP ranged from -85 to + 275 g Cm-2 yr(-1) for the 4 forest/site combinations,
and from -150 to 350 g C m(-2) yr(-1) for the region, with a regional average of 76 g Cm-2 yr(-1).
A combination of increased temperature (+6 degrees C), decreased precipitation (-15%) and
increased water use efficiency (2x, due to doubling of CO2) resulted generally in increases in NPP
and decreases in water yield over the region.

KEYWORDS: DEPOSITION, ECOSYSTEMS, ELEVATED CO2, MODEL, REGIONAL-ANALYSIS,
RESPONSES


     6    
Ackerly, D.D., and F.A. Bazzaz. 1995. Plant-growth and reproduction along co2 gradients -
nonlinear responses and implications for community change. Global Change Biology 1(3):199-207.

The effects of rising atmospheric CO2 concentrations on natural plant communities will depend upon
the cumulative responses of plant growth and reproduction to gradual, incremental changes in
climatic conditions. We analysed published studies of plant responses to elevated CO2 to address
whether reproductive and total biomass exhibit similar enhancement to elevated vs. ambient CO2
concentrations, and to assess the patterns of plant response along gradients of CO2 concentrations.
In six annual plant species, mean enhancement at double ambient vs. ambient CO2 was 1.13 for total
biomass and 1.30 for reproductive biomass. The two measures were significantly correlated, but there
was considerable scatter in the relationship, indicating that reproductive responses cannot be
consistently predicted from enhancement of total biomass. Along experimental CO2 gradients
utilizing three concentrations, there was a great diversity of response patterns, including positive,
negative, non-monotonic and non-significant (nat) responses. The distribution of response patterns
differed for plants grown in stands compared to those grown individually. Positive responses were
less frequent in competitive environments, and non- monotonic responses were more frequent. These
results emphasize that interpolation of plant response based on enhancement ratios measured at
elevated vs. ambient CO2 concentrations is not sufficient to predict community responses to
incremental changes in atmospheric conditions. The consequences of differential response patterns
were assessed in a simulation of community dynamics for four species of annual plants. The model
illustrates that the final community composition at a future point in time depends critically on both
the magnitude and the rate of increase of atmospheric CO2.

KEYWORDS: ANNUALS, ATMOSPHERIC CO2, CO2-INDUCED CLIMATE CHANGE,
COMPETITION, ELEVATED CO2, ENRICHMENT, LIQUIDAMBAR- STYRACIFLUA, OLD-
FIELD PERENNIALS, PINUS-TAEDA SEEDLINGS, RESOURCE USE


     7    
Ackerly, D.D., J.S. Coleman, S.R. Morse, and F.A. Bazzaz. 1992. Co2 and temperature effects
on leaf-area production in 2 annual plant-species. Ecology 73(4):1260-1269.

We studied leaf area production in two annual plant species, Abutilon theophrasti and Amaranthus
retroflexus, under three day/night temperature regimes (18-degrees/14-degrees, 28- degrees/22-
degrees, and 38-degrees/31-degrees-C) and two concentrations of carbon dioxide (400 and 700-mu-
L/L). The production of whole-plant leaf area during the first 30 d of growth was analyzed in terms
of the leaf initiation rate, leaf expansion, individual leaf area, and, in Amaranthus, production of
branch leaves. Temperature and CO2 influenced leaf area production through effects on the rate of
development, determined by the production of nodes on the main stem (the plastochron index), and
through shifts in the relationship between whole-plant leaf area and the number of main stem nodes.
In Abutilon, leaf initiation rate was highest at 38- degrees, but area of individual leaves was greatest
at 28- degrees. Total leaf area was greatly reduced at 18-degrees due to slow leaf initiation rates.
Elevated CO2 concentration increased leaf initiation rate at 28-degrees, resulting in an increase in
whole-plant leaf area. In Amaranthus, leaf initiation rate increased with temperature, and was
increased by elevated CO2 at 28-degrees. Individual leaf area was greatest at 28-degrees, and was
increased by elevated CO2 at 28-degrees but decreased at 38-degrees. Branch leaf area displayed a
similar response to CO2, but was greater at 38- degrees. Overall, whole-plant leaf area was slightly
increased at 38-degrees relative to 28-degrees, and elevated CO2 levels resulted in increased leaf area
at 28-degrees but decreased leaf area at 38-degrees. The effects on leaf area closely parallel rates of
biomass accumulation in the same experiment, suggesting that responses of developmental processes
to elevated CO2 and interacting factors may play an important role in mediating effects on plant
growth.

KEYWORDS: C-3, CANOPY, CARBON-DIOXIDE ENRICHMENT, ELEVATED CO2, GROWTH,
LEAVES, LIGHT, PHOTOSYNTHESIS, RESPONSES, SUNFLOWER


     8    
Acock, B., M.C. Acock, and D. Pasternak. 1990. Interactions of CO2 enrichment and temperature
on carbohydrate production and accumulation in muskmelon leaves. Journal of the American Society
for Horticultural Science 115(4):525-529.



     9    
Acock, B., and G.W. Wall. 1995. A simple conductimetric co2 analyzer with automatic recalibration
.1. Design, implementation, and functionality. Agronomy Journal 87(1):70-75.

Controlled-environment plant growth cabinets may be used to investigate the long-term effect of
elevated carbon dioxide concentration ([CO2]) on plant growth. Infrared gas analyzers (IRGAs) are
normally used to monitor and control [CO2] in plant cabinets. With many cabinets in use, however,
it soon becomes impractical to purchase an individual IRGA for each cabinet, A more economical
method of monitoring and controlling [CO2] relies on the change in electrical conductivity when CO2
is dissolved in demineralized water, This work describes the design, implementation, and functionality
of an inexpensive conductimetric system for controlling [CO2] in plant growth cabinets, Regressing
electrical conductivity against [CO2] over the range 0 to 1000 mu L L(-1) yields a quadratic
response. Calibration drift inherent in the conductimetric CO2 analyzer requires that each analyzer
be recalibrated periodically. Automatically recalibrating with an IRGA every 900 s gave control of
the [CO2] within the plant enclosures to within 10 to 15 mu L L(-1) of the set point, The [CO2]
control system is robust enough to maintain this accuracy regardless of the desired [CO2] set point
or the mass of plant material within the plant growth cabinet, In this approach, only one IRGA is
required to control [CO2] in many plant growth cabinets if each cabinet has a dedicated
conductimetric CO2 analyzer.



     10   
Adams, R.M., R.A. Fleming, C.C. Chang, B.A. McCarl, and C. Rosenzweig. 1995. A
reassessment of the economic-effects of global climate-change on US agriculture. Climatic Change
30(2):147-167.

This study uses recent GCM forecasts, improved plant science and water supply data and refined
economic modeling capabilities to reassess the economic consequences of long-term climate change
on U.S. agriculture. Changes in crop yields, crop water demand and irrigation water arising from
climate change result in changes in economic welfare. Economic consequences of the three GCM
scenarios are mixed; GISS and GFDL-QFlux result in aggregate economic gains, UKMO implies
losses. As in previous studies, the yield enhancing effects of atmospheric CO2 are an important
determinant of potential economic consequences. Inclusion of changes in world food production and
associated export changes generally have a positive affect on U.S. agriculture. As with previous
studies, the magnitude of economic effects estimated here are a small percentage of U. S. agricultural
value.



     11   
Adamse, P., and S.J. Britz. 1992. Amelioration of uv-b damage under high irradiance .1. Role of
photosynthesis. Photochemistry and photobiology 56(5):645-650.

Sensitivity to ultraviolet-B radiation (UV-B, 280-315 nm) is generally reduced when background
irradiance is high. We tested the involvement of photosynthesis in the amelioration of UV-B damage
by treating plants at high PAR (photosynthetically- active radiation. 400-700 nm; 1000 mumol m-2
s-1) with supplemental UV-B at double ambient levels of biologically- effective radiation (18 kJ m-2
d-1) and either ''ambient'' (450 mumol mol-1) or short term elevated (750 mumol mol-1) CO2 levels.
Responses to UV-B were assessed by photosynthetic gas exchange, leaf expansion and production
of UV-absorbing compounds (presumptive flavonoids) in cultivars of cucumber (Cucumis sativus L.)
previously demonstrated to be relatively sensitive (cv. Poinsett) and insensitive (cv. Ashley) to UV-B.
Except for marginal leaf interveinal chlorosis observed in Poinsett, both cultivars responded similarly.
UV-B had little direct effect on leaf photosynthesis, but it did cause reductions in leaf area and
corresponding increases in leaf dry matter per area. Increased CO2 stimulated plant growth,
counteracting the effect of UV-B on leaf growth and indicating an important role for photosynthesis.
In contrast, the accumulation of UV-absorbing flavonoid compounds was enhanced by UV-B
exposure but was not affected by CO2 enrichment.

KEYWORDS: ACCLIMATION, CARBON DIOXIDE, CELL-SUSPENSION CULTURES, LIGHT,
PETROSELINUM- HORTENSE, PHOTON FLUX- DENSITY, PHYTOCHROME, PLANTS,
RADIATION, SENSITIVITY


     12   
Adamsen, F.J., P.J. Pinter, E.M. Barnes, R.L. LaMorte, G.W. Wall, S.W. Leavitt, and B.A.
Kimball. 1999. Measuring wheat senescence with a digital camera. Crop Science 39(3):719-724.

Documenting crop senescence rates is often difficult because of the need for frequent sampling during
periods of rapid change and the subjective nature of human visual observations. The purpose of this
study was to determine the feasibility of using images produced by a digital camera to measure the
senescence rate of wheat and to compare the results with changes in greenness determined by two
established methods. Measurements were made as part of an experiment to determine the effects of
elevated CO2 and limited soil nitrogen on spring wheat (Triticum aestivum L.) at the University of
Arizona's Maricopa Agricultural Center, near Phoenix, AZ. "Greenness" measurements were made
during senescence of the crop with a color digital camera, a hand-held radiometer, and a SPAD
chlorophyll meter. The green to red (GIR) for each pixel in an image was calculated and the average
GIR computed for cropped images from a digital camera representing 1 m(2) for each treatment and
sample date. The normalized difference vegetation index (NDVI) was calculated from the red and
near-infrared canopy reflectances measured with a hand held radiometer. A SPAD reading was
obtained from randomly selected flag leaves. All three methods of measuring plant greenness showed
similar temporal trends. The relationships between GIR with NDVI and SPAD were linear over most
of the range of GIR. However, NDVI was more sensitive at low values than GIR. GIR was more
sensitive above G/R values of 1.2 than SPAD because the upper limits of SPAD measurements were
constrained by the amount of chlorophyll in the leaf, while GIR responded to both chlorophyll
concentration in the leaves as well as the number of leaves present. Color digital imaging appears
useful for quantifying the senescence of crop canopies. The cost of color digital cameras is expected
to decrease and the quality and convenience of use to improve.

KEYWORDS: CHLOROPHYLL METER, CROP, EFFICIENCY, RED, VEGETATION INDEXES,
WINTER-WHEAT, YIELD


     13   
Agar, I.T., J. Streif, and F. Bangerth. 1997. Effect of high CO2 and controlled atmosphere (CA)
on the ascorbic and dehydroascorbic acid content of some berry fruits. Postharvest Biology and
Technology 11(1):47-55.

High CO2 concentrations as well as controlled atmosphere storage are widely used to extend the
storage and shelf-life of many fruits. To investigate the effect of these storage procedures on several
berry fruits, strawberries, raspberries, currants and blackberries were stored at three different elevated
CO2 concentrations, with or without a parallel reduction in O-2. Vitamin C content (ascorbic acid
plus dehydroascorbic acid) was reduced by high CO2 concentrations (10-30% CO2), particularly in
strawberries. This reduction in vitamin C was moderate in black currants and blackberries and almost
absent in raspberries and red currants when compared with strawberries. Reducing the O-2
concentration in the storage atmosphere in the presence of high CO2 had little effect on the vitamin
C content. Ascorbic acid was more diminished al high CO2 than dehydroascorbic acid. This suggests
a stimulating effect of high CO2 concentrations on the oxidation of ascorbic acid and/or an inhibition
of mono- or dehydroascorbic acid reduction to ascorbic acid. (C) 1997 Elsevier Science B.V.

KEYWORDS: HYDROGEN- PEROXIDE, O2, PLANTS


     14   
Aggangan, R.T., A.M. O'Connell, J.F. McGrath, and B. Dell. 1999. The effects of Eucalyptus
globulus Labill. leaf letter on C and N mineralization in soils from pasture and native forest. Soil
Biology and Biochemistry 31(11):1481-1487.

The effects of addition of Eucalyptus globulus leaf litter on carbon and nitrogen mineralization in soils
from a pasture and a native forest were evaluated using a long-term laboratory aerobic incubation
assay (29 weeks at 20 degrees C) in leaching microlysimeters, The amount of added leaf litter
significantly influenced microbial respiration, microbial biomass and N turnover in both the native
forest and pasture soils. Cumulative CO2-C respired increased with increasing rate of leaf litter
addition when leaf litter was mixed through the soil or placed on the soil surface. These increases
were associated with increases in microbial biomass C content. Cumulative net N mineralization
declined in ail treatments when litter was added and was lowest when leaf litter was mixed with soil.
When leaf litter was added in increasing amounts to the soil surface, there was a concomitant increase
in microbial biomass N content (r(2) = 0.79, n = 8), indicating that the reduction in net N
mineralization was primarily due to immobilization of N in microbial tissues. In contrast, when litter
was mixed with soil in increasing amounts, there was a decrease in microbial biomass N in forest soil
and an increase in pasture soil. Consequently, changes in the rate of net N mineralization were not
well related to changes in microbial biomass N content. It is suggested that this may be due to the
greater activity and more rapid turnover of microorganisms where litter was incorporated resulting
in more of the immobilized N being partitioned into metabolic products or dead microbial cells.
Incorporation of litter may also have enhanced loss N through denitrification, (C) 1999 Published by
Elsevier Science Ltd. All rights reserved.

KEYWORDS: DECOMPOSITION, DENITRIFICATION, EXTRACTION METHOD,
IMMOBILIZATION, LITTER, MICROBIAL BIOMASS CARBON, NITROGEN MINERALIZATION,
PLANT RESIDUES, RESPIRATION, WESTERN-AUSTRALIA


     15   
Agren, G.I. 1996. Nitrogen productivity or photosynthesis minus respiration to calculate plant
growth? Oikos 76(3):529-535.

One approach to calculate plant growth rate is from models of photosynthesis, respiration and
allocation. This requires that processes with characteristic time constants of seconds to minutes be
scaled to hours or days. Another approach is to use aggregate models defined at the time scale of
growth, hours and days. I use such an aggregate model, the nutrient productivity, to compare the
performance of the two approaches on growth experiments with small, nitrogen-limited birch plants.
The problems of error aggregation when using the large number of parameters required to scale from
the detailed level of photosynthesis and respiration to the aggregate level of growth are in this case
such that whole plant growth rate is more accurately predicted with the nutrient productivity model.

KEYWORDS: ALLOCATION, BETULA-PENDULA ROTH, BIOMASS, BIRCH SEEDLINGS,
CARBON, CLIMATE, ECOSYSTEMS, ELEVATED CO2, NUTRITION, STRESS


     16   
Agren, G.I., R.E. McMurtrie, W.J. Parton, J. Pastor, and H.H. Shugart. 1991. State-of-the-art
of models of production decomposition linkages in conifer and grassland ecosystems. Ecological
Applications 1(2):118-138.

We review the state-of-the-art of models of forests and grasslands that could be used to predict the
impact of a future climate change arising from increased atmospheric carbon dioxide concentration.
Four levels of resolution are recognized: physiologically based models, population models, ecosystem
models, and regional or global models. At the physiological level a number of important processes
can be described in great detail, but these models often treat inadequately interactions with nutrient
cycles, which operate on longer time scales. Population and ecosystem models can, on the other hand,
encapsulate relationships between the plants and the soil system, but at the expense of requiring more
ad hoc formulations of processes. At the regional and global scale we have so far only steady-state
models, which cannot be used to predict transients caused by climate change. However, our
conclusion is that, in spite of the gaps in knowledge, there are several models based on dominant
processes that are well enough understood for the predictions of those models to be taken seriously.

KEYWORDS: ATMOSPHERIC CO2 ENRICHMENT, BOUTELOUA-GRACILIS, CARBON
DIOXIDE, CO2-INDUCED CLIMATE CHANGE, EVEN- AGED STANDS, LOLIUM-PERENNE
L, NITROGEN PRODUCTIVITY, PLANT GROWTH, SIMULATION-MODEL, THEORETICAL-
ANALYSIS


     17   
Ahmadi, H., W.V. Biasi, and E.J. Mitcham. 1999. Control of brown rot decay of nectarines with
15% carbon dioxide atmospheres. Journal of the American Society for Horticultural Science
124(6):708-712.

Effects of short-term exposure to a 15% CO2 atmosphere on nectarines [Prunus persica (L.) Batsch
(Nectarine Group) 'Summer Red'] inoculated with Monilinia fructicola (Wint.) Honey (causal agent
of brown rot) were investigated, Nectarines were inoculated with spores of M.fructicola and
incubated at 20 degrees C for 24, 48 or 72 hours and then transferred to storage in either air or air
enriched with 15% CO2 at 5 degrees C. Fruit were removed from storage after 5 and 16 days and
were examined for brown rot decay immediately and after ripening in air for 3 days at 20 degrees C.
Noninoculated nectarines were stored and treated likewise for evaluation of postharvest fruit
attributes to determine their tolerance to 15% CO2. Incubation period after inoculation, storage
duration, and storage atmosphere had highly significant effects on fruit decay, 'Summer Red'
nectarines tolerated a 15% CO2 atmosphere for 16 days at 5 degrees C. Development of brown rot
decay in fruit inoculated 24 hours before 5 or 16 days storage in 15% CO2 at 5 OC was arrested.
After 3 days ripening in air at 20 degrees C, the progression of brown rot disease was rapid in all
inoculated nectarines, demonstrating the fungistatic effect of 15% CO2. The quantity of fungal cell
wall materials (estimated by glucosamine concentration) was compared to visual estimation of
decayed area and visual rating of fungal sporulation. The glucosamine assay defined the onset and
progress of brown rot infection more precisely than either of the two visual tests.

KEYWORDS: FRUIT, IPRODIONE, MOLD, SUPPRESSION, SWEET CHERRIES, TISSUE,
TOMATO PRODUCTS


     18   
Ahmed, F.E., A.E. Hall, and M.A. Madore. 1993. Interactive effects of high-temperature and
elevated carbon- dioxide concentration on cowpea [vigna-unguiculata (L) walp]. Plant, Cell and
Environment 16(7):835-842.

Limitations in carbohydrate supplies have been implicated as a factor responsible for reproductive
failure under heat stress. Heat stress affects two stages of reproductive development in cowpea
[Vigna unguiculata (L.) Walp.], and genotypes are available with tolerance and sensitivity to heat
during these different stages. The objectives of this study were to determine the responses of these
cowpea lines to ambient and elevated [CO2], under heat stress and optimal temperature, and test
whether differences in carbohydrate supplies due to genotypes, CO2 enrichment and heat stress are
associated with differences in sensitivity to heat during reproductive development. Plants were grown
in reach-in growth chambers and subjected to day/night temperatures of either 33/20 or 33/30-
degrees-C, and [CO2] levels of either 350 or 700 mumol mol-1. Under intermediate night
temperature (33/20-degrees-C), all lines set substantial numbers of pods. Under high night
temperature (33/30-degrees-C) with either ambient or elevated [CO2], one heat-sensitive line
produced no flowers and the other set no pods, whereas the heat-tolerant line abundantly set pods.
High night temperature reduced the overall carbohydrate content of the plants, especially peduncle
sugars, and caused decreases in photosynthetic rates. The high pod set of the heat-tolerant line, under
high night temperature, was associated with higher levels of sugars in peduncles compared with the
heat-sensitive lines. The heat-tolerant line accumulated substantial shoot biomass, exhibited less
accumulation of starch in leaves, and possibly had less down- regulation of photosynthesis in response
to CO2 enrichment and heat stress than the heat-sensitive lines. Elevated [CO2] resulted in higher
overall carbohydrate levels in heat- sensitive lines (starch in leaves, stems and peduncles), but it did
not increase their heat tolerance with respect to flower production or pod set. Heat-induced damage
to floral buds and anthers in the sensitive lines was associated with low sugars levels in peduncles,
indicating that heat had greater effects on assimilate demand than on leaf assimilate supply. The heat-
tolerant line was the most responsive genotype to elevated [CO2] with respect to pod production
under either high or intermediate temperatures.

KEYWORDS: ABSCISSION, ACCLIMATION, AIR- TEMPERATURE, CO2, COTTON, HEAT-
STRESS, LEAVES, LONG-TERM EXPOSURE, PHOTOSYNTHETIC INHIBITION,
REPRODUCTIVE RESPONSES


     19   
Aikman, D.P. 1996. A procedure for optimizing carbon dioxide enrichment of a glasshouse tomato
crop. Journal of Agricultural Engineering Research 63(2):171-183.

The procedure consists of two parts. A Gompertz model for the kinetics of fruit growth is used
predict the time distribution of photosynthate subsequent harvests. This is combined with predictions
of future market prices to compute estimates, one for each day from first anthesis, of a factor to
convert CO2 assimilate to expected financial value, based on the worth anticipated from partitioning
to fruit. A model of the climate and the crop regime is used to predict temperatures and hence allow
for the temperature dependence of fruit growth. The conversion estimates are revised to include the
deferred benefit given by additional photosynthesis through increasing early vegetative growth, and
hence subsequent photosynthesis and yield. This revision also extends the set of conversion factors
to include any period before first anthesis. Given the current environmental variables and conversion
factor for that day, a real-time system can use a crop photosynthesis model to predict the cash benefit
for any CO2 concentration. The cost of maintaining a concentration can be obtained from a prediction
of the ventilation air exchange rate and the unit price of CO2. The CO2 set-point is evaluated as the
concentration that maximizes the net profit rate. (C) 1996 Silsoe Research Institute

KEYWORDS: CO2- ENRICHMENT, CUCUMBER, FRUIT- GROWTH, GREENHOUSES,
LYCOPERSICON-ESCULENTUM MILL, MODEL, PLANTS, TEMPERATURE, VENTILATION


     20   
Akimoto, M., A. Shirai, K. Ohtaguchi, and K. Koide. 1998. Carbon dioxide fixation and
polyunsaturated fatty acid production by the red alga Porphyridium cruentum. Applied Biochemistry
and Biotechnology 73(2-3):269-278.

Focusing on CO2 fixation, photoautotrophic cultivation of the red alga Porphyridium cruentum was
investigated by means of a batch culture under a 5% CO2-enriched atmosphere. The alg-al growth
kinetics was successfully described with a logistic model, and simulation of a continuous culture
under the optimum growth conditions (30 degrees C, 12 klux and 1.18 g-cells/L) showed that the
algal CO2-fixation activity could reach 0.66 g- CO2/(L X d). Under the same growth conditions,
eicosapentaenoic acid (20:5 n-3, EPA) and arachidonic acid (20:4 n-6, ARA) yields were similarly
calculated to be 3.6 mg-EPA/(L X d) and 6.5 mg-ARA/(L X d), respectively.

KEYWORDS: CULTIVATION, GROWTH, LIGHT-INTENSITY, TEMPERATURE


     21   
Akin, D.E., B.A. Kimball, J.R. Mauney, R.L. Lamorte, G.R. Hendrey, K. Lewin, J. Nagy, and
R.N. Gates. 1994. Influence of enhanced co2 concentration and irrigation on sudangrass digestibility.
Agricultural and Forest Meteorology 70(1-4):279-287.

An experimental line of sudangrass (Sorghum bicolor L. Moench) was included in the free-air CO2
enrichment (FACE) project in 1991 at the University of Arizona Maricopa Agricultural Center to
evaluate the effect of ambient (approximately 370 mumol mol- 1) and enriched (550 mumol mol-1)
CO2 in well-watered or water- stressed plots. Our specific objective was to determine modifications
caused by these environmental effects on the percentages of morphological parts and the fiber
components, and on the in vitro digestibility in vegetative and mature harvests. Enrichment with CO2
did not (P > 0.05) change the percentages of morphological parts or fiber components, or the
digestibility of any of the morphological components. Protein levels tended to be lower in CO2-
enriched plants. However, water-stressed plants tended to have a higher proportion of leaves (blades
and sheaths) and a lower proportion of stems, were more digestible, and had lower amounts of anti-
quality, aromatic compounds within the plant cell. Stems had the highest digestibility of all
morphological components (about 75% in vegetative plants) despite the lowest levels of protein.
Stems also showed the greatest changes caused by all treatments, including a 20% decline in
digestibility from vegetative to mature samples. The results indicate that enriching CO2 to 550 mumol
mol-1 did not reduce digestibility of sudangrass.

KEYWORDS: CARBON DIOXIDE, ENRICHMENT


     22   
Akin, D.E., B.A. Kimball, W.R. Windham, P.J. Pinter, G.W. Wall, R.L. Garcia, R.L. Lamorte,
and W.H. Morrison. 1995. Effect of free-air co2 enrichment (face) on forage quality of wheat.
Animal Feed Science and Technology 53(1):29-43.

Wheat (Triticum aestivum L., cultivar 'Yecora rojo') was grown in ambient (370 mu mol mol(-1)) or
enriched (550 mu mol mol(- 1)) concentrations of CO2 in the free-air CO2 enrichment (FACE)
project, and components were analyzed for in vitro digestibility, fiber constituents, and crude protein.
Four replicated plots of each CO2 treatment were split for irrigation: 'wet' regions received 60 cm
of water and 'dry' regions received 30 cm of water through underground tubes. Enriched CO2
concentrations had no effect on in vitro digestion of intact sections of young (26-32-day-old plants)
leaf blades except at 24-27 h incubation, at which time enriched leaves were lower in digestibility than
control ones. Enriched CO2 concentrations increased the content of acid detergent fiber (ADF) and
cellulose of young wet leaves, Sections of main shoots at 26 days tended to have increased
digestibility with elevated CO2 levels. Enriched CO2 concentrations did not alter the digestibility of
flag leaves from 105-day-old plants or of flag leaves, uppermost stems, and sheaths from plants at full
grain maturity, Enriched CO2 levels reduced the acid detergent lignin (ADL) and tended to reduce
the protein of leaves from 105-day-old plants. For mature leaf blades, neutral detergent fiber, ADF,
and cellulose were, or tended to be, higher while protein content tended to be lower in elevated CO2-
grown plants; for both CO2 treatments, 'dry' leaves were higher in digestibility and lower in ADL than
'wet' samples. Mature stems plus sheaths had lower protein contents in plants grown in elevated CO2.
Results indicated that enriched CO2 concentrations to 550 mu mol mol(-1) did not substantially alter
wheat in vitro digestibility, regardless of irrigation treatment. Elevated CO2 altered fiber components
and protein, but these were not consistent among parts and harvests.

KEYWORDS: CELL-WALLS, ECOSYSTEMS, MICROSPECTROPHOTOMETRY, PHENOLIC
CONSTITUENTS


     23   
Akin, D.E., L.L. Rigsby, G.R. Gamble, W.H. Morrison, B.A. Kimball, P.J. Pinter, G.W. Wall,
R.L. Garcia, and R.L. Lamorte. 1995. Biodegradation of plant-cell walls, wall carbohydrates, and
wall aromatics in wheat grown in ambient or enriched co2 concentrations. Journal of the Science of
Food and Agriculture 67(3):399-406.

Mature internodes from wheat (Triticum aestivum L) grown in control (ambient at c 370 mu mol
mol(-1)) or enriched (to 550 mu mol mol(-1)) concentrations of atmospheric CO2 in the free- air CO2
enrichment (FACE) system were analyzed for potential changes in biodegradation of constituents due
to predicted increases in atmospheric levels of CO2. The first internodes below the grain were
incubated with the lignocellulose- degrading white rot fungus, Phanerochaete chrysosporium K-3,
or incubated without microorganisms. Plant samples were then analyzed for dry weight loss,
disposition of specific cell types to biodegradation using electron microscopy, carbohydrates and
lignin using solid state NMR spectroscopy, and ester- and ether-linked aromatics using gas
chromatography. Phanerochaete chrysosporium extensively degraded stems cells (c 75%) and both
carbohydrate and aromatic portions of the wheat stems proportionately more carbohydrates were
removed by the fungus from the stems. Enriched CO2 did not affect the chemical composition of
wheat stems or the biodegradation by P chrysosporium of plant cell walls or wall components for the
most part. Data from various methods all indicated that enriched CO2 did not substantially alter the
biodegradation of wheat cell wall internodes or wall components. Evidence was not found for an
influence on C cycling due to CO2 concentrations in this study.

KEYWORDS: ECOSYSTEMS, LIGNINS, PHENOLIC CONSTITUENTS


     24   
Alagusundaram, K., D.S. Jayas, N.D.G. White, W.E. Muir, and R.N. Sinha. 1995. Controlling
cryptolestes-ferrugineus (stephens) adults in wheat stored in bolted-metal bins using elevated carbon-
dioxide. Canadian Agricultural Engineering 37(3):217-223.

Experiments were conducted in two 5.56 m-diameter farm bins to determine the mortality of caged
adult rusty grain beetles, Cryptolestes ferrugineus (Stephens) (Coleoptera: cucujidae), under elevated
carbon dioxide (CO2) concentrations. The bins were filled with wheat to a depth of 2.5 m. Dry ice
was used to create high CO2 concentrations in the wheat bulks. Two different modes of application
of dry ice were used: (i) pellets on the grain surface and in the aeration duct and (ii) pellets on the
grain surface and blocks in insulated boxes on the grain surface. The pellets exposed to the ambient
conditions on the grain surface and in the aeration duct sublimated quickly and had to be replenished
at frequent intervals. Dry ice blocks in insulated boxes, however, maintained high CO2 concentrations
without replenishment for over 15 d. In both modes of application, the observed CO2 concentrations
in the intergranular gas were about 15% and 30% (all the CO2 concentrations given in this article are
on a volume basis) at 2.05 m and 0.55 m above the floor, respectively. At 0.55 m above the floor, the
mortality of rusty grain beetle adults was more than 90% while in the top portions of the bulk (2.05
m above the floor) the mortality was only 30%. On an average about two thirds of the insects were
killed. The use of controlled atmosphere treatment within an integrated pest management context is
outlined.

KEYWORDS: INSECTS


     25   
Alberto, A.M.P., L.H. Ziska, C.R. Cervancia, and P.A. Manalo. 1996. The influence of increasing
carbon dioxide and temperature on competitive interactions between a C3 crop, rice (Oryza sativa)
and a C-4 weed (Echinochloa glabrescens). Australian Journal of Plant Physiology 23(6):795-802.

Many of the most troublesome weeds in agricultural systems are C-4 plants. As atmospheric CO2
increases it is conceivable that competitive ability of these weeds could be reduced relative to C-3
crops such as rice. At the International Rice Research Institute (IRRI) in the Philippines, rice (IR72)
and one of its associated C-4 weeds, Echinochloa glabrescens, were grown from seeding to maturity
using replacement series mixtures (100:0, 75:25, 50:50, 25:75, and 0:100, % rice:%weed) at two
different CO2 concentrations (393 and 594 mu L L(-1)) in naturally sunlit glasshouses. Since
increasing CO2 may also result in elevated growth temperatures, the response of rice to each CO2
concentration was also examined at day/night temperatures of 27/21 and 37/29 degrees C. At 27/21
degrees C, increasing the CO2 concentration resulted in a significant increase in above ground
biomass (+47%) and seed yield (+55%) of rice when averaged over all mixtures. For E. glabrescens,
the C-4 species, no significant effect of CO2 concentration on biomass or yield was observed. When
grown in mixture, the proportion of rice biomass increased significantly relative to that of the C- 4
weed at all mixtures at elevated CO2. Evaluation of changes in competitiveness (by calculation of
plant relative yield (PRY) and replacement series diagrams) of the two species demonstrated that, at
elevated CO2, the competitiveness of rice was increased relative to that of E. glabrescens. However,
at the higher growth temperature (37/29 degrees C), growth and reproductive stimulation of rice by
elevated CO2 was reduced compared to the lower growth temperature. This resulted in a reduction
in the proportion of rice:weed biomass present in all mixtures relative to 27/21 degrees C and a
greater reduction in PRY in rice relative to E. glabrescens. Data from this experiment suggest that
competitiveness could be enhanced in a C-3 crop (rice) relative to a C-4 weed (E. glabrescens) with
elevated CO2 alone, but that simultaneous increases in CO2 and temperature could still favour a C-4
species.

KEYWORDS: DRY-MATTER, ENRICHMENT, GROWTH, NITROGEN, PLANTS, WHEAT


     26   
Alcamo, J., G.J.J. Kreileman, M.S. Krol, and G. Zuidema. 1994. Modeling the global society-
biosphere-climate system .1. Model description and testing. Water, Air, and Soil Pollution 76(1-2):1-
35.

This paper describes the IMAGE 2.0 model, a multi-disciplinary, integrated model designed to
simulate the dynamics of the global society-biosphere-climate system. The objectives of the model
are to investigate linkages and feedbacks in the system, and to evaluate consequences of climate
policies. Dynamic calculations are performed to year 2100, with a spatial scale ranging from grid (0.5-
degrees x 0.5-degrees latitude- longitude) to world regional level, depending on the sub-model. The
model consists of three fully linked sub-systems: Energy- Industry, Terrestrial Environment, and
Atmosphere-Ocean. The Energy-Industry models compute the emissions of greenhouse gases in 13
world regions as a function of energy consumption and industrial production. End use energy
consumption is computed from var-ious economic/demographic driving forces. The Terrestrial
Environment models simulate the changes in global land cover on a grid-scale based on climatic and
economic factors, and the flux of CO2 and other greenhouse gases from the biosphere to the
atmosphere. The Atmosphere-Ocean models compute the buildup of greenhouse gases in the
atmosphere and the resulting zonal-average temperature and precipitation patterns. The fully linked
model has been tested against data from 1970 to 1990, and after calibration can reproduce the
following observed trends: regional energy consumption and energy-related emissions, terrestrial flux
of CO2 and emissions of greenhouse gases, concentrations of greenhouse gases in the atmosphere,
and transformation of land cover. The model can also simulate long term zonal average surface and
vertical temperatures.

KEYWORDS: CARBON-CYCLE, CO2, SENSITIVITY


     27   
Alcamo, J., G.J. Vandenborn, A.F. Bouwman, B.J. Dehaan, K.K. Goldewijk, O. Klepper, J.
Krabec, R. Leemans, J.G.J. Olivier, A.M.C. Toet, H.J.M. Devries, and H.J. Vanderwoerd.
1994. Modeling the global society-biosphere-climate system .2. Computed scenarios. Water, Air, and
Soil Pollution 76(1-2):37-78.

This paper presents scenarios computed with IMAGE 2.0, an integrated model of the global
environment and climate change. Results are presented for selected aspects of the society- biosphere-
climate system including primary energy consumption, emissions of various greenhouse gases,
atmospheric concentrations of gases, temperature, precipitation, land cover and other indicators.
Included are a ''Conventional Wisdom'' scenario, and three variations of this scenario: (i) the
Conventional Wisdom scenario is a reference case which is partly based on the input assumptions of
the IPCC's IS92a scenario; (ii) the ''Biofuel Crops'' scenario assumes that most biofuels will be derived
from new cropland; (iii) the ''No Biofuels'' scenario examines the sensitivity of the system to the use
of biofuels; and (iv) the ''Ocean Realignment'' scenario investigates the effect of a large-scale change
in ocean circulation on the biosphere and climate. Results of the biofuel scenarios illustrate the
importance of examining the impact of biofuels on the full range of greenhouse gases, rather than only
CO2. These scenarios also indicate possible side effects of the land requirements for energy crops.
The Ocean Realignment scenario shows that an unexpected, low probability event can both enhance
the build-up of greenhouse gases, and at the same time cause a temporary cooling of surface air
temperatures in the Northern Hemisphere. However, warming of the atmosphere is only delayed, not
avoided.



     28   
Allen, D.J., I.F. McKee, P.K. Farage, and N.R. Baker. 1997. Analysis of limitations to CO2
assimilation on exposure of leaves of two Brassica napus cultivars to UV-B. Plant, Cell and
Environment 20(5):633-640.

Apex and Bristol cultivars of oilseed rape (Brassica napus) were irradiated with 0.63 W m(-2) of UV-
B over 5 d. Analyses of the response of net leaf carbon assimilation to intercellular CO2 concentration
were used to examine the potential limitations imposed by stomata, carboxylation velocity and
capacity for regeneration of ribulose 1,5-bisphosphate on leaf photosynthesis. Simultaneous
measurements of chlorophyll fluorescence were used to estimate the maximum quantum efficiency
of photosystem II (PSII) photochemistry, the quantum efficiency of linear electron transport at
steady-state photosynthesis, and the light and CO2-saturated rate of linear electron transport.
Ribulose 1,5-bisphosphate carboxylase/oxygenase (Rubisco) content and activities were assayed in
vitro. In both cultivars the UV-B treatment resulted in decreases in the light-saturated rate of CO2
assimilation, which were accompanied by decreases in carboxylation velocity and Rubisco content
and activity. No major effects of UV-B were observed on end-product inhibition and stomatal
limitation of photosynthesis or the rate of photorespiration relative to CO2 assimilation. In the Bristol
cultivar, photoinhibition of PSII and loss of linear electron transport activity were observed when
CO2 assimilation was severely inhibited, However, the Apex cultivar exhibited no major inhibition
of PSII photochemistry or linear electron transport as the rate of CO2 assimilation decreased. It is
concluded that loss of Rubisco is a primary factor in UV-B inhibition of CO2 assimilation.

KEYWORDS: ENHANCED RADIATION, HIGHER-PLANTS, ORYZA-SATIVA,
PHOTOSYNTHETIC ELECTRON-TRANSPORT, PHOTOSYSTEM, PISUM-SATIVUM,
RIBULOSE-1;5-BISPHOSPHATE CARBOXYLASE, ULTRAVIOLET-RADIATION, VIGNA-
SINENSIS L


     29   
Allen, L.H. 1992. Free-air co-2 enrichment field experiments - an historical overview. Critical
Reviews in Plant Sciences 11(2-3):121-134.

KEYWORDS: CARBON DIOXIDE, CO2, COTTON, CROPS, FUMIGATION, GROWN SOYBEANS,
PHOTOSYNTHETIC ACCLIMATION, PLANTS, SULFUR-DIOXIDE, SYSTEM


     30   
Allen, L.H., E.C. Bisbal, and K.J. Boote. 1998. Nonstructural carbohydrates of soybean plants
grown in subambient and superambient levels of CO2. Photosynthesis Research 56(2):143-155.

Elevated carbon dioxide (CO2) concentration increases plant photosynthesis, biomass and
carbohydrate accumulation. Since plants have grown in low CO2 (200 to 300 mu mol mol(-1)) for
the last several million years, how will they use extra photoassimilate as the atmospheric CO(2
)continues to rise? The objectives were to determine the effects of past, present and projected future
levels of CO2 on diurnal and seasonal patterns of total nonstructural carbohydrate (TNC)
concentration of soybean [Glycine max (L.) Merr.] tissues. Plants were grown at 160, 220, 280, 330,
660 and 990 mu mol mol(-1) CO2 in outdoor, sunlit chambers wherein CO2 uptake rates were
measured continuously. Early morning and fate afternoon plant samples were taken at eight dates.
The TNC concentration of leaves, petioles and stems increased as CO:! increased. Canopy
photosynthetic rates also increased with increasing CO2, apparently without any negative impact of
increased leaf TNC. Concentrations of TNC in all vegetative tissues were lower in the morning than
the afternoon, which indicates overnight mobilization and utilization of carbohydrates for growth
processes. The concentration of TNC was lowest in ail plant components during rapid vegetative
growth at Vg to R2 developmental stages. Leaves of all plants, especially those grown in
superambient CO2, contained large pools of TNC at plant maturity, which indicated that not all of
the reserves were utilized for seed yield. Soybean cultivars for the future should be designed to utilize
carbohydrates more readily for seed production so that greater benefit can be realized from rising
atmospheric CO2.

KEYWORDS: CARBON-DIOXIDE ENRICHMENT, EXPORT, L MERR PLANTS, LEAF, LEAVES,
LIGHT, PHOTOSYNTHETIC RESPONSE, REPRODUCTIVE GROWTH, STARCH
CONCENTRATION, TEMPERATURE


     31   
Allen, L.H., E.C. Bisbal, K.J. Boote, and P.H. Jones. 1991. Soybean dry-matter allocation under
subambient and superambient levels of carbon-dioxide. Agronomy Journal 83(5):875-883.

Rising atmospheric carbon dioxide concentration [CO2] is expected to cause increases in crop growth
and yield. The objective of this study was to investigate effects of subambient, as well as
superambient, [CO2] on soybean [Glycine max (L.) Merr.] dry matter production and allocation for
two reasons: to assess response of plants to prehistoric as well as future expected CO2 levels and to
increase confidence in [CO2] response curves by imposing a wide range of [CO2] treatments.
Soybean was grown in outdoor, sunlit, controlled- environment chambers at CO2 levels of 160, 220,
280, 330, 660, and 990-mu-mol (CO2) mol-1 (air). Total dry matter growth rates during the linear
phase of vegetative growth were 5.0, 8.4, 10.9, 12.5, 18.2, and 20.7 g m-2 d-1 for the above
respective [CO2]. Samples taken from 24 to 94 d after planting showed that the percentage of total
plant mass in leaf trifoliolates decreased with increasing [CO2] whereas the percentage in structural
components (petioles and stems) increased. At final harvest the respective [CO2] treatments resulted
in 38, 53, 62, 100, 120, and 92% seed yield with respect to the 330-mu-mol mol-1 treatment. Total
dry weight responses were similar. Late season spider mite damage of the 990 and 280-mu-mol mol-1
treatments reduced yields. These data confirm not only that rising CO2 should increase plant growth,
but also that plant growth was probably seriously limited by atmospheric [CO2] in preindustrial
revolution times back to the previous global glaciation.

KEYWORDS: ATMOSPHERIC CO2 ENRICHMENT, CHAMBERS, DEVELOPMENTAL STAGES,
PHOTOSYNTHESIS, PLANT GROWTH, TRANSPIRATION RESPONSES, WATER-USE, WEIGHT,
YIELD


     32   
Allen, L.H., B.G. Drake, H.H. Rogers, and J.H. Shinn. 1992. Field techniques for exposure of
plants and ecosystems to elevated co-2 and other trace gases. Critical Reviews in Plant Sciences
11(2-3):85-119.

KEYWORDS: ATMOSPHERIC CO2 ENRICHMENT, CARBON-DIOXIDE CONCENTRATIONS,
ESTUARINE MARSH, OPEN-AIR FUMIGATION, OPEN-TOP CHAMBERS, PORTABLE
CHAMBER, SOYBEAN CANOPIES, TRANSPIRATION RESPONSES, VENTILATED CHAMBER,
WATER-VAPOR EXCHANGE


     33   
Allen, L.H., R.R. Valle, J.W. Jones, and P.H. Jones. 1998. Soybean leaf water potential responses
to carbon dioxide and drought. Agronomy Journal 90(3):375-383.

Rising CO2 can have direct effects on crop water relations and indirect effects on water available for
growth. We studied the effects of elevated CO2 and drought on leaf water relations of soybean
[Glycine max (L.) Merr. cv. Bragg] and considered the hypothesis of osmotic adjustment mediated
by increased photosynthesis (Hypothesis 1) vs. the hypothesis of water conservation mediated by
decreased stomatal conductance (Hypothesis 2) to explain improved water relations of plants growing
under elevated CO2. In Exp. 1, soybean was grown at 330, 450, 660, and 800 mu mol mol(-1) CO2
in sunlit, closed- circulation, controlled-environment chambers under well-watered conditions. Leaf
total water potential (WP), osmotic potential (OP), and turgor potential (TP) were measured at
midday during V4 to R6 stages of development. In Exp. 2 (well-watered, R1-R3) and Exp. 3 (13-d
drying cycle, R6 seed filling), soybean was grown at 330 and 660 mu mol mol(-1) CO2 and WP, OP,
and TP were measured five times per day on sunlit and shaded leaves. In Exp. 3, stomatal
conductance (g(s)) and transpiration rate (TR) of leaves were also measured. Experiments 1 and 2
showed that elevated CO2 increased TP and decreased OP, but did not affect leaf WP, thus favoring
Hypothesis 1. In Exp. 3, leaf WP was higher in elevated than ambient CO2. Diurnal TP was higher
in elevated than ambient CO2 at the beginning of drought, and was maintained longer each day as
drought progressed. At the end of drought, TP and WP was higher in elevated than ambient CO2.
Elevated CO2 leaves had lower TR because of lower g(s) than ambient CO2 counterparts. Thus, Exp.
3 supported Hypothesis 2, that both stressed and nonstressed plants in elevated CO2 have a better
water status (e.g., higher TP) than plants in ambient CO2 due to water conservation mediated by
decreased g(s). Remobilization of leaf nutrients during seed filling may limit the capability for osmotic
adjustment. Regardless of the mechanisms, growth of plants in elevated CO2 should be less affected
by drought than plants in ambient CO2.

KEYWORDS: DIFFERENT CO2 ENVIRONMENTS, FIELD, LEAVES, MAIZE, NITROGEN,
OSMOTIC ADJUSTMENT, PLANT GROWTH, STRESS, USE EFFICIENCY, YIELD


     34   
Allen, L.H., R.R. Valle, J.W. Mishoe, and J.W. Jones. 1994. Soybean leaf gas-exchange responses
to carbon-dioxide and water-stress. Agronomy Journal 86(4):625-636.

As global carbon dioxide concentrations rise, we need to understand the combination of direct effects
of this gas and the anticipated effects of climate change, including drought, on physiology and growth
of all crops. Effects Of CO2 on plants begin at the leaf level; our objectives, therefore, were to
determine interrelationships among factors governing gas exchange responses of soybean [Glycine
max (L.) Merr.] leaves to elevated CO2 and water stress. Photosynthetic CO2 assimilation and
transpiration rates were measured in cuvettes on leaflets of soybean (cv. Bragg) grown in controlled-
environment chambers at 330 and 660 mumol CO2 Mol-1 air. Leaflets at high CO2, either water-
stressed or well-watered, had higher photosynthetic and lower transpiration rates, and therefore
higher water-use efficiencies (WUE), than those at Control CO2 levels. As irrigation was withheld
during an 11-d period, WUE decreased about 30 to 50% with respect to the well- watered
treatments. Midday leaf temperature and leaf-to-air vapor pressure gradient levels increased as the
water stress progressed. For water stress treatments, midday leaf conductance (G(lw)) was generally
higher and residual internal conductance (G(r)) was generally lower in low than in high CO2. Ratios
of midday G(r)/G(lc), were nearly constant throughout the period in both the stressed and the well-
watered treatments. The ratios of intercellular C(i), to ambient C(a), CO2 concentration (i.e.,
C(i)/C(a)) during the water stress period remained similar to the respective nonstressed treatments
within each CO2 level. These findings support the concept that leaf conductances are governed by
CO2 assimilation rates under water-stressed as well as unstressed conditions.

KEYWORDS: ABSCISIC- ACID, CARBOXYLASE, DIFFERENT CO2 ENVIRONMENTS, FIELD,
GROWTH, LEAVES, PHOTOSYNTHESIS, STOMATAL CONDUCTANCE, TRANSPIRATION
RATE, WHEAT


     35   
Allen, L.H., R.R. Valle, J.W. Mishoe, J.W. Jones, and P.H. Jones. 1990. Soybean leaf gas-
exchange responses to CO2 enrichment. Soil and Crop Science Society of Florida Proceedings
49:192-198.



     36   
Almeida, J.P.F., A. Luscher, M. Frehner, A. Oberson, and J. Nosberger. 1999. Partitioning of
P and the activity of root acid phosphatase in white clover (Trifolium repens L.) are modified by
increased atmospheric CO2 and P fertilisation. Plant and Soil 210(2):159-166.

The growth response of white clover (Trifolium repens L.) to the expected increase in atmospheric
partial pressure of CO2 (p(CO2)) may depend on P availability. A decrease in the rate of transpiration
due to increased p(CO2) may reduce the amount of P transported to the shoot, thereby causing a
change in the partitioning of P between the root and shoot. To test these hypotheses, four
concentrations of P in the nutrient solution, combined with two p(CO2) treatments, were applied to
nodulated white clover plants. Compared to ambient p(CO2) (35 Pa), twice ambient p(CO2) (70 Pa)
reduced the rate of transpiration but did not impair the total P uptake per plant. However, at twice
ambient p(CO2) and a moderate to high supply of P, concentrations of structural P and soluble P (Pi)
were lower in the leaves and higher in the roots. The activity of root acid phosphatase was lower at
twice ambient p(CO2) than at ambient p(CO2); it depended on the Pi concentration in the roots. At
the highest P concentration, twice ambient p(CO2) stimulated photosynthesis and the growth rate of
the plant without affecting the concentration of nonstructural carbohydrates in the leaves. However,
at the lower P concentrations, plants at twice ambient p(CO2) lost their stimulation of photosynthesis
in the afternoon, they accumulated nonstructural carbohydrates in the leaves and their growth rate
was not stimulated; indicating C-sink limitation of growth. P nutrition will be crucial to the growth
of white clover under the expected future conditions of increased p(CO2).

KEYWORDS: AIR, BEAN-PLANTS, CARBON DIOXIDE, DRY-MATTER, ENRICHMENT,
GROWTH, MAGNESIUM-DEFICIENCY, PHOSPHORUS, SOURCE-SINK RELATIONS,
SUBTERRANEUM L


     37   
Alvarez, R., M. Alconada, and R. Lavado. 1999. Sewage sludge effects on carbon dioxide-carbon
production from a desurfaced soil. Communications in Soil Science and Plant Analysis 30(13-
14):1861-1866.

Desurfaced soils are found near cities in the Pampean Region of Argentina because A horizons were
used for brick production. These soils are not suitable for agriculture. Application of sewage sludge
is a tool for improving soil productivity, but its effects on the environment are not thoroughly
understood. Production of carbon dioxide (CO2)-carbon (C) in the field from a desurfaced soil in
which 25 Mg dry matter ha(-1) of sewage sludge were applied the first year and 10 Mg dry matter
ha(-1), the second year was evaluated during a corn (Zea mays L.) growing cycle. Microbial biomass
and metabolic activity were also measured. Sludge applications produced an increase of the CO2-C
efflux in the field of 30-50% during summer. Microbial biomass was not affected by sludge some
months after the application, but metabolic activity and organic matter mineralization were enhanced.
The increase of the CO2-C emission from the soil represented 21% of the sludge C applied the year
of the experiment and 15% of the C applied the year before. Consequently, an important quantity of
the sludge C was retained in the soil.

KEYWORDS: CROPS, GLUCOSE, HEAVY-METALS, MAIZE, MANURE, MICROBIAL BIOMASS
DYNAMICS, RESIDUE


     38   
Ambus, P., and G.P. Robertson. 1999. Fluxes of CH4 and N2O in aspen stands grown under
ambient and twice-ambient CO2. Plant and Soil 209(1):1-8.

Elevated atmospheric CO2 has the potential to change below- ground nutrient cycling and thereby
alter the soil-atmosphere exchange of biogenic trace gases. We measured fluxes of CH4 and N2O in
trembling aspen (Populus tremuloides Michx.) stands grown in open-top chambers under ambient and
twice-ambient CO2 concentrations crossed with `high' and low soil-N conditions. Flux measurements
with small static chambers indicated net CH4 oxidation in the open-top chambers. Across dates, CH4
oxidation activity was significantly (P < 0.05) greater with ambient CO2 (8.7 mu g CH4-C m(-2) h(-
1)) than with elevated CO2 (6.5 mu g CH4-C m(-2) h(-1)) in the low N soil. Likewise, across dates
and soil N treatments CH4 was oxidized more rapidly (P < 0.05) in chambers with ambient CO2 (9.5
mu g CH4-C m(-2) h(-1)) than in chambers with elevated CO2 (8.8 mu g CH4-C m(-2) h(-1)).
Methane oxidation in soils incubated in serum bottles did not show any response to the CO2
treatment. We suggest that the depressed CH4 oxidation under elevated CO2 in the field chambers
is due to soil moisture which tended to be higher in the twice-ambient CO2 treatment than in the
ambient CO2 treatment. Phase I denitrification (denitrification enzyme activity) was 12-26% greater
under elevated CO2 than under ambient CO2 in the `high' N soil; one sampling, however, showed a
39% lower enzyme activity with elevated CO2. In both soil N treatments, denitrification potentials
measured after 24 or 48 h were between 11% and 21% greater (P < 0.05) with twice- ambient CO2
than with ambient CO2. Fluxes of N2O in the open- top chambers and in separate 44 cm(2) cores +/-
N fertilization were not affected by CO2 treatment and soil N status. Our data show that elevated
atmospheric CO2 may have a negative effect on terrestrial CH4 oxidation. The data also indicated
temporary greater denitrification with elevated CO2 than with ambient CO2. In contrast, we found
no evidence for altered fluxes of N2O in response to increases in atmospheric CO2.

KEYWORDS: ATMOSPHERIC METHANE CONSUMPTION, DENITRIFICATION, ELEVATED
CARBON-DIOXIDE, ENRICHMENT, GAS FLUXES, GRASSLAND, NITROUS-OXIDE,
RESPONSES, TALLGRASS PRAIRIE, TEMPERATE FOREST SOILS


     39   
Amiro, B.D., J.I. MacPherson, and R.L. Desjardins. 1999. BOREAS flight measurements of
forest-fire effects on carbon dioxide and energy fluxes. Agricultural and Forest Meteorology
96(4):199-208.

Fire is the dominant stand-replacing agent in the Canadian boreal forest, but few quantitative
measurements are available on the micrometeorological effects of fire. Airborne flux measurements
during the BOREAS experiment were referenced to age of burn along a 500-km transect through
Saskatchewan and Manitoba, Canada. These data for 1-, 5-, and 7-year-old burns were supplemented
with 15- and 30-year-old-burn data from the BOREAS northern study site near Thompson, Manitoba.
Data were available near midday only and included the June, July and September campaigns during
1994, and July of 1996. Surface radiometric temperature increased by up to 6 degrees C and
remained elevated even 15 years after fire. Net radiation was largely unaffected whereas albedo
decreased in the first year post-fire but recovered by the fifth year. Sensible heat flux increased by 10-
20% for the first few years after the fire and then decreased. Latent heat flux slightly decreased after
the fire, causing the Bowen ratio to increase by ca. 50% for 7 years post-fire. The CO2 flux was
reduced for the 15-year period after fire with the greatest reduction to ca. 25% of control areas
during the year following fire. However, diurnal and annual data are needed to determine the total
impact of fire on the boreal-forest carbon balance. (C) 1999 Elsevier Science B.V. All rights reserved.

KEYWORDS: ASPEN FOREST, ATMOSPHERE, ECOSYSTEMS, EXCHANGES, MICROBIAL
BIOMASS, NORTHERN, PINE FOREST, SOIL RESPIRATION, WATER-VAPOR, WILDFIRE


     40   
Amoroso, G., C. Weber, D. Sultemeyer, and H. Fock. 1996. Intracellular carbonic anhydrase
activities in Dunaliella tertiolecta (Butcher) and Chlamydomonas reinhardtii (Dangeard) in relation
to inorganic carbon concentration during growth: Further evidence for the existence of two distinct
carbonic anhydrases associated with the chloroplasts. Planta 199(2):177-184.

Using mass-spectrometric measurements of O-18 exchange from (CO2)-C-13-O-18 intracellular
carbonic anhydrase (CA) activity was investigated in the unicellular green algae Dunaliella tertiolecta
and Chlamydomonas reinhardtii which were either grown on air enriched with 5% CO2 (high-C-i
cells) or on air (low-C-i cells). In D. tertiolecta high- and low-C-i cells had detectable levels of
internal CA activity when measured under in-vivo conditions and this activity could be split up into
three distinct forms. One CA was not associated with the chloroplasts, while two isozymes were
found to be located within the plastids. The activities of all intracellular CAs were always about
twofold higher in low than in high -C-i cells of D. tertiolecta and the chloroplastic enzymes were
completely induced within 4 h of adaptation to air. One of the chloroplastic CAs was found to be
soluble the other was insoluble. In addition to the physical differences, MgSO4 in vitro caused a more
than twofold stimulation of the soluble activity while the insoluble form of CA remained rather
unaffected. In C. reinhardtii, MgSO4 increased the soluble CA activity by 346% and the
concentration of MgSO4 required for half-maximum stimulation was between 10 and 15 mM. Again,
the insoluble CA activity was not affected by MgSO4. Furthermore, the soluble isoenzyme was
considerably more sensitive to ethoxyzolamide, a potent inhibitor of CA, than the insoluble enzyme.
The concentration of inhibitor causing 50% inhibition of soluble CA activity was 110 and 85 mu M
ethoxyzolamide for D. tertiolecta and C. reinhardtii, respectively. From these data we conclude that
the two chloroplast-associated CAs are distinct enzymes.

KEYWORDS: CELL-SURFACE, CO2, CYANOBACTERIUM SYNECHOCOCCUS PCC7942,
INCREASES, INTACT CHLOROPLASTS, MICROALGAE, O-18 EXCHANGE,
PHOTOSYNTHESIS, SALINA, TRANSPORT


     41   
Amthor, J.S. 1991. Respiration in a future, higher-CO2 world. Plant, Cell and Environment
14(1):13-20.

Apart from its impact on global warming, the annually increasing atmospheric [CO2] is of interest
to plant scientists primarily because of its direct influence on photosynthesis and photorespiration in
C3 species. But in addition, 'dark' respiration, another major component of the carbon budget of
higher plants, may be affected by a change in [CO2] independent of an increase in temperature.
Literature pertaining to an impact of [CO2] on respiration rate is reviewed. With an increase in
[CO2], respiration rate is increased in some cases, but decreased in others. The effects of [CO2] on
respiration rate may be direct or indirect. Mechanisms responsible for various observations are
proposed. These proposed mechanisms relate to changes in: (1) levels of nonstructural carbohydrates,
(2) growth rate and structural phytomass accumulation, (3) composition of phytomass, (4) direct
chemical interactions between CO2 and respiratory enzymes, (5) direct chemical interactions between
CO2 and other cellular components, (6) dark CO2 fixation rate, and (7) ethylene biosynthesis rate.
Because a range of (possibly interactive) effects exist, and present knowledge is limited, the impact
of future [CO2] on respiration rate cannot be predicted. Theoretical considerations and types of
experiments that can lead to an increase in the understanding of this issue are outlined.

KEYWORDS: CARBON DIOXIDE, CO2- ENRICHMENT, DARK RESPIRATION, ENERGY
OVERFLOW, GAS-EXCHANGE, GROWTH, LEAF, PHOTOSYNTHESIS, PLANTS,
TEMPERATURE


     42   
Amthor, J.S. 1994. Scaling co2-photosynthesis relationships from the leaf to the canopy.
Photosynthesis Research 39(3):321-350.

Responses of individual leaves to short-term changes in CO2 partial pressure have been relatively well
studied. Whole-plant and plant community responses to elevated CO2 are less well understood and
scaling up from leaves to canopies will be complicated if feedbacks at the small scale differ from
feedbacks at the large scale. Mathematical models of leaf, canopy, and ecosystem processes are
important tools in the study of effects on plants and ecosystems of global environmental change, and
in particular increasing atmospheric CO2, and might be used to scale from leaves to canopies. Models
are also important in assessing effects of the biosphere on the atmosphere. Presently, multilayer and
big leaf models of canopy photosynthesis and energy exchange exist. Big leaf models - which are
advocated here as being applicable to the evaluation of impacts of 'global change' on the biosphere -
simplify much of the underlying leaf-level physics, physiology, and biochemistry, yet can retain the
important features of plant- environment interactions with respect to leaf CO2 exchange processes
and are able to make useful, quantitative predictions of canopy and community responses to
environmental change. The basis of some big leaf models of photosynthesis, including a new model
described herein, is that photosynthetic capacity and activity are scaled vertically within a canopy (by
plants themselves) to match approximately the vertical profile of PPFD. The new big leaf model
combines physically based models of leaf and canopy level transport processes with a biochemically
based model of CO2 assimilation. Predictions made by the model are consistent with canopy CO2
exchange measurements, although a need exists for further testing of this and other canopy
physiology models with independent measurements of canopy mass and energy exchange at the time
scale of 1 h or less.

KEYWORDS: C-3 PLANTS, CARBON DIOXIDE, DARK RESPIRATION, LIGHT-INTENSITY,
PHOTOSYNTHETIC CO2 FIXATION, RIBULOSE-1;5-BISPHOSPHATE CARBOXYLASE,
SOURCE-SINK RELATIONS, STOMATAL CONDUCTANCE, SUNFLOWER LEAVES, WATER-
USE EFFICIENCY


     43   
Amthor, J.S. 1995. Predicting effects of atmospheric CO2 partial pressure on forest photosynthesis.
Journal of Biogeography 22(2-3):269-280.

A mechanistic (i.e. hierarchic or explanatory) model of forest canopy mass and energy exchange that
has been previously tested with eddy-correlation measurements in the field - albeit only at present
ambient CO2 partial pressure - was used to predict photosynthetic response of a deciduous Quercus-
Acer forest in eastern North America to atmospheric CO2 partial pressure. Four partial pressures of
CO2 were used in simulations: 28 (pre- industrial), 36 (present), 54 and 72 Pa. This is (one of) the
first set(s) of predictions of forest photosynthetic response to CO2 partial pressure made by a
mechanistic forest physiology model shown to accurately predict independent field measurements of
whole-forest CO2 exchange at the hourly time scale. The model includes a biochemically based
Farquhar-type model of leaf mesophyll CO2 assimilation, which is central to its ability to predict
photosynthetic response to different CO2 partial pressures. Whole-forest photosynthesis was
positively related to CO2 partial pressure, as expected. This was the case under both clear and cloudy
skies, but the relative response to CO2 was greater under a clear sky compared to a cloudy sky (the
clear sky day was also warmer). Instantaneous water use efficiency (mel CO2 assimilated per mol
H2O transpired) was positively related to atmospheric CO2 partial pressure for all conditions included
in the simulations. Model predictions indicate that (1) present forest photosynthesis and water use
efficiency may be significantly greater than they were in pre- industrial times (per unit ground area
of forest) and (2) future higher CO2 partial pressures could further stimulate forest photosynthesis
and water use efficiency, unless future climatic changes have significant negative effects on
photosynthesis or acclimation and adaptation processes markedly downregulate photosynthesis in
response to greater CO2 partial pressure.

KEYWORDS: C-3 PLANTS, CANOPY, DECIDUOUS FOREST, ELEVATED CO2, GAS-
EXCHANGE, GROWTH, MODELS, RIBULOSE-1;5-BISPHOSPHATE CARBOXYLASE, RISING
CO2, SOLAR RADIATION


     44   
Amthor, J.S. 1995. Terrestrial higher-plant response to increasing atmospheric [co2] in relation to
the global carbon-cycle. Global Change Biology 1(4):243-274.

Terrestrial higher plants exchange large amounts of CO2 with the atmosphere each year; c. 15% of
the atmospheric pool of C is assimilated in terrestrial-plant photosynthesis each year, with an about
equal amount returned to the atmosphere as CO2 in plant respiration and the decomposition of soil
organic matter and plant litter. Any global change in plant C metabolism can potentially affect
atmospheric CO2 content during the course of years to decades. In particular, plant responses to the
presently increasing atmospheric CO2 concentration might influence the rate of atmospheric CO2
increase through various biotic feedbacks. Climatic changes caused by increasing atmospheric CO2
concentration may modulate plant and ecosystem responses to CO2 concentration. Climatic changes
and increases in pollution associated with increasing atmospheric CO2 concentration may be as
significant to plant and ecosystem C balance as CO2 concentration itself. Moreover, human activities
such as deforestation and livestock grazing can have impacts on the C balance and structure of
individual terrestrial ecosystems that far outweigh effects of increasing CO2 concentration and
climatic change. In short-term experiments, which in this case means on the order of 10 years or less,
elevated atmospheric CO2 concentration affects terrestrial higher plants in several ways. Elevated
CO2 can stimulate photosynthesis, but plants may acclimate and (or) adapt to a change in
atmospheric CO2 concentration. Acclimation and adaptation of photosynthesis to increasing CO2
concentration is unlikely to be complete, however. Plant water-use efficiency is positively related to
CO2 concentration, implying the potential for more plant growth per unit of precipitation or soil
moisture with increasing atmospheric CO2 concentration. Plant respiration may be inhibited by
elevated CO2 concentration, and although a naive C balance perspective would count this as a benefit
to a plant, because respiration is essential for plant growth and health, an inhibition of respiration can
be detrimental. The net effect on terrestrial plants of elevated atmospheric CO2 concentration is
generally an increase in growth and C accumulation in phytomass. Published estimations, and
speculations about, the magnitude of global terrestrial- plant growth responses to increasing
atmospheric CO2 concentration range from negligible to fantastic. Well-reasoned analyses point to
moderate global plant responses to CO2 concentration. Transfer of C from plants to soils is likely to
increase with elevated CO2 concentrations because of greater plant growth, but quantitative effects
of those increased inputs to soils on soil C pool sizes are unknown. Whether increases in leaf-level
photosynthesis and short-term plant growth stimulations caused by elevated atmospheric CO2
concentration will have, by themselves, significant long-term (tens to hundreds of years) effects on
ecosystem C storage and atmospheric CO2 concentration is a matter for speculation, not firm
conclusion. Longterm field studies of plant responses to elevated atmospheric CO2 are needed. These
will be expensive, difficult, and by definition, results will not be forthcoming for at least decades.
Analyses of plants and ecosystems surrounding natural geological CO2 degassing vents may provide
the best surrogates for long-term controlled experiments, and therefore the most relevant information
pertaining to long-term terrestrial-plant responses to elevated CO2 concentration, but pollutants
associated with the vents are a concern in some cases, and quantitative knowledge of the history of
atmospheric CO2 concentrations near vents is limited. On the whole, terrestrial higher-plant responses
to increasing atmospheric CO2 concentration probably act as negative feedbacks on atmospheric CO2
concentration increases, but they cannot by themselves stop the fossil-fuel-oxidation-driven increase
in atmospheric CO2 concentration. And, in the very long-term, atmospheric CO2 concentration is
controlled by atmosphere-ocean C equilibrium rather than by terrestrial plant and ecosystem
responses to atmospheric CO2 concentration.

KEYWORDS: DIOXIDE CONCENTRATION, ELEVATED CO2, GAS-EXCHANGE, PARTIAL-
PRESSURE, PAST 2 CENTURIES, PHOTOSYNTHETIC ACCLIMATION, RIBULOSE-1;5-
BISPHOSPHATE CARBOXYLASE-OXYGENASE, STOMATAL DENSITY, VOSTOK ICE-CORE,
WATER-USE EFFICIENCY


     45   
Amthor, J.S. 1998. Perspective on the relative insignificance of increasing atmospheric CO2
concentration to crop yield. Field Crops Research 58(2):109-127.

Average yield of most crops in many countries increased significantly during the past 50 to 100 years.
Although atmospheric CO2 concentration, [CO2](a), also increased during that time period, and
although crop growth and yield can respond positively to [CO2](a) increase, yield increases were due
mainly to factors other than increasing [CO2](a). Similarly, some yield increases prior to 1900 were
also associated primarily with factors other than changes in [CO2](a). In particular, past national
average yield increases were the result chiefly of technological advances such as nitrogen fertilization;
selection of genotypes with increased harvest index and disease resistance; mechanization of planting,
cultivation, and harvesting; and chemical weed and pest control. If technology continues to increase
average yields at recent rates, near-future increases in [CO2](a) will have only small impacts on yield
in comparison to technology in many countries. Conversely, if future increases in [CO2](a) are the
main drivers of future yield increases, those yield increases will be small. These points are
demonstrated through a comparison of (i) long-term records of yield, (ii) data from key controlled-
[CO2] experiments, and (iii) records of past [CO2](a). Finally, it is noted that continued [CO2](a)
increase may bring with it climatic changes that could have negative or positive impacts on future
yield. (C) 1998 Elsevier Science B.V. All rights reserved.

KEYWORDS: 18TH-CENTURY ENGLAND, AGRICULTURAL PRODUCTIVITY, CARBON
DIOXIDE, CLIMATE, ENRICHMENT, PHOTOSYNTHESIS, RESPONSES, SPECULATIONS,
TRENDS, WHEAT


     46   
Amthor, J.S., R.J. Mitchell, G.B. Runion, H.H. Rogers, S.A. Prior, and C.W. Wood. 1994.
Energy content, construction cost and phytomass accumulation of glycine-max (L) merr and
sorghum-bicolor (L) moench grown in elevated co2 in the field. New Phytologist 128(3):443-450.

Grain sorghum [Sorghum] bicolor (L.) Moench, a C-4 crop] and soybean [Glycine max (L.) Merr.
cv. Stonewall, a C-3 crop] plants were grown in ambient (c. 360 mu l l(-1)) and twice- ambient (c.
720 mu l l(-1)) CO2 levels in open-top chambers in soil without root constriction. Plant dry mass,
energy content, composition and construction cost (i.e. amount of carbohydrate required to
synthesize a unit of plant dry mass) were assessed at the end of the growing season. Elevated CO2
(a) increased phytomass accumulation (kg per plant) in both species, (b) had little affect on energy
concentration (MJ kg(-1) plant) but caused large increases in the amount of plant energy per ground
area (MJ m(-2) ground), and (c) did not alter specific growth cost (kg carbohydrate kg(-1) plant
growth) but greatly increased growth cost per ground area (kg carbohydrate m(-2) ground) because
growth was enhanced. For soybean, twice-ambient CO2 resulted in a 50 % increase in the amount
of nitrogen and energy in grain (seed plus pod) per ground area. This response to elevated CO2 has
important implications for agricultural productivity during the next century because the rate of human
population growth is exceeding the rate of increase of land used for agriculture so that future food
demands can only be met by greater production per ground area.

KEYWORDS: CARBON DIOXIDE, ENRICHMENT, LEAVES, MAINTENANCE, NITROGEN,
PHOTOSYNTHESIS, PLANTS, RESPIRATION, RESPONSES, YIELD


     47   
Andalo, C., B. Godelle, M. Lefranc, M. Mousseau, and I. TillBottraud. 1996. Elevated CO2
decreases seed germination in Arabidopsis thaliana. Global Change Biology 2(2):129-135.

The impact of elevated [CO2] on seed germination was studied in different genotypes of Arabidopsis
thaliana from natural populations. Two generations of seeds were studied: the maternal generation
was produced in the greenhouse (present-day conditions), the offspring generation was produced in
two chambers where the CO2 concentration was either the present atmospheric concentration (about
350 ppm) or elevated (700 ppm). The seeds were tested for proportion of germinated seeds and mean
germination time in both chambers to study the impact of elevated [CO2] during seed production and
germination. Elevated [CO2] during maturation of seeds on the mother-plants decreased the
proportion of germinated seeds, while elevated [CO2] during germination had no effect on the
proportion of germinated seeds. However, when seeds were both produced and germinated under
elevated [CO2] (situation expected by the end of next century), germination was slow and low.
Moreover, the effect of the [CO2] treatment differs among genotypes of Arabidopsis: there is a
strong treatment x genotype interaction. This means that there is ample genetic variance for a
selective response modiying the effects of high levels of [COP] in natural populations of Arabidopsis
thaliana. The outcome at the community level will depend on what seeds are available, when they
germinate and the resulting competition following germination.

KEYWORDS: GROWTH, PLANTS


     48   
Andalo, C., C. Raquin, N. Machon, B. Godelle, and M. Mousseau. 1998. Direct and maternal
effects of elevated CO2 on early root growth of germinating Arabidopsis thaliana seedlings. Annals
of Botany 81(3):405-411.

Individuals of Arabidopsis thaliana, collected in different natural populations, were grown in
controlled and elevated CO2 in a glasshouse. Following germination, root growth of progeny of
different lines of these populations was studied in control and elevated atmospheric CO2. No
significant direct effect of atmospheric CO2 concentration could be demonstrated on root growth.
An important parental effect was apparent, namely that root length and branching were decreased in
seeds collected from a mother plant which had been grown in elevated CO2. This was correlated with
smaller seeds, containing less nitrogen. These parental effects were genetically variable. We conclude
that CO2 may affect plant fitness via parental effects on seed size and early root growth and that the
genetic variability shown in our study demonstrates that Arabidopsis populations will evolve in the
face of this new selective pressure. (C) 1998 Annals of Botany Company.

KEYWORDS: ATMOSPHERIC CARBON-DIOXIDE, ELONGATION, ENRICHMENT, PLANT,
QUALITY, SEED-GERMINATION, SENECIO-VULGARIS, TEMPERATURE, TRITICUM-
AESTIVUM L, WHEAT


     49   
Anderson, J.M. 1991. The effects of climate change on decomposition processes in grassland and
coniferous forests. Ecological Applications 1(3):326-347.

Current models of climate change predict a reduction of area covered by northern coniferous forests
and tundra, and an increase in grasslands. These scenarios also indicate a northerly shift in agricultural
regions, bringing virgin soils under cultivation. The direct effects of man on tundra,boreal forest, and
temperate grassland ecosystems are likely to result in less carbon mobilization from soils and
vegetation than from tropical forests. However, as a consequence of climate change, carbon
mineralization rates from arctic and sub-arctic soils could be very rapid under warmer and drier
conditions because of low stabilization of soil organic matter (SOM) and enhanced microbial
responses to small changes in soil moisture and temperature. Predicting the response of these systems
to climate change is complicated where the edaphic environment regulating SOM dynamics is not a
direct function of macroclimatic conditions. Grasslands contain a greater proportion of highly
stabilized SOM than coniferous forests, distributed over greater depth in the soil profile, which is less
susceptible to changes in mineralization rates. It is concluded that short-term responses of soil
processes to climate change are more predictable in well-drained grassland and forest soils than in
waterlogged soils of the tundra and boreal region. Over longer periods of time, however, plant
species and soil types will alter in response to new temperature and moisture regimes above- and
belowground interacting with the effects of carbon enrichment and changes in nutrient availability.
The dynamics of these plant-soil interactions and the future status of soils in different life zones as
sources or sinks of carbon is poorly understood. More data are also needed on the distribution of
waterlogged forest soils in the boreal zone and responses to warming, which include the production
of methane as well as CO2. The primary recommendation for future research is for integrated studies
on plant and soil processes.

KEYWORDS: ATMOSPHERIC CARBON-DIOXIDE, DOUGLAS-FIR, LEAF-LITTER
DECOMPOSITION, LONG-TERM DECOMPOSITION, NITROGEN-AVAILABILITY, NORTHERN
HARDWOODS, SCOTS PINE FOREST, SOIL ORGANIC MATTER, SPRUCE-LICHEN
WOODLAND, TEMPERATE ECOSYSTEMS


     50   
Anderson, P.D., and P.T. Tomlinson. 1998. Ontogeny affects response of northern red oak
seedlings to elevated CO2 and water stress - I. Carbon assimilation and biomass production. New
Phytologist 140(3):477-491.

The interactive influences of elevated carbon dioxide, water stress, and ontogeny on carbon
assimilation and biomass production were investigated in northern red oak, a species having episodic
shoot growth characteristics. Seedlings were grown from acorns through three shoot-growth hushes
(8-11 wk) in controlled-environment chambers at 400, 530 or 700 mu mol mol(-1) CO2 and under
well watered or water-stressed soil- moisture regimes. Increasing CO2 growth concentration from
400 to 700 mu mol mol(-1) resulted in a 34 % increase in net assimilation rate (A), a 31 % decrease
in stomatal conductance to water vapour (g(s)) and a 141 % increase in water use efficiency (WUE)
in well watered seedlings. In contrast, water- stressed seedlings grown at 700 mu mol mol(-1) CO2
demonstrated a 69 % increase in A, a 23 % decrease in g(s), and a 104 % increase in WUE.
However, physiological responses to increased CO2 and water stress were strongly modified by
ontogeny. During active third-flush shoot growth, A in first-flush and second- flush foliage of water-
stressed seedlings increased relative to the quiescent phase following cessation of second-flush
growth by an average of 115 %; g(s) increased by an average of 74 %. In contrast, neither A nor gs
in comparable foliage of well watered seedlings changed in response to active third-flush growth.
Whereas seedling growth was continuous through three flushes in well watered seedlings, growth of
water-stressed seedlings was minimal following the leaf-expansion stage of the third flush. Through
three growth flushes total seedling biomass and biomass allocation to root, shoot and foliage
components were very similar in water-stressed seedlings grown at 700 mu mol mol(-1) CO2 and
well watered seedlings grown at 400 mu mol mol(-1) CO2. Enhancement effects of elevated CO2 on
seedling carbon (C) assimilation and biomass production may offset the negative impact of moderate
water stress and are likely to be determined by ontogeny and stress impacts on carbon sink demand.

KEYWORDS: ATMOSPHERIC CO2, DIOXIDE ENRICHMENT, DROUGHT, GAS-EXCHANGE,
GROWTH-RESPONSE, LEAVES, PHOTOSYSTEM, QUERCUS-RUBRA L, RISING CO2, USE
EFFICIENCY


     51   
Andersson, N.E. 1991. The influence of constant and diurnally changing CO2 concentrations on
plant-growth and development. Journal of Horticultural Science 66(5):569-574.

Plants of Ficus benjamina and miniature rose (Rosa hybrida cv. Red Minimo) were grown under four
CO2 treatments. Two had constant CO2 levels (600 and 900 ppm) and the other two had diurnal
changes in CO2 levels, one increasing from 600 to 1500 ppm and one decreasing from 1500 to 600
ppm, each in four steps of 300 ppm during the day-time. In all treatments 900 ppm CO2 was
maintained during the night when supplementary light was used, except in the treatment with constant
600 ppm where 600 ppm was also continued throughout the night. Plant growth was monitored under
both decreasing and increasing natural daylength and irradiance. The tallest plants and greatest
increment in height for Ficus occurred with plants grown under constant CO2 concentration at 600
ppm and also with increasing CO2 concentration. In both experiments the dry weight per pot was
lowest when plants were grown under a constant CO2 concentration at 900 ppm. In both experiments
with miniature roses the number of flower buds was significantly increased under diurnally changing
CO2 concentration or when the CO2 level was constant at 600 ppm compared with a constant 900
ppm. Time to flowering was decreased by constant CO2 at 900 ppm as compared with the other
treatments.

KEYWORDS: ATMOSPHERES, CARBON-DIOXIDE ENRICHMENT, DURATION, EXCHANGE,
LIGHT-INTENSITY, ROSE, YIELD


     52   
Andrade, J.L., and P.S. Nobel. 1996. Habitat, CO2 uptake and growth for the CAM epiphytic
cactus Epiphyllum phyllanthus in a Panamanian tropical forest. Journal of Tropical Ecology 12:291-
306.

In the tropical forest of Barro Colorado Island, habitat characteristics, diel acidity changes, CO2
uptake and growth were investigated for the epiphytic cactus Epiphyllum phyllanthus (L.) Haw. It
occurred most frequently in tree cavities with its roots in canopy soil and was especially abundant on
two tree species: Platypodium elegans J. Vogel and Tabebuia guayacan (Seem.) Hemsl. Its maximum
net CO2 uptake rates were low under natural conditions (1.4 mu mol m(-2) s(- 1)) but were
comparable to those of other CAM and C-3 epiphytes under wet conditions in a screenhouse. Under
both natural conditions and in the screenhouse, partial shade enhanced growth and CAM activity.
When plants grew under a photosynthetic photon flux of c. 4 mol m(-2) d(-1), their nocturnal acidity
increase and total net CO2 uptake were twice as much as for plants growing at lower (an average of
2.4 mol m(-2) d(-1)) and higher (7.7 mol m(-2) d(-1)) photosynthetic photon fluxes. Stem elongation
was 27% greater at the intermediate photosynthetic photon flux. Seedlings of E. phyllanthus survived
three months of drought and responded rapidly to rewetting, recovering fully within three days.
Transpiration rates and nocturnal acidity increases also recovered to the values of well-watered plants
a few days after rewetting, indicating that this species can take advantage of episodic rainfall during
the dry season.

KEYWORDS: ACCUMULATION, C-3 BROMELIADS, COMPARATIVE ECOPHYSIOLOGY,
CRASSULACEAN ACID METABOLISM, LEAF, OPUNTIA FICUS INDICA, SHADE, VASCULAR
EPIPHYTES


     53   
Andre, M., and H. Ducloux. 1993. Interaction of co2 enrichment and water limitations on
photosynthesis and water efficiency in wheat. Plant Physiology and Biochemistry 31(1):103-112.

Wheat plants (Triticum aestivum L. cv. Capitole) were grown in twin closed growth chambers with
continuous monitoring of CO2 and water exchanges. During the vegetative stage the effect Of CO2
enrichment, from 330 to 660 mul-1, was studied under irradiance of 660 muE m-2 s-1 with an
optimum watering. Comparisons were made with successive experiments in which daily water supply
was fixed to a fraction (0.62-0.50-0.25) of the maximal transpiration of previous experiments. In a
well- watered canopy, doubling CO2 decreased transpiration by only 8%. Water use efficiency was
increased (factor 1.45) mainly by the stimulation of photosynthesis. Under restricted water supply,
photosynthesis of plants was more limited than transpiration. The inhibition of photosynthesis and the
increase of water use efficiency can be predicted by a simple diffusion model applied to the response
curve of photosynthesis to CO2, measured on canopy in standard conditions of watering. The main
hypothesis is that the equivalent stomatal conductance is reduced proportionally to the water
availability, without closure by patching. Under enriched CO2, the same reduction of leaf surface by
water limitation was observed. Photosynthesis was less affected. Therefore, water-use-efficiency was
again increased. Doubling CO2 concentration can compensate for water stress inhibition on CO2
assimilation. That model also predicts interactions of CO2 and water stress observed on water-use-
efficiency which was increased by a factor up to 5 in comparison with well-watered plants in standard
atmosphere. The implications of this study for global change models are discussed.

KEYWORDS: ASSIMILATION, CARBON-DIOXIDE ENRICHMENT, CONDUCTANCE,
EXCHANGES, GROWTH, PHASEOLUS-VULGARIS L, PLANTS, SEEDLINGS, STRESS, YIELD


     54   
Andrews, J.A., K.G. Harrison, R. Matamala, and W.H. Schlesinger. 1999. Separation of root
respiration from total soil respiration using carbon-13 labeling during Free-Air Carbon Dioxide
Enrichment (FACE). Soil Science Society of America Journal 63(5):1429-1435.

Soil respiration constitutes a major component of the global carbon cycle and is likely to be altered
by climatic change. However, there is an incomplete understanding of the extent to which various
processes contribute to total soil respiration, especially the contributions of root and rhizosphere
respiration. Here, using a stable carbon isotope tracer, we separate thf relative contributions of root
and soil heterotrophic respiration to total soil respiration in situ. The Free-Air Carbon dioxide
Enrichment (FACE) facility in the Duke University Forest (NC) fumigates plots of an undisturbed
loblolly pine (Pinus taeda L.) forest with CO2 that is strongly depleted in C-13. This labeled CO2 is
found in the soil pore space through live root and mycorrhizal respiration and soil heterotroph
respiration of labile root exudates. By measuring the depletion of (CO2)-C-13 in the soil system, we
found that the rhizosphere contribution to soil CO2 reflected the distribution of fine roots in the soil
and that late in the growing season roots contributed 55% of total soil respiration at the surface, This
estimate may represent an upper limit on the contribution of roots to soil respiration because high
atmospheric CO2 often increases in root density and/or root activity in the soil.

KEYWORDS: CO2, DECIDUOUS FOREST, FATE, FLUXES, LITTER, ORGANIC-MATTER,
PONDEROSA PINE, RHIZOSPHERE, SEEDLINGS


     55   
Andrews, T.J., G.S. Hudson, C.J. Mate, S. Voncaemmerer, J.R. Evans, and Y.B.C. Arvidsson.
1995. Rubisco - the consequences of altering its expression and activation in transgenic plants.
Journal of Experimental Botany 46:1293-1300.

Transgenic tobacco (Nicotiana tabacum W38) hemizygous for a single antisense gene directed against
Rubisco's small subunit had 35% of the Rubisco content of control leaves (15% when homozygous).
CO2 assimilation (at 1000 mu mol quanta m(-2) s(- 1) and 350 mu bar CO2) by the hemizygous
leaves was reduced to 40% of that of the controls without material effect on stomatal conductance,
chlorophyll content or other photosynthetic components. Leaf soluble protein was reduced
commensurately with the reduction in Rubisco. CO2 assimilation rate in the hemizygous leaves
remained limited by Rubisco activity at all, even very high, CO2 concentrations. This led to a simple,
hyperbolic response of photosynthesis to intraplastid CO2 concentration from which the in vivo
catalytic properties of Rubisco were inferred and compared with those of isolated Rubisco in vitro.
Using a similar approach, the content of Rubisco activase was suppressed by incorporating a partial
cDNA for activase into the tobacco genome in the antisense orientation with respect to a cauliflower
mosaic virus 35S promoter. The progeny of a primary transformant with two anti- activase inserts
had from <1% to 20% of the activase content of control plants. Quite severe suppression of activase,
to less than 5% of the amount present in control leaves, was required before effects on photosynthesis
and growth became apparent, indicating that one activase tetramer must be able to service,
continuously, as many as 200 Rubisco octamers. Plants with lower activase contents could not grow
unless the atmosphere was enriched with CO2. Their Rubisco was less carbamylated and they had
lower CO2 assimilation rates than the controls. The rate of release of 2'-carboxyarabinitol-1-
phosphate from Rubisco after illumination of the anti-activase leaves was also impaired. Older anti-
activase plants accumulated increasing amounts of Rubisco in their younger leaves, but were unable
to carbamylate it. The photosynthetic rate per carbamylated Rubisco active site in the strongly
suppressed anti-activase leaves was only approximately 25% of that seen in control leaves, suggesting
that activase may not only promote carbamylation of uncarbamylated Rubisco sites, but also
accelerate turnover at carbamylated sites.

KEYWORDS: 2-CARBOXYARABINITOL 1-PHOSPHATE, ACTIVITY INVIVO, ANTISENSE GENE,
CATALYSIS, GROWTH, PHOTOSYNTHESIS, RIBULOSE BISPHOSPHATE CARBOXYLASE,
RIBULOSE-1;5-BISPHOSPHATE CARBOXYLASE-OXYGENASE, SLOW INACTIVATION,
TOBACCO NICOTIANA-TABACUM


     56   
Andriolo, J.L., J. LeBot, C. Gary, G. Sappe, P. Orlando, B. Brunel, and C. Sarrouy. 1996. An
experimental set-up to study carbon, water and nitrate uptake rates by hydroponically grown plants.
Journal of Plant Nutrition 19(10-11):1441-1462.

The experimental system described allows concomitant hourly measurements of CO2, H2O, and NO3
uptake rates by plants grown hydroponically in a greenhouse. Plants are enclosed in an airtight
chamber through which air flows at a controlled speed. Carbon dioxide exchange and transpiration
rates are determined from respective differences of concentrations of CO2 and water vapor of the air
at the system inlet and outlet. This set-up is based on the ''open-system'' principle with improvements
made on existing systems. For instance, propeller anemometers are used to monitor air flow rates in
the chamber. From their signal it is possible to continuously adjust air speed to changing
environmental conditions and plant activity. The air temperature inside the system therefore never
rises above that outside. Water and NO3 uptake rates are calculated at time intervals from changes
in the volume and the NO3 concentration of the nutrient solution in contact with the roots. The
precise measurement of the volume of solution is achieved using a balance which has a higher
precision than any liquid level sensors. Nitrate concentration is determined in the laboratory from
aliquots of solution sampled at time intervals. A number of test runs are reported which validate the
measurements and confirm undisturbed conditions within the system. Results of typical diurnal
changes in CO2, H2O, and NO3 uptake rates by fruiting tomato plants are also presented.

KEYWORDS: CROP, DIOXIDE, ELEVATED CO2, GAS-EXCHANGE, LIFE-CYCLE, OPEN-TOP
CHAMBERS, PHOTOSYNTHESIS, SYSTEM, TOMATO, TRANSPIRATION


     57   
Angell, R., and T. Svejcar. 1999. A chamber design for measuring net CO2 exchange on rangeland.
Journal of Range Management 52(1):27-31.

Net carbon exchange of terrestrial ecosystems will likely change as atmospheric CO2 concentration
increases, Currently, little is known of the annual dynamics or magnitude of CO2 flux on many native
and agricultural ecosystems. Remoteness of many ecosystems has limited our ability to measure CO2
flux on undisturbed vegetation. Today, many plant ecologists have portable photosynthesis systems
with which they make single- leaf photosynthesis measurements. Utility of this equipment is enhanced
when canopy-level CO2 flux is also measured. We designed a portable 1-m(3) closed chamber for
use in measuring CO2 exchange in short statured vegetation with widely varied canopy structure. The
design includes external ductwork equipped with doors which are used to open the chamber for
ventilation with outside air between measurements. The chamber was tested on a Wyoming big
sagebrush (Artemisia tridentata ssp. Wyomingensis Nutt.)/Thurber's needlegrass (Stipa thurberiana
Piper) community using 10 plots equally divided between shrub and interspace, The ductwork and
doors provided adequate ventilation to allow consecutive measurements of CO2 nux without
removing the chamber from the plot. The chamber could differentiate CO2 flux between plots with
sagebrush and those with grass only, even at relatively low fluxes, Net CO2 uptake per unit ground
area was greater (P = 0.04) on sagebrush-grass plots (7.6 +/- 1.4 mu mol m(-2) s(-1)) than on
interspace plots without sagebrush (3.1 +/- 1.0 pmol m(-2) s(- 1)). Chamber and leaf temperature
increased by an average of 0.5 and 1.2 degrees C, respectively, during measurements.

KEYWORDS: CARBON-CYCLE, FLUXES, SYSTEM, TUNDRA ECOSYSTEMS


     58   
Apel, P., and M. Peisker. 1995. Variability of photosynthetic gas exchange parameters, dark
respiration, and stomatal numbers in species of Polygonum. Physiologia Plantarum 95(3):365-372.

Within the genus Polygonum a large variation was found between species with regard to stomatal
number, gas phase resistance, intracellular resistance and dark respiration. Interspecific variation in
CO2 compensation concentration and intercellular CO2 concentration at constant external
concentration were comparatively small. Correlations were found between stomatal number and gas
phase resistance, stomatal number and Gamma, and Gamma and the product of dark respiration rate
and intracellular resistance. The influence of dark respiration and stomatal number on photosynthetic
gas exchange is discussed. It was concluded that dark respiration in light was enhanced by 22% as
a mean value in 9 Polygonum species and by 62% in Polygonum lapathifolium.

KEYWORDS: CONDUCTANCE, LEAVES, PLANTS


     59   
Apple, M.E., M.S. Lucash, D.M. Olszyk, and D.T. Tingey. 1998. Morphogenesis of Douglas-fir
buds is altered at elevated temperature but not at elevated CO2. Environmental and Experimental
Botany 40(2):159-172.

Global climatic change as expressed by increased CO2 and temperature has the potential for dramatic
effects on trees. To determine what its effects may be on Pacific Northwest forests, Douglas-fir
(Pseudotsuga menziesii) seedlings were grown in sun-lit controlled environment chambers at ambient
or elevated (+ 4 degrees C above ambient) temperature, and at ambient or elevated (+ 200 ppm above
ambient) CO2. In 1995-1996 and 1996- 1997, elevated CO2 had no effect on vegetative bud
morphology, while the following unusual morphological characteristics were found with greater
frequency at elevated temperature than at ambient: rosetted buds with reflexed and loosened outer
scales, convoluted inner scales, clusters of small buds, needles elongating between scales, needle
primordia with white, hyaline apical extensions, and buds with hardened scales inside of unbroken
buds. Buds became rosetted in elevated temperature chambers after temperatures exceeded 40
degrees C in July, 1996. Rosettes were induced within 48-h in buds placed in a 40 degrees C oven;
fewer rosettes formed at 20 degrees C. Induction was reversible in buds transferred from 40 to 20
degrees C, implying that resetting is a physical rather than a growth phenomenon. It appears that
rosettes form after long- term exposure to elevated temperature and after shorter periods of exposure
to intense heat. Elevated temperature influences bud morphology and may therefore influence the
overall branching structure of Douglas-fir seedlings. (C) 1998 Elsevier Science B.V. All rights
reserved.

KEYWORDS: ACCUMULATION, BUDBURST, CHILLING REQUIREMENT, DORMANCY,
FROST DAMAGE, HEAT-SHOCK PROTEINS, INTERIOR, POPULATIONS, SEEDLINGS,
SHOOT


     60   
Arakelyan, V.V., G.B. Ibragimova, and Y.S. Nasyrov. 1993. Effects of light, co2, and temperature
on carbonic-anhydrase activity in C3-plants. Russian Journal of Plant Physiology 40(6):759-767.

Carbonic anhydrase activity was studied in cotton (Gossypium hirsutum L.) and Triticale plants
exposed to various light intensities, temperatures, and CO2 concentrations in the air. The activity was
measured using an original method based on the HCO3- dehydration reaction, which is carried out
in conditions resembling those occurring in the chloroplast stroma in vivo. Carbonic anhydrase
activity in stromal fractions from cotton and triticale plant chloroplasts appears to respond to
environmental changes. Plant exposure to increased light intensities and temperatures results in
increased activity, whereas high ambient CO2 concentrations lower carbonic anhydrase activity. After
examining in vitro the HCO3- dehydration reaction, which in vivo is catalyzed by carbonic anhydrase,
we concluded that the physiological role of the stromal enzyme consists of preventing local CO2
depletion in the carboxylation sites. Thus, high temperatures and low ambient CO2 concentrations
enhance carbonic anhydrase activity, while impeding CO2 transport from the air to the carboxylation
sites in the leaf. This accelerates HCO3- dehydration and reduces its concentration in the stroma,
thereby producing an additional driving force for HCO3- transport to the chloroplast.



     61   
Archer, S., D.S. Schimel, and E.A. Holland. 1995. Mechanisms of shrubland expansion - land-use,
climate or co-2. Climatic Change 29(1):91-99.

Encroachment of trees and shrubs into grasslands and the 'thicketization' of savannas has occurred
worldwide over the past century. These changes in vegetation structure are potentially relevant to
climatic change as they may be indicative of historical shifts in climate and as they may influence
biophysical aspects of land surface-atmosphere interactions and alter carbon and nitro en cycles.
Traditional explanations offered to account for the historic displacement of grasses by woody plants
in many arid and semi-arid ecosystems have centered around changes in climatic, livestock grazing
and fire regimes. More recently, it has been suggested that the increase in atmospheric CO2 since the
industrial revolution has been the driving force. In this paper we evaluate the CO2 enrichment
hypotheses and argue that historic, positive correlations between woody plant expansion and
atmospheric CO2 are not cause and effect.

KEYWORDS: AMERICAN SOUTHWEST, ATMOSPHERIC CO2, CARBON DIOXIDE,
DESERTIFICATION, ECOSYSTEMS, ELEVATED CO2, GROWTH, INCREASING CO2,
NATURAL VEGETATION, PAST 2 CENTURIES


     62   
Arienzo, M., G. Basile, R. Dandria, V. Magliulo, and A. Zena. 1995. Irrigation with carbonated
water and nutrient availability - tests on strawberry plants. Agrochimica 39(1):61-72.

A research was carried out to study the nutrient availability and yield performances of a strawberry
crop cv. 'Chandler' in response to equivalent depths (100% of ETM) of CO2 enriched water and plain
water applied with different irrigation frequencies. Plots were arranged in a complete randomized
block design replicated four times, using mulch and a drip irrigation system adopting 4 1/h emitters.
The crop was covered by a plastic tunnel following treatment differentiation. The statistical analysis
revealed an increased availability of Cu, Zn, Ca, Mg, and Mn for the CO2 treatment, probably linked
with the pH reduction (from 7,5 to 6,5). The increased nutrient uptake in the CO2 enriched water
treatment may be the cause of the commercial yield enhancement (8,6 %) and reduction in the weight
of deformed berries (-12,1 %).

KEYWORDS: DIOXIDE


     63   
Arisi, A.C.M., G. Cornic, L. Jouanin, and C.H. Foyer. 1998. Overexpression of iron superoxide
dismutase in transformed poplar modifies the regulation of photosynthesis at low CO2 partial
pressures or following exposure to the prooxidant herbicide methyl viologen. Plant Physiology
117(2):565-574.

Chloroplast-targeted overexpression of an Fe superoxide dismutase (SOD) from Arabidopsis thaliana
resulted in substantially increased foliar SOD activities. Ascorbate peroxidase, glutathione reductase,
and monodehydroascorbate reductase activities were similar in the leaves from all of the lines, but
dehydroascorbate reductase activity was increased in the leaves of the FeSOD transformants relative
to untransformed controls. Foliar H2O2, ascorbate, and glutathione contents were comparable in all
lines of plants. Irradiance-dependent changes in net CO, assimilation and chlorophyll a fluorescence
quenching parameters were similar in all lines both in air (21% O-2) and at low (1%) O-2. CO2-
response curves for photosynthesis showed similar net CO2-exchange characteristics in all lines. In
contrast, values of photochemical quenching declined in leaves from untransformed controls at
intercellular CO2 (Ci) values below 200 mu L L-1 but remained constant with decreasing Ci in leaves
of FeSOD transformants. When the O-2 concentration was decreased from 21 to 1%, the effect of
FeSOD overexpression on photochemical quenching at limiting Ci was abolished. At high light (1000
mu mol m(-2) s(-1)) a progressive decrease in the ratio of variable (F-v) to maximal (F-m)
fluorescence was observed with decreasing temperature. At 6 degrees C the high-light-induced
decrease in the F-v/F-m ratio was partially prevented by low O-2 but values were comparable in all
lines. Methyl viologen caused decreased F- v/F-m ratios, but this was less marked in the FeSOD
transformants than in the untransformed controls. These observations suggest that the rate of
superoxide dismutation limits flux through the Mehler-peroxidase cycle in certain conditions.

KEYWORDS: ASCORBATE PEROXIDASE, CHLOROPHYLL FLUORESCENCE, ELEVATED
LEVELS, HYDROGEN- PEROXIDE, OXIDATIVE STRESS TOLERANCE, PHOTOINHIBITION,
QUANTUM YIELD, SPINACH-CHLOROPLASTS, TEMPERATURE, TRANSGENIC PLANTS


     64   
Arnone, J.A. 1997. Indices of plant N availability in an alpine grassland under elevated atmospheric
CO2. Plant and Soil 190(1):61-66.

The objective of this study was to estimate whether elevated atmospheric [CO2] alters plant N
availability in a native high- elevation grassland in the Swiss Alps using two integrative, relatively
non-disruptive methods. Estimates based on seasonal net plant N uptake, and those based on the
amounts of NH4+-N plus NO3--N captured by ion exchange resin (IER) bags, did not differ in plots
treated with ambient (355 mu L L-1) and elevated (680 mu L L-1) [CO2] in either the second (1993)
or third (1994) growing season under treatment with elevated [CO2]. The results of this study
suggest that the effects of rising atmospheric [CO2] on plant N availability may be negligible in this
grassland. The results also contrast the relatively large effects of elevated atmospheric [CO2]
(increases and decreases) reported for highly disturbed artificial systems.

KEYWORDS: CARBON DIOXIDE, COMMUNITIES, EXCHANGE, FEEDBACK, GROWTH
FORMS, NITROGEN-AVAILABILITY, NUTRIENT AVAILABILITY, RESPONSES, SOIL-
NITROGEN, TUNDRA


     65   
Arnone, J.A. 1997. Temporal responses of community fine root populations to long- term elevated
atmospheric CO2 and soil nutrient patches in model tropical ecosystems. Acta Oecologica-
International Journal of Ecology 18(3):367-376.

Biomass and length density of fine roots, as well as overall allocation of dry matter to root growth,
of C-3 plants has been shown to increase under elevated CO2. However, it is uncertain whether the
stimulatory effect of elevated CO2 on fine root population size in plant communities will persist, or
whether fine root populations at high CO2 simply reach their maximum sooner (or possibly later) than
those produced under ambient CO2. It is also unclear whether increased nutrient demand at the stand-
level under elevated CO2 will lead to more intense nutrient foraging via enhanced fine root
proliferation into relatively nutrient-rich soil microsites. I addressed these questions in a 530 day
experiment with model tropical plant communities established in four equivalent ecosystem (17 m(3))
in which plants shared a common low fertility soil. Fine root (less than or equal to 2 mm empty set)
populations (biomass and length density) in ecosystems maintained at elevated CO2 (610 mu l l(-1))
increased more rapidly than those in ecosystems maintained at ambient CO2 (340 mu l l(-1)) during
the first half of the experiment and also remained greater over the entire experiment. The data also
indicate that: (1) fine root populations at both CO2 levels eventually stabilize, (2) stabilization occurs
sooner under elevated CO2 (occupation of the soil volume), and (3) steady-state populations under
elevated CO2 may be slightly larger than those maintained under ambient CO2. Fine root proliferation
into artifically nutrient- enriched microsites was dramatic in all ecosystems (22% to 75% greater than
into non-enriched soil). However, proliferation into enriched microsites was not enhanced by elevated
CO2. Thus, elevated CO2 may not enhance exploitation of nutrient- rich microsites even in low
fertility soils, suggesting that increased plant nutrient capture under elevated CO2 also may be
unlikely.

KEYWORDS: AMAZONIAN FORESTS, BIOMASS, CARBON DIOXIDE, ENRICHMENT,
GROWTH, MICROSITES, PLANT- COMMUNITIES, PROLIFERATION, RAIN-FOREST, UPTAKE
KINETICS


     66   
Arnone, J.A. 1999. Symbiotic N-2 fixation in a high Alpine grassland: effects of four growing
seasons of elevated CO2. Functional Ecology 13(3):383-387.

1. Increasing carbon dioxide concentration (E: 680 mu l CO2 litre(-1) vs ambient, A: 355 mu l CO2
litre(-1)) around late- successional Alpine sedge communities of the Swiss Central Alps (2450 m) for
four growing seasons (1992-1995) had no detectable effect on symbiotic N-2 fixation in Trifolium
alpinum-the sole N-2-fixing plant species in these communities (74 +/- 30 mg N m(-2) year(-1), A
and E plots pooled). 2. This result is based on data collected in the fourth growing season showing
that elevated CO2 had no effect on Trifolium above-ground biomass (4.4 +/- 1.7 g m(-2), A and E
plots pooled, n = 24) or N content per unit land area (124 +/- 51 mg N m(-2), A and E pooled), or
on the percentage of N Trifolium derived from the atmosphere through symbiotic N-2 fixation
(%Ndfa: 61.0 +/- 4.1 across A and E plots) estimated using the N-15 dilution method. 3. Thus, it
appears that N inputs to this ecosystem via symbiotic N-2 fixation will not be dramatically affected
in the foreseeable future even as atmospheric CO2 continues to rise.

KEYWORDS: ATMOSPHERIC CO2, ECOSYSTEM, ENRICHMENT, GAS-EXCHANGE,
NITROGENASE ACTIVITY, NODULATION, REDUCTION, RESPONSES, TRIFOLIUM-REPENS
L, TUNDRA


     67   
Arnone, J.A., and P.J. Bohlen. 1998. Stimulated N2O flux from intact grassland monoliths after
two growing seasons under elevated atmospheric CO2. Oecologia 116(3):331-335.

Long-term exposure of native vegetation to elevated atmospheric CO2 concentrations is expected
to increase C inputs to the soil and, in ecosystems with seasonally dry periods, to increase soil
moisture. We tested the hypothesis that these indirect effects of elevated CO2 (600 mu l l(-1) vs 350
mu l l(-1)) would improve conditions for microbial activity and stimulate emissions of nitrous oxide
(N2O), a very potent and long-lived greenhouse gas. After two growing seasons, the mean N2O
efflux from monoliths of calcareous grassland maintained at elevated CO2 was twice as high as that
measured from monoliths maintained at current ambient CO2 (70 +/- 9 vs 37 +/- 4 mu g N2O m(-2)
h(-1) in October, 27 +/- 5 vs 13 +/- 3 mu g N2O m(-2) h(-1) in November after aboveground
harvest). The higher N2O emission rates at elevated CO2 were associated with increases in soil
moisture, soil heterotrophic respiration, and plant biomass production, but appear to be mainly
attributable to higher soil moisture. Our results suggest that rising atmospheric CO2 may contribute
more to the total greenhouse effect than is currently estimated because of its plant- mediated effects
on soil processes which may ultimately lead to increased N2O emissions from native grasslands.

KEYWORDS: CALCAREOUS GRASSLAND, CARBON-DIOXIDE ENRICHMENT,
DENITRIFICATION, ECOSYSTEMS, INCREASE, METHANE, NITROUS-OXIDE PRODUCTION,
SHORTGRASS STEPPE, SOIL-NITROGEN, STOMATAL RESPONSES


     68   
Arnone, J.A., and J.C. Gordon. 1990. Effect of nodulation, nitrogen-fixation and CO2 enrichment
on the physiology, growth and dry mass allocation of seedlings of alnus-rubra bong. New Phytologist
116(1):55-66.



     69   
Arnone, J.A., and G. Hirschel. 1997. Does fertilizer application alter the effects of elevated CO2
on Carex leaf litter quality and in situ decomposition in an alpine grassland? Acta Oecologica-
International Journal of Ecology 18(3):201-206.

The purpose of our investigation was to determine: (1) whether fertilization with NPK would result
in an improvement in leaf litter quality of the dominant species (Carer curvula) in a high alpine
grassland in Switzerland; and especially (2) if fertilization improves the quality of leaf litter produced
under elevated atmospheric CO2 and compensates for the suppressive effects of high CO2 on the in
situ decomposition rates of C. curvula litter, observed at this site in an earlier study. Fertilizer
application (40 k(g) N ha(-1) yr(-1)) resulted in 34% higher leaf litter [N] but did not change C:N or
lignin N ratios, when viewed across both CO2 treatments. Improvement in the mean N quality of litter
produced under elevated CO2 resulting from fertilization appeared to lead to a significantly faster
mean decomposition rate (+ 60%), but fertilization had no significant effect on decomposition of litter
produced under ambient CO2. We conclude that the potential stimulatory effect of an increase in
atmospheric N deposition on litter quality and decomposition rates may partially compensate for the
inhibitory effects of rising atmospheric CO2 in these high alpine grassland ecosystems.

KEYWORDS: ECOSYSTEMS, NITROGEN, RESPONSES


     70   
Arnone, J.A., and C. Kestenholz. 1997. Root competition and elevated CO2: Effects on seedling
growth in Linum usitatissimum populations and Linum Silene cretica mixtures. Functional Ecology
11(2):209-214.

1. Root competition can be an important determinant of the performance of neighbours within plant
populations and communities. Because plants often maintain larger root systems and allocate more
of their carbon to root systems under elevated atmospheric CO2 than they do at lower CO2
concentrations, root-root interactions could play an increasingly important role in determining
competitive outcomes among individuals and plant species as global CO2 concentration continues
to rise. 2. We established 12 pure stands of Linum usitatissimum (flax) and 12 mixed stands of Linum
and its naturally co-occurring weed species Silene cretica in opaque plastic trays each filled with the
same amount of nutrient-rich soil mix. In half of the trays from each of these stand types, vertical
waterproof partitions separated the root systems of individual plants from each other to prevent root
competition, while in the other half no partitions were present. Half of the trays from all treatments
were allowed to grow under low atmospheric CO2 concentration (320 mu ll(-1)) and the other half
under elevated CO2 (600 mu ll(-1)), in daylight growth: chambers for 30 days from seedling
emergence until harvest in mid-June. All trays received equal amounts of water so that soils in the low
CO2 treatment were maintained at field capacity. 3. Our results indicate that under high soil fertilities:
(1) intra-specific root-root interactions alone play a relatively insignificant role in determining plant
biomass production within pure Linum populations and (2) the impact of an aggressive species
(Silene) on co-occurring less aggressive species (Linum) becomes more severe under elevated CO2
as a result of amplified interspecific root competition.

KEYWORDS: AMBIENT, ANNUALS, ATMOSPHERIC CO2, C-3, CARBON DIOXIDE,
COMMUNITIES, ECOSYSTEMS, ENRICHMENT, PLANTS, RESPONSES


     71   
Arnone, J.A., and C. Korner. 1993. Influence of elevated co2 on canopy development and red -
far- red ratios in 2-storied stands of ricinus-communis. Oecologia 94(4):510-515.

Vertical structure of plant stands and canopies may change under conditions of elevated CO2 due to
differential responses of overstory and understory plants or plant parts. In the long term, seedling
recruitment, competition, and thus population or community structure may be affected. Aside from
the possible differential direct effects of elevated CO2 on photosynthesis and growth, both the
quantity and quality of the light below the overstory canopy could be indirectly affected by CO2-
induced changes in overstory leaf area index (LAI) and/or changes in overstory leaf quality. In order
to explore such possible interactions, we compared canopy leaf area development, canopy light
extinction and the quality of light beneath overstory leaves of two-storied monospecific stands of
Ricinus communis exposed to ambient (340 mul-1) and elevated (610 mul-1) CO2. Plants in each
stand were grown in a common soil as closed ''artificial ecosystems'' with a ground area of 6.7 m2.
LAI of overstory plants in all ecosystems more than doubled during the experiment but was not
different between CO2 treatments at the end. As a consequence, extinction of photosynthetically
active radiation (PAR) was also not altered. However, under elevated CO2 the red to far-red ratio
(R: FR) measured beneath overstory leaves was 10% lower than in ecosystems treated with ambient
CO2. This reduction was associated with increased thickness of palisade layers of overstory leaves
and appears to be a plausible explanation for the specific enhancement of stem elongation of
understory plants (without a corresponding biomass response) under elevated CO2. Col enrichment
led to increased biomass of overstory plants (mainly stem biomass) but had no effect on understory
biomass. The results of this study raise the possibility of an important indirect effect of elevated CO2
at the stand-level. We suggest that, under elevated CO2, reductions in the R:FR ratio beneath
overstory canopies may affect understory plant development independently of the effects of PAR
extinction.

KEYWORDS: ATMOSPHERIC CO2, CARBON-DIOXIDE ENRICHMENT, CHLOROPHYLL
CONTENT, CLOVER TRIFOLIUM-REPENS, GROWTH, LEAF ANATOMY, LIGHT-QUALITY,
PLANTS, RAIN-FOREST, RESPONSES


     72   
Arnone, J.A., and C. Korner. 1995. Soil and biomass carbon pools in model communities of
tropical plants under elevated co2. Oecologia 104(1):61-71.

The experimental data presented here relate to the question of whether terrestrial ecosystems will
sequester more C in their soils, litter and biomass as atmospheric CO2 concentrations rise. Similar
to our previous study with relatively fertile growth conditions (Korner and Arnone 1992), we
constructed four rather nutrient-limited model communities of moist tropical plant species in
greenhouses (approximately 7 m(2) each). Plant communities were composed of seven species (77
individuals per community) representing major taxonomic groups and various life forms found in the
moist tropics. Two ecosystems were exposed to 340 mu l CO2 l(-1) and two to 610 mu l l(-1) for
530 days of humid tropical growth conditions. In order to permit precise determination of C
deposition in the soil, plant communities were initially established in C-free unwashed quartz sand.
Soils were then amended with known amounts of organic matter (containing C and nutrients).
Mineral nutrients were also supplied over the course of the experiment as timed-release full-balance
fertilizer pellets. Soils represented by far the largest repositories for fixed C in all ecosystems. Almost
5 times more C (ca. 80% of net C fixation) was sequestered in the soil than in the biomass, but this
did not differ between CO2 treatments. In addition, at the whole-ecosystem level we found a
remarkably small and statistically non-significant increase in C sequestration (+4%; the sum of C
accretion in the soil, biomass, litter and necromass). Total community biomass more than quadrupled
during the experiment, but at harvest was, on average, only 8% greater (i.e. 6% per year; n.s.) under
elevated CO2, mainly due to increased root biomass (+15%, P = 0.12). Time courses of leaf area
index of all ecosystems suggested that canopy expansion was approaching steady state by the time
systems were harvested. Net primary productivity (NPP) of all ecosystems - i.e. annual accumulation
of biomass, necromass, and leaf litter (but not plant-derived soil organic matter) - averaged 815 and
910 g m(-2) year(-1) at ambient and elevated CO2, respectively. These NPPs are remarkably similar
to those of many natural moist tropical forested ecosystems. At the same time net productivity of soil
organic matter reached 7000 g dry matter equivalent per m(2) and year (i.e. 3500 g C m(-2) year(-1)).
Very slight yet statistically significant CO2- induced shifts in the abundance of groups of species
occurred by the end of the experiment, with one group of species (Elettaria cardamomum, Ficus
benjamina, F: pumila, Epipremnum pinnatum) gaining slightly, and another group (Ctenanthe
lubbersiana, Heliconia humilis, Cecropia peltata) losing. Our results show that: (1) enormous amounts
of C can be deposited in the ground which are normally not accounted for in estimates of NPP and
net ecosystem productivity; (2) any enhancement of C sequestration under elevated atmospheric CO2
may be substantially smaller than is believed will occur (yet still very important), especially under
growth conditions which permit close to natural NPP; and (3) species dominance in plant
communities is likely to change under elevated CO2, but that changes may occur rather slowly.

KEYWORDS: AMBIENT, ATMOSPHERIC CO2, C-3, COMPETITION, DIOXIDE, ENRICHMENT,
ESTUARINE MARSH, GROWTH, NITROGEN, TUSSOCK TUNDRA


     73   
Arnone, J.A., J.G. Zaller, C. Ziegler, H. Zandt, and C. Korner. 1995. Leaf quality and insect
herbivory in model tropical plant- communities after long-term exposure to elevated atmospheric co2.
Oecologia 104(1):72-78.

Results from laboratory feeding experiments have shown that elevated atmospheric carbon dioxide
can affect interactions between plants and insect herbivores, primarily through changes in leaf
nutritional quality occurring at elevated CO2. Very few data are available on insect herbivory in plant
communities where insects can choose among species and positions in the canopy in which to feed.
Our objectives were to determine the extent to which CO2-induced changes in plant communities and
leaf nutritional quality may affect herbivory at the level of the entire canopy. We introduced
equivalent populations of fourth instar Spodoptera eridania, a lepidopteran generalist, to complex
model ecosystems containing seven species of moist tropical plants maintained under low mineral
nutrient supply. Larvae were allowed to feed freely for 14 days, by which time they had reached the
seventh instar. Prior to larval introductions, plant communities had been continuously exposed to
either 340 mu l CO2 l(-1) or to 610 mu l CO2 l(-1) for 1.5 years. No major shifts in leaf nutritional
quality [concentrations of N, total non-structural carbohydrates (TNC), sugar, and starch; ratios of:
C/N, TNC/N, sugar/N, starch/N; leaf toughness] were observed between CO2 treatments for any of
the species. Furthermore, no correlations were observed between these measures of leaf quality and
leaf biomass consumption. Total leaf area and biomass of all plant communities were similar when
caterpillars were introduced. However, leaf biomass of some species was slightly greater - and for
other species slightly less (e.g. Cecropia peltata) - in communities exposed to elevated CO2. Larvae
showed the strongest preference for C. peltata leaves, the plant species that was least abundant in all
communities, and fed relatively littie on plants species which were more abundant. Thus, our results
indicate that leaf tissue quality, as described by these parameters, is not necessarily affected by
elevated CO2 under relatively low nutrient conditions. Hence, the potential importance of CO2-
induced shifts in leaf nutritional quality, as determinants of herbivory, may be overestimated for many
plant communities growing on nutrient-poor sites if estimates are based on traditional laboratory
feeding studies. Finally, slight shifts in the abundance of leaf tissue of various species occurring under
elevated CO2 will probably not significantly affect herbivory by generalist insects. However,
generalist insect herbivores appear to become more dependent on less-preferred plant species in cases
where elevated CO2 results in reduced availability of leaves of a favoured plant species, and this
greater dependency may eventually affect insect populations adversely.

KEYWORDS: ALLOCATION, CARBON-DIOXIDE ATMOSPHERES, CHLOROPHYLL CONTENT,
ECOSYSTEMS, ENRICHMENT, FOREST, GROWTH, JUNONIA-COENIA, LEPIDOPTERA,
RESPONSES


     74   
Arp, W.J. 1991. Effects of source-sink relations on photosynthetic acclimation to elevated CO2.
Plant, Cell and Environment 14(8):869-875.

While photosynthesis of C3 plants is stimulated by an increase in the atmospheric CO2 concentration,
photosynthetic capacity is often reduced after long-term exposure to elevated CO2. This reduction
appears to be brought about by end product inhibition, resulting from an imbalance in the supply and
demand of carbohydrates. A review of the literature revealed that the reduction of photosynthetic
capacity in elevated CO2 was most pronounced when the increased supply of carbohydrates was
combined with small sink size. The volume of pots in which plants were grown affected the sink size
by restricting root growth. While plants grown in small pots had a reduced photosynthetic capacity,
plants grown in the field showed no reduction or an increase in this capacity. Pot volume also
determined the effect of elevated CO2 on the root/shoot ratio: the root/shoot ratio increased when
root growth was not restricted and decreased in plants grown in small pots. The data presented in this
paper suggest that plants growing in the field will maintain a high photosynthetic capacity as the
atmospheric CO2 level continues to rise.

KEYWORDS: ATMOSPHERIC CO2, CARBOHYDRATE CONTENT, CARBON-DIOXIDE
ENRICHMENT, CO2- ENRICHMENT, COTTON PLANTS, LEAVES, LIQUIDAMBAR-
STYRACIFLUA, LONG-TERM EXPOSURE, PINUS-TAEDA SEEDLINGS, PLANT GROWTH


     75   
Arp, W.J., and B.G. Drake. 1991. Increased photosynthetic capacity of scirpus-olneyi after 4 years
of exposure to elevated co2. Plant, Cell and Environment 14(9):1003-1006.

While a short-term exposure to elevated atmospheric CO2 induces a large increase in photosynthesis
in many plants, long-term growth in elevated CO2 often results in a smaller increase due to reduced
photosynthetic capacity. In this study, it was shown that, for a wild C3 species growing in its natural
environment and exposed to elevated CO2 for four growing seasons, the photosynthetic capacity has
actually increased by 31%. An increase in photosynthetic capacity has been observed in other species
growing in the field, which suggests that photosynthesis of certain field grown plants will continue
to respond to elevated levels of atmospheric CO2.

KEYWORDS: ATMOSPHERIC CO2, C-3, CARBON DIOXIDE, ESTUARINE MARSH, FIELD,
INSITU, LEAVES, PLANTS


     76   
Arp, W.J., B.G. Drake, W.T. Pockman, P.S. Curtis, and D.F. Whigham. 1993. Interactions
between C-3 and C-4 salt-marsh plant-species during 4 years of exposure to elevated atmospheric
co2. Vegetatio 104:133-143.

Elevated atmospheric CO2 is known to stimulate photosynthesis and growth of plants with the C3
pathway but less of plants with the C4 pathway. An increase in the CO2 concentration can therefore
be expected to change the competitive interactions between C3 and C4 species. The effect of long
term exposure to elevated CO2 (ambient CO2 concentration + 340 mumol CO2 mol-1) on a salt
marsh vegetation with both C3 and C4 species was investigated. Elevated CO2 increased the biomass
of the C3 sedge Scirpus olneyi growing in a pure stand, while the biomass of the C4 grass Spartina
patens in a monospecific community was not affected. In the mixed C3/C4 community the C3 sedge
showed a very large relative increase in biomass in elevated CO2 while the biomass of the C4 species
declined. The C4 grass Spartina patens dominated the higher areas of the salt marsh, while the C3
sedge Scirpus olneyi was most abundant at the lower elevations, and the mixed community occupied
intermediate elevations. Scirpus growth may have been restricted by drought and salt stress at the
higher elevations, while Spartina growth at the lower elevations may be affected by the higher
frequency of flooding. Elevated CO2 may affect the species distribution in the salt marsh if it allows
Scirpus to grow at higher elevations where it in turn may affect the growth of Spartina.

KEYWORDS: COMMUNITIES, COMPETITION, ENRICHMENT, FIELD, GRASS, GROWTH,
LIQUIDAMBAR- STYRACIFLUA, PERENNIALS, PINUS-TAEDA SEEDLINGS, STRESS


     77   
Arp, W.J., J.E.M. Van Mierlo, F. Berendse, and W. Snijders. 1998. Interactions between
elevated CO2 concentration, nitrogen and water: effects on growth and water use of six perennial
plant species. Plant, Cell and Environment 21(1):1-11.

Two experiments are described in which plants of six species mere grown for one full season in
greenhouse compartments with 350 or 560 mu mol mol(-1) COL. In the first experiment two levels
of nitrogen supply were applied to study the interaction between CO2 and nitrogen, In the second
experiment two levels of mater supply were added to the experimental set-up to investigate the three-
way interaction between CO2, nitrogen and water, Biomass and biomass distribution were determined
at harvests, while water use and soil moisture were monitored throughout the experiments, In both
experiments a positive effect of CO2 on growth was found at high nitrogen concentrations but not
at low nitrogen concentrations, However, plants used much less water in the presence of low nitrogen
concentrations, Drought stress increased the relative effect of elevated CO2 on growth, Available soil
moisture was used more slowly at high CO2 during drought or at high nitrogen concentrations, while
at low nitrogen concentrations decreased water use resulted in an increase in soil moisture, The
response to the treatments was similar in all the species used, Although potentially faster growing
species appeared to respond better to high CO2 when supplied with a high level of nitrogen,
inherently slow-growing species were more successful at low nitrogen concentrations.

KEYWORDS: ACCLIMATION, C-3, CARBON DIOXIDE, COTTON, DRY-MATTER,
ENRICHMENT, HEATHLAND ECOSYSTEMS, NUTRITION, STRESS, YIELD


     78   
Ashenden, T.W., R. Baxter, and C.R. Rafarel. 1992. An inexpensive system for exposing plants
in the field to elevated concentrations of co2. Plant, Cell and Environment 15(3):365-372.

An inexpensive, potentially mobile field exposure system is described which may be easily constructed
by a small workshop. It may be operated as an open-top with a frustrum or covered with a
polycarbonate 'lid'. The system is cost-effective for CO2 exposure work because the small size allows
provision of CO2-enriched atmospheres over prolonged periods at relatively low cost. A preliminary
assessment of the chambers has been made and concentrations can be maintained at +/- 6% for a
target atmosphere of 680 cm3 m-3 CO2 under normal operating conditions. Other chamber
environmental conditions are reported.

KEYWORDS: AIR-POLLUTION, CHAMBERS


     79   
Asner, G.P., T.R. Seastedt, and A.R. Townsend. 1997. The decoupling of terrestrial carbon and
nitrogen cycles. BioScience 47(4):226-234.

KEYWORDS: ATMOSPHERIC CARBON, BIOMASS, CO2, FOREST ECOSYSTEMS, GLOBAL
CHANGE, GRASSLAND, LAND-USE, LONG-TERM, NUTRIENT LIMITATION, SOILS


     80   
Atkin, O.K., M. Schortemeyer, N. McFarlane, and J.R. Evans. 1999. The response of fast- and
slow-growing Acacia species to elevated atmospheric CO2: an analysis of the underlying components
of relative growth rate. Oecologia 120(4):544-554.

In this study we assessed the impact of elevated CO2 with unlimited water and complete nutrient on
the growth and nitrogen economy of ten woody Acacia species that differ in relative growth rate
(RGR). Specifically. we asked whether fast- and slow-growing species systematically differ in their
response to elevated CO2. Four slow-growing species from semi- arid environments (Acacia aneura,
A. colei, A. coriacea and A. tetragonophylla) and six fast-growing species from mesic environments
(Acacia dealbata, A. implexa, A. mearnsii, A. melanoxylon, A. irrorata and A. saligna) were grown
in glasshouses with either ambient (similar to 350 ppm) or elevated (similar to 700 ppm) atmospheric
CO2. All species reached greater final plant mass with the exception of A. aneura, and RGR,
averaged across all species, increased by 10% over a 12-week period when plants were exposed to
elevated CO2. The stimulation of RGR was evident throughout the 12-week growth period. Elevated
CO2 resulted in less foliage area per unit foliage dry mass, which was mainly the result of an increase
in foliage thickness with a smaller contribution from greater dry matter content per unit fresh mass.
The net assimilation rate (NAR, increase in plant mass per unit foliage area and time) of the plants
grown at elevated CO2 was higher in all species (on average 30% higher than plants in ambient CO2)
and was responsible for the increase in RGR. The higher NAR was associated with a substantial
increase in foliar nitrogen productivity in all ten Acacia species. Plant nitrogen concentration was
unaltered by growth at elevated CO2 for the slow-growing Acacia species, but declined by 10% for
faster- growing species. The rate of nitrogen uptake per unit root mass was higher in seven of the
species when grown under elevated CO2, and leaf area per unit root mass was reduced by elevated
CO2 in seven of the species. The absolute increase in RGR due to growth under elevated CO2 was
greater for fast- than for slow-growing Acacia species.

KEYWORDS: ALPINE, CARBON DIOXIDE, EFFICIENCY, FOREST, GRASSLAND, LEAF-AREA,
NITROGEN ECONOMY, PLANTS, TREES


     81   
Atkinson, C.J., and J.M. Taylor. 1996. Effects of elevated CO2 on stem growth, vessel area and
hydraulic conductivity of oak and cherry seedlings. New Phytologist 133(4):617-626.

Plants of Quercus robur L. and Prunus avium L. x P. pseudocerasus Lind, were grown in either
ambient (350 vpm) or elevated (700 vpm) CO2. The intention was to examine the effects of elevated
CO2 on the morphological and functional development of the stem. The relationships between stem
longitudinal transport capacity and development were explored in several ways: stem hydraulic
function was related to stem cross-sectional area, supplied leaf area and total stem vessel lumen area.
The mean total vessel number and the total vessel lumen area per stem, for both species, was
determined from basal sections of the xylem. In Prunus seedlings grown in different CO2
concentrations there was no significant change in the mean vessel size or number of vessels per stem.
Quercus seedlings grown at elevated CO2 showed a significant increase in both vessel number and
mean vessel size. When total stem vessel area was calculated it had increased twofold for Quercus
plants grown at elevated CO2. Measured stem hydraulic conductivity was shown to increase linearly
with supplied leaf area, except in Quercus seedlings grown at elevated CO2. Stem hydraulic
conductivity for Quercus seedlings grown at elevated CO2 did not change with the increase in
supplied leaf area. This absence of an increase in the stem hydraulic conductivity appeared to relate
to changes in total stem vessel area. Despite total stem vessel area being greater at elevated CO2 than
that at ambient, it similarly did not increase with supplied leaf area. The implications of this change
in the relationship between leaf area and stem hydraulic conductivity are discussed with respect to
the possible effects the change might have on the plant's water balance. The possible causes and
significance of the changes in xylem anatomy are also considered in relation to direct effects caused
by CO2 or indirect effects on changes in cambial maturity and tree growth.

KEYWORDS: ATMOSPHERIC CO2, CAVITATION, DIAMETER, EMBOLISM, TRANSPIRATION,
TREES, WATER-STRESS, WOODY-PLANTS, XYLEM


     82   
Atkinson, C.J., J.M. Taylor, D. Wilkins, and R.T. Besford. 1997. Effects of elevated CO2 on
chloroplast components, gas exchange and growth of oak and cherry. Tree Physiology 17(5):319-
325.

Specific chloroplast proteins, gas exchange and dry matter production in oak (Quercus robur L.)
seedlings and clonal cherry (Prunus avium L. x pseudocerasus Lind.) plants were measured during
19 months of growth in climate-controlled greenhouses at ambient (350 vpm) or elevated (700 vpm)
CO2. In both species, the elevated CO2 treatment increased the PPFD saturated-rate of
photosynthesis and dry matter production. After two months at elevated CO2, Prunus plants showed
significant increases in leaf (55%) and stem (61%) dry mass but not in root dry mass. However, this
initial stimulation was not sustained: treatment differences in net assimilation rate (A) and plant dry
mass were less after 10 months of growth than after 2 months of growth, suggesting acclimation of
A to elevated CO2 in Prunus. In contrast, after 10 months of growth at elevated CO2, leaf dry mass
of Quercus increased (130%) along with shoot (356%) and root (219%) dry mass, and A was also
twice that of plants grown and measured at ambient CO2. The amounts of Rubisco and the thylakoid-
bound protein cytochrome f were higher in Quercus plants grown for 19 months in elevated CO2 than
in control plants, whereas in Prunus there was less Rubisco in plants grown for 19 months in elevated
CO2 than in control plants. Exposure to elevated CO2 for 10 months resulted in increased mean leaf
area in both species and increased abaxial stomatal density in Quercus. There was no change in leaf
epidermal cell size in either species in response to the elevated CO2 treatment. The lack of
acclimation of photosynthesis in oak grown at elevated CO2 is discussed in relation to the production
and allocation of dry matter. We propose that differences in carbohydrate utilization underlie the
differing long-term CO2 responses of the two species.

KEYWORDS: ATMOSPHERIC CO2, BIOCHEMISTRY, CARBON DIOXIDE, LEAF
DEVELOPMENT, PHOTOSYNTHETIC ACCLIMATION, PRODUCTIVITY, PRUNUS-AVIUM,
RESPONSES, TOMATO PLANTS, TREES


     83   
Atkinson, C.J., P.A. Wookey, and T.A. Mansfield. 1991. Atmospheric-pollution and the sensitivity
of stomata on barley leaves to abscisic-acid and carbon-dioxide. New Phytologist 117(4):535-541.

Spring barley (Hordeum vulgare L. cv. Klaxon) plants were exposed to mixtures of SO2 + NO2 (at
concentrations of 24-35 nl l-1 of each gas, depending upon fumigation system), or to charcoal-
filtered, or unfiltered ambient air during the period in which the second, and subsequent, leaves were
emerging. The ability of individual detached leaves to regulate water loss was then examined after
terminating the pollutant treatment. Observations of diurnal changes in stomatal resistance of well-
watered plants, using a viscous flow porometer, failed to indicate any major alterations which could
be attributed to prior exposure to SO2 + NO2. By contrast, when an ABA solution (10(-1) mol m-3)
was applied to detached leaves, the stomata of polluted plants were less responsive than plants
previously exposed to control air. The dynamics of the observed responses strongly implicated
impaired physiology of the guard cells rather than mechanical changes in the epidermis that might,
for example, result from damage to the cuticle. Stomatal closure was considerably slower in polluted
leaves compared with the controls. This decline in responsiveness to ABA was observed using leaves
excised from well-watered plants and in the absence of any externally visible injury. The ability of
stomata to respond to a range of CO2 concentrations from 195- 735-mu-mol mol-1 was also
examined using individual leaves, attached to the plant, in an environmentally controlled cuvette. Here
the stomata of leaves which had been fumigated with SO2 + NO2 behaved in a similar manner to the
non-fumigated leaves, both showing closure in elevated CO2 concentrations.

KEYWORDS: CONDUCTANCE, FUMIGATION, NITROGEN-DIOXIDE, NO2, PLANTS, SO2,
SULFUR-DIOXIDE, SYSTEM, WHEAT LEAVES


     84   
Austin, M.P. 1992. Modeling the environmental niche of plants - implications for plant community
response to elevated CO2 levels. Australian Journal of Botany 40(4-5):615-630.

No simple natural gradients in CO2 concentration exist for testing predictions about changes in plant
communities in response to elevated CO2. However indirect effects of CO2 via temperature increases
can be tested by reference to natural analogues. Physiologists, vegetation modellers of climate change
and community ecologists assume very different temperature responses for plants. Physiologists often
assume a skewed non-monotonic curve with a tail towards low temperatures, forest modellers using
FORET type models, a symmetric curve, and community ecologists a skewed response with a tail
towards high temperatures. These assumptions are reviewed in relation to niche theory, and recent
propositions concerning the continuum concept. Confusion exists between the different approaches
over the shape of response curves to temperature. Distinctions need to be made between responses
due to growth (physiological response), potential fitness (fundamental niche) and observed
performance (realised niche). These types of response should be quantified and related to each other
if process-models are to be tested for predictive success by reference to naturally occurring
communities and temperature gradients. An example of a statistical method for quantifying the
realised environmental niche respone of a species to temperature is provided. It is based on
generalised linear modelling (GLM) of presence/absence data on Eucalyptus fastigata for 8377 sites
in southern New South Wales, Australia. Seven environmental variables or factors are considered:
mean annual temperature, mean annual rainfall, mean monthly solar radiation, topographic position,
rainfall seasonality, lithology, and soil nutrient status. The temperature response is modelled with a
beta-function, log y = a + alpha log (t - a) + delta log (b - t), where t is temperature and letters are
parameters. The probability of occurrence is shown to be a skewed function of mean annual
temperature. Any process-models of climate change for vegetation incorporating temperature changes
due to elevated CO2 must be capable of generating such realised environmental niche responses for
species.

KEYWORDS: DISTRIBUTIONS, ECOSYSTEMS, FIELD, FOREST, GRADIENTS, GROWTH,
NORTH-AMERICA, SIMULATION, SPECIES RESPONSE, VEGETATION


     85   
Awmack, C.S., R. Harrington, and S.R. Leather. 1997. Host plant effects on the performance of
the aphid Aulacorthum solani (Kalt.) (Homoptera : Aphididae) at ambient and elevated CO2. Global
Change Biology 3(6):545-549.

In future elevated CO2 environments, chewing insects are likely to perform less well than at present
because of the effects of increased carbon fixation on their host plants. When the aphid, Aulacorthum
solani was reared on bean (Vicia faba) and tansy (Tanacetum vulgare) plants under ambient and
elevated CO2, performance was enhanced on both hosts at elevated CO2. The nature of the response
was different on each plant species suggesting that feeding strategy may influence an insect's response
to elevated CO2. On bean, the daily rate of production of nymphs was increased by 16% but there
was no difference in development time, whereas on tansy, development time was 10% shorter at
elevated CO2 but the rate of production of nymphs was not affected. The same aphid clone therefore
responded differently to elevated CO2 on different host plants. This increase in aphid performance
could lead to larger populations of aphids in a future elevated CO2 environment.

KEYWORDS: ALLOCATION, ATMOSPHERIC CO2, CARBON-DIOXIDE CONCENTRATION,
ENRICHMENT, INSECT HERBIVORE INTERACTIONS, LEPIDOPTERA, NOCTUIDAE,
PHYTOCHEMISTRY, POPULATIONS, RESPONSES


     86   
Azconbieto, J., M.A. Gonzalezmeler, W. Doherty, and B.G. Drake. 1994. Acclimation of
respiratory o-2 uptake in green tissues of field-grown native species after long-term exposure to
elevated atmospheric co2. Plant Physiology 106(3):1163-1168.

C-3 and C-4 plants were grown in open-top chambers in the field at two CO2 concentrations, normal
ambient (ambient) and normal ambient + 340 mu L L(-1) (elevated). Dark oxygen uptake was
measured in leaves and stems using a liquid-phase Clark-type oxygen electrode. High CO2 treatment
decreased dark oxygen uptake in stems of Scirpus olneyi (C-3) and leaves of Lindera benzoin (C-3)
expressed on either a dry weight or area basis. Respiration of Sparfina patens (C-4) leaves was
unaffected by CO2 treatment. Leaf dry weight per unit area was unchanged by CO2, but respiration
per unit of carbon or per unit of nitrogen was decreased in the C-3 species grown at high CO2. The
component of respiration in stems of S. olneyi and leaves of L. benzoin primarily affected by long-
term exposure to the elevated CO2 treatment was the activity of the cytochrome pathway. Elevated
CO2 had no effect on activity and capacity of the alternative pathway in S. olneyi. The cytochrome
c oxidase activity, assayed in a cell-free extract, was strongly decreased by growth at high CO2 in
stems of S. olneyi but it was unaffected in S. patens leaves. The activity of cytochrome c oxidase and
complex III extracted from mature leaves of L. benzoin was also decreased after one growing season
of plant exposure to elevated CO2 concentration. These results show that in some C-3 species
respiration will be reduced when plants are grown in elevated atmospheric CO2. The possible
physiological causes and implications of these effects are discussed.

KEYWORDS: CARBOHYDRATE STATUS, CARBON-DIOXIDE ENRICHMENT, DARK
RESPIRATION, EFFLUX, INHIBITION, LEAF RESPIRATION, LEAVES, PHOTOSYNTHESIS,
PLANTS, WORLD


     87   
Azevedo, R.A., R.M. Alas, R.J. Smith, and P.J. Lea. 1998. Response of antioxidant enzymes to
transfer from elevated carbon dioxide to air and ozone fumigation, in the leaves and roots of wild-
type and a catalase-deficient mutant of barley. Physiologia Plantarum 104(2):280-292.

A catalase-deficient mutant (RPr 794) and the wild-type (cv. Maris Mink) barley (Hordeum vulgare
L.) counterpart. were grown for 3 weeks in high CO2 (0.7%) and then transferred to air and ozone
(120 nl l(-1)) in the light and shade for a period of 3 days. Leaves and roots were analysed for
catalase (CAT, EC 1.11.1.6), superoxide dismutase (SOD. EC 1.15.1.1) and glutathione reductase
(GR, EC 1.6.4.2) activities. CAT activity in the leaves of the RPr 79/4 catalase-deficient mutant was
around 5 10% of that determined in Maris Mink. but in the roots, both genotypes contained
approximately the same levels of activity. CAT activity in Maris Mink increased in the leaves after
transferring plants from 0.7% CO2 to air or ozone, reaching a maximum of 5-fold. after 4 days in
shade and ozone. For the catalase-deficient mutant. only small increases in CAT activity were
observed in light/air and light/ozone treatments. In the roots. CAT activity decreased consistently in
both genotypes, after plants were transferred from 0.7% CO2. The total soluble SOD activity in the
leaves and roots of both genotypes increased after plants were transferred from 0.7% CO2. The
analysis of SOD isolated from leaves following non- denaturing PAGE, revealed the presence of up
to eight SOD isoenzymes classified as Mn-SOD or Cu/Zn-SODs: Fr-SOD was not detected.
Significant changes in Mn- and Cu/Zn-SOD isoenzymes were observed; however, they could not
account for the increase in total SOD activity. Ill leaves. GR activity also increased in Maris Mink and
RPr 79/4, following transfer from 0.7% CO2: however, no constant pattern could be established,
while in roots, GR activity was reduced after 4 days of the treatments. The data suggest that elevated
CO2 decreases oxidative stress in barley leaves and that soluble CAT and SOD activities increased
rapidly after plants were transferred from elevated CO2. irrespective of the treatment (light, shade,
air or ozone).

KEYWORDS: ARABIDOPSIS-THALIANA, ASCORBATE PEROXIDASE, DIFFERENTIAL
RESPONSE, GLUTAMINE-SYNTHETASE, GLUTATHIONE-REDUCTASE, HORDEUM
VULGARE L, NICOTIANA-PLUMBAGINIFOLIA L, OXIDATIVE STRESS, SUPEROXIDE-
DISMUTASE, TRANSGENIC TOBACCO


     88   
Baattrup-Pedersen, A., and T.V. Madsen. 1999. Interdependence of CO2 and inorganic nitrogen
on crassulacean acid metabolism and efficiency of nitrogen use by Littorella uniflora (L.) Aschers.
Plant, Cell and Environment 22(5):535-542.

The hypothesis is tested that crassulacean acid metabolism (CAM) in isoetids is a mechanism which
not only conserves inorganic carbon but also plays a role in nitrogen economy of the plants, This
hypothesis was tested in an outdoor experiment, where Littorella uniflora (L,) Aschers, were grown
at two CO2 and five inorganic nitrogen concentrations in a crossed factorial design. The growth of
Littorella responded positively to enhanced nitrogen availability at high but not at low CO2 indicating
that growth was limited by nitrogen at high CO2 only. For the nitrogen-limited plants, the capacity
for CAM (CAM(cap)) increased with the degree of nitrogen limitation of growth and an inverse
coupling between CAM and tissue-N was found. Although this might indicate a role of CAM in
economizing on nitrogen in Littorella, the hypothesis was rejected for the following reasons: (1)
although CAM(cap) was related to tissue-N no relationship between tissue-N and ambient CAM
activity (CAM(ambient)) was found whereas a close relationship would be expected if CAM was
regulated by nitrogen availability; (2) the photosynthetic nitrogen use efficiency for high CO2-grown
plants declined with increased CAM(ambient) and with CAM(cap); and (3) growth per unit tissue-N
per unit time declined with increased CAM(ambient) and CAM(cap).

KEYWORDS: ACCLIMATION, ACQUISITION, AQUATIC CAM PLANTS, CARBON
ASSIMILATION, GROWTH, MACROPHYTES, PHOTOSYNTHETIC PERFORMANCE


     89   
Bacanamwo, M., and J.E. Harper. 1997. Response of a hypernodulating soybean mutant to
increased photosynthate supply. Plant Science 124(2):119-129.

Growth chamber studies were conducted to determine if increased photoassimilate supply, through
light enhancement and CO2 enrichment, could reverse the deleterious plant growth and enhance
nodule function traits of NOD1-3, a hypernodulating mutant of Williams. Both light enhancement and
CO2 enrichment increased nodule number, acetylene reduction activity plant(-1) (but not specific
activity) and dry matter accumulation in all tissues in both genotypes. Total biomass and specific
nitrogenase activity were always less in the mutant than in Williams 82, indicating that the inferiority
of the mutant may not be reversed by enhanced photoassimilate supply. Under all growth conditions,
the mutant allocated relatively more photosynthate to nodules and less photosynthate to roots,
compared to the control. Despite this, the decreased growth of the mutant relative to the control was
not solely attributable to excessive nodulation of the mutant, since decreased growth was observed
even on uninoculated plants. It is suggested that light enhancement and CO2 enrichment may have
stimulated nodulation through increased photosynthate supply, independent of the nodulation
autoregulatory signal. (C) 1997 Elsevier Science Ireland Ltd.

KEYWORDS: ACETYLENE-REDUCTION ASSAY, CARBON DIOXIDE, CULTIVAR ENREI, CV
BRAGG, GLYCINE-MAX, NITROGENASE ACTIVITY, NODULATION MUTANTS, ROOT
NODULE ACTIVITY, SUPERNODULATING MUTANT, WILD-TYPE


     90   
Bachelet, D., D. Brown, M. Bohm, and P. Russell. 1992. Climate change in thailand and its
potential impact on rice yield. Climatic Change 21(4):347-366.

In Thailand, the world's largest rice exporter, rice constitutes a major export on which the economy
of the whole country depends. Climate change could affect rice growth and development and thus
jeopardize Thailand's wealth. Current climatic conditions in Thailand are compared to predictions
from four general circulation models (GCMs). Temperature predictions correlate well with the
observed values. Predictions of monthly rainfall correlate poorly. Virtually all models agree that
significant increases in temperature (from 1 to 7-degrees-C) will occur in the region including
Thailand following a doubling in atmospheric carbon dioxide (CO2) concentration. The regional
seasonality and extent of the rise in temperature varies with each model. Predictions of changes in
rainfall vary widely between models. Global warming should in principle allow a northward expansion
of rice-growing areas and a lengthening of the growing season now constrained by low temperatures.
The expected increase in water-use efficiency due to enhanced CO2 might decrease the water deficit
vulnerability of dryland rice areas and could make it possible to slightly expand them.

KEYWORDS: AMBIENT


     91   
Bachelet, D., and C.A. Gay. 1993. The impacts of climate change on rice yield - a comparison of
4 model performances. Ecological Modelling 65(1-2):71-93.

Increasing concentrations of carbon dioxide (CO2) and other greenhouse gases are expected to
modify the climate of the earth in the next 50-100 years. Mechanisms of plant response to these
changes need to be incorporated in models that predict crop yield estimates to obtain an
understanding of the potential consequences of such changes. This is particularly important in Asia
where demographic forecasts indicate that rice supplies worldwide will need to increase by 1.6%
annually to the year 2000 to match population growth estimates. The objectives of this paper are (1)
to review the major hypotheses and/or experimental results regarding rice sensitivity to climate
change and (2) to evaluate the suitability of existing rice models for assessing the impact of global
climate change on rice production. A review of four physiologically-based rice models (RICEMOD,
CERES-Rice, MACROS, RICESYS) illustrates their potential to predict rice responses to elevated
CO2 and increased temperature. RICEMOD does not respond to increases in CO2 nor to large
increases in temperature. Both MACROS and CERES (wetland rice) responses to temperature and
CO2 agree with recent experimental data. RICESYS is an ecosystem model which predicts herbivory
and inter-species competition between rice and weeds but does not respond to CO2. Its response to
increasing temperature also agrees with experimental data.

KEYWORDS: ATMOSPHERIC CO2, CARBON-DIOXIDE CONCENTRATION, CROP PLANTS,
DRY-MATTER PRODUCTION, DYNAMICS, ECOSYSTEMS, PLANT GROWTH, RESPONSES,
SIMULATION-MODEL, TEMPERATURE


     92   
Backhausen, J.E., and R. Scheibe. 1999. Adaptation of tobacco plants to elevated CO2: influence
of leaf age on changes in physiology, redox states and NADP-malate dehydrogenase activity. Journal
of Experimental Botany 50(334):665-675.

Transgenic tobacco plants (Nicotiana tabacum L. cv. Xanthi) with altered chloroplast NADP-malate
dehydrogenase (NADP-MDH) content were grown under ambient or under doubled atmospheric
CO2 in order to analyse the effect of elevated CO2 on the redox state of the chloroplasts. Since large
differences exist between the individual leaves of tobacco plants, gas exchange characteristics,
enzyme capacities and metabolite contents were measured separately for each leaf of the plants, Large
variations between leaves of different age were found in nearly every parameter analysed, and the
differences between younger and older leaves were, in most cases, larger than the differences between
comparable leaves at ambient or elevated CO2. For all parameters (chlorophyll fluorescence, P700
reduction, NADP-MDH activation) that are indicative for the redox situation in the electron transport
chains and in the chloroplast stroma, more oxidized values were determined under elevated CO2. The
increased redox state of ferredoxin, observed at ambient conditions in the NADP-MDH-under-
expressing plants, disappeared under elevated CO2. It was concluded that the reduced rate of
photorespiration under elevated CO2 decreases the amount of excess electrons. Interestingly, this
lowered not only the activation state of NADP-MDH, but also the expression of the enzyme in the
wild-type plants. The results are discussed with respect to a possible interaction between stromal
reduction state and gene expression.

KEYWORDS: ACCLIMATION, CHLOROPHYLL FLUORESCENCE, DEVELOPMENTAL-
CHANGES, EXPRESSION, ISOLATED SPINACH- CHLOROPLASTS, LEAVES,
PHOTOSYNTHETIC ELECTRON-TRANSPORT, QUANTUM YIELD, SATURATING LIGHT,
TRANSCRIPTION FACTOR


     93   
Badger, M. 1992. Manipulating agricultural plants for a future high CO2 environment. Australian
Journal of Botany 40(4-5):421-429.

This paper discusses the potential ways in which C3 plant performance may benefit from a future
high-CO2 environment. These include increases in the efficiencies for light, nitrogen and water
utilisation, particularly at elevated temperatures, resulting from the improvement which will occur in
the performance of the primary carboxylating enzyme, Rubisco. However, while growth experiments
at elevated CO2 indicate that C3 plants show stimulation of dry matter accumulation, the potential
gains are greatly ameliorated by a redistribution of plant resources. This primarily occurs via a
reduction in the leaf area ratio which offsets increases in the net assimilation rate. In addition, there
may be an overcommitment of nitrogen in key photosynthetic components such as Rubisco and the
thylakoid electron transport system. It is concluded that plants may not be genetically adapted to
optimise their growth and performance at elevated CO2 and that consideration should be given to
exploring avenues for manipulating plants for more optimal responses. Targets for improvement of
growth at elevated CO2 include (1) altering source-sink relations; (2) improving the redistribution
of nitrogen between the photosynthetic machinery and the rest of the plant; and (3) changing the
response of stomata to CO2 and humidity to increase water-use efficiency even further than is
currently predicted.

KEYWORDS: ACCLIMATION, C-3, CARBON DIOXIDE, DEPENDENCE, GROWTH,
PHOTOSYNTHESIS, RESPONSES, TEMPERATURE, TRANSPIRATION


     94   
Badiani, M., A. Dannibale, A.R. Paolacci, F. Miglietta, and A. Raschi. 1993. The antioxidant
status of soybean (glycine-max) leaves grown under natural co2 enrichment in the field. Australian
Journal of Plant Physiology 20(3):275-284.

The effects of progressively higher CO2 levels on the foliar antioxidant status were studied by
growing soybean (Glycine max Merrill cv. Cresir) plants at decreasing distances from natural CO2
sources of geothermal origin in central Italy. When compared with neighbouring controls grown
under normal CO2 concentration (C), soybean leaves grown at 2 x C, 7 x C and more than 20 x C
showed a substantial reduction in the size of ascorbate pool and in the activity of Cu,Zn-superoxide
dismutase; both the content of ascorbic acid and the activity of ascorbate peroxidase declined at 2 x
C and 7 x C and recovered to the control values at 20 x C. The foliar titre of glutathione disulfide and
the activities of glutathione disulfide reductase and Mn-superoxide dismutase progressively increased
as CO2 concentration increased in ambient air. The results obtained suggest that the immanent risk
of dioxygen toxicity associated with photosynthetic electron flow could be reduced in the presence
of high CO2 levels. On the other hand, depending on both the CO2 exposure regimes and the cell
compartment considered, high CO2 could promote oxidative processes which cause GSH oxidation
and require an enhanced cellular ability to scavenge superoxide anion and hydrogen peroxide.

KEYWORDS: ACCUMULATION, EXCESS SULFUR, FLOW, PLANTS, RESPIRATION,
TEMPERATURE


     95   
Badiani, M., A.R. Paolacci, A. Fusari, I. Bettarini, E. Brugnoli, M. Lauteri, F. Miglietta, and
A. Raschi. 1998. Foliar antioxidant status of plants from naturally high-CO2 sites. Physiologia
Plantarum 104(4):765-771.

We compared the foliar antioxidant status of native Agrostis stolonifera L. communities growing at
two distinct CO2-enriched sites of geothermal origin (E) and at a control field location with normal
CO2. Compared to the control, plants from both E- sites showed an increased size of the GSH pool,
essentially due to enhanced GSSG levels, and a consequent decrease in the ratio between reduced and
oxidised glutathione forms. Such differences were maintained and even enhanced in the vegetatively-
propagated progenies of control and E-plants, grown under both greenhouse conditions and normal
CO2 levels. The above results confirmed previous observations on native and crop plants exposed
to elevated CO2 It is therefore suggested that changes in the glutathione redox balance might be of
adaptive significance under conditions of permanent exposure to high CO2.

KEYWORDS: ACTIVE OXYGEN, DETOXIFICATION, DROUGHT STRESS, ELEVATED CO2,
ENZYMES, EXCESS SULFUR, GLUTATHIONE, GLYCINE, LEAVES, PICEA-ABIES


     96   
Bailey, S., J. Rebbeck, and K.V. Loats. 1999. Interactive effects of elevated ozone plus carbon
dioxide on duckweeds exposed in open-top chambers. Ohio Journal of Science 99(2):19-25.

The response of Lemna minor L. and Spirodela polyrhiza (L.) Schleiden to projected future ambient
levels of O-3 and CO2 was studied under field conditions. The two duckweed species were treated
with either charcoal-filtered air (CF), ambient O-3 (lXO(3)), tn ice ambient O-3 (2XO(3)), twice
ambient CO2 plus twice ambient O-3 (2XCO(2)+2XO(3)), or chamberless open-air (OA). Two
experiments were conducted. In Experiment I, L. minor was treated for 15 d with a cumulative O-3
exposure of 14.4 ppm.h. No O-3 effects were observed during Experiment I. Dry weight of individual
fronds and photosynthesis per frond increased in L minor exposed to 2XCO(2)+2XO(3)(-) air. In
Experiment II after 25 d of treatment (cumulative O-3 exposure of 16.2 ppm h), negative effects of
2XO(3) on the photosynthetic and growth rates of L. minor were observed. Dark respiration of L
minor significantly increased in 2XO(3)-air compared with controls, but declined significantly in
2XCO(2)+2XO(3)-air compared to those grown in 2XO(3)-air. Photosynthesis and drg weight per
frond increased in 2XCO(2)+2XO(3)-air when compared with all other treatments. Measurement of
A/C-i (assimilation versus intercellular CO2 concentration) curves in L. minor showed a significant
reduction in carboxylation efficiency and maximum rates of photosynthesis in 2XCO(2)+2XO(3)-air
compared with other treatments when expressed per weight. No differences in carboxylation
efficiency were detected between treatments when expressed per frond. After 25 d of treatment,
photosynthesis (per frond) and dry weight of S. polyrhiza were reduced in 2XO(3)-air, but final frond
number was unaffected. Dark respiration of S. polyrhiza was unaffected in 2XO(3)(-) air, but when
exposed to 2XCO(2)+2XO(3)-air, it declined significantly. Although S. polyrhiza photosynthesis per
frond increased in 2XCO(2)+2XO(3)-air, dry weight was unaffected when compared with all other
treatments. Only when comparisons were made between S. polyrhiza grown in 2XCO(2)+2XO(3)-air
and 2XO(3)-air, were significant increases in dry weight observed. The addition of 2XCO(2) to
2XO(3)-air resulted in amelioration of negative O-3 effects for most responses for both duckweed
species.

KEYWORDS: ASPEN CLONES, ATMOSPHERIC CO2, CO2 CONCENTRATION, FIELD,
GROWTH, O-3, PHASEOLUS-VULGARIS L, PHOTOSYNTHETIC RESPONSES, PLANTS,
SULFUR-DIOXIDE


     97   
Baille, M., R. RomeroAranda, and A. Baille. 1996. Gas-exchange responses of rose plants to CO2
enrichment and light. Journal of Horticultural Science 71(6):945-956.

This paper describes the response of gas exchange rates and water use efficiency of rose plants, by
means of the characterization in situ and the analysis of the response of photosynthesis, transpiration
and water use efficiency of whole plants to CO2 enrichment under the irradiance conditions prevailing
in greenhouses of southern France. Net CO2 assimilation (A(n)) and transpiration (E) of whole rose
plants (Rosa hybrida, cv. Sonia) were measured during winter and spring periods. The response of
A(n) to light and CO2 were fitted to a double hyperbola function (r(2) = 0.84). Maximum net
assimilation rate (A(nmax)), light and CO2 utilization efficiencies (alpha(1), alpha(c)) as well as light
and CO2 compensation points (Gamma(1), Gamma(c)) were calculated for the whole plant and
compared with leaf and canopy data in the literature. The whole-plant characteristics generally had
values intermediate between those related to leaf and canopy. Light saturation at subambient air CO2
concentration (C-a) was reached for relatively low PFFD values (300 mu mol m(-2) s(- 1)), whereas
at ambient and enriched C-a light saturation occurs for PPFD approximate to 1000 mu mol m(-2) s(-
1). Doubling C-a from 350 to 700 mu mol mol(-1) increased A(nmax) and alpha(1) by respectively
40% and 30%, while reducing Gamma(1) by 27%. A threefold increase of C-a from 350 to 1050 mu
mol mol(-1) induced a reduction of 20% of E. Instantaneous transpirational water use efficiency,
WUE (=A(n)/E), is relatively insensitive to PPFD, although a slight decrease with PPFD is observed
at high CO2 concentration, but shows marked variations with C-a and leaf to air vapour pressure
deficit (D- 1). Increase of C-a from 350 to 1000 mu mol mol(-1) gave about 50% increase in WUE.
Increase of D-1 from 0 to 2 kPa induced 30% decrease in WUE at ambient C-a and 50% decrease
at 1000 mu mol mol(-1).

KEYWORDS: CARBON DIOXIDE, CROP, LEAF CONDUCTANCE, LEAVES, NET
PHOTOSYNTHESIS, PRODUCTIVITY, SWEET-PEPPER, TOMATO, TRANSPIRATION, WATER-
USE EFFICIENCY


     98   
Bainbridge, G., P. Madgwick, S. Parmar, R. Mitchell, M. Paul, J. Pitts, A.J. Keys, and M.A.J.
Parry. 1995. Engineering rubisco to change its catalytic properties. Journal of Experimental Botany
46:1269-1276.

The initial steps of carbon assimilation and photorespiration are catalysed by ribulose-1,5-
bisphosphate carboxylase/oxygenase (EC 4.1.1.39). Natural variation in the kinetic properties of the
enzyme suggest that it is possible to alter the enzyme to favour the carboxylation activity relative to
oxygenation, Mutagenesis in vitro of the gene encoding the large subunit of the enzyme from
Anacystis nidulans has been used to modify catalytic properties. Residues at the C-terminal end of
loop 6 of the beta/alpha barrel structure of the large subunit influence specificity towards the gaseous
substrates, CO2 and O-2. None of the residues altered by mutagenesis appear to interact directly with
the transition state analogue and their effect on the reaction of the enediolate intermediate with the
gaseous substrates and stabilization of the resulting transition state intermediates by lysine 334 must
be indirect. Interactions with other parts of the enzyme must also be important in determining
substrate specificity, Backbone carbonyl groups close to lysine 334 interact with lysine 128; mutation
of lysine 128 to residues of less positive polarity reduces enzyme activity and favours oxygenation
relative to carboxylation, the likely effects on assimilation rates of altering the kinetic properties of
Rubisco have been modelled. A leaf with cyanobacterial Rubisco may out-perform a higher plant
Rubisco at elevated CO2 and cool temperatures.

KEYWORDS: 1,5-BISPHOSPHATE CARBOXYLASE, ACTIVE-SITE, CO2/O2 SPECIFICITY,
LARGE SUBUNIT, RHODOSPIRILLUM-RUBRUM, RIBULOSE BISPHOSPHATE
CARBOXYLASE, RIBULOSE-1;5-BISPHOSPHATE CARBOXYLASE, SITE-DIRECTED
MUTAGENESIS, SUBSTRATE-SPECIFICITY


     99   
Baker, J.T., S.L. Albrecht, D. Pan, L.H. Allen, N.B. Pickering, and K.J. Boote. 1994. Carbon-
dioxide and temperature effects on rice (oryza-sativa L, CV ir-72). Soil and Crop Science Society
of Florida Proceedings 53:90-97.

The current increase in atmospheric carbon dioxide concentration ([CO2]) along with predictions of
possible future increases in global air temperatures have stimulated interest in the effects of [CO2]
and temperature on the growth and yield of food crops. This study was conducted to determine the
effects and possible interactions of elevated [CO2] and temperature on the development, growth and
yield of rice (Oryza sativa L., cv. IR-72). Rice plants were grown season-long in outdoor, naturally
sunlit, controlled-environment, plant growth chambers. Chamber air temperatures were controlled
to follow a continuously and diurnally varying, near sine-wave control setpoint that operated between
maximum (daytime) and minimum (nighttime) values. Day/night (maximum/minimum) air temperature
treatments were: 32/23, 35/26, and 38/29-degrees-C. Dewpoint air temperatures were maintained at
18, 21, 24- degrees-C in the 32/23, 35/26, 38/29-degrees-C dry bulb air temperature treatment,
respectively. Daytime [CO2] was controlled to 330 and 660 mumol CO2 mol-1 air in each of the air
temperature treatments. The time interval between appearance of successive mainstrem leaves during
reproductive development was reduced by increasing air temperature treatment (P less-than-or-equal-
to 0.05) but was not affected by [CO2] enrichment. In this experiment [CO2] enrichment did not
affect (P less-than-or-equal-to 0.10) grain yield, components of grain yield, final above ground
biomass or harvest index. Increasing temperature during growth, particularly from the 35/26 to
38/29-degrees-C reduced grain yield, individual grain mass, and harvest index. The reduced grain
yields with increasing temperature treatment suggest potential detrimental effects on rice production
in some areas if air temperatures increase.



     100  
Baker, J.T., and L.H. Allen. 1993. Contrasting crop species responses to co2 and temperature -
rice, soybean and citrus. Vegetatio 104:239-260.

The continuing increase in atmospheric carbon dioxide concentration ([CO2]) and projections of
possible future increases in global air temperatures have stimulated interest in the effects of these
climate variables on plants and, in particular, on agriculturally important food crops. Mounting
evidence from many different experiments suggests that the magnitude and even direction of crop
responses to [CO2] and temperature is almost certain to be species dependent and very likely, within
a species, to be cultivar dependent. Over the last decade, [CO2] and temperature experiments have
been conducted on several crop species in the outdoor, naturally- sunlit, environmentally controlled,
plant growth chambers by USDA-ARS and the University of Florida, at Gainesville, Florida, USA.
The objectives for this paper are to summarize some of the major findings of these experiments and
further to compare and contrast species responses to [CO2] and temperature for three diverse crop
species: rice (Oryza sativa, L.). soybean (Glycine max, L.) and citrus (various species). Citrus had the
lowest growth and photosynthetic rates but under [CO2] enrichment displayed the greatest
percentage increases over ambient [CO2] control treatments. In all three species the direct effect of
[CO2] enrichment was always an increase in photosynthetic rate. In soybean, photosynthetic rate
depended on current [CO2] regardless of the long-term [CO2] history of the crop. In rice,
photosynthetic rate measured at a common [CO2], decreased with increasing long-term [CO2]
growth treatment due to a corresponding decline in RuBP carboxylase content and activity. Rice
specific respiration decreased from subambient to ambient and superambient [CO2] due to a decrease
in plant tissue nitrogen content and a decline in specific maintenance respiration rate. In all three
species, crop water use decreased with [CO2] enrichment but increased with increases in temperature.
For both rice and soybean, [CO2] enrichment increased growth and grain yield. Rice grain yields
declined by roughly 10% per each 1-degrees-C rise in day/night temperature above 28/21-degrees-C.

KEYWORDS: ATMOSPHERIC CO2, CANOPY PHOTOSYNTHESIS, CARBON-DIOXIDE
CONCENTRATION, CLIMATE SENSITIVITY, DARK RESPIRATION, DEVELOPMENTAL
STAGES, ELEVATED CO2, SHORT- TERM, SOUR ORANGE TREES, WATER-USE EFFICIENCY


     101  
Baker, J.T., and L.H. Allen. 1994. Assessment of the impact of rising carbon-dioxide and other
potential climate changes on vegetation. Environmental Pollution 83(1-2):223-235.

The projected doubling of current levels of atmospheric carbon dioxide concentration ([CO2]) during
the next century along with increases in other radiatively active gases have led to predictions of
increases in global air temperature and shifts in precipitation patterns. Additionally, stratospheric
ozone depletion may result in increased ultraviolet-B (UV-B) radiation incident at the Earth's surface
in some areas. Since these changes in the Earth's atmosphere may have profound effects on
vegetation, the objectives of this paper are to summarize some of the recent research on plant
responses to [CO2], temperature and UV-B radiation. Elevated [CO2] increases photosynthesis and
usually results in increased biomass, and seed yield. The magnitude of these increases and the specific
photosynthetic response depends on the plant species, and are strongly influenced by other
environmental factors including temperature, light level, and the availability of water and nutrients.
While elevated [CO2] reduces transpiration and increases photosynthetic water-use efficiency,
increasing air temperature can result in greater water use, accelerated plant developmental rate, and
shortened growth duration. Experiments on UV-B radiation exposure have demonstrated a wide
range of photobiological responses among plants with decreases in photosynthesis and plant growth
among more sensitive species. Although a few studies have addressed the interactive effects of [CO2]
and temperature on plants, information on the effects of UV-B radiation at elevated [CO2] is scarce.
Since [CO2], temperature and UV-B radiation may increase concurrently, more research is needed
to determine plant responses to the interactive effects of these environmental variables.

KEYWORDS: DIFFERENT CO2 ENVIRONMENTS, DRY-MATTER PRODUCTION, FIELD
CONDITIONS, HIGH ATMOSPHERIC CO2, MILD WATER-STRESS, NET PHOTOSYNTHESIS,
PHOTON FLUX- DENSITY, PLANT GROWTH, SOYBEAN CANOPY PHOTOSYNTHESIS,
ULTRAVIOLET-B RADIATION


     102  
Baker, J.T., L.H. Allen, and K.J. Boote. 1990. Growth and yield responses of rice to carbon-
dioxide concentration. Journal of Agricultural Science 115:313-320.

Rice plants (Oryza sativa L., cv. IR30) were grown in paddy culture in outdoor, naturally sunlit,
controlled-environment, plant growth chambers at Gainesville, Florida, USA, in 1987. The rice plants
were exposed throughout the season to subambient (160 and 250), ambient (330) or superambient
(500, 660, 900 mu-mol CO2/mol air) CO2 concentrations. Total shoot biomass, root biomass,
tillering, and final grain yield increased with increasing CO2 concentration, the greatest increase
occurring between the 160 and 500 mu-mol CO2/mol air treatments. Early in the growing season,
root:shoot biomass ratio increased with increasing CO2 concentration; although the ratio decreased
during the growing season, net assimilation rate increased with increasing CO2 concentration and
decreased during the growing season. Differences in biomass and lamina area among CO2 treatments
were largely due to corresponding differences in tillering response. The number of panicles/plant was
almost entirely responsible for differences in final grain yield among CO2 treatments. Doubling the
CO2 concentration from 330 to 660 mu-mol CO2/mol air resulted in a 32% increase in grain yield.
These results suggest that important changes in the growth and yield of rice may be expected in the
future as the CO2 concentration of the earth's atmosphere continues to rise.

KEYWORDS: ATMOSPHERIC CO2, CENTURIES, CROP PLANTS, DRY-MATTER,
ENRICHMENT, ICE CORE, LEAF-AREA, PLANT GROWTH, TEMPERATURE, WHEAT


     103  
Baker, J.T., L.H. Allen, and K.J. Boote. 1992. Response of rice to carbon-dioxide and
temperature. Agricultural and Forest Meteorology 60(3-4):153-166.

The current increase in atmospheric carbon dioxide concentration ([CO2]) along with predictions of
possible future increases in global air temperatures have stimulated interest in the effects of [CO2]
and temperature on the growth and yield of food crops. This study was conducted to determine the
effects and possible interactions of [CO2] and temperature on the growth and yield of rice (Oryza
sativa L., cultivar IR-30). Rice plants were grown for a season in outdoor, naturally sunlit, controlled-
environment, and plant growth chambers. Temperature treatments of 28/21/25, 34/27/31, and
40/33/37- degrees-C (daytime dry bulb air temperature/night-time dry bulb air temperature/paddy
water temperature) were maintained in [CO2] treatments of 330 and 660-mu-mol CO2 mol-1 air. In
the 40/33/37-degrees-C temperature treatment, plants in the 330-mu- mol mol-1 [CO2] treatment
died during stem extension while the [CO2] enriched plants survived but produced sterile panicles.
Plants in the 34/27/31-degrees-C temperature treatments accumulated biomass and leaf area at a
faster rate early in the growing season than plants in the 28/21/25-degrees-C temperature treatments.
Tillering increased with increasing temperature treatment. Grain yield increases owing to [CO2]
enrichment were small and non-significant. This lack of [CO2] response on grain yield was attributed
to the generally lower levels of solar irradiance encountered during the late fall and winter when this
experiment was conducted. Grain yields were affected much more strongly by temperature than
[CO2] treatment. Grain yields declined by an average of approximately 7-8% per 1-degrees-C rise
in temperature from the 28/21/25 to 34/27/31-degrees-C temperature treatment. The reduced grain
yields with increasing temperature treatment suggests potential detrimental effects on rice production
in some areas if air temperatures increase, especially under conditions of low solar irradiance.

KEYWORDS: AIR- TEMPERATURE, CLIMATE SENSITIVITY, CO2- ENRICHMENT,
ENVIRONMENTS, ORYZA SATIVA L, PHOTOSYNTHESIS, PLANT GROWTH, TRANSPIRATION,
WHEAT, YIELD


     104  
Baker, J.T., L.H. Allen, and K.J. Boote. 1992. Temperature effects on rice at elevated co2
concentration. Journal of Experimental Botany 43(252):959-964.

The continuing increase in atmospheric carbon dioxide concentration ([CO2]) and projections of
possible future increases in global air temperatures have stimulated interest in the effects of these
climate variables on agriculturally important food crops. This study was conducted to determine the
effects of [CO2] and temperature on rice (Oryza sativa L., cv. IR-30). Rice plants were grown
season-long in outdoor, naturally sunlit, controlled-environment, plant growth chambers in
temperature regimes ranging from 25/18/21-degrees-C to 37/30/34-degrees-C (daytime dry bulb air
temperature/night-time dry bulb air temperature/paddy water temperature) and [CO2] of 660-mu-mol
CO2 mol-1 air. An ambient chamber was maintained at a [CO2] of 330-mu-mol mol-1 and
temperature regime of 28/21/25- degrees-C. Carbon dioxide enrichment at 28/21/25-degrees-C
increased both biomass accumulation and tillering and increased grain yield by 60%. In the 660-mu-
mol mol-1 [CO2] treatment, grain yield decreased from 10.4 to 1.0 Mg ha-1 with increasing
temperature from 28/21/25-degrees-C to the 37/30/34-degrees-C temperature treatment. Across this
temperature range, the number of panicles plant-1 nearly doubled while the number of seeds panicle-1
declined sharply. These results indicate that while future increases in atmospheric [CO2] are likely
to be beneficial to rice growth and yield, potentially large negative effects on rice yield are possible
if air temperatures also rise.

KEYWORDS: CARBON-DIOXIDE CONCENTRATION, CLIMATE SENSITIVITY, ENRICHMENT,
GROWTH, ORYZA SATIVA L, PHOTOSYNTHESIS, RESPONSES, TRANSPIRATION, WHEAT,
YIELD


     105  
Baker, J.T., L.H. Allen, K.J. Boote, and N.B. Pickering. 1997. Rice responses to drought under
carbon dioxide enrichment .1. Growth and yield. Global Change Biology 3(2):119-128.

Projections of future climate change include a strong likelihood of a doubling of current atmospheric
carbon dioxide concentration ([CO2]) and possible shifts in precipitation patterns. Drought stress is
a major environmental limitation for crop growth and yield and is common in rainfed rice production
systems. This study was conducted to determine the growth and grain yield responses of rice to
drought stress under [CO2] enrichment. Rice (cv. IR-72) was grown to maturity in eight naturally
sunlit, plant growth chambers in atmospheric carbon dioxide concentrations [CO2] of 350 and 700
mu mol CO2 mol(-1) air. In both [CO2], water management treatments included continuously hooded
(CF) controls, flood water removed and drought stress imposed at panicle initiation (PI), anthesis
(ANT), and both panicle initiation and anthesis (PI & ANT). The [CO2] enrichment increased
growth, panicles plant(-1) and grain yield. Drought accelerated leaf senescence, reduced leaf area and
above-ground biomass and delayed crop ontogeny. The [CO2] enrichment allowed 1-2 days more
growth during drought stress cycles. Grain yields of the PI and PI & ANT droughts were similar to
the CF control treatments while the ANT drought treatment sharply reduced growth, grain yield and
individual grain mass. We conclude that in the absence of air temperature increases, future global
increases in [CO2] should promote rice growth and yield while providing a modest reduction of near
10% in water use and so increase drought avoidance.

KEYWORDS: CO2- ENRICHMENT, CULTIVAR, INCREASE, NUTRITION, ORYZA SATIVA L,
WHEAT


     106  
Baker, J.T., L.H. Allen, K.J. Boote, and N.B. Pickering. 1997. Rice responses to drought under
carbon dioxide enrichment .2. Photosynthesis and evapotranspiration. Global Change Biology
3(2):129-138.

Future climate change is projected to include a strong likelihood of continued increases in
atmospheric carbon dioxide concentration ([CO2]) and possible shifts in precipitation patterns. Due
mainly to uncertainties in the timing and amounts of monsoonal rainfall, drought is common in rainfed
rice production systems. The objectives of this study were to quantify the effects and possible
interactions of [CO2] and drought stress on rice (Oryza sativa, L.) photosynthesis, evapotranspiration
and water-use efficiency. Rice (cv. IR-72) was grown to maturity in eight naturally sunlit, plant
growth chambers in atmospheric carbon dioxide concentrations [CO2] of 350 and 700 mu mol CO2
mol(-1) air. In both [CO2], water management treatments included continuously flooded controls,
flood water removed and drought stress imposed at panicle initiation, anthesis, and both panicle
initiation and anthesis. Potential acclimation of rice photosynthesis to long-term [CO2] growth
treatments of 350 and 700 mu mol mol(-1) was tested by comparing canopy photosynthesis rates
across short-term [CO2] ranging from 160 to 1000 mu mol mol(-1). These tests showed essentially
no acclimation response with photosynthetic rate being a function of current short-term [CO2] rather
than long- term [CO2] growth treatment. In both long-term [CO2] treatments, photosynthetic rate
saturated with respect to [CO2] near 510 mu mol mol(-1). Carbon dioxide enrichment significantly
increased both canopy net photosynthetic rate (21-27%) and water-use efficiency while reducing
evapotranspiration by about 10%. This water saving under [CO2] enrichment allowed photosynthesis
to continue for about one to two days longer during drought in the enriched compared with the
ambient [CO2] control treatments.

KEYWORDS: ACCLIMATION, ATMOSPHERIC CO2, CARBOXYLASE, DIFFERENT CO2
ENVIRONMENTS, DRY-MATTER PRODUCTION, ELEVATED CO2, PLANT GROWTH,
SOYBEAN LEAVES, TEMPERATURE, TRANSPIRATION


     107  
Balaguer, L., J.D. Barnes, A. Panicucci, and A.M. Borland. 1995. Production and utilization of
assimilates in wheat (triticum- aestivum L) leaves exposed to elevated o-3 and/or co2. New
Phytologist 129(4):557-568.

This study examined the effects of elevated ozone (O-3) and/or carbon dioxide (CO2) on the diel
allocation of photosynthetically fixed carbon in fully expanded leaves of young (growth stages 4-5)
spring wheat (Triticum aestivum L. cv. Hanno). Plants were grown in controlled environment
chambers and exposed to two O-3 regimes ['non-polluted' air (CF), < 5 nmol mol(-1); 'polluted' air,
CF + 75 nmol mol(-1) 7 h d(-1)] and two CO2 treatments ('ambient', 354 mu mol mol(-1); 'elevated',
700 mu mol mol(-1)) over a 30 d period. Neutral sugars (predominantly sucrose) were found to be
the most abundant form of carbohydrate accumulated by leaves during the day, but significant
quantities of starch and high degree of polymerization (d.p.) fructans were also present. Elevated
concentrations of O-3 and/or CO2 were found to have marked effects on diel patterns of export,
storage and respiration, whilst the proportions of fixed carbon allocated to each of these processes
were broadly similar. O-3 depressed the rate of net CO2 assimilation (-20%) and reduced stomatal
conductance (- 19%). This was reflected in a reduced amount of carbohydrate accumulated in, and
exported by, source tissue during the day. Effects of O-3 on the rate of CO2 fixation were aggravated
by an increased demand for carbon by dark respiratory processes. In contrast, doubling the
atmospheric concentration of CO2 enhanced the rate of net CO2 assimilation (+ 47%) and reduced
the proportion of fixed carbon retained in the leaf blade, increasing the rate of export. The favourable
carbon balance of CO2 enriched leaves was further enhanced by a decrease in the cost of maintenance
respiration, whilst simultaneous measurements of CO2 efflux and O-2 uptake at night suggested a
shift in the substrates metabolized at high CO2. Effects of elevated CO2 and O-3 on the carbon
balance of individual leaf blades over a single 24 h light/dark cycle were entirely consistent with the
cumulative effects of the gases on plant growth over a 30 d period. O-3 reduced the rate of plant
growth (-10%), but there were differential effects of O-3 on the growth of root and shoot which
exacerbated the decrease in assimilate availability induced by O-3. In contrast the favourable effects
of CO2 enrichment on the carbon balance of individual source leaves was reflected in the enhanced
accumulation of dry matter in existing sinks, and the initiation of new sinks (i.e. increased tillering).
In the combined treatment (elevated CO2 + O-3), O-3 counteracted the favourable effects of CO2
enrichment on the carbon balance of individual leaves, and the combined effects of the individual
gases on the diel partitioning of photosynthetically fixed carbon in fully expanded leaf blades was
reflected in a decreased rate of plant growth at elevated CO2, a situation further exacerbated by O-3-
induced shifts in the relative partitioning of carbon between root and shoot. There was no evidence
that CO2 enrichment afforded additional protection against O-3 damage: the extent of the O-3-
induced reduction in photosynthesis, carbohydrate availability and growth observed at elevated CO2
was similar to that induced by O-3 in ambient air, despite additive effects of the gases on stomatal
conductance that would reduce the effective dose of O-3 by approximate to 30%. The wider
ecological significance of interactions between elevated CO2 and O-3 is discussed in the light of other
recent findings.

KEYWORDS: AIR- POLLUTANTS, CARBON DIOXIDE, CLIMATE CHANGE, GAS-EXCHANGE,
LEAF BLADES, MAINTENANCE RESPIRATION, OPEN-TOP CHAMBERS, OZONE, PICEA-
ABIES L, SOURCE-SINK RELATIONS


     108  
Balaguer, L., E. Manrique, A. de los Rios, C. Ascaso, K. Palmqvist, M. Fordham, and J.D.
Barnes. 1999. Long-term responses of the green-algal lichen Parmelia caperata to natural CO2
enrichment. Oecologia 119(2):166-174.

Acclimation to elevated CO2 was investigated in Parmelia caperata originating from the vicinity of
a natural CO2 spring, where the average daytime CO2 concentration was 729 +/- 39 mu mol mol(-1)
dry air. Thalli showed no evidence of a down- regulation in photosynthetic capacity following long-
term exposure to CO2 enrichment in the field; carboxylation efficiency, total Ribulose bisphosphate
carboxylase/oxygenase (Rubisco) content, apparent quantum yield of CO2 assimilation, and the light-
saturated rate of CO2 assimilation (measured under ambient and saturating CO2 concentrations) were
similar in thalli from the naturally CO2 enriched site and an adjacent control site where the average
long-term CO2 concentration was about 355 mu mol mol(-1). Thalli from both CO2 environments
exhibited low CO2 compensation points and early saturation of CO2 uptake kinetics in response to
increasing external CO2 concentrations, suggesting the presence of an active carbon- concentrating
mechanism. Consistent with the lack of significant effects on photosynthetic metabolism, no changes
were found in the nitrogen content of thalli following prolonged exposure to elevated CO2. Detailed
intrathalline analysis revealed a decreased investment of nitrogen in Rubisco in the pyrenoid of algae
located in the elongation zone of thalli originating from elevated CO2, an effect associated with a
reduction in the percentage of the cell volume occupied by lipid bodies and starch grains. Although
these differences did not affect the photosynthetic capacity of thalli, there was evidence of enhanced
limitations to CO2 assimilation in lichens originating from the CO2-enriched site. The light-saturated
rate of CO2 assimilation measured at the average growth CO2 concentration was found to be
significantly lower in thalli originating from a CO2-enriched atmosphere compared with that of thalli
originating and measured at ambient CO2, At lower photosynthetic photon flux densities, the light
compensation point of net CO2 assimilation was significantly higher in thalli originating from elevated
CO2 and this effect was associated with higher usnic acid content.

KEYWORDS: CARBON ISOTOPE DISCRIMINATION, CHLOROPHYTA, ELEVATED CO2,
EXCHANGE, GROWTH, PHOTOBIONTS, PHOTOSYNTHESIS, PLANTS, RISING
ATMOSPHERIC CO2, WATER-CONTENT


     109  
Balaguer, L., F. Valladares, C. Ascaso, J.D. Barnes, A. DelosRios, E. Manrique, and E.C.
Smith. 1996. Potential effects of rising tropospheric concentrations of CO2 and O-3 on green-algal
lichens. New Phytologist 132(4):641-652.

Parmelia sulcata Taylor was used as a model to examine the effects of elevated CO2 and/or O-3 on
green algal lichens. Thalli were exposed for 30 d in duplicate controlled- environment chambers to
two atmospheric concentrations of CO2 ('ambient' [350 mu mol mol(-1)] and 'elevated' [700 mu mol
mol(-1)] 24 h d(-1)) and two O-3 regimes ('non-polluted' air [CF, < 5 nmol mol(-1)] and 'polluted'
air [15 nmol mol(-1) overnight rising to a midday maximum of 75 nmol mol(-1)]), in a factorial
design. Elevated CO2 or elevated O-3 depressed the light saturated rate of CO2 assimilation (A(sat))
measured at ambient CO2 by 30%, and 18%, respectively. However, despite this effect ultrastructural
studies revealed increased lipid storage in cells of the photobiont in response to CO2- enrichment.
Simultaneous exposure to elevated O-3 reduced CO2- induced lipid accumulation and reduced A(sat)
in an additive manner. Gold-antibody labelling revealed that the decline in photosynthetic capacity
induced by elevated CO2 and/or O-3 was accompanied by a parallel decrease in the concentration of
Rubisco in the algal pyrenoid (r = 0.93). Interestingly, differences in the amount of Rubisco protein
were not correlated with changes in pyrenoid volume. Measurements of in vivo chlorophyll-
fluorescence induction kinetics showed that the decline in A(sat) induced by elevated CO2 and/or O-3
was not associated with significant changes in the photochemical efficiency of photosystem (PS)II.
Although the experimental conditions inevitably imposed some stress on the thalli, revealed a
significant decline in the efficiency of PS II photochemistry, and enhanced starch accumulation in the
photobiont over the fumigation period, the study shows that the green-algal lichen symbiosis might
be influenced by future changes in atmospheric composition. Photosynthetic capacity, measured at
ambient CO2, was found to be reduced after a controlled 30 d exposure to elevated CO2 and/or O-3
and this effect was associated with a parallel decline in the amount of Rubisco in the pyrenoid of algal
chloroplasts.

KEYWORDS: BISPHOSPHATE CARBOXYLASE OXYGENASE, CARBON, CHLORELLA,
CHLOROPHYLL FLUORESCENCE, GAS-EXCHANGE, GROWTH, OZONE, PARMELIA-
SULCATA, PHOTOSYNTHESIS, ULTRASTRUCTURE


     110  
Baldocchi, D. 1994. A comparative-study of mass and energy-exchange rates over a closed C-3
(wheat) and an open C-4 (corn) crop .2. Co2 exchange and water-use efficiency. Agricultural and
Forest Meteorology 67(3-4):291-321.

Major differences exist between the photosynthetic and transpiration rates Of C3 and C4 leaves as
a result of biochemical and physiological factors. Whether or not differences between CO2 and water
vapor exchange rates Of C3 and C4 species scale from leaf to field dimensions is poorly known. The
aim of this work is to improve our understanding on how environmental, architectural and
physiological variables affect the flux densities Of CO2 and water vapor over C3 and C4 crop stands
during day and night periods. Experimental data were obtained over a closed wheat and an open com
stand using the eddy correlation method. Interpretation of the field measurements is aided by the use
of a canopy photosynthesis/evaporation model. The flux density of absorbed photosynthetically active
radiation (Q(a)) had a disproportionate influence on CO2 flux densities measured over a closed C3
and an open C4 crop. Variations in Q(a) explained over 88% of the variance in daytime CO2 flux
densities, F(c). At night, canopy radiative temperature was the main environmental factor controlling
the respiratory CO2 efflux by the two crops. Leaf area index and growth stage were the plant
variables that affected F(c) most. Incremental increases in leaf area index enhanced the com crop's
ability to absorb incident solar radiation and enlarged the com's sink strength for CO2. Heading by
the wheat caused rates of daytime CO2 gains to decrease and rates of night-time CO2 losses to
increase. Water use efficiency of the wheat crop improved as the absolute humidity deficit of the
atmosphere decreased. Water use efficiency of the com, on the other hand, was relatively insensitive
to humidity deficits. With regard to canopy CO2 exchange and water use efficiency, differences in
canopy structure between the wheat and com overwhelmed physiological differences. The closed C3
wheat crop assimilated CO2 at a higher rate than the sparse C4 com canopy, even though com uses
a more efficient photosynthetic pathway. Consequently, water use efficiency of the com was not
greater than values measured over the wheat, Instead, water use efficiencies of the two crops were
similar. The com crop assimilated CO2 at a lower rate than wheat because the com's canopy quantum
yield was lower and because its sparse canopy absorbed less photosynthetically active radiation than
the closed wheat stand.

KEYWORDS: ASSIMILATION, CANOPY, CARBON DIOXIDE, FLUX MEASUREMENTS, LEAF-
AREA INDEX, PHOTOSYNTHESIS, SOIL RESPIRATION, STOMATAL CONDUCTANCE,
VAPOR, WINTER-WHEAT


     111  
Baldocchi, D.D., and P.C. Harley. 1995. Scaling carbon-dioxide and water-vapor exchange from
leaf to canopy in a deciduous forest .2. Model testing and application. Plant, Cell and Environment
18(10):1157-1173.

The scaling of CO2 and water vapour transfer from leaf to canopy dimensions was achieved by
integrating mechanistic models for physiological (photosynthesis, stomatal conductance and soil/root
and bole respiration) and micrometeorological (radiative transfer, turbulent transfer and surface
energy exchanges) processes, The main objectives of this paper are to describe a canopy
photosynthesis and evaporation model for a temperate broadleaf forest and to test it against field
measurements, The other goal of this paper is to use the validated model to address some
contemporary ecological and physiological questions concerning the transfer of carbon and water
between forest canopies and the atmosphere, In particular, we examine the role of simple versus
complex radiative transfer models and the effect of environmental (solar radiation and CO2) and
ecophysiological (photosynthetic capacity) variables on canopy-scale carbon and water vapour fluxes.

KEYWORDS: CLIMATE CHANGE, CO2 CONCENTRATIONS, ELEVATED CO2, PATTERNS,
PHOTOSYNTHESIS, PLANT CANOPIES, SENSIBLE HEAT, STOMATAL CONDUCTANCE,
TEMPERATURE, TRANSPIRATION


     112  
Ball, A.S. 1991. Degradation by Streptomyces viridosporus t7a of plant-material grown under
elevated CO2 conditions. Fems Microbiology Letters 84(2):139-142.

The biodegradability of plant material derived from wheat grown under different concentrations of
atmospheric CO2 was investigated using the lignocarbohydrate solubilising actinomycete,
Streptomyces viridosporus. Growth of S. viridosporus and solubilisation of lignocarbohydrate were
highest when wheat grown at ambient CO2 concentrations (350 ppm) was used as C-source. Growth
of S. viridosporus and solubilisation were reduced when the plant material was derived from wheat
grown at 645 PPM CO2. The results suggest that modifications in plant structure occur when wheat
is grown under conditions of elevated atmospheric CO2 which make it more resistant to microbial
digestion.

KEYWORDS: ENZYME, LIGNIN DEGRADATION, LIGNOCELLULOSE, POLYMERIC LIGNIN,
STRAW


     113  
Ball, A.S. 1997. Microbial decomposition at elevated CO2 levels: effect of litter quality. Global
Change Biology 3(4):379-386.

The decomposition of senesced plant litter represents an important intermediate step in the cycling
of nutrients between above-and below-ground systems. The rate of decomposition of plant litter is
sensitive to fluctuations in a number of parameters, including environmental conditions, and
particularly to changes in the quality of the litter. Increased C:N ratios of litter are thought to be one
possible consequence of growth of plants under elevated [CO2]. This response is likely to reduce the
rate of decomposition of the litter. Evidence from the growth of plants in both pot and field studies
suggests that growth of C3 plants in elevated atmospheric [CO2] (600-700 mu mol mol(-1)) may lead
to a significant increase in either/both the C:N and the lignin: N ratios of litter. Short-term
decomposition of lifter from plants showing this response in elevated [CO2] has confirmed that
decomposition occurs at a significantly lower rate. The limited studies of both the response of C4
plants to elevated [CO2] and the subsequent degradability of the senescent litter suggest that no
differences in litter quality or degradability occur. In terms of litter quality the response of plants
therefore appears to be dependent upon photosynthetic type; the C:N and lignin:N ratios of litter from
C3 plants exposed to elevated [CO2] are increased, leading to lower degradation rates, while the
nutrient ratios and degradation rates of lifter from C4 plants grown in elevated [CO2] remain
unchanged. To date, very few ecosystem studies of decomposition have been carried out. Further
work is required at the ecosystem level to determine whether the effects observed in laboratory, pot
and field studies are also observed in long-term, complex ecosystem studies. Clearly if these results
are repeated at the ecosystem level then significant changes in the cycling of C and N in important
terrestrial ecosystems may occur as a results of elevated [CO2].

KEYWORDS: ATMOSPHERIC CO2, CARBON-DIOXIDE CONCENTRATION, ECOSYSTEMS,
HARDWOOD LEAF LITTER, LIGNIN CONTENT, MASS-LOSS, NITROGEN DYNAMICS, PLANT-
MATERIAL, RESPONSES, SOIL


     114  
Ball, A.S., and B.G. Drake. 1997. Short-term decomposition of litter produced by plants grown in
ambient and elevated atmospheric CO2 concentrations. Global Change Biology 3(1):29-35.

The effects of elevated atmospheric CO2 (ambient + 340 mu mol mol(-1)) on above-ground litter
decomposition were investigated over a 6-week period using a field-based mesocosm system. Soil
respiratory activity in mesocosms incubated in ambient and elevated atmospheric CO2 concentrations
were not significantly different (t-test, P > 0.05) indicating that there were no direct effects of
elevated atmospheric CO2 on litter decomposition. A study of the indirect effects of CO2 on soil
respiration showed that soil mesocosms to which naturally senescent plant litter had been added
(0.5% w/w) from the C-3 sedge Scirpus olneyi grown in elevated atmospheric CO2 was reduced by
an average of 17% throughout the study when compared to soil mesocosms to which litter from
Scirpus olneyi grown in ambient conditions had been added. In contrast, similar experiments using
senescent material from the C-4 grass Spartina patens showed no difference in soil respiration rates
between mesocosms to which litter from plants grown in elevated or ambient CO2 conditions had
been added. Analysis of the C:N ratio and lignin content of the senescent material showed that, while
the C:N ratio and lignin content of the Spartina patens litter did not vary with atmospheric CO2
conditions, the C:N ratio (but not the lignin content) of the litter from Scirpus olneyi was significantly
greater (t-test; P < 0.05) when derived from plants grown under elevated CO2 (105:1 compared to
86:1 for litter derived from Scirpus olneyi grown under ambient conditions). The results suggest that
the increased C:N ratio of the litter from the C-3 plant Scirpus olneyi grown under elevated CO2 led
to the lower rates of biodegradation observed as reduced soil respiration in the mesocosms. Further
longterm experiments are now required to determine the effects of elevated CO2 on C partitioning
in terrestrial ecosystems.

KEYWORDS: CARBON-DIOXIDE CONCENTRATION, DYNAMICS, FORESTS, INSITU, LEAF
LITTER, LEAVES, NITROGEN, RESPIRATION, SOIL


     115  
Ball, A.S., and B.G. Drake. 1998. Stimulation of soil respiration by carbon dioxide enrichment of
marsh vegetation. Soil Biology and Biochemistry 30(8-9):1203-1205.

KEYWORDS: ELEVATED ATMOSPHERIC CO2, INSITU, NITROGEN, PLANTS


     116  
Ball, M.C., M.J. Cochrane, and H.M. Rawson. 1997. Growth and water use of the mangroves
Rhizophora apiculata and R-stylosa in response to salinity and humidity under ambient and elevated
concentrations of atmospheric CO2. Plant, Cell and Environment 20(9):1158-1166.

Two mangrove species, Rhizophora apiculata and R. stylosa, mere grown for 14 weeks in a
multifactorial combination of salinity (125 and 350 mol m(-3) NaCl), humidity (43 and 86% relative
humidity at 30 degrees C) and atmospheric CO2 concentration (340 and 700 cm(3) m(-3)). Under
ambient [CO2], growth responses to different combinations of salinity and humidity were consistent
with interspecific differences in distribution along natural gradients of salinity and aridity in northern
Australia. Elevated [CO2] had little effect on relative growth rate when it was limited by salinity but
stimulated growth when limited by humidity. Both species benefited most from elevated [CO2] under
relatively low salinity conditions in which growth was vigorous, but relative growth rate was
enhanced more in the less salt-tolerant and more rapidly growing species, R. apiculata. Changes in
both net assimilation rate and leaf area ratio contributed to changes in relative growth rates under
elevated [CO2], with leaf area ratio increasing with decrease in humidity. Increase in water use
efficiency under elevated [CO2] occurred with increase, decrease or no change in evaporation rates;
water use characteristics which depended an both the species and the growth conditions. In summary,
elevated [CO2] is unlikely to increase salt tolerance, but could alter competitive rankings of species
along salinity x aridity gradients.

KEYWORDS: AUSTRALIA, AVICENNIA-MARINA, CARBON DIOXIDE, COTTON,
ENRICHMENT, GAS-EXCHANGE, MANGLE L, PHOTOSYNTHETIC ACCLIMATION, PLANT-
RESPONSES, RED MANGROVE


     117  
Ball, M.C., and R. Munns. 1992. Plant-responses to salinity under elevated atmospheric
concentrations of CO2. Australian Journal of Botany 40(4-5):515-525.

This review explores effects of elevated CO2 concentrations on growth in relation to water use and
salt balance of halophytic and non-halophytic species. Under saline conditions, the uptake and
distribution of sodium and chloride must be regulated to protect sensitive metabolic sites from salt
toxicity. Salt-tolerant species exclude most of the salt from the transpiration stream, but the salt flux
from a highly saline soil is still considerable. To maintain internal ion concentrations within
physiologically acceptable levels, the salt influx to leaves must match the capacities of leaves for salt
storage and/or salt export by either retranslocation or secretion from glands. Hence the balance
between carbon gain and the expenditure of water in association with salt uptake is critical to leaf
longevity under saline conditions. Indeed, one of the striking features of halophytic vegetation, such
as mangroves, is the maintenance of high water use efficiencies coupled with relatively low rates of
water loss and growth. These low evaporation rates are further reduced under elevated CO2
conditions. This, with increased growth, leads to even higher water use efficiency. Leaves of plants
grown under elevated CO2 conditions might be expected to contain lower salt concentrations than
those grown under ambient CO2 if salt uptake is coupled with water uptake. However, salt
concentrations in shoot tissues are similar in plants grown under ambient and elevated CO2 conditions
despite major differences in water use efficiency. This phenomenon occurs in C3 halophytes and in
both C3 and C4 non-halophytes. These results imply shoot/root communication in regulation of the
salt balance to adjust to environmental factors affecting the availability of water and ions at the roots
(salinity) and those affecting carbon gain in relation to water loss at the leaves (atmospheric
concentrations of water vapour and carbon dioxide).

KEYWORDS: AUSTRALIAN MANGROVE FOREST, AVICENNIA-MARINA, BARLEY, CARBON
DIOXIDE, DROUGHT, GAS-EXCHANGE, GROWTH, LIMITATIONS, OSMOTIC ADJUSTMENT,
PHOTOSYNTHESIS


     118  
Bandara, D.C., H. Nobuyasu, K.G. Ofosu-Budu, T. Ando, and K. Fujita. 1998. Effect of CO2
enrichment on biomass production, photosynthesis, and sink activity in soybean cv. Bragg and its
supernodulating mutant nts 1007. Soil Science and Plant Nutrition 44(2):179-186.

Soybean (Glycine max L. Merr.) cv. Bragg and its supernodulating mutant nts 1007 were grown in
pots containing vermiculite with a N-free nutrient solution in order to examine the effect of elevated
CO2 concentration (100+20 Pa CO2) on biomass production, photosynthesis, and biological nitrogen
fixation. The whole plant weight increase in Bragg was higher than in the mutant at a high CO2
concentration. Apparent photosynthetic activities of the upper leaves in both Bragg and the mutant
increased up to 14 d after treatment initiation by the CO2 enrichment and thereafter decreased to
some extent. Both leaf area and leaf thickness of Bragg increased more than in nts 1007. With the
elevated CO2 concentration, biological nitrogen fixation (BNF) also responded in the same manner
as biomass production in both Bragg and nts 1007. The increase of BNF in Bragg was largely due
to an increase in nodule weight. Starch contents in the leaves of both Bragg and the mutant increased
significantly by CO2 enrichment, with a higher increase in Bragg than in its mutant. Sugar content
in leaf differed only slightly in both Bragg and the mutant. N content in leaf decreased in both Bragg
and its mutant, with the decrease being more pronounced in Bragg. However, in other plant parts
(roots, stem, and petiole + pods), N content increased in the mutant while in Bragg, it decreased in
the pod. N accumulation rate was higher in Bragg than in the mutant and increased more in Bragg
than in the mutant by CO2 enrichment. The ureide content in leaf decreased in Bragg but increased
in the mutant by elevated CO2 concentration. In the nodules, ureide content increased in both Bragg
and the mutant by CO2 enrichment. Based on these results, it is suggested that in terms of biomass
production and photosynthetic rate, Bragg responded more to elevated CO2 concentration than its
mutant nts 1007. The alleviation of the stunted vegetative growth of the mutant by CO2 enrichment
was limited despite the significant increase in the photosynthetic activity, presumably due to the
limitation of sink activity in the growing parts and not to insufficient supply of N through BNF.

KEYWORDS: CARBON, DINITROGEN FIXATION, GROWTH, L MERRILL MUTANTS,
LEGUMES, NITRATE APPLICATION, NITROGEN, NTS1007, PLANTS, ROOTS


     119  
Barnes, J.D., J.H. Ollerenshaw, and C.P. Whitfield. 1995. Effects of elevated co2 and/or o-3 on
growth, development and physiology of wheat (triticum-aestivum L). Global Change Biology
1(2):129-142.

Two cultivars of spring wheat (Triticum aestivum L. cvs. Alexandria and Hanno) and three cultivars
of winter wheat (cvs. Riband, Mercia and Haven) were grown at two concentrations of CO2 [ambient
(355 mu mol mol(-1)) and elevated (708 mu mol mol(-1))] under two O-3 regimes [clean air (< 5
nmol mol(-1) O- 3) and polluted air (15 nmol mol(-1) O-3 at night rising to a midday maximum of
75 nmol mol(-1))] in a phytotron at the University of Newcastle-upon-Tyne. Between the two-leaf
stage and anthesis, measurements of leaf gas-exchange, non-structural carbohydrate content, visible
O-3 damage, growth, dry matter partitioning, yield components and root development were made in
order to examine responses to elevated CO2 and/or O-3. Growth at elevated CO2 resulted in a
sustained increase in the rate of CO2 assimilation, but after roughly 6 weeks' exposure there was
evidence of a slight decline in the photosynthetic rate (c.-15%) measured under growth conditions
which was most pronounced in the winter cultivars. Enhanced rates of CO2 assimilation were
accompanied by a decrease in stomatal conductance which improved the instantaneous water use
efficiency of individual leaves. CO2 enrichment stimulated shoot and root growth to an equivalent
extent, and increased tillering and yield components, however, non-structural carbohydrates still
accumulated in source leaves. In contrast, long-term exposure to O-3 resulted in a decreased CO2
assimilation rate (c.-13%), partial stomatal closure, and the accumulation of fructan and starch in
leaves in the light. These effects were manifested in decreased rates of shoot and root growth, with
root growth more severely affected than shoot growth. In the combined treatment growth of O-3-
treated plants was enhanced by elevated CO2, but there was little evidence that CO2 enrichment
afforded additional protection against O-3 damage. The reduction in growth induced by O-3 at
elevated CO2 was similar to that induced by O-3 at ambient CO2 despite additive effects of the
individual gases on stomatal conductance that would be expected to reduce the O-3 flux by 20%, and
also CO2-induced increases in the provision of substrates for detoxification and repair processes.
These observations suggest that CO2 enrichment may render plants more susceptible to O-3 damage
at the cellular level. Possible mechanisms are discussed.

KEYWORDS: AIR- POLLUTANTS, ATMOSPHERIC CARBON-DIOXIDE, CARBOXYLASE-
OXYGENASE, GAS-EXCHANGE, MODERN GREEK CULTIVARS, PICEA-ABIES L, PLANT
GROWTH, SOURCE-SINK RELATIONS, SPRING WHEAT, WINTER-WHEAT


     120  
Barnes, J.D., and T. Pfirrmann. 1992. The influence of co2 and o-3, singly and in combination, on
gas-exchange, growth and nutrient status of radish (raphanus- sativus L). New Phytologist
121(3):403-412.

Five days after emergence radish (Raphanus sativus L. cv. Cherry Belle) plants were transferred to
a phytotron at the GSF Munchen, where they were exposed in four large controlled climate chambers
to two at atmospheric concentrations of CO2 ('ambient', daily means of almost-equal-to 385-mu-mol
mol-1; elevated, daily means of almost-equal-to 765-mu-mol mol-1) and two O3 regimes ('non-
polluted' air, 24 h mean of 20 nmol mol-1; polluted air, 24 h mean of 73 nmol mol-1) Leaf gas-
exchange measurements were made at intervals, and visible O3 damage, effects on growth, dry matter
partitioning and mineral composition were assessed at a final whole-plant harvest after 27 d. In 'non-
polluted air' CO2 enrichment resulted in a progressive stimulation in A(sat), whilst there was a decline
in g(s) which decreased E (i.e. improved WUE(i)). The extra carbon fixed in elevated CO2 stimulated
growth of the root (+ hypocotyl) by 43 %, but there was no significant effect on shoot growth or leaf
area. Moreover, a decline in SLA and LAR in CO2-enriched plants suggested that less dry matter was
invested in leaf area expansion. Tissue concentrations of N, S, P, Mg and Ca were lower (particularly
in the root + hypocotyl) in elevated CO2, indicating that total uptake of these nutrients was not
affected by CO2, and there was an increase in the C:N ratio in root (+ hypocotyl) tissue. In contrast,
O3 depressed A(sat), (almost-equal-to 26 %) and induced slight stomatal closure, with the result that
WUE(i) declined. All plants exposed to 'polluted' air developed typical visible symptoms of O3 injury,
and effects on carbon assimilation were reflected in reduced growth, with shoot growth maintained
at the expense of the root. In addition, O3 increased the P and K concentration in shoot and root
(+hypocotyl) tissue, indicating enhanced uptake of these nutrients from the growth medium.
However, there was no affect of O3 on tissue concentrations of N, S, Mg and Ca. Interactions
between the gases were complex, and often subtle. In general, elevated CO2 counteracted (at least
in part) the detrimental effects of phytotoxic concentrations of O3, whilst conversely, O3 reduced the
impact of elevated CO2. Moreover, there were indications that cumulative changes in source:sink
relations in O3-exposed plants may limit plant response to CO2-enrichment to an even greater extent
in the long-term. The future ecological significance of interactions between CO2 and O3 are
discussed.

KEYWORDS: ABIES L KARST, ACID MIST, AIR- POLLUTANTS, CARBON DIOXIDE,
ENRICHMENT, OZONE ALTERS, PHOTOSYNTHESIS, PLANTS, USE EFFICIENCY, WHEAT


     121  
Barnes, J.D., T. Pfirrmann, K. Steiner, C. Lutz, U. Busch, H. Kuchenhoff, and H.D. Payer.
1995. Effects of elevated CO2, elevated O-3 and potassium deficiency on Norway spruce [Picea abies
(L) Karst]: Seasonal changes in photosynthesis and non-structural carbohydrate content. Plant, Cell
and Environment 18(12):1345-1357.

Two clones of 5-year-old Norway spruce [Picea abies (L.) Karst.] were exposed to two atmospheric
concentrations of CO2 (350 and 750 mu mol mol(-1)) and O-3 (20 and 75 nmol mol(-1)) in a
phytotron at the GSF-Forschungszentrum (Munich) over the course of a single season (April to
October), The phytotron was programmed to recreate an artificial climate similar to that at a high
elevation site in the Inner Bavarian Forest, and trees were grown in Large containers of forest soil
fertilized to achieve contrasting levels of potassium nutrition, designated well-fertilized or K-deficient.
Measurements of the rate of net CO2 assimilation were made on individual needle year age classes
over the course of the season, chlorophyll fluorescence kinetics were recorded after approximately
23 weeks, and seasonal changes in non-structural carbohydrate composition of the current year's
foliage were monitored. Ozone was found to have contrasting effects on the rate of net CO2
assimilation in different needle age classes. After c. 5 months of fumigation, elevated O-3 increased
(by 33%) the rate of photosynthesis in the current year's needles, However, O-3 depressed (by 30%)
the photosynthetic rate of the previous year's needles throughout the period of exposure, Chlorophyll
fluorescence measurements indicated that changes in photosystem II electron transport played no
significant role in the effects of O-3 on photosynthesis, The reasons for the contrasting effects of O-3
on needles of different ages are discussed in the light of other recent findings, Although O-3 enhanced
the rate at which CO2 was fixed in the current year's foliage, this was not reflected in increases in the
non-structural carbohydrate ate content of the needles, The transfer of ambient CO2-grown trees to
a CO2-enriched atmosphere resulted in marked stimulation in the photosynthetic rate of current and
previous year's foliage, However, following expansion of the current year's growth, the
photosynthetic rate of the previous year's foliage declined, The extent of photosynthetic adjustment
in response to prolonged exposure to elevated CO2 depended upon the clone, providing evidence of
intraspecific variation in the long-term response of photosynthesis to elevated CO2, The increase in
photosynthesis induced by CO2 enrichment was associated with increased foliar concentrations of
glucose, fructose and starch (but no change in sucrose) in the new growth, CO2 enrichment
significantly enhanced the photosynthetic rate of K-deficient needles, but there was a strong CO2*soil
interaction in the current year's needles, indicating that the long-term response of trees to a high CO2
environment may depend on soil fertility, Although the rate of photosynthesis and non- structural
carbohydrate content of the new needles were increased in O-3-treated plants grown at higher levels
of CO2, there was no evidence that elevated CO2 provided additional protection against O-3 damage,
Simultaneous exposure to elevated O-3 modified the effects of elevated CO2 on needle
photosynthesis and non-structural carbohydrate content, emphasizing the need to take into account
not only soil nutrient status but also the impact of concurrent increases in photochemical oxidant
pollution in any serious consideration of the effects of climate change on plant production.

KEYWORDS: ACID MIST, AIR- POLLUTANTS, ATMOSPHERIC CO2, CARBON DIOXIDE, GAS-
EXCHANGE, LONG-TERM EXPOSURE, NET PHOTOSYNTHESIS, NONSTOMATAL
LIMITATION, OPEN-TOP CHAMBERS, STOMATAL CONDUCTANCE


     122  
Barr, A.G., K.M. King, G.W. Thurtell, and M.E.D. Graham. 1990. Humidity and soil-water
influence the transpiration response of maize to CO2 enrichment. Canadian Journal of Plant Science
70(4):941-948.



     123  
Barrett, D.J., and R.M. Gifford. 1995. Acclimation of photosynthesis and growth by cotton to
elevated CO2: Interactions with severe phosphate deficiency and restricted rooting volume.
Australian Journal of Plant Physiology 22(6):955-963.

Acclimation of photosynthesis and growth at three CO2 concentrations (376, 652 and 935 mu mol
mol(-1)) was examined in cotton grown under three growth-limiting phosphate (P) supplies (2.1, 6.1
and 18.2 mg P plant(-1)) and where biomass allocation between roots and shoots was altered by pots
of three different sizes (0.32 X 10(-3), 0.72 X 10(-3) and 1.56 x 10(-3) m(3) pot(-1)). Phosphate
supplies were chosen such that carbon gain at ambient CO2 increased linearly with P supply. Relative
growth rates of these plants were 5-10-times less and photosynthetic rates 3-16-times less than for
cotton supplied with abundant nutrients. Pot sizes were chosen so that root biomass and root:shoot
ratios decreased with a decrease in rooting volume. Maximum carboxylation rates per unit leaf area
(V-cmax) were lower in leaves grown at two elevated CO2 concentrations, compared with ambient
CO2 concentrations, under all P and pot size treatments indicating that acclimation of photosynthesis
had occurred. The degree of photosynthetic acclimation to elevated CO2 was not related to the
degree by which whole plant carbon gain was stimulated by elevated CO2 concentration at the
different P supplies, or to the degree by which allocation to root and shoots was altered by pot size.
Thus there is no simple relationship between photosynthetic and growth acclimation by cotton to
elevated CO2. At ambient CO2, the maximum carboxylation rate increased linearly with an increase
in leaf P per unit area (mg P m(-2)), but rates were lower at elevated CO2 for a given P content m(-
2). V-cmax also increased linearly with an increase in leaf P concentration (mg P g(-1) structural dry
weight). However, values of V-cmax were similar for plants grown at ambient and elevated CO2, for
a given P concentration. Acclimation of photosynthesis at elevated CO2 was associated with an
increase in leaf starch determined 5 h into the light period. However, increased starch concentration
with an increase in P supply was not associated with any decline in V-cmax.

KEYWORDS: ACCUMULATION, ATMOSPHERIC CO2, CARBON DIOXIDE, GLYCINE-MAX,
LEAVES, LONG-TERM EXPOSURE, NITROGEN, PHOSPHORUS-NUTRITION, PLANTS,
RESPONSES


     124  
Barrett, D.J., and R.M. Gifford. 1995. Photosynthetic acclimation to elevated CO2 in relation to
biomass allocation in cotton. Journal of Biogeography 22(2-3):331-339.

Biomass allocation to leaf tissues and photosynthetic acclimation to CO2 by cotton were investigated
in two experiments. Plants were grown at ambient and elevated CO2 concentrations with growth
restricting phosphorus supplies in both experiments and in root restricting pot volumes in the first
experiment. In both experiments, elevated CO2 concentrations decreased the maximum carboxylation
rate (V- cmax) and the CO2 saturated rate of photosynthesis indicative of photosynthetic acclimation
to elevated CO2 concentrations. In the first experiment, the percentage reduction in V-cmax under
elevated CO2 concentration was least at a P supply of 2.1 mg P plant(-1), greatest at 6.1 mg P plant(-
1), but then decreased at 18.2 mg P plant(-1). The greater acclimation at the middle P supply was
associated with a higher ratio of leaf mass to plant mass (LMR) than in other treatments and the lesser
acclimation at the highest P treatment coincided with a lower LMR. In the second experiment the
reduction in V-cmax at elevated CO2 was less than in the first experiment but was also associated
with a greater allocation of dry matter to leaf tissues during growth. In both experiments, V-cmax
was not correlated to the relative degree of biomass enhancement at elevated CO2 nor with the
degree of root growth restriction in small pots. These data support the hypothesis that acclimation
of photosynthesis to elevated CO2 concentrations is mediated by shifts in allocation between leaves
and the rest of the plant, induced by environmental conditions during growth, such that carbohydrate
supply remains in balance with the utilization capacity of sink tissues.

KEYWORDS: ATMOSPHERIC CARBON-DIOXIDE, GAS-EXCHANGE, GROWTH, LEAVES,
LIMITATIONS, PLANTS, SOURCE-SINK RELATIONS


     125  
Barrett, D.J., and R.M. Gifford. 1999. Increased C-gain by an endemic Australian pasture grass
at elevated atmospheric CO2 concentration when supplied with non- labile inorganic phosphorus.
Australian Journal of Plant Physiology 26(5):443-451.

Limited phosphorus (P) availability in Australia's highly weathered soils may constrain an increase in
terrestrial net primary productivity (NPP) with the globally increasing atmospheric CO2
concentration. We examined whether an Australian temperate pasture grass (Danthonia richardsonii)
grown in sand culture and supplied solely with virtually insoluble Al- and Fe-phosphate was able to
increase C-gain when exposed to elevated (731 mu mol mol(-1)) compared with ambient (379 mu
mol mol(-1)) CO2 concentrations. When supplied with 8 mg kg(-1) insoluble P concentration, total
citrate efflux by root systems (mu mol h(-1)), plant P uptake, shoot photosynthesis rates and plant
mass were all significantly greater at elevated than at ambient CO2 after a growth period of between
55 and 63 days. In this treatment, although the P concentration of the rooting medium limited growth
at ambient CO2, elevated CO2 increased P-uptake from the non-labile source, increased
photosynthesis rates per unit shoot soluble-P and increased plant mass. At P concentrations lower
than 8 mg kg(-1), plant mass, specific citrate efflux and maximum leaf carboxylation rates were
limited by the amount of P available in the rooting medium and no CO2 effect was observed. In all
treatments, carbon supply did not appear to limit citrate efflux. Where an increase in P uptake at
elevated CO2 was achieved, it was due to an increase in root mass (indicative of a potentially larger
soil volume explored) rather than to increased specific rates of citrate efflux. Above 8 mg kg(-1), the
supplied P concentration was sufficient that minimal rates of specific citrate efflux alone solubilised
enough P for growth and a strong CO2 effect on plant mass, photosynthesis and P uptake was
observed.

KEYWORDS: ACCLIMATION, GROWTH, LIMITATIONS, LUPINUS-ALBUS, ORGANIC-ACIDS,
PHOSPHATE, PHOTOSYNTHESIS, PROTEOID ROOTS, ROOT EXUDATION,
SOLUBILIZATION


     126  
Barrett, D.J., A.E. Richardson, and R.M. Gifford. 1998. Elevated atmospheric CO2
concentrations increase wheat root phosphatase activity when growth is limited by phosphorus.
Australian Journal of Plant Physiology 25(1):87-93.

Wheat seedlings were grown in solution culture under adequate and limited phosphorus treatments
at current ambient and elevated (approximately 2X ambient) CO2 concentrations. Acid
phosphomonoesterase ('phosphatase') activity of root segments was measured using p-nitrophenyl
phosphate as substrate. When plant growth was P-limited, elevated CO2 concentrations increased
phosphatase activity more than at ambient CO2. This result (1) was evident when expressed on a unit
root dry weight or root length basis, indicating that increased root enzyme activity was unlikely to
be associated with CO2-induced changes in root morphology; (2) occurred when plants were grown
aseptically, indicating that the increase in phosphatase activity originated from root cells rather than
root-associated microorganisms; (3) was associated with shoot P concentrations below 0.18%; (4)
occurred only when wheat roots were grown under P deficiency but not when a transient P deficiency
was imposed; and (5) suggest that a previously reported increase in phosphatase activity at elevated
CO2 by an Australian native pasture grass (Gifford, Lutze and Barrett 1996; Plant and Soil 187, 369-
387) was also a root mediated response. The observed increase in phosphatase activity by plant roots
at elevated CO2, if confirmed for a wide range of field pasture and crop species, is one factor which
may increase mineralisation of soil organic P as the anthropogenic increase of atmospheric CO2
concentrations continues. But, whether a concomitant increase in plant uptake of P occurs will
depend on the relative influence of root and microbial phosphatases, and soil geochemistry in
determining the rate of mineralisation of soil organic P for any given soil.

KEYWORDS: ACCLIMATION, BIOMASS, CARBON DIOXIDE, DEFICIENCY, EFFICIENCY,
ENRICHMENT, ORGANIC PHOSPHORUS, PHOTOSYNTHESIS, PLANT-ROOTS, SOIL


     127  
Bartak, M., I. Nijs, and I. Impens. 1996. The effect of long-term exposure of Lolium perenne L
plants to elevated CO2 and/or elevated air temperature on quantum yield of photosystem 2 and net
photosynthesis. Photosynthetica 32(4):549-562.

The effects of long-term exposure of Lolium perenne L. plants to CO2 concentration elevated to 700
mu mol (CO2) mol(-1) (EC) and air temperature elevated by 4 degrees C (ET) on the quantum yield
of electron transport of photosystem 2, PS2 (phi(2)) and on the potential yield of photochemical
reactions of PS2 (F- v/F-m) measured by the chlorophyll (Chl) fluorescence method, were studied.
The plants were exposed for 6 months in opened field greenhouses to four treatments simulating
global atmospheric changes: (1) ambient CO2 (AC) and ambient air temperature, AT (ACAT -
control), (2) EC and AT (ECAT), (3) AC and ET (ACET), and (4) EC and ET (ECET). When the
plants were exposed to stepwise increased irradiance, a decrease in phi(2) was found under both AC
and EC measuring concentrations. At high irradiances a significantly higher yield of PS2 was detected
when measured under EC compared to AC regardless of long-term CO2 and temperature treatment
(i.e., positive short- term. effect of EC). The short-term effect of EC on phi(2) as related to net
photosynthetic rate (P-N) Shift was detected from irradiance response curves. At high irradiances and
AC, phi(2) was reduced in comparison to control for the plants of EC and ET treatments (i.e.,
negative long-term effect of treatment). The long-term effect of both EC and ET on the yield of PS2
was attributed to a down-regulation of P-N caused by the treatment. The phi(2) was related to the
actual rate of photosynthesis and the relationship between phi(2) and phi(CO2) was linear over a wide
range of irradiances. No effect of long- term treatments on the dark-adapted F-v/F-m ratio was found
in plants cultivated under natural greenhouse irradiance.

KEYWORDS: ATMOSPHERIC CARBON-DIOXIDE, DEPENDENCE, ELECTRON-TRANSPORT,
FLOW, GROWTH, LEAVES, LIGHT, REDUCTION, RESPONSES, RISING CO2


     128  
Bartak, M., I. Nijs, and I. Impens. 1998. The susceptibility of PS II of Lolium perenne to a sudden
fall in air temperature - response of plants grown in elevated CO2 and/or increased air temperature.
Environmental and Experimental Botany 39(1):85-95.

The effect of a sudden fall in air temperature from 20 to 5 degrees C on fast kinetics of chlorophyll
fluorescence, maximum yield of the photosystem II photochemical reactions (Fv/Fm), quantum yield
of the photosystem II electron transport (Phi(II)) coefficients of photochemical (qP), non-
photochemical quenching (qN) was studied in Lolium perenne using a modulated chlorophyll
fluorescence technique. Before fluorescence measurement, the plants were cultivated in the
treatments simulating the likely future climate characterized with elevated air temperature and CO2
concentration and combination of both. On fast kinetics curves the risetimes of the I and D points
characterizing the redox state of Q(A) were affected by lowering the air temperature. At 5 degrees
C both the I and D points were reached later than at 20 degrees C. Also the I to D risetime was
prolonged at 5 degrees C and it was found significantly longer in plants cultivated in ambient + 4
degrees C temperature. While a significant difference was found in the area over the rising part of the
fluorescence curve between 20 and 5 degrees C, no difference was found in area over the relaxation
curve part. Lowering of air temperature to 5 degrees C had no effect on Fv/Fm values in control
plants and in the plants cultivated in elevated CO2 but brought significant decrease in plants cultivated
in the ambient + 4 degrees C air temperature. Both Phi(II) and qP decreased with the temperature
lowered to 5 degrees C while the values of qN increased. The changes in fluorescence parameters
indicated altered functioning of PS II at low temperature. The changes in parameters are discussed
as a consequense of decreased enzymatic activity, decreased turnover of plastoquinone pool and
photoinhibition. (C) 1998 Elsevier Science B.V. All rights reserved.

KEYWORDS: CARBON DIOXIDE, CENTERS, CHLOROPHYLL FLUORESCENCE, LEAVES,
PHOTOINHIBITION, PHOTOSYNTHESIS, PHOTOSYSTEM, QUANTUM YIELD, SENSITIVITY,
VIOLAXANTHIN DEEPOXIDATION


     129  
Barton, C.V.M., and P.G. Jarvis. 1999. Growth response of branches of Picea sitchensis to four
years exposure to elevated atmospheric carbon dioxide concentration. New Phytologist 144(2):233-
243.

Branch bags were used to expose branches on mature Sitka spruce trees to either ambient [CO2] (A)
or elevated [CO2] (E) for 4 yr. This paper reports the effects of this treatment on the growth,
development and phenology of the branches, including shoot expansion, shoot numbers, needle
dimensions, needle numbers and stomatal density. The effect of elevated [CO2] on the relationship
between leaf area and sapwood area was investigated. Exposure to elevated [CO2] doubled
photosynthetic rates in current-fear shoots and, despite some downregulation, 1-yr-old E shoots also
had higher rates of photosynthesis than their A counterparts. Thus, the amount of assimilate fixed by
E branches was substantially more than that fixed by A branches; hen-ever, this increase in the local
production of assimilate did not lead to an increase in non-structural carbohydrate or stimulate
growth or meristematic activity within the E branches. There was a very consistent relationship
between leaf area and stem cross-sectional area that was not influenced by [CO2]. However,
unbagged branches had thicker stems than bagged branches, resulting in a slightly lower ratio of leaf
area to cross-sectional area. The implications of the results for the modelling of growth and allocation
and the potential utility of the branch bag technique are discussed.

KEYWORDS: ALLOCATION, ASSIMILATION, CO2- ENRICHMENT, MORPHOLOGY,
NUTRITION, PHOTOSYNTHETIC ACCLIMATION, PINE, RESISTANCE, STOMATAL
CONDUCTANCE, TREES


     130  
Barton, C.V.M., H.S.J. Lee, and P.G. Jarvis. 1993. A branch bag and co2 control-system for long-
term co2 enrichment of mature sitka spruce [picea-sitchensis (bong) carr]. Plant, Cell and
Environment 16(9):1139-1148.

This paper describes the construction and performance of branch bags and a CO2 control system used
to fumigate branches of mature Sitka spruce trees with air enriched in CO2 (700 mu mol mol(-1)).
It contains some examples of results obtained using the system over the course of the first two
growing seasons. The branch bags have run continuously for 2 years with very few problems. CO2
concentrations were within 20 mu mol mol(-1) of the target concentration for more than 90% of the
time. Temperatures within the bags were slightly higher than ambient (1-2 degrees C) and this had
some effect on phenology. Attenuation of quantum flux density (photosynthetically active radiation)
was 10-15%. The branch bag system has enabled investigation into the effects of elevated CO2 on
mature tissue without the problems and expense of fumigating whole trees. Growth in elevated CO2
resulted in an increase in starch and a decrease in soluble protein content of needles. Stomatal
conductance was higher in elevated CO2 grown needles, and there was some evidence of an increase
in photosynthetic capacity.

KEYWORDS: TREES


     131  
Basile, G., M. Arienzo, and A. Zena. 1993. Soil nutrient mobility in response to irrigation with
carbon- dioxide enriched water. Communications in Soil Science and Plant Analysis 24(11-
12):1183-1195.

In our experiments, carbonated water (CW) modified the equilibria in soil. Application of CW
decreased the soil pH about 1.5 units one hour after irrigation ended. Minimal, though well defined,
differences in soil pH were observed between the two carbonated treatments. The same relationship
between the treatments was not found in pH levels of the leachate. This seems strictly related to the
temporal and spatial changes in the carbon dioxide (CO2) acidifying effect caused by chemical and
biological factors as water descended the soil column. The temporary reduction in soil pH in the CW
treatment induced the highest nutrient mobility for most of the elements.

KEYWORDS: CO2


     132  
BassiriRad, H., K.L. Griffin, J.F. Reynolds, and B.R. Strain. 1997. Changes in root NH4+ and
NO3- absorption rates of loblolly and ponderosa pine in response to CO2 enrichment. Plant and Soil
190(1):1-9.

Root growth and physiological uptake capacity for NH4+ and NO3- were examined for seedlings of
loblolly and ponderosa pine grown for 160 days under two CO2 levels, ambient (35 Pa) and ambient
plus 35 Pa (70 Pa). Fraction of biomass allocated to active fine roots as well as total N (NH4+ +
NO3-) absorption per unit root dry mass were unaffected by CO2. On a whole-plant basis, elevated
CO2 led to a significant increase in N acquisition in loblolly but not in ponderosa pine. However, even
in loblolly pine where CO2 significantly increased plant N acquisition, the relative increase, in biomass
far exceeded the gain in N, i.e. a 60% increase in total dry weight was accompanied by only a 30%
increase in N gain in response to high CO2. We suggest that the commonly reported decline in tissue
N concentration of these and other species at high CO2 is largely caused by inability of the root
systems to sufficiently compensate for increased N demand. Elevated CO2 significantly altered root
uptake capacity of the different N forms, i.e., high CO2 significantly increased NO3- absorption rates,
but decreased NH4+ absorption rates in both species though the decrease in loblolly was insignificant.
However, elevated CO2 increased root respiration rate in loblolly pine while significantly decreasing
it in ponderosa pine. This indicates that CO2-induced changes in plant preference for inorganic N
forms is not simply regulated by root energy status. If changes in plant preference for inorganic N
forms represent typical responses to elevated CO2, the results could have important implications for
N dynamics in managed and natural plant communities.

KEYWORDS: AMMONIUM, AVAILABILITY, BARLEY, CARBON DIOXIDE, ELEVATED
ATMOSPHERIC CO2, GROWTH, L SEEDLINGS, NITRATE ABSORPTION, NITROGEN
CONCENTRATION, PLANT NUTRITION


     133  
Bassirirad, H., K.L. Griffin, B.R. Strain, and J.F. Reynolds. 1996. Effects of CO2 enrichment
on growth and root (NH4+)-N-15 uptake rate of loblolly pine and ponderosa pine seedlings. Tree
Physiology 16(11-12):957-962.

We examined changes in root growth and (NH4+)-N-15 uptake capacity of loblolly pine (Pinus taeda
L.) and ponderosa pine (Pinus ponderosa Douglas. Ex Laws.) seedlings that were grown in pots in
a phytotron at CO2 partial pressures of 35 or 70 Pa with NH4+ as the sole N source. Kinetics of N-
15-labeled NH4+ uptake were determined in excised roots, whereas total NH4+ uptake and uptake
rates were determined in intact root systems following a 48-h labeling of intact seedlings with N-15.
In both species, the elevated CO2 treatment caused a significant downregulation of (NH4+)-N-15
uptake capacity in excised roots as a result of a severe inhibition of the maximum rate of root
(NH4+)-N-15 uptake (V-max). Rates of (NH4+)-N-15 uptake in intact roots were, however,
unaffected by CO2 treatment and were on average 4- to 10-fold less than the V-max in excised roots,
suggesting that (NH4+)-N-15 absorption from the soil was not limited by the kinetics of root
(NH4+)-N-15 uptake. Despite the lack of a CO2 effect on intact root absorption rates, (NH4+)-N-15
uptake on a per plant basis was enhanced at high CO2 concentrations in both species, with the relative
increase being markedly higher in ponderosa pine than in loblolly pine. High CO2 concentration
increased total (NH4+)-N-15 uptake and the fraction of total biomass allocated to fine roots (< 2 mm
in diameter) to a similar relative extent. We suggest that the increased uptake on a per plant basis in
response to CO2 enrichment is largely the result of a compensatory increase in root absorbing
surfaces.

KEYWORDS: AMMONIUM, CARBON-DIOXIDE CONCENTRATION, DRY-MATTER,
ELEVATED CO2, LIMITATION, NITROGEN, NUTRITION, PHOTOSYNTHESIS, PLANTS,
RESPONSES


     134  
Bassirirad, H., J.F. Reynolds, R.A. Virginia, and M.H. Brunelle. 1997. Growth and root NO3-
and PO43- uptake capacity of three desert species in response to atmospheric CO2 enrichment.
Australian Journal of Plant Physiology 24(3):353-358.

In a phytotron experiment, we examined growth and rates of NO3- and PO43- uptake in seedlings
of two desert C-3 shrubs (Larrea tridentata and Prosopis glandulosa) and a desert C-4 perennial grass
(Bouteloua eriopoda) grown under CO2 partial pressures of 35 or 70 Pa. Plants were grown in soil
but uptake studies were conducted on roots of intact seedlings placed in nutrient solutions containing
both NO3- and PO43-. Elevated CO2 increased total biomass by 69 and 55% in Larrea and Prosopis
seedlings and by 25% in Bouteloua. NO3- and PO43- uptake rates were more than doubled in
Bouteloua at high compared to ambient CO2. In contrast, CO2 enrichment inhibited root NO3-
uptake capacity in Larrea by about 55% without a significant effect on PO43- absorption rate; rates
of NO3- and PO43- and uptake in Prosopis were insensitive to CO2 treatment. Elevated CO2
enhanced the proportion of biomass allocated to the fine roots in Bouteloua but markedly reduced
this fraction in Larrea and Prosopis. Foliar N concentration of both shrubs decreased in response to
elevated CO2, but was unaffected in Bouteloua. We suggest that compensatory changes in root size
and activity are critical in determining interspecies variation in plant nutrient relations under high
CO2.

KEYWORDS: CARBON DIOXIDE, COMPETITION, DRY-MATTER, ELEVATED CO2, MINERAL
NUTRITION, NITROGEN, PHOSPHATE, PLANTS, RHIZOSPHERE, SEEDLINGS


     135  
Bassirirad, H., R.B. Thomas, J.F. Reynolds, and B.R. Strain. 1996. Differential responses of root
uptake kinetics of NH4+ and NO3- to enriched atmospheric CO2 concentration in field-grown
loblolly pine. Plant, Cell and Environment 19(3):367-371.

The nitrogen requirement of plants is predominantly supplied by NH4+ and/or NO3- from the soil
solution, but the energetic cost of uptake and assimilation is generally higher for NO3- than for
NH4+. We found that CO2 enrichment of the atmosphere enhanced the root uptake capacity for
NO3-, but not for NH4+, in field-grown loblolly pine saplings. Increased preference for NO3- at the
elevated CO2 concentration was accompanied by increased carbohydrate levels in roots. The results
have important implications for the potential consequences of global climate change on plant- and
ecosystem-level processes in many temperate forest ecosystems.

KEYWORDS: ABSORPTION, AMMONIUM, ASSIMILATION, BARLEY, FLUXES, FORESTS,
PLANTS, RESPIRATION


     136  
Bassirirad, H., D.T. Tissue, J.F. Reynolds, and F.S. Chapin. 1996. Response of Eriophorum
vaginatum to CO2 enrichment at different soil temperatures: Effects on growth, root respiration and
PO43- uptake kinetics. New Phytologist 133(3):423-430.

In a phytotron experiment, we examined responses of a tussock sedge, Eriophorum vaginatum L.,
to changes in atmospheric CO2 concentration and soil temperature. We were particularly interested
in phosphorus (P) acquisition and below ground plant characteristics that regulated its uptake in
response to CO2 enrichment. Plants were grown at two CO2 partial pressures, 35 and 70 Pa, three
soil temperature regimes, 5, 15 and 25 degrees C and a constant ambient air temperature of 15
degrees C. Elevated CO2 increased total plant biomass production, but decreased tissue P
concentration. Although high CO2 enhanced root carbohydrate concentration, it inhibited root
respiration with no significant effect on root PO43- absorption capacity or root:shoot ratio.
Surprisingly, there were no significant interactions between CO2 and soil temperature. The inability
of Eriophorum to exhibit root-level compensatory adjustments, e.g. increased root:shoot ratio or
PO43- absorption capacity, was largely responsible for the observed decline in tissue P concentration
under elevated CO2 conditions. This could ultimately limit longterm growth responses of Eriophorum
to CO2 enrichment in the field where P availability is limiting. We found that uptake of PO43- in
response to elevated CO2 was independent of changes in root respiration, but changes in root
respiration could have important implications for ecosystem carbon budget under elevated CO2
levels. Our data indicated that although root respiration on a per unit biomass basis declined in
response to CO2 enrichment, this effect was counterbalanced by increased root biomass, so that high
CO2 stimulated root respiration on a whole-plant basis by 30%. This might help to explain why long-
term exposure to high CO2 increases CO2 efflux from Eriophorum-dominated ecosystems.

KEYWORDS: ALASKAN TUSSOCK TUNDRA, CARBON DIOXIDE, ECOSYSTEMS, ELEVATED
CO2, NITROGEN, NUTRIENT ACQUISITION, NUTRITION, PHOSPHATE ABSORPTION,
PHOTOSYNTHESIS, PLANTS


     137  
Bassman, J.H., and J.C. Zwier. 1991. Gas-exchange characteristics of Populus trichocarpa,
Populus  deltoides and Populus trichocarpa X Populus deltoides clones. Tree Physiology 8(2):145-
159.

Responses of net photosynthesis, dark respiration, photorespiration, transpiration, and stomatal
conductance to irradiance, temperature, leaf-to-air vapor density difference (VDD), and plant water
stress were examined in two Populus trichocarpa clones (one from a moist, coastal climate in western
Washington and one from a dry, continental climate in eastern Washington), one P. deltoides clone,
and two P. trichocarpa x P. deltoides clones. Light saturation of photosynthesis in greenhouse-grown
trees occurred at about 800- mu-mol m-2 s-1 for P. deltoides, P. trichocarpa x P. deltoides, and the
eastern Washington ecotype of P. trichocarpa, but at about 600-mu-mol m-2 s-1 for the western
Washington ecotype of P. trichocarpa. Average net photosynthesis (at saturating irradiance and the
optimum temperature of 25-degrees-C) was 20.7, 18.8, 18.2 and 13.4-mu-mol CO2 m-2 s-1 for P.
deltoides, P. trichocarpa x P. deltoides, and the eastern and western Washington clones of P.
trichocarpa, respectively. In all clones, net photosynthesis decreased about 14% as VDD increased
from 3 to 18 g H2O m-3. Stomatal conductance decreased sharply with decreasing xylem pressure
potential (XPP) in all clones except the western Washington clone of P. trichocarpa. Stomata in this
clone were insensitive to changes in XPP and did not control water loss. Complete stomatal closure
(stomatal conductance < 0.05 cm s-1) occurred at about -2.0 MPa in the eastern Washington clone
of P. trichocarpa and around -1.25 MPa in the P. deltoides and P. trichocarpa x P. deltoides clones.
Transpiration rates were highest in the P. trichocarpa x P. deltoides clone and lowest in the western
Washington clone of P. trichocarpa. The P. deltoides clone and eastern Washington clone of P.
trichocarpa had the highest water use efficiency (WUE) and the western Washington clone of P.
trichocarpa had the lowest WUE. The hybrids were intermediate. It was concluded that: (1) gas
exchange characteristics of eastern and western Washington clones of P. trichocarpa reflected
adaptation to their native environment; (2) crossing the western Washington clone of P. trichocarpa
with the more drought resistant P. deltoides clone produced plants better adapted to the interior
Pacific Northwest climate, although the stomatal response to soil water deficits in the hybrid was
conservative compared with that of the eastern Washington clone of P. trichocarpa; and (3)
introducing eastern Washington clones of black cottonwood into breeding programs is likely to yield
lines with favorable growth characteristics combined with enhanced WUE and adaptation to soil
water deficits.



     138  
Bassow, S.L., K.D.M. McConnaughay, and F.A. Bazzaz. 1994. The response of temperate tree
seedlings grown in elevated co2 to extreme temperature events. Ecological Applications 4(3):593-
603.

Mean global temperatures have been predicted to increase in the next century, if so the frequency of
extreme temperature events may also increase. Extreme temperatures may damage plant tissue and
consequently limit the survival of certain plant species in a region. Elevated concentrations of CO2
in the atmosphere alter plant allocation, physiology, and growth, and may accentuate or ameliorate
the damage from extreme temperatures. In this paper we explore the interactive effects of
atmospheric CO2 concentration, nutrient levels, and exposure to extreme temperatures on seedlings
of three species of temperate deciduous trees. A1-d exposure to extreme heat (45-degrees-C)
significantly decreased conductance the following day and decreased biomass as measured at both
35 and 105 d following the extreme temperature event, regardless of atmospheric CO2 concentration.
The most shade-tolerant species, striped maple, was most severely impacted by the extreme heat
event in both CO2 environments. Furthermore, striped maple seedlings grown in elevated CO2
concentrations had a significantly greater decrease in biomass due to the extreme heat event as
compared with striped maple plants grown in ambient CO2 concentrations at 35 d after the heat
event; however, al the end of the growing season at 105 d post treatment, this difference was not
significant. A one-night exposure to low temperatures (4- degrees-C) did not affect biomass for any
of these species. With an increase in global mean temperatures, the frequency of extreme temperature
events, particularly hot weather events, may increase and may extend to shaded understory sites. If
the frequency of extremely high temperatures increases, the role that temperature extremes may play
in changing competitive interactions and thus affecting community composition may increase in
importance, as these temperatures appear to severely alter plant survival and growth in some species.

KEYWORDS: ATMOSPHERIC CO2, CLIMATE, ECOSYSTEMS, ENRICHMENT, FOLIAGE
TEMPERATURE, HEAT-SHOCK PROTEINS, NIGHT TEMPERATURE, PLANTS,
THERMOTOLERANCE, VARIABILITY


     139  
Batjes, N.H. 1998. Mitigation of atmospheric CO2 concentrations by increased carbon sequestration
in the soil. Biology and Fertility of Soils 27(3):230-235.

The International Panel on Climate Change distinguished three main options for the mitigation of
atmospheric CO2 concentrations by the agricultural sector: (1) reduction of agriculture-related
emissions, (2) creation and strengthening of C sinks in the soil, and (3) production of biofuels to
replace fossil fuels. Options for sustained sequestration of C in the soil through adapted management
of land resources are reviewed in the context of the ongoing discussion on the need to reduce
greenhouse gas concentrations in the atmosphere. Enhanced sequestration of atmospheric CO2 in the
soil, ultimately as stable humus, may well prove a more lasting solution than (temporarily)
sequestering CO2 in the standing biomass through reforestation and afforestation. Such actions will
also help to reverse processes of land degradation, thus contributing to sustained food productivity
and security for the people in the regions concerned.

KEYWORDS: C STORAGE, CYCLE, DECOMPOSITION, ELEVATED CO2, FERTILIZATION,
MANAGEMENT, NITROGEN, ORGANIC-MATTER, TURNOVER, WORLD


     140  
Battaglia, M., and P.J. Sands. 1998. Process-based forest productivity models and their application
in forest management. Forest Ecology and Management 102(1):13-32.

Few process-based forest productivity models have become incorporated into forest management
systems. The prevalent perception is that process-based models are suited only for research
applications and that management questions will be solved only by using descriptive empirical models.
This is despite the fact that the latter can neither deal satisfactorily with changing environmental and
management conditions nor answer all questions currently asked by managers. This paper develops
the proposition that the end-use specifies the design and scale of forest simulation models, and that
given the range of questions now asked in forest management a range of models is required. The
spatial and temporal resolution, and the input and output data required to address typical forest
management questions is examined. A survey of recent literature examines in which areas, and by
whom, existing forest productivity models are being applied. It is concluded that many current
management questions can be adequately answered using models in which a phenomenological
approach is applied to predict annual forest growth at the stand-scale. Lumped-parameter process-
based models and hybrid models provide the most immediate means through which our understanding
of the biological processes underlying forest growth can be included in forest management systems.
However, more detailed process-based models can Flay an important role in validating simpler
models, in the development of generalizations applicable over long time scales and for testing
hypotheses about the way trees function and respond to interacting stresses. Guidelines are also given
on model structures appropriate for different classes of management questions. (C) 1998 Elsevier
Science B.V.

KEYWORDS: DECISION-SUPPORT SYSTEMS, DOUGLAS-FIR, DRY-MATTER
ACCUMULATION, ELEVATED CO2, GROWTH-MODELS, ORIENTED GROWTH, PINUS-
RADIATA, SITE INDEX, SPRUCE, YIELD


     141  
Batts, G.R., R.H. Ellis, J.I.L. Morison, and P. Hadley. 1998. Canopy development and tillering
of field-grown crops of two contrasting cultivars of winter wheat (Triticum aestivum) in response to
CO2 and temperature. Annals of Applied Biology 133(1):101-109.

Elevated CO2 (691 cf. 371 mu mol CO2 mol(-1) air) and warmer temperatures (over the range 1.0
degrees C below to 1.6 degrees C above ambient) increased light interception by crops of two
contrasting cultivars (Hereward and Soissons) of winter wheat (Triticum aestivum L.) during winter
growth in the field. The fractional interception of light by the canopy increased more rapidly initially
in Soissons than in Hereward, but Hereward showed a much greater response to CO2 (35% increase
in Hereward but only 7% in Soissons) at 500 degrees Cd after sowing. By terminal spikelet
formation, in contrast, fractional interception was greater in Hereward than in Soissons, while the
effect of CO2 was the same in both cultivars (9%). Thus, although differences in the relative response
of canopy development to CO2 were detected between cultivars initially, differences were negligible
during later development. The greater interception of light by the canopy in elevated CO2, at any one
temperature, resulted from increased tillering. The number of tillers plant(-1) at terminal spikelet was
a linear function of main stem dry mass at this developmental stage but with a greater response in
elevated CO2, viz 2.3 and 3.8 tillers g(-1) main stem dry mass at 371 and 691 mu mol CO2 mol(-1)
air, respectively; these relations were unaffected by cultivar.

KEYWORDS: YIELD


     142  
Batts, G.R., R.H. Ellis, J.I.L. Morison, P.N. Nkemka, P.J. Gregory, and P. Hadley. 1998. Yield
and partitioning in crops of contrasting cultivars of winter wheat in response to CO2 and temperature
in field studies using temperature gradient tunnels. Journal of Agricultural Science 130:17-27.

Diverse cultivars of winter wheat (Triticum aestivum L.) were grown in the field in 1993/94 and
1994/95 at Reading UK in temperature gradient tunnels at normal atmospheric (c. 370) or elevated
CO2 concentration (c. 700 mu mol CO2 mol(-1) air). In 1993/94, grain yield of cv. Avalon was
insensitive to mean temperature (between 8.8 and 10.9 degrees C), while elevated CO2 increased
yield by 1.3 t ha(-1) (12.6%). In all other cultivars, warming reduced grain yield and CO2 increased
grain yield. In 1993/94, in cvs Galahad and Mercia the effects of CO2 and temperature on yield were
additive. However, for cv. Hereward in both years and for cv. Soissons in 1994/95, there were
negative interactions between the effects of CO2 and temperature on yield: the maximum benefit of
doubling CO2 to grain yield, 4.5 and 2.7 t ha(-1) (65 and 29%) respectively, occurred at cooler
temperatures; there was no benefit from doubling CO2 (i.e. 0%) once the temperature had increased
above the seasonal mean by 2.2-2.6 degrees C in cv. Hereward and by 1.3 degrees C in cv. Soissons.
The beneficial effect of doubling CO2 on grain yield in cvs Galahad, Hereward, Mercia and Soissons
was negated by an increase in mean seasonal temperature of only 0.7-2.0 degrees C. Warming
decreased root dry mass at anthesis in 1994/95 while it increased at elevated CO2 (49 and 186%,
coolest and warmest regime, respectively). Carbon partitioned to roots declined progressively with
warming, while at elevated CO2 there was an average of 56% increase in allocation to roots. The
relative impacts of both CO2 and temperature were greater on root dry mass than on either grain
yield or total above-ground biomass, while the effects on grain and biomass yield varied considerably
between cultivars, suggesting that the impact of rising CO2 and temperature are likely to be
dependent on cultivar.

KEYWORDS: CARBON DIOXIDE, DURATION, ENRICHMENT, NITROGEN,
PHOTOSYNTHESIS, PLANT-RESPONSES, PRODUCTIVITY, ROOT-GROWTH, SYSTEM,
TRITICUM-AESTIVUM CROPS


     143  
Batts, G.R., J.I.L. Morison, R.H. Ellis, P. Hadley, and T.R. Wheeler. 1997. Effects of CO2 and
temperature on growth and yield of crops of winter wheat over four seasons. European Journal of
Agronomy 7(1-3):43-52.

Crops of winter wheat (Triticum aestivum L. cv. Hereward) were grown in the field in four
consecutive seasons from 1991/1992 to 1994/1995 at Reading, UK, within polyethylene-covered
tunnels along which a temperature gradient was superimposed on the ambient temperature variation
at normal atmospheric (ca. 370) or an increased [CO2] (ca. 700 mu mol CO2 mol(-1) air), producing
many environments from one sowing date in each season at one location. Mean seasonal temperatures
varied by up to 4 degrees C along the temperature gradient. Increased [CO2] had no effect on crop
duration, or on the rate of reproductive development, which had the same temperature sensitivity
across all years, A 2 degrees C warming, on the 4-year ambient mean temperature (10 degrees C),
reduced crop duration by 42 days (from 254), and reduced the reproductive phase by 16 days (from
130). Crop biomass generally declined with increase in mean temperature, and was greater at
increased [CO2], with the effect of increased [CO2] varying with temperature and between years (6-
34% range in relative stimulation by increased [CO2]). Grain yield was substantially reduced by
warmer temperatures, and increased by doubling [CO2], but the effect varied greatly between pears
and with temperature (7-168% range). There were both positive and negative interactions of
temperature and increased [CO2] on biomass and grain yield. In all 4 years, the increase in grain yield
from doubling [CO2] was negated by an increase in mean seasonal temperature of only 1.0-2.0
degrees C, Year-to-year variation in the responses of biomass and grain yield to [CO2] and
temperature resulted from differences in environmental conditions, influencing biomass partitioning
and altering the role of different yield components. (C) 1997 Elsevier Science B.V.

KEYWORDS: CARBON DIOXIDE, DURATION, ELEVATED CO2, FIELD, MODEL,
PRODUCTIVITY, RESPONSES, TRITICUM-AESTIVUM CROPS, VARIABILITY


     144  
Batts, G.R., T.R. Wheeler, J.I.L. Morison, R.H. Ellis, and P. Hadley. 1996. Developmental and
tillering responses of winter wheat (Triticum aestivum) crops to CO2 and temperature. Journal of
Agricultural Science 127:23-35.

Winter wheat (Triticum aestivum L., cv. Hereward) was grown in the held within four double-walled
polyethylene-covered tunnels along which near-linear temperature gradients were imposed at normal
atmospheric or at an elevated CO2 concentration (c. 700 mu mol mol(-1) CO2) in 1991/92 and in a
further experiment in 1992/93. Development was more rapid the warmer the temperature. In 1991/92
an increase in mean seasonal temperature of 3.5 degrees C reduced the duration from sowing to
harvest maturity (the stage when grain moisture content reduced naturally to 15- 18%) by c. 38 days,
and reduced the duration from the double ridge stage to harvest maturity by c. 34 days. A similar
difference resulted from only 1.6 degrees C warming in 1992/93. Although the range of mean
seasonal temperatures differed between years, the relation between temperature and rate of
development from sowing to harvest maturity was common to both years (base temperature, -0.8
degrees C; thermal time 2410 degrees C d). Carbon dioxide concentration had no effect on this
relation or on that between temperature and the rate of development from solving to the double ridge
stage and from the double ridge stage to harvest maturity. Carbon dioxide enrichment increased
tillering substantially in 1991/92; there were 200 more shoots m(-2) at terminal spikelet formation in
crops grown at elevated compared to normal CO2 (additional shoots were principally coleoptile tillers
and those developing after tiller 2) and this difference was reduced to 100 shoots m(-2) approaching
harvest maturity (additional shoots remaining were those developing after tiller 2). In contrast, no
effect of CO2 enrichment on tillering was detected at any stage of development in 1992/93. The
number of tillers per plant at terminal spikelet formation was a linear function of main stem dry weight
at this developmental stage; this relationship was not affected by year or CO2. As CO2 enrichment
increased main stem dry weight in the first year only, when main stem dry weights at normal CO2
were only one half of those values determined in the following year, it is concluded that any benefit
of increase in CO2 concentration to tillering in winter wheat may be greatest in those crop production
environments where main stem dry weights at terminal spikelet are least and vice versa.

KEYWORDS: CARBON-DIOXIDE ENRICHMENT, ELEVATED CO2, ENVIRONMENT, FIELD,
GROWTH, IMPACT, INITIATION, LEAF APPEARANCE, SENSITIVITY, YIELD


     145  
Bawa, K.S., and S. Dayanandan. 1998. Global climate change and tropical forest genetic resources.
Climatic Change 39(2-3):473-485.

Global climate change may have a serious impact on genetic resources in tropical forest trees. Genetic
diversity plays a critical role in the survival of populations in rapidly changing environments.
Furthermore, most tropical plant species are known to have unique ecological niches, and therefore
changes in climate may directly affect the distribution of biomes, ecosystems, and constituent species.
Climate change may also indirectly affect plant genetic resources through effects on phenology,
breeding systems, and plant-pollinator and plant seed disperser interactions, and may reduce genetic
diversity and reproductive output. As a consequence, population densities may be reduced leading
to reduction in genetic diversity through genetic drift and inbreeding. Tropical forest plants may
respond to climate change through phenotypic plasticity, adaptive evolution, migration to suitable
site, or extinction. However, the potential to respond is limited by a rapid pace of change and the non-
availability of alternate habitats due to past and present trends of deforestation. Thus climate change
may result in extinction of many populations and species. Our ability to estimate the precise response
of tropical forest ecosystems to climate change is limited by lack of long-term data on parameters that
might be affected by climate change. Collection of correlative data from long-term monitoring of
climate as well as population and community responses at selected sites offer the most cost-effective
way to understand the effects of climate change on tropical tree populations. However, mitigation
strategies need to be implemented immediately. Because many effects of climate change may be
similar to the effects of habitat alteration and fragmentation, protected areas and buffer zones should
be enlarged, with an emphasis on connectivity among conserved landscapes. Taxa that are likely to
become extinct should be identified and protected through at situ conservation programs.

KEYWORDS: CARBON DIOXIDE, CO2- ENRICHMENT, DRY FOREST, ELEVATED CO2,
INCOMPATIBILITY, PHENOLOGY, PLANT, RESPONSES, SYSTEMS, TREES


     146  
Baxter, R., T.W. Ashenden, and J.F. Farrar. 1997. Effect of elevated CO2 and nutrient status on
growth, dry matter partitioning and nutrient content of Poa alpina var vivipara L. Journal of
Experimental Botany 48(312):1477-1486.

Poa alpina var, vivipara L, was grown in an atmosphere containing either 340 or 680 mu mol CO2
mol(-1) within controlled environment chambers, The available nutrient regime was varied by altering
the supply of nitrogen and phosphorus within a complete nutrient solution, At a high, but not low,
N and P supply regime, elevated CO2 markedly increased growth, Differences between nutrient
supply, but not atmospheric CO2 concentration, altered the allometric relations between root and
shoot, Net photosynthesis of mature leaf blades and leaf N and P concentration were reduced in
plants grown at the elevated CO, concentration, The question was asked: is it possible to ascribe all
of these effects to elevated CO2 or are some due to nutrient deficiency caused by dilution with excess
carbon? Several criteria, including the nutrient content of sink tissue, root:shoot allometry and the
use of divalent cations to estimate integrated water flows are suggested in order to make this
distinction, It is concluded that only at a low supply of N and P, and elevated CO2 concentration, was
low leaf N concentration due to induced nutrient deficiency, The data are consistent with a model
where the capacity of sinks to use photosynthetically assimilated carbon sets both the rate of import
into those sinks (and thus rate of export from source leaves) and the rate of photosynthesis of source
leaves themselves.

KEYWORDS: ALLOCATION, ANTISENSE RBCS, ATMOSPHERIC CARBON-DIOXIDE,
NITROGEN, PHOSPHATE STATUS, PHOSPHORUS, PHOTOSYNTHESIS, RESPONSES,
RIBULOSE-1;5-BISPHOSPHATE CARBOXYLASE-OXYGENASE, TOBACCO


     147  
Baxter, R., T.W. Ashenden, T.H. Sparks, and J.F. Farrar. 1994. Effects of elevated carbon-
dioxide on 3 montane grass species .1. Growth and dry-matter partitioning. Journal of Experimental
Botany 45(272):305-315.

Upland grasslands are a major component of natural vegetation within the UK. Such grasslands
support slow growing relatively stable plant communities. The response of native montane grass
species to elevated atmospheric carbon dioxide concentrations has received little attention to date.
Of such studies, most have only focused on short-term (days to weeks) responses, often under
favourable controlled environment conditions. In this study Agrostis capillaris L.(5), Festuca vivipara
L. and Poa alpina L. were grown under semi-natural conditions in outdoor open-top chambers at
either ambient (340 mu mol mol(- 1)) or elevated (680 mu mol mol(-1)) concentrations of
atmospheric carbon dioxide (CO2) for periods from 79 to 189 d, with a nutrient availability similar
to that of montane Agrostis-Fescue grassland in Snowdonia, N. Wales. Whole plant dry weight was
increased for A. capillaris and P. alpina, but decreased for F. vivipara, at elevated CO2. Major
components of relative growth rate (RGR) contributing to this change at elevated CO2 were transient
changes in specific leaf area (SLA) and leaf area ratio (LAR). Despite changes in growth rate at 680
mu mol mol(-1) CO2, partitioning of dry weight between shoot and root in plants of A. capillaris and
P. alpina was unaltered. There was a significant decrease in shoot relative to root growth at elevated
CO2 in F. vivipara which also showed marked discoloration of the leaves and increased senescence
of the foliage.

KEYWORDS: ATMOSPHERIC CO2, CO2- ENRICHMENT, COMMUNITIES, EXPOSURE,
PHOTOSYNTHESIS, PLANTS, RESPIRATION, SENESCENCE, STRESS, TEMPERATURE


     148  
Baxter, R., S.A. Bell, T.H. Sparks, T.W. Ashenden, and J.F. Farrar. 1995. Effects of elevated
co2 concentrations on 3 montane grass species .3. Source leaf metabolism and whole-plant carbon
partitioning. Journal of Experimental Botany 46(289):917-929.

Agrostis capillaris L.(5), Festuca vivipara L. and Poa alpina L. were grown in outdoor open-top
chambers at either ambient (340 +/- 3 mu mol mol(-1)) or elevated (680 +/- 4 mu mol mol(- 1))
concentrations of atmospheric carbon dioxide (GO,) for periods from 79-189 d. Photosynthetic
capacity of source leaves of plants grown at both ambient and elevated CO2 concentrations was
measured at saturating light and 5% CO2. Dark respiration of leaves was measured using a liquid
phase oxygen electrode with the buffer solution in equilibrium with air (21% O-2, 0.034% CO2).
Photosynthetic capacity of P. alpina was reduced by growth at 680 mu mol mol(-1) CO2 by 105 d,
and that of F. vivipara was reduced at 65 d and 189 d after CO2 enrichment began, suggesting down-
regulation or acclimation. Dark respiration of successive leaf blades of all three species was unaltered
by growth at 680 relative to 340 mu mol mol(-1) CO2. In F. vivipara, leaf respiration rate was
markedly lower at 189 d than at either 0 d or 65 d, irrespective of growth CO2 concentration. There
was a significantly lower total non- structural carbohydrate (TNC) concentration in the leaf blades
and leaf sheaths of A. capillaris grown at 680 mu mol mol(-1) CO2. TNC of roots of A. capillaris was
unaltered by CO2 treatment. TNC concentration was increased in both leaves and sheaths of P. alpina
and F. vivipara after 105 d and 65 d growth, respectively. A 4-fold increase in the water-soluble
fraction (fructan) in P. alpina and in all carbohydrate fractions in F. vivipara accounted for the
increased TNC content. In F. vivipara the relationship between leaf photosynthetic capacity and leaf
carbohydrate concentration was such that there was a strong positive correlation between
photosynthetic capacity and total leaf N concentration (expressed on a per unit structural dry weight
basis), and total nitrogen concentration of successive mature leaves reduced with time, Multiple
regression of leaf photosynthetic capacity upon leaf nitrogen and carbohydrate concentrations further
confirmed that leaf photosynthetic capacity was mainly determined by leaf N concentration. In P.
alpina, leaf photosynthetic capacity was mainly determined by leaf CHO concentration. Thus there
is evidence for downregulation of photosynthetic capacity in P. alpina resulting from increased
carbohydrate accumulation in source leaves. Leaf dark respiration and total N concentration were
positively correlated in P. alpina and F. vivipara. Leaf dark respiration and soluble carbohydrate
concentration of source leaves were positively correlated in A. capillaris. Changes in source leaf
photosynthetic capacity and carbohydrate concentration of plants grown at ambient or elevated CO,
are discussed in relation to plant growth, nutrient relations and availability of sinks for carbon.

KEYWORDS: ACCLIMATION, CALVIN CYCLE ENZYMES, CARBOHYDRATE CONTENT,
COTTON PLANTS, DIOXIDE EFFLUX, GROWTH, HIGH ATMOSPHERIC CO2,
PHOTOSYNTHETIC OXYGEN EVOLUTION, RESPIRATION, SPINACH LEAVES


     149  
Baxter, R., and J.F. Farrar. 1999. Export of carbon from leaf blades of Poa alpina L-at elevated
CO2 and two nutrient regimes. Journal of Experimental Botany 50(336):1215-1221.

The hypothesis was tested that, in plants of the alpine! meadow grass (Poa alpina L,) exposed to
elevated CO2, net photosynthesis and export from source leaves is; reduced as a result of feedback
from sinks. Nutrient supply was used as one way of reducing photosynthesis and export. Single plants
were grown in sand culture under specified controlled environmental conditions for a period of 50
d at two levels of nitrogen and phosphorus ('low': 0.2 mol m(-3) N, 0.04 mol m(-3) P;'high': 2.5 mol
m(-3) N, 0.5 mol m(-3) P). Compartmentation within, and export of carbon from, individual youngest
fully expanded leaves of acclimated plants was determined using C-14 feeding and efflux plus mass
balance calculations of carbohydrate export. Independent of treatment, the bulk of soluble
carbohydrate (65-75%) was present as fructan, with most of the remainder being sucrose. Depending
on nutrient supply, CO2 could alter export from source leaves either by a reduction in the amount of
sucrose present in a readily available pool for transport, or by altering the rate constant describing
phloem loading.

KEYWORDS: ATMOSPHERIC CO2, BARLEY, DIOXIDE, EXCISED LEAVES, GROWTH,
METABOLISM, PATTERNS, TEMPERATURE, TUSSOCK TUNDRA


     150  
Baxter, R., M. Gantley, T.W. Ashenden, and J.F. Farrar. 1994. Effects of elevated carbon-
dioxide on 3 grass species from montane pasture .2. Nutrient-uptake, allocation and efficiency of use.
Journal of Experimental Botany 45(278):1267-1278.

Agrostis capillaris L.(4), Festuca vivipara L. and Poa alpina L. were grown in outdoor open-top
chambers at either ambient (340 mu mol mol(-1) or elevated (680 mu mol mol(-1)) CO2 for periods
from 79 to 189 d. Under these conditions there is increased growth of A, capillaris and P. alpina, but
reduced growth of F. vivipara. Nutrient use efficiency, nutrient productivity (total plant dry weight
gain per unit of nutrient) and nutrient allocation of all three grass species were measured in an attempt
to understand their individual growth responses further and to determine whether altered nutrient-use
efficiencies and productivities enable plants exposed to an elevated atmospheric CO2 environment
to overcome potential limitations to growth imposed by soil fertility. Total uptake of nutrients was,
in general, greater in plants of A. capillaris and P. alpina (with the exception of N and K in the latter)
when grown at 680 mu mol mol(-1) CO2. In F. vivipara, however, uptake was considerably reduced
in plants grown at the higher CO2 concentration. Overall, a doubling of atmospheric CO2
concentration had little effect on the nutrient use efficiency or productivity of A, capillaris.
Reductions in tissue nutrient content resulted from increased plant growth and not altered nutrient
use efficiency. In P. alpina, potassium, magnesium and calcium productivities were significantly
reduced and photosynthetic nitrogen and phosphorus use efficiencies were doubled at elevated CO2
with respect to plants grown at ambient CO2. F. vivipara grown for 189 d showed the most marked
changes in nutrient use efficiency and nutrient productivity (on an extracted dry weight basis) when
grown at elevated CO2. F. vivipara grown at elevated CO2, however, showed large increases in the
ratio of nonstructural carbohydrate to nitrogen content of leaves and reproductive tissues, indicating
a substantial imbalance between the production and utilization of assimilate.

KEYWORDS: ACQUISITION, ATMOSPHERIC CO2, AVAILABILITY, CHENOPODIUM-ALBUM
L, CO2- ENRICHMENT, LEAF NITROGEN, NITROGEN CONCENTRATION,
PHOTOSYNTHETIC ACCLIMATION, PLANT GROWTH, SOURCE-SINK RELATIONS


     151  
Bazzaz, F.A. 1998. Tropical forests in a future climate: Changes in biological diversity and impact
on the global carbon cycle. Climatic Change 39(2-3):317-336.

Tropical forest ecosystems are large stores of carbon which supply millions of people with life
support requirements. Currently tropical forests are undergoing massive deforestation. Here, I
address the possible impact of global change conditions, including elevated CO2, temperature rise,
and nitrogen deposition on forest structure and dynamics. Tropical forests may be particularly
susceptible to climate change for the following reasons: (1) Phenological events (such as flowering
and fruiting) are highly tuned to climatic conditions. Thus a small change in climate can have a major
impact on the forest, its biological diversity and its role in the carbon cycle. (2) There are strong
coevolutionary interactions, such as pollination seed dispersal, with a high degree of specialization,
i.e., only certain animals can effect these activities for certain species. Global change can decouple
these tight coevolutionary interactions. (3) Because of high species diversity per unit area, species
of the tropical rain forest must have narrow niches. Thus changes in global climate can eliminate
species and therefore reduce biological diversity. (4) Deforestation and other forms of disturbance
may have significant feedback on hydrology both regionally and globally. The predicted decline in the
rainfall in the Amazon Basin and the intensification of the Indian monsoon can have a large effect on
water availability and floods which are already devastating low-lying areas. It is concluded that
tropical forests may be very sensitive to climate change. Under climatic change conditions their
structure and function may greatly change, their integrity may be violated and their services to people
may be greatly modified. Because they are large stores of great biological diversity, they require
immediate study before it is too late. The study requires the collaboration of scientists with a wide
range of backgrounds and experiences including biologists, climate modellers, atmospheric scientists,
economists, human demographers and sociologists in order to carry out holistic and urgently needed
work. Global climatic change brings a great challenge to science and to policy makers.

KEYWORDS: COOCCURRING BIRCH, DIOXIDE, ELEVATED ATMOSPHERIC CO2, GROWTH-
RESPONSE, INSECT HERBIVORE INTERACTIONS, MODEL SYSTEMS, PLANTS, RESOURCE
USE, TEMPERATURE, TREE SEEDLINGS


     152  
Bazzaz, F.A., D.D. Ackerly, F.I. Woodward, and L. Rochefort. 1992. Co2 enrichment and
dependence of reproduction on density in an annual plant and a simulation of its population-dynamics.
Journal of Ecology 80(4):643-651.

1. Populations of an annual plant, Abutilon theophrasti, were grown at four densities (100, 500, 1500
and 4000 m-2) and two CO2, concentrations (350 and 700 mul l-1) to examine the influence of CO2
environment on density-dependent patterns of demography and reproduction. Variables measured
included survivorship, proportion of plants flowering and fruiting, number of fruiting individuals,
number of seeds per individual, total seed production per population, mean seed mass, and
germination of seeds produced in each environment. 2. All variables, except the number of fruiting
individuals, declined with increasing density, and at the highest density no individuals set seed. The
number of fruiting individuals was highest at a density of 500m-2. In the elevated CO2 environment,
survivorship was significantly reduced but the proportion of plants flowering and fruiting and the
number of fruiting individuals in each population all increased. Total population seed production was
higher in the elevated CO2 environment at all densities, although the differences were not significant.
Significant effects of CO2, concentration were observed only for population-level variables, but not
for mean individual fecundity or seed size. Seed germination declined with increasing maternal
density, and no germination was recorded for seeds produced at 1500 m-2 3. Simple models of
population dynamics, utilizing difference equations, were constructed to examine potential
population-level consequences of these density and CO2 effects. In the absence of a persistent seed
pool, the simulated populations exhibited damped or stable oscillations under low germination values,
but displayed non-cyclic ('chaotic') oscillations or went extinct for higher germination due to the
complete failure of seed-set at high density. Because of its higher fecundity, the elevated- CO2
population generally exhibited greater oscillations, and the critical germination value at which the
simulated populations went extinct was much lower for the elevated-CO2 than for the ambient-CO2
population.

KEYWORDS: ABUTILON-THEOPHRASTI, COMPETITION, CYCLES, ELEVATED CO2,
GROWTH, NEIGHBORHOOD MODELS, SINGLE-SPECIES POPULATIONS


     153  
Bazzaz, F.A., J.S. Coleman, and S.R. Morse. 1990. Growth-responses of 7 major cooccurring tree
species of the northeastern united-states to elevated CO2. Canadian Journal of Forest Research-
Revue Canadienne De Recherche Forestiere 20(9):1479-1484.



     154  
Bazzaz, F.A., M. Jasienski, S.C. Thomas, and P. Wayne. 1995. Microevolutionary responses in
experimental populations of plants to co2-enriched environments - parallel results from 2 model
systems. Proceedings of the National Academy of Sciences of the United States of America
92(18):8161-8165.

Despite the critical role that terrestrial vegetation plays in the Earth's carbon cycle, very little is
known about the potential evolutionary responses of plants to anthropogenically induced increases
in concentrations of atmospheric CO2. We present experimental evidence that rising CO2
concentration may have a direct impact on the genetic composition and diversity of plant populations
but is unlikely to result in selection favoring genotypes that exhibit increased productivity in a CO2-
enriched atmosphere. Experimental populations of an annual plant (Abutilon theophrasti, velvetleaf)
and a temperate forest tree (Betula alleghaniensis, yellow birch) displayed responses to increased CO2
that were both strongly density-dependent and genotype-specific. In competitive stands, a higher
concentration of CO2 resulted in pronounced shifts in genetic composition, even though overall CO2-
induced productivity enhancements were small, For the annual species, quantitative estimates of
response to selection under competition were 3 times higher at the elevated CO2 level. However,
genotypes that displayed the highest growth responses to CO2 when grown in the absence of
competition did not have the highest fitness in competitive stands. We suggest that increased CO2
intensified interplant competition and that selection favored genotypes with a greater ability to
compete for resources other than CO2. Thus, while increased CO2 may enhance rates of selection
in populations of competing plants, it is unlikely to result in the evolution of increased CO2
responsiveness or to operate as an important feedback in the global carbon cycle, However, the
increased intensity of selection and drift driven by rising CO2 levels may have an impact on the
genetic diversity in plant populations.

KEYWORDS: AMBIENT, CO2- ENRICHMENT, COMPETITION, DENSITY, ECOSYSTEMS,
ELEVATED CARBON-DIOXIDE, GROWTH-RESPONSE, NITROGEN, SEEDLINGS, SELECTION


     155  
Bazzaz, F.A., and K.D.M. McConnaughay. 1992. Plant interactions in elevated CO2 environments.
Australian Journal of Botany 40(4-5):547-563.

Increasing atmospheric carbon dioxide concentrations present a novel resource condition for plant
communities. In order to understand and predict how plant community structure and function may
be altered in a high CO2 world, we need to understand how interactions among neighbouring plants
within a community will alter the growth and reproduction of component species. Because CO2 is
readily diffusible, plants have little influence on the CO2 acquisition of their neighbours, except within
particularly dense canopies. Thus, plants seldom compete directly for CO2. Rather, CO2 availability
is likely to alter plant-plant interactions indirectly through its effects on plant growth and competition
for other resources. As a consequence, competitive outcome under elevated CO2 atmospheres within
even simple systems is not easy to predict. For example, under some conditions, C4 species in
competitive assemblages have improved competitive ability relative to C3 competitors as a result of
CO2 enrichment, contrary to expectations based on their photosynthetic pathways. It is now clear that
individually grown plants can differ substantially from those within mono- or multispecific stands in
response to CO2 enrichment. At present, our understanding of how stands of interacting plants
modify the availability of CO2 and other resources is incomplete. We urgently need information about
how elevated CO2 atmospheres influence stand formation and population dynamics, specifically with
regard to the identities, numbers, sizes and reproductive fitnesses of individuals within single and
multiple species stands, if we are to make multi-generational predictions concerning the fate of
populations and communities in an elevated CO2 world.

KEYWORDS: ARCTIC TUNDRA, ATMOSPHERIC CARBON-DIOXIDE, DECIDUOUS FOREST,
ESTUARINE MARSH, OLD- FIELD PERENNIALS, QUERCUS-ALBA, SEEDLING GROWTH,
SIZE HIERARCHIES, SOIL RESPIRATION, TUSSOCK TUNDRA


     156  
Bazzaz, F.A., and S.L. Miao. 1993. Successional status, seed size, and responses of tree seedlings
to co2, light, and nutrients. Ecology 74(1):104-112.

We studied how an enriched CO2 atmosphere in a fully crossed design of light and nutrients,
influenced 1 st-yr seedling growth in six New England deciduous forest tree species. The species, in
the order of increasing shade tolerance, were gray birch (Betula populifolia), ash (Fraxinus americana
L.), red maple (Acer rubrum L.), red oak (Quercus rubra L.), yellow birch (Betula alleghaniensis
Britton), and striped maple (Acerpensylvanicum). Elevated CO2 environments significantly stimulated
the seedling growth of all six species. Generally this was more pronounced in low light. The greatest
stimulation was found under the condition of low light and high nutrients. However, individual
species responded differently to elevated CO2 levels. Among the three early-successional species,
gray birch, ash, and red maple, a significant increase in seedling growth under elevated CO2
conditions was found only with high nutrients. The three late-successional species grown under
elevated CO2 conditions (red oak, yellow birch, and striped maple) showed a greater percentage
increase in seedling growth in low light than in high light. Thus, for the early- successional species,
the degree of enhancement of seedling growth by elevated CO2 levels was more sensitive to nutrient
levels, while in the late-successional species the enhancement was more sensitive to the level of light.
Moreover, species with large seeds (e.g., red oak) exhibited a greater response to elevated CO2 levels
under low light than species with small seeds (e.g., gray birch). The results emphasize the importance
of plant species as well as other environmental resources in modifying the response of plants to
elevated CO2. Considering the light and nutrient environment observed in forest gaps of various sizes,
the results of the present experiment suggest seedling regeneration in New England deciduous forests
may be altered in a future high CO2 environment.

KEYWORDS: ECOSYSTEMS, ELEVATED CO2, ENRICHMENT, GROWTH-RESPONSES,
LIQUIDAMBAR- STYRACIFLUA, NORTHEASTERN UNITED-STATES, PHOTOSYNTHESIS,
PINUS-TAEDA SEEDLINGS, PLANTS, TEMPERATURE


     157  
Bazzaz, F.A., S.L. Miao, and P.M. Wayne. 1993. Co2-induced growth enhancements of
cooccurring tree species decline at different rates. Oecologia 96(4):478-482.

To elucidate how enriched CO2 atmospheres, soil fertility, and light availability interact to influence
the long-term growth of tree seedlings, six co-occurring members of temperature forest communities
including ash (Fraxinus americana L.), gray birch (Betula populifolia), red maple (Acer rubrum),
yellow birch (Betula alleghaniensis), striped maple (Acer pensylvanicum), and red oak (Quercus rubra
L.) were raised in a glasshouse for three years in a complete factorial design. After three years of
growth, plants growing in elevated CO2 atmospheres were generally larger than those in ambient
CO2 atmospheres, however, magnitudes of CO2-induced growth enhancements were contingent on
the availability of nitrogen and light, as well as species identity. For all species, magnitudes of CO2-
induced growth enhancements after one year of growth were greater than after three years of growth,
though species' growth enhancements over the three years declined at different rates. These results
suggest that CO2-induced enhancements in forest productivity may not be sustained for long periods
of time. Additionally, species' differential growth responses to elevated CO2 may indirectly influence
forest productivity via long-term species compositional changes in forests.

KEYWORDS: ATMOSPHERIC CARBON-DIOXIDE, COMMUNITIES, COOCCURRING BIRCH,
ELEVATED CO2, ENRICHMENT, PHOTOSYNTHETIC ACCLIMATION, RESPIRATION,
RESPONSES, SEEDLINGS, SOURCE-SINK RELATIONS


     158  
Beaudry, R.M. 1999. Effect of O-2 and CO2 partial pressure on selected phenomena affecting fruit
and vegetable quality. Postharvest Biology and Technology 15(3):293-303.

It is likely that from the time of the Roman Empire and perhaps before, people involved in the storage
of plant material as food recognized that atmospheric modification can provide some benefit in
improving storability. However, active, commercial modification of the atmosphere for the
preservation of fresh fruit and vegetables dates to the early part of this century. Early successes with
apple fruit has lead to the attempt to apply modified atmospheres to a wide range of commodities.
Responses to atmospheric modification are found to vary dramatically among plant species, organ
type and developmental stage and include both unwanted and beneficial physiological responses,
Desirable responses include a reduction in respiration, a reduction in oxidative tissue damage or
discoloration, a reduction in the rate of chlorophyll degradation and a reduction in ethylene sensitivity
with the concomitant reduction in the rate of ripening and other ethylene-mediated phenomena.
Undesirable responses have included the induction of fermentation, the development of disagreeable
flavors? a reduction in aroma biosynthesis, the induction of tissue injury and an alteration in the
makeup of microbial fauna. The physiological bases for some of these responses to elevated CO2 and
reduced O-2 are discussed. (C) 1999 Elsevier Science B.V. All rights reserved.

KEYWORDS: ATMOSPHERE, BIOSYNTHESIS, BLUEBERRY FRUIT, BROCCOLI, ENERGY-
CHARGE, ETHYLENE, MAIZE ROOT-TIPS, OXYGEN PARTIAL PRESSURES, POSTHARVEST
DECAY, VOLATILE COMPOUNDS


     159  
Becker, M., T.M. Nieminen, and F. Geremia. 1994. Short-term variations and long-term changes
in oak productivity in northeastern france - the role of climate and atmospheric co2. Annales Des
Sciences Forestieres 51(5):477-492.

A dendroecological study was carried out in 2 forests in northeastern France with the aim of
identifying and quantifying possible long-term trends in the radial growth of sessile oak (Quercus
petraea (Matt) Liebl) and pedunculate oak (Q robur L). A total of 150 sites were selected to represent
the ecological diversity of these forests. An index Cd was used to correct annual ring width in order
to compensate for the effect of different competition situations. The data were standardized with
reference to the mean curve 'basal area increment vs cambial age'. The growth index curves revealed
a strong increase in sessile oak growth (+ 64% during the period 1888 to 1987) as well as in that of
peduncutate oak (+40%). The growth increase in the 'young' rings (<60 years) of sessile oak was +
87 %, and that of young rings of pedunculate oak was + 49%. The corresponding increase in the 'old'
rings (>65 years) was + 48% and 15% respectively (not significant for the latter). It would thus
appear that pedunculate oak has benefited to a lesser extent than sessile oak from the progressive
changes in its environment. Years showing a strong growth decrease are more common for
pedunculate oak than for sessile oak. These results are consistent with a recent hypothesis about a
slow but general retreat of pedunculate oak, including severe episodic declines, in favour of sessile
oak in many regions of France. A model was created using a combination of meteorological data
(monthly precipitation and temperature) starting in 1881, and increasing atmospheric CO,
concentrations. The model explains 78.3% of the variance for sessile oak and 74.3% for pedunculate
oak. This includes some monthly parameters of year y (year of ring formation), and also some
parameters of the years y-1 to y-4 for sessile oak and y-1 to y-5 for pedunculate oak. The models
satisfactorily reproduce the long-term trends and the interannual variation. The climatic variables
alone (ie excluding the CO, concentration) were insufficient to explain the trends observed. The
possible direct and indirect effects of increasing CO2 concentration on the growth of both species are
discussed.

KEYWORDS: ABIES-ALBA MILL, CARBON DIOXIDE, FOREST, GROWTH, MOUNTAINS, PAST
VITALITY, PINE, TREES, TRENDS, VEGETATION


     160  
Beckmann, K., C. Dzuibany, K. Biehler, H. Fock, R. Hell, A. Migge, and T.W. Becker. 1997.
Photosynthesis and fluorescence quenching, and the mRNA levels of plastidic glutamine synthetase
or of mitochondrial serine hydroxymethyltransferase (SHMT) in the leaves of the wild-type and of
the SHMT-deficient stm mutant of Arabidopsis thaliana in relation to the rate of photorespiration.
Planta 202(3):379-386.

The regulation by photorespiration of the transcript level corresponding to plastidic glutamine
synthetase (GS-2) was investigated in the leaves of Arabidopsis thaliana (L.) Heynh. Photorespiration
was suppressed by growing the plants in an atmosphere containing 300 Pa CO2. Suppression of
photorespiration was demonstrated by the ability of the conditionally lethal serine
hydroxymethyltransferase (SHMT)- deficient stm mutant of A. thaliana to grow normally under these
conditions. In contrast to previous studies with bean or pea that were performed at very high CO2
partial pressure (2-4 kPa; Edwards and Coruzzi, 1989, Plant Cell 1: 241-248; Cock et al., 1991, Plant
Mol Biol 17: 761-771), suppression of photorespiration during growth of A. thaliana in an
atmosphere with 300 Pa CO2 had no effect on the leaf GS-2 transcript level. In the short term, neither
suppression of photorespiration induced by the transfer of air-grown A. thaliana plants into a CO2-
enriched atmosphere, nor an increase in the rate of photorespiration achieved by the transfer of high-
CO2-grown A. thaliana plants into air resulted in a change in the GS-2 mRNA level. The absence of
photorespiratory ammonium release in leaves of the stm mutant had no effect on the GS-2 transcript
level. Overall, our data argue against a control by photorespiration of the A. thaliana leaf GS-2
mRNA pool. In contrast, regulation of the leaf SHMT mRNA level may involve a negative feedback
effect of at least one metabolite derived from the glycine/serine conversion during photorespiration,
as indicated by the overexpression of SHMT transcripts in the leaves of the stm mutant.

KEYWORDS: ACCLIMATION, ATMOSPHERIC CO2, CARBON DIOXIDE, ELEVATED CO2,
EXCHANGE, EXPRESSION, GENES, LIGHT, SUNFLOWER LEAVES, TOBACCO


     161  
Beer, S., and E. Koch. 1996. Photosynthesis of marine macroalgae and seagrasses in globally
changing CO2 environments. Marine Ecology-Progress Series 141(1-3):199-204.

Photosynthetic rates of many marine macroalgae are saturated by the present day inorganic carbon
(Ci) composition of seawater, while those of seagrasses (or marine angiosperms) are CO2- limited.
In this study we attempted to simulate the Ci conditions of near-shore seawater during the time that
seagrasses colonised the sea (in the Cretaceous), and compare the photosynthetic performance of
representatives of the 2 plant groups under those versus present day conditions. The results show that
the seagrasses have an affinity for Ci at least as high as the algae under the low pH and high
CO2/HCO3- concentration ratios simulating near-shore areas of the Cretaceous seas, indicating that
their photosynthetic capacity then matched that of macroalgae. However, in the high pH and high
CO2/HCO3- ratios of today, their affinity for Ci is lower than that of the macroalgae, and it is
suggested that this deficiency renders them a lower ability for Ci utilisation. This situation may
possibly be reversed again as global CO2 levels of the atmosphere and, consequently, of near-shore
marine habitats increase in the future.

KEYWORDS: CELLS, ULVA SP


     162  
Beerling, D.J. 1994. Modeling palaeophotosynthesis - late cretaceous to present. Philosophical
Transactions of the Royal Society of London Series B-Biological Sciences 346(1318):421-432.

This paper presents an attempt to reconstruct potential changes in the photosynthetic rates of
terrestrial C3 leaves over the past 120 Ma. The approach has been to couple palaeoatmospheric
reconstructions of O-2, CO2 and temperature from geochemical modelling, and an independent
estimate of ancient CO2 changes from fossil porphyrins, with a mechanistic biochemical model of C3
photosynthesis. The model accounts for the effect of each of these palaeoenvironmental changes, at
the biochemical level, to predict leaf photosynthesis and has been parametrized for a typical
gymnosperm and angiosperm. The results indicate clear potential for increased photosynthetic C3
fixation in the warm Cretaceous for both angiosperms and gymnosperms, despite the increased O-2
content of the atmosphere prevailing at the time. Photosynthetic rates are then predicted to
progressively decline into the Tertiary, as a result of global cooling. The model simulations also point
towards some leaf-level ecophysiological explanations for the rise in angiosperm dominance and the
concomitant decline in gymnosperms from the late Cretaceous onwards, at mid-latitudes, which have
not been considered previously. This work provides a basis for scaling up to the canopy level to
predict the primary productivity of ancient ecosystems and their possible feedback on atmospheric
composition and climate.

KEYWORDS: ATMOSPHERIC CO2, CARBON DIOXIDE, CLIMATE CHANGE, ELEVATED CO2,
HIGH-LATITUDES, PHANEROZOIC TIME, PHOTOSYNTHESIS, PLANTS, TEMPERATURE,
TERTIARY BOUNDARY


     163  
Beerling, D.J. 1994. Predicting leaf gas-exchange and delta-C-13 responses to the past 30000 years
of global environmental-change. New Phytologist 128(3):425-433.

Theoretical developments in our understanding of leaf gas exchange processes and carbon isotope
composition (delta(13)C) mean that it should now be possible to model their responses to global
environmental change. Such a model would be of use for process-based interpretations of historical
changes in leaf delta(13)C and for understanding the global stable carbon isotope balance. This paper
describes the development and validation of a model towards this aim. The resulting model is used
to simulate changes in leaf photosynthesis, stomatal conductance and delta(13)C of limber pine (Pinus
flexilis) in response to the past 30000 y of global environmental change. The predictions of needle
delta(13)C are in line with reported measurements of delta(13)C from fossilized Pinus flexilis needles
preserved in packrat middens in western USA. Leaf gas exchange predictions show that the increased
water use efficiency (WUE) of these trees growing in present-day environments, relative to the past,
was brought about through an increase in photosynthetic rates and a decrease in stomatal
conductance. This contrasts with the explanation of the recent (past 200 y) increase in the WUE of
temperate and Mediterranean ecosystems inferred from delta(13)C measurements which are predicted
by the model to have arisen largely by a decrease in stomatal conductance in response to increases
in the concentration of atmospheric CO2 since the pre-industrial era. The model as described offers
the potential to contribute to our understanding of vegetation effects on the global carbon isotope
balance during the glacial periods, and therefore to provide a further constraint on the carbon cycle
models used to explain the low concentrations of atmospheric CO2 at these times.

KEYWORDS: ATMOSPHERIC CO2 CONCENTRATION, C-13/C-12 RATIO, CARBON ISOTOPE
DISCRIMINATION, DIOXIDE, EMPIRICAL-MODEL, ICE-CORE RECORD, LEAVES,
PHOTOSYNTHESIS, STOMATAL CONDUCTANCE, WATER-USE EFFICIENCY


     164  
Beerling, D.J. 1996. C-13 discrimination by fossil leaves during the late-glacial climate oscillation
12-10 ka BP: Measurements and physiological controls. Oecologia 108(1):29-37.

The late-glacial climatic oscillation, 12-10 ka BP, is characterised in ice core oxygen isotope profiles
by a rapid and abrupt return to glacial climate. Recent work has shown that associated with this
cooling was a drop in atmospheric CO2 concentration of ca. 50 ppm. In this paper, the impact of
these environmental changes on C-13 discrimination is reported, based on measurements made on
a continuous sequence of fossil Salix herbacea leaves from a single site. The plant responses were
interpreted using an integrated model of stomatal conductance, CO2 assimilation and intercellular
CO2 concentration, influenced by external environmental factors. According to the model,
temperature exerts a marked influence on C-13 discrimination by leaves and the pattern of C-13
changes recorded by the fossil leaves is consistent with other palaeotemperature curves for 12-10 ka
BP, particularly the deuterium isotope record from Alaskan Salix woods, which generally reflects
ocean temperatures. The gas exchange model correctly accounts for these changes and so permits
the reconstruction of ancient rates of leaf CO2 uptake and loss of water vapour in response to the
abrupt late-glacial changes in global climate and CO2. The approach provides the required
physiological underpinning for extracting quantitative estimates of past temperatures and for
contributing an ecophysiological explanation for changes in C-13 discrimination in the fossil record.

KEYWORDS: ATMOSPHERIC CO2, C-13/C-12 RATIOS, C-3 PLANTS, CARBON ISOTOPE
DISCRIMINATION, ELEVATED CO2, ENVIRONMENTAL-CHANGE, STOMATAL
CONDUCTANCE, WATER-USE EFFICIENCY, WESTERN NORWAY, YOUNGER DRYAS


     165  
Beerling, D.J. 1997. Carbon isotope discrimination and stomatal responses of mature Pinus sylvestris
L trees exposed in situ for three years to elevated CO2 and temperature. Acta Oecologica-
International Journal of Ecology 18(6):697-712.

The Climate Change Experiment (CLIMEX) is a unique large scale facility in which an entire
undisturbed catchment of boreal vegetation has been exposed to elevated CO2 (560 ppm) and
temperature (+3 degrees C summer, +5 degrees C winter) for the past three years with all the soil-
plant-atmosphere linkages intact. Here, carbon isotope composition end stomatal density have been
analysed from sequential year classes of needles of mature Scots pine trees (Pinus sylvestris L.) to
investigate the response of time-integrated water-use efficiency (WUE) and stomatal density to CO2
enrichment and climate change. Cal bon isotope discrimination decreased and WUE increased in
cohorts of needles developing under increased CO2 and temperature, compared to needles on the
same trees developing in pretreatment years. Mid-season instantaneous gas exchange, measured on
the same trees for the past four pears, indicated that these responses resulted from higher needle
photosynthetic rates and reduced stomatal conductance. Needles of P. sylvestris developing under
increased CO2 and temperature had consistently lower stomatal densities than their ambient grown
counterparts on the same trees. The stomatal density of P. sylvestris needles was inversely correlated
with delta(13)C- derived WUE, implying some effect of this morphological response on leaf gas
exchange. Future atmospheric CO2 and temperature increases are therefore likely to improve the
water economy of P. sylvestris, at least at the scale of individual needles, by affecting stomatal density
and gas exchange processes.

KEYWORDS: 4-YEAR EXPOSURE, BOREAL VEGETATION, C-3 PLANTS, DENSITY,
ENRICHMENT, GAS-EXCHANGE RESPONSES, LAST 3 CENTURIES, SCOTS PINE, WATER-
USE EFFICIENCY, WHOLE-CATCHMENT


     166  
Beerling, D.J. 1997. Interpreting environmental and biological signals from the stable carbon isotope
composition of fossilized organic and inorganic carbon. Journal of the Geological Society 154:303-
309.

Stable carbon isotope studies on marine and terrestrial organic and inorganic carbon provide a means
for detecting global climate change and for reconstructing past concentrations of atmospheric CO2.
Comparison between the CO2 estimates reconstructed from carbon isotope studies for the past 150
Ma show good agreement with the predictions of a long-term carbon- cycle model based on mass-
balance studies. Further, the CO2 estimates from these sources over the entire Phanerozoic show
agreement with the fossil record of leaf stomatal density change-a feature inversely related to the
concentration of atmospheric CO2. Isotopic studies on temporal sequences of fossilized terrestrial
organic matter have contributed to palaeoecological studies on shifts in the dominance of plants with
the C-4 photosynthetic pathway in ecosystems and historical changes in the metabolic processes of
leaves of individual species. The long-term perspective offered by these studies provides critical
information for assessing the responses of biological systems to future global environmental change.

KEYWORDS: ATMOSPHERIC CO2, C-4 PLANTS, CLIMATE CHANGE, DIOXIDE, ELEVATED
CO2, ICE-CORE RECORD, LATE QUATERNARY, PERMIAN TRIASSIC BOUNDARY,
STOMATAL DENSITY, WATER-USE EFFICIENCY


     167  
Beerling, D.J. 1998. The future as the key to the past for palaeobotany? Trends in Ecology and
Evolution 13(8):311-316.

Continued increase in the concentration of atmospheric CO2 and its possible effects on global climate
has generated intense research interest on the likely responses of terrestrial plants and vegetation.
Results from this new research provide quantitative information on plant function and growth in an
environment with a high CO2 concentration, but are also relevant to understanding plant growth in
the distant past and to the techniques employed by palaeobotanists for reconstructing past climates
from fossil plant remains. Experimental CO(2)enrichment of plants has demonstrated direct effects
on leaf physiognomy, the tolerance of plants to low temperature and the relationship between tree
rings, CO(2)and climate; it therefore signals the need for caution in interpreting palaeoclimates from
fossils.

KEYWORDS: ATMOSPHERIC CO2 CONCENTRATIONS, CLIMATE, EARLY TERTIARY,
ELEVATED CO2, ENRICHMENT, FOSSIL PLANTS, FROST HARDINESS, PHOTOSYNTHESIS,
TEMPERATURE, TREE GROWTH


     168  
Beerling, D.J. 1999. Long-term responses of boreal vegetation to global change: an experimental
and modelling investigation. Global Change Biology 5(1):55-74.

The response of boreal ecosystems to future global change is an uncertain but potentially critical
component of the feedback between the terrestrial biosphere and the atmosphere. To reduce some
of the uncertainties in predicting the responses of this key ecosystem, the climate change experiment
(CLIMEX) exposed an entire undisturbed catchment of boreal vegetation to CO2 enrichment (560
ppmv) and climate change (+ 5 degrees C in winter, + 3 degrees C in summer) for three years (1994-
96). This paper describes the leaf metabolic responses of the vegetation to the experimental treatment
and model simulations of possible future changes in the hydrological and carbon balance of the site.
Randomized intervention analysis of the leaf gas exchange measurements for the dominant species
indicated Pinus sylvestris had significantly (P < 0.01) higher photosynthetic rates and Betula
pubescens and Vaccinium myrtillus had significantly (P < 0.01) lower stomatal conductances after
three years treatment compared to the controls. These responses led to sustained increases in leaf
water-use efficiency of all species of trees and ground shrubs, as determined from carbon isotope
analyses. Photosynthesis (A) vs. intercellular CO2 (c(i)) response curves (A/c(i) responses), RuBisCo
analysis and leaf nitrogen data together suggested none of the species investigated exhibited down-
regulation in photosynthetic capacity. At the whole ecosystem level, the improved water economy
of the plants did not translate into increased catchment runoff. Modelling simulations for the site
indicate this was most likely brought about by a compensatory increase in evapotranspiration. In
terms of the carbon budget of the site, the ecosystem model indicates that increased CO2 and
temperature would lead to boreal ecosystems of the type used in CLIMEX, and typical of much of
southern Norway, acting as moderate net sinks for CO2.

KEYWORDS: CARBON ISOTOPE DISCRIMINATION, ECOSYSTEM EXPERIMENTS,
ELEVATED CO2, FOREST ECOSYSTEMS, GAS-EXCHANGE RESPONSES, PHOTOSYNTHETIC
RESPONSE, RISING ATMOSPHERIC CO2, SCOTS PINE, STOMATAL CONDUCTANCE,
WATER-USE EFFICIENCY


     169  
Beerling, D.J., and W.G. Chaloner. 1993. Evolutionary responses of stomatal density to global co2
change. Biological Journal of the Linnean Society 48(4):343-353.

KEYWORDS: ATMOSPHERIC CO2, CARBON DIOXIDE, ENRICHMENT, FORESTS, GAS-
EXCHANGE, GROWTH, INCREASE, PLANTS, POPLAR CLONES, WATER-USE EFFICIENCY


     170  
Beerling, D.J., and W.G. Chaloner. 1993. The impact of atmospheric co2 and temperature-change
on stomatal density - observations from quercus-robur lammas leaves. Annals of Botany 71(3):231-
235.

KEYWORDS: CARBON ISOTOPES, CENTURIES, DIOXIDE, ELEVATED CO2, GROWTH,
KRAKOW REGION, PLANTS, RECORD, RESPONSES


     171  
Beerling, D.J., and W.G. Chaloner. 1993. Stomatal density responses of egyptian olea-europaea
L leaves to co2 change since 1327 bc. Annals of Botany 71(5):431-435.

KEYWORDS: ATMOSPHERIC CO2, CENTURIES, ENRICHMENT, RECORD, VOSTOK ICE-
CORE


     172  
Beerling, D.J., W.G. Chaloner, B. Huntley, A. Pearson, and M.J. Tooley. 1991. Tracking
stomatal densities through a glacial cycle - their significance for predicting the response of plants to
changing atmospheric CO2 concentrations. Global Ecology and Biogeography Letters 1(5):136-142.

Continued increases in the global atmospheric CO2 concentration have been predicted from current
and projected rates of fossil fuel burning. Understanding the response of stomatal density as an
important ecophysiological parameter controlling the productivity of vegetation is essential if the role
of plants in the global carbon budget are to be predicted. Experimental exposure of plants to elevated
CO2 regimes in controlled environment chambers can only indicate immediate, phenotypic, short-term
responses. The investigation of fossil leaves of extant species growing under the different atmospheric
conditions of the last glacial and deglacial transition, when evidence from an Antarctic ice core
(Barnola et al., 1987) indicates CO2 levels markedly different from pre-industrial levels, provides one
means for eliciting long-term plant responses to changing CO2 regimes. We have prepared cuticles
from Quaternary leaf fossils, from which stomatal density and index can be calculated. Our
preliminary results give promise of extending the record of stomatal density response back at least
10,000 years.

KEYWORDS: ENRICHMENT, ICE, RECORD


     173  
Beerling, D.J., W.G. Chaloner, B. Huntley, J.A. Pearson, M.J. Tooley, and F.I. Woodward.
1992. Variations in the stomatal density of salix-herbacea L under the changing atmospheric co2
concentrations of late-glacial and postglacial time. Philosophical Transactions of the Royal Society
of London Series B-Biological Sciences 336(1277):215-224.

The rapidly rising CO2 concentration of the past 200 years has been shown to be accompanied by a
fall in stomatal density in the leaves of temperate trees. The present study attempts to investigate the
relationship of atmospheric CO2 change and stomatal density in the arctic-alpine shrub, Salix
herbacea, over the longer time span of 11 500 years offered by fossil leaves from post-glacial
deposits. Comparisons of fossil material from Scotland and Norway are made with leaves from living
populations growing in Austria, Greenland and Scotland. The Austrian material, from an altitudinal
gradient between 2000 and 2670 m above sea level, gives added comparison of contemporary
differences of CO2 partial pressure with altitude. The results of our investigation indicate, rather
surprisingly, that the rising CO2 concentration of the past 11 500 years has been accompanied by an
increase in the stomatal density of S. herbacea in contrast to the shorter-term observations on the
herbarium material of temperate trees. The most likely explanation appears to centre on the
temperatures and water availability of the early post-glacial environment overriding the effect of the
lower CO2 regime. However, the scale of the time interval involved may also be significant. Natural
selection over the 11 500 year period concerned may have favoured a different response to what is,
in effect, an acclimatory response observed in trees within the period of rapid CO2 rise of the past
200 years.

KEYWORDS: CARBON DIOXIDE, CLIMATE, ENRICHMENT, GRADIENT, GROWTH, LEAF
ANATOMY, PHOTOSYNTHESIS, RESPONSES, TEMPERATURE, WATER-USE EFFICIENCY


     174  
Beerling, D.J., J. Heath, F.I. Woodward, and T.A. Mansfield. 1996. Drought-CO2 interactions
in trees: Observations and mechanisms. New Phytologist 134(2):235-242.

It is sometimes assumed that because increases in atmospheric CO2 concentration usually enhance
water use efficiency per unit leaf area, there will be a tendency for plants to show greater drought
tolerance as well as increased biomass in the future. A critical examination of the responses to
elevated CO2 in three temperate tree species shows that this assumption might be incorrect in the
case of two of them. Both beech (Fagus sylvatica L.) and birch (Betula pubescens Ehrh.) display
minimal stomatal closing responses to elevated CO2, and in the case of F. sylvatica the stomatal
control of transpiration per unit leaf area appears to be unable to compensate for the greater
development of leaf area. By contrast, the stomata of oak (Quercus robur L.) close appreciably in
elevated CO2, to an extent which might be sufficient to compensate for an increase in total leaf area.
A simple model for the controls on water supply and consumption for the whole tree suggests that
in F. sylvatica the potential height attainment for a given sapwood area might decrease as the
atmospheric CO2 concentration rises. The conclusions drawn from experimental data and from
modelling are supported by field observations made in the UK in 1995, when the three species
responded very differently to severe drought. We suggest that the progressive increase in the
concentration of atmospheric CO2 over the past 200 yr might have accentuated differences in drought
sensitivity between these species.

KEYWORDS: ATMOSPHERIC CO2, BETULA-PENDULA ROTH, ELEVATED CARBON-
DIOXIDE, FAGUS-SYLVATICA, GAS-EXCHANGE, GLOBAL ENVIRONMENTAL-CHANGE,
GROWTH, PHOTOSYNTHESIS, PLANT-RESPONSES, TRANSPIRATION


     175  
Beerling, D.J., B. Huntley, and J.P. Bailey. 1995. Climate and the distribution of fallopia-japonica -
use of an introduced species to test the predictive capacity of response surfaces. Journal of
Vegetation Science 6(2):269-282.

The relationship between present climate and the distribution in Europe of the aggressively invasive
exotic Fallopia japonica is described by fitting a response surface based on three bioclimatic variables:
mean temperature of the coldest month, the annual temperature sum > 5 degrees C, and the ratio of
actual to potential evapotranspiration. The close fit between the observed and simulated distributions
suggests that the species' European distribution is climatically determined. The response surface also
provides a simulation of the extent of the area of native distribution of F. japonica in Southeast Asia
that is generally accurate, confirming the robustness of the static correlative model upon which it is
based. Simulations of the potential distribution of F. japonica under two alternative 2 x CO2 climate
change scenarios indicate the likelihood of considerable spread into higher latitudes and possible
eventual exclusion of the species from central Europe. However, despite the robustness of the
response surface with present-day climate, the reliability of these simulations as forecasts is likely to
be limited because no account is taken of the direct effects of CO2 and their interaction with the
species' physiological responses to climate. Similarly, no account is taken of the potential impact of
interactions with 'new' species as ecosystems change in composition in response to climate change.
Nevertheless, the simulations indicate both the possible magnitude of the impacts of forecast climate
changes and the regions that may be susceptible to invasion by F. japonica.



     176  
Beerling, D.J., and C.K. Kelly. 1997. Stomatal density responses of temperate woodland plants
over the past seven decades of CO2 increase: A comparison of Salisbury (1927) with contemporary
data. American Journal of Botany 84(11):1572-1583.

We investigated the possible effect of recent (1927-1995) increases in the concentration of
atmospheric CO2 on the stomatal densities of leaves of a wide range of tree, shrub, and herb species
(N = 60) by making new measurements for comparison with corresponding data reported by E. J.
Salisbury in 1917-a time when ice core studies indicate CO2 concentrations similar to 55 mu L/L
lower than present. A detailed intraspecific study of the herb Mercurialis perenius showed plants of
M. perennis in a Cambridgeshire woodland in 1994 had significantly lower stomatal densities,
irrespective of leaf insertion point, compared with their 1927 counterparts. Comparisons made across
species using evolutionary comparative methods (independent contrasts revealed a significant (P <
0.01) decrease in stomatal density over the past 70 yr. The results of both the inter-and intraspecific
comparisons are consistent with the hypothesis that historical CO2 increases have influenced leaf
morphology in a manner consistent with recent experiments and the palaeoecological record. Further
analyses suggested that the strength of the stomatal density response was independent of life form
but dependent on ''exposure'' and the initial leaf stomatal density. Consequently firmer predictions for
future changes in stomatal density across all species, expected as a possible result of
authropogenically related CO2 increases, may now be possible.

KEYWORDS: ATMOSPHERIC CO2, CENTURIES, DELTA C 13, ELEVATED CO2,
ENRICHMENT, ENVIRONMENTAL-CHANGE, GAS-EXCHANGE, GROWTH, LEAF-AREA,
TAXONOMIC RELATEDNESS


     177  
Beerling, D.J., J.C. McElwain, and C.P. Osborne. 1998. Stomatal responses of the 'living fossil'
Ginkgo biloba L. to changes in atmospheric CO2 concentrations. Journal of Experimental Botany
49(326):1603-1607.

Leaf stomatal density and index of Ginkgo biloba L. were both significantly (P < 0.05) reduced after
3 years growth at elevated CO2 (560 ppm), with values comparable to those of cuticles prepared
from Triassic and Jurassic fossil Ginkgo leaves thought to have developed in the high CO2
'greenhouse world' of the Mesozoic. A reciprocal transfer experiment indicated that reductions in
stomatal density and index irreversibly reduced stomatal conductance, particularly at low leaf-to-air
vapour pressure deficits and low internal leaf CO2 concentrations (C-i). These effects probably
contributed to the high water-use efficiency of Ginkgo spp. in the Mesozoic relative to those of the
present, as determined from carbon isotope measurements of extant and fossil cuticles.

KEYWORDS: CYCLE, DENSITY, ENVIRONMENTAL-CHANGE, LEAVES, RECORD


     178  
Beerling, D.J., and W.P. Quick. 1995. A new technique for estimating rates of carboxylation and
electron-transport in leaves of C-3 plants for use in dynamic global vegetation models. Global
Change Biology 1(4):289-294.

The possible responses of the terrestrial biosphere to future CO2 increases and associated climatic
change are being investigated using dynamic global vegetation models (DGVMs) which include the
Farquhar ef al. (1980) biochemical model of leaf assimilation as the primary means of carbon capture.
This model requires representative values of the maximum rates of Rubisco activity, V-max, and
electron transport, J(max), for different vegetation types when applied at the global scale. Here, we
describe an approach for calculating these values based on measurements of the maximum rate of leaf
photosynthesis (A(max)) and C-13 discrimination. The approach is tested and validated by
comparison with measurements of Rubisco activity assayed directly on wild-type and transgenic
Nicotiana tabacum (tobacco) plants with altered Rubisco activity grown under ambient and elevated
CO2 mole fractions with high and low N-supply. V-max and J(max) values are reported for 18
different vegetation types with global coverage. Both variables were linearly related reinforcing the
idea of optimal allocation of resources to photosynthesis (light harvesting vs. Rubisco) at the global
scale. The reported figures should be of value to the further development of vegetation and ecosystem
models employing mechanistic DGVMs.

KEYWORDS: ANTISENSE GENE, CARBON ISOTOPE DISCRIMINATION, CLIMATE, CO2
CONCENTRATIONS, GROWTH, IMPACT, OXYGENASE, PHOTOSYNTHETIC RESPONSE,
RBCS


     179  
Beerling, D.J., and F.I. Woodward. 1993. Ecophysiological responses of plants to global
environmental- change since the last glacial maximum. New Phytologist 125(3):641-648.

Ecophysiological information on the responses of plants to past global environmental changes may
be obtained from Quaternary fossil leaves by measurements of (i) stomatal density, (ii) stomatal
dimensions and (iii) C-13 discrimination (DELTA C-13). The stomatal density and stomatal
dimensions of leaves can be used to calculate stomatal conductance, while leaf DELTA C-13 values
provide independent information on stomatal conductance and plant water use efficiency. In this
paper, stomatal conductance is calculated for a sequence of radiocarbon dated fossil leaves of Salix
herbacea L. which, together with herbarium and fresh material, represents a time-series spanning from
the Last Glacial Maximum (LGM) (16 500 yr BP) to the present day. The calculated values were then
tested against leaf DELTA C-13 values previously reported for the same material. Our calculations
show that stomatal conductance is negatively correlated with increases in atmospheric CO2
concentration over the last 16 500 yr. This represents the first evidence of long-term response of
stomatal conductance to increases in atmospheric CO2 concentration and confirms the response
observed in experimental systems exposing plants to lower-than-present CO2 concentrations in
controlled environments. The calculated decrease in conductance was positively correlated with leaf
DELTA C-13 values, supporting this interpretation. The mean leaf DELTA C-13 value for the 18th
and 19th centuries was significantly (P < 0.05) lower than the mean for the interval LGM-Holocene
(10000 yr BP) implying an increase in plant water-use-efficiency over this time. These two lines of
evidence, together with the stomatal density record from a glacial cycle, and experimental studies
growing C3 plants in glacial-to-present CO2 concentrations, strongly imply that the water use
efficiency of vegetation during the LGM was lower than at present and that it has increased since that
time. Further evidence in support of this conclusion comes from the pattern of world vegetation types
present during the LGM previously reconstructed using palaeoecological data. This evidence
demonstrates that the distribution of vegetation types during the LGM was significantly different from
that of the present day and showed a contraction in the area of rain forest and a major expansion of
desert areas.

KEYWORDS: ATMOSPHERIC CO2 CONCENTRATION, CARBON ISOTOPE DISCRIMINATION,
CLIMATE CHANGE, FORESTS, RECORD, TEMPERATURES, TRANSPIRATION, VEGETATION,
VOSTOK ICE-CORE, WATER-USE EFFICIENCY


     180  
Beerling, D.J., and F.I. Woodward. 1994. The climate-change experiment (climex) - phenology and
gas- exchange responses of boreal vegetation to global change. Global Ecology and Biogeography
Letters 4(1):17-26.

Large-scale whole ecosystem experiments will become increasingly important for predicting and
testing hypotheses of complex ecosystem responses to global change. The Climate Change
Experiment (CLIMEX) uses a site with an entire undisturbed boreal-forested catchment enclosed
within an existing very large scale (1200m2 ground area) greenhouse. In the forthcoming year
temperature will be increased stepwise to +3-degrees-C in summer, +5-degrees-C in winter and the
atmospheric CO2 concentration enriched to 560 ppm which together simulate future changes in
global climate and atmospheric composition predicted by GCMs. Plants growing within this low
nutrient ecosystem are strongly dependent upon mycorrhizal associations for nutrient uptake and rates
of nutrient uptake. Therefore it will provide an important test of current ideas concerning how
mycorrhizas might modify plant responses to global change. We describe predictions of community
phenology and gas exchange at the CLIMEX site; in the latter case the effects of including and
excluding rates of on nutrient supply are considered. The results are discussed with reference to the
opportunities presented by CLIMEX to reveal important aspects of the physiological responses of
boreal ecosystems to global change.

KEYWORDS: ASSIMILATION, ATMOSPHERIC CO2, BUDBURST, CARBON DIOXIDE,
ELEVATED CO2, PLANT-RESPONSES, PRODUCTIVITY, TREES


     181  
Beerling, D.J., and F.I. Woodward. 1995. Leaf stable carbon-isotope composition records
increased water- use efficiency of C-3 plants in response to atmospheric co2 enrichment. Functional
Ecology 9(3):394-401.

1. A total of 17 temperate C-3 grass and herb species were grown for 5 weeks at three mole fraction
treatments of atmospheric CO2 (350, 525 and 700 mu mol mol(-1)). Leaf stable carbon isotope
compositions (delta(13)C) were determined to record long-term exchange responses together with
instantaneous gas exchange measurements. The isotopic composition of the atmospheric CO2
(delta(13)C(a)) integrated over the course of the CO2 treatments was recorded biologically using the
C-4 species Zea mays. 2. We found that increases in the mole fraction of atmospheric CO2 above
current levels resulted in a sustained increase in instantaneous (photosynthesis, A/conductance, g(s))
leaf water-use efficiency (IWUE), as calculated from carbon isotope-derived p(i)/p(a) ratios. Grass
species showed a marked decline in the magnitude of WUE increase as the CO2 mole fraction was
increased from 525 to 700 mu mol mol(-1), a response which was absent in herb species. 3. Isotopic
derivation of the ratio of intercellular CO2 mole fraction (p(i)) to that in the surrounding atmosphere
(p(a)), considered as a set point of leaf metabolism, showed no significant (P = 0.06) changes in
response to increases in the mole fraction of CO2, for herb and grass species. Measurements of
p(i)/p(a) determined from measurements of leaf gas exchange differed significantly (P<0.01) from
those derived from stable isotope ratios. These differences are attributed to contrasting stomatal
behaviour between herb and grass species. 4. Leaf intercellular CO2 mole fraction and previously
reported above- ground biomass responses to CO2 increases for the same species were positively
correlated (P < 0.05). This suggests that as atmospheric CO2 levels continue to rise species showing
sustained higher rates of leaf photosynthesis, may be translated into increased productivity depending
on soil water and nutrient status.

KEYWORDS: DELTA C 13, DIOXIDE, DISCRIMINATION, LEAVES, PHOTOSYNTHETIC
ACCLIMATION, SEEDLINGS, STOMATAL CONDUCTANCE


     182  
Beerling, D.J., and F.I. Woodward. 1995. Stomatal responses of variegated leaves to co2
enrichment. Annals of Botany 75(5):507-511.

The responses of stomatal density and stomatal index of five species of ornamental plants with
variegated leaves grown at two mole fractions of atmospheric CO2 (350 and 700 mu mol mol(- 1))
were measured. The use of variegated leaves allowed any potential effects of mesophyll
photosynthetic capacity to be uncoupled from the responses of stomatal density to changes in
atmospheric CO2 concentration. There was a decrease in stomatal density and stomatal index with
CO2 enrichment on both white (unpigmented) and green (pigmented) leaf areas. A similar response
of stomatal density and index was also observed on areas of leaves with pigmentation other than
green indicating that any differences in metabolic processes associated with coloured leaves are not
influencing the responses of stomatal density to CO2 concentrations. Therefore the carboxylation
capacity of mesophyll tissue has no direct influence on stomatal density and index responses as
suggested previously (Friend and Woodward 1990 Advances in Ecological Research 20: 59-124),
instead the responses were related to leaf structure. The stomatal characteristics (density and index)
of homobaric variegated leaves showed a greater sensitivity to CO2 on green portions, whereas
heterobaric leaves showed a greater sensitivity on white areas. These results provide evidence that
leaf structure may play an important role in determining the magnitude of stomatal density and index
responses to CO2 concentrations.

KEYWORDS: CHLOROPHYLL, LEAF


     183  
Beerling, D.J., and F.I. Woodward. 1996. In situ gas exchange responses of boreal vegetation to
elevated CO2 and temperature: First season results. Global Ecology and Biogeography Letters
5(3):117-127.

The climate change experiment (CLIMEX) uses a large greenhouse to investigate the responses of
an entire undisturbed boreal forested catchment to elevated CO2 (560 ppm) and temperature (+3
degrees C in summer and +5 degrees C in winter) treatments. In July and September of the first
season of treatment the two dominant tree species, Pinus sylvestris and Betula pubescens, and the
ground shrub Vaccinium myrtillus all showed an increase in leaf photosynthetic rates relative to the
plants growing in the control section of the greenhouse and in an outside reference catchment.
Stomatal density of needles of II sylvestris, and leaves of B. pubescens and V. myrtillus decreased
under CO2 enrichment and temperature increases relative to the controls. Gas exchange and stable
carbon isotope measurements will be made in future growing seasons to investigate whether
acclimatory adjustments in plant metabolism occur-a critical issue affecting the carbon balance of
these ecosystems.

KEYWORDS: CARBON DIOXIDE, NUTRITION, PHENOLOGY, PHOTOSYNTHESIS, STOMATAL
DENSITY, WATER-USE


     184  
Beerling, D.J., and F.I. Woodward. 1996. Palaeo-ecophysiological perspectives on plant responses
to global change. Trends in Ecology and Evolution 11(1):20-23.

Taxonomic classifications of plant species, based on morphological characteristics, provide a stable
and robust approach for Inferring taxonomic and phylogenetic relationships between extant and
extinct species. This implies that, although evolution is a continuous process for a species, there is
no whole-scale change in those suites of morphological characteristics that define higher order (genus
and greater) relationships. Recent research suggests that a higher order characteristic stomatal density
- may reflect not only the atmospheric CO2 concentration during initial evolution, but may also
strongly constrain the responses of higher order plant groups to future CO2-enrichment.

KEYWORDS: CO2, EVOLUTION, RECORD, VASCULAR PLANTS


     185  
Beerling, D.J., and F.I. Woodward. 1997. Changes in land plant function over the Phanerozoic:
Reconstructions based on the fossil record. Botanical Journal of the Linnean Society 124(2):137-
153.

Major fluctuations in the concentrations of atmospheric CO2 and O-2 are predicted by historical long-
term carbon and oxygen cycle models of atmospheric evolution and will have impacted directly on
past climates, plant function and evolutionary processes. Here, palaeobotanical evidence is presented
from the stomatal density record of fossil leaves spanning the past 400 Myr supporting the predicted
changes in atsmopheric CO2. Evidence from experiments on plants exposed to long-term high CO2
environments and the newly assembled fossil data indicate the potential for genetic modification of
stomatal characters. The influence of tile changes in fossil stomatal characteristics and atmospheric
composition on the rates of leaf gas exchange over the course of land plant evolution has been
investigated through modelling. Three contrasting cras of plant water economies emerge in the
Devonian (high), Carboniferous (low) and from the Upper Jurassic to the present- day (high but
declining). These patterns of change result from structural changes of the leaves and the impact of
atmospheric CO2 and O-2 concentrations on RuBisCO function and are consistent with the fossil
evidence of sequential appearances of novel plant anatomical changes. The modelling approach is
tested by comparing predicted leaf stable carbon isotope ratios with those measured on fossil plant
and organic material. Viewed in a geological contest, current and future increases in the concentration
of atmospheric CO2 might be considered as restoring-plant function to that more typically
experienced by plants over the majority of their evolutionary history. (C) 1997 The Linnean Society
of London.

KEYWORDS: C-3 PLANTS, CARBON ISOTOPE DISCRIMINATION, CO2- ENRICHMENT,
EPIDERMAL STRUCTURE, LEAF, LEAVES, NORTH-AMERICA, PHOTOSYNTHESIS,
RESPONSES, STOMATAL DENSITY


     186  
Beerling, D.J., F.I. Woodward, M. Lomas, and A.J. Jenkins. 1997. Testing the responses of a
dynamic global vegetation model to environmental change: a comparison of observations and
predictions. Global Ecology and Biogeography Letters 6(6):439-450.

Dynamic global vegetation - biogeochemistry models are required to predict the likely responses of
the terrestrial biosphere to anticipated future global environmental change and for improved
representation of an active vegetation surface within general circulation models of the Earth's global
climate system. Testing the predictions of such models is essential to their development prior to use
in a predictive capacity. The climate change experiment (CLIMEX) has exposed an entire catchment
of boreal vegetation to elevated CO2 (560 ppmv) and temperature (+3 degrees C in summer, +5
degrees C in winter) for the past three years and has a considerable archive of pre-and posttreatment
measurements of both CO2 and water vapour fluxes of the vegetation, catchment runoff and soil
nutrient status. These data have been used to test the predictions of the University of Sheffield
dynamic global vegetation model (SDGVM) for the same site using historical records of climate as
input. Comparisons of observations and predictions at the scale of individual leaves and whole
ecosystems are generally favourable, increasing our confidence in the application of the model to
forecasting the responses of the terrestrial biosphere to various global change scenarios. The SDGVM
has been used to predict the future responses of the ecosystem at the site into the year 2003AD. The
results indicate rather small changes in leaf area index and catchment runoff but quite large increases
in net primary productivity. The model predictions are now open to testing further as the CO2 and
temperature treatments continue in the CLIMEX greenhouse.

KEYWORDS: ATMOSPHERIC CO2, BOREAL VEGETATION, CARBON BALANCE, CLIMATE
CHANGE, ELEVATED CO2, FOREST, GAS-EXCHANGE RESPONSES, SCALE, TEMPERATURE,
WHOLE-CATCHMENT


     187  
Beeson, R.C., and M.E.D. Graham. 1991. CO2 enrichment of greenhouse roses affects neither
rubisco nor carbonic-anhydrase activities. Journal of the American Society for Horticultural Science
116(6):1040-1045.

The effect of prolonged CO2 enrichment on the activities of ribulose 1,5-bisphosphate
carboxylase/oxygenase (Rubisco) and carbonic anhydrase (CA) of greenhouse roses were studied.
Plants of Rosa X hybrida 'Red Success' were grown for 2 years at ambient and 900-mu-l CO2/liter
during winter and spring with 75-mu-mol.m-2.s-1 photosynthetically active radiation supplemental
lighting for 2 years. Measurements of initial and Mg+2-Co2-activated activities of Rubisco and CA
were made during shoot development and at different positions within the plant canopy. Generally,
there were no significant differences measured in the enzyme activities between the two CO2
concentrations. The results suggest that the photosynthetic capacity did not change and that there
were no characteristic adaptations to long-term growth (up to 20 weeks) at elevated C02
concentrations. The maintenance of Rubisco and CA activities with prolonged exposure to C02-
enriched atmospheres is proposed as the reason for long-term yield increases in roses when grown
in enriched environments.

KEYWORDS: ACCLIMATION, DIOXIDE, GROWTH, LEAVES, LONG-TERM,
PHOTOSYNTHETIC REINVIGORATION, RIBULOSE BISPHOSPHATE CARBOXYLASE,
RIBULOSE-1;5-BISPHOSPHATE CARBOXYLASE, SEEDLINGS, SHOOT DECAPITATION


     188  
Behboudian, M.H., and R. Lai. 1994. Carbon-dioxide enrichment in virosa tomato plant -
responses to enrichment duration and to temperature. Hortscience 29(12):1456-1459.

Responses of the tomato (Lycopersicon esculentum Mill. cv. Virosa) plant to elevated CO2
concentrations applied throughout the photoperiod or part of it were studied under two temperature
regimes. Plants were exposed to CO2 at 340 (control), 700, and 1000 mul-liter-1. The highest
concentration was applied only at 22/16C (day/night) and 700 mul-liter-1 at 22/16C and 25/16C.
Transpiration rates were lower and photosynthetic rates were higher under elevated CO2 than at the
ambient level. Biomass production was higher only for plants grown at 700 mul-liter-1 and 25/16C.
Concentrations of macronutrients were lower in plants exposed to 1000 mul CO2/liter than in the
control plants. Intermittent CO2 was applied using two timing methods. In method 1, plants were
exposed to 4- or 8-hour high-CO2 concentrations during their 12-hour photoperiod. In method 2,
plants were exposed for 3.5 days of each week to 700 mul CO2/liter. Only two of the 8-hour
exposures resulted in greater growth than the controls. The lack of higher growth for CO2-enriched
plants at 22/16C was attributed to a higher dark respiration rate and to respiration rate and a lack of
efficient transport of photosynthates out of leaves.

KEYWORDS: AMBIENT, ATMOSPHERIC CO2, GROWTH, PHOTOSYNTHETIC ACCLIMATION,
STARCH, TRANSPIRATION, YIELD


     189  
Behboudian, M.H., and R. Lai. 1995. Partitioning of photoassimilates in virosa tomatoes under
elevated co2 concentration. Journal of Plant Physiology 147(1):43-47.

The effect of CO2 enrichment on the distribution of assimilates in tomato plants, Lycopersicon
esculentum Mill. cv. 'Virosa', was studied using C-14-label. Plants were defoliated except for leaves
8, 9, and 10 (numbered acropetally). Depending on the experiment, truss 1 or trusses 1 and 2 were
maintained on the plant. Within a 24-h period, the labelled leaf (leaf 10) retained high levels of C-14
in both control and CO2-enriched plants. Truss 1 was the dominant sink for both CO2 treatments,
drawing on a considerable supply of C-14 re-exported from leaf 8 and leaf 9. The stem and root were
transitory sinks and had the capacity to re-export C-14 at different rates during the light and dark
periods. Pattern of photoassimilate partitioning was not affected by CO2 treatment.

KEYWORDS: ENRICHMENT, LEAVES, PATTERNS, SOURCE-SINK RELATIONSHIPS,
TRANSLOCATION


     190  
Behboudian, M.H., and C. Tod. 1995. Postharvest attributes of virosa tomato fruit produced in an
enriched carbon-dioxide environment. Hortscience 30(3):490-491.

The effect of preharvest CO2 enrichment (1000 mu l . liter(-1)) on postharvest quality of tomato fruit
(Lycopersicon esculentum Mill. 'Virosa') was studied with an emphasis on soluble sugars, ripening,
and mineral composition. High-CO2 fruit had higher concentrations of sucrose, glucose, fructose, and
total soluble solids than ambient-CO2 fruit. High-CO2 fruit also ripened more slowly and was
characterized by lower respiration and ethylene production rates than ambient-CO2 fruit.
Concentrations of N, P, and K were lower in the high-CO2 fruit than in the ambient- CO2 fruit,
whereas those of S, Ca, and Mg were the same for both treatments. Preharvest CO2 enrichment of
'Virosa' tomato enhances fruit desirability in terms of slower postharvest ripening and higher
concentrations of soluble sugars and total soluble solids.

KEYWORDS: CO2


     191  
Bellisario, L.M., J.L. Bubier, T.R. Moore, and J.P. Chanton. 1999. Controls on CH4 emissions
from a northern peatland. Global Biogeochemical Cycles 13(1):81-91.

We examined the controls on summer CH4 emission from five sites in a peatland complex near
Thompson, Manitoba, Canada, representing a minerotrophic gradient from bog to rich fen at wet
sites, where the water table positions ranged from -10 to - 1 cm. Average CH4 flux, determined by
static chambers on collars, ranged from 22 to 239 mg CH4-C m(-2) d(-1) and was related to peat
temperature. There was an inverse relationship between water table position and CH4 flux: higher
water tables led to smaller fluxes. The determination of anaerobic CH4 production and aerobic CH4
consumption potentials in laboratory incubations of peat samples was unable to explain much of the
variation in CH4 flux. Average net ecosystem exchange of CO2 ranged from 1.4 to 2.5 g CO2-C m(-
2) d(-1) and was strongly correlated with CH4 flux; CH4 emission averaged 4% of CO2 uptake. End-
of-season sedge biomass was also strongly related to CH4 flux, indicating the important role that
vascular plants play in regulating CH4 flux. Determination of isotopic signatures in peat pore water
CH4 revealed average delta(13)C values of between -50 and -73 parts per thousand and delta D of
between -368 and -388 parts per thousand. Sites with large CH4 emission rates also had high CO2
exchange rates and enriched delta(13)C CH4 signatures, suggesting the importance of the acetate
fermentation pathway of methanogenesis. Comparison of delta D and delta(13)C signatures in pore
water CH4 revealed a slope shallow enough to suggest that oxidation is not an important overall
control on CH4 emissions at these sites, though it appeared to be important at one site. Analysis of
C- 14 in pore water CH4 showed that most of the CH4 was of recent origin with percent of modern
carbon values of between 112 and 128%. The study has shown the importance of vascular plant
activities in controlling CH4 emissions from these wetland sites through influences on the availability
of fresh plant material for methanogenesis, rhizospheric oxidation, and plant transport of CH4.

KEYWORDS: ATMOSPHERE, CANADA, CARBON ISOTOPIC COMPOSITION, CO2
REDUCTION, DYNAMICS, HYDROGEN, METHANE-OXIDIZING BACTERIA, ONTARIO,
WATER, WETLANDS


     192  
BenBrahim, M., D. Loustau, J.P. Gaudillere, and E. Saur. 1996. Effects of phosphate deficiency
on photosynthesis and accumulation of starch and soluble sugars in 1-year-old seedlings of maritime
pine (Pinus pinaster Ait). Annales Des Sciences Forestieres 53(4):801-810.

Maritime pine seedlings were grown in 4 L pots filled with coarse sand in a greenhouse. Seedlings
were supplied with a nutrient solution with three different concentrations of phosphorus (0, 0.125 and
0.5 mM). After 1 year of growth, gas exchange measurements were performed on mature needles.
From these measurements, the main parameters of CO2 assimilation (the carboxylation efficiency, the
apparent quantum efficiency and the maximal rate of electron transport) were estimated using the
biochemical model of photosynthesis as described by Farquhar et al (1980). Leaf nonstructural
carbohydrates were also analyzed. Phosphorus deficiency decreased the phosphorus foliar
concentration, but did not affect foliar nitrogen concentration. The maximal rate of photosynthesis,
the carboxylation efficiency and the apparent quantum efficiency decreased in phosphorus deficient
seedlings. However, the maximal rate of electron transport and stomatal conductance were not
affected by phosphorus supply. Low phosphorus nutrition caused a dramatic increase in foliar starch
level at the end of the photoperiod. These results indicate that inadequate phosphorus nutrition
principally affected the dark reactions of photosynthesis, the apparent quantum efficiency and starch
accumulation.

KEYWORDS: CARBON, ELECTRON-TRANSPORT, ELEVATED CO2, EUCALYPTUS- GRANDIS
SEEDLINGS, GAS-EXCHANGE, GROWTH, MAIZE LEAVES, PHOSPHORUS-NUTRITION,
RIBULOSE-1;5-BISPHOSPHATE CARBOXYLASE-OXYGENASE, SITKA SPRUCE


     193  
Bender, J., U. Hertstein, and C.R. Black. 1999. Growth and yield responses of spring wheat to
increasing carbon dioxide, ozone and physiological stresses: a statistical analysis 'ESPACE-wheat'
results. European Journal of Agronomy 10(3-4):185-195.

One of the major goals of the European Stress Physiology and Climate Experiment (ESPACE-wheat)
was to investigate the sensitivity of wheat growth and productivity to the combined effects of changes
in CO2 concentration, ozone and other physiological stresses. Experiments were performed at
different sites throughout Europe, over three consecutive growing-seasons using open-top chambers.
This paper summarizes the main experimental findings of the effects of CO2 enrichment and other
factors i.e. ozone (O-3), drought stress or nitrogen supply on the biomass and yield of spring wheat
(Triticum aestivum cv. Minaret). Final harvest data from different sites and seasons were statistically
analysed: (1) to identify main effects and interactions between experimentally controlled factors; and
(2) to evaluate quantitative relationships between environmental variables and biological responses.
Generally, 'Minaret' wheat did not respond significantly to O-3, suggesting that this cultivar is
relatively tolerant to the O-3 levels applied. The main effect of CO2 was a significant enhancement
of grain yield and above-ground biomass in almost all experiments. Significant interactions between
CO2 and other factors were not common, although modifications in different N- and water supplies
also led to significant effects on grain yield and biomass. In addition, climatic factors (in particular:
mean air temperature and global radiation) were identified as important co-variables affecting grain
yield or biomass, respectively. On average, the yield increase as a result of a doubling of [CO2] was
35% compared with that observed at ambient CO2 concentrations. However, linear regressions of
grain yield or above-ground biomass for individual experiments revealed a large variability in the
quantitative responses of 'Minaret' wheat to CO2 enrichment (yield increase ranging from 11 to
121%). Hence, CO2 responsiveness was shown to differ considerably when the same cultivar of
wheat was grown at different European locations. Multiple regression analyses performed to evaluate
the relative importance of the measured environmental parameters on grain yield indicated that
although yield was significantly related to five independent variables (24 h mean CO2 concentration,
12 h mean O-3 concentration, temperature, radiation, and drought stress), a large proportion of the
observed variability remained unexplained. (C) 1999 Elsevier Science B.V. All rights reserved.

KEYWORDS: CO2- ENRICHMENT, CROP RESPONSES, IMPACTS, O-3, PLANT-RESPONSES,
PROTECT, RADIATION, VEGETATION


     194  
Bender, J., U. Hertstein, A. Fangmeier, M. van Oijen, H.J. Weigel, and H.J. Jager. 1998. The
impact of climate change on yield of wheat in Europe: Results of the European stress physiology and
climate experiment (ESPACE-wheat). Journal of Applied Botany-Angewandte Botanik 72(1-2):37-
42.

The European Stress Physiology and Climate Experiment (ESPACE- wheat) was funded by the EU
from 1994-1997. Major goals of the project were 1) to investigate by means of experiments the
sensitivity of wheat growth, development and productivity to the combined effects of changes in CO2
concentration, climatic variables and other physiological stresses, 2) to use experimental data for
extension and improvement of process- based wheat growth simulation models, and 3) to apply
models to assess the influences on crops of climatic change, CO2 concentration and additional
stresses in Europe. Experimental studies were performed at different sites in Europe through three
consecutive seasons by means of open-top chambers according to a common standard protocol, and
two simulation models were used for the analysis: AFRCWHEAT2 and LINTULCC. This paper
summarizes the main findings of the effects of CO2 enrichment and other factors such as ozone,
drought stress or nitrogen supply on the yield response of spring wheat (Triticum aestivum cv.
Minaret). A comparison of the measured data with the main outputs of the LINTULCC model
simulations is are presented. Generally, Minaret wheat did not respond significantly to ozone. CO2
enrichment had a positive influence on grain yield in almost all experiments, however, significant
interactions between CO2 and other factors were not common. The average measured yield increase
due to CO2 doubling was 35 % compared to grain yield measured at ambient CO2 concentrations,
although there was a great variability in yield responses between sites and years. LINTULCC
predicted a 42 % yield increase, but a much smaller variation between individual experiments.
Although the effects of CO2 and O-2 on crop growth and yield were acceptably simulated, observed
process-rates often showed variation not related to light intensity, temperature, CO2 or O-2, ie, not
related to the main driving variables of the models. This unexplained variability in the measured
datasets suggested a role of factors which were not accounted for in the models.

KEYWORDS: CARBON DIOXIDE, CO2, FIELD, GROWTH, OZONE, PLANT-RESPONSES,
STIMULATION, TRITICUM-AESTIVUM L


     195  
Bernstson, G.M., K.D.M. McConnaughay, and F.A. Bazzaz. 1993. Elevated co2 alters
deployment of roots in small growth containers. Oecologia 94(4):558-564.

Previously we examined how limited rooting space and nutrient supply influenced plant growth under
elevated atmospheric CO2 concentrations (McConnaughay et al. 1993). We demonstrated that plant
growth enhancement under elevated CO2 was influenced more by the concentration of nutrients
added to growth containers than to either the total nutrient content per pot or amount or the
dimensions of available rooting space. To gain insight into how elevated CO2 atmospheres affect how
plants utilize available belowground space when rooting space and nutrient supply are limited we
measured the deployment of roots within pots through time. Contrary to aboveground responses,
patterns of below-ground deployment were most strongly influenced by elevated CO2 in pots of
different volume and shape. Further, elevated CO2 conditions interacted differently with limited
belowground space for the two species we studied, Abutilon theophrasti, a C3 dicot with a deep
taproot, and Setaria faberii, a C4 monocot with a shallow fibrous root system. For Setaria, elevated
CO2 increased the size of the largest region of low root density at the pot surface in larger rooting
volumes independent of nutrient content, thereby decreasing their efficiency of deployment. For
Abutilon, plants responded to elevated CO2 concentrations by equalizing the pattern of deployment
in all the pots. Nutrient concentration, and not pot size or shape, greatly influenced the density of root
growth. Root densities for Abutilon and Setaria were similar to those observed in field conditions,
for annual dicots and monocots respectively, suggesting that studies using pots may successfully
mimic natural conditions.

KEYWORDS: ATMOSPHERIC CARBON-DIOXIDE, FIELD, PHOTOSYNTHETIC
ACCLIMATION, PLANTS, RESTRICTION, SEEDLINGS, WATER RELATIONS, YIELD


     196  
Berntson, G.M., and F.A. Bazzaz. 1996. The allometry of root production and loss in seedlings of
Acer rubrum (Aceraceae) and Betula papyrifera (Betulaceae): Implications for root dynamics in
elevated CO2. American Journal of Botany 83(5):608-616.

Total root production (Sigma P), total root loss (Sigma L), net root production (NP), and biomass
production were determined for seedlings of Betula papyrifera and Acer rubrum in ambient and
elevated CO2 environments. Sigma P, Sigma L, and NP were calculated from sequential, independent
observations of root length production through plexiglass windows. Elevated CO2 increased Sigma
P, Sigma L, and NP in seedlings of Betula papyrifera but not Acer rubntm. Root production and loss
were qualitatively similar to whole-plant growth responses to elevated CO2. Betula showed enhanced
Sigma P. Sigma L, and biomass with elevated CO2 but Acer did not. However, the observed effects
of CO2 on root production and loss did not alter the allometric relationship between root production
and root loss for either Acer or Betula. Thus, in this experiment, elevated CO2 did not affect the
relationship between root production and root loss. The results of this study have important
implications for the potential effects of elevated CO2 on root dynamics. Elevated CO2 may lead to
increases in root production and in root loss (turnover) where the changes in root turnover are largely
a function of the magnitude of root production increases.

KEYWORDS: ATMOSPHERIC CO2, CARBON, COOCCURRING BIRCH, ECOSYSTEMS, FINE
ROOTS, GROWTH-RESPONSE, LEAF LITTER, ORGANIC-MATTER, PLANTS, SYSTEM
ARCHITECTURE


     197  
Berntson, G.M., and F.A. Bazzaz. 1996. Belowground positive and negative feedbacks on CO2
growth enhancement. Plant and Soil 187(2):119-131.

In this paper we present a conceptual model of integrated plant-soil interactions which illustrates the
importance of identifying the primary belowground feedbacks, both positive and negative, which can
simultaneously affect plant growth responses to elevated CO2. The primary negative feedbacks share
the common feature of reducing the amount of nutrients available to plants. These negative feedbacks
include increased litter C/N ratios, and therefore reduced mineralization rates, increased
immobilization of available nutrients by a larger soil microbial pool, and increased storage of nutrients
in plant biomass and detritus due to increases in net primary productivity (NPP). Most of the primary
positive feedbacks share the common feature of being plant mediated feedbacks, the only exception
being Zak et al.'s hypothesis that increased microbial biomass will be accompanied by increased
mineralization rates. Plant nutrient uptake may be increased through alterations in root architecture,
physiology, or mycorrhizal symbioses. Further, the increased C/N ratios of plant tissue mean that a
given level of NPP can be achieved with a smaller supply of nitrogen. Identification of the net plant-
soil feedbacks to enhanced productivity with elevated CO2 are a critical first step for any ecosystem.
It is necessary, however, that we first identify how universally applicable the results are from one
study or one ecosystem before ecosystem models incorporate this information. The effect of elevated
CO2 on plant growth (including NPP, tissue quality, root architecture, mycorrhizal symbioses) can
vary greatly for different species and environmental conditions. Therefore it is reasonable to expect
that different ecosystems will show different patterns of interacting positive and negative feedbacks
within the plant-soil system. This inter-ecosystem variability in the potential for long-term growth
responses to rising CO2 levels implies that we need to parameterize mechanistic models of the impact
of elevated CO2 on ecosystem productivity using a detailed understanding of each ecosystem of
interest.

KEYWORDS: ATMOSPHERIC CARBON-DIOXIDE, DECOMPOSITION, ELEVATED CO2,
ENRICHMENT, FINE ROOTS, LONG-TERM RESPONSE, NITROGEN SATURATION, PLANT,
SOIL SYSTEM, TEMPERATE FOREST ECOSYSTEMS


     198  
Berntson, G.M., and F.A. Bazzaz. 1997. Elevated CO2 and the magnitude and seasonal dynamics
of root production and loss in Betula papyrifera. Plant and Soil 190(2):211-216.

The impact of elevated atmospheric CO2 on belowground plant growth is poorly understood relative
to its effects on aboveground growth. We carried out a study of the seasonal dynamics of gross root
production and death to determine how elevated CO2 affected the dynamics of net and gross root
production through a full growing season. We quantified gross root production and root loss from
sequential, in situ images of fine roots of Betula papyrifera in ambient (375 ppm.) and elevated (700
ppm) CO2 atmospheres from 2 weeks following germination through leaf senescence. We found that
elevated CO2 led to increases in the magnitude of cumulative gross production (Sigma P) and
cumulative gross loss (Sigma L) of roots. However, the effect of elevated CO2 on these processes
was seasonally dependent. Elevated CO2 led to greater levels of enhancement in Sigma P early in the
growing season, prior to maximum standing root length (NP). In contrast, elevated CO2 led to
greater levels of enhancement in Sigma L in the last half of the growing season, after maximum NP
had been reached. This difference in the timing of when elevated CO2 affects Sigma P and Sigma L
led to a transitory, early enhancement in NP. By the end of the growing season, there was no
significant effect of elevated CO2 on NP, and Sigma P was 87% greater than NP for ambient CO2
and 117% greater in elevated CO2. We conclude that static assessments of belowground productivity
may greatly underestimate gross fine root productivity and turnover and this bias can be exaggerated
with elevated CO2.

KEYWORDS: ATMOSPHERIC CARBON-DIOXIDE, ECOSYSTEMS, FINE ROOTS, LENGTH,
NITROGEN, NORTHERN HARDWOOD FOREST, RESPONSES, TURNOVER


     199  
Berntson, G.M., and F.A. Bazzaz. 1997. Nitrogen cycling in microcosms of yellow birch exposed
to elevated CO2: Simultaneous positive and negative below-ground feedbacks. Global Change
Biology 3(3):247-258.

This study investigated simultaneous plant and soil feedbacks on growth enhancement with elevated
[CO2] within microcosms of yellow birch (Betula alleghaniensis Britt.) in the second year of growth.
Understanding the integrated responses of model ecosystems may provide key insight into the
potential net nutrient feedbacks on [CO2] growth enhancements in temperate forests. We measured
the net biomass production, C:N ratios, root architecture, and mycorrhizal responses of yellow birch,
in situ rates gross nitrogen mineralization and the partitioning of available NH4+ between yellow
birch and soil microbes. Elevated atmospheric [CO2] resulted in significant alterations in the cycling
of N within the microcosms. Plant C/N ratios were significantly increased, gross mineralization and
NH4+ consumption rates were decreased, and relative microbial uptake of NH4+ was increased,
representing a suite of N cycling negative feedbacks on N availability. However, increased C/N ratios
may also be a mechanism which allows plants to maintain higher growth with a constant or reduced
N supply. Total plant N content was increased with elevated [CO2], suggesting that yellow birch had
successfully increased their ability to acquire nutrients during the first year of growth. However, plant
uptake rates of NH4+ had decreased in the second year. This discrepancy implies that, in this study,
nitrogen uptake skewed a trend through ontogeny of decreasing enhancement under elevated [CO2].
The reduced N mineralization and relatively increased N immobilization are a potential feedback
which may drive this ontogenetic trend. This study has demonstrated the importance of using an
integrated approach to exploring potential nutrient-cycling feedbacks in elevated [CO2].

KEYWORDS: ATMOSPHERIC CARBON-DIOXIDE, DECOMPOSITION DYNAMICS, DIRECT
EXTRACTION, FINE ROOTS, GROWTH ENHANCEMENT, HARDWOOD LEAF LITTER, LIGNIN
CONTENT, MICROBIAL BIOMASS NITROGEN, POOL DILUTION, SOIL ORGANIC MATTER


     200  
Berntson, G.M., and F.A. Bazzaz. 1998. Regenerating temperate forest mesocosms in elevated
CO2: belowground growth and nitrogen cycling. Oecologia 113(1):115-125.

The response of temperate forest ecosystems to elevated atmospheric CO2 concentrations is
important because these ecosystems represent a significant component of the global carbon cycle.
Two important but not well understood processes which elevated CO2 may substantially alter in these
systems are regeneration and nitrogen cycling. If elevated CO2 leads to changes in species
composition in regenerating forest communities then the structure and function of these ecosystems
may be affected. In most temperate forests, nitrogen appears to be a limiting nutrient. If elevated CO2
leads to reductions in nitrogen cycling through increased sequestration of nitrogen in plant biomass
or reductions in mineralization rates, long-term forest productivity may be constrained. To study
these processes, we established mesocosms of regenerating forest communities in controlled
environments maintained at either ambient (375 ppm) or elevated (700 ppm) CO2 concentrations.
Mesocosms were constructed from intact monoliths of organic forest soil. We maintained these
mesocosms for 2 years without any external inputs of nitrogen and allowed the plants naturally
present as seeds and rhizomes to regenerate. We used N-15 pool dilution techniques to quantify
nitrogen fluxes within the mesocosms at the end of the 2 years. Elevated atmospheric CO2
concentration significantly affected a number of plant and soil processes in the experimental
regenerating forest mesocosms. These changes included increases in total plant biomass production,
plant C/N ratios, ectomycorrhizal colonization of tree fine roots, changes in tree fine root
architecture, and decreases in plant NH4+ uptake rates, gross NH4+ mineralization rates, and gross
NH4+ consumption rates. In addition, there was a shift in the relative biomass contribution of the two
dominant regenerating tree species; the proportion of total biomass contributed by white birch (Betula
papyrifera) decreased and the proportion of total biomass contributed by yellow birch (B.
alleghaniensis) increased. However, elevated CO2 had no significant effect on the total amount of
nitrogen in plant and soil microbial biomass. In this study we observed a suite of effects due to
elevated CO2, some of which could lead to increases in potential long term growth responses to
elevated CO2, other to decreases. The reduced plant NH4+ uptake rates we observed are consistent
with reduced NH4+ availability due to reduced gross mineralization rates. Reduced NH4+
mineralization rates are consistent with the increases in C/N ratios we observed for leaf and fine root
material. Together, these data suggest the positive increases in plant root architectural parameters and
mycorrhizal colonization may not be as important as the potential negative effects of reduced nitrogen
availability through decreased decomposition rates in a future atmosphere with elevated CO2.

KEYWORDS: ATMOSPHERIC CARBON-DIOXIDE, DIRECT EXTRACTION, LEAF LITTER,
MICROBIAL BIOMASS NITROGEN, PLANT, POOL DILUTION, RESPONSES, SEEDLINGS,
SOIL, TERRESTRIAL ECOSYSTEMS


     201  
Berntson, G.M., N. Rajakaruna, and F.A. Bazzaz. 1998. Growth and nitrogen uptake in an
experimental community of annuals exposed to elevated atmospheric CO2. Global Change Biology
4(6):607-626.

Rising levels of atmospheric CO2 may alter patterns of plant biomass production. These changes will
be dependent on the ability of plants to acquire sufficient nutrients to maintain enhanced growth.
Species-specific differences in responsiveness to CO2 may lead to changes in plant community
composition and biodiversity. Differences in species-level growth responses to CO2 may be, in a large
part, driven by differences in the ability to acquire nutrients. To understand the mechanisms of how
elevated CO2 leads to changes in community-level productivity, we need to study the growth
responses and patterns of nutrient acquisition for each of the species that comprise the community.
In this paper, we present a study of how elevated CO2 affects community-level and species-level
patterns of nitrogen uptake and biomass production. As an experimental system we use experimental
communities of 11 co- occurring annuals common to disturbed seasonal grasslands in south-western
U.S.A. We established experimental communities with approximately even numbers of each species
in three different atmospheric CO2 concentrations (375, 550, and 700 ppm). We maintained these
communities for 1, 1.5, and 2 months at which times we applied a N-15 tracer ((NH4NO3)-N-15-N-
15) to quantify the nitrogen uptake and then measured plant biomass, nitrogen content, and nitrogen
uptake rates for the entire communities as well as for each species. Overall, community- level
responses to elevated CO2 were consistent with the majority of other studies of individual- and
multispecies assemblages, where elevated CO2 leads to enhanced biomass production early on, but
this enhancement declines through time. In contrast, the responses of the individual species within the
communities was highly variable, showing the full range of responses from positive to negative. Due
to the large variation in size between the different species, community- level responses were generally
determined by the responses of only one or a few species. Thus, while several of the smaller species
showed trends of increased biomass and nitrogen uptake in elevated CO2 at the end of the
experiment, community-level patterns showed a decrease in these parameters due to the significant
reduction in biomass and nitrogen content in the single largest species. The relationship between
enhancement of nitrogen uptake and biomass production in elevated CO2 was highly significant for
both 550 ppm and 700 ppm CO2. This relationship strongly suggests that the ability of plants to
increase nitrogen uptake (through changes in physiology, morphology, architecture, or mycorrhizal
symbionts) may be an important determinant of which species in a community will be able to respond
to increased CO2 levels with increased biomass production. The fact that the most dominant species
within the community showed reduced enhancement and the smaller species showed increased
enhancement suggest that through time, elevated CO2 may lead to significant changes in community
composition. At the community level, nitrogen uptake rates relative to plant nitrogen content were
invariable between the three different CO2 levels at each hardest. This was in contrast to significant
reductions in total plant nitrogen uptake and nitrogen uptake relative to total plant biomass. These
patterns support the hypothesis that plant nitrogen uptake is largely regulated by physiological
activity, assuming that physiological activity is controlled by nitrogen content and thus protein and
enzyme content.

KEYWORDS: ARCHITECTURE, BIODIVERSITY, CARBON DIOXIDE, ECOSYSTEMS,
ENRICHMENT, GAILLARDIA-PULCHELLA, LOBLOLLY-PINE, PHLOX, PLANTS, RESPONSES


     202  
Berntson, G.M., P.M. Wayne, and F.A. Bazzaz. 1997. Below-ground architectural and
mycorrhizal responses to elevated CO2 in Betula alleghaniensis populations. Functional Ecology
11(6):684-695.

1. Replicate populations of crowded, regenerating stands of Betula alleghaniensis were grown in
ambient and elevated (700 p.p.m.) atmospheric CO2 concentrations in monoliths of forest soil. Early
in the second year the seedlings were harvested and detailed measurements of individual plant root
architectural parameters and ectomycorrhizal colonization were made. 2. Comparing the average
responses of individual plants within the populations, elevated CO2 had no significant effects on
architectural parameters that improve a plant's ability to forage for and acquire soil resources. In
contrast, the intensity and magnitude of mycorrhizal colonization, and whole plant C/N ratios were
significantly enhanced with elevated CO2. 3. The allometric scaling relationship between total plant
biomass and root biomass was not affected by CO2, suggesting that relative allocation between roots
and shoots was not affected. However, the allometric scaling relationships between root architectural
parameters and plant biomass, and between fine root biomass and woody root biomass were
significantly altered by elevated CO2. For all of these relationships, elevated CO2 reduced the 'size
bias' of architectural components in relation to plant size within the populations; in elevated CO2 root
architectural size (e.g. root length) per unit biomass was more similar between the smallest and largest
individuals within the population than was the case for ambient CO2. 4. Overall, the results of this
study suggest that the average individual seedling biomass and architectural growth responses within
populations of plants exposed to elevated atmospheric CO2 levels may be unresponsive, but that
mycorrhizal responses and interactions among plants within populations may be altered significantly.
These findings have important implications for how we make predictions about plant growth
responses to elevated CO2 in natural ecosystems. Significant increases in mycorrhizal infection rates
and architecture-biomass allometries suggest that below-ground competitive interactions within plant
populations may be reduced in elevated CO2. Alterations in competitive interactions may lead to
shifts in productivity and plant population structure.

KEYWORDS: ATMOSPHERIC CARBON-DIOXIDE, COMPETITION, ENRICHMENT, FOREST
ECOSYSTEMS, GROWTH, PLANT-ROOT SYSTEMS, QUERCUS-ALBA, SEEDLINGS, SIZE
HIERARCHIES, SOIL


     203  
Berntson, G.M., and F.I. Woodward. 1992. The root-system architecture and development of
senecio- vulgaris in elevated co2 and drought. Functional Ecology 6(3):324-333.

1. The impact of elevated CO2 and drought on the architecture and development of root systems of
Senecio vulgaris was examined and implications for water and nutrient uptake discussed. Plants were
grown in miniature rhizotrons to non- destructively monitor the development of roots in situ at both
an elevated (700-mu-mol mol-1) and ambient (350-mu-mol mol-1) atmospheric CO2 concentration
and a high or a low supply of water. 2. CO2 and water had a significant impact on the way that S.
vulgaris root systems filled the soil matrix. Elevated CO2 resulted in more branched, longer root
systems that foraged through larger volumes of soil. Under elevated CO2 and a low water supply,
root systems had branching and foraging patterns and root length similar to those grown under
ambient CO2 with a high water supply. 3. Overall, water had a more pronounced impact on the
growth rate of S. vulgaris roots than did CO2. The density of rooting remained unchanged across all
treatments. Thus, under elevated CO2 the intensity of foraging S. vulgaris root systems might be
unchanged while the extent of foraging by these root systems, as indicated by the horizontal spread
of roots, may be increased.



     204  
Berry, S.C., G.T. Varney, and L.B. Flanagan. 1997. Leaf delta C-13 in Pinus resinosa trees and
understory plants: Variation associated with light and CO2 gradients. Oecologia 109(4):499-506.

Our objective was to evaluate the relative importance of gradients in light intensity and the isotopic
composition of atmospheric CO2 for variation in leaf carbon isotope ratios within a Pinus resinosa
forest. In addition, we measured photosynthetic gas exchange and leaf carbon isotope ratios on four
understory species (Dryopteris carthusiana, Epipactus helleborine, Hieracium floribundum, Rhamnus
frangula), in order to estimate the consequence of the variation in the understory light microclimate
for carbon gain in these plants. During midday, CO2 concentration was relatively constant at vertical
positions ranging from 15 m to 3 m above ground. Only at positions below 3 m was CO2
concentration significantly elevated above that measured at 15 m. Based on the strong linear
relationship between chan in CO2 concentration and delta(13)C values for air samples collected
during a diurnal cycle, we calculated the expected vertical profile for the carbon isotope ratio of
atmospheric CO2 within the forest. These calculations indicated that leaves at 3 m height and above
were exposed to CO2 of approximately the same isotopic composition during daylight periods. There
was no significant difference between the daily mean delta(13)C values at 15 m (- 7.77 parts per
thousand) and 3 m (-7.89 parts per thousand), but atmospheric CO2 was significantly depleted in C-
13 closer to the ground surface, with daily average delta(13)C values of -8.85 parts per thousand at
5 cm above ground. The light intensity gradient in the forest was substantial, with average
photosynthetically active radiation (PAR) on the forest floor approximately 6% of that received at
the top of the canopy. In contrast, there were only minor changes in air temperature, and so it is likely
that the leaf-air vapour pressure difference was relatively constant from the top of the canopy to the
forest floor. For red pine and elm tree samples, there was a significant correlation between leaf
delta(13)C value and the height at which the leaf sample was collected. Leaf tissue sampled near the
forest floor, on average, had lower delta(13)C values than samples collected near the top of the
canopy. We suggest that the average light intensity gradient through the canopy was the major factor
influencing vertical changes in tree leaf delta(13)C values. In addition, there was a wide range of
variation (greater than 4 parts per thousand) among the four understory plant species for average leaf
delta(13)C values. Measurements of leaf gas exchange, under natural light conditions and with
supplemental light, were used to estimate the influence of the light microclimate on the observed
variation in leaf carbon isotope ratios in the understory plants. Our data suggest that one species,
Epipactus helleborine, gained a substantial fraction of carbon during sunflecks.

KEYWORDS: AMAZONIAN RAIN FORESTS, ATMOSPHERIC CO2, C 13/C 12, CANOPIES,
CARBON ISOTOPE DISCRIMINATION, LEAVES, PHOTOSYNTHESIS, STRATIFICATION,
SUNFLECKS, VALUES


     205  
Berryman, C.A., D. Eamus, and G.A. Duff. 1993. The influence of co2 enrichment on growth,
nutrient content and biomass allocation of maranthes-corymbosa. Australian Journal of Botany
41(2):195-209.

Seedlings of Maranthes corymbosa Blume, an evergreen tree of tropical Australia and Indonesia were
grown for 32 weeks under conditions of ambient and elevated (700 mumol CO2 mol-1) CO2 in
tropical northern Australia. Seedlings were exposed to ambient temperature, vapour pressure deficit
and photon flux density fluctuations. Rates of germination and percentage germination were not
affected by elevated CO2.Total plant biomass, height growth, total plant leaf area, numbers of leaves
and branches and specific leaf weight were significantly increased by elevated CO2. Root:shoot ratio
and foliar P, K, Mg, Mn and Ca levels were unaffected but foliar nitrogen levels were decreased by
elevated CO2, Nutrient-use-efficiency was unaffected for phosphorus, magnesium, manganese,
calcium and potassium but nitrogen-use-efficiency increased in response to elevated CO2.

KEYWORDS: ACCLIMATION, CARBON-DIOXIDE ENRICHMENT, CARBOXYLASE, ECOLOGY,
ELEVATED CO2, FOREST, LIRIODENDRON-TULIPIFERA L, NITROGEN, PHOTOSYNTHESIS,
SEEDLING GROWTH


     206  
Berryman, C.A., D. Eamus, and G.A. Duff. 1994. Stomatal responses to a range of variables in
2 tropical tree species grown with co2, enrichment. Journal of Experimental Botany 45(274):539-
546.

Seedlings of Maranthes corymbosa (Blume) and Eucalyptus tetrodonta (F. Muell) were grown with
or without CO2 enrichment (700 mu mol CO2 mol(-1)). The response of stomatal conductance (g(s))
to leaf drying, exogenous abscisic acid and calcium ions was investigated in M. corymbosa.
Reciprocal transfer experiments were also conducted whereby plants were grown in one treatment
and then transferred to the other before g(s) was measured. Stomatal conductance in M. corymbosa
was more sensitive (a greater percentage decline in g(s) per unit percentage decline in leaf fresh
weight) to leaf water status under conditions of CO2 enrichment compared to ambient conditions.
However, the rate of reduction of g(s) in response to exogenous abscisic acid was not influenced by
CO2 treatment. In contrast, the rate of reduction of g(s) in response to exogenous CaCl2 was
decreased under conditions of CO2 enrichment. Reciprocal transfer experiments showed that
exposure to CO2 enrichment results in a short-term, reversible decline in g(s) as a result of decreased
stomatal aperture and a long-term, irreversible decline in g(s) as a result of a decreased stomatal
density. Seedlings of E. tetrodonta were used to investigate the response of g(s) to light flux density,
leaf-to-air vapour pressure difference (LAVPD), leaf internal CO2 concentration (C-i) and
temperature. Reciprocal transfer experiments were also conducted. CO2 enrichment did not influence
the pattern or sensitivity of response of g(s) to LAVPD and C-i in E. tetrodonta. In contrast, the
slope of the response of g(s) to temperature decreased for trees grown under elevated [CO2](a)
conditions and the equilibrium g(s) attained at saturating light was also decreased for plants grown
under elevated [CO2](a) conditions.

KEYWORDS: ABSCISIC- ACID, ATMOSPHERIC CO2, BEHAVIOR, CALCIUM, HUMIDITY,
LEAVES, PRESSURE, SOLANUM-MELONGENA, WATER-STRESS


     207  
Bertani, A., I. Brambilla, S. Mapelli, and R. Reggiani. 1997. Elongation growth in the absence
of oxygen: The rice coleoptile. Russian Journal of Plant Physiology 44(4):543-547.

Rice, one of the few plant species adapted to growth in wetland conditions, is able to germinate in
waterlogged soils promoting only the growth of a white coleoptile in order to reach the surface of
the water, contact the atmosphere, and transfer oxygen to the seed, allowing subsequent growth of
the radicle and leaf. In the anoxic cells of rice coleoptiles, an efficient alcoholic fermentation allows
an elevated energy charge to be maintained. Significant RNA and protein syntheses including
phosphorylation and glycosylation occur too. The cytoplasmic pH is maintained at a level far from
acidosis. The anoxic growth of rice coleoptiles, essentially an elongation growth, is sustained by a
high turgor pressure, with free amino acids and potassium as main components. Among the metabolic
processes involved in the regulation of the elongation of rice coleoptiles, a crucial role is played by
amino acid metabolism and the accumulation of putrescine, which is able to stimulate plasmalemma
ATPase activity. Anaerobic elongation is also stimulated in the presence of 20% CO2 in the growth
medium, inhibited by light and abscisic acid, unaffected by ethylene, and slightly promoted by auxin.
The role of both metabolites and hormones along with environmental factors in maintaining cellular
homeostasis and coleoptile elongation are reconsidered and discussed in Light of new data.

KEYWORDS: ACCUMULATION, ANAEROBIOSIS, ANOXIA, GERMINATION, METABOLIC-
RATE, ORYZA SATIVA L, PH, POLYAMINES, PROTEIN-SYNTHESIS, SEEDLINGS


     208  
Bertin, N., and C. Gary. 1993. Evaluation of tomgro, a dynamic-model of growth and development
of tomato (lycopersicon-esculentum mill) at various levels of assimilate supply-and-demand.
Agronomie 13(5):395-405.

TOMGRO, a tomato growth and development model, has been examined under different levels of
assimilate source and sink activities, induced by CO2 enrichment and truss thinning. The main
purpose was the evaluation of the assumptions on dry matter partitioning and fruit setting. The
photosynthesis submodel has been calibrated to fit the daily dry matter production. The main input
parameters to the development and growth submodels have been experimentally measured. The
calibrated model provides good simulations of the leaf area expansion, but it takes no account of the
variations in the assimilates stored in leaf blades. Total fruit growth is well simulated in spite of a
small underestimation for of development and simulations of source/sink balance leads to good
simulations of the number of set fruits. This result confirms the hypothesis that fruit set depends on
the ratio between assimilate source and sink activities. This calibration with a beef tomato cultivar
proves the robustness of the model and permits some improvements to be suggested. The surplus
assimilates should be stored in a pool, which could exert a buffer effect during low supply periods.
Sink strength of reproductive and vegetative parts should be measured for different cultivars, and
under various climatic conditions. Finally, whether the functions of assimilate distribution and fruit
set are still valid under very low supply conditions or whether some organs have priority over the
others remains to be determined.



     209  
Bertin, N., and C. Gary. 1998. Short and long term fluctuations of the leaf mass per area of tomato
plants - Implications for growth models. Annals of Botany 82(1):71-81.

The leaf mass per unit leaf area (LMA) is a key variable in many growth models, since it is often used
to predict leaf area expansion from leaf dry weight increase, or vice versa. Influences of source-sink
balance on leaf area, leaf dry weight, LMA, and leaf content in non-structural carbohydrates were
investigated in glasshouse tomato crops. The source-sink balance was manipulated by artificial
shading, CO2 enrichment or fruit removal using different tomato cultivars. Leaf area was hardly
affected by competition for assimilates except under extreme conditions. Iri contrast, leaf dry weight,
and consequently LMA, underwent large and rapid fluctuations in response to any factor that changed
source and sink activities. A 60% reduction of photosynthetically active radiation involved a 24%
decrease in LMA after 10 d. Carbon dioxide enrichment and fruit removal induced about a 45% and
15% increase in LMA, respectively, on plants with two fruiting trusses, but hardly affected LMA of
producing plants. No significant cultivar effect could be identified. Changes in starch and soluble
sugar content in leaves accounted for only 29% of diurnal variations in LMA, suggesting regular
fluctuations of other components. We propose that structural LMA varies between a maximum and
a minimum value according to the ratio of assimilate supply and demand during leaf development.
Leaf area is independent of the supply of assimilates when the minimum structural LMA is realised.
When the maximum structural LMA is attained, a storage pool of assimilates may accumulate in
leaves during periods of high supply and low demand. We present a model including these
hypotheses, which predicts structural and non- structural LMA variations of plants with different
source-sink ratios. (C) 1998 Annals of Botany Company.

KEYWORDS: CARBON-DIOXIDE ENRICHMENT, CROP, LEAVES, PHOTOSYNTHESIS,
SOURCE-SINK RELATIONSHIPS


     210  
Bertin, N., and E. Heuvelink. 1993. Dry-matter production in a tomato crop - comparison of 2
simulation-models. Journal of Horticultural Science 68(6):995-1011.

TOMSIM(1.0) and TOMGRO(1.0) are two dynamic models for tomato growth and development.
Their submodels for dry matter production are compared and discussed. In TOMSIM(1.0), dry matter
production is simulated by a modified version of SUCROS87 (Spitters et al., 1989). Single leaf
photosynthesis rates are calculated separately for shaded and sunlit leaf area at different depths in the
canopy, according to the direct and diffuse components of light; daily crop gross assimilation rate (A)
is computed by integration of these rates over the different depths and over the day. In TOMSIM(1.0)
leaf photochemical efficiency (epsilon) and potential leaf gross photosynthesis rate at saturating light
level (P(g,max)) both depend on temperature and CO2 level. In TOMGRO(1.0) crop gross
photosynthesis rate is calculated by the equation of Acock et al. (1978); epsilon is a constant and
P(g,max) is a linear function of CO2. In both models leaf photosynthesis characteristics are assumed
to be identical in the whole canopy. Maintenance respiration (R(m)) and conversion efficiency (C(f))
are taken into account in the same way, except that root maintenance respiration is neglected in
TOMGRO(1.0). For both models a sensitivity analysis was performed on the input variables (light
intensity, temperature, CO2 and leaf area index (LAI)) and on some of the model parameters. Under
most conditions considered, simulated A was found to be 5-30% higher in TOMSIM(1.0) than in
TOMGRO(1.0). At temperatures above 18-degrees-C R(m) was also higher in TOMSIM(1.0), and
C(f) was 4% higher in TOMGRO(1.0). The two models were very sensitive to changes in epsilon and
to a lesser extent to changes in the light extinction coefficient, whereas the scattering coefficient of
leaves had hardly any effect on the simulated A. TOMGRO(1.0) appeared to be rather sensitive to
the CO2 use efficiency, whereas at ambient CO2 level mesophyll resistance was quite important in
TOMSIM(1.0). Four sets of experimental data (differences in cultivar, CO2 enrichment and planting
date) from Wageningen (The Netherlands) and Montfavet (southern France) were used to validate
the models. Average 24 h temperature and average daily CO2 concentration values were used as
input to the models. For the Wageningen experiments, hourly PAR values were calculated from the
daily global radiation sum by TOMSIM(1.0) and used as input in both models. For the Montfavet
experiment, average hourly PAR measurements were used. Also measured LAI, dry matter
distribution and organ dry weights (for calculation of R(m)) were input to the simulation. In the
Wageningen experiments, total dry matter production was simulated reasonably well by both models,
whereas in the Montfavet experiment an under- estimation of about 35% occurred. TOMGRO(1.0)
and TOMSIM(1.0) simulated almost identical curves in all four experiments. Strong and weak points
of both models are discussed.

KEYWORDS: CANOPY, CO2, GAS-EXCHANGE, GROWTH, LEAVES, LIGHT,
PHOTOSYNTHESIS, YIELD


     211  
Bertoni, G.P., and W.M. Becker. 1996. Expression of the cucumber hydroxypyruvate reductase
gene is down-regulated by elevated CO2. Plant Physiology 112(2):599-605.

We examined the effects of CO2 concentration on the white- light-stimulated expression of the
cucumber (Cucumis sativus L.) Hpr gene. Hpr encodes hydroxypyruvate reductase, an enzyme
important in the photorespiratory glycolate pathway, which plays an integral role in carbon allocation
in C-3 plants. Because CO2 is an end product of this pathway and because increased CO2
concentrations lessen the need for photorespiration, we tested whether exposure of plants to elevated
CO2 would affect white-light-stimulated Hpr gene expression. Exposure of dark-adapted cucumber
seedlings to elevated CO2 (2 to 3 times ambient) during a 4-h white-light irradiation significantly
inhibited the accumulation of Hpr mRNA. Increasing the CO2 concentration during irradiation to 6
or 9 times ambient did not further inhibit Hpr mRNA accumulation. The depressing effect of high
CO2 on Hpr mRNA accumulation was seen in both high and low light, but was more pronounced in
higher light. These results suggest that maximum sensitivity to CO2 occurs in conditions near those
normally encountered by the plant (high light, CO2 concentration near ambient) and support a model
in which white-light-regulated Hpr expression is modulated in part by environmental CO2
concentration.

KEYWORDS: COTYLEDONS, PHOTORESPIRATION, PLANT, SEQUENCE


     212  
Besford, R.T. 1993. Photosynthetic acclimation in tomato plants grown in high co2. Vegetatio
104:441-448.

The effects of prolonged CO2 enrichment of tomato plants on photosynthetic performance and Calvin
cycle enzymes, including the amount and activity of ribulose-1,5-bisphosphate carboxylase (RuBPco),
were determined. Also the light-saturated rate of photosynthesis (P(max)) of the 5th leaf throughout
leaf development was predicted based on the amount and kinetics of RuBPco. With short-term CO2
enrichment, i.e. only during the photosynthesis measurements, P(max) of the young leaves did not
increase while the leaves reaching full expansion more than doubled their net rate of CO2 fixation.
However, with longer- term CO2 enrichment, i.e. growing the crop in high CO2, the plants did not
maintain this photosynthetic gain. Compared with leaves of plants grown in normal ambient CO2 the
high CO2-grown leaves, when almost fully expanded, contained only about half as much RuBPco
protein and P(max) in 300 and 1000 vpm CO2 was similarly reduced. The loss of RuBPco protein
may be a factor associated with the accelerated fall in P(max) since P(max) was close to that
predicted from the amount and kinetics of RuBPco assuming RuBP saturation. Acclimation to high
CO2 is fundamentally different from acclimation to high light. In contrast to acclimation to high light,
acclimation to high CO2 does not usually involve an increase in photosynthetic machinery so the
synthesis and maintenance costs (as indicated by the dark respiration rate) are generally lower.

KEYWORDS: ACTIVATION, CALVIN CYCLE ENZYMES, ENRICHMENT, HIGH ATMOSPHERIC
CO2, LEAVES, NITROGEN, RIBULOSE-1;5-BISPHOSPHATE CARBOXYLASE-OXYGENASE,
RICE, WHEAT


     213  
Betsche, T. 1994. Atmospheric co2 enrichment - kinetics of chlorophyll a fluorescence and
photosynthetic co2 uptake in individual, attached cotton leaves. Environmental and Experimental
Botany 34(1):75-86.

Chl fluorescence and gas exchange of attached cotton leaves (Gossypium hirsutum L.) were measured
in ambient air and in a highly CO2-enriched atmosphere (4000 mu l l(-1) CO2; photosynthetic
saturation). In the shore term (hours to one day), net CO2 uptake approximately doubled in all leaves
examined. Photochemical (q(P)) and nonphotochemical (q(NP)) quenching of chlorophyll
fluorescence, and calculated linear photosynthetic electron Row, did not change significantly when
CO2 rose from 250 to 4000 mu l l(-1) CO2. These results show that high CO2 concentration did not
inhibit photosynthesis in any leaf. In contrast, the long-term response of leaves to atmospheric CO2-
enrichment was variable, Some leaves sustained the initial high level of photosynthetic stimulation for
more than a week while in others photosynthetic CO2-uptake declined more or less. These leaves
turned yellowish-green although chlorophyll content declined little. Variance in the degree of leaf
yellowing was also encountered in experiments with clover when sets of plants were CO2-enriched.
Gas exchange and chi fluorescence results suggest that yellowing of cotton leaves in high CO2 was
not equivalent to 'natural' senescence although some chlorophyll fluorescence parameters changed
similarly. During extended high CO2 treatment the level of q(NP) increased notably in the yellowing
leaves. The high levels of q(NP) and relaxation kinetics of chi fluorescence quenching recorded upon
darkening demonstrate that thylakoid energization increased during the decline of photosynthetic CO2
uptake in high CO2. This shows that the photosynthetic decline was not caused by decreasing
thylakoid energization because of physical damage by oversized starch grains. Calculated
photosynthetic electron flow declined little suggesting that CO2 at ribulosebisphosphate carboxylase-
oxygenase fell and thus photorespiration rose. With regard to growth limitation in high CO2
concentration, these results support the concept that high CO2 concentration tends to induce low
inorganic phosphate concentrations (Morin et al. Plant Physiol. 99, 89-95, 1992; Duchein et al. J.
Exp. Bet. 44, 17-22, 1993) which can limit chloroplast ATP synthase and thus increase thylakoid
energization. It is proposed that the different responses of individual leaves to atmospheric CO2
enrichment reflects variety among leaves in the phosphate status or in the capacity for Pi-recycling
(assimilate utilization).

KEYWORDS: CARBON DIOXIDE, CROP RESPONSES, DROUGHT STRESS, ELECTRON-
TRANSPORT, ELEVATED CO2, GROWTH, INORGANIC- PHOSPHATE, PHASEOLUS-
VULGARIS L, PLANT NUTRITION, STARCH


     214  
Bettarini, I., G. Calderoni, F. Miglietta, A. Raschi, and J. Ehleringer. 1995. Isotopic carbon
discrimination and leaf nitrogen-content of erica-arborea L along a co2 concentration gradient in a
co2 spring in italy. Tree Physiology 15(5):327-332.

We studied a Mediterranean species (Erica arborea L.) growing in a CO2 spring in Italy that was
naturally exposed for generations to a gradient of atmospheric CO2 concentrations. The CO2
concentration gradient to which different individual plants were exposed was determined by an
indirect method based on radioisotope analysis. The stable carbon isotope ratio of sampled leaves was
determined by mass spectrometry, and isotopic discrimination was then calculated. Leaf nitrogen,
specific leaf area, total soil nitrogen, soil organic matter content and soil pH were also measured. In
one group of plants, grown on a homogeneous soil and exposed to moderate CO2 enrichment,
isotopic discrimination was significantly reduced in response to increasing CO2 concentrations,
whereas the intercellular CO2 concentration and leaf nitrogen content were almost unaffected. In a
second group of plants, grown along a gradient of CO2 concentration and soil nitrogen content, leaf
nitrogen content was reduced when nitrogen availability was limiting. However, when soil nitrogen
was available in excess, even very high CO2 concentrations did not result in increased discrimination
or reduced leaf nitrogen content in the long term. The results are discussed with respect to current
theories about the long-term CO2 response of plants based on several years of experimentation with
elevated atmospheric CO2 concentrations under controlled conditions.

KEYWORDS: ELEVATED CO2, ENVIRONMENT, LEAVES, PHOTOSYNTHESIS, PLANT-
RESPONSES, STOMATAL DENSITY


     215  
Bettarini, I., F.P. Vaccari, and F. Miglietta. 1998. Elevated CO2 concentrations and stomatal
density: observations from 17 plant species growing in a CO2 spring in central Italy. Global Change
Biology 4(1):17-22.

Stomatal density (SD) and stomatal conductance (g(s)) can be affected by an increase of atmospheric
CO2 concentration. This study was conducted on 17 species growing in a naturally enriched CO2
spring and belonging to three plant communities. Stomatal conductance, stomatal density and
stomatal index (SI) of plants from the spring, which were assumed to have been exposed for
generations to elevated [CO2], and of plants of the same species collected in a nearby control site,
were compared. Stomatal conductance was significantly lower in most of the species collected in the
CO2 spring and this indicated that CO2 effects on g, are not of a transitory nature but persist in the
long term and through plant generations. Such a decrease was, however, not associated with changes
in the anatomy of leaves: SD was unaffected in the majority of species (the decrease was only
significant in three out of the 17 species examined), and also SI values did not vary between the two
sites with the exception of two species that showed increased SI in plants grown in the CO2-enriched
area. These results did not support the hypothesis that long-term exposure to elevated [CO2] may
cause adaptive modification in stomatal number and in their distribution.

KEYWORDS: ATMOSPHERIC CO2, CARBON DIOXIDE, CONDUCTANCE, EXPOSURE, GAS-
EXCHANGE, GRASSLAND, INCREASE, LEAVES, RESPONSES, TREES


     216  
Betts, R.A., P.M. Cox, S.E. Lee, and F.I. Woodward. 1997. Contrasting physiological and
structural vegetation feedbacks in climate change simulations. Nature 387(6635):796-799.

Anthropogenic increases in the atmospheric concentration of carbon dioxide and other greenhouse
gases are predicted to cause a warming of the global climate by modifying radiative forcing(1).
Carbon dioxide concentration increases may make a further contribution to warming by inducing a
physiological response of the global vegetation-a reduced stomatal conductance, which suppresses
transpiration(2). Moreover, a CO2-enriched atmosphere and the corresponding change in climate may
also alter the density of vegetation cover, thus modifying the physical characteristics of the land
surface to provide yet another climate feedback(3-6). But such feedbacks from changes in vegetation
structure have not yet been incorporated into general circulation model predictions of future climate
change. Here we use a general circulation model iteratively coupled to an equilibrium vegetation
model to quantify the effects of both physiological and structural vegetation feedbacks on a doubled-
CO2 climate. On a global scale, changes in vegetation structure are found to partially offset
physiological vegetation-climate feedbacks in the long term, but overall vegetation feedbacks provide
significant regional-scale effects.

KEYWORDS: CANOPY, EUROPE, FOREST, IMPACT, LAND, MODEL, SENSITIVITY


     217  
Bezemer, T.M., and T.H. Jones. 1998. Plant-insect herbivore interactions in elevated atmospheric
CO2: quantitative analyses and guild effects. Oikos 82(2):212-222.

Interactions between insect herbivores and plants grown under conditions of ambient and elevated
CO2 were investigated by analysing data on 43 herbivores, representing 61 plant- herbivore
interactions. Changes in herbivore performance in enhanced CO2 environments were correlated with
changes in the quality of the host plants, measured as nitrogen content, water content, carbohydrate
content and secondary plant compounds. The data were analysed to determine whether CO2 mediated
effects on insect performance differed between feeding guilds (leaf-chewers, leaf miners, phloem-
feeders (root and shoot), xylem-feeders, whole-cell-feeders and seed-eaters) or instar stage. Host-
plant quality changed in elevated CO2; leaf nitrogen content decreased, on average, by 15% while
carbohydrates increased by 47% and secondary plant compounds (phenolics) by 31%. Water content
did not change. Of the variables measured, changes in nitrogen and carbohydrate levels only were
found to be correlated with changes in food consumption. No differences were found in CO2-
mediated herbivore responses on woody plant compared with non-woody plants. Insects from
different feeding guilds respond to CO2 mediated changes in host-plant quality in various ways. Leaf-
chewers generally seem able to compensate for the decreased nitrogen levels in the plant tissues by
increasing their food consumption (by 30%) and with no adverse effects on pupal weights. Leaf-
miners only slightly increase their food consumption. The negative effect on pupal weight suggests
that their population dynamics may change over several generations. Limited data on seed-eaters
suggest that enhanced CO2 conditions have no effect on these insects. Phloem-feeders and whole-
cell-feeders are the only insects to show a positive CO2 response. Population sizes generally increased
in elevated CO2 and development lime of phloem-feeders was reduced by 17%. Early instar larvae
are restricted more by CO2 enhancement than late instars. Although changes in food consumption
are similar, changes in development times are much more pronounced in young instars (18% vs 6%).

KEYWORDS: CARBON-DIOXIDE ATMOSPHERES, CLIMATE CHANGE, GROWTH, JUNONIA-
COENIA, LEPIDOPTERA, NOCTUIDAE, NUTRIENT BALANCE, PAPER BIRCH,
PERFORMANCE, RESPONSES


     218  
Bezemer, T.M., T.H. Jones, and K.J. Knight. 1998. Long-term effects of elevated CO2 and
temperature on populations of the peach potato aphid Myzus persicae and its parasitoid Aphidius
matricariae. Oecologia 116(1-2):128-135.

Model terrestrial ecosystems were set-up in the Ecotron controlled environment facility. The effects
of elevated CO2 (ambient + 200 mu mol/mol) and temperature (ambient + 2.0 degrees C) on plant
chemistry, the abundance of the peach potato aphid Myzus persicae, and on the performance of one
of its parasitoids Aphidius matricariae, were studied. Total above-ground plant biomass at the end
of the experiment was not affected by elevated atmospheric CO2, nor were foliar nitrogen and carbon
concentrations. Elevated temperature decreased final plant biomass while leaf nitrogen concentrations
increased. Aphid abundance was enhanced by both the CO2 and temperature treatment. Parasitism
rates remained unchanged in elevated CO2, but showed an increasing trend in conditions of elevated
temperature. Our results suggest that M. persicae, an important pest of many crops, might increase
its abundance under conditions of climate change.

KEYWORDS: ATMOSPHERIC CO2, CLIMATE CHANGE, DECOMPOSITION, DYNAMICS,
ECOSYSTEMS, HERBIVORY, HOMOPTERA, INSECT PERFORMANCE, PHYTOCHEMISTRY,
RESPONSES


     219  
Bezemer, T.M., K.J. Knight, J.E. Newington, and T.H. Jones. 1999. How general are aphid
responses to elevated atmospheric CO2? Annals of the Entomological Society of America 92(5):724-
730.

We studied the impact of elevated CO2 on 2 aphid pest species, Myzus persicae and Brevicoryne
brassicae (Homoptera: Aphididae), on a series of host plants in 3 independent studies each differing
in experimental complexity. Measurements on individual aphids showed that host plant and aphid
species significantly influenced the response to elevated CO2. These differences occurred not only
in the level of responsiveness but also directionally. B. brassicae reared on Brassica oleracea produced
significantly less offspring at elevated CO2, whereas the opposite was found for M. persicae on the
same host. No response was found for M. persicae on Senecio vulgaris. When populations of B.
brassicae and M. persicae were followed for a longer period, no differences were observed in
population sizes, Comparisons between different experimental systems show that long-term
population responses to elevated CO2 can not be reliably predicted from detailed measurements on
individual aphids. The consequences of these findings for climate change research are discussed.

KEYWORDS: BREVICORYNE-BRASSICAE, CARBON DIOXIDE, CLIMATE CHANGE,
DECIDUOUS TREES, HERBIVORE INTERACTIONS, INSECT PERFORMANCE, MYZUS-
PERSICAE, PLANT, POPULATION-DYNAMICS, TERRESTRIAL ECOSYSTEMS


     220  
Bezemer, T.M., L.J. Thompson, and T.H. Jones. 1998. Poa annua shows inter-generational
differences in response to elevated CO2. Global Change Biology 4(6):687-691.

Inter-generational effects on the growth of Poa annua (L.) in ambient and elevated atmospheric CO2
conditions (350 and 550 mu l l(-1), respectively) were studied in two different experiments. Both
experiments showed similar results. In a greenhouse experiment growth, measured as the numbers
of tillers produced per week, was compared for plants grown from first and second generation seeds.
Second generation seeds were obtained from plants grown for one whole generation in either ambient
or elevated atmospheric CO2 ('ambient' and 'elevated' seeds, respectively). First generation plants and
second generation 'ambient' plants did not respond to elevated CO2. Second generation 'elevated'
plants produced significantly more tillers in elevated CO2. In the second experiment model terrestrial
ecosystems growing in the Ecotron and which included Poa annua were used. Above-ground biomass
after one and two generations of growth were compared. At the end of Generation 1 no difference
was found in biomass production while at the end of Generation 2 biomass increased in elevated CO2
by 50%. The implications for climate change research are discussed.

KEYWORDS: ECOTRON, ENVIRONMENTS, FACILITY, GROWTH, PLANTS, POPULATION


     221  
Bhattacharya, N.C., D.R. Hileman, P.P. Ghosh, R.L. Musser, S. Bhattacharya, and P.K.
Biswas. 1990. Interaction of enriched CO2 and water-stress on the physiology of and biomass
production in sweet-potato grown in open-top chambers. Plant, Cell and Environment 13(9):933-
940.

The objective of this study was to investigate the effects of water stress in sweet potato (Ipomoea
batatas L. [Lam] 'Georgia Jet') on biomass production and plant-water relationships in an enriched
CO2 atmosphere. Plants were grown in pots containing sandy loam soil (Typic Paleudult) at two
concentrations of elevated CO2 and two water regimes in open-top field chambers. During the first
12 d of water stress, leaf xylem potentials were higher in plants grown in a CO2 concentration of 438
and 666-mu-mol mol-1 than in plants grown at 364-mu-mol mol-1. The 364-mu-mol mol-1 CO2
grown plants had to be rewatered 2d earlier than the high CO2-grown plants in response to water
stress. For plants grown under water stress, the yield of storage roots and root:shoot ratio were
greater at high CO2 than at 364-mu-mol mol-1; the increase, however, was not linear with increasing
CO2 concentrations. In well-watered plants, biomass production and storage root yield increased at
elevated CO2, and these were greater as compared to water-stressed plants grown at the same CO2
concentration.

KEYWORDS: ATMOSPHERIC CO2, ELEVATED CARBON-DIOXIDE, FIELD,
PHOTOSYNTHESIS, SOYBEANS, YIELD


     222  
Bhattacharya, N.C., J.W. Radin, B.A. Kimball, J.R. Mauney, G.R. Hendrey, J. Nagy, K.F.
Lewin, and D.C. Ponce. 1994. Leaf water relations of cotton in a free-air co2-enriched environment.
Agricultural and Forest Meteorology 70(1-4):171-182.

As part of an intensive study of crop response to CO2 enrichment in a free-air CO2 enrichment
(FACE) experiment in the field, we determined aspects of the water relations of a cotton crop on
selected dates in 1991. The atmosphere was enriched from 370 mumol CO2 mol-1 (control) to about
550 mumol mol-1 in free air during daylight hours. Under full irrigation, CO2 enrichment decreased
stomatal conductance and single-leaf transpiration only toward the end of the season, and these
changes led to increased leaf water potentials only at that time of year. Under water-stressed (deficit
irrigation) conditions, CO2 enrichment decreased conductance throughout the season but there was
no corresponding consistent effect on leaf water potentials. As with the fully irrigated controls, CO2
enrichment increased leaf water potentials only at the end of the season. CO2 enrichment increased
season-long biomass accumulation 39% under full irrigation and 34% under deficit irrigation. These
results are consistent with previous studies of cotton in open-top chambers that found only small
effects of CO2 enrichment on internal water relations of cotton, and no water stress-induced increase
in crop responsiveness to elevated CO2.

KEYWORDS: CARBON-DIOXIDE ENRICHMENT, CO2- ENRICHMENT, CONDUCTANCE,
GROWTH, PHOSPHORUS, PHOTOSYNTHESIS, RESPONSES, SEEDLINGS, STRESS, YIELD


     223  
Bialczyk, J., Z. Lechowski, and A. Libik. 1998. Modification of tannin concentration by abiotic
factors in Lycopersicon esculentum Mill. seedlings. Zeitschrift Fur Pflanzenkrankheiten Und
Pflanzenschutz-Journal of Plant Diseases and Protection 105(3):264-273.

Results of the study on the effect of some abiotic factors on the modification of Leaf tannin
concentration of greenhouse tomato seedlings are discussed in the work. The total content of soluble
and insoluble tannins was calculated as tannic acid equivalent x g(-1) dry matter. The cultivars of
tomato were characterized by the differentiated tannin content in leaves, stems; and roots, the
proportion being 1 : 1/2 and 1/3, respectively. Two of the investigated cultivars were characterized
by extreme values of che natural tannin content (cv. 'Baron' with the greatest content and cv. 'Perkoz'
with the smallest one), the differences between them reaching about 240 %. A partial defoliation-or
mechanical wounding of leaf blades increased the content of tannins in these organs, In relation to
the effect of the partial defoliation (about 50 % of leaves being cut oft), the content of tannins was
higher in the case of pricking the leaves with needles. Depending on the number of pricks per cm(2)
of the leaf blade (8, 20 or; 40), associated with a different degree of its wounding (1 %, 2.5 %, and
5 %, respectively), a maximum increase in tannin content was 180 % with 20 pricks x cm(-2) as
compared with the control. The intensity of photosynthetically active radiation (PAR) significantly
affected the kinetics of tannin synthesis. In the case of a 90 % reduction of daily PAR intensity, the
content of tannins was reduced by about 50 % after a 2-week experiment with the two cultivars.
Changes in CO2 concentration in the environment of seedlings differently modified the level of leaf
tannins. With CO2 concentration reduced to 170 mu mol x mol(-1) air, the content of tannins
decreased to about 76 % of the value evidenced in atmospheric air. CO, elevated to 680 mu mol x
mol(-1) air induced an increase in leaf tannins to about 112- 121 % in, relation to the control. The
enrichment of soil solution with phosphorus or nitrogen compounds had different and opposing
effects on tannin content. With phosphorus enrichment of the substrate, the content of tannins in
leaves increased to about 120 % in relation to the control. The elevated nitrogen concentration
reduced the content of tannins by about 30 % after a 2-week experiment. The results concerning the
effect of abiotic factors on the tannin level in the leaves of greenhouse tomato seedlings could lead
to the development of control measures based-on the activation of the natural defense system of
planes against herbivores.

KEYWORDS: CARBON NUTRIENT BALANCE, CO2, PATHWAY, PHYTOCHEMISTRY,
POLYPHENOL OXIDASE, RESPONSES


     224  
Bialczyk, J., Z. Lechowski, and A. Libik. 1999. The protective action of tannins against glasshouse
whitefly in tomato seedlings. Journal of Agricultural Science 133:197-201.

The synthesis and accumulation of tannins on tomato seedlings are regulated by environmental
factors. The variation in the content of tannins was sufficiently important to bring about the
occurrence of significant differences in the numbers of glasshouse whitefly on the seedlings. During
a 2-week experiment, the treatments included mechanical wounding (20 prickings per cm(2)),
spraying with kinetin solutions of 10(-4) mol/dm(3), plant growth regulators, and the atmosphere
enrichment to 680 mu mol CO2/mol air, the content of tannins being increased by c. 40, 70, 10-45
and 25 % above the values obtained in the control. These results were correlated with a decrease in
the numbers of insects occurring on the seedlings by c. 35, 45, 8-29 and 18 %, respectively. Contrary
to the above results the spraying with solutions of abscisic acid, gibberellic acid, and the incubation
of plants in an atmosphere containing 170 mu mol CO2/mol air, reduced the content of tannins by c.
69, 22 and 25 %, respectively. This was reflected in the respective increases by c. 70, 40 and 35%
in the numbers of insects occurring on the seedlings. The obtained results suggest that tannins seem
to have a dosage-dependent effect on glasshouse whitefly. Decreasing the host plant quality by
increasing tannin content may act as an important selective agent limiting the losses brought about
by glasshouse whitefly in tomato cultivation.

KEYWORDS: CHEMICAL DEFENSE, CO2, GROWTH, METABOLISM, NUTRIENT, PLANT
POLYPHENOLS, RESPONSES, TREE


     225  
Billes, G., H. Rouhier, and P. Bottner. 1993. Modifications of the carbon and nitrogen allocations
in the plant (triticum-aestivum L) soil system in response to increased atmospheric co2 concentration.
Plant and Soil 157(2):215-225.

The aim of this work was to examine the response of wheat plants to a doubling of the atmospheric
CO2 concentration on: (1) carbon and nitrogen partitioning in the plant, (2) carbon release by the
roots; and (3) the subsequent N uptake by the plants. The experiment was performed in controlled
laboratory conditions by exposing fast-growing spring wheat plants, during 28 days, to a (CO2)-C-14
concentration of 350 or 700 muL L-1 at two levels of soil nitrogen fertilization. Doubling CO2
availability increased total plant production by 34% for both N treatment. In the N-fertilized soil, the
CO2 enrichment resulted in an increase in dry mass production of 41% in the shoots and 23% in the
roots; without N fertilization this figure was 33% and 37%, respectively. In the N-fertilized soil, the
CO2 increase enhanced the total N uptake by 14% and lowered the N concentration in the shoots by
23%. The N concentration in the roots was unchanged. In the N-fertilized soil, doubling CO2
availability increased N uptake by 32% but did not change the N concentrations, in either shoots or
roots. The CO2 enrichment increased total root-derived carbon by 12% with N fertilization, and by
24% without N fertilization. Between 85 and 90% of the total root derived-C-14 came from
respiration, leaving only 10 to 15% in the soil as organic C-14. However, when total root-derived C-
14 was expressed as a function of root dry weight, these differences were only slightly significant.
Thus, it appears that the enhanced carbon release from the living roots in response to increased
atmospheric CO2, is not due to a modification of the activity of the roots, but is a result of the
increased size of the root system. The increase of root dry mass also resulted in a stimulation of the
soil N mineralization related to the doubling atmospheric CO2 concentration. The discussion is
focused on the interactions between the carbon and nitrogen allocation, especially to the root system,
and the implications for the acquisition of nutrients by plants in response to CO2 increase.

KEYWORDS: DIOXIDE, DRY-MATTER, ELEVATED CO2, ENRICHMENT, GROWTH,
METABOLISM, MICROBIAL BIOMASS, MINERAL NUTRITION, RESPIRATION, ROOT-
DERIVED MATERIAL


     226  
Bindi, M., L. Fibbi, B. Gozzini, S. Orlandini, and F. Miglietta. 1996. Modelling the impact of
future climate scenarios on yield and yield variability of grapevine. Climate Research 7(3):213-224.

A mechanistic growth model was used to evaluate the mean yield and yield variability of grapevine
Vitis vinifera L. under current and future climates. The model used was previously validated using
field experiment data. The effect of elevated CO2 on grapevine growth was also considered.
Adaptation of 2 varieties (Sangiovese and Cabernet Sauvignon) to scenarios of increased CO2 and
climate change, and potential changes in agricultural risk (i.e. inter-seasonal variability), were
examined. Before testing the effect of climate scenarios, we analysed the sensitivity of modelled
grapevine yield to arbitrary changes in the 3 driving variables (temperature, solar radiation and CO2).
The results showed the model to be more sensitive to changes in CO2 concentration and temperature
than to changes in radiation. Analyses made using transient GCM (general circulation model)
scenarios (UKTR and GFDL) showed different changes in mean fruit dry matter for the different
scenarios, whereas mean total dry matter, and fruit and total dry matter variability, were predicted
to increase under almost all the scenarios. Predictions based on equilibrium scenarios (UKLO and
UKHI) gave similar results. For Sangiovese, variety adaptation analysis suggested a better adaptation
in terms of mean production, but a worse adaptation in terms of yield variability.

KEYWORDS: CO2, RADIATION, TEMPERATURE


     227  
Biondi, F., and J.E. Fessenden. 1999. Response of lodgepole pine growth to CO2 degassing at
Mammoth Mountain, California. Ecology 80(7):2420-2426.

We conducted dendroclimatic and stable isotope analyses of lodgepole pines (Pinus contorta) located
in high-mortality sites at Mammoth Mountain (California, USA) to test for tree responses to
magmatic degassing. Existing climatic and tree- ring data from nearby Yellowstone National Park
were used for comparison. Sampled trees were scarcely sensitive to climate, and their growth showed
an overall decline during the 20th century. Past growth rates of currently dead and stressed pines
plummeted after 1990, when degassing of magmatic CO2 was first reported in the area. No consistent
or strong correlation was found with monthly and seasonal climatic parameters. Stable carbon
isotopes were measured on holocellulose extracted from annual rings of a dead pine, a stressed pine,
and a live pine. The delta(13)C signature of the dead and stressed pines showed enrichment in heavy
carbon beginning in 1990, which could be related to stomatal closure following impairment of root
systems by high levels of magmatic CO2 in the soil.

KEYWORDS: CARBON, EMISSION, ISOTOPE, LONG VALLEY CALDERA, RATIOS, RINGS,
UNREST


     228  
Bishop, D.L., and B.G. Bugbee. 1998. Photosynthetic capacity and dry mass partitioning in dwarf
and semi-dwarf wheat (Triticum aestivum L.). Journal of Plant Physiology 153(5-6):558-565.

Efficient use of space and high yields are critical for long- term food production aboard the
International Space Station. The selection of a full dwarf wheat (less than 30 cm tall) with high
photosynthetic and yield potential is a necessary prerequisite for growing wheat in the controlled,
volume- limited environments available aboard long-term spaceflight missions. This study evaluated
the photosynthetic capacity and carbon partitioning of a full-dwarf wheat cultivar, Super Dwarf,
which is routinely used in spaceflight studies aboard U.S. space shuttle and NASA/Mir missions and
made comparisons with other dwarf and semidwarf wheat cultivars utilized in other ground-based
studies in plant space biology. Photosynthetic capacity of the flag leaf in two dwarf (Super Dwarf,
BB-19), and three semi-dwarf (Veery-10, Yecora Rojo, IBWSN 199) wheat cultivars (Triticum
aestivum L.) was assessed by measuring: net maximum photosynthet ic rate, RuBP carboxylation
efficiency, chlorophyll concentration and flag leaf area. Dry mass partitioning of carbohydrates to the
leaves, sheaths, stems and ear was also assessed. Plants were grown under controlled environmental
conditions in three replicate studies: slightly enriched CO2 (370 mu mol mol(-1)), high photosynthetic
photon flux (1000 mu mol m(-2) s(-1); 58 mol m(-2) d(-1)) for a 16 h photoperiod, 22/15 degrees
C day/night temperatures, ample nutrients and water provided by one-half strength Hoagland's
nutrient solution (Hoagland and Amen, 1950). Photosynthetic capacity of the flag leaf was determined
at anthesis using net CO2 exchange rate versus internal CO2 concentration curves measured under
saturating light (2000 mu mol m(-2) s(-1)) and CO2 (1000 mu mol mol(-1)). Dwarf wheat cultivars
had greater photosynthetic capacities than the taller semi-dwarfs, they averaged 20 % higher
maximum net photosynthetic rates compared to the taller semi-dwarfs, but these higher rates occurred
only at anthesis, had slightly greater carboxylation efficiencies and significantly increased chlorophyll
concentrations per unit leaf area. The reduced- height wheat had significantly less dry mass fraction
in the stem but greater dry mass partitioned to the ear than the taller semi-dwarfs (Yecora rojo,
IBWSN-199). Studies with detached heads confirm that the head is a significant sink in the shorter
wheat cultivars.

KEYWORDS: BIOCHEMISTRY, CANOPY, FLAG LEAF, GAS-EXCHANGE, HEIGHT, LEAVES,
RIBULOSE-1;5-BISPHOSPHATE CARBOXYLASE, SPRING WHEAT, SUCROSE METABOLISM,
WINTER-WHEAT


     229  
Biswas, P.K., D.R. Hileman, P.P. Ghosh, N.C. Bhattacharya, and J.N. McCrimmon. 1996.
Growth and yield responses of field-grown sweetpotato to elevated carbon dioxide. Crop Science
36(5):1234-1239.

Root crops are important in developing countries, where food supplies are frequently marginal.
Increases in atmospheric CO2 usually lead to increases in plant growth and yield, but little is known
about the response of root crops to CO2 enrichment under field conditions, This experiment was
conducted to investigate the effects of CO2 enrichment on growth and yield of field-grown
sweetpotato [Ipomoea batatas (L.) Lam.]. Plants were grown in open-top chambers in the field at
four CO2 levels ranging from 354 (ambient) to 665 mu mol mol(-1) in two growing seasons, Shoot
growth was not affected significantly by elevated CO2. Yield of storage roots increased 46 and 75%
at the highest CO2 level in the 2 yr, The yield enhancement occurred through increases in the number
of storage roots in the first year and through increases in both the number and size of the storage
roots in the second year, Storage- root/shoot ratios increased 44% and leaf nitrogen concentrations
decreased by 24% at the highest CO2 level, A comparison of plants grown in the open field to plants
grown in open-top chambers at ambient CO2 concentrations indicated that open-top chambers
reduced shoot growth in the first year and storage-root yield in both years, These results are
consistent with the majority of CO2-enrichment studies done on pot-grown sweetpotato.

KEYWORDS: ATMOSPHERIC CO2 ENRICHMENT, COTTON, ENVIRONMENT, IRRIGATION,
NITROGEN, OPEN-TOP CHAMBERS, PHYSIOLOGY, PLANT-RESPONSES, SWEET-POTATO,
WATER-STRESS


     230  
Bjorn, L.O., T.V. Callaghan, I. Johnsen, J.A. Lee, Y. Manetas, N.D. Paul, M. Sonesson, A.R.
Wellburn, D. Coops, H.S. HeideJorgensen, C. Gehrke, D. GwynnJones, U. Johanson, A.
Kyparissis, E. Levizou, D. Nikolopoulos, Y. Petropoulou, and M. Stephanou. 1997. The effects
of UV-B radiation on European heathland species. Plant Ecology 128(1-2):252-264.

The effects of enhanced UV-B radiation on three examples of European shrub-dominated vegetation
were studied in situ. The experiments were in High Arctic Greenland, northern Sweden and Greece,
and at all sites investigated the interaction of enhanced UV-B radiation (simulating a 15% reduction
in the ozone layer) with artificially increased precipitation, The Swedish experiment also involved a
study of the interaction between enhanced UV-B radiation and elevated CO2 (600 ppm). These field
studies were supported by an outdoor controlled environment study in the United Kingdom involving
modulated enhancement of UV-B radiation in combination with elevated CO2 (700 ppm). Effects of
the treatments on plant growth, morphology, phenology and physiology were measured. The effects
observed were species specific, and included both positive and negative responses to the treatments.
In general the negative responses to UV-B treatments of up to three growing seasons were small, but
included reductions in shoot growth and premature leaf senescence. Positive responses included a
marked increase in flowering in some species and a stimulation of some photosynthetic processes.
UV-B treatment enhanced the drought tolerance of Pinus pinea and Pinus halepensis by increasing
leaf cuticle thickness. In general, there were few interactions between the elevated CO2 and enhanced
UV-B treatments. There was evidence to suggest that although the negative responses to the
treatments were small, damage may be increasing with time in some long-lived woody perennials.
There was also evidence in the third year of treatments for effects of UV-B on insect herbivory in
Vaccinium species. The experiments point to the necessity for long-term field investigations to predict
the likely ecological consequences of increasing UV-B radiation.

KEYWORDS: ACTION SPECTRA, DROUGHT, FIELD CONDITIONS, GROWTH, LEAVES,
PHOTOSYNTHESIS, SOLAR ULTRAVIOLET-RADIATION, STOMATAL CLOSURE, SURFACE,
TERRESTRIAL PLANTS


     231  
Bladier, C., and P. Chagvardieff. 1993. Growth and photosynthesis of photoautotrophic callus
derived from protoplasts of solanum-tuberosum L. Plant Cell Reports 12(6):307-311.

We describe a photoautotrophic culture procedure of potato (cvs Kennebec, Haig, DTO-33) callus
derived from mesophyll protoplasts. The protoplast culture was initiated at very low concentration
of glucose (down to 0.25 g l-1). Callus was subcultured under CO2 enriched air and glucose was
suppressed by the successive dilutions with glucose free media. Regeneration was successfully
obtained under photoautotrophic conditions. The characterization of oxygen exchange and of some
enzymes and metabolites of carbon assimilation indicated that chlorophyllous callus, grown on
carbohydrate free medium, developed the photosynthetic pathway typical of C3 plants. By comparing
the fresh weight of callus cultivated in the light or in non-photosynthetic conditions (in darkness or
in the light +3-(3,4-Dichlorophenyl)-1,1-dimethylurea) we concluded that growth depended to about
70 to 88 % on photosynthesis.

KEYWORDS: CELL-SUSPENSION CULTURES, CO2, LIGHT, METABOLISM, MUTANTS,
NICOTIANA-PLUMBAGINIFOLIA, OXYGEN- EXCHANGE, PLANTS, RESPIRATION, SUCROSE


     232  
Blobner, M., R. Bogdanski, E. Kochs, J. Henke, A. Findeis, and S. Jelen-Esselborn. 1998.
Effects of intraabdominally insufflated carbon dioxide and elevated intraabdominal pressure on
splanchnic circulation - An experimental study in pigs. Anesthesiology 89(2):475-482.

Background Intraabdominally insufflated carbon dioxide (CO2) during laparoscopy may have a
specific effect on splanchnic circulation that may be unrelated to the effects of increased
intraabdominal pressure alone. Therefore, the influences of insufflation with CO2 versus air on
splanchnic circulation were compared. Methods: Pigs were chronically instrumented for continuous
recording of mesenteric artery, portal venous, inferior vena cava, and pulmonary arterial blood flow
and portal venous pressure. After induction of anesthesia, CO2 or air was insufflated in 14 and 10
pigs, respectively. with the pigs in the supine position, intraabdominal pressure was increased in steps
of 4 mmHg up to 24 mmHg by graded gas insufflation, Results: During air insufflation, mesenteric
artery vascular resistance was unchanged, whereas mesenteric arterial blood flow decreased with
increasing intraabdominal pressure. Shortly after CO2 insufflation to an intraabdominal pressure of
4 mmHg, mean arterial pressure, mesenteric arterial blood flow, and mesenteric arterial vascular
resistance were increased by 21%, 12% and 9%, respectively. Subsequently, with the onset of CO2
resorption in the third minute, mean arterial pressure declined to baseline values and mesenteric
arterial vascular resistance declined to 85% of baseline values, whereas mesenteric arterial blood flow
continued to increase to a maximum of 24% higher than baseline values. At steady-state conditions
during CO2 insufflation, mesenteric arterial blood flow was increased up to an intraabdominal
pressure less than or equal to 16 mmHg but decreased at higher intraabdominal pressures.
Conclusions: in contrast to air insufflation, intraabdominal insufflation of CO2 resulted in a moderate
splanchnic hyperemia at an intraabdominal pressure less than or equal to 12 mmHg. At higher
intraabdominal pressure values, pressure-induced changes became more important than the type of
gas used.

KEYWORDS: BLOOD-FLOW, DOGS, HALOTHANE ANESTHESIA, INTRA-ABDOMINAL
PRESSURE, LAPAROSCOPIC CHOLECYSTECTOMY, PNEUMOPERITONEUM, RESPONSES,
TENSION, VASOPRESSIN RELEASE


     233  
Blum, H., G. Hendrey, and J. Nosberger. 1997. Effects of elevated CO2, N fertilization, and
cutting regime on the production and quality of Lolium perenne L. shoot necromass. Acta
Oecologica-International Journal of Ecology 18(3):291-295.

In the Swiss grassland FACE experiment, we measured the effect of elevated CO2 on the shoot
necromass production and quality of Lolium perenne in 1995. Dead stubble of reproductive tillers and
dead leaf sheaths were the main components of necromass. Elevated CO2 did not significantly change
the amount and the nitrogen concentration of necromass. Significantly more necromass was produced
and the N concentration was lower in the low N supply treatments. Total necromass amounted to
250-500 g m(-2). Necromass N content was in the order of 5-6 g m(-2) This underscores the
importance of the carbon and nitrogen fluxes included in necromass and their importance for soil
biology and fertility.



     234  
Blumenthal, C., H.M. Rawson, E. McKenzie, P.W. Gras, E.W.R. Barlow, and C.W. Wrigley.
1996. Changes in wheat grain quality due to doubling the level of atmospheric CO2. Cereal
Chemistry 73(6):762-766.

Elevated levels of atmospheric CO2 have been shown to increase grain yield and reduce grain
nitrogen concentration. The object of this study was to determine whether elevated CO2 levels would
modify other aspects of grain quality relevant to processing, particularly protein and starch quality.
Wheat of two genotypes (Hartog and Late Hartog) was grown in the field in controlled-atmosphere
tunnels at either the ambient level of CO2 (350 mu l/L) or an elevated level (700 mu l/L). This
elevated level of CO2 produced significant increases in grain yield, but decreases in 1,000-kernel
weight. Grain grown in the elevated CO2 atmosphere produced poorer dough and decreased loaf
volume, farinograph development time, and dough extensibility. These changes were largely
attributable to the lower protein content of the grain grown at elevated CO2. There did not appear
to be major changes in protein composition or in the functional properties of the protein. Grain
produced at elevated CO2 yielded starch with a significantly higher proportion of large (A-type)
starch granules but no overall change in amylose-to-amylopectin ratio. These studies indicate that
elevated levels of CO2 may result in decreased quality of bread wheats largely due to lowered protein
content.

KEYWORDS: CARBON DIOXIDE, CLIMATE, GENOTYPES, GROWTH, NITROGEN
APPLICATION, NUTRITION, SPRING WHEAT, TEMPERATURE, YIELD


     235  
Boerner, R.E.J., and J. Rebbeck. 1995. Decomposition and nitrogen release from leaves of 3
hardwood species grown under elevated o-3 and/or co2. Plant and Soil 170(1):149-157.

Elevated concentrations of O-3 and CO2 have both been shown to affect structure, nutrient status,
and deposition of secondary metabolites in leaves of forest trees. While such studies have produced
robust models of the effects of such air pollutants on tree ecophysiology and growth, few have
considered the potential for broader, ecosystem-level effects after these chemically and structurally
altered leaves fall as leaf litter and decay. To determine the effects of elevated O-3 and/or CO2 on
the subsequent decomposition and nutrient release from the leaves grown in such altered
atmospheres, we grew seedlings of three widespread North American forest trees, black cherry
(Prunus serotina) (BC), sugar maple (Acer saccharum) (SM), and yellow-poplar (Liriodendron
tulipifera) (YP) for two growing seasons in charcoal-filtered air (CF-air=approximately 25% ambient
O-3), ambient O-3 (1X) or twice-ambient O-3 (2X) in outdoor open-top chambers. We then assayed
the loss of mass and N from the litter derived from those seedlings through one year litterbag
incubations in the forest floor of a neighboring forest stand. Mass loss followed linear functions and
was not affected by the O-3 regime in which the leaves were grown. Instantaneous decay rates (i.e.
k values) averaged SM:-0.707 y(-1), BC:-0.613 y(-1), and YP:-0.859 y(-1). N loss from ambient (1X)
O-3-grown SM leaves was significantly greater than from CF-air leaves; N loss from BC leaves did
not differ among treatments. Significantly less N was released from CF-air-grown YP leaves than
from 1X or 2X O-3-treated leaves. YP leaves from plants grown in pots at 2X O-3 and 350 ppm
supplemental CO2 in indoor pollutant fumigation chambers (CSTRs or Continuously Stirred Tank
Reactors) loss 40% as much mass and 27% as much N over one year as did leaves from YP grown
in CF-air or 2X O-3. Thus, for leaves from plants grown in pots in controlled environment fumigation
chambers, the concentrations of both O-3 and CO2 can affect N release from litter incubated in the
field whereas mass loss rate was affected only by CO2. Because both mass loss and N release from
leaves grown at elevated CO2 were reduced significantly (at least for yellow-poplar), forests exposed
to elevated CO2 may have significantly reduced N turnover rates, thereby resulting in increased N
limitation of tree growth, especially in forests which are already N-limited.

KEYWORDS: ACIDIC RAIN, ATMOSPHERIC CO2, CARBON DIOXIDE, OZONE,
PHOTOSYNTHESIS, QUALITY, RESPONSES, SEEDLINGS, SULFUR-DIOXIDE, TREE


     236  
Boese, S.R., and D.W. Wolfe. 1995. Elevated-temperatures limit sink development and
photosynthetic benefit from elevated co2. Plant Physiology 108(2):26.



     237  
Boese, S.R., D.W. Wolfe, and J.J. Melkonian. 1997. Elevated CO2 mitigates chilling-induced
water stress and photosynthetic reduction during chilling. Plant, Cell and Environment 20(5):625-
632.

Bean, cucumber and corn plants were grown in controlled- environment chambers at 25/18 degrees
C day/night temperature and either ambient (350 mu mol mol(-1)) or elevated (700 mu mol mol(-1))
CO2 concentration, and at 20-30 d after emergence they were exposed to a 24 h chilling treatment
(6.5 +/- 1.5 degrees C) at their growth CO2 concentration. Whole-plant transpiration rates (per unit
leaf area basis) during the first 3 h of chilling were about 26, 28 and 13% lower at elevated than at
ambient CO2 for bean, cucumber and corn, respectively. The decline in leaf water potential (Psi(L))
and visible wilting of bean and cucumber during chilling were significantly less at elevated than at
ambient CO2. Corn Psi(L) was not significantly affected by chilling, and corn did not exhibit any
other symptoms of chilling-induced water stress. Leaf osmotic potentials (measured before chilling
only) of bean and cucumber were more negative at elevated than at ambient CO2, and the
corresponding calculated leaf turgor potentials were significantly higher at elevated than at ambient
CO2. Leaf relative water content (RWC) during chilling at ambient CO2 fell to 62 and 48% for bean
and cucumber, respectively, RWC during chilling at elevated CO2 was never below 79% for bean or
63% for cucumber. Corn RWC was not measured, After 24 h of chilling at ambient CO2, net
photosynthetic rate (PN) reductions were 83, 89 and 24% for bean, cucumber and corn, respectively.
P-N reductions during chilling were less at elevated CO2: 53, 40 and 4% for bean, cucumber and
corn, respectively. At ambient CO2, none of the species fully recovered to pre-chilling P-N, but at
elevated CO2 both bean and corn recovered fully. The average percentage leaf area with visible leaf
damage due to chilling was 20.6 and 9.6% at ambient and elevated CO2, respectively, for bean, and
32.4 and 23.6% at ambient and elevated CO2, respectively, for cucumber. Corn showed no significant
permanent leaf damage from chilling at either CO2 concentration. These results indicate that
cucumber was most sensitive to chilling as imposed in this study, followed by bean and corn. The
results support the hypothesis that, at least in young plants under controlled- environment conditions,
elevated CO2 improves plant water relations during chilling and can mitigate photosynthetic
depression and chilling damage. The implications for long-term growth and reproductive success in
managed and natural ecosystems will require testing of this hypothesis under field conditions.

KEYWORDS: ABSCISIC- ACID, LEAF GAS- EXCHANGE, LIGHT, LOW-TEMPERATURE,
PHASEOLUS-VULGARIS L, PHOTOINHIBITION, PISUM SATIVUM L, SENSITIVE PLANTS,
STOMATAL BEHAVIOR, ZEA-MAYS


     238  
Boetsch, J., J. Chin, M. Ling, and J. Croxdale. 1996. Elevated carbon dioxide affects the
patterning of subsidiary cells in Tradescantia stomatal complexes. Journal of Experimental Botany
47(300):925-931.

The influence of elevated CO2 concentration (670 ppm) on the structure, distribution, and patterning
of stomata in Tradescantia leaves was studied by making comparisons with plants grown at ambient
CO2. Extra subsidiary cells, beyond the normal complement of four per stoma, were associated with
nearly half the stomatal complexes on leaves grown in elevated CO2. The extra cells shared
characteristics, such as pigmentation and expansion, with the typical subsidiary cells, The position and
shape of the extra subsidiary cells in face view differed in the green and purple varieties of
Tradescantia. Substomatal cavities of complexes with extra subsidiary cells appeared larger than those
found in control leaves, Stomatal frequency expressed on the basis of leaf area did not differ from the
control. Stomatal frequency based on cell counts (stomatal index) was greater in leaves grown in
CO,enriched air when all subsidiary cells were counted as part of the stomatal complex. This
difference was eliminated when subsidiary cells were included in the count of epidermal cells, thereby
evaluating the frequency of guard cell pairs, The extra subsidiary cells were, therefore, recruited from
the epidermal cell population during development, Stomatal frequency in plants grown at elevated
temperature (29 degrees C) was not significantly different from that of the control (24 degrees C).
The linear aggregations of stomata were similar in plants grown in ambient and elevated CO2. Since
enriched CO2 had no effect on the structure or patterning of guard cells, but resulted in the formation
of additional subsidiary cells, it is likely that separate and independent events pattern the two cell
types. Plants grown at enriched CO2 levels had significantly greater internode lengths, but leaf area
and the time interval between the appearance of successive leaves were similar to that of control
plants. Porometric measurements revealed that stomatal conductance of plants grown under elevated
CO2 was lower than that of control leaves and those grown at elevated temperature, Tradescantia
was capable of regulating stomatal conductance in response to elevated CO2 without changing the
relative number of stomata present on the leaf.

KEYWORDS: ARABIDOPSIS, CO2- ENRICHMENT, DIFFERENTIATION, LEAF
DEVELOPMENT, MORPHOLOGY, PHASEOLUS-VULGARIS L, PHOTOSYNTHESIS, PLANTS,
RESPONSES, SEEDLINGS


     239  
Bolin, B. 1999. Effect on the biosphere of elevated atmospheric CO2 (pg 1851). Science
286(5440):684.



     240  
Bolin, B., J. Canadell, B. Moore, I. Noble, and W. Steffen. 1999. Effect on the biosphere of
elevated atmospheric CO2. Science 285(5435):1851-1852.



     241  
Bolker, B.M., S.W. Pacala, F.A. Bazzaz, C.D. Canham, and S.A. Levin. 1995. Species-diversity
and ecosystem response to carbon-dioxide fertilization - conclusions from a temperate forest model.
Global Change Biology 1(5):373-381.

This paper explores how the response of a temperate forest ecosystem to climate change might
depend on species diversity and community change. In particular, we look at the dynamics of a model
of temperate forest growth under doubled CO2. We combine a detailed, field-calibrated model of
forest dynamics (Pacala et al. 1993) with greenhouse data on the range of seedling biomass growth
response to doubled CO2 concentrations (Bazzaz et al. 1990; Bazzaz & Miao 1993). Because total
ecosystem response to climate change depends delicately on many environmental variables other than
CO2, we isolate the effects of community change by comparing runs of the regular model, allowing
dynamic community change, with runs of a reduced model that holds species composition static by
using a single tree species with average parameters. Simulations that allowed community change
instead of holding species composition constant showed a roughly 30% additional increase in total
basal area over time scales of 50-150 years. Although the model omits many possible feedbacks and
mechanisms associated with climate change, it suggests the large potential effects that species
differences and feedbacks can have in ecosystem models and reinforces the possible importance of
diversity to ecosystem function (Naeem et al. 1994; Tilman & Downing 1994) over time scales within
the planning horizon for global change policy.

KEYWORDS: ATMOSPHERIC CO2, CANOPY, CO2-INDUCED CLIMATE CHANGE,
ENRICHMENT, GROWTH, LIGHT, LIQUIDAMBAR- STYRACIFLUA, PINUS-TAEDA
SEEDLINGS, STORAGE, TERRESTRIAL ECOSYSTEMS


     242  
Bonghi, C., A. Ramina, B. Ruperti, R. Vidrih, and P. Tonutti. 1999. Peach fruit ripening and
quality in relation to picking time, and hypoxic and high CO2 short-term postharvest treatments.
Postharvest Biology and Technology 16(3):213-222.

Peach fruits (Prunus persica L. Batsch, cv Springcrest) were harvested at two ripening stages (flesh
firmness of 60 N, first harvest, and 45 N, second harvest) and maintained at 20 degrees C in air
(control) or for 24 and 48 h in streams of ultra low(<l%) oxygen (ULO) or high (30%) CO2
concentration and then transferred to air for up to 8 days. The decline in flesh firmness was strongly
reduced by ULO and CO2 treatments in fruits of both harvests, although the effect was stronger in
fruits picked earlier in which ethylene biosynthesis remained at the basal level. In fruits of the second
harvest, endo beta- 1,4-glucanase (EGase) activity was lower in ULO- and CO2- treated fruits than
in control fruits at the end of the 24 h treatment and the following two days in air. Acetaldehyde (AA)
gradually accumulated in control fruit and the highest concentrations were detected during late
ripening. Both treatments induced a strong accumulation of AA but, with the exception of the 24 and
48 h CO2 treatments performed on fruits of the second harvest, a decrease in AA content was
observed when the fruits were transferred to air. A slight increase in ethanol (EtOH) was found
throughout the ripening process in control fruits; ULO and CO2 strongly stimulated EtOH
production. When fruits were transferred to air, EtOH concentration declined rapidly. Alcohol
dehydrogenase (ADH) activity significantly increased in control fruit only in the late stages of
ripening. Greater ADH activity was found throughout the experimental period in fruits of the first
harvest treated for 24 h in ULO and CO2, whereas, at day 8, control and treated fruits of the second
harvest showed similar ADH activity values. Hypoxic and, to a lesser extent, CO2- enriched
atmospheres stimulated Adh gene expression. (C) 1999 Elsevier Science B.V. All rights reserved.

KEYWORDS: ETHYLENE, EXPRESSION, LOW-OXYGEN ATMOSPHERES, NECTARINES,
RESPONSES, STORAGE


     243  
Booker, F.L. 1997. Effects of elevated CO2 and nitrogen on proanthocyanidins in cotton. Plant
Physiology 114(3):489.



     244  
Booker, F.L., C.D. Reid, S. BrunschonHarti, E.L. Fiscus, and J.E. Miller. 1997. Photosynthesis
and photorespiration in soybean [Glycine max (L.) Merr.] chronically exposed to elevated carbon
dioxide and ozone. Journal of Experimental Botany 48(315):1843-1852.

The effects of elevated carbon dioxide (CO2) and ozone (O-3) on soybean [Glycine max (L.) Merr.]
photosynthesis and photorespiration-related parameters were determined periodically during the
growing season by measurements of gas exchange, photorespiratory enzyme activities and amino acid
levels, Plants were treated in open-top field chambers from emergence to harvest maturity with
seasonal mean concentrations of either 364 or 726 mu mol mol(-1) CO2 in combination with either
19 or 13 nmol mol(-1) O-3 (12 h daily averages). On average at growth CO2 concentrations, net
photosynthesis (A) increased 56% and photorespiration decreased 36% in terminal mainstem leaves
with CO2-enrichment. Net photosynthesis and photorespiration were suppressed 30% and 41%,
respectively, by elevated O-3 during late reproductive growth in the ambient CO2 treatment, but not
in the elevated CO2 treatment. The ratio of photorespiration to A at growth CO2 was decreased 61%
by elevated CO2. There was no statistically significant effect of elevated O-3 in the ratio of
photorespiration to A. Activities of glycolate oxidase, hydroxypyruvate reductase and catalase were
decreased 10-25% by elevated CO2, and by 46-66% by elevated O-3 at late reproductive growth.
The treatments had no significant effect on total amino acid or glycine levels, although serine
concentration was lower in the elevated CO2 and O-3 treatments at several sampling dates. The
inhibitory effects of elevated O-3 on photorespiration-related parameters were generally
commensurate with the O-3-induced decline in A. The results suggest that elevated CO2 could
promote productivity both through increased photoassimilation and suppressed photorespiration.

KEYWORDS: ARABIDOPSIS-THALIANA, ATMOSPHERIC CO2, CARBOXYLASE ACTIVITY,
GAS-EXCHANGE, L LEAVES, PHASEOLUS-VULGARIS L, PLANT-RESPONSES, SPRING
WHEAT, SUPEROXIDE-DISMUTASE, ULTRAVIOLET-B


     245  
Boone, R.D., K.J. Nadelhoffer, J.D. Canary, and J.P. Kaye. 1998. Roots exert a strong influence
on the temperature sensitivity of soil respiration. Nature 396(6711):570-572.

The temperature sensitivity of soil respiration will largely determine the effects of a warmer world
on net carbon flux from soils to the atmosphere. CO2 flux from soils to the atmosphere is estimated
to be 50-70 petagrams of carbon per year and makes up 20-38% of annual inputs of carbon (in the
form of CO2) to the atmosphere from terrestrial and marine sources(1,2). Here we show that, for a
mixed temperate forest, respiration by roots plus oxidation of rhizosphere carbon, which together
produce a large portion of total effluxed soil CO2, is more temperature-sensitive than the respiration
of bulk soil. We determine that the Q(10) value (the coefficient for the exponential relationship
between soil respiration and temperature, multiplied by ten) is 4.6 for autotrophic root respiration
plus rhizosphere decomposition, 2.5 for respiration by soil lacking roots and 3.5 for respiration by
bulk soil. If plants in a higher-CO2 atmosphere increase their allocation of photosynthate to roots(3-
6), these findings suggest that soil respiration should be more sensitive to elevated temperatures, thus
limiting carbon sequestration by soils.

KEYWORDS: ATMOSPHERIC CARBON-DIOXIDE, CLIMATE, CO2, EXCHANGE, FLUXES,
FOREST, LITTER, VEGETATION


     246  
Boote, K.J., and N.B. Pickering. 1994. Modeling photosynthesis of row crop canopies. Hortscience
29(12):1423-1434.

KEYWORDS: CARBON DIOXIDE, CARBOXYLASE-OXYGENASE, CO2/O2 SPECIFICITY,
DIRECT COMPONENT, ELEVATED CO2, GLOBAL RADIATION, LEAF NITROGEN, NET
PHOTOSYNTHESIS, SOYBEAN CANOPIES, USE EFFICIENCY


     247  
Borkhsenious, O.N., C.B. Mason, and J.V. Moroney. 1998. The intracellular localization of
ribulose-1,5-bisphosphate carboxylase/oxygenase in Chlamydomonas reinhardtii. Plant Physiology
116(4):1585-1591.

The pyrenoid is a proteinaceous structure round in the chloroplast of most unicellular algae. Various
studies indicate that ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) is present in the
pyrenoid, although the fraction of Rubisco localized there remains controversial. Estimates of the
amount of Rubisco in the pyrenoid of Chlamydomonas reinhardtii range from 5% to nearly 100%.
Using immunolocalization, the amount of Rubisco localized to the pyrenoid or to the chloroplast
stroma was estimated for C. reinhardtii cells grown under different conditions. It was observed that
the amount of Rubisco in the pyrenoid varied with growth condition; about 40% was in the pyrenoid
when the cells were grown under elevated CO2 and about 90% with ambient CO2. In addition, it is
likely that pyrenoidal Rubisco is active in CO2 fixation because in vitro activity measurements showed
that most of the Rubisco must be active to account for CO2-fixation rates observed in whole cells.
These results are consistent with the idea that the pyrenoid is the site of CO2 fixation in C. reinhardtii
and other unicellular algae containing CO2-concentrating mechanisms.

KEYWORDS: CARBONIC-ANHYDRASE, CHLOROPLAST, MECHANISM, OXYGENASE,
PHOTOSYNTHESIS


     248  
Borodin, V.B. 1995. Photosynthetic o-2 exchange in chlorella cells adapted to low co2 concentration
under blue or red-light. Russian Journal of Plant Physiology 42(1):31-36.

The effect of light quality on the adaptation to low atmospheric CO2 concentration was studied on
the cells of unicellular green al,oa Chlorella pyrenoidosa 82T grown under 2% CO2 concentration
and white light. The adaptation of Chlorella cells was more successful under blue than under red light.
Thus, the air-adapted cells under blue light showed a higher affinity for CO2, a higher quantum
efficiency of apparent photosynthesis at CO2 limitation, and acceleration of O-2 evolution at light
saturation, as compared to the red- light-adapted cells. In air-adapted cells, the photosynthetic rates
at low CO2 concentration were enhanced with increased intensities of both blue and red light, but the
differences between the two treatments were retained. It was inferred that Chlorella cell adaptation
depended on both light intensity and its spectral composition. The light intensity exerts its action via
photosynthetic apparatus while spectral composition of light exerts its effect via a system of
photoreception, which absorbs blue light. This additional blue light absorption is considered favorable
for Chlorella cell adaptation to low CO2 concentration.

KEYWORDS: ACETABULARIA- MEDITERRANEA, CARBONIC-ANHYDRASE,
CHLAMYDOMONAS-REINHARDTII, INDUCTION, PROTEIN


     249  
Bosac, C., S.D.L. Gardner, G. Taylor, and D. Wilkins. 1995. Elevated co2 and hybrid poplar -
a detailed investigation of root and shoot growth and physiology of populus-euramericana, primo.
Forest Ecology and Management 74(1-3):103-116.

Exposure of the hybrid poplar clone 'Primo' (Populus deltoides X Populus nigra) to 580 mu l 1(-1)
carbon dioxide for just 68 days significantly (P less than or equal to 0.05) increased stem height by
13% compared with trees grown in ambient CO2 concentrations. The stem diameter was significantly
(P less than or equal to 0.05) increased and both total biomass and woody stem biomass also showed
higher values (38% and 31% increases respectively) in elevated CO2. Trees in elevated CO2 had
more leaves and a greater total leaf area, whilst the specific leaf area was decreased in elevated CO2
on four out of five occasions and was significantly (P less than or equal to 0.05) lower after 68 days,
an effect indicating that leaves were thicker and/or heavier. Rates of photosynthesis (A) measured
after 49 and 67 days of exposure revealed that trees in the elevated CO2 treatment had lower values
of A when measured at either 350 or 580 mu l 1(-1) CO2. Sequential harvests at intervals during the
study in which the root and shoot components were analysed separately allowed the construction of
root:shoot ratios and allometric coefficients; there was no significant effect on the allometric
coefficient and the root:shoot ratio was significantly increased on only one occasion. However,
measurements of the 'apparent' root length suggested that root lengths were greater in the CO2
treatment. There was a significant increase in the number of fine root tips visible down the surface
of specially designed rooting tubes (P less than or equal to 0.05), indicating more fine roots or an
increase in fine root branching. The growth rates of individual fine or large roots over 24 h were
unaffected, again suggesting that increases in biomass may be due to more root segments rather than
longer individual roots. Root water relations were also examined and showed a tendency towards
solute accumulation and increases in turgor pressure (P) and effective tugor (P-e) at times when root
growth was stimulated, although these were not consistent. Cell wall plasticity of the tips of large
roots was significantly (P less than or equal to 0.01) reduced in elevated CO2, possibly indicating a
greater tendency to divert resources to the formation of root branches. The results of the study are
discussed in the light of the possible consequences of changes in poplar growth and physiology for
forestry practice in an increased CO2 environment.

KEYWORDS: ACCLIMATION, ATMOSPHERIC CARBON-DIOXIDE, CELL-WALLS, CLONES,
CONDUCTANCE, DROUGHT, ENRICHMENT, LEAF GROWTH, PHOTOSYNTHESIS, SOURCE-
SINK RELATIONS


     250  
Bottomley, P.A., H.H. Rogers, and S.A. Prior. 1993. Nmr imaging of root water distribution in
intact vicia-faba L plants in elevated atmospheric co2. Plant, Cell and Environment 16(3):335-338.

The effect of elevated atmospheric CO2 on water distribution in the intact roots of Vicia faba L. bean
seedlings grown in natural soil was studied noninvasively with proton (H-1) nuclear magnetic
resonance (NMR) imaging. Exposure of 24-d-old plants to atmospheric Co2-enriched air at 650 cm3
m-3 produced significant increases in water imaged in upper roots, hypogeal cotyledons and lower
stems in response to a short-term drying- stress cycle. Above ground, drying produced negligible stem
shrinkage and stomatal resistance was unchanged. In contrast, the same drying cycle caused
significant depletion of water imaged in the same upper root structures in control plants subject to
ambient CO2 (350 m3 m-3), and stem shrinkage and increased stomatal resistance. The results
suggest that inhibition of transpiration caused by elevated CO2 does not necessarily result in
attenuation of water transport from lower root structures. Inhibition of water loss from upper roots
and lower stem in elevated CO2 environments may be a mitigating factor in assessing deleterious
effects of greenhouse changes on crops during periods of dry climate.

KEYWORDS: CARBON DIOXIDE, INSITU, MAGNETIC-RESONANCE MICROSCOPY,
TRANSPORT


     251  
Bouma, T.J., K.L. Nielsen, D.M. Eissenstat, and J.P. Lynch. 1997. Estimating respiration of roots
in soil: Interactions with soil CO2, soil temperature and soil water content. Plant and Soil
195(2):221-232.

Little information is available on the variability of the dynamics of the actual and observed root
respiration rate in relation to abiotic factors. In this study, we describe I) interactions between soil
CO2 concentration, temperature, soil water content and root respiration, and II) the effect of short-
term fluctuations of these three environmental factors on the relation between actual and observed
root respiration rates. We designed an automated, open gas-exchange system that allows continuous
measurements on 12 chambers with intact roots in soil. By using three distinct chamber designs with
each a different path for the air flow, we were able to measure root respiration over a 50-fold range
of soil CO2 concentrations (400 to 25000 ppm) and to separate the effect of irrigation on observed
vs. actual root respiration rate. All respiration measurements were made on one-year-old citrus
seedlings in sterilized sandy soil with minimal organic material. Root respiration was strongly affected
by diurnal fluctuations in temperature (Q(10) = 2), which agrees well with the literature. In contrast
to earlier findings for Douglas-fir (Qi et al., 1994), root respiration rates of citrus were not affected
by soil CO2 concentrations (400 to 25000 ppm CO2; pH around 6). Soil CO2 was strongly affected
by soil water content but not by respiration measurements, unless the air flow for root respiration
measurements was directed through the soil. The latter method of measuring root respiration reduced
soil CO2 concentration to that of incoming air. Irrigation caused a temporary reduction in CO2
diffusion, decreasing the observed respiration rates obtained by techniques that depended on
diffusion. This apparent drop in respiration rate did not occur if the air flow was directed through the
soil. Our dynamic data are used to indicate the optimal method of measuring root respiration in soil,
in relation to the objectives and limitations of the experimental conditions.

KEYWORDS: CARBON DIOXIDE, DARK RESPIRATION, ELEVATED CO2, ENRICHMENT,
FIELD, GROWTH, PLANTS, RESPONSES, SEEDLINGS, SOUR ORANGE TREES


     252  
Bowden, R.D., K.M. Newkirk, and G.M. Rullo. 1998. Carbon dioxide and methane fluxes by a
forest soil under laboratory-controlled moisture and temperature conditions. Soil Biology and
Biochemistry 30(12):1591-1597.

Carbon dioxide and methane are important greenhouse gases whose exchange rates between soils and
the atmosphere are controlled strongly by soil temperature and moisture. We made a laboratory
investigation to quantify the relative importance of soil moisture and temperature on fluxes of CO2
and CH4 between forest soils and the atmosphere. Forest floor and mineral soil material were
collected from a mixed hardwood forest at the Harvard Forest. Long-Term Ecological Research Site
(MA) and were incubated in the laboratory under a range of moisture (air-dry to nearly saturated) and
temperature conditions (5-25 degrees C). Carbon dioxide emissions increased exponentially with
increasing temperature in forest floor material, with emissions reduced at the lowest and highest soil
moisture contents. The forest floor Q(10) of 2.03 (from 15-25 degrees C) suggests that CO2
emissions were controlled primarily by soil biological activity. Forest floor CO2 emissions were
predicted with a multiple polynomial regression model (r(2) = 0.88) of temperature and moisture, but
the fit predicting mineral soil respiration was weaker (r(2) = 0.59). Methane uptake was controlled
strongly by soil moisture, with reduced fluxes under conditions of very low or very high soil moisture
contents. A multiple polynomial model accurately described CH4 uptake by mineral soil material (r(2)
= 0.81), but only weakly (r(2) = 0.45) predicted uptake by forest floor material. The mineral soil
Q(10) of 1.11 for CH4 uptake indicates that methane uptake is controlled primarily by physical
processes. Our work suggests that inclusion of both moisture and temperature can improve
predictions of soil CO2 and CH4 exchanges between soils and the atmosphere. Additionally, global
change models need to consider interactions of temperature and moisture in evaluating effects of
global climate change on trace gas fluxes. (C) 1998 Elsevier Science Ltd. All rights reserved.

KEYWORDS: ATMOSPHERIC METHANE, CONSUMPTION, DYNAMICS, ECOSYSTEMS,
NITROGEN, OXIDATION, RESPIRATION, RESPONSES, WATER


     253  
Bowes, G. 1991. Growth at elevated CO2 - photosynthetic responses mediated through rubisco.
Plant, Cell and Environment 14(8):795-806.

The global uptake of CO2 in photosynthesis is about 120 gigatons (Gt) of carbon per year. Virtually
all passes through one enzyme, ribulose bisphosphate carboxylase/oxygenase (rubisco). which initiates
both the photosynthetic carbon reduction, and photorespiratory carbon oxidation, cycles. Both CO2
and O2 are substrates; CO2 also activates the enzyme. In C3 plants, rubisco has a low catalytic
activity, operates below its K(m) (CO2), and is inhibited by O2. Consequently, increases in the
CO2/O2 ratio stimulate C3 photosynthesis and inhibit photorespiration. CO2 enrichment usually
enhances the productivity of C3 plants, but the effect is marginal in C4 species. It also causes
acclimation in various ways: anatomically. morphologically, physiologically or biochemically. So,
CO2 exerts secondary effects in growth regulation, probably at the molecular level, that are not
predictable from its primary biochemical role in carboxylation. After an initial increase with CO2
enrichment, net photosynthesis often declines. This is a common acclimation phenomenon, less so in
field studies, that is ultimately mediated by a decline in rubisco activity, though the RuBP/P(i)-
regeneration capacities of the plant may play a role. The decline is due to decreased rubisco protein,
activation state, and/or specific activity, and it maintains the rubisco fixation and RuBP/P(i)-
regeneration capacities in balance. Carbohydrate accumulation is sometimes associated with reduced
net photosynthesis, possibly causing feedback inhibition of the RuBP/P(i)-regeneration capacities, or
chloroplast disruption. As exemplified by field-grown soybeans and salt marsh species, a reduction
in net photosynthesis and rubisco activity is not inevitable under CO2 enrichment. Strong sinks or
rapid translocation may avoid such acclimation responses. Over geological time, aquatic autotrophs
and terrestrial C4 and CAM plants have genetically adapted to a decline in the external CO2/O2 ratio,
by the development of mechanisms to concentrate CO2 internally; thus circumventing O2 inhibition
of rubisco. Here rubisco affinity for CO2 is less, but its catalytic activity is greater, a situation
compatible with a high-CO2 internal environment. In aquatic autotrophs, the CO2 concentrating
mechanisms acclimate to the external CO2, being suppressed at high-CO2. It is unclear, whether a
doubling in atmospheric CO2 will be sufficient to cause a de-adaptive trend in the rubisco kinetics
of future C3 plants, producing higher catalytic activities.

KEYWORDS: 1,5-DIPHOSPHATE CARBOXYLASE, CARBON-DIOXIDE CONCENTRATIONS,
CO2-ENRICHED ATMOSPHERE, ECHINOCHLOA CRUS GALLI, HIGH ATMOSPHERIC CO2,
KINETIC-PROPERTIES, LONG-TERM EXPOSURE, MONOECIOUS CUCUMBERS,
PHOSPHOENOLPYRUVATE CARBOXYLASE, RIBULOSE BISPHOSPHATE CARBOXYLASE


     254  
Bowes, G. 1993. Facing the inevitable - plants and increasing atmospheric co(2). Annual Review of
Plant Physiology and Plant Molecular Biology 44:309-332.

KEYWORDS: CARBON-DIOXIDE CONCENTRATION, CO2- ENRICHMENT, ELEVATED CO2,
INORGANIC CARBON, PHASEOLUS-VULGARIS L, RIBULOSE BISPHOSPHATE
CARBOXYLASE, RIBULOSE-1;5-BISPHOSPHATE CARBOXYLASE, SHORT- TERM, SOURCE-
SINK RELATIONS, SOYBEAN LEAVES


     255  
Bowes, G., J.C.V. Vu, M.W. Hussain, A.H. Pennanen, and L.H. Allen. 1996. An overview of
how rubisco and carbohydrate metabolism may be regulated at elevated atmospheric [CO2] and
temperature. Agricultural and Food Science in Finland 5(3):261-270.

Although atmospheric CO2 concentration ([CO2]) has been up to 16-fold higher than at present, the
past several million years have seen atypically low values. Thus, modern-day plants are adapted to
cope with a low [CO2]/[O-2] ratio. The present [CO2] does nor saturate C-3 photosynthesis, so its
doubling produces an ''efficiency effect'', but it is not always fully realized. Acclimation to high [CO2]
during growth can down-regulate photosynthesis, presumably to optimize carbon acquisition and
utilization. A primary factor in acclimation is a reduction in rubisco. Two crops, rice and soybean,
were used to study this phenomenon. Rice photosynthesis and growth peaked at 500 mu mol mol(-1),
whereas soybean responded up to 990 mu mol mol(-1) Rubisco concentration declined under CO2-
enrichment and increasing temperatures, more so in rice than soybean. The rubisco k(cat) Of rice was
unaffected by growth [CO2] or temperature, but that from soybean was increased by both. In rice the
capacity to handle carbohydrate, as measured by sucrose phosphate synthase activity was up-
regulated by CO2- enrichment, but not by temperature. Leaf carbohydrates were increased by [CO2],
but decreased by higher temperatures, starch more so than sucrose. Even though C-3 species differ
in response to [CO2] and temperature, CO2-enrichment can moderate adverse effects of temperature
extremes.

KEYWORDS: ACCLIMATION, CARBON-DIOXIDE CONCENTRATION, CARBOXYLASE,
EXPRESSION, GROWTH, LEAVES, PHOTOSYNTHESIS, PLANT-RESPONSES, RICE, SOURCE-
SINK RELATIONS


     256  
Bowler, J.M., and M.C. Press. 1993. Growth-responses of 2 contrasting upland grass species to
elevated co2 and nitrogen concentration. New Phytologist 124(3):515-522.

Growth parameters of Agrostis capillaris L. and Nardus stricta L. were measured in relation to
ambient and elevated concentrations of CO2 (340 and 550 mul CO2 l-1, respectively) and at low and
high concentrations of nitrogen (0.8 and 3 mm NH4NO3, respectively). After 60 d of growth A.
capillaris had attained approx. four times the total dry weight of N. stricta in all treatments, which was
attributed to the greater leaf area ratio of the former. A. capillaris grown at the low nitrogen
concentration attained 30% of the total dry weight of plants grown at high nitrogen. Over the 60 d
period, destructive harvests (seven in total) showed the growth of N. stricta to be less sensitive than
that of A. capillaris to the concentration of nitrogen, but in both species growth analysis showed the
lower total dry weight at low nitrogen to be attributable to lower unit leaf rate. There was a
differential response of both species to elevated concentrations of CO2 which was nitrogen
dependent. A. capillaris grown at elevated CO2 attained a greater total dry weight than at ambient
CO2 and this response was proportionately greater at low nitrogen (78% increase) than at high
nitrogen (58% increase). In contrast, in N. stricta there was no effect of CO2 concentration on the
total dry weight at low nitrogen whilst at high nitrogen plants grown at elevated CO2 had a greater
total dry weight after 48 d of growth. Calculation of the allometric coefficient (K) relating root
growth to shoot growth indicated that the effect of the lower nitrogen concentration was to increase
partitioning to the roots while the higher CO2 concentration did not alter partitioning.

KEYWORDS: AVAILABILITY, CARBON-DIOXIDE ENRICHMENT, IRRADIANCE, MINERAL
NUTRITION, PHOTOSYNTHESIS, PLANTS, SEEDLINGS, SOURCE-SINK RELATIONS,
TEMPERATURE, WHEAT


     257  
Bowler, J.M., and M.C. Press. 1996. Effects of elevated CO2, nitrogen form and concentration on
growth and photosynthesis of a fast- and slow-growing grass. New Phytologist 132(3):391-401.

Growth and photosynthesis of Agrostis capillaris L. and Nardus stricta L. were measured for plants
grown under ambient and elevated concentrations of CO2 (340 and 550 mu l CO2 l(-1) respectively)
and a range of nitrogen concentrations (0.01, 0.1, 1 and 5 mg N l(-1)) supplied as either ammonium
sulphate or sodium nitrate. After 42 d of growth for A. capillaris and 49 d of growth for N. stricta,
the higher nitrogen concentrations resulted in stimulation of growth. The form of nitrogen did not
affect the total dry weight attained by A. capillaris. However, ammonium-grown N. stricta attained
a greater total dry weight than did nitrate-grown plants. Nitrogen form influenced leaf area ratio,
which was greater in nitrate-grown A. capillaris and in ammonium-grown N. stricta. At the two
lowest nitrogen concentrations there was no effect of elevated CO2 on total dry weight in either
species, whilst at the two highest nitrogen concentrations positive growth responses to elevated CO2
were observed. Photosynthetic capacity and carboxylation efficiency were lower in plants grown in
elevated CO2 at the two lowest nitrogen concentrations, and were associated with greater leaf soluble
carbohydrate content and lower foliar nitrogen concentrations. By contrast, the CO2 treatment did
not affect these parameters at the two highest nitrogen concentrations employed.

KEYWORDS: ACCLIMATION, CARBON DIOXIDE, ENRICHMENT, EXPOSURE, GAS-
EXCHANGE, HIGH ATMOSPHERIC CO2, LEAVES, NUTRITION, PLANTS, RIBULOSE-1;5-
BISPHOSPHATE CARBOXYLASE-OXYGENASE


     258  
Brailsford, R.W., L.A.C.J. Voesenek, C.W.P.M. Blom, A.R. Smith, M.A. Hall, and M.B.
Jackson. 1993. Enhanced ethylene production by primary roots of zea-mays L in response to sub-
ambient partial pressures of oxygen. Plant, Cell and Environment 16(9):1071-1080.

Ethylene production by primary roots of 72-h-old intact seedlings of Zea mays L. cv. LG11 was
studied under ambient and sub-ambient oxygen partial pressures (pO(2)) using a gas how- through
system linked to a photoacoustic laser detector. Despite precautions to minimize physical perturbation
to seedlings while setting-up, ethylene production in air was faster during the first 6h than later, in
association with a small temporary swelling of the roots. When roots were switched from air (20.8kPa
O-2) to 3 or 5kPa O-2 after 6h, ethylene production increased within 2-3h. When, the roots were
returned to air 16h later, ethylene production decreased within 2-3h. The presence of 1OkPa CO2
did not interfere with the effect of 3kPa O-2. Transferring roots from air to 12.5kPa did not change
ethylene production, while a reduction to 1kPa O-2 induced a small increase. The extra ethylene
formed in 3 and 5kPa O-2 was associated with plagiotropism, swelling, root hair production, and
after 72h, increased amounts of intercellular space (aerenchyma) in the root cortex. Root extension
was also slowed down, but the pattern of response to oxygen shortage did not always match that of
ethylene production. On return to air, subsequent growth patterns became normal within a few hours.
In the complete absence of oxygen, no ethylene production was detected, even when anaerobic roots
were returned to air after 16h.

KEYWORDS: ANOXIA, BIOSYNTHESIS, DEEP-WATER RICE, FORMING ENZYME, GROWTH,
PLANTS, STIMULATION, SUBMERGENCE


     259  
Brakke, M., and L.H. Allen. 1995. Gas-exchange of citrus seedlings at different temperatures,
vapor-pressure deficits, and soil-water contents. Journal of the American Society for Horticultural
Science 120(3):497-504.

Midday reductions of stomatal conductance and carbon dioxide assimilation rates (A(CO2)) in Citrus
are typically attributed to large leaf-to-air vapor-pressure differences or high atmospheric vapor-
pressure deficits (VPD). This study investigated air temperature (T-a) and available soil water (ASW)
level as corollary factors of atmospheric VPD that influence midday reduction of net gas exchange
in citrus leaves. The influence of elevated atmospheric CO2 under conditions that inhibit net canopy
A(CO2) was also investigated. Net canopy A(CO2) and evapotranspiration rates of Carrizo citrange
[Poncirus trifoliata Raf x Citrus sinensis (L.) Osbeck] and Swingle citrumelo (P. trifoliata Raf x C.
paradisii Macf.) seedlings grown in outdoor controlled- environment growth chambers were
measured under two levels of T-a with concomitant changes in VPD and two levels of atmospheric
CO2 concentration, which were changed in steps over time. Cyclical depletion of ASW was allowed
to occur at each set of T-a/VPD and CO2 combinations. Highest net canopy A(CO2) rates at ambient
CO2 concentration (330 mu mol . mol(-1)) were obtained at the low T-a/VPD level (29C/2.4 kPa)
and ASW >50%. Diurnal canopy CO2 uptake rates decreased at the high T-a/VPD level (37C/3.6
kPa), and midday depression of canopy A(CO2) was observed at ASW levels <50%. Net canopy
A(CO2) decreased at higher levels of ASW under the high T-a/VPD treatment than at the low T-
a/VPD treatment. At the elevated CO2 concentration (840 mu mol . mol(-1)) net canopy CO2 uptake
rates were double those that occurred at ambient CO2 levels and they did not exhibit midday
reduction. Our data indicate that, when soil water is not readily available, citrus seedlings are more
sensitive to high levels of T-a and VPD which results in reduction of CO2 uptake. The inhibitory
effects of elevated VPD and reduced ASW on citrus net A(CO2) were lessened at the elevated
atmospheric CO2 level.

KEYWORDS: CARBON DIOXIDE, GROWTH, HUMIDITY, LEAVES, PHOTOSYNTHESIS,
RESPONSES, TRANSPIRATION, TREES, VALENCIA ORANGE


     260  
Brandrud, T.E., and J.G.M. Roelofs. 1995. Enhanced growth of the macrophyte Juncus bulbosus
in S Norwegian limed lakes. A regional survey. Water, Air, and Soil Pollution 85(2):913-918.

The effects of liming on the aquatic macrophyte vegetation have been investigated in S and SW
Norway. In the western part of the study area, Juncus bulbosus was considerably more frequent in
the limed than in the unlimed lakes, whilst in the eastern part there were no such differences, and the
J. bulbosus populations were generally not so vital. In some southwestern areas a luxuriant and
massiv nuisance growth of Juncus bulbosus in the depth zone 0-4 m was recorded. The most vital
plants produced up to 1 m long annual shoots, and developed extensive, dense and vital surface mats
in shallow areas (depth zone 0-3 m) after 4-5 years. The original isoetid vegetation had disappeared
in the areas of dense J. bulbosus populations, and this development seems to be more or less
irreversible. The massive J. bulbosus expansion is seen mainly in directly limed lakes with a sometimes
visible layer of calcium carbonate on the sediment surface, but enhanched growth has been observed
also in lakes downstream liming. The massive expansion is believed to be due to an increase of CO2
and ammonium in the sediment pore water, combined with a mild climate with a very high
precipitation. In many areas the liming has led to an increase in species diversity, and a (re-
)establishment of some acid-intolerant species such as Myriophyllum alterniflorum and Potamogeton
spp.

KEYWORDS: ACIDIFICATION


     261  
Bransby, D.I., S.B. McLaughlin, and D.J. Parrish. 1998. A review of carbon and nitrogen
balances in switchgrass grown for energy. Biomass & Bioenergy 14(4):379-384.

Increased atmospheric CO2, caused partly by burning fossil fuels, is assumed to elevate the risk of
global warming, while nitrate contamination of surface runoff and groundwater from fertilizer and
agricultural wastes constitutes a serious environmental hazard on a regional scale. Switchgrass
(Panicum virgatum L.) grown as an energy crop could reduce atmospheric CO2 accumulation by
replacing fossil fuels and sequestering C. It could also improve soil productivity by C sequestration,
and reduce NO3-1 contamination of water by absorbing N lost from fertilizer and agricultural waste
if planted in filter strips on adjacent land. The objective of this study was to assess potential impacts
of switchgrass on C and N balances by reviewing and synthesizing information from current literature,
unpublished data and on-going research. Replacing fossil fuels with switchgrass, or any other
biomass, will have a much greater effect on atmospheric CO2 than C sequestration. This is because
replacing fossil fuels provides a cumulative effect, while C sequestration offers only a one-time
benefit. Furthermore, switchgrass will provide net gains in C sequestration only if it replaces annual
row crops, but not if it replaces grazed pasture. Nitrogen recovery by switchgrass in an Alabama
study was 65.6%, which compares favorably with the 50% recovery frequently quoted as the norm
for wheal (Triticum aestivum L.) and corn (Zea mays L). (C) 1998 Elsevier Science Ltd. All rights
reserved.



     262  
Brearley, J., M.A. Venis, and M.R. Blatt. 1997. The effect of elevated CO2 concentrations on K+
and anion channels of Vicia faba L. guard cells. Planta 203(2):145-154.

The effects of elevated CO2 concentrations on stomatal movement, anion-and K+-channel activities
were examined in guard cells from epidermal strips of Vicia faba. Membrane voltage was measured
using intracellular, double-barrelled microelectrodes and ion-channel currents were recorded under
voltage clamp during exposure to media equilibrated with ambient (350 mu l . l(-1)), 1000 mu l . l(-1)
and 10 000 mu l . l(-1) CO2 in 20% O-2 and 80% N-2. The addition of 1000 mu l . l(-1) CO2 to the
bathing solution caused stomata to close with a halftime of approx. 40 min, and with 10 000 mu l .
l(-1) CO2 closure occurred with a similar time course. Under voltage clamp, exposure to 1000 mu
l . l(-1) and 10 000 mu l . l(-1) CO2 resulted in a rapid increase (mean, 1.5 +/- 0.2-fold, n = 8; range
1.3- to 2.5-fold) in the magnitude of current carried by outward-rectifying K+ channels (I-K,I-out).
The effect of CO2 on I-K,I-out was essentially complete within 30 s and was independent of clamp
voltage, but was associated with 25-40% (mean, 30 +/- 4%) decrease in the halftime for current
activation. Exposure to CO2 also resulted in a four-fold increase in background current near the free-
running membrane voltage, recorded as the instantaneous current at the start of depolarising and
hyperpolarising voltage steps, and a decrease in the magnitude of current carried by inward-rectifying
K+ channels (I-K,I-in). The effect of CO2 on I-K,I-in was generally slower than on I-K,I-out; it was
allied with a transient acceleration of its activation kinetics during the first 60-120 s of treatment; and
it was associated with a negative shift in the voltage-sensitivity of gating over a period of 3-5 min.
Measurements carried out to isolate the background currents attributable to anion channels (I-Cl),
using tetraethylammonium chloride and CsCl, showed that CO2 also stimulated I-CL and dramatically
altered its relaxation kinetics. Within the timeframe of CO2 action at the membrane, no significant
effect was observed on cytosolic pH, measured using the fluorescent dye 2',7'-bis-(2-carboxyethyl)-
5,6- carboxyflourescein (BCECF) and ratio fluorescence microphotometry. These results are broadly
consistent with the pattern of guard-cell response to abscisic acid, and indicate that guard cells control
both anion and K+ channels to achieve net solute loss in CO2. By contrast with the effects of abscisic
acid, however, the data indicate that CO2 action is not mediated through changes in cytosolic pH and
thereby implicate new and, as yet, unidentified pathway(s) for channel regulation in the guard cells.

KEYWORDS: ABSCISIC- ACID, CYTOSOLIC-FREE CALCIUM, ELECTRICAL
CHARACTERISTICS, FUSICOCCIN ACTION, PLASMA-MEMBRANE, PROTEIN
PHOSPHATASE, SIGNAL-TRANSDUCTION, STOMATAL CLOSURE, TRANSPORT, VOLTAGE


     263  
Bremer, D.J., J.M. Ham, and C.E. Owensby. 1996. Effect of elevated atmospheric carbon dioxide
and open-top chambers on transpiration in a tallgrass prairie. Journal of Environmental Quality
25(4):691-701.

Increasing concentrations of atmospheric carbon dioxide (CO2) may influence plant-water relations
in natural and agricultural ecosystems. A tallgrass prairie near Manhattan, KS, was exposed to
elevated atmospheric CO2 using open-top chambers (OTCs). Heat balance sap Bow gauges were
used to measure transpiration in ironweed [Vernonia baldwini var. interior (Small) Schub.], a C-3
forb, and on individual grass culms of big bluestem (Andropogon gerardii Vitman) and indiangrass
[Sorghastrum nutans (L.) Nash], both C-4 grasses, in each of three treatments: (i) CE (chamber
enriched, 2x ambient CO2); (ii) CA (chamber ambient, no CO2 enrichment); and (iii) NC (no
chamber, no CO2 enrichment). Sap Bow data were coupled with measurements of stomatal
conductance, plant/canopy resistance, and whole- chamber evapotranspiration (ET) to determine the
effect of elevated CO2 on water use at different scales. Because of frequent rainfall during the study,
all data were collected under well-watered conditions, Comparisons of CE and CA showed that sap
Bow was reduced by 33% in ironweed, 18% in big bluestem, and 22% in indiangrass under CO2
enrichment. Whole- chamber ET was reduced by 23 to 27% under CO2 enrichment. Comparisons
of CA and NC showed that the environmental effect of the OTCs caused a 21 to 24% reduction in
transpiration, Stomatal conductance decreased from 7.9 to 3.6 mm s(-1) in big bluestem and from 5.3
to 3.2 mm s(-1) in indiangrass under CO2 enrichment. Soil water was consistently highest under
elevated CO2, reflecting the large reductions in transpiration, During sap flow measurements, whole-
plant stomatal resistance to water vapor Bur in big bluestem increased from 103 to 194 s m(-1) under
elevated CO2.

KEYWORDS: CO2, FLOW, PHOTOSYNTHESIS, RESPONSES, WATER RELATIONS


     264  
Bremer, D.J., J.M. Ham, C.E. Owensby, and A.K. Knapp. 1998. Responses of soil respiration
to clipping and grazing in a tallgrass prairie. Journal of Environmental Quality 27(6):1539-1548.

Soil-surface CO2 flux (F-s) is an important component in prairie C budgets. Although grazing Is
common in grasslands, its effects on F-s have not been well documented. Three clipping treatments:
(i) early-season clipping (EC); (ii) full- season clipping (FC); and (iii) no clipping (NC); which
represented two grazing strategies and a control, were applied to plots in a tallgrass prairie in
northeastern Kansas, USA. Measurements of F-s were made with a portable gas-exchange system
at weekly to monthly intervals for 1 yr. Concurrent measurements of soil temperature and volumetric
soil water content at 0.1 m were obtained with dual-probe heat-rapacity sensors. Measurements of
F-s also were obtained in grazed pastures. F-s ranged annually from 8.8 x 10(-3) mg m(-2) s(-1)
during the winter to 0.51 mg m(-2) s(-1) during the summer, following the patterns of soil
temperature and canopy growth and phenology. Clipping typically reduced F-s 21 to 49% by the
second day after clipping despite higher soil temperatures in clipped plots. Cumulative annual F-s
were 4.94 4.04, and 4.11 kg m(-2) yr(-1) in NC, EC, and FC treatments, respectively; thus, clipping
reduced annual F-s by 17.5%. Differences in F-s between EC and FC were minimal, suggesting that
different grazing strategies had little additional impact on annual F-s. Daily F-s in grazed pastures was
20 to 37% less than F-s in ungrazed pastures. Results suggest that grazing moderates F-s during the
growing season by reducing canopy photosynthesis and slowing translocation of carbon to the
rhizosphere.

KEYWORDS: ANDROPOGON-GERARDII, ATMOSPHERIC CO2, CARBON, ELEVATED CO2,
EXCHANGE, FLUXES, PANICUM-VIRGATUM, PLANT, ROOT RESPIRATION, TEMPERATE
GRASSLAND


     265  
Briones, G.L., P. Varoquaux, Y. Chambroy, J. Bouquant, G. Bureau, and B. Pascat. 1992.
Storage of common mushroom under controlled atmospheres. International Journal of Food Science
and Technology 27(5):493-505.

The effect of controlled atmosphere (CA) on the shelf-life of the common mushroom (Agaricus
bisporus) was assessed using six parameters correlated with its commerical qualities. Low CO2
concentrations (up to 2.5%) reduced brown discolouration compared to the control in air. Higher
CO2 concentrations enhanced both internal and external browning. Low O2 concentrations reduced
growth of micro-organisms, including pseudomonads. Respiration rate, when the mushrooms are
placed again in normal air, is proportional to CO2 concentration during storage suggesting that CO2
exhibits a phytotoxic effect on mushrooms. A lower mannitol content was noted in mushrooms stored
under CA than those stored in air (control). Mushrooms stored in a 5% CO2 atmosphere for 7 days
did not break their veil but their texture was very soft and spongy. Texture losses decreased when
CO2 concentrations increased.

KEYWORDS: AGARICUS-BISPORUS


     266  
Brioua, A.H., and C.T. Wheeler. 1994. Growth and nitrogen-fixation in alnus-glutinosa (L) gaertn
under carbon-dioxide enrichment of the root atmosphere. Plant and Soil 162(2):183-191.

The effects of aeration of the N-free rooting medium with elevated CO2 on (a) acetylene reduction
by perlite-grown plants and (b) N-2-fixation and long-term growth of nutrient solution- grown plants
were determined for nodulated Alnus glutinosa (L.) Gaertn. In the former experiments, roots of intact
plants were incubated in acetylene in air in darkened glass jars for 3 hr, followed by a further 3 hr
incubation period in air enriched with CO2 (0-5%). During incubation, the CO2 content of the jars
increased by 0.17% per hour due to respiration of the root system, so that the CO2 content at 3 hr
was 0.5%. Additional enrichment of the rooting medium gas-phase with CO2 equivalent to 1.1% and
1.75% CO2 of the gas volume significantly increased nitrogenase activity (ethylene production) by
55% and 50% respectively, while enrichment with greater than 2.5% CO2 decreased activity. In
contrast, ethylene production by control plants, where CO2 was not added to the assay jars,
decreased by 8% over the assay period. In long-term growth experiments, nodulated roots of intact
Alnus glutinosa plants were sealed into jars containing N-free nutrient solution (pH 6.3) and aerated
with air, or air containing elevated levels of CO2 (1.5% and 5%). Comparison of the appearance of
CO2-treated with air treated plants suggested that 1.5% CO2 stimulated plant growth. However, at
harvest after 5 or 6 weeks variability between plants masked the significance of differences in plant
dry weight. A significant increase of 33% in total nitrogen of plants aerated with 1.5% CO2,
compared with air-treated plants, was demonstrated, broadly in line with the short-term increase in
acetylene reducing activity observed following incubations with similar CO2 concentrations. Shoot
dry weight was not affected significantly by long-term exposure to 5% CO2, the main effect on
growth being a 20% reduction in dry weight of the root system, possibly through inhibition of root
system respiration. However, in contrast to the inhibitory effects of high CO2 on acetylene reduction
there was no significant effect on the amounts of N-2 fixed.

KEYWORDS: ACETYLENE-REDUCTION, CO2- ENRICHMENT, METABOLISM, N2 FIXATION,
NODULATION, NODULE DEVELOPMENT, PHOSPHOENOLPYRUVATE CARBOXYLASE,
PHYSIOLOGY, PISUM-SATIVUM, RESPIRATION


     267  
Britz, S.J., D.T. Krizek, D.R. Lee, W.G. Harris, W.E. Hungerford, and W.A. Bailey. 1993.
Soybean growth under microwave-powered lamps, high-irradiance- discharge lamps, or solar-
radiation at ambient or elevated co2. Plant Physiology 102(1):141.



     268  
Brklacich, M., P. Curran, and D. Brunt. 1996. The application of agricultural land rating and crop
models to CO2 and climate change issues in Northern regions: The Mackenzie Basin case study.
Agricultural and Food Science in Finland 5(3):351-365.

The Mackenzie Basin in northwestern Canada covers approximately 1.8 million km(2) and extends
from 52 degrees N to 70 degrees N. Much of the Basin is currently too cool and remote from markets
to support a viable agricultural sector, but the southern portion of the Basin has the physical potential
to support commercial agriculture. This case study employed agricultural land rating and crop models
to estimate the degree to which a CO2-induced global warming might alter the physical potential for
commercial agriculture throughout the Basin. The two climate change scenarios considered in this
analysis would relax the current constraints imposed by a short and cool frost-free season, but
without adaptive measures, drier conditions and accelerated crop development rates were estimated
to offset potential gains stemming from elevated CO2 levels and warmer temperatures. In addition
to striving for a better understanding of the extent to which physical constraints on agriculture might
be modified by climate change, there is a need to expand the research context and to consider the
capacity of agriculture to adapt to altered climates.

KEYWORDS: CANADA


     269  
Broadmeadow, M.S.J., J. Heath, and T.J. Randle. 1999. Environmental limitations to O-3 uptake
- Some key results from young trees growing at elevated CO2 concentrations. Water, Air, and Soil
Pollution 116(1-2):299-310.

Elevated carbon dioxide concentrations and limited water supply have been shown to reduce the
impact of ozone pollution on the growth and physiology of Quercus petraea in a long-term factorial
experiment. These responses can be explained by observed reductions in stomatal conductance, and
thus potential ozone exposure of 28% and 40% for CO2 and drought treatments respectively.
However, parameterisation of a stomatal conductance model for Quercus robur and Fagus sylvatica
grown under ambient and elevated CO2 concentrations in a separate experiment has demonstrated
that elevated CO2 also reduces the responsiveness of stomata to both saturation deficit (LAVPD) and
soil moisture deficit (psi) in beech, and to a lesser extent, in oak. Season-long model simulations of
ozone fluxes suggest that LAVPD and psi conductance parameters derived at ambient CO2
concentrations will lead to these fluxes being underestimated by 24% and 2% for beech and oak
respectively at 615 ppm CO2.

KEYWORDS: ATMOSPHERIC CO2, CARBON DIOXIDE, ENRICHMENT, FOREST TREES, GAS-
EXCHANGE, OZONE UPTAKE, PLANTS, SENSITIVITY, SITCHENSIS BONG CARR, STOMATAL
RESPONSE


     270  
Brooks, G.L., and J.B. Whittaker. 1998. Responses of multiple generations of Gastrophysa
viridula, feeding on Rumex obtusifolius, to elevated CO2. Global Change Biology 4(1):63-75.

Rumex obtusifolius plants and three generations of the tri- voltine leaf beetle Gastrophysa viridula
were simultaneously exposed to elevated CO2 (600 ppm) to determine its effect on plant quality and
insect performance. This exposure resulted in a reduction in leaf nitrogen, an increase in the C/N ratio
and lower concentrations of oxalate in the leaves than in ambient air (350 ppm). Despite these
changes in food quality, the effect of elevated CO2 on larvae of Gastrophysa viridula over three
generations was minimal. However, the effect of CO2 did differ slightly between the generations of
the insect. For the first generation, the results obtained were different from many of the published
results in that elevated CO2 had no measurable effects on performance, except that third instar larvae
showed compensatory feeding. Food quality, including leaf nitrogen content, declined over time in
material grown in both ambient and elevated CO2. The results obtained for the second generation
were similar to the first except that first instar larvae showed reduced relative growth rate in elevated
CO2. Development time from hatching to pupation decreased over each generation, probably as a
result of increasing temperatures. Measurements of adult performance showed that fecundity at the
end of the second generation was reduced relative to the first, in line with the reduction in food
quality. In addition at the end of the second generation, but not at the end of the first generation, adult
females in elevated CO2 laid 30% fewer eggs per day and the eggs laid were 15% lighter than those
in ambient conditions. These lighter eggs, coupled with no effect of elevated CO2 on growth during
the third generation, meant that the larvae were consistently smaller in elevated CO2 during this
generation. These results offer further insights into the effect that elevated CO2 will have on insect
herbivores and provide a more detailed basis for population predictions.

KEYWORDS: CARBON DIOXIDE, DIETARY NITROGEN, GAS-EXCHANGE, GROWTH,
JUNONIA-COENIA, LARVAE, LEPIDOPTERA, MANDUCA-SEXTA CATERPILLARS,
NUTRITIONAL ECOLOGY, PERFORMANCE


     271  
Brooks, G.L., and J.B. Whittaker. 1999. Responses of three generations of a xylem-feeding insect,
Neophilaenus lineatus (Homoptera), to elevated CO2. Global Change Biology 5(4):395-401.

A population of the xylem-feeding spittlebug, Neophilaenus lineatus, on blocks of natural vegetation
transferred to large hemispherical chambers was studied over two generations with continuous
exposure to elevated CO2 (600 ppm). The third generation was transferred from the blocks to potted
Juncus squarrosus to enable measurements of fecundity. The principal food plant throughout was
Juncus squarrosus. Survival of the nymphs was reduced by more than 20% in elevated CO2 relative
to ambient (350 ppm) in both years of the main experiment. Elevated CO2 also delayed development
by one or more nymphal instars in each year. Fecundity was not significantly affected. The C/N ratio
of whole Juncus leaves was increased in elevated CO2 and the transpiration rates of the plants were
reduced. These changes may have been responsible for the effect of elevated CO2 on spittlebug
performance. However, other factors such as plant architecture and microclimate may also be
important.

KEYWORDS: CICADELLIDAE, FLUID, GROWTH, HOMALODISCA-COAGULATA,
LEAFHOPPER, PERFORMANCE, PREFERENCE, RUMEX, SAP, SPITTLEBUG


     272  
Brooks, J.R., L.B. Flanagan, N. Buchmann, and J.R. Ehleringer. 1997. Carbon isotope
composition of boreal plants: Functional grouping of life forms. Oecologia 110(3):301-311.

We tested the hypothesis that life forms (trees, shrubs, forbs, and mosses; deciduous or evergreen)
can be used to group plants with similar physiological characteristics. Carbon isotope ratios
(delta(13)C) and carbon isotope discrimination (Delta) were used as functional characteristics because
delta(13)C and Delta integrate information about CO2 and water fluxes, and so are useful in global
change and scaling studies. We examined delta(13)C values of the dominant species in three boreal
forest ecosystems: wet Picea mariana stands, mesic Populus tremuloides stands, and dry Pinus
banksiana stands. Life form groups explained a significant fraction of the variation in leaf carbon
isotope composition; seven life-form categories explained 50% of the variation in delta(13)C and 42%
of the variation in Delta and 52% of the variance not due to intraspecific genetic differences (n=335).
The life forms were ranked in the following order based on their values: evergreen trees<deciduous
trees=evergreen and deciduous shrubs=evergreen forbs<deciduous forbs=mosses. This ranking of the
life forms differed between deciduous (Populus) and evergreen (Pinus and Picea) ecosystems.
Furthermore, life forms in the Populus ecosystem had higher discrimination values than life forms in
the dry Pinus ecosystem; the Picea ecosystem had intermediate Delta values. These correlations
between Delta and life form were related to differences in plant stature and leaf longevity. Shorter
plants had lower Delta values than taller plants, resulting from reduced light intensity at lower levels
in the forest. After height differences were accounted for, deciduous leaves had higher discrimination
values than evergreen leaves, indicating that deciduous leaves maintained higher ratios of intracellular
to ambient CO2 (c(i)/c(a)) than did evergreen leaves in a similar environment within these boreal
ecosystems. We found the same pattern of carbon isotope discrimination in a year with above-average
precipitation as in a year with below-average precipitation, indicating that environmental fluctuations
did not affect the ranking of life forms. Furthermore, plants from sites near the northern and southern
boundaries of the boreal forest had similar patterns of discrimination. We concluded that life forms
are robust indicators of functional groups that are related to carbon and water fluxes within boreal
ecosystems.

KEYWORDS: C-13, COMMUNITIES, CONSEQUENCES, DISCRIMINATION, FOREST, MODEL,
PHOTOSYNTHESIS, TEMPERATURE, TRANSPIRATION, WATER-USE EFFICIENCY


     273  
Brooks, J.R., L.B. Flanagan, G.T. Varney, and J.R. Ehleringer. 1997. Vertical gradients in
photosynthetic gas exchange characteristics and refixation of respired CO2 within boreal forest
canopies. Tree Physiology 17(1):1-12.

We compared vertical gradients in leaf gas exchange, CO2 concentrations, and refixation of respired
CO2 in stands of Populus tremuloides Michx., Pinus banksiana Lamb. and Picea mariana (Mill.)
B.S.P. at the northern and southern boundaries of the central Canadian boreal forest. Midsummer gas
exchange rates in Populus tremuloides were over twice those of the two conifer species, and Pinus
banksiana rates were greater than Picea mariana rates. Gas exchange differences among the species
were attributed to variation in leaf nitrogen concentration. Despite these differences, ratios of
intercellular CO2 to ambient CO2 (c(i)/c(a)) were similar among species, indicating a common
balance between photosynthesis and stomatal conductance in boreal trees. At night, CO2
concentrations were high and vertically stratified within the canopy, with maximum concentrations
near the soil surface. Daytime CO2 gradients were reduced and concentrations throughout the canopy
were similar to the CO2 concentration in the well-mixed atmosphere above the canopy space.
Photosynthesis had a diurnal pattern opposite to the CO2 profile, with the highest rates of
photosynthesis occurring when CO2 concentrations and gradients were lowest. After accounting for
this diurnal interaction, we determined that photosynthesizing leaves in the understory experienced
greater daily CO2 concentrations than leaves at the top of the canopy. These elevated CO2
concentrations were the result of plant and soil respiration. We estimated that understory leaves in
the Picea mariana and Pinus banksiana stands gained approximately 5 to 6% of their carbon from
respired CO2.

KEYWORDS: ATMOSPHERE, CARBON ISOTOPE DISCRIMINATION, DIOXIDE, PLANTS,
RATIOS, SEEDLINGS, SPATIAL VARIATION, STOMATAL CONDUCTANCE, TEMPERATURE,
USE EFFICIENCY


     274  
Brooks, P.D., D.H. Campbell, K.A. Tonnessen, and K. Heuer. 1999. Natural variability in N
export from headwater catchments: snow cover controls on ecosystem N retention. Hydrological
Processes 13(14-15):2191-2201.

The causes of natural variability in catchment scale N export need to be understood and quantified
before the effects of increased N deposition in high elevation catchments can be evaluated. This study
evaluates controls on the size of the leachable soil N pool concurrent with the spring hydrologic flush
that is primarily responsible for the transport of N to surface water. In high elevation catchments in
the western United States, sources of N during this snowmelt flush include both atmospheric N
deposition stored in the snowpack until melt and mobile soil N pools, and sinks are dominated by
biogeochemical processes that occur in soil under snow cover. Because soil processes may serve
either as a source or sink for N, controls on the amount of inorganic N leached from soil during the
snowmelt period were evaluated in the major landscape types in four catchments in Colorado.
Measurements of leached N were inversely related to measurements of over-winter CO2 flux at all
sites, indicating that N was immobilized in soil heterotrophic biomass. Because over-winter soil
heterotrophic activity is controlled primarily by the depth and timing of snow accumulation, the
importance of these plot scale measurements to catchment scale N export were evaluated using a
long-term record of winter precipitation, N deposition, and N export from Loch Vale in Rocky
Mountain National Park. This data set identified a strong, linear relationship (r(2) = 0.68) between
catchment scale N retention and winter snow cover, consistent with subnivean, soil based controls
on the mobile N pool identified at the plot scale. These results indicate that the winter snow pack is
the major control both on hydrologic N export and on soil source/sink relationships for N concurrent
with this transport mechanism. The effect of winter snow cover on the fate of both atmospheric and
soil N needs to be considered when evaluating potential the effects of increased N deposition on
either terrestrial or aquatic ecosystems in seasonally snow-covered watersheds. In these systems,
changes in surface water chemistry are likely to occur in high deposition, snow-covered sites during
low snow years before terrestrial vegetation is affected. Copyright (C) 1999 John Wiley & Sons, Ltd.

KEYWORDS: ALPINE TUNDRA, CO2, COLORADO, FLUX, FOREST, FRONT RANGE,
INORGANIC NITROGEN, NITROGEN MINERALIZATION, NIWOT RIDGE, SATURATION


     275  
Brown, K.R. 1991. Carbon-dioxide enrichment accelerates the decline in nutrient status and relative
growth-rate of Populus tremuloides Michx seedlings. Tree Physiology 8(2):161-173.

Changes in growth dynamics and mineral nutrient concentrations were measured in Populus
tremuloides Michx., trembling aspen, grown for 100 days following germination in atmospheres
containing 350 or 750-mu-l l-1 CO2. Seedlings were fertilized with nitrogen (N) at concentrations
of 15.5 mM (high-N), 1.55 mM (medium-N), or 0.155 mM (low-N). Initially, relative growth rates
were enhanced by CO2 enrichment in each N regime, but the effects did not persist. In plants grown
in high-N or medium-N, foliar concentrations of Ca and Mg decreased in response to CO2
enrichment. During the 100-day study, whole-plant concentrations of N and P decreased in all
treatments. The decreases in mineral nutrient concentrations over time were accelerated in CO2-
enriched plants and accompanied the disappearance of the CO2-induced growth enhancement. It is
concluded that the depression of relative growth rates often associated with long-term CO2
enrichment of plants may result from decreases in plant nutrient status.



     276  
Brown, R.A., and N.J. Rosenberg. 1999. Climate change impacts on the potential productivity of
corn and winter wheat in their primary United States growing regions. Climatic Change 41(1):73-
107.

We calculate the impacts of climate effects inferred from three atmospheric general circulation models
(GCMs) at three levels of climate change severity associated with change in global mean temperature
(GMT) of 1.0, 2.5 and 5.0 degrees C and three levels of atmospheric CO2 concentration ([CO2]) -
365 (no CO2 fertilization effect), 560 and 750 ppm - on the potential production of dryland winter
wheat (Triticum aestivum L.) and corn (Zea mays L.) for the primary (current) U.S. growing regions
of each crop. This analysis is a subset of the Global Change Assessment Model (GCAM) which has
the goal of integrating the linkages and feedbacks among human activities and resulting greenhouse
gas emissions, changes in atmospheric composition and resulting climate change, and impacts on
terrestrial systems. A set of representative farms was designed for each of the primary production
regions studied and the Erosion Productivity Impact Calculator (EPIC) was used to simulate crop
response to climate change. The GCMs applied were the Goddard Institute of Space Studies (GISS),
the United Kingdom Meteorological Transient (UKTR) and the Australian Bureau of Meteorological
Research Center (BMRC), each regionalized by means of a scenario generator (SCENGEN). The
GISS scenarios have the least impact on corn and wheat production, reducing national potential
production for corn by 6% and wheat by 7% at a GMT of 2.5 degrees C and no CO2 fertilization
effect, the UKTR scenario had the most severe impact on wheat, reducing production by 18% under
the same conditions; BMRC had the greatest negative impact on corn, reducing produc tion by 20%.
A GMT increase of 1.0 degrees marginally decreased corn and wheat production. Increasing GMT
had a detrimental impact on both corn and wheat production, with wheat production suffering the
greatest losses. Decreases for wheat production at GMT 5.0 and [CO2] = 365 ppm range from 36%
for the GISS to 76% for the UKTR scenario. Increases in atmospheric [CO2] had a positive impact
on both corn and wheat production. AT GMT 1.0, an increase in [CO2] to 560 ppm resulted in a net
increase in corn and wheat production above baseline levels (from 18 to 29% for wheat and 2 to 5%
for corn). Increases in [CO2] help to offset yield reductions at higher GMT levels; in most cases,
however, these increases are not sufficient to return crop production to baseline levels.

KEYWORDS: ATMOSPHERIC CARBON-DIOXIDE, CO2, EPIC MODEL, EROSION,
METHODOLOGY, RESPONSES, SENSITIVITY, SIMULATION, VARIABILITY, YIELD


     277  
Brown, S., C.A.S. Hall, W. Knabe, J. Raich, M.C. Trexler, and P. Woomer. 1993. Tropical
forests - their past, present, and potential future- role in the terrestrial carbon budget. Water, Air, and
Soil Pollution 70(1-4):71-94.

In this paper we review results of research to summarize the state-of-knowledge of the past, present,
and potential future roles of tropical forests in the global C cycle. In the pre- industrial period (ca.
1850), the flux from changes in tropical land use amounted to a small C source of about 0.06 Pg yr-1.
By 1990, the C source had increased to 1.7 +/- 0.5 Pg yr-1. The C pools in forest vegetation and soils
in 1990 was estimated to be 159 Pg and 216 Pg, respectively. No concrete evidence is available for
predicting how tropical forest ecosystems am likely to respond to CO2 enrichment and/or climate
change. However, C sources from continuing deforestation are likely to overwhelm any change in C
fluxes unless land management efforts become more aggressive. Future changes in land use under a
''business as usual'' scenario could release 41-77 Pg C over the next 60 yr. Carbon fluxes from losses
in tropical forests may be lessened by aggressively pursued agricultural and forestry measures. These
measures could reduce the magnitude of the tropical C source by 50 Pg by the year 2050. Policies
to mitigate C losses must be multiple and concurrent, including reform of forestry, land tenure, arid
agricultural policies, forest protection, promotion of on-farm forestry, and establishment of
plantations on non-forested lands. Policies should support improved agricultural productivity,
especially replacing non-traditional slash-and-burn agriculture with more sustainable and approaches.

KEYWORDS: ATMOSPHERIC CO2, BIOMASS, CYCLE, DIOXIDE, LAND-USE CHANGE,
MODEL, NET, ORGANIC-MATTER, PRIMARY PRODUCTIVITY, SINKS


     278  
Bryant, J., G. Taylor, and M. Frehner. 1998. Photosynthetic acclimation to elevated CO2 is
modified by source : sink balance in three component species of chalk grassland swards grown in a
free air carbon dioxide enrichment (FACE) experiment. Plant, Cell and Environment 21(2):159-168.

Artificial chalk grassland swards were exposed to either ambient air or air enriched to 600 mu mol
mol(-1) CO2, using free-air CO2 enrichment technology, and subjected to an 8 week simulated
grazing regime. After 14 months of treatment, ribulose-1,5-bisphosphate carboxylase (Rubisco)
activity (V- c,V-max) and electron transport mediated ribulose-1,5- bisphosphate (RuBP)
regeneration capacity (J(max)), estimated from leaf gas exchange, were significantly lower in fully
expanded leaves of Anthyllis vulneraria L. (a legume) and Sanguisorba minor Scop, grown in elevated
CO2. After a change in source:sink balance brought about by defoliation, photosynthetic capacity was
fully restored in A. vulneraria and S. minor, but acclimation continued in the grass Bromopsis erecta
(Hudson) Fourr. Changes in net photosynthesis (P-n) with growth at elevated CO2 ranged from a
1.6% reduction in precut leaves of A. vulneraria to a 47.1% stimulation in postcut leaves of S. minor.
Stomatal acclimation was observed in leaves of A. vulneraria (reduced stomatal density) and B. erecta
(reduced stomatal conductance). The results are discussed in terms of whole-plant resource-use
optimization and chalk grassland community competitive interactions at elevated CO2.

KEYWORDS: ATMOSPHERIC CO2, BIOCHEMISTRY, C-3, GAS-EXCHANGE, LEAVES,
METABOLISM, PLANT GROWTH, STOMATAL DENSITY


     279  
Bucher, J.B., D.P. Tarjan, R.T.W. Siegwolf, M. Saurer, H. Blum, and G.R. Hendrey. 1998.
Growth of a deciduous tree seedling community in response to elevated CO2 and nutrient supply.
Chemosphere 36(4-5):777-782.

In a FACE experiment, one year old alder, ash, beech, and oak seedlings were planted together in
tubs containing calcareous sandy alluvial soil with or without a slow release NPK- fertilizer, and
exposed to ambient and elevated CO2 concentrations (360 and 600 mu l mol(-1)) for 20 weeks. In
addition to the fertilizer, all tubs received N-15-ammonium nitrate as a marker. Elevated CO2
significantly increased biomass production in alder, but had no effect on oak and ash. In beech, due
to disease and mortality in all treatments, any possible effects were obscured. The addition of fertilizer
had no effect on biomass production in alder, but increased production in oak and ash significantly.
In oak a treatment synergism may be present. The non-appearance of a synergistic CO2 and fertilizer
effect in alder may be explained by a fertilizer induced reduction of the N-fixing root-nodule biomass
concurrent with a switch of the N-assimilation from atmospheric N to soil N supply, as the delta(15)N
measurements in the leaves of alder as opposed to oak indicate. Although elevated CO2 resulted in
a significant biomass increase in alder, it did not lead to an appreciable increase in the proportional
presence of the species as measured on total plant biomass in the tub. Increasing the nutrient supply
in the soil, however, did lead to appreciable gains in the proportional presence of oak and ash.

KEYWORDS: ATMOSPHERE, ECOSYSTEMS, ENRICHMENT


     280  
Buchi, R., M. Bachmann, and F. Keller. 1998. Carbohydrate metabolism in source leaves of sweet
basil (Ocimum basilicum L.), a starch-storing and stachyose-translocating labiate. Journal of Plant
Physiology 153(3-4):308-315.

Sweet basil (Ocimum basilicum L.) is an annual aromatic herb that grows in temperate to tropical
regions. During ontogeny, the predominant non-structural carbohydrate of mature leaves of plants
older than 2 months after sowing was starch (up to 66 mg.g fresh weight(-1)), followed by the
raffinose family oligosaccharides (RFO) and galactinol (metabolic RFO precursor) (both up to 1.0
mg.g fresh weight(-1)). Sucrose was only a minor component (up to 0.5 mg.g fresh weight(-1)). All
of these carbohydrates displayed distinct diurnal patterns with an increase during the day and a
decrease during the night. Starch concentrations showed the most pronounced diurnal change, with
an almost tenfold increase during the day. A treatment combining leaf excision, continuous
illumination, and high CO2 levels was aimed at elevating the leaf carbohydrate status and resulted in
an increase of the concentrations of starch and soluble carbohydrates (mainly glucose and fructose)
of 60- and 12-fold, respectively. We conclude that sweet basil leaves use starch as their main storage
carbohydrate, and nor RFO or sucrose. Phloem exudates were collected by the classical EDTA-
method and analyzed by HPLC. More than 85 % of the translocated sugars were RFO (mainly
stachyose) and only 5 % sucrose. To study the tissue compartmentation of stachyose synthesis in
source leaves, leaf pieces and mesophyll protoplasts isolated from them were compared. Stachyose
and its anabolic enzyme, stachyose synthase, were totally absent from mesophyll protoplasts.
Likewise, isolated mesophyll protoplasts were not capable of photosynthesizing [C-14]stachyose from
(CO2)-C-14, even after GO min, whereas osmotically stressed leaf pieces were. These results are in
support of the current polymer tray model of symplastic phloem loading of stachyose, which states
that stachyose is synthesized in the intermediary cells of minor vein phloem.

KEYWORDS: ACCUMULATION, AJUGA- REPTANS L, CELL, COMPARTMENTATION,
CUCUMIS-MELO L, DIURNAL PATTERN, MESOPHYLL, MINOR-VEIN ANATOMY,
PROTOPLASTS, RAFFINOSE FAMILY OLIGOSACCHARIDES


     281  
Buchmann, N., J.R. Brooks, K.D. Rapp, and J.R. Ehleringer. 1996. Carbon isotope composition
of C-4 grasses is influenced by light and water supply. Plant, Cell and Environment 19(4):392-402.

The carbon isotope composition of C-4 grasses has the potential to be used as an indicator of changes
in the isotopic composition and concentration of atmospheric CO2, especially for climate
reconstruction. The usefulness of C-4 grasses far this purpose hinges on the assumption that their
photosynthetic discrimination against C-13 remains constant in a wide range of environmental
conditions. We tested this assumption by examining the effects of light and water stress on the carbon
isotope composition of C-4 grasses using different biochemical subtypes (NADP-ME, NAD-ME,
PCK) in glasshouse experiments. We grew 14 different C-4 grass species in four treatments: sun-
watered, sun-drought, shade-watered and shade-drought. Carbon isotope discrimination (Delta) rarely
remained constant. In general, Delta values were lowest in sun-watered grasses, greater for sun-
drought plants and even higher for plants of the shade-watered treatment. The highest Delta values
were generally found in the most stressed grasses, the shade-drought plants. Grasses of the NADP-
ME subtype were the least influenced by a change in environmental variables, followed by PCK and
NAD-ME subtypes. Water availability affected the carbon isotope discrimination less than light
limitation in PCK and NAB-ME subtypes, but similarly in NADP-ME subtypes. In another
experiment, we studied the effect of increasing light levels (150 to 1500 mu mol photons m(-2) s(-1))
on the Delta values of 18 well-watered C-4 grass species. Carbon isotope discrimination remained
constant until photon flux density (PFD) was less than 700 mu mol photons m(-2) s(-1). Below this
light level, Delta values increased with decreasing irradiance for all biochemical subtypes. The change
in Delta was less pronounced in NADP-ME and PCK than in NAD-ME grasses. Grasses grown in
the field and in the glasshouse showed a similar pattern. Thus, caution should be exercised when using
C-4 plants under varying environmental conditions to monitor the concentration or carbon isotopic
composition of atmospheric CO2 in field/glasshouse studies or climate reconstruction.

KEYWORDS: ATMOSPHERIC CO2, C-4 PLANTS, CO2 ASSIMILATION, DISCRIMINATION,
IRRADIANCE, LEAF CONDUCTANCE, LEAVES, NUTRITION, PARTIAL-PRESSURE,
PHOTOSYNTHESIS


     282  
Buddendorfjoosten, J.M.C., and E.J. Woltering. 1994. Components of the gaseous environment
and their effects on plant-growth and development in-vitro. Plant Growth Regulation 15(1):1-16.

KEYWORDS: CARBON DIOXIDE, CO2- ENRICHMENT, CONTROLLED INVITRO
ENVIRONMENT, DENOVO SHOOT REGENERATION, ETHYLENE INHIBITORS,
PHOTOSYNTHETIC CHARACTERISTICS, STAGE-II MICROPROPAGATION, STRAWBERRY
PLANTLETS, TISSUE-CULTURE, VOLATILE EMISSIONS


     283  
Bugbee, B., B. Spanarkel, S. Johnson, O. Monje, and G. Koerner. 1994. Co2 crop growth
enhancement and toxicity in wheat and rice. Life Sciences and Space Research XXV (3) 14(11):257-
267.

The effects of elevated CO2 on plant growth are reviewed and the implications for crop yields in
regenerative systems are discussed. There is considerable theoretical and experimental evidence
indicating that the beneficial effects of CO2 are saturated at about 0.12% CO2 in air. However, CO2
can easily rise above 1% of the total gas in a closed system, and we have thus studied continuous
exposure to CO2 levels as high as 2%. Elevating CO2 from 340 to 1200 mu mol mol(-1) can increase
the seed yield of wheat and rice by 30 to 40%; unfortunately, further CO2 elevation to 2500 mu mol
mol(-1) (0.25%) has consistently reduced yield by 25% compared to plants grown at 1200 mu mol
mol(-1); fortunately, there was only an additional 10% decrease in yield as the CO2 level was further
elevated to 2% (20,000 mu mol mol(-1)). Yield increases in both rice and wheat were primarily the
result of increased number of heads per m(2), with minor effects on seed number per head and seed
size. Yield increases were greatest in the highest photosynthetic photon flux. We used photosynthetic
gas exchange to analyze CO2 effects on radiation interception, canopy quantum yield, and canopy
carbon use efficiency. We were suprised to find that radiation interception during early growth was
not improved by elevated CO2. As expected, CO2 increased quantum yield, but there was also a small
increase in carbon use efficiency. Super-optimal CO2 levels did not reduce vegetative growth, but
decreased seed set and thus yield. The reduced seed set is not visually apparent until final yield is
measured. The physiological mechanism underlying CO2 toxicity is not yet known, but elevated CO2
levels (0.1 to 1% CO2) increase ethylene synthesis in some plants and ethylene is a potent inhibitor
of seed set in wheat.

KEYWORDS: ACCLIMATION, ATMOSPHERIC CARBON-DIOXIDE, C-4 PLANTS, ELEVATED
CO2, ETHYLENE RELEASE, LONG-TERM EXPOSURE, PHOTOSYNTHETIC INHIBITION,
QUANTUM YIELD, SOURCE-SINK RELATIONS, WATER-STRESS


     284  
Bugmann, H. 1997. Sensitivity of forests in the European Alps to future climatic change. Climate
Research 8(1):35-44.

Model-based assessments of the impacts of climatic change on forests are confronted with 2
fundamental problems: first, there is a considerable uncertainty in the predictions of future climate;
second, the forest models contain simplified parameterizations of ecological processes. In this paper,
the sensitivity of forest models to different steady-state climate scenarios, to different process
formulations and to different assumptions on the transient behaviour of climate is studied. The effects
of 3 scenarios of climatic change and the behaviour of 5 forest gap models of the
FORECE/FORCLIM family are compared at sites along an elevational gradient in the European Alps.
A wide variety of species compositions may be obtained al a given site depending on the scenario of
future climate. At some sites all future forests differ radically from today's forest, suggesting that
these current forests are highly sensitive to climatic change. At some sites, the results of the 5 forest
models differ strongly with respect to species composition and carbon storage when subjected to the
same climate scenario, showing that the models need to be improved in order to arrive at reliable and
robust parameterizations of abiotic and biotic influences in forest models. When comparing the effects
of step, Linear, and sigmoid changes of the mean climatic parameters over 100 yr, it becomes evident
that the type of change modelled is not crucial because the climatic change proceeds fast compared
to the successional dynamics. It is concluded that simulations of the possible effects of climatic
change on forests should be considered as sensitivity tests, not as predictions. Given the current
uncertainties in atmospheric sciences (climate predictions) and in ecology (modelling of long-term
forest dynamics), the most promising research strategy is to compare the effects of several climate
scenarios and the projections of several forest models to arrive at slate-of-the-art ecological impact
assessments.

KEYWORDS: CO2, MATTER, MODEL


     285  
Bukhov, N.G., N. Boucher, and R. Carpentier. 1997. Aftereffect of short-term heat shock on
photosynthetic reactions in barley leaves. Russian Journal of Plant Physiology 44(4):526-532.

Effects of preheating 8- to 10-day-old barley (Hordeum vulgare L.) leaves at 40-46 degrees C on
oxygen evolution, chlorophyll fluorescence, and photoacoustic signals were examined. Preheating of
leaves at 40 degrees C led to a threefold decrease in the initial slope of the light-response curve of
photosynthesis and a marked enhancement of the nonphotochemical quenching of chlorophyll
fluorescence, which indicates a drastic increase in the nonradiative dissipation of absorbed light
quanta. The maximum photosynthetic activity attained at saturating light and elevated CO2
concentration was suppressed by this heat treatment by no more than 30%. The photochemical
activity of PS LT reaction centers in dark-adapted leaves also decreased to the same extent after the
heat treatment. In preheated leaves, strong light pulses increased the photobaric component of the
photoacoustic signal (measured at 35 Hz) instead of suppressing the signal. The magnitude of the
rise- phase of the photoacoustic signal increased with the preheating temperature. An enhancement
of the photoacoustic signal induced by strong light pulses was also observed in leaves in which the
normal photosynthetic process was disturbed by feeding them methylviologen. It is concluded that
the short-term heating of leaves impairs photochemical conversion of light quanta in reaction centers
of PS II due to an increase in the magnitude of the proton gradient across the thylakoid membrane.
This indicates that dark reactions of photosynthesis in preheated leaves cannot efficiently use the ATP
and reduced NADP formed in the course of photosynthetic electron transport.

KEYWORDS: CHLOROPHYLL FLUORESCENCE, CHLOROPLASTS, INDUCTION, OXYGEN
EVOLUTION, PHOTOINHIBITION, PHOTOSYSTEM-I, RESOLUTION, SPINACH LEAVES,
STIMULATION, TEMPERATURE


     286  
Bunce, J.A. 1992. Light, temperature and nutrients as factors in photosynthetic adjustment to an
elevated concentration of carbon-dioxide. Physiologia Plantarum 86(1):173-179.

The short-term stimulation of the net rate of carbon dioxide exchange of leaves by elevated
concentrations of CO2 usually observed in C3 plants sometimes does not persist. Experiments were
conducted to test whether the patterns of response to the environment during growth were consistent
with the hypotheses that photosynthetic adjustment to elevated CO2 concentration is due to (1)
feedback inhibition or (2) nutrient stress. Soybean [Glycine max (L.) Merr. cv. Williams] and sugar
beet (Beta vulgaris L. cv. Mono Hye-4) were grown from seed at 350 and 700 mul l-1 CO2, at 20
and 25-degrees-C, at a photon flux density of 0.5 and 1.0 mmol m-2 s-1 and with three nutrient
regimes until the third trifoliolate leaf of soybean or the sixth leaf of sugar beet had finished
expanding. Net rates Of CO2 exchange of the most recently expanded leaves were then measured at
both 350 and 700 mul l-1 CO2. Plants grown at the elevated CO2 concentration had net rates of leaf
CO2 exchange which were reduced by 33% in sugar beet and 23% in soybean when measured at 350
mul l-1 CO2 and when averaged over all treatments. Negative photosynthetic adjustment to elevated
CO2 concentration was not greater at 20 than at 25-degrees-C, was not greater at a photon flux
density of 1.0 than at 0.5 mmol M- 2 s-1 and was not greater with limiting nutrients. Furthermore,
in soybean, negative photosynthetic adjustment could be induced by a single night at elevated CO2
concentration, with net rates of CO2 exchange the next day equal to those of leaves of plants grown
from seed at the elevated concentration Of CO2. These patterns do not support either the feedback-
inhibition or the nutrient-stress hypothesis of photosynthetic adjustment to elevated concentrations
of CO2.

KEYWORDS: CO2, COTTON, ENRICHMENT, EXCHANGE, GROWTH, LEAVES, LONG-TERM
EXPOSURE, PLANTS, RESPONSES


     287  
Bunce, J.A. 1992. Stomatal conductance, photosynthesis and respiration of temperate deciduous tree
seedlings grown outdoors at an elevated concentration of carbon-dioxide. Plant, Cell and
Environment 15(5):541-549.

Seedlings of temperate deciduous tree species were grown outdoors at ambient and at an elevated
concentration of carbon dioxide to examine how aspects of their gas exchange would be altered by
growth at elevated carbon dioxide concentration. Leaf conductances to water vapour and net carbon
dioxide exchange rates were determined periodically near midday. Whole- plant carbon dioxide efflux
rates in darkness were also determined. The stomatal conductance of leaves of plants grown and
measured at 700 cm3 m-3 carbon dioxide did not differ from that of plants grown and measured at
350 cm3 m-3 in Malus domestica, Quercus prinus and Quercus robur at any measurement time. In
Acer saccharinum, lower conductances occurred for plants grown and measured at elevated carbon
dioxide concentration only at measurement temperatures above 33- degrees-C. Photosynthetic
adjustment to elevated carbon dioxide concentration was evident only in Q. robur. All species
examined had lower rates of dark respiration per unit of mass when grown and measured at elevated
carbon dioxide concentration.

KEYWORDS: CO2 CONCENTRATION, FORESTS, RESPONSES


     288  
Bunce, J.A. 1993. Effects of doubled atmospheric carbon-dioxide concentration on the responses
of assimilation and conductance to humidity. Plant, Cell and Environment 16(2):189-197.

Experiments were performed to determine if growth at elevated partial pressure of CO2 altered the
sensitivity of leaf water vapour conductance and rate of CO2 assimilation to the leaf-to- air difference
in the partial pressure of water vapour (DELTAw). Comparisons were made between plants grown
and measured at 350 and 700 muPa Pa-1 partial pressures of CO2 for amaranth, soybean and
sunflower grown in controlled environment chambers, soybean grown outdoors in pots, and orchard
grass grown in field plots. In amaranth, soybean and orchard grass, both the absolute and the relative
sensitivity of conductance to DELTAw at the leaf surface were less in plants grown and measured
at the elevated CO2. In sunflower, there was no change in the sensitivity of conductance to DELTAw
for the two CO2 partial pressures. Tests in soybeans and amaranth showed that the change in
sensitivity resulted from elevated CO2 during the measurement of the DELTAw response.
Assimilation rate of CO2 was not altered by DELTAw in amaranth, which has C4 metabolism. In
sunflower, the assimilation rate of plants grown and measured at elevated CO2 was insensitive to
DELTAw, consistent with the response of assimilation rate to intercellular CO2 partial pressure in
the prevailing range. In soybean, the sensitivity of assimilation rate to DELTAw was not different
between CO2 treatments, in contrast to what would be expected from the response of assimilation
rate to intercellular CO2 partial pressure.

KEYWORDS: ARBUTUS-UNEDO, EFFICIENCY, LEAVES, MIDDAY DEPRESSION, NET CO2
UPTAKE, PHOTOSYNTHETIC CAPACITY, SUNFLOWER, TRANSPIRATION, VAPOR-
PRESSURE DEFICIT, WATER-STRESS


     289  
Bunce, J.A. 1993. Growth, survival competition, and canopy carbon-dioxide and water-vapor
exchange of 1st year alfalfa at an elevated co2 concentration. Photosynthetica 29(4):557-565.

Alfalfa was grown in field plots at the current CO2 concentration (350 mumol mol-1 = c350) and at
350 mumol mol-1 above the current concentration (= c700). Alfalfa and weed growth, and canopy
water vapor (E) and carbon dioxide exchange (F) were determined for the first year. Alfalfa yield
summed for the three harvests.in the first year was greater for the c700 treatment in two of the years
studied, but significantly less in a third year. Weed growth was unaffected. Survival of alfalfa plants
was greater at c700 for years in which there was substantial mortality, even when yield was not
increased by the c700 treatment. In spite of a persistent reduction in leaf conductance to water vapor
(g(l)), total canopy conductance (g(c)) to water vapor did not differ between CO2 treatments when
averaged over years, because of compensating changes in canopy leaf area. CO2 efflux (F) at night
per unit of ground area was consistently less in the c700 treatment even when daytime CO2 uptake
was higher. Hence the periodic harvesting of alfalfa crops does not necessarily allow elevated CO2
to cause persistent growth stimulation nor reduced water use.

KEYWORDS: ENRICHMENT, PHOTOSYNTHESIS, PLANTS, RESPIRATION, RESPONSES,
TEMPERATURE, WHEAT, YIELD


     290  
Bunce, J.A. 1995. The effect of carbon-dioxide concentration on respiration of growing and mature
soybean leaves. Plant, Cell and Environment 18(5):575-581.

Soybean plants were grown continuously at 350 and 700cm(3)m(-3) CO2 at constant temperature,
Respiration rates of third trifoliolate leaves were measured at the growth CO2 concentration for the
whole dark period from 5d before through to 5d after full area expansion, The short-term response
of respiration rate to the measurement CO2 concentration was also determined at each age,
Respiration rates per unit of dry mass declined with age and were significantly less at a given age or
RGR in leaves grown and measured at the elevated CO2. The difference in respiration rate was
largest in mature leaves and resulted from the different measurement CO2 concentrations, The
respiratory costs of the tissue synthesis, estimated from the elemental composition of the tissue, did
not differ substantially between CO2 treatments, The response of respiration rate to carbon dioxide
concentration was not strongly affected by the form of nitrogen supplied. Maintenance respiration
calculated by subtracting growth respiration from total respiration was negative in rapidly growing
leaves for both CO2 treatments, This indicates that CO2 efflux in the dark does not accurately reflect
the average 24h rate of energy expenditure on growth and maintenance for soybean leaves.

KEYWORDS: CO2- ENRICHMENT, DARK RESPIRATION, EFFLUX, ELEVATED CO2,
GROWTH, INHIBITION, MAINTENANCE, PLANT RESPIRATION, TERM


     291  
Bunce, J.A. 1995. Effects of elevated carbon-dioxide concentration in the dark on the growth of
soybean seedlings. Annals of Botany 75(4):365-368.

Previous work has shown that elevated carbon dioxide (CO2) concentrations in the dark reversibly
reduce the rate of CO2 efflux from soybeans. Experiments were performed exposing soybean plants
continually to concentrations of 350 or 700 cm(3) m(-3) for 24 h d(-1), or to 350 during the day and
700 cm(3) m(-3) at night, in order to determine the importance of the reduced rate of dark CO2 efflux
for plant growth. High CO2 applied only at night conserved carbon and increased dry mass during
initial growth compared with the constant 350 cm(3) m-3 treatment. Long-term net assimilation rate
was increased by high CO2 in the dark, without any increase in daytime leaf photosynthesis.
However, leaf area ratio was reduced by the dark CO2 treatment to values equal to those of plants
continually exposed to the higher concentration. From days 14- 21, leaf area was less for the elevated
night-time CO2 treatment than for either the constant 350 or 700 cm(3) m(-3) treatments. For the
day 7-21-period, relative growth rate was significantly reduced by the high night CO2 treatment
compared with the 350 cm(3) m(-3) continuous treatment. The results indicate that some functionally
significant component of respiration was reduced by the elevated CO2 concentration in the dark.

KEYWORDS: RESPIRATION, TEMPERATURE


     292  
Bunce, J.A. 1995. Long-term growth of alfalfa and orchard grass plots at elevated carbon dioxide.
Journal of Biogeography 22(2-3):341-348.

Alfalfa (Medicago sativa L.) and orchard grass (Dactylis glomerata L.) plots were exposed to ambient
or ambient plus 350 cm(3) m(-3) carbon dioxide concentrations at Beltsville, Maryland, U.S.A.
Replicate plots were established in different years and fertilized annually. We report here data for the
second and third years after establishment. There has been no increase in the yearly production of
either species at the elevated carbon dioxide concentration after the first season. In orchard grass,
reduced growth at the high carbon dioxide concentration in the spring offset growth stimulation in
the summer. Weed growth was consistently increased by carbon dioxide enrichment, but weed species
composition was unaffected. Leaf photosynthetic capacity was reduced by the high carbon dioxide
concentration in both crop species, as was leaf nitrogen content. Canopy carbon dioxide uptake was
slightly higher in the elevated carbon dioxide treatments, consistent with the increased weed growth.
In alfalfa, elevated carbon dioxide significantly reduced canopy carbon dioxide efflux at night for the
same daytime uptake rate and temperature. The growth conversion efficiency estimated from
elemental composition of the tissue was not substantially altered by carbon dioxide treatment in either
crop species, indicating little effect of carbon dioxide treatment on the respiratory cost of tissue
synthesis. Canopy conductance to water vapour averaged 23% less at high than at low carbon dioxide
in the orchard grass plots, and 14% less in the alfalfa plots. This was consistent with the smaller short-
term response of conductance to carbon dioxide concentration in the alfalfa plots. It is concluded that
a warm climate and fertile soil does not guarantee a persistent response of production to elevated
carbon dioxide concentration in these herbaceous perennial species.

KEYWORDS: ATMOSPHERIC CO2, PHOTOSYNTHESIS, PRODUCTIVITY, RESPONSES,
TRANSPIRATION, TREES


     293  
Bunce, J.A. 1996. Growth at elevated carbon dioxide concentration reduces hydraulic conductance
in alfalfa and soybean. Global Change Biology 2(2):155-158.

Hydraulic conductances of alfalfa and soybean plants grown in controlled environment chambers at
the current ambient carbon dioxide concentration and at twice the current ambient concentration were
determined from measurements of transpiration rate and leaf and stem water potentials in the growth
conditions. Growth at elevated carbon dioxide concentration reduced both transpiration rate and
hydraulic conductance from the soil to the leaf in both species. Hydraulic conductance from the soil
to the base of the stem was also lower at elevated carbon dioxide in soybean, but not alfalfa. These
measurements identified the stem to leaf hydraulic pathway as a major target of the carbon dioxide
effect in both species. The conductance of excised stem segments was much less in plants grown at
elevated carbon dioxide in soybeans.

KEYWORDS: ATMOSPHERIC CO2, WATER RELATIONS


     294  
Bunce, J.A. 1997. Variation in growth stimulation by elevated carbon dioxide in seedlings of some
C-3 crop and weed species. Global Change Biology 3(1):61-66.

Seven C-3 crop and three C-3 weed species were grown from seed at 360 and at 700 cm(3) m(-3)
carbon dioxide concentrations in a controlled environment chamber to compare dry mass, relative
growth rate (RGR), net assimilation rate (NAR), leaf area ratio (LAR) and photosynthetic acclimation
at ambient and elevated carbon dioxide. The dry mass at the final harvest at elevated carbon dioxide
relative to that at ambient carbon dioxide was highly correlated with the RGR at the lower carbon
dioxide concentration. This relationship could be quite common, because it does not require that
species differ in the response of RGR or photosynthesis to elevated carbon dioxide, and holds even
when species differ moderately in these responses. RGR was also measured for a limited period at
the end of the experiment to determine relationships with leaf gas exchange measured at this time.
Relative increases in RGR at elevated carbon dioxide at this time were more highly correlated with
the relative increase in NAR at elevated carbon dioxide than with the response of LAR. The amount
of acclimation of photosynthesis was a good predictor of the relative increase in NAR at elevated
carbon dioxide, and the longterm increase in photosynthesis in the growth environment. No
differences between crops and weeds or between cool and warm climate species were found in the
responses of growth or photosynthetic acclimation to elevated carbon dioxide.

KEYWORDS: CO2- ENRICHMENT


     295  
Bunce, J.A. 1998. Effects of environment during growth on the sensitivity of leaf conductance to
changes in humidity. Global Change Biology 4(3):269-274.

Soybeans (Glycine max) and grain amaranth (Amaranthus hypochondriacus) were grown at a range
of temperatures, carbon dioxide concentrations and light conditions in controlled environment
chambers, and the response of leaf conductance to water vapour to changes in humidity was then
measured under a standard set of conditions. The sensitivity of conductance was analysed in terms
of (i) the absolute sensitivity of conductance to changes in leaf to air water vapour pressure difference
(LAVPD), (ii) the sensitivity of conductance relative to the absolute value of conductance, and (iii)
the slope of the relationship between conductance and an index incorporating assimilation rate,
carbon dioxide concentration and relative humidity. The sensitivity of conductance varied
substantially with growth conditions for all three analyses in both species. The growth temperature
of 25 degrees C increased the sensitivity of conductance by all three measures compared with growth
at 20 or 30 degrees C in amaranth, with little difference between 25 and 30 degrees C in soybean.
Growth at elevated carbon dioxide decreased sensitivity in amaranth by all three measures, and
decreased the absolute but not the relative sensitivity in soybean. Growth at reduced photon flux
density and growth at high stand density reduced sensitivity in amaranth by all three measures. In
soybean, growth at high stand density reduced sensitivity by all three measures, but growth at low
photon flux density increased the relative sensitivity. The sensitivity of leaf conductance to changes
in humidity varied by a factor of two or more with growth environment by all measures of sensitivity
in both the C3 and the C4 species.

KEYWORDS: C-3, CARBON DIOXIDE, CO2, MODEL, PHOTOSYNTHESIS, RESPONSES,
TRANSPIRATION


     296  
Bunce, J.A. 1998. The temperature dependence of the stimulation of photosynthesis by elevated
carbon dioxide in wheat and barley. Journal of Experimental Botany 49(326):1555-1561.

The temperature dependencies of the solubility of carbon dioxide and oxygen in water and the
temperature dependency of the kinetic characteristics of the ribulose-1,5 bisphosphate
carboxylase/oxygenase (Rubisco) enzyme result in the short-term stimulation of photosynthesis with
a doubling of carbon dioxide from 350 to 700 mu mol mol(-1) usually decreasing from about 90%
at 30 degrees C to about 25% at 10 degrees C at high photon flux. In field-grown wheat and barley,
the expected values at 30 degrees C were observed, but also values as high as 60% at 10 degrees C.
The much larger than expected stimulation at cool temperatures in these species also occurred in
plants grown at 15 degrees C, but not at 23 degrees C in controlled environment chambers. Gas
exchange analysis indicated that an unusually high diffusive limitation was not an explanation for the
large response. Assessment of the apparent in vivo specificity of Rubisco by determining the carbon
dioxide concentration at which carboxylation equalled carbon dioxide release from oxygenation,
indicated that growth at row temperatures altered the apparent enzyme specificity in these species
compared to these species grown at the warmer temperature. Inserting the observed specificities into
a biochemical model of photosynthesis indicated that altered Rubisco specificity was consistent with
the observed rates of assimilation. Whether altered apparent Rubisco specificity is caused by altered
stoichiometry of photorespiration or an actual change in enzyme specificity, the results indicate that
the temperature dependence of the stimulation of photosynthesis by elevated carbon dioxide may vary
greatly with species and with prior exposure to low temperatures.

KEYWORDS: ASSIMILATION, CO2/O2 SPECIFICITY, EXCHANGE, LIGHT, PLANTS,
RESPIRATION, RIBULOSE 1;5-BISPHOSPHATE, RIBULOSE-1;5-BISPHOSPHATE
CARBOXYLASE-OXYGENASE


     297  
Bunce, J.A., K.B. Wilson, and T.N. Carlson. 1997. The effect of doubled CO2 on water use by
alfalfa and orchard grass: Simulating evapotranspiration using canopy conductance measurements.
Global Change Biology 3(1):81-87.

Alfalfa and orchard grass crops were grown at ambient and twice ambient carbon dioxide
concentrations in field plots for several years in Beltsville, MD, using semiopen chambers. Canopy
conductances throughout many days were determined from water vapour exchange measurements,
and indicated significant reductions in canopy conductance to water vapour at elevated carbon
dioxide in both species. However, recognizing that the artificial ventilation in the chambers made
direct comparisons of evapotranspiration rates questionable, we used a soil- vegetation-atmosphere
model to determine what field-scale evapotranspiration rates would have been with natural
ventilation. Unlike the 'omega' approach, the model used allowed feedbacks between the canopy and
the atmosphere, such that, for example, canopy conductance responses affected profiles of
temperature and water vapour. Simulations indicated that although canopy conductances were lower
at elevated carbon dioxide by as much as 20% in alfalfa and 60% in orchard grass, evapotranspiration
rates never differed by more than 3% in alfalfa or 8% in orchard grass. Daily totals of
evapotranspiration were only 1-2% lower at elevated carbon dioxide in alfalfa, and 2-5% lower in
orchard grass. The results are partly explained by the fact that aerodynamic conductances to water
vapour were generally smaller than the stomatal conductance, and also by canopy-atmosphere
feedback processes which largely compensated for the lower conductance at elevated carbon dioxide
by increasing the gradient for evaporation.

KEYWORDS: ASSIMILATION, CARBON DIOXIDE, ELEVATED CO2, GROWTH, LEAF,
RESPONSES, STOMATAL CONDUCTANCE, TRANSPIRATION


     298  
Bunce, J.A., and L.H. Ziska. 1996. Responses of respiration to increases in carbon dioxide
concentration and temperature in three soybean cultivars. Annals of Botany 77(5):507-514.

The purpose of this experiment was to determine how respiration of soybeans may respond to
potential increases in atmospheric carbon dioxide concentration and growth temperature. Three
cultivars of soybeans (Glycine max L. Merr.), from maturity groups 00, IV, and VIII, were grown
at 370, 555 and 740 cm(3) m(-3) carbon dioxide concentrations at 20/15, 25/20, and 31/26 degrees
C day/night temperatures. Rates of carbon dioxide efflux in the dark were measured for whole plants
several times during exponential growth. These measurements were made at the night temperature
and the carbon dioxide concentra:ion at which the plants were grown. For the lowest and highest
temperature treatments, the short term response of respiration rate to measurement at the three
growth carbon dioxide concentrations was also determined. Elemental analysis of the tissue was used
to estimate the growth conversion efficiency. This was combined with the observed relative growth
rates to estimate growth respiration. Maintenance respiration was estimated as the difference between
growth respiration and total respiration. Respiration rates were generally sensitive to short term
changes in the measurement carbon dioxide concentration for plants grown at the lowest, but not the
highest carbon dioxide concentration. At all temperatures, growth at elevated carbon dioxide
concentrations decreased total respiration measured at the growth concentration, with no significant
differences among cultivars. Total respiration increased very little with increasing growth
temperature, despite an increase in relative growth rate. Growth respiration was not affected by
carbon dioxide treatment at any temperature, but increased with temperature because of the increase
in relative growth rare. Values calculated for maintenance respiration decreased with increasing
carbon dioxide concentration and also decreased with increasing temperature. Calculated values of
maintenance respiration were sometimes zero or negative at the warmer temperatures. This suggests
that respiration rates measured in the dark may not have reflected average 24-h rates of energy use.
The results indicate that increasing astmospheric carbon dioxide concentration may reduce respiration
in soybeans, and respiration may be insensitive to climate warming. (C) 1996 Annals of Botany
Company

KEYWORDS: EFFLUX, ELEVATED CO2, ENRICHMENT, GROWTH, INHIBITION, LEAVES,
MAINTENANCE REQUIREMENTS, PHOTOSYNTHESIS, PLANT RESPIRATION, WHITE
CLOVER


     299  
Bunce, J.A., and L.H. Ziska. 1998. Decreased hydraulic conductance in plants at elevated carbon
dioxide. Plant, Cell and Environment 21(1):121-126.

Previous work indicated that long-term exposure to elevated carbon dioxide levels can reduce
hydraulic conductance in some species, but the basis of the response was not determined, In this
study, hydraulic conductance was measured at concentrations of both 350 and 700 cm(3) m(-3)
carbon dioxide for plants grown at both concentrations, to determine the reversibility of the response,
In Zea mays and Amaranthus hypochondriacus, exposure to the higher carbon dioxide concentration
for several hours reduced whole-plant transpiration rate by 22-40%, without any consistent change
in leaf water potential, indicating reversible reductions in hydraulic conductance at elevated carbon
dioxide levels, Hydraulic conductance in these species grown at both carbon dioxide concentrations
responded similarly to measurement concentration of carbon dioxide, indicating that the response was
reversible, In Glycine max, which in earlier work had shown a long-term decrease in hydraulic
conductance at elevated carbon dioxide levels, and in Abutilon theophrasti, no short- term changes
in hydraulic conductance with measurement concentration of carbon dioxide were found, despite
lower transpiration rates at elevated carbon dioxide, In G. max and Medicago sativa, growth at high
dew-point temperature reduced transpiration rate and decreased hydraulic conductance, The results
indicate that both reversible and irreversible decreases in hydraulic conductance can occur at elevated
carbon dioxide concentrations, and that both could be responses to reduced transpiration rate, rather
than to carbon dioxide concentration itself.

KEYWORDS: ATMOSPHERIC CO2, CONDUCTIVITY, COTTON PLANTS, ENRICHMENT,
GRASSLAND, GROWTH, RESISTANCE, STRESS, WATER TRANSPORT, YIELD


     300  
Burton, A.J., G.P. Zogg, K.S. Pregitzer, and D.R. Zak. 1997. Effect of measurement CO2
concentration on sugar maple root respiration. Tree Physiology 17(7):421-427.

Accurate estimates of root respiration are crucial to predicting belowground C cycling in forest
ecosystems. Inhibition of respiration has been reported as a short-term response of plant tissue to
elevated measurement [CO2]. We sought to determine if measurement [CO2] affected root
respiration in samples from mature sugar maple (Acer saccharum Marsh.) forests and to assess
possible errors associated with root respiration measurements made at [CO2]s lower than that typical
of the soil atmosphere. Root respiration was measured as both CO2 production and O-2 consumption
on excised fine roots (less than or equal to 1.0 mm) at [CO2]s ranging from 350 to > 20,000 mu l l(-
1). Root respiration was significantly affected by the [CO2] at which measurements were made for
both CO2 production and O-2 consumption. Root respiration was most sensitive to [CO2] near and
below normal soil concentrations (< 1500 mu l l(-1)). Respiration rates changed little at [CO2]s above
3000 mu l l(-1) and were essentially constant above 6000 mu l l(-1) CO2. These findings call into
question estimates of root respiration made at or near atmospheric [CO2], suggesting that they
overestimate actual rates in the soil. Our results indicate that sugar maple root respiration at
atmospheric [CO2] (350 mu l l(-1)) is about 139% of that at soil [CO2]. Although the causal
mechanism remains unknown, the increase in root respiration at low measurement [CO2] is significant
and should be accounted for when estimating or modeling root respiration. Until the direct effect of
[CO2] on root respiration is fully understood, we recommend making measurements at a [CO2]
representative of, or higher than, soil [CO2]. In all cases, the [CO2] at which measurements are made
and the [CO2] typical of the soil atmosphere should be reported.

KEYWORDS: CARBON-DIOXIDE CONCENTRATIONS, ENRICHMENT, FOREST ECOSYSTEMS,
HIGHER-PLANTS, INTRACELLULAR PH, MAINTENANCE RESPIRATION, PINE
PLANTATIONS, SHORT- TERM, SOIL O2, TEMPERATURE


     301  
Burton, P.J., and S.G. Cumming. 1995. Potential effects of climatic-change on some western
canadian forests, based on phenological enhancements to a patch model of forest succession. Water,
Air, and Soil Pollution 82(1-2):401-414.

We enhanced the forest patch model, Zelig, to explore the implications of 2xCO(2) climate change
scenarios on several forest regions in British Columbia and Alberta, Canada. In addition to the
processes and phenomena commonly represented in individual-based models of forest stand dynamics,
we added some species-specific phenology and sire-specific frost events. The consideration of bud-
break heat sum requirements, growing season limits, and chilling requirements for the induction of
dormancy and cold hardiness slightly improved the ability of Zelig to predict the present composition
of B.C. forests. Simulations of the predicted effects of future climatic regimes (based on the averaged
predictions of four general circulation models) include some major shifts in equilibrial, forest
composition and productivity. Lowland temperate coastal forests are predicted to be severely stressed
because indigenous species will no longer have their winter chilling requirements met. High-elevation
coastal forests are expected to increase in productivity, while interior subalpine forests are expected
to remain stable in productivity but will gradually be replaced by species currently characteristic of
lower elevations. Dry, interior low-elevation forests in southern B.C. are likely to persist relatively
unchanged, while wet interior forests are expected to support dramatic increases in yield, primarily
by western hemlock. Northern interior sub-boreal forests are likewise expected to increase in
productivity through enhanced growth of lodgepole pine. Conversely, the precipitous collapse of
spruce stands in the true boreal forests of northeastern B.C. is expected to be associated with reduced
productivity as they are replaced by pine species. Boreal-Cordilleran and Moist Boreal Mixedwood
forests in Alberta are less likely to undergo compositional change, while becoming somewhat more
productive. We believe these model enhancements to be a significant improvement over existing
formulations, but the resulting predictions must still be viewed with caution. Model limitations
include: (1) the current inability of climate models to predict future variation in monthly temperature
and precipitation; (2) sparse information on the phenological behaviour of several important tree
species; and (3) a poor understanding of the degree to which growth is constrained by different
suboptimal climatic events.

KEYWORDS: BUDBURST, CARBON, CO2, FREEZING RESISTANCE, GLOBAL CLIMATE,
SCALE, SENSITIVITY, TREES


     302  
Buse, A., and J.E.G. Good. 1996. Synchronization of larval emergence in winter moth (Operophtera
brumata L) and budburst in pedunculate oak (Quercus robur L) under simulated climate change.
Ecological Entomology 21(4):335-343.

1. The hypothesis that a 3 degrees C elevation in temperature and doubled CO2 concentration would
have no effect on the synchronization of winter moth egg hatch with budburst in oak was tested by
comparing the separate and interactive effects of ambient and elevated (+ 3 degrees C) temperature
and ambient and elevated (doubled to 340 p.p.m.) CO2 in eight experimental Solardomes. In addition,
an outdoor control was compared with the ambient temperature/CO2 treatment combination. 2.
Elevated temperature accelerated darkening (preceding egg hatch by about 5-10 days) and hatching
of eggs developing off the trees; elevated CO2 had no effect. The same effects were observed in eggs
developing on the trees. 3. Within treatments, date of egg hatch was the same on trees with early or
late budburst. 4. Egg darkening and budburst were closely synchronized at both ambient and elevated
temperatures. 5. Both eggs and trees required fewer cumulative heat units (day degrees > 4 degrees
C), for hatching and budburst, respectively, at ambient than elevated temperatures. The requirements
in the outdoor control treatment were similar to those in the ambient Solardome treatment. 6. Egg
hatch between 10 and 25 degrees C, on a temperature gradient in the laboratory, required a constant
number of heat units; fewer were required below 10 degrees C. 7. Elevated temperatures, in the
Solardomes and the field, delayed adult emergence from the pupae. 8. The results suggest that a
general increase in temperature with climatic change would not affect the closeness of the
synchronization between egg hatch of winter moth and budburst of oak.

KEYWORDS: BRITAIN, GEOMETRIDAE, LEPIDOPTERA, OUTBREAKS, SCOTLAND, SITKA
SPRUCE, TEMPERATURE, TREES


     303  
Buse, A., J.E.G. Good, S. Dury, and C.M. Perrins. 1998. Effects of elevated temperature and
carbon dioxide on the nutritional quality of leaves of oak (Quercus robur L.) as food for the Winter
Moth (Operophtera brumata L.). Functional Ecology 12(5):742-749.

1. Pedunculate Oak trees were grown in ambient and elevated temperatures and CO2. Leaves were
fed to Winter Moth caterpillars reared either in constant conditions or with the trees (caged or on-
tree). 2. Caterpillars in constant conditions ate the same mass and produced the same mass of faeces
whether fed elevated or ambient temperature leaves. However, less was assimilated from elevated
leaves, resulting in lighter pupae and fewer, lighter eggs. 3. Caterpillars in constant conditions ate
more and produced more faeces when fed elevated CO2 leaves than when fed ambient CO2 leaves,
but the mass assimilated and pupal mass were unchanged. 4. Caged caterpillars reared with the trees
from which they were fed had constant pupal mass in all treatments, but pupated earlier at elevated
temperature. Pupal mass was also unaffected when caterpillars fed on the trees. 5. Nitrogen was
reduced in both elevated temperature and elevated CO2 leaves. Increased fibre in the former
prevented increased consumption and resulted in reduced pupal mass and fecundity. Reduced fibre
in the latter allowed increased consumption, resulting in pupae of normal mass. 6. Despite the clear
effect of nutrient quality, experiments rearing caterpillars and trees together suggest that anticipated
climatic change will have no nutritional effect on Winter Moth development.

KEYWORDS: ATMOSPHERIC CO2, DECIDUOUS TREES, FEEDING RESPONSE, GROWTH,
HERBIVORE INTERACTIONS, HOST PLANTS, INSECT PERFORMANCE, LYMANTRIA-
DISPAR, NITROGEN, PLANT-RESPONSES


     304  
Bytnerowicz, A. 1996. Physiological aspects of air pollution stress in forests. Phyton-Annales Rei
Botanicae 36(3):15-22.

Air pollutants, such as ozone, sulfur dioxide, nitrogen compounds and others, affect health of forests
in Europe and North America. Gaseous air pollutants enter plants mainly through stomata, although
transcuticular transport can also be important for some pollutants. Toxic effects of pollutants depend
on their effective dose that is proportional to pollutant ambient concentration and plant stomatal
conductance. Mechanisms of air pollution toxicity are very complex and depend on various
physiological and biochemical properties of plants. These mechanisms (including formation of free
radicals) are still poorly understood. In addition, physiological responses of forest plants to air
pollution stress can be modified by various biotic (e.g., insects, pathogens, mycorrhizae associations,
genetic variation) and abiotic (e.g., increasing CO2 concentrations, ultraviolet-B radiation, nitrogen
deposition, nutrient deficiencies, drought) factors. An example of air pollution effects on forest trees
may be responses of ponderosa pine seedlings to elevated concentrations of ozone in the Sierra
Nevada. Various physiological changes caused by ozone (e.g., lowered net photosynthesis, altered
carbon allocation, deterioration of photosynthetic pigments, etc.) have led to the reduced growth and
biomass of the seedlings.

KEYWORDS: ATMOSPHERIC OZONE, B RADIATION, NITROGEN, PINE, SULFUR,
VEGETATION


     305  
Cairney, J.W.G., and A.A. Meharg. 1999. Influences of anthropogenic pollution on mycorrhizal
fungal communities. Environmental Pollution 106(2):169-182.

Mycorrhizal fungi form complex communities in the root systems of most plant species and are
thought to be important in terrestrial ecosystem sustainability. We have reviewed the literature
relating to the influence of the major forms of anthropogenic pollution on the structure and dynamics
of mycorrhizal fungal communities. All forms of pollution have been reported to alter the structure
of below-ground communities of mycorrhizal fungi to some degree, although the extent to which such
changes will be sustained in the longer term is at present not clear. The major limitation to predicting
the consequences of pollution-mediated changes in mycorrhizal fungal communities to terrestrial
habitats is our limited understanding of the functional significance of mycorrhizal fungal diversity.
While this is identified as a priority area for future research, it is suggested that, in the absence of such
data, an understanding of pollution-mediated changes in mycorrhizal mycelial systems in soil may
provide useful indicators for sustainability of mycorrhizal systems. (C) 1999 Elsevier Science Ltd. All
rights reserved.

KEYWORDS: ABIES L KARST, ELEVATED ATMOSPHERIC CO2, LANDFILL SITE
RESTORATION, LOBLOLLY-PINE SEEDLINGS, NORWAY SPRUCE, RED SPRUCE
SEEDLINGS, SCOTS PINE, SIMULATED ACID-RAIN, TAEDA L SEEDLINGS, VESICULAR-
ARBUSCULAR MYCORRHIZAE


     306  
Callaway, R.M., E.H. Delucia, E.M. Thomas, and W.H. Schlesinger. 1994. Compensatory
responses of co2 exchange and biomass allocation and their effects on the relative growth-rate of
ponderosa pine in different co2 and temperature regimes. Oecologia 98(2):159-166.

Increases in the concentration of atmospheric carbon dioxide may have a fertilizing effect on plant
growth by increasing photosynthetic rates and therefore may offset potential growth decreases caused
by the stress associated with higher temperatures and lower precipitation. However, plant growth is
determined both by rates of net photosynthesis and by proportional allocation of fixed carbon to
autotrophic tissue and heterotrophic tissue. Although CO2 fertilization may enhance growth by
increasing leaf-level assimilation rates, reallocation of biomass from leaves to stems and roots in
response to higher concentrations of CO2 and higher temperatures may reduce whole-plant
assimilation and offset photosynthetic gains. We measured growth parameters, photosynthesis,
respiration, and biomass allocation of Pinus ponderosa seedlings grown for 2 months in 2 x 2 factorial
treatments of 350 or 650mu bar CO2 and 10/25-degrees-C or 15/30-degrees-C night/day
temperatures. After 1 month in treatment conditions, total seedling biomass was higher in elevated
CO2, and temperature significantly enhanced the positive CO2 effect. However, after 2 months the
effect of CO2 on total biomass decreased and relative growth rates did not differ among CO2 and
temperature treatments over the 2-month growth period even though photosynthetic rates increased
almost-equal-to 7% in high CO2 treatments and decreased almost- equal-to 10% in high temperature
treatments. Additionally, CO2 enhancement decreased root respiration and high temperatures
increased shoot respiration. Based on CO2 exchange rates, CO2 fertilization should have increased
relative growth rates (RGR) and high temperatures should have decreased RGR. Higher
photosynthetic rates caused by CO2 fertilization appear to have been mitigated during the second
month of exposure to treatment conditions by a almost-equal-to 3% decrease in allocation of biomass
to leaves and a almost-equal-to 9% increase in root:shoot ratio. It was not clear why diminished
photosynthetic rates and increased respiration rates at high temperatures did not result in lower RGR.
Significant diametrical and potentially compensatory responses of CO2 exchange and biomass
allocation and the lack of differences in RGR of ponderosa pine after 2 months of exposure of high
CO2 indicate that the effects of CO2 fertilization and temperature on whole-plant growth are
determined by complex shifts in biomass allocation and gas exchange that may, for some species,
maintain constant growth rates as climate and atmospheric CO2 concentrations change. These
complex responses must be considered together to predict plant growth reactions to global
atmospheric change, and the potential of forest ecosystems to sequester larger amounts of carbon in
the future.

KEYWORDS: ATMOSPHERIC CARBON-DIOXIDE, ENRICHMENT, GREAT-BASIN, LEAF-
AREA, RESPIRATION, SEEDLINGS, SOIL, VEGETATION, WATER-USE EFFICIENCY, WOODY-
PLANTS


     307  
Campbell, B.D., W.A. Laing, D.H. Greer, J.R. Crush, H. Clark, D.Y. Williamson, and M.D.J.
Given. 1995. Variation in grassland populations and species and the implications for community
responses to elevated CO2. Journal of Biogeography 22(2-3):315-322.

Variation in plant characteristics and potential responses to CO2 was measured in controlled
environments for a set of different forage plant species and populations. The response of the plants
to elevated CO2 was strongly determined by temperature. The greatest responses to elevated CO2
were observed at warm temperatures in C3 species with high potential growth rates at these
temperatures. This suggests that the community composition could change most rapidly in response
to CO2 in warm seasons, with the greatest positive responses to CO2 occurring in warm-season
active species. This prediction was tested in a microcosm experiment. The prediction was confirmed
under well-watered conditions but water stress resulted in an ingress of C4 species with low potential
responses to CO2. The results suggest that variation between populations and species must be
considered when predicting grassland community responses to CO2, and that it is inappropriate to
ignore compositional changes in communities when modelling CO2 effects on pasture production.
Given the importance of temperature in determining CO2 responsiveness, phenology may prove to
be a useful attribute in plant functional type analyses of community responses to CO2.

KEYWORDS: ENRICHMENT


     308  
Campbell, B.D., D.M.S. Smith, and G.M. McKeon. 1997. Elevated CO2 and water supply
interactions in grasslands: A pastures and rangelands management perspective. Global Change
Biology 3(3):177-187.

Water is a key variable driving the composition and productivity of pastures and rangelands, and
many of the ecosystems in these grasslands are highly sensitive to changes in water supply. The
possibility that elevated CO2 concentrations may alter plant water relations is therefore particularly
relevant to pastures and rangelands, and may have important consequences for grassland ecosystem
function, water use, carbon storage and nutrient cycling. The planning of effective research to better
understand these changes requires attention to both: (i) gaps in knowledge about CO2 and water
interactions, and (ii) knowledge of how precisely the effects of CO2 must be understood in relation
to other factors, in order to predict changes in grassland structure and production. A recent
microcosm experiment illustrates that non-linear effects of CO2 and water stress could perturb
primary production by triggering changes in grassland community composition. The magnitudes of
the effects of CO2 on key grassland ecosystems remain to be precisely determined through
ecosystem-level experiments. A simplified simulation of the impact of different levels of productivity
change in a water- limited Australian rangeland system was conducted by varying effects of CO2 on
radiation and water use efficiency. The results indicate that direct effects of CO2 may be moderated
at the enterprise scale by accompanying changes in adaptive management by farmers. We conclude
that future research should aim to construct quantitative relationships and identify thresholds of
response for different grassland systems. The sensitivity of these systems to management (such as
grazing pressure) should also be considered when developing integrated predictions of future effects
of CO2 on water supply to grassland ecosystems.

KEYWORDS: DESERT ECOSYSTEMS, TALLGRASS PRAIRIE, UNITED-STATES


     309  
Campbell, W.J. 1997. Intraspecific variation of rubisco and rubisco activase protein levels in tomato
leaves grown at elevated CO2 concentration. Plant Physiology 114(3):1056.



     310  
Canadell, J.G., L.F. Pitelka, and J.S.I. Ingram. 1996. The effects of elevated [CO2] on plant-soil
carbon below- ground: A summary and synthesis. Plant and Soil 187(2):391-400.

We undertake a synthesis of the most relevant results from the presentations at the meeting ''Plant-
Soil Carbon Below-Ground: The Effects of Elevated CO2'' (Oxford-UK, September 1995), many of
which are published in this Special Issue. Below-ground responses to elevated [CO2] are important
because the capacity of soils for long-term carbon sequestration. We draw the following conclusions:
(i) several ecosystems exposed to elevated [CO2] showed sustained increased CO2 uptake at the plot
level for many years. A few systems, however, showed complete down-regulation of net CO2 uptake
after several years of elevated [CO2] exposure; (ii) under elevated [CO2], a greater proportion of
fixed carbon is generally allocated below-ground, potentially increasing the capacity of below- ground
sinks; and (iii) some of the increased capacity of these sinks may lead to increased long-term soil
carbon sequestration, although strong evidence is still lacking. We highlight the need for more soil
studies to be undertaken within ongoing ecosystem-level experiments, and suggest that while some
key experiments already established should be maintained to allow long term effects and feedbacks
to lake place, more research effort should be directed to mechanisms of soil organic matter
stabilization.

KEYWORDS: DIOXIDE, ECOSYSTEMS, GAS-EXCHANGE, GRASSLAND, INCREASING
ATMOSPHERIC CO2, NITROGEN, ORGANIC-MATTER, PHOTOSYNTHESIS, RESPONSES,
TURNOVER


     311  
Cannell, M.G.R., and J.H.M. Thornley. 1998. N-poor ecosystems may respond more to elevated
[CO2] than N- rich ones in the long term. A model analysis of grassland. Global Change Biology
4(4):431-442.

The Hurley Pasture Model was used to examine the short and long-term responses of grazed
grasslands in the British uplands to a step increase from 350 to 700 mu mol mol(-1) CO2
concentration ([CO2]) with inputs of 5 or 100 kg N ha(-1) y(- 1). In N-rich grassland, [CO2]
doubling quickly increased net primary productivity (NPP), total carbon (C-sys) and plant biomass
by about 30%. By contrast, the N-poor grassland underwent a prolonged 'transient', when there was
little response, but eventually NPP, C-sys and plant biomass more than doubled. The 'transient' was
due to N immobilization and severe depletion of the soil mineral N pool. The large long-term
response was due to slow N accumulation, as a result of decreased leaching, decreased gaseous N
losses and increased N- 2-fixation, which amplified the CO2 response much more in the N-poor than
in the N-rich grassland. It was concluded that (i) ecosystems use extra carbon fixed at high [CO2]
to acquire and retain nutrients, supporting the contention of Gifford et al. (1996), (ii) in the long term,
and perhaps on the real timescale of increasing [CO2], the response (in NPP, C-sys and plant
biomass) of nutrient-poor ecosystems may be proportionately greater than that of nutrient-rich ones,
(iii) short-term experiments on nutrient-poor ecosystems may observe only the transient responses,
(iv) the speed of ecosystem responses may be limited by the rate of nutrient accumulation rather than
by internal rate constants, and (v) ecosystem models must represent processes affecting nutrient
acquisition and retention to be able to simulate likely real-world CO2 responses.

KEYWORDS: ATMOSPHERIC CO2, DIOXIDE, ENRICHMENT, FOREST ECOSYSTEMS, GAS-
EXCHANGE, GLOBAL CARBON-CYCLE, GROWTH-RESPONSES, PLANT-RESPONSES, ROOT-
GROWTH, TERRESTRIAL ECOSYSTEMS


     312  
Cannell, M.G.R., and J.H.M. Thornley. 1998. Temperature and CO2 responses of leaf and canopy
photosynthesis: A clarification using the non-rectangular hyperbola model of photosynthesis. Annals
of Botany 82(6):883-892.

The responses of C-3 leaf and canopy gross photosynthesis to increasing temperature and CO2 can
be readily understood in terms of the temperature and CO2 dependencies of quantum yield (phi(i))
and light-saturated photosynthesis (A(sat)) the two principal parameters in the non-rectangular
hyperbola model of photosynthesis. Here, we define these dependencies within the mid-range for C-3
herbaceous plants, based on a review of the literature. Then, using illustrative parameter values, we
deduce leaf and canopy photosynthesis responses to temperature and CO, in different environmental
conditions (including shifts in the temperature optimum) from the assumed sensitivities of phi(i) and
A(sat) to temperature and CO2. We show that: (1) elevated CO2 increases photosynthesis more at
warm than at cool temperatures because of the large combined CO2-responses of both phi(i) and
A(sat) at high temperatures; (2) elevated CO2 may substantially raise the temperature optimum of
photosynthesis at warm temperatures, but not at the cool temperatures which prevail for much of the
time at temperate and high latitudes; (3) large upward shifts in the temperature optimum of canopy
gross photosynthesis occur at high irradiances, following the response of A(sat), and are probably
important for global carbon fixation; (4) canopy gross photosynthesis shows smaller CO2-
temperature interactions than leaf photosynthesis, because leaves in canopies receive lower average
irradiances and sep more strongly follow the dependencies of phi(i); and (5) at very low irradiances,
the temperature optimum of photosynthesis is low and is raised very little by increasing CO2 .(C)
1998 Annals of Botany Company.

KEYWORDS: C-4 PLANTS, CARBON DIOXIDE, CARBOXYLASE-OXYGENASE, CHLOROPHYLL
FLUORESCENCE, CLIMATE CHANGE, DEPENDENCE, EUCALYPTUS-PAUCIFLORA, LIGHT,
QUANTUM YIELDS, VASCULAR PLANTS


     313  
Cannon, R.J.C. 1998. The implications of predicted climate change for insect pests in the UK, with
emphasis on non-indigenous species. Global Change Biology 4(7):785-796.

Recent estimates for global warming predict increases in global mean surface air temperatures
(relative to 1990) of between 1 and 3.5 degrees C, by 2100. The impact of such changes on
agricultural systems in mid- to high-latitude regions are predicted to be less severe than in low-
latitude regions, and possibly even beneficial, although the influence of pests and diseases is rarely
taken into account. Most studies have concluded that insect pests will generally become more
abundant as temperatures increase, through a number of inter-related processes, including range
extensions and phenological changes, as well as increased rates of population development, growth,
migration and overwintering. A gradual, continuing rise in atmospheric CO2 will affect pest species
directly (i.e. the CO2 fertilization effect) and indirectly (via interactions with other environmental
variables). However, individual species responses to elevated CO2 vary: consumption rates of insect
herbivores generally increase, but this does not necessarily compensate fully for reduced leaf nitrogen.
The consequent effects on performance are strongly mediated via the host species. Some recent
experiments under elevated CO2 have suggested that aphids may become more serious pests,
although other studies have discerned no significant effects on sap- feeding homopterans. However,
few, if any of these experiments have fully considered the effects on pest population dynamics.
Climate change is also considered from the perspective of changes in the distribution and abundance
of species and communities. Marked changes in the distribution of well- documented species -
including Odonata, Orthoptera and Lepidoptera - in northwestern Europe, in response to unusually
hot summers, provide useful indications of the potential effects of climate change. Migrant pests are
expected to respond more quickly to climate change than plants, and may be able to colonize newly
available crops/habitats. Range expansions, and the removal of edge effects, could result in the
increased abundance of species presently near the northern limits of their ranges in the UK. However,
barriers to range expansions, or shifts, may include biotic (competition, predation, parasitism and
disease), as well as abiotic, factors. Climatic phenomena, ecosystem processes and human activities
are interactive and interdependent, making long-term predictions extremely tenuous. Nevertheless,
it appears prudent to prepare for the possibility of increases in the diversity and abundance of pest
species in the UK, in the context of climate change.

KEYWORDS: BRITISH BUTTERFLY FAUNA, CARBON-DIOXIDE ATMOSPHERES,
DECIDUOUS TREES, ELEVATED CO2, ENRICHED CO2 ATMOSPHERES, GLOBAL CHANGE,
HERBIVORE INTERACTIONS, JUNONIA-COENIA, LARVAL EMERGENCE, POPULATION-
DYNAMICS


     314  
Cantin, D., M.F. Tremblay, M.J. Lechowicz, and C. Potvin. 1997. Effects of CO2 enrichment,
elevated temperature, and nitrogen availability on the growth and gas exchange of different families
of jack pine seedlings. Canadian Journal of Forest Research-Revue Canadienne De Recherche
Forestiere 27(4):510-520.

Many economically important tree species respond positively to an elevated CO2 environment.
However, the variability and stability in growth responses among genotypes grown in a global change
environment are generally not documented. The present study investigated the differences, at the
seedling stage, among 15 maternal families of jack pine (Pinus banksiana Lamb.) in response to an
elevated CO2-temperature environment (CO2T) (700 mu L CO2.L-1 with temperatures 4 degrees
C higher than in the ambient CO2T environment), with different nitrogen concentrations. While the
elevated CO2T did not significantly alter the overall height growth of seedlings, it significantly
increased their total biomass, with needle and root biomass being most responsive. Growth in the
elevated CO2T resulted in a 24% reduction in the leaf weight ratio as more biomass was allocated
to roots. Significant genotypic differences were observed for height, biomass, and water-use
efficiency. Generally, most families kept their rank relative to other families, from the ambient to the
elevated CO2T. Also, rank correlations between height of families grown in elevated CO2T and
height of families at 10 years of age in the field were significant. This result, combined with the
stability we observed in family response from the ambient to the elevated CO2T, suggested that jack
pine families currently chosen for their fast-growing capacity will probably remain as such in a global
change environment, at least during the seedling establishment stage.

KEYWORDS: AGE-AGE CORRELATIONS, ATMOSPHERIC CO2, BLACK SPRUCE SEEDLINGS,
CLIMATE CHANGE, EARLY SELECTION, PATTERNS, PHENOTYPIC PLASTICITY, PICEA
MARIANA, RESPONSES, X ENVIRONMENT INTERACTIONS


     315  
Cao, M.K., and F.I. Woodward. 1998. Net primary and ecosystem production and carbon stocks
of terrestrial ecosystems and their responses to climate change. Global Change Biology 4(2):185-
198.

Evaluating the role of terrestrial ecosystems in the global carbon cycle requires a detailed
understanding of carbon exchange between vegetation, soil, and the atmosphere. Global climatic
change may modify the net carbon balance of terrestrial ecosystems, causing feedbacks on
atmospheric CO2 and climate. We describe a model for investigating terrestrial carbon exchange and
its response to climatic variation based on the processes of plant photosynthesis, carbon allocation,
litter production, and soil organic carbon decomposition. The model is used to produce geographical
patterns of net primary production (NPP), carbon stocks in vegetation and soils, and the seasonal
variations in net ecosystem production (NEP) under both contemporary and future climates. For
contemporary climate, the estimated global NPP is 57.0 Gt C y(-1), carbon stocks in vegetation and
soils are 640 Gt C and 1358 Gt C, respectively, and NEP varies from -0.5 Gt C in October to 1.6 Gt
C in July. For a doubled atmospheric CO2 concentration and the corresponding climate, we predict
that global NPP will rise to 69.6 Gt C y(-1), carbon stocks in vegetation and soils will increase by,
respectively, 133 Gt C and 160 Gt C, and the seasonal amplitude of NEP will increase by 76%. A
doubling of atmospheric CO2 without climate change may enhance NPP by 25% and result in a
substantial increase in carbon stocks in vegetation and soils. Climate change without CO2 elevation
will reduce the global NPP and soil carbon stocks, but leads to an increase in vegetation carbon
because of a forest extension and NPP enhancement in the north. By combining the effects of CO2
doubling, climate change, and the consequent redistribution of vegetation, we predict a strong
enhancement in NPP and carbon stocks of terrestrial ecosystems. This study simulates the possible
variation in the carbon exchange at equilibrium state. We anticipate to investigate the dynamic
responses in the carbon exchange to atmospheric CO2 elevation and climate change in the past and
future.

KEYWORDS: ATMOSPHERIC CO2, DECOMPOSITION, DYNAMICS, FOREST ECOSYSTEMS,
GLOBAL-MODEL, PHOTOSYNTHESIS, PLANT, SIMULATION, SINK, SOIL


     316  
Cao, W.X., and T.W. Tibbitts. 1997. Starch concentration and impact on specific leaf weight and
element concentrations in potato leaves under varied carbon dioxide and temperature. Journal of
Plant Nutrition 20(7-8):871-881.

Foliar concentrations of starch and major elements, nitrogen (N), phosphorus (P), potassium (K),
calcium (Ca), and magnesium (Mg), along with specific leaf weight (SLW) were determined in the
potato (Solanum tuberosum L.) cvs 'Denali', 'Norland', and 'Russet Burbank' grown for 35 days under
CO2 concentrations of 500, 1,000, 1,500 and 2,000 mu mol . mol(-1) at both 16 degrees C and 20
degrees C air temperature. The starch concentration, pooled from the three cultivars, increased with
increasing CO, concentration at both 16 degrees C and 20 degrees C and was consistently higher at
16 degrees C than at 20 degrees C. The SLW (g . m(-2)) was positively related to the foliar starch
concentration on the basis of leaf area or dry weight. The concentrations of N, P, Ca, and Mg in
leaves were negatively related to starch concentration under approximate to 14% starch on a dry
weight basis. Above 14% starch, there was no significant relationship between element and starch
concentrations. Similar patterns were seen when the SLW and element concentrations were expressed
on a starch-free basis. In contrast, the leaf concentration of K was not closely related to the starch
concentration because the K concentration was similar at varied CO2 levels. The results of this study
indicate that the changes in SLW and concentrations of N, P, Ca, and Mg in potato leaves only
partially resulted from the changed starch concentration.

KEYWORDS: CO2- ENRICHMENT, GROWTH, LIFE SUPPORT SYSTEMS, NITROGEN,
PHOTOPERIODS, RESPONSES, WHEAT


     317  
Cao, W., T.W. Tibbitts, and R.M. Wheeler. 1994. Carbon-dioxide interactions with irradiance and
temperature in potatoes. Life Sciences and Space Research XXV (3) 14(11):243-250.

Separate controlled environment studies were conducted to determine the interaction of CO2 with
irradiance and interaction of CO2 with temperature on growth of three potato cultivars. In the first
study, an elevated CO2 concentration of 1000 mu mol mol(-1) and an ambient CO2 of 350 mu mol
mol(-1) were maintained at the photosynthetic photon fluxes (PPF) of 17 and 34 mol m(-2) d(-1) with
12 h photoperiod, and at the PPF of 34 and 68 mol m(-2) d(-1) with 24 h photoperiod (400 and 800
mu mol m(-2) s(-1) PPF at each photoperiod). Tuber and total dry weights of 90-day old potatoes
were significantly increased with CO2 enrichment, but the CO2 stimulation was less with higher PPF
and longer photoperiod. Shoot dry weight was affected more by photoperiod than by PPF and CO2
concentrations. The elevated CO2 concentration increased leaf CO2 assimilation rates and decreased
stomatal conductance with 12 h photoperiod, but had only a marginal effect with 24 h photoperiod.
In the second study, four CO2 concentrations of 500, 1000, 1500 and 2000 mu mol mol(-1) were
combined with two air temperature regimes of 16 and 20 degrees C under a 12 h photoperiod. At
harvest, 35 days after transplanting, tuber and total dry weights of potatoes reached a maximum with
1000 mu mol mol(-1) CO2 at 16 degrees C, but continued to increase up to 2000 mu mol mol(-1)
CO2 at 20 degrees C. Plant growth was greater at 20 degrees C than at 16 degrees C under all CO2
concentrations. At 16 degrees C specific leaf weight increased substantially with increasing CO2
concentrations as compared to 500 mu mol mol(-1) CO2, but increased only slightly at 20 degrees
C. This suggests a carbohydrate build-up in the leaves at 16 degrees C temperature that reduces plant
response to increased CO2 concentrations. The data in the two studies indicate that a PPF of 34 mol
m(-2) d(-1), 20 degrees C temperature, and 1000-2000 mu mol mol(-1) CO2 produces optimal tuber
yield in potatoes.

KEYWORDS: 24-H, CO2- ENRICHMENT, GROWTH, LIFE SUPPORT SYSTEMS,
PHOTOPERIODS, PHOTOSYNTHESIS, PLANTS, RESPONSES, SOLANUM-TUBEROSUM,
SPACE


     318  
Caporn, S.J.M., A.L. Brooks, M.C. Press, and J.A. Lee. 1999. Effects of long-term exposure to
elevated CO2 and increased nutrient supply on bracken (Pteridium aquilinum). Functional Ecology
13:107-115.

1. Bracken (Pteridium aquilinum) is an important fern with a global distribution. Little is known of
the response of this species to elevated CO2. We investigated the effects of high CO2 (570 compared
with 370 mu mol mol(-1)) with and without an increased nutrient supply (a combined N, P, K
application) on the growth and physiology of bracken, growing in containers in controlled-
environment glasshouses, over two full growing seasons. Results of growth and physiology
determinations are reported for the second season. 2. Elevated CO2 had little impact on the growth
or allocation of dry mass in bracken. No significant changes were detected in dry mass of the total
plant or any of the organs: rhizomes, roots and fronds. In contrast to the small effects of high CO2
the high nutrient treatment caused a three-fold stimulation of total plant dry mass and an increase in
the allocation of dry mass to above ground when compared with low nutrient controls. 3. Net
photosynthetic rates in saturating light were increased by both high CO2 and nutrient treatments,
particularly in spring months (May and June). Growth in elevated CO2 did not cause a down-
regulation in light-saturated rates of photosynthesis. The increased carbon gain in the high CO2
treatments was accompanied, in the low-nutrient plants, by higher concentrations of carbohydrates.
However, in high-nutrient plants the CO2 treatment did not cause an accumulation of carbohydrates.
The absence of a growth response to elevated CO2 in bracken despite significant increases in
photosynthesis requires further investigation.

KEYWORDS: ENGLAND, GROWTH, MANAGEMENT, NITROGEN, PHOTOSYNTHESIS


     319  
Caporn, S.J.M., D.W. Hand, T.A. Mansfield, and A.R. Wellburn. 1994. Canopy photosynthesis
of co2-enriched lettuce (lactuca-sativa L) - response to short-term changes in co2, temperature and
oxides of nitrogen. New Phytologist 126(1):45-52.

The canopy net photosynthesis (P-n) of lettuce (Lactuca sativa L. cv. 'Ambassador') was analyzed
under controlled conditions simulating the winter glasshouse atmosphere. Prior to measurements the
plants were grown in CO2- enriched air of 1000 mu mol mol(-1), at a photosynthetic photon flux
density (PPFD) of 280 mu mol m(2) s(-1) (400-700 nm) and a day/night air temperature of 16/13
degrees C. Short-term changes in CO2 concentration significantly changed the initial gradient of the
photosynthetic response to incident PPFD. Maximum photosynthetic efficiency of the crop increased
from 0.041 mol CO2 mol photons(-1) (equivalent to 8.2 mu g CO2 J(-1) and 9.4% on an energy
basis) at 350 mu mol mol(-1) to 0.055 mol CO2 photons(-1) (10.9 mu g CO2 J(-1) and 12.7% on an
energy basis) at 1000 mu mol mol(-1). Transfer from low to high CO2 also lowered the light
compensation point, but did not affect dark respiration. The large response of P-n to transient
changes in CO2 indicated that the lettuce canopy did not acclimate to growth in 1000 mu mol CO2
mol(-1), in contrast with the effect of growth in high CO2 on P-n in single mature leaves reported
earlier. A reduction in air temperature from 16 to 6 degrees C at a concentration of 1000 mu mol
CO2 mol(-1) halved the rate of dark respiration and reduced the light compensation point, but had
no direct effect on the maximum efficiency with which the crop utilized light. Subsequently, at low
light (below 200 mu mol m(-2) s(-1)) P-n was greater at 6 than 16 degrees C. Between a PPFD of
250 and 300 mu mol m(-2) s(-1) canopy P-n was similar at all temperatures. Addition of 2.0 mu mol
mol(-1) nitric oxide to an atmosphere of 1000 mu mol CO2 mol(-1) caused a rapid and reversible
reduction of canopy P-n which was greater at the lowest temperatures. The average inhibition was
6.6% at 16 degrees C and 28.8% at 6 degrees C; this was not explained by differences in the rate of
pollutant uptake, which was less in the cooler conditions. The results are discussed in relation to
development of optimal growing conditions for production of glasshouse lettuce at low light and low
temperature during winter in the UK.

KEYWORDS: CONTROLLED-ENVIRONMENT CHAMBER, DIOXIDE, ENRICHMENT,
GROWTH, INHIBITION, INTEGRATED ANALYSIS, LEAF PHOTOSYNTHESIS, LIGHT
INTERCEPTION, PLANTS, WINTER LETTUCE


     320  
Caporn, S.J.M., T.A. Mansfield, and D.W. Hand. 1991. Low temperature-enhanced inhibition of
photosynthesis by oxides of nitrogen in lettuce (Lactuca sativa L). New Phytologist 118(2):309-313.

The response of photosynthetic gas exchange to oxides of nitrogen (NO(x)) was studied in leaves of
lettuce (Lactuca sativa L.) at different temperatures. Exposure to high concentrations (e.g. 1.3-mu-
mol NO(x) mol-1), similar to those often found in commercial glasshouses, caused a rapid inhibition
of the net assimilation of CO2. This appeared to be by a direct effect on photosynthesis rather than
by a change in the stomatal conductance. In ambient CO2 (345-mu-mol mol-1), the percentage
inhibition at 10 and 5-degrees-C was approximately 3 x and 5 x, respectively, that measured at 20-
degrees-C. This effect of temperature also occurred when measured in CO2 enriched air (1050-mu-
mol mol-1), which would normally accompany NO(x) in a glasshouse. The extent of photosynthetic
inhibition caused by NO(x) was, however, always less in high than in low CO2. The results suggest
that when burning fuel to raise the CO2 concentration and heat the glasshouse air, growers should
avoid generating high concentrations of NO(x) in conditions of low temperature.

KEYWORDS: CO2- ENRICHMENT, GROWTH, NO2, PLANTS, SO2, SULFUR-DIOXIDE,
TOMATO


     321  
Cardon, Z.G. 1996. Influence of rhizodeposition under elevated CO2 on plant nutrition and soil
organic matter. Plant and Soil 187(2):277-288.

Atmospheric CO2 concentrations can influence ecosystem carbon storage through net primary
production (NPP), soil carbon storage, or both. In assessing the potential for carbon storage in
terrestrial ecosystems under elevated CO2, both NPP and processing of soil organic matter (SOM),
as well as the multiple links between them, must be examined. Within this context, both the quantity
and quality of carbon flux from roots to soil are important, since roots produce specialized
compounds that enhance nutrient acquisition (affecting NPP), and since the flux of organic
compounds from roots to soil fuels soil microbial activity (affecting processing of SOM). From the
perspective of root physiology, a technique is described which uses genetically engineered bacteria
to detect the distribution and amount of flux of particular compounds from single roots to non-sterile
soils. Other experiments from several labs are noted which explore effects of elevated CO2 on root
acid phosphatase, phosphomonoesterase, and citrate production, all associated with phosphorus
nutrition. From a soil perspective, effects of elevated CO2 on the processing of SOM developed
under a C4 grassland but planted with C3 California grassland species were examined under low
(unamended) and high (amended with 20 g m(-2) NPK) nutrients; measurements of soil atmosphere
delta(13)C combined with soil respiration rates show that during vegetative growth in February,
elevated CO2 decreased respiration of carbon from C4 SOM in high nutrient soils but not in
unamended soils. This emphasis on the impacts of carbon loss from roots on both NPP and SOM
processing will be essential to understanding terrestrial ecosystem carbon storage under changing
atmospheric CO2 concentrations.

KEYWORDS: ATMOSPHERIC CARBON-DIOXIDE, DECOMPOSITION, ECOSYSTEMS,
ENRICHMENT, GROWTH, NITROGEN, RESPONSES, RHIZOSPHERE, ROOTS, TALLGRASS
PRAIRIE


     322  
Cardon, Z.G., J.A. Berry, and I.E. Woodrow. 1995. Fluctuating [CO2] drives species-specific
changes in water use efficiency. Journal of Biogeography 22(2-3):203-208.

We have investigated the effects of fluctuating carbon dioxide (CO2) concentration on water use
efficiency of Zea mays L. and Phaseolus vulgaris L. We found that species-specific kinetics of
stomatal movements combine with photosynthetic characteristics to influence shea-term water use
efficiency strongly under fluctuating environmental conditions. Specifically, under oscillating [CO2],
average transpiration in Z. mays was driven higher than that observed at steady-state at the median
CO2 concentration, while average photosynthesis remained fairly constant. Consequently, water use
efficiency was lower during the fluctuations in [CO2] than it was at the steady, median [CO2]. Under
similar oscillations in [CO2], stomatal conductance and transpiration of P. vulgaris were driven lower
than observed at steady-state at the median [CO2]. A concomitant slight restriction of photosynthesis
balanced this decrease in transpiration, and in this case water use efficiency under fluctuating [CO2]
remained practically constant in P. vulgaris. The frequency of oscillations in [CO2] interacted with
asymmetries in stomatal opening and closing kinetics in both Z. mays and P. vulgaris to determine
the extent to which average transpiration (and water use efficiency in Z. mays) departed during
fluctuations from the steady-state condition at the median CO2 level.

KEYWORDS: LIGHT, RESPONSES


     323  
Cardon, Z.G., and R.B. Jckson. 1995. Root acid-phosphatase-activity in bromus-hordeaceus and
avena- barbata remains unchanged under elevated [co2]. Plant Physiology 108(2):148.



     324  
Carey, E.V., R.M. Callaway, and E.H. DeLucia. 1997. Stem respiration of ponderosa pines grown
in contrasting climates: Implications for global climate change. Oecologia 111(1):19-25.

We examined the effects of climate and allocation patterns on stem respiration in ponderosa pine
(Pinus ponderosa) growing on identical substrate in the cool, moist Sierra Nevada mountains and the
warm, dry, Great Basin Desert. These environments are representative of current climatic conditions
and those predicted to accompany a doubling of atmospheric CO2, respectively, throughout the range
of many western north American conifers. A previous study found that trees growing in the desert
allocate proportionally more biomass to sapwood and less to leaf area than montane trees. We tested
the hypothesis that respiration rates of sapwood are lower in desert trees than in montane trees due
to reduced stem maintenance respiration (physiological acclimation) or reduced construction cost of
stem tissue (structural acclimation). Maintenance respiration per unit sapwood Volume at 15 degrees
C did not differ between populations (desert: 6.39 +/- 1.14 SE mu mol m(- 3) s(-1), montane: 6.54
+/- 1.13 SE mu mol m(-3) s(-1), P = 0.71) and declined with increasing stem diameter (P = 0.001).
The temperature coefficient of respiration (Q(10)) varied seasonally within both environments (P =
0.05). Construction cost of stem sapwood was the same in both environments (desert: 1.46 +/- 0.009
SE g glucose g(-1) sapwood, montane: 1.48 +/- 0.009 SE glucose g(-1) sapwood, P = 0.14). Annual
construction respiration calculated from construction cost, percent carbon and relative growth rate
was greater in montane populations due to higher growth rates. These data provide no evidence of
respiratory acclimation by desert trees. Estimated yearly stem maintenance respiration was greater
in large desert trees than in large montane trees because of higher temperatures in the desert and
because of increased allocation of biomass to sapwood. By analogy, these data suggest that under
predicted increases in temperature and aridity, potential increases in aboveground carbon gain due
to enhanced photosynthetic rates may be partially offset by increases in maintenance respiration in
large trees growing in CO2-enriched atmospheres.

KEYWORDS: ABOVEGROUND PARTS, ACCLIMATION, ALLOCATION, CARBON, CO2,
HINOKI FOREST TREE, MAINTENANCE RESPIRATION, PINUS-TAEDA, SCOTS PINE,
TEMPERATURE


     325  
Carey, E.V., E.H. DeLucia, and J.T. Ball. 1996. Stem maintenance and construction respiration
in Pinus ponderosa grown in different concentrations of atmospheric CO2. Tree Physiology 16(1-
2):125-130.

To determine whether long-term growth in enriched CO2 atmospheres changes the woody tissue
respiration component of aboveground carbon budgets, we measured woody tissue respiration of
stems of 3-year-old ponderosa pine (Pinus ponderosa Laws.) grown in ambient (350 ppm) or twice
ambient (700 ppm) atmospheric CO2 concentrations in open-top field chambers located in Placerville,
CA. Total respiration rate was measured by gas exchange, and construction respiration was calculated
from the construction cost, percent carbon of stem samples and relative growth rate. Maintenance
respiration was determined as the difference between total and construction respiration. The Q(10)
of respiration was greater in stems grown in elevated CO2 than in stems grown in ambient CO2 (2.20
versus 1.67). As a result, mean daily respiration per unit volume of wood modeled for the month of
September was greater in trees growing in elevated CO2 than in ambient CO2 (46.75 versus 40.45
mol m(-3) day(-1)). These effects of atmospheric CO? concentration were not the result of differences
in relative growth rate. Calorimetric analyses of woody tissue construction cost indicated no
difference between treatments; however, trees in the elevated CO2 treatment showed a 1% lower
carbon concentration than trees in the ambient CO2 treatment. Estimates of construction respiration
did not differ between treatments, confirming that the treatment differences in mean daily respiration
rate were attributable to the maintenance component. Under future predicted atmospheric conditions,
changes in the maintenance respiration of woody tissue may lead to an increase in the respiration
component of whole-plant carbon budgets of ponderosa pine. Our results suggest that potential
increases in the maintenance component of stem respiration should be considered when modeling the
response of forest stand growth to enriched CO2 atmospheres.

KEYWORDS: COST, ELEVATED CARBON-DIOXIDE, ENRICHMENT, FIELD, FOREST TREE,
LEAVES, PLANT RESPIRATION, SEEDLINGS, TEMPERATURE


     326  
Carlsson, A.S., G. Wallin, and A.S. Sandelius. 1996. Species- and age-dependent sensitivity to
ozone in young plants of pea, wheat and spinach: Effects on acyl lipid and pigment content and
metabolism. Physiologia Plantarum 98(2):271-280.

Acyl lipids and pigments were analyzed in young plants of garden pea, spring wheat and spinach
exposed to <5 or 65 nl l(- 1) ozone 12 h per day for 6 days. In one set of experiments, the plants were
exposed to (CO2)-C-14 for 2 h 3 days prior to ozone exposure. The plants responded differently to
the moderately enhanced level of ozone used Spinach was not at all sensitive while in both pea and
wheat, leaves of different ages differed in ozone sensitivity. In pea, ozone sensitivity increased with
leaf age. In the second and third oldest leaves, the amounts of galactolipids per leaf area and the
proportions of 18:3 of the total lipid extract and of phosphatidylglycerol decreased. In the second
oldest leaf, ozone also caused a decreased proportion of 18:3 of monogalactosyldiacylglycerol. In the
fourth oldest leaf, Lipid composition and galactolipid unsaturation was unaffected, but ozone caused
decreased leaf expansion resulting in increased acyl lipid content per leaf area. In both the first and
second leaves of wheat, ozone fumigation caused a marked decrease in the content of
monogalactosyldiacylglycerol and in the first leaf, the contents of phosphatidylcholine and
phosphatidylethanolamine increased. The proportion of 18:3 in phosphatidylcholine was larger in
ozone-fumigated than in control plants, while the reverse applied for phosphatidylglycerol. In the
oldest sampled leaves of pea and wheat, ozone caused an increase in the radioactivity associated with
beta-carotene, indicating increased turnover. Thus, while spinach was unaffected, in both pea and
wheat ozone caused a decrease in the proportion of chloroplast membrane lipids to non-chloroplast
membrane lipids in older leaves while younger leaves were less sensitive.

KEYWORDS: LEAVES, MODERATELY ENHANCED LEVELS, PISUM-SATIVUM, POLAR
LIPIDS, PROTECTION, TRITICUM-AESTIVUM


     327  
Carlsson, B.A., and T.V. Callaghan. 1994. Impact of climate-change factors on the clonal sedge
carer bigelowii - implications for population-growth and vegetative spread. Ecography 17(4):321-
330.

Hypothesized life-cycle responses to climate change for the arctic, clonal perennial Carer bigelowii
are constructed using a range of earlier observations and experiments together with new information
from monitoring and an environmental perturbation study. These data suggest, that under current
climate change scenarios, increases in CO2, temperature and nutrient availability would promote
growth in a qualitatively similar way. The evidence suggests that both tiller size and daughter tiller
production will increase, and be shifted towards production of phalanx tillers which have a greater
propensity for flowering. Furthermore, age at tillering as well as tiller life span may decrease, whereas
survival of younger age classes might be higher. Mathematical models using experimental data
incorporating these hypotheses were used to a) integrate the various responses and to calculate the
order of magnitude of changes in population growth rate (lambda), and b) to explore the implications
of responses in individual demographic parameters for population growth rate. The models suggest
that population growth rate following climate change might increase significantly, but not
unrealistically so, with the younger, larger, guerilla tillers being the most important tiller categories
contributing to lambda. The rate of vegetative spread is calculated to more than double, while cyclical
trends in flowering and population growth are predicted to decrease substantially.

KEYWORDS: CARBON DIOXIDE, DWARF-SHRUB, DYNAMICS, ELEVATED CO2,
ENVIRONMENTAL-CHANGE, ERIOPHORUM VAGINATUM, PLANTS, RESPONSES, SIZE,
TUSSOCK TUNDRA


     328  
Carmi, A. 1993. Effects of shading and co2 enrichment on photosynthesis and yield of winter grown
tomatoes in subtropical regions. Photosynthetica 28(3):455-463.

The effects of exposing winter-grown tomato (Lycopersicon esculentum L.) to various sunlight
irradiances and CO2 concentrations, on dark respiration (R(D)), night respiration (R(N)), net
photosynthetic-rate (P(N)), dry matter production (DMP), yield earliness and yield amount were
studied. Plants were grown in greenhouses under controlled temperatures and exposed to: full (FS)
or half (HS) sunlight irradiance in combinafion with atmospheric (A) or enriched (E) concentrations
of 300-330 or 1400-1500 g(CO2) m-3, respectively. The P(N) of intact leaves at noontime reached
10.7, 15.2, 5.9 and 9.6 mumol(CO2) m-2 s-1 in treatments of FSA, FSE, HSA and HSE, respectively.
The irradiances on the upper leaf surface during the P(N) measurements ranged between 160-190 and
450-550 mumol m-2 s-1 in the HS and FS treatments, respectively. R(D) of leaves which were kept
in darkness following the P(N) measurement arrived at efflux of 2.6, 2.5, 1.4 and 1.4 mumol(CO2)
m-2 s-1 While their R(N) (between 20:00 and 24:00) reached values of 0.9, 1.3, 0.8 and 0.8
mumol(CO2) m-2 s-1 in treatments of FSA, FSE, HSA and HSE, respectively. Elevating the CO2
concentration from 300 to 1500 g m-3 increased P(N) by 16, 28, 30 and 46% under an irradiance of
160 mumol m-2 s-1, and 19, 34, 59 and 44% under irradiance of 320 mumol m-2 s-1 in the FSA,
FSE, HSA and HSE treatments, respectively. Increasing the measurement irradiance from 160 to 320
mumol m-2 s-1 enhanced P(N) by 69, 78, 23 and 49% in an atmosphere of 300 g m-3 CO2, and by
73, 84, 49 and 47% in an atmosphere of 1500 g m-3 CO2, in the FSA, FSE, HSA and HSE
treatments, respectively. DMP was strongly influenced by the different environmental conditions and
the total dry matter accumulation in the shoot per plant during 145 d reached 580, 347, 398 and 235
g in the FSA, FSE, HSA and 14SE treatments, respectively. CO2 enrichment promoted early yield
under both full and partial sunlight irradiance. The HSE treatment led to earlier yield harvesting than
the FSA and HSA treatments. The yield of the seven first trusses reached 6.8, 4.6, 5.7 and 3.2 kg per
plant in the FSA, FSE, HSA and HSE treatments, respectively. Some increase in fruit fresh matter
and diameter of fruits was detected in the CO2-enriched treatments as compared to the non-enriched
ones. Thus the combination of moderate shading and CO2 enrichment might provide a more
productive option for winter-grown tomatoes in regions of subtropical climate, even in the winter,
than the conventional management of aerated greenhouses without CO2 enrichment which are
exposed to full sunlight.



     329  
Carpenter, S.R., S.G. Fisher, N.B. Grimm, and J.F. Kitchell. 1992. Global change and fresh-
water ecosystems. Annual Review of Ecology and Systematics 23:119-139.

KEYWORDS: AQUATIC SYSTEMS, CADDISFLY POPULATION, CO2-INDUCED CLIMATIC-
CHANGE, DESERT STREAM, GRADIENT HEADWATER STREAMS, GREAT- LAKES BASIN,
ORGANIC-CARBON, POTENTIAL CHANGES, THERMAL HABITAT, WATER-RESOURCES


     330  
Carter, E.B., M.K. Theodorou, and P. Morris. 1997. Responses of Lotus corniculatus to
environmental change .1. Effects of elevated CO2, temperature and drought on growth and plant
development. New Phytologist 136(2):245-253.

Five clonal plants of three genotypes of Lotus corniculatus were grown in each of eight controlled
environments under combinations of two temperature regimes (18/10 degrees C and 25/15 degrees
C), two CO2 concentrations (ambient and 700 ppmv) and two water applications (ad libitum or 60%
droughted). Plants were harvested at full flower and measurements made of plant growth and
development. Of the three environmental variables studied, higher growth temperatures resulted in
the largest number of significant changes to the measured variables. Reproductive capacity, growth
rate, shoot biomass, water use efficiency and chlorophyll content were all enhanced by raising the
growth temperature from 18 to 25 degrees C. Doubling the CO2 concentration enhanced the growth
rate, shoot biomass and water use efficiency and ameliorated some of the effects of drought, including
reproductive capacity, and biomass production, but reduced flowering lime, specific leaf area, and
chlorophyll content of both droughted and undroughted plants. Drought alone reduced reproductive
capacity, growth rate and above ground biomass but significantly increased root biomass in all
environments. The agronomic effects resulting from a combined increase in growth temperature,
doubled CO2 concentration and mild drought in this experiment were a shorter vegetative period and
an increase in biomass, but a fall in reproductive capacity.

KEYWORDS: CARBON DIOXIDE, EFFICIENCY, ENRICHMENT, INCREASING CO2, N2
FIXATION, PHOTOSYNTHESIS, RESPIRATION, WATER-STRESS, WHITE CLOVER, YIELD


     331  
Carter, E.B., M.K. Theodorou, and P. Morris. 1999. Responses of Lotus corniculatus to
environmental change. 2. Effect of elevated CO2, temperature and drought on tissue digestion in
relation to condensed tannin and carbohydrate accumulation. Journal of the Science of Food and
Agriculture 79(11):1431-1440.

Clonal plants of three genotypes of Lotus corniculatus (cv Lee) were grown in eight controlled
environments under combinations of two temperature regimes, two CO2 concentrations and two
watering regimes. Condensed tannins (proanthocyanidins), in- vitro digestibility, initial rates of gas
evolution las an indicator of the initial rates of fermentation of the substrate), volatile fatty acid
evolution, and non-structural carbohydrate (NSC) levels were determined in leaves, stems and roots
at full flowering. Under control conditions (average midsummer conditions in the United Kingdom)
the total condensed tannin content of leaves varied six-fold between genotypes but condensed tannin
contents in stems and roots were similar. Condensed tannin levels were significantly increased in
leaves and stems of all three genotypes by doubling the CO2 concentration while raising the
temperature towards the optimum for growth significantly reduced condensed tannin levels. Drought
stress significantly reduced condensed tannin levels in leaves and, particularly, in roots. Nutritive
value was inversely related to condensed tannin levels in leaves and a negative relationship was
observed between condensed tannin concentrations of more than 25-30 g kg(-1) dry matter and the
initial rates of gas evolution when subjected to in-vitro fermentation with rumen micro-organisms.
In leaves, digestibility was significantly increased by drought and by increasing temperature but
reduced by high CO2. In stems, digestibility was significantly increased by drought, but not
significantly affected by increasing temperature, or by high CO2 alone. In roots, digestibility was
significantly increased by drought, and decreased by increasing temperature or CO2. Increasing the
growth temperature towards optimum growth reduced the content of NSC in all tissues with the
greatest changes occurring in root tissue. Doubling the CO2 concentration increased NSC levels in
leaves and stems with starch content more than doubled under high CO2 while, in roots, increased
levels were only observed in combination with drought stress. There was a linear correlation between
condensed tannin concentration and total NSC that was positive for leaves, neutral for stems and
negative for roots. The relationship between carbohydrate levels and rates of gas production was
negative for leaves and positive for stem and roots. (C) 1999 Society of Chemical Industry.

KEYWORDS: DIGESTIBILITY, GAS-PRODUCTION, GROWTH, ISOSYNTHETIC STRAINS,
METABOLISM, PEDUNCULATUS, PROANTHOCYANIDINS, PROTEIN, RUMEN, SHEEP


     332  
Carter, G.A., J. Rebbeck, and K.E. Percy. 1995. Leaf optical-properties in liriodendron-tulipifera
and pinus- strobus as influenced by increased atmospheric ozone and carbon-dioxide. Canadian
Journal of Forest Research-Revue Canadienne De Recherche Forestiere 25(3):407-412.

Seedlings of Liriodendron tulipifera L. and Pinus strobus L. were grown in open-top chambers in the
field to determine leaf optical responses to increased ozone (O-3) or O-3 and carbon dioxide (CO2).
In both species, seedlings were exposed to charcoal-filtered air, air with 1.3 times ambient O-3
concentrations (1.3X), or air with 1.3 times ambient O-3 and 700 mu L . L(-1) CO2 (1.3X + CO2).
Exposure to 1.3X increased reflectance in the 633-697 nm range in L. tulipifera. Also, 1.3X
decreased transmittance within the 400-420 nm range, increased transmittance at 686-691 nm, and
decreased absorptance at 655-695 nm. With 700 mu L . L(-1) CO2, O-3 did not affect reflectance
in L. tulipifera, but decreased transmittance and increased absorptance within the 400-421 nm range
and increased transmittance and decreased absorptance in the 694-697 nm range. Under 1.3X,
reflectance in P. strobus was not affected. However, 1.3X + CO2 increased pine reflectance in the
538-647, 650, and 691-716 nm ranges. Transmittances and absorptances were not determined for P.
strobus. Reflectance in both species, and transmittance and absorptance in L. tulipifera, were most
sensitive to O-3 near 695 nm. Reflectance at 695 nm, but particularly the ratio of reflectance at 695
nm to reflectance at 760 nm, was related closely to ozone-induced decreases in leaf chlorophyll
contents, particularly chlorophyll a (r(2) = 0.82).

KEYWORDS: CHLOROPHYLL CONTENT, ELEVATED CO2, INJURY, LEAVES, NITROGEN,
RED EDGE, RESPONSES, SLASH PINE, SPECTRAL REFLECTANCE


     333  
Case, A.L., P.S. Curtis, and A.A. Snow. 1998. Heritable variation in stomatal responses to elevated
CO2 in wild radish, Raphanus raphanistrum (Brassicaceae). American Journal of Botany 85(2):253-
258.

Rising atmospheric carbon dioxide may affect plant populations in the short term through effects on
photosynthesis and carbon allocation, and over the long term as an agent of natural selection. To test
for heritable effects of elevated CO2 on stomatal responses and plant fecundity in Raphanus
raphanistrum, we grew plants from 12 paternal families in outdoor open-top chambers at ambient (35
Pa) or elevated (67 Pa) CO2. Contrary to results from a previous study of this species, total flower
and fruit production were marginally lower under elevated CO2. Across families, stomatal index and
guard cell length showed little response to CO2 enrichment, but these characters varied significantly
among paternal families in both the direction and magnitude of their response to changing CO2.
Although these family-by-CO2, interactions suggest that natural selection might affect stomatal
characters when ambient CO2 levels increase, we found no significant correlation between either
character and flower or fruit production. Therefore, our data suggest that while heritable variation
for stomatal index and guard cell length exists in this population, selection due to increasing CO2 is
not likely to act on these traits because they had no detectable effect on lifetime fecundity.

KEYWORDS: ATMOSPHERIC CO2, CARBON DIOXIDE, DENSITY, ENRICHMENT,
EVOLUTION, GAS-EXCHANGE, GROWTH, LEAVES, PERFORMANCE, PLANTS


     334  
Casella, E., and J.F. Soussana. 1997. Long-term effects of CO2 enrichment and temperature
increase on the carbon balance of a temperate grass sward. Journal of Experimental Botany
48(311):1309-1321.

Perennial ryegrass swards were grown in large containers on a soil, at two N fertilizer supplies and
were exposed during two years in highly ventilated plastic tunnels to elevated (700 mu l l(-1) [CO2])
or ambient atmospheric CO2 concentration at outdoor temperature and to a 3 degrees C increase in
air temperature in elevated CO2. The irrigation was adjusted to obtain a soil water deficit during
summer. The daily net C assimilation was increased in elevated CO2 by 29 and 36% at the low and
high N supplies, respectively, Canopies grown in elevated CO2 for 14 to 27 months photosynthetized
significantly less rapidly, in both elevated and normal CO2 concentrations, than their counterparts
developed in ambient CO2, but the magnitude of this effect was small (-8% to -13%). Elevated CO2
resulted in a large increase in the fructan concentration in the pseudostems and laminae (+46% and
+189%, respectively). In elevated CO2, the hexose and sucrose pool increased by 28% in the laminae,
whereas it did not vary significantly in the pseudo-stems, A 3 degrees C temperature increase in
elevated CO2 did not affect significantly the average WSC concentrations in the pseudostems and
laminae, The elevated CO2 effects on the net C assimilation and on the nocturnal shoot respiration
were greater in summer than in spring. On average, a 35% increase in the below-ground respiration
was measured in elevated CO2. At the high N supply, a 3 degrees C increase in air temperature led
to a decline in the below-ground respiration due to a low soil moisture, The below-ground carbon
storage was increased by 32% and 96% in elevated CO2 at the low and high N supplies, respectively,
with no significant increased temperature effect. The role for the below-ground carbon storage of
CO2-induced changes in the root fraction of the grass and of temperature- induced changes in the
moisture content of the soil are discussed.

KEYWORDS: ACCLIMATION, ATMOSPHERE, DIOXIDE CONCENTRATION, ELEVATED CO2,
GROWTH, LOLIUM-PERENNE, NET PHOTOSYNTHESIS, NITROGEN, PLANT-RESPONSES,
SOIL CARBON


     335  
Casella, E., J.F. Soussana, and P. Loiseau. 1996. Long-term effects of CO2 enrichment and
temperature increase on a temperate grass sward .1. Productivity and water use. Plant and Soil
182(1):83-99.

Perennial ryegrass swards were grown in large containers on a soil, at two N fertilizer supplies, and
were exposed over two years in highly ventilated plastic tunnels to elevated (700 mu L L(-1) [CO2])
or ambient atmospheric CO2 concentration at outdoor temperature and to a 3 degrees C increase in
air temperature in elevated CO2. These swards were either fully irrigated (kept at field capacity) in
each climatic condition (W+), or received the same amount of water in the three climate treatments
(W-). In the latter case, the irrigation was adjusted to obtain a soil water deficit during summer and
drainage in winter. Using a lysimeter approach, the evapotranspiration, the soil water balance, the
productivity (dry-matter yield) and the water use efficiency of the grass swards were measured.
During both years, elevated CO2 increased the annual above-ground drymatter yield of the W-swards,
by 19% at N- and by 14% at N+. Elevated CO2 modified yield to a variable extent during the
growing season: a small, and sometime not significant effect (+6%, on average) was obtained in
spring and in autumn, while the summer growth response was stronger (+48%, on average). In
elevated CO2, the temperature increase effect on the annual above-ground dry-matter yield was not
significant, due to a gain in dry-matter yield in spring and in autumn which was compensated for by
a lower summer productivity. Elevated CO2 slightly reduced the evapotranspiration during the
growing season and increased drainage by 9% during winter. A supplemental 3 degrees C in elevated
CO2 reduced the drainage by 29-34%, whereas the evapotranspiration was increased by 8 and 63%
during the growing season and in winter, respectively. During the growing season, the soil moisture
content at W- and at the high N supply declined gradually in the control climate, down to 20- 30%
of the water holding capacity at the last cut (September) before rewatering. This decline was partly
alleviated under elevated CO2 in 1993, but not in 1994, and was enhanced at +3 degrees C in
elevated CO2. The water use efficiency of the grass sward increased in elevated CO2, on average,
by 17 to 30% with no significant interaction with N supply or with the soil water deficit. The
temperature increase effect on the annual mean of the water use efficiency was not significant. Highly
significant multiple regression models show that elevated CO2 effect on the dry-matter yield increased
with air temperatures above 14.5 degrees C and was promoted by a larger soil moisture in elevated
compared to ambient CO2. The rate of change in relative dry-matter yield at +3 degrees C in elevated
CO2 became negative for air temperatures above 18.5 degrees C and was reduced by a lower soil
moisture at the increased air temperature. Therefore, the altered climatic conditions acted both
directly on the productivity and on the water use of the grass swards and, indirectly, through changes
in the soil moisture content.

KEYWORDS: ATMOSPHERIC CARBON-DIOXIDE, CROP YIELD, EFFICIENCY, ELEVATED
CO2, GROWTH, LEAF-AREA, LIMITED CONDITIONS, LOLIUM-PERENNE, PERENNIAL
RYEGRASS, PHOTOSYNTHESIS


     336  
Cater, M., P. Simoncic, and F. Batic. 1999. Pre-dawn water potential and nutritional status of
pedunculate oak (Quercus robur L.) in the north-east of Slovenia. Phyton-Annales Rei Botanicae
39(4):13-21.

In the 1997 growth period monthly measurements of pre-dawn water potential, electrical resistance
of the cambial zone, groundwater level and quality together with annual dynamics of macronutrive
elements in leaves and heavy metals (Zn, Ph, Cd) were performed. Two plots having different
groundwater tables and crown defoliation were studied in the pedunculate oak forest complex
(Querco Roboris-Carpinetum M. Wraber) in the north-east of Slovenia. Results showed lower (more
negative) values of pre-dawn water potential and higher values of cambial electrical resistance on the
plot with greater crown defoliation, which also had a lower groundwater table. Groundwater seems
to be the key factor in the process of oak decline.

KEYWORDS: DECLINE, DROUGHT, ELEVATED CO2, EMBOLISM, FIR, GROWTH,
PHOTOSYNTHESIS, SEEDLINGS, STANDS, STRESS


     337  
Catovsky, S., and F.A. Bazzaz. 1999. Elevated CO2 influences the responses of two birch species
to soil moisture: implications for forest community structure. Global Change Biology 5(5):507-518.

Increased levels of atmospheric CO2 may alter the structure and composition of plant communities
by affecting how species respond to their physical and biological environment. We investigated how
elevated CO2 influenced the response of paper birch (Betula papyrifera Marsh.) and yellow birch
(Betula alleghaniensis Britt.) seedlings to variation in soil moisture. Seedlings were grown for four
months on a soil moisture gradient, individually and in mixed species stands, in controlled
environment facilities at ambient (375 mu L L-1) and elevated (700 mu L L-1) atmospheric CO2. For
both individually and competitively grown paper birch seedlings, there was a greater CO2 growth
enhancement for seedlings watered less frequently than for well-watered seedlings. This differential
change in CO2 responsiveness across the moisture gradient reduced the difference in seedling growth
between high and low water levels and effectively broadened the regeneration niche of paper birch.
In contrast, for yellow birch seedlings, elevated CO2 only produced a significant growth enhancement
at the wet end of the soil moisture gradient, and increased the size difference between seedlings at
the two ends of the gradient. Gas exchange measurements showed that paper birch seedlings were
more sensitive than yellow birch seedlings to declines in soil moisture, and that elevated CO2 reduced
this sensitivity. Additionally, elevated CO2 improved survival of yellow birch seedlings growing in
competition with paper birch in dry stands. Thus, elevated CO2 may influence regeneration patterns
of paper birch and yellow birch on sites of differing soil moisture. In the future, as atmospheric CO2
levels rise, growth of paper birch seedlings and survival of yellow birch seedlings may be enhanced
on xeric sites, while yellow birch may show improved growth on mesic sites.

KEYWORDS: ATMOSPHERIC CO2, CARBON DIOXIDE, CONTRASTING SHADE TOLERANCE,
COOCCURRING BIRCH, GAS-EXCHANGE, LIQUIDAMBAR- STYRACIFLUA, LOBLOLLY-
PINE, PINUS-TAEDA SEEDLINGS, TERRESTRIAL ECOSYSTEMS, WATER-STRESS


     338  
Catsky, J., J. Pospisilova, J. Solarova, H. Synkova, and N. Wilhelmova. 1995. Limitations on
photosynthesis under environment-simulating culture in-vitro. Biologia Plantarum 37(1):35-48.

Limitations on photosynthesis, characterized by leaf CO2 exchange, chlorophyll fluorescence, and
thylakoid structure, were studied under environmental conditions simulating culture in vitro. These
were simulated by growing Phaseolus vulgaris plants in nutrient solution under high relative humidity
of air (> 90%), and CO2 concentrations (c(a)) that decreased with the development of photosynthetic
activities during plant ontogeny (1200 to 300 mg m-3). The ontogeny of such model plants was more
rapid, primary leaves reached photosynthetic maturity 2 to 3 d earlier and their life span was 7 to 14
d shorter than in control plants. Their photosynthetic activity in situ was limited, after reaching
''photosynthetic maturity'', similarly to plants grown in vitro. When measured under optimal
conditions, however, 50 to 70% higher net photosynthetic rate (P(N)) were found in leaves of
different ages as compared with plants grown under c(a) of 700 mg m-3 and a lower air humidity (30
- 35%). This increase in P(N) was associated with a high conductance for CO2 transfer by adaxial
and abaxial epidermes. In model plants, the dark respiration rate (R(D)) was almost twice that in the
control, while the photorespiration rates were similar to controls; CO2 compensation concentration
was about 50% of that in controls. The ratios P(N)/R(D) were similar in control and in model plants.
Chlorophyll a+b content in leaves of the model plants was lower than that in the control plants. Grana
extent increased with plant age in the model plants while it decreased in the control ones. In both the
stomal and granal membranes of the chloroplasts in model plants, a marked accumulation of
carotenoids occurred independent of age. The ratio of variable to maximal fluorescence, F(v)/F(m),
did not differ in the model and the control plants. In the control plants, photochemical quenching (qp)
slightly increased with plant age and was not affected by CO2 concentration present during
measurement. In the model plants, qp increased with elevated CO2 concentration in young plants and
decreased in saturating CO2 concentrations in older plants. Nonphotochemical quenching (q(NP))
was lower in the model plants and increased under CO2 saturating conditions. Vitality index, Rfd,
was markedly lower in the model plants than in the control ones and a decline was found in saturating
CO2 concentration.



     339  
Caulfield, F., and J.A. Bunce. 1994. Elevated atmospheric carbon-dioxide concentration affects
interactions between spodoptera-exigua (lepidoptera, noctuidae) larvae and 2 host-plant species
outdoors. Environmental Entomology 23(4):999-1005.

Beet armyworm, Spodoptera exigua (Hubner), larvae were placed on sugarbeet (Beta vulgaris L.)
and pigweed (Amaranthus hybridus L.) plants in outdoor chambers in which the plants were growing
at either the ambient (almost-equal-to 350 mul liter-1) or ambient plus 350 mul liter-1 (almost-equal-
to 700 mul liter-1) carbon dioxide concentration. A series of experiments was performed to determine
if larvae reduced plant growth differently at the two carbon dioxide concentrations in either species
and if the insect growth or survival differed with carbon dioxide concentration. Leaf nitrogen, water,
starch, and soluble carbohydrate contents were measured to assess carbon dioxide concentration
effects on leaf quality. Insect feeding significantly reduced plant growth in sugarbeet plants at 350 mul
liter-1 but not at 700 mul liter-1 nor in pigweed at either carbon dioxide concentration. Larval
survival was greater on sugarbeet plants at the elevated carbon dioxide concentration. Increased
survival occurred only if the insects were at the elevated carbon dioxide concentration and consumed
leaf material grown at the elevated concentration. Leaf quality was only marginally affected by growth
at elevated carbon dioxide concentration in these experiments. The results indicate that in designing
experiments to predict effects of elevated atmospheric carbon dioxide concentrations on plant- insect
interactions, both plants and insects should be exposed to the experimental carbon dioxide
concentrations, as well as to as realistic environmental conditions as possible.

KEYWORDS: COTTON, ENRICHED CO2 ATMOSPHERES, GROWTH, INSECT HERBIVORE
INTERACTIONS, JUNONIA-COENIA, LEAVES, PERIODS, PHOTOSYNTHESIS, RESPONSES,
STARCH


     340  
Cavender-Bares, J.M., P.B. Voss, and F.A. Bazzaz. 1998. Consequences of incongruency in
diurnally varying resources for seedlings of Rumex crispus (Polygonaceae). American Journal of
Botany 85(9):1216-1223.

The incongruency of diurnally varying resources essential to plants may detrimentally affect plants
early in their development as indicated by reduced water use efficiency and carbon gain. Typical
diurnal patterns of light and CO2 availability in a midsized temperate herbaceous or forest gap were
simulated in specially designed growth chambers. A sinusoidally varying CO2 treatment (400 ppm
minimum, 800 ppm maximum) approximated the diurnal cycle of CO2 at the soil surface, while a
steady-state CO2 treatment (600 ppm) with the same average CO2 concentration provided a control.
Crossed with these two CO2 treatments were two light regimes, one with 3 h of high light (850 mu
mol.m(-2).s(-1)) in the morning (west side of a gap), and the other with 3 h of high light in the
afternoon (east side). All treatments received baseline low light (55 mu mol.m(-2).s(-1)) for 14 h
during the day. Rumex crispus was selected as a model species because of its rosette leaves, which
grow close to the ground where diurnal CO2 variation is greatest. The relative timing of diurnal
variations in light and CO2 significantly affected seedling water use efficiency, carbon gain, and
morphology. Total biomass, photosynthetic rates, daily integrated carbon, water use efficiency, and
leaf area were enhanced by morning exposure to high light. Seedlings that were exposed to peak
values of light and CO2 incongruently, i.e., those plants receiving intense afternoon light with
diurnally varying CO2, were detrimentally affected relative to control plants receiving intense
afternoon light with steady-state CO2. The results of this experiment indicate that the incongruent
availability of required resources-such as light and CO2-can detrimentally affect performance relative
to when resources are congruent. These contrasting resource regimes can occur on the east and west
side of gaps.

KEYWORDS: ATMOSPHERIC CO2, CARBON DIOXIDE, ELEVATED CO2, FOREST, GAS-
EXCHANGE, GROWTH, LIGHT, PLANTS, RESPONSES, WATER RELATIONS


     341  
Cebrian, J. 1999. Patterns in the fate of production in plant communities. The American Naturalist
154(4):449-468.

I examine, through an extensive compilation of published reports, the nature and variability of carbon
flow (i.e., primary production, herbivory, detrital production, decomposition, export, and biomass
and detrital storage) in a range of aquatic and terrestrial plant communities. Communities composed
of more nutritional plants (i.e., higher nutrient concentrations) lose higher percentages of production
to herbivores, channel lower percentages as detritus, experience faster decomposition rates, and, as
a result, store smaller carbon pools. These results suggest plant palatability as a main limiting factor
of consumer metabolical and feeding rates across communities. Hence, across communities, plant
nutritional qualify may be regarded as a descriptor of the importance of herbivore control on plant
biomass ("top-down" control), the rapidity of nutrient and energy recycling, and the magnitude of
carbon storage. These results contribute to an understanding of how much and why the trophic routes
of carbon flow, and their ecological implications, vary across plant communities. They also offer a
basis to predict the effects of widespread enhancement of plant nutritional quality due to large-scale
anthropogenic eutrophication on carbon balances in ecosystems.

KEYWORDS: CARBON BALANCE, ECOSYSTEMS, ELEVATED CO2, FRESH-WATER, GROWTH
RATE, HERBIVORY, MARINE WATERS, NITROGEN, NUTRIENT LIMITATION, ORGANIC-
MATTER


     342  
Centritto, M., and P.G. Jarvis. 1999. Long-term effects of elevated carbon dioxide concentration
and provenance on four clones of Sitka spruce (Picea sitchensis). II. Photosynthetic capacity and
nitrogen use efficiency. Tree Physiology 19(12):807-814.

Four clones of Sitka spruce (Picea sitchensis (Bong.) Carr.) from two provenances, at 53.2 degrees
N (Skidegate a and Skidegate b) and at 41.3 degrees N (North Bend a and North Bend b, were grown
for three growing seasons in ambient (similar to 350 mu mol mol(-1)) and elevated (similar to 700
mu mol mol(- 1)) CO2 concentrations. The clones were grown in stress-free conditions (adequate
nutrition and water) to assess the effect of elevated [CO2] on tree physiology. Growth in elevated
[CO2] significantly increased instantaneous photosynthetic rates of the clonal Sitka spruce saplings
by about 62%. Downward acclimation of photosynthesis (A) was found in all four clones grown in
elevated [CO2]. Rubisco activity and total chlorophyll concentration were also significantly reduced
in elevated [CO2]. Provenance did not influence photosynthetic capacity. Best-fit estimates of J(max)
(maximum rate of electron transport), V-cmax (RuBP-saturated rate of Rubisco) and A(max)
(maximum rate of assimilation) were derived from responses of A to intercellular [CO2] by using the
model of Farquharetal.(1980). At any leaf N concentration, the photosynthetic parameters were
reduced by growth in elevated [CO2]. However, the ratio between J(max) and V-cmax was
unaffected by CO2 growth concentration, indicating a tight coordination in the allocation of N
between thylakoid and soluble proteins. In elevated [CO2] the more southerly clones had a higher
initial N use efficiency (more carbon assimilated per unit of leaf N) than the more northerly clones,
so that they had more N available for those processes or organs that were most limiting to growth
at a particular time. This may explain the initial higher growth stimulation by elevated [CO2] in the
North Bend clones than in the Skidegate clones.

KEYWORDS: ACCLIMATION, ASSIMILATION, ATMOSPHERIC CO2, GAS-EXCHANGE, GENE-
EXPRESSION, LOBLOLLY-PINE TREES, NUTRITION, PLANTS, SEEDLINGS, TEMPERATURE


     343  
Centritto, M., H.S.J. Lee, and P.G. Jarvis. 1999. Increased growth in elevated [CO2]: an early,
short-term response? Global Change Biology 5(6):623-633.

Saplings of four clones of Sitka spruce and cherry were grown for three and two growing seasons,
respectively, in open top chambers at two CO2 concentrations (approximate to 350 and approximate
to 700 mu mol mol(-1)) to determine whether the increase in total biomass brought about by
enhanced [CO2] is a result of a transient or persistent effect in nonlimiting conditions. Classical
growth analysis was applied to both species and mean current relative growth rate of total dry mass
(R-T) and leaf dry mass (R-L), and period relative growth rate of total dry mass (R-T(t)) and leaf dry
mass (R-L(t)) were calculated. Sitka spruce saplings and cherry seedlings showed a positive growth
response to elevated [CO2], and at the end of the experiments both species were approximate to 40%
larger in elevated [CO2] than in ambient [CO2]. As a result, the period mean R-T(t) and R-L(t) were
significantly higher in elevated [CO2]. The differences in plant dry mass at the end of the experiments
were a consequence of the more rapid growth in the early phase of exposure to elevated [CO2]. After
this initial phase mean R-T and R-L were similar or even lower in elevated [CO2] than in ambient
[CO2]. NAR of both species was much higher in elevated [CO2], whereas both LAR, SLA, and LMR
showed the opposite trend. The higher LAR and SLA of plants in ambient [CO2] contributed to a
compensation by which they maintained R- T Similar to that of elevated [CO2] saplings despite lower
NAR and photosynthetic rate. However, when the same size the trees were similar amongst the
[CO2] treatments, indicating that one of the main effect of elevated [CO2] on tree growth is to speed-
up early development in all aspects.

KEYWORDS: ACCLIMATION, AMBIENT, ATMOSPHERIC CO2, BETULA-PENDULA ROTH,
BIOMASS ALLOCATION, CARBON, PHOTOSYNTHESIS, PLANTAGO-MAJOR, PONDEROSA
PINE, RESPIRATION


     344  
Centritto, M., H.S.J. Lee, and P.G. Jarvis. 1999. Interactive effects of elevated [CO2] and drought
on cherry (Prunus avium) seedlings - I. Growth, whole-plant water use efficiency and water loss. New
Phytologist 141(1):129-140.

Seeds of cherry (Prunus avium) were germinated and grown for two growing seasons in ambient
(similar to 350 mu mol mol(-1)) or elevated (ambient + similar to 350 mu mol mol(-1)) CO2 mole
fractions in six open-top chambers. The seedlings were fertilized once a week, following Ingestad
principles in order to supply mineral nutrients at free-access rates. In the first growing season gradual
drought was imposed on rapidly growing cherry seedlings by withholding water for a 6-wk drying
cycle. In the second growing season, the rapid onset of drought was imposed at the height of the
growing season on the seedlings which had already experienced drought in the first growing season.
Elevated [CO2] significantly increased total dry-mass production in both water regimes, but did not
ameliorate the growth response to drought of the cherry seedlings subjected to two sequential drying
cycles. Water loss did not differ in either well watered or droughted seedlings between elevated and
ambient [CO2]; consequently whole-plant water-use efficiency (the ratio of total dry mass produced
to total water consumption) was significantly increased. Similar patterns of carbon allocation between
shoot and root were found in elevated and ambient [CO2] when the seedlings were the same size.
Thus, elevated [CO2] did not improve drought tolerance, but it accelerated ontogenetic development
irrespective of water status.

KEYWORDS: ATMOSPHERIC CARBON-DIOXIDE, DRY-WEIGHT, ENRICHMENT, GAS-
EXCHANGE, LEAF-AREA, NUTRIENT AVAILABILITY, RESPONSES, SITCHENSIS BONG
CARR, STRESS, WHEAT


     345  
Centritto, M., H.S.J. Lee, and P.G. Jarvis. 1999. Long-term effects of elevated carbon dioxide
concentration and provenance on four clones of Sitka spruce (Picea sitchensis). I. Plant growth,
allocation and ontogeny. Tree Physiology 19(12):799-806.

Four clones of Sitka spruce (Picea sitchensis (Bong.) Carr.) from two provenances, at 53.2 degrees
N (Skidegate a and Skidegate b) and at 41.3 degrees N (North Bend a and North Bend b), were
grown near Edinburgh (55.5 degrees N), U.K., for three growing seasons in ambient (similar to 350
mu mol mol(-1)) and elevated (similar to 700 mu mol mol(-1)) CO2 concentrations under conditions
of non-limiting water and nutrient supply. Bud phenology was not affected by elevated [CO2] in the
second growing season, but in the third year, the duration of shoot extension growth in three of the
four clones (North Bend clones and Skidegate a) was significantly shortened, because of the
suppression of lammas growth. Saplings in elevated [CO2] had significantly greater dry masses of all
components than saplings in ambient [CO2]. However, comparison of relative component dry masses
between plants of similar size showed no effect of [CO2] treatment on plant allometric relationships.
This finding, and the observed suppression of lammas growth by high [CO2] during the third growing
season suggests that the main effect of increasing [CO2] is to accelerate sapling development. Clonal
provenance did not affect dry mass production in ambient [CO2]. However in elevated [CO2] the
more southerly clones significantly out-performed the more northerly clones when grown at a latitude
close to the latitudinal provenance of the Skidegate clones. As atmospheric carbon dioxide
concentration rises, such changes in the relative performance of genotypes may be exploited for
economic gain through appropriate selection of provenances for forest plantings.

KEYWORDS: ACCLIMATION, ATMOSPHERIC CO2, BONG CARR, ENRICHMENT, FROST
HARDINESS, INCREASE, NUTRITION, PHOTOSYNTHESIS, PHYSIOLOGY, SEEDLINGS


     346  
Centritto, M., F. Magnani, H.S.J. Lee, and P.G. Jarvis. 1999. Interactive effects of elevated
[CO2] and drought on cherry (Prunus avium) seedlings - II. Photosynthetic capacity and water
relations. New Phytologist 141(1):141-153.

Cherry seedlings (Prunus avium) were grown from seed for two growing seasons in three ambient
[CO2] (similar to 350 mu mol mol(-1)) and three elevated [CO2] (ambient + similar to 350 mu mol
mol(-1)) open-top chambers, and in three outside blocks. A drying cycle was imposed in both the
growing seasons to half the seedlings: days 69-115 in the first growing season, and in the second
growing season days 212-251 on the same seedlings which had already experienced drought.
Stomatal conductance was significantly reduced in elevated [CO2]-grown, unstressed seedlings in
both the first and second growing seasons, but was not caused by a decrease in stomatal density.
Droughted seedlings showed little or no reduction in stomatal conductance in response to elevated
[CO,]. However, stomatal conductance was highly correlated with soil water status. Photosynthetic
rate increased significantly in response to elevated [CO2] in both water regimes, leading to
improvement in instantaneous transpiration efficiency over the whole duration of the experiment, bur
there was no relationship between instantaneous transpiration efficiency and long-term water use
efficiency. The A(max) was strongly reduced in the second growing season, but unaffected by [CO2]
treatment. Although photosynthetic rate was not down-regulated, Rubisco activity was decreased by
elevated [CO2], possibly because of the increased leaf carbon:nitrogen ratio which had occurred by
the ends of the two growing seasons. Elevated [CO2] did not improve plant water relations (for
example, bulk leaf - water potential, osmotic potentials at full and zero turgor, relative water content
at zero turgor, bulk modulus of elasticity of the cell) and thus did not increase water-stress tolerance
of cherry seedlings.

KEYWORDS: ACCLIMATION, ATMOSPHERIC CO2, CARBON DIOXIDE, ENRICHMENT, GAS-
EXCHANGE, GROWTH, LEAVES, STOMATAL CONTROL, TRANSPIRATION, TREES


     347  
Ceulemans, R., I.A. Janssens, and M.E. Jach. 1999. Effects of CO2 enrichment on trees and
forests: Lessons to be learned in view of future ecosystem studies. Annals of Botany 84(5):577-590.

Because of their prominent role in global bioproductivity and because of their complex structure and
function, forests and tree species deserve particular attention in studies on the likely impact of
elevated atmospheric CO2 on terrestrial vegetation. Besides a synoptic review of some of the most
prominent above-ground response processes, particular attention is given to below-ground responses
of trees to elevated atmospheric CO2, while some feedback processes and interactions with Various
biotic and abiotic factors are also briefly summarized. At the leaf level there is little evidence of the
long-term loss of sensitivity to CO2 that was suggested by earlier experiments with tree seedlings in
pots. Future studies on photosynthesis measurements will probably not alter our conclusions about
acclimation, but should focus more on respiration under elevated CO2, which is still poorly
understood. At the tree level, the increase in growth observed in elevated CO2 results from an
increase in both leaf area and leaf photosynthetic rate (per unit leaf area). Tree growth enhancement
is generally larger at high rates of nutrient supply; when nutrient supply rates do not meet growth
rates, tree nutrient status declines and nutrients become limiting. In many studies at the canopy level,
a shift in whole-tree carbon allocation pattern towards below-ground parts has been associated with
increased atmospheric CO2 concentrations. At the ecosystem level, a larger amount of carbon being
allocated below-ground could show up by either (1) more root growth and turnover, (2) enhanced
activity of root-associated microorganisms, (3) larger microbial biomass pools and enhanced
microbial activity, or (4) increased losses of soil carbon through soil respiration. Fine root production
is generally enhanced, but it is not clear whether this response would persist in a forest. As elevated
CO2 stimulates biomass production, litterfall and rhizodeposition also increase. This increased
delivery of labile organic matter to the soil could influence soil microbial communities and subsequent
decomposition rates, nutrient availability and carbon storage in soil. There are, however,
contradictory hypothesis about the direction in which nutrient availability will be affected. Knowledge
of the response of these and other ecophysiological processes to elevated CO2 is the key to
understanding the functioning of the whole forest ecosystem. Our current knowledge is sufficiently
large with regard to how the carbon uptake process and individual tree growth respond under
atmospheric changes, but more emphasis should be put in future experiments on the interactions
between various processes, such as the carbon and nitrogen cycles, and on below-ground responses.
(C) 1999 Annals of Botany Company.

KEYWORDS: CARBON-DIOXIDE ENRICHMENT, ELEVATED ATMOSPHERIC CO2, LEAF
GAS- EXCHANGE, LONG-TERM CO2, MYCORRHIZAL COLONIZATION, OPEN-TOP
CHAMBERS, PHOTOSYNTHETIC ACCLIMATION, PINE PINUS-PONDEROSA, SCOTS PINE,
SOIL ORGANIC MATTER


     348  
Ceulemans, R., X.N. Jiang, and B.Y. Shao. 1995. Effects of elevated atmospheric CO2 on growth,
biomass production and nitrogen allocation of two Populus clones. Journal of Biogeography 22(2-
3):261-268.

Two hybrid poplar (Populus) clones (i.e. fast growing clone Beaupre and slower growing clone
Robusta) were grown from cuttings at close spacings in four open top chambers (OTCs) on the
Campus of the University of Antwerpen, Belgium. The four OTCs represented two atmospheric CO2
treatments, i.e. ambient and elevated (= ambient + 350 mu mol mol(-1)). Treatments lasted for a full
growing season (April-November 1993) and results of the first growing season are being reported.
In both clones the elevated CO2 treatment resulted in a significant increase in plant height and in
biomass production, both of stems and branches. Plants of both clones produced significantly more,
but shorter, side branches under the elevated CO2 treatment. In terms of biomass accumulation the
slower growing clone Robusta benefited relatively more (+ 37%) from the elevated CO2
concentrations than the fast growing clone Beaupre (+ 24%). In terms of leaf weight ratio, the slower
growing clone became relatively more efficient under elevated CO2 than the fast growing clone. The
elevated atmospheric CO2 treatment significantly increased the total leaf area per plant and leaf area
index per OTC; maximum LAI increased by 18% in clone Beaupre and by only 8% in the slower
growing clone Robusta. In the fast growing elope the increase in leaf area index was entirely caused
by an increase in individual leaf area, while in the slower growing clone also a 5% higher leaf
production was observed under the elevated CO2. The total length of the growing season was on
average reduced by the elevated CO2 treatment; in the slower growing clone mainly by an
advancement of bud set and in the faster growing clone by a slight delay of bud break in early spring.
In both clones elevated CO2 decreased nitrogen concentration and increased C/N ratio in all plant
organs, but no data for the below-ground compartment were available. Therefore, although similar
trends in the responses to elevated atmospheric CO2 were observed in both clones, the relative
efficiency of these responses differed between the fast and the slower growing poplar clones,
suggesting interactions between growth rate, growth strategy and response to elevated atmospheric
CO2.

KEYWORDS: ENRICHMENT, POPLAR CLONES, SEEDLINGS, SOIL, TEMPERATURE


     349  
Ceulemans, R., X.N. Jiang, and B.Y. Shao. 1995. Growth and physiology of one-year-old poplar
(populus) under elevated atmospheric co2 levels. Annals of Botany 75(6):609-617.

The effects of elevated atmospheric CO2 concentrations on the ecophysiological responses (gas
exchange, chlorophyll a fluorescence, Rubisco activity, leaf area development) as well as on the
growth and biomass production of two poplar clones (i.e. Populus trichocarpa x P. deltoides clone
Beaupre and P. x euramericana clone Robusta) were examined under open top chamber conditions.
The elevated CO2 treatment (ambient + 350 mu mol mol-1) stimulated above-ground biomass of
clones Robusta and Beaupre after the first growing season by 55 and 38 %, respectively. This
increased biomass production under elevated CO2 was associated with a significant increase in plant
height, the latter being the result of enhanced internode elongation rather than an increased
production of leaves or internodes. Both an increased leaf area index (LAI) and a stimulated net
photosynthesis per unit leaf contributed to a significantly higher stem biomass per unit leaf area, and
thus to the increased above-ground biomass production under the elevated CO2 concentrations in
both clones. The larger LAI was caused by a larger individual leaf size and leaf growth rate; the
number of leaves was not altered by the elevated CO2 treatment. The higher net leaf photosynthesis
was the result of an increase in the photochemical (maximal chlorophyll fluorescence Fm and
photochemical efficiency Fv/Fm) as well as in the biochemical (increased Rubisco activity) process
capacities. No significant differences were found in dark respiration rate, neither between clones nor
between treatments, but specific leaf area significantly decreased under elevated CO2 conditions. (C)
1995 Annals of Botany Company

KEYWORDS: BRANCH BAG, CARBON DIOXIDE, CLONES, ENRICHMENT, GAS-EXCHANGE,
LEAF-AREA, LIQUIDAMBAR- STYRACIFLUA, PINUS-TAEDA SEEDLINGS, RESPONSES,
WATER-STRESS


     350  
Ceulemans, R., and M. Mousseau. 1994. Tansley review no-71 - effects of elevated atmospheric
co2 on woody-plants. New Phytologist 127(3):425-446.

Because of their prominent role in the global carbon balance and their possible carbon sequestration,
trees are very important organisms in relation to global climatic changes. Knowledge of these
processes is the key to understanding the functioning of the whole forest ecosystem which can be
modelled and predicted based on the physiological process information. This paper reviews the major
methods and techniques used to examine the likely effects of elevated CO2 on woody plants, as well
as the major physiological responses of trees to elevated CO2. The available exposure techniques and
approaches are described. An overview table with all relevant literature data over the period 1989-93
summarizes the percent changes in biomass, root/shoot ratio, photosynthesis, leaf area and water use
efficiency under elevated CO2. Interaction between growth, photosynthesis and nutrition is discussed
with a special emphasis on downward regulation of photosynthesis. The stimulation or reduction
found in the respiratory processes of woody plants are reviewed, as well as the effect of elevated CO2
on stomatal density, conductance and water use efficiency. Changes in plant quality and their
consequences are examined. Changes in underground processes under elevated CO2 are especially
emphasized and related to the functioning of the ecosystem. Some directions for future research are
put forward.

KEYWORDS: BETULA-PENDULA ROTH, BLACK SPRUCE SEEDLINGS, CARBON-DIOXIDE
ENRICHMENT, CASTANEA-SATIVA MILL, INSECT HERBIVORE INTERACTIONS,
LIRIODENDRON-TULIPIFERA L, LOBLOLLY-PINE SEEDLINGS, SITCHENSIS BONG CARR,
SOUR ORANGE TREES, SOURCE-SINK RELATIONS


     351  
Ceulemans, R., and M. Mousseau. 1995. Effects of elevated atmospheric co2 on woody-plants (vol
12m, pg 425, 1995). New Phytologist 129(3):535.



     352  
Ceulemans, R., B.Y. Shao, X.N. Jiang, and J. Kalina. 1996. First- and second-year aboveground
growth and productivity of two Populus hybrids grown at ambient and elevated CO2. Tree
Physiology 16(1-2):61-68.

Two hybrid poplar (Populus) clones (the fast-growing clone Beaupre (P trichocarpa Torr. and Gray
x P. deltoides Bartr. ex Marsh.) and the slow-growing clone Robusta (P deltoides Bartr. ex Marsh.
x P. nigra L.)) were grown from hardwood cuttings for one or two growing seasons (1993-1994) in
either ambient or elevated (= ambient + 350 mu mol mol(-1)) CO2 in open-top chambers at the
University of Antwerpen. Both clones responded positively to the elevated CO2 treatment with
increased stem volume and aboveground biomass production; however, the clones exhibited different
response strategies to the elevated CO2 treatment, and the responses varied with cutting age and
duration of exposure. Clone Beaupre responded to the elevated CO2 treatment with increases in leaf
area and leaf area index during both the first and second growing seasons, but little increase in height
growth. Clone Robusta exhibited increased height growth, leaf biomass and total leaf nitrogen content
in response to elevated CO2, but no increase in leaf area index. The elevated CO2 treatment increased
the total number of branches and total branch biomass in both clones during both growing seasons.
At the end of the first growing season, woody stem biomass of the fast- and slow-growing clones was
increased by 38 and 55%, respectively. At the end of the second growing season, stem volume was
increased by 43% in clone Beaupre and by 58% in clone Robusta. The increase in stem volume was
a result of the stimulation of both height and diameter growth in the slow-growing clone, whereas
only height growth was stimulated in the fast-growing clone. In the fall of the first growing season,
the average date of bud set in clone Robusta was advanced by 4 days in the elevated CO2 treatment;
there were no other significant effects of the elevated CO2 treatment on bud set. The elevated CO2
treatment enhanced leaf C/N ratios in both clones in both years.

KEYWORDS: ATMOSPHERIC CO2, CARBON DIOXIDE, CASTANEA-SATIVA MILL, CLONES,
ENRICHMENT, GAS-EXCHANGE, PLANTS, RESPONSES, SEEDLINGS, TREES


     353  
Ceulemans, R., G. Taylor, C. Bosac, D. Wilkins, and R.T. Besford. 1997. Photosynthetic
acclimation to elevated CO2 in poplar grown in glasshouse cabinets or in open top chambers depends
on duration of exposure. Journal of Experimental Botany 48(314):1681-1689.

The effects of elevated CO2 were studied on the photosynthetic gas exchange behaviour and leaf
physiology of two contrasting poplar (Populus) hybrids grown and treated in open top chambers
(OTCs in Antwerp, Belgium) and in closed glasshouse cabinets (GHCs in Sussex, UK). The CO2
concentrations used in the OTCs were ambient and ambient +350 mu mol mol(-1), while in the GHCs
they were c, 360 mu mol mol(-1) versus 719 mu mol mol(-1). Measurements of photosynthetic gas
exchange were made for euramerican and interamerican poplar hybrids in combination with
measurements of dark respiration rate and Rubisco activity. Significant differences in the leaf anatomy
and structure (leaf mass per area and chlorophyll content) were observed between the leaves grown
in the OTCs and those grown in the GHCs. Elevated CO2 stimulated net photosynthesis in the poplar
hybrids after 1 month in the GHCs and after 4 months in the OTCs, and there was no evidence of
downward acclimation (or downregulation) of photosynthesis when the plants in the two treatments
were measured in their growth CO2 concentration. There was also no evidence of downregulation
of Rubisco activity and there were even examples of increases in Rubisco activity. Rubisco exerted
a strong control over the light- saturated rate of photosynthesis, which was demonstrated by the close
agreement between observed net photosynthetic rates and those that were predicted from Rubisco
activities and Michaelis-Menten kinetics. After 17 months in elevated CO2 in the OTCs there was a
significant loss of Rubisco activity for one of the hybrid clones, i.e. Beaupre, but not for clone
Robusta, The effect of the CO2 measurement concentration (i.e. the short-term treatment effect) on
net photosynthesis was always larger than the effect of the growth concentration in both the OTCs
or GHCs (i.e. the long-term growth CO2 effect), with one exception, For the interamerican hybrid
Beaupre dark respiration rates in the OTCs were not significantly affected by the elevated CO2
concentrations. The results suggest that for rapidly growing tree species, such as poplars, there is
little evidence for downward acclimation of photosynthesis when plants are exposed to elevated CO2
for up to 4 months; longer term exposure reveals loss of Rubisco activity.

KEYWORDS: ATMOSPHERIC CO2, CARBON DIOXIDE, GAS-EXCHANGE, HYBRID POPLAR,
LEAF DEVELOPMENT, LONG-TERM ELEVATION, POPULUS- EURAMERICANA, RIBULOSE-
1;5-BISPHOSPHATE CARBOXYLASE, TEMPERATURE, TOMATO


     354  
Ceulemans, R., L. Vanpraet, and X.N. Jiang. 1995. Effects of co2 enrichment, leaf position and
clone on stomatal index and epidermal-cell density in poplar (populus). New Phytologist 131(1):99-
107.

The effects of CO2 enrichment and leaf position on stomatal characteristics (stomatal density,
stomatal index and stomatal pore length) and epidermal cell density were examined for two different
Populus clones, Beaupre and Robusta, grown from cuttings in open-top chambers under ambient and
elevated atmospheric CO2 conditions. Both clones had amphistomatous leaves, and stomatal density
was significantly larger on the abaxial leaf surface than on the adaxial. Significant interactions
between CO2 enrichment, leaf position and clone were observed for most stomatal and epidermal
characteristics. A significant reduction of the number of stomata mm(-2) under elevated CO2 was
observed in expanding leaves near the upper portion of the plant for both leaf surface sides and in
both clones. For the abaxial leaf side only, this reduction under elevated CO2 was accompanied by
a similar reduction of the stomatal index in both clones. In mature leaves on the middle and lower
portion of the plants, there was no significant effect of the CO2 treatment on stomatal density. In
young, expanding leaves near the upper part of the plant there were significant interactions between
the CO2 treatment and leaf surface side for epidermal cell density. The latter increased under elevated
CO2 at the abaxial leaf surface, but decreased at the adaxial surface on the upper part of the plant.
Total epidermal cell numbers of mature, fully expanded leaves increased under elevated CO2 in both
clones. The observation that interactions with leaf age and/or leaf position significantly confound the
CO2 treatment effect on stomatal and epidermal cell densities, might contribute to the elucidation of
the problem of the phenomenon of stomatal density reduction under elevated atmospheric CO2.

KEYWORDS: ANATOMY, ATMOSPHERIC CO2, GROWTH, INCREASE, NUMBERS, OAK
LEAVES, TEMPERATURE


     355  
Chabot, S., R. Belrhlid, R. Chenevert, and Y. Piche. 1992. Hyphal growth promotion invitro of
the va mycorrhizal fungus, gigaspora-margarita becker and hall, by the activity of structurally specific
flavonoid compounds under co2-enriched conditions. New Phytologist 122(3):461-467.

Plant phenolic compounds are known to be inducers of virulence genes in plant-pathogen interactions
such as those involving Agrobacterium, and flavonoids are known to be inducers or inhibitors of Nod
genes in Rhizobium-legume symbiosis. More recent studies suggest that some of these compounds
act as molecular signals in the development of vesicular-arbuscular mycorrhizas (VAM). The present
study has shown that hyphal growth of the VAM fungus, Gigaspora margarita Becker & Hall, is
affected by both stimulatory and inhibitory flavonoids, when applied at 10 muM together with an
optimal carbon dioxide enrichment. Stimulatory compounds were all flavonols (kaempferol, quercetin
and morin) and possessed at least one hydroxyl group on the B ring. Conversely, two isoflavones
(biochanin A, and genistein), a single flavanone (hesperetin) and two compounds without any
hydroxyl group on the B ring, galangin (flavonol) and chrysin (flavone), were all inhibitors of hyphal
growth.

KEYWORDS: AGROBACTERIUM-TUMEFACIENS, DNA TRANSFORMED ROOTS,
EXPRESSION, HOST, IDENTIFICATION, MELILOTI NODULATION GENES, PHENOLIC-
COMPOUNDS, RHIZOBIUM, SIGNAL COMPOUNDS, SPORE GERMINATION


     356  
Chagvardieff, P., T. Daletto, and M. Andre. 1994. Specific effects of irradiance and co2
concentration doublings on productivity and mineral-content in lettuce. Life Sciences and Space
Research XXV (3) 14(11):269-275.

Experiments in growth chambers with controlled atmosphere were performed to compare the effects
on the productivity of two treatments stimulating photosynthesis : the doubling of CO2 concentration,
the doubling of irradiance; the combining of both was also tested. A large effect of light was noticed
: (i) the accumulation of carbon was, contrarily to CO2 effect, amplified within time, and led to the
most important dry matter production. (ii) the specific leaf weight was about two-fold increased. (iii)
the nitrate content was 2-3 fold less. A significant positive effect of CO2 was detected on the fresh
biomass production and the iron content of lettuce. A synergy was observed on dry matter production
by the interaction of the two factors.

KEYWORDS: CARBOHYDRATE, ENRICHMENT, GROWTH, HIGH-PRESSURE SODIUM,
LAMPS, LIGHT, PHOTOSYNTHESIS


     357  
Chagvardieff, P., B. Dimon, A. Souleimanov, D. Massimino, S. Le Bras, M. Pean, and D.
Louche-Teissandier. UNKNOWN YEAR. Effects of modified atmosphere on crop productivity and
mineral content. Life Sciences: Life Support Systems Studies-I :1971-1974.

Wheat, potato, pea and tomato crops were cultivated from seeding to harvest in a controlled and
confined growth chamber at elevated CO2 concentration (3700 mu L.L-1) to examine the effects on
biomass production and edible part yields. Different responses to high CO2 were recorded, ranging
from a decline in productivity for wheat, to slight stimulation for potatoes, moderate increase for
tomatoes, and very large enhancement for pea. Mineral content in wheat and pea seeds was not
greatly modified by the elevated CO2. Short-term experiments (17 d) were conducted on potato at
high (3700 mu L.L-1) and very high (20,000 mu L.L-1) CO2 concentration and/or low O-2 partial
pressure (similar to 20,600 mu L.L-1 or 2 kPa). Low O-2 was more effective than high CO2 in total
biomass accumulation, but development was affected: Low O-2 inhibited tuberization, while high
CO2 significantly increased production of tubers. (C) 1997 COSPAR. Published by Elsevier Science
Ltd.

KEYWORDS: INCOMPLETE, CARBON DIOXIDE, CO2 CONCENTRATION, GROWTH,
IRRADIANCE, POTATO, TEMPERATURE, WHEAT


     358  
Chalabi, Z., and J.E. Fernandez. 1992. Spatiotemporal responses of a glasshouse to gaseous
enrichment. Journal of Agricultural Engineering Research 51(2):139-151.

KEYWORDS: SUMMER CO2 ENRICHMENT, SYSTEMS, YIELD


     359  
Chalabi, Z.S., and J.E. Fernandez. 1994. Estimation of net photosynthesis of a greenhouse canopy
using a mass-balance method and mechanistic models. Agricultural and Forest Meteorology 71(1-
2):165-182.

Two mechanistic models for estimating net photosynthesis of a greenhouse canopy are evaluated
against measurements using mass balance of CO2 fluxes. The discrepancies observed between the
mechanistic models and the CO2 mass balance measurement method are attributed to the
underestimation of leakage rate, the error in estimating radiation transmission in direct light
conditions, and the spatial inhomogeneity of the CO2 concentration inside the glasshouse.

KEYWORDS: CO2- ENRICHMENT, CROP, OPTIMIZATION, STRATEGY, VENTILATION


     360  
Chan, Y.S.G., M.H. Wong, and B.A. Whitton. 1998. Effects of landfill gas on growth and nitrogen
fixation of two leguminous trees (Acacia confusa, Leucaena leucocephala). Water, Air, and Soil
Pollution 107(1-4):409-421.

A study was made on the effects of landfill gas on ARA (acetylene reducing activity) of nodules of
two woody legumes (Acacia confusa and Leucaena leucocephala) widespread on landfill sites in Hong
Kong. The effects of the three main components of landfill gas, O2, CO2 and CH4, were first
measured separately over a I-hr period. Maximum ARA was found at 20% O2 (close to atmospheric
partial pressure) and ARA decreased as the O2 decreased in the range of 16-1%. Acacia confusa
nodular ARA was significantly inhibited at 30-50% CO2, but not Leucaena leucocephala nodular
ARA. CH4 had no significant effect on ARA of either species. As the landfill gas concentrations in
the landfill topsoil were mostly > 10% O2 and < 10% CO2, root nodules should fix N2 effectively
over these ranges of gases. A four-week test was conducted to assess the long-term influence of
landfill gas on seedlings of the two legumes. Landfill gas and elevated CO2 both suppressed their
growth and their nodular ARA. Even under the influence of the gases, however, seedlings with
nodules formed a higher biomass than seedlings lacking nodules. The growth of the two legumes
under actual landfill conditions was investigated by transplanting non-inoculated and pre-inoculated
seedlings to two landfill sites in Hong Kong: Junk Bay and Shuen Wan Landfill. After six months,
most of the non-inoculated seedlings became infected: Acacia confusa 63 and 70%, Leucaena
leucocephala 17 and 89%, respectively, at the test sites. The results indicate that there were free
rhizobia at these landfill sites to infect the legumes and they had formed effective nodules to fix N2
under landfill conditions.

KEYWORDS: CARBON DIOXIDE, NODULES, PLANTS


     361  
Chapin, F.S., E. Rincon, and P. Huante. 1993. Environmental responses of plants and ecosystems
as predictors of the impact of global change. Journal of Biosciences 18(4):515-524.

An understanding of plant responses to fluctuations in environment is critical to predictions of plant
and ecosystem responses to climate change. In the northern hemisphere, the northern limits of
distribution of major biomes are probably determined by the tolerance of their dominant physiognomic
types (e.g., deciduous hardwood trees) to minimum winter temperatures and can thus be predicted
from long-term patterns of temperature fluctuations. At a more detailed level, the responses of
functional groups of plants to altered climate can be predicted from their known responses to
fluctuations in soil resources (nutrients and water) and the expected effect of climatic change on these
soil resources. Laboratory and field experiments demonstrate the feasibility of this approach.

KEYWORDS: CO2-INDUCED CLIMATE CHANGE, CONTRASTED ECOLOGY, ENRICHMENT,
FOREST, GROWTH, MEXICO, NORTH-AMERICA, PLASTICITY, ROOT-SYSTEM, SEEDLINGS


     362  
Chaves, M.M., and J.S. Pereira. 1992. Water-stress, co2 and climate change. Journal of
Experimental Botany 43(253):1131-1139.

Climatic change may bring about increased aridity to large areas of Europe. Higher temperatures,
larger water deficits and high light stress are likely to occur in conjunction with elevated atmospheric
CO2. This raises the question whether a high CO2 concentration in the atmosphere can compensate
for the decrease in carbon gain in water-stressed plants. The processes which determine dry matter
production and the ways they are affected by soil water deficits are discussed. It is now well
established that in most species and under most circumstances stomata are the main limiting factor
to carbon uptake under water deficit, the photosynthetic machinery being highly resistant to
dehydration. However, when other stresses are superimposed, a decline in photosynthetic capacity
may be observed. In the short term, under drought conditions, the increase in CO2 in the atmosphere
may diminish the importance of stomatal limitation for carbon assimilation, inhibit photorespiration,
stimulate carbon partitioning to soluble sugars and increase water-use efficiency. Some recent
evidence seems to indicate that under conditions of high irradiance, plants growing at elevated CO2
may develop protection towards photoinhibition, which might otherwise result in significant losses
in plant production under stress conditions. In the longer term though, a negative acclimation of
photosynthesis appears to occur in many species, an explanation for which still needs to be clearly
identified. Similarly, the effects of extended exposure to elevated CO2 under arid conditions are not
known. Plant production is more closely related to the integral of photosynthesis over time and total
foliage area than to the instantaneous rates of the photosynthetic process. Water deficits result in a
decrease in foliage area biomass and, therefore, in productivity. On the other hand, the increase in air
temperature may result in more respiratory losses. However, experimental as well as simulatory
evidence suggests that doubling CO2 concentration in the air may improve carbon assimilation and
compensate partially for the negative effects of water stress even if we assume a down-regulation of
the photosynthetic process as a result of acclimation to elevated CO2.

KEYWORDS: ATMOSPHERIC CARBON-DIOXIDE, DROUGHT STRESS, DRY-WEIGHT,
ELEVATED CO2, LONG-TERM EXPOSURE, PHASEOLUS-VULGARIS L, PHOTOSYNTHETIC
INHIBITION, RIBULOSE BISPHOSPHATE CARBOXYLASE, STOMATAL DENSITY, SUCROSE
PHOSPHATE SYNTHASE


     363  
Chaves, M.M., J.S. Pereira, S. Cerasoli, J. CliftonBrown, F. Miglietta, and A. Raschi. 1995.
Leaf metabolism during summer drought in Quercus ilex trees with lifetime exposure to elevated
CO2. Journal of Biogeography 22(2-3):255-259.

A marginal improvement in the response of Quercus ilex adult trees to drought appears to occur
under a long-term natural CO2 enrichment. This is expressed, for example, by the absence of midday
stomatal closure in trees growing under elevated CO2. Some protection against high irradiance and
high temperature seems also to occur at the photochemical level, presumably as a result of more
carbon available to the consumption of excess light energy. This would allow a better performance
of the plants grown under elevated CO2 during the warmer hours of the day and therefore playing
an important adaptation role under drought conditions. A marginal increase in the concentration of
soluble sugars and starch was observed in the leaves of trees growing at elevated CO2 as compared
with plants at ambient CO2, mainly during the midday hours. We may speculate that this will be
advantageous both in terms of carbohydrate reserves for growth (e.g. more roots) and osmotic
adjustment.

KEYWORDS: FIELD, LEAVES, QUANTUM YIELD


     364  
Chemeris, Y.K., L.V. Shenderova, and P.S. Venediktov. 1996. Chloroplast respiration in
Chlorella pyrenoidosa CALU-175: Effects of nitrogen deficiency, exogenous glucose, and elevated
temperature. Russian Journal of Plant Physiology 43(4):474-479.

The rate of chloroplast respiration in Chlorella was studied with respect to some changes in the
physiological state induced by nitrogen deficiency, heterotrophic growth, and incubation at
supraoptimal temperature. Iodoacetamide (an inhibitor of glycolysis), salicylhydroxamate (an inhibitor
of nonmitochondrial respiration), and 2-deoxy-D-glucose (a nonmetabolizable analogue of glucose),
inhibited the respiration of chloroplasts. Treatments that inactivate photosystem II (PS II), i.e., the
addition of glucose, nitrogen deprivation, or dark incubation at elevated temperatures (39-43 degrees
C), drastically (8-10 times) increased the rate of chloroplast respiration. In the absence of CO2, no
enhancement of chloroplast respiration was recorded in nitrogen-starved cells. Cycloheximide, an
inhibitor of cytoplasmic protein synthesis, and 2-deoxy-D-glucose prevented the increase in the
chloroplast respiration rate caused by the addition of glucose or incubation at elevated temperatures.
It is suggested that the inhibition of PS II, previously described in Chlorella incubated for a long time
at supraoptimal temperature, is associated with the enhancement of chloroplast respiration.

KEYWORDS: CELLS, CHLAMYDOMONAS-REINHARDTII, CHLORORESPIRATION,
TRANSPORT


     365  
Chemeris, Y.K., P.S. Venediktov, and A.B. Rubin. 1996. Role of chloroplast respiration in the
inactivation of photosystem II in Chlorella. Russian Journal of Plant Physiology 43(6):716-723.

Nitrogen deficiency, dark incubation on glucose, and dark incubation at an elevated temperature (41
degrees C) were previously shown to inactivate photosystem II (PS LI) in Chlorella pyrenoidosa
Chick, strain CALU-175. These treatments also increased chloroplast respiration by 7-11 times, At
the same time, any attempt to inhibit the accumulation of substrates for chloroplast respiration (CO2
deprivation during nitrogen starvation, inhibition of glucose metabolism by a nonmetabolizable analog
of glucose, 2-deoxy-D-glucose, or inhibition of protein synthesis by cycloheximide during dark
incubation on glucose or by heat shock) prevented the stimulation of chloroplast respiration and PS
II inactivation, Inhibition of the oxygen-dependent oxidation of the plastoquinone pool under
anaerobic conditions or in the presence of salicylhydroxamate, an inhibitor of chloroplast oxidases,
markedly increased the extent and rate of PS II inactivation in cells subjected to heat shock. The
dependencies of chloroplast respiration and the PS II inactivation rate on the hear-shock temperature
exactly matched one another. Diuron, an inhibitor of photosynthetic electron transport between the
primary and secondary quinone electron accepters, did not affect the rate of chloroplast respiration,
but prevented PS II inactivation. We propose that the inactivation of PS II caused by these treatments
is due to the loss of the primary quinone electron acceptor as a consequence of its two-electron
reduction from the plastoquinone reduced by the electron flow from the substrates of chloroplast
respiration.

KEYWORDS: CHLAMYDOMONAS-REINHARDTII, CHLORORESPIRATION


     366  
Chen, C.L., C.C. Li, and J.M. Sung. 1994. Carbohydrate-metabolism enzymes in co2-enriched
developing rice grains of cultivars varying in grain-size. Physiologia Plantarum 90(1):79-85.

The increased supply of photosynthate from maternal tissue is known to promote grain growth in
several crop species. However, the effect of increasing photosynthate supply on grain growth receives
little attention in rice. This study was aimed at evaluating the effect of increasing photosynthate
supply through CO2 enrichment (650 mul l-1) on grain growth in three rice cultivars differing in grain
size. CO2 enrichment was applied to the pot-grown plants between anthesis and final harvest. The
results indicated that high CO2 treatment enhanced the CO2 exchange rate of leaf tissue, and
subsequently increased the sucrose level of peduncle exudate, but it did not promote starch
accumulation in the developing grains. This phenomenon was linked to the poor CO2 responses for
the grain activities of sucrose synthase, UDP-glucose pyrophosphorylase, ADP-glucose
pyrophosphorylase, and starch synthases involved in the converison of sucrose to starch. Significant
cultivar differences also existed for the activities of sucrose to starch conversion enzymes with larger
grain size cultivars tending to have higher enzymes activities (expressed on a grain basis), resulting
in a greater carbohydrate accumulation.

KEYWORDS: ACCUMULATION, CARBON DIOXIDE, CO2, GROWTH, MAIZE, ORYZA-SATIVA,
STARCH, SUCROSE SYNTHASE, ULTRAVIOLET-B RADIATION, WHEAT


     367  
Chen, C.T., and T.L. Setter. 1997. Potato response to elevated CO2 and temperature. Plant
Physiology 114(3):490.



     368  
Chen, D.X., and M.B. Coughenour. 1996. A mechanistic model for submerged aquatic macrophyte
photosynthesis: Hydrilla in ambient and elevated CO2. Ecological Modelling 89(1-3):133-146.

There are significant knowledge gaps about the responses of submerged aquatic macrophytes to CO2
enrichment and global warming. A mechanistic steady-state photosynthesis model for submerged
aquatic macrophytes was developed to provide an analysis tool to investigate the responses of plant
photosynthesis to CO2, temperature and light. The model was based upon a general simplified scheme
for inorganic carbon assimilation of submerged aquatic macrophytes which integrated the knowledge
about aquatic plant photosynthesis from previous research, mainly on Hydrilla. The model includes:
(1) diffusion and/or active transfer of inorganic carbon (CO2 and/or HCO3-) in the bathing medium
into the leaf mesophyll and cytosol; (2) diffusion and/or 'pumping' of CO2 through the PEPcase-
related C-4 pathway into the chloroplast; (3) inter-conversions between CO2 and HCO3- inside cells;
(4) photosynthetic carbon reduction cycle (PCR) in the chloroplast. In the model, the PCR processes
in the chloroplast were described using the widely accepted C-3 photosynthesis model. The activity
of the C-4 cycle was related to environmental CO2 'stress'. In this way, the model can simulate the
shift between C-3-like and C-4-like photosynthesis under different environmental conditions. The
model was validated using gas exchange data from Hydrilla plants grown in ambient and elevated
CO2. The model predicted quite well photosynthetic responses to incident PAR, temperature and
ambient CO2 for both ambient and elevated atmospheric CO2 treatments. Model predictions agreed
well with measured Hydrilla gas exchange data. The simulated and measured CO compensation points
of Hydrilla leaf photosynthesis were about 100 ppm. The light compensation point of photosynthesis
was about 25 mu mol m(-2)s(-1) (PAR), and photosynthesis rate was saturated at about 100 mu mol
m(-2)s(-1) (PAR). Higher pH slightly increased photosynthesis rates at ambient CO2 (similar to 350
ppm). There was no significant acclimation of Hydrilla photosynthesis to elevated CO2 within the
experimental period. Simulated CO2 compensation point decreased with increasing activity of C-4-
cycle processes.

KEYWORDS: ASSIMILATION, CARBOXYLASE, FIXATION, LEAVES, OXYGEN, PLANTS,
RESPIRATION, TEMPERATURE-DEPENDENCE


     369  
Chen, D.X., M.B. Coughenour, D. Eberts, and J.S. Thullen. 1994. Interactive effects of co2
enrichment and temperature on the growth of dioecious hydrilla-verticillata. Environmental and
Experimental Botany 34(4):345-353.

Experiments of plant growth responses to different CO2 concentrations and temperatures were
conducted in growth chambers to explore the interactive effects of atmospheric CO2 enrichment and
temperature on the growth and dry matter allocation of dioecious Hydrilla [Hydrilla verticillata (L.f.)
Royle]. Hydrilla plants were exposed to two atmospheric CO2 concentrations (350 and 700 ppm) and
three temperatures (15, 25 and 32 degrees C) under a 12-hr photoperiod for about 2 months. The
plant growth analysis showed that elevated CO2 appeared to enhance the growth of Hydrilla, and that
the percentage of the enhancement is strongly temperature-dependent. Maximum biomass production
was achieved at 700 ppm CO2 and 32 degrees C. At 15 degrees C, the total dry matter production
was increased about 27% by doubling CO2, due to a 26% enhancement of leaf biomass, a 34%
enhancement of stem biomass and 16% enhancement of root biomass. At 25 degrees C, the dry
matter production was increased about 46% by doubling CO2, due to a 29% enhancement of leaf
biomass, a 27% enhancement of stem biomass and 40% enhancement of root biomass. At 32 degrees
C, however, the percentage of the enhancement of total dry matter production by doubling CO2 was
only about 7%. The dry matter allocation among different plant parts was influenced by temperature
but not by elevated CO2 concentration.

KEYWORDS: AQUATIC MACROPHYTES, CARBON DIOXIDE, ELEVATED ATMOSPHERIC
CO2, ENVIRONMENT, PHOTOSYNTHETIC RESPONSE, YIELD


     370  
Chen, D.X., M.B. Coughenour, A.K. Knapp, and C.E. Owensby. 1994. Mathematical simulation
of C4 grass photosynthesis in ambient and elevated co2. Ecological Modelling 73(1-2):63-80.

A mechanistic leaf photosynthesis model was developed for C4 grasses based on a general simplified
scheme of C4 plant carbon metabolism. In the model, the PEPcase-dependent C4-cycle was described
in terms of CO2 concentration in the mesophyll space using Michaelis-Menten kinetics, and the
activity of PEPcase was related to the incident PAR to take account of the influence of light on the
activty of C4-cycle processes. The CO2 refixation by Rubisco in the bundle sheath was described
using a widely accepted C3 photosynthesis model. The model assumes a steady state balance among
CO2 diffusion from surrounding atmosphere into the mesophyll space, CO2 transport into the bundle
sheath by the C4-cycle, CO2 refixation by the C3-cycle in the bundle sheath, and CO2 leakage from
the bundle sheath. The response to temperature of photosynthesis was incorporated via the
temperature dependence of model parameters. The photosynthesis model was coupled with a stomatal
conductance model in order to predict leaf photosynthesis rates at different atmospheric conditions.
The empirical model of Ball et al. (1987) was adopted and slightly modified to describe responses in
stomatal conductance. The coupled model was parameterized for the C4 grass Andropogon gerardii
grown in both ambient (350 ppm) and elevated (700 PPM) CO2 atmospheres. The key parameters
of the model were estimated by fitting the model to the measured data using non-linear regression.
The model was validated by comparison the predicted photosynthetic response to PAR in both CO2-
pretreatments with the measured data from an independent gas exchange experiment. The predicted
photosynthesis and stomatal conductance matched the measured data quite well for both atmospheric
CO2- pretreatments. At 25-degrees-C, the estimated maximum carboxylation rate of Rubisco
V(cm,25), potential electron transport rate J(m,25) and quantum efficiency alpha were increased by
CO2 enrichment. The maximum PEPcase activity V(pm,25) was lower in elevated CO2. The model
predicted that the light-saturated leaf photosynthesis will increase by about 10% with the rising of
atmospheric CO2 from 350 to 700 ppm at 30-degrees-C, and that the optimal temperature of
photosynthesis will shift from 37 to 38.5-degrees-C. The estimated slope of the stomatal conductance
model was increased by atmospheric CO2 enrichment. Stomatal conductance was significantly
reduced by increasing atmospheric CO2 concentration.

KEYWORDS: 1,5-BISPHOSPHATE CARBOXYLASE OXYGENASE, BUNDLE SHEATH-CELLS,
C-4, INORGANIC CARBON, LEAVES, MECHANISM, MODEL, PLANTS, TALLGRASS PRAIRIE,
TEMPERATURE-DEPENDENCE


     371  
Chen, D.X., H.W. Hunt, and J.A. Morgan. 1996. Responses of a C-3 and C-4 perennial grass to
CO2 enrichment and climate change: Comparison between model predictions and experimental data.
Ecological Modelling 87(1-3):11-27.

Ecological responses to CO2 enrichment and climate change are expressed at several interacting
levels: photosynthesis and stomatal movement at the leaf level, energy and gas exchanges at the
canopy level, photosynthate allocation and plant growth at the plant level, and water budget and
nitrogen cycling at the ecosystem level. Predictions of these ecosystem responses require coupling
of ecophysiological and ecosystem processes. Version GEM2 of the grassland ecosystem model
linked biochemical, ecophysiological and ecosystem processes in a hierarchical approach. The model
included biochemical level mechanisms of C-3 and C-4 photosynthetic pathways to represent direct
effects of CO2 on plant growth, mechanistically simulated biophysical processes which control
interactions between the ecosystem and the atmosphere, and linked with detailed biogeochemical
process submodels. The model was tested using two-year full factorial (CO2, temperature and
precipitation) growth chamber data for the grasses Pascopyrum smithii (C-3) and Bouteloua gracilis
(C-4). The C-3-C-4 photosynthesis submodels fitted the measured photosynthesis data from both the
C-3 and the C-4 species subjected to different CO2, temperature and precipitation conditions. The
whole GEM2 model accurately fitted plant biomass dynamics and plant N content data over a wide
range of temperature, precipitation and atmospheric CO2 concentration. Both data and simulation
results showed that elevated CO2 enhanced plant biomass production in both P. smithii (C-3) and B.
gracilis (C- 4). The enhancement of shoot production by elevated CO2 varied with temperature and
precipitation. Doubling CO2 increased modeled annual net primary production (NPP) of P. smithii
by 36% and 43% under normal and elevated temperature regimes, respectively, and increased NPP
of B. gracilis by 29% and 24%. Doubling CO2 decreased modeled net N mineralization rate (Nmin)
of soil associated with P. smithii by 3% and 2% at normal and high temperatures, respectively. Nmin
of B. gracilsi soil decreased with doubled CO2 by 5% and 6% at normal and high temperatures. NPP
increased with precipitation. The average NPP and Nmin of P. smithii across the treatments was
greater than that of B. gracilis. In the C-3 species the response of NPP to increased temperatures was
negative under dry conditions with ambient CO2, but was positive under wet conditions or doubled
CO2. The responses of NPP to elevated CO2 in the C-4 species were positive under all temperature
and precipitation treatments. Nmin increased with precipitation in both the C-3 and C-4 species.
Elevated CO2 decreased Nmin in the C-4 system. The effects of elevated CO2 on Nmin in the C-3
system varied with precipitation and temperature. Elevated temperature decreased Nmin under dry
conditions, but increased it under wet conditions. Thus, there are strong interactions among the
effects of CO2 enrichment, precipitation, temperature and species on NPP and Nmin. Interactions
between ecophysiological processes and ecosystem processes were strong. GEM2 coupled these
processes, and was able to represent the interactions and feedbacks that mediate ecological responses
to CO2 enrichment and climate change. More information about the feedbacks between water and
N cycling is required to further validate the model. More experimental and modeling efforts are
needed to address the possible effects of CO2 enrichment and climate change on the competitive
balance between different species in a plant community and the feedbacks to ecosystem function.

KEYWORDS: AMBIENT, CARBON, ELEVATED ATMOSPHERIC CO2, GROWTH, LEAVES,
PLANTS, RISING CO2, SIMULATION-MODEL, TEMPERATURE-DEPENDENCE, WATER-
USE


     372  
Chen, J.L., and J.F. Reynolds. 1997. GePSi: A generic plant simulator based on object-oriented
principles. Ecological Modelling 94(1):53-66.

The Generic Plant Simulator (GePSi) is a physiologically-based model that combines modules for
canopy, root environment, water relations, and potential growth to generate whole-plant carbon,
nitrogen, and water balances. The version presented here is coded in the object-oriented programming
(OOP) language, C++, to enhance the implementation of modularity. In the aboveground aerial
environment, the Weather module defines the weather conditions above a canopy, and MicroWeather
defines the vertical profiles of micro-meteorological variables in a canopy. The belowground soil
environment contains the SoilProperty modules, which define vertical profiles of physical and
chemical variables in a soil column. The 'part-of' hierarchy in GePSi follows the structure of a real
plant: the Plant module calls canopy and root system modules; the Canopy module, in turn, calls leaf,
stem and fruit modules, and the RootSystem module calls coarse and fine root modules, etc. Our
long-term goal is for GePSi to serve as a template for building a plant growth simulator by simply
selecting appropriate modules for the question being asked. We are building a suite of plant modules
(and their interfaces) based on general principles that are fundamentally similar for different kinds of
plants. This includes photosynthesis, growth, nutrient and carbon allocation, water uptake, etc. These
modules can be parameterized for specific species, related groups of species, life-forms, or broader
groups depending on how variable the processes are across the groupings and the amount of
unexplained variability that is acceptable for the question being investigated. Our modular-based
approach has numerous advantages, including improving the understanding of the model, reducing
duplication of effort, and facilitating the adaptation of the model for different sites and ecosystems.
(C) 1997 Elsevier Science B.V.

KEYWORDS: DESIGN, ECOLOGICAL MODEL, GROWTH, SYSTEMS


     373  
Chen, K., G.Q. Ha, N. Keutgen, M.J.J. Janssens, and F. Lenz. 1999. Effects of NaCl salinity and
CO2 enrichment on pepino (Solanum muricatum Ait.) - I. Growth and yield. Scientia Horticulturae
81(1):25-41.

One-month old, rooted, semi-hardwood cutting plants of pepino cv. Xotus in sand-potted culture
were treated with 200 mi Hoagland nutrient solution with or without additional 25 mM NaCl twice
a week for 2 months, and exposed to 350 +/- 10, 700 +/- 10 or 1050 +/- 10 ppm CO2 in controlled
environment chambers during the last month of the experiment. NaCl salinity in the rhizosphere
reduced growth of all the organs, but raised stem dry weight ratio and root dry weight ratio. In
contrast, atmospheric CO2 enrichment increased plant and fruit growth. Leaf dry weight ratio and
fruit dry weight ratio rose, but stem dry weight ratio and root dry weight Patio decreased at high CO2
levels. Daily expansion rate of leaf area, growth rate of side-shoot length, rate of plant dry mass
production, and increased rate of fresh fruit weight decreased due to NaCl stress, but increased with
CO2 enrichment. Side-shoot diameter rose, whereas specific leaf area, leaf area ratio, and side- shoot
dry weight ratio declined under both NaCl-stressed and CO2-enriched conditions. In comparison with
the 350 ppm CO2 treatment without NaCl salinity in the rhizosphere, net assimilation rate and relative
growth rate of plants were reduced by 8-13% and 16-32% due to NaCl salinity, and enhanced by 22-
23% and 42-64% at 700 ppm CO2, and by 36-44% and 64-101% at 1050 pm CO2, respectively. The
simultaneous treatments of NaCl salinity and high CO2 resulted in indefinite effects on vegetative and
reproductive growth as well as on dry mass production of different plant organs. Nevertheless, the
negative impacts of NaCl stress on plant growth and fruit yield diminished at high CO2 levels.
Atmospheric CO2 enrichment increased the tolerance of pepino to NaCl salinity in the root medium.
(C) 1999 Elsevier Science B.V. All rights reserved.

KEYWORDS: ATMOSPHERIC CO2, CARBON DIOXIDE, CELLS, ECOSYSTEMS, FRUIT,
PHOTOSYNTHESIS, PLANTS, RESPONSES


     374  
Chen, K., G.Q. Hu, N. Keutgen, M. Blanke, and F. Lenz. 1997. Effects of CO2 concentration
on strawberry. II. Leaf photosynthetic function. Journal of Applied Botany-Angewandte Botanik
71(5-6):173-178.

Two-week-old strawberry (Fragaria x ananassa Duch, cv. 'Elsanta') plants were acclimatized to 300,
450, 600, 750 or 900 ppm CO2 in controlled environment chambers for 50 days. An elevated CO2
concentration up to 750 ppm reduced total chlorophyll, chlorophyll a and chlorophyll b contents as
well as the a/b ratio. Long-term CO2 enrichment induced leaf senescence and decreased
photosynthetic efficiency as well as photochemical conversion efficiency of PS II. Intercellular CO2
concentration significantly increased with CO2 enrichment. Stomatal conductance, transpiration rate,
and net photosynthesis rate of young leaves increased with raising CO2 concentrations. However,
CO2 levels above 600 ppm markedly reduced net photosynthetic rate of adult and old leaves. High
CO2 concentrations up to 900 ppm did not significantly affect dark respiration rate of the leaves.
Photosynthetic water-use efficiency was highest in old leaves and lowest in young ones. Increased
CO2 concentrations up to 600-750 ppm improved leaf photosynthetic capacity by increasing
photosynthetic water-use efficiency.

KEYWORDS: ATMOSPHERIC CO2, CARBON DIOXIDE, CHLOROPHYLL FLUORESCENCE,
PLANTS, RESPONSES, WATER-USE


     375  
Chen, K., G.Q. Hu, N. Keutgen, M.J.J. Janssens, and F. Lenz. 1999. Effects of NaCl salinity and
CO2 enrichment on pepino (Solanum muricatum Ait.) - II. Leaf photosynthetic properties and gas
exchange. Scientia Horticulturae 81(1):43-56.

One-month old, rooted semi-hardwood cutting plants of pepino cv. Xotus in sand-potted culture were
treated with 200 ml Hoagland nutrient solution with or without additional 25 mM NaCl twice a week
for 2 months, and exposed to 350 +/- 10, 700 +/- 10 or 1050 +/- 10 ppm CO2 in controlled
environment chambers during the last month of the experiment. Both NaCl salinity in the rhizosphere
and atmospheric CO2 enrichment reduced the leaf content of total chlorophyll, chlorophyll a and
chlorophyll b, as well as stomatal conductance and transpiration rate, but raised intercellular CO2
concentration and C2H4 emission of leaves. Minimal fluorescence yield, maximal fluorescence yield,
variable fluorescence yield of dark-adapted leaves, optimal quantum yield and effective quantum yield
of PS II, photochemical quenching coefficient, net photosynthetic rate, leaf water-potential, and
photosynthetic water-use efficiency decreased under NaCl stress, but rose with an increase of the
atmospheric CO2 concentration. In addition, the non-photochemical quenching coefficient and the
dark respiration rate of leaves increased due to NaCl salinity and decreased at high CO2 conditions.
On average, net photosynthetic rate and photosynthetic water-use efficiency of leaves decreased by
26-35% and 19-29% due to the presence of NaCl stress in the root medium, but increased by 75-98%
and 85-123% at 700 ppm CO2, and by 72-91% and 124-147% at 1050 ppm CO2 in comparison with
350 ppm CO2 treatments. Under NaCl stress, high CO2 improved photosynthetic water-use
efficiency of leaves. (C) 1999 Elsevier Science B.V. All rights reserved.

KEYWORDS: ATMOSPHERIC CO2, ELEVATED CO2, GROWTH, RESPIRATION, RESPONSES,
STRAWBERRY, STRESS


     376  
Chen, K., G.Q. Hu, N. Keutgen, and F. Lenz. 1997. Effects of CO2 concentration on strawberry.
I. Plant Growth analysis. Journal of Applied Botany-Angewandte Botanik 71(5-6):168-172.

Two-week-old strawberry (Fragaria x ananassa Duch. cv. 'Elsanta') plants were acclimatized to 300,
450, 600, 750 or 900 ppm CO2 in controlled environment chambers for 50 days, Elevated CO2
promoted plant growth as indicated by a higher number of leaves, runners and daughter plants, larger
leaf area index and dry mass per unit leaf area, increased total length of runners, plant height, canopy
diameter, and enhanced daily growth of leaf area, runner and plant biomass. In contrast, specific leaf
area and leaf area ratio of the plants decreased with increasing CO2 concentration, whereas neither
average leaf area nor average runner length was significantly affected by CO2 enrichment. When
compared with the 300 ppm CO2 treatment, 600 and 900 ppm CO2-treated plants led to a daily
increment of 1.6 and 1.9 total leaf area, 1.1 and 1.8 total runner length, and 2.5 and 3.9 plant biomass,
respectively, Increased CO2 concentration from 300 to 600 and 750 ppm markedly accelerated both
relative growth rate and net assimilation rate of the plants. Leaf weight ratio and root weight ratio
were significantly higher, while stem weight ratio was significantly lower above 600 ppm CO2 as a
result of proportionally more biomass allocated to leaves and roots than to stems. Apart from an
enhancement of plant growth, the long-term CO2 enrichment boosted vegetative propagation of
strawberry plants as well. From an economical point of view, however, it is more efficient to use
elevated CO2 concentrations of up to 600-750 ppm rather than 900 ppm for greenhouse cultivation
of strawberry.

KEYWORDS: SCIENCE


     377  
Chen, K., G.Q. Hu, N. Keutgen, and F. Lenz. 1997. Effects of CO2 concentration on strawberry.
III. Dry matter production and water consumption. Journal of Applied Botany-Angewandte Botanik
71(5-6):179-182.

Two-week-old strawberry (Fragaria x ananassa Duch. cv. 'Elsanta') plants were acclimatized to 300,
450, 600, 750 or 900 ppm CO2 in controlled environment chambers for 50 days. Elevated CO2
concentrations enhanced dry matter production, the root/shoot ratio and total water consumption of
the plants. High CO2 promoted total dry matter increment and total leaf area increment of the plants,
and improved dry matter- production efficiency and plant water-use efficiency. Water- consumption
rate of plants and water-uptake efficiency of roots, however, declined at CO2-enriched conditions.
In comparison with the 300 ppm CO2 treatment, 600 and 900 ppm CO2- grown plants increased dry
matter-production efficiency by 37 % and 67 %, water-use efficiency by 137 % and 272 %, while
reduced water-consumption rate by 39 % and 55 %, and water- uptake efficiency of roots by 53 %
and 76 %, respectively. Increasing CO2 concentrations from 300 to 900 ppm enabled strawberry
plants to produce dry matter more efficiently and to use soil water more economically because it
reduced the impact of water stress on plant productivity.

KEYWORDS: ATMOSPHERIC CARBON-DIOXIDE, ECOSYSTEMS, PLANTS, RESPONSES,
ROOTS


     378  
Chen, K., G.Q. Hu, and F. Lenz. 1997. Effects of CO2 concentration on strawberry. IV.
Carbohydrate production and accumulation. Journal of Applied Botany-Angewandte Botanik 71(5-
6):183-188.

Two-week-old strawberry (Fragaria x ananassa Duch. cv. 'Elsanta') plants were acclimatized to 300,
450, 600, 750 or 900 ppm CO2 in controlled environment chambers for 50 days. Increasing CO2
concentration from 300 to 900 ppm promoted carbohydrate production of the plants, and
subsequently increased carbohydrate accumulation in the plant organs, especially starch in leaves.
Relative distribution of non- structural carbohydrates decreased in leaves and stems at 750 and 900
ppm CO2, increased in roots from 300 to 750 ppm CO2. Elevating CO2 concentration from 300 to
750 ppm reduced the proportions of glucose, fructose, and sucrose, but raised the proportion of
starch in non-structural carbohydrates of the plants, as well as increased starch/sucrose ratio in leaves,
stems, and whole plants. CO2 enrichment up to 900 ppm improved carbohydrate-production
efficiency of the plants. This effect was particularly pronounced for starch. In comparison with 300
ppm CO2-grown plants, those treated by 600 and 900 ppm CO2 raised starch-, glucose-, fructose-,
sucrose-, and non- structural carbohydrate-production efficiency by 2.6 and 16.1 fold, 1.6 and 2.1
fold, 0.6 and 1.0 fold, 0.8 and 1.6 fold, and 1.2 and 3.5 fold, respectively.

KEYWORDS: CARBON DIOXIDE, ENRICHMENT, ROOTS


     379  
Chen, K., G.Q. Hu, and F. Lenz. 1997. Effects of CO2 concentration on strawberry. V.
Macronutrient uptake and utilization. Journal of Applied Botany-Angewandte Botanik 71(5-6):189-
194.

Two-week-old strawberry (Fragaria x ananassa Duch. cv. 'Elsanta') plants were acclimatized to 300,
450, 600, 750 or 900 ppm CO2 in controlled environment chambers for 50 days. Raising CO2
concentration from 300 to 900 ppm promoted macronutrient accumulation in all organs of the plants,
particularly in roots. It, however, reduced contents of macronutrients in most organs of the plants,
especially in leaves, because of the dilution effect of larger amounts of carbohydrate accumulation
in the plant organs. When compared with the 300 ppm CO2 treatment, 600 and 900 ppm CO2
increased accumulation of N by 93 % and 87 %, P by 113 % and 122 %, K by 98 % and 92 %, Ca
by 212 % and 244 %, and Mg by 177 % and 200 %, respectively CO2 enrichment decreased the
proportions of N and K, increased those of Ca and Mg, but did not affect the proportion of P in the
plants. Increasing CO2 levels depressed macronutrient-uptake efficiency of the plant roots, but
promoted macronutrient-use efficiency of the plants. In comparison with the 300 ppm CO2-treated
plants, those treated with 600 and 900 ppm CO2 showed lower N-, P-, K-, Ca, and Mg- uptake
efficiency of the roots and higher N-, P-, K-, Ca-, and Mg-use effficiency of the plants.

KEYWORDS: ECOSYSTEMS, ELEVATED CO2, ENRICHMENT, GROWTH, NITROGEN,
PHOSPHORUS, RESPONSES, STRESS, TREES


     380  
Chen, K., G.Q. Hu, and F. Lenz. 1997. Effects of CO2 concentration on strawberry. VI. Fruit yield
and quality. Journal of Applied Botany-Angewandte Botanik 71(5-6):195-200.

Two-week-old strawberry (Fragaria x ananassa Duch. cv. 'Elsanta') plants were acclimatized to 300,
450, 600, 750 or 900 ppm CO2 in controlled environment chambers for 50 and 60 days during
vegetative growth in late autumn of 1995 and reproductive growth in early spring of 1996. High CO2
promoted branch-crown and pedicel development as well as flower-bud differentiation. It also
induced a second bloom. Flowering and fruit ripening started earlier and lasted for a longer period
under high rather than low CO2 concentrations. CO2 enrichment shortened the periods of anthesis
and single fruit growth but prolonged the periods of flowering and fruit harvest. Elevated CO2
concentrations enhanced fruit productivity as indicated by increases in pedicel number per plant, fruit
setting per pedicel, fruit size, and dry matter content of the fruits. In comparison with the 300 ppm
CO2 treatment, 450, 600, 750, and 900 ppm CO2 increased average fruit yield per plant by 0.7, 2.7,
3.6, and 4.1 fold, daily growth per fresh fruit by 0.4, 1.0, 1.1, and 1.3 fold, and growth rate of fruit
biomass per plant by 1.0, 3.9, 5.5, and 6.9 fold, respectively. High CO2 tended to improve fruit
quality as well. Raising CO2 concentrations accelerated dry matter increment and total sugar
accumulation in the fruits, especially for sucrose, and decreased titratable acid content, resulting in
a higher sugar/acid ratio of the fruits. Contents of starch and minerals in the fruits slightly decreased
when CO2 rose.

KEYWORDS: ENRICHMENT


     381  
Chen, K., and F. Lenz. 1997. Responses of strawberry to doubled CO2 concentration and
phosphorus deficiency .1. Distribution of dry matter, macronutrients, and carbohydrates.
Gartenbauwissenschaft 62(1):30-37.

One-year-old strawberry (Fragaria x ananassa Duch. cv. 'Elsanta') plants grown in controlled
environmental chambers were supplied with a modified P-sufficient (0.5 mmol P l(-1)) or P-deficient
(0.05 mmol P l(-1)) Hoagland nutrient solution and acclimatized by an ambient CO2 (340 +/- 20
ppm) or doubled CO2 (680 +/- 20 ppm) concentration for one month. Doubled CO2 concentration
promoted plant vegetative growth and dry matter assimilation, especially in leaf area enlargement,
leaf dry weight, and runner extending growth. The plant responses to doubled CO2 concentration
were more pronounced under P- sufficient than P-deficient conditions. P deficiency not only
moderated the above plant responses to CO2 enrichment, but also accelerated premature leaf
senescence and aggravated P- deficient symptoms at doubled CO2 concentration. The mean
increment in total dry matter of the plants in virtue of doubled CO2 concentration and P-sufficiency
were 25-63 % and 123-191 %, respectively. Doubled CO2 concentration reduced N level in the plant
organs, particularly in both new and old leaves and runners, while increased the contents of starch,
glucose, fructose, sucrose, and total non-structural carbohydrates in most organs; but not particularly
affected contents of P, K, Ca, and Mg. P deficiency decreased contents of N, P, K, Mg, and soluble
carbohydrates, while increased root : shoot ratio and starch level in roots, stems, runners, and leaves
whether at the ambient CO2 or at doubled CO2 condition. Neither doubled CO2 nor P deficiency
definitely altered Ca content in the plant organs.

KEYWORDS: ATMOSPHERIC CO2, CARBON DIOXIDE, ENRICHMENT, GROWTH,
INCREASES, PLANTS, YIELD


     382  
Chen, S.G., I. Impens, and R. Ceulemans. 1997. Modelling the effects of elevated atmospheric
CO2 on crown development, light interception and photosynthesis of poplar in open top chambers.
Global Change Biology 3(2):97-106.

An open-top chamber experiment was carried out to examine the likely effects of elevated
atmospheric [CO2] on architectural as well as on physiological characteristics of two poplar clones
(Populus trichocarpa x P. deltoides clone Beaupre and P. deltoides x P. nigra clone Robusta). Crown
architectural parameters required as input parameters for a three-dimensional (3D) model of poplar
structure, such as branching frequency and position, branch angle, internode length and its distribution
pattern, leaf size and orientation, were measured following growth in ambient and elevated [CO2]
(ambient + 350 mu mol mol(-1)) treated open-top chambers. Based on this information, the light
interception and photosynthesis of poplar canopies in different [CO2] treatments were simulated using
the 3D poplar tree model and a 3D radiative transfer model at various stages of the growing season.
The first year experiments and modelling results showed that the [CO2] enrichment had effects on
light intercepting canopy structure as well as on leaf photosynthesis properties. The elevated [CO2]
treatment resulted in an increase of leaf area, canopy photosynthetic rate and above- ground biomass
production of the two poplar clones studied. However, the structural components responded less than
the process components to the [CO2] enrichment. Among the structural components, the increase
of LAI contributed the most to the canopy light interception and canopy photosynthesis; the change
of other structural aspects as a whole caused by the [CO2] enrichment had little effect on daily
canopy light interception and photosynthesis.

KEYWORDS: CANOPY STRUCTURE, CARBON DIOXIDE, FORESTS, GROWTH, PLANTS,
POPULUS, SYSTEM


     383  
Chen, S.G., I. Impens, and R. Ceulemans. 1997. Modelling the effects of elevated atmospheric
CO2 on crown development, light interception and photosynthesis of poplar in open top chambers
(vol 3, pg 97, 1997). Global Change Biology 3(6):550.



     384  
Chen, X.M., G.B. Begonia, D.M. Alm, and J.D. Hesketh. 1993. Responses of soybean leaf
photosynthesis to co2 and drought. Photosynthetica 29(3):447-454.

Soybean [Glycine max (L.) Merr. cv. Jack] was grown in the field in rain-protected plots to study
effects of drought and atmospheric CO2 enrichment. on leaf gas exchange. Midday depressions in leaf
photosynthetic CO2 exchange rates (P(N)) were found in drought-stressed plants and the diurnal
changes were mostly stomatal-regulated, although accumulated drought stress eventually resulted in
some non-stomatal limitations. However, seasonal changes in P(N) were mostly limited by non-
stomatal factors. Water use efficiency was always higher for drought stressed plants and depended
on the severity of stress and associated stomatal or nonstomatal limitations. At enriched atmospheric
CO2 levels, stomatal limitations to P(N) under drought stress were less important than at ambient
atmospheric CO2 levels. Morning and afternoon leaf starch levels were enhanced in both irrigated and
nonirrigated plants in enriched CO2. Afternoon starch levels were higher in stressed leaves than in
non-stressed leaves at normal CO2 levels.

KEYWORDS: AIR, EXPOSURE, RATES, STRESS, WATER DEFICIT


     385  
Chen, X.M., G.B. Begonia, and J.D. Hesketh. 1995. Soybean stomatal acclimation to long-term
exposure to co2- enriched atmospheres. Photosynthetica 31(1):51-57.

Soybean [Glycine max (L.) cv. Jack] grown in open top chambers under controlled laboratory and
field conditions was used to study the acclimation of leaf gas exchange processes to CO2 enrichment.
Air inside the open top chambers was maintained at either 700-800 or 350-400 mu mol(CO2) mol(-
1)(air). Leaf gas exchange rates were measured for some plants switched between treatments. When
measured in the CO2-enriched atmosphere, stomatal conductances (g(s)) were higher in leaves grown
in CO2-enriched atmospheres than in those grown under ambient conditions, and the lower g(s)
values for plants in the CO2- enriched atmospheres were limiting to leaf net photosynthetic CO2
exchange rates (P-N). P-N of enriched leaves was higher than those of the ambient controls when
measured at elevated CO2 levels in both controlled environment and field studies, while it was
depressed in enriched leaves when measured under ambient CO2 conditions, and this drop in P-N did
not recover until 6-15 d after plants were placed back in ambient conditions.

KEYWORDS: CARBON DIOXIDE, CO2- ENRICHMENT, PHOTOSYNTHETIC INHIBITION


     386  
Chenevard, D., C. Jayallemand, M. Gendraud, and J.S. Frossard. 1995. The effect of sucrose
on the development of hybrid walnut microcuttings (juglans-nigra X juglans-regia) - consequences
on their survival during acclimatization. Annales Des Sciences Forestieres 52(2):147-156.

We studied the effect of sucrose concentration in the root- development medium on the formation
of adventitious roots and survival of microcuttings during acclimatization in 2 interspecific hybrid
walnut (Juglans nigra n degrees 23 x J regia) clones. Sucrose increased the rooting percentage (fig
1), the number of adventitious roots (fig 2A) and the dry- matter content (table I) per rooted shoot.
These effects were due to the energy properties of sucrose rather than to its osmotic function. High
sucrose concentrations in the root- development medium (> 20 g.l(-1)) resulted in a high soluble
carbohydrate content in the plantlets (fig 3), mainly located in roots and callus. The 2-clones showed
different capacities in rooting and growth. Survival of microcuttings during acclimatization was not
directly influenced by the sucrose concentration (fig 5) but was correlated with the number of
adventitious roots (fig 6A) as well as with the number of leaves (fig 6B) present at the time of transfer
to the growth chamber for each individual plant.

KEYWORDS: ACCUMULATION, CO2- ENRICHMENT, CULTURE, GROWTH, INVITRO,
PLANTS, PROPAGATION, SHOOT, TEMPERATURE


     387  
Cheng, S.H., B.D. Moore, and J.R. Seemann. 1998. Effects of short- and long-term elevated CO2
on the expression of ribulose-1,5-bisphosphate carboxylase/oxygenase genes and carbohydrate
accumulation in leaves of Arabidopsis thaliana (L) Heynh. Plant Physiology 116(2):715-723.

To investigate the proposed molecular characteristics of sugar- mediated repression of photosynthetic
genes during plant acclimation to elevated CO2, we examined the relationship between the
accumulation and metabolism of,nonstructural carbohydrates and changes in ribulose-1,5-
bisphosphate carboxylase/oxygenase (Rubisco) gene expression in leaves of Arabidopsis thaliana
exposed to elevated CO2. Long-term growth of Arabidopsis at high CO2 (1000 mu L L-1) resulted
in a 2-fold increase in nonstructural carbohydrates, a large decrease in the expression of Rubisco
protein and in the transcript of rbcL, the gene encoding the large subunit of Rubisco (approximately
35-40%), and an even greater decline in mRNA of rbcS, the gene encoding the small subunit
(approximately 60%). This differential response of protein and mRNAs suggests that
transcriptional/posttranscriptional processes and protein turnover may determine the final amount of
leaf Rubisco protein at high CO2. Analysis of mRNA levels of individual rbcS genes indicated that
reduction in total rbcS transcripts was caused by decreased expression of all four rbcS genes. Short-
term transfer of Arabidopsis plants grown at ambient CO2 to high CO2 resulted in a decrease in total
rbcS mRNA by d 6, whereas Rubisco content and rbcL mRNA decreased by d 9. Transfer to high
CO2 reduced the maximum expression level of the primary rbcS genes (1A and, particularly, 3B) by
limiting their normal pattern of accumulation through the night period. The decreased nighttime levels
of rbcS mRNA were associated with a nocturnal increase in leaf hexoses. We suggest that prolonged
nighttime hexose metabolism resulting from exposure to elevated CO2 affects rbcS transcript
accumulation and, ultimately, the level of Rubisco protein.

KEYWORDS: CARBON METABOLISM, LEAF DEVELOPMENT, MESSENGER-RNA,
METABOLIC REPRESSION, PHOTOSYNTHESIS, RBCS GENES, SMALL-SUBUNIT, TOMATO
PLANTS, TRANSGENIC TOBACCO PLANTS, YEAST- DERIVED INVERTASE


     388  
Cheng, W.X. 1999. Rhizosphere feedbacks in elevated CO2. Tree Physiology 19(4-5):313-320.

Understanding rhizosphere processes in relation to increasing atmospheric CO2 concentrations is
important for predicting the response of forest ecosystems to environmental changes, because
rhizosphere processes are intimately linked with nutrient cycling and soil organic matter
decomposition, both of which feedback to tree growth and soil carbon storage. Plants grown in
elevated CO2 substantially increase C input to the rhizosphere. Although it is known that elevated
CO2 enhances rhizosphere respiration more than it enhances root biomass, the fate and function of
this extra carbon input to the rhizosphere in response to elevated CO2 are not clear. Depending on
specific plant and soil conditions, the increased carbon input to the rhizosphere can result in an
increase, a decrease, or no effect on soil organic matter decomposition and nutrient mineralization.
Three mechanisms may account for these inconsistent results: (1) the "preferential substrate
utilization" hypothesis; (2) the "priming effect" hypothesis; and (3) the "competition" hypothesis, i.e.,
competition for mineral nutrients between plants and soil microorganisms. A microbial growth model
is developed that quantitatively links the increased rhizosphere input in response to elevated CO2 with
soil organic matter decomposition. The model incorporates the three proposed mechanisms, and
simulates the complexity of the rhizosphere processes. The model also illustrates mechanistically the
interactions among nitrogen availability, substrate quality, and microbial dynamics when the system
is exposed to elevated CO2.

KEYWORDS: ATMOSPHERIC CARBON-DIOXIDE, CLIMATE CHANGE, LONG-TERM,
MICROBIAL BIOMASS, MYCORRHIZAL COLONIZATION, NITROGENASE ACTIVITY, PINE
SEEDLINGS, PISUM-SATIVUM, QUERCUS-ALBA, SOIL ORGANIC MATTER


     389  
Cheng, W.X., and D.W. Johnson. 1998. Elevated CO2, rhizosphere processes, and soil organic
matter decomposition. Plant and Soil 202(2):167-174.

The rhizosphere is one of the key fine-scale components of C cycles. This study was undertaken to
improve understanding of the potential effects of atmospheric CO2 increase on rhizosphere processes.
Using C isotope techniques, we found that elevated atmospheric CO2 significantly increased wheat
plant growth, dry mass accumulation, rhizosphere respiration, and soluble C concentrations in the
rhizosphere. When plants were grown under elevated CO2 concentration, soluble C concentration
in the rhizosphere increased by approximately 60%. The degree of elevated CO2 enhancement on
rhizosphere respiration was much higher than on root biomass. Averaged between the two nitrogen
treatments and compared with the ambient CO2 treatment, wheat rhizosphere respiration rate
increased 60% and root biomass only increased 26% under the elevated CO2 treatment. These results
indicated that elevated atmospheric CO2 in a wheat-soil system significantly increased substrate input
to the rhizosphere due to both increased root growth and increased root activities per unit of roots.
Nitrogen treatments changed the effect of elevated CO2 on soil organic matter decomposition.
Elevated CO2 increased soil organic matter decomposition (22%) in the nitrogen-added treatment
but decreased soil organic matter decomposition (18%) without nitrogen addition. Soil nitrogen
status was therefore found to be important in determining the directions of the effect of elevated CO2
on soil organic matter decomposition.

KEYWORDS: ATMOSPHERIC CARBON-DIOXIDE, CLIMATE CHANGE, ENRICHMENT,
GLOBAL CHANGE, GROWTH, NITROGENASE ACTIVITY, PINE SEEDLINGS, PISUM-
SATIVUM, RESPONSES, SYSTEM


     390  
Chernikova, T., J.M. Robinson, E.H. Lee, and C.L. Mulchi. 1997. Evaluation of ozone tolerance
mechanisms in soybean cultivars exposed to ambient and elevated CO2. Plant Physiology
114(3):201.



     391  
Chmora, S.N., and A.T. Mokronosov. 1994. The global increase of co2 in the atmosphere -
adaptive strategies in plants. Russian Journal of Plant Physiology 41(5):677-685.

The effects of short- and long-term exposure to increased CO2 concentrations on the life activity and
productivity of plants are discussed. Two strategies of plant adaptation to an increasing CO2
concentration are outlined that reflect the diversity of adaptive plant responses at the ecological and
physiological levels: physiological adaptation that occurs at all organization levels from molecular to
cenotic and changes in areas of species that lead to changes in ecosystem composition occurring in
correspondence to the biochemical diversity of photosynthetic pathways.

KEYWORDS: CARBON DIOXIDE, ELEVATED CO2, ENRICHMENT, GROWTH,
PHOTOSYNTHESIS, WHEAT, YIELD


     392  
Chomba, B.M., R.D. Guy, and H.G. Weger. 1993. Carbohydrate reserve accumulation and
depletion in engelmann spruce (picea-engelmannii parry) - effects of cold-storage and prestorage co2
enrichment. Tree Physiology 13(4):351-364.

The effects of pre-storage CO2 enrichment on growth, non- structural carbohydrates and post-
storage root growth potential of Engelmann spruce (Picea engelmannii Parry) seedlings were studied.
Seedlings were grown from seed for 202 days in growth chambers with ambient (340 mu l l(-1)) or
CO(2)ched (1000 mu l l(-1)) air. Some seedlings were transferred between CO2 treatments at 60 and
120 days. Photoperiod was reduced at 100 days to induce bud set and temperature was reduced at
180 days to promote frost hardiness development for storage at -5 degrees C for 2 or 4 months.
Stored seedlings were planted in a growth chamber after thawing for one week at +5 degrees C. At
80, 120, 140 and 202 days, and at each planting time after storage, seedlings were harvested for
growth measurements and analysis of starch and soluble sugar concentrations. Planted seedlings were
assessed for bud break every two days and new roots > 5 mm long were counted after four weeks.
Carbon dioxide enrichment increased root collar diameter and almost doubled seedling biomass, with
the most obvious effects occurring after bud set. Stem height was affected only slightly and
shoot/root ratios were not affected at all. Carbon dioxide enrichment increased the rate of reserve
carbohydrate accumulation, but did not influence the final concentration attained before storage
(accounting for 32% of seedling dry weight). Needles were the major storage organ for soluble
sugars, whereas roots were the major storage organ for starch. Soluble sugars were not strongly
affected by two or four months of storage, but starch was reduced by more than 50% in all plant
parts. None of the CO2 treatments had an impact on bud break or root growth potential.



     393  
Christ, R.A., and C. Korner. 1995. Responses of shoot and root gas-exchange, leaf blade expansion
and biomass production to pulses of elevated co2 in hydroponic wheat. Journal of Experimental
Botany 46(292):1661-1667.

Short-term effects of elevated CO2 during the early life phase of plants may have long lasting
consequences for growth and biomass in later periods. We exposed hydroponically grown wheat
seedlings to 5 d pulses of elevated CO2 while leaf expansion growth as well as shoot and root gas
exchange were measured simultaneously and continuously. Shoot photosynthesis, night- time shoot
respiration and below-ground respiration (largely by roots) roughly doubled when atmospheric CO2
concentration was doubled. An interruption of CO2 enrichment caused CO2 assimilation and
respiration to return to control levels, However, while the response of photosynthesis was immediate,
that of respiration showed a hysteresis of about 3 d. Since shoot biomass increased at elevated CO2
(with no change in allocation pattern) equal fluxes per shoot or root system after a return to control
CO2 concentrations indicate substantial downward adjustment of the capacity for CO2 fixation and
release in high-CO2 grown plants. Leaf expansion growth was completely unaffected by CO2
enrichment, whereas tiller initiation was significantly increased (doubled in 18 d). We conclude that
leaf growth in these wheat plants was already carbon-saturated at ambient CO2 concentration at
optimum mineral nutrient supply. The stimulation of growth of whole plants was exclusively due to
enhanced tillering during this very early part of the life of these wheat plants.

KEYWORDS: CARBON-DIOXIDE ENRICHMENT, EXTENSION, FIELD, GROWTH, LEAVES,
PLANTS, RESPIRATION, TEMPERATURE, WINTER-WHEAT, YIELD


     394  
Christensen, T.R., S. Jonasson, T.V. Callaghan, and M. Havstrom. 1999. On the potential CO2
release from tundra soils in a changing climate. Applied Soil Ecology 11(2-3):127-134.

About 30% of the carbon in terrestrial ecosystems is stored in northern wetlands and boreal forest
regions. Prevailing cold and wet soil conditions have largely been responsible for this carbon
accumulation. It has been suggested that a warmer and drier climate in these regions might increase
the decomposition rate and, hence, release more CO2 to the atmosphere than at present. This study
reports on the spatial variability and temperature dependence of the potential carbon release after
incubating highly organic soils from the European Arctic and Siberia at different temperatures. We
found that the decay potential, measured as CO2 production in laboratory experiments, differed
strongly within and among sites, particularly at higher soil temperatures. Furthermore, both the decay
potential and its temperature response decreased significantly with depth in the soil, presumably
because the older soils at deeper layers contained higher proportions of recalcitrant carbon than the
younger soil organic matter at the surface. These results have implications for global models of
potential feedbacks on climate change inferred from changes in the carbon balance of northern
wetlands and tundra. Firstly, because the decay potential of the organic matter varies locally as well
as regionally, predictions of how the tundra carbon balance may change will be unreliable if these are
based on measurements at a few sites only. Secondly, any increase in CO2 production may be
transitional as both the carbon flux and its temperature sensitivity decrease when the most easily
degradable organic material near the soil surface has decomposed. Consequently, it is crucial to
account for transient responses and regional differences in the models of potential feedbacks on
climate change from changed carbon cycling in northern terrestrial ecosystems. (C) 1999 Elsevier
Science B.V.

KEYWORDS: ARCTIC TUNDRA, ATMOSPHERIC CARBON-DIOXIDE, FLUX, SINK


     395  
Christensen, T.R., S. Jonasson, T.V. Callaghan, M. Havstrom, and F.R. Livens. 1999. Carbon
cycling and methane exchange in Eurasian tundra ecosystems. Ambio 28(3):239-244.

This paper provides an overview of data and results obtained through a number of studies of actual
and potential trace gas exchanges in northern Eurasia, made possible through the Swedish-Russian
Tundra Ecology -94 expedition. It was found that: i) long-term accumulation rates of carbon in
organic tundra soils, i.e. net uptake of atmospheric CO2, correlated with simple climatic parameters,
such as mean July temperature and annual precipitation; ii) the release of carbon through ecosystem
respiration is also strongly controlled by climate. Increased temperature and decrease of water-
logging enhanced the CO2 flux. However, the release of organic soil carbon as CO2 is also
constrained by other factors such as poor decomposability of the stored organic compounds; and iii)
methane emissions from typical tundra habitats in northern Eurasia were found to be slightly lower
than from seemingly similar habitats in North America. This difference can probably be attributed to
lower temperatures along the Russian arctic coast than at North American sites in general.

KEYWORDS: DIOXIDE, EMISSION


     396  
Chu, C.C., J.S. Coleman, and H.A. Mooney. 1992. Controls of biomass partitioning between roots
and shoots - atmospheric co2 enrichment and the acquisition and allocation of carbon and nitrogen
in wild radish. Oecologia 89(4):580-587.

The effects of CO2 enrichment on plant growth, carbon and nitrogen acquisition and resource
allocation were investigated in order to examine several hypotheses about the mechanisms that govern
dry matter partitioning between shoots and roots. Wild radish plants (Raphanus sativus x
raphanistrum) were grown for 25 d under three different atmospheric CO2 concentrations (200 ppm,
330 ppm and 600 ppm) with a stable hydroponic 150-mu- mol l-1 nitrate supply. Radish biomass
accumulation, photosynthetic rate, water use efficiency, nitrogen per unit leaf area, and starch and
soluble sugar levels in leaves increased with increasing atmospheric CO2 concentration, whereas
specific leaf area and nitrogen concentration of leaves significantly decreased. Despite substantial
changes in radish growth, resource acquisition and resource partitioning, the rate at which leaves
accumulated starch over the course of the light period and the partitioning of biomass between roots
and shoots were not affected by CO2 treatment. This phenomenon was consistent with the hypothesis
that root/shoot partitioning is related to the daily rate of starch accumulation by leaves during the
photoperiod, but is inconsistent with hypotheses suggesting that root/shoot partitioning is controlled
by some aspect of plant C/N balance.

KEYWORDS: CARROT, COMPETITION, DIOXIDE, ELEVATED CO2, MODEL, NITRATE,
PLANT GROWTH, PROGRAM, RESPONSES, TOMATO


     397  
Chu, C.C., C.B. Field, and H.A. Mooney. 1996. Effects of CO2 and nutrient enrichment on tissue
quality of two California annuals. Oecologia 107(4):433-440.

The effects of CO2 enrichment and soil nutrient status on tissue quality were investigated and related
to the potential effect on growth and decomposition. Two California annuals, Avena fatua and
Plantago erecta, were grown at ambient and ambient plus 35 Pa atmospheric CO2 in nutrient
unamended and amended serpentine soil. Elevated CO2 led to significantly increased Avena shoot
nitrogen concentrations in the nutrient amended treatment. It also led to decreased lignin
concentrations in Avena roots in both nutrient treatments, and in Plantago shoots and roots with
nutrient addition. Concentrations of total nonstructural carbohydrate (TNC) and carbon did not
change with elevated CO2 in either species. As a consequence of increased biomass accumulation,
increased CO2 led to larger total pools of TNC, lignin, total carbon, and total nitrogen in Avena with
nutrient additions. Doubling CO2 had no significant effect on Plantago. Given the limited changes in
the compounds related to decomposibility and plant growth, effects of increased atmospheric CO2
mediated through tissue composition on Avena and Plantago are likely to be minor and depend on
site fertility. This study suggests that other factors such as litter moisture, whether or not litter is on
the ground, and biomass allocation among roots and shoots, are likely to be more important in this
California grassland ecosystem. CO2 could influence those directly as well as indirectly.

KEYWORDS: ATMOSPHERIC CO2, CARBON DIOXIDE, ELEVATED CO2, LIGNIN CONTROL,
LITTER DECOMPOSITION, LONG-TERM DECOMPOSITION, NITROGEN, PLANTS,
RESPONSES, SCOTS PINE FOREST


     398  
Ciais, P., P. Friedlingstein, D.S. Schimel, and P.P. Tans. 1999. A global calculation of the delta
C-13 of soil respired carbon: Implications for the biospheric uptake of anthropogenic CO2. Global
Biogeochemical Cycles 13(2):519-530.

The continuing emissions of fossil CO2 depleted in C-13 have been causing a gradual decrease in
atmospheric delta(13)C by roughly 1.4 parts per thousand since preindustrial times. The progressive
penetration of this perturbation into the land biota causes the soil organic matter to be enriched in
13C with respect to recently formed plant material. This effect which we call the "biotic isotope
disequilibrium" is important when it comes to deducing the terrestrial carbon fluxes by using
delta(13)C in atmospheric CO2. We have estimated the geographical distribution of the isotopic
disequilibrium, which is primarily influenced by the turnover of carbon in the various ecosystems,
from the output of two biospheric models, (SLAVE and CENTURY). The disequilibrium is estimated
to shift up the delta(13)C of atmospheric CO2 by the same amount as a net sink of 0.6 Gt C yr(-1)
in the land biota. This "fake" terrestrial sink due to the isotopic disequilibrium is distributed mainly
in northern midlatitudes (0.2 Gt C yr(-1)) and tropical forests (0.3 Gt C yr(-1)).

KEYWORDS: ATMOSPHERIC CO2, ISOTOPE, SIMULATION, TURNOVER, WORLDWIDE


     399  
Cipollini, M.L., B.G. Drake, and D. Whigham. 1993. Effects of elevated co2 on growth and
carbon/nutrient balance in the deciduous woody shrub lindera benzoin (L.) blume (lauraceae).
Oecologia 96(3):339-346.

We examined the effects of elevated CO2 on growth and carbon/nutrient balance in a natural
population of the deciduous temperate zone shrub Lindera benzoin. Our data concern whole plant,
leaf, and stem growth for the first two seasons of a long-term field experiment in which CO2 levels
were manipulated in situ. In addition to growth parameters, we evaluated changes in leaf and stem
chemistry, including total nitrogen, nonstructural carbohydrates, and total phenolics. Over the course
of this study, L. benzoin appeared to respond to elevated CO2 primarily by physiological and
biochemical changes, with only a slight enhancement in aboveground growth (ramet height). Positive
effects on aboveground growth were primarily evident in young (nonreproductive) ramets. Our
results suggest that nitrogen limitation may have constrained plants to allocate carbohydrates
produced in response to elevated CO2 primarily to storage and belowground growth, and perhaps
to increased secondary chemical production, rather than to increased stem and leaf growth. We
discuss our results in terms of changes in carbon/nutrient balance induced by elevated CO2, and
provide predictions for future changes in this system based upon constraints imposed by intrinsic and
extrinsic factors and their potential effects on the reallocation of stored reserves.

KEYWORDS: ATMOSPHERIC CO2, AVAILABILITY, CARBON-DIOXIDE CONCENTRATION,
ENRICHMENT, FOREST, NITROGEN, PHOTOSYNTHESIS, PLANTS, RESPONSES, TREES


     400  
Clark, D.G., J.W. Kelly, and N.C. Rajapakse. 1993. Production and postharvest characteristics
of rosa-hybrida L meijikatar grown in pots under carbon-dioxide enrichment. Journal of the American
Society for Horticultural Science 118(5):613-617.

The effects of carbon dioxide enrichment on growth, photosynthesis, and postharvest characteristics
of 'Meijikatar' potted roses were determined. Plants were grown in 350, 700, or 1050 mul CO2/liter
until they reached 50% flower bud coloration and then were placed into dark storage for 5 days at
4 or 16C. Plants grown in 700 or 1050 mul CO2/liter reached the harvest stage earlier and were taller
at harvest than plants produced in 350 mul CO2/liter, but there were no differences in the number of
flowers and flower buds per plant among CO2 treatments. Plants grown in early spring were taller
and had more flowers and flower buds than plants grown in late winter. Shoot and root growth of
plants grown in 700 or 1050 mul CO2/liter were higher than in plants produced in 350 mul CO2/liter,
with plants grown in early spring showing greater increases than plants grown in late winter.
Immediately after storage, plants grown in 350 mul CO2/liter and stored at 4C had the fewest
etiolated shoots, while plants grown in 1050 mul CO2/liter and stored at 16C had the most. Five days
after removal from storage, chlorophyll concentration of upper and lower leaves had been reduced
by almost-equal-to 50% from the day of harvest. Carbon dioxide enrichment had no effect on
postharvest leaf chlorosis, but plants grown in early spring and stored at 16C had the most leaf
chlorosis while plants grown in late winter and stored at 4C had the least leaf chlorosis.

KEYWORDS: CO2- ENRICHMENT, ENVIRONMENT, LIGHT, MORIFOLIUM RAMAT, N,N-
DIMETHYLFORMAMIDE, PLANTS, RESPONSES


     401  
Clark, H., P.C.D. Newton, and D.J. Barker. 1999. Physiological and morphological responses to
elevated CO2 and a soil moisture deficit of temperate pasture species growing in an established plant
community. Journal of Experimental Botany 50(331):233-242.

Periods of limited soil water availability are a feature of many temperate pasture systems and these
have the potential to modify pasture plant and community responses to elevated atmospheric CO2.
Using large pasture turves, previously exposed to elevated CO2 concentrations of 350 or 700 mu mol
mol(-1) for 324 d under well-watered conditions, the morphological and physiological responses of
pasture species growing at these CO2 concentrations were compared when subjected to a soil
moisture deficit-and to recovery from the deficit-with those that continued to be well watered. Net
leaf photosynthesis of Trifolium repens (C-3 legume), Plantago lanceolata (C-3) and Paspalum
dilatatum (C-4) was increased by exposure to elevated CO2, but there was no consistent effect of
CO2 on stomatal conductance. At low soil moistures, net photosynthesis declined and stomatal
conductance increased in these three species. There was a strong CO2 x water interaction in respect
of net photosynthesis; in Trifolium repens, for example, elevated CO2 increased net photosynthesis
by approximately 50% under well- watered conditions and this increased to over 300% when soil
moisture levels reached their minimum values. Similar values were recorded for both Paspalum
dilatatum and Plantago lanceolata. Potential water use efficiency (net photosynthesis/stomatal
conductance) was increased by both exposure to elevated CO2 and drought. Leaf water status was
measured in three species: Trifolium repens, Paspalum dilatatum and Holcus lanatus (C-3). Total leaf
water potential (psi(t)) and osmotic potential (psi(pi)) were decreased by drought, but CO2
concentration had no consistent effect. psi(t) and psi(pi) were highest in the C-4 species Paspalum
dilatatum and lowest in the legume Trifolium repens. In the wet turves, rates of leaf extension of the
C-3 grasses Holcus lanatus and Lolium perenne at elevated CO2 were frequently higher than those
at ambient CO2, but there was no effect of CO2 concentration on the rate recorded in the C-4 grass
Paspalum dilatatum or the rate of leaf appearance in the legume Trifolium repens. Drought reduced
leaf extension rate irrespective of CO2 in all species, but in Holcus lanatus the reduction was less
severe at elevated CO2. Immediately after the dry turves were rewatered the leaf extension rates on
tillers of Holcus lanatus and Lolium perenne were higher than on tillers in the wet turves, but only
at ambient CO2. Consequently, despite the greater leaf extension rate during the soil moisture deficit
at elevated CO2, because of the overcompensation after rewatering at ambient CO2, total leaf
extension over both the drying and rewetting period did not differ between CO2 concentrations for
these C-3 grass species. Further investigation of this difference in response between CO2 treatments
is warranted given the frequent drying and wetting cycles experienced by many temperate grasslands.

KEYWORDS: BIOMASS PRODUCTION, C-4 GRASS, CARBON-DIOXIDE CONCENTRATIONS,
GAS-EXCHANGE, LOLIUM-PERENNE, SIMULATED SEASONAL-CHANGES, STOMATAL
RESPONSES, TRIFOLIUM- REPENS, WATER-USE, WHITE CLOVER


     402  
Clark, H., P.C.D. Newton, C.C. Bell, and E.M. Glasgow. 1995. The influence of elevated co2 and
simulated seasonal-changes in temperature on tissue turnover in pasture turves dominated by
perennial ryegrass (lolium-perenne) and white clover (trifolium-repens). Journal of Applied Ecology
32(1):128-136.

1. Tissue turnover, leaf morphology and population dynamics of perennial ryegrass and white clover
were studied in pasture turves grown at ambient (350 mu molmol(-1)) or double ambient (700 mu
molmol(-1)) CO2 concentrations for 217 days in controlled environment rooms. The turves were
subjected sequentially to three day/night temperature regimes; 10/4 degrees C, 16/10 degrees C and
22/16 degrees C and harvested at 3-week intervals. The photoperiod was 12 hours for all of the
temperature treatments with a mean photon flux density of 480 mu E m(-2) s(-1). 2. Ryegrass leaf
extension and leaf death rates did not differ between CO2 treatments and there was no effect of CO2
on rates of leaf appearance in white clover. Weight per unit length of ryegrass laminae was unaffected
by elevated CO but lamina weight per unit area, lamina area and petiole weight per unit length in
white clover showed a small positive response, especially at the two higher temperatures. Rates of
growth and senescence per ryegrass tiller were therefore similar between CO2 treatments, but rates
of growth per white clover growing point were increased by 4, 23 and 13% at 10/4 degrees C, 16/10
degrees C and 22/16 degrees C, respectively, at elevated CO2. Responses to CO2 could not be
attributed to any consistent change in morphological characteristics in either species and exposure
to elevated concentrations of CO2 did not appear to change the relationship between growth and
senescence per meristem. 3. Total grass tiller populations were similar at both CO2 concentrations,
but ryegrass tiller densities more than halved in both CO2 treatments as the temperature was
increased. The fall was most severe at 700 mu mol mol(-1) and at the end of the experiment ryegrass
tiller densities in this treatment were only 47% of those found at 350 mu molmol(-1). There was no
consistent effect of CO2 concentration on clover growing point numbers and they increased from 800
m(-2) to over 3000 m(-2) in both treatments with maximum densities occurring at 22/16 degrees C.
4. The results imply that, in plant communities dominated by ryegrass and white clover, exposure to
elevated CO2 concentrations will alter the species composition in favour of white clover. Responses
in above-ground dry matter yield to elevated CO2 will be a balance between the positive response
shown by white clover and the negative response of perennial ryegrass. Temperature will have a
major influence on the magnitude of this response since both the response of white clover to CO2 and
the ratio of white clover growing points to ryegrass tillers are temperature-dependent.

KEYWORDS: ATMOSPHERIC CO2, CARBON-DIOXIDE CONCENTRATION, COMMUNITIES,
DEATH, LEAF, PHOTOSYNTHESIS, REPRODUCTIVE GROWTH, SENESCENCE, SWARDS,
TILLER


     403  
Clark, H., P.C.D. Newton, C.C. Bell, and E.M. Glasgow. 1997. Dry matter yield, leaf growth and
population dynamics in Lolium perenne Trifolium repens-dominated pasture turves exposed to two
levels of elevated CO2. Journal of Applied Ecology 34(2):304-316.

1. Dry matter yield, leaf growth and population dynamics of turves taken from an old Lolium
perenne/Trifolium repens- dominated pasture were studied in controlled environment rooms at CO2
concentrations of 350 mu mol mol(-1), 525 mu mol mol(-1) and 700 mu mol mol(-1). Starting with
September data the turves were subjected sequentially to the mean monthly temperature and
photoperiod taken from long-term climatic data for the area of New Zealand where the pasture was
located. Each temperature and photoperiod regime was applied for 21 days to provide 12 different
simulated 'months' of environmental conditions. The experiment ran for 14 simulated months, with
September and October conditions being repeated at the end of the first simulated 'year'. Mean photon
flux density throughout was 500 mu E m(-2) s(-1). 2. The total quantity of herbage harvested was
increased by 7% and 14% at 525 mu mol mol(-1) and 700 mu mol mol(-1) CO2, respectively. The
increase in the amount of T. repens harvested by the end of the experiment was 63% at 525 mu mol
mol(-1) CO2 and 48% at 700 mu mol mol(-1) CO2. In contrast, neither the yield of C3 grasses nor
the yield of the only C4 grass present, Paspalum dilatatum, was significantly affected by CO2
concentration. The implications of this increase in the proportion of T. repens in temperate pastures
at elevated CO2 is discussed briefly. 3. With the exception of a small increase in the specific leaf area
of T. repens, detailed measurements of leaf growth on marked tillers (L. perenne and P. dilatatum)
and growing points (T. repens) showed no consistent effects of exposure to elevated CO2
concentrations. 4. Differences in yield between CO2 concentrations were mainly attributable to
changes in the number and balance of population units. By the middle of the 'winter' conditions T.
repens growing point densities at 700 mu mol mol(-1) CO2 were more than double those found at
350 mu mol mol(-1) but total grass tiller densities were unchanged. Growing point densities were also
more than doubled at 525 mu mol mol(-1) CO2 compared with 350 mu mol mol(-1) but grass tiller
densities were reduced significantly below those recorded in the other two treatments. The
relationship between the stability of herbage production and population densities is discussed and the
potential interaction between population density, elevated CO2 and grazing considered. 5. Although
exposure to elevated levels of CO2 did result in large changes in population numbers, this did not
happen immediately and so the yield response of this particular community to CO2 varied with time.
The average yield increases recorded here at elevated CO2 may therefore tend to underestimate those
likely to be shown by communities that, at the population level, have become fully adapted to growth
in a CO2-enriched atmosphere.

KEYWORDS: BIOMASS PRODUCTION, CARBON DIOXIDE, ENRICHMENT, INCREASING
CO2, PHOTOSYNTHESIS, PLANT GROWTH, RESPONSES, SIMULATED SEASONAL-
CHANGES, TEMPERATURE, WHITE CLOVER


     404  
Claussen, M., and M. Esch. 1994. Biomes computed from simulated climatologies. Climate
Dynamics 9(4-5):235-243.

The biome model of Prentice et al. (1992a) is used to predict global patterns of potential natural plant
formations, or biomes, from climatologies simulated by ECHAM, a model used for climate
simulations at the Max-Planck-Institut fur Meteorologie, This study is undertaken in order to show
the advantage of this biome model in diagnosing the performance of a climate model and assessing
effects of past and future climate changes predicted by a climate model. Good overall agreement is
found between global patterns of biomes computed from observed and simulated data of present
climate. But there are also major discrepancies indicated by a difference in biomes in Australia, in the
Kalahari Desert, and in the Middle West of North America, These discrepancies can be traced back
to failures in simulated rainfall as well as summer or winter temperatures. Global patterns of biomes
computed from an ice age simulation reveal that North America, Europe, and Siberia should have
been covered largely by tundra and taiga, whereas only small differences are seen for the tropical rain
forests. A potential northeast shift of biomes is expected from a simulation with enhanced CO2
concentration according to the IPCC Scenario A. Little change is seen in the tropical rain forest and
the Sahara. Since the biome model used is not capable of predicting changes in vegetation pat terns
due to a rapid climate change, the latter simulation has to be taken as a prediction of changes in
conditions favourable for the existence of certain biomes, not as a prediction of a future distribution
of biomes.

KEYWORDS: ATMOSPHERE, MODEL


     405  
Clifford, S.C., C.R. Black, J.A. Roberts, I.M. Stronach, P.R. Singletonjones, A.D. Mohamed,
and S.N. Azamali. 1995. The effect of elevated atmospheric co2 and drought on stomatal frequency
in groundnut (arachis-hypogaea (L)). Journal of Experimental Botany 46(288):847-852.

The effects of elevated atmospheric CO2, alone or in combination with water stress, on stomatal
frequency in groundnut (Arachis hypogaea (L.) cv. Kadiri-3) were investigated. CO2 exerted
significant effects on stomatal frequency only in irrigated plants. The effects of drought on leaf
development outweighed the smaller effects of CO2 concentration, although reductions in stomatal
frequency induced by elevated atmospheric CO2 were still observed. When stands of groundnut were
grown under irrigated conditions with unrestricted root systems, an increase in atmospheric CO2
from 375 to 700 ppmv decreased stomatal frequency on both leaf surfaces by up to 16%; in
droughted plants, stomatal frequency was reduced by 8% on the adaxial leaf surface only, Elevated
atmospheric CO2 promoted larger reductions in leaf conductance than the changes in stomatal
frequency, indicating partial stomatal closure. As a result, the groundnut stands grown at elevated
CO2 utilized the available soil moisture more slowly than those grown under ambient CO2, thereby
extending the growing period. Despite the large variations in cell frequencies induced by drought,
there was no treatment effect on either stomatal index or the adaxial/abaxial stomatal frequency ratio.
The data suggest that the effects of future increases in atmospheric CO2 concentration on stomatal
frequency in groundnut are likely to be small, especially under conditions of water stress, but that the
combination of associated reductions in leaf conductance and enhanced assimilation at elevated CO2
will be important in semi-arid regions.

KEYWORDS: DENSITY, ENRICHMENT, INCREASE, RESPONSES


     406  
Clifford, S.C., I.M. Stronach, A.D. Mohamed, S.N. Azamali, and N.M.J. Crout. 1993. The
effects of elevated atmospheric carbon-dioxide and water- stress on light interception, dry-matter
production and yield in stands of groundnut (arachis-hypogaea L). Journal of Experimental Botany
44(269):1763-1770.

Stands of groundnut (Arachis hypogaea L.), a C-3 legume, were grown in controlled-environment
glasshouses at 28 degrees C (15 degrees C) under two levels of atmospheric CO2 (350 ppmv or 700
ppmv) and two levels of soil moisture (irrigated weekly or no water from 35 d after sowing). Elevated
CO2 increased the maximum rate of net photosynthesis by up to 40%, with an increase in conversion
coefficient for intercepted radiation of 30% (from 1.66 to 2.16 g MJ(-1)) in well-irrigated conditions,
and 94% (from 0.64 to 1.24 g MJ(-1)) on a drying soil profile. In plants well supplied with water,
elevated CO2 increased dry matter accumulation by 16% (from 13.79 to 16.03 t ha(-1)) and pod yield
by 25% (from 2.7 to 3.4 t ha(-1)). However, the harvest index (total pod dry weight/above-ground
dry weight) was unaffected by CO2 treatment. The beneficial effects of elevated CO2 were enhanced
under severe water stress, dry matter production increased by 112% (from 4.13 to 8.87 t ha(- 1)) and
a pod yield of 1.34 t ha(-1) was obtained in elevated CO2, whereas comparable plots at 350 ppmv
CO2 only yielded 0.22 t ha(-1). There was a corresponding decrease in harvest index from 0.15 to
0.05. Following the withholding of irrigation, plants growing on a stored soil water profile in elevated
CO2 could maintain significantly less negative leaf water potentials (P<0.01) for the remainder of the
season than comparable plants grown in ambient CO2, allowing prolonged plant activity during
drought. In plants which were well supplied with water, allocation of dry matter between leaves,
stems, roots, and pods was similar in both CO2 treatments. On a drying soil profile, allocation in
plants grown in 350 ppmv CO2 changed in favour of root development far earlier in the season than
plants grown at 700 ppmv CO2, indicating that severe water stress was reached earlier at 350 ppmv
CO2. The primary effects of elevated CO2 on growth and yield of groundnut stands were mediated
by an increase in the conversion coefficient for intercepted radiation and the prolonged maintenance
of higher leaf water potentials during increasing drought stress.

KEYWORDS: CO2- ENRICHMENT, ECOSYSTEMS, FIELD, GROWTH, RESPONSES


     407  
Clinton, B.D., and J.M. Vose. 1999. Fine root respiration in mature eastern white pine (Pinus
strobus) in situ: the importance of CO2 in controlled environments. Tree Physiology 19(7):475-479.

We measured seasonal fine root respiration rate in situ while controlling chamber temperature and
[CO2]. Atmospheric [CO2] ([CO2](a)) and measured soil [CO2] ([CO2](s)) were alternately
delivered to a cuvette containing intact fine roots of eastern white pine (Pinus strobus L.). Respiration
rates were consistently higher in [CO2](a) than in [CO2](s) and were almost three times higher during
midsummer. Respiration rates were immediately reversed after returning to the alternate [CO2] (i.e.,
[CO2](a) --> [CO2](s) --> [CO2](a), and vice versa) suggesting a direct effect of elevated [CO2] on
apparent respiration. Soil-[CO2]-based respiration rates decreased with increasing [CO2] on a dry
mass and tissue [N] basis. We conclude that estimates of soil CO2 flux and soil carbon budgets may
be improved by more completely accounting for the rhizosphere microclimate (i.e., soil temperature
and [CO2](s)) during measurement of fine root respiration.

KEYWORDS: CLIMATE, EXCHANGE, FOREST, SEEDLINGS, SOIL CARBON-DIOXIDE,
TEMPERATURE, WORLD


     408  
Colelli, G., F.G. Mitchell, and A.A. Kader. 1991. Extension of postharvest life of mission figs by
CO2-enriched atmospheres. Hortscience 26(9):1193-1195.

Good quality of fresh 'Mission' figs (Ficus carica L.) was maintained for up to 4 weeks when kept at
0, 2.2, or 5C in atmospheres enriched with 15% or 20% CO2. The visible benefits of exposure to high
CO2 levels were reduction of decay incidence and maintenance of bright external appearance.
Ethylene production was lower, and fruit softening (as measured with a deformation tester) was
slower in the high-CO2-stored figs than in those kept in air. Ethanol content of the CO2-treated fruit
increased slightly during the first 3 weeks and moderately during the 4th week, while acetaldehyde
concentration increased during the first week, then decreased. The results may be applicable to the
transport and storage of fresh 'Mission' figs, as high CO2 extended their postharvest life, especially
near 0C.



     409  
Coleman, J.S., and F.A. Bazzaz. 1992. Effects of co2 and temperature on growth and resource use
of cooccurring C3 and C4 annuals. Ecology 73(4):1244-1259.

We examined how CO2 concentrations and temperature interacted to affect growth, resource
acquisition, and resource allocation of two annual plants that were supplied with a single pulse of
nutrients. Physiological and growth measurements were made on individuals of Abutilon theophrasti
(C3) and Amaranthus retroflexus (C4) grown in environments with atmospheric CO2 levels of 400
or 700-muL/L and with light/dark temperatures of 28-degrees/22-degrees or 38-degrees/31-degrees-
C. Elevated CO2 and temperature treatments had significant independent and interactive effects on
plant growth, resource allocation, and resource acquisition (i.e., photosynthesis and nitrogen uptake),
and the strength and direction of these effects were often dependent on plant species. For example,
final biomass of Amaranthus was enhanced by elevated CO2 at 28-degrees but was depressed at 38-
degrees. For Abutilon, elevated CO2 increased initial plant relative growth rates at 28-degrees but
not at 38-degrees, and had no significant effects on final biomass at either temperature. These results
are interpreted in light of the interactive effects of CO2 and temperature on the rates of net leaf area
production and loss, and on net whole- plant nitrogen retention. At 28-degrees-C, elevated CO2
stimulated the initial production of leaf area in both species, which led to an initial stimulation of
biomass accumulation at the higher CO2 level. However, in elevated CO2 at 28-degrees, the rate of
net leaf area loss for Abutilon increased while that of Amaranthus decreased. Furthermore, high CO2
apparently enhanced the ability of Amaranthus to retain nitrogen at this temperature, which may have
helped to enhance photosynthesis, whereas nitrogen retention was unaffected in Abutilon. Thus, at
28-degrees, final biomass of Abutilon was not stimulated in a high CO2 environment whereas the final
biomass of Amaranthus was. At 38-degrees, Abutilon had slightly reduced peak leaf areas under
elevated CO2 in comparison to ambient CO2 grown plants, but increased rates of photosynthesis per
unit leaf area early in the experiment apparently compensated for reduced leaf area. For Amaranthus
at 38-degrees, peak leaf area production was not affected by CO2 treatment, but the rate of net leaf
area loss hastened under elevated CO2 conditions and was accompanied by substantial reductions of
whole-plant nitrogen content and leaf photosynthesis. This may have led to the reduced biomass
accumulation of high CO2 grown plants that we observed during the last 30 d of growth. Plants of
both species grown in elevated CO2 exhibited reduced tissue-specific rates of nitrogen absorption,
increased plant photosynthetic rate per unit of conductance, and increased initial allocation of biomass
to roots, irrespective of temperature. Plants of both species grown under an elevated temperature
regime had substantially decreased reproductive allocation, increased allocation to stem biomass, and
increased plant water flux at both CO2 treatments. The age of plants also affected our interpretations
of plant responses to CO2 and temperature treatments. For example, significant effects of CO2
treatment on the growth of Abutilon were evident early, prior to the initiation of flowering, when
nitrogen availability would have been highest and pot space would not have been limited.
Nevertheless, the opposite was true for Amaranthus, in which significant effects of CO2 treatment
on plant growth were not detectable until the final 30 d of the experiment. Elevated CO2 interacted
with temperature to affect plant productivity in different ways than would have been predicted from
plant responses to elevated CO2 alone. Furthermore, a majority of the interactive effects of CO2
concentration and temperature on plant growth could be interpreted in light of their effects on the
rates of net leaf area production and loss, nitrogen retention, and, to a lesser degree, photosynthesis
and resource partitioning.

KEYWORDS: ALLOCATION, ATMOSPHERIC CO2, C-4 PLANTS, CHENOPODIUM-ALBUM L,
ELEVATED CO2, ENRICHMENT, LEAF NITROGEN, NITROGEN-USE EFFICIENCY, OLD-
FIELD ANNUALS, PHOTOSYNTHETIC RESPONSE


     410  
Coleman, J.S., K.D.M. McConnaughay, and F.A. Bazzaz. 1993. Elevated co2 and plant nitrogen-
use - is reduced tissue nitrogen concentration size-dependent. Oecologia 93(2):195-200.

Plants often respond to elevated atmospheric CO2 levels with reduced tissue nitrogen concentrations
relative to ambient CO2- grown plants when comparisons are made at a common time. Another
common response to enriched CO2 atmospheres is an acceleration in plant growth rates. Because
plant nitrogen concentrations are often highest in seedlings and subsequently decrease during growth,
comparisons between ambient and elevated CO2-grown plants made at a common time may not
demonstrate CO2-induced reductions in plant nitrogen concentration per se. Rather, this comparison
may be highlighting differences in nitrogen concentration between bigger, more developed plants and
smaller, less developed plants. In this study, we directly examined whether elevated CO2
environments reduce plant nitrogen concentrations independent of changes in plant growth rates. We
grew two annual plant species, Abutilon theophrasti (C3 photosynthetic pathway) and Amaranthus
retroflexus (C, photosynthetic pathway), from seed in glass-sided growth chambers with atmospheric
CO2 levels of 350 mumol . mol-1 or 700 mumol . mol- 1 and with high or low fertilizer applications.
Individual plants were harvested every 2 days starting 3 days after germination to determine plant
biomass and nitrogen concentration. We found: 1. High CO2-grown plants had reduced nitrogen
concentrations and increased biomass relative to ambient CO2-grown plants when compared at a
common time; 2. Tissue nitrogen concentrations did not vary as a function of CO2 level when plants
were compared at a common size; and 3. The rate of biomass accumulation per rate of increase in
plant nitrogen was unaffected by CO2 availability, but was altered by nutrient availability. These
results indicate that a CO2- induced reduction in plant nitrogen concentration may not be due to
physiological changes in plant nitrogen use efficiency, but is probably a size-dependent phenomenon
resulting from accelerated plant growth.

KEYWORDS: ALLOCATION, CARBON-DIOXIDE ATMOSPHERES, ENRICHMENT, GROWTH,
INCREASE, INSECT HERBIVORE, LEAF LITTER, NUTRITION, ROOT, SHOOT RATIO


     411  
Coleman, J.S., L. Rochefort, F.A. Bazzaz, and F.I. Woodward. 1991. Atmospheric CO2, plant
nitrogen status and the susceptibility of plants to an acute increase in temperature. Plant, Cell and
Environment 14(7):667-674.

Elevated levels of CO2 in the atmosphere are expected to affect plant performance and may alter
global temperature patterns. Changes in mean air temperatures that might be induced by rising levels
of CO2 and other greenhouse gases could also be accompanied by increased variability in daily
temperatures such that acute increases in air temperature may be more likely than at present.
Consequently, we investigated whether plants grown in a CO2 enriched atmosphere would be
differently affected by a heat shock than plants grown at ambient CO2 levels. Plants of a C3 annual
(Abutilon theophrasti), a C3 annual crop (Sinapis alba) and a C4 annual (Amaranthus retroflexus)
were grown from seed in growth chambers under either 400 or 700 cm3 m-3 CO2, and were fertilized
with either a high or low nutrient regime. Young seedlings of S. alba, as well as plants of all species
in either the vegetative or reproductive phase of growth were exposed to a 4-h heat shock in which
the temperature was raised an additional 14-23-degrees-C (depending on plant age). Total biomass
and reproductive biomass were examined to determine the effect of CO2, nutrient and heat shock
treatments on plant performance. Heat shock, CO2, and nutrient treatments, all had some significant
effects on plant performance, but plants from both CO2 treatments responded similarly to heat
shocks. We also found, as expected, that plants grown under high CO2 had dramatically decreased
tissue N concentrations relative to plants grown under ambient conditions. We predicted that high-
CO2-grown plants would be more susceptible to a heat shock than ambient-CO2-grown plants,
because the reduced N concentrations of high-CO2 grown plants could result in the reduced synthesis
of heat shock proteins and reduced thermotolerance. Although we did not examine heat shock
proteins, our results showed little relationship between plant nitrogen status and the ability of a plant
to tolerate an acute increase in temperature.

KEYWORDS: C-3, ELEVATED CO2, ENRICHMENT, GROWTH, HEAT-SHOCK PROTEINS,
INSECT HERBIVORE, RESPONSES, THERMOTOLERANCE


     412  
Coleman, W.K., and J. McInerney. 1997. Enhanced dormancy release and emergence from potato
tubers after exposure to a controlled atmosphere. American Potato Journal 74(3):173-182.

The North American potato industry requires an effective and environmentally-appropriate,
dormancy-release methodology. The present study examined dormancy release and subsequent sprout
emergence based on a modified, controlled-atmosphere (CA) approach using such environmentally-
compatible gases as nitrogen, carbon dioxide and oxygen with or without trace amounts of ethylene
(50 ppm). This paper is the first published report of a semi-automated, controlled-atmosphere system
for dormancy release of potato tubers. The system allows computer- controlled gas application and
analysis for up to four gas mixtures simultaneously. Low oxygen concentrations (<10%) for 10 days
in the presence of 10 to 60% carbon dioxide or a high carbon dioxide (60%)/oxygen (40%) treatment
caused tuber break- down regardless of cultivar. The most effective mixtures for enhanced dormancy
release and sprout emergence were 20% CO2/40% O-2 or 60% CO2/18-20% O-2 and their effects
were further enhanced by 50 ppm C2H4 (ethylene). In the presence of 50 ppm C2H4, the 20%
CO2/40% O-2 mixture was comparable to bromoethane in effectiveness. Temperature and light
exposure affected subsequent Russet Burbank tuber responses to CO2/O-2/C2H4 gas mixtures.



     413  
Coley, P.D. 1998. Possible effects of climate change on plant/herbivore interactions in moist tropical
forests. Climatic Change 39(2-3):455-472.

The interactions between plants and herbivores are key determinants of community structure world
wide. Their role is particularly important in lowland tropical rain forests where rates of herbivory are
higher, plants are better defended chemically and physically, and herbivores have specialized diets.
In contrast to the temperate zone, most of the herbivory in the tropics occurs on ephemeral young
leaves (>70%), which requires herbivores to have finely tuned host-finding abilities. As a consequence
of these tight ecological and evolutionary linkages, the interplay between plants and herbivores in the
tropics may be more susceptible to perturbations of climate change. Increases in global temperature,
atmospheric CO2, and the length of the dry season are all likely to have ramifications for
plant/herbivore interactions in the tropics. Here I extrapolate from our current and incomplete
understanding of the mechanisms regulating plant/herbivore interactions and present a scenario for
possible trends under a changing climate. Although elevated CO2 tends to enhance plant growth
rates, the larger effects of increased drought stress will probably result in lower growth. In
atmospheres experimentally enriched in CO2, the nutritional quality of leaves declines substantially
due to a dilution of nitrogen by 10-30%. This response is buffered in plant species associated with
nitrogen fixers. Elevated CO2 should also cause a slight decrease in nitrogen-based defenses(e.g.,
alkaloids) and a slight increase in carbon-based defenses (e.g., tannins). The most dramatic and robust
predicted effect of climate change is on rates of herbivory. Lower foliar nitrogen due to CO2
fertilization of plants causes an increase in consumption per herbivore by as much as 40% and
unusually severe drought appears to cause herbivore populations to explode. In areas where elevated
CO2 is combined with drying, rates of herbivory may rise 2-4 fold. The frequency of insect outbreaks
is also expected to increase. Higher herbivory should further reduce plant growth rates, perhaps
favoring plant species that are well-defended or fix nitrogen. The predicted increase in the number
of herbivores is primarily due to relaxed pressure from predators and parasitoids. Elevated
temperatures may increase herbivore developmental times, affording them partial escape from
discovery by natural enemies, and drought appears to decimate parasitoid populations. The expected
decline in parasitoid numbers may be due to direct effects of dry season drought or to the relative
scarcity of herbivores during that period. As a consequence, the relative abundance of species will
change, and overall biodiversity should decline.

KEYWORDS: CARBON-DIOXIDE ATMOSPHERES, ELEVATED ATMOSPHERIC CO2, INSECT
HERBIVORE INTERACTIONS, LEAF PRODUCTION, LONG-TERM EXPOSURE, MULTIPLE
ALLELOCHEMICALS, PAPER BIRCH, PERFORMANCE, PLANT, UNDERSTORY COMMUNITY


     414  
Colinvaux, P.A. 1998. A new vicariance model for Amazonian endemics. Global Ecology and
Biogeography Letters 7(2):95-96.

It is unlikely that ice age climates of the Amazon were sufficiently arid to fragment the forest as
required by the Haffer refugial hypothesis. However, glacial Amazon climates were colder and had
reduced CO2 concentrations that would have had their strongest effects on the biota in the elevated
areas stipulated to have been refugia. If local endemicity of butterflies or birds records Pleistocene
speciation, this is because glacial climates provided cool, CO2 starved islands in a sea of continuous
forest.

KEYWORDS: TEMPERATURE DEPRESSION


     415  
Combe, L., J.M. Bertolini, and P. Quetin. 1993. Effects of carbon-dioxide and light on
photosynthesis of primrose (primula-obconica hance). Canadian Journal of Plant Science
73(4):1149-1161.

Net CO2 exchange rates were measured on a 1 m2 crop of Primula obconica placed in a closed loop
growing chamber as a function of irradiation and CO2 concentration. Greenhouse cultivation with
CO2 enrichment (700 ppm) or without (350 ppm) had only very little effect on dry weight or on
flowering rate and did not modify photosynthetic capacity of primrose. Productivity differences
between horticultural techniques, such as supplemental lighting and/or CO, enrichment, can be partly
explained by study of photosynthesis curves: light increase is more efficient than carbon dioxide
increase, the latter giving the best results with young primroses under strong irradiation.

KEYWORDS: ACCLIMATION, CARBOXYLASE, ELEVATED CO2, ENRICHMENT,
ENVIRONMENTS, GAS-EXCHANGE, GROWTH, HIGH ATMOSPHERIC CO2, TEMPERATURE,
YIELD


     416  
Comins, H.N. 1994. Equilibrium-analysis of integrated plant-soil models for prediction of the
nutrient limited growth-response to co2 enrichment. Journal of Theoretical Biology 171(4):369-385.

Although higher ambient CO, concentration is known to promote increased plant productivity under
optimal growing conditions, it is not obvious if there will be a sustained growth response in natural
and plantation ecosystems, where other resources, such as nutrients, may become limiting. Comins
and McMurtrie (1993, Ecol. Applic. 3, 666-681) have constructed the G'DAY (Generic
Decomposition A nd Field) integrated plant-soil model to investigate this CO2-nutrient interaction,
and have described an analytic method for predicting the long-term response of their model to a step
change in CO2 concentration, using the analytic ''two timing'' approximation. This analysis gives
insights into the interactions of the numerous parameters in a comprehensive plant-soil model, and
may be generalizable to other such models. The current paper explores the accuracy of the
approximation, and discusses various generalizations of the basic model to which the analytic model
can still be applied. The very long-term CO2 response of G'DAY was predicted by considering the
dynamics of the passive soil organic matter pool in the ''two timing'' approximation. It was found that
the two-timing approximation underestimates the 50-100 year CO2 response in systems that lose a
very small proportion of nitrogen per recycling cycle. The other areas considered here are as follows.
(i) More complex relationships between N:C ratios and carbon allocation fractions for plant organs,
including variable heartwood N:C ratio (which has been identified as an important determinant of
long-term CO2 response). Typical results are presented for a range of sensitivities of heartwood N:C
ratio to changes in foliar N:C ratio. (ii) Variants of the CENTURY soil model were examined, having
variable N:C ratios in the soil organic matter pools and/or carbon flux partition fractions influenced
by N:C ratios. (iii) Results are presented for a preliminary analysis of variable nitrogen fixation.

KEYWORDS: CLIMATE, DECOMPOSITION, ECOSYSTEMS, FORESTS, GRASSLANDS


     417  
Comins, H.N., and R.E. McMurtrie. 1993. Long-term response of nutrient-limited forests to co2
enrichment - equilibrium behavior of plant-soil models. Ecological Applications 3(4):666-681.

Established process-based models of forest biomass production in relation to atmospheric CO2
concentration (McMurtrie 1991) and soil carbon/nutrient dynamics (Parton et al. 1987) are integrated
to derive the ''Generic Decomposition and Yield'' model (G'DAY). The model is used to describe how
photosynthesis and nutritional factors interact to determine the productivity of forests growing under
nitrogen-limited conditions. A simulated instantaneous doubling of atmospheric CO2 concentration
leads to a growth response that is initially large (27% above productivity at current CO2) but declines
to <10% elevation within 5 yr. The decline occurs because increases in photosynthetic carbon gain
at elevated CO2 are not matched by increases in nutrient supply. Lower foliar N concentrations at
elevated CO2 have two countervailing effects on forest production: decreased rates of N cycling
between vegetation and soils (with negative consequences for productivity), and reduced rates of N
loss through gaseous emission, fire, and leaching. Theoretical analysis reveals that there is an enduring
response to CO2 enrichment, but that the magnitude of the long-term equilibrium response is
extremely sensitive to the assumed rate of gaseous emission resulting from mineralization of nitrogen.
Theory developed to analyze G'DAY is applicable to other published production-decomposition
models describing the partitioning of soil carbon among compartments with widely differing decay-
time constants.

KEYWORDS: CLIMATE, COMMUNITIES, DYNAMICS, ELEVATED ATMOSPHERIC CO2,
ESTUARINE MARSH, GRASSLANDS, GROWTH, PRODUCTIVITY, TEMPERATURE,
TERRESTRIAL ECOSYSTEMS


     418  
Conroy, J.P. 1992. Influence of elevated atmospheric CO2 concentrations on plant nutrition.
Australian Journal of Botany 40(4-5):445-456.

The rising levels of atmospheric CO2 are likely to increase biomass production of C3 species in both
natural and managed ecosystems because photosynthetic rates will be higher. The greatest absolute
increase in productivity will occur when nitrogen and phosphorus availability in the soil is high. Low
nitrogen does not preclude a growth response to high CO2, whereas some C3 species fail to respond
to high CO2 when phosphorus is low, possibly because insufficient phosphorus is available to
maintain maximum photosynthetic activity at high CO2. C3 plants response to high CO2 because the
flux of carbon through the photoreductive cycle is increased and photorespiration is suppressed. This
change in metabolism appears to alter the foliar nutrient concentration required to promote maximum
productivity (critical concentration). Higher phosphorus concentrations are needed at elevated CO2,
whereas the nitrogen requirement is reduced by CO2 enrichment. Since critical concentrations are
used to evaluate nutrient status of crop and forest species and to manage fertiliser programs, they will
need reassessing as the atmospheric CO2 concentration rises. Another consequence of the altered
nutrient requirement at high CO2 is that the nitrogen concentrations of foliage, roots and grain are
consistently lower in plants grown at elevated CO2, irrespective of availability of nitrogen in the soil.
In natural ecosystems, the lower nitrogen to carbon ratio of the litter may alter rates of nutrient
cycling. For farmers, the rising CO2 concentrations could cause reductions in grain nitrogen, and
therefore protein content. This could have important implications for baking quality of hard wheats
as well as affecting the nutrient value of grain such as rice.

KEYWORDS: C-3, CARBON DIOXIDE, ENRICHMENT, GROWTH, NITROGEN
CONCENTRATIONS, PHOTOSYNTHESIS, RADIATA D-DON, STRESS, WATER-USE, WHEAT


     419  
Conroy, J.P. 1993. Influence of elevated atmospheric co2 concentrations on plant nutrition (vol 40,
pg 445, 1992). Australian Journal of Botany 41(1):143.



     420  
Conroy, J., and P. Hocking. 1993. Nitrogen nutrition of C-3 plants at elevated atmospheric co2
concentrations. Physiologia Plantarum 89(3):570-576.

The atmospheric CO2 concentration has risen from the preindustrial level of approximately 290 mu
1 1(-1) to more than 350 mu 1 1(-1) in 1993. The current rate of rise is such that concentrations of
420 mu 1 1(-1) are expected in the next 20 years. For C-3 plants, higher CO2 levels favour the
photosynthetic carbon reduction cycle over the photorespiratory cycle, resulting in higher rates of
carbohydrate production and plant productivity. The change in balance between the two
photosynthetic cycles appears to alter nitrogen and carbon metabolism in the leaf, possibly causing
decreases in nitrogen concentrations in the leaf. This may result from increases in the concentration
of storage carbohydrates of high molecular weight (soluble or insoluble) and/or changes in
distribution of protein or other nitrogen containing compounds. Uptake of nitrogen may also be
reduced at high CO2 due to lower transpiration rates. Decreases in foliar nitrogen levels have
important implications for production of crops such as wheat, because fertilizer management is often
based on leaf chemical analysis, using standards estimated when the CO2 levels were considerably
lower. These standards will need to be re- evaluated as the CO2 concentration continues to rise.
Lower levels of leaf nitrogen will also have implications for the quality of wheat grain produced,
because it is likely that less nitrogen would be retranslocated during grain filling.

KEYWORDS: ACCLIMATION, CARBOHYDRATE, CARBON DIOXIDE, DRY-MATTER,
ENRICHMENT, GROWTH, MINERAL NUTRITION, NITRATE, PHOTOSYNTHESIS, WHEAT


     421  
Conroy, J.P., P.J. Milham, and E.W.R. Barlow. 1992. Effect of nitrogen and phosphorus
availability on the growth- response of eucalyptus-grandis to high co2. Plant, Cell and Environment
15(7):843-847.

The response of Eucalyptus grandis seedlings to elevated atmospheric CO2 concentrations was
examined by growing seedlings at either 340 or 660-mu-mol CO2 mol-1 for 6 weeks. Graded
increments of phosphorus and nitrogen fertilizers were added to a soil deficient in these nutrients to
establish if the growth response to increasing nutrient availability was affected by CO2 concentration.
At 660-mu-mol CO2 mol-1, seedling dry weight was up to five times greater than at 340- mu-mol
CO2 mol-1. The absolute response was largest when both nitrogen and phosphorus availability was
high but the relative increase in dry weight was greatest at low phosphorus availability. At 340-mu-
mol CO2 mol-1 and high nitrogen availability, growth was stimulated by addition of phosphorus up
to 76 mg kg-1 soil. Further additions of phosphorus had little effect. However, at 660-mu-mol CO2
mol-1, growth only began to plateau at a phosphorus addition rate of 920 mg kg-1 soil. At 340-mu-
mol CO2 mol-1 and high phosphorus availability, increasing nitrogen from 40 to 160 mg kg-1 soil
had little effect on plant growth. At high CO2, growth reached a maximum at between 80 and 160
mg nitrogen kg-1 soil. Total uptake of phosphorus was greater at high CO2 concentration at all
fertilizer addition rates, but nitrogen uptake was either lower or unchanged at high CO2 concentration
except at the highest nitrogen fertilizer rate. The shoot to root ratio was increased by CO2
enrichment, primarily because the specific leaf weight was greater. The nitrogen and phosphorus
concentration in the foliage was lower at elevated CO2 concentration partly because of the higher
specific leaf weight. These results indicate that critical foliar concentrations currently used to define
nutritional status and fertilizer management may need to be reassessed as the atmospheric CO2
concentration rises.

KEYWORDS: CARBON DIOXIDE, DEFICIENCY, ENRICHMENT, METABOLISM, PLANTS,
RADIATA D-DON, SEEDLINGS, STRESS, WHEAT


     422  
Conroy, J.P., P.J. Milham, D.I. Bevege, and E.W.R. Barlow. 1990. Influence of phosphorus
deficiency on the growth-response of 4 families of Pinus radiata seedlings to CO2-enriched
atmospheres. Forest Ecology and Management 30(1-4):175-188.



     423  
Conroy, J.P., P.J. Milham, M. Mazur, and E.W.R. Barlow. 1990. Growth, dry-weight
partitioning and wood properties of Pinus radiata d don after 2 years of CO2 enrichment. Plant, Cell
and Environment 13(4):329-337.



     424  
Conroy, J.P., P.J. Milham, M.L. Reed, and E.W. Barlow. 1990. Increases in phosphorus
requirements for CO2-enriched pine species. Plant Physiology 92(4):977-982.



     425  
Conroy, J.P., S. Seneweera, A.S. Basra, G. Rogers, and B. Nissenwooller. 1994. Influence of
rising atmospheric co2 concentrations and temperature on growth, yield and grain quality of cereal
crops. Australian Journal of Plant Physiology 21(6):741-758.

A possible scenario for the end of the 21st century is that the atmospheric CO2 concentration will be
in the range of 510-760 mu L L(-1) and that the mean global temperature will be 1.5-4.5 degrees C
higher. Further, there may be greater incidences of extreme climatic events, which together with the
CO2 and temperature changes will influence development, growth and grain yield of cereals such as
rice and wheat. For these C-3, plants, the driving force for the growth response to elevated CO2 is
higher leaf CO2 assimilation rates (4). However, the response of A to CO2 depends on temperature
with maximum absolute increases occuring at temperatures which do not cause flower abortion, while
negligible increases are observed at low temperatures. At high temperatures, where A is reduced
because of partial inactivation of photosynthetic enzymes, the increase in A due to CO2 enrichment
is still observed. Other factors, such as changes in shoot water relations or hormone concentrations,
may influence growth at elevated CO2 concentrations. Wheat and rice development is accelerated
by high temperature and consequently grain yield is reduced because there is less time for radiation
to be intercepted during the vegetative phase. Although high CO2 also accelerates development in
rice and, to a lesser extent in wheat, the extra carbohydrate produced by increases in A results in at
least a 40% increase in grain yield at temperatures which do not cause flower abortion. This is due
mainly to increased tiller numbers rather than increases in the number or weight of individual grains.
However, the yield enhancement due to high CO2 will not necessarily compensate for decreases in
yield caused by accelerated development at high temperatures. As predicted by the response of A to
high CO2, the relative increase in yield, due to rising CO2 concentrations, is smaller at lower
temperatures. Elevated atmospheric CO2 may improve the tolerance of plants to heat-induced
drought stress by facilitating the maintenance of cell volume and photosynthetic function in the leaves.
Increased carbohydrate storage in the stems may also be an advantage during grain filling if the flag
leaves senesce prematurely. However, it is unlikely that the effect of very high temperatures on newer
abortion will be ameliorated by high CO2. For bread making, the quality of flour produced from grain
developed at high temperatures is poorer. High CO2 may also have an effect through a reduction in
the protein content of wheat grain. For rice, the amylose content of the grain, a major determinant
of cooking quality is increased under elevated CO2.

KEYWORDS: C-3 PLANTS, CARBON-DIOXIDE CONCENTRATION, ELEVATED CO2,
NITROGEN, PARTIAL-PRESSURE, PHOTOSYNTHESIS, PLANT GROWTH, RICE, WATER
RELATIONS, WHEAT PLANTS


     426  
Constable, J.V.H., A.B. Guenther, D.S. Schimel, and R.K. Monson. 1999. Modelling changes
in VOC emission in response to climate change in the continental United States. Global Change
Biology 5(7):791-806.

The alteration of climate is driven not only by anthropogenic activities, but also by biosphere
processes that change in conjunction with climate. Emission of volatile organic compounds (VOCs)
from vegetation may be particularly sensitive to changes in climate and may play an important role
in climate forcing through their influence on the atmospheric oxidative balance, greenhouse gas
concentration, and the formation of aerosols. Using the VEMAP vegetation database and associated
vegetation responses to climate change, this study examined the independent and combined effects
of simulated changes in temperature, CO2 concentration, and vegetation distribution on annual
emissions of isoprene, monoterpenes, and other reactive VOCs (ORVOCs) from potential vegetation
of the continental United States. Temperature effects were modelled according to the direct influence
of temperature on enzymatic isoprene production and the vapour pressure of monoterpenes and
ORVOCs. The effect of elevated CO2 concentration was modelled according to increases in foliar
biomass per unit of emitting surface area. The effects of vegetation distribution reflects simulated
changes in species spatial distribution and areal coverage by 21 different vegetation classes. Simulated
climate warming associated with a doubled atmospheric CO2 concentration enhanced total modelled
VOC emission by 81.8% (isoprene + 82.1%, monoterpenes + 81.6%, ORVOC + 81.1%), whereas
a simulated doubled CO2 alone enhanced total modelled VOC emission by only + 11.8% (isoprene
+ 13.7%, monoterpenes + 4.1%, ORVOC + 11.7%). A simulated redistribution of vegetation in
response to altered temperatures and precipitation patterns caused total modelled VOC emission to
decline by 10.4% (isoprene -11.7%, monoterpenes -18.6%, ORVOC 0.0%) driven by a decline in
area covered by vegetation classes emitting VOCs at high rates. Thus, the positive effect of leaf-level
adjustments to elevated CO2 (i.e. increases in foliar biomass) is balanced by the negative effect of
ecosystem-level adjustments to climate (i.e. decreases in areal coverage of species emitting VOC at
high rates).

KEYWORDS: AEROSOL FORMATION, ALPHA- PINENE, BETA-PINENE, BIOGENIC
EMISSIONS, CARBON DIOXIDE, ELEVATED CO2, FOREST, GROWTH, ISOPRENE,
ORGANIC-COMPOUND EMISSIONS


     427  
Constable, J.V.H., M.E. Litvak, J.P. Greenberg, and R.K. Monson. 1999. Monoterpene emission
from coniferous trees in response to elevated CO2 concentration and climate warming. Global
Change Biology 5(3):255-267.

It was hypothesized that high CO2 availability would increase monoterpene emission to the
atmosphere. This hypothesis was based on resource allocation theory which predicts increased
production of plant secondary compounds when carbon is in excess of that required for growth.
Monoterpene emission rates were measured from needles of (a) Ponderosa pine grown at different
CO2 concentrations and soil nitrogen levels, and (b) Douglas fir grown at different CO2
concentrations. Ponderosa pine grown at 700 mu mol mol(-1) CO2 exhibited increased
photosynthetic rates and needle starch to nitrogen (N) ratios when compared to trees grown at 350
mu mol mol(-1) CO2. Nitrogen availability had no consistent effect on photosynthesis. Douglas fir
grown at 550 mu mol mol(-1) CO2 exhibited increased photosynthetic rates as compared to growth
at 350 mu mol mol(-1) CO2 in old, but not young needles, and there was no influence on the starch/N
ratio. In neither species was there a significant effect of elevated growth CO2 on needle monoterpene
concentration or emission rate. The influence of climate warming and leaf area index LAD on
monoterpene emission were also investigated. Douglas fir grown at elevated CO2 plus a 4 degrees
C increase in growth temperature exhibited no change in needle monoterpene concentration, despite
a predicted 50% increase in emission rate. At elevated CO2 concentration the LAI increased in
Ponderosa pine, but not Douglas fir. The combination of increased LAI and climate warming are
predicted to cause an 80% increase in monoterpene emissions from Ponderosa pine forests and a 50%
increase in emissions from Douglas fir forests. This study demonstrates that although growth at
elevated CO2 may not affect the rate of monoterpene emission per unit biomass, the effect of elevated
CO2 on LAI, and the effect of climate warming on monoterpene biosynthesis and volatilization, could
increase canopy monoterpene emission rate.

KEYWORDS: ATMOSPHERIC CHEMISTRY, CARBON, GROWTH, ISOPRENE, NITROGEN,
PONDEROSA PINE, RATE VARIABILITY, SEEDLINGS


     428  
Constable, J.V.H., G.E. Taylor, J.A. Laurence, and J.A. Weber. 1996. Climatic change effects
on the physiology and growth of Pinus ponderosa: Expectations from simulation modeling. Canadian
Journal of Forest Research-Revue Canadienne De Recherche Forestiere 26(8):1315-1325.

The TREGRO model was used to simulate the growth response of mature Piizus ponderosa Dougl.
ex Laws. to the interacting effects of changes in CO2 (+200 mu L/L), temperature (+4 degrees C),
and O-3 (0.5x, 1x, and 2x ambient). Relative to simulated growth under the base-line climate in
Corvallis, Oregon, elevated CO2 and temperature individually increased total-tree biomass gain by
29% and 13%, respectively, but when combined increased biomass gain by 49%. Ozone at all
exposures reduced total-tree biomass gain by 1%, 19%, and 39%, respectively, as compared with
simulated base-line conditions. Elevated CO2 increased photosynthesis and reduced stomatal
conductance and partially offset growth reductions due to 2 x O-3. Elevated temperature, however,
increased both photosynthesis and stomatal conductance and was less effective at mitigating growth
reductions due to 2x O-3. Growth at 2x O-3 in elevated CO2 and temperature conditions had little
effect on total-tree growth, but decreased fine-root growth by 61%. The simulated changes in
stomatal conductance and fine-root biomass are expected to interact with the availability of soil
resources to affect tree growth and possibly alter the distribution of Pinus ponderosa.

KEYWORDS: COMPENSATORY RESPONSES, DROUGHT, ELEVATED CO2, GAS-EXCHANGE,
NET PHOTOSYNTHESIS, OZONE EXPOSURE, PHOTOSYNTHETIC CAPACITY, STOMATAL
CONDUCTANCE, STRESSES, USE EFFICIENCY


     429  
Conway, T.J., L.P. Steele, and P.C. Novelli. 1993. Correlations among atmospheric co2, ch4 and
co in the arctic, march 1989. Atmospheric Environment Part A-General Topics 27(17-18):2881-
2894.

During six aircraft flights conducted as part of the third Arctic Gas and Aerosol Sampling Program
(AGASP III, March 1989), 189 air samples were collected throughout the Arctic troposphere and
lower stratosphere for analysis of CO2, CH4 and CO. The mixing ratios of the three gases varied
significantly both horizontally and vertically. Elevated concentrations were found in layers with high
anthropogenic aerosol concentrations (Arctic Haze), The mixing ratios of CO2, CH4 and CO were
highly correlated on all flights. A linear regression of CH4 vs CO2 for pooled data from all flights
yielded a correlation coefficient (r(2)) of 0.88 and a slope of 13.5 ppb CH4/ppm CO2 (n = 186). For
CO vs CO2 a pooled linear regression gave r(2) = 0.91 and a slope of 15.8 ppb CO/ppm CO2 (n =
182). Carbon dioxide, CH4 and CO also exhibited mean vertical gradients with slopes of 0.37, -4.4
and -4.2 ppb km(-1), respectively. Since the carbon dioxide variations observed in the Arctic
atmosphere during winter are due primarily to variations in the emissions and transport of
anthropogenic CO2 from Europe and Asia, the strong correlations that we have found suggest that
a similar interpretation applies to CH4 and CO. Using reliable estimates of CO2 emissions for the
source regions and the measured CH4/CO2 and CO/CO2 ratios, we estimate a regional European
CH4 source of 47+/-6 Tg CH4 yr(-1) that may be associated with fossil fuel combustion. A similar
calculation for CO results in an estimated regional CO source of 82+/- 2Tg CO yr(-1).

KEYWORDS: AEROSOL, AGASP, AIR-POLLUTION, ALASKA, APRIL, ARCTIC HAZE,
BARROW, CARBON DIOXIDE, METHANE, VARIABILITY


     430  
Cook, A.C., D.T. Tissue, S.W. Roberts, and W.C. Oechel. 1998. Effects of long-term elevated
[CO2] from natural CO2 springs on Nardus stricta: Photosynthesis, biochemistry, growth and
phenology. Plant, Cell and Environment 21(4):417-425.

Plants of Nardus stricta growing near a cold, naturally emitting CO2 spring in Iceland were used to
investigate the long-term (> 100 years) effects of elevated [CO2] on photosynthesis, biochemistry,
growth and phenology in a northern grassland ecosystem. Comparisons were made between plants
growing in an atmosphere naturally enriched with CO2 (approximate to 790 mu mol mol(-1)) near
the CO2 spring and plants of the same species growing in adjacent areas exposed to ambient CO2
concentrations (approximate to 360 mu mol mol(-1)). Nardus stricta growing near the spring
exhibited earlier senescence and reductions in photosynthetic capacity (approximate to 25%), Rubisco
content (approximate to 26%), Rubisco activity (approximate to 40%), Rubisco activation state
(approximate to 23%), chlorophyll content (approximate to 33%) and leaf area index (approximate
to 22%) compared,vith plants growing away from the spring. The potential positive effects of
elevated [CO2] on grassland ecosystems in Iceland are likely to be reduced by strong down-regulation
in the photosynthetic apparatus of the abundant N, stricta species.

KEYWORDS: ACCLIMATION, ALASKAN TUSSOCK TUNDRA, ATMOSPHERIC CARBON-
DIOXIDE, CARBOXYLASE ACTIVITY, ENRICHMENT, ERIOPHORUM VAGINATUM, PLANTS,
RESPONSES, RUBISCO, SEEDLINGS


     431  
Corey, K.A., M.E. Bates, and S.L. Adams. UNKNOWN YEAR. Carbon-dioxide exchange of
lettuce plants under hypobaric conditions. Physical, Chemical, Biochemical and Biological
Techniques and Processes :301-308.

Growth of plants in a Controlled Ecological Life Support System (CELSS) may involve the use of
hypobaric pressures enabling lower mass requirements for atmospheres and possible enhancement of
crop productivity, A controlled environment plant growth chamber with hypobaric capability designed
and built at Ames Research Center was used to determine if reduced pressures influence the rates of
photosynthesis (Ps) and dark respiration (DR) of hydroponically grown lettuce plants, The chamber,
referred to as a plant volatiles chamber (PVC), has a growing area of about 0.2 m(2), a total gas
volume of about 0.7 m(3), and a leak rate at 50 kPa of < 0.1%/day. When the pressure in the chamber
was reduced from ambient to 51 kPa, the rate of net Ps increased by 25% and the rate of DR
decreased by 40%, The rate of Ps increased linearly with decreasing pressure, There was a greater
effect of reduced pressure at 41 Pa CO2 than at 81 Pa CO2. This is consistent with reports showing
greater inhibition of photorespiration (Pr) in reduced O-2 at low CO2 concentrations. When the
partial pressure of O-2 was held constant but the total pressure was varied between 51 and 101 kPa,
the rate of CO2 uptake was nearly constant, suggesting that low pressure enhancement of Ps may be
mainly attributable to lowered partial pressure of O-2 and the accompanying reduction in Pr, The
effects of lowered partial pressure of O-2 on Ps and DR could result in substantial increases in the
rates of biomass production, enabling rapid throughput of crops or allowing flexibility in the use of
mass and energy resources for a CELSS.

KEYWORDS: INCOMPLETE, ENVIRONMENTS, PRODUCTIVITY, WHEAT


     432  
Corlett, R.T., and J.V. LaFrankie. 1998. Potential impacts of climate change on tropical Asian
forests through an influence on phenology. Climatic Change 39(2-3):439-453.

Changes in plant phenology will be one of the earliest responses to rapid global climate change and
could potentially have serious consequences both for plants and for animals that depend on
periodically available plant resources. Phenological patterns are most diverse and least understood
in the tropics. In those parts of tropical Asia where low temperature or drought impose a seasonal
rest period, regular annual cycles of growth and reproduction predominate at the individual,
population, and community level. In aseasonal areas, individuals and populations show a range of sub-
to supra- annual periodicities, with an overall supra-annual reproductive periodicity at the community
level. There is no evidence for photoperiod control of phenology in the Asian tropics, and seasonal
changes in temperature are a likely factor only near the northern margins. An opportunistic response
to water availability is the simplest explanation for most observed patterns where water is seasonally
limiting, while the great diversity of phenological patterns in the aseasonal tropics suggests an equal
diversity of controls. The robustness of current phenological patterns to high interannual and spatial
variability suggests that most plant species will not be seriously affected by the phenological
consequences alone of climate change. However, some individual plant species may suffer, and the
consequences of changes in plant phenology for flower- and fruit-dependent animals in fragmented
forests could be serious.

KEYWORDS: ASEASONAL TROPICS, CONSEQUENCES, COSTA-RICA, DRY FOREST,
ELEVATED CO2, MOIST FOREST, PATTERNS, RAIN-FOREST, REPRODUCTIVE
PHENOLOGY, TREES


     433  
Cornelissen, J.H.C., A.L. Carnelli, and T.V. Callaghan. 1999. Generalities in the growth,
allocation and leaf quality responses to elevated CO2 in eight woody species. New Phytologist
141(3):401-409.

This paper reports general patterns of relative growth rate and related traits in response to elevated
atmospheric CO2 in eight woody species ranging widely in life form, leaf habit, taxonomy and
ecology. Young plants of these species, all of comparable ontogenetic phases, R-ere grown
simultaneously in large containers with favourable nutrient and water availability in transparent
outdoor chambers at 350 and 700 mu l l(-1) CO2 for one growing season. We found the following
consistent responses. (1) All species grew faster at elevated CO2, whereas the following leaf and
allocation traits were consistently lower in CO2-enriched environments: specific leaf area (quotient
of leaf area and leaf weight), leaf area ratio (quotient of total leaf area and plant weight), weight-
based foliar N concentration and, to a smaller extent, leaf weight fraction (quotient of leaf weight and
plant weight). (2) There was important interspecific variation in the magnitude of the response of
relative growth rate to CO2. Specific leaf area at ambient CO2 explained 88% of the variation in
relative growth rate response to CO2 among the eight species. At ambient CO2, relative growth rate
itself, was significantly correlated with the relative growth rate response to CO2 only if the leafless
species Ulex gallii was excluded from analysis. (3) The four deciduous species had a significantly
stronger relative growth rate response to CO2 than the four evergreens. This corresponded with their
generally higher specific leaf area. (4) Specific leaf area and leaf habit might be useful for scaling up
exercises, as easy-to-measure substitutes for growth responses of (woody) vegetation to elevated
CO2. However, the usefulness of such traits in this contest needs to be tested in realistic, longer-term
manipulative experiments in real ecosystems.

KEYWORDS: ATMOSPHERIC CO2, CARBON DIOXIDE, CHEMICAL-COMPOSITION,
ECOSYSTEMS, MODEL, NITROGEN, PLANT-RESPONSES, SEEDLINGS, TREE, WIDE-RANGE


     434  
Corrigan, V.K., and A. Carpenter. 1993. Effects of treatment with elevated carbon-dioxide levels
on the sensory quality of asparagus. New Zealand Journal of Crop and Horticultural Science
21(4):349-357.

Asparagus spears (Asparagus officinalis L. cv. Limbras 10) were stored for 3-5 days in atmospheres
containing between 40 and 90% carbon dioxide (CO2) to evaluate the effect of insecticidal CO2
atmospheres on sensory quality based on sensory panel ratings of characteristic asparagus flavour,
off-flavours, flavour acceptability, and overall acceptability. Sensory quality of spears after 4 days
storage in 60% CO2 was similar to air-stored spears but 5 days storage caused deterioration in the
CO2-stored spears relative to the air-stored spears. Using higher CO2 levels than this for shorter
storage times resulted in spears with CO2 injury and poor sensory quality. Spear quality deteriorated
with shelf period but previous CO2 treatment did not affect the rate of deterioration. Storing spears
at 5-degrees-C in 60% CO2 or 0-degrees-C in air gave consistently higher (lower for off-flavours)
sensory quality ratings for all characteristics assessed than vice versa. Thick spears had more flavour
and were more acceptable than thin spears. Thick spears had more flavour than thin spears when
stored in CO2, but thin spears had more flavour when stored in air than in CO2. In 60% CO2, spears
stored dry had a more acceptable flavour and were more acceptable overall (where panellists
considered aspects such as flavour, texture, and off-flavours in the overall rating) than those stored
with their butts in water. Spears stored in air with their butts in water had a more acceptable flavour
and were more acceptable overall, spears stored with their butts in water had less characteristic
asparagus flavour than those stored dry. High levels of CO2 could be used as a disinfestation
treatment of fresh asparagus spears without significant effect on spear quality (compared to spears
stored in air under similar conditions) providing levels >60% CO2 are not used, and storage time in
the atmosphere is kept to 4 days or less.

KEYWORDS: CONTROLLED-ATMOSPHERE STORAGE, HARVEST, SPEARS


     435  
Cotrufo, M.E., and P. Ineson. 1995. Effects of enhanced atmospheric co2 and nutrient supply on
the quality and subsequent decomposition of fine roots of betula- pendula roth and picea-sitchensis
(bong) carr. Plant and Soil 170(2):267-277.

Fine root litter derived from birch (Betula pendula Roth.) and Sitka spruce (Picea sitchensis (Bong.)
Carr.) plants grown under two CO2 atmospheric concentrations (350 ppm and 600 ppm) and two
nutrient regimes was used for decomposition studies in laboratory microcosms. Although there were
interactions between litter type, CO2/fertiliser treatments and decomposition rates, in general, an
increase in the C/N ratio of the root tissue was observed for roots of both species grown under
elevated CO2 in unfertilized soil. Both weight loss and respiration of decomposing birch roots were
significantly reduced in materials derived from enriched CO2, whilst the decomposition of spruce
roots showed no such effect. A parallel experiment was performed using Betula pendula root litter
grown under different N regimes, in order to test the relationship between C/N ratio of litter and root
decomposition rate. A highly significant (p < 0.001) negative correlation between C/N ratio and root
litter respiration was found, with an r(2) = 0.97. The results suggest that the increased C/N ratio of
plant tissues induced by elevated CO2 can result in a reduction of decomposition rate, with a resulting
increase in forest soil C stores.

KEYWORDS: ECOSYSTEMS, ELEVATED CARBON-DIOXIDE, ENRICHMENT,
FERTILIZATION, FOREST, GROWTH, NITROGEN, ORGANIC-MATTER, PINE, RESPONSES


     436  
Cotrufo, M.F., M.J.I. Briones, and P. Ineson. 1998. Elevated CO2 affects field decomposition rate
and palatability of tree leaf litter: Importance of changes in substrate quality. Soil Biology and
Biochemistry 30(12):1565-1571.

Field decomposition rates of ash (Fraxinus excelsior L.) and sycamore (Acer pseudoplatanus L.) leaf
litters were measured for litters grown at ambient and elevated concentration of atmospheric CO2
inside solar domes. Litter raised at 600 mu l l(-1) CO2 retained significantly more mass at the end of
the first year of field decomposition than material raised at 350 mu l l(-1). This reduction in
decomposition could be related to changes in tissue quality resulting from growing the plants at
higher CO2 concentrations, with C-to-N ratios and lignin contents being significantly increased. The
elevated CO2 treatment also affected the rate of consumption of ash leaf litter by Oniscus asellus L.
(Isopoda: Oniscoidea), with significantly less (-16%) material being consumed for litter derived from
the high CO2 regime. Our results indicate that changes in litter quality, which we may expect under
elevated CO2, may affect litter palatability for soil fauna. (C) 1998 Elsevier Science Ltd. All rights
reserved.

KEYWORDS: ATMOSPHERIC CARBON-DIOXIDE, GRASS, GROWTH, NITROGEN, ONISCUS-
ASELLUS, PLANTS, RESPONSES, SOIL BIOTA


     437  
Cotrufo, M.F., and A. Gorissen. 1997. Elevated CO2 enhances below-ground C allocation in three
perennial grass species at different levels of N availability. New Phytologist 137(3):421-431.

Three perennial grass species, Lolium perenne L., Agrostis capillaris L. and Festuca ovina L., were
homogeneously labelled in phytotrons with (CO2)-C-14 at two CO2 concentrations (350 and 700 mu
l l(-1)). Plants were grown under two nitrogen regimes: one with a minor addition of 8 kg N ha(-1),
the other with an addition of 278 kg N ha2(-1). Carbon allocation over the different compartments
of the plant/soil systems was measured: shoots, roots, rhizosphere soil (soil solution, microbial
biomass and soil residue), and bulk soil. Elevated CO2 increased total net C-14 recovery in all species
by 14%, and significantly enhanced the below-ground C-14 allocation by 26%, this enhancement was
24%, 39% and 21%, for root, rhizosphere soil and bulk soil, respectively. Within the rhizosphere soil,
the C-14 amounts in the soil solution (+ 69 %) and soil residue (+ 49 %) increased significantly. Total
microbial biomass-C in the rhizosphere soil was also increased (15%) by the elevated CO2 treatment,
but only in proportion to the increased root mass. No interactions were observed between the
elevated CO2 and N treatments. The N treatment increased total net C-14 recovery by more than
300% and C-14 was preferentially allocated to the shoots, leading to a significant increase in shoot-
to-root ratio. However, N fertilization also increased(+ 111 %)the absolute amount of C- 14 in soil.
The three species behaved differently, but no interactions were observed between CO2 treatment and
plant species. These results show that elevated CO2 induces an increased C input into soil for all three
grass species at both N levels. However, the highest absolute amounts were found in the soils of the
fastest growing species and at the highest N level.

KEYWORDS: ATMOSPHERIC CO2, BIOMASS CARBON, CARBON DIOXIDE, CO2-
ENRICHMENT, DECOMPOSITION, GROWTH, NITROGEN, RESPONSES, ROOT, SOIL SYSTEM


     438  
Cotrufo, M.F., and P. Ineson. 1996. Elevated CO2 reduces field decomposition rates of Betula
pendula (Roth) leaf litter. Oecologia 106(4):525-530.

The effect of elevated atmospheric CO2 and nutrient supply on elemental composition and
decomposition rates of tree leaf litter was studied using litters derived from birch (Betula pendula
Roth.) plants grown under two levels of atmospheric CO2 (ambient and ambient+250 ppm) and two
nutrient regimes in solar domes. CO2 and nutrient treatments affected the chemical composition of
leaves, both independently and interactively. The elevated CO2 and unfertilized soil regime
significantly enhanced lignin/N and C/N ratios of birch leaves. Decomposition was studied using field
litter-bags, and marked differences were observed in the decomposition rates of litters derived from
the two treatments, with the highest weight remaining being associated with litter derived from the
enhanced CO2 and unfertilized regime. Highly significant correlations were shown between birch
litter decomposition rates and lignin/N and C/N ratios. It can be concluded, from this study, that at
levels of atmospheric CO2 predicted for the middle of the next century a deterioration of litter quality
will result in decreased decomposition rates, leading to reduction of nutrient mineralization and
increased C storage in forest ecosystems. However, such conclusions are difficult to generalize, since
tree responses to elevated CO2 depend on soil nutritional status.

KEYWORDS: ATMOSPHERIC CO2, AVAILABILITY, CARBON DIOXIDE, CASTANEA-SATIVA
MILL, ENRICHMENT, LIGNIN CONTROL, NITROGEN, PLANTS, QUALITY, SEEDLINGS


     439  
Cotrufo, M.F., P. Ineson, and A.P. Rowland. 1994. Decomposition of tree leaf litters grown under
elevated co2 - effect of litter quality. Plant and Soil 163(1):121-130.

Ash (Fraxinus excelsior L.), birch (Betula pubescens Ehrh.), sycamore (Acer pseudoplatanus L.) and
Sitka spruce (Picea sitchensis (Bong.) Carr.) leaf litters were monitored for decomposition rates and
nutrient release in a laboratory microcosm experiment. Litters were derived from solar domes where
plants had been exposed to two different CO2 regimes: ambient (350 mu L L(-1) CO2) and enriched
(600 mu L L(-1) CO2). Elevated CO2 significantly affected some of the major litter quality
parameters, with lower N, higher lignin concentrations and higher ratios of C/N and lignin/N for
litters derived from enriched CO2. Respiration rates of the deciduous species were significantly
decreased for litters grown under elevated CO2, and reductions in mass loss at the end of the
experiment were generally observed in litters derived from the 600 ppm CO2 treatment. Nutrient
mineralization, dissolved organic carbon, and pH in microcosm leachates did not differ significantly
between the two CO2 treatments for any of the species studied. Litter quality parameters were
examined for correlations with cumulative respiration and decomposition rates: N concentration, C/N
and lignin/N ratios showed the highest correlations, with differences between litter types. The results
indicate that higher C storage will occur in soil as a consequence of litter quality changes resulting
from higher atmospheric concentrations of CO2.

KEYWORDS: ATMOSPHERIC CO2, CARBON DIOXIDE, ENRICHMENT, LIGNIN CONTROL,
NITROGEN, NUTRIENT-UPTAKE, ORGANIC-MATTER, RESPONSES, SEEDLINGS,
SUBSTRATE QUALITY


     440  
Cotrufo, M.F., P. Ineson, and A. Scott. 1998. Elevated CO2 reduces the nitrogen concentration
of plant tissues. Global Change Biology 4(1):43-54.

We summarize the impacts of elevated CO2 on the N concentration of plant tissues and present data
to support the hypothesis that reductions in the quality of plant tissue commonly occur when plants
are grown under elevated CO2. Synthesis of existing data showed an average 14% reduction of N
concentrations in plant tissue generated under elevated CO2 regimes. However, elevated CO2
appeared to have different effects on the N concentrations of different plant types, as the reported
reductions in N have been larger in C3 plants than in C4 plants and N-2-fixers. Under elevated CO2
plants changed their allocation of N between above-and below-ground components: root N
concentrations were reduced by an average of 9% compared to a 14% average reduction for above-
ground tissues. Although the concentration of CO2 treatments represented a significant source of
variance for plant N concentration, no consistent trends were observed between them.

KEYWORDS: ALLOCATION PATTERNS, ATMOSPHERIC CARBON-DIOXIDE, BETULA-
PENDULA ROTH, CLOVER TRIFOLIUM-REPENS, INSECT PERFORMANCE, LEAF GAS-
EXCHANGE, LIRIODENDRON-TULIPIFERA L, LITTER DECOMPOSITION, MINERAL
NUTRITION, NUTRIENT STATUS


     441  
Cotrufo, M.F., A. Raschi, M. Lanini, and P. Ineson. 1999. Decomposition and nutrient dynamics
of Quercus pubescens leaf litter in a naturally enriched CO2 Mediterranean ecosystem. Functional
Ecology 13(3):343-351.

1. The chemical composition (i.e. N, P, C, lignin and polyphenol concentrations) of Quercus
pubescens leaf litter derived from a natural CO2 spring in Tuscany (Italy) was analysed and compared
to litter from a nearby reference site. Litter was incubated for 25 months at both the natural CO2
spring and the reference site, and monitored for decomposition rates, nutrient and lignin
concentrations. 2. Long-term exposure to elevated CO2 concentrations from the natural spring was
associated with a change in the chemical composition of the Oak leaf litter, with decreases in P and
polyphenol concentrations and increases in lignin. No differences in N concentrations were observed
between the enriched CO2 litter from the natural spring and the reference litter. 3. Decomposition
was reduced in the CO2 spring, with the lower P concentration of the native litter, combined with the
lack of soil fauna observed at that site, being the factors most probably responsible for the measured
decreases in mass loss. However, litter from the CO2 spring and reference litter decomposed at the
reference site showed similar rates of decomposition. 4. All litter showed similar N concentrations
during decomposition, with N being mineralized throughout the incubation period from both litter
regardless of the site of incubation. In contrast, P dynamics differed between litter, with P being
immobilized in the litter derived from the spring, and mineralized from the reference litter. When the
litter from the spring was incubated at the reference site, there was a trend for net P uptake from the
surrounding environment. The chemical composition of decomposing litter from the spring appeared
to match that of the reference litter after 3 months of incubation at the reference site. 5. The results
from the CO2 spring suggest that litter decomposition may be retarded under elevated levels of
atmospheric CO2. However, results from field surveys around CO2 vents should be viewed with
caution because differences may relate to factors other than the known differences in CO2
concentrations.

KEYWORDS: CARBON DIOXIDE, ELEVATED ATMOSPHERIC CO2, LIGNIN CONTROL,
NITROGEN, QUALITY, RATES, RELEASE, SCOTS PINE FOREST, SOIL CARBON, TALLGRASS
PRAIRIE


     442  
Coughenour, M.B., and D.X. Chen. 1997. Assessment of grassland ecosystem responses to
atmospheric change using linked plant-soil process models. Ecological Applications 7(3):802-827.

Models of photosynthesis, plant growth, and biophysical processes were linked with models that
simulate water, nutrient, and carbon flows through plant-soil ecosystems. The linked ecosystem
model was applied to examine ecosystem-level responses to CO2, temperature, precipitation, and
global- warming scenarios in grasslands of Colorado and Kansas, USA, and Kenya. The model
predicted that increased temperatures would decrease primary production at current CO2 levels, but
decreases were reversed by doubling atmospheric CO2 concentration. Greater increases in daily
minimum temperatures than daily maximum temperatures mitigated reductions in photosynthesis and
water-use efficiency (WUE) later in the day, more than offseting increases in nighttime respiration
rates under warmer temperatures. A temperature increase of 5 degrees C reduced organic carbon in
grassland soils by 20-30%, through effects on plant growth and decomposition, but the doubled CO2
negated soil carbon losses by increasing plant growth. Under higher precipitation and doubled CO2,
soil carbon stocks increased, or decreased little, in response to warmer temperatures. Doubling CO2
increased net primary production (NPP) by 31-45% in a simulated Colorado C-4 grassland, by 20-
70% in a Colorado C-3 grassland, by 23-31% in a Kansas C-4 grassland, and by 23-35% in a Kenya
C-4 grassland at ambient precipitation levels. Growth was shifted belowground, thus weakening
aboveground responses. Higher temperatures strengthened the positive NPP responses to CO2.
Larger positive responses to elevated CO2 were modeled under drier conditions, and smaller
responses were modeled under wetter conditions. NPP increases under elevated CO2 were mostly
caused by increased plant WUE at all sites, which was brought about by partial stomatal closure.
Decreased N concentrations in plant litter under elevated CO2 slowed N mineralization, but greater
plant production and thus greater litter inputs into the soil under elevated CO2 offset the negative
effects of lower litter quality. Decreases in plant N concentration under elevated CO2 also reduced
plant N requirements. At current atmospheric CO2 (350 mu mol/mol), a general circulation model
(GCM) climate- change scenario decreased NPP and soil organic matter (SOM) in Colorado but not
in Kansas or Kenya. A second GCM climate- change scenario either affected NPP and SOM little,
or increased NPP and SOM at current CO2. NPP and SOM responses in the simulated grasslands
were very sensitive to precipitation, which GCMs predict with relatively low confidence. Doubled
CO2 partially or completely offset decreases in NPP and SOM under climate-change scenarios.

KEYWORDS: CANOPY PHOTOSYNTHESIS, CARBON DIOXIDE, CLIMATE CHANGE,
ELEVATED CO2 CONCENTRATIONS, LEAF GAS- EXCHANGE, MIXED-LAYER MODEL,
RISING CO2, STOMATAL CONDUCTANCE, TALLGRASS PRAIRIE, WATER-USE


     443  
Cournac, L., B. Dimon, P. Carrier, A. Lohou, and P. Chagvardieff. 1991. Growth and
photosynthetic characteristics of Solanum tuberosum plantlets cultivated invitro in different
conditions of aeration, sucrose supply, and CO2 enrichment. Plant Physiology 97(1):112-117.

Growth characteristics, oxygen exchange, and carbohydrate and chlorophyll contents were
determined 30 days after subculturing of single node-derived plantlets of Solanum tuberosum cv Haig
cultivated in vitro. Cultivation conditions were: (a) photomixotrophy in closed vessel, (b)
photomixotrophy in closed vessel on medium supplemented with silver thiosulfate, (c)
photomixotrophy in aerated vessel, (d) photoautotrophy in air, (e) photoautotrophy in CO2-enriched
air. In photomixotrophic conditions, aeration of the vessel enhanced sucrose utilization and had a
positive effect on plantlet growth. In photoautotrophic conditions, growth of the plantlets was slow
in air and was strongly enhanced by CO2 enrichment of the atmosphere. Starch to sucrose ratios were
higher in plants grown photoautotrophically than in plants grown with sucrose in the medium. Oxygen
exchange characteristics on a chlorophyll basis were similar between the plantlets when measured
under moderate light, and resembled those of greenhouse plant leaves. In high light, however,
plantlets grown photoautotrophically in a CO2-enriched atmosphere had higher oxygen exchange
rates. We concluded from these results that potato plantlets in vitro in conditions (c), (d), and (e)
developed C3-plant photosynthetic characteristics, which were in photoautotrophically grown
plantlets comparable to those of field-grown plants.

KEYWORDS: CARBON DIOXIDE, CULTURE, ETHYLENE, EXCHANGE, LEAVES, LIGHT, O2,
POTATO, RESPIRATION, SPECIFICITY


     444  
Cournac, L., B. Dimon, and G. Peltier. 1993. Evidence for o-18 labeling of photorespiratory co2
in photoautotrophic cell-cultures of higher-plants illuminated in the presence of o-18(2). Planta
190(3):407-414.

The O-18-enrichment of CO2 produced in the light or during the post-illumination burst was
measured by mass spectrometry when a photoautotrophic cell suspension of Euphorbia characias L.
was placed in photorespiratory conditions in the presence of molecular O-18(2). The only O-18-
labeled species produced was (COO)-O-18-O-16; no (COO)-O-18-O-16 could be detected.
Production of (COO)-O-18-O-16 ceased after addition of two inhibitors of the photosynthetic
carbon-oxidation cycle, aminooxyacetate or aminoacetonitrile, and was inhibited by high levels of
CO2. The average enrichment during the post- illumination burst was estimated to be 46+/-15% of
the enrichment of the O2 present during the preceding light period. Addition of exogenous carbonic
anhydrase, by catalyzing the exchange between CO2 and H2O, drastically diminished the O-18-
enrichment of the produced CO2. The very low carbonio-anhydrase level of the photoautotrophic cell
suspension probably explains why the O-18 labeling of photorespiratory CO2 Could be observed for
the first time. These data allow the establishment of a direct link between O2 consumption and CO2
production in the light, and the conclusion that CO2 produced in the light results, at least partially,
from the mitochondrial decarboxylation of the glycine pool synthesized through the photosynthetic
carbon-oxidation cycle. Analysis of the (COO)-O- 18-O-16 and CO2 kinetics provides a direct and
reliable way to assess in vivo the real contribution of photorespiratory metabolism to CO2 production
in the light.

KEYWORDS: INHIBITION, LEAVES, LIGHT, MASS-SPECTROMETRIC DETERMINATION, O2,
OXYGEN- EXCHANGE, PHOSPHOGLYCOLATE, PHOTORESPIRATION, PHOTOSYNTHESIS,
WHEAT


     445  
Couteaux, M.M., C. Kurz, P. Bottner, and A. Raschi. 1999. Influence of increased atmospheric
CO2 concentration on quality of plant material and litter decomposition. Tree Physiology 19(4-
5):301-311.

Nitrogen (N) and lignin concentrations in plant tissues and litter of plants grown in greenhouses or
open-top chambers in elevated atmospheric CO2 concentration were compared with those of plants
grown in ambient air in shortterm studies. We also compared the N concentration of plant material
of Quercus ilex L. and Q. pubescens Willd. growing in the vicinity of natural CO2-springs with that
of the same species growing at a control site. In the short-term studies, elevated CO2 caused
significant decreases in tissue N concentration and the extent of the decrease varied with species.
Nitrogen amendment of the soil lessened the CO2-enrichment effect. Lignin concentration was
modified by elevated CO2 and the effect was species specific, but no general positive or negative
trend was evident. A comparison of trees growing under natural conditions near a natural CO2-spring
and at a control site revealed no site differences in N concentration of the plant material. A
comparison of published results on decomposition rates of litter produced in elevated atmospheric
CO2 and in ambient air indicated that CO2 enrichment can cause both enhancements and decreases
of carbon mineralization. We conclude that (1) long- term responses to elevated CO2 could differ
from the results obtained from short-term studies and that (2) biodiversity could be an important
factor altering the sign of the feedback on atmospheric CO2 concentration. We also discuss the
implications of our finding of a long-term, inhibitory effect of the initial N concentration of litter on
the decomposition rate of litter and its consequence on ecosystem feedback.

KEYWORDS: BETULA-PENDULA ROTH, CARBON DIOXIDE, ELEVATED CO2, LEAF LITTER,
LIGNIN CONTROL, NITROGEN, ORGANIC-MATTER, RATES, SOIL CARBON, TERM
DECOMPOSITION


     446  
Couteaux, M.M., L.J. Monrozier, and P. Bottner. 1996. Increased atmospheric CO2: Chemical
changes in decomposing sweet chestnut (Castanea sativa) leaf litter incubated in microcosms under
increasing food web complexity. Oikos 76(3):553-563.

Increased concentrations of atmospheric CO2 induced a lower nitrogen concentration in sweet
chestnut litter. The C:N ratio was about 35 at a 350 mu l 1(-1) CO2 concentration and about 70 at
700 mu l 1(-1). The CO2 enrichment increased the proportion of hemicelluloses and cellulose and
decreased the proportion of lignin. Both litters were decomposed in microcosms with animal food
webs of different complexities. The chemical composition of the decomposed litter (nitrogen, water-
soluble compounds, cellulose. hemicelluloses and lignin) was related to the initial composition and
to the mass loss. Rates of hemicelluloses and lignin decomposition and nitrogen dynamics were the
most affected by the change in litter quality due to atmospheric CO2 enrichment. In N-rich litter,
hemicelluloses were almost completely decomposed and lignin remained intact without effect of
animal grazing. In N-poor litter derived From CO2-enriched atmosphere, increased complexity of
invertebrates food webs significantly enhanced decomposition of all the chemical components. By
adding different groups of animals, some limiting factors were overcome and new substrates were
liberated for microbial decomposition. It was hypothesized that the decomposition process was
controlled by the interaction between lignin and nitrogen.

KEYWORDS: DYNAMICS, ELEVATED CO2, FOREST, LIGNIN CONTROL, LONG-TERM
DECOMPOSITION, MASS-LOSS, NITROGEN, PINE NEEDLE LITTER, SOIL, SUBSTRATE
QUALITY


     447  
Couteaux, M.M., M. Mousseau, M.L. Celerier, and P. Bottner. 1991. Increased atmospheric
CO2 and litter quality - decomposition of sweet chestnut leaf litter with animal food webs of different
complexities. Oikos 61(1):54-64.

Two-year-old chestnut trees were grown for two yr under ambient (350 ppm) and enriched (700
ppm) CO2 concentrations, in two naturally lit growth chambers. The doubling of CO2 resulted in a
dilution of the nitrogen concentration in the leaf litter, with C:N ratios of 40 and 75 for the ambient
and enriched CO2 concentrations, respectively. The litter was sterilized and inoculated with
microflora and animal groups of increasing complexity (microflora + Protozoa; + nematodes; +
Collembola; + Isopoda) and incubated over 24 wk. Every two wk, the CO2 release was measured
and the litter was leached with demineralized H2O. The following analyses were performed on the
leachates: pH, total nitrogen, dissolved and particulate carbon, inorganic nitrogen (NH4+ and NO3-),
phosphate, and biological counts (Protozoa, nematodes and Rotifera). The initial decomposition
stages (the first 12 wk) were dominated by the litter quality factor: CO2 release and nitrogen losses
in leachates were higher and carbon losses lower in water leaching from the litter with low C:N ratio.
Towards the late stages, when carbon mineralization decreased in the control litter, the animal effect
emerged in litter with a high C:N ratio. Two groups appeared: (1) In the microflora + Protozoa units,
carbon mineralization was reduced by 60% compared with the control litter. (2) In the diversified
food web combinations, it became progressively higher with increasing complexity of the animal
community and was enhanced by 30% compared with the control litter. This unexpected fundamental
difference was explained by a change in the composition and activity of the microflora. Litter
bleaching, respiration, C and N leaching and acidification rose with increasing animal complexity of
the systems. Biological and chemical reasons explaining the invasion by white-rot fungi and its activity
only in the material with a high C:N ratio are discussed. During the 24 wk. nitrogen and phosphorus
mineralization was very low, indicating a high incorporation of the nutrient in the soil biomass.

KEYWORDS: BREAKDOWN, CARBON, CASTANEA-SATIVA MILL, DECIDUOUS WOODLAND
SOILS, FAUNA, LIGNIN CONTROL, MINERALIZATION, NITROGEN, RAW HUMUS, WEIGHT-
LOSS


     448  
Coviella, C.E., and J.T. Trumble. 1999. Effects of elevated atmospheric carbon dioxide on insect-
plant interactions. Conservation Biology 13(4):700-712.

In the enriched carbon dioxide atmosphere expected in the next century, many, species of herbivorous
insects will confront less nutritious host plants that will induce both lengthened larval developmental
times and greater mortality The limited data currently available suggest that the effect of increased
atmospheric CO2 on herbivory will be nor only highly species- specific brit also specific to each
insect-plant system. Several scenarios can be predicted however. (1) local extinctions will occur; (2)
the endangered species status as well as the pest status of some insect species will change; (3)
geographic distributions for some insect species will shift with host-plant ranges; and (4) changes in
the population dynamics of affected insect species will influence their interactions with other insects
and plants. For insect conservation purposes, it is critical to begin long-term studies on the effects of
enhanced CO2 levels on insect populations. An analysis of the available literature indicates that many
orders containing insect species important for ecosystem conservation, and even those important as
agricultural or medical pests, have not been examined. Without a major increase in research on this
topic, we will be unprepared for the species changes that will occur, we will lose the opportunity to
document just how some insects adapt to elevated CO2 levels, and we will lack the information
necessary for effective conservation efforts.

KEYWORDS: CACTOBLASTIS-CACTORUM, CLIMATE CHANGE, CORN-ROOTWORM
COLEOPTERA, ENRICHED CO2 ATMOSPHERES, GYPSY-MOTH, HERBIVORE
INTERACTIONS, LOBLOLLY-PINE, SECONDARY METABOLITES, SOUR ORANGE TREES,
SPODOPTERA-EXIGUA


     449  
Cowling, S.A. 1999. Simulated effects of low atmospheric CO2 on structure and composition of
North American vegetation at the Last Glacial Maximum. Global Ecology and Biogeography
8(2):81-93.

1. Physiological experiments have indicated that the lower CO2 levels of the last glaciation (200 mu
mol mol(-1)) probably reduced plant water-use efficiency (WUE) and that they combined with
increased aridity and colder temperatures to alter vegetation structure and composition at the Last
Glacial Maximum (LGM). 2. The effects of low CO2 on vegetation structure were investigated using
BIOME3 simulations of leaf area index (LAI), and a two-by-two factorial experimental design
(modern/LGM CO2, modern/ LGM climate). 3. Using BIOME3, and a combination bf lowered CO2
and simulated LGM climate (from the NCAR-CCM1 model), results in the introduction of additional
xeric vegetation types between open woodland and closed-canopy forest along a latitudinal gradient
in eastern North America. 4. The simulated LAI of LGM vegetation was 25- 60% lower in many
regions of central and eastern United States relative to modern climate, indicating that glacial
vegetation was much more open than today. 5. Comparison of factorial simulations show that low
atmospheric CO2 has the potential to alter vegetation structure (LAI) to a greater extent than LGM
climate. 6. If the magnitude of LAI reductions simulated for glacial North America were global, then
low atmospheric CO2 may have promoted atmospheric warming and increased aridity, through
alteration of rates of water and heat exchange with the atmosphere.

KEYWORDS: C-4 ANNUALS, CARBON ISOTOPE DISCRIMINATION, CLIMATE CHANGE,
ELEVATED CO2, FOREST ECOSYSTEMS, GENERAL-CIRCULATION MODEL, ICE CORE,
LEAF-AREA INDEX, STOMATAL CONDUCTANCE, WATER-USE EFFICIENCY


     450  
Cowling, S.A., and R.F. Sage. 1998. Interactive effects of low atmospheric CO2 and elevated
temperature on growth, photosynthesis and respiration in Phaseolus vulgaris. Plant, Cell and
Environment 21(4):427-435.

For most of the past 250 000 years, atmospheric CO, has been 30-50% lower than the current level
of 360 mu mol CO2 mol-l air. Although the effects of CO2 on plant performance are well recognized,
the effects of low CO2 in combination with abiotic stress remain poorly understood. In this study, a
growth chamber experiment using a two-by-two factorial design of CO2 (380 mu mol mol(-1), 200
mu mol mol(-1)) and temperature (25/20 degrees C day/night, 36/29 degrees C) was conducted to
evaluate the interactive effects of CO2 and temperature variation on growth, tissue chemistry and leaf
gas exchange of Phaseolus vulgaris. Relative to plants grown at 380 pmol mol(-1) and 25/20 degrees
C, whole plant biomass was 36% less at 380 mu mol mol(-1) x 36/29 degrees C, and 37% less at 200
mu mol mol(-1) x 25/20 degrees C, Most significantly, growth at 200 mu mol mol(- 1) x 36/29
degrees C resulted in 77% less biomass relative to plants grown at 380 pmol mol(-1) x 25/20 degrees
C, The net CO2 assimilation rate of leaves grown in 200 mu mol mol(-1) x 25/20 degrees C was 40%
lower than in leaves from 380 pmol mol(-1) x 25/20 degrees C, but similar to leaves in 200 mu mol
mol(-1) x 36/29 degrees C. The leaves produced in low CO2 and high temperature respired at a rate
that was double that of leaves from the 380 mu mol mol(-1) x 25/20 degrees C treatment. Despite
this, there was little evidence that leaves at low CO2 and high temperature were carbohydrate
deficient, because soluble sugars, starch and total non-structural carbohydrates of leaves from the 200
mu mol mol(-1) x 36/29 degrees C treatment were not significantly different in leaves from the 380
mu mol mol(-1) x 25/20 degrees C treatment. Similarly, there was no significant difference in
percentage root carbon, leaf chlorophyll and leaf/root nitrogen between the low CO2 x high
temperature treatment and ambient CO2 controls. Decreased plant growth was correlated with
neither leaf gas exchange nor tissue chemistry. Rather, leaf and root growth were the most affected
responses, declining in equivalent proportions as total biomass production. Because of this close
association, the mechanisms controlling leaf and root growth appear to have the greatest control over
the response to heat stress and CO2 reduction in P. vulgaris.

KEYWORDS: ACCLIMATION, ALLOCATION, BIOCHEMISTRY, C-4 ANNUALS, CARBON
DIOXIDE, GAS-EXCHANGE, LEAF RESPIRATION, LEAVES, PLANTS, SENESCENCE


     451  
Cowling, S.A., and M.T. Sykes. 1999. Physiological significance of low atmospheric CO2 for plant-
climate interactions. Quaternary Research 52(2):237-242.

Methods of palaeoclimate reconstruction from pollen are built upon the assumption that plant-climate
interactions remain the same through time or that these interactions are independent of changes in
atmospheric CO2. The latter may be problematic because air trapped in polar ice caps indicates that
atmospheric CO2 has fluctuated significantly over at least the past 400,000 yr, and likely the last 1.6
million yr, Three other points indicate potential biases for vegetation-based climate proxies. First, C-
3-plant physiological research shows that the processes that determine growth optima in plants
(photosynthesis, mitochondrial respiration, photorespiration) are all highly CO2-dependent, and thus
were likely affected by the lower CO2 levels of the last glacial maximum. Second, the ratio of carbon
assimilation per unit transpiration (called water-use efficiency) is sensitive to changes in atmospheric
CO2 through effects on stomatal conductance and may have altered C-3-plant responses to drought,
Third, leaf gas- exchange experiments indicate that the response of plants to carbon-depleting
environmental stresses are strengthened under low CO2 relative to today. This paper reviews the
scope of research addressing the consequences of low atmospheric CO2 for plant and ecosystem
processes and highlights why consideration of the physiological effects of low atmospheric CO2 on
plant function is recommended for any future refinements to pollen- based palaeoclimatic
reconstructions. (C) 1999 University of Washington.

KEYWORDS: CARBON ISOTOPE DISCRIMINATION, DIOXIDE STARVATION, ECOSYSTEMS,
ELEVATED CO2, LAST GLACIAL MAXIMUM, PHASEOLUS-VULGARIS, PHOTOSYNTHESIS,
POLLEN, VEGETATION, WATER-USE EFFICIENCY


     452  
Cox, P.M., R.A. Betts, C.B. Bunton, R.L.H. Essery, P.R. Rowntree, and J. Smith. 1999. The
impact of new land surface physics on the GCM simulation of climate and climate sensitivity. Climate
Dynamics 15(3):183-203.

Recent improvements to the Hadley Centre climate model include the introduction of a new land
surface scheme called "MOSES" (Met Office Surface Exchange Scheme). MOSES is built on the
previous scheme, but incorporates in addition an interactive plant photosynthesis and conductance
module, and a new soil thermodynamics scheme which simulates the freezing and melting of soil
water, and takes account of the dependence of soil thermal characteristics on the frozen and unfrozen
components. The impact of these new features is demonstrated by comparing 1 x CO2 and 2 x CO2
climate simulations carried out using the old (UKMO) and new (MOSES) land surface schemes.
MOSES is found to improve the simulation of current climate. Soil water freezing tends to warm the
high-latitude land in the northern Hemisphere during autumn and winter, whilst the increased soil
water availability in MOSES alleviates a spurious summer drying in the mid-latitudes. The interactive
canopy conductance responds directly to CO2, suppressing transpiration as the concentration
increases and producing a significant enhancement of the warming due to the radiative effects of CO2
alone.

KEYWORDS: GENERAL-CIRCULATION MODELS, INCREASED CO2, PARAMETRIZATION,
PHOTOSYNTHESIS, PROJECT, SCALE, SCHEMES, SOILS, STOMATAL CONDUCTANCE,
TRANSPIRATION


     453  
Craig, S.G., and K.J. Holmen. 1995. Uncertainties in future co2 projections. Global
Biogeochemical Cycles 9(1):139-152.

The perceived budget imbalance in the global carbon cycle has been suggested to result from, among
other processes, CO2 fertilization of the terrestrial biosphere and/or enhanced regrowth of previously
felled temperate forest. These two processes are incorporated into a box diffusion model of the
ocean-atmosphere system coupled to a five-box terrestrial biosphere. The extent to which historical
fossil fuel and land use change emission data can be reconciled with the observed atmospheric CO2
concentration record is examined. Furthermore, the sensitivity of future CO2 projections to the nature
of the budget imbalance is investigated. It is found that the CO2 record can accommodate a carbon
budget balanced by CO2 fertilization but that the balance with forest regrowth is more difficult.
Future CO2 projections are found to be sensitive to how the carbon budget is balanced, even relative
to uncertainties in future emissions.

KEYWORDS: ATMOSPHERIC CARBON-DIOXIDE, CLIMATE, CYCLE, DIFFUSION-MODEL,
EMISSIONS, FORESTS, FOSSIL-FUELS, PAST 2 CENTURIES, SINKS, STORAGE


     454  
Cramer, M.D., Z.F. Gao, and S.H. Lips. 1999. The influence of dissolved inorganic carbon in the
rhizosphere on carbon and nitrogen metabolism in salinity-treated tomato plants. New Phytologist
142(3):441-450.

The influence of variation in the concentration of dissolved inorganic carbon (DIC) in the form of
CO2 and HCO3- in the root media on the C and N metabolism of Lycopersicon esculentum cv. F144
was investigated under both saline and non-saline conditions. Tomato seedlings were grown in
hydroponic culture (pH 6.5) with or without NaCl, and the root solution was aerated with either
ambient CO2 (360 mol mol(-1)) or CO2- enriched air (5000 mu mol mol(-1)). Nitrate uptake and
root tissue NO3- concentrations were increased slightly by elevated rhizosphere DIC concentrations
in both control and salinity- treated plants. This is associated with 46% higher nitrate reductase
activity in the roots of control plants supplied with elevated DIC than in those supplied with ambient
DIG. The activity of phosphoenolpyruvate carboxylase (PEPc) in vitro in control and salinity-treated
plants was unaffected by the supply of elevated rhizosphere DIC concentrations. However, PEPc
activity in vitro was considerably higher than the rates of PEPc activity in vivo reported previously,
indicating that PEPc activity was not in itself a limitation on the provision of anaplerotic C. Therefore
elevated DIC concentration in the rhizosphere stimulated the uptake of NO3- and provided alternative
C skeletons for the assimilation of the NH4+ resulting from NO3- reduction into amino acids within
the roots. Salinity stimulated root glutamine synthetase (GS) activity up to double that in control
plants. Furthermore, elevated DIC caused an increase in leaf and root GS activity of control plants
while inhibiting GS activity in the roots of salinity-treated plants. Glutamine:2-oxoglutarate
aminotransferase (GOGAT) activity of salinity-treated plants was doubled by elevated rhizosphere
DIC concentrations. These changes in GS and GOGAT activity must reflect changes in amino acid
synthesis. Under saline conditions the xylem transport of NO3- is partly blocked and a larger root
assimilation develops, requiring not only the transamination of 2-oxoglutarate to glutamate but also
that of oxaloacetate to aspartate and the transamidation of aspartate to asparagine.

KEYWORDS: AMMONIUM NUTRITION, ANHYDRASE ACTIVITY, ASSIMILATION, BARLEY,
CO2, FIXATION, NITRATE REDUCTASE, PHOSPHOENOLPYRUVATE CARBOXYLASE,
ROOTS, SEEDLINGS


     455  
Cramer, M.D., and S.H. Lips. 1995. Enriched rhizosphere co2 concentrations can ameliorate the
influence of salinity on hydroponically grown tomato plants. Physiologia Plantarum 94(3):425-432.

Our previous work indicated that salinity caused a shift in the predominant site of nitrate reduction
and assimilation from the shoot to the root in tomato plants. In the present work we tested whether
an enhanced supply of dissolved inorganic carbon (DIC, CO2 + HCO3-) to the root solution could
increase anaplerotic provision of carbon compounds for the increased nitrogen assimilation in the root
of salinity-stressed Lycopersicon esculentum (L.) Mill. cv. F144. The seedlings were grown in
hydroponic culture with 0 or 100 mM NaCl and aeration of the root solution with either ambient or
CO2-enriched air (5 000 mu mol mol(-1)). The salinity-treated plants accumulated more dry weight
and higher total N when the roots were supplied with CO2-enriched aeration than when aerated with
ambient air. Plants grown with salinity and enriched DIC also had higher rates of NO3- uptake and
translocated more NO3- and reduced N in the xylem sap than did equivalent plants grown with
ambient DIC. Incorporation of DIC was measured by supplying a 1-h pulse of (HCO3-)-C-14 to the
roots followed by extraction with 80% ethanol. Enriched DIC increased root incorporation of DIC
10- fold in both salinized and non-salinized plants. In salinity- stressed plants, the products of
dissolved inorganic C-14 were preferentially diverted into amino acid synthesis to a greater extent
than in non-salinized plants in which label was accumulated in organic acids. It was concluded that
enriched DIC can increase the supply of N and anaplerotic carbon for amino acid synthesis in roots
of salinized plants. Thus enriched DIC could relieve the limitation of carbon supply for ammonium
assimilation and thus ameliorate the influence of salinity on NO3- uptake and assimilation as well as
on plant growth.

KEYWORDS: AMMONIUM, INORGANIC CARBON, METABOLISM, NITRATE ASSIMILATION,
NITROGEN, NUTRITION, REDUCTION, ROOTS, SEEDLINGS, SHOOT


     456  
Cramer, M.D., and S.H. Lips. 1995. The influence of enriched root-zone CO2 concentrations on
growth, nitrogen metabolism and root HCO3- incorporation in salinity stressed Lycopersicon
esculentum. Acta Phytopathologica Et Entomologica Hungarica 30(1-2):105-118.

Tomato plants grown with salinity reduce/assimilate a larger proportion of NO3- taken up in the roots
than do non-salinized plants. We investigated whether enriched CO2 in the root solution could
increase anaplerotic provision of carbon for root nitrogen assimilation in salinity stressed plants.
Tomato seedlings were grown in hydroponic culture with and without 100 mM NaCl and with
aeration of the root solution with either ambient or CO2 enriched air (5000 mu mol mol(-1)). The
salinity treated plants accumulated more dry weight and higher total N when the roots were supplied
with CO2 enriched aeration than when aerated with ambient air. Concentrations of K+ in the leaves
and roots were higher in plants treated with enriched CO2. Enriched root-zone CO2 increased root
incorporation of dissolved inorganic carbon (DIC). In salinity stressed plants the products of (DIC)-
C-14 were diverted into amino acid synthesis to a greater extent than in non-salinized plants. It was
concluded that enriched root-zone DIC could provide an increased anaplerotic source of carbon for
amino acid synthesis in roots, partially ameliorating the influence of salinity on plant growth.

KEYWORDS: AMMONIUM, CARBON DIOXIDE, LEAF RESPIRATION, NITRATE
ASSIMILATION, NUTRITION, PLANTS, REDUCTION, RESPONSES, SHOOT


     457  
Cramer, M.D., and M.B. Richards. 1999. The effect of rhizosphere dissolved inorganic carbon on
gas exchange characteristics and growth rates of tomato seedlings. Journal of Experimental Botany
50(330):79-87.

The possibility that an enhanced supply of dissolved inorganic carbon (DIC = CO2 + HCO3-) to the
root solution could increase the growth of Lycopersicon esculentum (L,) Mill. cv, F144 was
investigated under both saline and non-saline root medium conditions, Tomato seedlings were grown
in hydroponic culture with and without NaCl and the root solution was aerated with CO2
concentrations in the range between 0 and 5000 mu mol mol(- 1). The biomass of both control and
salinity-stressed plants grown at high temperatures (daily maximum of 37 degrees C) and an
irradiance of 1500 mu mol m(-2) s(-1) was increased by up to 200% by enriched rhizosphere DIG.
The growth rates of plants grown with irradiances of less than 1000 mu mol m(-2) s(-1) were
increased by elevated rhizosphere DIC concentrations only when grown at high shoot temperatures
(35 degrees C) or with salinity (28 degrees C), At high light intensities, the photosynthetic rate, the
CO2 and light-saturated photosynthetic rate (J(max)) and the stomatal conductance of plants grown
at high light intensity were lower in plants supplied with enriched compared to ambient DIG. This was
interpreted as 'down-regulation' of the photosynthetic system in plants supplied with elevated DIG.
Labelled organic carbon in the xylem sap derived from root (DIC)-C-14 incorporation was found to
be sufficient to deliver carbon to the shoot at rates equivalent to 1% and 10% of the photosynthetic
rate of the plants supplied with ambient- and enriched-DIC, respectively. It was concluded that
organic carbon derived from DIC incorporation and translocated in the xylem from the root to the
shoot may provide a source of carbon for the shoots, especially under conditions where low stomatal
conductance may be advantageous, such as salinity stress, high shoot temperatures and high light
intensities.

KEYWORDS: AMMONIUM NUTRITION, ASSIMILATION, BARLEY, CO2, METABOLISM,
NITRATE, PHOSPHOENOLPYRUVATE CARBOXYLASE, PLANTS, ROOTS, SALINITY


     458  
Cramer, M.D., N.A. Savidov, and S.H. Lips. 1996. The influence of enriched rhizosphere CO2 on
N uptake and metabolism in wild-type and NR-deficient barley plants. Physiologia Plantarum
97(1):47-54.

Positive influences of high concentrations of dissolved inorganic carbon (DIC) in the growth medium
of salinity- stressed plants are associated with carbon assimilation through phosphoenolpyruvate
carboxylase (PEPc) activity in roots; and also in salinity-stressed tomato plants, enriched CO2 in the
rhizosphere increases NO(3)(-)uptake. In the present study, wild-type and nitrate reductase-deficient
plants of barley (Hordeum vulgare L. cv. Steptoe) were used to determine whether the influence of
enriched CO2 on NO(3)(-)uptake and metabolism is dependent on the activity of nitrate reductase
(NR) in the plant. Plants grown in NH4+ and aerated with ambient air, were transferred to either
NO3- or NH4+ solutions and aerated with air containing between 0 and 6500 mu mol mol(-1) CO2.
Nitrogen uptake acid tissue concentrations of NO3- and NH4+ were measured as well as activities
of NR and PEPc. The uptake of NO3- by the wild-type was increased by increasing CO2. This was
associated with increased in vitro NR activity, but increased uptake of NO3- was found also in the
NR-deficient genotype when exposed to high CO2 concentrations; so that the influence of CO2 on
NO3- uptake was independent of the reduction of NO3- and assimilation into amino acids. The
increase in uptake of NO; in wild-type plants with enriched CO2 was the same at pH 7 as at pH 5,
indicating that the relative abundance of HCO3- or CO2 in the medium did not influence NO3-
uptake. Uptake of NH4+ was decreased by enriched CO2 in a pH (5 or 7) independent fashion. Thus
NO3- and NH4+ uptakes are influenced by the CO2 component of DIC independently of anaplerotic
carbon provision for amino acid synthesis, and CO2 may directly affect the uptake of NO3- and
NH4+ in ways unrelated to the NR activity in the tissue.

KEYWORDS: AMMONIUM NUTRITION, INORGANIC CARBON, MAIZE ROOTS, NH4,
NITRATE ASSIMILATION, NO3, PHOSPHOENOLPYRUVATE CARBOXYLASE, SHOOT


     459  
Crick, S.G., and R. McConchie. 1999. Ethanol vapour reduces leaf blackening in cut flower Protea
'Pink Ice' stems. Postharvest Biology and Technology 17(3):227-231.

The effect of ethanol vapour on postharvest leaf blackening of Protea susannae X compacta 'Pink Ice'
stems stored in plastic bags under darkness at 20 degrees C (+/- 1 degrees C) was assessed over a
19 day period. Application of ethanol vapour to the stems significantly reduced leaf blackening. Stems
exposed to 5.6 g ethanol kg(-1) stem weight, had the least amount of leaf blackening with less than
20% of leaves blackened by day 14. In contrast, the control stems had 50% of leaves blackened by
day 9, and 100% by day 15. The highest ethanol treatment at 11.2 g ethanol kg(-1) stem weight
caused substantial blackening within the first 24 h of the treatment being applied. Ethanol vapour
concentrations in the bag head space decreased rapidly in comparison with the bags with no stems,
suggesting that ethanol was rapidly taken up by the stems. Only the highest ethanol treatment had
detectable levels of ethanol in the bags after 17 days, and ethanol vapour had no effect on CO2
concentration in the bag head space. Carbon dioxide concentrations ranged between 1.0 and 2.5%.
The rate of leaf blackening on the bagged stems without ethanol was significantly less than on stems
not in bags, suggesting that elevated CO2 levels may have contributed to reduced blackening. (C)
1999 Elsevier Science B.V. All rights reserved.

KEYWORDS: FRUIT, NERIIFOLIA R


     460  
Crookshanks, M., G. Taylor, and M. Broadmeadow. 1998. Elevated CO2 and tree root growth:
contrasting responses in Fraxinus excelsior, Quercus petraea and Pinus sylvestris. New Phytologist
138(2):241-250.

Root growth and respiration in elevated CO2 (700 mu mol mol(- 1)) was studied in three tree species,
Fraxinus excelsior L., Quercus petraea. L. and Pinus sylvestris L. grown in open-top chambers
(OTCs) during a long-term exposure (20 months), during which root systems were allowed to
develop without restriction imposed by pots. Root growth, measured as root length using root in-
growth bags was increased significantly in trees exposed to elevated CO2, although the magnitude
of the response differed considerably between species and with time of sampling, the greatest effect
observed after 6 months in ash (ratio of elevated:ambient, e:a; 3.40) and the smallest effect observed
in oak (e:a; 1.95). This was accompanied by changes in specific root length, with a significant
decrease in all species after 6 months, suggesting that root diameter or root density were increased
in elevated CO2. Increases in root length might have resulted from an acceleration in root cell
expansion, since epidermal cell size was significantly increased in the zone of elongation in ash root
tips (P < 0.05). Contrasting effects of elevated CO2 were observed for root carbohydrates, with
significant increases in soluble sugars for all species (P < 0.05), but both increases and decreases in
starch content were observed, depending on species, and producing a significant interaction between
species and CO2 (P < 0.001). Exposure to elevated CO2 increased the total root d. wt for whole trees
of all three species after 8 months of exposure, although the magnitude of this effect, in contrast to
the root in-growth study, was greatest in Scots pine and smallest in ash. No significant effect of
elevated CO2 was observed on the root:shoot ratio. Further detailed analysis of whole root systems
after 20 months confirmed that species differences in root responses to elevated CO2 were apparent,
with increased coarse and fine root production in elevated CO2 for Scots pine and ash respectively.
Lateral root number was increased in elevated CO2 for all species, as was mean root diameter. Root
respiration rates were significantly reduced in elevated CO2 for all three species. These results
provide firm evidence that exposure of trees to future CO2 concentrations will have large effects on
root system development, growth, carbohydrate status and respiration. The magnitude and direction
of such effects will differ, depending on species. The consequences of such responses for the three
species studied are discussed.

KEYWORDS: ARCHITECTURE, ATMOSPHERIC CARBON-DIOXIDE, EFFICIENCY,
ENRICHMENT, HYBRID POPLAR, PLANT, RESPIRATION, SOIL, TEMPERATURE, WATER-
USE


     461  
Crookshanks, M., G. Taylor, and L. Dolan. 1998. A model system to study the effects of elevated
CO2 on the developmental physiology of roots: the use of Arabidopsis thaliana. Journal of
Experimental Botany 49(320):593-597.

Three developmental changes were observed in the roots of Arabidopsis thaliana (Columbia) when
shoots were exposed to elevated CO2, (i) The allometric coefficient, k, was enhanced significantly
(P<0.001), (ii) primary root length and root extension rate were enhanced (P<0.001), Accelerated
cortical cell expansion contributed to this effect and was associated with increased cell wall
extensibility, measured as % plasticity. (iii) Lateral root formation and extension were also increased
in elevated CO2 (P<0.05). These results illustrate that root growth and structure was altered
following exposure to elevated CO2, The changes observed suggest that Arabidopsis provides a
useful model which should, in future, be amenable to study using appropriate mutants allowing the
genetic basis of the responses to be identified.

KEYWORDS: CELLULAR MECHANISMS, ENRICHMENT, EXPANSION, GROWTH, MUTANTS,
RESPONSES


     462  
Crosson, P.R., and N.J. Rosenberg. 1993. An overview of the mink study. Climatic Change 24(1-
2):159-173.

Highlights of the previous papers in this series are reviewed. Methodology developed for the MINK
study has improved the ability of impacts analysis to deal with questions of (1) spatial and temporal
variability in climate change; (2) CO2- enrichment effects; (3) the reactions of complex enterprises
(farms and forests) to climate change and their ability to adjust and adapt; and (4) integrated effects
on current and, more particularly, on future regional economies. The methodology also provides for
systematic study of adjustment and adaptation opportunities and of the inter-industry linkages that
determine what the overall impacts on the regional economy might be. The analysis shows that with
a 1930s 'dust bowl' climate the region-wide economic impacts would be small, after adjustments in
affected sectors. In this final paper we consider whether synergistic effects among sectoral impacts
and more severe climate change scenarios might alter this conclusion. The MINK analysis, as is, leads
to the conclusion that a strong research capacity will be required to ensure that technologies
facilitating adaptation to climate change will be available when needed. The capacity to deal with
climate change also requires an open economy allowing for free trade and movement of people and
for institutions that protect unpriced environmental values. More severe climate scenarios and
negative synergisms can only strengthen these conclusions.



     463  
Crowley, T.J., and S.K. Baum. 1997. Effect of vegetation on an ice-age climate model simulation.
Journal of Geophysical Research-Atmospheres 102(D14):16463-16480.

A growing number of studies suggest that vegetation changes can significantly influence regional
climate variations. Herein we utilize a climate model (GENESIS) with a land surface vegetation
package to evaluate the potential role of the very large vegetation changes that occurred during the
last glacial maximum (LGM), In particular, we focus on the potential response to a significant
reduction in the area of tropical rainforest. Simulations employed a global vegetation reconstruction
for the LGM and Climate/Long-Range Investigation, Mapping and Prediction (CLIMAP) sea surface
temperature (SST) estimates. Results indicate that expansion of dryland vegetation causes a 15-30%
additional LGM cooling for Australia (0.4 degrees C) and Africa (0.9 degrees C), respectively,
Turnover from conifer to tundra also causes cooling of 2 degrees-4 degrees C or mon in western
Europe and Siberia. However, for the largest rainforest area (Amazon Basin), inclusion of realistic
vegetation increased modeled temperatures 2 degrees-4 degrees C and decreased precipitation by 10-
35%. These latter results are similar to those obtained with sensitivity experiments of the effects of
future Amazon deforestation, Initial assessment of the potential effect of decreased stomatal
resistance due to lower ice age CO2 levels indicates little significant response to this effect.
Comparison of model-predicted low-elevation LGM temperature Changes with estimates from proxy
data indicate that inclusion of realistic vegetation estimates for the LGM results in slightly more than
50% agreement between models and data for low-elevation sites in low-mid latitudes. Data at
variance with model predictions would appear to be explainable by considering additional changes
in vegetation, ice age dust, or a 1 degrees- 2 degrees C cooling below CLIMAP values. This
conclusion is at Variance with a 3 degrees-4 degrees C tropical cooling suggested by some studies
for explaining estimated land temperature changes during the LGM. In some western European sites
model temperatures are colder than proxy data by 2 degrees-8 degrees C. This model-data
discrepancy may be explained by less sea ice in the subpolar North Atlantic than stipulated by
CLIMAP, a conclusion consistent with new marine data from that region.

KEYWORDS: BOUNDARY-CONDITIONS, EURASIAN SNOW COVER, GENERAL-
CIRCULATION MODELS, GLOBAL CLIMATE, LAST GLACIAL MAXIMUM, LATE
QUATERNARY, SEA-SURFACE TEMPERATURE, STOMATAL-RESISTANCE, TERRESTRIAL
CARBON STORAGE, TRANSFER SCHEME LSX


     464  
Crush, J.R. 1993. Hydrogen evolution from root-nodules of trifolium-repens and medicago-sativa
plants grown under elevated atmospheric co2. New Zealand Journal of Agricultural Research
36(2):177-183.

Nitrogenase activity and hydrogen (H-2) evolution from nodules of Trifolium repens L. and Medicago
sativa L. were measured on plants grown under 700 or 350 mul/l atmospheric CO2 and day/night
temperatures of 18/13-degrees-C or 28/23-degrees-C. Assays were done after 39, 47, and 54 days'
exposure to the treatments. In Trifolium, nitrogenase activity/plant was stimulated by elevated CO2
and higher temperatures but in Medicago only temperature had an effect. Hydrogen emission/plant
was greater in Trifolium plants grown at 700 mul/l CO2 than in plants at 350 mul/l CO2, but in
Medicago, H-2 emission rates did not respond to elevated CO2. Elevated CO2 reduced nodule
relative efficiency (RE) in 39-day-old Trifolium plants growing at 18/13-degrees-C, but not under
other conditions. It is concluded that predicted future CO2 concentration will lead to a greater
contribution from legume nitrogen (N) fixation to global H-2 sources. The magnitude of the increase
will be influenced by the legume species involved and temperature.

KEYWORDS: ECONOMY, EFFICIENCY, LEGUME, MOLECULAR-HYDROGEN, NITROGEN-
FIXATION, REDUCTION, RHIZOBIA, WHITE CLOVER


     465  
Crush, J.R. 1994. Elevated atmospheric co2 concentration and rhizosphere nitrogen-fixation in 4
forage plants. New Zealand Journal of Agricultural Research 37(4):455-463.

Lolium x boucheanum (2n and 4n), Plantago lanceolata, and Pennisetum clandestinum were grown
in pots of soil in growth rooms with factorial combinations of 350 or 700 mul/l atmospheric CO2 and
day/night temperatures of 28/23-degrees-C or 18/13-degrees-C. Both cultivars of Lolium and P.
lanceolata grew faster with elevated CO2 but P. clandestinum was unaffected. Rhizosphere
nitrogenase activity, assessed by acetylene reduction, was reduced by the 700 mul/l CO2 treatment
in the tetraploid Lolium but otherwise did not vary significantly with CO2 level.

KEYWORDS: ACETYLENE-REDUCTION ASSAY, ASSOCIATION, CARBON, CEREALS,
GRASSES, GRASSLAND, GROWTH, ROOTS, SPECIFICITY, TRIFOLIUM- REPENS


     466  
Cruz, C., S.H. Lips, and M.A. Martinsloucao. 1993. The effect of nitrogen-source on
photosynthesis of carob at high co2 concentrations. Physiologia Plantarum 89(3):552-556.

Carob seedlings (Ceratonia siliqua L. cv. Mulata), fed with nitrate or ammonium, were grown in
growth chambers containing two levels of CO2 (360 or 800 mu 1 1(-1)), three root temperatures (15,
20 or 25 degrees C), and the same shoot temperature (20/24 degrees C, night/day temperature). The
response of the plants to CO2 enrichment was affected by environmental factors such as the type of
inorganic nitrogen in the medium and root temperature. Increasing root temperature enhanced
photosynthesis rate more in the presence of nitrate than in the presence of ammonium. Differences
in photosynthetic products were also observed between nitrate- and ammonium-fed carob seedlings.
Nitrate-grown plants showed an enhanced content of sucrose, while ammonium led to enhanced
storage of starch. Increase in root temperature caused an increase in dry mass of the plants of similar
proportions in both nitrogen sources. The enhancement of the rates of photosynthesis by CO2
enrichment was proportionally much larger than the resulting increases in dry mass production when
nitrate was the nitrogen source. Ammonium was the preferred nitrogen source for carob at both
ambient and high CO, concentrations. The level of photosynthesis of a plant is limited not only by
atmospheric CO2 concentration but also by the nutritional and environmental conditions of the root.

KEYWORDS: AMMONIUM, CELLS, LEAVES, PLANTS


     467  
Cruz, C., S.H. Lips, and M.A. Martins-Loucao. 1997. Changes in the morphology of roots and
leaves of carob seedlings induced by nitrogen source and atmospheric carbon dioxide. Annals of
Botany 80(6):817-823.

Carob seedlings were grown hydroponically for 9 weeks under 360 and 800 mu l l(-1) CO2. One of
two nitrogen sources, nitrate or ammonium, was added to the nutrient medium at concentrations of
3 mol m(-3). Root systems of the developing plants supplied with nitrate compared to those supplied
with ammonium were characterized by: (a) more biomass on the lower part of the root; (b) fewer
lateral roots of first and second order; (c) longer roots; (d) higher specific root length; (e) a smaller
root diameter. The morphology of the root systems of nitrate- fed plants changed in the presence of
elevated carbon dioxide concentrations, resembling, more closely, that of ammonium-fed plants. Total
leaf area was higher in ammonium-than in nitrate- fed plants. Nitrate-fed plants had greater total leaf
area in the presence of high carbon dioxide than in normal CO2, due to an increase in epidermal cell
size that led to development of larger leaflets with lower stomatal frequency. The observed changes
in the morphology of roots and shoots agreed with the results observed for total biomass production.
Nitrate-fed plants increased their biomass production by 100% in the presence of elevated CO2
compared to 15% in ammonium-fed plants, indicating that the response of carob to high CO2
concentrations is very dependent on the nitrogen source. Under elevated CO2, nitrate grown plants
had a larger content of sucrose in both roots and shoots, while no significant difference was observed
in the content of sucrose in ammonium- grown plants, whether in ambient or enriched carbon dioxide.
Hence, the differences in soluble carbohydrate contents can, at least partly, account for differences
in root and shoot morphology. (C) 1997 Annals of Botany Company.

KEYWORDS: AMMONIUM ASSIMILATION, CELLULAR MECHANISMS, CERATONIA-
SILIQUA, CO2- ENRICHMENT, ELEVATED CO2, GROWTH, NITRATE, PHOTOSYNTHESIS,
PLANTS, RESPONSES


     468  
Csintalan, Z., Z. Tuba, H.K. Lichtenthaler, and J. Grace. 1996. Reconstitution of photosynthesis
upon rehydration in the desiccated leaves of the poikilochlorophyllous shrub Xerophyta scabrida at
elevated CO2. Journal of Plant Physiology 148(3-4):345-350.

We report the resynthesis of the photosynthetic apparatus and the restoration of its function in the
monocotyledonous C-3 shrub Xerophyta scabrida (Pax) Th. Dur. et Schinz (Velloziaceae) following
a period of 5 years in the air-dried state. Detached leaves were rehydrated at present (350 mu mol
mol(-1)) and at elevated CO2 (700 mu mol mol(-1)). Elevated CO2 concentration had no effect on
the rate of rehydration, nor on the de novo resynthesis pattern of the chlorophylls and carotenoids
or the development of photochemical activity in the reviving desiccated leaves. The time required to
fully reconstitute the photosynthetic apparatus and its function in the air-dried achlorophyllous leaves
on rehydration did not differ at the two CO2 concentrations. However, respiratory activity during
rehydration was more intensive and of longer duration at high CO2 and net CO2 assimilation first
became apparent 12 h later than in the leaves rehydrated at present CO2. After reconstitution of the
photosynthetic apparatus, the net CO2 assimilation rate was higher in the high CO2 leaves, however
it rapidly declined to a value lower than that in the present CO2 plants due to acclimation. This
acclimation to elevated CO2 occurred only after complete reconstitution of the photosynthetic
apparatus. The downward acclimation of photosynthesis was accompanied by a decrease in content
of photosynthetic pigments (chlorophyll a + b and carotenoids x + c) and stomatal conductance. The
initial slope of the A/c(i) curve for the high CO2 leaves was much lower and net CO2 assimilation
rates were lower at all c(i)'s than in the present CO2 plants. The rate of respiration also decreased and
the C- balance of the high CO2 leaves therefore remained similar to that of leaves in present CO2.

KEYWORDS: ATMOSPHERIC CARBON-DIOXIDE, CAPACITY, EXPOSURE, PLANTS,
RESPIRATION


     469  
Cui, M., P.M. Miller, and P.S. Nobel. 1993. Co2 exchange and growth of the crassulacean acid
metabolism plant opuntia-ficus-indica under elevated co2 in open-top chambers. Plant Physiology
103(2):519-524.

CO2 uptake, water vapor conductance, and biomass production of Opuntia ficus-indica, a
Crassulacean acid metabolism species, were studied at CO2 concentrations of 370, 520, and 720 muL
L-1 in open-top chambers during a 23-week period. Nine weeks after planting, daily net CO2 uptake
for basal cladodes at 520 and 720 muL L-1 Of CO2 was 76 and 98% higher, respectively, than at 370
muL L-1. Eight weeks after daughter cladodes emerged, their daily net CO2 uptake was 35 and 49%
higher at 520 and 720 muL L-1 of CO2, respectively, than at 370 muL L-1. Daily water-use efficiency
was 88% higher under elevated CO2 for basal cladodes and 57% higher for daughter cladodes. The
daily net CO2 uptake capacity for basal cladodes increased for 4 weeks after planting and then
remained fairly constant, whereas for daughter cladodes, it increased with cladode age, became
maximal at 8 to 14 weeks, and then declined. The percentage enhancement in daily net CO2 uptake
caused by elevated CO2 was greatest initially for basal cladodes and at 8 to 14 weeks for daughter
cladodes. The chlorophyll content per unit fresh weight of chlorenchyma for daughter cladodes at 8
weeks was 19 and 62% lower in 520 and 720 muL L-1 Of CO2, respectively, compared with 370
muL L-1. Despite the reduced chlorophyll content, plant biomass production during 23 weeks in 520
and 720 muL L-1 of CO2 was 21 and 55% higher, respectively, than at 370 muL L-1. The root dry
weight nearly tripled as the CO2 concentration was doubled, causing the root/shoot ratio to increase
with CO2 concentration. During the 23-week period, elevated CO2 significantly increased CO2
uptake and biomass production of O. ficus-indica.

KEYWORDS: AGAVE-VILMORINIANA, ATMOSPHERIC CARBON-DIOXIDE, ENRICHMENT,
PHOTOSYNTHESIS, PRODUCTIVITY, RESPIRATION, RESPONSES, TEMPERATURE, WATER-
USE, YIELD


     470  
Cui, M., and P.S. Nobel. 1994. Gas-exchange and growth-responses to elevated co2 and light levels
in the cam species opuntia-ficus-indica. Plant, Cell and Environment 17(8):935-944.

Gas exchange and dry-weight production in Opuntia ficus-indica, a CAM species cultivated
worldwide for its fruit and cladodes, were studied in 370 and 750 mu mol mol(-1) CO2 at three
photosynthetic photon flux densities (PPFD: 5, 13 and 20 mol m(-2) d(-1)). Elevated CO2 and PPFD
enhanced the growth of basal cladodes and roots during the 12-week study. A rise in the PPFD
increased the growth of daughter cladodes; elevated CO2 enhanced the growth of first-daughter
cladodes but decreased the growth of the second-daughter cladodes produced on them. CO2
enrichment enhanced daily net CO2 uptake during the initial 8 weeks after planting for both basal and
first- daughter cladodes. Water vapour conductance was 9 to 15% lower in 750 than in 370 mu mol
mol(-1) CO2. Cladode chlorophyll content was lower in elevated CO2 and at higher PPFD. Soluble
sugar and starch contents increased with time and were higher in elevated CO2 and at higher PPFD.
The total plant nitrogen content was lower in elevated CO2. The effect of elevated CO2 on net CO2
uptake disappeared at 12 weeks after planting, possibly due to acclimation or feedback inhibition,
which in turn could reflect decreases in the sink strength of roots. Despite this decreased effect on
net CO2 uptake, the total plant dry weight at 12 weeks averaged 32% higher in 750 than in 370 mu
mol mol(-1) CO2. Averaged for the two CO2 treatments, the total plant dry weight increased by 66%
from low to medium PPFD and by 37% from medium to high PPFD.

KEYWORDS: AGAVE-VILMORINIANA, CARBON DIOXIDE, CO2- ENRICHMENT,
CRASSULACEAN ACID METABOLISM, PHOTOSYNTHESIS, PHYSIOLOGY, PLANT GROWTH,
PRODUCTIVITY, SHORT- TERM, WATER-USE EFFICIENCY


     471  
Cure, J.D., T.W. Rufty, and D.W. Israel. 1989. Alterations in soybean leaf development and
photosynthesis in a CO2-enriched atmosphere. Botanical Gazette 150(4):337-345.



     472  
Cure, J.D., T.W. Rufty, and D.W. Israel. 1991. Assimilate relations in source and sink leaves
during acclimation to a co2-enriched atmosphere. Physiologia Plantarum 83(4):687-695.

Evidence from previous studies suggested that adjustments in assimilate formation and partitioning
in leaves might occur over time when plants are exposed to enriched atmospheric CO2. We examined
assimilate relations of source (primary unifoliolate) and developing sink (second mainstem trifoliolate)
leaves of soybean [Glycine max (L.) Merr. cv. Lee] plants for 12 days after transfer from a control
(350-mu-l l-1) to a high (700-mu-l l-1) CO2 environment. Similar responses were evident in the two
leaf types. Net CO2 exchange rate (CER) immediately increased and remained elevated in high CO2.
Initially, the additional assimilate at high CO2 levels in the light and was utilized in the subsequent
dark period. After approximately 7 days, assimilate export in the light began to increase and by 12
days reached rates 3 to 5 times that of the control. In the developing sink leaf, high rates of export
in the light occurred as the leaf approached full expansion. The results indicate that a specific
acclimation process occurs in source leaves which increases the capacity for assimilate export in the
light phase of the diurnal cycle as plants adjust to enriched CO2 and a more rapid growth rate.

KEYWORDS: CO2- ENRICHMENT, ELEVATED CARBON-DIOXIDE, GROWTH, NITROGEN,
PHOTOSYNTHESIS, PLANTS, SEED YIELD, STARCH FORMATION, TRANSLOCATION,
WATER-STRESS


     473  
Curtis, P.S. 1996. A meta-analysis of leaf gas exchange and nitrogen in trees grown under elevated
carbon dioxide. Plant, Cell and Environment 19(2):127-137.

The response of trees to rising atmospheric CO2 concentration ([CO2]) is of concern to forest
ecologists and global carbon modellers and is the focus of an increasing body of research work, I
review studies published up to May 1994, and several unpublished works, which reported at least one
of the following: net CO2 assimilation (A), stomatal conductance (g(s)), leaf dark respiration (R(d)),
leaf nitrogen or specific leaf area (SLA) in woody plants grown at <400 mu mol mol(-1) CO2 or at
600-800 mu mol mol(-1) CO2, The resulting data from 41 species were categorized according to
growth conditions (unstressed versus stressed), length of CO2 exposure, pot size and exposure
facility [growth chamber (GC), greenhouse (GH), or open-top chamber (OTC)] and interpreted using
meta-analytic methods, Overall, A showed a large and signifcant increase at elevated [CO2] but
length of CO2 exposure and the exposure facility were important modifiers of this response, Plants
exposed for <50 d had a significantly greater response, and those from GCs had a significantly lower
response than plants from longer exposures or from OTC studies, Negative acclimation of A was
significant and general among stressed plants, but in unstressed plants was influenced by length of
CO2 exposure, the exposure facility and/or pot size, Growth at elevated [CO2] resulted in moderate
reductions in g(s) in unstressed plants, but there was no significant effect of CO2 on g(s) in stressed
plants, Leaf dark respiration (mass or area basis) was reduced strongly by growth at high [CO2],
while leaf N was reduced only when expressed on a mass basis, This review is the first meta- analysis
of elevated CO2 studies and provides statistical confirmation of several general responses of trees to
elevated [CO2]. It also highlights important areas of continued uncertainty in our understanding of
these responses.

KEYWORDS: ATMOSPHERIC CO2, CLUTCH-SIZE, CO2 CONCENTRATION, DARK
RESPIRATION, LIRIODENDRON-TULIPIFERA L, PHOSPHORUS DEFICIENCY, PINUS-
RADIATA, SEEDLINGS, STOMATAL CONDUCTANCE, WATER-USE


     474  
Curtis, P.S., L.M. Balduman, B.G. Drake, and D.F. Whigham. 1990. Elevated atmospheric CO2
effects on belowground processes in C3 and C4 estuarine marsh communities. Ecology 71(5):2001-
2006.



     475  
Curtis, P.S., A.A. Snow, and A.S. Miller. 1994. Genotype-specific effects of elevated co2 on
fecundity in wild radish (raphanus-raphanistrum). Oecologia 97(1):100-105.

Rising atmospheric CO2 may lead to natural selection for genotypes that exhibit greater fitness under
these conditions. The potential for such evolutionary change will depend on the extent of within-
population genetic variation in CO2 responses of wild species. We tested for heritable variation in
CO2- dependent life history responses in a weedy, cosmopolitan annual, Raphanus raphanistrum.
Progeny from five paternal families were grown at ambient and twice ambient CO2 using outdoor
open-top chambers (160 plants per CO2 treatment). Elevated CO2 stimulated net assimilation rates,
especially in plants that had begun flowering. Across paternal families, elevated CO2 led to significant
increases in flower and seed production (by 22% and 13% respectively), but no effect was seen on
time to bolting, leaf area at bolting, fruit set, or number of seeds per fruit. Paternal families differed
in their response to the CO2 treatment: in three families there were no significant CO2 effects, while
in one family lifetime fecundity increased by > 50%. These genotype-specific effects altered fitness
rankings among the five paternal families. Although we did not detect a significant genotype X CO2
interaction, our results provide evidence for heritable responses to elevated CO2. In a subset of
plants, we found that the magnitude of CO2 effects on fecundity was also influenced by soil fertility.

KEYWORDS: ATMOSPHERIC CO2, CARBON DIOXIDE, ENRICHMENT, GAS-EXCHANGE,
INTRASPECIFIC VARIATION, L BRASSICACEAE, LIFE-HISTORY, SATIVUS L, SEED-WEIGHT
VARIATION, SIZE VARIATION


     476  
Curtis, P.S., and J.A. Teeri. 1992. Seasonal responses of leaf gas-exchange to elevated carbon-
dioxide in populus-grandidentata. Canadian Journal of Forest Research-Revue Canadienne De
Recherche Forestiere 22(9):1320-1325.

Rising atmospheric carbon dioxide concentrations may have important consequences for forest
ecosystems. We studied above- and below-ground growth and leaf gas exchange responses of
Populus grandidentata Michx. to elevated CO2 under natural forest conditions over the course of a
growing season. Recently emerged P. grandidentata seedlings were grown in native, nutrient-poor
soils at ambient and twice ambient (707 mubar (1 bar = 100 kPa)) CO2 partial pressure for 70 days
in open-top chambers in northern lower Michigan. Total leaf area and shoot and root dry weight all
increased in high CO2 grown plants. Photosynthetic light and CO2 response characteristics were
measured 28, 45, and 68 days after exposure to elevated CO2. In ambient grown plants, light
saturated assimilation rates increased from day 28 to day 45 and then declined at day 68 (15
September). This late-season decline, typical of senescing Populus leaves, was due both to a decrease
in the initial slope of the net CO2 assimilation versus intercellular CO2 Partial pressure relationship
and to decreased CO2 saturated assimilation rates. Specific leaf nitrogen (mg N . (cm2 leaf area)-1)
did not change during this period, although leaf carbon content and leaf weight (mg . cm-2) both
increased. In ambient grown plants stomatal conductance also declined at day 68. In contrast, plants
grown at elevated CO2 showed no late- season decline in photosynthetic capacity or changes in leaf
weight, suggesting a delay in senescence with long-term exposure to high CO2. High CO2 grown
plants also maintained photosynthetic sensitivity to increasing C(i) throughout the exposure period,
while ambient CO2 grown plants were insensitive to C(i) above 400 mubar on day 68. These results
indicate the potential for direct CO2 fertilization of P. grandidentata in the field and provide evidence
for a new mechanism by which elevated atmospheric CO2 could influence seasonal carbon gain.

KEYWORDS: ACCLIMATION, ATMOSPHERIC CO2 ENRICHMENT, GROWTH-RESPONSES,
IRRADIANCE, LEAVES, LIQUIDAMBAR- STYRACIFLUA, LONG-TERM EXPOSURE,
PHOTOSYNTHETIC INHIBITION, PINUS-TAEDA SEEDLINGS, VEGETATION


     477  
Curtis, P.S., C.S. Vogel, K.S. Pregitzer, D.R. Zak, and J.A. Teeri. 1995. Interacting effects of
soil fertility and atmospheric co2 on leaf-area growth and carbon gain physiology in populus X
euramericana (dode) guinier. New Phytologist 129(2):253-263.

Two important processes which may limit productivity gains in forest ecosystems with rising
atmospheric CO2 are reduction in photosynthetic capacity following prolonged exposure to high CO2
and diminution of positive growth responses when soil nutrients, particularly N, are limiting. To
examine the interacting effects of soil fertility and CO2 enrichment on photosynthesis and growth in
trees we grew hybrid poplar (Populus x euramericana) for 158 d in the field at ambient and twice
ambient CO2 and in soil with low or high N availability. We measured the timing and rate of canopy
development, the seasonal dynamics of leaf level photosynthetic capacity, respiration, and N and
carbohydrate concentration, and final above- and belowground dry weight. Single leaf net CO2
assimilation (A) increased at elevated CO2 over the majority of the growing season in both fertility
treatments. At high fertility, the maximum size of individual leaves, total leaf number, and seasonal
leaf area duration (LAD) also increased at elevated CO2, leading to a 49% increase in total dry
weight. In contrast, at low fertility leaf area growth was unaffected by CO2 treatment. Total dry
weight nonetheless increased 25% due to CO2 effects on A. Photosynthetic capacity (A at constant
internal p(CO2), (C-i)) was reduced in high CO2 plants after 100 d growth at low fertility and 135
d growth at high fertility. Analysis of A responses to changing C-i indicated that this negative
adjustment of photosynthesis was due to a reduction in the maximum rate of CO2 fixation by
Rubisco. Maximum rate of electron transport and phosphate regeneration capacity were either
unaffected or declined at elevated CO2. Carbon dioxide effects on leaf respiration were most
pronounced at high fertility, with increased respiration mid-season and no change (area basis) or
reduced (mass basis) respiration late- season in elevated compared to ambient CO2 plants. This
temporal variation correlated with changes in leaf N concentration and leaf mass per area. Our results
demonstrate the importance of considering both structural and physiological pathways of net C gain
in predicting tree responses to rising CO2 under conditions of suboptimal soil fertility.

KEYWORDS: DIOXIDE CONCENTRATION, DRY-MATTER, ELEVATED CO2, ENRICHMENT,
FEEDBACK, GAS-EXCHANGE, NITROGEN, PHOTOSYNTHESIS, PLANTS, SHORT- TERM


     478  
Curtis, P.S., and X.Z. Wang. 1998. A meta-analysis of elevated CO2 effects on woody plant mass,
form, and physiology. Oecologia 113(3):299-313.

Quantitative integration of the literature on the effect of elevated CO2 on woody plants is important
to aid our understanding of forest health in coming decades and to better predict terrestrial feedbacks
on the global carbon cycle. We used meta-analytic methods to summarize and interpret more than 500
reports of effects of elevated CO2 on woody plant biomass accumulation and partitioning, gas
exchange, and leaf nitrogen and starch content. The CO2 effect size metric we used was the log-
transformed ratio of elevated compared to ambient response means weighted by the inverse of the
variance of the log ratio. Variation in effect size among studies was partitioned according to the
presence of interacting stress factors, length of CO2 exposure, functional group status, pot size, and
type of CO2 exposure facility. Both total biomass (WT) and net CO2 assimilation (A) increased
significantly at about twice ambient CO2, regardless of growth conditions. Low soil nutrient
availability reduced the CO2 stimulation of WT by half, from + 31 % under optimal conditions to +
16 %, while low light increased the response to + 52 %. We found no significant shifts in biomass
allocation under high CO2. Interacting stress factors had no effect on the magnitude of responses of
A to CO2, although plants grown in growth chambers had significantly lower responses (+ 19 %)
than those grown in greenhouses or in open-top chambers (+ 54 %). We found no consistent evidence
for photosynthetic acclimation to CO2 enrichment except in trees grown in pots < 0.51 (- 36 %) and
no significant CO2 effect on stomatal conductance. Both leaf dark respiration and leaf nitrogen were
significantly reduced under elevated CO2 (- 18 % and - 16 % respectively, data expressed on a leaf
mass basis), while leaf starch content increased significantly except in low nutrient grown
gymnosperms. Our results provide robust, statistically defensible estimates of elevated CO2 effect
sizes against which new results may be compared or for use in forest and climate model
parameterization.

KEYWORDS: ATMOSPHERIC CARBON-DIOXIDE, BETULA-PENDULA ROTH, CASTANEA-
SATIVA MILL, LEAF GAS- EXCHANGE, LOBLOLLY-PINE SEEDLINGS, NET PRIMARY
PRODUCTION, PICEA-ABIES L, QUERCUS-ALBA, RELATIVE GROWTH-RATE, STOMATAL
CONDUCTANCE


     479  
Curtis, P.S., D.R. Zak, K.S. Pregitzer, and J.A. Teeri. 1994. Aboveground and belowground
response of populus grandidentata to elevated atmospheric co2 and soil n-availability. Plant and Soil
165(1):45-51.

Soil N availability may play an important role in regulating the long-term responses of plants to rising
atmospheric CO2 partial pressure. To further examine the linkage between above- and belowground
C and N cycles at elevated CO2, we grew clonally propagated cuttings of Populus grandidentata in
the field at ambient and twice ambient CO2 in open bottom root boxes filled with organic matter poor
native soil. Nitrogen was added to all root boxes at a rate equivalent to net N mineralization in local
dry oak forests. Nitrogen added during August was enriched with N-25 to trace the flux of N within
the plant-soil system. Above- and belowground growth, CO2 assimilation, and leaf N content were
measured non- destructively over 142 d. After final destructive harvest, roots, stems, and leaves were
analyzed for total N and N-15. There was no CO2 treatment effect on leaf area, root length, or net
assimilation prior to the completion of N addition. Following the N addition, leaf N content increased
in both CO2 treatments, but net assimilation showed a sustained increase only in elevated CO2 grown
plants. Root relative extension rate was greater at elevated CO2, both before and after the N addition.
Although final root biomass was greater at elevated CO2, there was no CO2 effect on plant N uptake
or allocation. While low soil N availability severely inhibited CO2 responses, high CO2 grown plants
were more responsive to N. This differential behavior must be considered in light of the temporal and
spatial heterogeneity of soil resources, particularly N which often limits plant growth in temperate
forests.

KEYWORDS: CARBON DIOXIDE, ENRICHMENT, NITROGEN, PHOTOSYNTHESIS, QUERCUS-
ALBA, SEEDLING GROWTH, TREES


     480  
Cushman, J.C., and H.J. Bohnert. 1997. Molecular genetics of Crassulacean acid metabolism.
Plant Physiology 113(3):667-676.

Most higher plants assimilate atmospheric CO2 through the C-3 pathway of photosynthesis using
ributose-1,5-bisphosphate carboxylase/oxygenase (Rubisco). However, when CO2 availability is
reduced by environmental stress conditions, the incomplete discrimination of CO2 over O-2 by
Rubisco leads to increased photorespiration, a process that reduces the efficiency of C-3
photosynthesis. To overcome the wasteful process of photorespiration, approximately 10% of higher
plant species have evolved two alternate strategies for photosynthetic CO2 assimilation, C-3
photosynthesis and Crassulacean acid metabolism. Both of these biochemical pathways employ a
''CO2 pump'' to elevate intracellular CO2 concentrations in the vicinity of Rubisco, suppressing
photorespiration and therefore improving the competitiveness of these plants under conditions of high
light intensity, high temperature, or low water availability. This CO2 pump consists of a primary
carboxylating enzyme, phosphoenolpyruvate carboxylase. In C-4 plants, this CO2-concentrating
mechanism is achieved by the coordination of two carboxylating reactions that are spatially separated
into mesophyll and bundle-sheath cell types (for review, see R.T. Furbank, W.C. Taylor [1995] Plant
Cell 7:797-802; M.S.B. Ku, Y. Kano-Murakami, M. Matsuoka [1996] Plant Physiol 111:949-957).
In contrast, Crassulacean acid metabolism plants perform both carboxylation reactions within one cell
type, but the two reactions are separated in time. Both pathways involve cell- specific changes in the
expression of many genes that are not present in C-3 plants.

KEYWORDS: ABSCISIC- ACID, C-3 PHOTOSYNTHESIS, CAM, COMMON ICE PLANT,
DIFFERENTIAL EXPRESSION, INDUCTION, MESEMBRYANTHEMUM-CRYSTALLINUM L,
NADP-MALIC ENZYME, PHOSPHOENOLPYRUVATE CARBOXYLASE, SALT STRESS


     481  
Dacey, J.W.H., B.G. Drake, and M.J. Klug. 1994. Stimulation of methane emission by carbon-
dioxide enrichment of marsh vegetation. Nature 370(6484):47-49.

THERE is substantial evidence that many plants respond to increased concentrations of atmospheric
carbon dioxide by increasing their productivity(1-4) This observation has led to the suggestion that,
by taking up CO2, the terrestrial biosphere might mitigate the potential greenhouse warming
associated with anthropogenic CO2 emissions(5). Whiting and Chanton(6) have found, however, that
for wetlands of varying productivity around the world, higher net primary production is associated
with higher emissions of methane-another important greenhouse gas. Here we present measurements
of methane emissions from a marsh that has been exposed to twice the present ambient concentration
of atmospheric CO2. We find that over a one-week period, the CO2-enriched sites had significantly
higher emissions of methane than the control sites. Our results suggest that future increases in
atmospheric CO2 concentration may lead to significant increases in methane emissions from wetlands.

KEYWORDS: COMMUNITIES, ELEVATED CO2, ESTUARINE MARSH, FIELD, GROWTH,
PLANTS, PRODUCTIVITY, RESPONSES, RICE PADDIES, WETLANDS


     482  
Dahlman, R.C. 1993. Co2 and plants - revisited. Vegetatio 104:339-355.

The decade-long USA research program on the direct effects of CO2 enrichment on vegetation has
achieved important milestones and has produced a number of interesting and exciting findings.
Research beginning in 1980 focused on field experiments to determine whether phenomena observed
in the laboratory indeed occurred in natural environments. The answer is yes. Data obtained from
numerous field studies show mixed response of crop and native species to CO2 enrichment however.
Nearly all experiments demonstrate that plants exhibit positive gain when grown at elevated CO2;
although the magnitude varies greatly. Most crop responses range from 30 to 50 % increase in yield.
Results from long-term experiments with woody species and ecosystems are even more variable.
Huge growth responses (100 to nearly 300 % increase relative to controls) are reported from several
tree experiments and the salt-marsh ecosystem experiment. Other results from experiments with
woody species and the tundra ecosystem suggest little no effect of CO2 on physiology, growth or
productivity. Numerous studies of the physiology of the CO2 effect are continuing in attempts to
understand controlling mechanisms and to explain the variable growth responses. Particular emphasis
needs to be given to physiological measures of interactions involving the CO2 effect and other
environmental influences, and to the wide-ranging observations of photosynthesis acclimation to CO2.
Prospects for future research are identified.

KEYWORDS: ACCLIMATION, ATMOSPHERIC CARBON-DIOXIDE, ELEVATED LEVELS,
ENRICHMENT, GROWTH, INHIBITION, PHOTOSYNTHESIS, SEEDLINGS, SHORT- TERM,
TEMPERATURE


     483  
Dale, H., and M.C. Press. 1998. Elevated atmospheric CO2 influences the interaction between the
parasitic angiosperm Orobanche minor and its host Trifolium repens. New Phytologist 140(1):65-73.

The influence of the root holoparasitic angiosperm Orobanche minor Sm. on the biomass,
photosynthesis, carbohydrate and nitrogen content of Trifolium repens L. was determined for plants
grown at two CO2 concentrations (350 and 550 mu mol mol(-1)). Infected plants accumulated less
biomass than their uninfected counterparts, although early in the association there was a transient
stimulation of growth. Infection also influenced biomass allocation both between tissues (infected
plants had lower root:shoot ratios) and within tissues: infected roots were considerably thicker before
the point of parasite attachment and thinner below. Higher concentrations of starch were also found
in roots above the point of attachment, particularly for plants grown in elevated CO2. Elevated CO2
stimulated the growth of T. repens only during the early stages of development. There was a
significant interaction between infection and CO2 on growth, with infected plants showing a greater
response, such that elevated CO2 partly alleviated the effects of the parasite on host growth. Elevated
CO2 did not affect total O. minor biomass per host, the number of individual parasites supported by
each host, or their time of attachment to the host root system. Photosynthesis was stimulated by
elevated CO2 but was unaffected by O. minor. There was no evidence of down-regulation of
photosynthesis in T. repens grown at elevated CO2 in either infected or uninfected plants. The data
are discussed with regard to the influence of elevated CO2 on other parasitic angiosperm-host
associations and factors which control plant responses to elevated CO2.

KEYWORDS: CARBON DIOXIDE, GROWTH, METABOLISM, N2 FIXATION, NITROGEN,
PHOTOSYNTHETIC ACCLIMATION, SORGHUM, STRIGA-HERMONTHICA, TEMPERATURE,
WHITE CLOVER


     484  
Dalen, L.S., O. Johnsen, and G. Ogner. 1997. Frost hardiness development in young Picea abies
seedlings under simulated autumn conditions in a phytotron - effects of elevated CO2, nitrogen and
provenance. Plant Physiology 114(3):576.



     485  
Damesin, C., C. Galera, S. Rambal, and R. Joffre. 1996. Effects of elevated carbon dioxide on
leaf gas exchange and growth of cork-oak (Quercus suber L) seedlings. Annales Des Sciences
Forestieres 53(2-3):461-467.

Leaf gas exchange and growth were determined on cork-oak (Quercus suber L) seedlings which were
grown from acorns for periods of up to 4 months in greenhouses at ambient (350 mu mol mol(-1))
and at elevated (700 mu mol mol(-1)) concentrations of carbon dioxide. In well-watered conditions,
daily maximum photosynthesis (15 mu mol m(-2) s(-1)) and stomatal conductance (440 mmol m(-2)
s(-1)) of plants grown and measured at 700 mu mol mol(-1) CO2 did not differ from those of plants
grown and measured at 350 mu mol mol(-1). In conditions of moderate drought, net CO2 assimilation
was at least twice as great in elevated CO2, but stomatal conductance was unchanged. Elevated CO2
affected total biomass production, the average increase being 76 and 97% at 3 and 4 months,
respectively. Shoot biomass, root biomass, stem height and total leaf area were increased by elevated
CO2. Root and stem ramification were also enhanced by elevated CO2, but no change in root/shoot
ratio was observed.

KEYWORDS: AMBIENT, ATMOSPHERIC CO2, CO2 CONCENTRATION, PHOTOSYNTHESIS,
PLANTS, PRODUCTIVITY, RESPONSES, STOMATAL CONDUCTANCE, TREES, WATER


     486  
Daniel, E. 1997. The temperature dependence of photoinhibition in leaves of Phaseolus vulgaris (L) -
Influence of CO2 and O-2 concentrations. Plant Science 124(1):1-8.

The interactive effect of temperature and CO2 concentration on the susceptibility to photoinhibition
was assessed using chlorophyll a fluorescence to estimate the reduction of the quantum yield of PSII
photochemistry (F-w/F-m) after high-light exposure. Leaves exposed to high photon flux density
always exhibit a decrease in F-w/F-m, resulting from both a decrease in the rate constant for
photochemistry and an increase in the rate constant for non photochemical dissipation of excess
excitation energy. At a-given CO2 concentration, there was almost no difference in the degree of
photoinhibition between leaves exposed to high light in 10 or 210 mmol O-2/mol. But photoinhibition
was more pronounced at 10 mmol O-2/mol and 0 mu mol CO2/mol than at 210 mmol O-2/mol and
50 pmol CO2/mol, i.e. when both photorespiration and CO2 refixation are suppressed. Despite this
photoprotective role of photorespiration, photoinhibition was enhanced by decreasing CO2
concentration in bean leaves, especially at elevated (30-35 degrees C)temperatures. (C) 1997 Elsevier
Science Ireland Ltd.

KEYWORDS: ASSIMILATION, CHLOROPHYLL FLUORESCENCE, CHLOROPLAST PROTEIN,
DROUGHT, LIGHT, PHOTOCHEMICAL EFFICIENCY, PHOTORESPIRATION,
PHOTOSYNTHETIC ELECTRON FLOW, PHOTOSYSTEM, WATER-STRESS


     487  
Darrah, P.R. 1996. Rhizodeposition under ambient and elevated CO2 levels. Plant and Soil
187(2):265-275.

As global CO2 levels rise, can soils store more carbon and so buffer atmospheric CO2 levels?
Answering this question requires a knowledge of the rates of C inputs to soil and of CO2 outputs via
decomposition. Below-ground inputs from roots are a major component of the C flow into soils but
are still poorly understood. In this article, new techniques for measuring rhizodeposition are reviewed
and discussed and the need for cross-comparisons between methods is identified. One component of
rhizodeposition, root exudation, is examined in more detail and evidence is presented which suggests
that current estimates of exudate flow into soils are incorrect. A mechanistic mathematical model is
used to explore how exudate hows might change under elevated CO2.

KEYWORDS: AMINO-ACIDS, ARBUSCULAR MYCORRHIZAL FUNGUS, BRASSICA-NAPUS L,
CARBON FLUXES, CITRIC-ACID, CUCUMIS-SATIVUS L, PSEUDOMONAS- FLUORESCENS,
SOIL-ROOT INTERFACE, WHEAT RHIZOSPHERE, ZEA MAYS L


     488  
Darrigo, R.D., and G.C. Jacoby. 1993. Tree growth-climate relationships at the northern boreal
forest tree line of north-america - evaluation of potential response to increasing carbon-dioxide.
Global Biogeochemical Cycles 7(3):525-535.

Tree growth at the northern limit of the range of boreal forests is primarily limited by temperature-
related factors. Thus the position of this range limit, and the growth rates of trees along the northern
forest border, may undergo significant change if predictions of enhanced greenhouse warming at
northern latitudes are realized. In this paper we evaluate tree ring width and maximum latewood
density chronologies of white spruce for three temperature-sensitive tree line sites in northern North
America: in the Brooks Range, Alaska, the Franklin Mountains, Northwest Territories, and Churchill,
Manitoba. The ring width data, which more strongly integrate low-frequency temperature trends than
the density series, show overall enhanced growth and inferred warming during the period of
anthropogenic increase in greenhouse gases. The recent growth at these sites equals or exceeds that
which has occurred during earlier centuries of more clearly natural climate variability. When the ring
width and density variations are estimated using temperature and precipitation data in principal
components regession analysis, no substantial residual trends are detected which might require CO2
or other nutrient fertilization as an additional explanation for recent growth changes.

KEYWORDS: ATMOSPHERIC CO2, CANADA, CHRONOLOGY, CIRCULATION, DENSITY,
ENHANCEMENT, RING DATA, TEMPERATURE, TRENDS, WIDTH


     489  
Davey, P.A., A.J. Parsons, L. Atkinson, K. Wadge, and S.P. Long. 1999. Does photosynthetic
acclimation to elevated CO2 increase photosynthetic nitrogen-use efficiency? A study of three native
UK grassland species in open-top chambers. Functional Ecology 13:21-28.

1, The photosynthetic response to elevated CO2 and nutrient stress was investigated in Agrostis
capillaris, Lolium perenne and Trifolium repens grown in an open-top chamber facility for 2 years
under two nutrient regimes. Acclimation was evaluated by measuring the response of light-saturated
photosynthesis to changes in the substomatal CO2 concentration. 2. Growth at elevated CO2 resulted
in reductions in apparent Rubisco activity in vivo in all three species, which were associated with
reductions of total leaf nitrogen content on a unit area basis for A. capillaris and L. perenne. Despite
this acclimation, photosynthesis was significantly higher at elevated CO2 for T. repens and A.
capillaris, the latter exhibiting the greatest increase of carbon uptake at the lowest nutrient supply.
3. The photosynthetic nitrogen-use efficiency (the rate of carbon assimilation per unit leaf nitrogen)
increased at elevated CO2, Mot purely owing to higher values of photosynthesis at elevated CO2,
but also as a result of lower leaf nitrogen contents. 4. Contrary to most previous studies, this
investigation indicates that elevated CO2 can stimulate photosynthesis under a severely limited
nutrient supply. Changes in photosynthetic nitrogen-use efficiency may be a critical determinant of
competition within low nutrient ecosystems and low input agricultural systems.

KEYWORDS: C-3 PLANTS, CAPACITY, COTTON, GAS-EXCHANGE, GROWTH, LEAVES,
NUTRIENT STATUS, NUTRITION, RISING ATMOSPHERIC CO2, SEEDLINGS


     490  
Davies, S.J., and L. Unam. 1999. Smoke-haze from the 1997 Indonesian forest fires: effects on
pollution levels, local climate, atmospheric CO2 concentrations, and tree photosynthesis. Forest
Ecology and Management 124(2-3):137-144.

Atmospheric composition, local climate and sapling gas exchange were monitored to assess the short-
term effects of smoke-haze from the 1997 Indonesian forest fires. Atmospheric concentrations of
particulate matter, SO2, CO, CH4 and CO2, and relative humidity were elevated, and
photosynthetically active radiation and ambient temperature were reduced by the smoke- haze.
Despite elevated CO2 levels, photosynthesis in three tree species was reduced by the smoke-haze,
both indirectly through reduced PAR levels, and directly through elevated aerosol and atmospheric
pollutant levels. (C) 1999 Elsevier Science B.V. All rights reserved.

KEYWORDS: ASIA, BIOMASS, CARBON DIOXIDE, DEFORESTATION, ELEVATED CO2,
EMISSIONS, GROWTH, LAND-USE CHANGE, LATIN-AMERICA, PLANTS


     491  
Day, F.P., E.P. Weber, C.R. Hinkle, and B.G. Drake. 1996. Effects of elevated atmospheric CO2
on fine root length and distribution in an oak-palmetto scrub ecosystem in central Florida. Global
Change Biology 2(2):143-148.

Atmospheric CO2 concentration is rising and it has been suggested that a portion of the additional
carbon is being sequestered in terrestrial vegetation and much of that in below-ground structures. The
objective of the present study was to quantify the effects of elevated atmospheric CO2 on fine root
length and distribution with depth with minirhizotrons in an open-top chamber experiment in an oak-
palmetto scrub ecosystem at Kennedy Space Centre, Florida, USA. Observations were made five
times over a period of one and a half years in three ambient chambers (350 p.p.m. CO2), three CO2
enriched chambers (700 p.p.m. CO2), and three unchambered plots. Greater root length densities
were produced in the elevated CO2 chambers (14.2 mm cm(-2)) compared to the ambient chambers
(8.7 mm cm(-2)). More roots may presumably lead to more efficient acquisition of resources. Fine
root abundance varied significantly with soil depth, and there appeared to be enhanced proliferation
of fine roots near the surface (0-12 cm) and at greater depth (49-61 cm) in the elevated CO2
chambers. The vertical root distribution pattern may be a response to availability of nutrients and
water. More studies are needed to determine if increased root length under CO2 enriched conditions
actually results in greater sequestering of carbon below ground.

KEYWORDS: CARBON, CLIMATE CHANGE, GROWTH, HETEROGENEITY, MICROSITES,
RESPONSES


     492  
Dayan, E., H. Vankeulen, J.W. Jones, I. Zipori, D. Shmuel, and H. Challa. 1993. Development,
calibration and validation of a greenhouse tomato growth-model .1. Description of the model.
Agricultural Systems 43(2):145-163.

A dynamic crop growth model. TOMGRO, for an indeterminate tomato variety is presented. The
model describes the phenological development and increase in dry weight of various organs (roots,
stem nodes, leaves and fruits) from planting till maturity under variable environmental conditions.
Phenological development is governed by genetic plant properties and environmental conditions (e.g.
air temperature and CO2 level) and expressed in a plastochron index, i.e. the current stem node
number. Total dry matter accumulation is based on a quantitative description of the carbon balance,
including gross CO2 assimilation, maintenance respiration and growth respiration. Partitioning of dry
matter increase over the various organs is governed by their relative sink strengh, defined on the basis
of a genetically determined 'potential' growth rate, achieved under non-limiting carbohydrate supply.
The model is both schematic and modular in set-up. This means it can be adapted easily and most of
its subroutines can be replaced easily by others if better descriptions become available. It can also be
combined with a more comprehensive model describing greenhouse climate and appears robust for
use in procedures of economic optimization of climate conditions in greenhouses or for management
purposes.

KEYWORDS: CARBON-DIOXIDE ENRICHMENT, FRUIT- GROWTH, IMPORT, LEAF,
LYCOPERSICON-ESCULENTUM MILL, NITROGEN, PHOTOSYNTHESIS, PLANTS,
RESPONSES, TRANSLOCATION


     493  
Daymond, A.J., T.R. Wheeler, P. Hadley, R.H. Ellis, and J.I.L. Morison. 1997. The growth,
development and yield of onion (Allium cepa L) in response to temperature and CO2. Journal of
Horticultural Science 72(1):135-145.

Stands of two cultivars (cv. Hysam and Site) of onion (Allium cepa L.) were grown in the held within
polyethylene-covered tunnels along which a temperature adient was imposed. Pairs of tunnels were
maintained at either 374 or 532 mu mol mol(-1) CO2. The rates of progress from transplanting to
bulbing, and from bulbing to harvest maturity, were positive linear functions of mean temperature for
each cultivar. At a given temperature, the time of bulbing was earlier, but the duration of bulb growth
longer, at elevated compared with normal CO2. Canopy architecture was not affected by CO2,
temperature or cultivar; an estimate of 0.25 for the canopy light extinction coefficient was common
to all treatment combinations. Radiation use efficiency was greater at elevated compared with normal
CO2 in the period up to bulbing, but was the same at both CO2 concentrations during subsequent
bulb growth. Total crop dry weight at bulbing was increased by 32-44% due to elevated CO2. Bulb
yields at harvest maturity declined with progressively warmer temperatures and to a greater extent
in cv. Site than cv. Hysam. Enrichment with CO2 increased bulb yields by 29-37% and by 35-51%
in cvs Hysam and Site, respectively. From comparison of the temperature rise needed to offset
entirely the yield increases of each cultivar due to elevated CO2, it is concluded that current estimates
of climate change should be beneficial for bulb onion production, particularly for long- season
cultivars.

KEYWORDS: AIR- TEMPERATURE, ATMOSPHERIC CO2, CARBON DIOXIDE, ENRICHMENT,
FIELD, LEAF-AREA, NITROGEN, PHOTOSYNTHESIS, PLANT GROWTH, PRODUCTIVITY


     494  
De Angelis, P., and G.E. Scarascia-Mugnozza. 1998. Long-term CO2-enrichment in a
Mediterranean natural forest: An application of large open top chambers. Chemosphere 36(4-5):763-
770.

It is crucial to be able to anticipate the possible effects of environmental changes on the
Mediterranean woodland communities given their essential role on protecting lands that are under a
strong pressure by man and climate. Predictions of the effects of increasing CO2 concentration on
plants have been inferred by short- and long-term studies, conducted at different scales and by
different technologies. Open Top Chambers (OTCs) are experimental facilities that have been widely
used to expose field grown plants to different pollutant gases, and more recently to elevated [CO2].
In this paper, we present the natural site and the experimental system (six large OTCs enclosing
clumps of natural vegetation) that we have been utilizing for 3 years, to assess the impact of elevated
[CO2] on a Mediterranean natural forest community. The results show that large OTCs can be
usefully used to simulate CO2 doubling even under the harsh environmental conditions of the
mediterranean region. (C) 1998 Elsevier Science Ltd.

KEYWORDS: BALANCE, CARBON DIOXIDE, CLIMATE, ECOSYSTEMS, ELEVATED CO2,
EXCHANGE, RESPONSES


     495  
Debevec, E.M., and S.F. Maclean. 1993. Design of greenhouses for the manipulation of
temperature in tundra plant-communities. Arctic and Alpine Research 25(1):56-62.

Passive greenhouses can be used to elevate the temperature of natural communities, but they also
introduce other effects. We tested the effects of potential greenhouse materials-clear polyethylene
plastic film, polyester fabric, and rigid fiberglass panels-on light transmission, photosynthesis of Salix
planifolia, elevation of air and soil temperature, and thaw depth. Plastic had the greatest light
transmittance and caused the least depression of photosynthesis (- 5%). Greenhouses covered with
plastic elevated daily maximum and daily mean air temperatures by an average of 7.8 and 2.0-
degrees-C and depressed daily minimum temperature by 1.1- degrees-C compared with the control.
Plastic is impervious to gases and may alter CO2 concentration and humidity within greenhouses.
Fiberglass had lower transmittance, especially of short wavelength radiation. Fabric had the lowest
light transmission and reduced photosynthesis by 10%, but it has the advantage of permeability to
CO2 and water vapor. Greenhouses covered with fabric, alone, produced only a small effect (daily
mean temperature elevated 0.4-degrees-C above controls). A mixed greenhouse design (plastic and
fabric) raised daily mean temperatures by 0.9-degrees-C and may minimize adverse effects on gas
diffusion. Because of the effect of the materials on amount and spectral distribution of radiation and
on photosynthesis, the appropriate treatment control for any greenhouse design is an open plot
shaded with the same material. Soil temperature at 10 cm depth was elevated in all greenhouses, but
no effect on depth of thaw was detected.

KEYWORDS: CARBON NUTRIENT BALANCE


     496  
Debruin, H.A.R., and C.M.J. Jacobs. 1993. Impact of co2 enrichment on the regional
evapotranspiration of agroecosystems, a theoretical and numerical modeling study. Vegetatio
104:307-318.

This paper gives a brief overview of factors determining evapotranspiration of vegetated surfaces.
It indicates which of these factors are sensitive to CO2 enrichment. A qualitative analysis is presented
of the impact of large scale climate changes. Data in literature indicate that the surface resistance of
vegetated areas may change within the range -25 % and +50 % if the atmospheric CO2-concentration
doubles. The impact of such changes on regional scale transpiration is evaluated using a numerical
model in which the interaction between the evapotranspiration and the Planetary Boundary Layer is
accounted for. It is concluded that the impact of CO2 enrichment on the transpiration at the regional
scale is relatively small for aerodynamically smooth surfaces (between +7 % and -11 %). For
aerodynamically rough surfaces the effects are somewhat larger (between +15 % and -21 %).

KEYWORDS: ATMOSPHERIC BOUNDARY-LAYER, CANOPY RESISTANCE, CARBON
DIOXIDE, CONDUCTANCE, EVAPORATION, FOREST, SCALE, SENSITIVITY, STOMATAL
CONTROL, TRANSPIRATION


     497  
Deepak, S.S., and M. Agrawal. 1999. Growth and yield responses of wheat plants to elevated levels
of CO2 and SO2, singly and in combination. Environmental Pollution 104(3):411-419.

Wheat plants (Triticum aestivum L. cv. Malviya 234) were exposed to 600 ppm of carbon dioxide
(CO2) and 0.06 ppm sulphur dioxide (SO2), singly and in combination for 8 h daily (8 a.m. to 4 p.m.)
from germination to maturity in open top chambers (OTCs) in field conditions to investigate their
individual as well as interactive influence on plant growth and yield. Exposure of plants to 0.06 ppm
SO2 significantly reduced plant height, leaf area, biomass and yield. Elevated CO2, on the other hand,
stimulated the growth and yield of plants. Combination of CO2 and SO2 showed a similar response
pattern as that of CO2 alone. Pattern of biomass allocation also varied in response to different
treatments. RGR was significantly increased due to CO2 and CO2 + SO2 treatments, whereas the
same reduced due to SO2 exposure. Root/shoot ratio decreased significantly due to CO2 and CO2
+ SO2 treatment at 45 days age. CO2 modified the responses of plants to SO2. Combined exposure
of SO2 and CO2 stimulated the growth as well as the yield maximally. This suggests that the CO2
enrichment has not only reduced the adverse effect of low level of SO2, but at the same time the extra
carbon provided by CO2 enrichment took the advantage of air borne sulphur as nutrient and showed
maximum increment in growth and yield. (C) 1999 Elsevier Science Ltd. All rights reserved.

KEYWORDS: AIR- POLLUTANTS, CARBON DIOXIDE, FUMIGATION, LEAVES,
PHOTOSYNTHESIS, RESPIRATION, STOMATAL CONDUCTANCE, SULFUR-DIOXIDE,
TEMPERATURE, WINTER-WHEAT


     498  
Dehaan, B.J., M. Jonas, O. Klepper, J. Krabec, M.S. Krol, and K. Olendrzynski. 1994. An
atmosphere-ocean model for integrated assessment of global change. Water, Air, and Soil Pollution
76(1-2):283-318.

This paper describes the atmosphere-ocean system of the integrated model IMAGE 2.0. The system
consists of four linked models, for atmospheric composition, atmospheric climate, ocean climate and
for ocean biosphere and chemistry. The first model is globally averaged, the latter are zonally
averaged with additional resolution in the vertical. The models reflect a compromise between
describing the physical, chemical and biological processes and moderate computational requirements.
The system is validated with direct observations for current conditions (climate, chemistry) and is
consistent with results from General Circulation Model experiments. The system is used in the
integrated setting of the IMAGE 2.0 model to give transient climate projections. Global surface
temperature is simulated to increase by 2.5 K over the next century for socio- economic scenarios
with continuing economic and population growth. In a scenario study with reduced ocean circulation,
the climate system and the global C cycle are found to be appreciably sensitive to such changes.

KEYWORDS: ANTHROPOGENIC CO2, BALANCE, BUDGET, CARBON DIOXIDE, CLIMATE,
SEA


     499  
Delatorre, A., B. Delgado, and C. Lara. 1991. Nitrate-dependent O2 evolution in intact leaves.
Plant Physiology 96(3):898-901.

Evolution Of O2 by illuminated intact detached leaves from barley (Hordeum vulgare L. cv Athos)
and pea (Pisum sativum L. cv Lincoln) in a CO2-saturating atmosphere was enhanced when KNO3
(1-2.5 millimolar) had been previously supplied through the transpiration stream. The extra O2
evolution observed after feeding KNO3 increased with the light intensity, being maximal at near
saturating photon flux densities and resulting in no changes in the initial slope of the O2 versus light-
intensity curve. No stimulation Of O2 evolution was otherwise observed after feeding KCl or NH4Cl.
The data indicate that nitrate assimilation uses photosynthetically generated reductant and stimulates
the rate of noncyclic electron flow by acting as a second electron-accepting assimilatory process in
addition to CO2 fixation.

KEYWORDS: ANACYSTIS-NIDULANS, ASSIMILATION, CHLOROPLASTS, OXYGEN,
REDUCTION, TRANSLOCATOR


     500  
de la Vina, G., F. Pliego-Alfaro, S.P. Driscoll, V.J. Mitchell, M.A. Parry, and D.W. Lawlor.
1999. Effects of CO2 and sugars on photosynthesis and composition of avocado leaves grown in
vitro. Plant Physiology and Biochemistry 37(7-8):587-595.

The effects of micropropagation conditions on avocado (Persea americana Mill.) have been measured
in leaves and plants cultured in vitro. The consequences of the type and concentration of sugar in the
medium and of carbon dioxide concentration in the atmosphere on the rates of photosynthesis and
amounts of ribulose 1,5-biphosphate carboxylase-oxygenase (EC 4.1.1.39; Rubisco) and total soluble
protein (TSP) were measured. At the highest sucrose supply (87.6 mM), Rubisco content was
substantially decreased in leaves, and even more when elevated CO2 (1 000 mu mol mol(-1)) was
supplied. Maximum photosynthetic rate (P-max) was significantly decreased when plants developed
in high sucrose and elevated CO2. However, Rubisco concentration was significantly greater when
glucose was supplied at the same molar concentration or when the concentration of sucrose was small
(14.6 mM), and no differences were observed due to the CO2 concentration in the air in these
treatments. The ratio of Rubisco to total soluble protein (Rubisco/TSP) was dramatically decreased
in plants grown in the highest concentration of sucrose and with elevated CO2. Leaf area and ratio
of leaf fresh weight/(stem + root) fresh weight, were greater in plants grown with CO2, enriched air.
However, upon transplanting, survival was poorer in plants grown on low sucrose/high CO2
compared to those grown on high sucrose/high CO2. (C) Elsevier, Paris.

KEYWORDS: (CO2) C 14, ACCLIMATIZATION, EXPRESSION, FIXATION, INHIBITION,
INVITRO, MECHANISM, PLANTS, RIBULOSE-1;5-BISPHOSPHATE CARBOXYLASE-
OXYGENASE, SINK REGULATION


     501  
Delesalle, V.A., and S. Blum. 1994. Variation in germination and survival among families of
sagittaria-latifolia in response to salinity and temperature. International Journal of Plant Science
155(2):187-195.

We studied seed germination and seedling growth in eight maternal families of Sagittaria latifolia
(Alismataceae), a freshwater perennial, in response to salinity (four levels) and temperature effects
(two levels) in the greenhouse. Salinity decreased germination, delayed emergence, and decreased
survival and growth rates. The negative effects of salinity on germination were greater at the high-
temperature regime, but the effects on growth were greater at the low-temperature regime. Some
seeds were capable of germinating and surviving (with minimal growth) even in 0.8% NaCl solution.
Families also differed in their response to salinity but not to temperature. In particular, high salinities
had little effect on the germination of some families. Growth rate always decreased with increasing
salinity, but again the magnitude of the effect differed among maternal families. Our data show that
S. latifolia can germinate but cannot grow well under low-salinity conditions; thus, S. latifolia might
be minimally affected by short-term salt intrusions. In order to understand how plant populations
respond to disturbances, such as increased salinity or increased temperature, we need to consider the
source, either environmental or genetic, of maternal effects.

KEYWORDS: ECOPHYSIOLOGY, ELEVATED CO2, EVOLUTIONARY CONSEQUENCES,
GROWTH, HORDEUM-JUBATUM, INBREEDING DEPRESSION, INTRASPECIFIC VARIATION,
PLANTS, SEED-GERMINATION, SIZE


     502  
Delgado, E., R.A.C. Mitchell, M.A.J. Parry, S.P. Driscoll, V.J. Mitchell, and D.W. Lawlor.
1994. Interacting effects of co2 concentration, temperature and nitrogen supply on the photosynthesis
and composition of winter-wheat leaves. Plant, Cell and Environment 17(11):1205-1213.

Winter wheat (Triticum aestivum L., cv. Mercia) was grown at two different atmospheric CO,
concentrations (350 and 700 mu mol mol(-1)) two temperatures [ambient temperature (i.e. tracking
the open air) and ambient +4 degrees C] and two rates of nitrogen supply (equivalent to 489 kg ha(-
1) and 87 kg ha(- 1)). Leaves grown at 700 mu mol mol(-1) CO2 had slightly greater photosynthetic
capacity (10% mean increase over the experiment) than those grown at ambient CO2 concentration,
but there were no differences in carboxylation efficiency or apparent quantum yield. The amounts of
chlorophyll, soluble protein and ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) per unit
leaf area did not change with long-term exposure to elevated CO2 concentration. Thus winter wheat,
grown under simulated field conditions, for which total biomass was large compared to normal field
production, did not experience loss of components of the photosynthetic system or loss of
photosynthetic competence with elevated CO2 concentration. However, nitrogen supply and
temperature had large effects on photosynthetic characteristics but did not interact with elevated CO2
concentration. Nitrogen deficiency resulted in decreases in the contents of protein, including Rubisco,
and chlorophyll, and decreased photosynthetic capacity and carboxylation efficiency. An increase in
temperature also reduced these components and shortened the effective life of the leaves, reducing
the duration of high photosynthetic capacity.

KEYWORDS: ACCLIMATION, CARBON-DIOXIDE CONCENTRATION, CARBOXYLASE-
OXYGENASE, ELEVATED CO2, GROWTH, HIGH ATMOSPHERIC CO2, PLANTS, PROTEIN,
RESPONSES, RUBISCO


     503  
Delmas, R.J. 1998. Ice-core records of global climate and environment changes. Proceedings of the
Indian Academy of Sciences-Earth and Planetary Sciences 107(4):307-319.

Precipitation accumulating on the Greenland and Antarctic ice sheets records several key parameters
(temperature, accumulation, composition of atmospheric gases and aerosols) of primary interest for
documenting the past global environment over recent climatic cycles and the chemistry of the
preindustrial, atmosphere. Several deep ice cores from Antarctica and Greenland have been studied
over the last fifteen years. In both hemispheres, temperature records (based on stable isotope
measurements in water) show the succession of glacial and interglacial periods. However, detailed
features of the climatic stages are not identical in Antarctica and in Greenland. A tight link between
global climate and greenhouse gas concentrations was discovered, CO2 and CH4 concentrations
being lower in glacial conditions by about 80 and 0.3 ppmv, respectively, with respect to their pre-
industrial levels of 280 and 0.65 ppmv. Coldest stages are also characterized by higher sea-salt and
crustal aerosol concentrations. In Greenland, contrary to Antarctica, ice-age ice is alkaline. Gas-
derived aerosol (in particular, sulfate) concentrations are generally higher for glacial periods, but not
similar in both the hemispheres. Marine and continental biomass-related species are significant in
Antarctica and Greenland ice, respectively. Finally, the growing impact of anthropogenic activities
on the atmospheric composition is well recorded in both polar regions for long-lived compounds (in
particular greenhouse gases), but mostly in Greenland for short-lived pollutants.

KEYWORDS: ANTARCTIC ICE, ATMOSPHERIC METHANE, CENTRAL GREENLAND ICE,
CYCLE, DUST, GLACIAL PERIOD, HYDROGEN- PEROXIDE, NITRATE CONCENTRATIONS,
SUMMIT, VOSTOK


     504  
Delucia, E.H., R.M. Callaway, and W.H. Schlesinger. 1994. Offsetting changes in biomass
allocation and photosynthesis in ponderosa pine (pinus-ponderosa) in response to climate-change.
Tree Physiology 14(7-9):669-677.

We examined the effect of climate on aboveground biomass allocation of ponderosa pine (Pinus
ponderosa) by measuring trees in disjunct forest stands growing on the same substrate at high-
elevation montane sites and low-elevation desert sites. Climatic differences between the sites were
comparable to the difference between present and future climates of interior North America that is
expected to result from a doubling of atmospheric CO2 concentration. Relative to the montane
populations, the desert populations allocated a greater proportion of biomass to sapwood (functional
xylem) at the expense of foliage. The leaf/sapwood area ratio and percent of aboveground biomass
in sapwood for trees of the same height were 0.201 m2 cm-2 and 58% for montane trees and 0.104
m2 cm-2 and 71% for desert trees. In a phytotron experiment, increases in net photosynthesis and
net assimilation rate for seedlings grown under future conditions of high CO2 and temperature were
offset by a decrease in leaf area ratio. As was observed for large trees at different elevations,
increased temperatures caused an increase in biomass allocation to stem in the phytotron seedlings.
Thus, CO2- and temperature-driven shifts in biomass allocation negated the effect on growth of the
CO2- driven increase in carbon assimilation rate. Our data from the controlled growth chamber and
field experiments suggest that future climate conditions, including elevated atmospheric CO2, may
not stimulate growth and productivity of ponderosa pine.



     505  
Delucia, E.H., R.M. Callaway, E.M. Thomas, and W.H. Schlesinger. 1997. Mechanisms of
phosphorus acquisition for ponderosa pine seedlings under high CO2 and temperature. Annals of
Botany 79(2):111-120.

To test the hypothesis that elevated atmospheric CO2 and elevated temperature, simulating current
and predicted future growing season conditions, act antagonistically on phosphorus acquisition of
ponderosa pine, seedlings were grown in controlled-environment chambers in a two temperature
(25/10 degrees C and 30/15 degrees C)xtwo CO2 (350 and 700 mu l(-1)) experimental design.
Mycorrhizal seedlings were watered daily with a nutrient solution with P added in organic form as
inositol hexaphosphate (64ppm P). Thus seedlings were challenged to use active forms of P
acquisition. Elevated CO2 increased the relative growth rate by approx. 5% which resulted in an
approx. 33% increase in biomass after 4 months. There was no main effect of temperature on growth.
Increased growth under elevated CO2 and temperature was supported by increases in specific
absorption rate and the specific utilization rate of P. The contribution of mycorrhizae to P uptake may
have been greater under simulated future conditions, as elevated CO2 increased the number of
mycorrhizal roots. There was no main effect of temperature on root phosphatase activity, but elevated
CO2 caused a decrease in activity. The inverse pattern of root phosphatase activity and mycorrhizal
infection across treatments suggests a physiological coordination between these avenues of P
acquisition. The concentration of oxalate in the soil increased under elevated CO2 and decreased
under elevated temperature. This small molecular weight acid solubilizes inorganic P making it
available for uptake. Increased mycorrhizal infection and exudation of oxalate increased P uptake in
ponderosa pine seedlings under elevated CO2, and there was no net negative effect of increased
temperature. The increased carbon status of pine under elevated CO2 may facilitate uptake of limiting
P in native ecosystems. (C) 1997 Annals of Botany Company.

KEYWORDS: CALCIUM-OXALATE, CARBON DIOXIDE, COMPENSATORY RESPONSES,
ELEVATED ATMOSPHERIC CO2, NUTRIENT, PHOSPHATASE-ACTIVITY, PLANTS,
RHIZOSPHERE, SOILS, TAEDA L SEEDLINGS


     506  
DeLucia, E.H., J.G. Hamilton, S.L. Naidu, R.B. Thomas, J.A. Andrews, A. Finzi, M. Lavine,
R. Matamala, J.E. Mohan, G.R. Hendrey, and W.H. Schlesinger. 1999. Net primary production
of a forest ecosystem with experimental CO2 enrichment. Science 284(5417):1177-1179.

The concentration of atmospheric carbon dioxide was increased by 200 microliters per Liter in a
forest plantation, where competition between organisms, resource Limitations, and environmental
stresses may modulate biotic responses. After 2 years the growth rate of the dominant pine trees
increased by about 26 percent relative to trees under ambient conditions. Carbon dioxide enrichment
also increased Litterfall and fine- root increment. These changes increased the total net primary
production by 25 percent. Such an increase in forest net primary production globally would fix about
50 percent of the anthropogenic carbon dioxide projected to be released into the atmosphere in the
year 2050. The response of this young, rapidly growing forest to carbon dioxide may represent the
upper Limit for forest carbon sequestration.

KEYWORDS: BIOMASS, CLIMATE, ELEVATED CO2, GROWTH TRENDS, LOBLOLLY-PINE,
RESPONSES, RISING ATMOSPHERIC CO2, SODA-LIME, TREE GROWTH, UNITED-STATES


     507  
DeLucia, E.H., and W.H. Schlesinger. 1999. Effect on the biosphere of elevated atmospheric CO2
- Response. Science 285(5435):1852.



     508  
De Luis, I., J.J. Irigoyen, and M. Sanchez-Diaz. 1999. Elevated CO2 enhances plant growth in
droughted N-2-fixing alfalfa without improving water status. Physiologia Plantarum 107(1):84-89.

The long-term interaction between elevated CO2 and soil mater deficit was analysed in N-2-fixing
alfalfa plants in order to assess the possible drought tolerance effect of CO2. Elevated CO2 could
delay the onset of drought stress by decreasing transpiration rates, but this effect was avoided by
subjecting plants to the same soil water content. Nodulated alfalfa plants subjected to ambient (400
mu mol mol(-1)) or elevated (700 mu mol mol(-1)) CO2 were either men watered or partially watered
by restricting water to obtain 30% of the water content at field capacity (approximately 0.55 g water
cm(-3)). The negative effects of sop water deficit on plant growth were counterbalanced by elevated
CO2. In droughted plants, elevated CO2 stimulated carbon fixation and, as a result, biomass
production was even greater than in well-watered plants grown in ambient CO2. Below-ground
production was preferentially stimulated by elevated CO2 in droughted plants, increasing nodule
biomass production and the availability of photosynthates to the nodules. As a result, total nitrogen
content in droughted plants was higher than in well-watered plants grown in ambient CO2. The
beneficial effect of elevated CO2 was not correlated with a better plant water status. It is concluded
that elevated CO2 enhances growth of droughted plants by stimulating carbon fixation, preferentially
increasing the availability of photosynthates to below-ground production (roots and nodules) without
improving water status. This means that elevated CO2 enhances the ability to produce more biomass
in N-2-fixing alfalfa under given soil water stress, improving drought tolerance.

KEYWORDS: ACCLIMATION, ATMOSPHERIC CARBON-DIOXIDE, ENRICHMENT, N2
FIXATION, PHOTOSYNTHESIS, PRODUCTIVITY, RESPONSES, SOIL, STARCH,
TEMPERATURE


     509  
Demmers-Derks, H., R.A.C. Mitchell, V.J. Mitchell, and D.W. Lawlor. 1998. Response of sugar
beet (Beta vulgaris L.) yield and biochemical composition to elevated CO2 and temperature at two
nitrogen applications. Plant, Cell and Environment 21(8):829-836.

Effects on sugar beet (Beta vulgaris L.) of current and elevated CO2 and temperature alone and in
combination and their interactions with abundant and deficient nitrogen supply (HN and LN,
respectively) have been studied in three experiments in 1993, 1994 and 1995. Averaged over all
experiments, elevated CO2 (600 mu mol mol(-1) in 1993 and 700 mu mol mol-l in 1994 and 1995)
increased total dry mass at final harvest by 21% (95% confidence interval (CI) = 21, 22) and 11%
(CI = 6, 15) and root dry mass by 26% (CI = 19, 32) and 12% (CI = 6, 18) for HN and LN plants,
respectively. Warmer temperature decreased total dry mass by 11% (CI = - 15, - 7) and 9% (CI = -
15, - 5) and root dry mass by 7% (CI = - 12, - 2) and 7% (CI = - 10, 0) for HN and LN plants,
respectively. There was no significant interaction between temperature and CO2 on total or root dry
mass. Neither elevated CO2 nor temperature significantly affected sucrose concentration per unit root
dry mass. Concentrations of glycinebetaine and of amino acids, measured as alpha-amino-N,
decreased in elevated CO2 in both N applications; glycinebetaine by 13% (CI = - 21, - 5) and 16%
(CI = - 24, - 8) and alpha-amino-N by 24% (CI = - 36, - 11) and 16% (CI = - 26, - 5) for HN and
LN, respectively. Warmer temperature increased alpha-amino-N, by 76% (CI = 50, 107) for HN and
21% (CI = 7, 36) for LN plants, but not glycinebetaine.

KEYWORDS: CARBON DIOXIDE, CROPS, FIELD, GROWTH, PLANT, PRODUCTIVITY,
SOURCE-SINK RELATIONS, WINTER-WHEAT


     510  
DeMothes, M.A.G. 1996. Effects of enhanced CO2 concentration on wheat photosynthesis and
long- and short-term stomatal behaviour. Photosynthetica 32(2):193-202.

Wheat (Triticum aestivum L.) plants were cultivated in a growth chamber at normal (35 Pa = c(35))
and increased (70 Pa = c(70)) CO2 partial pressure. Environmental conditions other than CO2
concentration were similar for the c(35) and the c(70) plants. For the c(35) and the c(70) plants
stomatal density was similar. When both variants were measured at growth conditions, the net
photosynthetic rate (P-N) Of c(70) plants was 44 % higher and stomatal conductance to water vapour
pressure (g(s)) was 22 % lower than those of the c(35) plants, while the relation between internal
partial pressure of CO2 (pci) and external partial pressure (pea) was similar for both variants. Plants
were also submitted to a sequence of increments in CO2 concentration (from 10 Pa up to saturating
CO2 concentration) at saturating photosynthetically active radiation (PAR). Following 1.5 h at
saturating CO2 concentration and PAR, CO2 concentration was decreased stepwise. Both variants
showed hysteresis in the response of P-N, transpiration rate (E), g(s) and water use efficiency (WUE)
to pci. While CO2 concentration was incremented, P-N and g(s) were linearly related indicating that
mesophyll activity and g(s) were correlated. At saturating CO2 concentration and PAR, end product
feedback inhibition on photosynthesis disrupted this correlation for both variants. Plants were also
submitted to a sequence of increments in PAR (from 40 mu mol m(-2), s(-1) up to saturating PAR)
at saturating CO2 concentration. Following 1.5 h at saturating CO2 concentration and PAR, PAR
was decreased stepwise. While both variants showed hysteresis in the response of P-N, E and g(s),
the c(35) plants showed also hysteresis in the response of pci/pca and WUE to PAR. Stomatal
conductance and activity of mesophyll remained co-ordinated during the whole experiment for the
c(70) plants, while for the c(35) plants the correlation between g(s) and mesophyll activity present
during step-up PAR response was disrupted at saturating CO2 concentration and PAR.

KEYWORDS: FIELD, LEAF, WATER-USE EFFICIENCY


     511  
DeMothes, M.A.G., M. Baumgarten, and D. Knoppik. 1996. Hysteresis in the response of
photosynthesis to CO2 and saccharide pools of wheat leaves grown at normal and enhanced CO2.
Photosynthetica 32(2):181-191.

Wheat plants were cultivated in a growth chamber at 35 Pa (c(35) variant) and 70 Pa CO2 partial
pressure (c(70) variant) during the whole vegetation period. The response of net photosynthetic rate
(P-N) Of the nag leaf of both variants to successive increases in CO2 partial pressure (step-up curve)
showed hysteresis when the direction of the sequence was reversed (step-down curve) after 1.5 h at
saturating CO2 partial pressure and photosynthetically active radiation (PAR). Saccharose, glucose
and fructose accumulated during the measurement of a step-up CO2 curve for the c(35) and c(70)
plants as the export rate was not able to keep pace with the rate of saccharide synthesis. Remaining
1.5 h at saturating CO2 partial pressure and PAR, the saccharose pool increased further for both
variants while glucose and fructose decreased reaching the values at growth conditions. The electron
transport rate decreased after 1.5 h at saturating CO2 partial pressure and PAR for the two variants
due to end product feedback. Glucose and fructose contents fell 50 % below the initial contents when
partial pressure of CO2 was lowered stepwise. The c(35) plants showed a double fold increase in the
content of saccharose at the end point of the hysteresis curve. Contents of saccharose for the c(70)
variant in contrast were similar to the initial values.

KEYWORDS: ACCLIMATION, ASSIMILATION, CARBON DIOXIDE, ELECTRON-TRANSPORT,
ELEVATED CO2, ENRICHMENT, PHASEOLUS-VULGARIS L, RESPIRATION, TEMPERATURE


     512  
Demothes, M.A.G., and D. Knoppik. 1994. Effects of long-term enhanced co2 partial-pressure on
gas- exchange parameters and saccharide pools of wheat leaves. Photosynthetica 30(3):435-445.

Wheat plants were cultivated in a growth chamber at normal (35 Pa, c35 plants) and enhanced (70
Pa, c70 plants) CO2 partial pressure. In C35 plants the net photosynthetic rate (P(N)) of flag leaves
and the concentrations of saccharides such as sucrose, glucose, fructose and starch were increased.
The c70 plants possessed higher chlorophyll (Chl) a and Chl b contents. The CO2 response of P(N)
at saturating photosynthetically active radiation (PAR) was very similar for both variants. At the
highest CO2 concentration saccharides accumulated in both variants as a consequence of decreased
export rate. The response of P(N) to PAR at saturating CO2 concentrations was similar in the two
variants. On the other hand, the response of water vapour pressure conductance (gH2O) to PAR in
c35 plants followed a hyperbolic response to PAR, while in the c70 plants it was linearly related to
PAR up to the mean PAR used for growth. In this variant gH2O seemed to change parallelly to
changes in the mesophyll demand for CO2 caused by PAR.

KEYWORDS: ACCLIMATION, ASSIMILATION, ATMOSPHERIC CO2, CARBON DIOXIDE,
ELEVATED CO2, PHOTOSYNTHESIS, RESPIRATION, RESPONSES, TEMPERATURE, YIELD


     513  
Denelzen, M.G.J., and J. Rotmans. 1993. Modeling climate related feedback processes. Journal
of Environmental Science and Health Part A- Environmental Science and Engineering & Toxic and
Hazardous Substance Control 28(9):2095-2151.

Feedback mechanisms play a crucial role in the climate system, amplifying or dampening the climate
response to enhanced concentrations of greenhouse gases from anthropogenic perturbations. Many
of these feedbacks are known, but most of them only potentially. This article evaluates the role of a
number of these feedback processes within the climate system. In order to assess their impact, the
feedbacks which at present can be quantified reasonably are built into the Integrated Model to Assess
the Greenhouse Effect (IMAGE). Unlike previous studies, this study describes the scenario- and time-
dependent role of biogeochemical feedbacks. A number of simulation experiments are performed with
IMAGE to project climate changes. Besides estimates of their absolute importance, the relative
importance of individual biogeochemical feedbacks is considered by calculating the gain for each
feedback process. This study focuses on feedback processes in the carbon cycle and the methane
(semi-) cycle. Modeled feedbacks are then used to balance the past and present carbon budget. This
results in substantially lower projections for atmospheric carbon dioxide than the Intergovernmental
Panel on Climate Change (IPCC) estimates. The difference is approximately 18% from the 1990 level
for the IPCC ''Business-as-Usual'' scenario. Furthermore, the IPCC's ''best guess'' value of the CO2
concentration in the year 2100 falls outside the uncertainty range estimated with our balanced
modeling approach. For the IPCC ''Business-as- Usual'' scenario, the calculated total gain of the
feedbacks within the carbon cycle appears to be negative, a result of the dominant role of the
fertilization feedback. This study also shows that if temperature feedbacks on methane emissions from
wetlands, rice paddies, and hydrates do materialize, methane concentrations might be increased by
30% by 2100. The total effect of the methane feedbacks and the carbon dioxide feedbacks modeled
can be expressed in the carbon dioxide- equivalent concentrations. Our simulated CO2-equivalent
concentrations are lower than the IPCC estimates.

KEYWORDS: ATMOSPHERIC CO2, ECOSYSTEMS, GLOBAL CLIMATE, GREENHOUSE, ICE
CORE, INCREASE, METHANE EMISSIONS, PAST 2 CENTURIES, SENSITIVITY, SIMULATION


     514  
Deng, R., and D.J. Donnelly. 1993. In-vitro hardening of red raspberry by co2 enrichment and
reduced medium sucrose concentration. Hortscience 28(10):1048-1051.

Micropropagated 'Festival' red raspberry (Rubus idaeus L.) shoots were rooted in specially
constructed plexiglass chambers in ambient (340 +/- 20 ppm) or enriched (1500 +/- 50 ppm) CO2
conditions on a medium containing 0, 10, 20, or 30 g sucrose/liter. Plantlet growth and leaf (CO2)-C-
14 fixation rates were evaluated before and 4 weeks after ex vitro transplantation. In vitro CO2
enrichment promoted in vitro hardening; it increased root count and length, plantlet fresh weight, and
photosynthetic capacity but did not affect other variables such as plantlet height, dry weight, or leaf
count and area. No residual effects of in vitro CO2 enrichment were observed on 4-week-old
transplants. Sucrose in the medium promoted plantlet growth but depressed photosynthesis and
reduced in vitro hardening. Photoautotrophic plantlets were obtained on sucrose-free rooting medium
under ambient and enriched CO2 conditions and they performed better ex vitro than mixotrophic
plantlets grown with sucrose. Root hairs were more abundant and longer on root tips of
photoautotrophic plantlets than on mixotrophic plantlets. The maximum CO2 uptake rate of plantlet
leaves was 52% that of greenhouse control plant leaves. This did not change in the persistent leaves
up to 4 weeks after ex vitro transplantation. The photosynthetic ability of persistent and new leaves
of 4-week-old ex vitro transplants related neither to in vitro CO2 nor medium sucrose concentration.
Consecutive new leaves of transplants took up more CO2 than persistent leaves. The third new leaf
of transplants had photosynthetic rates up to 90% that of greenhouse control plant leaves. These
results indicate that in vitro CO2 enrichment was beneficial to in vitro hardening and that sucrose may
be reduced substantially or eliminated from red raspberry rooting medium when CO2 enrichment is
used.

KEYWORDS: ACCLIMATIZATION, CULTURE, EXVITRO, FIXATION, GROWTH, LEAF
ANATOMY, LEAVES, SOIL, STRAWBERRY PLANTLETS


     515  
Deng, R., and D.J. Donnelly. 1993. In-vitro hardening of red raspberry through co2 enrichment and
relative-humidity reduction on sugar-free medium. Canadian Journal of Plant Science 73(4):1105-
1113.

Micropropagated shoots of red raspberry (Rubus idaeus L. 'Comet') were rooted on modified
Murashige-Skoog medium lacking sucrose, in specially 'constructed plexiglass chambers, under
ambient (340 +/- 20 ppm) or enriched (1500 +/- 50 PPM) CO2 and ambient (ca. 100 %) or reduced
(90 +/- 5 %) relative humidity. Cultured plantlets were evaluated for their survival, rooting and
relative vigor, leaf and root number, stem and root length, total leaf area, total fresh and dry weight,
gas exchange rate, and stomatal features, prior to transplantation to soil and at intervals for 6 wk ex
vitro. In vitro CO2 enrichment promoted plantlet growth, rooting and both the survival and early
growth of transplants. CO2 enrichment increased stomatal aperture of plantlet leaves but did not
apparently increase water stress at transplantation. Reduced in vitro RH did not affect plantlet growth
but decreased stomatal apertures and stomatal index on leaves of cultured plantlets and promoted
both the survival and early growth of transplants. In vitro CO2 and RH levels did not affect the
photosynthetic rate of either plantlets or transplants. Only the stomata on leaves of plantlets from the
ambient CO2 and reduced RH treatment were functional. Normal stomatal function was not observed
in persistent leaves of transplants from the other treatments, even 2 wk after transplantation. In vitro
CO2 enrichment acted synergistically with RH reduction in improving growth of plantlets both in
vitro and ex vitro. Hardened red raspberry plantlets obtained through CO2 enrichment and RH
reduction survived direct transfer to ambient greenhouse conditions without the necessity for
specialized ex vitro acclimatization treatment.

KEYWORDS: ANATOMY, CULTURE, GROWTH, LEAVES, LIGHT, PLANTLETS INVITRO, SOIL,
STRAWBERRY


     516  
Deng, X., and F.I. Woodward. 1998. The growth and yield responses of Fragaria ananassa to
elevated CO2 and N supply. Annals of Botany 81(1):67-71.

Strawberry plants (Fragaria ananassa Duchesne var. Elsanta) were grown in pots at two
concentrations of carbon dioxide (partial pressures of 39 and 56 Pa) and with three rates of nitrogen
supply (0.04, 0.4 and 4 mM as nutrient solution) to study their individual and interactive effects on
plant growth and fruit yield. Nitrogen deficiency reduced total dry biomass and relative growth rate
(RGR), mainly through reductions in leaf area ratio (LAR) and plant N concentration (PNC),
although both the net assimilation rare (NAR) and root weight ratio (RWR) increased. Elevated CO2
increased the N productivity (NP) but reduced the LAR. High CO2 increased the fruit yield by 42%
at high N supply and by 17% at low N supply. The CO2 yield enhancement occurred through an
increase in the flower and fruit number of individual plants. This resulted in an increase in the fruit
weight ratio (FWR) of plants at high CO2. Nitrogen deficiency reduced the fruit yield by about 50%
through decreases in fruit size, fruit set and the number of fruits. However, N deficiency increased
the proportion of total plant dry biomass allocated to fruits. There were no significant interactions
between CO2 and N supply on yield. (C) 1998 Annals of Botany Company.

KEYWORDS: ATMOSPHERIC CO2, AVAILABILITY, CARBON-DIOXIDE ENRICHMENT, DRY-
MATTER, GRASSES, NITROGEN, NUTRITION, WHEAT


     517  
denHertog, J., I. Stulen, F. Fonseca, and P. Delea. 1996. Modulation of carbon and nitrogen
allocation in Urtica dioica and Plantago major by elevated CO2: Impact of accumulation of
nonstructural carbohydrates and ontogenetic drift. Physiologia Plantarum 98(1):77-88.

Doubling the atmospheric CO2 concentration from 350 to 700 mu l l(-1) increased the relative
growth rate (RGR) of hydroponically grown Urtica dioica L. and Plantago major ssp. pleiosperma
Pilger only for the first 10-14 days. Previous experiments with P. major led to the conclusion that
RGR did not respond in proportion to the rate of photosynthesis. The present paper is focussed on
the analysis of the impact of changes in leaf morphology, dry matter partitioning, dry matter chemical
composition and ontogenetic drift on this discrepancy. Soon after the start of the treatment,
carbohydrate concentrations were higher at elevated CO2; a reaction that was largely due to starch
accumulation. An increase in the percentage of leaf dry matter and decreases in the specific leaf area
(SLA) and the shoot nitrogen concentration were correlated with an increase in the total
nonstructural carbohydrate concentration (TNC). A combination of accumulation of soluble sugars
and starch and ontogenetic drift explains the decrease in SLA at the elevated CO2 level. A similar
ontogenetic effect of elevated CO2 was observed on the specific root length (SRL). Other variables
such as shoot nitrogen concentration and percentage leaf dry matter were not affected by correction
of data for TNC levels. The net diurnal fluctuation of the carbohydrate pool in P. major was equal
for both CO2 concentrations, indicating that the growth response to elevated CO2 may be ruled by
variables other than photosynthesis, as for instance sink strength. Elevated CO2 did not greatly
influence the partitioning of nitrogen between soluble and insoluble, reduced N and nitrate, nor the
allocation of dry matter between leaf, stem and root. The finding that the root to shoot ratio (R/S)
was not affected by elevated CO2 implies that, in order to maintain a balanced activity between roots
and shoot, no shift in partitioning of dry matter upon doubling of the atmospheric CO2 concentration
is required. Our data on R/S are in good agreement with the response of R/S to high CO2 predicted
by models based on such a theorem.

KEYWORDS: ASSIMILATION, ATMOSPHERIC CO2, DIOXIDE ENRICHMENT, LEAF-AREA,
NITRATE, PHOTOSYNTHESIS, PRODUCTIVITY, RELATIVE GROWTH-RATE, ROOT, SHOOT
RATIO


     518  
Denhertog, J., I. Stulen, and H. Lambers. 1993. Assimilation, respiration and allocation of carbon
in plantago major as affected by atmospheric co2 levels - a case-study. Vegetatio 104:369-378.

The response of Plantago major ssp. pleiosperma plants, grown on nutrient solution in a climate
chamber, to a doubling of the ambient atmospheric CO2 concentration was investigated. Total dry
matter production was increased by 30 % after 3 weeks of exposure, due to a transient stimulation
of the relative growth rate (RGR) during the first 10 days. Thereafter RGR returned to the level of
control plants. Photosynthesis, expressed per unit leaf area, was stimulated during the first two weeks
of the experiment, thereafter it dropped and nearly reached the level of the control plants. Root
respiration was not affected by increased atmospheric CO2 levels, whereas shoot, dark respiration
was stimulated throughout the experimental period. Dry matter allocation over leaves stems and roots
was not affected by the CO2 level. SLA was reduced by 10%, which can partly be explained by an
increased dry matter content of the leaves. Both in the early and later stages of the experiment, shoot
respiration accounted for a larger part of the carbon budget in plants grown at elevated atmospheric
CO2. Shifts in the total carbon budget were mainly due to the effects on shoot respiration. Leaf
growth accounted for nearly 50 % of the C budget at all stages of the experiment and in both
treatments.

KEYWORDS: DIOXIDE, ENRICHMENT, NITROGEN, PHOTOSYNTHESIS, RELATIVE
GROWTH-RATE


     519  
den Hertog, J., I. Stulen, F. Posthumus, and H. Poorter. 1998. Interactive effects of growth-
limiting N supply and elevated atmospheric CO2 concentration on growth and carbon balance of
Plantago major. Physiologia Plantarum 103(4):451-460.

To assess the interactions between concentration of atmospheric CO2 and N supply, the response of
Plantago major ssp. pleiosperma Pilger to a doubling of the ambient CO2 concentration of 350 mu
l l(-1) was investigated in a range of exponential rates of N addition. The relative growth rate (RGR)
as a function of the internal plant nitrogen concentration (Ni), was increased by elevated CO2 at
optimal and intermediate N-i. The rate of photosynthesis, expressed per unit leaf area and plotted
Versus N-i, was increased by 20-30% at elevated CO2 for N-i above 30 mg N g(-1) dry weight.
However, the rate of photosynthesis, expressed on a leaf dry matter basis and plotted versus N-i, was
not affected by the CO2 concentration. The allocation of dry matter between shoot and root was not
affected by the CO2 concentration at any of the N addition rates. This is in good agreement with
theoretical models, based on a balance between the rate of photosynthesis of the shoot and the
acquisition of N by the roots. The concentration of total nonstructural carbohydrates (TNC) was
increased at elevated CO2 and at N limitation, resulting in a shift in the partitioning of photosynthates
from structural to nonstructural and, in terms of carbon balance, unproductive dry matter. The
increase in concentration of TNC led to a decrease in both specific leaf area (SLA) and Ni at all levels
of nutrient supply, and was the cause of the increased rate of photosynthesis per unit leaf area.
Correction of the relationship between RGR and Ni for the accumulation of TNC made the effect of
elevated CO2 on the relationship between RGR and Ni disappear. We conclude that the shift in the
relationship between RGR and Ni was due to the accumulation of TNC and not due to differences
in physiological variables such as photosynthesis and shoot and root respiration, changes in leaf
morphology or allocation of dry matter.

KEYWORDS: BETULA-PENDULA ROTH, DRY-MATTER, ENRICHMENT, LEAF-AREA,
MINERAL NUTRITION, NITROGEN CONCENTRATION, NUTRIENT AVAILABILITY, PHOTON
FLUX- DENSITY, PHOTOSYNTHETIC ACCLIMATION, SHOOT RATIO


     520  
Denmead, O.T., F.X. Dunin, S.C. Wong, and E.A.N. Greenwood. 1993. Measuring water-use
efficiency of eucalypt trees with chambers and micrometeorological techniques. Journal of Hydrology
150(2-4):649-664.

Enclosure appears to be the only feasible way to examine the gas exchange of small groups of trees
or to answer questions about the effects of increased atmospheric CO2 on the assimilation,
evaporation and water use efficiency of forests. To be effective, enclosures must necessarily change
the microclimate, but few studies have been made of the consequences. In this paper, the assimilation,
evaporation and water use efficiency of a community of Eucalyptus trees inside a ventilated chamber
are compared with the same attributes for the surrounding forest. Assimilation and evaporation for
the chamber were measured by the depletion in CO2 and the enrichment in water vapour of air
passing through the chamber. For the forest, assimilation and evaporation were determined by
micrometeorological techniques based on the energy balance, and for CO2, additional chamber
measurements of the soil efflux. Water use efficiencies were calculated as the ratio of mol CO2
assimilated to mol water evaporated. There are some important microclimatic differences between
chamber and forest: net radiation is reduced by about 30% in the chamber, the vapour pressure deficit
of the chamber air is lower, and the light climate there tends to be diffuse rather than direct. Despite
these differences, evaporation rates for both chamber and forest were generally similar, perhaps due
to compensating effects in the chamber from higher boundary layer conductances (because of greater
ventilation rates) and higher stomatal conductances (because of increased humidity). However,
assimilation rates and water use efficiencies were markedly different for the two communities in clear
sky conditions, with higher values of both being recorded in the chamber for most of the daylight
hours. Only on cloudy days, when the light climate was diffuse in both chamber and forest, were
similar assimilation rates and water use efficiencies observed. This behaviour seems to be attributable
in part to the light climate in the chamber being predominantly diffuse and that in the forest
predominantly direct. Diffuse light enhances the photosynthesis of lower leaves in the canopy. This
contention is supported by model calculations of canopy assimilation under diffuse and direct
radiation which produced qualitatively the same light response functions as observed for chamber and
forest. The study suggests that the use of chambers for exploring questions of forest productivity and
water use efficiency must be circumspect. The act of enclosure, by itself, can change the daily water
use efficiency of the tree community by as much as 50%.

KEYWORDS: FOREST, PHOTOSYNTHESIS, TRANSPIRATION, VENTILATED CHAMBER


     521  
Desjardins, Y., A. Gosselin, and M. Lamarre. 1990. Growth of transplants and invitro-cultured
clones of asparagus in response to CO2 enrichment and supplemental lighting. Journal of the
American Society for Horticultural Science 115(3):364-368.



     522  
Devakumar, A.S., M.S.S. Shayee, M. Udayakumar, and T.G. Prasad. 1998. Effect of elevated
CO2 concentration on seedling growth rate and photosynthesis in Hevea brasiliensis. Journal of
Biosciences 23(1):33-36.

To study the effect of elevated CO2 concentration on plant growth and photosynthesis, two clones
of Hevea brasiliensis were grown in polybags and exposed to elevated concentration (700+/-25 ppm)
for 60 days. There was higher biomass accumulation, leaf area and better growth when compared to
ambient air grown plants. From A/Ci curves it is clear that photosynthetic rates increases with
increase in CO2 concentrations. After 60 days of exposure to higher CO2 concentration, a decrease
in the carbon assimilation rate was noticed.

KEYWORDS: ACCLIMATION, ATMOSPHERIC CO2, CARBON DIOXIDE, ENRICHMENT,
FIELD, TEMPERATURE, YIELD


     523  
Devakumar, A.S., M. Udayakumar, and T.G. Prasad. 1996. A simple technique to expose tree
seedlings to elevated CO2 for increased initial growth rates. Current Science 71(6):469-472.

Initial growth rates of most tree species that are used in afforestation programmes are very low.
Therefore, polybag planted seedlings have to be maintained in the nurseries for a long period of time.
Growing plants in an elevated CO2 atmosphere increases the growth rates as well as biomass
production in many annual crop and tree species. Higher temperature and relative humidity in
association with elevated CO2 concentration helps to boost the biomass and leaf area production. We
demonstrate here an easy and cost-effective method for obtaining elevated CO2 concentrations for
better growth of tree seedlings in the nursery.

KEYWORDS: ATMOSPHERIC CO2, CARBON DIOXIDE, PLANTS, RESPIRATION,
TEMPERATURE


     524  
de Wild, H.P.J., E.J. Woltering, and H.W. Peppelenbos. 1999. Carbon dioxide and 1-MCP inhibit
ethylene production and respiration of pear fruit by different mechanisms. Journal of Experimental
Botany 50(335):837-844.

Ethylene production in relation to O-2 partial pressure of whole pear fruit stored at 2 degrees C could
be described by a Michaelis-Menten equation. This was indicated by the use of a gas exchange model.
The maximum ethylene production rate was strongly inhibited while the K-mO2 value (1.25 kPa) was
not affected by elevated CO2. Ethylene production was also inhibited by 1-MCP, an inhibitor of
ethylene perception. The reduction in ethylene production by CO2 was similar for 1-MCP treated and
untreated pears. Elevated CO2, therefore, must have had an influence on ethylene production other
than through ethylene perception. A possible site of inhibition by CO2 is the conversion of ACC to
ethylene. The O-2 uptake rate in relation to O-2 partial pressure of whole pear fruit could be
described by a Michaelis-Menten equation. The O-2 uptake rate was inhibited by elevated CO2 at a
level similar to the inhibition of ethylene production. Again the K-mO2 value (0.68 kPa) was not
affected by CO2. Using 1-MCP treatments it was shown that there was no direct effect of inhibited
ethylene production on O-2 uptake rate.

KEYWORDS: 1-AMINOCYCLOPROPANE-1-CARBOXYLIC ACID, ACC OXIDASE, APPLES,
ATMOSPHERES, AVOCADO FRUIT, BIOSYNTHESIS, ELEVATED CO2 CONCENTRATIONS,
INTRACELLULAR PH, TISSUE, VEGETABLES


     525  
Deyton, D.E., C.E. Sams, and J.C. Cummins. 1992. Application of dormant oil to peach-trees
modifies bud twig internal atmosphere. Hortscience 27(12):1304-1305.

Treatments of single applications of 0%, 3%, 6%, 9%, or 12% dormant oil were sprayed on peach
(Prunus persica L. Batsch) trees on 6 Feb. 1990. A repeat application of 6% oil plus 6% oil applied
6 days later was also made. Internal CO2 concentrations of oil-treated buds and twigs were higher
than the control the day after treatment and continued to be higher for 6 days. The second application
of 10% oil prolonged the elevated CO2 concentration. Applications of 9% or 12% oil delayed flower
bud development and bloom. The repeated application of 6% oil delayed bud development and bloom
more than a single application of 6% oil. Damage to fruit buds increased as oil concentration
increased, but repeated application of 6% oil resulted in less damage than a single application of 12%
oil.



     526  
Dhakhwa, G.B., and C.L. Campbell. 1998. Potential effects of differential day-night warming in
global climate change on crop production. Climatic Change 40(3-4):647-667.

Recent studies on the nature of global warming indicate the likelihood of an asymmetric change in
temperature, where night- time minimum temperature increases more rapidly than the daytime
maximum temperature. We used a physically based scenario of asymmetric warming combined with
climate change scenarios from General Circulation Models (GCMs) outputs and the EPIC (Erosion
Productivity Impact Calculator) plant process model to examine the effects of asymmetric
temperature change on crop productivity. Our results indicated that the potential effects of global
change on crop productivity may be less severe with asymmetric day-night warming than with equal
day- night warming.

KEYWORDS: ATMOSPHERIC CARBON-DIOXIDE, CO2 CONCENTRATIONS, EPIC MODEL,
GROWTH, MAXIMUM, MINIMUM TEMPERATURE, SENSITIVITY, SOUR ORANGE TREES,
VARIABILITY, YIELD


     527  
Dhakhwa, G.B., C.L. Campbell, S.K. LeDuc, and E.J. Cooter. 1997. Maize growth: assessing
the effects of global warming and CO2 fertilization with crop models. Agricultural and Forest
Meteorology 87(4):253-272.

Projected future climate change scenarios derived from two General Circulation Models (GCMs):
Geophysical Fluid Dynamics Laboratory (GFDL) and United Kingdom Meteorological Office
(UKMO), and two crop models: Crop Estimation through Resources and Environmental Synthesis
(CERES), and Erosion/Productivity Impact Calculator (EPIC), were considered to assess the climate
change impact on the yield and biomass of maize. Climate change scenarios included changes in
temperature, precipitation and solar radiation from two GCMs interpolated to 1 degrees x1 degrees
grid cells in the central Piedmont in North Carolina. Changes in mean monthly temperature and
precipitation from the GCMs were used to adjust observed daily climate records from 1949-1988.
There is convincing evidence that future temperature linked to global warming might be characterized
by asymmetric change between daily daytime maxima and daily nighttime minima. Two hypotheses
regarding how GCM temperature would alter observational record were examined. The first
hypothesis assumed that daytime and nighttime warming occurs symmetrically, i.e., maximum and
minimum temperatures are raised equally. The second hypothesis assumed that nighttime minima
change is three times greater than daytime maxima change and the change in mean diurnal
temperature range is approximately equal to the change in daily mean temperature. For the equal day-
night warming scenario, when only the effects of climate change (i.e., changes in temperature,
precipitation and solar radiation) were considered, simulations with CERES and EPIC indicated
substantial losses in maize grain yield and total above ground biomass with both the GCM scenarios.
For the asymmetric warming, the reduction in biomass and yield due to climate change was less than
that obtained with symmetric warming. Simulated maize yield and biomass with CERES and EPIC
increased when only effects due to CO2-fertilization were considered. The inclusion of CO2
fertilization effects with those due to climate change resulted in higher biomass and yield compared
to values obtained with effects of climate change alone. When CERES was used with the GFDL
scenario, and the effects of CO2 fertilization and the climate change were combined, no difference
in simulated yield was found between the two hypotheses; only an 8% difference in aboveground
biomass was found when the UKMO scenario was used. When EPIC was used, the differential day-
night warming hypothesis resulted in 9-13% less reduction in biomass and yield than did the use of
the equal day-night warming hypothesis. (C) 1997 Elsevier Science B.V.

KEYWORDS: ATMOSPHERIC CARBON-DIOXIDE, CLIMATE CHANGE, ENRICHMENT, EPIC
MODEL, PRODUCTIVITY, RESPONSES, TEMPERATURE, UNITED-STATES, WATER-USE,
YIELD


     528  
Dhillion, S.S., J. Roy, and M. Abrams. 1996. Assessing the impact of elevated CO2 on soil
microbial activity in a Mediterranean model ecosystem. Plant and Soil 187(2):333-342.

The fate, as well as the consequence for plant nutrition, of the additional carbon entering soil under
elevated CO2 is largely determined by the activity of soil microorganisms. However, most elevated
CO2 studies have documented changes (generally increases) in microbial biomass and total infection
by symbiotic organisms, which is only a first step in the understanding of the modification of soil
processes. Using a Mediterranean model ecosystem, we complemented these variables by analyzing
changes in enzymatic activities, hyphal lengths, and bacterial substrate assimilation, to tentatively
identify the specific components affected under elevated CO2 and those which suggest changes in soil
organic matter pools. We also investigated changes in the functional structures of arbuscular
mycorrhizas. Most of the microbial variables assessed showed significant and substantial increase
under elevated CO? of the same order or less than those observed for root mass and length. The
increase in dehydrogenase activity indicates that the larger biomass of microbes was accompanied by
an increase in their activity. The increase in hyphal length (predominantly of saprophytic fungi), and
xylanase, cellulase and phosphatase activities, suggests an overall stimulation of organic matter
decomposition. The higher number of substrates utilized by microorganisms from the soil under
elevated CO2 was significant for the amine/amide group. Total arbuscular and vesicular mycorrhizal
infection of roots was higher under elevated CO2, but the proportion of functional structures was not
modified. These insights into the CO2-induced changes in soil biological activity point towards
potential areas of investigation complementary to a direct analysis of the soil organic matter pools.

KEYWORDS: ATMOSPHERIC CARBON-DIOXIDE, BIOCIDAL TREATMENTS, BIOMASS,
COMMUNITIES, ENRICHMENT, MYCORRHIZAL COLONIZATION, RESPIRATION,
RESPONSES, RHIZOSPHERE, ROOTS


     529  
Diaz, S. 1995. Elevated CO2 responsiveness, interactions at the community level and plant functional
types. Journal of Biogeography 22(2-3):289-295.

Plant responsiveness to elevated carbon dioxide (CO2) is a relevant dimension for the definition of
functional types in the face of global change. Most traits reported to be associated with high CO2
responsiveness are derived from laboratory experiments on individually grown species. This paper
suggests that physiological traits such as photosynthetic pathway and internal sink strength are
necessary, but not enough for the prediction of plant responses in mixed stands. A number of
examples from the literature are presented to illustrate how predictions based on single-species
experiments may not match the behaviour of multi-species assemblages. Individual attributes
associated to the interaction of the species with other members of the community should be also
considered. Morphogenetic and architectural traits, as well as characteristics related to other trophic
levels, such as the presence of root symbionts or the preferential allocation to growth or defences
against herbivory, may be useful for a better prediction of plant responsiveness to high CO2 in the
field.

KEYWORDS: ALLOCATION PATTERNS, ATMOSPHERIC CARBON-DIOXIDE, ECOSYSTEMS,
ENRICHMENT, INSECT HERBIVORE, NITROGEN, PHOTOSYNTHESIS, RESPONSES,
SEEDLING GROWTH, WATER-STRESS


     530  
Diaz, S. 1996. Effects of elevated [CO2] at the community level mediated by root symbionts. Plant
and Soil 187(2):309-320.

This review examines the effects of elevated [CO2] on plant symbioses with mycorrhizal fungi and
root nodule bacteria, with emphasis on community and ecosystem processes. The effects of elevated
[CO2] on the relationships between single plant species and root symbionts are considered first. There
is some evidence that plant infection by and/or biomass of root symbionts are stimulated by elevated
[CO2], but growth enhancement of the host seemingly depends on its degree of dependence on
symbiosis and on soil nutrient availability. Second, the effects of elevated [CO2] on the relationships
between plant multispecies assemblages and soil, and likely impacts on above-ground and
belowground diversity, are analysed. Experimental and modelling work have suggested the existence
of complex feedbacks in the responses of plants and the rhizosphere to CO2 enrichment. By
modifying C inputs from plants to soil, elevated [CO2] may affect the biomass, the infectivity, and
the species/isolate composition of root symbionts. This has the potential to alter community structure
and ecosystem functioning. Finally, the incorporation of type and degree of symbiotic dependence
into the definition of plant functional types, and into experimental work within the context of global
change research, are discussed. More experimental work on the effects of elevated [CO2] at the
community/ecosystem level, explicitly considering the role of root symbioses, is urgently needed.

KEYWORDS: ATMOSPHERIC CARBON-DIOXIDE, BOUTELOUA-GRACILIS,
ECTOMYCORRHIZAL FUNGI, EXTERNAL HYPHAE, NITROGEN NUTRITION, PLANT
COMMUNITY, QUERCUS-ALBA, SEEDLING GROWTH, VESICULAR-ARBUSCULAR
MYCORRHIZAS, WATER RELATIONS


     531  
Diaz, S., and M. Cabido. 1997. Plant functional types and ecosystem function in relation to global
change. Journal of Vegetation Science 8(4):463-474.

Plant functional types (PFTs) bridge the gap between plant physiology and community and ecosystem
processes, thus providing a powerful tool in climate change research. We aimed at identifying PFTs
within the flora of central-western Argentina, and to explore their possible consequences for
ecosystem function. We analyzed 24 vegetative and regenerative traits of the 100 most abundant
species along a steep climatic gradient. Based on plant traits and standard multivariate techniques,
we identified eight PFTs. Our results confirmed, over a wide range of climatic conditions, the
occurrence of broad recurrent patterns of association among plant traits reported for other floras;
namely trade-offs between high investment in photosynthesis and growth on the one hand, and
preferential allocation to storage and defence on the other. Regenerative traits were only partially
coupled with vegetative traits. Using easily-measured plant traits and individual species cover in 63
sites, we predicted main community- ecosystem processes along the regional gradient. We
hypothesized likely impacts of global climatic change on PFTs and ecosystems ill situ, and analysed
their probabilities of migrating in response to changing climatic conditions. Finally, we discuss the
advantages and limitations of this kind of approach in predicting changes in plant distribution and in
ecosystem processes over the next century.

KEYWORDS: ATTRIBUTES, CLASSIFICATION, CO2- ENRICHMENT, COMMUNITIES,
ECOLOGY, GROWTH RATE, RESPONSES, SEED SIZE, STRATEGIES, VEGETATION


     532  
Diaz, S., M. Cabido, M. Zak, E.M. Carretero, and J. Aranibar. 1999. Plant functional traits,
ecosystem structure and land-use history along a climatic gradient in central-western Argentina.
Journal of Vegetation Science 10(5):651-660.

This paper deals with theoretical concepts, methodological steps, and case studies related to the use
of plant functional traits in the assessment of vegetation responses to climate and land use. Trait-
environment links are considered, and special emphasis is put on the links between vegetation
structure and ecosystem function, and on the role of disturbance history in determining vegetation
responses to land use at present. As a basis for discussion, published and new case studies from
central-western Argentina are presented. Similar plant traits measured with different levels of
precision are utilized in the description of ecosystem structure in different land-use situations along
a steep regional climatic gradient. The general protocol followed in the case studies represents a data-
driven, non-hierarchical, low-tech approach, that can be applied to a wide range of spatial scales,
from plots to regions. Climatic factors (including extreme events and seasonality), disturbance
frequency and intensity, and disturbance history are suggested as key factors to be considered in
global comparisons of vegetation responses to land use and in predictive models of ecosystem
dynamics.

KEYWORDS: ATMOSPHERIC CO2, BIODIVERSITY, COMMUNITIES, GLOBAL CHANGE,
GRASSLAND, VEGETATION


     533  
Diaz, S., L.H. Fraser, J.P. Grime, and V. Falczuk. 1998. The impact of elevated CO2 on plant-
herbivore interactions: experimental evidence of moderating effects at the community level.
Oecologia 117(1-2):177-186.

Surprisingly little research has been published on the responses to elevated [CO2] at the community
level, where herbivores can select their preferred food. We investigated the combined effects of
atmospheric [CO2] and herbivory on synthesised plant communities growing on soils of different
fertility. Factorial combinations of two [CO2] (350 or 700 mu l l(-1)), two fertility (fertilised or non-
fertilised), and two herbivory (herbivores present or absent) treatments were applied to a standard
mixture of seven fast- and eight slow- growing plants in outdoor microcosms. The herbivores used
were the grain aphid (Sitobion avenae) and the garden snail (Helix aspersa). We measured plant
biomass, foliar nitrogen and soluble tannin concentration, aphid fecundity, and snail growth,
fecundity, and feeding preferences over one growing season. Elevated [CO2] did not have a
significant impact on(1)the combined biomass of fast-growing or slow-growing plants, (2) herbivore
feeding preferences, or (3) herbivore fitness. There was, however, a significant biomass increase of
Carex flacca (which represented in all cases less than 5% of total live biomass), and some chemical
changes in unpalatable plants under elevated [CO2]. The herbivory treatment significantly increased
the biomass of slow-growing plants over fast-growing plants, whereas fertilisation significantly
increased the abundance of fast-growing plants over slow- growing plants. Predictions on the effects
of elevated [CO2] based on published single-species experiments were not supported by the results
of this microcosm study.

KEYWORDS: ATMOSPHERIC CO2, CALCAREOUS GRASSLAND, CARBON DIOXIDE,
CHEMICAL-COMPOSITION, DECOMPOSITION, EXPERIMENTAL MICROCOSMS, INSECT
HERBIVORE, PERFORMANCE, RELATIVE GROWTH-RATE, RESPONSES


     534  
Diaz, S., J.P. Grime, J. Harris, and E. McPherson. 1993. Evidence of a feedback mechanism
limiting plant-response to elevated carbon-dioxide. Nature 364(6438):616-617.

IN short-term experiments under productive laboratory conditions, native herbaceous plants differ
widely in their potential to achieve higher yields at elevated concentrations of atmospheric carbon
dioxide1-8. The most responsive species appear to be large fast-growing perennials of recently
disturbed fertile soils7,8. These types of plants are currently increasing in abundance9 but it is not
known whether this is an effect of rising carbon dioxide or is due to other factors. Doubts concerning
the potential of natural vegetation for sustained response to rising carbon dioxide have arisen from
experiments on infertile soils, where the stimulus to growth was curtailed by mineral nutrient
limitations2,3,10. Here we present evidence that mineral nutrient constraints on the fertilizer effect
of elevated carbon dioxide can also occur on fertile soil and in the earliest stages of secondary
succession. Our data indicate that there may be a feedback mechanism in which elevated carbon
dioxide causes an increase in substrate release into the rhizosphere by non-mycorrhizal plants, leading
to mineral nutrient sequestration by the expanded microflora and a consequent nutritional limitation
on plant growth.

KEYWORDS: CO2- ENRICHMENT, ECOSYSTEMS, GROWTH, NUTRITION, POPULATIONS,
SOIL, TUNDRA


     535  
Dickson, R.E., M.D. Coleman, D.E. Riemenschneider, J.G. Isebrands, G.D. Hogan, and D.F.
Karnosky. 1998. Growth of five hybrid poplar genotypes exposed to interacting elevated CO2 and
O-3. Canadian Journal of Forest Research-Revue Canadienne De Recherche Forestiere
28(11):1706-1716.

A wide variety of hybrid poplar clones are being introduced for intensive culture biomass production,
but the potential clonal or genotypic response to increasing tropospheric carbon dioxide (CO2),
ozone (O-3), and their interactions are unknown. To study these effects, we exposed five different
hybrid Populus clones to increased concentrations of CO2, O-3, and CO2 + O-3 in open-top
chambers for one growing season and determined growth responses. Exposure to elevated CO2
increased height growth, dry mass, and basal area; exposure to O-3 decreased all three of these
growth responses. Exposure impact differed among the different plant parts (leaf, stem, and roots)
and among the crones. These differences were associated with different growth strategies or carbon
allocation patterns inherent in the different clones. The fastest growing clones had the greatest
response to O-3 treatment. The addition of CO2 to the O-3 exposure counteracted the negative
impact of O-3 in all plant components except leaf mass (e.g., CO2 + O-3 plant mass equaled control
plant mass) in all of the clones. But correspondingly, added O-3 negated increased growth from CO2.
Genetic variation in response to atmospheric pollutants must be considered even in closely related
genotypes found in Populus culture.

KEYWORDS: AIR-POLLUTION, ASPEN CLONES, ATMOSPHERIC CO2, BETULA-PUBESCENS
EHRH, CARBON DIOXIDE, ESTABLISHMENT-YEAR, FOREST ECOSYSTEMS, PLANT
GROWTH, POPULUS X EURAMERICANA, TROPOSPHERIC OZONE


     536  
Didham, R.K. 1998. Altered leaf-litter decomposition rates in tropical forest fragments. Oecologia
116(3):397-406.

The effects of forest fragmentation on leaf-litter decomposition rates were investigated for the first
time in an experimentally fragmented tropical forest landscape in Central Amazonia. Leaf-litter
decomposition rates were measured at seven distances (0-420 m) along forest edge-to-interior
transects in two 100-ha fragments, two continuous forest edges, and at an identical series of distances
along two deep continuous forest transects, as well as at the centers of two 1-ha and two 10-ha
fragments. Decomposition rates increased significantly towards the edge of 100-ha forest fragments.
Litter turnover times were 3-4 times faster within 50 m of the edge of 100-ha fragments than normally
found in deep continuous forest. In contrast, there was no significant change in the rate of leaf-litter
decomposition from the interior to the edge of continuous forest. It is difficult to account for these
very different edge responses. Decomposition rates were not correlated with air temperature
differentials, evaporative drying rates, litter depth, biomass or moisture content, or with total
invertebrate densities, either within individual edge transects or across all sites. The difference in edge
response may be due to chance, particularly the patchy removal of vast quantities of litter by litter-
feeding termites, or may be a real, area-dependent phenomenon. Clearly, however, forest
fragmentation increases the variability and unpredictability of litter decomposition rates near forest
edges. In addition to edge effects, decomposition. rates were strongly affected by decreasing fragment
area. While sites at the centers of 10-ha and 100-ha forest fragments and continuous forest had
equivalent decomposition rates, rates were markedly lower at the centers of 1-ha fragments. Litter
turnover times were 2-3 times slower in I-ha fragments than in continuous forest, and up to 13 times
slower than at 100-ha edges. Litter structure and nutrient cycling dynamics are inevitably altered by
forest fragmentation.

KEYWORDS: AMAZON, CLEAR-CUT, DECAY-RATES, DOUGLAS-FIR FOREST, ELEVATED
CO2, GROWTH, LIGNIN CONTROL, NITROGEN, NUTRIENT DYNAMICS, RAIN FORESTS


     537  
Diemer, M.C., and C. Korner. 1996. Lifetime leaf carbon balances of herbaceous perennial plants
from low and high altitudes in the central Alps. Functional Ecology 10(1):33-43.

1. A combination of demographic analysis of leaf growth, age- specific CO2 gas exchange and
microclimate were employed to calculate lifetime sums of net photosynthesis and dark respiration,
in order to obtain leaf carbon balances (Q(c)) of altitudinally disjunct Ranunculus and Geum species,
as well as two altitudinal populations of Potentilla crantzii. If carbon costs for construction of leaf
tissue are included, leaves fixed a lifetime carbon surplus ranging from 0.4 to 2.0 mmol CO2 cm(-2)
independent of altitude, thereby exceeding initial investments by the plant three- to sixfold. 2. The
lack of a consistent difference between the Q(c) of high and related low elevation taxa with similar
leaf area ratios (LAR) challenges the view that carbon gain impairs growth and persistence of
herbaceous perennials in harsh alpine climates to a greater extent than at low elevation. 3. Evidence
from a sensitivity analysis of our carbon balance model as well as rank correlations indicate that the
primary determinant of a leaf's carbon balance is its longevity. A comparison of leaf carbon balance
data from the literature on wild plants of the temperate zone suggests that daily carbon gain on a leaf
area basis is higher in herbaceous plants, compared to deciduous woody shrubs, which could explain
the predominance of the herbaceous growth form at high altitudes.

KEYWORDS: COST, LONGEVITY, PHOTOSYNTHETIC CHARACTERISTICS, SEASONAL-
CHANGES, SHRUB, SPANS


     538  
Diemer, M. 1992. Population-dynamics and spatial arrangement of ranunculus- glacialis L, an alpine
perennial herb, in permanent plots. Vegetatio 103(2):159-166.

In 1986 sixteen permanent plots (625 cm2 each) were established in scree slopes dominated by
Ranunculus glacialis at Mt. Glungezer, Austria (2600 m elevation) in order to document the
population dynamics of herbaceous perennials near the upper altitudinal limits of plant existence. The
abundance and sizes of individual R. glacialis shoots, their leaf numbers and reproductive status were
evaluated over a 6-year period. On South-facing slopes the population sizes of adult and juvenile
shoots remained constant over the years, while seedling numbers fluctuated significantly. Overall
density of all developmental stages of R. glacialis was significantly lower on North-facing slopes and
year-to-year fluctuations were greater, than on thermally-favorable Southern slopes. The spatial
pattern of adult shoots and seedlings was clumped, while juvenile shoots had a random or clumped
distribution. Fertilization had no effects on population dynamics. Proposed greenhouse effects, e.g.
increases in CO2 and temperature, should result in population growth on North-facing slopes and
may increase mortality on South-facing sites.

KEYWORDS: AREA, FINNISH LAPLAND, PLANTS


     539  
Diemer, M.W. 1994. Mid-season gas-exchange of an alpine grassland under elevated co2. Oecologia
98(3-4):429-435.

Ecosystem net CO2 uptake, evapotranspiration (ET) and night- time CO2 efflux were measured in
an alpine grassland dominated by Carex curvula, treated with doubled ambient partial pressure of
CO2 via open-top chambers. One quarter of the plots were treated with mineral nutrients to simulate
the effect of lowland nitrogen deposition rates. Depending upon fertilizer supply, ecosystem net CO2
uptake per ground area in full sunlight (NCE(max)) was 41-81% higher in open-top chambers
supplied with doubled ambient partial pressure (p(a)) of CO2 than in plots receiving ambient CO2.
Short-term reversals of the CO2 level suggest that the extent of downward adjustment of canopy
photosynthesis under elevated CO2 was 30-40%. ET tended to decline, while water use efficiency
(WUE), expressed as the NCE(max):ET ratio, increased more than twofold under elevated CO2.
Night-time ecosystem CO2 efflux did not respond to changes in CO2 p(a). NCE(max) and night-time
CO2 efflux were more responsive to mineral fertilizer than the doubling of CO2. This suggests that
in these alpine plant communities, atmospheric nutrient input may induce equal or greater effects on
gas exchange than increased CO2.

KEYWORDS: ATMOSPHERIC CO2, BALANCE, CARBON DIOXIDE, COMMUNITIES,
ECOSYSTEMS, RESPONSES, TUSSOCK TUNDRA


     540  
Diemer, M. 1996. The incidence of herbivory in high-elevation populations of Ranunculus glacialis:
A re-evaluation of stress-tolerance in alpine environments. Oikos 75(3):486-492.

Growing conditions in the upper alpine zone are characterized by low temperature, low partial
pressures of CO2 and, in the temperate zone, a short growing period. The plants which have evolved
under these conditions presumably share a number of characteristics that were ascribed to stress-
tolerance, namely slow growth, extended longevity, resource limitation and low palatability to
herbivores. Hence chronic biomass removals by herbivores should be a threat to plant persistence in
alpine environments. as predicted by Grime's C-S-R theory. I tested this hypothesis on populations
of an alpine buttercup, Ranunculus glacialis. A survey along an altitudinal transect in the Central Alps
of Austria indicated that between 15 and 26% of the R. glacialis plants in each population examined
exhibited signs of herbivory damage. Merely a small population, isolated by glaciers, at the highest
site (3310 m a.s.l.) showed no traces of herbivory. Ar two sites (2600 m and 3180 m a.s.l.) twenty
plants each were tagged and examined for a two- year period. Herbivory damage was considerable:
on an average nearly 25% of a plant's total leaf area was removed in 1987. primarily by snow mice
(Microtus nivalis). Inflorescences of 65-85% of all flowering plants were removed as well. Ar the
lower sire (2600 m, roughly 600 m above the treeline) up to 5 g dry matter and 140 mg nitrogen m(-
2) were consumed in one season. Despite the magnitude of these losses both reproductive investment
and the number of leaves initiated per plant did not change appreciably in the subsequent year. Since
populations of R. glacialis are able to support populations of herbivores at the altitudinal limits of
plant growth without obvious reductions in vigor,these plants and other food species (e.g. Oxyria
digyna) cannot fit the stress-tolerator scheme proposed by Grime. The widespread occurrence of
herbivory at high elevations and plant traits challenge the concept of stress- tolerance as it is
commonly applied to alpine environments.

KEYWORDS: AVAILABILITY, DYNAMICS, GRADIENTS, HERB, LEAF, LIFE, PLANTS, SEED,
ZONE


     541  
Diemer, M. 1997. Effects of elevated CO2 on gas exchange characteristics of alpine grassland. Acta
Oecologica-International Journal of Ecology 18(3):177-182.

The ecosystem-level gas exchange characteristics of an alpine grassland treated with a combination
of elevated CO2 and moderate additions of NPK fertilizer during the third season of experimental
treatments are described. Mid-season maximum daytime net ecosystem CO2 flux (NEC)increased
significantly under elevated CO2 (+45%), whereas nighttime NEC was unaffected by the CO2
treatment. Since daytime NEC under elevated CO2 underwent a seasonal decline, only moderate
carbon surpluses accumulated under elevated CO2. The observed seasonal decline in daytime NEC
may be due to reduced sink strength once maximum aboveground biomass is attained, and appears
to be a reg ulatory mechanism of ecosystem carbon accumulation. Moderate additions of NPK
fertilizer stimulated both day- (+39%) and nighttime NEC (+29%) due to increased plant biomass,
independent of CO2 treatment. Yet there is no indication that enhanced mineral nutrient status will
increase ecosystem responsiveness to elevated CO2.

KEYWORDS: CARBON BALANCE


     542  
Diemer, M., and C. Korner. 1998. Transient enhancement of carbon uptake in an alpine grassland
ecosystem under elevated CO2. Arctic and Alpine Research 30(4):381-387.

We investigated the carbon uptake and release of a Central European alpine grassland community
subjected to doubled ambient CO2 during the third (1994) and fourth (1995) season of CO2
enrichment. Within this period net carbon uptake under elevated CO2 declined successively,
providing evidence of carbon saturation in this high-elevation environment. Third year data were used
to calculate a CO2 balance for the 13-wk growing season and indicated that the grassland still served
as net carbon sink in 1994. Integrated over the growth period, plots exposed to doubled ambient CO2
fixed 22% more CO2 than control treatments receiving ambient CO2. Increased carbon uptake under
elevated CO2 was entirely due to a stimulation of daytime net CO2 uptake, since nighttime CO2
release remained unaffected. However, enhancement of net canopy CO2 uptake showed a distinct
seasonal response: following substantial net CO2 gains from snowmelt until attainment of peak
biomass (ca. 6 wk), the relative effect of elevated CO2 declined over the remainder of the season. In
contrast to controls, the C balance became negative under CO2 enrichment during the final weeks
of the growth period. Estimates of wintertime respiratory CO2 losses of unfertilized plots (ca, 9 mo
during which soils remain thawed under the snow) indicate a release of 73 to 89% of the amount of
CO2 fixed during the snow-free period. Under elevated CO2 an estimated mean surplus of 41 g C
m(-2) accreted during the third year of CO2 enrichment, which we hypothesize must been transferred
belowground, since aboveground biomass remained unchanged. Moderate additions of mineral
fertilizer (NPK) alone had a strong positive effect on seasonal net CO2 balance (57% increase)
mediated by enhanced plant biomass. NPK- treated plots under elevated CO2 had a 38% higher
seasonal CO2 balance, relative to NPK-plots at ambient CO2 concentration. Fourth-year (1995) data
indicate no further stimulation of daytime net ecosystem CO2 flux under elevated CO2, both in
unfertilized plots and plots treated with NPK. Hence, it is unlikely that alpine grasslands will serve
as carbon sinks in a CO2-rich world in the long term.

KEYWORDS: ATMOSPHERIC CO2, CLIMATE, ENRICHMENT, ENVIRONMENTAL-CHANGE,
GAS-EXCHANGE, GROWTH, HIGH- ALTITUDES, PLANTS, RESPONSES, TUSSOCK TUNDRA


     543  
Dietz, T., and E.A. Rosa. 1997. Effects of population and affluence on CO2 emissions. Proceedings
of the National Academy of Sciences of the United States of America 94(1):175-179.

We developed a stochastic version of the Impact = Population Affluence Technology (IPAT) model
to estimate the effects of population, affluence, and technology on national CO2 emissions. Our
results suggest that, for population, there are diseconomies of scale for the largest nations that are
not consistent with the assumption of direct proportionality (log- linear effects) common to most
previous research. In contrast, the effects of affluence on CO2 emissions appear to reach a maximum
at about $10,000 in per-capita gross domestic product and to decline at higher levels of affluence.
These results confirm the general value of the IPAT model as a starting point for understanding the
anthropogenic driving forces of global change and suggest that population and economic growth
anticipated over the next decade will exacerbate greenhouse gas emissions.

KEYWORDS: ECONOMIC-GROWTH, ENVIRONMENTAL-QUALITY, ROBUST


     544  
Diiorio, A.A., R.D. Cheetham, and P.J. Weathers. 1992. Carbon-dioxide improves the growth of
hairy roots cultured on solid medium and in nutrient mists. Applied Microbiology and Biotechnology
37(4):463-467.

The effect of varying CO2 concentrations on the growth of beet and safflower hairy roots was
measured for tissues cultured in nutrient mists and on solid media in chambers fed mixtures of
humidified air supplemented with different CO2 concentrations. Hairy root tissue grown on solid
media in air enriched with CO2 showed increased growth, as measured by dry weight increases vs
air-fed controls. Growth increased with CO2 enrichment as much as 2.5 times more than the air-fed
control for safflower at 1.0 % CO2 and 1.4 times more than the air-fed control for beets at 1.5 %
CO2 over a 12-day period. Beet hairy root tissue was also cultured aeroponically in nutrient mists.
Beet hairy root cultured in nutrients mists enriched with 1.0 % CO2 showed a 15 % increase in
biomass over a 7-day period vs tissue cultured in nutrient mists (with ambient air) or in shake flasks.
The stimulation of root growth via CO2 enrichment reduced the time required for biomass
accumulation.

KEYWORDS: ACID


     545  
Dijkstra, P., A.H.M.C. Schapendonk, K. Groenwold, M. Jansen, and S.C. Van de Geijn. 1999.
Seasonal changes in the response of winter wheat to elevated atmospheric CO2 concentration grown
in Open-Top Chambers and field tracking enclosures. Global Change Biology 5(5):563-576.

Winter wheat was grown at ambient and elevated (ambient plus 350 mu L L-1) CO2 concentrations
in open top chambers and in field-tracking sun-lit climatized enclosures (elevated is 718 mu L L-1).
There was no significant effect of CO2 concentration on sheath, leaf and root biomass and leaf area
in the early spring (January to April). 24-h canopy CO2 exchange rate (CCER) was not significantly
affected either. However, elevated CO2 concentration increased CCER at midday, decreased
evapotranspiration rate and increased instantaneous water-use- efficiency during early spring. Leaf,
sheath and root nitrogen concentration per unit dry weight decreased and nonstructural carbohydrate
concentration increased under elevated CO2, and N- uptake per unit ground area decreased
significantly (-22%) towards the end of this period. These results contrast with results from the final
harvest, when grain yield and biomass were increased by 19% under elevated CO2. N concentration
per dry weight was reduced by 5%, but N-uptake per unit ground area was significantly higher
(+11%) for the elevated CO2 treatment. 24-h and midday-CCER increased significantly more in late
spring (period of 21 April to 30 May) (respectively by + 40% and 53%) than in the early spring
(respectively 5% and 19%) in response to elevated CO2. Midday evapotranspiration rate was reduced
less by elevated CO2 in the late spring (-13%) than in early spring (-21%). The CO2 response of
midday and 24-h CCER decreased again (+ 27% and + 23% resp.) towards the end of the growing
season. We conclude that the low response to CO2 concentration during the early spring was
associated with a growth-restriction, caused by low temperature and irradiance levels. The reduction
of nitrogen concentration, the increase of nonstructural carbohydrate, and the lower
evapotranspiration indicated that CO2 did have an effect towards the end of early spring; but not on
biomass accumulation. Regression analysis showed that both irradiance and temperature affected the
response to CO2.

KEYWORDS: ACCLIMATION, C-3, CARBON DIOXIDE, CARBOXYLASE-OXYGENASE,
ENRICHMENT, LOLIUM-PERENNE, TEMPERATURE, TRITICUM-AESTIVUM L, WATER-USE
EFFICIENCY, YIELD


     546  
Ding, L., C.H. Zhang, K.Z. Bai, and T.Y. Kuang. 1997. Relation between seed size in different
plant species and response of their seedlings to double CO2. Chinese Science Bulletin 42(4):331-333.



     547  
Dippery, J.K., D.T. Tissue, R.B. Thomas, and B.R. Strain. 1995. Effects of low and elevated co2
on C-3 and C-4 annuals .1. Growth and biomass allocation. Oecologia 101(1):13-20.

In order to study C-3 and C-4 plant growth in atmospheric CO2 levels ranging from past through
predicted future levels, Abutilon theophrasti (C-3) and Amaran thus retroflexus (C-4) were grown
from seed in growth chambers controlled at CO2 partial pressures of 15 Pa (below Pleistocene
minimum) 27 Pa (pre-industrial), 35 Pa (current) and 70 Pa (predicted future). After 35 days of
growth, CO2 had no effect on the relative growth rate, total biomass or partitioning of biomass in the
C- 4 species. However, the C-3 species had greater biomass accumulation with increasing CO2 partial
pressure. C-3 plants grown in 15 Pa CO2 for 35 days had only 8% of the total biomass of plants
grown in 35 Pa CO2. In 15 Pa CO2, C-3 plants had lower relative growth rates and lower specific
leaf mass than plants grown in higher CO2 partial pressures, and aborted reproduction. C-3 plants
grown in 70 Pa CO2 had greater root mass and root-to-shoot ratios than plants grown in lower CO2
partial pressures. These findings support other studies that show C-3 plant growth is more responsive
to CO2 partial pressure than C-4 plant growth. Differences in growth responses to CO2 levels of the
Pleistocene through the future suggest that competitive interactions of C-3 and C-4 annuals have
changed through geologic time. This study also provided evidence that C-3 annuals may be operating
near a minimum CO2 partial pressure for growth and reproduction at 15 Pa CO2.

KEYWORDS: ATMOSPHERIC CO2, CARBON DIOXIDE, COMPETITION, ENRICHMENT,
PERENNIALS, PHOTOSYNTHESIS, PLANTS, RESPONSES, SEEDLINGS, SUBAMBIENT


     548  
Dixon, M., D. Lethiec, and J.P. Garrec. 1995. The growth and gas-exchange response of soil-
planted norway spruce [picea-abies (L) karst] and red oak (quercus-rubra L) exposed to elevated co2
and to naturally-occurring drought. New Phytologist 129(2):265-273.

Norway spruce and red oak trees were planted directly into the soil and exposed to 700 mu mol mol(-
1) CO2 in open-top chambers. There were large inter-specific differences in response to naturally
occurring drought during the second pear of exposure to elevated CO2. Both species had decreased
assimilation rates. CO2-treated red oak had no loss of photosynthetic enhancement when
undroughted, whereas CO2- treated Norway spruce showed a relative increase in assimilation rates
only when droughted. The effect of CO2 on radial growth of both species was less marked in the
second growing season, but this may have been a result of different biomass partitioning as Norway
spruce shoot extension had a different pattern of growth in elevated CO2. Stomatal density and
chlorophyll content were largely unaffected by the CO2 treatment. A precise method for measuring
Norway spruce needle surface area was also developed.

KEYWORDS: ENHANCEMENT, ENRICHMENT, INCREASE, LIMITATIONS,
PHOTOSYNTHESIS, SEEDLINGS, SITCHENSIS BONG CARR, STOMATAL DENSITY, WATER-
STRESS


     549  
Dixon, R.K. 1995. Agroforestry systems - sources or sinks of greenhouse gases. Agroforestry
Systems 31(2):99-116.

The prominent role of forestry and agroforestry systems in the flux and long-term storage of carbon
(C) in the terrestrial biosphere has increased global interest in these land-use options to stabilize
greenhouse gas (GHG) emissions. Preliminary assessments suggest that some agroforestry systems
(e.g., agrosilvicultural) can be CO2 sinks and temporarily store C, while other systems (e.g.,
ruminant-based silvopastoral systems) are probably sources of GHG (e.g., CH4).
Agroforestry;systems can be significant sources of GHG emissions, especially at low latitudes.
Practices such as tillage, burning, manuring, chemical fertilization, and frequent disturbance can lead
to emission of CO2, CH4, and N2O from soils and vegetation to the atmosphere. Establishment and
management of agroforestry systems incompatible with prevailing edaphic and climatic conditions can
accelerate soil GHG emissions. Non-sustainable agroforestry systems are quickly degraded, and
woody and herbaceous crops can become significant GHG sources. Silvopastoral systems can result
in soil compaction and erosion with significant loss of labile C and N compounds to the atmosphere.
Ruminant-based silvopastoral systems and rice paddy agrisilvicultural systems are well documented
sources of CH4 which significantly contribute to the global CH4 budget. Early assessments of
national and global terrestrial CO2 sinks reveal two primary beneficial attributes of agroforestry
systems: 1) direct near-term C storage (decades to centuries) in trees and soils, and, 2) potential to
offset immediate GHG emissions associated with deforestation and subsequent shifting agriculture.
Within the tropical latitudes, it is estimated that one ha of sustainable agroforestry can provide goods
and services which potentially offset 5-20 ha of deforestation. At a global scale, agroforestry systems
could potentially be established on 585-1275 x 10(6) ha of technically suitable land, and these systems
could store 12-228 (median 95) Mg C ha(-1) under current climate and edaphic conditions.



     550  
Dixon, R.K., S. Brown, R.A. Houghton, A.M. Solomon, M.C. Trexler, and J. Wisniewski. 1994.
Carbon pools and flux of global forest ecosystems. Science 263(5144):185-190.

Forest systems cover more than 4.1 x 10(9) hectares of the Earth's land area. Globally, forest
vegetation and soils contain about 1146 petagrams of carbon, with approximately 37 percent of this
carbon in low-latitude forests, 14 percent in mid-latitudes, and 49 percent at high latitudes. Over two-
thirds of the carbon in forest ecosystems is contained in soils and associated peat deposits. In 1990,
deforestation in the low latitudes emitted 1.6 +/- 0.4 petagrams of carbon per year, whereas forest
area expansion and growth in mid- and high- latitude forest sequestered 0.7 +/- 0.2 petagrams of
carbon per year, for a net flux to the atmosphere of 0.9 +/- 0.4 petagrams of carbon per year. Slowing
deforestation, combined with an increase in forestation and other management measures to improve
forest ecosystem productivity, could conserve or sequester significant quantities of carbon. Future
forest carbon cycling trends attributable to losses and regrowth associated with global climate and
land-use change are uncertain. Model projections and some results suggest that forests could be
carbon sinks or sources in the future.

KEYWORDS: ATMOSPHERIC CARBON, BIOMASS, CLIMATE CHANGE, CO2
CONCENTRATION, ELEVATED CO2, INCREASING CO2, STORAGE, TRANSIENT-RESPONSE,
TROPICAL FORESTS, UNITED-STATES


     551  
Dixon, R.K., J.B. Smith, S. Brown, O. Masera, L.J. Mata, and I. Buksha. 1999. Simulations of
forest system response and feedbacks to global change: experiences and results from the US Country
Studies Program. Ecological Modelling 122(3):289-305.

Large shifts in the response and feedbacks of forest systems are implied by models and systems
analysis driven by global change scenarios of general circulation models (GCMs). Prior climate
change analyses and modeling efforts have been reported at a global scale in a few developed
countries, but relatively few national assessments have been successfully completed in developing
countries. Under the auspices of the U.S. Country Studies Program, analysts from 55 countries
employed a common set of methods and models to characterize current carbon (C) pools in forests,
future impacts of global change on forest distribution, and management options for conserving and
sequestering carbon dioxide (CO2) in forest systems. The analysis revealed that the response and
feedbacks of forest systems to global climate change will be profound in the 55 countries studied on
five continents. Globally, forest vegetation and soils contain about 1146 Pg C, with approximately
37% of this C in low-latitude forests, 14% in mid-latitudes, and 49% at high latitudes. The impacts
of future global change on forest distribution and productivity will be most significant at high
latitudes, with more modest changes in distribution and productivity at low latitudes. Future
opportunities to conserve and sequester CO2 in forest systems are potentially significant, but land-use
practices and global change will influence the size of this C pool and CO2 sink. In the future, a
greater proportion of forests at all latitudes could become a greenhouse gas (GHG) source if
sustained management and conservation policies are not employed. The timing and magnitude of
future changes in forest systems are dependent on global environmental factors (for example, global
change, biogeochemical Sulphur and Nitrogen cycles), as well as on human factors such as
demographics, economic growth, technology, and resource management policies. (C) 1999 Elsevier
Science B.V. All rights reserved.

KEYWORDS: AGROFOREST MANAGEMENT-PRACTICES, ATMOSPHERIC CARBON-
DIOXIDE, BIOMASS, BUDGET, CO2-INDUCED CLIMATE CHANGE, EMISSIONS, MODEL,
SENSITIVITY, STORAGE, TRANSIENT-RESPONSE


     552  
Dixon, R.K., J.K. Winjum, and P.E. Schroeder. 1993. Conservation and sequestration of carbon -
the potential of forest and agroforest management-practices. Global Environmental Change-Human
and Policy Dimensions 3(2):159-173.

Forests play a major role in Earth's carbon cycle through assimilation, storage, and emission of CO2.
Establishment and management of boreal, temperate, and tropical forest and agroforest systems could
potentially enhance sequestration of carbon in the terrestrial biosphere. A biological and economic
analysis of forest establishment and management options from 94 nations revealed that forestation,
agroforestry, and silviculture could be employed to conserve and sequester one Petagram (Pg) of
carbon annually over a 50-year period. The marginal cost of implementing these options to sequester
55 Pg of carbon would be approximately $10/Mg.



     553  
Dixon, R.K., and J. Wisniewski. 1995. Global forest systems: An uncertain response to atmospheric
pollutants and global climate change? Water, Air, and Soil Pollution 85(1):101-110.

Forest systems cover more than 4.1 x 10(9) ha of the Earth's land area. The future response and
feedbacks of forest systems to atmospheric pollutants and projected climate change may be
significant. Boreal, temperate and tropical forest systems play a prominent role in carbon (C),
nitrogen (N) and sulfur (S) biogeochemical cycles at regional and global scales. The timing and
magnitude of future changes in forest systems will depend on environmental factors such as a
changing global climate, an accumulation of CO2 in the atmosphere, and increase global
mineralization of nutrients such as N and S. The interactive effects of all these factors on the world's
forest regions are complex and not intuitively obvious and are likely to differ among geographic
regions. Although the potential effects of some atmospheric pollutants on forest systems have been
observed or simulated, large uncertainty exists in our ability to project future forest distribution,
composition and productivity under transient or nontransient global climate change scenarios. The
potential to manage and adapt forests to future global environmental conditions varies widely among
nations. Mitigation practices, such as liming or fertilization to ameliorate excess NOx or SOx or
forest management to sequester CO2 are now being applied in selected nations worldwide.

KEYWORDS: CARBON, ECOSYSTEMS, ELEVATED CO2, NITROGEN DEPOSITION, SINK


     554  
Docherty, M., D.K. Hurst, J.K. Holopainen, J.B. Whittaker, P.J. Lea, and A.D. Watt. 1996.
Carbon dioxide-induced changes in beech foliage cause female beech weevil larvae to feed in a
compensatory manner. Global Change Biology 2(4):335-341.

The phenology of Fagus sylvatica was unaffected by exposure to an atmosphere of elevated CO2
(600 mu L L(-1)) after two years of fumigation. Non-significant changes in nitrogen and phenolic
content of the leaves decreased the nutritional status of beech for female larvae in elevated CO2 such
that they responded by eating in a compensatory manner; males were unaffected. Rates of
development, mortality and adult biomass of Rhynchaenus fagi were no different from those in
ambient CO2 concentrations (355 mu L L(-1)). It is possible that, with the changes in leaf chemistry
affecting the females, fecundity will be altered, with important consequences for populations of beech
weevil.

KEYWORDS: ATMOSPHERIC CO2, ELEVATED CO2, GROWTH, INSECT HERBIVORE
INTERACTIONS, LEAF-MINER, PICEA-SITCHENSIS, RESPONSES, RHYNCHAENUS-FAGI,
SITKA SPRUCE, WINTER MOTH


     555  
Docherty, M., F.A. Wade, D.K. Hurst, J.B. Whittaker, and P.J. Lea. 1997. Responses of tree
sap-feeding herbivores to elevated CO2. Global Change Biology 3(1):51-59.

Five species of sap-feeding homoptera were studied on Fagus sylvatica and Acer pseudoplatanus and
exposed to elevated concentrations of carbon dioxide (600 mu L L(-1)). The concentration of total
soluble amino acids in foliage of F. sylvatica was unaffected by growing saplings in elevated
atmospheric CO2 concentrations. Although experiments on individual aphids indicated poorer
performance of Phyllaphis fagi (fewer, smaller nymphs produced), resultant populations did not differ
from those in ambient (350 mu L L(-1)) conditions. The area of beech foliage stippled by the
leafhopper Fagocyba cruenta was similar at ambient and elevated CO2 concentrations. The
concentration of total amino acids and that of serine of A. pseudoplatanus foliage were significantly
lower at elevated CO2 concentrations. However, the relative growth rates of two aphid species
Drepanosiphum platanoidis and Periphyllus testudinaceus and one leafhopper Ossiannilssonola callosa
were not significantly different in elevated CO2. No evidence was found that, under the conditions
of these experiments, populations of aphids and leafhoppers will change as concentrations of CO2
increase.

KEYWORDS: AIR-POLLUTION, CARBON DIOXIDE, GROWTH, INFESTATION, INSECT
PERFORMANCE, PHLOEM SAP, PLANTS, POPULATIONS, REPRODUCTIVE ACTIVITY,
SYCAMORE APHID


     556  
Doi, M., H. Oda, N. Ogasawara, and T. Asahira. 1992. Effects of co2 enrichment on the growth
and development of invitro cultured plantlets. Journal of the Japanese Society for Horticultural
Science 60(4):963-970.

Plantlets of Caladium bicolor (C3 plant), Saccharum officinarum (C4 plant), and Phalaenopsis hybrid
(CAM plant) at the preparation stage for acclimatization (the final stage of in vitro culture) were
cultured on the medium containing 2% sucrose. The culture vessels were kept under continuous, 16
hr, or 8 hr lighting conditions; half of the vessels were ventilated continuously with 0.8 +/- 0.4% CO2
enriched atmosphere; while the remainder was exposed to ambient atmosphere. The growth of
plantlets was promoted with an increase in daylength under both ambient and CO2 enriched
atmospheres. When the plantlets were supplied with adequate CO2, dry matter production increased
under all daylength treatments except Caladium cultured under continuous lighting. This promotive
effect of CO2 enrichment was especially noticeable in root growth. In Caladium and Phalaenopsis,
the leaf chlorophyll content of plantlets cultured under CO2 enriched atmosphere was less than that
of leaves from plantlets grown in ambient atmosphere. Although the chlorophyll was less
concentrated in leaves of plantlets growing under the CO2 enriched treatment, the rate of CO2 uptake
of these plantlets measured at the midpoint of the light period was higher than that of leaves exposed
to ambient atmosphere. Increasing the O2 concentration in culture vessels to 37% also promoted the
growth of Caladium and Dendrobium phalaenopsis (CAM plant) under CO2 enriched condition.
Because of the development of photoautotrophy, the Caladium plantlets exposed to enriched CO2
atmosphere and cultured on sugar-free medium using ceramic wool plug system responded with
vigorous growth when transplanted into pots.



     557  
DolcetSanjuan, R., E. Claveria, and A. Huerta. 1997. Androgenesis in Capsicum annuum L -
Effects of carbohydrate and carbon dioxide enrichment. Journal of the American Society for
Horticultural Science 122(4):468-475.

A new and simple protocol for androgenesis in bell pepper is described. The initial medium, a
modification of Nitsch and Nitsch's H medium, consisted of a two-phase system of semi- solid and
liquid medium and contained maltose as carbon source. The total number of embryos formed was
greater with maltose at 40 g . L-1, but embryos developed better at 10 to 20 g . L-1. Depending on
the genotype, the number of embryos and plants recovered ranged from 3 to 750 and 0.25 to 8,
respectively, per 100 flowers. Further increases in the number of embryos (up to 3561 per 100
flowers) and plants (up to 23 per 100 flowers) could be attained by flushing cultures with air enriched
with CO2 at 900 mu L . L-1. The ploidy level and the microspore origin of the recovered plants were
determined by flow cytometry and zymograms for isocitrate dehydrogenase. Nearly 65% of the
acclimated plants had undergone spontaneous doubling of the chromosome number, as confirmed by
flow cytometry of leaf nuclei. Isocitrate dehydrogenase zymograms demonstrated that plants
originated from microspores and that the two parental alleles were equally represented among the
haploid and dihaploid plants.

KEYWORDS: ACTIVATED-CHARCOAL, ANTHER-CULTURE RESPONSE, GENETIC-
MARKERS, HORDEUM VULGARE L, INDUCTION, INHERITANCE, MEDIA, PEPPER, PLANTS,
SEGREGATION


     558  
Donnelly, A., M.B. Jones, J.I. Burke, and B. Schnieders. 1999. Does elevated CO2 protect grain
yield of wheat from the effects of ozone stress? Zeitschrift Fur Naturforschung C-A Journal of
Biosciences 54(9-10):802-811.

This study has investigated the effects of elevated CO2 and elevated O-3, both singly and in
combination, on the yield of spring wheat (Triticum aestivum L., cv. Minaret). Plants were grown in
open-top chambers and exposed to three CO2 concentrations (ambient, 510 and 680 ppmv) and two
O-3 concentrations (ambient and ambient +50 or +90 ppbv) either from anthesis onwards or for the
full growing season. To date, experiments that have investigated the interactive effects of these gases
have shown a variety of responses, ranging from an amelioration of the damaging effects of high O-3
to a greater sensitivity to O-3, at elevated CO2. The effects on grain yield and yield components were
determined. Our results confirm that elevated CO2 provides some protection to a wheat crop against
the damaging effects of O-3 On grain yield. However, the level of protection varies from one growing
season to the next and also appears to be related particularly to the timing of exposure to elevated
O-3.

KEYWORDS: ATMOSPHERIC CO2, CARBON DIOXIDE, DRY-MATTER, LEAF-AREA, OPEN-
TOP CHAMBERS, PLANT GROWTH, SPRING WHEAT, TRITICUM-AESTIVUM L,
TROPOSPHERIC OZONE, WATER-STRESS


     559  
Dorais, M., J. Charbonneau, and A. Gosselin. 1993. Gas-exchange in greenhouse tomatoes grown
under supplemental light. Canadian Journal of Plant Science 73(2):577-585.

This study reports on in situ gas-exchange measurements in tomatoes grown under a sequential
intercropping system with supplemental lighting provided by high-pressure sodium-vapour lamps. A
supplemental photosynthetic photon flux (PPF) of 150 mumol m-2 s-1 significantly increased the
amount of light energy penetrating the canopy of intercropped tomato seedlings. During the day, the
supplemental 150 mumol m-2 s-1 light regime increased the photosynthetic rate of leaves 5 and 10
by 67%, while at night the increases were 93 and 12%, respectively. Regression analysis of the
photosynthetic rate of leaves 5 and 10 as a function of PPF received accounts for 58 and 45% of the
variation, respectively. Hierarchical analysis demonstrated a significant linear relationship between
PPF received during the day and photosynthetic activity of leaves 5 and 10 accounting for 46 and
28%, respectively, of the variance in the model. Regression analysis of the photosynthetic activity as
a function of PPF received at night accounts for 41 and 32 %, respectively, of the variation in the
photosynthetic rate of leaves 5 and 10. Using a high level of supplemental lighting during the day or
at night had no significant effect on stomatic conductance or on the transpiration rate of leaves.

KEYWORDS: CO2- ENRICHMENT, LEAF, PHOTOINHIBITION, PHOTOSYNTHESIS,
PRODUCTIVITY, RESPONSES, TRANSPIRATION, TRANSPORT, YIELD


     560  
Downing, J.P., and D.A. Cataldo. 1992. Natural sinks of co2 - technical synthesis from the palmas-
del- mar workshop. Water, Air, and Soil Pollution 64(1-2):439-453.

Natural CO2 sinks in terrestrial and marine environments are important components of the global
carbon cycle, yet the sign and magnitudes of key fluxes among them are unknown. The results of the
Palmas Del Mar Workshop - Natural Sinks of CO2 presented in this special issue and its companion
hard-bound volume of Water, Air, & Soil Pollution, provide a synthesis of current research on the
carbon cycle, CO2 sinks and associated processes and fluxes, and critical research needs to assess the
potential role of forest and land-use management in carbon sequestration. The papers in this volume
present data, observations, and model simulations that demonstrate: 1) the existence of natural CO2
sinks that could mitigate a significant amount of CO2 emissions from fossil-fuel combustion; 2)
probable, human-caused imbalances in C exchanges among vegetation, soils, and the atmosphere; 3)
enhanced C storage in vegetation in response to excess atmospheric CO2; 4) strong interactions
among carbon, nutrient and hydrological cycles; and 5) an excess of carbon production over
consumption in several, large managed forests. Although it appears unlikely that the search for the
"missing" C sink required to balance the C budget will end in the open ocean, new estimates of C
storage in mangrove wood and peat, suggest that coastal ecosystems have the capacity to store
significant amounts of carbon in vegetation and sediments. Convincing analyses are also presented
indicating the technical and economical feasibility of managing existing lands to sequester additional
carbon. Long-term field studies of CO2 fertilization effects and carbon cycling by plants and soils in
geographically important systems, native forests, and coastal ecosystems will go a long way toward
meeting the research needs identified at the workshop.

KEYWORDS: MODEL, OCEAN


     561  
Downton, W.J.S., and W.J.R. Grant. 1994. Photosynthetic and growth-responses of variegated
ornamental species to elevated co2. Australian Journal of Plant Physiology 21(3):273-279.

Variegated and completely green cultivars of oleander (Nerium oleander L.) and willow myrtle
(Agonis flexuosa (Willd.) Sweet) were grown in controlled environment cabinets for 3 and 5 months,
respectively, under either ambient levels of CO2 or with supplementary CO2 to a partial pressure of
800 mu bar. Photosynthesis of entirely green leaves and the green portions of variegated leaves on
both species was greatly stimulated by high CO2 and there was no evidence of downward adjustment
(acclimation) of photosynthetic rates to high CO2 during the experiment. Dark respiration rates of
these leaves were lowered by high CO2. The yellow portions of willow myrtle leaves showed a low
level of photosynthetic activity which was stimulated by high CO2; however, dark respiration rates
showed little response to elevated CO2. Green and yellow areas on variegated leaves of willow myrtle
had much lower dark respiration rates than completely green leaves, but this difference was not
evident for oleander. Yellow portions of oleander leaves showed little evidence of photosynthetic
capacity. This was also confirmed by a low photochemical efficiency as determined by chlorophyll
fluorescence. A major effect of variegation was to slow overall plant growth compared with
completely green plants. The respective 3-fold and 6-7-fold differences in biomass between fully
green and variegated cultivars of oleander and willow myrtle was closely related to estimated net
carbon gain per day by the plant canopy. Variegation for both species averaged close to 50:50,
green:yellow areas. Variegated plants developed about twice the leaf area ratio and specific leaf area
compared with their completely green counterparts. The relative growth response to high CO2 was
significantly greater for the variegated plants compared to the completely green plants.

KEYWORDS: ACCLIMATION, CARBON DIOXIDE, DARK RESPIRATION, LEAVES, PLANTS


     562  
Drake, B.G. 1992. A field-study of the effects of elevated CO2 on ecosystem processes in a
Chesapeake Bay wetland. Australian Journal of Botany 40(4-5):579-595.

Open top chambers are being used in a long-term project to determine the effects of elevated CO2
on ecosystem processes on a Chesapeake Bay wetland. Three communities are studied: mono-specific
stands of the C3 sedge, Scirpus olneyi, and the C4 grass, Spartina patens, and a mixed community
of these two species and the C4 grass, Distichlis spicata. Treatment began in the spring of 1987 and
will continue through the 1994 growing season. During the first 4 years of exposure, elevated CO2
had the following effects on mono-specific stands of the C3 sedge, Scirpus olneyi: increased quantum
yield and photosynthetic capacity, reduced dark respiration, increased numbers of shoots, roots and
rhizomes, reduced nitrogen concentration of all tissues, increased nitrogen fixation and increased
ecosystem carbon accumulation. In a mixed community of the sedge and C4 grass species, Spartina
patens and Distichlis spicata, biomass of the C3 component increased over 100% and this was
accompanied by decreased biomass in the C4 component of the community. Elevated CO2 reduced
water loss, increased water potential and delayed senescence in all three species. Many factors
contributed to CO2 stimulated carbon accumulation in the plant community dominated by the C3
sedge, Scirpus olneyi, including: sustained high photosynthetic capacity, decreased respiration,
delayed senescence, and allocation of the additional carbon to roots and rhizomes. The complex
interaction of these diverse responses suggests that the rising atmospheric CO2 may have a significant
impact on ecosystem processes.

KEYWORDS: ATMOSPHERIC CO2, CANOPY PHOTOSYNTHESIS, CARBON-DIOXIDE
ENRICHMENT, ELECTRON-TRANSPORT CAPACITY, ESTUARINE MARSH, LONG-TERM
EXPOSURE, PHOTOSYNTHETIC ACCLIMATION, RIBULOSE 1;5-BISPHOSPHATE, SOYBEAN
CANOPIES, TRANSPIRATION RESPONSES


     563  
Drake, B.G. 1992. The impact of rising co2 on ecosystem production. Water, Air, and Soil Pollution
64(1-2):25-44.

A fundamental property of green plants is that the rate of photosynthesis is dependent in the ambient
CO2 concentration. There is overwhelming experimental evidence that this effect increases plant
production in most C3 Plants: hundreds of experiments with many species show that plant growth
increases an average 30% to 40% for a doubling of the present normal ambient CO2 concentration
(Kimball, 1986). External environmental factors, such as temperature and the availability of nutrients,
modify this response. The greatest stimulation of photosynthesis and growth can be expected to occur
at high temperatures and much smaller responses at low temperature. Factors which restrict growth,
such as low nutrients, will reduce but usually do not eliminate the stimulation of production with
increasing CO2 even when nitrogen is severly limiting. There are also reports of direct effects of
ambient CO2 concentration on dark respiration which show that there is an immediate reduction in
the rate of CO2 efflux or O2 consumption when the CO2 around plant tissues is increased. There
have been very few long-term field studies of the effects of increased CO2 on whole plants and
ecosystem processes but the data from these studies are consistent in showing an increase in plant
production with an increase in CO2 concentration of the ambient air.

KEYWORDS: ABSCISIC- ACID, CARBON-DIOXIDE ENRICHMENT, ELEVATED
ATMOSPHERIC CO2, GAS-EXCHANGE, LONG-TERM EXPOSURE, PHOTOSYNTHETIC
INHIBITION, SOYBEAN LEAVES, STOMATAL CONDUCTANCE, TRANSPIRATION
RESPONSES, TUSSOCK TUNDRA


     564  
Drake, B.G., J. Azcon-Bieto, J. Berry, J. Bunce, P. Dijkstra, J. Farrar, R.M. Gifford, M.A.
Gonzalez-Meler, G. Koch, H. Lambers, J. Siedow, and S. Wullschleger. 1999. Does elevated
atmospheric CO2 concentration inhibit mitochondrial respiration in green plants? Plant, Cell and
Environment 22(6):649-657.

There is abundant evidence that a reduction in mitochondrial respiration of plants occurs when
atmospheric CO2 (C-a) is increased. Recent reviews suggest that doubling the present C-a will reduce
the respiration rate [per unit dry weight (DW)] by 15 to 18%. The effect has two components: an
immediate, reversible effect observed in leaves, stems, and roots of plants as well as soil microbes,
and an irreversible effect which occurs as a consequence of growth in elevated C-a and appears to
be specific to C-3 species. The direct effect has been correlated with inhibition of certain respiratory
enzymes, namely cytochrome-c-oxidase and succinate dehydrogenase, and the indirect or acclimation
effect may be related to changes in tissue composition. Although no satisfactory mechanisms to
explain these effects have been demonstrated, plausible mechanisms have been proposed and await
experimental testing. These are carbamylation of proteins and direct inhibition of enzymes of
respiration. A reduction of foliar respiration of 15% by doubling present ambient C-a would represent
3 Gt of carbon per annum in the global carbon budget.

KEYWORDS: CARBON-DIOXIDE CONCENTRATION, CHEMICAL-COMPOSITION,
CONSTRUCTION COSTS, DARK RESPIRATION, GAS-EXCHANGE, GROWTH, LEAF
RESPIRATION, LOLIUM-PERENNE, MAINTENANCE RESPIRATION, WHEAT LEAVES


     565  
Drake, B.G., M.A. GonzalezMeler, and S.P. Long. 1997. More efficient plants: A consequence
of rising atmospheric CO2? Annual Review of Plant Physiology and Plant Molecular Biology
48:609-639.

The primary effect of the response of plants to rising atmospheric CO2 (C-a) is to increase resource
use efficiency. Elevated C-a reduces stomatal conductance and transpiration and improves water use
efficiency, and at the same time it stimulates higher rates of photosynthesis and increases light- use
efficiency. Acclimation of photosynthesis during long-term exposure to elevated C-a reduces key
enzymes of the photosynthetic carbon reduction cycle, and this increases nutrient use efficiency.
Improved soil-water balance, increased carbon uptake in the shade, greater carbon to nitrogen ratio,
and reduced nutrient quality for insect and animal grazers are all possibilities that have been observed
in field studies of the effects of elevated C-a. These effects have major consequences for agriculture
and native ecosystems in a world of rising atmospheric C-a and climate change.

KEYWORDS: BETULA-PENDULA ROTH, CARBON-DIOXIDE ENRICHMENT, ELEVATED CO2,
LEAF GAS- EXCHANGE, LIRIODENDRON-TULIPIFERA L, LONG-TERM EXPOSURE,
PHASEOLUS-VULGARIS L, RIBULOSE-1;5-BISPHOSPHATE CARBOXYLASE-OXYGENASE,
SOURCE-SINK RELATIONS, WATER-USE EFFICIENCY


     566  
Drake, B.G., and P.W. Leadley. 1991. Canopy photosynthesis of crops and native plant-
communities exposed to long-term elevated CO2. Plant, Cell and Environment 14(8):853-860.

There have been seven studies of canopy photosynthesis of plants grown in elevated atmospheric
CO2: three of seed crops, two of forage crops and two of native plant ecosystems. Growth in
elevated CO2 increased canopy photosynthesis in all cases. The relative effect of CO2 was correlated
with increasing temperature: the least stimulation occurred in tundra vegetation grown at an average
temperature near 10-degrees-C and the greatest in rice grown at 43-degrees-C. In soybean, effects
of CO2 were greater during leaf expansion and pod fill than at other stages of crop maturation. In the
longest running experiment with elevated CO2 treatment to date, monospecific stands of a C3 sedge,
Scirpus olneyi (Grey), and a C4 grass, Spartina patens (Ait.) Muhl., have been exposed to twice
normal ambient CO2 concentrations for four growing seasons, in open top chambers on a Chesapeake
Bay salt marsh. Net ecosystem CO2 exchange per unit green biomass (NCE(b)) increased by an
average of 48% throughout the growing season of 1988, the second year of treatment. Elevated CO2
increased net ecosystem carbon assimilation by 88% in the Scirpus olneyi community and 40% in the
Spartina patens community.

KEYWORDS: ATMOSPHERIC CARBON-DIOXIDE, CO2- ENRICHMENT, ENRICHMENT,
ESTUARINE MARSH, GROWTH, SALT-MARSH, SOYBEAN PHYSIOLOGY, TEMPERATURE,
TRANSPIRATION RESPONSES, TUSSOCK TUNDRA


     567  
Drake, B.G., M.S. Muehe, G. Peresta, M.A. GonzalezMeler, and R. Matamala. 1996.
Acclimation of photosynthesis, respiration and ecosystem carbon flux of a wetland on Chesapeake
Bay, Maryland to elevated atmospheric CO2 concentration. Plant and Soil 187(2):111-118.

Acclimation of photosynthesis and respiration in shoots and ecosystem carbon dioxide fluxes to rising
atmospheric carbon dioxide concentration (C-a) was studied in a brackish wetland. Open top
chambers were used to create test atmospheres of normal ambient and elevated C-a(=normal
ambient+34 Pa CO2) over mono-specific stands of the C-3 sedge Scirpus olneyi, the dominant C-3
species in the wetland ecosystem, throughout each growing season since April of 1987. Acclimation
of photosynthesis and respiration were evaluated by measurements of gas exchange in excised shoots.
The impact of elevated C-a on the accumulation of carbon in the ecosystem was determined by
ecosystem gas exchange measurements made using the open top chamber as a cuvette. Elevated C-a
increased carbohydrate and reduced Rubisco and soluble protein concentrations as well as
photosynthetic capacity(A) and dark respiration (R-d; dry weight basis) in excised shoots and
canopies (leaf area area basis) of Scirpus olneyi, Nevertheless, the rate of photosynthesis was
stimulated 53% in shoots and 30% in canopies growing in elevated C-a compared to normal ambient
concentration. Elevated C-a inhibited R-d measured in excised shoots (-19 to -40%) and in seasonally
integrated ecosystem respiration (R-e; -36 to -57%). Growth of shoots in elevated C- a was
stimulated 14-21%, but this effect was not statistically significant at peak standing biomass in
midseason. Although the effect of elevated C-a on growth of shoots was relatively small, the
combined effect of increased number of shoots and stimulation of photosynthesis produced a 30%
stimulation in seasonally integrated gross primary production (GPP). The stimulation of
photosynthesis and inhibition of respiration by elevated C-a increased net ecosystem production
(NEP=GPP-R-e) 59% in 1993 and 50% in 1994. While this study consistently showed that elevated
C-a produced a significant increase in NEP, we have not identified a correspondingly large pool of
carbon below ground.

KEYWORDS: ENRICHMENT, ESTUARINE MARSH, EXPOSURE, FIELD, GAS-EXCHANGE,
OPEN-TOP CHAMBERS, PERSPECTIVE, PLANT, SCIRPUS- OLNEYI, TUNDRA


     568  
Drake, S.R. 1994. Elevated carbon-dioxide storage of anjou pears using purge- controlled
atmosphere. Hortscience 29(4):299-301.

'Anjou' pears (Pyrus communis L.) were placed in controlled- atmosphere (CA) storage immediately
after harvest (<24 hours) or after a 10-day delay in refrigerated storage, and held there for 9 months
at 1C. Oxygen in all atmospheres was 1.5% and CO2 was at either 1% or 3%. Atmospheres in the
flow-through system were computer-controlled at +/- 0.1%. After removal from CA storage, pears
were evaluated immediately and after ripening at 21C for 8 days. Pears stored in 3% CO2 were
firmer, greener, and displayed less scald, internal breakdown, and stem-end decay than pears stored
in 1% CO2. In addition, no internal discoloration of 'Anjou' pears was evident when held with 3%
CO2. 'Anjou' pears held in 3% CO2 retained the ability to ripen after long-term storage. A 10-day
delay in atmosphere establishment had little or no influence on the long-term keeping quality or
ripening ability of 'Anjou' pears.

KEYWORDS: DANJOU PEAR


     569  
Drake, S.R. 1999. Quality of 'Bosc' pears as influenced by elevated carbon dioxide storage. Journal
of Food Quality 22(4):417-425.

'Bosc' pears (Pyrus communis L.) were placed in a purge-type controlled-atmosphere (CA) storage
immediately after harvest (<24 h) and held for 180 days at IC. Oxygen in all atmospheres was 1.5%
and CO2 was 1%, 3% or 5%. Pears were evaluated immediately after removal from CA storage and
after ripening for an additional 7 days at 21 C. Pears stored in 3% CO2 were firmer, had a superior
finish, with significantly reduced decay and internal breakdown than pears stored in 1% CO2. In 3%
CO2, pears retained the ability to ripen after long-term storage. A 10 day delay in atmosphere
establishment had little or no influence on the long-term keeping quality or ripening ability of 'Bosc
'pears. Firmness, soluble solids content and starch either alone or together were good indices of
maturity for 'Bosc 'pears.

KEYWORDS: ATMOSPHERE, DANJOU PEAR


     570  
Drake, S.R., and D.C. Elfving. 1999. Response of three strains of 'Gala' apples to high carbon
dioxide prior to controlled atmosphere storage. Fruit Varieties Journal 53(1):16-21.

The postharvest fruit quality of three strains ('Royal Gala: 'Imperial Gala' and 'Crimson Gala') of
apples was evaluated over two or three storage seasons. To determine the influence of carbon dioxide
treatment on storage quality, apples were stored in normal controlled atmosphere (1% O-2 & 1%
CO2), or treated with 12% CO2 for 7 or 14 days prior to normal CA and evaluated after 90 or 150
days of storage. The use of 12% CO2 prior to storage helped to maintain firmness of 'Royal Gala'
apples in 1 of 3 seasons. Firmness of 'Imperial Gala' and 'Crimson Gala' apples was not influenced by
high CO2 treatment, regardless of storage season. Other quality factors (color, soluble solids, acidity
and carbohydrates) were not influenced to the extent that high CO(2)would be a viable option for the
quality enhancement of 'Gala' apples during storage, regardless of strain. Use of normal CA
maintained 'Gala' apple quality for 150 days of storage. Harvest date had a major influence on 'Gala'
apple quality. A delay of one week reduced firmness and acidity, but enhanced color and content of
sucrose, glucose and fructose in 'Royal Gala: 'Imperial Gala' and 'Crimson Gala' apples.

KEYWORDS: CA


     571  
Drake, S.R., and A. Yazdaniha. 1999. Short-term controlled atmosphere storage for shelf-life
extension of apricots. Journal of Food Processing and Preservation 23(1):57-70.

Shelf-life of 'Perfection' and 'Rival' apricots can be enhanced with the use of controlled atmosphere
(CA) storage. Apricots were harvested at commercial maturity and immediately stored in CA at 1 or
2 % O-2 and 3, 6, 9, 12 or 15 % CO2 for 30, 45 and 60 days. No differences in fruit quality were
evident between O-2 atmospheres of 1 and 2 %, except that fruit stored in 1 % O-2 displayed less
rot development and higher acid content. Apricots stored in 9 % or less CO2 displayed reduced
external and internal color, inadequate finish, increased internal breakdown and more rot development
with unacceptable firmness retention for additional handling. Apricots stored in 12 or 15 % CO2
retained firmness and displayed enhanced finish with reduced rots and very little internal breakdown
with storage duration of 60 days. Color was much slower to develop in apricots stored in 12 or 15
% CO2 for all storage periods.

KEYWORDS: NECTARINES, PHYSIOLOGICAL DISORDERS


     572  
Drennan, P.M., and P.S. Nobel. 1996. Temperature influences on root growth for Encelia farinosa
(Asteraceae), Pleuraphis rigida (Poaceae), and Agave deserti (Agavaceae) under current and doubled
CO2 concentrations. American Journal of Botany 83(2):133-139.

To help evaluate root distribution patterns, elongation rates of individual roots were measured as a
function of soil temperature for Encelia farinosa (a C-3 species), Pleuraphis rigida (C-4), and Agave
deserti (CAM), sympatric codominants in the northwestern Sonoran Desert. Measurements were
made at current and doubled CO2 concentrations under winter and summer conditions of air
temperature (day/night temperatures of 17 C/10 C and 33 C/22 C, respectively). The three species
had different optimal temperatures for root elongation (T-opt) under winter conditions (25 C for E.
farinosa, 35 C for P. rigida, and 30 C for A. deserti); T-opt increased by 2-3 C under summer
conditions for all three species. The limiting temperatures for elongation also acclimated from winter
to summer conditions. The rate of root elongation at T-opt was higher under summer than winter
conditions for E. farinosa (3 vs. 6 mm d(-1)) and P. rigida (20 vs. 14 mm d(-1)), reflecting conditions
for maximum photosynthesis; no difference occurred for A. deserti (9 vs. 10 mm d(-1)). Decreased
elongation rates at extreme temperatures were associated with less cell division and reduced cell
extension. The doubled CO2 concentration increased average daily root elongation rates for A.
deserti under both winter (7%) and summer (12%) conditions, reflecting increased cell extension, but
had no effect for the other two species. Simulations of root elongation as a function of soil
temperatures showed that maximum elongation would occur at different depths (16-20 cm for E.
farinosa, 4-8 cm for P. rigida, and 0-4 cm for A. deserti) and during different seasons (winter to
spring for E. farinosa, spring to summer for P. rigida, and all year for A. deserti), contributing to their
niche separation. Shading of the soil surface moderated daily variations in soil temperature, reducing
seasonal root elongation for winter and spring and increasing elongation for summer. Shading also
altered root distribution patterns, e.g., optimal rooting depth for A. deserti and especially P. rigida
increased for a hot summer day.

KEYWORDS: C-4, CAM PLANT, CARBON DIOXIDE, COMPETITION, ELEVATED CO2,
HILARIA-RIGIDA, RESPONSES, SUCCULENTS, WATER RELATIONS


     573  
Drennan, P.M., and P.S. Nobel. 1998. Root growth dependence on soil temperature for Opuntia
ficus- indica: influences of air temperature and a doubled CO2 concentration. Functional Ecology
12(6):959-964.

1. Root elongation as a function of soil temperature was determined for the CAM succulent Opuntia
ficus-indica, under three different day/night air temperatures (15 degrees C/5 degrees C, 25 degrees
C/15 degrees C and 35 degrees C/25 degrees C) and an ambient (360 mu mol mol(-1)) vs a doubled
CO2 concentration (720 mu mol mol(-1)) at 25 degrees C/15 degrees C, the optimum temperature
for net CO2 uptake. 2. Root elongation occurred at soil temperatures from 12 degrees C (at 15
degrees C/5 degrees C) to 43 degrees C (at 35 degrees C/25 degrees C) with optimum temperatures
of 27-30 degrees C, similar to other CAM succulents and consistent with the distribution of this
shallow-rooted species in warm regions. Although a doubled CO2 concentration did not alter the
optimum or limiting soil temperatures, increases of up to 5 degrees C in these temperatures
accompanied the 20 degrees C increase in day/night air temperatures. 3. Root elongation rates at
optimum soil temperatures ranged from 5.4 mm day(-1) (15 degrees C/5 degrees C), through 6.6 mm
day(-1) (25 degrees C/15 degrees C), to 10.4 mm day(-1) (35 degrees C/25 degrees C) with a 25%
increase under a doubled CO2 concentration. Highest root elongation rates at 35 degrees C/25
degrees C may reflect changing root vs shoot sink strengths in a species with a highly plastic root
system. 4. At limiting soil temperatures, the length of the cell division zone was reduced by an
average of 20% and cell length at the mid-point of-the elongation zone by 10%. Increased root
elongation rates under a doubled CO2 concentration reflected increased cell elongation. 5. The
temperature response for the roots of O. ficus-indica and stimulation of elongation by a doubled CO2
concentration indicate that root growth for this highly productive species should be enhanced by
predicted global climate change.

KEYWORDS: CAM PLANT, DESERT SUCCULENTS, ELEVATED CO2, ELONGATION,
EXCHANGE, GLOBAL CLIMATE-CHANGE, NITROGEN, RESPONSES, WATER


     574  
Dube, S.L., and W. Vidaver. 1992. Photosynthetic competence of plantlets grown-invitro - an
automated-system for measurement of photosynthesis invitro. Physiologia Plantarum 84(3):409-416.

An aseptic gas exchange and hydroponic system (AGEHS) has been developed in an attempt for
characterization of physiological requirements for photoautotrophic growth in vitro and alleviation
of the needs for ex vitro acclimatization. The AGEHS monitors and controls several parameters
relevant to plant growth. Shootlets of Chrysanthemum, x morifolium Ramat. cv. Envy were treated
with flow of air or CO2-enriched air under controlled relative humidity, elevated photosynthetic
photon flux density (PPFD) and hydroponic irrigation. After 15 days of treatment, plantlets gained
more than 3 times as much dry weight as those from a conventional culture tube treatment. This study
shows that it is possible to favour photoautotrophic growth when elevated PPFD, enhanced air-
exchange and hydroponic medium flow are provided concurrently. This enhancement is achievable
through careful increments of light quanta, balanced with increments of humidified air flow and/or
CO2 content in air which seem to be necessary to avoid potential photoinhibition and premature
water exhaustion from gelled media.

KEYWORDS: ACCLIMATIZATION, CO2- ENRICHMENT, CULTURE, LEAVES, REGENERANTS,
SOIL, SOYBEANS


     575  
Duchein, M.C., A. Bonicel, and T. Betsche. 1993. Photosynthetic net co2 uptake and leaf
phosphate concentrations in co2 enriched clover (trifolium-subterraneum L) at 3 levels of phosphate
nutrition. Journal of Experimental Botany 44(258):17-22.

Net CO2-uptake of sets of clover plants (Trifolium subterraneum L. was measured over three weeks
in ambient air and in a highly CO2-enriched atmosphere (400 Pa CO2). Phosphate (P) in the nutrient
solution was varied between 0-05 mol m-3 P (reduced P) and 2.0 mol m-3 P (high P). In ambient air,
the daily increments of the daily rate of net CO2-uptake (DICU; a parameter related to relative
growth) were higher at reduced P than at high P. Stimulation by high CO2 of net CO2-uptake in the
first day was less at reduced P than at high P. In the following days, high CO2 markedly inhibited
DICU at reduced P, and thus growth stimulation by high CO2 ceased after between 4 and 12 d. By
contrast, at high P, DICU increased more than 2- fold upon CO2-enrichment, and thus growth
stimulation by high CO2 was maintained. Intermediate results were obtained with half-strength
Hoagland's solution (0-5 mol m-3 P). Leaf pools of inorganic ortho P, soluble esterified P, and total
P declined markedly in high CO2 when P-nutrition had been reduced. Considerable decline also
occurred in high CO2 when P- nutrition had been increased suggesting that P-uptake was not well
tuned with net CO2-uptake (growth). It is proposed that high CO2 can perturb the P-metabolism of
clover, the impairment being less at high levels of P-nutrition. With regard to high CO2 as a growth
stimulus, these results demonstrate that increasing P-nutrition to a level supraoptimal in ambient air
can considerably improve the growth of a C3-plant in high CO2.

KEYWORDS: ACCLIMATION, ATMOSPHERIC CARBON-DIOXIDE, ELEVATED CO2,
GROWTH, PHOSPHORUS, PLANTS, RESPONSES, SOURCE-SINK RELATIONS, SPINACH
LEAVES, TEMPERATURE


     576  
Duff, G.A., C.A. Berryman, and D. Eamus. 1994. Growth, biomass allocation and foliar nutrient
contents of 2 eucalyptus species of the wet dry tropics of australia grown under co2 enrichment.
Functional Ecology 8(4):502-508.

1. Seeds of Eucalyptus tetrodonta and E. miniata were sown in duplicated air-conditioned tents which
were ventilated with either ambient or CO2-enriched (700 mumol mol-1) air. Growth, foliar nutrient
content, soluble protein and biomass allocation were investigated over the subsequent 32-week
experimental period. 2. It was found that CO2 enrichment significantly increased the total biomass
and tree height of E. tetrodonta, but had no effect on total biomass or tree height of E. miniata. 3.
Allocation of biomass to main-stem wood and main- stem leaf mass increased and allocation to
branch wood and branch leaves declined, under CO2 enrichment for E. tetrodonta. No change in
allocation patterns for E miniata was observed in response to CO2 enrichment. 4. Foliar nitrogen,
manganese and phosphorus contents were decreased under CO2 enrichment in E tetrodonta, but there
was no effect of CO2 concentration in E. miniata. Soluble protein contents were not affected by CO2
enrichment in either species. These results are discussed in relation to the competitive relationship
between these two species in northern Australia.



     577  
Dufrene, E., J.Y. Pontailler, and B. Saugier. 1993. A branch bag technique for simultaneous co2
enrichment and assimilation measurements on beech (fagus-sylvatica L). Plant, Cell and Environment
16(9):1131-1138.

A cheap CO2 enrichment system was designed to perform continuous gas exchange measurements
of branches of mature European beech trees (Fagus sylvatica L.). Branches were grown at ambient
(350 cm(3) m(-3)) and elevated CO2 (700 cm(3) m(-3)) during the whole 1992 leafy period. Leaks
resulting from airtightness defaults in the system appeared to be low enough to measure accurately
net CO2 assimilation and transpiration rates during the day. However, the CO2 exchange rates during
the night (respiration) were too low to allow accurate measurements. Elevated CO2 had a great effect
on the net assimilation rate of branches via its influence on both the C-3 photosynthetic pathway and
the shade-tolerance of beech frees (85% increase). The A/C-a curves showed no acclimation effect
to high CO2, both control and enriched branches increasing their net assimilation in the same way.
The decrease of net assimilation rates in mature leaves was similar for both control and enriched
branches. The pattern of daily transpiration rates remained the same for both control and enriched
branches, hence we can assume that there was no visible CO2 effect on stomata.

KEYWORDS: ATMOSPHERIC CO2, ELEVATED CARBON-DIOXIDE, GAS-EXCHANGE,
GROWTH, PHOTOSYNTHETIC ACCLIMATION, PLANTS, RESPONSES, TREES


     578  
Dugal, A., S. Yelle, and A. Gosselin. 1990. Influence of CO2 enrichment and its method of
distribution on the evolution of gas exchanges in greenhouse tomatoes. Canadian Journal of Plant
Science 70(1):345-356.



     579  
Dugas, W.A., M.L. Heuer, D. Hunsaker, B.A. Kimball, K.F. Lewin, J. Nagy, and M. Johnson.
1994. Sap flow measurements of transpiration from cotton grown under ambient and enriched co2
concentrations. Agricultural and Forest Meteorology 70(1-4):231-245.

Increasing atmospheric CO2 concentration has many implications for agriculture and forestry, one
of which is the effect it will have on transpiration (T). The objective of this work was to quantify T
of cotton (Gossypium hirsutum L.) grown in the field under ambient (370 mumol mol-1) and enriched
(550 mumol mol-1) CO2 concentrations. Measurements were made in 1990 and 1991 at the
Maricopa Agricultural Center, Arizona. Constant- power sap flow gauges were used to measure T.
In 1990, three plants and in 1991, 10 plants were simultaneously instrumented with gauges in each
of the CO2 treatments. Leaf area of plants with gauges was measured. T measured by sap flow was
compared with evapotranspiration (ET) calculated by water balance in 1990 and with T calculated
by water balance in 1991. Soil evaporation was measured using microlysimeters in 1991, and was
found to be essentially equal (approximately 0.8 mm day-1, or about 10% of T) in the two CO2
treatments. There were no consistent differences in leaf area of plants with gauges between the two
CO2 treatments. Sap flow, for periods from 15 min to 2 weeks, was not significantly different
between the two CO2 treatments in either year, except for a few days in 1990. In 1991, the
coefficient of variation of daily sap flow across plants was the same (about 30%) for both CO2
treatments throughout the year. The water balance ET (1990) and T (1991) were similar to sap flow
in both years, and also showed no effect of CO2 treatment. These results show that for this crop,
grown under well-watered and high-fertility conditions, there was no effect of CO2 on T, on a per
unit ground area or per plant basis. These results are relevant for assessing the effects of increasing
atmospheric CO2 concentrations on transpiration by cotton.

KEYWORDS: CARBON DIOXIDE, CROP YIELD, ELEVATED CO2, EVAPORATION, HEAT-
BALANCE, LEAF CONDUCTANCE, MASS-FLOW, PLANTS, STEM-FLOW, WATER-USE


     580  
Dugas, W.A., S.A. Prior, and H.H. Rogers. 1997. Transpiration from sorghum and soybean
growing under ambient and elevated CO2 concentrations. Agricultural and Forest Meteorology 83(1-
2):37-48.

The increasing concentration of carbon dioxide in the atmosphere ([CO2]) has several direct effects
on plants and these effects may be different for C-3 and C-4 plants. Our objective was to measure
hourly and daily whole-plant transpiration rates from the C-4 plant grain sorghum (Sorghum bicolor
(L.) Moench) and the C-3 plant soybean (Glycine max (L.) Merr.) grown under ambient (359 mu
molCO(2) mol(-1) dry atmospheric air) and elevated (705 mu molmol(-1)) [CO2] values.
Transpiration measurements were made for 22 days in August 1994 at Auburn, Alabama, USA, using
stem flow gauges on plants growing in open top chambers, n = 8 for each [CO2] and species. Leaf
area averaged slightly more than 0.1m(2) per plant for sorghum and about 0.2 m(2) per plant for
soybean, Averages (15 min and daily) of transpiration, per unit leaf area, were consistently greater
from plants growing under the ambient [CO2,] for both sorghum and soybean. Average daily
transpiration from plants growing under the elevated [CO2] was significantly smaller (P = 0.05) on
all but 2 days for soybean and on 9 of the 22 days of measurements for sorghum. Average daily
sorghum transpiration was 1128 gm(-2) day(-1) and 772 gm(-2) day(-1) from plants growing under
an ambient and elevated [CO2], respectively. Corresponding soybean averages were 731 gm(-2) day(-
1) and 416 gm(-2) day(-1). The transpiration reduction under elevated [CO2] was greater for the C-3
plant soybean than for the C-4, plant sorghum. These results support previous studies showing that
transpiration, per unit leaf area, from sorghum and soybean will both be reduced if atmospheric [CO2]
continues to increase, although the reduction may be greater for C-3, plants.

KEYWORDS: ATMOSPHERIC CO2, CARBON-DIOXIDE ENRICHMENT, COTTON, CROP
TRANSPIRATION, HEAT-BALANCE, LEAF CONDUCTANCE, SAP FLOW, STEM-FLOW
GAUGE, WATER-USE EFFICIENCY, YIELD


     581  
Dukes, J.S., and H.A. Mooney. 1999. Does global change increase the success of biological
invaders? Trends in Ecology and Evolution 14(4):135-139.

Biological invasions are gaining attention as a major threat to biodiversity and an important element
of global change. Recent research indicates that other components of global change, such as increases
in nitrogen deposition and atmospheric CO2 concentration, favor groups of species that share certain
physiological or life history traits. New evidence suggests that many invasive species share traits that
will allow them to capitalize on the various elements of global change. Increases in the prevalence of
some of these biological invaders would alter basic ecosystem properties in ways that feed back to
affect many components of global change.

KEYWORDS: CARBON DIOXIDE, CLIMATE, COMMUNITY, CONSEQUENCES,
DISTURBANCE, ELEVATED CO2, ENRICHMENT, MORPHOLOGY, NITROGEN, VEGETATION


     582  
Duquesnay, A., N. Breda, M. Stievenard, and J.L. Dupouey. 1998. Changes of tree-ring delta
C-13 and water-use efficiency of beech (Fagus sylvatica L.) in north-eastern France during the past
century. Plant, Cell and Environment 21(6):565-572.

We investigated variation in intrinsic water-use efficiency during the past century by analysing
delta(13)C in tree rings of beech growing in north-eastern France. Two different silvicultural systems
were studied: high forest and coppice- with-standards, We studied separately effects related to the
age of the tree at the time the ring was formed and effects attributable to environmental changes. At
young ages, delta(13)C shows an increase of more than 1 parts per thousand. However, age-related
trends differ in high forest and coppice- with-standards. Changes in microenvironmental variables
during stand maturation, and physiological changes related to structural development of the trees with
ageing, could explain these results. During the past century, delta(13)C in tree rings shows a pattern
of decline that is not paralleled by air delta(13)C changes. Isotopic discrimination has significantly
decreased from 18.1 to 16.4 parts per thousand in high forest and varied insignificantly between 17.4
and 16.9 parts per thousand in coppice-with-standards, As a consequence, intrinsic water-use
efficiency has increased by 44% in high forest and 23% in coppice-with-standards during the past
century. These results accord with the increased water-use efficiency observed in controlled
experiments under a CO2-enriched atmosphere. However other environmental changes, such as
nitrogen deposition, may be responsible for such trends.

KEYWORDS: ANTARCTIC ICE, ATMOSPHERIC CO2 CONCENTRATION, C 13/C 12, CARBON
ISOTOPE DISCRIMINATION, CENTURIES, DIOXIDE, DOUGLAS-FIR, GAS-EXCHANGE,
POLAR ICE CORES, STOMATAL DENSITY


     583  
During, H., and M. Harst. 1996. Stomatal behaviour, photosynthesis and photorespiration of in
vitro-grown grapevines: Effects of light and CO2. Vitis 35(4):163-167.

To improve photosynthesis and growth of grapevines cultivated in vitro (Seyval blanc and SO 4)
effects of light intensity, spectral irradiance and CO2 concentration on stomatal behaviour, CO2
fixation and photorespiration were studied. Stomata were shown to respond to changes of light
intensity but, unlike photosynthesis, their reactions were delayed and stomatal closure was incomplete
in the dark. In contrast, alterations of the CO2 concentration in the headspace (50-2200 ppm) did not
cause stomatal reactions. Photosynthesis vs, light intensity relationships indicated lower light
compensation points, higher quantum yield and higher rates of light- saturated photosynthesis with
''Fluora'' lamps (maximal spectral irradiance al 460 and 680 nm) compared to ''projector'' lamps
(maximal spectral irradiance at 620 nm). Photosynthesis vs. intercellular CO2 concentration
relationships indicated varietal differences, the carboxylation efficiency and rates of photosynthesis
at CO2 saturation being distinctly higher in the more vigorous variety SO 4 compared to Seyval
blanc. Under the usual light conditions of our in vitro culture (50-60 mu mol quanta . m(-2). s(-1),
Fluora) the headspace CO2 concentration ranged from 145 to 155 ppm while at the end of a 10-hour
dark period it increased to values >3000 ppm. Rates of photorespiration were high (>50 % of
photosynthesis) due to the relative low CO2 concentrations and, presumably, due to elevated O-2
concentrations in the headspace. It is concluded that the often observed low rates of photosynthesis
of in vitro plantlets are mainly due to low light intensity and CO2 concentration in the headspace, the
latter depending on the low rates of gas diffusion between ambient air and headspace.

KEYWORDS: CULTURED INVITRO, LEAVES, PLANTLETS, VITIS


     584  
Dury, S.J., J.E.G. Good, C.M. Perrins, A. Buse, and T. Kaye. 1998. The effects of increasing
CO2 and temperature on oak leaf palatability and the implications for herbivorous insects. Global
Change Biology 4(1):55-61.

Rising levels of atmospheric CO2 are expected to perturb forest ecosystems, although the extent to
which specific ecological interactions will be modified is unclear. This research evaluates the effects
of elevated CO2 and temperature, alone and in combination, on the leaf nutritional quality of
Pendunculate oak (Qeurcus robur L.), and the implications for herbiverous insect defoliators are
discussed. A 3 degrees C temperature rise reduced leaf nutritional quality, by reducing foliar nitrogen
concentration and increasing condensed tannin content. Doubling atmospheric CO2 temporarily
increased total phenolics, but also reduced leaf toughness. The nutritional quality of the second leaf
flush (lammas growth) was considerably reduced at elevated CO2. It is concluded that larval
development of spring-feeding defoliators and hence adult fecundity may be adversely affected by
increased temperatures.

KEYWORDS: CARBON-DIOXIDE ATMOSPHERES, ELEVATED ATMOSPHERIC CO2, LARVAL
EMERGENCE, LEPIDOPTERA, MOTH, NUTRIENT BALANCE, PERFORMANCE,
PHYTOCHEMISTRY, PLANTS, QUERCUS-ROBUR L


     585  
Eamus, D. 1991. The interaction of rising CO2 and temperatures with water-use efficiency. Plant,
Cell and Environment 14(8):843-852.

Recent data concerning the impact of elevated atmospheric CO2 upon water use efficiency (WUE)
and the related measure, instantaneous transpiration efficiency (ITE), are reviewed. It is concluded
from both short and long-term studies that, at the scale of the individual leaf or plant, an increase in
WUE or ITE is generally observed in response to increased atmospheric CO2 levels. However, the
magnitude of this increase may decline with time. The opinion that elevated CO2 may substantially
decrease transpiration at the regional scale is discussed. The mechanisms by which elevated CO2 may
cause a change in these measures are discussed in terms of stomatal conductance, assimilation and
respiration responses to elevated CO2. Finally, recent experimental data and model outputs
concerning the impact of the interaction of increased temperature with elevated CO2 on WUE, ITE
and yield are reviewed. It is concluded that substantially more data is required before reliable
predictions about the regional scale response of WUE and catchment hydrology can be made.

KEYWORDS: ABSCISIC- ACID, ATMOSPHERIC CARBON-DIOXIDE, ELEVATED CO2,
ENRICHMENT, GAS-EXCHANGE, LEAF, PLANT GROWTH, RESPONSES, STOMATAL GUARD-
CELLS, STRESS


     586  
Eamus, D. 1996. Tree responses to CO2 enrichment: CO2 and temperature interactions, biomass
allocation and stand-scale modeling. Tree Physiology 16(1-2):43-47.

In this review, I focus on modeling studies of tree responses to CO2 enrichment. First, I examine leaf-
scale models of assimilation with respect to the interaction between low temperature and CO2
enrichment. Second, because changes in allocation within a tree may be significant in determining the
growth response of trees to CO2 enrichment and low temperatures, I review models of the control
of allocation in plants. Finally, models of stand-scale processes are discussed with respect to their
ability to make reliable estimates of likely vegetation responses to predicted climate change. I
conclude that our ability to make reliable predictions is hindered by our lack of understanding of
several processes, namely: the interaction between increased atmospheric CO2 concentration and low
temperatures; the control of allocation in plants; and the modeling of stand-scale processes.

KEYWORDS: AIR- TEMPERATURE, ATMOSPHERIC CO2, BALANCE, CARBON-DIOXIDE
CONCENTRATION, ELEVATED CO2, GROWTH, PHOTOSYNTHESIS, ROOT, SEEDLINGS,
TERM


     587  
Eamus, D., C.A. Berryman, and G.A. Duff. 1993. Assimilation, stomatal conductance, specific
leaf-area and chlorophyll responses to elevated co2 of maranthes corymbosa, a tropical monsoon rain-
forest species. Australian Journal of Plant Physiology 20(6):741-755.

Seeds of Maranthes corymbosa Blume, a monsoon rain forest species of northern Australia, were
sown under ambient or elevated CO2 concentrations in tropical Australia. Seedlings were grown
under conditions of photon flux density, temperature and atmospheric vapour pressure deficit which
followed ambient variations as closely as possible. Specific leaf area, chlorophyll, stomatal density,
stomatal conductance and assimilation responses to photon flux density were measured after 30
weeks growth. Gas exchange characteristics were divided into morning and afternoon data sets and
analysed separately. Stomatal density decreased and leaf area:dry weight ratio decreased in response
to elevated CO2. In contrast there was no effect of elevated CO2 upon chlorophyll (total or ratio of
a:b). Apparent quantum yield and rates of light saturated assimilation (A(max)) increased in response
to elevated CO2. There was a significant decline in apparent quantum yield for both treatments
between morning and afternoon. Stomatal conductance (g(s)) declined in response to elevated CO2.
There was no significant difference in g(s) between morning and afternoon for ambient grown trees,
but g(s) declined significantly between morning and afternoon for elevated CO2 grown trees.
Instantaneous transpiration efficiency (ITE) was higher for elevated CO2 grown trees compared with
control trees. There was a significant increase in ITE between morning and afternoon data for
ambient grown trees; in contrast a significant decline in ITE was observed for elevated CO2 grown
trees between morning anf afternoon data sets. The slope of the regression between assimilation rate
and stomatal conductance increased for plants grown under elevated CO2. These data are discussed
and compared with the responses of plants adapting to different photon flux densities.

KEYWORDS: ATMOSPHERIC CO2, CARBON-DIOXIDE ENRICHMENT, GROWTH,
INCREASES, IRRADIANCE, LIGHT, ORANGE, PHOTOSYNTHESIS, SEEDLINGS, TREES


     588  
Eamus, D., C.A. Berryman, and G.A. Duff. 1995. The impact of co2 enrichment on water relations
in maranthes- corymbosa and eucalyptus-tetrodonta. Australian Journal of Botany 43(3):273-282.

Seeds of Maranthes corymbosa Blume and Eucalyptus tetrodonta F.Muell were sown under ambient
or CO2 enriched conditions (two replicate tents per treatment) in tropical Australia and allowed to
grow, rooted in the ground, for 20 months. For both species, periodic measurements of leaf water
potential, stomatal conductance and leaf temperature were made on four replicate leaves on each of
four replicate trees within each tent. Measurements were made in November (M. corymbosa) and
June (E. tetrodonta). At the same time, atmospheric wet and dry bulb temperatures were recorded
and hence leaf-to-air vapour presure difference (LAVPD) calculated. Measurements of pre-dawn leaf
water potential were also made on E. tetrodonta. Leaves were also taken to the laboratory,
rehydrated to full turgor and pressure-volume analyses undertaken. For M. corymbosa, leaf water
potential was lower throughout the day for control leaves compared to leaves growing in CO2
enriched air. Similarly, pre dawn leaf water potential was lower for control E. tetrodonta trees than
for trees grown with CO2 enrichment. However, mid- morning and mid-afternoon values of leaf
water potential for E. tetrodonta were slightly lower for plants growing in CO, enriched air compared
to control plants. In both species, stomatal conductance was consistently lower for trees grown in
CO2 enriched air than for controls. Whole plant hydraulic conductivity of both species was
significantly lower for trees grown in CO2 enriched air than for control trees. For both species,
maximum turgor and bulk volumetric elastic modulus increased and osmotic potential at zero turgor
decreased for trees grown in CO2 enriched air.

KEYWORDS: ANATOMY, ATMOSPHERIC CO2, CARBON DIOXIDE, ELEVATED CO2,
GROWTH, MORPHOLOGY, SEEDLINGS, STRESS


     589  
Eamus, D., G.A. Duff, and C.A. Berryman. 1995. Photosynthetic responses to temperature, light
flux-density, co2 concentration and vapor-pressure deficit in eucalyptus tetrodonta crown under co2
enrichment. Environmental Pollution 90(1):41-49.

Seeds of Eucalyptus tetrodonta were sown under ambient or CO2 enriched (700 mu l litre(-1))
conditions in tropical Australia. Four sets of measurements were made, the first two after 12 months,
on trees growing either in pots or planted in the ground. The third and fourth set were made after 18
and 30 months exposure to CO2 enrichment, on trees growing in the ground After 12 months
exposure to CO2 enrichment, the rate of light-saturated assimilation (A(max)) of plants growing in
the ground was determined. Responses of CO2 assimilation to variations in leaf temperature, leaf-to-
air vapour,pressure deficit (LAVPD), Eight flux density and CO2 concentration were also measured
in the laboratory using plants growing in large pots. There was no significant difference in A(max)
between pot and ground located plants. Assimilation of E. tetrodonta was relatively insensitive to
changes in LAVPD for both ambient and CO2 enriched plants but the temperature optimum of
assimilation was increased in plants grown and measured under CO2 enrichment. Plants grown with
CO2 enrichment had an increased rate of light-saturated assimilation and apparent quantum yield I-
vas significantly inn eased by CO2 enrichment. rn contrast, carboxylation efficiency was decreased
significantly by CO2 enrichment. After 18 months growth with CO2 enrichment, there was no sign
of a decline in assimilation I ate compared to measurements undertaken after 12 months, At low
LAVPD values, assimilation rate was not influenced by CO2 treatment but at moderate to high
LAVPD, plants grown under CO2 enrichment exhibited a larger assimilation rate than control plants.
Specific leaf area and chlorophyll contents decreased in response to CO2 enrichment, whilst foliar
soluble protein contents and chlorophyll a/b ratios were unaffected by CO2 treatment. Changes in
soluble protein and chlorophyll contents in response to CO2 enrichment did not account for changes
in assimilation between treatments. After 30 months exposure to CO2 enrichment, the rate of light-
saturated assimilation was approximately 50% larger than controls and this enhancement was larger
than that observed after 18 months exposure to CO2 enrichment.

KEYWORDS: ACCLIMATION, CARBON DIOXIDE, CARBOXYLASE, ELEVATED CO2,
GROWTH, L LEAVES, MARANTHES-CORYMBOSA, PHASEOLUS-VULGARIS L, SEEDLINGS,
STOMATAL CONDUCTANCE


     590  
Eamus, D., and M. Murray. 1991. Photosynthetic and stomatal conductance responses of norway
spruce and beech to ozone, acid mist and frost - a conceptual-model. Environmental Pollution
72(1):23-44.

Two-year-old beech and Norway spruce seedlings were exposed to a combination of ozone and acid
mist treatments in open-top chambers in Scotland during the months of July through to September
1988. Replicate pairs of chambers received charcoal- filtered air (control), ozone-enriched air (140
nl ozone litre- 1) or 140 nl ozone litre-1 plus a synthetic acid mist (pH 2.5) composed of ammonium
nitrate and sulphuric acid. Field measurements of assimilation and stomatal conductance were made
during August. In addition, measurements of assimilation and conductance were made during
September in the laboratory. Light response curves of assimilation and conductance were determined
using a GENSTAT non-rectangular hyperbolic model. During February 1988/9 the Norway spruce
were subject to a four day warming period at 12-degrees-C and the light response of assimilation
determined. The same plants were then subject to a 3-h night-time frost of -10-degrees-C. The
following day the time-course of the recovery of assimilation was determined. It was found that
ozone fumigation did not influence the light response of assimilation of beech trees in the field,
although stomatal conductance was reduced in the ozone-fumigated trees. The rate of light-saturated
assimilation of Norway spruce was increased by ozone fumigation when measured in the field.
Measurements of assimilation of Norway spruce made during the winter showed that prior to
rewarming there was no difference in the rate of light-saturated assimilation for control and ozone-
fumigated trees. However, the ozone plus acid mist- treated trees exhibited a significantly higher rate.
The 4-day period of warming to 12-degrees-C increased the rate of light-saturated assimilation in all
treatments but only the ozone plus acid mist-treated trees showed a significant increase. Following
a 3-h frost to -10-degrees-C the control trees exhibited a reduction in the rate of light-saturated
assimilation (A(max)) to 80% of the pre-frost value. In comparison, following the frost, the ozone-
fumigated trees showed an A(max) of 74% of the pre-frost value. The ozone plus acid mist-treated
trees showed an A(max) of 64% of the pre- frost trees. The time taken for A(max) to attain 50% of
the pre-frost value increased from 30 min (control) to 85 min for ozone-fumigated trees to 190 min
(ozone plus acid mist). These results are discussed in relation to the impact of mild, short- term frosts,
which are known to occur with greater frequency than extreme, more catastrophic frost events. A
simple conceptual framework is proposed to explain the variable results obtained in the literature with
respect to the impact of ozone upon tree physiology.

KEYWORDS: ABIES L KARST, CO2 ASSIMILATION, FOREST DECLINE, GROWTH,
HARDINESS, PINUS SYLVESTRIS, RAIN, SCOTS PINE, SEEDLINGS, TEMPERATURES


     591  
Easterling, W.E., P.R. Crosson, N.J. Rosenberg, M.S. McKenney, L.A. Katz, and K.M.
Lemon. 1993. Agricultural impacts of and responses to climate-change in the missouri-iowa-
nebraska-kansas (mink) region. Climatic Change 24(1-2):23-61.

The climate of the 1930s was used as an analog of the climate that might occur in Missouri, Iowa,
Nebraska and Kansas (the MINK region) as a consequence of global warming. The analog climate
was imposed on the agriculture of the region under technological and economic conditions prevailing
in 1984/87 and again under a scenario of conditions that might prevail in 2030. The EPIC model of
Williams et al. (1984), modified to allow consideration of the yield enhancing effects of CO2
enrichment, was used to evaluate the impacts of the analog climate on the productivity and water use
of some 50 representative farm enterprises. Before farm level adjustments and adaptations to the
changed climate, and absent CO2 enrichment (from 350 to 450 ppm), production of corn, sorghum
and soybeans was depressed by the analog climate in about the same percent under both current and
2030 conditions. Production of dryland wheat was unaffected. Irrigated wheat production actually
increased. Farm level adjustments using low-cost currently available technologies, combined with
CO2 enrichment, eliminated about 80% of the negative impact of the analog climate on 1984/87
baseline crop production. The same farm level adjustments, plus new technologies developed in
response to the analog climate, when combined with CO2 enrichment, converted the negative impact
on 2030 crop production to a small increase. The analog climate would have little direct effect on
animal production in MINK. The effect, if any, would be by way of the impact on production of feed-
grains and soybeans. Since this impact would be small after on-farm adjustments and CO2
enrichment, animal production in MINK would be little affected by the analog climate.

KEYWORDS: CO2, CORN, EPIC MODEL, EROSION, PRODUCTIVITY


     592  
Easterling, W.E., N.J. Rosenberg, K.M. Lemon, and M.S. McKenney. 1992. Simulations of crop
responses to climate change - effects with present technology and currently available adjustments (the
smart farmer scenario). Agricultural and Forest Meteorology 59(1-2):75-102.

If climate changes, farmers will have to adapt to a new set of climate constraints. In this paper we
examine the efficacy of strategies for dealing with climate change that are currently available to
farmers and that are inexpensive to use; we refer to this group of strategies as 'adjustments'.
Adjustment schemes of various kinds were identified for us by agricultural experts in the Missouri-
Iowa-Nebraska-Kansas (MINK) states. These can involve changes in land use, changes in variety and
crop selection, changes in planting and harvesting practices, and changes in fertility and pest
management. Using the erosion productivity impact calculator (EPIC) model on a small set of
representative farms, we tested adjustments of these kinds. The simulations show that earlier planting,
longer- season cultivars and the use of furrow diking for moisture conservation would offset some
of the yield losses induced by climate change in warm-season crops. Longer-season varieties of wheat
(a cool-season crop) and shorter-season varieties of the perennials wheatgrass and alfalfa were also
effective. The adjustments to climate change diminished yield losses in all crops but irrigated wheat.
Despite the positive effects of adjustments, however, yields of all dryland warm-season crops
remained lower than control levels. The adjustments also increased demand for irrigation water.
Carbon dioxide enrichment had the same incremental effect on crop yields with or without
adjustments (see the fourth paper in this issue), except in the case of alfalfa and sorghum, where a
CO2- adjustment interaction was found. We conclude that currently available techniques would
partially offset the yield reductions caused by a 1930s-like climate, but that in most crops the yield
reductions would still be substantial.

KEYWORDS: AGRICULTURE


     593  
Edwards, N.T., and R.J. Norby. 1998. Below-ground respiratory responses of sugar maple and red
maple saplings to atmospheric CO2 enrichment and elevated air temperature. Plant and Soil
206(1):85-97.

The research described in this paper represents a part of a much broader research project with the
general objective of describing the effects of elevated [CO2] and temperature on tree growth,
physiological processes, and ecosystem-level processes. The specific objective of this research was
to examine the below-ground respiratory responses of sugar maple (Acer saccharum Marsh.) and red
maple (Acer rubrum L.) seedlings to elevated atmospheric [CO2] and temperature. Red maple and
sugar maple seedlings were planted in the ground in each of 12 open-top chambers and exposed from
1994 through 1997 to ambient air or air enriched with 30 Pa CO2, in combination with ambient or
elevated (+4 degrees C) air temperatures. Carbon dioxide efflux was measured around the base of
the seedlings and from root-exclusion zones at intervals during 1995 and 1996 and early 1997. The
CO2 efflux rates averaged 0.4 mu mol CO2 m(-2) s(-1) in the root-exclusion zones and 0.75 mu mol
CO2 m(-2) s-1 around the base of the seedlings. Mineral soil respiration in root-exclusion zones
averaged 12% higher in the high temperature treatments than at ambient temperature, but was not
affected by CO2 treatments. The fraction of total efflux attributable to root + rhizosphere respiration
ranged from 14 to 61% in measurements made around red maple plants, and from 35 to 62% around
sugar maple plants. Root respiration rates ranged from 0 to 0.94 mu mol CO2 s(-1) m(-2) of soil
surface in red maple and from 0 to 1.02 in sugar maple. In both 1995 and 1996 root respiration rates
of red maple were highest in high-CO2 treatments and lowest in high temperature treatments. Specific
red maple root respiration rates of excised roots from near the soil surface in 1996 were also highest
under CO2 enrichment and lowest in high temperature treatments. In sugar maple the highest rates
of CO2 efflux were from around the base of plants exposed to both high temperature and high-CO2,
even though specific respiration rates were lowest for this species under the high temperature and
CO2 enrichment regime. In both species, patterns of response to treatments were similar in root
respiration and root mass, indicating that the root respiration responses were due in part to
differences in root mass. The results underscore the need for separating the processes occurring in
the roots from those in the forest floor and mineral soil in order to increase our understanding of the
effects of global climate change on carbon sequestration and cycling in the below-ground systems of
forests.

KEYWORDS: CARBON DIOXIDE, DECIDUOUS FOREST FLOOR, DROUGHT, EVOLUTION,
GROWTH, NITROGEN, PONDEROSA PINE, ROOT RESPIRATION, SEEDLINGS, SOIL
RESPIRATION


     594  
Egli, P., and C. Korner. 1997. Growth responses to elevated CO2 and soil quality in beech- spruce
model ecosystems. Acta Oecologica-International Journal of Ecology 18(3):343-349.

Growth responses of beech (Fagus sylvatica L.) and Norway spruce (Picea abies Karst.) to elevated
atmospheric CO2 (366 and 550 mu l CO2 l(-1)) and increased wet deposition of nitrogen (2.5 and
25 kg N ha(-1) a(-1)) in combination with two soil types were studied in open-top chambers. Eight
young beech and spruce trees, together with five understory species, were established in each of 32
model ecosystems. We present initial growth responses of trees during the first year of treatment
which may set the trends for longer term responses to elevated CO2. Above-ground biomass
production at the system level (biometric data) during the first year and root biomass (coring data)
did not show significant responses to elevated CO2, irrespectively of other cc-treatments. Increased
nitrogen deposition (treatment commencing by mid-season) also had no effect on above-ground
biomass, whereas end of season root biomass was significantly increased in the high-nitrogen treated
low fertility acidic soil (74 g m(-2) in the high-N versus 49 g m(-2)? in the low N-treatment), but not-
in the more fertile calcareous soil. Stem diameter increment of beech was significantly increased
(+9%) under elevated CO, in the calcareous soil, but not in the acidic soil. The opposite was found
for spruce stems, which responded positively to elevated CO2 in the acidic soil (+ 11%; P < 0.05)
but nor in the calcareous soil. These results suggest that soil type co- determines the CO2 response
of young forest trees and that these interactions are species specific. These initial differences are likely
to affect long-term responses of community structure and ecosystem functioning. Soil type appears
to be a key factor in predictions of forest responses to continued atmospheric CO2 enrichment.

KEYWORDS: ATMOSPHERE, COMMUNITIES, PLANTS, TREES


     595  
Egli, P., S. Maurer, M.S. Gunthardt-Goerg, and C. Korner. 1998. Effects of elevated CO2 and
soil quality on leaf gas exchange and above-ground growth in beech-spruce model ecosystems. New
Phytologist 140(2):185-196.

Responses of leaf gas exchange and above-ground growth of beech (Fagus sylvatica L.) and Norway
spruce (Picea abies Karst.) to atmospheric CO2 enrichment (374 mu l l(-1) VS. 590 mu l l(-1)) and
increased wet deposition of N (5 vs. 50 kg N ha(-1) a(-1)) in combination with two natural forest soil
types ('acidic' and 'calcareous') were studied in large open-top chambers. Eight juvenile beech and
spruce trees from different provenances, together with a ground cover composed of five understorey
species, were established in each of 32 model ecosystems. Both beech and spruce showed sustained
enhancement of photosynthesis in response to atmospheric CO2 enrichment during the first 2 yr of
treatment. Nevertheless, switching measurement CO2 concentrations revealed partial downward
adjustment of photosynthesis in trees grown in elevated CO2, beech generally showing more
pronounced downward adjustment than spruce. The responsiveness of photosynthesis to CO2
enrichment did not vary significantly among trees from different provenances. Stomatal conductance
was reduced under elevated CO2 in both tree species. In spruce, the radial growth of the main stem
and the annual production of wood (shoot-wood dry mass of current-year lateral shoots), needle dry
mass, and assimilation area per tree were stimulated both by CO2 enrichment and increased N
deposition, but were not significantly affected by soil type by year 2. In contrast, in beech, the radial
growth of the stem and the total leaf number, foliage dry mass, and assimilation area per tree were
all not significantly affected by elevated CO2 and increased N deposition when responses of the two
soil types were pooled, but were greater on calcareous than on acidic soil by year 2. However, CO2
interacted with soil type in beech: irrespective of the N deposition rate, saplings showed growth
stimulation on the calcareous soil but responded negatively to CO2 enrichment on the acidic soil
(where growth was slower). Our results suggest that complex interactions between CO2, species and
soil quality need to be accounted for when attempting to predict forest development in a future CO2-
rich world.

KEYWORDS: ATMOSPHERIC CO2, BRANCH BAG, CARBON DIOXIDE, ENRICHMENT,
FAGUS-SYLVATICA, PHOTOSYNTHETIC ACCLIMATION, PINUS-TAEDA, RESPONSES,
RISING CO2, TREES


     596  
Ehler, N., and P. Karlsen. 1993. Optico - a model-based real-time expert-system for dynamic
optimization of co2 enrichment of greenhouse vegetable crops. Journal of Horticultural Science
68(4):485-494.

To improve the economic yield of CO2 enrichment for greenhouse crops, an expert system
(OPTICO) was constructed. The system continually adapts the setpoints of a standard climate
computer to the climate, the greenhouse regulation equipment and the crop's physiological status and
stage of development. Models describing air loss and photosynthesis were used for selecting an
optimized CO2 setpoint by choosing the largest positive difference between expected income and
cost. During the autumn of 1991 the sweet pepper (Capsicum annuum L.) cv. Trophy was used as
experimental plant in two standard greenhouse compartments. One treatment used the optimized CO2
enrichment, the other a fixed CO2 level of 600 ppm. The optimized treatment resulted in greater yield
using less CO2. The results stress the importance of adapting the CO2 level to the immediate
irradiance and current leaf area and carbon partitioning behaviour of the crop.



     597  
Ehleringer, J.R., and T.E. Cerling. 1995. Atmospheric co2 and the ratio of intercellular to ambient
co2 concentrations in plants. Tree Physiology 15(2):105-111.

Much attention is focused today on predicting how plants will respond to anticipated changes in
atmospheric composition and climate, and in particular to increases in CO2 concentration. Here we
review the long-term global fluctuations in atmospheric CO2 concentration as a framework for
understanding how current trends in atmospheric CO2 concentration fit into a selective, evolutionary
context. We then focus on an integrated approach for understanding how gas exchange metabolism
responds to current environmental conditions, how it previously responded to glacial-interglacial
conditions, and how it may respond to future changes in atmospheric CO2 concentration.

KEYWORDS: CARBON ISOTOPE DISCRIMINATION, GAS-EXCHANGE, LAST 3 CENTURIES,
LEAVES, PHOTOSYNTHESIS, SOIL CARBONATE, STOMATAL DENSITY, TRANSPIRATION
EFFICIENCY, VOSTOK ICE-CORE, WATER-USE EFFICIENCY


     598  
Ehleringer, J.R., T.E. Cerling, and B.R. Helliker. 1997. C-4 photosynthesis, atmospheric CO2 and
climate. Oecologia 112(3):285-299.

The objectives of this synthesis are (1) to review the factors that influence the ecological,
geographical, and palaeoecological distributions of plants possessing C-4 photosynthesis and (2) to
propose a hypothesis/model to explain both the distribution of C-4 plants with respect to temperature
and CO2 and why C-4 photosynthesis is relatively uncommon in dicotyledonous plants (hereafter
dicots), especially in comparison with its widespread distribution in monocotyledonous species
(hereafter monocots). Our goal is to stimulate discussion of the factors controlling distributions of
C-4 plants today, historically, and under future elevated CO2 environments. Understanding the
distributions of C-3/C-4 plants impacts not only primary productivity, but also the distribution,
evolution, and migration of both invertebrates and vertebrates that graze on these plants. Sixteen
separate studies all indicate that the current distributions of C-4 monocots are tightly correlated with
temperature: elevated temperatures during the growing season favor C-4 monocots. In contrast, the
seven studies on C-4 dicot distributions suggest that a different environmental parameter, such as
aridity (combination of temperature and evaporative potential), more closely describes their
distributions. Differences in the temperature dependence of the quantum yield for CO2 uptake (light-
use efficiency) of C-3 and C-4 species relate well to observed plant distributions and light-use
efficiency is the only mechanism that has been proposed to explain distributional differences in C-3/C-
4 monocots. Modeling of C-3 and C-4 light- use efficiencies under different combinations of
atmospheric CO2 and temperature predicts that C-4-dominated ecosystems should not have expanded
until atmospheric CO2 concentrations reached the lower levels that are thought to have existed
beginning near the end of the Miocene. At that time, palaeocarbonate and fossil data indicate a
simultaneous, global expansion of C-4-dominated grasslands. The C-4 monocots generally have a
higher quantum yield than C-4 dicots and it is proposed that leaf venation patterns play a role in
increasing the light-use efficiency of most C-4 monocots. The reduced quantum yield of most C-4
dicots is consistent with their rarity, and it is suggested that C-4 dicots may not have been selected
until CO2 concentrations reached their lowest levels during glacial maxima in the Quaternary. Given
the intrinsic light-use efficiency advantage of C-4 monocots, C-4 dicots may have been limited in their
distributions to the warmest ecosystems, saline ecosystems, and/or to highly disturbed ecosystems.
All C-4 plants have a significant advantage over C- 3 plants under low atmospheric CO2 conditions
and are predicted to have expanded significantly on a global scale during full- glacial periods,
especially in tropical regions. Bog and lake sediment cores as well as pedogenic carbonates support
the hypothesis that C-4 ecosystems were more extensive during the last glacial maximum and then
decreased in abundance following deglaciation as atmospheric CO2 levels increased.

KEYWORDS: BUNDLE-SHEATH, C-4 PHOTOSYNTHESIS, CARBOXYLASE-OXYGENASE,
ECOLOGICAL DISTRIBUTION, GEOGRAPHICAL-DISTRIBUTION, ICE CORE, LAST GLACIAL
MAXIMUM, LEAF ANATOMY, ORGANIC-MATTER, QUANTUM YIELD


     599  
Eichelmann, H., and A. Laisk. 1994. Co2 uptake and electron-transport rates in wild-type and a
starchless mutant of nicotiana-sylvestris - the role and regulation of starch synthesis at saturating co2
concentrations. Plant Physiology 106(2):679-687.

CO2 uptake rate, chlorophyll fluorescence, and 830-nm absorbance were measured in wild-type (wt)
Nicotiana sylvestris (Speg. et Comes) and starchless mutant NS 458 leaves at different light intensities
and CO2 concentrations. Initial slopes of the relationships between CO2 uptake and light and CO2
were similar, but the maximum rate at CO2 and light saturation was only 30% in the mutant
compared with the wt. O-2 enhancement of photosynthesis at CO2 and tight saturation was relatively
much greater in the mutant than in the wt. In 21% O- 2, the electron transport rate (ETR) calculated
from fluorescence peaked near the beginning of the CO2 saturation of photosynthesis. With the
further increase of CO2 concentration ETR remained nearly constant or declined a little in the wt but
drastically declined in the mutant. Absorbance measurements at 830 nm indicated photosystem I
acceptor side reduction in both plants at saturating CO2 and light. Assimilatory charge
(postillumination CO2 uptake) measurements indicated trapping of chloroplast inorganic phosphate,
supposedly in hexose phosphates, in the mutant. It is concluded that starch synthesis gradually
substitutes for photorespiration as electron acceptor with increasing CO2 concentration in the wt but
not in the mutant. It is suggested that starch synthesis is co-controlled by the activity of the
chloroplast fructose bisphosphatase.

KEYWORDS: CARBON METABOLISM, CHLOROPLAST, FLUORESCENCE, LEAVES,
MATHEMATICAL-MODEL, PHOTOSYNTHESIS, PLASTID PHOSPHOGLUCOMUTASE,
REDUCED-ACTIVITY, STEADY-STATE, SUCROSE SYNTHESIS


     600  
Elhottova, D., J. Triska, H. Santruckova, J. Kveton, J. Santrucek, and M. Simkova. 1997.
Rhizosphere microflora of winter wheat plants cultivated under elevated CO2. Plant and Soil
197(2):251-259.

We studied an effect of elevated atmospheric CO2 on rhizosphere microorganisms in a hydroponics
system where young wheat plants provided the only source of C for microorganisms. Plants were
cultivated in mineral solution in sterile silica sand and exposed to control (ambient) and elevated
(double) CO2 concentrations for periods of 13, 20, 25 and 34 days. Microbial biomass C (C content
in fraction of size 0.3-2.7 mu m) was not affected by the elevated CO2 concentration during the first
25 days of plant growth and was increased after 34 days of plant growth. A content of poly-beta-
hydroxybutyrate (PHB) reserve compounds (measured as derivatized product of 3-hydroxy-butyric
acid and N-tert-butyldimethylsilyl-N-methyltrifluoracetamide using GC-MS) was lowered significantly
(p<0.001) in the elevated CO2 after 25 and 34 days. It was accompanied with a shift of bacterial
distribution towards the nutritional groups utilising more complex organic material (number of CFUs
on media with different sources of C and N). A coincidence of several events connected with plant
and microbial carbon economy (decrease of an assimilation rate and relative growth rate of plants,
small increase of microbial biomass, PHB decrease and suppression within the bacterial nutritional
group requiring the most readily available source of C and energy) was observed in the system under
elevated CO2 on the 25th day. A modification of the CC-MS method for the detection of low levels
of PHB compounds in natural samples was developed. We excluded the lipids fractionation step and
we used EI MS/MS detection of the main fragment ions of the derivatized compound. This
guarantees that the ion profiles have high signal-to-noise ratio at correct retention time. The detection
limit is then about 30 pg g(-1) of sand or soil. The rhizosphere microflora responded very sensitively
to the short- term changes in C partitioning in plants caused by the elevated CO2.

KEYWORDS: ATMOSPHERIC CO2, AZOSPIRILLUM- BRASILENSE, CARBON, GROWTH,
METABOLISM, POLY BETA HYDROXYBUTYRATE, RESPONSES


     601  
Elkohen, A., and M. Mousseau. 1994. Interactive effects of elevated co2 and mineral-nutrition on
growth and co2 exchange of sweet chestnut seedlings (castanea- sativa). Tree Physiology 14(7-
9):679-690.

The effects of elevated atmospheric CO2 (700 mumol mol-1) and fertilization were investigated on
2-year-old sweet chestnut (Castanea sativa Mill.) seedlings grown outdoors in pots in constantly
ventilated open-sided chambers. Plants were divided into four groups: fertilized controls (+F/-CO2),
unfertilized controls (-F/-CO2), fertilized + CO2-treated plants (+F/+CO2) and unfertilized + CO2-
treated plants (-F/+CO2). Dry matter accumulation and allocation were measured after one growing
season and CO2 exchange of whole shoots was measured throughout the growing season. Shoot
growth and total leaf area of unfertilized plants were not affected by elevated CO2, whereas both
parameters were enhanced by elevated CO2 in fertilized plants. Elevated CO2 increased total biomass
by about 20% in both fertilized and unfertilized plants; however, biomass partitioning differed. In
unfertilized plants, elevated CO2 caused an increase in root growth, whereas in fertilized plants, it
stimulated aboveground growth. At the whole-shoot and leaf levels, photosynthetic activity of both
fertilized and unfertilized plants increased in response to elevated CO2, but the seasonal pattern of
this enhancement varied with nutrient treatment. In unfertilized plants, a downward acclimation of
photosynthesis was observed early in the season (June), and was related to reductions in nitrogen and
chlorophyll content and to starch accumulation. The decrease in the slope of the A/Ci curve suggested
a decrease in Rubisco activity. In both fertilized and unfertilized plants, shoot respiration decreased
during the night in response to elevated CO2 until mid-July. The decrease was not related to changes
in sugar concentration.



     602  
Elkohen, A., J.Y. Pontailler, and M. Mousseau. 1991. Effect of doubling of atmospheric CO2
concentration on dark respiration in aerial parts of young chestnut trees (Castanea sativa mill).
Comptes Rendus De L Academie Des Sciences Serie III-Sciences De La Vie-Life Sciences
312(9):477-481.

Two-year-old sweet chestnut seedlings were grown in constantly ventilated tunnels at ambient (350
vpm) or double (700 vpm) CO2 concentration during a full growing season. End-of-night dark
respiration of aerial parts was measured in each CO2 concentration throughout the growing season.
Dark respiration rate of enriched plants showed a net decrease as compared to control plants during
the first half of the growing season. This difference decreased with time and became negligible in the
fall. Atmospheric CO2 concentration acted instantaneously on the respiration rate: when doubled, it
decreased control plant respiration and when decreased, it enhanced CO2 enriched plant respiration.
The explanation of these findings remains hypothetical. It is concluded that the rise in carbon dioxide
level of the atmosphere will affect the carbon balance of young trees not only through an increase in
net photosynthesis during the day, but also at night by reducing respiratory losses.

KEYWORDS: CARBON DIOXIDE, ENRICHMENT, LEAF


     603  
Elkohen, A., H. Rouhier, and M. Mousseau. 1992. Changes in dry-weight and nitrogen
partitioning induced by elevated co2 depend on soil nutrient availability in sweet chestnut (castanea-
sativa mill). Annales Des Sciences Forestieres 49(2):83-90.

The effect of 2 levels of atmospheric carbon dioxide (ambient, ie 350 ppm, and double, ie 700 ppm)
and 2 contrasting levels of mineral nutrition on dry weight, nitrogen accumulation and partitioning
were examined in 2-year-old chestnut seedlings (Castanea sativa Mill), grown in pots outdoors
throughout the vegetative season. Fertilization had a pronounced effect on dry weight accumulation,
tree height, leaf area, and plant nitrogen content. Carbon dioxide enrichment significantly increased
total biomass by about 20%, both on fertilized and on unfertilized forest soil. However, the
partitioning of biomass was very different: on the unfertilized soil, only the root biomass was
increased, leading to an increase in the root: shoot ratio. Contrastingly, on fertilized soil only stem
biomass and diameter but not height were increased. Carbon dioxide enrichment significantly reduced
the nitrogen concentration in all organs, irrespective of the nutrient availability. However, the biomass
increase made up for this reduction in such a way that the total nitrogen pool per tree remained
unchanged.

KEYWORDS: CARBON DIOXIDE, ENRICHMENT, FORESTS, GROWTH, PLANTS, QUERCUS-
ALBA, ROOT, SEEDLINGS


     604  
Elkohen, A., L. Venet, and M. Mousseau. 1993. Growth and photosynthesis of 2 deciduous forest
species at elevated carbon-dioxide. Functional Ecology 7(4):480-486.

1. Two-year-old sweet chestnut (Castanea sativa) and beech (Fagus sylvatica) seedlings were grown
in large pots of forest soil, at ambient (+/-350 mul l-1) and double (700 mul l-1) atmospheric CO2
Concentration in constantly ventilated.mini- green-houses during an entire growing season. 2. CO2
enrichment caused very different changes in these two temperate deciduous species. A 20% dry
weight enhancement was obtained for sweet chestnut, and a 60% enhancement in beech. This greater
effect of elevated CO2 in beech was the result of a significant increase of net photosynthesis of the
seedlings occurring during the whole season. However, in sweet chestnut, this increase in
photosynthesis lasted only a few weeks and then an acclimation process took place. 3. No effect of
increased CO2 could be found on sweet chestnut leaf area or leaf number, while a significant effect
was found with beech, in which total leaf area per plant increased, owing to a greater number of
growth flushes, of progressively larger leaves. 4. The partitioning of the biomass increase due to
elevated CO2 was very different in the two species. All additional dry matter was allocated to the
roots in sweet chestnut, while it was partitioned equally amongst all organs of the beech seedling. 5.
The reactions to elevated CO2 of different tree species is discussed in relation to their specific growth
strategy.



     605  
Ellert, B.H., and H.H. Janzen. 1999. Short-term influence of tillage on CO2 fluxes from a semi-arid
soil on the Canadian Prairies. Soil & Tillage Research 50(1):21-32.

The flux of CO2 from soil determines the extent to which carbon (C) deposited as plant litter is
retained in the soil. Retention of soil C is beneficial for soil physical, chemical and biological
properties, and is essential if soils are to be used as a repository of C to mitigate atmospheric CO2
increases. Although tillage is assumed to have a major influence on soil C retention, the extent to
which tillage enhances the transfer of soil C to the atmosphere is uncertain. We assessed the short-
term (50 h) influence of tillage on CO2 fluxes from Chernozemic soils under a two-year wheat
(Triticum aestivum L.)-summerfallow rotation in a semi-arid region of the Canadian Prairie, The
tillage effect and its persistence were assessed by using a portable CO2 analyzer to record several
temporal series of CO2 fluxes, along undisturbed and tilled transects, at successive time intervals
(from -0.5 to 50 h) after a single pass with a heavy-duty cultivator. Immediately after tillage, CO2
fluxes along the tilled transects increased from 2 to 4-fold above pre-tillage fluxes, but the increases
were short-lived and fluxes along undisturbed and tilled transects were again similar within 24 h of
cultivation. Total amounts of CO2 released by a tillage operation were quantified by: 1. linear
interpolations among successive fluxes along tilled and undisturbed transects, and 2. by fitting a
model to successive differences between fluxes along the transects. Both methods estimated the
amounts of tillage-susceptible CO2 to be in the range of 3.6-7.2 kg C ha(-1). The tillage-induced flush
of CO2 was attributed mainly to enhanced transport of CO2 already in the soil, but enhanced
production of CO2 by heterotrophic soil organisms also may have contributed to the flush. Regardless
of the sources of CO2 released by single tillage operations, amounts of tillage-susceptible soil C were
minor; even 10 passes with a cultivator would account for less than 5% of annual soil CO2 emissions
or crop residue production in these cropping systems. Our study suggested that the short- term
influence of tillage on the transfer of soil C to atmospheric CO2 is small under semi-arid conditions
like those in southern Alberta, Canada. Crown copyright (C) 1999 Published by Elsevier Science B.V,
All rights reserved.

KEYWORDS: CARBON-DIOXIDE FLUX, COVER, CROPPING SYSTEMS, EVOLUTION, LIGHT
FRACTION, MICROORGANISMS, ORGANIC-MATTER, RESPIRATION


     606  
Ellis, R.H., P.Q. Craufurd, R.J. Summerfield, and E.H. Roberts. 1995. Linear relations between
carbon-dioxide concentration and rate - of development towards flowering in sorghum, cowpea and
soybean. Annals of Botany 75(2):193-198.

Negative linear relations were detected (P < 0.005) between the rate of progress from sowing to
panicle initiation and CO2 concentration (210-720 mu mol CO2 mol(-1) air) for two genotypes of
sorghum [Sorghum bicolor (L.) Moench]. Relations between CO2 concentration and the rate of
progress from sewing to first flowering were also negative in soyabean [Glycine max (L). Merrill] (P
< 0.025), but positive in cowpea [Vigna unguiculata (L.) Walp.] (P < 0.025), albeit that in both grain
legumes sensitivity was much less than in sorghum. Thus CO2 elevation does not delay flowering in
all short-day species. The considerable effect of CO2 concentration on times to panicle initiation
resulted in large differences among the sorghum plants at this developmental stage; with increase in
CO2 concentration, plants were taller with slightly more leaves and more pronounced apical
extension. At the same time after sowing however, sorghum plants were heavier (P < 0.05) at 210
than at 360 mu mol CO2 mol(-1) air. In contrast, relations between the dry masses of the soyabean
and cowpea plants and CO2 concentration were positive and curvilinear (P < 0.05). It is suggested
that the impact of global environmental change could be severe for sorghum production in the semi-
arid tropics.

KEYWORDS: BICOLOR, CLIMATE, CO2- ENRICHMENT, ELEVATED CO2, FLORAL
INITIATION, GROWTH, TEMPERATURE, VIGNA UNGUICULATA L, YIELD


     607  
Ellsworth, D.S. 1999. CO2 enrichment in a maturing pine forest: are CO2 exchange and water status
in the canopy affected? Plant, Cell and Environment 22(5):461-472.

Elevated CO2 is expected to reduce forest water use as a result of CO2-induced stomatal closure,
which has implications for ecosystem-scale phenomena controlled by water availability. Leaf-level
CO2 and H2O exchange responses and plant and soil water relations were examined in a maturing
loblolly pine (Pinus taeda L,) stand in a free-air CO2 enrichment (FACE) experiment in North
Carolina, USA to test if these parameters were affected by elevated CO2, Current-year foliage in the
canopy was continuously exposed to elevated CO2 (ambient CO2 + 200 mu mol mol(-1)) in free-air
during needle growth and development for lip to 400 d. Photosynthesis in upper canopy foliage was
stimulated by 50-60% by elevated CO2 compared with ambient controls. This enhancement was
similar in current-year, ambient-grown foliage temporarily measured at elevated CO2 compared with
long-term elevated CO2 grown foliage, Significant photosynthetic enhancement by CO2 was
maintained over a range of conditions except during peak drought. There was no evidence of water
savings in elevated CO2 plots in FACE compared to ambient plots under drought and non-drought
conditions. This was supported by evidence from three independent measures. First, stomatal
conductance was not significantly different in elevated CO2 versus ambient trees of P. taeda,
Calculations of time-integrated c(i)/c(a) ratios from analysis of foliar delta(13)C showed that these
ratios were maintained in foliage under elevated CO2. Second, soil moisture was not significantly
different between ambient and elevated CO2 plots during drought. Third, pre-dawn and mid-day leaf
water potentials were also unaffected by the seasonal CO2 exposure, as were tissue osmotic
potentials and turgor loss points. Together the results strongly support the hypothesis that maturing
P. taeda trees have low stomatal responsiveness to elevated CO2. Elevated CO2 effects on water
relations in loblolly pine-dominated forest ecosystems may be absent or small apart from those
mediated by leaf area. Large photosynthetic enhancements in the upper canopy of P. taeda by elevated
CO2 indicate that this maturing forest may have a large carbon sequestration capacity with limiting
water supply.

KEYWORDS: DROUGHT, ELEVATED CARBON-DIOXIDE, GROWTH, INCREASING
ATMOSPHERIC CO2, LEAF GAS- EXCHANGE, LOBLOLLY-PINE, NET PHOTOSYNTHESIS,
RESPONSES, SEEDLINGS, STOMATAL CONDUCTANCE


     608  
Ellsworth, D.S., R. Oren, C. Huang, N. Phillips, and G.R. Hendrey. 1995. Leaf and canopy
responses to elevated co2 in a pine forest under free-air co2 enrichment. Oecologia 104(2):139-146.

Physiological responses to elevated CO2 at the leaf and canopy- level were studied in an intact pine
(Pinus taeda) forest ecosystem exposed to elevated CO2 using a free-air CO2 enrichment (FACE)
technique. Normalized canopy water-use of trees exposed to elevated CO2 over an 8-day exposure
period was similar to that of trees exposed to current ambient CO2 under sunny conditions. During
a portion of the exposure period when sky conditions were cloudy, CO2-exposed trees showed minor
(less than or equal to 7%) but significant reductions in relative sap flux density compared to trees
under ambient CO2 conditions. Short-term (minutes) direct stomatal responses to elevated CO2 were
also relatively weak (approximate to 5% reduction in stomatal aperture in response to high CO2
concentrations). We observed no evidence of adjustment in stomatal conductance in foliage grown
under elevated CO2 for nearly 80 days compared to foliage grown under current ambient CO2 so
intrinsic leaf water-use efficiency at elevated CO2 was enhanced primarily by direct responses of
photosynthesis to CO2. We did not detect statistical differences in parameters from photosynthetic
responses to intercellular CO2 (A(net)-C-i curves) for Pinus taeda foliage grown under elevated CO2
(550 mu mol mol(-1)) for 50-80 days compared to those for foliage grown under current ambient
CO2 from similar-sized reference trees nearby. In both cases, leaf net photosynthetic rate at 550 mu
mol mol(-1) CO2 was enhanced by approximately 65% compared to the rate at ambient CO2 (350
mu mol mol(-1)). A similar level of enhancement under elevated CO2 was observed for daily
photosynthesis under field conditions on a sunny day. While enhancement of photosynthesis by
elevated CO2 during the study period appears to be primarily attributable to direct photosynthetic
responses to CO2 in the pine forest, longer-term CO2 responses and feedbacks remain to be
evaluated.

KEYWORDS: AREA, CARBON-DIOXIDE ENRICHMENT, CONDUCTANCE, GAS-EXCHANGE,
GROWTH, PHOTOSYNTHESIS, RISING CO2, SEEDLINGS, TREES, WATER-STRESS


     609  
Ellsworth, D.S., R. Oren, C. Huang, N. Phillips, and G.R. Hendrey. 1996. Leaf and canopy
responses to elevated CO2 in a pine forest under free-air CO2 enrichment (vol 104, pg 139, 1995).
Oecologia 106(3):416.



     610  
ElMaayar, M., B. Singh, P. Andre, C.R. Bryant, and J.P. Thouez. 1997. The effects of climatic
change and CO2 fertilisation on agriculture in Quebec. Agricultural and Forest Meteorology 85(3-
4):193-208.

The agricultural sector forms an important part of the economy of Quebec. The risk of global increase
of atmospheric CO2 concentration and associated climatic change and their influence on agriculture
need to be assessed. Although many studies have been conducted on the effect of climate change on
agriculture in various parts of the world, fewer studies have focused on the combined effects of
climatic change and CO2 fertilisation on agriculture. This study, using the outputs of the Canadian
Climate Centre (CCC) general circulation model coupled with the Food and Agricultural Organization
(FAG) crop model, attempts to assess the response of agricultural productivity to both direct (or
fertilisation) and indirect (or climatic) effects of increased atmospheric CO2 concentration, for a
variety of crops including C-3 and C-4 cereals, legumes, vegetables and special crops grown in
Quebec. It appears that C-4 cereal (corn and sorghum) crops would benefit by climate change but
would be least favoured by CO2 fertilisation effect. (C) 1997 Published by Elsevier Science B.V.

KEYWORDS: CARBON DIOXIDE, CROP, DRY-WEIGHT, ENRICHMENT, GROWTH,
SCENARIO, TEMPERATURE, UNITED-STATES, WHEAT, YIELD


     611  
Elmeskaoui, A., J.P. Damont, M.J. Poulin, Y. Piche, and Y. Desjardins. 1995. A tripartite
culture system for endomycorrhizal inoculation of micropropagated strawberry plantlets in-vitro.
Mycorrhiza 5(5):313-319.

The objective of the current investigation was to develop a reliable method to obtain vesicular-
arbuscular mycorrhizae (VAM) in micropropagated plantlets and to determine their influence on
growth, An in vitro system for culturing the VA mycorrhizal fungus Glomus intraradices with Ri T-
DNA- transformed carrot roots or nontransformed tomato roots was used in this study as a potential
active source of inoculum for the colonization of micropropagated plantlets. After root induction,
micropropagated plantlets grown on cellulose plugs (sorbarod) were placed in contact with the
primary mycorrhizae in growth chambers enriched with 5000 ppm CO2 and fed with a minimal
medium. After 20 days of tripartite culture, all plantlets placed in contact with the primary symbiosis
were colonized by the VAM fungus. As inoculum source, 30-day-old VA mycorrhizal transformed
carrot roots had a substantially higher infection potential than 5-, 10- or 20-day-old VAM. Colonized
plantlets had more extensive root systems and better shoot growth than control plants. The VAM
symbiosis reduced the plantlet osmotic potential. This response may be a useful pre- adaptation for
plantlets during transfer to the acclimatization stage.

KEYWORDS: ASPARAGUS, FUNGI, GROWTH, INFECTION, INVITRO, PROPAGATION,
SYMBIOSIS, TRANSPORT, VA-MYCORRHIZAL, VESICULAR-ARBUSCULAR MYCORRHIZAE


     612  
Endo, M., and I. Ikushima. 1997. Effects of CO2 enrichment on yields and preservability of cut
flowers in Phalaenopsis. Journal of the Japanese Society for Horticultural Science 66(1):169-174.

The effect of CO2 enrichment on Phalaenopsis cut flower production was examined for 30 months
throughout five flowering cycles. The plant was cultured in three greenhouses with different CO2
levels of (A) : control, daily mean of ambient air = 438 ppm; (B) : 700 ppm; and (C) : 1000 ppm. 1.
The fresh weight of cut flowers, the numbers of inflorescence and flowers per 20 plants varied,
depending on the CO2 concentration for each flowering cycle. 2. The preservability (vase life) of cut
flowers always improved under higher CO2 levels. Organic acid contents of plants were also higher
under higher CO2 levels. The malic acid content in the flowers was higher than in the younger leaf
and flower stalk at 1:00 PM and 10:00 PM; and it was also higher in the younger leaf than in the
flower stalk at 10:00 PM, but lower at 1:00 PM. The pH value of plants was always lower at higher
ambient CO2 levels, and lower in the younger leaf and flower stalk at 1:00 PM than at 10:00 PM,
wheras at those same times the sugar content at the higher ambient CO2 levels reached its maximum.

KEYWORDS: LEAF, PHOTOSYNTHESIS


     613  
Endo, M., and I. Ikusima. 1997. Effects of CO2 enrichment by complete combustion of liquid
petroleum gas on growth of Doritaenopsis. Journal of the Japanese Society for Horticultural Science
66(1):163-168.

The effects of increasing ambient CO2 levels on the growth of developing Doritaenopsis plants in a
greenhouse were studied for 840 days. Leaf area, dry weight, and content of total carbon and total
nitrogen in dry matter were measured every three months, and the time course of the relative growth
rate (RGR) was investigated. Leaf area and dry weight increased with increasing CO2 concentration
from 438 ppm to 946 ppm in the atmosphere. In an initial growth stage when plants were transplanted
from flasks to pots, RGR increased as the CO2 level increased. RGR during a later vegetative growth
stage was not affected by the CO2 concentration, and its value was 0.006/day. The value of RGR was
less than that of the other C- 3, C-4, and CAM plants.

KEYWORDS: LIGHT, PLANTS, RESPONSES


     614  
Enoch, H.Z., and J.M. Olesen. 1993. Plant-response to irrigation with water enriched with carbon-
dioxide. New Phytologist 125(2):249-258.

The influence of irrigation with CO2-enriched water on plant development and yield is reviewed. The
reason for irrigation with CO2-enriched water was - in most cases - to increase yield. The present
evaluation considers results from over a hundred studies performed since the first experiment in 1866.
Special emphasis is given to the comparison of 85 experiments made by Mitscherlich in 1910 with
358 irrigation experiments made in the last 80 years. In a statistical analysis of these experiments, the
measured plant parameter (often growth and/or gas exchange rates) showed a highly significant mean
increase of 2.9 % in plants irrigated with CO2-enriched water as compared with control. Evidence
of five mechanisms was found. The subterranean carbon dioxide concentration influences: (a) the rate
of nitrification and hence of nitrogen availability; (b) the rate of weathering and pH, and hence the
availability of other plant nutrients; (c) the CO2 uptake via roots into the transpiration stream,
contributing to the rate of leaf photosynthesis; (d) the hormone levels in the plant; and (e) the rate of
pesticide decomposition in soils. After examining the available evidence we found that (a) and (b) in
some experiments are important to plant growth, since they change the physiochemical environment
of the roots. On the other hand, while (c) could theoretically contribute up to 5% of plant carbon
assimilation, it usually contributes less than 1%, while (d) contributes most of the observed effects
of CO2-enriched water on plants. In addition, pesticide decomposition in soils can be delayed by
supra- or sub-optimal CO2 concentrations.

KEYWORDS: ETHYLENE, GASEOUS CO2 TRANSPORT, GROWTH, ROOT ENVIRONMENT,
SEEDLINGS, SOIL, TUBERIZATION


     615  
Entry, J.A., G.B. Runion, S.A. Prior, R.J. Mitchell, and H.H. Rogers. 1998. Influence of CO2
enrichment and nitrogen fertilization on tissue chemistry and carbon allocation in longleaf pine
seedlings. Plant and Soil 200(1):3-11.

One-year old, nursery-grown longleaf pine (Pinus palustris Mill.) seedlings were grown in 45-L pots
containing a coarse sandy medium and were exposed to two concentrations of atmospheric CO2 (365
or 720 mu mol(-1)) and two levels of nitrogen (N) fertility (40 or 400 kg N ha(-1) yr(-1)) within open
top chambers for 20 months. At harvest, needles, stems, coarse roots, and fine roots were separated
and weighed. Subsamples of each tissue were frozen in liquid N, lyophilized at -50 degrees C, and
ground to pass a 0.2 mm sieve. Tissue samples were analyzed for carbon (C), N, nonpolar extractives
(fats, waxes, and oils = FWO), nonstructural carbohydrates (total sugars and starch), and structural
carbohydrates (cellulose, lignin, and tannins). Increased dry weights of each tissue were observed
under elevated CO2 and with high N; however, main effects of CO2 were significant only on
belowground tissues. The high N fertility tended to result in increased partitioning of biomass
aboveground, resulting in significantly lower root to shoot ratios. Elevated CO2 did not affect
biomass allocation among tissues. Both atmospheric CO2 and N fertility tended to affect
concentration of C compounds in belowground, more than aboveground, tissues. Elevated CO2
resulted in lower concentrations of starch, cellulose, and lignin, but increased concentrations of FWO
in root tissues. High N fertility increased the concentration of starch, cellulose, and tannins, but
resulted in lower concentrations of lignin and FWO in roots. Differences between CO2 concentrations
tended to occur only with high N fertility. Atmospheric CO2 did not affect allocation patterns for any
compound; however the high N treatment tended to result in a lower percentage of sugars, cellulose,
and lignin belowground.

KEYWORDS: ALLELOCHEMICALS, COTTON PLANTS, DIOXIDE, ELEVATED ATMOSPHERIC
CO2, GROWTH, PLANT-RESPONSES, PRODUCTIVITY, RESPIRATORY RESPONSES, ROOTS,
SOIL


     616  
Epron, D., E. Dreyer, C. Picon, and J.M. Guehl. 1994. Relationship between co2-dependent o-2
evolution and photosystem-II activity in oak (quercus-petraea) trees grown in the field and in
seedlings grown in ambient or elevated co2. Tree Physiology 14(7-9):725-733.

The light-response of the apparent quantum yield of photosynthetic O2 evolution (PHI(O2)) under
non- photorespiratory conditions was measured together with the photochemical efficiency Of PS II
(DELTAF/F(m)'), the photochemical efficiency of open PS II reaction centers (F(v)'/F(m)') and the
photochemical fluorescence quenching (q(p)) of leaf disks punched from oak leaves of seedlings
grown in ambient (350 mumol mol-1) or elevated (700 mumol mol- 1) CO2 in a greenhouse, and
from sunlit leaves of mature oak trees (Quercus petraea (Matt.) Liebl.). There were marked
differences between seedlings and trees. In seedlings, CO2 concentration during growth did not
modify the light response of photosynthesis or PS II activity. There was a single linear relationship
between PHI(O2) and DELTAF/F(m)' in seedling leaves that was independent of the CO2
concentration imposed during growth. In contrast, this relationship was curvilinear in sunlit leaves
of adult trees. In seedling leaves, the decrease in q(p) (i.e., the proportion of open PS II reaction
centers) largely accounted for the decrease in DELTAF/F(m)', whereas the decrease in
DELTAF/F(m)' in sunlit leaves of mature oak trees was dependent on both q(p) and F(v)'/F(m)'.



     617  
Epron, D., D. Godard, G. Cornic, and B. Genty. 1995. Limitation of net co2 assimilation rate by
internal resistances to co2 transfer in the leaves of 2 tree species (fagus- sylvatica L and castanea-
sativa mill). Plant, Cell and Environment 18(1):43-51.

Using a combination of gas-exchange and chlorophyll fluorescence measurements, low apparent
CO2/O-2 specificity factors (1300 mol mol(-1)) were estimated for the leaves of two deciduous tree
species (Fagus sylvatica and Castanea sativa), These low values contrasted with those estimated for
two herbaceous species and were ascribed to a drop in the CO2 mole fraction between the
intercellular airspace (C-i) and the catalytic site of Rubisco (C-c) due to internal resistances to CO2
transfer, C-c was calculated assuming a specificity of Rubisco value of 2560 mol mol(-1). The drop
between C-i and C-c was used to calculate the internal conductance for CO2 (g(i)), A good
correlation between mean values of net CO2 assimilation rate (A) and g(i) was observed within a set
of data obtained using 13 woody plant species, including our own data, We report that the relative
limitation of A, which can be ascribed to internal resistances to CO2 transfer, was 24-30%, High
internal resistances to CO2 transfer may explain the low apparent maximal rates of carboxylation and
electron transport of some woody plant species calculated from A/C-i curves.

KEYWORDS: CHLOROPHYLL FLUORESCENCE, ELEVATED CO2, GAS-EXCHANGE,
MESOPHYLL CONDUCTANCE, PHOTOSYNTHETIC ELECTRON-TRANSPORT, PLANTS,
RESPIRATION, RIBULOSE-1;5-BISPHOSPHATE CARBOXYLASE-OXYGENASE, SPECIFICITY
FACTOR, STOMATAL CONDUCTANCE


     618  
Epron, D., R. Liozon, and M. Mousseau. 1996. Effects of elevated CO2 concentration on leaf
characteristics and photosynthetic capacity of beech (Fagus sylvatica) during the growing season.
Tree Physiology 16(4):425-432.

Two-year-old beech (Fagus sylvatica L.) saplings were planted directly in the ground at high density
(100 per m(2)), in an experimental design that realistically mimicked field conditions, and grown for
two years in air containing CO2 at either ambient or an elevated (ambient + 350 ppm) concentration.
Plant dry mass and leaf area were increased by a two-year exposure to elevated CO2. The saplings
produced physiologically distinct types of sun leaves associated with the first and second growth
flushes. Leaves of the second flush had a higher leaf mass per unit area and less chlorophyll per unit
area, per unit dry mass and per unit nitrogen than leaves of the first flush. Chlorophyll content
expressed per unit nitrogen decreased over time in plants grown in elevated CO2, which suggests
that, in elevated CO2, less nitrogen was invested in machinery of the photosynthetic light reactions.
In early summer, the photosynthetic capacity measured at saturating irradiance and CO2 was slightly
but not significantly higher in saplings grown in elevated CO2 than in saplings grown in ambient CO2.
However, a decrease in photosynthetic capacity was observed after July in leaves of saplings grown
in CO2-enriched air. The results demonstrate that photosynthetic acclimation to elevated CO2 can
occur in field-grown saplings in late summer, at the time of growth cessation.

KEYWORDS: ACCLIMATION, CARBON DIOXIDE, CHLOROPHYLL, ENRICHMENT, GAS-
EXCHANGE, GROWTH, LEAVES, RESPONSES, SEEDLINGS, SHADE PLANTS


     619  
Erhardt, A., and H.P. Rusterholz. 1997. Effects of elevated CO2 on flowering phenology and
nectar production. Acta Oecologica-International Journal of Ecology 18(3):249-253.

Effects of elevated CO2 on flowering phenology and nectar production were studied in five important
nectar plants of calcareous grasslands, i.e. Lotus corniculatus, Trifolium pratense, Betonica officinalis,
Scabiosa columbaria ia and Centaurea jacea. Glasshouse experiments showed that flowering
probability was significantly enhanced in C. jacea. B. officinalis flowered earlier and L. corniculatus
produced more flowers under elevated CO2. In contrast, the number of flowers decreased in T.
pratense. The amount of nectar produced per flower was not affected in the investigated legumes (T.
pratense, L. corniculatus), but was significantly reduced in the other forbs. Elevated CO2 did not
significantly affect nectarsugar concentration and sugar composition. However, S. columbaria and
C: jacea produced significantly less total sugar per flower under elevated CO2. The nectar amino acid
concentration remained unaffected in all investigated plant species whereas the total of amino acids
produced per flower was significantly reduced in all nan-legumes. In addition, the amino acid
composition changed significantly in all investigated species except for C. jacea. The observed effects
are unexpected and are a potential threat to flower visitors such as most butterflies which have no
alternative food resources except nectar. Changes in nectar production due to elevated CO2 could
also generally have detrimental effects on the interactions of flowers and their pollinators.



     620  
Erickson, D.J. 1999. Nitrogen deposition, terrestrial carbon uptake and changes in the seasonal cycle
of atmospheric CO2. Geophysical Research Letters 26(21):3313-3316.

Observational evidence indicates an increasing trend in the amplitude of the seasonal cycle of
atmospheric CO2 over the last several decades. Here, the influence of nitrogen deposition on the
seasonal cycle of atmospheric CO2 is investigated using a global carbon cycle model embedded in a
3- D general circulation model. We employ a recently published estimate of the enhancement of
carbon dioxide uptake induced by the atmospheric deposition of NOy and NHx. We partition the
carbon sink related to nitrogen deposition over the seasonal cycle of CO2 uptake. The modeled
increase in the amplitude of the seasonal cycle of CO2 in the Northern Hemisphere related to the
simulated nitrogen deposition alone is 25%-50% of observed. At Mauna Loa the increased amplitude
in the CO2 seasonal cycle due to nitrogen deposition is 50-90% of that observed. The subtle
interaction between 3-D atmospheric transport, atmospheric nitrogen deposition, and seasonal CO2
uptake results in significant changes in the amplitude of the seasonal cycle of atmospheric CO2. The
magnitude of these nitrogen deposition-induced changes in the atmospheric behavior of CO2 is
comparable to other processes that are thought to influence global carbon cycle dynamics.

KEYWORDS: DIOXIDE, EXCHANGE, GROWTH, MODEL, SINK


     621  
Ericsson, T. 1995. Growth and shoot - root ratio of seedlings in relation to nutrient availability. Plant
and Soil 169:205-214.

The influence of mineral nutrient availability, light intensity and CO2 on growth and shoot:root ratio
in young plants is reviewed. Special emphasis in this evaluation is given to data from laboratory
experiments with small Betula pendula plants, in which the concept of steady-state nutrition has been
applied. Three distinctly different dry matter allocation patterns were observed when growth was
limited by the availability of mineral nutrients: 1, Root growth was favoured when N, P or S were the
major growth constraints. 2, The opposite pattern obtained when K, Mg and Mn restricted growth.
3, Shortage of Ca, Fe and Zn had almost no effect on the shoot:root ratio. The light regime had no
effect on dry matter allocation except at very low photon flux densities (< 6.5 mol m(-2) day(-1)),
in which a small decrease in the root fraction was observed. Shortage of CO2 on the other hand,
strongly decreased root development, while an increase of the atmospheric CO2 concentration had
no influence on dry matter partitioning. An increased allocation of dry matter to below- ground parts
was associated with an increased amount of starch in the tissues. Depletion of the carbohydrate stores
occurred under all conditions in which root development was inhibited. It is concluded that the
internal balance between labile nitrogen and carbon in the root and the shoot system determines how
dry matter is being partitioned in the plant. The consistency of this statement with literature data and
existing models for shoot:root regulation is examined.

KEYWORDS: ASSIMILATION, BETULA-PENDULA ROTH, BIRCH SEEDLINGS, ELEVATED
CO2, NITROGEN STRESS, PHOTON FLUX- DENSITY, PHOTOSYNTHESIS, PLANT
NUTRITION, TRANSLOCATION, WHEAT TRITICUM- AESTIVUM


     622  
Ershova, A.N., and V.A. Khripach. 1996. Effect of epibrassinolide on lipid peroxidation in Pisum
sativum at normal aeration and under oxygen deficiency. Russian Journal of Plant Physiology
43(6):750-752.

The effect of epibrassinolide on oxidative lipid degradation in pea seedlings was studied at normal
aeration and in oxygen- deprived and CO2-enriched media. The content of various products of lipid
peroxidation (POL), including the primary derivatives (conjugated dienoic acids) and end products
(malonyl dialdehyde, MDA), was shown to decrease in seedlings treated with epibrassinolide (10
mg/l). Epibrassinolide inhibited POL in pea seedlings more strongly than kinetin. These effects
became even more pronounced in plants under hypoxia or in the CO2-enriched medium. The content
of conjugated dienes declined by 13 and 21% at hypoxia and in the CO2-medium compared to their
content in air-grown seedlings, whereas the content of MDA was 38 and 26% below the level in the
untreated plants, respectively. We presume that as a protector, epibrassinolide can inhibit the
oxidative degradation of lipids in biological membranes and prevent the disruption of membrane
structures. Thus it increases the tolerance of plants to deleterious factors.



     623  
Esler, K.J., P.W. Rundel, and P. Vorster. 1999. Biogeography of prostrate-leaved geophytes in
semi-arid South Africa: hypotheses on functionality. Plant Ecology 142(1-2):105-120.

Nowhere is the species diversity of geophytes greater than in the five mediterranean-climate
ecosystems of the world. Of these, the Cape mediterranean zone of South Africa is the most speciose.
While the relative diversity and importance of geophytes of all of the other four mediterranean regions
of the world drops off sharply as one moves into adjacent winter- rainfall desert regions, geophytes
in the semi-arid to arid Succulent Karoo (including Namaqualand) remain a very important
component of the flora, both in terms of abundance and diversity (comprising 13 to 29% of the
regional floras in this region). Apart from species richness, there are also a number of interesting
geophyte growth forms in this region. One unusual growth form is geophytes with flattened leaves
that lie prostrate on the soil surface. At least eight families (Amaryllidaceae, Colchicaceae,
Eriospermaceae, Geraniaceae, Hyacinthaceae, Iridaceae, Orchidaceae and Oxalidaceae) exhibit this
growth form. While this growth form is relatively common in many geophyte lineages in the
Succulent Karoo biome and the Cape mediterranean zone (Fynbos biome), and occurs infrequently
through the summer-rainfall temperate regions of Africa, it is virtually absent in other regions
worldwide. A null hypothesis is that the prostrate leaved trait is a neutral characteristic, however
biogeographical data do not support this. A neutral trait would be unlikely to show such a clear
pattern of distribution. Several alternative hypotheses on the adaptive significance of this growth form
are discussed. These include: avoidance of herbivory, reduction in competition from neighbors,
creation of a CO2 enriched environment below the leaves, reduction of water loss around the roots,
reduction of water loss through transpiration, precipitation of dew on the leaves and maintenance of
optimal leaf temperatures for growth.

KEYWORDS: ALLOCATION, BIOMASS, FLORA, LOWLAND COASTAL FYNBOS, SUBSPECIES
PUBESCENS


     624  
Estiarte, M., J. Penuelas, B.A. Kimball, D.L. Hendrix, P.J. Pinter, G.W. Wall, R.L. LaMorte,
and D.J. Hunsaker. 1999. Free-air CO2 enrichment of wheat: leaf flavonoid concentration
throughout the growth cycle. Physiologia Plantarum 105(3):423-433.

To test the predictions that plants will have a larger flavonoid concentration in a future world with
a CO2-enriched atmosphere, wheat (Triticum aestivum L. cv. Yecora Rojo) was grown in a field
experiment using FACE (free-air CO2 enrichment) technology under two levels of atmospheric CO2
concentration: ambient (370 pmol mol(-1)) and enriched (550 pmol mol(-1)), and under two levels
of irrigation: well-watered (100% replacement of potential evapotranspiration) and half- watered. We
also studied the effects of CO2 on the concentration of total non-structural carbohydrates (TNC) and
nitrogen (N), two parameters hypothesized to be linked to flavonoid metabolism. Throughout the
growth cycle the concentration of isoorientin, the most abundant flavonoid, decreased by 62% (from
an average of 12.5 mg g(-1) on day of year (DOY) 41 to an average of 4.8 mg g(-1) on DOY 123),
whereas the concentration of tricin, another characteristic flavone, increased by two orders of
magnitude (from an average of 0.007 mg g(-1) of isoorientin equivalents on DOY 41 to an average
of 0.6 mg g(-1) of isoorientin equivalents on DIOY 123). Although flavonoid concentration was
dependent on growth stage, the effects of treatments on phenology did not invalidate the comparisons
between treatments. CO2-enriched plants had higher flavonoid concentrations (14% more isoorientin,
an average of 7.0 mg g(-1) for ambient CO2 vs an average of 8.0 mg g(-1) for enriched CO2), higher
TNC concentrations and lower N concentrations in upper canopy leaves throughout the growth cycle.
Well-irrigated plants had higher flavonoid concentrations (11% more isoorientin, an average of 7.1
mg g(-1) for half watered vs an average of 7.9 mg g(-1) for well-watered) throughout the growth
cycle, whereas the effect of irrigation treatments on TNC and N was more variable. These results are
in accordance with the hypotheses that higher carbon availability promoted by CO2-enrichment
provides carbon that can be invested in carbon-based secondary compounds such as flavonoids. The
rise in atmospheric CO2 may thus indirectly affect wheat-pest relations, alter the pathogen
predisposition and improve the UV-B protection by changing flavonoid concentrations.

KEYWORDS: ATMOSPHERIC CARBON-DIOXIDE, CHEMICAL-COMPOSITION, ELEVATED
CO2, LEAVES, N-AVAILABILITY, NITROGEN, NUTRIENT BALANCE, SOURCE-SINK
RELATIONS, UV-B, WATER-USE


     625  
Estiarte, M., J. Penuelas, B.A. Kimball, S.B. Idso, R.L. Lamorte, P.J. Pinter, G.W. Wall, and
R.L. Garcia. 1994. Elevated co2 effects on stomatal density of wheat and sour orange trees. Journal
of Experimental Botany 45(280):1665-1668.

No significant differences were found in stomatal densities or stomatal indices of wheat or sour
orange trees grown at high CO2 concentrations in two different CO2 enrichment systems (Free-Air
CO2 enrichment for wheat and Open-Top Chambers for orange trees). These results are in
accordance with most of the previous results obtained in short-term experimental studies which
suggest that plants do not acclimate to increasing CO2 concentration by changing stomatal density
within a single generation.

KEYWORDS: ANATOMY, ENRICHMENT, GROWTH


     626  
Ewert, F., and H. Pleijel. 1999. Phenological development, leaf emergence, tillering and leaf area
index, and duration of spring wheat across Europe in response to CO2 and ozone. European Journal
of Agronomy 10(3-4):171-184.

Phenological development, leaf emergence, tillering and leaf area index (LAI), and duration (LAD)
of spring wheat cv. Minaret, grown in open-top chambers at different sites throughout Europe for
up to 3 years at each site, were investigated in response to elevated CO2 (ambient CO2 x2) and
ozone (ambient ozone x1.5) concentrations. Phenological development varied among experiments
and was partly explained by differences in temperature among sites and years. There was a weak
positive relationship between the thermal rate of development and the mean daylength for the period
from emergence to anthesis. Main stems produced on average 7.7 leaves with little variation among
experiments. Variation was higher for the thermal rate of leaf emergence, which was partly explained
by differences in the rate of change of daylength at plant emergence among seasons. Phenological
development, rate of leaf emergence and final leaf number were not affected by CO2 and ozone
exposure. Responses of tillering and LAI to CO2 and ozone exposure were significant only in some
experiments. However, the direction of responses was consistent for most experiments. The number
of tillers and ears per plant, respectively, was increased as a result of CO2 enrichment by about 13%
at the beginning of stem elongation (DC31), at anthesis and at maturity. Exposure to ozone had no
effect on tillering. LAI was increased as a result of CO2 elevation by about 11% at DC31 and by
about 14% at anthesis. Ozone exposure reduced LAI at anthesis by about 9%. No such effect was
observed at DC31. There were very few interactive effects of CO2 and ozone on tillering and LAI.
Variations in tillering and LAI, and their responses to CO2 and ozone exposure, were partly explained
by single linear relationships considering differences in plant density, tiller density and the duration
of developmental phases among experiments. Consideration of temperature and incident
photosynthetically active radiation in this analysis did not reduce the unexplained variation. There was
a negative effect of ozone exposure on leaf area duration at most sites. Direct effects of elevated CO2
concentration on leaf senescence, both positive and negative, were observed in some experiments.
There was evidence in several experiments that elevated CO2 concentration ameliorated the negative
effect of ozone on leaf area duration. It was concluded from these results that an analysis of the
interactive effects of climate, CO2 and ozone on canopy development requires reference to the
physiological processes involved. (C) 1999 Elsevier Science B.V. All rights reserved.

KEYWORDS: CARBON-DIOXIDE ENRICHMENT, CROPS, ELEVATED CO2, GRAIN QUALITY,
GROWTH, TEMPERATURE, TOP FIELD CHAMBERS, TRITICUM-AESTIVUM L, WINTER-
WHEAT, YIELD COMPONENTS


     627  
Ewert, F., M. van Oijen, and J.R. Porter. 1999. Simulation of growth and development processes
of spring wheat in response to CO2 and ozone for different sites and years in Europe using
mechanistic crop simulation models. European Journal of Agronomy 10(3-4):231-247.

The response of crop growth and yield to CO2 and ozone is known to depend on climatic conditions
and is difficult to quantify due to the complexity of the processes involved. Two modified mechanistic
crop simulation models (AFRCWHEAT2-O3 and LINTULCC), which differ in the levels of
mechanistic detail, were used to simulate the effects of CO2 (ambient, ambient x2) and ozone
(ambient, ambient x1.5) on growth and developmental processes of spring wheat in response to
climatic conditions. Simulations were analysed using data from the ESPACE-wheat project in which
spring wheat cv. Minaret was grown in open-top chambers at nine sites throughout Europe and for
up to 3 years at each site. Both models closely predicted phenological development and the average
measured biomass at maturity. However, intermediate growth variables such as biomass and leaf area
index (LAI) at anthesis, seasonal accumulated photosynthetically active radiation intercepted by the
crop (Sigma IPAR), the average seasonal light use efficiency (LUE) and the light saturated rate of
flag leaf photosynthesis (A(sat)) were predicted differently and less accurately by the two models. The
effect of CO2 on the final biomass was underestimated by AFRCWHEAT2-O3 due to its poor
simulation of the effect of CO2 on tillering, and LAI.LINTULCC overestimated the response of
biomass production to changes in CO2 level due to an overprediction of the effect of CO2 on LUE.
The measured effect of ozone exposure on final biomass was predicted closely by the two models.
The models also simulated the observed interactive effect of CO2 and ozone on biomass production.
However, the effects of ozone on LAI, Sigma IPAR and A(sat) were simulated differently by the
models and less accurately with LINTULCC for the ozone effects on LAI and Sigma IPAR.
Predictions of the variation between sites and years of growth and development parameters and of
their responses to CO2 and ozone were poor for both AFRCWHEAT2-O3 and LINTULCC. It was
concluded that other factors than those considered in the models such as chamber design and soil
properties may have affected the growth and development of cv. Minaret. An analysis of the
relationships between growth parameters calculated from the simulations supported this conclusion.
In order to apply models for global change impact assessment studies, the difficulties in simulating
biomass production in response to CO2 need to be considered. We suggest that the simulation of leaf
area dynamics deserves particular attention in this regard. (C) 1999 Elsevier Science B.V. All rights
reserved.

KEYWORDS: AIR, CLIMATE, EXPOSURE, OPEN-TOP CHAMBERS, PHOTOSYNTHESIS,
PLANTS, PRODUCTIVITY, TRITICUM-AESTIVUM, WINTER-WHEAT, YIELD


     628  
Fajer, E.D. 1989. The effects of enriched CO2 atmospheres on plant-insect herbivore interactions-
growth-responses of larvae of the specialist butterfly, Junonia coenia (lepidoptera, nymphalidae).
Oecologia 81(4):514-520.



     629  
Fajer, E.D., M.D. Bowers, and F.A. Bazzaz. 1991. The effects of enriched CO2 atmospheres on
the buckeye butterfly, Junonia coenia. Ecology 72(2):751-754.

KEYWORDS: CARBON-DIOXIDE ATMOSPHERES, CLIMATE, LEPIDOPTERA, NOCTUIDAE


     630  
Fajer, E.D., M.D. Bowers, and F.A. Bazzaz. 1991. Performance and allocation patterns of the
perennial herb, Plantago lanceolata, in response to simulated herbivory and elevated CO2
environments. Oecologia 87(1):37-42.

We tested the prediction that plants grown in elevated CO2 environments are better able to
compensate for biomass lost to herbivory than plants grown in ambient CO2 environments. The
herbaceous perennial Plantago lanceolata (Plantaginaceae) was grown in either near ambient (380
ppm) or enriched (700 ppm) CO2 atmospheres, and then after 4 weeks, plants experienced either 1)
no defoliation; 2) every fourth leaf removed by cutting; or 3) every other leaf removed by cutting.
Plants were harvested at week 13 (9 weeks after simulated herbivory treatments). Vegetative and
reproductive weights were compared, and seeds were counted, weighed, and germinated to assess
viability. Plants grown in enriched CO2 environments had significantly greater shoot weights, leaf
areas, and root weights, yet had significantly lower reproductive weights (i.e. stalks + spikes + seeds)
and produced fewer seeds, than plants grown in ambient CO2 environments. Relative biomass
allocation patterns further illustrated differences in plant responses to enriched CO2 atmospheres:
enriched CO2-grown plants only allocated 10% of their carbon resources to reproduction whereas
ambient CO2-grown plants allocated over 20%. Effects of simulated herbivory on plant performance
were much less dramatic than those induced by enriched CO2 atmospheres. Leaf area removal did
not reduce shoot weights or reproductive weights of plants in either CO2 treatment relative to control
plants. However, plants from both CO2 treatments experienced reductions in root weights with leaf
area removal, indicating that plants compensated for lost above-ground tissues, and maintained
comparable levels of reproductive output and seed viability, at the expense of root growth.

KEYWORDS: GROWTH


     631  
Fajer, E.D., M.D. Bowers, and F.A. Bazzaz. 1992. The effect of nutrients and enriched co2
environments on production of carbon-based allelochemicals in plantago - a test of the carbon nutrient
balance hypothesis. The American Naturalist 140(4):707-723.

In a test of the carbon/nutrient (C/N) balance hypothesis, we grew the perennial herb Plantago
lanceolata in different CO2 and nutrient environments and then (1) measured the total allocation to
shoots, roots, and reproductive parts and (2) quantified aucubin, catalpol, and verbascoside contents
of replicate plants of six genotypes. Plants grown under low- nutrient conditions do have higher
concentrations of carbon- based allelochemicals than plants grown under high-nutrient conditions.
However, in contrast to the C/N balance hypothesis, plants grown in elevated (700-mu-L.L-1) CO2
conditions had similar, or lower, concentrations of carbon-based allelochemicals than plants grown
in ambient (350-mu-L.L-1) CO2 conditions. We suggest that augmented substrate concentrations
(i.e., excess carbohydrates) are a necessary but insufficient trigger for increased secondary
metabolism; instead, hormonal and/or direct physical cues (such as light) may be essential to
synthesize or activate the appropriate enzyme systems. Moreover, although plant genotype
significantly affected plant growth, reproduction, and chemistry, we never observed significant
genotype-by-CO2 interactions for these factors, which suggests that changing CO2 environments may
not improve the fitness of certain genotypes over others.

KEYWORDS: CHEMICAL DEFENSE, DIOXIDE ATMOSPHERES, EXPERIMENTAL
ECOLOGICAL GENETICS, HETEROTHECA-SUBAXILLARIS, INSECT HERBIVORE
INTERACTIONS, JUNONIA-COENIA, LANCEOLATA L, LIMITING CONDITIONS,
REPRODUCTIVE EFFORT, VOLATILE LEAF TERPENES


     632  
Falge, E., R.J. Ryel, M. Alsheimer, and J.D. Tenhunen. 1997. Effects of stand structure and
physiology on forest gas exchange: a simulation study for Norway spruce. Trees-Structure and
Function 11(7):436-448.

The process-based simulation model STAND-FLUX describes canopy water vapor and carbon
dioxide exchange based on rates calculated for individual trees and as affected by local gradients in
photon flux density (PFD), atmospheric humidity, atmospheric carbon dioxide concentration, and air
temperature. Direct, diffuse, and reflected PFD incident on foliage elements within compartments of
individual trees (defined by vertical layers and a series of concentric cylinders centered on the trunk)
is calculated for a 3-dimensional matrix of points. Foliage element gas exchange rates are based on
estimates of carboxylation, RuBP regeneration, and respiratory capacities as well as the correlated
behavior found between stomatal conductance and assimilation rate. Because of the difficulties
associated with effective sampling and description of spatial variation in structure and leaf level gas
exchange parameters for trees comprising the forest canopy, the significance for canopy water and
carbon dioxide exchange of varied representations of tree foliage distribution and of physiology is
examined. The additional interactive effects encountered due to changes in tree density and, thus,
spatial aggregation or disaggregation of foliage is also studied. The analysis is conducted within the
context of observed structural and physiological variation encountered in Norway spruce (Picea
abies) stands in the Fichtelgebirge region of central Germany. Potentials for simplifying the three-
dimensional canopy gas exchange model without sizable influence on canopy flux rates were small.
A relatively large number of sample points within the tree crowns is necessary to obtain consistent
calculations of flux rates because of the nonlinear relationship between PFD and net photosynthesis.
Transpiration and net photosynthesis for stands with a low leaf area index (LAI) may be obtained
from single tree estimates for each tree class weighted by class frequency, while 30 or more trees per
class in differing relation to neighboring trees may be necessary to calculate reliable estimates of net
photosynthesis in canopies with high LAI. The complexity in structure assumed for modeled trees was
important, especially when overall canopy foliage area was either high or low due to spatial
heterogeneity in clumping, e.g., potential canopy overlaps or side-lighting. Effects were greater for
calculated net photosynthesis than for transpiration, reflecting higher sensitivity of net photosynthesis
to differences in light distribution within individual trees. Accuracy in estimates of physiological
parameters is equally important, and these characteristics have profound effects on estimated canopy
gas exchange rates. While one-dimensional representations of canopy structure or approximations
of tree physiological characteristics from other canopies or species may often be necessary in
assessing vegetation/atmosphere exchanges, especially in the study of water balance of landscapes
or regions, STANDFLUX provides a tool that can aid in evaluating the limitations of these simpler
approaches.

KEYWORDS: CANOPY, CONDUCTANCE, DECIDUOUS FOREST, ELEVATED CO2, LEAF,
MODEL, PHOTOSYNTHESIS, SCALING CARBON-DIOXIDE, TUSSOCK GRASSES, WATER-
VAPOR EXCHANGE


     633  
Falloon, P.D., P. Smith, J.U. Smith, J. Szabo, K. Coleman, and S. Marshall. 1998. Regional
estimates of carbon sequestration potential: linking the Rothamsted Carbon Model to GIS databases.
Biology and Fertility of Soils 27(3):236-241.

Soil organic matter (SOM) represents a major pool of carbon within the biosphere. It is estimated at
about 1400 Pg globally, which is roughly twice that in atmospheric CO2. The soil can act as both a
source and a sink for carbon and nutrients, Changes in agricultural land use and climate can lead to
changes in the amount of carbon held in soils, thus, affecting the fluxes of CO2 to and from the
atmosphere. Some agricultural management practices will lead to a net sequestration of carbon in the
soil. Regional estimates of the carbon sequestration potential of these practices are crucial if policy
makers are to plan future land uses to reduce national CO, emissions. In Europe, carbon sequestration
potential has previously been estimated using data from the Global Change and Terrestrial
Ecosystems Soil Organic Matter Network (GCTE SOMNET). Linear relationships between
management practices and yearly changes in soil organic carbon were developed and used to estimate
changes in the total carbon stock of European soils. To refine these semi-quantitative estimates, the
local soil type, meteorological conditions and land use must also be taken into account. To this end,
we have modified the Rothamsted Carbon Model, so that it can be used in a predictive manner. with
SOMNET data. The data is then adjusted for local conditions using Geographical Information
Systems databases. In this paper, we describe how these developments call be used to estimate carbon
sequestration at the regional level using a dynamic simulation model linked to spatially explicit data.
Some calculations of the potential effects of afforestation on soil carbon stocks in Central Hungary
provide a simple example of the system in use.

KEYWORDS: CLIMATE, CO2, SOILS, STORAGE


     634  
Fangmeier, A., L. De Temmerman, L. Mortensen, K. Kemp, J. Burke, R. Mitchell, M. van
Oijen, and H.J. Weigel. 1999. Effects on nutrients and on grain quality in spring wheat crops grown
under elevated CO2 concentrations and stress conditions in the European, multiple-site experiment
'ESPACE-wheat'. European Journal of Agronomy 10(3-4):215-229.

Nutrient element concentrations and grain quality were assessed in spring wheat grown under
elevated CO2 concentrations and contrasting levels of tropospheric ozone at different nitrogen supply
rates at several European sites. Carbon dioxide enrichment proved to affect nutrient concentrations
in a complex manner, In green leaves, all elements (with exception of phosphorus and iron)
decreased. In contrast, effects on the element composition of grains were restricted to reductions in
nitrogen, calcium, sulphur and iron. Ozone exposure resulted in no significant effects on nutrient
element concentrations in different tissues in the overall analysis. The nitrogen demand of green
tissues was reduced due to CO2 enrichment as shown by reductions in the critical leaf nitrogen
concentration and also enhanced nitrogen use efficiency. Reductions in the content of ribulose-
bisphosphate carboxylase/oxygenase and repression of the photorespiratory pathway and reduced
nitrogen allocation to enzymes driving the photosynthetic carbon oxidation cycle were chiefly
responsible for this effect. Thus, nitrogen acquisition by the crop did not match carbon acquisition
under CO2 enrichment, Since crop nitrogen uptake from the soil was already completed at anthesis,
nitrogen allocated to the grain after anthesis originated from vegetative poors-causing grain nitrogen
concentrations to decrease under CO2 enrichment (on average by 15% when CO2 concentrations
increased from 360 to 680 mu mol mol(-1)). Correspondingly, grain quality was reduced by CO2
enrichment. The Zeleny value, Hagberg value and dry/wet gluten content decreased significantly with
increasing [CO2]. Despite the beneficial impact of CO2 enrichment on growth and yield of C-3 cereal
crops, declines in flour quality due to reduced nitrogen content are likely in a future, [CO2]-rich
world. (C) 1999 Elsevier Science B.V. All rights reserved.

KEYWORDS: AMBIENT AIR, CLIMATE CHANGE, LITTER QUALITY, MINERAL NUTRITION,
NORWAY SPRUCE, RISING ATMOSPHERIC CO2, SPRUCE PICEA-ABIES, TOP FIELD
CHAMBERS, TRITICUM-AESTIVUM L, TROPOSPHERIC OZONE


     635  
Fangmeier, A., U. Gruters, U. Hertstein, A. SandhageHofmann, B. Vermehren, and H.J. Jager.
1996. Effects of elevated CO2, nitrogen supply and tropospheric ozone on spring wheat .1. Growth
and yield. Environmental Pollution 91(3):381-390.

Spring wheat (Triticum aestivum L. cv. Minaret) was exposed to three CO2 levels, in combination
with two nitrogen fertilizer levels and two levels of tropospheric ozone, from sowing to ripening in
open-top chambers. Three additional nitrogen fertilizer treatments were carried out at the lowest and
the highest CO2 level, respectively. Plants were harvested at growth stages 31, 65 and 93 and
separated into up to eight fractions to gain information about biomass partitioning. CO2 enrichment
(263 mu l litre(-1) above ambient levels) drastically increased biomass of organs serving as long-term
carbohydrate pools. Peduncle weight increased by 92%, stem weight by 73% and flag leaf sheath
weight by 59% at growth stage 65. Average increase in shoot biomass due to CO2 enrichment
amounted to 51% at growth stage 65 and 36% at final harvest. Average yield increase was 34%.
Elevated nitrogen application was most effective on biomass of green tissues. Yield was increased
by 30% when nitrogen application was increased from 150 to 270 kg N ha(-1). Significant
interactions were observed between CO2 enrichment and nitrogen application. Yield increase due to
CO2 ranged from 23% at 120 kg N to 47% at 330 kg N. Triticum aestivum cv. Minaret was not very
responsive to ozone at 1.5 times ambient levels. 1000 grain weight was slightly decreased, which was
compensated by an increased number of grains.

KEYWORDS: CARBOHYDRATE, CARBON DIOXIDE, DRY-MATTER, NUTRITION,
RESPONSES, STEMS, STORAGE, STRESS, TEMPERATURE, WINTER-WHEAT


     636  
Fangmeier, A., U. Gruters, P. Hogy, B. Vermehren, and H.J. Jager. 1997. Effects of elevated
CO2 nitrogen supply and tropospheric ozone on spring wheat .2. Nutrients (N, P, K, S, Ca, Mg, Fe,
Mn, Zn). Environmental Pollution 96(1):43-59.

CO2 enrichment is expected to alter leaf demand for nitrogen and phosphorus in plant species with
C-3 carbon dioxide fixation pathway, thus possibly causing nutrient imbalances in the tissues and
disturbance of distribution and redistribution patterns within the plants. To test the influence of CO2
enrichment and elevated tropospheric ozone in combination with different nitrogen supply, spring
wheat (Tritium aestivum L. cv. Minaret) was exposed to three levels of CO2 (361, 523, and 639 mu
l liter(-1), 24 h mean from sowing to final harvest), two levels of ozone (28.4 and 51.3 nl litre(-1))
and two levels of nitrogen supply (150 and 270 kg ha(-1)) in a full-factorial design in open-top field
chambers. Additional fertilization experiments (120, 210, and 330 kg N ha(-1)) were carried out at
low and high CO2 levels. Macronutrients (N, P, K, S, Ca, Mg) and three micronutrients (Mn, Fe, Zn)
were analysed in samples obtained at three different developmental stages: beginning of shoot
elongation, anthesis, and ripening. At each harvest, plant samples were separated into different organs
(green and senescent leaves, stem sections, ears, grains). According to analyses of tissue
concentrations at the beginning of shoot elongation, the plants were sufficiently equipped with
nutrients. Elevated ozone levels neither affected tissue concentrations nor shoot uptake of the
nutrients. CO2 and nitrogen treatments affected nutrient uptake, distribution and redistribution in a
complex manner. CO2 enrichment increased nitrogen-use efficiency and caused a lower demand for
nitrogen in green tissues which was reflected in a decrease of critical nitrogen concentrations, lower
leaf nitrogen concentrations and lower nitrogen pools in the leaves. Since grain nitrogen uptake
during grain filling depended completely on redistribution from vegetative pools in green tissues, grain
nitrogen concentrations fell considerably with severe implications for grain quality. Ca, S, Mg and
Zn in green tissues were influenced by CO2 enrichment in a similar manner to nitrogen. Phosphorus
concentrations in green tissues, on the other hand, were not, or only slightly, affected by elevated
CO2. In stems, 'dilution' of all nutrients except manganese was observed, caused by the huge
accumulation of water soluble carbohydrates, mainly fructans, in these tissues under CO2 enrichment.
Whole shoot uptake was either remarkably increased (K, Mn, P, Mg), nearly unaffected (N, S, Fe,
Zn) or decreased (Ca) under CO2 enrichment. Thus, nutrient cycling in plant-soil systems is expected
to be altered under CO2 enrichment. (C) 1997 Elsevier Science Ltd.

KEYWORDS: ACCLIMATION, ATMOSPHERIC CO2, CARBOHYDRATE, CARBON DIOXIDE,
GROWTH-RESPONSE, MINERAL NUTRITION, PHOTOSYNTHESIS, SOURCE-SINK
RELATIONS, STRESS, VEGETATION


     637  
Fangmeier, A., U. Gruters, B. Vermehren, and H.J. Jager. 1996. Responses of some cereal
cultivars to CO2 enrichment and tropospheric ozone at different levels of nitrogen supply. Journal
of Applied Botany-Angewandte Botanik 70(1-2):12-18.

Two cultivars of spring wheat (Triticum aestivum L. cv. 'Nandu' and cv. 'Minaret') and one cultivar
of spring barley (Hordeum vulgare L. cv. 'Alexis') were exposed to CO2 enrichment (concentrations
ranging from 363 to 650 mu l l(-1)), ozone (ambient and 1.7 times ambient levels) at different levels
of nitrogen nutrition in open-top field chambers from sowing to maturity. CO2 increased grain yield
and shoot biomass, barley showing the smallest response and wheat 'Nandu' being most responsive.
The cultivars were rather insensitive to ozone, however, a decrease of thousand grain weight was
observed in one of the wheat cultivars ('Minaret') at high ozone levels. In this cultivar, interactions
between CO2 and ozone were observed. Elevated CO2 appeared to be protective against impairments
caused by ozone. CO2 and nitrogen supply strongly interacted. CO2 fertilizing effects on grain yield
of wheat 'Minaret' ranged from 22.9 % at 120 kg N ha(-1) to 47.4 % at 330 kg N ha(-1). Increase
in grain yield by CO2 was accompanied with a decrease of grain nitrogen content. Grain yield
increase and grain nitrogen content depression exactly compensated each other and led to constant
amounts of nitrogen stored in the grains on an area unit basis independent from the applied CO2
concentration. The grain quality, assessed as nitrogen content, was severely decreased by CO2
enrichment. The regressions obtained from the data suggest that nearly twice the nitrogen supply will
be required to maintain the nitrogen content in grains at the same level if CO2 concentrations rise
from the current 363 mu l l(-1) (seasonal mean 1994) to 650 mu l l(-1).

KEYWORDS: CARBON DIOXIDE, ELEVATED CO2, GROWTH, OPEN-AIR FUMIGATION,
PHOTOSYNTHESIS, TOP FIELD CHAMBERS, TRITICUM-AESTIVUM L, VEGETATION,
WINTER-WHEAT, YIELD


     638  
Farage, P.K., I.F. McKee, and S.P. Long. 1998. Does a low nitrogen supply necessarily lead to
acclimation of photosynthesis to elevated CO2? Plant Physiology 118(2):573-580.

Long-term exposure of plants to elevated partial pressures of CO, (pCO(2)) often depresses
photosynthetic capacity. The mechanistic basis for this photosynthetic acclimation may involve
accumulation of carbohydrate and may be promoted by nutrient limitation. However, our current
knowledge is inadequate for making reliable predictions concerning the onset and extent of
acclimation. Many studies have sought to investigate the effects of N supply but the methodologies
used generally do not allow separation of the direct effects of limited N availability from those caused
by a N dilution effect due to accelerated growth at elevated pCO(2). To dissociate these interactions,
wheat (Triticum aestivum L.) was grown hydroponically and N was added in direct proportion to
plant growth. Photosynthesis did not acclimate to elevated pCO(2) even when growth was restricted
by a low-N relative addition rate. Ribulose-l, 5-bisphosphate carboxylase/oxygenase activity and
quantity were maintained, there was no evidence for triose phosphate limitation of photosynthesis,
and tissue N content remained within the range recorded for healthy wheat plants. In contrast, wheat
grown in sand culture with N supplied at a fixed concentration suffered photosynthetic acclimation
at elevated pCO(2) in a low-N treatment. This was accompanied by a significant reduction in the
quantity of active ribulose-l, 5- bisphosphate carboxylase/oxygenase and leaf N content.

KEYWORDS: C-3 PLANTS, CARBON, ENRICHMENT, GROWTH, PERSPECTIVE,
PRODUCTIVITY, RESPONSES, RISING ATMOSPHERIC CO2, TREES, WHEAT


     639  
Faria, T., M. Vaz, P. Schwanz, A. Polle, J.S. Pereira, and M.M. Chaves. 1999. Responses of
photosynthetic and defence systems to high temperature stress in Quercus suber L-seedlings crown
under elevated CO2. Plant Biology 1(3):365-371.

Growth in elevated CO2 led to an increase in biomass production per plant as a result of enhanced
carbon uptake and lower rates of respiration, compared to ambient CO2-grown plants. No down-
regulation of photosynthesis was found after six months of growth under elevated CO2.
Photosynthetic rates at 15 degrees C or 35 degrees C were also higher in elevated than in ambient
CO2-grown plants, when measured at their respective CO2 growth condition. Stomata of elevated
CO2-grown plants were less responsive to temperature as compared to ambient CO2 plants. The after
effect of a heat-shock treatment (4 h at 45 degrees C in a chamber with 80% of relative humidity and
800-1000 mu mol m(-2) s(-1) photon flux density) on A(max) was less in elevated than in ambient
CO2-grown plants. At the photochemical level, the negative effect of the heat-shock treatment was
slightly more pronounced in ambient than in elevated CO2-grown plants. A greater tolerance to
oxidative stress caused by high temperatures in elevated CO2-grown plants, in comparison to ambient
CO2 plants, is suggested by the increase in superoxide dismutase activity, after 1 h at 45 degrees C,
as well as its relatively high activity after 2 and 4 h of the heat shock in the elevated CO2-grown
plants in contrast with the decrease to residual levels of superoxide dismutase activity in ambient
CO2-grown plants immediately after 1 h at 45 degrees C. The observed increase in catalase after 1
h at 45 degrees C in both ambient and elevated CO2-grown plants, can be ascribed to the higher rates
of photorespiration and respiration under this high temperature.

KEYWORDS: ACCLIMATION, ANTIOXIDATIVE ENZYMES, CARBON DIOXIDE,
CHLOROPHYLL FLUORESCENCE, DOWN- REGULATION, PHOTOSYSTEM, PICEA-ABIES
L, PLANTS, RISING ATMOSPHERIC CO2, SUPEROXIDE-DISMUTASE


     640  
Faria, T., D. Wilkins, R.T. Besford, M. Vaz, J.S. Pereira, and M.M. Chaves. 1996. Growth at
elevated CO2 leads to down-regulation of photosynthesis and altered response to high temperature
in Quercus suber L seedlings. Journal of Experimental Botany 47(304):1755-1761.

The effects of growth at elevated CO2 on the response to high temperatures in terms of carbon
assimilation (net photosynthesis, stomatal conductance, amount and activity of Rubisco, and
concentrations of total soluble sugars and starch) and of photochemistry (for example, the efficiency
of excitation energy captured by open photosystem II reaction centres) were studied in cork oak
(Quercus suber L.). Plants grown in elevated CO2 (700 ppm) showed a down-regulation of
photosynthesis and had lower amounts and activity of Rubisco than plants grown at ambient CO2
(350 ppm), after 14 months in the greenhouse. At that time plants were subjected to a heat- shock
treatment (4 h at 45 degrees C in a chamber with 80% relative humidity and 800-1000 mu mol m(-2)
s(-1) photon flux density). Growth in a CO2-enriched atmosphere seems to protect cork oak leaves
from the short-term effects of high temperature. Elevated CO2 plants had positive net carbon uptake
rates during the heat shock treatment whereas plants grown at ambient CO2 showed negative rates.
Moreover, recovery was faster in high CO2-grown plants which, after 30 min at 25 degrees C,
exhibited higher net carbon uptake rates and lower decreases in photosynthetic capacity (A(max) as
well as in the efficiency of excitation energy captured by open photosystem II reaction centres (F-v/F-
m) than plants grown at ambient CO2. The stomata of elevated CO2 plants were also less responsive
when exposed to high temperature.

KEYWORDS: ACCLIMATION, CHLOROPHYLL FLUORESCENCE, ENZYMES, EXPRESSION,
GENES, LEAVES, MECHANISM, PROTEINS, RUBISCO, TREES


     641  
Farnsworth, E.J., and F.A. Bazzaz. 1995. Inter-generic and intra-generic differences in growth,
reproduction, and fitness of 9 herbaceous annual species grown in elevated co2 environments.
Oecologia 104(4):454-466.

In assessing the capacity of plants to adapt to rapidly changing global climate, we must elucidate the
impacts of elevated carbon dioxide on reproduction, fitness and evolution. We investigated how
elevated CO2 influenced reproduction and growth of plants exhibiting a range of floral morphologies,
the implications of shifts in allocation for fitness in these species, and whether related taxa would
show similar patterns of response. Three herbaceous, annual species each of the genera Polygonum,
Ipomoea, and Cassia were grown under 350 or 700 ppm CO2. Vegetative growth and reproductive
output were measured non-destructively throughout the full life span, and vegetative biomass was
quantified for a subsample of plants in a harvest at first flowering. Viability and germination studies
of seed progeny were conducted to characterize fitness precisely. Early vegetative growth was often
enhanced in high- CO2 grown plants of Polygonum and Cassia (but not Ipomoea). However, early
vegetative growth was not a strong predictor of subsequent reproduction. Phenology and production
of floral buds, flowers, unripe and abscised fruits differed between CO2 treatments, and genera
differed in their reproductive and fitness responses to elevated CO2. Polygonum and Cassia species
showed accelerated, enhanced reproduction, while Ipomoea species generally declined in reproductive
output in elevated CO2. Seed ''quality'' and fitness (in terms of viability and percentage germination)
were not always directly correlated with quantity produced, indicating that output alone may not
reliably indicate fitness or evolutionary potential. Species within genera typically responded more
consistently to CO2 than unrelated species. Cluster analyses were performed separately on suites of
vegetative and reproductive characters. Some species assorted within genera when these reproductive
responses were considered, but vegetative responses did not reflect taxonomic affinity in these plants.
Congeners may respond similarly in terms of reproductive output under global change, but fitness and
prognoses of population persistence and evolutionary performance can be inferred only rarely from
examination of vegetative characters alone.

KEYWORDS: ALLOCATION, AMBIENT, CARBON DIOXIDE, CASSIA-FASCICULATA,
ENRICHMENT, FECUNDITY, INTRASPECIFIC VARIATION, OVULE ABORTION, PLANTS,
SEED PRODUCTION


     642  
Farnsworth, E.J., A.M. Ellison, and W.K. Gong. 1996. Elevated CO2 alters anatomy, physiology,
growth, and reproduction of red mangrove (Rhizophora mangle L). Oecologia 108(4):599-609.

Mangroves, woody halophytes restricted to protected tropical coasts, form some of the most
productive ecosystems in the world, but their capacity to act as a carbon source or sink under climate
change is unknown. Their ability to adjust growth or to function as potential carbon sinks under
conditions of rising atmospheric CO2 during global change may affect global carbon cycling, but as
yet has not been investigated experimentally. Halophyte responses to CO2 doubling may be
constrained by the need to use carbon conservatively under water-limited conditions, but data are
lacking to issue general predictions. We describe the growth, architecture, biomass allocation,
anatomy, and photosynthetic physiology of the predominant neotropical mangrove tree, Rhizophora
mangle L., grown solitarily in ambient (350 mu ll(-1)) and double-ambient (700 mu ll(-1)) CO2
concentrations for over 1 year. Mangrove seedlings exhibited significantly increased biomass, total
stem length, branching activity, and total leaf area in elevated CO2. Enhanced total plant biomass
under high CO2 was associated with higher root:shoot ratios, relative growth rates, and net
assimilation rates, but few allometric shifts were attributable to CO2 treatment independent of plant
size. Maximal photosynthetic rates were enhanced among high-CO2 plants while stomatal
conductances were lower, but the magnitude of the treatment difference declined over time, and high-
CO2 seedlings showed a lower P-max at 700 mu ll(-1) CO2 than low-CO2 plants transferred to 700
mu ll(-1) CO2: possible evidence of downregulation. The relative thicknesses of leaf cell layers were
not affected by treatment. Stomatal density decreased as epidermal cells enlarged in elevated CO2.
Foliar chlorophyll, nitrogen, and sodium concentrations were lower in high CO2. Mangroves grown
in high CO2 were reproductive after only 1 year of growth (fully 2 years before they typically
reproduce in the field), produced aerial roots, and showed extensive lignification of the main stem;
hence, elevated CO2 appeared to accelerate maturation as well as growth. Data from this long- term
study suggest that certain mangrove growth characters will change flexibly as atmospheric CO2
increases, and accord with responses previously shown in Rhizophora apiculata. Such results must
be integrated with data from sea-level rise studies to yield predictions of mangrove performance under
changing climate.

KEYWORDS: ATMOSPHERIC CO2, AVICENNIA-MARINA, CARBON DIOXIDE, CARIBBEAN
REGION, CLIMATE CHANGE, ECOSYSTEM COLLAPSE, ESTUARINE MARSH, HOLOCENE
ANALOGS, INTERSPECIFIC VARIATION, SEA-LEVEL RISE


     643  
Farrar, J.F., and M.L. Williams. 1991. The effects of increased atmospheric carbon-dioxide and
temperature on carbon partitioning, source-sink relations and respiration. Plant, Cell and
Environment 14(8):819-830.

Herbaceous C3 plants grown in elevated CO2 show increases in carbon assimilation and carbohydrate
accumulation (particularly starch) within source leaves. Although changes in the partitioning of
biomass between root and shoot occur, the proportion of this extra assimilate made available for sink
growth is not known. Root:shoot ratios tend to increase for CO2-enriched herbaceous plants and
decrease for CO2-enriched trees. Root:shoot ratios for cereals tend to remain constant. In contrast,
elevated temperatures decrease carbohydrate accumulation within source and sink regions of a plant
and decrease root:shoot ratios. Allometric analysis of at least two species showing changes in
root:shoot ratios due to elevated CO2 show no alteration in the whole-plant partitioning of biomass.
Little information is available for interactions between temperature and CO2. Cold-adapted plants
show little response to elevated levels of CO2, with some species showing a decline in biomass
accumulation. In general though, increasing temperature will increase sucrose synthesis, transport and
utilization for CO2-enriched plants and decrease carbohydrate accumulation within the leaf. Literature
reports are discussed in relation to the hypothesis that sucrose is a major factor in the control of plant
carbon partitioning. A model is presented in support.

KEYWORDS: ABSCISIC- ACID, CARBOHYDRATE CONTENT, CO2- ENRICHMENT, DARK
RESPIRATION, ELEVATED CO2, PHASEOLUS-VULGARIS, PLANT GROWTH, POTATO-
TUBERS, SOYBEAN PHYSIOLOGY, SUGAR-BEET


     644  
Favis-Mortlock, D.T., and S.J.T. Guerra. 1999. The implications of general circulation model
estimates of rainfall for future erosion: a case study from Brazil. Catena 37(3-4):329-354.

One consequence of global change will be shifts in the probability of occurrence of soil erosion by
water. This could have serious consequences for those areas of the world which are present-day
'hotspots' for erosion. By means of a case study, this paper suggests an approach to quantifying the
change in risk of serious erosion for sites in such areas. The case study focuses on future erosion
under intensive soya bean cultivation in the Mate Grosso area of Brazil. On the area's highly erodible
latosols, current erosion problems are severe. Scenarios of change future climate change are taken
from general circulation models (GCMs) and used to perturb current- climate weather data. These
are input to an erosion model (water erosion prediction project (WEPP)-CO2), together with local
knowledge regarding current and probable future land use, in order to estimate future changes in
erosion rates. WEPP- simulated average annual sediment yield increases in one of the scenarios and
decreases in the other two, reflecting the range of uncertainty in predictions of future rainfall. Using
the 'best-guess' climate scenario from the UK Meteorological Office's HADCM2 GCM, the increase
in mean annual sediment yield is 27%. Increases are disproportionately greater in wetter years.
Average rates for individual months increase by over 100%. Erosion increases most on those parts
of the hillslope profile which are currently hardest-hit by erosion. At present, an annual sediment yield
of 5 t ha(-1) is currently exceeded in about 1 year in 2. The HADCM2 simulations suggest that an
equal or greater rate will occur in about 70% of years by around 2050. A rate of at least 10 t ha(-1)
yr(-1) is currently exceeded in about 1 year in 5. The HADCM2 simulations suggest that this will rise,
to about 1 year in 4. (C) 1999 Elsevier Science B.V. All rights reserved.

KEYWORDS: ADJUSTMENTS, CLIMATE CHANGE, ELEVATED CO2, FARMER SCENARIO,
PRESENT TECHNOLOGY, RESPONSES, SIMULATIONS, SOIL-EROSION, SOUTH-DOWNS,
WHEAT YIELD


     645  
Fearnside, P.M. 1999. Plantation forestry in Brazil: the potential impacts of climatic change.
Biomass & Bioenergy 16(2):91-102.

Most climatic changes predicted to occur in Brazil would reduce yields of silvicultural plantations,
mainly through increased frequency and severity of droughts brought on by global warming and by
reduction of water vapor sources in Amazonia caused by deforestation. Some additional negative
effects could result from changes in temperature, and positive effects could result from CO2
enrichment. The net effects would be negative, forcing the country to expand plantations onto less-
productive land, requiring increased plantation area land consequent economic losses) out of
proportion to the climatic change itself. These impacts would affect carbon sequestration and storage
consequences of any plans for subsidizing silviculture as a global warming mitigation option. Climate
change can be expected to increase the area of plantations needed to supply projected internal demand
for and exports of end products from Brazil. June-July-August (dry season) precipitation reductions
indicated by simulations reported by the Intergovernmental Panel on Climate Change (IPCC)
correspond to rainfall declines in this critical season of approximately 34% in Amazonia, 39% in
Southern Brazil and 61% in the Northeast. As an example, if rainfall in Brazilian plantation areas
(most of which are now in Southern Brazil) were to decline by 50%, the area needed in 2050 would
expand by an estimated 38% over the constant climate case, bringing the total plantation area to 4.5
times the 1991 area. These large areas of additional plantations imply substantial social and
environmental impacts. Further addition of plantation area as a global warming response option
would augment these impacts, indicating the need for caution in evaluating carbon sequestration
proposals. (C) 1999 Elsevier Science Ltd. All rights reserved.

KEYWORDS: AMAZON BASIN, CARBON


     646  
Feng, X.H., and S. Epstein. 1996. Climatic trends from isotopic records of tree rings: The past 100-
200 years. Climatic Change 33(4):551-562.

There has been a great deal of discussion about global warming from accumulation of anthropogenic
greenhouse gases in the atmosphere (Houghton et al., 1990). Relatively less attention has been paid
to spatial and/or temporal climatic variations that may be associated with a warmer climate (Rind et
al., 1989) or with anthropogenic activities (Schneider, 1994). In this article; we show that an increase
in climatic variability may have started. Fourteen isotopic time series of tree rings are presented.
These trees were randomly collected from world- wide locations and cover time periods of 120 to
over 200 years. The isotopic records show increasing delta D values that suggest a consistent and
progressive warming occurred in the 19th century in all locations where the trees were sampled. The
rate of warming is greater at relatively cold locations than at warm locations with two exceptions.
The records also suggest greater climatic variations both temporally and spatially in the 20th century
than in the 19th century.

KEYWORDS: ATMOSPHERIC CO2, CELLULOSE, D-H RATIO, D/H RATIOS, ENRICHMENT,
LEAF WATER, NON-EXCHANGEABLE HYDROGEN, NORTH-AMERICA, PRECIPITATION,
VARIABILITY


     647  
Ferguson, S.A. 1997. A climate-change scenario for the Columbia River basin. Usda Forest Service
Pacific Northwest Research Station Research Paper (499):CP1-CP&.

This work describes the method used to generate a climate- change scenario for the Columbia River
basin. The scenario considers climate patterns that may change if the atmospheric concentration of
carbon dioxide (CO2), or its greenhouse gas equivalent, were to double over pre-Industrial
Revolution values. Given the current rate of increase in atmospheric CO2 concentration, doubling
could occur within the next 50 to 100 years. The Columbia River basin is in a transition climate zone
between predominating maritime to the west, arctic to the north, and continental to the east.
Consequently, it is difficult to characterize through means and averages. Therefore, many of the
current stochastic methods for developing climate-change scenarios cannot directly apply to the basin.
To circumvent this problem, a composite approach was taken to generate a climate scenario that
considers knowledge of current regional climate controls, available output from general circulation
and regional climate models, and observed changes in climate. The resulting climate-change scenario
suggests that precipitation could increase substantially during winter (+20 to +50 percent) and
moderately during spring and autumn (+5 to +35 percent). A slight decrease (0 to -5 percent) in
summer precipitation is possible, except for the southeastern portions of the basin that may
experience an increase in convective precipitation (+5 percent). Low- elevation (<1 kilometer)
temperatures throughout the year may increase 1 to 3 degrees C, with greatest increases during
winter. This amount of temperature change is possible because of an expected loss of low-elevation
snow cover. At high elevations, increased cloud cover could cause average temperatures to decrease
during winter but be synchronized with possible warming at low elevations during summer. The
diurnal range of temperature could decrease, especially in summer and autumn.

KEYWORDS: INCOMPLETE, MODEL, PRECIPITATION, TEMPERATURE, UNITED-STATES


     648  
Fernandez, M.D., A. Pieters, C. Donoso, W. Tezara, M. Azkue, C. Herrera, E. Rengifo, and
A. Herrera. 1998. Effects of a natural source of very high CO2 concentration on the leaf gas
exchange, xylem water potential and stomatal characteristics of plants of Spatiphylum cannifolium
and Bauhinia multinervia. New Phytologist 138(4):689-697.

The effect of a very high CO2 mole fraction (27 000-35 000 mu mol mol(-1)) on photosynthesis and
water relations was studied during the dry and the rainy season in plants of Spatiphylum cannifolium
(Dryand.) Schott and Bauhinia multinervia (H.B.K.) DC. growing near natural cold CO2 springs.
Xylem water potential in plants of both species was lowered by drought, high CO2 growth-
concentration decreasing it further in S. cannifolium. In plants of both species growing under high
CO2 concentration photosynthetic rates measured at a CO2 mole fraction of 1000 mu mol mol(-1)
were higher than in plants growing at ambient CO2 mole fraction and measured at 350 mu mol mol(-
1). The response was the result of a direct effect of CO2 on the photosynthetic machinery. Changes
in carboxylation efficiency in response to high CO2 were found during the rainy season, with an
increase in S. cannifolium and a decrease in B. multinervia; a significant interaction between growth
CO2 concentration and season in B. multinervia resulted from significant effects of both factors. An
increase in intrinsic water-use efficiency due to high CO2 was determined in both species by an
increase in photosynthetic rate as well as a decrease in leaf conductance. In high-CO2 plants of S.
cannifolium a 71 % decrease in stomatal density and 73 % in stomatal index suggested that CO2
affected stomatal initiation, whereas in B. multinervia an 85 % decrease in stomatal index and a 72
% decrease in stomatal density indicated that CO2 influenced stomatal initiation as well as epidermal
cell expansion. Our results indicate that very high CO2 concentrations did not inhibit photosynthesis
in these species, and that growth under high CO2 allowed plants to attain carbon balances higher than
those of plants growing under low CO2. This was particularly so during the dry season, since the
photosynthetic rates at the corresponding ambient concentration were higher in plants nearer the
springs, and carboxylation efficiency and some stomatal characteristics of both species apparently
acclimated to high CO2, but patterns were not consistent and bore no obvious relationship to
photosynthetic capacity.

KEYWORDS: ATMOSPHERIC CO2, BIOMASS ALLOCATION, DENSITY, ELEVATED CARBON-
DIOXIDE, ENRICHMENT, GROWTH, LEAVES, PHOTOSYNTHESIS, SCIRPUS- OLNEYI, USE
EFFICIENCY


     649  
FerrarioMery, S., M.C. Thibaud, T. Betsche, M.H. Valadier, and C.H. Foyer. 1997. Modulation
of carbon and nitrogen metabolism, and of nitrate reductase, in untransformed and transformed
Nicotiana plumbaginifolia during CO2 enrichment of plants grown in pots and in hydroponic culture.
Planta 202(4):510-521.

Transformed plants of Nicotiana plumbaginifolia Viv. constitutively expressing nitrate reductase
(35S-NR) or beta- glucuronidase (35S-GUS) and untransformed controls were grown for two weeks
in a CO2-enriched atmosphere. Whereas CO2 enrichment (1000 mu l. 1(-1)) resulted in an increase
in the carbon (C) to nitrogen (N) ratio of both the tobacco lines grown in pots with vermiculite, the
C/N ratio was only slightly modified when plants were grown in hydroponic culture in high CO2
compared to those grown in air. Constitutive nitrate reductase (NR) expression per se did not change
the C/N ratio of the shoots or roots. Biomass accumulation was similar in both types of plant when
hydroponic or pot-grown material, grown in air or high CO2, were compared. Shoot dry matter
accumulation was primarily related to the presence of stored carbohydrate (starch and sucrose) in the
leaves. In the pot- grown tobacco, growth at elevated CO2 levels caused a concomitant decrease in
the N content of the leaves involving losses in NO3- and amino contrast, the N content and
composition were similar in all plants grown in hydroponic culture. The 35S-NR plants grown in air
had higher foliar maximum extractable NR activities and increased glutamine levels (on a chlorophyll
or protein basis) than the untransformed controls. These increases were maintained following CO2
enrichment when the plants were grown in hydroponic culture, suggesting that an increased flux
through nitrogen assimilation was possible in the 35S-NR plants. Under CO2 enrichment the NR
activation state in the leaves was similar in all plants. When the 35S-NR plants were grown in pots,
however, foliar NR activity and glutamine content fell in the 35S-NR transformants to levels similar
to those of the untransformed controls. The differences in NR activity between untransformed and
35S-NR leaves were much less pronounced in the hydroponic than in the pst-grown material but the
difference in total extractable NR activity was more marked following CO2 enrichment. Foliar NR
message levels were decreased by CO2 enrichment in all growth conditions but this was much more
pronounced in pot-grown material than in that grown hydroponically. Since beta-glucuronidase
(GUS) activity and message levels in 35S-GUS plants grown under the same conditions of CO2
enrichment (to test the effects of CO2 enrichment on the activity of the 35S promoter) were found
to be constant, we conclude that NR message turnover was specifically accelerated in the 35S-NR
plants as well as in the untransformed controls as a result of CO2 enrichment. The molecular and
metabolic signals involved in increased NR message and protein turnover are not known but possible
effecters include NO3-, glutamine and asparagine. We conclude that plants grown in hydroponic
culture have greater access to N than those grown in pots. Regardless of the culture method, CO2
enrichment has a direct effect on NR mRNA stability.

KEYWORDS: ACCLIMATION, ATMOSPHERIC CO2, CONSTITUTIVE EXPRESSION, DIOXIDE
ENRICHMENT, ETIOLATED BARLEY LEAVES, GENE-EXPRESSION, GLUTAMINE-
SYNTHETASE, LIGHT, PHOTOSYNTHESIS, TOMATO


     650  
Ferris, R., I. Nijs, T. Behaeghe, and I. Impens. 1996. Contrasting CO2 and temperature effects
on leaf growth of perennial ryegrass in spring and summer. Journal of Experimental Botany
47(301):1033-1043.

The effects of increased atmospheric carbon dioxide (CO2) of 700 mu mol mol(-1) and increased air
temperature of +4 degrees C were examined in Lolium perenne L. cv. Vigor, growing in semi-
controlled greenhouses, Leaf growth, segmental elongation rates (SER), water relations, cell wall
(tensiometric) extensibility (%P) and epidermal cell lengths (ECL) were measured in expanding leaves
in spring and summer. In elevated CO2, shoot dry weight (SDW) increased in mid-summer, In both
seasons, SDW decreased in elevated air temperatures with this reduction being greater in summer as
compared to spring, Specific leaf area (SLA) decreased in elevated CO2 and in CO2 x temperature
in both seasons, In spring, increased leaf extension and SER in elevated CO2 were linked with
increased ECL, %P and final leaf size whilst in summer all were reduced, In high temperature, leaf
extension, SER, %P and final leaf size were reduced in both seasons. In elevated CO2 x temperature,
leaf extension, SER, %P, and ECL increased in spring, but final leaf size remained unaltered, whilst
in summer all decreased. Mid-morning water potential did not differ with CO2 or temperature
treatments. Leaf turgor pressure increased in elevated CO2 in spring and remained similar to the
control in summer whilst solute potential decreased in spring and increased in summer, Contrasting
seasonal growth responses of L. perenne in response to elevated CO2 and temperature suggests
pasture management may change in the future, The grazing season may be prolonged, but whole
season productivity may become more variable than today.

KEYWORDS: CARBON-DIOXIDE CONCENTRATION, CELL-GROWTH, DIVERSE
ALTITUDINAL RANGES, ELEVATED CO2, EXPANSION, GROWING LEAVES, LOLIUM-
TEMULENTUM, PLANT GROWTH, RESPONSES, WATER RELATIONS


     651  
Ferris, R., I. Nijs, T. Behaeghe, and I. Impens. 1996. Elevated CO2 and temperature have different
effects on leaf anatomy of perennial ryegrass in spring and summer. Annals of Botany 78(4):489-497.

Mature second leaves of Lolium perenne L. cv. Vigor, were sampled in a spring and summer
regrowth period. Effects of CO2 enrichment and increased air temperature on stomatal density,
stomatal index, guard cell length, epidermal cell density, epidermal cell length and mesophyll cell area
were examined for different positions on the leaf and seasons of growth. Leaf stomatal density was
smaller in spring but greater in summer in elevated CO2 and higher in both seasons in elevated
temperature and in elevated CO2 x temperature relative to the respective controls. In spring, leaf
stomatal index was reduced in elevated CO2 but in summer it varied with position on the leaf. In
elevated temperature, stomatal index in both seasons was lower at the tip/middle of the leaf but
slightly higher at the base. In elevated CO2 x temperature, stomatal index varied with position on the
leaf and between seasons. Leaf epidermal cell density was higher in all treatments relative to controls
except in elevated CO2 (spring) and elevated CO2 x temperature (summer), it was reduced at the leaf
base. In all treatments, stomatal density and epidermal cell density declined from leaf tip to base,
whilst guard cell length showed an inverse relationship, increasing towards the base. Leaf epidermal
cell length and mesophyll cell area increased in elevated CO2 in spring and decreased in summer. In
elevated CO2 x temperature leaf epidermal cell length remained unaltered in spring compared to the
control but decreased in summer. Stomatal conductance was lower in all treatments except in summer
in elevated CO2 it was higher than in the ambient CO2. These contrasting responses in anatomy to
elevated CO2 and temperature provide information that might account. for differences in seasonal
leaf area development observed in L. perenne under the same conditions. (C) 1996 Annals of Botany
Company

KEYWORDS: ATMOSPHERIC CO2, CARBON-DIOXIDE CONCENTRATION, ENRICHMENT,
GAS-EXCHANGE, GROWTH, LEAVES, POPLAR CLONES, RESPONSES, STOMATAL DENSITY,
WATER


     652  
Ferris, R., and G. Taylor. 1993. Contrasting effects of elevated co2 on the root and shoot growth
of 4 native herbs commonly found in chalk grassland. New Phytologist 125(4):855-866.

The aim of this study was to investigate the impact of ambient (345 mu l l(-1)) and elevated (590 mu
l l(-1)) CO2 on the root and shoot growth of four native chalk grassland herbs: Sanguisorba minor
Scop. (salad burnet), Lotus corniculatus L. (birdsfoot trefoil), Anthyllis vulneraria L. (kidney vetch)
and Plantage media L. (hoary plantain). Elevated CO2 had contrasting effects on both shoot and root
growth of the four species studied. Both leaf expansion and production were stimulated by elevated
CO2 for S. minor, L. corniculatus and P. media, whilst for A. vulneraria, only leaflet shape appeared
to be altered by elevated CO2, with the production of broader leaflets, compared with those produced
in ambient CO2. After 100 d shoot biomass was enhanced in elevated CO2 for S. minor and L.
corniculatus, whilst there was no effect of elevated CO2 on shoot biomass for A. vulneraria or P.
media. Contrasting effects of CO2 were also apparent for measurements of specific leaf area (SLA),
which increased for L. corniculatus, decreased for A. vulneraria and remained unaltered for S. minor
and P. media in elevated compared with ambient CO2. Elevated CO2 also had contrasting effects on
both the growth and morphology of roots. The accumulation of root biomass was stimulated
following exposure to elevated CO2 for S. minor and L. corniculatus whilst there was no effect on
root biomass for A. vulneraria or P. media. Root length was measured on three occasions during the
100 d and revealed that exposure to elevated CO2 promoted root extension in S. minor, L.
corniculatus and P. media, but not in A. vulneraria. Specific root length (SRL, length per unit dry
weight) was increased in elevated CO2 for one species, P. media, whilst the root to shoot ratio of all
four species remained unchanged by CO2. These results show that four native herbs differ in their
response to CO2, suggesting that the structure of this plant community may be altered in the future.

KEYWORDS: ACCLIMATION, ATMOSPHERIC CARBON-DIOXIDE, COMMUNITIES,
ECOSYSTEMS, ENRICHMENT, LEAF ANATOMY, PHOTOSYNTHESIS, RESPONSES, SOURCE-
SINK RELATIONS, TEMPERATURE


     653  
Ferris, R., and G. Taylor. 1994. Elevated co2, water relations and biophysics of leaf extension in
4 chalk grassland herbs. New Phytologist 127(2):297-307.

Diurnal measurements of leaf or leaflet extension, water relations and cell wall extensibility (phi) were
made on young growing leaves of four chalk downland herbs (Sanguisorba minor Scop., Lotus
corniculatus L., Anthyllis vulneraria L. and Plantago media L.) growing in controlled environment
cabinets and exposed to either ambient or elevated CO2. This study revealed differences in the effect
of CO2 and the control of leaf growth between the four species. Leaf extension rate (LER) increased
significantly at night (average over 8 h) in elevated CO2 for S. minor, A. vulneraria and P. media with
a significant increase over the first 4 h of darkness for S. mines, L. corniculatus and P. media, whilst
for S. minor and P. media average day-time LER (over 16 h) also increased significantly in elevated
CO2 as compared with ambient CO2. Water potential (Psi), solute potential (Psi(s)), turgor pressure
(P), yield turgor (Y) and the effective turgor for growth (Pe) were measured using psychrometers.
Solute potentials of S. minor, A. vulneraria acid P. media decreased significantly following exposure
to elevated CO2 with a significant reduction in Psi(s) during the day in A. vulneraria. Turgor pressure
increased significantly in elevated CO2 as compared with ambient CO2 in A. vulneraria but there was
no effect of elevated CO2 on P in the other species. No effects of CO2 on Psi, Y or Pe were
observed. Leaf cell wall extensibility (phi) increased significantly in leaves of S. minor, L. corniculatus
and P. media exposed to elevated CO2, whereas in A. vulneraria, there was no effect of CO2 on
extensibility. These results suggest that the mechanism by which elevated CO2 promotes leaf growth
differs between species since in S. minor, L. corniculatus and P. media, CO2 promoted growth
through an influence on cell wall properties, whilst in A. vulneraria, higher values of P explain the
increased leaf growth in elevated CO2 for this species.

KEYWORDS: EXPANSION, LEAVES, PHOTOSYNTHESIS, PLANT-CELL GROWTH,
PRODUCTIVITY, SALIX-VIMINALIS, TEMPERATURE, WALL EXTENSIBILITY, XYLOGLUCAN
ENDOTRANSGLYCOSYLASE, YIELD TURGOR


     654  
Ferris, R., and G. Taylor. 1994. Increased root-growth in elevated co2 - a biophysical analysis of
root cell elongation. Journal of Experimental Botany 45(280):1603-1612.

A biophysical analysis of root expansion was conducted in four chalk downland herbs (Sanguisorba
minor Scop., Lotus corniculatus L., Anthyllis vulneraria L. and Plantago media L.) exposed to either
ambient or elevated CO, in controlled environment cabinets. Measurements of fine (F) and extra-fine
(EF) root extension rate (RER), water relations, and cell wall tensiometric extensibility revealed
differences in the diurnal pattern of root growth between species. After 35 d of exposure to elevated
CO2, RER of both F and EF roots increased significantly in darkness and on illumination for S.
minor, whilst for A. vulneraria (EF roots only) and L. corniculatus a significant increase occurred at
night whereas for P. media a significant increase occurred during the day. Cells measured in the zone
of elongation were longer in all species exposed to elevated CO2. Water potential (Psi), solute
potential (Psi(s)), turgor pressure (P), yield turgor (Y) and effective turgor (Pe) were measured by
stress-relaxation of excised root tips placed in psychrometers. Solute potentials decreased
significantly for all species following exposure to elevated CO2. In S. minor and L. corniculatus, P
and Pe, respectively, were higher in elevated CO2. No significant effects of CO2 on Y were observed
(not shown). Root cell wall tensiometric extensibility, measured as % plasticity, increased in all
species exposed to elevated CO2. These results suggest that root growth is enhanced following
increased cell expansion and that increased P and cell wall tensiometric extensibility are both
important for root growth in elevated CO2.

KEYWORDS: ATMOSPHERIC CARBON-DIOXIDE, LEAF GROWTH, MAIZE ROOTS, PLANTS,
PRESSURE PROBE, TURGOR, WALL EXTENSIBILITY, WATER RELATIONS, XYLOGLUCAN
ENDOTRANSGLYCOSYLASE, YIELD THRESHOLD


     655  
Ferris, R., and G. Taylor. 1994. Stomatal characteristics of 4 native herbs following exposure to
elevated co2. Annals of Botany 73(4):447-453.

KEYWORDS: ALLIUM, CARBON DIOXIDE, CELLS, DENSITY, ENRICHMENT, GROWTH,
INCREASES, LEAF ANATOMY, NUMBERS, POPLAR CLONES


     656  
Ferris, R., and G. Taylor. 1995. Contrasting effects of elevated CO2 and water deficit on two native
herbs. New Phytologist 131(4):491-501.

This study investigated the effects of carbon dioxide (CO2) enrichment and soil water deficit on the
water use efficiency (WUE) and growth of Sanguisorba minor Scop. (salad burnet) and Anthyllis
vulneraria L. (kidney vetch), growing in controlled environments. Instantaneous WUE (IWUE)
increased in both species in elevated CO2, with a higher average increase in unwatered (UW) A.
vulneraria over the drying cycle. Total plant WUE of A. vulneraria increased in elevated CO2 and
under water deficit: the UW plants in elevated CO2 had higher WUE and reduced water loss. By
contrast, thee was only an effect of water supply on S. minor: total plant WUE increased and water
loss decreased in the UW plants in both CO2 treatments. Total apparent root length (ARL) of both
species increased with CO2 enrichment and in UW S. minor total ARL was increased. By contrast,
for A. vulneraria, total ARL of UW plants increased in ambient CO2, but decreased in elevated CO2
as compared with well-watered (WW) plants. Shoot dry weight (SDW) and root dry weight increased
in both species (WW and UW) with CO2 enrichment. For UW S. minor, SDW decreased relative to
WW plants in both CO2 treatments. By contrast, ANOVA showed no significant effect of water
supply on SDW of A. vulneraria. Leaflet length increased in both species in elevated CO2 and
decreased following drought. Cell wall tensiometric extensibility (%P) increased in expanding leaves
of S. minor in elevated CO2 and for both species %P decreased in the UW plants as compared with
those WW. Leaf water potential (Psi) of both species was lower in growing leaves of WW plants in
elevated CO2. Water deficit reduced the Psi of growing leaves in both CO2 treatments. The different
responses of these species suggest that in a drier, enriched CO2 environment survival in a community
might depend on their ability to maintain growth at the same time as conserving water.

KEYWORDS: BETULA, CARBON DIOXIDE, DROUGHT, ENRICHMENT, GROWTH, LIMITED
CONDITIONS, SEEDLINGS, STRESS, USE EFFICIENCY, YIELD


     657  
Ferris, R., T.R. Wheeler, R.H. Ellis, and P. Hadley. 1999. Seed yield after environmental stress
in soybean grown under elevated CO2. Crop Science 39(3):710-718.

Episodes of high temperature and drought are predicted to occur more frequently under conditions
of future climate change, This study investigated whether an episode of high air temperature (HT +
15 degrees C), water deficit (WD), or both (HTWD), for 8 d, had the same effects on the yield of
soybean [Glycine max (L.) Merrill, cv. Fiskeby V] grown under either ambient (aCO(2); 360 mu mol
mol(-1) CO2) or elevated (eCO(2); 700 mu mol mol(-1) CO2) CO2 concentrations. Plants were
grown in a glasshouse at either aCO(2) or at eCO(2) until 52 d after sowing (DAS). The 8-d stress
treatments were then imposed before the plants were returned to their original environments. Across
harvests, total biomass was 41% greater under eCO(2) than under aCO(2) but reduced by HT, WD,
and HTWD under both CO2 concentrations, The relative response of total biomass to HT,WD, and
HTWD episodes was the same for plants grown under either aCO(2) or eCO(2). At maturity, seed
dry weight and number per plant under eCO(2) were increased by an average of 32 and 22%,
respectively, compared with aCO(2). The same parameters were reduced after HTWD by 29 and
30%, respectively, in aCO(2) and eCO(2), Seed filling was earlier under HT and HTWD The rate of
change in harvest index was unaltered by CO2 while under HTWD, it decreased. Seed number
explained 85% of the variation in yield, but yield was also related linearly to photosynthesis during
seed filling, suggesting both are important determinants of yields under stress.

KEYWORDS: CARBON DIOXIDE, CLIMATIC VARIABILITY, CROP YIELDS, LONG-TERM,
LUPINUS-ANGUSTIFOLIUS L, PHOTOSYNTHESIS, PRODUCTIVITY, RESPONSES,
TRANSIENT HIGH-TEMPERATURES, WATER-STRESS


     658  
Ferris, R., T.R. Wheeler, P. Hadley, and R.H. Ellis. 1998. Recovery of photosynthesis after
environmental stress in soybean grown under elevated CO2. Crop Science 38(4):948-955.

Episodes of high temperature and water deficit may be more frequent under predicted future climates
of warmer mean temperatures and elevated CO2. This study investigated whether the effects of an
episode of high sir temperature (HT, 43 degrees C as a daily maximum), water deficit (WD), or both,
had the same effect on the recovery of photosynthesis and on leaf water relations of soybean [Glycine
max (L.) Merr., cv. Fiskeby V] grown at ambient CO2 (aCO(2)) or elevated CO2 (eCO(2)). An 8-d
period of HT, WD, or both (HTWD) were imposed during early seed filling of soybean grown in
glasshouses at either 362 or 685 mu mol mol(-1) CO2. Photosynthesis (Amax), stomatal conductance
(g(s)), and water relations were measured in fully expanded upper-canopy leaves. Immediately after
the 8-d treatments at 60 d after sowing (DAS), Amax was reduced by 31, 48, and 64% in aCO(2) and
by 28, 39, and 49% in eCO(2) under HT, WD, and HTWD, respectively, but no significant
interactions were detected. At 60 DAS, g(s) was reduced by WD and HTWD in aCO(2) but not by
HT while there was little change in g(s) by WD, HT, and HTWD under eCO(2). Amar fully recovered
under WD in eCO(2) by 66 DAS, while Amax remained reduced under WD in aCO(2). Under each
CO2 concentration, almost full recovery of Amar occurred under HT by 75 DAS but under HTWD
Amar never attained control values. At 60 DAS, early morning leaf water potential (Psi) was lower
after HT, WD, and HTWD and Amax was a negative function of Psi, at each CO2 concentration. The
results suggest that full recovery of Amax from WD was only possible under eCO(2), because at
aCO(2), immediately after the stress episode, Psi was below the threshold for chloroplast damage.

KEYWORDS: ATMOSPHERIC CARBON-DIOXIDE, CLIMATIC VARIABILITY, CROP YIELDS,
ENRICHMENT, GAS-EXCHANGE, LEAF WATER POTENTIALS, PERENNIAL RYEGRASS,
PLANTS, RESPONSES, TEMPERATURE


     659  
Field, C.B. 1994. Carbon-cycle - arctic chill for co2 uptake. Nature 371(6497):472-473.

KEYWORDS: AMBIENT, ATMOSPHERIC CO2, ELEVATED CO2, TUSSOCK TUNDRA


     660  
Field, C.B., F.S. Chapin, P.A. Matson, and H.A. Mooney. 1992. Responses of terrestrial
ecosystems to the changing atmosphere - a resource-based approach. Annual Review of Ecology and
Systematics 23:201-235.

KEYWORDS: ALASKAN TUSSOCK TUNDRA, ALPINE LIFE ZONE, CARBON NUTRIENT
BALANCE, ELEVATED CO2 CONCENTRATIONS, HARDWOOD LEAF LITTER, L KARST
STANDS, NITROGEN-USE EFFICIENCY, SOURCE-SINK RELATIONS, TEMPERATE FOREST
ECOSYSTEMS, WATER-USE EFFICIENCY


     661  
Field, C.B., R.B. Jackson, and H.A. Mooney. 1995. Stomatal responses to increased co2 -
implications from the plant to the global-scale. Plant, Cell and Environment 18(10):1214-1225.

Increased atmospheric CO2 Often but not always leads to large decreases in leaf conductance,
Decreased leaf conductance has important implications for a number of components of CO2
responses, from the plant to the global scale, All of the factors that are sensitive to a change in soil
moisture, either amount or timing, may be affected by increased CO2. The list of potentially sensitive
processes includes soil evaporation, run- off, decomposition, and physiological adjustments of plants,
as well as factors such as canopy development and the composition of the plant and microbial
communities, Experimental evidence concerning ecosystem-scale consequences of the effects of CO2
on water use is only beginning to accumulate, but the initial indication is that, in water-limited areas,
the effects of CO2- induced changes in leaf conductance are comparable in importance to those of
CO2-induced changes in photosynthesis, Above the leaf scale, a number of processes interact to
modulate the response of canopy or regional evapotranspiration to increased CO2. While some
components of these processes tend to amplify the sensitivity of evapotranspiration to altered leaf
conductance, the most likely overall pattern is one in which the responses of canopy and regional
evapotranspiration are substantially smaller than the responses of canopy conductance, The effects
of increased CO2 on canopy evapotranspiration are likely to be smallest in aerodynamically smooth
canopies with high leaf conductances, Under these circumstances, which are largely restricted to
agriculture, decreases in evapotranspiration may be only one-fourth as large as decreases in canopy
conductance, Decreased canopy conductances over large regions may lead to altered climate,
including increased temperature and decreased precipitation, The simulation experiments to date
predict small effects globally, but these could be important regionally, especially in combination with
radiative (greenhouse) effects of increased CO2.

KEYWORDS: ATMOSPHERIC CO2, CONDUCTANCE, ELEVATED CARBON-DIOXIDE, GAS-
EXCHANGE, GROWTH, LEAF-AREA, PHOTOSYNTHESIS, SCIRPUS- OLNEYI,
TRANSPIRATION, WATER-STRESS


     662  
Field, C.B., C.P. Lund, N.R. Chiariello, and B.E. Mortimer. 1997. CO2 effects on the water
budget of grassland microcosm communities. Global Change Biology 3(3):197-206.

Experimental grassland ecosystems, in microcosms 0.2 m in diameter and with a 0.95 m soil column,
varied in their responses to elevated partial pressure of CO2 (pCO(2)) and altered moisture inputs.
Ecosystems on moderately fertile sandstone soil and with a typical mix of moderately fast- growing
sandstone species, responded to elevated pCO(2) with decreases in mid-season evapotranspiration
of nearly 50%. This pattern reversed at the end of the growing season, and sandstone ecosystems
under elevated pCO(2) continued active transpiration farther into the summer drought. The sandstone
ecosystems appeared to convert mid-season water conservation into increased late-season growth.
Effects of increased pCO(2) on ecosystem evapotranspiration were much smaller in ecosystems with
very infertile serpentine soil and a diverse mixture of slow-growing serpentine species.

KEYWORDS: AMBIENT, COTTON, ELEVATED CO2, ENRICHMENT, EVAPOTRANSPIRATION,
INCREASES, RESPONSES, SIMULATIONS, STOMATAL CONDUCTANCE, TRANSPIRATION


     663  
Field, C.D. 1995. Impact of expected climate-change on mangroves. Hydrobiologia 295(1-3):75-81.

There is a consensus of scientific opinion that the activities of man will cause a significant change in
the global climate over the next hundred years. The rising level of carbon dioxide and other industrial
gases in the atmosphere may lead to global warming with an accompanying rise in sea-level.
Mangrove ecosystems grow in the intertidal zones in tropical and sub- tropical regions and are likely
to be early indicators of the effects of climate change. The best estimates of predicted climate change
in the literature are presented. It is suggested that a rise in mean sea-level may be the most important
factor influencing the future distribution of mangroves but that the effect will vary dramatically
depending on the local rate of sea-level rise and the availability of sediment to support reestablishment
of the mangroves. The predicted rise in mean air temperature will probably be of little consequence
to the development of mangroves in general but it may mean that the presence of mangroves will
move further north and south, though this will depend on a number of additional factors. The effect
of enhanced atmospheric CO2 on the growth of mangroves is unknown at this time but that there is
some evidence that not all species of mangroves will respond similarly. The socio- economic impacts
of the effects of climate change on mangrove ecosystems may include increased risk of flooding,
increased erosion of coast lines, saline intrusion and increased storm surges.

KEYWORDS: AVICENNIA-MARINA, ELEVATED CO2, GREY MANGROVE, GROWTH, PLANT-
RESPONSES, SALINITY, SEA-LEVEL, STOMATAL RESPONSES


     664  
Fierro, A., N. Tremblay, and A. Gosselin. 1994. Supplemental carbon-dioxide and light improved
tomato and pepper seedling growth and yield. Hortscience 29(3):152-154.

The experiment was conducted to determine the effects of CO2 enrichment (900 mul.liter-1, 8
hours/day) in combination with supplementary lighting of 100 mumol.s-1.m-2 (16-h photoperiod) on
tomato (Lycopersicon esculentum Mill.) and sweet pepper (Capsicum annuum L.) seedling growth
in the greenhouse and subsequent yield in the field. Enrichment with CO2 and supplementary lighting
for almost-equal-to 3 weeks before transplanting increased accumulation of dry matter in shoots by
almost-equal-to 50% compared with the control, while root dry weight increased 49% for tomato and
62% for pepper. Early yields increased by almost-equal-to 15% and 11% for tomato and pepper,
respectively.

KEYWORDS: CO2, NITROGEN- FERTILIZATION, VEGETABLE TRANSPLANT PRODUCTION


     665  
Figueira, A., and J. Janick. 1994. Optimizing carbon-dioxide and light levels during in-vitro culture
of theobroma-cacao. Journal of the American Society for Horticultural Science 119(4):865-871.

In vitro culture of axillary cotyledonary shoots of Theobroma cacao L. (cacao) under increasing CO2
concentration from ambient to 24,000 ppm (culture tube levels) significantly increased total shoot
elongation, number of leaves, leaf area per explant, and shoot dry and fresh weight. Although light
was necessary for the CO2 response, the effect of various photon fluxes was not significant for the
measured growth parameters. Net photosynthesis estimated on the basis of CO2 depletion in culture
tubes increased 3.5 times from 463 to 2639 ppm CO2, and increased 1.5 times from 2639 to 14,849
ppm CO2, but declined from 14,849 to 24,015 ppm CO2. Ethylene concentration in culture vessels
increased under enriched CO2 conditions. Depletion of nutrients (fructose, K, Ca, Mg, and P) from
the medium was increased under enriched CO2 conditions.

KEYWORDS: AMELONADO, CO2- ENRICHMENT, GROWTH, PLANTLETS, SHOOT
PROLIFERATION, STRAWBERRY, TISSUE


     666  
Figueira, A., A. Whipkey, and J. Janick. 1991. Increased co2 and light promote invitro shoot
growth and development of theobroma-cacao. Journal of the American Society for Horticultural
Science 116(3):585-589.

Axillary shoots of cacao (Theobroma cacao L.), induced in vitro with cytokinins (BA or TDZ),
elongated and produced leaves only in the presence of cotyledons and/or roots. Detached axillary
shoots, which do not grow in vitro under conventional tissue culture protocols, rooted with auxin and
developed normally in vivo. Detached axillary shoots from cotyledonary nodes and single-node
cuttings from mature plants were induced to elongate and produce normal leaves in the presence of
20,000 ppm CO2 and a photosynthetic photon flux density (PPFD) of 150 to 200-mu-mol.s-1.m-2.
Subcultured nodal cuttings continued to elongate and produce leaves under elevated CO2 and light
levels, and some formed roots. Subculture of microcuttings under CO2 enrichment could be the basis
for a rapid system of micropropagation for cacao. Chemical names used: N- (phenylmethyl)-1H-
purin-6-amine (BA); 1H-indole-3-butyric acid (IBA); alpha-naphthaleneacetic acid (NAA);
thidiazuron (TDZ).

KEYWORDS: CULTIVATED INVITRO, L VAR AMELONADO, PROLIFERATION,
PROPAGATION, TISSUES


     667  
Finlayson, S.A., and D.M. Reid. 1996. The effect of CO2 On ethylene evolution and elongation rate
in roots of sunflower (Helianthus annuus) seedlings. Physiologia Plantarum 98(4):875-881.

Both carbon dioxide and ethylene can affect the rate of root elongation. Carbon dioxide can also
promote ethylene biosynthesis by enhancing the activity of 1-aminocylopropane-1- carboxylic acid
(ACC) oxidase. Since the amount of CO2 in the soil air, and in the atmosphere surrounding roots held
in enclosed containers, is known to vary widely, we investigated the effects of varying CO2
concentrations on ethylene production by excised and intact sunflower roots (Helianthus annuus L.
cv. Dahlgren 131). Seedlings were germinated in an aeroponic system in which the roots hung freely
in a chamber and were misted with nutrient solution. This allowed for treatment, manipulation and
harvest of undamaged and minimally disturbed roots. While exposure of excised roots to 0.5% CO2
could produce a small increase in ethylene production (compared to roots in ambient CO2), CO2
concentrations of 2% and above always inhibited ethylene evolution. This inhibition of ethylene
production by CO2 was attributed to a reduction in the availability of ACC; however, elevated CO2
had no effect on ACC oxidase activity. ACC levels in excised roots were depressed by CO2 at a
concentration of 2% (as compared to ambient CO2), but n-malonyl-ACC (MACC) levels were not
affected. Treating intact roots with 2% CO2 inhibited elongation by over 50%. Maximum inhibition
of elongation occurred 1 h after the CO2 treatment began, but elongation rates returned to untreated
values by 6 h. Supplying these same intact roots with 2% CO2 did not alter ethylene evolution. Thus,
in excised sunflower roots 2% CO2 treatment reduces ethylene evolution by lowering the availability
of ACC. Intact seedlings respond differently in that 2% CO2 does not affect ethylene production in
roots. These intact roots also temporarily exhibit a significantly reduced rate of elongation in response
to 2% CO2.

KEYWORDS: 1-AMINOCYCLOPROPANE-1-CARBOXYLATE OXIDASE, ACC OXIDASE,
ACTIVATION, CARBON DIOXIDE, FORMING ENZYME, GROWTH, PLANTS, RESPIRATION,
SOIL O2, WATER


     668  
Firbank, L.G., A.R. Watkinson, L.R. Norton, and T.W. Ashenden. 1995. Plant-populations and
global environmental-change - the effects of different temperature, carbon-dioxide and nutrient
regimes on density-dependence in populations of vulpia-ciliata. Functional Ecology 9(3):432-441.

1. Monocultures of Vulpia ciliata spp. ambigua were subjected to a range of temperatures, CO2,
nutrient and density regimes in a factorial design housed within solar-domes. Temperature treatments
were imposed at ambient and +3 degrees C levels, CO2 at ambient and +340 ppm, and there were
three levels of nutrients and eight levels of densities ranging from 156 to 31250 seeds m(-2). The
abiotic treatments were imposed after emergence. 2. There was little mortality and this was unrelated
to the treatments. Plants grew more quickly at the high temperature, high nutrient and low density
regimes, and flowering was earlier at the high temperature regime. 3. At seed set, biomass per plant
and seed production per plant were analysed by analysis of variance and by fitting mean yield- density
models expanded to account for different environmental conditions. Biomass and fecundity were
greatest at high temperature, high nutrient and low density regimes. Allocation of biomass to shoots
was greater at the high temperatures, as were seed number/shoot biomass ratios. Any effects of CO2
were negligible. The parameter b describing the nature of the relationship between seed production
per plant and density was always less than unity but was greater at the higher temperature regime.
The response to density was therefore undercompensating in all conditions, implying that populations
would display monotonic damping to equilibrium densities. 4. Under proposed future environmental
regimes, V. ciliata has the capacity for more rapid population growth from low levels and for a
northwards range shift. However, if open ground is not maintained, its habitat may become dominated
by species that are more competitive or that have a higher rate of increase.

KEYWORDS: BRECKLAND, CLIMATE, CO2- ENRICHMENT, ELEVATED CO2, FASCICULATA,
GROWTH-RESPONSES, PHYSIOLOGY, SIMULATION, SINGLE-SPECIES POPULATIONS,
SOURCE-SINK RELATIONS


     669  
Fischer, B.U., M. Frehner, T. Hebeisen, S. Zanetti, F. Stadelmann, A. Luscher, U.A. Hartwig,
G.R. Hendrey, H. Blum, and J. Nosberger. 1997. Source-sink relations in Lolium perenne L. as
reflected by carbohydrate concentrations in leaves and pseudo-stems during regrowth in a free air
carbon dioxide enrichment (FACE) experiment. Plant, Cell and Environment 20(7):945-952.

The effect of an elevated partial pressure of CO2 (P-CO2) on carbohydrate concentrations in source
leaves and pseudostems (stubble) of Lolium perenne L., (perennial ryegrass) during regrowth was
studied in a regularly defoliated grass sward in the field, The free air carbon dioxide enrichment
(FACE) technology enabled natural environmental conditions to be provided, Two levels of nitrogen
(N) supply were used to modulate potential plant growth. Carbohydrate concentrations in source
leaves were increased at elevated P-CO2, particularly at low N supply, Elevated leaf carbohydrate
concentrations were related to an increased structural carbon (C) to N ratio and thus reflected an
increased C availability together with a N- dependent sink limitation, Immediately after defoliation,
apparent assimilate export rates (differences in the carbohydrate concentrations of young source
leaves measured in the evening and on the following morning) showed a greater increase at elevated
p(CO2) than at ambient p(CO2); however, replenishment of carbohydrate reserves was not
accelerated Distinct, treatment-dependent carbohydrate concentrations in pseudo-stems suggested
an increasing degree of C-sink limitation from the treatment at ambient p(CO2) with high N supply
to that at elevated P-CO2 With low N supply. During two growing seasons, no evidence of a
substantial change in the response of the carbohydrate source in L. perenne to elevated p(CO2) was
found, Our results support the view that the response of L. perenne to elevated p(CO2) is restricted
by a C- sink limitation, which is particularly severe at low N supply.

KEYWORDS: ELEVATED CO2, GROWTH, LEAF, PASTURE TURVES, PLANTS, RESPIRATION,
RYEGRASS, SIMULATED SEASONAL-CHANGES, TEMPERATURE, TRIFOLIUM- REPENS


     670  
Fischer, M., D. Matthies, and B. Schmid. 1997. Responses of rare calcareous grassland plants to
elevated CO2: a field experiment with Gentianella germanica and Gentiana cruciata. Journal of
Ecology 85(5):681-691.

1 Endangered plant species may be particularly vulnerable to global change. We investigated
differences in the behaviour of the rare calcareous grassland species Gentiana cruciata and Gentianella
germanica under ambient (360 mu l l(-1)) and elevated CO2 (600 mu l l(-1)) in a field experiment.
2 Rosettes of G. germanica and C. cruciata were planted into grassland plots with 29 other plant
species. Each of the 30 rosettes of G. germanica in a plot represented a different maternal seed family,
whereas G. cruciata was grown from a mixture of seeds from one field site. After overwintering, eight
of the 12 plots were equipped with open-top chambers, four of which were run at ambient and four
at elevated CO2 concentrations; the remaining four plots were left without chambers. 3 CO2
concentration did not significantly affect growth and survival of G. cruciata. Rosette diameter
increased by 70% over 1 year. 4 Overall only 13.6% of transplanted G. germanica survived for 1 year.
Elevated CO2 reduced survival by 57% (this reduction was only marginally significant due to large
variation between plots) and seed set by 46%. Both these effects appeared to be mediated by
competition from other species since survival and seed set were negatively correlated with total plot
biomass at the time of fastest growth in June 1994 and at the time of fruit set in October, respectively.
Compared with plots under ambient CO2, population growth rate (based on survival and
reproduction) was reduced by 56% under elevated CO2. 5 There were no significant effects of
elevated CO2 on leaf characters in either species. 6 The sugar concentration of the nectar of G.
germanica was increased by 36% under elevated CO2 but its composition remained unchanged. 7
Significant interactions between the effects of seed family and CO2 concentration on demographic
parameters in G. germanica indicated large genetic variation in the response to elevated CO2, which
represents evolutionary potential. Although predictions based on mean responses are therefore
unreliable, the majority of genotypes reacted negatively to elevated CO2, suggesting that competitive
exclusion and extinction of G. germanica would occur at many sites before populations could adapt
to increased concentrations of CO2.

KEYWORDS: ATMOSPHERIC CO2, BIOMASS PRODUCTION, CHALK GRASSLANDS, CLOVER
TRIFOLIUM-REPENS, GROWTH, PERFORMANCE, RYEGRASS LOLIUM-PERENNE, SHORT-
LIVED FORBS, TEMPERATURE, WHITE CLOVER


     671  
Fiscus, E.L., and C.D. Reid. 1995. Pollutant ozone does not affect stomatal limitation to
photosynthesis in soybean in ambient or elevated co2. Plant Physiology 108(2):63.



     672  
Fiscus, E.L., C.D. Reid, J.E. Miller, and A.S. Heagle. 1997. Elevated CO2 reduces O-3 flux and
O-3-induced yield losses in soybeans: Possible implications for elevated CO2 studies. Journal of
Experimental Botany 48(307):307-313.

Soybeans were grown for three seasons in open-top field chambers to determine (1) whether elevated
CO2 (360 Versus 700 mu mol mol(-1)) alleviates some of the yield loss due to pollutant O-3, (2)
whether the partial stomatal closure resulting froth chronic O-3 exposure (charcoal-filtered air versus
1.5 x ambient concentrations) is a cause or result of decreased photosynthesis, and (3) possible
implications of CO2/O-3 interactions to climate change studies using elevated CO2. Leaf conductance
was reduced by elevated CO2, regardless of O-3 level, or by exposure to O-3 alone. AS a result of
these effects on conductance, high CO2 reduced estimated midday O-3 flux into the leaf by an
average of 50% in charcoal-filtered air and 35% in the high O-3 treatment. However, while exposure
to O-3 reduced seed yields by 41% at ambient CO2 levels, the yield reduction was completely
ameliorated by elevated CO2. The threshold midday O-3 flux for yield loss appears to be 20-30 nmol
m(-2) s(-1) in this study. Although elevated CO2 increased total biomass production, it did not
increase seed yields. A/C- i curves show a large reduction in the stomatal limitation to photosynthesis
due to elevated CO2, but no effect of O-3. These data demonstrate that (1) reduced conductance due
to O-3 is the result, and not the cause, of reduced photosynthesis, (2) 700 mu mol mol(-1) CO2 can
completely ameliorate yield losses due to O-3 within the limits of these experiments, and (3) some
reports of increased yields under elevated CO2 treatments may, at least in part, reflect the
amelioration of unrecognized suppression of yield by O-3 or other stresses.

KEYWORDS: ATMOSPHERIC CARBON-DIOXIDE, B RADIATION, CONDUCTANCE,
ENRICHMENT, GROWTH, LEAF RESPIRATION, OZONE, PHOTOSYNTHESIS, POLLUTANTS,
WATER DEFICIT


     673  
Fitter, A.H., J.D. Graves, J. Wolfenden, G.K. Self, T.K. Brown, D. Bogie, and T.A. Mansfield.
1997. Root production and turnover and carbon budgets of two contrasting grasslands under ambient
and elevated atmospheric carbon dioxide concentrations. New Phytologist 137(2):247-255.

Monoliths of two contrasting vegetation types, a species-rich grassland on a brown earth soil over
limestone and a species- poor community on a peaty gley, were transferred to solardomes and grown
under ambient (350 mu l l(-1)) and elevated (600 mu l l(-1)) CO2 for 2 yr. Shoot biomass was
unaltered but root biomass increased by 40-50% under elevated CO2. Root production was increased
by elevated CO2 in the peat soil, measured both as instantaneous and cumulative rates, but only the
latter measure was increased in the limestone soil. Root growth was stimulated more at 6 cm depth
than at 10 cm in the limestone soil. Turnover was faster under elevated CO2 in the peat soil, but there
was only a small effect on turnover in the limestone soil. Elevated CO, reduced nitrogen
concentration in roots and might have increased mycorrhizal colonization. Respiration rate was
correlated with N concentration, and was therefore lower in roots grown at elevated CO2. Estimates
of the C budget of the two communities, based upon root production and on net C uptake, suggest
that C sequestration in the peat soil increases by c. 0.2 kg C m(-2) yr(-1) (= 2 t ha yr(-1)) under
elevated CO2.

KEYWORDS: BIOMASS, CO2- ENRICHMENT, GROWTH, STORAGE


     674  
Fitter, A.H., G.K. Self, J. Wolfenden, M.M.I. vanVuuren, T.K. Brown, L. Williamson, J.D.
Graves, and D. Robinson. 1996. Root production and mortality under elevated atmospheric carbon
dioxide. Plant and Soil 187(2):299-306.

An essential component of an understanding of carbon flux is the quantification of movement through
the root carbon pool. Although estimates have been made using radiocarbon, the use of
minirhizotrons provides a direct measurement of rates of root birth and death. We have measured
root demographic parameters under a semi-natural grassland and for wheat. The grassland was
studied along a natural altitudinal gradient in northern England, and similar turf from the site was
grown in elevated CO2 in solardomes. Root biomass was enhanced under elevated CO2. Root birth
and death rates were both increased to a similar extent in elevated CO2, so that the throughput of
carbon was greater than in ambient CO2, but root half-lives were shorter under elevated CO2 only
under a Juncus/Nardus sward on a peaty gley soil, and not under a Festuca turf on a brown earth soil.
In a separate experiment, wheat also responded to elevated CO2 by increased root production, and
there was a marked shift towards surface rooting: root development at a depth of 80-85 cm was both
reduced and delayed. In conjunction with published results for trees, these data suggest that the
impact of elevated CO2 will be system- dependent, affecting the spatio-temporal pattern of root
growth in some ecosystems and the rate of turnover in others. Turrnover is also sensitive to
temperature, soil fertility and other environmental variables, all of which are likely to change in
tandem with atmospheric CO2 concentrations. Differences in turnover and time and location of
rhizodeposition may have a large effect on rates of carbon cycling.

KEYWORDS: CO2- ENRICHMENT, FORESTS, GRASSES, GROWTH, PATTERNS, RESPONSES,
TURNOVER


     675  
Flagella, Z., R.G. Campanile, M.C. Stoppelli, A. De Caro, and N. Di Fonzo. 1998. Drought
tolerance of photosynthetic electron transport under CO2-enriched and normal air in cereal species.
Physiologia Plantarum 104(4):753-759.

The quantum yield of photosynthetic electron transport (Phi PSII), evaluated by means of chlorophyll
(Chl) fluorescence analysis, has proven to be a useful screening test for drought tolerance in durum
wheat (Triticum durum Desf.). To explore the potential of this parameter further in detecting
drought- tolerant genotypes, three cereal species were studied; Phi PSII measurements were carried
out under two different gas mixtures, at three points of the induction curve (to obtain the maximal
Phi PSII and both the transient and steady-state actual Phi PSII), and at three different water stress
levels (moderate, severe and drastic). The species investigated were durum and bread wheat (Triticum
aestivum L.) and barley (Hordeum vulgare L.); two cultivars per species, characterized by different
levels of drought tolerance, were tested. The two gas mixtures used were normal air (21% O-2,
0.035% CO2 in N-2) to monitor the whole photosynthetic process under physiological conditions,
and CO2 enriched-low O-2 air (1% O-2, 5% CO2 in N- 2) to monitor Phi PSII reduction under stress
mainly related to Calvin cycle activity. When Phi PSII related to both assimilatory and non-
assimilatory metabolism was evaluated, the cultivar differences observed under normal air were more
representative of the agronomic performance upon drought stress than under high CO2-low O-2 air.
Maximal Phi PSII showed no difference among either cultivars, gas mixtures or stress levels, the
efficiency of excitation capture being highly resistant to drought. The Phi PSII evaluated during the
transient yielded predictable values in respect of drought tolerance for durum wheat and barley
cultivars, highlighting the key role of regulatory processes such as the Mehler peroxidase reaction and
possibly also cyclic electron transport, in preventing overreduction under stress. The results clearly
show that when Chi fluorescence analysis is used as a parameter in plant breeding, different
experimental conditions should be used depending on the physiological mechanism that is bred or
selected for.

KEYWORDS: CARBON ASSIMILATION, CHLOROPHYLL FLUORESCENCE, CULTIVARS,
DURUM-WHEAT, EFFICIENCIES, LIGHT, PHOTOINHIBITION, PHOTOSYSTEM, QUANTUM
YIELD, WATER


     676  
Flanagan, L.B., S.L. Phillips, J.R. Ehleringer, J. Lloyd, and G.D. Farquhar. 1994. Effect of
changes in leaf water oxygen isotopic composition on discrimination against (coo)-o-18-o-16 during
photosynthetic gas-exchange. Australian Journal of Plant Physiology 21(2):221-234.

Photosynthetic gas exchange measurements were combined with measurements of the carbon and
oxygen stable isotopic composition of CO2 after it passed over a leaf of Phaseolus vulgaris or
Senecio spp. plants held in a controlled environment chamber. Calculations were then made of
discrimination by the leaf against (CO2)-C-13 and (COO)-O-18-O- 16. Leaves were maintained at
different vapour pressure gradients in order to generate a range of leaf water O-18/O-16 ratios. The
O-18 content of leaf water increased when plants were exposed to higher vapour pressure deficits.
The observed (COO)-O-18-O-16 discrimination values also increased with an increase in the leaf-air
vapour pressure gradient and the associated change in leaf water 18/(OO)-O-16 values. In addition,
the observed (COO)-O-18-O-16 discrimination values were strongly correlated with values predicted
by a mechanistic model of isotopic fractionation.

KEYWORDS: CARBONIC-ANHYDRASE, CO2 DIFFUSION, DEUTERIUM, ENRICHMENT,
HYDROGEN, LEAVES, O-18, PLANTS, RIBULOSE-1;5-BISPHOSPHATE CARBOXYLASE,
STABLE OXYGEN


     677  
Flexas, J., M. Badger, W.S. Chow, H. Medrano, and C.B. Osmond. 1999. Analysis of the relative
increase in photosynthetic O-2 uptake when photosynthesis in grapevine leaves is inhibited following
low night temperatures and/or water stress. Plant Physiology 121(2):675-684.

We found similarities between the effects of low night temperatures (5 degrees C-10 degrees C) and
slowly imposed water stress on photosynthesis in grapevine (Vitis vinifera L.) leaves. Exposure of
plants growing outdoors to successive chilling nights caused light- and CO2 saturated photosynthetic
O-2 evolution to decline to zero within 5 d. Plants recovered after four warm nights. These
photosynthetic responses were confirmed in potted plants, even when roots were heated. The
inhibitory effects of chilling were greater after a period of illumination, probably because transpiration
induced higher water deficit. Stomatal closure only accounted for part of the inhibition of
photosynthesis. Fluorescence measurements showed no evidence of photoinhibition, but
nonphotochemical quenching increased in stressed plants. The most characteristic response to both
stresses was an increase in the ratio of electron transport to net O-2 evolution, even at high external
CO2 concentrations. Oxygen isotope exchange revealed that this imbalance was due to increased O-2
uptake, which probably has two components: photorespiration and the Mehler reaction. Chilling- and
drought-induced water stress enhanced both O-2 uptake processes, and both processes maintained
relatively high rates of electron flow as CO2 exchange approached zero in stressed leaves.
Presumably, high electron transport associated with O-2 uptake processes also maintained a high
Delta pH, thus affording photoprotection.

KEYWORDS: CHLOROPHYLL FLUORESCENCE, CO2 ASSIMILATION, ELECTRON-
TRANSPORT, LIGHT, MEHLER-PEROXIDASE REACTION, OXYGEN- EXCHANGE,
PHOTOINHIBITION, PLANTS, QUANTUM YIELD, VITIS-VINIFERA L


     678  
Foley, J.A., S. Levis, I.C. Prentice, D. Pollard, and S.L. Thompson. 1998. Coupling dynamic
models of climate and vegetation. Global Change Biology 4(5):561-579.

Numerous studies have underscored the importance of terrestrial ecosystems as an integral
component of the Earth's climate system. This realization has already led to efforts to link simple
equilibrium vegetation models with Atmospheric General Circulation Models through iterative
coupling procedures. While these linked models have pointed to several possible climate- vegetation
feedback mechanisms, they have been limited by two shortcomings: (i) they only consider the
equilibrium response of vegetation to shifting climatic conditions and therefore cannot be used to
explore transient interactions between climate and vegetation; and (ii) the representations of
vegetation processes and land-atmosphere exchange processes are still treated by two separate
models and, as a result, may contain physical or ecological inconsistencies. Here we present, as a
proof concept, a more tightly integrated framework for simulating global climate and vegetation
interactions. The prototype coupled model consists of the GENESIS (version 2) Atmospheric General
Circulation Model and the IBIS (version 1) Dynamic Global Vegetation Model. The two models are
directly coupled through a common treatment of land surface and ecophysiological processes, which
is used to calculate the energy, water, carbon, and momentum fluxes between vegetation, soils, and
the atmosphere. On one side of the interface, GENESIS simulates the physics and general circulation
of the atmosphere. On the other side, IBIS predicts transient changes in the vegetation structure
through changes in the carbon balance and competition among plants within terrestrial ecosystems.
As an initial test of this modelling framework, we perform a 30 year simulation in which the coupled
model is supplied with modern CO2 concentrations, observed ocean temperatures, and modern
insolation. In this exploratory study, we run the GENESIS atmospheric model at relatively coarse
horizontal resolution (4.50 latitude by 7.5 degrees longitude) and IBIS at moderate resolution (2
degrees latitude by 2 degrees longitude). We initialize the models with globally uniform climatic
conditions and the modern distribution of potential vegetation cover. While the simulation does not
fully reach equilibrium by the end of the run, several general features of the coupled model behaviour
emerge. We compare the results of the coupled model against the observed patterns of modern
climate. The model correctly simulates the basic zonal distribution of temperature and precipitation,
but several important regional biases remain. In particular, there is a significant warm bias in the high
northern latitudes, and cooler than observed conditions over the Himalayas, central South America,
and north-central Africa. In terms of precipitation, the model simulates drier than observed conditions
in much of South America, equatorial Africa and Indonesia, with wetter than observed conditions in
northern Africa and China. Comparing the model results against observed patterns of vegetation
coves shows that the general placement of forests and grasslands is roughly captured by the model.
In addition, the model simulates a roughly correct separation of evergreen and deciduous forests in
the tropical, temperate and boreal zones. However, the general patterns of global vegetation cover
are only approximately correct: there are still significant regional biases in the simulation. In
particular, forest cover is not simulated correctly in large portions of central Canada and southern
South America, and grasslands extend too far into northern Africa. These preliminary results
demonstrate the feasibility of coupling climate models with fully dynamic representations of the
terrestrial biosphere. Continued development of fully coupled climate-vegetation models will facilitate
the exploration of a broad range of global change issues, including the potential role of vegetation
feedbacks within the climate system, and the impact of climate variability and transient climate change
on the terrestrial biosphere.

KEYWORDS: ATMOSPHERIC CO2, GENERAL-CIRCULATION MODELS, LEAF,
PHOTOSYNTHESIS, PLANT FUNCTIONAL TYPES, SENSITIVITY, STOMATAL
CONDUCTANCE, TERRESTRIAL BIOSPHERE, TRANSFER SCHEME LSX, TRANSPIRATION


     679  
Fonseca, F., C.G. Bowsher, and I. Stulen. 1997. Impact of elevated atmospheric CO2 on nitrate
reductase transcription and activity in leaves and roots of Plantago major. Physiologia Plantarum
100(4):940-948.

Vegetative plants of an inbred line, A4, of Plantage major ssp. pleiosperma (L.) Pilger were grown
at 350 mu l 1(-1) or at elevated (700 mu l l(-1)) CO2 in non-limiting nutrient solution with nitrate.
Both the relative growth rate (RGR) and the root to total plant weight ratio (RWR) were increased
by elevated CO2. However, the stimulation of both RGR and RWR was transient and did not last
longer than 8 days. To investigate the physiological mechanisms involved in this stimulation, related
changes in C/N metabolism were examined. In the roots soluble sugar concentration increased during
the transient period of RGR stimulation (up to 23%), as did the root respiration rate. Changes in
nitrogen metabolism were also restricted to this period and consisted of an increase in (1) in vivo and
in vitro root nitrate reductase (EC 1.6.6.1) activity, (2) in vitro leaf nitrate reductase activity, (3) leaf
and root nitrate reductase mRNA and (4) reduced nitrogen concentration in the roots. The elevated
CO2-related signal for the increase in nitrate reductase transcript levels in the roots is discussed in
terms of the increased availability of soluble sugars. The results suggest that the short-term
enhancement of root carbon and nitrogen metabolism may be responsible for the transient effect of
elevated CO, on whole plant RGR.

KEYWORDS: ASSIMILATION, CARBOHYDRATE CONTENT, CARBON DIOXIDE,
EXPRESSION, GROWTH, MAIZE, METABOLISM, NITRITE-REDUCTASE, PHOTOSYNTHESIS,
RAPID MODULATION


     680  
Fonseca, F., J. DenHertog, and I. Stulen. 1996. The response of Plantago major ssp pleiosperma
to elevated CO2 is modulated by the formation of secondary shoots. New Phytologist 133(4):627-
635.

The effect of elevated CO2 on the relative growth rate (RGR) of Plantago major ssp. pleiosperma
was studied during the vegetative stage, in relation to plant development, by growing plants at 350
mu l l(-1) or at 700 mu l l(-1) CO2 in non- limiting nutrient solution with nitrate. To minimize
interference by the accumulation of non-structural carbohydrates in the interpretation of results, RGR
was expressed on a f. wt basis (RGR(FW)), as were all plant weight ratios. Stimulation of the
RGR(FW) Of the whole plant by elevated CO2 was transient, and did not last longer than 8 d. At the
same time a transient increase in root weight ratio (RWR) was observed. In order to investigate
whether the transient effect of elevated CO2 on RGR(FW) was size-dependent, the data were plotted
versus total f. wt (log(e) transformed). The transient period of stimulation of RGR(FW) and of RWR
by elevated CO2 was still found, but in both CO2 treatments RGR(FW) decreased after a certain
plant size had been reached. This size coincided with the stage at which secondary shoots started to
develop, and was reached earlier in plants grown at elevated CO2. The RGR of these secondary
shoots (RGR(see)) was Still increased when the period of whole plant stimulation of RGR(FW) had
ended, indicating that the development of these new sinks took priority over a continuation of the
stimulation of RWR. It is hypothesized that in this Plantago subspecies the response of the RGR(FW)
of the whole plants to elevated CO2 is modulated by the formation of secondary shoots. Apparently,
partitioning of the extra soluble carbohydrates at elevated CO2 to this tissue takes precedence over
partitioning to the roots. resulting in a cessation of stimulation of plant RGR(FW) by elevated CO2.

KEYWORDS: ACCLIMATION, ATMOSPHERIC CARBON-DIOXIDE, COTTON, ENRICHMENT,
PHOTOSYNTHESIS, PHYSIOLOGY, RELATIVE GROWTH-RATE, RESPIRATION, SEEDLINGS,
TEMPERATURE


     681  
Fordham, M., J.D. Barnes, I. Bettarini, A. Polle, N. Slee, C. Raines, F. Miglietta, and A.
Raschi. 1997. The impact of elevated CO2 on growth and photosynthesis in Agrostis canina L ssp
monteluccii adapted to contrasting atmospheric CO2 concentrations. Oecologia 110(2):169-178.

The aim of this study was to characterise growth and photosynthetic capacity in plants adapted to
long-term contrasting atmospheric CO2 concentrations (C-a). Seeds of Agrostis canina L. ssp.
monteluccii were collected from a natural CO2 transect in central-western Italy and plants grown in
controlled environment chambers at both ambient and elevated CO2 (350 and 700 mu mol mol(-1))
in nutrient-rich soil. Seasonal mean C-a at the source of the plant material ranged from 610 to 451
mu mol CO2 mol(-1), derived from C-4 leaf stable carbon isotope discrimination (delta(13)C). Under
chamber conditions, CO2 enrichment stimulated the growth of all populations. However, plants
originating from elevated C-a exhibited higher initial relative growth rates (RGRs) irrespective of
chamber CO2 concentrations and a positive relationship was found between RGR and C-a at the seed
source. Seed weight was positively correlated with C-a, but differences in seed weight were found
to explain no more than 34% of the variation in RGRs at elevated CO2. Longer-term experiments
(over 98 days) on two populations originating from the extremes of the transect (451 and 610 mu mol
CO2 mol(-1)) indicated that differences in growth between populations were maintained when plants
were grown at both 350 and 700 mu mol CO2 mol(-1). Analysis of leaf material revealed an increase
in the cell wall fraction (CWF) in plants grown at elevated CO2, with plants originating from high C-a
exhibiting constitutively lower levels but a variable response in terms of the degree of lignification.
In vivo gas exchange measurements revealed no significant differences in light and CO2 saturated
rates of photosynthesis and carboxylation efficiency between populations or with CO2 treatment.
Moreover, SDS-PAGE/LISA quantification of leaf ribulose bisphosphate carboxylase/oxygenase
(Rubisco) showed no difference in Rubisco content between populations or CO2 treatments. These
findings suggest that long-term adaptation to growth at elevated CO2 may be associated with a
potential for increased growth, but this does not appear to be linked with differences in the intrinsic
capacity for photosynthesis.

KEYWORDS: ACCLIMATION, CARBOXYLASE, ECOSYSTEMS, EFFICIENCY, ENRICHMENT,
ENVIRONMENT, PLANTS, PROTEINS, RESPONSES, WHEAT


     682  
Fournioux, J.C., and R. Bessis. 1993. Use of carbon-dioxide enrichment to obtain adult
morphology of grapevine invitro. Plant Cell Tissue and Organ Culture 33(1):51-57.

A procedure has been developed for in vitro propagation of Vitis vinifera 'Pinot noir' from lateral-bud
cuttings under high CO2 concentration (1200 mumol mol-1). Because of inhibition of rooting by
CO2, this procedure requires a rooting pre-culture of explants on medium with sucrose before the
CO2- enriched culture on sucrose-free medium. Shoot growth was enhanced by CO2 enrichment as
a result of both a higher rate of leaf production and greater internode elongation. Leaf expansion and
tendril growth were promoted and better rooting was obtained. The more significant effect of CO2
enrichment was to promote adult morphology with, in particular, the tendril pattern. Thus, for the
first time, grapevine plants have been produced in vitro without typical juvenile characteristics. CO2
enrichment appears to be an interesting process to improve the in vitro propagation of grapevines.

KEYWORDS: CULTURE, MORPHOGENESIS, VITIS-VINIFERA L


     683  
Fowler, D., J.N. Cape, M. Coyle, C. Flechard, J. Kuylenstierna, K. Hicks, D. Derwent, C.
Johnson, and D. Stevenson. 1999. The global exposure of forests to air pollutants. Water, Air, and
Soil Pollution 116(1-2):5-32.

The tall, aerodynamically rough surfaces of forests provide for the efficient exchange of heat and
momentum between terrestrial surfaces and the atmosphere. The same properties of forests also
provide for large potential rates of deposition of pollutant gases, aerosols and cloud droplets. For
some reactive pollutant gases, including SO2, HNO3 and NH3, rates of deposition may be large and
substantially larger than onto shorter vegetation and is the cause of the so called "filtering effect" of
forest canopies. Pollutant inputs to moorland and forest have been compared using measured ambient
concentrations from an unpolluted site in southern Scotland and a more polluted site in south eastern
Germany. The inputs of S and N to forest at the Scottish site exceed moorland by 16% and 31%
respectively with inputs of 7.3 kg S ha(-1) y and 10.6 kg N ha(-1) y(-1). At the continental site inputs
to the forest were 43% and 48% larger than over moorland for S and N deposition with totals of 53.6
kg S ha(-1) y(-1) and 69.5 kg N ha(-)1 y(- )1 respectively. The inputs of acidity to global forests
show that in 1985 most of the areas receiving > 1 kg H+ ha(-1) y(-1) as S are in the temperate
latitudes, with 8% of total global forest exceeding this threshold. By 2050, 17% of global forest will
be receiving > 1 kg H-1 ha(-1) as S and most of the increase is in tropical and sub-tropical countries.
Forests throughout the world are also exposed to elevated concentrations of ozone. Taking 60 ppb
O-3 as a concentration likely to be phytotoxic to sensitive forest species, a global model has been
used to simulate the global exposure of forests to potentially phytotoxic O-3 concentrations for the
years 1860, 1950, 1970, 1990 and 2100. The model shows no exposure to concentrations in excess
of 60 ppb in 1860, and of the 6% of global forest exposed to concentrations > 60 ppb in 1950, 75%
were in temperate latitudes and 25% in the tropics. By 1990 24% of global forest is exposed to O-3
concentrates > 60 ppb, and this increases to almost 50% of global forest by 2100. While the
uncertainty in the future pollution climate of global forest is considerable, the likely impact of O-3 and
acid deposition is even more difficult to assess because of interactions between these pollutants and
substantial changes in ambient CO2 concentration, N deposition and climate over the same period,
but the effects are unlikely to be beneficial overall.

KEYWORDS: ATMOSPHERIC AMMONIA, DIOXIDE, DRY DEPOSITION, EXCHANGE,
MOORLAND, NITROGEN, POLLUTION, TEMPERATE, TROPOSPHERIC OZONE, VEGETATED
SURFACES


     684  
Franchito, S.H., V.B. Rao, and R.R. da Silva. 1998. A parameterization of radiative fluxes suitable
for use in a statistical-dynamical model. Meteorology and Atmospheric Physics 69(1-2):23-38.

A parameterization of shortwave and longwave radiation fluxes derived from detailed radiative
transfer models is included in a global primitive equation statistical-dynamical model (SDM) with two
bulk atmospheric layers. The model is validated comparing the model simulations with the observed
mean annual and seasonal zonally averaged climate. The results show that the simulation of the
shortwave and longwave radiation fluxes matches well with the observations. The SDM variables
such as surface and 500hPa temperatures, zonal winds at 250hPa and 750 hPa, vertical velocity at
500 hPa and precipitation are also in good agreement with the observations. A comparison between
the results obtained with the present SDM and those with the previous version of the model indicates
that the model results improved when the parameterization of the radiative fluxes based on detailed
radiative transfer models are included into the SDM. The SDM is used to investigate its response to
the greenhouse effect. Sensitivity experiments regarding the doubling of CO2 and the changing of the
cloud amount and height an performed. In the case 2xCO(2) the model results are consistent with
those obtained from GCMs, showing a warming of the climate system. An enhancement of the
greenhouse effect is also noted when the cloud layer is higher. However, an increase of the cloud
amount in all the latitude belts provokes an increase of the surface temperature near poles and a
decrease in all the other regions. This suggests that the greenhouse effect overcomes the albedo effect
in the polar latitudes and the opposite occurs in other regions. In all the experiments the changes in
the surface temperature an larger near poles, mainly in the Southern Hemisphere.

KEYWORDS: CLIMATE MODEL, CO2, EARTH, ENERGY-BALANCE, GENERAL-CIRCULATION
MODEL, MACROCLIMATE, SEASONAL CYCLE, SENSITIVITY, SOLAR RADIATION,
SURFACE-TEMPERATURE


     685  
Franck, V.M., B.A. Hungate, F.S. Chapin, and C.B. Field. 1997. Decomposition of litter
produced under elevated CO2: Dependence on plant species and nutrient supply. Biogeochemistry
36(3):223-237.

We investigated the effect of CO2 concentration and soil nutrient availability during growth on the
subsequent decomposition and nitrogen (N) release from litter of four annual grasses that differ in
resource requirements and native habitat. Vulpia microstachys is a native grass found on California
serpentine soils, whereas Avena fatua, Bromus hordaceus, and Lolium multiflorum are introduced
grasses restricted to more fertile sandstone soils (Hobbs & Mooney 1991). Growth in elevated CO2
altered litter C:N ratio, decomposition, and N release, but the direction and magnitude of the changes
differed among plant species and nutrient treatments, Elevated CO2 had relatively modest effects on
C:N ratio of litter, increasing this ratio in Lolium roots (and shoots at high nutrients), but decreasing
C:N ratio in Avena shoots. Growth of plants under elevated CO2 decreased the decomposition rate
of Vulpia litter, but increased decomposition of Avena litter from the high-nutrient treatment. The
impact of elevated CO2 on N loss from litter also differed among species, with Vulpia litter from
high-CO2 plants releasing N more slowly than ambient-CO2 litter, whereas growth under elevated
CO2 caused increased N loss from Avena litter. CO2 effects on N release in Lolium and Bromus
depended on the nutrient regime in which plants were grown. There was no overall relationship
between litter C:N ratio and decomposition rate or N release across species and treatments. Based
on our study and the literature, we conclude chat the effects of elevated CO2 on decomposition and
N release from litter are highly species-specific. These results do not support the hypothesis that CO2
effects on litter quality consistently lead to decreased nutrient availability in nutrient-limited
ecosystems exposed to elevated CO2.

KEYWORDS: ATMOSPHERIC CO2, DIOXIDE, ENRICHMENT, GLOBAL CARBON-CYCLE,
GROWTH, LEAF LITTER, NITROGEN, QUALITY, RESPONSES, SERPENTINE GRASSLAND


     686  
Frank, A.B., and A. Bauer. 1996. Temperature, nitrogen, and carbon dioxide effects on spring
wheat development and spikelet numbers. Crop Science 36(3):659-665.

Spring wheat (Triticum aestivum L.) responds favorably to elevated atmospheric carbon dioxide
concentration ([CO2]) at optimum temperatures. Predictions are for air temperatures to increase as
global [CO2] increases. Since spring wheat grain yields generally decline as temperature increases,
there is a need to understand the effects of both [CO2] and temperature on spring wheat growth,
development, and yield potential. Objectives were to evaluate combinations of [CO2], air
temperature, and applied N levels on leaf and apex development, spike components, tiller numbers,
dry matter, plant height, and water use in spring wheat. 'Amidon' spring wheat was grown in
controlled environment chambers at all combinations of 350, 650, and 950 mu L L(-1) [CO2], 0, 100,
and 300 kg N ha(-1), and 14/18 degrees C and 22/26 degrees C night/day air temperatures.
Temperature affected the Haun stage by growth degree-days (GDD) relationship more than N or
[CO2]. The phyllochron in GDD was greater for plants grown at 22/26 degrees C (433 GDD) than
at 14/18 degrees C (345 GDD). The Haun stage at apex double ridge and terminal spikelet increased
as applied N and [CO2] increased. Fertile spikelet numbers increased as [CO2] and N level increased
at 14/18 degrees C, but at 22/26 degrees C, spikelets increased as N increased and decreased as
[CO2] increased. Fertile spikelets were greatest at 14/18 degrees C and 650 mu L L(-1) [CO2].
Results suggest that at elevated [CO2] and adequate soil water, air temperature is more important
than [CO2] in controlling grain yield potential. Because wheat yield potential at higher temperatures
decreased as [CO2] increased, a northly shift in the spring wheat growing areas may occur if global
temperatures increased in concert with [CO2].

KEYWORDS: AIR- TEMPERATURE, CO2- ENRICHMENT, GROWTH, PHYSIOLOGY, PLANTS,
RATES, RESPONSES, SOIL-WATER, WINTER-WHEAT, YIELD


     687  
Fredeen, A.L., and C.B. Field. 1995. Contrasting leaf and ecosystem co2 and h2o exchange in
avena- fatua monoculture - growth at ambient and elevated co2. Photosynthesis Research 43(3):263-
271.

Elevated CO2 (ambient + 35 Pa) increased shoot dry mass production in Avena fatua by similar to
68% at maturity. This increase in shoot biomass was paralleled by an 81% increase in average net
CO2 uptake (A) per unit of leaf area and a 65% increase in average A at the 'ecosystem' level per unit
of ground area. Elevated CO2 also increased 'ecosystem' A per unit of biomass. However, the
products of total leaf area and light- saturated leaf A divided by the ground surface area over time
appeared to lie on a single response curve for both CO2 treatments. The approximate slope of the
response suggests that the integrated light saturated capacity for leaf photosynthesis is similar to 10-
fold greater than the 'ecosystem' rate. 'Ecosystem' respiration (night) per unit of ground area, which
includes soil and plant respiration, ranged from -20 (at day 19) to -18 (at day 40) mu mol m(-2) s(-1)
for both elevated and ambient CO2 Avena. 'Ecosystem' below-ground respiration at the time of
seedling emergence was similar to -10 mu mol m(-2) s(- 1), while that occuring after shoot removal
at the termination of the experiment ranged from -5 to -6 mu mol m(-2) s(-1). Hence, no significant
differences between elevated and ambient CO2 treatments were found in any respiration measure on
a ground area basis, though 'ecosystem' respiration on a shoot biomass basis was clearly reduced by
elevated CO2. Significant differences existed between leaf and 'ecosystem' water flux. In general, leaf
transpiration (E) decreased over the course of the experiment, possibly in response to leaf aging,
while 'ecosystem' rates of evapotranspiration (ET) remained constant, probably because falling leaf
rates were offset by an increasing total leaf biomass. Transpiration was lower in plants grown at
elevated CO2, though variation was high because of variability in leaf age and ambient light
conditions and differences were not significant. In contrast, 'ecosystem' evapotranspiration (ET) was
significantly decreased by elevated CO2 on 5 out of 8 measurement dates. Photosynthetic water use
efficiencies (A/E at the leaf level, A/ET at the 'ecosystem' level) were increased by elevated CO2.
Increases were due to both increased A at leaf and 'ecosystem' level and decreased leaf E and
'ecosystem' ET.

KEYWORDS: ATMOSPHERIC CO2, CARBON DIOXIDE, LIMITATION, NUTRIENTS,
PHOTOSYNTHESIS, PLANTS, RESPONSES, WATER-USE EFFICIENCY


     688  
Fredeen, A.L., G.W. Koch, and C.B. Field. 1995. Effects of atmospheric CO2 enrichment on
ecosystem CO2 exchange in a nutrient and water limited grassland. Journal of Biogeography 22(2-
3):215-219.

We have completed 3 years of a study aimed at understanding the impact of elevated atmospheric
CO2 on ecosystem properties of annual grasslands at the Jasper Ridge Biological Preserve, Stanford,
CA, U.S.A. Measurements of net ecosystem CO2 uptake were made on intact grassland (on
serpentine and sandstone derived soils grown in open-top chambers since December 1991). We
measured CO2 exchange in the field with transparent Teflon- lined acrylic chambers coupled to an
open gas exchange system. Net ecosystem CO2 uptake for both the high productivity sandstone and
the low productivity serpentine grassland communities ranged from 2 to 11 mu mol m(-2) ground s(-
1) in 1992 and 1993, similar to rates obtained with eddy covariance techniques on the sandstone and
serpentine grasslands at Jasper Ridge in a previous study. There was a significant effect of elevated
CO2 on net ecosystem CO2 uptake rate (40-48% increase in 1992 and 17-117% increase in 1993:
ANOVA P = 0.018). Although elevated CO2 consistently enhanced net ecosystem CO2 uptake at
the growth CO2 concentrations, acclimation occurred such that elevated CO2-grown ecosystems had
reduced rates of CO2 uptake relative to ambient CO2-grown ecosystems at either ambient or elevated
CO2 measurement concentrations of CO2. The reduction in ecosystem level photosynthetic capacity
in elevated CO2 treatments was accompanied by decreased foliar ribulose-bis-phosphate carboxylase
(rubisco) activity on a weight basis in the species dominant in both grassland communities. Decreases
in rubisco activity resulted largely from increases in leaf mass per area in elevated CO2 plants. In
general, net ecosystem CO2 uptake was positively correlated with peak biomass. However, the data
suggest that biomass yield for a given level of net ecosystem CO2 uptake may be lower in elevated
CO2 chambers, especially in the higher productivity sandstone community.

KEYWORDS: AVAILABILITY, CARBON DIOXIDE, ELEVATED CO2, NITROGEN,
PHOTOSYNTHESIS, RESPONSES


     689  
Fredeen, A.L., G.W. Koch, and C.B. Field. 1998. Influence of fertilization and atmospheric CO2
enrichment on ecosystem CO2 and H2O exchanges in single- and multiple-species grassland
microcosms. Environmental and Experimental Botany 40(2):147-157.

This paper reports on measurements of net CO2 and H2O exchange from single- and multiple-species
microcosms composed of California annual grassland species grown at either ambient or elevated
(ambient + 36 Pa) CO2. Microcosms consisted of grassland species grown in PVC tubes (similar to
0.95 m deep x 0.2 m diameter) containing similar to 45 kg of either serpentine or sandstone derived
soil or parent material in open-top enclosures under ambient meteorological conditions. Half of the
microcosms were left unfertilized (low nutrient) while the other half received an intermediate level
of a slow- release (N,P,K) fertilizer (high nutrient). Gas exchange was performed by sealing individual
microcosms within a transparent chamber (on clear sunny days) and coupling this to an open gas-
exchange system. In fertilized single-species microcosms, elevated CO2 consistently enhanced net
'ecosystem' CO2 exchange (NCE) on a ground area basis in both early and late spring. Among
unfertilized single-species microcosms, no significant trends or differences were observed in NCE
between those grown at ambient versus elevated CO2. The NCE in sandstone and serpentine
multiple-species microcosms was monitored seasonally over a majority of the 1993-1994 growing
season. Rates were largely unaffected by growth CO2 or fertilization until after mid-February, 1994.
Water-use efficiency (WUE = NCE/evapotranspiration (ET)) was generally enhanced by elevated
CO2, but this was primarily a result of enhancements in NCE as opposed to decreases in ET.
Enhancements in NCE by elevated CO2 in fertilized single-species microcosms at the growth-CO2,
concentration were partially explained by higher above-ground biomass in elevated CO2 microcosms.
However, ecosystem-level 'acclimation' occurred such that microcosms grown at elevated CO2
consistently had lower NCE than ambient CO2 treatments at a single measurement CO2
concentration (ambient or elevated). The reduction in apparent ecosystem-level photosynthetic
capacity in elevated CO2 microcosms was accompanied by decreases in foliar Rubisco activity, such
that NCE measured at ambient CO2 was highly correlated (r = 0.98) with foliar Rubisco activity
across the three single-species microcosms in which it was measured. (C) 1998 Published by Elsevier
Science B.V. All rights reserved.

KEYWORDS: ALPINE GRASSLAND, AVAILABILITY, CARBON DIOXIDE, ELEVATED CO2,
GROWTH-RESPONSES, NITROGEN, PHOTOSYNTHESIS, PLANTS, USE EFFICIENCY, WATER-
LIMITED GRASSLAND


     690  
Fredeen, A.L., J.T. Randerson, N.M. Holbrook, and C.B. Field. 1997. Elevated atmospheric CO2
increases water availability in a water-limited grassland ecosystem. Journal of the American Water
Resources Association 33(5):1033-1039.

Californian annual grassland on sandstone (moderately fertile) and serpentine (very infertile) soils at
the Jasper Ridge Biological Preserve, Stanford, California, were exposed to ambient or elevated
(ambient + 36 Pa CO2) atmospheric CO2 in open-top chambers since December 1991. We measured
ecosystem evapotranspiration with open gas-exchange systems, and soil moisture with time-domain
reflectometry (TDR) over 0-15 cm (serpentine) and 0-30 cm (sandstone) depths, at times of peak
above ground physiological activity. Evapotranspiration decreased by 12 to 63 percent under elevated
CO2 in three consecutive years in the sandstone ecosystem (p = 0.053, p = 0.162, p = 0.082 in 1992,
1993, and 1994, respectively). In correspondence with decreased evapotranspiration, late-season soil
moisture reserves in the sandstone were extended temporally by 10 +/- 3 days in 1993 and by 28 +/-
11 days in 1994. The effect of elevated CO2 on soil moisture was greater in the drier spring of 1994
(419 mm annual rainfall) than in 1993 (905 mm annual rainfall). In the serpentine ecosystem,
evapotranspiration and soil moisture reserves were not clearly affected by elevated CO2. Soil water
may be conserved in drought-affected ecosystems exposed to elevated CO2, but the amount of
conservation appears to depend on the relative importance of transpiration and soil evaporation in
controlling water flux.

KEYWORDS: AMBIENT, ELECTROMAGNETIC DETERMINATION, EVAPORATION,
EXCHANGE, PATTERNS, PLANT, RESPONSES, SCALE, STOMATAL CONTROL,
TRANSPIRATION


     691  
Frederick, J.R., D.M. Alm, J.D. Hesketh, and F.E. Below. 1990. Overcoming drought-induced
decreases in soybean leaf photosynthesis by measuring with co2-enriched air. Photosynthesis
Research 25(1):49-57.



     692  
Frederick, K.D. 1993. Climate-change impacts on water-resources and possible responses in the
mink region. Climatic Change 24(1-2):83-115.

The capacity to supply both instream and offstream water uses under alternative climate conditions
and likely future changes in population, technology, and water-using practices are examined through
an adaptation of the framework developed in the Second National Water Assessment. Two measures
of the adequacy of water supplies - the availability of renewable supplies to provide for withdrawal
and instream uses and the relation between desired instream flows and current streamflows - are used
to examine the impact of the 1931-1940 analog climate (with and without CO2 enrichment) on
Missouri, Iowa, Nebraska, and Kansas (MINK). The impacts of the analog climate on water supplies
are estimated from actual streamflow data and estimates of the differences in reservoir evaporation
under the 1931-1940 analog and the 1951-1980 control climates. A modification of the Erosion
Productivity Inventory Calculator (EPIC) model is used to estimate the impacts of the analog climate
(with and without CO2 enrichment) on irrigation water use. Water, which is already a scarce resource
in the MINK region, would become much scarcer if the climate of the 1930s were to become the
norm. Mean assessed total streamflow would drop to 69% of the control climate level for the
Missouri River Basin, 71% for the Upper Mississippi, and 93% for the Arkansas. Even in the absence
of climate change, MINK will have less water in the year 2030 than it does today because
groundwater stocks are being depleted and increased upstream diversions would reduce surface flows
into these states. Irrigation and instream uses such as navigation, hydroelectric power production,
recreation, and fish and wildlife habitat would be most adversely, impacted by the climate-induced
changes in water supplies.



     693  
Freeman, C., R. Baxter, J.F. Farrar, S.E. Jones, S. Plum, T.W. Ashendon, and C. Stirling.
1998. Could competition between plants and microbes regulate plant nutrition and atmospheric CO2
concentrations? The Science of the Total Environment 220(2-3):181-184.

It has been proposed that under high CO2, soil microbes may outcompete plants for access to
inorganic nutrients, leading to a negative feedback to the fertilising effects of that CO2. However,
tests of the hypothesis using radioisotope tracers indicate that, in the competition for inorganic
nutrients, higher CO2 concentrations may actually favour the plants rather than the microflora. The
relatively lower microbial metabolism could, however, have an indirect adverse effect on plant
nutrition by restricting nutrient cycling in soils, and has the potential to induce negative feedback to
rising atmospheric CO2 concentrations. (C) 1998 Elsevier Science B.V. All rights reserved.

KEYWORDS: DISSOLVED ORGANIC-MATTER, ELEVATED CARBON-DIOXIDE


     694  
Frehner, M., A. Luscher, T. Hebeisen, S. Zanetti, F. Schubiger, and M. Scalet. 1997. Effects
of elevated partial pressure of carbon dioxide and season of the year on forage quality and cyanide
concentration of Trifolium repens L. from a FACE experiment. Acta Oecologica-International
Journal of Ecology 18(3):297-304.

Differently managed (cutting frequency and N fertilization) Trifolium repens monocultures were
grown at 60 Pa and 35 Pa of pCO(2) (partial pressure of CO2) in a Free Air Carbon dioxide
Enrichment (FACE) array. The concentrations of cyanide, digestible organic matter, crude protein
and net energy for lactation were measured at different harvests throughout the growing season. The
average cyanide concentrations differed significantly in the years and the seasons within the year;
however, the concentrations were not affected by CO2. Digestible organic matter, crude protein and
net energy for lactation differed significantly with the seasons of the year and cutting frequencies.
While digestible organic matter and net energy for lactation were not affected by elevated pCO(2),
the concentration of crude protein decreased from 288 g kg(-1) at ambient to 251 g kg(-1) at elevated
pCO(2). Since the crude protein concentration in herbage from Trifolium monocultures was very high
even at elevated CO2, it is suggested that this decrease in crude protein concentration does not
negatively affect forage quality. We conclude that, in Trifolium herbage, the seasons of the year and
management practices are more decisive for forage quality than changes in pCO(2). We shall discuss
how forage quality and cyanide intake by ruminants may, however, be affected by CO2-induced shifts
in the proportion of species in mixed plant communities.

KEYWORDS: ECOSYSTEM, HERBIVORE INTERACTIONS, INSECT HERBIVORE, NITROGEN,
PHOTOSYNTHESIS, PLANTS, RESPONSES, RISING CO2, ROOT FRACTION, TEMPERATURE


     695  
Frick, J., S.S. Nielsen, and C.A. Mitchell. 1994. Yield and seed oil content response of dwarf,
rapid-cycling brassica to nitrogen treatments, planting density, and carbon- dioxide enrichment.
Journal of the American Society for Horticultural Science 119(6):1137-1143.

Effects of N level (15 to 30 mM), time of N increase (14 to 28 days after planting), and planting
density (1163 to 2093 plants/m(2)) were determined for crop yield responses of dwarf, rapid-cycling
brassica (Brassica napus L., CrGC 5-2, Genome: ACaacc). Crops were grown in solid-matrix
hydroponic systems and under controlled-environment conditions, including nonsupplemented
(ambient) or elevated CO2 concentrations (998 +/- 12 mumol mol(-1)). The highest seed yield rate
obtained (4.4 g.m(-2).day(-1)) occurred with the lowest N level (15 mM) applied at the latest
treatment time (day 28). In all trials, CO2 enrichment reduced seed yield rate and harvest index by
delaying the onset of flowering and senescence and stimulating vegetative shoot growth. The highest
shoot biomass accumulation rate (55.5 g.m-2.day(-1)) occurred with the highest N level (30 mM)
applied at the earliest time (day 14). Seed oil content was not significantly affected by CO2
enrichment. Maximum seed oil content (30% to 34%, dry weight basis) was obtained using the lowest
N level (15 mM) initiated at the latest treatment time (day 28). In general, an increase in seed oil
content was accompanied by a decrease in seed protein. Seed carbohydrate, moisture, and ash
contents did not vary significantly in response to experimental treatments. Effects of N level and time
of N increase were consistently significant for most crop responses. Planting density was significant
only under elevated CO2 conditions.

KEYWORDS: AUTUMN, GROWTH, NAPUS, OILSEED RAPE, SIZE


     696  
Friedlingstein, P., I. Fung, E. Holland, J. John, G. Brasseur, D. Erickson, and D. Schimel.
1995. On the contribution of co2 fertilization to the missing biospheric sink. Global Biogeochemical
Cycles 9(4):541-556.

A gridded biospheric carbon model is used to investigate the impact of the atmospheric CO2 increase
on terrestrial carbon storage. The analysis shows that the calculated CO2 fertilization sink is
dependent not just on the mathematical formulation of the ''beta factor'' but also on the relative
controls of net primary productivity (NPP), carbon residence times, and resource availability. The
modeled evolution of the biosphere for the period 1850-1990 shows an increasing lag between NPP
and the heterotrophic respiration. The time evolution of the modeled biospheric sink (i.e., difference
between enhanced NPP and enhanced respiration) does not match that obtained by deconvolution of
the ice core CO2 time series. Agreement between the two is reasonable for the first half of the period,
but during the recent decades the deconvoluted CO2 increase is much too fast to be explained by the
CO2 fertilization effect only. Therefore other mechanisms than CO2 fertilization should also
contribute to the missing sink. Our results suggest that about two thirds to three fourths of the 1850-
1990 integrated missing sink is due to the CO2 greening of the biosphere. The remainder may be due
to the increased level of nitrogen deposition starting around 1950.

KEYWORDS: ATMOSPHERIC CARBON-DIOXIDE, CLIMATE, DECOMPOSITION DYNAMICS,
ECOSYSTEMS, ELEVATED CO2, MODEL, NITROGEN, RESPONSES, SIMULATION, TROPICAL
DEFORESTATION


     697  
Friedlingstein, P., G. Joel, C.B. Field, and I.Y. Fung. 1999. Toward an allocation scheme for
global terrestrial carbon models. Global Change Biology 5(7):755-770.

The distribution of assimilated carbon among the plant parts has a profound effect on plant growth,
and at a larger scale, on terrestrial biogeochemistry. Although important progress has been made in
modelling photosynthesis, less effort has been spent on understanding the carbon allocation, especially
at large spatial scales. Whereas several individual-level models of plant growth include an allocation
scheme, most global terrestrial models still assume constant allocation of net primary production
(NPP) among plant parts, without any environmental coupling. Here, we use the CASA biosphere
model as a platform for exploring a new global allocation scheme that estimates allocation of
photosynthesis products among leaves, stems, and roots depending on resource availability. The
philosophy underlying the model is that-allocation patterns result from evolved responses that adjust
carbon investments to facilitate capture of the most limiting resources, i.e. light, water, and mineral
nitrogen. In addition, we allow allocation of NPP to vary in response to changes in atmospheric CO2.
The relative magnitudes of changes in NPP and resource-use efficiency control the response of
root:shoot allocation. For ambient CO2, the model produces realistic changes in above- ground
allocation along productivity gradients. In comparison to the CASA standard estimate using fixed
allocation ratios, the new allocation scheme tends to favour root allocation, leading to a 10% lower
global biomass. Elevated CO2, which alters the balance between growth and available resources,
generally leads to reduced water stress and consequently, decreased root:shoot ratio. The major
exception is forest ecosystems, where increased nitrogen stress induces a larger root allocation.

KEYWORDS: ATMOSPHERIC CO2 CONCENTRATION, BIOMASS ALLOCATION, BIOSPHERE-
MODEL, INTERNAL NITROGEN CONCENTRATION, LONG-TERM ELEVATION, NET
PRIMARY PRODUCTION, PARTITIONING MODEL, PLANT-RESPONSES, SHOOT RATIOS,
SURFACE PARAMETERIZATION SIB2


     698  
Friend, A.D., and P.M. Cox. 1995. Modeling the effects of atmospheric co2 on vegetation
atmosphere interactions. Agricultural and Forest Meteorology 73(3-4):285-295.

The effect of doubling atmospheric CO2 concentration (C-a) on climate and vegetation is investigated
using a combined climate-vegetation model. The vegetation model predicts the response of leaf area
index, canopy transpiration (E(T)) and whole-plant carbon balance to changes in climate, soil
moisture, and atmospheric CO2 forcing. This model has been embedded in the UK Meteorological
Office Single Column Model (SCM), which provides the climate feedback to the vegetation. The
vegetation model uses an optimisation approach to predict stomatal resistance, a biochemical model
to predict photosynthesis and a simple carbon balance model to predict leaf area. Respiration is
calculated as a function of leaf area and vegetation height. Clouds are assumed to be radiatively
passive in the SCM to avoid unrealistic feedbacks. Simulations were performed with the fully
interactive vegetation-climate model for an Amazon location with the present-day value of C-a (1 x
CO2), and twice this value (2 x CO2). In addition, two other types of simulation were performed at
both CO2 concentrations: one in which the vegetation component was forced only with 1 x CO2, and
one using a fixed surface resistance. The latter case is equivalent to simulations using most current
general circulation models. In all the simulations, increased atmospheric CO2 caused an increase in
surface temperature owing to increased radiative forcing. With a fixed resistance, mean E(T) was
increased by 5.6% and sensible heat flux was reduced by 3.8%. The fully interactive model had
significant effects on the response of both climate and productivity to C-a. Increased C-a caused
stomatal closure, which resulted in a reduction in mean E(T) Of 25%. The effect of C-a on E(T) was
amplified by the positive feedback resulting from the effect of increased air humidity deficit on
stomatal resistance.

KEYWORDS: CARBON DIOXIDE, ELEVATED CO2, FIELD, PHOTOSYNTHESIS, SEEDLINGS,
STOMATAL CONDUCTANCE, TRANSPIRATION


     699  
Fritschi, F.B., K.J. Boote, L.E. Sollenberger, and L.H. Allen. 1999. Carbon dioxide and
temperature effects on forage establishment: tissue composition and nutritive value. Global Change
Biology 5(7):743-753.

Atmospheric CO2 concentration ([CO2]) and temperature are likely to increase in the future and may
change plant growth and composition characteristics. Rhizoma peanut (Arachis glabrata Benth.) and
bahiagrass (Paspalum notatum Flugge) were grown on a natural field soil in temperature-gradient
greenhouses to evaluate the effects of elevated [CO2] and temperature on tissue composition and
digestibility during the establishment year. Carbon dioxide levels were maintained at 365 (ambient)
and 640 mu L CO2 L-1 air. The temperature- gradient greenhouses were regulated to obtain air
temperature sectors of 0.2, 1.5, 2.9, and 4.5 degrees C above ambient. Samples were taken of
previously undefoliated herbage at 57, 86, 121, 148, and 217 days after planting and entire plots were
harvested at 218 days after planting. Elevated [CO2] increased total nonstructural carbohydrate
concentration in rhizoma peanut leaves by almost 50%. Rhizoma peanut leaf N concentration was 6%
lower at elevated than at ambient [CO2]. The N concentration in new rhizomes of rhizoma peanut
was increased by high [CO2], while the N concentration in bahiagrass was not affected by
temperature or [CO2]. No effects of [CO2] and temperature were found on neutral detergent fibre
in rhizoma peanut leaves or stems; however, elevated [CO2] increased neutral detergent fibre in
bahiagrass leaves. Only at season end was in vitro organic matter digestion of rhizoma peanut higher
at ambient (623 g kg(-1)) than at elevated [CO2] (609 g kg(-1)). Elevated [CO2] had a greater effect
on tissue composition of rhizoma peanut than of bahiagrass. These data suggest that elevated
temperature and CO2-induced changes in chemical composition of forage species adapted to humid
subtropics will be relatively small, particularly for C4 species.

KEYWORDS: DECIDUOUS TREES, ELEVATED ATMOSPHERIC CO2, GAS-EXCHANGE,
GRACILIS C-4, INSECT PERFORMANCE, LEAF, NITROGEN, PASCOPYRUM-SMITHII C-3,
PLANT, ROOT FRACTION


     700  
Fritschi, F.B., K.J. Boote, L.E. Sollenberger, L.H. Allen, and T.R. Sinclair. 1999. Carbon
dioxide and temperature effects on forage establishment: photosynthesis and biomass production.
Global Change Biology 5(4):441-453.

Concerns about climatic change have stimulated interest in the response of plants to increasing CO2
concentration ([CO2]), temperature, and their possible interactions. The purpose of this study was
to determine the effects of elevated [CO2] and air temperature on photosynthesis, development, and
biomass production of rhizoma peanut (Arachis glabrata Benth.) and bahiagrass (Paspalum notatum
Flugge) during the establishment year. Forages were grown in four temperature-gradient greenhouses
on a natural Grossarenic Paleudult soil profile at temperatures of 0.2, 1.5, 2.9, and 4.5 degrees C
above ambient, and at [CO2] of 365 and 640 mu L CO2 L-1 air. Elevated [CO2] accelerated
establishment and ground cover of both species. Leaf and canopy photosynthesis of both species
increased at elevated [CO2], with greater increases in rhizoma peanut than bahiagrass. Averaged
across five sampling dates, total biomass production of rhizoma peanut and bahiagrass responded to
elevated [CO2] with a 52 and 9% increase, respectively. Increasing temperature enhanced biomass
production of bahiagrass but not rhizoma peanut. Forage yield at the end of the growing season in
CO2-enriched treatments was increased over that in ambient [CO2] treatments (385 vs. 318 g m(-2)
for rhizoma peanut and 376 vs. 321 g m(-2) for bahiagrass). Overall, the enhancement of rhizoma
peanut under elevated [CO2] was greater than that of bahiagrass; however, bahiagrass responded
more positively to increasing temperature.

KEYWORDS: AIR CO-2 ENRICHMENT, CLIMATE, ELEVATED ATMOSPHERIC CO2,
GRACILIS C-4, GROWTH, LEAF GAS- EXCHANGE, LEAVES, LOLIUM, PASCOPYRUM-
SMITHII C-3, RESPONSES


     701  
Fujii, N., M. Watanabe, Y. Watanabe, and N. Shimada. 1994. Relationship between oxalate
synthesis and glycolate cycle in spinach. Journal of the Japanese Society for Horticultural Science
62(4):789-794.

The relationship between oxalate synthesis and glycolate pathway in spinach (Spinacia oleracea L.
cv. Sunlight) was studied by exposing seedling to 1,000 PPM CO2-enriched atmosphere. It was
observed that CO2-enrichment increased the content of ascorbic acid but decreased that of oxalate.
It was presumed that reducing the rate of glycolate synthesis would reduce the content of oxalate.
Mature leaves of spinach grown under normal conditions, were fed with [2-C-14] glycolate and [1-C-
14] ascorbic acid to compare their contribution as a precursor of oxalate. Using the values of the C-
14 distribution to oxalate, photorespiratory glycolate metabolic rate and the turnover rate of ascorbic
acid, the rate of oxalate synthesis was calculated. It was observed that glycolate was more efficient
as a precursor of oxalate synthesis than it was for ascorbic acid. From these results, we postulate that
the oxalate synthesis is closely related to the glycolate cycle.

KEYWORDS: CALCIUM


     702  
Gahrooee, F.R. 1998. Impacts of elevated atmospheric CO2 on litter quality, litter decomposability
and nitrogen turnover rate of two oak species in a Mediterranean forest ecosystem. Global Change
Biology 4(6):667-677.

Elevated CO2 may affect litter quality of plants, and subsequently C and N cycling in terrestrial
ecosystems, but changes in litter quality associated with elevated CO2 are poorly known. Abscised
leaf litter of two oak species (Quercus cerris L. and a. pubescens Willd.) exposed to long-term
elevated CO2 around a natural CO2 spring in Tuscany (Italy) was used to study the impact of
increasing concentration of atmospheric CO2 on litter quality and C and N turnover rates in a
Mediterranean-type ecosystem. Litter samples were collected in an area with elevated CO2 (>500
ppm) and in an area with ambient CO2 concentration (360 ppm). Leaf samples were analysed for
concentrations of total C, N, lignin, cellulose, acid detergent residue (ADR) and polyphenol. The
decomposition rate of litter was studied using a litter bag experiment (12 months) and laboratory
incubations (3 months). In the laboratory incubations, N mineralization in litter samples was measured
as well (125 days). Litter quality was expressed in terms of chemical composition and element ratios.
None of the litter quality parameters was affected by elevated CO2 for the two Quercus species.
Remaining mass in a. cerris and Q. pubescens litter from elevated CO2 was similar to that from
ambient conditions. C mineralization in Q. pubescens litter from elevated CO2 was lower than that
from ambient CO2, but the difference was insignificant. This effect was not observed for Q. cerris.
N mineralization was higher from litter grown at elevated CO2, but this difference disappeared at the
end of the incubation. Litter of a. pubescens had a higher quality than Q. cerris, and indeed
mineralized more rapidly in the laboratory, but not under field conditions.

KEYWORDS: CARBON DIOXIDE, CLIMATE CHANGE, DECOMPOSITION, GROWTH, LEAF
LITTER, PHOTOSYNTHESIS, RESPIRATION, RESPONSES, SOIL, TERRESTRIAL ECOSYSTEMS


     703  
Gallardo, A., and J. Merino. 1998. Soil nitrogen dynamics in response to carbon increase in a
Mediterranean shrubland of SW Spain. Soil Biology and Biochemistry 30(10-11):1349-1358.

Most models predict that high atmospheric CO2 concentrations will lead to an increase in the C-to-N
ratio of litter production in terrestrial ecosystems. The effect of an increase in the soil C-to-N ratio
on the nitrogen dynamics in a Mediterranean shrubland was simulated by mixing with the lifter layer
wood shavings with a high C-to-N ratio. Samples of mineral soil, taken subsequently eight times
during 404 d, were analyzed for total C, total N, total soil carbohydrates, potential net N
mineralization, potential net nitrification and microbial biomass-N. We found significant increases in
the concentration of total carbohydrates, C-to-N ratio and microbial biomass N in amended soils
during the experiment, while potential net N mineralization rate and net nitrification rate significantly
decreased; amounts of available nitrogen (NH4+-N + NO3-N) were unaffected by the amendment
treatment. However, by the end of the experiment, no significant differences between amended and
control soil samples were found. The total carbohydrates-to-K2SO4-extractable total-N ratio was the
best predictor of both net mineralization rate and microbial biomass N, showing that the available C-
to- available-N ratio is a better indicator of N dynamics than the total C to total N ratio. Our results
support the hypothesis that increasing C availability in soils leads to a decrease in N availability for
plants through the immobilization of N in microbial biomass and to an increase in the temporal
heterogeneity of soil properties in a Mediterranean shrubland. (C) 1998 Elsevier Science Ltd. All
rights reserved.

KEYWORDS: ANNUAL GRASSLAND, DIOXIDE, ECOSYSTEMS, ELEVATED ATMOSPHERIC
CO2, MICROBIAL BIOMASS, MINERAL-SOIL, NITRIFICATION, OLD-GROWTH FOREST,
PLANTS, TALLGRASS PRAIRIE


     704  
Galtier, N., C.H. Foyer, E. Murchie, R. Alred, P. Quick, T.A. Voelker, C. Thepenier, G.
Lasceve, and T. Betsche. 1995. Effects of light and atmospheric carbon-dioxide enrichment on
photosynthesis and carbon partitioning in the leaves of tomato (lycopersicon-esculentum L) plants
over-expressing sucrose- phosphate synthase. Journal of Experimental Botany 46:1335-1344.

Photosynthetic carbon assimilation, carbon partitioning and foliar carbon budgets were measured in
the leaves of transformed tomato plants expressing a maize sucrose-phosphate synthase (SPS) gene
in addition to the native enzyme, and in untransformed controls. The maize SPS gene was expressed
under control of either the promoter of the small subunit of ribulose 1,5-bisphosphate carboxylase
(rbcS promoter; lines 2, 9 and 18) or the 35S promoter from cauliflower mosaic virus (CaMV
promoter; line 13). The rate of sucrose synthesis was increased relative to that of starch and
sucrose/starch ratios were higher throughout the photoperiod in the leaves of all plants expressing
high SPS activity. The leaf carbon budget over the day/night cycle in air at low irradiance (180 mu
mol photon m(- 2) s(-1)) was similar in all plants. Net photosynthesis measured in air and at elevated
CO2 (800-1500 mu l I-1) on whole plants grown in air at 400 mu mol m(-2) s(-1) irradiance was
significantly increased in the high SPS expressors compared to the untransformed controls and was
highest where SPS activity was greatest. At high CO2 the stimulation of photosynthesis was more
pronounced, We conclude that SPS activity is a major point of control of photosynthesis particularly
under saturating light and CO2.

KEYWORDS: ACCLIMATION, BIOSYNTHESIS, CARBOHYDRATE, ELEVATED CO2, GROWTH,
INHIBITION, PHASEOLUS-VULGARIS L, RIBULOSE-1;5-BISPHOSPHATE CARBOXYLASE-
OXYGENASE, SPINACH LEAVES, STARCH


     705  
Gao, K., Y. Aruga, K. Asada, T. Ishihara, T. Akano, and M. Kiyohara. 1991. Enhanced growth
of the red alga porphyra-yezoensis ueda in high co2 concentrations. Journal of Applied Phycology
3(4):355-362.

Leafy thalli of the red alga Porphyra yezoensis Ueda, initiated from conchospores released from free-
living conchocelis, were cultured using aeration with high CO2. It was found that the higher the CO2
concentration, the faster the growth of the thalli. Aeration with elevated CO2 lowered pH in dark,
but raised pH remarkably in light with the thalli, because the photosynthetic conversion of HCO3-
to OH- and CO2 proceeded much faster than the dissociation of hydrated CO2 releasing H+.
Photosynthesis of the alga was found to be enhanced in the seawater of elevated dissolved inorganic
carbon (DIC, CO2 + HC O3- + CO3-). It is concluded that the increased pH in the light resulted in
the increase of DIC in the culture media, thus enhancing photosynthesis and growth. The relevance
of the results to removal of atmospheric CO2 by marine algae is discussed.

KEYWORDS: ASSIMILATION, CHONDRUS-CRISPUS, DIATOM, INORGANIC-CARBON
UPTAKE, MARINE MACROALGAE, PHAEOPHYTA, PHOTOSYNTHESIS, PLANTS,
TRANSPORT, WATER


     706  
Gao, K., Y. Aruga, K. Asada, T. Ishihara, T. Akano, and M. Kiyohara. 1993. Calcification in
the articulated coralline alga corallina- pilulifera, with special reference to the effect of elevated co2
concentration. Marine Biology 117(1):129-132.

Calcification in Corallina pilulifera Postels et Ruprecht displayed diurnal variations in aerated (350
ppm CO2) culture media, with faster rates during the light than during the dark period. Addition of
CO2 (air + 1250 ppm) inhibited calcification. This was attributable to the decreased pH resulting from
CO2 addition. Both photosynthesis and calcification were enhanced in seawater, with elevated
dissolved inorganic carbon concentrations at a constant pH of 8.2.

KEYWORDS: CAULERPALES, CHLOROPHYCEAE, GROWTH, HALIMEDA, MARINE PLANTS,
PHOTOSYNTHESIS, RESPIRATION


     707  
Gao, K., Y. Aruga, K. Asada, and M. Kiyohara. 1993. Influence of enhanced co2 on growth and
photosynthesis of the red algae gracilaria sp and g-chilensis. Journal of Applied Phycology 5(6):563-
571.

The influence of elevated CO2 concentrations on growth and photosynthesis of Gracilaria sp. and G.
chilensis was investigated in order to procure information on the effective utilization of CO2. Growth
of both was enhanced by CO2 enrichment (air + 650 ppm CO2, air + 1250 ppm CO2), the
enhancement being greater in Gracilaria sp. Both species increased uptake of NO, with CO,
enrichment. Photosynthetic inorganic carbon uptake was depressed in G. chilensis by pre- culture (15
days) with CO2 enrichment, but little affected in Gracilaria sp. Mass spectrometric analysis showed
that O-2 uptake was higher in the light than in the dark for both species and in both cases was higher
in Gracilaria sp. The higher growth enhancement in Gracilaria sp. was attributed to greater depression
of photorespiration by the enrichment of CO2 in culture.

KEYWORDS: ANHYDRASE, INORGANIC CARBON, MARINE MACROALGAE, PHYSIOLOGY


     708  
Gao, Q., and M. Yu. 1998. A model of regional vegetation dynamics and its application to the study
of Northeast China Transect (NECT) responses to global change. Global Biogeochemical Cycles
12(2):329-344.

We developed a dynamic regional vegetation model to address problems of responses of regional
vegetation to elevated ambient CO2 and climatic change. The model takes into consideration both
local ecosystem processes within a patch or grid cell, such as plant growth and death, and mass and
energy flow, such as plant migration, across adjacent grid cells. The model is able to couple
vegetation structure dynamics and primary production processes. The normalized differential
vegetation index from meteorological satellite AVHRR was used to parameterize the model. Plant
migration rates were derived based on effective seedling distribution around parent plants. The model
was applied to Northeast China Transect at a spatial resolution of 10 min latitude by 10 min longitude
per grid cell and a temporal resolution of 1 month. The results indicated that with doubled CO2
concentration, a 20% increase in precipitation and a 4 degrees C increase in temperature, the model
predicted that net primary productivity (NPP) of Larix forests, conifer-broadleaf mixed forests,
Aneurolepidium chinense steppes, Stipa grandis steppes, and wetland and salty meadows would
decrease by 15% to 20%. However, NPP of deciduous broadleaf forests, woodland and shrubs, Stipa
baicalensis meadow steppes, and desert grasslands would increase by 20% to 115%, as predicted by
the model for the same climatic scenario. The average NPP of natural vegetation over the whole
transect would decrease slightly, largely because of the compensation between the positive effects
of increased CO2 and precipitation and the negative effect of increased evapotranspiration induced
by increased temperature.

KEYWORDS: BIOMASS, CLIMATE, FOREST ECOSYSTEM PROCESSES, GENERAL-MODEL,
NET PRIMARY PRODUCTIVITY, PHOTOSYNTHESIS, SATELLITE, SENSITIVITY, SIMULATION,
TERRESTRIAL BIOSPHERE


     709  
Gao, Q., and X.S. Zhang. 1997. A simulation study of responses of the northeast China transect to
elevated CO2 and climate change. Ecological Applications 7(2):470-483.

The spatiotemporal variations of vegetation biomass of the ecological transect in northeast China
were simulated. Slate variables of the model included green biomass and nongreen biomass of 12
vegetation categories and water contents of three soil layers. The simulated monthly green biomass
was converted into NDVI, or Normalized Differential Vegetation Index of AVHRR (Advanced Very
High Resolution Radiometry). A comparison between the modeled and the observed NDVI was made
at 10' spatial resolution, Atmospheric CO2 concentration and montiiiy precipitation were used as two
driving variables for global change simulation. Effects of precipitation increments on percentage
sunshine, relative humidity, radiation, evapotranspiration, and eventually soil water and plant growth,
were considered, Two levers of CO2 concentration (present, doubled) and seven levels of
precipitation increments (0, 0.05, 0.1, 0.15, 0.2, 0.25, and 0.30) were prescribed for a total of 14
simulation runs. A steady-state solution was obtained for each simulation run. The results of
simulation showed that with the present climate conditions, doubling atmospheric CO2 concentration
led approximately to a 20.3% increase in green biomass, 11.0% increase in nongreen biomass, 19,0%
increase in green NPP, 12.8% increase in nongreen NPP, and 24.9% increase in overall average NPP
at steady state, These increases go, respectively, to 32.9, 13.9, 30.0, 20.1, and 23.4% when a 30%
precipitation increase was superimposed on the doubled CO2 concentration.

KEYWORDS: FORESTS, LEAF-AREA INDEX, MODEL, PHOTOSYNTHESIS, PRODUCTIVITY,
SATELLITE, VEGETATION


     710  
Garbutt, K., W.E. Williams, and F.A. Bazzaz. 1990. Analysis of the differential response of 5
annuals to elevated CO2 during growth. Ecology 71(3):1185-1194.



     711  
Garcia, J.M. 1993. Effect of co2 in fruit storage atmosphere on olive oil quality. Grasas Y Aceites
44(3):169-174.

Olive fruits (Olea europaea, cv. ''Picual'') were stored at 5- degrees-C and four different atmospheres
(% CO2/% O2/%N2: 0/21/78: 5/20/75; 10/19/71 and 20/17/63). At 5-degrees-C the enrichment of
the fruit storage atmosphere with concentrations of CO2 above 5% resulted in a linear increase of the
acidity of extracted oils after 60 days of fruit storage time. This fact showed a strong relationship with
the appearence of fruit decay. Simple refrigeration of fruits at 5-degrees-C for 60 days was sufficient
to mantain the commercial quality of ''virgin extra'' in oil extracted from them. Oils obtained from
fruits stored at 5-degrees-C in CO2 enriched atmospheres showed lower peroxide index and UV
absorbance (270 nm), but developed off-flavor. Therefore, greater-than-or-equal-to 5% CO2
concentrations in storage atmosphere of olive fruits for oil production at 5-degrees-C must be
avoided.



     712  
Garcia, J.M., and J. Streif. 1993. Quality and storage potential of pear .1. Influence of ca- storage
and ulo-storage conditions. Gartenbauwissenschaft 58(1):36-41.

In a CA experiment the storage potential of different pear cultivars was investigated, especially the
behaviour of the fruits against elevated CO2 concentrations and/or ultra low oxygen (ULO).The
following CA combinations were tested: < 1 % CO2 + 3 % O2; 3 % CO2 + 3 % O2; < 1 % CO2 +
1 % O2; 3 % CO2 + 1 % O2, and refrigerated storage at - 1-degrees-C 'Packham's Triumph' showed
the best storage potential of all tested cultivars followed by 'Conference' and 'Doyenne' du Comice.
The keepability of 'General Leclerc' was only slightly improved by CA conditions compared with cold
stored pears. CA storage of 'Alexander Lucas' and 'Bristol Cross' didn't show an obvious advantage
because of high CO2 damages. Therefore, CO2 concentrations in CA storage of these two cultivars
should be < 1 %. 'Conference' and 'General Leclerc' tolerate up to 2 % CO2, 'Doyenne du Comice'
and 'Packham's Triumph' up to 3 % CO2. ULO conditions amplified the CO2 damages in the CO2
sensitive cultivars, but improved the keepability of 'Doyenne du Comice' and 'Packham's Triumph'.



     713  
Garcia, R.L., S.B. Idso, and B.A. Kimball. 1994. Net photosynthesis as a function of carbon-
dioxide concentration in pine trees grown at ambient and elevated co2. Environmental and
Experimental Botany 34(3):337-341.

Pinus eldarica seedlings were grown in a field of Avondale loam at Phoenix, Arizona within
transparent open-top enclosures maintained for 15 months at mean CO2 concentrations of 402 and
788 mu l 1(-1), after which whole-tree net photosynthetic rates were measured at a number of CO2
concentrations ranging from ambient (360 mu l 1(-1)) to 3000 mu l 1(-1). Rates of the low- CO2-
treatment trees saturated at approximately five times their ambient-concentration value; while rates
of the high-CO2- treatment trees rose linearly across the entire CO2 range investigated to more than
10 times their value al 360 mu l 1(- 1). These findings suggest that long-term exposure to elevated
CO2 can increase the ability of trees with unrestricted root systems to respond positively to still
higher CO2 concentrations.

KEYWORDS: ACCLIMATION, ENRICHMENT, PLANTS, RESPIRATION


     714  
Garcia, R.L., S.B. Idso, G.W. Wall, and B.A. Kimball. 1994. Changes in net photosynthesis and
growth of pinus-eldarica seedlings in response to atmospheric co2 enrichment. Plant, Cell and
Environment 17(8):971-978.

Pinus eldarica L. trees, rooted in the natural soil of an agricultural field at Phoenix, Arizona, were
grown from the seedling stage in clear-plastic-wall open-top enclosures maintained at four different
atmospheric CO2 concentrations for 15 months. Light response functions were determined for one
tree from each treatment by means of whole-tree net CO2 exchange measurements at the end of this
period, after which rates of carbon assimilation of an ambient-treatment tree were measured across
a range of atmospheric COP concentrations. The first of these data sets incorporates the
consequences of both the CO2-induced enhancement of net photosynthesis per unit needle area and
the CO2-induced enhancement of needle area itself (due primarily to the production of more needles),
whereas the second data set reflects only the first of these effects. Hence the division of the
normalized results of the first data set by the normalized results of the second set yields a
representation of the increase in whole-tree net photosynthesis due to enhanced needle production
caused by atmospheric CO2 enrichment. In the solitary trees we studied, the relative contribution of
this effect increased rapidly with the CO2 concentration of the air to increase whole-tree net
photosynthesis by nearly 50% at a CO2 concentration approximately 300 mu mol mol(-1) above
ambient.

KEYWORDS: AMBIENT, CARBON DIOXIDE, ELEVATED CO2, FIELD, LIGHT,
PRODUCTIVITY, SCIRPUS- OLNEYI, SOUR ORANGE TREES, TEMPERATURE, YIELD


     715  
Garcia, R.L., S.P. Long, G.W. Wall, C.P. Osborne, B.A. Kimball, G.Y. Nie, P.J. Pinter, R.L.
Lamorte, and F. Wechsung. 1998. Photosynthesis and conductance of spring-wheat leaves: field
response to continuous free-air atmospheric CO2 enrichment. Plant, Cell and Environment
21(7):659-669.

Spring wheat was grown from emergence to grain maturity in two partial pressures of CO2 (pCO(2)):
ambient air of nominally 37 Pa and air enriched with CO2 to 55 Pa using a free-air CO2 enrichment
(FACE) apparatus. This experiment was the first of its kind to be conducted within a cereal field
without the modifications or disturbance of microclimate and rooting environment that accompanied
previous studies, It provided a unique opportunity to examine the hypothesis that continuous
exposure of wheat to elevated pCO(2) will lead to acclimatory loss of photosynthetic capacity. The
diurnal courses of photosynthesis and conductance for upper canopy leaves were followed throughout
the development of the crop and compared to model-predicted rates of photosynthesis. The seasonal
average of midday photosynthesis rates was 28% greater in plants exposed to elevated pCO(2) than
in contols and the seasonal average of the daily integrals of photosynthesis was 21% greater in
elevated pCO(2) than in ambient air. The mean conductance at midday was reduced by 36%. The
observed enhancement of photosynthesis in elevated pCO(2) agreed closely with that predicted from
a mechanistic biochemical model that assumed no acclimation of photosynthetic capacity. Measured
values fell below predicted only in the flag leaves in the mid afternoon before the onset of grain-filling
and over the whole diurnal course at the end of grain-filling. The loss of enhancement at this final
stage was attributed to the earlier senescence of flag leaves in elevated pCO(2). In contrast to some
controlled-environment and field-enclosure studies, this field-scale study of wheat using free-air CO2
enrichment found little evidence of acclimatory loss of photosynthetic capacity with growth in
elevated pCO(2) and a significant and substantial increase in leaf photosynthesis throughout the life
of the crop.

KEYWORDS: ACCLIMATION, CAPACITY, CARBON-DIOXIDE ENRICHMENT, ELEVATED
CO2, GROWTH, LEAF, PRODUCTIVITY, PROTEINS, WATER-USE EFFICIENCY, WINTER-
WHEAT


     716  
Garcia-Ibilcieta, D., and J.C. Pushnik. 1997. Differential gene displays from Pinus ponderosa
seedlings experiencing elevated CO2 stress. Faseb Journal 11(9):A1104.



     717  
Gardner, S.D.L., G. Taylor, and C. Bosac. 1995. Leaf growth of hybrid poplar following exposure
to elevated co2. New Phytologist 131(1):81-90.

Leaf extension was stimulated following exposure of three interamerican hybrid poplar clones
(Populus trichocarpa x P. deltoides); 'Unal', 'Boelare', and 'Beaupre' and a euramerican clone 'Primo'
(Populus nigra x P. deltoides) to elevated CO2 in controlled environment chambers. For all three
interamerican clones the evidence suggests that this was the result of increased leaf cell expansion
associated with enhanced cell wall extensibility (WEx), measured as tensiometric increases in cell wall
plasticity. For the interamerican clone 'Boelare', there was also a significant increase in cell wall
elasticity following exposure to elevated CO2 (P less than or equal to 0.001). The effect of elevated
CO2 in stimulating cell wall extensibility was confirmed in a detailed spatial analysis of extensibility
made across the lamina of expanding leaves of the clone 'Boelare'. For two of the interamerican
hybrids, 'Unal' and 'Beaupre', both leaf cell water potential (psi) and turgor pressure (P) were lower
in elevated than in ambient CO2 By contrast, no significant effects on the cell wall properties or leaf
water relations for the euramerican hybrid 'Primo' were observed following exposure to elevated
CO2, suggesting that the mechanism for increased leaf extension in elevated CO2 differed, depending
on clone. The cumulative total length of leaves of 'Boelare' grown in elevated CO2 was significantly
increased (P less than or equal to 0.05) and since leaf number was not significantly increased in any
inter-american clone it is hypothesized that final leaf size was stimulated in elevated CO2 for these
clones. By contrast, there was no significant effect of CO2 on cumulative total leaf length for the
euramerican clone 'Primo', but leaf number was significantly increased by elevated CO2. The
measurements suggest that total tree leaf area was stimulated for a range of poplar hybrids exposed
to elevated CO2. Given the short rotation of a coppiced crop, it is likely that increased leaf areas will
result in enhanced stemwood production when hybrid poplars are grown in the CO2 concentrations
predicted for the next century.

KEYWORDS: ATMOSPHERIC CARBON-DIOXIDE, BIOPHYSICS, ENRICHMENT, FORESTS,
PLANT-CELL GROWTH, SALIX-VIMINALIS, SEEDLINGS, WALL EXTENSIBILITY, WATER-
LIMITED CONDITIONS, YIELD


     718  
Gary, C., N. Bertin, J.S. Frossard, and J. Le Bot. 1998. High mineral contents explain the low
construction cost of leaves, stems and fruits of tomato plants. Journal of Experimental Botany
49(318):49-57.

The construction cost of plant tissues is used in crop models to convert the products of
photosynthesis into biomass. As for other greenhouse crops, tomato tissues are specific in that they
have a high mineral content. The consequences of this accumulation of minerals on the construction
cost of the tissues and the possible interactions with the physiological age of the organs and with the
CO2 concentration in the atmosphere was examined. For that purpose, three methods of estimating
the construction cost were used and compared. Large quantities of minerals accumulated in the
tissues of tomato plants (ranging from 0.05 in fruits to 0.26 g g(-1) DM in leaves). The subsequent
dilution of the organic matter explained why the estimated construction cost of the dry matter
(organic matter + minerals) was fairly low in comparison to that of other crop species. The
construction cost was higher in fruits than in vegetative organs, partly because of a lower mineral
content. It decreased by 7-12% from top to bottom of the canopy, following the increase in the
physiological age of the tissues. This ontogenic drift was partly explained by the accumulation of
minerals in the older organs. In the conditions of CO2 enrichment of a commercial greenhouse, no
effect of CO2 concentration on the mineral content and on the construction cost of tissues was
observed. Such a variability of the construction cost of tomato plant tissues due to the accumulation
of minerals or to the ontogeny questions the use of standard values in crop models.

KEYWORDS: CARBON CONTENT, COMBUSTION, CROP, DARK RESPIRATION, EFFICIENCY,
ELEVATED CO2, GRAIN-SORGHUM, GREENHOUSE TOMATO, GROWTH, TEMPERATURE


     719  
Gay, A.P., and B. Hauck. 1994. Acclimation of lolium-temulentum to enhanced carbon-dioxide
concentration. Journal of Experimental Botany 45(277):1133-1141.

Acclimation of single plants of Lolium temulentum to changing [CO2] was studied on plants grown
in controlled environments at 20 degrees C with an 8 h photoperiod. In the first experiment plants
were grown at 135 mu mol m(-2) s(-1) photosynthetic photon flux density (PPFD) at m s 415 mu l
l(-1) or 550 mu l l(-1) [CO2] with some plants transferred from the lower to the higher [CO2] at
emergence of leaf 4. In the second experiment plants were grown at 135 and 500 mu mol m(-2) s(-1)
PPFD at 345 and 575 mu l l(-1) [CO2]. High [CO2] during growth had little effect on stomatal
density, total soluble proteins, chlorophyll a content, amount of Rubisco or cytochrome f. However,
increasing [CO2] during measurement increased photosynthetic rates, particularly in high light. Plants
grown in the higher [CO2] had greater leaf extension, leaf and plant growth rates in low but not in
high light. The results are discussed in relation to the limitation of growth by sink capacity and the
modifications in the plant which allow the storage of extra assimilates at high [CO2].

KEYWORDS: ATMOSPHERIC CO2, ELEVATED CO2, FESTUCA-PRATENSIS, GROWTH, LEAF,
LEAVES, PERENNIAL RYEGRASS, PHOTOSYNTHESIS, PROTEINS, STOMATAL DENSITY


     720  
Gebauer, R.L.E., J.F. Reynolds, and B.R. Strain. 1996. Allometric relations and growth in Pinus
taeda: The effect of elevated CO2 and changing N availability. New Phytologist 134(1):85-93.

Loblolly pine (Pinus taeda L.) seedlings were grown for 138 d at two CO2 partial pressures (35 and
70 Pa CO2) and four N solution concentrations (0.5, 1.5, 3.5 and 6.5 mM NH4NO3). Allometric
regression analysis was used to determine whether patterns of biomass allocation among functionally
distinct plant-parts were directly controlled by CO2 and N availability or whether differences between
treatments were the result of size-dependent changes in allocation. Both CO2 and N availability
affected growth of loblolly pine. Growth stimulation by CO2 at nonlimiting N solution concentrations
(3.5 and 6.5 mM NH4NO3) was c. 90%. At the lowest N solution concentration (0.5 mM NH4NO3),
total plant biomass was still enhanced by 35% under elevated CO2. Relative growth rates were highly
correlated with net assimilation rates, whereas leaf mass ratio remained unchanged under the wide
range of CO2 and N solution concentrations. When differences in plant size were adjusted apparent
CO2 effects on biomass allocation among different plant parts disappeared, indicating that CO2 only
indirectly affected allocation through accelerated growth. N availability, by contrast, had a direct
effect on biomass allocation, but primarily at the lowest N solution concentration (0.5 mM
NH4NO3). Loblolly pine compensated for N limitation by increasing specific lateral root length and
proportional biomass allocation to the lateral root system. The results emphasize the significance of
distinguishing size- dependent effects on biomass allocation from functional adjustments made in
direct response to changing resource availability.

KEYWORDS: ATMOSPHERIC CO2, CARBON DIOXIDE, ENRICHMENT, LOBLOLLY-PINE,
NITROGEN CONCENTRATION, PHOTOSYNTHESIS, ROOT LENGTH, SEEDLINGS, SHOOT,
WOODY-PLANTS


     721  
Gebauer, R.L.E., B.R. Strain, and J.P. Reynolds. 1998. The effect of elevated CO2 and N
availability on tissue concentrations and whole plant pools of carbon-based secondary compounds
in loblolly pine (Pinus taeda). Oecologia 113(1):29-36.

We examined the extent to which carbon investment into secondary compounds in loblolly pine (Pinus
taeda L.) is changed by the interactive effect of elevated CO2 and N availability and whether
differences among treatments are the result of size-dependent changes. Seedlings were grown for 138
days at two CO2 partial pressures (35 and 70 Pa CO2) and four N solution concentrations (0.5, 1.5,
3.5, and 6.5 mmol l(-1) NO3NH4) and concentrations of total phenolics and condensed tannins were
determined four times during plant development in primary and fascicular needles, stems and lateral
and tap roots. Concentrations of total phenolics in lateral roots and condensed tannins in tap roots
were relatively high regardless of treatment. In the smallest seedlings secondary compound
concentrations were relatively high and decreased in the initial growth phase. Thereafter condensed
tannins accumulated strongly during plant maturation in all plant parts except in lateral roots, where
concentrations did not change. Concentrations of total phenolics continued to decrease in lateral roots
while they remained constant in all other plant parts. At the final harvest plants grown at elevated
CO2 or low N availability showed increased concentrations of condensed tannins in aboveground
parts. The CO2 effect, however, disappeared when size differences were adjusted for, indicating that
CO2 only indirectly affected concentrations of condensed tannins through accelerating growth.
Concentrations of total phenolics increased directly in response to low N availability and elevated
CO2 in primary and fascicular needles and in lateral roots, which is consistent with predictions of the
carbon-nutrient balance (CNB) hypothesis. The CNB hypothesis is also supported by the strong
positive correlations between soluble sugar and total phenolics and between starch and condensed
tannins. The results suggest that predictions of the CNB hypothesis could be improved if
developmentally induced changes of secondary compounds were included.

KEYWORDS: DECOMPOSITION, DEFENSE, GROWTH, HERBIVORY, METABOLISM,
NITROGEN, NUTRIENT BALANCE, PAPER BIRCH, PERFORMANCE, PHENOLIC-
COMPOUNDS


     722  
Gedroc, J.J., K.D.M. McConnaughay, and J.S. Coleman. 1996. Plasticity in root shoot
partitioning: Optimal, ontogenetic, or both? Functional Ecology 10(1):44-50.

1. We tested whether plants increase root,shoot ratios to compensate for limitations of below-ground
resources in a manner consistent with optimal partitioning theory or whether the relative production
of roots and shoots is controlled by species-specific developmental patterns. Individuals of two annual
plant species, Abutilon theophrasti and Chenopodium album, were grown from seed in controlled
greenhouse conditions under high- or low-nutrient regimes. Mid-way through the experiment, a sub-
set of low-nutrient-grown plants were given high nutrient availability and a sub-set of high-nutrient-
grown plants were transferred to a low nutrient environment. 2. Under continuous nutrient regimes:
(1) high-nutrient-grown plants of both species grew faster and had a lower root:shoot ratio than low-
nutrient-grown plants, consistent with optimal partitioning theory; (2) both species exhibited a
substantial amount of ontogenetic drift as root:shoot ratios decreased through ontogeny (subsequent
to an initial increase in R/S shortly after germination); (3) allometric analyses revealed that increased
allocation to roots occurred very early in ontogeny for both species, after which the relative growth
of shoots exceeded that of roots in low-nutrient-grown plants compared to their high nutrient-grown
counterparts - a result inconsistent with optimal partitioning theory. 3. Under temporally varying
nutrient regimes: (1) growth substantially increased in low- nutrient-grown plants that were switched
to a high-nutrient environment without a change in root:shoot partitioning; (2) there was no change
in growth or partitioning when plants were switched from a high- to a low-nutrient regime. 4. We
conclude that, for these annual species, root/shoot partitioning is partially consistent with optimal
partitioning theory but that is also highly ontogenetically constrained. This constraint is evident both
in substantive ontogenetic drift in partitioning and in the period during development that plasticity
in partitioning can be expressed.

KEYWORDS: CARBON DIOXIDE, CONSEQUENCES, ELEVATED CO2, FRAGMENTATION,
GROWTH, NITROGEN CONCENTRATION, PERFORMANCE, PLANT, SIZE, SPACE


     723  
Geethakumari, V.L., and K. Shivashankar. 1991. Studies on organic amendment and CO2
enrichment in ragi soybean intercropping systems. Indian Journal of Agronomy 36(2):202-206.

Organic amendment comprising of ragi husk and FYM mixed in 1:1 ratio by weight promoted organic
carbon content and available P status of the soil. A level of 4 t/ha of organic amendment promoted
the uptake of N significantly by both ragi and soybean. Availability of P and K were also favourably
influenced. Uptake of nutrients by soybean was promoted by CO2 enrichment. Available P status was
higher in intercropped ragi and soybean as compared to pure crops but nutrient uptake was higher
by pure crops.



     724  
Geiger, M., V. Haake, F. Ludewig, U. Sonnewald, and M. Stitt. 1999. The nitrate and ammonium
nitrate supply have a major influence on the response of photosynthesis, carbon metabolism, nitrogen
metabolism and growth to elevated carbon dioxide in tobacco. Plant, Cell and Environment
22(10):1177-1199.

The effect of elevated [CO2] on biomass, nitrate, ammonium, amino acids, protein, nitrate reductase
activity, carbohydrates, photosynthesis, the activities of Rubisco and Sig other Calvin cycle enzymes,
and transcripts for Rubisco small subunit, Rubisco activase, chlorophyll a binding protein, NADP-
glyceraldehyde-3-phosphate dehydrogenase, aldolase, transketolase, plastid fructose-1,6-
bisphosphatase and ADP- glucose pyrophosphorylase was investigated in tobacco growing an 2, 6
and 20 mM nitrate and 1, 3 and 10 mM ammonium nitate. (i) The growth stimulation in elevated
[CO2] was attenuated in intermediate and abolished in low nitrogen. (ii) Elevated [CO2] led to a
decline of nitrate, ammonium, amino acids especially glutamine, and protein in low nitrogen and a
dramatic decrease in intermediate nitrogen, but not in high nitrogen. (iii) Elevated [CO2] led to a
decrease of nitrate reductase activity in low, intermediate and high ammonium nitrate and in
intermediate nitrate, but not in high nitrate, (iii) At low nitrogen, starch increased relative to sugars.
Elevated [CO2] exaggerated this shift. ADP-glucose pyrophosphorylase transcript increased in low
nitrogen, and in elevated [CO2]. (iv) In high nitrogen, sugars rose in elevated [CO2], but there was
no acclimation of photosynthetic rate, only a small decrease of Rubisco and no decrease of other
Calvin cycle enzymes and no decrease of the corresponding transcripts. In lower nitrogen, there was
a marked acclimation of photosynthetic rate and a general decrease of Calvin cycle enzymes, even
though sugar levels did not increase. The decreased activities were due to a general decrease of leaf
protein. The corresponding transcripts did not decrease except at very low nitrogen. (v) It is
concluded that many of the effects of elevated [CO2] on nitrate metabolism, photosynthate allocation,
photosynthetic acclimation and growth are due to a shift in nitrogen status.

KEYWORDS: ADP-GLUCOSE PYROPHOSPHORYLASE, ATMOSPHERIC CO2 ENRICHMENT,
GAS-EXCHANGE, LOBLOLLY-PINE, MINERAL NUTRITION, PINUS-TAEDA, PLANT
GROWTH, RIBULOSE-1;5-BISPHOSPHATE CARBOXYLASE-OXYGENASE, SOUR ORANGE
TREES, TAEDA L SEEDLINGS


     725  
Geiger, M., P. Walch-Liu, C. Engels, J. Harnecker, E.D. Schulze, F. Ludewig, U. Sonnewald,
W.R. Scheible, and M. Stitt. 1998. Enhanced carbon dioxide leads to a modified diurnal rhythm of
nitrate reductase activity in older plants, and a large stimulation of nitrate reductase activity and
higher levels of amino acids in young tobacco plants. Plant, Cell and Environment 21(3):253-268.

Higher rates of nitrate assimilation are required to support faster growth in enhanced carbon dioxide.
To investigate how this is achieved, tobacco plants were grown on high nitrate and high light in
ambient and enhanced (700 mu mol mol(-1)) carbon dioxide. Surprisingly, enhanced carbon dioxide
did not increase leaf nitrate reductase (MR) activity in the middle of the photoperiod. Possible reasons
for this anomalous result were investigated. (a) Measurements of biomass, nitrate, amino acids and
glutamine in plants fertilized once and twice daily with 12 mol m(-3) nitrate showed that enhanced
carbon dioxide did not lead to a nitrate limitation in these plants. (b) Enhanced carbon dioxide
modified the diurnal regulation of NR activity in source leaves. The transcript for nia declined during
the light period in a similar manner in ambient and enhanced carbon dioxide. The decline of the
transcript correlated with a decrease of nitrate in the leaf, and was temporarily reversed after re-
irrigating with nitrate in the second part of the photoperiod. The decline of the transcript was not
correlated with changes of sugars or glutamine. NR activity and protein decline in the second part of
the photoperiod, and NR is inactivated in the dark in ambient carbon dioxide. The decline of NR
activity was smaller and dark inactivation was partially reversed in enhanced carbon dioxide,
indicating that post- transcriptional or post-translational regulation of NR has been modified. The
increased activation and stability of NR in enhanced carbon dioxide was correlated with higher sugars
and lower glutamine in the leaves. (c) Enhanced carbon dioxide led to increased levels of the minor
amino acids in leaves. (d) Enhanced carbon dioxide led to a large decrease of glycine and a small
decrease of serine in leaves of mature plants. The glycine:serine ratio decreased in source leaves of
older plants and seedlings. The consequences of a lower rate of photorespiration for the levels of
glutamine and the regulation of nitrogen metabolism are discussed. (e) Enhanced carbon dioxide also
modified the diurnal regulation of NR in roots. The nia transcript increased after nitrate fertilization
in the early and the second part of the photoperiod. The response of the transcript was not
accentuated in enhanced carbon dioxide. NR activity declined slightly during the photoperiod in
ambient carbon dioxide, whereas it increased 2-fold in enhanced carbon dioxide. The increase of root
NR activity in enhanced carbon dioxide was preceded by a transient increase of sugars, and was
followed by a decline of sugars, a faster decrease of nitrate than in ambient carbon dioxide, and an
increase of nitrite in the roots. (f) To interpret the physiological significance of these changes-in
nitrate metabolism, they were compared with the current growth rate of the plants. (g) In 4-5-week-
old plants, the current rate of growth was similar in ambient and enhanced carbon dioxide
(approximate to 0.4 g(-1) d(-1)). Enhanced carbon dioxide only led to small changes of NR activity,
nitrate decreased, and overall amino acids were not significantly increased. (h) Young seedlings had
a high growth rate (0.5 g(-1) d(-1)) in ambient carbon dioxide, that was increased by another 20%
in enhanced carbon dioxide. Enhanced carbon dioxide led to larger increases of NR activity and NR
activation, a 2-3-fold increase of glutamine, a 50% increase of glutamate, and a 2-3-fold increase in
minor amino acids. It also led to a higher nitrate level. It is argued that enhanced carbon dioxide leads
to a very effective stimulation of nitrate uptake, nitrate assimilation and amino acid synthesis in
seedlings. This will play an important role in allowing faster growth rates in enhanced carbon dioxide
at this stage.

KEYWORDS: ATMOSPHERIC CO2 CONCENTRATION, ELEVATED CO2, ENRICHMENT,
GROWTH, MINERAL NUTRITION, NITRITE-REDUCTASE, NITROGEN, POSTTRANSLATIONAL
REGULATION, RIBULOSE-1;5-BISPHOSPHATE CARBOXYLASE-OXYGENASE, SINK
REGULATION


     726  
GenoudGourichon, C., H. Sallanon, and A. Coudret. 1996. Effects of sucrose, agar, irradiance
and CO2 concentration during the rooting phase on the acclimation of Rosa hybrida plantlets to ex
vitro conditions. Photosynthetica 32(2):263-270.

Plantlets of Rosa hybrida cv. Deladel Madame Delbard were grown in vitro under different CO2
concentrations and irradiances, The medium was solid or liquid with or without sucrose,
Morphological (shoot length, leaf number, leaf area, root number and root length) and photosynthetic
parameters (photosynthesis/irradiance curves and phosphoenolpyruvate carboxylase and ribulose-1,5-
bisphosphate carboxylase/oxygenase activities) were measured. Sucrose was necessary for root
formation but not for root initiation, Culture in sucrose-free and liquid medium, under CO2
enrichment and high photosynthetic photon flux density increased the photosynthetic abilities and
improved acclimation of plantlets to ex vitro conditions even if these plants had no roots after the
rooting initiation phase.

KEYWORDS: CULTURED INVITRO, PHOTOSYNTHESIS


     727  
George, V., D. Cantin, D. Gerant, and P. Dizengremel. 1997. Long-term effects of elevated CO2
concentration on respiratory enzymes and dark respiration in pedunculate oak leaves. Plant
Physiology 114(3):657.



     728  
George, V., D. Gerant, and P. Dizengremel. 1996. Photosynthesis, Rubisco activity and
mitochondrial malate oxidation in pedunculate oak (Quercus robur L) seedlings grown under present
and elevated atmospheric CO2 concentrations. Annales Des Sciences Forestieres 53(2-3):469-474.

Pedunculate oak seedlings were grown at 350 and 700 mu L/L CO2 in controlled chambers. After
130 days at elevated CO2, the biomass of the whole plant did not significantly increase.
Photosynthesis, Rubisco activity, mitochondrial malate oxidation, carbohydrates and nitrogen
contents were examined in the fourth growth flush. At 700 mu L/L CO2, the leaf net photosynthetic
rate was 220% higher than at 350 mu L/L CO2. The decreased activity of Rubisco was accompanied
by an accumulation of sucrose and glucose. The decreased oxidative capacity of crude leaf
mitochondria from elevated CO2 plants was driven by the lower nitrogen and protein contents rather
than by the higher carbohydrates contents in the leaves. Nevertheless, direct effects of elevated CO2
on the respiratory biochemistry cannot be excluded.

KEYWORDS: RESPIRATION, TREES


     729  
Gesch, R.W., K.J. Boote, J.C.V. Vu, L.H. Allen, and G. Bowes. 1998. Changes in growth CO2
result in rapid adjustments of ribulose- 1,5-bisphosphate carboxylase/oxygenase small subunit gene
expression in expanding and mature leaves of rice. Plant Physiology 118(2):521-529.

The accumulation of soluble carbohydrates resulting from growth under elevated CO2 may potentially
signal the repression of gene activity for the small subunit of ribulose-1,5- bisphosphate
carboxylase/oxygenase (rbcS). To test this hypothesis we grew rice (Oryza sativa L.) under ambient
(350 mu L L-1) and high (700 mu L L-1) CO2 in outdoor, sunlit, environment-controlled chambers
and performed a cross-switching of growth CO2 concentration at the late-vegetative phase. Within
24 h, plants switched to high CO2 showed a 15% and 23% decrease in rbcS mRNA, whereas plants
switched to ambient CO2 increased 27% and 11% in expanding and mature leaves, respectively.
Ribulose-1,5-bisphosphate carboxylase/oxygenase total activity and protein content 8 d after the
switch increased up to 27% and 20%, respectively, in plants switched to ambient CO2, but changed
very little in plants switched to high CO2. Plants maintained at high CO2 showed greater
carbohydrate pool sizes and lower rbcS transcript levels than plants kept at ambient CO2. However,
after switching growth CO2 concentration, there was not a simple correlation between carbohydrate
and rbcS transcript levels. We conclude that although carbohydrates may be important in the
regulation of rbcS expression, changes in total pool size alone could not predict the rapid changes in
expression that we observed.

KEYWORDS: ACCLIMATION, ACCUMULATION, ATMOSPHERIC CARBON-DIOXIDE,
ELEVATED CO2, HIGHER-PLANTS, MECHANISM, PHOTOSYNTHESIS, RUBISCO, SOURCE-
SINK RELATIONS, TEMPERATURE


     730  
Ghannoum, O., and J.P. Conroy. 1998. Nitrogen deficiency precludes a growth response to CO2
enrichment in C-3 and C-4 Panicum grasses. Australian Journal of Plant Physiology 25(5):627-636.

We investigated the interaction of nitrogen (N) supply and CO2 enrichment on the growth and
photosynthesis of Panicum laxum (C-3), P. coloratum (C-4) and P. antidotale (C-4). Plants were
grown at ambient CO2 partial pressures (p(a)) of either 36 (low) or 71 (high) Pa, in potted soil
supplied with 0 (low) or 60 (high) mg N kg(-1) soil week(-1). Elevated CO2 enhanced total plant dry
mass of all three species by approximately 28% under high N supply, but had no effect on biomass
accumulation under N deficiency. CO2 enrichment resulted in reductions of CO2 assimilation rates
(A; measured at comparable p(a)) of P. laxum, indicating acclimation of photosynthesis. This
acclimation, which was more pronounced under N stress, was unrelated to changes in leaf N or non-
structural carbohydrate concentrations, because neither were affected by CO2 enrichment. In the C-4
grasses grown at low N, A were fully saturated at the current ambient p(a), whereas at high N, A
increased slightly when CO2 was raised to 71 Pa. N deficiency reduced the initial slope of the CO2
response curve of A in P. antidotale, and this effect was more pronounced at high CO2. In
conclusion, the preclusion of a growth response to CO2 enrichment by N deficiency was correlated
with a strong inhibition of A in the C-3 species, and the saturation of A at below current atmospheric
p(a) in C-4 species.

KEYWORDS: ACCLIMATION, CARBON DIOXIDE, CARBOXYLASE, DRY-MATTER, ELEVATED
CO2, NUTRITION, PHOTOSYNTHESIS, RESPIRATION, SOURCE-SINK RELATIONS,
TEMPERATURE


     731  
Ghannoum, O., K. Siebke, S. Von Caemmerer, and J.P. Conroy. 1998. The photosynthesis of
young Panicum C-4 leaves is not C-3-like. Plant, Cell and Environment 21(11):1123-1131.

Evidence is presented contrary to the suggestion that C-4 plants grow larger at elevated CO2 because
the C-4 pathway of young C-4 leaves has C-3-like characteristics, making their photosynthesis O-2
sensitive and responsive to high CO2, We combined PAM fluorescence with gas exchange
measurements to examine the O-2 dependence of photosynthesis in young and mature leaves of
Panicum antidotale (C-4, NADP-ME) and P. coloratum (C4, NAD-ME), at an intercellular CO2
concentration of 5 Pa. P. laxum (C-3) was used for comparison, The young C, leaves had COL and
light response curves typical of C-4 photosynthesis. When the O-2 concentration was gradually
increased between 2 and 40%, CO2 assimilation rates (A) of both mature and young C-4 leaves were
little affected, while the ratio of the quantum yield of photosystem II to that of CO2 assimilation
(Phi(PSII)/Phi(CO2)) increased more in young (up to 31%) than mature (up to 10%) C-4 leaves. A
of C-3 leaves decreased by 1.3 and Phi(PSII)/Phi(CO2) increased by 9-fold, over the same range of
O-2 concentrations. Larger increases in electron transport requirements in young, relative to mature,
C-4 leaves at low CO2 are indicative of greater O-2 sensitivity of photorespiration, Photosynthesis
modelling showed that young C-4 leaves have lower bundle sheath CO2 concentration, brought about
by higher bundle sheath conductance relative to the activity of the C-4 and C-3 cycles and/or lower
ratio of activities of the C-4 to C-3 cycles.

KEYWORDS: ATMOSPHERIC CO2 ENRICHMENT, CARBON ASSIMILATION, CHLOROPHYLL
FLUORESCENCE, DEVELOPING MAIZE LEAVES, ELECTRON-TRANSPORT, GENE-
EXPRESSION, IRRADIANCE, LEAF DEVELOPMENT, PHOTOSYSTEM, QUANTUM YIELD


     732  
Ghannoum, O., S. vonCaemmerer, E.W.R. Barlow, and J.P. Conroy. 1996. Effect of CO2
enrichment on growth, morphology and gas exchange of a C-3 (Panicum laxum) and a C-4 (Panicum
antidotale) grass grown at two irradiance levels. Plant Physiology 111(2):211.



     733  
Ghannoum, O., S. vonCaemmerer, E.W.R. Barlow, and J.P. Conroy. 1997. The effect of CO2
enrichment and irradiance on the growth, morphology and gas exchange of a C-3 (Panicum laxum)
and a C-4 (Panicum antidotale) grass. Australian Journal of Plant Physiology 24(2):227-237.

The effect of CO2 enrichment and irradiance on the growth and gas exchange of two tropical grasses,
Panicum laxum (C-3) and Panicum antidotale (C-4) were investigated. The two species were grown
at either 350 (low) or 700 (high) mu L L-1 CO2 concentration, under 40% (low) or 100% (high) of
direct sunlight and supplied with ample water and nutrition. Elevated CO2 enhanced plant dry weight
at both irradiances in the C-3 species (1.41-fold and 1.71-fold increase at low and high light,
respectively) but only at high light in the C-4 species (1.28 fold increase). CO2 enrichment had no
effect on the dry weight of P. antidotale, when stem development was suppressed by growth under
artificial lighting. When measured at the CO2 concentration at which they were grown, assimilation
rates were similar in the low and high CO2 grown plants, for both species. However, when
measurements made at low CO2 were compared, CO2 assimilation rates of the high light, high CO2
grown C-3 and C- 4 species were lower than those of their low CO2 grown counterparts. High CO2
strongly reduced the stomatal conductance of both species, while it affected the Rubisco content
(30% decrease) of the high light C-3 species only. This work shows clearly that C-4 species can
respond to CO2 enrichment under favourable growth conditions, and that acclimation to elevated
CO2 in pasture grasses does not necessarily involve accumulation of non-structural carbohydrates
or reduction of total N or soluble proteins in source leaves.

KEYWORDS: ACCLIMATION, ASSIMILATION, CARBON DIOXIDE, ELEVATED
ATMOSPHERIC CO2, NITROGEN-USE EFFICIENCY, PARTIAL-PRESSURE,
PHOTOSYNTHETIC CAPACITY, PLANTS, RESPONSES, TEMPERATURE


     734  
Ghannoum, O., S. vonCaemmerer, E.W.R. Barlow, and J.P. Conroy. 1997. The effect of CO2
enrichment and irradiance on the growth, morphology and gas exchange of a C-3 (Panicum laxum)
and a C-4 (Panicum antidotale) grass (vol 24, pg 227, 1997). Australian Journal of Plant Physiology
24(3):U2.



     735  
Gifford, R.M. 1992. Implications of the globally increasing atmospheric CO2 concentration and
temperature for the Australian terrestrial carbon budget - integration using a simple-model. Australian
Journal of Botany 40(4-5):527-543.

A simple continentally aggregated model of the Australian terrestrial carbon budget (CQUESTA)
integrates information on CO2 and temperature effects and is applied to evaluating whether
vegetation is absorbing anthropogenic CO2. Information from the literature is used to parameterise
CQUESTA. A standard set of parameters is adopted for exploratory purposes. Historical information
is used to describe the average CO2 concentration and temperature over the southern hemisphere
from 1750 AD to the present. From the present to 2050 AD the 'business-as-usual' scenario described
by the Intergovernmental Panel on Climate Change (IPCC) is applied. The standard parameterisation
of the model suggests that the changing CO2 concentration and temperature regime since 1750 AD
has been causing continuous net sequestration of carbon into Australian live vegetation and soils. The
present modelled rate of net sequestration is of a similar magnitude to CO2 emissions from
continental fossil fuel burning and land clearing combined. The rate of sequestration is predicted to
continue to increase until 2050 AD and beyond if atmospheric CO2 concentration and temperature
continue to increase. However, there remains considerable experimental uncertainty about the correct
parameterisation of the model. The findings have implications for policies on greenhouse effect gas
emissions.

KEYWORDS: ACCLIMATION, DIOXIDE, DYNAMICS, ELEVATED CO2, GROWTH, NITROGEN,
PHOTOSYNTHESIS, SOIL, TUSSOCK TUNDRA, WATER


     736  
Gifford, R.M. 1994. The global carbon-cycle - a viewpoint on the missing sink. Australian Journal
of Plant Physiology 21(1):1-15.

Atmospheric carbon budgets that ignore the possibility of terrestrial ecosystem responses to global
atmospheric change do not balance; there is a 'missing sink' of about 0.4 - 4 Gt C yr(-1). This paper
argues a case that mechanistically it is well within the bounds of possibility that increasing carbon
storage in vegetation and soils in response to the globally increasing CO2 concentration, temperature
and nitrogen deposition can account for the missing C sink. Global warming conditions considered
alone would be unlikely to cause most ecosystems to emit CO2, because the N mineralised by any
enhanced soil organic matter decomposition would be largely taken up by plants and reconverted into
organic matter having a much higher C:N ratio than that in the soil. Models of the global terrestrial
C cycle indicate that an extra 0.5 - 4 Gt C yr(-1) could well be being stored in soils and vegetation
today in response to the CO2 fertilising effect, having regard for the interactions with growth
restricting water, light and nitrogen levels. To obtain direct proof as to whether that this is happening
or not is a major challenge.

KEYWORDS: BIOSPHERE, BUDGET, CLIMATE, DIOXIDE, ECOSYSTEMS, ELEVATED CO2,
INCREASING ATMOSPHERIC CO2, PLANT GROWTH, RESPONSES, TEMPERATURE


     737  
Gifford, R.M. 1995. Whole plant respiration and photosynthesis of wheat under increased CO2
concentration and temperature: Long-term vs short-term distinctions for modelling. Global Change
Biology 1(6):385-396.

Short- and long-term effects of elevated CO2 concentration and temperature on whole plant
respiratory relationships are examined for wheat grown at four constant temperatures and at two CO2
concentrations. Whole plant CO2 exchange was measured on a 24 h basis and measurement
conditions varied both to observe short-term effects and to determine the growth respiration
coefficient (r(g))r dry weight maintenance coefficient (r(g)), basal (i.e. dark acclimated) respiration
coefficient (r(b)), and 24 h respiration:photosynthesis ratio (R:P). There was no response of r(b) to
short-term variation in CO2 concentration. For plants with adequate N-supply, r(g) was unaffected
by the growth-CO2 despite a 10% reduction in the plant's N concentration (%N). However, r(m) was
decreased 13%, and r(b) was decreased 20% by growth in elevated CO2 concentration relative to
ambient. Nevertheless, R:P was not affected by growth in elevated CO2. Whole plant respiration
responded to short-term variation of + 5 degrees C around the growth temperature with low
sensitivity (Q(10) = 1.8 at 15 degrees C, 1.3 at 30 degrees C). The shape of the response of whole
plant respiration to growth temperature was different from that of the short term response, being a
slanted S-shape declining between 25 and 30 degrees C. While r(m) increased, r(g) decreased when
growth temperature increased between 15 and 20 degrees C. Above 20 degrees C r(m) became
temperature insensitive while r(g) increased with growth temperature. Despite these complex
component responses, R:P increased only from 0.40 to 0.43 between 15 degrees and 30 degrees C
growth temperatures. Giving the plants a step increase in temperature caused a transient increase in
R:P which recovered to the pre- transient value in 3 days. It is concluded that use of a constant R:P
with respect to average temperature and CO2 concentration may be a more simple and accurate way
to model the responses of wheat crop respiration to 'climate change' than the more complex and
mechanistically dubious functional analysis into growth and maintenance components.

KEYWORDS: ELEVATED CO2, GROWTH


     738  
Gifford, R.M., J.L. Lutze, and D. Barrett. 1996. Global atmospheric change effects on terrestrial
carbon sequestration: Exploration with a global C- and N-cycle model (CQUESTN). Plant and Soil
187(2):369-387.

A model of the interacting global carbon and nitrogen cycles (CQUESTN) is developed to explore
the possible history of C- sequestration into the terrestrial biosphere in response to the global
increases (past and possible future) in atmospheric CO2 concentration, temperature and N-deposition.
The model is based on published estimates of pre-industrial C and N pools and fluxes into vegetation,
litter and soil compartments. It was found necessary to assign low estimates of N pools and fluxes
to be compatible with the more firmly established C-cycle data. Net primary production was made
responsive to phytomass N level, and to CO2 and temperature deviation from preindustrial values
with sensitivities covering the ranges in the literature. Biological N-fixation could be made either
unresponsive to soil C:N ratio, or could act to tend to restore the preindustrial C:N of humus with
different N-fixation intensities. As for all such simulation models, uncertainties in both data and
functional relationships render it more useful for qualitative evaluation than for quantitative
prediction. With the N-fixation response turned off, the historic CO2 increase led to standard-model
sequestration into terrestrial ecosystems in 1995AD of 1.8 Ct C yr(-1). With N-fixation restoring
humus C:N strongly, C sequestration was 3 Ct yr(-1) in 1995. In both cases C:N of phytomass and
litter increased with time and these increases were plausible when compared with experimental data
on CO2 effects. The temperature increase also caused net C sequestration in the model biosphere
because decrease in soil organic matter was more than offset by the increase in phytomass deriving
from the extra N mineralised. For temperature increase to reduce system C pool size, the biosphere
''leakiness'' to N would have to increase substantially with temperature. Assuming a constant N-loss
coefficient, the historic temperature increase alone caused standard-model net C sequestration to be
about 0.6 Gt C in 1995. Given the disparity of plant and microbial C:N, the modelled impact of
anthropogenic N-deposition on C- sequestration depends substantially on whether the deposited N
is initially taken up by plants or by soil microorganisms. Assuming the latter, standard-model net
sequestration in 1995 was 0.2 Ct C in 1995 from the N-deposition effect alone. Combining the effects
of the historic courses of CO2, temperature and N-deposition, the standard-model gave C-
sequestration of 3.5 Ct in 1995. This involved an assumed weak response of biological N-fixation to
the increased carbon status of the ecosystem. For N-fixation to track ecosystem C- fixation in the
long term however, more phosphorus must enter the biological cycle. New experimental evidence
shows that plants in elevated CO2 have the capacity to mobilize more phosphorus from so-called
''unavailable'' sources using mechanisms involving exudation of organic acids and phosphatases.

KEYWORDS: BIOSPHERE, CO2 CONCENTRATION, ELEVATED CO2, LITTER
DECOMPOSITION, NITROGEN, ORGANIC-ACIDS, PLANT, SOIL, STORAGE, TEMPERATURE-
DEPENDENCE


     739  
Gil, M.I., D.M. Holcroft, and A.A. Kader. 1997. Changes in strawberry anthocyanins and other
polyphenols in response to carbon dioxide treatments. Journal of Agricultural and Food Chemistry
45(5):1662-1667.

Carbon dioxide-enriched atmospheres are used to reduce the incidence and severity of decay and to
extend the postharvest life of strawberries. The influence of CO2 on the postharvest quality
parameters of strawberries, particularly the stability of anthocyanins and other phenolic compounds,
was investigated. Freshly harvested strawberries were placed in jars ventilated continuously with air
or air enriched with 10%, 20%, or 40% CO2 at 5 degrees C for 10 days. Samples were taken initially,
and after 5 and 10 days of storage, and color (L* a* b* color space), pH, TA, TSS, and firmness
were measured. Anthocyanins and other phenolics were analyzed by HPLC. Elevated CO2 degraded
internal color while air-treated fruit remained red. Internal and external tissues differed in composition
and concentration of phenolic compounds. CO2 had a minimal effect on the anthocyanin content of
external tissues but induced a remarkable decrease in anthocyanin content of internal tissues. Factors,
such as pH and copigmentation, that could explain this degradation are discussed.

KEYWORDS: COLOR, FIRMNESS, FRUITS, JUICE, MODIFIED ATMOSPHERES, QUALITY


     740  
Gilmanov, T.G., and W.C. Oechel. 1995. New estimates of organic matter reserves and net primary
productivity of the North American tundra ecosystems. Journal of Biogeography 22(4-5):723-741.

The reserves and fluxes of carbon in ecosystems of the circumpolar tundra biome should be among
the most responsive to climatic change, including their transformation from a CO2 sink to a CO2
source with respect to the atmosphere. To estimate accurately the significance of Arctic tundra to
global carbon stocks and balances, quantitative geographically referenced estimates of the masses and
fluxes of carbon are needed. Although new empirically based estimates of reserves and productivity
were recently obtained for the Eurasian part of the tundra biome using GIS technology, the figures
currently used for carbon reserves and productivity of the North American tundra ecosystems are
based on earlier expert estimates or large scale models based on data primarily for non-tundra areas.
To obtain new more empirically based estimates of the reserves and fluxes of carbon in North
American tundra ecosystems a set of records of North American tundra ecosystems was obtained
from the Global Arctic/Alpine Climate/Soil/Plant Productivity Data Base (Global Change Research
Group, San Diego State University). This data base contains phytomass, productivity, climatic and
soil characteristics for nearly fifty tundra-type ecosystems studied during the past 30 years in Alaska
and Northern Canada. This information was used to interpolate the necessary data for all the tundra
cells (1 X 1 degree) of the simple GIS, based on the Global Vegetation Map and the FAO/UNESCO
Soil Map of the World. By integrating the corresponding maps of phytomass and productivity the
quantitative estimates of the reserves and. productivity fluxes of organic matter in tundra ecosystems
of North America and Greenland (4.12 x 10(6) km(2) total area) were obtained: 2.26 Gt above-
ground phytomass, 4.99 Gt total phytomass, 91.3 Gt soil organic matter of the active layer; 0.56
Gt/yr above- ground net primary production; 0.98 Gt/yrotal net primary production. As an alternative
means of determining the productivity totals for North American tundra ecosystems, the
phenomenological model of the form: NPP=f(T,H,G), relating net primary production of tundra
ecosystems to climatic, soil and vegetation factors, was applied to the GIS layers of mean annual
temperature (T), soil organic matter content (H), and above-ground phytomass density (G) to
produce a map of modelled NPP estimates for North American tundra ecosystems. The subroutine
of spatial integration of the local production estimates takes into account geographical changes in the
landscape composition (proportions of the zonal, meadow, mire and aquatic ecosystem types) and
results in totals of 0.58 Gt/yr for above-ground and 1.16 Gt/yr for total net primary production of
tundra ecosystems of North America and Greenland.

KEYWORDS: ACCUMULATION, ALASKA, ARCTIC TUNDRA, BIOMASS, CLIMATE,
NUTRIENT, PLANT, SOIL PROPERTIES, VEGETATION TYPES


     741  
Gimenez, C., V.J. Mitchell, and D.W. Lawlor. 1992. Regulation of photosynthetic rate of 2
sunflower hybrids under water-stress. Plant Physiology 98(2):516-524.

The effect of short-term water stress on photosynthesis of two sunflower hybrids (Helianthus annuus
L. cv Sungro-380 and cv SH-3622), differing in productivity under field conditions, was measured.
The rate of CO2 assimilation of young, mature leaves of SH-3622 under well-watered conditions was
approximately 30% greater than that of Sungro-380 in bright light and elevated CO2; the
carboxylation efficiency was also larger. Growth at large photon flux increased assimilation rates of
both hybrids. The changes in leaf composition, including cell numbers and sizes, chlorophyll content,
and amounts of total soluble and ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) protein,
and in Rubisco activity and amount of ribulose-1,5- bisphosphate (RuBP) were determined to assess
the factors regulating the differences in assimilation of the hybrids at high and low water potentials.
The amounts of chlorophyll, soluble protein, Rubisco protein and the initial activity of Rubisco and
its activation state did not differ significantly between hybrids. However, unstressed leaves of SH-
3622 had more, smaller cells per unit area and 60% more RuBP per unit leaf area than that of Sungro-
380. Water stress developing over 4 days decreased the assimilation of both hybrids similarly.
Changes in the amounts of chlorophyll, soluble and Rubisco protein, and Rubisco activity and
activation state were small and were not sufficient to explain the decrease in photosynthesis; neither
was decreased stomatal conductance (or stomatal "patchiness"). Reduction of photosynthesis per unit
leaf area from 25 to 5 micromoles CO2 per square meter per second in both hybrids was caused by
a decrease in the amount of RuBP from approximately 130 to 40 micromoles per square meter in SH-
3622 and from 80 to 40 micromoles per square meter in Sungro. Differences between hybrids and
their response to water stress is discussed in relation to control of RuBP regeneration.

KEYWORDS: BISPHOSPHATE CARBOXYLASE ACTIVITY, C-3, INHIBITION, LEAVES,
OXYGENASE, PLANTS, POTENTIALS, PROTEIN, RIBULOSE-1;5-BISPHOSPHATE
CARBOXYLASE, WHEAT GENOTYPES


     742  
Giordano, M., J.S. Davis, and G. Bowes. 1994. Organic-carbon release by dunaliella-salina
(chlorophyta) under different growth-conditions of co2, nitrogen, and salinity. Journal of Phycology
30(2):249-257.

Two strains of Dunaliella salina (Dunal) Teod., UTEX 1644 and UTEX 200, were cultured under
different growth regimes, including 10 mM NO3- or NH4+, 1.5 or 3.0 M NaCl, and low (0.035%)
or high (5%) CO2 in air. The release of C-14-labeled dissolved organic carbon (DOC), expressed as
a rate and as a percentage of photo synthetic (CO2)-C-14, assimilation, was subsequently determined.
The percentage of DOC released was inversely related to cell density in the assay medium, but
photosynthesis on a per-cell basis was not. Release of DOC was low, in the range of 1-5% of
photosynthesis, but during acclimation to growth on NH4+, it rose to 11%. The presence of NH4+
rather than NO3- in the growth medium increased the rate of release by both strains, but the
percentage release was stimulated only in UTEX 200 cells, because their photosynthetic ra te was
depressed by NH4+. For UTEX 1644, high, as compared to low, CO2-grown cells, had somewhat
higher rates a nd percentages of DOC release, but release from UTEX 200 cells was unaffected by
the growth-CO2. The rate of DOC release by high CO2-grown cells was not enhanced at a low
concentration of dissolved inorganic carbon, indicating that the released material did not originate
from the photorespiratory pathway. The effects of NaCl on DOC release varied with strain a nd
growth conditions. For UTEX 200, the cells in NO3-, but not NH4+, exhibited a doubling or more
in percentage Of release with a doubling in NaCl concentration, irrespective of growth- CO2. With
UTEX 1644 the low CO2-grown cells showed the greatest enhancement in 3.0 M NaCl. Organic
matter accumulated on the external surface of the cell membrane and constituted a well- defined cell-
coat, which was more dense in NH4+ than in NO3-- grown cells. Microtubules, which may play a role
in maintaining cell shape, were observed just below the plasma membrane. From a practical
viewpoint, the presence of organic material in the hypersaline ponds of salt-works is detrimental to
salt production. When D. salina cells become abundant in such ponds, the attendant, continuous
release of DOC may make a significant contribution to the problem.

KEYWORDS: BIOCULATA, COAT, EXCRETION, GREEN-ALGA, HEALTHY CELLS,
INTRACELLULAR GLYCEROL, MARINE-PHYTOPLANKTON, METABOLISM, TEMPERATURE,
TERTIOLECTA


     743  
Gleadow, R.M., W.J. Foley, and I.E. Woodrow. 1998. Enhanced CO2 alters the relationship
between photosynthesis and defence in cyanogenic Eucalyptus cladocalyx F. Muell. Plant, Cell and
Environment 21(1):12-22.

The effect of elevated CO2 and different levels of nitrogen on the partitioning of nitrogen between
photosynthesis and a constitutive nitrogen-based secondary metabolite (the cyanogenic glycoside
prunasin) was examined in Eucalyptus cladocalyx. Our hypothesis was that the expected increase in
photosynthetic nitrogen-use efficiency of plants grown at elevated CO2 concentrations would lead
to an effective reallocation of available nitrogen from photosynthesis to prunasin, Seedlings were
grown at two concentrations of CO2 and nitrogen, and the proportion of leaf nitrogen allocated to
photosynthesis, ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco), protein and prunasin
compared, Up to 20% of leaf nitrogen was allocated to the cyanogenic glycoside, although this
proportion varied with leaf age, position and growth conditions, Leaf prunasin concentration,vas
strongly affected by nitrogen supply, but did not increase, on a dry weight basis, in the leaves from
the elevated CO2 treatments, However, the proportion of nitrogen allocated to prunasin increased
significantly, in spite of a decreasing pool of leaf nitrogen, in the plants grown at elevated
concentrations of CO2. There was less protein in leaves of plants grown at elevated CO2 in both
nitrogen treatments, while the concentration of active sites of Rubisco only decreased in plants from
the low-nitrogen treatment. These changes in leaf chemistry may have significant implications in terms
of the palatability of foliage and defence against herbivores.

KEYWORDS: ACCLIMATION, C-3 PLANTS, CARBON NUTRIENT BALANCE, ELEVATED
ATMOSPHERIC CO2, GAS-EXCHANGE, GROWTH, HERBIVORE INTERACTIONS, NITROGEN,
RISING CO2, TOMATO PLANTS


     744  
Glenn, D.M., and W.V. Welker. 1997. Effects of rhizosphere carbon dioxide on the nutrition and
growth of peach trees. Hortscience 32(7):1197-1199.

Our objectives in this study were to measure the effects of low levels of root system carbon dioxide
on peach tree growth (Prunus persica L. Batsch) and nutrient uptake. Using soil and hydroponic
systems, we found that increased root CO2: 1) increased root growth without increasing shoot
growth, 2) increased leaf P concentration, 3) decreased leaf N concentration, and 4) reduced water
use relative to air injection or no treatment.

KEYWORDS: ATMOSPHERIC CO2 ENRICHMENT, INORGANIC CARBON, METABOLISM,
PLANTS, RESPIRATION, RESPONSES, ROOT-GROWTH, SEEDLINGS, SOIL, WATER


     745  
Gloser, J., and M. Bartak. 1994. Net photosynthesis, growth-rate and biomass allocation in a
rhizomatous grass calamagrostis-epigejos grown at elevated co2 concentration. Photosynthetica
30(1):143-150.

Young plants of Calamagrostis epigejos (L.) Roth were grown in controlled environments with two
regimes of CO2 in the air: normal (350 cm(3) m(-3)) and elevated (700 cm(3) m(-3)). The relative
growth rate of plants grown at elevated CO2 was increased by about 20 % in comparison with
control plants cultivated at ambient CO2 concentration. Partitioning of assimilates into roots (+
rhizomes) and shoots was the same in both treatments. Slightly lower values of specific leaf area, leaf
mass ratio and leaf area ratio were found in the plants grown at elevated CO2. The net photosynthetic
rate (P-N) was measured gasometrically in plants from both treatments at 350 and 700 cm(3) m(-3)
CO2 in the leaf chamber. There were no significant differences between plants grown at either CO2
concentration in their responses to radiation and CO2 conditions during measurements, i.e., no
regulation of photosynthetic processes in response to elevated CO2 was detectable. P-N at saturating
irradiance and maximum apparent quantum yield of photosynthesis were always considerably higher
at doubled CO2 concentration during measurements.

KEYWORDS: CARBON DIOXIDE, ECOSYSTEMS, PLANTS, PRODUCTIVITY, RESPIRATION,
RESPONSES, TEMPERATURE


     746  
Godbold, D.L., and G.M. Berntson. 1997. Elevated atmospheric CO2 concentration changes
ectomycorrhizal morphotype assemblages in Betula papyrifera. Tree Physiology 17(5):347-350.

Ectomycorrhizae are extremely diverse, with different species of fungi having very different
physiologies and morphologies that, in turn, confer a range of different benefits to the host plant. To
test the hypothesis that elevated CO2 leads to changes in the assemblage of ectomycorrhizae
associated with trees, we examined the number and frequency of ectomycorrhizal morphotypes
colonizing roots of Betula papyrifera Marsh. saplings grown at an ambient or elevated (700 ppm)
atmospheric CO2 concentration for 24 weeks. Elevated CO2 resulted in significant changes in the
composition of the ectomycorrhizal assemblage toward morphotypes with a higher incidence of
emanating hyphae and rhizomorphs. We conclude that B. papyrifera saplings will be able to support
a more costly mycorrhization in future elevated-CO2 atmospheres.

KEYWORDS: CARBON DIOXIDE, FUNGI, GROWTH, INFECTION, MYCELIUM, PINE,
RESPONSES, ROOTS, SEEDLINGS


     747  
Godbold, D.L., G.M. Berntson, and F.A. Bazzaz. 1997. Growth and mycorrhizal colonization of
three North American tree species under elevated atmospheric CO2. New Phytologist 137(3):433-
440.

We investigated the effect of elevated CO2 on the growth and mycorrhizal colonization of three tree
species native to north- eastern American forests (Betula papyrifera Marsh., Pinus strobus L. and
Tsuga canadensis L. Carr). Saplings of the tree species were collected from Harvard Forest,
Massachusetts, and grown in forest soil under ambient (c. 375 ppm) and elevated (700 ppm)
atmospheric CO2 concentrations for 27-35 wk. In all three species there was a trend to increasing
whole-plant, total-root and fine-root biomass in elevated CO2, and a significant increase in the degree
of ectomycorrhizal colonization in B. papyrifera and P. strobus, but not in T. canadensis. However,
in T. canadensis the degree of colonization with arbuscular mycorrhizas increased significantly. In
both the ambient and elevated environments, on the roots of B. papyrifera and P. strobus 12 distinct
ectomycorrhizal morphotypes were identified. Distinct changes in the ectomycorrhizal morphotype
assemblage of B. papyrifera were observed under CO2 enrichment. This change resulted in an
increase in the frequency of ectomycorrhizas with a higher incidence of emanating hyphae and
rhizomorphs, and resulted in a higher density of fungal hyphae in a root exclusion chamber.

KEYWORDS: CARBON DIOXIDE, ECTOMYCORRHIZAL PLANTS, ENRICHMENT, FUNGI,
LOBLOLLY-PINE, NUTRIENT, RESPONSES, ROOTS, SEEDLINGS, VEGETATIVE MYCELIUM


     748  
Goettel, M.S., G.M. Duke, and D.W. Goerzen. 1997. Pathogenicity of Ascosphaera larvis to larvae
of the alfalfa leafcutting bee, Megachile rotundata. Canadian Entomologist 129(6):1059-1065.

Laboratory assays and field surveys showed that Ascosphaera larvis (Bissett) is a pathogen of alfalfa
leafcutting bee larvae, capable of causing high mortality in commercial populations. In one population
over 21% of bees were found to be infected by A. larvis. However, overall levels of the disease are
low and it is unlikely that this pathogen poses an immediate threat to commercial leafcutting bee
populations in Canada. The LD50 was determined to be 1.9 x 10(5) spores/bee. Elevated levels of
CO2 are required for in vitro spore germination. The disease can easily be diagnosed within bee cells
by X-ray radiography, thereby enabling disease levels to be monitored using conventional methods
utilized by the industry to monitor leafcutting bee quality.

KEYWORDS: CHALKBROOD


     749  
Goldewijk, K.K., J.G. Vanminnen, G.J.J. Kreileman, M. Vloedbeld, and R. Leemans. 1994.
Simulating the carbon flux between the terrestrial environment and the atmosphere. Water, Air, and
Soil Pollution 76(1-2):199-230.

A Terrestrial C Cycle model that is incorporated in the Integrated Model to Assess the Greenhouse
Effect (IMAGE 2.0) is described. The model is a geographically explicit implementation of a model
that simulates the major C fluxes in different compartments of the terrestrial biosphere and between
the biosphere and the atmosphere. Climatic parameters, land cover and atmospheric C concentrations
determine the result of the dynamic C simulations. The impact of changing land cover patterns,
caused by anthropogenic activities (shifting agriculture, de- and afforestation) and climatic change
are modeled implicitly. Feedback processes such as CO2 fertilization and temperature effects on
photosynthesis, respiration and decomposition are modeled explicitly. The major innovation of this
approach is that the consequences of climate change are taken into account instantly and that their
results can be quantified on a global medium-resolution grid. The objectives of this paper are to
describe the C cycle model in detail, present the linkages with other parts of the IMAGE 2.0
framework, and give an array of different simulations to validate and test the robustness of this
modeling approach. The computed global net primary production (NPP) for the terrestrial biosphere
in 1990 was 60.6 Gt C a-1, with a global net ecosystem production (NEP) of 2.4 Gt C a-1. The
simulated C flux as result from land cover changes was 1.1 Gt C a-1, so that the terrestrial biosphere
in 1990 acted as a C sink of 1.3 Gt C a-1. Global phytomass amounted 567.5 Gt C and the dead
biomass pool was 1517.7 Gt C. IMAGE 2.0 simulated for the period 1970 - 2050 a global average
temperature increase of 1.6-degrees-C and a global average precipitation increase of 0.1 mm/day. The
CO2 concentration in 2050 was 522.2 ppm. The computed NPP for the year 2050 is 82.5 Gt C a-1,
with a NEP of 8.1 Gt C a-1. Projected land cover changes result in a C flux of 0.9 Gt C a-1, so that
the terrestrial biosphere will be a strong sink of 7.2 Gt C a-1. The amount of phytomass hardly
changed (600.7 Gt C) but the distribution over the different regions had. Dead biomass increased
significantly to 1667.2 Gt C.

KEYWORDS: BIOSPHERE, CO2 CONCENTRATIONS, ELEVATED CO2, FEEDBACK
PROCESSES, GLOBAL CHANGE, LAND-USE, MANAGED FORESTS, MODEL, STORAGE,
WATER-USE EFFICIENCY


     750  
Gong, H., S. Nilsen, and J.F. Allen. 1993. Photoinhibition of photosynthesis invivo - involvement
of multiple sites in a photodamage process under co2-free and o2- free conditions. Biochimica Et
Biophysica Acta 1142(1-2):115-122.

Intact Lemna gibba plants were illuminated by photoinhibitory light in air, in air minus O2, in air
minus CO2, and in pure N2. In pure N2, the degree of photoinhibition increased 3-5- times compared
with that in air. This high degree of photoinhibition is described as photodamage. Photodamage was
found to constitute a syndrome, that is, it is due to inactivation of multiple sites. These sites include
RC II component(s) from P680 to Q(A); the Q(B)-Site; and a component of PS I. In photodamage,
the donor side of PS II and PS II excitation energy transfer remain unimpaired, but the size of the PS
I antenna seems to decrease. Photodamage is distinguishable from photoinactivation.
Photoinactivation occurred in air and could be attributed to inhibition of electron transport from
Q(A)- to Q(B). During photoinactivation the D1 protein of RC II became degraded faster than the
detectable inhibition of Q(B) reduction. The photoinhibition- induced rise in F0 occurred only during
the process of photodamage but not during that of photoinactivation, and was a secondary event
which arose as a consequence of photodamage. Atmospheric O2 alleviated photodamage but
increased photoinactivation. The light-induced Dl degradation and inhibition of Q(A) to Q(B) electron
transfer were enhanced in vivo not only by O2 but also by depletion of CO2.

KEYWORDS: ANAEROBIC CONDITIONS, CHLAMYDOMONAS-REINHARDTII,
CHLOROPHYLL FLUORESCENCE, D1 PROTEIN, DEGRADATION, ENERGY-DISTRIBUTION,
ISOLATED- CHLOROPLASTS, MECHANISM, PHOTOSYSTEM, REACTION CENTERS


     751  
GonzalezMeler, M.A., M. RibasCarbo, J.N. Siedow, and B.G. Drake. 1996. Direct inhibition of
plant mitochondrial respiration by elevated CO2. Plant Physiology 112(3):1349-1355.

Doubling the concentration of atmospheric CO2 often inhibits plant respiration, but the mechanistic
basis of this effect is unknown. We investigated the direct effects of increasing the concentration of
CO2 by 360 mu L L(-1) above ambient on O-2 uptake in isolated mitochondria from soybean
(Glycine max L. cv Ransom) cotyledons. Increasing the CO2 concentration inhibited the oxidation
of succinate, external NADH, and succinate and external NADH combined. The inhibition was
greater when mitochondria were preincubated for 10 min in the presence of the elevated CO2
concentration prior to the measurement of O-2 uptake. Elevated CO2 concentration inhibited the
salicylhydroxamic acid-resistant cytochrome pathway, but had no direct effect on the cyanide-resistant
alternative pathway. We also investigated the direct effects of elevated CO2 concentration on the
activities of cytochrome c oxidase and succinate dehydrogenase (SDH) and found that the activity
of both enzymes was inhibited. The kinetics of inhibition of cytochrome c oxidase were time-
dependent. The level of SDH inhibition depended on the concentration of succinate in the reaction
mixture. Direct inhibition of respiration by elevated CO2 in plants and intact tissues may be due at
least in part to the inhibition of cytochrome c oxidase and SDH.

KEYWORDS: ATMOSPHERIC CO2, CARBON-DIOXIDE EFFLUX, DARK RESPIRATION,
GROWTH, LEAF RESPIRATION, PATHWAYS, PEAR FRUIT, ROOT RESPIRATION, SHORT-
TERM, SOIL


     752  
Gonzalez-Meler, M.A., and J.N. Siedow. 1999. Direct inhibition of mitochondrial respiratory
enzymes by elevated CO2: does it matter at the tissue or whole-plant level? Tree Physiology 19(4-
5):253-259.

On average, a doubling in current atmospheric [CO2] results in a 15 to 20% direct inhibition of
respiration, although the variability associated with this value is large within and among species.
Direct effects of CO2 on respiration may also be relevant to tree canopies because of dynamic
fluctuations between nighttime and daytime [CO2] throughout the growing season. The mechanism
by which CO2 inhibits respiration is not known. A doubling of ambient [CO2] inhibits the activity of
the mitochondrial enzymes, cytochrome c oxidase and succinate dehydrogenase. If inhibition of these
enzymes is the only factor involved in the direct inhibition of respiration, the overall inhibition of
specific respiration will be proportional to the control that such enzymes exert on the overall
respiratory rate. We analyzed the effects of [CO2] on respiration in an attempt to scale the direct
effects of CO2 on respiratory enzymes to the whole-plant level. Sensitivity analysis showed that
inhibition of mitochondrial enzymes by doubling current atmospheric [CO2] does not explain entirely
the CO2 inhibition of tissue or whole-plant respiration. We conclude that CO2-dependent suppression
of respiratory enzymatic activity will be minimal when cytochrome c oxidase inhibition is scaled up
from the mitochondria to the whole tree and that the primary mechanism for the direct inhibitory
effect remains to be identified.

KEYWORDS: ATMOSPHERIC CO2, CARBOHYDRATE STATUS, CARBON-DIOXIDE
CONCENTRATIONS, DARK RESPIRATION, GROWTH, LEAF RESPIRATION,
PHOTOSYNTHESIS, RESPONSES, ROOT RESPIRATION, SHORT- TERM


     753  
Goodale, C.L., J.D. Aber, and E.P. Farrell. 1998. Predicting the relative sensitivity of forest
production in Ireland to site quality and climate change. Climate Research 10(1):51-67.

Most model-based predictions of climate change effects on forest ecosystems have used either
potential or static descriptions of vegetation and site, removing the effects of direct management or
land use. In this paper we use a previously developed and validated model of carbon and water
balances in forest ecosystems (PnET-II) to assess the relative sensitivity of forest production in
Ireland to predicted climate change and to ambient variability in site quality. After validating the
model against measured productivity for 2 sets of stands, we ran the model using existing variation
in site quality, represented as differences in foliar N concentration, and also for predicted changes in
climate and atmospheric CO2. Resulting variations in productivity were compared with those due to
potential errors in the specification of input parameters and to variation in current ambient climate
across the region. The effects on net primary production (NPP) and wood production of either
ambient variation in climate or predicted changes in temperature, precipitation and CO2 are quite
small (0 to 30%) relative to the effects of ambient variability in site quality (up to 400%). The range
of possible variation in other user-specified physiological parameters resulted in changes of less than
10% in model predictions. We conclude that site-specific conditions and management practices result
in a range of forest productivity that is much greater than any likely to be induced by climate change
or CO2 enrichment. We also suggest that it is essential to understand and map spatial variability in
site quality, as well as to understand how the productive capacity of landscapes will change in
response to management and pollution loading, if we are to predict the actual role that climate change
will play in altering forest productivity and global biogeochemistry.

KEYWORDS: BIOMASS DISTRIBUTION, GENERAL-CIRCULATION MODEL, LEAF CO2
EXCHANGE, NET PRIMARY PRODUCTION, PACIFIC NORTHWEST, PHOTOSYNTHESIS-
NITROGEN RELATIONS, PICEA-SITCHENSIS, SITCHENSIS BONG CARR, STOMATAL
CONDUCTANCE, WATER-USE EFFICIENCY


     754  
Goodfellow, J., D. Eamus, and G. Duff. 1997. Diurnal and seasonal changes in the impact of CO2
enrichment on assimilation, stomatal conductance and growth in a long-term study of Mangifera
indica in the wet-dry tropics of Australia. Tree Physiology 17(5):291-299.

We studied assimilation, stomatal conductance and growth of Mangifera indica L. saplings during
long-term exposure to a CO2-enriched atmosphere in the seasonally wet-dry tropics of northern
Australia. Grafted saplings of M. indica were planted in the ground in four air-conditioned, sunlit,
plastic-covered chambers and exposed to CO2 at the ambient or an elevated (700 mu mol mol(-1))
concentration for 28 months. Light-saturating assimilation (A(max)), stomatal conductance (g(s)),
apparent quantum yield (phi), biomass and leaf area were measured periodically. After 28 months,
the CO2 treatments were changed in all four chambers from ambient to the elevated concentration
or vice versa, and A(max) and g(s) were remeasured during a two-week exposure to the new regime.
Throughout the 28-month period of exposure, A(max) and apparent quantum yield of leaves in the
elevated CO2 treatment were enhanced, whereas stomatal conductance and stomatal density of leaves
were reduced. The relative impacts of atmospheric CO2 enrichment on assimilation and stomatal
conductance were significantly larger in the dry season than in the wet season. Total tree biomass was
substantially increased in response to atmospheric CO2 enrichment throughout the experimental
period, but total canopy area did not differ between CO2 treatments at either the first or the last
harvest. During the two-week period following the change in CO2 concentration, A(max) of plants
grown in ambient air but measured in CO2-enriched air was significantly larger than that of trees
grown and measured in CO2-enriched air. There was no difference in A(max) between trees grown
and measured in ambient air compared to trees grown in CO2-enriched air but measured in ambient
air. No evidence of down-regulation of assimilation in response to atmospheric CO2 enrichment was
observed when rates of assimilation were compared at a common intercellular CO2 concentration.
Reduced stomatal conductance in response to atmospheric CO2 enrichment was attributed to a
decline in both stomatal aperture and stomatal density.

KEYWORDS: CARBON DIOXIDE, ELEVATED ATMOSPHERIC CO2, FIELD, FOLIAR GAS-
EXCHANGE, LEAF, MARANTHES-CORYMBOSA, NET PHOTOSYNTHESIS, PHOTOSYNTHETIC
RESPONSE, PLANTS, TREES


     755  
Goodfellow, J.E., D. Eamus, and G.A. Duff. 1997. The impact of CO2 enrichment on assimilation,
stomatal conductance and growth in a long-term study of Mangifera indica in the wet-dry tropics of
Australia. Plant Physiology 114(3):480.



     756  
Gordon, D.C., M.M.I. VanVuuren, B. Marshall, and D. Robinson. 1995. Plant growth chambers
for the simultaneous control of soil and air temperatures, and of atmospheric carbon dioxide
concentration. Global Change Biology 1(6):455-464.

Many facilities for growing plants at elevated atmospheric concentrations of CO2 ([CO2]) neglect
the control of temperature, especially of the soil. Soil and root temperatures in conventional, free-
standing pots often exceed those which would occur in the field at a given air temperature. A plant
growth facility is described in which atmospheric CO2 can be maintained at different concentrations
while soil and air temperatures mimic spatial and temporal patterns seen in the field. It consists of
glasshouse-located chambers in which [CO2] is monitored by an infra-red gas analyser and maintained
by injection of CO2 from a cylinder. Air is cooled by a heat exchange unit. Plants grow in soil in 1.2
m long containers that are surrounded by cooling coils and thermal insulation. Both [CO2] and
temperature are controlled by customized software. Air temperature is programmed to follow a sine
function of diurnal time. Soil temperature at a depth of 0.55 m is programmed to be constant.
Temperature at 0.1 m depth varies as a damped, lagged function of air temperature; that at 1.0 m as
a similar function of the 0.55 m temperature. [CO2] is maintained within 20 mu mol mol(-1) of target
concentrations during daylight. A feature of the system is that plant material is labelled with a C-13
enrichment different from that of carbon in soil organic matter. The operation of the system is
illustrated with data collected in an experiment with spring wheat (Triticum aestivum L., cv Tonic)
grown at ambient [CO2] and at [CO2] 350 mu mol mol(-1) greater than ambient.

KEYWORDS: CO2


     757  
Gordon, H.B., P.H. Whetton, A.B. Pittock, A.M. Fowler, and M.R. Haylock. 1992. Simulated
changes in daily rainfall intensity due to the enhanced greenhouse-effect - implications for extreme
rainfall events. Climate Dynamics 8(2):83-102.

In this study we present rainfall results from equilibrium 1 x - and 2 x CO2 experiments with the
CSIRO 4-level general circulation model. The 1 X CO2 results are discussed in relation to observed
climate. Discussion of the 2 x CO2 results focuses upon changes in convective and non-convective
rainfall as simulated in the model, and the consequences these changes have for simulated daily rainfall
intensity and the frequency of heavy rainfall events. In doing this analysis, we recognize the significant
shortcomings of GCM simulations of precipitation processes. However, because of the potential
significance of any changes in heavy rainfall events as a result of the enhanced greenhouse effect, we
believe a first examination of relevant GCM rainfall results is warranted. Generally, the model results
show a marked increase in rainfall originating from penetrative convection and, in the mid- latitudes,
a decline in large-scale (non-convective) rainfall. It is argued that these changes in rainfall type are
a consequence of the increased moisture holding capacity of the warmer atmosphere simulated for
2 x CO2 conditions. Related to changes in rainfall type, rainfall intensity (rain per rain day) increases
in the model for most regions of the globe. Increases extend even to regions where total rainfall
decreases. Indeed, the greater intensity of daily rainfall is a much clearer response of the model to
increased greenhouse gases than the changes in total rainfall. We also find a decrease in the number
of rainy days in the middle latitudes of both the Northern and Southern Hemispheres. To further
elucidate these results daily rainfall frequency distributions are examined globally and for four selected
regions of interest. In all regions the frequency of high rainfall events increases, and the return period
of such events decreases markedly. If realistic, the findings have potentially serious practical
implications in terms of an increased frequency and severity of floods in most regions. However, we
discuss various important sources of uncertainty in the results presented, and indicate the need for
rainfall intensity results to be examined in enhanced greenhouse experiments with other GCMs.

KEYWORDS: CLIMATE VARIABILITY, CO2, GENERAL-CIRCULATION MODEL, OCEAN,
TEMPERATURE, WATER-VAPOR


     758  
Gorissen, A. 1996. Elevated CO2 evokes quantitative and qualitative changes in carbon dynamics
in a plant/soil system: Mechanisms and implications. Plant and Soil 187(2):289-298.

It is hypothesized that carbon storage in soil will increase under an elevated atmospheric CO2
concentration due to a combination of an increased net CO2 uptake, a shift in carbon allocation
pattern in the plant/soil system and a decreased decomposition rate of plant residues. An overview
of several studies, performed in our laboratory, on the effects of elevated CO2 on net carbon uptake,
allocation to the soil and decomposition of roots is given to test this hypothesis. The studies included
wheat, ryegrass and Douglas-fir and comprised both short-term and long-term studies. Total dry
weight of the plants increased up to 62%, but depended on nutrient availability. These results were
supported by the data on net (CO2)-C-14 uptake. A shift in C-14-carbon distribution from shoots to
roots was found in perennial species, although this depended on nutrient availability. The
decomposition experiments showed that roots cultivated at 700 mu L L-1 CO2 were decomposed
more slowly than those cultivated at 350 mu L L-1 CO2. Even after two growing seasons differences
up to 13% were observed, although this was found to be dependent on the nitrogen level at which
the roots were grown. Both an increased carbon allocation to the soil due to an increased carbon
uptake, whether or not combined with a shift in distribution pattern, and a decreased decomposition
of root residues will enhance the possibilities of carbon sequestration in soil, thus supporting our
hypothesis. However, nutrient availability and the response of the soil microbial biomass (size and
activity) play a major role in the processes involved and require attention to clarify plant/soil
responses in the long term with regard to sustained stimulation of carbon input into soils and the
decomposability of roots and rhizodeposition. Soil texture will also have a strong effect on
decomposition rates as a result of differences in the protecting capacity for organic matter. More
detailed information on these changes is needed for a proper use of models simulating soil carbon
dynamics in the long term.

KEYWORDS: ATMOSPHERIC CO2, DECOMPOSITION, FINE ROOTS, LEAF LITTER,
MICROBIAL BIOMASS, NITROGEN, ORGANIC-MATTER, ROOT-DERIVED MATERIAL, SOIL
SYSTEM, TURNOVER


     759  
Gorissen, A., P.J. Kuikman, and H. Vandebeek. 1995. Carbon allocation and water-use in juvenile
douglas-fir under elevated co2. New Phytologist 129(2):275-282.

In this study the impact of an elevated CO2 level on allocation of assimilates and water use efficiency
of Douglas fir [Pseudotsuga menziesii (Mirb.) France] was investigated. Juvenile Douglas firs were
exposed to a long-term treatment at 350 and 700 pi l(-1) CO2 for 14 months and subsequently
crosswise transferred to phytotrons for a short-term treatment with 350 and 700 mu l l(-1) CO2 for
4 wk in an atmosphere continuously labelled with (CO2)-C-14. No interactive effects on total net
uptake of (CO2)-C-14 between long-term treatment and short-term treatment were observed. The
short-term treatment with 700 mu l l(-1) CO2 increased the total net uptake of (CO2)-C-14 by 22%,
compared with the 350 mu l l(-1) CO2 treatment. The long-term pretreatment did not affect the total
net uptake, suggesting that photosynthetic acclimation had not occurred. However, expressed per unit
of needle mass a 14% reduction was observed in the trees pretreated at 700 mu l l(-1) CO2. This was
not because of a reduced sink strength of the root system. This reduced uptake per unit of needle
mass after long-term treatment may have implications for carbon storage in forest ecosystems. The
results showed that an initial growth stimulation can eventually be annulled by developing
physiological or morphological adaptions. (CO2)-C-14 the root/soil respiration increased in the short-
term treatment with 700 mu l l(-1) CO2, indicating a stimulated use of current carbon compounds
either by roots or microorganisms. The water use efficiency during the short-term treatment with 700
mu l l(-1) CO2 increased by 32%, but was not affected by the long- term pretreatment. Water use per
unit needle mass during the short-term treatment was decreased both by the short-term treatment and
by the long-term pretreatment by about 15%. Some of the observed effects appeared to be persistent,
such as decreased water use per unit needle mass, whereas others, stimulation of total net (CO2)-C-
14 uptake and water use efficiency, were transient.

KEYWORDS: BLACK SPRUCE SEEDLINGS, DIOXIDE, ECOSYSTEMS, ENRICHMENT,
GROWTH, LIQUIDAMBAR- STYRACIFLUA, PHOTOSYNTHETIC ACCLIMATION, PINUS-
TAEDA SEEDLINGS, RESPONSES, ROOT-DERIVED MATERIAL


     760  
Gorissen, A., P.J. Kuikman, J.H. vanGinkel, H. vandeBeek, and A.G. Jansen. 1996. ESPAS -
An advanced phytotron for measuring carbon dynamics in a whole plant-soil system. Plant and Soil
179(1):81-87.

The use of carbon isotopes as tracers is essential for measuring carbon flows in an intact whole plant-
soil system. Here, we describe an Experimental Soil Plant Atmosphere System (ESPAS) to perform
pulse-labelling and steady-state labelling experiments with (CO2)-C-13 and (CO2)-C-14. The ESPAS
facility is an environmental research tool that is used to measure the carbon fluxes from the
atmosphere to the roots and into the soil and the microbial biomass and to study decomposition of
plant residues and soil organic matter. The influence of environmental conditions in the atmosphere
or in soil on the carbon allocation and turnover in the plant-soil ecosystem can be quantified. The
design and the technical description of the phytotrons is presented and evidence is provided that the
phytotrons are equivalent. For this purpose, Triticum aestivum plants were cultivated in the
phytotrons for 39 days and shoot growth, root growth and water use were compared. No significant
differences were observed for plant growth and water use. As an example of the practical application
of the equipment, an experiment with elevated atmospheric CO2 is presented. Data are given on the
uptake of C-14 under ambient (350 mu L L(-1)) and elevated (700 mu L L(-1)CO(2) in Lolium
perenne and Festuca arundinacea and the distribution of C-14 among different plant- soil
compartments i.e. shoot, root, root-soil respiration, and soil. We conclude that these phytotrons yield
detailed information on gross carbon flows in a whole plant-soil system that can not be obtained
without sensitive carbon tracers. Such data are important for proper calibration of simulation models
on soil organic matter.

KEYWORDS: DIOXIDE, DOUGLAS-FIR, OZONE, RHIZOSPHERE, ROOT-DERIVED
MATERIAL, TRANSLOCATION, TURNOVER, WHEAT


     761  
Gorissen, A., J.H. Vanginkel, J.J.B. Keurentjes, and J.A. Vanveen. 1995. Grass root
decomposition is retarded when grass has been grown under elevated co2. Soil Biology and
Biochemistry 27(1):117-120.

KEYWORDS: ATMOSPHERIC CO2, CARBON DIOXIDE, CYCLE, INCREASE, LEAF LITTER,
NITROGEN, SOIL


     762  
Gorny, J.R., and A.A. Kader. 1996. Controlled-atmosphere suppression of ACC synthase and ACC
oxidase in 'Golden Delicious' apples during long-term cold storage. Journal of the American Society
for Horticultural Science 121(4):751-755.

Preclimacteric 'Golden Delicious' apples (Malus domestica Borkh.) were stored at 0 degrees C in: air;
air + 5% CO2; 2% O- 2 + 98% N-2; or 2% O-2 + 5% CO2 + 93% N-2, and sampled monthly for 4
months to investigate the mechanism(s) by which reduced O-2 and/or elevated CO2 atmospheres
inhibit C2H4 biosynthesis. Ethylene biosynthesis rates and in vitro ACS activity were closely
correlated in all treatments, while in vitro ACO activity significantly increased over time regardless
of the treatment. Only a small amount of C2H4 biosynthesis inhibition by lowered O-2 and/or
elevated CO2 atmospheres could be accounted for by suppressed induction of ACO activity, Western
blot analysis demonstrated that apples held for 2 months in lowered O-2 and/or elevated CO2
atmospheres had significantly reduced abundance of ACO protein, compared to fruit held in air.
Northern blot analysis of ACS and ACO transcript abundance revealed that reduced O-2 and/or
elevated CO2 atmospheres delay induction and reduce the abundance of both transcripts, Reduced
O-2 and/or elevated CO2 atmospheres reduce C2H4 biosynthesis by delaying and suppressing
expression of ACS at the transcriptional level and by reducing the abundance of active ACO protein.
Chemical names used: 1-aminocyclopropane-1- carboxylic acid (ACC), ACC synthase (ACS), ACC
oxidase (ACO), ethylene (C2H4), S-adenosylmethionine (AdoMet).

KEYWORDS: 1-AMINOCYCLOPROPANE-1-CARBOXYLIC ACID, ETHYLENE PRODUCTION,
EXPRESSION, FRUIT, PROTEIN, PURIFICATION


     763  
Gorny, J.R., and A.A. Kader. 1996. Regulation of ethylene biosynthesis in climacteric apple fruit
by elevated CO2 and reduced O-2 atmospheres. Postharvest Biology and Technology 9(3):311-323.

Autocatalytic (System II) C2H4 biosynthesis in climacteric 'Golden Delicious' apples (Malus
domestica Borkh) was effectively inhibited at 20 degrees C by atmospheres of 20% CO2-enriched
air (17% O-2 + 63% N-2) or 0.25% O-2 (balance N- 2). In vitro 1-aminocyclopropane-1-carboxylic
acid (ACC) synthase (ACC-S) activity of apples held in atmospheres of air + 20% CO2 or 0.25% O-2
was significantly inhibited when compared to apples kept in air, and correlated well with fruit C2H4
production rates. In vivo and in vitro ACC oxidase (ACC-O) activity of fruit held in atmospheres of
air, air + 20% CO2 or 0.25% O-2 were similar when the assays were performed under standard assay
conditions (i.e., in vivo assay performed in air, in vitro assay performed in air + 6% CO2). However,
if the in vivo or in vitro ACC-O enzyme activity assays were performed in an atmosphere of 0.25%
O-2, ACC-O catalytic competency and activity were significantly reduced. When the in vivo or in
vitro ACC-O enzyme activity assays were performed in an atmosphere of air + 20% CO2, ACC-O
enzyme activity was actually stimulated. These data indicate that elevated levels of CO2 do not inhibit
ACC-O catalytic competency. Western blot analysis revealed that ACC-O protein abundance was not
significantly affected by any of the treatments tested, and only the 0.25% O- 2 atmosphere
significantly inhibited ACC-O activity. ACC-S activity was significantly reduced by atmospheres of
air + 20% CO2 or 0.25% O-2 but not via direct inhibition of ACC-S catalytic competency.

KEYWORDS: 1-AMINOCYCLOPROPANE-1-CARBOXYLIC ACID, CARBON DIOXIDE,
OXIDASE, PH, PURIFICATION, SYNTHASE


     764  
Gorny, J.R., and A.A. Kader. 1997. Low oxygen and elevated carbon dioxide atmospheres inhibit
ethylene biosynthesis in preclimacteric and climacteric apple fruit. Journal of the American Society
for Horticultural Science 122(4):542-546.

Autocatalytic C2H4 biosynthesis in preclimacteric apple fruit (Malus domestica Borkh, 'Golden
Delicious') was prevented by storage in atmospheres of 20% CO2-enriched air (17% O-2+ 63% N-
2) or 0.25% O-2 (balance N-2). In preclimacteric fruit, both treatments inhibited C2H4 biosynthesis
by suppressing expression of ACC synthase (ACC-S) at the mRNA level. ACC oxidase (ACC-O)
mRNA abundance and in vitro enzyme activity also were impaired by these treatments. However, the
conversion of ACC to C2H4 never became the rate limiting step in C2H4 biosynthesis, C2H4
biosynthesis also was effectively inhibited in climacteric apple fruit kept in air + 20% CO2 or 0.25%
O-2. Climacteric apples also exhibited suppressed expression of ACC- S at the mRNA level, while
ACC-O transcript abundance, enzyme activity, and protein abundance mere reduced only slightly.
ACC-S is the key regulatory enzyme of C2H4 biosynthesis and is the major site at which elevated
CO2 and reduced O-2 atmospheres inhibit C2H4 biosynthesis, irrespective of fruit physiological
maturity. Chemical names used: 1- aminocyclopropane-1-carboxcylic acid (ACC).

KEYWORDS: 1-AMINOCYCLOPROPANE-1-CARBOXYLIC ACID, EXPRESSION, OXIDASE,
PROPYLENE, PROTEIN, PURIFICATION, SYNTHASE, TOMATO


     765  
Goudriaan, J. 1992. Where goes the carbon-dioxide - the role of vegetation. Recherche
23(243):597.

KEYWORDS: AGRICULTURAL YIELD, ASSEMBLAGE, CO2- ENRICHMENT, PLANT, SOYBEAN
LEAVES


     766  
Gouk, S.S., J. He, and C.S. Hew. 1999. Changes in photosynthetic capability and carbohydrate
production in an epiphytic CAM orchid plantlet exposed to super-elevated CO2. Environmental and
Experimental Botany 41(3):219-230.

The effects on growth in super-elevated (1%) CO2 in terms of photosynthetic capability and
carbohydrate production were studied in an epiphytic CAM (Crassulacean acid metabolism) orchid
plantlet, Mokara Yellow (Arachmis hookeriana x Ascocenda Madame Kenny). The growth of the
plantlets was greatly enhanced after growing for 3 months at 1% CO2 compared with the control
plantlets (0.035% CO2). CO2 enrichment produced more than a 2- fold increase in dry matter
production. The enhanced root growth at 1% CO2 led to a higher root:shoot ratio. Plantlets grown
at super-elevated CO2 had higher F-v/F-m values, a higher photochemical quenching (q(P)) and a
relatively lower non- photochemical quenching (q(N)). CO2 at 1% appeared to enhance the utilization
of captured light energy in the orchid plantlets. CO2 enrichment also increased contents of soluble
sugars (glucose and sucrose) and starch in the orchid plantlets. The extra starch formed under 1%
CO, did not cause a disruption of the chloroplasts. Chlorophyll content was higher and a clear granal
stacking was evident in young leaves and roots of plantlets grown at 1% CO2. An extensive thylakoid
system was observed in the young leaf chloroplasts of the CO2- enriched plantlets indicating an
improved development of the photosynthetic apparatus when compared to that of the control
plantlets. The increased photosynthetic capacity and enhanced growth of the epiphytic roots under
CO, enrichment would facilitate the generation of more photoassimilates and acquisition of essential
resources, thereby increasing the survival rate of orchid plantlets under stressful field conditions. (C)
1999 Elsevier Science B.V. All rights reserved.

KEYWORDS: ATMOSPHERIC CARBON-DIOXIDE, CHLOROPHYLL FLUORESCENCE,
CULTURE, ENRICHMENT, GROWTH, INVITRO, RESPONSES, ROOTS, STRAWBERRY
PLANTLETS, ULTRASTRUCTURE


     767  
Gouk, S.S., J.W.H. Yong, and C.S. Hew. 1997. Effects of super-elevated CO2 on the growth and
carboxylating enzymes in an epiphytic CAM orchid plantlet. Journal of Plant Physiology 151(2):129-
136.

Responses of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) and phosphoenolpyruvate
carboxylase (PEPCase) to super-elevated CO2 were determined along with dry mass production,
chlorophyll, soluble protein and nocturnal malate increases (NMI) for an epiphytic Crassulacean acid
metabolism (CAM) orchid plantlet, Mokara Yellow. After S-month culture period, the total dry mass
under super-elevated CO2 was 170% higher than the plantlets grown in 0.03% CO2; young leaf dry
mass was 4-fold higher while the root dry mass increased 278% and 344% under 1% and 5% CO2
respectively. Higher root:shoot ratio was observed under super-elevated CO2; 0.22 in 0.03% CO2,
0.32 in 1% CO2 and 0.38 in 5% CO2. The averaged increase in total young leaf area was 244% and
373% under 1% and 5% CO2 respectively Leaf chlorophyll expressed per unit fresh weight was
reduced under 5% CO2 but it increased 19% and 67% in old and young leaves of 3-month plantlets
under 1% CO2. The root chlorophyll content increased 108% and 154% under 1%;, and 5% CO2
respectively. Soluble protein in young leaves increased 32% under 1% CO2 and 75% under 5% CO2,
while the increase in root protein varied from 36% to 100%. The activities of Rubisco and PEPCase
el:pressed per unit protein were reduced under super- elevated CO2, particularly in 5% CO2, the
decreases ranged from 12% to 90% in Rubisco and 27% to 90% in PEPCase. Nevertheless, the leaf
Rubisco:PEPCase ratio increased 110% to 362% under super-elevated CO2. Increased NMI, ranged
from 23% to 182% under super-elevated CO2, contributed to the increased dry matter accumulation
in Mokara plantlets. Throughout the S-month culture period, the CO2-enriched plantlets showed
enhanced growth particularly under 1% CO2 in terms of biomass production, chlorophyll, soluble
protein and NMI despite a concomitant decrease in the activities of the carboxylating enzymes.

KEYWORDS: CARBON DIOXIDE, CRASSULACEAN ACID METABOLISM, ENRICHMENT,
INVITRO, OPUNTIA FICUS INDICA, PHOTOSYNTHESIS, STRAWBERRY PLANTLETS,
SUCROSE, TEMPERATURE, TISSUE-CULTURE


     768  
Goulart, B.L., P.E. Hammer, K.B. Evensen, W. Janisiewicz, and F. Takeda. 1992. Pyrrolnitrin,
captan + benomyl, and high co2 enhance raspberry shelf-life at 0C or 18C. Journal of the American
Society for Horticultural Science 117(2):265-270.

The effects of preharvest applications of pyrrolnitrin (a biologically derived fungicide) on postharvest
longevity of 'Bristol' black raspberry (Rubus occidentalis L.) and 'Heritage' red raspberry [R. idaeus
L. var. strigosus (Michx.) Maxim] were evaluated at two storage temperatures. Preharvest fungicide
treatments were 200 mg pyrrolnitrin/liter, a standard fungicide treatment (captan + benomyl or
iprodione) or a distilled water control applied 1 day before first harvest. Black raspberries were stored
at 18 or 0 +/- 1C in air or 20% CO2. Red raspberries were stored at the same temperatures in air
only. Pyrrolnitrin-treated berries often had less gray mold (Botrytis cinerea Pers. ex Fr.) in storage
than the control but more than berries treated with the standard fungicides. Storage in a modified
atmosphere of 20% CO2 greatly improved postharvest quality of black raspberries at both storage
temperatures by reducing gray mold development. The combination of standard fungicide or
pyrrolnitrin, high CO2, and low temperature resulted in more than 2 weeks of storage with less than
5% disease on black raspberries; however, discoloration limited marketability after almost- equal-to
8 days under these conditions. Chemical names used: 3-chloro-4-(2'-nitro-3'-chlorophenyl)-pyrrole
(pyrrolnitrin); N-trichloromethylthio-4-cyclohexene-1,2-dicarboximide (captan); methyl 1-
(butylcarbamoyl)-2-benzimidazolecarbamate) (benomyl); 3-(3,5-dichlorophenyl)-N-(1-methylethyl)-
2,4-dioxo-1- imidazolidinecarboxamide (Rovral, iprodione).

KEYWORDS: STRAWBERRIES


     769  
Graham, E.A., and P.S. Nobel. 1996. Long-term effects of a doubled atmospheric CO2
concentration on the CAM species Agave deserti. Journal of Experimental Botany 47(294):61-69.

To examine the effects of a doubled atmospheric CO2 concentration and other aspects of global
climate change on a common CAM species native to the Sonoran Desert, Agave deserti was grown
under 370 and 750 mu mol CO2 mol(-1) air and gas exchange was measured under various
environmental conditions. Doubling the CO2 concentration increased daily net CO2 uptake by 49%
throughout the 17 months and decreased daily transpiration by 24%, leading to a 110% increase in
water-use efficiency, Under the doubled CO2 concentration, the activity of ribulose-1,5-bisphosphate
carboxylase/oxygenase (Rubisco) was 11% lower, phosphoenolpyruvate carboxylase was 34% lower,
and the activated:total ratio for Rubisco was 25% greater than under the current CO2 concentration.
Less leaf epicuticular wax occurred on plants under the doubled CO2 concentration, which decreased
the reflectance of photosynthetic photon flux (PPF); the chlorophyll content per unit leaf area was
also less, The enhancement of daily net CO2 uptake by doubling the CO2 concentration increased
when the PPF was decreased below 25 mol m(-2) d(-1), when water was withheld, and when
day/night temperatures were below 17/12 degrees C, More leaves, each with a greater surface area,
were produced per plant under the doubled CO2 concentration. The combination of increased total
leaf surface area and increased daily net CO2 uptake led to an 88% stimulation of dry mass
accumulation under the doubled CO2 concentration, A rising atmospheric CO2 concentration,
together with accompanying changes in temperature, precipitation, and PPF, should increase growth
and productivity of native populations of A. deserti.

KEYWORDS: CROP RESPONSES, ELEVATED CARBON-DIOXIDE, ENRICHMENT,
ENVIRONMENTAL PHYSIOLOGY, EPICUTICULAR WAX LOAD, GROWTH,
PHOTOSYNTHESIS, PLANT, RIBULOSE-1;5-BISPHOSPHATE CARBOXYLASE, RISING CO2


     770  
Grams, T.E.E., S. Anegg, K.H. Haberle, C. Langebartels, and R. Matyssek. 1999. Interactions
of chronic exposure to elevated CO2 and O-3 levels in the photosynthetic light and dark reactions
of European beech (Fagus sylvatica). New Phytologist 144(1):95-107.

Young trees of European beech (Fagus sylvatica) acclimated for one growing season to ambient (c.
367 mu l l(-1)) or elevated CO2 levels (c. 660 mu l l(-1)) were exposed during the subsequent year
to combinations of the same CO2 regimes and ambient or twice-ambient ozone (O-3) levels
(generated from the database of a rural site). By the end of June, before the development of
macroscopic leaf injury, the raised O-3 levels had not affected the light and dark reactions of
photosynthesis. However, acclimation to elevated CO2 had resulted in lowered chlorophyll and
nitrogen concentrations, whereas photosynthetic performance, examined over a wide range of
parameters from light and dark reactions, remained unchanged or showed only slight reductions (e.g.
apparent electron transport rate, ETR; apparent quantum yield of CO2 gas exchange, Phi(CO2);
apparent carboxylation efficiency, CE; and photosynthetic capacity at light and CO2 saturation, PC).
In August, after the appearance of leaf necroses, plants grown under ambient CO2 and twice-ambient
O-3 conditions declined in both the photosynthetic light reactions (optimum electron quantum yield,
Fv/F-m, non-photochemical energy quenching, NPQ, reduction state of Q(A), apparent electron
quantum yield, Phi(PSI)I, maximum electron transport rates) and the dark reactions as reflected by
CE, Phi(CO2), as well as the maximum CO2 uptake rate (i.e. PC). CE, Phi(CO2) and PC were
reduced by c. 75, 40 and 75%, respectively, relative to plants exposed to ambient CO2 and O-3
levels. By contrast, plants exposed to twice-ambient O-3 and elevated CO2 levels maintained a
photosynthetic performance similar to individuals grown either under ambient CO2 and ambient O-3,
or elevated CO2 and ambient O-3 conditions. The long-term exposure to elevated CO2 therefore
tended to counteract adverse chronic effects of enhanced O-3 levels on photosynthesis. Possible
reasons for this compensatory effect in F. sylvatica are discussed.

KEYWORDS: ATMOSPHERIC CO2, BETULA-PENDULA, CARBON DIOXIDE, CHLOROPHYLL
FLUORESCENCE, LEAF GAS- EXCHANGE, LOW OZONE CONCENTRATIONS, NORWAY
SPRUCE, PHOTOSYSTEM, SPRUCE PICEA-ABIES, TROPOSPHERIC OZONE


     771  
Grams, T.E.E., and R. Matyssek. 1999. Elevated CO2 counteracts the limitation by chronic ozone
exposure on photosynthesis in Fagus sylvatica L.: Comparison between chlorophyll fluorescence and
leaf gas exchange. Phyton-Annales Rei Botanicae 39(4):31-39.

The interaction of elevated CO2 and enhanced chronic ozone (O- 3) impact was analysed throughout
the growing season in the photosynthetic response (chlorophyll fluorescence and leaf gas exchange)
of beech saplings (Fagus sylvatica) which had been acclimated to CO2 supply during the year prior
to the experiment. Both light and dark reactions (i.e. electron transport rate and photosynthetic
capacity) of plants grown at ambient CO2 and twice-ambient O-3 concentrations were distinctly
reduced by August. The O-3-induced decline was counteracted by elevated CO2 supply (i.e. ambient
+300 ppm). Plants grown at high CO2 supply and ambient or twice-ambient O- 3 concentrations
displayed a photosynthetic performance similar to plants exposed to ambient CO2 and O-3
conditions. Responses in chlorophyll fluorescence were found to be consistent with those in leaf gas
exchange.

KEYWORDS: BEECH, CARBON DIOXIDE, GROWTH, LEAVES, NORWAY SPRUCE, O-3,
RESPONSES, SPRING WHEAT, TROPOSPHERIC OZONE, YIELD


     772  
Grant, R.F. 1998. Simulation in ecosys of root growth response to contrasting soil water and
nitrogen. Ecological Modelling 107(2-3):237-264.

If mathematical models of plant growth are to perform reliably under diverse conditions of soil and
climate, then the effects of these conditions on root growth must be represented. A mathematical
model of root and mycorrhizal growth is proposed to represent the effects of soil and climate on
growth using the hypothesis that a functional equilibrium exists among root axes and shoot branches.
In this model access to growth resources (C, N, P, water) by different axes or branches depends upon
(1) proximity of the axis or branch to the point of resource acquisition, and (2) the rate at which
resources are consumed by the axis or branch in relation to that by other axes or branches. This model
was coupled to a plant growth model as part of the ecosystem simulation model ecosys, and its
sensitivity to changes in model parameters and soil boundary conditions was tested. Simulated root
growth was less sensitive to changes in soil water and nitrogen than was simulated shoot growth. This
lower sensitivity allowed the model to simulate changes in root,shoot ratios with changes in soil water
and nitrogen that were consistent with those commonly reported in the literature. Changes in soil
water also caused changes in vertical distributions of root length density to be simulated that were
also consistent with those reported. Changes in root,shoot partitioning and in root density
distributions allowed improved access by plants in the model to limiting growth resources. The root
model was parameterized from basic root growth studies conducted independently of the model, and
without reference to site-specific patterns of seasonal root growth. Consequently the model is likely
to be of general value in the simulation of root growth under diverse soil conditions, although such
generality needs to be established through further testing under different soils, climates and crops. The
precision of some of the model parameters is uncertain and the sensitivity of the model to this
uncertainty is discussed. (C) 1998 Elsevier Science B.V. All rights reserved.

KEYWORDS: AIR CO-2 ENRICHMENT, CARBON DIOXIDE, FACE EXPERIMENT, MODEL,
MYCORRHIZAL FUNGI, PHOSPHORUS, PLANTS, SHOOT DEVELOPMENT, WINTER-WHEAT,
ZEA-MAYS


     773  
Grant, R.F., T.A. Black, G. den Hartog, J.A. Berry, H.H. Neumann, P.D. Blanken, P.C. Yang,
C. Russell, and I.A. Nalder. 1999. Diurnal and annual exchanges of mass and energy between an
aspen-hazelnut forest and the atmosphere: Testing the mathematical model Ecosys with data from
the BOREAS experiment. Journal of Geophysical Research-Atmospheres 104(D22):27699-27717.

There is much uncertainty about the net carbon (C) exchange of boreal forest ecosystems, although
this exchange may be an important part of global C dynamics. To resolve this uncertainty, net C
exchange has been measured at several sites in the boreal forest of Canada as part of the Boreal
Ecosystem- Atmosphere Study (BOREAS). One of these sites is the Southern Old Aspen site at
which diurnal CO2 and energy (radiation, latent, and sensible heat) fluxes were measured during 1994
using eddy correlation techniques at different positions within a mixed 70 year old aspen-hazelnut
forest. These measurements were used to test a complex ecosystem model "ecosys" in which mass
and energy exchanges between terrestrial ecosystems and the atmosphere are simulated hourly under
diverse conditions of soil, management, and climate. These simulations explained between 70% and
80% of diurnal variation in ecosystem CO2 and energy fluxes measured during three 1 week intervals
in late April, early June, and mid-July. Total annual CO2 fluxes indicated that during 1994, aspen was
a net sink of 540 (modeled) versus 670 (measured) g C m(-2) yr(-1), while hazelnut plus soil were
a net source of 472 (modeled) versus 540 (measured) g C m(-2) yr(-1). The aspen-hazelnut forest
at the BOREAS site was therefore estimated to be a net sink of about 68 (modeled) versus 130
(measured) g C m(-2) yr(-1) during 1994. Long-term simulations indicated that this sink may be
larger during cooler years and smaller during warmer years because C fixation in the model was less
sensitive to temperature than respiration. These simulations also indicated that the magnitude of this
sink declines with forest age because respiration increases with respect to fixation as standing
phytomass grows. Confidence in the predictive capabilities of ecosystem models at decadal or
centennial timescales is improved by well-constrained tests of these models at hourly timescales.

KEYWORDS: BLACK SPRUCE, CO2- ENRICHMENT, ELEVATED CARBON-DIOXIDE, JACK
PINE, NITROUS-OXIDE, PHOSPHORUS UPTAKE, ROOT-GROWTH, SIMULATION-MODEL,
SOIL ORGANIC MATTER, TREMBLING ASPEN


     774  
Grant, R.F., R.L. Garcia, P.J. Pinter, D. Hunsaker, G.W. Wall, B.A. Kimball, and R.L.
LaMorte. 1995. Interaction between atmospheric CO2 concentration and water deficit on gas
exchange and crop growth: Testing of ecosys with data from the Free Air CO2 Enrichment (FACE)
experiment. Global Change Biology 1(6):443-454.

Soil water deficits are likely to influence the response of crop growth and yield to changes in
atmospheric CO2 concentrations (C-a), but the extent of this influence is uncertain. To study the
interaction of water deficits and C-a on crop growth, the ecosystem simulation model ecosys was
tested with data for diurnal gas exchange and seasonal wheat growth measured during 1993 under
high and low irrigation at C- a = 370 and 550 mu mol mol(-1) in the Free Air CO2 Enrichment
(FACE) experiment near Phoenix, AZ. The model, supported by the data from canopy gas exchange
enclosures, indicated that under high irrigation canopy conductance (g(c)) at C-a = 550 mu mol mol(-
1) was reduced to about 0.75 that at C-a = 370 mu mol mol(-1), but that under low irrigation, g(c)
was reduced less. Consequently when C-a was increased from 370 to 550 mu mol mol(-1), canopy
transpiration was reduced less, and net CO2 fixation was increased more, under low irrigation than
under high irrigation. The simulated effects of C-a and irrigation on diurnal gas exchange were also
apparent on seasonal water use and grain yield. Simulated vs. measured seasonal water use by wheat
under high irrigation was reduced by 6% vs. 4% at C-a = 550 vs. 370 mu mol mol(-1), but that under
low irrigation was increased by 3% vs. 5%. Simulated vs. measured grain yield of wheat under high
irrigation was increased by 16% vs. 8%, but that under low irrigation was increased by 38% vs. 21%.
In ecosys, the interaction between C-a and irrigation on diurnal gas exchange, and hence on seasonal
crop growth and water use, was attributed to a convergence of simulated g(c) towards common
values under both C-a as canopy turgor declined. This convergence caused transpiration to decrease
comparatively less, but CO2 fixation to increase comparatively more, under high vs. low C-a.
Convergence of g(c) was in turn attributed to improved turgor maintenance under elevated C-a
caused by greater storage C concentrations in the leaves, and by greater rooting density in the soil.

KEYWORDS: BIOCHEMICAL-MODEL, CANOPY PHOTOSYNTHESIS, CARBOXYLASE-
OXYGENASE, ELEVATED CARBON-DIOXIDE, MAIZE, ROOT-GROWTH, SIMULATION-
MODEL, SOYBEAN LEAVES, TEMPERATURE, WINTER-WHEAT


     775  
Grant, R.F., B.A. Kimball, P.J. Pinter, G.W. Wall, R.L. Garcia, R.L. Lamorte, and D.J.
Hunsaker. 1995. Carbon-dioxide effects on crop energy-balance - testing ecosys with a free-air co2
enrichment (face) experiment. Agronomy Journal 87(3):446-457.

Elevated CO2 concentrations (C-e) have been observed to decrease short-term plant water use under
controlled conditions by increasing stomatal resistance. The extent to which this decrease occurs over
a growing season in the held is uncertain, however, because stomatal resistance is only one of many
mechanisms that control water use. In this study, we tested the ecosystem simulation model ecosys,
which reproduces an hourly energy balance through soil-vegetation systems under defined
atmospheric boundary renditions, using energy exchange data measured as part of the Free-Air CO2
Enrichment (FACE) experiment at C-e = 550 vs. 370 mu mol mol(-1). The model reproduced
reductions in measured upward latent heat fluxes that varied from -10 to +40 W m(-2), depending
on atmospheric conditions. In the model, the primary effect of elevated C-e on latent heat fluxes was
through canopy stomatal conductance. This effect was largely offset by secondary effects through
canopy temperature that enabled the model to reproduce measured changes in sensible heat fluxes.
The total effect simulated by ecosys of C-e = 550 vs. 370 mu mol mol(-1) on evapotranspiration
during the entire PACE experiment was a reduction of 7%. This reduction compares with one of 11%
estimated from accumulated daily measurements of latent heat flux. In the model, the different effects
of C-e on plant water use depend on atmosphere and soil boundary conditions, and are highly
dynamic. Consequently the simulated C-e-water use relationship is likely to be site-specific. The use
of models such as ecosys allows site-specific boundary conditions to be considered in the study of C-e
effects on plant growth and water use.

KEYWORDS: BIOCHEMICAL-MODEL, CANOPY PHOTOSYNTHESIS, EXPERIMENTAL-
VERIFICATION, OSMOTIC ADJUSTMENT, PLANT GROWTH, ROOT-GROWTH, SIMULATION-
MODEL, SOIL COMPACTION, STOMATAL CONDUCTANCE, WATER-USE EFFICIENCY


     776  
Grant, R.F., G.W. Wall, B.A. Kimball, K.F.A. Frumau, P.J. Pinter, D.J. Hunsaker, and R.L.
Lamorte. 1999. Crop water relations under different CO2 and irrigation: testing of ecosys with the
free air CO2 enrichment (FACE) experiment. Agricultural and Forest Meteorology 95(1):27-51.

Increases in crop growth under elevated atmospheric CO2 concentration (C-A) have frequently been
observed to be greater under water-limited versus non-limited conditions. Crop simulation models
used in climate change studies should be capable of reproducing such changes in growth response to
C-A with changes in environmental conditions. We propose that changes with soil water status in
crop growth response to C-A can be simulated if stomatal resistance is considered to vary directly
with air-leaf C-A gradient, inversely with leaf carboxylation rate, and exponentially with leaf turgor.
Resistance simulated in this way increases with C-A relatively less, and CO2 fixation increases with
C-A relatively more, under water-limited versus non-limited conditions. As part of the ecosystem
model ecosys, this simulation technique caused changes in leaf conductance and CO2 fixation, and
in canopy water potential, temperature and energy balance in a modelling experiment that were
consistent with changes measured under 355 versus 550 mu mol mol(-1) C-A and low versus high
irrigation in a free air CO2 enrichment (FACE) experiment on wheat. Changes with C-A in simulated
crop water relations allowed the model to reproduce under 550 mu mol mol(-1) C-A and low versus
high irrigation a measured increase of 20 versus 10% in seasonal wheat biomass, and a measured
decrease of 2 versus 5% in seasonal evapotranspiration, The basic nature of the processes simulated
in this model is intended to enable its use under a wide range of soil, management and climate
conditions. (C) 1999 Elsevier Science B.V. All rights reserved.

KEYWORDS: ATMOSPHERIC CO2, CARBON-DIOXIDE ENRICHMENT, ENERGY-BALANCE,
EXPERIMENTAL- VERIFICATION, GAS-EXCHANGE, ROOT-GROWTH, SIMULATION-
MODEL, SOIL TEMPERATURE, STOMATAL CONDUCTANCE, USE EFFICIENCY


     777  
Grant, W.J.R., H.M. Fan, W.J.S. Downton, and B.R. Loveys. 1992. Effects of co2 enrichment
on the physiology and propagation of 2 australian ornamental plants, chamelaucium-uncinatum
(schauer) X chamelaucium-floriferum (ms) and correa- schlechtendalii (behr). Scientia Horticulturae
52(4):337-342.

Root formation on both Chamelaucium and Correa cuttings maintained at high humidity in an
enclosed fog tunnel was significantly enhanced when ambient CO2 was increased from 350 to 800
mubar. CO2 enrichment resulted in decreased transpiration and increased water potential of cuttings
implying an effect of CO2 on stomatal conductance. CO2 enrichment led to increased starch levels
in cuttings of both species probably by raising the intercellular partial pressure of CO2. Increased
starch content with CO2 enrichment was able to account for 70-90% of the dry weight increase in
Correa, but only for 10-30% of the dry weight increase in Chamelaucium. It is suggested that the
stimulation of rooting associated with CO2 enrichment probably derives from the improved water
relations of the cuttings rather than from increased carbohydrate levels.

KEYWORDS: CUTTINGS


     778  
Grant, W.J.R., and B.R. Loveys. 1996. Controlling rootstock sprouts of Agonis flexuosa (Willd)
Sweet at ambient and elevated CO2 by multiple applications of low concentration NAA. Australian
Journal of Experimental Agriculture 36(5):619-624.

A method for grafting variegated scion material to green leafed Agonis flexuosa (Willd.) Sweet stock
was developed to overcome the difficulty of striking cuttings. However sprouting of both seedling
and cutting-grown A. flexuosa rootstocks was a significant problem. Microwedge grafting of actively
growing leafy scions and stocks in fog at 32/22 degrees C gave 90-100% success and scion bud
activity was stimulated within 2 weeks. Weekly or fortnightly spray applications of 100 mg NAA/L
(napthaleneacetic acid), starting at the time of grafting, gave effective sprout control whereas a single
pregraft spray of 200 mg NAA/L was not effective. CO2 enrichment of the fog environment was
investigated as a means of enhancing scion growth. CO2 at 80 kPa increased scion dry weight (DW),
leaf and branch numbers, but had no effect on rootstock sprout or stem DW or sprout numbers.
Optimum NAA concentrations for rootstock sprout suppression under elevated CO2 with fog, were
50-100 mg/L, which were not deleterious to scion shoot length, when sprayed on the stock portion
only. Stock sprout numbers, scion leaf and branch numbers were negatively correlated with NAA
concentration. Sprout growth at 100 mg NAA/L was about 5% of control sprout growth.
Concentrations greater than or equal to 200 mg NAA/L caused leaf tip necrosis and excess stem
callusing. Scion growth was inversely related to the degree of resprouting in control treatments.

KEYWORDS: ENRICHMENT, GROWTH, TREES


     779  
Grashoff, C., P. Dijkstra, S. Nonhebel, A.H.C.M. Schapendonk, and S.C. VandeGeijn. 1995.
Effects of climate change on productivity of cereals and legumes; model evaluation of observed year-
to-year variability of the CO2 response. Global Change Biology 1(6):417-428.

The effect of elevated [CO2] on the productivity of spring wheat, winter wheat and faba bean was
studied in experiments in climatized crop enclosures in the Wageningen Rhizolab in 1991- 93.
Simulation models for crop growth were used to explore possible causes for the observed differences
in the CO2 response. Measurements of the canopy gas exchange (CO2 and water vapour) were made
continuously from emergence until harvest. At an external [CO2] of 700 mu mol mol(-1), Maximum
Canopy CO2 Exchange Rate (CCFRmax) at canopy closure was stimulated by 51% for spring wheat
and by 71% for faba bean. At the end of the growing season, above ground biomass increase at 700
mu mol mol(-1) was 58% (faba bean), 35% (spring wheat) and 19% (winter wheat) and the harvest
index did not change. For model exploration, weather data sets for the period 1975-88 and 1991-93
were used, assuming adequate water supply and [CO2] at 350 and 700 mu mol mol(-1). For spring
wheat the simulated responses (35-50%) were at the upper end of the experimental results. In
agreement with experiments, simulations showed smaller responses for winter wheat and larger
responses for faba bean. Further model explorations showed that this differential effect in the CO2
response may not be primarily due to fundamental physiological differences between the crops, but
may be at least partly due to differences in the daily air temperatures during comparable stages of
growth of these crops. Simulations also showed that variations between years in CO2 response can
be largely explained by differences in weather conditions (especially temperature) between growing
seasons.

KEYWORDS: ATMOSPHERIC CO2, CARBON DIOXIDE, DRY-MATTER, ELEVATED CO2,
GROWTH, PATTERN, PHOTOSYNTHESIS, VICIA-FABA L, WHEAT, YIELD VARIABILITY


     780  
Graumlich, L.J. 1991. Sub-alpine tree growth, climate, and increasing CO2 - an assessment of
recent growth trends. Ecology 72(1):1-11.

LaMarche et al. (1984) hypothesized that recent trends of increasing ring widths in subalpine conifers
may be due to the fertilizing effects of increased atmospheric CO2. Five tree- ring series from foxtail
pine (Pinus balfouriana), lodgepole pine (P. murrayana), and western juniper (Juniperus occidentalis)
collected in the Sierra Nevada, California, were analyzed to determine if the temporal and spatial
patterns of recent growth were consistent with the hypothesized CO2-induced growth enhancement.
Specifically, I address the following questions: (1) Can growth trends be explained solely in terms of
climatic variation? (2) Are recent growth trends unusual with respect to long-term growth records?
For three of the five sites, 20th-century growth variation can be adequately modeled as a function of
climatic variation. For the remaining two sites, trends in the residuals from the growth/climate models
indicate systematic underestimation of growth during the past decade that could be interpreted as
either CO2 fertilization or as a response to extreme climatic events during the mid 1970s. At all five
sites, current growth levels have been equalled or exceeded during some preindustrial periods. Taken
together, these results do not indicate that CO2-induced growth enhancement is occurring among
subalpine conifers in the Sierra Nevada. While the results presented here offer no support for the
hypothesized CO2 fertilization effect, they do provide insights into the response of subalpine conifers
to climatic variation. Response surfaces demonstrate that precipitation during previous winter and
temperature during the current summer interact in controlling growth and that the response can be
nonlinear. Although maximum growth rates occur under conditions of high winter precipitation and
warm summers for all three species, substantial species-to-species variation occurs in the response
to these two variables.

KEYWORDS: ATMOSPHERIC CARBON-DIOXIDE, CALIFORNIA, FORESTS, PINE,
RESPONSES, SIERRA NEVADA


     781  
Graybill, D.A., and S.B. Idso. 1993. Detecting the aerial fertilization effect of atmospheric co2
enrichment in tree-ring chronologies. Global Biogeochemical Cycles 7(1):81-95.

The growth-promoting effects of the historical increase in the air's CO2 content are not yet evident
in tree-ring records where yearly biomass additions are apportioned among all plant parts. When
almost all new biomass goes into cambial enlargement, however, a growth increase of 60% or more
is observed over the past two centuries. As a result, calibration of tree-ring records of this nature with
instrumental climate records may not be feasible because of such growth changes. However, climate
signals prior to about the mid-19th century may yet be discovered by calibrating such tree-ring series
with independently derived proxy climate records for those times.

KEYWORDS: CARBON DIOXIDE, ELEVATED CO2, FOREST, GROWTH TRENDS, PAST 2
CENTURIES, PHOTOSYNTHETIC ACCLIMATION, SOUR ORANGE TREES


     782  
Grayston, S.J., C.D. Campbell, J.L. Lutze, and R.M. Gifford. 1998. Impact of elevated CO2 on
the metabolic diversity of microbial communities in N-limited grass swards. Plant and Soil
203(2):289-300.

The impact of elevated atmospheric CO2 on qualitative and quantitative changes in rhizosphere
carbon flow will have important consequences for nutrient cycling and storage in soil, through the
effect on the activity, biomass size and composition of soil microbial communities. We hypothesized
that microbial communities from the rhizosphere of Danthonia richardsonii, a native C3 Australian
grass, growing at ambient and twice ambient CO2 and varying rates of low N application (20, 60, 180
kg N ha(-1)) will be different as a consequence of qualitative and quantitative change in rhizosphere
carbon flow. We used the Biolog(TM) system to construct sole carbon source utilisation profiles of
these communities from the rhizosphere of D. richardsonii. Biolog(TM) GN and MT plates, the latter
to which more ecologically relevant root exudate carbon sources were added, were used to
characterise the communities. Microbial communities from the rhizosphere of D. richardsonii grown
for four years at twice ambient CO2 had significantly greater utilisation of all carbon sources except
those with a low C:N ratio (neutral and acidic amino acids, amides, N- heterocycles, long chain
aliphatic acids) than communities from plants grown at ambient CO2. This indicates a change in
microbial community composition suggesting that under elevated CO2 compounds with a higher C:N
ratio were exuded. Enumeration of microorganisms, using plate counts, indicated that there was a
preferential stimulation of fungal growth at elevated CO2 and confirmed that bacterial metabolic
activity (C utilisation rates), not population size (counts), were stimulated by additional C flow at
elevated CO2. Nitrogen was an additional rate-limiting factor for microbial growth in soil and had
a significant impact on the microbial response to elevated CO2. Microbial populations were higher
in the rhizosphere of plants receiving the highest N application, but the communities receiving the
lowest N application were most active. These results have important implications for carbon turnover
and storage in soils where changes in soil microbial community structure and stimulation of the
activity of microorganisms which prefer to grow on rhizodeposits may lead to a decrease in the
composition of organic matter and result in an accumulation of soil carbon.

KEYWORDS: ATMOSPHERIC CO2, C SOURCE UTILIZATION, CARBON-SOURCE
UTILIZATION, DIOXIDE, ENRICHMENT, GROWTH, NITROGEN, PLANT-RESPONSES,
RHIZOSPHERE, SOIL


     783  
Greaves, A.J., and J.G. Buwalda. 1996. Observations of diurnal decline of photosynthetic gas
exchange in kiwifruit and the effect of external CO2 concentration. New Zealand Journal of Crop
and Horticultural Science 24(4):361-369.

The prevalence of diurnal decline of photosynthesis in field- grown kiwifruit (Actinidia deliciosa (A.
Chev.) C.F. Liang et A.R. Ferguson var. deliciosa 'Hayward') and the effects of elevated CO2
concentration during decline were studied. During the seasonal period from soon after fruit set to
harvest, marked diurnal reductions of photosynthesis rate were found that could not be correlated
with levels of photosynthetically active radiation (PAR), temperature, and transpiration. Declines of
photosynthesis were observed only on clear days characterised by benign environmental conditions
other than sustained irradiance at saturating or near saturating levels. Elevation of CO2 concentration
to 200 mu mol/mol above ambient during photosynthesis decline overcame the decline effect,
allowing photosynthesis to track irradiance levels throughout the day. Possible mechanisms
generating the diurnal decline and the alleviation by elevation of CO2 concentration are discussed.

KEYWORDS: ACTINIDIA-DELICIOSA VINES, C-3 PLANTS, CAPACITY, DEPRESSION, FIELD,
GROWTH, LEAVES, RADIATION


     784  
Greer, D.H., W.A. Laing, and B.D. Campbell. 1995. Photosynthetic responses of 13 pasture
species to elevated co2 and temperature. Australian Journal of Plant Physiology 22(5):713-722.

Thirteen common pasture species, (eleven C-3 and two C-4), were grown in controlled environments
at 12/7, 18/13 and 28/23 degrees C and at 350 and 700 ppm CO2 to evaluate the effects of elevated
CO2 on their photosynthetic responses. Photosynthesis was measured at the growth temperatures and
at both 350 and 700 ppm CO2. In C-3 species, short-term (within minutes) increases in CO2 had the
greatest effect on photosynthesis, with an average of 50-60% higher rates in plants exposed to 700
ppm CO2 at each temperature. However, there was a continuum of response between the C-3 species
whereas C-4 species were unaffected by short-term changes in CO2 There was also a long-term (4-8
weeks) response to high CO2, with an average of about 40-50% higher rates of photosynthesis, with
some response by C-4 species. Both short- and long-term responses were negatively correlated with
the photosynthetic rate of each species at 350 ppm CO2 and all species were less efficient at
converting photosynthate to dry matter at elevated CO2. These data show clearly that photosynthesis
of these cool temperate pasture species can respond to elevated CO2, especially at low temperatures.
This will have consequences for predicting the potential effects of climate change, accompanied by
rising CO2, on pasture ecosystems.

KEYWORDS: ACCLIMATION, ATMOSPHERIC CARBON-DIOXIDE, ENVIRONMENTS,
GROWTH, PERENNIAL RYEGRASS, PRODUCTIVITY, RESPIRATION, SOURCE-SINK
RELATIONS, WHITE CLOVER, YIELD


     785  
Gregor, H.D. 1992. The potential role of temperate forests as sinks for co2 - examples from the
german environmental-policy against global warming. Water, Air, and Soil Pollution 64(1-2):197-
212.

Among industrialized nations Germany ranks fourth in CO2 emissions. Most of these originate from
the use of fossil fuels. Based on reports of a parliamentary study commission, established in 1987, and
other expert groups in Germany this article adresses possible environmental effects of increasing
atmospheric CO2, the sink potential of temperate forests and the influence of forest damage on this
potential. A strategy for a 25 to 30% or 250 to 300 X 10(6) t yr-1 CO2 emissions reduction by 2005
(which Germany has itself committed to) is described in which measures to enhance C sequestration
by forests play an important role. Expansion of forest area, a further increase of C storage by
appropriate management and the restoration and protection of forest health impaired by air pollution
would result in an additional storage of 17 to 20 x 10(6) t yr-1 of CO2, equaling 6 to 8% of the
reduction target.



     786  
Gregory, K.M. 1996. Are paleoclimate estimates biased by foliar physiognomic responses to
increased atmospheric CO2? Palaeogeography Palaeoclimatology Palaeoecology 124(1-2):39-51.

Physiognomic analysis of fossil angiosperm leaves has provided an important quantitative database
of Tertiary terrestrial paleoclimate. However, atmospheric CO2 level, a critical control on plant
growth, may have been higher in the Tertiary. It is thus crucial to investigate whether elevated CO2
affects leaf physiognomy. In this study, leaves were collected from white oak (Quercus alba L.)
seedlings grown in open-top growth chambers at Oak Ridge National Laboratory. The only
physiognomic change noted is an increase in length to width ratio with increasing CO2. In the
literature, leaf size has been observed to increase, decrease or remain unchanged for woody C-3
species grown in elevated CO2. Typically, one sees more variation due to microsite or phenotype than
due to CO2 level. By applying these observed physiognomic trends to two fossil floras, it is argued
that estimates of mean annual temperature and growing season precipitation may be biased on the
order of 1 degrees C and 20 cm, respectively. These are relatively small effects, as the values are
similar to the standard errors of the regression models used to estimate paleoclimate. The lack of
data, the variability of response to CO2 associated with microsite and phenotype, and the question
of whether observed short-term trends with elevated CO2 are sustained make it impossible to propose
a correction factor. Adequate sample size and sampling of several sites are the best way to attempt
to compensate for CO2 effects on a given fossil flora until response to CO2 is better understood.

KEYWORDS: CARBON-DIOXIDE ENRICHMENT, ELEVATED CO2, GAS-EXCHANGE, LEAF
ANATOMY, LEAVES, LIRIODENDRON-TULIPIFERA L, NORTH-AMERICA, SEEDLINGS, TREE
GROWTH, WATER-USE


     787  
Gregory, P.J., J.A. Palta, and G.R. Batts. 1996. Root systems and root:mass ratio - Carbon
allocation under current and projected atmospheric conditions in arable crops. Plant and Soil
187(2):221-228.

Roots of annual crop plants are a major sink for carbon particularly during early, vegetative growth
when up to one- half of all assimilated carbon may be translocated belowground. Flowering marks
a particularly important change in resource allocation, especially in determinate species, with
considerably less allocation to roots and, depending on environmental conditions, there may be
insufficient for maintenance. Studies with C-14 indicate the rapid transfer belowground of assimilates
with typically 50% translocated in young cereal plants of which 50% is respired;
exudation/rhizodeposition is generally <5% of the fixed carbon. Root:total plant mass decreases
through the season and is affected by soil and atmospheric conditions. Limited water availability
increased the allocation of C-13 to roots of wheat grown in columns so that at booting 0.38 of shoot
C (ignoring shoot respiration) was belowground compared to 0.31 in well- watered plants. Elevated
CO2 (700 mu mol CO2 mol(-1) air) increased the proportion of root:total mass by 55% compared
with normal concentration, while increasing the air temperature by a mean of 3 degrees C decreased
the proportion from 0.093 in the cool treatment to 0.055 in the warm treatment.

KEYWORDS: CO2- ENRICHMENT, DUPLEX SOIL, FIELD CONDITIONS, GRAIN-SORGHUM,
PLANT-RESPONSES, SHOOT GROWTH, SOWING DATE, VULGARE L CULTIVARS, WATER-
USE, WINTER-WHEAT


     788  
Grieb, B., U. Gross, E. Pleschka, B. Arnholdtschmitt, and K.H. Neumann. 1994. Embryogenesis
of photoautotrophic cell-cultures of daucus- carota L. Plant Cell Tissue and Organ Culture 38(2-
3):115-122.

In this paper photoautotrophic carrot (Daucus carota L.) suspension cultures are described which are
able to produce somatic embryos. The development of somatic embryos, however, requires a sucrose
supplement. Although an elevation of the CO2 concentration up to 2.3% results in the same level of
dry weight production as with sucrose in the medium, somatic embryos could not be observed.
Results on the influence of sucrose on some aspects of the photosynthetic apparatus of cultured cells
are discussed.

KEYWORDS: CARROT, EMBRYOS, PHOTOSYNTHESIS, SOMATIC EMBRYOGENESIS,
STORAGE PROTEINS, SUSPENSION


     789  
Gries, C., B.A. Kimball, and S.B. Idso. 1993. Nutrient-uptake during the course of a year by sour
orange trees growing in ambient and elevated atmospheric carbon- dioxide concentrations. Journal
of Plant Nutrition 16(1):129-147.

During the third year of a long-term carbon dioxide (CO2) enrichment study, macro- and micro-
nutrient concentrations in leaves and roots of sour orange trees were analyzed. Data for yearly
courses of the macronutrients Ca, Mg, N, P, K, Na, and S and the micronutrients B, Cu, Fe, Mn, and
Zn are presented. Significantly higher concentrations of N, K, Ca, and Mn were found in leaves of
the control trees. The degree of difference varied seasonally: the greatest differences occured in
summer, whereas essentially no differences were found in spring and winter.

KEYWORDS: CO2- ENRICHMENT, GROWTH, NITROGEN, PLANTS, RESPONSES,
SEEDLINGS, YIELD


     790  
Griffin, K.L., J.T. Ball, and B.R. Strain. 1996. Direct and indirect effects of elevated CO2 on
whole-shoot respiration in ponderosa pine seedlings. Tree Physiology 16(1-2):33-41.

We determined the short-term direct and longterm indirect effects of CO2 on apparent dark
respiration (CO2 efflux in the dark) in ponderosa pine (Pinus ponderosa Dougl. ex Laws.) seedlings
grown in 35 or 70 Pa CO2 partial pressure for 163 days in naturally lit, controlled-environment
chambers. Two soil N treatments (7 and 107 ppm total N, low-N and high-N treatments, respectively)
were imposed by watering half the plants every 2 weeks with 15/15/18 fertilizer (N,P,K) and the other
half with demineralized water. Direct effects of ambient CO2 partial pressure on apparent dark
respiration were measured during short-term manipulations (from minutes to hours) of the CO2
environment surrounding the aboveground portion of individual seedlings. Shea-term increases in the
ambient CO2 partial pressure consistently resulted in significant decreases in CO2 efflux of seedling
in all treatments. Efflux of CO2 decreased by 3 to 13% when measurement CO2 partial pressure was
increased from 35 to 70 Pa, and by 8 to 46% over the entire measurement range from 0 to 100 Pa.
No significant interactions between the indirect effects of growth CO2 partial pressure and the direct
effects of the measurement CO2 partial pressure were found. Seedlings grown in the high-N
treatment were significantly less sensitive to short-term changes in CO2 partial pressures than
seedlings grown in the low-N treatment. Apparent respiration tended to decrease in seedlings grown
in elevated CO2, but the decrease was not significant. Nitrogen had a large effect on CO2 efflux,
increasing apparent respiration more than twofold on both a leaf area and a leaf or shoot mass basis.
Both the direct and indirect effects of elevated CO2 were correlated with change's in the C/N ratio.
A model of cumulative CO2 efflux for a 160-day period demonstrated that, despite a 49% increase
in total plant biomass, seedlings grown in the high-N + high-CO2 treatment lost only 2% more carbon
than seedlings grown in the high-N + low-CO2 treatment, suggesting increased carbon use efficiency
in plants grown in elevated CO2. We conclude that small changes in instantaneous CO2 efflux, such
as those observed in ponderosa pine seedlings, could scale to large changes in carbon sequestration.

KEYWORDS: ATMOSPHERIC CO2, CARBON DIOXIDE, ECOSYSTEMS, GROWTH, LEAVES,
PARTIAL-PRESSURE, PHOTOSYNTHESIS, PLANTS, TEMPERATURE, TREES


     791  
Griffin, K.L., M.A. Bashkin, R.B. Thomas, and B.R. Strain. 1997. Interactive effects of soil
nitrogen and atmospheric carbon dioxide on root/rhizosphere carbon dioxide efflux from loblolly and
ponderosa pine seedlings. Plant and Soil 190(1):11-18.

We measured CO2 efflux from intact root/rhizosphere systems of 155 day old loblolly (Pinus taeda
L.) and ponderosa (Pinus ponderosa Dougl, ex Laws.) pine seedlings in order to study the effects of
elevated atmospheric CO2 on the below-ground carbon balance of coniferous tree seedlings.
Seedlings were grown in sterilized sand culture, watered daily with either 1, 3.5 or 7 mM NH4+, and
maintained in an atmosphere of either 35 or 70 Pa CO2. Carbon dioxide efflux (mu mol CO2 plant(-
1) s(-1)) from the root/rhizosphere system of both species significantly increased when seedlings were
grown in elevated CO2, primarily due to large increases in root mass. Specific CO2 efflux (mu mol
CO2 g root(-1) s(-1)) responded to CO2 only under conditions of adequate soil nitrogen availability
(3.5 mM). Under these conditions, CO2 efflux rates from loblolly pine increased 70% from 0.0089
to 0.0151 mu mol g(-1) s(-1) with elevated CO2 while ponderosa pine responded with a 59%
decrease, from 0.0187 to 0.0077 mu mol g(-1) s(-1). Although below ground CO2 efflux from
seedlings grown in either sub- optimal (I mM) or supra-optimal (7 mM) nitrogen availability did not
respond to CO2, there was a significant nitrogen treatment effect. Seedlings grown in supra-optimal
soil nitrogen had significantly increased specific CO2 efflux rates, and significantly lower total
biomass compared to either of the other two nitrogen treatments. These results indicate that carbon
losses from the root/rhizosphere systems are responsive to environmental resource availability, that
the magnitude and direction of these responses are species dependent, and may lead to significantly
different effects on whole plant carbon balance of these two forest tree species.

KEYWORDS: ECOSYSTEMS, ELEVATED CO2, ENRICHMENT, FEEDBACK, GROWTH, PLANT,
RESPONSES, RHIZOSPHERE, ROOT RESPIRATION, TAEDA L SEEDLINGS


     792  
Griffin, K.L., and Y.Q. Luo. 1999. Sensitivity and acclimation of Glycine max (L.) Merr. leaf gas
exchange to CO2 partial pressure. Environmental and Experimental Botany 42(2):141-153.

Theoretical studies suggest that partitioning leaf photosynthetic responses to CO2 partial pressures
into two components, sensitivity and acclimation, facilitates both scaling-up photosynthetic responses
and predicting global terrestrial carbon influx. Here, we experimentally examine these two
components by growing soybean (Glycine max) in two CO2 partial pressures, 35 and 70 Pa, and
making a suite of ecophysiological measurements on expanding and fully expanded leaves. These
CO2 treatments resulted in a variety of acclimation responses, including changes in net photosynthetic
rate and capacity, stomatal conductance, transpiration, and respiration. These responses were strongly
dependent on leaf age. Despite the wide variety of acclimation responses, the experimentally derived
photosynthetic sensitivity did not vary with CO2 treatments or leaf age. In addition, the
photosynthetic sensitivity to ambient CO2 partial pressure was consistent with the sensitivity to
intercellular CO2 partial pressure, indicating little effect of stomatal conductance on photosynthetic
sensitivity. This study supports the theoretical conclusion that photosynthetic sensitivity is
independent of growth environment and leaf age, as well as photosynthetic acclimation, even though
the latter varies with both environmental and developmental factors. Accordingly, photosynthetic
sensitivity may be directly extrapolated from leaf to globe to predict the increment in terrestrial
carbon influx stimulated by the yearly increase in atmospheric CO2, whereas the acclimation
component must be used to adjust the overall global estimate. (C) 1999 Elsevier Science B.V. All
rights reserved.

KEYWORDS: ASSIMILATION, ATMOSPHERIC CARBON-DIOXIDE, C-3 PLANTS,
CONDUCTANCE, ELEVATED CO2, LONG-TERM EXPOSURE, PHASEOLUS-VULGARIS L,
PHOTOSYNTHETIC ACCLIMATION, TEMPERATURE, WATER-STRESS


     793  
Griffin, K.L., P.D. Ross, D.A. Sims, Y. Luo, J.R. Seemann, C.A. Fox, and J.T. Ball. 1996.
EcoCELLs: Tools for mesocosm scale measurements of gas exchange. Plant, Cell and Environment
19(10):1210-1221.

We describe the use of a unique plant growth facility, which has as its centerpiece four 'EcoCELLs',
or 5x7 m mesocosms designed as open-flow, mass-balance systems for the measurement of carbon,
water and trace gas fluxes. This system is unique in that it was conceived specifically to bridge the
gap between measurement scales during long-term experiments examining the function and
development of model ecosystems. There are several advantages to using EcoCELLs, including (i)
the same theory of operation as leaf level gas exchange systems, but with continuous operation at a
much larger scale; (ii) the ability to independently evaluate canopy-level and ecosystem models; (iii)
simultaneous manipulation of environmental factors and measurement of system-level responses, and
(iv) maximum access to, and manipulation of, a large rooting volume. In addition to discussing the
theory, construction and relative merits of EcoCELLs, we describe the calibration and use of the
EcoCELLs during a 'proof of concept' experiment, This experiment involved growing soybeans under
two ambient CO2 concentrations (similar to 360 and 710 mu mol mol(-1)). During this experiment,
we asked 'How accurate is the simplest model that can be used to scale from leaf-level to canopy-level
responses?' in order to illustrate the utility of the EcoCELLs in validating canopy-scale models.

KEYWORDS: ARCTIC TUNDRA, ATMOSPHERIC CARBON-DIOXIDE, BRANCH BAG,
CLIMATE CHANGE, ELEVATED CO2, FIELD, OPEN-TOP CHAMBERS, PLANT-RESPONSES,
TRACE GASES, TUSSOCK TUNDRA


     794  
Griffin, K.L., and J.R. Seemann. 1996. Plants, CO2 and photosynthesis in the 21st century.
Chemistry & Biology 3(4):245-254.

Human activity in the last 200 years has led to a marked increase in the level of CO2 in the
atmosphere. Plants sense increases in CO2 levels and initially respond with an increase in
photosynthetic rate, which may then slow as the plant adapts. This increase in photosynthetic rate
may account in part for the 'disappearance' of an estimated 1.8 gigatons of carbon per year.

KEYWORDS: ATMOSPHERIC CO2, CARBON DIOXIDE, CLIMATE CHANGE, ELEVATED CO2,
GAS-EXCHANGE, LONG-TERM EXPOSURE, METABOLITE LEVELS, PHASEOLUS-VULGARIS
L, RIBULOSE BISPHOSPHATE CARBOXYLASE, TUSSOCK TUNDRA


     795  
Griffin, K.L., D.A. Sims, and J.R. Seemann. 1999. Altered night-time CO2 concentration affects
the growth, physiology and biochemistry of soybean. Plant, Cell and Environment 22(1):91-99.

Soybean plants (Glycine max (L.) Merr. c. v. Williams) were grown in CO2 controlled, natural-light
growth chambers under one of four atmospheric CO2 concentrations ([CO2]): (1) 250 mu mol mol(-
1) 24 h d(-1) [250/250]; (2) 1000 mu mol mol(-1) 24 h d(-1) [1000/1000]; (3) 250 mu mol mol(-1)
during daylight hours and 1000 mmol mol(-1) during nighttime hours [250/1000] or (4) 1000 mu mol
mol(-1) during daylight hours and 250 mmol mol(-1) during night-time hours [1000/250]. During the
vegetative growth phase few physiological differences were observed between plants exposed to a
constant 24 h [CO2] (250/250 and 1000/1000) and those that were switched to a higher or lower
[CO2] at night (250/1000 and 1000/250), suggesting that the primary physiological responses of
plants to growth in elevated [CO2] is apparently a response to daytime [CO2] only. However, by the
end of the reproductive growth phase, major differences were observed. Plants grown in the
1000/250 regime, when compared with those in the 1000/1000 regime, had significantly more leaf
area and leaf mass, 27% more total plant dry mass, but only 18% of the fruit mass. After 12 weeks
of growth these plants also had 19% higher respiration rates and 32% lower photosynthetic rates than
the 1000/1000 plants. As a result the ratio of carbon gain to carbon loss was reduced significantly in
the plants exposed to the reduced night-time [CO2]. Plants grown in the opposite switching
environment, 250/1000 versus 250/250, showed no major differences in biomass accumulation or
allocation with the exception of a significant increase in the amount of leaf mass per unit area.
Physiologically, those plants exposed to elevated night-time [CO2] had 21% lower respiration rates,
14% lower photosynthetic rates and a significant increase in the ratio of carbon gain to carbon loss,
again when compared with the 250/250 plants. Biochemical differences also were found. Ribulose-
1,5-bisphosphate carboxylase/ oxygenase concentrations decreased in the 250/1000 treatment
compared with the 250/250 plants, and phosphoenolpyruvate carboxylase activity decreased in the
1000/250 compared with the 1000/1000 plants. Glucose, fructose and to a lesser extent sucrose
concentrations also were reduced in the 1000/250 treatment compared with the 1000/1000 plants.
These results indicate that experimental protocols that do not maintain elevated CO2 levels 24 h d(-1)
can have significant effects on plant biomass, carbon allocation and physiology, at least for fast-
growing annual crop plants. Furthermore, the results suggest some plant processes other than
photosynthesis are sensitive to [CO2] and under ecologically relevant conditions, such as high night-
time [CO2], whole plant carbon balance can be affected.

KEYWORDS: CARBON-DIOXIDE CONCENTRATION, DARK RESPIRATION, ELEVATED
ATMOSPHERIC CO2, HIGH AMBIENT CO2, MAX L MERR, PHOSPHOENOLPYRUVATE
CARBOXYLASE, PHOTOSYNTHESIS, PLANTS, RIBULOSE-1;5-BISPHOSPHATE
CARBOXYLASE-OXYGENASE, SHORT- TERM


     796  
Griffin, K.L., R.B. Thomas, and B.R. Strain. 1993. Effects of nitrogen supply and elevated
carbon-dioxide on construction cost in leaves of pinus-taeda (L) seedlings. Oecologia 95(4):575-580.

Seedlings of loblolly pine (Pinus taeda L.) were grown under varying conditions of soil nitrogen and
atmospheric carbon dioxide availability to investigate the interactive effects of these resources on the
energetic requirements for leaf growth. Increasing the ambient CO2 partial pressure from 35 to 65
Pa increased seedling growth only when soil nitrogen was high. Biomass increased by 55% and
photosynthesis increased by 13% after 100 days of CO2 enrichment. Leaves from seedlings grown
in high soil nitrogen were 7.0% more expensive on a g glucose g-1 dry mass basis to produce than
those grown in low nitrogen, while elevated CO2 decreased leaf cost by 3.5%. Nitrogen and CO2
availability had an interactive effect on leaf construction cost expressed on an area basis, reflecting
source-sink interactions. When both resources were abundant, leaf construction cost on an area basis
was relatively high (81.8 +/- 3.0 g glucose m-2) compared to leaves from high nitrogen, low CO2
seedlings (56.3 +/- 3.0 g glucose m-2) and low nitrogen, low CO2 seedlings (67.1 +/- 2.7 g glucose
m-2). Leaf construction cost appears to respond to alterations in the utilization of photoassimilates
mediated by resource availability.

KEYWORDS: ACCLIMATION, ALLOCATION, ATMOSPHERIC CO2 ENRICHMENT,
CHLOROPHYLL CONTENT, GROWTH, LONG-TERM EXPOSURE, MAINTENANCE
RESPIRATION, PHOTOSYNTHETIC INHIBITION, RESPONSES, WATER


     797  
Griffin, K.L., W.E. Winner, and B.R. Strain. 1995. Growth and dry-matter partitioning in loblolly
and ponderosa pine-seedlings in response to carbon and nitrogen availability. New Phytologist
129(4):547-556.

We grew loblolly pine (Pinus taeda L.) and ponderosa pine (Pinus ponderosa Dougl. ex Laws.)
seedlings in a factorial experiment with two CO2 partial pressures (35 and 70 Pa) and two nitrogen
treatments (1.0 and 3.5 mM NH4+) for one growing season in a 'common garden' experiment
designed to examine the extent that dry matter and nitrogen accumulation and partitioning are
environmentally controlled. Ponderosa pine seedlings grown in 35 Pa CO2 and 3.5 mM NH4+
showed symptoms of nitrogen toxicity, characterized by greatly reduced growth, and moderately
reduced total plant N. With the exception of this treatment combination, there were no significant
differences between species in total plant dry matter or total plant nitrogen, suggesting that responses
of growth to environmental conditions were stronger than heritable responses. There were however
large differences in dry matter and N partitioning between the two species. Increases in leaf mass
were largest in loblolly pine, whilst ponderosa pine tended to have higher root:shoot (R:S) ratios. R:S
ratio of loblolly increased in response to C availability and decreased in response to N availability,
whilst R: S ratio of ponderosa pine was much less responsive to resource availability. Total plant N
varied with N supply, and N partitioning was related to plant growth and carbon partitioning. Carbon
and N were interactive, such that an increase in the accumulation of either resource was always
accompanied by an increase in the other. Over several seasons the different patterns of resource
acquisition and biomass allocation that we observed in a uniform environment could potentially result
in different growth rates at most resource levels. In the first season, contrary to our expectations,
heritable differences in growth rate did not appear.

KEYWORDS: ATMOSPHERIC CO2, DIFFERENT IRRADIANCE LEVELS, DIOXIDE,
ECOSYSTEMS, ENRICHMENT, FORESTS, LIQUIDAMBAR- STYRACIFLUA, NITRATE, TAEDA
SEEDLINGS, WATER-STRESS


     798  
Griffin, K.L., W.E. Winner, and B.R. Strain. 1996. Construction cost of loblolly and ponderosa
pine leaves grown with varying carbon and nitrogen availability. Plant, Cell and Environment
19(6):729-739.

We grew loblolly and ponderosa pine seedlings in a factorial experiment with two CO2 partial
pressures (35 and 70 Pa), and two nitrogen treatments (1 . 0 and 3 . 5 mol m(-3) NH4+), for one
growing season to examine the effects of carbon and nitrogen availability on leaf construction cost,
Growth in elevated CO2 reduced leaf nitrogen concentrations by 17 to 40%, and increased C:N by
22 to 68%. Elevated N availability increased leaf N concentrations and decreased C:N, Non-
structural carbohydrates increased in high-CO2-grown loblolly seedlings, except in fascicles from low
N, and in ponderosa primary and fascicle leaves grown in high N, In loblolly, increases in starch were
nearly 2-fold greater than the increases in soluble sugars, In ponderosa, only the soluble sugars were
affected by CO2. Leaf construction cost (g glucose g(-1) dm) varied by 9 . 3% across all treatments,
All of the variation in loblolly leaf construction cost could be explained by changes in non-structural
carbohydrates. A model of the response of construction cost to changes in the mass of different
biochemical fractions suggests that the remainder of the variation in ponderosa, not explained by non-
structural carbohydrates, is probably attributable to changes in lignin, phenolic or protein
concentrations.

KEYWORDS: ALLOCATION, BIOMASS, DIOXIDE, ENERGY, NUTRIENTS, PLANTS,
SEEDLINGS, TAEDA


     799  
Griffiths, B.S., K. Ritz, N. Ebblewhite, and G. Dobson. 1999. Soil microbial community structure:
Effects of substrate loading rates. Soil Biology and Biochemistry 31(1):145-153.

A fuller understanding of the interactions which affect rhizosphere microbial community structure
requires experimental manipulation of the individual components of that interaction (e.g. amount and
composition of exudate, soil moisture and soil nutrient status). We describe an experiment where a
synthetic root exudate was applied continuously to a soil held at constant water potential. The
solution contained compounds characteristic of root exudates (fructose, glucose, sucrose, succinic
acid, malic acid, arginine, serine and cysteine), which were added at a range of concentrations. After
14 d of such substrate addition, a central portion of soil, known to be influenced by the added
substrate, was removed for analysis. Microbial community structure of this central core was
determined by the broad-scale measurements; community DNA hybridisation and %G + C profiling,
and phospholipid-fatty acid analysis (PLFA). The trend was that microbial community structure
changed consistently as substrate loading increased, and that fungi dominated over bacteria at high
substrate loading rates. The DNA and the PLFA analyses both indicated that there was a coherent
gradient of changes with increased substrate loading. This may have arisen as a consequence of the
competitive ability of soil microorganisms being dependent on the quantity of available substrate. (C)
1998 Elsevier Science Ltd. All rights reserved.

KEYWORDS: BACTERIOPLANKTON, BIOMASS, CARBON, DNA HYBRIDIZATION, ELEVATED
ATMOSPHERIC CO2, FATTY-ACIDS, GLUCOSE, MASS- SPECTROMETRY, PROFILES,
RHIZOSPHERE


     800  
Griffiths, B.S., K. Ritz, N. Ebblewhite, E. Paterson, and K. Killham. 1998. Ryegrass rhizosphere
microbial community structure under elevated carbon dioxide concentrations, with observations on
wheat rhizosphere. Soil Biology and Biochemistry 30(3):315-321.

The structure of microbial communities in the rhizospheres of ryegrass and wheat, growing at an
elevated atmospheric CO2 concentration, was investigated using broad-scale DNA techniques.
Community DNA hybridisation and %G + C base profiling by thermal denaturation assess changes
at the whole microbial community level. DNA analysis of the rhizosphere of ryegrass grown in soil
microcosms for 28 or 42 d, showed only minor differences between plants grown at 450 or 720 mu
l CO2 l(-1). In a second experiment with ryegrass, 5 of 10 replicate microcosms were pulse labelled
with (CO2)-C-14 and 5 simultaneously sampled for DNA analysis. Carbon partitioning below ground
showed changes due to the elevated CO2, notably an increased proportion of fi?ted carbon in non-
microbial biomass residue in the rhizosphere. There was again no effect of elevated CO2 on
rhizosphere microbial community structure. Community DNA hybridisation indicated that the
rhizosphere communities under ambient and elevated CO2 were 86% similar (unlikely to be a
biologically relevant change), with indistinguishable %G + C profiles. Wheat was grown to maturity
(129 d) in a different soil microcosm design, and rhizosphere microbial communities from plants
grown at 350 and 700 mu l CO2 l(-1) were identical according to the DNA analyses. In these
experiments rhizosphere microbial community structure at the broad scale was unaffected by the
interactions occurring below ground as a result of elevated concentrations of CO2. (C) 1998 Elsevier
Science Ltd. All rights reserved.

KEYWORDS: ATMOSPHERIC CO2 CONCENTRATION, DNA HYBRIDIZATION, ENRICHMENT,
FEEDBACK, GROWTH, HYBRIDIZATION TECHNIQUE, POPULATIONS, RESPONSES, ROOTS,
SOIL


     801  
Grime, J.P., K. Thompson, R. Hunt, J.G. Hodgson, J.H.C. Cornelissen, I.H. Rorison, G.A.F.
Hendry, T.W. Ashenden, A.P. Askew, S.R. Band, R.E. Booth, C.C. Bossard, B.D. Campbell,
J.E.L. Cooper, A.W. Davison, P.L. Gupta, W. Hall, D.W. Hand, M.A. Hannah, S.H. Hillier,
D.J. Hodkinson, A. Jalili, Z. Liu, J.M.L. Mackey, N. Matthews, M.A. Mowforth, A.M. Neal,
R.J. Reader, K. Reiling, W. RossFraser, R.E. Spencer, F. Sutton, D.E. Tasker, P.C. Thorpe,
and J. Whitehouse. 1997. Integrated screening validates primary axes of specialisation in plants.
Oikos 79(2):259-281.

Standardised procedures have been used to measure 67 traits in 43 common plants of the British
flora. This paper provides an interpretation of the most consistent patterns in the resulting matrix by
means of correlation, ordination and classification analyses. Only a weak coupling was observed
between attributes of the regenerative and established phases of the life history. However, within each
phase, attributes were strongly aggregated into sets and a high proportion of the variation between
species coincided with a single axis. Attributes of the established phase displayed remarkably
consistent trends, with a strong 'Axis 1' being identified by three different multivariate methods. There
was a marked correlation between foliar concentrations of N, P, K, Ca and Mg, high concentrations
of which coincided with the capacity for rapid growth in productive conditions and an inability to
sustain yield under limiting supplies of nutrients. A diverse array of other traits, less immediately
involving mineral nutrients, were also entrained in Axis 1; these included life history, root and shoot
foraging, the morphology, longevity, tensile strength and palatability of leaves, and the decomposition
rate of leaf litter. This pattern occurred in both monocotyledons and dicotyledons and appeared to
reflect a tradeoff between attributes conferring an ability for high rates of resource acquisition in
productive habitats and those responsible for retention of resource capital in unproductive conditions.
The second axis of variation evident in the established phase was related to phylogeny and
distinguished between monocotyledons and dicotyledons on the basis of a diverse set of traits
including genome size, cell size, root and shoot foraging characteristics and vascular tissues. A third
axis was detected in which ephemerals and perennials were separated by differences in attributes such
as breeding system, leaf decomposition rate and a set of traits reflecting the small stature of many
short-lived plants. In the regenerative phase, the leading axis was clearly related to the widely
recognised tradeoff between seed size and seed number and was consistent with current
understanding of seed banks, and with modern theories explaining species coexistence in terms of
complementary responses to temporal and spatial variation in vegetation gap dynamics. The data
provide strong evidence of functional integration between evolutionary specialisations in root and
shoot and support Donald's unified theory of competitive ability. The data are not consistent with
theories of functional types based upon evolutionary tradeoffs in allocation between root and shoot.
We suggest that the evidence assembled here and elsewhere in the current literature points to the
existence of primary functional types, including those recognised by Ramenskii and Grime. These
functional types can be reconciled with the individuality of plant ecologies in the field and provide an
effective basis For interpretation and prediction at various scales from the plant community to
regional floras. There are particular opportunities for prediction of successional trajectories, the role
of herbivores in vegetation succession and the response of vegetation to eutrophication and extreme
climatic events. It is also suggested that aspects of this investigation may provide a Darwinian
underpinning for Odum's theory of ecosystem maturation.

KEYWORDS: ALLOCATION, CO2- ENRICHMENT, COMPETITION, ECOLOGICAL
STRATEGIES, GERMINATION CHARACTERISTICS, LIFE-HISTORY STRATEGIES, LOCAL
FLORA, RELATIVE GROWTH-RATE, SUCCESSION, VEGETATION


     802  
Grimm, A.G., and J. Fuhrer. 1992. The response of spring wheat (triticum-aestivum L) to ozone
at higher elevations .1. Measurement of ozone and carbon-dioxide fluxes in open-top field chambers.
New Phytologist 121(2):201-210.

The flux of O3 was determined in open-top chambers (OTC) used to investigate its effect on spring
wheat (Triticum aestivum L., cv. Albis) in 1989 and 1990. The experimental site was located at 900
m above sea level at Zimmerwald, near Bern (Switzerland). The aims were to evaluate the use of
OTCs for O3 flux measurements under field conditions, to assess the role of stomata in controlling
the O3 fluxes, and to establish a quantitative relationship between radiation-weighted O3
concentrations and O3 flux. Measurements were carried out from full expansion of flag leaves until
the onset of senescence. Ozone flux was determined by mass balance using the concentrations of O3
measured at the inlet and outlet of the OTC. The CO2 exchange rate was corrected for soil-borne
CO2 and used as a reference. Measurements of temperature, photosynthetically active radiation
(PAR), saturated water vapour pressure deficit (SVPD), and boundary layer conductance were used
to describe the microclimate inside OTCs. In the warmer microclimate in 1989, the plant canopy was
characterized by a smaller leaf area index (LAI) than in 1990, while the fluxes of O3 and CO2 during
daytime were generally larger in 1989. The diurnal patterns of fluxes of O3 and CO2 in OTCs
supplied with unfiltered air were similar. It is estimated that O3 absorption via the stomata
contributed 50-70 % of its total flux. Identical relationships between leaf conductance for O3
measured by porometry and leaf conductance calculated from O3 flux were found in both years, but
measured leaf conductance during daytime was generally smaller in 1990 than in 1989. The results
indicate that stomatal conductance largely controlled O3 flux, and that the canopy structure has an
influence on the overall conductance of the canopy. Different linear functions were obtained for the
relationship between radiation-weighted O3 concentration and O3 flux, using data from OTCs
supplied with either charcoal-filtered air, unfiltered air or unfiltered air enriched with O3 (two levels).
These relationships form the basis for the calculation of mean O3 fluxes which can be used as an
exposure index in the exposure-response analysis.

KEYWORDS: ABIES L KARST, BARLEY, CROP YIELD, DEPOSITION, GAS-EXCHANGE,
INJURY, PHOTOSYNTHESIS, RESISTANCES, SITCHENSIS BONG CARR, TRANSPIRATION


     803  
Grimmer, C., T. Bachfischer, and E. Komor. 1999. Carbohydrate partitioning into starch in leaves
of Ricinus communis L-grown under elevated CO2 is controlled by sucrose. Plant, Cell and
Environment 22(10):1275-1280.

Ricinus communis plants were grown. under normal (350 ppm) and elevated (700 ppm) CO2
atmosphere and the growth and carbohydrate status of leaf 2 (first leaf above the pair of primary
leaves) was studied. Elevated carbon dioxide stimulated the growth of leaves 1.7-fold. The glucose
and fructose concentrations exhibited the same diurnal rhythm under both growth conditions. The
sucrose concentrations stayed relatively constant and at 700 ppm were one-third higher than at 350
ppm. The starch content increased steadily during the day and disappeared overnight at 350 ppm
CO2, but remained partially in plants at 700 ppm CO2, Consequently at 700 ppm CO2, the leaves
accumulated starch continuously over their life time, The rate of starch synthesis was correlated to
the activity of ADP- glucose pyrophosphorylase, which was related to the sucrose concentration in
the leaf, It is concluded that sucrose controls the expression of ADP-glucose pyrophosphorylase,
leading to a shift of carbohydrate partitioning into starch when more sucrose is produced than
consumed or exported, a situation which is especially pertinent at elevated CO2, These results show
that the previously experimentally observed transscriptional regulation of starch synthesis by sucrose
occurs in vivo in the daily life of a leaf.

KEYWORDS: ADP-GLUCOSE PYROPHOSPHORYLASE, CARBON DIOXIDE, GENES, PLANTS,
POTATO, TUBERS


     804  
Grimmer, C., and E. Komor. 1999. Assimilate export by leaves of Ricinus communis L. growing
under normal and elevated carbon dioxide concentrations: the same rate during the day, a different
rate at night. Planta 209(3):275-281.

Castor bean (Ricinus communis L.) plants were grown for 5-7 weeks in a controlled environment at
350 mu l l(-1) or 700 mu l l(-1) CO2. Carbon assimilation, assimilate deposition, dark respiration and
assimilate mobilization were measured in leaves 2, 3 and 4 (counted from the base of the plant), and
a balance sheet of carbon input and export was elaborated for both CO2 concentrations. Carbon
dioxide assimilation was nearly constant over the illumination period, with only a slight depression
occurring at the end of the day in mature source leaves, not in young source leaves, Assimilation was
ca. 40% higher at 700 mu l l(-1) than at 350 mu l l(-1) CO2. The source leaves increased steadily in
weight per unit area during the first 3 weeks, more at 700 mu l l(-1) than at 350 mu l l(-1) CO2. On
top of an irreversible weight increase, there was a large gain in dry weight during the day, which was
reversed during the night. This reversible weight gain was constant over the life time of the leaf and
ca. 80% higher at 700 mu l l(-1) than at 350 yl l(-1). Most of it was due to carbohydrates. The carbon
content (as a percentage) was not altered by the CO2 treatment. Respiration was 25% higher in high-
CO2 plants when based on leaf area, but the same when based on dry weight. The rate of carbon
export via the phloem was the same during the daytime in plants grown at 350 mu l l(-1) and 700 mu
l l(-1) CO2. During the night the low-CO2 plants had only 50% of the daytime export rate, in contrast
to the high-CO2 plants which maintained the high export rate. It was concluded that the phloem
loading system is saturated during the daytime in both CO2 regimes, whereas during the night the
assimilate supply is reduced in plants in the normal CO2 concentration. Two-thirds of the carbon
exported from the leaves was permanently incorporated as plant dry matter in the residual plant parts.
This "assimilation efficiency" was the same for both CO2 regimes. It is speculated that under 350 mu
l l(-1) CO2 the growing Ricinus plant operates at sink limitation during the day and at source
limitation during the night.

KEYWORDS: ACCLIMATION, ATMOSPHERIC CO2, GROWTH, PHOTOSYNTHESIS, PLANTS,
STARCH, SUCROSE


     805  
Grobbelaar, N., W.M. Chou, and T.C. Huang. 1992. Effect of co2, o2, dcmu, fccp, and dl-
glyceraldehyde on the nitrogenase activity of synechococcus rf-1. Botanical Bulletin of Academia
Sinica 33(2):167-174.

Elevated atmospheric CO2 concentrations drastically inhibit nitrogenase activity of the unicellular
Synechococcus RF-1 but stimulate photosynthetic CO2 assimilation. The inhibitory effect on
nitrogenase activity is stronger in the light than in the dark. During three hours, 1% CO2 in air can
reduce nitrogenase activity in the light by about 50% compared to that in unenriched air. The
inhibitory effect of elevated CO2 concentrations on nitrogenase activity persists for many hours after
the organism has been returned to air not enriched with CO2. The nitrogenase activity of
heterocystous cyanobacteria, generally, does not appear to be affected by 5% CO2 in the air. DCMU
strongly enhanced nitrogenase activity and inhibited the assimilation of CO2 by Synechococcus RF-1
in the light, and elevated atmospheric O2 concentrations reduced the nitrogenase activity, especially
in the dark. DL-glyceraldehyde at a concentration of 19.4 mM strongly inhibited nitrogenase activity,
dark respiration, and photosynthesis. FCCP had no effect on dark respiration but depressed
nitrogenase activity and photosynthesis of Synechococcus RF-1. The inhibitory effect of FCCP on
nitrogenase activity was stronger in the dark than in the light.

KEYWORDS: BLUE GREEN ALGA, DINITROGEN, LIGHT, PHOTOSYNTHESIS, RHYTHM


     806  
Grodzinski, B. 1992. Plant nutrition and growth-regulation by co2 enrichment. BioScience
42(7):517-525.

KEYWORDS: ABSCISIC- ACID, ACCLIMATION, ATMOSPHERIC CO2, CARBONIC-
ANHYDRASE, CARBOXYLASE, ETHYLENE, EXCHANGE, PHOTOSYNTHESIS, STOMATAL
DENSITY, WHOLE PLANT


     807  
Grodzinski, B., J.R. Jiao, and E.D. Leonardos. 1998. Estimating photosynthesis and concurrent
export rates in C-3 and C-4 species at ambient and elevated CO2. Plant Physiology 117(1):207-215.

The ability of 21 C-3 and C-4 monocot and dicot species to rapidly export newly fixed C in the light
at both ambient and enriched CO2 levels was compared. Photosynthesis and concurrent export rates
were estimated during isotopic equilibrium of the transport sugars using a steady-state (CO2)-C-14-
labeling procedure. At ambient CO2 photosynthesis and export rates for C-3 species were 5 to 15 and
1 to 10 mu mol C m(-2) s(-1), respectively, and 20 to 30 and 15 to 22 mu mol C m(-2) s(-1),
respectively, for C-4 species. A linear regression plot of export on photosynthesis rate of all species
had a correlation coefficient of 0.87. When concurrent export was expressed as a percentage of
photosynthesis, several C-3 dicots that produced transport sugars other than Suc had high efflux rates
relative to photosynthesis, comparable to those of C-4 species. At high CO2 photosynthetic and
export rates were only slightly altered in C, species, and photosynthesis increased but export rates
did not in all C(3)species. The C-3 species that had high efflux rates relative to photosynthesis at
ambient CO2 exported at rates comparable to those of C-4 species on both an absolute basis and as
a percentage of photosynthesis. At ambient CO2 there were strong linear relationships between
photosynthesis, sugar synthesis, and concurrent export. However, at high CO2 the relationships
between photosynthesis and export rate and between sugar synthesis and export rate were not as
strong because sugars and starch were accumulated.

KEYWORDS: HIGHER-PLANTS, LEAF, LEAVES, SALVIA-SPLENDENS, STARCH, STEADY-
STATE PHOTOSYNTHESIS, SUCROSE, TEMPERATURE


     808  
Grodzinski, B., L. Woodrow, E.D. Leonardos, M. Dixon, and M.J. Tsujita. UNKNOWN YEAR.
Plant responses to short- and long-term exposures to high carbon dioxide levels in closed
environments. Natural and Artificial Ecosystems :203-211.

When higher plants are exposed to elevated levels of CO2 for both short- and long-term periods
photosynthetic C-gain and photoassimilate export from leaves are generally increased. Water use
efficiency is increased on a leaf area basis. During long-term exposures, photosynthesis rates on leaf
and whole plant bases are altered in a species specific manner. The most common pattern in C-3
plants is an enhanced rate of whole plant photosynthesis in a well irradiated canopy. Nevertheless,
in some herbaceous species prolonged exposure to high CO2 results in remobilization of nitrogenous
reserves (i.e., leaf protein degradation) and reduced rates of mature leaf photosynthesis when assayed
at ambient CO2 and O-2 levels. Both short- and long-term exposures to those CO2 levels (i.e., 100
to 2,000 mu l.l(-1)) which modify photosynthesis and export, also modify both endogenous ethylene
gas (C2H4) release, and substrate, 1- aminocyclopropane-1-carboxylic acid (ACC), saturated C2H4
release rates from irradiated leaves. Photosynthetically active canopy leaves contribute most of the
C2H4 released from the canopy. Prolonged growth at high CO2 results in a persistent increase in the
rate of endogenous C2H4 release from leaves which can, only in part, be attributed to the increase
of the endogenous pools of C2H4 pathway intermediates (e.g., methionine, M-ACC, and ACC). The
capacity for increasing the rate of C2H4 release in response to short-term exposures to varying CO2
levels does not decline after prolonged growth at high CO2. When leaves, whole plants, and model
canopies of tomato plants are exposed to exogenous C2H4 a reduction in the rate of photosynthesis
can, in each case, be attributed to the classical effects of C2H4 on plant development and
morphology. The effect of C2H4 on CO2 gas exchange of plant canopies is shown to be dependent
on the canopy leaf area index.

KEYWORDS: INCOMPLETE, ACCLIMATION, ATMOSPHERIC CO2, ETHYLENE RELEASE,
GAS-EXCHANGE, LEAVES, LYCOPERSICON-ESCULENTUM MILL, PHOTOSYNTHESIS,
TOMATO, XANTHIUM-STRUMARIUM L, ZEA-MAYS


     809  
Groninger, J.W., K.H. Johnsen, J.R. Seiler, R.E. Will, D.S. Ellsworth, and C.A. Maier. 1999.
Elevated carbon dioxide in the atmosphere - What might it mean for loblolly pine plantation forestry?
Journal of Forestry 97(7):4-10.

Research with loblolly pine suggests that projected increases iii atmospheric CO2 concentration will
accelerate early growth and could result in shouter rotation length, reduced time until first commercial
thinning, higher optimal planting density, and possibly higher maximum stocking level in managed
stands. We discuss some of the physiological processes and stand dynamics that underlie these
changes, as well as silvicultural strategies that may serve to ensure sustainability of intensively
managed forest systems in the face of increasing CO2 and possible climate change.

KEYWORDS: CO2 CONCENTRATIONS, GAS-EXCHANGE, GROWTH, NET PHOTOSYNTHESIS,
PHOTOSYNTHETIC CAPACITY, ROOT RESTRICTION, SEEDLINGS, STOMATAL
CONDUCTANCE, TAEDA TREES, WATER


     810  
Groninger, J.W., J.R. Seiler, S.M. Zedaker, and P.C. Berrang. 1995. Effects of elevated co2,
water-stress, and nitrogen level on competitive interactions of simulated loblolly-pine and sweetgum
stands. Canadian Journal of Forest Research-Revue Canadienne De Recherche Forestiere
25(7):1077-1083.

Loblolly pine (Pinus taeda L.) and sweetgum (Liquidambar styraciflua L.) were grown in mixed
stands and in monocultures at 2.54 X 2.54 cm spacing in controlled-environment chambers.
Treatments consisted of present (ambient) and projected future (ambient + 400 ppm) carbon dioxide
(CO2) concentrations, drought-stressed, and well-watered conditions, and low (20 kg N/ha) and high
(474 kg N/ha) nitrogen application rates. After two accelerated growing cycles, total biomass of both
species was significantly greater under elevated CO2. No significant interactions between CO2
concentration and water availability, nitrogen availability, or stand type were observed. Competitive
interactions between loblolly pine and sweetgum were strongly influenced by water availability, but
not CO2 concentration. Assessment of species response to CO2 was dependent upon growth in
monoculture or mixture. Under low water availability, data from monocultures suggested that
sweetgum had a stronger growth response to elevated CO2 concentrations than loblolly pine. In
contrast, results from mixed-species stands showed that the competitive status of loblolly pine and
sweetgum did not change under the high CO2 concentration. These results underscore the value of
growing co-occurring species in mixed stands under varying levels of multiple resources for the
determination of relative performance under future environments.

KEYWORDS: CARBON DIOXIDE, ENRICHMENT, FIELD, GROWTH, INTERFERENCE,
LIQUIDAMBAR- STYRACIFLUA, PLANTS, RESPONSES, TAEDA SEEDLINGS


     811  
Groninger, J.W., J.R. Seiler, S.M. Zedaker, and P.C. Berrang. 1996. Effects of CO2
concentration and water availability on growth and gas exchange in greenhouse-grown miniature
stands of Loblolly Pine and Red Maple. Functional Ecology 10(6):708-716.

1. The study assesses the effects of atmospheric CO2 concentration and water availability on stand
development and photosynthetic characteristics of Loblolly Pine (Pinus taeda) and Red Maple (Acer
rubrum). Miniature stands of these species were grown from seed in monoculture and in a 50:50
replacement mixture for two accelerated growing seasons. 2. Both species had greater biomass under
the higher levels of CO2 and water availability. Biomass of Loblolly Pine seedlings in mixed stands
exceeded that in monocultures, while the opposite was true for Red Maple. No significant treatment
interactions were detected for total biomass. Significant main effects for water and stand type were
detected for stem height of Loblolly Pine. CO2, water and stand type interactions were observed for
height of Red Maple. 3. Net photosynthetic rates were measured on miniature stand canopies and
constituent seedlings from these stands. Both species exhibited higher photosynthetic rates under
elevated CO2. However, expression of photosynthesis on a leaf mass or soil area basis affected
conclusions regarding the role of water availability on stand-level response to elevated CO2.

KEYWORDS: ATMOSPHERIC CO2, BEECH STANDS, ELEVATED CARBON-DIOXIDE,
ENRICHMENT, INTERFERENCE INTERACTIONS, LIQUIDAMBAR- STYRACIFLUA,
RESPONSES, STRESS, TAEDA SEEDLINGS, TREE SEEDLINGS


     812  
Groninger, J.W., J.R. Seiler, S.M. Zedaker, and P.C. Berrang. 1996. Photosynthetic response
of loblolly pine and sweetgum seedling stands to elevated carbon dioxide, water stress, and nitrogen
level. Canadian Journal of Forest Research-Revue Canadienne De Recherche Forestiere 26(1):95-
102.

Seedling stands of loblolly pine (Pinus taeda L.) and sweetgum (Liquidambar styraciflua L.) were
grown in monoculture or mixed stands for two growing cycles in controlled-environment chambers.
Treatments consisted of ambient (408 ppm) and elevated (806 ppm) CO2 concentrations, water-
stressed and well- watered conditions, and low (20 kg N/ha) and high (215 kg N/ha) nitrogen
application rates. Photosynthesis rates were measured under ambient and elevated cuvette CO2
concentrations for both whole stands and individual seedlings from these stands. Significant
interactions between CO2 and water suggested that elevated CO2 concentration compensated for low
water availability in individually measured loblolly pine and in whole seedling stands regardless of
stand type. Expressing photosynthesis on a soil area versus a leaf-mass basis influenced the
photosynthetic rankings of the three stand types relative to one another. Net photosynthetic rates per
unit leaf mass were 390 and 880% higher in individually measured seedlings than in whole
monoculture stands for loblolly pine and sweetgum, respectively. Lower photosynthetic contributions
from lower canopy leaves in whole seedling stands compared with the upper canopy leaves used in
individual-seedling measurements were thought to be responsible for lower photosynthetic rates in
seedling stands. These results suggest that photosynthetic response is influenced by canopy dynamics
that are unaccounted for by individual-seedling measurements of photosynthesis. Differences in
photosynthetic response between loblolly pine and sweetgum stands and individuals are thought to
be largely due to species-specific differences in canopy light extinction characteristics.

KEYWORDS: CO2- ENRICHMENT, FORESTS, GAS-EXCHANGE, GROWTH, LIQUIDAMBAR-
STYRACIFLUA, RUBISCO, TAEDA SEEDLINGS


     813  
Gross, U., F. Gilles, L. Bender, P. Berghofer, and K.H. Neumann. 1993. The influence of sucrose
and an elevated co2 concentration on photosynthesis of photoautotrophic peanut (arachis-hypogaea
L) cell-cultures. Plant Cell Tissue and Organ Culture 33(2):143-150.

Using photoautotrophic cells of Arachis hypogaea (L.) growing at ambient CO2, it was shown that
exogenous sucrose supplied to the liquid medium reduced (CO2)-C-14 fixation (supplied as NaH
(CO3)-C-14) . This was mostly due to a reduced labelling in P-esters, and to a lesser extent, in the
serine/glycine moiety. However, radioactivity in the neutral sugar fraction was increased upon
supplement of exogenous sucrose. The reduced labelling of P-esters and serine/glycine agrees with
a lower concentration and specific activity of Rubisco in the sucrose supplied treatments as compared
to the control. Following a transfer into a sugar free nutrient medium the concentration and activity
of Rubisco is increased. The concentration of PEPCase was not influenced by sucrose application,
although its specific activity was increased. At elevated CO2 concentration (2.34% v/v) the Rubisco
concentration and specific activity was at the same level as in the control (0.03% V/V CO2).
However, the concentration and the specific activity of PEPCase was increased and dry weight
increase was about 8-9-fold higher than at ambient CO2.

KEYWORDS: ENZYME, FLAGELLATE CHLOROGONIUM-ELONGATUM, LEAVES, RIBULOSE-
1;5-BISPHOSPHATE CARBOXYLASE, SUBUNITS


     814  
Grossman, S., T. Kartschall, B.A. Kimball, D.J. Hunsaker, R.L. LaMorte, R.L. Garcia, G.W.
Wall, and P.J. Pinter. 1995. Simulated responses of energy and water fluxes to ambient atmosphere
and free-air carbon dioxide enrichment in wheat. Journal of Biogeography 22(4-5):601-609.

Increased ambient carbon dioxide has been associated with CO2- induced stomatal closure which
affects growth and evapotranspiration of crop canopies. This results in changes of the energy balance
components of the soil-plant-atmosphere system. The agroecosystem wheat model DEMETER was
linked to a soil-vegetation-atmosphere-transfer module which includes the energy balance of the crop
canopy and the energy balance of the soil surface. Thus, it was possible to calculate
evapotranspiration, canopy temperature and the changed ratio of sensible and latent heat fluxes in
response to elevated atmospheric CO2 concentrations. The free-air carbon dioxide enrichment
(FACE) technique provided a largely undisturbed regime for atmospheric exchange. During the
FACE wheat experiment at Maricopa in 1992-93, the effects of elevated atmospheric CO2
concentrations on energy balance and evapotranspiration of the wheat canopy at about 350-370 mu
mol/mol (control) and 550 mu mol/mol (FACE) were investigated. The recorded data were used for
model validation. Diurnal trends of all energy balance components and the canopy temperature were
simulated for FACE and control conditions using hourly weather data. Results were compared with
the observed data on 16 March 1993. Simulated cumulative seasonal evapotranspiration was found
in good accordance to the observed one. Consistent with observations, the simulations suggest that
there was a small reduction in evapotranspiration of about 4%. Of course, with the observed increases
in growth, there were even larger increases in water use efficiency.

KEYWORDS: TEMPERATURE


     815  
Grossman-Clarke, S., B.A. Kimball, D.J. Hunsaker, S.P. Long, R.L. Garcia, T. Kartschall,
G.W. Wall, P.J. Printer, F. Wechsung, and R.L. LaMorte. 1999. Effects of elevated atmospheric
CO2 on canopy transpiration in senescent spring wheat. Agricultural and Forest Meteorology
93(2):95-109.

The seasonal course of canopy transpiration and the diurnal courses of latent heat flux of a spring
wheat crop were simulated for atmospheric CO2 concentrations of 370 and 550 mu mol mol(-1). The
hourly weather data, soil parameters and the irrigation and fertilizer treatments of the Free-Air
Carbon Dioxide Enrichment wheat experiment in Arizona (1992-1993) were used to drive the model.
The simulation results were tested against field measurements with special emphasis on the period
between anthesis and maturity. A model integrating leaf photosynthesis and stomatal conductance
was scaled to canopy level in order to be used in the wheat growth model. The simulated intercellular
CO2 concentration, C-i, was determined from the ratio of C-i to the CO2 concentration at the leaf
surface, C-s, the leaf-to-air specific humidity deficit and a possibly unfulfilled transpiration demand,
After anthesis, the measured assimilation rates of the flag leaves decreased more rapidly than their
stomatal conductances, leading to a rise in the C-i/C-s ratio. In order to describe this observation, an
empirical model approach was developed which took into account the leaf nitrogen content for the
calculation of the C-i/C-s ratio. Simulation results obtained with the new model version were in good
agreement with the measurements. If changes in the C-i/C-s ratio in accordance with the decrease in
leaf nitrogen content during leaf senescence were not considered in the model, simulations revealed
an underestimation of the daily canopy transpiration of up to 20% and a decrease in simulated
seasonal canopy transpiration by 10%. The measured reduction in the seasonal sum of canopy
transpiration and soil evaporation owing to CO2 enrichment, in comparison, was only about 5%. (C)
1999 Elsevier Science B.V. All rights reserved.

KEYWORDS: AMBIENT ATMOSPHERE, C-3 PLANTS, CARBON-DIOXIDE ENRICHMENT,
LEAF, LEAVES, MODEL, NITROGEN, PHOTOSYNTHESIS, STOMATAL CONDUCTANCE,
WATER-USE


     816  
Grotenhuis, T.P., and B. Bugbee. 1997. Super-optimal CO2 reduces seed yield but not vegetative
growth in wheat. Crop Science 37(4):1215-1222.

Although terrestrial atmospheric CO2 levels will not reach 1000 mu mol mol(-1) (0.1%) for decades,
CO2 levels in growth chambers and greenhouses routinely exceed that concentration. CO2 levels in
life support systems in space can exceed 10 000 mu mol mol(-1)(1%). Numerous studies have
examined CO2 effects up to 1000 mu mol mol(-1), but biochemical measurements indicate that the
beneficial effects of CO2 can continue beyond this concentration. We studied the effects of near-
optimal (approximate to 1200 mu mol mol(-1)) and super-optimal CO2 levels (2400 mu mol mol(-1))
on yield of two cultivars of hydroponically grown wheat (Triticum aestivum L.) in 12 trials in growth
chambers. Increasing CO2 from sub-optimal to near- optimal (350-1200 mu mol mol(-1)) increased
vegetative growth by 25% and seed yield by 15% in both cultivars. Yield increases were primarily
the result of an increased number of heads per square meter. Further elevation of CO2 to 2500 mu
mol mol(-1) reduced seed yield by 22% (P < 0.001) in cv. Veery-10 and by 15% (P < 0.001) in cv.
USU-Apogee. Super-optimal CO2 did not decrease the number of heads per square meter, but
reduced seeds per head by 10% and mass per seed by 11%. The toxic effect of CO2 was similar over
a range of light levels from half to full sunlight. Subsequent trials revealed that super- optimal CO2
during the interval between 2 wk before and after anthesis mimicked the effect of constant super-
optimal CO2. Furthermore, near-optimal CO2 during the same interval mimicked the effect of
constant near-optimal CO2. Nutrient concentration of leaves and heads was not affected by CO2.
These results suggest that super optimal CO2 inhibits some process that occurs near the time of seed
set resulting in decreased seed set, seed mass, and yield.

KEYWORDS: CARBON DIOXIDE, EFFICIENCY, ENRICHMENT, ETHYLENE BIOSYNTHESIS,
GAS-EXCHANGE, INTACT SUNFLOWER PLANTS, LEAVES, LIGHT, PHOTOSYNTHETIC
ACCLIMATION, RESPIRATION


     817  
Grotenhuis, T., J. Reuveni, and B. Bugbee. UNKNOWN YEAR. Super-optimal CO2 reduces
wheat yield in growth chamber and greenhouse environments. Life Sciences: Life Support Systems
Studies-I :1901-1904.

Seven growth chamber trials (six replicate trials using 0.035, 0.12, and 0.25 % CO2 in air and one
trial using 0.12, 0.80, and 2.0% CO2 in air) and three replicate greenhouse trials (0.035, 0.10, 0.18,
0.26, 0.50, and 1.0% CO2 in air) compare the effects of super-optimal CO2 on the seed yield, harvest
index, and vegetative growth rate of wheat (Triticum aestivum L. cvs. USU-Apogee and Veery-10).
Plants in the growth chamber trials were grown hydroponically under fluorescent lamps, while the
greenhouse trials were grown under sunlight and high pressure sodium lamps and in soilless media.
Plants in the greenhouse trials responded similarly to those in the growth chamber trials; maximum
yields occurred near 0.10 and 0.12 % CO2 and decreased significantly thereafter. This research
indicates that the toxic effects of elevated CO2 are not specific to only one environment and has
important implications for the design of bio-regenerative life support systems in space, and for the
future of terrestrial agriculture. (C) 1997 COSPAR. Published by Elsevier Science Ltd.

KEYWORDS: INCOMPLETE, ETHYLENE


     818  
Grulke, N.E., J.L. Hom, and S.W. Roberts. 1993. Physiological adjustment of 2 full-sib families
of ponderosa pine to elevated co2. Tree Physiology 12(4):391-401.

Seeds from two full-sib families of ponderosa pine (Pinus ponderosa) with known differences in
growth rates were germinated and grown in an ambient (350 mul l-1) or elevated (700 mul l-1) CO2
concentration. Gas exchange at both ambient and elevated CO2 concentrations was measured 1, 6,39,
and 112 days after the seed coat was shed. Initial stimulation of CO2 exchange rate (CER) by
elevated CO2 was large (> 100%). On Day 1, CER of seedlings grown in elevated CO2 and measured
at ambient CO2 was significantly lower than the CER of seedlings grown and measured at ambient
CO2, indicating physiological adjustment of the seedlings exposed to elevated CO2. Physiological
acclimation to elevated CO2 was complete by Day 39 when there was no significant difference in
CER between seedlings grown and measured at ambient CO2 and seedlings grown and measured at
elevated CO2. After 4 months, the light response of seedlings in the two treatments was determined
at both ambient and elevated CO2. Light compensation point, CER at light saturation, and apparent
quantum efficiency of seedlings grown and measured at ambient CO2 were not significantly different
from those of seedlings grown and measured at elevated CO2. With a short-term increase in CO2,
CER at light saturation (5.16 +/- 0.52 versus 3.13 +/- 0.30 mumol CO2 m-2 s- 1 ) and apparent
quantum efficiency (0.082 +/- 0.011 versus 0.045 +/- 0.003 mumol CO2 mumol-1 quanta) were
significantly increased. Leaf C/N ratio was significantly increased in the elevated CO2 treatment.
There were few significant differences between families for any response to elevated CO2. Under the
experimental conditions, high growth rate was not correlated with a greater response to elevated
CO2.



     819  
Grulke, N.E., G.H. Riechers, W.C. Oechel, U. Hjelm, and C. Jaeger. 1990. Carbon balance in
tussock tundra under ambient and elevated atmospheric CO2. Oecologia 83(4):485-494.



     820  
Gruters, U. 1999. On the role of wheat stem reserves when source-sink balance is disturbed by
elevated CO2. Journal of Applied Botany-Angewandte Botanik 73(1-2):55-62.

Spring wheat (Triticum aestivum L. cv. Minaret) was exposed to 360 and 680 mu mol mol(-1) CO2
in open top chambers during the vegetation periods of 1994/1995. In 1994 fractionated harvests were
carried out at weekly intervals from the onset of stem elongation,. At final harvest CO, enhanced
aboveground biomass and yield by 49.7 and 43.2%, respectively. From all plant organs stem dry
weights showed the largest increases under doubled CO2, whereas leaf-blade dry weights increased
only slightly. Since stems are known as sites of intermediary carbohydrate-storage, carbohydrate
composition was analysed in the internodes of the main stem. Carbohydrates were determined as
fructans, sucrose and reducing sugars. CO2 stimulated the amounts per organ of all components, but
fructans showed the largest increases. Fructan accumulation lasted about one week longer and
remobilisation was faster under elevated CO2. The results are consistent with current knowledge, that
temporary storage pools accomodate source photosynthate supply to sink demand and suggested a
predominant role of the intermediary stem reserves, when source-sink relations are changed under
elevated CO2. The contribution of the main stem reserves to the main stem yield was also enhanced
by elevated CO2 (6.1-8.7% compared to 10.0-14.2%). In 1995 growth and yield increase due to
elevated CO2 (50.6 and 53%) was comparable to 1994. A functional growth analysis of the stem dry
weight was carried out in this year. There was only a slightly longer accumulation phase in response
to elevated CO2. Combined stem reserves contributed 12-18% to the final grain yield thereby
contradicting, the suggestions based on the results of the year 1994.

KEYWORDS: FRUCTAN ACCUMULATION, GROWTH, PLANTS, SPRING WHEAT,
TEMPERATURE, YIELD


     821  
Guak, S., D.M. Olsyzk, L.H. Fuchigami, and D.T. Tingey. 1998. Effects of elevated CO2 and
temperature on cold hardiness and spring bud burst and growth in Douglas-fir (Pseudotsuga
menziesii). Tree Physiology 18(10):671-679.

We examined effects of elevated CO2 and temperature on cold hardiness and bud burst of Douglas-fir
(Pseudotsuga menziesii (Mirb.) France) seedlings. Two-year-old seedlings were grown for 2.5 years
in semi-closed, sunlit chambers at either ambient or elevated (ambient + approximate to 4 degrees C)
air temperature in the presence of an ambient or elevated (ambient + approximate to 200 ppm) CO2
concentration. The elevated temperature treatment delayed needle cold hardening in the autumn and
slowed dehardening in the spring. At maximum hardiness, trees in the elevated temperature treatment
were less hardy by about 7 degrees C than trees in the ambient temperature treatment. In general,
trees exposed to elevated CO2 were slightly less hardy during hardening and dehardening than trees
exposed to ambient CO2. For trees in the elevated temperature treatments, date to 30% burst of
branch terminal buds was advanced by about 6 and 15 days in the presence of elevated CO2 and
ambient CO2, respectively. After bud burst started, however, the rate of increase in % bud burst was
slower in the elevated temperature treatments than in the ambient temperature treatments. Time of
bud burst was more synchronous and bud burst was completed within a shorter period in trees at
ambient temperature (with and without elevated CO2) than in trees at elevated temperature. Exposure
to elevated temperature reduced final % bud burst of both leader and branch terminal buds and
reduced growth of the leader shoot. We conclude that climatic warming will influence the
physiological processes of dormancy and cold hardiness development in Douglas-fir growing in the
relatively mild temperate region of western Oregon, reducing bud burst and shoot growth.

KEYWORDS: BUDBURST, DORMANCY, FROST DAMAGE, PICEA-SITCHENSIS,
PROBABILITY, RISK, TREES


     822  
Guehl, J.M., C. Picon, G. Aussenac, and P. Gross. 1994. Interactive effects of elevated co2 and
soil drought on growth and transpiration efficiency and its determinants in 2 european forest tree
species. Tree Physiology 14(7-9):707-724.

The responses of growth and transpiration efficiency (W = biomass accumulation/water consumption)
to ambient and elevated atmospheric CO2 concentrations (350 and 700 mumol mol-1, respectively)
were investigated under optimal nutrient supply in well-watered and in drought conditions in two
temperate- forest tree species: Quercus petraea Liebl. and Pinus pinaster Ait. Under well-watered
conditions, doubling the CO2 concentration for one growing season increased biomass growth by
138% in Q. petraea and by 63% in P. pinaster. In contrast, under drought conditions, elevated CO2
increased biomass growth by only 47% in Q. petraea and had no significant effect on biomass growth
in P. pinaster. Transpiration efficiency was higher in Q. petraea than in P. pinaster in all treatments.
This difference was linked (i) to lower carbon isotope discrimination (DELTA), and thus lower values
of the intercellular/ambient CO2 concentration (c(i)/c(a)) ratio, in Q. petraea, (ii) to lower values of
leaf mass ratio (LMR, leaf mass/whole plant mass), which we suggest was positively related to the
proportion of daytime carbon fixation lost by respiration (PHI), in Q. petraea, and (iii) to slightly
lower C concentrations in Q. petraea than in P. pinaster. The CO2- promoted increase in W was
higher in Q. petraea (+80%) than in P. pinaster (+50%), and the difference was associated with a
more pronounced decrease in PHI in response to elevated CO2 in Q. petraea than in P. pinaster,
which could be linked with the N dilution effect observed in Q. petraea. Because PHI also directly
affects growth, the CO2-induced enhancement of PHI in Q. petraea is a crucial determinant of the
growth stimulation observed in this species. Leaf gas exchange regulation was not the only factor
involved in the responses of growth and W to elevated CO2 and drought, other physiological
processes that have crucial roles include carbon and N allocation and respiration.



     823  
Gunderson, C.A., R.J. Norby, and S.D. Wullschleger. 1993. Foliar gas-exchange responses of 2
deciduous hardwoods during 3 years of growth in elevated co2 - no loss of photosynthetic
enhancement. Plant, Cell and Environment 16(7):797-807.

Responses of photosynthesis and stomatal conductance were monitored throughout a 3-year field
exposure of Liriodendron tulipifera (yellow-poplar) and Quercus alba (white oak) to elevated
concentrations of atmospheric CO2. Exposure to atmospheres enriched with +150 and +300 mumol
mol-1 CO2 increased net photosynthesis by 12-144% over the course of the study. Net
photosynthesis was consistently higher at +300 than at +150 mumol mol-1 CO2. The effect Of CO2
enrichment on stomatal conductance was limited, but instantaneous leaf-level water use efficiency
increased significantly. No decrease in the responsiveness of photosynthesis to CO2 enrichment over
time was detected, and the responses were consistent throughout the canopy and across successive
growth flushes and seasons. The relationships between internal CO2 concentration and photosynthesis
(e.g. photosynthetic capacity and carboxylation efficiency) were not altered by growth at elevated
concentrations of CO2. No alteration in the timing of leaf senescence or abscission was detected,
suggesting that the seasonal duration of effective gas-exchange was unaffected by CO2 treatment.
These results are consistent with data previously reported for these species in controlled-environment
studies, and suggest that leaf-level photosynthesis does not down-regulate in these species as a result
of acclimation to CO2 enrichment in the field. This sustained enhancement of photosynthesis provides
the opportunity for increased growth and carbon storage by trees as the atmospheric concentration
of CO2 rises, but many additional factors interact in determining whole-plant and forest responses
to global change.

KEYWORDS: ATMOSPHERIC CO2, CARBON-DIOXIDE ENRICHMENT, CO2-ENRICHED
ATMOSPHERES, LEAVES, LIRIODENDRON-TULIPIFERA L, LONG-TERM EXPOSURE,
SCIRPUS- OLNEYI, SEEDLINGS, TUSSOCK TUNDRA, WATER-USE


     824  
Gunderson, C.A., and S.D. Wullschleger. 1994. Photosynthetic acclimation in trees to rising
atmospheric co2 - a broader perspective. Photosynthesis Research 39(3):369-388.

Analysis of leaf-level photosynthetic responses of 39 tree species grown in elevated concentrations
of atmospheric CO2 indicated an average photosynthetic enhancement of 44% when measured at the
growth [CO2]. When photosynthesis was measured at a common ambient [CO2], photosynthesis of
plants grown at elevated [CO2] was reduced, on average, 21% relative to ambient-grown trees, but
variability was high. The evidence linking photosynthetic acclimation in trees with changes at the
biochemical level is examined, along with anatomical and morphological changes in trees that impact
leaf- and canopy- level photosynthetic response to CO2 enrichment. Nutrient limitations and
variations in sink strength appear to influence photosynthetic acclimation, but the evidence in trees
for one predominant factor controlling acclimation is lacking. Regardless of the mechanisms that
underlie photosynthetic acclimation, it is doubtful that this response will be complete. A new focus
on adjustments to rising [CO2] at canopy, stand, and forest scales is needed to predict ecosystem
response to a changing environment.

KEYWORDS: CASTANEA-SATIVA MILL, ELEVATED CARBON-DIOXIDE, GAS-EXCHANGE,
PHOSPHORUS DEFICIENCY, PINUS-RADIATA, PLANT-RESPONSES, POPLAR CLONES,
RADIATA D-DON, STOMATAL CONDUCTANCE, WATER-STRESS


     825  
Gunn, S., S.J. Bailey, and J.F. Farrar. 1999. Partitioning of dry mass and leaf area within plants
of three species grown at elevated CO2. Functional Ecology 13:3-11.

1. We tested the hypothesis that the net partitioning of dry mass and dry mass:area relationships is
unaltered when plants are grown at elevated atmospheric CO2 concentrations. 2. The total dry mass
of Dactylis glomerata, Bellis perennis and Trifolium repens was higher for plants in 700 compared
to 350 mu mol CO2 mol(-1) when grown hydroponically in controlled- environment cabinets. 3.
Shoot:root ratios were higher and leaf area ratios and specific leaf areas lower in all species grown
at elevated CO2. Leaf mass ratio was higher in plants of B. perennis and D. glomerata grown at
elevated CO2. 4. Whilst these data suggest that CO2 alters the net partitioning of dry mass and dry
mass:leaf area relationships, allometric comparisons of the components of dry mass and leaf area
suggest at most a small effect of CO2. CO2 changed only two of a total of 12 allometric coefficients
we calculated for the three species: v relating shoot to root dry mass was higher in D. glomerata,
whilst v relating leaf area to total dry mass was lower in T. repens. 5. CO2 alone has very little effect
on partitioning when the size of the plant is taken into account.

KEYWORDS: ALLOCATION, ATMOSPHERIC CARBON-DIOXIDE, COMMUNITIES, CROP
RESPONSES, ENRICHMENT, MATTER, NITROGEN, RESPIRATION, ROOT, TEMPERATURE


     826  
GunthardtGoerg, M.S. 1997. Leaf and shoot formation of young spruce and beech exposed to
elevated CO2. Acta Oecologica-International Journal of Ecology 18(3):335-341.

Sixteen open-top chambers (divided into two halves each containing either calcareous or acidic soil)
were supplied in four combinations with either 366 or 550 mu l CO2 L-1, and either 2.5 or 25 kg N
ha-(1) y(-1) (ammonium nitrate by irrigation). The development of young spruce (Picea abies) and
beech (Fagus sylvatica) trees planted in the chambers together with understory plants will be studied
over four years. The presented data are preliminary results from the first year of this experiment and
refer to 64 spruce and 64 beech trees from two different Swiss spruce and beech provenances; two
trees each per soil type, sampled in July and September in each chamber. Specific current-year spruce
nee die length (length/dry mass) was reduced by elevated CO2 due to an increase in dry mass. Beech
specific leaf area was only temporarily reduced in July. Elevated CO2 induced an earlier autumnal leaf
discoloration. Total current-year shoot length per spruce and total number of leaves per beech tree
were not influenced by the first year treatment with elevated CO2. N deposition had no effect on
these parameters, but soil type influenced spruce needle colour Spruce, in contrast to beech, may
therefore profit from elevated CO2 (when other resources are unlimited) by increasing shoot and
needle dry mass.

KEYWORDS: ACCLIMATION, GROWTH, PLANT-RESPONSES, PRODUCTIVITY, TREES


     827  
Guy, M., G. Granoth, and J. Gale. 1990. Cultivation of Lemna gibba under desert conditions .2.
the effect of raised winter temperature, CO2 enrichment and shading on productivity. Biomass
23(1):1-11.



     828  
GwynnJones, D., J.A. Lee, and T.V. Callaghan. 1997. Effects of enhanced UV-B radiation and
elevated carbon dioxide concentrations on a sub-Arctic forest heath ecosystem. Plant Ecology 128(1-
2):242-249.

An experiment is described which studies the effects of enhanced UV-B radiation (simulating a 15%
reduction in the Ozone layer) and elevated atmospheric concentrations of CO2 (600 ppm) on the
dwarf shrub layer of a sub-arctic forest heath ecosystem at Abisko, North Sweden. The experimental
treatments were first applied in 1993, and have covered most of the snow- free season (late May to
early September) 1993-1995. Effects of the treatments on the four dwarf shrub species have been
recorded largely using non-destructive measures (Vaccinium uliginosum, Vaccinium myrtillus -
deciduous species and Vaccinium vitis-idaea and Empetrum hermaphroditum - evergreen species).
Effects of the treatments on stem growth and leaf thickness have so far been small, although CO2
treatments initially stimulated stem extension in Vaccinium myrtillus 1993 and depressed growth in
V. vitis idaea in 1994 and E. hermaphroditum during 1995. UV-B treatments stimulated fruit
production in V. myrtillus in both 1994 and 1995, but there was no effect on reproductive phenology.
There were also marked effects of UV-B treatments on insect herbivory in the deciduous dwarf
shrubs; with leaf area loss being greater than the control in the UV-B treatment in V. myrtillus and
less in V. uliginosum. The results point to the possibility of important effects of the treatments on
physiological and chemical processes within the plants. The ecological results of such effects may not
be immediately apparent, but may be far reaching, pointing to the need for long-term in situ
experimentation in predicting the effects of these global change variables.

KEYWORDS: CO2, DWARF SHRUBS, GROWTH, PEA, PLANTS, RESPONSES, ULTRAVIOLET-
RADIATION


     829  
Habash, D.Z., M.A.J. Parry, S. Parmar, M.J. Paul, S. Driscoll, J. Knight, J.C. Gray, and D.W.
Lawlor. 1996. The regulation of component processes of photosynthesis in transgenic tobacco with
decreased phosphoribulokinase activity. Photosynthesis Research 49(2):159-167.

Tobacco plants (Nicotiana tabacum L.) transformed with an inverted cDNA encoding ribulose 5-
phosphate kinase (phosphoribulokinase,PRK;EC 2.7.1.19) were employed to study the in vivo
relationship between photosynthetic electron transport and the partitioning of electron transport
products to major carbon metabolism sinks under conditions of elevated ATP concentrations and
limited ribulose 1,5-bisphosphate (RuBP) regeneration. Simultaneous measurements of room
temperature chlorophyll fluorescence and CO2 gas exchange were conducted on intact leaves. Under
ambient CO2 concentrations and light intensities above those at which the plants were grown,
transformants with only 5% of PRK activity showed 'down- regulation' of PS II activity and electron
transport in response to a decrease in net carbon assimilation when compared to wild-type. This was
manifested as a decline in the efficiency of PS II electron transport (Phi(PS II)), an increase in
dissipation of excess absorbed light in the antennae of PS II and a decline in : total linear electron
transport (J(1)), electron transport dedicated to carbon assimilation (J(A)) and electron transport
allocated to photorespiration (J(L)). The transformants showed no alteration in the Rubisco
specificity factor measured in vitro and calculated in vivo but had a relatively smaller ratio of RuBP
oxygenation to carboxylation rates (v(o)/v(c)), due to a higher CO2 concentration at the
carboxylation site (C-c). The relationship between Phi(PS II) and Phi(CO2) was similar in
transformants and wild-type under photorespiratory conditions demonstrating no change in the
intrinsic relationship between PS II function and carbon assimilation, however, a novel result of this
study is that this similar relationship occurred at different values of quantum flux, J(1), J(A), J(L) and
v(o)/v(c) in the transformant. For both wild-type and transformants, an assessment was made of the
possible presence of a third major sink for electron transport products, beside RuBP oxygenation and
carboxylation, the data provided no evidence for such a sink.

KEYWORDS: CHLOROPHYLL FLUORESCENCE, DROUGHT STRESS, ELECTRON-
TRANSPORT, GAS-EXCHANGE, LEAVES, NET CO2 ASSIMILATION, PHOTORESPIRATION,
REDUCTION, RIBULOSE-1;5-BISPHOSPHATE CARBOXYLASE-OXYGENASE, RUBISCO


     830  
Habash, D.Z., M.J. Paul, M.A.J. Parry, A.J. Keys, and D.W. Lawlor. 1995. Increased capacity
for photosynthesis in wheat grown at elevated co2 - the relationship between electron-transport and
carbon metabolism. Planta 197(3):482-489.

Spring wheat (Triticum aestivum L.) was grown under optimal nutrition for six weeks at 700 and 350
mu mol . mol(-1) CO2 and simultaneous measurements of photosystem-II (PSII) chlorophyll
fluorescence and gas exchange were conducted on intact attached leaves. Plants grown at elevated
CO2 had double the concentration of CO2 at the carboxylation site (C-c) despite a lowered stomatal
(g(s)) and mesophyll (g(m)) conductance compared with ambient-grown plants. Plants grown at
elevated CO2 had a higher relative quantum yield of PSII electron transport (Phi(PSII)) and a higher
relative quantum yield of CO2 fixation (Phi CO2). The higher Phi(PSII) was due to a larger
proportion of open PSII centres, estimated by the coefficient of photochemical quenching of
fluorescence (q(p)), with no change in the efficiency of light harvesting and energy transduction by
open PSII centres (F'(v)/F'(m)). Analysis of the relationship between Phi(PSII) and Phi(CO2)
conducted under various CO2 and O-2 concentrations showed that the higher Phi(CO2) for a given
Phi(PSII) in leaves developed under elevated CO2 was similar to that obtained in leaves upon a partial
reduction in photorespiration. Calculation of the allocation of photosynthetic electron-transport
products to CO2 and O-2 showed that for leaves developed in elevated CO2, there was an increase
in both total linear electron flow and electron flow to CO2 and a decrease in electron flow to O-2.
Plants developed under elevated CO, showed positive acclimation manifested by a higher Phi(CO2)
when measured under ambient CO2 and higher assimilation rates in A/C-i curves. Initial and to tal
activity of ribulose-1,5- bisphosphate carboxylase- oxygenase (Rubisco EC 4.1.1.39) measured in
vitro increased by 16 and 15% respectively in leaves from plants grown in elevated CO2, which was
in agreement with a 15% higher in vivo carboxylation efficiency. It is concluded that growth of spring
wheat at elevated CO2 enhances photosynthesis due to a change in the balance of component
processes manifested as an increased capacity for carbon fixation, total electron transport and Rubisco
activity, and a concomitant partial reduction of photorespiration.

KEYWORDS: CARBOXYLASE, CHLOROPHYLL FLUORESCENCE, FIELD, GAS-EXCHANGE,
LEAVES, PHYSIOLOGY, QUANTUM YIELD, STRESS


     831  
Hadley, P., G.R. Batts, R.H. Ellis, J.I.L. Morison, S. Pearson, and T.R. Wheeler. 1995.
Temperature-gradient chambers for research on global environment change .2. a twin-wall tunnel
system for low- stature, field-grown crops using a split heat-pump. Plant, Cell and Environment
18(9):1055-1063.

A temperature gradient chamber (TGC) is described which enables elevated CO2 concentrations and
a dynamic temperature gradient to be imposed on field crops throughout their life cycle under
standard husbandry. Air is circulated through two double-walled polyethylene-covered tunnels
connected to a split heat pump system to give a near-linear temperature gradient along each tunnel,
Solar energy gain along each tunnel and exchange with outer tunnel air flow contribute to the
temperature gradient and also produce diurnal and seasonal temperature fluctuations corresponding
to ambient conditions, Mean temperature gradients of between 3 and 5 degrees C have been recorded
throughout the growing seasons of crops of lettuce, carrot, cauliflower and winter wheat, Elevated
or present CO2 concentrations are maintained in each of two pairs of tunnels throughout the cropping
season using pure CO2 injected through motorized needle valves. This system can realistically
simulate aspects of the effects of projected future environmental change on crop growth, development
and yield, and in particular the possible interaction of the effects of increased CO2 and temperature.

KEYWORDS: CO2


     832  
Hager, C., G. Wurth, and G.H. Kohlmaier. 1999. Biomass of forest stands under climatic change:
a German case study with the Frankfurt biosphere model (FBM). Tellus Series B-Chemical and
Physical Meteorology 51(2):385-401.

In this contribution, we perform a case study of the German forests. We couple the Frankfurt
biosphere model (FBM) with a model of the age class development (AGEDYN). The coupled model
is applied to simulate the temporal development of carbon pools in German forests under the
influence of climate change taking into account changes in the age class structure. In the base case,
the growth of forest stands is simulated using a temporally averaged climate dataset, being
representative for the contemporary climate conditions. To assess the sensitivity of forest growth to
changes in environmental conditions, the FBM is run in several scenarios. In these simulations the
effects both of climate change and of the direct effect of increased levels of atmospheric CO2 on
photosynthesis (CO2 fertilization) on forest growth are assessed. In another simulation run with the
FBM both effects - climate change and CO2 fertilization are combined. In simulations under present
day's climate conditions a good agreement is gained between simulation results and statistical data
of the present standing stock carbon density of Germany's forests. A pure climate change leads to a
decrease of the annual increments as well as to the climax standing stocks. The negative effect of
climate change alone is overcompensated by enhanced photosynthesis in the simulations with
combined climate change and CO2 fertilization. In the transient case, the coupled model is used in
two scenarios describing first a continuation of present day's climate conditions and second a transient
climate change from present conditions (1990) to 2 x CO2 conditions in 2090. Here, the simulations
indicate that changes in the forest's age class structure can have a stronger influence on the future
carbon balance of the forests in the considered region than the combined effect of climate change and
CO2 fertilization.

KEYWORDS: ATMOSPHERE, BOREAL FORESTS, CARBON DYNAMICS, CO2, EXCHANGE,
GLOBAL VEGETATION, PRODUCTIVITY, RESPONSES, TERRESTRIAL ECOSYSTEMS


     833  
Hakala, K. 1998. Growth and yield potential of spring wheat in a simulated changed climate with
increased CO2 and higher temperature. European Journal of Agronomy 9(1):41-52.

The effects of climatic change on the growth, yield and nitrogen content of spring wheat (Triticum
aestivum L., cv. Polkka) were studied from 1992 to 1994. The crop was sown directly in the field,
at a normal sowing density. Leaf canopies were exposed to CO2 concentrations of 700 mu l l(-1) and
temperatures 3 degrees C higher than ambient throughout the growing season. CO2 concentrations
were elevated in open-top chambers 3m in diameter. Temperatures were elevated in an automatically
controlled greenhouse built over the experimental field. To simulate conditions predicted for a future
warmer climate, the wheat crop was sown 2-3 weeks earlier in the elevated temperature (future
warmer climate) than in the ambient temperature treatment (present climate). In the elevated
temperature experiment, the average temperatures and development rates were not increased during
the period from sowing to anthesis, but from anthesis to maturity, both temperatures and development
rates were increased. The small increase in the development rate after anthesis at elevated
temperatures in 1992 and 1994 did not affect the grain weight, but the considerable increase in
development rate in 1993 was accompanied by a decrease in grain weight. CO2 enrichment had no
effect on development rate. The total biomass at harvest was significantly higher in CO2 enrichment
in both temperature treatments. Although the mean increase in grain yield was not significant, the
yields tended to be higher in CO2 enrichment. The magnitude of the increase in biomass and grain
yield in CO2 enrichment ranged from about 5 to 60%. The increase in yield was mainly attributed to
an increase in the number of ear- bearing shoots m(-2). Seed number per main shoot and seed weight
were in general not increased with CO2 enrichment unless these were exceptionally low in the
ambient CO2 conditions (in 1993). The harvest index was decreased at elevated temperatures, but
there was no significant effect of CO2 enrichment. There was a small (7%) but significant decrease
in the nitrogen content of the grain in CO2 enrichment at ambient temperatures. (C) 1998 Elsevier
Science B.V.

KEYWORDS: ATMOSPHERIC CO2, CARBON DIOXIDE, DRY-MATTER, ELEVATED CO2,
ENRICHMENT, FIELD, NITROGEN, PHOTOSYNTHESIS, PLANT GROWTH, RESPONSES


     834  
Hakala, K., and T. Mela. 1996. The effects of prolonged exposure to elevated temperatures and
elevated CO2 levels on the growth, yield and dry matter partitioning of field-sown meadow fescue.
Agricultural and Food Science in Finland 5(3):285-298.

Field-sown meadow fescue (Festuca pratensis, cv. Kalevi) stands were exposed to elevated
temperatures (+3 degrees C) and elevated CO2 (700 ppm) levels in two experiments conducted in
1992-1993 (experiment 1) and in 1994-1995 (experiment 2). Total aboveground yield was, on
average, 38% higher at elevated than at ambient temperatures. At ambient temperatures elevated CO2
increased the number of tillers by 63% in 1992, 24% in 1993, 90% in 1994 and 14% in 1995. At
elevated temperatures, the increase in tiller number in elevated CO2 was seen only in the first growing
seasons after sowing. The total yield in a growing season was about 10% higher in elevated CO2 in
experiment 1. In experiment 2 the yield was more than 20% higher in elevated CO2 at elevated
temperatures, whereas at ambient temperatures the rise in CO2 level had no effect on the yield; the
root biomass, however, increased by more than 30%. In elevated CO2 at ambient temperatures the
root biomass also increased in experiment 1, but at elevated temperatures there was no consistent
change. The soluble carbohydrate content of above-ground biomass was 5-48% higher in elevated
CO2 at most of the measuring times during the growing season, but the nitrogen content did not
show a clear decrease. The reasons for the lack of a marked increase in biomass in elevated CO2
despite a 40-60% increase in photosynthesis are discussed.

KEYWORDS: ACCLIMATION, ATMOSPHERIC CO2, CARBON-DIOXIDE CONCENTRATION,
ENRICHMENT, GAS-EXCHANGE, LOLIUM-PERENNE, NITROGEN, PERENNIAL RYEGRASS,
PHOTOSYNTHESIS, RESPONSES


     835  
Hakala, K., T. Mela, H. Laurila, and T. Kaukoranta. 1996. Arrangement of experiments for
simulating the effects of elevated temperatures and elevated CO2 levels on field-sown crops in
Finland. Agricultural and Food Science in Finland 5(1):25-47.

The experimental plants: spring wheat, winter wheat, spring barley, meadow fescue, potato,
strawberry and black currant were sown or planted directly in the field, part of which was covered
by an automatically controlled greenhouse to elevate the temperature by 3 degrees C. The
temperature of the other part of the field (open field) was not elevated, but the field was covered with
the same plastic film as the greenhouse to achieve radiation and rainfall conditions comparable to
those in the greenhouse. To elevate the CO2 concentrations, four open top chambers (OTC) were
built for the greenhouse, and four for the open field. Two of these, both in the greenhouse and in the
open field, were supplied with pure CO2 to elevate their CO2 level to 700 ppm. The temperatures
inside the greenhouse followed accurately the desired level. The relative humidity was somewhat
higher in the greenhouse and in the OTC:s than in the open field, especially after the modifications
in the ventilation of the greenhouse and in the OTC:s in 1994. Because the OTC:s were large (3 m
in diameter), the temperatures inside them differed very little from the surrounding air temperature.
The short-term variation in the CO2 concentrations in the OTC:s with elevated CO2 was, however,
quite high. The control of the CO2 concentrations improved each year from 1992 to 1994, as the
CO2 supplying system was modified. The effects of the experimental conditions on plant growth and
phenology are discussed.

KEYWORDS: PHOTOSYNTHESIS, PLANTS


     836  
Hall, D.O., D.S. Ojima, W.J. Parton, and J.M.O. Scurlock. 1995. Response of temperate and
tropical grasslands to CO2 and climate change. Journal of Biogeography 22(2-3):537-547.

Under a recent SCOPE collaborative project, longterm data from eleven tropical and temperate
grassland sites were used (a) to validate the CENTURY model of plant-soil ecosystems and (b) to
model climate change and CO2 effects for thirty-one temperate and tropical grassland sites,
representing seven ecoregions of the world. Model calibration and testing showed that soil carbon
and nitrogen dynamics can be well simulated for the grassland biome worldwide, over a wide range
of climate and soil types. The interannual response of above ground biomass and plant residue to
variation in climate resulted in a good correspondence between simulated and observed dynamics on
a monthly basis. These results are useful for analysis and description of grassland carbon dynamics,
and as a reference point for testing predictions of net primary production (NPP) and biomass
dynamics from levels of more physiologically based models. Prediction of plant and soil organic
matter C and N dynamics requires knowledge of climate, soil texture, N inputs and fire and grazing
patterns. CENTURY simulations of climate change and CO2 effects showed increased NPP for
climate change alone, except in cold desert steppe regions, and CO2 increased production
everywhere. Climate changes, predominantly a warming of these ecosystems, caused soil carbon to
decrease overall, especially in cold desert and temperate steppes. Increased production due to
elevated CO2 tended to ameliorate soil carbon losses and tropical savannas were actually soil carbon
sinks. Climate change alone projected a carbon loss of 3-4 Pg after 50 years, and 1-2 Pg for the
combined climate change and CO2 simulated effects. We analysed the dynamic response of some of
the major CENTURY output parameters (e.g. NPP, soil organic matter, N mineralization and
decomposition) for their sensitivity to climate change and increasing CO2 for one of the two general
circulation models (GFHI scenario). This analysis was limited to a subset of five well-known study
sites, representing five of the seven ecoregions.

KEYWORDS: BIOMASS, CARBON, CONIFEROUS FORESTS, DECOMPOSITION, DYNAMICS,
MODEL, PRODUCTIVITY, SOIL


     837  
Hall, D.O., and J.M.O. Scurlock. 1991. Climate change and productivity of natural grasslands.
Annals of Botany 67:49-55.

KEYWORDS: BIOSPHERE, CARBON, DYNAMICS, ELEVATED CO2, ESTUARINE MARSH,
NITROGEN, PLANTS


     838  
Hall, F.G. 1999. Introduction to special section: BOREAS in 1999: Experiment and science
overview. Journal of Geophysical Research-Atmospheres 104(D22):27627-27639.

The goal of BOREAS is to improve our understanding of the interactions between the boreal forest
biome and the atmosphere in order to clarify their roles in global change. This overview briefly
reviews the science background and motivations for the Boreal Ecosystem-Atmosphere Study
(BOREAS). The findings of the 27 papers in this journal special issue are reviewed. Important
scientific results of the project to date are summarized, and future research directions are identified.

KEYWORDS: ATMOSPHERE INTERACTIONS, BALANCE, CARBON DIOXIDE, CO2, FOREST,
HIGH-LATITUDES, LAND-ATMOSPHERE, MODEL, NORTHERN, WATER


     839  
Hall, J.M., E. Paterson, and K. Killham. 1998. The effect of elevated CO2 concentration and soil
pH on the relationship between plant growth and rhizosphere denitrification potential. Global Change
Biology 4(2):209-216.

The effect of CO2 concentration on plant growth and the size of the rhizosphere denitrifier population
was investigated for ryegrass grown at 3 different soil pH values (pH 4.3, 5.9 and 7.0). Soil
microcosms were planted with ryegrass and maintained under constant growth conditions at either
ambient (450ppm) or elevated (720ppm) CO2 concentration. At harvest, the rhizosphere soil was
collected and subjected to a potential denitrification assay to provide an estimate of the size of the
denitrifier population present. Ryegrass dry matter production varied across the pH range studied and
contrary to other studies, elevated CO2 concentration did not consistently increase growth. Plant
growth was reduced by approximate to 35% and 23% at pH 4.3 and pH 5.9, respectively, under
elevated CO2 concentration. At pH 7.0, however, plant growth was increased by approximate to 45%
under elevated CO2. Potential denitrification rates within the rhizosphere followed a similar pattern
to plant growth in the different treatments, suggesting that plant growth and the size of denitrifier
population within the rhizosphere are coupled. This study investigates the relationship between plant
growth and rhizosphere denitrification potential, thereby providing an estimate of the size of the
denitrifier population under increased CO2 concentration and soil pH.

KEYWORDS: ATMOSPHERIC CARBON-DIOXIDE, ENRICHMENT, FIELD, FLOW, LOLIUM-
PERENNE, MICROBIAL BIOMASS, NITROGEN, PHOTOSYNTHESIS, RESPONSES, ROOTS


     840  
Halloy, S.R.P., and A.F. Mark. 1996. Comparative leaf morphology spectra of plant communities
in New Zealand, the Andes and the European Alps. Journal of the Royal Society of New Zealand
26(1):41-78.

Leaf morphology of native vegetation tias often been interpreted as a sensitive indicator of
environmental conditions, presumably as a result of natural selection. If environmental pressures act
as a selective force on community leaf morphology, then we would expect a high degree of similarity
in similar environments, regardless of biogeographic origin of the flora. A comparative study of full
regional floras of alpine vascular plants was undertaken to test the sensitivity of leaf morphology to
macro-environmental conditions. Five alpine sites and one lowland (control) site were selected in
southern New Zealand spanning 1.5 degrees latitude and 2323 m. Three sites with equivalent alpine
environments were selected in South America across a 60 degrees latitudinal and 4200 m altitudinal
span with subtropical forest used as a control. A further alpine site from the European Alps was
included as an outlier. Twenty leaf parameters were obtained for 2143 taxonomic entities x sites.
Both the mean and the frequency distribution of leaf size and shape parameters were distinctive for
each locality. Several morphological trends were found. Means of New Zealand contiguous low-
alpine and high-alpine site pairs differed in. length -33%, width - 14%, length/width -20%, leaf area
-44%, entire margin -2% (variable), coriaceousness -18%, folded +22%, pubescence +40%. At higher
elevations, leaves become smaller but rounder, considerably softer, are more often folded into crypts
or similar structures and are more often pubescent. These changes corresponded to reductions of 2-3
degrees C in mean annual air temperature, c. 10% in mean minimum relative humidity and 7% in CO2
partial pressure. Despite the biogeographic and environmental differences, New Zealand and South
American low- alpine sites were consistently similar in their morphological parameters and
consistently different from high-alpine sites (except in Tierra del Fuego). High alpine sites were also
consistently similar across the Pacific. Several parameters were found to have multimodal frequency
distributions that were not significantly different in widely separate localities with different floras. The
results suggest that plant community morphology is an emergent property, the magnitude of which
is environmentally constrained.

KEYWORDS: ALPINE LIFE ZONE, ALTITUDINAL VARIATION, ANATOMY, CLIMATE,
CONDUCTANCE, FLORA, FOSSILS, LATITUDINAL GRADIENT, RADIATION, SIZE


     841  
Ham, J.M., C.E. Owensby, and P.I. Coyne. 1993. Technique for measuring air-flow and carbon-
dioxide flux in large, open-top chambers. Journal of Environmental Quality 22(4):759-766.

Open-Top Chambers (OTCs) are commonly used to evaluate the effect of CO2, O3, and other trace
gases on vegetation. A study was conducted to develop and test a new technique for measuring
forced air flow and net CO2 flux from OTCs. Experiments were performed with a 4.5-m diam. OTC
that had a sealed floor and a specialized air delivery system. Air flow through the chamber was
computed with the Bernoulli equation using measurements of the pressure differential between the
air delivery ducts and the chamber interior. An independent measurement of air flow was made
simultaneously to calibrate and verify the accuracy of the Bernoulli relationship. The CO2 flux density
was calculated as the product of chamber air flow and the difference in CO2 concentration between
the air entering and exhausting from the OTC (C(in) - C(out)). Accuracy of the system was evaluated
by releasing CO2 within the OTC at known rates to emulate respiration from the field surface. Data
were collected with OTCs at ambient and elevated CO2 (almost-equal-to 700 mumol mol-1). Results
showed that the Bernoulli equation, with a flow coefficient of 0.7, accurately measured air flow in
the OTC to within +/- 5% regardless of flow rate and air duct geometry. Experiments in ambient
OTCs showed that CO2 flux density (mumol m-2 s-1), computed from 2-min averages of air flow and
C(in) - C(out), was typically within +/- 10% of actual flux, provided that the exit air velocity at the
top of the OTC was greater than 0.6 m s-1. Obtaining the same level of accuracy in CO2- enriched
OTCs, however, required a critical exit velocity near 1.2 m s-1 to minimize the incursion of ambient
air and prevent contamination of the exit gas sample. When flux data were integrated over time to
estimate daily CO2 flux (mumol m-2 d- 1), actual and measured values agreed to within +/- 2% for
both ambient and CO2-enriched chambers, suggesting that accurate measurements of daily net C
exchange are possible with this technique.

KEYWORDS: CO2, EXCHANGE, FIELD CHAMBERS, WIND-TUNNEL


     842  
Ham, J.M., C.E. Owensby, P.I. Coyne, and D.J. Bremer. 1995. Fluxes of co2 and water-vapor
from a prairie ecosystem exposed to ambient and elevated atmospheric co2. Agricultural and Forest
Meteorology 77(1-2):73-93.

Increasing concentrations of atmospheric CO2 may alter the carbon and water relations of prairie
ecosystems. A C-4- dominated tallgrass prairie near Manhattan, KS, was exposed to 2x ambient CO2
concentrations using 4.5 m-diameter open-top chambers. Whole-chamber net CO2 exchange (NCE)
and evapotranspiration (ET) were continuously monitored in CO2- enriched and ambient (no
enrichment) plots over a 34-d period encompassing the time of peak biomass in July and August,
1993. Soil-surface CO2 fluxes were measured with a portable surface chamber, and sap flow (water
transport in xylem) in individual grass culms was monitored with heat balance techniques.
Environmental measurements were used to determine the effect of CO2 on the surface energy balance
and canopy resistances to vapor flux. In 1993, frequent rainfall kept soil water near field capacity and
minimized plant water stress. Over the 34-d measurement period, average daily NCE (canopy
photosynthesis - soil and canopy respiration) was 9.3 g CO2 m(-2) in the ambient treatment and 11.4
g CO2 m(-2) under CO2 enrichment. However, differences in NCE were caused mainly by delayed
senescence in the CO2-enriched plots at the end of the growing season. At earlier stages of growth,
elevated CO2 had no effect on NCE. Soil-surface CO2 fluxes typically ranged from 0.4 to 0.66 mg
CO2 m(-2) s(-1), but were slightly greater in the CO2-enriched chambers. CO2 enrichment reduced
daily ET by 22%, reduced sap flow by 18%, and increased canopy resistance to vapor flux by 24 s
m(-1). Greater NCE and lower ET resulted in higher daytime water use efficiency (WUE) under CO2
enrichment vs. ambient (9.84 vs. 7.26 g CO2 kg(-1) H2O). However, record high precipitation during
the 1993 season moderated the effect of WUE on plant growth, and elevated CO2 had no effect on
peak aboveground biomass. CO2-induced stomatal closure also affected the energy balance of the
surface by reducing latent heat flux (LE), thereby causing a consequent change in sensible heat flux
(H). The daytime Bowen ratio (H/LE) for the study period was near zero for the ambient treatment
and 0.21 under CO2 enrichment.

KEYWORDS: CANOPY PHOTOSYNTHESIS, CARBON DIOXIDE, CROP, EXCHANGE, FLOW,
RESPONSES


     843  
Hamerlynck, E.P., C.A. McAllister, A.K. Knapp, J.M. Ham, and C.E. Owensby. 1997.
Photosynthetic gas exchange and water relation responses of three tallgrass prairie species to elevated
carbon dioxide and moderate drought. International Journal of Plant Science 158(5):608-616.

Undisturbed tallgrass prairie was exposed to ambient and elevated (twice-ambient) levels of
atmospheric CO, and experimental dry periods. Seasonal and diurnal midday leaf water potential
(Psi(leaf)), net photosynthesis (A(net)), and stomatal conductance (g(s)) responses of three tallgrass
prairie growth forms-a C-4 grass, Andropogon gerardii; a broad- leaved woody C, shrub,
Symphiocarpos orbiculatus; and a C-3 perennial forb, Salvia pitcheri-were assessed. Psi(leaf) in A.
gerardii and S, orbiculatus was higher under elevated CO2, regardless of soil moisture, while Psi(leaf)
in S. pitcheri responded only to drought. Elevated CO2 always stimulated A(net) in the C-3 species,
while A. gerardii A(net) increased only under dry conditions. However, A(net) under elevated CO2
in the C-3 species declined with drought but not in the C,grass, Under wet conditions, g(s) reduced
in elevated CO2 for all species. During dry periods, g, at elevated CO, was sometimes higher than
in ambient CO2. Our results support claims that elevated CO2 will stimulate tallgrass prairie
productivity during dry periods and possibly reduce temporal and spatial variability in productivity
in these grasslands.

KEYWORDS: AMBIENT, ATMOSPHERIC CO2, BIOMASS PRODUCTION, BOUTELOUA-
GRACILIS, C-4 GRASS, GRASS ANDROPOGON-GERARDII, NITROGEN, PASCOPYRUM-
SMITHII, SOIL MOISTURE, TOPOGRAPHIC POSITION


     844  
Hanba, Y.T., E. Wada, M. Osaki, and T. Nakamura. 1996. Growth and delta C-13 responses to
increasing atmospheric carbon dioxide concentrations for several crop species. Isotopes in
Environmental and Health Studies 32(1):41-54.

The responses of plant growth and carbon isotope discrimination (Delta) to elevated atmospheric
CO2 concentrations for several crop species (lettuce: Lactuca sativa L.; corn: Zea mays L. var.
P3540; wheat: Triticum aestivum L. var Haruyutaka; and soybean: Glycine max (L). Merr. var.
Kitamusume) were investigated. Shoot relative growth rate was used to indicate plant growth, and
delta(13)C value of leaf materials in corn (C4 species) was used to calculate Delta for C3 species.
Plant growth was stimulated by enriched CO2, while Delta remained almost constant as CO2
concentration changed. Delta showed interspecific difference, and the plant species of larger Delta
had larger relative growth rates. Relative growth rates of the plants of larger Delta were stimulated
by CO2 enrichment more than those of the plants of smaller Delta. We propose that plant Delta could
be a possible parameter to assess the interspecific difference of plant response to the increasing
atmospheric CO2 concentrations.

KEYWORDS: CO2 CONCENTRATIONS, COOL-SEASON GRASSES, ELEVATED CO2,
ENVIRONMENTS, GAS-EXCHANGE, ISOTOPE DISCRIMINATION, PHOTOSYNTHESIS,
PLANTS, SPRING WHEAT, WATER-USE EFFICIENCY


     845  
Hand, D.W., J.W. Wilson, and B. Acock. 1993. Effects of light and co2 on net photosynthetic rates
of stands of aubergine and amaranthus. Annals of Botany 71(3):209-216.

KEYWORDS: CARBON DIOXIDE, CROP PHOTOSYNTHESIS, ENRICHMENT, ENVIRONMENT,
PLANT GROWTH, RESPONSES


     846  
Handel, M.D., and J.S. Risbey. 1992. An annotated-bibliography on the greenhouse-effect and
climate change. Climatic Change 21(2):97-253.

The literature on climate change from an enhanced greenhouse effect is large and growing rapidly.
The problems considered are increasingly interdisciplinary. For these reasons many workers will find
useful pointers to the literature in the fields interacting with, but outside of, their own. We present
here an annotated bibliography on issues relating to changes in the concentrations of Earth's
greenhouse gases. The areas covered include theory and numerical modelling of climate change;
cycles involving carbon dioxide and other radiatively important trace gases; observations of climate
change and the problems associated with those observations; paleoclimatology as it relates to
previous changes in the greenhouse gases; the impacts on and interactions with managed and natural
ecosystems from climate change; policy issues related to climate change and to the limitation of
climate change; history of the study of the greenhouse effect; and some other causes of climate
change. Selection of papers has been made to facilitate rapid introduction to most of the important
issues and findings in an area. Over 600 articles, reports, and books are discussed.

KEYWORDS: ATMOSPHERIC CARBON-DIOXIDE, DOUBLED CO2 CLIMATE, EARTHS
RADIATION BUDGET, GENERAL-CIRCULATION MODEL, GLOBAL CLIMATE, NORTH-
ATLANTIC OCEAN, RISING SEA-LEVEL, SURFACE AIR-TEMPERATURE, TRACE GASES,
VOSTOK ICE-CORE


     847  
Hanninen, H. 1995. Effects of climatic-change on trees from cool and temperate regions - an
ecophysiological approach to modeling of bud burst phenology. Canadian Journal of Botany-Revue
Canadienne De Botanique 73(2):183-199.

A framework is presented for meddling bud burst phenology of trees from the cool and temperate
regions. Three ecophysiological aspects affecting the timing of bud burst are considered: (i) effects
of environmental factors on the rest status of the bud, (ii) effect of rest status on the ability for bud
burst, and (iii) direct effect of air temperature on the rate of development towards bud burst. Any
model for bud burst phenology can be presented within the framework with three submodels, each
of them addressing one of the corresponding three ecophysiological aspects. A total of 96
hypothetical models were synthesized by combining submodels presented in the literature. The models
were tested in two experiments with saplings of Pinus sylvestris L. growing in experimental chambers
at their natural site in eastern Finland. In the first experiment, air temperature and (or) concentration
of atmospheric CO2 was elevated. Elevation of the air temperature hastened bud burst, whereas
elevation of the concentration of CO2 did not affect it. Several models accurately predicted the timing
of bud burst for natural conditions but too early for bud burst at the elevated temperatures. This
finding suggests that (i) the risk of a premature bud burst with subsequent frost damage, as a result
of climatic warming, was overestimated in a recent simulation study, and (ii) bud burst observations
in natural conditions alone are not sufficient for the testing of these mechanistic models. Several
models did predict the timing of bud burst accurately for all treatments, but none of them obtained
sufficiently strong support from the findings to stand out as superior or uniquely correct. In the
second experiment a photoperiod submodel for rest break was tested by exposing the saplings to
short-day conditions. The short-day treatment had only a minor effect on the timing of bud burst.
These results demonstrated the importance of the concept of model realism: the accuracy of a model
can be lost in new conditions (e.g., global warming), unless the model correctly addresses the
essential ecophysiological aspects of the regulation of timing of bud burst.

KEYWORDS: BUDBURST, CORNUS-SERICEA L, DORMANCY RELEASE, DOUGLAS-FIR,
FLUSHING TEMPERATURE, FROST DAMAGE, PHOTOPERIOD, PLANTS, SEEDLINGS,
THERMAL TIME


     848  
Hanson, J.D., B.B. Baker, and R.M. Bourdon. 1993. Comparison of the effects of different climate
change scenarios on rangeland livestock production. Agricultural Systems 41(4):487-502.

The effect of climate change on plant and livestock production in the Great Plains of North America
is an important issue. The purpose of this study was to modify an existing rangeland ecosystem model
and to simulate a cow/calf production system under different climate scenarios. The project required
the capability of simulating rangeland livestock production under different ambient CO2
concentrations, temperatures and precipitation patterns. Climate change scenarios were created from
three general circulation models (GCMs): GISS (Goddard Institute for Space Studies model), GFDL
(Geophysical Fluid Dynamic Laboratory model), and UKMO (United Kingdom Meteorological Office
model). Results from the GCMs were used to modify the climate record for a site in northeastern
Colorado. Concomitantly, modifications were made to the SPUR model to help predict the effect of
predicted climate change on selected variables of the range/livestock ecosystem. Simulation runs
showed that predicted climate change will affect plant and animal production for rangelands. Changes
in production were more closely related to changes in temperature and precipitation than to enhanced
[CO2] alone. The effect of climate change on livestock production was very complex and results were
dependent on the particular GCM scenario being simulated.

KEYWORDS: BIOMASS, MODEL


     849  
Hao, X.M., B.A. Hale, and D.P. Ormrod. 1997. The effects of ultraviolet-B radiation and carbon
dioxide on growth and photosynthesis of tomato. Canadian Journal of Botany-Revue Canadienne
De Botanique 75(2):213-219.

Tomato (Lycopersicon esculentum Mill.) plants were exposed, in controlled environments with 2.7
Wi(m(2).day) background ultraviolet-B (UV-B) radiation from fluorescent and incandescent lamps,
to ambient (380 mu L.L-1) or elevated (600 mu L.L-1) CO2 combined with a total of 7.2 or 13.1
kJ/(m(2).day) UV-B radiation to determine effects on growth and photosynthesis. Ten consecutive
days of exposure to the higher level of UV-B significantly reduced total and stem dry weight, leaf
area, and plant height compared with the lower level. Only leaf area and plant height were
significantly reduced after 19 consecutive days of exposure. To investigate whether plants recover
from UV-B damage, the UV-B exposures were halted for 3 days after 19 days of UV-B exposure and
then restarted for a further 2 days. The largest reduction in plant growth was found after 3 days with
no UV-B followed by 2 days of the higher level of UV-B. Plants did not recover from UV-B damage
during the 3 days with background UV-B. Significant CO(2)xUV-B interactions were detected on
stem dry weight after 10 consecutive days of the higher level of UV-B and on total dry weight, leaf
dry weight, stem dry weight, and plant height after 3 days with no UV-B followed by 2 days of the
higher level of UV-B. The higher dose of enhanced UV-B resulted in more severe damage at 600 mu
L.L-1 CO than at ambient CO2. The higher level of UV-B did not affect the leaf net photosynthesis
rate on a leaf area basis, although this UV-B level may have inhibited tomato growth through
reducing the photosynthetic area. UV-absorbing compounds in leaves in the highest UV-B radiation
level for 19 days were greater than for leaves with the lower dose. These UV-absorbing compounds
in the higher UV-B dose diminished more than in the lower dose plants during the 3 days without
UV-B. The UV-absorbing compounds maintained by plants exposed to the highest level of UV-B
radiation may have protected plants from UV-B damage, particularly between 10 and 19 consecutive
days of exposure.

KEYWORDS: CO2, EXPOSURE, IRRADIATION, MUTANTS, N,N-DIMETHYLFORMAMIDE,
OZONE, PLANTS, QUALITY, RICE, YIELD


     850  
Hao, Y.Y., and R.E. Brackett. 1993. Influence of modified atmosphere on growth of vegetable
spoilage bacteria in media. Journal of Food Protection 56(3):223-228.

Six gas mixtures (CO2/O2/N2: 0/5/95, 0/10/90, 5/10/85, 5/20/75, 10/5/85, and 10/20/70) and air
were used to investigate the effect of modified atmosphere (MA) on growth of four vegetable
spoilage bacteria. In addition, we determined the ability of the MA which most inhibited spoilage
bacteria to reduce spoilage in bell peppers inoculated with the respective bacteria. In general, MA did
not significantly affect growth of the bacteria tested. Growth of Erwinia, Pseudomonas,
Xanthomonas, and Pepper # 15 (a pectinolytic Pseudomonas) at 10 and 20-degrees-C was not
significantly affected regardless of gas mixtures. At 5-degrees-C, growth of Erwinia, Xanthomonas,
and Pepper # 15 was slightly reduced by some gas mixtures (CO2/O2/N2: 0/5/95, 0/10/90, and
10/5/85; 10/5/85; 0/5/95 and 10/5/85, respectively). Modified atmosphere containing 10% CO2, 5%
O2, and 85% N2 did not reduce the ability of bacteria tested to grow at elevated concentrations of
sodium chloride. In addition, this MA composition did not change the percentage of bell peppers
spoiled by test bacteria inoculated. However, overall visual quality was enhanced by MA.

KEYWORDS: BACILLUS-CEREUS, CARBON DIOXIDE, CO2, MARKET QUALITY, MINIMALLY
PROCESSED FRUITS, PSEUDOMONAS- FLUORESCENS, SHELF-LIFE, STORAGE LIFE,
STORED BROCCOLI, ZUCCHINI SQUASH


     851  
Harley, P.C., R.B. Thomas, J.F. Reynolds, and B.R. Strain. 1992. Modeling photosynthesis of
cotton grown in elevated co2. Plant, Cell and Environment 15(3):271-282.

Cotton plants were grown in CO2-controlled growth chambers in atmospheres of either 35 or 65 Pa
CO2. A widely accepted model of C3 leaf photosynthesis was parameterized for leaves from both
CO2 treatments using non-linear least squares regression techniques, but in order to achieve
reasonable fits, it was necessary to include a phosphate limitation resulting from inadequate triose
phosphate utilization. Despite the accumulation of large amounts of starch (> 50 g m-2) in the high
CO2 plants, the photosynthetic characteristics of leaves in both treatments were similar, although the
maximum rate of Rubisco activity (Vc(max)), estimated from A versus C(i) response curves measured
at 29-degrees-C, was almost-equal-to 10% lower in leaves from plants grown in high CO2. The
relationship between key model parameters and total leaf N was linear, the only difference between
CO2 treatments being a slight reduction in the slope of the line relating Vc(max) to leaf N in plants
grown at high CO2, Stomatal conductance of leaves of plants grown and measured at 65 Pa CO2 was
approximately 32% lower than that of plants grown and measured at 35 Pa. Because photosynthetic
capacity of leaves grown in high CO2 was only slightly less than that of leaves grown in 35Pa CO2,
net photosynthesis measured at the growth CO2, light and temperature conditions was approximately
25% greater in leaves of plants grown in high CO2, despite the reduction in leaf conductance. Greater
assimilation rate was one factor allowing plants grown in high CO2 to incorporate 30% more biomass
during the first 36 d of growth.

KEYWORDS: C-3 PLANTS, CARBON DIOXIDE, DEPENDENCE, ENRICHMENT, GAS-
EXCHANGE, LEAVES, LIMITATIONS, RIBULOSE-1;5-BISPHOSPHATE CARBOXYLASE,
SPECIFICITY, TEMPERATURE


     852  
Harrison, K., W. Broecker, and G. Bonani. 1993. A strategy for estimating the impact of co2
fertilization on soil carbon storage. Global Biogeochemical Cycles 7(1):69-80.

As soils are a likely candidate for the so-called missing carbon sink, we explore the possible impact
of CO2 fertilization on the global humus inventory. For any given greening-induced enhancement of
plant growth, the increase in soil carbon inventory will depend on the spectrum of turnover times with
respect to oxidation. Here we develop estimates of carbon turnover rates based on soil radiocarbon
measurements.

KEYWORDS: BOMB-PRODUCED C-14, DIOXIDE, DISTRIBUTIONS, DYNAMICS, ORGANIC-
MATTER, RADIOCARBON, SIMULATIONS, TURNOVER, WORLD OCEAN MODEL, ZEALAND


     853  
Harrison, P.A., and R.E. Butterfield. 1996. Effects of climate change on Europe-wide winter
wheat and sunflower productivity. Climate Research 7(3):225-241.

Spatially explicit crop models were developed from mechanistic principles to investigate the regional
impacts of climate change. The approach highlights the spatial variability of crop responses to altered
environmental conditions. The mechanistic nature of the models allows some confidence to be placed
in the results that are produced under climate change scenarios. Two crop models have been
constructed and applied across a large European region: EuroWheat (winter wheat) and EuroSunfl
(sunflower). Model results were compared with observed phenology and yield across a variety of
scales and found to capture the current spatial variability in wheat and sunflower productivity.
Climate change scenarios from both equilibrium and transient general circulation model experiments
were applied to each crop model. Wheat yields are predicted to increase throughout Europe for all
climate change scenarios. Conversely, water-limited sunflower yields decrease in most regions and
scenarios. More positive effects are predicted for winter wheat than sunflower due to a lower
sensitivity to increased temperature and a higher sensitivity to elevated concentrations of CO2. The
lowest yield increases for wheat and the largest yield decreases for sunflower are found in western
Europe, whilst the most positive responses for both crops occur in central and eastern Europe.
Predictions for southern Europe are highly sensitive both within the region and between the scenarios.
The old generation of equilibrium climate change scenarios gives the worst predictions (lowest yield
increases or highest yield decreases). More beneficial responses are observed for the new generation
of transient scenarios for both wheat and sunflower. Area averaged results for Europe, based on the
United Kingdom Meterorological Office transient experiment (UKTR), indicate a rate of increase in
winter wheat yields of 0.2 t ha(-1) decade(-1) up to the 2020s and 0.36 t ha(-1) decade(-1) beyond.
Smaller changes are predicted for sunflower: a rate of decrease of 0.05 t ha(-1) decade(-1) up to the
2020s followed by an increase of 0.05 t ha(-1) decade(-1).

KEYWORDS: CO2 CONCENTRATION, GRADUAL CHANGES, GROWTH, INCREASING
CARBON-DIOXIDE, OCEAN-ATMOSPHERE MODEL, PHENOLOGY, SIMULATION-MODEL,
TEMPERATURE, TRANSIENT RESPONSES, WATER


     854  
Hartz, T.K., A. Baameur, and D.B. Holt. 1991. Carbon-dioxide enrichment of high-value crops
under tunnel culture. Journal of the American Society for Horticultural Science 116(6):970-973.

The feasibility of field-scale CO2 enrichment of vegetable crops grown under tunnel culture was
studied with cucumber (Cucumis sativus L. cv. Dasher II, summer squash (Cucurbita pepo L. cv.
Gold Bar), and tomato (Lycopersicon esculentum Mill. cv. Bingo) grown under polyethylene tunnels.
The drip irrigation system was used to uniformly deliver a CO2-enriched air stream independent of
irrigation. Carbon dioxide was maintained between 700 and 1000-mu-l.liter-1 during daylight hours.
Enrichment began immediately after crop establishment and continued for almost-equal-to 4 weeks.
At the end of the treatment phase, enrichment had significantly increased plant dry weight in the 2
years of tests. This growth advantage continued through harvest, with enriched cucumber, squash,
and tomato plots yielding 30%, 20%, and 32% more fruit, respectively, in 1989. In 1990, cucumber
and squash yields were increased 20%, and 16%, respectively. As performed, the expense of CO2
enrichment represented less than a 10% increase in total preharvest costs. A similar test was
conducted on fall-planted strawberries (Fragaria X ananassa Duch. cvs. Irvine and Chandler). Carbon
dioxide enrichment under tunnel culture modestly increased 'Irvine' yields but did not affect 'Chandler'.

KEYWORDS: CO2, GROWTH, POTATO PLANTS, RESPONSES, ROOT ZONE


     855  
Harvey, L.D.D. 1996. Development of a risk-hedging CO2-emission policy .2. Risks associated with
measures to limit emissions, synthesis, and conclusions. Climatic Change 34(1):41-71.

This paper is Part II of a two-part series in which the risks associated with unrestrained greenhouse-
gas emissions, and with measures to limit emissions, are reviewed. A sustained limitation of global
CO2 emissions requires global population stabilization, a reduction in per capita emissions in the
developed world, and a limitation of the increase in per capita emissions in the developing world.
Reducing or limiting per capita emissions requires a major effort to improve the efficiency with which
energy is transformed and used; urban development which minimizes the need for the private
automobile and facilitates district heating, cooling, and cogeneration systems; and accelerated
development of renewable energy. The following risks associated with these efforts to limit CO2
emissions are reviewed here: (i) resources might be diverted from other urgent needs; (ii) economic
growth might be reduced; (iii) reduction measures might cost more than expected; (iv) early action
might cost more than later action; (v) reduction measures might have undesired side effects; (vi)
reduction measures might require heavy-handed government intervention; and (vii) reduction
measures might not work. With gradual implementation of a diversified portfolio of measures, these
risks can be greatly reduced. Net risk is further reduced by the fact that a number of non-climatic
benefits would result from measures to limit CO2 emissions. Based on the review of risks associated
with measures to limit emissions here, and the review of the risks associated with unrestrained
emissions presented in Part I, it is concluded that a reasonable near- term (20-30 year) risk hedging
strategy is one which seeks to stabilize global fossil CO2 emissions at the present (early 1990's) level.
This in turn implies an emission reduction of 26% for industrialized countries as a whole and 40-50%
for Canada and the USA if developing country emissions are to increase by no more than 60%, which
in itself would require major assistance from the industrialized countries. The effectiveness of global
CO2-emission stabilization in slowing down the buildup of atmospheric CO2 is enhanced by the fact
that the airborne fraction (ratio of annual atmospheric CO2 increase to total annual anthropogenic
emissions) decreases if emissions are stabilized, whereas it increases if emissions continue to grow
exponentially. The framework and conclusions presented here are critically compared with so-called
optimization frameworks.

KEYWORDS: CO2 EMISSIONS, CONSERVATION, ELECTRICITY, ENERGY EFFICIENCY,
FUTURE, GLOBAL CLIMATE-CHANGE, GREENHOUSE, PERSPECTIVES, REDUCTION,
UNITED-STATES


     856  
Harwood, K.G., J.S. Gillon, A. Roberts, and H. Griffiths. 1999. Determinants of isotopic
coupling of CO2 and water vapour within a Quercus petraea forest canopy. Oecologia 119(1):109-
119.

Concentration and isotopic composition (delta(13)C and delta(18)O) of ambient CO2 and water
vapour were determined within a Quercus petraea canopy, Northumberland, UK. From continuous
measurements made across a 36-h period from three heights within the forest canopy, we generated
mixing lines (Keeling plots) for delta(a) (CO2)-C-13, delta(a) (COO)-O-18-O- 16 and delta(a)
(H2O)-O-18, to derive the isotopic composition of the signal being released from forest to
atmosphere. These were compared directly with measurements of different respective pools within
the forest system, i.e. delta(13)C of organic matter input for delta(a) (CO2)-C-13 delta(18)O Of
exchangeable water for delta(a) (COO)-O-18-O-16 and transpired water vapour for delta(a) (H2O)-
O-18. [CO2] and delta(a) (CO2)- C-13 showed strong coupling, where the released CO2 was, on
average, 4 per mil enriched compared to the organic matter of plant material in the system?
suggesting either fractionation of organic material before eventual release as soil-respired CO2, or
temporal differences in ecosystem discrimination. delta(a) (COO)-O-18-O-16 was less well coupled
to [CO2], probably due to the heterogeneity and transient nature of water pools (soil, leaf and moss)
within the forest. Similarly, delta(a) (H2O)-O-18 was less coupled to [H2O], again reflecting the
transient nature of water transpired to the forest, seen as uncoupling during times of large changes
in vapour pressure deficit. The delta(18)O of transpired water vapour, inferred from both mixing lines
at the canopy scale and direct measurement at the leaf level, approximated that of source water,
confirming that an isotopic steady state held for the forest integrated over the daily cycle. This
demonstrates that isotopic coupling of CO2 and water vapour within a forest canopy will depend on
absolute differences in the isotopic composition of the respective pools involved in exchange and on
the stability of each of these pools with time.

KEYWORDS: 3-DIMENSIONAL SYNTHESIS, ATMOSPHERIC CO2, CARBON DIOXIDE,
DISCRIMINATION, LEAF WATER, O-18 CONTENT, RAIN-FOREST, RESPIRED CO2, SPATIAL
VARIATIONS, STABLE OXYGEN


     857  
Haszpra, L. 1999. On the representativeness of carbon dioxide measurements. Journal of
Geophysical Research-Atmospheres 104(D21):26953-26960.

On the basis of the measurements at two monitoring sites located close to each other (220 km) in
plain regions in Hungary, the representativeness of low-elevation continental CO2 measurements is
estimated. It is shown that under such conditions only the measurements carried out in the early
afternoon hours can be considered as regionally representative for the CO2 content of the planetary
boundary layer (PBL). Filtering the data in this way, it is calculated that the characteristic CO2 mixing
ratio in the PBL may be about 2.5 ppm higher over this part of Europe than at the Mauna Loa
Observatory (National Oceanic and Atmospheric Administration), Hawaii.

KEYWORDS: ATMOSPHERIC CO2, BUDGET, LATITUDINAL DISTRIBUTION, MODEL,
OCEANIC UPTAKE, SINKS


     858  
Hattenschwiler, S., S. Buhler, and C. Korner. 1999. Quality, decomposition and isopod
consumption of tree litter produced under elevated CO2. Oikos 85(2):271-281.

Rising atmospheric CO2 is expected to alter plant tissue quality which in turn could affect litter
quality, decomposition, and carbon and nutrient turnover. We tested this hypothesis using leaf litter
of beech (Fagus sylvatica) and branchlets (wood + bark) of spruce (Picea abies) produced under
contrasting CO2 concentrations in model ecosystems. Both types of litter produced under elevated
CO2 had significantly lower N concentrations, but showed no CO2-related differences in carbon and
lignin concentrations. Decomposition rates (mass loss) assessed in a natural temperate forest were
significantly slower in litter produced at high CO2. However, this effect became stronger in beech
leaves but gradually disappeared in spruce branchlets over the 331-d exposure period. Irrespective
of CO2 treatment beech leaf litter lost 16% of its initial N content. Spruce branchlets produced at low
CO2 lost 50% of their initial N content, and those produced at high CO2 lost 26%. Two isopod
species representing native macro-decomposers consumed 36% more of the high CO2-produced
beech litter than they did of low CO2-produced beech litter. Only small, and non- significant increases
in consumption of high CO2-produced spruce branchlets were observed. Isopods feeding on high CO,
litter also produced more feces than those feeding litter from low CO2. Our results indicate that CO2-
induced litter quality changes influence only certain stages of decomposition. and that these stages
differ between different litter types. Inhibitory effects of elevated CO2, however, may be compensated
by the positive feed-back of intensified "litter processing" of low quality litter by macro-decomposers.
Consequently, the entire cycle of litter production and decomposition must be included in the analysis
of the potential effects of rising CO2 on litter decomposition. This includes both micro- and macro-
decomposer specific effects.

KEYWORDS: ATMOSPHERIC CO2, FOREST LITTER, HARDWOOD LEAF LITTER, LEAVES,
LIGNIN CONTENT, NEEDLE LITTER, NITROGEN DYNAMICS, RATES, SPRUCE MODEL-
ECOSYSTEMS, TERRESTRIAL ISOPODS


     859  
Hattenschwiler, S., and C. Korner. 1996. Effects of elevated CO2 and increased nitrogen
deposition on photosynthesis and growth of understory plants in spruce model ecosystems. Oecologia
106(2):172-180.

We studied the effects of-atmospheric CO, enrichment (280, 420 and 560 mu l CO2 l(-1)) and
increased N deposition (0.30 and 90 kg ha(-1) year(-1)) on the spruce-forest understory species
Oxalis acetosella, Homogyne alpina and Rubus hirtus. Clones of these species formed the ground
cover in nine 0.7 m(2) model ecosystems with 5-year-old Picea abies trees (leaf area index of approx.
2.2). Communities grew on natural forest soil in a simulated montane climate. Independently of N
deposition, the rate of light-saturated net photosynthesis of leaves grown and measured at 420 mu
l CO2 l(-1) was higher in Oxalis and in Homogyne, but was not significantly different in Rubus
compared to leaves grown and measured at the pre-industrial CO2 concentration of 280 mu l l(-1).
Remark ably, further CO2 enrichment to 560 mu l l(-1) caused no additional increase of CO2 uptake.
With increasing CO2 supply concentrations of non- structural carbohydrates in leaves increased and
N concentrations decreased in all species, whereas N deposition had no significant effect on these
traits. Above-ground biomass and leaf area production were not significantly affected by elevated
CO2 in the more vigorously growing species O. acetosella and R. hirtus, but the ''slow growing'' H.
alpina produced almost twice as much biomass and 50% more leaf area per plant under 420 mu l CO2
l(-1) compared to 280 mu l l(-1) (again no further stimulation at 560 mu l l(-1)). In contrast, increased
N addition stimulated growth in Oxalis and Rubus but had no effect on Homogyne. in Oxalis (only)
biomass per plant was positively correlated with microhabitat quantum flux density at low CO2, but
not at high CO2 indicating carbon saturation. On the other hand, the less shade-tolerant Homogyne
profited from CO2 enrichment at all understory light levels facilitating its spread into more shady
micro-habitats under elevated CO2. These species-specific responses to CO2 and N deposition will
affect community structure. The non-linear responses to elevated CO2 of several of the traits studied
here suggest that the largest responses to rising atmospheric CO2 are under way now or have already
occurred and possible future responses to further increases in CO2 concentration are likely to be
much smaller in these understory species.

KEYWORDS: ATMOSPHERIC DEPOSITION, CARBON, DECIDUOUS FOREST, HERB,
LEAVES, LIGHT, RESPONSES, VEGETATION


     860  
Hattenschwiler, S., and C. Korner. 1996. System-level adjustments to elevated CO2 in model
spruce ecosystems. Global Change Biology 2(4):377-387.

Atmospheric carbon dioxide enrichment and increasing nitrogen deposition are often predicted to
increase forest productivity based on currently available data for isolated forest tree seedlings or their
leaves. However, it is highly uncertain whether such seedling responses will scale to the stand level.
Therefore, we studied the effects of increasing CO2 (280, 420 and 560 mu L L(-1)) and increasing
rates of wet N deposition (0, 30 and 90 kg ha(-1) y(-1)) on whole stands of 4-year-old spruce trees
(Picea abies). One tree from each of six clones, together with two herbaceous understory species,
were established in each of nine 0.7 m(2) model ecosystems in nutrient poor forest soil and grown
in a simulated montane climate for two years. Shoot level light-saturated net photosynthesis measured
at growth CO2 concentrations increased with increasing CO2, as well as with increasing N
deposition. However, predawn shoot respiration was unaffected by treatments. When measured at
a common CO2 concentration of 420 mu L L(-1) 37% down-regulation of photosynthesis was
observed in plants grown at 560 mu L CO2 L(-1). Length growth of shoots and stem diameter were
not affected by CO2 or N deposition. Bud burst was delayed, leaf area index (LAI) was lower, needle
litter fall increased and soil CO2 efflux increased with increasing CO2. N deposition had no effect on
these traits. At the ecosystem level the rate of net CO2 exchange was not significantly different
between CO2 and N treatments. Most of the responses to CO2 studied here were non-linear with the
most significant differences between 280 and 420 mu L CO2 L(-1) and relatively small changes
between 420 and 560 mu L CO2 L(-1). Our results suggest that the lack of above-ground growth
responses to elevated CO2 is due to the combined effects of physiological down-regulation of
photosynthesis at the leaf level, allometric adjustment at the canopy level (reduced LAI), and
increasing strength of below-ground carbon sinks. The non- linearity of treatment effects further
suggests that major responses of coniferous forests to atmospheric CO2 enrichment might already
be under way and that future responses may be comparatively smaller.

KEYWORDS: AIR-POLLUTION, ATMOSPHERIC CO2, CARBON DIOXIDE, COMMUNITIES,
DECIDUOUS FOREST, GLOBAL CHANGE, PLANT GROWTH, RESPONSES, SEEDLINGS,
TREES


     861  
Hattenschwiler, S., and C. Korner. 1997. Annual CO2 budget of spruce model ecosystems in the
third year of exposure to elevated CO2. Acta Oecologica-International Journal of Ecology
18(3):319-325.

Clones of 4-year-old spruce trees (Picea abies) were grown in competition in model ecosystems with
nutrient-poor natural forest soil and natural understory vegetation and were exposed to three CO,
concentrations (280, 420 and 560 mu mol mol(-1)) for three years. Diurnal net ecosystem CO2
uptake (NECd), nocturnal net ecosystem CO2 loss (NECn) and soil CO2 efflux were measured
repeatedly in the third year of CO2 exposure and were used to estimate an annual ecosystem CO2
budget. The CO2 induced stimulation of NECd varied over the year with no measurable stimulation
in spring and fall but a high mid-season CO2 stimulation. Respiratory losses of whole ecosystems and
soil CO2 efflux alone were both progressively increased with increasing CO2, thus counteracting the
CO2 stimulation of photosynthesis per unit ground area. Consequently, the annual net ecosystem
CO2 uptake was only moderately and non-linearly stimulated by CO2 (+8% = 84 g C m(-2) a(-1) at
420 and +9% = 90 g C m(-2) a(-1) at 560 compared to 280 mu mol CO2 mol(-1)). We conclude that
the rising atmospheric CO2 concentration may lead to an increase in annual net ecosystem carbon
gain of rather nutrient-poor spruce communities. Our results further suggest that CO2 fertilization
effects may be greatest under current CO2 concentration and that relative increases of net ecosystem
CO2 uptake will become relatively smaller as atmospheric CO2 will continue to rise.

KEYWORDS: ALPINE GRASSLAND, CARBON DIOXIDE, CYCLE, RESPONSES


     862  
Hattenschwiler, S., and C. Korner. 1997. Growth of autotrophic and root-hemiparasitic understory
plants under elevated CO2 and increased N deposition. Acta Oecologica-International Journal of
Ecology 18(3):327-333.

Effects of atmospheric CO2 enrichment (280, 420 and 560 mu mol CO2 mol(-1)) and increased N
deposition (0, 30 and 90 kg ha(-1) a(-1)) on Oxalis acetosella, Homogyne alpina, and Melampyrum
sylvaticum, growing in model ecosystems beneath spruce stands, were studied. Aboveground biomass
in the less-shade-tolerant Homogyne and in the annual hemiparasite Melampyrum was strongly
increased with increasing CO2, but not in the more shade- adapted Oxalis. In contrast, increased N
deposition stimulated growth in Oxalis, but had no effect on Homogyne and Melampyrum. Due to
spruce canopy closure Homogyne,le became light limited and its survivorship was strongly correlated
with spruce canopy LAI in the second year of the experiment. Our results suggest, that elevated CO2
facilitates the expansion of Hamogyne into less favourable micro-habitats (deeper shade) and that
increasing N deposition enables more vigorously growing species like Oxalis to increase in
abundance. Growth of the hemiparasite Melampyrum was stimulated indirectly by increased
heterotrophic carbon supply (carbon isotope data) from the host (Picea abies), and thus, this species
may also increase in abundance with increasing CO2. However, possible indirect effects (canopy
feedbacks) make predictions of long-term understory development difficult.

KEYWORDS: CARBON, ECOSYSTEMS


     863  
Hattenschwiler, S., and C. Korner. 1998. Biomass allocation and canopy development in spruce
model ecosystems under elevated CO2 and increased N deposition. Oecologia 113(1):104-114.

Ecosystem-level experiments on the effects of atmospheric CO2 enrichment and N deposition on
forest trees are urgently needed. Here we present data for nine model ecosystems of spruce (Picea
abies) on natural nutrient-poor montane forest soil (0.7 m(2) of ground and 350 kg weight). Each
system was composed of six 7-year-old (at harvest) trees each representing a different genotype, and
a herbaceous understory layer (three species). The model ecosystems were exposed to three different
CO2 concentrations (280, 420, 560 mu l l(-1)) and three different rates of wet N deposition (0, 30,
90 kg ha(-1) year(- 1)) in a simulated annual course of Swiss montane climate for 3 years. The total
ecosystem biomass was not affected by CO2 concentration, but increased with increasing N
deposition. However, biomass allocation to roots increased with increasing CO2 leading to
significantly lower leaf mass ratios (LMRs) and leaf area ratios (LARs) in trees grown at elevated
CO2. In contrast to CO2 enrichment, N deposition increased biomass allocation to the aboveground
plant parts, and thus LMR and LAR were higher with increasing N deposition. We observed no CO2
x N interactions on growth, biomass production, or allocation, and there were also no genotype x
treatment interactions. The final leaf area index (LAI) of the spruce canopies was 19% smaller at 420
and 27% smaller at 560 than that measured at 280 mu l CO2 l(-1), but was not significantly altered
by increasing N deposition. Lower LAIs at elevated CO2 largely resulted from shorter branches (less
needles per individual tree) and partially from increased needle litterfall. Independently of N
deposition, total aboveground N content in the spruce communities declined with increasing CO2 (-
18% at 420 and -31% at 560 compared to 280 mu l CO2 l(-1)). N deposition had the opposite effect
on total above ground N content (+18% at 30 and +52% at 90 compared to 0 kg N ha(-1) year(-1)).
Our results suggest that under competitive conditions on natural forest soil, atmospheric CO2
enrichment may not lead to higher ecosystem biomass production, but N deposition is likely to do so.
The reduction in LAI under elevated CO2 suggests allometric down-regulation of photosynthetic
carbon uptake at the canopy level. The strong decline in the tree nitrogen mass per unit ground area
in response to elevated CO2 may indicate CO2- induced reductions of soil N availability.

KEYWORDS: AIR-POLLUTION, ATMOSPHERIC CO2, CARBON DIOXIDE, COMPENSATORY
RESPONSES, GLOBAL CHANGE, LEAF-AREA, MINERAL NUTRITION, NITROGEN
DEPOSITION, NORWAY SPRUCE, TERRESTRIAL ECOSYSTEMS


     864  
Hattenschwiler, S., F. Miglietta, A. Raschi, and C. Korner. 1997. Morphological adjustments of
mature Quercus ilex trees to elevated CO2. Acta Oecologica-International Journal of Ecology
18(3):361-365.

It is still not known whether mature forest trees. respond to increasing atmospheric CO2
concentrations in similar ways as seedlings do. Mature Mediterranean oaks (Quercus ilex) growing
in a CO2 enriched atmosphere around natural CO2 vents since the seedling stage showed a moderate,
age dependent increase in stem biomass production, but had significantly lower biomass of 6-year-old
branches, decreased branching, and lower leaf area per unit branch biomass, compared to control
trees at a nearby unenriched site. Our data indicate that trees in natural forest stands morphologically
adjust to increasing CO2 and reduce CO2 induced initial growth stimulations. Allometric adjustments
such as reduction in leaf area may be regarded as a ''down- regulation'' of canopy photosynthesis and
may be an effective mechanism for saving water.

KEYWORDS: ENRICHMENT, GROWTH, SEEDLINGS


     865  
Hattenschwiler, S., F. Miglietta, A. Raschi, and C. Korner. 1997. Thirty years of in situ tree
growth under elevated CO2: a model for future forest responses? Global Change Biology 3(5):463-
471.

Rising concentrations of atmospheric carbon dioxide have been predicted to stimulate the growth of
forest trees. However, long-term effects on trees growing to maturity and to canopy closure while
exposed to elevated CO2 have never been examined. We compared tree ring chronologies of
Mediterranean Quercus ilex which have been continuously exposed to elevated CO2 (around 650 mu
mol mol(-1)) since they were seedlings, near two separate natural CO2 springs with those from trees
at nearby ambient-CO2 'control' sites. Trees grown under high CO2 for 30 years (1964-93) showed
a 12% greater final radial stem width than those growing at the ambient-CO2 control sites. However,
this stimulation was largely due to responses when trees were young. By the time trees were 25-30
y old the annual difference in tree ring width between low and high CO2 grown trees had
disappeared. At any given tree age, elevated CO2 had a relatively greater positive effect on tree ring
width in years with a dry spring compared to years with more rainfall between April and May. This
indicates a beneficial effect of elevated CO2 on tree water relations under drought stress. Our data
suggest that the early regeneration phase of forest stands can be accelerated in CO2-enriched
atmospheres and that maximum biomass per land area may be reached sooner than under lower CO2
concentrations. In our study, high CO2 grown Q. ilex trees reached the same stem basal area at the
age of 26 y as control trees at 29 y,i.e. three years earlier (faster turnover of carbon?). Reliable
predictions of the future development of forests need to account for the variable responses of trees
over their entire lifetime. Such responses to elevated CO2 can presently only be assessed at such
unique field sites.

KEYWORDS: ATMOSPHERIC CO2, CARBON DIOXIDE, CHRONOLOGIES, CLIMATE,
ECOSYSTEMS, PLANTS, PRODUCTIVITY, RING-WIDTH, VEGETATION


     866  
Hattenschwiler, S., and C. Schafellner. 1999. Opposing effects of elevated CO2 and N deposition
on Lymantria monacha larvae feeding on spruce trees. Oecologia 118(2):210-217.

The effects of elevated atmospheric CO and increased wet N deposition on leaf quality and insect
herbivory were evaluated in nine model ecosystems composed of 7-year-old spruce trees (Picea abies)
and three understorey species established on natural forest soil. Each model ecosystem was grown
in a simulated montane climate, and was exposed to one of three CO2 concentrations (280, 420, and
560 mu l l(-1)) and to one of three levels of N deposition (0, 30, and 90 kg ha(-1) year(-1)) for 3
years. In the 3rd year of the experiment second to third instars of the nun moth (Lymantria monacha)
were allowed to feed directly on current-year needles of top canopy branches of each tree for 13 days.
Specific leaf area (SLA), water content, and N concentration decreased in needles exposed to
elevated CO2, whereas the concentrations of starch, condensed tannins, and total phenolics increased.
Increased N deposition had no significant effect on SLA, and water content, but the concentrations
of starch, condensed tannins, and total phenolics decreased, and sugar and N concentrations
increased. Despite higher relative consumption rates (RCRs) larvae consumed 33% less N per unit
larval biomass and per day at the two high CO2 treatments, compared to those feeding on 280 mu
l l(-1)-needles, but they maintained similar N accumulation rates due to increased N utilization
efficiencies (NUE). However, over the 12-day experimental period larvae gained less N overall and
reached a 35% lower biomass in the two high-CO2 treatments compared to those at 280 mu l l(-1).
The effects of increased N deposition on needle quality and insect performance were generally
opposite to those of CO enrichment, but were lower in magnitude. We conclude that altered needle
quality in response to elevated CO2 will impair the growth and development of L. monacha larvae.
Increasing N deposition may mitigate these effects, which could lead to altered insect herbivore
distributions depending on regional patterns of N deposition.

KEYWORDS: ATMOSPHERIC CO2, CARBON DIOXIDE, DECIDUOUS TREES, FOLIAGE,
FOOD PLANTS, GROWTH, INSECT HERBIVORE INTERACTIONS, NITROGEN,
PERFORMANCE, RESPONSES


     867  
Hattenschwiler, S., F.H. Schweingruber, and C. Korner. 1996. Tree ring responses to elevated
CO2 and increased N deposition in Picea abies. Plant, Cell and Environment 19(12):1369-1378.

Four- to seven-year-old spruce trees (Picea abies) were exposed to three CO2 concentrations (280,
420 and 560 cm(3) m(-3)) and three rates of wet N deposition (0, 30 and 90 kg ha(-1) year(- 1)) for
3 years in a simulated montane forest climate, Six trees from each of six clones were grown in
competition in each of nine 100 x 70 x 36 cm model ecosystems with nutrient-poor natural forest soil,
Stem discs were analysed using X-ray densitometry, The radial stem increment was not affected by
[CO2] but increased with increasing rates of N deposition, Wood density was increased by [CO2],
but decreased by N deposition, Woodstarch concentration increased, and wood nitrogen
concentration decreased with increasing [CO2], but neither was affected by N deposition, The lignin
concentration in wood was affected by neither [CO2] nor N deposition, Our results suggest that,
under natural growth conditions, rising atmospheric [CO2] will not lead to enhanced radial stem
growth of spruce, but atmospheric N deposition will, and in some regions is probably already doing
so, Elevated [CO2], however, will lead to denser wood unless this effect is compensated by massive
atmospheric N deposition, It can be speculated that greater wood density under elevated [CO2] may
alter the mechanical properties of wood, and higher ratios of C/N and lignin/N in wood grown at
elevated [CO2] may affect nutrient cycles of forest ecosystems.

KEYWORDS: CARBON DIOXIDE, CHRONOLOGIES, COMMUNITIES, DECOMPOSITION,
FOREST, GROWTH, NORTH-AMERICA, PLANTS, RISING ATMOSPHERIC CO2, SUMMER
TEMPERATURES


     868  
Hatton, T.J., J. Walker, W.R. Dawes, and F.X. Dunin. 1992. Simulations of hydroecological
responses to elevated CO2 at the catchment scale. Australian Journal of Botany 40(4-5):679-696.

A spatially explicit hydroecological landscape model of water, carbon and energy balances (Topog-
IRM) is described. The landscape is envisaged as a catchment forested with a single stratum
comprising Eucalyptus maculata trees. The model was used to simulate the direct effects of a 2X
elevation in atmospheric carbon dioxide at two levels of nitrogen on catchment water yield, soil
moisture status and tree growth, Experimental results used to parameterise the model are detailed.
Key features of the model are (1) an ability to scale hydrological processes at the catchment scale in
three dimensions, and (2) a means to integrate multiple factors/stresses on plant growth. The effects
of CO2 on catchment hydrology (water yield or soil moisture content) and forest growth (expressed
as leaf area index, LAI) were modelled for a 2-year period, and contrasted with the effects of added
nitrogen. Results were expressed as totals for the catchment or spatially distributed across the
catchment. For the total catchment, water yield increased in the order: high CO2 with low N, high
CO2 with high N, ambient CO2 with low N, ambient CO2 with high N. LAI increased from 3.3 to
5.7 in the order: ambient CO2 with low N, ambient CO2 with high N, high CO2 with low N, high
CO2 with high N. These results agree with previous data. New findings are: (1) with elevated CO2
a new equilibrium in transpiration is established in which leaf area increases offset decreases in
stomatal conductance; (2) the addition of nitrogen increases transpiration without any indication of
a new equilibrium being reached during the simulated period; (3) the spatial distribution of soil
moisture changes, presenting a new resource base for spatial changes to species composition and
growth rates. The major hydroecological responses to elevated CO2 are seen as increased maximum
upper canopy leaf area, increased litter inputs, especially at times of drought (hence changed fire
regimes), changes in the composition of the understorey (hence litter composition, soil microfauna,
and the spatial expression of biological diversity) and a slight increase in water yield.

KEYWORDS: ASSIMILATION, CARBON BALANCE, CLIMATE CHANGE, FOREST ECOSYSTEM
PROCESSES, GENERAL-MODEL, LEAF CONDUCTANCE, PARTIAL-PRESSURE,
PHOTOSYNTHESIS, REGIONAL APPLICATIONS, TRANSPIRATION


     869  
Hausler, R.E., P.J. Lea, and R.C. Leegood. 1994. Control of photosynthesis in barley leaves with
reduced activities of glutamine-synthetase or glutamate synthase .2. Control of electron-transport and
co2 assimilation. Planta 194(3):418-435.

Heterozygous plants of barley (Hordeum vulgare L. cv. Maris Mink) with activities of chloroplastic
glutamine synthetase (GS) between 47% and 97% of the wild-type and ferredoxin- dependent
glutamate synthase (Fd-GOGAT) activities down to 63% of the wild-type have been used to study
the control of photosynthetic fluxes. Rates of CO2 assimilation measured over a range of intercellular
CO2 concentrations and photon flux densities (PFDs) were little different in the wild-type and a
mutant with 47% GS, although total activities of ribulose-1, 5- bisphosphate carboxylase/oxygenase
(Rubisco) decreased by about 20% with a decrease in GS to 50% of the wild-type. The quantum
efficiencies of photosystem II electron transport (Phi PSII) and CO2 assimilation (Phi CO2) were
determined. Phi PSII was lower than expected in mutants with 50% less GS under conditions which
enhance the photorespiratory flux, but were identical to the wildtype under non-photorespiratory
conditions, suggesting that at high rates of photorespiration the electron requirement for net CO2
assimilation declines in plants with decreased GS. This discrepancy in the electron requirement
between the wild-type and the 47% GS mutant was enhanced at high temperatures and low CO2,
conditions which favour oxygenation by Rubisco. Photochemical and non- photochemical chlorophyll
a fluorescence quenching as well as the quantum efficiency of excitation-energy capture by open
photosystem II reaction centres were differentially affected in mutants with less GS relative to the
wild-type when CO2 was lowered or the PFD was varied. The quantum efficiencies of electron
transport in photosystems I and II were closely correlated under a range of PFDs and CO2
concentrations, confirming that the rate of linear electron transport was much lower in plants with
less GS. It is shown that GS exerts considerable control (flux control coefficients between 0.5 and
1.0) on the electron requirement for CO2 assimilation at high fluxes of photorespiration relative to
CO2 assimilation. Apart from the control of GS on protein and Rubisco contents, GS in the wild-type
has also some direct positive control on CO2 assimilation. However, negative control on CO2
assimilation was found in mutants with 50% less GS. These data, taken with the data on electron
requirements for CO2 assimilation, suggest that CO2-fixing processes other than that catalysed by
Rubisco, such as carboxylation of phosphoenolpyruvate, or an inhibition of photorespiration (e.g.
glycine decarboxylation), may contribute to the observed CO2 exchange and photosystem II electron
transport in plants with less GS. In the 63%-Fd-GOGAT mutant, rates of CO2 assimilation were
appreciably lower than in the wild-type under a range of PFDs and CO2 concentrations, which largely
reflected lower contents of Rubisco in the Fd- GOGAT mutants. Assimilation of CO2 was inhibited
appreciably at high CO2 concentrations. There was little difference in the electron requirement for
CO2 assimilation between the wild-type and mutants with less Fd-GOGAT, although there were
indications that a triose-phosphate/glycerate-3-phosphate shuttle or cyclic electron transport operates
to balance ATP generation and NADP reduction. The latter was supported by a curvilinear
relationship of photosystem I and II electron transport in the 63% Fd-GOGAT mutant. A positive
control is exerted by Fd-GOGAT on the amounts of protein and Rubisco and on CO2 assimilation.

KEYWORDS: CHLOROPHYLL FLUORESCENCE, GAS-EXCHANGE, LIGHT, PHOTOSYSTEM,
QUANTUM YIELDS, RIBULOSE-1;5-BISPHOSPHATE CARBOXYLASE-OXYGENASE, SERINE,
SPECIFICITY, SPINACH-CHLOROPLASTS, TOBACCO-LEAVES


     870  
Havstrom, M., T.V. Callaghan, and S. Jonasson. 1993. Differential growth-responses of cassiope-
tetragona, an arctic dwarf-shrub, to environmental perturbations among 3 contrasting high sites and
sub-arctic sites. Oikos 66(3):389-402.

Three populations of Cassiope tetragona (Ericaceae) were subjected to in situ environmental
perturbations simulating predictions of global warming. The populations were selected to represent
different parts of the range of the species, one growing in a high arctic coastal heath at Ny-Alesund
(Svalbard, northern part of the species' range), one at a subarctic fellfield at 1150 m a.s.l. at Abisko,
Swedish Lapland, and one in a subarctic tree-line heath at 450 m a.s.l. at Abisko, southern part of the
species' range. The manipulations included nutrient addition, shading and two levels of temperature
enhancement using passive greenhouses. The micrometeorological effects of the shading treatment
was similar to that of a mountain birch canopy and the temperature enhancement treatments had the
desired effect to increase the average air temperature by 2-4-degrees-C. Greenhouses which had a
gap between the soil and the greenhouse plastic were particularly successful in creating the desired
climatic perturbation without causing extreme maximum temperatures or other unwanted side-effects.
The environmental manipulations caused strikingly different responses in the vegetative growth
pattern of main shoots of C. tetragona among the three populations: at the subarctic tree-line heath,
nutrient addition caused a substantial increase in growth, whereas it was the temperature enhancement
treatments that caused increases, although smaller, at the subarctic fellfield and the high arctic heath
sites. At the high arctic site, we also found growth reduced in response to shading, but at the
subarctic sites, and particularly at the tree-line heath site, shading caused a marked etiolation of the
shoots. Hence, different factors seem to produce very different responses in the vegetative growth
of C. tetragona in different parts of its geographical range. We conclude that competition for nutrients
and light are the main limiting factors for the growth of Cassiope tetragona near the lower
distributional limit (LODIL) of the species, but that temperature is the main limiting factor in the
northern parts of its range, and at high altitudes in the southern parts of its range. We also suggest
that the direct effect of predicted future climatic warming on the growth of Cassiope tetragona will
increase towards the north, whereas a possible indirect effect of increasing nutrient availability
following a temperature increase will be the main effect in the southern and lower parts of its range.
These responses could, however, be modified by shading from other species responding to
environmental change by increased growth.

KEYWORDS: CLIMATIC CHANGE, ELEVATED CO2 CONCENTRATIONS, GREENHOUSE,
PLANT- COMMUNITIES, TUSSOCK TUNDRA


     871  
Haxeltine, A., and I.C. Prentice. 1996. A general model for the light-use efficiency of primary
production. Functional Ecology 10(5):551-561.

1. Net primary production (NPP) by terrestrial ecosystems appears to be proportional to absorbed
photosynthetically active radiation (APAR) on a seasonal and annual basis. This observation has been
used in 'diagnostic' models that estimate NPP from remotely sensed vegetation indices. In 'prognostic'
process-based models carbon fluxes are more commonly integrated with respect to leaf area index
assuming invariant leaf photosynthetic parameters. This approach does not lead to a proportional
relationship between NPP and APAR. However, leaf nitrogen content and Rubisco activity are known
to vary seasonally and with canopy position, and there is evidence that this variation takes place in
such a way as to nearly optimize total canopy net photosynthesis. 2. Using standard formulations for
the instantaneous response of leaf net photosynthesis to APAR, we show that the optimized canopy
net photosynthesis is proportional to APAR. This theory leads to reasonable values for the maximum
(unstressed) light-use efficiency of gross and net primary production of C-3 plants at current ambient
CO2, comparable with empirical estimates for agricultural crops and forest plantations. 3. By relating
the standard formulations to the Collatz-Farquhar model of photosynthesis, we show that a range of
observed physiological responses to temperature and CO2 can be understood as consequences of the
optimization. These responses include the CO2 fertilization response and stomatal closure in C-3
plants, the increase of leaf N concentration with decreasing growing season temperature, and the
downward acclimation of leaf respiration and N content with increasing ambient CO2. The theory
provides a way to integrate diverse experimental observations into a general framework for modelling
terrestrial primary production.

KEYWORDS: ATMOSPHERIC CO2, CARBON GAIN, CLIMATE CHANGE, CO2
CONCENTRATIONS, DAILY CANOPY PHOTOSYNTHESIS, ELEVATED CO2, LEAF NITROGEN
DISTRIBUTION, PLANTS, SOLAR RADIATION, STOMATAL CONDUCTANCE


     872  
Hdider, C., L.P. Vezina, and Y. Desjardins. 1994. Short-term studies of (no3-)-n-15 and (nh4+)-n-
15 uptake by micropropagated strawberry shoots cultured with or without co2 enrichment. Plant Cell
Tissue and Organ Culture 37(2):185-191.

The uptake of (NO3-)-N-15 and (NH4+)-N-15 has been examined in 5-,10- and 28-day-old
micropropagated strawberry (Fragaria x ananassa Duch. cv. Kent) shoots rooted in one-half strength
Murashige and Skoog (MS) liquid medium on cellulose plugs (Sorbarods). The results indicated that
the plantlets absorbed both NO3- and NH4+ during the culture with a greater uptake of NH4+ at 5
days of culture. Furthermore, a pronounced reduction in NO3- and NH4+ uptake at 10 and 28 days
of culture Ras observed within 6 h of the short-term uptake study. This reduction could be explained
by the low CO2 concentration in test tubes during the photoperiod, since no reduction in nitrogen
uptake occurred in the CO2 enriched condition. The results are interpreted as an indication of the
important role for photosynthetic CO2 fixation in the process of nitrogen uptake by the plantlets
during the rooting stage.

KEYWORDS: GROWTH, INVITRO, NITROGEN, PLANTLETS


     873  
He, P., K.P. Bader, A. Radunz, U. Kahmann, G.H. Ruppel, and G.H. Schmid. 1998. Gas
exchange characteristics in leaves of the Euphorbiacea Aleurites montana as consequence of growth
under 700 ppm CO2 in air - A study on photosynthesis and photorespiration in the Chinese tung-oil
tree. Zeitschrift Fur Naturforschung C-A Journal of Biosciences 53(3-4):151-158.

Three months old plants of the Chinese tung-oil tree Aleurites montana (Euphorbiaceae) were
cultivated for 4 months in air containing 700 ppm CO2. These plants, which grow substantially better
in the CO2-enriched atmosphere, were analyzed by mass spectrometry for photosynthesis and
photorespiration together with control plants grown all the lime in normal (350 ppm CO2) air.
Thereafter part of the plants was subjected for two weeks to 0.3 ppm SO2 in the atmosphere and
again analyzed for photosynthesis and photorespiration. Aleurites montana exhibits a strongly CO2-
dependent photosynthesis which partially explains the observed stimulatory effect of 700 ppm CO2
on growth of the plant. In control plants grown in normal air, photorespiration measured
simultaneously with photosynthesis via the uptake of O-18(2) in the light, is much lower than in C-3-
plants like tobacco (He et at, 1995, Z. Naturforsch. 50c, 781-788). In Aleurites grown in 700 ppm
CO2, however, photorespiration is completely absent in contrast to tobacco when grown under 700
ppm CO2. In tobacco, photorespiration is not inhibited to the extent of the in vitro experiments in
which plants grown at 350 ppm CO2 are measured under the increased CO2 content of 700 ppm. Gas
exchange measurements carried out by mass spectrometry show that the ratio of O-2 evolved to CO2
fixed is about 0.5. Apparently, part of the CO2 fixed is channelled into a metabolic path without
concomitant O-2-evolution. Although the plant has no succulent appearance (its leaves somehow
resemble maple leaves) apparently a Crassulacean type metabolism is performed. When Aleurites
plants grown all the time in normal air with 350 ppm, are exposed for two weeks to 0.3 ppm SO2 the
treatment completely inhibits this CO2-fixing portion which is tentatively attributed to a Crassulacean
type of metabolism. This is demonstrated by a normal C-3-type ratio O-2 evolved/CO2 fixed of 1.
When Aleurites plants, grown for 4 months in a CO2- enriched atmosphere of 700 ppm CO2, are
subjected for two weeks to 0.3 ppm SO2, the features of control plants show up again. When these
plants are tested under 350 ppm CO2 the Crassulacean type CO2-fixation apparently is not inhibited
by SO2. Photorespiration, although low is present in the same activity as in the controls. Seemingly,
an increased level of CO2 in air tends to alleviate the impact of the SO2 at least in the Chinese lung-
oil tree.

KEYWORDS: LIGHT, RATES, TOBACCO MUTANTS


     874  
He, P., K.P. Bader, A. Radunz, and G.H. Schmid. 1995. Consequences of high CO2-
concentrations in air on growth and gas-exchange rates in tobacco mutants. Zeitschrift Fur
Naturforschung C-A Journal of Biosciences 50(11-12):781-788.

Wild type tobacco N. tabacum var. John William's Broadleaf and the tobacco aurea mutant Su/su
were permanently grown under 700 ppm CO2 in air. In comparison to plants grown under 350 ppm
CO2 in air but under otherwise identical conditions growth was substantially enhanced. Gas exchange
measurements carried out by mass spectrometry show that the rate of photosynthesis in the wild type
and in the mutant is increased by more than 100%. The photorespiratory rate in the wild type
measured;as O-18(2)- uptake in the light in the ''700 ppm CO2-plants'' is not reduced to the extent
expected or deduced from experiments in which the 350 ppm system responds under in vitro
conditions to 700 ppm CO2. An analysis of the induction kinetics of room temperature fluorescence
kinetics of the adapted (700 ppm CO2) system and the control system (350 ppm CO2) under various
CO2- partial pressures shows that permanent growth under the elevated CO2-partial pressure leads
to a structural modification of the photosynthetic apparatus.

KEYWORDS: AUREA MUTANT, LIGHT, PARAMETERS, PHOTOSYNTHESIS, RESPIRATION


     875  
He, P., A. Radunz, K.P. Bader, and G.H. Schmid. 1996. Influence of CO2 and SO2 on growth
and structure of photosystem II of the Chinese tung-oil tree Aleurites montana. Zeitschrift Fur
Naturforschung C-A Journal of Biosciences 51(7-8):441-453.

Three months old plants of the Chinese tung-oil tree Alenrites montana were cultivated for 4 months
in air containing an increased amount of 700 ppm CO2. During the exposure to 700 ppm CO2 the
plants exhibited a considerably stronger growth (30- 40%) in comparison to the control plants (grown
in normal air). In these CO2-plants during the entire analyzing period the amount of soluble proteins,
of soluble sugars and the chlorophyll content were lower than in control plants. The protein content,
referred to leaf area, increased during this time in both plant types by approx. 50% but with a different
time course. The increase is faster in CO2-plants compared to control plants, and ends up with similar
values in both plants after 4 months. No difference is seen between sun and shade leaves. The
chlorophyll content in both sun and shade leaves is 20% lower in CO2-plants. Whereas the
chlorophyll content in sun leaves stays constant during development, it has increased in shade leaves
by 20% at the end of the 4 months period. The content of soluble sugars is lower in CO2-plants
compared to control plants. The difference is bigger in sun leaves than in shade leaves. The ribulose
1.5-bisphosphate carboxylase/oxygenase content almost doubles within the experimentation period,
but seems to be subject to large variations. CO2-plants contain in general less ribulose 1.5-
bisphosphate carboxylase/oxygenase than control plants. The content of coupling factor of
photophosphorylation is 20% lower in CO2-plants when compared to control plants and remains
during development more constant in CO2-plants. The molecular structure of the photosystem II-
complex undergoes under the influence of the increased CO2-content a quantitative modification. The
light harvesting complex (LHCP) and the extrinsic peptide with the molecular mass of 33 kDa
increase in CO2-plants. Gassing with SO2 (0.3 ppm in air) leads to a strong damage of the plants. The
damaging influence is already seen after 6 days and leads to a partial leaf-shedding of the tree. In the
visually still intact remaining leaves the chlorophyll content referred to unit leaf area decreases by
63%, that of soluble sugars by 65%, the content of soluble proteins and that of Rubisco decrease by
26% and 36% respectively. The light harvesting complex and the chlorophyll-binding peptides (43
and 47 kDa) increase whereas the extrinsic peptides decrease. It looks as if the simultaneous
application of SO2 (0.3 ppm) and increased CO2 (700 ppm) releaves the damaging effect of SO2.
Plant growth does not exhibit a difference in comparison to control plants. Soluble proteins and
chlorophyll increase by 27% and 33% and the ribulose 1.5-bisphosphate carboxylase/oxygenase
content as well as that of soluble sugars increases by 18 respectively 14%. The peptide composition
of photosystem II shows a quantitative modification. The LHCP increases and the chlorophyll-binding
peptides and the peptides with a molecular mass smaller than 24 kDa are reduced. The quantity of
extrinsic peptides appears unchanged. Ribulose 1,5- bisphosphate carboxylase/oxygenase and the
CF1-complex of Aleurites are immunochemically only partially identical to the corresponding
enzymes of Nicotiana tabacum as demonstrated by tandem-cross-immune electrophoresis.

KEYWORDS: ACCLIMATION, ELEVATED CO2, LEAVES, NICOTIANA-TABACUM,
ORGANIZATION, PHOTOSYNTHETIC APPARATUS, RUBISCO, SHADE PLANTS, SUN,
THYLAKOID MEMBRANES


     876  
He, X.Q., Y.H. Lin, J.X. Lin, and Y.X. Hu. 1998. Relationship between stomatal density and the
changes of atmospheric CO2 concentrations. Chinese Science Bulletin 43(11):928-930.

The relationship between the stomatal density of five woody plants endemic to China, i.e. Eucommia
ulmoides, Quercus liaotungensis, Q. glandulifera var. brevipetiolata, Cyclocarya paliurus and Ficus
heteromorpha, and the atmospheric CO2 concentrations was studied by observations on leaves of the
herbarium-stored specimens( 1920s-1990s). The results showed that the stomatal density in
Eucommia ulmoides, Quercus liaotungensis and Q. glandulifera var. brevipetiolata decreased
significantly in response to the elevated atmospheric CO2 concentrations, while in Cyclocarya
paliurus it decreased slightly and in Ficus heteromorpha there were no responses.

KEYWORDS: INCREASE, NUMBERS


     877  
He, Y., X.S. Yang, D.R. Miller, G.R. Hendrey, K.F. Lewin, and J. Nagy. 1996. Effects of face
system operation on the micrometeorology of a loblolly pine stand. Transactions of the Asae
39(4):1551-1556.

The effects of the gas injection operation on air movement in the loblolly pine stand at the Duke
Forest prototype BNL-FACE User Facility were investigated The micrometeorological conditions
were measured using three-dimensional sonic anemometers in the center of the FACE ring at two
heights, one just above the canopy (median height of the canopy = 9 m) at 11.6 m and another at 6.8
m above the ground where the canopy war the most dense. While the micrometeorological
parameters were sampled continuously at 10 Hz, the gas injection system was turned alternatively on
and off every 5 min for about 100 h. The analyses indicated that the system operation had little effect
on the micrometeorology processes above the canopy. There were small magnitude but detectable
changes in some of the micrometeorological parameters within the canopy, primarily during stable
atmospheric conditions, in response to this 5-min alternation. The gas injection operation created a
slightly diverging windfield in the top half of the canopy in the enclosed stand A slight dampening of
the vertical wind and air temperature fluctuations was detected No detectable effects on the mean,
or accumulated, heat and momentum fluxes at the measurement locations were found. in general, the
system was shown to cause minimal disturbances to the natural environment compared to traditional
carbon dioxide (CO2) enrichment facilities and it provides a better alternative for long-term ecological
studies.

KEYWORDS: CO2- ENRICHMENT


     878  
He, Z.L., S. von Caemmerer, G.S. Hudson, G.D. Price, M.R. Badger, and T.J. Andrews. 1997.
Ribulose-1,5-bisphosphate carboxylase/oxygenase activase deficiency delays senescence of ribulose-
1,5-bisphosphate carboxylase/oxygenase but progressively impairs its catalysis during tobacco leaf
development. Plant Physiology 115(4):1569-1580.

Transgenic tobacco (Nicotiana tabacum L. cv W38) plants with an antisense gene directed against
the mRNA of ribulose-1,5- biphosphate carboxylase/oxygenase (Rubisco) activase grew more slowly
than wild-type plants in a CO2-enriched atmosphere, but eventually attained the same height and
number of leaves. Compared with the wild type, the anti-activase plants had reduced CO2 assimilation
rates, normal contents of chlorophyll and soluble leaf protein, and much higher Rubisco contents,
particularly in older leaves. Activase deficiency greatly delayed the usual developmental decline in
Rubisco content seen in wild-type leaves. This effect was much less obvious in another transgenic
tobacco with an antisense gene directed against chloroplast-located glyceraldehyde-3-phosphate
dehydrogenase, which also had reduced photosynthetic rates and delayed development. Although
Rubisco carbamylation was reduced in the anti-activase plants, the reduction was not sufficient to
explain the reduced photosynthetic rate of older anti- activase leaves. Instead, up to a 10-fold
reduction in the catalytic turnover rate of carbamylated Rubisco in vivo appeared to be the main
cause. Slower catalytic turnover by carbamylated Rubisco was particularly obvious in high-CO2-
grown leaves but was also detectable in air-grown leaves. Rubisco activity measured immediately
after rapid extraction of anti- activase leaves was not much less than that predicted from its degree
of carbamylation, ruling out slow release of an inhibitor from carbamylated sites as a major cause of
the phenomenon. Nor could substrate scarcity or product inhibition account for the impairment. We
conclude that activase must have a role in vivo, direct or indirect, in promoting the activity of
carbamylated Rubisco in addition to its role in promoting carbamylation.

KEYWORDS: 1,5-BISPHOSPHATE CARBOXYLASE, CARBAMYLATION, GAS-EXCHANGE,
GENE-EXPRESSION, INHIBITION, LEAVES, OXYGENASE, PHOTOSYNTHESIS, RIBULOSE
BISPHOSPHATE CARBOXYLASE, RUBISCO ACTIVASE


     879  
Heagle, A.S., F.L. Booker, J.E. Miller, W.A. Pursley, and L.A. Stefanski. 1999. Influence of
daily carbon dioxide exposure duration and root environment on soybean response to elevated carbon
dioxide. Journal of Environmental Quality 28(2):666-675.

Little is known about effects of daily CO2 enrichment duration and root environment on plant
response to elevated CO2. Two experiments were performed,vith Essex soybean (Glycine max L,
Merr,) in open-top field chambers to address these questions. In one experiment, effects of 12 and
24 h d(-1) exposures to double-ambient CO2 were compared for plants grown in 14 L pots that were
either insulated to moderate soil temperature or not insulated. Although never significant statistically,
trends at some growth stages suggested that nighttime CO2 enrichment contributed to growth and
yield. Plants grew and yielded more in insulated than noninsulated pots, but there were no significant
CO2 enrichment X insulation interactions. In the second experiment, response to approximately 1.3,
1.6, and 1.9 times ambient CO2 was compared for plants grown in the ground or 14 L pots.
Enhancement of photosynthesis, growth, and yield by CO2 enrichment was similar in pots and in the
ground. Linear responses to different CO2 concentrations were significant for all yield components
in both root environments, whereas quadratic responses were significant for plants in pots but not for
plants in the ground. Tests of proportionality of response for yield components shelved no evidence
of significant differences between plants in pots and in the ground except weight per 100 seeds. Seed
yield enhancement at 1.9 times ambient CO2 was 36% for plants in pots and 33% for plants in the
ground. Overall, proportional response of soybean to CO2 enrichment was relatively uniform in spite
of large differences in baseline growth and yield.

KEYWORDS: ATMOSPHERIC CO2 ENRICHMENT, CHAMBERS, ENHANCEMENT, FIELD,
GROWTH, OZONE, PHOTOSYNTHETIC ACCLIMATION, PLANT-RESPONSES, YIELD
RESPONSE


     880  
Heagle, A.S., R.L. Brandenburg, J.C. Burns, and J.E. Miller. 1994. Ozone and carbon-dioxide
effects on spider-mites in white clover and peanut. Journal of Environmental Quality 23(6):1168-
1176.

Effects of O-3 and/or elevated CO2 on two-spotted spider mites (Tetranychus urticae Koch) grown
on an On-sensitive and an O-3- resistant clone of white clover (Trifolium repens L.) were measured
in greenhouse and field experiments. Peanut (Arachis hypogeae L.) 'NC-9' was used in one
greenhouse study with O-3. In field studies, O-3 treatments were charcoal filtered air (CF),
nonfiltered air (NF), and two NF treatments with On added for 12 h d(-1) at proportions of
approximate to 1.25 and 1.50 times the ambient O-3 concentration. In greenhouse studies, constant
amounts of O-3 were added to CF for 6 h d(-1) to achieve mean concentrations ranging from 5 to
100 nL L(-1). For the greenhouse O-3 X CO2 experiment, CO2 concentrations were ambient and
approximately twice-ambient for 24 h d(-1). Plants were exposed to O-3 and/or CO2 for approximate
to 7 d before infestation with mites; daily exposures continued for 14 to 28 d to allow reproduction
for at least two generations. Leaves were sampled to count eggs, larvae, nymphs, and adults. Ozone
caused more chlorosis and necrosis on the O-3-sensitive clover clone (NC-S) than on the Oa-resistant
clone (NC-R). Carbon dioxide enrichment increased shoot growth of both clones by approximate to
33%. Statistical analyses indicated significant O-3 effects in some experiments and nonsignificant O-3
effects in others. A trend toward increased mite populations with increased O-3 occurred, however,
on NC-S in all trials. No consistent trends occurred with NC-R. With peanut, a significant linear
increase in mite population occurred with increased O-3. Carbon dioxide enrichment increased the
rate of population increase on both clover clones, but more so on NC-R. At 22 to 28 d after
infestation, the total population in the twice-ambient CO2 treatment was 65% greater than in the
ambient treatment for NC-R and 22% greater than in the ambient treatment for NC-S. There were
no statistically significant interactive effects between CO2 and O-3 On mite population growth. The
apparent clone effects on mite population response to O-3 and CO2 strongly suggest that responses
were mediated through the host plants.

KEYWORDS: ALTERED FEEDING PREFERENCE, AMBIENT AIR-POLLUTION, APHID
INFESTATION, BEETLE EPILACHNA- VARIVESTIS, GROWTH, HERBIVORE INTERACTIONS,
HOST PLANTS, INSECT HERBIVORE, RESPONSES, TOP FIELD CHAMBERS


     881  
Heagle, A.S., J.E. Miller, and F.L. Booker. 1998. Influence of ozone stress on soybean response
to carbon dioxide enrichment: I. Foliar properties. Crop Science 38(1):113-121.

Tropospheric O-3 can cause foliar injury, decreased growth, and decreased yield, whereas CO2
enrichment generally causes opposite effects. Little is known about plant response to mixtures of O-3
and CO2. Open-top field chambers were ere used to determine if foliar responses of soybean [Glycine
max (L.) Merr.] to CO2 enrichment are affected by O-3 stress and vice versa. Plants were grown in
14-L pots and exposed to four CO2 and three O-3 concentrations in 12 combinations. The CO2
treatments were ambient (366 mu L L-1) and three treatments with CO2 added for 24 h d(-1) at
approximately 1.3, 1.6, and 2.0 times ambient. The O-3 treatments were charcoal-filtered air (CF),
nonfiltered air (NF), and NF with O-3 added for 12 h d(-1) (NF+), resulting in seasonal
concentrations of approximately 20, 46, and 75 nL L-1. Foliar effects of CO2 enrichment were
dependent on the amount of stress caused by O-3 In the CF treatment, plants were not stressed by
O-3, and CO2 enrichment caused chlorosis and decreased chlorophyll. In the IVF and NF+
treatments, plants were stressed by O-3, and CO2 enrichment suppressed chlorosis and increased
chlorophyll. Ozone decreased specific leaf weight, increased foliar N and C, and decreased C/N
ratios, whereas CO2 caused opposite responses for these measures. Ozone increased foliar S and B
but did not affect P or K concentrations. Conversely, CO2 enrichment suppressed foliar S, B, P, and
K concentrations. These interactions between O-3 and CO2 emphasize a need to consider the amount
of plant stress caused by O-3 in studies to measure effects of CO2 enrichment.

KEYWORDS: AGRICULTURAL CROPS, ASSESSING IMPACTS, ATMOSPHERIC CO2
ENRICHMENT, CHLOROPHYLL CONTENT, ELEVATED CO2, EXCHANGE-RATE, GAS-
EXCHANGE, GROWTH, NITROGEN NUTRITION, PLANT-RESPONSES


     882  
Heagle, A.S., J.E. Miller, F.L. Booker, and W.A. Pursley. 1999. Ozone stress, carbon dioxide
enrichment, and nitrogen fertility interactions in cotton. Crop Science 39(3):731-741.

Ozone (O-3) in the troposphere can cause plant stress leading to foliar injury and suppressed growth
and yield, whereas elevated CO2 generally enhances growth and yield. Numerous studies have been
performed to determine effects of O-3 and CO2 separately, but relatively few have been performed
to determine if O-3 can affect plant response to CO2 or vice versa. Open-top field chambers were
used to determine if such interactions occur for cotton (Gossypium hirsutum L.), which is relatively
sensitive to O-3. Nitrogen nutrition is especially important in cotton production so N nutrition was
included as an experimental factor. Plants were grown in 14-L pots at low, medium, and high soil N
levels and exposed to three CO2 and two or three O-3 treatments in all combinations during two
seasons. The CO2 treatments were ambient (370 mu L L-1) and two treatments with CO2 added for
24 h d(-1) at approximately 1.5 and 2.0 Limes ambient. In 1995, the O-3 treatments were charcoal
filtered air (CP), and nonfiltered air (NF) with O-3 added for 12 h d(-1) (NF+). In 1996, a NF
treatment was also included to represent ambient O-3 conditions. The CF, NF, and NF+ treatments
resulted in seasonal O-3 concentrations of approximately 23, 51, and 75 nL L-1. Carbon dioxide
enrichment generally stimulated growth and yield whereas O-3 exposure suppressed growth. and
yield. Stimulation induced by CO2 increased as O-3 stress increased. For example, in 1995 at medium
N, the percentage increase in yield caused by doubling CO2 in CF air was 0%, but was 52% in NF+
air. Comparable values for 1996 were 23% in CF air and 140% in NF+ air. These interactions
occurred for a range of soil N levels, and were probably caused by CO2-induced prevention of O-3
stress. The results emphasize the need to consider O-3 x CO2 interactions to ensure correct
interpretation of cause-effect relationships in CO2 enrichment studies with crops that are sensitive
to O-3.

KEYWORDS: ATMOSPHERIC CO2, CHAMBERS, ELEVATED CO2, FACE, GROWTH, INJURY,
PLANT-RESPONSES, SOIL MOISTURE, SOYBEAN RESPONSE, YIELD RESPONSE


     883  
Heagle, A.S., J.E. Miller, and W.A. Pursley. 1998. Influence of ozone stress on soybean response
to carbon dioxide enrichment: III. Yield and seed quality. Crop Science 38(1):128-134.

Ozone in the troposphere can cause plant stress, whereas elevated CO2 generally causes positive
responses. Little is known of how these gases interact to affect plant response. Interactive effects on
yield and seed quality of soybean [Glycine max (L.) Merr.] grown in 14-L pots were measured in
open-top field chambers. Essex was tested in 1993, and Essex, Holladay, and NK 6955 were tested
in 1994. Plants were exposed from emergence to maturity to four CO2 levels (ambient and 1.3, 1.6,
and 2.0 times ambient) and three O-3 levels (0.4, 0.9, and 1.5 times ambient) in 12 combinations.
Increasing O-3 suppressed growth and yield, whereas CO2 enrichment stimulated growth and yield.
Carbon dioxide-induced stimulation was greater for plants stressed by O-3 than for non stressed
plants. For example, CO2 at 2.0 times ambient increased 2-yr mean seed yield of Essex by 16, 24, and
81% at O-3 levels of O.4, 0.9, and 1.5 times ambient, respectively. Effects of O-3 and CO2 on seed
oil content were variable with numerous cultivar differences. Seed protein content was never affected.
Elevated O-3 suppressed oleic acid content in seeds, whereas CO2 increased it; the nature of the O-3
x CO2 interaction for oleic acid was similar to that observed for most yield measures. Carbon
dioxide-induced stimulation of plants stressed by O-3 was apparently caused partly by amelioration
of O-3 stress. Interactions between O-3 and CO2 must be considered for proper interpretation of
cause-effect relationships in CO2 enrichment studies.

KEYWORDS: CHAMBERS, CO2, FIELD, GROWTH, O-3


     884  
Heagle, A.S., J.E. Miller, D.E. Sherrill, and J.O. Rawlings. 1993. Effects of ozone and carbon-
dioxide mixtures on 2 clones of white clover. New Phytologist 123(4):751-762.

The effects of mixtures of ozone and carbon dioxide on growth and physiology of an O3-sensitive
(NC-S) and an O3-resistant (NC-R) clone of white clover (Trifolium repens L.) were determined. The
experiment was performed in a greenhouse with O3 treatments of 5 and 82 nl l-1 (ppb) for 6 h d-1
and CO2 treatments of 380 (ambient), 490,600, and 710 mul l-1 (ppm) for 24 h d-1. Enrichment with
CO2 decreased foliar gas exchange (measured as stomatal resistance) of NC-R more than that of NC-
S whereas O3 decreased gas exchange of NC-S more than that of NC-R. Ozone caused extensive
foliar injury of NC-S but caused only slight injury of NC-R. CO2 enrichment suppressed O3- induced
foliar injury of NC-S as measured after 4 wk of exposure, but this effect diminished after 8 wk of
exposure. CO2 enrichment decreased the relative chlorophyll content (mug of chlorophyll mg-1 of
leaf tissue sampled) but not the total chlorophyll (total chlorophyll in the leaves sampled). There were
no O3 x CO2 interactions for foliar chlorophyll. High concentrations of CO2 caused reddening of
new leaves near the end of the 8 wk exposure period. CO2 enrichment decreased foliar concentrations
of N, P, K, S, Cu, B, and Fe, increased foliar concentrations of Mn, but did not affect Zn, Ca, or Mg.
Ozone exposure did not modify the CO2 effects on foliar nutrient concentration. Ozone decreased
growth of NC-S but not NC-R while CO2 enrichment stimulated growth of both clones. The highest
CO2 concentration appeared to decrease the effects of O3 on growth of NC-S. However, except for
a transitory effect on foliar injury, there was no evidence that CO2, at concentrations less than the
highest used in this study, will protect white clover from the effects of tropospheric O3.

KEYWORDS: AGRICULTURAL CROPS, ASSESSING IMPACTS, ATMOSPHERIC CO2
ENRICHMENT, ELEVATED CO2, GROWTH, LADINO CLOVER, LOLIUM-PERENNE L,
MANAGED MODEL-ECOSYSTEMS, TALL FESCUE PASTURE, WATER-USE


     885  
Heath, J. 1998. Stomata of trees growing in CO2-enriched air show reduced sensitivity to vapour
pressure deficit and drought. Plant, Cell and Environment 21(11):1077-1088.

Stomatal conductance (g(s)) and photosynthetic rate (A) mere measured in young beech (Fagus
sylvatica), chestnut (Castanea sativa) and oak (Quercus robur) growing in ambient or CO2- enriched
air. In oak, g(s) was consistently reduced in elevated CO2, However, in beech and chestnut, the
stomata of trees growing in elevated CO2 failed to close normally in response to increased leaf-to-air
vapour pressure deficit (LAVPD). Consequently, while g(s) was reduced in elevated CO2 on days
with low LAVPD, on warm sunny days (with correspondingly high LAVPD) g(s) was unchanged or
even slightly higher in elevated CO2. Furthermore, during drought, g(s) of beech and chestnut was
unresponsive to [CO2], over a wide range of ambient LAVPD, whereas in oak g(s) was reduced by
an average of 50% in elevated CO2. Stimulation of A by elevated CO2 in beech and chestnut was
restricted to days with high irradiance, and was greatest in beech during drought. Hence, most of the
additional carbon gain in elevated CO2 was made at the expense of water economy, at precisely those
times (drought, high evaporative demand) when mater conservation was most important. Such effects
could have serious consequences for drought tolerance, growth and, ultimately, survival as
atmospheric [CO2] increases.

KEYWORDS: ABSCISIC- ACID, ATMOSPHERIC CO2, ELEVATED CARBON-DIOXIDE, FAGUS-
SYLVATICA, GUARD-CELL, HYDRAULIC CONDUCTANCE, LEAF GAS- EXCHANGE,
RESPONSES, SIGNAL-TRANSDUCTION, WATER-LOSS REGULATION


     886  
Heath, J., and G. Kerstiens. 1997. Effects of elevated CO2 on leaf gas exchange in beech and oak
at two levels of nutrient supply: Consequences for sensitivity to drought in beech. Plant, Cell and
Environment 20(1):57-67.

Beech (Fagus sylvatica L.) and pedunculate oak (Quercus robur L,) were grown from seed for two
whole seasons at two CO, concentrations (ambient and ambient + 250 mu mol mol(-1)) with two
levels of soil nutrient supply, Measurements of net leaf photosynthetic rate (A) and stomatal
conductance (g(s)) of well-watered plants were taken over both seasons; a drought treatment was
applied in the middle of the second growing season to a separate sample of beech drawn from the
same population, The net leaf photosynthetic rate of well-watered plants was stimulated in elevated
CO2 by an average of 75% in beech and 33% in oak; the effect continued through both growing
seasons at both nutrient levels, There were no interactive effects of CO2 concentration and nutrient
level on A or g(s) in beech or oak, Stomatal conductance was reduced in elevated CO2 by an average
of 34% in oak, but in beech there were no significant reductions in g(s) except under cloudy
conditions (-22% in elevated CO2), During drought, there was no effect of CO2 concentration on
g(s) in beech grown with high nutrients, but for beech grown with low nutrients, g(s) was significantly
higher in elevated CO2, causing more rapid soil drying, With high nutrient supply, soil drying was
more rapid at elevated CO2 due to increased leaf area, It appears that beech may substantially
increase whole-plant water consumption in elevated CO2, especially under conditions of high
temperature and irradiance when damage due to high evaporative demand is most likely to occur,
thereby putting itself at risk during periods of drought.

KEYWORDS: ATMOSPHERIC CO2, CARBON DIOXIDE, FAGUS-SYLVATICA L, FOREST,
GROWTH, PHOTOSYNTHESIS, PLANTS, RESPONSES, SEEDLINGS, WATER-USE EFFICIENCY


     887  
Heath, J., G. Kerstiens, and M.T. Tyree. 1997. Stem hydraulic conductance of European beech
(Fagus sylvatica L.) and pedunculate oak (Quercus robur L.) grown in elevated CO2. Journal of
Experimental Botany 48(312):1487-1489.

Over two seasons in c. 600 ppm CO2, oak had lower stomatal conductance in CO2-enriched
compared to ambient air, Beech showed no response to CO2 concentration on sunny days, Mirroring
this pattern, exposure to elevated CO2 reduced whole- shoot hydraulic conductance per unit leaf area
in oak, but not in beech.

KEYWORDS: CARBON DIOXIDE, DROUGHT, PLANTS, SEEDLINGS, WATER-USE


     888  
Hebeisen, T., A. Luscher, and J. Nosberger. 1997. Effects of elevated atmospheric CO2 and
nitrogen fertilisation on yield of Trifolium repens and Lolium perenne. Acta Oecologica-International
Journal of Ecology 18(3):277-284.

Trifolium repens L. and Lolium perenne L. were grown in monocultures and bi-species mixture in a
Free Air Carbon Dioxide Enrichment (FACE) experiment at elevated (60 Pa) and ambient (35 Pa)
CO2 partial pressure (pCO(2)) for two years. The effects of nitrogen fertilisation (10 and 42 g N m(-
2) a(- 1) in 1993; 14 and 56 g N m(-2) a(-1) in 1994) on the growth response to pCO, were
investigated in frequently defoliated (7 cuts in 1993; 8 cuts in 1994) swards. The yield of Trifolium
in monocultures increased by 22% when grown at elevated pCO(2). In contrast, the yield of Lolium
monocultures was not affected (2%) by elevated pCO(2), whereas Lolium increased its root mass
considerably. The consequence of these interspecific differences in the CO2 response was an increase
in the proportion of Trifolium in the mixed swards from 39% at ambient to 50% at elevated pCO(2).
However, the proportion of the species was more strongly affected by N fertilisation than by elevated
pCO(2). Based on these 2' results, we conclude that the species proportion in managed grassland may
change as the CO2 concentration increases. However, an adapted management may, at least partially,
counteract such CO2 induced changes in the proportion of the species.

KEYWORDS: CARBON, ENRICHMENT, GRASSLAND, GROWTH, RYEGRASS, WHITE CLOVER


     889  
Hebeisen, T., A. Luscher, S. Zanetti, B.U. Fischer, U.A. Hartwig, M. Frehner, G.R. Hendrey,
H. Blum, and J. Nosberger. 1997. Growth response of Trifolium repens L and Lolium perenne L
as monocultures and bi-species mixture to free air CO2 enrichment and management. Global Change
Biology 3(2):149-160.

Trifolium repens L. and Lolium perenne L. were grown in monocultures and bi-species mixture in a
Free Air Carbon Dioxide Enrichment (FACE) experiment at elevated (60 Pa) and ambient (35 Pa)
CO2 partial pressure (pCO(2)) for three years. The effects of defoliation frequencies (4 and 7 cuts
in 1993; 4 and 8 cuts in 1994/95) and nitrogen fertilization (10 and 42 g m(-2) y(-1) N in 1993; 14
and 56 g m(-2) y(-1) in 1994/95) on the growth response to pCO(2) were investigated. There were
significant interspecific differences in the CO2 responses during the first two years, while in the third
growing season, these interspecific differences disappeared. Yield of T. repens in monocultures
increased in the first two years by 20% when grown at elevated pCO(2). This CO2 response was
independent of defoliation frequency and nitrogen fertilization. In the third year, the CO2 response
of T. repens declined to 11%. In contrast, yield of L. perenne monocultures increased by only 7% on
average over three years at elevated pCO(2). The yield response of L. perenne to CO2 changed
according to defoliation frequency and nitrogen fertilization, mainly in the second and third year. The
ratio of root/yield of L. perenne increased under elevated pCO(2), low N fertilizer rate, and frequent
defoliation, but it remained unchanged in T. repens. We suggest that the more abundant root growth
of L. perenne was related to increased N limitation under elevated pCO(2). The consequence of these
interspecific differences in the CO2 response was a higher proportion of T. repens in the mixed
swards at elevated pCO(2). This was evident in all combinations of defoliation and nitrogen
treatments. However, the proportion of the species was more strongly affected by N fertilization and
defoliation frequency than by elevated pCO(2). Based on these results, we conclude that the species
proportion in managed grassland may change as the CO2 concentration increases. However, an
adapted management could, at least partially, counteract such CO2 induced changes in the proportion
of the species. Since the availability of mineral N in the soil may be important for the species'
responses to elevated pCO(2), more long-term studies, particularly of processes in the soil, are
required to predict the entire ecosystem response.

KEYWORDS: ATMOSPHERIC CO2, CARBON-DIOXIDE CONCENTRATION, ELEVATED CO2,
GRASS, MINERAL NUTRITION, NITROGEN-FERTILIZER, ROOT-GROWTH, RYEGRASS,
TALLGRASS PRAIRIE, WHITE CLOVER


     890  
Hedges, L.V., J. Gurevitch, and P.S. Curtis. 1999. The meta-analysis of response ratios in
experimental ecology. Ecology 80(4):1150-1156.

Meta-analysis provides formal statistical techniques for summarizing the results of independent
experiments and is increasingly being used in ecology. The response ratio (the ratio of mean outcome
in the experimental group to that in the control group) and closely related measures of proportionate
change are often used as measures of effect magnitude in ecology. Using these metrics for meta-
analysis requires knowledge of their statistical properties, but these have not been previously derived.
We give the approximate sampling distribution of the log response ratio, discuss why it is a
particularly useful metric for many applications in ecology, and demonstrate how to use it in meta-
analysis. The meta- analysis of response-ratio data is illustrated using experimental data on the effects
of increased atmospheric CO2 on plant biomass responses.

KEYWORDS: CO2, METAANALYSIS


     891  
Heifetz, P.B., A. Lers, D.H. Turpin, N.W. Gillham, J.E. Boynton, and C.B. Osmond. 1997. dr
and spr/sr mutations of Chlamydomonas reinhardtii affecting D1 protein function and synthesis define
two independent steps leading to chronic photoinhibition and confer differential fitness. Plant, Cell
and Environment 20(9):1145-1157.

The effects of introduced chloroplast gene mutations affecting D1 synthesis, turnover and function
on photosynthesis, growth and competitive ability were examined in autotrophic cultures of
Chlamydomonas reinhardtii (Chlorophyta) adapted to low or high irradiance. Few discernible effects
were evident when the mutants were grown in low light (LL, 70 mu mol m(-2) s(-1)). The herbicide-
resistant psbA mutation Ser(264) --> Ala (dr) slowed electron transfer and accelerated D1
degradation in cells grown under high light (HL, 600 mu mol m(-2) s(-1)). The maximum rate of
light- and CO2-saturated photosynthesis, cell growth rate and competitive ability in the dr mutant
were reduced compared to wild type under HL. However, the wild-type rate of D1 synthesis in dr
was adequate to compensate for accelerated D1 degradation. 16S rRNA mutations conferring
resistance to streptomycin and spectinomycin (spr/sr) that altered chloroplast ribosome structure and
assembly were used to inhibit chloroplast protein synthesis. In spr/sr cells grown under HL, D1
synthesis was reduced by 40-60% compared to wild type and D1 degradation was accelerated,
leading to a 4-fold reduction in D1 pool size. The reduced D1 levels were accompanied by an
elevation of F-o and a decline in F-v/F-m, quantum yield and maximum rate of CO2-saturated
photosynthesis. Chemostat experiments showed that the growth rate and competitive ability of spr/sr
were reduced against both wild type and dr.

KEYWORDS: 32-KILODALTON PROTEIN, CHLOROPHYLL FLUORESCENCE,
CHLOROPLAST, LIGHT-INTENSITY, PHALARIS-PARADOXA, PHOTOSYNTHESIS,
PHOTOSYSTEM, RIBOSOMAL-RNA GENES, TRIAZINE RESISTANCE, ULVA-ROTUNDATA


     892  
Heilman, J.L., D.R. Cobos, F.A. Heinsch, C.S. Campbell, and K.J. McInnes. 1999. Tower-based
conditional sampling for measuring ecosystem-scale carbon dioxide exchange in coastal wetlands.
Estuaries 22(3A):584-591.

Long-term measurements of CO2 exchange between coastal wetlands and the atmosphere are
necessary to improve our understanding of the role these ecosystems play in the global carbon cycle,
and the response of these systems to environmental change. We conducted research to adapt and
evaluate tower-based conditional sampling as a method for measuring net CO2 exchange (NCE) at
the ecosystem scale on a continuous basis. With conditional sampling, NCE is determined from the
product of the standard deviation of vertical wind velocity, the difference in CO2 concentration
between updrafts and downdrafts in the constant flux portion of the boundary layer above the surface,
and an empirical coefficient. We constructed a system that used a sonic anemometer to measure
vertical wind velocity (w) and control a high-speed three-way valve that diverted air from updrafts
and down,drafts into separate sample lines, depending on the direction of w. An infrared gas analyzer
was used to measure the concentration difference. The conditional sampling system was installed and
tested in a marsh in the Nueces River Delta near Corpus Christi, Texas, as part of a long-term study
of effects of freshwater inflow on CO2 flux. System accuracy was evaluated by comparing conditional
sampling measurements of water vapor flux with independent estimates obtained with the Bowen
ratio method. Average daily flux estimates for the two methods agreed to within 13%. Measurements
showed that freshwater inflow due to flooding of the Nueces River increased NCE by increasing CO2
assimilation and decreasing CO2 efflux. Over a 65-d period, daily NCE varied from a maximum gain
of 0.16 mol CO2 m(-2) d(-1) during flooding to a maximum loss of - 0.14 mol CO2 m(-2) d(-1) when
the marsh dried. Our study showed that conditional sampling was well suited for quantifying CO2
exchange in coastal wetlands on a diel, daily, and seasonal basis.

KEYWORDS: ATMOSPHERIC CO2 CONCENTRATION, CANOPY PHOTOSYNTHESIS,
CHESAPEAKE BAY, CROP, ELEVATED CO2, FIELD, FLUX MEASUREMENT,
SEQUESTRATION, USE EFFICIENCY, WATER


     893  
Heineke, D., F. Kauder, W. Frommer, C. Kuhn, B. Gillissen, F. Ludewig, and U. Sonnewald.
1999. Application of transgenic plants in understanding responses to atmospheric change. Plant, Cell
and Environment 22(6):623-628.

Acclimation of plants to an increase in atmospheric carbon dioxide concentration is a well described
phenomenon, It is characterized by an increase in leaf carbohydrates and a degradation of ribulose
1,5-bisphosphate carboxylase protein (Rubisco) leading in the long term to a lower rate of CO2
assimilation than expected from the kinetic constants of Rubisco, This article summarizes studies with
transgenic plants grown in elevated pCO(2) which are modified in their capacity of CO2 fixation, of
sucrose and starch synthesis, of triosephosphate and sucrose transport and of sink metabolism of
sucrose, These studies show that a feedback accumulation of carbohydrates in leaves play only a
minor role in acclimation, because leaf starch synthesis functions as an efficient buffer for
photoassimilates. There is some evidence that in elevated pCO(2), plants grow faster and senescence
is induced earlier.

KEYWORDS: ANTISENSE REPRESSION, ELEVATED CO2, EXPRESSION, INHIBITION,
PHOTOSYNTHETIC ACCLIMATION, POTATO PLANTS, RIBULOSE-1;5-BISPHOSPHATE
CARBOXYLASE-OXYGENASE, TOBACCO, TRIOSE-PHOSPHATE TRANSLOCATOR, YEAST-
DERIVED INVERTASE


     894  
Heissner, A. 1996. A simple model of greenhouse climate for short term control of temperature, air
humidity, and CO2 concentration. Gartenbauwissenschaft 61(6):289-300.

A simple greenhouse climate model was designed for short term control of temperature, air humidity,
and CO2 concentration. The model is based on the balances of thermal energy, water vapour, and
carbon dioxide and is represented by a system of three nonlinear differential equations of the first
order. The reaction of the canopy is taken into consideration through empirical models of CO2 gas
exchange and transpiration of tomato plants. Model inputs are the meteorological conditions in the
open (temperature, air humidity, CO2 concentration, global radiation, and wind velocity), the
temperature of the ground surface in the greenhouse, and the temperature on the greenhouse cover
as well as four control variables (heating, ventilation, CO2 enrichment, and moistening of the air).
Measurements were carried out in two greenhouses with glass and plastic film cover under conditions
of ventilation to estimate model quantities and to test the suitability of the model fort prognosis. By
means of simulations possibilities for the comparison of control strategies were demonstrated.

KEYWORDS: SYSTEM, TRANSPIRATION


     895  
Hemming, J.D.C., and R.L. Lindroth. 1999. Effects of light and nutrient availability on aspen:
Growth, phytochemistry, and insect performance. Journal of Chemical Ecology 25(7):1687-1714.

This study explored the effect of resource availability on plant phytochemical composition within the
framework of carbon- nutrient balance (CNB) theory. We grew quaking aspen (Populus tremuloides)
under two levels of light and three levels of nutrient availability and measured photosynthesis,
productivity, and foliar chemistry [water, total nonstructural carbohydrates (TNC), condensed
tannins, and phenolic glycosides]. Gypsy moths (Lymantria dispar) and forest tent caterpillars
(Malacosoma disstria) were reared on foliage from each of the treatments to determine effects on
insect performance. Photosynthetic rates increased under high light, but were not influenced by
nutrient availability. Tree growth increased in response to both the direct and interactive effects of
light and nutrient availability. Increasing light reduced foliar nitrogen, while increasing nutrient
availability increased foliar nitrogen. TNC levels were elevated under high light conditions, but were
not influenced by nutrient availability. Starch and condensed tannins responded to changes in resource
availability in a manner consistent with CNB theory; levels were highest under conditions where tree
growth was limited more than photosynthesis (i.e., high light-low nutrient availability).
Concentrations of phenolic glycosides, however, were only moderately influenced by resource
availability. In general, insect performance varied relatively little among treatments. Both species
performed most poorly on the high light-low nutrient availability treatment. Because phenolic
glycosides are the primary factor determining aspen quality for these insects, and because levels of
these compounds were minimally affected by the treatments, the limited response of the insects was
not surprising. Thus, the ability of CNB theory to accurately predict allocation to defense compounds
depends on the response of specific allelochemicals to changes in resource availability. Moreover,
whether allelochemicals serve to defend the plant depends on the response of insects to specific
allelochemicals. Finally, in contrast to predictions of CNB theory, we found substantial allocation to
storage and defense compounds under conditions in which growth was carbon-limited (e.g., low
light), suggesting a cost to defense in terms of reduced growth.

KEYWORDS: BETULA-PENDULA ROTH, CLONAL VARIATION, ELEVATED ATMOSPHERIC
CO2, FOLIAR CHEMISTRY, FOREST TENT CATERPILLARS, HARDWOOD SEEDLINGS,
MINERAL NUTRITION, NO3 AVAILABILITY, POPULUS-TREMULOIDES MICHX,
SUCCESSIONAL STATUS


     896  
Hendrey, G.R. 1992. Global greenhouse studies - need for a new approach to ecosystem
manipulation. Critical Reviews in Plant Sciences 11(2-3):61-74.

KEYWORDS: BALANCE, CARBON DIOXIDE, ELEVATED ATMOSPHERIC CO2,
ENRICHMENT, FIELD, GROWTH, PHOTOSYNTHESIS, RESPONSES, TEMPERATURE,
TUSSOCK TUNDRA


     897  
Hendrey, G.R., D.S. Ellsworth, K.F. Lewin, and J. Nagy. 1999. A free-air enrichment system for
exposing tall forest vegetation to elevated atmospheric CO2. Global Change Biology 5(3):293-309.

A free-air CO2 enrichment (FACE) system was designed to permit the experimental exposure of tall
vegetation such as stands of forest trees to elevated atmospheric CO2 concentrations ([CO2](a))
without enclosures that alter tree microenvironment. We describe a prototype FACE system currently
in operation in forest plots in a maturing loblolly pine(Pinus taeda L.) stand in North Carolina, USA.
The system uses feedback control technology to control [CO2] in a 26 m diameter forest plot that
is over 10 m tall, while monitoring the 3D plot volume to characterize the whole-stand CO2 regime
achieved during enrichment. in the second summer season of operation of the FACE system,
atmospheric CO2 enrichment was conducted in the forest during all daylight hours for 96.7% of the
scheduled running time from 23 May to 14 October with a preset target [CO2] of 550 mu mol mol(-
1), approximate to 200 mu mol mol(-1) above ambient [CO2]. The system provided spatial and
temporal control of [CO2] similar to that reported for open-top chambers over trees, but without
enclosing the vegetation. The daily average daytime [CO2] within the upper forest canopy at the
centre of the FACE plot was 552 +/- 9 mu mol mol-l (mean +/- SD). The FACE system maintained
I-minute average [CO2] to within +/- 110 mu mol mol(-1) of the target [CO2] for 92% of the
operating time. Deviations of [CO2] outside of this range were short-lived (most lasting < 60 s) and
rare, with fewer than 4 excursion events of a minute or longer per day. Acceptable spatial control of
[CO2] by the system was achieved,,with over 90% of the entire canopy volume within +/- 10% of
the target [CO2] over the exposure season. CO2 consumption by the FACE system was much higher
than for open- top chambers on an absolute basis, but similar to that of open- top chambers and
branch bag chambers on a per unit volume basis. CO2 consumption by the FACE system was strongly
related to windspeed, averaging 50 g CO2 m(-3) h(-1) for thestand for an average windspeed of 1.5
m s(-1) during summer. The [CO2] control results show that the free-air approach is a tractable way
to study long-term and short-term alterations in trace gases, even within entire tall forest ecosystems.
The FACE approach permits the study of a wide range of forest stand and ecosystem processes under
manipulated [CO2](a) that were previously impossible or intractable to study in true forest
ecosystems.

KEYWORDS: CARBON-DIOXIDE CONCENTRATION, FACE, FIELD CROPS, GROWTH, OPEN-
TOP CHAMBERS, PHOTOSYNTHESIS, PINE PINUS- TAEDA, SHORT- TERM, STOMATAL
CONDUCTANCE, TEMPERATE TREES


     898  
Hendrey, G.R., and B.A. Kimball. 1994. The face program. Agricultural and Forest Meteorology
70(1-4):3-14.

A large, cooperative, integrated experimental program utilizing free-air CO2 enrichment (FACE) is
being conducted to expose plants to elevated concentrations of CO2. The goals are to evaluate the
effects of increasing atmospheric CO2 on plants and ecosystems and, in the long run, to contribute
to the evaluation of terrestrial plant feedback regulation on the rate of change of CO2 in the
atmosphere. Having no walls, the FACE system allows plants to be grown under realistic
microclimate and CO2 conditions expected to prevail in the mid-twenty-first century. Data obtained
under such conditions are needed for validation of models being developed to predict the effects of
increasing CO2 and changing climate variables on plants, ecosystems, agricultural productivity and
water resources. Setup costs for the FACE systems used in these experiments are similar to the costs
of field chamber systems. Although annual operating costs are about three times the cost of field
chambers, FACE plots are relatively large, leading to an economy of scale, so that per unit of treated
plant material, FACE systems are the least expensive approach for well- integrated field experiments.
These features have provided an incentive to conduct comprehensive FACE experiments with many
cooperating scientists working together to measure numerous plant, soil and micrometeorological
parameters, as described in the collection of papers in this special issue of 'Agricultural and Forest
Meterology'.

KEYWORDS: AIR CO-2 ENRICHMENT, ATMOSPHERIC CARBON-DIOXIDE, ECOSYSTEMS,
ELEVATED CO2, EXPOSURE, FIELD, OPEN-TOP CHAMBER, PHOTOSYNTHESIS,
POPULATIONS, VEGETATION


     899  
Hendrey, G.R., K.F. Lewin, and J. Nagy. 1993. Free air carbon-dioxide enrichment - development,
progress, results. Vegetatio 104:17-31.

Credible predictions of climate change depend in part on predictions of future CO2 concentrations
in the atmosphere. Terrestrial plants are a large sink for atmospheric CO2 and the sink rate is
influenced by the atmospheric CO2 concentration. Reliable field experiments are needed to evaluate
how terrestrial plants will adjust to increasing CO2 and thereby influence the rate of change of
atmospheric CO2. Brookhaven National Laboratory (BNL) has developed a unique Free-Air CO2
Enrichment (FACE) system for a cooperative research program sponsored by the U.S. Department
of Energy and U.S. Department of Agriculture, currently operating as the FACE User Facility at the
Maricopa Agricultural Center (MAC) of the University of Arizona. The BNL FACE system is a tool
for studying the effects of CO2 enrichment on vegetation and natural ecosystems, and the exchange
of carbon between the biosphere and the atmosphere, in open-air settings without any containment.
The FACE system provides stable control of CO2 at 550 ppm +/- 10%, based on 1- min averages,
over 90% of the time. In 1990, this level of control was achieved over an area as large as 380 m2,
at an annual operating cost of $668 m-2. During two field seasons of enrichment with cotton
(Gossypium hirsutum) as the test plant, enrichment to 550 ppm CO2 resulted in significant increases
in photosynthesis and biomass of leaves, stems and roots, reduced evapotranspiration, and changes
in root morphology. In addition, soil respiration increased and evapotranspiration decreased.

KEYWORDS: FIELD CROPS, FUMIGATION, POLLUTION, SYSTEM


     900  
Hendrey, G.R., S.P. Long, I.F. McKee, and N.R. Baker. 1997. Can photosynthesis respond to
short-term fluctuations in atmospheric carbon dioxide? Photosynthesis Research 51(3):179-184.

Rapid and irregular variations of atmospheric CO2 concentrations (c(a)) occur in nature but are often
very much more pronounced and frequent when artificially enriching CO2 concentrations in
simulating the future atmosphere. Therefore, there is the danger that plant responses at elevated CO2
in fumigation experiments might reflect the increased Frequency and amplitude of fluctuation in
concentration as well as the increase in average concentration. Tests were conducted to determine
whether the photosynthetic process could sense such fluctuations in c(a). Instantaneous chlorophyll
fluorescence (F-t) was monitored for wheat leaves (Triticum aestivum cv. Hereward) exposed to c(a)
oscillating symmetrically by 225 mu mol mol(-1) about a c(a) set point concentration of 575 or 650
mu mol mol(-1). No F-t response was detected to half-cycle step changes in c(a) lasting less than two
seconds, but at half- cycles of two seconds or longer, the response of F-t was pronounced. In order
to determine the in vivo linear electron transport rate (J) the O-2 concentration was maintained at 21
mmol mol(-1) to eliminate photorespiration. J which is directly proportional to the rate of CO2
uptake under these conditions, was not significantly changed at half-cycles of 30 s or less but was
decreased by half-cycles of 60 s or longer. It was inferred that if duration of an oscillation is less than
1 minute and is symmetrical with respect to mean CO2 concentration, then there is no effect on
current carbon uptake, but oscillations of 1 minute or more decrease photosynthetic CO2 uptake in
wheat.

KEYWORDS: ELECTRON-TRANSPORT, LEAVES, MESOPHYLL CONDUCTANCE, ZEA-MAYS


     901  
Hendrix, D.L., J.R. Mauney, B.A. Kimball, K. Lewin, J. Nagy, and G.R. Hendrey. 1994.
Influence of elevated co2 and mild water-stress on nonstructural carbohydrates in field-grown cotton
tissues. Agricultural and Forest Meteorology 70(1-4):153-162.

Root, stem and leaf tissues, from cotton plants exposed to CO2 at ambient (370 mumol mol-1
(control)) or elevated (550 mumol mol-1 (FACE; free-air carbon dioxide enrichment)) levels in the
field during the 1990 and 1991 growing seasons, were analyzed for nonstructural carbohydrates
(glucose, fructose, sucrose and starch). Besides the FACE treatment, these plants were also exposed
to two irrigation levels: 100% and 67% replacement of evapotranspiration. FACE had a greater effect
upon cotton plant nonstructural carbohydrates than did irrigation treatments. Leaf carbohydrate
content was increased by FACE, but this increase was much more pronounced in the stems and roots.
Starch and soluble sugars in leaves in FACE plots tended to be consistently greater than in control
leaves, without much change in carbohydrate content during the growing season. In contrast, root
and stem, starch and soluble sugar pools were strongly increased by FACE and fluctuated strongly
during the growing season. In both seasons, stem and taproot nonstructural carbohydrate content
passed through a minimum during periods of heavy boll set. The fluctuations in stem and root
carbohydrate content were therefore probably caused by the varying metabolic demands of the
developing plant. These results suggest that a significant effect of CO2 enrichment on starch-
accumulating plants is an increase of nonstructural carbohydrate, especially starch, in nonleaf storage
pools. This buildup occurs somewhat independently of the water status of the plant, and these
enlarged pools can be drawn upon by the growing plant to maintain growth during periods of high
metabolic demand.

KEYWORDS: ATMOSPHERIC CO2, CO2, ENRICHMENT, EXPORT, PLANT GROWTH,
TEMPERATURE, TUSSOCK TUNDRA, YIELD


     902  
Hendry, M.J., C.A. Mendoza, R.A. Kirkland, and J.R. Lawrence. 1999. Quantification of
transient CO2 production in a sandy unsaturated zone. Water Resources Research 35(7):2189-2198.

Temporal and spatial respiration rates were determined in a 5.7-m thick, sandy, unsaturated zone over
a 550-day period using measured CO2 concentrations, CO2 fluxes to the atmosphere, moisture
contents, and temperatures. Cyclical patterns in CO2 concentrations were measured in duplicate nests
of nine gas samplers. Maximum CO2 gas concentrations occurred during the summer (0.85-1.22%),
and minimum concentrations occurred during the winter (0.04-0.24%). CO2 gas concentrations
decreased with increasing depth during the summer and increased with depth during the winter. A
one-dimensional finite element model was developed to quantify transient respiration rates through
the unsaturated zone. The model was calibrated to the measured CO2 concentrations. Temperature
and moisture content variations were represented with an analytical expression and linear
interpolation of field-measured values, respectively, in the model. Simulation results provided very
good approximations to the field-measured CO2 concentrations, but predicted CO2 fluxes to the
atmosphere were higher than measured. Respiration rates ranged from 5 mu g C g(-1) d(-1) in the
soil horizon during the summer to about <10(-4) mu g C g(-1) d(-1) in unsaturated sections of the
C horizon. A sensitivity analysis showed that the respiration rates in the C horizon must be <10(-3)
mu g C g(-1) d(-1) and that the majority of the elevated CO2 concentrations in this thick unsaturated
zone are the result of respiration in the soil horizon. Overall, roots contribute about 75% of the CO2
in the summer months. O-2 gas, microbial analyses, and the distribution of root biomass supported
this conclusion. These observations also imply that although microorganisms are present in subsurface
environments their in situ activity in this sandy unsaturated zone may be very low.

KEYWORDS: AQUIFER, ATMOSPHERE, BIODEGRADATION, CARBON DIOXIDE, FIELD
CONDITIONS, FOREST, MICROBIAL ACTIVITY, SOIL RESPIRATION, TEMPERATURES,
TRANSPORT


     903  
Henning, F.P., C.W. Wood, H.H. Rogers, G.B. Runion, and S.A. Prior. 1996. Composition and
decomposition of soybean and sorghum tissues grown under elevated atmospheric carbon dioxide.
Journal of Environmental Quality 25(4):822-827.

It has been hypothesized that changes in both quantity and quality of plant residue inputs to soils as
atmospheric carbon dioxide (CO2) concentration increases may alter carbon (C) and nitrogen (N)
turnover rates and pool sizes, We determined the effect of elevated atmospheric CO2 on plant tissue
quality, and flow modifications in tissue quality affect C and N mineralization. Soybean [C-3; Glycine
max (L.) Merr. cv. Stonewall] and sorghum [C-4; Sorghum bicolor (L.) Moen, cv. Savanna 5] were
grown under elevated (704.96 +/- 0.33 mu mol CO2 mol(-1)) and ambient (357.44 +/- 0.12 mu mol
CO2 mol(-1)) atmospheric CO2 in open-top chambers, Leaf and stem tissues were separated from
harvested plants and analyzed for C, N, lignin, and cellulose. Tissues were applied to Norfolk loamy
sand (fine-loamy, siliceous, thermic Typic Kandiudult) and aerobically incubated for 70-d to
determine C and N mineralization, C turnover, relative N mineralization, and C/N mineralized.
Elevated CO2 had no effect on plant residue C concentration, but N concentration of soybean leaves
and stems and sorghum stems was reduced; however, CO2 enrichment increased C/N ratio and lignin
concentration for only sorghum stems and soybean leaves, respectively. Source of plant residue (i.e.,
produced under either elevated or ambient CO2) had no impact on soil C turnover, relative N
mineralization, cumulative C and N mineralization, and C/N mineralized, These data suggest that
increasing atmospheric CO2 will have little effect on composition or decomposition of field crop
residues. Thus, since CO2 enrichment results in increased photosynthetic C fixation, the possibility
exists For increased soil C storage under field crops in an elevated CO2 world.

KEYWORDS: CO2 LEVELS, DYNAMICS, NITROGEN, ORGANIC-MATTER, RESPONSES,
SYSTEMS


     904  
Herbert, D.A., E.B. Rastetter, G.R. Shaver, and G.I. Agren. 1999. Effects of plant growth
characteristics on biogeochemistry and community composition in a changing climate. Ecosystems
2(4):367-382.

Vegetation growth characteristics influence ecosystem biogeochemistry and must be incorporated in
models used to project biogeochemical responses to climate variations. We used a multiple-element
limitation model (MEL) to examine how variations in nutrient use efficiency (NUE) and net primary
production to biomass ratio (nPBR) affect changes in ecosystem C stocks after an increase in
temperature and atmospheric CO2. nPBR influences the initial rates of response, but the magnitude
and direction of long-term responses are determined NUE. MEL was used to simulate responses to
climate change in communities composed of two species differing in nPBR and/or NUE. When only
nPBR differed between the species, the high-nPBR species outgrew the low-nPBR species early in
the simulations, but the shift in dominance was transitory because of secondary N limitations. High-
NUE and were therefore favored under elevated CO2. Increased temperature stimulated N release
from soil organic matter (SOM) and therefore favored low-NUE species. The combined release from
C and N limitation under the combination of increased temperature and elevated CO2 favored high-
NUE species. High C:N litter from high-NUE species limited the N-supply rate from SOM, which
favors the dominance of the high-NUE species in the short term. However, in the long term increased
litter production resulted in SOM accumulation, which reestablished a N supply rate favorable to the
reestablishment and dominance of the low-NUE species. Conditions then reverted to a state favorable
to the high-NUE species.

KEYWORDS: ALASKAN TUNDRA, BIOLOGICAL INVASION, CARBON STORAGE, GLOBAL
CHANGE, MYRICA-FAYA, NITROGEN, RESPONSES, TERRESTRIAL ECOSYSTEMS, TROPICAL
FORESTS, VEGETATION TYPES


     905  
Herbst, M., and G. Hormann. 1998. Predicting effects of temperature increase on the water balance
of beech forest - An application of the 'KAUSHA' model. Climatic Change 40(3-4):683-698.

The water balance model 'KAUSHA' (Halldin, 1989) was applied to a 100-year-old beech (Fagus
sylvatica L.) forest in northern Germany. Overall, a satisfying agreement between modelled
evapotranspiration values and independent micrometeorological measurements (Bowen ratio energy
balance method) could be observed, although for rainy days KAUSHA showed a tendency to
overestimate evapotranspiration. The model was used to predict the effects of a climate warming on
the water budgets of the forest. It is shown that a temperature increase of 2 degrees C due to a rising
CO2 content of the atmosphere will not change the yearly totals of evapotranspiration significantly,
but could have serious effects on the soil water balance during the vegetation period. Because under
climate change conditions a higher amount of the available soil water has already been evaporated
in winter and spring, soil water content will limit the transpiration of the trees from July to September
much more strongly. Therefore, the yield of beech forest might also suffer from drought effects. It
can be concluded that a better knowledge of the seasonal distribution of rainfall under climate change
conditions is indispensable for predicting effects of rising temperatures and CO2 concentrations on
ecosystems.

KEYWORDS: CLIMATE-CHANGE SCENARIOS, CO2- ENRICHMENT, ECOSYSTEMS,
ELEVATED CARBON-DIOXIDE, EVAPOTRANSPIRATION, GROWTH, OCEAN-ATMOSPHERE
MODEL, RESPONSES, SCOTS PINE, SIMULATION


     906  
Herrick, J.D., and R.B. Thomas. 1999. Effects of CO2 enrichment on the photosynthetic light
response of sun and shade leaves of canopy sweetgum trees (Liquidambar styraciflua) in a forest
ecosystem. Tree Physiology 19(12):779-786.

To investigate whether sun and shade leaves respond differently to CO2 enrichment, we examined
photosynthetic light response of sun and shade leaves in canopy sweetgum (Liquidambar styraciflua
L.) trees growing at ambient and elevated (ambient + 200 mu l l(-1)) atmospheric CO2 in the
Brookhaven National Laboratory/Duke University Free Air CO2 Enrichment (FACE) experiment.
The sweetgum trees were naturally established in a 15-year-old forest dominated by loblolly pine
(Pinus taeda L.). Measurements were made in early June and late August 1997 during the first full
year of CO2 fumigation in the Duke Forest FACE experiment. Sun leaves had a 68% greater leaf
mass per unit area, 63% more leaf N per unit leaf area, 27% more chlorophyll per unit leaf area and
77% greater light-saturated photosynthetic rates than shade leaves. Elevated CO2 strongly stimulated
light-saturated photosynthesis of sun and shade leaves in June and August; however, the relative
photosynthetic enhancement by elevated CO2 for sun leaves was mon than double the relative
enhancement of shade leaves. Elevated CO2 stimulated apparent quantum yield by 30%. but there
was no interaction between CO2 and leaf position. Daytime leaf-level carbon gain extrapolated from
photosynthetic light response curves indicated that sun leaves were enhanced 98% by elevated CO2,
whereas shade leaves were enhanced 41%. Elevated CO2 did not significantly affect leaf N per unit
area in sun or shade leaves during either measurement period. Thus, the greater CO2 enhancement
of light-saturated photosynthesis in sun leaves than in shade leaves was probably a result of a greater
amount of nitrogen per unit leaf area in sun leaves. A full understanding of the effects of increasing
atmospheric CO2 concentrations on forest ecosystems must take account of the complex nature of
the light environment through the canopy and how light interacts with CO2 to affect photosynthesis.

KEYWORDS: ATMOSPHERIC CO2, DECIDUOUS FOREST, DIFFERENT IRRADIANCE
LEVELS, ELEVATED CARBON-DIOXIDE, GAS-EXCHANGE, LOBLOLLY-PINE, LONG-TERM
ELEVATION, NITROGEN LEVEL, PINUS-TAEDA SEEDLINGS, WATER-STRESS


     907  
Herrmann, B., and U. Feller. 1998. CO2, light and temperature influence senescence and protein
degradation in wheat leaf segments. Physiologia Plantarum 103(3):320-326.

Effects of environmental conditions influencing photosynthesis and photorespiration on senescence
and net protein degradation were investigated in segments from the first leaf of young wheat
(Triticum aestivum cv. Arina) plants. The segments were floated on H2O at 25, 30 or 35 degrees C
in continuous light (PAR: 50 or 150 mu mol m(-2) s(-1)) in ambient air and in CO2- depleted air.
Stromal enzymes, including phosphoglycolate phosphatase, glutamine synthetase, ferredoxin-
dependent glutamate synthase, phosphoribulokinase, and the peroxisomal enzyme, glycolate oxidase,
were detected by SDS-PAGE followed by immunoblotting with specific antibodies. In general, the
net degradation of proteins and chlorophylls was delayed in CO2- depleted air. However, little effect
of CO2 on protein degradation was observed at 25 degrees C under the lower level of irradiance. The
senescence retardation by the removal of CO2 was most pronounced at 30 degrees C and at the
higher irradiance. The stromal enzymes declined in a coordinated manner. Immunoreactive fragments
from the degraded polypeptides were in most cases not detectable. However, an insolubilized
fragment of glycolate oxidase accumulated in vivo, especially at 25 degrees C in the presence of CO2.
Detection of this fragment was minimal after incubation at 30 degrees C and completely absent on
blots from segments kept at 35 degrees C. In CO2-depleted air, the fragment was only weakly
detectable after incubation at 25 degrees C. The results from these investigations indicate that
environmental conditions that influence photosynthesis may interfere with senescence and protein
catabolism in wheat leaves.

KEYWORDS: ACCLIMATION, ACCUMULATION, CALVIN-CYCLE, DETACHED LEAVES,
ELEVATED CO2, EXPRESSION, GLUTAMINE-SYNTHETASE, LIMITING CO2,
PHOTOSYNTHESIS, RIBULOSE-1;5-BISPHOSPHATE CARBOXYLASE-OXYGENASE


     908  
Hertstein, U., J. Colls, F. Ewert, and M. van Oijen. 1999. Climatic conditions and concentrations
of carbon dioxide and air pollutants during 'ESPACE-wheat' experiments. European Journal of
Agronomy 10(3-4):163-169.

A major objective of the ESPACE-wheat programme was to perform by means of open-top chambers
(OTCs) 'standardised' experimental investigations of spring wheat responses to increased atmospheric
CO2 and O-3 concentrations and to other environmental stresses at different locations in Europe,
representing a broad range of different climatic conditions. From 1994 to 1996 a total number of 25
OTC experiments were carried out. In addition, four growth chamber experiments focusing on key
physiological processes of wheat growth in CO2- enriched air were performed. According to the
specific needs for subsequent modelling purposes, environmental data were collected during
experiments, i.e. air temperature, global radiation, humidity and trace gas concentrations. In the
present paper results of these measurements are summarised. It was shown, that the OTC-
experiments covered a considerable range of growing season mean-air-temperatures (13.0-23.4
degrees C) and global irradiances (10.8-18.1 MJ m(-2) d(-1)), the most important driving variables
for crop growth simulation models. Mean concentrations of CO2 and O-3 in ambient air and in
different treatments illustrated the observed variability of trace gas exposures between different
experiments. Implications for subsequent analyses of biological response data are discussed. (C) 1999
Elsevier Science B.V. All rights reserved.



     909  
Hertstein, U., A. Fangmeier, and H.J. Jager. 1996. ESPACE-wheat (European Stress Physiology
and Climate Experiment-project 1: Wheat): Objectives, general approach, and first results. Journal
of Applied Botany-Angewandte Botanik 70(5-6):172-180.

The ''European Stress Physiology and Climate Experiment - project 1: wheat'' (acronym: ESPACE-
wheat) is funded by the EU since 1994. In the present paper the projects goals, the general
methodological approach, and a summary of the experimental work performed in 1994 and 1995 are
described. Main objectives of the project are 1) to investigate experimentally the sensitivity of wheat
growth, development and productivity to changes in CO2 concentration, climatic variables and other
physiological stresses, 2) to use experimental data for extension, improvement and validation of
process-based wheat growth simulation models, and 3) to use models for assessments of the
influences on crops of climatic change, increasing CO2 concentration and additional physiological
stresses in Europe. Most experimental investigations are being performed by means of open-top
chambers (OTC's) according to a common standard protocol to meet specific data requirements for
model construction and validation. ESPACE-wheat OTC-experiments in 1994 and 1995 are
summarized and the principal methods of data evaluation are presented by analyzing responses of
grain yield and aboveground biomass of spring wheat, cv. Minaret, to CO2 enrichment and other
factors varied in experiments at different sites. The mean observed CO2-doubling responses was
about 1.4, i.e. grain yield and biomass production were increased by about 40% compared to growth
in ambient CO2 concentration. However, there was a large variability of responses between sites and
years. Results are discussed with respect to modeling attempts.

KEYWORDS: ATMOSPHERIC CO2, CARBON DIOXIDE, CROP RESPONSES, IMPACTS,
OZONE, PLANTS, VEGETATION


     910  
Hew, C.S., S.E. Hin, J.W.H. Yong, S.S. Gouk, and M. Tanaka. 1995. In-vitro co2 enrichment
of cam orchid plantlets. Journal of Horticultural Science 70(5):721-736.

Increased growth of an in vitro-propagated CAM orchid hybrid Mokara 'White' was obtained using
a novel method of COP enrichment in an optimized photoautotrophic open system compared with
the conventional closed system of culture. The optimization process for the open system involved the
manipulation of external CO2 concentrations (0.03%, 1% and 10%), sucrose requirements, light
intensities (80 and 200 mu mol m(-2) s(-1)) and the venting of headspace ethylene from the culture
vessels. The physiological basis for increased growth in these CAM orchid plantlets after three
months was attributed to the direct effects of elevated CO2 resulting in higher CAM activity for the
plantlets and to the elevated CO2 present in the system which might interact with the ethylene present
thereby reducing the inhibition of growth of plantlets due to ethylene.

KEYWORDS: FIXATION, GROWTH, INVITRO


     911  
Heyworth, C.J., G.R. Iason, V. Temperton, P.G. Jarvis, and A.J. Duncan. 1998. The effect of
elevated CO2 concentration and nutrient supply on carbon-based plant secondary metabolites in Pinus
sylvestris L. Oecologia 115(3):344-350.

This study investigated changes in carbon-based plant secondary metabolite concentrations in the
needles of Pinus sylvestris saplings, in response to longterm elevation of atmospheric CO?, at two
rates of nutrient supply. Experimental trees were grown for 3 years in eight open-top chambers
(OTCs), four of which were maintained at ambient (similar to 350 mu mol mol(-1)) and four at
elevated (700 mu mol mol(-1)) CO2 concentrations, plus four open air control plots. Within each of
these treatments, plants received either high (7.0 g N m(-2) year(-1) added) or low (no nutrients
added) races of nutrient supply for two years. Needles from lateral branches were analysed chemically
for concentrations of condensed tannins and monoterpenes. Biochemical determinations of cellulase
digestibility and protein precipitating capacity of their phenolic extracts were made because of their
potential of importance in ecological interactions between pine and other organisms including
herbivores and decomposers. Elevated CO2 concentration caused an increase (P < 0.05) in dry mass
per needle, tree height and the concentration of the monoterpene alpha-pinene, but there were no
direct effects of CO2 concentration on any of the other chemical measurements made. High nutrient
availability increased cellulase digestibility of pine needles. There was a significant negative effect of
the OTCs on protein precipitating capacity of the needle extracts in comparison to the open-air
controls. Results suggest that predicted changes in atmospheric CO2 concentration will be insufficient
to produce large changes in the concentration of condensed tannins and monoterpenes in Scots pine.
Processes which are influenced by these compounds, such as decomposition and herbivore food
selection; along with their effects on ecosystem functioning, are therefore unlikely to be directly
affected through changes in these secondary metabolites.

KEYWORDS: ALLELOCHEMICALS, ATMOSPHERIC CO2, BALANCE, CONTORTA, DIOXIDE
CONCENTRATION, ECOSYSTEMS, FERTILIZATION, PERFORMANCE, RESPONSES, TANNIN


     912  
Hibberd, J.M., P. Richardson, R. Whitbread, and J.F. Farrar. 1996. Effects of leaf age, basal
meristem and infection with powdery mildew on photosynthesis in barley grown in 700 mu mol mol(-
1) CO2. New Phytologist 134(2):317-325.

The rate of net photosynthesis in the second leaf of barley was higher in 700 than 350 mu mol mol(-1)
CO2 when measured in the CO2 concentration in which the plants were grown, but the magnitude
of this difference decreased as the leaf aged. Infection by powdery mildew accelerated the decline in
net photosynthesis of leaves grown in either 350 or 700 mu mol mol(-1) CO2. A/C-i curves allowed
the reduction in net photosynthesis of plants exposed to 700 mu mol mol(-1) CO2 or after infection
by powdery mildew to be related to changes in the carboxylation efficiency or in the regeneration of
ribulose 1,5-bisphosphate. The carboxylation efficiency declined in plants exposed to 700 mu mol
mol(-1) CO2. In plants infected with powdery mildew, the reduction in net photosynthesis was
associated with both reduced carboxylation efficiency and reduced ability to regenerate ribulose 1,5-
bisphosphate. Reduced carboxylation efficiency of the second leaf of plants grown in 700 mu mol
mol(-1) CO2 was not associated with a reduction in the concentration of rubisco within the leaf. In
contrast to the presence of a close exogenous sink, leaf age had large effects on the acclimation of
photosynthesis to 700 mu mol mol(-1) CO2.

KEYWORDS: ACCLIMATION, BROWN RUST, CARBON DIOXIDE, GAS-EXCHANGE, LEAVES,
PROTEIN, RIBULOSE BISPHOSPHATE CARBOXYLASE, RIBULOSE-1;5-BISPHOSPHATE
CARBOXYLASE-OXYGENASE, STOMATAL CONDUCTANCE, TOMATO PLANTS


     913  
Hibberd, J.M., R. Whitbread, and J.F. Farrar. 1996. Carbohydrate metabolism in source leaves
of barley grown in 700 mu mol mol(-1) CO2 and infected with powdery mildew. New Phytologist
133(4):659-671.

Soluble carbohydrate accumulated faster in second leaf blades of barley when plants were grown in
700 mu mol mol(-1) CO2 rather than 350 mu mol mol(-1) CO2. Infection of the second leaf blade
by powdery mildew had no effect on the concentration of soluble carbohydrate until 6 d after
inoculation when it was lower than in controls. The accumulation of soluble carbohydrate in the
second leaf of uninfected plants grown in 700 mu mol mol(-1) CO2 was due largely to earlier and
faster accumulation of fructan. TLC showed that the series of fructan was not different in plants
grown in 700 mu mol mu mol(-1) CO2 relative to plants grown in 350 mu mol mol(-1) CO2, neither
did infection by powdery mildew affect the series of fructan present in the second leaf blade. The rate
constant for phloem loading obtained by compartmental analysis of C-14 efflux from the leaf blade
was not reduced in plants grown in 700 mu mol mol(-1) CO2, indicating that carbohydrate
accumulation was not caused by reduced ability of the leaf to export carbon.

KEYWORDS: CARBON, COMPARTMENTAL ANALYSIS, ELEVATED CO2, FLUXES, FRUCTAN
ACCUMULATION, LEAF BLADES, PLANTS, STARCH, SUCROSE


     914  
Hibberd, J.M., R. Whitbread, and J.F. Farrar. 1996. Effect of 700 mu mol mol(-1) CO2 and
infection with powdery mildew on the growth and carbon partitioning of barley. New Phytologist
134(2):309-315.

The dry weight of barley plants in 700 mu mol mol(-1) CO2 was increased by 19 d after planting
relative to plants grown in 350 mu mol mol(-1) CO2. Infection of the second leaf by powdery mildew
led to reduced growth rates in both 350 and 700 mu mol mol(-1) CO2, but the reduction in growth
was transitory in 350 mu mol mol(-1) CO2. Neither the alIometric coefficient k between shoot and
root, nor the leaf weight ratio, was altered by growth in 700 mu mol mol(-1) CO2 or by infection with
powdery mildew. The number of tillers produced increased per plant but not per unit d. wt in 700 mu
mol mol(-1) CO2. The growth response of barley to increased concentrations of CO2 and/or to
infection with powdery mildew was not associated with alterations in net carbon partitioning, so a
change in the ratio of photosynthetic to non-photosynthetic tissue, contributed to neither the growth
response of barley to 700 mu mol mol(-1) CO2 nor to infection with powdery mildew. The increase
in the growth rate of barley in 700 mu mol mol(-1) CO2 and the reduction in the growth rate after
infection occurred at the same time as increased and reduced rates of net photosynthesis respectively.

KEYWORDS: DIOXIDE, ELEVATED CO2, PHOTOSYNTHESIS, ROOT, RUST, TEMPERATURE


     915  
Hibberd, J.M., R. Whitbread, and J.F. Farrar. 1996. Effect of elevated concentrations of CO2
on infection of barley by Erysiphe graminis. Physiological and Molecular Plant Pathology 48(1):37-
53.

Although there was no difference in the percentage of powdery mildew conidia that germinated on
the second leaf of barley plants grown in either 350 or 700 ppm CO2, the percentage of conidia that
progressed to produce colonies was lower in plants grown in 700 than in 350 ppm CO2. The lower
percentage of conidia producing hyphae in 700 ppm CO2 was due to a higher proportion of the
spores being arrested at the appressorial stage. The reduction in penetration of spores in 700 ppm
CO2 was due neither to 700 ppm CO2 per se, nor to ontogenetic changes in the host tissue.
Removing the epicuticular waxes from the surface of the leaf had no effect on the development of
conidia on the surface of leaves in 350 or 700 ppm CO2, showing that increased epicuticular waxes
were not causing the increased resistance to primary penetration of powdery mildew in 700 ppm
CO2. We relate reduced rates of primary penetration in barley grown in 700 ppm CO2 to higher rates
of net photosynthesis allowing increased mobilisation of resources into resistance including the
production of papillae and accumulation of silicon at the sites of appressorial penetration. Established
colonies of powdery mildew grew faster in 700 ppm CO2 than in 350 ppm CO2, coincident with
accumulation of host carbohydrate in the source leaf.

KEYWORDS: AGE, CARBON DIOXIDE, GERMLING DEVELOPMENT, INSOLUBLE SILICON,
LEAVES, POWDERY MILDEW, PRIMARY PENETRATION, RESISTANCE, SPRING BARLEY,
WHEAT


     916  
Hibbs, D.E., S.S. Chan, M. Castellano, and C.H. Niu. 1995. Response of red alder seedlings to
co2 enrichment and water- stress. New Phytologist 129(4):569-577.

Red alder (Alnus rubra Bong.) is a nitrogen-fixing pioneer tree species of the Pacific Northwest of
North America. We investigated the response of different seed sources of red alder to elevated
atmospheric CO2 and to varied levels of water stress. Seeds were stratified, germinated and grown
for up to 147 d under ambient (350 mu l l(-1)) or elevated (700 mu l l(- 1)) CO2. There were no
significant interactions of seed source latitude with either treatment, although seedlings from more
northerly sources were larger. Elevated CO2 and low moisture stress resulted in larger plants with
more leaf area; effects of the two factors appeared additive. Effects of both factors on biomass
allocation, including root:shoot ratios, were small or nonsignificant. Elevated CO2 decreased specific
nitrogenase activity and generally increased photosynthesis (A) and stomatal conductance (g). The
ratio A:g, potential water use efficiency, also increased when plants were under water stress. Elevated
CO2 appears to improve drought tolerance in red alder. Overall, these results indicate that red alder
would benefit in total plant growth from increased ambient CO2 and could tolerate changes in
precipitation.

KEYWORDS: ALLOCATION, ALNUS-RUBRA, ATMOSPHERIC CARBON-DIOXIDE, ELEVATED
CO2, GROWTH, NODULATION


     917  
Hikosaka, K. 1997. Modelling optimal temperature acclimation of the photosynthetic apparatus in
C-3 plants with respect to nitrogen use. Annals of Botany 80(6):721-730.

A new hypothesis for temperature acclimation by the photosynthetic apparatus is presented. An
optimization model is developed to examined effects of changes in the organization of photosynthetic
components on leaf photosynthesis under various growth temperatures where the photosynthetic
apparatus is not damaged. In this model, photosynthetic rate is limited either by the capacity of
ribulose bisphosphate carboxylase (RuBPCase) to consume ribulose bisphosphate (RuBP), or by the
capacity of RuBP regeneration. For temperature dependence of the RuBPCase activity, data from
Spinacia oleracea L., which have a temperature optimum of 30 degrees C, are used. For temperature
dependence of the capacity of RuBP regeneration, two contrasting curves that have temperature
optima of 30 degrees C (Eucalyptus pauciflora Sieb. ex Spreng) and 40 degrees C (Larrea divaricata
Cav.) are applied. The temperature dependence of each process is fixed for respective species, but
the rate of each process varies with changes in the amounts of components. The cost of proteins, in
terms of nitrogen, required to carry out each process is calculated when nitrogen is partitioned
differently among photosynthetic components. The optimal nitrogen partitioning that maximizes daily
photosynthesis at a given temperature is obtained. The predicted temperature optimum of the
photosynthetic rate in Larrea divaricata exhibits large shifts with changes in target temperature, while
shifts are negligible in Eucalyptus pauciflora. It is suggested that the shift in temperature optimum of
photosynthetic rate is large when the temperature dependences of the capacities of RuBPCase and
RuBP regeneration differ from each other. (C) 1997 Annals of Botany Company.

KEYWORDS: CO2/O2 SPECIFICITY, DESERT SHRUB, ELECTRON-TRANSPORT, ELEVATED
CO2, GAS-EXCHANGE, GROWTH TEMPERATURE, INTACT LEAVES, LARREA- DIVARICATA,
NERIUM-OLEANDER, RIBULOSE-1;5-BISPHOSPHATE CARBOXYLASE


     918  
Hikosaka, K., and T. Hirose. 1998. Leaf and canopy photosynthesis of C-3 plants at elevated CO2
in relation to optimal partitioning of nitrogen among photosynthetic components: theoretical
prediction. Ecological Modelling 106(2-3):247-259.

Effects of changes in the organization of photosynthetic components on leaf photosynthesis under
contrasting atmospheric CO2 conditions (35 and 70 Pa) are evaluated using an optimization model,
in which the photosynthetic rate is limited either by the capacity of ribulose bisphosphate carboxylase
(RuBPCase) to consume ribulose bisphosphate (RuBP) or by the capacity of RuBP regeneration. The
nitrogen cost of photosynthetic components to carry out each process is calculated for the optimal
partitioning of nitrogen among the components. The model predicts that nitrogen allocation to the
components carrying out RuBP regeneration should be increased with reduction in allocation to
RuBPCase to maximize daily photosynthesis at 70 Pa CO2. Al a temperature of 25 degrees C,
doubling the current CO2 level increases daily photosynthesis by 60% with optimal reallocation of
the nitrogen partitioning while the increase without reallocation of nitrogen is 40%. However, at
lower growth irradiance, the advantage in daily photosynthesis due to the reallocation decreases with
increasing nitrogen content. The ratio of photosynthesis at 70 Pa to that at 35 Pa increases with
increasing temperature. The effects of CO2 levels on photosynthesis of a canopy in which nitrogen
is optimally allocated among leaf layers are also examined. At 25 degrees C, canopy photosynthesis
at the doubled CO2 level is predicted to increase 60 and 40% with and without the optimization of
nitrogen partitioning among photosynthetic components, respectively. Doubling the CO2 level does
not affect the optimal nitrogen distribution among leaf layers in the canopy irrespective of
optimization of nitrogen partitioning among photosynthetic components. (C) 1998 Elsevier Science
B.V. All rights reserved.

KEYWORDS: ACCLIMATION, ALLOCATION, ASSIMILATION, ATMOSPHERIC CO2, LEAVES,
LIMITATIONS, MODEL, RESPECT, SYSTEM, TEMPERATURE


     919  
Hilbert, D.W., A. Larigauderie, and J.F. Reynolds. 1991. The influence of carbon-dioxide and
daily photon-flux density on optimal leaf nitrogen concentration and root - shoot ratio. Annals of
Botany 68(4):365-376.

KEYWORDS: ALLOCATION, CO2- ENRICHMENT, GROWTH, LEAVES, LIGHT,
PHOTOSYNTHETIC CHARACTERISTICS, SEEDLINGS, SHADE PLANTS, STOMATAL
CONDUCTANCE, USE EFFICIENCY


     920  
Hileman, D.R., N.C. Bhattacharya, P.P. Ghosh, P.K. Biswas, K.F. Lewin, and G.R. Hendrey.
1992. Responses of photosynthesis and stomatal conductance to elevated carbon-dioxide in field-
grown cotton. Critical Reviews in Plant Sciences 11(2-3):227-231.

KEYWORDS: BEHAVIOR, CO2- ENRICHMENT, NITROGEN DEFICIENCY, PLANTS,
SORGHUM, SUNFLOWER, WATER RELATIONS


     921  
Hileman, D.R., G. Huluka, P.K. Kenjige, N. Sinha, N.C. Bhattacharya, P.K. Biswas, K.F.
Lewin, J. Nagy, and G.R. Hendrey. 1994. Canopy photosynthesis and transpiration of field-grown
cotton exposed to free-air co2 enrichment (face) and differential irrigation. Agricultural and Forest
Meteorology 70(1-4):189-207.

Growth, yield and leaf photosynthetic rates of cotton (Gossypium hirsutum L. ) all respond strongly
to CO2 enrichment, but the gas exchange of whole cotton canopies grown under elevated CO2 has
not been investigated. We compared the effects of CO2 enrichment on both single-leaf and whole-
canopy photosynthetic rates in cotton. We also determined whole- canopy photosynthetic and
transpiration rates in cotton in response to CO2 enrichment and differential irrigation. Field- grown
cotton was exposed to either 550 mumol mol-1 of CO2 using the free-air carbon dioxide enrichment
(FACE) system or to 370 mumol mol-1 in control plots. In the second year of the experiment, half
of each plot received reduced levels of irrigation. Rates of photosynthesis and stomatal conductance
of single leaves were determined using a portable photosynthesis system and a portable steady-state
porometer, respectively. Rates of whole-canopy photosynthesis and transpiration were determined
using a custom-built chamber (about 1 m x 1 m). Midday net photosynthesis rates of both leaves and
canopies were 19-41% higher in the CO2-enriched plots than in control plots. The CO2 effect on leaf
photosynthesis was greatest in July, whereas the CO2 effect on canopy photosynthesis was greatest
in June and decreased thereafter as mutual shading of leaves and the amount of non- photosynthetic
biomass increased. Midday stomatal conductance values of leaves were 13-44% greater in control
plants than in CO2-enriched plants. Except for late in the second season, canopy transpiration rates
were not affected by the CO2 treatment because the decrease in stomatal conductance was offset by
an increase in plant size. Differential irrigation led to no significant differences in either canopy
photosynthesis or transpiration, possibly because differential irrigation was applied only during the
second half of the season. It appears that cotton crops grown in a future, higher-CO2 climate may
have increased photosynthetic rates, but water requirements may not be reduced.

KEYWORDS: CARBON DIOXIDE, ELEVATED CO2, LEAF, NITROGEN DEFICIENCY, PLANTS,
RESPONSES, STOMATAL CONDUCTANCE, STRESS, WATER-USE EFFICIENCY, YIELD


     922  
Hirose, T., D.D. Ackerly, M.B. Traw, and F.A. Bazzaz. 1996. Effects of CO2 elevation on canopy
development in the stands of two co-occurring annuals. Oecologia 108(2):215-223.

Elevated CO2 may increase dry mass production of canopies directly through increasing net
assimilation rate of leaves and also indirectly through increasing leaf area index (LAI). We studied
the effects of CO2 elevation on canopy productivity and development in monospecific and mixed
(1:1) stands of two co- occurring C-3 annual species, Abutilon theophrasti and Ambrosia
artemisiifolia. The stands were established in the glasshouse with two CO2 levels (360 and 700 mu
l/l) under natural light conditions. The planting density was 100 per m(2) and LAI increased up to 2.6
in 53 days of growth. Root competition was excluded by growing each plant in an individual pot.
However, interference was apparent in the amount of photons absorbed by the plants and in photon
absorption per unit leaf area. Greater photon absorption by Abutilon in the mixed stand was due to
different canopy structures: Abutilon distributed leaves in the upper layers in the canopy while
Ambrosia distributed leaves more to the lower layers. CO2 elevation did not affect the relative
performance and light interception of the two species in mixed stands. Total aboveground dry mass
was significantly increased with CO2 elevation, while no significant effects on leaf area development
were observed. CO2 elevation increased dry mass production by 30-50%, which was mediated by 35-
38% increase in the net assimilation rate (NAR) and 37-60% increase in the nitrogen use efficiency
(NUE, net assimilation rate per unit leaf nitrogen). Since there was a strong overall correlation
between LAI and aboveground nitrogen and no significant difference was found in the regression of
LAI against aboveground nitrogen between the two CO2 levels, we hypothesized that leaf area
development was controlled by the amount of nitrogen taken up from the soil. This hypothesis
suggests that the increased LAI with CO2 elevation observed by several authors might be due to
increased uptake of nitrogen with increased root growth.

KEYWORDS: ACCLIMATION, ATMOSPHERIC CARBON-DIOXIDE, C-4 ANNUALS, GAS-
EXCHANGE, GROWTH, LEAF, NITROGEN CONCENTRATION, PHOTOSYNTHESIS,
TEMPERATURE, TUSSOCK TUNDRA


     923  
Hirose, T., D.D. Ackerly, M.B. Traw, D. Ramseier, and F.A. Bazzaz. 1997. CO2 elevation,
canopy photosynthesis, and optimal leaf area index. Ecology 78(8):2339-2350.

We studied the effects of CO2 elevation on leaf and canopy photosynthesis and optimal leaf area
index (LAI) for stands of the annual species Abutilon theophrasti and Ambrosia artemisiifolia. Leaf
photosynthesis was modeled as a function of photosynthetic photon flux density (PPFD) and nitrogen
content per unit leaf area (N-L). There was a curvilinear relationship between the light-saturated rates
of leaf photosynthesis (P-max) and N-L. CO2 elevation significantly increased P-max as a function
of N, in both species. Dark respiration (R-d) was linearly correlated with N-L. CO2 elevation slightly
but significantly increased R-d in Abutilon, while it had no significant effect on R-d in Ambrosia. The
initial slope of a light-response curve was determined from quantum yield (phi(abs)) multiplied by leaf
absorptance and then calibrated against N-L. Daily canopy photosynthesis, calculated by integration
of leaf photosynthesis with the actual distribution of leaf area, leaf N, and PPFD within a canopy,
showed fairly good agreement with the canopy photosynthesis estimated from growth analysis. CO2
elevation increased canopy photosynthesis by 30-50%. Based on the leaf photosynthesis model for
Abutilon, we calculated daily canopy photosynthesis for a given LAI and N availability, in which N
was assumed to be distributed optimally within a leaf canopy to maximize daily canopy
photosynthesis. An optimal LAI to maximize daily canopy photosynthesis was obtained for each level
of N availability and this optimum increased with increasing N availability. Contrary to the often
predicted increase in LAI with CO2 elevation, the optimum LAI did not increase at high CO2 when
N availability was limited. Two factors were suggested to be involved in counteracting the increase
in LAI in a high-CO2 world. One is the higher phi(abs) of plants grown in elevated CO2, which
makes leaves in the canopy more N limited, favors higher N-L and thus lowers optimal LAI. The
other is the higher R-d in elevated CO2, which leads to higher light compensation points, and lowers
optimal LAI.

KEYWORDS: ANNUALS, C-3, CARBON-DIOXIDE CONCENTRATION, ECOSYSTEMS, GAS-
EXCHANGE, GROWTH, NITROGEN DISTRIBUTION, RESPIRATION, RESPONSES,
TEMPERATURE


     924  
Hirose, T., and F.A. Bazzaz. 1998. Trade-off between light- and nitrogen-use efficiency in canopy
photosynthesis. Annals of Botany 82(2):195-202.

If the light-use efficiency (LUE) of species in a canopy is constant, canopy photosynthesis (CP) is
proportional to the number of photons (Phi) absorbed by the canopy (CP = LUE x Phi). Likewise,
if nitrogen-use efficiency (NUE) is constant, canopy photosynthesis is proportional to the amount of
total leaf nitrogen (LN) (CP = NUE x LN). We applied these concepts to monospecific and mixed
(1:1) stands of annuals (Abutilon theophrasti and Ambrosia artemisiifolia) at two stages, established
in an ambient (360 mu l l(-1)) or elevated (700 mu l l(-1)) CO2 atmosphere. In both CO2
concentrations, across the two species, daily canopy photosynthesis gave strong linear regressions
with zero intercepts both against the number of absorbed photons and against total leaf nitrogen in
the canopy. Doubling CO2 increased LUE by 20-80 % and NUE by 20-100 %. LUE tended to be
higher in Ambrosia than in Abutilon, and also higher in the later stage of canopy development than
in the younger stage. Interference by Abutilon increased the LUE of Ambrosia. On the other hand,
NUE tended to be higher in Abutilon than in Ambrosia, and to be higher in younger than in later
stages. Interference by Abutilon decreased the NUE of Ambrosia. Thus, there are trade-offs (negative
correlations) between LUE and NUE, which result from differences in leaf nitrogen per unit leaf area
and from differences in leaf area development in the canopy. LUE increased with increasing leaf
nitrogen concentration, while NUE increased with increasing light availability in the canopy. (C) 1998
Annals of Botany Company.

KEYWORDS: ABSORPTION, ALLOCATION, AREA, C-3 PLANTS, CARBON GAIN, CO2
ELEVATION, LEAF NITROGEN, LEAVES, MODEL, RADIATION


     925  
Hirschel, G., C. Korner, and J.A. Arnone. 1997. Will rising atmospheric CO2 affect leaf litter
quality and in situ decomposition rates in native plant communities? Oecologia 110(3):387-392.

Though field data for naturally senesced leaf litter are rare, it is commonly assumed that rising
atmospheric CO2 concentrations will reduce leaf litter quality and decomposition rates in terrestrial
ecosystems and that this will lead to decreased rates of nutrient cycling and increased carbon
sequestration in native ecosystems. We generally found that the quality of naturally senesced leaf litter
(i.e. concentrations of C, N and lignin; C:N, lignin:N) of a variety of native plant species produced
in alpine, temperate and tropical communities maintained at elevated CO2 (600-680 mu l(- 1)) was
not significantly different from that produced in similar communities maintained at current ambient
CO2 concentrations (340-355 mu l l(-1)). When this litter was allowed to decompose in situ in a
humid tropical forest in Panama (Cecropia peltata, Elettaria cardamomum, and Ficus benjamina, 130
days exposure) and in a lowland temperate calcareous grassland in Switzerland (Carex flacca and a
graminoid species mixture; 261 days exposure), decomposition rates of litter produced under ambient
and elevated CO2 did not differ significantly. The one exception to this pattern occurred in the high
alpine sedge, Carex curvula, growing in the Swiss Alps. Decomposition of litter produced in situ
under elevated CO2 was significantly slower than that of litter produced under ambient CO2 (14%
vs. 21% of the initial litter mass had decomposed over a 61-day exposure period, respectively).
Overall, our results indicate that relatively little or no change in leaf litter quality can be expected in
plant communities growing under soil fertilities common in many native ecosystems as atmospheric
CO2 concentrations continue to rise. Even in situations where small reductions in litter quality do
occur, these may not necessarily lead to significantly slower rates of decomposition. Hence in many
native species in situ litter decomposition rates, and the time course of decomposition, may remain
relatively unaffected by rising CO2.

KEYWORDS: BIOMASS, CARBON DIOXIDE, DYNAMICS, ECOSYSTEMS, ELEVATED CO2,
FOREST, GRASSLAND, NITROGEN, PRODUCTIVITY, RESPONSES


     926  
Hobbie, J.E., B.L. Kwiatkowski, E.B. Rastetter, D.A. Walker, and R.B. McKane. 1998. Carbon
cycling in the Kuparuk basin: Plant production, carbon storage, and sensitivity to future changes.
Journal of Geophysical Research-Atmospheres 103(D22):29065-29073.

The Marine Biological Laboratory General Ecosystem Model was calibrated for an arctic tussock
tundra system using data from long-term observations and experiments at Toolik Lake, Alaska. These
experiments include the effects of changes in temperature, light, CO2, and nutrients, so the model
could be applied to five regions comprising the entire Kuparuk River basin. Met primary production,
averaged for the entire basin, was 92 g C m(-2) yr(-1). A 150 year simulation of carbon storage under
a doubling of CO2 (slow ramp-up) and a temperature increase of 3.5 degrees C gave an estimate of
+400 g C m(-2) when soil moisture increased and +500 g C m(-2) when soil moisture decreased.
Drier soils stimulated decomposition producing an increase in nitrogen availability; the increased N
led to increased net primary production. If this result is applicable to other arctic ecosystems, then
it is unlikely that warming will enhance carbon loss to the atmosphere to further enhance warming.

KEYWORDS: ARCTIC TUNDRA, BALANCE, CLIMATE CHANGE, CO2, DIOXIDE, GLOBAL
CHANGE, MODEL, RESPONSES, TERRESTRIAL ECOSYSTEMS


     927  
Hocking, P.J., and C.P. Meyer. 1991. Carbon-dioxide enrichment decreases critical nitrate and
nitrogen concentrations in wheat. Journal of Plant Nutrition 14(6):571-584.

Atmospheric carbon dioxide (CO2) levels are increasing. In a glasshouse experiment with wheat
grown at 5 levels of nitrate (NO3) supply, CO2 enrichment (1500 cm3/m3) substantially decreased
critical concentrations of NO3-N and total-N in stem bases and leaves. For example, critical NO3-N
concentrations in stem bases at Feekes Stages 1.5, 5, and 10.3, were 4.5, 2.0, and 2.0 mg/g dry wt,
respectively, for CO2-enriched plants, compared with 7.5, 6.2 and 6.4 mg/g dry wt, respectively, for
control plants grown at the ambient level of CO2. However, concentrations of NO3-N in the rooting
medium required to produce maximum dry matter accumulation by CO2-enriched plants were similar
to those of control plants at the three growth stages. Critical concentrations of NO3-N and total-N
declined with time in stem bases and leaves of plants grown at both ambient and elevated CO2 levels,
but the decline was greater for CO2-enriched plants. It was concluded that diagnostic criteria based
on current critical N concentrations may become invalid as the atmospheric level of CO2 increases.

KEYWORDS: AVAILABILITY, CO2- ENRICHMENT, DEFICIENCY, DRY-MATTER, GROWTH,
NUTRITION, SOIL, SPRING WHEAT, YIELD


     928  
Hocking, P.J., and C.P. Meyer. 1991. Effects of CO2 enrichment and nitrogen stress on growth,
and partitioning of dry-matter and nitrogen in wheat and maize. Australian Journal of Plant
Physiology 18(4):339-356.

Atmospheric CO2 levels are increasing, but little is known about how this will affect tissue
concentrations and the partitioning of agriculturally important nutrients such as nitrogen (N) within
crop plants. To investigate this, a glasshouse experiment was conducted in which wheat, a C3 species,
and maize, a C4 species, were grown for 8 weeks at high CO2 (1500 cm3 m-3) on N supplies ranging
from deficient (0.5 mol m-3) to more than adequate for maximum growth (25 mol m-3). Wheat
responded to both CO2 enrichment and N supply; maize responded only to N supply. CO2-enriched
wheat produced about twice the dry matter of control plants at all levels of N supply. Tiller and ear
numbers were increased by CO2 enrichment irrespective of N supply. Enriched wheat plants had a
lower Leaf Area Ratio but higher Net Assimilation Rate and Relative Growth Rate than control
plants. There was no effect of CO2 enrichment on specific leaf weight. The enriched plants had lower
shoot to root dry matter ratios than thecontrols at 6 mol m-3 N and higher. Shoot to root dry matter
ratios of both wheat and maize increased with increasing N supply. CO2-enriched wheat plants
accumulated more N than the controls but the proportional increase in N content was not as great
as that in dry matter, with the result that concentrations of total-N and nitrate-N were lower in all
organs of enriched plants, including ears. Nitrate reductase activity was lower in enriched than in
control wheat plants. N-use efficiency by wheat was increased by CO2 enrichment. From a practical
point of view, the study indicates that critical total-N and NO3-N concentrations used to diagnose
the N status of wheat will need to be reassessed as global CO2 levels increase. Elevated CO2 may
also reduce the protein content of grain and thus the baking quality of hard wheats.

KEYWORDS: CARBON-DIOXIDE CONCENTRATION, MINERAL NUTRITION, NITRATE,
NUTRIENT CONCENTRATION, PHOSPHORUS, PHOTOSYNTHESIS, PLANT GROWTH, USE
EFFICIENCY, WATER, YIELD


     929  
Hoddinott, J., and R. Scott. 1996. The influence of light quality and carbon dioxide enrichment on
the growth and physiology of seedlings of three conifer species .1. Growth responses. Canadian
Journal of Botany-Revue Canadienne De Botanique 74(3):383-390.

Plant growth responds to light quality, as evaluated by the red/far-red (R/FR) quantum flux ratio, and
to the level of CO2. Pinus banksiana, Picea mariana and Picea glauca seedlings were raised at 350,
700, or 1050 at mu L . L(-1) CO2 and high or low R/FR ratios and growth was measured over a 16-
week growth period. Far-red rich light enhanced the whole plant and height relative growth rates of
Pinus banksiana. The three species showed species specific responses in plant organ relative growth
rates and partitioning ratios. On the basis of their biomass partitioning the species would be ranked
Pinus banksiana < Picea mariana < Picea glauca for shade tolerance. In commercial operations,
seedlings grown for outplanting are selected, in part, on the basis of plant form as described by the
stem height/diameter ratio. More desirable ratios were obtained at ambient CO2 concentrations for
Pinus banksiana and Picea mariana in red rich light and for Picea glauca in far-red rich light.

KEYWORDS: ATMOSPHERIC CO2 ENRICHMENT, BLACK SPRUCE SEEDLINGS, FORESTS,
NATURAL- ENVIRONMENT, PHYTOCHROME


     930  
Hoddinott, J., and R. Scott. 1996. The influence of light quality and carbon dioxide enrichment on
the growth and physiology of seedlings of three conifer species .2. Physiological responses. Canadian
Journal of Botany-Revue Canadienne De Botanique 74(3):391-402.

Pinus banksiana, Picea mariana, and Picea glauca were grown at 350, 700, or 1050 mu L . L(-1) CO2
and either high or low red/far-red quantum flux ratios. After a 16-week, long day growth period,
seedlings were subjected sequentially to short daylengths, then short days with low temperatures.
Various physiological parameters were determined at the end of each treatment phase to monitor how
those treatments influenced the onset of seedling dormancy. After the long day treatments, high ratios
increased the total chlorophyll content and reduced the original level of chlorophyll fluorescence and
the shoot total nonstructural carbohydrate content in very shade-intolerant Pinus banksiana. In shade-
tolerant Picea mariana, high CO2 levels caused the main effects on these parameters while neither
light quality or CO2 had significant effects on them in shade-tolerant Picea glauca. Short days and
low temperature induced a proportional increase in the partitioning of total nonstructural
carbohydrate to the roots in all species and produced other species and treatment-specific responses.

KEYWORDS: ATMOSPHERIC CO2 ENRICHMENT, BLACK SPRUCE SEEDLINGS,
CHLOROPHYLL FLUORESCENCE, FORESTS, FROST HARDINESS, PHOTOSYNTHESIS,
PHYTOCHROME, PINUS-RADIATA, PLANTS, TEMPERATURE


     931  
Hodge, A. 1996. Impact of elevated CO2 on mycorrhizal associations and implications for plant
growth. Biology and Fertility of Soils 23(4):388-398.

The impact of increasing concentrations of atmospheric CO2 upon plant physiology has been widely
investigated. Plant, and in particular root, growth is nearly always enhanced as a direct consequence
of CO2 enrichment, with C-3 species generally more responsive than C-4 species. Such alterations
in plant productivity will have consequence for below-ground processes and increased carbon
allocation to the roots may favour symbiotic relationships. This paper discusses the current
information available for the consequences of these changes upon mycorrhizal relationships. Generally
mycorrhizal plants grown under CO2 enrichment show enhanced phosphorus uptake but nitrogen
uptake is unaffected. This increased nutrient uptake is not correlated with increased mycorrhizal
colonization of the roots. Similarly root exudation does not increase under CO2 enrichment but
qualitative differences have yet to be assessed. However, it is predicted that total rhizodeposition of
materials will increase as will litter inputs, although mineral and biochemical alterations to these plant
derived inputs may occur. The consequences of such changes within the rhizosphere are discussed
and future research priorities identified.

KEYWORDS: ATMOSPHERIC CARBON-DIOXIDE, BOUTELOUA-GRACILIS, CASTANEA-
SATIVA MILL, ECTOMYCORRHIZAL FUNGI, GAS-EXCHANGE, GLOMUS-MOSSEAE,
NUTRIENT-UPTAKE, PHOTOSYNTHETIC ACCLIMATION, SEEDLING GROWTH, WOODY-
PLANTS


     932  
Hodge, A., and P. Millard. 1998. Effect of elevated CO2 on carbon partitioning and exudate release
from Plantago lanceolata seedlings. Physiologia Plantarum 103(2):280-286.

Plantago lanceolata L. seedlings were grown in sand microcosm units over a 43-day experimental
period under two CO2 regimes (800 or 400 mu mol mol(-1)) to investigate the effect of elevated
atmospheric CO2 concentration on carbon partitioning and exudate release. Total organic carbon
(TOC) content of the collected exudate material was measured throughout the experimental period.
After 42 days growth the seedlings were labelled with [C-14]-CO2 and the fate of the label within
the plant and its release by the roots monitored. Elevated CO2 significantly (P less than or equal to
0.001) enhanced shoot, root and total dry matter production although the R:S ratio was unaltered,
suggesting no alteration in press carbon partitioning. The cumulative release of TOC (in mg C) over
0-42 days was unaltered by CO2 treatment however, when expressed as a percentage of net
assimilated C, ambient-grown plants released a significantly (P less than or equal to 0.001) higher
percentage from their roots compared to elevated CO2-grown plants (i.e. 8 vs 3%). The distribution
of C-14-label was markedly altered by CO2 treatment with significantly (P less than or equal to
0.001) greater per cent label partitioned to the roots under elevated CO2. This indicates increased
partitioning of recent assimilate belowground under elevated CO2 treatment although there was no
significant difference in the percentage of C-14-label released by the roots. Comparison of plant C
budgets based on C-14-pulse-chase methodology and TOC measurements is discussed.

KEYWORDS: ATMOSPHERIC CO2, ENRICHMENT, FLOW, GROWTH, MAIZE, RESPONSES,
RHIZOSPHERE, ROOT EXUDATION, SOIL BIOTA, ZEA MAYS L


     933  
Hodge, A., E. Paterson, S.J. Grayston, C.D. Campbell, B.G. Ord, and K. Killham. 1998.
Characterisation and microbial utilisation of exudate material from the rhizosphere of Lolium perenne
grown under CO2 enrichment. Soil Biology and Biochemistry 30(8-9):1033-1043.

The effects of elevated atmospheric CO2 concentration on alterations, both qualitatively and
quantitatively, of exuded compounds from the roots of Lolium perenne seedlings were investigated
by growing plants in a sterilised sand microcosm unit. In addition, the effect of CO2 treatment on
carbon substrate utilisation of microbial populations extracted from the rhizosphere of L. perenne
seedlings grown in soil microcosm units was examined and alterations on microbial activity and
diversity assessed using a commercially-available redox-based sole C source utilisation test
(Biolog(R)) including additional exudate compounds. Both types of microcosm units (sand and soil)
were maintained at specific growth conditions under two CO2 regimes (450 and 720 mu mol mol(-
1)). Growth of L. perenne seedlings from both types of microcosm units was enhanced under elevated
atmospheric CO2 although the root-to-shoot ratios were not significantly altered, indicating no gross
change in dry matter partitioning. Cumulative total organic carbon (TOC) release in the exudate
material over the duration of the experiment was significantly (P less than or equal to 0.05) higher
from ambient-grown seedlings despite a significant (P less than or equal to 0.05) increase in the dry
weight of roots of the elevated CO2 grown seedlings as determined at harvest. Over the individual
sampling periods TOC release was significantly (P less than or equal to 0.05) higher from elevated
CO2 grown seedlings on only one occasion (21 d). Qualitative differences, measured between d 1-6
and 14-18, also occurred with elevated CO2 treatment decreasing the amount of phenolic acids and
total sugars at the latter sampling period compared to ambient CO2 seedlings. Total numbers of
bacteria were significantly (P less than or equal to 0.05) decreased under elevated CO2 although
culturable numbers significantly (P less than or equal to 0.05) increased. This increase in culturable
microorganisms may explain the faster carbon source utilisation rates of the elevated CO2 treatment.
No change in morphotypes of microbial colonies were observed suggesting a quantitative difference
due to elevated CO2 treatment only. (C) 1998 Elsevier Science Ltd. All rights reserved.

KEYWORDS: BIOMASS, CARBON DIOXIDE, COMMUNITIES, ELEVATED ATMOSPHERIC
CO2, NITROGEN, PLANT-RESPONSES, ROOTS, SEEDLINGS, SOIL BIOTA, ZEA MAYS L


     934  
Hoen, H.F., and B. Solberg. 1994. Potential and economic-efficiency of carbon sequestration in
forest biomass through silvicultural management. Forest Science 40(3):429-451.

This paper has two main objectives: First, to discuss in principle some vital methodological issues
which have to be considered when analyzing bow preferable measures in forestry are to decrease the
atmospheric concentration of greenhouse gases (GHGs). Economic evaluation of the flow of carbon
in and out of the atmosphere is discussed, related particularly to two important problems: (1) the
determination of the utility of reducing the quantity of CO2 in the atmosphere at a given point in time;
and (2) the intertemporal evaluation of a flow of atmospheric CO2 reductions. The marginal cost,
measured as the change in net present value, is proposed as a proper measure for ranking of
alternative projects. Secondly, a case study is reported. The case study is based on forest-level
optimization with a model estimating carbon flows related to forest biomass growth and decay, linked
to a long-range forest management planning (LFMP) model. Alternative stand treatment schedules
are simulated, and the forest management problem is solved by linear programming in a model I type
LFMP model for the county of Buskerud, with a forest area of 574,000 ha. The potential for
increasing the net carbon sequestration related to timber production by changes in the forest
management over a time period of 30 yr is studied. A total of 253 stand treatment schedules was
calculated for the 40 stand types, allowing for the following stand treatment options, (1) continued
growth, (2) release thinnings of young growth, (3) thinning, (4) fertilization, (5) clear felling, (6) clear
felling with retention of seed trees, and (7) planting or natural regeneration depending on the felling
regime. The study shows that there is a significant potential for increasing the present value of the
flow of net CO2 fixations (NPV(CO2)) by changing the forest management on the productive forest
area of Buskerud. Compared with the NPV(CO2) obtained when the net present value of the timber
cash flow (NPV(NOK)) for the area is maximized (BASE problem), an increase between 8.4%-17.9%
in NPV(CO2) can be obtained. The potential for increasing the NPV(CO2) depends on the real rate
of discount. The corresponding decrease in the NPV(NOK) lies between 8.1% and 14.9%. The
results further indicate that a large proportion of the increase in NPV(CO2) can be obtained by
changes in forest management at a moderate marginal cost. If we assume that 80% of the maximum
potential increase in NPV(CO2) is obtained, this gives a yearly increase (30-yr annuity) in net CO2
fixation in the range from 145,000 to 250,000 tons (depending on the real rate of discount and
assumptions about fertilization) by changing the management of the 574,000 ha of productive
forestland in Buskerud, compared to the current forest management practice (BASE problem).
Obtaining 80% of the maximum potential increase in NPV(CO2) imposes a decrease in the
NPV(NOK) in the range of 22% to 65% of the total potential difference in NPV(NOK) between the
BASE problem and the NPV(CO2) maximizing problem. The annual decrease (30-yr annuity) in
NPV(NOK) corresponding to the 80% of the maximum potential NPV(CO2) increase, is ranging
between 7.6 and 25 million NOK. The results indicate that at a RRD of 4%, 5%, and 7% p.a., 80%
of the increase in NPV(CO2) can be reached at a marginal cost (shadow price) below 150 NOK
(21/US$) per ton NPV(CO2). Measured per ton C, the corresponding marginal cost is 551 NOK (79
US$) per ton C. For RRDs at 3% p.a. and 2% p.a., the marginal costs are significantly higher, but
relaxing the NPV(CO2) constraint to 60% of the total increase brings the marginal costs down and
below half of this level (59 NOK or 8 US$ per ton NPV(CO2)) for 3% p.a. and to a comparable level
(182 NOK or 26 US$ per ton NPV(CO2)) for 2% p.a. These results are related to changes in the
management of the forested area in even-aged stands and do not take into account measures such as
afforestation of marginal agricultural land or changes of tree species. Fertilization, avoiding release
thinning in young growth, and changes in clear felling priorities were the most cost-efficient changes
in stand treatment management in order to increase the net CO2 fixation.

KEYWORDS: ELEVATED CO2, RESPONSES


     935  
Hogan, K.P., I. Fleck, R. Bungard, J.M. Cheeseman, and D. Whitehead. 1997. Effect of elevated
CO2 on the utilization of light energy in Nothofagus fusca and Pinus radiata. Journal of Experimental
Botany 48(311):1289-1297.

Red beech (Nothofagus fusca (Hook. F.) Oerst.; Fagaceae) and radiata pine (Pinus radiata D. non;
Pinaceae) were grown for 16 months in large open-top chambers at ambient (37 Pa) and elevated (66
Pa) atmospheric partial pressure of CO2, and in control plots (no chamber). Summer-time
measurements showed that photosynthetic capacity was similar at elevated CO2 (light and CO2-
saturated value of 17.2 mu mol m(-2) s(-1) for beech, 13.5 mu mol m(-2) s(-1) for pine), plants
grown at ambient CO2 (beech 21.0 mu mol m(-2) s(-1), pine 14.9 mu mol m(-2) s(-1)) or control
plants grown without chambers (beech 23.2 mu mol m(- 2) s(-1), pine 12.9 mu mol m(-2) s(-1)).
However, the higher CO2 partial pressure had a direct effect on photosynthetic rate, such that under
their respective growth conditions, photosynthesis for the elevated CO2 treatment (measured at 70
Pa CO2 partial pressure: beech 14.1 mu mol m(-2) s(-1) pine 10.3) was greater than in ambient
(measured at 35 Pa CO2: beech 9.7 mu mol m(-2) s(-1), pine 7.0 mu mol m(-2) s(-1)) or control
plants (beech 10.3 mu mol m(-2) s(-1), pine 7.2 mu mol m(-2) s(-1)). Measurements of chlorophyll
fluorescence revealed no evidence of photodamage in any treatment for either species. the quantity
of the photoprotective xanthophyll cycle pigments and their degree of de-epoxidation at midday did
not differ among treatments for either species. The photochemical efficiency of photosystem II (yield)
was lower in control plants than in chamber-grown plants, and was higher in chamber plants at
ambient than at elevated CO2. These results suggest that at lower (ambient) CO2 partial pressure,
beech plants may have dissipated excess energy by a mechanism that does not involve the xanthophyll
cycle pigments.

KEYWORDS: CARBON METABOLISM, CAROTENOIDS, CHLOROPHYLL FLUORESCENCE,
ELECTRON-TRANSPORT, INHIBITION, PHOTOINHIBITION, PHOTOSYNTHESIS, PLANTS,
RESPONSES, TEMPERATURE


     936  
Hogan, K.P., A.P. Smith, and L.H. Ziska. 1991. Potential effects of elevated CO2 and changes in
temperature on tropical plants. Plant, Cell and Environment 14(8):763-778.

Very little attention has been directed at the responses of tropical plants to increases in global
atmospheric CO2 concentrations and the potential climatic changes. The available data, from
greenhouse and laboratory studies, indicate that the photosynthesis, growth and water use efficiency
of tropical plants can increase at higher CO2 Concentrations. However, under field conditions abiotic
(light, water or nutrients) or biotic (competition or herbivory) factors might limit these responses. In
general, elevated atmospheric CO2 concentrations seem to increase plant tolerance to stress,
including low water availability, high or low temperature, and photoinhibition. Thus, some species
may be able to extend their ranges into physically less favourable sites, and biological interactions may
become relatively more important in determining the distribution and abundance of species. Tropical
plants may be more narrowly adapted to prevailing temperature regimes than are temperate plants,
so expected changes in temperature might be relatively more important in the tropics. Reduced
transpiration due to decreased stomatal conductance could modify the effects of water stress as a cue
for vegetative or reproductive phenology of plants of seasonal tropical areas. The available
information suggests that changes in atmospheric CO2 concentrations could affect processes as varied
as plant/herbivore interactions, decomposition and nutrient cycling, local and geographic distributions
of species and community types, and ecosystem productivity. However, data on tropical plants are
few, and there seem to be no published tropical studies carried out in the field. Immediate steps
should be undertaken to reduce our ignorance of this critical area.

KEYWORDS: AMAZON DEFORESTATION, ATMOSPHERIC CO2, CLIMATE CHANGE, COSTA-
RICA, GLOBAL CARBON-CYCLE, INSECT HERBIVORE, PHOTOSYNTHETIC RESPONSES,
RAIN-FOREST, ULTRAVIOLET-B RADIATION, WATER RELATIONS


     937  
Hogan, K.P., D. Whitehead, J. Kallarackal, J.G. Buwalda, J. Meekings, and G.N.D. Rogers.
1996. Photosynthetic activity of leaves of Pinus radiata and Nothofagus fusca after 1 year of growth
at elevated CO2. Australian Journal of Plant Physiology 23(5):623-630.

Radiata pine (Pinus radiata D.Don) and red beech (Nothofagus fused (Hook.f.) Oerst.) were grown
for over 1 year at elevated (ELEV, 64 Pa) and ambient (AMB, 38 Pa) CO2 partial pressure in open-
top chambers. Springtime measurements of overwintering leaves showed that light- and CO2-
saturated photosynthetic rates (A,,) of pine leaves were similar for the two treatments (AMB: 6.7 +/-
1.08 mu mol m(-2) s(-1), mean +/- 1 s.e.; ELEV: 6.6 +/- 0.47) but, for beech leaves, A(max) was
greater for AMB plants (8.8 +/- 0.90 mu mol m(-2) s(-1)) than for ELEV plants (6.10 +/- 0.71).
Summertime measurements of leaves grown that spring showed that for pine, A(max) was similar in
the two CO2 treatments (AMB 14.9 mu mol m(-2) s(-1) +/- 0.80; ELEV: 13.5 +/- 1.9) while, for
beech, A(max) was higher in AMB plants (21.0 +/- 1.1) than in ELEV plants (17.2 +/- 1.9), although
the difference was not statistically significant. These results indicate downregulation of photosynthetic
capacity of beech but not pine. V-cmax did not differ between treatments within species, suggesting
that there was no acclimation of rubisco activity. Triose phosphate utilisation limitation may have
contributed to the downregulation of A(max) in beech. For pine, photosynthesis at treatment CO2
partial pressures was greater in ELEV plants in both spring and summer. For beech measured at
treatment CO2 partial pressures, photosynthesis was greater in ELEV plants in summer, but was
similar between treatments in the springtime.

KEYWORDS: ACCLIMATION, ASSIMILATION, ATMOSPHERIC CO2, C-3 PLANTS, CARBON
DIOXIDE, ENHANCEMENT, LIMITATIONS, LOBLOLLY-PINE, NUTRITION, SENESCENCE


     938  
Holbrook, G.P., J. Hansen, K. Wallick, and T.M. Zinnen. 1993. Starch accumulation during
hydroponic growth of spinach and basil plants under carbon-dioxide enrichment. Environmental and
Experimental Botany 33(2):313-321.

The effects of CO2 enrichment, photoperiod duration, and inorganic phosphate levels on growth and
starch accumulation by spinach and basil plants were studied in a commercial hydroponic facility.
During a 3-week growth period, both species exhibited increased whole-plant fresh weight as a result
of an increase in atmospheric CO2 concentration from 400 to 1500 mul/l. However, basil leaves
exhibited a 1.5- to 2-fold greater increase in specific leaf weight (SLW), and accumulated starch to
much greater levels than did leaves of spinach. At 1500 mul CO2/l, starch accounted for up to 38%
of SLW with basil compared to < 10% of SLW with spinach. The maximum ratio of
starch/chlorophyll was 55.0 in basil leaves vs 8.0 in spinach leaves. High ratio values were associated
with the appearance of chlorotic symptoms in leaves of basil grown under CO2 enrichment
(WALLICK and ZINNEN (1990) Plant Disease 74, 171-173), whereas spinach did not exhibit
chlorosis. Increasing inorganic phosphate concentrations from 0.7 to 1.8 mM in the hydroponic
medium did not appreciably affect leaf starch accumulation in either species. Starch accumulation in
basil leaves was not consistently related to the duration of the photoperiod. However, photoperiod-
induced changes in leaf starch levels were much greater in basil than spinach. The results clearly
indicate that different horticultural crops can show diverse responses to CO2 enrichment, and thus
highlight the need to develop individual growth strategies to optimize production quality of each
species.

KEYWORDS: ACCLIMATION, ACTIVATION, ATMOSPHERES, CO2- ENRICHMENT, CROP
RESPONSES, LEAVES, PHOTOSYNTHESIS, SUCROSE PHOSPHATE SYNTHASE, TOMATO,
YIELD


     939  
Holcroft, D.M., M.I. Gil, and A.A. Kader. 1998. Effect of carbon dioxide on anthocyanins,
phenylalanine ammonia lyase and glucosyltransferase in the arils of stored pomegranates. Journal of
the American Society for Horticultural Science 123(1):136-140.

Wonderful' Pomegranates (Punica granatum L.) were placed in jars ventilated continuously with air
or air enriched with 10 or 20 kPa CO2 at 10 degrees C for 6 weeks. Samples were taken initially and
after 1, 2, 4, and 6 weeks, and postharvest quality attributes were measured. The arils of the
pomegranates stored in air were deeper red than the initial controls and than those stored in CO2-
enriched atmospheres. This increased color was associated with increased anthocyanin concentration.
Arils from fruit stored in air enriched with 10 kPa CO2 had a lower anthocyanin concentration than
air-stored fruit, and atmospheres enriched with 20 kPa CO2 had even lower levels, possibly from
suppressed anthocyanin biosynthesis. Anthocyanin concentration correlated well with the activity of
phenylalanine ammonia lyase but not with glucosyltransferase activity. Moderate CO2 atmospheres
(10 kPa) prolong the storage life and maintain quality of pomegranates, including adequate red color
intensity of the arils.

KEYWORDS: APPLE, ATMOSPHERE, BIOSYNTHESIS, CO2, CULTIVARS, LETTUCE TISSUE,
PHENOLICS, PIGMENTATION, STORAGE, STRAWBERRY FRUIT


     940  
Holcroft, D.M., and A.A. Kader. 1999. Carbon dioxide-induced changes in color and anthocyanin
synthesis of stored strawberry fruit. Hortscience 34(7):1244-1248.

Anthocyanin concentrations increased in both external and internal tissues of 'Selva' strawberries
(Fragaria xananassa Duch.) stored in air at 5 degrees C for 10 days, but the increase was lower in fruit
stored in air enriched with 10 or 20 kPa CO2. Flesh red color was less intense in CO2 storage than
in air storage. Activities of phenylalanine ammonia lyase (PAL) and UDP glucose : flavonoid
glucosyltransferase (GT) decreased during storage, with decreases being greater in both external and
internal tissues of strawberry fruit stored in air + 20 kPa CO2 than in those kept in air. Activities of
both PAL and GT in external tissues of strawberries stored in air + 10 kPa CO2 were similar to those
in fruit stored in air, while enzyme activities in internal tissues more closely resembled those from fruit
stored in air +20 kPa CO2. Phenolic compounds increased during storage but were not affected by
the storage atmosphere. The pH increased and titratable acidity decreased during storage; these
effects were enhanced in internal tissues by the CO2 treatments, and may in turn have influenced
anthocyanin expression.

KEYWORDS: BIOSYNTHESIS, CULTIVARS, PHENYLALANINE AMMONIA-LYASE


     941  
Holland, E.A., A.R. Townsend, and P.M. Vitousek. 1995. Variability in temperature regulation
of co2 fluxes and n mineralization from 5 hawaiian soils - implications for a changing climate. Global
Change Biology 1(2):115-123.

We examined the possibility that microbial adaptation to temperature could affect rates of CO2, N2O
and CH4 release from soils. Laboratory incubations were used to determine the functional relationship
between temperature and CO2, N2O and CH4 fluxes for five soils collected across an elevational
range in Hawaii. Initial rates of CO2 production and net N mineralization increased exponentially
from 15 degrees C to 55 degrees C; initial rates of CH4 and N2O release were more complex. No
optimum temperature (in which rates decline at higher and lower temperatures) was apparent for any
of the gases, but respiration declined with time at higher temperatures, suggesting rapid depletion of
readily available substrate. Mean Q(10)s for respiration varied from 1.4 to 2.0, a typical range for
tropical soils. The functional relationship between CO2 production and temperature was consistent
among all five soils, despite the substantial differences in mean annual temperature, soils, and land-use
among the sites. Temperature responses of N2O and CH4 fluxes did not follow simple Q(10)
relationships suggesting that temperature functions developed for CO2 release from heterotrophic
respiration cannot be simply extrapolated. Expanding this study to tropical heterotrophic respiration,
the flux is more sensitive to changes in Q(10) than to changes in temperature on a per unit basis: the
partial derivative with respect to temperature is 2.4 Gt C . degrees C- 1, with respect to Q(10) it is
3.5 Gt C . Q(10) unit(-1). Therefore, what appears to be minor variability might still produce
substantial uncertainty in regional estimates of gas exchange.

KEYWORDS: ATMOSPHERE, CARBON DIOXIDE, EMISSIONS, GRASSLANDS, MODEL,
VEGETATION


     942  
Hollander, B., and H. Krug. 1991. Effects of high CO2 concentrations on vegetable species .1.
Symptoms, ranges of injuries, and reactions of species. Gartenbauwissenschaft 56(5):193-205.

To test the reactions of various vegetable species to high CO2-concentrations, the plants were treated
with 1-3% technical CO2 day and night for 10-42 days in growth chambers (table 1). The
development of CO2 injury symptoms as well as growth rates were noted and measured. With
exception of spinach and sweet pepper, which showed no symptoms in the range tested, CO2 injuries
occurred in the form of morphological alterations (epinastic and hyponastic rolling of the leaves,
crisping, reduction and thickening of the leaf lamina), chlorosis (marginal or in areas between the
veins), necrosis, wilting, drying up and browning ot the veins (kohlrabi). The symptoms mentioned
varied between the species and between the cultivars. The injuries occurred at young leaves only
(beans), at older leaves (kohlrabi) or at all leaves (fig. 1-5, table 6). Moreover, high CO2-
concentrations caused a remarkable reduction of growth (fig. 6). Ensuring favourable growth
conditions the cold-season species tolerated concentrations of 1% CO2 for 4-6 weeks showing only
week (radish var. niger, kohlrabi, corn salad) or no significant growth reductions (radish, var. sativus,
lettuce). Light injuries and morphological alterations were identifiable after 2-3 weeks. Higher
concentrations caused stronger growth reductions, injuries appeared after 1 week using 2% CO2 and
after 2-3 days using 3% CO2. The warm-season species tested reacted more sensitive. Cucumbers
tolerated 1% CO2 for 2-3 weeks, using 2% CO2 wilting and driving injuries occurred already after
1 day table 2). In case of disturbances of the water status of the plants by transplanting, top dressing
or sharp decrease of air humidity cucumber wilted with 1% CO2 already after a few days. Equal
reactions were observed with radish, var. sativus. With tomatoes strong injuries of the leaves causing
leaf death were observed after 7 days with 1% CO2 and after 5 days with 2% CO2. Bush beans
reacted by a distinct reduction of leaf area growth and by chlorotic discolorations.

KEYWORDS: ACCLIMATION, CARBON DIOXIDE, ENRICHMENT, MONOECIOUS
CUCUMBERS, PHARBITIS, PLANT GROWTH


     943  
Hollander, B., and H. Krug. 1992. Effects of high co2-concentrations on vegetable species .2.
Growth, co2-gas-exchange and stomata resistance. Gartenbauwissenschaft 57(1):32-43.

In the climatic conditions tested the growth of young cucumber plants (3-7 leaf stage) was slightly
promoted as well by day as by continuous enrichment with 5000-mu-l/l CO2 compared to the control
(400-mu-l/l CO2). A definite effect of enrichment during the night was not evident. The analysis of
the growth components and gas exchange measurements revealed, that CO2 enrichment during the
day as well as during day and night increased net assimilation rate and dark respiration distinctly.
Enrichment during the night showed no effect on net assimilation rate and increased dark respiration
only slightly. The specific leaf area was strongly reduced by the high CO2 concentration, but leaf
weight ratio was rarely changed. By these morphogenetic effects growth promotion by an increased
net assimilation rate was diminished. Continuous CO2 enrichment to cucumber plants with CO2
concentrations greater- than-or-equal-to 1000-mu-l/l decreased stomata resistance. This effect
increased with higher CO2 concentrations and longer treatments. The stomata remained open even
at night and at low air humidity. Also with CO2 enrichment up to 5000-mu-l/l during the day or
during the night only the stomata remained wider open than in the control plants. The reaction of
stomata to high CO2-concentrations is reversible. The regeneration proceeds all the faster as lower
the proceeding concentration and shorter the exposition. The actions of high CO2- concentrations
on stomata movement of cucumbers were confirmed with other species.

KEYWORDS: CARBON-DIOXIDE CONCENTRATION, CO2- ENRICHMENT, DARK
RESPIRATION, DRY-MATTER PRODUCTION, LEAVES, PHOTOSYNTHETIC RATE, PLANT
GROWTH, RESPONSES, TRANSPIRATION, VICIA-FABA


     944  
Homma, K., H. Nakagawa, T. Horie, H. Ohnishi, H.Y. Kim, and M. Ohnishi. 1999. Energy
budget and transpiration characteristics of rice grown under elevated CO2 and high temperature
conditions as determined by remotely sensed canopy temperatures. Japanese Journal of Crop Science
68(1):137-145.

The effects of elevated CO2 concentration and high temperatures on transpiration and gaseous
diffusive resistances of rice canopy were investigated. Akihikari and IR36 cultivars were grown under
two CO2 concentrations ([CO2], 365 and 700 mu L L- 1) X three temperatures (29.8, 30.4 and 32.5
degrees C on average over the experimental period), created by two Temperature Gradient
Chambers. From 2 August (panicle initiation) to 22 August (booting), measurements were made of
dry and wet bulb temperatures, canopy surface temperatures (T- c) and net radiation along with
evapotranspiration (E) measurements by microlysimeters. Aerodynamic resistance (r(a)), obtained
from the measured E and microclimate data, showed a fairly constant value (11.7 s m(-1). Then, r(a),
T-c and microclimates data were substituted into energy budget equations to obtain E and canopy
resistance (r(c)). In all plots, calculated E was in good agreement with measurement by lysimeters,
and r(c) reached minimum values (r(c,min)) at solar radiation above 500 W m(-2). Elevated [CO2]
at the lowest temperature plot increased r(c,min) by 40-49% and T-c by 1.4- 1.6 degrees C and it
reduced E by 14-16% of those under ambient CO2 conditions. With the rising growth temperature,
these effects of elevated [CO2] drastically decreased. The observed r(c,min) responses to temperature
and [CO2] seemed to have reflected a long-term acclimation of rice to these environments. These
results indicate that anticipated global warming significantly reduces the advantageous effects of
elevated [CO2] on plant water use.

KEYWORDS: CARBON DIOXIDE


     945  
Hopkins, D.W., J.A. Chudek, E.A. Webster, and D. Barraclough. 1997. Following the
decomposition of ryegrass labelled with C-13 and N-15 in soil by solid-state nuclear magnetic
resonance spectroscopy. European Journal of Soil Science 48(4):623-631.

Investigating the biogeochemistry of plant material decomposition in soil has been restricted by
difficulties extracting and identifying organic compounds. In this study the decomposition of C-13-
and N-15-labelled Lolium perenne leaves mixed with mineral soil has been investigated over 224 days
of incubation under laboratory conditions. Decomposition was followed using short-term rates of
CO2 evolution, the amounts of C-13 and N-15 remaining were determined by mass spectrometry, and
C-13 and N-15 solid-state nuclear magnetic resonance (NMR) spectroscopy was used to characterize
chemically the plant material as it decomposed. After 224 days 48% of the added C-13 had been lost
with a rapid period of CO2 evolution over the first 56 days. The fraction of cross- polarization magic
angle spinning (CP MAS) C-13 NMR spectra represented by O-alkyl-C signal probably in
carbohydrates (chemical shift, 60-90 p.p.m.) declined from 60 to 20% of the spectrum (chemical shift,
0-200 p.p.m.) over 224 days. The rate of decline of the total C-13 exceeded that of the 60-90 p.p.m.
signal during the first 56 days and was similar thereafter. The fraction of the CP MAS C-13 NMR
spectra represented by the alkyl- and methyl-C (chemical shift, 10-45 p.p.m.) signal increased from
5 to 14% over the first 14 days and was 19% after 224 days. CP MAS C-13 NMR of C-13- and N-
15-L. perenne contained in 100-mu m aperture mesh bags incubated in the soil for 56 days indicated
that the remaining material was mainly carbohydrate but there was an increase in the alkyl-and
methyl- C associated with the bag's contents. After 224 days incubation of the labelled C-13- and N-
15-L. perenne mixed with the soil, 40% of the added N-15 had been lost. Throughout the incubation
there was only one signal centred around 100 p.p.m, detectable in the CP MAS N-15 NMR spectra.
This signal corresponded to amide N-15 in peptides and may have been of plant or microbial origin
or both. Although there had been substantial interaction between the added N-15 and the soil
microorganisms, the associated redistribution of N-15 from plant to microbial tissues occurred within
the amide region. The feasibility of following some of the component processes of plant material
decomposition in soil using NMR has been demonstrated in this study and evidence that microbial
synthesis contributes to the increase in alkyl- and methyl-C content of soil during decomposition has
been represented.

KEYWORDS: CPMAS, ELEVATED CO2, IMMOBILIZATION, MICROBIAL BIOMASS,
MINERALIZATION, NMR-SPECTROSCOPY, ORGANIC-MATTER, PARTICLE-SIZE, PLANT-
MATERIAL, WHOLE SOILS


     946  
Horie, T., H. Nakagawa, J. Nakano, K. Hamotani, and H.Y. Kim. 1995. Temperature-gradient
chambers for research on global environment change .3. a system designed for rice in kyoto, japan.
Plant, Cell and Environment 18(9):1064-1069.

Synthesis and validation of crop models for assessment of of the impact of elevated atmospheric CO2
concentration and anticipated global warming on crop production require crop response data obtained
under field-like conditions, The temperature gradient chamber (TGC) with the facility for CO2
enrichment allows the creation of various CO2 and temperature regimes for crops over the entire
growth period with relatively inexpensive construction and running costs, The TGC develops a
temperature gradient along its longitudinal axis using solar energy during the day and heating at night
while maintaining the natural diurnal cycle, The temperature gradient and the CO2 concentration in
the TGC are regulated by computer control of the air ventilation rate through the TGC and of the
CO2 release rate, Longitudinal gradients of CO2 concentration and water vapour pressure deficit of
air in the TGC were generally less than 5% and +/-0.2 kPa, respectively. A CO2 enrichment
experiment on rice in the TGC showed that a doubling of the CO2 concentration markedly enhanced
crop dry matter production, Temperature had less effect on dry matter production, although panicle
dry weight was greatly decreased at higher temperature as a result of high-temperature-induced
sterility of rice spikelets, Since rice spikelets are most sensitive to high temperature at the moment
of flowering, and their flowering habit is highly synchronized with the diurnal courses of
environmental conditions, the TGC is a useful tool in understanding rice responses to changes in
atmosphere and temperature.

KEYWORDS: CARBON DIOXIDE, RESPONSES


     947  
Horn, M.E., and J.M. Widholm. 1994. Photoautotrophic growth of soybean cells in suspension-
culture .3. Characterization of carbon fixation products under high and low co2 levels. Plant Cell
Tissue and Organ Culture 39(3):239-244.

A photoautotrophic soybean suspension culture (SB-P) was used to study CO2 assimilation while
exposed to elevated or ambient CO2 levels. These studies showed that under elevated CO2 (5% v/v)
malate is the dominant fixation product, strongly suggesting that phosphoenolpyruvate carboxylase
(PEPCase) is the primary enzyme involved in carbon fixation in these cells under their normal growth
conditions. Citrate and [aspartate + glutamate] were also significant fixation products during fifteen
minutes of exposure to (CO2)-C-14. During the ten minute unlabeled CO2 chase however, C-14-
malate continued to increase while citrate and [aspartate + glutamate] declined. Fixation of (CO2)-C-
14 under ambient CO2 levels (0.037%) showed a very different product pattern as 3-
phosphoglycerate was very high in the first one to two minutes followed by increases in [serine +
glycine] and [aspartate + glutamate]. Hexose phosphates were also quite high initially but then
declined relatively rapidly. Thus, the carbon fixation pattern at ambient CO2 levels resembles
somewhat that seen in C3 leaf cells while that seen at elevated CO2 levels more closely resembles that
of a C-4 plant. The initial fixation product of C-3 plants, 3-PGA, was never detectable under high
CO2 conditions. These data suggest that an in vitro photoautotrophic system would be suitable for
studying carbon fixation physiology during photosynthetic and non- photosynthetic growth.

KEYWORDS: CHENOPODIUM-RUBRUM, METABOLISM, PHOTOSYNTHESIS


     948  
Hostetler, S.W., and F. Giorgi. 1995. Effects of a 2-times-co2 climate on 2 large lake systems -
pyramid lake, nevada, and yellowstone lake, wyoming. Global and Planetary Change 10(1-4):43-54.

The possible effects of trace-gas induced climatic changes on Pyramid and Yellowstone Lakes are
assessed using a model of lake temperature. The model is driven by 3 1/2 years of hourly
meteorological data obtained directly from the output of doubled-CO2 experiments (2 x CO2)
conducted with a regional climate model nested in a general circulation model. The regional
atmospheric model is the climate version of the National Center for Atmospheric
Research/Pennsylvania State University mesoscale model, MM4. Average annual surface temperature
of Pyramid Lake for the 2 X CO2 climate is 15.5 +/- 5.4 degrees C (+/- 1 sigma), 2.8 degrees C
higher than the control. Annual overturn of the lake ceases as a result of these higher temperatures
for the 2 x CO2 climate. Evaporation increases from 1400 mm yr(-1) in the control to 1595 mm yr(-
1) in the 2 X CO2 simulation, but net water supplied to the Pyramid Lake basin increases from -6 mm
yr(-1) in the control to +27 mm yr(-1) in the 2 x CO2 simulation due to increased precipitation. For
the open water periods, the average annual surface temperature of Yellowstone Lake is 13.2 +/- 5.1
degrees C for the 2 x CO2 climate, a temperature 1.6 degrees C higher than the control. The annual
duration of ice cover on the lake is 152 days in the 2 X CO2 simulation, a reduction of 44 days
relative to the control, Warming of the lake for the 2 x CO2 climate is mostly confined to the near-
surface. Simulated spring overturn for the 2 X CO2 climate occurs earlier in the year and fall overturn
later than in the control. Evaporation increases from 544 mm yr(-1) to 600 mm yr(-1) in the 2 X CO2
simulation, but net water supplied to the Yellowstone Lake basin increases from +373 mm yr(-1) in
the control to +619 mm yr(-1) due to increased precipitation. The effects of these climatic changes
suggest possible deterioration of water quality and productivity in Pyramid Lake and possible
enhancement of productivity in Yellowstone Lake.

KEYWORDS: EVAPORATION, FISH, MODEL, POTENTIAL CHANGES, SIMULATION,
THERMAL HABITAT


     949  
Houghton, R.A. 1996. Converting terrestrial ecosystems from sources to sinks of carbon. Ambio
25(4):267-272.

It may be possible to sequester carbon in forests and forest products, but to date global trends in land
management have resulted in a release of terrestrial carbon to the atmosphere. Over 100 PgC were
released between 1850 and 1980, and during the 1980s global changes in land use (predominantly
deforestation) caused a net release of 1.6 PgC yr(-1), about 25% of the total emissions of carbon
dioxide from human activities and about 15% of the enhanced radiative forcing. Management
practices that could change this release of terrestrial carbon to an accumulation include (i) a halt to
deforestation; (ii) an expansion in the land area of forests; (iii) an increase in the stocks of carbon in
existing forests; (iv) more efficient harvest and greater use of wood in long- lasting products; and (v)
the substitution of wood fuels for fossil fuels. However, the rate of global warming needs
management as well. Unless the warming is gradual enough to avoid widespread mortality of forests,
the additional releases of carbon caused by the warming itself, through increased respiration, decay,
and fires, may cancel the intended effects of forest management.

KEYWORDS: CLIMATE, CO2, DEFORESTATION, DIOXIDE, FLUX, LAND-USE CHANGE,
SEQUESTRATION, TRANSIENT-RESPONSE, TROPICAL FORESTS, VEGETATION


     950  
Houpis, J.L.J., P.D. Anderson, J.C. Pushnik, and D.J. Anschel. 1999. Among-provenance
variability of gas exchange and growth in response to long-term elevated CO2 exposure. Water, Air,
and Soil Pollution 116(1-2):403-412.

Genetic variability can have profound effects on the interpretation of results from elevated CO2
studies, and future forest management decisions. Information on which varieties are best suited to
future atmospheric conditions is needed to develop future forest management practices. A large-scale
screening study of the effects of elevated CO2 on 15 half- sibling sources of genetically superior
ponderosa pine (Pinus ponderosa Dougl ex P. Laws.) is presented. These sources represent multiple
elevations and latitudes throughout California. Among-provenance variability in the effects of
elevated CO2 on gas exchange and growth, and their correlation with geographic origin were
investigated in ponderosa pine seedlings subjected to ambient or elevated CO2 concentrations (525
mu mol mol(-1) CO2, and 700 mu mol mol(-1) CO2) for more than two years in open-top chambers.
Substantial among- provenance variability in growth response to elevated CO2 was evident, with 8
sources demonstrating no significant growth response to elevated CO2 while 7 sources responded
positively. For all sources, elevated CO2 increased photosynthesis (ranging from 19% increase at 525
mu mol mol(-1) CO2 to 49% increase at 700 mu mol mol(-1) CO2). A modest correlation existed
between geographic origin and above ground growth response to elevated CO2.

KEYWORDS: ATMOSPHERIC CO2, BIOMASS ALLOCATION, CARBON DIOXIDE, CLIMATE
CHANGE, ENRICHMENT, FAMILIES, LEAVES, PHOTOSYNTHESIS, PLANT-RESPONSES,
PONDEROSA PINE


     951  
Houpis, J.L.J., J. Pushnik, D. Anschel, P. Anderson, and R. Demaree. 1995. Intraspecific
variability of photosynthetic traits of pinus- ponderosa subjected to long-term exposure to elevated
co2. Plant Physiology 108(2):62.



     952  
Howden, S.M., G.M. McKeon, L. Walker, J.O. Carter, J.P. Conroy, K.A. Day, W.B. Hall, A.J.
Ash, and O. Ghannoum. 1999. Global change impacts on native pastures in south-east Queensland,
Australia. Environmental Modelling & Software 14(4):307-316.

Increases in atmospheric concentrations of greenhouse gases such as carbon dioxide (CO2) are likely
to impact on grazing industries through direct effects on plant growth and through possible changes
in climate. Assessment of the likely direction and magnitude of these impacts requires development
of appropriate modelling capacities linked with experimental work. This paper documents the
adaptation of an existing soil- pasture-livestock model, GRASP, to simulate system responses to
changes in CO2. The adapted model is then used to compare these responses under current climate
and CO2 conditions with four possible future scenarios: (1) doubled CO2; (2) doubled CO2 and
increased temperature; (3) as in the previous scenario but with a drier climate; and (4) as in (2) but
with a wetter climate. These studies suggest that CO2 changes alone are likely to have beneficial
effects, with increased pasture growth, increased and less variable liveweight gain, and increased
ground cover. However, subsoil drainage is likely to increase. Growth responses to CO2 are likely
to be greater in drier years than in wetter years partly due to nitrogen limitations in the soils of the
region. Increases in temperature in combination with CO2 further increased animal production due
to the increased number of growing days in the cooler months. The increased rainfall scenario had
few additional positive effects but further increased subsoil drainage. In contrast, the drier scenario
had reduced plant and animal production when compared with current conditions even though
seasonal transpiration efficiency was increased by 20% due to increased CO2. (C) 1999 Elsevier
Science Ltd. All rights reserved.

KEYWORDS: ATMOSPHERIC CO2, BOUTELOUA-GRACILIS C-4, CLIMATE, ELEVATED
CARBON-DIOXIDE, GAS-EXCHANGE, GRASS, GROWTH, PASCOPYRUM-SMITHII C-3,
RESPONSES, WATER-USE


     953  
Hu, S.J., M.K. Firestone, and F.S. Chapin. 1998. Elevated atmospheric CO2 and soil biota.
Science 281(5376):518.



     954  
Hu, S.J., M.K. Firestone, and F.S. Chapin. 1999. Soil microbial feedbacks to atmospheric CO2
enrichment. Trends in Ecology and Evolution 14(11):433-437.

Increased atmospheric CO2 concentration often stimulates plant photosynthesis, enhances carbon (C)
allocation belowground, increases plant nutrient uptake and improves the efficiency of plant water
use. Recent studies suggest that microbial responses to CO2-induced alterations in soil C, water and
nutrient availability play an important role in determining ecosystem feedback to CO2 elevation.
However, to date, most of the published results have been obtained from short-term experiments or
from studies using high-nutrient or disturbed soils. Information on microbial responses to CO2-
induced changes in natural and/or mature ecosystems with nutrient limitations is critical to predict
changes in terrestrial ecosystem C storage under future CO2 scenarios.

KEYWORDS: DECOMPOSITION RATES, ELEVATED CARBON-DIOXIDE, LITTER QUALITY,
MODEL ECOSYSTEM, N-AVAILABILITY, NITROGEN CYCLES, ORGANIC-MATTER,
TALLGRASS PRAIRIE, TERRESTRIAL ECOSYSTEMS, WHITE CLOVER


     955  
Huang, B.R., J.W. Johnson, and D.S. NeSmith. 1997. Responses to root-zone CO2 enrichment
and hypoxia of wheat genotypes differing in waterlogging tolerance. Crop Science 37(2):464-468.

Knowledge of wheat (Triticum aestivum L.) responses to CO2 and O-2 in the root environment could
improve understanding of the mechanisms of waterlogging tolerance and thus help develop
waterlogging-tolerant wheat plants. This experiment was designed to investigate the responses to
elevated CO2 and hypoxia of two wheat genotypes, Bayles and Savannah, which differ in
waterlogging tolerance. Plants were grown in a growth chamber in nutrient solutions. Nutrient
solutions were bubbled with ambient air (control), N-2 containing 5 kPa O-2 and ambient CO2
(hypoxia), N-2 containing 10 kPa CO2 and ambient O- 2 (high CO2, ambient O-2), and N-2
containing 10 kPa CO2 and 5 kPa O-2 (high CO2, low O-2). Hypoxia alone had adverse effects on
net photosynthesis (P-n), stomatal conductance (g(s)), water relations, leaf chlorophyll (chi) content,
and shoot and root growth. The effects were greater for waterlogging-sensitive Bayles. When
compared with the aerated control, the combination of elevated CO2 and hypoxia caused significant
reductions in P- n, g(s), leaf water potential, and leaf chi content for Bayles, and in shoot and root
growth for both Bayles and Savannah. Photosynthetic rate and leaf chi content of Savannah were
increased when roots of hypoxic plants were exposed to elevated CO2, but this was not true for
Bayles. Root-zone CO2 enrichment at ambient O-2 had no significant effects on shoot growth, but
reduced root growth In both genotypes. The results showed that CO2 enrichment under root hypoxia
can alleviate some negative effects of hypoxia on P-n, leaf chl content, and shoot growth, the effect
being larger for waterlogging-tolerant Savannah.

KEYWORDS: AERENCHYMA, O2, RESPIRATION, SOIL CARBON-DIOXIDE, TOMATO
PLANTS, TRANSPORT, WATER RELATIONS


     956  
Huang, Y.S., F.A. Street-Perrott, R.A. Perrot, P. Metzger, and G. Eglinton. 1999. Glacial-
interglacial environmental changes inferred from molecular and compound-specific delta C-13
analyses of sediments from Sacred Lake, Mt. Kenya. Geochimica et Cosmochimica Acta 63(9):1383-
1404.

Molecular Stratigraphic analyses, including lipid distributions and compound-specific delta(13)C
measurements, have been performed at 15 levels in a sediment core from Sacred Lake, Mt. Kenya,
a high-altitude (2350 m a.s.l.) freshwater lake with a record extending from the last glacial (>40,000
cal. yr BP) through the present interglacial; Terrestrial and aquatic organic-matter sources were
independently assessed using source-specific biomarkers. delta(13)C values of long-chain n- alkyl
lipids from terrestrial higher plants exhibit large glacial to interglacial shifts: those from the last glacial
maximum (LGM) (-20 to -18 parts per thousand) indicate a terrestrial vegetation dominated by C-4
grasses or sedges, whereas those from the early Holocene (-34 to -27 parts per thousand) reflect
recolonization of the catchment area by C-3 plants, consistent with a rapid rise in the upper treeline.
Specific algal biomarkers, including five unsaturated hydrocarbons of novel structure ascribed to the
microalga Botryococcus braunii, were abundant, as confirmed by scanning electronic microscopy
(SEM). An extreme delta(13)C shift of over 25 parts per thousand is displayed by the algal
biomarkers, an elevated value of -5.1 parts per thousand at the last glacial maximum (LGM)
contrasting with a minimum value of -30.3 parts per thousand at the beginning of the Holocene. A
major change in the molecular distributions of the algal biomarkers parallels this large delta(13)C
shift, with acyclic isoprenoid hydrocarbons dominating the last glacial and cyclic isoprenoid
hydrocarbons the Holocene. The low atmospheric partial pressure of CO2 (pCO(2)) at the LGM
would favour photosynthetic organisms possessing CO2-concentrating mechanisms, including
terrestrial C-4 grasses and freshwater green algae. Hence, glacial/interglacial changes in pCO(2), and
in the CO2:O-2 ratio in particular, had a significant impact on both terrestrial and aquatic ecosystems
on Mt. Kenya, in addition to the effects of climate and local environmental factors. Copyright (C)
1999 Elsevier Science Ltd.

KEYWORDS: ALGA BOTRYOCOCCUS-BRAUNII, ATMOSPHERIC CO2, C-4 GRASSES,
CARBON-ISOTOPE FRACTIONATION, DIOXIDE METABOLISMS, FRESH- WATER PLANTS,
MOUNT KENYA, N-ALKANES, ORGANIC-MATTER, VEGETATION CHANGE


     957  
Hufton, C.A., R.T. Besford, and A.R. Wellburn. 1996. Effects of NO (+NO2) pollution on
growth, nitrate reductase activities and associated protein contents in glasshouse lettuce grown
hydroponically in winter with CO2 enrichment. New Phytologist 133(3):495-501.

Winter hydroponic growth of several lettuce cultivars under glass showed considerable inhibition (up
to 47%) of growth after 6 wk exposure to concentrations of NO (+ NO2; 450 nl l(- 1) in total) typical
of emissions from propane burners used for direct heating and CO2 enrichment. After a further 4 wk
under similar conditions, however, these growth depressions were replaced by a swing into benefit
so that, by harvest, pollutant-exposed lettuces were bigger and had faster assimilation rates than those
growing in clean CO2-enriched air. This adaptation may partly be explained by enhanced use of NO2-
derived N by lettuce leaves, a consequence of increased nitrate reductase (NaR) activities and
amounts of associated NaR proteins, despite adequate nitrate also being available in the hydroponic
fluid. Rates of NaR activity in the roots, by contrast, were depressed by NO (+ NO2) pollution. NaR
activities were highest in early afternoon in clean or polluted air but these daily patterns did not
coincide with the content of NaR-associated proteins determined by ELISA. Other mechanisms of
modulating NaR activity must therefore be responsible.

KEYWORDS: DIOXIDE, EXPRESSION, GENES, LIGHT-DARK MODULATION, LONG-TERM
EXPOSURES, NITRITE-REDUCTASE, NITROGEN- METABOLISM, OXIDES, PLANTS,
TOMATO


     958  
Hughes, L., and F.A. Bazzaz. 1997. Effect of elevated CO2 on interactions between the western
flower thrips, Frankliniella occidentalis (Thysanoptera: Thripidae) and the common milkweed,
Asclepias syriaca. Oecologia 109(2):286-290.

We measured the effect of elevated CO2 on populations of the western flower thrips, Frankliniella
occidentalis and on the amount of leaf damage inflicted by the thrips to one of its host plants, the
common milkweed, Asclepias syriaca. Plants grown at elevated CO2 had significantly greater
aboveground biomass and C:N ratios, and significantly reduced percentage nitrogen. The number of
thrips per plant was not affected by CO2 treatment, but the density of thrips (numbers per gram
aboveground biomass), was significantly reduced at high CO2. Consumption by thrips, expressed as
the amount of damaged leaf area per capita, was significantly greater at high CO2, and the amount
of leaf area damaged by thrips was increased by 33%. However overall leaf area at elevated CO2
increased by 62%, more than compensating for the increase in thrips consumption. The net outcome
was that plants at elevated CO2 had 3.6 times more undamaged leaf area available for photosynthesis
than plants at ambient CO2, even though they had only 1.6 times the overall amount of leaf area. This
study highlights the need for measuring the effects of herbivory at the whole-plant level and also the
importance of taking herbivory into account when predicting plant responses to elevated CO2.

KEYWORDS: CARBON-DIOXIDE ATMOSPHERES, CHAMBERS, GROWTH, INSECT
HERBIVORE INTERACTIONS, LEPIDOPTERA, NOCTUIDAE, PAPER BIRCH,
PERFORMANCE, PLANTS, RESPONSES


     959  
Huluka, G., D.R. Hileman, P.K. Biswas, K.F. Lewin, J. Nagy, and G.R. Hendrey. 1994. Effects
of elevated co2 and water-stress on mineral concentration of cotton. Agricultural and Forest
Meteorology 70(1-4):141-152.

Projected increases in atmospheric CO2 concentrations may alter mineral and protein levels in plant
tissues, systematically affecting growth, nutrient cycling and utilization, residue decomposition, and
insect-plant interactions in the future. The free-air CO2 enrichment (FACE) system provided an
opportunity to monitor seasonal trends in nutrient status and crude protein content of cotton
(Gossypium hirsutum L. cv. Deltapine 77) grown in a natural field setting without the limitations
often imposed by growth chambers or reduced rooting volumes. In 1990, plants were exposed to two
levels of atmospheric CO2 (FACE, almost-equal-to 550 mumol mol-1 and CONTROL, almost-equal-
to 370 mumol mol-1) and two irrigation regimes (100% and 75% replacement of evapotranspiration)
beginning in early July. Cotton leaves, stem, and roots were sampled at different times during the
season and analyzed for C, N, Ca, K, Mg, P, Cu, Fe, Mn, Zn, B, Mo, Si and protein. The N and
protein concentrations of leaves, stems and roots were significantly lower in FACE plants than in
CONTROL plants, but C:N ratios were higher for the FACE plants than the CONTROL plants. Some
other elements were significantly affected by CO2 enrichment, but not for all dates and all plant
tissues. There were no significant effects in any of the data because of the irrigation treatment or the
irrigation-CO2 interaction. Reductions in tissue N and protein concentrations and the increases in the
C:N with CO2 enrichment have important implications for agricultural and natural systems and
demand additional research.

KEYWORDS: ACCLIMATION, CARBON DIOXIDE, DRY-MATTER, ENRICHMENT, GROWTH,
LEPIDOPTERA, NITROGEN, NUTRIENT CONCENTRATIONS, PLANTS, STARCH


     960  
Humphries, S.W., and S.P. Long. 1995. Wimovac - a software package for modeling the dynamics
of plant leaf and canopy photosynthesis. Computer Applications in the Biosciences 11(4):361-371.

The ability to predict net carbon exchange and production of vegetation in response to predicted
atmospheric and climate change is critical to assessing the potential impacts of these changes.
Mathematical models provide an important tool in the study of whole plant, canopy and ecosystem
responses to global environmental change. Because this requires prediction beyond experience,
mechanistic rather than empirical models are needed. The uniformity and strong understanding of the
photosynthetic process, which is the primary point of response of plant production to global
atmospheric change, provides a basis for such an approach. Existing modelling systems have been
developed primarily for expert modellers and have not been easily accessible to experimentalists,
managers and students. Here we describe a modular modelling system operating within Winnows to
provide this access. WIMOVAC (Windows Intuitive Model of Vegetation response to Atmosphere
and Climate Change) is designed to facilitate the modelling of various aspects of plant photosynthesis
with particular emphasis on the effects of global climate change. WIMOVAC has been designed to
run on IBM PC-compatible computers running Microsoft Windows. The package allows the
sophisticated control of the simulation processes for photosynthesis through a standardized Windows
user interface and provides automatically formatted results as either tabulated data or as a range of
customizable graphs. WIMOVAC has been written in Microsoft Visual Basic, to facilitate the rapid
development of user-friendly modules within the familiar Windows framework, while allowing a
structured development. The highly interactive nature of controls adopted by WIMOVAC makes it
suitable for research, management and educational purposes.

KEYWORDS: C-3, CARBON DIOXIDE, ELEVATED CO2, RESPONSES, YIELD


     961  
Hungate, B.A., J. Canadell, and F.S. Chapin. 1996. Plant species mediate changes in soil microbial
N in response to elevated CO2. Ecology 77(8):2505-2515.

The effect of elevated CO2 on plant-microbial interactions and nitrogen (N) cycling is critical to
predicting plant growth responses to elevated CO2, because plant growth is often N- limited. We
investigated whether the effects of elevated CO2 on plant-microbial N dynamics differed among six
annual plant species: three European grasses that have invaded California grasslands, and one grass
and two forbs native to California serpentine grassland. Elevated CO2 altered plant N pools and
(NH4+)-N-15 uptake, but the direction and magnitude of the changes were species dependent. The
introduced grasses showed increased plant N pools and (NH4+)-N-15 uptake, whereas the native
species showed smaller increases or even decreases in plant N pools and N-15(4)+ uptake. Under
nutrient enrichment, soil microbial N and (NH4+)-N-15 uptake differed among soils with different
plant species, but they were not affected by elevated CO2. At low nutrients, elevated CO2 altered soil
microbial N and (NH4+)-N-15 uptake, but the direction and magnitude of the changes were species
dependent. The changes in soil microbial N were positively correlated with changes in the plant N
pool, suggesting that there was no trade-off in N uptake between plants and microbes. These results
also suggest that plant species composition will partly determine the direction of changes in soil N
cycling in response to elevated CO2.

KEYWORDS: ANNUAL GRASSLAND, ATMOSPHERIC CO2, CARBON DIOXIDE,
DECOMPOSITION, DYNAMICS, ECOSYSTEMS, FOREST, GROWTH, LEAF LITTER,
NITROGEN CYCLES


     962  
Hungate, B.A., F.S. Chapin, H. Zhong, E.A. Holland, and C.B. Field. 1997. Stimulation of
grassland nitrogen cycling under carbon dioxide enrichment. Oecologia 109(1):149-153.

Nitrogen (N) limits plant growth in many terrestrial ecosystems, potentially constraining terrestrial
ecosystem response to elevated CO2. In this study, elevated CO2 stimulated gross N mineralization
and plant N uptake in two annual grasslands. In contrast to other studies that have invoked increased
C input to soil as the mechanism altering soil N cycling in response to elevated CO2, increased soil
moisture, due to decreased plant transpiration in elevated CO2, best explains the changes we
observed. This study suggests that atmospheric CO2 concentration may influence ecosystem
biogeochemistry through plant control of soil moisture.

KEYWORDS: ATMOSPHERIC CO2, BACTERIA, ECOSYSTEMS, FEEDBACK,
MINERALIZATION, NITRATE, NITRIFICATION, PLANT, RESPONSES, SOILS


     963  
Hungate, B.A., P. Dijkstra, D.W. Johnson, C.R. Hinkle, and B.G. Drake. 1999. Elevated CO2
increases nitrogen fixation and decreases soil nitrogen mineralization in Florida scrub oak. Global
Change Biology 5(7):781-789.

We report changes in nitrogen cycling in Florida scrub oak in response to elevated atmospheric CO2
during the first 14 months of experimental treatment. Elevated CO2 stimulated above-ground growth,
nitrogen mass, and root nodule production of the nitrogen-fixing vine, Galactia elliottii Nuttall.
During this period, elevated CO2 reduced rates of gross nitrogen mineralization in soil, and resulted
in lower recovery of nitrate on resin lysimeters. Elevated CO2 did not alter nitrogen in the soil
microbial biomass, but increased the specific rate of ammonium immobilization (NH4+ immobilized
per unit microbial N) measured over a 24-h period. Increased carbon input to soil through greater
root growth combined with a decrease in the quality of that carbon in elevated CO2 best explains
these changes. These results demonstrate that atmospheric CO2 concentration influences both the
internal cycling of nitrogen (mineralization, immobilization, and nitrification) as well as the processes
that regulate total ecosystem nitrogen mass (nitrogen fixation and nitrate leaching) in Florida coastal
scrub oak. If these changes in nitrogen cycling are sustained, they could cause long-term feedbacks
to the growth responses of plants to elevated CO2. Greater nitrogen fixation and reduced leaching
could stimulate nitrogen-limited plant growth by increasing the mass of labile nitrogen in the
ecosystem. By contrast, reduced nitrogen mineralization and increased immobilization will restrict
the supply rate of plant-available nitrogen, potentially reducing plant growth. Thus, the net feedback
to plant growth will depend on the balance of these effects through time.

KEYWORDS: ANNUAL GRASSLAND, ATMOSPHERIC CO2, CARBON-DIOXIDE
ENRICHMENT, GROWTH-RESPONSE, LONG-TERM, PLANTS, ROOT NODULE ACTIVITY,
SYMBIOTIC N-2 FIXATION, TRIFOLIUM- REPENS, WHITE CLOVER


     964  
Hungate, B.A., E.A. Holland, R.B. Jackson, F.S. Chapin, H.A. Mooney, and C.B. Field. 1997.
The fate of carbon in grasslands under carbon dioxide enrichment. Nature 388(6642):576-579.

The concentration of carbon dioxide (CO2) in the Earth's atmosphere is rising rapidly(1), with the
potential to alter many ecosystem processes. Elevated CO2 often stimulates photosynthesis(2),
creating the possibility that the terrestrial biosphere will sequester carbon in response to rising
atmospheric CO2 concentration, partly offsetting emissions from fossil-fuel combustion, cement
manufacture, and deforestation(3,4). However, the responses of intact ecosystems to elevated CO2
concentration, particularly the below-ground responses, are not well understood. Here we present
an annual budget focusing on below-ground carbon cycling for two grassland ecosystems exposed
to elevated CO2 concentrations. Three years of experimental CO2 doubling increased ecosystem
carbon uptake, but greatly increased carbon partitioning to rapidly cycling carbon pools below
ground, This provides an explanation for the imbalance observed in numerous CO2 experiments,
where the carbon increment from increased photosynthesis is greater than the increments in ecosystem
carbon stocks. The shift in ecosystem carbon partitioning suggests that elevated CO2 concentration
causes a greater increase in carbon cycling than in carbon storage in grasslands.

KEYWORDS: ATMOSPHERIC CO2 ENRICHMENT, BUDGET, GROWTH, IMPACT, NITROGEN,
PHOTOSYNTHESIS, RESPONSES, ROOT, TERRESTRIAL ECOSYSTEMS, WATER


     965  
Hungate, B.A., R.B. Jackson, C.B. Field, and F.S. Chapin. 1996. Detecting changes in soil carbon
in CO2 enrichment experiments. Plant and Soil 187(2):135-145.

After four growing seasons, elevated CO did not significantly alter surface soil C pools in two intact
annual grasslands. However, soil C pools in these systems are large compared to the likely changes
caused by elevated CO2. We calculated statistical power to detect changes in soil C, using an
approach applicable to all elevated CO2 experiments. The distinctive isotopic signature of the fossil-
fuel-derived CO2 added to the elevated CO2 treatment provides a C tracer to determine the rate of
incorporation of newly-fixed C into soil. This rate constrains the size of the possible effect of elevated
CO2 on soil C, Even after four years of treatment, statistical power to detect plausible changes in soil
C under elevated CO2 is quite low. Analysis of other elevated CO2 experiments in the literature
indicates that either CO2 does not affect soil C content, or that reported CO2 effects on soil C are
too large to be a simple consequence of increased plant carbon inputs, suggesting that other
mechanisms are involved, or that the differences are due to chance. Determining the effects of
elevated CO2 on total soil C and long-term C storage requires more powerful experimental
techniques or experiments of longer duration.

KEYWORDS: AMBIENT, BIOMASS PRODUCTION, DYNAMICS, ELEVATED CO2,
GRASSLAND, NITROGEN, PLANTS, RESPONSES, TALLGRASS PRAIRIE, TEMPERATURE


     966  
Hungate, B.A., T.E. Jordan, R.B. Jackson, and B.G. Drake. 1997. Atmospheric nitrogen
deposition. Science 275(5301):739-740.

KEYWORDS: CARBON DIOXIDE, CO2- ENRICHMENT, GROWTH, PISUM-SATIVUM, PLANTS


     967  
Hungate, B.A., C.P. Lund, H.L. Pearson, and F.S. Chapin. 1997. Elevated CO2 and nutrient
addition alter soil N cycling and N trace gas fluxes with early season wet-up in a California annual
grassland. Biogeochemistry 37(2):89-109.

We examined the effects of growth carbon dioxide (CO2) concentration and soil nutrient availability
on nitrogen (N) transformations and N trace gas fluxes in California grassland microcosms during
early-season wet-up, a time when rates of N transformation and N trace gas flux are high. After plant
senescence and summer drought, we simulated the first fall rains and examined N cycling. Growth
at elevated CO2 increased root production and root carbon:nitrogen ratio, Under nutrient enrichment,
elevated CO2 increased microbial N immobilization during wet-up, leading to a 43% reduction in
gross nitrification and a 55% reduction in NO emission from soil. Elevated CO2 increased microbial
N immobilization at ambient nutrients, but did not alter nitrification or NO emission. Elevated CO2
did not alter soil emission of N2O at either nutrient level. Addition of NPK fertilizer (1:1:1)
stimulated N mineralization and nitrification, leading to increased N2O and NO emission from soil,
The results of our study support a mechanistic model in which elevated CO2 alters soil N cycling and
NO emission: increased root production and increased C:N ratio in elevated CO2 stimulate N
immobilization, thereby decreasing nitrification and associated NO emission when nutrients are
abundant. This model is consistent with OUT basic understanding of how C availability influences soil
N cycling and thus may apply to many terrestrial ecosystems.

KEYWORDS: DECOMPOSITION, DRY SOIL, EMISSIONS, FOREST, LITTER QUALITY,
MICROBIAL BIOMASS, NITRIC-OXIDE, NITROGEN


     968  
Hunsaker, D.J., G.R. Hendrey, B.A. Kimball, K.F. Lewin, J.R. Mauney, and J. Nagy. 1994.
Cotton evapotranspiration under field conditions with co2 enrichment and variable soil-moisture
regimes. Agricultural and Forest Meteorology 70(1-4):247-258.

The CO2 concentration of the atmosphere is predicted to double by the next century, and this is
expected to increase significantly the growth and yield of many important agricultural crops. One
consequence of larger and more vigorous plants may be increased crop evapotranspiration (ET) and
irrigation water requirements. The objective of this work was to determine ET of cotton (Gossypium
hirsutum L. cv. 'Deltapine 77') grown under ambient (about 370 mumol mol-1) and enriched (550
mumol mol-1) CO2 concentrations for both well- watered and water-stress irrigation managements.
Studies were conducted in 1990 and 1991 within a large, drip-irrigated cotton field in central Arizona.
Cotton ET was measured during the growing seasons using a soil water balance, based on neutron
gauge soil water measurements. ET, for periods from 7 to 14 days, was not significantly different
between ambient and enriched CO2 treatments at the 0.05 probability level, and the total seasonal ET
for the CO2 treatments varied by 2% or less in either year. However, water-stress treatments, which
were initiated on 3 July (day of year (DOY) 184) in 1990 and on 20 May (DOY 128) in 1991, had
significantly lower (P < 0.05) ET than well-watered treatments starting at the end of July in 1990 and
in early July in 1991 when the plants were about 75-90 days old. The result that CO2 enrichment to
550 mumol mol-1 did not significantly change the ET of cotton was consistent with the results of co-
investigators who measured ET in the same experiments using stem flow gauges and an energy
balance. This result implies that irrigation water use would not have to be increased to produce cotton
in a future high-CO2 world. However, if a concomitant change in climate occurs, such as global
warming, cotton evapotranspiration may change in response to the changed weather condition.

KEYWORDS: CARBON DIOXIDE, WATER-USE, YIELD


     969  
Hunsaker, D.J., B.A. Kimball, P.J. Pinter, R.L. LaMorte, and G.W. Wall. 1996. Carbon dioxide
enrichment and irrigation effects on wheat evapotranspiration and water use efficiency. Transactions
of the Asae 39(4):1345-1355.

Evapotranspiration (ET) and water use efficiency were evaluated for two spring wheat crops, grown
in a drip-irrigated field under ambient (about 370 mu mol mol(-1)) and enriched (550 mu mol mol(-
1)) carbon dioxide (CO2) concentrations during the 1992-1993, and 1993-1994, Free-Air CO
Enrichment (FACE) experiments in central Arizona. CO2-enriched (FACE) and ambient CO2
(CONTROL) treatments were replicated in four circular plots, 25 m in diameter, and well-watered
(WET) and water- stressed (DRY) irrigation treatments were imposed on one-half of each plot.
Wheat ET, measured over discrete time periods of several days by a soil water balance, was
significantly higher for WET than DRY irrigation treatments after the first week in March in both
years. Differences in ET between CO2 treatments during the season were generally small, although
there was a consistent trend towards decreased ET for the FACE over CONTROL under the well-
watered irrigation regime. The two-year average reduction in seasonal ET owing to the FACE
treatment was about 5% under WET irrigation and was consistent with the results from two parallel
investigations that used an energy balance and sap flow measurements. Under the DRY irrigation
treatment, seasonal ET was 5 and 0.9% higher for the FACE treatment in the first and second years,
respectively. Water use efficiency (grain yield per unit seasonal ET) was significantly higher for FACE
treatments; 15 and 24% higher than CONTROL under DRY irrigation, and 13 and 18% higher than
CONTROL under WET irrigation. The results indicate that irrigation requirements for fully irrigated
wheat may be slightly lower in the future high-CO2 environment.

KEYWORDS: CO2- ENRICHMENT, COTTON, FACILITY, FIELD, TRANSPIRATION, YIELD


     970  
Hunt, H.W., E.T. Elliott, J.K. Detling, J.A. Morgan, and D.X. Chen. 1996. Responses of a C-3
and a C-4 perennial grass to elevated CO2 and temperature under different water regimes. Global
Change Biology 2(1):35-47.

An experiment was carried out to determine the effects of elevated CO2, elevated temperatures, and
altered water regimes in native shortgrass steppe. Intact soil cores dominated by Bouteloua gracilis,
a C-4 perennial grass, or Pascopyrum smithii, a C-3 perennial grass, were placed in growth chambers
with 350 or 700 mu L L(-1) atmospheric CO2, and under either normal or elevated temperatures. The
normal regime mimicked field patterns of diurnal and seasonal temperatures, and the high-temperature
regime was 4 degrees C warmer. Water was supplied at three different levels in a seasonal pattern
similar to that observed in the field. Total biomass after two growing seasons was 19% greater under
elevated CO2, with no significant difference between the C-3 and C-4 grass. The effect of elevated
CO2 on biomass was greatest at the intermediate water level. The positive effect of elevated CO2 on
shoot biomass was greater at normal temperatures in B. gracilis, and greater at elevated temperatures
in P. smithii. Neither root-to-shoot ratio nor production of seed heads was affected by elevated CO2.
Plant tissue N and soil inorganic N concentrations were lower under elevated CO2, but no more so
in the C-3 than the C-4 plant. Elevated CO2 appeared to increase plant N limitation, but there was
no strong evidence for an increase in N limitation or a decrease in the size of the CO2 effect from the
first to the second growing season. Autumn samples of large roots plus crowns, the perennial organs,
had 11% greater total N under elevated CO2, in spite of greater N limitation.

KEYWORDS: ATMOSPHERIC CARBON-DIOXIDE, ECOSYSTEMS, GROWTH-RESPONSE,
NITROGEN CONCENTRATION, PHOTOSYNTHESIS, RISING CO2, ROOT, SHORTGRASS
PRAIRIE, TALLGRASS PRAIRIE, TUSSOCK TUNDRA


     971  
Hunt, H.W., J.A. Morgan, and J.J. Read. 1998. Simulating growth and root-shoot partitioning
in prairie grasses under elevated atmospheric CO2 and water stress. Annals of Botany 81(4):489-501.

We constructed a model simulating growth, shoot-root partitioning, plant nitrogen (N) concentration
and total nonstructural carbohydrates in perennial grasses. Carbon (C) allocation was based on the
concept of a functional balance between root and shoot growth, which responded to variable plant
C and N supplies. Interactions between the plant and environment were made explicit by way of
variables for soil water and soil inorganic N. The model was fitted to data on the growth of two
species of perennial grass subjected to elevated atmospheric CO2 and water stress treatments. The
model exhibited complex feedbacks between plant and environment, and the indirect effects of CO2
and water treatments on soil water and soil inorganic N supplies were important in interpreting
observed plant responses. Growth was surprisingly insensitive to shoot-root partitioning in the model,
apparently because of the limited soil N supply, which weakened the expected positive relationship
between root growth and total N uptake. Alternative models for the regulation of allocation between
shoots and roots were objectively compared by using optimization to find the least squares fit of each
model to the data. Regulation by various combinations of C and N uptake rates, C and N substrate
concentrations, and shoot and root biomass gave nearly equivalent fits to the data, apparently because
these variables were correlated with each other. A partitioning function that maximized growth
predicted too high a root to shoot ratio, suggesting that partitioning did not serve to maximize growth
under the conditions of the experiment (C) 1998 Annals of Botany Company.

KEYWORDS: ALLOCATION, C-4 PLANTS, CARBON, CLIMATE CHANGE, MODEL,
NITROGEN, PLANT GROWTH, RESPONSES, SHORTGRASS PRAIRIE, SOIL


     972  
Hunt, H.W., M.J. Trlica, E.F. Redente, J.C. Moore, J.K. Detling, T.G.F. Kittel, D.E. Walter,
M.C. Fowler, D.A. Klein, and E.T. Elliott. 1991. Simulation-model for the effects of climate
change on temperate grassland ecosystems. Ecological Modelling 53(3-4):205-246.

We studied the responses of temperate grasslands to climate change using a grassland ecosystem
model which simulates seasonal dynamics of shoots, roots, soil water, mycorrhizal fungi, saprophytic
microbes, soil fauna, inorganic nitrogen, plant residues and soil organic matter. Forty-year simulations
were made for several climate change scenarios. The model was driven with observed weather and
with combinations of elevated atmospheric CO2, elevated temperature, and either increased or
decreased precipitation. Precipitation and CO2 level accounted for most of the variation among
climate change treatments in the responses of soil, plants, animals and microbes. Elevated temperature
extended the growing season but depressed photosynthesis in the summer, with little net effect on
annual primary production. Doubling CO2 (1) caused persistent increases in primary production, in
spite of greater nitrogen limitation, and (2) led to greater storage of carbon in plant residues and soil
organic matter. The increased carbon storage was not great enough to keep pace with the present rate
of increase in atmospheric CO2.

KEYWORDS: ATMOSPHERIC CO2 ENRICHMENT, BIOMASS DYNAMICS, BLUE-GRAMA,
BOUTELOUA-GRACILIS, CARBON DIOXIDE, CRESTED WHEATGRASS, ELEVATED CO2,
NATIVE SHORTGRASS ECOSYSTEM, SOIL-WATER, USE EFFICIENCY


     973  
Hunt, R., and G.M. Constable. 1993. Multifactorial growth-responses in holcus-lanatus - optima
and limiting factors. Annals of Botany 71(4):357-368.

KEYWORDS: CO2- ENRICHMENT, INTEGRATED ANALYSIS, LIGHT INTERCEPTION, LOCAL
FLORA, PLANT GROWTH, TEMPERATURE, WEIGHT, WHEAT, YIELD


     974  
Hunt, R., and J.H.C. Cornelissen. 1997. Components of relative growth rate and their interrelations
in 59 temperate plant species. New Phytologist 135(3):395-417.

Three groups of species (21 herbaceous monocotyledons, 22 herbaceous dicotyledons and 16 woody
dicotyledons), including representatives of a wide range of natural habitats and life forms in inland
Britain, were grown in the seedling phase in a resource-rich controlled environment and assessed over
a 14-day period (21 d in the case of woody species). Mean values of relative growth rate (RGR), Unit
leaf rate (ULR), leaf area ratio (LAR), leaf weight fraction (LWF), specific leaf area (SLA), and the
root-shoot allometric coefficient were derived. In herbaceous species, the grand mean RGR was 0.20
d(-1), comparable to values previously recorded. For woody species, the mean was 0.09 d(-1). An
existing assumption linking high RGR to high allocation to photosynthetic biomass was upheld by
comparisons made between groups. Within groups, however, no pattern of this kind could be
demonstrated. When photosynthetically active radiation was increased from 125 to 250 mu mol m(-2)
s(-1), ULR was increased almost pro rata. The parallel response in RGR was only slight, being offset
by considerable reductions in LAR. The apparent mean quantum yield for photosynthesis in
herbaceous species (whole-plant d. wt basis) was 0.60 g mol(-1). There was no significant
dependence of RGR on ULR in any of the three groups of species, although the absolute magnitude
of ULR declined in the order: herbaceous monocotyledons > herbaceous dicotyledons > woody
dicotyledons. In all three groups, RGR was strongly dependent upon LAR but no differences emerged
in absolute scale of LAR. The absolute scale of mean LWF decreased from herbaceous to woody
species, but the dependence of LAR on LWF strengthened. Groups showed no systematic differences
in magnitude of SLA, but the correlation of LAR with SLA was strong throughout. Multiple
regression showed that the leading determinants of RGR were ULR and SLA in herbaceous species
and LWF in woody species. Principal components analyses (PCA) on each of the three groups
explained at least 77% of variation and agreed closely with an optimal (non-hierarchical)
classification. Only six cluster 'types' were recognized out of the 16 theoretically possible
combinations of 'high' or 'low' values of the four growth parameters. Strong evidence of evolutionary
trade-offs emerged, most strikingly in that high RGR was never seen in combination with low SLA.
The morphological/physiological types identified by an all-groups PCA separated woody from the
herbaceous species, but dicotyledons were almost congruent with the monocotyledons. The non-
growth-analytical attributes most strongly correlated with mean RGR were percentage yield at a low
level of mineral nutrients, leaf nitrogen concentration, and seed weight. It was concluded that mean
RGR plays a central role in the identification of pathways of evolutionary specialization in herbaceous
species.

KEYWORDS: ALLOCATION PATTERNS, CARBON DIOXIDE, CHEMICAL-COMPOSITION,
CO2- ENRICHMENT, EMERGENT MACROPHYTES, GRASS, LEAF, ROOT, SEED, STRATEGIES


     975  
Hunt, R., D.W. Hand, M.A. Hannah, and A.M. Neal. 1991. Response to CO2 enrichment in 27
herbaceous species. Functional Ecology 5(3):410-421.

CO2-enrichment experiments were performed on 25 British native species of widely differing
ecology. Two crops, one C3 (sunflower) and one C4 (maize), were also included. The background
regime involved full-light, glasshouse conditions, non-limiting supplies of water and mineral nutrients
and a daytime mean temperature of 18-degrees-C. Four CO2 treatments were maintained at nominal
concentrations of 350, 500, 650 or 800 v.p.m. over a 56-day period. Hyperbolic functions were fitted
to yield vs CO2 concentration. The functions were then used to generate predictions of Q540/350
(the quotient of present yield under the CO2 regime predicted for the year 2050) and Q700/350 (the
quotient of present yield predicted for a doubling of ambient CO2 concentration). Values of
Q540/350 for whole-plant dry weight ranged from below 1.01 to 1.49, the upper values being at least
similar in magnitude to those already observed in C3 crops. The mean value of whole-plant Q700/350
for 11 species of near-competitive strategy was 1.43. Four species of stress-tolerant or ruderal
strategy had a mean Q700/350 of only 1.05. High CO2 responsiveness was common only within the
competitive strategy and its close relations. The fitted Q540/350 for species of the pure strategy was
1.38. In the centre of the strategic range the fitted value was 1.12, and at the far extreme, the value
for species of ruderal or stress-tolerant strategy was only 1.03.



     976  
Hunt, R., D.W. Hand, M.A. Hannah, and A.M. Neal. 1993. Further responses to co2 enrichment
in british herbaceous species. Functional Ecology 7(6):661-668.

1. CO2-enrichment experiments have been performed on 15 British herbaceous species of widely
differing ecology The conditions of growth were very similar to those used in a previous study and
involved full-light glasshouse conditions, non-Limiting supplies of water and mineral nutrients and
a daytime mean temperature of 18 degrees C. Four CO2 treatments were maintained (350, 500, 650
or 800 vpm) over periods of 49 or 52 days. 2. Hyperbolic functions were fitted to yield vs CO2
concentration. The functions were used to generate predictions of Q(540/350) (the quotient of the
'present' yield which is predicted for the CO2 regime expected by the year 2050) and Q(700/350) (the
quotient predicted for a doubling of the present ambient CO2 concentration). Values of Q(540/350)
for whole-plant dry weight ranged from below 1.00 to 1.19. The mean Value of whole-plant
Q(700/350) for eight species of 'competitive' functional type was 1.13. Six species of 'stress- tolerant'
or 'ruderal' type had a mean Q(700/350) Of only 1.07. 3. The new data support and amplify an earlier
conclusion that high CO2 responsiveness is normal only within the competitive functional type (or
'strategy') and its close relations. A simplified and more broadly based general prediction now gives
a fitted percentage increase after approximately 7 weeks' growth of 27% for species of broadly
competitive strategy In the centre of the range of functional types the fitted values now range from
13 to 20%, and at the far extremes, the value for species of either the ruderal or the stress-tolerant
type is now 6%. The gradient of this response is statistically significant, but less steep than that
previously reported.



     977  
Hunt, R., D.W. Hand, M.A. Hannah, and A.M. Neal. 1995. Temporal and nutritional influences
on the response to elevated co2 in selected british grasses. Annals of Botany 75(2):207-216.

To investigate the duration of the CO2 response and its interaction with mineral nutrition, CO2-
enrichment experiments were performed on four British grasses of differing ecology and functional
type: Arrhenatherum elatius (L.) Beauv., Festuca ovina L., Festuca rubra L. and Poa annua L.
Naturally-lit, glasshouse cabinets were used, with a non-limiting water supply and a daytime mean
temperature of 18 degrees C. Two CO2 treatments were maintained at nominal concentrations of 350
and 700 vpm and were combined factorially with two levels of balanced mineral nutrition at
conductivities of 0.1 and 1 mS cm(-1). Harvests took place at planting-out, and at 16, 37 and 58 d
thereafter. Fitted curves were used to derive instantaneous values of total dry weight, relative growth
rate (RGR), shoot weight fraction (SWF) and unit shoot rate (USR) for all combinations of species,
CO2 level, nutrient level and time of harvesting. At the higher nutrient level there was a reasonably
close agreement with previous estimates of the CO2 response in the four species. The response, if
any, most often arose from an increase in USR being accompanied by a less than proportionate
decline in SWF. Responses were sustained throughout the period studied. At the lower nutrient level,
all species showed a CO2 response initially, but this declined at a rate which was inversely related to
the CO2- responsiveness of the species at the higher nutrient level. The underlying ontogenetic drift
appeared to be markedly towards adjustment in SWF and away from that of USR. However, this drift
was retarded, suspended or even reversed by low-nutrient conditions and/or by high CO2
responsiveness in the species itself.

KEYWORDS: CARBON DIOXIDE, ENRICHMENT, GROWTH-ANALYSIS, NITROGEN, PLANT
GROWTH, RATIO, ROOT, SEEDLINGS, SHOOT, TREES


     978  
Huntley, B. 1995. Plant-species response to climate-change - implications for the conservation of
european birds. Ibis 137:S127-S138.

Wildlife conservation faces new and extreme challenges in adapting to the accelerating dynamics of
a world responding to global change, The Quaternary record shows that migration has been the usual
response of organisms to environmental change, This record also reveals that forecast future climate
changes are of a magnitude and in a direction unprecedented in recent earth history: the rate of these
changes is likely also to surpass that of any comparable change during the last 2.4 million years, The
relationship between a species' geographical distribution and present climate may be modelled by a
surface representing the probability of encountering that species under given combinations of climate
conditions, This 'climate response surface' then may be used to simulate potential future distributions
of the species in response to forecast climate scenarios, Such simulations reveal the magnitude of the
impacts of these forecast climate changes. Although to date this approach has been applied in Europe
only to plants, it promises to be valuable also for other groups of organisms, including birds. Some
bird species, however, may respond more directly to either habitat structure or presence of specific
food plants; such factors may be incorporated into the models when required, The magnitude of likely
vegetation changes necessitates a global approach to conservation if there is to be any hope of long-
term success, Successful conservation of global biodiversity will depend upon conservation of the
global environment and limitation of the human population much more than upon parochial efforts
to conserve locally rare organisms or habitats.

KEYWORDS: CO2, COMMUNITIES, GRADIENTS, MIGRATION, MODEL, NORTH-AMERICA,
POLLEN, SURFACES


     979  
Huntley, B., P.M. Berry, W. Cramer, and A.P. McDonald. 1995. Modelling present and potential
future ranges of some European higher plants using climate response surfaces. Journal of
Biogeography 22(6):967-1001.

It is hypothesized that the principal features of higher plant distributions at continental scales are
determined by the macroclimate. Bioclimate data have been computed on a 50 km grid across
Europe. Along with published maps of higher plant distributions based upon the same grid, these data
have been used to derive climate response surfaces that model the relationship between a species'
distribution and the present climate. Eight species representative of a variety of phytogeographic
patterns have been investigated. The results support the hypothesis that the European distributions
of all eight species are principally determined by macroclimate and illustrate the nature of the climatic
constraints upon each species. Simulated future distributions in equilibrium with 2 x CO2 climate
scenarios derived from two alternative GCMs show that all of the species are likely to experience
major shifts in their potential range if such climatic changes take place. Some species may suffer
substantial range and population reductions and others may face the threat of extinction. The rate of
the forecast climate changes is such that few, if any, species may be able to maintain their ranges in
equilibrium with the changing climate. In consequence, the transient impacts upon ecosystems will
be varied but often may lead to a period of dominance by opportunist, early-successional species. Our
simulations of potential ranges take no account of such factors as photoperiod or the direct effects
of CO2, both of which may substantially alter the realized future equilibrium.

KEYWORDS: BRITISH-ISLES, GRADIENTS, MIGRATION, NORTH-AMERICA, POLLEN,
REGRESSION, SPECIES RESPONSE, TILIA-CORDATA, VEGETATION


     980  
Hurry, V., M. Tobiaeson, S. Kromer, P. Gardestrom, and G. Oquist. 1995. Mitochondria
contribute to increased photosynthetic capacity of leaves of winter rye (secale-cereale L) following
cold- hardening. Plant, Cell and Environment 18(1):69-76.

Cold-hardening of winter rye (Secale cereale L. cv. Musketeer) increased dark respiration from -2.2
to -3.9 mu mol O-2 m(- 2)s(-1) and doubled light- and CO2-saturated photosynthesis at 20 degrees
C from 18.1 to 37.0 mu mol O-2 m(-2) s(-1). We added oligomycin at a concentration that
specifically inhibits oxidative phosphorylation to see whether the observed increase in dark respiration
reflected an increase in respiration in the light, and whether this contributed to the enhanced
photosynthesis of cold-hardened leaves, Oligomycin inhibited light- and CO2-saturated rates of
photosynthesis in non- hardened and cold-hardened leaves by 14 and 25%, respectively, and
decreased photochemical quenching of chlorophyll a fluorescence to a greater degree in cold-
hardened than in non- hardened leaves, These data indicate an increase both in the rate of respiration
in the light, and in the importance of respiration to photosynthesis following cold-hardening, Analysis
of metabolite pools indicated that oligomycin inhibited photosynthesis by limiting regeneration of
ribulose- 1,5-bisphosphate, This limitation was particularly severe in cold-hardened leaves, and the
resulting low 3-phosphoglycerate pools led to a feed-forward inhibition of sucrose-phosphate
synthase activity, Thus, it does not appear that oxidative phosphorylation supports the increase in
photosynthetic O-2 evolution following cold-hardening by increasing the availability of cytosolic
ATP, The data instead support the hypothesis that the mitochondria function in the light by using the
reducing equivalents generated by nan-cyclic photosynthetic electron transport.

KEYWORDS: ACCUMULATION, BARLEY HORDEUM-VULGARE, LOW-TEMPERATURE,
METABOLISM, OXIDATIVE- PHOSPHORYLATION, PROTOPLASTS, RESPIRATION, SUCROSE
PHOSPHATE SYNTHASE, TERM PHOTOINHIBITION, WHEAT


     981  
Hussain, M.W., L.H. Allen, and G. Bowes. 1999. Up-regulation of sucrose phosphate synthase in
rice grown under elevated CO2 and temperature. Photosynthesis Research 60(2-3):199-208.

Rice (Oryza sativa L. cv. IR-30) was grown season-long in outdoor, controlled-environment
chambers at 33 Pa CO2 with day/night/paddy-water temperatures of 28/21/25 degrees C, and at 66
Pa CO2 with five different day/night/paddy-water temperature regimes (25/18/21, 28/21/25,
31/24/28, 34/27/31 and 37/30/34 degrees C). Sucrose phosphate synthase (SPS) activities in leaf
extracts at 21, 48 and 81 days after planting (DAP) were assayed under saturating and selective
(limiting) conditions. Diel SPS activity data indicated that rice SPS was light regulated; with up to
2.2-fold higher rates during the day. Throughout the growth season, leaf SPS activities were up-
regulated in the CO2-enriched plants, averaging 20 and 12% higher than in ambient-CO2 grown
plants in selective and saturating assays, respectively. Similarly, SPS activities increased 2.4% for
each 1 degrees C rise in growth temperature from 25 to 34 degrees C, but decreased 11.5% at 37
degrees C. Leaf sucrose content was higher, and mirrored SPS activity better, than starch, although
starch was more responsive to CO2 treatment. Leaf sucrose and starch contents were significantly
higher throughout the season in plants at elevated CO2, but the N content averaged 6.5% lower.
Increasing growth temperatures from 25 to 37 degrees C caused a linear decrease (62%) in leaf starch
content, but not in sucrose. Consequently, the starch:sucrose ratio declined with growth temperature.
The data are consistent with the hypothesis that the up-regulation of leaf SPS may be an acclimation
response of rice to optimize the utilization and export of organic-C with the increased rates of
inorganic-C fixation in elevated CO2 or temperature growth regimes.

KEYWORDS: ACCLIMATION, ATMOSPHERIC CO2, CARBON-DIOXIDE CONCENTRATION,
GENE-EXPRESSION, LEAVES, METABOLISM, PHASEOLUS-VULGARIS, PHOTOSYNTHESIS,
PLANT GROWTH, RESPONSES


     982  
Hutchin, P.R., M.C. Press, J.A. Lee, and T.W. Ashenden. 1995. Elevated concentrations of co2
may double methane emissions from mires. Global Change Biology 1(2):125-128.

The potential impact of an increase in methane emissions from natural wetlands on climate change
models could be very large. We report a profound increase in methane emissions from cores of mire
peat and vegetation as a direct result of increasing the CO2 concentration from 355 to 550 mu mol
mol(-1) (a 60% increase). Increased CH4 fluxes were observed throughout the four month period of
study. Seasonal variation in CH4 flux, consistent with that seen in the field, was observed under both
ambient and elevated CO2. Under ambient CO2 methane fluxes rose from 0.02 mu mol m(-2) s(-1)
in May to 0.11 mu mol m(-2) s(-3) in July before declining again in August. Under elevated CO2,
methane fluxes were at least 100% greater throughout the experiment, rising from 0.05 mu mol m(-2)
s(-1) in May to a peak of 0.27 mu mol m(-2) s(-1) in July. The stimulation of CH4 emissions was
accompanied by a 100% increase in rates of photosynthesis from 4.6 (+/- 0.3) under ambient CO2
to 9.3 (+/- 0.7) mu mol m(-2) s(-1). Root and shoot biomass were unaffected.

KEYWORDS: PADDY FIELDS, RICE PADDY, SOIL TEMPERATURE, TUNDRA, WETLANDS


     983  
Hutjes, R.W.A., P. Kabat, S.W. Running, W.J. Shuttleworth, C. Field, B. Bass, M.A.F.D. Dias,
R. Avissar, A. Becker, M. Claussen, A.J. Dolman, R.A. Feddes, M. Fosberg, Y. Fukushima,
J.H.C. Gash, L. Guenni, H. Hoff, P.G. Jarvis, I. Kayane, A.N. Krenke, C. Liu, M. Meybeck,
C.A. Nobre, L. Oyebande, A. Pitman, R.A. Pielke, M. Raupach, B. Saugier, E.D. Schulze, P.J.
Sellers, J.D. Tenhunen, R. Valentini, R.L. Victoria, and C.J. Vorosmarty. 1998. Biospheric
aspects of the hydrological cycle - Preface. Journal of Hydrology 213(1-4):1-21.

The Core Project Biospheric Aspects of the Hydrological Cycle (BAHC) of the International
Geosphere Biosphere Programme (IGBP) addresses the biospheric aspects of the hydrological cycle
through experiments and modelling of energy, water, carbon dioxide and sediment fluxes in the soil-
vegetation- atmosphere system at a variety of spatial and temporal scales. Active regulation of water,
energy and carbon dioxide fluxes by the vegetation make it an important factor in regulating the
Earth's hydrological cycle and in the formation of the climate. Consequently, human induced
conversion of vegetation cover is an important driver for climate change. A number of recent studies,
discussed in this paper, emphasise the importance of the terrestrial biosphere for the climate system.
Initially, these studies demonstrate the influence of the land surface on tropical weather and climate,
revealing the mechanisms, acting at various scales, that connect increasing temperatures and
decreasing rainfall to large-scale deforestation and other forms of land degradation. More recently,
the significance of the land surface processes for water cycle and for weather and climate in temperate
and boreal zones was demonstrated. In addition the terrestrial biosphere plays a significant role in the
carbon dioxide fluxes and in global carbon balance. Recent work suggests that many ecosystems both
in the tropics and in temperate zones may act as a substantial sink for carbon dioxide, though the
temporal variability of this sink strength is yet unclear. Further, carbon dioxide uptake and
evaporation by vegetation are intrinsically coupled leading to Links and feedbacks between land
surface and climate that are hardly explored yet. Earth's vegetation cover and its changes owing to
human impact have a profound influence on a lateral redistribution of water and transported
constituents, such as nutrients and sediments, and acts therefore as an important moderator of Earth's
biogeochemical cycles. In the BAHC science programme, the importance of studying the influence
of climate and human activities on mobilisation and river-borne transport of constituents is explicitly
articulated. The terrestrial water and associated material cycles are studied as highly dynamic in space
and time, and reflect a complex interplay among climatic forcing, topography, land cover and
vegetation dynamics. Despite a large progress in our understanding of how the terrestrial biosphere
interacts with Earth's and climate system and with the terrestrial part of its hydrological cycle, a
number of basic issues still remain unresolved. Limited to the scope of BAHC, the paper briefly
assesses the present status and identifies the most important outstanding issues, which require further
research. Two, arguably most important outstanding issues are identified: a limited understanding of
natural variability, especially with respect to seasonal to inter-annual cycles, and of a complex
ecosystem behaviour resulting from multiple feedbacks and multiple coupled biogeochemical cycles
within the overall climate system. This leads to two major challenges for the future science agenda
related to global change research. First, there is a need for a strong multidisciplinary integration of
research efforts in both modelling and experiments, the latter extending to inter- annual timescales.
Second, the ever increasing complexity in characterisation and modelling of the climate system, which
is mainly owing to incorporation of the biosphere's and human feedbacks, may call for a new
approach in global change impact studies. Methodologies need to be developed to identify risks to,
and vulnerability of environmental systems, taking into account all important interactions between
atmospheric, ecological and hydrological processes at relevant scales. With respect to the influence
of climate and human activities on mobilisation and river-borne transport of constituents, the main
issues for the future are related to declining availability and quality of ground data for quantity and
quality of water discharge. Such assessments presented in this paper, in combination with community
wide science evaluation, has lead to an update of the science agenda for BAHC, a summary of which
is provided in the appendix. (C) 1998 Elsevier Science B.V. All rights reserved.

KEYWORDS: ATMOSPHERIC CO2, CLIMATIC IMPACTS, DROUGHT, FIELD EXPERIMENT,
FLUXES, GENERAL-CIRCULATION MODEL, SCALING CHARACTERISTICS, SEMI-ARID
REGIONS, TERRESTRIAL ECOSYSTEMS, VEGETATION


     984  
Huxman, K.A., S.D. Smith, and D.S. Neuman. 1999. Root hydraulic conductivity of Larrea
tridentata and Helianthus annuus under elevated CO2. Plant, Cell and Environment 22(3):325-330.

While investigations into shoot responses to elevated atmospheric CO2 are extensive, few studies
have focused on how an elevated atmospheric CO2 environment might impact root functions such
as water uptake and transport. Knowledge of functional root responses may be particularly important
in ecosystems where water is limiting if predictions about global climate change are true. In this study
we investigated the effect of elevated CO2 on the root hydraulic conductivity (L-p) of a C-3
perennial, Lawea tridentata, and a C-3 annual, Helianthus annuus. The plants were grown in a
glasshouse under ambient (360 mu mol mol(-1)) and elevated (700 mu mol mol(-1)) CO2. The L-p
through intact root systems was measured using a hydrostatic pressure-induced flow system. Leaf gas
exchange was also determined for both species and leaf water potential (psi(leaf)) was determined
in L, tridentata, The L-p of L, tridentata roots was unchanged by an elevated CO2 growth
environment. Stomatal conductance (g(s)) and transpiration (E) decreased and photosynthetic rate
(A(net)) and psi(leaf) increased in L, tridentata, There were no changes in biomass, leaf area, stem
diameter or root : shoot (R : S) ratio for L, tridentata. In H, annuus, elevated CO2 induced a nearly
two- fold decrease in root L-p. There was no effect of growth under elevated CO2 on A(net), g(s),
E, above- and below-ground dry mass, R : S ratio, leaf area, root length or stem diameter in this
species. The results demonstrate that rising atmospheric CO2 can impact water uptake and transport
in roots in a species-specific manner. Possible mechanisms for the observed decrease in root L-p in
H, annuus under elevated CO2 are currently under investigation and may relate to either axial or
radial components of root L-p.

KEYWORDS: ANATOMY, C-3, CARBON-DIOXIDE CONCENTRATION, CONDUCTANCE,
ENRICHMENT, ENVIRONMENT, GROWTH, PLANTS, RESPONSES, WHEAT


     985  
Huxman, T.E., E.P. Hamerlynck, D.N. Jordan, K.J. Salsman, and S.D. Smith. 1998. The effects
of parental CO2 environment on seed quality and subsequent seedling performance in Bromus rubens.
Oecologia 114(2):202-208.

Seeds were collected and compared from parent plants of Bromus rubens L. (Poaceae), an exotic
Mojave Desert annual grass, grown in ambient (360 mu mol mol(-1)) and elevated (700 mu mol mol(-
1)) CO2 to determine if parental CO2 growth conditions affected seed quality. Performance of seeds
developed on the above plants was evaluated to determine the influence of parental CO2 growth
conditions on germination, growth rate, and leaf production, Seeds of B. rubens developed oil parents
grown in elevated CO2 had a larger pericarp surface area, higher C:N ratio, and less total mass than
ambient-developed seeds, Parental CO2 environment did not have an effect on germination
percentage or mean germination timer as determined by radicle emergence. Seedlings from elevated-
CO2-developed seeds had a reduced relative growth rate and achieved smaller final mass over the
same growth period. Elevated-CO2-developed seeds had smaller seed reset-yes than ambient seeds,
as determined by growing seedlings in sterile media and monitoring senescence. It appears that
increased seed C:N ratios associated with plants grown under elevated CO2 may have a major effect
on seed quality (morphology, nutrition) and seedling performance (e.g., growth rate and leaf
production). Since the invasive success of B. rubens is primarily due to its ability to rapidly germinate,
increase leaf area and maintain a relatively high growth rate compared to native annuals and perennial
grasses, reductions in seed duality and seedling performance in elevated CO2 may have significant
impacts on future community composition in the Mojave Desert.

KEYWORDS: ALLOCATION, ELEVATED CO2, ENRICHMENT, GERMINATION, GRASSLAND,
GROWTH, PLANTS, RESPONSES


     986  
Huxman, T.E., E.P. Hamerlynck, M.E. Loik, and S.D. Smith. 1998. Gas exchange and
chlorophyll fluorescence responses of three south-western Yucca species to elevated CO2 and high
temperature. Plant, Cell and Environment 21(12):1275-1283.

The ability of seedlings to tolerate temperature extremes is important in determining the distribution
of perennial plants in the arid south-western USA, and the manner in which elevated CO2 impacts
the ability of plants to tolerate high temperatures is relatively unknown, Whereas the effects of
chronic high temperature (30-38 degrees C) and elevated CO2 are comparatively well understood,
little research has assessed plant performance in elevated CO2 during extreme (> 45 degrees C)
temperature events, We exposed three species of Yucca to 360 and 700 mu mol CO, mol(-1) for 8
months, then 9 d of high temperature (up to 53 degrees C) to evaluate the impacts of elevated CO2
on the potential for photosynthetic function during external high temperature. Seedlings of a coastal
C-3 species (Yucca whipplei), a desert C-3 species (Yucca brevifolia), and a desert CAM species
(Yucca schidigera), were used to test for differences among functional groups. In general, Yuccas
exposed to elevated CO2 showed decreases in carboxylation efficiency as compared with plants
grown at ambient before the initiation of high temperature, The coastal species (Y. whipplei) showed
significant reductions (33%) in CO2 saturated maximum assimilation rate (A(max)), but the desert
species (Y. brevifolia and Y. schidigera) showed no such reductions in A(max). Stomatal conductance
was lower in elevated CO2 as compared with ambient throughout the temperature event; however,
there were species-specific differences over time. Elevated CO2 enhanced photosynthesis in Y.
whipplei at high temperatures for a period of 4 d, but not for Y. brevifolia or Y. schidigera, Elevated
CO2 offset photoinhibition (measured as F-v/F-m) in Y. whipplei as compared with ambient CO2,
depending on exposure time to high temperature. Stable F-v/F-m in Y. whipplei occurred in parallel
with increases in the quantum yield of photosystem II (Phi PSII) at high temperatures in elevated
CO2. The value of Phi PSII remained constant or decreased with increasing temperature in all other
treatment and species combinations, This suggests that the reductions in F-v/F-m resulted from
thermal energy dissipation in the pigment bed for Y. brevifolia and Y. schidigera, The greater
efficiency of photosystem II in Y. whipplei helped to maintain photosynthetic function at high
temperatures in elevated CO2. These patterns are in contrast to the hypothesis that high temperatures
in elevated CO2 would increase the potential for photoinhibition, Our results suggest that elevated
CO2 may offset high-temperature stress in coastal Yucca, but not in those species native to drier
systems, Therefore, in the case of Y. whipplei, elevated CO2 may allow plants to survive extreme
temperature events, potentially relaxing the effects of high temperature on the establishment in novel
habitats.

KEYWORDS: ACCLIMATION, AGAVE-DESERTI, ATMOSPHERIC CO2, AVAILABILITY,
BREVIFOLIA, GROWTH, PHOTOSYNTHESIS, PHYSIOLOGY, PLANTS, STRESS


     987  
Huxman, T.E., E.P. Hamerlynck, B.D. Moore, S.D. Smith, D.N. Jordan, S.F. Zitzer, R.S.
Nowak, J.S. Coleman, and J.R. Seemann. 1998. Photosynthetic down-regulation in Larrea
tridentata exposed to elevated atmospheric CO2: interaction with drought under glasshouse and field
(FACE) exposure. Plant, Cell and Environment 21(11):1153-1161.

The photosynthetic response of Larrea tridentata Cav,, an evergreen Mojave Desert shrub, to elevated
atmospheric CO2 and drought was examined to assist in the understanding of how plants from water-
limited ecosystems will respond to rising CO2, We hypothesized that photosynthetic down-regulation
would disappear during periods of water Limitation, and would, therefore, likely be a seasonally
transient event. To test this we measured photosynthetic, water relations and fluorescence responses
during periods of increased and decreased mater availability in two different treatment
implementations: (1) from seedlings exposed to 360, 550, and 700 mu mol mol(-1) CO2 in a
glasshouse; and (2) from intact adults exposed to 360 and 550 mu mol mol(-1) CO2 at the Nevada
Desert FACE (Free Air CO2 Enrichment) Facility. FACE and glasshouse wed-watered Larrea
significantly down-regulated photosynthesis at elevated CO2, reducing maximum photosynthetic rate
(A(max)), carboxylation efficiency (CE), and Rubisco catalytic sites, whereas droughted Larrea
showed a differing response depending on treatment technique. A(max) and CE were lower in
droughted Larrea compared with well-watered plants, and CO2 had no effect on these reduced
photosynthetic parameters. However, Rubisco catalytic sites decreased in droughted Larrea at
elevated CO2. Operating C-i increased at elevated CO2 in droughted plants, resulting in greater
photosynthetic rates at elevated CO2 as compared with ambient CO2. In well-watered plants, the
changes in operating C-i, CE andA(max) resulted in similar photosynthetic rates across CO2
treatments. Our results suggest that drought can diminish photosynthetic down-regulation to elevated
CO2 in Larrea, resulting in seasonally transient patterns of enhanced carbon gain. These results
suggest that water status may ultimately control the photosynthetic response of desert systems to
rising CO2.

KEYWORDS: ACCLIMATION, CARBON DIOXIDE, DESERT, ECOSYSTEMS, GAS-EXCHANGE,
GROWTH, INTACT LEAVES, RESPONSES, RIBULOSE-1;5-BISPHOSPHATE CARBOXYLASE,
TEMPERATURE


     988  
Hymus, G.J., D.S. Ellsworth, N.R. Baker, and S.P. Long. 1999. Does free-air carbon dioxide
enrichment affect photochemical energy use by evergreen trees in different seasons? A chlorophyll
fluorescence study of mature loblolly pine. Plant Physiology 120(4):1183-1191.

Previous studies of the effects of growth at elevated CO2 on energy partitioning in the photosynthetic
apparatus have produced conflicting results. The hypothesis was developed and tested that elevated
CO2 increases photochemical energy use when there is a high demand for assimilates and decreases
usage when demand is low. Modulated chlorophyll a fluorescence and leaf gas exchange were
measured on needles at the top of a mature, 12-m loblolly pine (Pinus taeda L.) forest. Trees were
exposed to ambient CO2 or ambient plus 20 Pa CO2 using free-air CO2 enrichment. During April
and August, periods of shoot growth, light-saturated photosynthesis and linear electron transport
were increased by elevated CO2. In November, when growth had ceased but temperatures were still
moderate, CO2 treatment had no significant effect on linear electron transport. In February, when low
temperatures were likely to inhibit translocation, CO2 treatment caused a significant decrease in linear
electron transport. This coincided with a slower recovery of the maximum photosystem II efficiency
on transfer of needles to the shade, indicating that growth in elevated CO2 induced a more persistent
photoinhibition. Both the summer increase and the winter decrease in linear electron transport in
elevated CO2 resulted from a change in photochemical quenching, not in the efficiency of energy
transfer within the photosystem II antenna. There was no evidence of any effect of CO2 on
photochemical energy sinks other than carbon metabolism. Our results suggest that elevated CO2 may
increase the effects of winter stress on evergreen foliage.

KEYWORDS: ANTIOXIDATIVE ENZYMES, ASSIMILATION, ELEVATED CO2, LEAVES, LONG-
TERM EXPOSURE, NET PHOTOSYNTHESIS, PHOTOSYNTHETIC ELECTRON-TRANSPORT,
PHOTOSYSTEM-II ACTIVITY, QUANTUM YIELD, RISING ATMOSPHERIC CO2


     989  
Hyodo, H., C. Hashimoto, S. Morozumi, W.Z. Hu, and K. Tanaka. 1993. Characterization and
induction of the activity of 1- aminocyclopropane-1-carboxylate oxidase in the wounded mesocarp
tissue of cucurbita-maxima. Plant and Cell Physiology 34(5):667-671.

1-Aminocyclopropane-1-carboxylate (ACC) oxidase (ethylene- forming enzyme) was isolated from
wounded mesocarp tissue of Cucurbita maxima (winter squash) fruit, and its enzymatic properties
were investigated. The enzyme required Fe2+ and ascorbate for its activity as well as ACC and O2
as substrates. The in vitro enzyme activity was enhanced by CO2. The apparent K(m) value for ACC
was 175 muM under atmospheric conditions. The enzyme activity was inhibited by sulfhydryl
inhibitors and divalent cations such as Co2+, Cu2+, and Zn2+. ACC oxidase activity was induced at
a rapid rate by wounding in parallel with an increase in the rate of ethylene production. The exposure
of excised discs of mesocarp to 2,5-norbornadiene (NBD), an inhibitor of ethylene action, strongly
suppressed induction of the enzyme, and the application of ethylene significantly accelerated the
induction of the activity of ACC oxidase in the wounded mesocarp tissue. These results suggests that
endogenous ethylene produced in response to wounding may function in promoting the induction of
ACC oxidase.

KEYWORDS: ACID SYNTHASE, APPLE FRUIT, BIOSYNTHESIS, CANTALOUPE,
CONVERSION, ETHYLENE-FORMING ENZYME, WINTER SQUASH FRUIT


     990  
Idso, C.D., S.B. Idso, and R.C. Balling. 1998. The urban CO2 dome of Phoenix, Arizona. Physical
Geography 19(2):95-108.

Air temperatures, relative humidities, and atmospheric carbon dioxide concentrations were measured
at a height of 2 m at approximate 1.6-km intervals prior to sunrise and in the middle of the afternoon
on five days in January along a number of different transects through the extended metropolitan area
of Phoenix, Arizona. Spatially interpolated maps of the data indicate the presence of an "urban CO2
dome" that reaches concentrations as high as 555 ppmv in the city center and decreases to a value
of approximately 370 ppmv on the outskirts of the city at this time of year. Pre-dawn CO2 values
inside the dome are considerably higher than mid-afternoon values, suggesting that solar-induced
convective mixing and the photosynthetic uptake of CO2 by urban vegetation may play significant
roles in diurnally redistributing the anthropogenically produced CO2 that, together with that produced
by plant respiration, accumulates near the ground during the night and early morning hours.
Temperature and relative humidity appear to have little influence on either the concentration or
location of the CO2 dome, but variations in wind speed and direction at times may disrupt the pattern
that develops under normally fair conditions. The high CO2 concentrations within the dome may help
to ameliorate the deleterious effects of urban air pollution on vegetation growing within the city.
Together with the urban heat island phenomenon, they may also provide a natural laboratory for
studying the effects of contemporaneous warming and atmospheric CO2 enrichment within the
context of predicted future global change.

KEYWORDS: ATMOSPHERIC CARBON-DIOXIDE, ELEVATED CO2, HEAT-ISLAND, NET
PHOTOSYNTHESIS, PLANT-RESPONSES, RURAL TRANSECT, SULFUR-DIOXIDE, TEMPORAL
ANALYSIS, WATER-USE, YIELD


     991  
Idso, K.E., and S.B. Idso. 1994. Plant-responses to atmospheric co2 enrichment in the face of
environmental constraints - a review of the past 10 years research. Agricultural and Forest
Meteorology 69(3-4):153-203.

This paper presents a detailed analysis of several hundred plant carbon exchange rate (CER) and dry
weight (DW) responses to atmospheric CO2 enrichment determined over the past 10 years. It
demonstrates that the percentage increase in plant growth produced by raising the air's CO2 content
is generally not reduced by less than optimal levels of light, water or soil nutrients, nor by high
temperatures, salinity or gaseous air pollution. More often than not, in fact, the data show the relative
growth-enhancing effects of atmospheric CO2 enrichment to be greatest when resource limitations
and environmental stresses are most severe.

KEYWORDS: CARBON-DIOXIDE ENRICHMENT, DRY-MATTER PRODUCTION, ELEVATED
CO2, GAS-EXCHANGE, NET PHOTOSYNTHESIS, PINUS-TAEDA SEEDLINGS, RADIATA D-
DON, SOUR ORANGE TREES, SOYBEAN CANOPY PHOTOSYNTHESIS, WATER-USE
EFFICIENCY


     992  
Idso, S.B. 1991. A general relationship between CO2-induced increases in net photosynthesis and
concomitant reductions in stomatal conductance. Environmental and Experimental Botany
31(4):381-383.

Simultaneous measurements of net photosynthesis and stomatal conductance of leaves of sour orange
trees growing in normal and CO2-enriched air, together with similar data for cotton, cotton, soybeans
and water hyacinth, suggest that a plant's photosynthetic response to atmospheric CO2 enrichment
is inversely proportional to its degree of CO2-induced stomatal closure.

KEYWORDS: ATMOSPHERIC CO2 ENRICHMENT


     993  
Idso, S.B. 1992. Net photosynthesis - corrections required of leaf chamber measurements.
Agricultural and Forest Meteorology 58(1-2):35-42.

Direct measurements of trunk and branch volumes and fine-root biomass confirm that the growth rate
of sour orange trees supplied with an extra 300 cm3 of CO2 m-3 of air is approximately 2.8 times
greater than that of similar trees growing in ambient air. Net CO2 exchange measurements made on
individual leaves over three 24 h periods in May, June and July 1990, however, suggest a relative
growth enhancement for the CO2-enriched trees of the order of five to seven, which is clearly
impossible on the basis of the direct growth measurements. It is shown that this discrepancy is due
to a problem inherent in the act of enclosing a leaf in a leaf chamber, but that its effects can be
removed by means of a simple correction procedure.

KEYWORDS: BASE-LINE ANALYSIS, COMPATIBILITY, HUMIDITY, POROMETRY,
TEMPERATURE, WATER-STRESS


     994  
Idso, S.B. 1992. Shrubland expansion in the american southwest. Climatic Change 22(1):85-86.

KEYWORDS: CARBON DIOXIDE, CO2, ENRICHMENT, SOUR ORANGE TREES


     995  
Idso, S.B. 1997. The poor man's biosphere, including simple techniques for conducting CO2
enrichment and depletion experiments on aquatic and terrestrial plants. Environmental and
Experimental Botany 38(1):15-38.

This paper reports the results of a 3-year experimental program designed to develop an inexpensive,
low-technology approach for conducting atmospheric CO2 enrichment and depletion studies of
aquatic and terrestrial plants. It begins by demonstrating the effectiveness of a number of simple
techniques for creating a wide range of sub-and supra-ambient atmospheric CO2 concentrations in
a set of low-cost experimental enclosures. It then describes the utilization of this approach in a variety
of experiments that lead to the derivation of CO2-growth response relationships for a common
terrestrial plant and for both a submerged and a floating aquatic species. Finally, it provides a
description of a simple procedure for obtaining accurate assessments of atmospheric CO,
concentrations in such experiments. (C) 1997 Elsevier Science B.V.

KEYWORDS: ATMOSPHERIC CO2, GROWTH, TEMPERATURE


     996  
Idso, S.B. 1998. CO2-induced global warming: a skeptic's view of potential climate change. Climate
Research 10(1):69-82.

Over the course of the past 2 decades, I have analyzed a number of natural phenomena that reveal
how Earth's near-surface air temperature responds to surface radiative perturbations. These studies
all suggest that a 300 to 600 ppm doubling of the atmosphere's CO2 concentration could raise the
planet's mean surface air temperature by only about 0.4 degrees C. Even this modicum of warming
may never be realized, however, for it could be negated by a number of planetary cooling forces that
are intensified by warmer temperatures and by the strengthening of biological processes that are
enhanced by the same rise in atmospheric CO2 concentration that drives the warming. Several of
these cooling forces have individually been estimated to be of equivalent magnitude, but of opposite
sign, to the typically predicted greenhouse effect of a doubling of the air's CO2 content, which
suggests to me that little net temperature change will ultimately result from the ongoing buildup of
CO2 in Earth's atmosphere. Consequently, I am skeptical of the predictions of significant CO2-
induced global warming that are being made by state-of-the-art climate models and believe that much
more work on a wide variety of research fronts will be required to properly resolve the issue.

KEYWORDS: ATMOSPHERIC CARBON-DIOXIDE, CO2- ENRICHMENT, DIMETHYL SULFIDE,
EQUATORIAL PACIFIC-OCEAN, ICE-FORMING NUCLEI, INORGANIC CARBON, RADIATION
BUDGET EXPERIMENT, SOLAR IRRADIANCE, SUBMERSED MACROPHYTE GROWTH,
SURFACE AIR-TEMPERATURE


     997  
Idso, S.B. 1999. The long-term response of trees to atmospheric CO2 enrichment. Global Change
Biology 5(4):493-495.

KEYWORDS: GROWTH, PLANTS


     998  
Idso, S.B., S.G. Allen, and B.A. Kimball. 1990. Growth-response of water lily to atmospheric CO2
enrichment. Aquatic Botany 37(1):87-92.



     999  
Idso, S.B., and R.C. Balling. 1992. United-states drought trends of the past century. Agricultural
and Forest Meteorology 60(3-4):279-284.

One of the primary concerns about potential global change is that the steadily rising CO2 content of
earth's atmosphere may lead to significant increases in the severity and frequency of drought,
especially in the agricultural heartland of the USA (Manabe et al., 1981; Gleick, 1987; Manabe and
Wetherald, 1986, 1987, McCabe et al., 1990). This consequence has been postulated to result from
minor changes in the atmospheric supply of moisture (precipitation) and major changes in the
atmospheric demand for moisture (potential evapotranspiration), as a result of increased surface
temperatures. Waggoner (1989), for example, has shown how a 10% drop in precipitation can lead
to a 46% increase in the frequency of drought; while Rind et al. (1990) have demonstrated that CO2-
induced global warming, if it occurs as projected, could raise the frequency of severe drought in the
USA from 5 to 50% by the year 2050. If drought is truly this responsive to changes in precipitation
and potential evapotranspiration, and there is little reason to believe it is not, it could serve as a
sensitive indicator of global warming and as a reliable test for identifying its onset. Hence, as the
effective CO2 content of the atmosphere has already risen by nearly 50% above its pre-industrial level
(Michaels, 1990; Houghton et al., 1990), studies of drought trends of the past century might even
now provide evidence for the reality of global warming. However, there are three separate factors
that could complicate this simple test.

KEYWORDS: ATMOSPHERIC CARBON-DIOXIDE, INCREASE, PRECIPITATION, RECORD


     1000 
Idso, S.B., K.E. Idso, R.L. Garcia, B.A. Kimball, and J.K. Hoober. 1995. Effects of atmospheric
co2 enrichment and foliar methanol application on net photosynthesis of sour orange tree (citrus-
aurantium, rutaceae) leaves. American Journal of Botany 82(1):26-30.

Foliar spray applications of 40% aqueous methanol were made to sunlit leaves of sour orange trees
that had been grown continuously in clear-plastic-wall open-top enclosures maintained out-of-doors
at Phoenix, Arizona, for over 5.5 years in ambient air of approximately 400 mu mol mol(-1) CO2 and
in air enriched with CO2 to a concentration of approximately 700 mu mol mol(-1). No unambiguous
effects of the methanol applications were detected in net photosynthesis measurements made on
foliage in either of the two CO2 treatments. The 75% increase in CO2 however, raised the upper-
limiting leaf temperature for positive net photosynthesis by approximately 7 C, which resulted in a
75% enhancement in net photosynthesis at a leaf temperature of 31 C, a 100% enhancement at a leaf
temperature of 35 C, and a 200% enhancement at 42 C.

KEYWORDS: ELEVATED CO2, FIELD, GAS-EXCHANGE, GROWTH, TEMPERATURE


     1001 
Idso, S.B., and B.A. Kimball. 1991. Downward regulation of photosynthesis and growth at high
CO2 levels - no evidence for either phenomenon in 3-year study of sour orange trees. Plant
Physiology 96(3):990-992.

Numerous photosynthesis and growth measurements of sour orange (Citrus aurantium L.) trees
maintained in ambient air and air enriched with an extra 300 microliters per liter of CO2 have revealed
the CO2-enriched trees to have consistently sequestered approximately 2.8 times more carbon than
the control trees over a period of three full years. Under field conditions in the natural environment,
plants may not experience the downward regulation of photosynthetic capacity typically observed in
long-term CO2 enrichment experiments with plants growing in pots.

KEYWORDS: ATMOSPHERIC CARBON-DIOXIDE, COTTON, ELEVATED LEVELS,
EXPOSURE, INHIBITION, PLANTS


     1002 
Idso, S.B., and B.A. Kimball. 1991. Effects of 2 and a half years of atmospheric CO2 enrichment
on the root density distribution of 3-year-old sour orange trees. Agricultural and Forest Meteorology
55(3-4):345-349.

Eight sour orange trees planted directly into the ground at Phoenix, Arizona, as small seedlings in July
1987 have been enclosed by four clear-plastic-wall, open-top chambers since November of that year,
half of which have been continuously supplied with a CO2 enriched atmosphere consisting of an extra
300 cm3 CO2 m-3 of air. Extensive soil coring of the trees' root zones conducted in July 1990
indicated that two and a half years of growth under these conditions produced a fine root biomass
enhancement of 175% in the CO2 enriched trees. This growth enhancement is of the same order of
magnitude as our previously reported results for net photosynthesis and trunk and branch volumes
for these trees.



     1003 
Idso, S.B., and B.A. Kimball. 1992. Aboveground inventory of sour orange trees exposed to
different atmospheric co2 concentrations for 3 full years. Agricultural and Forest Meteorology 60(1-
2):145-151.

Sour orange trees have been grown from the seedling stage out- of-doors at Pheonix, Arizona in
clear-plastic-wall, open-top enclosures for 3.5 years. For the last 3 years of this period, half of the
trees have been continuously exposed to air enriched with an extra 300 cm3 of CO2 m-3 of air.
Inventories of all aboveground plant parts conducted at the conclusions of the second and third years
of the study reveal that the total number of branches per tree, the total number of leaves per tree, and
the total trunk plus branch volume per tree can all be adequately inferred from measurements of trunk
cross- sectional area. They also reveal a sustained beneficial impact of atmospheric CO2 enrichment.
After 3 full years of differential CO2 exposure, the CO2-enriched trees had nearly 100% more
branches, 75% more leaves, approximately 160% more trunk and branch volume, and 190% more
trunk, branch and fruit rind volume than the ambient-treatment trees.

KEYWORDS: ENRICHMENT


     1004 
Idso, S.B., and B.A. Kimball. 1992. Effects of atmospheric co2 enrichment on photosynthesis,
respiration, and growth of sour orange trees. Plant Physiology 99(1):341-343.

Numerous net photosynthetic and dark respiratory measurements were made over a period of 4 years
on leaves of 24 sour orange (Citrus aurantium) trees; 8 of them growing in ambient air at a mean CO2
concentration of 400 microliters per liter, and 16 growing in air enriched with CO2 to concentrations
approaching 1000 microliters per liter. Over this CO2 concentration range, net photosynthesis
increased linearly with CO2 by more than 200%, whereas dark respiration decreased linearly to only
20% of its initial value. These results, together with those of a comprehensive fine-root biomass
determination and two independent above-ground trunk and branch volume inventories, suggest that
a doubling of the air's current mean CO2 concentration of 360 microliters per liter would enhance the
growth of the trees by a factor of 3.8.

KEYWORDS: CARBON DIOXIDE, YIELD


     1005 
Idso, S.B., and B.A. Kimball. 1992. Seasonal fine-root biomass development of sour orange trees
grown in atmospheres of ambient and elevated co2 concentration. Plant, Cell and Environment
15(3):337-341.

Sour orange trees have been grown from the seedling stage out- of-doors at Phoenix, Arizona, USA,
in open-top enclosures with clear plastic walls for 3.5 years. For the last 3 years of this period, half
of the trees have been continuously exposed to air enriched with CO2 to 300-mu-mol mol-1 above
the ambient concentration. At 2-month intervals over the last 12 months, we have determined the
fine-root biomass in the top 0.4 m of the soil profile beneath the trees. Results from both treatments
define a single relationship between fine-root biomass and trunk cross-sectional area. The data also
show the CO2-enriched trees to have approximately 2.3 times more fine-root biomass in this soil layer
than the trees grown in ambient air.

KEYWORDS: ENRICHMENT, GLOBAL CARBON-CYCLE, STORAGE


     1006 
Idso, S.B., and B.A. Kimball. 1993. Effects of atmospheric co2 enrichment on net photosynthesis
and dark respiration rates of 3 australian tree species. Journal of Plant Physiology 141(2):166-171.

Net photosynthesis and dark respiration rates of leaves of three Australian tree species exposed to
a range of atmospheric CO2 concentrations were measured throughout the summer of 1991. For all
three species - the Australian bottle tree (Brachychiton populneum (Schott.) R. Br.) and two
eucalyptus (Eucalyptus microtheca F. Muell. and E. polyanthemus Schauer) - dark respiration
dropped by approximately 50 % for a 360 to 720 muL/L doubling of the air's CO2 concentration,
while net photosynthesis rose by a factor of two. These results were not significantly different from
results obtained previously for the common sour orange tree (Citrus aurantium L.).

KEYWORDS: CARBON DIOXIDE, CO2- ENRICHMENT, ELEVATED CO2, SOUR ORANGE
TREES, TERM


     1007 
Idso, S.B., and B.A. Kimball. 1993. Tree growth in carbon-dioxide enriched air and its implications
for global carbon cycling and maximum levels of atmospheric co2. Global Biogeochemical Cycles
7(3):537-555.

In the longest carbon dioxide enrichment experiment ever conducted, well-watered and adequately
fertilized sour orange tree seedlings were planted directly into the ground at Phoenix, Arizona, in July
1987 and continuously exposed, from mid-November of that year, to either ambient air or air
enriched, with an extra 300 ppmv of CO2 in clear-plastic-wall open-top enclosures. Only 18 months
later, the CO2-enriched trees had grown 2.8 times larger than the ambient-treated trees; and they have
maintained that productivity differential to the present day. This tremendous growth advantage is due
to two major factors: a CO2-induced increase in daytime net photosynthesis and a CO2-induced
reduction in nighttime dark respiration. Measurements of these physiological processes in another
experiment have shown three Australlian tree species to respond similarly; while an independent study
of the atmosphere's seasonal CO2 cycle suggests that all earth's trees, in the mean, probably share this
same response. A brief review of the plant science literature outlines how such a large growth
response to atmospheric CO2 enrichment might possibly be maintained in light of resource limitations
existing in nature. Finally, it is noted that a CO2 ''fertilization effect'' of this magnitude should
substantially slow the rate at which anthropogenic carbon dioxide would otherwise accumulate in the
atmosphere, possibly putting an acceptable upper limit on the level to which the CO2 content of the
air may ultimately rise.

KEYWORDS: BUSH PLANT- RESPONSE, ELEVATED CO2, LYCOPERSICON-ESCULENTUM
MILL, PHOTOSYNTHETIC ACCLIMATION, PINUS-RADIATA, RADIATA D-DON, ROOT
RESTRICTION, SOUR ORANGE TREES, STOMATAL CONDUCTANCE, WATER-USE


     1008 
Idso, S.B., and B.A. Kimball. 1994. Effects of atmospheric co2 enrichment on biomass
accumulation and distribution in eldarica pine trees. Journal of Experimental Botany 45(280):1669-
1672.

Eight Eldarica pine tree (Pinus eldarica L.) seedlings planted directly into the ground at Phoenix,
Arizona within four clear- plastic-wall open-top enclosures were grown for a period of 2 years at
mean atmospheric CO2 concentrations of 408, 554, 680, and 812 mu L L(-1). Biomass accumulations
in needles, branches and boles were all linear functions of CO2 over this concentration range. For a
75% increase in ambient CO2, i.e. for an increase from 400-700 mu L L(-1), the trees experienced
a 3.42-fold increase in total above-ground biomass; while for a CO2 concentration doubling from
400-800 mu L L(-1), they experienced a 4.23-fold increase. Bore biomass responded similarly. Needle
biomass, however, increased by a smaller amount (2.84-fold and 3.45-fold, respectively, for 400-700
and 400-800 mu L L(-1) increases in CO2); while branch biomass was increased considerably more
(by 4.73-fold and 5.97-fold for corresponding increases in CO2).

KEYWORDS: CARBON DIOXIDE, GROWTH, PHOTOSYNTHETIC ACCLIMATION,
SEEDLINGS, SOUR ORANGE TREES


     1009 
Idso, S.B., and B.A. Kimball. 1994. Effects of atmospheric co2 enrichment on regrowth of sour
orange trees (citrus-aurantium rutaceae) after coppicing. American Journal of Botany 81(7):843-846.

Sixteen sour orange tree (Citrus aurantium L.) seedlings were grown out-of-doors at Phoenix,
Arizona, in eight clear-plastic- wall open-top enclosures maintained at four different atmospheric CO2
concentrations for a period of 2 years. Over the last year of this period, the trees were coppiced five
times. The amount of dry matter harvested at each of these cuttings was a linear function of the
atmospheric CO2 concentration to which the trees were exposed. For a 75% increase in atmospheric
CO2 from 400 to 700 microliter per liter (mu L liter(-1)), total aboveground biomass rose, in the
mean, by a factor of 3.19; while for a 400 to 800 mu L liter(- 1) doubling of the air's CO2 content,
it rose by a factor of 3.92. The relative summer (mean air temperature of 32.8 C) response to CO2
was about 20% greater than the relative winter (mean air temperature of 16.4 C) response.

KEYWORDS: AIR, CARBON DIOXIDE, CROP RESPONSES, GROWTH, PAST 2 CENTURIES,
PHOTOSYNTHETIC ACCLIMATION, SEEDLINGS


     1010 
Idso, S.B., and B.A. Kimball. 1995. Effects of atmospheric CO2 enrichment on the growth of a
desert succulent: Agave vilmoriniana Berger. Journal of Arid Environments 31(4):377-382.

Small well-watered 'plantlets' of Agave vilmoriniana Berger collected from the flower stalk of a single
parent plant were grown out-of-doors at Phoenix, Arizona in clear-plastic-wall open-top enclosures
exposed to ambient air and air enriched with CO2 to 300 mu l. l(-1) above ambient. Analysis of 12
harvests of three plantings conducted over a period of 4 years revealed a temperature-dependent
CO2-induced growth enhancement for this desert succulent. The linear function used to describe the
relationship was indistinguishable from a similar relationship previously derived for 16 non-CAM
plants. (C)1995 Academic Press Limited

KEYWORDS: CROP RESPONSES, ELEVATED CARBON-DIOXIDE, PHOTOSYNTHETIC
ACCLIMATION, PLANTS, PRODUCTIVITY, SEEDLINGS


     1011 
Idso, S.B., and B.A. Kimball. 1997. Effects of long-term atmospheric CO2 enrichment on the
growth and fruit production of sour orange trees. Global Change Biology 3(2):89-96.

In July of 1987, we planted eight 30-cm-tall sour orange tree seedlings in a field of Avondale loam
at Phoenix, Arizona and enclosed them in pairs in clear-plastic-wall open-top chambers. Since 18
November of that year, we have continuously pumped ambient air of approximate to 400 ppmv
[CO2] through two of these enclosures, while through the other two we have continuously pumped
air of approximate to 700 ppmv [CO2]. By the end of the second year of the study, the trunk plus
branch volume of the [CO2]-enriched trees was approximate to 2.75 times greater than that of the
ambient-treatment trees. Three years later, this factor had dropped to approximate to 2.0; but the
decline in the [CO2]-enriched/ambient-treatment ratio of trunk plus branch volume was nearly
perfectly offset by the relative fruit production advantage enjoyed by the [CO2]- enriched trees over
that period. In Years 6, 7 and 8, however, there was a moderate drop in total productivity
enhancement. This decline may be a delayed acclimation response, or it could be due to enhanced
self-shading in the [CO2]-enriched trees or to the fact that, starting early in Year 6, many branches
of the [CO2]-enriched trees grew all the way to the walls of their enclosures, so that many blossoms
and young fruit were destroyed by intermittent physical trauma produced by the action of wind
against the taut plastic in that year and in all succeeding years. Hence, we will have to maintain our
experiment for several more years for this lateral growth obstruction to occur to the same degree in
the ambient-air chambers as it has in the [CO2]-enriched chambers, in order to determine the long-
term equilibrium effects of atmospheric [CO2] enrichment in a spatially confined environment.

KEYWORDS: BRANCH BAG, CARBON DIOXIDE, ELEVATED CO2, EXPOSURE, FIELD,
FOLIAR GAS-EXCHANGE, PHOTOSYNTHETIC ACCLIMATION, RESPONSES, SCIRPUS-
OLNEYI, TUSSOCK TUNDRA


     1012 
Idso, S.B., B.A. Kimball, D.E. Akin, and J. Kridler. 1993. A general relationship between co2-
induced reductions in stomatal conductance and concomitant increases in foliage temperature.
Environmental and Experimental Botany 33(3):443-446.

Simultaneous measurements of the temperatures and stomatal conductances of leaves of sour orange
trees growing in normal and CO2-enriched air, together with similar data for water hyacinths and
cotton, suggest that a plant's foliage temperature response to atmospheric CO2-enrichment is directly
proportional to its degree of stomatal closure, i.e. that plants that experience a greater stomatal
closure in response to atmospheric CO2 enrichment experience a greater warming of their foliage.
The data also suggest that this primary relationship may be modified by CO2-induced changes in leaf
chlorophyll content that may have implications for global climate change.

KEYWORDS: ATMOSPHERIC CO2, CARBON-DIOXIDE ENRICHMENT, CROP YIELD,
GROWTH, PHOTOSYNTHETIC ACCLIMATION, WATER-USE


     1013 
Idso, S.B., B.A. Kimball, and S.G. Allen. 1991. CO2 enrichment of sour orange trees - 2.5 years
into a long- term experiment. Plant, Cell and Environment 14(3):351-353.

Eight sour orange trees have been grown from seedling stage in the field at Phoenix, Arizona, U.S.A.,
in four identically-vented, open-top, clear-plastic-wall chambers for close to 2.5 years. Half of the
chambers have been maintained at ambient atmospheric CO2 concentrations over this period, while
half of them have been maintained at 300 ppm (300-mu-mol CO2 per mol air) above ambient.
Initially, the trees in each treatment were essentially identical; but in less than 2 years, the trunks of
the CO2-enriched trees had become twice as large as their ambient-treatment counterparts. After 2
full years of growth, the enriched trees had 79% more leaves, 56% more primary branches with 172%
more volume, 70% more secondary branches with 190% more volume, and 240% more tertiary
branches with 855% more volume. In addition, the CO2-enriched trees also had fourth-, fifth- and
sixth-order branches, while the ambient- treatment trees had no branches above third order. Total
trunk plus branch volume of the CO2-enriched trees was 2.79 times that of the ambient-treatment
trees after 2 full years of growth.

KEYWORDS: CARBON DIOXIDE


     1014 
Idso, S.B., B.A. Kimball, and S.G. Allen. 1991. Net photosynthesis of sour orange trees maintained
in atmospheres of ambient and elevated CO2 concentration. Agricultural and Forest Meteorology
54(1):95-101.

Eight sour orange trees planted directly into the ground at Phoenix, Arizona, as small seedlings in July
1987 have been enclosed by four clear-plastic-wall, open-top chambers since November of that year.
Half of the trees have been continuously supplied with a CO2-enriched atmosphere consisting of an
extra 300 cm3 of CO2 per m3 of air. Data from a comprehensive inventory of all above-ground plant
parts at the conclusion of two full years of growth under these conditions have revealed that the net
effect of the CO2-enriched air was to more than double the normal production of biomass over that
time interval. Here we report net photosynthesis measurements made throughout the last summer of
the period, which suggest that the primary impetus for this large growth response was an equivalent
enhancement of the net photosynthetic rates of the CO2-enriched trees.

KEYWORDS: CARBON DIOXIDE, ENRICHMENT


     1015 
Idso, S.B., B.A. Kimball, and D.L. Hendrix. 1993. Air-temperature modifies the size-enhancing
effects of atmospheric co2 enrichment on sour orange tree leaves. Environmental and Experimental
Botany 33(2):293-299.

Every other month for a period of 2 years, leaf area and dry weight measurements were made on the
foliage of sour orange trees growing in ambient air and in air enriched with an extra 300 mul/l CO2.
Leaf starch content measurements were made at approximate 2-month intervals for a period of 1 year.
The data demonstrated that all three plant parameters were significantly increased by atmospheric
CO2 enrichment, except in the coldest portion of the year. A plot of the ratio of CO2-enriched leaf
dry weight to ambient-treatment leaf dry weight against the mean air temperature of the preceding
month revealed this relationship with temperature to be linear. The relationship shows atmospheric
CO2 enrichment to have a negligible effect on leaf dry weight at a mean air temperature of
approximately 5- degrees-C. At a mean air temperature of 35-degrees-C, however, it shows individual
CO2-enriched leaves of our experiment to weigh 40% more than their ambient-treatment
counterparts. This phenomenon helps to explain the vastly different effects of atmospheric CO2
enrichment that have been reported for a number of diverse ecosystems.

KEYWORDS: CARBON, COMMUNITIES, ELEVATED CO2, ENVIRONMENT, ESTUARINE
MARSH, GROWTH-RESPONSE, PHOTOSYNTHETIC ACCLIMATION, PLANTS,
PRODUCTIVITY, TUSSOCK TUNDRA


     1016 
Idso, S.B., B.A. Kimball, and D.L. Hendrix. 1996. Effects of atmospheric CO2 enrichment on
chlorophyll and nitrogen concentrations of sour orange tree leaves. Environmental and Experimental
Botany 36(3):323-331.

Since 18 November 1987, eight sour orange (Citrus aurantium L.) trees have been maintained under
well watered and fertilized conditions within four clear-plastic-wall open-top enclosures, two of
which have been continuously supplied with ambient air of approximately 400 mu l 1(-1) CO2 and
two of which have been supplied with air enriched to approximately 700 mu l 1(-1) CO2. At weekly
intervals throughout years 4-7 of this long-term experiment, we measured chlorophyll a contents of
60 leaves on each of the trees with a hand-held chlorophyl meter that was specifically calibrated for
our study. At bi-monthly intervals, we also measured the areas, dry weights and nitrogen contents of
68 leaves from each tree. Expressed on a per-unit-leaf-area basis, leaves from the CO2-enriched trees
contained 4.8% less chlorophyll and nitrogen than leaves from the trees exposed to ambient air.
Because of their greater leaf numbers, however, the CO2-enriched trees contained 75% more total
chlorophyll and nitrogen than thr ambient-treatment trees; the total productivity of the CO2-enriched
trees was 175% greater. Consequently, although per-unit-leaf-area chlorophyll and nitrogen contents
were slightly lowered by atmospheric CO2 enrichment in our experiment, their use efficiencies were
greatly enhanced.

KEYWORDS: EXTRACTABLE CHLOROPHYLL, GROWTH, LEAF GREENNESS, METER,
PHOTOSYNTHESIS, TEMPERATURE, WHEAT


     1017 
Idso, S.B., B.A. Kimball, G.W. Wall, R.L. Garcia, R. Lamorte, P.J. Pinter, J.R. Mauney, G.R.
Hendrey, K. Lewin, and J. Nagy. 1994. Effects of free-air co2 enrichment on the light response
curve of net photosynthesis in cotton leaves. Agricultural and Forest Meteorology 70(1-4):183-188.

Daytime measurements of leaf CO2 exchange rates in a free-air CO2 enrichment (FACE) experiment
reveal that at photosynthetically active radiation (PAR) flux rates in excess of 1000 mumol m-2 s-1,
cotton leaves exposed to an atmospheric CO2 concentration of approximately 500 mumol mol-1
exhibit net photosynthetic rates about 30% greater than those for leaves of similar plants growing in
ambient air. As PAR flux rates drop below this value, the stimulatory effect of elevated CO2 rises,
suggesting that the relative benefits of atmospheric CO2 enrichment will be greater for shaded cotton
leaves that for those exposed to full sunlight.

KEYWORDS: CARBON DIOXIDE, GROWTH, QUANTUM YIELD, TRANSPIRATION


     1018 
Idso, S.B., G.W. Wall, and B.A. Kimball. 1993. Interactive effects of atmospheric co2 enrichment
and light- intensity reductions on net photosynthesis of sour orange tree leaves. Environmental and
Experimental Botany 33(3):367-375.

In a tong-term study of the effects of a 300 mul l-1 enrichment of the air's CO2 content on the growth
of sour orange trees, a comprehensive set of net photosynthesis and light intensity data was obtained.
From these measurements we derived single- leaf light response curves, which together with
complementary leaf area index data allowed us to derive full-canopy light response curves. The results
showed our 85% enhancement of the air's CO2 content to more than double canopy net
photosynthesis at full sunlight. Our analysis demonstrated that the positive direct effect of
atmospheric CO2 enrichment on net photosynthesis more than compensated for the negative self-
shading effect produced by the CO2-induced proliferation of leaf area.

KEYWORDS: AMBIENT, CARBON DIOXIDE, GROWTH, PLANTS, QUANTUM YIELD,
RESPIRATION, RESPONSES, TRANSPIRATION


     1019 
Igamberdiev, A.U., and I.V. Zabrovskaya. 1994. The effect of light, carbon nutrition, and salinity
on the oxidative-metabolism of wolffia-arrhiza. Russian Journal of Plant Physiology 41(2):208-214.

The effects of varying conditions of carbon nutrition (sucrose and an inorganic source of carbon in
the growth medium), light, and salinity on oxidative metabolism were studied in Wolffia arrhiza (L.)
Hork. ex Wimmer. In cells grown on 1% sucrose, the level of the cyanide-resistant (CO2)-C-14
evolution from 1,4-C- 14-succinate as a respiratory substrate was considerably higher than in
autotrophically grown plants. When the medium was enriched in inorganic carbon (CO2 or
bicarbonate), the rate of metabolization of glucose and other respiratory substrates diminished, and
total protein and chlorophyll content decreased. Light incubation enhanced glucose metabolization
two- to threefold, whereas succinate transformation was increased by a factor of 1.5 to 2, with a
concomitant rise in the electron flow via the cyanide-resistant pathway. Inhibition of the
photorespiratory metabolism with alpha-hydroxypyridine- 2-methanesulfonate slowed down glucose
and succinate metabolism. NaCl activated glycolate metabolism in autotrophically grown plants and
did not influence the rates of glucose and succinate transformation. In contrast, under
photoheterotrophic (mixothrophic) growth conditions on sucrose, NaCl added to the cultivation
medium led to a considerably higher (three- to fourfold) (CO2)-C-14 evolution from 1,4-C-14-
succinate and 1-C-14-glucose. The authors conclude that the adaptation of Wolffia plants to different
environmental conditions is accompanied by changes in the metabolic fluxes via cyanide-resistant
oxidase, along the glycolate pathway, and other oxidative pathways. These changes conform to the
alterations in enzyme activities participating in the oxidative metabolism.

KEYWORDS: CYANIDE, DEHYDROGENASE, PLANTS


     1020 
Igamberdiev, A.U., G.Q. Zhou, G. Malmberg, and P. Gardestrom. 1997. Respiration of barley
protoplasts before and after illumination. Physiologia Plantarum 99(1):15-22.

Respiratory O-2 consumption was investigated in dark-adapted barley (Hordeum vulgare L. cv.
Gunilla) protoplasts and after illumination for 10 min at high and very low CO2 in the presence of
respiratory and photorespiratory inhibitors. In dark-adapted protoplasts no difference was observed
between inhibitor treatments in high and very low CO2. The respiratory rate increased somewhat after
illumination and a difference in responce to inhibitors was in some cases observed between high and
very low CO2. Thus, the operation of the mitochondrial electron transport chain is affected following
a period of active photosynthesis. In all situations tested, oligomycin inhibited respiratiory O-2 uptake
indicating that respiration of mitochondria in protoplasts is not strictly ADP limited. Antimycin A
inhibited respiration more in dark-adapted protoplasts than after illumination whereas SHAM gave
the opposite response. Rotenone inhibited respiration both in dark adapted protoplasts (about 30%)
and after illumination where the inhibition was much greater in very low CO2 (50%) than in high CO2
(10%). After iilumination in very low CO2, SHAM + rotenone inhibited respiration almost completely
(70%). Photorespiratory inhibitors had very small effect on O-2 consumption in darkness. After
illumination the effect of aminoacetonitrile (AAN) was also very low whereas a- hydroxypyridine-2-
methane sulphonate (HPMS) in photorespiratory conditions inhibited O-2 uptake much stronger
(35%). The addition of glyoxylate enhanced respiration in the presence of HPMS up to the control
level suggesting that alternative pathways of glyoxylate conversion might be operating. The
differences in inhibitor responses may reflect fine mechanisms for the regulation of energetic balance
in the plant cell which consists of switching from electron transport coupled to ATP production to
non-coupled transport. Photorespiratory flux is also very flexible, and the suppression of glycine
decarboxylation can induce bypass reactions of glyoxylate metabolism.

KEYWORDS: ALTERNATIVE OXIDASE ACTIVITY, CARBOHYDRATE STATUS, CELLS,
CHLOROPLASTS, LEAVES, MESOPHYLL PROTOPLASTS, PATHWAY, PEA,
PHOTOSYNTHETIC METABOLISM, PLANT-MITOCHONDRIA


     1021 
Imai, K., and M. Okamotosato. 1991. Effects of temperature on CO2 dependence of gas exchanges
in C3 and C4 crop plants. Japanese Journal of Crop Science 60(1):139-145.

The effects of elevated CO2 in the atmosphere and the accompanied temperature rise predicted for
the future on gas exchanges of two summer C3 (rice, soybean) and two C4 (Japanese millet, finger
millet) crop plants were examined. Plants were grown in artificially illuminated growth cabinets under
350 and 500-mu-mol mol-1 ambient CO2 (C(a)) and were measured for rates of CO2 exchange
(CER) and transpiration (E) of leaves at 23, 28 and 33-degrees-C in terms of C(a) (0-500-mu-mol
mol-1). The responses of CER to C(a) were slightly lower in plants grown in high C(a) than those
in normal C(a) and were largely influenced by temperature. The promotive effect of elevating C(a)
on CER was larger at higher temperatures, especially in C4 crop plants. With the rise of C(a), the E
in C4 crop plants decreased more than in C3 crop plants and it was correlated with the decrease in
stomatal conductance to CO2 transfer. The water use efficiency (WUE) of leaves increased with the
rise in C(a) but the effect of temperature on WUE was unclear. It is concluded that, whthin limits,
under high C(a), C4 crop plants expand their photosynthetic capacity in an environment of high
temperature.



     1022 
Ineichen, K., V. Wiemken, and A. Wiemken. 1995. Shoots, roots and ectomycorrhiza formation
of pine-seedlings at elevated atmospheric carbon-dioxide. Plant, Cell and Environment 18(6):703-
707.

The effect of elevated atmospheric CO2 concentration on the growth of shoots, roots, mycorrhizas
and extraradical mycorrhizal mycelia of pine (Pinus silvestris L.) was examined, Two and a half-
month-old seedlings were inoculated axenically with the mycorrhizal fungus Pisolithus tinctorius
(Pers,) by a method allowing rapid mycorrhiza formation in Petri dishes, The plants were then
cultivated for 3 months in growth chambers with daily concentrations of 350 and 600 mu mol mol(-1)
CO2 during the day, Whereas plants harvested after 1 and 2 months did not differ appreciably
between ambient and increased CO2 concentrations, after 3 months they developed a considerably
higher root biomass (+57%) at elevated CO2, but did not increase significantly in root length, The
mycorrhizal fungus Pisolithus tinctorius, which depended entirely on the plant assimilates in the model
system, grew much faster at increased CO2: 3 times more mycorrhizal root clusters were formed and
the extraradical mycelium produced had twice the biomass at elevated as at ambient CO2. No
difference in shoot biomass was found between the two treatments after 91d, However, since the total
water consumption of seedlings was similar in the two treatments, the water use efficiency was
appreciably higher for the seedlings at increased CO2 because of the higher below- ground biomass.

KEYWORDS: AMBIENT, CO2 CONCENTRATION, ENRICHMENT, GROWTH, PLANTS, TREES


     1023 
Ineson, P., M.F. Cotrufo, R. Bol, D.D. Harkness, and H. Blum. 1996. Quantification of soil
carbon inputs under elevated CO2:C-3 plants in a C-4 soil. Plant and Soil 187(2):345-350.

The objective of this investigation was to quantify the differences in soil carbon stores after exposure
of birch seedlings (Betula pendula Roth.) over one growing season to ambient and elevated carbon
dioxide concentrations. One-year- old seedlings of birch were transplanted to pots containing 'C- 4
soil' derived from beneath a maize crop, and placed in ambient (350 mu L L-1) and elevated (600 mu
L L-1) plots in a free-air carbon dioxide enrichment (FACE) experiment. After 186 days the plants
and soils were destructively sampled, and analysed for differences in root and stem biomass, total
plant tissue and soil C contents and delta(13)C values. The trees showed a significant increase
(+50%) in root biomass, but stem and leaf biomasses were not significantly affected by treatment. C
isotope analyses of leaves and fine roots showed that the isotopic signal from the ambient and
elevated CO2 supply was sufficiently distinct from that of the 'C-4 soil' to enable quantification of net
root C input to the soil under both ambient and elevated CO2. After 186 days, the pots under ambient
conditions contained 3.5 g of C as intact root material, and had gained an additional 0.6 g C added
to the soil through root exudation/turnover; comparable figures for the pots under elevated CO2 were
5.9 g C and 1.5 g C, respectively. These data confirm the importance of soils as an enhanced sink for
C under elevated atmospheric CO2 concentrations. We propose the use of 'C-4 soils' in elevated CO2
experiments as an important technique for the quantification of root net C inputs under both ambient
and elevated CO2 treatments.

KEYWORDS: ATMOSPHERIC CO2 CONCENTRATION, DIOXIDE, ENRICHMENT,
RESPONSES, ROOTS, SYSTEM


     1024 
Ineson, P., P.A. Coward, and U.A. Hartwig. 1998. Soil gas fluxes of N2O, CH4 and CO2 beneath
Lolium perenne under elevated CO2: The Swiss free air carbon dioxide enrichment experiment. Plant
and Soil 198(1):89-95.

Fluxes of nitrous oxide, methane and carbon dioxide were measured from soils under ambient (350
mu L L-1) and enhanced (600 mu L L-1) carbon dioxide partial pressures (pCO(2)) at the 'Free Air
Carbon Dioxide Enrichment' (FACE) experiment, Eidgenossische Technische Hochschule (ETH),
Eschikon, Switzerland in July 1995, using a GC housed in a mobile laboratory. Measurements were
made in plots of Lolium perenne maintained under high N input. During the data collection period
N fertiliser was applied at a rate of 14 g m(-2) of N. Elevated pCO(2) appeared to result in an
increased (27%) output of N2O, thought to be the consequence of enhanced root-derived available
soil C, acting as an energy source for denitrification. The climate, agricultural practices and soils at
the FACE experiment combined to give rise to some of the largest N2O emissions recorded for any
terrestrial ecosystem. The amount of CO2-C being lost from the control plot was higher (10%) than
for the enhanced CO2 plot, and is the reverse of that predicted. The control plot oxidised consistently
more CH4 than the enhanced plot, oxidising 25.5 +/- 0.8 mu g m(-2) hr(- 1) of CH4 for the control
plot, with an average of 8.5 +/- 0.4 mu g m(-2) hr(-1) of CH4 for the enhanced CO2 plot. This
suggests that elevated pCO(2) may lead to a feedback whereby less CH4 is removed from the
atmosphere. Despite the limited nature of the current study (in time and space), the observations
made here on the interactions of elevated pCO(2) and soil trace gas release suggest that significant
interactions are occurring. The feedbacks involved could have importance at the global scale.

KEYWORDS: ATMOSPHERIC CO2, DENITRIFICATION, STIMULATION


     1025 
Ingestad, T., O. Hellgren, H. Hesseldahl, and A.B.L. Ingestad. 1996. Methods and applications
to control the uptake rate of carbon. Physiologia Plantarum 98(3):667-676.

Methods to control carbon and nutrient uptake at different availability of carbon were tested on plants
of birch (Betula pendula Roth.) and tomato (Lycopersicon esculentum Mill. cv. Solentos). The
present paper accounts for the methods and the possibility to maintain steady-state, i.e., a long-term
and stable physiological state of acclimated plants. Steady-state comprises, by definition, equality
between constant relative growth rates, and relative uptake rates of carbon and nutrients. Two
methods were tested. The first, not previously applied, method (a), was based on a constant relative
addition rate of carbon, R(AC). In the second method (b), a constant concentration of CO2 in the air,
c(a), was used to attain non- limiting conditions. The methods are analogous to those used by us to
control plant nutrition, and the generality of fluxes to quantify supply as well as uptake and growth
was verified. Thus, different R(AC) resulted suited in clear-cut responses, from strong reduction to
non-limitation of uptake and growth, whereas different c(a) levels in the range 100 to 700 ppm had
comparatively small effects, with an unclear causality. Non- limiting conditions were achieved at c(a)
greater than or equal to 200 ppm. Effects reported in the literature have been based upon the control
of c(a), similarly to method (b), whereas results comparable to those obtained with method (a) are
lacking. Transpiration rate increased rapidly at c(a) < 200 ppm CO2, and at low R(AC) levels, less
than or equal to 0.1 day(- 1), wilting tendencies were observed. Elevated c(a) 500 or 700 ppm, did
not increase the relative growth rate (R(G)) but reduced transpiration and increased both nitrogen
productivity (growth rate per unit of nitrogen in the plant) and transpiration productivity (growth rate
per unit of water transpired by the plant). Obviously, effects of c(a) may be due to changed
transpiration rate rather than to changed quantitative availability of CO2. Relative uptake (R(OC))
and growth (R(G)) rates were closely equal to the R(AC) applied (R(AC) approximate to R(UC)
approximate to R(G)); i.e., the purely mathematical conditions defining steady-state were fulfilled.
This unambiguous and straightforward test of reliability confirms that experimental artefacts did not
produce uncontrolled or unintended effects, so that the new technique allows an accurate control of
CO2 uptake and plant growth. The results add to previous databases and reference systems, where
limiting conditions grade and classify plant performance as deviations from maximum growth.
Evidently, methodology in experimentation and in evaluation of plant responses, can be based upon
unifying concepts and general theories.

KEYWORDS: BIRCH SEEDLINGS, GROWTH, NITROGEN STRESS, PLANT NUTRITION


     1026 
Ingvardsen, C., and B. Veierskov. 1994. Response of young barley plants to co2 enrichment.
Journal of Experimental Botany 45(279):1373-1378.

Barley (Hordeum vulgare L. cv. Digger) was grown for 22 d in enclosed chambers with a CO2
enrichment of 35, 155, 400 or 675 mu mol CO2 mol(-1). CO2 enrichment increased photosynthetic
capacity in the plants grown at either of the two highest levels of pCO(2). A CO2 enrichment of 675
mu mol CO2 caused a significant increment of shoot dry weight, whereas no changes were observed
in fresh weight, chlorophyll or protein levels. At a light intensity of 860 mu mol m(-2) s(-1) CO2
enrichment caused photosynthetic capacity to increase by 250%, whereas no effect was observed at
80 mu mol m(-2) s(-1). Over time, photosynthesis decreased by 70% independent of CO2. A time-
dependent increase in the level of extractable fructose was observed whereas total extractable
carbohydrate only changed slightly.

KEYWORDS: ATMOSPHERIC CO2, CARBON DIOXIDE, GROWTH, LEAVES,
PHOTOSYNTHESIS, PHYSIOLOGY, RESPIRATION, WHEAT, YIELD


     1027 
Innes, J.L. 1994. Climatic sensitivity of temperature forests. Environmental Pollution 83(1-2):237-
243.

Climatic change and associated global changes are of major interest to foresters, both in terms of
forest ecology and of future forest production. Predicting the likely effects of global change on forests
is extremely difficult due to the critical lack of information on regional changes in meteorological
factors relevant to forests. However, existing models of forest production and forest distribution fail
to take adequate account of what is already known. Climate and carbon dioxide concentrations have
shown substantial changes over the last 100 years. Although the rate of change is likely to increase,
recent proposed and implemented control strategies, together with better climatic models, are tending
to suggest that the rate of change will be less than initially thought. This means that past changes may
provide an increasingly useful source of information. In particular, information on the impact on
forests of both long-term climate change and short-term climatic events is rapidly increasing. Such
information should be built into future forest response models.

KEYWORDS: CO2, EMISSIONS, FERTILIZATION, GERMANY, GROWTH, INCREASE,
MOUNTAINS, NITROGEN, PRODUCTIVITY, RESPONSES


     1028 
Inoue, Y., B.A. Kimball, J.R. Mauney, R.D. Jackson, P.J. Pinter, and R.J. Reginato. 1990.
Stomatal behavior and relationship between photosynthesis and transpiration in field-grown cotton
as affected by CO2 enrichment. Japanese Journal of Crop Science 59(3):510-517.



     1029 
Insam, H., E. Baath, M. Berreck, A. Frostegard, M.H. Gerzabek, A. Kraft, F. Schinner, P.
Schweiger, and G. Tschuggnall. 1999. Responses of the soil microbiota to elevated CO2 in an
artificial tropical ecosystem. Journal of Microbiological Methods 36(1-2):45-54.

Plants in artificial tropical ecosystems were grown under ambient (340 mu l l(-1)) and elevated (610
mu l l(-1)) atmospheric CO2 for 530 d under low-nutrient conditions on a substrate free of organic
C. At the end of the experiment a number of soil chemical and microbiological variables were
determined. Although we found no changes in total soil organic matter under elevated CO2, we did
find that after physical fractionation the amount of organic C in the supernatant (< 0.2 mu m) and the
amount of water extractable organic C (WEOC) was lower under elevated CO2. The extractable
optical density (OD) indicated a higher degree of humification for the elevated than for the ambient
CO2 samples (P = 0.032). Microbial biomass C was not significantly altered under high CO2, but
total bacterial counts were significantly higher. The microbial biomass C-to-N ratio was also higher
at elevated (15.0) than at ambient CO2 (10.0). The number of mycorrhizal spores was lower at high
CO2, but ergosterol contents and fungal hyphal lengths were not significantly affected. Changes were
found neither in community level physiological profiles (CLPPs) nor in the structural attributes
(phospholipid fatty acids, PLFAs) of the microbial community. Overall, the effects on the soil
microbiota were small, perhaps as a result of the low nutrient supply and low organic matter content
of the soil used in our study. The few significant results showing changes in specific, though relatively
minor, organic matter pools may point to possible long-term changes of the more major pools.
Furthermore, the data suggest increased competition between plants and microbes for N at high CO2.
(C) 1999 Elsevier Science B.V. All rights reserved.

KEYWORDS: ATMOSPHERIC CARBON-DIOXIDE, BIOMASS, BOUTELOUA-GRACILIS,
COMMUNITIES, COTTON, DECOMPOSITION, ENRICHMENT, NITROGEN, ORGANIC-
MATTER, ROOT


     1030 
Inubushi, K., W.G. Cheng, and K. Chander. 1999. Carbon dynamics in submerged soil
microcosms as influenced by elevated CO2 and temperature. Soil Science and Plant Nutrition
45(4):863-872.

A 45-d incubation experiment was conducted under controlled laboratory conditions to study the
interactive effects of elevated CO2 and temperature on the dynamics of microbial biomass C and
organic C in hooded paddy soil microcosms amended or unamended with rice straw. The microcosms
with the two treatments were transferred separately to four growth chambers to incubate them under
16 h/8 h light and dark conditions. Two of the growth chambers set at 25 and 35 degrees C provided
a continuous how of elevated CO2 (equivalent to 800 mu L L-1). Similarly the other two growth
chambers were run under near ambient CO2 (400 mu L L-1) conditions at each of the two
temperatures. The amounts of soluble carbon, microbial biomass C, chlorophyll-type compounds, and
organic C in the surface (0- 1 cm) and sub-surface (below 1 cm) soil layers were measured at 15, 30,
and 45 d after incubation. The amount of soluble carbon in the straw-amended soil gradually
decreased throughout the incubation period, while no significant differences were detected among
the four different conditions. The interactive effects of both elevated CO2 and temperature were
found to be positive in terms of the size of the microbial biomass in surface soil, although no
significant differences were detected in the subsurface. However, the amount of total soil organic C
was larger in the soils incubated at a lower temperature. The amounts of chlorophyll-type compounds
doubled in the surface soil when the soils were incubated under elevated CO2 conditions, indicating
that the higher incubation concentration of CO2 promoted the growth of algae in surface soil.

KEYWORDS: ATMOSPHERIC CO2, MICROBIAL BIOMASS, NITROGEN, ORGANIC-MATTER


     1031 
Ioslovich, I., I. Seginer, P.O. Gutman, and M. Borshchevsky. 1995. Suboptimal co2 enrichment
of greenhouses. Journal of Agricultural Engineering Research 60(2):117-136.

Greenhouse CO2 enrichment in warm climates is restricted by the need to ventilate, leading some
growers to intermittent enrichment, where enrichment and ventilation alternate several times an hour.
This strategy relies on the heat and CO2 capacity of the system, characterized by a heating time
constant of the order of 10 min, during which period ventilation may be suspended. It is shown that,
for slowly changing weather, the optimal CO2 enrichment is basically not intermittent (bang-bang
control), but rather quasi steady state (smoothly varying singular control). As the disturbance
(weather) frequency increases, the quasi steady-state (QSS) solution becomes less and less optimal.
Nevertheless, due to the difficulties involved in implementing a truly optimal control (the need for
accurate weather forecast and high control fluxes), the sub-optimal QSS control may be a better
choice. We chose to try a controller which aims to follow the QSS temperature and CO2 setpoints
at all disturbance frequencies. The performance of this controller for high disturbance frequencies is
a few per cent lower than the truly optimal solution, but over the whole season this effect may not
be significant. On the other hand, the controller is likely to be more robust. Implementation of the
QSS solution requires simulaneous ventilation and enrichment, properly balanced.

KEYWORDS: GROWTH, INTERMITTENT


     1032 
Islam, K.R., C.L. Mulchi, and A.A. Ali. 1999. Tropospheric carbon dioxide or ozone enrichments
and moisture effects on soil organic carbon quality. Journal of Environmental Quality 28(5):1629-
1636.

Carbon, as an active component of organic matter, has considerable effects on soil quality and
productivity. The objective of this study was to examine the effect of climate change variables on soil
organic C (C-T) quality in an agroecosystem. Wheat (Triticum aestivum L.) and soybean [Glycine
max (L.) Merr] plants were grown in 3 m in diam, open- top field chambers and exposed to charcoal-
filtered (CF) air at 350 mu L CO2 L-1; CF air + 150 mu L CO2 L-1; nonfiltered (NF) air + 35 nL O-3
L-1; and NF air + 35 nL O-3 L-1 + 150 mu L CO2 L-1 at two soil moisture levels from 1994 to
1996. The 150 mu L CO2 L-1 addition was 18 h d(-1) and the 35 nL O-3 L-l was 7 h d(-1) from
April until late October. In response to treatments, the CT contents did not change significantly;
however, particulate, oxidizable, dissolved, humic (C-HA) and fulvic (C- FA) acid, and carbohydrate
C pools increased in soils under CO2 enrichment and well-watered conditions but decreased under
O-3 stress compared with soils under CF ambient air quality. Tropospheric CO2 enrichment and well-
watered condition increased, and O-3, stress decreased the log optical density slope for both C-HA
and C-FA fractions more than CF ambient air and restricted moisture treatment. Also, the E-465/E-
665 ratios of both C-HA and C-FA fractions were higher for the CO2 enrichment and smaller for the
O-3 stress compared With CF ambient air quality, Results suggest that tropospheric CO2 enrichment
and well-watered conditions may favor an accumulation of low molecular weight and more aliphatic
quality of C and O-3 stress favor high molecular weight and more aromatic quality of C.

KEYWORDS: ALLOCATION, DECOMPOSITION, FERTILIZATION, HUMIC SUBSTANCES,
INCREASING ATMOSPHERIC CO2, LEAF LITTER, LITTER QUALITY, MATTER DYNAMICS,
O-3, WATER


     1033 
Islam, M.S., T. Matsui, and Y. Yoshida. 1995. Effect of preharvest carbon dioxide enrichment on
the postharvest quality of tomatoes. Journal of the Japanese Society for Horticultural Science
64(3):649-655.

The effect of preharvest application of elevated CO2 throughout the fruit growing period on organic
acid, sugar content, acid invertase activity (beta-fructofuranoside fructohydrolase, EC 3.2.1.26), and
color quality in tomato (Lycopersicon esculentum Mill. cv. Momotaro) fruit during storage at 20
degrees C was determined. The CO2-enriched tomato fruits contained significantly lower
concentrations of citric, malic and oxalic acids, but had significantly higher reducing sugars and acid
invertase activity at harvest and during storage. The concentration of these acids decreased with
storage, whereas the activity of acid invertase and reducing sugar contents increased in the treated
fruits; they were relatively constant in the control fruits. Furthermore, the elevated CO2 resulted in
a deeper red color during storage.

KEYWORDS: ACCUMULATION, FLAVOR, FRUITS, INVERTASE, STARCH, SUGAR


     1034 
Islam, M.S., T. Matsui, and Y. Yoshida. 1996. Effect of carbon dioxide enrichment on physico-
chemical and enzymatic changes in tomato fruits at various stages of maturity. Scientia Horticulturae
65(2-3):137-149.

The influence of CO2 enrichment on fruit growth, firmness and colour, together with its effect on the
concentrations of ascorbic acid, organic acids and sugars, and the activities of sucrose synthase (SS)
(UDP glucose: D-fructose 2- glucosyltransferase, E. C. 2, 4, 1, 13) and sucrose phosphate synthase
(SPS) (UDP glucose: D-fructose-6-phosphate 2- glucosyltransferase, E. C. 2. 4. 1. 14) were
determined at various stages of maturity in fruits of tomato (Lycopersicon esculentum Mill. cv.
Momotaro), CO2 enriched tomatoes had lower amounts of citric, malic and oxalic acids, and higher
amounts of ascorbic acid, fructose, glucose and sucrose synthase activity than the control. Elevated
CO2 enhanced fruit growth and colouring during development. Citric acid was the primary organic
acid followed by malic and oxalic acids. The concentration of organic acids (mg g(-1) fresh weight)
and of ascorbic acid (mg 100g(-1) fresh weight) increased with the maturity of fruits; their maximum
concentrations were found at the pink stage of ripening, but declined slightly at the red stage. The
amount of reducing sugars (mg g(-1) fresh weight) increased with the advancement of maturity, with
fructose being the predominant sugar. The decrease in SS activity was accompanied by an increase
in the concentrations of reducing sugars. There were no significant differences in fruit firmness,
sucrose concentration and SPS activity between the treatments. The SPS activity did not change, but
remained relatively constant throughout fruit development. The results also suggest that SS levels
correlated positively with sucrose concentration but negatively with the concentration of reducing
sugars.

KEYWORDS: CO2, ENZYMES, GREENHOUSES, INVERTASE, MUSKMELON FRUIT,
RESPONSES, SINK METABOLISM, SUCROSE PHOSPHATE SYNTHASE, SUGAR
ACCUMULATION


     1035 
Israel, A.A., and P.S. Nobel. 1994. Activities of carboxylating enzymes in the cam species opuntia-
ficus-indica grown under current and elevated co2 concentrations. Photosynthesis Research
40(3):223-229.

Responses of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) and phosphoenolpyruvate
carboxylase (PEPCase) to an elevated atmospheric CO2 concentration were determined along with
net CO2 uptake rates for the Crassulacean acid metabolism species Opuntia ficus-indica growing in
open-top chambers. During the spring 13 months after planting, total daily net CO2 uptake of basal
and first-order daughter cladodes was 28% higher at 720 than at 360 mu l CO2 1(-1). The
enhancement, caused mainly by higher CO2 assimilation during the early part of the night, was also
observed during late summer (5 months after planting) and the following winter. The activities of
Rubisco and PEPCase measured in vitro were both lower at the elevated CO2 concentration,
particularly under the more favorable growth conditions in the spring and late summer. Enzyme
activity in second-order daughter cladodes increased with cladode age, becoming maximal at 6 to 10
days. The effect of elevated CO2 on Rubisco and PEPCase activity declined with decreasing
irradiance, especially for Rubisco. Throughout the 13-month observation period, O. ficus-indica thus
showed increased CO2 uptake when the atmospheric CO2 concentration was doubled despite lower
activities of both carboxylating enzymes.

KEYWORDS: ACCLIMATION, AGAVE-VILMORINIANA, ATMOSPHERIC CO2, CARBON
DIOXIDE, CRASSULACEAN ACID METABOLISM, PHOTOSYNTHESIS, PLANTS,
PRODUCTIVITY, RESPONSES, SHORT- TERM


     1036 
Israel, D.W., T.W. Rufty, and J.D. Cure. 1990. Nitrogen and phosphorus nutritional interactions
in a CO2 enriched environment. Journal of Plant Nutrition 13(11):1419-1433.

Nonnodulated soybean plants (Glycine max. [L.] Merr. 'Lee') were supplied with nutrient solutions
containing growth limiting concentrations of N or P to examine effects on N- and P-uptake
efficiencies (mg nutrient accumulated/gdw root) and utilization efficiencies in dry matter production
(gdw2/mg nutrient). Nutritional treatments were imposed in aerial environments containing either 350
or 700-mu-L/L atmospheric CO2 to determine whether the nutrient interactions were modified when
growth rates were altered. Nutrient-stress treatments decreased growth and N- and P-uptake and
utilization efficiencies at 27 days after transplanting (DAT) and seed yield at maturity (98 DAT).
Atmospheric CO2 enrichment increased growth and N- and P-utilization efficiencies at 27 DAT and
seed yield in all nutritional treatments and did not affect N- and P-uptake efficiencies at 27 DAT.
Parameter responses to nutrient stress at 27 DAT were not altered by atmospheric CO2 enrichment
and vice versa. Nutrient-stress treatments lowered the relative seed yield response to atmospheric
CO2 enrichment. Decreased total-N uptake by P- stressed plants was associated with both decreased
root growth and N-uptake efficiency of the roots. Nitrogen-utilization efficiency was also decreased
by P-stress. This response was associated with decreased plant growth as total-N uptake and plant
growth were decreased to the same extent by P stress resulting in unaltered tissue N concentrations.
In contrast, decreased total P-uptake by N-stressed plants was associated with a restriction in root
growth as P-uptake efficiency of the roots was unaltered. This response was coupled with an
increased root-to-shoot dry weight ratio; thus shoot and wholeplant growth were decreased to a
much greater extent than total-P uptake which resulted in elevated P concentrations in the tissue.
Therefore, P-utilization efficiency was markedly reduced by N stress.

KEYWORDS: AMMONIUM, ELEVATED CARBON-DIOXIDE, GROWTH, NITRATE, PLANTS,
RESPONSES, SEED YIELD, TRANSPORT


     1037 
Isutsa, D.K., M.P. Pritts, and K.W. Mudge. 1994. Rapid propagation of blueberry plants using
ex-vitro rooting and controlled acclimatization of micropropagules. Hortscience 29(10):1124-1126.

A protocol is presented that enables a propagator to produce field-sized blueberry transplants within
6 months of obtaining microshoots from tissue culture. The protocol involves subjecting microshoots
to ex vitro rooting in a fog chamber under 100 mumol.m-2.s-1 photosynthetic photon flux for 7
weeks, transferring plants to a fog tunnel for 2 weeks, then to a greenhouse for 7 more weeks. Plant
survival and rooting of cultivars Berkeley (Vaccinium corymbosum L.) and Northsky (Vaccinium
angustifolium xcorymbosum) were near 100% under these conditions. Plantlets in fog chambers
receiving 100 mumol.m-2.s-1 grew rapidly, while those at lower irradiance levels grew more slowly,
and supplemental CO, enhanced growth only at 50 mumol.m-2.s-1. Growth rates slowed when plants
were moved into the fog tunnel; but by the end of 16 weeks, plants that were under high irradiance
in the fog chamber had root systems that were 15 to 30 times larger than plants under low irradiance.
Within 6 months, these plants were 30 to 60 cm tall and suitable for field planting.

KEYWORDS: CO2, CULTURE, ENRICHMENT, GROWTH, HIGHBUSH BLUEBERRY, INVITRO,
LIGHT, LOWBUSH BLUEBERRY


     1038 
Ito, J., S. Hasegawa, K. Fujita, S. Ogasawara, and T. Fujiwara. 1999. Effect of CO2 enrichment
on fruit growth and quality in Japanese pear (Pyrus serotina reheder cv. Kosui). Soil Science and
Plant Nutrition 45(2):385-393.

Six year-old Japanese pear (Pyrus serotina Reheder cv. Kosui) trees grafted on P. serotina cv.
Nihonyamanashi were grown in containers filled with Granite Regosol under glasshouse conditions.
At different stages of fruit growth, pear trees were exposed to an elevated CO2 concentration (130
Pa CO2) along with a control (35 Pa CO2). For one group of plants, CO2 enrichment was applied
for 79 d from 52 d after full bloom (DAB) to fruit maturity (long-term CO2 enrichment) and for
another group the same treatment was applied for 35 d from 96 DAB to fruit maturity (short-term
CO2 enrichment). The effects of the elevated CO2 concentration on vegetative growth, mineral
contents, and fruit production and quality were examined. Long- term CO2 enrichment enhanced
vegetative growth, without any significant effect on the mineral contents in either flower bud or fruit
except for a remarkable increase in the K content. Long-term CO2 enrichment increased the fruit size
and fresh weight, but had no significant effect on the fruit quality. On the other hand, the short-term
CO2 enrichment did not induce any significant change in the fruit size but increased the fruit sugar
concentration. Along with the reduction of the sorbitol concentration in fruit, the fructose and sucrose
concentrations increased and these changes occurred earlier at elevated CO2 than at ambient CO2
concentrations. From these results, we concluded that the effect of CO2 enrichment on fruit growth
varies depending upon the growth stages of fruit: during the initial and fruitlet stages when fruit
expansion occurs, CO2 enrichment increases the fruit size, whereas, during maturation when fruit
expansion has slowed down and sugar accumulation in fruit is active, it increases the fruit sugar
concentration.

KEYWORDS: ACCLIMATION, ATMOSPHERIC CO2, CARBON DIOXIDE, INVERTASE,
METABOLISM, PASTURE, PHOTOSYNTHESIS, PLANTS, SORBITOL-RELATED ENZYMES,
SOUR ORANGE TREES


     1039 
Iverson, L.R., and A.M. Prasad. 1998. Predicting abundance of 80 tree species following climate
change in the eastern United States. Ecological Monographs 68(4):465-485.

Projected climate warming will potentially have profound effects on the earth's biota, including a large
redistribution of tree species. We developed models to evaluate potential shifts for 80 individual tree
species in the eastern United States. First, environmental factors associated with current ranges of
tree species were assessed using geographic information systems (GIS) in conjunction with regression
tree analysis (RTA). The method was then extended to better understand the potential of species to
survive and/or migrate under a changed climate. We collected, summarized, and analyzed data for
climate, soils, land use, elevation, and species assemblages for >2100 counties east of the 100th
meridian. Forest Inventory Analysis (FIA) data for >100000 forested plots in the East provided the
tree species range and abundance information for the trees. RTA was used to devise prediction rules
from current species-environment relationships, which were then used to replicate the current
distribution as well as predict the future potential distributions under two scenarios of climate change
with twofold increases in the level of atmospheric CO2. Validation measures prove the utility of the
RTA modeling approach for mapping current tree importance values across large areas, leading to
increased confidence in the predictions of potential future species distributions. With our analysis of
potential effects, we show that roughly 30 species could expand their range and/or weighted
importance at least 10%, while an additional 30 species could decrease by at least 10%, following
equilibrium after a changed climate. Depending on the global change scenario used, 4-9 species would
potentially move out of the United States to the north. Nearly half of the species assessed (36 out of
80) showed the potential for the ecological optima to shift at least 100 km to the north, including
seven that could move >250 km. Given these potential future distributions, actual species
redistributions will be controlled by migration rates possible through fragmented landscapes.

KEYWORDS: BALANCE, CLASSIFICATION, CONTINENTAL-SCALE, DECISION-TREE,
FORESTS, MODEL, PINE, RESPONSES, TEMPERATURE, VEGETATION


     1040 
Iverson, L.R., A. Prasad, and M.W. Schwartz. 1999. Modeling potential future individual tree-
species distributions in the eastern United States under a climate change scenario: a case study with
Pinus virginiana. Ecological Modelling 115(1):77-93.

We are using a deterministic regression tree analysis model (DISTRIB) and a stochastic migration
model (SHIFT) to examine potential distributions of similar to 66 individual species of eastern US
trees under a 2 x CO2 climate change scenario. This process is demonstrated for Virginia pine (Pinus
virginiana). USDA Forest Service Forest Inventory and Analysis data for more than 100 000 plots
and nearly 3 million trees east of the 100th meridian were analyzed and aggregated to the county level
to provide species importance values for each of more than 2100 counties. County-level data also
were compiled on climate, soils, land use, elevation, and spatial pattern. Regression tree analysis
(RTA) was used to devise prediction rules from current species-environment relationships, which
were then used to replicate the current distribution and predict the potential future distributions under
two scenarios of climate change (2 x CO2). RTA allows different variables to control importance
value predictions at different regions, e.g. at the northern versus southern range limits of a species.
RTA outputs represent the potential 'environmental envelope' shifts required by species, while the
migration model predicts the more realistic shifts based on colonization probabilities from varying
species abundances within a fragmented landscape. The model shows severely limited migration in
regions of high forest fragmentation, particularly when the species is low in abundance near the range
boundary. These tools are providing mechanisms for evaluating the relationships among various
environmental and landscape factors associated with tree- species importance and potential migration
in a changing global climate. (C) 1999 Elsevier Science B.V. All rights reserved.

KEYWORDS: BALANCE, FORESTS, MIGRATION, RANGE, RESPONSES, VEGETATION


     1041 
Iwasaki, I., N. Kurano, and S. Miyachi. 1996. Effects of high-CO2 stress on photosystem II in a
green alga, Chlorococcum littorale, which has a tolerance to high CO2. Journal of Photochemistry
and Photobiology B-Biology 36(3):327-332.

A green alga, Chlorococcum littorale, is known to have a tolerance to high CO2 conditions. By a
sudden change from stir to high CO2, PSII activity of C. littorale decreased temporarily and then
recovered, while PSI activity showed the opposite change (Pesheva et al., Plant Cell Physiol, 35
(1994) 379-387). To investigate the efficiency of energy captured by open PSII reaction centers, the
quenching of chlorophyll fluorescence of intact cells of C. littorale was analyzed. The data obtained
are compared with those obtained with cells of Stichococcus bacillaris which has little tolerance to
high CO2. Activities of photosynthetic oxygen evolution of the intact cells and DCIP photoreduction
with the crude membrane fraction of C. littorale decreased within 1-2 days, and after about 4 days
both activities recovered and/or were elevated to higher levels than those in the air conditions. During
this temporal decrease in these activities, the effective quantum yield of PSII also lowered to about
50% of that in air. The values of F- v/F-m transiently decreased indicating photoinhibition in PSII.
Such fluorescence quenching parameters recovered after about 4 days. On the other hand, the
activities of PSII and other photosynthetic characteristics did not recover in S. bacillaris.

KEYWORDS: CHLOROPHYLL FLUORESCENCE, FLUOROMETER, LIGHT, PH,
PHOTOSYNTHESIS


     1042 
Izrael, Y.A., S.M. Semenov, I.M. Kunina, and T.V. Zamaraeva. 1994. Modification of direct
effect of carbon-dioxide on higher- plants due to tropospheric ozone impact. Doklady Akademii Nauk
338(5):711-713.

KEYWORDS: ATMOSPHERIC CO2 ENRICHMENT, GROWTH


     1043 
Jablonski, L.M. 1997. Responses of vegetative and reproductive traits to elevated CO2 and nitrogen
in Raphanus varieties. Canadian Journal of Botany-Revue Canadienne De Botanique 75(4):533-545.

The relationships between the responses to elevated CO2 of the vegetative and reproductive phase
were investigated in radish, used as a test system. The hypothesis that an increase in nonfoliar
vegetative storage capacity promotes reproductive output was tested. Three cultivars of Raphanus
sarivus and the wild, Raphanus raphanistrum, differing in root to shoot ratios, were grown under two
levels of CO2 and two levels of nitrogen fertilization. Varieties possessed different strategies of
carbon storage and showed distinct responses to CO2 at each vegetative harvest time. Vegetative
sinks of hypocotyls, petioles, and young blades were enhanced by CO2. Nitrogen promoted
vegetative shoot growth, but did not enhance the reproductive response to CO2. By the end of the
reproductive phase, varieties did not differ in total biomass. Reproductive response to CO2 may have
been limited by the lack of an effect on the timing of flowering. Correlations in CO2 enhancement
ratios were examined in 12 traits of each phase. Only vegetative total leaf area correlated with
reproductive mass. Foliar starch correlated with decreased abortion. Enhancements in vegetative
biomass did not correlate with any reproductive response. Detailed studies of the reproductive phase
are needed to understand the whole-plant response to elevated CO2.

KEYWORDS: C-3 PLANTS, CARBON-DIOXIDE ENRICHMENT, GROWTH, LEAVES, NITRATE,
NUTRITION, PHOTOSYNTHESIS, PRODUCTIVITY, RAPHANISTRUM, WILD RADISH


     1044 
Jach, M.E., and R. Ceulemans. 1999. Effects of elevated atmospheric CO2 on phenology, growth
and crown structure of Scots pine (Pinus sylvestris) seedlings after two years of exposure in the field.
Tree Physiology 19(4-5):289-300.

Three-year-old Scots pine (Pinus sylvestris L.) seedlings were grown for two years in the ground in
open-top chambers supplied with either an ambient or elevated (ambient + 400 mu mol mol(- 1)) CO2
concentration. Phenological observations and measurements of height and stem diameter growth,
absolute and relative growth rates, starch and soluble carbohydrate concentrations of the needles, and
crown structure and needle properties were made at frequent intervals throughout the two growing
seasons. Elevated CO2 significantly advanced the date of bud burst in both years. The increase in total
needle area in response to elevated CO2 was accounted for by longer shoots and an increase in
individual needle area in the first year, and by an increase in the number and length of shoots in the
second year. Stem diameter and tree height were enhanced more by the elevated CO2 treatment in
the first year than in the second, indicating a decreased effect of CO2 on growth over time. This was
confirmed by a study of absolute and relative growth rates of leader shoots. During the first growing
season of CO2 enrichment, mean weekly relative growth rates over the growing season (RGR(m))
were significantly enhanced. During the second year, RGR(m) in ambient CO2 closely matched that
in elevated CO2.

KEYWORDS: ABIES L KARST, BIOMASS ALLOCATION, CARBON-DIOXIDE ENRICHMENT,
FROST DAMAGE, MINERAL NUTRITION, PHOTOSYNTHESIS, PLANT-RESPONSES,
SEASONAL-CHANGES, SPRUCE PICEA-SITCHENSIS, WATER-STRESS


     1045 
Jackson, R.B., Y. Luo, Z.G. Cardon, O.E. Sala, C.B. Field, and H.A. Mooney. 1995.
Photosynthesis, growth and density for the dominant species in a CO2-enriched grassland. Journal
of Biogeography 22(2-3):221-225.

Although increased atmospheric CO2 frequently increases short- term photosynthetic rates, longer-
term photosynthetic responses are more variable. Plant size, reproduction and ecosystem carbon gain
are determined, in part, by such photosynthetic responses. Here we examine photosynthetic regulation
for the dominant species in a grassland exposed to elevated CO2 and examine whether the observed
photosynthetic responses contribute to changes in growth, reproduction and plant density in the same
grassland. Avena barbata in the field showed little evidence of photosynthetic downregulation with
elevated CO2 at the end of the growing season (differences between treatments <10%). Glasshouse
studies also showed little evidence for downregulation of photosynthesis measured at various light
and intercellular CO2. concentrations. Although specific leaf mass (leaf mass per unit leaf area) for
Avena increased 20% in the field with elevated CO2, leaf nitrogen concentrations decreased 25%,
resulting in an 11% reduction in leaf N on a leaf-area basis. For the relatively wet 1993 growing
season, Avena barbata increased its size and reproduction approximately 30% in elevated CO2, with
a 21% decrease in population density. For the relatively dry 1994 season Avena density was almost
doubled in elevated CO2, but increases in individual size and reproduction with CO2 were small (6-
18%). The primary effect of CO2 in the drier year appears to have been greater Avena survival, rather
than increased individual size.

KEYWORDS: AMBIENT, ATMOSPHERIC CO2, CARBON DIOXIDE, ECOSYSTEM RESPONSES,
ELEVATED CO2 CONCENTRATIONS, EXPOSURE, PLANT


     1046 
Jackson, R.B., and H.L. Reynolds. 1996. Nitrate and ammonium uptake for single- and mixed-
species communities grown at elevated CO2. Oecologia 105(1):74-80.

Sustained increases in plant production in elevated CO2 depend on adequate belowground resources.
Mechanisms for acquiring additional soil resources include increased root allocation and changes in
root morphology or physiology. CO2 research to date has focused almost exclusively on changes in
biomass and allocation. We examined physiological changes in nitrate and ammonium uptake in
elevated CO2, hypothesizing that uptake rates would increase with the amount of available CO2. We
combined our physiological estimates of nitrogen uptake with measurements of root biomass to assess
whole root-system rates of nitrogen uptake. Surprisingly, physiological rates of ammonium uptake
were unchanged with CO2, and rates of nitrate uptake actually decreased significantly (P<0.005).
Root biomass increased 23% in elevated CO2 (P<0.005), but almost all of this increase came in
fertilized replicates. Rates of root-system nitrogen uptake in elevated CO2 increased for ammonium
in nutrient-rich soil (P<0.05) and were unchanged for nitrate (P>0.80). Root-system rates of nitrogen
uptake were more strongly correlated with physiological uptake rates than with root biomass in
unamended soil, but the reverse was true in fertilized replicates. We discuss nitrogen uptake and
changes in root biomass in the context of root nutrient concentrations (which were generally
unchanged with CO2) and standing pools of belowground plant nitrogen. In research to date, there
appears to be a fairly general increase in root biomass with elevated CO2, and little evidence of up-
regulation in root physiology.

KEYWORDS: ANNUAL GRASSLAND, ATMOSPHERE, CARBON DIOXIDE, ECOSYSTEMS,
ENRICHMENT, NITROGEN, PLANT, PRODUCTIVITY, RESPONSES, SOIL


     1047 
Jackson, R.B., O.E. Sala, C.B. Field, and H.A. Mooney. 1994. Co2 alters water-use, carbon gain,
and yield for the dominant species in a natural grassland. Oecologia 98(3-4):257-262.

Global atmospheric CO2 is increasing at a rate of 1.5-2 ppm per year and is predicted to double by
the end of the next century. Understanding how terrestrial ecosystems will respond in this changing
environment is an important goal of current research. Here we present results from a field study of
elevated CO2 in a California annual grassland. Elevated CO2 led to lower leaf- level stomatal
conductance and transpiration (approximately 50%) and higher mid-day leaf water potentials (30-
35%) in the most abundant species of the grassland, Avena barbata Brot. Higher CO2 concentrations
also resulted in greater midday photosynthetic rates (70% on average). The effects of CO2 on
stomatal conductance and leaf water potential decreased towards the end of the growing season,
when Avena began to show signs of senescence. Water-use efficiency was approximately doubled in
elevated CO2, as estimated by instantaneous gas-exchange measurements and seasonal carbon isotope
discrimination. Increases in CO2 and photosynthesis resulted in more seeds per plant (30%) and taller
and heavier plants (27% and 41%, respectively). Elevated CO2 also reduced seed N concentrations
(9%).

KEYWORDS: ANNUALS, ELEVATED CO2, ENRICHMENT, GROWTH, PLANTS, RESPONSES,
SEEDLINGS, TREES


     1048 
Jackson, R.B., O.E. Sala, J.M. Paruelo, and H.A. Mooney. 1998. Ecosystem water fluxes for two
grasslands in elevated CO2: a modeling analysis. Oecologia 113(4):537-546.

The need to combine data from CO2 field experiments with climate data remains urgent, particularly
because each CO2 experiment cannot run for decades to centuries. Furthermore, predictions for a
given biome need to take into account differences in productivity and leaf area index (LAI)
independent of CO2-derived changes. In this study, we use long- term weather records and field data
from the Jasper Ridge CO2 experiment in Pale Alto, California, to model the effects of CO2 and
climate variability on ecosystem water fluxes. The sandstone and serpentine grasslands at Jasper
Ridge provide a range of primary productivity and LAI, with the sandstone as the more productive
system. Modeled soil water availability agreed well with published observations of time-domain
reflectometry in the CO2 experiment. Simulated water fluxes based on 10-year weather data (January
1985-December 1994) showed that the sandstone grassland had a much greater proportion of water
movement through plants than did the serpentine; transpiration accounted for approximately 30% of
annual fluxes in the sandstone and only 10% in the serpentine. Although simulated physiological and
biomass changes were similar in both grasslands, the consequences of elevated CO2 were greater for
the sandstone water budget. Elevated CO2 increased soil drainage by 20% in the sandstone, despite
an approximately one-fifth increase in plant biomass; in the serpentine, drainage increased by <10%
and soil evaporation was unchanged for the same simulated biomass change. Phenological changes,
simulated by a 15-day lengthening of the growing season, had minimal impacts on the water budget.
Annual variation in the timing and amount of rainfall was important for water fluxes in both
grasslands. Elevated CO2 increased sandstone drainage > 50 mm in seven of ten years, but the
relative increase in drainage varied from 10% to 300% depending on the year. Early-season
transpiration in the sandstone decreased between 26% and 41%, with elevated CO2 resulting in a
simulated water savings of 54-76 mm. Even in years when precipitation was similar (e.g., 505 and
479 mm in years 3 and 4), the effect of CO2 varied dramatically. The response of grassland water
budgets to CO2 depends on the productivity and structure of the grassland, the amount and timing
of rainfall, and CO2-induced changes in physiology. In systems with low LAT, large physiological
changes may not necessarily alter total ecosystem water budgets dramatically.

KEYWORDS: ATMOSPHERIC CARBON-DIOXIDE, CANOPY, EXCHANGE, GROWTH, LEAF,
NITROGEN, PHOTOSYNTHESIS, PLANT, RESPONSES, TRANSPIRATION


     1049 
Jacob, J., and B.G. Drake. 1993. Long-term co2 enrichment effects on the rubisco content and
activity in 2 field-grown C3 plants. Plant Physiology 102(1):46.



     1050 
Jacob, J., C. Greitner, and B.G. Drake. 1995. Acclimation of photosynthesis in relation to rubisco
and nonstructural carbohydrate contents and in-situ carboxylase activity in scirpus-olneyi grown at
elevated co2 in the field. Plant, Cell and Environment 18(8):875-884.

Stands of Scirpus olneyi, a native saltmarsh sedge with C-3 photosynthesis, had been exposed to
normal ambient and elevated atmospheric CO2 concentrations (C-a) in their native habitat since 1987,
The objective of this investigation was to characterize the acclimation of photosynthesis of Scirpus
olneyi stems, the photosynthesizing organs of this species, to long-term elevated C-a treatment in
relation to the concentrations of Rubisco and non-structural carbohydrates, Measurements were made
on intact stems in the field under existing natural conditions and in the laboratory under controlled
conditions on stems excised in the field early in the morning, Plants grown at elevated C-a had a
significantly higher (30-59%) net CO2 assimilation rate (A) than those grown at ambient C-a when
measurements were performed on excised stems at the respective growth C-a. However, when
measurements were made at normal ambient C-a, A was smaller (45-53%) in plants grown at elevated
C-a than in those grown at ambient C- a. The reductions in A at normal ambient C-a, carboxylation
efficiency and in situ carboxylase activity were caused by a decreased Rubisco concentration (30-
58%) in plants grown at elevated C-a; these plants also contained less soluble protein (39-52%). The
Rubisco content was 43 to 58% of soluble protein, and this relationship was not significantly altered
by the growth CO2 concentrations. The Rubisco activation state increased slightly, but the in situ
carboxylase activity decreased substantially in plants grown at elevated C-a. When measurements
were made on intact stems in the field, the elevated C-a treatment caused a greater stimulation of A
(100%) and a smaller reduction in carboxylation efficiency (which was not statistically significant)
than when measurements were made on excised stems in the laboratory. The possible reasons for this
are discussed. Plants grown at elevated C-a contained more non-structural carbohydrates (25-53%)
than those grown at ambient C-a. Plants grown at elevated C-a appear to have sufficient sink capacity
to utilize the additional carbohydrates formed during photosynthesis. Overall, our results are in
agreement with the hypothesis that elevated C-a leads to an increased carbohydrate concentration and
the ensuing acclimation of the photosynthetic apparatus in C-3 plants results in a reduction in the
protein complement, especially Rubisco, which reduces the photosynthetic capacity in plants grown
at elevated C-a, relative to plants grown at normal ambient C-a. Nevertheless, when compared at their
respective growth C-a, Scirpus olneyi plants grown at elevated C-a in their native habitat maintained
a substantially higher rate of photosynthesis than those grown at normal ambient C-a even after 8
years of growth at elevated C-a.

KEYWORDS: ACTIVATION, C-3, CARBON-DIOXIDE CONCENTRATION, ENRICHMENT, HIGH
ATMOSPHERIC CO2, LEAVES, PLANTS, RESPONSES, RIBULOSE-1;5-BISPHOSPHATE
CARBOXYLASE, SUNFLOWER


     1051 
Jacoby, G.C., and R.D. DArrigo. 1997. Tree rings, carbon dioxide, and climatic change.
Proceedings of the National Academy of Sciences of the United States of America 94(16):8350-
8353.

Tree rings have been used in various applications to reconstruct past climates as well as to assess the
effects of recent climatic and environmental change on tree growth, In this paper we briefly review
two wags that tree rings provide information about climate change and CO2: (i) in determining
whether recent: warming during the period of instrumental observations is unusual relative to prior
centuries to millennia, and thus might be related to increasing greenhouse gases; and (ii) in evaluating
whether enhanced radial growth has taken place in recent decades that appears to be unexplained by
climate and might instead be due to increasing atmospheric CO2 or other nutrient fertilization, It is
found that a number of tree-ring studies from temperature-sensitive settings indicate unusual recent
warming, although there are also exceptions al. certain sires, The present tree-ring evidence for a
possible CO2 fertilization effect under natural environmental conditions appears to be very limited.

KEYWORDS: AMERICA, ATMOSPHERIC CO2, ENHANCEMENT, GROWTH, TRENDS


     1052 
Jager, H.J., U. Hertstein, and A. Fangmeier. 1999. The European Stress Physiology and Climate
Experiment - project 1. wheat (ESPACE-wheat): introduction, aims and methodology. European
Journal of Agronomy 10(3-4):155-162.

The response of crops to CO2 enrichment represents an issue of major concern both for scientists and
for policymakers. In a concerted programme funded by the Commission of the European
Communities, a Europe-wide experimental and modeling study was carried out to investigate the
effects of increasing atmospheric CO2 concentrations, and of environmental stresses such as ozone
or water/nutrient shortage, under different climatic conditions on wheat (Triticum aestivum L.). This
contribution describes the experimental network and the standard protocol set-up for the assessments
which served to improve and to validate process-orientated wheat growth simulation models. (C)
1999 Elsevier Science B.V. All rights reserved.

KEYWORDS: AIR CO-2 ENRICHMENT, ATMOSPHERIC CO2, CARBON DIOXIDE, ELEVATED
CO2, GROWTH, O-3, OZONE, RESPONSES, TEMPERATURE, YIELD


     1053 
Jalil, A., and R.M. Carlson. 1993. Potassium uptake by marianna plum under limited oxygen and
elevated carbon-dioxide levels in the root atmosphere. Journal of Plant Nutrition 16(4):723-737.

Potassium (K) uptake rates were determined for Marianna 2624 rootstocks with 'French' prune scions
using th nutrient solution depletion technique. The nutrient solutions were bubbled with factorial
combinations of nitrogen (N2), oxygen (O2), and carbon dioxide (CO2) to create treatment root
atmospheres with O2 ranging from 0.01 to 0.10 m3/m3 and CO2 ranging from 0 to 0.05 m3/m3. The
K+ uptake rate was more susceptible to 02 deprivation than to elevated CO2 in the root atmosphere.
Decreasing 02 levels from 0.10 M3/M3 decreased K+ uptake in a hyperbolic fashion to no net uptake
at 0.01 M3/M3 02. Increasing root atmosphere CO2 from 0 to 0.05 M3/M3 had a small depressing
effect on net K+ influx from 60 muM K+ solutions at 0.10 and 0.05 M3/M3 02, but no effect when
02 was 0.025 or 0.01 M3/M3. Elevating CO2 decreased Km for the net K+ influx rate at 0.10 and
0.05 M3/M3 02. Increased pH buffering from higher HCO3 concentration at the plasma membrane
surface was suggested to explain the CO2 effect on Km.

KEYWORDS: GROWTH, WHEAT SEEDLINGS


     1054 
Jansen, D.M. 1990. Potential rice yields in future weather conditions in different parts of asia.
Netherlands Journal of Agricultural Science 38(4):661-680.

Future climate change is expected to vary between regions, with possible different effects on crop
growth. Various sites in Asia were selected to represent major rice growing environments. Historic
weather data of these sites were adapted to possible changes in temperature and in CO2 level, to
mimic climate change. Potential rice yields at present, and for the years 2020 and 2100 were
calculated with a crop growth simulation model. Simulated yields rose in low and middle temperature
change scenarios, but decreased in the high temperature scenario. Effects were stronger in the year
2100, when also regional differences became clear: more than elsewhere, yields were affected by high
temperatures between 10 and 35-degrees-N. Water use efficiency decreased in the high temperature
scenario irrespective of CO2 scenario, and increased otherwise.

KEYWORDS: CO2- ENRICHMENT, GROWTH, NITROGEN, ORYZA SATIVA L,
PHOTOSYNTHESIS, TEMPERATURE


     1055 
Janssens, I.A., M. Crookshanks, G. Taylor, and R. Ceulemans. 1998. Elevated atmospheric CO2
increases fine root production, respiration, rhizosphere respiration and soil CO2 efflux in Scots pine
seedlings. Global Change Biology 4(8):871-878.

In this study, we investigated the impact of elevated atmospheric CO2 (ambient + 350 mu mol mol(-
1)) on fine root production and respiration in Scots pine (Pinus sylvestris L.) seedlings. After six
months exposure to elevated CO2, root production measured by root in-growth bags, showed
significant increases in mean total root length and biomass, which were more than 100% greater
compared to the ambient treatment. This increased root length may have lead to a more intensive soil
exploration. Chemical analysis of the roofs showed that the roots in the elevated treatment
accumulated more starch and had a lower C/N-ratio. Specific root respiration rates were significantly
higher in the elevated treatment and this was probably attributed to increased nitrogen concentrations
in the roots. Rhizospheric respiration and soil CO2 efflux were also enhanced in the elevated
treatment. These results clearly indicate that under elevated atmospheric CO2 root production and
development in Scots pine seedlings is altered and respiratory carbon losses through the root system
are increased.

KEYWORDS: ALLOCATION, CARBON-DIOXIDE ENRICHMENT, COMPENSATORY
RESPONSES, GROWTH, LOBLOLLY-PINE, NITROGEN, PLANTAGO-MAJOR, PONDEROSA
PINE, TEMPERATURE, TREES


     1056 
Jarvis, A.J., T.A. Mansfield, and W.J. Davies. 1999. Stomatal behaviour, photosynthesis and
transpiration under rising CO2. Plant, Cell and Environment 22(6):639-648.

The literature reports enormous variation between species in the extent of stomatal responses to rising
CO2. This paper attempts to provide a framework within which some of this diversity can be
explained. We describe the role of stomata in the short-term response of leaf gas exchange to
increases in ambient CO2 concentration by developing the recently proposed stomatal model of Jarvis
gr Davies (1998). In this model stomatal conductance is correlated with the functioning of the
photosynthetic system so that the effects of increases in CO2 on stomata are experienced through
changes in the rate of photosynthesis in a simple and mechanistically transparent way This model also
allows us to consider the effects of evaporative demand and soil moisture availability on stomatal
responses to photosynthesis and therefore provides a means of considering these additional sources
of variation. We emphasize that the relationship between the rate of photosynthesis and the internal
CO2 concentration and also drought will have important effects on the relative gains to be achieved
under rising CO2.

KEYWORDS: ASSIMILATION, ATMOSPHERIC CO2, CARBON DIOXIDE, CONDUCTANCE,
ELEVATED CO2, EMPIRICAL-MODEL, LEAF GAS- EXCHANGE, PARTIAL-PRESSURE,
RESPONSES, WATER-VAPOR


     1057 
Jarvis, P.G. 1995. The role of temperate trees and forests in CO2 fixation. Vegetatio 121(1-2):157-
174.

The global flask network data indicate that the temperate and boreal forests of the northern
hemisphere are a significant sink for anthropogenic CO2. Bowen ratio and eddy covariance
technology have been used to measure the net CO2 exchange of deciduous and coniferous forest.
Some results from an earlier study on spruce with the Bowen ratio technique are presented. New
technology that has been developed to measure fluxes continuously by forest stands is described and
data are presented to show the net exchange flux of CO2 by temperate forests. These data support
the hypothesis that temperate and boreal forests are significant sinks for carbon dioxide. An extensive
programme of experimental impact studies is being carried out by a network of 12 laboratories in
Europe funded by the European Commission. Parallel studies are in progress in North America and
elsewhere. These studies indicate that doubling the atmospheric CO2 concentration results in
increases in tree biomass of 30-40%. Interactions with nutrition are particularly significant. If nitrogen
is added at a commensurate rate, the overall effect is that trees grow larger more quickly in elevated
CO2 than in ambient air but they are essentially very similar in structure and physiology. However,
if nutrients are in short supply, developmental and physiological changes occur. Then elevated CO2
causes changes in dry mass allocation to roots, in phenology of bud burst and set, in photosynthesis,
in respiration, and in tree water relations. These changes are exaggerated in low nutrition situations.
Process-based models have been developed to scale- up from leaf and tree to the stand scale. These
models contain explicit description of processes affected by CO2, and are parameterised using the
data collected in the impact studies. It is concluded that forests in the temperate and boreal region
can effectively contribute to the removal of anthropogenic CO2 from the atmosphere and that tree
growth and production of long-lived wood products should be encouraged as a major contribution
towards off-setting the greenhouse effect caused by the burning of fossil fuels.

KEYWORDS: ATMOSPHERE-BIOSPHERE EXCHANGE, CARBON, ENRICHMENT,
EVAPOTRANSPIRATION, MAESTRO, SINKS, SITKA SPRUCE, STANDS, STORAGE, WEATHER


     1058 
Jauhiainen, J., and J. Silvola. 1999. Photosynthesis of Sphagnum fuscum at long-term raised CO2
concentrations. Annales Botanici Fennici 36(1):11-19.

Rate of net photosynthesis in Sphagnum fuscum (Schimp.) Klinggr. was measured during long-term
(50-122 days), and subsequently during short-term (1/2 h), exposure to 350, 700, 1000 or 2000 ppm
CO2 concentrations. Raised CO2 concentrations caused a general increase in the rate of net
photosynthesis, increasing the rate of photosynthesis at light saturation and causing a given rate of
net CO2 exchange to be reached at lower light fluxes. The relative increase in the rate of net
photosynthesis by increasing radiation fluxes was independent of the CO2 treatment. The rates of net
photosynthesis at enhanced CO2 concentrations gradually decreased compared to rates found with
the 350 ppm treatment and this acclimation was also noticed during short-term exposure to all four
CO2 concentrations. At 2000 ppm of CO2, the depression of net photosynthesis at high water
contents, found at lower CO2 concentrations, was removed. Observed rates of net photosynthesis
indicated that water-use efficiency of Sphagna was not coupled with constant long-term CO2
concentrations.

KEYWORDS: ACCLIMATION, ATMOSPHERIC CO2, CARBON DIOXIDE, CARBOXYLASE,
ELEVATED CO2, EXPOSURE, MOSS HYLOCOMIUM-SPLENDENS, NORTHERN PEATLANDS,
PEAT MOSSES, WATER-CONTENT


     1059 
Jauhiainen, J., J. Silvola, K. Tolonen, and H. Vasander. 1997. Response of Sphagnum fuscum
to water levels and CO2 concentration. Journal of Bryology 19:391-400.

Sphagnum fuscum samples collected from an ombrotrophic bog were grown in a greenhouse at six
water levels (0,5. 10, 15, 25 and 30 cm) below the capitulam level and in four concentrations of CO2
(350, 700, 1000 and 2000 ppm). The cores of S, fuscum were treated for 87 days and length
increment was measured by the plastic strip method and by innate time markers, Water content of the
shoot, dry mass of the capitulum, dry mass per unit length of stem and production of dry mass were
measured at the end of the experiment. The water content, capitulum dry mass, dry mass per unit
length of stem, length increment and dry mass production differed markedly for S. fuscum grown in
different water levels. With lower water levels, the water content of the shoot decreased and the dry
mass of both the capitulum and unit length of stem increased. The total length increment was highest
when the water level was at or near the capitulum level (0-10 cm). No clear trend in dry mass
production on an areal basis could be found due to uncoupled responses in length increment and stem
dry mass at the experimental water levels. Neither capitulum dry mass nor dry mass per unit length
of stem showed distinct trends in S. fuscum grown at different ambient CO2 concentrations. Some
increase in length increment and in dry mass production was detected at CO2 concentrations above
350 ppm, but this effect appeared only at high water levels. It is suggested that the low response in
length increment and production to CO2 concentration resulted in part from insufficient moisture for
photosynthesis at the lower water levels. Also, the possibility of increased nonstructural production
is discussed.

KEYWORDS: DECAY, ELEVATED CO2, ENVIRONMENT, FOREST, GROWTH, HABITAT, PEAT
MOSSES, PHOTOSYNTHESIS, SOUTHERN FINLAND, SWEDISH RAISED BOG


     1060 
Jauhiainen, J., H. Vasander, and J. Silvola. 1994. Response of sphagnum-fuscum to n deposition
and increased co2. Journal of Bryology 18:83-96.

The length increment and production of Sphagnum fuscum with enhanced nitrogen deposition (0, 10,
30 and 100 kg N ha(-1) yr(-1)) and CO2 concentration (350, 700, 1000 and 2000 ppm) were
measured. The experiment was carried out in the glasshouse, where S. fuscum was grown with the
water table maintained at 10 cm below the moss surface for 120 d. For length growth, 10 kg N ha(-1)
yr(-1): and for biomass production, 30 kg N ha(-1) yr(-1) were found to be the optimal loads. A load
of 100 kg N ha(-1) yr(-1) inhibited elongation and biomass production almost completely. An
increased CO2 concentration reduced length increment slightly, but it did not have a significant effect
on biomass production. However, above ambient CO2 concentrations increased capitulum density
and stem dry mass per unit length. In addition, increased CO2 concentration accelerated relative
growth in Sphagnum carpets when these also received additional nitrogen. The study highlights the
high degree of spatial variability that occurs within Sphagnum fuscum. Differences in growth and
biomass production between samples, not found in natural conditions, emerged during the
experiment. On the basis of our results, the present nitrogen deposition load in Southern Finland (ca
6-10 kg N ha(-1) yr(-1)) is quite suitable for the growth and production of S. fuscum. If N deposition
increased substantially, differences in the vitality of the species might be expected.

KEYWORDS: ATMOSPHERIC NITROGEN, BALANCE, CARBON DIOXIDE, GROWTH,
MOSSES, PHOTOSYNTHESIS, RAISED BOG, SOUTHERN FINLAND, TEMPERATURE,
TUSSOCK TUNDRA


     1061 
Jauhiainen, J., H. Vasander, and J. Silvola. 1998. Nutrient concentration in Sphagna at increased
N-deposition rates and raised atmospheric CO2 concentrations. Plant Ecology 138(2):149-160.

Sphagnum fuscum, S. magellanicum, S. angustifolium and S. warnstorfii were treated with N
deposition rates (0, 10, 30 and 100 kg ha(-1) a(-1)) and with four atmospheric CO2 concentrations
(350, 700, 1000 and 2000 ppm) in greenhouse for 71-120 days. Thereafter, concentrations of total
N, P, K, Ca and Mg in the capitulae of the Sphagna were determined. The response of each species
to N deposition was related to ecological differences. With increasing N deposition treatments, moss
N concentrations increased and higher N:P- ratios were found, the increase being especially clear at
the highest N load. Sphagnum fuscum, which occupies ombrotrophic habitats, was the most affected
by the increased nitrogen load and as a consequence the other elements were decreased. Oligotrophic
S. magellanicum, wide nutrient status tolerant S. angustifolium and meso-eutrophic S. warnstorfii
tolerated better increased N deposition, though there were increased concentrations of Ca and Mg
in S. warnstorfii and Mg in S. magellanicum. Nitrogen and P concentrations decreased with raised
CO2 concentrations, except for S. magellanicum. This seems to be the first time this kind of response
in nutrient concentrations to enhanced CO2 concentration has been shown to exist in bryophytes. The
concentration of K clearly decreased in S. fuscum as did the concentration of Mg in the other
Sphagna with increasing CO2. Sphagnum angustifolium and S. magellanicum, which are the less
specialized species, were the least affected by the CO2 treatments.

KEYWORDS: ELEMENT CONCENTRATIONS, ELEVATED CARBON-DIOXIDE, GROWTH,
MIRE WATER, NITRATE REDUCTASE, NITROGEN, PEAT BOGS, PHOTOSYNTHESIS,
RESPONSES, WATER CHEMISTRY


     1062 
Jenkinson, D.S., D.E. Adams, and A. Wild. 1991. Model estimates of CO2 emissions from soil in
response to global warming. Nature 351(6324):304-306.

ONE effect of global warming will be to accelerate the decomposition of soil organic matter, thereby
releasing CO2 to the atmosphere, which will further enhance the warming trend 1- 7. Such a feedback
mechanism could be quantitatively important, because CO2 is thought to be responsible for
approximately 55% of the increase in radiative forcing arising from anthropogenic emissions of gases
to the atmosphere 8, and there is about twice as much carbon in the top metre of soil as in the
atmosphere 9. Here we use the Rothamsted model for the turnover of organic matter in soil 3 to
calculate the amount of CO2 that would be released from the world stock of soil organic matter if
temperatures increase as predicted, the annual return of plant debris to the soil being held constant.
If world temperatures rise by 0.03-degrees-C yr-1 (the increase considered as most likely by the
Intergovernmental Panel on Climate Change 8), we estimate that the additional release of CO2 from
soil organic matter over the next 60 years will be 61 x 10(15) gC. This is approximately 19% of the
CO2 that will be released by combustion of fossil fuel during the next 60 years if present use of fuel
continues unabated.

KEYWORDS: C-14-LABELED RYEGRASS, DECOMPOSITION, FIELD, PLANT- MATERIAL,
STRAW, TERRESTRIAL CARBON STORAGE


     1063 
Jiang, G.M., and G.H. Lin. 1997. Changes of photosynthetic capacity of some plant species under
very high CO2 concentrations in Biosphere 2. Chinese Science Bulletin 42(10):859-864.

KEYWORDS: ATMOSPHERIC CO2, ENRICHMENT, RESPONSES


     1064 
Jiang, W.B., A. Lers, E. Lomaniec, and N. Aharoni. 1999. Senescence-related serine protease in
parsley. Phytochemistry 50(3):377-382.

During leaf senescence protein degradation is enhanced. In order to obtain information on the
enzymes involved in this process, a study was initiated to identify and characterize proteases whose
activity is elevated in artificially senescing parsley leaves. A 70-kDa serine protease (EC 3.4.21) was
identified by an activity gel assay. This protease activity, which is low in young leaves, was found to
increase considerably in parallel to the advance of senescence and the reduction in the protein content
of the leaves. A high correlation between the progress of senescence and the increase in the activity
of the 70 kDa serine protease was demonstrated. Treatments with CO2 or gibberellic acid, which
retard senescence, reduced the protease's activity, whereas acceleration of senescence with ethylene
enhanced it. (C) 1998 Elsevier Science Ltd. All rights reserved.

KEYWORDS: CYSTEINE, INDUCTION, PLANTS


     1065 
Jiao, J., P. Goodwin, and B. Grodzinski. 1999. Inhibition of photosynthesis and export in geranium
grown at two CO2 levels and infected with Xanthomonas campestris pv. Pelargonii. Plant, Cell and
Environment 22(1):15-25.

The effects of CO2 enrichment on growth of Xanthomonas campestris pv. pelargonii and the impact
of infection on the photosynthesis and export of attached, intact, 'source' leaves of geranium
(Pelargonium x domesticum, 'Scarlet Orbit Improved') are reported. Two experiments were
performed, one with plants without flower buds, and another with plants which were flowering.
Measurements were made on healthy and diseased leaves at the CO2 levels (35 Pa or 90 Pa) at which
the plants were grown. There were no losses of chlorophyll, or any signs of visible chlorosis or
necrosis due to infection. Lower numbers of bacteria were found in leaves at high CO2, suggesting
growth at elevated CO2 created a less favourable condition in the leaf for bacterial growth. Although
high CO2 lowered the bacterial number in infected leaves, reductions in photosynthesis and export
were greater than at ambient CO2. The capacity of infected source leaves to export photoassimilates
at rates observed in the controls was reduced in both light and darkness. In summary, the severity of
infection on source leaf function by the bacteria was increased, rather than reduced by CO2
enrichment, underscoring the need for further assessment of plant diseases and bacterial virulence in
plants growing under varying CO2 levels.

KEYWORDS: ACCLIMATION, ATMOSPHERIC CO2, C-3, CARBOXYLASE, ELEVATED CO2,
LEAF, LEAVES, PLANTS, STEADY-STATE PHOTOSYNTHESIS, TRANSLOCATION


     1066 
Jiao, J.R., and B. Grodzinski. 1998. Environmental influences on photosynthesis and carbon export
in greenhouse roses during development of the flowering shoot. Journal of the American Society for
Horticultural Science 123(6):1081-1088.

Photosynthesis and concurrent export rates of expanded leaves on the flowering shoot of Rosa
hybrida L. 'Samantha' were measured at three stages of shoot and flower bud development. At 35 and
90 Pa CO2 photosynthesis and concurrent export rates of the upper expanded leaves were greater
at Stage 3 (i.e., when petal color of the flower bud was visible) than at the two earlier stages of shoot
and flower development. The optimum for leaf photosynthesis and concurrent export at ambient CO2
and saturating irradiance were approximate to 25 degrees C. Export was more sensitive to increased
temperature than was carbon fixation. For example, at 40 degrees C photosynthesis was 40% lower
while the export rate during photosynthesis was reduced by 80 %. Increasing the photon fluence flux
rate from 200 to 1000 mu mol.m(-2).s(-1) PAR increased the photosynthetic rate and the concurrent
export rate at 35 and 90 Pa CO2, but the increase in export was proportionally greater than that of
photosynthesis. At 35 Pa CO2, the rate of C export during photosynthesis increased from 31 to 59%
of the concurrent C fixation rate. At 90 Pa CO2, export during photosynthesis increased from 38 to
62% of the photosynthesis rate. The importance of irradiance on translocation processes was further
demonstrated by comparing the disappearance of label during the feed period and during an extended
night period. Plants grown at each CO2 level exported about three times as much of the C- 14 fixed
during a 2-hour feed period in the light as during a subsequent 15-hour dark chase period. The
nighttime export and respiration rates of leaves which had been exposed to elevated CO2 levels
during the feed were higher than those rates observed at ambient CO2. However, at the end of the
chase period, the leaves of plants which had been exposed to CO2 enrichment during the feed also
retained more C-14 than did the leaves of the plants which were at ambient CO2. Thus, although
more C-14 was fixed and exported under high CO2, the same proportion of labelled assimilates were
exported, respired, and retained in the dark as at ambient CO2.

KEYWORDS: ACCLIMATION, ATMOSPHERIC CO2, CO2- ENRICHMENT, LEAF AGE,
LEAVES, NET CO-2 EXCHANGE, PLANTS, TEMPERATURE, TOMATO, TRANSLOCATION


     1067 
Jiao, J., M.J. Tsujita, and B. Grodzinski. 1991. Influence of radiation and CO2 enrichment on
whole plant net CO2 exchange in roses. Canadian Journal of Plant Science 71(1):245-252.

At three stages of flowering shoot development, varying the irradiance and CO2 levels had a similar
effect on the whole- plant net CO2 exchange rate (NCER) of Samantha rose plants. At 22-degrees-C,
the NCER was saturated at 1000-mu-mol m-2 s-1 photosynthetically active radiation (PAR). The
duration of the light period was also important in determining daily carbon (C) gain. When roses were
exposed to a constant daily radiant energy dose of 17.6-mu-mol m-2 provided either as a 12-h
irradiation interval at 410-mu-mol m-2 s-1 PAR or 24 h of irradiation at 204-mu-mol m-2 s-1 PAR,
the plants exposed to 24 h of continuous irradiation at the lower photon flux density retained 80%
more C. Under saturating irradiance, the net photosynthetic rate at an enriched (1000-mu-L L-1) CO2
level was almost double that at ambient (350-mu-L L-1) CO2. However, plants grown at ambient and
enriched CO2 levels had similar whole-plant NCERs when compared at the same assay CO2 level.
Under CO2 enrichment the flower stem was longer and thicker but the flower bud size at harvest was
not significantly different to that of roses grown at the ambient CO2 level.

KEYWORDS: CARBON DIOXIDE, CO2, GROWTH, PHOTOSYNTHESIS


     1068 
Jiao, J., M.J. Tsujita, and B. Grodzinski. 1991. Influence of temperature on net CO2 exchange
in roses. Canadian Journal of Plant Science 71(1):235-243.

The effect of temperature on net CO2 exchange of source and sink tissues of the flowering shoots
and of whole plants was examined using single-stemmed Samantha roses. At all stages of shoot
development, the optimal temperature range for whole-plant carbon (C) gain at saturating irradiance
and ambient CO2 level was between 20-degrees and 25-degrees-C, narrower than the temperature
range for optimal leaf net photosynthesis. Dark respiration increased more dramatically than
photosynthesis with temperatures between 15 and 35-degrees-C. At 25-degrees-C, C loss due to
respiration from the flower bud at colour bud stage accounted for 45% of the C loss of the flowering
shoot. At low irradiance levels (e.g. 200-mu-mol m-2 s-1) whole-plant net photosynthesis was greater
at 16-degrees than at 22-degrees-C because of a greater reduction in respiration. Lowering the night
temperature from 27 to 17- degrees-C also increased daily C gain due to a reduction in the C lost at
night. Whole-plant net photosynthesis of plants grown and measured at enriched (1000 +/- 100-mu-L
L-1) CO2 was greater than that of plants grown and measured at ambient (350 +/- 50-mu-L L-1)
level at temperatures between 15-degrees and 35-degrees-C. Furthermore, the optimal temperatures
for whole- plant net photosynthesis in CO2 enrichment was higher than at ambient CO2 level.

KEYWORDS: AGE, CARBON, LEAF, PHOTOSYNTHESIS, PLANTS, TRANSPORT


     1069 
Jifon, J.L., A.L. Friend, and P.C. Berrang. 1995. Species mixture and soil-resource availability
affect the root- growth response of tree seedlings to elevated atmospheric co21. Canadian Journal
of Forest Research-Revue Canadienne De Recherche Forestiere 25(5):824-832.

The effects of CO2 enrichment on root proliferation of loblolly pine (Pinus taeda L.) and sweetgum
(Liquidambar styraciflua L.) seedlings were studied under varied water and nitrogen (N) regimes and
in competitive interaction. Seedlings of each species were grown from seed as monocultures or as
50:50 pine- sweetgum mixtures in 22-L pots filled with forest soil. Seedlings were exposed to either
ambient (400 ppm) or CO2- enriched (ambient plus 400 ppm) air for 32 weeks in continuously stirred
tank reactors. Detailed sampling of very fine roots (<0.5 mm diam.) showed a general increase (up
to 2- fold) in root length density (RLD, cm . cm(-3)) with elevated CO2; however, the effects of CO2
on RLD differed according to species, culture type, water, and N availability. In monoculture, low
water with low N conditions produced the largest RLD responses to elevated CO2: 75% increase for
sweetgum and 31% increase for pine. In mixed culture, by contrast, the largest RLD responses to
CO2 were observed under high water, high N regimes: pine showed a 110% increase and sweetgum
a 96% increase. The total RLD of the standing crop in mixture under elevated CO2, high water, and
high N was 2.6 cm . cm(-3) compared with 1.6 cm . cm(-3) in ambient CO2, with sweetgum
accounting for >75% of the total RLD in both cases. These findings suggest that resource-rich rather
than resource- poor soil environments could be the circumstances under which belowground
interference from sweetgum would intensify in pine- sweetgum mixtures with rising atmospheric
CO2.

KEYWORDS: CARBON DIOXIDE, COMPETITION, ECOSYSTEMS, ENRICHMENT,
LIQUIDAMBAR- STYRACIFLUA, LOBLOLLY-PINE SEEDLINGS, PATTERNS, PLANTS,
QUANTIFICATION, TAEDA SEEDLINGS


     1070 
Jitla, D.S., G.S. Rogers, S.P. Seneweera, A.S. Basra, R.J. Oldfield, and J.P. Conroy. 1997.
Accelerated early growth of rice at elevated CO2 - Is it related to developmental changes in the shoot
apex? Plant Physiology 115(1):15-22.

The influence of elevated CO2 on the development of the shoot apex and on subsequent vegetative
growth and grain yield was investigated using rice (Oryza sativa L. cv Jarrah) grown in flooded soil
at either 350 or 700 mu L CO2 L-1. At 8 d after planting (DAP), elevated CO2 increased the height
and diameter of the apical dome and lengths of leaf primordia and tiller buds but had no effect on their
numbers. By 16 DAP, there were five tiller buds in the apex at 700 mu L CO2 L-1 compared with
only three tiller buds at 350 mu L CO2 L-1. These changes in development of the shoot apex at high
CO2 were forerunners to faster development of the vegetative shoot at elevated CO2 between 11 and
26 DAP as evidenced by increases in the relative growth rates of the shoot and tillers. Accelerated
development at high CO2 was responsible for the 42% increase in tiller number at the maximum
tillering stage and the 57% enhancement of grain yield at the final harvest. The link between high CO2
effects on development during the first 15 DAP and final tiller number and grain yield was
demonstrated by delaying exposure of plants to high CO2 for 15 d. The delay totally inhibited the
tillering response to high CO2, and the increase in grain yield of 20% arose from a greater number
of grains per panicle. Consequently, it can be concluded that accelerated development in the shoot
apex early in development is crucial for obtaining maximum increases in grain yield at elevated
atmospheric CO2 concentrations.

KEYWORDS: ACCLIMATION, ATMOSPHERIC CO2, CELL, ELONGATION, LEAF, LEAVES,
PLANTS, PROTEINS, YIELD


     1071 
John-McKay, M.E., and B. Colman. 1997. Variation in the occurrence of external carbonic
anhydrase among strains of the marine diatom Phaeodactylum tricornutum (Bacillariophyceae).
Journal of Phycology 33(6):988-990.

Eleven different strains of Phaeodactylum tricornutum Bohlin were obtained from three culture
collections and were examined for the presence of external and internal carbonic anhydrase (CA).
Cells of all strains, grown in standing culture at alkaline pH and low dissolved inorganic carbon had
internal CA, but only eight were found to have external CA. External CA activity was reduced when
cultures were bubbled with air and was completely repressed when they were grown on 5% CO2.
Expression of external CA activity appears to be regulated by CO2 concentration in the growth
medium, but within one species, there appears to be a variation in occurrence of external CA and
consequently in the mode of inorganic carbon acquisition.

KEYWORDS: ACCUMULATION, CHLORELLA-SACCHAROPHILA, CO2, CYANOBACTERIA,
DISSOLVED INORGANIC CARBON, HIGHER-PLANTS, MICROALGAE, PHYTOPLANKTON


     1072 
Johnsen, K.H. 1993. Growth and ecophysiological responses of black spruce seedlings to elevated
co2 under varied water and nutrient additions. Canadian Journal of Forest Research-Revue
Canadienne De Recherche Forestiere 23(6):1033-1042.

Two controlled-environment studies examined growth and ecophysiological responses of black spruce
(Picea mariana (Mill.) B.S.P.) seedlings to elevated CO2 under varied water and nutrient additions.
Growth analyses were conducted followed by measurements of gas exchange, xylem pressure
potential and foliar N concentrations. Growth under elevated CO2 (700 ppm) increased final seedling
dry weights by 20-48% compared with seedling growth under ambient CO2 (350 ppm). Percent
increases in seedling dry weight were greater under drought versus well- watered conditions and
higher versus lower nutrient additions. Seedlings grown under elevated CO2 displayed higher water
use efficiency than seedlings grown under ambient CO2. This was apparent based upon instantaneous
gas exchange as well as xylem potential pressure measurements. Elevated CO2-induced stimulation
of relative growth rate was greatest shortly after seedling emergence and decreased with increased
seedling size. Acclimation of net photosynthesis was observed and was reversible. Analyses using
allometric principles indicate net photosynthetic acclimation resulted from: (i) growth-induced
nutrient dilution; (ii) a decrease in foliar N levels not owing to dilution; and (iii) a decrease in net
photosynthetic activity.

KEYWORDS: ANATOMY, ATMOSPHERIC CARBON-DIOXIDE, ENRICHMENT, FORESTS,
LIQUIDAMBAR- STYRACIFLUA, LOBLOLLY-PINE, PHYSIOLOGY, PINUS-TAEDA
SEEDLINGS, ROOT, SHOOT


     1073 
Johnsen, K.H. 1994. Growth and ecophysiological responses of black spruce seedlings to elevated
co2 under varied water and nutrient additions (vol 23, pg 1033, 1993). Canadian Journal of Forest
Research-Revue Canadienne De Recherche Forestiere 24(3):646.



     1074 
Johnsen, K.H., and J.E. Major. 1998. Black spruce family growth performance under ambient and
elevated atmospheric CO2. New Forests 15(3):271-281.

Seedlings from 20 families of black spruce (Picea mariana (Mill.) B.S.P.), representing a large range
in field productivity, were subjected to a greenhouse retrospective test under ambient (409 ppm - year
1, 384 ppm - year 2) and high (686 ppm - year 1, 711 ppm - year 2) atmospheric CO2 environments.
After one and two growth cycles, seedling height and diameter growth significantly increased under
elevated CO2. At the end of the experiment, seedlings grown under high CO2 had a mean above-
ground dry weight of 48.77 g as compared to 26.36 g for seedlings grown under ambient atmospheric
CO2. Families were a significant source of variation for all growth parameters. Although the family
x CO2 environment interaction was not a statistically significant source of variation in the analysis
of variance, the correlation between greenhouse and IS-year field height growth was weaker (r =
0.29, p = 0.2177) under elevated CO2 compared to ambient CO2 (r = 0.51, p = 0.0223) following
the first growth cycle. However, following the second growth cycle, greenhouse-field correlations
were similar between the two CO2 environments (ambient CO2: r = 0.55, p = 0.0115; elevated CO2:
r = 0.56, p = 0.0101). Thus, with this set of families, growth performance ranking after two years
appears relatively stable under ambient and elevated CO2.

KEYWORDS: EARLY SELECTION, FULL-SIB FAMILIES, GAS-EXCHANGE, PHENOLOGY,
RESPONSES, SEEDLINGS, TREES, WATER-STRESS


     1075 
Johnsen, K.H., and J.R. Seiler. 1996. Growth, shoot phenology and physiology of diverse seed
sources of black spruce .1. Seedling responses to varied atmospheric CO2 concentrations and
photoperiods. Tree Physiology 16(3):367-373.

We conducted a greenhouse experiment to determine: (1) if diverse provenances of black spruce
(Picea mariana (Mill.) B.S.P.) respond similarly in growth, phenology and physiology to an
approximately 300 ppm increase in atmospheric CO2 concentration, and (2) the influence of
photoperiod on both provenance and provenance x CO2 interaction effects. Seedlings from
provenances that originated from the Yukon (63 degrees 34' N, 135 degrees 55' W), British Columbia
(58 degrees 47' N, 123 degrees 38' W), Alberta (52 degrees 22' N, 115 degrees 15' W),
Newfoundland (50 degrees 54' N, 56 degrees 06' W) and Ontario (48 degrees 59' N, 80 degrees 38'
W and 45 degrees 10' N, 77 degrees 10' W) were subjected to growth analysis in greenhouse growth
chambers supplied with 712 +/- 93 (SD) ppm CO2 (elevated) or 394 +/- 59 ppm CO2 (ambient).
Seedlings from Provenances 7000 and 6901 were also subjected to an extended photoperiod
treatment and periodically measured for shoot and root gas exchange. In response to a natural
photoperiod, southern provenances grew more, broke and set bud later, and partitioned more biomass
to shoot versus root than northern provenances. These differences among provenances were
influenced by the extended photoperiod treatment but not by the elevated CO2 treatment. Averaged
across all provenances, elevated CO2 increased seedling final weights by 55%; however, the elevated
CO2 treatment had no effect on the provenance differences in any measured trait. We conclude that
the large differences in physiology, phenology and growth among these diverse provenances of black
spruce were expressed similarly in both ambient and elevated atmospheric CO2 concentrations.

KEYWORDS: ELEVATED CO2, FAMILIES, LOBLOLLY-PINE


     1076 
Johnson, B.G., B.A. Hale, and D.P. Ormrod. 1996. Carbon dioxide and ozone effects on growth
of a legume-grass mixture. Journal of Environmental Quality 25(4):908-916.

Atmospheric carbon dioxide (CO2) and photochemical ozone (O-3) have been increasing in the
biosphere and will continue to do so with further industrialization and burning of fossil fuels, The
purpose of this study was to examine the interaction of CO2 and O-3 on plant growth and
aboveground competition using a forage mixture of alfalfa (Medicago sativa L.) and timothy (Phleum
pratense L.). Mixtures were grown at two CO2 levels (350 and 700 mu L/L) in controlled
environment chambers and exposed to four weekly O-3 episodes of 8-h duration with peak daily
concentrations of 0.03, 0.08, 0.13, or 0.18 mu L/L on Days (d) 21, 28, 35, and 42 after seeding.
Roots of individual plants were in separate containers, The plants were harvested 2 d after the fmal
O-3 exposure. Total dry biomass of alfalfa and timothy was 50 and 40%, respectively, greater at 700
than at 350 mu L CO2/L with low O-3. Increasing peak O-3 concentration decreased alfalfa shoot
dry biomass at 700 mu L CO2/L but not at 350 mu L/L and decreased root dry biomass at both CO2
levels. In timothy, intermediate O-3 levels reduced shoot growth but the highest level of O-3 resulted
in more shoot growth in the mixture at both CO2 levels. Partitioning of dry matter to alfalfa roots was
strongly retarded by increasing O- 3, particularly in the CO2-enriched environment, while timothy
root growth vias unaffected by O-3. The enhancement of timothy shoot biomass is, the mixture by
exposure to the highest level of O-3 at either CO2 level could not be fully explained by changes in
competition between timothy and alfalfa in relation to differential O-3 tolerance.

KEYWORDS: AIR- POLLUTANTS, CLOVER, FORAGE, PASTURE, PLANTS, QUALITY, YIELD


     1077 
Johnson, D.W. 1999. Simulated nitrogen cycling response to elevated CO2 in Pinus taeda and mixed
deciduous forests. Tree Physiology 19(4-5):321-327.

Interactions between elevated CO2 and N cycling Introduction were explored with a nutrient cycling
model (NuCM, Johnson et ai. 1993, 1995) for a Pinus taeda L, site at Duke University, North
Carolina, and a mixed deciduous site at Walker Branch, Tennessee. The simulations tested whether
N limitation would prevent growth increases in response to elevated CO2, and whether growth
responses to CO2 in N-limited systems could be facilitated by increasing the biomass/N ratio
(reducing N concentration) or increasing litter N mineralization, or both. Nitrogen limitation
precluded additional growth when target growth rates and litterfall were increased (simulating
potential response to elevated CO2) at the Duke University site. At the Walker Branch site, increasing
target growth and litterfall caused a 7% increase in growth. Reducing foliar N concentrations reduced
growth because of N limitation created by reduced litter quality (C:N ratio), reduced decomposition
and increased N accumulation on the forest floor. These effects were most pronounced at the Duke
University site, because the forest floor N turnover rate was lower than at the Walker Branch site.
Reducing wood N concentration allowed prolonged increases in growth because of greater
biomass/N; however, N uptake was reduced, allowing greater N immobilization on the forest floor
and in soil. Increased N mineralization caused increased growth at the Duke University site, but not
at the Walker Branch site. These simulations pose the counterintuitive hypothesis that increased
biogeochemical cycling of N (as a result of increased litterfall N) causes reduced growth in an N-
limited system because of increased accumulations of N on the forest floor and in soil. Translocation
of N from senescing leaves before litterfall mitigates this response by allowing the trees to retain a
greater proportion of N taken up rather than recycle it back to the forest floor and soil where it can
be immobilized. Eliminating N translocation at Walker Branch changed the direction as well as the
magnitude of the responses in three of the four scenarios simulated. Because the NuCM model does
not currently allow translocation in coniferous species, the effects of translocation on N cycling in the
Duke University simulations are not known.

KEYWORDS: CARBON DIOXIDE, CYCLES, DEPOSITION, ECOSYSTEMS, FEEDBACK,
MODEL, STORAGE


     1078 
Johnson, D.W., and J.T. Ball. 1990. Environmental-pollution and impacts on soils and forests
nutrition in north-america. Water, Air, and Soil Pollution 54:3-20.

The effects of acid deposition, excess N deposition, and elevated CO2 on forest soils and nutrition
in North America are reviewed. While there remains the possibility that acid deposition and excess
N deposition are contributing to declines in red spruce, sugar maple, and southern pines, clear-cut
cause and effects are still not evident. Climate is clearly a major factor in red spruce decline in the
northeastern U.S., but air pollution may contribute. There is some evidence that soil solution Al may
be approaching deleterious levels in southeastern red spruce forests. Lack of proper management may
be a major factor in the sugar maple and southern pine declines, but once again, air pollution as a
potential contributor cannot be ignored. Nutrient budget analyses and discoveries of soils base cation
depletion in certain sites suggest that base cation status is declining in forests of the southeastern
U.S., but thus far, base cation deficiences are uncommon. Recent research has revealed that there are
more cases of N-saturated forests in North America than was previously suspected. These systems
are characterized by high rates of soil N mineralization, high atmospheric N inputs, low uptakes, or
some combination of these factors. Soil leaching and Al mobilization in such systems is often
dominated by nitrate. However, the geographical extent of these types of systems is limited, and the
traditional view that most forest ecosystems are N limited remains valid, especially where forest
management is intensive. The limited information available on tree response to CO2 suggests N-
deficient plants often grow faster with elevated CO2, whereas P-deficient plants often do not.
Research is needed to 1) determine if the differences in response between N- and P-deficient plants
is common, 2) the responses of plants deficient in other nutrients to elevated CO2, and 3) the
interactions of CO2 increase, nutrient deficiencies, climate change.

KEYWORDS: CARBON-DIOXIDE ENRICHMENT, CO2- ENRICHMENT, DECIDUOUS FOREST,
EASTERN UNITED STATES, ELEVATED CO2, LOBLOLLY-PINE, NITROGEN
MINERALIZATION, PINUS-RADIATA SEEDLINGS, RED SPRUCE, SIMULATED ACID-RAIN


     1079 
Johnson, D.W., J.T. Ball, and R.F. Walker. 1997. Effects of CO2 and nitrogen fertilization on
vegetation and soil nutrient content in juvenile ponderosa pine. Plant and Soil 190(1):29-40.

This paper summarizes the data on nutrient uptake and soil responses in opentop chambers planted
with ponderosa pine (Pinus ponderosa Laws.) treated with both N and CO2. Based upon the
literature, we hypothesized that 1) elevated CO2 would cause increased growth and yield of biomass
per unit uptake of N even if N is limiting, and 2) elevated CO2 would cause increased biomass yield
per unit uptake of other nutrients only by growth dilution and only if they are non-limiting.
Hypothesis 1 was supported only in part: there were greater yields of biomass per unit N uptake in
the first two years of growth but not in the third year. Hypothesis 2 was supported in many cases:
elevated CO2 caused growth dilution (decreased concentrations but not decreased uptake) of P, S,
and Mg. Effects of elevated CO2 on K, Ca, and B concentrations were smaller and mostly non-
significant. There was no evidence that N responded in a unique manner to elevated CO2, despite its
unique role in rubisco. Simple growth dilution seemed to explain nutrient responses in almost all
cases. There were significant declines in soil exchangeable K+, Ca2+, Mg2+ and extractable P over
time which were attributed to disturbance effects associated with plowing. The only statistically
significant treatment effects on soils were negative effects of elevated CO2 on mineralizeable N and
extractable P, and positive effects of both N fertilization and CO2 on exchangeable Al3+. Soil
exchangeable K+, Ca2+, and Mg2+ pools remained much higher than vegetation pools, but
extractable P pools were lower than vegetation pools in the third year of growth. There were also
large losses of both native soil N and fertilizer N over time. These soil N losses could account for the
observed losses in exchangeable K+, Ca2+, Mg2+ if N was nitrified and leached as NO3-.

KEYWORDS: CARBON DIOXIDE, DEFICIENCY, ELEVATED ATMOSPHERIC CO2,
ENHANCEMENT, ENRICHMENT, FEEDBACK, FOREST, GROWTH-RESPONSES,
PHOSPHORUS, SPRUCE SEEDLINGS


     1080 
Johnson, D.W., T. Ball, and R.F. Walker. 1995. Effects of elevated co2 and nitrogen on nutrient-
uptake in ponderosa pine-seedlings. Plant and Soil 169:535-545.

This paper reports on the results of a controlled-environment study on the effects of CO2 (370, 525,
and 700 mu mol mel(-1)) and N [0, 200, and 400 mu g N g soil(-1) as (NH4)SO4] on ponderosa pine
(Pinus ponderosa) seedlings. Based upon a review of the literature, we hypothesized that N
limitations would not prevent a growth response to elevated CO2. The hypothesis was not supported
under conditions of extreme N deficiency (no fertilizer added to a very poor soil), but was supported
when N limitations were less severe but still suboptimal (lower rate of fertilization), The growth
increases in N-fertilized seedlings occurred mainly between 36 and 58 weeks without any additional
N uptake. Thus, it appeared that elevated CO2 allowed more efficient use of internal N reserves in
the previously-fertilized seedlings, whereas internal N reserves in the unfertilized seedlings were
insufficient to allow this response, Uptake rates of other nutrients were generally proportional to
growth. Nitrogen treatment caused reductions in soil exchangeable K+, Ca2+, and Mg2+ (presumably
because of nitrification and NO3- leaching) but increases in extractable P (presumably due to
stimulation of phosphatase activity). The results of this and other seedling studies show that elevated
CO2 causes a reduction in tissue N concentration, even under N- rich conditions. The unique
response of N is consistent with the hypothesis that the efficiency of Rubisco increases with elevated
CO2. These results collectively have significant implications for the response of mature, N-deficient
forests to elevated CO2.

KEYWORDS: ATMOSPHERIC CO2, DIOXIDE, ECOSYSTEMS, ENRICHMENT, FOREST,
GLOBAL CARBON-CYCLE, GROWTH-RESPONSES, LIMITATIONS, SOIL, SPRUCE
SEEDLINGS


     1081 
Johnson, D., D. Geisinger, R. Walker, J. Newman, J. Vose, K. Elliot, and T. Ball. 1994. Soil
pco(2), soil respiration, and root activity in co2- fumigated and nitrogen-fertilized ponderosa pine.
Plant and Soil 165(1):129-138.

The purpose of this paper is to describe the effects of CO2 and N treatments on soil pCO(2),
calculated CO2 efflux, root biomass and soil carbon in open-top chambers planted with Pinus
ponderosa seedlings. Based upon the literature, it was hypothesized that both elevated CO2 and N
would cause increased foot biomass which would in turn cause increases in both total soil CO2 efflux
and microbial respiration. This hypothesis was only supported in part: both CO2 and N treatments
caused significant increases in root biomass, soil pCO(2), and calculated CO2 efflux, but there were
no differences in soil microbial respiration measured in the laboratory. Both correlative and
quantitative comparisons of CO2 efflux rates indicated that microbial respiration contributes little to
total soil CO2 efflux in the field. Measurements of soil pCO(2) and calculated CO2 efflux provided
inexpensive, non-invasive, and relatively sensitive indices of belowground response to CO2 and N
treatments.

KEYWORDS: ATMOSPHERIC CO2, CARBON DIOXIDE, CO2 EVOLUTION, ECOSYSTEMS,
PLANTATIONS, RESPONSES


     1082 
Johnson, D.W., R.B. Thomas, K.L. Griffin, D.T. Tissue, J.T. Ball, B.R. Strain, and R.F.
Walker. 1998. Effects of carbon dioxide and nitrogen on growth and nitrogen uptake in ponderosa
and loblolly pine. Journal of Environmental Quality 27(2):414-425.

The purpose of this paper is to summarize the results of a series of greenhouse and open-top chamber
studies on the effects of N and elevated atmospheric CO2 on ponderosa and loblolly pine (Pinus
ponderosa Laws, and P. taeda L.) to evaluate common patterns of response. Growth response to
elevated CO2 ranged from zero to more than 1000%, depending largely upon N status, In both
species, growth response to CO2 was greater under moderate N deficiency than under extreme N
deficiency or N sufficiency/excess. Elevated CO2 generally caused lowered tissue N concentrations
in many (but not all) cases, which in turn resulted in smaller increases in N uptake than in biomass.
Growth response to N ranged from -50 (in ponderosa pine) to more than 1000%, depending upon
the N status of the control medium. Growth response to N was enhanced by elevated CO2 when N
was in the extreme deficiency range but not when N was in the moderate deficiency range. In two
separate studies, ponderosa pine responded negatively to high N inputs, and in each case this response
was mitigated by elevated CO2. Collectively, these results show that (i) N deficiency is a continuum
rather than a step function, (ii) responses to elevated CO2 vary across this continuum of N deficiency,
and (iii) elevated CO2 greatly enhances growth response to N additions when N is initially in the
extremely deficient range.

KEYWORDS: ATMOSPHERIC CO2 ENRICHMENT, ECOSYSTEMS, ELEVATED CO2, FOREST,
LEAF LITTER, LITTER QUALITY, NUTRIENT STATUS, RESPONSES, SOIL N, SPRUCE
SEEDLINGS


     1083 
Johnson, D.W., R.F. Walker, and J.T. Ball. 1995. Combined effects of nitrogen and elevated CO2
on soils from controlled environment studies. Water, Air, and Soil Pollution 85(3):1551-1556.

This paper describes the effects of elevated CO2 and N fertilization on soils planted with ponderosa
pine (Pinus Ponderosa) seedlings in short-term greenhouse studies. The high degree of homogeneity
in the soils used allowed sensitive evaluation of soil changes in response to treatments. Elevated CO2
had no detectable effect upon soil N availability, but both CO2 and N fertilization caused significant
changes in soil available (NH4F/HCl-extractable) P. Some of these changes could be accounted for
by plant uptake, some were apparently due to differences in P immobilization (biotic or abiotic). N
fertilization caused reductions in exchangeable K, Ca and Mg which could not be accounted for by
plant uptake and were probably due to increased leaching. None of the reductions in soil available
nutrients observed were of sufficient magnitude to cause nutrient deficiencies over the approximate
1-year duration of these studies.

KEYWORDS: CARBON DIOXIDE, ECOSYSTEMS, RESPONSES


     1084 
Johnson, D.W., R.F. Walker, and J.T. Ball. 1995. Lessons from lysimeters - soil n release from
disturbance compromises controlled environment study. Ecological Applications 5(2):395-400.

A controlled environment study of the effects of carbon dioxide (CO2) and nitrogen (N) on growth
of ponderosa pine seedlings produced results contradictory to those obtained in the field with the
same species, soil, and treatments. In the controlled environment study, there was a significant
negative growth response to N fertilization, whereas in the field there was a significant positive
response to N. The difference was due to high rates of native N mineralization after soil disturbance
during potting. This was evident from soil solution NO3- concentrations that peaked at approximate
to 5000 mu mol/L in the unfertilized pots and 20 000 mu mol/L in the fertilized pots. These
concentrations are orders of magnitude greater than those typically observed in the field. The effects
of soil disturbance on N mineralization and nitrification need to be carefully considered before
initiating controlled environment studies. The results of this study show that excessive N
mineralization caused by soil disturbance can seriously compromise the results of controlled
environment studies

KEYWORDS: ECOSYSTEMS, ELEVATED CARBON-DIOXIDE, FOREST


     1085 
Johnson, H.B., H.W. Polley, and H.S. Mayeux. 1993. Increasing co2 and plant-plant interactions -
effects on natural vegetation. Vegetatio 104:157-170.

Plant species and functional groups of species show marked differences in photosynthesis and growth
in relation to rising atmospheric CO2 concentrations through the range of the 30 % increase of the
recent past and the 100 % increase since the last glaciation. A large shift was found in the
compositional mix of 26 species of C3's and 17 species of C4's grown from a native soil seed bank
in a competitive mode along a CO2 gradient that approximated the CO2 increase of the past 150
years and before. The biomass of C3's increased from near zero to 50 % of the total while that of the
C4's was reduced 25 % as CO2 levels approached current ambient. The proposition that acclimation
to rising CO2 will largely negate the fertilization effect of higher CO2 levels on C3's is not supported.
No signs of photosynthetic acclimation were evident for Avena sativa, Prosopis glandulosa, and
Schizachyrium scoparium plants grown in subambient CO2. The effects of changing CO2 levels on
vegetation since the last glaciation are thought to have been at least as great, if not greater, than those
which should be expected for a doubling of current CO2 levels. Atmospheric CO2 concentrations
below 200 ppm are thought to have been instrumental in the rise of the C4 grasslands of North
America and other extensive C4 grasslands and savannas of the world. Dramatic invasion of these
areas by woody C3 species are accompanying the historical increase in atmospheric CO2
concentration now in progress.

KEYWORDS: C-3, CARBON-DIOXIDE CONCENTRATION, CLIMATE CHANGE, ELEVATED
ATMOSPHERIC CO2, ENRICHMENT, ESTUARINE MARSH, GROWTH, OLD- FIELD
PERENNIALS, PHOTOSYNTHESIS, TUSSOCK TUNDRA


     1086 
Johnson, L.C., G.R. Shaver, A.E. Giblin, K.J. Nadelhoffer, E.R. Rastetter, J.A. Laundre, and
G.L. Murray. 1996. Effects of drainage and temperature on carbon balance of tussock tundra
microcosms. Oecologia 108(4):737-748.

We examined the importance of temperature (7 degrees C or 15 degrees C) and soil moisture regime
(saturated or field capacity) on the carbon (C) balance of arctic tussock tundra microcosms (intact
blocks of soil and vege tation) in growth chambers over an 81-day simulated growing season. We
measured gaseous CO2 exchanges, methane (CH4) emissions, and dissolved C losses on intact blocks
of tussock (Eriophorum vaginatum) and in tertussock (moss-dominated). We hypothesized that under
increased temperature and/or enhanced drainage, C losses from ecosystem respiration (CO2 respired
by plants and heterotrophs) would exceed gains from gross photosynthesis causing tussock tundra
to become a net source of C to the atmosphere. The field capacity moisture regime caused a decrease
in net CO2 storage (NEP) in tussock tundra microcosms. This resulted from a stimulation of
ecosystem respiration (probably mostly microbial) with enhanced drainage, rather than a decrease in
gross photosynthesis. Elevated temperature alone had no effect on NEP because CO2 losses from
increased ecosystem respiration at elevated temperature were compensated by increased CO2 uptake
(gross photosynthesis). Although CO2 losses from ecosystem respiration were primarily limited by
drainage, CH4 emissions, in contrast, were dependent on temperature. Furthermore, substantial
dissolved C losses, especially organic C, and important microhabitat differences must be considered
in estimating C balance for the tussock tundra system. As much as similar to 20% of total C fixed in
photosynthesis was lost as dissolved organic C. Tussocks stored similar to 2x more C and emitted
5x more methane than intertussocks. In spite of the limitations of this microcosm experiment, this
study has further elucidated the critical role of soil moisture regime and dissolved C losses in
regulating net C balance of arctic tussock tundra.

KEYWORDS: ALASKAN TUNDRA, ARCTIC TUNDRA, ATMOSPHERIC CO2, CLIMATIC
CHANGE, DIOXIDE, GREENHOUSE, METHANE, RESPONSES, TERRESTRIAL ECOSYSTEMS,
WATER-TABLE


     1087 
Johnson, R.H., and D.E. Lincoln. 1991. Sagebrush carbon allocation patterns and grasshopper
nutrition - the influence of CO2 enrichment and soil mineral limitation. Oecologia 87(1):127-134.

Artemisia tridentata seedlings were grown under carbon dioxide concentrations of 350 and 650-mu-l
l-1 and two levels of soil nutrition. In the high nutrient treatment, increasing CO2 led to a doubling
of shoot mass, whereas nutrient limitation completely constrained the response to elevated CO2. Root
biomass was unaffected by any treatment. Plant root/shoot ratios declined under carbon dioxide
enrichment but increased under low nutrient availability, thus the ratio was apparently controlled by
changes in carbon allocation to shoot mass alone. Growth under CO2 enrichment increased the starch
concentrations of leaves grown under both nutrient regimes, while increased CO2 and low nutrient
availability acted in concert to reduce leaf nitrogen concentration and water content. Carbon dioxide
enrichment and soil nutrient limitation both acted to increase the balance of leaf storage carbohydrate
versus nitrogen (C/N). The two treatment effects were significantly interactive in that nutrient
limitation slightly reduced the C/N balance among the high-CO2 plants. Leaf volatile terpene
concentration increased only in the nutrient limited plants and did not follow the overall increase in
leaf C/N ratio. Grasshopper consumption was significantly greater on host leaves grown under CO2
enrichment but was reduced on leaves grown under low nutrient availability. An overall negative
relationship of consumption versus leaf volatile concentration suggests that terpenes may have been
one of several important leaf characteristics limiting consumption of the low nutrient hosts.
Digestibility of host leaves grown under the high CO2 treatment was significantly increased and was
related to high leaf starch content. Grasshopper growth efficiency (ECI) was significantly reduced
by the nutrient limitation treatment but co-varied with leaf water content.

KEYWORDS: DIOXIDE ATMOSPHERES, ELEVATED CO2, GROWTH, INSECT HERBIVORE,
LEPIDOPTERA, LIMITING CONDITIONS, NITROGEN, NOCTUIDAE, PLANT-TISSUE,
VOLATILE LEAF TERPENES


     1088 
Johnston, K.M., and O.J. Schmitz. 1997. Wildlife and climate change: Assessing the sensitivity of
selected species to simulated doubling of atmospheric CO2. Global Change Biology 3(6):531-544.

We explored, using computer simulations, the sensitivity of four mammal species (elk, Cervus
canadensis; white-tailed deer, Odocoileus virginianus; Columbian ground squirrel, Spermophilus
columbianus; and chipmunk, Tamias striatus) within the continental USA to the effect of anticipated
levels of global climate change brought about by a doubling of atmospheric CO2. Sensitivity to the
direct effects of climate change were evaluated using a climate-space approach to delineate the range
of thermal conditions tolerable by each species. Sensitivity to indirect effects were evaluated by
quantifying the association of each species to the current vegetation distribution within the continental
USA and using this association to assess whether wildlife species distributions might shift in response
to vegetation shifts under climate change. Results indicate that altered thermal conditions alone
should have little or no effect on the wildlife species' distributions as physiological tolerance to heat
load would allow them to survive. Analyses of the effects of vegetation change indicate that deer and
chipmunks should retain their current distributions and possibly expand westward in the USA. For
Elk and ground squirrels, there is a possibility that their current distributions would shrink and there
is little possibility that each species would spread to new regions. This work emphasizes that the
distributions of the four mammalian species are likely to be influenced more by vegetation changes
than by thermal conditions. Future efforts to understand the effects of global change on wildlife
species should focus on animal-habitat and climate-vegetation linkages.

KEYWORDS: CONSTRAINTS, ECOLOGY, MODELS, SCALE, VEGETATION, WHITE-TAILED
DEER


     1089 
Joles, D.W., A.C. Cameron, A. Shirazi, P.D. Petracek, and R.M. Beaudry. 1994. Modified-
atmosphere packaging of heritage red raspberry fruit - respiratory response to reduced oxygen,
enhanced carbon- dioxide, and temperature. Journal of the American Society for Horticultural
Science 119(3):540-545.

'Heritage' raspberries (Rubus idaeus L.) were sealed in low- density polyethylene packages and stored
at 0, 10, and 20C during Fall 1990 and 1991 to study respiratory responses under modified
atmospheres. A range of steady-state O2 and CO2 partial pressures were achieved by varying fruit
weight in packages of a specific surface area and film thickness. Film permeability to O2 and CO2
was measured and combined with surface area and film thickness to estimate total package
permeability. Rates of O2 uptake and CO2 production and respiratory quotient (RQ) were calculated
using steady-state O2 and CO2 partial pressures, total package permeability, and fruit weight. The
O2 uptake rate decreased with decreasing O2 partial pressure over the range of partial pressure
studied. The Michaelis-Menten equation was used to model O2 uptake as a function of O2 partial
pressure and temperature. The apparent K(m) (K1/2) remained constant (5.6 kPa O2) with
temperature, while Q10 was estimated to be 1.9. RQ was modeled as a function of O2 partial
pressure and temperature. Headspace ethanol increased at RQs >1.3 to 1.5. Based on RQ, ethanol
production, and flavor, we recommend that raspberries be stored at O2 levels above 4 kPa at 0C, 6
kPa at 10C, and 8 kPa at 20C. Steady-state CO2 partial pressures of 3 to 17 kPa had little or no
effect on O2 uptake or headspace ethanol partial pressures at 20C.

KEYWORDS: BLUEBERRY, CO2, FRESH PRODUCE, QUALITY, STORAGE


     1090 
Jones, C.G., and S.E. Hartley. 1999. A protein competition model of phenolic allocation. Oikos
86(1):27-44.

We present a Protein Competition Model (PCM) for predicting total phenolic allocation and
concentration in leaves of terrestrial higher plants. In contrast to predictions based on the carbon
composition of end products, the PCM is based on metabolic origins of pathway constituents,
alternative fates of pathway precursors, and biochemical regulatory mechanisms. Protein and phenolic
synthesis compete for the common, limiting resource phenylalanine, so protein and phenolic allocation
are inversely correlated. Phenolic allocation can be predicted from the effects of development,
inherent growth rate and environment on leaf functions that create competing demands for proteins
or phenolics. We present the model general principles. We predict phenolic concentrations as leaves
develop; in inherently fast versus slow growing species; and in response to the environment (nitrogen,
light, phosphorus, heat shock, herbivore and pathogen injury, and carbon dioxide). Because
predictions generally fit observed patterns, we argue that, for phenylalanine-derived phenolics, the
mechanistically distinctive PCM complements the Growth Differentiation and Resource Availability
Hypotheses, and is a viable, testable alternative to the Carbon Nutrient Balance Hypothesis.

KEYWORDS: CARBON NUTRIENT BALANCE, CHEMICAL-COMPOSITION, DELAYED
INDUCIBLE RESISTANCE, ELEVATED ATMOSPHERIC CO2, MINERAL NUTRITION,
PHENYLALANINE AMMONIA-LYASE, PHENYLPROPANOID METABOLISM, PLANT- GROWTH
RATE, RESOURCE AVAILABILITY HYPOTHESIS, SECONDARY METABOLISM


     1091 
Jones, M.B., J.C. Brown, A. Raschi, and F. Miglietta. 1995. The effects on arbutus-unedo L of
long-term exposure to elevated co2. Global Change Biology 1(4):295-302.

Arbutus unedo is a sclerophyllous evergreen, characteristic of Mediterranean coastal scrub
vegetation. In Italy, trees of A. unedo have been found close to natural CO2 vents where the mean
atmospheric carbon dioxide concentration is about 2200 mu mol mol(-1). Comparisons were made
between trees growing in elevated and ambient CO2 concentrations to test for evidence of adaptation
to long-term exposure to elevated CO2. Leaves formed at elevated CO2 have a lower stomatal
density and stomatal index and higher specific leaf area than those formed at ambient CO2, but there
was no change in carbon to nitrogen ratios of the leaf tissue. Stomatal conductance was lower at
elevated CO2 during rapid growth in the spring. In mid-summer, under drought stress, stomatal
closure of all leaves occurred and in the autumn, when stress was relieved, the conductance of leaves
at both elevated and ambient CO2 increased. In the spring, the stomatal conductance of the new flush
of leaves at ambient CO2 was higher than the leaves at elevated CO2, increasing instantaneous water
use efficiency at elevated CO2. Chlorophyll fluorescence measurements suggested that elevated CO2
provided some protection against photoinhibition in mid- summer. Analysis of A/C-i curves showed
that there was no evidence of either upward or downward regulation of photosynthesis at elevated
CO2. It is therefore anticipated that A. unedo will have higher growth rates as the ambient CO2
concentrations increase.

KEYWORDS: ACCLIMATION, ATMOSPHERIC CO2, ENRICHMENT, GAS-EXCHANGE,
INCREASE, LEAVES, PHOTOSYNTHESIS, PLANTS, STOMATAL DENSITY, TREES


     1092 
Jones, M.B., and M. Jongen. 1996. Sensitivity of temperate grassland species to elevated
atmospheric CO2 and the interaction with temperature and water stress. Agricultural and Food
Science in Finland 5(3):271-283.

The annual cycle of growth of many temperate grasses is limited by low temperatures during the
winter and spring and water stress during the summer. Climate change, induced by increase in the
concentration of greenhouse gases in the atmosphere, can affect the growth and community structure
of temperature grasslands in two ways. The first is directly through changes in atmospheric
concentration of CO2 and the second is indirectly through changes in temperature and rainfall. At
higher latitudes, where growth is largely temperature limited, it is probable that the direct effects of
enhanced CO2 will be less than at low latitudes. However, interactions with increasing temperature
and water stress are complex. Temperate grasslands range from intensively managed monocultures
of sown species to species-rich natural and semi-natural communities whose local distributions are
controlled by variations in soil type and drainage. The different species can show marked differences
in their responses to increasing CO2 concentrations, rising temperatures and water stress. This will
probably result in major alterations in the community structure of temperate grasslands in the future.
In addition to impacts on primary productivity and community structure, a long-term effect of
elevated CO2 on grasslands is likely to be a significant increase in soil carbon storage. However, this
may be counteracted by increases in temperature.

KEYWORDS: CARBON DIOXIDE, CLIMATE CHANGE, ENRICHMENT, GAS-EXCHANGE,
GROWTH, PHOTOSYNTHESIS, PLANT, RESPONSES, STOMATAL CONTROL, USE
EFFICIENCY


     1093 
Jones, M.B., M. Jongen, and T. Doyle. 1996. Effects of elevated carbon dioxide concentrations
on agricultural grassland production. Agricultural and Forest Meteorology 79(4):243-252.

Open-top chambers have been used on a field-grown perennial ryegrass (Lolium perenne) sward to
investigate the long-term responses to elevated CO2 concentrations. A concentration of 2 x ambient
CO2 increased annual harvestable yield by about 20%, but the proportional stimulation was not
constant throughout the growing season nor from one season to the next. Other effects of elevated
CO2 were an increase in carbon/nitrogen ratio of tissues and a decrease in specific leaf area and
canopy conductance. There was no effect of CO2 on the digestibility of the harvested grass. It is
likely that climate change during the next century will lead to significant increases in agricultural
grassland production in northern Europe. Production will be stimulated by a direct fertiliser effect due
to the increasing CO2 concentration of the atmosphere.

KEYWORDS: CANOPIES, CO2 CONCENTRATION, FIELD, LOLIUM-PERENNE, PERENNIAL
RYEGRASS, PHOTOSYNTHESIS, RESPONSES


     1094 
Jones, M.H., J.T. Fahnestock, D.A. Walker, M.D. Walker, and J.M. Welker. 1998. Carbon
dioxide fluxes in moist and dry arctic tundra during season: Responses to increases in summer
temperature and winter snow accumulation. Arctic and Alpine Research 30(4):373-380.

Climate-induced environmental changes are likely to have pronounced impacts on CO2 flux patterns
in arctic ecosystems. We initiated a long-term experiment in 1994 in moist tussock and dry heath
tundra in arctic Alaska in which we increased summer air temperature (ca. 2 degrees C) and increased
winter snow accumulation (shortening the growing season approximately 4 wk). During the 1996
snow-free season, we measured ecosystem CO2 flux weekly in order to quantify net carbon gain or
loss from these systems. Over the duration of the snow-free season, both dry heath and moist tussock
tundra exhibited a net loss of carbon to the atmosphere, ranging from 12 to 81 g C m(-2) depending
upon experimental treatment. Elevated summer temperatures accelerated net CO2 loss rates over
ambient temperatures in both deep and ambient snow treatments, and increased the total amount of
carbon emitted during the snow- free season by 26 to 38% in ambient snow plots and by 112 to 326%
in deep snow plots. Increased snow accumulation had less impact on CO2 flux than did warming, and
snow effects on total carbon loss were not consistent between the two temperature regimes.
Ecosystem respiration exceeded assimilation on most sampling dates throughout the season. These
data, coupled with winter carbon losses recently demonstrated in the same ecosystems, indicate that
the moist and dry arctic ecosystems we examined are currently net sources of atmospheric carbon on
an annual basis, and that anticipated global warming may increase carbon losses from these systems.

KEYWORDS: ALASKA, BALANCE, CLIMATE CHANGE, CO2, ECOSYSTEMS, EFFLUX, SOILS,
STORAGE, TUSSOCK TUNDRA, USA


     1095 
Jones, M.H., S.E. Macdonald, and G.H.R. Henry. 1999. Sex- and habitat-specific responses of
a high arctic willow, Salix arctica, to experimental climate change. Oikos 87(1):129-138.

Dioecious plant species and those occupying diverse habitats may present special analytical problems
to researchers examining effects of climate change. Here we report the results from two
complementary studies designed to determine the importance of sex and habitat on gas exchange and
growth of male and female individuals of a dioecious, circumpolar willow, Salix arctica, in the
Canadian High Arctic. In field studies, male and female willows from dry and wet habitats were
subjected to passively enhanced summer temperature (similar to 1.3 degrees C) using small open-top
chambers over three years. Peak season gas exchange varied significantly by willow sex and habitat.
Overall net assimilation was higher in the dry habitat than in the wet, and higher in females than in
males. In the dry habitat, net assimilation of females was enhanced by experimental warming, but
decreased in males. In the wet habitat, net assimilation of females was substantially depressed by
experimental warming, while males showed an inconsistent response. Development and growth of
male and female catkins were enhanced by elevated temperature more than leaf fascicles, but leaf
fascicle development and growth varied more between the two habitats, particularly in males. In a
controlled environment study, male and female willows from these same wet and dry habitats were
grown in a 2x2 factorial experiment including 1 x or 2 x ambient [CO2] and 5 or 12 degrees C. The
sexes responded very differently to the experimental treatments, but we found no effect of original
habitat. Net assimilation in males was affected by the interaction of temperature and CO2, but in
females by CO2 only. Our results demonstrate (a) significant intraspecific and intersexual differences
in arctic willow physiology and growth, (b) that these differences are affected by environmental
conditions expected to accompany global climate change, and (c) that sex- and habitat-specific
responses should be explicitly accounted for in studies of dioecious species.

KEYWORDS: DWARF WILLOW, ELEVATED CO2, GAS-EXCHANGE, GROWTH, PHYSIOLOGY,
PLANT SILENE LATIFOLIA, WATER RELATIONS


     1096 
Jones, P., L.M. Collins, and K.T. Ingram. 1995. Open-top chambers for field studies of crop
response to elevated co2 and temperature. Transactions of the Asae 38(4):1195-1201.

A new design for Open Top Chambers (OTCs) is described. In addition to providing CO2 controls
as do several other existing OTCs, the system is designed to provide elevated temperature control.
To provide a more natural vertical microclimate profile, the newly designed system pulls air down
through the chamber and out the bottom rather than injecting air at the bottom and venting it out the
top of the chamber. A prototype was constructed and performance tests were conducted. Over a 24-h
test period with a CO2 concentration setpoint of 660 ppm, individual measurements of concentration
taken every 5 min averaged 660.5 ppm with a standard deviation of 26.6 ppm. Temperature controls
were rested over 24-h periods for two different setpoints-ambient +4 degrees C and ambient +6
degrees C. For the two test periods the average chamber temperature measurements were 3.98
degrees and 5.99 degrees C above ambient, respectively. Twenty chambers based on the prototype
design were constructed and installed at the International Rice Research Institute, Los Banos,
Philippines. As intended, the chambers are currently being used to conduct research on rice crop
response to elevated CO2 and temperature.

KEYWORDS: CARBON DIOXIDE, CO2, DESIGN, ENVIRONMENT, EXPOSURE, PLANTS


     1097 
Jones, T.H., L.J. Thompson, J.H. Lawton, T.M. Bezemer, R.D. Bardgett, T.M. Blackburn,
K.D. Bruce, P.F. Cannon, G.S. Hall, S.E. Hartley, G. Howson, C.G. Jones, C. Kampichler, E.
Kandeler, and D.A. Ritchie. 1998. Impacts of rising atmospheric carbon dioxide on model
terrestrial ecosystems. Science 280(5362):441-443.

In model terrestrial ecosystems maintained for three plant generations at elevated concentrations of
atmospheric carbon dioxide, increases in photosynthetically fixed carbon were allocated below
ground, raising concentrations of dissolved organic carbon in soil. These effects were then transmitted
up the decomposer food chain. Soil microbial biomass was unaffected, but the composition of soil
fungal species changed, with increases in rates of cellulose decomposition. There were also changes
in the abundance and species composition of Collembola, fungal-feeding arthropods. These results
have implications for long-term feedback processes in soil ecosystems that are subject to rising global
atmospheric carbon dioxide concentrations.

KEYWORDS: COLLEMBOLA, COLONIZATION, COMMUNITIES, DECOMPOSITION,
ELEVATED CO2, FUNGI, PLANT-RESPONSES, PREFERENCES, RHIZOSPHERE, SOIL


     1098 
Jongen, M., P. Fay, and M.B. Jones. 1996. Effects of elevated carbon dioxide and arbuscular
mycorrhizal infection on Trifolium repens. New Phytologist 132(3):413-423.

Trifolium repens L. cv. aran was grown for 58 d at ambient (350 mu mol mol(-1)) and elevated (700
mu mol mol(-1)) atmospheric CO2, with and without the arbuscular mycorrhizal fungus Glomus
mosseae (Nicol. & Gerd.) Gerd. St Trappe cv. YV. Plant biomass, mycorrhizal infection, non-
structural carbohydrates, C, N and P content were examined. Elevated CO2 (a) significantly increased
above- and below-ground biomass, (b) decreased specific leaf area and specific root length, (c)
decreased tissue %N and increased the C:N ratio, and (d) significantly increased total non-structural
carbohydrates. Inoculating T. repens with Glomus mosseae (a) significantly increased above- and
below-ground biomass, (b) increased the total root length and total leaf area, and (c) significantly
decreased tissue %P. Evidence of an increased influence of mycorhiza on the P nutrition of T. repens
at elevated CO2 was found in the 22% increase in leaf total P (P less than or equal to 0.05) of
mycorrhizal plants grown at elevated CO2 compared with nonmycorrhizal plants. No significant
interactions were found between CO2 and mycorrhiza treatments. The proportion of T. repens root
length colonized by Glomus mosseae was not affected by CO2 concentration. The percentage
mycorrhizal infection was 29% at ambient CO2 and 35% at elevated CO2. However, exposure to
elevated CO2 significantly increased the total mycorrhizal root length from 3.4 to 6.1 m per plant.
The results show little evidence that the role of arbuscular mycorrhiza in the growth and nutrition of
T. repens would increase if atmospheric CO2 were to increase as predicted.

KEYWORDS: ATMOSPHERIC CO2, DYNAMICS, GROWTH, INSECT HERBIVORE, NITROGEN,
PHOSPHATE, PHOTOSYNTHESIS, PLANTS, SUBTERRANEUM L, WHITE CLOVER


     1099 
Jongen, M., and M.B. Jones. 1998. Effects of elevated carbon dioxide on plant biomass production
and competition in a simulated neutral grassland community. Annals of Botany 82(1):111-123.

Using open-top chambers, four prominent species (Lolium perenne, Cynosurus cristatus, Holcus
lanatus and Agrostis capillaris) of Irish neutral grasslands were grown at ambient and elevated (700
mu mol mol(-1)) atmospheric CO2 for a period of 8 months. The effects of interspecific competition
on plant responses to CO2 enrichment were investigated by growing the species in a four-species
mixture. The results indicate that the species differ in their ability to respond to elevated CO2. CO2-
enrichment had the largest effect on the biomass production of H. lanatus, but substantial stimulations
in biomass production were also found for the other three species. The CO2-stimulation of biomass
production for H. lanatus was accompanied by increased tillering. In addition, reductions in specific
leaf area were found for all species. Exposure to elevated CO2 increased the community biomass of
the four- species mixture. This increase can be mainly attributed to a significant increase in the
biomass of H. lanatus at elevated CO2. No statistically-significant changes in species composition of
community biomass were found. However, H. lanatus did increase its share of community biomass
at each of the harvests, with the other three species, mainly L. perenne, suffering losses in their shares
at elevated CO2. The results show that: (1) the species varied in their response to elevated CO2; and
(2) species composition in natural plant communities is likely to change at elevated CO2, but these
changes may occur rather slowly. Much longer periods of exposure to elevated atmospheric CO2 may
be required to permit detection of significant changes in species composition. (C) 1998 Annals of
Botany Company.

KEYWORDS: ATMOSPHERIC CO2, CO2- ENRICHMENT, DRY-MATTER, GROWTH, HOLCUS-
LANATUS, LOLIUM-PERENNE, PASTURE TURVES, SEASONAL-CHANGES, TRIFOLIUM-
REPENS, WHITE CLOVER


     1100 
Jongen, M., M.B. Jones, T. Hebeisen, H. Blum, and G. Hendrey. 1995. The effects of elevated
co2 concentrations on the root-growth of lolium-perenne and trifolium-repens grown in a face
system. Global Change Biology 1(5):361-371.

Lolium perenne and Trifolium repens were grown in a Free Air CO2 Enrichment (FACE) system at
elevated (600 mu mol mol(-1)) and ambient (340 mu mol mol(-1)) carbon dioxide concentrations
during a whole growing season. Using a root ingrowth bag technique the extent to which CO2
enrichment influenced the growth of L. perenne and T. repens roots under two contrasting nutrient
regimes was examined. Root ingrowth bags were inserted for a fixed time into the soil in order to trap
roots. It was also possible to follow the mortality of roots in bags inserted for different time intervals.
Root ingrowth of both L. perenne and T. repens increased under elevated CO2 conditions. In L.
perenne, root ingrowth decreased with increasing nutrient fertilizer level, but for T. repens the root
ingrowth was not affected by the nutrient application rate. Besides biomass measurements, root
length estimates were made for T. repens. These showed an increase under elevated CO2
concentrations. Root decomposition appeared to decrease under elevated CO2 concentrations. A
possible explanation for this effect is the observed changes in tissue composition, such as the increase
in the carbon:nitrogen ratio in roots of L. perenne at elevated CO2 concentrations.

KEYWORDS: ALLOCATION, ATMOSPHERIC CO2, CARBON DIOXIDE, CO2- ENRICHMENT,
DRY-MATTER, INSECT HERBIVORE, NITROGEN, PHOSPHORUS, PLANT, RESPONSES


     1101 
Jordan, D.N., S.F. Zitzer, G.R. Hendrey, K.F. Lewin, J. Nagy, R.S. Nowak, S.D. Smith, J.S.
Coleman, and J.R. Seeman. 1999. Biotic, abiotic and performance aspects of the Nevada Desert
Free-Air CO2 Enrichment (FACE) Facility. Global Change Biology 5(6):659-668.

Arid and semiarid climates comprise roughly 40% of the earth's terrestrial surface. Deserts are
predicted to be extremely responsive to global change because they are stressful environments where
small absolute changes in water availability or use represent large proportional changes. Water and
carbon dioxide fluxes are inherently coupled in plant growth. No documented global change has been
more substantial or more rapid than the increase in atmospheric CO2. Free Air CO2 Enrichment
(FACE) technology permits manipulation of CO2 in intact communities without altering factors such
as light intensity or quality, humidity or wind. The Nevada Desert FACE Facility (NDFF) consists
of three 491 m(2) plots in the Mojave Desert receiving 550 mu L L-1 CO2, and six ambient plots to
assess both CO2 and fan effects. The shrub community was characterized as a Larrea-Ambrosia-
Lycium species complex. Data are reported through 12 months of operation.

KEYWORDS: DIOXIDE, FIELD, WINTER ANNUALS


     1102 
Julkunentiitto, R., J. Tahvanainen, and J. Silvola. 1993. Increased co2 and nutrient status
changes affect phytomass and the production of plant defensive secondary chemicals in salix-
myrsinifolia (salisb). Oecologia 95(4):495-498.

The effect of CO2 enrichment (700 and 1050 ppm) on phytomass, soluble sugars, leaf nitrogen and
secondary chemicals of three Salix myrsinifolia clones was studied in plants cultivated at very poor
(sand seedlings) and moderate (peat seedlings) nutrient availability and under low illumination. The
total shoot phytomass production of sand seedlings was less than 10% of that of the peat seedlings.
Carbon dioxide increased the total shoot phytomass of peat seedlings. When the ambient carbon
supply was doubled (to 700 ppm) the growth of sand seedlings was slightly enhanced but 1050 ppm
CO2 gave growth figures similar to those at the control CO2 level. Leaf nitrogen content and total
soluble sugar contents were significantly higher in peat seedlings than in sand seedlings. Leaf nitrogen
showed a decreasing trend in relation to CO2 increase. On the other hand, CO2 did not have any
clear-cut effect on total sugars. At the control CO2 level the content of salicortin, which is a dynamic
phenolic, was higher in the peat seedlings than in the sand seedlings, but salicin showed the opposite
trend. CO2 enrichment considerably decreased these phenolics in the peat seedlings. At the control
CO2 level, the content of more static phenolics, such as proanthocyanidins, was higher in sand
seedlings. An increased carbon supply considerably increased static phenolics in the peat seedlings.
Willow defence against generalist herbivores is moderately decreased by enhancement of atmospheric
carbon dioxide.

KEYWORDS: ALLOCATION, BALANCE, PERFORMANCE, PHENOLIC CONSTITUENTS,
WILLOWS


     1103 
Kainulainen, P., J.K. Holopainen, and T. Holopainen. 1998. The influence of elevated CO2 and
O-3 concentrations on Scots pine needles: changes in starch and secondary metabolites over three
exposure years. Oecologia 114(4):455-460.

Scots pine (Pinus sylvestris L.) trees, aged about 20 years old, growing on a natural pine heath were
exposed to two concentrations of CO2 (ambient CO2 and double-ambient CO2) and two O-3 regimes
(ambient O-3 and double-ambient O-3) and their combination in open-top chambers during growing
seasons 1994, 1995 and 1996. Concentrations of foliar starch and secondary compounds are reported
in this paper. Starch concentrations remained unaffected by elevated CO2 and/or O-3 concentrations
during the first 2 study years. But in the autumn of the last study year, a significantly higher
concentration of starch was found in current-year needles of trees exposed to elevated CO2 compared
with ambient air. There were large differences in concentrations of starch and secondary compounds
between individual trees. Elevated concentrations of CO2 and/or O-3 did not have any significant
effects on the concentrations of foliar total monoterpenes, total resin acids or total phenolics.
Significantly higher concentrations of monoterpenes and resin acids and mostly lower concentrations
of starch were found in trees growing without chambers than in those growing in open-top chambers,
while there were no differences in concentrations of total phenolics between trees growing without
or in chambers. The results suggest that elevated concentrations of CO2 might increase foliar starch
concentrations in Scots pine, while secondary metabolites remain unaffected. Realistically elevated
O-3 concentrations do not have clear effects on carbon allocation to starch and secondary compounds
even after 3 exposure years.

KEYWORDS: ACID-RAIN, CARBON NUTRIENT BALANCE, DIOXIDE, GROWTH, L KARST,
NORWAY SPRUCE, OZONE, SEEDLINGS, SPRUCE PICEA-ABIES, SYLVESTRIS L


     1104 
Kajfezbogataj, L., and A. Hocevar. 1994. Assessment of climate-change effects on productivity
of beech stand in slovenia using simulation methods. Agricultural and Forest Meteorology 72(1-
2):47-56.

On the basis of observed climatic trends in Slovenia obtained from 142 years of meteorological
observation in Ljubljana (Slovenia) 15 climatic scenarios for the next 60 years are constructed
regarding temperature rise and various levels of increasing CO2 concentration. Yearly gross primary
production of 80 year old beech stand (Fagus sylvatica) is simulated in daily scale by the PERUN 3
model for healthy trees assuming no water stress. The influence of increased CO2 concentration on
physiological processes is assessed over enhanced maximal photosynthesis, lower compensation point
and increased stomatal resistance. Results of the simulation, giving decreased primary production of
beech stand under the mentioned assumption, are discussed.

KEYWORDS: CARBON DIOXIDE


     1105 
Kaji, H., M. Ueno, T. Ikebe, and Y. Osajima. 1993. Effects of low o-2 and elevated co2
concentrations on the quality of matsutake [tricholoma-matsutake (s ito et imai) sing] during storage.
Bioscience Biotechnology and Biochemistry 57(3):363-366.

Matsutake [Tricholoma matsutake (S. ITO et IMAI) SING.] was stored under conditions of low O2
and elevated CO2 concentrations. The storage conditions were as follows: with an O2 concentration
of 2.5+/-0.5%, the CO2 concentrations were 5%, 10%, 15%, and 20%, and relative humidity (RH)
was about 100%; with an O2 concentration of 2.0+/-0.5%, the CO2 concentrations were 0%, 5%,
10%, and 15%, and RH was about 100%; the storage temperature was 1.0+/-0.1-degrees-C. The fruit
was also stored in air and under 100% N2 as controls. Quality factors such as 'neto' (slimy microbial
flora which develop on the moist surface of the fruiting body), weight loss, whiteness, firmness, and
off-odor were measured. The development of neto and browning (loss of whiteness) of the inner stipe
were suppressed for more than 14 days, except with storage under 100% N2. Storage in air and under
0% or a high concentration (> 10%) of CO2 caused an early development of off-odor, compared to
storage under 5% and 10% CO2. In air, the development of mold was observed after 14 days. Under
a low O2 concentration and 5% to 10% CO2, the quality factors of matsutake were most retained,
and the fruit was still acceptable after 14 days of storage. A weight decrease of the fruit was
recognized as the CO2 concentration was increased.

KEYWORDS: MUSHROOMS


     1106 
Kalina, J., and R. Ceulemans. 1997. Clonal differences in the response of dark and light reactions
of photosynthesis to elevated atmospheric CO2 in poplar. Photosynthetica 33(1):51-61.

Two hybrid poplar (Populus) clones (i.e., fast growing clone Beaupre and slow growing clone
Robusta) were grown for two years from cuttings at close spacings in open top chambers (OTCs)
under ambient (AC) and elevated [EC = AC + 350 mu mol(CO2) mol(-1)] CO2 treatments, For clone
Beaupre no down- regulation of photosynthesis was observed. Two years of growing under EC
resulted in an increase in quantum yield of photosystem 2 (PS2), steady state irradiance saturated rate
of net photosynthesis (P-Nmax), chlorophyll (Chl) content, and ribulose-1,5-bisphosphate
carboxylase/oxygenase (RuBPC) activity for this clone. We suppose that under nonlimiting conditions
of nitrogen and phosphorus content the response to EC was by building up light-harvesting
complexes of PS2 and increasing photochemical efficiency of PS2, Due to a high rate of the primary
reactions of photosynthesis and a high RuBPCO activity the end product of the response to EC was
an increase in P-Nmax and a larger saccharides content, The Robusta clone showed a depression in
the primary reactions of photosynthesis under EC, We found a decrease in quantum yield of PS2, Chl
and phosphorus contents, and in RuBPCO activity. However, an increase in P-Nmax, saccharides
content and Chi a/b ratio was observed. We speculate (1) that the phosphorus deficiency in
combination with an increase in CO2 concentrations may lead to a potential damage of the
assimilation apparatus of the primary reactions of photosynthesis and to a decrease in photochemical
efficiency of PS2; (2) that the primary target of ''down- regulation'' takes place at PS2 for irradiances
above 150 mu mol m(-2) s(-1).

KEYWORDS: ACCLIMATION, CARBON DIOXIDE, CHLOROPHYLL FLUORESCENCE,
GROWTH, PHOTOSYSTEM, PLANTS, POPULUS, RIBULOSE-1;5-BISPHOSPHATE
CARBOXYLASE-OXYGENASE, RUBISCO, TOBACCO


     1107 
Kampichler, C., E. Kandeler, R.D. Bardgett, T.H. Jones, and L.J. Thompson. 1998. Impact of
elevated atmospheric CO2 concentration on soil microbial biomass and activity in a complex, weedy
field model ecosystem. Global Change Biology 4(3):335-346.

Although soil organisms play an essential role in the cycling of elements in terrestrial ecosystems, little
is known of the impact of increasing atmospheric CO2 concentrations on soil microbial processes.
We determined microbial biomass and activity in the soil of multitrophic model ecosystems housed
in the Ecotron (NERC Centre for Population Biology, Ascot, UK) under two atmospheric CO2
concentrations (ambient vs. ambient + 200 ppm). The model communities consist of four annual plant
species which naturally co-occur in weedy fields and disturbed ground throughout southern England,
together with their herbivores, parasitoids and soil biota. At the end of two experimental runs lasting
9 and 4.5 months, respectively, root dry weight and quality showed contradictory responses to
elevated CO2 concentrations, probably as a consequence of the different time-periods (and hence
number of plant generations) in the two experiments. Despite significant root responses no differences
in microbial biomass could be detected. Effects of CO2 concentration on microbial activity were also
negligible. Specific enzymes (protease and xylanase) showed a significant decrease in activity in one
of the experimental runs. This could be related to the higher C:N ratio of root tissue. We compare
the results with data from the literature and conclude that the response of complex communities
cannot be predicted on the basis of oversimplified experimental set-ups.

KEYWORDS: CARBON DIOXIDE, DECOMPOSITION, ENRICHMENT, LEAF LITTERS, LITTER
QUALITY, NITROGEN-CONTENT, NUTRIENT-UPTAKE, PLANT GROWTH, RESPONSES,
TALLGRASS PRAIRIE


     1108 
Kandeler, E., D. Tscherko, R.D. Bardgett, P.J. Hobbs, C. Kampichler, and T.H. Jones. 1998.
The response of soil microorganisms and roots to elevated CO2 and temperature in a terrestrial model
ecosystem. Plant and Soil 202(2):251-262.

We investigate the response of soil microorganisms to atmospheric CO2 and temperature change
within model terrestrial ecosystems in the Ecotron. The model communities consisted of four plant
species (Cardamine hirsuta, Poa annua, Senecio vulgaris, Spergula arvensis), four herbivorous insect
species (two aphids, a leaf-miner, and a whitefly) and their parasitoids, snails, earthworms, woodlice,
soil-dwelling Collembola (springtails), nematodes and soil microorganisms (bacteria, fungi,
mycorrhizae and Protista). In two successive experiments, the effects of elevated temperature
(ambient plus 2 degrees C) at both ambient and elevated CO2 conditions (ambient plus 200 ppm)
were investigated. A 40:60 sand:Surrey loam mixture with relatively low nutrient levels was used.
Each experiment ran for 9 months and soil microbial biomass (C-mic and N-mic), soil microbial
community (fungal and bacterial phospholipid fatty acids), basal respiration, and enzymes involved
in the carbon cycling (xylanase, trehalase) were measured at depths of 0-2, 0-10 and 10-20 cm. In
addition, root biomass and tissue C:N ratio were determined to provide information on the amount
and quality of substrates for microbial growth. Elevated temperature under both ambient and elevated
CO2 did not show consistent treatment effects. Elevation of air temperature at ambient CO2 induced
an increase in C-mic of the 0-10 cm layer, while at elevated CO2 total phospholipid fatty acids
(PLFA) increased after the third generation. The metabolic quotient qCO(2) decreased at elevated
temperature in the ambient CO2 run. Xylanase and trehalase skewed no changes in both runs. Root
biomass and C:N ratio were not influenced by elevated temperature in ambient CO2. In elevated CO2,
however, elevated temperature reduced root biomass in the 0-10 cm and 30-40 cm layers and
increased N content of roots in the deeper layers. The different response of root biomass and C:N
ratio to elevated temperature may be caused by differences in the dynamics of root decomposition
and/or in allocation patterns to coarse or fine roots (i.e. storage vs. resource capture functions).
Overall, our data suggests that in soils of low nutrient availability, the effects of climate change on
the soil microbial community and processes are likely to be minimal and largely unpredicatable.

KEYWORDS: ATMOSPHERIC CARBON-DIOXIDE, COMMUNITIES, ENRICHMENT,
GRASSLAND, MANAGEMENT, MICROBIAL BIOMASS, NINHYDRIN-REACTIVE NITROGEN,
RESPIRATION, SYSTEMS, TALLGRASS PRAIRIE


     1109 
Kanechi, M., M. Ochi, M. Abe, N. Inagaki, and S. Maekawa. 1998. The effects of carbon dioxide
enrichment, natural ventilation, and light intensity on growth, photosynthesis, and transpiration of
cauliflower plantlets cultured in vitro photoautotrophically and photomixotrophically. Journal of the
American Society for Horticultural Science 123(2):176-181.

The effects of natural ventilation and CO2 enrichment during the rooting stage on the growth and the
rates of photosynthesis and transpiration of in vitro cauliflower (Brassica oleracea L.) plantlets were
investigated. In vitro plantlets were established in airtight or ventilated vessels with or without CO2
supplied (approximate to 1200.mu g L-1) through gas permeable films attached to the vessel's cap
for 15 days before transplanting ex vitro. Leaves generated in vitro in ventilated vessels had a higher
photosynthetic rate than those produced in airtight vessels, which lead to greater leaf expansion and
shoot and root dry matter accumulation during in vitro culture and acclimatization. Enhanced
photosynthesis in leaves of ventilated plantlets was positively correlated with chlorophyll content.
Increasing photosynthetically active radiation from 70 to 200 mu mol.m(-1)-s(-1) enhanced the
growth of in vitro plantlets under ventilated conditions but it depressed photosynthesis of the leaves
grown photomixotrophically with sugar and CO2 enrichment which might be due to the feedback
inhibition caused by marked accumulations of sucrose and starch. Higher CO2 levels during in vitro
culture enhanced photosynthesis under photoautotrophic conditions, but inhibited it under
photomixotrophic conditions. Fifteen days after transplanting ex vitro, high photosynthetic ability and
stomatal resistance to transpiratory water loss of ventilated plantlets in vitro had important
contributions to rooting and acclimatization. Our findings show that the ventilated culture is effective
for accelerating photoautotrophic growth of plantlets by increasing photosynthesis, suggesting that,
especially for plantlets growing in vitro without sugar, CO2 enrichment may be necessary to enhance
photosynthetic ability.

KEYWORDS: ACCLIMATIZATION, GREENHOUSE, INVITRO, MERISTEM CULTURE,
MICROPROPAGATION, SUCROSE, ULTRASTRUCTURE, WATER-LOSS


     1110 
Kano, A., Y. Fukazawa, M. Aono, and K. Ohkawa. 1992. Effect of age of cuttings, propagation
media, and cutting methods on rooting of stephanotis-floribunda brongn. Journal of the Japanese
Society for Horticultural Science 61(3):619-624.

The effects of cutting methods, cutting media, and age of cutting on rooting capacity of Stephanotis
floribunda Brongn. were investigated to improve propagation efficiency. The effects of CO2
enrichment and a new acclimatization technique for cutting were also tested. 1. Cuttings made from
older shoots showed a higher rooting percentage than those made from younger ones. 2. Rockwool
mats were found to be useful as a cutting medium for S. floribunda. 3. Cuttings with differentiated
leaf buds showed higher rooting percentage than those without buds. 4. Rooting was stimulated by
placing cuttings in a closed frame, especially when CO2 concentration was high. 5. An acclimatization
technique using a computer controlled fan was developed to decrease water stress during the
acclimatization period.



     1111 
Karban, R., and J.S. Thaler. 1999. Plant phase change and resistance to herbivory. Ecology
80(2):510-517.

All plants pass through a series of predictable developmental stages during their lives, called phase
changes. The phase change from juvenile to adult leaves is known to be associated with changes in
resistance against plant pathogens and herbivores in several species. Virtually nothing is known about
changes in resistance associated with the transition from embryonic tissue to autotrophic tissue in
seedlings. We studied the consequences of transitions from cotyledons to juvenile true leaves to adult
true leaves in cotton seedlings (Gossypium hirsutum) for their resistance to spider mites (Tetranychus
urticae). Mite populations grew much more rapidly on cotyledons than on true leaves. However, there
was no detectable difference in the population growth of mites on juvenile vs. adult true leaves. We
suggest that population growth of mites is positively affected by the high rates of photosynthesis of
cotyledons relative to true leaves, or by some process or attribute correlated with photosynthesis.
Conditions that caused increased rates of photosynthesis (exposure to light and elevated
concentrations of CO2) caused mite populations to increase. Greater mite population growth on
cotyledons was not associated with stored reserves in the cotyledons, as the mites did poorly on
cotyledons kept in the dark. This study indicates that phase changes can have profound effects on
plant resistance to herbivores. Because the seedling stage is so vulnerable to herbivory and so critical
to understanding plant population dynamics, a broader consideration of phase changes associated with
seedlings is warranted.

KEYWORDS: AGE, CARBON DIOXIDE, COTTON, LEAF ABSCISSION, MATURATION, MITES,
PHOTOSYNTHESIS, TREE


     1112 
Karnosky, D.F., B. Mankovska, K. Percy, R.E. Dickson, G.K. Podila, J. Sober, A. Noormets,
G. Hendrey, M.D. Coleman, M. Kubiske, K.S. Pregitzer, and J.G. Isebrands. 1999. Effects of
tropospheric O-3 on trembling aspen and interaction with CO2: Results from an O-3-gradient and
a face experiment. Water, Air, and Soil Pollution 116(1-2):311-322.

Over the years, a series of trembling aspen (Populus tremuloides Michx.) clones differing in O-3
sensitivity have been identified from OTC studies. Three clones (216 and 271[(O- 3 tolerant] and 259
[O-3 sensitive]) have been characterized for O-3 sensitivity by growth and biomass responses, foliar
symptoms, gas exchange, chlorophyll content, epicuticular wax characteristics, and antioxidant
production. In this study we compared the responses of these same clones exposed to O-3 under field
conditions along a natural O-3 gradient and in a Free-Air CO2 and O-3 Enrichment (FACE) facility.
In addition, we examined how elevated CO2 affected O-3 symptom development. Visible O-3
symptoms were consistently seen (5 out of 6 years) at two of the three sites along the O-3 gradient
and where daily one-hour maximum concentrations were in the range of 96 to 125 ppb. Clonal
differences in O-3 sensitivity were consistent with our OTC rankings. Elevated CO2 (200 ppm over
ambient and applied during daylight hours during the growing season) reduced visible foliar
symptoms for all three clones from 31 to 96% as determined by symptom development in elevated
O-3 versus elevated O-3 + CO2 treatments. Degradation of the epicuticular wax surface of all three
clones was found at the two elevated O-3 gradient sites. This degradation was quantified by a
coefficient of occlusion which was a measure of stomatal occlusion by epicuticular waxes. Statistically
significant increases in stomatal occlusion compared to controls were found for all three clones and
for all treatments including elevated CO2, elevated O-3, and elevated CO2 + O-3. Our results provide
additional evidence that current ambient O- 3 levels in the Great Lakes region are causing adverse
effects on trembling aspen. Whether or not elevated CO2 in the future will alleviate some of these
adverse effects, as occurred with visible symptoms but not with epicuticular wax degradation, is
unknown.

KEYWORDS: ATMOSPHERIC CO2, CARBON DIOXIDE, CLONES, GROWTH, NATURAL-
SELECTION, OZONE TOLERANCE, PHOTOSYNTHESIS, PHYSIOLOGY, POPULUS-
TREMULOIDES, SENSITIVITY


     1113 
Karnosky, D.F., G.K. Podila, Z. Gagnon, P. Pechter, A. Akkapeddi, Y. Sheng, D.E.
Riemenschneider, M.D. Coleman, R.E. Dickson, and J.G. Isebrands. 1998. Genetic control of
responses to interacting tropospheric ozone and CO2 in Populus tremuloides. Chemosphere 36(4-
5):807-812.

We exposed trembling aspen (Populus tremuloides Michx.) clones differing in tropospheric ozone (O-
3) tolerance in various open-top chamber studies for three growing seasons, and examined the effects
of O-3, CO2, and O-3 + CO2 on growth and physiological processes. Ozone in the range of 80 ppm
hr (Sum 00) per growing season decreased height, diameter, and stem and leaf biomass slightly in a
tolerant clone but severely in a sensitive clone. Elevated CO2 (150 ppm over ambient) did not
compensate for the O-3 effects. Antioxidant enzyme analysis showed elevated SOD levels in the
tolerant clone but not in the sensitive clone following O-3 exposure. Northern blot analysis indicated
that the chloroplastic and cytosolic Cu/Zn SOD's were significantly increased in response to O-3 in
the tolerant but not the sensitive clone. Currently, we are conducting molecular analysis to determine
the functional significance of SOD's in regulating O-3 tolerance in aspen. (C) 1997 Elsevier Science
Ltd.

KEYWORDS: ALLOCATION, ASPEN CLONES, ATMOSPHERIC CO2, BIOMASS, EXPOSURES,
FIELD, GROWTH, NATURAL-SELECTION, PRODUCTIVITY, SENSITIVITY


     1114 
Karowe, D.N., D.H. Seimens, and T. Mitchell-Olds. 1997. Species-specific response of
glucosinolate content to elevated atmospheric CO2. Journal of Chemical Ecology 23(11):2569-2582.

The carbon/nutrient balance hypothesis has recently been interpreted to predict that plants grown
under elevated CO2 environments will allocate excess carbon to defense, resulting in an increase in
carbon-based secondary compounds. A related prediction is that, because plant growth will be
increasingly nitrogen-limited under elevated CO2 environments, plants will allocate less nitrogen to
defense, resulting in decreased levels of nitrogen-containing secondary compounds. We present the
first evidence of decreased investment in nitrogen- containing secondary compounds for a plant
grown under elevated CO2. We also present evidence that plant response is species specific and is
not correlated with changes in leaf nitrogen content or leaf carbon-nitrogen ratio. When three
crucifers were grown at 724 +/- 8 ppm CO2, total foliar glucosinolate content decreased significantly
for mustard, but not for radish or turnip. Glucosinolate content of the second and fourth young est
mustard leaves decreased by 45% and 31%, respectively. In contrast, no significant change in total
glucosinolate content was observed in turnip or radish leaves, despite significant decreases in leaf
nitrogen content. Total glucosinolate content differed significantly among leaves of different age;
however, the trend differed among species. For both mustard and turnip, glucosinolate content was
significantly higher in older leaves, while the opposite was true for radish. No significant CO2 x leaf
age interaction was observed, suggesting that intraplant patterns of allocation to defense will not
change for these species. Changes in nitrogen allocation strategy are likely to be species-specific as
plants experience increasing atmospheric CO2 levels. The ecological consequences of CO2-induced
changes in plant defensive investment remain to be investigated.

KEYWORDS: ALLELOCHEMICALS, CARBON-DIOXIDE ATMOSPHERES, CRUCIFERAE,
DIAMONDBACK MOTH, GROWTH, HERBIVORY, IDENTIFICATION, MUSTARD, NUTRIENT
BALANCE, PLUTELLA-XYLOSTELLA


     1115 
Kartschall, T., S. Grossman, P.J. Pinter, R.L. Garcia, B.A. Kimball, G.W. Wall, D.J.
Hunsaker, and R.L. LaMorte. 1995. A simulation of phenology, growth, carbon dioxide exchange
and yields under ambient atmosphere and free-air carbon dioxide enrichment (FACE) Maricopa,
Arizona, for wheat. Journal of Biogeography 22(4-5):611-622.

The impact of increased atmospheric CO2 concentration on the growth and productivity of field
grown wheat has been evaluated. Meteorological and soil information from this study were used to
validate a model (DEMETER) for simulation of vegetation response to climate change scenarios. The
model simulations of phenology, carbon exchange rate, growth and yield for the treatment conditions
of the experiment show a reasonable accordance with the experimental data.

KEYWORDS: LEAVES, MODEL


     1116 
Karunaratne, C., G.A. Moore, R. Jones, and R. Ryan. 1997. Phosphine and its effect on some
common insects in cut flowers. Postharvest Biology and Technology 10(3):255-262.

The most effective fumigant for insect disinfestation of cut flowers is currently methyl bromide, which
will soon be unavailable in several countries. The toxicity of an alternative fumigant, phosphine (2%
PH3 and 98% N-2), was tested at 24 degrees C on adult greenhouse thrips (Heliothrips
haemorrhoidalis), adult aphids (Myzus persicae) and lightbrown apple moth larvae (LBAM; Epiphyas
postvittana). These are commonly found as insect pests on many cut flower crops. Thrips were
exposed to phosphine concentrations ranging from 20-600 mu l/l for 1 or 2 h. All thrips were killed
within 18 h of exposure after a treatment of 300 mu l/l phosphine for 2 h. Adult aphids and fifth instar
LBAM larvae were more resistant to phosphine, and trials were therefore conducted using higher
phosphine concentrations (> 500 mu l/l) combined with atmospheric (0.035%) or elevated (33%)
CO2. The most effective treatment for aphids was 1000 mu l/l phosphine +33% CO2 for 4 h, which
killed all insects within 36 h of exposure. Under atmospheric CO2 levels, 92% of aphids were killed
within 36 h after exposure to 1000 mu l/l phosphine for 6 h, with 100% kill attained after exposure
to 5000-8000 mu l/l phosphine for 6 h. Elevated CO2 levels did not improve the efficacy of phosphine
on LBAM larvae. The optimal treatment was 2000-2500 mu l/l phosphine for 4 or 6 h, which killed
96 or 100% of the larvae, respectively. Under atmospheric CO2 levels, 4000 mu l/l phosphine killed
74% of LBAM larvae after 4 h. and 94% after 6 h exposure. (C) 1997 Elsevier Science B.V.

KEYWORDS: ATMOSPHERES, CARBON DIOXIDE, TOXIC ACTION


     1117 
Kasurinen, A., H.S. Helmisaari, and T. Holopainen. 1999. The influence of elevated CO2 and O-3
on fine roots and mycorrhizas of naturally growing young Scots pine trees during three exposure
years. Global Change Biology 5(7):771-780.

Young Scots pine trees naturally established at a pine heath were exposed to two concentrations of
CO2 (ambient and doubled ambient) and two O-3 regimes (ambient and doubled ambient) and their
combination in open-top field chambers during growing seasons 1994, 1995 and 1996 (late May to
15 September). Filtered ozone treatment and chamberless control trees were also included in the
treatment comparisons. Root in-growth cores were inserted to the undisturbed soil below the branch
projection of each tree at the beginning of the fumigation period in 1994 and were harvested at the
end of the fumigation periods in 1995 and 1996. Root biomasses were determined from different soil
layers in the ingrowth cores, and the infection levels of different mycorrhizal types were calculated.
Elevated O-3 and CO2 did not have significant effects on the biomass production of Scots pine coarse
(diameter >2 mm) or fine roots (diameter <2 mm) and roots of grasses and dwarf shrubs. Elevated
O-3 caused a transient stimulation, observable in 1995, in the proportion of tuber-like mycorrhizas,
total mycorrhizas and total short roots but this stimulation disappeared during the last study year.
Elevated CO2 did not enhance carbon allocation to root,growth or mycorrhiza formation, although
a diminishing trend in the mycorrhiza formation was observed. In the combination treatment increased
CO2 inhibited the transient stimulating effect of ozone, and a significant increase of old mycorrhizas
was observed. Our conclusion is that doubled CO2 is not able to increase carbon allocation to growth
of fine roots or mycorrhizas in nutrient poor forest sites and realistically elevated ozone does not
cause a measurable limitation to roots within a period of three exposure years.

KEYWORDS: ATMOSPHERIC CARBON-DIOXIDE, COLONIZATION, ENRICHMENT, FIELD,
GROWTH, LOBLOLLY-PINE, PHOTOSYNTHESIS, RESPONSES, SOIL, TROPOSPHERIC
OZONE


     1118 
Kaufman, Y.J., and M.D. Chou. 1993. Model simulations of the competing climatic effects of so2
and co2. Journal of Climate 6(7):1241-1252.

Sulfur dioxide-derived cloud condensation nuclei are expected to enhance the planetary albedo,
thereby cooling the planet. This effect might counteract the global warming expected from enhanced
greenhouse gases. A detailed treatment of the relationship between fossil fuel burning and the SO2
effect on cloud albedo is implemented in a two-dimensional model for assessing the climate impact.
Although there are large gaps in our knowledge of the atmospheric sources and sinks of sulfate
aerosol, it is possible to reach some general conclusions. Using a conservative approach, results show
that the cooling induced by the SO2 emission can presently counteract 50% of the CO2 greenhouse
warming. Since 1980, a strong warming trend has been predicted by the model, 0.15-degrees-C,
during the 1980- 1990 period alone. The model predicts that by the year 2060 the SO2 cooling
reduces climate warming by 0.5-degrees-C or 25% for the Intergovernmental Panel on Climate
Change (IPCC) business as usual (BAU) scenario and 0.2-degrees-C or 20% for scenario D (for a
slow pace of fossil fuel burning). The hypothesis is examined that the different responses between the
Northern Hemisphere (NH) and the Southern Hemisphere (SH) can be used to validate the presence
of the SO2-induced cooling. Despite the fact that most of the SO2-induced cooling takes place in the
Northern Hemispheric continents, the model-predicted difference in the temperature response
between the NH and the SH of -0.2- degrees-C in 1980 is expected to remain about the same at least
until 2060. This result is a combined effect of the much faster response of the continents than the
oceans and of the larger forcing due to CO2 than due to the SO2. The climatic response to a
complete filtering of SO2 from the emission products in order to reduce acid rain is also examined.
The result is a warming surge of 0.4-degrees-C in the first few years after the elimination of the SO2
emission.

KEYWORDS: AEROSOLS, ATMOSPHERIC SULFUR, EFFECTIVE PARTICLE RADIUS,
FEEDBACK PROCESSES, GLOBAL CLOUD ALBEDO, OPTICAL- THICKNESS,
PARAMETERIZATIONS, POLLUTION, SENSITIVITY, SOLAR-RADIATION MEASUREMENTS


     1119 
Ke, D.Y., E. Yahia, M. Mateos, and A.A. Kader. 1994. Ethanolic fermentation of bartlett pears
as influenced by ripening stage and atmospheric composition. Journal of the American Society for
Horticultural Science 119(5):976-982.

Changes in fermentation volatiles and enzymes were studied in preclimacteric and postclimacteric
'Bartlett' pears (Pyrus communis L.) kept in air, 0.25% O2, 20% O2 + 80% CO2, or 0.25% O2 +
80% CO2 at 20C for 1, 2, or 3 days. All three atmospheres resulted in accumulation of acetaldehyde,
ethanol, and ethyl acetate. The postctimacteric pears had higher activity of pyruvate decarboxylase
(PDC) and higher concentrations of fermentation volatiles than those of the preclimacteric fruit. For
the preclimacteric pears, the 0.25% O2 treatment dramatically increased alcohol dehydrogenase
(ADH) activity, which was largely due to the enhancement of one ADH isozyme. Exposure to 20%
O2 + 80% CO2 slightly increased ADH activity, but the combination of 0.25% O2 + 80% Co2
resulted in lower ADH activity than 0.25% O2 alone. For the postclimacteric pears, the three
atmospheres resulted in higher PDC and ADH activities than those of air control fruit. Ethanolic
fermentation in 'Bartlett' pears could be induced by low O2 and/or high CO2 via 1) increased amounts
of PDC and ADH; 2) PDC and ADH activation caused by decreased cytoplasmic pH; or 3) PDC and
ADH activation or more rapid fermentation due to increased concentrations of their substrates
(pyruvate, acetaldehyde, or NADH).

KEYWORDS: ALCOHOL-DEHYDROGENASE, ANAEROBIC NITROGEN, CARBON-DIOXIDE
ATMOSPHERES, FRUIT TOLERANCE, INDUCTION, LOW-OXYGEN ATMOSPHERES, POST-
HARVEST QUALITY, PYRUVATE DECARBOXYLASE, SHORT- TERM, STORAGE


     1120 
Ke, D.Y., L.L. Zhou, and A.A. Kader. 1994. Mode of oxygen and carbon-dioxide action on
strawberry ester biosynthesis. Journal of the American Society for Horticultural Science 119(5):971-
975.

'Chandler' strawberries (Fragaria ananassa Duck.) were kept in air, 0.25% O2, 21% O2 + 50% CO2,
or 0.25 O2 + 50% CO2 (balance N2) at 5C for 1 to 7 days to study the effects of controlled
atmospheres (CAs) on volatiles and fermentation enzymes. Concentrations of acetaldehyde, ethanol,
ethyl acetate, and ethyl butyrate were greatly increased, while concentrations of isopropyl acetate,
propyl acetate, and butyl acetate were reduced by the three CA treatments compared to those of air-
control fruit. The CA treatments enhanced activities of pyruvate decarboxylase (PDC) and alcohol
dehydrogenase (ADH) but slightly decreased activity of alcohol acetyltransferase (AAT). The results
indicate that the enhanced PDC and ADH activities by CA treatments cause ethanol accumulation,
which in turn drives the biosynthesis of ethyl esters. The increased ethanol concentration also
competes with other alcohols for carboxyl groups for esterification reactions. The reduced AAT
activity and limited availability of carboxyl groups due to ethanol competition decrease production
of other acetate esters.

KEYWORDS: ATMOSPHERES, CO2, DECAY, FRUIT, QUALITY, SHORT-TERM EXPOSURE,
STORAGE, VOLATILES


     1121 
Keeling, R.F. 1995. The atmospheric oxygen cycle - the oxygen isotopes of atmospheric co2 and
o-2 and the o-2/n-2 ratio. Reviews of Geophysics 33:1253-1262.

KEYWORDS: DIOXIDE, ENRICHMENT, FRACTIONATION, GLOBAL CARBON-CYCLE, ICE,
LEAF WATER, LEAVES, PLANTS, RESPIRATION, SEA


     1122 
Keith, H., R.J. Raison, and K.L. Jacobsen. 1997. Allocation of carbon in a mature eucalypt forest
and some effects of soil phosphorus availability. Plant and Soil 196(1):81-99.

Pools and annual fluxes of carbon (C) were estimated for a mature Eucalyptus pauciflora (snowgum)
forest with and without phosphorus (P) fertilizer addition to determine the effect of soil P availability
on allocation of C in the stand. Aboveground biomass was estimated from allometric equations
relating stem and branch diameters of individual trees to their biomass. Biomass production was
calculated from annual increments in tree diameters and measurements of litterfall. Maintenance and
construction respiration were calculated for each component using equations given by Ryan (1991a).
Total belowground C flux was estimated from measurements of annual soil CO2 efflux less the C
content of annual litterfall (assuming forest floor and soil C were at approximate steady state for the
year that soil CO2 efflux was measured). The total C content of the standing biomass of the
unfertilized stand was 138 t ha(-1), with approximately 80% aboveground and 20% belowground.
Forest floor C was 8.5 t ha(-1). Soil C content (0-1 m) was 369 t ha(-1) representing 70% of the total
C pool in the ecosystem. Total gross annual C flux aboveground (biomass increment plus litterfall
plus respiration) was 11.9 t ha(-1) and gross flux belowground (coarse root increment plus fine root
production plus root respiration) was 5.1 t ha(-1). Total annual soil efflux was 7.1 t ha(-1), of which
2.5 t ha(- 1) (35%) was contributed by litter decomposition. The short- term effect of changing the
availability of P compared with C on allocation to aboveground versus belowground processes was
estimated by comparing fertilized and unfertilized stands during the year after treatment. In the P-
fertilized stand annual wood biomass increment increased by 30%, there was no evidence of change
in canopy biomass, and belowground C allocation decreased by 19% relative to the unfertilized stand.
Total annual C flux was 16.97 and 16.75 t ha(-1) yr(-1) and the ratio of below-to aboveground C
allocation was 0.43 and 0.35 in the unfertilized and P-fertilized stands, respectively. Therefore, the
major response of the forest stand to increased soil P availability appeared to be a shift in C
allocation; with little change in total productivity. These results emphasise that both growth rate and
allocation need to be estimated to predict changes in fluxes and storage of C in forests that may occur
in response to disturbance or climate change.

KEYWORDS: BIOMASS, CLIMATE CHANGE, DIOXIDE EVOLUTION, ECOSYSTEMS,
ELEVATED ATMOSPHERIC CO2, FINE ROOTS, LITTER, NET PRIMARY PRODUCTION, PINE
PLANTATIONS, RESPIRATION


     1123 
Keller, T., J. Guiot, and L. Tessier. 1997. Climatic effect of atmospheric CO2 doubling on radial
tree growth in south eastern France. Journal of Biogeography 24(6):857-864.

The climatic effect of a doubling of atmospheric CO2 on radial growth of trees was studied in ten
populations of three species in south eastern France using an Atmospheric General Circulation Model
(AGCM) predicting a 3 degrees C increase of mean temperature and a light rise of precipitation.
Results are based on empirical growth climate models, involving an Artificial Neural Network (ANN)
technique. Only two of the studied populations, on the boundaries of their ecological area, are
sensitive to the climatic variations. One is the larch (Larix decidua Mill.) population located at 2300m
on elevation (near the timberline) which shows a radial growth increase. The other is the most
southern French Scots pine (Pinus sylvestris L.) population which reacts with a severe growth rate
reduction.



     1124 
Kellogg, E.A., E.J. Farnsworth, E.T. Russo, and F. Bazzaz. 1999. Growth responses of C-4
grasses of contrasting origin to elevated CO2. Annals of Botany 84(3):279-288.

Nine grass species representing three independent origins of the C-4 photosynthetic pathway were
grown at ambient (350 ppm) and elevated (700 ppm) CO2 and were harvested after flowering. Setaria
and Arundinella are both members of the subfamily Panicoideae, and represent a single origin of the
pathway. Aristida and Stipagrostis are sister genera in the subfamily Aristidoideae (formerly classified
in subfamily Arundinoideae), and represent a second origin. Sporobolus, a member of the subfamily
Chloridoideae, represents the third. By investigating two genera each within Panicoideae and
Aristidoideae, we test the hypothesis that genera sharing the same origin of C-4 respond similarly.
To explore variation among congeneric species, five species of Setaria were also examined to test the
hypothesis that congeneric species have similar responses. Plant height and numbers of tillers,
branches and inflorescences were measured, both over time and at final harvest. Biomass of roots,
shoots, and inflorescences was also measured. Members of the Aristidoideae were generally
significantly larger in elevated CO2, as indicated by measurements of biomass and plant height,
whereas representatives of the Panicoideae varied considerably in their response. The two subfamilies
differed significantly in their responses to elevated CO2 and this effect outweighed any effect of CO2
alone. Sporobolus, though equally distantly related to Panicoideae and Aristidoideae, had a CO2
response similar to that of some panicoid species. Even within the genus Setaria, some species were
significantly smaller at elevated than at ambient CO2, whereas others were larger. This may reflect
diversity in internal regulation rather than acclimation or changes in source-sink allocation of carbon.
The variation complicates any prediction of responses of C-4 plants to future atmospheric change.
Comparison of closely related species, however, may well lead to intriguing new insights into how
regulatory pathways of CO2 assimilation are modified during evolution. (C) 1999 Annals of Botany
Company.

KEYWORDS: ATMOSPHERIC CO2, CARBON DIOXIDE, ENRICHMENT, FAMILY POACEAE,
GAS-EXCHANGE, GENE-EXPRESSION, PHOTOSYNTHETIC ACCLIMATION, PLANTS,
SEQUENCE DATA, STRESS


     1125 
Kellomaki, S., T. Karjalainen, and H. Vaisanen. 1997. More timber from boreal forests under
changing climate? Forest Ecology and Management 94(1-3):195-208.

The effects of increases in temperature, precipitation and atmospheric CO2 concentration on timber
yields from stands of Scots pine (Pinus sylvestris L.) in southern Finland (61 degrees N) are
addressed. The assessment is based on simulations using a process-based model in which temperature,
precipitation, and atmospheric CO2 are among the main drivers linking the dynamics of the tree
stands directly and indirectly with the changing climate. These factors control photosynthesis,
respiration, transpiration and the uptake of nitrogen and water, with consequent effects on the growth
and development of tree stands. The timing of thinnings and the length of the rotation were related
to the dynamics of the tree stand in compliance with the thinning rules applied in practical forestry.
The simulations indicated that an increase in precipitation of 9 mm per decade alone did not affect
timber yields. However, a temperature increase of 0.4 degrees C per decade, and the combination of
temperature and precipitation increases would increase timber yields by 10% during one rotation. An
elevation in the concentration of atmospheric CO2 by 33 mu mol mol(-1) per decade alone would
increase removals of timber by 20%, and a combination of increases in temperature, precipitation and
CO2 concentration would increase removals by 30%. A rise in precipitation did not have any effect
on the length of the rotation, but the other combinations shortened the rotation; by 9 years in the case
of elevating temperature, by 17 years in the case of elevating atmospheric CO2 concentration, and
by 23 years in the case of the combined elevation of temperature, precipitation, and CO2
concentration due to more rapid tree growth and development. These changes can be expected to
affect the supply of timber and also the profitability of forestry. (C) 1997 Elsevier Science B.V.

KEYWORDS: ATMOSPHERIC CO2, CARBON, ELEVATED CO2, GAS-EXCHANGE, MATTER,
PHOTOSYNTHESIS, SCOTS PINE, SIMULATION, SOIL MOISTURE, TEMPERATURE


     1126 
Kellomaki, S., and H. Vaisanen. 1997. Modelling the dynamics of the forest ecosystem for climate
change studies in the boreal conditions. Ecological Modelling 97(1-2):121-140.

This paper summarizes a forest ecosystem model developed for assessing the effects of climate
change on the functioning and structure of boreal coniferous forests under the assumption that
temperature and precipitation are the basic dimensions of the niche occupied by any one tree species.
Special attention is paid to specifying weather patterns to a level representing the time constant of
different physiological and ecological processes relevant to the regeneration, growth and death of
trees. The long-term dynamics of the forest ecosystem have been coupled with climatic factors at the
level of mechanisms, e.g., photosynthesis and respiration, in terms of the energy flow through the
ecosystem. Furthermore, hydrological and nutrient cycles couple the dynamics of the forest ecosystem
with climate change through soil processes representing the thermal and hydraulic properties of the
soil and the decomposition of litter and humus with the mineralization of nutrients. Simulations for
southern Finland (62 degrees N) and northern Finland (66 degrees N) indicated that a transient
increase in temperature by 4 degrees C over a period of 100 years could substantially increase soil
temperature and reduce soil moisture in forest ecosystems dominated by Scots pine. At the same time,
the temperature increase could enhance photosynthetic production and consequent stemwood growth
in southern Finland by about 8% and in northern Finland by about 19%. Given the current
temperature but elevating CO2 concentration, the increase in photosynthesis in southern Finland
could be about 23% and in northern Finland about 21%, but the concurrent elevation in temperature
and CO2 concentration increased photosynthesis by about 32% in southern Finland and by about 40%
in northern Finland. Transpiration decreased by as much as 10-20% under the changing climate with
the consequence that water-use efficiency increased by as much as 25-45%, the higher values
representing southern Finland. (C) 1997 Elsevier Science B.V.

KEYWORDS: ELEVATED CO2, GAS-EXCHANGE, HABITAT, IRRADIANCE, NITROGEN,
PHOTOSYNTHESIS, REGENERATION, RESPIRATION, SCOTS PINE, SIMULATION


     1127 
Kellomaki, S., H. Vaisanen, and T. Kolstrom. 1997. Model computations on the effects of
elevating temperature and atmospheric CO2 on the regeneration of Scots pine at the timber line in
Finland. Climatic Change 37(4):683-708.

Based on model computations, the regeneration of Scots pine (Pinus sylvestris L.) was studied at the
northern timber line in Finland (70 degrees N) in relation to elevating temperature and atmospheric
CO2. If a transient increase of 4 degrees C was assumed during the next 100 years, the length of
growing season increased from the current 110-120 days to 150-160 days. This was associated with
ca. 5 degrees C increase in the soil temperature over June-August with larger variability in
temperature and deeper freezing of the soil due to the reduced depth and duration of the snow cover,
At the same time, the moisture content of the surface soil decreased ca. 10% and was more variable,
due to less infiltration of water into the soil as a consequence of the enhanced evapotranspiration and
deeper freezing of the soil. The temperature elevation alone, or combined with elevating CO2,
increased flowering and the subsequent seed crop of Scots pine with a decrease in the frequency of
zero crops. In both cases, temperature elevation substantially increased the success of regeneration
in terms of the number of seedlings produced after each seed crop. The increasing number of mature
seeds was mainly responsible for the enhanced regeneration, but increasing soil temperature also
increased the success of regeneration. The soil moisture was seldom limited for seed germination. In
terms of the density of seedling stands, and the height and diameter growth of the seedlings, the
establishment of a seedling stand was substantially improved under the combined elevation of
temperature and CO2 in such a way that the temperature increased the number of mature seeds and
enhanced germination of seeds and CO2 increased seedling growth. Even under the changing climatic
conditions, however, the growth of the seedling stands was slow, which indicated that the northward
advance of the timber line would probably be very slow, even though regeneration was no longer a
limiting factor.

KEYWORDS: CHANGING CLIMATE, FORESTS, HABITAT, NITROGEN, PHOTOSYNTHESIS,
SIMULATION, SOIL MOISTURE, TREES, WATER


     1128 
Kellomaki, S., and K.Y. Wang. 1996. Photosynthetic responses to needle water potentials in Scots
pine after a four-year exposure to elevated CO2 and temperature. Tree Physiology 16(9):765-772.

Effects of needle water potential (psi(1)) on gas exchange of Scots pine (Pinus sylvestris L.) grown
for 4 years in open-top chambers with elevated temperature (ET), elevated CO2 (EC) or a
combination of elevated temperature and CO2 (EC + ET) were examined at a high photon flux
density (PPFD), saturated leaf to air water vapor pressure deficit (VPD) and optimal temperature (T).
We used the Farquhar model of photosynthesis to estimate the separate effects of psi 1 and the
treatments on maximum carboxylation efficiency (V-c,V-max), ribulose-1,5- bisphosphate
regeneration capacity (J), rate of respiration in the light (R(d)), intercellular partial pressure of CO2
(Ci) and stomatal conductance (G(s)). Depression of CO2 assimilation rate at low psi(1) was the
result of both stomatal and non- stomatal limitations on photosynthetic processes; however, stomatal
limitations dominated during short-term water stress (psi(1)<-1.2 MPa), whereas nonstomatal
limitations dominated during severe water stress. Among the nonstomatal components, the decrease
in J contributed more to the decline in photosynthesis than the decrease in Long-term elevation of
CO2 and temperature led to differences in the maximum values of the parameters, the threshold
values of psi(1) and the sensitivity of the parameters to decreasing psi(1). The CO2 treatment
decreased the maximum values of V-c,V-max J and R(d) but significantly increased the sensitivity of
V-c,V-max J and Rd to decreasing psi(1) (P < 0.05). The effects of the ET and EC + ET treatments
on V-c,V-max J and R(d) were opposite to the effects of the EC treatment on these parameters. The
values of G(s), which were measured simultaneously with maximum net rate of assimilation (A(max)),
declined in a curvilinear fashion as psi(1) decreased. Both the EC + ET and ET treatments
significantly decreased the sensitivity of G(s) to decreasing psi(1-). We conclude that, in the future,
acclimation to increased atmospheric CO2 and temperature could increase the tolerance of Scots pine
to water stress.

KEYWORDS: COTTON, DROUGHT, GAS-EXCHANGE, IRRADIANCE, LEAVES, STOMATAL
CONDUCTANCE, STRESS


     1129 
Kellomaki, S., and K.Y. Wang. 1997. Effects of elevated O-3 and CO2 concentrations on
photosynthesis and stomatal conductance in Scots pine. Plant, Cell and Environment 20(8):995-
1006.

Naturally regenerated Scots pines (Pinus sylvestris L.), aged 28-30 years old, were grown in open-top
chambers and subjected in situ to three ozone (O-3) regimes, two concentrations of CO2, and a
combination of O-3 and CO2 treatments from 15 April to 15 September for two growing seasons
(1994 and 1995), The gas exchanges of current-year and 1-year-old shoots were measured, along
with the nitrogen content of needles, In order to investigate the factors underlying modifications in
photosynthesis, five parameters linked to photosynthetic performance and three to stomatal
conductance were determined, Elevated O-3 concentrations led to a significant decline in the CO2
compensation point (I*), maximum RuP2-saturated rate of carboxylation (V-emax), maximum rate
of electron transport (J(max)) maximum stomatal conductance (g(smax)) and sensitivity of stomatal
conductance to changes in leaf-to-air vapour pressure difference (partial derivative g(s)/partial
derivative D-v) in both shoot-age classes, However, the effect of elevated O-3 concentrations on the
respiration rate in light (R-d) was dependent on shoot age, Elevated CO2 (700 mu mol mol(-1))
significantly decreased J(max) and g(smax) but increased R-d in 1-year-old shoots and the partial
derivative(s)/partial derivative D-v in both shoot-age classes, The interactive effects of O-3 and CO2
on some key parameters (e.g. V-emax and J(max)) were significant. This may be closely related to
regulation of the maximum stomatal conductance and stomatal sensitivity induced by elevated CO2.
As a consequence, the injury induced by O-3 was reduced through decreased ozone uptake in 1-year-
old shoots, but not in the current-year shoots, Compared to ambient O-3 concentration, reduced O-3
concentrations (charcoal-filtered air) did not lead to significant changes in any of the measured
parameters, Compared to the control treatment, calculations showed that elevated O-3 concentrations
decreased the apparent quantum yield by 35% and by 18%, and the maximum rate of photosynthesis
by 21% and by 29% in the current-year and 1-year-old shoots, respectively, Changes in the nitrogen
content of needles resulting from the various treatments were associated with modifications in
photosynthetic components.

KEYWORDS: CARBON DIOXIDE, DARK RESPIRATION, GAS-EXCHANGE, L KARST, LONG-
TERM EXPOSURE, NET PHOTOSYNTHESIS, NORWAY SPRUCE, OPEN-TOP CHAMBERS,
PICEA-ABIES L, SOURCE-SINK RELATIONS


     1130 
Kellomaki, S., and K.Y. Wang. 1997. Effects of elevated O-3 and CO2 on chlorophyll fluorescence
and gas exchange in Scots pine during the third growing season. Environmental Pollution 97(1-
2):17-27.

Naturally regenerated, 30-year-old Scots pines (Pinus Sylvestris L.) were grown in open-top
chambers and exposed in situ to doubled ambient O-3, doubled ambient CO2 and a combination of
elevated O-3 and CO2 from 15 April to 15 September for three growing seasons (1994-1996). To
examine the effects of O-3 and/or CO2 on photosynthesis, chlorophyll a fluorescence and gas
exchange were measured simultaneously. Doubled ambient O-3 significantly decreased the rates of
photosynthesis at all levels of photon flux density. This was related mainly to a significant decrease
in the photochemical efficiency of photosystem II (PS II) and the rate of whole electron transport,
rather than to a decrease in stomatal conductance. When measurements were made at doubled
ambient concentration of CO2 (700 mu mol mol(-1)), doubled ambient CO2 treatment did not lend
to a significant change in the intrinsic capacity of photosynthesis, as manifested by no changes in PS
II, the rate of electron transport, the maximal rate of photosynthesis and the apparent quantum yield
of CO2 assimilation. However, elevated CO2 increased the sensitivity of stomatal conductance to
light and decreased maximal stomatal conductance. When O-3 and CO2 were combined, the O-3-
induced decrease in photosynthesis rate was reduced significantly by a high concentration of CO2.
This may be partly related to the decrease in stomatal conductance induced by the high concentration
of CO2. The complete mechanism behind this interaction is, however, still unclear. (C) 1997 Elsevier
Science Ltd.

KEYWORDS: ABIES L KARST, CARBON DIOXIDE, ELECTRON-TRANSPORT, LIGHT-
RESPONSE CURVES, LONG-TERM EXPOSURE, NET PHOTOSYNTHESIS, NORWAY SPRUCE,
OPEN-TOP CHAMBERS, PHOTOSYSTEM-II ACTIVITY, SOURCE-SINK RELATIONS


     1131 
Kellomaki, S., and K.Y. Wang. 1997. Effects of long-term CO2 and temperature elevation on
crown nitrogen distribution and daily photosynthetic performance of Scots pine. Forest Ecology and
Management 99(3):309-326.

Single Scots pines (Pinus sylvestris L.), aged 20-25 years, were grown in open-top chambers and
exposed to elevated temperature (Elev. T), elevated CO2 (Elev. C) and a combination of elevated
CO2 and temperature (Elev. C + T) for 3 years. The vertical distribution of needle nitrogen
concentration was measured simultaneously with gas exchange of attached shoots. Based on the
measurements, the dependencies on needle nitrogen concentrations of four photosynthetic
parameters, i.e., RuP2 (ribulose 1,5-bisphosphate)-saturated rate of carboxylation (V- cmax),
maximum potential electron transport (J(max)), the rate of respiration in the light (R-d) and light-use-
efficiency factor (delta), were determined. Using a crown multilayer model, the performance of daily
crown photosynthesis in Scots pine was predicted. Compared to the control treatment, the mean
concentration of nitrogen in the foliage decreased by 20% and by 17% for trees grown under Elev.
C and under Elev. C + T, respectively, but increased by 4% for trees grown under Elev. T. However,
the total content of foliage nitrogen per unit ground area increased by 25% for trees grown under
Elev. C, by 19% for trees grown under Elev. C + T and by 6% for trees grown under Elev. T; these
were due to the increase in the total needle area index. Regressions showed that the foliage grown
under Elev. C and Elev. C + T had steeper slopes representing the responses of V-cmax, and R-d and
delta to leaf nitrogen concentrations, while Elev. C + T and Elev. T had steeper slopes representing
the response of J(max) to needle nitrogen concentrations. Predictions showed that, on a typical sunny
day, the daily total of crown photosynthesis increased 22% and 27%, separately for Elev. C and Elev.
C + T, and by only 9% for Elev. T alone. Furthermore, the increased daily crown photosynthesis,
resulting from treatments involving elevated CO2, can be attributed mainly to an increase in the
ambient CO2 concentration and the needle area index, while modification of the intrinsic
photosynthetic capacity had only a marginal effect. Based on the current pattern of crown nitrogen
allocation, the prediction showed also that the relationship between daily crown photosynthesis and
crown nitrogen content was strongly dependent on the daily incident PAR and air temperature. The
CO2-elevated treatments led to an increase in the sensitivity of daily crown photosynthesis to changes
in crown nitrogen content, daily incident PAR and temperature, while the temperature-elevated
treatment had the opposite effect on the sensitivity. (C) 1997 Elsevier Science B.V.

KEYWORDS: ACCLIMATION, CANOPY PHOTOSYNTHESIS, CARBON GAIN, ENRICHMENT,
EUCALYPTUS-GRANDIS, GAS-EXCHANGE, GROWTH, LEAF NITROGEN, MINERAL
NUTRITION, SPATIAL DISTRIBUTIONS


     1132 
Kellomaki, S., and K.Y. Wang. 1997. Photosynthetic responses of Scots pine to elevated CO2 and
nitrogen supply: Results of a branch-in-bag experiment. Tree Physiology 17(4):231-240.

Naturally seeded Scots pine (Pinus sylvestris L.) trees, age 25-30 years, were subjected to two soil-
nitrogen-supply regimes and to elevated atmospheric CO2 concentrations by the branch- in-bag
method from April 15 to September 15 for two or three years. Gas exchange in detached shoots was
measured in a diffuse radiation field. Seven parameters associated with photosynthetic performance
and two describing stomatal conductance were determined to assess the effects of treatments on
photosynthetic components. An elevated concentration of CO2 did not lead to a significant
downward regulation in maximum carboxylation rate (V-cmax) or maximum electron transport rate
(J(max)), but it significantly decreased light-saturated stomatal conductance (g(sat)) and increased
minimum stomatal conductance (g(min)). Light-saturated rates of CO2 assimilation were higher (24-
31 %) in shoots grown and measured at elevated CO2 concentration than in shoots grown and
measured ured at ambient CO2 concentration, regardless of treatment time or nitrogen-supply regime.
High soil-nitrogen supply significantly increased photosynthetic capacity, corresponding to significant
increases in V-cmax and J(max). However, the combined elevated CO2 + high nitrogen-supply
treatment did not enhance the photosynthetic response above that observed in the elevated CO2
treatment alone.

KEYWORDS: ATMOSPHERIC CO2, C-3 PLANTS, CARBON DIOXIDE, DARK RESPIRATION,
ELECTRON-TRANSPORT, GAS-EXCHANGE, GROWTH, QUANTUM YIELD, RIBULOSE-1;5-
BISPHOSPHATE CARBOXYLASE, TERM


     1133 
Kellomaki, S., and K.Y. Wang. 1998. Daily and seasonal CO2 exchange in Scots pine grown under
elevated O-3 and CO2: experiment and simulation. Plant Ecology 136(2):229-248.

Starting in early spring of 1994, naturally regenerated, 30- year-old Scots pine (Pinus sylvestris L.)
trees were grown in open-top chambers and exposed in situ to doubled ambient O-3, doubled ambient
CO2 and a combination of O-3 and CO2 from 15 April to 15 September. To investigate daily and
seasonal responses of CO2 exchange to elevated O-3 and CO2, the CO2 exchange of shoots was
measured continuously by an automatic system for measuring gas exchange during the course of one
year (from 1 Januray to 31 December 1996). A process-based model of shoot photosynthesis was
constructed to quantify modifications in the intrinsic capacity of photosynthesis and stomatal
conductance by simulating the daily CO2 exchange data from the field. Results showed that on most
days of the year the model simulated well the daily course of shoot photosynthesis. Elevated O-3
significantly decreased photosynthetic capacity and stomatal conductance during the whole
photosynthetic period. Elevated O-3 also led to a delay in onset of photosynthetic recovery in early
spring and an increase in the sensitivity of photosynthesis to environmental stress conditions. The
combination of elevated O-3 and CO2 had an effect on photosynthesis and stomatal conductance
similar to that of elevated O-3 alone, but significantly reduced the O-3 induced depression of
photosynthesis. Elevated CO2 significantly increased the photosynthetic capacity of Scots pine during
the main growing season but slightly decreased it in early spring and late autumn. The model
calculation showed that, compared to the control treatment, elevated O-3 alone and the combination
of elevated O-3 and CO2 decreased the annual total of net photosynthesis per unit leaf area by 55%
and 38%, respectively. Elevated CO2 increased the annual total of net photosynthesis by 13%.

KEYWORDS: 4-YEAR EXPOSURE, ABIES L KARST, AIR- POLLUTANTS, CARBON DIOXIDE,
CHLOROPHYLL FLUORESCENCE, MIDDAY STOMATAL CLOSURE, NET PHOTOSYNTHESIS,
OZONE POLLUTION, PHOTOSYNTHETIC RESPONSES, SOLAR RADIATION


     1134 
Kellomaki, S., and K.Y. Wang. 1998. Growth, respiration and nitrogen content in needles of Scots
pine exposed to elevated ozone and carbon dioxide in the field. Environmental Pollution 101(2):263-
274.

Single Scots pine (Pinus sylvestris L.) trees, aged 30 years, were grown in open-top chambers and
exposed to two atmospheric concentrations of ozone (O-3; ambient and elevation) and carbon dioxide
(CO2) as single variables or in combination for 3 years (1994-96). Needle growth, respiration and
nitrogen content were measured simultaneously over the period of needle expansion. Compared to
ambient treatment (33 nmol mol(-1) O-3 and 350 mu mol mol(-1) CO2) doubled ambient O-3 (69
nmol mol(-1)) significantly reduced the specific growth rates (SGRs) of the needles in the early stage
of needle expansion and needle nitrogen concentration (N-1) in the late stage, but increased apparent
respiration rates (ARRs) in the late stage. Doubled ambient CO2 (about 650 mu mol mol(-1))
significantly increased maximum SGR but reduced ARR and N-1 in the late stage of needle
expansion. The changes in ARR induced by the different treatments may be associated with
treatment-induced changes in needle growth, metabolic activities and turnover of nitrogenous
compounds. When ARR was partitioned into its two functional components, growth and maintenance
respiration, the results showed that neither doubled ambient O-3 nor doubled ambient CO2 influenced
the growth respiration coefficients (R-g). However, doubled ambient O-3 significantly increased the
maintenance respiration coefficients (R-m) regardless of the needle development stage, while doubled
ambient CO2 significantly reduced R-m only in the late stage of needle expansion. The increase in R-
m under doubled ambient O-3 conditions appeared to be related to an increase in metabolic activities,
whereas the decrease in R-m under doubled ambient CO2 conditions may be attributed to the reduced
N-1 and turnover rate of nitrogenous compounds per unit. The combination of elevated O-3 and CO2
had very similar effects on growth, respiration and N-1 to doubled ambient O-3 alone, but the
interactive mechanism of the two gases is still not clear. (C) 1998 Elsevier Science Ltd. All rights
reserved.

KEYWORDS: CO2- ENRICHMENT, DARK RESPIRATION, GAS-EXCHANGE, L KARST,
MAINTENANCE RESPIRATION, NONSTRUCTURAL CARBOHYDRATE CONTENT, NORWAY
SPRUCE, OPEN-TOP CHAMBERS, PICEA-ABIES L, PLANT RESPIRATION


     1135 
Kellomaki, S., and K.Y. Wang. 1998. Sap flow in Scots pines growing under conditions of year-
round carbon dioxide enrichment and temperature elevation. Plant, Cell and Environment
21(10):969-981.

Starting in 1996, individual trees of Scots pine (Pinus sylvestris L.) aged 30 years were grown in
closed-top chambers and exposed to normal ambient conditions (CON), elevated CO2 (Elev. C),
elevated temperature (Elev. T) and a combination of elevated CO2 and temperature (Elev. C + T).
Using the constant- power heat balance method, sap flow was monitored simultaneously in a total
of 16 trees, four for each treatment, over a 32 d period (after the completion of needle expansion and
branch elongation in 1997). An overall variation in diurnal sap flow totals (F-t) was evident during
the period of measurement (days 167-198, 1997) regardless of the treatments, with a range from 0.15
to 2.82 kg tree(-1) d(-1). Elev. C reduced F-t by 4.1-13.7% compared with CON on most days (P
varies from 0.042 to 0.108), but slightly increased it on some days (P greater than or equal to 0.131),
depending on the weather conditions. Although the decrease in F-t caused by Elev. C was statistically
significant on only a few days (P < 0.042), the cumulative F-t, for the 32 d decreased by 14.4% (P
= 0.047), indicating that Elev. C may have an important influence on seasonal water use of the Scots
pine. Analysis of the diurnal courses of sap flow combined with corresponding weather factors
indicated that the CO2-induced decrease in F-t could be largely attributed to an increase in stomatal
sensitivity to vapour pressure deficit (VPD), whereas the CO2- induced increase in F-t related to an
increase in stomatal sensitivity to low light levels. Elev. T increased F-t by 11.2- 35.6% throughout
the measuring period and the cumulative F-t for the 32 d by 32.5% (P = 0.019), which could be
largely attributed to the temperature-induced increase in current-year needle area and decrease in
stomatal sensitivity to high levels of VPD. There were no significant interactive effects of CO2 and
temperature on sap flow, so that Elev. C + T had approximately the same F-t as Elev. T and similar
diurnal patterns of sap flow, suggesting that the temperature factor played a dominant role in the case
of Elev. C + T.

KEYWORDS: 4-YEAR EXPOSURE, ATMOSPHERIC CO2, CLIMATE CHANGE, CO2-
ENRICHMENT, GROWTH, PHOTOSYNTHETIC RESPONSES, SOIL MOISTURE, STOMATAL
CONDUCTANCE, TRANSPIRATION RESPONSES, WATER-USE EFFICIENCY


     1136 
Kellomaki, S., and K.Y. Wang. 1999. Short-term environmental controls of heat and water vapour
fluxes above a boreal coniferous forest: model computations compared with measurements by eddy
correlation. Ecological Modelling 124(2-3):145-173.

Eddy correlation and stern how measurements were coupled with detailed microclimate and soil
measurements made in a boreal Scots pine forest in the late growing season of 1998 to determine
sensible and latent heat fluxes from the soil and the canopy separately. A 'resistance/energy' model
is constructed and parametrized in order to reproduce the dynamics of water and heat exchange
between the soil, the canopy and the atmosphere as a part of a larger forest ecosystem model
(FinnFor; Kellomaki and Vaisanen, 1997). Unique features of the present model are that (1) energy
flux equations are expressed in terms of conceptual resistances and their solutions are obtained by
closing two surface energy budget equations defined separately for canopy and soil surface; (2) the
forest canopy is divided into shaded and sunlit fractions in the radiation transfer submodel and the
canopy resistance submodels; (3) a numerical integrating solutions are derived separately for net
radiation absorption in the canopy, bulk canopy resistance and the bulk aerodynamic resistances of
the forest; and (4) iterative determinations of canopy water potential based on a classical one-
dimensional water how model enable the model to represent explicitly the interaction between the
above-ground and the below-ground water dynamics. The model is validated against 19-day flux
measurements. In general, the total system sensible heat flux (H), total system latent heat flux (lambda
E), canopy latent heat flux (lambda E-c), and soil surface heat flux (G(s)) computed by the model
matched well with the measured data. Based on 1/2 h flux measurements, daily lambda E varied from
0.50-7.38 MW m(-2), H from 0.64-8.3 MW m(-2): and lambda E-c from 0.30-6.93 MW m(-2). The
Bowen ratio (H/lambda E) ranged from -4.5 to 9.8, but 82% of the values for the Bowen ratio were
within 0.5-2.5. The model computations showed that daily lambda E-c and H-c accounted for 21-
64% and 43-66% of the daily total system flux, respectively. Daily soil latent heat (lambda E,) and
soil sensible heat (H-s) fluxes accounted for 0.02-4.5% and 0.05-7.6%, respectively, and the daily
energy storage within the canopy (S-c) and G(s) accounted for 0.1-7.2% and 0.8-5.6%, respectively.
Plotting of 1/2 h flux data against a single environmental factor indicated that a 68% change in lambda
E-c and a 72% change in H-c can be explained by a change in canopy radiation absorption (R-nc) at
the 5% probability level. The high correlation between the canopy fluxes and R-nc could be related
to the moderate weather conditions and high soil water content during the selected days, whereas
lambda E- s, H-s, S-c and G(s) give no significant correlation with R-n. As expected. lambda E-c was
strongly dependent on canopy resistance (r(cs)), but less impact on aerodynamic resistances during
most of the measuring time. The proportion of energy partitioning in H and lambda E exhibited a
clear diurnal trend and was mainly controlled by the system total resistance and the vapour pressure
deficit, but less related to changes in soil water content. (C) 1999 Elsevier Science B.V. All rights
reserved.

KEYWORDS: 4-YEAR EXPOSURE, DOUGLAS-FIR, ELEVATED CO2, ENERGY- TRANSPORT,
PINUS-PINASTER AIT, SAP FLOW, SCOTS PINE, SPARSE CROPS, STOMATAL
CONDUCTANCE, SURFACE-TEMPERATURE


     1137 
Kelly, D.W., P.R. Hicklenton, and E.G. Reekie. 1991. Photosynthetic response of geranium to
elevated co2 as affected by leaf age and time of co2 exposure. Canadian Journal of Botany-Revue
Canadienne De Botanique 69(11):2482-2488.

Geranium plants were grown from seed in chambers maintained at 350 or 1000-mu-L.L-1 CO2.
Photopsynthesis as affected by leaf age and by leaf position was determined. Elevated CO2 enhanced
photosynthesis to the greatest extent in middle-aged leaves; very young leaves exhibited little
enhancement, and net photosynthesis in the oldest leaves was depressed by elevated CO2. Temporary
increases in net photosynthesis (relative to leaves developed at high CO2) resulted when young leaves
grown at 350-mu-L.L-1 CO2 were switched to 1000-mu-L.L-1 CO2. Leaves switched later in
development exhibited permanent enhancement. Middle-aged leaves exhibited a temporary depression
followed by permanent enhancement. Leaves developed at high CO2 and switched to low CO2 did
not exhibit any photosynthetic depression relative to plants grown continuously at low CO2.
Similarly, leaves developed at low CO2 switched to high CO2 for various lengths of time, and
returned to low CO2 showed no photosynthetic depression. Leaves developed at low CO2 and
switched to high CO2 exhibited increases in specific leaf weight and leaf thickness. The increase in
leaf thickness was proportional to length of time spent at high CO2. High CO2 depressed the rate at
which stomata developed but did not affect final stomatal density. Results suggest that photosynthesis
at low CO2 was limited by CO2 regardless of developmental environment, whereas photosynthesis
at high CO2 was limited by the developmental characteristics of the leaf. Further, both biochemical
and structural modifications appear to be involved in this response. Because of the very different
responses of young versus old leaves, future studies should be careful to consider leaf age in assessing
response to elevated CO2.

KEYWORDS: ACCLIMATION, CARBON DIOXIDE, ENRICHMENT, EXCHANGE, LEAVES,
LONG-TERM EXPOSURE, PLANTS, RIBULOSE BISPHOSPHATE CARBOXYLASE, SOYBEAN
PHYSIOLOGY, STARCH


     1138 
Kemp, P.R., D.G. Waldecker, C.E. Owensby, J.F. Reynolds, and R.A. Virginia. 1994. Effects
of elevated co2 and nitrogen-fertilization pretreatments on decomposition on tallgrass prairie leaf-
litter. Plant and Soil 165(1):115-127.

Standing dead and green foliage litter was collected in early November 1990 from Andropogon
gerardii (C-4), Sorghastrum nutans (C-4), and Poa pratensis (C-3) plants that were grown in large
open-top chambers under ambient or twice ambient CO2 and with or without nitrogen fertilization
(45 kg N ha(-1)). The litter was placed in mesh bags on the soil surface of pristine prairie adjacent
to the growth treatment plots and allowed to decay under natural conditions. Litter bags were
retrieved at fixed intervals and litter was analyzed for mass loss, carbon chemistry, and total Kjeldahl
nitrogen and phosphorus. The results indicate that growth treatments had a relatively minor effect on
the initial chemical composition of the litter and its subsequent rate of decay or chemical composition.
This suggests that a large indirect effect of CO2 on surface litter decomposition in the tallgrass prairie
would not occur by way of changes in chemistry of leaf litter However, there was a large difference
in characteristics of leaf Litter decomposition among the species. Paa leaf fitter had a different initial
chemistry and decayed more rapidly than C-4 grasses. We conclude that an indirect effect of CO2 on
decomposition and nutrient cycling could occur if CO2 induces changes in the relative aboveground
biomass of the prairie species.

KEYWORDS: ACCUMULATION, ATMOSPHERIC CO2, CHIHUAHUAN DESERT, DETRITUS,
ECOSYSTEMS, LIGNIN CONTENT, PHOSPHORUS DYNAMICS, PINE NEEDLE LITTER,
PLANTS, RESPONSES


     1139 
Kennedy, A.D. 1995. Antarctic terrestrial ecosystem response to global environmental-change.
Annual Review of Ecology and Systematics 26:683-704.

Geographical isolation and climatic constraints are responsible for the low biodiversity and structural
simplicity of the antarctic terrestrial ecosystem Under projected scenarios of global change, both
limiting factors may be released. Alien species immigration is likely to be facilitated as modified ocean
and atmospheric circulation introduce exotic water- and air-borne propagules from neighboring
continents. Elevated temperature, UV radiation, CO2, and precipitation will combine additively and
synergistically to favor new trajectories of community development. It can be predicted that existing
patterns of colonization, recruitment, succession, phenology and mortality will be perturbed with
concomitant effects for ecosystem function through changes in biomass, trophodynamics, nutrient
cycling, and resource partitioning. Soil propagule banks will play an important role through founder
effects. Uniquely in Antarctica, many of the short-term consequences of global change will depend
on the ecophysiological relationships of cryptogamic plants. However, in the long term, climatic
warming will favor an increase in phanerogamic biomass since these species are currently excluded
by the low cumulative degree-days > 0 degrees C. It has been suggested that antarctic communities
may be particularly vulnerable to global change: Their slow rate of development and restricted gene
flow limit response to new conditions. However, vulnerability must be defined with respect to both
the direction and rate of change and it is likely that some perturbations will enhance the complexity
and productivity of the biota, with negative feedback to the global carbon cycle. The chapter
concludes with a discussion of institutional issues surrounding this topic.

KEYWORDS: ATMOSPHERIC CO2, CARBON DIOXIDE, CLIMATIC CHANGE, COLD
TOLERANCE, CONTINENTAL ANTARCTICA, CRYPTOPYGUS- ANTARCTICUS, ICE CORES,
OZONE DEPLETION, PHOTOSYNTHETIC RESPONSE, TUSSOCK TUNDRA


     1140 
Kennedy, A.D. 1995. Simulated climate-change - are passive greenhouses a valid microcosm for
testing the biological effects of environmental perturbations. Global Change Biology 1(1):29-42.

This paper considers the use of passive greenhouse apparatus in field experiments investigating the
biological consequences of climate change. The litreature contains many accounts of such
experiments claiming relevance of greenhouse treatment effects to global change scenarios. However,
inadequacies in microclimate monitoring, together with incomplete understanding of greenhouse
modes of action, cast doubt upon such claims. Here, treatment effects upon temperature (magnitude,
range, variation, rates of change), moisture (humidity, precipitation, soil water content), light
(intensity, spectral distribution), gas composition, snow cover, and wind speed are reviewed in the
context of Intergovernmental Panel on Climate Change (IPCC) predictions. It is revealed that
greenhouses modify each of these potentially limiting factors in a complex and interactive manner,
but that the relationship between this modification and forecast conditions of climate change is poor.
Interpretation of biological responses, and their extrapolation to predictive models, is thus unreliable.
In order that future greenhouse experiments may overcome criticisms of artefact and lack of rigour,
two amendments to methodology are proposed: (1) objective-orientated design of greenhouse
apparatus (2) multiple controls addressing individual environmental factors. The importance of a
priori testing of microclimate treatment effects is stressed.

KEYWORDS: ALASKAN TUSSOCK TUNDRA, CO2, ERIOPHORUM VAGINATUM, GROWTH,
PLANTS, RESPONSES, SENSITIVITY, TEMPERATURE, ULTRAVIOLET-RADIATION,
VEGETATION


     1141 
Kennedy, A.D. 1995. Temperature effects of passive greenhouse apparatus in high- latitude climate-
change experiments. Functional Ecology 9(2):340-350.

1. Passive greenhouse apparatus is commonly used to investigate the in situ biological response of
terrestrial communities to global warming. 2. Although close conformity of greenhouse treatment
effects to general circulation model (GCM) scenarios is widely claimed, no proof of such a
relationship has yet been published. 3. Here, the relationship between passive greenhouse thermal
environment and future climate conditions is considered using temperature data collected from within
and without greenhouses deployed in the maritime Antarctic. It is revealed that in terms of thermal
extremes, diel and annual variation, and overall distribution across the temperature spectrum, such
apparatus achieves only poor simulation of GCM forecasts. 4. During summer, greenhouses induce
an amplified daily range of temperatures, elevated maxima and accelerated rates of change. 5. During
spring and autumn, diel temperature variation continues inside the greenhouses while snow cover
protects the controls. 6. During winter, an inverse treatment effect occurs, in which the relative depth
of snow cover causes lower temperatures in greenhouses than in controls. 7. These treatment effects
differ significantly from GCM climate predictions. Changes recorded in the composition, structure
and function of greenhouse biota may thus be artefacts of the methodology. 8. Thorough a priori
testing of greenhouse treatment effects is recommended for future climate change studies that are to
be conducted in environments subject to seasonal snowfall, solar elevation and day length.

KEYWORDS: ALASKAN TUSSOCK TUNDRA, COLD TOLERANCE, DESIGN, ECOSYSTEMS,
ELEVATED CO2, ERIOPHORUM VAGINATUM, GROWTH, HABITATS, POLAR, RESPONSES


     1142 
Kerbel, E.L., A.A. Kader, and R.J. Romani. 1990. Respiratory and glycolytic response of
suspension-cultured passe-crassane pear fruit cells to elevated CO2 concentrations. Journal of the
American Society for Horticultural Science 115(1):111-114.



     1143 
Kerslake, J.E., S.J. Woodin, and S.E. Hartley. 1998. Effects of carbon dioxide and nitrogen
enrichment on a plant- insect interaction: the quality of Calluna vulgaris as a host for Operophtera
brumata. New Phytologist 140(1):43-53.

Calluna vulgaris L. (Hull) is not one of the usual hosts of the winter moth, Operophtera brumata L.,
but outbreaks have caused extensive damage to heather moorland in Scotland in recent years. This
study investigated the potential role of environmental change in such outbreaks by rearing O. brumata
larvae on C. vulgaris plants grown in open-top chambers for 20 months with enriched CO2 (600 ppm)
and nitrogen supply (average 52.5 kg N ha(-1) yr(-1)) in factorial combination. This prolonged
exposure to elevated CO2 caused no change in shoot growth, photosynthesis or foliar C:N ratio of
C, vulgaris, even with increased N supply, indicating that the absence of response was not due to N
limitation. Increased N supply itself resulted in increased shoot growth and a decrease in tissue C:N
ratio. Phenolic content did not change in response to either CO2 or N enrichment, contrary to the
predictions of the carbon/nutrient balance hypothesis. In line with the absence of plant response, there
was no effect of CO2 on the development of Operophtera brumata on C, vulgaris, and so continued
increase in atmospheric CO2 concentration is unlikely to affect directly O. brumata outbreaks on
heather moorland. Operophtera brumata showed increased larval development, growth rate and pupal
weight on N-treated plants, correlated both to the decrease in foliar C:N ratio, and to the increase in
shoot extension which was predictive of survivorship. Thus, increased atmospheric N deposition, or
increased rates of mineralization in a warmer environment, might increase the severity of O. brumata
outbreaks on C. vulgaris. Since the combination of high N availability and disturbance of heather
canopy by herbivory is known to result in increased dominance of grasses, it is suggested that this
could lead to further degradation of moorland in upland Britain.

KEYWORDS: AVAILABILITY, DECIDUOUS TREES, ELEVATED ATMOSPHERIC CO2,
GROWTH, HEATHER MOORLAND, HERBIVORE INTERACTIONS, L HULL, LARVAL
EMERGENCE, NUTRIENT BALANCE HYPOTHESIS, SOIL NUTRIENT


     1144 
Kerstiens, G. 1995. Cuticular water permeance of european trees and shrubs grown in polluted and
unpolluted atmospheres, and its relation to stomatal response to humidity in beech (fagus-sylvatica
L). New Phytologist 129(3):495-503.

Cuticular water permeance (P) of astomatous adaxial surfaces of intact leaves was determined in Acer
pseudoplatanus L., Betula pubescens Ehrh., Corylus avellana L., Fagus sylvatica L. and Prunus avium
L. Water evaporating from the stomata-bearing abaxial leaf surface could not reach the moisture
analyzer and the values of P presented here are therefore free from errors that often arise from
unintentional inclusion of residual stomatal transpiration. Plants were exposed from before bud- break
for several months to 20-50 ppb SO2 (Fagus), a combination of 50-60 ppb SO2 and 50-60 ppb NO2
(Betula), 300- 400 ppb NO (Acer, Corylus, Fagus), regular ozone episodes of up to 120 ppb (Fagus,
Prunus), or an elevated level of CO2 (600 ppm for 2 yr; Acer, Fagus). Permeances were in the range
0.6- 2.9 x 10(-5) m s-1 and were unaffected by most treatments. In Prunus, P increased slightly but
significantly in the NO treatment. In Corylus and Fagus, P was sometimes found to be reduced by
fumigation with NO, but not always. Betula leaves grown under elevated SO2 and NO2 showed
higher values of P only if they were visibly damaged. Minimum conductances (g(min) estimated from
water loss rates of both sides of detached hypostomatous leaves were higher than P, and were more
strongly affected by treatments. In these cases, the most probable explanation is some damage to
stomatal function resulting in a reduced ability to close after leaf excision. Effects of growing
conditions and time of year on P were found, which allowed a hypothetical interaction between P and
stomatal sensitivity to air humidity to be tested in beech. No unambiguous indication of such a
relationship was found.

KEYWORDS: AIR-POLLUTION, CARBON DIOXIDE, FUMIGATION, LEAVES, OZONE,
PERMEABILITY, PLANT CUTICLES, STRESS, SYSTEM, TRANSPIRATION


     1145 
Kerstiens, G. 1997. Why is increasing shade-tolerance of trees correlated with increasing stimulation
of growth by elevated CO2? Plant Physiology 114(3):371.



     1146 
Kerstiens, G. 1998. Shade-tolerance as a predictor of responses to elevated CO2 in trees.
Physiologia Plantarum 102(3):472-480.

Evidence from 10 studies comparing angiosperm trees and 5 studies comparing conifers or differing
shade-tolerance was analysed. The number of intraphyletic comparisons in which the more shade-
tolerant species showed the greater relative increase of biomass in elevated CO2 was significantly
higher than would be expected by chance alone. It is suggested that more shade-tolerant species are
inherently better disposed. in terms of plant architecture and partitioning of biomass and nitrogen, to
utilise resources (light, water, nutrients) that are potentially limiting in elevated CO2 and that these
traitu are responsible for the interaction between shade-tolerance and CO2 concentration. Compared
with less shade-tolerant angiosperm trees, more shade-tolerant angiosperm species generally have a
lower lear area ratio in ambient CO2 and show a smaller relative reduction in elevated CO2.
Furthermore, leaf nitrogen content is usually lower in more shads-tolerant angiosperm species and
tends to be more strongly reduced by elevated CO2 in those species. Within angiosperm trees, more
shade-tolerant species showed a stronger stimulation of net leaf photosynthetic I ate in most
experiments, but this trend was not significant.

KEYWORDS: ATMOSPHERIC CO2, C-3 PHOTOSYNTHETIC SYSTEM, CARBON-DIOXIDE
ENRICHMENT, FAGUS-SYLVATICA L, GROWTH-RESPONSES, LEAF GAS- EXCHANGE, LOW-
LIGHT, NITROGEN-AVAILABILITY, RAIN-FOREST TREES, SUCCESSIONAL STATUS


     1147 
Kerstiens, G., and C.V. Hawes. 1994. Response of growth and carbon allocation to elevated co2
in young cherry (prunus-avium L) saplings in relation to root environment. New Phytologist
128(4):607-614.

The hypothesis that inadequate rooting volume may reduce the growth stimulation by elevated CO2
in potted tree seedlings and saplings was tested experimentally and by surveying the literature. One-
year-old cherry saplings were grown for one season in naturally lit growth chambers in eight
combinations of CO2 concentration (ambient; ambient + 250 ppm) and root environment (four types).
The latter included (1) moderately restrictive pot volume (4 l) in combination with two levels of
fertilizer addition (1a, 1b); (2) 10 l pots with total fertilizer content per pot as in treatment 1a, and
(3) 20 l pots with five plants sharing five times the space and nutrient resources of treatment 1a.
Plants were harvested in April, May, June, August and September. The overall mean effect of high
CO2 plant dry mass by the end of the season was +24%. Interactive effects of root environments and
CO2 concentrations on dry mass were not significant at the 5% level, but repeated measurements of
basal stem diameter of individual plants indicated a significant impact of root environment on the
response to CO2. Overall growth enhancement by elevated CO2 did not differ significantly between
harvests, but it tended to increase during the season in those root environments which restricted
growth in ambient CO2 most strongly (1a and 3). The hypothesis was rejected for this experiment.
Leaf area and stem height were not affected by any treatment. The variation of carbon allocation to
roots and shoots with plant size was very similar in all treatments. Plants grew faster in elevated CO2
very early in the season, and this resulted in small but significant differences between seasonal patterns
of biomass partitioning in ambient and elevated CO2. A survey of 33 studies on growth responses of
47 tree species to elevated CO2 (600-800 ppm) showed that the relative change in biomass was not
related to the ratio of plant biomass and pot volume found in either ambient or elevated CO2. We
conclude that there is no evidence that inadequate pot volume had a negative impact on the
stimulation of growth of tree species in elevated CO2.

KEYWORDS: DIOXIDE, PHOTOSYNTHETIC ACCLIMATION, PLANTS, SEEDLINGS


     1148 
Kerstiens, G., J. Townend, J. Heath, and T.A. Mansfield. 1995. Effects of water and nutrient
availability on physiological- responses of woody species to elevated co2. Forestry 68(4):303-315.

The growth responses to elevated CO2 found in experiments are highly variable and depend on other
experimental parameters such as irrigation, fertilization, light regime, etc. As yet, the strength or even
the sign of most interactions is all but impossible to predict from first principles. Experiments in
ambient and CO2-enriched ambient air (+250 p.p.m.) have been conducted in specially adapted
greenhouses (Solardomes) at Lancaster University for the past four seasons on Sitka spruce (Picea
sitchensis (Bong.) Carr.), wild cherry (Prunus avium L.), beech (Fagus sylvatica L.) and pedunculate
oak (Quercus robur L.). These experiments are reviewed together with other published studies on
interactive effects of elevated CO2 and water and nutrient supply on physiological processes, in
particular gas exchange, in tree species. It is often assumed that drought tolerance will increase in
elevated CO2 because of a suppression of stomatal conductance and an increase in instantaneous
water use efficiency. There is, however, some evidence that such effects could be more than offset
in beech by CO2-induced increases in leaf area. It is tentatively suggested that in beech, drought
tolerance could already have been reduced by the increase in atmospheric CO2 over the last century.

KEYWORDS: ATMOSPHERIC CO2, CARBON DIOXIDE, ENRICHMENT, GAS-EXCHANGE,
GROWTH, LIQUIDAMBAR- STYRACIFLUA, LOBLOLLY-PINE SEEDLINGS,
PHOTOSYNTHETIC ACCLIMATION, PLANTS, TAEDA SEEDLINGS


     1149 
Keutgen, N., K. Chen, and F. Lenz. 1997. Responses of strawberry leaf photosynthesis, chlorophyll
fluorescence and macronutrient contents to elevated CO2. Journal of Plant Physiology 150(4):395-
400.

Gas exchange, chlorophyll fluorescence parameters, and macronutrient contents were investigated
in young (< 3 weeks), medium (4 - 6 weeks) and old (7 - 9 weeks) strawberry leaves growing at 300,
450, 600, 750, and 300 ppm CO2. An increase of the CO2 level to 600 ppm promoted leaf net
photosynthesis, but a further rise led to a decrease of net CO2 assimilation. The reduction of net
photosynthetic rate was less distinct in young leaves exposed to CO2 levels above 600 ppm for less
than 3 weeks, indicating that the reduction might depend on the period of exposition or leaf age.
Transpiration and stomatal conductance were significantly affected by leaf age, but not by CO2
concentrations. Medium leaves were characterised by a higher transpiration rate and stomatal
conductance than young and old ones. In leaves growing at high CO2 levels Chl a and b contents as
well as the a/b ratio decreased. The contents of N, P, K, Ca and Mg were lower in leaves growing
at high CO2 concentrations than in those at low ones. An elevated CO2 level above 750 ppm led to
a general macronutrient deficiency and was accompanied by a distinct decrease of optimal quantum
yield, due to a rise of basal fluorescence, and an increase of non- photochemical energy dissipation
in old leaves.

KEYWORDS: BIOCHEMISTRY, GAS-EXCHANGE, GROWTH, LEAVES, STEADY-STATE
PHOTOSYNTHESIS, TOMATO PLANTS


     1150 
KhavariNejad, R.A. 1996. Growth of tomato plants under carbon dioxide enrichment.
Photosynthetica 32(3):471-474.

Under short-term CO2 enrichment (1200 cm(3) m(-3)) Of 4-weeks old tomato plants (Lycopersicon
esculentum Mill., Eurocross BB, F-1-hybrid) net assimilation rate increased by about 58 %, leaf area
increased slightly, fresh matters were not much influenced, but dry matters (except for roots)
increased. Stomatal opening in tomato plants was enhanced under CO2 enrichment and the
enhancement decreased with time.

KEYWORDS: CO2-ENRICHED ATMOSPHERES


     1151 
Kickert, R.N., G. Tonella, A. Simonov, and S.V. Krupa. 1999. Predictive modeling of effects
under global change. Environmental Pollution 100(1-3):87-132.

The status of computer simulation models from around the world for evaluating the possible
ecological, environmental, and societal consequences of global change is presented in this paper. In
addition, a brief synopsis of the state of the science of these impacts is included. Issues considered
include future changes in climate and patterns of land use for societal needs, Models dis cussed relate
to vegetation (e.g, crop), soil, bio-geochemistry, water, and wildlife responses to conventional,
forecasted changes in temperature and precipitation. Also described are models of these responses,
alone and interactively, to increased CO2, other air pollutants and UV-B radiation, as the state of the
science allows. Further, models of land-use change are included. Additionally, global multiple sector
models of environment, natural resources, human population dynamics, economics, energy, and
political relations are reviewed for integrated impact assessment. To the extent available, information
on computer software and hardware requirements is presented for the various models. The paper
concludes with comments about using these technologies as they relate to ecological risk assessment
for policy decision analysis. Such an effort is hampered by considerable uncertainties with the output
of existing models, because of the uncertainties associated with input data and the definitions of their
dose-response relationships. The concluding suggestions point the direction for new developments
in modeling and analyses that are needed for the 21st century. (C) 1999 Elsevier Science Ltd. All
rights reserved.

KEYWORDS: ATMOSPHERIC CARBON-DIOXIDE, BIOSPHERE-MODEL, CLIMATE-CHANGE
SCENARIOS, ELEVATED CO2, FOREST ECOSYSTEM PROCESSES, GENERIC PLANT
SIMULATOR, LAND-USE CHANGE, OF-THE- ART, ORGANIC-MATTER DYNAMICS, SOLLING
SPRUCE SITE


     1152 
Kicklighter, D.W., M. Bruno, S. Donges, G. Esser, M. Heimann, J. Helfrich, F. Ift, F. Joos, J.
Kaduk, G.H. Kohlmaier, A.D. McGuire, J.M. Melillo, R. Meyer, B. Moore, A. Nadler, I.C.
Prentice, W. Sauf, A.L. Schloss, S. Sitch, U. Wittenberg, and G. Wurth. 1999. A first-order
analysis of the potential role of CO2 fertilization to affect the global carbon budget: a comparison of
four terrestrial biosphere models. Tellus Series B-Chemical and Physical Meteorology 51(2):343-
366.

We compared the simulated responses of net primary production, heterotrophic respiration, net
ecosystem production and carbon storage in natural terrestrial ecosystems to historical (1765 to
1990) and projected (1990 to 2300) changes of atmospheric CO2 concentration of four terrestrial
biosphere models: the Bern model, the Frankfurt Biosphere Model (FBM), the High- Resolution
Biosphere Model (HRBM) and the Terrestrial Ecosystem Model (TEM). The results of the model
intercomparison suggest that CO2 fertilization of natural terrestrial vegetation has the potential to
account for a large fraction of the so-called "missing carbon sink" of 2.0 Pg C in 1990. Estimates of
this potential are reduced when the models incorporate the concept that CO2 fertilization can be
limited by nutrient availability. Although the model estimates differ on the potential size (126 to 461
Pg C) of the future terrestrial sink caused by CO2 fertilization, the results of the four models suggest
that natural terrestrial ecosystems will have a limited capacity to act as a sink of atmospheric CO2
in the future as a result of physiological constraints and nutrient constraints on NPP. All the spatially
explicit models estimate a carbon sink in both tropical and northern temperate regions, but the
strength of these sinks varies over time. Differences in the simulated response of terrestrial
ecosystems to CO2 fertilization among the models in this intercomparison study reflect the fact that
the models have highlighted different aspects of the effect of CO2 fertilization on carbon dynamics
of natural terrestrial ecosystems including feedback mechanisms. As interactions with nitrogen
fertilization, climate change and forest regrowth may play an important role in simulating the response
of terrestrial ecosystems to CO2 fertilization, these factors should be included in future analyses.
Improvements in spatially explicit data sets, whole-ecosystem experiments and the availability of net
carbon exchange measurements across the globe will also help to improve future evaluations of the
role of CO2 fertilization on terrestrial carbon storage.

KEYWORDS: ATMOSPHERIC CARBON, CLIMATE CHANGE, DIOXIDE ENRICHMENT, EDDY-
COVARIANCE, LAND-USE CHANGE, NET PRIMARY PRODUCTION, NITROGEN
DEPOSITION, RAIN-FOREST, TROPICAL DEFORESTATION, WATER-VAPOR


     1153 
Kim, H.Y., T. Horie, H. Nakagawa, and K. Wada. 1996. Effects of elevated CO2 concentration
and high temperature on growth and yield of rice. Japanese Journal of Crop Science 65(4):634-643.

Phenological development, biomass production and the related growth characteristics of rice (cv
Akihikari) in canopy were measured over the entire growth period under different CO2
concentrations and air temperature regimes in temperature gradient chambers (TGCs), in order to
clarify the effects of anticipated global climate change on rice production. The TGC is a plastic tunnel
with the dimensions of 26m in length, 2. 05m in width and 1.7m in height in which air was ventilated
at varying rates to created a 4 degrees C temperature gradient along its longitudinal axis. Two TGCs
were used for this experiment;one was kept at ambient CO2 (congruent to 350 mu LL(-1))
concentration and the other at 690 mu LL(-1) throughout the entire growth period. CO2 x
temperature treatmets were applied to potted rice plants displaced in TGC at the density of 20 hills
m(-2) in 1991, and on transplanted plants on soil bed in TGC at 25 hills m(-2) in 1992. In both years,
a sufficient amount of nutrition was applied in split. The nearly doubled CO2 concentration (690 mu
LL(-1)) accelerated phenological development of rice toward heading with more pronounced effects
at higher temperatures. The number of days to heading of elevated CO2 plants at 30 degrees C was
11% less than that of ambient CO2 plants. The elevated CO2 concentration remarkably promoted
both total and productive tiller numbers, whereas it gave a negligibly small effect on plant height.
Also, the elevated CO2 concentration gave minor effects on leaf area index except at the initial
growth stage, coinciding with the previous workers' results. The elevated CO2 concentration
markedly promoted crop dry matter production, on which temperature appeared to give negligibly
small effects. The relative enhancement rate by the doubled CO2 on crop dry weight at maturity was
estimated to be 24% as average over the entire temperature range (26 similar to 30 degrees C) in both
years. The insensitive temperature response in the enhancement rate was contrary to previous
workers' results. This is considered to be due to previous workers' results being based on largely
isolated plants where radiation might less limit the growth than in the present experiment in the
canopy condition.

KEYWORDS: ACCLIMATION, CARBON DIOXIDE, ORYZA-SATIVA


     1154 
Kim, H.Y., T. Horie, H. Nakagawa, and K. Wada. 1996. Effects of elevated CO2 concentration
and high temperature on growth and yield of rice .2. The effect on yield and its components of
Ahihikari rice. Japanese Journal of Crop Science 65(4):644-651.

Yield and its component organs of rice (cv. Akihikari) were examined for populations grown under
two different CO2 concentrations (350 and 690 mu LL(-1)) x four temperature regimes in
temperature gradient chambers (TGCs) in two cropping seasons of 1991 and 1992. The temperature
treatments ranged 27.2 similar to 31.1 degrees C in 1991 and 26.0 similar to 29.3 degrees C in 1992
on average over the entire growth period. The relative yield increases by nearly doubling the CO2
concentration under the lowest temperature conditions were 40% and 22% in 1991 and 1992,
respectively. These yield increases were mainly attributable to the increased spikelet number per unit
area by elevated CO2, whereas the CO2 effects on ripening percentage and weight of single grain
mass were relatively small. The difference in the CO2 enhancement rate in the spikelet number and
hence in the yield between the two years was considered to reflect the difference in the nitrogen (N)
application rate, as total amounts of N applied were 24 g m(-2) in 1991 and 12 g m(-2) in 1992. With
the increase in temperature, yields at ambient and elevated CO2 concentrations decreased drastically
with a more pronounced reduction with elevated CO2, resulting in no CO2 enrichment effect on rice
yield at higher temperatures. The yield decline at higher temperatures was primarily due to an increase
in the number of sterile spikelets and slightly due to the increase in imperfectly ripened grains. The
spikelet sterility was most closely related to the daily maximum temperature averaged over the
flowering period.

KEYWORDS: CARBON DIOXIDE, ORYZA-SATIVA


     1155 
Kimball, B.A., R.L. LaMorte, P.J. Pinter, G.W. Wall, D.J. Hunsaker, F.J. Adamsen, S.W.
Leavitt, T.L. Thompson, A.D. Matthias, and T.J. Brooks. 1999. Free-air CO2 enrichment and
soil nitrogen effects on energy balance and evapotranspiration of wheat. Water Resources Research
35(4):1179-1190.

In order to determine the likely effects of the increasing atmospheric CO, concentration on future
evapotranspiration, ET, plots of field-grown wheat were exposed to concentrations of 550 mu
mol/mol CO2 (or 200 mu mol/mol above current ambient levels of about 360 mu mol/mol) using a
free-air CO2 enrichment (FACE) facility. Data were collected for four growing seasons at ample
water and fertilizer (high N) and for two seasons when soil nitrogen was limited (low N).
Measurements were made of net radiation, R-n; soil heat flux; air and soil temperatures; canopy
temperature, T-s; and wind speed. Sensible heat flux was calculated from the wind and temperature
measurements. ET, that is, latent heat flux, was determined as a residual in the energy balance. The
FACE treatment increased daytime T-s about 0.6 degrees and 1.1 degrees C at high and low N,
respectively. Daily total R-n was reduced by 1.3% at both levels of N. Daily ET was consistently
lower in the FACE plots, by about 6.7% and 19.5% for high and low N, respectively.

KEYWORDS: 1989 FACE EXPERIMENT, ATMOSPHERIC CO2, CARBON-DIOXIDE
ENRICHMENT, COTTON, DOWNWIND EVOLUTION, LOCAL ADVECTION, RADIATIVE
SURFACE-TEMPERATURE, SAP FLOW, SCALAR FLUXES, WATER-USE


     1156 
Kimball, B.A., R.L. Lamorte, R.S. Seay, P.J. Pinter, R.R. Rokey, D.J. Hunsaker, W.A. Dugas,
M.L. Heuer, J.R. Mauney, G.R. Hendrey, K.F. Lewin, and J. Nagy. 1994. Effects of free-air co2
enrichment on energy-balance and evapotranspiration of cotton. Agricultural and Forest Meteorology
70(1-4):259-278.

The effects of free-air CO2 enrichment (FACE) at 550 mumol mol- 1 on the energy balance and
evapotranspiration, ET, of cotton (Gossypium hirsutum L.) were investigated. Latent heat flux,
lambdaET, was calculated as the residual in an energy balance approach from determinations of net
radiation, R(n), minus surface soil heat flux, G0, minus sensible heat flux, H. R(n) was directly
measured. G0 was determined from measurements with soil heat flux plates at 10 mm depth,
corrected for temperature changes in the soil above. H was determined from measurements of air
temperature with aspirated psychrometers, of foliage temperature with IR thermometers, and of wind
speed with cup anemometers. Under ambient CO2 (control) conditions (about 370 mumol mol-1),
the lambdaET from the energy balance approach agreed fairly well with values from several other
methods, including the Bowen ratio method, lending credence to the technique. However, the results
had an uncertainty of the order of 20% associated with the R(n) measurements. Therefore, an
apparent increase in ET of about 13% in the FACE plots was judged insignificant. The conclusion
that any effects of CO2 enrichment to 550 mumol mol-1 on the ET of cotton were too small to be
detected was consistent with the results of other investigators who determined ET in the same
experiment using stem flow gauges and the soil water balance.

KEYWORDS: CARBON DIOXIDE, CROP YIELD, EVAPORATION, INCREASING
ATMOSPHERIC CO2, LATENT-HEAT, RADIATIVE SURFACE-TEMPERATURE, WATER-USE,
WHEAT CANOPY


     1157 
Kimball, B.A., and J.R. Mauney. 1993. Response of cotton to varying co2, irrigation, and nitrogen
- yield and growth. Agronomy Journal 85(3):706-712.

The CO2 concentration of the atmosphere is increasing and is expected to double sometime near the
middle of the next century. To determine the effects of such a CO2 increase on cotton (Gossypium
hirsutum L.) growth and productivity, a series of experiments from 1983 through 1987 were
conducted with open-top CO2-enriched field chambers at ample as well as limiting levels of water
and N at Phoenix, AZ. Comparisons with open-field plots showed that there was a significant
chamber effect, amounting to a 30% average increase in growth inside, but under dry conditions in
1985, the situation was reversed. No significant effects of CO2 on harvest index, root-shoot ratio,
or lint percentage were found, so the primary effect of elevated CO2 was to produce plants that were
larger. Comparing the results of 500 and 650 mumol mol-1 CO2 treatments, the increments of growth
from ambient (about 350 mumol mol-1) to 500 mumol mol-1 were not significantly different from
increments from 500 to 650 mumol mol-1. No statistically significant interactions were detected
between CO2 level and either irrigation or nitrogen level, even when these variables were sufficiently
low enough to limit growth. However, under well-maintained water stress conditions, the growth
response to CO2 tended to be somewhat larger than under normal irrigation levels. Averaging over
all the data available from these experiments, seed cotton yield (lint plus seed) and above- ground
biomass were increased by 60 and 63%, respectively, by CO2 enrichment to 650 mumol mol-1.

KEYWORDS: CARBON DIOXIDE, CHAMBERS, ELEVATED LEVELS, ENRICHMENT, FIELD,
PLANT GROWTH, POPULATIONS, SOIL, STRESS, WATER-USE


     1158 
Kimball, B.A., J.R. Mauney, F.S. Nakayama, and S.B. Idso. 1993. Effects of elevated co2 and
climate variables on plants. Journal of Soil and Water Conservation 48(1):9-14.

KEYWORDS: CARBON DIOXIDE, ENRICHMENT, TEMPERATURE, YIELD


     1159 
Kimball, B.A., J.R. Mauney, F.S. Nakayama, and S.B. Idso. 1993. Effects of increasing
atmospheric co2 on vegetation. Vegetatio 104:65-75.

The increasing atmospheric CO2 concentration probably will have significant direct effects on
vegetation whether predicted changes in climate occur or not. Averaging over many prior greenhouse
and growth chamber studies, plant growth and yield have typically increased more than 30%, with
a doubling of CO2 concentration. Such a doubling also causes stomatal conductance to decrease
about 37 which typically increases leaf temperatures more than 1-degrees-C, and which may decrease
evapotranspiration, although increases in leaf area counteract the latter effect. Interactions between
CO2 and climate variables also appear important. In one study the growth increase from near-doubled
CO2 ranged from minus 60% at 12- degrees-C to 0% at 19-degrees-C to plus 130% at 34-degrees-C,
suggesting that if the climate warms, the average growth response to doubled CO2 could be
consistently higher than the 30% mentioned above. Even when growing in nutrient-poor soil, the
growth response to elevated CO2 has been large, in contrast to nutrient solution studies which
showed little response. Several studies have suggested that under water-stress, the CO2 growth
stimulation is as large or larger than under wellwatered conditions. Therefore, the direct CO2 effect
will compensate somewhat, if not completely, for a hotter drier climate. And if any climate change
is small, then plant growth and crop yields will probably be significantly higher in the future high-CO2
world.

KEYWORDS: CARBON DIOXIDE, ENRICHMENT, TEMPERATURE, YIELD


     1160 
Kimball, B.A., P.J. Pinter, R.L. Garcia, R.L. LaMorte, G.W. Wall, D.J. Hunsaker, G.
Wechsung, F. Wechsung, and T. Kartschall. 1995. Productivity and water use of wheat under
free-air CO2 enrichment. Global Change Biology 1(6):429-442.

A free-air CO2 enrichment (FACE) experiment was conducted at Maricopa, Arizona, on wheat from
December 1992 through May 1993. The FACE apparatus maintained the CO2 concentration, [CO2],
at 550 mu mol mol(-1) across four replicate 25-m- diameter circular plots under natural conditions
in an open field. Four matching Control plots at ambient [CO2] (about 370 mu mol mol(-1)) were
also installed in the field. In addition to the two levels of [CO2], there were ample (Wet) and limiting
(Dry) levels of water supplied through a subsurface drip irrigation system in a strip, split-plot design.
Measurements were made of net radiation, R(n); soil heat flux, G(o); soil temperature; foliage or
surface temperature; air dry and wet bulb temperatures; and wind speed. Sensible heat flux, H, was
calculated from the wind and temperature measurements. Latent heat nux, lambda ET, and
evapotranspiration, ET, were determined as the residual in the energy balance. The FACE treatment
reduced daily total R(n) by an average 4%. Daily FACE sensible heat flux, H, was higher in the FACE
plots. Daily latent heat flux, lambda ET, and evapotranspiration, ET, were consistently lower in the
FACE plots than in the Control plots for most of the growing season, about 8% on the average. Net
canopy photosynthesis was stimulated by an average 19 and 44% in the Wet and Dry plots,
respectively, by elevated [CO2] for most of the growing season. No significant acclimation or down
regulation was observed. There was little above-ground growth response to elevated [CO2] early in
the season when temperatures were cool. Then, as temperatures warmed into spring, the FACE plants
grew about 20% more than the Control plants at ambient [CO2], as shown by above-ground biomass
accumulation. Root biomass accumulation was also stimulated about 20%. In May the FACE plants
matured and senesced about a week earlier than the Controls in the Wet plots. The FACE plants
averaged 0.6 degrees C warmer than the Controls from February through April in the well-watered
plots, and we speculate that this temperature rise contributed to the earlier maturity. Because of the
acceleration of senescence, there was a shortening of the duration of grain filling, and consequently,
there was a narrowing of the final biomass and yield differences. The 20% mid-season growth
advantage of FACE shrunk to about an 8% yield advantage in the Wet plots, while the yield
differences between FACE and Control remained at about 20% in the Dry plots.

KEYWORDS: ATMOSPHERIC CO2, CARBON DIOXIDE, COTTON, CROP YIELD, GROWTH,
TEMPERATURE


     1161 
King, A.W., W.R. Emanuel, S.D. Wullschleger, and W.M. Post. 1995. In search of the missing
carbon sink - a model of terrestrial biospheric response to land-use change and atmospheric co2.
Tellus Series B-Chemical and Physical Meteorology 47(4):501-519.

Estimates of the net exchange of carbon between the terrestrial biosphere and the atmosphere may
be too large because the models of carbon release from changes in land use do not allow for enhanced
carbon assimilation by the terrestrial biosphere in response to increasing atmospheric CO2. We
address this deficiency with a model of terrestrial biosphere that includes both ecosystem response
to land-use perturbation and vegetation response to atmospheric CO2. Model inputs specify the areas
affected by land-use change since 1700. The carbon dynamics of