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 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,pA^7337^As experimental elevation of CO2 in short-term experiments may produce organic matter with decomposition characteri Key features of the model are (1) an ability to scale hydrological processes at the catchment scale in three dimensions, a nd (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 A^3153^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. s on greenhouse effect gas emissions.al differences in gas exchange and response to environmental stress in dioecious {iS150^4^Hatton,TJ^Walker,J^Dawes,WR^Dunin,FX^1992^1^Simulations of hydroecological responses to elevated CO2 at the catchment scale^182^40^4-5^679-696^^^^^^^^^^3154nental 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 policieanel 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 contion 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 Pralian terrestrial carbon budget - integration using a simple-model^182^40^4-5^527-543^^^^^^^^^^3152ospheric environment^A^3151^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. Informati148^4^Field,CB^Chapin,FS^Matson,PA^Mooney,HA^1992^1^Responses of terrestrial ecosystems to the changing atmosphere - a resource-based approach^27^23^^201-235^149^1^Gifford,RM^1992^1^Implications of the globally increasing atmospheric CO2 concentration and temperature for the Aust"creased respiration, delayed senescence, and allocation of the additional carbon to roots and rhizomes. The complex intera#ction of these diverse responses suggests that the rising atmospheric CO2 may have a significant impact on ecosystem processes.ssess%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 accumulati!on in the plant community dominated by the C3 sedge, Scirpus olneyi, including: sustained high photosynthetic capacity, de(otosynthetic capacity, reduced dark respiration, increased numbers of shoots, roots and rhizomes, reduced nitrogen concent)ration of all tissues, increased nitrogen fixation and increased ecosystem carbon accumulation. In a mixed community of th$e sedge and C4 grass species, Spartina patens and Distichlis spicata, biomass of the C3 component increased over 100% 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, elev'ated CO2 had the following effects on mono-specific stands of the C3 sedge, Scirpus olneyi: increased quantum yield and ph40^4-5^579-595^^^^^^^^^^3149 R^1993^1^Gender-specific physiology, carbon isotope discrimination, and habitat distribution/A^3148^Open top chambers are being used in a long-term project to determine the effects of elevated CO2 on ecosystem proce*sses on a Chesapeake Bay wetland. Three communities are studied: mono-specific stands of the C3 sedge, Scirpus olneyi, andl as affecting the nutrient value of grain such as rice.y and clonal foraging of Calamagrostis canadensis in response to ^3147t heterogeneity^12^81^^769-776^^34^^^^^^^^^^^^^^^^^^^^^^^^-147^1^Drake,BG^1992^1^A field-study of the effects of elevated CO2 on ecosystem processes in a Chesapeake Bay wetland^182^4ed CO2, irrespective of availability of nitrogen in the soil. In natural ecosystems, the lower nitrogen to carbon ratio of5 the litter may alter rates of nutrient cycling. For farmers, the rising CO2 concentrations could cause reductions in grai0n nitrogen, and therefore protein content. This could have important implications for baking quality of hard wheats as wel7 concentrations are used to evaluate nutrient status of crop and forest species and to manage fertiliser programs, they wi8ll need reassessing as the atmospheric CO2 concentration rises. Another consequence of the altered nutrient requirement at3 high CO2 is that the nitrogen concentrations of foliage, roots and grain are consistently lower in plants grown at elevat:n through the photoreductive cycle is increased and photorespiration is suppressed. This change in metabolism appears to a;lter the foliar nutrient concentration required to promote maximum productivity (critical concentration). Higher phosphoru6s concentrations are needed at elevated CO2, whereas the nitrogen requirement is reduced by CO2 enrichment. Since critical=naged ecosystems because photosynthetic rates will be higher. The greatest absolute increase in productivity will occur wh>en 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 a9vailable to maintain maximum photosynthetic activity at high CO2. C3 plants response to high CO2 because the flux of carbo=2286^3^Yeates,G W^Newton,P C D^Ross,D J^1999^1^Response of soil nematode fauna to naturally elevated CO2 levels influenced1146^1^Conroy,JP^1992^1^Influence of elevated atmospheric CO2 concentrations on plant nutrition^182^40^4-5^445-456^^^^^^^^^eat shock proteins, our results showed little relationship between plant nitrogen status and the ability of a plant to tolerate an acute increase in temperature.ns of QTLs affecting the correlated traits DFF, LLF, LL35 and NN suggest that thes@ore susceptible to a heat shock than ambient-CO2-grown plants, because the reduced N concentrations of high-CO2 grown plan=ts could result in the reduced synthesis of heat shock proteins and reduced thermotolerance. Although we did not examine hBand nutrient treatments, all had some significant effects on plant performance, but plants from both CO2 treatments responCded similarly to heat shocks. We also found, as expected, that plants grown under high CO2 had dramatically decreased tiss?ue N concentrations relative to plants grown under ambient conditions. We predicted that high- CO2-grown plants would be mEas plants of all species in either the vegetative or reproductive phase of growth were exposed to a 4-h heat shock in whicFh the temperature was raised an additional 14-23-degrees-C (depending on plant age). Total biomass and reproductive biomasAs were examined to determine the effect of CO2, nutrient and heat shock treatments on plant performance. Heat shock, CO2, Hntly affected by a heat shock than plants grown at ambient CO2 levels. Plants of a C3 annual (Abutilon theophrasti), a C3 Iannual crop (Sinapis alba) and a C4 annual (Amaranthus retroflexus) were grown from seed in growth chambers under either 4D00 or 700 cm3 m-3 CO2, and were fertilized with either a high or low nutrient regime. Young seedlings of S. alba, as well Kpatterns. Changes in mean air temperatures that might be induced by rising levels of CO2 and other greenhouse gases could Lalso be accompanied by increased variability in daily temperatures such that acute increases in air temperature may be morGe likely than at present. Consequently, we investigated whether plants grown in a CO2 enriched atmosphere would be differeN43^4^Coleman,JS^Rochefort,L^Bazzaz,FA^Woodward,FI^1991^1^Atmospheric CO2, plant nitrogen status and the susceptibility of plants to an acute increase in temperature^9^14^7^667-674^^^^^Sep^^^^^2947JA^2946^Elevated levels of CO2 in the atmosphere are expected to affect plant performance and may alter global temperature Q high-CO2 internal environment. In aquatic autotrophs, the CO2 concentrating mechanisms acclimate to the external CO2, beiRng 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.29451^no, cameron lib. QC 879.7 I62Uonses. Over geological time, aquatic autotrophs and terrestrial C4 and CAM plants have genetically adapted to a decline inV the external CO2/O2 ratio, by the development of mechanisms to concentrate CO2 internally; thus circumventing O2 inhibitiPon of rubisco. Here rubisco affinity for CO2 is less, but its catalytic activity is greater, a situation compatible with aXd with reduced net photosynthesis, possibly causing feedback inhibition of the RuBP/P(i)-regeneration capacities, or chlorYoplast disruption. As exemplified by field-grown soybeans and salt marsh species, a reduction in net photosynthesis and ruTbisco activity is not inevitable under CO2 enrichment. Strong sinks or rapid translocation may avoid such acclimation resp[that is ultimately mediated by a decline in rubisco activity, though the RuBP/P(i)-regeneration capacities of the plant ma\y play a role. The decline is due to decreased rubisco protein, activation state, and/or specific activity, and it maintaiWns the rubisco fixation and RuBP/P(i)-regeneration capacities in balance. Carbohydrate accumulation is sometimes associate^ 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 wZith CO2 enrichment, net photosynthesis often declines. This is a common acclimation phenomenon, less so in field studies, a plants, rubisco has a low catalytic activity, operates below its K(m) (CO2), and is inhibited by O2. Consequently, increabses in the CO2/O2 ratio stimulate C3 photosynthesis and inhibit photorespiration. CO2 enrichment usually enhances the prod]uctivity of C3 plants, but the effect is marginal in C4 species. It also causes acclimation in various ways: anatomically.d289^7^Shaver,GR^Billings,WD^Chapin,FS^Giblin,AE^Nadelhoffer,KJ^Oechel,WC^Rastetter,EB^1992^1^Global change and the carbon balance of arctic ecosystems^14^42^6^433-441^^^^^Junfsurements of C-13/C-12 in shells of foraminiferas support the hypothesis that these CO2 changes are caused by changes in the ocean's biological pump, i.e. the flux of detrital organic carbon from the surface to the deep ocean, which affects thehthe oil-embargo in 1973. - Of special interest regarding the understanding of the carbon cycle and its role in controllingi the climate of the Earth are the observations in polar ice cores covering the past 160.000 years, corresponding to one aned a half glaciation cycles. They show variations of atmospheric CO2, CH4, and N2O parallel to the climatic variations. Meakere, of natural and nuclear weapon produced C-14 in the ocean and in the biota and of other natural or anthropogenic tracelrs. - Based essentially on such information, models for the CO2 uptake by the carbon system have been developed which are gcapable of reproducing the result of the drop in the rate of increase of CO2 emissions from 4.5% to 2% per year following nA^3412^For the estimate of the distribution in the carbon system of the CO2 emitted into the atmosphere due to human activoities, the exchange of carbon between atmosphere and ocean, and between atmosphere and biosphere needs to be considered. Ijnformation on this spreading of excess CO2 can be obtained from measurements of a.o. CO2, C-13/C-12, C-14/C in the atmosphqf the current zones. Despite these uncertainties, the direction of these models indicates future developments and could be used for policy purposes.^^^288^1^Oeschger,H^1992^1^Atmospheric co2 - global change and regulation mechanisms^203^96^3^252-257^^^^^Mar^^^^^3413t addressed. Examples are drawn from different impact studies on large-scale vegetation patterns, forest dynamics and agricuultural systems. General conclusions of these studies are that vegetation and agricultural zones will shift on global, conptinental and regional scales, but that large uncertainties still exist in the timing, actual response and rate of change ow2^3^Garbutt,K^Williams,WE^Bazzaz,FA^1990^1^Analysis of the differential response of 5 annuals to elevated CO2 during growth^11^71^3^1185-1194^^^^^Junmic Press^San Diego, CA^^Y^^1974^^^^^^^^^^^^^^^^^^^^^^^^3^5^Grulke,NE^Riechers,GH^Oechel,WC^Hjelm,U^Jaeger,C^1990^1^Carbon balance in tussock tundra under ambient and elevated atzA^3410^The changing composition of the atmosphere could lead to significant changes in regional and continental climate. T{he methodology to develop consistent climate-change scenarios and to link them to different impact-models is discussed. Ressults of both static and dynamic models are presented and the advantages and disadvantages of the different approaches aree three separate factors that could complicate this simple test.black spruce seedlings to elevated CO{-2} under varied wa~287^1^Leemans,R^1992^1^Modeling ecological and agricultural impacts of global change on a global scale^202^51^8-9^709-724^^^^^Aug-Sep^^^^^3411indicator 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 arhile 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 A^3167^An analysis of elevated CO2 effects (2-4 times ambient) on dark respiration rate and carbon content was undertaken for a wide range of plant species, using both published reports and new data. On average, leaf respiration per unit leaf area was slightly higher for plants grown at high CO2 (16%), whereas a small decrease was found when respiration was express 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; w286^2^Idso,SB^Balling,RC^1992^1^United-states drought trends of the past century^107^60^3-4^279-284^^^^^31 Aug^^^^^3409moA^3408^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 haSIGMA-CO2 was found necessary to maintain a maximal growth rate of 0.7 doublings/day. We also found that the increased productivity more than offsets the cost of adding the CO2.285^4^Carpenter,SR^Fisher,SG^Grimm,NB^Kitchell,JF^1992^1^Global change and fresh-water ecosystems^27^23^^119-139^ionship between inorganic carbon availability and algal production. Our results suggest that through additions of CO2 gas we were able to maintain sufficient dissolved carbon to stabilize outdoor algal cultures. Increases in the rate of addition of CO2 increased levels of dissolved CO2, total dissolved inorganic carbon (SIGMA-CO2), and decreased pH in the growth medium. This translated into improved buffering capacity of the culture medium and higher growth rate. A minimum of 2.4 mM 284^3^Olaizola,M^Duerr,EO^Freeman,DW^1991^1^Effect of co2 enhancement in an outdoor algal production system using tetraselmis^187^3^4^363-366^^^^^Dec^^^^^3406sts^Advances in ecological research^Academic Press^London^2-55^^1994^^19^^^^^^^^^^^^^A^3405^One of the objectives of microalgal culture is to provide reliable production technology for important live aquaculture feed organisms. Presented here are the results of experiments designed to provide a better understanding of the relatlish them. The kinetics of the stimulation indicate that the rate of photosynthesis is affected by two blue-light- dependent components with different time courses of induction and decay. The faster component seemed to be at least partially suppressed at red-light irradiances which were not saturating for photosynthesis. Lowering the pH of the medium had the same effects as an increase of the carbon concentration to levels of approx. 10 mM. This indicates that Ectocarpus takes up free CO2 only and not bicarbonate, although additional physiological mechanisms may enhance the availability of CO2.A^3369^Geochemical models that deduce latitudinal source/sink relationships of atmospheric CO2 suggest that, in tropical regions, there is almost zero net exchange of CO2 between the atmosphere and the terrestrial biosphere. The implication is  both the troughs and the peaks of the rhythm and before and after blue-light pulses. Only at very low carbon concentrations was a clear deviation found from these lines for photosynthesis at the rhythm maxima (red and blue light), which indicated that the strong carbon limitation specifically affected photosynthesis at the peak phases of the rhythm. Very high inorganic carbon concentrations (20 mM) in the medium diminished the responses to blue light, although they did not fully aboo under very low red-light irradiances after a period of adaptation, provided that the inorganic-carbon concentration was not in excess. Double-reciprocal plots of light-saturated photosynthetic rates versus the concentration of total inorganic carbon (up to 10 mM total inorganic carbon) were linear and had a common constant for half-saturation (3.6 mM at pH 8) atffected photosynthesis, the effects of inorganic carbon on photosynthetic light saturation curves were studied under different irradiation conditions. The circadian rhythm of photosynthesis was apparent only at irradiances which were not limiting for photosynthesis. The same was found for blue- light-stimulated photosynthesis, although stimulation was observed als266^2^Polglase,PJ^Wang,YP^1992^1^Potential co2-enhanced carbon storage by the terrestrial biosphere^182^40^4-5^641-656^^^^A^3403^Photosynthesis of Ectocarpus siliculosus (Dillwyn) Lyngb. under continuous saturating red irradiation follows a circadian rhythm. Blue-light pulses rapidly stimulate photosynthesis with high effectiveness in the troughs of this rhythm but the effectiveness of such pulses is much lower at its peaks. In an attempt to understand how blue light and the rhythm a402^Holsinger,K S^1993^3^The evolutionary dynamics of fragmented plant populations^Biotic interactions and global change^283^3^Schmid,R^Forster,R^Dring,MJ^1992^1^Circadian-rhythm and fast responses to blue-light of photosynthesis in ectocarpus (phaeophyta, ectocarpales) .2. Light and co2 dependence of photosynthesis^6^187^1^60-66^^^^^Apr^^^^^340490, 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.essrees 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 19282^1^Idso,SB^1992^1^Net photosynthesis - corrections required of leaf chamber measurements^107^58^1-2^35-42^^^^^Mar^^^^^3A^3401^Direct measurements of trunk and branch volumes and fine-root biomass confirm that the growth rate of sour orange tonditions. 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).ostharvest 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 cd 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 pA^3399^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 standaritical CO2, the only parameter determined from the dynamic extraction rate data, increases with temperature and pressure.281^5^Goulart,BL^Hammer,PE^Evensen,KB^Janisiewicz,W^Takeda,F^1992^1^Pyrrolnitrin, captan + benomyl, and high co2 enhance raspberry shelf-life at 0C or 18C^154^117^2^265-270^^^^^Mar^^^^^3400158^1^Rawson,HM^1992^1^Plant-responses to temperature under conditions of elevated CO2^182^40^4-5^473-490^^^^^^^^^^3170^^A^3169^A literature survey of the interactive effects of CO2 enrichment and temperature on plant development and growth, itndicated that the responses cannot be interpreted within a simple framework. For example, although plant development is gefluenced by both intraparticle diffusion in the water-soaked beans and external mass transfer. A mathematical model based on a linear-driving-force approximation of mass transfer and partitioning of caffeine between the water and the supercritical CO2 describes the time-dependent process. The partition coefficient for caffeine distributed between water and supercrow extraction apparatus. Decaffeination rates were determined as a function of CO2 flow rate, temperature and pressure by continuously monitoring the caffeine in the effluent with aflame ionization detector. Soaking the raw beans in water prior to decaffeination enhanced the rate of extraction, which increased markedly with water content. Using CO2 saturated with water also increased the rate of extraction. The rate of decaffeination increased with pressure and temperature and was in280^4^Peker,H^Srinivasan,MP^Smith,JM^McCoy,BJ^1992^1^Caffeine extraction rates from coffee beans with supercritical carbon-dioxide^201^38^5^761-770^^^^^May^^^^^339825^^2032^^^^^^^^^^^^^^^^^^^^^^^^^^^^^Bliss,L C^Heal,O W^Moore,J JA^3397^The extraction of caffeine from whole coffee beans with supercritical carbon dioxide was studied in a continuous-fl(commercial classification: 'Select' and 'No. 1') was enhanced for this period compared with the same period the previous year when no supplemental carbon dioxide was provided. Generally the planting scheme of two parallel rows gave the best overall results.131^1^Peterson,RB^1991^1^Effects of O2 and CO2 concentrations on quantum yields of photosystem-I and photosystem-II in tobacco leaf tissue^8^97^4^1388-1394^^^^^Dec^^^^^3117^^^^^^^^A^3116^The interactive effects of irradiance and O2 and CO2 levels on the quantum yields of photosystems I and II have beeth of the plants compared to plants grown in ambient light conditions. Marketable yield per plant was increased significantly by 79% (P< 0.05) for the crop period from 1 January to 24 March 1988 when a PPFD of 50-mu-mol s-1 m-2 was added to ambient light conditions. Carbon dioxide enrichment increased yield by 113% when a PPFD of 50-mu-mol s-1 m-2 was added to ambient light during the crop period of 1 January to 24 March, 1989. The number of flowers per plant in the superior classes ality of RosaXhybrida cultivar 'Royalty' was investigated. Three planting schemes (two, three, and four parallel rows) and three light treatments (ambient light and ambient light Plus supplemental lighting with either 50 or 100-mu-mol s-1 m-2 PPFD (high pressure sodium lamps) were studied. Generally, supplementary PPFD enhanced the vegetative and reproductive grow279^2^Menard,C^Dansereau,B^1992^1^Influence of photosynthetic photon flux-density and planting scheme on growth and development of cultivar royalty roses^165^50^3^197-207^^^^^May^^^^^3396A^3395^The influence of photosynthetic photon flux density (PPFD) and planting scheme on growth, development, yield and qu latitudes the median values are 71 tCha-1 (n=401) and 66 tCha-1 (n=170), respectively. Preliminary projections are that if these practices were implemented on 0.6 to 1.2 x 10(9) ha of available land over a 50-yr period, approximately 50 to 100 GtC could be sequestered.es. Results indicate that the most promising management practices are reforestation in the temperate and tropical latitudes, afforestation in the temperate regions, and agroforestry and natural reforestation in the tropics. Across all practices, the median of the mean C storage values for the boreal latitudes is 16 tCha-1 (n=46) while in the temperate and tropicalCO2. The question is how much C can be sequestered by forest and agroforest management practices. To address the question, a global database of information was compiled to assess quantitatively the potential of forestry practices to sequester C. The database presently has information for 94 forested nations that represent the boreal, temperate and tropical latitudlowering of rosa L and kalanchoe- blossfeldiana V poelln^165^51^1-2^145-153^^^^^Jul^^^^^3324412^^2221^^^^^^^^^^^^^^^^^^^^A^3323^The effects of increasing the CO2 concentration from 350 to 700-mu-l l-1 on growth and flowering of Rosa L. and Kaltrunk and branch volume, and 190% more trunk, branch and fruit rind volume than the ambient-treatment trees.ross- 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 aves per tree, and the total trunk plus branch volume per tree can all be adequately inferred from measurements of trunk co 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 leopen-top enclosures for 3.5 years. For the last 3 years of this period, half of the trees have been continuously exposed tions for 3 full years^107^60^1-2^145-151^^^^^15 Aug^^^^^3322ater requirements of C{-3} plants grown at glacial to presentA^3321^Sour orange trees have been grown from the seedling stage out- of-doors at Pheonix, Arizona in clear-plastic-wall, 240^2^Idso,SB^Kimball,BA^1992^1^Aboveground inventory of sour orange trees exposed to different atmospheric co2 concentrattion.Fitter,A H^Fitter,R S R^Harris,I T B^Williamson,M H^1995^1^Relationships between first flowering date and temperatur239^1^Idso,SB^1992^1^Shrubland expansion in the american southwest^50^22^1^85-86^^^^^Sep air) or in shake flasks. The stimulation of root growth via CO2 enrichment reduced the time required for biomass accumulaet 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 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 concenatrations within physiologically acceptable levels, the salt influx to leaves must match the capacities of leaves for salt 25^^^^^^^^^^3143L^Vitt,DH^and K.P. Timoney^1989^1^Patterns of community structure and morphology of bryophytes and lichenA^3142^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 behetic 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.76144^2^Ball,MC^Munns,R^1992^1^Plant-responses to salinity under elevated atmospheric concentrations of CO2^182^40^4-5^515-5 lants may not be genetically adapted to optimise their growth and performance at elevated CO2 and that consideration shoul d 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 photosyntotential 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 nit rogen in key photosynthetic components such as Rubisco and the thylakoid electron transport system. It is concluded that pt. 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. Ho wever, while growth experiments at elevated CO2 indicate that C3 plants show stimulation of dry matter accumulation, the p CO2 must be capable of generating such realised environmental niche responses for species.s at some localities in northe143^1^Badger,M^1992^1^Manipulating agricultural plants for a future high CO2 environment^182^40^4-5^421-429^^^^^^^^^^3141A^3140^This paper discusses the potential ways in which C3 plant performance may benefit from a future high-CO2 environmen 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 elevateds 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),odels 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 siteinuum concept. Confusion exists between the different approaches over the shape of response curves to temperature. Distinc tions 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-m"ure responses for plants. Physiologists often assume a skewed non-monotonic curve with a tail towards low temperatures, fo#rest 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 cont%A^3138^No simple natural gradients in CO2 concentration exist for testing predictions about changes in plant communities i&n response to elevated CO2. However indirect effects of CO2 via temperature increases can be tested by reference to natura!l analogues. Physiologists, vegetation modellers of climate change and community ecologists assume very different temperat(142^1^Austin,MP^1992^1^Modeling the environmental niche of plants - implications for plant community response to elevated CO2 levels^182^40^4-5^615-630^^^^^^^^^^3139* the reliability of these models in conditions where Rubisco has a flux-control coefficient approach unity (i.e. "limits" +photosynthesis), but also indicates that these models are less useful in conditions where control is shared between Rubisco and other components of the photosynthetic apparatus...-saturating irradiance and CO2 are suppressed in decreased- activity transformants before the steady-state rate of photosyn.thesis is affected. This provides direct evidence that these oscillations reveal the presence of "excess" Rubisco. (vi) Co)mparison of the flux-control coefficients of Rubisco with mechanistic models of photosynthesis provides direct support for0l coefficient of stomata for photosynthesis was calculated from the flux- control coefficient of Rubisco and the internal 1CO2 concentration, by applying the connectivity theorem. Control by the stomata varies between zero and about 0.25. It is ,increased by increased irradiance, decreased CO2 or decreased vapour-pressure deficit. (v) Photosynthetic oscillations in 3hat Rubisco still exerts marginal control in these conditions because decreased Rubisco leads to increased thylakoid energ/isation and high-energy dependent dissipation of light energy, and lower light-harvesting efficiency. (iv) The flux-contro5e available capacity is being used. Control increases as utilisation rises to 80%, and approaches unity (i.e. strict limit6ation) when more than 80% of the available capacity is being used. (iii) In low light, plants with reduced Rubisco have ve2ry high energy-dependent quenching of chlorophyll fluorescence (qE) and a decreased apparent quantum yield. It is argued t8r) or low light (310 mumol m-2 s-1) and was also decreased at high vapour- pressure deficit (17 mbar). No control was exer9ted in 5% CO2. (ii) The flux-control coefficients of Rubisco were compared with the fractional demand placed on the calcul4ated available Rubisco capacity. Only a marginal control on photosynthetic flux is exerted by Rubisco until over 50% of th;ntent versus assimilation rate. The flux-control coefficient had a value of 0.8 or more in high irradiance, (1050 mumol m-72 s-1), low-vapour pressure deficit (4 mbar) and ambient CO2 (350-mu-bar). Control was marginal in enhanced CO2 (450-mu-ba=estigate the contribution of Rubsico to the control of photosynthesis at different irradiance, CO2 concentrations and vapo>ur-pressure deficits. Assimilation rates, transpiration, the internal CO2 concentration and chlorophyll fluorescence were :measured in each plant. (i) The flux-control coefficient of Rubisco was estimated from the slope of the plot of Rubisco co@A^3136^Transgenic tobacco (Nicotiana tabacum L.) plants transformed with 'antisense' rbcS to produce a series of plants wiin the atmosphere 9. Here we use the Rothamsted model for the turnover of organic matter in soil 3 to calculate the amountDA^3126^ONE effect of global warming will be to accelerate the decomposition of soil organic matter, thereby releasing CO2 Eto the atmosphere, which will further enhance the warming trend 1- 7. Such a feedback mechanism could be quantitatively imAportant, because CO2 is thought to be responsible for approximately 55% of the increase in radiative forcing arising from acting as a second electron-accepting assimilatory process in addition to CO2 fixation.vegetation types in Alaska^10^11^^H136^3^Jenkinson,DS^Adams,DE^Wild,A^1991^1^Model estimates of CO2 emissions from soil in response to global warming^36^351^6324^304-306^^^^^23 May^^^^^3127Jht-intensity curve. No stimulation Of O2 evolution was otherwise observed after feeding KCl or NH4Cl. The data indicate thFat nitrate assimilation uses photosynthetically generated reductant and stimulates the rate of noncyclic electron flow by Lvum L. cv Lincoln) in a CO2-saturating atmosphere was enhanced when KNO3 (1-2.5 millimolar) had been previously supplied tMhrough the transpiration stream. The extra O2 evolution observed after feeding KNO3 increased with the light intensity, beIing maximal at near saturating photon flux densities and resulting in no changes in the initial slope of the O2 versus lig of safe strategies to minimize the negative impacts and maximize the benefits of these changes.s accumulation in Eriopho135^3^Delatorre,A^Delgado,B^Lara,C^1991^1^Nitrate-dependent O2 evolution in intact leaves^8^96^3^898-901^^^^^Jul^^^^^3125KA^3124^Evolution Of O2 by illuminated intact detached leaves from barley (Hordeum vulgare L. cv Athos) and pea (Pisum satiRt in interior western Canada. Increases in annual temperature of 3 to 7-degrees-C are projected for Alberta under a 2 x COS2 scenario by 2030-2050 A.D. Such an unprecedented rate of change has many short- and long-term implications for forest maNnagement and for industries. As the boreal forest is highly sensitive to climatic changes, foresters need to develop a setU134^2^Singh,T^Wheaton,EE^1991^1^Boreal forest sensitivity to global warming - implications for forest management in western interior canada^66^67^4^342-348^^^^^Aug^^^^^3123QA^3122^Unmitigated global warming due to the enhanced greenhouse effect could have significant impacts on the boreal foresXowth to readjust the sink-source balance. In the final part of the review, I argue that similar changes of Rubisco and, possibly, other proteins are probably also involved during acclimation to high CO2.Znt, involving decreases in amounts of key photosynthetic enzymes, including Rubisco. This decreases the rate of photosynthWesis, and potentially would allow resources (e.g. amino acids) to be remobilized from the leaves and reinvested in sink gr\mportant in the short-term regulation of partitioning to sucrose and starch, but that its contribution to 'sink' regulatioYn has not yet been conclusively demonstrated. Indirect or 'adaptive' regulation of photosynthesis is probably more importa^'sink' regulation of photosynthesis. Accumulating carbohydrate could lead to a direct inhibition of photosynthesis, involv[ing mechanical damage by large starch grains or Pi-limitation due to inhibition of sucrose synthesis. I argue that Pi is i`to an inadequate demand for carbohydrate in the remainder of the plant. Differences in the long-term response to CO2 may bae explained by differences in the sink-source status of plants. depending upon the species, the developmental stage, and t]he developmental conditions. In the third part of the review, I consider the biochemical mechanisms which are involved in cs sensitively), and that photosynthesis will be stimulated by 25- 75% when the CO2 concentration is doubled from 35 to 70 dPa. This is in good agreement with the published responses. In the next part of the review, I discuss the evidence that mo_st plants undergo a gradual inhibition of photosynthesis during acclimation to enhanced CO2. I argue that this is related fe demand on partial processes like carboxylation, light harvesting and electron transport, the Calvin cycle, and end-produgct synthesis; and (2) the extent to which these various processes actually control the rate of photosynthesis. I conclude bthat control is usually shared between Rubisco (which responds sensitively to CO2) and other components (which respond lesiA^3120^In the first part of this review, I discuss how we can predict the direct short-term effect of enhanced CO2 on photeosynthetic rate in C3 terrestrial plants. To do this, I consider: (1) to what extent enhanced CO2 Will stimulate or relievted plants was found for both salinity and water stress. the sensitivity of tundra ecosystems to climate change^76^72^^8l133^1^Stitt,M^1991^1^Rising CO2 levels and their potential significance for carbon flow in photosynthetic cells^9^14^8^741-762^^^^^Oct^^^^^3121nly, in journalned only 5% of the total increase in solutes in salinity- acclimated and 10 to 20% in water-stress-acclimated plants. This oacclimation was interpreted in light of the higher protein content per unit leaf area and the enhanced ribulose bisphosphajte carboxylase activity. At saturating CO2 Partial pressure, the declined inhibition in CO2 assimilation of stress-acclimaqn acclimated than in nonacclimated plants, resulting in turgor maintenance even at -0.9 megapascal. In nonacclimated plantrs, turgor pressure reached zero at approximately -0.5 megapascal. The accumulation of Cl- and Na+ in the salinity-acclimatmed plants fully accounted for the decrease in leaf osmotic potential. The rise in concentration of organic solutes compristonship, were increased in plants acclimated to salinity of -0.3 and -0.6 megapascal but not in nonacclimated plants. In plpants acclimated to water stress, this change in slopes was not significant. Leaf osmotic potential was reduced much more iv nonacclimated plants. The decrease of CO2 assimilation in salinity-exposed plants was significantly less in acclimated asw compared with nonacclimated plants. Such a difference was not found under water stress at ambient CO2 partial pressure. Tshe slopes of net CO2 assimilation versus intercellular CO2 partial pressure, for the initial linear portion of this relatiyA^3118^Cotton (Gossypium hirsutum L. cv Acala SJ2) plants were exposed to three levels of osmotic or matric potentials. Thze first was obtained by salt and the latter by withholding irrigation water. Plants were acclimated to the two stress typeus by reducing the rate of stress development by a factor of 4 to 7. CO2 assimilation was then determined on acclimated andrescence was unaffected by CO2 concentration.d food quality influences feeding behavior, assimilation efficiency and grow}132^2^Plaut,Z^Federman,E^1991^1^Acclimation of CO2 assimilation in cotton leaves to water- stress and salinity^8^97^2^515-522^^^^^Oct^^^^^3119 on photosystem II arising from a build-up in the thylakoid proton gradient during electron transport to O2. Covariation between quantum yields of photosystems I and II was not affected by concentrations of either O2 or CO2. The dependence of q{uantum yield of electron transport to CO2 measured by gas exchange upon photosystem II quantum yield as determined by fluotion is suspected to mediate such positive effects of O2 through increases in the availability of CO2 and recycling of orthophosphate. Conversely, at low intercellular CO2 concentrations, 41.2% O2 was associated with lower photosystem II quantu~m yield compared with that observed at 20.5% O2. Inhibitory effects of 41.2% O2 may occur in response to negative feedbacksorbance change at 830 nanometers, the absorption band of P700+. Normal (i.e. 20.5%, v/v) levels of O2 generally enhanced photosystem II quantum yield relative to that measured under 1.6% O2 as the irradiance approached saturation. Photorespiran studied under steady-state conditions at 25-degrees-C in leaf tissue of tobacco (Nicotiana tabacum). Assessment of radiant energy utilization in photosystem II was based on changes in chlorophyll fluorescence yield excited by a weak measuring beam of modulated red light. Independent estimates of photosystem I quantum yield were based on the light-dark in vivo abons above ambient. Increasing CO2 concentration had no effect on the carbohydrate concentration in the grain at maturity.130^1^Wittwer,SH^1990^1^Implications of the greenhouse-effect on crop productivity^170^25^12^1560-1567^^^^^Decon. At maturity, increasing CO2 concentration resulted in an increase in total non-structural carbohydrate (TNC) concentration in leaf blades, leaf sheaths and culms. Carbohydrates that were stored in vegetative plant parts before heading made a smaller contribution to grain dry weight at CO2 concentrations below 330 mu-mol mol-1 than for treatments at concentrati-1 CO2. Similarly, photosynthesis also increased with CO2 concentrations up to 500 mu-mol mol-1 and then reached a plateau at higher concentrations. The ratio of starch to sucrose concentration was positively correlated with the CO2 concentrati0, 250, 330, 500, 660, and 900 mu-mol CO2 mol-1 air. In leaf blades, the priority between the partitioning of carbon into storage carbohydrates or into export changed with development stage and CO2 concentration. During vegetative growth, leaf sucrose and starch concentrations increased with increasing CO2 concentration but tended to level off above 500 mu-mol molcentration sometime during the next century. The objective of this investigation was to determine the long-term effects of different CO2 concentrations on carbohydrate status and partitioning in rice (Oryza sativa L. cv. IR-30). Rice plants were grown season-long in outdoor, naturally sunlit, environmentally controlled growth chambers with CO2 concentrations of 16129^4^Rowlandbamford,AJ^Allen,LH^Baker,JT^Boote,KJ^1990^1^Carbon-dioxide effects on carbohydrate status and partitioning in rice^78^41^233^1601-1608^^^^^Dec^^^^^3114A^3113^The atmospheric carbon dioxide (CO2) concentration has been rising and is predicted to reach double the present concement by CO2 enrichment was 2.3. Two genotypes showed significant genotype x CO2 interaction. The consequences of these results for tomato breeding are discussed.108^4^Couteaux,MM^Mousseau,M^Celerier,ML^Bottner,P^1991^1^Increased atmospheric CO2 and litter quality - decomposition of sweet chestnut leaf litter with animal food webs of different complexities^15^61^1^54-64^^^^^May^^^^^3073notypes were found for average plant fresh and dry weights and for relative growth rates. The average overall growth enhanex can be calculated. Our preliminary results give promise of extending the record of stomatal density response back at least 10,000 years. 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 indxperimental 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)A^3070^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. E107^5^Beerling,DJ^Chaloner,WG^Huntley,B^Pearson,A^Tooley,MJ^1991^1^Tracking stomatal densities through a glacial cycle - their significance for predicting the response of plants to changing atmospheric CO2 concentrations^175^1^5^136-142^^^^^Sep^^^^^3071re 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.atural 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 miniatuo 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 nent^174^66^5^569-574^^^^^Sep^^^^^30691^The sensitivity of phenological events to changes in nutrient availability for sevA^3068^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 tearch is for integrated studies on plant and soil processes.hotosynthesis in arctic plants^31^5^^158-163^^1166106^1^Andersson,NE^1991^1^The influence of constant and diurnally changing CO2 concentrations on plant-growth and developm 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 resre 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. Thement 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 ae 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 environ 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 climat105^1^Anderson,JM^1991^1^The effects of climate change on decomposition processes in grassland and coniferous forests^56^1^3^326-347^^^^^Aug^^^^^3067e^2^62^^196-198^^1178A^3066^Current models of climate change predict a reduction of area covered by northern coniferous forests and tundra, andson 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.e 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 seamu-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 thture 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-A^3064^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 fu104^4^Allen,LH^Bisbal,EC^Boote,KJ^Jones,PH^1991^1^Soybean dry-matter allocation under subambient and superambient levels of carbon-dioxide^48^83^5^875-883^^^^^Sep-Oct^^^^^3065 treatments, while tuber yields of Russet Burbank and Norland were increased 18 and 9%, respectively. The results show a pattern of greater plant growth from CO2 enrichment under lower PPF and a short photoperiod.total plant dry weight by 39 and 34%, respectively, under a 12-h photoperiod at 400-mu-mol m-2 s-1; 27 and 19% under 12 h at 800-mu-mol m-2 s-1; 9 and 9% under 24 h at 400-mu-mol m-2 s-1. It decreased dry weights by 9 and 9% under 24 h at 800-mu-mol m-2 s-1. Tuber yield of Denali showed the greatest increase (21%) in response to increased CO2 across all irradianceher at 350 or 100-mu-mol mol-1 and applied in combination with 12- or 24-h photoperiods at 400 or 800-mu-mol m-2 s-1 photosynthetic photon flux. Air temperatures and relative humidity were held constant at 16-degrees-C and 70%, respectively, and plants were harvested 90 d after planting. When averaged across all cultivars, CO2 enrichment increased tuber yield and A^3062^Carbon dioxide concentration can exert a strong influence on plant growth, but this influence can vary depending on irradiance. To study this, potato plants (Solanum tuberosum L.) cultivars 'Norland'. 'Russet Burbank', and 'Denali' were grown in controlled-environment rooms at different levels of CO2 and irradiance. Carbon dioxide levels were maintained eittor that induces the CCM, although secondary regulation must also be involved.love Lowland, Devon Island, N.W.T., Canada^103^3^Wheeler,RM^Tibbitts,TW^Fitzpatrick,AH^1991^1^Carbon-dioxide effects on potato growth under different photoperiods and irradiance^164^31^5^1209-1213^^^^^Sep-Oct^^^^^3063 activities. Other known mutants of the CCM show patterns of PGPase and glycolate DH activity after transfer to limiting CO2 which are different from WT and cia-5 but which are consistent with changes in activity being initiated by the same facells is double that seen in CO2-enriched cells. Unlike WT, the high-CO2-requiring mutant, cia-5, does not respond to limiting CO2 conditions: it does not induce any known aspects of the CCM and it does not show changes in PGPase or glycolate DHoxygenase. PGPase in cell extracts shows a transient increase in activity that reaches a maximum 3 to 5 hours after transfer and then declines to the original level within 48 hours. The decline in PGPase activity begins at about the time that physiological evidence indicates the CCM is approaching maximal activity. Glycolate DH activity in 24 hour air-adapted WT c. Adaptation to air levels of CO2 by Chlamydomonas involves induction of a CO2-concentrating mechanism (CCM) which increases the internal inorganic carbon concentration and suppresses oxygenase activity of ribulose-1,5-bisphosphate carboxylase/A^3060^The activity of two photorespiratory enzymes, phosphoglycolate phosphatase (PGPase) and glycolate dehydrogenase (glycolate DH), changes when CO2-enriched wild-type (WT) Chlamydomonas reinhardtii cells are transferred to air levels of CO2102^2^Marek,LF^Spalding,MH^1991^1^Changes in photorespiratory enzyme-activity in response to limiting CO2 in Chlamydomonas reinhardtii^8^97^1^420-425^^^^^Sep^^^^^3061ant's photosynthetic response to atmospheric CO2 enrichment is inversely proportional to its degree of CO2-induced stomatal closure. in stomatal conductance^173^31^4^381-383^^^^^Oct^^^^^3059ing, sexual selection, and the evolution of dioecy in plants^16A^3058^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 pl by a distinct reduction of leaf area growth and by chlorotic discolorations. in plants^32^250^^923-930^^1218101^1^Idso,SB^1991^1^A general relationship between CO2-induced increases in net photosynthesis and concomitant reductionsith 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 reactedk 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 w photosynthesis is limited by the rate of RuBP regeneration. in biologically active ultraviolet radiation reaching the gr93^2^Sasek,TW^Strain,BR^1991^1^Effects of CO2 enrichment on the growth and morphology of a native and an introduced honeysuckle vine^5^78^1^69-75^^^^^Jan^^^^^3044s per square meter per second increased the activation state of rubisco but had little effect on the K(cat). These results support modelled simulations of the rubisco response to light and CO2, where rubisco is assumed to be down-regulated when state of rubisco was dependent on C(i). Otherwise, RuBP pool sizes increases as C(i) was reduced. ATP pools in C. album tended to increase as C(i) was reduced. In P. vulgaris, decreasing C(i) at a subsaturating light intensity of 190 micromole C(i) was elevated above 120 microbars at 550 micromoles per square meter per second and above 300 microbars at 1750 micromoles per square meter per second. The pool size of RuBP was independent of C(i) only under conditions when the activation 550, and 150 micromoles per square meter per second) and at intercellular CO2 partial pressures (C(i)) between the CO2 com pensation point and 500 microbars. Above a C(i) of 120 microbars, the activation state of rubisco was light dependent. At light intensities of 550 and 1750 micromoles per square meter per second, it was also dependent on C(i), decreasing as theBP regeneration limited photosynthesis, but not when rubisco capacity limited photosynthesis. Measured observations closel y matched modeled simulations. The activation state of rubisco was measured at three light intensities in C. album (1750,  square meter per second in C. album and below 200 micromoles per square meter per second in P. vulgaris). Modeled simulat ions indicated that the initial slope of the CO2 response of photosynthesis exhibited light dependency when the rate of Ru ADP were studied in the C3 annuals Chenopodium album and Phaseolus vulgaris at 25-degrees-C. The initial slope of the photosynthetic CO2 response curve was dependent on light intensity at reduced light levels only (less than 450 micromoles pert-intensity and CO2 in the C3 annuals Chenopodium album L and Phaseolus vulgaris L^8^94^4^1735-1742^^^^^Dec^^^^^3042n^75A^3041^The light and CO2 response of (a) photosynthesis, (b) the activation state and total catalytic efficiency (K(cata)) of ribulose-1,5-bisphosphate carboxylase (rubisco), and (c) the pool sizes of ribulose 1,5-bisphosphate, (RuBP), ATP, and, the activity of rubisco is downregulated to balance the limitation in the rate of RuBP regeneration. Comparisons with published data demonstrate a general consistency between modelled predictions and measured results.92^3^Sage,RF^Sharkey,TD^Seemann,JR^1990^1^Regulation of ribulose-1,5-bisphosphate carboxylase activity in response to lighion are down-regulated in order that the rate of RuBP regeneration matches the rate of RuBP consumption by rubisco. Similarly, at subsaturating light intensity or elevated CO2, when electron transport or Pi regeneration may limit photosynthesisre regulated to balance the capacity of limiting processes. Thus, at CO2 partial pressures below ambient, when a limitation on photosynthesis by the capacity of rubisco is postulated, the activities of electron transport and phosphate regeneratA^3039^A model of the regulation of the activity of ribulose-1,5-bis- phosphate carboxylase, electron transport, and the rate of orthophosphate regeneration by starch and sucrose synthesis in response to changes in light intensity and partial pressures of CO2 and O2 is presented. The key assumption behind the model is that nonlimiting processes of photosynthesis a!91^1^Sage,RF^1990^1^A model describing the regulation of ribulose-1,5-bisphosphate carboxylase, electron-transport, and triose phosphate use in response to light-intensity and CO2 in C3 plants^8^94^4^1728-1734^^^^^Dec^^^^^3040#of all species was increased by elevated CO2. In the case of Scirpus (C3), this increase was caused by increased net photo$synthesis, for Spartina patens (C4) photosynthesis was not increased, but transpiration was reduced. The water potential of the shoot was less negative under conditions of CO2 enrichment, in particular at increased salinity (250 mM NaCl).&ent, no such increase was found in the C4 grass species. High salinity reduced growth of the C3 species tested, but this r'elative growth reduction was not prevented by elevated CO2 concentration. The growth increase at elevated CO2 of Scirpus m"aritimus and Puccinellia maritima is greater under aerated than under anaerobic solution conditions. Water-use efficiency ) anglica C.E. Hubbard and Spartina patens (Ait.) Muhl. were grown at ambient (340 p.p.m. CO2) and elevated (580 p.p.m. CO2*) atmospheric CO2 concentration, at low (10 mM NaCl) and high salinity (250 mM NaCl) under aerated and anaerobic condition%s in the culture solution. The relative growth rate of both the C3 grass species was enhanced with atmospheric CO2 enrichm,90^7^Rozema,J^Dorel,F^Janissen,R^Lenssen,G^Broekman,R^Arp,W^Drake,BG^1991^1^Effect of elevated atmospheric CO2 on growth, photosynthesis and water relations of salt-marsh grass species^159^39^1-2^45-55^^^^^Feb^^^^^3038(A^3037^The C3 grass species Scirpus maritimus L. and Puccinellia maritima (Huds.) Parl., and the C4 grass species Spartina/nthesis; however, during pod fill potential increased significantly with increasing CO2 concentration, as elevated CO2 dec0reased water use rates, lowering soil water stress. Alleviation of water stress during critical reproductive phases was strongly suggested.2resistance, except near the end of the sampling period when a sudden increase in resistance was observed under low CO2 owi3ng to low soil water availability. Midday xylem potential for well-watered plants was greater than values for stressed pla.nts and was unaffected by CO2 treatment. Under low moisture conditions, elevated CO2 had no effect on xylem potential at a5d pod fill, plants grown under CO2 enrichment exhibited greater leaf area. Nevertheless, water use per plant either remain6ed constant (stressed plants at anthesis) or else declined (well- watered plants at pod fill; both moisture levels during 1pod fill) in response to CO2 enrichment. At pod fill, leaves of CO2-enriched plants generally displayed a higher stomatal 8 treatments started to decrease under well-watered conditions during anthesis and by early pod formation under water-stres9sed conditions. During reproductive growth, normal and stressed plants at 349-mu-l-l-1 (ambient level) received irrigation4 water 29 and 12 times, respectively, compared with 21 and 9 times, respectively, at 946-mu-l-l-1 CO2. At both anthesis an69^35^1^13-25^^^^^Mar^^^^^3036c and alpine vegetations: similarities, differences, and susceptibility to disturbance^14^2grees- C at least once during the 10 years simulated, which would be lethal to most prickly pear cacti, was reduced from 49 to 18% by the general warming expected to accompany an approximate doubling of the atmospheric CO2 concentration.:89^4^Prior,SA^Rogers,HH^Sionit,N^Patterson,RP^1991^1^Effects of elevated atmospheric CO2 on water relations of soya bean^1And Northwest where the PAR index lowered EPI. The predicted annual dry weight productivity for O. ficus-indica was 12.8 MgB ha-1 yr-1 under current conditions, and 16.3 Mg ha-1 yr-1 under those associated with 650-mu-L L-1 CO2. Both productiviti=es are relatively high compared with other agronomic plants. The percentage of sites where temperatures fall below - 15-deD of maximal net CO2 uptake during a 24-h period for the prevailing plant water status). For closely spaced plants that leaEd to a high productivity per unit ground area, EPI averaged about 0.10, except in desert regions where the water index low@ered EPI, in the far North or South and at high elevations where the temperature index lowered EPI, and in the Northeast aG O. ficus-indica was directly measured, and low temperature limitations on productivity were considered. The dry weight gaHin of O. ficus-indica during 6 mo in an environmental growth chamber was 23% greater at 650 compared with 350-mu-L L-1 CO2C and increased as the duration of the wet period increased, in agreement with predictions of the water index (the fractionJty can be predicted. This investigation calculated the water index the temperature index, and the PAR index, whose productK equals EPI, for 169 sites distributed approximately uniformly across the contiguous USA for present climatic conditions aFs well as for those associated with an elevated CO2 concentration of 650-mu-L L-1. The effect of elevated CO2 on growth ofMA^3033^Opuntia ficus-indica (L.) Mill., a prickly pear cactus cultivated worldwide for its fruits and stem segments, can hNave an annual dry weight productivity exceeding that of many crops. Using a recently introduced environmental productivityI index (EPI), the influences of water status, temperature, and photosynthetically active radiation (PAR) on its productivions^14^41^2^96-104^^^^^Feban Veldhuizen,RM^and C.E. Teutsch^1983^1^Artificial regeneration of trees and tall shrubs in exQ88^2^Nobel,PS^Decortazar,VG^1991^1^Growth and predicted productivity of Opuntia ficus-indica for current and elevated carbon-dioxide^48^83^1^224-230^^^^^Jan-Feb^^^^^3034Shyll synthesis is not disturbed, and growth and biomass accumulation intensify in plants under conditions of elevated CO2 concentration. black spruce/feather moss sites in interior Alaska^53^1987^^84-88^^1342O87^5^Mooney,HA^Drake,BG^Luxmoore,RJ^Oechel,WC^Pitelka,LF^1991^1^Predicting ecosystem responses to elevated CO2 concentratiVclined. The excess of amino acids (alanine and aspartic acid) is evacuated from the metabolic pool into vacuoles, with theR result that a normal metabolic pool of amino acids is preserved. A state of homeostasis is preserved, protein and chloropXmosphere. Intensification of nitrogen metabolism occurred mainly due to increase of NR activity. Activity of GS and GO incYreased to a lesser extent. Significant changes were detected in the rates of synthesis of separate amino acids. Thus, formUation of alanine and aspartic acid increased by 84 and 40%, respectively, but the rates of glycine and serine synthesis de[ of nitrogen metabolism in leaves of mustard plants in the vegetative phase of growth are higher under conditions of elevaWted atmospheric CO2 concentration than in leaves of plants that developed under conditions of normal CO2 content in the atnd nitrogen-metabolism of mustard plants^168^37^5^687-692^^^^^Sep-Oct^^^^^3031ce, Picea glauca, seed^72^97^^104-106^^1350^A^3030^We investigated the effect of prolonged (8- to 10-day) influence of elevated atmospheric CO2 content (0.14%) on theZ photosynthetic rate and nitrogen metabolism in mustard plants (Brassica juncea L.). The photosynthetic rate and intensity`io; 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.\86^4^Maevskaya,SN^Andreeva,TF^Voevudskaya,SY^Cherkanova,NN^1990^1^Effect of elevated CO2 concentration on photosynthesis acrowth as total-N uptake and plant growth were decreased to the same extent by P stress resulting in unaltered tissue N condcentrations. In contrast, decreased total P-uptake by N-stressed plants was associated with a restriction in root growth a_s P-uptake efficiency of the roots was unaltered. This response was coupled with an increased root-to-shoot dry weight ratfent and vice versa. Nutrient-stress treatments lowered the relative seed yield response to atmospheric CO2 enrichment. Decgreased total-N uptake by P- stressed plants was associated with both decreased root growth and N-uptake efficiency of the broots. Nitrogen-utilization efficiency was also decreased by P-stress. This response was associated with decreased plant giies at 27 days after transplanting (DAT) and seed yield at maturity (98 DAT). Atmospheric CO2 enrichment increased growth jand N- and P-utilization efficiencies at 27 DAT and seed yield in all nutritional treatments and did not affect N- and P-ueptake efficiencies at 27 DAT. Parameter responses to nutrient stress at 27 DAT were not altered by atmospheric CO2 enrichmlnd utilization efficiencies in dry matter production (gdw2/mg nutrient). Nutritional treatments were imposed in aerial envmironments containing either 350 or 700-mu-L/L atmospheric CO2 to determine whether the nutrient interactions were modifiedh when growth rates were altered. Nutrient-stress treatments decreased growth and N- and P-uptake and utilization efficienc13^11^1419-1433^^^^^^^^^^3029,P^McPeters,RD^Herman,JR^1991^1^Total ozone trends deduced from Nimbus 7 TOMS data^65^18^^10pA^3028^Nonnodulated soybean plants (Glycine max. [L.] Merr. 'Lee') were supplied with nutrient solutions containing growthk limiting concentrations of N or P to examine effects on N- and P-uptake efficiencies (mg nutrient accumulated/gdw root) ar 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.n85^3^Israel,DW^Rufty,TW^Cure,JD^1990^1^Nitrogen and phosphorus nutritional interactions in a CO2 enriched environment^166^ully 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 corqrelated with the decrease in stomatal conductance to CO2 transfer. The water use efficiency (WUE) of leaves increased withwfor 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 xmol-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 ltargely influenced by temperature. The promotive effect of elevating C(a) on CER was larger at higher temperatures, especiazA^3026^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 wvere grown in artificially illuminated growth cabinets under 350 and 500-mu-mol mol-1 ambient CO2 (C(a)) and were measured }84^2^Imai,K^Okamotosato,M^1991^1^Effects of temperature on CO2 dependence of gas exchanges in C3 and C4 crop plants^160^60^1^139-145^^^^^Mar^^^^^3027 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.25375^yestion 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] '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 concentra83^6^Bhattacharya,NC^Hileman,DR^Ghosh,PP^Musser,RL^Bhattacharya,S^Biswas,PK^1990^1^Interaction of enriched CO2 and water-stress on the physiology of and biomass production in sweet-potato grown in open-top chambers^9^13^9^933-940^^^^^Dec^^^^^30A^3024^The objective of this study was to investigate the effects of water stress in sweet potato (Ipomoea batatas L. [Lamon with long term exposure to elevated CO2. This experiment suggests that: (1) a global rise in CO2 may have significant effects on photosynthesis and productivity in a wide variety of tropical species, and (2) increases in productivity and photosynthesis may be related to physiological adaptation(s) to increased CO2. were noted for the C4 grass, Paspallum conjugatum. Increases in the apparent quantum efficiency (AQE) for all C3 species suggest that elevated CO2 may increase photosynthetic rate relative to ambient CO2 over a wide range of light conditions. The response of CO2 assimilation to internal C(i) suggested a reduction in either the RuBP and/or Pi regeneration limitatiignificant increases in total plant dry weight were also noted for 4 out of the 5 C3 species tested and in one CAM species, Aechmea magdalenae at high CO2. In contrast, no significant increases in either photosynthesis or total plant dry weightincreases in photosynthesis and greater water use efficiency (WUE) for all species possessing C3 metabolism, when compared to the ambient condition. No desensitization of photosynthesis to increased CO2 was observed during the 3 month period. Sposure to elevated carbon-dioxide^2^86^3^383-389^^^^^^^^^^3023centrations and whole plant senescence^11^64^^1311-1314^^13A^3022^Seedlings of nine tropical species varying in growth and carbon metabolism were exposed to twice the current atmospheric level of CO2 for a 3 month period on Barro Colorado Island, Panama. A doubling of the CO2 concentration resulted in hinochloa under low-N. These experiments show that for these species nitrogen was more important than light or elevated pCO2 in determining the extent of competitive interactions in mixed culture.82^4^Ziska,LH^Hogan,KP^Smith,AP^Drake,BG^1991^1^Growth and photosynthetic response of 9 tropical species with long-term exeatments but this was insufficient to offset a marked decline in shoot growth with increasing proportion of C3 plants in mixed cultures. The unexpected stimulation of growth of C4 plants by elevated CO2 was correlated with more negative delta- C-13 values of C4 root biomass, suggesting a partial failure of the CO2 concentrating mechanism of C4 photosynthesis in Ec. Root growth of the C3 plants was generally stimulated by elevated CO2, but was only occasionally sensitive to the presence of C4 plants in mixed culture. However, growth of the C4 plants was often sensitive to the presence of C3 plants in mixed culture. In mixed cultures, elevated CO2 plants stimulated growth of C4 plants at high PPFD, high-N and in all low-N trbut C4 plants had overtaken them by the time of the second harvest. Elevated atmospheric CO2 (640-mu-bar) stimulated shoot growth of Triticum in 15 of 16 treatment combinations and the stimulation was greatest in plants provided with low NO3BARt biomass. In air (320-mu-bar CO2) at high PPFD and with high root zone-N, the shoot biomass of C3 and C4 components at the first harvest (28 days) was in proportion to the sowing ratio. However, by the second harvest (36 days) the C4 component predominated in both mixtures. Under the same conditions, but with low PPFD, C3 plants predominated at the first harvest 640-mu-bar), two photosynthetic photon flux densities (PPFDs) (daily maximum 2000 and 500-mu-mol m-2 s-1) and two levels of nitrogen nutrition (12 mM and 2 mM NO3BAR). Growth of shoots of both components in mixed culture was measured by physical separation, and the proportions of root biomass due to each component were calculated from delta-C-13 value of total rooA^3020^Wheat (Triticum aestivum L.), a C3 species, and Japanese millet (Echinochloa frumentacea Link), a C4 species, were grown in pots in monoculture and mixed culture (2 C3:1 C4 and 1 C3:2 C4) at two ambient partial pressures of CO2 (320 and cum aestivum (C3) and Echinochloa frumentacea (C4) during growth in mixed culture under different CO2, N-nutrition and irradiance treatments, with emphasis on belowground responses estimated using the delta-C-13 value of root biomass^92^18^2^137-152^^^^^^^^^^3021ts into the soil as well as the subsequent microbial turnover of root-derived carbon are reviewed. We discuss possible consequences of an increased CO2 level in the atmosphere on these processes.81^2^Wong,SC^Osmond,CB^1991^1^Elevated atmospheric partial-pressure of CO2 and plant-growth .3. Interactions between Triti input of organic carbon into the soil due to the expected increase in primary production. Whether this will lead to accumulation of greater amounts of organic carbon in soil depends on the flow of carbon through the plant into the soil and its subsequent transformation in the soil by microorganisms. In this paper the major controls of carbon translocation via rooA^3018^The flow of carbon from photosynthesizing tissues of higher plants, through the roots and into the soil is one of the key processes in terrestrial ecosystems. An increased level of CO2 in the atmosphere will likely result in an increased80^4^Vanveen,JA^Liljeroth,E^Lekkerkerk,LJA^Vandegeijn,SC^1991^1^Carbon fluxes in plant-soil systems at elevated atmospheric CO2 levels^56^1^2^175-181^^^^^May^^^^^3019mation of photosynthesis was reversible. Reductions in photosynthetic capacity as root growth was progressively restricted suggest sink-limited feedback inhibition as a possible mechanism for regulating net photosynthesis of plants grown in elevated CO2.owth was restricted suggesting that ribulose-1,5- bisphosphate carboxylase/oxygenase activity may be responsive to plant source-sink balance rather than to CO2 concentration as a single factor. When root-restricted plants were transplanted into large pots, carboxylation efficiency and ribulose-1, 5-bisphosphate regeneration capacity increased indicating that accliwas found to be primarily an accumulation of leaf starch. Reduced photosynthetic capacity of plants grown at elevated levels Of CO2 was clearly associated with inadequate rooting volume. Reductions in net photosynthesis were not associated with decreased stomatal conductance. Reduced carboxylation efficiency in response to CO2 enrichment occurred only when root gromass and leaf area of plants grown in 270 and 350 microbars Of CO2 were not significantly different. Plants grown in small pots in 650 microbars Of CO2 produced greater total biomass than plants grown in 350 microbars, but the dry weight gain ted from small pots into large pots after 20 days. Reduction of root biomass resulting from growth in small pots was accompanied by decreased shoot biomass and leaf area. When root growth was less restricted, plants exposed to higher CO2 partial pressures produced more shoot and root biomass than plants exposed to lower levels of CO2. In small pots, whole plant biA^3016^Interactive effects of root restriction and atmospheric CO2 enrichment on plant growth, photosynthetic capacity, and carbohydrate partitioning were studied in cotton seedlings (Gossypium hirsutum L.) grown for 28 days in three atmospheric CO2 partial pressures (270, 350, and 650 microbars) and two pot sizes (0.38 and 1.75 liters). Some plants were transplan79^2^Thomas,RB^Strain,BR^1991^1^Root restriction as a factor in photosynthetic acclimation of cotton seedlings grown in elevated carbon-dioxide^8^96^2^627-634^^^^^Jun^^^^^3017t from the above considerations of the effects of natural leaf temperature regimes and prevailing lapse conditions on CO2 uptake potential. A(P) with altitude when predicted leaf temperatures and moist lapse conditions were simulated. There was a significant (almost-equal-to 10%) increase in A(P) with altitude when leaf temperature was held constant at 30-degrees- C (regardless of altitude) under moist lapse conditions. Future studies evaluating the effects of elevation on photosynthesis could benefite of 0.003-degrees-C m-1 resulted in less than a 4% decrease in A(P) over the same altitude range. When natural leaf temperatures (predicted from heat balance analyses) were simulated, A(P) was significantly greater (almost-equal-to 20%) than when leaf temperatures were considered equal to air temperature for all lapse conditions. There was virtually no change inncentration, and (4) the diffusion coefficient for CO2 in air. When a dry lapse rate (0.01-degrees-C m-1) in air temperature was simulated, significant declines (up to 14%) in A(P) were predicted from sea level to 4km altitude. A moist lapse ra3-136^^^^^Jan^^^^^3015a,L^1989^1^Sex expression and sex ratios in intra- and interspecific hybrid families of Salix L^67^A^3014^A simulation of the quantitative influence of altitude on photosynthetic CO2 uptake capability (A(P)) included the effects of predicted changes (1) in air temperature (lapse rate) and (2) leaf temperature, (3) ambient pressure and CO2 coway and acclimation of respiration rates to different climates are poorly understood, but may substantially affect the reliability of model estimates of plant respiration.78^2^Smith,WK^Donahue,RA^1991^1^Simulated influence of altitude on photosynthetic CO2 uptake potential in plants^9^14^1^13ation may decline under CO2 enrichment, but the mechanism, independence from changes in protein content, and acclimation are unknown. Response of respiration to temperature can be modelled as a Q10 relationship, if corrections for bias arising from daily and annual temperature amplitude are applied. Occurrence and control of the cyanide- resistant respiratory pathurnover, water stress, and atmospheric pollutants. For a wide variety of plant tissues, maintenance respiration, corrected for temperature, appears to be linearly related to Kjeldahl nitrogen content of live tissue. Total and maintenance respirm carbon flux will change as the balance between photosynthesis and respiration changes. Partitioning respiration into the functional components of construction, maintenance, and ion uptake will aid the estimation of plant respiration for ecosystems. Maintenance respiration is the component most sensitive to changes in temperature, CO2, protein concentration and tort elicited a large transient engagement of the alternative oxidase when present uninhibited.ns pallida and Impatiens ca77^1^Ryan,MG^1991^1^Effects of climate change on plant respiration^56^1^2^157-167^^^^^May^^^^^3013A^3012^Plant respiration is a large, environmentally sensitive component of the ecosystem carbon balance, and net ecosyster in the presence of the uncoupler carbonyl-cyanide m-chlorophenyl hydrazone. The activity of cytochrome c oxidase of callus tissue homogenates was also inhibited by CO2/bicarbonate. The results suggested that high carbon dioxide levels (mainly free CO2) Partially inhibited the cytochrome pathway (apparently at the oxidase level), and this block in electron transption did not occur in animal tissues such as rat diaphragm and isolated hepatocytes, and was inhibited by salicylhydroxamic acid in carnation callus cells and E. canadensis leaves. This suggested that the alternative oxidase was engaged during the stimulation in plant tissues. The cytochrome pathway was severely inhibited by CO2/bicarbonate either in the absence ooncentration of gaseous CO2 in the solution. These stimulatory responses lasted several minutes and then decreased, but additional bicarbonate or gaseous CO2 again stimulated respiration, suggesting a reversible effect. Carbonic anhydrase in the solution increased the stimulatory effect of potassium bicarbonate. The CO2/bicarbonate dependent stimulation of respira photomixotrophic and heterotrophic carnation (Dianthus caryophyllus L.) callus, of Elodea canadensis (Michx) leaves, and of other plant tissues. This phenomenon occurred at pH values lower than 7.2 to 7.8, and the stimulation depended on the chaping the response of a plant to CO2.^1989^1^Ecophysiology of exotic and native shrubs in southern Wisconsin. I. Relatio76^4^Palet,A^Ribascarbo,M^Argiles,JM^Azconbieto,J^1991^1^Short-term effects of carbon-dioxide on carnation callus cell respiration^8^96^2^467-472^^^^^Jun^^^^^3011A^3010^The addition of potassium bicarbonate to the electrode cuvette immediately stimulated the rate of dark O2 uptake of increase in carbon assimilation per unit leaf area. Although the compensation between photosynthesis and leaf area reduced the potential growth response to CO2, the reduction in leaf area ratio was associated with a significant increase in water-use efficiency. This unexpected result demonstrated the importance of feedbacks and interactions between resources in sal mineral nutrients and in unfertilized plants, although the fertilized plants grew 10-fold larger. The increase in dry weight resulting from elevated CO2 occurred only in root systems. Although leaves were produced continuously during the experiment, leaf area was slightly reduced in elevated CO2, and the whole-plant growth response was wholly attributable to anof mineral nutrients (unfertilized or weekly additions of complete nutrient solution), and three harvests (6, 12, and 24 weeks). Plant growth rate, water use, foliar gas exchange, component dry weights, and nutrient contents were measured. Both hypotheses were rejected. Whole-plant dry weight increased similarly with CO2 enrichment in plants provided with additiones were tested in an experiment in which yellow-poplar plants were grown from seed for 24 weeks in controlled- environment chambers. The experimental design comprised three atmospheric CO2 concentrations (371, 493, and 787 cm3 m-3), two levels tion and nutrient requirements of the species, it was predicted that (1) CO2 enrichment would enhance growth of yellow-poplar seedlings both through accelerated leaf area production and through higher rates of carbon assimilation per unit leaf s that terpenes may have been one of several important leaf characteristics limiting consumption of the low nutrient hostsinteractive 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. Grato 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 tly 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  tation 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 apparen A^2996^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 limite change.ild,AE^Cody,WJ^1980^2^Vascular plants of continental Northwest Territories, Canada^National Museums of Canada^O69^2^Johnson,RH^Lincoln,DE^1991^1^Sagebrush carbon allocation patterns and grasshopper nutrition - the influence of CO2 enrichment and soil mineral limitation^2^87^1^127-134^^^^^^^^^^29976Ȅ/o/\\i/c?Έ3g`Fz(67^3^Idso,SB^Kimball,BA^Allen,SG^1991^1^Net photosynthesis of sour orange trees maintained in atmospheres of ambient and e-increases in primary production, in spite of greater nitrogen limitation, and (2) led to greater storage of carbon in plan*t residues and soil organic matter. The increased carbon storage was not great enough to keep pace with the present rate o/tments in the responses of soil, plants, animals and microbes. Elevated temperature extended the growing season but depres,sed photosynthesis in the summer, with little net effect on annual primary production. Doubling CO2 (1) caused persistent 1was driven with observed weather and with combinations of elevated atmospheric CO2, elevated temperature, and either incre.ased or decreased precipitation. Precipitation and CO2 level accounted for most of the variation among climate change trea3s seasonal dynamics of shoots, roots, soil water, mycorrhizal fungi, saprophytic microbes, soil fauna, inorganic nitrogen,0 plant residues and soil organic matter. Forty-year simulations were made for several climate change scenarios. The model n-model for the effects of climate change on temperate grassland ecosystems^81^53^3-4^205-246^^^^^Apr^^^^^2991$hرyvd2A^2990^We studied the responses of temperate grasslands to climate change using a grassland ecosystem model which simulate7phenylmethyl)-1H-purin-6-amine (BA); 1H-indole-3-butyric acid (IBA); alpha-naphthaleneacetic acid (NAA); thidiazuron (TDZ).al Academy of Sciences (USA), Washington^D.C^^N^^1585S^d&Ɔ>Y÷3!DppRrph466^10^Hunt,HW^Trlica,MJ^Redente,EF^Moore,JC^Detling,JK^Kittel,TGF^Walter,DE^Fowler,MC^Klein,DA^Elliott,ET^1991^1^Simulatio:f 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 microcu6ttings under CO2 enrichment could be the basis for a rapid system of micropropagation for cacao. Chemical names used: N- (a-cacao^154^116^3^585-589^^^^^May^^^^^2989ltraviolet radiation^IN J.G. Titus, ed. Effects of changes in stratospheric ozo>A^2988^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 conven@tional tissue culture protocols, rooted with auxin and developed normally in vivo. Detached axillary shoots from cotyledon9ary nodes and single-node cuttings from mature plants were induced to elongate and produce normal leaves in the presence oBemoval did not reduce shoot weights or reproductive weights of plants in either CO2 treatment relative to control plants. CHowever, plants from both CO2 treatments experienced reductions in root weights with leaf area removal, indicating that plDants compensated for lost above-ground tissues, and maintained comparable levels of reproductive output and seed viability, at the expense of root growth.N^^1591UpPRp#(Т EC/5}7[u9V{W 笈l<65^3^Figueira,A^Whipkey,A^Janick,J^1991^1^Increased co2 and light promote invitro shoot growth and development of theobromGallocated 10% of their carbon resources to reproduction whereas ambient CO2-grown plants allocated over 20%. Effects of siAmulated herbivory on plant performance were much less dramatic than those induced by enriched CO2 atmospheres. Leaf area rIgnificantly greater shoot weights, leaf areas, and root weights, yet had significantly lower reproductive weights (i.e. stJalks + spikes + seeds) and produced fewer seeds, than plants grown in ambient CO2 environments. Relative biomass allocatioFn patterns further illustrated differences in plant responses to enriched CO2 atmospheres: enriched CO2-grown plants only Lae) was grown in either near ambient (380 ppm) or enriched (700 ppm) CO2 atmospheres, and then after 4 weeks, plants experMienced either 1) no defoliation; 2) every fourth leaf removed by cutting; or 3) every other leaf removed by cutting. PlantNs were harvested at week 13 (9 weeks after simulated herbivory treatments). Vegetative and reproductive weights were compaHred, and seeds were counted, weighed, and germinated to assess viability. Plants grown in enriched CO2 environments had sin response to simulated herbivory and elevated CO2 environments^2^87^1^37-42^^^^^^^^^^2987IN B.R. Strain and J.D. Cure, eQA^2986^We tested the prediction that plants grown in elevated CO2 environments are better able to compensate for biomass lKost to herbivory than plants grown in ambient CO2 environments. The herbaceous perennial Plantago lanceolata (PlantaginaceSm 195- 735-mu-mol mol-1 was also examined using individual leaves, attached to the plant, in an environmentally controlledT 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.mps*BхHzoycQaHovSβCqBދDO64^3^Fajer,ED^Bowers,MD^Bazzaz,FA^1991^1^Performance and allocation patterns of the perennial herb, Plantago lanceolata, iWed responses strongly implicated impaired physiology of the guard cells rather than mechanical changes in the epidermis thXat might, for example, result from damage to the cuticle. Stomatal closure was considerably slower in polluted leaves compYared with the controls. This decline in responsiveness to ABA was observed using leaves excised from well-watered plants aRnd in the absence of any externally visible injury. The ability of stomata to respond to a range of CO2 concentrations fro[er loss was then examined after terminating the pollutant treatment. Observations of diurnal changes in stomatal resistanc\e of well- watered plants, using a viscous flow porometer, failed to indicate any major alterations which could be attribu]ted to prior exposure to SO2 + NO2. By contrast, when an ABA solution (10(-1) mol m-3) was applied to detached leaves, theV stomata of polluted plants were less responsive than plants previously exposed to control air. The dynamics of the observ_63^3^Atkinson,CJ^Wookey,PA^Mansfield,TA^1991^1^Atmospheric-pollution and the sensitivity of stomata on barley leaves to abscisic-acid and carbon-dioxide^84^117^4^535-541^^^^^Apr^^^^^2985evaluation of methods and initial results^IN J.H. McBeathaA^2984^Spring barley (Hordeum vulgare L. cv. Klaxon) plants were exposed to mixtures of SO2 + NO2 (at concentrations of 24b-35 nl l-1 of each gas, depending upon fumigation system), or to charcoal-filtered, or unfiltered ambient air during the pZeriod in which the second, and subsequent, leaves were emerging. The ability of individual detached leaves to regulate watd62^3^Woodward,FI^Thompson,GB^McKee,IF^1991^1^The effects of elevated concentrations of carbon-dioxide on individual plants, populations, communities and ecosystems^52^67^^23-38^^^^^Jun3:6:MqdkT3Eھ:-n :_bPو%ifmation severity. Foliar K decreased while deformation increased. In another study, foliage of half the plants of one genotgype received foliar applications of 7 millimolar KH2PO4. Untreated foliage showed significantly greater deformation than threated foliage. Reduced foliar K concentration may cause CO2- enhanced foliar deformation. Reduced K may occur following decreased nutrient uptake resulting from reduced root mass due to the change in partitioning from root to fruit.6`F?LTjth CO2 enrichment exhibited nonepinastic foliar deformation similar to nutrient deficiency symptoms. Foliar deformation vakried among genotypes, increased throughout the season, and became most severe at elevated CO2. Foliar deformation was posiltively related to fruit yield. Foliage from the lower canopy was sampled throughout the growing season and analysed for stearch, K, P, Ca, Mg, Fe, and Mn concentrations. Foliar K and Mn concentrations were the only elements correlated with defornA^2981^Yield increases observed among eight genotypes of tomato (Lycopersicon esculentum Mill.) grown at ambient CO2 (abouot 350) or 1000 microliters per liter CO2 were not due to carbon exchange rate increases. Yield varied among genotypes whilie carbon exchange rate did not. Yield increases were due to a change in partitioning from root to fruit. Tomatoes grown wico protein in the leaf.The measurement of viability^IN Roberts, E.H., ed. Viability of seeds. Chapman and Hall^London^^N^r61^5^Tripp,KE^Peet,MM^Pharr,DM^Willits,DH^Nelson,PV^1991^1^CO2-enhanced yield and foliar deformation among tomato genotypes in elevated CO2 environments^8^96^3^713-719^^^^^Jul^^^^^2982;>rFɱr~GŠ L'ڪ(d܈#lC9Ď@Ƹte (CA-1-P). However, the inhibitor did not seem to be involved in the acclimation response. The degree of carbamylation ofu the rubisco enzyme was unchanged by the CO2 growth regime, except at 900-mu-mol mol-1 where it was reduced by 24%. The acpclimation of rice to different atmospheric CO2 conditions involved the modulation of both the activity and amount of rubiswein, and by 60% on a leaf area basis. For leaves in the dark, the total rubisco activity (CO2/Mg2+- activated) was reduceds by more than 60%. This indicates that rice accumulated an inhibitor in the dark, probably 2- carboxyarabinitol 1-phosphatyr the CO2 concentration range 160 to 900-mu- mol mol-1. When expressed on a leaf area basis, rubisco activity decreased byv 66%. This was accompanied by a 32% decrease in the amount of rubisco protein as a fraction of the total soluble leaf prot{sed significantly with increasing CO2. Although leaf dry weight and leaf area index increased, the overall response was no|t statistically significant. Leaf nitrogen content dropped slightly with elevated CO2, but the response was not statisticaxlly significant. The specific activity of ribulose bisphosphate carboxylase/oxygenase (rubisco) declined significantly ove~mospheric CO2 concentrations in outdoor, computer-controlled, environment chambers under natural solar radiation. The CO2 concentrations were maintained at 160, 250, 330, 500, 660 and 900-mu-mol mol-1 air. Photosynthesis increased with increasizng growth CO2 concentrations up to 500-mu-mol mol-1, but levelled off at higher CO2 values. Specific leaf area also increa60^4^Rowlandbamford,AJ^Baker,JT^Allen,LH^Bowes,G^1991^1^Acclimation of rice to changing atmospheric carbon-dioxide concentration^9^14^6^577-583^^^^^Aug^^^^^2980&Qnm&Dx\E"Jʎ\+-lr*\~\++O <n<]\ :}A^2979^The effects were studied of season-long (75 and 88 d) exposure of rice (Oryza sativa L. cv. IR-30) to a range of atunction for polyamines. The ability of increased CO2 to protect soybeans from O3 damage, however, does not appear to involve polyamine accumulation.`U Un 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 qualitand 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 thaspective 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 500 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 irreA^2971^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 (155^2^Hall,DO^Scurlock,JMO^1991^1^Climate change and productivity of natural grasslands^52^67^^49-55^^^^^Junannotinum L. a56^2^Hocking,PJ^Meyer,CP^1991^1^Effects of CO2 enrichment and nitrogen stress on growth, and partitioning of dry-matter and nitrogen in wheat and maize^92^18^4^339-356^^^^^^^^^^29722>侑Q6yP@؞QU{ikJW=ch concentration and deformation severity. Foliar C exchange rates in the lower canopy were not affected by severity of deformation. Data from these experiments do not support the hypothesis that excess foliar starch is responsible for foliar deformation at elevated CO2.Fbtxݓײ͍!DFj|H-v{ mH0]hr=5AZ*-TϰKҷ lNg#=QZuring Jan.-June 1987 and 1988. In both years, CO2-enrichment increased foliar deformation and foliar starch, but during the season, foliar starch levels decreased while deformation increased. 'Laura' had more deformation, while 'Michigan-Ohio' had higher foliar starch concentration. During an entire season, there was no significant relationship between foliar star54^4^Tripp,KE^Peet,MM^Willits,DH^Pharr,DM^1991^1^CO2-enhanced foliar deformation of tomato-relationship to foliar starch concentration^154^116^5^876-880^^^^^Sep^^^^^29699A^2968^Two cultivars of greenhouse tomato (Lycopersicon esculentum Mill.) were grown with ambient or 1000-mu-l CO2/liter dd. Results support the contention that increasing atmospheric CO2 partial pressures will enhance productivity and N-fixing activity of N-fixing tree seedlings, but that the magnitude of early seedling response to CO2 will depend greatly on plant and soil nutrient status.age nodule weight, total nodule weight per plant, and the amount of leaf nitrogen provided by N-fixation (as indicated by leaf delta-N-15). While CO2 enrichment reduced the N concentration of some plant tissues, whole plant N accretion increasecreased 50% by CO2 enrichment but there was little indication that photosynthate translocation from leaves to roots or that plant N (fixed by Rhizobium) was altered by elevated CO2. In seedlings supplied with soil N, elevated CO2 increased averwithout available soil N, a condition in which seedlings initially experienced severe N deficiency because bacterial N-fixation was the sole source of N. Biomass of leaves, stems, and roots increased significantly with CO2 enrichment (by 32%, 15% and 26%, respectively) provided seedlings were supplied with N fertilizer. Leaf biomass of N-deficient seedlings was inl pressures of 350 and 650-mu-bar (current ambient and a predicted partial pressure of the mid-21st century) and with plus N or minus N nutrient solutions to control soil N status. Of particular interest was seedling response to CO2 when grown lated with N-fixing Rhizobium bacteria and grown in growth chambers for 71 days to investigate interactive effects of atmospheric CO2 and plant N status on early seedling growth, nodulation, and N accretion. Seedlings were grown with CO2 partiairicidia sepium (jacq) walp) exposed to elevated atmospheric carbon-dioxide^2^88^3^415-421^^^^^^^^^^296727-55^^1688A^2966^Seeds of Gliricidia sepium (Jacq.) Walp., a tree native to seasonal tropical forests of Central America, were inocufruiting period stimulated canopy CER, decreased chlorophyll and leaf protein loss, and enhanced fruit set and consequent fruit production.1627-1637^^169253^5^Thomas,RB^Richter,DD^Ye,H^Heine,PR^Strain,BR^1991^1^Nitrogen dynamics and growth of seedlings of an n-fixing tree (Gl41-251^^^^^Nov^^^^^2965^Temperature observations in high arctic plants in relation to microclimate in the vegetation of PA^2964^Short-term carbon dioxide (CO2) enrichment (1000-mu-l l-1 for 10 days), starting 2 weeks after initial bloom, enhanced the leaf CO2 exchange rate (CER) in rockwool-cultured strawberry (Fragaria x ananassa). CO2 enrichment throughout the t effects of the atmospheric CO2 level on net CO2 uptake. In summary, simulations based on EPI indicate that O. ficus-indica may presently be advantageously cultivated over a substantial fraction of the earth's surface, such regions increasing markedly with a future doubling in atmospheric CO2 levels.me^United States Environmental Protection Agency^^N^^169652^2^Sung,FJM^Chen,JJ^1991^1^Gas-exchange rate and yield response of strawberry to carbon- dioxide enrichment^165^48^3-4^2es increased by 43 and 5%, respectively, for the global warming accompanying the elevated CO2. Productivity of O. ficus-indica was at least 15 tonnes dry weight hectare-1 year-1, comparable to that of many agronomic crops, for 20 sites with temperatures always above -10-degrees-C in the contiguous United States and for 12 such sites worldwide under current climatic conditions; such sites increased by 85 and 117%, respectively, under the elevated CO2 condition, mainly because of direcity index (EPI), was used to predict the productivity of O. ficus-indica under current climatic conditions and under those accompanying a possible increase in the atmospheric CO2 level to 650-mu-mol mol-1. Sites with temperatures always above -10- degrees-C and hence suitable for prickly-pear cultivation numbered 37 in the United States and 110 worldwide; such sitsynthetic photon flux density (PPFD). Each of these environmental factors was represented by an index with a maximum value of unity when that factor was not limiting net CO2 uptake over a 24-h period. The water index, the temperature index, and the PPFD index were determined for 87 sites in the contiguous United States using data from 189 weather stations and for 148 sites worldwide using data from 1464 weather stations. The product of these three indices, the environmental productived atmospheric CO2 levels^9^14^7^637-646^^^^^Sep^^^^^2963ts^E.R. Lemon, ed. CO2 and plants. The response of plants to risA^2962^The productivity of the prickly-pear cactus Opuntia ficus- indica, which is cultivated worldwide for its fruits and stem segments, was predicted based on the responses of its net CO2 uptake to soil water status, air temperature and photociated with elevated CO2 concentration, ameliorated the response to the greenhouse climate. Grain yields for the greenhouse climates as compared to current conditions increased, or decreased only slightly, except when the greenhouse climate was assumed to result in severely decreased rainfall.^Reynolds,JF^Shaver,GR^Svoboda,J51^1^Nobel,PS^1991^1^Environmental productivity indexes and productivity for Opuntia ficus-indica under current and elevaties of crop performance under alternate conditions. One such study, presented here, was a yield assessment for rainfed maize under possible "greenhouse" climates where temperature and atmospheric CO2 concentration were increased. An increase in temperature combined with decreased rainfall lowered grain yield, although the increase in crop water use efficiency asso gas exchange to the soil water budget were developed from experimental studies. The model was used to interpret a range of field experiments using observed daily values of temperature, solar radiation, and rainfall or irrigation, where water deficits of varying durations developed at different stages of growth. The relative simplicity of the model and its robustness in simulating maize yields under a range of water-availability conditions allows the model to be readily used for studechanistic model in which temperature regulates crop development and intercepted solar radiation is used to calculate crop biomass accumulation. A soil water budget was incorporated into the model by accounting for inputs from rainfall and irrigation, and water use by soil evaporation and crop transpiration. The response functions of leaf area development and crop3^6^1052-1059^^^^^Nov-Dec^^^^^2961^Effects of global change on the carbon balance of arctic plants and ecosystems^Arctic A^2960^The availability of water imposes one of the major limits on rainfed maize (Zea mays L.) productivity. This analysis was undertaken in an attempt to quantify the effects of limited water on maize growth and yield by extending a simple, mfor which there are few data (e.g. rice). Field studies on the effects of elevated CO2 in combination with temperature, water and nutrition are essential; they should be related to the development and improvement of mechanistic crop models, and designed to test their predictions.ffries,RL^Reynolds,JF^Shaver,GR^Svoboda,J50^2^Muchow,RC^Sinclair,TR^1991^1^Water deficit effects on maize yields modeled under current and greenhouse climates^48^8ater-use efficiency in all plants. The increased productivity of crops with CO2 enrichment is also related to the greater S42^1^Bowes,G^1991^1^Growth at elevated CO2 - photosynthetic responses mediated through rubisco^9^14^8^795-806^^^^^Oct^^^^^A^2944^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 redu`ction, and photorespiratory carbon oxidation, cycles. Both CO2 and O2 are substrates; CO2 also activates the enzyme. In C3ces 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.!2뺏7-6,p; o) and carbonic anhydrase (CA) of greenhouse roses were studied. Plants of Rosa X hybrida 'Red Success' were grown for 2 y ears 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 differen41^2^Beeson,RC^Graham,MED^1991^1^CO2 enrichment of greenhouse roses affects neither rubisco nor carbonic-anhydrase activities^154^116^6^1040-1045^^^^^Nov^^^^^2943^^^^^^^^^^^^^^/%OķX8{{}0_53+ඊ9\@oKKnt-w A^2942^The effect of prolonged CO2 enrichment on the activities of ribulose 1,5-bisphosphate carboxylase/oxygenase (Rubiscs 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.H-:̗W9tn#WCD:/fql}P ^^^2939arion,G M^Henry,G H R^Molgaard,P^Oechel,W C^Jones,M H^Vourlitis,G L^1993^5^Open-top devices for manipulating field40^1^Ball,AS^1991^1^Degradation by Streptomyces viridosporus t7a of plant-material grown under elevated CO2 conditions^163^84^2^139-142^^^^^15 Nov^^^^^2941ld Regions, 28 Sept.-1 Oct. 1993. U.S. Army Cold Regions Research and Engineering LaboraA^2940^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. viridosporu 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.<^xrvZGh ܖ(nL}U]v+!A):P>iOkF- reduction or an increase in this capacity. Pot volume also determined the effect of elevated CO2 on the root/shoot ratio:d 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!38^4^Yelle,S^Beeson,RC^Trudel,MJ^Gosselin,A^1990^1^Duration of CO2 enrichment influences growth, yield, and gas- exchange of 2 tomato species^154^115^1^52-57^^^^^Janer different weather and soil moisture conditions^2^88^^317-324^^1811^^^^^^^^^# 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 reveale%37^2^Wallick,K^Zinnen,TM^1990^1^Basil chlorosis - a physiological disorder in CO2-enriched atmospheres^162^74^2^171-173^^^^^Feb^do not possess\^AXW Wg gk<>'^)eJuą/pоxoQ  f֒CH*lanata^161^164^3^168-173^^^^^Apr85^1^Intraspecific variation in the response to CO{-2} enrichment in seeds and seedlings (36^3^Titus,JE^Feldman,RS^Grise,D^1990^1^Submersed macrophyte growth at low ph .1. CO2 enrichment effects with fertile sediment^2^84^3^307-313^2 -(o #` ^9S9*䃴0 gIxVAN8 :0X51r vV 8BdmZV&Bsס*34^2^Sasek,TW^Strain,BR^1990^1^Implications of atmospheric CO2 enrichment and climatic-change for the geographical-distribution of 2 introduced vines in the USA^50^16^1^31-51^^^^^Feb^^`Y L RhZfQ$%l]ym޶@ڂX*.sť.&35^2^Stuhlfauth,T^Fock,HP^1990^1^Effect of whole season CO2 enrichment on the cultivation of a medicinal plant, digitalis--32^2^Radoglou,KM^Jarvis,PG^1990^1^Effects of CO2 enrichment on 4 poplar clones .2. Leaf surface- properties^52^65^6^627-632^^^^^Junn the xylem of the trunk of Larix and Picea trees--a comparison of xylem flow, porometer and cuvette measurement/33^3^Rey,P^Eymery,F^Peltier,G^1990^1^Effects of CO2-enrichment and of aminoacetonitrile on growth and photosynthesis of photoautotrophic calli of Nicotiana plumbaginifolia^8^93^2^549-554^^^^^Jun<+z<#X>\ʙ 3'rs,mIn_Sֱ-580^^^^^Aug,C L^Neilson,R E^Talbot,H^Jarvis,P G^1985^1^Stomatal conductance and photosynthesis in a mature Scots pine fo231^2^Radoglou,KM^Jarvis,PG^1990^1^Effects of CO2 enrichment on 4 poplar clones .1. Growth and leaf anatomy^52^65^6^617-626^^^^^Junssess)PPFiM9cM; , &lYz[Vvv9{7E)3 l-/PlVC-$Y~1IvpP\rlJ4 of these models required to incorporate directional migration of species are described. To predict establishment success 5of species, we suggest that a more fundamental understanding is needed of how establishment ability under different conditFions relates to seed and seedling attributes and how this may be affected by elevated CO2. Finally, we examine whether pla7ce long distance dispersal events will be critically important in determining migration rates. We examine the JABOWA-deriv8ed gap replacement models and vital attributes/FATE models and ask: what do we need to know about dispersal and establishm3ent to make improved projections of vegetation dynamics under climate change using these models? The minimal modifications:A^3157^The distribution of many plant species will change with global climate change, depending on their ability to disper;se into, and establish in, new communities. Past migrations of species under climate change have been an order of magnitud6e slower than the rate of predicted climate change for the next century. The limited evidence available suggests that chan=tes that are both important in population regulation and responsive to global change. This analysis shows that elevated CO>2 is not likely to have a major influence on probability of insect outbreak, except possibly in systems in which nitrogen-based defensive compounds are produced by plants in response to herbivory. Systems that will have high potential to outbre@ being reached during the simulated period; (3) the spatial distribution of soil moisture changes, presenting a new resourAce base for spatial changes to species composition and growth rates. The major hydroecological responses to elevated CO2 aIre seen as increased maximum upper canopy leaf area, increased litter inputs, especially at times of drought (hence changelobal atmospheric change^182^40^4-5^565-577^^^^^^^^^^3156nthesis in seedlings of three conifers^49^29^^71-78^^1833^^^^^^^DA^3155^There are many possible ways in which changes in the global atmosphere could influence the outbreak potential of heͨH%ڣ$Dnry mass allocation of seedlings of alnus-rubra bong^84^116^1^55-66^^^^^Sepic CO{-2} concentration on growth, photosynthes13^4^Barr,AG^King,KM^Thurtell,GW^Graham,MED^1990^1^Humidity and soil-water influence the transpiration response of maize to CO2 enrichment^146^70^4^941-948^^^^^Oct> J5}(l,aļe߷#3<7S7!/9a̩n;?#|o>Z>11^5^Allen,LH^Valle,RR^Mishoe,JW^Jones,JW^Jones,PH^1990^1^Soybean leaf gas-exchange responses to CO2 enrichment^156^49^^192-198^in intact willow leaves^6^166^^380-388^^1906^^^^^^^^^^^^^^^^^^^^^^^^o@M/E}%Kpy&<-4NC12^2^Arnone,JA^Gordon,JC^1990^1^Effect of nodulation, nitrogen-fixation and CO2 enrichment on the physiology, growth and dtates to elevated CO2^155^20^9^1479-1484^^^^^Sep^1^Effects of CO{-2} enrichment and carbohydrate content on the dark resp10^3^Acock,B^Acock,MC^Pasternak,D^1990^1^Interactions of CO2 enrichment and temperature on carbohydrate production and accumulation in muskmelon leaves^154^115^4^525-529^^^^^JulϘP:! SYCDT:k\"R[gsrʕ2W5sJjujy`Nn~'}Wɽ+ changed from 18 to a 24 h day-1 the diurnal rhythm disappeared. Transpiration followed the same diurnal rhythm as that for photosynthesis. The water-use efficiency was enhanced by raising the CO2 concentration. A decrease in the CO2 concentration from 700 to 350-mu-mol mol-1 after six days at high CO2 first significantly decreased the photosynthesis, but three damu-mol mol-1). Net photosynthesis increased to a maximum after 5-6 and 6-7 h of light at 12 and 18 h day-1 photoperiods, r espectively, followed by a decrease towards the end of the photoperiod. At a photoperiod of 18 h day-1 similar diurnal curves were found at 350 and 700-mu-mol mol-1 CO2, and at 40 and 120-mu-mol m-2 s-1 PPFD. Five days after the photoperiod wasod, co2 concentration and light level^200^42^2^100-105^^^^^Jun^^^^^3388carbon, and water relations of a xylem-tapping mis#A^3387^The diurnal net photosynthesis of Ficus benjamina L., cultivar Cleo, was studied at different daylengths (12, 18 and 24 h day- 1), photosynthetic photon flux densities (40 and 120-mu-mol m-2 s-1 PPFD) and CO2 concentrations (350 and 700-% 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.œ7Ϙnteractions among carbon, nutrient and hydrological cycles; and 5) an excess of carbon production over consumption in seveCificant amount of CO2 emissions from fossil-fuel combustion; 2) probable, human-caused imbalances in C exchanges among vegAetation, soils, and the atmosphere; 3) enhanced C storage in vegetation in response to excess atmospheric CO2; 4) strong iBta, observations, and model simulations that demonstrate: 1) the existence of natural CO2 sinks that could mitigate a signFsis of current research on the carbon cycle, CO2 sinks and associated processes and fluxes, and critical research needs toD assess the potential role of forest and land-use management in carbon sequestration. The papers in this volume present daE CO2 presented in this special issue and its companion hard-bound volume of Water, Air, & Soil Pollution, provide a syntheIA^3381^Natural CO2 sinks in terrestrial and marine environments are important components of the global carbon cycle, yet tGhe sign and magnitudes of key fluxes among them are unknown. The results of the Palmas Del Mar Workshop - Natural Sinks of439-453^^^^^Aug^^^^^3382}i Ѥ":QHmH"~XK-Hj?_/$zL*NfZ;.dryland rice areas and could make it possible to slightly expand them.s for monitoring vegetation^102^8^^127-150^^2098^^^J272^2^Downing,JP^Cataldo,DA^1992^1^Natural sinks of co2 - technical synthesis from the palmas-del- mar workshop^94^64^1-2^Kures. The expected increase in water-use efficiency due to enhanced CO2 might decrease the water deficit vulnerability of O varies with each model. Predictions of changes in rainfall vary widely between models. Global warming should in principleM allow a northward expansion of rice-growing areas and a lengthening of the growing season now constrained by low temperatNdoubling in atmospheric carbon dioxide (CO2) concentration. The regional seasonality and extent of the rise in temperatureRons correlate well with the observed values. Predictions of monthly rainfall correlate poorly. Virtually all models agree Pthat significant increases in temperature (from 1 to 7-degrees-C) will occur in the region including Thailand following a Qmatic conditions in Thailand are compared to predictions from four general circulation models (GCMs). Temperature predictiUA^3379^In Thailand, the world's largest rice exporter, rice constitutes a major export on which the economy of the whole cSountry depends. Climate change could affect rice growth and development and thus jeopardize Thailand's wealth. Current cli^347-366^^^^^Aug^^^^^3380ƛ&‘кZ9 jB D 3-day eggs > first instar. The four species exhibited a trend of tolerance of C pomonella > E. postvittana = P. oct\tolerance to this CA was similar for E. postvittana, C. pomonella, P. octo, and C. obliquana i.e., fifth instar > third in_levating the treatment temperature enhanced controlled atmosphere (CA) efficacy more than did increasing the CO2 concentra]tion. Thus at 20-degrees-C, a 0.4% O2/5.0% CO2 CA gave the most rapid kill of the mixtures tested. The order of lifestage ^s reviewed and additional data are presented. For both E. postvittana and C pomonella, reducing the O2 concentration and ebA^3377^Work on the mortality responses of four lepidopteran pests of apples in New Zealand-Epiphyas postvittana (Walker), `Cydia pomonella (L.), Planotortrix octo Dugdale, and Ctenopseustis obliquana (Walker)-to low O2/moderate CO2 atmospheres ist disinfestation of new-zealand apples^199^20^2^217-222^^^^^^^^^^3378Zt<"Hwp b)6|2pYd(4,Fated before making a general recommendation.xide concentration on respiration of growing and mature soybean leaves^9^18^^c270^3^Whiting,DC^Vandenheuvel,J^Foster,SP^1992^1^Potential of low oxygen moderate carbon-dioxide atmospheres for postharvedrs and preventing over-ripening, further work is needed on other cultivars, and lower O2 concentrations should be investighsed O2 concentration in absence of high CO2 showed some benefit in 'July Red'. No deleterious effect of CO2 concentrationsf even as high as 20% could be detected. Thus, even though high CO2 in CA conditions showed promise for controlling disordegng ripening, the best results being mostly obtained with 20% CO2. O2 levels assayed did not show clear effects, but decreaked water loss and ripening, increasing fruit softening markedly. Conversely, high CO2 delayed fruit ripening in CA storagei, keeping the fruit firmer, and preventing the development of woolliness, internal browning and reddish discoloration durijbsence of elevated CO2 levels but did not affect internal browning and increased reddish discoloration; further, it enhancn. The fruit was evaluated following cold storage, 31 days after harvest, and after four and eight days under 'shelf conditlions'(ripening at 15-18-degrees-C). Warming of the fruit at 20-degrees-C before cold storage prevented woolliness in the amcontrolled atmosphere (CA) conditions at 0-degrees-C. Combinations of 0, 10, 15 and 20% CO2 with 8 and 16% O2 were assayedep^^^^^3376k,L G^Watkinson,A R^Norton,L R^Ashenden,T W^1995^1^Plant populations and global environmental change: the efferA^3375^A storage experiment was aimed at preventing low temperature storage disorders in nectarine fruits, of cvs July Redo and Autumn Grand. Fruit was either cooled immediately after harvest or kept at 20-degrees-C for 48 h, before transfer to p269^4^Retamales,J^Cooper,T^Streif,J^Kania,JC^1992^1^Preventing cold-storage disorders in nectarines^174^67^5^619-626^^^^^Su Finally, building on the previous example by using two different models, this study illustrates that results can be strongly model dependent and encourages extreme caution in their interpretation. ͵S +`0& `ӲKapF 0$ N tstudy, the analysis of the results shows how, in a greenhouse warmed world, St Paul, MN, might look like North Platte, NE.xered in future studies of this kind. The paper also provides explanations regarding the movement of ecotones, defined as tvhe transition zones between different vegetation assemblages. Taking the North American forest/prairie boundary as a case w are likely major factors in determining the ecosystem response to greenhouse warming. Consequently, they should be consid{tput of an atmospheric general circulation model (GCM). Within this context, the paper demonstrates through the examples iyt analyses that both potential stomatal response to CO2 and the possible range of changes in atmospheric relative humidity~y (predator or parasitoid) control of the dormant phase of herbivorous insects may be very important in preventing or allo|bal changes that increase environmental stress on host plants are most likely to favour sap-feeding insects. Critical enem R163^4^Allen,LH^Drake,BG^Rogers,HH^Shinn,JH^1992^1^Field techniques for exposure of plants and ecosystems to elevated co-2 teraction are discernible in different combinations of factors. All three factors at the upper level appreciably induced activity of phosphoenolpyruvate carboxylase (PEPCase) in cotton leaves.^^^^^^^^^^^^^^^^^^^8 ])~5rsTd X zlogically based water budget and an explicit treatment of ecological dynamics. In principle, EXE could be forced by the ounts the results of numerical simulations performed with the Energy, water and momentum exchange, and Ecological dynamics (EXE) model at a local scale over periods of 400-800 (simulation) years. EXE constitutes a first attempt to couple a physiotions of the interactions between climate, plant physiology and ecology are badly needed. In this spirit, this paper preseanges in the ambient concentration of CO2. This may have important consequences for agriculture and natural resource exploitation. A formal recognition of atmosphere/biosphere interrelationships is crucial but insufficient. Systematic investigaeric chemistry. In particular, it partially controls the carbon cycle. In turn, vegetation is influenced by climate and chA^3373^Vegetation plays a significant role in determining the local and regional hydrology of ice-free continental surfaces and the dynamics of the atmosphere above it. Vegetation also influences the global climate directly by affecting atmosphas not significantly affected. In both data sets direction of responses was variable. A sensitivity analysis of carbon budsed on a leaf weight basis (14%). For the few data on root respiration, no significant change due to high CO2 could be detected. Carbon content of leaves and stem showed a small increase (1.2 and 1.7% respectively), whereas C-content of roots wfactors in the growth-response of plants to elevated CO2^182^40^4-5^501-513^^^^^^^^^^3168L@HpϷ uV$b؇$0*Elevated CO2 might not increase survival of C3 Plants under dry conditions, if temperatures are too high for them.em.pre157^4^Poorter,H^Gifford,RM^Kriedemann,PE^Wong,SC^1992^1^A quantitative-analysis of dark respiration and carbon content as 82^40^4-5^717-735^^^^^^^^^^3374il㖊m1#e!Pt};|;|H+7; ܑcɜw!`iCpjS` Z"Sig?gets under elevated CO2 identified changes in respiration rate, and to a lesser extent carbon content, as important factors affecting the growth response to elevated CO2 in quite a number of cases. Any comprehensive analysis of growth responseseginning of the study, Poa pratensis (Kentucky bluegrass), the dominant C3 species, had the highest frequency of 43.3%, bundrical plastic chambers were placed on the prairie to maintain two levels of CO2 (ambient or twice ambient) during two growing seasons in 1989 and 1990. Frequency of species was determined on 25 July 1989 and on 5 and 10 October 1990. At the bwater regime, the reverse occurred (frequencies: 3.6 % and 11.0 % for high and low CO2, respectively). The frequency of mat decreased with time. However, at the end of the experiment and under the high soil-water level, there were more P. pratensis plants in the elevated CO2 treatment (frequency: 13.5%) than in the ambient CO2 treatment (1.0%). Under the low soil f the climate becomes drier, A. scoparius will flourish more than S. nutans or A. gerardii, and P. pratensis may die out. d of the study, Indian grass grown with high water had the highest frequency of all species on the prairie (frequency at the end of the study in October, 1990, of 44.4% and 47.4% for the high and low CO2 levels, respectively). Unlike Indian grass, little bluestem grew better under low water conditions than under high water conditions. These results suggest that, ibetween 1989 and 1990. Under both soil moisture levels, the frequencies of S. nutans and A. scoparius increased. At the enjor C4 plants, Andropogon gerardii (big bluestem), A. scoparius (little bluestem) and Sorghastrum nutans (Indian grass) was not affected by CO2. However, water did affect their frequency. Under low water, the frequency of A. gerardii decreased f deforestation, would result in much higher predicted concentrations and rates of increase of atmospheric CO2 and, as a cic CO2 concentrations. Predictions which take account of the combined effects of deforestation, the return of carbon previously stored through the CO2 'fertilisation effect' and the loss of a large proportion of the 'missing sink' as a result oe effects have not been considered in the IPCC (Intergovernmental Panel on Climate Change) projections of future atmospherredicting future CO2 concentrations. If tropical rainforest destruction continues then much of the CO2 stored as a result of the CO2 'fertilisation effect' will be rereleased to the atmosphere and much of the 'missing sink' will disappear. Theself be playing an important role in enhanced carbon storage by tropical rainforests. This has important implications for pte the possibility that a significant net CO2 uptake (> 1 Pg C yr- 1), a CO2 'fertilisation effect', may be occurring in tropical rainforests, effectively accounting for much of the 'missing sink'. This sink may currently balance much of the CO2 added to the atmosphere from deforestation and biomass burning. Interestingly, CO2 released from biomass burning may itsprobable rates of carbon sequestration for the major ecosystem complexes and global 3-D tracer transport model runs indicaA^3371^The biosphere plays an important role in determining the sources, sinks, levels and rates of change of atmospheric CO2 concentrations. Significant uncertainties remain in estimates of the fluxes of CO2 from biomass burning and deforestation, and uptake and storage of CO2 by the biosphere arising from increased atmospheric CO2 concentrations. Calculation of 267^2^Taylor,JA^Lloyd,J^1992^1^Sources and sinks of atmospheric co2^182^40^4-5^407-418^^^^^^^^^^3372have underestimated tropical NPP by a factor of about 2, then it is unlikely that CO2-ECS could have negated the 1.5- 3.0 Gt of carbon that are estimated to have been emitted by tropical deforestation in 1990.ween plants and microbes?^2^103^^4^^^^^^33702^^^^^^^^^^^^^^^^^^^^^^^^rtainties in this (and other) models; total CO2-ECS is particularly sensitive to changes in NPP. Unless published surveys ere in 1990 was 1.1 Gt. When more appropriate values of beta were used (derived from a theoretical response of vegetation to increasing temperature and CO2), CO2-ECS was 1.3 Gt, of which tropical biomes accounted for 0.7 Gt. There are many uncery production (NPP) and atmospheric CO2 concentration. Using beta = 0.3 as a reference state, CO2-ECS by the global biosphthat CO2-enhanced carbon storage (CO2-ECS) by tropical biomes is negating the output of CO2 from deforestation. We describe here a 10-biome model for CO2-ECS, in which carbon accumulation in living vegetation is coupled to the Rothamsted soil carbon model. A biotic growth factor (beta) was used to describe the relationship between literature estimates of net primae experiments with other GCMs.s 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 greenhousriod of such events decreases markedly. If realistic, the findings have potentially serious practical implications in terman CO2 treatments.988^1^Variation in leaf dissection and leaf energy budgets among populations of {iAchillea} from an altd for four selected regions of interest. In all regions the frequency of high rainfall events increases, and the return pe feed back inhibition. Carbohydrate partitioning within the plant organs were predominantly governed by N supply levels th starch glucose, fructose, and sucrose and in tuber starch concentrations. Photosynthetic reduction at low N supply showed a significant correlation with leaf starch concentration at both CO2 levels indicating that the inhibition is a result ofls, after seven weeks of reduction in NO3 supply. In leaves lowest NO3 treatment increased starch and sucrose and in rootsas not affected by N deficiency at both CO2 levels. Low NO3 had a lesser effect on photosynthesis than on leaf area growth; photosynthetic rates of mature leaves at both CO2 levels were lowered by about 30 % as compared to the respective contros-1 per mu-l intercellular CO2 l-1) was reduced by both low N supply and CO2 enrichment. Intercellular CO2 concentration w uptake of plants at all N supply levels. Water use efficiency, photosynthesis and stomatal conductance were increased by high CO2 only at 1.0 and 6.0 mM supply and reduced at the lowest N level. Photosynthetic efficiency (mu-Mol CO2 fixed m-2 f N-nutritional regimes (0.1, 1.0 or 6.0 mM nitrate supply). Carbon dioxide enrichment significantly increased total waterr gongylodes L) .1. Water-use, gas-exchange, and carbohydrate partitioning^172^57^3^138-145^^^^^May-Jun^^^^^3328 S^YurtseA^3327^Six weeks old kohlrabi plants (Brassica oleracea var, gongylodes [L.] cv. Express Forcer) were grown in growth chambers for three weeks at two levels of CO2 concentration (300-mu-l CO2 l-1-low or 900-mu-l CO2 l-1-high) and three levels o243^2^Sritharan,R^Lenz,F^1992^1^Effects of carbon-dioxide enrichment and nitrogen supply on kohlrabi (brassica-oleracea vad complexities in understanding mineral availability and plant mineral nutrition.ber traps": some considerations^113^28^^69-242^^2202^^^^^^^^^^^^^^^^^^^^^^^^c evaluations of the effects of climate change on plant growth will be challenged to contend with the large uncertainty an organic matter deposition in the soil. On the other hand, increased temperature and altered rainfall patterns may result in increased losses of soil minerals. Even the direction in the net change in available soil minerals is unclear. RealistiA^3325^The limiting factor concept has often been used to describe plant growth responses to altered availability of resoufree-living organisms and symbiotic systems, and improve soil properties for mineral availability as a result of increasedls. Consequently, it is very difficult to predict the plant growth response to climate change because of the large uncertainty about mineral availability. On the one hand, increased CO2 concentrations should stimulate nitrogen fixation by both e response to increased CO2 concentration, for example, requires an increase in plant uptake of the total amount of mineraously limiting. Further, in considering the limitation in plant growth to mineral nutrition it is important to consider both the solution concentration and the total amount of the individual minerals available to the plant. Sustaining a positivneral availability on plant growth. It is proposed that these resources for plant growth may be better viewed as simultanerces. However, even preliminary experiments, where atmospheric CO2 concentrations and solution mineral concentrations were varied, demonstrated that a more complex concept was required to interpret the potential effects of climate change and mi0/20- degrees-C) and the 23/14-degrees-C treatments gave the shortest and tallest plants, respectively.^^^^^^^^^^^^^^^^^^242^1^Sinclair,TR^1992^1^Mineral-nutrition and plant-growth response to climate change^78^43^253^1141-1146^^^^^Aug^^^^^332ith the 23/14-degrees-C treatment compared with the effects of the other temperature treatments. A constant temperature (2icant interactions between CO2 and temperature were found. Plant dry weight and fresh weight of flowers in Kalanchoe were generally enhanced by CO2 enrichment. The effects of CO2 on dry weight, plant height and flower stem length were greater wer than with the other temperature treatments. The results were the same for Rosa cultivars 'Frisco' and 'Kiss'. No signiflength and diameter of the rose shoot, while the number of days until flowering was not affected. With the 17/26-degrees-C treatment, rose shoots were 3-4 cm shorter, and with the 23/14- degrees-C treatment flowering occurred about 2 days earlirease in the CO2 concentration resulted in enhanced total dry weight, stem: leaf fresh weight ratio, flower fresh weight, rees-C day/night, and 20/20-degrees-C with 2 h at 14- degrees-C in the morning) were studied in 16 growth chambers. An incanchoe blossfeldiana at four different day/night temperature combinations (20/20-degrees-C, 23/14-degrees-C and 17/26- deg241^2^Mortensen,LM^Moe,R^1992^1^Effects of co2 enrichment and different day night temperature combinations on growth and fet ecosystem CO2 flux can be accurately tracked with this system. Field measurements indicate net ecosystem CO2 loss under temperatures, or net ecosystem CO2 flux. Chamber effects are generally small, and the experimental design allows separatio n and interpretation of treatment effects despite any unavoidable chamber effects. Both diurnal and seasonal patterns of n of ambient values. Comparison to unenclosed tundra indicates minimal chamber effects on depth of thaw, air, leaf, or soil mbers average within 1-degrees-C of ambient or target temperatures over a 24-h period and carbon dioxide concentration con trol rivals that of laboratory-based, control- environment systems. Photon flux density within the chambers is within 93% olved in tracking a naturally fluctuating environment, the CO2LT system performs very well. Temperatures in individual cha (150-200-mu-l l-1) to more than 900-mu-l l-1. Air temperature can be fixed, set to track ambient, or can track ambient tem perature with a specified offset allowing studies of the interaction of CO2 and temperature. Despite the complications inv concentration and temperature. Carbon dioxide can be maintained in each chamber at concentrations from well below ambient measure the instantaneous ecosystem-level CO2 exchange rates within each of the plots under the treatments imposed. This is a computer-controlled, closed, null-balance greenhouse system consisting of 12 chambers with individual control of CO2 u ecosystem-level manipulation of atmospheric CO2 concentration and temperature for intact plots of tussock tundra, and to 228^6^Oechel,WC^Riechers,G^Lawrence,WT^Prudhomme,TJ^Grulke,N^Hastings,SJ^1992^1^Co2lt an automated, null-balance system for studying the effects of elevated co2 and global climate change on unmanaged ecosystems^43^6^1^86-100^^^^^^^^^^3301itrog A^3300^An automated, CO2-controlled, long-term greenhouse system ('CO2LT') has been developed to provide replicated in sit to consider leaf age in assessing response to elevated CO2.  K y the developmental characteristics of the leaf. Further, both biochemical and structural modifications appear to be invol ved in this response. Because of the very different responses of young versus old leaves, future studies should be careful is at low CO2 was limited by CO2 regardless of developmental environment, whereas photosynthesis at high CO2 was limited b ed 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 photosynthes "227^3^Kelly,DW^Hicklenton,PR^Reekie,EG^1991^1^Photosynthetic response of geranium to elevated co2 as affected by leaf age r in Sungro. Differences between hybrids and their response to water stress is discussed in relation to control of RuBP regeneration.asses: an evaluation with {+13}C labeling^2^105^^151-159^^2320^^^^^^^^^^^^^^^^^^^^^^^^ CO2. Similarly, leaves developed at low CO2 switched to high CO2 for various lengths of time, and returned to low CO2 show enhancement. Middle-aged leaves exhibited a temporary depression followed by permanent enhancement. Leaves developed at hi gh CO2 and switched to low CO2 did not exhibit any photosynthetic depression relative to plants grown continuously at low es grown at 350-mu-L.L-1 CO2 were switched to 1000-mu-L.L-1 CO2. Leaves switched later in development exhibited permanent ged leaves; very young leaves exhibited little enhancement, and net photosynthesis in the oldest leaves was depressed by e levated CO2. Temporary increases in net photosynthesis (relative to leaves developed at high CO2) resulted when young leav d by leaf age and by leaf position was determined. Elevated CO2 enhanced photosynthesis to the greatest extent in middle-aand time of co2 exposure^188^69^11^2482-2488^^^^^Nov^^^^^3299es among temperate, subarctic, and arctic species grown unde !A^3298^Geranium plants were grown from seed in chambers maintained at 350 or 1000-mu-L.L-1 CO2. Photopsynthesis as affecte t of RuBP from approximately 130 to 40 micromoles per square meter in SH-3622 and from 80 to 40 micromoles per square mete & photosynthesis; neither was decreased stomatal conductance (or stomatal "patchiness"). Reduction of photosynthesis per un $it leaf area from 25 to 5 micromoles CO2 per square meter per second in both hybrids was caused by a decrease in the amoun %d Rubisco protein, and Rubisco activity and activation state were small and were not sufficient to explain the decrease in )3622 had more, smaller cells per unit area and 60% more RuBP per unit leaf area than that of Sungro-380. Water stress deve 'loping over 4 days decreased the assimilation of both hybrids similarly. Changes in the amounts of chlorophyll, soluble an (tivity of Rubisco and its activation state did not differ significantly between hybrids. However, unstressed leaves of SH- , ribulose-1,5- bisphosphate (RuBP) were determined to assess the factors regulating the differences in assimilation of the * hybrids at high and low water potentials. The amounts of chlorophyll, soluble protein, Rubisco protein and the initial ac +total soluble and ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) protein, and in Rubisco activity and amount of /ht and elevated CO2; the carboxylation efficiency was also larger. Growth at large photon flux increased assimilation rate -s of both hybrids. The changes in leaf composition, including cell numbers and sizes, chlorophyll content, and amounts of .mature leaves of SH-3622 under well-watered conditions was approximately 30% greater than that of Sungro-380 in bright lig 2A^3296^The effect of short-term water stress on photosynthesis of two sunflower hybrids (Helianthus annuus L. cv Sungro-38 00 and cv SH-3622), differing in productivity under field conditions, was measured. The rate of CO2 assimilation of young, ^98^2^516-524^^^^^Feb^^^^^3297'6^ܐF+F9Ft >^ܐ$F^㋏$"؎&^ܐF discussed.ja,E^Kapiainen,K^Niemel,P^Tuomi,J^1983^1^Plant availability hypothesis and other epxlanations of herbivore cy 3226^3^Gimenez,C^Mitchell,VJ^Lawlor,DW^1992^1^Regulation of photosynthetic rate of 2 sunflower hybrids under water-stress^8 4a, thus enhancing photosynthesis and growth. The relevance of the results to removal of atmospheric CO2 by marine algae is 8ng H+. Photosynthesis of the alga was found to be enhanced in the seawater of elevated dissolved inorganic carbon (DIC, CO 62 + HC O3- + CO3-). It is concluded that the increased pH in the light resulted in the increase of DIC in the culture medi 7 the photosynthetic conversion of HCO3- to OH- and CO2 proceeded much faster than the dissociation of hydrated CO2 releasi ;elis, were cultured using aeration with high CO2. It was found that the higher the CO2 concentration, the faster the growt 9h of the thalli. Aeration with elevated CO2 lowered pH in dark, but raised pH remarkably in light with the thalli, because :A^3294^Leafy thalli of the red alga Porphyra yezoensis Ueda, initiated from conchospores released from free-living conchoc >225^6^Gao,K^Aruga,Y^Asada,K^Ishihara,T^Akano,T^Kiyohara,M^1991^1^Enhanced growth of the red alga porphyra-yezoensis ueda in high co2 concentrations^187^3^4^355-362^^^^^Dec^^^^^3295>t\FI^㋇FFLN؎&L xport in the light phase of the diurnal cycle as plants adjust to enriched CO2 and a more rapid growth rate."  Antrol. 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 e @ximately 7 days, assimilate export in the light began to increase and by 12 days reached rates 3 to 5 times that of the co Devident in the two leaf types. Net CO2 exchange rate (CER) immediately increased and remained elevated in high CO2. Initia Blly, the additional assimilate at high CO2 levels in the light and was utilized in the subsequent dark period. After appro Cfor 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 Goccur over time when plants are exposed to enriched atmospheric CO2. We examined assimilate relations of source (primary u Enifoliolate) and developing sink (second mainstem trifoliolate) leaves of soybean [Glycine max (L.) Merr. cv. Lee] plants FA^3292^Evidence from previous studies suggested that adjustments in assimilate formation and partitioning in leaves might J224^3^Cure,JD^Rufty,TW^Israel,DW^1991^1^Assimilate relations in source and sink leaves during acclimation to a co2-enriched atmosphere^37^83^4^687-695^^^^^Dec^^^^^3293^^^^^^^^^^^^^؎F&FL 9F@!F搛"rFFto respond to elevated levels of atmospheric CO2.^ʐ>L tFF؎&^F M seasons, the photosynthetic capacity has actually increased by 31%. An increase in photosynthetic capacity has been obser Kved in other species growing in the field, which suggests that photosynthesis of certain field grown plants will continue L, it was shown that, for a wild C3 species growing in its natural environment and exposed to elevated CO2 for four growing PA^3290^While a short-term exposure to elevated atmospheric CO2 induces a large increase in photosynthesis in many plants, Nlong-term growth in elevated CO2 often results in a smaller increase due to reduced photosynthetic capacity. In this study^9^14^9^1003-1006^^^^^Dec^^^^^3291t >L t[FH^㋇vvp$r$؎&F environment.L^Ericson,L^1987^1^Dynamics of tundra and taiga populations of herbaceous plants in relation to the Tihomiro Q223^2^Arp,WJ^Drake,BG^1991^1^Increased photosynthetic capacity of scirpus-olneyi after 4 years of exposure to elevated co2 R two cultivars suggest that lines of rice could be identified that would maximize reproductive output in a future high CO2 Vrences in reproductive characteristics were also observed between cultivars at an elevated CO2 environment with a signific Tant increase in harvest index for IR-36 but not for Fujiyama-5. Changes in carbon allocation in reproduction between these Upproximately the same in both cultivars, although differences in allocation patterns were noted in root/shoot ratio. Diffe Ytosynthetic response at 5% CO2 and the response of CO2 assimilation (A) to internal CO2 (C(i)) suggest a reallocation of b Wiochemical resources from RuBP carboxylation to RuBP regeneration. Increases in total plant biomass at elevated CO2 were a dA^3288^Two rice (Oryza sativa L.) cultivars of contrasting morphologies, IR-36 and Fujiyama-5, were exposed to ambient (36 \222^2^Ziska,LH^Teramura,AH^1992^1^Intraspecific variation in the response of rice (oryza-sativa) to increased co2 - photosynthetic, biomass and reproductive characteristics^37^84^2^269-276^^^^^Feb^^^^^3289w ݆f^ҐF!9F>@ ularge and small subunit transcripts.v >t |^Fx$>F" >uE>x$t _th subunit polypeptides. We have found that this decrease in synthesis of large and small subunits results from specific a ]nd coordinated down-regulation of translation of both subunits possibly resulting, at least in part, from modification of ^ells that had been transferred from elevated CO2 to limiting CO2 exhibit transient declines of label incorporation into bo borganic carbon. A correlation between limiting inorganic carbon-induced induction of the CO2-concentrating mechanism and d `ecreased synthesis of the large and small subunits of ribulose 1,5-bisphosphate carboxylase/oxygenase has been observed. C Xh cultivars and photosynthetic enhancement was still evident after 3 months of exposure to a high CO2 environment. The pho e0-mu-l l-1) and ambient plus 300-mu-l l-1 CO2 from time of emergence until ca 50% grain fill at the Duke University Phytot cron, Durham, North Carolina. Exposure to increased CO2 resulted in about a 50% increase in the photosynthetic rate for bot a enables the cell to photosynthesize efficiently with little oxygen inhibition, even in conditions of limiting external in hA^3286^In conditions of limiting external inorganic carbon, the unicellular alga Chlamydomonas reinhardtii induces a mecha fnism to actively transport and accumulate inorganic carbon within the cell. A high internal inorganic carbon concentration1414^^^^^Apr^^^^^3287!6! 6@  " D Fi^㋇FFmass development, but is favoured by elevated CO2 levels even more than the leaves.hapin,FS,III^1996^1^Siberian CO{-2} ef l221^3^Winder,TL^Anderson,JC^Spalding,MH^1992^1^Translational regulation of the large and small subunits of ribulose bispho isphate carboxylase oxygenase during induction of the co2-concentrating mechanism in chlamydomonas-reinhardtii^8^98^4^1409- jation somewhat higher than in air (500 ppm). while higher CO2 pressure restrains growth. Root growth reflects the leaf bio oa CO2 deficit. Decrease in growth rate during the summer can be avoided through CO2 addition in July when CO2 availability m is low and epiphytes are thriving. Growth of J. bulbosus in the laboratory is stimulated by CO2 addition up to a concentr nA^3284^The unusual growth pattern exhibited by Juncus bulbosus L. in a slightly acidic Swedish brown-water lake is due to r220^1^Svedang,MU^1992^1^Carbon-dioxide as a factor regulating the growth dynamics of juncus-bulbosus^159^42^3^231-240^^^^^Apr^^^^^3285ge at Barrow, Alaska^56^5^^846-855^^2378^^^^^^^^^^^^^^^^^^^^^^^^$?Qlnd biodegradation of this very complex compound.F####$$$"#( uinhibited both growth and chlorophyll synthesis. Release of lignin into the nutrient medium was observed in several experi vments, especially in slow-growing cultures supplemented with sucrose. Only a few successive passages of suspensions that p sroduced lignin could be cultured before cell death. The cultures releasing lignin may be unique for studies on synthesis a twith low (0.5%) sucrose or without any carbohydrate source, suggesting photomixotrophism. A high concentration of kinetin yved on a medium containing 2% sucrose and a low level of organic nitrogen (0.25 mM arginine and 0.5 mM glutamine) suppleme nted with 2,4-D (0.5-mu-M) and kinetin (2.5-mu-M). The same medium with 4% sucrose gave the best growth response, but a ne x chlorophyllous embryo callus in an elevated CO2 (2%) atmosphere. A continuous chlorophyllous suspension culture was achie |A^3282^The effect of different concentrations of sucrose (0-4%) and of two growth regulators (0-50-mu-M 2,4-D and 0-25-mu- zM kinetin) was tested on growth and chlorophyll content of suspension cultures of Picea abies (L.) Karst. originating from^37^84^3^374-379^^^^^Mar^^^^^3283: ? b        ants that experienced long-term low humidity.sodium and potassium on mineral balance in captive meadow voles ({iMicrotus }219^3^Simola,LK^Lemmetyinen,J^Santanen,A^1992^1^Lignin release and photomixotrophism in suspension-cultures of picea-abies ~curred only in the plants grown in low humidity. These results may be related to enhanced dehydration resistance of the pl n both high and low humidities were caused by CO2 enrichment. Elevated water content (kg m-2 leaf area) caused by CO2 enri chment, higher water content at a given water potential, and notably lower rate in desiccation from detached leaves all oc s-C and CO2 concentrations of 350 or 650-mu-mol mol-1. Elevated leaf water potentials of the water-stressed plants grown imidity, and carbon-dioxide^4^139^5^600-604^^^^^Mar^^^^^3281ent mineralization and fungal spore composition of fecal pelle A^3280^Well watered and water-stressed Abutilon theophrastic, were grown with relative humidity of 45% or 85% at 30-degree 218^2^Luo,YH^Strain,BR^1992^1^Leaf water status in velvetleaf under long-term interactions of water-stress, atmospheric hu 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 a 12 months, we have determined the fine-root biomass in the top 0.4 m of the soil profile beneath the trees. Results from sures with clear plastic walls for 3.5 years. For the last 3 years of this period, half of the trees have been continuousl y exposed to air enriched with CO2 to 300-mu-mol mol-1 above the ambient concentration. At 2-month intervals over the last A^3278^Sour orange trees have been grown from the seedling stage out- of-doors at Phoenix, Arizona, USA, in open-top enclo 217^2^Idso,SB^Kimball,BA^1992^1^Seasonal fine-root biomass development of sour orange trees grown in atmospheres of ambient and elevated co2 concentration^9^15^3^337-341^^^^^Apr^^^^^3279^^^^^^^^^^^^^^^^^^^^^^^^7!;!?!E!first 36 d of growth.^!c!i!n!r!v!!!!!!! re conditions was approximately 25% greater in leaves of plants grown in high CO2, despite the reduction in leaf conductan ce. Greater assimilation rate was one factor allowing plants grown in high CO2 to incorporate 30% more biomass during the ly slightly less than that of leaves grown in 35Pa CO2, net photosynthesis measured at the growth CO2, light and temperatu n 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 on the only difference between CO2 treatments being a slight reduction in the slope of the line relating Vc(max) to leaf N i 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, gh CO2 plants, the photosynthetic characteristics of leaves in both treatments were similar, although the maximum rate of egression techniques, but in order to achieve reasonable fits, it was necessary to include a phosphate limitation resultin g from inadequate triose phosphate utilization. Despite the accumulation of large amounts of starch (> 50 g m-2) in the hi ted model of C3 leaf photosynthesis was parameterized for leaves from both CO2 treatments using non-linear least squares r282^^^^^Apr^^^^^3277^Predicting the response of populations to environmental change^11^76^^926-941^^2406^^^^^^^^^^^^^^^^^ A^3276^Cotton plants were grown in CO2-controlled growth chambers in atmospheres of either 35 or 65 Pa CO2. A widely accep 216^4^Harley,PC^Thomas,RB^Reynolds,JF^Strain,BR^1992^1^Modeling photosynthesis of cotton grown in elevated co2^9^15^3^271- ty. However, the biomass increase made up for this reduction in such a way that the total nitrogen pool per tree remained unchanged.rnicus}^2^59^^167-177^^2408^^^^^^^^^^^^^^^^^^^^^^^^!!""["}"" dioxide enrichment significantly reduced the nitrogen concentration in all organs, irrespective of the nutrient availabili 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 tly increased total biomass by about 20%, both on fertilized and on unfertilized forest soil. However, the partitioning of eedlings (Castanea sativa Mill), grown in pots outdoors throughout the vegetative season. Fertilization had a pronounced e ffect on dry weight accumulation, tree height, leaf area, and plant nitrogen content. Carbon dioxide enrichment significan g levels of mineral nutrition on dry weight, nitrogen accumulation and partitioning were examined in 2-year-old chestnut s on soil nutrient availability in sweet chestnut (castanea-sativa mill)^186^49^2^83-90^^^^^^^^^^3275 {iMicrotus californi A^3274^The effect of 2 levels of atmospheric carbon dioxide (ambient, ie 350 ppm, and double, ie 700 ppm) and 2 contrastin ontent in air which seem to be necessary to avoid potential photoinhibition and premature water exhaustion from gelled med 215^3^Elkohen,A^Rouhier,H^Mousseau,M^1992^1^Changes in dry-weight and nitrogen partitioning induced by elevated co2 dependia.^^^^^^^^^^^^^^^^^^^^^^6J6H6d6b6 6 =t^&G 6 6 jl=tt ent is achievable through careful increments of light quanta, balanced with increments of humidified air flow and/or CO2 c dry weight as those from a conventional culture tube treatment. This study shows that it is possible to favour photoautotr ophic growth when elevated PPFD, enhanced air-exchange and hydroponic medium flow are provided concurrently. This enhancem ton flux density (PPFD) and hydroponic irrigation. After 15 days of treatment, plantlets gained more than 3 times as much 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 pho iological requirements for photoautotrophic growth in vitro and alleviation of the needs for ex vitro acclimatization. The A^3272^An aseptic gas exchange and hydroponic system (AGEHS) has been developed in an attempt for characterization of physof photosynthesis invitro^37^84^3^409-416^^^^^Mar^^^^^3273FVFVFVFVp$r$FV¡$$FȉV 214^2^Dube,SL^Vidaver,W^1992^1^Photosynthetic competence of plantlets grown-invitro - an automated-system for measurement heses suggesting that root/shoot partitioning is controlled by some aspect of plant C/N balance.؎&F9 } and shoots were not affected by CO2 treatment. This phenomenon was consistent with the hypothesis that root/shoot partiti oning is related to the daily rate of starch accumulation by leaves during the photoperiod, but is inconsistent with hypot rate at which leaves accumulated starch over the course of the light period and the partitioning of biomass between roots ion, 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 ntrations (200 ppm, 330 ppm and 600 ppm) with a stable hydroponic 150-mu- mol l-1 nitrate supply. Radish biomass accumulat gated in order to examine several hypotheses about the mechanisms that govern dry matter partitioning between shoots and r oots. Wild radish plants (Raphanus sativus x raphanistrum) were grown for 25 d under three different atmospheric CO2 conce A^3270^The effects of CO2 enrichment on plant growth, carbon and nitrogen acquisition and resource allocation were investi 213^3^Chu,CC^Coleman,JS^Mooney,HA^1992^1^Controls of biomass partitioning between roots and shoots - atmospheric co2 enrichment and the acquisition and allocation of carbon and nitrogen in wild radish^2^89^4^580-587^^^^^Apr^^^^^3271P`ported..ssessFPHJ=tt FP =tt  latively low cost. A preliminary assessment of the chambers has been made and concentrations can be maintained at +/- 6% f or a target atmosphere of 680 cm3 m-3 CO2 under normal operating conditions. Other chamber environmental conditions are re0A^3268^An inexpensive, potentially mobile field exposure system is described which may be easily constructed by a small wo 212^3^Ashenden,TW^Baxter,R^Rafarel,CR^1992^1^An inexpensive system for exposing plants in the field to elevated concentrations of co2^9^15^3^365-372^^^^^Apr^^^^^3269. 0 >zt >|u6|6zHz|>$t >$u a result of enhanced CO2 may be eliminated or reduced if UV-B radiation continues to increase.6H higher concentration of these compounds than IR-36 in all environments, and the production of these compounds in Fujiyama -5 was stimulated by UV-B fluence. Results from this study suggest that in rice alterations in growth or photosynthesis as ons with increased UV-B radiation appeared to be related to leaf production of UV-B- absorbing compounds. Fujiyama-5 had a of photosystem II as estimated from the ratio of variable to maximum chlorophyll fluorescence. Little change in RuBP rege neration and photochemistry was evident in cultivar Fujiyama-5, however. The degree of sensitivity of photochemical reacti ficiency. Changes in the RuBP regeneration limitation in IR-36 were consistent with damage to the photochemical efficiency tion to photosynthesis with increased UV- B radiation was the capacity for regeneration of ribulose bisphosphate (RuBP), w hereas for Fujiyama-5 the primary photosynthetic decrease appeared to be related to a decline in apparent carboxylation ef response of CO2 uptake to internal CO2 concentration at light saturation suggested that, for IR-36, the predominant limita n, CO2 enhancement effects on respiration, photosynthesis, and biomass were eliminated in IR-36 and significantly reduced in Fujiyama-5. UV-B radiation simulated a 25% depletion in stratospheric ozone at Durham, North Carolina. Analysis of the nd yield for both curtivars. However, in plants exposed to simultaneous increases in CO2 and ultraviolet-B (UV-B) radiatio (660 microbars) from germination through reproduction in unshaded greenhouses at the Duke University Phytotron. Growth at elevated CO2 resulted in significant decreases in nighttime respiration and increases in photosynthesis, total biomass, a A^3266^Two cultivars of rice (Oryza sativa L.) IR-36 and Fujiyama-5 were grown at ambient (360 microbars) and elevated CO2 211^2^Ziska,LH^Teramura,AH^1992^1^Co2 enhancement of growth and photosynthesis in rice (oryza- sativa) - modification by increased ultraviolet-b radiation^8^99^2^473-481^^^^^Jun^^^^^3267^s8F\^؎&FF\^on levels of organization.ɚKv8F$$؎&FF$$؎&F\^ of the growth form, 2) our understanding about the clonal biology and population ecology of this growth form is still evol ving and 3) the modular construction of this growth form may result in variable responses at the ramet, clone and populati cult to anticipate because: 1) caespitose graminoids consist of both C3 and C4 species which will complicate the response se proximity requires further evaluation but may center on intra-plant competitive interactions. The response of this larg e sub-group of clonal plants to climate change will significantly impact community structure and function because of their diversity and dominance in numerous biomes. The impact of climate change on the caespitose graminoid growth form is diffi ue conferred by a clonal architecture composed of an assemblage of autonomous physiological individuals growing within clo nd longevity of individual ramets. Restricted resource allocation among ramet sequences within clones is primarily caused by the disintegration of vascular connections among ramet sequences following death of the seminal ramet. The survival val t generations comprising the physiological individual is determined by demographic variables influencing the recruitment a trated that physiological integration in the caespitose graminoid Schizachyrium scoparium is restricted to individual rame t sequences consisting of three connected ramet generations as opposed to all ramets within the clone. This number of rame low level of continuous resource allocation between parental and juvenile ramets. Isotopic and severing experiments demons A^3264^Caespitose graminoids are characterized by the compact spatial arrangement of ramets within clones and the absence of rhizomes or stolons. Resource allocation is principally acropetal with established ramets supporting juvenile ramets du ring early development. However, after juvenile ramet maturation a responsive resource transfer system is maintained by a sis with reference to climate change^15^63^3^357-365^^^^^Apr^^^^^3265secific recommendation of the creation of a tropical research center.,N R^Hodkinson,I D^1995^1^Climatic severity and the r 210^2^Welker,JM^Briske,DD^1992^1^Clonal biology of the temperate, caespitose, graminoid schizachyrium-scoparium - a synthe development and application of equipment for field measurements in several representative natural ecosystems and makes sp draws heavily on studies from artificial environments and conditions in an attempt to summarize knowledge of global envir onmental change on forests and other non-agricultural ecosystems. Finally the paper concludes that there is a need for the of larger scale field studies in natural vegetation. This paper lists and summarizes the best field studies available but s. A few field microcosm studies have been completed and a system for the free air release of CO2 has been applied in cott on fields. Unfortunately, the requirement of large amounts of CO2 and financial restrictions have precluded the initiation op chambers are being used in several autecological field studies in an attempt to obtain more realistic field environment nd growth chambers. Several lines of evidence indicate that controlled environment studies using plants growing in pots in duce experimental artifacts that reduce confidence in the use of results for prediction of future global responses. Open t field conditions. Most measurements have been conducted in the synthetic environments of totally controlled greenhouses a mptions are valid and how natural systems might respond under future scenarios of CO2 increase and possible climate change s. Few measurements of the effects of CO2 and global climate change have been made on "natural" ecosystems under realistic ironmental conditions. There is also evidence that CO2 acts as a plant fertilizer. It is of interest to know if these assu45-60^^^^^Aug^^^^^3263t,K R^1991^1^Loess ecosystems of northern Alaska: regional gradient and toposequence at Prudhoe Bay A^3262^It is generally assumed that healthy, natural ecosystems have the potential to sequester carbon under favorable env 209^2^Strain,BR^Thomas,RB^1992^1^Field-measurements of co2 enhancement and climate change in natural vegetation^94^64^1-2^d zones, with an increase in the areal extent of tropical forests and a shift of the boreal forest zone into the region cu^ture. Plants of both species grown under an elevated temperature regime had substantially decreased reproductive allocatio have led to the reduced biomass accumulation of high CO2 grown plants that we observed during the last 30 d of growth. Pla nts 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 temperaf an effect on tillering is not known.c JU| imarily due to the fact that CO2 concentration did not influence tiller (branch) numbers. In the absence of an effect on t iller numbers, any possible weight increment was restricted to the c. 2.5 leaves of each tiller. The reason for the lack o onditions and was accompanied by substantial reductions of whole-plant nitrogen content and leaf photosynthesis. This may per unit leaf area early in the experiment apparently compensated for reduced leaf area. For Amaranthus at 38-degrees, pea k leaf area production was not affected by CO2 treatment, but the rate of net leaf area loss hastened under elevated CO2 c duced peak leaf areas under elevated CO2 in comparison to ambient CO2 grown plants, but increased rates of photosynthesis tosynthesis, 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 re apparently enhanced the ability of Amaranthus to retain nitrogen at this temperature, which may have helped to enhance pho ecies, 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 t whole- plant nitrogen retention. At 28-degrees-C, elevated CO2 stimulated the initial production of leaf area in both sp  but not at 38-degrees, and had no significant effects on final biomass at either temperature. These results are interpret ed in light of the interactive effects of CO2 and temperature on the rates of net leaf area production and loss, and on ne es but was depressed at 38-degrees. For Abutilon, elevated CO2 increased initial plant relative growth rates at 28-degrees ation, and resource acquisition (i.e., photosynthesis and nitrogen uptake), and the strength and direction of these effect s were often dependent on plant species. For example, final biomass of Amaranthus was enhanced by elevated CO2 at 28-degre levated CO2 and temperature treatments had significant independent and interactive effects on plant growth, resource alloc  were made on individuals of Abutilon theophrasti (C3) and Amaranthus retroflexus (C4) grown in environments with atmosphe ric CO2 levels of 400 or 700-muL/L and with light/dark temperatures of 28-degrees/22-degrees or 38-degrees/31-degrees-C. E allocation of two annual plants that were supplied with a single pulse of nutrients. Physiological and growth measurementsls^11^73^4^1244-1259^^^^^Aug^^^^^32431988^1^Respiratory burst after freezing and thawing of soil: experiments with soil b A^3242^We examined how CO2 concentrations and temperature interacted to affect growth, resource acquisition, and resource 199^2^Coleman,JS^Bazzaz,FA^1992^1^Effects of co2 and temperature on growth and resource use of cooccurring C3 and C4 annua hotosynthetic 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. manipul plants grown and measured at elevated carbon dioxide concentration only at measurement temperatures above 33- degrees-C. P " 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 !le- plant carbon dioxide efflux rates in darkness were also determined. The stomatal conductance of leaves of plants grown %rbon dioxide to examine how aspects of their gas exchange would be altered by growth at elevated carbon dioxide concentrat #ion. Leaf conductances to water vapour and net carbon dioxide exchange rates were determined periodically near midday. Who $A^3240^Seedlings of temperate deciduous tree species were grown outdoors at ambient and at an elevated concentration of ca of foraging by these root systems, as indicated by the horizontal spread of roots, may be increased.iannikova,OV^1993^1^ )198^1^Bunce,JA^1992^1^Stomatal conductance, photosynthesis and respiration of temperate deciduous tree seedlings grown outdoors at an elevated concentration of carbon-dioxide^9^15^5^541-549^^^^^Jun^^^^^3241y 'reatments. Thus, under elevated CO2 the intensity of foraging S. vulgaris root systems might be unchanged while the extent ,terns and root length similar to those grown under ambient CO2 with a high water supply. 3. Overall, water had a more pron *ounced impact on the growth rate of S. vulgaris roots than did CO2. The density of rooting remained unchanged across all t +ged through larger volumes of soil. Under elevated CO2 and a low water supply, root systems had branching and foraging pat / atmospheric CO2 concentration and a high or a low supply of water. 2. CO2 and water had a significant impact on the way t -hat S. vulgaris root systems filled the soil matrix. Elevated CO2 resulted in more branched, longer root systems that fora .structively monitor the development of roots in situ at both an elevated (700-mu-mol mol-1) and ambient (350-mu-mol mol-1) 2A^3238^1. The impact of elevated CO2 and drought on the architecture and development of root systems of Senecio vulgaris w 0as examined and implications for water and nutrient uptake discussed. Plants were grown in miniature rhizotrons to non- de drought^43^6^3^324-333^^^^^^^^^^3239ͷͷͷͷͷͷͷͳͷͷͷͷͷͷͷͷͷͷͷͷͷͷͷͷ]cV]`uD rures also rise.,R A^Massman,W J^Musselman,R C^Mosier,A R^1996^1^Diffusional flux of CO{-2} through snow: spatial and temp 3197^2^Berntson,GM^Woodward,FI^1992^1^The root-system architecture and development of senecio- vulgaris in elevated co2 and 4y to be beneficial to rice growth and yield, potentially large negative effects on rice yield are possible if air temperat 8egrees-C temperature treatment. Across this temperature range, the number of panicles plant-1 nearly doubled while the num 6ber of seeds panicle-1 declined sharply. These results indicate that while future increases in atmospheric [CO2] are likel 7ment, 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-d ;t 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 9-C increased both biomass accumulation and tillering and increased grain yield by 60%. In the 660-mu-mol mol-1 [CO2] treat :y bulb air temperature/paddy water temperature) and [CO2] of 660-mu-mol CO2 mol-1 air. An ambient chamber was maintained a > 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 dr =rtant food crops. This study was conducted to determine the effects of [CO2] and temperature on rice (Oryza sativa L., cv. AA^3236^The continuing increase in atmospheric carbon dioxide concentration ([CO2]) and projections of possible future incr ?eases in global air temperatures have stimulated interest in the effects of these climate variables on agriculturally impol^^^^^3237essors may play an important role in mediating effects on plant growth.991^1^Biogeochemical diversity along a riverside topo B196^3^Baker,JT^Allen,LH^Boote,KJ^1992^1^Temperature effects on rice at elevated co2 concentration^78^43^252^959-964^^^^^Ju Cmulation in the same experiment, suggesting that responses of developmental processes to elevated CO2 and interacting fact G leaf area was slightly increased at 38-degrees relative to 28-degrees, and elevated CO2 levels resulted in increased leaf E area at 28-degrees but decreased leaf area at 38-degrees. The effects on leaf area closely parallel rates of biomass accu F at 38-degrees. Branch leaf area displayed a similar response to CO2, but was greater at 38- degrees. Overall, whole-plant Jole-plant leaf area. In Amaranthus, leaf initiation rate increased with temperature, and was increased by elevated CO2 at H28-degrees. Individual leaf area was greatest at 28-degrees, and was increased by elevated CO2 at 28-degrees but decreased I initiation rates. Elevated CO2 concentration increased leaf initiation rate at 28-degrees, resulting in an increase in wh Mwhole-plant leaf area and the number of main stem nodes. In Abutilon, leaf initiation rate was highest at 38- degrees, but K area of individual leaves was greatest at 28- degrees. Total leaf area was greatly reduced at 18-degrees due to slow leaf Lmined by the production of nodes on the main stem (the plastochron index), and through shifts in the relationship between Powth was analyzed in terms of the leaf initiation rate, leaf expansion, individual leaf area, and, in Amaranthus, producti Non of branch leaves. Temperature and CO2 influenced leaf area production through effects on the rate of development, deter Oconcentrations of carbon dioxide (400 and 700-mu-L/L). The production of whole-plant leaf area during the first 30 d of gr SA^3234^We studied leaf area production in two annual plant species, Abutilon theophrasti and Amaranthus retroflexus, under Q three day/night temperature regimes (18-degrees/14-degrees, 28- degrees/22-degrees, and 38-degrees/31-degrees-C) and two t-species^11^73^4^1260-1269^^^^^Aug^^^^^3235t Par 15,/4$t D T$" ]a c exposed to elevated CO2 remains unresolved. density and season on the population rate of change in the meadow vole^15^78 T195^4^Ackerly,DD^Coleman,JS^Morse,SR^Bazzaz,FA^1992^1^Co2 and temperature effects on leaf-area production in 2 annual plan Uase in other metabolic processes. Whether these reductions are beneficial or detrimental to the long-term growth of plants Ywth respiration was largely offset by a greater dry mass for leaves grown at elevated CO2 concentrations. Although reducti Wons in the respiratory loss of carbon could be beneficial, respiration is unlikely to decrease without a concomitant decre Xpiration were dominated by a lower rate of maintenance respiration, while the contribution of a lower specific rate of gro \eaf growth simulation model indicated that total respiration would be reduced by 21 to 26 % for a leaf exposed to + 150 or Z + 300 cm3 m-3 CO2 throughout its 50-d lifespan compared with one grown at ambient CO2 conditions. Reductions in total resdthe site were differentiated most of the significant correlations were with soil microbial carbon; they were positive in t [135 mg CO2 g-1 d-1 for leaves from the ambient treatment. Incorporating these growth and maintenance coefficients into a l `enance respiration, SRR was a linear function of SGR. Ambient-grown leaves had a growth respiration coefficient of 704 mg aCO2 g-1 dry mass compared with 572 and 570 mg CO2 g-1 for leaves grown at the two higher CO2 concentrations. Leaves from t ^he elevated CO2 treatments had an average maintenance respiration coefficient of 88 mg CO2 g-1 dry mass d-1 compared with _tes were correlated with reduced leaf nitrogen concentrations. As described by the two-component model of growth and maint dce of a CO2 effect on individual leaf expansion or specific growth rate (SGR), increasing the CO2 concentration to ambient b + 150 or + 300 cm3 m-3 decreased SRR by 28 to 45 % compared with ambient- grown controls. These lower leaf respiration ra cs of yellow-poplar (Liriodendron tulipifera L.) after 3 vr of CO2 enrichment in open-top field chambers. Despite the absena L exposed to long-term carbon-dioxide enrichment in the field^84^121^4^515-523^^^^^Aug^^^^^3233etween woody plants and eA^3232^Specific respiration rate (SRR) was mathematically partitioned into its growth and maintenance components for leave f194^3^Wullschleger,SD^Norby,RJ^Gunderson,CA^1992^1^Growth and maintenance respiration in leaves of liriodendron- tulipiferly, but are, as yet, unpredictable.of winter grazing by reindeer on vegetation^15^40^^337-343^^2629^^^^^^^^^^^^^^^^^^^^^^^^^^3231s opposed to N. Sweden for V. Uliginosum. We also postulate that the differences in the spring and autumn cliamt i However, response to elevated CO2 vanes among species. Thus, shifts in composition within plant communities are also like mreased drought frequency may increase plant stress and thereby increase the frequency of insect outbreaks and disease. Pre kdictions of species responses are complicated by direct effects of increased CO2, such as increased water-use. efficiency. lrange. Insect pests and microbial pathogens should respond to climatic warming faster than long-lived trees. Predicted inc p rates much lower than Pleistocene observations. Thus migration response is likely to lag far behind rates of climatic cha nnge, potentially threatening narrowly distributed species whose predicted future ranges do not overlap with their current oy. A simulation model that predicts the migration response of trees through modem fragmented landscapes predicts migration ss northward range shifts in response to climate change vary from 100 km to over 500 km. Historical evidence of species ran qge movements following the Pleistocene indicate that tree species typically migrated at rates of 10 km to 40 km per centur re changes will be greater at high latitudes. Mid-continental regions will experience lower rainfall. Predictions of specie tbled atmospheric CO2 predict that mean temperatures will increase between 1.5 and 4.5-degrees-C globally; these temperatur uCO2 levels could double the pre-industrial level of 280 ppm by the year 2100, perphaps much earlier. Climate models of dou j193^1^Schwartz,MW^1992^1^Potential effects of global climate change on the biodiversity of plants^66^68^4^462-471^^^^^Aug^ vA^3230^Climatologists have observed a consistent increase in atmospheric CO2 over the past 30 years. It is predicted that -565^^^^^Junsrainfall conditions (Haglund  s4< (#-1981). Tillering or vegetaive reproduction y192^2^Ryle,GJA^Stanley,J^1992^1^Effect of elevated co2 on stomatal size and distribution in perennial ryegrass^52^69^6^563ses could be enormous.le displacement #F\  PC=^P#of C4 #d\  PCP# }ts were an increase in root length (110%) and root dry weight (143%). Root diameter, stele diameter, cortex width, root/sh {oot and root weight ratios all increased; root numbers did not increase. The long-term implications for belowground proces |ion demonstrate substantial effects on root system architecture, micromorphology and physiology. The most pronounced effec5^6^749-752^^^^^Aug^^^^^32281987^1^Small rodents with social and trophic interactions in a seasonally varying environment ~A^3227^Plant root response to atmospheric CO2 enrichment can be great. Results from this controlled environment investigat 191^4^Rogers,HH^Peterson,CM^McCrimmon,JN^Cure,JD^1992^1^Response of plant-roots to elevated atmospheric carbon-dioxide^9^1 O2 treatment was found to alleviate the afternoon depression in A observed in ambient CO2. A temperature optimum shift or/and a larger carbohydrate sink capacity through altered root/shoot ratio are proposed in explanation.g 20 cm in depth, ar tween temperature and light intensity, there was evidence that temperature rather than light determined M. Further, high C on average twice as large in high compared to ambient CO2. This response (called M = A in high CO2/A in ambient CO2) coul d not be explained by changes in canopy conductance for CO2 diffusion (GC). In spite of interaction and strong coupling be ver the entire range of temperature and light conditions (which were strongly coupled and increased simultaneously), A was the day, was examined in full-cover vegetative Lolium perenne canopies after 17 days of regrowth. The stands were grown at ambient (358 +/- 50-mu-mol mol-1) and increased (626 +/- 50-mu-mol mol- 1) CO2 concentration in sunlit growth chambers. O A^3225^The relative increase with elevated CO2 of canopy CO2 uptake rate (A), derived from continuous measurements during 190^3^Nijs,I^Impens,I^Vanhecke,P^1992^1^Diurnal changes in the response of canopy photosynthetic rate to elevated co2 in a coupled temperature-light environment^91^32^2^121-130^^^^^May^^^^^3226*2" without warmer and or wetter condding to a change in forest tree growth.,**2" ofecosystem microclimate, though the presence of spores, se nt species, which may be related to their developmental strategies, are largely ignored. Much experimental effort is neede d to parameterize all the physiological processes which are susceptible to change with an increase in atmospheric CO2, lea n leaf area development. The paper emphasizes large areas of ignorance: the reasons for the different responses of differe increase in root investment in elevated CO2 is related to a poor mineral status. The mineral content of trees grown in el evated CO2 is generally lowered compared to controls. No general rule has yet been found for the effect of increased CO2 o ts are still controversial. Biomass partitioning in elevated CO2 is clearly related to the mineral supply of the trees: An ncreased photosynthetic rate, as predicted by leaf models. In longer experiments this increase is reduced after a few week s or months by mechanisms that remain to be found. Elevated CO2 seems to decrease the dark respiration rate, but the resul mental approaches are described, as well as the principal results already obtained. Short-term experiments have shown an i A^3223^CO2 enrichment of the atmosphere is now well documented and its effect on the growth of world forests is being ques tioned by the scientific community. The direct effects of increased CO2 on tree species are reviewed: the different experi43^253^1121-1130^^^^^Aug^^^^^3224d some of the original species such as the moss, Chorisodontium.  atment.lringer,J R^Dawson,T E^1992^1^Water uptake by plants: perspectives from stable isotope composition^9^15^^1073-1082 189^2^Mousseau,M^Saugier,B^1992^1^The direct effect of increased co2 on gas-exchange and growth of forest tree species^78^ dry weight, which was greatest under the high water, ambient CO2 treatment. The shoot: root ratio did not change with tre cant effect on root dry weight in the 0-40 cm depth. In the 0-10 cm depth, doubled CO2 reduced dry weight and length of ro ots of plants grown under the high water level by 47 and 31 %, respectively. Warm-season, C4 grasses had the highest shoot re determined. Shoot growth also was measured to determine shoot: root ratios. The CO2 and water treatments had no signifi ). Sixteen cylindrical plastic chambers were placed on the prairie to maintain two levels of CO2 (ambient or twice ambient ). At the end of two seasons' exposure to the different treatments, dry weight and length of roots in the 0-40 cm depth we airie kept at a high water level (73 cm of water in a 200 cm soil profile) and a low water level (66 cm of water in 200 cm A^3221^The atmospheric concentration of carbon dioxide (CO2) is increasing and knowing how this will affect native vegetat ion is important. The objective of this study was to determine the effect of elevated CO2 on root growth in a tallgrass prer elevated carbon-dioxide^173^32^3^193-201^^^^^Jul^^^^^32221990). These disturbances may have cascading effects on nutrophic, as indicated by the changes in titratable acidity, delta-C-13 values and (CO2)-C-14 fixation. results from a Taraw 188^7^Mo,G^Nie,D^Kirkham,MB^He,H^Ballou,LK^Caldwell,FW^Kanemasu,ET^1992^1^Root and shoot weight in a tallgrass prairie und decreased. CO2 enrichment did not increase ion uptake or growth. The nutrition of plantlets in culture was mainly heterotr supplemented with sugar. Ammonium uptake was also affected by light. However, the rates of ammonium and nitrate uptake we re sluggish. The fresh weight of plantlets increased with the presence of sugar in the media but the relative growth rate itrate. Uptake of nitrate was relatively low and increased with increase in light intensity or when the culture medium wasuptake of dendrobium plantlets^174^67^5^601-611^^^^^Sep^^^^^3220 Holocene hydrologic change along boreal treeline reveale A^3219^The effects of light intensity, sugar and CO2 concentrations on nitrate and ammonium uptake, growth and photosynthe tic activity of dendrobium plantlets grown on agar medium were studied. There was a preferential uptake of ammonium over n 187^4^Lim,LY^Hew,YC^Wong,SC^Hew,CS^1992^1^Effects of light-intensity, sugar and co-2 concentrations on growth and mineral ons among components, and it emphasizes the urgent need for whole-system experimental approaches in global-change research.otope measurements^36^380^^515-517^^2677^^^^^^^^^^^^^^^^^^^^^^^^es by denuding the areas of vegetation and compacting s s study points at the inadequacy of scaling-up from physiological baselines to ecosystems without accounting for interacti h accumulation in the tops of canopies, increased fine-root production, and a doubling of CO2 evolution from the soil. Sti mulated rhizosphere activity was accompanied by increased loss of soil carbon and increased mineral nutrient leaching. Thi avior were detected between ambient and elevated CO2 treatments. Major responses under elevated CO2 included massive starc tropical plant communities treated with CO2-enriched atmospheres. Despite vigorous growth, no significant differences in stand biomass (of both the understory and overstory), leaf area index, nitrogen or water consumption, or leaf stomatal beh A^3217^Carbon, nutrient, and water balance as well as key plant and soil processes were simultaneously monitored for humid 186^2^Korner,C^Arnone,JA^1992^1^Responses to elevated carbon-dioxide in artificial tropical ecosystems^32^257^5077^1672-1675^^^^^18 Sep^^^^^3218^^^^^^^^^^^^^^^^^^^^^olonization of Antarctic habitats as has been reported for other polar regionts that changing CO2 environments may not improve the fitness of certain genotypes over others.tundra where vehicles remo ynthesize or activate the appropriate enzyme systems. Moreover, although plant genotype significantly affected plant growt h, reproduction, and chemistry, we never observed significant genotype-by-CO2 interactions for these factors, which sugges er for increased secondary metabolism; instead, hormonal and/or direct physical cues (such as light) may be essential to s similar, or lower, concentrations of carbon-based allelochemicals than plants grown in ambient (350-mu-L.L-1) CO2 conditio ns. We suggest that augmented substrate concentrations (i.e., excess carbohydrates) are a necessary but insufficient trigg onditions. However, in contrast to the C/N balance hypothesis, plants grown in elevated (700-mu-L.L-1) CO2 conditions had (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 c ent CO2 and nutrient environments and then (1) measured the total allocation to shoots, roots, and reproductive parts and sed allelochemicals in plantago - a test of the carbon nutrient balance hypothesis^16^140^4^707-723^^^^^Oct^^^^^3216blish A^3215^In a test of the carbon/nutrient (C/N) balance hypothesis, we grew the perennial herb Plantago lanceolata in differGC4-4}{++}re incipient communities are established (Matthews and Whittaker 1987, Chapin et al. 1994, Smith 1994a). In ou 185^3^Fajer,ED^Bowers,MD^Bazzaz,FA^1992^1^The effect of nutrients and enriched co2 environments on production of carbon-ba al foliar concentrations currently used to define nutritional status and fertilizer management may need to be reassessed as the atmospheric CO2 concentration rises.4^^^^^^^^^^^^^^^^^^^^^^^^ site (Komarkova 1983, 1984), and the surrounding hab lower at elevated CO2 concentration partly because of the higher specific leaf weight. These results indicate that critic 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 enrich ment, primarily because the specific leaf weight was greater. The nitrogen and phosphorus concentration in the foliage was growth. At high CO2, growth reached a maximum at between 80 and 160 mg nitrogen kg-1 soil. Total uptake of phosphorus was wever, 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 owth was stimulated by addition of phosphorus up to 76 mg kg-1 soil. Further additions of phosphorus had little effect. Ho CO2 mol-1. The absolute response was largest when both nitrogen and phosphorus availability was high but the relative incr ease in dry weight was greatest at low phosphorus availability. At 340-mu-mol CO2 mol-1 and high nitrogen availability, gr ected by CO2 concentration. At 660-mu-mol CO2 mol-1, seedling dry weight was up to five times greater than at 340- mu-mol dlings at either 340 or 660-mu-mol CO2 mol-1 for 6 weeks. Graded increments of phosphorus and nitrogen fertilizers were ad ded to a soil deficient in these nutrients to establish if the growth response to increasing nutrient availability was aff A^3213^The response of Eucalyptus grandis seedlings to elevated atmospheric CO2 concentrations was examined by growing see 184^3^Conroy,JP^Milham,PJ^Barlow,EWR^1992^1^Effect of nitrogen and phosphorus availability on the growth- response of eucalyptus-grandis to high co2^9^15^7^843-847^^^^^Sep^^^^^3214etely attributable to warmer temperatures, because dilute solutsynthetic process as a result of acclimation to elevated CO2.tion of water may have been just as important as the warmer , experimental as well as simulatory evidence suggests that doubling CO2 concentration in the air may improve carbon assim ilation and compensate partially for the negative effects of water stress even if we assume a down-regulation of the photo refore, in productivity. On the other hand, the increase in air temperature may result in more respiratory losses. However own. Plant production is more closely related to the integral of photosynthesis over time and total foliage area than to t he instantaneous rates of the photosynthetic process. Water deficits result in a decrease in foliage area biomass and, the eds to be clearly identified. Similarly, the effects of extended exposure to elevated CO2 under arid conditions are not kn oinhibition, 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 ne s to indicate that under conditions of high irradiance, plants growing at elevated CO2 may develop protection towards phot increase in CO2 in the atmosphere may diminish the importance of stomatal limitation for carbon assimilation, inhibit phot orespiration, stimulate carbon partitioning to soluble sugars and increase water-use efficiency. Some recent evidence seem are superimposed, a decline in photosynthetic capacity may be observed. In the short term, under drought conditions, the take under water deficit, the photosynthetic machinery being highly resistant to dehydration. However, when other stresses s now well established that in most species and under most circumstances stomata are the main limiting factor to carbon up er 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 i its and high light stress are likely to occur in conjunction with elevated atmospheric CO2. This raises the question wheth183^2^Chaves,MM^Pereira,JS^1992^1^Water-stress, co2 and climate change^78^43^253^1131-1139^^^^^Aug^^^^^3212pen meadow in A^3211^Climatic change may bring about increased aridity to large areas of Europe. Higher temperatures, larger water deficactions between CO2 and O3 are discussed. wetter conditions which will be expressed by longer annual growth segments and vated CO2. Moreover, there were indications that cumulative changes in source:sink relations in O3-exposed plants may limi t plant response to CO2-enrichment to an even greater extent in the long-term. The future ecological significance of inter wgative correlation between chlorophyll level and growth was observed. The chlorophyllous cultures grew slowly in a medium mbient air.his for caribou trail ms and control recolonization and ecosystem recovery. To achieve our objective, we w least in part) the detrimental effects of phytotoxic concentrations of O3, whilst conversely, O3 reduced the impact of ele N, S, Mg and Ca. Interactions between the gases were complex, and often subtle. In general, elevated CO2 counteracted (at enhanced uptake of these nutrients from the growth medium. However, there was no affect of O3 on tissue concentrations of s of O3 injury, and effects on carbon assimilation were reflected in reduced growth, with shoot growth maintained at the e xpense of the root. In addition, O3 increased the P and K concentration in shoot and root (+hypocotyl) tissue, indicating atal closure, with the result that WUE(i) declined. All plants exposed to 'polluted' air developed typical visible symptom in elevated CO2, indicating that total uptake of these nutrients was not affected by CO2, and there was an increase in th e C:N ratio in root (+ hypocotyl) tissue. In contrast, O3 depressed A(sat), (almost-equal-to 26 %) and induced slight stom sted in leaf area expansion. Tissue concentrations of N, S, P, Mg and Ca were lower (particularly in the root + hypocotyl) oot growth or leaf area. Moreover, a decline in SLA and LAR in CO2-enriched plants suggested that less dry matter was inve arbon fixed in elevated CO2 stimulated growth of the root (+ hypocotyl) by 43 %, but there was no significant effect on sh composition were assessed at a final whole-plant harvest after 27 d. In 'non-polluted air' CO2 enrichment resulted in a p rogressive stimulation in A(sat), whilst there was a decline in g(s) which decreased E (i.e. improved WUE(i)). The extra cled CO2 was slightly more (36.9 mumol m-2 s-1) than that of plants grown with ambient CO2 (31.7 mumol m-2 s-1). This obser sults are consistent with previous findings, which showed that the photosynthetic rate of C4 plants on rangeland was not a ugmented when the CO2 concentration was increased. Under the low-water treatment, photosynthesis of plants grown with doub g chambers with the different CO2 and water treatments, but late in the season, differences occurred among chambers, possi bly because of the amount of tall grasses that shaded the radiometers. Under the high-water treatment, canopy photosynthes is of plants grown with doubled and ambient CO2 averaged 41.8 mumol m-2 s-1 and 44.5 mumol m-2 s-1, respectively. These re he chambered plots averaged 2.7-degrees-C warmer than outside. Early in the season, net radiation was usually similar amon ean concentrations varied from 710.8 to 720.1 cm3 CO2 m-3. For chambers with ambient CO2, the chamber-to-chamber variation  was minor, with mean values ranging from 350.8 to 356.0 cm3 CO2 m- 3. Daytime air temperatures at 100 cm aboveground in t 6 chambers on 49 sunny days during the season. The target value for high- CO2 chambers was 720 cm3 CO2 m-3; the measured m ilty clay loam) was kept at a high water (field capacity) or a low water level (no water added). Carbon dioxide concentrat ion, air temperature, net radiation, canopy photosynthetic rate, and canopy evapotranspiration rate were measured in the 1 d on the prairie to maintain two levels of CO2 (ambient and twice ambient) over a full growing season in 1990. The soil (s  of prairie (rangeland) plants growing under natural field conditions. The dominant plants were warm-season grasses with t he C4 type of photosynthesis. Sixteen closed-top, cylindrical, plastic chambers (1.5 m in diameter; 1.8 m tall) were place agricultural plants. The objective of this study was to determine the effect of elevated CO2 on canopy photosynthetic rate doubled carbon-dioxide in closed-top chambers^107^61^3-4^205-217^^^^^Oct^^^^^3189rctic soils^137^11^^163-172^^2826^^^^^^ A^3188^It is important to know how the increasing atmospheric concentration of carbon dioxide (CO2) will affect growth of 169^5^Nie,D^He,H^Mo,G^Kirkham,MB^Kanemasu,ET^1992^1^Canopy photosynthesis and evapotranspiration of rangeland plants under , E. vaginatum may shift from being a nutrient-limited to a carbon-limited system and, consequently, increased season length and elevated CO2 concentrations may play an important role in controlling E. vaginatum productivity.<5.JjD΁|wY apidly because the plant becomes limited by carbon uptake. Thus, if nitrogen availabilities more than double in the future aginatum to climate change is linearly (and almost exclusively) dependent on our ability to predict the effects of climate  change on nitrogen cycling. At nitrogen availabilities > 2 x current availabilities, the relationship flattens out very r nitrogen availabilities. Therefore, at low- to-moderate increases in nitrogen availability, the predicted response of E. v  in nitrogen alone. In essence, the model predicts that climate change will have substantial effects on E. vaginatum only indirectly through changes in nitrogen availability. Simulated peak biomass responds linearly up to a doubling of current nt changes in climate and nitrogen availability, the model predicts a slight decline in peak biomass compared to increases importance in productivity. The model predicts that a simultaneous increase in the direct effects of temperature, season l ength, and CO2, with no change in nitrogen availability, will result in a slight decrease in peak biomass. A simulated lon g-term doubling of nitrogen availability results in an almost-equal-to 70% increase in peak biomass, whereas with concurre 680 muL/L). Similarly, a wide range of nitrogen availabilities (from 9 to 18 g.m 2.vr-1) was also examined because of its "n E. vaginatum photosynthesis. The effect of a 50-yr period of climate change on peak biomass (overwintering biomass plus #seasonal production) in E. vaginatum was explored. We use climate change here to refer to linear increases over a 50-yr pe riod in temperature (from 8-degrees to 13-degrees-C), season length (from 100 to 120 d), and atmospheric CO2 (from 340 to ! on the growth responses of E. vaginatum to temperature and shading, and (2) the effects of elevated CO2 and temperature o &imate change. Our simulation model utilizes a mechanistic framework and includes the effects of light, temperature, season ' length, nitrogen availability, and CO2 concentration on E. vaginatum growth dynamics. The model was parameterized based o $n a series of published studies of the growth responses of E. vaginatum to nutrients and validated using (1) field studies %d physiology, we chose this species as a test case to model the potential long-term response of arctic plants to global cl *A^3186^It appears that polar regions of the Ear-th will bear the brunt of global temperature increases. Because of the eco (logical importance of the sedge Eriophorum vaginatum in the arctic and the large amount ot data available on its growth an3-340^^^^^Nov^^^^^3187JZJRBZJZJZJZJRJZJZJZJZJZJZJZJRJB9nductance to elevated carbon-dioxide in field-grown cotton^183^11^2-3^227-231^nnial plants from low and high altitudes in +168^2^Leadley,PW^Reynolds,JF^1992^1^Long-term response of an arctic sedge to climate change - a simulation study^56^2^4^32 ,167^6^Hileman,DR^Bhattacharya,NC^Ghosh,PP^Biswas,PK^Lewin,KF^Hendrey,GR^1992^1^Responses of photosynthesis and stomatal cohe field and provide evidence for a new mechanism by which elevated atmospheric CO2 could influence seasonal carbon gain.166^1^Hendrey,GR^1992^1^Global greenhouse studies - need for a new approach to ecosystem manipulation^183^11^2-3^61-74^Y> /C(i) above 400 mubar on day 68. These results indicate the potential for direct CO2 fertilization of P. grandidentata in t 3eight, suggesting a delay in senescence with long-term exposure to high CO2. High CO2 grown plants also maintained photosy 1nthetic sensitivity to increasing C(i) throughout the exposure period, while ambient CO2 grown plants were insensitive to 2. In contrast, plants grown at elevated CO2 showed no late- season decline in photosynthetic capacity or changes in leaf w 6similation rates. Specific leaf nitrogen (mg N . (cm2 leaf area)-1) did not change during this period, although leaf carbo 4n content and leaf weight (mg . cm-2) both increased. In ambient grown plants stomatal conductance also declined at day 68 5slope of the net CO2 assimilation versus intercellular CO2 Partial pressure relationship and to decreased CO2 saturated as 92. In ambient grown plants, light saturated assimilation rates increased from day 28 to day 45 and then declined at day 68 7 (15 September). This late-season decline, typical of senescing Populus leaves, was due both to a decrease in the initial 8nts. Photosynthetic light and CO2 response characteristics were measured 28, 45, and 68 days after exposure to elevated CO A^3182^Rising atmospheric carbon dioxide concentrations may have important consequences for forest ecosystems. We studied ?165^2^Curtis,PS^Teeri,JA^1992^1^Seasonal responses of leaf gas-exchange to elevated carbon- dioxide in populus-grandidenta Centration Of CO2. These patterns do not support either the feedback-inhibition or the nutrient-stress hypothesis of photosynthetic adjustment to elevated concentrations of CO2.lication^^^^^^^^^^^^^^^^^^^^^^^^^^Merritt,J F\:V5[F22/!ED>I_#-2RFH Bation, with net rates of CO2 exchange the next day equal to those of leaves of plants grown from seed at the elevated conc Fes-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 nutrient Ds. Furthermore, in soybean, negative photosynthetic adjustment could be induced by a single night at elevated CO2 concentr Eer all treatments. Negative photosynthetic adjustment to elevated CO2 concentration was not greater at 20 than at 25-degre Ire then measured at both 350 and 700 mul l-1 CO2. Plants grown at the elevated CO2 concentration had net rates of leaf CO2 G exchange which were reduced by 33% in sugar beet and 23% in soybean when measured at 350 mul l-1 CO2 and when averaged ov H or the sixth leaf of sugar beet had finished expanding. Net rates Of CO2 exchange of the most recently expanded leaves we Lar 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 ph Joton 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 Kcentration is due to (1) feedback inhibition or (2) nutrient stress. Soybean [Glycine max (L.) Merr. cv. Williams] and sug OA^3180^The short-term stimulation of the net rate of carbon dioxide exchange of leaves by elevated concentrations of CO2 u Psually observed in C3 plants sometimes does not persist. Experiments were conducted to test whether the patterns of respon Mse to the environment during growth were consistent with the hypotheses that photosynthetic adjustment to elevated CO2 conn of carbon-dioxide^37^86^1^173-179^^^^^Sep^^^^^3181TYA8QHW2AQC: MH<3B&6E)I+LRSE[Q]?8B;0V(9UJ6JT)RV6VP(4`2;*CQQS%,9;EW,4and other trace gases^183^11^2-3^85-119^ponses of the Norwegian alpine {iBetula nana} community to nitrogen fertilization Q164^1^Bunce,JA^1992^1^Light, temperature and nutrients as factors in photosynthetic adjustment to an elevated concentratio c C-14 in SDP, GMP, and malate, but decrease of it in sucrose, alanine, glycine, and serine. Very perceptible effects of inv Ved temperature increased accumulation of the label in PGA, sucrose, and malate, but lowered it in GMP, alanine, glycine, ax Tnd serine. Growing plants at enhanced CO2 concentration led to acceleration of photosynthesis and increase of the share of Uperature increase by itself and in any combination with other factors at the upper level suppressed photosynthesis. Elevat Yynthesis and stimulated incorporation of C-14 into phosphoglyceric acid (PGA), sugar diphosphate (SDP), fructose monophosp Whate (FMP), and malate, but suppressed incorporation of C-14 into sucrose, glucose monophosphate (GMP), and glycerate. Tem Xon metabolism in the cotton (Gossypium hirsutum L.) leaf Increase of light intensity during cultivation accelerated photos \A^3177^We used the method of mathematical experiment planning (a 2(3) scheme) to study the influence of environmental fact Zors separately or in combination on the photosynthetic rate and distribution of C-14 among products of photosynthetic carbhotosynthetic metabolism of carbon in cotton leaves^168^39^2^140-144^^^^^Mar-Apr^^^^^3178H])OB*'$D&_;MLW7]- M?1-R[XEX#O/phenomenon.I^1997^1^Growth, herbivory and disease in relation to gender in {iSalix viminalis} L^2^111^^61-68^^2874^^^^^^^ ]162^5^Abdullaev,AA^Dzhumaev,BB^Abdurakhmanova,ZN^Kaler,VL^Magmedov,IM^1992^1^Integral effect of environmental-factors on p ^ respiration are affected by CO2 enrichment and as such should provide useful information for the future modeling of this b bvely. The maintenance coefficient was similarly reduced from a control rate of 114 mg CO2.g-1 d-1 to below 65 mg CO2.g-1.dd `-1 for leaves exposed to CO2 enrichment. Our results quantitatively describe the magnitude by which growth and maintenance_ d1^4^Curtis,PS^Balduman,LM^Drake,BG^Whigham,DF^1990^1^Elevated atmospheric CO2 effects on belowground processes in C3 and Ca4 estuarine marsh communities^11^71^5^2001-2006^^^^^Octctngton, DC USA^257-288^^^^^^^^^^^^^^^^^^^^^^^^^^H@T@\gs that had been planted directly into the ground within open-top chambers and exposed to ambient, ambient + 150 muL.L-1, X gnnials. It has vet to be determined, however, whether these reductions reflect changes in maintenance respiration alone orZ e whether CO2 might affect growth respiration as well. This possibility was examined in white oak (Quercus alba L.) seedlinV pauciflora. Growth indices for E. camaldulensis and E. cypellocarpa species, and especially E. camaldulensis, generally eR jvated CO2 in all species on either N treatment. Moreover, high N increased NAR under either CO2 treatment in all species. hThere was a positive N X CO2 interaction on NAR in E. camaldulensis and E. cypellocarpa, but not in E. pulverulenta and E.Q lreased in E. camaldulensis and E. cypellocarpa, but decreased in E. pulverulenta and E. pauciflora. Whole plant NUE showedM i no consistent response to elevated CO2 when plants were supplied high N. Net assimilation rate (NAR) was increased by eleO nlar order. A distinction can be made between N and CO2 effects on growth processes as follows. When trees were grown on loJ kw N, elevated CO2 increased nitrogen-use efficiency (NUE) at both leaf and whole plant levels. On high N, leaf NUE was incG p species throughout the study period. In E. camaldulensis and E. cypellocarpa, plant mass was doubled by high N at 33 Pa CE qO2, compared with a three to four- fold increase at 66 Pa to reach 34 g by final harvest. In E. pulverulenta and E. paucifF mlora, slower growth resulted in about 50% less mass at a given age, but relative increases due to CO2 and N were of a simi1 s (33 Pa) and CO2-enriched (66 Pa) greenhouses. Analysis of growth response to treatments (2 X 2 factorial) was based on de, tstructive harvest of plants sampled on four occasions over 84 days for E. camaldulensis and E. cypellocarpa, and 100 days . ofor E. pulverulenta and E. pauciflora. A positive CO2 X N interaction on plant dry mass and leaf area was expressed in all) vast, E. pauciflora and E. pulverulenta become smaller trees, and show a more limited distribution. Seedlings were establis+ rhed in pots (5 L) of a loamy soil and supplied with nutrient solution containing either 1.2 or 6.0 mM NO3- in both ambient' uellocarpa were taken as examples of fast-growing species with a wide distribution, that develop into large trees. By contr$40^4-5^457-472^^^^^^^^^^3174B^Boer,G J^Cubasch,U^Meleshko,V P^1992^3^Climate modelling, climate prediction and model vali zA^3173^Four eucalypt species were selected to represent two ecologically disparate groups which would be expected to contrT wast in seedling vigour and in the nature of growth responses to CO2 X nitrogen supply. Eucalyptus camaldulensis and E. cypPely related birch species differ in their habitat preferences and successional status.s.nstitute, Inc.^Cary, NJ^^N^846^^ x160^3^Wong,SC^Kriedemann,PE^Farquhar,GD^1992^1^CO2 X nitrogen interaction on seedling growth of 4 species of eucalypt^182^ {in comparison to unrelated species of the same ecosystem that had been studied by others, despite the fact that these clos cies. (iv) The presence and identity of a neighbor did not influence the magnitude or pattern of response to CO2 in birche }s of a given community. Our results suggest that congeneric species might be more similar in their response to global CO2  ~ation, shoot architecture, and leaf nitrogen content were affected differently by CO2 concentrations for the different spe . The most shade-intolerant, fast-growing species (grey birch; Betula populifolia Marsh.) took greater advantage of the elM evated CO2 resource than the more shade-tolerant, later successional species (e.g., yellow birch). (iii) Patterns of allocO pecies were significantly stimulated by enriched CO2 Conditions, but the magnitude of response was different among species: es. We found the following: (i) yellow birch (Betula alleghaniensis Britton) was the only species whose survival differed < among CO2 treatments. Survival was slightly increased by elevated CO2. (ii) All growth parameters considered in all four s. 159^2^Rochefort,L^Bazzaz,FA^1992^1^Growth-response to elevated CO2 in seedlings of 4 cooccurring birch species^155^22^11^1/583-1587^^^^^Nov^^^^^3172^^-0SR5IEF'(H2V$%"D=@B%O9-A"O*.:V)MC M0?(8QC&'8>O!I.08<2EU>13@2A"V5&*%*2A)(=2E1;)4(Q2E8<(KDSYC# environmental variables.DK9`.(N/^(KJ]DX;7533WO=2-89)XU#3&^. MG8!&QX>H,/>>;0G44T8O.@]TH_FFQV>QL"E04`1^32+(%0(46`-)<>)+< 297^3^Dufrene,E^Pontailler,JY^Saugier,B^1993^1^A branch bag technique for simultaneous co2 enrichment and assimilation measurements on beech (fagus-sylvatica L)^9^16^9^1131-1138^^^^^Dec^^^^^3429@_,PQY`KAU, M*P:5P'#F\-E""$CRKLVTJ-FTDFVVT"X"D5J A^3428^A cheap CO2 enrichment system was designed to perform continuous gas exchange measurements of branches of mature Eu ropean beech trees (Fagus sylvatica L.). Branches were grown at ambient (350 cm(3) m(-3)) and elevated CO2 (700 cm(3) m(-3 )) during the whole 1992 leafy period. Leaks resulting from airtightness defaults in the system appeared to be low enough  to measure accurately net CO2 assimilation and transpiration rates during the day. However, the CO2 exchange rates during  the night (respiration) were too low to allow accurate measurements. Elevated CO2 had a great effect on the net assimilati on rate of branches via its influence on both the C-3 photosynthetic pathway and the shade-tolerance of beech frees (85% iq ncrease). The A/C-a curves showed no acclimation effect to high CO2, both control and enriched branches increasing their nm et assimilation in the same way. The decrease of net assimilation rates in mature leaves was similar for both control and c enriched branches. The pattern of daily transpiration rates remained the same for both control and enriched branches, henc^e we can assume that there was no visible CO2 effect on stomata.\8N M";JUEIN%KEB@K^[JO-'15$)?L-;3M=LJ6PEP!`<@W(&0Q'EOBJI` 298^3^Eamus,D^Berryman,CA^Duff,GA^1993^1^Assimilation, stomatal conductance, specific leaf-area and chlorophyll responses Uto elevated co2 of maranthes corymbosa, a tropical monsoon rain-forest species^92^20^6^741-755^^^^^^^^^^3431/'_"-?Q1Q`Z_<P A^3430^Seeds of Maranthes corymbosa Blume, a monsoon rain forest species of northern Australia, were sown under ambient orE elevated CO2 concentrations in tropical Australia. Seedlings were grown under conditions of photon flux density, temperat= ure and atmospheric vapour pressure deficit which followed ambient variations as closely as possible. Specific leaf area, 8 chlorophyll, stomatal density, stomatal conductance and assimilation responses to photon flux density were measured after 5 30 weeks growth. Gas exchange characteristics were divided into morning and afternoon data sets and analysed separately. S+ tomatal density decreased and leaf area:dry weight ratio decreased in response to elevated CO2. In contrast there was no e) ffect of elevated CO2 upon chlorophyll (total or ratio of a:b). Apparent quantum yield and rates of light saturated assimi! lation (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 s ignificant difference in g(s) between morning and afternoon for ambient grown trees, but g(s) declined significantly betwe en morning and afternoon for elevated CO2 grown trees. Instantaneous transpiration efficiency (ITE) was higher for elevate d 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 mornin g anf afternoon data sets. The slope of the regression between assimilation rate and stomatal conductance increased for pl ants grown under elevated CO2. These data are discussed and compared with the responses of plants adapting to different photon flux densities.YC7FMYB<6\QXK9V MA^" A^3432^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. Experi ments were performed with a 4.5-m diam. OTC that had a sealed floor and a specialized air delivery system. Air flow throug h the chamber was computed with the Bernoulli equation using measurements of the pressure differential between the air del ivery ducts and the chamber interior. An independent measurement of air flow was made simultaneously to calibrate and veri fy 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 w ere collected with OTCs at ambient and elevated CO2 (almost-equal-to 700 mumol mol-1). Results showed that the Bernoulli e quation, 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 avera ges of air flow and C(in) - C(out), was typically within +/- 10% of actual flux, provided that the exit air velocity at th e 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 ga s 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.(#S$#=`I0JT""BM"1`V4#Y M?<0\/<#_`"FAS09Q1;(^7M]X)KN7O.OE_4015,USKXKY-1&DAC'V99 300^3^Masle,J^Hudson,GS^Badger,MR^1993^1^Effects of ambient co2 concentration on growth and nitrogen use in tobacco (nicot iana-tabacum) plants transformed with an antisense gene to the small-subunit of ribulose-1,5- bisphosphate carboxylase oxygenase^8^103^4^1075-1088^^^^^Dec^^^^^3435'@^+C#A+M&7*2EF9S M`X!K[31B@>:RG>9JB6GF#1)+4@.#VD@D/R;/7&&HE)1O$UO9)M+T"A*8%LH/ A^3434^Growth of the R1 progeny of a tobacco plant (Nicotiana tabacum) transformed with an antisense gene to the small sub| unit of ribulose-1,5-carboxylase/oxygenase (Rubisco) was analyzed under 330 and 930 mubar of CO2, at an irradiance of 1000y mumol quanta m-2 s-1. Rubisco activity was reduced to 30 to 50% and 13 to 18% of that in the wild type when one and two cs opies of the antisense gene, respectively, were present in the genome, whereas null plants and wild-type plants had similao r phenotypes. At 330 mubar of CO2 all antisense plants were smaller than the wild type. There was no indication that Rubisa co is present in excess in the wild type with respect to growth under high light. Raising ambient CO2 pressure to 930 muba] r caused plants with one copy of the DNA transferred from plasmid to plant genome to achieve the same size as the wild typT e at 330 mubar, but plants with two copies remained smaller. Differences in final size were due mostly to early differenceP s in relative rate of leaf area expansion (m2 m-2 d-1) or of biomass accumulation (g g-1 d-1): within less than 2 weeks afL ter germination relative growth rates reached a steady-state value similar for all plants. Plants with greater carboxylati? on rates were characterized by a higher ratio of leaf carbon to leaf area, and at later stages, they were characterized al; so by a relatively greater allocation of structural and nonstructural carbon to roots versus leaves. However, these change+ s per se did not appear to be causing the long-term insensitivity of relative growth rates to variations in carboxylation - rate. Nor was this insensitivity due to feedback inhibition of photosynthesis in leaves grown at high partial pressure of  CO2 in the air (p(a)) or with high Rubisco activity, even when the amount of starch approached 40% of leaf dry weight. We  propose that other intrinsic rate-limiting processes that are independent of carbohydrate supply were involved. Under plen tiful nitrogen supply, reduction in the amount of nitrogen invested in Rubisco was more than compensated for by an increas e in leaf nitrate. Nitrogen content of organic matter, excluding Rubisco, was unaffected by the antisense gene. In contras t, it was systematically lower at elevated p(a) than at normal p(a). Combined with the positive effects of p(a) on growth, this resulted in the single-dose antisense plants growing as fast at 930 mubar of CO2 as the wild-type plants at 330 mubar of CO2 but at a lower organic nitrogen cost.ƥ 301^5^Owensby,CE^Coyne,PI^Ham,JM^Auen,LM^Knapp,AK^1993^1^Biomass production in a tallgrass prairie ecosystem exposed to ambient and elevated co2^56^3^4^644-653^^^^^Nov^^^^^3437s A^3436^Responses to elevated CO2 have not been measured for natural grassland ecosystems. Global carbon budgets will likel} y be affected by changes in biomass production and allocation in the major terrestrial ecosystems. Whether ecosystems sequz ester or release excess carbon to the atmosphere will partly determine the extent and rate that atmospheric CO2 concentratj ion rises. Elevated CO2 also may change plant community species composition and water status. We determined above- and bell owground biomass production, plant community species composition, and measured and modeled water status of a tallgrass prae irie ecosystem in Kansas exposed to ambient and twice-ambient CO2 concentrations in open-top chambers during the entire grb owing season from 1989 through 1991. Dominant species were Andropogon gerardii, A. scoparius, and Sorghastrum nutans (C-4 X metabolism) and Poa pratensis (C-3). Aboveground biomass and leaf area were estimated by periodic sampling throughout the T growing season in 1989 and 1990. In 1991, peak biomass and leaf area were estimated by an early August harvest. Relative rV oot production among treatments was estimated using root ingrowth bags which remained in place throughout the growing seas on. Latent heat flux was simulated with and without water stress. Botanical composition was estimated annually. Compared t o ambient CO2 levels, elevated CO2 increased production of C-4 grass species, but not of C-3 grass species. Species compos ition of C-4 grasses did not change, but Poa pratensis (C-3) declined, and C-3 forbs increased in the stand with elevated  CO2 compared to ambient. Open-top chambers appeared to reduce latent heat flux and increase water-use efficiency similar t o the elevated CO2 treatment when water stress was not severe, but under severe water stress, the chamber effect on water- use efficiency was limited. In natural ecosystems with periodic moisture stress, increased water-use efficiency under elevated CO2 apparently would have a greater impact on productivity irrespective of photosynthetic pathway. 302^3^Pettersson,R^McDonald,AJS^Stadenberg,I^1993^1^Response of small birch plants (betula-pendula roth) to elevated co2 and nitrogen supply^9^16^9^1115-1121^^^^^Dec^^^^^3439 A^3438^Small birch plants were grown for up to 80 d in a climate chamber at varied relative addition rates of nitrogen in  culture solution, and at ambient (350 mu mol mol(-1)) or elevated (700 mu mol mol(-1)) concentrations of CO2. The relative addition rate of nitrogen controlled relative growth rate accurately and independently of CO2 concentration at sub- optim um levels. During free access to nutrients, relative growth rate was higher at elevated CO2. Higher values of relative gro wth rate and net assimilation rate were associated with higher values of plant N-concentration. At all N-supply rates, elevated CO2 resulted in higher values of net assimilation rate, whereas leaf weight ratio was independent of CO2. Specific l  A^3072^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 le  af litter, with C:N ratios of 40 and 75 for the ambient and enriched CO2 concentrations, respectively. The litter was ster + ilized and inoculated with microflora and animal groups of increasing complexity (microflora + Protozoa; + nematodes; + Co , llembola; + Isopoda) and incubated over 24 wk. Every two wk, the CO2 release was measured and the litter was leached with 9 demineralized H2O. The following analyses were performed on the leachates: pH, total nitrogen, dissolved and particulate c ; arbon, inorganic nitrogen (NH4+ and NO3-), phosphate, and biological counts (Protozoa, nematodes and Rotifera). The initia A l decomposition stages (the first 12 wk) were dominated by the litter quality factor: CO2 release and nitrogen losses in l C eachates were higher and carbon losses lower in water leaching from the litter with low C:N ratio. Towards the late stages N , when carbon mineralization decreased in the control litter, the animal effect emerged in litter with a high C:N ratio. T P wo groups appeared: (1) In the microflora + Protozoa units, carbon mineralization was reduced by 60% compared with the con ` trol litter. (2) In the diversified food web combinations, it became progressively higher with increasing complexity of th b e animal community and was enhanced by 30% compared with the control litter. This unexpected fundamental difference was ex l plained by a change in the composition and activity of the microflora. Litter bleaching, respiration, C and N leaching and m  acidification rose with increasing animal complexity of the systems. Biological and chemical reasons explaining the invas y ion by white-rot fungi and its activity only in the material with a high C:N ratio are discussed. During the 24 wk. nitrog {en and phosphorus mineralization was very low, indicating a high incorporation of the nutrient in the soil biomass.n mine 109^2^Eamus,D^Murray,M^1991^1^Photosynthetic and stomatal conductance responses of norway spruce and beech to ozone, acid mist and frost - a conceptual-model^35^72^1^23-44^^^^^^^^^^3075s enhanced by 30% compared with the control litter. This A^3074^Two-year-old beech and Norway spruce seedlings were exposed to a combination of ozone and acid mist treatments in o pen-top chambers in Scotland during the months of July through to September 1988. Replicate pairs of chambers received cha rcoal- filtered air (control), ozone-enriched air (140 nl ozone litre- 1) or 140 nl ozone litre-1 plus a synthetic acid mi st (pH 2.5) composed of ammonium nitrate and sulphuric acid. Field measurements of assimilation and stomatal conductance w ere made during August. In addition, measurements of assimilation and conductance were made during September in the labora tory. Light response curves of assimilation and conductance were determined using a GENSTAT non-rectangular hyperbolic mod el. During February 1988/9 the Norway spruce were subject to a four day warming period at 12-degrees-C and the light respo nse of assimilation determined. The same plants were then subject to a 3-h night-time frost of -10-degrees-C. The followin g 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-fu migated trees. The rate of light-saturated assimilation of Norway spruce was increased by ozone fumigation when measured i n 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 significan $t 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- t )erm frosts, which are known to occur with greater frequency than extreme, more catastrophic frost events. A simple concept *ual framework is proposed to explain the variable results obtained in the literature with respect to the impact of ozone upon tree physiology.g signal at g = 2.0007 is attributed to a rapidly tumbling CO2- radical. An axial CO2- radical is s 8110^4^Hunt,R^Hand,DW^Hannah,MA^Neal,AM^1991^1^Response to CO2 enrichment in 27 herbaceous species^43^5^3^410-421^^^^^^^^^^ -A^3076^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, n| /on-limiting supplies of water and mineral nutrients and a daytime mean temperature of 18-degrees-C. Four CO2 treatments wex 0re maintained at nominal concentrations of 350, 500, 650 or 800 v.p.m. over a 56-day period. Hyperbolic functions were fitk 1ted to yield vs CO2 concentration. The functions were then used to generate predictions of Q540/350 (the quotient of preseh 2nt yield under the CO2 regime predicted for the year 2050) and Q700/350 (the quotient of present yield predicted for a douT 3bling of ambient CO2 concentration). Values of Q540/350 for whole-plant dry weight ranged from below 1.01 to 1.49, the uppV 4er values being at least similar in magnitude to those already observed in C3 crops. The mean value of whole-plant Q700/35O 50 for 11 species of near-competitive strategy was 1.43. Four species of stress-tolerant or ruderal strategy had a mean Q70P 60/350 of only 1.05. High CO2 responsiveness was common only within the competitive strategy and its close relations. The fG 7itted Q540/350 for species of the pure strategy was 1.38. In the centre of the strategic range the fitted value was 1.12, Cand at the far extreme, the value for species of ruderal or stress-tolerant strategy was only 1.03.f beech trees in the f=3077ugh stomatal conductance was reduced in the ozone-fumigated trees. The rate of light-saturated assimilation of Norway: :111^2^Idso,SB^Kimball,BA^1991^1^Effects of 2 and a half years of atmospheric CO2 enrichment on the root density distributi%on of 3-year-old sour orange trees^107^55^3-4^345-349^^^^^Jun^^^^^3079of light-saturated assimilation for control and oz! sly supplied with a CO2 enriched atmosphere consisting of an extra 300 cm3 CO2 m-3 of air. Extensive soil coring of the tr ?ees' root zones conducted in July 1990 indicated that two and a half years of growth under these conditions produced a fin @e root biomass enhancement of 175% in the CO2 enriched trees. This growth enhancement is of the same order of magnitude asE our previously reported results for net photosynthesis and trunk and branch volumes for these trees. min (control) to 85? B112^4^Laforge,F^Lussier,C^Desjardins,Y^Gosselin,A^1991^1^Effect of light-intensity and CO2 enrichment during invitro rooti' Mng on subsequent growth of plantlets of strawberry, raspberry and asparagus in acclimatization^165^47^3-4^259-269^^^^^Jul^$ DA^3080^Growth of plantlets of asparagus (Asparagus officinalis L.), raspberry (Rubus idaeus L.) and strawberry (Fragaria X E ananassa Duch.), treated during the in vitro rooting stage under three photosynthetic photon flux densities (PPFD) (80, 1 F25 and 250- mu-mol s-1 m-2) (17.5, 26.9 and 53.8 W m-2 (PAR), respectively) and three CO2 enrichment levels (CDE) (330, 16 G50 and 3000-mu- mol mol-1), was monitored during the acclimatization stage. For the three species, generic differences wer He observed in the plant response to treatments. A significant residual growth enhancement was caused by CDE. High PPFD in Z Ivitro increased the dry weight of strawberry and fresh weight of asparagus in acclimatization. Raspberry leaf dry weight wU Jas increased by 262% in acclimatization after in vitro treatment with high CDE. This enhanced the performance of micropropA Kagated plantlets in acclimatization and reduced by 2 weeks the acclimatization period with raspberry. Our results suggest B Lthat in vitro leaves may be a source of nutritional reserves for leaves initiated ex vitro, but do not exclude a morphogen2etic effect of CO2 during the in vitro rooting stage.weights were compared, and seeds were counted, weighed, and germinat.^^^^3081ability. Plants grown in enriched CO2 environments had significantly greater shoot weights, leaf areas, and root  O113^5^Novero,R^Smith,DH^Moore,FD^Shanahan,JF^Dandria,R^1991^1^Field-grown tomato response to carbonated water application^ 48^83^5^911-916^^^^^Sep-Oct^^^^^3083 biomass allocation patterns further illustrated differences in plant responses to en QA^3082^Direct release of CO2 gas to achieve a cost-effective method of atmospheric CO2 enrichment has not been proven feas Rible under field conditions. We hypothesized that greater efficiency of application would occur by applying CO2 via carbon Sated water and that application would also result in beneficial modifications of the soil environment. Our objectives wereK T to evaluate crop, soil, and atmospheric CO2 responses to application of carbonated water under pressure through a drip irC Urigation system. Studies were conducted under mulched and unmulched conditions in 1988 using tomato (Lycopersicon esculent Vum Mill.). In 1989, carbonated water was applied at approximately 2-, 4-, and 6-d intervals to determine the effect of irr9 Wigation frequency. In 1988, a positive yield response of 9% was obtained in the presence of mulch. No response was observe Xd in open beds. Fruit yields were increased at all three irrigation frequencies in 1989, with increases in fresh-market an Yd total fruit yields averaging 16.4 and 15.9%, respectively. Atmospheric enrichment was observed during carbonated water a Zpplication, but residual enrichment between irrigations was difficult to detect. Significant increase in soil-air CO2 from [ carbonated water application was noted throughout the intervals between successive irrigation events. Carbonated water ap \plication also decreased soil pH for periods of up to 5 d after irrigation and increased apparent uptake of P, K, Ca, Mg,  ]Zn, Fe, Mn, Cu, and B. Based on the limited duration of enrichment relative to the entire growing season for any of the cag ^rbonated water treatments, the yield responses observed could not be attributed solely to atmospheric enrichment. Thus, wei _ conclude that yield increases resulted from the combined effects of limited atmospheric CO2 enrichment and soil environment modifications leading to improved nutrient uptake.es in isotopic distribution patterns for diamonds of ultrabasic and a114^5^Agren,GI^McMurtrie,RE^Parton,WJ^Pastor,J^Shugart,HH^1991^1^State-of-the-art of models of production decomposition linkages in conifer and grassland ecosystems^56^1^2^118-138^^^^^May^^^^^3085lues of the early generation vary widely, where cA^3084^We review the state-of-the-art of models of forests and grasslands that could be used to predict the impact of a fu dture climate change arising from increased atmospheric carbon dioxide concentration. Four levels of resolution are recogni ezed: physiologically based models, population models, ecosystem models, and regional or global models. At the physiologica | fl level a number of important processes can be described in great detail, but these models often treat inadequately intera y gctions with nutrient cycles, which operate on longer time scales. Population and ecosystem models can, on the other hand,  hencapsulate relationships between the plants and the soil system, but at the expense of requiring more ad hoc formulations i of processes. At the regional and global scale we have so far only steady-state models, which cannot be used to predict t _ jransients caused by climate change. However, our conclusion is that, in spite of the gaps in knowledge, there are several [ kmodels based on dominant processes that are well enough understood for the predictions of those models to be taken serious~ly.FECTS OF CO2 ENRICHMENT AND NITROGEN STRESS ON GROWTH, AND PARTITIONING OF DRY-MATTER AND NITROGEN IN WHEAT AND MAIZE S115^1^Amthor,JS^1991^1^Respiration in a future, higher-CO2 world^9^14^1^13-20^^^^^Jan^^^^^3087 AUSTRALIA. ID CARBON-DIOXI N nA^3086^Apart from its impact on global warming, the annually increasing atmospheric [CO2] is of interest to plant scientis A ots primarily because of its direct influence on photosynthesis and photorespiration in C3 species. But in addition, 'dark' @ p respiration, another major component of the carbon budget of higher plants, may be affected by a change in [CO2] independ 0 qent of an increase in temperature. Literature pertaining to an impact of [CO2] on respiration rate is reviewed. With an in . rcrease in [CO2], respiration rate is increased in some cases, but decreased in others. The effects of [CO2] on respiration - s rate may be direct or indirect. Mechanisms responsible for various observations are proposed. These proposed mechanisms r ) telate to changes in: (1) levels of nonstructural carbohydrates, (2) growth rate and structural phytomass accumulation, (3)  u composition of phytomass, (4) direct chemical interactions between CO2 and respiratory enzymes, (5) direct chemical inter  vactions between CO2 and other cellular components, (6) dark CO2 fixation rate, and (7) ethylene biosynthesis rate. Because w a range of (possibly interactive) effects exist, and present knowledge is limited, the impact of future [CO2] on respirat xion rate cannot be predicted. Theoretical considerations and types of experiments that can lead to an increase in the understanding of this issue are outlined.hat concentrations of total-N and nitrate-N were lower in all organs of enriched pla z116^1^Brown,KR^1991^1^Carbon-dioxide enrichment accelerates the decline in nutrient status and relative growth-rate of Populus tremuloides Michx seedlings^13^8^2^161-173^^^^^Mar^^^^^3089udy indicates that critical total-N and NO3-N concentrati |A^3088^Changes in growth dynamics and mineral nutrient concentrations were measured in Populus tremuloides Michx., trembli }ng aspen, grown for 100 days following germination in atmospheres containing 350 or 750-mu-l l-1 CO2. Seedlings were ferti ~lized with nitrogen (N) at concentrations of 15.5 mM (high-N), 1.55 mM (medium-N), or 0.155 mM (low-N). Initially, relativ e 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 w ere accelerated in CO2-enriched plants and accompanied the disappearance of the CO2-induced growth enhancement. It is conc luded that the depression of relative growth rates often associated with long-term CO2 enrichment of plants may result from decreases in plant nutrient status.ed with 7.5, 6.2 and 6.4 mg/g dry wt, respectively, for control plants grown at the 117^3^Caporn,SJM^Mansfield,TA^Hand,DW^1991^1^Low temperature-enhanced inhibition of photosynthesis by oxides of nitrogen in lettuce (Lactuca sativa L)^84^118^2^309-313^^^^^Jun^^^^^3091the three growth stages. Critical concentrations of NO3-N  A^3090^The response of photosynthetic gas exchange to oxides of nitrogen (NO(x)) was studied in leaves of lettuce (Lactucap sativa L.) at different temperatures. Exposure to high concentrations (e.g. 1.3-mu-mol NO(x) mol-1), similar to those oftq en found in commercial glasshouses, caused a rapid inhibition of the net assimilation of CO2. This appeared to be by a dird ect effect on photosynthesis rather than by a change in the stomatal conductance. In ambient CO2 (345-mu-mol mol-1), the pf ercentage inhibition at 10 and 5-degrees-C was approximately 3 x and 5 x, respectively, that measured at 20- degrees-C. Th is effect of temperature also occurred when measured in CO2 enriched air (1050-mu-mol mol-1), which would normally accompa ny NO(x) in a glasshouse. The extent of photosynthetic inhibition caused by NO(x) was, however, always less in high than i n 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.ominal concentrations of 350, 500, 118^3^Elkohen,A^Pontailler,JY^Mousseau,M^1991^1^Effect of doubling of atmospheric CO2 concentration on dark respiration in aerial parts of young chestnut trees (Castanea sativa mill)^176^312^9^477-481^^^^^25 Apr^^^^^3093r the year 2050) and Q A^3092^Two-year-old sweet chestnut seedlings were grown in constantly ventilated tunnels at ambient (350 vpm) or double (7 00 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 compar ed to control plants during the first half of the growing season. This difference decreased with time and became negligibl e in the fall. Atmospheric CO2 concentration acted instantaneously on the respiration rate: when doubled, it decreased con trol plant respiration and when decreased, it enhanced CO2 enriched plant respiration. The explanation of these findings r emains hypothetical. It is concluded that the rise in carbon dioxide level of the atmosphere will affect the carbon balanc e of young trees not only through an increase in net photosynthesis during the day, but also at night by reducing respirat ory losses.& TECHNOL, DEPT BIOCHEM & APPL MOLEC BIOL, POB 88, MANCHESTER M60 1QD, LANCS, ENGLAND. ID ACETATE CATABOLISM; 119^3^Idso,SB^Kimball,BA^Allen,SG^1991^1^CO2 enrichment of sour orange trees - 2.5 years into a long- term experiment^9^14 ^3^351-353^^^^^Apr^^^^^3095d an acetoclastic culture for the methanogenic stage. In continuous culture, A. kivui ferment A^3094^Eight sour orange trees have been grown from seedling stage in the field at Phoenix, Arizona, U.S.A., in four ident z ically-vented, open-top, clear-plastic-wall chambers for close to 2.5 years. Half of the chambers have been maintained at w ambient atmospheric CO2 concentrations over this period, while half of them have been maintained at 300 ppm (300-mu-mol CO x 2 per mol air) above ambient. Initially, the trees in each treatment were essentially identical; but in less than 2 years, h the trunks of the CO2-enriched trees had become twice as large as their ambient-treatment counterparts. After 2 full year g s of growth, the enriched trees had 79% more leaves, 56% more primary branches with 172% more volume, 70% more secondary b V ranches with 190% more volume, and 240% more tertiary branches with 855% more volume. In addition, the CO2-enriched trees R also had fourth-, fifth- and sixth-order branches, while the ambient- treatment trees had no branches above third order. T D otal trunk plus branch volume of the CO2-enriched trees was 2.79 times that of the ambient-treatment trees after 2 full ye @ars of growth.ated negative feedbacks related to cloud characteristics may be a moderate increase in nighttime minimum t 5 120^3^Jiao,J^Tsujita,MJ^Grodzinski,B^1991^1^Influence of temperature on net CO2 exchange in roses^146^71^1^235-243^^^^^Jan 1^^^^^3097educe low temperature stresses on biological and mechanical systems, significantly amplify many of the positive ( A^3096^The effect of temperature on net CO2 exchange of source and sink tissues of the flowering shoots and of whole plant & s 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, narrow  er than the temperature range for optimal leaf net photosynthesis. Dark respiration increased more dramatically than photoX synthesis with temperatures between 15 and 35-degrees-C. At 25-degrees-C, C loss due to respiration from the flower bud atU 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-H 1) whole-plant net photosynthesis was greater at 16-degrees than at 22-degrees-C because of a greater reduction in respiraF tion. 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-d egrees-C. Furthermore, the optimal temperatures for whole- plant net photosynthesis in CO2 enrichment was higher than at ambient CO2 level.HIGH CO2 LEVELS - NO EVIDENCE FOR EITHER PHENOMENON IN 3-YEAR STUDY OF SOUR ORANGE TREES SO PLANT PHYSI 121^4^Kozai,T^Iwabuchi,K^Watanabe,K^Watanabe,I^1991^1^Photoautotrophic and photomixotrophic growth of strawberry plantlets invitro and changes in nutrient composition of the medium^177^25^2^107-115^^^^^May^^^^^3099antium L.) trees maintained i A^3098^Explants excised from strawberry (Fragaria x ananassa Duch.) plantlets were cultured in vitro for 21 days on half-s trength MS (Murashige & Skoog 1962) basal liquid medium with 20 g l-1 sucrose and without sugar in the vessels capped with gas permeable microporous polypropylene film. The experiments were conducted under CO2 nonenriched (350-450-mu-mol mol-1 in the culture room) and CO2 enriched (2,000-mu-mol mol-1 during the photoperiod in the culture room) conditions with a PP F (photosynthetic photon flux) of 200-mu-mol m-2 s-1. The CO2 concentration in the vessels decreased to approximately 200- mu- mol mol-1 during the photoperiod on day 21 under CO2 nonenriched conditions. The fresh and dry weight, net photosynthe tic rate (NPR) per plantlet, NPR per g leaf fresh weight, NPR per g leaf dry weight, the number of unfolded leaves, and io n uptake of PO4(3-), NO3-, Ca2+, Mg2+ and K+ on day 21 were the greatest under photoautotrophic (no sugar in the medium) a nd CO2 enriched conditions. The residual percent of PO4(3-) was 3% on day 21 under photoautotrophic and CO2 enriched condi tions.n on cyclic AMP synthesis was studied in glia-free, low-density, monolayer cultures of chick retinal photoreceptors 122^2^Paffen,BGP^Roelofs,JGM^1991^1^Impact of carbon-dioxide and ammonium on the growth of submerged Sphagnum cuspidatum^1 59^40^1^61-71^^^^^Apr^^^^^3101lar concentration of cyclic AMP and stimulated the conversion of [H-3]adenine to [H-3]cycli A^3100^In a culture experiment, the influence of carbon dioxide and ammonium on the growth of Sphagnum cuspidatum Hoffin. was studied. During a 12-week period, S. cuspidatum was grown in a solution with various concentrations of carbon dioxide and ammonium. The culture experiment clearly demonstrated that the biomass and the length of S. cuspidatum only increased strongly when the carbon dioxide concentration of the water was high. Further it is shown that ammonium enrichment without CO2 enrichment does not lead to an increase in biomass of S. cuspidatum.photoreceptor-enriched cultures. BP 615-621 PG 7 123^3^Baker,JT^Allen,LH^Boote,KJ^1990^1^Growth and yield responses of rice to carbon-dioxide concentration^178^115^^313-32 0^^^^^Dec^^^^^3103SO2 RECOVERY FROM FLUE-GAS BY PRESSURE SWING ADSORPTION SO INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH A^3102^Rice plants (Oryza sativa L., cv. IR30) were grown in paddy culture in outdoor, naturally sunlit, controlled-enviro nment, 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 increas e occurring between the 160 and 500 mu-mol CO2/mol air treatments. Early in the growing season, root:shoot biomass ratio i ncreased 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 are a among CO2 treatments were largely due to corresponding differences in tillering response. The number of panicles/plant w as almost entirely responsible for differences in final grain yield among CO2 treatments. Doubling the CO2 concentration f  rom 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 q to rise. indicate that the results of the present work can be further improved by using these polymeric sorbents. BP 198 p 124^3^Fajer,ED^Bowers,MD^Bazzaz,FA^1991^1^The effects of enriched CO2 atmospheres on the buckeye butterfly, Junonia coenia k^11^72^2^751-754^^^^^AprT OF LIGHT-INTENSITY AND CO2 ENRICHMENT DURING INVITRO ROOTING ON SUBSEQUENT GROWTH OF PLANTLETS g 125^1^Jansen,DM^1990^1^Potential rice yields in future weather conditions in different parts of asia^179^38^4^661-680^^^^^ [Dec^^^^^3106ORT, DEPT PHYTOL, QUEBEC CITY G1K 7P4, QUEBEC, CANADA. DE ASPARAGUS-OFFICINALIS; FRAGARIAXANANASSA; LIGHT; MI Z A^3105^Future climate change is expected to vary between regions, with possible different effects on crop growth. Various S sites in Asia were selected to represent major rice growing environments. Historic weather data of these sites were adapte O d to possible changes in temperature and in CO2 level, to mimic climate change. Potential rice yields at present, and for I the years 2020 and 2100 were calculated with a crop growth simulation model. Simulated yields rose in low and middle tempe H rature 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-degre < es-N. Water use efficiency decreased in the high temperature scenario irrespective of CO2 scenario, and increased otherwis 5e.e of micropropagated plantlets in acclimatization and reduced by 2 weeks the acclimatization period with raspberry. Ou 1 126^3^Jiao,J^Tsujita,MJ^Grodzinski,B^1991^1^Influence of radiation and CO2 enrichment on whole plant net CO2 exchange in r oses^146^71^1^245-252^^^^^Jan^^^^^31088tro rooting stage. BP 259-269 PG 11 JI Sci. Hortic. PY 1991 PD JUL VL 47 IS 3-4 G # A^3107^At three stages of flowering shoot development, varying the irradiance and CO2 levels had a similar effect on the w  hole- 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 t o 24 h of continuous irradiation at the lower photon flux density retained 80% more C. Under saturating irradiance, the ne t photosynthetic rate at an enriched (1000-mu-L L-1) CO2 level was almost double that at ambient (350-mu-L L-1) CO2. Howev er, plants grown at ambient and enriched CO2 levels had similar whole-plant NCERs when compared at the same assay CO2 leve l. 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.bjects studied. Superimposed on this increase were short-term non 127^5^Kurooka,H^Fukunaga,S^Yuda,E^Nakagawa,S^Horiuchi,S^1990^1^Effect of carbon-dioxide enrichment on vine growth and berry quality of kyoho grapes^180^59^3^463-470^^^^^Dec^^^^^3110nential models. Triglyceride FSR of the subjects over the firs A^3109^Although ambient temperature is kept adequate, grape cultivation under covered facilities during winter months in J apan gives rise to low yields of poor quality berries because of low light intensities. This investigation was conducted i n leaf chamber, using Vitis labruscana Bailey cv. Kyoho, to determine the influence of leaf age, light intensity, and CO2 concentrations on photosynthesis. The effects of CO2 enrichment on vine growth and fruit quality were also investigated in growth chambers. 1. The rate of photosynthesis per unit leaf area (Pn) between May 28 and September 19 rapidly increased ~ with leaf growth, reaching a maximum of 18.9 mg CO2/dm2/hr, 37 days after the unfolding of a leaf. Pn then gradually decre| ased with leaf age. In young leaves, higher CO2 concentrations and stronger light intensities resulted in a significant inj crease in Pn. Older leaves exhibited a similar enhancement of Pn upon exposure to high light intensity. Pn was saturated ai t 828 ppm CO2. 2. Administration of 1,000 to 1,100 ppm CO2 to vines for an 8 hr/day at a late stage of berry development u ntil harvest had no effect on berry size but resulted in an increase in sugar and anthocyanin contents but a decrease in o rganic acid content. Dry weight of newly developed roots doubled as a result of CO2 enrichment. 3. Application of CO2 unde r a long-day photoperiod at an early stage of berry development to a week before veraison markedly promoted shoot elongati on. Furthermore, CO2 enrichment gave a 36% increase in both berry and cluster weights and also a higher sugar-acid ratio at harvest.O2 production in grain at 17% water content (table I and fig 6). This led to oxygen consumption within a few d 128^2^Lindhout,P^Pet,G^1990^1^Effects of CO2 enrichment on young plant-growth of 96 genotypes of tomato (Lycopersicon esculentum)^181^51^2^191-196^^^^^Dec^^^^^3112s 1-2). The adsorption-desorption effect was quantitatively assessed. This per A^3111^The early growth of 96 genotypes of tomato was studied at 320 ppm CO2 and at 750 ppm CO2 in separate climate rooms. Plants were harvested at 40 and 55 days after sowing. Fresh and dry weights were determined. Large differences between ge  244^6^Beerling,DJ^Chaloner,WG^Huntley,B^Pearson,JA^Tooley,MJ^Woodward,FI^1992^1^Variations in the stomatal density of sali  x-herbacea L under the changing atmospheric co2 concentrations of late-glacial and postglacial time^190^336^1277^215-224^^ ^^^29 May^^^^^3330 Assuming a population of a short-lived perennial (or annual?) with a short-lived seed bank and high  A^3329^The rapidly rising CO2 concentration of the past 200 years has been shown to be accompanied by a fall in stomatal d % ensity in the leaves of temperate trees. The present study attempts to investigate the relationship of atmospheric CO2 cha & nge 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 fro / m living populations growing in Austria, Greenland and Scotland. The Austrian material, from an altitudinal gradient betwe 2 en 2000 and 2670 m above sea level, gives added comparison of contemporary differences of CO2 partial pressure with altitu < de. The results of our investigation indicate, rather surprisingly, that the rising CO2 concentration of the past 11 500 y > ears has been accompanied by an increase in the stomatal density of S. herbacea in contrast to the shorter-term observatio N ns on the herbarium material of temperate trees. The most likely explanation appears to centre on the temperatures and wat P er availability of the early post-glacial environment overriding the effect of the lower CO2 regime. However, the scale of a  the time interval involved may also be significant. Natural selection over the 11 500 year period concerned may have favo c ured a different response to what is, in effect, an acclimatory response observed in trees within the period of rapid CO2 irise of the past 200 years.ime.ease.lsoft.com [209.119.1.41]) by mx2.osu.edu (PMDF V5.2-29 #34303) with ESMTP id <0F7 j 245^2^Grimm,AG^Fuhrer,J^1992^1^The response of spring wheat (triticum-aestivum L) to ozone at higher elevations .1. Measur lement of ozone and carbon-dioxide fluxes in open-top field chambers^84^121^2^201-210^^^^^Jun^^^^^333299 15:31:52 -0500 D z A^3331^The flux of O3 was determined in open-top chambers (OTC) used to investigate its effect on spring wheat (Triticum a | estivum L., cv. Albis) in 1989 and 1990. The experimental site was located at 900 m above sea level at Zimmerwald, near Be rn (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. Th e CO2 exchange rate was corrected for soil-borne CO2 and used as a reference. Measurements of temperature, photosynthetica lly active radiation (PAR), saturated water vapour pressure deficit (SVPD), and boundary layer conductance were used to de scribe the microclimate inside OTCs. In the warmer microclimate in 1989, the plant canopy was characterized by a smaller l eaf area index (LAI) than in 1990, while the fluxes of O3 and CO2 during daytime were generally larger in 1989. The diurna l patterns of fluxes of O3 and CO2 in OTCs supplied with unfiltered air were similar. It is estimated that O3 absorption v ia 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 dayt !ime 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.v 246^1^Grodzinski,B^1992^1^Plant nutrition and growth-regulation by co2 enrichment^14^42^7^517-525^^^^^Jul-Aug '247^2^Idso,SB^Kimball,BA^1992^1^Effects of atmospheric co2 enrichment on photosynthesis, respiration, and growth of sour o range trees^8^99^1^341-343^^^^^May^^^^^3335arperspective )A^3334^Numerous net photosynthetic and dark respiratory measurements were made over a period of 4 years on leaves of 24 so *ur orange (Citrus aurantium) trees; 8 of them growing in ambient air at a mean CO2 concentration of 400 microliters per li +ter, and 16 growing in air enriched with CO2 to concentrations approaching 1000 microliters per liter. Over this CO2 conce ,ntration range, net photosynthesis increased linearly with CO2 by more than 200%, whereas dark respiration decreased linea -rly to only 20% of its initial value. These results, together with those of a comprehensive fine-root biomass determinatio .n 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.sland Sound, CT/Ns 0248^4^Kozai,T^Kushihashi,S^Kubota,C^Fujiwara,K^1992^1^Effect of the difference between photoperiod and dark period temperaq 1tures, and photosynthetic photon flux-density on the shoot length and growth of potato plantlets invitro^180^61^1^93-98^^^e^^Jun^^^^^3337v 609:02 PM 17 02 1999 -0600John Madsena 3A^3336^Potato plantlets (Solanum tuberosum L. cv. Benimaru) under CO2 enriched and photoautotrophic culture conditions werW 4e subjected to three different photo-/dark period temperature combinations (25-degrees/15-degrees-C, 200/20-degrees-C and T 515-degrees/25- degrees-C) and two levels of photosynthetic photon flux densities (74 and 147-mu-mol.m-2.sec-1). The shoot L 6length of the plantlets under the same photosytnthetic photon flux density (PPF) was reduced with decreasing the differencH 7e between photoperiod and dark period temperatures (it is named DIF, photoperiod temperature minus dark period temperature8 8). No marked differences in the fresh and dry weights per plantlet were observed among the three DIF treatments in each PP: 9F treatment. The higher PPF led to a decrease in the shoot length, an increase in the fresh weight, dry weight and leaf ar. :ea per plantlet in each DIF treatment. It is suggested that shoot length of plantlets in vitro under CO2 enriched and phot0 ;oautotrophic culture conditions can be controlled without reducing the weight increments and leaf area per plantlet by reg&ulating the difference between photoperiod and dark period temperatures.1999 -0500Martin Mitchell" =249^3^Nederhoff,EM^Dekoning,ANM^Rijsdijk,AA^1992^1^Leaf deformation and fruit production of glasshouse grown tomato (lycopersicon-esculentum mill) as affected by co-2 plant-density and pruning^174^67^3^411-420^^^^^May^^^^^3339USGS # ?A^3338^During summer, glasshouse grown tomato plants (Lycopersicon esculentum Mill.) often demonstrate leaf deformation, r @educed leaf area (short leaves) and low Specific Leaf Area (SLA), sometimes accompanied by higher dry matter content of le Aaves and stems and higher leaf starch content. This so-called "Short Leaves Syndrome" (SLS), which decreases the productio Bn capacity, was investigated with emphasis on the effects of CO2 concentration. As a working hypothesis it was postulated  Cthat SLS is indirectly caused by an oversupply of assimilates relative to the sink capacity. An experiment was conducted b Detween 10 May and 31 July 1990 in 12 glasshouse compartments. The sink/source ratio was varied by maintaining two levels o Ef CO2, multifactorially combined with two plant densities and three pruning treatments. CO2 enrichment and wider planting  Fenhanced SLS and decreased leaf area and SLA of upper leaves. Leaf pruning and fruit pruning, however, did not give clear  Geffects on vegetative characteristics, although the impact on the sink/source ratio was of the same order of magnitude. As H a mechanism for these effects, we suggest that SLS is caused by calcium deficiency in the apex, a condition more severe w Ihen much phloem sap (with low calcium content) is available, i.e. when the sink/source ratio is lower. Stronger effects of J CO2 and plant density than of pruning on the incidence of SLS, may be due to local effects of sink/source relationships o Kr to involvement of other processes, like transpiration. In crops with little SLS-symptoms, CO2 enrichment increased the w Leight of fruits grown during the treatment period by 31%, whereas in crops with severe SLS, CO2 enrichment aggravated SLS  Mand had no significant effect on fruit production. CO2 enrichment in summer is beneficial if SLS is prevented, which can be achieved by maintaining a higher plant density or, in an early crop, an extra shoot on the plants in spring and summer. O250^2^Rastetter,EB^Shaver,GR^1992^1^A model of multiple-element limitation for acclimating vegetation^11^73^4^1157-1174^^^^^Aug^^^^^3341ntervals to determine the effect of irrigation frequency. In 1988, a positive yield response of 9% was obt QA^3340^In this paper we present a simple model of multiple-element limitation of plant production and biomass accumulation R. The primary aim of this model is to develop a theoretical framework for examining multiple-element limitation vs. single} S-element limitation and for examining the relationship between short- term and long-term responses to changes in element ay Tvailability. In the model we assume that there is an "optimal" ratio of mineral elements in vegetation biomass, and that tr Uhe vegetation continually adjusts its relative element uptake capacities to compensate for shifts away from this optimum. m VWe examine the responses of this model to changes in element availability in the plant environment, where "availability" ic Ws defined either as fixed concentrations of non-depletable elements or as fixed replenishment rates of depletable elements X. The model results suggest that the nature of the controls on element availability has a major impact on whether single-  Yor multiple-element limitation prevails, even when plants can acclimate so as to maintain an "optimal" nutritional balance Z. Single-element limitation occurs when the replenishment rate of an essential element to the available pool is limited an [d sustainable plant uptake of that element equals the replenishment rate. Furthermore, when single- element limitation pre \vails, there is little or no correlation between short-term responses to a change in element availability and long-term, e ]quilibrium responses. In general, previous experimental studies and models of plant growth in response to changes in relat ^ive availability of multiple, essential elements have either not specified how those resources are controlled, or have exa _mined only one type of control. Our results help to explain the diversity of results of past studies of multiple-element l `imitation, suggest some improvements in experimental design for future studies, and have important implications for the extrapolation of the results of controlled experiments to field situations.th CO2-enriched solution (pH0 6.0) resulted in f b251^3^Watanabe,Y^Ohmura,N^Saiki,H^1992^1^Isolation and determination of cultural-characteristics of microalgae which funct ions under co2 enriched atmosphere^191^33^5-8^545-552^^^^^May-Aug^^^^^3343New Opportunity for Ecology Education dA^3342^A fresh-water microalgae, which functions under CO2 enriched atmosphere conditions, was isolated and its cultural c eharacteristics were investigated. The HA-1 strain, identified as genus Chlorella, was newly isolated from a paddy field by f an enrichment culture using reproduced stack gases from a thermal power plant with a concentration of CO2 and O2 of 15 % gand 2 % respectively. It showed maximum growth at 10 % CO2 enriched air flowing condition, and showed a good growth rate i hn a broad range of physically controllable conditions, including CO2 enriched air flow rate, temperature and pH value. The results indicated the feasibility of the HA-1 strain for mass cultivation using stack gases.:54 AM 11 02 1999 -0700 252^1^Goudriaan,J^1992^1^Where goes the carbon-dioxide - the role of vegetation^192^23^243^597^^^^^May k253^4^Doi,M^Oda,H^Ogasawara,N^Asahira,T^1992^1^Effects of co2 enrichment on the growth and development of invitro cultured plantlets^180^60^4^963-970^^^^^Mar^^^^^3346U3  mA^3345^Plantlets of Caladium bicolor (C3 plant), Saccharum officinarum (C4 plant), and Phalaenopsis hybrid (CAM plant) at nthe preparation stage for acclimatization (the final stage of in vitro culture) were cultured on the medium containing 2% osucrose. The culture vessels were kept under continuous, 16 hr, or 8 hr lighting conditions; half of the vessels were vent pilated continuously with 0.8 +/- 0.4% CO2 enriched atmosphere; while the remainder was exposed to ambient atmosphere. The  qgrowth of plantlets was promoted with an increase in daylength under both ambient and CO2 enriched atmospheres. When the p rlantlets were supplied with adequate CO2, dry matter production increased under all daylength treatments except Caladium c sultured under continuous lighting. This promotive effect of CO2 enrichment was especially noticeable in root growth. In Ca tladium and Phalaenopsis, the leaf chlorophyll content of plantlets cultured under CO2 enriched atmosphere was less than th uat of leaves from plantlets grown in ambient atmosphere. Although the chlorophyll was less concentrated in leaves of plant vlets growing under the CO2 enriched treatment, the rate of CO2 uptake of these plantlets measured at the midpoint of the l wight period was higher than that of leaves exposed to ambient atmosphere. Increasing the O2 concentration in culture vesse xls to 37% also promoted the growth of Caladium and Dendrobium phalaenopsis (CAM plant) under CO2 enriched condition. Becau* yse 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.PIENZA, DIPARTMENTO7 {254^4^Easterling,WE^Rosenberg,NJ^Lemon,KM^McKenney,MS^1992^1^Simulations of crop responses to climate change - effects wit9 h present technology and currently available adjustments (the smart farmer scenario)^107^59^1-2^75-102^^^^^15 Apr^^^^^3348E }A^3347^If climate changes, farmers will have to adapt to a new set of climate constraints. In this paper we examine the efG ~ficacy of strategies for dealing with climate change that are currently available to farmers and that are inexpensive to u[ se; we refer to this group of strategies as 'adjustments'. Adjustment schemes of various kinds were identified for us by a] gricultural experts in the Missouri-Iowa-Nebraska-Kansas (MINK) states. These can involve changes in land use, changes in s variety and crop selection, changes in planting and harvesting practices, and changes in fertility and pest management. Usu ing 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 mois ture conservation would offset some of the yield losses induced by climate change in warm-season crops. Longer-season vari eties of wheat (a cool-season crop) and shorter-season varieties of the perennials wheatgrass and alfalfa were also effect ive. The adjustments to climate change diminished yield losses in all crops but irrigated wheat. Despite the positive effe cts of adjustments, however, yields of all dryland warm-season crops remained lower than control levels. The adjustments a lso increased demand for irrigation water. Carbon dioxide enrichment had the same incremental effect on crop yields with o r without adjustments (see the fourth paper in this issue), except in the case of alfalfa and sorghum, where a CO2- adjust ment 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.nt, in particular atsed salinity (250 mM NaCl). BP 45-55 PG 11 JI Aquat. Bot. PY 1991 PD FEB VL 39 IS 1-2 GA FC985 RP ROZEMA J J9 AQUAT BOT E 255^3^Grobbelaar,N^Chou,WM^Huang,TC^1992^1^Effect of co2, o2, dcmu, fccp, and dl-glyceraldehyde on the nitrogenase activity of synechococcus rf-1^193^33^2^167-174^^^^^Apr^^^^^3350STRUCTION RESPIRATION; MAINTENANCE RESPIRATION; NITROGEN; PLANT  A^3349^Elevated atmospheric CO2 concentrations drastically inhibit nitrogenase activity of the unicellular Synechococcus R F-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 hou rs after the organism has been returned to air not enriched with CO2. The nitrogenase activity of heterocystous cyanobacte ria, generally, does not appear to be affected by 5% CO2 in the air. DCMU strongly enhanced nitrogenase activity and inhib ited the assimilation of CO2 by Synechococcus RF-1 in the light, and elevated atmospheric O2 concentrations reduced the ni trogenase 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 4than in the light.climation of respiration rates to different climates are poorly understood, but may substantially affec6 256^2^Hollander,B^Krug,H^1992^1^Effects of high co2-concentrations on vegetable species .2. Growth, co2-gas-exchange and s<tomata resistance^172^57^1^32-43^^^^^Jan-Feb^^^^^3352TASSIC AND SODIC ALTERATION ACCOMPANYING GOLD MINERALIZATION IN THE > A^3351^In the climatic conditions tested the growth of young cucumber plants (3-7 leaf stage) was slightly promoted as welF l 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 eH nrichment during the night was not evident. The analysis of the growth components and gas exchange measurements revealed, O that CO2 enrichment during the day as well as during day and night increased net assimilation rate and dark respiration diQ stinctly. Enrichment during the night showed no effect on net assimilation rate and increased dark respiration only slight\ ly. The specific leaf area was strongly reduced by the high CO2 concentration, but leaf weight ratio was rarely changed. B^ y these morphogenetic effects growth promotion by an increased net assimilation rate was diminished. Continuous CO2 enrichk ment to cucumber plants with CO2 concentrations greater- than-or-equal-to 1000-mu-l/l decreased stomata resistance. This em ffect increased with higher CO2 concentrations and longer treatments. The stomata remained open even at night and at low a{ ir 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 proce eds 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.teration episodes are considered to be part of the 257^1^Smith,RB^1992^1^Controlled-atmosphere storage of redcoat strawberry fruit^154^117^2^260-264^^^^^Mar^^^^^3354the cru A^3353^Strawberries (Fragaria x ananassa Duch.) cv. Redcoat were stored at several temperatures and for various intervals  in controlled atmospheres (CA) containing 0% to 18% CO2 and 15% to 21% O2. Bioyield point forces recorded on the CA-stored fresh fruit indicated that the addition of CO2 to the storage environment enhanced fruit firmness. Fruit kept under 15% C O2 for 18 hours was 48% firmer than untreated samples were initially. Response to increasing CO2 concentrations was linear . There was no response to changing O2 concentrations. Maximum enhancement of firmness was achieved at a fruit temperature of 0C; there was essentially no enhancement at 21C. In some instances, there was a moderate firmness enhancement as time  in storage increased. Carbon dioxide acted to reduce the quantity of fruit lost due to rot. Fruit that was soft and bruised after harvest became drier and firmer in a CO2-enriched environment.ZENES; AROMATIC COMPOUNDS ID SULFATE-REDUCING BACTE 258^2^Vanhinsberg,N^Horton,RF^1992^1^Ethylene metabolism in pulvini of phaseolus-vulgaris L^194^188^1^51-55^^^^^Feb^^^^^33 A^3355^The ability of leaf blade, pulvinar and petiolar tissue from primary leaves of Phaseolus vulgaris to release ethyle ne when incubated in a 1 mM solution of the ethylene-biosynthesis precursor, 1-aminocyclopropane-1-carboxylic acid, was de termined over a 6h period. Ethylene release was measured under CO2-enriched and CO2-depleted conditions in the light and d ark. In contrast to blade and petiolar tissue, the pulvini released more ethylene in the light than in the dark when held in sealed flanks. The amount of the gas released is largely independent of external levels of carbon dioxide.roquinone as56 donor. The strain grew in sulfide-reduced mineral medium supplemented with 7 vitamins. The DNA base ratio was 59% G + 259^3^Wilson,JW^Hand,DW^Hannah,MA^1992^1^Light interception and photosynthetic efficiency in some glasshouse crops^78^43^248^363-373^^^^^Mar^^^^^3358ogallol-grown cells showed different kinetics of hydroxyhydroquinone and pyrogallol degradatio A^3357^Productivity of glasshouse crops is strongly limited by light receipt, and efficient interception and use of light  in photosynthesis is correspondingly important. Mature row crop canopies of cucumber and tomato intercepted about 76% of t he light incident on their upper surfaces; about 18% was lost through gaps between the rows. Light transmitted through the entire depth of the canopy was reflected back by white plastic on the ground, so that the lower surface of the canopy rec eived approximately 13% of the light incident on the upper surface. The light flux incident on the sides of these canopies! (c. 2 m tall and 6 m x 16 m in area) amounted to some 20-30% of that incident on the upper surface. About 32% of daylight# falling on the glasshouse (c. 9 m x 18 m in area) was intercepted by the glasshouse structure and glazing; of the 68% ent3 ering the house, some fell on headlands occupying 35% of the glasshouse area. The loss of light to headlands, and the gain5 from canopy side-lighting, would be relatively smaller for larger glasshouses. At near-ambient CO2 concentrations, net phK otosynthetic rates of the cucumber canopy were comparable to those of closed canopies of other glasshouse and field crops M which have maximum light conversion efficiencies of 5-8-mu-g CO2 J-1 at 50-200 W m-2 incident light flux density. EfficienY cy decreases only slightly with stronger light. Glasshouse crops with CO2 enrichment to 1200 vpm achieve conversion effici[ encies of 7-10-mu-g CO2 J-1. Efficiencies of utilization of intercepted light, on an energy basis, reach 6-10% in various l field and glasshouse crops with near-ambient CO2, and reached an exceptional 11% for the cucumber canopy. Glasshouse cropsn with CO2 enrichment achieve maximum efficiency of light energy utilization between 12% and 13%.out significant decomposi| 260^2^Chalabi,Z^Fernandez,JE^1992^1^Spatiotemporal responses of a glasshouse to gaseous enrichment^195^51^2^139-151^^^^^Fe~bction. However, by reaction with NO, PtCl3(CO)- in the CuCl-CuCl2-HCl system evolves CO2 and N2O rapidly. The presence  261^1^Mortensen,LM^1992^1^Effects of ozone concentration on growth of tomato at various light, air humidity and carbon-dioxide levels^165^49^1-2^17-24^^^^^Jan^^^^^3361the observed behavior of the system, the results of kinetic studies may be e A^3360^The effect of ozone (O3) Concentration on the growth of Lycopersicon esculentum was studied at different photosynth etic photon flux densities (PPFD), relative air humidities (RH) and carbon dioxide (CO2) concentrations. Increasing the O3 concentration from < 10 to 85 nl l-1 for 6 h per day reduced the shoot dry weight 35% at 70% RH and 62% at 90% RH. Increa sing the PPFD from 100 to 350-mu-mol m-2 s-1 significantly reduced the effect of O3 in one of two experiments. The most pr onounced interaction between RH, PPFD and O3 was found on plant height. High O3 levels generally decreased plant height at low PPFD and had no, or a stimulating, effect at high PPFD. Raising the RH from 70 to 90% significantly increased the neg ative effect of O3 on height. Increasing the O3 concentration from < 10 to 65 nl l-1 significantly decreased plant height at low CO2 concentration (300-340-mu-l l-1), but small effects were found at high CO2 concentration (700-800-mu-l l-1).NN 262^3^Suzuki,T^Ohtaguchi,K^Koide,K^1991^1^Effects of gas-flow rate of co2-enriched air, high co2 concentration, and anaerobic atmosphere on the growth of blue- green-alga anacystis-nidulans^196^24^6^797-798^^^^^Dec Precision laboratory isotopi 263^3^Wullschleger,SD^Norby,RJ^Hendrix,DL^1992^1^Carbon exchange-rates, chlorophyll content, and carbohydrate status of 2 forest tree species exposed to carbon-dioxide enrichment^13^10^1^21-31^^^^^Jan^^^^^3364s was 9 to 16% in 50O3 and 8 to 11 A^3363^Seedlings of yellow-poplar (Liriodendron tulipifera L.) and white oak (Quercus alba L.) were exposed continuously t o one of three CO2 concentrations in open-top chambers under field conditions and evaluated after 24 weeks with respect to carbon exchange rates (CER), chlorophyll (Chl) content, and diurnal carbohydrate status. Increasing the CO2 concentration from ambient to +150 or +300-mu-l l-1 stimulated CER of yellow- poplar and white oak seedlings by 60 and over 35%, respec tively, compared to ambient-grown seedlings. The increases in CER were not associated with a significant change in stomata l conductance and occurred despite a reduction in the amounts of Chl and accessory pigments in the leaves of plants grown  in CO2-enriched air. Total Chl contents of yellow-poplar and white oak seedlings grown at +300-mu-l l-1 were reduced by 27 and over 55%, respectively, compared with ambient-grown seedlings. Yellow-poplar and white oak seedlings grown at +300-mu -l l-1 contained 72 and 67% more morning starch, respectively, than did ambient-grown plants. In contrast, yellow-poplar a nd white oak seedlings grown at +300-mu-l l-1 contained 17 and 27% less evening sucrose, respectively, than did plants gro" wn at ambient CO2 concentration. Diurnal starch accumulation and the subsequent depletion of sucrose contributed to a pron$ ounced increase in the starch/sucrose ratio of plants grown in CO2-enriched air. All seedlings exhibited a substantial red/ uction in dark respiration as CO2 concentration increased, but the significance of this increase to the carbohydrate statu1s and carbon economy of plants grown in CO2-enriched air remains unclear.alyst prereduced and used in CO hydrogenation at@ 264^6^Briones,GL^Varoquaux,P^Chambroy,Y^Bouquant,J^Bureau,G^Pascat,B^1992^1^Storage of common mushroom under controlled atBmospheres^197^27^5^493-505^^^^^Oct^^^^^3366u enrichment occurs on the topmost layer of catalysts. BP 335-344 PG 10 JI CatD A^3365^The effect of controlled atmosphere (CA) on the shelf-life of the common mushroom (Agaricus bisporus) was assessed N using six parameters correlated with its commerical qualities. Low CO2 concentrations (up to 2.5%) reduced brown discolourP ation compared to the control in air. Higher CO2 concentrations enhanced both internal and external browning. Low O2 conce] ntrations 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 mup shrooms. A lower mannitol content was noted in mushrooms stored under CA than those stored in air (control). Mushrooms stor red in a 5% CO2 atmosphere for 7 days did not break their veil but their texture was very soft and spongy. Texture losses tdecreased when CO2 concentrations increased.pected increase in primary production. Whether this will lead to accumulation} 265^5^Gordon,HB^Whetton,PH^Pittock,AB^Fowler,AM^Haylock,MR^1992^1^Simulated changes in daily rainfall intensity due to the enhanced greenhouse-effect - implications for extreme rainfall events^198^8^2^83-102^^^^^Dec^^^^^3368ots into the soil a A^3367^In this study we present rainfall results from equilibrium 1 x - and 2 x CO2 experiments with the CSIRO 4-level gen eral circulation model. The 1 X CO2 results are discussed in relation to observed climate. Discussion of the 2 x CO2 resul ts focuses upon changes in convective and non-convective rainfall as simulated in the model, and the consequences these ch anges have for simulated daily rainfall intensity and the frequency of heavy rainfall events. In doing this analysis, we r ecognize the significant shortcomings of GCM simulations of precipitation processes. However, because of the potential sig nificance of any changes in heavy rainfall events as a result of the enhanced greenhouse effect, we believe a first examin ation of relevant GCM rainfall results is warranted. Generally, the model results show a marked increase in rainfall origi nating from penetrative convection and, in the mid- latitudes, a decline in large-scale (non-convective) rainfall. It is a rgued that these changes in rainfall type are a consequence of the increased moisture holding capacity of the warmer atmos phere simulated for 2 x CO2 conditions. Related to changes in rainfall type, rainfall intensity (rain per rain day) increa ses in the model for most regions of the globe. Increases extend even to regions where total rainfall decreases. Indeed, t he 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 anA^3442^Two-year-old Sitka spruce (Picea sitchensis (Bong.) Carr.) plants from four clones were grown in naturally lit growth chambers for 6 months at either ambient (350 ppm) or ambient + 250 ppm (600 ppm) CO2 concentration. Plants were grown in large boxes filled with peat, in a system that allowed the roots of individual plants to be harvested easily at the end of the growing season. Half of the boxes were kept well watered and half were allowed to dry out slowly over the summer. Plants growing in elevated CO2 showed a 6.9% increase in mean relative growth rate compared to controls in the drought treatment and a 9.8% increase compared to controls in the well-watered treatment, though there was considerable variation in response among the different clones and water treatments. Rates of net CO2 assimilation were higher and stomatal conductanc es were lower in plants grown in elevated CO2 than in ambient CO2 in both the well-watered and drought treatments. Both of  these factors contributed to the doubling of instantaneous water use efficiency. The partitioning of biomass to roots was unaffected by elevated CO2, but the ratio of needle mass/stems + branches mass decreased. Together with reduced stomatal conductance, this probably caused the observed increases in xylem pressure potentials with elevated CO2.CELLS; GONADOTROP! 305^2^Tremmel,DC^Patterson,DT^1993^1^Responses of soybean and 5 weeds to co2 enrichment under 2 temperature regimes^146^73,^4^1249-1260^^^^^Oct^^^^^3445TS; CA-2+ AB The patch-clamp technique has been used to measure changes in membrane capacita.A^3444^Rising atmospheric CO2 levels could affect plant growth both directly, through effects on physiology, and indirectl:y, through the effects of possible CO2-induced temperature increases. In this study we examined the interacting effects of< CO2 enrichment and temperature on the growth and allocation of soybean and five weeds. individual plants of soybean [GlycNine max (L.) Merr. 'Braxton'] , johnsongrass [Sorghum halepense (L.) Pers. quackgrass [Elytrigia repens (L.) Nevski] , redOroot pigweed (Amaranthus retroflexus L.), sicklepod (Cassia obtusifolia L.). and velvetleaf (Abutilon theophrasti Medic.) \were grown in growth chambers in all combinations of two temperatures (avg. day/night of 26/19-degrees-C and 30/23- degree^s-C) and two CO2 concentrations (350 and 700 ppm) for 35 d. Leaf area and plant biomass were greater at higher temperaturels, regardless of CO2 level, in all species except quackgrass. Quackgrass (C3) produced its greatest leaf area and biomass nat elevated CO2, whereas johnsongrass (C4) showed little response. Redroot pigweed (C4) and the C3 dicotyledenous species y(soybean, sicklepod, velvetleaf) produced their greatest biomass at high CO2, though effects on leaf area were less consis{tent or absent. In general, when significant CO2 by temperature interactions were found, CO2 responses were smallest at higher temperatures. These differential responses to elevated CO2 concentrations may cause changes in the relative importance of competitive pressure from these weeds.306^3^Tschaplinski,TJ^Norby,RJ^Wullschleger,SD^1993^1^Responses of loblolly-pine seedlings to elevated co2 and fluctuating water-supply^13^13^3^283-296^^^^^Oct^^^^^3447A^3446^Osmotic adjustment of loblolly pine (Pinus taeda L.) seedlings to fluctuating water supply in elevated CO2 was investigated. Seedlings were grown in controlled-environment chambers in either 350 or 700 mul l-1 CO2 with weekly watering fo r four months, after which they were either watered weekly (well- watered treatment) or every two weeks (water-stress trea!tment) for 59 days. Osmotic adjustment was assessed by pressure-volume analysis of shoots and by analysis of soluble carbo"hydrates and free amino acids in roots during the last drying cycle. In well-watered seedlings, elevated CO2 increased the# concentration of soluble sugars in roots by 68%. Water stress reduced the soluble sugar concentration in roots of seedlin$g growing in ambient CO2 to 26% of that in roots of well-watered seedlings. Elevated CO2 mitigated the water stress-induce%d decrease in the concentration of soluble sugars in roots. However, this was probably due, in part, to carbohydrate loadi&ng during the first four months when all seedlings were grown in the presence of a high water supply, rather than to osmot'ic adjustment to water stress. Water stress caused a doubling in the concentration of free primary amino acids in roots, w(hereas elevated CO2 reduced primary amino acid and nitrogen concentrations to 32 and 74%, respectively, of those in roots )of seedlings grown in ambient CO2. There was no indication of large-scale osmotic adjustment to water stress or that elevated CO2 enhanced osmotic adjustment in loblolly pine.p/y!8@GM+307^2^Williams,TG^Colman,B^1993^1^Identification of distinct internal and external isozymes of carbonic-anhydrase in chlorella-saccharophila^8^103^3^943-948^^^^^Nov^^^^^3449-A^3448^External carbonic anhydrase (CA) was detected in whole cells of alkaline-grown Chlorella saccharophila but was supp.ressed by growth at acid pH or growth on elevated levels of CO2. Internal CA activity was measured potentiometrically as a /n increase in activity in cell extracts over that of intact cells. Cells grown under all conditions had equal levels of in,0ternal CA activity. Two isozymes were identified after electrophoretic separation of soluble proteins on cellulose acetate.1 plates. The fast isozyme was found in cells grown under all conditions, whereas the slow isozyme was found only in cells 32grown at alkaline pH. Western blot analysis following sodium dodecyl sulfate-polyacrylamide gel electrophoresis using anti53bodies produced against the periplasmic form of CA from Chlamydomonas reinhardtii revealed a single band at 39 kD, which dA4id not change in intensity between growth conditions and was associated only with proteins eluted from the fast band. The C5slow isozyme was inactivated by incubation of cell extract at 30 degrees C and by incubation in 10 mM dithiothreitol, wherN6eas the internal form was unaffected. These results indicate that external and internal forms of CA differ in structure anPd their activities respond differently to environmental conditions.2244>9I9O9_9g9n9t9{99X8308^1^Muller,J^1993^1^Dry-matter production, co2 exchange, carbohydrate and nitrogen- content of winter-wheat at elevated Yco2 concentration and drought stress^161^171^4^217-235^^^^^Nov^^^^^3451dc:A^3450^Methods of mathematical modelling and simulation are being used to an increasing degree in estimating the effects oe;f rising atmospheric CO2 concentration and changing climatic conditions on agricultural ecosystems. In this context, detaipitrogen content was studied in two winter wheat varieties from shooting to milk ripeness. Elevated CO2 concentration leads? to a compensation of drought stress and at optimal water supply to an increase of vegetative dry matter and of yield to t@he fourfold value. This effects were caused by enhanced growth of secondary tillers which were reduced in plants cultivateAd at atmospheric CO2 concentration. Analogous effects in the development of ear organs were influenced additionally by comBpetitive interactions between the developing organs. The content and the mass of ethanol soluble carbohydrates in leaves aCnd stems were increased after the CO2 treatment and exhausted more completely during the grain filling period after droughDt stress. Plants cultivated from shooting to milk ripeness at elevated CO2 concentration showed a reduced response of net photosynthesis rate to increasing CO2 concentration by comparison with untreated plants.F309^3^Ahmed,FE^Hall,AE^Madore,MA^1993^1^Interactive effects of high-temperature and elevated carbon- dioxide concentration on cowpea [vigna-unguiculata (L) walp]^9^16^7^835-842^^^^^Sep^^^^^3453VVVWvWX]_h_m_z___HA^3452^Limitations in carbohydrate supplies have been implicated as a factor responsible for reproductive failure under heIat stress. Heat stress affects two stages of reproductive development in cowpea [Vigna unguiculata (L.) Walp.], and genotyJpes are available with tolerance and sensitivity to heat during these different stages. The objectives of this study were Kto determine the responses of these cowpea lines to ambient and elevated [CO2], under heat stress and optimal temperature,L and test whether differences in carbohydrate supplies due to genotypes, CO2 enrichment and heat stress are associated witMh differences in sensitivity to heat during reproductive development. Plants were grown in reach-in growth chambers and suNbjected to day/night temperatures of either 33/20 or 33/30- degrees-C, and [CO2] levels of either 350 or 700 mumol mol-1. OUnder intermediate night temperature (33/20-degrees-C), all lines set substantial numbers of pods. Under high night temperPature (33/30-degrees-C) with either ambient or elevated [CO2], one heat-sensitive line produced no flowers and the other sQet no pods, whereas the heat-tolerant line abundantly set pods. High night temperature reduced the overall carbohydrate coRntent of the plants, especially peduncle sugars, and caused decreases in photosynthetic rates. The high pod set of the heaSt-tolerant line, under high night temperature, was associated with higher levels of sugars in peduncles compared with the Theat-sensitive lines. The heat-tolerant line accumulated substantial shoot biomass, exhibited less accumulation of starch Uin leaves, and possibly had less down- regulation of photosynthesis in response to CO2 enrichment and heat stress than theV heat-sensitive lines. Elevated [CO2] resulted in higher overall carbohydrate levels in heat- sensitive lines (starch in lWeaves, stems and peduncles), but it did not increase their heat tolerance with respect to flower production or pod set. He'Xat-induced damage to floral buds and anthers in the sensitive lines was associated with low sugars levels in peduncles, in)Ydicating that heat had greater effects on assimilate demand than on leaf assimilate supply. The heat- tolerant line was th0Ze most responsive genotype to elevated [CO2] with respect to pod production under either high or intermediate temperatures2.{vv5w{{{{{{{{{| | ||&|[|u|||^}~~"(-6<\310^1^Carmi,A^1993^1^Effects of shading and co2 enrichment on photosynthesis and yield of winter grown tomatoes in subtrop>ical regions^79^28^3^455-463^^^^^^^^^^3455dK^A^3454^The effects of exposing winter-grown tomato (Lycopersicon esculentum L.) to various sunlight irradiances and CO2 coM_ncentrations, on dark respiration (R(D)), night respiration (R(N)), net photosynthetic-rate (P(N)), dry matter production R`(DMP), yield earliness and yield amount were studied. Plants were grown in greenhouses under controlled temperatures and eTaxposed to: full (FS) or half (HS) sunlight irradiance in combinafion with atmospheric (A) or enriched (E) concentrations o]bf 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 mum^col(CO2) m-2 s-1 in treatments of FSA, FSE, HSA and HSE, respectively. The irradiances on the upper leaf surface during thedd 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 leafeves 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 spf-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 rgFSA, FSE, HSA and HSE, respectively. Elevating the CO2 concentration from 300 to 1500 g m-3 increased P(N) by 16, 28, 30 a~hnd 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, iFSE, HSA and HSE treatments, respectively. Increasing the measurement irradiance from 160 to 320 mumol m-2 s-1 enhanced P(jN) 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, kin the FSA, FSE, HSA and HSE treatments, respectively. DMP was strongly influenced by the different environmental conditiolns and the total dry matter accumulation in the shoot per plant during 145 d reached 580, 347, 398 and 235 g in the FSA, FmSE, HSA and 14SE treatments, respectively. CO2 enrichment promoted early yield under both full and partial sunlight irradinance. The HSE treatment led to earlier yield harvesting than the FSA and HSA treatments. The yield of the seven first trusoses 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 frupit fresh matter and diameter of fruits was detected in the CO2-enriched treatments as compared to the non-enriched ones. Tqhus the combination of moderate shading and CO2 enrichment might provide a more productive option for winter-grown tomatoers 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.t311^3^Elkohen,A^Venet,L^Mousseau,M^1993^1^Growth and photosynthesis of 2 deciduous forest species at elevated carbon-dioxide^43^7^4^480-486^^^^^Aug^^^^^3457vA^3456^1. Two-year-old sweet chestnut (Castanea sativa) and beech (Fagus sylvatica) seedlings were grown in large pots of wforest soil, at ambient (+/-350 mul l-1) and double (700 mul l-1) atmospheric CO2 Concentration in constantly ventilated.mxini- green-houses during an entire growing season. 2. CO2 enrichment caused very different changes in these two temperate ydeciduous species. A 20% dry weight enhancement was obtained for sweet chestnut, and a 60% enhancement in beech. This greazter effect of elevated CO2 in beech was the result of a significant increase of net photosynthesis of the seedlings occurr{ing 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 ve<ry different in the two species. All additional dry matter was allocated to the roots in sweet chestnut, while it was partJitioned equally amongst all organs of the beech seedling. 5. The reactions to elevated CO2 of different tree species is diKscussed in relation to their specific growth strategy.dR312^3^Griffin,KL^Thomas,RB^Strain,BR^1993^1^Effects of nitrogen supply and elevated carbon-dioxide on construction cost inT leaves of pinus-taeda (L) seedlings^2^95^4^575-580^^^^^Oct^^^^^3459aA^3458^Seedlings of loblolly pine (Pinus taeda L.) were grown under varying conditions of soil nitrogen and atmospheric cadrbon dioxide availability to investigate the interactive effects of these resources on the energetic requirements for leafk growth. Increasing the ambient CO2 partial pressure from 35 to 65 Pa increased seedling growth only when soil nitrogen wams high. Biomass increased by 55% and photosynthesis increased by 13% after 100 days of CO2 enrichment. Leaves from seedlinvgs 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 lxow 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.!0PSTYz pH$)=ELSXan313^3^Gunderson,CA^Norby,RJ^Wullschleger,SD^1993^1^Foliar gas-exchange responses of 2 deciduous hardwoods during 3 years of growth in elevated co2 - no loss of photosynthetic enhancement^9^16^7^797-807^^^^^Sep^^^^^3461tA^3460^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.314^2^Kostkarick,R^Manning,WJ^1993^1^Radish (raphanus-sativus L) - a model for studying plant- responses to air-pollutants and other environmental stresses^35^82^2^107-138^^^^^^^^^^3463 A^3462^The use of Raphanus sativus L. as a model crop for studies on plant response to environmental stresses is reviewed  with emphasis on the effects of different atmospheric pollutants (O3, SO2, NO2, acidic precipitation) and their combinations. Responses to temperature, light supply, water stress, and atmospheric CO2 are also studied and discussed. In addition, the references reviewed are evaluated in terms of their experimental protocols on growth conditions and recommendations f%or optimal ranges of environmental and cultural variables, i.e. light, temperature, nutrient supply are given. Its distinc't pattern of biomass partitioning, the small dimensions along with short and easy culture make radish an excellent experim/ental plant. The fleshy below-ground storage organ, formed by the hypocotyl and upper radicle, acts as the major sink duri1ng vegetative development. Abundant assimilate supply due to elevated levels of CO2 along with high irradiation frequently7 promote hypocotyl growth more than shoot growth, whereas under conditions of stress shoot growth is maintained at the exp9ense of the hypocotyl. This makes the hypocotyl:shoot ratio of radish a very sensitive and suitable indicator for various @environmental stresses. Potential weaknesses and short- comings of radish in its role as a model crop, particularly the hiBgh variability of injury and growth responses, are discussed along with possible solutions. Future research needs are deriDved from the summarized results presented and from some disparities among findings within the literature reviewed.E315^3^Luxmoore,RJ^Wullschleger,SD^Hanson,PJ^1993^1^Forest responses to co2 enrichment and climate warming^94^70^1-4^309-32O3^^^^^Oct^^^^^3465@4 Plain Text CJOJQJ R   M +QA^3464^Two of the major uncertainties in forecasting future terrestrial sources and SinkS Of CO2 are the CO2-enhanced growSth response of forests and soil warming effects on net CO2 efflux from forests. Carbon dioxide enrichment of tree seedling[s over time periods less than 1 yr has generally resulted in enhanced rates of photosynthesis, decreased respiration, and ]increased growth, with minor increases in leaf area and small changes in C allocation. Exposure of woody species to elevat_ed CO2 over several years has shown that high rates of photosynthesis may be sustained, but net C accumulation may not necgessarily increase if CO2 release from soil respiration increases. The impact of the 25% rise in atmospheric CO2 with indusitrialization has been examined in tree ring chronologies from a range of species and locations. In contrast to the seedlintg tree results, there is no convincing evidence for CO2-enhanced stem growth of mature trees during the last several decadves. However, if mature trees show a preferential root growth response to CO2 enrichment, the gain in root mass for an oak-xhickory forest in eastern Tennessee is estimated to be only 9% over the last 40 years. Root data bases are inadequate for detecting such an effect. A very small shift in ecosystem nutrients from soil to vegetation could support CO2-enhanced growth. Climate warming and the accompanying increase in mean soil temperature could have a greater effect than CO2 enrichment on terrestrial sources and sinks Of CO2. Soil respiration and N mineralization have been shown to increase with soil temperature. If plant growth increases with increased N availability, and more C is fixed in growth than is released by soil respiration, then a negative feedback on climate warming will occur. If warming results in a net increase in CO2 efflux from forests, then a positive feedback will follow. A 2 to 4-degrees-C increase in soil temperature could increase CO2 efflux from soil by 15 to 32% in eastern deciduous forests. Quantifying C budget responses of forests to future global change scenarios will be speculative until mature tree responses to CO2 enrichment and the effects of temperature on terrestrial sources and sinks of CO2 can be determined.IXdv{(.FNX`fn316^6^McGuire,AD^Joyce,LA^Kicklighter,DW^Melillo,JM^Esser,G^Vorosmarty,CJ^1993^1^Productivity response of climax temperate forests to elevated- temperature and carbon-dioxide - a north-american comparison between 2 global-models^50^24^4^287-310^^^^^Aug^^^^^3467&3pt LY!zA^3466^We assess the appropriateness of using regression- and process- based approaches for predicting biogeochemical responses of ecosystems to global change. We applied a regression-based model, the Osnabruck Model (OBM), and a process-based model, the Terrestrial Ecosystem Model (TEM), to the historical range of temperate forests in North America in a factorial experiment with three levels of temperature (+0-degrees-C, +2-degrees-C, and +5-degrees-C) and two levels Of CO2 (350 ppmv and 700 ppmv) at a spatial resolution of 0.5-degrees latitude by 0.5-degrees longitude. For contemporary climate (+0-degrees-C, 3 50 ppmv), OBM and TEM estimate the total net primary productivity (NPP) for temperate forests in North America to be 2.250 and 2.602 x 10(15) g C . yr-1, respectively. Although the continental predictions for contemporary climate are similar, the responses of NPP to altered changes qualitatively differ; at +0-degrees-C and 700 PPMV CO2, OBM and TEM predict median increases in NPP of 12.5% and 2.5%, respectively. The response of NPP to elevated temperature agrees most betwee n the models in northern areas of moist temperate forest, but disagrees in southern areas and in regions of dry temperate forest. In all regions, the response to CO2 is qualitatively different between the models. These differences occur, in part, because TEM includes known feedbacks between temperature and ecosystem processes that affect N availability, photosynthesis, respiration, and soil moisture. Also, it may not be appropriate to extrapolate regression-based models for climatic *conditions that are not now experienced by ecosystems. The results of this study suggest that the process-based approach i,s able to progress beyond the limitations of the regression-based approach for predicting biogeochemical responses to glob7al change.D9317^5^Miglietta,F^Raschi,A^Bettarini,I^Resti,R^Selvi,F^1993^1^Natural co2 springs in italy - a resource for examining longD- term response of vegetation to rising atmospheric co2 concentrations^9^16^7^873-878^^^^^Sep^^^^^3469Times NFA^3468^It is estimated that more than 100 geothermal CO2 springs exist in central-western Italy. Eight springs were selectRed in which the atmospheric CO2 concentrations were consistently observed to be above the current atmospheric average of 3S54 mumol mol-1. CO2 concentration measurements at some of the springs are reported. The springs are described, and their meajor topographic and vegetational features are reported. Preliminary observations made on natural vegetation growing aroungd the gas vents are then illustrated. An azonal pattern of vegetation distribution occurs around every CO2 spring regardlekss of soil type and phytoclimatic areas. This is composed of pioneer populations of a Northern Eurasiatic species (Agrostims canina L.) which is often associated with Scirpus lacustris L. The potential of these sites for studying the long-term rzesponse of vegetation to rising atmospheric CO2 concentrations is discussed.ss Normal.dot{318^4^Miglietta,F^Raschi,A^Resti,R^Badiani,M^1993^1^Growth and onto-morphogenesis of soybean (glycine-max merril) in an open, naturally co2-enriched environment^9^16^8^909-918^^^^^Nov^^^^^3471A^3470^Springs emitting carbon dioxide are frequent in Central Italy and provide a way of testing the response of plants to CO2 enrichment under natural conditions. Results of a CO2 enrichment experiment on soybean at a CO2 spring (Solfatara) are presented. The experimental site is characterized by significant anomalies in atmospheric CO2 concentration produced by a large number of vents emitting almost pure CO2 (93%) plus small amounts of hydrogen sulphide, methane, nitrogen and oxygen. Within the gas vent area, plants were grown at three sub-areas whose mean CO2 concentrations during daytime were 350, 652 and 2370 mumol mol-1, respectively. Weekly harvests were made to measure biomass growth, leaf area and ontogenetic development. Biomass growth rate and seed yield were enhanced by elevated CO2. In particular, onto-morphogenetic development was affected by elevated CO2 with high levels of CO2 increasing the total number of main stem leaf nodes and the area of the main stem trifoliolate leaves. Biochemical analysis of plant tissue suggested that there was no effect of the small amounts of H2S on the response to CO2 enrichment. Non-protein sulphydryl compounds did not accumulate in leaf tissues and the overall capacity of leaf extracts to oxidize exogenously added NADH was not decreased. The limitations and advantages of experimenting with crop plants at elevated CO2 in the open and in the proximity of carbon dioxide springs are discussed.319^4^Morse,SR^Wayne,P^Miao,SL^Bazzaz,FA^1993^1^Elevated co2 and drought alter tissue water relations of birch (betula-populifolia marsh) seedlings^2^95^4^599-602^^^^^Oct^^^^^3473A^3472^The effect of increasing atmospheric CO2 concentrations on tissue water relations was examined in Betula populifolia, a common pioneer tree species of the northeastern U.S. deciduous forests. Components of tissue water relations were estimated from pressure volume curves of tree seedlings grown in either ambient (350 mul l-1) or elevated CO2 (700 mul l-1), and both mesic and xeric water regimes. Both CO2 and water treatment had significant effects on osmotic potential at full hydration, apoplasmic fractions, and tissue elastic moduli. Under xeric conditions and ambient CO2 concentrations, plants showed a decrease in osmotic potentials of 0.15 MPa and an increase in tissue elastic moduli at full hydration of 1.5 MPa. The decrease in elasticity may enable plants to improve the soil- plant water potential gradient given a small change in  water content, while lower osmotic potentials shift the zero turgor loss point to lower water potentials. Under elevated CO2, Plants in xeric conditions had osmotic potentials 0.2 MPa lower than mesic plants and decreased elastic moduli at full hydration. The increase in tissue elasticity at elevated CO2 enabled the xeric plants to maintain positive turgor pressures at lower water potentials and tissue water contents. Surprisingly, the elevated CO2 plants under mesic conditions had t"he most inelastic tissues. We propose that this inelasticity may enable plants to generate a favorable water potential gra$dient from the soil to the plant despite the low stomatal conductances observed under elevated CO2 conditions./320^1^Overdieck,D^1993^1^Effects of atmospheric co2 enrichment on co2 exchange-rates of beech stands in small model-ecosys1tems^94^70^1-4^259-277^^^^^Oct^^^^^3475՜.+,D hp Ddling dry weight decreased with high UV treatment but was unaffected by CO2 enrichment. High UV treatment also shifted bioFmass partitioning in favor of leaf production. Both CO2 and UV treatments decreased the dark respiration rate and light coTmpensation point. High UV light inhibited photosynthesis at 350 but not at 750 mumol mol-1 CO2 due to a UV induced increasVA^3474^CO2 enrichment experiments were performed during two vegetation periods on young beech stands in four closed mini-g`reenhouses. The houses were climatized according to the outside microclimate (+/- 0,5-degrees-C, +/- 15 % rel. air humiditby, wind speed approximately to outside in the range of 0.5 - 2.5 m s-1, max. 17 % PAR reduction). The model ecosystems - cjonsisting of 36 young beech (2.5 yr-old) in a soil block of 0.38 m3 and an air volume of 0.64 m3 - were exposed to CO2 conlcentrations of the unchanged ambient air (350 +/- 34 ppmv, control) and of 700 ppmv (698 +/- 10 ppmv). Plant growth parameyters were measured non distructively and at the end of the 1st season samples were taken for weighing the phytomass. CO2 g{as exchange of the stands taken as a whole were continuously measured with two entire mini-greenhouses and, in addition, a compact mini-cuvette system (CMS 400, Walz) was used for measuring dark respiration and CO2 net assimilation rates of sin gle leaves in both stands. Under the influence of the additional CO2 supply stem diameter (2 cm above the first lateral ro ots) was increased by 13.5 %, stem height by 27.4 %, and the number of leaves/tree by 33 % at the end of the 2nd season. T he number of buds was not significantly different and the effect on mean area per leaf was insignificant. Leaf area index  was by 1.4 units greater. All dry weights of the main organs were increased after the 1st season: leaf 60 %, stem 34 %, bud 54 %. Roots < 2 mm phi weighed 1.5-fold more and roots > 2 mm phi 1.7-fold more under elevated CO2. CO2 gas exchange of two systems was measured. Whole system CO2 losses during night as well as photosynthetic CO2 gains during days were greater at 700 ppmv than in the control system. However, if one balances CO2 gains with CO2 losses over a period of five days in August both model-ecosystems taken as a whole were sinks for CO2. During this selected time period of 5 days at the peak of the season the beech stand at 350 ppmv was the greater sink. At 350 ppmv CO2 (control) the average leaf respiration for 20-degrees- C amounted to 0.31 +/- 0.18 and at 700 ppmv to 0.57 +/- 0.42 mumol CO2 m-2 s-1 (n = 35/40, t = 3.48, alpha < 0.05), and correlated positively with leaf temperature. At light saturation the mean net assimilation rate was 4.48 mumol m-2 (leaf area) s-1 in the control and 6.21 mumol m-2 s-1 at the high CO2 concentration corresponding with an enhancement factor of 1.39 for the selected time period. Results from the whole stand and from single leaf measurements are compared by means of mathematical modelling procedures in order to quantify CO2 enrichment effects on beech model ecosystems.321^1^Owensby,CE^1993^1^Potential impacts of elevated co2 and aboveground and belowground litter quality of a tallgrass prairie^94^70^1-4^413-424^^^^^Oct^^^^^3477A^3476^Increased atmospheric CO2 will likely impact the productivity of arid and semiarid ecosystems through increased C, N, and water use efficiencies at the individual plant level. Tallgrass prairie has had increased above- and belowground biomass production under elevated CO2, primarily due to increased water use efficiency. There is an apparent decreased N requirement to sustain increased productivity in CO2-enriched tallgrass prairie, and C:N ratios of plant litter above and bel"ow ground have increased. The tallgrass prairie ecosystem level response to elevated CO2 on the C cycle could potentially #increase C storage. Reduced litter quality associated with elevated CO2 in tallgrass prairie has the potential to reduce d0 ecomposition rates, and ruminant digestion rate of plant biomass apparently has been lowered. Reduced intake by ruminants 2!would shunt more of the plant biomass directly into the detrital food chain, thereby slowing decomposition further. The poBtential impact is for increased C to be retained as soil organic matter in the tallgrass prairie.D#322^3^Owensby,CE^Coyne,PI^Auen,LM^1993^1^Nitrogen and phosphorus dynamics of a tallgrass prairie ecosystem exposed to elevQated carbon-dioxide^9^16^7^843-850^^^^^Sep^^^^^3479S%A^3478^A tallgrass prairie ecosystem was exposed to ambient and twice- ambient CO2 ConCentrations in open-top chambers andd& compared to unchambered ambient CO2 during the entire growing season from 1989 through 1991. Dominant species were Andropf'ogon gerardii (C4), A. scoparius (C4), Sorghastrum nutans (C4) and Poa pratensis (C3). Nitrogen and phosphorus concentratix(ons in A. gerardii, P. pratensis and dicotyledonous herbs above ground biomass were estimated by periodic sampling throughz)out the growing season in 1989 and 1990. In 1991, N and P concentrations in peak biomass were estimated by an early August* harvest. N and P concentrations in root production as a function of treatment were estimated using root ingrowth bags tha+t remained in place throughout the growing season. Total N and P in above- and belowground biomass were calculated as prod,ucts of concentration and peak biomass by species groups. N concentration in A. gerardii and dicotyledonous herb abovegrou-nd biomass was lower and total N higher in elevated CO2 plots than in ambient CO2 PlOts. N concentration in P. pratensis a.boveground biomass was lower in elevated CO2 plots than in ambient, but total N did not differ among treatments in 2 out o/f 3 years. In 1990, N concentration in root ingrowth bag biomass was lower and total N greater in elevated CO2 than in amb0ient CO2 plots. Root ingrowth bag biomass N concentration did not differ among treatments in 1991, but total N was greater1 in elevated CO2 plots than in ambient CO2 Plots. P concentration was lower under elevated CO2 compared to ambient in 19892, but did not differ substantially among treatments in 1990 or 1991. In all years, total P in aboveground A. gerardii and 3root ingrowth bag biomass was greater under elevated CO2 than ambient. P concentration and total P in P. pratensis was similar among treatments.5323^2^Penuelas,J^Matamala,R^1993^1^Variations in the mineral-composition of herbarium plant- species collected during the last 3 centuries^78^44^266^1523-1525^^^^^Sep^^^^^3481m qqRqTqssftltttuuu"uvv7A^3480^Mineral content (dry weight basis) was determined for herbarium specimens of 12 C3 plants (trees, shrubs and herbs)8 collected during the last 250 years in N.E. Spain. Present values of Al, Ca, Cu, Sr, Fe, P, Mg, Mn, K, Na, S, and Zn were9 always lower than in any other period of the last three centuries. Only one C4 plant was analysed. It presented a similar: pattern to the C3 plants. These results are in accordance with experimental results that have shown that the mineral cont;ent of plants grown in elevated CO2 is generally lowered. Increased atmospheric CO2 and other anthropogenic environmental changes are suggested as possible causes of the changes in mineral content. Q[ft=324^4^Smernoff,DT^Gale,J^Macler,BA^Reuveni,J^1993^1^Inhibition of photosynthesis in duckweed by elevated co2 concentration$ is rapid and is not offset by a temperature- induced increase in metabolic-rate^79^28^1^17-28^^^^^^^^^^3483p¼̼&?A^3482^The rates of net photosynthesis (P(N)), respiration and growth of Lemna gibba L. were measured as functions of time1@ across ranges of temperature, irradiance and carbon dioxide concentrations. P(N) on an area basis increased with temperat3Aure up to 30-degrees-C but decreased dramatically with a few hours of exposure to elevated CO2, when reported on a dry mas8Bs basis. Reductions in the apparent quantum efficiency, photosynthetic capacity and the affinity of ribulose- 1,5-bisphosp:Chate carboxylase/oxygenase for CO2 were observed for plants grown at elevated CO2. Starch concentration was not significanFDtly affected by elevated CO2. Although elevated temperature increased metabolic activity, it only partially alleviated theHE inhibition of P(N). L. gibba exhibits a characteristic C3-type response to elevated CO2 and the methodology described is Wuseful for further elucidating the mechanism of photosynthetic acclimation to elevated CO2.jXG325^6^Smith,TM^Cramer,WP^Dixon,RK^Leemans,R^Neilson,RP^Solomon,AM^1993^1^The global terrestrial carbon-cycle^94^70^1-4^19-Z37^^^^^Oct^^^^^3485 @ Q       BL lqsv/3hIA^3484^There is great uncertainty with regard to the future role of the terrestrial biosphere in the global carbon cycle. kJThe uncertainty arises from both an inadequate understanding of current pools and fluxes as well as the potential effects |Kof rising atmospheric concentrations of CO2 on natural ecosystems. Despite these limitations, a number of studies have est~Limated current and future patterns of terrestrial carbon storage. Future estimates focus on the effects of a climate changMe associated with a doubled atmospheric concentration of CO2. Available models for examining the dynamics of terrestrial cNarbon storage and the potential role of forest management and landuse practices on carbon conservation and sequestration are discussed.IIIYJcJ KK3K;KvK~KKKKK#L2LRLaLLLMMQQRRP326^3^Tissue,DT^Thomas,RB^Strain,BR^1993^1^Long-term effects of elevated co2 and nutrients on photosynthesis and rubisco in loblolly-pine seedlings^9^16^7^859-865^^^^^Sep^^^^^3487ZZZZZZL]R]j]s]t]}]]]]]RA^3486^The effects of long-term CO2 enhancement and varying nutrient availability on photosynthesis and ribulose-1,5-bisphSosphate carboxylase/oxygenase (rubisco) were studied on loblolly pine (Pinus taeda L.) seedlings grown in two atmospheric TCO2 partial pressures (35 and 65 Pa) and three nutrient treatments (low N, low P, and high N and P). Measurements taken inU late autumn (November) after 2 years Of CO2 enrichment and nutrient addition showed that photosynthetic rates were higherV for plants grown at elevated CO2 only when they received supplemental N. Total rubisco activity and rubisco content decreWased at elevated CO2, but there was an increase in activation state. At elevated CO2, proportionately less N was found in Xrubisco and more N was found in the light reaction components. These results demonstrate acclimation of photosynthetic proYcesses to elevated CO2 through reallocation of N. Loblolly pine grown in nutrient conditions similar to native soils (low ZN availability) had lower needle N and chlorophyll content, lower total rubisco activity and content, and lower photosynth[etic rates than plants grown at high N and P. This suggests that the magnitude of the photosynthetic response to a future, high-CO2 environment will be dependent on soil fertility in the system.]327^2^Vloedbeld,M^Leemans,R^1993^1^Quantifying feedback processes in the response of the terrestrial carbon-cycle to global change - the modeling approach of image-2^94^70^1-4^615-628^^^^^Oct^^^^^3489$_A^3488^The terrestrial biosphere component of the Integrated Model to Assess the Greenhouse Effect (IMAGE 2) uses changes &`in land cover to compute dynamically the C fluxes between the terrestrial biosphere and the atmosphere. The model explores5a the potential impact of feedback processes incorporated in the model, which are the enhancement of plant growth (CO2 fert7bilization) and a more efficient use of water under increased CO2 concentrations in the atmosphere; the temperature responsDce of photosynthesis and respiration of plants; the temperature and soil water response of decomposition processes; and theFd climate-induced changes in vegetation and agricultural patterns with the consequent changes in land cover. In this paper Xewe discuss the implementation and operation of the different feedback processes in the IMAGE 2 model. Results are shown foZfr each process separately as well as the combined processes. The aim of this paper is to quantify the importance of these cgfeedback processes geographically. The main results are that vegetation shifts due to climatic change and increased water ehuse efficiency, CO2 fertilization decreases net C emissions, while changed decomposition rates strongly increase C emissiorins to the atmosphere. Changes in the global balance between photosynthesis and respiration make little net difference. Wittjh the IPPC business-as-usual scenario the terrestrial biosphere continues to emit C into the atmosphere. This behavior is zgoverned by changes in land-use, caused by a multitude of anthropogenic processes.|l328^2^Bowler,JM^Press,MC^1993^1^Growth-responses of 2 contrasting upland grass species to elevated co2 and nitrogen concentration^84^124^3^515-522^^^^^Jul^^^^^3491nA^3490^Growth parameters of Agrostis capillaris L. and Nardus stricta L. were measured in relation to ambient and elevatedo concentrations of CO2 (340 and 550 mul CO2 l-1, respectively) and at low and high concentrations of nitrogen (0.8 and 3 mpm NH4NO3, respectively). After 60 d of growth A. capillaris had attained approx. four times the total dry weight of N. strqicta in all treatments, which was attributed to the greater leaf area ratio of the former. A. capillaris grown at the low rnitrogen concentration attained 30% of the total dry weight of plants grown at high nitrogen. Over the 60 d period, destrusctive harvests (seven in total) showed the growth of N. stricta to be less sensitive than that of A. capillaris to the contcentration of nitrogen, but in both species growth analysis showed the lower total dry weight at low nitrogen to be attribuutable to lower unit leaf rate. There was a differential response of both species to elevated concentrations of CO2 which vwas nitrogen dependent. A. capillaris grown at elevated CO2 attained a greater total dry weight than at ambient CO2 and thwis response was proportionately greater at low nitrogen (78% increase) than at high nitrogen (58% increase). In contrast, xin N. stricta there was no effect of CO2 concentration on the total dry weight at low nitrogen whilst at high nitrogen playnts grown at elevated CO2 had a greater total dry weight after 48 d of growth. Calculation of the allometric coefficient (zK) 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.|329^1^Crush,JR^1993^1^Hydrogen evolution from root-nodules of trifolium-repens and medicago-sativa plants grown under elevated atmospheric co2^167^36^2^177-183^^^^^^^^^^3493~A^3492^Nitrogenase activity and hydrogen (H-2) evolution from nodules of Trifolium repens L. and Medicago sativa L. were m easured 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 wa1s stimulated by elevated CO2 and higher temperatures but in Medicago only temperature had an effect. Hydrogen emission/pla3nt 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 r=ates 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 lJead to a greater contribution from legume nitrogen (N) fixation to global H-2 sources. The magnitude of the increase will Lbe influenced by the legume species involved and temperature.[330^4^Diaz,S^Grime,JP^Harris,J^McPherson,E^1993^1^Evidence of a feedback mechanism limiting plant-response to elevated car]bon-dioxide^36^364^6438^616-617^^^^^12 Aug^^^^^3495gA^3494^IN short-term experiments under productive laboratory conditions, native herbaceous plants differ widely in their piotential to achieve higher yields at elevated concentrations of atmospheric carbon dioxide1-8. The most responsive speciesp appear to be large fast-growing perennials of recently disturbed fertile soils7,8. These types of plants are currently inrcreasing 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.331^2^Idso,SB^Kimball,BA^1993^1^Tree growth in carbon-dioxide enriched air and its implications for global carbon cycling and maximum levels of atmospheric co2^137^7^3^537-555^^^^^Sep^^^^^3497A^3496^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. 332^1^Johnsen,KH^1993^1^Growth and ecophysiological responses of black spruce seedlings to elevated co2 under varied water* and nutrient additions^155^23^6^1033-1042^^^^^Jun^^^^^3499,A^3498^Two controlled-environment studies examined growth and ecophysiological responses of black spruce (Picea mariana (M<ill.) 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 ppmI) increased final seedling dry weights by 20-48% compared with seedling growth under ambient CO2 (350 ppm). Percent increaKses in seedling dry weight were greater under drought versus well- watered conditions and higher versus lower nutrient addWitions. Seedlings grown under elevated CO2 displayed higher water use efficiency than seedlings grown under ambient CO2. TZhis was apparent based upon instantaneous gas exchange as well as xylem potential pressure measurements. Elevated CO2-indunced stimulation of relative growth rate was greatest shortly after seedling emergence and decreased with increased seedlinpg size. Acclimation of net photosynthesis was observed and was reversible. Analyses using allometric principles indicate n|et 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. 333^4^Kubo,Y^Tsuji,H^Inaba,A^Nakamura,R^1993^1^Effects of elevated co2 concentrations on the ripening in banana fruit by exogenous C2h4^180^62^2^451-455^^^^^Sep^^^^^3501OPQRSTUVWXYZ[\]^_`A^3500^Green bananas were treated with 0 to 60% CO2 and 1 to 100 PPM C2H4 to study their interaction on the ripening process. 1. The CO2 treatment did not block completely the initiation of ripening of banana by exogenous C2H4. When the concentration of applied C2H4 was kept constant and the CO2 concentration high, the appearance of the yellow pigment in the peel was delayed. 2. The combination of various concentrations of CO2 and C2H4 on the respiratory climacterics in green banana, monitored with an automated microcomputer system, revealed that the onset of the climacteric rise of bananas under any CO2 concentration combined with 1 PPM C2H4 commenced simultaneously with fruits which were kept under air and 1 PPM C2H4. However, the progress of the climacteric rise was slower and the peaks were lower at high CO2 concentration than they were at low CO2 concentrations. With 60% CO2 and 100 PPM C2H4, the fruit color remained green until the end of the gas treatment, in spite of the slow respiratory rise and ripening of the flesh. Our results suggest that the elevated CO2 concentration has no effect on the initiation-time of banana ripening induced.by exogenous C2H4 but lowers the progress rate of ripening.e!334^6^Lawlor,DW^Mitchell,RAC^Franklin,J^Mitchell,VJ^Driscoll,SP^Delgado,E^1993^1^Facility for studying the effects of elevated carbon-dioxide concentration and increased temperature on crops^9^16^5^603-608^^^^^Jun^^^^^3503A^3502^The requirements for the experimental study of the effects of global climate change conditions on plants are outlined. A semi-controlled plant growth facility is described which allows the study of elevated CO2 and temperature, and their interaction on the growth of plants under radiation and temperature conditions similar to the field. During an experiment# on winter wheat (cv. Mercia), which ran from December 1990 through to August 1991, the facility maintained mean daytime C%O2 concentrations of 363 and 692 cm3 m-3 for targets of 350 and 700 cm3 m-3 respectively. Temperatures were set to follow 6outside ambient or outside ambient +4-degrees-C, and hourly means were within 0.5-degrees-C of the target for 92% of the t8ime for target temperatures greater than 6-degrees- C. Total photosynthetically active radiation incident on the crop (solDar radiation supplemented by artifical light with natural photoperiod) was 2% greater than the total measured outside overF the same period.FMicrosoft Word Document MSWordDocWord.Document.89qP335^12^Lawton,JH^Naeem,S^Woodfin,RM^Brown,VK^Gange,A^Godfray,HJC^Heads,PA^Lawler,S^Magda,D^Thomas,CD^Thompson,LJ^Young,S^1R993^1^The ecotron - a controlled environmental facility for the investigation of population and ecosystem processes^190^34g1^1296^181-194^^^^^29 Jul^^^^^3505iA^3504^This paper reports on aspects of the design and philosophy of the Ecotron, an integrated series of 16 controlled enrvironmental chambers at the NERC Centre for Population Biology. The Ecotron serves as an experimental means for analysing tpopulation and community dynamics and ecosystem processes under controlled physical conditions. Within the chambers, terrestrial experimental communities are assembled into foodwebs of desired complexity from a pool of species selected for their preadaptations to the physical conditions of the Ecotron. These species include decomposers (earthworms, snails, microarthropods and microbes), primary producers (16 species of plants), primary consumers (four species of herbivorous arthropods), and secondary consumers (four species of parasitoids). The design of the Ecotron is unique in several aspects with respect to its blend of biology and technology. It supports small, dynamic communities of up to 30 plant and metazoan species, thereby making it among the more biologically complex controlled environmental systems currently in use. Its architecture permits replication and variation of spatial scale in experimental design. Its artificial climate simulates natural environmental conditions within chambers allowing experimental control over light, water, temperature, humidity, and in the near future CO2 and uv-B radiation. Sensors monitor both macro- and micro-environmental conditions of a number of physical factors within the chambers. Preliminary experiments show the Ecotron to be an excellent facility for long-term population and community-level experiments. We discuss the results of one of these early experiments and briefly consider ongoing and future experiments.336^5^Mitchell,RAC^Mitchell,VJ^Driscoll,SP^Franklin,J^Lawlor,DW^1993^1^Effects of increased co2 concentration and temperature on growth and yield of winter-wheat at 2 levels of nitrogen application^9^16^5^521-529^^^^^Jun^^^^^3507A^3506^Winter wheat (Triticum aestivum L., cv. Mercia) was grown in chambers under light and temperature conditions similar to the UK field environment for the 1990/1991 growing season at two levels each of atmospheric CO2 concentration (seasonal means: 361 and 692 mumol mol-1), temperature (tracking ambient and ambient +4-degrees-C) and nitrogen application (equivalent to 87 and 489 kg ha-1 total N applied). Total dry matter productivity through the season, the maximum number of shoots and final ear number were stimulated by CO2 enrichment at both levels of the temperature and N treatments. At high N, there was a CO2-induced stimulation of grain yield (+15%) similar to that for total crop dry mass (+12%), and there was no significant interaction with temperature. This contrasts with other studies, where positive interactions between the effe cts of increases in temperature and CO2 have been found. Temperature had a direct, negative effect on yield at both levels" of the N and CO2 treatments. This could be explained by the temperature-dependent shortening of the phenological stages, 4and therefore, the time available for accumulating resources for grain formation. At high N, there was also a reduction in6 grain set at ambient +4-degrees-C temperature, but the overall negative effect of warmer temperature was greater on the nBumber of grains (-37%) than on yield (-18%), due to a compensating increase in average grain mass. At low N, despite increDasing total crop dry mass and the number of ears, elevated CO2 did not increase grain yield and caused a significant decreSase under ambient temperature conditions. This can be explained in terms of a stimulation of early vegetative growth by COU2 enrichment leading to a reduction in the amount of N available later for the formation and filling of grain.,c337^2^Retuerto,R^Woodward,FI^1993^1^The influences of increased co2 and water-supply on growth, biomass allocation and wateer-use efficiency of sinapis-alba L grown under different wind speeds^2^94^3^415-427^^^^^Jun^^^^^3509mA^3508^We examined how independent and interactive effects of CO2 concentrations, water supply and wind speed affect growtoh rates, biomass partitioning, water use efficiency, diffusive conductance and stomatal density of plants. To test the prediction that wind stress will be ameliorated by increased CO2 and/or by unrestricted water supply we grew Sinapis alba L. plants in controlled chambers under combinations of two levels of CO2 (350 ppmv, 700 ppmv), two water regimes and two wind speeds (0.3 ms-1, 3.7 ms-1). We harvested at ten different dates over a period of 60 days. A growth analysis was carried out to evaluate treatment effects on plant responses. Plants grown both in increased CO2 and in low wind conditions had significantly greater stem length, leaf area and dry weights of plant parts. Water supply significantly affected stem diameter, root weight and leaf area. CO2 enrichment significantly increased the rate of biomass accumulation and the relative ratio of biomass increase to leaf area expansion. High wind speed significantly reduced plant growth rates and the rate of leaf area expansion was reduced more than the rate of biomass accumulation. Regression analysis showed significant CO2 effects on the proportion of leaf and stem dry weight to total dry weight. A marked plant-age effect was dependent on water supply, wind speed and CO2 concentration. A reduced water supply significantly decreased the stomatal conductance, and water use efficiency significantly increased with a limited water supply, low wind and increased CO2. We found significant CO2 x wind effects for water diffusion resistance, adaxial number of stomata and water use efficiencies and significant wind x water effect for water use efficiency. In conclusion, wind stress was ameliorated by growing in unrestricted water but not by growing in increased CO2.er mite damage of the 990 and 280-mu-mol mol-1 treatments reduced yields. These data confi338^3^Reuveni,J^Gale,J^Mayer,AM^1993^1^Reduction of respiration by high ambient co2 and the resulting error in measurements of respiration made with o2 electrodes^52^72^2^129-131^^^^^Augglaciation. BP 875-883 PG 9 JI Agron. J. PY 1991 PD SEP-O339^2^Stewart,JD^Hoddinott,J^1993^1^Photosynthetic acclimation to elevated atmospheric carbon- dioxide and uv irradiation in pinus-banksiana^37^88^3^493-500^^^^^Jul^^^^^3512CATIONS SN 1051-0761 C1 EXETER UNIV, DEPT BIOL SCI, EXETER EX4 4PS, ENA^3511^Pinus banksiana seedlings were grown for 9 months in enclosures in greenhouses at CO2 concentrations of 350 or 750 mumol mol-1 with either low (0.005 to 0.3 W M-2) or high (0.25 to 0.90 W M- 2) ultraviolet-B (UV-B) irradiances. Total see A^3513^Elevated atmospheric carbon dioxide partial pressures have been shown to have variable direct and indirect effects on plant respiration rates. In this study, growth, leaf respiration, and leaf nitrogen and carbohydrate partitioning were measured in Gossypium hirsutum L. grown in 35 and 65Pa CO2 for 30 d. Growth and maintenance coefficients of leaf respirati on were estimated using gas exchange techniques both at night and during the day. Elevated CO2 stimulated biomass producti on (107%) and net photosynthetic rates (35-50%). Total day-time respiration (R(d)) was not significantly affected by growt h CO2 partial pressure. However, night respiration (R(n)) of leaves grown in 65 Pa CO2 Was significantly greater than that , of plants grown in 35 Pa CO2. Correlation of R(d) and R(n) with leaf expansion rates indicated that plants in both CO2 tr . eatments had equivalent growth respiration coefficients but maintenance respiration was significantly greater in elevated 6 CO2. Increased maintenance coefficients in elevated CO2 appeared to be related to increased starch accumulation rather tha 8n to changes in leaf nitrogen.h is less susceptible to changes in mineralization rates. It is concluded that short-term r C 341^3^Thompson,GB^Brown,JKM^Woodward,FI^1993^1^The effects of host carbon-dioxide, nitrogen and water-supply on the infect Eion of wheat by powdery mildew and aphids^9^16^6^687-694^^^^^Aug^^^^^3516ant species and soil types will alter in respons UA^3515^In two experiments, winter wheat (Triticum aestivum cv. Cerco) was grown in 350 (ambient) and 700 mumol mol-1 (elev Wated) atmospheric CO2 concentrations. In the first experiment, plants were grown at five levels of nitrogen fertilization, c and in the second experiment, plants were grown at three levels of water supply. All plants were infected with powdery mi eldew, caused by the fungus Erysiphe graminis. Plants grown in elevated atmospheric CO2 concentrations had significantly re oduced % shoot nitrogen contents and significantly increased % shoot water contents. At elevated atmospheric CO2 concentrat qions, where plant nitrogen content was significantly reduced, the severity of mildew infection was significantly reduced, |and where host water content was significantly increased, the severity of mildew infection was significantly increased. In ~ a moderate water supply treatment, the plants grown in elevated atmospheric CO2 concentrations had significantly reduced nitrogen contents (9.9%) and significantly increased water content (4%), the amount of mildew infection was unchanged. The severity of mildew infection appeared to be more sensitive to host water content than to host nitrogen content.500 ppm a 342^2^Ueda,Y^Bai,JH^1993^1^Effect of short-term exposure of elevated co2 on flesh firmness and ester production of strawbe rry^180^62^2^457-464^^^^^Sep^^^^^3518 light was used, except in the treatment with constant 600 ppm where 600 ppm was als A^3517^Strawberry fruits (Fragaria X ananasa cv. Hokowase) were treated with 20% CO2 for 12 to 48 hr at 1-degrees-C and th en stored at the same temperature for an additional 24 to 48 hr; subsequently they were transferred to 20-degrees-C and he ld for 8 hours. 1. Berries exposed to CO2, including those stored for 8 hr at 20-degrees-C were firmer than the control be rries exposed to air. 2. The CO2 treatment had a little effect on the evolution of methyl acetate and methyl butyrate, the  predominant volatiles. However, the evolution of ethyl acetate and ethyl butyrate, the minor volatiles, was increased sha rply by the CO2 treatment. These changes in the concentration of volatiles gave the berries an unnatural aroma. 3. In berr  ies given the same CO2 treatment for 24 hr but stored longer period at 1-degrees-C, the abnormal aroma formation persisted for at least 5 days. MJ TI TRACKING STOMATAL DENSITIES THROUGH A GLACIAL CYCLE - THEIR SIGNIFICANCE FOR PREDICTING THE R "343^4^Volin,JC^Tjoelker,MG^Oleksyn,J^Reich,PB^1993^1^Light environment alters response to ozone stress in seedlings of ace r-saccharum marsh and hybrid populus L .2. Diagnostic gas-exchange and leaf chemistry^84^124^4^637-646^^^^^Aug^^^^^3520UR!$A^3519^Diagnostic gas exchange measurements and foliar chemical assays were conducted on hybrid poplar (Populus tristis Fi!%sch. x P. balsamifera L. cv. Tristis) and sugar maple (Acer saccharum Marsh.) seedlings grown under contrasting light and !&ozone treatments. Seedlings were grown in low irradiance (c. 2.5 mol m-2 d-1) and six-fold greater irradiance (c. 16.6 mol!' m-2 d-1) in combination with low (< 10 nl l-1) and elevated (99-115 nl l-1) ozone. Analysis of light response curves show!((ed ozone- induced reductions in photosynthetic capacity and quantum yield for unshaded poplar and shaded sugar maple, but !*)not the contrasting light treatments. Photosynthesis at saturating CO2 concentrations was decreased in the elevated ozone !;*treatment in both the unshaded and shaded poplar and in shaded sugar maple. Poplar had significant reductions in chlorophy!<+ll concentration due to ozone exposure in both unshaded and shaded treatments. Older leaves of unshaded poplar plants had !F,significantly greater reductions in chlorophyll levels due to ozone than older leaves of shaded plants. In maple, only sha!H-de-grown leaves had significant decreases in chlorophyll concentration due to ozone exposure. The diagnostic gas exchange !T.measurements in conjunction with chlorophyll measurements indicate that in hybrid poplar, unshaded leaves may be more sens!U/itive to ozone than shade leaves, while in sugar maple, shade leaves are more sensitive to ozone. For hybrid poplar a decr!h0ease in photosynthetic capacity, quantum yield and chlorophyll concentration in the unshaded, moderately high light enviro!j1nment due to elevated ozone is consistent with prior studies. The results indicating that sugar maple seedlings may be mor!w2e detrimentally affected by elevated ozone in the lower light environment may have serious implications for this and other!y shade-adapted species with respect to their performance in an understorey environment. RESPONSES; THERMOTOLERANCE; ENRIC!4344^6^Zak,DR^Pregitzer,KS^Curtis,PS^Teeri,JA^Fogel,R^Randlett,DL^1993^1^Elevated atmospheric co2 and feedback between carb!on and nitrogen cycles^206^151^1^105-117^^^^^Apr^^^^^3522d by rising levels of CO2 and other greenhouse gases could also !6A^3521^We tested a conceptual model describing the influence of elevated atmospheric CO2 on plant production, soil microor!7ganisms, and the cycling of C and N in the plant-soil system. Our model is based on the observation that in nutrient- poor!8 soils. plants (C3) grown in an elevated CO2 atmosphere often increase production and allocation to belowground structures!9. We predicted that greater belowground C inputs at elevated CO, should elicit an increase in soil microbial biomass and i!:ncreased rates of organic matter turnover and nitrogen availability. We measured photosynthesis, biomass production, and C!; allocation of Populus grandidentata Michx. grown in nutrient-poor soil for one field season at ambient and twice-ambient !<(i.e., elevated) atmospheric CO2 concentrations. Plants were grown in a sandy subsurface soil i) at ambient CO2 with no op!=en top chamber, ii) at ambient CO2 in an open top chamber, and iii) at twice-ambient CO2 in an open top chamber. Plants we!>re fertilized with 4.5 g N m 2 over a 47 d period midway through the growing season. Following 152 d of growth, we quantif!?ied microbial biomass and the availabilities of C and N in rhizosphere and bulk soil. We tested for a significant CO2 effe!@ct on plant growth and soil C and N dynamics by comparing the means of the chambered ambient and chambered elevated CO2 tr!Aeatments. Rates of photosynthesis in plants grown at elevated CO2 were significantly greater than those measured under amb!Bient conditions. The number of roots, root length, and root length increment were also substantially greater at elevated C!CO2. Total and belowground biomass were significantly greater at elevated CO2. Under N-limited conditions, plants allocated!D 50-70% of their biomass to roots. Labile C in the rhizosphere of elevated-grown plants was significantly greater than tha"Et measured in the ambient treatments; there were no significant differences between labile C pools in the bulk soil of amb"Fient and elevated-grown plants. Microbial biomass C was significantly greater in the rhizosphere and bulk soil of plants g" Grown at elevated CO2 compared to that in the ambient treatment. Moreover, a short-term laboratory assay of N mineralizatio"Hn indicated that N availability was significantly greater in the bulk soil of the elevated-grown plants. Our results sugge"Ist that elevated atmospheric CO2 concentrations can have a positive feedback effect on soil C and N dynamics producing gre"Jater N availability. Experiments conducted for longer periods of time will be necessary to test the potential for negative" feedback due to altered leaf litter chemistry.ns, respectively. The litter was sterilized and inoculated with microflor""L345^2^Ziska,LH^Bunce,JA^1993^1^The influence of elevated co2 and temperature on seed- germination and emergence from soil^"/207^34^2^147-157^^^^^Aug^^^^^3524measured and the litter was leached with demineralized H2O. The following analyses were"1NA^3523^Seed of six crop species, alfalfa, Medicago sativa L. cv. 'Arc', soybean, Glycine max L. (Merrill) cv. 'Williams', "9Omaize, Zea mays L. cv. SS 885, pea, Pisum sativum L. cv. 'Maestro', sunflower, Helianthus annuus L. cv. 'Mammoth', and pum":Ppkin Cucurbita pepo L. cv. 'Big Max' and four weedy species, Amaranthus hypochondriacus L., Amaranthus hybridus L., Chenop"BQodium album L. and Abutilon theophrasti, were grown at two different CO2 concentrations of 350 mul l-1 (ambient) and 700 m"DRul l-1 (elevated) in controlled-environment chambers to determine the effect of elevated CO2 on germination and emergence."FS Doubling the CO2 concentration resulted in an increase in the rate and final percentage of germination, for M. sativa, A."LT hybridus and C album. In a separate field experiment (silt-loam soil), elevated CO2 resulted in a significant increase in"NU the total number of weed seedlings present 3 weeks after tilling. In a second set of experiments using controlled-environ"cVment chambers, the interaction between increased temperature and CO2 was examined in seven of the species used previously."fW No significant interaction was observed between CO2 and temperature on the germination response. Overall, this investigat"sXion suggests that as CO2 increases, differential changes in germination and/or emergence between crops and weeds could occ"uur.s. BP 54-64 PG 11 JI Oikos PY 1991 PD MAY VL 61 IS 1 GA FR485 J9 OIKOS ER PT J AU EAMUS, D MURRAY, M TI PHOTOSYNTHETI"~Z346^2^Arnone,JA^Korner,C^1993^1^Influence of elevated co2 on canopy development and red - far- red ratios in 2-storied sta"nds of ricinus-communis^2^94^4^510-515^^^^^Jul^^^^^3526QB, MIDLOTHIAN, SCOTLAND. ID ABIES L KARST; CO2 ASSIMILATION; PINU"\A^3525^Vertical structure of plant stands and canopies may change under conditions of elevated CO2 due to differential res"]ponses of overstory and understory plants or plant parts. In the long term, seedling recruitment, competition, and thus po"^pulation or community structure may be affected. Aside from the possible differential direct effects of elevated CO2 on ph"_otosynthesis and growth, both the quantity and quality of the light below the overstory canopy could be indirectly affecte"`d by CO2- induced changes in overstory leaf area index (LAI) and/or changes in overstory leaf quality. In order to explore"a such possible interactions, we compared canopy leaf area development, canopy light extinction and the quality of light be"bneath overstory leaves of two-storied monospecific stands of Ricinus communis exposed to ambient (340 mul-1) and elevated "c(610 mul-1) CO2. Plants in each stand were grown in a common soil as closed ''artificial ecosystems'' with a ground area o"df 6.7 m2. LAI of overstory plants in all ecosystems more than doubled during the experiment but was not different between "eCO2 treatments at the end. As a consequence, extinction of photosynthetically active radiation (PAR) was also not altered."f However, under elevated CO2 the red to far-red ratio (R: FR) measured beneath overstory leaves was 10% lower than in ecos"gystems treated with ambient CO2. This reduction was associated with increased thickness of palisade layers of overstory le"haves and appears to be a plausible explanation for the specific enhancement of stem elongation of understory plants (witho"iut a corresponding biomass response) under elevated CO2. Col enrichment led to increased biomass of overstory plants (main"jly stem biomass) but had no effect on understory biomass. The results of this study raise the possibility of an important "kindirect effect of elevated CO2 at the stand-level. We suggest that, under elevated CO2, reductions in the R:FR ratio bene"ath overstory canopies may affect understory plant development independently of the effects of PAR extinction.owed an A(m"m347^3^Bernstson,GM^McConnaughay,KDM^Bazzaz,FA^1993^1^Elevated co2 alters deployment of roots in small growth containers^2^"94^4^558-564^^^^^Jul^^^^^3528 of the pre-frost value increased from 30 min (control) to 85 min for ozone-fumigated trees "oA^3527^Previously we examined how limited rooting space and nutrient supply influenced plant growth under elevated atmosph"peric CO2 concentrations (McConnaughay et al. 1993). We demonstrated that plant growth enhancement under elevated CO2 was i#qnfluenced more by the concentration of nutrients added to growth containers than to either the total nutrient content per # rpot or amount or the dimensions of available rooting space. To gain insight into how elevated CO2 atmospheres affect how p#slants utilize available belowground space when rooting space and nutrient supply are limited we measured the deployment of#t roots within pots through time. Contrary to aboveground responses, patterns of below-ground deployment were most strongly#!u influenced by elevated CO2 in pots of different volume and shape. Further, elevated CO2 conditions interacted differently##v with limited belowground space for the two species we studied, Abutilon theophrasti, a C3 dicot with a deep taproot, and #+wSetaria faberii, a C4 monocot with a shallow fibrous root system. For Setaria, elevated CO2 increased the size of the larg#-xest region of low root density at the pot surface in larger rooting volumes independent of nutrient content, thereby decre#6yasing their efficiency of deployment. For Abutilon, plants responded to elevated CO2 concentrations by equalizing the patt#8zern of deployment in all the pots. Nutrient concentration, and not pot size or shape, greatly influenced the density of ro#A{ot growth. Root densities for Abutilon and Setaria were similar to those observed in field conditions, for annual dicots a#Bnd monocots respectively, suggesting that studies using pots may successfully mimic natural conditions.nt CO2 environment#P}348^3^Berryman,CA^Eamus,D^Duff,GA^1993^1^The influence of co2 enrichment on growth, nutrient content and biomass allocatio#Rn of maranthes-corymbosa^182^41^2^195-209^^^^^^^^^^3530es to reproduction whereas ambient CO2-grown plants allocated over#aA^3529^Seedlings of Maranthes corymbosa Blume, an evergreen tree of tropical Australia and Indonesia were grown for 32 wee#cks under conditions of ambient and elevated (700 mumol CO2 mol-1) CO2 in tropical northern Australia. Seedlings were expos#jed to ambient temperature, vapour pressure deficit and photon flux density fluctuations. Rates of germination and percenta#lge germination were not affected by elevated CO2.Total plant biomass, height growth, total plant leaf area, numbers of lea#tves and branches and specific leaf weight were significantly increased by elevated CO2. Root:shoot ratio and foliar P, K, #vMg, Mn and Ca levels were unaffected but foliar nitrogen levels were decreased by elevated CO2, Nutrient-use-efficiency wa#s unaffected for phosphorus, magnesium, manganese, calcium and potassium but nitrogen-use-efficiency increased in response# to elevated CO2.AL-NUTRITION; USE EFFICIENCY; NUTRIENT CONCENTRATION; PLANT-GROWTH; NITRATE; YIELD; WATER; PHOTOSYNTHESI#349^1^Bowes,G^1993^1^Facing the inevitable - plants and increasing atmospheric co(2)^208^44^^309-332^e concentrations and#350^6^Britz,SJ^Krizek,DT^Lee,DR^Harris,WG^Hungerford,WE^Bailey,WA^1993^1^Soybean growth under microwave-powered lamps, hig#h-irradiance- discharge lamps, or solar-radiation at ambient or elevated co2^8^102^1^141^^^^^Mayeks at high CO2 (1500 cm3#351^3^Grulke,NE^Hom,JL^Roberts,SW^1993^1^Physiological adjustment of 2 full-sib families of ponderosa pine to elevated co2#^13^12^4^391-401^^^^^Jun^^^^^3534ze responded only to N supply. CO2-enriched wheat produced about twice the dry matter o#A^3533^Seeds from two full-sib families of ponderosa pine (Pinus ponderosa) with known differences in growth rates were ge#rminated and grown in an ambient (350 mul l-1) or elevated (700 mul l-1) CO2 concentration. Gas exchange at both ambient a#nd 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 me#asured at elevated CO2. After 4 months, the light response of seedlings in the two treatments was determined at both ambie#nt 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 ap#parent 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 f#amilies for any response to elevated CO2. Under the experimental conditions, high growth rate was not correlated with a gr$eater response to elevated CO2.antially decreased critical concentrations of NO3-N and total-N in stem bases and leaves. $352^4^Heagle,AS^Miller,JE^Sherrill,DE^Rawlings,JO^1993^1^Effects of ozone and carbon-dioxide mixtures on 2 clones of white$ clover^84^123^4^751-762^^^^^Apr^^^^^3536 with 7.5, 6.2 and 6.4 mg/g dry wt, respectively, for control plants grown at th$A^3535^The effects of mixtures of ozone and carbon dioxide on growth and physiology of an O3-sensitive (NC-S) and an O3-re$sistant (NC-R) clone of white clover (Trifolium repens L.) were determined. The experiment was performed in a greenhouse w$ ith 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 bu$1t caused only slight injury of NC-R. CO2 enrichment suppressed O3- induced foliar injury of NC-S as measured after 4 wk of$: exposure, but this effect diminished after 8 wk of exposure. CO2 enrichment decreased the relative chlorophyll content (m$<ug of chlorophyll mg-1 of leaf tissue sampled) but not the total chlorophyll (total chlorophyll in the leaves sampled). Th$Gere were no O3 x CO2 interactions for foliar chlorophyll. High concentrations of CO2 caused reddening of new leaves near t$Ihe end of the 8 wk exposure period. CO2 enrichment decreased foliar concentrations of N, P, K, S, Cu, B, and Fe, increased$S foliar concentrations of Mn, but did not affect Zn, Ca, or Mg. Ozone exposure did not modify the CO2 effects on foliar nu$Ttrient concentration. Ozone decreased growth of NC-S but not NC-R while CO2 enrichment stimulated growth of both clones. The highest CO2 concentration appeared to decrease the effects of O3 on growth of NC-S. However, except for a transitory effect on foliar injury, there was no evidence that CO2, at concentrations less than the highest used in this study, will pr$votect white clover from the effects of tropospheric O3. being at least similar in magnitude to those already observed in $x353^2^Kimball,BA^Mauney,JR^1993^1^Response of cotton to varying co2, irrigation, and nitrogen - yield and growth^48^85^3^7$06-712^^^^^May-Jun^^^^^3538mean Q700/350 of only 1.05. High CO2 responsiveness was common only within the competitive str$A^3537^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 reverse$d. No significant effects of CO2 on harvest index, root-shoot ratio, or lint percentage were found, so the primary effect $of elevated CO2 was to produce plants that were larger. Comparing the results of 500 and 650 mumol mol-1 CO2 treatments, t$he increments of growth from ambient (about 350 mumol mol-1) to 500 mumol mol-1 were not significantly different from incr$ements from 500 to 650 mumol mol-1. No statistically significant interactions were detected between CO2 level and either i$rrigation or nitrogen level, even when these variables were sufficiently low enough to limit growth. However, under well-m$aintained water stress conditions, the growth response to CO2 tended to be somewhat larger than under normal irrigation le$vels. Averaging over all the data available from these experiments, seed cotton yield (lint plus seed) and above- ground b$iomass were increased by 60 and 63%, respectively, by CO2 enrichment to 650 mumol mol-1.5287. ID ATMOSPHERIC CO2 ENRICHME%354^4^Krapp,A^Hofmann,B^Schafer,C^Stitt,M^1993^1^Regulation of the expression of rbcs and other photosynthetic genes by ca%rbohydrates - a mechanism for the sink regulation of photosynthesis^209^3^6^817-828^^^^^Jun^^^^^3540nd summer mean maximu%A^3539^These experiments were carried out to investigate whether accumulation of carbohydrate leads to decreased expressio%n of genes involved in photosynthesis. Addition of glucose to autotrophic cell suspension cultures of Chenopodium led to a%% large and reversible decrease of the steady state transcript levels of rbcS, cab and atp-delta within 5 h, but did not de%&crease 18S rRNA or transcript for two glycolytic enzymes. Run-on transcription in isolated nuclei showed that transcriptio%4n rate had been decreased. [S-35]Methionine feeding showed that de novo synthesis of Rubisco was inhibited. Decreased rbcS%6 transcript was also found after feeding glucose to detached leaves, and in transgenic plants expressing invertase in the %Eapoplast to inhibit phloem transport, and in leaves on intact tobacco and potato plants which were cold- girdled to decrea%Gse export. The decrease of rbcS transcript level occurred within 12 h of cold-girdling. Comparison of carbohydrate content%U and rbcS transcript level indicated that carbohydrate content per se is not the direct signal for regulation of gene expr%Wession. Feeding of transported analogues indicates that metabolism rather than transport of the sugars is required. Over-e%ixpression of rbcS was found in low CO2, again indicating metabolic control of expression. ft is proposed that photosynthet%kic gene expression is inhibited by metabolic factors related to high carbohydrate content, and that this represents a basi%c mechanism for the 'sink regulation' of photosynthesis.ancement is of the same order of magnitude as our previously repo%355^2^Luo,YQ^Nobel,PS^1993^1^Growth-characteristics of newly initiated cladodes of opuntia- ficus-indica as affected by sh%ading, drought and elevated co2^37^87^4^467-474^^^^^Apr^^^^^3542T J AU IDSO, SB KIMBALL, BA TI DOWNWARD REGULATION OF PHO%A^3541^Biomass accumulation and area expansion of newly initiated cladodes of Opuntia ficus-indica were studied to help un%derstand the high productivity of this Crassulacena acid metabolism species. In a glasshouse, both dry weight and area inc%reased more and more rapidly for about 30 days and then increased linearly with time up to 63 days. The relative growth ra%te averaged 0.12 day-1, comparable to values for productive C3 and C, plants. New cladodes initiated on basal cladodes wit%h 2-fold higher initial dry weight grew twice as fast. Drought reduced biomass accumulation and area expansion of new clad%odes by 62 and 52%, respectively. A 70% reduction in irradiation decreased biomass accumulation of new cladodes by 17% and% their thickness by 11%. In a growth chamber containing 720 mumol CO2 (mol air)-1, biomass of newly initiated cladodes was% 7% higher, area was 8% less, specific mass was 16% higher and less carbohydrate was translocated from basal cladodes than% for 360 mumol CO2 mol-1. The large capacity for storage of carbohydrate and water in basal cladodes of O. ficus-indica ap%parently buffered environmental stresses, thereby reducing their effects on growth of daughter cladodes. 30322. DE CYCLIC%356^3^McConnaughay,KDM^Berntson,GM^Bazzaz,FA^1993^1^Limitations to co2-induced growth enhancement in pot studies^2^94^4^55%0-557^^^^^Jul^^^^^3544NT; OUTER SEGMENT; MOUSE RETINA; GMP; LIGHT; DARK; CONDUCTANCE; INDUCTION AB The effect of membrane%A^3543^Recently, it has been suggested that small pots may reduce or eliminate plant responses to enriched CO2, atmosphere%s due to root restriction. While smaller pot volumes provide less physical space available for root growth, they also prov%ide less nutrients. Reduced nutrient availability alone may reduce growth enhancement under elevated CO2. To investigate t%he relative importance of limited physical rooting space separate from and in conjunction with soil nutrients, we grew pla&nts at ambient and double-ambient CO2 levels in growth containers of varied volume, shape, nutrient concentration, and tot&al nutrient content. Two species (Abutilon theophrasti, a C3 dicot with a deep tap root and Setaria faberii, a C4 monocot &with a shallow diffuse root system) were selected for their contrasting physiology and root architecture. Shoot demography&( was determined weekly and biomass was determined after eight and ten weeks of growth. Increasing total nutrients, either &*by increasing nutrient concentration or by increasing pot size, increased plant growth. Further, increasing pot size while&8 maintaining equal total nutrients per pot resulted in increased total biomass for both species. CO2-induced growth and re&:productive yield enhancements were greatest in pots with high nutrient concentrations, regardless of total nutrient conten&Et or pot size, and were also mediated by the shape of the pot. CO2-induced growth and reproductive yield enhancements were&F unaffected by pot size (growth) or were greater in small pots (reproductive yield), regardless of total nutrient content,&V contrary to predictions based on earlier studies. These results suggest that several aspects of growth conditions within &Xpots may influence the CO2 responses of plants; pot size, pot shape, the concentration and total amount of nutrient additi&cons to pots may lead to over- or underestimates of the CO2 responses of real-world plants.he enrichment ratio are also il&e357^6^Melillo,JM^McGuire,AD^Kicklighter,DW^Moore,B^Vorosmarty,CJ^Schloss,AL^1993^1^Global climate-change and terrestrial n&qet primary production^36^363^6426^234-240^^^^^20 May^^^^^3546rption stream contains 7% SO2. Further improvement can be o&tA^3545^A process-based model was used to estimate global patterns of net primary production and soil nitrogen cycling for &{contemporary climate conditions and current atmospheric CO2 concentration. Over half of the global annual net primary prod&}uction was estimated to occur in the tropics, with most of the production attributable to tropical evergreen forest. The e&ffects of CO2 doubling and associated climate changes were also explored. The responses in tropical and dry temperate ecos&ystems were dominated by CO2, but those in northern and moist temperate ecosystems reflected the effects of temperature on& nitrogen availability.ECT OF LIGHT-INTENSITY AND CO2 ENRICHMENT DURING INVITRO ROOTING ON SUBSEQUENT GROWTH OF PLANTLETS&358^5^Nakadai,T^Koizumi,H^Usami,Y^Satoh,M^Oikawa,T^1993^1^Examination of the method for measuring soil respiration in cult&ivated land - effect of carbon-dioxide concentration on soil respiration^143^8^1^65-71^^^^^Apr^^^^^3548ANANASSA; LIGHT; M&A^3547^An acceleration of soil respiration with decreasing CO2 concentration was suggested in the field measurements. The &result supports that obtained in laboratory experiments in our previous study. The CO2 concentrations in a chamber of the &alkali absorption method (the AA-method) were about 150-250 parts/10(6) lower than that in the atmosphere (about 350 parts&/ 10(6)), while those observed in the open-flow IRGA method (the OF-method) were nearly equal to the soil surface CO2 leve&ls. The AA-method at such low CO2 levels in the chamber appears to overestimate the soil respiration. Our results showed t&hat the rates obtained by the AA-method were about twice as large as those by the OF-method in field and laboratory measur&ements. This finding has important consequences with respect to the validity of the existing data obtained by the AA-metho&d and the estimation of changes in the terrestrial carbon flow with elevated CO2 concentrations.period with raspberry. O&359^4^Nicolas,ME^Munns,R^Samarakoon,AB^Gifford,RM^1993^1^Elevated co2 improves the growth of wheat under salinity^92^20^3^&349-360^^^^^^^^^^3550CO2 during the in vitro rooting stage. BP 259-269 PG 11 JI Sci. Hortic. PY 1991 PD JUL VL 47 IS 3-4 &382^4^Polley,HW^Johnson,HB^Mayeux,HS^Malone,SR^1993^1^Physiology and growth of wheat across a subambient carbon- dioxide g&radient^52^71^4^347-356^^^^^AprIO MASS-SPECTROMETRY SO BIOLOGICAL MASS SPECTROMETRY SN 1052-9306 C1 UNIV BRITISH COLUMBIA&383^1^Possingham,HP^1993^1^Impact of elevated atmospheric co2 on biodiversity - mechanistic population-dynamic perspective&^182^41^1^11-21^^^^^^^^^^3592de (TG) synthesis was measured over 48 h in four healthy males from the incorporation rate o&iochemically not only to interspecific differences in host chemistry, but also to resource-mediated, intraspecific changes' in host chemistry. Such responses are likely to be important for the dynamics of plant-insect interactions as they occur 'A^3549^Wheat plants (Triticum aestivum cv. Matong and T. durum cv. Modoc) were grown at ambient and elevated CO2 (350 cm3 ')m-3 above ambient) in soil with or without 150 mol m-3 NaCl for 6 weeks. The increase in dry matter, leaf area and tilleri'+ng under high CO2 was relatively greater under saline than non- saline conditions for both cultivars. Tillering was the pr'3imary component of growth affected by both salinity and high CO2. Salinity greatly reduced tillering and high CO2 partly r'5eversed the effects of salinity. High CO2 increased dry matter accumulation of the salt-sensitive Modoc to a greater exten'Dt (+ 104%) than that of the more salt-tolerant Matong (+ 73 %) in the salt treatment. Transpiration rates were greatly red'Euced by salinity for both cultivars. Under high CO2, increased leaf areas compensated for reduced transpiration rates per 'Z unit leaf area (i.e. greater stomatal closure), and total transpiration was little affected by CO2 level within each treat'\ ment. The more salt-tolerant Matong showed greater stomatal closure and higher transpiration efficiencies than the salt-se'k nsitive Modoc under salinity. High CO2 reduced transpiration rate (per unit dry weight) by 40 to 50%, but did not signific'm antly change the rate of sodium accumulation (per unit dry weight), indicating that salt uptake was largely independent of' water uptake, and that high CO2 did not increase growth by reducing the salt load. Our results suggest that high CO2 incr'eased growth by stimulating the development of tiller buds that would otherwise have been inhibited.nditions, a trial on '360^3^Nie,GY^Long,SP^Webber,A^1993^1^The effect of nitrogen supply on down-regulation of photosynthesis in spring wheat gr'own in an elevated co2 concentration^8^102^1^138^^^^^Mayage); - hermetic storage; - initial purge with gas mixture, 50% C'361^3^Rogers,HH^Prior,SA^Runion,GB^1993^1^Effects of elevated atmospheric co2 on soybean and sorghum root-growth^8^102^1^1'73^^^^^Mayae. Weekly sampling over a 3-month storage period permitted determination of the lethal effects on insects, CO'362^2^Samuelson,LJ^Seiler,JR^1993^1^Interactive role of elevated co2, nutrient limitations, and water-stress in the growth'-responses of red spruce seedlings^49^39^2^348-358^^^^^May^^^^^3554compensated for by microfloral respiration which is th'A^3553^Red spruce (Picea rubens Sarg.) seedlings were grown from seed for 5 mo in ambient (362 ppm) or elevated (711 ppm) 'CO2 to determine the potential effect of an increase in global CO2 concentration on seedling growth and establishment. CO2' exposure treatments were crossed with two levels of soil fertility and water stress treatments to determine if seedling d'ry weight, size, and fixed growth responses to elevated CO2 depended on nutrient and water supply. Seedling dry weight and& size responses to elevated CO2 at 5 mo did not depend on nutrient and water supply. Seedlings grown in both soil fertilit(y treatments and water stress treatments responded similarly to CO2 treatment. Water stress and CO2 treatments did have an(  interactive influence on the fixed growth potential of the terminal leader. Leaf weight, leaf area, and height of the ter(minal leader of water-stressed seedlings were greater in seedlings exposed to elevated CO2 during budset than seedlings ex(posed to ambient CO2. Total new fixed growth (lateral plus terminal) and total terminal fixed growth (leaf plus stem) were(! greater in seedlings that formed shoot primordia in elevated CO2 than in ambient CO2. Red spruce seedlings grown in eleva(2ted CO2 for 5 mo had greater stem diameter, height, branching density, leaf weight, root weight, stem weight, total weight(4 , and mean relative growth rate (RGR) from 3 to 5 mo than seedlings grown in ambient CO2. Red spruce seedling responses to(?! elevated CO2 suggest that seedling establishment in natural environments may be enhanced when ambient CO2 concentrations (Arise even if water and nutrient availabilities are limited.thousand; dioritic and anorthositic rocks: 5.5 to 7.6 parts p(S#363^2^Silvola,J^Ahlholm,U^1993^1^Effects of co2 concentration and nutrient status on growth, growth rhythm and biomass par(Utitioning in a willow, salix- phylicifolia^15^67^2^227-234^^^^^Jun^^^^^3556 in unaltered plutonic rocks of equivalent com(`%A^3555^Cuttings of the willow Salix phylicifolia were grown in pots containing moist organic-rich soil for four months in (b&closed chambers at 4 CO2 concentrations (300). 500, 700, 1000 ppm) and 4 nutrient levels (fertilization of 0, 100, 500, 10(k'00 kg ha-1 monthly). The plants received natural light, but the average temperature was 3-6-degrees-C higher than out of d(m(oors. Both CO2 concentration and fertilization affected biomass production. the average increase caused by CO2 enhancement(z) being approx. 100%. Nutrient level had a considerable effect on the increased biomass production achieved by CO2 enhancem(|*ent, since the increase was minimal at lower nutrient levels. At the same time the effect of fertilization was dependent o(+n the CO2 concentration, the production increase caused by fertilization being much less at 300 ppm than at the other CO2 (,concentrations. CO2 concentration and fertilization had the opposite effects on biomass partitioning, a higher nutrient le(-vel increasing the proportion of the biomass located in the stems and a higher CO2 concentration that in the roots. Both f(.ertilization and CO2 concentration affected the growth rhythm, a high CO2/nutrient ratio leading to a shorter growing seas(on and a low ratio to a longer one.osition appear to have occurred during granulite facies metamorphism, implying limited(0364^2^Ziska,LH^Bunce,JA^1993^1^Inhibition of whole-plant respiration by elevated co2 as modified by growth temperature^37^(87^4^459-466^^^^^Apr^^^^^3558A model involving an association between mantle-derived mafic magma and O-18- enriched crust(2A^3557^Plants of alfalfa (Medicago sativa) and orchard grass (Dactylus glomerata) were grown in controlled environment cha(3mbers at two CO2 concentrations (350 and 700 mumol mol-1) and 4 constant day/night growth temperatures of 15, 20, 25 and 3(40-degrees-C for 50-90 days to determine changes in growth and whole plant CO2 efflux (dark respiration). To facilitate com(5parisons with other studies, respiration data were expressed on the basis of leaf area, dry weight and protein. Growth at (6elevated CO2 increased total plant biomass at all temperatures relative to ambient CO2, but the relative enhancement decli) 7ned (P less- than-or-equal-to 0.05) as temperature increased. Whole plant respiration (R(d)) at elevated CO2 declined at 1)85 and 20- degrees-C in D. glomerata on an area, weight or protein basis and in M. sativa on a weight or protein basis when)9 compared to ambient CO2. Separation of R(d) into respiration required for growth (R(g)) and maintenance (R(m)) showed a s):ignificant effect of elevated CO2 on both components. R(m) was reduced in both species but only at lower temperatures (15-)(;degrees-C in M. sativa and 15 and 20-degrees-C in D. glomerata). The effect on R(m) could not be accounted for by protein )*perennial species used in the present study, the data suggest that both R(g) and R(m) can be reduced by anticipated increa)??ses in atmospheric CO2; however, CO2 inhibition of total plant respiration may decline as a function of increasing tempera)Ature.e section). Consideration of these data in the context of delta- temperature relations suggests that 1) surface wat)SA365^2^Beerling,DJ^Chaloner,WG^1993^1^The impact of atmospheric co2 and temperature-change on stomatal density - observatio)Uns from quercus-robur lammas leaves^52^71^3^231-235^^^^^Marom the highest, 2) the increasing delta-O-18 values also refle)`C366^3^Bottomley,PA^Rogers,HH^Prior,SA^1993^1^Nmr imaging of root water distribution in intact vicia-faba L plants in eleva)bted atmospheric co2^9^16^3^335-338^^^^^Apr^^^^^3561peratures, and 3) the significant variation in delta-O-18 from oldest )oEA^3560^The effect of elevated atmospheric CO2 on water distribution in the intact roots of Vicia faba L. bean seedlings gr)qFown in natural soil was studied noninvasively with proton (H-1) nuclear magnetic resonance (NMR) imaging. Exposure of 24-d)wG-old plants to atmospheric Co2-enriched air at 650 cm3 m-3 produced significant increases in water imaged in upper roots, )xHhypogeal cotyledons and lower stems in response to a short-term drying- stress cycle. Above ground, drying produced neglig)Iible stem shrinkage and stomatal resistance was unchanged. In contrast, the same drying cycle caused significant depletion)J of water imaged in the same upper root structures in control plants subject to ambient CO2 (350 m3 m-3), and stem shrinka)Kge and increased stomatal resistance. The results suggest that inhibition of transpiration caused by elevated CO2 does not)L necessarily result in attenuation of water transport from lower root structures. Inhibition of water loss from upper root)Ms and lower stem in elevated CO2 environments may be a mitigating factor in assessing deleterious effects of greenhouse ch)anges on crops during periods of dry climate.ARK BASIN, SOUTHWEST PACIFIC SO GEOCHIMICA ET COSMOCHIMICA ACTA SN 0016-7037)O367^1^Bunce,JA^1993^1^Effects of doubled atmospheric carbon-dioxide concentration on the responses of assimilation and con)ductance to humidity^9^16^2^189-197^^^^^Mar^^^^^3563TASMANIA, HOBART, TAS 7001, AUSTRALIA. ID OCEAN-RIDGE BASALT; CARBON-)QA^3562^Experiments were performed to determine if growth at elevated partial pressure of CO2 altered the sensitivity of le)Raf water vapour conductance and rate of CO2 assimilation to the leaf-to- air difference in the partial pressure of water v)Sapour (DELTAw). Comparisons were made between plants grown and measured at 350 and 700 muPa Pa-1 partial pressures of CO2 )Tfor amaranth, soybean and sunflower grown in controlled environment chambers, soybean grown outdoors in pots, and orchard )Ugrass grown in field plots. In amaranth, soybean and orchard grass, both the absolute and the relative sensitivity of cond*Vuctance to DELTAw at the leaf surface were less in plants grown and measured at the elevated CO2. In sunflower, there was *Wno change in the sensitivity of conductance to DELTAw for the two CO2 partial pressures. Tests in soybeans and amaranth sh*Xowed that the change in sensitivity resulted from elevated CO2 during the measurement of the DELTAw response. Assimilation*Y rate of CO2 was not altered by DELTAw in amaranth, which has C4 metabolism. In sunflower, the assimilation rate of plants*(Z grown and measured at elevated CO2 was insensitive to DELTAw, consistent with the response of assimilation rate to interc**[ellular CO2 partial pressure in the prevailing range. In soybean, the sensitivity of assimilation rate to DELTAw was not d*,\ifferent between CO2 treatments, in contrast to what would be expected from the response of assimilation rate to intercell*:ular CO2 partial pressure.n and partial melting. It appears that the Woodlark Basin basalts have at least three differen*<^368^3^Coleman,JS^McConnaughay,KDM^Bazzaz,FA^1993^1^Elevated co2 and plant nitrogen-use - is reduced tissue nitrogen concen*>tration size-dependent^2^93^2^195-200^^^^^Mar^^^^^3565a PY 1991 PD AUG VL 55 IS 8 GA GC439 RP MUENOW DW J9 GEOCHIM COSMOC*F`A^3564^Plants often respond to elevated atmospheric CO2 levels with reduced tissue nitrogen concentrations relative to amb*Haient CO2- grown plants when comparisons are made at a common time. Another common response to enriched CO2 atmospheres is *Jban acceleration in plant growth rates. Because plant nitrogen concentrations are often highest in seedlings and subsequent*Tcly decrease during growth, comparisons between ambient and elevated CO2-grown plants made at a common time may not demonst*Vdrate CO2-induced reductions in plant nitrogen concentration per se. Rather, this comparison may be highlighting difference*des in nitrogen concentration between bigger, more developed plants and smaller, less developed plants. In this study, we di*ffrectly examined whether elevated CO2 environments reduce plant nitrogen concentrations independent of changes in plant gro*tgwth rates. We grew two annual plant species, Abutilon theophrasti (C3 photosynthetic pathway) and Amaranthus retroflexus (*vhC, photosynthetic pathway), from seed in glass-sided growth chambers with atmospheric CO2 levels of 350 mumol . mol-1 or 7*i00 mumol . mol- 1 and with high or low fertilizer applications. Individual plants were harvested every 2 days starting 3 d*jays after germination to determine plant biomass and nitrogen concentration. We found: 1. High CO2-grown plants had reduce*kd nitrogen concentrations and increased biomass relative to ambient CO2-grown plants when compared at a common time; 2. Ti*lssue nitrogen concentrations did not vary as a function of CO2 level when plants were compared at a common size; and 3. Th*me rate of biomass accumulation per rate of increase in plant nitrogen was unaffected by CO2 availability, but was altered *nby nutrient availability. These results indicate that a CO2- induced reduction in plant nitrogen concentration may not be *odue to physiological changes in plant nitrogen use efficiency, but is probably a size-dependent phenomenon resulting from *accelerated plant growth.hat yield increases resulted from the combined effects of limited atmospheric CO2 enrichment and*q369^1^Conroy,JP^1993^1^Influence of elevated atmospheric co2 concentrations on plant nutrition (vol 40, pg 445, 1992)^182^*41^1^143^N J ER PT J AU PLONSKY, IM DUNINABARKOVSKAYA, AY CHAILAKHYAN, LM TI EFFECT OF CO2 ON CELL-CELL JUNCTION CONDUCT*s370^2^Garcia,JM^Streif,J^1993^1^Quality and storage potential of pear .1. Influence of ca- storage and ulo-storage conditi*ons^172^58^1^36-41^^^^^Jan-Feb^^^^^3568MISS PROBLEMS, MOSCOW V-71, USSR. AN BELOZERSKII MOLEC BIOL & BIOORGAN CHEM LAB, M*uA^3567^In a CA experiment the storage potential of different pear cultivars was investigated, especially the behaviour of *vthe fruits against elevated CO2 concentrations and/or ultra low oxygen (ULO).The following CA combinations were tested: < *w1 % CO2 + 3 % O2; 3 % CO2 + 3 % O2; < 1 % CO2 + 1 % O2; 3 % CO2 + 1 % O2, and refrigerated storage at - 1-degrees-C 'Packh*xam's Triumph' showed the best storage potential of all tested cultivars followed by 'Conference' and 'Doyenne' du Comice. *yThe keepability of 'General Leclerc' was only slightly improved by CA conditions compared with cold stored pears. CA stora*zge of 'Alexander Lucas' and 'Bristol Cross' didn't show an obvious advantage because of high CO2 damages. Therefore, CO2 c*{oncentrations 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 sensit+ive cultivars, but improved the keepability of 'Doyenne du Comice' and 'Packham's Triumph'.Ca greater-than-or-equal-to 9.+~371^2^Graybill,DA^Idso,SB^1993^1^Detecting the aerial fertilization effect of atmospheric co2 enrichment in tree-ring chro+nologies^137^7^1^81-95^^^^^Mar^^^^^3570periments CO2 was still capable of uncoupling the cells. We conclude that the eff+A^3569^The growth-promoting effects of the historical increase in the air's CO2 content are not yet evident in tree-ring r+ecords 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 wi+0th independently derived proxy climate records for those times.ar junction conductance in isolated pairs of mouse hepatoc+2372^5^Gross,U^Gilles,F^Bender,L^Berghofer,P^Neumann,KH^1993^1^The influence of sucrose and an elevated co2 concentration o+Bn photosynthesis of photoautotrophic peanut (arachis-hypogaea L) cell-cultures^177^33^2^143-150^^^^^May^^^^^3572he extern+DA^3571^Using photoautotrophic cells of Arachis hypogaea (L.) growing at ambient CO2, it was shown that exogenous sucrose s+Rupplied to the liquid medium reduced (CO2)-C-14 fixation (supplied as NaH (CO3)-C-14) . This was mostly due to a reduced l+Tabelling in P-esters, and to a lesser extent, in the serine/glycine moiety. However, radioactivity in the neutral sugar fr+Vaction was increased upon supplement of exogenous sucrose. The reduced labelling of P-esters and serine/glycine agrees wit+dh a lower concentration and specific activity of Rubisco in the sucrose supplied treatments as compared to the control. Fo+fllowing a transfer into a sugar free nutrient medium the concentration and activity of Rubisco is increased. The concentra+ytion of PEPCase was not influenced by sucrose application, although its specific activity was increased. At elevated CO2 c+{oncentration (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.AGONE, R FIERRO, G INVERSI, M LOJACONO, M MORETTI, G TI COPPER COBALT HYDROXYSALTS AND +373^2^Hao,YY^Brackett,RE^1993^1^Influence of modified atmosphere on growth of vegetable spoilage bacteria in media^210^56^+3^223-228^^^^^Mar^^^^^3574ITA CATALIT SISTEMI OSSIDI, I-00185 ROME, ITALY. DE COPPER-COBALT OXYSALT; MIXED OXIDE PRECURSO+A^3573^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 investi+gate 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, Xant+homonas, 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 (C+O2/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. I+n 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.weaker at increasing cobalt loading. The observed decrease in volume of the )374^3^Havstrom,M^Callaghan,TV^Jonasson,S^1993^1^Differential growth-responses of cassiope-tetragona, an arctic dwarf-shrub,, to environmental perturbations among 3 contrasting high sites and sub-arctic sites^15^66^3^389-402^^^^^Apr^^^^^3576d by, A^3575^Three populations of Cassiope tetragona (Ericaceae) were subjected to in situ environmental perturbations simulatin, g predictions of global warming. The populations were selected to represent different parts of the range of the species, o,ne growing in a high arctic coastal heath at Ny-Alesund (Svalbard, northern part of the species' range), one at a subarcti,c 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 m,3ountain birch canopy and the temperature enhancement treatments had the desired effect to increase the average air tempera,5ture by 2-4-degrees-C. Greenhouses which had a gap between the soil and the greenhouse plastic were particularly successfu,Cl in creating the desired climatic perturbation without causing extreme maximum temperatures or other unwanted side-effect,Fs. The environmental manipulations caused strikingly different responses in the vegetative growth pattern of main shoots o,^f C. tetragona among the three populations: at the subarctic tree-line heath, nutrient addition caused a substantial incre,`ase in growth, whereas it was the temperature enhancement treatments that caused increases, although smaller, at the subar,octic fellfield and the high arctic heath sites. At the high arctic site, we also found growth reduced in response to shadi,qng, but at the subarctic sites, and particularly at the tree-line heath site, shading caused a marked etiolation of the sh,oots. Hence, different factors seem to produce very different responses in the vegetative growth of C. tetragona in differ,ent parts of its geographical range. We conclude that competition for nutrients and light are the main limiting factors fo,r 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 als,o suggest that the direct effect of predicted future climatic warming on the growth of Cassiope tetragona will increase to,wards the north, whereas a possible indirect effect of increasing nutrient availability following a temperature increase w,ill be the main effect in the southern and lower parts of its range. These responses could, however, be modified by shadin,g from other species responding to environmental change by increased growth.ith CO2 enrichment of aquatic habitats from r,375^3^Idso,SB^Kimball,BA^Hendrix,DL^1993^1^Air-temperature modifies the size-enhancing effects of atmospheric co2 enrichme,nt on sour orange tree leaves^173^33^2^293-299^^^^^Apr^^^^^3578s based on laboratory data and on theoretical consideratio,A^3577^Every other month for a period of 2 years, leaf area and dry weight measurements were made on the foliage of sour o,range trees growing in ambient air and in air enriched with an extra 300 mul/l CO2. Leaf starch content measurements were $made at approximate 2-month intervals for a period of 1 year. The data demonstrated that all three plant parameters were s$ignificantly increased by atmospheric CO2 enrichment, except in the coldest portion of the year. A plot of the ratio of CO$2-enriched leaf dry weight to ambient-treatment leaf dry weight against the mean air temperature of the preceding month re$vealed this relationship with temperature to be linear. The relationship shows atmospheric CO2 enrichment to have a neglig$ible effect on leaf dry weight at a mean air temperature of approximately 5- degrees-C. At a mean air temperature of 35-de$grees-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.ate, propionate, butyrate, or a mixture of aliphatic fatty acids (C4 through - 376^2^Jalil,A^Carlson,RM^1993^1^Potassium uptake by marianna plum under limited oxygen and elevated carbon-dioxide levels - in the root atmosphere^166^16^4^723-737^^^^^^^^^^3580ids such as formate, propionate, butyrate, caproate, valerate, pyruv-A^3579^Potassium (K) uptake rates were determined for Marianna 2624 rootstocks with 'French' prune scions using th nutrien-t 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 atmosphe-5re. 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. In-7creasing root atmosphere CO2 from 0 to 0.05 M3/M3 had a small depressing effect on net K+ influx from 60 muM K+ solutions -Cat 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-E rate at 0.10 and 0.05 M3/M3 02. Increased pH buffering from higher HCO3 concentration at the plasma membrane surface was -Nsuggested to explain the CO2 effect on Km.scussed. BP 2302-2307 PG 6 JI Appl. Environ. Microbiol. PY 1991 PD AUG VL 57 IS-P377^4^Kimball,BA^Mauney,JR^Nakayama,FS^Idso,SB^1993^1^Effects of elevated co2 and climate variables on plants^211^48^1^9-1-Y4^^^^^Jan-FebMOSPHERIC CARBON-DIOXIDE CONCENTRATION SO PLANT CELL AND ENVIRONMENT SN 0140-7791 C1 UNIV FLORIDA, DEPT AGRO-[378^1^Krauchi,N^1993^1^Potential impacts of a climate change on forest ecosystems^212^23^1^28-50^^^^^Apr^^^^^3583AINESVIL-fA^3582^Review of literature indicates that many uncertainties and assumptions exist in predicting the impacts of a climate-h change on forest ecosystems. However, current knowledge is sufficient to encourage any measures that are combating climat-se change, that is to reduce first and foremost the release of harmful substances to the atmosphere, lithosphere and biosph-uere. a range of atmospheric CO2 concentrations in outdoor, computer-controlled, environment chambers under natural solar -379^7^Lucas,WJ^Olesinski,A^Hull,RJ^Haudenshield,JS^Deom,CM^Beachy,RN^Wolf,S^1993^1^Influence of the tobacco mosaic-virus 3-0-kda movement protein on carbon metabolism and photosynthate partitioning in transgenic tobacco plants^6^190^1^88-96^^^^^-May^^^^^3585antly with increasing CO2. Although leaf dry weight and leaf area index increased, the overall response was n-A^3584^Transgenic tobacco (Nicotiana tabacum L.) plants expressing the 30-kDa movement protein of tobacco mosaic virus (TM-V-MP) were employed to investigate the influence of a localized change in mesophyll-bundle sheath plasmodesmal size exclus-ion limit on photosynthetic performance and on carbon metabolism and allocation. Under conditions of saturating irradiance-, tobacco plants expressing the TMV-MP were found to have higher photosynthetic CO2-response curves compared with vector c-ontrol plants. However, this difference was significant only in the presence of elevated CO2 levels. Photosynthetic measur-ements made in the greenhouse, under endogenous growth conditions, revealed that there was little difference between TMV-M-P- expressing and control tobacco plants. However, analysis of carbon metabolites within source leaves where a TMV-MP-indu-ced increase in plasmodesmal size exclusion limit had recently taken place established that the levels of sucrose, glucose-, fructose and starch were considerably elevated above those present in equivalent control leaves. Although expression of -the TMV-MP did not alter total plant biomass, it reduced carbon allocation to the lower region of the stem and roots. This- difference in biomass distribution was clearly evident in the lower root-to-shoot ratios for the TMV-MP transgenic plants-. Microinjection (dye-coupling) studies established that the TMV- MP-associated reduction in photosynthate delivery (alloc-ation) to the roots was not due to a direct effect on root cortical plasmodesmata. Rather, this change appeared to result .from an alteration in phloem transport from young source leaves in which the TMV-MP had yet to exert its influence over pl.asmodesmal size exclusion limits. These results are discussed in terms of the rate-limiting steps involved in sucrose move.ment into the phloem.ntial increase in phosphorus loading from urban sources (approximately 1940-70), and decreased phosp.380^4^Nie,D^He,H^Kirkham,MB^Kanemasu,ET^1992^1^Photosynthesis of a C3 grass and a C4 grass under elevated co2^79^26^2^189-.'198^^^^^^^^^^3587storical dynamics and cycling of major nutrients. The temporal pattern of organic carbon production clos.)A^3586^The net photosynthetic rate (P(N)), intercellular CO2 concentration (C(i)), transpiration rate (E), stomatal resist.9ance (r(s)), and water potential (PSI(W)) of a C3 grass (Kentucky bluegrass, Poa pratensis L.) and a C4 grass (big blueste.;m, Andropogon gerardii Vitman) growing in the spring in a tallgrass prairie under two levels of CO2 (ambient and twice amb.Fient) were compared. Elevated CO2 (HC) increased P(N) of Kentucky bluegrass (C3) by 47.0 % but did not affect P(N) of big .Hbluestem (C4). HC increased C(i) of both grasses by about the same amount (is-approximately-equal-to cm3 m-3), but reduced.S E (and parallelly increased r(s)) of big bluestem more than those of Kentucky bluegrass. HC increased PSI(W) of both gras.Uses by about 30 %. Kentucky bluegrass had a lower PSI(W) than big bluestem, but HC increased PSI(W) of Kentucky bluegrass .ato values more similar to those of big bluestem under ambient CO2 (LC). Hence a high PSI(W), resulting from HC, was necess.cary for a high P(N).VEY, DIV WATER RESOURCES, MS 408, LAKEWOOD, CO 80225. WOODS HOLE OCEANOG INST, DEPT BIOL, WOODS HOLE,.e381^4^Polle,A^Pfirrmann,T^Chakrabarti,S^Rennenberg,H^1993^1^The effects of enhanced ozone and enhanced carbon-dioxide conc.nentrations on biomass, pigments and antioxidative enzymes in spruce needles (picea-abies L)^9^16^3^311-316^^^^^Apr^^^^^358.pA^3588^During one growing period, 5-year-old spruce trees (Picea abies L., Karst.) were exposed in environmental chambers .{to elevated concentrations of carbon dioxide (750 cm3 m-3) and ozone (0.08 cm3 m-3) as single variables or in combination..} Control concentrations of the gases were 350 cm 3 m-3 CO2 and 0.02 cm3 m-3 ozone. To investigate whether an elevated CO2 .concentration can prevent adverse ozone effects by reducing oxidative stress, the activities of the protective enzymes sup.eroxide dismutase, catalase and peroxidase were determined. Furthermore, shoot biomass, pigment and protein contents of tw.o needle age classes were investigated. Ozone caused pigment reduction and visible injury in the previous year's needles a.nd growth reduction in the current year's shoots. In the presence of elevated concentrations of ozone and CO2, growth redu.ction in the current year's shoots was prevented, but emergence of visible damage in the previous year's needles was only .delayed and pigment reduction was still found. Elevated concentrations of ozone or CO2 as single variables caused a signif.icant reduction in the activities of superoxide dismutase and catalase in the current year's needles. Minimum activities o.f superoxide dismutase and catalase and decreased peroxidase activities were found in both needle age classes from spruce .trees grown at enhanced concentrations of both CO2 and ozone. These results suggest a reduced tolerance to oxidative stres.s in spruce trees under conditions of elevated concentrations of both CO2 and ozone.equately quantify the processes contr.9 and N transport and transformation within these environments. BP 1815-1825 PG 11 JI Geochim. Cosmochim. Acta PY 1991 P.A^3591^Biodiversity is characteristically defined on three levels: genetic diversity, species diversity and ecosystem dive.rsity. In this paper I consider the impact of elevated CO2 and associated climate change on the biodiversity of terrestria.l systems at the species level. I attempt to understand the impact of a rapidly changing physical environment mechanistica.lly. The direct impact of elevated CO2 is emphasised. A changing physical environment will cause behavioural and physiolog.ical responses in organisms that will affect population dynamics and interspecific relationships. In the short term, extin/ctions will occur via the direct interaction of species with their changing environment. Species exposed to new diseases, /and species dependent on mutualists or keystone species that become extinct or change geographical range, may become extin/  ct rapidly through interactions with other species. I hypothesise that the effect of environmental change on competitive i/ nteractions will play a minor role in causing declines in biodiversity. Existing literature on the impact of climate chang/ e on terrestrial ecosystems emphasises the way in which ecosystems and species should track suitable climates across the l/! andscape. Here I argue that each species will be affected in one, or a combination, of the following ways: range change to/) track shifting climate zones, tolerating the environmental change, microevolutionary change, and extinction.tored Prod. /+384^2^Woodrow,L^Grodzinski,B^1993^1^Ethylene exchange in lycopersicon-esculentum mill - leaves during short-term and long-/3term exposures to co2^78^44^259^471-480^^^^^Feb^^^^^3594YME PATTERN AND INTRACELLULAR LOCATION SO PLANTA SN 0032-0935 C1 /5A^3593^The effects of long-term and transient exposure to elevated CO2 concentrations on photosynthetic gas exchange and e/Athylene release by tomato leaves were investigated. The net CO2 assimilation rate was enhanced when leaf tissue grown at a/Cmbient (35 Pa CO2) levels was assayed at 100 Pa CO2. Leaf tissue grown at high (130 Pa) CO2 exhibited a lower net CO2 assi/Tmilation rate at high CO2 levels than leaf tissue grown at ambient (35 Pa) CO2. This decrease in CO2 exchange rate in resp/Uonse to growth at high CO2 is typical Of C3 species. Rates of endogenous and 1-aminocyclopropane-1-carboxylic acid (ACC)- /hStimulated ethylene release from leaf tissue were enhanced by exposure to elevated CO2 levels whether the leaf tissue had /jbeen grown at ambient or enriched CO2 levels, The data demonstrate that CO2 enhanced C2H4 release from leaf tissue in resp/xonse to both short-term perturbations in CO2 concentration and long-term growth and development under high CO2. Prolonged /zgrowth at elevated CO2 concentrations induced a higher endogenous rate of C2H4 release relative to that of leaf tissue gro/~wn at lower CO2 levels. Leaf tissue from all leaf positions of plants grown at high CO2 consistently evolved more C2H4 tha/n corresponding tissue from ambient-grown plants when assayed under standardized conditions. Endogenous (ACC) tissue conte/nts and rates of ACC-stimulated ethylene release were also higher at all leaf positions in CO2-enriched tissue. Thus the h/igher rates appeared to be due to both higher endogenous precursor (ACC) levels in the tissue and greater ACC to C2H4 conv/ersion capacity. Growth at elevated CO2 levels resulted in a persistent increase in the rate of endogenous C2H4 release in/ leaf tissue. The capacity for increased ethylene release in response to CO2 did not decline after prolonged growth at hig/h CO2.STRAIN, BR TI ROOT RESTRICTION AS A FACTOR IN PHOTOSYNTHETIC ACCLIMATION OF COTTON SEEDLINGS GROWN IN ELEVATED CARB/ 385^2^Adamse,P^Britz,SJ^1992^1^Amelioration of uv-b damage under high irradiance .1. Role of photosynthesis^63^56^5^645-65/0^^^^^Nov^^^^^3596NRICHMENT; INHIBITION; TEMPERATURE; CARBOXYLASE; EXCHANGE; SOYBEANS AB Interactive effects of root rest/"A^3595^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 (photosynthe/$tically- 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) CO/&2 levels. Responses to UV-B were assessed by photosynthetic gas exchange, leaf expansion and production of UV-absorbing co/'mpounds (presumptive flavonoids) in cultivars of cucumber (Cucumis sativus L.) previously demonstrated to be relatively se/(nsitive (cv. Poinsett) and insensitive (cv. Ashley) to UV-B. Except for marginal leaf interveinal chlorosis observed in Po/)insett, both cultivars responded similarly. UV-B had little direct effect on leaf photosynthesis, but it did cause reducti0*ons in leaf area and corresponding increases in leaf dry matter per area. Increased CO2 stimulated plant growth, counterac0+ting the effect of UV-B on leaf growth and indicating an important role for photosynthesis. In contrast, the accumulation 0of UV-absorbing flavonoid compounds was enhanced by UV-B exposure but was not affected by CO2 enrichment.vity may be resp0/-386^5^Arp,WJ^Drake,BG^Pockman,WT^Curtis,PS^Whigham,DF^1993^1^Interactions between C-3 and C-4 salt-marsh plant-species dur01ing 4 years of exposure to elevated atmospheric co2^24^104^^133-143^^^^^Jan^^^^^3598n capacity increased indicating that 0D/A^3597^Elevated atmospheric CO2 is known to stimulate photosynthesis and growth of plants with the C3 pathway but less of 0F0plants with the C4 pathway. An increase in the CO2 concentration can therefore be expected to change the competitive inter0O1actions between C3 and C4 species. The effect of long term exposure to elevated CO2 (ambient CO2 concentration + 340 mumol0R2 CO2 mol-1) on a salt marsh vegetation with both C3 and C4 species was investigated. Elevated CO2 increased the biomass of0Z3 the C3 sedge Scirpus olneyi growing in a pure stand, while the biomass of the C4 grass Spartina patens in a monospecific 0[4community was not affected. In the mixed C3/C4 community the C3 sedge showed a very large relative increase in biomass in 0h5elevated CO2 while the biomass of the C4 species declined. The C4 grass Spartina patens dominated the higher areas of the 0j6salt marsh, while the C3 sedge Scirpus olneyi was most abundant at the lower elevations, and the mixed community occupied 0z7intermediate elevations. Scirpus growth may have been restricted by drought and salt stress at the higher elevations, whil0|8e Spartina growth at the lower elevations may be affected by the higher frequency of flooding. Elevated CO2 may affect the09 species distribution in the salt marsh if it allows Scirpus to grow at higher elevations where it in turn may affect the 0growth of Spartina.out the growing season and analysed for starch, K, P, Ca, Mg, Fe, and Mn concentrations. Foliar K and 0;387^2^Baker,JT^Allen,LH^1993^1^Contrasting crop species responses to co2 and temperature - rice, soybean and citrus^24^1040^^239-260^^^^^Jan^^^^^3600the plants of one genotype received foliar applications of 7 millimolar KH2PO4. Untreated folia0=A^3599^The continuing increase in atmospheric carbon dioxide concentration ([CO2]) and projections of possible future incr0>eases in global air temperatures have stimulated interest in the effects of these climate variables on plants and, in part0?icular, on agriculturally important food crops. Mounting evidence from many different experiments suggests that the magnit0@ude and even direction of crop responses to [CO2] and temperature is almost certain to be species dependent and very likel0Ay, within a species, to be cultivar dependent. Over the last decade, [CO2] and temperature experiments have been conducted0B on several crop species in the outdoor, naturally- sunlit, environmentally controlled, plant growth chambers by USDA-ARS 0Cand the University of Florida, at Gainesville, Florida, USA. The objectives for this paper are to summarize some of the ma0Djor findings of these experiments and further to compare and contrast species responses to [CO2] and temperature for three0E diverse crop species: rice (Oryza sativa, L.). soybean (Glycine max, L.) and citrus (various species). Citrus had the low0Fest growth and photosynthetic rates but under [CO2] enrichment displayed the greatest percentage increases over ambient [C0GO2] control treatments. In all three species the direct effect of [CO2] enrichment was always an increase in photosyntheti0Hc rate. In soybean, photosynthetic rate depended on current [CO2] regardless of the long-term [CO2] history of the crop. I1In rice, photosynthetic rate measured at a common [CO2], decreased with increasing long-term [CO2] growth treatment due to 1Ja corresponding decline in RuBP carboxylase content and activity. Rice specific respiration decreased from subambient to a1Kmbient and superambient [CO2] due to a decrease in plant tissue nitrogen content and a decline in specific maintenance res1Lpiration rate. In all three species, crop water use decreased with [CO2] enrichment but increased with increases in temper1Mature. For both rice and soybean, [CO2] enrichment increased growth and grain yield. Rice grain yields declined by roughly1 10% per each 1-degrees-C rise in day/night temperature above 28/21-degrees-C.GENASE; OXIDATION; LACTATE; ALANINE; INJURY11388^1^Dahlman,RC^1993^1^Co2 and plants - revisited^24^104^^339-355^^^^^Jan^^^^^3602lucose metabolism that makes the sever13PA^3601^The decade-long USA research program on the direct effects of CO2 enrichment on vegetation has achieved important m1>Qilestones and has produced a number of interesting and exciting findings. Research beginning in 1980 focused on field expe1@Rriments to determine whether phenomena observed in the laboratory indeed occurred in natural environments. The answer is y1OSes. Data obtained from numerous field studies show mixed response of crop and native species to CO2 enrichment however. Ne1QTarly all experiments demonstrate that plants exhibit positive gain when grown at elevated CO2; although the magnitude vari1^Ues greatly. Most crop responses range from 30 to 50 % increase in yield. Results from long-term experiments with woody spe1`Vcies and ecosystems are even more variable. Huge growth responses (100 to nearly 300 % increase relative to controls) are 1sWreported from several tree experiments and the salt-marsh ecosystem experiment. Other results from experiments with woody 1uXspecies and the tundra ecosystem suggest little no effect of CO2 on physiology, growth or productivity. Numerous studies o1Yf the physiology of the CO2 effect are continuing in attempts to understand controlling mechanisms and to explain the vari1Zable growth responses. Particular emphasis needs to be given to physiological measures of interactions involving the CO2 e1[ffect and other environmental influences, and to the wide-ranging observations of photosynthesis acclimation to CO2. Prosp1ects for future research are identified.t of pyruvate directed to oxidation, thereby reducing the conversion of pyruvate 1]389^2^Debevec,EM^Maclean,SF^1993^1^Design of greenhouses for the manipulation of temperature in tundra plant-communities^110^25^1^56-62^^^^^Feb^^^^^3604dichloroacetate treatment, no unique effect of dichloroacetate on glucose or protein kinetic1_A^3603^Passive greenhouses can be used to elevate the temperature of natural communities, but they also introduce other ef1`fects. We tested the effects of potential greenhouse materials-clear polyethylene plastic film, polyester fabric, and rigi1ad fiberglass panels-on light transmission, photosynthesis of Salix planifolia, elevation of air and soil temperature, and 1bthaw depth. Plastic had the greatest light transmittance and caused the least depression of photosynthesis (- 5%). Greenho1cuses covered with plastic elevated daily maximum and daily mean air temperatures by an average of 7.8 and 2.0- degrees-C a1dnd depressed daily minimum temperature by 1.1- degrees-C compared with the control. Plastic is impervious to gases and may1e alter CO2 concentration and humidity within greenhouses. Fiberglass had lower transmittance, especially of short waveleng1fth radiation. Fabric had the lowest light transmission and reduced photosynthesis by 10%, but it has the advantage of perm1geability to CO2 and water vapor. Greenhouses covered with fabric, alone, produced only a small effect (daily mean temperat1hure elevated 0.4-degrees-C above controls). A mixed greenhouse design (plastic and fabric) raised daily mean temperatures 1iby 0.9-degrees-C and may minimize adverse effects on gas diffusion. Because of the effect of the materials on amount and s1jpectral distribution of radiation and on photosynthesis, the appropriate treatment control for any greenhouse design is an1k open plot shaded with the same material. Soil temperature at 10 cm depth was elevated in all greenhouses, but no effect o1n depth of thaw was detected.ive strains. Catabolism of benzyl alcohol by phototrophic bacteria has not been previously 1m390^3^Denhertog,J^Stulen,I^Lambers,H^1993^1^Assimilation, respiration and allocation of carbon in plantago major as affect1ed by atmospheric co2 levels - a case-study^24^104^^369-378^^^^^Jan^^^^^3606thoxybenzoate). However, catabolism of vanil1oA^3605^The response of Plantago major ssp. pleiosperma plants, grown on nutrient solution in a climate chamber, to a doubl/ping of the ambient atmospheric CO2 concentration was investigated. Total dry matter production was increased by 30 % after/q 3 weeks of exposure, due to a transient stimulation of the relative growth rate (RGR) during the first 10 days. Thereafte0rr RGR returned to the level of control plants. Photosynthesis, expressed per unit leaf area, was stimulated during the fir2sst two weeks of the experiment, thereafter it dropped and nearly reached the level of the control plants. Root respiration2 t was not affected by increased atmospheric CO2 levels, whereas shoot, dark respiration was stimulated throughout the exper2uimental period. Dry matter allocation over leaves stems and roots was not affected by the CO2 level. SLA was reduced by 102!v%, which can partly be explained by an increased dry matter content of the leaves. Both in the early and later stages of t2#whe experiment, shoot respiration accounted for a larger part of the carbon budget in plants grown at elevated atmospheric 2:xCO2. Shifts in the total carbon budget were mainly due to the effects on shoot respiration. Leaf growth accounted for near2<ly 50 % of the C budget at all stages of the experiment and in both treatments.) were studied in isolated perfused rat li2Nz391^2^Idso,SB^Kimball,BA^1993^1^Effects of atmospheric co2 enrichment on net photosynthesis and dark respiration rates of 2Q3 australian tree species^4^141^2^166-171^^^^^Feb^^^^^3608pH 7.4), which was recycled through the liver for 2 hr. Individ2i|A^3607^Net photosynthesis and dark respiration rates of leaves of three Australian tree species exposed to a range of atmo2k}spheric CO2 concentrations were measured throughout the summer of 1991. For all three species - the Australian bottle tree2{~ (Brachychiton populneum (Schott.) R. Br.) and two eucalyptus (Eucalyptus microtheca F. Muell. and E. polyanthemus Schauer2}) - dark respiration dropped by approximately 50 % for a 360 to 720 muL/L doubling of the air's CO2 concentration, while n2et photosynthesis rose by a factor of two. These results were not significantly different from results obtained previously2 for the common sour orange tree (Citrus aurantium L.). Additionally, the perfusate concentration of oleate in the free f2392^3^Johnson,HB^Polley,HW^Mayeux,HS^1993^1^Increasing co2 and plant-plant interactions - effects on natural vegetation^242^104^^157-170^^^^^Jan^^^^^3610genously supplied fatty acid. The net secretion rate of VLDL lipids and protein was stimula2A^3609^Plant species and functional groups of species show marked differences in photosynthesis and growth in relation to 2rising atmospheric CO2 concentrations through the range of the 30 % increase of the recent past and the 100 % increase sin2ce the last glaciation. A large shift was found in the compositional mix of 26 species of C3's and 17 species of C4's grow2n from a native soil seed bank in a competitive mode along a CO2 gradient that approximated the CO2 increase of the past 1250 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 225 % as CO2 levels approached current ambient. The proposition that acclimation to rising CO2 will largely negate the fert2ilization effect of higher CO2 levels on C3's is not supported. No signs of photosynthetic acclimation were evident for Av2ena sativa, Prosopis glandulosa, and Schizachyrium scoparium plants grown in subambient CO2. The effects of changing CO2 l2evels on vegetation since the last glaciation are thought to have been at least as great, if not greater, than those which2 should be expected for a doubling of current CO2 levels. Atmospheric CO2 concentrations below 200 ppm are thought to have2 been instrumental in the rise of the C4 grasslands of North America and other extensive C4 grasslands and savannas of the2 world. Dramatic invasion of these areas by woody C3 species are accompanying the historical increase in atmospheric CO2 c2oncentration now in progress. that of oleate or DHA. Furthermore, utilization of endogenous fatty acids for TG synthesis 2393^4^Kaji,H^Ueno,M^Ikebe,T^Osajima,Y^1993^1^Effects of low o-2 and elevated co2 concentrations on the quality of matsutak3 e [tricholoma-matsutake (s ito et imai) sing] during storage^213^57^3^363-366^^^^^Mar^^^^^3612n of EPA provide substantia3 A^3611^Matsutake [Tricholoma matsutake (S. ITO et IMAI) SING.] was stored under conditions of low O2 and elevated CO2 conc3 entrations. The storage conditions were as follows: with an O2 concentration of 2.5+/-0.5%, the CO2 concentrations were 5%3", 10%, 15%, and 20%, and relative humidity (RH) was about 100%; with an O2 concentration of 2.0+/-0.5%, the CO2 concentrat31ions were 0%, 5%, 10%, and 15%, and RH was about 100%; the storage temperature was 1.0+/-0.1-degrees-C. The fruit was also33 stored in air and under 100% N2 as controls. Quality factors such as 'neto' (slimy microbial flora which develop on the m3Doist surface of the fruiting body), weight loss, whiteness, firmness, and off-odor were measured. The development of neto 3Fand browning (loss of whiteness) of the inner stipe were suppressed for more than 14 days, except with storage under 100% 3VN2. Storage in air and under 0% or a high concentration (> 10%) of CO2 caused an early development of off-odor, compared t3Xo storage under 5% and 10% CO2. In air, the development of mold was observed after 14 days. Under a low O2 concentration a3knd 5% to 10% CO2, the quality factors of matsutake were most retained, and the fruit was still acceptable after 14 days of3m storage. A weight decrease of the fruit was recognized as the CO2 concentration was increased.3y394^4^Kimball,BA^Mauney,JR^Nakayama,FS^Idso,SB^1993^1^Effects of increasing atmospheric co2 on vegetation^24^104^^65-75^^^3{^^Jan^^^^^36143A^3613^The increasing atmospheric CO2 concentration probably will have significant direct effects on vegetation whether pr3edicted changes in climate occur or not. Averaging over many prior greenhouse and growth chamber studies, plant growth and3 yield have typically increased more than 30%, with a doubling of CO2 concentration. Such a doubling also causes stomatal 3conductance to decrease about 37 which typically increases leaf temperatures more than 1-degrees-C, and which may decrease3 evapotranspiration, although increases in leaf area counteract the latter effect. Interactions between CO2 and climate va3riables also appear important. In one study the growth increase from near-doubled CO2 ranged from minus 60% at 12- degrees3-C to 0% at 19-degrees-C to plus 130% at 34-degrees-C, suggesting that if the climate warms, the average growth response t3o doubled CO2 could be consistently higher than the 30% mentioned above. Even when growing in nutrient-poor soil, the grow3th response to elevated CO2 has been large, in contrast to nutrient solution studies which showed little response. Several3 studies have suggested that under water-stress, the CO2 growth stimulation is as large or larger than under wellwatered c3onditions. Therefore, the direct CO2 effect will compensate somewhat, if not completely, for a hotter drier climate. And i3f any climate change is small, then plant growth and crop yields will probably be significantly higher in the future high-3CO2 world.3395^2^Krupa,SV^Kickert,RN^1993^1^The greenhouse-effect - the impacts of carbon-dioxide (co2), ultraviolet-b (uv-b) radiati3on and ozone (o3) on vegetation (crops)^24^104^^223-238^^^^^Jan^^^^^3616s/0 000p199993A^3615^Man's influence on the 'greenhouse effect,' the heating of the atmosphere due to increasing concentrations of tropo3spheric trace gases, is of much international concern. Among the climatic variables, elevated levels of carbon dioxide (CO32), ultraviolet-B (UV-B) radiation and ozone (O3) are known to have a direct effect on vegetation. Our current knowledge o3f these effects is mainly based on studies involving single stress mode. Thus, the joint effects of CO2, UV-B and O3 on ve4getation are poorly understood. Nevertheless, based on the literature analysis of plant response to individual stress fact4ors, it can be concluded that sorghum, pea, bean, potato, oat, lettuce, cucumber, rice and tomato are among the crop speci4es potentially sensitive to the joint effects of the aforementioned three variables. Similar information for tree species 4 is essentially lacking. At least with some climatic variables such as O3, present modeling efforts of cause-effect relatio4"nships have proven to be controversial. While at a regional geographic scale ambient CO2 concentrations appear to be relat4)ively homogeneous, ambient concentrations of O3 exhibit significant temporal and spatial variability. Because of the prote4+ctive action of O3 against UV-B, similar but inverse temporal and spatial variability is expected in the surface levels of4: UV-B. Thus, future experimental designs should consider these exposure dynamics and modeling cause-effect relationships s4<hould be directed to stochastic processes.4K396^1^Lambers,H^1993^1^Rising co2, secondary plant-metabolism, plant-herbivore interactions and litter decomposition - the4Moretical considerations^24^104^^263-271^^^^^Jan^^^^^36184ZA^3617^A brief account is given of the ecological significance of quantitatively important secondary plant compounds, main4\ly those of a phenolic nature, in herbivory and decomposition. Phenolic compounds accumulate to a greater extent in slow- 4hgrowing species than in fast-growing ones, particularly when soil conditions (nutrients, water) restrict growth. Two hypot4jheses to explain the increased concentration of phenolics when soil conditions are unfavorable are presented. The first hy4vpothesis (the 'carbon supply model of secondary plant metabolism') considers the increased levels of non-structural carboh4xydrates as the major trigger. The second hypothesis (the 'amino acid diversion model of secondary plant metabolism') state4s that increased accumulation of phenolics stems from a decreased use of a common precursor (phenylalanine or tyrosine) fo4r protein synthesis. Current experimental evidence, though still fairly limited, supports the second hypothesis, but furth4er testing is required before the first model can be rejected. So far, there is very little evidence for a direct effect o4f atmospheric CO2 on the concentration of secondary compounds in higher plants. However, there are likely to be indirect e4ffects, due to a stronger limitation by the nitrogen supply in plants whose growth has been promoted by atmospheric CO2. I4t is concluded that it is very likely that phenolic compounds accumulate to a greater extent in plants exposed to elevated4 CO2, due to a greater limitation of nutrients, rather than as a direct effect of elevated CO2.o@oMoo4397^2^Leadley,PW^Drake,BG^1993^1^Open top chambers for exposing plant canopies to elevated co2 concentration and for measu4ring net gas-exchange^24^104^^3-15^^^^^Jan^^^^^36204A^3619^Open top chamber design and function are reviewed. All of the chambers described maintain CO2 concentrations measur4ed at a central location within +/- 30 ppm of a desired target when averaged over the growing season, but the spatial and 4temporal range within any chamber may be closer to 100 ppm. Compared with unchambered companion plots, open top chambers m4odify the microenvironment in the following ways: temperatures are increased up to 3-degrees-C depending on the chamber de4sign and location of the measurement; light intensity is typically diminished by as much as 20%; wind velocity is lower an4d constant; and relative humidity is higher. The chamber environment may significantly alter plant growth when compared wi4th unchambered controls, but the chamber effect on growth has not been clearly attributed to a single or even a few enviro4nmental factors. A method for modifying an open top chamber for tracking gas exchange between natural vegetation and the a4mbient air is described. This modification consists of the addition of a top with exit chimney to reduce dilution of chamb5er CO2 by external ambient air, is quickly made and permits estimation of the effects of elevated CO2 and water vapor exch5ange. The relatively simple design and construction of open top chambers make them the most likely method to be used in th5e near future for long-term elevated CO2 exposure of small trees, crops and grassland ecosystems. Improvements in the basi5c geometry to improve control of temperature, reduce the variation of CO2 concentrations, and increase the turbulence and 5wind speed in the canopy boundary layer are desirable objectives. Similarly, modifications for measuring water vapor and c5*arbon dioxide gas exchange will extend the usefulness of open top chambers to include non-destructive monitoring of the re5,sponses of ecosystems to rising atmospheric CO2.5?398^4^Lenssen,GM^Lamers,J^Stroetenga,M^Rozema,J^1993^1^Interactive effects of atmospheric co2 enrichment, salinity and flo5Aoding on growth of C-3 (elymus-athericus) and C-4 (spartina- anglica) salt-marsh species^24^104^^379-388^^^^^Jan^^^^^36225OA^3621^The growth response of Dutch salt marsh species (C3 and C4) to atmospheric CO2 enrichment was investigated. Tillers5Q of the C3 species Elymus athericus were grown in combinations of 380 and 720 mul l-1 CO2 and low (0) and high (300 mM NaC5]l) soil salinity. CO2 enrichment increased dry matter production and leaf area development while both parameters were redu5^ced at high salinity. The relative growth response to CO2 enrichment was higher under saline conditions. Growth increase a5gt elevated CO2 was higher after 34 than 71 days. A lower response to CO2 enrichment after 71 days was associated with a de5icreased specific leaf area (SLA). In two other experiments the effect of CO2 (380 and 720 mul l-1) on growth of the C4 spe5ucies Spartina anglica was studied. In the first experiment total plant dry weight was reduced by 20% at elevated CO2. SLA 5walso decreased at high CO2. The effect of elevated CO2 was also studied in combination with soil salinity (50 and 400 mM N5aCl) and flooding. Again plant weight was reduced (10%) at elevated CO2, except under the combined treatment high salinity5/non- flooded. But these effects were not significant. High salinity reduced total plant weight while flooding had no effe5ct. Causes of the salinity-dependent effect of CO2 enrichment on growth and consequences of elevated CO2 for competition b5etween C3 and C4 species are discussed.Xciqx~ٳQt5399^1^Lincoln,DE^1993^1^The influence of plant carbon-dioxide and nutrient supply on susceptibility to insect herbivores^254^104^^273-280^^^^^Jan^^^^^36245A^3623^The carbon/nutrient ratio of plants has been hypothesized to be a significant regulator of plant susceptibility of 5leaf-eating insects. As rising atmospheric carbon dioxide stimulates photosynthesis, host plant carbon supply is increased5 and the accompanying higher levels of carbohydrates, especially starch, apparently 'dilute' the protein content of the le5af. When host plant nitrogen supply is limited, plant responses include increased carbohydrate accumulation, reduced leaf 5protein content, but also increased carbon-based defensive chemicals. No change, however, has been observed in the concent5ration of leaf defensive allelochemicals with elevated carbon dioxide during host plant growth. Insect responses to carbon5-fertilized leaves include increased consumption with little change in growth, or alternatively, little change in consumpt5ion with decreased growth, as well as enhanced leaf digestibility, reduced nitrogen use efficiency, and reduced fecundity.5 The effects of plant carbon and nutrient supply on herbivores appear to result, at least in part, from independent proces5ses affecting secondary metabolism.js-O\ 5400^3^Lindroth,RL^Jung,SM^Feuker,AM^1993^1^Detoxication activity in the gypsy-moth - effects of host co2 and no3-availabil5ity^112^19^2^357-367^^^^^Feb^^^^^36266A^3625^We investigated the effects of host species and resource (carbon dioxide, nitrate) availability on activity of deto3xication enzymes in the gypsy moth, Lymantria dispar. Larvae were fed foliage from quaking aspen or sugar maple grown unde#r ambient or elevated atmospheric CO2, with low or high soil NO3- availability. Enzyme solutions were prepared from larval6 midguts and assayed for activity of cytochrome P-450 monooxygenase, esterase, glutathione transferase, and carbonyl reduc6tase enzymes. Activity of each enzyme system was influenced by larval host species, CO2 or NO3- availability, or an intera6ction of factors. Activity of all but glutathione transferases was highest in larvae reared on aspen. Elevated atmospheric6% CO2 promoted all but transferase activity in larvae reared on aspen, but had little if any impact on enzyme activities of6' larvae reared on maple. High NO3- availability enhanced activity of most enzyme systems in gypsy moths fed high CO2 folia62ge, but the effect was less consistent for insects fed ambient CO2 foliage. This research shows that gypsy moths respond b64401^3^Lindroth,RL^Kinney,KK^Platz,CL^1993^1^Responses of deciduous trees to elevated atmospheric co2 - productivity, phyto6Bchemistry, and insect performance^11^74^3^763-777^^^^^Apr^^^^^36286DA^3627^Although rising levels of atmospheric carbon dioxide are expected to directly affect forest ecosystems, little is k6Qnown of how specific ecological interactions will be modified. This research evaluated the effects of enriched CO2 on the 6Sproductivity and phytochemistry of forest trees and performance of associated insects. Our experimental system consisted o6_f three tree species (quaking aspen [Populus tremuloides], red oak [Quercus rubra], sugar maple [Acer saccharum]) that spa6an a range from fast to slow growing, and two species of leaf- feeding insects (gypsy moth [Lymantria dispar] and forest te6p nt caterpillar [Malacosoma disstria]). Carbon-nutrient balance theory provided a framework for tests of three hypotheses; 6r in response to enriched CO2: (1) relative increases in tree growth rates will be greatest for aspen and least for maple, (6 2) relative decreases in protein and increases in carbon-based compounds will be greatest for aspen and least for maple, a6 nd (3) relative reductions in performance will be greatest for insects fed aspen and least for insects fed maple. We grew 6 1- yr-old seedlings for 60 d under ambient (385 +/- 5 muL/L) or elevated (642 +/- 2 muL/L) CO2 regimes at the University o6f Wisconsin Biotron. After 50 d, we conducted feeding trials with penultimate-instar gypsy moth and forest tent caterpilla6rs. After 60 d, a second set of trees was harvested and partitioned into root, stem, and leaf tissues. We subsequently ana6lyzed leaf material for a variety of compounds known to affect performance of insect herbivores. In terms of actual dry-ma6tter production, aspen responded the most to enriched CO2 atmospheres whereas maple responded the least. Proportional grow6th increases (relative to ambient plants), however, were highest for oak and least for maple. Effects of elevated CO2 on b6iomass allocation patterns differed among the three species; root-to-shoot ratios increased in aspen, decreased in oak, an6d did not change in maple. Enriched CO2 altered concentrations of primary and secondary metabolites in leaves, but the mag6nitude and direction of effects were species-specific. Aspen showed the largest change in storage carbon compounds (starch6), whereas maple experienced the largest change in defensive carbon compounds (condensed and hydrolyzable tannins). Consum6ption rates of insects fed high-CO2 aspen increased dramatically, but growth rates declined. The two species of insects di6ffered in response to oak and maple grown under enriched CO2. Gypsy moths grew better on high-CO2 Oak, whereas forest tent6 caterpillars were unaffected; tent caterpillars tended to grow less on high-CO2 maple, whereas gypsy moths were unaffecte6d. Changes in insect performance parameters were related to changes in foliar chemistry. Responses of plants and insects a6greed with some, but not all, of the predictions of carbon-nutrient balance theory. This study illustrates that tree produ7ctivity and chemistry, and the performance of associated insects, will change under CO2 atmospheres predicted for the next7  century. Changes in higher level ecological processes, such as community structure and nutrient cycling, are also implica7ted.%%%%%%%%%'&&&&%'l',,,,,,,,,,,,,'-7402^3^Long,SP^Baker,NR^Raines,CA^1993^1^Analyzing the responses of photosynthetic co2 assimilation to long-term elevation 7(of atmospheric co2 concentration^24^104^^33-45^^^^^Jan^^^^^3630@@%@*@3@B@M@P@Q@V@p@@AA7*!A^3629^Understanding how photosynthetic capacity acclimatises when plants are grown in an atmosphere of rising CO2 concent77"rations will be vital to the development of mechanistic models of the response of plant productivity to global environment79#al change. A limitation to the study of acclimatisation is the small amount of material that may be destructively harveste7F$d from long-term studies of the effects of elevation of CO2 concentration. Technological developments in the measurement o7H%f gas exchange, fluorescence and absorption spectroscopy, coupled with theoretical developments in the interpretation of m7S&easured values now allow detailed analyses of limitations to photosynthesis in vivo. The use of leaf chambers with Ulbrich7U't integrating spheres allows separation of change in the maximum efficiency of energy transduction in the assimilation of 7a(CO2 from changes in tissue absorptance. Analysis of the response of CO2 assimilation to intercellular CO2 concentration al7c)lows quantitative determination of the limitation imposed by stomata, carboxylation efficiency, and the rate of regenerati7m*on of ribulose 1:5 bisphosphate. Chlorophyll fluorescence provides a rapid method for detecting photoinhibition in heterog7o+eneously illuminated leaves within canopies in the field. Modulated fluorescence and absorption spectroscopy allow paralle7}l measurements of the efficiency of light utilisation in electron transport through photosystems I and II in situ.7-403^1^Lurie,S^1993^1^Modified atmosphere storage of peaches and nectarines to reduce storage disorders^214^16^1^57-65^^^^^7Feb^^^^^3632ion6;6j6!08:31 AM 29 01 17/A^3631^Low density polyethylene or polyolefin films were used to seal pack various varieties of peaches and nectarines. Lo70w density polyethylene film of 40 micron thickness was beneficial in extending storage life of these fruits and decreasing71 internal flesh breakdown and reddening, while polyolefin film was ineffective. Six fruits per pack generated a higher CO272 and lower O2 modified atmosphere than two or four fruits per pack and gave better quality fruit after storage. The improv7ement of fruit quality was correlated with elevated CO2 levels rather than with decreased O2 levels.1?RGw60574404^3^Madsen,TV^Sandjensen,K^Beer,S^1993^1^Comparison of photosynthetic performance and carboxylation capacity in a range 7of aquatic macrophytes of different growth forms^159^44^4^373-384^^^^^Feb^^^^^36340:16 AM 30 01 1999 -0500CO2MAP76A^3633^Photosynthesis, carbon extraction capacity and ribulose-1,5- biphosphate carboxylase/oxygenase (RUBISCO) activity w77ere determined for 35 species of submerged aquatic macrophytes differing with respect to taxonomy, growth form and habitat78. Photosynthetic rates per unit of chlorophyll and dry weight at ambient CO2 concentrations (about 15 muM) as well as carb79on extraction capacity increased among plant groups in the order: isoetids, amphibious species, elodeids with no apparent 7:HCO3- use, elodeids with HCO3- use, marine angiosperms and marine macroalgae. Photosynthetic rates at elevated CO2 concent7;rations (300-350 muM) showed the same pattern but smaller differences among the groups. Only for some of the marine macroa8ume ratio. The opposite pattern was found among species with low carbon extraction capacity. The low chlorophyll content a8?nd high chlorophyll specific photosynthesis of species with high carbon transport capability (i.e. particularly the marine8@ algae), suggest that running costs associated with inorganic carbon assimilation are reduced when a CO2 concentrating sys8!tem operates.Dby|610:33 AM 01 02 1999 -0500CURTIS Peter80B405^2^McMurtrie,RE^Wang,YP^1993^1^Mathematical-models of the photosynthetic response of tree stands to rising co2 concentr82ations and temperatures^9^16^1^1-13^^^^^Jan^^^^^3636 -0500CO2MAP8?DA^3635^Two published models of canopy photosynthesis, MAESTRO and BIOMASS, are simulated to examine the response of tree s8AEtands to increasing ambient concentrations of carbon dioxide (C(a)) and temperatures. The models employ the same equations8ZF to described leaf gas exchange, but differ considerably in the level of detail employed to represent canopy structure and8\G radiation environment. Daily rates of canopy photosynthesis simulated by the two models agree to within 10% across a rang8nHe of CO2 concentrations and temperatures. A doubling of C(a) leads to modest increases of simulated daily canopy photosynt8pIhesis at low temperatures (10% increase at 10-degrees- C), but larger increases at higher temperatures (60% increase at 308|J-degrees-C). The temperature and CO2 dependencies of canopy photosynthesis are interpreted in terms of simulated contribut8~Kions by quantum-saturated and non-saturated foliage. Simulations are presented for periods ranging from a diurnal cycle to8L several years. Annual canopy photosynthesis simulated by BIOMASS for trees experiencing no water stress is linearly relat8Med to simulated annual absorbed photosynthetically active radiation, with light utilization coefficients for carbon of eps8ilon = 1.66 and 2.07 g MJ-1 derived for C(a) of 350 and 700 mumol mol-1, respectively.M8O406^2^Miglietta,F^Raschi,A^1993^1^Studying the effect of elevated co2 in the open in a naturally enriched environment in c8entral italy^24^104^^391-400^^^^^Jan^^^^^3638Nt}I604:54 PM8QA^3637^A gas vents area was recently localized in Central Italy. The gas emitted from the vents is composed by 92% of carb8Ron dioxide and this produces an anomaly in the composition of the atmosphere over an area of about 2 ha. Atmospheric carbo8Sn dioxide concentration was measured by means of an infrared gas analyzer and diffusion tubes in several points and for so8Tme days within the area. Measurements revealed that the site can be at least divided into three sub-areas having increasin8Ug CO2 concentration in the air. A preliminary analysis of natural vegetation in the area was conducted by counting stomata8Vl and epidermal cells number and measuring guard cell size on leaves of several oak trees growing both near and far away f8Wrom the vents. This analysis suggested that elevated CO2 may have reduced the size of guard cells leaving stomatal density8 and stomatal index unaltered.Thanks!8407^1^Morison,JIL^1993^1^Response of plants to co2 under water limited conditions^24^104^^193-209^^^^^Jan^^^^^36408ZA^3639^The influence of increased atmospheric CO2 on the interaction between plant growth and water use is proving to be o8[ne of the most profound impacts of the anthropogenic 'Greenhouse Effect'. This paper illustrates the interaction between C9\O2 and water in plant growth at a range of scales. Most published work has concentrated on water use efficiency, especiall9]y at shorter time scales, and has shown large increases of leaf water use efficiency with increased CO2. However, the magn9^itude of the effect is variable, and does not consistently agree with predictions from simple leaf gas exchange considerat9_ions. The longer the time scales considered, the less the information and the more the uncertainty in the response to CO2,9 ` because of the additional factors that have to be considered, such as changes in leaf area, respiration of non-photosynth9"aetic tissues and soil evaporation. The need for more detailed studies of the interactions between plant evaporation, water9.b supply, water status and growth is stressed, as increased CO2 can affect all of these either directly, or indirectly thro90ugh feedbacks with leaf gas exchange, carbon partitioning, leaf growth, canopy development and root growth.LEEGE Liss9Id408^1^Mousseau,M^1993^1^Effects of elevated co2 on growth, photosynthesis and respiration of sweet chestnut (castanea-sati9Kva mill)^24^104^^413-419^^^^^Jan^^^^^364209:05 AM 04 02 1999 -0500Joy Curley9QfA^3641^Two year old sweet chestnut seedlings (Castanea sativa Mill) were grown in pots at ambient (350 mumol.mol-1) and do9Sguble (700 mumol.mol-1) atmospheric CO2 concentration in constantly ventilated greenhouses during entire growing seasons. C9chO2 enrichment caused either no significant change or a decrease in shoot growth response, depending on yearly weather cond9eiition either reduced or unchanged under elevated CO2. However, when grown under controlled conditions in a growth chamber,9sj leaf area was enlarged with elevated CO2. The CO2 exchanges of whole plants were measured during the growing season. In e9uklevated CO2, net photosynthetic rate was maximum in May and then decreased, reaching the level of the control at the end o9lf the season. End of night dark respiration of enriched plants was significantly lower than that of control plants; this d9mifference decreased with time and became negligible in the fall. The original CO2 level acted instantaneously on the respi9nration rate: a double concentration in CO2 decreased the respiration of control plants and a reduced concentration enhance9od the respiration of enriched plants. The carbon balance of a chestnut seedling may then be modified in elevated CO2 by in9creased carbon inputs and decreased carbon outputs.e9q409^2^Nijs,I^Impens,I^1993^1^Effects of long-term elevated atmospheric carbon-dioxide on lolium-perenne and trifolium-repe9ns, using a simple photosynthesis model^24^104^^421-431^^^^^Jan^^^^^3644fZ7F6!9sA^3643^Changes in gross canopy photosynthetic rate (PGc), produced by long-term exposure to an elevated atmospheric CO2 le9tvel (626 +/- 50 mumol mol-1), were modelled for Lolium perenne L. cv. Vigor and Trifolium repens L. cv. Blanca, using a si9umple photosynthesis model, based on biochemical and physiological information (leaf gross CO2 uptake in saturating light, 9vP(max), and leaf quantum efficiency, alpha) and structural vegetation parameters (leaf area index, LAI, canopy extinction 9wcoefficient, k, leaf transmission, M). Correction of PGc for leaf respiration allowed comparison with previously measured 9xcanopy net CO2 exchange rates, with the average divergence from model prediction amounting to about 6%. Sensitivity analys9yis showed that for a three-week old canopy, the PGc increase in high CO2 could be attributed largely to changes in P(max) 9zand alpha, while differences in canopy architecture were no longer important for the PGc-stimulation (which they were in t:{he early growth stages). As a consequence of this increasing LAI with canopy age, the gain of daytime CO2 uptake is progre:|ssively eroded by the increasing burden of canopy respiration in high- CO2 grown Lolium perenne. Modelling canopy photosyn:}thesis in different regrowth stages after cutting (one week, two weeks,...), revealed that the difference in a 24-h CO2 ba:~lance between the ambient and the high CO2 treatment is reduced with regrowth time and completely disappears after 6 weeks:.9 -0500Elizabeth MarschallRe: tomorrow?:)410^1^Overdieck,D^1993^1^Elevated co2 and the mineral-content of herbaceous and woody- plants^24^104^^403-411^^^^^Jan^^^^^:+A^3645^The CO2 enrichment effects (300-650 mumol mol-1) on mineral concentration (N, P, K, Ca, Mg, Mn, Fe, Zn), absolute t:8otal mineral contents per individual and of whole stands of four herbaceous (Trifolium repens L., Trifolium pratense L., L::olium perenne L., Festuca pratensis HUDS.) and two woody species (Acer pseudo-platanus L., Fagus sylvatica L.) were invest:Rigated. In general, the mineral concentration of the plant tissues decreased (all six species: N > Ca > K > Mg) with the e:Txception of P. Mn and Fe were only determined for the tree species. Both decreased in concentration (Mn > Fe). Zn was only:_ analysed for Trifolium pratense and Festuca pratensis and decreased significantly in the grass. Despite of decreases in c:`oncentrations of as much as 20 % in some cases there were increases in absolute amounts per individual and, therefore, in :ithe whole vegetation up to 25 % because of the enhanced dry matter accumulation at elevated CO2 supply.:k3646612:14 PM 09 02 1999 -0500SWENSON Steveminitab:~411^2^Pal,RK^Buescher,RW^1993^1^Respiration and ethylene evolution of certain fruits and vegetables in response to carbon-:dioxide in controlled- atmosphere storage^215^30^1^29-32^^^^^Jan-Feb^^^^^3648sdf:A^3647^Respiration was depressed by 10-30% CO2 in ripening bananas, pink tomatoes and pickling cucumbers; increased by 20-:30% in carrot roots and unaffected by CO2 exposure in guava, orange and onion bulb. Changes in respiration seldom coincide:d with changes in C2H4 evolution. Evolution of C2H4 from guavas and tomatoes was substantially reduced by all levels of CO:2. However, 30% CO2, accelerated C2H4 evolution in bananas, carrot roots, cucumbers, onions and potatoes which may have be:en due to an early injury response.nd Tammybiopsy:412^1^Poorter,H^1993^1^Interspecific variation in the growth-response of plants to an elevated ambient co2 concentration^2:4^104^^77-97^^^^^Jan^^^^^3650No Subject:A^3649^The effect of a doubling in the atmospheric CO2 concentration on the growth of vegetative whole plants was investig:ated. In a compilation of literature sources, the growth stimulation of 156 plant species was found to be on average 37%. :This enhancement is small compared to what could be expected on the basis of CO2-response curves of photosynthesis. The ca:uses for this stimulation being so modest were investigated, partly on the basis of an experiment with 10 wild plant speci:es. Both the source-sink relationship and size constraints on growth can cause the growth-stimulating effect to be transie:nt. Data on the 156 plant species were used to explore interspecific variation in the response of plants to high CO2. The :growth stimulation was larger for C3 species than for C4 plants. However the difference in growth stimulation is not as la:rge as expected as C4 plants also significantly increased in weight (41% for C3 vs. 22 % for C4). The few investigated CAM: species were stimulated less in growth (15%) than the average C4 species. Within the group of C3 species, herbaceous crop: plants responded more strongly than herbaceous wild species (58% vs. 35%) and potentially fast-growing wild species incre:ased more in weight than slow-growing species (54% vs. 23%). C3 species capable of symbiosis with N2-fixing organisms had ; higher growth stimulations compared to other C3 species. A common denominator in these 3 groups of more responsive C3 plan;ts might be their large sink strength. Finally, there was some tendency for herbaceous dicots to show a larger response th;an monocots. Thus, on the basis of this literature compilation, it is concluded that also within the group of C3 species d;ifferences exist in the growth response to high CO2.but...;&413^2^Rogers,HH^Dahlman,RC^1993^1^Crop responses to co2 enrichment^24^104^^117-131^^^^^Jan^^^^^36529 -0500Michael ;(A^3651^Carbon dioxide is rising in the global atmosphere, and this increase can be expected to continue into the foreseeab;3le future. This compound is an essential input to plant life. Crop function is affected across all scales from biochemical;5 to agro-ecosystem. An array of methods (leaf cuvettes, field chambers, free-air release systems) are available for experi;Amental studies of CO2 effects. Carbon dioxide enrichment of the air in which crops grow usually stimulates their growth an;Dd yield. Plant structure and physiology are markedly altered. Interactions between CO2 and environmental factors that infl;Vuence plants are known to occur. Implications for crop growth and yield are enormous. Strategies designed to assure future;X global food security must include a consideration of crop responses to elevated atmospheric CO2. Future research should i;^nclude these targets: search for new insights, development of new techniques, construction of better simulation models, in;`vestigation of belowground processes, study of interactions, and the elimination of major discrepancies in the scientific ;nknowledge base.ܚg603:48 PM 16 ;p414^1^Rozema,J^1993^1^Plant-responses to atmospheric carbon-dioxide enrichment - interactions with some soil and atmospher;wic conditions^24^104^^173-190^^^^^Jan^^^^^3654C P 6!08:24 AM 17 02 1999 -0500Holly Wagner;yA^3653^In general, C3 plant species are more responsive to atmospheric carbon dioxide (CO2) enrichment than C4-plants. Inc;reased relative growth rate at elevated CO2 primarily relates to increased Net Assimilation Rate (NAR), and enhancement of; net photosynthesis and reduced photorespiration. Transpiration and stomatal conductance decrease with elevated CO2, water; use efficiency and shoot water potential increase, particularly in plants grown at high soil salinity. Leaf area per plan;t and leaf area per leaf may increase in an early growth stage with increased CO2, after a period of time Leaf Area Ratio ;(LAR) and Specific Leaf Area (SLA) generally decrease. Starch may accumulate with time in leaves grown at elevated CO2, Pl;ants grown under salt stress with increased (dark) respiration as a sink for photosynthates, may not show such acclimation; to increased atmospheric CO2 levels. Plant growth may be stimulated by atmospheric carbon dioxide enrichment and reduced ;by enhanced UV-B radiation but the limited data available on the effect of combined elevated CO2 and ultraviolet B (280-32;0 nm) (UV-B) radiation allow no general conclusion. CO2-induced increase of growth rate can be markedly modified at elevat;ed UV-B radiation. Plant responses to elevated atmospheric CO2 and other environmental factors such as soil salinity and U;V-B tend to be species-specific, because plant species differ in sensitivity to salinity and UV-B radiation, as well as to; other environmental stress factors (drought, nutrient deficiency). Therefore, the effects of joint elevated atmospheric C;O2 and increased soil salinity or elevated CO2 and enhanced UV-B to plants are physiologically complex.N;415^1^Schlesinger,WH^1993^1^Response of the terrestrial biosphere to global climate change and human perturbation^24^104^^;295-305^^^^^Jan^^^^^3656;A^3655^Despite 20 years of intensive effort to understand the global carbon cycle, the budget for carbon dioxide in the at;mosphere is unbalanced. To explain why atmospheric CO2 is not increasing as rapidly as it should be, various workers have <suggested that land vegetation acts as a sink for carbon dioxide. Here, I examine various possibilities and find that the <evidence for a sink of sufficient magnitude on land is poor. Moreover, it is unlikely that the land vegetation will act as< a sink in the postulated warmer global climates of the future. In response to rapid human population growth, destruction <$of natural ecosystems in the tropics remains a large net source of CO2 for the atmosphere, which is only partially compens<&ated by the potential for carbon storage in temperate and boreal regions. Direct and inadvertent human effects on land veg<6etation might increase the magnitude of regional CO2 storage on land, but they are unlikely to play a significant role in <8moderating the potential rate of greenhouse warming in the future.j<||~??<418^2^Viil,J^Parnik,T^1992^1^Fast regulation of ribulose-1,5-bisphosphate carboxylase oxygenase activity during light dark< light transitions^168^39^4^483-487^^^^^Jul-Aug^^^^^3662, PB 694*c16476D(016476X*p315X*p2595YDepartment of Plant Biol=A^3661^On the basis of estimates of rubisco activity in leaves of barley (Hordeum vulgare L.), we established that it decl=ined by 30-50% in 3-4 sec following disconnection of light in the presence of CO2. In a medium without CO2, rubisco activi= ty did not change in this time. Keeping leaves at elevated CO2 concentration lowered rubisco activity. This effect had a l="asting aftereffect. With a sharp change of CO2 concentration, the rate of assimilation in the first second was proportiona=3l to the increase of CO2 concentration up to at least 1000 mul- liter-1. It is recorded that CO2 binds directly with the e=5nol form of ribulose-1,5-bisphosphate (RuBP) without preliminary binding with the enzyme molecule.?==419^1^Wong,SC^1993^1^Interaction between elevated atmospheric concentration of co2 and humidity on plant-growth - comparis=?on between cotton and radish^24^104^^211-221^^^^^Jan^^^^^3664476X*p315X*p2832YSessional Lecturer. Department of Biologi=LA^3663^Cotton plants (Gossypium hirsutum L. var Deltapine 90) and radish plants (Raphanus sativus L var Round Red) were gr=Nown under full sunlight using a factorial combination of atmospheric CO2 concentrations (350 mumol mol-1 and 700 mumol mol=`-1) and humidities (35% and 90% RH at 32-degrees-C during the day). Cotton plants showed large responses to increased humi=cdity and to doubled CO2. In cotton plants, the enhanced dry matter yield due to doubled CO2 concentration was 1.6-fold gre=oater at low humidity than at high humidity. Apart from the direct effect of elevated CO2 level on photosynthesis, the grea=qter effect of doubled CO2 concentration on dry matter yield at low humidity was probably due to: (1) increased leaf water =~potential caused by reduction of transpiration resulting from the negative CO2 response of stomata to increased CO2 concen=tration the consequence being greater leaf area expansion. (2) reduction of CO2 assimilation rate at low humidity and norm=al CO2 concentration as a result of humidity response of stomata causing reduction of intercellular CO2 concentration. In =contrast, apart from the very early stage of development, radish plants do not respond to increased humidity but had a rel=atively large response to doubled CO2 concentration. Furthermore, due to the determinate growth pattern as well as having =a prominent storage root, the extra photoassimilate derived at doubled CO2 level is allocated to the storage root.c74E(s=420^2^Bachelet,D^Gay,CA^1993^1^The impacts of climate change on rice yield - a comparison of 4 model performances^81^65^1-=2^71-93^^^^^Jan^^^^^3666|?သ*c44E(s24W p *c112E(s60W@{<<8=A^3665^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 p=redict 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% annuall=y to the year 2000 to match population growth estimates. The objectives of this paper are (1) to review the major hypothes=es and/or experimental results regarding rice sensitivity to climate change and (2) to evaluate the suitability of existin=g 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 mo> del which predicts herbivory and inter-species competition between rice and weeds but does not respond to CO2. Its respons>e to increasing temperature also agrees with experimental data.@|}?*c44E(s31W0<~w 0@>421^4^Bazzaz,FA^Ackerly,DD^Woodward,FI^Rochefort,L^1992^1^Co2 enrichment and dependence of reproduction on density in an a>nnual plant and a simulation of its population-dynamics^12^80^4^643-651^^^^^^^^^^3668 df9d8ef1bd8fb536275b070f8878ee61 <0>,A^3667^1. 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 patter>=ns 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 >Kgermination of seeds produced in each environment. 2. All variables, except the number of fruiting individuals, declined w>M ith 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 pla>^ nts flowering and fruiting and the number of fruiting individuals in each population all increased. Total population seed >g production was higher in the elevated CO2 environment at all densities, although the differences were not significant. Sig>i nificant effects of CO2, concentration were observed only for population-level variables, but not for mean individual fecu>zndity 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 si>mulated populations exhibited damped or stable oscillations under low germination values, but displayed non-cyclic ('chaot>ic') 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 germinati>on value at which the simulated populations went extinct was much lower for the elevated-CO2 than for the ambient-CO2 popu>lation.9ddff5c1081dd2 <0F3Z00D46217HH@mx4.osu.edu>-14-Dec-1998-15:38:32--0500-(EST 913650173 Ndel Nskip Nsave read Nget 2>422^2^Bazzaz,FA^Miao,SL^1993^1^Successional status, seed size, and responses of tree seedlings to co2, light, and nutrient>s^11^74^1^104-112^^^^^Jan^^^^^3670f95ac0aa6abe494e34efc716 <3.0.5.32.19981214150128.00827b00@spot.colorado.edu>-14-Dec-19>A^3669^We studied how an enriched CO2 atmosphere in a fully crossed design of light and nutrients, influenced 1 st-yr seed>ling growth in six New England deciduous forest tree species. The species, in the order of increasing shade tolerance, wer>e gray birch (Betula populifolia), ash (Fraxinus americana L.), red maple (Acer rubrum L.), red oak (Quercus rubra L.), ye>llow 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 stimulat>ion was found under the condition of low light and high nutrients. However, individual species responded differently to el>evated CO2 levels. Among the three early-successional species, gray birch, ash, and red maple, a significant increase in s>eedling 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 enhancemen?#t was more sensitive to the level of light. Moreover, species with large seeds (e.g., red oak) exhibited a greater respons? $e to elevated CO2 levels under low light than species with small seeds (e.g., gray birch). The results emphasize the impor?.%tance of plant species as well as other environmental resources in modifying the response of plants to elevated CO2. Consi?0&dering 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.ES\MI?A(423^3^Deyton,DE^Sams,CE^Cummins,JC^1992^1^Application of dormant oil to peach-trees modifies bud twig internal atmosphere^?O170^27^12^1304-1305^^^^^Dec^^^^^3672MICROSOFT OFFICE\OFFICE\URGENT.DOT,Mic?Q*A^3671^Treatments of single applications of 0%, 3%, 6%, 9%, or 12% dormant oil were sprayed on peach (Prunus persica L. Ba?S+tsch) trees on 6 Feb. 1990. A repeat application of 6% oil plus 6% oil applied 6 days later was also made. Internal CO2 co?`,ncentrations of oil-treated buds and twigs were higher than the control the day after treatment and continued to be higher?b- for 6 days. The second application of 10% oil prolonged the elevated CO2 concentration. Applications of 9% or 12% oil del?n.ayed flower bud development and bloom. The repeated application of 6% oil delayed bud development and bloom more than a si?q/ngle 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.icrosoft Corporation fPROG?1424^1^Diemer,M^1992^1^Population-dynamics and spatial arrangement of ranunculus- glacialis L, an alpine perennial herb, in? permanent plots^24^103^2^159-166^^^^^Dec^^^^^3674ROSOFT OFFICE\OFFICE\XL8GALRY.XLS?3A^3673^In 1986 sixteen permanent plots (625 cm2 each) were established in scree slopes dominated by Ranunculus glacialis a?4t Mt. Glungezer, Austria (2600 m elevation) in order to document the population dynamics of herbaceous perennials near the?5 upper altitudinal limits of plant existence. The abundance and sizes of individual R. glacialis shoots, their leaf number?6s and reproductive status were evaluated over a 6-year period. On South-facing slopes the population sizes of adult and ju?7venile shoots remained constant over the years, while seedling numbers fluctuated significantly. Overall density of all de?8velopmental stages of R. glacialis was significantly lower on North-facing slopes and year-to-year fluctuations were great?9er, than on thermally-favorable Southern slopes. The spatial pattern of adult shoots and seedlings was clumped, while juve?:nile 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 increas?e mortality on South-facing sites.SOFT OFFICE\OFFICE\FLAME.DOT,Microsoft ?=425^3^Duchein,MC^Bonicel,A^Betsche,T^1993^1^Photosynthetic net co2 uptake and leaf phosphate concentrations in co2 enriche?d clover (trifolium-subterraneum L) at 3 levels of phosphate nutrition^78^44^258^17-22^^^^^Jan^^^^^3676OFFICE\OF??A^3675^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 ?AP (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; @Ba parameter related to relative growth) were higher at reduced P than at high P. Stimulation by high CO2 of net CO2-uptake@C in the first day was less at reduced P than at high P. In the following days, high CO2 markedly inhibited DICU at reduced@D P, and thus growth stimulation by high CO2 ceased after between 4 and 12 d. By contrast, at high P, DICU increased more t@Ehan 2- fold upon CO2-enrichment, and thus growth stimulation by high CO2 was maintained. Intermediate results were obtaine@:Fd with half-strength Hoagland's solution (0-5 mol m-3 P). Leaf pools of inorganic ortho P, soluble esterified P, and total@<G P declined markedly in high CO2 when P-nutrition had been reduced. Considerable decline also occurred in high CO2 when P-@GH nutrition had been increased suggesting that P-uptake was not well tuned with net CO2-uptake (growth). It is proposed tha@IIt high CO2 can perturb the P-metabolism of clover, the impairment being less at high levels of P-nutrition. With regard to@KJ high CO2 as a growth stimulus, these results demonstrate that increasing P-nutrition to a level supraoptimal in ambient a@Vir can considerably improve the growth of a C3-plant in high CO2.Microsoft Excel vPROGRAM F@YL426^3^Gries,C^Kimball,BA^Idso,SB^1993^1^Nutrient-uptake during the course of a year by sour orange trees growing in ambien@gt and elevated atmospheric carbon- dioxide concentrations^166^16^1^129-147^^^^^^^^^^3678IBRARY\AUTOSAVE.@iNA^3677^During the third year of a long-term carbon dioxide (CO2) enrichment study, macro- and micro-nutrient concentration@pOs in leaves and roots of sour orange trees were analyzed. Data for yearly courses of the macronutrients Ca, Mg, N, P, K, N@sPa, and S and the micronutrients B, Cu, Fe, Mn, and Zn are presented. Significantly higher concentrations of N, K, Ca, and @QMn 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. OFFICE\OFFICE\LIBRAR@S427^3^Lincoln,DE^Fajer,ED^Johnson,RH^1993^1^Plant insect herbivore interactions in elevated co2 environments^57^8^2^64-68^@^^^^Feb^^^^^3680LIBRARY\LOOKUP.XLA Microsoft Excel pPROGRAM FI@UA^3679^The increasing concentration of CO2 in the atmosphere is expected to lead to global changes in the physical environ@Vment of terrestrial organisms. We are beginning to understand how these changes are transmitted into pervasive effects on @Wthe interactions between plants and their leaf-feeding insect herbivores. An elevated CO2 atmosphere often stimulates plan@Xt carbon assimilation and growth and alters carbon allocation patterns. This, in turn, determines the quality of plants as@Y resources for herbivorous insects. These 'quality' factors include: the concentrations of water, nitrogen and allelochemi@Zcals in host-plant leaves, and the toughness and starch and fiber content of leaf tissue. Because these parameters change @[in plants grown in enriched CO2 environments, the doubled CO2 levels anticipated for the next century will alter the dynam@\ics of plant-insect herbivore interactions because herbivore consumption, growth and fitness are affected by the typically@ lower quality of plants grown under these conditions.oft Word 8.0 `PROGRAM FILES\MIC@428^1^Malanson,GP^1993^1^Comment on modeling ecological response to climatic-change^50^23^2^95-109^^^^^Feb^^^^^3682RAM@_A^3681^Researchers have developed many computer simulation models to project ecological responses to climatic change. Thre@`e general types of models are examined: transfer functions, stand models, and physiological models. Criteria for evaluatioAan are, first, ability to represent observed and theoretical responses to climatic change i.e., geographical migration, indA bividualistic responses, and disequilibrium or inertia, and second, ability to provide useful information on biological divAcersity and impacts on society. Because of their roots in ecological interactions at the species level, stand models best mAeet these criteria at present, but physiological models have greater potential, given unlimited computing power.ord A(e429^2^Radoglou,KM^Jarvis,PG^1993^1^Effects of atmospheric co2 enrichment on early growth of vivia- faba, a plant with largA+e cotyledons^9^16^1^93-98^^^^^Jan^^^^^3684AM FILES\MICROSOFT OFFICE\OFFICE\OCEAN.A:gA^3683^Seedlings of Vicia faba L. were grown in open-top growth chambers at present (P=350 mumol-1) and at elevated (E=700A<h mumol mol-1) atmospheric CO2 concentration. The effects Of CO2 enrichment on the first phase of growth after germination AIiwere examined over 45d. There were no positive effects Of CO2 enrichment on growth of the seedlings during this early phasAKje. No differences were observed in leaf area or in total dry weight. No differences were found in morphology or anatomy ofAMk the leaves. The numbers of stomatal and epidermal cells, thickness of leaf, of epidermis and of mesophyll cell-layers werA[le unaffected by CO2 enrichment. Also, no differences were observed in leaf concentrations of chlorophyll, reducing carbohyA]mdrates or starch. These results contrast markedly with results from similar experiments on poplar hybrids and Phaseolus vuAlnlgaris obtained in the same growth facility. It seems that the intitial growth is under internal control such that the atmAnoospheric CO2 concentration has no effects. The lack of response in this case may be attributed to the presence and longeviAyty of the large cotyledons which provided available substrate for growth.MICROSOFT OFFICE\OFFICE\A{q430^2^Samuelson,LJ^Seiler,JR^1992^1^Fraser fir seedling gas-exchange and growth in response to elevated co2^173^32^4^351-3A56^^^^^Oct^^^^^3686CE\EXAMPLES\SOLVER\SOLVSAMP.XLS State&pPROGRAAsA^3685^Growth and gas exchange characteristics were examined in Fraser fir (Abies fraseri (Pursh.) Poir.) seedlings grown Atfrom seed in elevated (713 ppm) or ambient (374 ppm) CO2 for 1 year (two artificial growing seasons) to determine the poteAuntial influence of a twice-ambient CO, concentration on this species. A subset of seedlings was transplanted from 172 cm3 Avpots into 1000 cm3 pots at 7 months to determine if CO2 effects were dependent on rooting volume. At 5 and 12 months, net Awphotosynthesis (P(net)) and leaf conductance (g1) were lower in elevated CO2-grown seedlings grown in 172 cm3 pots than inAx ambient CO2-grown seedlings when measured at either 346 or 796 ppm CO2. For 12-month-old seedlings grown in 1000 cm3 potsAy, P(net) was reduced by an elevated CO2 growth environment only when measured at 346 ppm CO2, although g1 was lower in theAzse seedlings when measured at either CO2 measurement level. Seedlings grown in both pot sizes and in elevated CO2 for 1 yeA{ar had greater height, diameter, and leaf, stem, root and total dry weights than seedlings grown in ambient CO2. Specific A|leaf weight (SLW) was greater in elevated than in ambient CO2- grown needles only in the large pot size treatment. These rA}esults suggest that Fraser fir seedling growth will increase in a future elevated CO2 environment despite changes in gas eAxchange characteristics.ROSOFT OFFICE\OFFICE\LIBRARY\BSHXL.XLAZIP CA431^3^Socias,FX^Medrano,H^Sharkey,TD^1993^1^Feedback limitation of photosynthesis of phaseolus-vulgaris L grown in elevateAd co2^9^16^1^81-86^^^^^Jan^^^^^3688ES\MICROSOFT OFFICE\OFFICE\FLAME.DOTvAA^3687^The capacity for photosynthesis is often affected when plants are grown in air with elevated CO2 partial pressure. >We grew Phaseolus vulgaris L. in 35 and 65Pa CO2 and measured photosynthetic parameters. When assayed at the growth CO2 leBvel, photosynthesis was equal in the two CO2 treatments. The maximum rate of ribulose-1,5-bisphosphate (RuBP) consumption Bwas lower in plants grown at 65Pa, but the CO2 partial pressure at which the maximum occurred was higher in the high-CO2-gBrown plants, indicating acclimation to high CO2. The acclimation of RuBP consumption to CO2 involved a reduction of the acB(tivity of RuBP carboxylase which resulted from reduced carbamylation, not a loss of protein. The rate of RuBP consumption B*declined with CO2 when the CO2 partial pressure was above 50Pa in plants grown under both CO2 levels. This was caused by fB5eedback inhibition as judged by a lack of response to removing O2 from the air stream. The rate of photosynthesis at high B7CO2 was lower in the high-CO2-grown plants and this was correlated with reduced activity of sucrose-phosphate synthase. ThBBis is only the second report Of O2-insensitive photosynthesis under growth conditions for plants grown in high CO2.AM BD432^3^Sritharan,R^Caspari,H^Lenz,F^1992^1^Influence of co2 enrichment and phosphorus supply on growth, carbohydrates and nBSitrate utilization of kohlrabi plants^172^57^5^246-251^^^^^Sep-Oct^^^^^3690ER\SOLVSAMP.XLSBUA^3689^Kohlrabi (Brassica oleracea var. gongylodes (L.) cv. Express Forcer) plants were grown in sand with adequate nutrieBbnt supply. From two weeks after germination until harvest they were treated with two levels of phosphorus supply (1.0 or 0Bd.005 mM P). Four weeks after introducing the P supply regimes the plants were exposed to either a low (300 muL CO2 L-1) orBp high (900 muL CO2 L-1) CO2 concentration in growth chambers for three weeks. At elevated CO2 concentration plants with 1.Br0 mM phosphorus produced a larger leaf area and dry matter than those grown at low CO2. At reduced P supply CO2 enrichmentB promoted leaf senescence and did not increase growth and dry matter. Phosphorus deficiency resulted in increased accumulaBtion of starch in leaves, tuber, and roots and reduced NO3-N concentrations in all plant parts. The CO2 enrichment reducedB N and NO3 concentration and increased nitrate utilization efficiency at both P levels. Phosphorus deficiency decreased niBtrogen, potassium, calcium, and magnesium concentrations in leaves particularly at high CO2.AM FILES\MICROB433^3^Vantelgen,HJ^Vanmil,A^Kunneman,B^1992^1^Effect of propagation and rooting conditions on acclimatization of micropropBagated plants^216^41^4^453-459^^^^^Dec^^^^^3692RY\LOOKUP.XLApPROGRAM FILEBA^3691^Plantlets of Calathea ornata rooted at frequencies varying between 75 and 100% irrespective of the presence of 6- bBenzylaminopurine (BAP) or indolebutyric acid (IBA). After transfer to soil all plants grew rapidly with the exception of BBAP-rooted plants, probably because these plants lacked lateral roots. Plantlets of Malus showed slightly improved rooting Band considerably improved survival at increasing sucrose concentration from 20 to 30 g l(-1) during multiplication. Their Bsurvival and performance after planting in soil depended upon the number of roots formed in rooting medium. Elevated CO2-lBevels (800 ml m-3) during acclimatization increased survival rate and plant height of rooted and non-rooted plantlets.FB434^5^Woodin,S^Graham,B^Killick,A^Skiba,U^Cresser,M^1992^1^Nutrient limitation of the long-term response of heather [calluBna-vulgaris (L) hull] to co2 enrichment^84^122^4^635-642^^^^^Dec^^^^^3694TpPROGRAM FILBA^3693^In a 27-month C2-enrichment experiment, Calluna vulgaris plants were grown on peat obtained from an upland heath inB NE Scotland and given a nutrient supply which mimicked that in precipitation in the area. Three CO2 concentrations were uBsed; ambient, + 100 ppm and + 200 ppm. Calluna showed a negative growth response to increased CO2 over the first year of tBreatment and a positive response by the end of the experiment. Final above-ground biomass was greatest in the enriched CO2C treatments, showing an increase of 30 % in + 100 ppm CO2. Determination of tissue nutrient concentration, and calculationC of total nutrient uptake, demonstrated that nutrient uptake did not increase with increased growth, resulting in significC ant dilution of elements in leaf tissue. This suggests that, in its typical, nutrient poor habitats, the growth response oC f Calluna to CO2 will be limited by nutrient deficiency, and will reach a maximum with a relatively small increase in CO2 Cconcentration. Flowering was advanced and extremely prolific in + 100 ppm CO2 grown plants, but the ecological significancCe of this is uncertain. The results highlight the need for long term studies of native species on their natural soils, usiC&ng lower CO2 concentrations than the usual 'double CO2'.fPROGRAM FILES\MICROSOFT OFFICE\C(435^2^Bertin,N^Gary,C^1993^1^Evaluation of tomgro, a dynamic-model of growth and development of tomato (lycopersicon-esculC4entum mill) at various levels of assimilate supply-and-demand^217^13^5^395-405^^^^^^^^^^3696OFFICE\OFFICE\C6A^3695^TOMGRO, a tomato growth and development model, has been examined under different levels of assimilate source and siCBnk activities, induced by CO2 enrichment and truss thinning. The main purpose was the evaluation of the assumptions on dryCD matter partitioning and fruit setting. The photosynthesis submodel has been calibrated to fit the daily dry matter producCUtion. The main input parameters to the development and growth submodels have been experimentally measured. The calibrated CWmodel provides good simulations of the leaf area expansion, but it takes no account of the variations in the assimilates sCetored in leaf blades. Total fruit growth is well simulated in spite of a small underestimation for of development and simuCglations of source/sink balance leads to good simulations of the number of set fruits. This result confirms the hypothesis Cuthat fruit set depends on the ratio between assimilate source and sink activities. This calibration with a beef tomato culCxtivar proves the robustness of the model and permits some improvements to be suggested. The surplus assimilates should be Cstored in a pool, which could exert a buffer effect during low supply periods. Sink strength of reproductive and vegetativCe parts should be measured for different cultivars, and under various climatic conditions. Finally, whether the functions Cof assimilate distribution and fruit set are still valid under very low supply conditions or whether some organs have prioCrity over the others remains to be determined.M FILES\MICROSOFT OFFICE\OFFICE\HTML.C436^2^Bertin,N^Heuvelink,E^1993^1^Dry-matter production in a tomato crop - comparison of 2 simulation-models^174^68^6^995-C1011^^^^^Nov^^^^^3698RAM FILES\MICROSOFT OFFICE\OFFICE\MIDNIGHT.DOTvCA^3697^TOMSIM(1.0) and TOMGRO(1.0) are two dynamic models for tomato growth and development. Their submodels for dry matteCr production are compared and discussed. In TOMSIM(1.0), dry matter production is simulated by a modified version of SUCROCS87 (Spitters et al., 1989). Single leaf photosynthesis rates are calculated separately for shaded and sunlit leaf area atC different depths in the canopy, according to the direct and diffuse components of light; daily crop gross assimilation raCte (A) is computed by integration of these rates over the different depths and over the day. In TOMSIM(1.0) leaf photochemCical efficiency (epsilon) and potential leaf gross photosynthesis rate at saturating light level (P(g,max)) both depend onC temperature and CO2 level. In TOMGRO(1.0) crop gross photosynthesis rate is calculated by the equation of Acock et al. (1C978); epsilon is a constant and P(g,max) is a linear function of CO2. In both models leaf photosynthesis characteristics aCre assumed to be identical in the whole canopy. Maintenance respiration (R(m)) and conversion efficiency (C(f)) are taken Cinto account in the same way, except that root maintenance respiration is neglected in TOMGRO(1.0). For both models a sensCitivity analysis was performed on the input variables (light intensity, temperature, CO2 and leaf area index (LAI)) and onD some of the model parameters. Under most conditions considered, simulated A was found to be 5-30% higher in TOMSIM(1.0) tDhan 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 TOMGDRO(1.0). The two models were very sensitive to changes in epsilon and to a lesser extent to changes in the light extinctioDn coefficient, whereas the scattering coefficient of leaves had hardly any effect on the simulated A. TOMGRO(1.0) appearedD* to be rather sensitive to the CO2 use efficiency, whereas at ambient CO2 level mesophyll resistance was quite important iD,n TOMSIM(1.0). Four sets of experimental data (differences in cultivar, CO2 enrichment and planting date) from Wageningen D<(The Netherlands) and Montfavet (southern France) were used to validate the models. Average 24 h temperature and average dD>aily CO2 concentration values were used as input to the models. For the Wageningen experiments, hourly PAR values were calDKculated from the daily global radiation sum by TOMSIM(1.0) and used as input in both models. For the Montfavet experiment,DN average hourly PAR measurements were used. Also measured LAI, dry matter distribution and organ dry weights (for calculatD[ion of R(m)) were input to the simulation. In the Wageningen experiments, total dry matter production was simulated reasonD]ably well by both models, whereas in the Montfavet experiment an under- estimation of about 35% occurred. TOMGRO(1.0) and DfTOMSIM(1.0) simulated almost identical curves in all four experiments. Strong and weak points of both models are discussedDh..DOC"@PROGRAM FILES\MICROSOFT OFFICE\OFFICE\ARCTICDy437^3^Chomba,BM^Guy,RD^Weger,HG^1993^1^Carbohydrate reserve accumulation and depletion in engelmann spruce (picea-engelmanD{nii parry) - effects of cold-storage and prestorage co2 enrichment^13^13^4^351-364^^^^^Dec^^^^^3700CROSOFT OFFDA^3699^The effects of pre-storage CO2 enrichment on growth, non- structural carbohydrates and post-storage root growth potDential of Engelmann spruce (Picea engelmannii Parry) seedlings were studied. Seedlings were grown from seed for 202 days iDn growth chambers with ambient (340 mu l l(-1)) or CO(2)ched (1000 mu l l(-1)) air. Some seedlings were transferred betweeDn CO2 treatments at 60 and 120 days. Photoperiod was reduced at 100 days to induce bud set and temperature was reduced at D180 days to promote frost hardiness development for storage at -5 degrees C for 2 or 4 months. Stored seedlings were plantDed in a growth chamber after thawing for one week at +5 degrees C. At 80, 120, 140 and 202 days, and at each planting timeD after storage, seedlings were harvested for growth measurements and analysis of starch and soluble sugar concentrations. DPlanted seedlings were assessed for bud break every two days and new roots > 5 mm long were counted after four weeks. CarbDon dioxide enrichment increased root collar diameter and almost doubled seedling biomass, with the most obvious effects ocDcurring after bud set. Stem height was affected only slightly and shoot/root ratios were not affected at all. Carbon dioxiDde enrichment increased the rate of reserve carbohydrate accumulation, but did not influence the final concentration attaiDned before storage (accounting for 32% of seedling dry weight). Needles were the major storage organ for soluble sugars, wDhereas roots were the major storage organ for starch. Soluble sugars were not strongly affected by two or four months of sDtorage, but starch was reduced by more than 50% in all plant parts. None of the CO2 treatments had an impact on bud break Dor root growth potential.AM FILES\MICROSOFT OFFICE\OFFICE\PPCENTRL.PPSpE438^3^Clark,DG^Kelly,JW^Rajapakse,NC^1993^1^Production and postharvest characteristics of rosa-hybrida L meijikatar grown E in pots under carbon-dioxide enrichment^154^118^5^613-617^^^^^Sep^^^^^3702.TXTpY@ZPROGRAME A^3701^The effects of carbon dioxide enrichment on growth, photosynthesis, and postharvest characteristics of 'Meijikatar'E potted roses were determined. Plants were grown in 350, 700, or 1050 mul CO2/liter until they reached 50% flower bud coloEration and then were placed into dark storage for 5 days at 4 or 16C. Plants grown in 700 or 1050 mul CO2/liter reached thE5e harvest stage earlier and were taller at harvest than plants produced in 350 mul CO2/liter, but there were no differenceE7s in the number of flowers and flower buds per plant among CO2 treatments. Plants grown in early spring were taller and haEAd more flowers and flower buds than plants grown in late winter. Shoot and root growth of plants grown in 700 or 1050 mul ECCO2/liter were higher than in plants produced in 350 mul CO2/liter, with plants grown in early spring showing greater incrEMeases than plants grown in late winter. Immediately after storage, plants grown in 350 mul CO2/liter and stored at 4C had EOthe fewest etiolated shoots, while plants grown in 1050 mul CO2/liter and stored at 16C had the most. Five days after remoEZval from storage, chlorophyll concentration of upper and lower leaves had been reduced by almost-equal-to 50% from the dayE] of harvest. Carbon dioxide enrichment had no effect on postharvest leaf chlorosis, but plants grown in early spring and sEktored at 16C had the most leaf chlorosis while plants grown in late winter and stored at 4C had the least leaf chlorosis.Em439^2^Deng,R^Donnelly,DJ^1993^1^In-vitro hardening of red raspberry by co2 enrichment and reduced medium sucrose concentraEytion^170^28^10^1048-1051^^^^^Oct^^^^^3704FICE\OLREADME.TXT@@vPROGRAM FILE{ycine max Merrill cv. Cresir) plants at decreasing distances from natural CO2 sources of geothermal origin in central ItalEy. When compared with neighbouring controls grown under normal CO2 concentration (C), soybean leaves grown at 2 x C, 7 x CE and more than 20 x C showed a substantial reduction in the size of ascorbate pool and in the activity of Cu,Zn-superoxideE dismutase; both the content of ascorbic acid and the activity of ascorbate peroxidase declined at 2 x C and 7 x C and recEovered to the control values at 20 x C. The foliar titre of glutathione disulfide and the activities of glutathione disulfEide reductase and Mn-superoxide dismutase progressively increased as CO2 concentration increased in ambient air. The resulEts obtained suggest that the immanent risk of dioxygen toxicity associated with photosynthetic electron flow could be reduEced in the presence of high CO2 levels. On the other hand, depending on both the CO2 exposure regimes and the cell compartEment considered, high CO2 could promote oxidative processes which cause GSH oxidation and require an enhanced cellular abiElity to scavenge superoxide anion and hydrogen peroxide.OGRAM FILES\MICROSOFT OFFICE\OFFE458^3^Basile,G^Arienzo,M^Zena,A^1993^1^Soil nutrient mobility in response to irrigation with carbon- dioxide enriched wateEr^222^24^11-12^1183-1195^^^^^^^^^^3742SOLVSAMP.XLSAvPROGRAM FILES\MICEA^3703^Micropropagated 'Festival' red raspberry (Rubus idaeus L.) shoots were rooted in specially constructed plexiglass cEhambers in ambient (340 +/- 20 ppm) or enriched (1500 +/- 50 ppm) CO2 conditions on a medium containing 0, 10, 20, or 30 gE sucrose/liter. Plantlet growth and leaf (CO2)-C-14 fixation rates were evaluated before and 4 weeks after ex vitro transpElantation. In vitro CO2 enrichment promoted in vitro hardening; it increased root count and length, plantlet fresh weight,E and photosynthetic capacity but did not affect other variables such as plantlet height, dry weight, or leaf count and areFa. No residual effects of in vitro CO2 enrichment were observed on 4-week-old transplants. Sucrose in the medium promoted Fplantlet growth but depressed photosynthesis and reduced in vitro hardening. Photoautotrophic plantlets were obtained on sF  ucrose-free rooting medium under ambient and enriched CO2 conditions and they performed better ex vitro than mixotrophic pF  lantlets grown with sucrose. Root hairs were more abundant and longer on root tips of photoautotrophic plantlets than on mF ixotrophic plantlets. The maximum CO2 uptake rate of plantlet leaves was 52% that of greenhouse control plant leaves. ThisF did not change in the persistent leaves up to 4 weeks after ex vitro transplantation. The photosynthetic ability of persiF, stent and new leaves of 4-week-old ex vitro transplants related neither to in vitro CO2 nor medium sucrose concentration. F.Consecutive new leaves of transplants took up more CO2 than persistent leaves. The third new leaf of transplants had photoF>synthetic rates up to 90% that of greenhouse control plant leaves. These results indicate that in vitro CO2 enrichment wasF@ beneficial to in vitro hardening and that sucrose may be reduced substantially or eliminated from red raspberry rooting mFNedium when CO2 enrichment is used.Fwd: Post Doc Opportunity: Assistant to the Director--Ohio Seau3 FP440^2^Deng,R^Donnelly,DJ^1993^1^In-vitro hardening of red raspberry through co2 enrichment and relative-humidity reductionF` on sugar-free medium^146^73^4^1105-1113^^^^^Oct^^^^^3706#K4.  e608FbA^3705^Micropropagated shoots of red raspberry (Rubus idaeus L. 'Comet') were rooted on modified Murashige-Skoog medium laFmcking sucrose, in specially 'constructed plexiglass chambers, under ambient (340 +/- 20 ppm) or enriched (1500 +/- 50 PPM)Fo CO2 and ambient (ca. 100 %) or reduced (90 +/- 5 %) relative humidity. Cultured plantlets were evaluated for their survivF{al, rooting and relative vigor, leaf and root number, stem and root length, total leaf area, total fresh and dry weight, gF}as exchange rate, and stomatal features, prior to transplantation to soil and at intervals for 6 wk ex vitro. In vitro CO2F enrichment promoted plantlet growth, rooting and both the survival and early growth of transplants. CO2 enrichment increaFsed stomatal aperture of plantlet leaves but did not apparently increase water stress at transplantation. Reduced in vitroF RH did not affect plantlet growth but decreased stomatal apertures and stomatal index on leaves of cultured plantlets andF promoted both the survival and early growth of transplants. In vitro CO2 and RH levels did not affect the photosynthetic Frate of either plantlets or transplants. Only the stomata on leaves of plantlets from the ambient CO2 and reduced RH treatFment were functional. Normal stomatal function was not observed in persistent leaves of transplants from the other treatmeFnts, even 2 wk after transplantation. In vitro CO2 enrichment acted synergistically with RH reduction in improving growth F of plantlets both in vitro and ex vitro. Hardened red raspberry plantlets obtained through CO2 enrichment and RH reductionF! survived direct transfer to ambient greenhouse conditions without the necessity for specialized ex vitro acclimatization Ftreatment.RAM FILES\MICROSOFT OFFICE\OFFICE\LIBRARY\FILECONV.XLAF#441^4^Denmead,OT^Dunin,FX^Wong,SC^Greenwood,EAN^1993^1^Measuring water-use efficiency of eucalypt trees with chambers and Fmicrometeorological techniques^218^150^2-4^649-664^^^^^1 Oct^^^^^3708FFICE\OFFICE\LIBRARY\SUMIFF%A^3707^Enclosure appears to be the only feasible way to examine the gas exchange of small groups of trees or to answer queF&stions about the effects of increased atmospheric CO2 on the assimilation, evaporation and water use efficiency of forestsF'. To be effective, enclosures must necessarily change the microclimate, but few studies have been made of the consequencesF(. In this paper, the assimilation, evaporation and water use efficiency of a community of Eucalyptus trees inside a ventilG )ated chamber are compared with the same attributes for the surrounding forest. Assimilation and evaporation for the chambeG *r were measured by the depletion in CO2 and the enrichment in water vapour of air passing through the chamber. For the forG+est, assimilation and evaporation were determined by micrometeorological techniques based on the energy balance, and for CG,O2, additional chamber measurements of the soil efflux. Water use efficiencies were calculated as the ratio of mol CO2 assG.-imilated to mol water evaporated. There are some important microclimatic differences between chamber and forest: net radiaG0.tion is reduced by about 30% in the chamber, the vapour pressure deficit of the chamber air is lower, and the light climatGC/e there tends to be diffuse rather than direct. Despite these differences, evaporation rates for both chamber and forest wGE0ere generally similar, perhaps due to compensating effects in the chamber from higher boundary layer conductances (becauseGV1 of greater ventilation rates) and higher stomatal conductances (because of increased humidity). However, assimilation ratGX2es and water use efficiencies were markedly different for the two communities in clear sky conditions, with higher values Ge3of both being recorded in the chamber for most of the daylight hours. Only on cloudy days, when the light climate was diffGg4use in both chamber and forest, were similar assimilation rates and water use efficiencies observed. This behaviour seems Gu5to be attributable in part to the light climate in the chamber being predominantly diffuse and that in the forest predominGv6antly direct. Diffuse light enhances the photosynthesis of lower leaves in the canopy. This contention is supported by modG7el calculations of canopy assimilation under diffuse and direct radiation which produced qualitatively the same light respG8onse functions as observed for chamber and forest. The study suggests that the use of chambers for exploring questions of G9forest productivity and water use efficiency must be circumspect. The act of enclosure, by itself, can change the daily waGter use efficiency of the tree community by as much as 50%.\MICROSOFT OFFICE\OFFICE\HEADERG;442^2^Enoch,HZ^Olesen,JM^1993^1^Plant-response to irrigation with water enriched with carbon- dioxide^84^125^2^249-258^^^^G^Oct^^^^^3710NUM.XLAHh׻tPROGRAM FILES\MICROSOFT OFFICE\OFFIG=A^3709^The influence of irrigation with CO2-enriched water on plant development and yield is reviewed. The reason for irriG>gation with CO2-enriched water was - in most cases - to increase yield. The present evaluation considers results from overG? a hundred studies performed since the first experiment in 1866. Special emphasis is given to the comparison of 85 experimG@ents made by Mitscherlich in 1910 with 358 irrigation experiments made in the last 80 years. In a statistical analysis of GAthese experiments, the measured plant parameter (often growth and/or gas exchange rates) showed a highly significant mean GBincrease of 2.9 % in plants irrigated with CO2-enriched water as compared with control. Evidence of five mechanisms was foGCund. The subterranean carbon dioxide concentration influences: (a) the rate of nitrification and hence of nitrogen availabGDility; (b) the rate of weathering and pH, and hence the availability of other plant nutrients; (c) the CO2 uptake via rootDEs into the transpiration stream, contributing to the rate of leaf photosynthesis; (d) the hormone levels in the plant; andHF (e) the rate of pesticide decomposition in soils. After examining the available evidence we found that (a) and (b) in somHGe experiments are important to plant growth, since they change the physiochemical environment of the roots. On the other hHHand, while (c) could theoretically contribute up to 5% of plant carbon assimilation, it usually contributes less than 1%, HIwhile (d) contributes most of the observed effects of CO2-enriched water on plants. In addition, pesticide decomposition iHn soils can be delayed by supra- or sub-optimal CO2 concentrations.TOSAVE.XLAvHh׻`PROGRH0Q443^1^Martos,JMG^1993^1^Effect of co2 in storage atmosphere on mill olive fruit physiology^219^44^2^81-84^^^^^Mar-Apr^^^^^H2LA^3711^Olive fruits (Olea europaea) used for oil production were stored at 5-degrees-C and four different atmospheres (%COH=M2/%O2/%N2: 0/21/78; 5/20/75; 10/19/71 and 20/17/63). At 5- degrees-C the enrichment of the storage atmosphere with greaterH?N-than-or-equal-to 5% CO2 concentrations produced a proportional increase of the physiological disorder occurring in storedHLO fruits. This occurrence had a strong relationship with the appearence of fruit decay. Simple refrigeration at 5- degrees-HNPC was sufficient to mantain the same degree of ripening of olive fruits for 60 days. However, a longer period of storage aHWt 5-degrees-C originated a remarkable incidence of chilling injuries in the fruits.Hh׻fPROGRAM FILHY3712ROSOFT OFFICE\OFFICE\OLREADME.TXTHh׻rPROGRAM FILESHeS444^2^Nederhoff,EM^Degraaf,R^1993^1^Effects of co2 on leaf conductance and canopy transpiration of greenhouse-grown cucumbHger and tomato^174^68^6^925-937^^^^^Nov^^^^^3714E\HEADERS\TASKHDR.RTFtHh׻^PROGHwUA^3713^The effects of carbon dioxide (CO2) on stomatal opening and canopy transpiration were investigated in cucumber (CucHxVumis sativus L., cv. Jessica) and tomato (Lycopersicon esculentum Mill., cv. Calypso). Stomatal opening (i.e. leaf conductHWance, g) was measured with a porometer, and canopy transpiration rate (E) with weighing lysimeters on intact plants in larHXge greenhouses. Regression analysis was applied to account for the effects of radiation, air humidity, leaf temperature anHYd CO2 on g. The effect of CO2 on E, which is primarily through g and secondarily through adjusted air humidity, was investHZigated by combining the regression equation for g with the Penman- Monteith equation for E. The relative effect of CO2, asH[ calculated with the fitted regression equations, was a decrease of about 4% in g for cucumber and of about 3% for tomato,H\ per 100 muol mol-1 increase in CO2, in the range of about 300 to 1200 mumol mol-1 CO2. The effect of CO2 on E was smallerH] than on g and the extent of the effect depended on the conditions, mainly ventilation rate. The ratio K (relative change H^in calculated E divided by relative change in calculated g) was estimated at less than 0.2, except at low radiation. In reH_ality, K will be even lower, because feedback mechanisms enforce the reduction in g and counteract the reduction in E. So H`the reduction of the transpiration rate of greenhouse cucumber and tomato caused by moderate CO2 enrichment is small and mHostly negligible, except under low light conditions.NTSMART\TUTORIAL\TUTORIAL.HTMHb445^4^Poulin,MJ^Belrhlid,R^Piche,Y^Chenevert,R^1993^1^Flavonoids released by carrot (daucus-carota) seedlings stimulate hyHcphal development of vesicular-arbuscular mycorrhizal fungi in the presence of optimal co2 enrichment^112^19^10^2317-2327^^H^^^Oct^^^^^3716OSYSTEMS.DOCPCXD PROGRAM FILES\MICROSOFT OFFICIeA^3715^Carbon dioxide has been previously identified as a critical volatile factor that stimulates hyphal growth of GigaspIfora margarita, a vesicular-arbuscular mycorrhizal fungus, and we determined the optimal concentration at 2.0%. The beneficIgial effect of CO2 On fungal development is also visible in the presence of stimulatory (quercetin, myricetin) or inhibitorIhy (naringenin) flavonoids. Sterile root exudates from carrot seedlings stimulate the hyphal development of G. margarita inI3i the presence of optimal CO2 enrichment. Three flavonols (quercetin, kaempferol, rutin or quercetin 3-rutinoside) and two I5jflavones (apigenin, luteolin) were identified in carrot root exudates by means of HPLC retention time. Flavonols like querIFcetin and kaempferol are known to have stimulatory effects on hyphal growth of G. margarita.LES\MICROSOFT IHl446^2^Prade,K^Hagelgans,V^1993^1^Enrichment of n2 and ar in the atmosphere of co2-consuming soils^220^156^5^421-426^^^^^OcISt^^^^^3718EMAIL.DOT|?fPROGRAM FILES\MICROSOFT OFFICE\OFFIUnA^3717^The phenomenon of unexplained N2/Ar-enrichment in soil air is quite frequently to be encountered in soil air studieI[os on anthropogenically influenced sites. In the present study two anthropogenic deposits and a calcareous fluvisol were inI]pvestigated for their soil air composition. While in the alkaline deposits extreme enrichments of N2 and Ar (N2 + Ar: up toIdq 99%, v/v) were found as persistent site characteristics, the fluvisol showed only slight (about 1%, v/v) transient N2/Ar-Ifr enrichments in summer. All sites, which did not show substantial vertical seepage percolation, exhibited enhanced CO2-SolIssubility either due to strong calcite precipitation or dissolution. So, it was concluded that intensive continuous depletioIttn Of CO2 was responsible for the subsequent convective influx of atmospheric air. From the results obtained it was concludI}ued that an encasement of the concerned soil volume rather impermeable to gas transport as well as intense dissolution of CIO2 in the pore water are prerequisites for substantial N2/Ar-enrichments in soil air.PLATES\CONTENT\FORIw447^3^Righetti,B^Magnanini,E^Rossi,F^1993^1^Photosynthetic carbon-dioxide uptake and oxygen accumulation during in-vitro cIulture of actinidia-deliciosa CV tomuri^173^33^4^523-528^^^^^Oct^^^^^3720DOCPROGRAM FILEIyA^3719^Proliferating cultures of Actinidia deliciosa cv Tomuri were grown in vitro under a photosynthetic photon flux densIzity (PPFD) of 120 mumol m2/s. Some jars were daily enriched with 2000 mul/l CO2 administered at the end of the dark periodI{. Head space analysis revealed that CO2 accumulated up to 9500 mul/l during the dark period and was drastically reduced byI| photosynthetic activity to 150-200 mul/l during the photoperiod without any significant difference between CO2-enriched aI}nd non-enriched cultures. Oxygen concentration assayed at the end of the photoperiod showed a steady increase during the 4I~4 days of culture and was not reduced to atmospheric values by respiratory processes during the dark period. CO2 enrichmenIt enhanced O2 production and accumulation to 32.5% at the end of the culture period. Oxygen photoreduction and its photo- Ioxidative damage to green tissue cells are discussed. OFFICE\OFFICE\MACROS\SUPPORT8.DOTI448^3^Sombroek,WG^Nachtergaele,FO^Hebel,A^1993^1^Amounts, dynamics and sequestering of carbon in tropical and subtropical Isoils^221^22^7^417-426^^^^^Nov^^^^^3722CK.DOCPROGRAM FILES\MICROSOFT OFIA^3721^The organic carbon pool in the upper 1 m of the world's soils contains 1220 Gt organic carbon, 1.5 times the total Ifor the standing biomass. In the widespread deep soils in the tropics the carbon stored below 1 m may add about 50 Gt C. TIhe contributions of charcoal, roots and soil fauna should be added to these totals. The much less dynamic carbonate-carbonJ pool amounts to 720 Gt C. Changes in land use, particularly by clearing of forests, reduce organic carbon by 20 to 50% inJ  the upper soil layers, but little in deeper layers. On the other hand, there are indications that a human-induced enrichmJent of soil organic matter can be maintained over centuries. Research on the causative soil processes should be supported,J because an improved understanding of this phenomenon might lead to better management strategies and sound programs to stiJmulate organic carbon storage and fertility levels in tropical and subtropical soils. Recent research data on the CO2 fertJ%ilization effect and the associated antitranspiration effect due to an increase of CO2 in the atmosphere indicate that a pJ'ositive influence on soil organic carbon levels can be expected.ICROSOFT OFFICE\OFFICE\WEB PJ2449^6^Brown,S^Hall,CAS^Knabe,W^Raich,J^Trexler,MC^Woomer,P^1993^1^Tropical forests - their past, present, and potential fuJ4ture- role in the terrestrial carbon budget^94^70^1-4^71-94^^^^^Oct^^^^^3724OCPROGRAM FILJ:A^3723^In this paper we review results of research to summarize the state-of-knowledge of the past, present, and potentialJ< future roles of tropical forests in the global C cycle. In the pre- industrial period (ca. 1850), the flux from changes iJLn 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 +/- 0.5JO Pg yr-1. The C pools in forest vegetation and soils in 1990 was estimated to be 159 Pg and 216 Pg, respectively. No concrJ[ete evidence is available for predicting how tropical forest ecosystems am likely to respond to CO2 enrichment and/or climJ\ate change. However, C sources from continuing deforestation are likely to overwhelm any change in C fluxes unless land maJcnagement efforts become more aggressive. Future changes in land use under a ''business as usual'' scenario could release 4Jf1-77 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 agricultJural policies, forest protection, promotion of on-farm forestry, and establishment of plantations on non-forested lands. PJolicies should support improved agricultural productivity, especially replacing non-traditional slash-and-burn agricultureJ with more sustainable and approaches.STRATION.DOCPROGRAM FILES\MICROSJ450^2^Crosson,PR^Rosenberg,NJ^1993^1^An overview of the mink study^50^24^1-2^159-173^^^^^Jun^^^^^3726HOME PAGE.JA^3725^Highlights of the previous papers in this series are reviewed. Methodology developed for the MINK study has improveJd the ability of impacts analysis to deal with questions of (1) spatial and temporal variability in climate change; (2) COJ2- enrichment effects; (3) the reactions of complex enterprises (farms and forests) to climate change and their ability toJ adjust and adapt; and (4) integrated effects on current and, more particularly, on future regional economies. The methodoJlogy also provides for systematic study of adjustment and adaptation opportunities and of the inter-industry linkages thatJ determine what the overall impacts on the regional economy might be. The analysis shows that with a 1930s 'dust bowl' cliJmate the region-wide economic impacts would be small, after adjustments in affected sectors. In this final paper we considJer whether synergistic effects among sectoral impacts and more severe climate change scenarios might alter this conclusionJ. The MINK analysis, as is, leads to the conclusion that a strong research capacity will be required to ensure that technoJlogies facilitating adaptation to climate change will be available when needed. The capacity to deal with climate change aJlso requires an open economy allowing for free trade and movement of people and for institutions that protect unpriced envJironmental values. More severe climate scenarios and negative synergisms can only strengthen these conclusions.UERY\J451^6^Easterling,WE^Crosson,PR^Rosenberg,NJ^McKenney,MS^Katz,LA^Lemon,KM^1993^1^Agricultural impacts of and responses to cJlimate-change in the missouri-iowa-nebraska-kansas (mink) region^50^24^1-2^23-61^^^^^Jun^^^^^3728OFT OFFICE\OJA^3727^The climate of the 1930s was used as an analog of the climate that might occur in Missouri, Iowa, Nebraska and KansJas (the MINK region) as a consequence of global warming. The analog climate was imposed on the agriculture of the region uKnder technological and economic conditions prevailing in 1984/87 and again under a scenario of conditions that might prevaKil in 2030. The EPIC model of Williams et al. (1984), modified to allow consideration of the yield enhancing effects of COK2 enrichment, was used to evaluate the impacts of the analog climate on the productivity and water use of some 50 represenKtative farm enterprises. Before farm level adjustments and adaptations to the changed climate, and absent CO2 enrichment (Kfrom 350 to 450 ppm), production of corn, sorghum and soybeans was depressed by the analog climate in about the same perceK$nt under both current and 2030 conditions. Production of dryland wheat was unaffected. Irrigated wheat production actuallyK' increased. Farm level adjustments using low-cost currently available technologies, combined with CO2 enrichment, eliminatK+ed about 80% of the negative impact of the analog climate on 1984/87 baseline crop production. The same farm level adjustmK-ents, plus new technologies developed in response to the analog climate, when combined with CO2 enrichment, converted the K2negative impact on 2030 crop production to a small increase. The analog climate would have little direct effect on animal K4production in MINK. The effect, if any, would be by way of the impact on production of feed-grains and soybeans. Since thiKEs impact would be small after on-farm adjustments and CO2 enrichment, animal production in MINK would be little affected bKGy the analog climate.ing products to add to our existing livPROGRAMKP452^1^Frederick,KD^1993^1^Climate-change impacts on water-resources and possible responses in the mink region^50^24^1-2^83KR-115^^^^^Jun^^^^^3730L 1 GENERATOR Internet Assistant for Microsoft WorKeA^3729^The capacity to supply both instream and offstream water uses under alternative climate conditions and likely futurKge changes in population, technology, and water-using practices are examined through an adaptation of the framework developKned in the Second National Water Assessment. Two measures of the adequacy of water supplies - the availability of renewableKp supplies to provide for withdrawal and instream uses and the relation between desired instream flows and current streamflKyows - are used to examine the impact of the 1931-1940 analog climate (with and without CO2 enrichment) on Missouri, Iowa, K{Nebraska, and Kansas (MINK). The impacts of the analog climate on water supplies are estimated from actual streamflow dataK and estimates of the differences in reservoir evaporation under the 1931-1940 analog and the 1951-1980 control climates. KA modification of the Erosion Productivity Inventory Calculator (EPIC) model is used to estimate the impacts of the analogK climate (with and without CO2 enrichment) on irrigation water use. Water, which is already a scarce resource in the MINK Kregion, would become much scarcer if the climate of the 1930s were to become the norm. Mean assessed total streamflow woulKd drop to 69% of the control climate level for the Missouri River Basin, 71% for the Upper Mississippi, and 93% for the ArKkansas. Even in the absence of climate change, MINK will have less water in the year 2030 than it does today because grounKdwater stocks are being depleted and increased upstream diversions would reduce surface flows into these states. IrrigatioKn and instream uses such as navigation, hydroelectric power production, recreation, and fish and wildlife habitat would beK most adversely, impacted by the climate-induced changes in water supplies.COLUMN LAYOUT.DOC3K453^3^Julkunentiitto,R^Tahvanainen,J^Silvola,J^1993^1^Increased co2 and nutrient status changes affect phytomass and the pKroduction of plant defensive secondary chemicals in salix- myrsinifolia (salisb)^2^95^4^495-498^^^^^Oct^^^^^3732T OFKA^3731^The effect of CO2 enrichment (700 and 1050 ppm) on phytomass, soluble sugars, leaf nitrogen and secondary chemicalsK of three Salix myrsinifolia clones was studied in plants cultivated at very poor (sand seedlings) and moderate (peat seedKlings) nutrient availability and under low illumination. The total shoot phytomass production of sand seedlings was less tKhan 10% of that of the peat seedlings. Carbon dioxide increased the total shoot phytomass of peat seedlings. When the ambiKent carbon supply was doubled (to 700 ppm) the growth of sand seedlings was slightly enhanced but 1050 ppm CO2 gave growthL figures similar to those at the control CO2 level. Leaf nitrogen content and total soluble sugar contents were significanLtly higher in peat seedlings than in sand seedlings. Leaf nitrogen showed a decreasing trend in relation to CO2 increase. LOn the other hand, CO2 did not have any clear-cut effect on total sugars. At the control CO2 level the content of salicortL!in, which is a dynamic phenolic, was higher in the peat seedlings than in the sand seedlings, but salicin showed the opposL,ite trend. CO2 enrichment considerably decreased these phenolics in the peat seedlings. At the control CO2 level, the contL.ent of more static phenolics, such as proanthocyanidins, was higher in sand seedlings. An increased carbon supply considerL<ably increased static phenolics in the peat seedlings. Willow defence against generalist herbivores is moderately decreaseL>d by enhancement of atmospheric carbon dioxide.ENT\FORM - REGISTRATION.DOC8.0.3LG454^3^Tanimoto,H^Kagi,T^Morita,S^1993^1^Relationship between the utilization of sugars by cultured petiole segments of begLIoniaxhiemalis and the optimum time for co2 enrichment^180^62^2^437-441^^^^^Sep^^^^^3734GRAM FILES\MICROSLTA^3733^By monitoring the utilization of sugars by petiole segments of Begonia X hiemalis cultured in medium containing theLV plant grwoth regulators, kinetin (1 PPM), NAA (1 ppm), the optimum time for beginning the CO2 enrichment treatment was esL^tablished. The total sugar concentration in the medium decreased rapidly after 40 days of culturing. The cessation of sugaL`r depletion by the tissues after 60 days is attributed to the onset of photosynthesis by the plantlets. CO2 administrationLo at this time promoted leaf development, whereas CO2 enrichment 10 to 20 days earlier halted the development of adventitioLqus shoots. These observations suggest that the optimum period to begin CO2 enrichment to promote shoot growth and to enhanL}ce photosynthesis is about 60 days after the culturing the petiole segments.9/23/96"PROGRAM FILL455^6^West,DC^Doyle,TW^Tharp,ML^Beauchamp,JJ^Platt,WJ^Downing,DJ^1993^1^Recent growth increases in old-growth longleaf pinLe^155^23^5^846-853^^^^^May^^^^^3736"PROGRAM FILES\MICROSOFT OFFICE\OFFICE\WLA^3735^Longleaf pine (Pinus palustris Mill.) tree-ring data were obtained from an old-growth stand located in Thomas County, Georgia. The tree-ring chronology from the pine stand is composed of a collection of cores extracted from 26 trees ranging in age from approximately 100 to 400 years. These cores were prepared, dated, and measured, and the resulting data were examined with dendrochronological and statistical techniques. Beginning in approximately 1950 and continuing to the present, annual increments of all age classes examined in this study have increased. resulting in an average annual ring increment approximately 40% greater in 1987 than in 1950. When compared with expected annual increment, the increase for 100- to 150- year-old trees is approximately 45%, while the increase for 200- to 400-year-old trees is approximately 35%. In terms of stand-level aboveground biomass accumulation, the increased growth has resulted in approximately 5% more biomass than expected. The increased growth cannot be explained by disturbance; stand history; or trends in precipitation, temperature, or Palmer drought severity index over the last 57 years. Increased atmospheric CO2 is a possible explanation for initiation of the observed trend, while SO(x) and NO(x) may be augmenting continuation of this phenomenon.CDB.XLAL456^4^Wheeler,RM^Mackowiak,CL^Siegriest,LM^Sager,JC^1993^1^Supraoptimal carbon-dioxide effects on growth of soybean [glyciLne-max (L) merr]^4^142^2^173-178^^^^^Aug^^^^^3738DOCcentered.doc.PROGRAM FILELA^3737^In tightly closed environments used for human life support in space, carbon dioxide (CO2) partial pressures can reaLch 500 to 1000 Pa, which may be supraoptimal or toxic to plants used for life support. To study this, soybeans [Glycine maLx (L.) Merr. cvs. McCall and Pixie] were grown for 90 days at 50, 100, 200, and 500 Pa partial pressure CO2 (500, 1000, 20L00, and 5000 ppm). Plants were grown using recirculating nutrient film technique with a 12-h photoperiod, a 26-degrees-C/2L0-degrees-C thermoperiod, and approximately 300 mumol m-2 s-1 photosynthetic photon flux (PPF). Seed yield and total biomaLss were greatest at 100 Pa for cv. McCall, suggesting that higher CO2 levels were supraoptimal. Seed yield and total biomaLss for cv. Pixie showed little difference between CO2 treatments. Average stomatal conductance of upper canopy leaves at 5L0 Pa CO2 almost-equal-to 500 Pa > 200 Pa > 100 Pa. Total water use over 90 d for both cultivars (combined on one recirculaLting system) equalled 822 kg water for 100 Pa CO2, 845 kg for 50 Pa, 879 kg for 200 Pa, and 1194kg for 500 Pa. Water use eLfficiences for both cultivars combined equaled 3.03 (g biomass kg-1 water) for 100 Pa CO2, 2.54 g kg-1 for 200 Pa, 2.42 g Lkg-1 for 50 Pa, and 1.91 g kg-1 for 500 Pa. The increased stomatal conductance and stand water use at the highest CO2 leveLl (500 Pa) were unexpected and pose interesting considerations,for managing plants in a tightly closed system where CO2 coM ncentrations may reach high levels.E TEMPLATES\CONTENT\CALENDAR.DOCHtml.dM 457^5^Badiani,M^Dannibale,A^Paolacci,AR^Miglietta,F^Raschi,A^1993^1^The antioxidant status of soybean (glycine-max) leavesM grown under natural co2 enrichment in the field^92^20^3^275-284^^^^^^^^^^3740PROGRAM FILES\MICRMA^3739^The effects of progressively higher CO2 levels on the foliar antioxidant status were studied by growing soybean (GlM'A^3741^In our experiments, carbonated water (CW) modified the equilibria in soil. Application of CW decreased the soil pH M)about 1.5 units one hour after irrigation ended. Minimal, though well defined, differences in soil pH were observed betweeM1n the two carbonated treatments. The same relationship between the treatments was not found in pH levels of the leachate. M3This seems strictly related to the temporal and spatial changes in the carbon dioxide (CO2) acidifying effect caused by chM=emical and biological factors as water descended the soil column. The temporary reduction in soil pH in the CW treatment iM?nduced the highest nutrient mobility for most of the elements.0-(EST) 918031637 Ndel Nskip Nsave read Nget 1618428005 5bMP459^2^Beerling,DJ^Chaloner,WG^1993^1^Stomatal density responses of egyptian olea-europaea L leaves to co2 change since 132MR7 bc^52^71^5^431-435^^^^^May43ca3bbe73eaea9994f9f15ab0f661 <199902031715.MAA27750@mail2.uts.ohio-state.edu>-3-Feb-1999-12MY 460^3^Cournac,L^Dimon,B^Peltier,G^1993^1^Evidence for o-18 labeling of photorespiratory co2 in photoautotrophic cell-cultuM[res of higher-plants illuminated in the presence of o-18(2)^6^190^3^407-414^^^^^Jun^^^^^374519b0ff3ef7585fb56f9e8107 <3.0Md A^3744^The O-18-enrichment of CO2 produced in the light or during the post-illumination burst was measured by mass spectroMf metry when a photoautotrophic cell suspension of Euphorbia characias L. was placed in photorespiratory conditions in the pMmresence 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 deteMocted. Production of (COO)-O-18-O-16 ceased after addition of two inhibitors of the photosynthetic carbon-oxidation cycle, Myaminooxyacetate or aminoacetonitrile, and was inhibited by high levels of CO2. The average enrichment during the post- illM{umination burst was estimated to be 46+/-15% of the enrichment of the O2 present during the preceding light period. AdditiMon of exogenous carbonic anhydrase, by catalyzing the exchange between CO2 and H2O, drastically diminished the O-18- enricMhment of the produced CO2. The very low carbonio-anhydrase level of the photoautotrophic cell suspension probably explainsM why the O-18 labeling of photorespiratory CO2 Could be observed for the first time. These data allow the establishment ofM a direct link between O2 consumption and CO2 production in the light, and the conclusion that CO2 produced in the light rMesults, at least partially, from the mitochondrial decarboxylation of the glycine pool synthesized through the photosyntheMtic carbon-oxidation cycle. Analysis of the (COO)-O- 18-O-16 and CO2 kinetics provides a direct and reliable way to assessM in vivo the real contribution of photorespiratory metabolism to CO2 production in the light.2:17--0500-(EST) 918466818 NM461^6^Dayan,E^Vankeulen,H^Jones,JW^Zipori,I^Shmuel,D^Challa,H^1993^1^Development, calibration and validation of a greenhouMse tomato growth-model .1. Description of the model^223^43^2^145-163^^^^^^^^^^37474020a11b2e4f99427b7@[192.168.1.31]>-8-FMA^3746^A dynamic crop growth model. TOMGRO, for an indeterminate tomato variety is presented. The model describes the phenMological development and increase in dry weight of various organs (roots, stem nodes, leaves and fruits) from planting tilMl maturity under variable environmental conditions. Phenological development is governed by genetic plant properties and eMnvironmental conditions (e.g. air temperature and CO2 level) and expressed in a plastochron index, i.e. the current stem nMode number. Total dry matter accumulation is based on a quantitative description of the carbon balance, including gross COE 2 assimilation, maintenance respiration and growth respiration. Partitioning of dry matter increase over the various organN!s is governed by their relative sink strengh, defined on the basis of a genetically determined 'potential' growth rate, acN "hieved under non-limiting carbohydrate supply. The model is both schematic and modular in set-up. This means it can be adaN#pted easily and most of its subroutines can be replaced easily by others if better descriptions become available. It can aN$lso be combined with a more comprehensive model describing greenhouse climate and appears robust for use in procedures of Neconomic optimization of climate conditions in greenhouses or for management purposes.168.1.30]>-12-Feb-1999-21:44:08--05N(&462^2^Ehler,N^Karlsen,P^1993^1^Optico - a model-based real-time expert-system for dynamic optimization of co2 enrichment oN*f greenhouse vegetable crops^174^68^4^485-494^^^^^Jul^^^^^3749read Nget 868656267 7a8089ae8b15c275ba0e5eddc02b1d61 )e system continually adapts the setpoints of a standard climate computer to the climate, the greenhouse regulation equipmeNM*nt and the crop's physiological status and stage of development. Models describing air loss and photosynthesis were used fNO+or selecting an optimized CO2 setpoint by choosing the largest positive difference between expected income and cost. DurinN[,g the autumn of 1991 the sweet pepper (Capsicum annuum L.) cv. Trophy was used as experimental plant in two standard greenN]-house compartments. One treatment used the optimized CO2 enrichment, the other a fixed CO2 level of 600 ppm. The optimizedNl. treatment resulted in greater yield using less CO2. The results stress the importance of adapting the CO2 level to the imNnmediate irradiance and current leaf area and carbon partitioning behaviour of the crop.legraph.uwyo.edu>-17-Feb-1999-18:3N0463^4^Idso,SB^Kimball,BA^Akin,DE^Kridler,J^1993^1^A general relationship between co2-induced reductions in stomatal conducNtance and concomitant increases in foliage temperature^173^33^3^443-446^^^^^Jul^^^^^37515 9d7630bb0ee8c1749e9ef9110e2cfeN2A^3750^Simultaneous measurements of the temperatures and stomatal conductances of leaves of sour orange trees growing in nN3ormal and CO2-enriched air, together with similar data for water hyacinths and cotton, suggest that a plant's foliage tempN4erature response to atmospheric CO2-enrichment is directly proportional to its degree of stomatal closure, i.e. that plantN5s that experience a greater stomatal closure in response to atmospheric CO2 enrichment experience a greater warming of theN6ir foliage. The data also suggest that this primary relationship may be modified by CO2-induced changes in leaf chlorophylNl content that may have implications for global climate change. Nsave read Nget 1755720812 166405902e59380b02bf81a1b3974N8464^3^Idso,SB^Wall,GW^Kimball,BA^1993^1^Interactive effects of atmospheric co2 enrichment and light- intensity reductions Non net photosynthesis of sour orange tree leaves^173^33^3^367-375^^^^^Jul^^^^^37539-14:10:09--0500-(EST 919866127 Ndel NsN:A^3752^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 oranN;ge trees, a comprehensive set of net photosynthesis and light intensity data was obtained. From these measurements we deriNt photosynthesis at full sunlight. Our analysis demonstrated that the positive direct effect of atmospheric CO2 enrichmentN? on net photosynthesis more than compensated for the negative self- shading effect produced by the CO2-induced proliferatiOon of leaf area.0F7O00D8SIC1W9@mx3.osu.edu>-24-Feb-1999-17:10:02--0500-(EST 919928326 Ndel Nskip Nsave read Nget 89468391OA465^2^Jacob,J^Drake,BG^1993^1^Long-term co2 enrichment effects on the rubisco content and activity in 2 field-grown C3 plaO#nts^8^102^1^46^^^^^Mayda6b172f6f27ee457a67 -24-Feb-1999-17:22:27--0500-(EST 91992O%C466^3^Prior,SA^Rogers,HH^Runion,GB^1993^1^Effects of free-air co2 enrichment on cotton root morphology^8^102^1^173^^^^^MayO2ST 919928326 Ndel Nskip Nsave read Nget 933301851 f1da0e4c3fac6cf487911863ffefb9c3 <0F7O00M7GJL8V9@mx2.osu.edu>-24-Feb-1O4N467^3^Rabbinge,R^Vanlatesteijn,HC^Goudriaan,J^1993^1^Assessing the greenhouse-effect in agriculture^224^175^^62-79^^^^^^^^O<FA^3756^Evidence that concentrations of CO2 and trace gases in the atmosphere have increased is irrefutable. Whether or notO>G these increased concentrations will lead to climate changes is still open to debate. Direct effects of increased CO2 concOJHentrations on physiological processes and individual plants have been demonstrated and the consequences for crop growth anOLId production under various circumstances are evaluated with simulation models. The consequences of CO2 enrichment are consOTJiderable under optimal growing conditions. However, the majority of crops are grown under sub-optimal conditions where theOVK effects of changes in CO2 are often less. The same holds for the possible indirect effects of environmental changes such O_Las temperature rise. Studies on individual plants under optimal conditions are therefore not sufficient for evaluating theOaM effects at a farm, regional, national or supra-national level. Simulation studies help to bridge the gap between the variOkous aggregation levels and provide a basis for various studies of policy options at various aggregation levels.9292 f5e5Om^^3757bf54cade85f44ad -25-Feb-1999-09:46:27--0500-(EST 919936414 Ndel Nskip Nsave read Nget O~P468^3^Sicher,RC^Kremer,DF^Rodermel,SR^1993^1^Role of rubisco during acclimation of transformed tobacco to co2 enriched atmOospheres^8^102^1^88^^^^^May OR469^1^Woodward,FI^1993^1^The lowland-to-upland transition modeling plant-responses to environmental-change^56^3^3^404-408^O^^^^Aug^^^^^3760ROGRAM FILES\MICROSOFT OFFICE\OFFICE\WEB PAGE TEMPLAOTA^3759^A published correlative model has predicted that the distributional limits of plants and vegetation zones on mountaOUins will increase in altitude with global warming. I test this hypothesis using results from published experimental studieOVs. Investigations and models of the responses of leaf growth to temperature are in accord with the prediction. However, thOWe individualistic responses of species to CO2 enrichment indicate that the prediction is unlikely to be true for all speciOXes: growth is stimulated by CO2 enrichment for some species but not for others. Wind speed generally increases with altituOYde on mountains, and plants from high altitude tend to be more wind resistant than species from the lowland. Therefore it OZis expected that, particularly on wind-swept mountains, global warming will not necessarily be followed by the spread of lOowland species into the uplands. Word 8.0 PROGRAM FILES\MICROSOFT OFFICE\O\470^2^Beerling,DJ^Chaloner,WG^1993^1^Evolutionary responses of stomatal density to global co2 change^225^48^4^343-353^^^^^OAprord for Windows 95 vPROGRAM FILES\MICROSOFT OFFICE\OFFICEO^471^2^Bladier,C^Chagvardieff,P^1993^1^Growth and photosynthesis of photoautotrophic callus derived from protoplasts of solOanum-tuberosum L^226^12^6^307-311^^^^^Apr^^^^^3763T OFFICE\OFFICE\LIBRARY\MSQUERY\XLQO`A^3762^We describe a photoautotrophic culture procedure of potato (cvs Kennebec, Haig, DTO-33) callus derived from mesophyOall protoplasts. The protoplast culture was initiated at very low concentration of glucose (down to 0.25 g l-1). Callus wasPb subcultured under CO2 enriched air and glucose was suppressed by the successive dilutions with glucose free media. RegenePcration was successfully obtained under photoautotrophic conditions. The characterization of oxygen exchange and of some enP dzymes and metabolites of carbon assimilation indicated that chlorophyllous callus, grown on carbohydrate free medium, devePeloped the photosynthetic pathway typical of C3 plants. By comparing the fresh weight of callus cultivated in the light or P$fin non-photosynthetic conditions (in darkness or in the light +3-(3,4-Dichlorophenyl)-1,1-dimethylurea) we concluded that P&growth depended to about 70 to 88 % on photosynthesis. P9h472^3^Dorais,M^Charbonneau,J^Gosselin,A^1993^1^Gas-exchange in greenhouse tomatoes grown under supplemental light^146^73^2P:^577-585^^^^^Apr^^^^^3765XLLLLLXPDjA^3764^This study reports on in situ gas-exchange measurements in tomatoes grown under a sequential intercropping system wPFkith supplemental lighting provided by high-pressure sodium-vapour lamps. A supplemental photosynthetic photon flux (PPF) oPYlf 150 mumol m-2 s-1 significantly increased the amount of light energy penetrating the canopy of intercropped tomato seedlP[mings. During the day, the supplemental 150 mumol m-2 s-1 light regime increased the photosynthetic rate of leaves 5 and 10Pen by 67%, while at night the increases were 93 and 12%, respectively. Regression analysis of the photosynthetic rate of leaPgoves 5 and 10 as a function of PPF received accounts for 58 and 45% of the variation, respectively. Hierarchical analysis dPvpemonstrated a significant linear relationship between PPF received during the day and photosynthetic activity of leaves 5 Pxqand 10 accounting for 46 and 28%, respectively, of the variance in the model. Regression analysis of the photosynthetic acPrtivity as a function of PPF received at night accounts for 41 and 32 %, respectively, of the variation in the photosynthetPsic rate of leaves 5 and 10. Using a high level of supplemental lighting during the day or at night had no significant effePct on stomatic conductance or on the transpiration rate of leaves.and genotypes are available with tolerance and sensitivPu473^3^Hand,DW^Wilson,JW^Acock,B^1993^1^Effects of light and co2 on net photosynthetic rates of stands of aubergine and amaPranthus^52^71^3^209-216^^^^^Mart stress and optimal temperature, and test whether differences in carbohydrate supplies duPw474^4^Holbrook,GP^Hansen,J^Wallick,K^Zinnen,TM^1993^1^Starch accumulation during hydroponic growth of spinach and basil plPants under carbon-dioxide enrichment^173^33^2^313-321^^^^^Apr^^^^^3768ht temperatures of either 33/20 or 33/30- degrees-CPyA^3767^The effects of CO2 enrichment, photoperiod duration, and inorganic phosphate levels on growth and starch accumulatiPzon by spinach and basil plants were studied in a commercial hydroponic facility. During a 3-week growth period, both speciP{es exhibited increased whole-plant fresh weight as a result of an increase in atmospheric CO2 concentration from 400 to 15P|00 mul/l. However, basil leaves exhibited a 1.5- to 2-fold greater increase in specific leaf weight (SLW), and accumulatedP} starch to much greater levels than did leaves of spinach. At 1500 mul CO2/l, starch accounted for up to 38% of SLW with bP~asil compared to < 10% of SLW with spinach. The maximum ratio of starch/chlorophyll was 55.0 in basil leaves vs 8.0 in spiPnach leaves. High ratio values were associated with the appearance of chlorotic symptoms in leaves of basil grown under COP2 enrichment (WALLICK and ZINNEN (1990) Plant Disease 74, 171-173), whereas spinach did not exhibit chlorosis. Increasing Pinorganic phosphate concentrations from 0.7 to 1.8 mM in the hydroponic medium did not appreciably affect leaf starch accuQmulation in either species. Starch accumulation in basil leaves was not consistently related to the duration of the photopQ eriod. However, photoperiod-induced changes in leaf starch levels were much greater in basil than spinach. The results cleQ arly indicate that different horticultural crops can show diverse responses to CO2 enrichment, and thus highlight the needQ to develop individual growth strategies to optimize production quality of each species.ER, JM PRESS, MC TI GROWTH-RESPONQ475^2^Hunt,R^Constable,GM^1993^1^Multifactorial growth-responses in holcus-lanatus - optima and limiting factors^52^71^4^3Q%57-368^^^^^Apr, DEPT ENVIRONM BIOL, OXFORD RD, MANCHESTER M13 9PL, LANCS, ENGLAND. DE GROWTH ANALYSIS; CO2; NITROGEN; AGRQ'476^4^Tanigawa,T^Nagaoka,M^Ikeda,H^Shimizu,A^1993^1^Effects of co-2 enrichment on growth, photosynthesis and physiologicalQ>-activity of roots of dendranthema X grandiflorum (ramat) kitamura^180^61^4^873-878^^^^^Mar^^^^^3771nd Nardus stricta L. Q@A^3770^To assess the effect of CO2 enrichment on growth of greenhouse chrysanthemum, the plants were cultivated in the phyQNtotron with 300, 600 and 1,200 ppm CO2. i. CO2 enriched plants showed a significant increase in stem length, number of leaQPves, leaf area, and fresh and dry weights. The greatest rate of increase after 60 days of CO2 enrichment was observed in tQ]he dry weight of roots (39%). Flower bud formation was delayed 3 days under CO2 enriched condition. 2. No difference in phQ_otosynthetic rates of whole plants measured in 400 and 800 ppm CO2 was observed among those grown under high CO2 (600 or 1Qn,200 ppm) and those grown in ambient air (300 ppm). After 60 days of exposure to ambient and high CO2, the photosynthetic Qprate measured in 800 PPM CO2 declined markedly compared to the rate at the beginning of the treatment. 3. TTC (2, 3, 5-triQ}phenyl tetrazolium chloride) reductive activity of roots decreased under CO2 enriched atmosphere, but it increased on a peQ~r plant basis because fresh weight of the roots increased. There was a high positive correlation between TTC reduction perQ plant and the fresh weight of the top (aerial part).al dry weight at low nitrogen whilst at high nitrogen plants grown aQ477^2^Andre,M^Ducloux,H^1993^1^Interaction of co2 enrichment and water limitations on photosynthesis and water efficiency Qin wheat^184^31^1^103-112^^^^^Jan-Feb^^^^^3773he lower nitrogen concentration was to increase partitioning to the roots wQA^3772^Wheat plants (Triticum aestivum L. cv. Capitole) were grown in twin closed growth chambers with continuous monitoriQng of CO2 and water exchanges. During the vegetative stage the effect Of CO2 enrichment, from 330 to 660 mul-1, was studieQd under irradiance of 660 muE m-2 s-1 with an optimum watering. Comparisons were made with successive experiments in whichQ daily water supply was fixed to a fraction (0.62-0.50-0.25) of the maximal transpiration of previous experiments. In a weQll- watered canopy, doubling CO2 decreased transpiration by only 8%. Water use efficiency was increased (factor 1.45) mainQly by the stimulation of photosynthesis. Under restricted water supply, photosynthesis of plants was more limited than traQnspiration. The inhibition of photosynthesis and the increase of water use efficiency can be predicted by a simple diffusiQon model applied to the response curve of photosynthesis to CO2, measured on canopy in standard conditions of watering. ThQe main hypothesis is that the equivalent stomatal conductance is reduced proportionally to the water availability, withoutQ closure by patching. Under enriched CO2, the same reduction of leaf surface by water limitation was observed. PhotosyntheQsis was less affected. Therefore, water-use-efficiency was again increased. Doubling CO2 concentration can compensate for Qwater stress inhibition on CO2 assimilation. That model also predicts interactions of CO2 and water stress observed on watQer-use- efficiency which was increased by a factor up to 5 in comparison with well-watered plants in standard atmosphere. RThe implications of this study for global change models are discussed. fluxes from losses in tropical forests may be lessR478^1^Besford,RT^1993^1^Photosynthetic acclimation in tomato plants grown in high co2^24^104^^441-448^^^^^Jan^^^^^3775souR A^3774^The effects of prolonged CO2 enrichment of tomato plants on photosynthetic performance and Calvin cycle enzymes, inR cluding the amount and activity of ribulose-1,5-bisphosphate carboxylase (RuBPco), were determined. Also the light-saturatRed rate of photosynthesis (P(max)) of the 5th leaf throughout leaf development was predicted based on the amount and kinetRics of RuBPco. With short-term CO2 enrichment, i.e. only during the photosynthesis measurements, P(max) of the young leaveR*s did not increase while the leaves reaching full expansion more than doubled their net rate of CO2 fixation. However, witR-h longer- term CO2 enrichment, i.e. growing the crop in high CO2, the plants did not maintain this photosynthetic gain. CoR9mpared with leaves of plants grown in normal ambient CO2 the high CO2-grown leaves, when almost fully expanded, contained R;only about half as much RuBPco protein and P(max) in 300 and 1000 vpm CO2 was similarly reduced. The loss of RuBPco proteiRFn may be a factor associated with the accelerated fall in P(max) since P(max) was close to that predicted from the amount RHand kinetics of RuBPco assuming RuBP saturation. Acclimation to high CO2 is fundamentally different from acclimation to hiRTgh light. In contrast to acclimation to high light, acclimation to high CO2 does not usually involve an increase in photosRVynthetic machinery so the synthesis and maintenance costs (as indicated by the dark respiration rate) are generally lower.Raetween 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 darRc479^2^Debruin,HAR^Jacobs,CMJ^1993^1^Impact of co2 enrichment on the regional evapotranspiration of agroecosystems, a theorRjetical and numerical modeling study^24^104^^307-318^^^^^Jan^^^^^3777 treatments of FSA, FSE, HSA and HSE, respectively. ERlA^3776^This paper gives a brief overview of factors determining evapotranspiration of vegetated surfaces. It indicates whiRwch of these factors are sensitive to CO2 enrichment. A qualitative analysis is presented of the impact of large scale climRzate changes. Data in literature indicate that the surface resistance of vegetated areas may change within the range -25 % Rand +50 % if the atmospheric CO2-concentration doubles. The impact of such changes on regional scale transpiration is evalRuated using a numerical model in which the interaction between the evapotranspiration and the Planetary Boundary Layer is Raccounted for. It is concluded that the impact of CO2 enrichment on the transpiration at the regional scale is relatively Rsmall for aerodynamically smooth surfaces (between +7 % and -11 %). For aerodynamically rough surfaces the effects are somRewhat larger (between +15 % and -21 %).reached 6.8, 4.6, 5.7 and 3.2 kg per plant in the FSA, FSE, HSA and HSE treatmentsR480^2^Fournioux,JC^Bessis,R^1993^1^Use of carbon-dioxide enrichment to obtain adult morphology of grapevine invitro^177^33R^1^51-57^^^^^Apr^^^^^3779s the combination of moderate shading and CO2 enrichment might provide a more productive option RA^3778^A procedure has been developed for in vitro propagation of Vitis vinifera 'Pinot noir' from lateral-bud cuttings unRder high CO2 concentration (1200 mumol mol-1). Because of inhibition of rooting by CO2, this procedure requires a rooting Rpre-culture of explants on medium with sucrose before the CO2- enriched culture on sucrose-free medium. Shoot growth was eRnhanced by CO2 enrichment as a result of both a higher rate of leaf production and greater internode elongation. Leaf expaRnsion and tendril growth were promoted and better rooting was obtained. The more significant effect of CO2 enrichment was Rto promote adult morphology with, in particular, the tendril pattern. Thus, for the first time, grapevine plants have beenR produced in vitro without typical juvenile characteristics. CO2 enrichment appears to be an interesting process to improvRe the in vitro propagation of grapevines.on future regional economies. The methodology also provides for systematic studyR481^4^Grant,WJR^Fan,HM^Downton,WJS^Loveys,BR^1992^1^Effects of co2 enrichment on the physiology and propagation of 2 austrRalian ornamental plants, chamelaucium-uncinatum (schauer) X chamelaucium-floriferum (ms) and correa- schlechtendalii (behrR)^165^52^4^337-342^^^^^Dec^^^^^3781 In this final paper we consider whether synergistic effects among sectoral impacts anSA^3780^Root formation on both Chamelaucium and Correa cuttings maintained at high humidity in an enclosed fog tunnel was sSignificantly enhanced when ambient CO2 was increased from 350 to 800 mubar. CO2 enrichment resulted in decreased transpiraStion and increased water potential of cuttings implying an effect of CO2 on stomatal conductance. CO2 enrichment led to inScreased starch levels in cuttings of both species probably by raising the intercellular partial pressure of CO2. IncreasedS  starch content with CO2 enrichment was able to account for 70-90% of the dry weight increase in Correa, but only for 10-3S"0% of the dry weight increase in Chamelaucium. It is suggested that the stimulation of rooting associated with CO2 enrichmS+ent probably derives from the improved water relations of the cuttings rather than from increased carbohydrate levels., AS-482^3^Hendrey,GR^Lewin,KF^Nagy,J^1993^1^Free air carbon-dioxide enrichment - development, progress, results^24^104^^17-31^S:^^^^Jan^^^^^3783 RES UNIT, LONDON E15 4LZ, ENGLAND. ID CO2 ENRICHMENT; GROWTH; ECOSYSTEMS; SOIL; POPULATIONS; NUTRITION; S<A^3782^Credible predictions of climate change depend in part on predictions of future CO2 concentrations in the atmosphereSN. Terrestrial plants are a large sink for atmospheric CO2 and the sink rate is influenced by the atmospheric CO2 concentraSPtion. Reliable field experiments are needed to evaluate how terrestrial plants will adjust to increasing CO2 and thereby iSenfluence the rate of change of atmospheric CO2. Brookhaven National Laboratory (BNL) has developed a unique Free-Air CO2 ESgnrichment (FACE) system for a cooperative research program sponsored by the U.S. Department of Energy and U.S. Department Stof Agriculture, currently operating as the FACE User Facility at the Maricopa Agricultural Center (MAC) of the University Svof Arizona. The BNL FACE system is a tool for studying the effects of CO2 enrichment on vegetation and natural ecosystems,S and the exchange of carbon between the biosphere and the atmosphere, in open-air settings without any containment. The FASCE system provides stable control of CO2 at 550 ppm +/- 10%, based on 1- min averages, over 90% of the time. In 1990, thisS 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 Sseasons of enrichment with cotton (Gossypium hirsutum) as the test plant, enrichment to 550 ppm CO2 resulted in significanSt increases in photosynthesis and biomass of leaves, stems and roots, reduced evapotranspiration, and changes in root morpShology. In addition, soil respiration increased and evapotranspiration decreased.RCES FUTURE INC, WASHINGTON, DC 20036. BS483^3^Lord,D^Morissette,S^Allaire,J^1993^1^Influence of light-intensity, nocturnal air-temperature and carbon-dioxide leveSls on greenhouse black spruce seedlings (picea-marianna)^155^23^1^101-110^^^^^Jan^^^^^3785N; CO2 AB The climate of the 19SA^3784^Growth of containerized black spruce seedlings grown in greenhouses was studied in relation to factors known to infSluence plant growth. Artificial light intensity (3.80 and 72.04 mumol.m-2.s-1) and night air temperature (5, 10, 12.5, 15,S and 20-degrees-C) were considered in a first experiment and artificial light intensity (4.24 and 59.57 mumol.m-2.s-1) andS CO2 air concentration (ambient and 1000 muL.L-1) in a second one. Higher light intensity and CO2 enrichment increased dryS biomass of seedlings as well as growth in height and stem diameter. Both factors similarly enhanced the last two parameteSrs since height/diameter ratios showed little variation among treatments. Reducing night air temperature down to 10- degreSes-C did not significantly influence height growth nor biomass increase when high intensity light was provided. Lower lighSt intensity raised the threshold to 12.5-degrees-C. Shoot height, diameter, and dry biomass as well as the number of brancShes and buds per millimeter were strongly reduced by a 5- degrees-C night air temperature. High intensity light enhanced gSrowth of containerized black spruce seedlings more than CO2 enrichment or a 5-degrees-C night air temperature. When used sSimultaneously, these growth enhancing factors had a synergistic effect during most of the treatment period; thereafter, thSe effect became partially additive. The relative growth rate peaked at the onset of exponential shoot growth and decreasedS after this point. However, the enhancing factors were still efficient since absolute growth differences between seedlingsS grown under the most-favorable conditions and controls kept increasing, The faster growing pace imposed by these growth eSnhancing conditions during the treatment period was maintained over the entire first growing season. OF CARBON FIXATION IS484^3^Pospisilova,J^Solarova,J^Catsky,J^1992^1^Photosynthetic responses to stresses during invitro cultivation^79^26^1^3-1S8^^^^^^^^^^3787IOCHEM, LICHTENBERG STR 4, W-8046 GARCHING, GERMANY. UNIV ULM, ANGEW MIKROBIOL ABT, W-7900 ULM, GERMANY. UTA^3786^Present knowledge of photosynthesis, biomass production and water relations of plantlets cultivated in vitro and thT eir responses to environmental conditions is reviewed. Acclimation of plantlets, firstly to very special in vitro conditioTns and secondly after transplantating to ex vitro conditions, is considered. Low irradiance and CO2 concentration inside cTultivation vessels restrict photosynthetic rate and accumulation of biomass by plantlets in situ. Nevertheless the photosyTnthetic apparatus is often fully developed. Therefore net photosynthetic rate and hence biomass accumulation can increase Timmediately after artificial increase in CO2 concentration inside the vessels (this enables autotrophic cultivation of plaTntlets as one of important future technologies) or after transplanting to glasshouse or field. On the other hand, under veT!ry high humidity and low irradiance in vitro, efficient regulation of gas exchange does not operate. The development of fuT,nctional stomata and cuticle requires some weeks of acclimation to natural conditions.coupling patterns suggest a novel cT. 485^2^Stulen,I^Denhertog,J^1993^1^Root-growth and functioning under atmospheric co2 enrichment^24^104^^99-115^^^^^Jan^^^^^T9bacterial production (measured in anoxic, in vitro incubations) which could account for only 50% of the whole-core flux. PT;resumably the remainder was CO2 and CH4 stored in the peat cores at the time of collection. Overall, the results suggest tTHhat a temperate climate imposed on northern peatlands could mobilize stored carbon and increase CO2 and CH4 efflux into thTJe troposphere. Studies involving peat cores must insure that CO2 and CH4 dynamics measured in vitro mimic those in situ.OTY505^3^Gong,H^Nilsen,S^Allen,JF^1993^1^Photoinhibition of photosynthesis invivo - involvement of multiple sites in a photodT[amage process under co2-free and o2- free conditions^235^1142^1-2^115-122^^^^^5 Apr^^^^^3829121, BATIMENT 362, F-91405 OTgA^3788^This paper examines the extent to which atmospheric CO2 enrichment may influence growth of plant roots and functionTi in terms of uptake of water and nutrients, and carbon allocation towards symbionts. It is concluded that changes in dry mTwatter allocation greatly depend on the experimental conditions during the experiment, the growth phase of the plant, and iTyts morphological characteristics. Under non-limiting conditions of water and nutrients for growth, dry matter partitioningT to the root is not changed by CO2 enrichment. The increase in root/shoot ratio, frequently observed under limiting conditTions of water and/or nutrients, enables the plant to explore a greater soil volume, and hence acquire more water and nutriTents. However, more data on changes in dry matter allocation within the root due to atmospheric CO2 are needed. It is concT luded that nitrogen fixation is favored by CO2 enrichment since nodule mass is increased, concomitant with an increase in T root length. The papers available so far on the influence of CO2 enrichment on mycorrhizal functioning suggest that carbonT allocation to the roots might be increased, but also here more experiments are needed. All additional dry matter was allT3789he roots in sweet chestnut, while it was partitioned equally amongst all organs of the beech seedling. 5. The reactioT 486^1^Vugts,HF^1993^1^The need for micrometeorological research of the response of the energy-balance of vegetated surfaceTs to co2 enrichment^24^104^^321-328^^^^^Jan^^^^^3791 PT J AU FIROUZBAKHT, ML SCHLYER, DJ GATLEY, SJ WOLF, AP TI A CRYOGETA^3790^A Penman-Monteith equation has been used to evaluate a change in canopy resistance on the evapotranspiration of a sTavannah and agricultural area in Botswana. After a short introduction, some problems concerning the K-theory or 'first ordTer closure' are indicated when one uses it for transport modelling within and above a canopy. The Penman-Monteith equationT was used to calculate the canopy resistance for a savannah vegetation and sorghum under the same environmental conditionsT. After that, by changing the stomatal resistance due to an increase of the CO2 content, the change in the evapotranspiratTion was estimated. Finally some recommendations for future research are given and an outline of a proposed FACE experimentT is presented.ecovered by warming the target and cryogenically transferring the gas into a storage bulb. After transfer, T487^4^Wheeler,RM^Corey,KA^Sager,JC^Knott,WM^1993^1^Gas-exchange characteristics of wheat stands grown in a closed, controlTled environment^164^33^1^161-168^^^^^Jan-Feb^^^^^3793ography and the reactivity has been verified by use in the synthesisTA^3792^Information on gas exchange of crop stands grown in controlled environments is limited, but is vital for assessing Tthe use of crops for human life-support in closed habitats envisioned for space. Two studies were conducted to measure gasU exchange of wheat stands (Triticum aestivum L. cv. Yecora Rojo) grown from planting to maturity in a large (20 m2 canopy Uarea), closed growth chamber. Daily rates of dark-period respiration and net photosynthesis of the stand were calculated fUrom rates of CO2 build-up during dark cycles and subsequent CO2 drawdown in the light (i.e., a closed-system approach). LiU ghting was provided as a 20-h photoperiod by high-pressure sodium lamps, with canopy-level photosynthetic photon flux densU"ity (PPFD) ranging from 500 to 800 mumol m-2 s-1 as canopy height increased. Net photosynthesis rates peaked near 27 mumolU9 CO2 m-2 s-1 at 25 d after planting, which corresponded closely with stand closure, and then declined slowly with age. SimU; ilarly, dark-period respiration rates peaked near 14 mumol CO2 m-2 s-1 at 25 d and then gradually declined with age. RespoUN!nses to short-term changes in irradiance after canopy closure indicated the stand light compensation point for photosyntheUP"sis to be near 200 mumol m-2 s-1 PPFD. Tests in which CO2 concentration was raised to almost-equal-to 2000 mumol mol-1 andUj# then allowed to draw down to a compensation point showed that net photosynthesis was nearly saturated at > 1000 mumol molUm$-1; below almost-equal-to 500 mumol mol-1, net photosynthesis rates dropped sharply with decreasing CO2. The CO2 compensatU%ion point for photosynthesis occurred near 50 mumol mol-1. Short-term (24 h) temperature tests showed net photosynthesis aU&t 20-degrees-C greater-than- or-equal-to 16-degrees-C > 24-degrees-C, while dark-period respiration at 24-degrees-C > 20-dU'egrees-C > 16-degrees-C. Rates of stand evapotranspiration peaked near Day 25 and remained relatively constant until aboutU( Day 75, after which rates declined slowly. Results from these tests will be used to model the use of plants for CO2 removU)al, O2 production, and water evaporation for controlled ecological life support systems proposed for extraterrestrial enviUronments.23-631 PG 9 JI Plant Cell Environ. PY 1993 PD AUG VL 16 IS 6 GA LW930 RP FLANAGAN LB J9 PLANT CELL ENVIRON ER PU+488^1^Tate,KR^1992^1^Assessment, based on a climosequence of soils in tussock grasslands, of soil carbon storage and releaUse in response to global warming^227^43^4^697-707^^^^^Dec^^^^^3795AB The capacity to supply both instream and offstream wU-A^3794^A soil climosequence in tussock grasslands in South Island, New Zealand, encompassing climates ranging from cold toU. warm temperate provided a spatial analogue of climate change for investigating the effects of global warming on soil C coU/ntents and turnover. Mean annual temperature (T) and annual precipitation (P) ranged from 2 to 10-degrees-C, and 350 to 50U000 mm, respectively. Soil C contents were curvilinearly related to T/P across the sequence (r = -0.95, significant at P < U10.01), indicating that east of the Southern Alps, increased decomposition of organic matter with global warming would provV2ide a positive feedback to further increase atmospheric CO2. This decrease in New Zealand's soil C, estimated to be up to V310% of the current content for a global temperature rise of 0.03 K a-1 to 2050, could contribute about 0.5 x 10(15) g C toV4 the atmosphere over the next 60 years. These conclusions were generally supported by changes in soil C turnover estimatedV"5 from 'bomb' C-14 enrichment. The unexpectedly slow turnover found for two soils was explained by a 'memory' effect from tV$6he former southern beech forest that grew on these soils in prehistoric times. Accumulation of Al-humus under the forest mV8ay be responsible for the slow C turnover observed.ll have less water in the year 2030 than it does today because groundwV:8489^7^Abarzua,S^Altenburger,R^Callies,R^Grimme,LH^Mayer,A^Leibfritz,D^Schiewer,U^1993^1^Ammonium rhythm in cultures of theVK cyanobacterium microcystis- firma^37^89^3^659-663^^^^^Nov^^^^^3797, and fish and wildlife habitat would be most adverselVM:A^3796^Over a period of several days, rhythmic changes in extracellular NH4+ concentration take place in cultures of the cVd;yanobacterium Microcystis firma (Breb et Lenorm.) Schmidle, strain Gromov/St. Petersb. 398, under conditions of restrictedVf< CO2 supply and light/dark alternation. The changes are enhanced by nitrate supply. Among the various processes generatingVx= intracellular NH4+ (NH4+ uptake, NO3- reduction, protein and amino acid degradation, photorespiration), NO3- reduction apVz>pears as the one most important. This can be concluded from experiments with and without nitrate and/or ammonium in the meV?dium. In the presence of saturating CO2, continuous light, or continuous darkness, rhythmic NH4+ oscillations are not induV@ced. Studies of the incorporation of NH4+ nitrogen by in vivo N-15-NMR show that if CO2 is supplied, N-15 is accumulated iVAn several components with the following time course: in the first hour in Gln (delta), in the second hour in the alpha- amVBino groups of most nonbranched amino acids, in the third hour in gamma-aminobutyric acid (GABA), Orn (delta) and Lys (epsiVClon), and in the sixth hour in Ala. Carbon limitation, however, results in accumulation of label in the amide nitrogen of Vglutamine only.se in deltaC-13 values; however, the relative content of plant products, especially of the soluble polar cVE490^6^Brailsford,RW^Voesenek,LACJ^Blom,CWPM^Smith,AR^Hall,MA^Jackson,MB^1993^1^Enhanced ethylene production by primary rooVts of zea-mays L in response to sub-ambient partial pressures of oxygen^9^16^9^1071-1080^^^^^Dec^^^^^3799, BasidiomycetesVGA^3798^Ethylene production by primary roots of 72-h-old intact seedlings of Zea mays L. cv. LG11 was studied under ambientVH and sub-ambient oxygen partial pressures (pO(2)) using a gas how- through system linked to a photoacoustic laser detectorVI. Despite precautions to minimize physical perturbation to seedlings while setting-up, ethylene production in air was fastVJer during the first 6h than later, in association with a small temporary swelling of the roots. When roots were switched fVKrom air (20.8kPa O-2) to 3 or 5kPa O-2 after 6h, ethylene production increased within 2-3h. When, the roots were returned VLto air 16h later, ethylene production decreased within 2-3h. The presence of 1OkPa CO2 did not interfere with the effect oVMf 3kPa O-2. Transferring roots from air to 12.5kPa did not change ethylene production, while a reduction to 1kPa O-2 inducVNed a small increase. The extra ethylene formed in 3 and 5kPa O-2 was associated with plagiotropism, swelling, root hair prPOoduction, and after 72h, increased amounts of intercellular space (aerenchyma) in the root cortex. Root extension was alsoWP slowed down, but the pattern of response to oxygen shortage did not always match that of ethylene production. On return tWQo air, subsequent growth patterns became normal within a few hours. In the complete absence of oxygen, no ethylene productWion was detected, even when anaerobic roots were returned to air after 16h.trogen, while elevated CO2 decreased leaf costW491^2^Denelzen,MGJ^Rotmans,J^1993^1^Modeling climate related feedback processes^228^28^9^2095-2151^^^^^^^^^^3801 reflectiWTA^3800^Feedback mechanisms play a crucial role in the climate system, amplifying or dampening the climate response to enhaW&Unced concentrations of greenhouse gases from anthropogenic perturbations. Many of these feedbacks are known, but most of tW)Vhem only potentially. This article evaluates the role of a number of these feedback processes within the climate system. IW7Wn order to assess their impact, the feedbacks which at present can be quantified reasonably are built into the Integrated W9XModel to Assess the Greenhouse Effect (IMAGE). Unlike previous studies, this study describes the scenario- and time-dependWHYent role of biogeochemical feedbacks. A number of simulation experiments are performed with IMAGE to project climate changWJZes. Besides estimates of their absolute importance, the relative importance of individual biogeochemical feedbacks is consWX[idered by calculating the gain for each feedback process. This study focuses on feedback processes in the carbon cycle andWZ\ the methane (semi-) cycle. Modeled feedbacks are then used to balance the past and present carbon budget. This results inWj] substantially lower projections for atmospheric carbon dioxide than the Intergovernmental Panel on Climate Change (IPCC) Wl^estimates. The difference is approximately 18% from the 1990 level for the IPCC ''Business-as-Usual'' scenario. FurthermorW|_e, the IPCC's ''best guess'' value of the CO2 concentration in the year 2100 falls outside the uncertainty range estimatedW}` with our balanced modeling approach. For the IPCC ''Business-as- Usual'' scenario, the calculated total gain of the feedbWaacks within the carbon cycle appears to be negative, a result of the dominant role of the fertilization feedback. This stuWbdy also shows that if temperature feedbacks on methane emissions from wetlands, rice paddies, and hydrates do materialize,Wc methane concentrations might be increased by 30% by 2100. The total effect of the methane feedbacks and the carbon dioxidWde feedbacks modeled can be expressed in the carbon dioxide- equivalent concentrations. Our simulated CO2-equivalent concenWtrations are lower than the IPCC estimates.cence or abscission was detected, suggesting that the seasonal duration of effWf492^6^Gao,K^Aruga,Y^Asada,K^Ishihara,T^Akano,T^Kiyohara,M^1993^1^Calcification in the articulated coralline alga corallinaW- pilulifera, with special reference to the effect of elevated co2 concentration^229^117^1^129-132^^^^^Sep^^^^^3803 a resWhA^3802^Calcification in Corallina pilulifera Postels et Ruprecht displayed diurnal variations in aerated (350 ppm CO2) culWiture media, with faster rates during the light than during the dark period. Addition of CO2 (air + 1250 ppm) inhibited calWjcification. This was attributable to the decreased pH resulting from CO2 addition. Both photosynthesis and calcification wWere enhanced in seawater, with elevated dissolved inorganic carbon concentrations at a constant pH of 8.2.GANIC LAKE-SEDIWl493^5^Ojima,DS^Parton,WJ^Schimel,DS^Scurlock,JMO^Kittel,TGF^1993^1^Modeling the effects of climatic and co2 changes on graWssland storage of soil-C^94^70^1-4^643-657^^^^^Oct^^^^^3805SE AB Values of deltaC-13 obtained from conventional bulk sediWnA^3804^We present results from analyses of the sensitivity of global grassland ecosystems to modified climate and atmospheWoric CO2 levels. We assess 31 grassland sites from around the world under two different General Circulation Models (GCM) doWpuble CO2 climates. These grasslands are representative of mostly naturally occurring ecosystems, however, in many regions Wqof the world, grasslands have been greatly modified by recent land use changes. In this paper we focus on the ecosystem dyXrnamics of natural grasslands. The climate change results indicate that simulated soil C losses occur in all but one grasslX sand ecoregion, ranging from 0 to 14% of current soil C levels for the surface 20 cm. The Eurasian grasslands lost the greaXttest amount of soil C (approximately 1200 g C m-2) and the other temperate grasslands losses ranged froM 0 to 1000 g C m-2Xu, averaging approximately 350 g C m-2. The tropical grasslands and savannas lost the least amount of soil C per unit area X8vranging from no change to 300 g C m-2 losses, averaging approximately 70 g C m-2. plant production varies according to modX:wifications in rainfall under the altered climate and to altered nitrogen mineralization rates. The two GCM's differed in pXHxredictions of rainfall with a doubling of CO2, and these differences are reflected in plant production. Soil decompositionXJy rates responded most predictably to changes in temperature. Direct CO2 enhancement effects on decomposition and plant proXXduction tended to reduce the net impact of climate alterations alone.CHLOROETHENE TO GROWTH SO APPLIED AND ENVIRONMENTAL XZ494^2^Woods,J^Barkmann,W^1993^1^The plankton multiplier - positive feedback in the greenhouse^230^15^9^1053-1074^^^^^Sep^^Xe|A^3806^The plankton multiplier is a positive feedback mechanism linking the greenhouse effect and biological pump (Woods,JXf}.D., Royal Commission on Environmental Pollution, 1990). As pollution increases the atmospheric concentration of carbon diXv~oxide, the enhanced greenhouse effect induces radiative forcing of the ocean, which diminishes the depth of winter convectXxion, reducing the annual resupply of nutrients to the euphotic zone and therefore the annual primary production. That weakXens the biological pump, which contributes to oceanic uptake of CO2. As the ocean takes up less CO2, more remains in the aXtmosphere, accelerating the rise in radiative forcing. We have used a mathematical model of the upper ocean ecosystem, basXed on the Lagrangian Ensemble method, to estimate the sensitivity of the biological pump to radiative forcing, which lies Xat the heart of the plankton multiplier. We conclude that increasing radiative forcing by 5 W m-2 (equivalent to doubling Xatmospheric CO2) reduces the deep flux of particulate carbon by 10%. That sensitivity is sufficient to produce significantX positive feedback in the greenhouse. It means that the plankton multiplier will increase the rate of climate change in thXe 21st century. It also suggests that the plankton multiplier is the mechanism linking the Milankovich effect to the enhanXced greenhouse effect that produces global warming at the end of ice ages.hat all electrons derived from H-2 or formate cX^^^3807e recovered in dechlorination products and biomass. Exponential growth could be achieved only in gently shaken culX495^2^Darrigo,RD^Jacoby,GC^1993^1^Tree growth-climate relationships at the northern boreal forest tree line of north-ameriXca - evaluation of potential response to increasing carbon-dioxide^137^7^3^525-535^^^^^Sep^^^^^3809nder the growth conditXA^3808^Tree growth at the northern limit of the range of boreal forests is primarily limited by temperature-related factorXs. Thus the position of this range limit, and the growth rates of trees along the northern forest border, may undergo signXificant change if predictions of enhanced greenhouse warming at northern latitudes are realized. In this paper we evaluateX tree ring width and maximum latewood density chronologies of white spruce for three temperature-sensitive tree line sitesX in northern North America: in the Brooks Range, Alaska, the Franklin Mountains, Northwest Territories, and Churchill, ManY itoba. The ring width data, which more strongly integrate low-frequency temperature trends than the density series, show oY verall enhanced growth and inferred warming during the period of anthropogenic increase in greenhouse gases. The recent grYowth at these sites equals or exceeds that which has occurred during earlier centuries of more clearly natural climate varYiability. When the ring width and density variations are estimated using temperature and precipitation data in principal cY(omponents regession analysis, no substantial residual trends are detected which might require CO2 or other nutrient fertilY+ization as an additional explanation for recent growth changes.t productivity differential to the present day. This tremeY7496^5^Hyodo,H^Hashimoto,C^Morozumi,S^Hu,WZ^Tanaka,K^1993^1^Characterization and induction of the activity of 1- aminocycloY9propane-1-carboxylate oxidase in the wounded mesocarp tissue of cucurbita-maxima^231^34^5^667-671^^^^^Jul^^^^^3811AustralYCA^3810^1-Aminocyclopropane-1-carboxylate (ACC) oxidase (ethylene- forming enzyme) was isolated from wounded mesocarp tissuYEe of Cucurbita maxima (winter squash) fruit, and its enzymatic properties were investigated. The enzyme required Fe2+ and YVascorbate for its activity as well as ACC and O2 as substrates. The in vitro enzyme activity was enhanced by CO2. The appaYXrent K(m) value for ACC was 175 muM under atmospheric conditions. The enzyme activity was inhibited by sulfhydryl inhibitoY_rs and divalent cations such as Co2+, Cu2+, and Zn2+. ACC oxidase activity was induced at a rapid rate by wounding in paraYallel with an increase in the rate of ethylene production. The exposure of excised discs of mesocarp to 2,5-norbornadiene (YqNBD), an inhibitor of ethylene action, strongly suppressed induction of the enzyme, and the application of ethylene signifYsicantly accelerated the induction of the activity of ACC oxidase in the wounded mesocarp tissue. These results suggests thY}at endogenous ethylene produced in response to wounding may function in promoting the induction of ACC oxidase.REASE; PRIY497^2^Kaufman,YJ^Chou,MD^1993^1^Model simulations of the competing climatic effects of so2 and co2^126^6^7^1241-1252^^^^^JYul^^^^^3813nd 1050 ppm) on phytomass, soluble sugars, leaf nitrogen and secondary chemicals of three Salix myrsinifolia cYA^3812^Sulfur dioxide-derived cloud condensation nuclei are expected to enhance the planetary albedo, thereby cooling the Yplanet. This effect might counteract the global warming expected from enhanced greenhouse gases. A detailed treatment of tYhe relationship between fossil fuel burning and the SO2 effect on cloud albedo is implemented in a two-dimensional model fYor assessing the climate impact. Although there are large gaps in our knowledge of the atmospheric sources and sinks of suYlfate aerosol, it is possible to reach some general conclusions. Using a conservative approach, results show that the coolYing induced by the SO2 emission can presently counteract 50% of the CO2 greenhouse warming. Since 1980, a strong warming tYrend has been predicted by the model, 0.15-degrees-C, during the 1980- 1990 period alone. The model predicts that by the yYear 2060 the SO2 cooling reduces climate warming by 0.5-degrees-C or 25% for the Intergovernmental Panel on Climate ChangeY (IPCC) business as usual (BAU) scenario and 0.2-degrees-C or 20% for scenario D (for a slow pace of fossil fuel burning).Y The hypothesis is examined that the different responses between the Northern Hemisphere (NH) and the Southern Hemisphere Y(SH) can be used to validate the presence of the SO2-induced cooling. Despite the fact that most of the SO2-induced coolinYg takes place in the Northern Hemispheric continents, the model-predicted difference in the temperature response between tYhe 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 comYbined effect of the much faster response of the continents than the oceans and of the larger forcing due to CO2 than due tYo the SO2. The climatic response to a complete filtering of SO2 from the emission products in order to reduce acid rain isY also examined. The result is a warming surge of 0.4-degrees-C in the first few years after the elimination of the SO2 emiYssion.ion of toluene with methane have been compared for superbasic catalysts prepared by promoting MgO, CaO, SrO or BaO Z498^4^Lasceve,G^Gautier,H^Jappe,J^Vavasseur,A^1993^1^Modulation of the blue-light response of stomata of commelina- communZis by co2^37^88^3^453-459^^^^^Jul^^^^^3815a+ + 5 mol- % (Cs+) /CaO gave a toluene conversion as high as 45.0 mol-% and a ZA^3814^Effects of CO2 on stomatal movements of Commelina communis L. were studied with plants, epidermal strips and guard Z#cell protoplasts. With plants, the stomatal response induced by a blue light pulse was studied for different ambient CO2 cZ%oncentration ranging from CO2-deprived air to 100 Pa in darkness or under red light. It was observed that the blue light rZ0esponse could be obtained not only under a red light background but also in darkness and CO2-free air, the two responses bZ2eing quite similar. With epidermal strips, the effect of CO2 on ferricyanide reductase activity at the guard cell plasmaleZAmma was studied by transmission electron microscopy. In the presence of ferric ions, reduced ferricyanide gives an electroZCn dense precipitate of Prussian Blue. In darkness and air, no precipitate was observed. In darkness and CO2-free air as weZ[ll as under light and normal air, a precipitate was found along the plasmalemma of the guard cells, indicating a ferricyanZ]ide reductase activity. With guard cell protoplasts suspended in a medium either in equilibrium with air or in a CO2-free Zfmedium the H+ extrusion induced by a blue light pulse added to a red light background was measured. A low CO2 content was Zgobtained by adding photosynthetic algae to the suspension of guard cell protoplasts. In a CO2-free medium the rate of H+ eZnxtrusion was enhanced. The results are discussed on the basis of a possible competition for reducing power between CO2 fixZpation and a putative blue light dependent redox chain located on the plasma membrane.N SN 0269-7491 C1 UNIV MASSACHUSETTSZ499^3^Tremblin,G^Jolivet,P^Coudret,A^1993^1^Light quality effects on subsequent dark 14co2-fixation in fucus-serratus^232^Z261^^471-475^^^^^18 Jun^^^^^3817URY; WINTER CONDITIONS; VEGETABLE PLANTS; GROWTH-RESPONSE; CARBON-DIOXIDE AB The use of RZA^3816^The intensity and fate Of (CO2)-C-14-fixation in the dark are studied on Fucus serratus apices previously maintaineZd under low illumination conditions using white, blue, red or yellow isoquantic lights. In the case of a 180 s pulse, lighZt quality affected dark carbon-fixation, with a higher level of incorporation into ethanol-soluble organic matter in the cZase of yellow light cultivated apices. After a 30 s pulse C-14 was mainly fixed into glycerate and aspartate-malate pools Zwhatever the pre-treatment light conditions, with a higher level into glycerate when apices were pre-illuminated with blueZ or yellow light. After a 180 s pulse, C-14 was mainly transferred into amino acids (glutamate and alanine) at the expenseZ of aspartate and malate in red and yellow pre-illumination conditions, as found in the white light reference experiment, Zand only at the expense of glycerate in blue light pre-illumination conditions. The metabolic pathway of glycerate formatiZon, principally enhanced by blue light preillumination, remains unexplained under these non-photosynthetic conditions. ResZults are discussed with reference to CO2-fixation via phosphoenolpyruvate carboxykinase and light quality effects on its iZn vitro activity.particularly the high variability of injury and growth responses, are discussed along with possible soluZ500^2^Whiting,GJ^Chanton,JP^1993^1^Primary production control of methane emission from wetlands^36^364^6440^794-795^^^^^26Z Aug^^^^^3819ed. BP 107-138 PG 32 JI Environ. Pollut. PY 1993 VL 82 IS 2 GA LV929 J9 ENVIRON POLLUT ER PT J AU KUMAR, MDZA^3818^WETLANDS, both natural and agricultural, contribute an estimated 40 to 50% of the total methane emitted to the atmo[sphere each year. Recent efforts in atmospheric modelling1 and attempts to constrain CH4 source strengths2 have indicated [the need to delineate the processes responsible for the large variations in emission rates found within and across wetland[ types. Numerous biogeochemical factors are known to affect the activity of methanogenic bacteria3,4 and although there ha[s been some success in relating water level5-7 and temperature8,9 to CH4 emissions within particular systems, these variab['les are insufficient for predicting emissions across a variety of wetlands2,10. From simultaneous measurements of CO2 and [)CH4 exchange in wetlands extending from subarctic peatlands to subtropical marshes, we report here a positive correlation [7between CH4 emission and net ecosystem production and suggest that net ecosystem production is a master variable, integrat[9ing many factors which control CH4 emission in vegetated wetlands. We find that about 3 per cent of the daily net ecosyste[Gm production is emitted back to the atmosphere as CH4. With projected stimulation of primary production and soil microbial[I activity in wetlands associated with elevated atmospheric CO2 concentrations11, we envisage the potential for increasing [TCH4 emissions from inundated wetlands, further enhancing the greenhouse effect.rove precision and sensitivity of stable i[V501^3^Dixon,RK^Winjum,JK^Schroeder,PE^1993^1^Conservation and sequestration of carbon - the potential of forest and agrofo[qrest management-practices^233^3^2^159-173^^^^^Jun^^^^^3821e analyte in the chemical reaction interface in the presence of[sA^3820^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 o[f carbon in the terrestrial biosphere. A biological and economic analysis of forest establishment and management options f[rom 94 nations revealed that forestation, agroforestry, and silviculture could be employed to conserve and sequester one P[etagram (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.he state-of-the-art, which is a gas chromatograph coupled to a chemical combustor[502^1^Michaels,PJ^1993^1^Benign greenhouse^234^9^2^222-233^^^^^Spring^^^^^3823Spectrom. PY 1993 PD SEP VL 22 IS 9 GA LV94[A^3822^Several lines of evidence are emerging that suggest that the ''popular vision'' of global warming-major agricultura[l damage, disastrous sea-level rise, and ecological disequilibrium-is flawed. The popular vision is driven primarily by th[e prospect of enhanced daytime warming, particularly in summer What has been observed is a warming that is beneath the pro[jections that support the popular vision, and a warming that has occurred virtually all during the night in the Northern H[emisphere. In the Southern Hemisphere there is also evidence of disproportionate night warming. Several sources of data in[dicate that this night warming has been caused by an increase in cloudiness that could be a consequence of the greenhouse [enhancement itself. The results of the night warming-longer growing seasons, little change in moisture stress, and a possi[ble increase in ice volume-are opposite to the popular vision of climatic change., but net C accumulation may not necessa[503^2^Rosenzweig,C^Hillel,D^1993^1^Agriculture in a greenhouse world^234^9^2^208-221^^^^^Spring^^^^^3825h industrializati[A^3824^While agriculture in some temperate regions may benefit from global climate change, tropical and subtropical region\ s may suffer. Even where potential production will improve, the required adjustments may disrupt ecosystems and land-use p\ atterns. Agricultural zones will shift toward high latitudes, while heat stress and increased droughts will reduce product\ivity in lower latitudes. On the positive side, higher CO2 may enhance photosynthesis and water-use efficiency. Future haz\!ards include sea-level rise, insect infestation, and greater evaporation losses. Some agricultural activities augment the \/greenhouse effect by releasing CO2, CH4, and N2O. Understanding the potential impacts of climate change is a prerequisite \1to developing societal responses.been shown to increase with soil temperature. If plant growth increases with increased N\<504^3^Yavitt,JB^Wieder,RK^Lang,GE^1993^1^Co2 and ch4 dynamics of a sphagnum-dominated peatland in west- virginia^137^7^2^2\>59-274^^^^^Jun^^^^^3827in a net increase in CO2 efflux from forests, then a positive feedback will follow. A 2 to 4-degre\KA^3826^Climatic change could bring about net release of carbon dioxide (CO2) and/or methane (CH4) from the deep peat depos\Mits in northern peatlands into the atmosphere. To provide insight into this hypothesis, we studied net flux of CO2 and CH4\\ in Big Run Bog, West Virginia, which has a temperate climate, making it an analog to evaluate climatic change imposed on \_more northern counterparts. Net CO2 flux ranged from -564 to 300 mg C m-2 hr- 1. Measurements made during the nighttime sh\oowed that net CO2 flux increased exponentially with increasing air temperature, whereas CO2 sequestration increased with i\qncreasing air temperature for daytime measurements. Net CH4 flux ranged from -2.3 to 70 mg C m-2 hr-1, showing no consiste\nt relationship to temperature or water table level. Net efflux for both CO2 and CH4 was tenfold higher from peat cores in\cubated in a greenhouse compared to field measurements. Even cores drained and allowed to dry for 8 days showed moderately\ high flux for both CO2 and CH4. The enhanced efflux seemed to be due to altered hydrology rather than increased rates of \A^3828^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 inactiv\ation 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 co\uld 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 o\f CO2.LDFTMS) ID PROPYLENE OXIDATION; BISMUTH MOLYBDATE; LI/MGO CATALYST; OXIDE AB Oxygen pathways for CH4 partial oxidat]506^3^Harrison,K^Broecker,W^Bonani,G^1993^1^A strategy for estimating the impact of co2 fertilization on soil carbon stora]ge^137^7^1^69-80^^^^^Mar^^^^^3831 initial source of oxygen in the products is masked by rapid and extensive oxygen exchan]A^3830^As soils are a likely candidate for the so-called missing carbon sink, we explore the possible impact of CO2 fertil]ization on the global humus inventory. For any given greening-induced enhancement of plant growth, the increase in soil ca]!rbon inventory will depend on the spectrum of turnover times with respect to oxidation. Here we develop estimates of carbo]2n turnover rates based on soil radiocarbon measurements.LYSIS LETT ER PT J AU MCGUIRE, AD JOYCE, LA KICKLIGHTER, DW MELI]4507^3^Nunes,MA^Ramalho,JDC^Dias,MA^1993^1^Effect of nitrogen supply on the photosynthetic performance of leaves from coffe]@e plants exposed to bright light^78^44^262^893-899^^^^^May^^^^^3833SN 0165-0009 C1 MARINE BIOL LAB, CTR ECOSYST, WOODS HO]BA^3832^Although Coffea arabica L. grows naturally in shaded habitats, it can be cultivated under high light intensity, but]N not without severe photoinhibition mainly during the period of transfer from the nursery into the field. The present work]P examines some of the changes in the photosynthetic performance induced by exposure to high light and the possibility of u]bsing enhanced nitrogen levels to overcome photoinhibition. For that purpose, young plants of Coffea arabica L. (cv. Catuai]d) grown in a shaded greenhouse were treated with 0, 1 and 2 mmol of nitrogen and 4 weeks later exposed to full solar irrad]niation, outside. Visible damage due to exposure to full sunlight appeared within 2 d in all plants, resulting in a reduced]p photosynthetic leaf area and drastic shedding of leaves in the unfertilized plants. These effects were considerably less ]yin plants with the highest N dose. After 130 d of exposure, there was 100% mortality in plants receiving no extra nitrogen]{, compared with 30% in the plants treated with 2 mmol nitrogen. Photosynthesis rates, leaf conductance and transpiration p]resented minimum values after 4 d of light stress. Large changes in the photosynthetic capacity (measured at high CO2 conc] entration and high light intensity), quantum efficiency and fluorescence yield (F(v)/F(m)) indicate that net photosynthesi]!s rate in the air had been reduced by both stomatal closure and by changes at the photochemical level. All indicators show] that N-fertilized plants were less affected by photoinhibition.t. In all regions, the response to CO2 is qualitatively d]#508^3^Hanson,JD^Baker,BB^Bourdon,RM^1993^1^Comparison of the effects of different climate change scenarios on rangeland li]vestock production^223^41^4^487-502^^^^^^^^^^3835is, respiration, and soil moisture. Also, it may not be appropriate to e]%A^3834^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 productio]'n system under different climate scenarios. The project required the capability of simulating rangeland livestock producti](on under different ambient CO2 concentrations, temperatures and precipitation patterns. Climate change scenarios were crea])ted from three general circulation models (GCMs): GISS (Goddard Institute for Space Studies model), GFDL (Geophysical Flui]*d Dynamic Laboratory model), and UKMO (United Kingdom Meteorological Office model). Results from the GCMs were used to mod]+ify the climate record for a site in northeastern Colorado. Concomitantly, modifications were made to the SPUR model to he],lp 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 mo].re 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.Prelim^0509^4^Naidu,SL^Sullivan,JH^Teramura,AH^Delucia,EH^1993^1^The effects of ultraviolet-b radiation on photosynthesis of diffe^rent aged needles in field-grown loblolly-pine^13^12^2^151-162^^^^^Mar^^^^^3837 areas. This is composed of pioneer popula^2A^3836^We examined the effect of supplemental UV-B radiation (290-320 nm) on photosynthetic characteristics of different a^$3ged needles of 3-year-old, field-grown loblolly pine (Pinus taeda L.). Needles in four age classes were examined: I, most ^&4recently fully expanded, year 3; II, first flush, year 3; III, final flush, year 2; and IV, oldest needles still present, ^.5year 2. Enhanced UV-B radiation caused a statistically significant decrease (6%) in the ratio of variable to maximum fluor^06escence (F(v)/F(m)) following dark adaptation only in needles from the youngest age class, suggesting transient damage to ^A7photosynthesis. However, no effects of enhanced UV-B radiation on other instantaneous measures of photosynthesis, includin^D8g maximum photosynthesis, apparent quantum yield and dark respiration, were seen for needles of any age. Foliar nitrogen c^R9oncentration was unaffected by UV-B treatment. However, the C- 13/C-12 carbon isotope ratios (deltaC-13-a time integrated ^T:measure of photosynthetic function) of needles in age classes II and IV were 3% (P < 0.01) and 2% (P < 0.05) more negative^`;. respectively, in treated plants than in control plants. Exposure to enhanced UV-B radiation caused a 20% decrease in tot^bss suggest subtle damage to photosynthesis, although overall growth reductions were probably a result of decreased total l^x?eaf surface rather than decreased photosynthetic capacity. Needles of age class IV had lower light- and CO2-saturated maxi^z@mum photosynthetic rates (39%), lower dark respiration (34%), lower light saturation points (37%), lower foliar nitrogen c^Aoncentration (28%), and lower delta-C-13 (14%) values than needles of age class I. Apparent quantum yield and F(v)/F(m) di^Bd not change with needle age. The observed changes in photosynthesis and foliage chemical composition with needle age are ^Cconsistent with previous studies of coniferous trees and may represent adaptations of older needles to shaded conditions w^ithin the canopy.w stomatal conductances observed under elevated CO2 conditions. BP 599-602 PG 4 JI Oecologia PY 1993 PD ^E510^3^Nederhoff,EM^Rijsdijk,AA^Degraaf,R^1992^1^Leaf conductance and rate of crop transpiration of greenhouse grown sweet-^pepper (capsicum-annuum-L) as affected by carbon- dioxide^165^52^4^283-301^^^^^Dec^^^^^3839 INST AGROENVIRONM SCI, TSUKUB^GA^3838^The effects of carbon dioxide concentration (CO2) in the range 300-1100 mumol mol-1 on leaf conductance (g) and rat^He of crop transpiration (E) of sweet pepper (Capsicum annuum L.) were investigated in spring 1990. In two greenhouse compa^Irtments (154 m2) that were simultaneously exposed to different CO2 levels, leaf conductance of the upper leaves was measur^Jed with a steady state diffusion porometer and crop transpiration rates were measured with three weighing lysimeters per g^Kreenhouse compartment. Multiple regression equations, describing the effects of photosynthetic active radiation (PAR), vap^Lour pressure deficit (VPD)-leaf-air, CO2 and optionally leaf temperature on g, were fitted to the measured data. The fitte^Md regression curves demonstrated that 100 mumol mol-1 increase in CO2 reduced g by about 3%, at any level of CO2, VPD and ^NPAR, if VPD and PAR would remain constant. Measured rates of crop transpiration were highly correlated to radiation and we^Ore in reasonable accordance with the Penman-Monteith combination equation. With this equation it was estimated that a 10% ^Pdecrease in g would reduce E by 1.5-3% at high levels of g (high radiation) and by 4-7% at low g (dark weather), at least _Qif VPD would remain constant. In a greenhouse-crop system, however. owing to thermal and hydrologic feedbacks, an increase_R in CO2 leads to a considerable increase in VPD-leaf-air. This enforces the effect of CO2 on g and counteracts the effect _Sof CO2 on E, because the driving force for transpiration is enhanced. Thus, in general the apparent response of g to chang_es in CO2 is far greater than the mentioned percentage, whereas the apparent response of E is relatively small. AB CO2 en_U511^4^Polley,HW^Johnson,HB^Marino,BD^Mayeux,HS^1993^1^Increase in C3 plant water-use efficiency and biomass over glacial t_o present co2 concentrations^36^361^6407^61-64^^^^^7 Jan^^^^^3841es-C, +/- 15 % rel. air humidity, wind speed approximate_ WA^3840^ATMOSPHERIC CO2 concentration was 160 to 200 mumol mol-1 during the Last Glacial Maximum (LGM; about 18,000 years a_)Xgo)1, rose to about 275 mumol mol-1 10,000 years ago2,3, and has increased to about 350 mumol mol-1 since 1800 (ref. 4). H_+Yere we present data indicating that this increase in CO2 has enhanced biospheric carbon fixation and altered species abund_5Zances by increasing the water-use efficiency of biomass production of C3 plants, the bulk of the Earth's vegetation. We gr_7[ew oats (Avena sativa), wild mustard (Brassica kaber) and wheat (Triticum aestivum cv. Seri M82 and Yaqui 54), all C3 annu_@\als, and selected C4 grasses along daytime gradients of Glacial to present atmospheric CO2 concentrations in a 38-m-long c_B]hamber. We calculated parameters related to leaf photosynthesis and water-use efficiency from stable carbon isotope ratios_Z^ (C-13/C- 12) of whole leaves. Leaf water-use efficiency and above-ground biomass/plant of C3 species increased linearly a_\_nd nearly proportionally with increasing CO2 concentrations. Direct effects of increasing CO2 on plants must be considered_l when modelling the global carbon cycle and effects of climate change on vegetation.nd roots > 2 mm phi 1.7-fold more und_na512^5^Mayeux,HS^Johnson,HB^Polley,HW^Dumesnil,MJ^Spanel,GA^1993^1^A controlled environment chamber for growing plants acro_ss a subambient co2 gradient^43^7^1^125-133^^^^^^^^^^3843 system. However, if one balances CO2 gains with CO2 losses over_cA^3842^1. An elongated, controlled environment chamber is described in which a continuous, reproducible gradient of subamb_dient CO2 Concentration ([CO2]) is maintained during daylight hours to assess plant responses to past increases in atmosphe_eric [CO2]. 2. The [CO2] of air moved unidirectionally through the 37-6-m long chamber by a blower is progressively deplete_fd by photosynthesis of plants growing in the chamber. 3. Plant top- growth is contained in a transparent film tunnel which_g rests upon an enclosed soil volume that is 45 cm wide and 76 cm deep. 4. The desired minimum concentration to which CO2 i_hs depleted at the end of the chamber, usually 150 or 200 mul l-1, is maintained by varying the blower speed with a microlo_igger program dependent upon real-time sensing Of [CO2] and light intensity. 5. Dewpoint and dry bulb temperatures are also_ controlled by a micrologger- and computer-monitored air- conditioning system.SOIL POLLUT ER PT J AU OWENSBY, CE TI POTE_k513^10^Sampson,RN^Apps,M^Brown,S^Cole,CV^Downing,J^Heath,LS^Ojima,DS^Smith,TM^Solomon,AM^Wisniewski,J^1993^1^Workshop summ_xary statement - terrestrial biospheric carbon fluxes - quantification of sinks and sources of co2^94^70^1-4^3-15^^^^^Oct^^_mA^3844^Understanding the role of terrestrial ecosystems in the global carbon (C) cycle has become increasingly important a_ns policymakers consider options to address the issues associated with global change, particularly climate change. Sound sc_oientific theories are critical in predicting how these systems may respond in the future, both to climate change and human_p actions. In March 1993, 60 scientists from 13 nations gathered in Bad Harzburg, Germany, to develop a state-of-the- scien_qce assessment of the present and likely future C fluxes associated with the major components of the earth's terrestrial bi\rosphere. In the process, particular emphasis was placed on the potential for improving C sinks and managing long-term C se`squestration. The majority of the week's work was conducted in eight working groups which independently considered a partic`tular biome or subject area. The working groups considered: the Global Carbon Cycle; Boreal Forests and Tundra; Temperate F`uorests; Tropical Forests; Grasslands, Savannas and Deserts; Land and Water Interface Zones; Agroecosystems; and Biomass Ma`+vnagement. This paper presents a brief overview of their major conclusions and findings. In addition, Table 1 brings togeth`-wer the best estimates from each group as to the current magnitude and estimated future direction of changes in the terrest`9rial C fluxes. ECOSYSTEM EXPOSED TO ELEVATED CARBON-DIOXIDE SO PLANT CELL AND ENVIRONMENT SN 0140-7791 C1 KANSAS STATE UN`;^^^3845SCI, DEPT AGRON, THROCKMORTON HALL, MANHATTAN, KS 66506. KANSAS STATE UNIV AGR & APPL SCI, FT HAYS BRANCH EXPT STN`Hz514^2^Schindler,DW^Bayley,SE^1993^1^The biosphere as an increasing sink for atmospheric carbon - estimates from increased `Initrogen deposition^137^7^4^717-733^^^^^Dec^^^^^3847YCORRHIZAL FUNGI; INSECT HERBIVORE; PLANTS; GROWTH; COMMUNITIES; ENRI`T|A^3846^Estimates of carbon uptake and storage based on global nitrogen deposition, C:N ratios for typical terrestrial ecos`V}ystems, and recent ecosystem-scale nutrient studies indicate that 1.0-2.3 Gt C yr-1 of carbon storage may be stimulated by`c~ anthropogenically caused increases in nitrogen deposition in the past century. Sixty four to eighty four percent of globa`el nitrogen uptake appears to occur on northern continents, with the remainder largely in northern coastal oceans. Increase`ud nitrogen input by terrestrial ecosystems causes increased accumulation of carbon as plant tissue, with C:N ratios genera`wlly 50 to 200:1. Calculations suggest that northern continents are a major sink for carbon and that nitrogen- stimulated c`arbon uptake may more or less balance global carbon losses to the atmosphere from deforestation and agriculture. Much of t`he uptake appears to occur in aggrading forests, and the question of how long it can continue has important consequences f`or global carbon budgets.ts than in ambient CO2 PlOts. N concentration in P. pratensis aboveground biomass was lower in e`515^4^Vourlitis,GL^Oechel,WC^Hastings,SJ^Jenkins,MA^1993^1^A system for measuring insitu co2 and ch4 flux in unmanaged eco`systems - an arctic example^43^7^3^369-379^^^^^Jun^^^^^3849d CO2 than in ambient CO2 plots. Root ingrowth bag biomass N c`A^3848^1. A passive, rapid response, closed system was developed to measure in situ ecosystem CO2 and CH4 flux in 0.5-m2 p`lots over diurnal, seasonal, and annual time scales in arctic tundra ecosystems. The system consists of a chamber measurin`g 0.75 m on a side, 0.3 m in height, with acrylic sides, a mylar top, and 6-10 cm radial fans to ensure thorough mixing of` the chamber environment. 2. CO2 concentration and flux rates were measured using a Li-Cor 6200 Portable Photosynthesis Sy`stem, which is capable of measuring 0.1 p.p.m. s-1 changes in CO2 concentration. CH4 flux rates were measured by sequentia`l sampling of the CH4 concentration in the chamber over the duration of a 15-20-min incubation period. 3. Performance anal`yses indicate that light attenuation was less-than-or- equal-to 10% of ambient light. The rate of temperature increase wit`hin the chamber over the duration of the measurement period was approximately 1-5-degrees-C and 0.2-degrees-C for the majo`rity of the sampling days at tussuck tundra and wet coastal tundra sites, respectively. The maximum increase in thaw depth` due to the bases was approximately 10%, and was a function of the site water balance and the amount of time that the base`s were in place. Generally, thaw depth in plots with bases was greater when the bases were in place for a longer period of` time (greater-than-or-equal-to 1 year), while the bases that were installed during the current growing season had a small` effect on plot thaw depths. 4. The system had a minimal effect on ecosystem CO2 flux, compared to plots that lacked bases` in a wet coastal tundra and southern California turf ecosystem. 5. The system was successfully used to measure the effect` of light intensity, soil temperature, and water balance on ecosystem CO2 flux. 6. Due to the rapid response of the system`, high sensitivity to low flux rates, high portability, low cost, potential for use in field experiments, and non-invasivea sampling design, the system allows for the reliable measurement of CO2, CH4, and other trace gas flux rates in a variety aof ecosystem types. ERROR IN MEASUREMENTS OF RESPIRATION MADE WITH O2 ELECTRODES SO ANNALS OF BOTANY SN 0305-7364 C1 HEBRa516^4^Azconbieto,J^Gonzalezmeler,MA^Doherty,W^Drake,BG^1994^1^Acclimation of respiratory o-2 uptake in green tissues of fia#eld-grown native species after long-term exposure to elevated atmospheric co2^8^106^3^1163-1168^^^^^Nov^^^^^3851; PHOTOSYa%A^3850^C-3 and C-4 plants were grown in open-top chambers in the field at two CO2 concentrations, normal ambient (ambient)a; and normal ambient + 340 mu L L(-1) (elevated). Dark oxygen uptake was measured in leaves and stems using a liquid-phase a=Clark-type oxygen electrode. High CO2 treatment decreased dark oxygen uptake in stems of Scirpus olneyi (C-3) and leaves oaJf Lindera benzoin (C-3) expressed on either a dry weight or area basis. Respiration of Sparfina patens (C-4) leaves was unaLaffected by CO2 treatment. Leaf dry weight per unit area was unchanged by CO2, but respiration per unit of carbon or per ua[nit of nitrogen was decreased in the C-3 species grown at high CO2. The component of respiration in stems of S. olneyi anda^ leaves of L. benzoin primarily affected by long-term exposure to the elevated CO2 treatment was the activity of the cytocaohrome pathway. Elevated CO2 had no effect on activity and capacity of the alternative pathway in S. olneyi. The cytochromeaq c oxidase activity, assayed in a cell-free extract, was strongly decreased by growth at high CO2 in stems of S. olneyi buat it was unaffected in S. patens leaves. The activity of cytochrome c oxidase and complex III extracted from mature leavesa of L. benzoin was also decreased after one growing season of plant exposure to elevated CO2 concentration. These results ashow that in some C-3 species respiration will be reduced when plants are grown in elevated atmospheric CO2. The possible aphysiological causes and implications of these effects are discussed.bs free energy of this reaction was generally very la517^6^Baker,JT^Albrecht,SL^Pan,D^Allen,LH^Pickering,NB^Boote,KJ^1994^1^Carbon-dioxide and temperature effects on rice (oryaza-sativa L, CV ir-72)^156^53^^90-97^^^^^^^^^^3853suming that propionate, 2-propanol, caproate and valerate were converteaA^3852^The current increase in atmospheric carbon dioxide concentration ([CO2]) along with predictions of possible future aincreases in global air temperatures have stimulated interest in the effects of [CO2] and temperature on the growth and yiaeld of food crops. This study was conducted to determine the effects and possible interactions of elevated [CO2] and tempearature on the development, growth and yield of rice (Oryza sativa L., cv. IR-72). Rice plants were grown season-long in ouatdoor, naturally sunlit, controlled-environment, plant growth chambers. Chamber air temperatures were controlled to followa a continuously and diurnally varying, near sine-wave control setpoint that operated between maximum (daytime) and minimuma (nighttime) values. Day/night (maximum/minimum) air temperature treatments were: 32/23, 35/26, and 38/29-degrees-C. Dewpoaint air temperatures were maintained at 18, 21, 24- degrees-C in the 32/23, 35/26, 38/29-degrees-C dry bulb air temperaturbe treatment, respectively. Daytime [CO2] was controlled to 330 and 660 mumol CO2 mol-1 air in each of the air temperature btreatments. The time interval between appearance of successive mainstrem leaves during reproductive development was reducebd by increasing air temperature treatment (P less-than-or-equal-to 0.05) but was not affected by [CO2] enrichment. In thisb! experiment [CO2] enrichment did not affect (P less-than-or-equal-to 0.10) grain yield, components of grain yield, final ab*bove ground biomass or harvest index. Increasing temperature during growth, particularly from the 35/26 to 38/29-degrees-Cb, reduced grain yield, individual grain mass, and harvest index. The reduced grain yields with increasing temperature treatb?ment suggest potential detrimental effects on rice production in some areas if air temperatures increase.jacent to calcsibA518^2^Beerling,DJ^Woodward,FI^1994^1^The climate-change experiment (climex) - phenology and gas- exchange responses of borbOeal vegetation to global change^175^4^1^17-26^^^^^Jan^^^^^3855es in disseminated graphite flakes within adjacent metapelibQA^3854^Large-scale whole ecosystem experiments will become increasingly important for predicting and testing hypotheses ofb^ complex ecosystem responses to global change. The Climate Change Experiment (CLIMEX) uses a site with an entire undisturbb`ed boreal-forested catchment enclosed within an existing very large scale (1200m2 ground area) greenhouse. In the forthcombping year temperature will be increased stepwise to +3-degrees-C in summer, +5-degrees-C in winter and the atmospheric CO2 brconcentration enriched to 560 ppm which together simulate future changes in global climate and atmospheric composition prebdicted by GCMs. Plants growing within this low nutrient ecosystem are strongly dependent upon mycorrhizal associations forb nutrient uptake and rates of nutrient uptake. Therefore it will provide an important test of current ideas concerning howb mycorrhizas might modify plant responses to global change. We describe predictions of community phenology and gas exchangbe at the CLIMEX site; in the latter case the effects of including and excluding rates of on nutrient supply are consideredb. The results are discussed with reference to the opportunities presented by CLIMEX to reveal important aspects of the phybsiological responses of boreal ecosystems to global change.an surface. The maxmum growth rate was 0.9d-1. The ratio of inb519^2^Behboudian,MH^Lai,R^1994^1^Carbon-dioxide enrichment in virosa tomato plant - responses to enrichment duration and tbo temperature^170^29^12^1456-1459^^^^^Dec^^^^^3857by a cell were little affected by CO2 enrichment. A similar result wasbA^3856^Responses of the tomato (Lycopersicon esculentum Mill. cv. Virosa) plant to elevated CO2 concentrations applied thrboughout the photoperiod or part of it were studied under two temperature regimes. Plants were exposed to CO2 at 340 (contrbol), 700, and 1000 mul-liter-1. The highest concentration was applied only at 22/16C (day/night) and 700 mul-liter-1 at 22b/16C and 25/16C. Transpiration rates were lower and photosynthetic rates were higher under elevated CO2 than at the ambienbt level. Biomass production was higher only for plants grown at 700 mul-liter-1 and 25/16C. Concentrations of macronutrienbts were lower in plants exposed to 1000 mul CO2/liter than in the control plants. Intermittent CO2 was applied using two tbiming methods. In method 1, plants were exposed to 4- or 8-hour high-CO2 concentrations during their 12-hour photoperiod. bIn method 2, plants were exposed for 3.5 days of each week to 700 mul CO2/liter. Only two of the 8-hour exposures resultedb in greater growth than the controls. The lack of higher growth for CO2-enriched plants at 22/16C was attributed to a highcer dark respiration rate and to respiration rate and a lack of efficient transport of photosynthates out of leaves. pigs,c520^2^Boote,KJ^Pickering,NB^1994^1^Modeling photosynthesis of row crop canopies^170^29^12^1423-1434^^^^^Decnted with lincc521^6^Delgado,E^Mitchell,RAC^Parry,MAJ^Driscoll,SP^Mitchell,VJ^Lawlor,DW^1994^1^Interacting effects of co2 concentration, c.temperature and nitrogen supply on the photosynthesis and composition of winter-wheat leaves^9^17^11^1205-1213^^^^^Nov^^^^c0A^3859^Winter wheat (Triticum aestivum L., cv. Mercia) was grown at two different atmospheric CO, concentrations (350 and c<700 mu mol mol(-1)) two temperatures [ambient temperature (i.e. tracking the open air) and ambient +4 degrees C] and two rc>ates of nitrogen supply (equivalent to 489 kg ha(-1) and 87 kg ha(- 1)). Leaves grown at 700 mu mol mol(-1) CO2 had slightcGly greater photosynthetic capacity (10% mean increase over the experiment) than those grown at ambient CO2 concentration, cIbut there were no differences in carboxylation efficiency or apparent quantum yield. The amounts of chlorophyll, soluble pcUrotein and ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) per unit leaf area did not change with long-term expocWsure to elevated CO2 concentration. Thus winter wheat, grown under simulated field conditions, for which total biomass wasce large compared to normal field production, did not experience loss of components of the photosynthetic system or loss of cgphotosynthetic competence with elevated CO2 concentration. However, nitrogen supply and temperature had large effects on pcphotosynthetic characteristics but did not interact with elevated CO2 concentration. Nitrogen deficiency resulted in decreacrses in the contents of protein, including Rubisco, and chlorophyll, and decreased photosynthetic capacity and carboxylatiocn efficiency. An increase in temperature also reduced these components and shortened the effective life of the leaves, redcucing the duration of high photosynthetic capacity.h concentration was not significantly affected by elevated CO2. Althouc^3860temperature increased metabolic activity, it only partially alleviated the inhibition of P(N). L. gibba exhibits a cc522^8^Estiarte,M^Penuelas,J^Kimball,BA^Idso,SB^Lamorte,RL^Pinter,PJ^Wall,GW^Garcia,RL^1994^1^Elevated co2 effects on stomactal density of wheat and sour orange trees^78^45^280^1665-1668^^^^^Nov^^^^^3862VL 28 IS 1 GA LW193 RP SMERNOFF DT J9 PHOTcA^3861^No significant differences were found in stomatal densities or stomatal indices of wheat or sour orange trees grownc at high CO2 concentrations in two different CO2 enrichment systems (Free-Air CO2 enrichment for wheat and Open-Top Chambecrs for orange trees). These results are in accordance with most of the previous results obtained in short-term experimentacl studies which suggest that plants do not acclimate to increasing CO2 concentration by changing stomatal density within ac single generation. for 9 months in enclosures in greenhouses at CO2 concentrations of 350 or 750 mumol mol-1 with eitherc523^2^Ferris,R^Taylor,G^1994^1^Increased root-growth in elevated co2 - a biophysical analysis of root cell elongation^78^4c5^280^1603-1612^^^^^Nov^^^^^3864d by CO2 enrichment. High UV treatment also shifted biomass partitioning in favor of leafcA^3863^A biophysical analysis of root expansion was conducted in four chalk downland herbs (Sanguisorba minor Scop., Lotusc corniculatus L., Anthyllis vulneraria L. and Plantago media L.) exposed to either ambient or elevated CO, in controlled ecnvironment cabinets. Measurements of fine (F) and extra-fine (EF) root extension rate (RER), water relations, and cell walcl tensiometric extensibility revealed differences in the diurnal pattern of root growth between species. After 35 d of expcosure to elevated CO2, RER of both F and EF roots increased significantly in darkness and on illumination for S. minor, whcilst for A. vulneraria (EF roots only) and L. corniculatus a significant increase occurred at night whereas for P. media ac significant increase occurred during the day. Cells measured in the zone of elongation were longer in all species exposedd to elevated CO2. Water potential (Psi), solute potential (Psi(s)), turgor pressure (P), yield turgor (Y) and effective tudrgor (Pe) were measured by stress-relaxation of excised root tips placed in psychrometers. Solute potentials decreased sigdnificantly for all species following exposure to elevated CO2. In S. minor and L. corniculatus, P and Pe, respectively, wedre higher in elevated CO2. No significant effects of CO2 on Y were observed (not shown). Root cell wall tensiometric extendsibility, measured as % plasticity, increased in all species exposed to elevated CO2. These results suggest that root growd$th is enhanced following increased cell expansion and that increased P and cell wall tensiometric extensibility are both id%mportant for root growth in elevated CO2.of inhibitor for methanogenesis, ranged from -43 to -30 parts per thousand. The d,524^3^Frick,J^Nielsen,SS^Mitchell,CA^1994^1^Yield and seed oil content response of dwarf, rapid-cycling brassica to nitrogd.en treatments, planting density, and carbon- dioxide enrichment^154^119^6^1137-1143^^^^^Nov^^^^^3866C-13 of CO2 localizedd9rature by 4 degrees C, however, reduced the total lipid content of grains. Wheat plants treated with high concentrations od;f nitrogen fertilizer accumulated less lipid compared to low nitrogen controls. Qualitative changes were also observed in dEthe proportions of non-starch and starch lipid classes. However, changes in total acyl composition were limited to starch dGgrain acyl lipids, as a result of changes in atmospheric carbon dioxide, growth temperature and nitrogen fertilizer applicdIation. The alterations in wheat lipids observed are likely to affect the properties of the flour produced from the grains.dWpleted freshwater areas. BP 4015-4027 PG 13 JI Geochim. Cosmochim. Acta PY 1993 PD AUG VL 57 IS 16 GA LW389 J9 GEOCHIM CdZA^3865^Effects of N level (15 to 30 mM), time of N increase (14 to 28 days after planting), and planting density (1163 to di2093 plants/m(2)) were determined for crop yield responses of dwarf, rapid-cycling brassica (Brassica napus L., CrGC 5-2, dkGenome: ACaacc). Crops were grown in solid-matrix hydroponic systems and under controlled-environment conditions, includindmg 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 stimuldating vegetative shoot growth. The highest shoot biomass accumulation rate (55.5 g.m-2.day(-1)) occurred with the highest d N level (30 mM) applied at the earliest time (day 14). Seed oil content was not significantly affected by CO2 enrichment. d Maximum seed oil content (30% to 34%, dry weight basis) was obtained using the lowest N level (15 mM) initiated at the latd est treatment time (day 28). In general, an increase in seed oil content was accompanied by a decrease in seed protein. Sed ed carbohydrate, moisture, and ash contents did not vary significantly in response to experimental treatments. Effects of d N level and time of N increase were consistently significant for most crop responses. Planting density was significant onldy under elevated CO2 conditions.T, NORWICH NR4 7JU, ENGLAND. DE TRITICUM-AESTIVUM; ERYSIPHE-GRAMINIS; WHEAT; POWDERY MILDd525^4^Heagle,AS^Brandenburg,RL^Burns,JC^Miller,JE^1994^1^Ozone and carbon-dioxide effects on spider-mites in white clover dand peanut^204^23^6^1168-1176^^^^^Nov-Dec^^^^^3868FERTILIZATION AB In two experiments, winter wheat (Triticum aestivum cvdA^3867^Effects of O-3 and/or elevated CO2 on two-spotted spider mites (Tetranychus urticae Koch) grown on an On-sensitive dand an O-3- resistant clone of white clover (Trifolium repens L.) were measured in greenhouse and field experiments. Peanudt (Arachis hypogeae L.) 'NC-9' was used in one greenhouse study with O-3. In field studies, O-3 treatments were charcoal feiltered air (CF), nonfiltered air (NF), and two NF treatments with On added for 12 h d(-1) at proportions of approximate teo 1.25 and 1.50 times the ambient O-3 concentration. In greenhouse studies, constant amounts of O-3 were added to CF for 6e h d(-1) to achieve mean concentrations ranging from 5 to 100 nL L(-1). For the greenhouse O-3 X CO2 experiment, CO2 conceentrations were ambient and approximately twice-ambient for 24 h d(-1). Plants were exposed to O-3 and/or CO2 for approximae%te to 7 d before infestation with mites; daily exposures continued for 14 to 28 d to allow reproduction for at least two ge'enerations. Leaves were sampled to count eggs, larvae, nymphs, and adults. Ozone caused more chlorosis and necrosis on thee3 O-3-sensitive clover clone (NC-S) than on the Oa-resistant clone (NC-R). Carbon dioxide enrichment increased shoot growthe5 of both clones by approximate to 33%. Statistical analyses indicated significant O-3 effects in some experiments and nonse@ignificant O-3 effects in others. A trend toward increased mite populations with increased O-3 occurred, however, on NC-S eBin all trials. No consistent trends occurred with NC-R. With peanut, a significant linear increase in mite population occueKrred with increased O-3. Carbon dioxide enrichment increased the rate of population increase on both clover clones, but moeMre so on NC-R. At 22 to 28 d after infestation, the total population in the twice-ambient CO2 treatment was 65% greater theZ an in the ambient treatment for NC-R and 22% greater than in the ambient treatment for NC-S. There were no statistically se\!ignificant interactive effects between CO2 and O-3 On mite population growth. The apparent clone effects on mite populatioein response to O-3 and CO2 strongly suggest that responses were mediated through the host plants.when they received suppleek526^2^Hendrey,GR^Kimball,BA^1994^1^The face program^107^70^1-4^3-14^^^^^Sep^^^^^3870as an increase in activation state. Ae$A^3869^A large, cooperative, integrated experimental program utilizing free-air CO2 enrichment (FACE) is being conducted te%o expose plants to elevated concentrations of CO2. The goals are to evaluate the effects of increasing atmospheric CO2 on e&plants and ecosystems and, in the long run, to contribute to the evaluation of terrestrial plant feedback regulation on the'e rate of change of CO2 in the atmosphere. Having no walls, the FACE system allows plants to be grown under realistic micre(oclimate and CO2 conditions expected to prevail in the mid-twenty-first century. Data obtained under such conditions are ne)eeded for validation of models being developed to predict the effects of increasing CO2 and changing climate variables on e*plants, ecosystems, agricultural productivity and water resources. Setup costs for the FACE systems used in these experimee+nts are similar to the costs of field chamber systems. Although annual operating costs are about three times the cost of fe,ield chambers, FACE plots are relatively large, leading to an economy of scale, so that per unit of treated plant materiale-, FACE systems are the least expensive approach for well- integrated field experiments. These features have provided an ine.centive to conduct comprehensive FACE experiments with many cooperating scientists working together to measure numerous ple/ant, soil and micrometeorological parameters, as described in the collection of papers in this special issue of 'Agricultueral and Forest Meterology'. water under increased CO2 concentrations in the atmosphere; the temperature response of photoe1527^2^Korner,C^Miglietta,F^1994^1^Long-term effects of naturally elevated co2 on mediterranean grassland and forest trees^e2^99^3-4^343-351^^^^^Oct^^^^^3872patterns with the consequent changes in land cover. In this paper we discuss the implemee3A^3871^We investigated the carbon supply status in species-rich mediterranean plant communities growing in a bowl-shaped 14-ha ''CO2 spring'' area near Sienna, Italy. A geothermic ''lime- kiln'' has provided these communities, for as long as his5torical records are available, with pure CO2 that mixes with ambient air at canopy level to daytime means of 500-1000 ppm b6CO2. Immediately outside the spring area similar plant communities are growing on similar substrate, and in the same climaf7te, but under ca. 355 ppm CO2. We found no evidence that plants in the CO2 spring area grow faster, flower earlier or becof8me larger. However, we found very large differences in tissue quality among the 40 species studied inside and outside the f9spring area. Depending on weather conditions, the mean concentration of total non-structural carbohydrates (TNC, sugars anf#:d starch) in leaves of herbaceous plants was 38-47% higher in the spring area. Fast growing ruderals growing on garden soif%;l inside and outside the spring area show the same response. Among trees, leaves of the deciduous Quercus pubscens containf0< twice as much TNC inside as outside the vent area, whereas evergreen Q. ilex leaves show no significant difference. TNC lf2=evels in branch wood paralleled leaf values. TNC in shade leaves was also higher. Elevated CO2 had no effect on the sugar f=>fraction, therefore differences in TNC are due to starch accumulation. Leaf nitrogen concentration decreases under elevatef??d CO2. These observations suggest that the commonly reported TNC accumulation and N depletion in leaves growing under elevfM@ated CO2 are not restricted to the artificial conditions of short-term CO2 enrichment experiments but persist over very lofQAng periods. Such an alteration of tissue composition can be expected to occur in other plant communities also if atmospherfnic CO2 levels continue to rise. Effects on food webs and nutrient cycling are likely.50 and continuing to the present, anfpC528^2^Lavola,A^Julkunentiitto,R^1994^1^The effect of elevated carbon-dioxide and fertilization on primary and secondary meftabolites in birch, betula-pendula (roth)^2^99^3-4^315-321^^^^^Oct^^^^^3874nt, the increase for 100- to 150- year-old trefEA^3873^Seedlings of European white birch (Betula pendula Roth) were grown in growth chambers for one growth season under ffFour carbon dioxide regimes (350, 700, 1050 and 1400 pm) and at three fertilization levels (0, 100 and 500 kg ha(-1) monthlfGy). The soluble carbohydrates and secondary phenolics in the leaves and stems were analysed. It was found that fertilizer fHaddition reduced the amounts of glucose and fructose while sucrose remained almost unaffected. The sugar content of leavesfI increased at 700 ppm and 1050 ppm of CO2 and decreased at the highest CO2 concentration (1400 ppm). The amounts of proantJhocyanidins and flavonoids in leaves decreased with fertilization addition and increased with CO2 enrichment. The productiKon of simple phenolic glucosides varied according to the fertilization and CO2 treatments. The triterpenoid content of stefLms seemed to increase with fertilization and CO2 addition. Our results indicate that the production of phytochemicals in tfMhe birch seedlings is very sensitive to both fertilization and CO2 addition, which is in agreement with earlier studies, afNnd thus provide some support for the hypothesis of carbon allocation to plant defence when there is an excess of carbon anfOd nutrient. The considerable variation in the production of secondary components may indicate that the synthesis of these Pdefensive metabolites can be regulated by a plant to certain extent, depending on the ability of the plant to acclimate to changes in the physical environment.2000, and 5000 ppm). Plants were grown using recirculating nutrient film technique wfR529^4^Lewin,KF^Hendrey,GR^Nagy,J^Lamorte,RL^1994^1^Design and application of a free-air carbon-dioxide enrichment facilityf^107^70^1-4^15-29^^^^^Sep^^^^^3876 greatest at 100 Pa for cv. McCall, suggesting that higher CO2 levels were supraoptimalgTA^3875^Growth chambers and other enclosures used in plant physiology and growth studies tend to introduce chamber effects gUthat alter the microclimate around the plants compared with the natural environment. A free-air (chamberless) carbon dioxigVde enrichment (FACE) system has been developed by Brookhaven National Laboratory (BNL) to provide controlled fumigation cogWnditions while minimizing the potential to impose a discernible chamber effect. This system is capable of exposing large ng,Xumbers of field-grown plants to elevated levels of atmospheric carbon dioxide (CO2) from seedling emergence until physiolog.Ygic maturity. A FACE User Facility was established at the Maricopa Agricultural Center, University of Arizona, for continug<Zous enrichment of CO2 at a set point of 550 mumol mol-1 during daylight hours throughout the cotton crop growing seasons og=[f 1989-1991. The facility consisted of four circular BNL FACE arrays and associated equipment placed in a commercial cottog?\n plantation. FACE array diameters of 23, 25, and 27 m were tested. The FACE facility included the ability to operate the gG]experimental plots under two watering regimes using an automated, sub-surface irrigation system. CO2 was stored in a 48 00gI^0 kg receiver and vaporized with a heat exchanger that used water at ambient temperature as the energy source. The 1 min agS_verage CO2 concentration was held to within +/- 20% of the set point more than 98% of the time that the arrays were operatgU`ing during all three seasons. In 1991, the long term average CO2 concentration measured at 63 points throughout the volumegea of a 20 m diameter experimental plot (ground to canopy top) centered within a 25 m diameter FACE array was 568 mumol mol-ggb1. All of the FACE arrays operated for more than 99% of the planned experimental period in 1991. These 3 years of operatiogpcn have demonstrated that the BNL FACE technology can be used as a basis for a large scale facility devoted to studying thegr fate of carbon in the terrestrial environment.gze530^3^Luo,Y^Field,CB^Mooney,HA^1994^1^Predicting responses of photosynthesis and root fraction to elevated [co2](a) - integ|ractions among carbon, nitrogen, and growth^9^17^11^1195-1204^^^^^Nov^^^^^3878Uhu">INggA^3877^At elevated atmospheric CO2 concentrations ([CO2](a)), photosynthetic capacity (A(max)) and root fraction (eta(R), ghthe ratio of root to plant dry mass) increased in some studies and decreased in others. Here, we have explored possible cagiuses of this, focusing on the relative magnitudes of the effects of elevated [CO2](a) on specific leaf (n(m)) and plant (ngj(p)) nitrogen concentrations, leaf mass per unit area (h), and plant nitrogen productivity (alpha). In our survey of 39 stgkudies with 35 species, we found that elevated [CO2](a) led to decreased n(m) and n(p) in all the studies and to increased glh and alpha in most of the studies. The magnitudes of these changes varied with species and with experimental conditions. gmBased on a model that integrated [CO2](a)-induced changes in leaf nitrogen into a biochemically based model of leaf photosgnynthesis, we predicted that, to a first approximation, photosynthesis will be upregulated (A(max) will increase) when growgoth at increased [CO2](a) leads to increases in h that are larger than decreases in n(m). Photosynthesis will be downregulagpted (A(max) will decrease) when increases in h are smaller than decreases in n(m). The model suggests that photosynthetic gqcapacity increases at elevated [CO2](a) only when additional leaf mesophyll more than compensates the effects of nitrogen grdilution. We considered two kinds of regulatory paradigms that could lead to varying responses of eta(R) to elevated [CO2]gs(a), and compared the predictions of each with the data. A simple static model based on the functional balance concept pregtdicts that eta(R) should increase when neither n(p) nor h is very responsive to elevated [CO2](a). The quantitative and qugualitative agreement of the predictions with data from the literature, however, is poor. A model that predicts eta(R) from gvthe relative sensitivities of photosynthesis and relative growth rate to elevated [CO2](a) corresponds much more closely tgwo the observations. In general, root fraction increases if the response of photosynthesis to [CO2](a) is greater than thatg of relative growth rate."T+T9TjHjNj^jfjmjsjzjjjhsA^3881^Storage of broccoli (Brassica oleracea L., Italica Group) under conditions of low O-2 concentration extends its shehlf life. Excessively low O-2, however, leads to the formation of an offensive odour which is primarily due to the emissionh of methanethiol. In this study, we investigated the initial induction and control of methanethiol production of broccoli hflorets exposed to various levels of O-2 and CO2 over short- term periods of 10 h or less. Lowering the O-2 concentration hsurrounding the broccoli florets by continuously flowing N-2 through the sample containers acted to initiate the productiohn of methanethiol within 1 h after the 0(2) concentration had reached 0.5 %. After initiation the rate of production showehd a slow but steady increase during the 10 h of experimentation. In contrast, introduction of O-2 into the sample containehrs while the broccoli florets were actively producing methanethiol led to a rapid 79% drop in the amount of methanethiol dhetected within 15 min, followed by a complete absence of methanethiol within another 15 min. Resumption of N-2 flow acted hto reinitiate methanethiol production, with the initiation requiring a lesser amount of time than that required for the inhitial induction of methanethiol production. Experiments with elevated CO2 concentrations of up to 26.5% determined that COh2 is an inhibitor of methanethiol production.ŃfqvƉch533^3^Parton,WJ^Ojima,DS^Schimel,DS^1994^1^Environmental-change in grasslands - assessment using models^50^28^1-2^111-141^h^^^^Oct^^^^^3884hA^3883^Modeling studies and observed data suggest that plant production, species distribution, disturbance regimes, grasslhand biome boundaries and secondary production (i.e., animal productivity) could be affected by potential changes in climathe and by changes in land use practices. There are many studies in which computer models have been used to assess the impacht of climate changes on grassland ecosystems. A global assessment of climate change impacts suggest that some grassland echosystems will have higher plant production (humid temperate grasslands) while the production of extreme continental steppehs (e.g., more arid regions of the temperate grasslands of North America and Eurasia) could be reduced substantially. All oif the grassland systems studied are projected to lose soil carbon, with the greatest losses in the extreme continental grai ssland systems. There are large differences in the projected changes in plant production for some regions, while alteratioins in soil C are relatively similar over a range of climate change projections drawn from various General Circulation Modeils (GCM's). The potential impact of climatic change on cattle weight gains is unclear. The results of modeling studies alsi&o suggest that the direct impact of increased atmospheric CO2 on photosynthesis and water use in grasslands must be considi(ered since these direct impacts could be as large as those due to climatic changes. In addition to its direct effects on pi9hotosynthesis and water use, elevated CO2 concentrations lower N content and reduce digestibility of the forage.i<534^4^Perezsoba,M^Vandereerden,LJM^Stulen,I^Kuiper,PJC^1994^1^Gaseous ammonia counteracts the response of scots pine needliMes to elevated atmospheric carbon-dioxide^84^128^2^307-313^^^^^Oct^^^^^3886iOA^3885^Four-year-old saplings of Scots pine (Pinus sylvestris L.) were exposed for 8 wk in controlled-environment chambersiY to charcoal-filtered air (FB), FA supplemented with 754 mg m(-3) (650 mu l l(-1)) CO2, FA supplemented with 100 mu g m(-3i[) NH3 and FA + CO2 + NH3. Elevated CO2 induced a significant increase in the concentrations of NH4+ and NO3- in the soil siholution, while exposure to NH3 enhanced the soil NH4+ concentration. Elevated CO2 significantly increased needle biomass aijnd area, and decreased specific leaf area (SLA) and N concentration in the needles. The activity of peroxidase (POD) was dixecreased, while the activities of glutamine synthetase (GS) and glutamate dehydrogenase (GDH) were only slightly affected.iz Gaseous NH3 enhanced the concentration of N, soluble proteins and the GS activity in the needles, while it decreased the iPOD and GDH activities. The effects of elevated CO2 + NH3 on needle biomass production, N metabolism and POD activity werei smaller than the effects of single exposures to elevated CO2 or NH3, suggesting that elevated CO2 and NH3 counteract eachi other and disturb needle physiology. The possible mechanisms underlying the negative interactions of elevated CO2 and NH3i are discussed. The expected stimulation of biomass production by elevated CO2 may be reduced in the presence of atmospheriic NH3.i535^2^Sicher,RC^Kremer,DF^1994^1^Responses of nicotiana-tabacum to co2 enrichment at low-photon flux-density^37^92^3^383-3i88^^^^^Nov^^^^^3888iA^3887^Effects of CO2 enrichment on photosynthesis and on dry matter allocation were examined in two tobacco (Nicotiana taibacum L.) genotypes, Samsun and W38. Plants were grown from seed in controlled environment chambers at a photosynthetic phioton flux density of 450 mu mol m(-2) s(-1). Averaged over the 9 day study, net photosynthesis rates were 14.2 +/- 0.5 andi 13.0 +/- 0.4 mu mol m(-2) s(-1) in elevated (70 Pa) and in ambient (35 Pa) CO2 air, respectively, when measured at the iriradiance and CO2 partial pressure employed for plant growth. However, photosynthesis rates of plants grown in elevated CO2i were 50% less than those of the ambient controls on the last day of treatment, when measured at 70 Pa CO2 air and an irraidiance of 900 mu mol m(-2) s(-1). Total plant dry weight and specific leaf weight were greater (P<0.05) in enriched-CO2-griown than in ambient-CO2-grown plants. Leaf starch, measured during the first hour of the photoperiod, increased over 7 dayis of treatment in elevated-CO2-grown but not in ambient-CO2-grown plants. Ribulose 1,5-bisphosphate carboxylase/oxygenase j(Rubisco) activities of tobacco plants grown at 35 and 70 Pa CO2 air were 58.5 +/- 4.5 and 48.5 +/- 3.7 mu mol m(-2) s(-1)j, respectively, between days 0 and 9 of the study. Rubisco activation stale, Rubisco protein concentration, soluble proteijn and total chlorophyll were unaffected by CO2 enrichment. The above findings demonstrated that photosynthesis was down rejgulated in tobacco plants after 7 to 9 days of CO2 enrichment at low photosynthetic photon flux density, but less than at jmoderate irradiances.j536^6^Stronach,IM^Clifford,SC^Mohamed,AD^Singletonjones,PR^Azamali,SN^Crout,NMJ^1994^1^The effects of elevated carbon-dioxj2ide, temperature and soil- moisture on the water-use of stands of groundnut (arachis- hypogaea L)^78^45^280^1633-1638^^^^^j4Nov^^^^^3890Y5Xchu}<N[!jAA^3889^Stands of groundnut (Arachis hypogaea L. cv. Kadiri 3) were grown in controlled environment glasshouses at two meanjC air temperatures (28 degrees C and 32 degrees C), two atmospheric CO2 concentrations (375 ppmv and 700 ppmv) and two soiljK moisture treatments (irrigated weekly to field capacity or allowed to dry from 22 d after sowing). The transpiration equijMvalent, Omega(W) (g kPa kg(-1))-the product of the accumulated biomass/transpired water ratio and the saturation deficit-wj_as calculated for all the treatments using aboveground harvest, root core and neutron probe measurements. Neither temperatjaure nor soil moisture treatment was found to have an effect on Omega(W). Increased CO2 concentration raised Omega(W) from jr6.21 +/- 0.30 to 7.67 +/- 0.29 g kPa kg(-1), an increase of 24% (P < 0.005). The importance of accounting for root materiajtl and pod composition when calculating Omega(W) was highlighted.j 9DJdlsyj}537^5^Taylor,G^Ranasinghe,S^Bosac,C^Gardner,SDL^Ferris,R^1994^1^Elevated co2 and plant-growth - cellular mechanisms and rejsponses of whole plants^78^45^280^1761-1774^^^^^Nov^^^^^3892UjA^3891^Much research has focused on the photosynthetic responses of plants to elevated CO2, with less attention given to tjhe post- photosynthetic events which may lead to changes in the growth of tissues, organs and whole plants. The aim of thijs review is to identify how plant growth is altered in elevated CO2 and to determine which growth processes or cellular mejchanisms are sensitive to carbon supply. For leaves, both the expansion of individual leaves and the initiation of leaf prjimordia are stimulated in elevated CO2. When lamina growth is promoted, this is usually associated with increased leaf celjl expansion rather than increased leaf cell production. Using several clones of hybrid poplar (Populus euramericana, P. injteramericana) two native herbs (Plantago media, Sanguisorba minor) and bean (Phaseolus vulgaris) we have identified the mejchanism through which leaf cell expansion is promoted in elevated CO2. Changes in the water relations, turgor pressure (P)j and yield turgor (Y) of growing leaves cannot explain increased cell expansion; this appears to occur because cell wall ljoosening is promoted, as suggested by three pieces of evidence. (i) The rate of decline of water potential (psi) with timej is accelerated when growing leaves are placed in psychrometers and allowed to relax, (ii) Instron-measured cell wall extejnsibility (WEX), is greater for leaves exposed to elevated CO2 and (iii) the activity of the putative wall loosening enzymje, XET is increased for leaves of P. vulgaris exposed to elevated CO2. Species differences do, however, exist; in the herbj Lotus corniculatus small stimulations of leaf growth in elevated CO2 are due to increased leaf cell production and decreajsed cell size in elevated CO2. These results are discussed in relation to the concept of functional types. There is evidenkce to suggest that both cell production and cell expansion are promoted in roots of plants exposed to elevated CO2. For naktive herbs (Anthyllis vulneraria, Lotus corniculatus, P. media and S. minor), increased root growth in elevated CO2 is duek to increased cell elongation. In contrast to leaves, this appears to occur because both root cell turgor pressure (P) andk" root cell wall extensibility (WEX) are promoted by exposure of shoots to elevated CO2. In longer-term studies on root grok$wth, the effects of additional carbon on the production of root primordia and root branching are of overriding importance,k8 suggesting that carbon supply may influence some aspect of the cell cycle, when effects on the extension of individual rok:ots may not be apparent.#,$,),Y,,,,,-222.262=2C2H2Q2[2v2y2z2kL538^3^Tuba,Z^Szente,K^Koch,J^1994^1^Response of photosynthesis, stomatal conductance, water-use efficiency and production kNto long-term elevated co2 in winter- wheat^4^144^6^661-668^^^^^Nov^^^^^3894k[A^3893^Responses of photosynthesis, stomatal conductance, water use efficiency (at the beginning of flowering) and productk]ion allocation (at full ear/grain ripening) to long-term elevated CO2 were assessed in winter wheat (Triticum aestivum L. kocv. MV16). Plants were grown in open top chambers under a temperate-continental climate from germination at ambient (350 mkqu molmol(-1)) and elevated (700 mu molmol(-1)) CO2 concentrations. High CO2 plants displayed a decreased initial slope of kthe A/C-i response curve, with the assimilation rate (A) continuing to increase above 400 mu molmol(-1) internal CO2 concekntration (C-i). A in the ambient plants showed P regeneration limitation while RuBP regeneration appeared to be limiting Ak in the high CO2 treatment. Variable fluorescence ratios (Rfd 690) were lower in the high CO2 plants indicating a lower poktential photochemical activity. The increase in the values for the chlorophyll fluorescence ratio F690/F735 in the high COk2 plants was in agreement with the lower chlorophyll a+b concentrations. The high CO2 plants had higher concentrations of kstarch in their leaves and roots that the ambient plants. Stomatal conductance (g(s)) was lower in the high CO2 plants at kevery CO2 concentration (C-a) and C-i and the C-i-dependent g(s) response had a large influence on the A/g(s), function. Tkhe higher water use efficiency (WUE) values (at C-a's > 350 mu molmol(-1)) in the high CO2 wheat plants were the result ofk a larger decrease in transpiration rate (E) in the high CO2 plants than in the ambient plants, and of a simultaneous largker increase in A in the range of C-a above 350 mu molmol(-1) COP. The integrated and combined effect of the photosynthetick and stomatal acclimation to elevated CO2 produced a higher C- assimilation in high CO2 plants at elevated CO2 than in thek ambient plants, however, this was not followed by an acclimation in C-allocation. These were reflected in a slightly incrkeased (6.7%) overall dry matter production and lower reproductive allocation (RA).k539^3^Williams,M^Shewry,PR^Harwood,JL^1994^1^The influence of the greenhouse-effect on wheat (triticum- aestivum L) grain klipids^78^45^279^1379-1385^^^^^Oct^^^^^3896kA^3895^There have been few studies conducted with the objective of investigating comprehensively the 'greenhouse effect' oln wheat growth using field-grown crops and even less on the effects on the lipid composition of harvested grains. Thereforle, the aim of this study was to define any changes in wheat grain acyl lipids which could result from alterations in envirlonmental growth conditions predicted to mimic the 'greenhouse effect'. Quantitative changes were recorded for both the nonl-starch and starch lipids. When supplied with low concentrations of nitrogen fertilizer, plants showed increased amounts olf total grain lipids when grown under an elevated (700 mu l l(-1)) carbon dioxide atmosphere. Increasing the ambient tempel 540^2^Winter,K^Engelbrecht,B^1994^1^Short-term co2 responses of light and dark co2 fixation in the crassulacean acid metabl"olism plant kalanchoe-pinnata^4^144^4-5^462-467^^^^^Oct^^^^^3898l2A^3897^Short-term responses of net CO2 assimilation rate (A), in the light and dark, to ambient CO2 partial pressure (betwl4een about 30 and 1000 mu bar) were studied in leaves of the crassulacean acid metabolism (CAM) plant, Kalanchoe pinnata. TlChe results show that it is possible to extrapolate from instantaneous measurements of net CO2 exchange to diurnal and noctlFurnal CO2 balances at different CO2 partial pressures. Instantaneous CO2 response curves were obtained by altering CO2 levl[els at 10-min intervals during the middle of the 12-h dark period (phase I of CAM) and during the last third of the 12-h ll] ight period (phase IV of CAM). CO2 partial pressures were also altered at longer, 12- to 24-h intervals and maximum rates lp of net CO2 uptake (A(max)) during light and dark periods were analysed in response to intercellular CO2 partial pressures lr (p(i)) occurring at the time of A(max). A(max)-p(i) relationships were identical to A-p(i)-curves from rapidly performed dlw eterminations during phases I and IV. Corresponding to previous findings with non-CAM species, A(max) and integrated net cly arbon gain during light and dark periods, respectively, showed a linear relationship. Nocturnal CO2 uptake in normal air wlas barely affected when light-period carbon gain was manipulated by alterations in CO2 partial pressure. Carbon gain durinlg light periods, measured in normal air, was also independent of CO2-related changes in nocturnal carbon gain. Only after l12 h of darkness at the lowest CO2 concentration used (about 30 mu bar), was carbon gain increased under lighted conditionls.l541^4^Baxter,R^Gantley,M^Ashenden,TW^Farrar,JF^1994^1^Effects of elevated carbon-dioxide on 3 grass species from montane plasture .2. Nutrient-uptake, allocation and efficiency of use^78^45^278^1267-1278^^^^^Sep^^^^^3900>!3;lA^3899^Agrostis capillaris L.(4), Festuca vivipara L. and Poa alpina L. were grown in outdoor open-top chambers at either lambient (340 mu mol mol(-1) or elevated (680 mu mol mol(-1)) CO2 for periods from 79 to 189 d. Under these conditions therle is increased growth of A, capillaris and P. alpina, but reduced growth of F. vivipara. Nutrient use efficiency, nutrientl productivity (total plant dry weight gain per unit of nutrient) and nutrient allocation of all three grass species were mleasured in an attempt to understand their individual growth responses further and to determine whether altered nutrient-usle efficiencies and productivities enable plants exposed to an elevated atmospheric CO2 environment to overcome potential lm imitations to growth imposed by soil fertility. Total uptake of nutrients was, in general, greater in plants of A. capillamris 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, howemver, uptake was considerably reduced in plants grown at the higher CO2 concentration. Overall, a doubling of atmospheric CmO2 concentration had little effect on the nutrient use efficiency or productivity of A, capillaris. Reductions in tissue nm*utrient content resulted from increased plant growth and not altered nutrient use efficiency. In P. alpina, potassium, magm,nesium and calcium productivities were significantly reduced and photosynthetic nitrogen and phosphorus use efficiencies wm7 ere doubled at elevated CO2 with respect to plants grown at ambient CO2. F. vivipara grown for 189 d showed the most markem9!d changes in nutrient use efficiency and nutrient productivity (on an extracted dry weight basis) when grown at elevated CmA"O2. F. vivipara grown at elevated CO2, however, showed large increases in the ratio of nonstructural carbohydrate to nitromC#gen content of leaves and reproductive tissues, indicating a substantial imbalance between the production and utilization mSof assimilate.FOï̯ݯ̳ճBLU^նݶøʸmU%542^8^Bhattacharya,NC^Radin,JW^Kimball,BA^Mauney,JR^Hendrey,GR^Nagy,J^Lewin,KF^Ponce,DC^1994^1^Leaf water relations of cotmaton in a free-air co2-enriched environment^107^70^1-4^171-182^^^^^Sep^^^^^3902JOmc'A^3901^As part of an intensive study of crop response to CO2 enrichment in a free-air CO2 enrichment (FACE) experiment in ms(the field, we determined aspects of the water relations of a cotton crop on selected dates in 1991. The atmosphere was enrmt)iched from 370 mumol CO2 mol-1 (control) to about 550 mumol mol-1 in free air during daylight hours. Under full irrigationm*, CO2 enrichment decreased stomatal conductance and single-leaf transpiration only toward the end of the season, and thesem+ changes led to increased leaf water potentials only at that time of year. Under water-stressed (deficit irrigation) condim,tions, CO2 enrichment decreased conductance throughout the season but there was no corresponding consistent effect on leafm- water potentials. As with the fully irrigated controls, CO2 enrichment increased leaf water potentials only at the end ofm. the season. CO2 enrichment increased season-long biomass accumulation 39% under full irrigation and 34% under deficit irrm/igation. These results are consistent with previous studies of cotton in open-top chambers that found only small effects om0f CO2 enrichment on internal water relations of cotton, and no water stress-induced increase in crop responsiveness to elemvated CO2.11|22222222e3s3t333333 444*4Z4f44495=5m2543^2^Chmora,SN^Mokronosov,AT^1994^1^The global increase of co2 in the atmosphere - adaptive strategies in plants^236^41^5m^677-685^^^^^Sep-Oct^^^^^39042DEExF~FG"GNG\GGGIIIIIIKKKKKKm4A^3903^The effects of short- and long-term exposure to increased CO2 concentrations on the life activity and productivity m5of plants are discussed. Two strategies of plant adaptation to an increasing CO2 concentration are outlined that reflect tm6he diversity of adaptive plant responses at the ecological and physiological levels: physiological adaptation that occurs m7at all organization levels from molecular to cenotic and changes in areas of species that lead to changes in ecosystem commposition occurring in correspondence to the biochemical diversity of photosynthetic pathways.n9544^3^Cotrufo,MF^Ineson,P^Rowland,AP^1994^1^Decomposition of tree leaf litters grown under elevated co2 - effect of littern quality^206^163^1^121-130^^^^^Jun^^^^^3906n;A^3905^Ash (Fraxinus excelsior L.), birch (Betula pubescens Ehrh.), sycamore (Acer pseudoplatanus L.) and Sitka spruce (Pin&nt (350 mu L L(-1) CO2) and enriched (600 mu L L(-1) CO2). Elevated CO2 significantly affected some of the major litter qun6?ality parameters, with lower N, higher lignin concentrations and higher ratios of C/N and lignin/N for litters derived fron?@m enriched CO2. Respiration rates of the deciduous species were significantly decreased for litters grown under elevated CnAAO2, and reductions in mass loss at the end of the experiment were generally observed in litters derived from the 600 ppm CnTBO2 treatment. Nutrient mineralization, dissolved organic carbon, and pH in microcosm leachates did not differ significantlnVCy between the two CO2 treatments for any of the species studied. Litter quality parameters were examined for correlations ndDwith cumulative respiration and decomposition rates: N concentration, C/N and lignin/N ratios showed the highest correlatinfEons, with differences between litter types. The results indicate that higher C storage will occur in soil as a consequencenq of litter quality changes resulting from higher atmospheric concentrations of CO2.nsG545^7^Dugas,WA^Heuer,ML^Hunsaker,D^Kimball,BA^Lewin,KF^Nagy,J^Johnson,M^1994^1^Sap flow measurements of transpiration fromn cotton grown under ambient and enriched co2 concentrations^107^70^1-4^231-245^^^^^Sep^^^^^3908@GnIA^3907^Increasing atmospheric CO2 concentration has many implications for agriculture and forestry, one of which is the efnJfect it will have on transpiration (T). The objective of this work was to quantify T of cotton (Gossypium hirsutum L.) gronKwn in the field under ambient (370 mumol mol-1) and enriched (550 mumol mol-1) CO2 concentrations. Measurements were made nLin 1990 and 1991 at the Maricopa Agricultural Center, Arizona. Constant- power sap flow gauges were used to measure T. In nM1990, three plants and in 1991, 10 plants were simultaneously instrumented with gauges in each of the CO2 treatments. LeafnN area of plants with gauges was measured. T measured by sap flow was compared with evapotranspiration (ET) calculated by wnOater balance in 1990 and with T calculated by water balance in 1991. Soil evaporation was measured using microlysimeters inPn 1991, and was found to be essentially equal (approximately 0.8 mm day-1, or about 10% of T) in the two CO2 treatments. TnQhere were no consistent differences in leaf area of plants with gauges between the two CO2 treatments. Sap flow, for perionRds from 15 min to 2 weeks, was not significantly different between the two CO2 treatments in either year, except for a fewnS days in 1990. In 1991, the coefficient of variation of daily sap flow across plants was the same (about 30%) for both CO2nT treatments throughout the year. The water balance ET (1990) and T (1991) were similar to sap flow in both years, and alsonU showed no effect of CO2 treatment. These results show that for this crop, grown under well-watered and high-fertility connVditions, there was no effect of CO2 on T, on a per unit ground area or per plant basis. These results are relevant for assnessing the effects of increasing atmospheric CO2 concentrations on transpiration by cotton.n546^1^Field,CB^1994^1^Carbon-cycle - arctic chill for co2 uptake^36^371^6497^472-473^^^^^6 OctnY547^6^Hendrix,DL^Mauney,JR^Kimball,BA^Lewin,K^Nagy,J^Hendrey,GR^1994^1^Influence of elevated co2 and mild water-stress on ononstructural carbohydrates in field-grown cotton tissues^107^70^1-4^153-162^^^^^Sep^^^^^3911o[A^3910^Root, stem and leaf tissues, from cotton plants exposed to CO2 at ambient (370 mumol mol-1 (control)) or elevated (o\550 mumol mol-1 (FACE; free-air carbon dioxide enrichment)) levels in the field during the 1990 and 1991 growing seasons, o]were analyzed for nonstructural carbohydrates (glucose, fructose, sucrose and starch). Besides the FACE treatment, these po-^lants were also exposed to two irrigation levels: 100% and 67% replacement of evapotranspiration. FACE had a greater effeco/_t upon cotton plant nonstructural carbohydrates than did irrigation treatments. Leaf carbohydrate content was increased byo7` FACE, but this increase was much more pronounced in the stems and roots. Starch and soluble sugars in leaves in FACE ploto8as tended to be consistently greater than in control leaves, without much change in carbohydrate content during the growingoJb season. In contrast, root and stem, starch and soluble sugar pools were strongly increased by FACE and fluctuated strongloLcy during the growing season. In both seasons, stem and taproot nonstructural carbohydrate content passed through a minimumo^d during periods of heavy boll set. The fluctuations in stem and root carbohydrate content were therefore probably caused bo`ey the varying metabolic demands of the developing plant. These results suggest that a significant effect of CO2 enrichmentogf on starch-accumulating plants is an increase of nonstructural carbohydrate, especially starch, in nonleaf storage pools. oigThis buildup occurs somewhat independently of the water status of the plant, and these enlarged pools can be drawn upon byo the growing plant to maintain growth during periods of high metabolic demand.oi548^9^Hileman,DR^Huluka,G^Kenjige,PK^Sinha,N^Bhattacharya,NC^Biswas,PK^Lewin,KF^Nagy,J^Hendrey,GR^1994^1^Canopy photosynthojesis and transpiration of field-grown cotton exposed to free-air co2 enrichment (face) and differential irrigation^107^70^o1-4^189-207^^^^^Sep^^^^^3913olA^3912^Growth, yield and leaf photosynthetic rates of cotton (Gossypium hirsutum L. ) all respond strongly to CO2 enrichmeomnt, but the gas exchange of whole cotton canopies grown under elevated CO2 has not been investigated. We compared the effeoncts of CO2 enrichment on both single-leaf and whole-canopy photosynthetic rates in cotton. We also determined whole- canopooy photosynthetic and transpiration rates in cotton in response to CO2 enrichment and differential irrigation. Field- grownop cotton was exposed to either 550 mumol mol-1 of CO2 using the free-air carbon dioxide enrichment (FACE) system or to 370 oqmumol mol-1 in control plots. In the second year of the experiment, half of each plot received reduced levels of irrigatioorn. Rates of photosynthesis and stomatal conductance of single leaves were determined using a portable photosynthesis systeosm and a portable steady-state porometer, respectively. Rates of whole-canopy photosynthesis and transpiration were determiotned using a custom-built chamber (about 1 m x 1 m). Midday net photosynthesis rates of both leaves and canopies were 19-41ou% higher in the CO2-enriched plots than in control plots. The CO2 effect on leaf photosynthesis was greatest in July, wherpveas the CO2 effect on canopy photosynthesis was greatest in June and decreased thereafter as mutual shading of leaves and pwthe amount of non- photosynthetic biomass increased. Midday stomatal conductance values of leaves were 13-44% greater in cpxontrol plants than in CO2-enriched plants. Except for late in the second season, canopy transpiration rates were not affecpyted by the CO2 treatment because the decrease in stomatal conductance was offset by an increase in plant size. Differentiap,zl irrigation led to no significant differences in either canopy photosynthesis or transpiration, possibly because differenp.{tial irrigation was applied only during the second half of the season. It appears that cotton crops grown in a future, higp<her-CO2 climate may have increased photosynthetic rates, but water requirements may not be reduced.p=}549^6^Huluka,G^Hileman,DR^Biswas,PK^Lewin,KF^Nagy,J^Hendrey,GR^1994^1^Effects of elevated co2 and water-stress on mineral pIconcentration of cotton^107^70^1-4^141-152^^^^^Sep^^^^^3915pKA^3914^Projected increases in atmospheric CO2 concentrations may alter mineral and protein levels in plant tissues, systemp^atically affecting growth, nutrient cycling and utilization, residue decomposition, and insect-plant interactions in the fp`uture. The free-air CO2 enrichment (FACE) system provided an opportunity to monitor seasonal trends in nutrient status andpn crude protein content of cotton (Gossypium hirsutum L. cv. Deltapine 77) grown in a natural field setting without the limppitations often imposed by growth chambers or reduced rooting volumes. In 1990, plants were exposed to two levels of atmospp|heric CO2 (FACE, almost-equal-to 550 mumol mol-1 and CONTROL, almost-equal-to 370 mumol mol-1) and two irrigation regimes p~(100% and 75% replacement of evapotranspiration) beginning in early July. Cotton leaves, stem, and roots were sampled at dpifferent 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 proptein concentrations of leaves, stems and roots were significantly lower in FACE plants than in CONTROL plants, but C:N ratpios were higher for the FACE plants than the CONTROL plants. Some other elements were significantly affected by CO2 enrichpment, but not for all dates and all plant tissues. There were no significant effects in any of the data because of the irrpigation treatment or the irrigation-CO2 interaction. Reductions in tissue N and protein concentrations and the increases ipn the C:N with CO2 enrichment have important implications for agricultural and natural systems and demand additional reseaprch.p550^10^Idso,SB^Kimball,BA^Wall,GW^Garcia,RL^Lamorte,R^Pinter,PJ^Mauney,JR^Hendrey,GR^Lewin,K^Nagy,J^1994^1^Effects of freep-air co2 enrichment on the light response curve of net photosynthesis in cotton leaves^107^70^1-4^183-188^^^^^Sep^^^^^3917pA^3916^Daytime measurements of leaf CO2 exchange rates in a free-air CO2 enrichment (FACE) experiment reveal that at photopsynthetically active radiation (PAR) flux rates in excess of 1000 mumol m-2 s-1, cotton leaves exposed to an atmospheric CpO2 concentration of approximately 500 mumol mol-1 exhibit net photosynthetic rates about 30% greater than those for leavesp of similar plants growing in ambient air. As PAR flux rates drop below this value, the stimulatory effect of elevated CO2p rises, suggesting that the relative benefits of atmospheric CO2 enrichment will be greater for shaded cotton leaves that pfor those exposed to full sunlight.LMNOPQRSTUVWXYZ[\]^_`pcdefghijklmnopqrstuvwxyz{|}~q551^11^Kirschbaum,MUF^King,DA^Comins,HN^McMurtrie,RE^Medlyn,BE^Pongracic,S^Murty,D^Keith,H^Raison,RJ^Khanna,PK^Sheriff,DW^q1994^1^Modeling forest response to increasing co2 concentration under nutrient-limited conditions^9^17^10^1081-1099^^^^^Ocqt^^^^^3919qA^3918^The growth rates of woody plants depend on both the rate of photosynthetic carbon gain and the availability of esseq&ntial nutrients. Instantaneous carbon gain is known to increase in response to increasing atmospheric CO2 concentration, bq(ut it is uncertain whether this will translate into increased growth in the longer term under nutrient-limited conditions.q6 An analytical model to address this question was developed by Comins and McMurtrie (1993, Ecological Applications 3, 666-q8 681). Their model was further tested and analysed. Manipulation of various assumptions in the model revealed its key assuqFmptions and allowed a more confident prediction of expected growth responses to CO2 enrichment under nutrient-limited condqGitions. The analysis indicated that conclusions about the CO2 sensitivity of production were strongly influenced by assumpqNtions about the relationship between foliar and heartwood nitrogen concentrations. With heartwood nitrogen concentration pqProportional to foliar nitrogen concentration, the model predicted a strong response of plant productivity to increasing COqb2 concentration, whereas with heartwood nitrogen concentration set constant, the model predicted only a very slight growthqd response to changing CO2 concentration. On the other hand, predictions were only slightly affected by: (1) assumptions abqnout the extent of nitrogen retranslocation out of senescing roots and foliage or wood during heartwood formation; (2) the qpeffects of nitrogen status on specific Leaf area or (3) leaf longevity; (4) carbon allocation between different plant partqs; or (5) changes in the N:C ratio of organic matter sequestered in the passive pool of soil organic matter. Modification qof the effect of foliar nitrogen concentration on the light utilization coefficient had only a small effect on the CO2 senqsitivity for pines. However, this conclusion was strongly dependent on the chosen relationship between single- leaf photosqynthesis and leaf nitrogen concentration. Overall, the analysis suggested that trees growing under nitrogen- limited condiqtions can respond to increasing atmospheric CO2 concentration with considerable increases in growth.q552^4^Lewis,JD^Griffin,KL^Thomas,RB^Strain,BR^1994^1^Phosphorus supply affects the photosynthetic capacity of loblolly-pinqe grown in elevated carbon-dioxide^13^14^11^1229-1244^^^^^Nov^^^^^3921qA^3920^Effects of phosphorus supply and mycorrhizal status on the response of photosynthetic capacity to elevated CO2 wereq investigated in loblolly pine (Pinus taeda L.) seedlings. Seedlings were grown in greenhouses maintained at either 35.5 oqr 71.0 Pa CO2 in a full factorial experiment with or without mycorrhizal inoculum (Pisolithus tinctorius (Pers.) Coker & Cqouch) and with an adequate or a limiting supply of phosphorus. Assimilation versus internal CO2 partial pressure (C(i)) cuqrves were used to estimate maximum Rubisco activity (V(c,max)), electron transport mediated ribulose 1,5-bisphosphate regeqneration capacity (J(max)), phosphate regeneration capacity (PiRC) and daytime respiration rates (R(d)). Nonmycorrhizal seqedlings grown with limiting phosphorus had significantly reduced V(c,max) and PiRC compared to seedlings in other treatmenqts. Elevated CO2 increased photosynthetic capacity in nonmycorrhizal seedlings in the low phosphorus treatment by increasiqng PiRC, whereas it induced phosphorus limitation in mycorrhizal seedlings in the low phosphorus treatment and did not affrect the photosynthetic capacity of seedlings in the high phosphorus treatment. Despite the variety of effects on photosyntrhetic capacity, seedlings in the elevated CO2 treatments had higher net assimilation rates than seedlings in the ambient CrO2 treatments. We conclude that phosphorus supply affects photosynthetic capacity during long-term exposure to elevated COr2 through effects on Rubisco activity and ribulose 1,5-bisphosphate regeneration rates.RS & FAXES\CONTEMr*553^1^Mortensen,LM^1994^1^The influence of carbon-dioxide or ozone concentration on growth and assimilate partitioning in r,seedlings of 9 conifers^200^44^3^157-163^^^^^Sep^^^^^3923FAX.DOT>@PROGRAM FILESr:A^3922^Seedlings of nine different conifers were exposed to 355 and 730 mu mol mol(-1) CO2, or low (< 15 nmol mol(-1)) andr< elevated O-3 concentration (70 nmol mol(-1)) for 81-116 days. The experiments were conducted in growth chambers placed inrA a greenhouse. Increased CO2 concentration enhanced the mean relative growth rate (RGR) and total plant dry weight by 4 anrCd 33% in Larix leptolepis, by 4 and 38% in Larix sibirica, by 7 and 47% in Picea glauca and by 3 and 16% in Picea sitchensrNis, respectively. The growth rates and dry weights of Pinus contorta, Pinus mugo and Pseudotsuga menziesii were not signifrPicantly affected. Carbon dioxide enrichment enhanced RGR of two provenances of Picea abies by 4 and 6%, respectively, whilr\e a third provenance was unaffected. In Pinus sylvestris, only the RGR of one of three provenances was stimulated by CO2 er^nrichment (4%). After two growth seasons CO2 enrichment enhanced RGR and total plant dry weight by 11 and 35% in Picea abirnes and by 12 and 36% in Pinus sylvestris, respectively. Elevated CO2 decreased the shoot:root ratio in Larix leptolepis, arpnd decreased the needle:stem ratio in Picea glauca, but increased it in Pseudotsuga menziesii. Elevated O-3 significantly rdecreased the plant dry weight in Picea sitchensis, Pseudotsuga menziesii and in one of three provenances of Pinus sylvestrris, while the other species and provenances were unaffected. Increased O-3 concentration increased the shoot:root dry weirght ratio in one of three Picea abies provenances, in all three Pinus sylvestris provenances and in Pinus contorta. The neredle:stem ratio was enhanced by O- 3 in seven of the nine species. The O-3 exposure caused chlorosis of needles in all spercies except Pseudotsuga menziesii.,,nnn,B,,r554^1^Mortensen,LM^1994^1^Effects of carbon-dioxide concentration on assimilate partitioning, photosynthesis and transpirartion of betula- pendula roth and picea-abies (L) karst seedlings at 2 temperatures^200^44^3^164-169^^^^^Sep^^^^^3925rA^3924^Seedlings of Betula pendula Roth. and Picea abies (L.) Karat. were grown at 350 and 700 mu mol mol(-1) CO2 for 35 orr 45 days at 15 and 20 degrees C in eight growth chambers. The mean photosynthetic flux was 15-22 mol m(-2) day(-1). The mrean relative growth rate was increased by 7% in Betula and by 10% in Picea at the highest CO2 concentration. This correspornded to an increase in the total plant dry weight of 20 and 19%, respectively The shoot:root and leaf:stem ratios were unarffected by the CO2 concentration in both species. High CO2 levels increased the stem diameter and the number of lateral shroots in Betula. Increasing the temperature did not affect the assimilate partitioning between leaf stem and root in Betular, but the needle:stem ratio decreased in Picea. Elevated CO2 concentration increased the number of lateral shoots in Betuls a more at 15 than at 20 degrees C, however, the total weight of the lateral shoots was not affected. With this exception ts he effect of CO2 was generally the same at both temperatures. Measurements of the CO2 exchange rates indicated that a sligsht acclimation to high CO2 had taken place at the end of the experimental period in the two species. Elevated CO2 slightlys decreased the transpiration rate of Betula.associated with differences in sensitivity to heat during reproductive develos#555^5^Nagy,J^Lewin,KF^Hendrey,GR^Hassinger,E^Lamorte,R^1994^1^Face facility co2 concentration control and co2 use in 1990 s2and 1991^107^70^1-4^31-48^^^^^Sep^^^^^3927-1. Under intermediate night temperature (33/20-degrees-C), all lines set substs4A^3926^CO2 treatment level control and CO2 use are reported for free- air carbon dioxide enrichment (FACE) facility operats6ions at the University of Arizona's Maricopa Agricultural Center in 1990 and 1991. These are required for evaluation of thsHe validity of biological experiments conducted in four replicates of paired experimental and control plots in a large cottsIon field and the cost-effectiveness of the plant fumigation facility. Gas concentration was controlled to 550 mumol mol-1 sNat the center of each experimental plot, just above the canopy. In both years, season-long (April-September) average CO2 lsPevels during treatment hours (05:00-19:00 h Mountain Standard Time) were 550 mumol mol-1 measured at treatment plot centersZs when the facility was operating. Including downtime, the season average was 548 mumol mol-1 in 1991. In 1990, the seasons\ averages for the four elevated CO2 treatments varied from 522 to 544 mumol mol-1, owing to extended periods of downtime asefter lightning damage. Ambient CO2 concentration during treatment was 370 mumol mol-1. Instantaneous measurements of CO2 csgoncentration were within 10% of the target concentration of 550 mumol mol-1 more than 65% of the time when the facility waszs operating, and 1 min averages were within 10% of the target concentration for 90% of the time. The long-term average of s|CO2 concentration measured over the 20 m diameter experimental area of one array at the height of the canopy was in the rasnge 550-580 mumol mol- 1 during July 1991, with the higher values near the edges. In 1991, CO2 demand averaged 1250 kg pers array per 14 h treatment day, or 4 kg m-2 of fumigated plant canopy. The FACE facility provided good temporal and spatials control of CO2 concentration and was a cost-effective method for large-scale field evaluations of the biological effects sof CO2.HESIS; AVAILABILITY; TEMPERATURE; IRRADIANCE AB Growth parameters of Agrostis capillaris L. and Nardus stricta L. s556^10^Oechel,WC^Cowles,S^Grulke,N^Hastings,SJ^Lawrence,B^Prudhomme,T^Riechers,G^Strain,B^Tissue,D^Vourlitis,G^1994^1^Transsient nature of co2 fertilization in arctic tundra^36^371^6497^500-503^^^^^6 Oct^^^^^3929llaris had attained approx. foursA^3928^THERE has been much debate about the effect of increased atmospheric CO2 concentrations on plant net primary producstion(1,3) and on net ecosystem CO2 flux(3-10). Apparently conflicting experimental findings could be the result of differesnces in genetic potential(11-15) and resource availability(16-20), different experimental conditions(21-24) and the fact tshat many studies have focused on individual components of the system(2,21,25-27) rather than the whole ecosystem. Here we spresent results of an in situ experiment on the response of an intact native ecosystem to elevated CO2. An undisturbed patsch of tussock tundra at Toolik Lake, Alaska, was enclosed in greenhouses in which the CO2 level, moisture and temperature scould be controlled(28), and was subjected to ambient (340 p.p.m.) and elevated (680 p.p.m.) levels of CO2 and temperaturet (+4 degrees C). Air humidity, precipitation and soil water table were maintained at ambient control levels. For a doubledt CO2 level alone, complete homeostasis of the CO2 flux was re-established within three Sears, whereas the regions exposed tto a combination of higher temperatures and doubled CO2 showed persistent fertilization effect on net ecosystem carbon seqtuestration over this time. This difference may be due to enhanced sink activity from the direct effects of higher temperattures on growth(16,29-33) and to indirect effects from enhanced nutrient supply caused by increased mineralization(10,11,19t!,27,34). These results indicate that the responses of native ecosystems to elevated CO2 may not always be positive, and art*e unlikely to be straightforward. Clearly, CO2 fertilization effects must always be considered in the context of genetic lt+imitation, resource availability and other such factors.-4330 MULHEIM, GERMANY. IOWA STATE UNIV SCI & TECHNOL, DEPT BOT, t>557^3^Pearson,M^Besford,RT^Hand,DW^1994^1^The effects of oxides of nitrogen and carbon-dioxide enrichment on growth and cotAntent of ribulose-1, 5-bisphosphate carboxylase-oxygenase and nitrite reductase in glasshouse lettuce^174^69^2^257-266^^^^tM^Mar^^^^^3931e state-of-knowledge of the past, present, and potential future roles of tropical forests in the global C cytOts. Hence the division of the normalized results of the first data set by the normalized results of the second set yields t[a representation of the increase in whole-tree net photosynthesis due to enhanced needle production caused by atmospheric t]CO2 enrichment. In the solitary trees we studied, the relative contribution of this effect increased rapidly with the CO2 toconcentration of the air to increase whole-tree net photosynthesis by nearly 50% at a CO2 concentration approximately 300 tqA^3930^Different systems of CO2 enrichment and heating were used to produce glasshouse atmospheres with varying concentrattions of NO(x) and CO2 (ambient NO(x) and CO2, ambient NO(x) and 1000 vpm CO2, and three concentrations of NO(x) varying bettween 0.5 and 2.5 vpm with concurrent CO2 concentrations between 1000- 2500 vpm). The growth response of winter lettuce int these environments was assessed for three contrasting cultivars (Ambassador, Berlo and Pascal). Contents of ribulose-1, 5t- bisphosphate carboxylase-oxygenase (RuBPco) and nitrite reductase (NiR) in the leaf tissue were also determined using imtmunoblotting and enzyme-linked immunosorbent assay (ELISA). 'Ambassador' produced the heaviest ''head'' weights, but on matrketable criteria 'Berlo' performed better. CO2 enrichment enhanced yields, but the High NO(x) treatments reduced growth rt elative to that in the Low NO(x) and unpolluted environments. Growth assessments suggested a greater tolerance of NO(x) int cvs Berlo and Pascal than in cv. Ambassador. Immunoblots showed that the antibodies used here were specific. Using these t antibodies in ELISA, 'Pascal' was found to contain more RuBPco and NiR on a leaf area basis than 'Ambassador'. There were t reductions in RuBPco and NiR contents in response to growth in elevated CO2. Elevated CO2 caused a reduction in RuBPco andt NiR in 'Ambassador', but in 'Pascal' only RuBPco levels were reduced. This may account for the greater relative tolerancet of 'Pascal' and the sensitivity of 'Ambassador' to NO(x) pollution.ospheric (A) or enriched (E) concentrations of 300-33t558^6^Pinter,PJ^Kimball,BA^Mauney,JR^Hendrey,GR^Lewin,KF^Nagy,J^1994^1^Effects of free-air carbon-dioxide enrichment on patr absorption and conversion efficiency by cotton^107^70^1-4^209-230^^^^^Sep^^^^^3933urface during the P(N) measurements rtA^3932^Anticipated changes in global climate and atmospheric CO2 concentrations have very important, albeit poorly understtood consequences for production agriculture. Effects of these changes on plants have usually been examined in controlled- uenvironment enclosures, glass-houses, or open-top field chambers. Beginning in 1989, an innovative experimental free- air uCO2 enrichment (FACE) facility was operated in central Arizona to evaluate crop response to increased CO2 levels within a ularge, open-field production environment. Cotton (Gossypium hirsutum L.) was grown for three consecutive seasons under expuosed to either ambient (control, about 370 mumol mol- 1) or elevated (FACE, 550 mumol mol-1) CO2 concentrations. Deficit iu&rrigation regimes supplying 75% (beginning in July 1990) or 67% (beginning in mid-May 1991) of the crop's evapotranspiratiu(on requirement were included as additional treatment variables. Plant growth was monitored by periodic sampling. Canopy reu*flectances in visible (blue, 0.45-0.52 mum; green, 0.05-0.59 mum; red, 0.61-0.68 mum) and near-infrared (NIR; 0.79-0.89 muu7m) wavebands were measured frequently with an Exotech radiometer and related to absorbed photosynthetically active radiatiu9on (PAR; 0.4-0.7 mum) measured with a line quantum sensor. Dry biomass of plants in the FACE treatment was significantly (uGP < 0.05) greater than control values during each year of the study. The FACE plant canopy also absorbed significantly moruIe PAR than controls during the early and middle portion of the 1990 and 1991 seasons. Light use efficiency (LUE, biomass puTroduced per unit absorbed PAR) was significantly higher in FACE plots during each year. In the well-watered irrigation treuVatment, the 3 year mean LUE was 1.97 g MJ-1 for FACE and 1.56 g MJ-1 for controls. The deficit irrigation treatment in 199ud 1 produced significantly smaller plants, which absorbed less PAR and had lower LUE than plants in the well-watered treatmeue!nt (P < 0.05). No interaction was observed between CO2 and irrigation treatments. FACE research under realistic field conduq"itions revealed positive consequences of increased CO2 on cotton plant biomass, PAR absorption, and LUE. It also demonstraus#ted the effectiveness of this new technology for examining community-level plant responses to possible changes in global eunvironment.omplex enterprises (farms and forests) to climate change and their ability to adjust and adapt; and (4) integru%559^4^Prior,SA^Rogers,HH^Runion,GB^Mauney,JR^1994^1^Effects of free-air co2 enrichment on cotton root-growth^107^70^1-4^69u-86^^^^^Sep^^^^^3935on opportunities and of the inter-industry linkages that determine what the overall impacts on the reu'A^3934^The rise in atmospheric CO2 concentration is predicted to have a positive effect on agro-ecosystem productivity. Hou(wever, an area which requires further investigation centers on responses of crop root systems to elevated atmospheric CO2 u)under field conditions. The advent of free-air CO2 enrichment (FACE) technology provides a new method of CO2 exposure withu* minimal alteration of plant microclimate. In 1990 and 1991, cotton (Gossypium hirsutum (L.) 'Deltapine 77') was grown undu+er two atmospheric CO2 levels (370 and 550 mumol mol-1) and two water regimes (wet (100% of ET replaced) and dry (75% of Eu,T replaced in 1990 and 67% in 1991)). Plant root samples were collected at early vegetative and mid-reproductive growth. Tu-aproots of CO2-enriched plants displayed greater volume, dry weight, length, and tissue density. Water treatment effects wu.ere noted for length, volume and dry weight of roots at the second sampling in 1991. In general, whole soil profile root du/ensities (both length and dry weight densities) and root weight per unit length at the initial sampling were increased undu0er CO2 enrichment at each of three positions (0.00, 0.25, and 0.50 m) from row center to the middle of the inter-row spacev1. At the second sampling, root length density and root dry weight density were generally unaffected by water stress, wherev2as root weight per unit length was somewhat higher. In addition, extra CO2 increased whole profile root length density onlv3y at the 0.50 m inter-row position, whereas whole profile root dry weight density and root weight per unit length were genv'4erally higher under elevated CO2 at all three positions. The results from this field experiment strongly indicated that inv)creased atmospheric CO2 level would enhance plant root growth.n dioxide or is due to other factors. Doubts concerning thev66560^5^Reeves,DW^Rogers,HH^Prior,SA^Wood,CW^Runion,GB^1994^1^Elevated atmospheric carbon-dioxide effects on sorghum and soyv8bean nutrient status^166^17^11^1939-1954^^^^^^^^^^3937ent limitations2,3,10. Here we present evidence that mineral nutrievF8A^3936^Increasing atmospheric carbon dioxide (CO2) concentration could have significant implications on technologies for mvH9anaging plant nutrition to sustain crop productivity in the future. Soybean (Glycine max [L.] Merr.) (C3 species) and graivU:n sorghum (Sorghum bicolor [L.] Moench) (C4 species) were grown in a replicated split-plot design using open-top field chavW;mbers under ambient (357 mu mol/mol) and elevated (705 mu mol/mol) atmospheric CO2. At anthesis, leaf disks were taken froveweight were also measured. Above-ground dry matter and seed yield were determined at maturiry. Seed yield of sorghum increvv?ased 17.5% and soybean seed yield increased 34.7% with elevated CO2. There were no differences in extractable chlorophyll v@concentration or chlorophyll meter readings due to CO2 treatment, but meter readings were reduced 6% when sorghum was growvAn in chambers as compared in the open. Leaf nitrogen (N) concentration of soybean decreased from 54.5 to 39.1 g/kg at the vBhigher CO2 concentration. Neither the chambers nor CO2 had an effect on concentrations of other plant nutrients in either vCspecies. Further work under field conditions is needed to determine if current critical values for tissue N in crops, espevcially C3 crops, should be adjusted for future increases in atmospheric CO2 concentration.d to evaluate the impacts of thvE561^6^Runion,GB^Curl,EA^Rogers,HH^Backman,PA^Rodriguezkabana,R^Helms,BE^1994^1^Effects of free-air co2 enrichment on microvbial-populations in the rhizosphere and phyllosphere of cotton^107^70^1-4^117-130^^^^^Sep^^^^^3939 sorghum and soybeans wvGA^3938^Cotton (Gossypium hirsutum L.) plants were exposed to free-air CO2 enriched (FACE = 550 mumol mol-1) or ambient (COvHNTROL = 370 mumol mol-1) levels of atmospheric CO2 and to wet (100% of evapotranspiration replaced) or dry (67% of ET replvIaced) soil water content treatments. Foliar, soil and root samples were collected in June and August 1991 to determine thevJ effects of elevated CO2 on selected groups of phyllosphere and rhizosphere microorganisms. Foliage and rhizosphere soil wvKere analyzed for bacteria and/or fungi using dilution plating. Mycorrhizal colonization of cotton roots was assessed. RootvL-zone soil was analyzed for populations of nematodes, microarthropods and Rhizoctonia using various extraction methods. A vMdehydrogenase assay for total microbial respiration and a bioassay for cotton root infecting organisms were also conductedvN using root-zone soil. Populations of fungi on cotton leaves varied, by genera, in response to CO2 enrichment, but none wavOs affected by soil water content treatments; populations of foliar bacteria were not affected by either CO2 or soil water wPcontent treatments. In August, higher total numbers of rhizosphere fungi were found under the wet compared with the dry sowQil water treatment, but differences related to CO2 were not detected. There was a trend for infestation by Rhizoctonia solwRani to be higher under FACE in the August sample, but the soil bioassay demonstrated no increase in damping-off potential.w S There was a significant interaction between CO2 concentration and soil water content for populations of saprophagous nemawTtodes; populations were different between the CO2 levels in the dry soil treatment only, with higher numbers under FACE. MwUicroarthropod numbers were low; however, there was a trend for Collembola populations to be higher under FACE in the Augusw(Vt sample and more fungi were isolated from Collembola in June. Total microbial activity was higher under FACE at both sampw*Wle dates. Effects of elevated atmospheric CO2 on plant-microbe interactions could have profound influence on the productivw6ity of agro-ecosystems, and deserve further research.eaf area or leaf number, while a significant effect was found with bw9Y562^6^Tarnawski,MG^Green,TGA^Buedel,B^Meyer,A^Zellner,H^Lange,OL^1994^1^Diel changes of atmospheric co2 concentration withw@in, and above, cryptogam stands in a new-zealand temperate rain-forest^237^32^3^329-336^^^^^^^^^^3941additional dry mattewB^3940^Atmospheric CO2 levels were determined (at 2m height) in the rainforest and in a clearing outside the forest, durinwN\g spring (November) 1991, Urewera National Park, New Zealand. CO2 levels within the forest were 30 ppm higher and showed awP] more variable diel pattern (range up to 70 ppm) than outside the forest. CO2 levels were generally higher at night than dwf^uring the day. Detailed measurements were made at several sites at a depth of 25 mm in the phylloplane of three moss speciwg_es and under, or between, the thalli of four lichen species. Mean levels were 50% (moss phylloplane) and 10% (lichen thallwp`i) higher than the levels in the clearing and, in 80% of sites, also higher than air within the rainforest. The diel pattewrarn of the CO2 concentration at each of the sites was not predictable from measurements of CO2 in the bulk air of the foresw|bt. High levels of CO2 may be important in elevating photosynthetic rates of mosses and, to a lesser extent, lichens in thew~ field. the impact of the 1931-1940 analog climate (with and without CO2 enrichment) on Missouri, Iowa, Nebraska, and Kanwd563^3^Wall,GW^Amthor,JS^Kimball,BA^1994^1^Cotco2 - a cotton growth simulation-model for global change^107^70^1-4^289-342^^w^^^Sep^^^^^3943r evaporation under the 1931-1940 analog and the 1951-1980 control climates. A modification of the ErosionwfA^3942^In conjunction with the Free-Air-CO2-Enrichment (FACE) project, a new, physiologically based, mechanistic, modular wgsimulation model of cotton (Gossypium hirsutum L.) physiology, growth, development, yield and water use has been constructwhed. It is named COTCO2 for cotton response to atmospheric CO2 concentration. The model is capable of predicting cotton crowip responses to elevated atmospheric CO2 concentrations and potential concomitant changing climate variables. The major plawjnt processes known to be influenced by CO2 are simulated explicitly, i.e. photosynthesis, photorespiration, and stomatal cwkonductance, and its role in leaf energy balance. The model explicitly simulates the impact of atmospheric CO2 concentratiowln on C3 photosynthesis and photorespiration at the level of carboxylation and oxygenation. Growth is simulated for individwmual organs, i.e. leaf blade, stem segment, taproot and lateral roots, and fruit which includes squares and bolls. Potentiawnl growth is calculated and the carbohydrate and nitrogen required to meet this potential are calculated. Actual growth is wobased on substrate availability, the potential growth, and water stress. Our intent here is to describe the overall structwpure of the model, its present status, and future development plans. Further development, documentation, calibration, and vwqalidation of the model is in progress. The long range goal of the project is to provide quantitative estimates of global cwotton production in a future higher-CO2 world. carbon dioxide availability to investigate the interactive effects of thesws564^3^Wilsey,BJ^McNaughton,SJ^Coleman,JS^1994^1^Will increases in atmospheric co2 affect regrowth following grazing in C-4x grasses from tropical grasslands - a test with sporobolus-kentrophyllus^2^99^1-2^141-144^^^^^Sep^^^^^3945after 100 days x uA^3944^We grew a C-4 grass from the Serengeti ecosystem under ambient (370 ppm) and elevated (700 ppm) CO2, and under clipxvped and unclipped conditions to test whether regrowth following grazing would be affected by elevated CO2. Above-ground prxwoductivity was slightly decreased under elevated CO2, and was similar between clipped and unclipped plants. Regrowth (clipxxping offtake) following clipping was similar in the two CO2 treatments, and there was no CO2 by clipping interaction on bix!yomass, productivity, or leaf nutrient concentrations. Based on this evidence, we suggest that C-4 grasses from the Serengex-ti will show little direct response to future increases in atmospheric CO2. photoassimilates mediated by resource availabx/{565^5^Wood,CW^Torbert,HA^Rogers,HH^Runion,GB^Prior,SA^1994^1^Free-air co2 enrichment effects on soil carbon and nitrogen^1x>07^70^1-4^103-116^^^^^Sep^^^^^3947ANGE RESPONSES OF 2 DECIDUOUS HARDWOODS DURING 3 YEARS OF GROWTH IN ELEVATED CO2 - NO Lx@}A^3946^Since the onset of the industrial revolution, atmospheric CO2 concentration has increased exponentially to the currxN~ent 370 mumol mol-1 level, and continued increases are expected. Previous research has demonstrated that elevated atmosphexPric CO2 results in larger plants returning greater amounts of C to the soil. However, the effects of elevated CO2 on C andx^ N cycling and long-term storage of C in soil have not been examined. Soil samples (in 0-50, 50-100, and 100-200 mm depth x`increments) were collected after 3 years of cotton (Gossypium hirsutum L.) production under free-air CO2 enrichment (FACE,xq at 550 mumol CO2 mol-1), in combination with 2 years of different soil moisture regimes (wet, 100% of evapotranspiration xsreplaced, or dry, 75% and 67% of evapotranspiration replaced in 1990 and 1991, respectively) on a Trix clay loam (fine, lox~amy, mixed (calcareous), hyperthermic Typic Torrifluvent) at Maricopa, Arizona. Ambient plots (370 mumol CO2 mol-1 (controxl)), in combination with the wet and dry soil moisture regimes, were also included in the study. Soil organic C and N concxentrations, potential C and N mineralization, and C turnover were measured. Increased input of cotton plant residues underx FACE resulted in treatment differences and trends toward increased organic C in all three soil depths. During the first 3x0 days of laboratory incubation, available N apparently limited potential C mineralization and C turnover in all treatmentxs. Between 30 and 60 days of incubation, soils from FACE plots had greater potential C mineralization with both water regixmes, but C turnover increased in soils from the dry treatment and decreased in soils where cotton was not water stressed. xThese data indicate that in high-CO2 environments without water stress, increased C storage in soil is likely, but it is lxess likely where water stress is a factor. More research is needed before the ability of soil to store additional C in a hxigh-CO2 world can be determined.ses, but many additional factors interact in determining whole-plant and forest responsesx566^3^Xu,DQ^Gifford,RM^Chow,WS^1994^1^Photosynthetic acclimation in pea and soybean to high atmospheric co2 partial-pressuxre^8^106^2^661-671^^^^^Oct^^^^^3949MS, AJM ZEHNDER, AJB TI A HIGHLY PURIFIED ENRICHMENT CULTURE COUPLES THE REDUCTIVE DECxA^3948^Nonnodulated pea (Pisum sativum L. cv Frosty) and soybean (Glycine max [L.] Merr. cv Wye) plants were grown under axrtificial lights from germination with ample nutrients, 600 mu mol photons m(-2) s(-1), and either 34 to 36 (control) or 6x4 to 68 Pa (enriched) CO2. For soybean, pod removal and whole-plant shading treatments were used to alter the source-sink xbalance and carbohydrate status of the plants. Growth of both species was substantially increased by CO2 enrichment despitye some down-regulation of photosynthesis rate per unit leaf area (''acclimation''). Acclimation was observed in young pea yleaves but not old and in old soybean leaves but not young. Acclimation was neither evident in quantum yield nor was it reylated to triose phosphate limitation of net photosynthesis. A correlation between levels of starch and sugars in the leaf yand the amount of acclimation was apparent but was loose and only weakly related to the source-sink balance of the plant. yA consistent feature of acclimation was reduced ribulose bisphosphate carboxylase (RuBPCase) content, although in vivo RuByPCase activity was not necessarily diminished by elevated growth CO2 owing to increased percentage of activation of the eny1zyme. A proposal is discussed that the complexity of photosynthetic acclimation responses to elevated CO2 is as an expressy3ion of re-optimization of deployment of within-plant resources at three levels of competition. temperature of 25 to 35-deyD567^4^Allen,LH^Valle,RR^Mishoe,JW^Jones,JW^1994^1^Soybean leaf gas-exchange responses to carbon-dioxide and water-stress^4yF8^86^4^625-636^^^^^Jul-Aug^^^^^3951 derived from H-2 or formate consumption were recovered in dechlorination products andy\A^3950^As global carbon dioxide concentrations rise, we need to understand the combination of direct effects of this gas ay^nd the anticipated effects of climate change, including drought, on physiology and growth of all crops. Effects Of CO2 on ycplants begin at the leaf level; our objectives, therefore, were to determine interrelationships among factors governing gayfs exchange responses of soybean [Glycine max (L.) Merr.] leaves to elevated CO2 and water stress. Photosynthetic CO2 assimyrilation and transpiration rates were measured in cuvettes on leaflets of soybean (cv. Bragg) grown in controlled- environmytent chambers at 330 and 660 mumol CO2 Mol-1 air. Leaflets at high CO2, either water-stressed or well-watered, had higher py}hotosynthetic and lower transpiration rates, and therefore higher water-use efficiencies (WUE), than those at Control CO2 ylevels. As irrigation was withheld during an 11-d period, WUE decreased about 30 to 50% with respect to the well- watered ytreatments. Midday leaf temperature and leaf-to-air vapor pressure gradient levels increased as the water stress progresseyd. For water stress treatments, midday leaf conductance (G(lw)) was generally higher and residual internal conductance (G(yr)) was generally lower in low than in high CO2. Ratios of midday G(r)/G(lc), were nearly constant throughout the period iyn both the stressed and the well-watered treatments. The ratios of intercellular C(i), to ambient C(a), CO2 concentration y(i.e., C(i)/C(a)) during the water stress period remained similar to the respective nonstressed treatments within each CO2y level. These findings support the concept that leaf conductances are governed by CO2 assimilation rates under water-stresysed as well as unstressed conditions.esis and a CO2-induced reduction in nighttime dark respiration. Measurements of thesy568^2^Brioua,AH^Wheeler,CT^1994^1^Growth and nitrogen-fixation in alnus-glutinosa (L) gaertn under carbon-dioxide enrichmeynt of the root atmosphere^206^162^2^183-191^^^^^May^^^^^3953 earth's trees, in the mean, probably share this same responsyA^3952^The effects of aeration of the N-free rooting medium with elevated CO2 on (a) acetylene reduction by perlite-grown yplants and (b) N-2-fixation and long-term growth of nutrient solution- grown plants were determined for nodulated Alnus glyutinosa (L.) Gaertn. In the former experiments, roots of intact plants were incubated in acetylene in air in darkened glasys jars for 3 hr, followed by a further 3 hr incubation period in air enriched with CO2 (0-5%). During incubation, the CO2 ycontent of the jars increased by 0.17% per hour due to respiration of the root system, so that the CO2 content at 3 hr wasu 0.5%. Additional enrichment of the rooting medium gas-phase with CO2 equivalent to 1.1% and 1.75% CO2 of the gas volume szignificantly increased nitrogenase activity (ethylene production) by 55% and 50% respectively, while enrichment with greatz er than 2.5% CO2 decreased activity. In contrast, ethylene production by control plants, where CO2 was not added to the aszsay jars, decreased by 8% over the assay period. In long-term growth experiments, nodulated roots of intact Alnus glutinosza plants were sealed into jars containing N-free nutrient solution (pH 6.3) and aerated with air, or air containing elevatzed levels of CO2 (1.5% and 5%). Comparison of the appearance of CO2-treated with air treated plants suggested that 1.5% COz)2 stimulated plant growth. However, at harvest after 5 or 6 weeks variability between plants masked the significance of diz+fferences in plant dry weight. A significant increase of 33% in total nitrogen of plants aerated with 1.5% CO2, compared wz5ith air-treated plants, was demonstrated, broadly in line with the short-term increase in acetylene reducing activity obsez7rved following incubations with similar CO2 concentrations. Shoot dry weight was not affected significantly by long-term ezBxposure to 5% CO2, the main effect on growth being a 20% reduction in dry weight of the root system, possibly through inhizDbition of root system respiration. However, in contrast to the inhibitory effects of high CO2 on acetylene reduction therezO was no significant effect on the amounts of N-2 fixed.the peat seedlings. At the control CO2 level, the content of more zQ569^2^Caulfield,F^Bunce,JA^1994^1^Elevated atmospheric carbon-dioxide concentration affects interactions between spodopterz^a-exigua (lepidoptera, noctuidae) larvae and 2 host-plant species outdoors^238^23^4^999-1005^^^^^Aug^^^^^3955ment of atmozaA^3954^Beet armyworm, Spodoptera exigua (Hubner), larvae were placed on sugarbeet (Beta vulgaris L.) and pigweed (Amaranthzpus hybridus L.) plants in outdoor chambers in which the plants were growing at either the ambient (almost-equal-to 350 mulzr liter-1) or ambient plus 350 mul liter-1 (almost-equal-to 700 mul liter-1) carbon dioxide concentration. A series of expezriments was performed to determine if larvae reduced plant growth differently at the two carbon dioxide concentrations in zeither species and if the insect growth or survival differed with carbon dioxide concentration. Leaf nitrogen, water, starzch, and soluble carbohydrate contents were measured to assess carbon dioxide concentration effects on leaf quality. Insectz feeding significantly reduced plant growth in sugarbeet plants at 350 mul liter-1 but not at 700 mul liter-1 nor in pigwezed at either carbon dioxide concentration. Larval survival was greater on sugarbeet plants at the elevated carbon dioxide zconcentration. Increased survival occurred only if the insects were at the elevated carbon dioxide concentration and consuzmed leaf material grown at the elevated concentration. Leaf quality was only marginally affected by growth at elevated carzbon dioxide concentration in these experiments. The results indicate that in designing experiments to predict effects of ezlevated atmospheric carbon dioxide concentrations on plant- insect interactions, both plants and insects should be exposedz to the experimental carbon dioxide concentrations, as well as to as realistic environmental conditions as possible.ith tz570^2^Ceulemans,R^Mousseau,M^1994^1^Tansley review no-71 - effects of elevated atmospheric co2 on woody-plants^84^127^3^42z5-446^^^^^Jul^^^^^3957lkali-promoted CaO or MgO compared to the mono-alkali ones are attributed to the synergistic increazA^3956^Because of their prominent role in the global carbon balance and their possible carbon sequestration, trees are verzy important organisms in relation to global climatic changes. Knowledge of these processes is the key to understanding thez functioning of the whole forest ecosystem which can be modelled and predicted based on the physiological process informatzion. This paper reviews the major methods and techniques used to examine the likely effects of elevated CO2 on woody plantzs, as well as the major physiological responses of trees to elevated CO2. The available exposure techniques and approachesz 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 st{imulation 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 examine{$d. Changes in underground processes under elevated CO2 are especially emphasized and related to the functioning of the eco{&system. Some directions for future research are put forward.luated in terms of their experimental protocols on growth con{5571^2^Cui,M^Nobel,PS^1994^1^Gas-exchange and growth-responses to elevated co2 and light levels in the cam species opuntia-{7ficus-indica^9^17^8^935-944^^^^^Aug^^^^^3959oning, the small dimensions along with short and easy culture make radish an {DA^3958^Gas exchange and dry-weight production in Opuntia ficus-indica, a CAM species cultivated worldwide for its fruit an{Fd cladodes, were studied in 370 and 750 mu mol mol(-1) CO2 at three photosynthetic photon flux densities (PPFD: 5, 13 and {T20 mol m(-2) d(-1)). Elevated CO2 and PPFD enhanced the growth of basal cladodes and roots during the 12-week study. A ris{Ve in the PPFD increased the growth of daughter cladodes; elevated CO2 enhanced the growth of first-daughter cladodes but d{becreased the growth of the second-daughter cladodes produced on them. CO2 enrichment enhanced daily net CO2 uptake during {dthe initial 8 weeks after planting for both basal and first- daughter cladodes. Water vapour conductance was 9 to 15% lowe{mr in 750 than in 370 mu mol mol(-1) CO2. Cladode chlorophyll content was lower in elevated CO2 and at higher PPFD. Soluble{o sugar and starch contents increased with time and were higher in elevated CO2 and at higher PPFD. The total plant nitroge{vn content was lower in elevated CO2. The effect of elevated CO2 on net CO2 uptake disappeared at 12 weeks after planting, {ypossibly due to acclimation or feedback inhibition, which in turn could reflect decreases in the sink strength of roots. D{espite 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 mediu{m PPFD and by 37% from medium to high PPFD. tidal currents. BP 221-224 PG 4 JI Indian J. Mar. Sci. PY 1993 PD SEP VL 22 I{572^1^Diemer,MW^1994^1^Mid-season gas-exchange of an alpine grassland under elevated co2^2^98^3-4^429-435^^^^^Aug^^^^^3961{A^3960^Ecosystem net CO2 uptake, evapotranspiration (ET) and night- time CO2 efflux were measured in an alpine grassland d{ominated 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 fert{ilizer 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 t{ended 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 w{ere 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.f two compared to the V{ system, and by more than an order of magnitude compared to our older results. With the optimum system we are now able to{573^4^Garcia,RL^Idso,SB^Wall,GW^Kimball,BA^1994^1^Changes in net photosynthesis and growth of pinus-eldarica seedlings in {response to atmospheric co2 enrichment^9^17^8^971-978^^^^^Aug^^^^^3963gas chromatography/mass spectrometry and the state-{A^3962^Pinus eldarica L. trees, rooted in the natural soil of an agricultural field at Phoenix, Arizona, were grown from t| he seedling stage in clear-plastic-wall open-top enclosures maintained at four different atmospheric CO2 concentrations fo|r 15 months. Light response functions were determined for one tree from each treatment by means of whole-tree net CO2 exch|ange measurements at the end of this period, after which rates of carbon assimilation of an ambient-treatment tree were me|asured across a range of atmospheric COP concentrations. The first of these data sets incorporates the consequences of bot|h the CO2-induced enhancement of net photosynthesis per unit needle area and the CO2-induced enhancement of needle area it|%self (due primarily to the production of more needles), whereas the second data set reflects only the first of these effec|'574^2^Gay,AP^Hauck,B^1994^1^Acclimation of lolium-temulentum to enhanced carbon-dioxide concentration^78^45^277^1133-1141^|/^^^^Aug^^^^^3965n C allocation. Exposure of woody species to elevated CO2 over several years has shown that high rates of|1A^3964^Acclimation of single plants of Lolium temulentum to changing [CO2] was studied on plants grown in controlled envir|8onments at 20 degrees C with an 8 h photoperiod. In the first experiment plants were grown at 135 mu mol m(-2) s(-1) photo|:synthetic 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 l|Iower 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(|K-1) PPFD at 345 and 575 mu l l(-1) [CO2]. High [CO2] during growth had little effect on stomatal density, total soluble pr|` oteins, chlorophyll a content, amount of Rubisco or cytochrome f. However, increasing [CO2] during measurement increased p|b hotosynthetic rates, particularly in high light. Plants grown in the higher [CO2] had greater leaf extension, leaf and pla|i nt growth rates in low but not in high light. The results are discussed in relation to the limitation of growth by sink ca|kpacity and the modifications in the plant which allow the storage of extra assimilates at high [CO2].n growth than is rel|r 575^2^Hoen,HF^Solberg,B^1994^1^Potential and economic-efficiency of carbon sequestration in forest biomass through silvicu|tltural management^49^40^3^429-451^^^^^Aug^^^^^3967 A 2 to 4-degrees-C increase in soil temperature could increase CO2 eff|A^3966^This paper has two main objectives: First, to discuss in principle some vital methodological issues which have to b|e considered when analyzing bow preferable measures in forestry are to decrease the atmospheric concentration of greenhous|e 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 giv|en point in time; and (2) the intertemporal evaluation of a flow of atmospheric CO2 reductions. The marginal cost, measure|d as the change in net present value, is proposed as a proper measure for ranking of alternative projects. Secondly, a cas|e 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 treatme|nt 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 r|elated to timber production by changes in the forest management over a time period of 30 yr is studied. A total of 253 sta|nd treatment schedules was calculated for the 40 stand types, allowing for the following stand treatment options, (1) cont|inued 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 t} hat there is a significant potential for increasing the present value of the flow of net CO2 fixations (NPV(CO2)) by chang} ing the forest management on the productive forest area of Buskerud. Compared with the NPV(CO2) obtained when the net pres}ent value of the timber cash flow (NPV(NOK)) for the area is maximized (BASE problem), an increase between 8.4%-17.9% in N} PV(CO2) can be obtained. The potential for increasing the NPV(CO2) depends on the real rate of discount. The corresponding}3! decrease in the NPV(NOK) lies between 8.1% and 14.9%. The results further indicate that a large proportion of the increas}5"e in NPV(CO2) can be obtained by changes in forest management at a moderate marginal cost. If we assume that 80% of the ma}G#ximum potential increase in NPV(CO2) is obtained, this gives a yearly increase (30-yr annuity) in net CO2 fixation in the }I$range from 145,000 to 250,000 tons (depending on the real rate of discount and assumptions about fertilization) by changin}]%g the management of the 574,000 ha of productive forestland in Buskerud, compared to the current forest management practic}_&e (BASE problem). Obtaining 80% of the maximum potential increase in NPV(CO2) imposes a decrease in the NPV(NOK) in the ra}e'nge of 22% to 65% of the total potential difference in NPV(NOK) between the BASE problem and the NPV(CO2) maximizing probl}g(em. The annual decrease (30-yr annuity) in NPV(NOK) corresponding to the 80% of the maximum potential NPV(CO2) increase, i}o)s 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 i}q*n NPV(CO2) can be reached at a marginal cost (shadow price) below 150 NOK (21/US$) per ton NPV(CO2). Measured per ton C, t}+he corresponding marginal cost is 551 NOK (79 US$) per ton C. For RRDs at 3% p.a. and 2% p.a., the marginal costs are sign},ificantly higher, but relaxing the NPV(CO2) constraint to 60% of the total increase brings the marginal costs down and bel}-ow 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. Fertiliz0ation, avoiding release thinning in young growth, and changes in clear felling priorities were the most cost-efficient cha}nges in stand treatment management in order to increase the net CO2 fixation. temperature (+0-degrees-C, +2-degrees-C, an}2576^4^Jackson,RB^Sala,OE^Field,CB^Mooney,HA^1994^1^Co2 alters water-use, carbon gain, and yield for the dominant species i}n a natural grassland^2^98^3-4^257-262^^^^^Aug^^^^^3969M and TEM estimate the total net primary productivity (NPP) for te}4A^3968^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 n}5ext century. Understanding how terrestrial ecosystems will respond in this changing environment is an important goal of cu}6rrent research. Here we present results from a field study of elevated CO2 in a California annual grassland. Elevated CO2 7led to lower leaf- level stomatal conductance and transpiration (approximately 50%) and higher mid-day leaf water potentia8ls (30-35%) in the most abundant species of the grassland, Avena barbata Brot. Higher CO2 concentrations also resulted in }9greater 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 ap~;proximately doubled in elevated CO2, as estimated by instantaneous gas-exchange measurements and seasonal carbon isotope d~577^2^McKee,IF^Woodward,FI^1994^1^Co2 enrichment responses of wheat - interactions with temperature, nitrate and phosphate~'^84^127^3^447-453^^^^^Jul^^^^^3971ANT CELL AND ENVIRONMENT SN 0140-7791 C1 INST ENVIRONM ANAL & REMOTE SENSING AGR, NATL ~)@A^3970^Rising levels of atmospheric CO2, climate change, and fertilizer pollution provide the ecological imperative for in~/Avestigating the interaction between plant responses to atmospheric CO2 concentration, temperature and nutrient supply. In ~1Bthis study spring wheat (Triticum aestivum L. cv. Wembley) was grown at 40, 50, 60 and 70 Pa atmospheric CO2 pressure and Cthree experiments were conducted to investigate interactions between growth responses to the CO2 treatment and: (i) temperDature (24/16 degrees C vs. 18/10 degrees C - day/night), (ii) nutrient solution nitrate concentration (2.5, 5, 10 and 15 m~[EM Ca(NO3)(2).4H(2)O), and (iii) phosphate concentration (0.025 and 0.5 mM KH2PO4). Dry mass and root/shoot ratio increased~]F with CO2 level at the higher temperature. These responses were reversed at the lower temperature. The increase in yield w~mGith CO2 enhancement was limited by low rates of nutrient supply in both absolute and relative terms. In the elevated CO2 t~oHreatments, the shoot nitrogen concentration was reduced, as was the proportional allocation to the uppermost leaves. These~I results are discussed with respect to possible physiological mechanisms and potential for improved crop performance in a ~future, elevated CO2 world.LL ENVIRON ER PT J AU MORSE, SR WAYNE, P MIAO, SL BAZZAZ, FA TI ELEVATED CO2 AND DROUGHT ALTE~K578^4^Morgan,JA^Hunt,HW^Monz,CA^Lecain,DR^1994^1^Consequences of growth at 2 carbon-dioxide concentrations and 2 temperatu~res for leaf gas-exchange in pascopyrum-smithii (C-3) and bouteloua-gracilis (C-4)^9^17^9^1023-1033^^^^^Sep^^^^^3973DIOXI~MA^3972^Continually rising atmospheric CO2 concentrations and possible climatic change may cause significant changes in pla~Nnt communities. This study was undertaken to investigate gas exchange in two important grass species of the short-grass st~Oeppe, Pascopyrum smithii (western wheatgrass), C-3, and Bouteloua gracilis (blue grama), C4, grown at different CO2 concen~Ptrations and temperatures. Intact soil cores containing each species were extracted from grasslands in north-eastern Color~Qado, USA, placed in growth chambers, and grown at combinations of two CO2 concentrations (350 and 700 mu mol mol(-1)) and ~Rtwo temperature regimes (field average and elevated by 4 degrees C). Leaf gas exchange was measured during the second, thi~Srd and fourth growth seasons. All plants exhibited higher leaf CO2 assimilation rates (A) with increasing measurement CO2 ~Tconcentration, with greater responses being observed in the cool-season C-3 species P. smithii. Changes in the shape of in~Utercellular CO2 response curves of A for both species indicated photosynthetic acclimation to the different growth environ~Vments, The photosynthetic capacity of P. smithii leaves tended to be reduced in plants grown at high CO2 concentrations, a~Wlthough A for plants grown and measured at 700 mu mol mol(-1) CO2 was 41% greater than that in plants grown and measured a~Xt 350 mu mol mol(-1) CO2. Low leaf N concentration may have contributed to photosynthetic acclimation to CO2. A severe red~Yuction in photosynthetic capacity was exhibited in P. smithii plants grown long-term at elevated temperatures. As a result~Z, the potential response of photosynthesis to CO2 enrichment was reduced in P. smithii plants grown long-term at the highe~r temperature.ND CARBON-DIOXIDE CONCENTRATIONS OF SOILS AS INFLUENCED BY RHIZOSPHERE OF CROPS UNDER FIELD AND POT CONDITI~\579^1^Mortensen,LM^1994^1^Effects of elevated co2 concentrations on growth and yield of 8 vegetable species in a cool clim ate^165^58^3^177-185^^^^^Jul^^^^^3975MAYS ID ROOTS; BIOSYNTHESIS; ACCUMULATION; RESPONSES; OXYGEN AB A method for collect ^A^3974^The effects of elevated CO2 concentrations on the yield of Allium cepa (onion), Allium ampeloprasum (leek), Apium g_raveolens var. dulce (celery), Apium graveolens var. rapaceum (celery root), Brassica pekinensis (chinese cabbage), Daucus` carota (carrot), Lactuca sativa (lettuce) and Petroselinum crispum (parsley) grown in containers, were studied in SiX 9-M0a2 large field plots surrounded by 1.8-m high plastic foil walls ('field chambers'). Three of the chambers were supplied wi3bth pure CO2 gas through perforated tubes. Increasing the CO2 concentration from ambient (355 mumol mol-1) to 800-900 mumolAc mol-1 increased the yield (fresh weight) by 23% in onion (two cultivars) and by 8% in carrot (three cultivars). The dry wDdeight based yield increase was 18% in lettuce (three cultivars), 19% in carrot and 17% in parsley (one cultivar). The yielSeds of leek (two cultivars), chinese cabbage (three cultivars), celery (one cultivar) and celery root (one cultivar) were nUfot significantly affected by the CO2 concentration. Generally, no 'chamber effect' was found on the yields of the differenct species.993 PD MAR VL 150 IS 2 GA LQ501 RP OTANI T J9 PLANT SOIL ER PT J AU OVERDIECK, D TI EFFECTS OF ATMOSPHERIC CO2eh580^2^Oechel,WC^Vourlitis,GL^1994^1^The effects of climate-change on land atmosphere feedbacks in arctic tundra regions^57n^9^9^324-329^^^^^Sep^^^^^3977 OKOL, KONIGIN LUISE STR 22, W-1000 BERLIN 33, GERMANY. ID ELEVATED CARBON-DIOXIDE; SEEDLINGpjA^3976^Recently reported high-latitude warming has the potential to affect arctic ecosystem structure and function in the kshort and long term. Arctic ecosystems are known sources of atmospheric CH4, and recent CO2 flux measurements indicate thalt these ecosystems are now, at least regionally, net sources of atmospheric CO2. It appears that over the short term (decamdes to centuries), arctic ecosystems may represent a positive feedback on global atmospheric CO2 concentrations and associnated greenhouse gas-induced climate change. In addition, short-term feedbacks may be large enough to affect both local ando global surface temperatures. Over the long term, changes in the structure, function and composition of arctic ecosystems may increase C accumulation relatively more than the amount lost, thus restoring the sink status of arctic ecosystems. anq581^5^Rouhier,H^Billes,G^Elkohen,A^Mousseau,M^Bottner,P^1994^1^Effect of elevated co2 on carbon and nitrogen distribution within a tree (castanea-sativa mill) soil system^206^162^2^281-292^^^^^May^^^^^3979m diameter (2 cm above the first latersA^3978^Two-year-old sweet chestnut trees were grown outside in normal or double CO2 atmospheric concentration. In spring atnd in autumn of two growing seasons, a six day labelling pulse of C- 14 labelled CO2 was used to follow the carbon assimiluation and distribution in the plant-soil system. Doubling atmospheric CO2 had a significant effect on the tree net carbon vuptake. A large proportion of the additional C uptake was 'lost' through the root system. This suggests that increased C uwptake under elevated CO2 conditions increases C cycling without necessarily increasing C storage in the plant. Total root xderived material represented a significant amount of the 'extra-assimilated' carbon due to the CO2 treatment and was stronygly correlated with the phenological stage of the tree. Increasing root rhizodeposition led to a stimulation of microbial zactivity, particularly near the end of the growing season. When plant rhizodeposition was expressed as a function of the r {oot dry weight, the effect of increasing CO2 resulted in a higher root activity. The C to N ratios were significantly high |er for trees grown under elevated CO2 except for the fine root compartment. An evaluation of the plant-soil system nitroge}n dynamics showed, during the second season of CO2 treatment, a decrease of soil N mineralization rate and total N uptake !for trees grown at elevated CO2 levels. are compared by means of mathematical modelling procedures in order to quantify C-582^5^Santrucek,J^Santruckova,H^Kveton,J^Simkova,M^Rohacek,K^1994^1^The effect of elevated co2 concentration on photosynth/etic co2 fixation, respiration and carbon economy of wheat plants^239^40^8^689-696^^^^^^^^^^3981ND ABOVEGROUND AND BELOWG;A^3980^Winter wheat plants were grown under controlled atmospheric and light conditions for 25 days to assess the response= of photosynthesis, respiration and carbon allocation to elevated ambient CO2 concentration. Daily balance of carbon fixatFion and loss was measured separately for shoots and roots including root exudation. Doubled CO2 (700 mumol CO2 mol-1) stimHulated photosynthetic CO2 uptake and dark respiration rate when calculated on the leaf area basis. However, total daily caWrbon gain per plant and total dry matter of shoot was lower for high-CO2-grown plants due to reduced leaf area. After 23 dZays of exposition to high CO2, photosynthesis was depressed probably due to limiting regeneration of ribulose bisphosphateg. Both stomatal resistance and water use efficiency were markedly higher in high-CO2-grown plants. Higher evaporative demaind in low-CO2-grown plants promoted root elongation. Total root length was 160% of that in high-CO2-grown plants. Root exuzdation of high-CO2-grown plants was higher in the first days of plant development, but the inhibition of net photosynthesi|s was followed by a decrease in exudation.more of the plant biomass directly into the detrital food chain, thereby slowin583^2^Taylor,J^Ball,AS^1994^1^The effect of plant-material grown under elevated co2 on soil respiratory activity^206^162^2^315-318^^^^^May^^^^^3983oil Pollut. PY 1993 PD OCT VL 70 IS 1-4 GA LZ846 RP OWENSBY CE J9 WATER AIR SOIL POLLUT ER PT JA^3982^The biodegradability of aerial material from a C4 plant, sorghum grown under ambient (345 mu mol mol(-1)) and elevated (700 mu mol mol(-1)) atmospheric CO2 concentrations were compared by measuring soil respiratory activity. Initial daily respiratory activity (measured over 10 h per day) increased four fold from 110 to 440 cm(3) CO2 100g dry weight soil(-1) in soils amended with sorghum grown under either elevated or ambient CO2. Although soil respiratory activity decreased over the following 30 days, respiration remained significantly higher (t-test; p>0.05) in soils amended with sorghum grown under elevated CO2 concentrations. Analysis of the plant material revealed no significant differences in C:N ratios between sorghum grown under elevated or ambient CO2. The reason for the differences in soil respiratory activity have yet to be elucidated. However if this trend is repeated in natural ecosystems, this may have important implications for C and N cycling. ground biomass were estimated by periodic sampling throughout the growing season in 1989 and 1990. In 1991, N and P c584^2^Thompson,GB^Drake,BG^1994^1^Insects and fungi on a C-3 sedge and a C-4 grass exposed to elevated atmospheric co2 concentrations in open-top chambers in the field^9^17^10^1161-1167^^^^^Oct^^^^^3985 the growing season. Total N and P in aboA^3984^The effects of elevated atmospheric CO2 concentration on plant- fungi and plant-insect interactions were studied in an emergent marsh in the Chesapeake Bay. Stands of the C-3 sedge Scirpus olneyi Grey. and the C-4 grass Spartina patens (Ait.) Muhl. have been exposed to elevated atmospheric CO2 concentrations during each growing season since 1987. In August -1991 the severities of fungal infections and insect infestations were quantified. Shoot nitrogen concentration ([N]) and w.ater content (WC) were determined. In elevated concentrations of atmospheric CO2, 32% fewer S. olneyi plants were infested4 by insects, and there was a 37% reduction in the severity of a pathogenic fungal infection, compared with plants grown in7 ambient CO2 concentrations. S. olneyi also had reduced [N], which correlated positively with the severities of fungal infections and insect infestations. Conversely, S. patens had increased WC but unchanged [N] in elevated concentrations of atmospheric CO2 and the severity of fungal infection increased. Elevated atmospheric CO2 concentration increased or decreaseOd the severity of fungal infection depending on at least two interacting factors, [N] and WC; but it did not change the nuQmber of plants that were infected with fungi. In contrast, the major results for insects were that the number of plants in^fected with insects decreased, and that the amount of tissue that each insect ate also decreased.NDIA. DE HYPERAMMONEMIA;`585^3^Vanoosten,JJ^Wilkins,D^Besford,RT^1994^1^Regulation of the expression of photosynthetic nuclear genes by co2 is mimi>cked by regulation by carbohydrates - a mechanism for the acclimation of photosynthesis to high co2^9^17^8^913-923^^^^^AugL^^^^^3987somal enriched fractions of rat cerebral cortex. Production of (CO2)-C-14 from [U-C-14] glucose was enhanced in A^3986^The abundance of transcripts of cab-7 and cab-3C, which code for the chlorophyll a/b binding proteins of the light- harvesting complexes I and II, respectively, and the abundance of transcripts of Rca, which encodes Rubisco activase, wer<e reduced in tomato plants exposed to high CO2 for up to 9d, whereas the abundance of mRNA from psa A-psa B and psb A, whi@ch encode the proteins of the core complex of PSI and the D1 protein of PSII, respectively, and the abundance of glycolate oxidase, which is involved in photorespiration, were not affected. However, the abundance of the transcript for the B subdunit of ADP-glucose pyrophosphorylase was increased after 1 d at elevated CO2. The chlorophyll am ratio decreased significdantly over 9 d of exposure to elevated CO2. The responses of the nuclear genes to high CO2 were enhanced when leaves were Jzdetached so as to deprive them of any major sink. The responses of these transcripts to high CO2 were mimicked when sucrosJ|e or glucose was supplied to the leaf tissue, whereas acetate or sorbitol had no effect. Carbohydrate analyses of leaves gGrown in high CO2 or supplied with sucrose revealed that major increases occurred in the amount of glucose and fructose. BaIsed on these and other published data, a molecular model involving the repression or activation of the transcription of nu}clear genes coding for chloroplast proteins by photosynthetic end-products is proposed to account for photosynthetic accli}mation to high CO2 in tomato plants and other species., GERMANY. DE METHANOGENESIS; GIBBS FREE ENERGY; LITTORAL SEDIMENT;f586^3^Bassow,SL^McConnaughay,KDM^Bazzaz,FA^1994^1^The response of temperate tree seedlings grown in elevated co2 to extremfe temperature events^56^4^3^593-603^^^^^Aug^^^^^3989URE; ENERGETICS; TURNOVER AB In anoxic methanogenic sediments organicA^3988^Mean global temperatures have been predicted to increase in the next century, if so the frequency of extreme temper!ature events may also increase. Extreme temperatures may damage plant tissue and consequently limit the survival of certaifn plant species in a region. Elevated concentrations of CO2 in the atmosphere alter plant allocation, physiology, and growfth, and may accentuate or ameliorate the damage from extreme temperatures. In this paper we explore the interactive effectfs of atmospheric CO2 concentration, nutrient levels, and exposure to extreme temperatures on seedlings of three species off temperate deciduous trees. A1-d exposure to extreme heat (45-degrees-C) significantly decreased conductance the following~A day and decreased biomass as measured at both 35 and 105 d following the extreme temperature event, regardless of atmosph~Ceric CO2 concentration. The most shade-tolerant species, striped maple, was most severely impacted by the extreme heat eve}nt 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 conc}entrations at 35 d after the heat event; however, al the end of the growing season at 105 d post treatment, this differenc}e was not significant. A one-night exposure to low temperatures (4- degrees-C) did not affect biomass for any of these spehcies. With an increase in global mean temperatures, the frequency of extreme temperature events, particularly hot weather hevents, may increase and may extend to shaded understory sites. If the frequency of extremely high temperatures increases,h the role that temperature extremes may play in changing competitive interactions and thus affecting community compositionh may increase in importance, as these temperatures appear to severely alter plant survival and growth in some species.ITE587^3^Berryman,CA^Eamus,D^Duff,GA^1994^1^Stomatal responses to a range of variables in 2 tropical tree species grown with co2, enrichment^78^45^274^539-546^^^^^May^^^^^3991es supracrustal belt of southern Kerala suggest paleo-fluid channels. WA^3990^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.CARBON FIXATION; SEMICONTINUOUS CULTURE AB 588^4^Callaway,RM^Delucia,EH^Thomas,EM^Schlesinger,WH^1994^1^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^2^98^2^159-166^^^^^Jul^^^^^3993 on specific growth rate was determined and formulated using a semi-continuous culture system. The specifiA^3992^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.1 We measured growth parameters, photosynthesis, respiration, and biomass allocation of Pinus ponderosa seedlings grown for3 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 temperatuCres. After 1 month in treatment conditions, total seedling biomass was higher in elevated CO2, and temperature significantEly enhanced the positive CO2 effect. However, after 2 months the effect of CO2 on total biomass decreased and relative groWwth rates did not differ among CO2 and temperature treatments over the 2-month growth period even though photosynthetic raYtes increased almost-equal-to 7% in high CO2 treatments and decreased almost- equal-to 10% in high temperature treatments.h Additionally, CO2 enhancement decreased root respiration and high temperatures increased shoot respiration. Based on CO2 jexchange rates, CO2 fertilization should have increased relative growth rates (RGR) and high temperatures should have decrxeased RGR. Higher photosynthetic rates caused by CO2 fertilization appear to have been mitigated during the second month ozf 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.M, INST LIF589^3^Delucia,EH^Callaway,RM^Schlesinger,WH^1994^1^Offsetting changes in biomass allocation and photosynthesis in ponderosa pine (pinus-ponderosa) in response to climate-change^13^14^7-9^669-677^^^^^Jul-Sep^^^^^3995respiration and growth of LeA^3994^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 ca!used an increase in biomass allocation to stem in the phytotron seedlings. Thus, CO2- and temperature-driven shifts in bio#mass allocation negated the effect on growth of the CO2- driven increase in carbon assimilation rate. Our data from the co2ntrolled growth chamber and field experiments suggest that future climate conditions, including elevated atmospheric CO2, 4may not stimulate growth and productivity of ponderosa pine.ither low (0.005 to 0.3 W M-2) or high (0.25 to 0.90 W M- 2) @590^2^Elkohen,A^Mousseau,M^1994^1^Interactive effects of elevated co2 and mineral-nutrition on growth and co2 exchange of Asweet chestnut seedlings (castanea- sativa)^13^14^7-9^679-690^^^^^Jul-Sep^^^^^3997 CO2 and UV treatments decreased the dCA^3996^The effects of elevated atmospheric CO2 (700 mumol mol-1) and fertilization were investigated on 2-year-old sweet cXhestnut (Castanea sativa Mill.) seedlings grown outdoors in pots in constantly ventilated open-sided chambers. Plants wereZ divided into four groups: fertilized controls (+F/-CO2), unfertilized controls (-F/-CO2), fertilized + CO2-treated plantsk (+F/+CO2) and unfertilized + CO2-treated plants (-F/+CO2). Dry matter accumulation and allocation were measured after onem 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, bio mass 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 a nd unfertilized plants increased in response to elevated CO2, but the seasonal pattern of this enhancement varied with nut rient 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.ts per thousand, after acetate depletion. The deltaC- 13 value of CH4 from CO2/H-2 reduction was estimated to 591^4^Epron,D^Dreyer,E^Picon,C^Guehl,JM^1994^1^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 co2^13^14^7-9^725-733^^^^^Jul-Sep^^^^^3999dmembers of CH4, the change of acetate contribution for CH4 production was calculated: less than 12% unA^3998^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)'.eaf development, whereas CO2 enrichment 10 to 20 days earlier halted the development of adventitious sh592^2^Gloser,J^Bartak,M^1994^1^Net photosynthesis, growth-rate and biomass allocation in a rhizomatous grass calamagrostis%-epigejos grown at elevated co2 concentration^79^30^1^143-150^^^^^^^^^^4001JI J. Jpn. Soc. Hortic. Sci. PY 1993 PD SEP VL&!A^4000^Young plants of Calamagrostis epigejos (L.) Roth were grown in controlled environments with two regimes of CO2 in t,"he 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 ass<$imilates 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 L&measured gasometrically in plants from both treatments at 350 and 700 cm(3) m(-3) CO2 in the leaf chamber. There were no sN'ignificant 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 sa)aturating irradiance and maximum apparent quantum yield of photosynthesis were always considerably higher at doubled CO2 choncentration during measurements.reased % shoot water contents. At elevated atmospheric CO2 concentrations, where plant nj+593^4^Guehl,JM^Picon,C^Aussenac,G^Gross,P^1994^1^Interactive effects of elevated co2 and soil drought on growth and transpriration efficiency and its determinants in 2 european forest tree species^13^14^7-9^707-724^^^^^Jul-Sep^^^^^4003ly treatmu-A^4002^The responses of growth and transpiration efficiency (W = biomass accumulation/water consumption) to ambient and el.evated atmospheric CO2 concentrations (350 and 700 mumol mol-1, respectively) were investigated under optimal nutrient sup/ply in well-watered and in drought conditions in two temperate- forest tree species: Quercus petraea Liebl. and Pinus pina0ster Ait. Under well-watered conditions, doubling the CO2 concentration for one growing season increased biomass growth by1 138% in Q. petraea and by 63% in P. pinaster. In contrast, under drought conditions, elevated CO2 increased biomass growt2h by only 47% in Q. petraea and had no significant effect on biomass growth in P. pinaster. Transpiration efficiency was h3igher in Q. petraea than in P. pinaster in all treatments. This difference was linked (i) to lower carbon isotope discrimi4nation (DELTA), and thus lower values of the intercellular/ambient CO2 concentration (c(i)/c(a)) ratio, in Q. petraea, (ii5) to lower values of leaf mass ratio (LMR, leaf mass/whole plant mass), which we suggest was positively related to the pro6portion of daytime carbon fixation lost by respiration (PHI), in Q. petraea, and (iii) to slightly lower C concentrations 7in Q. petraea than in P. pinaster. The CO2- promoted increase in W was higher in Q. petraea (+80%) than in P. pinaster (+580%), and the difference was associated with a more pronounced decrease in PHI in response to elevated CO2 in Q. petraea th9an in P. pinaster, which could be linked with the N dilution effect observed in Q. petraea. Because PHI also directly affe:cts growth, the CO2-induced enhancement of PHI in Q. petraea is a crucial determinant of the growth stimulation observed i;n 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.s=594^2^Israel,AA^Nobel,PS^1994^1^Activities of carboxylating enzymes in the cam species opuntia- ficus-indica grown under c urrent and elevated co2 concentrations^91^40^3^223-229^^^^^Jun^^^^^4005iron. PY 1993 PD SEP VL 16 IS 7 GA LZ893 RP TISSUE ?A^4004^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 mAetabolism species Opuntia ficus-indica growing in open-top chambers. During the spring 13 months after planting, total dai+Bly net CO2 uptake of basal and first-order daughter cladodes was 28% higher at 720 than at 360 mu l CO2 1(-1). The enhance-Cment, caused mainly by higher CO2 assimilation during the early part of the night, was also observed during late summer (57D months after planting) and the following winter. The activities of Rubisco and PEPCase measured in vitro were both lower 9Eat the elevated CO2 concentration, particularly under the more favorable growth conditions in the spring and late summer. BFEnzyme activity in second-order daughter cladodes increased with cladode age, becoming maximal at 6 to 10 days. The effectEG of elevated CO2 on Rubisco and PEPCase activity declined with decreasing irradiance, especially for Rubisco. Throughout tWHhe 13-month observation period, O. ficus-indica thus showed increased CO2 uptake when the atmospheric CO2 concentration waYs doubled despite lower activities of both carboxylating enzymes. well as the combined processes. The aim of this paper igJ595^2^McKee,IF^Woodward,FI^1994^1^The effect of growth at elevated co2 concentrations on photosynthesis in wheat^9^17^7^85j3-859^^^^^Jul^^^^^4007er use efficiency, CO2 fertilization decreases net C emissions, while changed decomposition rates s~LA^4006^Rising levels of atmospheric CO2 will have profound, direct effects on plant carbon metabolism. In this study we usMed gas exchange measurements, models describing the instantaneous response of leaf net CO2 assimilation rate (A) to intercNellular CO2 partial pressure (C-i), in vitro enzyme activity assay, and carbohydrate assay in order to investigate the phoOtosynthetic responses of wheat (Triticum aestivum L., cv. Wembley) to growth under elevated partial pressures of atmospherPic CO2 (C- a). At flag leaf ligule emergence, the modelled, in vivo, maximum carboxylation velocity for RuBisCO was signifQicantly lower in plants grown at elevated C-a than in plants grown at ambient C-a (70 Pa compared with 40 Pa). By 12 d aftRer ligule emergence, no significant difference in this parameter was detectable. At ligule emergence, plants grown at elevSated C-a exhibited reduced in vitro initial activities and activation states of RuBisCO. At their respective growth C-i vaTlues, the photosynthesis of 40-Pa-grown plants was sensitive to p(O-2) and to p(CO2), whereas that of 70-Pa-grown plants wUas insensitive. Both sucrose and starch accumulated more rapidly in the leaves of plants grown at 70 Pa. At flag leaf liguVle emergence, modelled non-photorespiratory respiration in the light (R(d)) was significantly higher in 70-Pa-grown plants than in 40-Pa-grown plants. By 12 d after ligule emergence no significant differences in R(d) were detectable.ical technX596^7^Murray,MB^Smith,RI^Leith,ID^Fowler,D^Lee,HSJ^Friend,AD^Jarvis,PG^1994^1^Effects of elevated co2, nutrition and climaYtic warming on bud phenology in sitka spruce (picea-sitchensis) and their impact on the risk of frost damage^13^14^7-9^691-706^^^^^Jul-Sep^^^^^4009e increase for 100- to 150- year-old trees is approximately 45%, while the increase for 200- to [A^4008^Effects of elevated CO2, clone and plant nutrition on bud dormancy of Sitka spruce (Picea sitchensis (Bong.) Carr.)\ were examined. Sitka spruce seedlings were fumigated with ambient or elevated (ambient + 350 mumol mol-1) concentrations ]of CO2 in open-top chambers for three growing seasons. In 1991 and 1992, elevated CO2 delayed bud burst in the spring and ^advanced bud set in the autumn. The effect of the open-top chamber on the thermal requirement for bud burst was greater th_an the effect of elevated CO2 (50 and 30 day degrees (D(d)), respectively). In a second study, four clones of Sitka spruce` taken from two provenances, at 43 and 54-degrees-N, were fumigated with ambient or elevated CO2. There was a large natura!al variation in the timing of bud burst and bud set among the clones. Elevated CO2 had no effect on bud dormancy of the Ski#bdegate a clone, but it reduced the growing season of the North Bend b clone by 20 days. In a third study, Sitka spruce see/cdlings growing in ambient or elevated CO2, were supplied with one of three nutrient regimes, low (0.1 x potential), medium1d (0.5 x potential) or high (2.0 x potential), using a method and solution based on the Ingestad technique. Elevated CO2 di;ed not affect bud dormancy in the high-nutrient treatment, but it reduced the growing season of plants in the low-nutrient =ftreatment by 22 days. Increasing plant nutrient supply lengthened the growing season, plants flushed earlier in the springIg and set bud later in the autumn. The effects of elevated CO2 plus a 0, 2 or 4-degrees-C climatic warming on the timing ofLh bud burst and the subsequent risk of frost damage were assessed using a simulation model and meteorological data from thrXiee sites, Edinburgh, Braemar and Masset. The model predicted that (i) doubling the CO2 concentration in die absence of cliZjmatic warming, will delay the onset of bud burst at all three sites, (ii) climatic warming in ambient CO2 will hasten bud rkburst and (iii) climatic warming in elevated CO2 will hasten bud burst at Edinburgh and Braemar but to a lesser extent thatln climatic warming alone. At Masset, a 4-degrees-C warming was required to advance the date of bud burst of seedlings in tmhe elevated CO2 treatment. At all three sites, elevated CO2 and climatic warming increased the mean daily temperature on the date of bud burst, thus reducing the risk of subsequent frost damage.) were unexpected and pose interesting considerato597^2^Overdieck,D^Forstreuter,M^1994^1^Evapotranspiration of beech stands and transpiration of beech leaves subject to atmospheric co2 enrichment^13^14^7-9^997-1003^^^^^Jul-Sep^^^^^4011PHYSIOL ER qA^4010^Beech trees (Fagus sylvatica L.) show reduced stomatal conductance and increased leaf area index in response to incrreased atmospheric CO2 concentration. To determine whether the reduction in stomatal conductance results in lower stand evsapotranspiration, we compared transpiration on a leaf-area basis and stand evapotranspiration on a ground-area basis in yotung European beech trees growing in greenhouses at ambient (360 +/- 34 mumol mol-1) and elevated (698 +/- 10 mumol mol-1) uCO2 concentrations. Trees were grown in homogenized natural soil at constant soil water supply for two growing seasons. Atv light saturation, leaf transpiration rates were, on average, 18% lower in the elevated CO2 treatment than in the ambient wC02 treatment. Mean transpiration coefficients (transpiration/net CO2 uptake) of leaves were 179 and 110 in the ambient anxd elevated CO2 treatments, respectively, indicating improved water use efficiency in trees in the elevated CO2 treatment. yTotal leaf conductance was decreased by 32% at light saturation. The elevated CO2 treatment resulted in a 14% reduction inz stand evapotranspiration. In both CO2 treatments, evapotranspiration increased linearly at a rate of 0.2 kg H2O m-2 day-1{ for each 1-degrees-C rise in air temperature between 14 and 25-degrees-C. We conclude that, under Central European conditions, water losses from deciduous forest stands will be reduced by a doubling of tropospheric CO2 concentration.33}598^2^Roth,SK^Lindroth,RL^1994^1^Effects of co2-mediated changes in paper birch and white-pine chemistry on gypsy-moth performance^2^98^2^133-138^^^^^Jul^^^^^4013JjwV1!:!@!Z!b!i!o!v!!!A^4012^We examined the effects of CO2-mediated changes in the foliar chemistry of paper birch (Betula papyrifera) and white pine (Pinus strobus) on performance of the gypsy moth (Lymantria dispar). Trees were grown under ambient or enriched CO2 conditions, and foliage was subjected to plant chemical assays and insect bioassays. Enriched CO2 atmospheres reduced foliar nitrogen levels and increased condensed tannin levels in birch but not in pine. Foliar carbohydrate concentrations wer+e not markedly altered by CO2 environment. Gypsy moth performance was significantly affected by CO2 level, species, and th-e CO2 x species interaction. Under elevated CO2 conditions, growth was reduced for larvae fed birch, while development was8 prolonged for larvae fed pine. Although gypsy moths performed better overall on birch than pine, birch-fed larvae were in:fluenced more by CO2-mediated changes in host quality.4456:::::::; ;;;D599^4^Rufty,TW^Thomas,RB^Cure,JD^Cure,WW^1994^1^Growth-response of cotton to co2 enrichment in differing light environmentFs^37^91^3^503-509^^^^^Jul^^^^^4015YA^4014^Experiments were conducted to examine the growth responses of cotton (Gossypium hirsutum L. cv. Coker 315) to CO2 e[nrichment under different light regimes. Plants were exposed to 350 or 700 mu l(-1) CO2 and six light treatments differingj in photosynthetic period length (8 or 16 h) and in photosynthetic photon flux density (PPFD) for 32 days of vegetative grlowth. Higher PPFD (1100 mu mol m(-2) s(-1)) was provided by a combination of high intensity discharge and incandescent lamyps (HID), and lower PPFD (550 mu mol m(-2) s(-1)) was provided by fluorescent and incandescent lamps (F) or HID and incand{escent lamps with shade cloth (HIDs). Growth was generally much slower with the 8-h photosynthetic periods, but the growth stimulation by CO2 enrichment was larger than with 16-h photosynthetic periods. After 28 to 32 days of treatment, the growth enhancement with CO2 enrichment was 152 and 78% for 8- and 16-h photosynthetic periods, respectively, under HID; 100 and 77% in F, and 77 and 56% in HIDs. The higher PPFD of HID positively influenced the CO2 effect only at the slower growth rate in the 8-h light period. The stimulation of leaf area expansion by CO2 enrichment was also greater with the 8-h photosynthetic period for all light sources. These results, and others on net assimilation rate, shoot to root dry weight ratios and specific leaf weights, suggest that the growth response to CO2 enrichment with the longer photosynthetic period was depressed by limiting factors, perhaps nutritional, in the growth environment. The results also show that extensive variability in CO2 response can occur under light intensities which are often used in growth chamber experiments.[600^5^Segal,M^Alpert,P^Stein,U^Mandel,M^Mitchell,MJ^1994^1^Some assessments of the potential 2 X co2 climatic effects on water-balance components in the eastern mediterranean^50^27^4^351-371^^^^^Aug^^^^^4017A^4016^General circulation model (GCM) coarse evaluations of the climatological impact in the Eastern Mediterranean due to global doubling of the atmospheriC CO2 concentration were used as input for a preliminary estimation of modifications in local processes affecting the water balance in this region. It is suggested that: (i) in the 2 x CO2 climate the average regional change of precipitation associated with typical mid-winter cyclonic systems is relatively small, however, it is associated with redistribution of the regional rainfall; (ii) in the elevated terrain in the northern part of the region, daytime snowmelt due to warm air advection may be enhanced, as much as 2.8 cm per day; and (iii) transpiration in the coasta l area of the Eastern Mediterranean may increase by approximately 13% of its current level in the summer and somewhat more in the winter.601^3^Thomas,RB^Lewis,JD^Strain,BR^1994^1^Effects of leaf nutrient status on photosynthetic capacity in loblolly-pine (pinus-taeda L) seedlings grown in elevated atmospheric co2^13^14^7-9^947-960^^^^^Jul-Sep^^^^^4019vvvv+w*A^4018^We measured needle photosynthesis of loblolly pine seedlings grown in a factorial experiment with two CO2 partial p,ressures (35 and 65 Pa) and three nutrient treatments (7 mM NH4NO3 + 1 mM PO4; 7 mM NH4NO3 + 0.2 mM PO4; 1 mM NH4NO3 + 1 m:M PO4). The data were used to parameterize a physiologically based photosynthetic model that included limitations imposed <by ribulose-1,5-bisphosphate carboxylase/oxygenase activity, electron transport capacity and inorganic phosphate availabilKity. With nonlimiting nutrients, seedlings grown at 65 Pa CO2 had significantly higher net photosynthesis and lower stomatMal conductance than seedlings grown at 35 Pa CO2. Nutrient limitations by either N or P significantly reduced photosynthet^ic capacity. When either N or P was limiting, there was no effect of growth CO2 partial pressure on photosynthesis, but st`omatal conductance was significantly lower for seedlings grown at 65 Pa CO2. Modeled biochemical parameters suggest that, qin all cases, photosynthesis was co-limited by carboxylation, electron transport and phosphate regeneration. Acclimation tso growth in elevated CO2 involved a reduction in leaf N content. In the low-N and low-P treatments, modeled parameters indicated that the biochemical processes of photosynthesis were down regulated to the point that there was no effect of increasing CO2 partial pressure. The capacity to regenerate phosphate was reduced in both low nutrient treatments, but was only reduced by elevated C02 when seedlings were grown under low soil P conditions. Increased photosynthetic water use efficiency and nutrient use efficiency in response to CO2 enrichment occurred in all three nutrient treatments and have important implications for whole-plant water and nutrient balance. These data support the contention that soil nutrient status in forest ecosystems will be a critical influence on tree seedling response to increasing atmospheric CO2 partial pressures.602^2^Thompson,GB^Woodward,FI^1994^1^Some influences of co2 enrichment, nitrogen nutrition and competition on grain-yield and quality in spring wheat and barley^78^45^276^937-942^^^^^Jul^^^^^4021A^4020^Spring wheat and spring barley were grown in elevated atmospheric CO2 in controlled environments. Wheat was grown in monoculture and in competition with three weed species. In monoculture, wheat had 30% more grain yield and 28% less grain nitrogen in elevated compared to ambient atmospheric CO2. In competition, wheat had no significant increase in yield with elevated atmospheric CO2. In competition, grain nitrogen concentration was reduced in response to CO2 with the largest reduction occurring with the smallest competitor and the smallest reduction occurring with the largest competitor. Spring barley was grown in monoculture at three nitrogen fertilizer supplies. In elevated atmospheric CO2 there were significant increases in grain yield and reductions in grain nitrogen concentration at all levels of nitrogen supply. In both species the reductions in grain nitrogen concentration were large enough to affect current bread making processes. 603^3^Vaisanen,H^Standman,H^Kellomaki,S^1994^1^A model for simulating the effects of changing climate on the functioning a nd structure of the boreal forest ecosystem - an approach based on object-oriented design^13^14^7-9^1081-1095^^^^^Jul-Sep^A^4022^We have developed a forest ecosystem model to assess the effects of climate change on the functioning and structure! Of boreal coniferoUS forests assuming that temperature and precipitation are the major variables of the niche occupied by* a tree species. We specified weather patterns to a level representing the time constant of different physiological and ec-ological processes relevant to the survival, growth and death of trees. We thereby coupled the long-term dynamics of the f?orest ecosystem with climate through physiological mechanisms such as photosynthesis and respiration in terms of energy flAow through the ecosystem. The hydrological and nutrient cycles couple the dynamics of the forest ecosystem with climate chUange through soil processes, which represent the thermal and hydraulic properties of the soil, and the decomposition of liWtter and humus with mineralization of nutrients. Simulations for southern Finland (62-degrees-N) indicated that an increasme in temperature of 5-degrees-C over one hundred years could reduce soil water in Scots pine-dominated forest ecosystems. oAt the same time, the temperature increase could enhance photosynthesis up to 6-8% under current CO2 concentrations (330 pwpm) and up to 8-10% under elevated CO2 concentrations (660 ppm). Because the elevated temperature and CO2 concentration cayused an increase in respiration (12-14% more than under the current climate), total stem production increased only up to 4% with a 5-degrees-C increase in temperature and up to 6% when temperature and atmospheric CO2 concentration were increased simultaneously. Because transpiration only increased up to 5% in response to elevated temperature and C02 Concentration, the water use efficiency of Scots-pine dominated forest ecosystems increased up to 3%, particularly during the late rotation.Lly?),-2A2^^^^4023604^5^Vandegeijn,SC^Vos,J^Groenwold,J^Goudriaan,J^Leffelaar,PA^1994^1^The wageningen rhizolab - a facility to study soil-root-shoot- atmosphere interactions in crops .1. Description of main functions^206^161^2^275-287^^^^^Apr^^^^^4025A^4024^A research facility is described for the integrated study of soil-root-shoot-atmosphere relationships in crops. The Wageningen Rhizolab has been in use since 1990, and consists of two rows, each with eight below-ground compartments aligned along a corridor. A rain shelter automatically covers the experimental area at the start of rainfall. Compartments are 125 cm x 125 cm and 200 cm deep. Each compartment has a separate drip irrigation system. Crop canopy photosynthesis, respiration, and transpiration can be measured simultaneously and continuously on four out of eight compartments at a time. Each compartment can be filled with a selected soil material (repacked soil) and is accessible from the corridor over its full depth. Multiple sensors for measuring soil moisture status, electrical conductivity, temperature, soil respiration, trace gases and oxygen are installed in spatial patterns in accordance with the requirements of the experiments. Sensors are connected to control and data-acquisition devices. Likewise, provisions have been made to sample manually the soil solution! and soil atmosphere. Root observation tubes (minirhizotrons) are installed horizontally at depth intervals ranging from 5# cm (upper soil layers) to 25 cm (below 1 m). The facility is at present in use to study growth and development of vegetat+ion (crops) in relation to drought, nutrient status, soil-borne diseases, and underground root competition. One important -application is the study of elevated CO2 concentration and climate change and the way they affect crops and their carbon e;conomy. Growth and development of field grown vegetables and winter cover crops are also evaluated. The common aspect of t=hose studies is to gain a better understanding of crop growth under varying environmental conditions, and to collect datasPets that may help to improve mechanistic crop growth simulation models that can address suboptimal growth conditions.R605^3^Wang,ZM^Lechowicz,MJ^Potvin,C^1994^1^Early selection of black spruce seedlings and global change - which genotypes s\hould we favor^56^4^3^604-616^^^^^Aug^^^^^4027         # > A B G  Vc^A^4026^We investigated the effects of both soil fertility and predicted changes in climate on the performance of differentk families of black spruce, Picea mariana (Mill.) B.S.P., during the first growing season. The results were used to examinem whether reforestation programs should consider changing their preferred family lines in anticipation of altered performan{ce given global climate change. We grew seedlings of 16 open- pollinated maternal families of black spruce under phytotron} conditions simulating present and mid-21 st century climatic conditions during the growing season. The realistic, simulated future climate included both elevated CO2 levels and seasonally appropriate increases in mean daily temperature. To explore the dependence of climatic responses on site quality, seedlings were irrigated with solutions having either 5 or 100 mg/L of nitrogen. The lower nitrogen level represents a poor site for black spruce growth and survival, but the higher level provides ample nitrogen. We also recorded seed size for each seedling to evaluate the degree to which maternal investments might buffer responses to future climate and fertility during the first year on the seedbed. Seedling survival and growth increased both under the future climate regime and with nitrogen fertilization. The two factors interacted synergistically, with nitrogen enrichment significantly enhancing the positive effects of the future climate regime. Nitrogen-poor conditions, however, did not preclude a positive seedling response to the future climate. Our results indicate that seedling survival and height growth are highly dependent upon initial seed mass: larger seeds produced more vigorous 1 st-yr seedlings. The families differed in seed mass, seed germination, and seedling survival and growth, but their relative performances did not vary significantly among the treatments. These results suggest that black spruce families selected for rapid growth under present conditions will also do well in the future, at least in terms of early establishment and performance on sites regenerated by seeding.606^3^Wilkins,D^Vanoosten,JJ^Besford,RT^1994^1^Effects of elevated co2 on growth and chloroplast proteins in prunus-avium^ 13^14^7-9^769-779^^^^^Jul-Sep^^^^^4029-R-o-w-~----------_.}.. /|/04 623^3^Polley,HW^Johnson,HB^Mayeux,HS^1994^1^Increasing co2 - comparative responses of the C-4 grass schizachyrium and grassland invader prosopis^11^75^4^976-988^^^^^Jun^^^^^4062d elevated CO2 occurred (as much as 7.1 mu mol m(-2) s(-1)) over a broad range of temperatures (17-35 C), but the temperatu"re optimum for A was similar at both 350 and 700 mu L L(-1) CO2. In 1992, no differences in A, A(max), Q(r), LCP, or R(d) $were detected when ambient and elevated CO2 plants were compared. In plants collected from field plots, R(d), LCP, and lea)f N were significantly higher than in plants within the chambers indicating that a chamber effect exists for these paramet+ers. In both years, g was significantly reduced (21%-51%) when measured at 700 vs. 350 mu L L(-1) CO2. Peak aboveground bi7omass was increased at elevated CO2 in 1991 but not in 1992. These data indicate that for C-4 grasses, effects of elevated8 CO2 may only be detectable in years with significant water stress, a common occurrence in the central North American tallCgrass prairies.EA^4028^To predict the future carbon sequestering capacity of trees, we need information about the possible acclimatory mecShanisms of plant growth and photosynthesis in rising atmospheric CO2 under a variety of environmental conditions. We have,U therefore, studied the growth response of a tree species (Prunus avium L. Stella (wild cherry)) to elevated CO2 and chara_cterized the associated changes in photosynthetic machinery of the leaf tissue. Self-pollinated seedlings and mature cuttiangs (clones) from the same parent plant of P. avium were grown for two consecutive growing seasons (about 60 days each) inr ambient CO2 (350 mumol mol-1 CO2) or elevated CO2 (700 mumol Mol-1 CO2) with a high or low nutrient supply. The degree oft acclimation of leaf biochemistry and growth response to elevated CO2 was dependent on the plant material (seedling or mat~ ure cutting) and nutrient supply. There was little or no growth response to elevated CO2 in seedlings or cuttings in the l ow nutrient supply treatments, whereas, in both seasons, there was a strongly positive growth response to elevated CO2 in  seedlings and cuttings in the high nutrient supply regimes, resulting in increases in the root/shoot ratio and in carbon a llocation to the roots. In contrast, the protein content and activity of ribulose-1,5-bisphosphate carboxylase-oxygenase ( Rubisco, EC 4.1.1.39) were down regulated in elevated CO2. The loss of Rubisco on an area basis in plants in the elevated CO2 treatments was compensated for at the canopy level by increased leaf area. The loss of Rubisco protein was accompanied by decreases in the contents of chlorophyll and the thylakoid membrane proteins D1, D2 and cytochrome f, which are involved in light harvesting and photo-electron transport. We conclude that, in the medium- to long-term, the initial stimulation of biomass production by elevated CO2 may be increasingly offset by a lower photosynthetic capacity per unit leaf area in perennial plants.%607^5^Bugbee,B^Spanarkel,B^Johnson,S^Monje,O^Koerner,G^1994^1^Co2 crop growth enhancement and toxicity in wheat and rice^240^14^11^257-267^^^^^XXX^^^^^4031A^4030^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 addi tional 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 supri,sed to find that radiation interception during early growth was not improved by elevated CO2. As expected, CO2 increased q. uantum yield, but there was also a small increase in carbon use efficiency. Super-optimal CO2 levels did not reduce vegeta>!tive growth, but decreased seed set and thus yield. The reduced seed set is not visually apparent until final yield is mea@"sured. The physiological mechanism underlying CO2 toxicity is not yet known, but elevated CO2 levels (0.1 to 1% CO2) increPase ethylene synthesis in some plants and ethylene is a potent inhibitor of seed set in wheat.Z]`cfiR$608^3^Cao,W^Tibbitts,TW^Wheeler,RM^1994^1^Carbon-dioxide interactions with irradiance and temperature in potatoes^240^14^1_1^243-250^^^^^XXX^^^^^4033}jt &eh|a&A^4032^Separate controlled environment studies were conducted to determine the interaction of CO2 with irradiance and inteo'raction of CO2 with temperature on growth of three potato cultivars. In the first study, an elevated CO2 concentration of q(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 an*d 800 mu mol m(-2) s(-1) PPF at each photoperiod). Tuber and total dry weights of 90-day old potatoes were significantly i+ncreased with CO2 enrichment, but the CO2 stimulation was less with higher PPF and longer photoperiod. Shoot dry weight wa,s affected more by photoperiod than by PPF and CO2 concentrations. The elevated CO2 concentration increased leaf CO2 assim-ilation rates and decreased stomatal conductance with 12 h photoperiod, but had only a marginal effect with 24 h photoperi.od. In the second study, four CO2 concentrations of 500, 1000, 1500 and 2000 mu mol mol(-1) were combined with two air tem/perature regimes of 16 and 20 degrees C under a 12 h photoperiod. At harvest, 35 days after transplanting, tuber and total0 dry weights of potatoes reached a maximum with 1000 mu mol mol(-1) CO2 at 16 degrees C, but continued to increase up to 21000 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 concen2trations. At 16 degrees C specific leaf weight increased substantially with increasing CO2 concentrations as compared to 5300 mu mol mol(-1) CO2, but increased only slightly at 20 degrees C. This suggests a carbohydrate build-up in the leaves at4 16 degrees C temperature that reduces plant response to increased CO2 concentrations. The data in the two studies indicat5e 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.55687?7H@U@@@oCtCuC~CDDHHKKKKLL L LLL7609^9^Loretan,PA^Bonsi,CK^Mortley,DG^Wheeler,RM^Mackowiak,CL^Hill,WA^Morris,CE^Trotman,AA^David,PP^1994^1^Effects of several environmental-factors on sweet-potato growth^240^14^11^277-280^^^^^XXX^^^^^4035 9A^4034^Effects of relative humidity, light intensity and photoperiod on growth of 'Ga Jet' and 'TI-155' sweetpotato cultiv :ars, using the nutrient film technique (NFT), have been reported. In this study, the effect of ambient temperature regimes; (constant 28 degrees C and diurnal 28:22 degrees C day:night) and different CO2 levels (ambient, 400,1 000, and 10 000 mu< L/L - 400, 1 000 and 10 000 ppm) on growth of one or both of these cultivars in NFT are reported. For a 24-h photoperiod,-= no storage roots were produced for either cultivar in NFT when sweetpotato plants were grown at a constant temperature of/> 28 degrees C. For the same photoperiod, when a 28:22 degrees C diurnal temperature variation was used, there were still n:?o storage roots for 'TI- 155' but the cv. 'Ga Jet' produced 537 g/plant of storage roots. For both a 12-h and 24-h photope<@riod,'Ga Jet' storage root fresh and dry weight tended to be higher with a 28:22 degrees C diurnal temperature variation tIAhan with a constant 28 degrees C temperature regime. Preliminary results with both 'Ga Jet' and 'TI-155' cultivars indicatKBe a distinctive diurnal stomatal response for sweetpotato grown in NFT under an ambient CO2 level. The stomatal conductancbCe values observed for 'Ga Jet' at elevated CO2 levels indicated that the difference between the light- and dark-period condductance rates persisted at 400, 1 000, and 10 000 mu L/L.sE610^1^Bunce,JA^1993^1^Growth, survival competition, and canopy carbon-dioxide and water-vapor exchange of 1st year alfalfau at an elevated co2 concentration^79^29^4^557-565^^^^^^^^^^4037Dr. MGA^4036^Alfalfa was grown in field plots at the current CO2 concentration (350 mumol mol-1 = c350) and at 350 mumol mol-1 aHbove the current concentration (= c700). Alfalfa and weed growth, and canopy water vapor (E) and carbon dioxide exchange (IF) were determined for the first year. Alfalfa yield summed for the three harvests.in the first year was greater for the cJ700 treatment in two of the years studied, but significantly less in a third year. Weed growth was unaffected. Survival ofK alfalfa plants was greater at c700 for years in which there was substantial mortality, even when yield was not increased Lby the c700 treatment. In spite of a persistent reduction in leaf conductance to water vapor (g(l)), total canopy conductaMnce (g(c)) to water vapor did not differ between CO2 treatments when averaged over years, because of compensating changes Nin canopy leaf area. CO2 efflux (F) at night per unit of ground area was consistently less in the c700 treatment even whenO 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.Q611^4^Chen,DX^Coughenour,MB^Knapp,AK^Owensby,CE^1994^1^Mathematical simulation of C4 grass photosynthesis in ambient and elevated co2^81^73^1-2^63-80^^^^^May^^^^^4039 SA^4038^A mechanistic leaf photosynthesis model was developed for C4 grasses based on a general simplified scheme of C4 plaTnt carbon metabolism. In the model, the PEPcase-dependent C4-cycle was described in terms of CO2 concentration in the mesoUphyll space using Michaelis-Menten kinetics, and the activity of PEPcase was related to the incident PAR to take account oVf the influence of light on the activty of C4-cycle processes. The CO2 refixation by Rubisco in the bundle sheath was descWribed using a widely accepted C3 photosynthesis model. The model assumes a steady state balance among CO2 diffusion from sXurrounding atmosphere into the mesophyll space, CO2 transport into the bundle sheath by the C4-cycle, CO2 refixation by th Ye C3-cycle in the bundle sheath, and CO2 leakage from the bundle sheath. The response to temperature of photosynthesis wasZ incorporated via the temperature dependence of model parameters. The photosynthesis model was coupled with a stomatal con[ductance model in order to predict leaf photosynthesis rates at different atmospheric conditions. The empirical model of B\all et al. (1987) was adopted and slightly modified to describe responses in stomatal conductance. The coupled model was p]arameterized 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 measu8ared data quite well for both atmospheric CO2- pretreatments. At 25-degrees-C, the estimated maximum carboxylation rate of :bRubisco V(cm,25), potential electron transport rate J(m,25) and quantum efficiency alpha were increased by CO2 enrichment.Jc The maximum PEPcase activity V(pm,25) was lower in elevated CO2. The model predicted that the light-saturated leaf photosLdynthesis will increase by about 10% with the rising of atmospheric CO2 from 350 to 700 ppm at 30-degrees-C, and that the oYeptimal temperature of photosynthesis will shift from 37 to 38.5-degrees-C. The estimated slope of the stomatal conductance[f model was increased by atmospheric CO2 enrichment. Stomatal conductance was significantly reduced by increasing atmospherhic CO2 concentration.jh612^3^Dacey,JWH^Drake,BG^Klug,MJ^1994^1^Stimulation of methane emission by carbon-dioxide enrichment of marsh vegetation^3y6^370^6484^47-49^^^^^7 Jul^^^^^4041{jA^4040^THERE is substantial evidence that many plants respond to increased concentrations of atmospheric carbon dioxide byk increasing their productivity(1-4) This observation has led to the suggestion that, by taking up CO2, the terrestrial biolsphere might mitigate the potential greenhouse warming associated with anthropogenic CO2 emissions(5). Whiting and Chantonm(6) have found, however, that for wetlands of varying productivity around the world, higher net primary production is assonciated with higher emissions of methane-another important greenhouse gas. Here we present measurements of methane emissionos from a marsh that has been exposed to twice the present ambient concentration of atmospheric CO2. We find that over a onpe-week period, the CO2-enriched sites had significantly higher emissions of methane than the control sites. Our results suqggest that future increases in atmospheric CO2 concentration may lead to significant increases in methane emissions from wetlands.՜.+,D՜.+,D hp s613^2^Delesalle,VA^Blum,S^1994^1^Variation in germination and survival among families of sagittaria-latifolia in response to salinity and temperature^104^155^2^187-195^^^^^Mar^^^^^4043 6> _PID_GUIDuA^4042^We studied seed germination and seedling growth in eight maternal families of Sagittaria latifolia (Alismataceae), va freshwater perennial, in response to salinity (four levels) and temperature effects (two levels) in the greenhouse. Saliwnity decreased germination, delayed emergence, and decreased survival and growth rates. The negative effects of salinity oxn germination were greater at the high-temperature regime, but the effects on growth were greater at the low-temperature ryegime. Some seeds were capable of germinating and surviving (with minimal growth) even in 0.8% NaCl solution. Families alszo differed in their response to salinity but not to temperature. In particular, high salinities had little effect on the g{ermination 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 co}nditions; thus, S. latifolia might be minimally affected by short-term salt intrusions. In order to understand how plant p ~opulations respond to disturbances, such as increased salinity or increased temperature, we need to consider the source, either environmental or genetic, of maternal effects.614^2^Downton,WJS^Grant,WJR^1994^1^Photosynthetic and growth-responses of variegated ornamental species to elevated co2^92)^21^3^273-279^^^^^^^^^^4045,A^4044^Variegated and completely green cultivars of oleander (Nerium oleander L.) and willow myrtle (Agonis flexuosa (Will;d.) 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 pOortions of variegated leaves on both species was greatly stimulated by high CO2 and there was no evidence of downward adjuQstment (acclimation) of photosynthetic rates to high CO2 during the experiment. Dark respiration rates of these leaves werde lowered by high CO2. The yellow portions of willow myrtle leaves showed a low level of photosynthetic activity which wasf stimulated by high CO2; however, dark respiration rates showed little response to elevated CO2. Green and yellow areas onx variegated leaves of willow myrtle had much lower dark respiration rates than completely green leaves, but this differencze 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. 615^2^Ferris,R^Taylor,G^1994^1^Elevated co2, water relations and biophysics of leaf extension in 4 chalk grassland herbs^84^127^2^297-307^^^^^Jun^^^^^4047 A^4046^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 s'ignificantly in leaves of S. minor, L. corniculatus and P. media exposed to elevated CO2, whereas in A. vulneraria, there 5was no effect of CO2 on extensibility. These results suggest that the mechanism by which elevated CO2 promotes leaf growth7 differs between species since in S. minor, L. corniculatus and P. media, CO2 promoted growth through an influence on cellC wall properties, whilst in A. vulneraria, higher values of P explain the increased leaf growth in elevated CO2 for this sEpecies.R616^5^Goldewijk,KK^Vanminnen,JG^Kreileman,GJJ^Vloedbeld,M^Leemans,R^1994^1^Simulating the carbon flux between the terrestrSial environment and the atmosphere^94^76^1-2^199-230^^^^^Jul^^^^^4049\A^4048^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 diffperent compartments of the terrestrial biosphere and between the biosphere and the atmosphere. Climatic parameters, land cosver 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.617^2^Idso,KE^Idso,SB^1994^1^Plant-responses to atmospheric co2 enrichment in the face of environmental constraints - a review of the past 10 years research^107^69^3-4^153-203^^^^^Jul^^^^^4051 F  X`A^4050^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 environ!mental stresses are most severe.'618^1^Kirschbaum,MUF^1994^1^The sensitivity of C-3 photosynthesis to increasing co2 concentration - a theoretical-analysis) of its dependence on temperature and background co2 concentration^9^17^6^747-754^^^^^Jun^^^^^4053:A^4052^The atmospheric CO2 concentration has increased from the pre- industrial concentration of about 280 mu mol mol(-1) <to its present concentration of over 350 mu mol mol(-1), and continues to increase. As the rate of photosynthesis in C-3 pIlants is strongly dependent on CO2 concentration, this should have a marked effect on photosynthesis, and hence on plant gKrowth and productivity. The magnitude of photosynthetic responses can be calculated based on the well-developed theory of \photosynthetic response to intercellular CO2 concentration. A simple biochemically based model of photosynthesis was coupl^ed to a model of stomatal conductance to calculate photosynthetic responses to ambient CO2 concentration. In the combined lmodel, photosynthesis was much more responsive to CO2 at high than at low temperatures. At 350 mu mol mol(-1), photosynthensis at 35 degrees C reached 51% of the rate that would have been possible with non-limiting CO2, whereas at 5 degrees C, 7y7% of the CO2 non-limited rate was attained. Relative CO2 sensitivity also became smaller at elevated CO2, as CO2 concentr{ation increased towards saturation. As photosynthesis was far from being saturated at the current ambient CO2 concentration, considerable further gains in photosynthesis were predicted through continuing increases in CO2 concentration. The strong interaction with temperature also leads to photosynthesis in different global regions experiencing very different sensitivities to increasing CO2 concentrations.Text version619^1^Kojima,S^1994^1^Effects of global climatic warming on the boreal forest^241^107^1085^91-97^^^^^Mar^^^^^4055A^4054^On the basis of the predictions of the global climatic warming induced by anthropogenic activities, as provided by climatologists, current state of knowledge regarding possible ecological consequences of the warming on the boreal biome was discussed. A 600 to 700 km northward advance of the biome along with the warming was predicted. Such a shift could take place for half a century or so, which would be an unprecedentedly fast rate of progression. This might cause a serious disorder in species composition of the biome, particularly in the boundary regions. As to the carbon sink or source issues, considerable uncertainties and knowledge gaps existed. Elevated temperature and CO2 levels would stimulate photosynthesis to result in an increase of CO2 uptake, while the temperature increase would promote decomposition of organic matter especially that stored in the soils to release CO2 to the atmosphere. Behaviors of northern peat bogs, where ca. 700 Gt of organic matter was thought to be accumulated, would seriously affect the balance. However, overall ecosystematic carbon balance was yet to be fully studied. It was realized that multifunctional approaches needed to be developed so as to integrate pieces of various information into a holistic picture. Need for international collaboration research efforts was also addressed.b,_QP hM605:23 PM 24 02 1999 -0500Amy E. Faivre620^1^Makino,A^1994^1^Biochemistry of C3-photosynthesis in high co2^241^107^1085^79-84^^^^^Mar^^^^^4057S A^4056^The short-term responses of C3 photosynthesis to high CO2 are described first. Regulation of photosynthesis in the short term is determined by interaction among the capacities of light harvesting, electron transport, ribulose-1, 5-bispho sphate carboxylase (Rubisco) and orthophosphate (Pi) regeneration during starch and sucrose synthesis. Photosynthesis under high CO2 conditions is limited by either electron transport or Pi regeneration capacities, and Rubisco is deactivated to maintain a balance between each step in the photosynthetic pathway. Subsequently, the long-term effects on photosynthesis are discussed. Long-term CO2 enhancement leads to carbohydrate accumulation. Accumulation of carbohydrates is not associa ted with a Pi-regeneration limitation on photosynthesis, and this limitation is apparently removed during long-term exposu.re to high CO2. Enhanced CO2 does not affect Rubisco content and electron transport capacity for a given leaf-nitrogen con0tent. In addition, the deactivated Rubisco immediately after exposure to high CO2 does not recover during the subsequent p>rolonged exposure. Such evidence may indicate that plants do not necessarily have an ideal acclimation response to high CO@2 at the biochemical level.JABLONSKI LeanneCall for 18th Polar LibrK621^2^Morse,SR^Bazzaz,FA^1994^1^Elevated co2 and temperature alter recruitment and size hierarchies in C-3 and C-4 annualsM^11^75^4^966-975^^^^^Jun^^^^^4059RE: thule ms^A^4058^In order to understand the implications of changes in global CO2 concentrations and temperature for the growth and `fitness of individual plants, performance must be investigated in relation to the performance of other plants within a popoulation. In this study we examined patterns of recruitment, mortality, and size structure of monospecific stands in responqse to ambient (400 mu L/L) and elevated CO2 concentrations (700 mu L/L) across three temperature regimes; 18 degrees, 28 dzegrees, and 38 degrees C. We created experimental populations of two annual plants that differ in their photosynthetic pat|hway and water use patterns: Abutilon theophrasti (C-3) and Amaranthus retroflexus (C-4). The effects of CO2, temperature, and their interactions on population structure were complex and species dependent. For both species increasing temperature resulted in higher germination and faster initial growth rates. These initial temperature responses increased the intensity and role of competition in determining stand size and structure. Postemergence responses to elevated CO2 differed markedly between the two species. For Abutilon, the C-3 species, serf-thinning and the mean biomass of the survivors increased under elevated CO2. For Amaranthus, survivorship, but not growth, increased under elevated CO2 conditions. We attribute differences in response between species not only to photosynthetic pathway, but also to differences in the onset of competition mediated through differences in plant form and in resource uptake and deployment. The patterns of stand development in response to CO2 and temperature suggest that the effects of changing CO2 and temperature may be understood within mechanistically based models of resource use. Temperature regulates the rate of resource use and the onset of interference among plants, while CO2 functions both as a resource and a resource regulator. Although mortality was concentrated later in stand development for Abutilon than Amaranthus, overall patterns of stand size and structure were similar for both species; mortality and size inequalities increased with increasing temperature and CO2. Because size is often correlated with fecundity, an increase in size hierarchies in response to elevated CO2, in conjunction with a decrease in survivorship, may result in a smaller effective population size. Our ability to predict changes in effective population size due to changing size hierarchies alone, however, should also consider developmental shifts in response to elevated CO2 that may result in, as in this study, a decrease in the minimum size at the onset of flowering.journal, etc.622^1^Pitelka,LF^1994^1^Ecosystem response to elevated co2^57^9^6^204-207^^^^^Jun1 02 1999 -0500CURTIS Peter A^4061^The woody C-3 Prosopis glandulosa (honey mesquite) and C-4 perennial grass Schizachyrium scoparium (little bluestem,) were grown along a gradient of daytime carbon dioxide concentrations from near 340 to 200 mu mol/mol air in a 38 m long .controlled environment chamber. We sought to determine effects of historical and prehistorical increases in atmospheric CO=2 concentration on growth, resource use, and competitive interactions of a species representative of C-4-dominated grassla@nds in the southwestern United States and the invasive legume P. glandulosa. Increasing CO2 concentration stimulated N-2 fOixation by individually grown P. glandulosa and elicited in C-3 seedlings a similar relative increase in leaf intercellulaQr CO2 concentration, net assimilation rate, and intrinsic water use efficiency (leaf net assimilation rate/stomatal conduc] tance). Aboveground biomass of P. glandulosa was not altered by CO2 concentration, but belowground biomass and whole-plant^ water and nitrogen use efficiencies increased linearly with CO2 concentration in seedlings that were grown alone. Biomassj produced by P. glandulosa that was grown with S. scoparium was not affected by CO2 concentration. Stomatal conductance del clined and leaf assimilation rates of S. scoparium at near maximum incident light increased at higher CO2 concentration, bz ut there was no effect of CO2 concentration on biomass production or whole- plant water use efficiency of the C-4 grass. R|ising CO2 concentration, especially the 27% increase since the beginning of the 19th century, may have contributed to more abundant P. glandulosa on C-4 grasslands by stimulating the shrub's growth or reducing the amount of resources that the C-3 required. Much of the potential response of P. glandulosa to CO2 concentration, however, appears to be contingent on the shrub's escaping competition with neighboring grasses.phylogeny624^3^Reekie,JYC^Hicklenton,PR^Reekie,EG^1994^1^Effects of elevated co2 on time of flowering in 4 short-day and 4 long-day species^188^72^4^533-538^^^^^Apr^^^^^4064No SubjectA^4063^This study was undertaken to determine if the effect of elevated CO2 on flowering phenology is a function of the photoperiodic response of the species involved. Four long-day plants, Achillea millefolium, Callistephus chinensis, Campanula isophylla, and Trachelium caeruleum, and four short-day plants, Dendranthema grandiflora, Kalanchoe blossfeldiana, Pharbitis nil, and Xanthium pensylvanicum, were grown under inductive photoperiods (9 h for short day and 17 h for long day) at either 350 or 1000 mu L/L CO2. Time of visible flower bud formation, flower opening, and final plant biomass were assessed. Elevated CO2 advanced flower opening in all four long-day species and delayed flowering in all four short-day species. In the long-day species, the effect of CO2 was primarily on bud initiation; all four species formed buds earlier at high CO,. Bud development, the difference in time between flower opening and bud initiation, was advanced in only one long-day species, Callistephus chinensis. Mixed results were obtained for the short-day species. Elevated CO, exerted no effects on bud initiation but delayed bud development in Dendranthema and Kalanchoe. In Xanthium, bud initiation rather than bud development was delayed. Data on bud initiation and development were not obtained for Pharbitis. The negative effect of CO, upon phenology in the short-day species was not associated with negative effects on growth. Elevated CO2 increased plant siz e in both long-day and short-day species. 1999 -0500CARTER Jody lab!625^2^Reid,CD^Strain,BR^1994^1^Effects of co(2) enrichment on whole-plant carbon budget of seedlings of fagus-grandifolia and acer-saccharum in low irradiance^2^98^1^31-39^^^^^Jun^^^^^4066apologies'#A^4065^Carbon exchange rates (CER) and whole-plant carbon balances of beech (Fagus grandifolia) and sugar maple (Acer sacc)$harum) were compared for seedlings grown under low irradiance to determine the effects of atmospheric CO2 enrichment on sh9%ade-tolerant seedlings of co-dominant species. Under contemporary atmospheric CO2, photosynthetic rate per unit mass of be;&ech was lower than for sugar maple, and atmospheric CO2 enrichment enhanced photosynthesis for beech only. Aboveground resK'piration per unit mass decreased with CO2 enrichment for both species while root respiration per unit mass decreased for sM(ugar maple only. Under contemporary atmospheric CO2, beech had lower C uptake per plant than sugar maple, while C losses pe)er plant to nocturnal aboveground and root respiration were similar for both species. Under elevated CO2, C uptake per plag*nt was similar for both species, indicating a significant relative increase in whole-seedling CER with CO2 enrich ment forz+ beech but not for sugar maple. Total C loss per plant to aboveground respiration was decreased for beech only because inc|,rease in sugar maple leaf mass counterbalanced a reduction in respiration rates. Carbon loss to root respiration per plant- was not changed by CO2 enrichment for either species. However, changes in maintenance respiration cost and nitrogen level. suggest changes in tissue composition with elevated CO2. Beech had a greater net daily C gain with CO2 enrichment than di/d sugar maple in contrast to a lower one under contemporary CO2. Elevated CO2 preferentially enhances the net C balance of0 beech by increasing photosynthesis and reducing respiration cost. In all cases, the greatest C lost was by roots, indicat1ing the importance of belowground biomass in net C gain. Relative growth rate estimated from biomass accumulation was not 2affected by CO2 enrichment for either species possibly because of slow growth under low light. This study indicates the im3portance of direct effects of CO2 enrichment when predicting potential change in species distribution with global climate change.g \I6!09:41 AM 05 02 1999 -0500Holly 5626^2^Samuelson,LJ^Seiler,JR^1994^1^Red spruce seedling gas-exchange in response to elevated co2, water-stress, and soil fertility treatments^155^24^5^954-959^^^^^May^^^^^4068 05 02 1999 -0500Jodi Carter7A^4067^The interactive influences of ambient (374 muL.L-1) or elevated (713 muL.L-1) CO2, low or high soil fertility, well8-watered or water-stressed treatment, and rooting volume on gas exchange and growth were examined in red spruce (Picea rub9ens Sarg.) grown from seed through two growing seasons. Leaf gas exchange throughout two growing seasons and growth after :two growing seasons in response to elevated CO2 were independent of soil fertility and water-stress treatments, and rootin;g volume. During the first growing season, no reduction in leaf photosynthesis of seedlings grown in elevated CO2 compared< with seedlings grown in ambient CO2 was observed when measured at the same CO2 concentration. During the second growing s=eason, net photosynthesis was up to 21% lower for elevated CO2-grown seedlings than for ambient CO2-grown seedlings when m>easured at 358 muL.L-1. Thus, photosynthetic acclimation to growth in elevated CO2 occurred gradually and was not a functi?on of root- sink strength or soil-fertility treatment. However, net photosynthesis of seedlings grown and measured at an e@levated CO2 concentration was still over 2 times greater than the photosynthesis of seedlings grown and measured at an ambAient CO2 concentration. Growth enhancement by CO2 was maintained, since seedlings grown in elevated CO2 were 40% larger in both size and weight after two growing seasons.2 1999 -0500SWENSON SteveC627^3^Seneweera,S^Milham,P^Conroy,J^1994^1^Influence of elevated co2 and phosphorus-nutrition on the growth and yield of a) short-duration rice (oryza-sativa L CV jarrah)^92^21^3^281-292^^^^^^^^^^4070family+EA^4069^The growth and development of a short-duration rice cultivar (Oryza sativa L. cv. Jarrah), grown in flooded soil wi6Fth a range of phosphorus (P) levels and exposed to atmospheric CO2 concentrations of either 350 or 700 mu L L(-1) was foll8Gowed for 146 days after planting (DAP). Development (estimated by rate of tiller production and time to flowering) was fasCHter with higher soil P levels and CO2 enrichment, the effect being more pronounced with CO2 enrichment. During the early vEIegetative phase (up to 35 DAP), when rates of tiller production were low, shoot growth and rates of leaf expansion were faPJster at elevated CO2 concentrations and high soil P levels. Rates of tiller production were greater with these treatments RKduring the 35-56 DAP period, when tillering was at a maximum. Shoot elongation was reduced at elevated CO2 levels and at h_Ligh soil P levels during this period. By 146 DAP leaf weight was greater at high P levels, but CO2 enrichment accelerated aMtiller production to such an extent that final leaf weight was lower at high CO2, probably because there were fewer, and slNmaller, leaves on each tiller. Despite this, grain yield was increased by up to 58% by CO2 enrichment, with increases occunOrring even at low soil P levels. This was due mainly to an increase in grain number per panicle, although panicle number a{Plso increased. Higher soil P levels also increased grain number and yield. The P concentration in the foliage was unaffect}Qed by the CO2 treatments and the concentration required to produce maximum yield was 0.18% (dry wt basis) at both CO2 leveRls. Greater starch accumulation in the stems of high-CO2-grown plants may have accounted for the higher number of grains in each panicle.9eV609:12 AM 10 02 1999 -0500SWENSON SteveT628^3^Sheppard,MI^Ewing,LL^Hawkins,JL^1994^1^Soil processes and chemical-transport - soil degassing of C-14 dioxide - rates and factors^204^23^3^461-468^^^^^May-Jun^^^^^4072Re: Hi!VA^4071^Soil air normally contains elevated levels of CO2 relative to the atmosphere. The primary source of soil C is plantW-root and microbial respiration. The exchange of soil and atmospheric CO2 is important to many environmental concerns, sucXh as acid rain, global warming and waste management. Proposed disposal of high- level nuclear wastes containing primarily Yinorganic C-14 may provide a source of (CO2)-C-14 to the atmosphere. Field and laboratory experiments show that (CO2)-C-14Z Soil degassing rate constants, the flux density (Bq.M2.s-1) divided by soil inventory (Bq-m-2), range from -10(-7) to -10[(-2) S-1, and that the loss of inorganic C-14 is driven primarily by gaseous diffusion. These constants are affected by so\il pH and porosity, with smaller influences of soil temperature, moisture and organic matter content. Degassing rate const]ants derived through mass balance calculations to estimate loss differ only by 20% from direct trapping methods. Frozen so^il degassing rate constants were up to 25 times smaller than lab values, indicating that annual C-14 loss rates in norther_n climates would be lower because of reduced gaseous diffusion during the winter months. Using our field data, we recommen`d an annual C- 14 soil degassing rate constant of -1 x 10(-6) s-1 for acidic soils and a value of -5 x 10(-7) S-1 for calcaareous soils. For probabilistic assessment modelling, we recommend a geometric mean degassing constant of -4.3 X 10(-7) S-b1 with a geometric standard deviation of 3.26 for three different soils. This indicates the median half-life of C-14 in su rface soils is 18 d, with a 99% confidence interval of 13 h and 640 d.d629^2^Stanghellini,C^Bunce,JA^1993^1^Response of photosynthesis and conductance to light, co2, temperature and humidity in tomato plants acclimated to ambient and elevated co2^79^29^4^487-497^^^^^^^^^^4074i>fA^4073^In tomato (Lycopersicon esculentum L.) plants, net carbon dioxide exchange rate (P(N)) response curves to both irra@gdiance (I) and short-term [CO2] were similar for plants grown at both 350 and 700 cm3(CO2) m-3. However, water vapor conduKhctance (gH2O) of plants grown at high [CO2] was less sensitive to short term [CO2] variations, when measured at low vapor Mipressure difference, and was larger than the conductance of ''ambient [CO2]'' plants when both were exposed to high [CO2].]j P(N) and g(H2O) under high I increased with temperature over the range 18 to 32-degrees-C. P(N) of plants grown in both [_kCO2] treatments increased at most about 25 % from 350 to 700 cm3 m-3 at 18 and 25-degrees-C, and decreased when exposed totl 1000 cm3 m-3 at these temperatures. Thus increasing atmospheric [CO2] might not increase P(N) by as much as expected and vwater use of crops might not decrease.home...n630^3^Williams,RS^Lincoln,DE^Thomas,RB^1994^1^Loblolly-pine grown under elevated co2 affects early instar pine sawfly performance^2^98^1^64-71^^^^^Jun^^^^^4076Re: releasepA^4075^Seedlings of loblolly pine Pinus taeda (L.), were grown in open-topped field chambers under three CO2 regimes: ambiqent, 150 mul l-1 CO2 above ambient, and 300 mul l-1 CO2 above ambient. A fourth, non-chambered ambient treatment was inclurded to assess chamber effects. Needles were used in 96 h feeding trials to determine the performance of young, second instsar larvae of loblolly pine's principal leaf herbivore, red-headed pine sawfly, Neodiprion lecontei (Fitch). The relative ctonsumption rate of larvae significantly increased on plants grown under elevated CO2, and needles grown in the highest CO2u regime were consumed 21% more rapidly than needles grown in ambient CO2. Both the significant decline in leaf nitrogen covntent and the substantial increase in leaf starch content contributed to a significant increase in the starch:nitrogen ratwio in plants grown in elevated CO2. Insect consumption rate was negatively related to leaf nitrogen content and positivelyx related to the starch:nitrogen ratio. Of the four volatile leaf monoterpenes measured, only beta-pinene exhibited a signiyficant CO2 effect and declined in plants grown in elevated CO2. Although consumption changed, the relative growth rates ofz larvae were not different among CO2 treatments. Despite lower nitrogen consumption rates by larvae feeding on the plants {grown in elevated CO2, nitrogen accumulation rates were the same for all treatments due to a significant increase in nitro|gen utilization efficiency. The ability of this insect to respond at an early, potentially susceptible larval stage to poo}rer food quality and declining levels of a leaf monoterpene suggest that changes in needle quality within pines in future ~elevated-CO2 atmospheres may not especially affect young insects and that tree-feeding sawflies may respond in a manner similar to herb-feeding lepidopterans.Կ601:25 PM 19 02 1999 -0500MOBYDOG1@aol.c%631^2^Ziska,LH^Bunce,JA^1994^1^Increasing growth temperature reduces the stimulatory effect of elevated co2 on photosynthe'sis or biomass in 2 perennial species^37^91^2^183-190^^^^^Jun^^^^^4078O2MAP7A^4077^We examined how anticipated changes in CO2 concentration and temperature interacted to alter plant growth, harvest :characteristics and photosynthesis in two cold-adapted herbaceous perennials, alfalfa (Medicago sativa L. cv. Are) and orcJhard grass (Dactylis glomerata L. cv. Potomac). Plants were grown at two CO2 concentrations (362 [ambient] and 717 [elevatLed] mu mol mol(-1) CO2) and four constant day/night temperatures of 15, 20, 25 and 30 degrees C in controlled environmental chambers. Elevated CO2 significantly increased total plant biomass and protein over a wide range of temperatures in both species. Stimulation of photosynthetic rare, however, was eliminated at the highest growth temperature in M. sativa and rrelative stimulation of plant biomass and protein at high CO2 declined as temperature increased in both species. Lack of a tsynergistic effect between temperature and CO2 was unexpected since elevated CO2 reduces the amount of carbon lost via photorespiration and photorespiration increases with temperature. Differences between anticipated stimulatory effects of CO2 and temperature and whole plant single and leaf measurements are discussed. Data from this study suggest that stimulatory effects of atmospheric CO2 on growth and photosynthesis may decline with anticipated increases in global temperature, limiting the degree of carbon storage in these two perennial species.f492a3c344c0213f31ac9296f707 -19-Jan-1999-15:46:27--0500-(EST 916760779 Ndel Nskip Nsave read Nget 19890783633^1^Amthor,JS^1994^1^Scaling co2-photosynthesis relationships from the leaf to the canopy^91^39^3^321-350^^^^^Mar^^^^^40A^4081^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, ca%nopy, 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 ph?otosynthesis 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 processTes and are able to make useful, quantitative predictions of canopy and community responses to environmental change. The baVsis of some big leaf models of photosynthesis, including a new model described herein, is that photosynthetic capacity andg activity are scaled vertically within a canopy (by plants themselves) to match approximately the vertical profile of PPFDj. The new big leaf model combines physically based models of leaf and canopy level transport processes with a biochemicallqy based model of CO2 assimilation. Predictions made by the model are consistent with canopy CO2 exchange measurements, altshough 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.el Nskip Nsave read Nget 1461501043 c6a76f94343428931802a23d482199901222244.RAA15221@mail2.uts.ohio-state.edu>-22-Jan-1999-17:44:47--0500-(EST 917253364 Ndel Nskip Nsave read Nget 10634^4^Baxter,R^Ashenden,TW^Sparks,TH^Farrar,JF^1994^1^Effects of elevated carbon-dioxide on 3 montane grass species .1. Growth and dry-matter partitioning^78^45^272^305-315^^^^^Mar^^^^^4084A03144@sideshow.stanford.edu>-24-Jan-1999-12:06:25--05A^4083^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.--0500-(EST 917542356 Ndel Nskip Nsave read Nget 1707357751 af2e2050f340d09f95e743283236cdbf <0F6A0 635^2^Corrigan,VK^Carpenter,A^1993^1^Effects of treatment with elevated carbon-dioxide levels on the sensory quality of asparagus^199^21^4^349-357^^^^^^^^^^4086802FB@nsfmail01.nsf.gov>-29-Jan-1999-16:39:24--0500-(EST 917627988 Ndel Nskip Nsave!A^4085^Asparagus spears (Asparagus officinalis L. cv. Limbras 10) were stored for 3-5 days in atmospheres containing betwe#en 40 and 90% carbon dioxide (CO2) to evaluate the effect of insecticidal CO2 atmospheres on sensory quality based on sens1ory panel ratings of characteristic asparagus flavour, off-flavours, flavour acceptability, and overall acceptability. Sen3sory quality of spears after 4 days storage in 60% CO2 was similar to air-stored spears but 5 days storage caused deterior;ation in the CO2-stored spears relative to the air-stored spears. Using higher CO2 levels than this for shorter storage ti>mes resulted in spears with CO2 injury and poor sensory quality. Spear quality deteriorated with shelf period but previousN CO2 treatment did not affect the rate of deterioration. Storing spears at 5-degrees-C in 60% CO2 or 0-degrees-C in air gaPve consistently higher (lower for off-flavours) sensory quality ratings for all characteristics assessed than vice versa. aThick spears had more flavour and were more acceptable than thin spears. Thick spears had more flavour than thin spears whcen 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.18:53--0500-(EST) 9636^3^Curtis,PS^Snow,AA^Miller,AS^1994^1^Genotype-specific effects of elevated co2 on fecundity in wild radish (raphanus-raphanistrum)^2^97^1^100-105^^^^^Feb^^^^^4088kip Nsave read Nget 832874204 18e2380b5a87885a878dbd665db3d3af <199902051333A^4087^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 ther