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 4P