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Experimental systems to simulate future elevated CO2 conditions in the field often have large, rapid fluctuations in CO2. To examine possible impacts of such fluctuations on photosynthesis, the intact leaves of the field-grown plants of five species were exposed to two-minute cycles of CO2 between 400 and 800 μmol mol−1, lasting a total of 10 min,...
Attempts to identify crop genetic material with larger growth stimulation at projected elevated atmospheric CO2 concentrations are becoming more common. The probability of reductions in photosynthesis and yield caused by short-term variation in CO2 concentration within elevated CO2 treatments in the free-air CO2 enrichment plots raises the question...
Recent in vivo assays of the responses of Rubisco to temperature in C3 plants have revealed substantial diversity. Three cultivars of soybean (Glycine max L. Merr.), Holt, Fiskeby V, and Spencer, were grown in indoor chambers at 15, 20, and 25 oC. Leaf photosynthesis was measured over the range of 15 to 30 oC, deliberately avoiding higher temperatu...
Our previous published results demonstrated that elevated CO2 can reprogram photosynthetic carbon metabolism (PCM) during sudden heat stress (SHS) treatments. However, the mechanism explaining how elevated CO2 could regulate the metabolites through SHS-induced proteins is poorly understood. Here, we combined metabolism and transcriptomes analysis t...
High intrinsic water-use efficiency (WUEi), the ratio of leaf photosynthesis to stomatal conductance, may be a useful trait in adapting crops to water-limited environments. In soybean, cultivar differences in stomatal response to vapor pressure deficit have not consistently translated into differences in WUEi in the field. In this study, six cultiv...
Whether the mesophyll conductance to CO2 movement (gm) within leaves of C3 plants changes with CO2 concentration remains a matter of debate, particularly at low CO2 concentrations. We tested for changes in gm over the range of sub-stomatal CO2 concentrations (Ci) for which Rubisco activity limited photosynthesis (A) in three plant species grown und...
Plants would experience more complex environments, such as sudden heat shock (SHS) stress combined with elevated CO2 in the future, and might adapt to this stressful condition by optimizing photosynthetic carbon metabolism (PCM). It is interesting to understand whether this acclimation process would be altered in different genotypes of maize under...
Improving water use efficiency (WUE) may prove a useful way to adapt crop species to drought. Since the recognition of the importance of mesophyll conductance to CO2 movement from inside stomatal pores to the sites of photosynthetic carboxylation, there has been interest in how much intraspecific variation in mesophyll conductance (gm) exists, and...
C3 photosynthesis at high light is often modeled by assuming limitation by the maximum capacity of Rubisco carboxylation (VCmax) at low CO2 concentrations, by electron transport capacity (Jmax) at higher CO2 concentrations, and sometimes by triose-phosphate utilization rate at the highest CO2 concentrations. Net photosynthetic rate (P
N) at lower l...
High CO2 and high temperature have an antagonistic interaction effect on rice yield potential and present a unique challenge to adapting rice to projected future climates. Understanding how the differences in response to these two abiotic variables are partitioned across rice germplasm accessions may be key to identifying potentially useful sources...
Changes in the phenology of flowering in soybeans caused by long-term growth at elevated CO 2 may be important to the responses of seed yield to elevated CO 2. Here we utilized near-isogenic lines of soybeans differing in three genes influencing photoperiod sensitivity to determine whether these genes affected the response of flowering time to elev...
In this chapter, we argue that responses of plant growth and yield to CO2 enrichment and to elevated growth temperatures are principally mediated by changes in photosynthesis. Crop plants such as soybean, which possess the C3 cycle, exhibit increased photosynthetic rates in response to CO2 enrichment. Conversely, maize, which uses the C4 cycle, is...
Responses to drought were studied using two maize inbred lines (B76 and B106) and a commercial maize hybrid (Zea mays L. cv. Silver Queen) with differing resistance to abiotic stress. Maize seedlings were grown in pots in controlled environment chambers for 17 days and watering was withheld from one half the plants for an additional 11 days. On the...
Seed yield increases in soybean [Glycine max (L.) Merr.] caused by increased growth at elevated carbon dioxide concentrations primarily result from increased numbers of pods. Reasons for differences among cultivars in the increases in pod number are not clear. In experiments in controlled environment chambers, cultivars varied in how much elevated...
Many experiments to determine the crop yield increase expected with rising atmospheric carbon dioxide concentration added carbon dioxide only during the daytime, without tests of whether elevation of carbon dioxide at night affected plant growth. In this experiment, two cultivars of common bean (Phaseolus vulgaris L.) were grown in the field for 4...
We hypothesized that decreased stomatal conductance (g s) at elevated CO2 might decrease transpiration (E), increase leaf water potential (ΨW), and thereby protect net photosynthesis rate (P N) from heat damage in maize (Zea mays L) seedlings. To separate long-term effects of elevated CO2, plants grew at either ambient CO2 or elevated CO2. During h...
Three different injection molded bioplastic (BP) pots, BP 29, BP 32, and BP 45 pots, containing processed feather fibers, were evaluated. Growth and flowering of Lilium hybrid ‘Triumphator’ and Begonia ‘Bonfire’ were evaluated in new and reused BP pots. Net photosynthesis was measured and macro- and micro-elements were analyzed in ‘Triumphator’ lil...
Maize (Zea mays L.) hybrids varying in drought tolerance were treated with water stress in controlled environments. Experiments were performed during vegetative growth and water was withheld for 19 days beginning 17 days after sowing. Genotypic comparisons used measured changes of leaf water potential or results were expressed by time of treatment....
Systems for exposing plants to elevated concentrations of CO(2) may expose plants to pulses of CO(2) concentrations considerably above the control set-point. The importance of such pulses to plant function is unknown. I exposed single leaves of wheat (Triticum aestivum cv Choptank) and rice (Oryza sativa cv Akitakomachi) for 30 minutes to pulses of...
High leaf transpiration efficiency (TE) occurs in some cultivars of corn (Zea mays L.) and could be a useful trait to improve yield under water deficits. The CO2 concentration in the atmosphere continues to increase rapidly, and it is not certain that cultivar differences in leaf TE occurring at the current CO2 concentration would still occur at el...
Background / Purpose:
Because high temperatures under field conditions are often associated with high water vapor pressure deficits, we hypothesized that decreased stomatal conductance at elevated CO 2 levels may protect photosynthesis in C4 species from damage caused by high temperature stress. This hypothesis was tested using Zea mays L. grown...
The carbon dioxide concentration in free air carbon dioxide enrichment (FACE) systems typically has rapid fluctuations. In our FACE system, power spectral analysis of CO2 concentration measured every second with an open path analyzer indicated peaks in variation with a period of about one minute. I used open-top chambers to expose cotton and wheat...
Agricultural production is under increasing pressure by global anthropogenic changes, including rising population, diversion of cereals to biofuels, increased protein demands and climatic extremes. Because of the immediate and dynamic nature of these changes, adaptation measures are urgently needed to ensure both the stability and continued increas...
Soil water deficits remain one of the most important factors reducing the yield of crop plants and may become even more limiting with changes in the global climate and competition for fresh water resources. Soil water deficits reduce plant growth partly by reducing photosynthesis. However, it remains unclear how important non-stomatal factors are i...
Leaves developed at high irradiance (I) often have higher photosynthetic capacity than those developed at low I, while leaves developed at elevated CO2 concentration [CO2] often have reduced photosynthetic capacity compared with leaves developed at lower [CO2]. Because both high I and elevated [CO2] stimulate photosynthesis of developing leaves, th...
Excessive use of nitrogen (N) in crop production has impacted ecosystems by contaminating soil and water. Management of N in agriculture is therefore of global concern. Sustainable agriculture systems that use leguminous cover crops such as hairy vetch (Vicia villosa Roth) to fix N and enrich soil organic matter by fixing carbon provide an alternat...
While numerous studies have shown that elevated CO2 can delay soil water depletion by causing partial stomatal closure, few studies have compared responses of plant growth to the same soil water deficits imposed at ambient and elevated CO2. We applied a vacuum to ceramic cups in pots filled with soil to reduce the soil water matric potential to −0....
I tested whether elevated [CO 2 ] affected which genotypes of Taraxacum officinale had highest fitness in two field exp-eriments. In one experiment, T. officinale plants which persisted as weeds in alfalfa plots in open top chambers at ambi-ent and elevated [CO 2 ] were compared. In a second experiment, T. officinale seeds collected from local habi...
Crotalarias are tropical legumes grown as cover crops or as green manure to improve soil fertility. As an understory plant in plantation systems, these cover crops receive low levels of irradiance and are subjected to elevated levels of CO 2 and temperatures. A greenhouse experiment was conducted to evaluate the independent short-term effects of ph...
Soil water deficits remain one of the most important factors reducing the yield of crop plants, and may become even more limiting with changes in the global climate and competition for fresh water resources. Soil water deficits reduce plant growth partly by reducing photosynthesis. However, it remains unclear how important non-stomatal factors are...
Free air carbon dioxide enrichment (FACE) systems rely primarily on wind to distribute CO2 across treatment plots. Most current FACE designs inject CO2 at the perimeter of the plot, and low wind speeds can result in large horizontal gradients of CO2 concentration. These gradients can be reduced by using blowers to inject CO2 or a mixture of CO2 and...
When measured under midday field conditions, modern varieties of maize (Zea mays L.) often have substomatal carbon dioxide concentration (Ci) values in excess of those required to saturate the photosynthetic carbon dioxide assimilation rate (A). This results in lower leaf transpiration efficiency (TE), the ratio of photosynthesis to transpiration,...
It has been reported that for osmotically stressed leaf slices of a wide range of species, carbon dioxide saturated photosynthesis is uniformly inhibited by stress when water status is expressed as relative volume. Comparable data for intact leaves of a range of species are lacking. It is also unknown whether the same pattern of response applies to...
Net photosynthetic rates and leaf conductances to water vapor were measured in Abutilon theophrasti, Amaranthus hypochondriacus, and Glycine max after injecting abscisic acid into petioles of attached leaves. Changes in substomatal carbon dioxide partial pressure were measured in air in each species for various degrees of inhibition of the photosyn...
Comparisons of photosynthesis and stomatal and mesophyll conductance of CO2 at high leaf water potentials were made in four populations of Taraxacum officinale and in drought tolerant and intolerant individuals within cultivars of four crop species. Plants with the highest rates of photosynthesis at high leaf water potentials were least tolerant of...
Net photosynthetic rates, stomatal and mesophyll conductances to CO2 uptake, water soluble and total nonstructural carbohydrates contents, specific leaf weights of fully expanded source leaves, and elongation rates of rapidly expanding leaves were measured on 2 days during a period of water stress in soybean and sunflower plants in a controlled env...
Respiration in the light, dark respiration, and leaf water status were monitored once a day in leaves of woody plants as seedlings dried during 7- to 10-day periods. Light respiration was estimated from an electrical analogue model of the response of net photosynthesis to ambient CO2 concentration and also by the rate of CO2 evolution into CO2-free...
Soybeans and cotton were subjected to humidities from 40 to 80% at 23 °C and to soil drought during early vegetative growth under controlled conditions. Measurements were made of leaf water potentials, leaf expansion rates, leaf diffusive resistances to water vapor, and whole-shoot net photosynthesis rates. Net assimilation rates were calculated fr...
Some reports indicate that mesophyll conductance (g
m) to carbon dioxide varies greatly with the substomatal carbon dioxide concentration (C
i) during the measurement, while other reports indicate little or no change in g
m with C
i. I used the oxygen sensitivity of photosynthesis to determine the response of g
m to C
i over the range of about 100...
Field measurements of leaf gas exchange in maize (Zea mays L.) often indicate stomatal conductances higher than required to provide substomatal carbon dioxide concentrations saturating to photosynthesis. Thus maize leaves often operate at lower transpiration efficiency (TE) than potentially achievable for species with C, metabolism. I tested whethe...
Responses to CO2 enrichment were determined for a dwarf (MiniMax) and a normal-sized (Fiskeby) soybean [Glycine max (L.) Merr.]. Plants were grown in growth chambers with ambient (36 Pa) or elevated (98 Pa) CO2 using a 2 × 2 × 2 factorial design. Harvests for MiniMax and Fiskeby were increased 6 and 26 d, respectively, by CO2 enrichment. At final m...
In plantation crops, perennial tropical legumes are grown as understory plants, where they receive limited irradiance and can be subjected to elevated levels of CO 2 . Independent short-term effects of photosynthetic photon flux density (PPFD), external carbon dioxide concentration [CO 2 ] and temperature on net photosynthesis (Pn), internal CO 2 (...
Methods of estimating the mesophyll conductance (g(m)) to the movement of CO(2) from the substomatal airspace to the site of fixation are expensive or rely upon numerous assumptions. It is proposed that, for C(3) species, measurement of the response of photosynthesis to [O(2)] at limiting [CO(2)], combined with a standard biochemical model of photo...
To examine the impact of projected climate changes on secondary succession, we exposed the same fallow soil with a common seed bank to an in situ gradient of urban to rural macroenvironments that differed in temperature and CO2 concentration ([CO2]). This gradient was established at three locations: Baltimore city center (urban), a city park on the...
The rising concentration of carbon dioxide [CO₂] in the atmosphere represents an increase in a growth-limiting resource for C₃ crop species. Identification of lines or characteristics of lines which have superior yield at elevated [CO₂] could aid in adaptation to this global change. While intraspecific variation in responses to elevated [CO₂] has b...
Plants differ in how much the response of net photosynthetic rate (P
N) to temperature (T) changes with the T during leaf development, and also in the biochemical basis of such changes in response. The amount of photosynthetic acclimation to T and the components of the photosynthetic system involved were compared in Arabidopsis thaliana and Brassic...
Background and aims:
Nitrogen (N) is a major factor affecting yield gain of crops under elevated atmospheric carbon dioxide concentrations [CO(2)]. It is well established that elevated [CO(2)] increases root mass, but there are inconsistent reports on the effects on N uptake capacity per root mass. In the present study, it was hypothesized that th...
Plant growth, photosynthesis and leaf constituents were examined in the wild-type (WT) and mutant nar1 of barley (Hordeum vulgare L. cv. Steptoe) that contains a defective structural gene encoding NADH-dependent nitrate reductase (NADH-NAR). In controlled environment experiments, total biomass, rates of photosynthesis, stomatal conductance, interce...
Independent short-term effects of photosynthetic photon flux density (PPFD) of 50–400 µmol m−2 s−1, external CO2 concentration (C
a) of 85–850 cm3 m−3, and vapor pressure deficit (VPD) of 0.9–2.2 kPa on net photosynthetic rate (P
N), stomatal conductance (g
s), leaf internal CO2 concentration (C
i), and transpiration rates (E) were investigated in...
The ratios of root length and root weight to leaf area differed within and between cultivars of soybean. Plants with low ratios of root length or weight to leaf area had leaf conductances and net photosynthetic rates more reduced by a given increase in the leaf to air water vapour pressure difference around a single leaf than plants with high ratio...
The heat island effect and the high use of fossil fuels in large city centers are well documented, but by how much fossil fuel consumption is elevating atmospheric CO2 concentrations and whether elevations in both atmospheric CO2 and air temperature from rural to urban areas are consistently different from year to year are less well known. Our aim...
Leaf water potentials below threshold values result in reduced stomatal conductance (gs). Stomatal closure at low leaf water potentials may serve to protect against cavitation of xylem. Possible control of gs by leaf water potential or hydraulic conductance was tested by drying the rooting medium in four herbaceous annual species until gs was reduc...
Accounting for the acclimation of respiration of plants to temperature remains a major problem in analysis of carbon balances of plants and ecosystems. Translocation of carbohydrates out of leaves in the dark requires energy from respiration. In this study relationships between the responses of leaf respiration and translocation to temperature are...
Summary 607
Acknowledgements 615
References 615
Recent breakthroughs in CO2 fumigation methods using free-air CO2 enrichment (FACE) technology have prompted comparisons between FACE experiments and ‘enclosure studies’ with respect to quantification of the effects of projected atmospheric CO2 concentrations on crop yields. On the basis of one such c...
Alfalfa was grown at ambient and elevated (ambient + 350 ppm) carbon dioxide concentrations at Beltsville, Maryland, using open top chambers in field plots. Periodic harvests and measurements of leaf photosynthesis were used to test the hypothesis that the stimulation of yield and photosynthesis by elevated carbon dioxide would increase with temper...
Most methods of measuring the diffusive conductance to water vapor of individual plant leaves potentially change the leaf environment by enclosing part of the leaf in order to measure the rate of water vapor exchange and the driving force for that exchange. There have been questions about whether leaf to air water vapor pressure difference varies s...
A reduction in leaf stomatal conductance (g) with increasing leaf-to-air difference in water vapour pressure (D) is nearly ubiquitous. Ecological comparisons of sensitivity have led to the hypothesis that the reduction in g with increasing D serves to maintain leaf water potentials above those that would cause loss of hydraulic conductance. A reduc...
Although the respiratory response of native and agricultural plants to atmospheric CO2 enrichment has been reported over the past 75 years, only recently have these effects emerged as prominent measures of plant and ecosystem response to the earth's changing climate. In this review we discuss this rapidly expanding field of study and propose that b...
Seedlings of temperate deciduous tree species were grown outdoors at ambient and at an elevated concentration of carbon dioxide to examine how aspects of their gas exchange would be altered by growth at elevated carbon dioxide concentration. Leaf conductances to water vapour and net carbon dioxide exchange rates were determined periodically near mi...
Leaf conductance responses to leaf to air water vapour partial pressure difference (VPD) have been measured at air speeds of 0.5 and 3.0 ms−1 in single attached leaves of three species in order to test the hypothesis that leaf conductance response to VPD is controlled by evaporation from the outer surface of the epidermis, rather than by evaporatio...
Leaf area expansion, photosynthetic carbon dioxide uptake and leaf dry mass accumulation were compared for expanding leaves of well-watered soybean (Glycine max [L.] Merr.) plants, mildly dehydrated plants and well-watered plants treated with abscisic acid (ABA). Both ABA treatment and dehydration reduced area expansion in the light and over a 24 h...
Soybean (Glycine max cv. Clark) was grown at both ambient (ca 350 μmol mol−1) and elevated (ca 700 μmol mol−1) CO2 concentration at 5 growth temperatures (constant day/night temperatures of 20, 25, 30, 35 and 40°C) for 17–22 days after sowing to determine the interaction between temperature and CO2 concentration on photosynthesis (measured as A, th...
Two herbaceous perennials, alfalfa (Medicago sativa L. cv. Arc) and orchard grass (Dactylus glomerata L. cv. Potomac), were grown at ambient (367 μmol mol−1) and elevated (729 μmol mol−1) CO2 concentrations at constant temperatures of 15, 20, 25 and 30°C in order to examine direct and indirect changes in nighttime CO2 efflux rate (respiration) of s...
Soybean plants were grown continuously at 350 and 700cm3m−3 CO2 at constant temperature. Respiration rates of third trifoliolate leaves were measured at the growth CO2 concentration for the whole dark period from 5d before through to 5d after full area expansion. The short-term response of respiration rate to the measurement CO2 concentration was a...
The carbon dioxide concentrating system in C4 photosynthesis allows high net photosynthetic rates (PN) at low internal carbon dioxide concentrations (Ci), permitting higher PN relative to stomatal conductance (gs) than in C3 plants. This relation would be reflected in the ratio of Ci to external ambient (Ca) carbon dioxide concentration, which is o...
![Fig. 2. The seed yield of the daytime elevation of [CO 2 ] (EC d )](profile/James-Bunce/publication/225663618/figure/fig2/AS:302616039968783@1449160694632/The-seed-yield-of-the-daytime-elevation-of-CO-2-EC-d_Q320.jpg)
Some studies of responses of plants to elevated concentrations of carbon dioxide (EC) added CO2 only in the daytime, while others supplied CO2 continuously. I tested whether these two methods of EC treatments produced differences in the seed yield of soybeans. Tests
were conducted for four growing seasons, using open top chambers, with soybeans roo...
The effect of elevated carbon dioxide on fruit quality and aroma volatile composition in field-grown strawberries (Fragavia x ananassa Duch) was studied. Elevating the ambient CO2 concentration (ambient + 300, and ambient + 600 mumol mol(-1) CO2) resulted in high fruit dry matter, fructose, glucose and total sugar contents and low citric and malic...
To examine the impact of climate change on vegetative productivity, we exposed fallow agricultural soil to an in situ temperature and CO2 gradient between urban, suburban and rural areas in 2002. Along the gradient, average daytime CO2 concentration increased by 21% and maximum (daytime) and minimum (nighttime) daily temperatures increased by 1.6 a...
Reductions in leaf stomatal conductance with rising atmospheric carbon dioxide concentration ([CO2]) could reduce water use by vegetation and potentially alter climate. Crop plants have among the largest reductions in stomatal conductance at elevated [CO2]. The relative reduction in stomatal conductance caused by a given increase in [CO2] is often...
The fundamental cause of down-regulation of photosynthesis at elevated carbon dioxide concentration (EC) is thought to be a slower rate of utilization of saccharides than their stimulated rate of production, but there are few studies directly supporting this idea under field conditions. We hypothesized that within Brassica oleracea, down-regulation...
The effects of elevated CO2 concentrations on the antioxidant capacity and flavonoid content in strawberry fruit (Fragaria x ananassa Duch.) were studied under field conditions. Increased CO(2) (300 and 600 micromol mol(-1) above ambient) concentrations resulted in increases in ascorbic acid (AsA), glutathione (GSH), and ratios of AsA to dehydroasc...
In some studies of ecosystem responses to elevated carbon dioxide, supplemental carbon dioxide is supplied only during the daytime, while in others it is supplied continuously. The purpose of my work was to determine for several species whether seedling growth differed depending on whether carbon dioxide was elevated only during the daytime or cont...
High leaf to air water vapor pressure differences often substantially reduce rates of assimilation of carbon dioxide, especially in C3 species. Rising concentrations of carbon dioxide [CO2] in the atmosphere could reduce the sensitivity of assimilation rate to partial stomatal closure caused by high vapor pressure difference by a variety of mechani...
Studies have indicated that the concentration of carbon dioxide [CO2] during the dark period may influence plant dry matter accumulation. It is often suggested that these effects on growth result from effects of [CO2] on rates of respiration, but responses of respiration to [CO2] remain controversial, and connections between changes in respiration...
The magnitude of the response of stomatal conductance to a change in the concentration of carbon dioxide external to the leaf from 350 to 700 cm3 m–3 was found to be extremely variable from day to day in the field in Glycine max, Hordeum vulgare and Triticum aestivum. It was found that the leaf-to-air water vapour pressure difference (LAVPD) during...
ATP, adenosine triphosphate
Km, Michaelis-Menton coefficient
Ca, concentration of CO2 in the air (μmol mol–1)
NAD, oxidized nicotin adenine dinucleotide
NADH, reduced nicotin adenine dinucleotide
NADP, oxidized nicotin adenine phosphate dinucleotide
NADPH, reduced nicotine adenine phosphate dinucleotide
R, rate of respiration per unit DW [μmol g
DW...
Use of infrared analyzers to measure water vapor concentrations in photosynthesis systems is becoming common. It is known that sensitivity of infrared carbon dioxide and water vapor analyzers is affected by the oxygen concentration in the background gas, particularly for absolute analyzers, but the potential for large errors in estimates of stomata...
The concentration of carbon dioxide [CO2] in the atmosphere has risen from about 280 μmol mol-1 in 1870 to about 370 μmol mol-1 currently, and this concentration continues to increase rapidly. In planning for future, higher atmospheric [CO2], the question arises whether genetic modifications of crop plants are required in order to fully exploit the...
For most studies involving the response of plants to future concentrations of atmospheric carbon dioxide (CO2), a current concentration of 360–370 μatm is assumed, based on recent data obtained from the Mauna Loa observatory. In the present study, average seasonal diurnal values of ambient CO2 obtained at ground level from three global locations (A...
Single leaf photosynthetic rates and various leaf components of potato (Solanum tuberosum L.) were studied 1-3 days after reciprocally transferring plants between the ambient and elevated growth CO2 treatments. Plants were raised from individual tuber sections in controlled environment chambers at either ambient (36 Pa) or elevated (72 Pa) CO2. One...
Predicting responses of plant and global carbon balance to the increasing concentration of carbon dioxide in the atmosphere requires an understanding of the response of plant respiration to carbon dioxide concentration ([CO2]). Direct effects of the carbon dioxide concentration at which rates of respiration of plant tissue are measured are quite va...
Midday measurements of single leaf gas exchange rates of upper canopy leaves of soybeans grown in the field at 350 (AC) and 700 (EC) mol(CO2) mol–1 in open topped chambers sometimes indicated up to 50 % higher net photosynthetic rates (P
N) measured at EC in plants grown at AC compared to EC. On other days mean P
N were nearly identical in the two...
In order to separate the net effect of growth at elevated [CO2] on stomatal conductance (gs) into direct and acclimatory responses, mid-day values of gs were measured for plants grown in field plots in open-topped chambers at the current ambient [CO2], which averaged 350 μmol mol−1 in the daytime, and at ambient + 350 μmol mol−1[CO2] for winter whe...
