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1.
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, the rate of CO2 assimilation per unit leaf area) at both the single leaf and whole plant level. Single leaves of soybean demonstrated increasingly greater stimulation of A at elevated CO2 as temperature increased from 25 to 35°C (i.e. optimal growth rates). At 40°C, primary leaves failed to develop and plants eventually died. In contrast, for both whole plant A and total biomass production, increasing temperature resulted in less stimulation by elevated CO2 concentration. For whole plants, increased CO2 stimulated leaf area more as growth temperature increased. Differences between the response of A to elevated CO2 for single leaves and whole plants may be related to increased self-shading experienced by whole plants at elevated CO2 as temperature increased. Results from the present study suggest that self-shading could limit the response of CO2 assimilation rate and the growth response of soybean plants if temperature and CO2 increase concurrently, and illustrate that light may be an important consideration in predicting the relative stimulation of photosynthesis by elevated CO2 at the whole plant level.  相似文献   

2.
In the CAM plants, Kalanchoë tubiflora (Harvey) Hasset, Sedum morganianum E. Walth and Sedum rubrotinctum R. T. Clausen, the effects of CO2 concentrations on the light-dependent 14C transfer from the nocturnally synthetized [14C]-malic acid to starch have been studied. CO2 concentrations up to 5 × 103 μ1 1–1 did not inhibit this carbon transfer. Higher CO2 concentrations, however, were increasingly inhibitory. At 104 μl 1–1 CO2, the carbon transfer was practically prevented.
The malic acid consumption in the light showed the same response to CO2 concentrations as the [l4C]-transfer. Photosynthesis itself was not inhibited by the CO2 concentrations applied. It is assumed that, during phase III of CAM, light controls the internal CO2 concentration via photosynthesis; and that the internal CO2 concentration then controls the rate of malate decarboxylation.  相似文献   

3.
Mature trees have already experienced substantial increases in CO2 concentrations during their lifetimes, and will experience continuing increases in the future. Small open-top chambers were used to enclose branchlets that were at a height of between 20 and 25 m in the canopy of the tree species Luehea seemannii Tr. & Planch. in a tropical forest in Panamá. Elevated concentrations of CO2 increased the rate of photosynthetic carbon fixation and decreased stomatal conductance of leaves, but did not influence the growth of leaf area per chamber, the production of flower buds and fruit nor the concentration of nonstructural carbohydrates within leaves. The production of flower buds was highly correlated with the leaf area produced in the second flush of leaves, indicating that the branchlets of mature trees of Luehea seemannii are autonomous to a considerable extent. Elevated levels of CO2 did increase the concentration of nonstructural carbohydrates in woody stem tissue. Elevated CO2 concentration also they increased the ratio of leaf area to total biomass of branchlets, and tended to reduce individual fruit weight. These data suggest that the biomass allocation patterns of mature trees may change under future elevated levels of CO2. Although there were no effects on growth during the experiment, the possibility of increased growth in the season following CO2 enrichment due to increased carbohydrate concentrations in woody tissue cannot be excluded.  相似文献   

4.
Variation in stomatal development and physiology of mature leaves from Alnus glutinosa plants grown under reference (current ambient, 360 μmol mol−1 CO2) and double ambient (720 μmol mol−1 CO2) carbon dioxide (CO2) mole fractions is assessed in terms of relative plant growth, stomatal characters (i.e. stomatal index and density) and leaf photosynthetic characters. This is the first study to consider the effects of elevated CO2 concentration on the distribution of stomata and epidermal cells across the whole leaf and to try to ascertain the cause of intraleaf variation. In general, a doubling of the atmospheric CO2 concentration enhanced plant growth and significantly increased stomatal index. However, there was no significant change in relative stomatal density. Under elevated CO2 concentration there was a significant decrease in stomatal conductance and an increase in assimilation rate. However, no significant differences were found for the maximum rate of carboxylation ( V cmax) and the light saturated rate of electron transport ( J max) between the control and elevated CO2 treatment.  相似文献   

5.
Stomatal responses to light and CO2 are dependent on KCI concentration   总被引:1,自引:0,他引:1  
Abstract. The responses of stomata on detached epidermis of Commelina communis to light and CO2 have been shown to be strongly dependent on the concentration of KCI in the incubation medium. There was a high sensitivity to the two stimuli in 50 mM KCI, but there were much reduced responses at lower and higher concentrations. It is considered that an appropriate choice of medium is essential if useful physiological studies of stomata are to be made using epidermal strips. At lower KCI concentrations, the ability of the stomata to open is thought to be limited by the availability of K+ ions, and at higher concentrations their ability to close may be affected because of an inhibition of the net efflux of K+. The production of malate was related to KCI concentration, and was largest in the medium containing zero KCI which supported poor stomatal responses to light and CO2It is concluded that malate metabolism is unlikely to play a central part in the changes in guard cell turgor that are brought about by light and CO2.  相似文献   

6.
We tested the hypothesis that acclimation of foliar dark respiration to CO2 concentration and temperature is associated with adjustments in leaf structure and chemistry. Populus tremuloides Michx. , Betula papyrifera Marsh. , Larix laricina (Du Roi) K. Koch , Pinus banksiana Lamb., and Picea mariana (Mill.) B.S.P. were grown from seed in combined CO2 (370 or 580 μ mol mol–1) and temperature treatments (18/12, 24/18, or 30/24 °C). Temperature and CO2 effects were predominately independent. Specific respiration rates partially acclimated to warmer thermal environments through downward adjustment in the intercept, but not Q 10 of the temperature–response functions. Temperature acclimation of respiration was larger for conifers than broad-leaved species and was associated with pronounced reductions in leaf nitrogen concentrations in conifers at higher growth temperatures. Short-term increases in CO2 concentration did not inhibit respiration. Growth in the elevated CO2 concentration reduced leaf nitrogen and increased non-structural carbohydrate concentrations. However, for a given nitrogen concentration, respiration was higher in leaves grown in the elevated CO2 concentration, as rates increased with increasing carbohydrates. Across species and treatments, respiration rates were a function of both leaf nitrogen and carbohydrate concentrations ( R 2 = 0·71, P < 0·0001). Long-term acclimation of foliar dark respiration to temperature and CO2 concentration is largely associated with changes in nitrogen and carbohydrate concentrations.  相似文献   

7.
CO2 enrichment of soybeans. Effects of leaf/pod ratio   总被引:2,自引:0,他引:2  
The effect of varying leaf number on response of soybean ( Glycine max (L.) Merr. cv. Fiskeby V) to CO2 enrichment was studied. Plants were trimmed at pod set to 15 pods and 1 or 3 leaves (15:1 and 5:1 pod/leaf ratio) and placed in 350 or 1000 μl/l CO2 growth chambers. Photosynthetic rates and dry weights were measured 6 times in all plants at each CO2 concentration over a period of 39 days. Measured at treatment CO2 concentration, photosynthetic rates deelined rapidly in enriched plants, but remained higher than those of non-enriched plants. When all plants were measured at the same CO2 concentration, for most sampling dates, neither growth, CO2 concentration or pod/leaf ratio significantly affected rates of photosynthesis per unit area of comparable leaves. CO2 enrichment significantly increased total weights and pod weights in 15:1 but not 5:1 pod/leaf ratio plants. Plants with a 5:1 pod/leaf ratio had significantly higher total and pod weights than 15:1 ratio plants. Both the photosynthesis and dry weight data suggest that plants in the 5:1 ratio enriched treatment were sink-limited, but plants in all other treatments were source limited.  相似文献   

8.
Evidence from previous studies suggested that adjustments in assimilate formation and partitioning in leaves might occur over time when plants are exposed to enriched atmospheric CO2. We examined assimilate relations of source (primary unifoliolate) and developing sink (second mainstem trifoliolate) leaves of soybean [ Glycine max (L.) Merr. cv. Lee] plants for 12 days after transfer from a control (350 μl l−1) to a high (700 μ l−1) CO2 environment. Similar responses were evident in the two leaf types. Net CO2 exchange rate (CER) immediately increased and remained elevated in high CO2. Initially, the additional assimilate at high CO2 levels in the light and was utilized in the subsequent dark period. After approximately 7 days, assimilate export in the light began to increase and by 12 days reached rates 3 to 5 times that of the control. In the developing sink leaf, high rates of export in the light occurred as the leaf approached full expansion. The results indicate that a specific acclimation process occurs in source leaves which increases the capacity for assimilate export in the light phase of the diurnal cycle as plants adjust to enriched CO2 and a more rapid growth rate.  相似文献   

9.
The effect of drought on CO2 assimilation and leaf conductance was studied in three northern hardwood species: Quercus rubra L., Acer rubrum L. and Populus grandidentata Michx. Leaf gas exchange characteristics at two CO2 levels (320 and 620 μl I−1) and temperatures from 20 to 35°C were measured at the end of a dry period and shortly after 10 cm of rainfall. The effects of drought varied with species, temperature and CO2 level. Calculated values of internal CO2 concentration showed little or no decline during drought. Differences in assimilation, before vs after the rains, were most apparent at the higher CO2 level. These latter two observations indicate nonstomatal disruption of CO2 assimilation during the dry period. In P. grandidentata there was a substantial interaction between drought and temperature, with a resultant shift in the temperature for maximum assimilation to lower temperatures during drought. During drought, internal CO2 concentrations increased sharply in all three species under the combined conditions of high temperatures and the higher CO2 level.  相似文献   

10.
Evidence from 10 studies comparing angiosperm trees and 5 studies comparing conifers of differing shade‐tolerance was analysed. The number of intraphyletic comparisons in which the more shade‐tolerant species showed the greater relative increase of biomass in elevated CO2 was significantly higher than would be expected by chance alone. It is suggested that more shade‐tolerant species are inherently better disposed, in terms of plant architecture and partitioning of biomass and nitrogen, to utilise resources (light, water, nutrients) that are potentially limiting in elevated CO2 and that these traits are responsible for the interaction between shade‐tolerance and CO2 concentration. Compared with less shade‐tolerant angiosperm trees, more shade‐tolerant angiosperm species generally have a lower leaf area ratio in ambient CO2 and show a smaller relative reduction in elevated CO2. Furthermore, leaf nitrogen content is usually lower in more shade‐tolerant angiosperm species and tends to be more strongly reduced by elevated CO2 in those species. Within angiosperm trees, more shade‐tolerant species showed a stronger stimulation of net leaf photosynthetic rate in most experiments, but this trend was not significant.  相似文献   

11.
Nitrogen nutrition of C3 plants at elevated atmospheric CO2 concentrations   总被引:5,自引:0,他引:5  
The atmospheric CO2 concentration has risen from the preindustrial level of approximately 290 μl l−1 to more than 350 μl l−1 in 1993. The current rate of rise is such that concentrations of 420 μl l−1 are expected in the next 20 years. For C3 plants, higher CO2 levels favour the photosynthetic carbon reduction cycle over the photorespiratory cycle, resulting in higher rates of carbohydrate production and plant productivity. The change in balance between the two photosynthetic cycles appears to alter nitrogen and carbon metabolism in the leaf, possibly causing decreases in nitrogen concentrations in the leaf. This may result from increases in the concentration of storage carbohydrates of high molecular weight (soluble or insoluble) and/or changes in distribution of protein or other nitrogen containing compounds. Uptake of nitrogen may also be reduced at high CO2 due to lower transpiration rates. Decreases in foliar nitrogen levels have important implications for production of crops such as wheat, because fertilizer management is often based on leaf chemical analysis, using standards estimated when the CO2 levels were considerably lower. These standards will need to be re-evaluated as the CO2 concentration continues to rise. Lower levels of leaf nitrogen will also have implications for the quality of wheat grain produced, because it is likely that less nitrogen would be retranslocated during grain filling.  相似文献   

12.
The variations in δ 13C in both leaf carbohydrates (starch and sucrose) and CO2 respired in the dark from the cotyledonary leaves of Phaseolus vulgaris L. were investigated during a progressive drought. As expected, sucrose and starch became heavier (enriched in 13C) with decreasing stomatal conductance and decreasing p i/ p a during the first half (15 d) of the dehydration cycle. Thereafter, when stomata remained closed and leaf net photosynthesis was near zero, the tendency was reversed: the carbohydrates became lighter (depleted in 13C). This may be explained by increased p i/ p a but other possible explanations are also discussed. Interestingly, the variations in δ 13C of CO2 respired in the dark were correlated with those of sucrose for both well-watered and dehydrated plants. A linear relationship was obtained between δ 13C of CO2 respired in the dark and sucrose, respired CO2 always being enriched in 13C compared with sucrose by ≈ 6‰. The whole leaf organic matter was depleted in 13C compared with leaf carbohydrates by at least 1‰. These results suggest that: (i) a discrimination by ≈ 6‰ occurs during dark respiration processes releasing 13C-enriched CO2; and that (ii) this leads to 13C depletion in the remaining leaf material.  相似文献   

13.
Dry weight (DW) and nitrogen (N) accumulation and allocation were measured in isolated plants of Danthonia richardsonii (Wallaby Grass) for 37 d following seed imbibition. Plants were grown at ≈ 365 or 735 μ L L–1 CO2 with N supply of 0·05, 0·2 or 0·5 mg N plant–1 d–1. Elevated CO2 increased DW accumulation by 28% (low-N) to 103% (high-N), following an initial stimulation of relative growth rate. Net assimilation rate and leaf nitrogen productivity were increased by elevated CO2, while N concentration was reduced. N uptake per unit root surface area was unaffected by CO2 enrichment. The ratio of leaf area to root surface area was decreased by CO2 enrichment. Allometric analysis revealed a decrease in the shoot-N to root-N ratio at elevated CO2, while the shoot-DW to root-DW ratio was unchanged. Allometric analysis showed leaf area was reduced, while root surface area was unchanged by elevated CO2, indicating a down-regulation of total plant capacity for carbon gain rather than a stimulation of mineral nutrient acquisition capacity. Overall, growth in elevated CO2 resulted in changes in plant morphology and nitrogen use, other than those associated simply with changing plant size and non-structural carbohydrate content.  相似文献   

14.
The responses of individual stomata to CO2 concentrations ranging from 0 to 900 μmol mol−1 air were analysed in Ipomoea pes-caprae L. Sweet (Convolvulaceae). The stomata were directly observed using a measurement system that permitted continuous observation of stomatal movement under controlled light and CO2 conditions. A CO2 concentration of 350 μmol mol−1 or higher induced stomatal closure, whereas concentrations below 350 μmol mol−1 did not. The time lag before stomatal closure decreased with increasing CO2 concentration, as did the steady-state aperture of the stomata after a change in CO2 concentration. However, the rate of stomatal closure increased with increasing CO2 concentration. Therefore, not only the stomatal closure rate but also the time from the CO2 concentration change to the beginning of stomatal closure changed with increasing CO2 concentration. These results suggest that atmospheric CO2 may be the stimulus for the closure of guard cells. No significant differences were observed between adaxial and abaxial stomata in terms of their responses to CO2. However, heterogeneous responses were detected between neighbouring stomata on each leaf surface.  相似文献   

15.
There is considerable interest in modeling isoprene emissions from terrestrial vegetation, because these emissions exert a principal control over the oxidative capacity of the troposphere. We used a unique field experiment that employs a continuous gradient in CO2 concentration from 240 to 520 ppmv to demonstrate that isoprene emissions in Eucalyptus globulus were enhanced at the lowest CO2 concentration, which was similar to the estimated CO2 concentrations during the last Glacial Maximum, compared with 380 ppmv, the current CO2 concentration. Leaves of Liquidambar styraciflua did not show an increase in isoprene emission at the lowest CO2 concentration. However, isoprene emission rates from both species were lower for trees grown at 520 ppmv CO2 compared with trees grown at 380 ppmv CO2. When grown in environmentally controlled chambers, trees of Populus deltoides and Populus tremuloides exhibited a 30–40% reduction in isoprene emission rate when grown at 800 ppmv CO2, compared with 400 ppmv CO2. P. tremuloides exhibited a 33% reduction when grown at 1200 ppmv CO2, compared with 600 ppmv CO2. We used current models of leaf isoprene emission to demonstrate that significant errors occur if the CO2 inhibition of isoprene is not taken into account. In order to alleviate these errors, we present a new model of isoprene emission that describes its response to changes in atmospheric CO2 concentration. The model logic is based on assumed competition between cytosolic and chloroplastic processes for pyruvate, one of the principal substrates of isoprene biosynthesis.  相似文献   

16.
Abstract. A portable apparatus has been constructed to measure simultaneously the quantum yield of CO2 assimilation, light absorption, chlorophyll fluorescence emission and water vapour exchange of attached intact leaves in the field. The core of the instrument is a light-integrating spherical leaf chamber which includes ports for a light source, photosynthetically active radiation sensor, fluorescence probes and gas inlet and outlet manifolds. Measurement of the quantum flux inside the empty chamber and with a leaf present allows determination of leaf absorptance. An open gas exchange system is employed using an infra-red analyser to measure leaf CO2 exchange. Using a DC white light source the quantum yield of CO2 assimilation based on absorbed light (φabs) may be determined rapidly in either ambient air or artificial gas mixtures. Inclusion of capacitance humidity probes into the gas inlet and outlet ports allows simultaneous determination of water vapour exchange and subsequent estimation of stomatal conductance to CO2 and intercellular CO2 concentration. Measurement of fluorescence emission by the sample leaf exposed to white light is achieved by a modulated fluorescence detection system. In addition to determination of the minimal, maximal and variable fluorescence levels, a further analysis allows the photochemical and non-photochemical components of fluorescence quenching, to be estimated. The theory and design of this apparatus is described in detail. The use of the apparatus in the field is demonstrated through a study of the photosynthetic performance of a maize and bean crop during the growing season and by analysis of the photosynthetic performance of crops subjected to nitrogen-stress and a herbicide treatment.  相似文献   

17.
LIMITATIONS OF PHOTOSYNTHESIS IN DIFFERENT REGIONS OF THE ZEA MAYS LEAF   总被引:3,自引:0,他引:3  
The progressive development of the photosynthetic apparatus occurring along the length of the Zea mays leaf offers a convenient system with which to examine the limitations to photosynthetic CO2 assimilation during biogenesis of a C4 leaf. Changes in light-induced O2 evolution and CO2 assimilation, chlorophyll content, activity of PEP-carboxylase, NADP-malic enzyme and the 'R5P system' (consisting of d -ribose-5-phosphate-keto isomerase, ATP- d -ribulose-5 phosphate 1-phosphotransferase and d -ribulose-1,5-bisphosphate carboxylase) and fluorescence emission characteristics were examined along the length of the second leaf of 7-day-old plants grown under a diurnal light regime. The results suggest that the major limitation to CO2 assimilation in the leaf sheath lies within the chlorenchyma and is either energy supply for carboxylation or the capacity of key photosynthetic enzymes. In the leaf blade stomatal resistance to CO2 diffusion constitutes a major fraction of the total leaf resistance to CO2 assimilation implicating the stoma as the major limiting factor to photosynthetic CO2 assimilation.  相似文献   

18.
1. The affinity of photosynthesis for CO2 is calculated here as the initial slope of net-photosynthetic rate against concentration of CO2. The affinity for CO2 for pairs of freshwater macrophytes with similar leaf morphology but able or unable to use HCO3 as a carbon source was compared.
2. Species restricted to CO2 had a higher affinity for CO2 than species that were also able to use HCO3 when rates were expressed on the basis of area, dry mass and content of chlorophyll a .
3. Published values for the affinity for CO2 and the concentration of CO2 which half-saturated rate of photosynthesis were compiled and compared. Despite a large range of values, affinity for CO2 was greater for species restricted to CO2 than for those also able to use HCO3 and statistically different when the slope was expressed on the basis of dry mass and chlorophyll a content.
4. The difference in affinity is consistent with predicted benefits of a high permeability to CO2 for species relying on passive diffusion of CO2 and a lower permeability for species able to use HCO3 in order to reduce efflux of CO2 from a high internal concentration generated by active transport.
5. The implications of the different affinities are discussed in terms of species distribution.  相似文献   

19.
Few studies have investigated the interaction of ultraviolet (UV)-B radiation and CO2 concentration on plants. We studied the combined effects of UV-B radiation and CO2 concentration on canola ( Brassica napus cv. 46A65) under four growth conditions – ambient CO2 with UV-B (control), elevated CO2 with UV-B, ambient CO2 without UV-B, and elevated CO2 without UV-B – to determine whether the adverse effects of UV-B are mitigated by elevated CO2. Elevated CO2 significantly increased plant height and seed yield, whereas UV-B decreased them. Elevated CO2 ameliorated the adverse effects of UV-B in plant height. UV-B did not affect the physical characteristics of leaf but CO2 did. Certain flower and fruit characteristics were affected negatively by UV-B and positively by CO2. UV-B did not affect net photosynthesis, transpiration and stomatal conductance but decreased water use efficiency (WUE). Elevated CO2 significantly increased net photosynthesis and WUE. Neither UV-B nor CO2 affected chlorophyll (Chl) fluorescence. UV-B significantly decreased Chl b and increased the ratio of Chl a / b . Elevated CO2 decreased only the ratio of Chl a / b . UV-B significantly increased UV-absorbing compounds while CO2 had no effect on them. Both UV-B and CO2 significantly increased epicuticular wax content. Many significant relationships were found between morphological, physiological, and chemical parameters. This study showed that elevated CO2 can partially ameliorate some of the adverse effects of UV-B radiation in B . napus .  相似文献   

20.

A , carbon assimilation rate
ABA, abscisic acid
Ci , intercellular space CO2 concentration
g , leaf conductance
WUE, water use efficiency

Carbon dioxide and abscisic acid (ABA) are two major signals triggering stomatal closure. Their putative interaction in stomatal regulation was investigated in well-watered air-grown or double CO2-grown Arabidopsis thaliana plants, using gas exchange and epidermal strip experiments. With plants grown in normal air, a doubling of the CO2 concentration resulted in a rapid and transient drop in leaf conductance followed by recovery to the pre-treatment level after about two photoperiods. Despite the fact that plants placed in air or in double CO2 for 2 d exhibited similar levels of leaf conductance, their stomatal responses to an osmotic stress (0·16–0·24 MPa) were different. The decrease in leaf conductance in response to the osmotic stress was strongly enhanced at elevated CO2. Similarly, the drop in leaf conductance triggered by 1 μ M ABA applied at the root level was stronger at double CO2. Identical experiments were performed with plants fully grown at double CO2. Levels of leaf conductance and carbon assimilation rate measured at double CO2 were similar for air-grown and elevated CO2-grown plants. An enhanced response to ABA was still observed at high CO2 in pre-conditioned plants. It is concluded that: (i) in the absence of stress, elevated CO2 slightly affects leaf conductance in A. thaliana ; (ii) there is a strong interaction in stomatal responses to CO2 and ABA which is not modified by growth at elevated CO2.  相似文献   

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