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1.
The aim of this study was to assess the temperature response of photosynthesis in rubber trees ( Hevea brasiliensis Müll. Arg.) to provide data for process-based growth modeling, and to test whether photosynthetic capacity and temperature
response of photosynthesis acclimates to changes in ambient temperature. Net CO 2 assimilation rate ( A) was measured in rubber saplings grown in a nursery or in growth chambers at 18 and 28°C. The temperature response of A was measured from 9 to 45°C and the data were fitted to an empirical model. Photosynthetic capacity (maximal carboxylation
rate, V
cmax, and maximal light driven electron flux, J
max) of plants acclimated to 18 and 28°C were estimated by fitting a biochemical photosynthesis model to the CO 2 response curves ( A– C
i curves) at six temperatures: 15, 22, 28, 32, 36 and 40°C. The optimal temperature for A ( T
opt) was much lower in plants grown at 18°C compared to 28°C and nursery. Net CO 2 assimilation rate at optimal temperature ( A
opt), V
cmax and J
max at a reference temperature of 25°C ( V
cmax25 and J
max25) as well as activation energy of V
cmax and J
max ( E
aV and E
aJ) decreased in individuals acclimated to 18°C. The optimal temperature for V
cmax and J
max could not be clearly defined from our response curves, as they always were above 36°C and not far from 40°C. The ratio J
max25/ V
cmax25 was larger in plants acclimated to 18°C. Less nitrogen was present and photosynthetic nitrogen use efficiency ( V
cmax25/ N
a) was smaller in leaves acclimated to 18°C. These results indicate that rubber saplings acclimated their photosynthetic characteristics
in response to growth temperature, and that higher temperatures resulted in an enhanced photosynthetic capacity in the leaves,
as well as larger activation energy for photosynthesis. 相似文献
2.
The occurrence of photorespiration in soybean ( Glycine max [L.] Merr.) leaf cells was demonstrated by the presence of an O 2-dependent CO 2 compensation concentration, a nonlinear time course for photosynthetic 14CO 2 uptake at low CO 2 and high O 2 concentrations, and an O 2 stimulation of glycine and serine synthesis which was reversed by high CO 2 concentration. The compensation concentration was a linear function of O 2 concentration and increased as temperature increased. At atmospheric CO 2 concentration, 21% O 2 inhibited photosynthesis at 25 C by 27%. Oxygen inhibition of photosynthesis was competitive with respect to CO 2 and increased with increasing temperature. The K m (CO 2) of photosynthesis was also temperature-dependent, increasing from 12 μ m CO 2 at 15 C to 38 μ m at 35 C. In contrast, the K i (O 2) was similar at all temperatures. Oxygen inhibition of photosynthesis was independent of irradiance except at 10 m m bicarbonate and 100% O 2, where inhibition decreased with increasing irradiance up to the point of light saturation of photosynthesis. Concomitant with increasing O 2 inhibition of photosynthesis was an increased incorporation of carbon into glycine and serine, intermediates of the photorespiratory pathway, and a decreased incorporation into starch. The effects of CO 2 and O 2 concentration and temperature on soybean cell photosynthesis and photorespiration provide further evidence that these processes are regulated by the kinetic properties of ribulose-1,5-diphosphate carboxylase with respect to CO 2 and O 2. 相似文献
3.
Changes in photosynthesis and the ribulose 1,5-bisphosphate (RuBP) carboxylase level were examined in the 12th leaf blades of rice ( Oryza sativa L.) grown under different N levels. Photosynthesis was determined using an open infrared gas analysis system. The level of RuBP carboxylase was measured by rocket immunoelectrophoresis. These changes were followed with respect to changes in the activities of RuBP carboxylase, ribulose 5-phosphate kinase, NADP-glyceraldehyde 3-phosphate dehydrogenase, and 3-phosphoglyceric acid kinase. RuBP carboxylase activity was highly correlated with the net rate of photosynthesis (r = 0.968). Although high correlations between the activities of other enzymes and photosynthesis were also found, the activity per leaf of RuBP carboxylase was much lower than those of other enzymes throughout the leaf life. The specific activity of RuBP carboxylase on a milligram of the enzyme protein basis remained fairly constant (1.16 ± 0.07 micromoles of CO2 per minute per milligram at 25°C) throughout the experimental period. Kinetic parameters related to CO2 fixation were examined using the purified carboxylase. The Km(CO2) and Vmax values were 12 micromolar and 1.45 micromoles of CO2 per minute per milligram, respectively (pH 8.2 and 25°C). The in vitro specific activity calculated at the atomospheric CO2 level from the parameters was comparable to the in situ true photosynthetic rate per milligram of the carboxylase throughout the leaf life. The results indicated that the level of RuBP carboxylase protein can be a limiting factor in photosynthesis throughout the life span of the leaf. 相似文献
4.
Application of the widely used Farquhar model of photosynthesis in interpretation of gas exchange data assumes that photosynthetic properties are homogeneous throughout the leaf. Previous studies showed that heterogeneity in stomatal conductance ( gs) across a leaf could affect the shape of the measured leaf photosynthetic CO 2 uptake rate ( A) versus intercellular CO 2 concentration ( Ci) response curve and, in turn, estimation of the critical biochemical parameters of this model. These are the maximum rates of carboxylation ( Vc,max), whole-chain electron transport ( Jmax), and triose-P utilization ( VTPU). The effects of spatial variation in Vc,max, Jmax, and VTPU on estimation of leaf averages of these parameters from A-Ci curves measured on a whole leaf have not been investigated. A mathematical model incorporating defined degrees of spatial variability in Vc,max and Jmax was constructed. One hundred and ten theoretical leaves were simulated, each with the same average Vc,max and Jmax, but different coefficients of variation of the mean (CV VJ) and varying correlation between Vc,max and Jmax (Ω). Additionally, the interaction of variation in Vc,max and Jmax with heterogeneity in VTPU, gs, and light gradients within the leaf was also investigated. Transition from Vc,max- to Jmax-limited photosynthesis in the A-Ci curve was smooth in the most heterogeneous leaves, in contrast to a distinct inflection in the absence of heterogeneity. Spatial variability had little effect on the accuracy of estimation of Vc,max and Jmax from A-Ci curves when the two varied in concert (Ω = 1.0), but resulted in underestimation of both parameters when they varied independently (up to 12.5% in Vc,max and 17.7% in Jmax at CV VJ = 50%; Ω = 0.3). Heterogeneity in VTPU also significantly affected parameter estimates, but effects of heterogeneity in gs or light gradients were comparatively small. If Vc,max and Jmax derived from such heterogeneous leaves are used in models to project leaf photosynthesis, actual A is overestimated by up to 12% at the transition between Vc,max- and Jmax-limited photosynthesis. This could have implications for both crop production and Earth system models, including projections of the effects of atmospheric change. 相似文献
5.
The effects of elevated atmospheric CO 2 concentration on growth of forest tree species are difficult to predict because practical limitations restrict experiments to much shorter than the average life-span of a tree. Long-term, process-based computer models must be used to extrapolate from shorter-term experiments. A key problem is to ensure a strong flow of information between experiments and models. In this study, meta-analysis techniques were used to summarize a suite of photosynthetic model parameters obtained from 15 field-based elevated [CO 2] experiments on European forest tree species. The parameters studied are commonly used in modelling photosynthesis, and include observed light-saturated photosynthetic rates ( Amax), the potential electron transport rate ( Jmax), the maximum Rubisco activity ( Vcmax) and leaf nitrogen concentration on mass ( Nm) and area ( Na) bases. Across all experiments, light-saturated photosynthesis was strongly stimulated by growth in elevated [CO 2]. However, significant down-regulation of photosynthesis was also observed; when measured at the same CO 2 concentration, photosynthesis was reduced by 10–20%. The underlying biochemistry of photosynthesis was affected, as shown by a down-regulation of the parameters Jmax and Vcmax of the order of 10%. This reduction in Jmax and Vcmax was linked to the effects of elevated [CO 2] on leaf nitrogen concentration. It was concluded that the current model is adequate to model photosynthesis in elevated [CO 2]. Tables of model parameter values for different European forest species are given. 相似文献
6.
The regulation of ribulose-1,5-bisphosphate (RuBP) carboxylase (rubisco) activity in Phaseolus vulgaris was studied under moderate CO 2 and high light, conditions in which photosynthesis in C 3 plants can be insensitive to changes in O 2 partial pressure. Steady state RuBP concentrations were higher, the calculated rate of RuBP use was lower and the activation state of rubisco was lower in low O 2 relative to values observed in normal O 2. It is suggested that the reduced activity of rubisco observed here is related to feedback effects which occur when the rate of net CO 2 assimilation approaches the maximum capacity for starch and sucrose synthesis (triose phosphate utilization). The activation state of rubisco was independent of O 2 partial pressure when light or CO 2 was limiting for photosynthesis. Reduced activity of rubisco was also observed at limiting light. However, in this species light dependent changes in the concentration of an inhibitor of rubisco controlled the apparent Vmax of rubisco in low light while changes in the CO 2-Mg 2+ dependent activation of rubisco controlled the apparent Vmax in high light. 相似文献
7.
Abutilon theophrasti (C 3) and Amaranthus retroflexus (C 4), were grown from seed at four partial pressures of CO 2: 15 Pa (below Pleistocene minimum), 27 Pa (pre-industrial), 35 Pa (current), and 70 Pa (future) in the Duke Phytotron under high light, high nutrient, and wellwatered conditions to evaluate their photosynthetic response to historic and future levels of CO 2. Net photosynthesis at growth CO 2 partial pressures increased with increasing CO 2 for C 3 plants, but not C 4 plants. Net photosynthesis of Abutilon at 15 Pa CO 2 was 70% less than that of plants grown at 35 Pa CO 2, due to greater stomatal and biochemical limitations at 15 Pa CO 2. Relative stomatal limitation (RSL) of Abutilon at 15 Pa CO 2 was nearly 3 times greater than at 35 Pa CO 2. A photosynthesis model was used to estimate ribulose-1,5-bisphosphate carboxylase (rubisco) activity (Vc max), electron transport mediated RuBP regeneration capacity ( J
max), and phosphate regeneration capacity (PiRC) in Abutilon from net photosynthesis versus intercellular CO 2 ( A– C
i) curves. All three component processes decreased by approximately 25% in Abutilon grown at 15 Pa compared with 35 Pa CO 2. Abutilon grown at 15 Pa CO 2 had significant reductions in total rubisco activity (25%), rubisco content (30%), activation state (29%), chlorophyll content (39%), N content (32%), and starch content (68%) compared with plants grown at 35 Pa CO 2. Greater allocation to rubisco relative to light reaction components and concomitant decreases in J
max and PiRC suggest co-regulation of biochemical processes occurred in Abutilon grown at 15 Pa CO 2. There were no significant differences in photosynthesis or leaf properties in Abutilon grown at 27 Pa CO 2 compared with 35 Pa CO 2, suggesting that the rise in CO 2 since the beginning of the industrial age has had little effect on the photosynthetic performance of Abutilon. For Amaranthus, limitations of photosynthesis were balanced between stomatal and biochemical factors such that net photosynthesis was similar in all CO 2 treatments. Differences in photosynthetic response to growth over a wide range of CO 2 partial pressures suggest changes in the relative performance of C 3 and C 4 annuals as atmospheric CO 2 has fluctuated over geologic time. 相似文献
8.
The aim of this work was to study the acclimation of photosynthesis in a boreal grass ( Phalaris arundinacea L.) grown in controlled environment chambers under elevated temperature (ambient + 3.5°C) and CO 2 (700 μmol mol −1) with varying soil water regimes. More specifically, we studied, during two development stages (early: heading; late: florescence
completed), how the temperature response of light-saturated net photosynthetic rate ( P
sat), maximum rate of ribulose-1,5-bisphosphate carboxylase/oxygenase activity ( V
cmax) and potential rate of electron transport ( J
max) acclimatized to the changed environment. During the early growing period, we found a greater temperature-induced enhancement
of P
sat at higher measurement temperatures, which disappeared during the late stage. Under elevated growth temperature, V
cmax and J
max at lower measurement temperatures (5–15°C) were lower than those under ambient growth temperature during the early period.
When the measurements were done at 20–30°C, the situation was the opposite. During the late growing period, V
cmax and J
max under elevated growth temperature were consistently lower across measurement temperatures. CO 2 enrichment significantly increased P
sat with higher intercellular CO 2 compared to ambient CO 2 treatment, however, elevated CO 2 slightly decreased V
cmax and J
max across measurement temperatures, probably due to down-regulation acclimation. For two growing periods, soil water availability
affected the variation in photosynthesis and biochemical parameters much more than climatic treatment did. Over two growing
periods, V
cmax and J
max were on average 36.4 and 30.6%, respectively, lower with low water availability compared to high water availability across
measurement temperatures. During the late growing period, elevated growth temperature further reduced the photosynthesis under
low water availability. V
cmax and J
max declined along with the decrease in nitrogen content of leaves as growing period progressed, regardless of climatic treatment
and water regime. We suggest that, for grass species, seasonal acclimation of the photosynthetic parameters under varying
environmental conditions needed to be identified to fairly estimate the whole-life photosynthesis. 相似文献
9.
We investigated the effects of increased atmospheric CO 2 on the biomass, photosynthesis, protein and phenolic concentrations and content of Plantago maritima and Armeria maritima. This enabled us to test the protein competition model (PCM) for predicting C allocation to phenolics. Three contrasting responses to elevated CO 2 (600 μmol CO 2 mol −1) between the two study species were observed. (1) In P. maritima, plant biomass increased and the maximum carboxylation rate of Rubisco ( Vc,max) was decreased. However, in A. maritima, shoot biomass decreased and the Vc,max of Rubisco was unchanged. (2) The total phenolic content increased in P. maritima but decreased in A. maritima. (3) Protein concentrations and content decreased in P. maritima and root protein concentrations and content increased in A. maritima. We conclude that C and N allocation to phenolics and proteins is species- and organ-specific and the PCM predictions were correct when phenolics and proteins were expressed on a per plant content basis. 相似文献
10.
The possible responses of the terrestrial biosphere to future CO 2 increases and associated climatic change are being investigated using dynamic global vegetation models (DG VMs) which include the Farquhar et al. (1980) biochemical model of leaf assimilation as the primary means of carbon capture. This model requires representative values of the maximum rates of Rubisco activity, V max, and electron transport, J max, for different vegetation types when applied at the global scale. Here, we describe an approach for calculating these values based on measurements of the maximum rate of leaf photosynthesis (A max) 13C discrimination. The approach is tested and validated by comparison with measurements of Rubisco activity assayed directly on wild-type and transgenic Nicotiana tabacum (tobacco) plants with altered Rubisco activity grown under ambient and elevated CO 2 mole fractions with high and low N-supply. Vmax and Jmax values are reported for 18 different vegetation types with global coverage. Both variables were linearly related reinforcing the idea of optimal allocation of resources to photosynthesis (light harvesting vs. Rubisco) at the global scale. The reported figures should be of value to the further development of vegetation and ecosystem models employing mechanistic DGVMs. 相似文献
11.
Mesophyll cells were rapidly isolated from soybean ( Glycine max [L.]) leaves using a combined Macerase enzyme-stirring technique. About 50% to 70% of the leaf cells on a chlorophyll basis from 3 grams of leaves could be isolated in 15 minutes. The cells obtained by this method were capable of high rates of photosynthesis even after storage in the dark for periods of up to 9 hours. The CO 2-saturated rate of photosynthesis increased from 5 μm CO 2/mg Chl·hour at 5 C to 170 μm CO 2/mg Chl·hour at 40 C. At atmospheric CO 2 concentration, the rate varied from 5 to 55 μm CO 2/mg Chl·hour over this temperature range. The reduced temperature response of photosynthesis at low CO 2 concentration was due to an increased K m(CO 2) of the cells with increasing temperature. The products of photosynthesis in the isolated cells were similar to the products of leaf photosynthesis. 相似文献
12.
With an experimental system developed for aquatic plants using the mass spectrometry technique and infrared gas analysis of CO 2, we studied the responses to various O 2 concentrations of gas exchanges with the red macroalga Chondrus crispus S. The results were as follows. (a) Irrespective of the CO 2 concentration, net photosynthesis was O 2 sensitive with a 45 to 70% stimulation at 2% O 2. Even with high CO 2, a significant Warburg effect was detected. (b) Although photosynthesis was CO 2 sensitive, O 2 photoconsumption was only weakly affected by CO 2 even at high CO 2 where it was still photodependent. (c) O 2 photoconsumption was always sensitive to O 2 concentration whatever the CO 2 concentration, but with O 2 exceeding 20% the kinetics disagreed with the Michaelis-Menten model, with saturation being reached more rapidly. With various CO 2 concentrations, the apparent Km (O 2) ranged from 4 to 16% O 2 with a relatively constant Vmax (O 2) of about one-third the Vmax (CO 2). (d) Dark respiration seemed to be O 2 insensitive. These results are discussed in relation to the nature of the processes able to consume O 2 in the light, and seem to be consistent with a significant involvement of a Mehlertype reaction. 相似文献
13.
Background and Aims Plants growing under elevated atmospheric CO 2 concentrations often have reduced stomatal conductance and subsequently increased leaf temperature. This study therefore tested the hypothesis that under long-term elevated CO 2 the temperature optima of photosynthetic processes will shift towards higher temperatures and the thermostability of the photosynthetic apparatus will increase.Methods The hypothesis was tested for saplings of broadleaved Fagus sylvatica and coniferous Picea abies exposed for 4–5 years to either ambient (AC; 385 µmol mol −1) or elevated (EC; 700 µmol mol −1) CO 2 concentrations. Temperature response curves of photosynthetic processes were determined by gas-exchange and chlorophyll fluorescence techniques.Key Results Initial assumptions of reduced light-saturated stomatal conductance and increased leaf temperatures for EC plants were confirmed. Temperature response curves revealed stimulation of light-saturated rates of CO 2 assimilation ( Amax) and a decline in photorespiration ( RL) as a result of EC within a wide temperature range. However, these effects were negligible or reduced at low and high temperatures. Higher temperature optima ( Topt) of Amax, Rubisco carboxylation rates ( VCmax) and RL were found for EC saplings compared with AC saplings. However, the shifts in Topt of Amax were instantaneous, and disappeared when measured at identical CO 2 concentrations. Higher values of Topt at elevated CO 2 were attributed particularly to reduced photorespiration and prevailing limitation of photosynthesis by ribulose-1,5-bisphosphate (RuBP) regeneration. Temperature response curves of fluorescence parameters suggested a negligible effect of EC on enhancement of thermostability of photosystem II photochemistry.Conclusions Elevated CO 2 instantaneously increases temperature optima of Amax due to reduced photorespiration and limitation of photosynthesis by RuBP regeneration. However, this increase disappears when plants are exposed to identical CO 2 concentrations. In addition, increased heat-stress tolerance of primary photochemistry in plants grown at elevated CO 2 is unlikely. The hypothesis that long-term cultivation at elevated CO 2 leads to acclimation of photosynthesis to higher temperatures is therefore rejected. Nevertheless, incorporating acclimation mechanisms into models simulating carbon flux between the atmosphere and vegetation is necessary. 相似文献
14.
Abstract Some characteristics of photosynthetic inorganic carbon uptake by Palmaria palmata, a marine red macroalga, have been measured under physiological conditions in artificial seawater. The apparent affinity of thallus for CO 2 [K 1/2(CO 2)] at pH 8.0 and 15°C was 21.4±3.0mmol m ?3 CO 2 under air, and 25.7±70mmol m ?3 CO 2 under N 2. The corresponding values of Vmax were 2.98 ± 0.42 and 3.65±0.87 mmol O 2 evolved g Chr ?1 s ?l. The apparent K m(CO 2) of isolated ribulose bisphosphate carboxylase was determined at pH 8.0 and 30 °C to be 30.2 mmol m ?3 CO 2, and the corresponding value of V max was 19.67 μniol CO 2 g protein ?1 s ?1. The CO 2 compensation points of the thallus were measured in artificial seawater at pH 8.0 under air and N 2, using a gas-chromatographic method. The values were relatively low, rising from 10 cm 3 m ?3 at 15°C, to 35 cm 3 m ?3 at 25°C, but were not affected by the O 2 concentration. The lack of an effect of O 2 on photosynthesis and on compensation point indicates that there is little photorespiratory CO 2 loss in this macroalga. The high affinity of the thallus for CO 2, and the low CO 2 compensation concentrations, are consistent with the occurrence of bicarbonate uptake in this alga. 相似文献
15.
As part of an extensive analysis of the factors regulating photosynthesis in Agropyron smithii Rydb., a C 3 grass, we have examined the response of leaf gas exchange and ribulose-1,5-bisphosphate (RuBP) carboxylase activity to temperature. Emphasis was placed on elucidating the specific processes which regulate the temperature response pattern. The inhibitory effects of above-optimal temperatures on net CO 2 uptake were fully reversible up to 40°C. Below 40°C, temperature inhibition was primarily due to O 2 inhibition of photosynthesis, which reached a maximum of 65% at 45°C. The response of stomatal conductance to temperature did not appear to have a significant role in determining the overall temperature response of photosynthesis. The intracellular conductance to CO 2 increased over the entire experimental temperature range, having a Q 10 of 1.2 to 1.4. Increases in the apparent Michaelis constant ( Kc) for RuBP carboxylase were observed in both in vitro and in vivo assays. The Q 10 values for the maximum velocity ( Vmax) of CO 2 fixation by RuBP carboxylase in vivo was lower (1.3-1.6) than those calculated from in vitro assays (1.8-2.2). The results suggest that temperature-dependent changes in enzyme capacity may have a role in above-optimum temperature limitations below 40°C. At leaf temperatures above 40°C, decreases in photosynthetic capacity were partially dependent on temperature-induced irreversible reductions in the quantum yield for CO 2 uptake. 相似文献
16.
Down-regulation of light-saturated photosynthesis ( Asat) at elevated atmospheric CO 2 concentration, [CO 2], has been demonstrated for many C 3 species and is often associated with inability to utilize additional photosynthate and/or nitrogen limitation. In soybean, a nitrogen-fixing species, both limitations are less likely than in crops lacking an N-fixing symbiont. Prior studies have used controlled environment or field enclosures where the artificial environment can modify responses to [CO 2]. A soybean free air [CO 2] enrichment (FACE) facility has provided the first opportunity to analyze the effects of elevated [CO 2] on photosynthesis under fully open-air conditions. Potential ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) carboxylation ( Vc,max) and electron transport through photosystem II ( Jmax) were determined from the responses of Asat to intercellular [CO 2] ( Ci) throughout two growing seasons. Mesophyll conductance to CO 2 ( gm) was determined from the responses of Asat and whole chain electron transport ( J) to light. Elevated [CO 2] increased Asat by 15–20% even though there was a small, statistically significant, decrease in Vc,max. This differs from previous studies in that Vc,max/ Jmax decreased, inferring a shift in resource investment away from Rubisco. This raised the Ci at which the transition from Rubisco-limited to ribulose-1,5-bisphosphate regeneration-limited photosynthesis occurred. The decrease in Vc,max was not the result of a change in gm, which was unchanged by elevated [CO 2]. This first analysis of limitations to soybean photosynthesis under fully open-air conditions reveals important differences to prior studies that have used enclosures to elevate [CO 2], most significantly a smaller response of Asat and an apparent shift in resources away from Rubisco relative to capacity for electron transport.Abbreviations FACE Free air [CO 2] enrichment - Rubisco Ribulose-1,5-bisphosphate carboxylase/oxygenase - RuBP Ribulose-1,5-bisphosphate - SoyFACE Soybean free air [CO 2] enrichment - VPD Vapor pressure deficit 相似文献
17.
Plants grown at elevated pCO 2 often fail to sustain the initial stimulation of net CO 2 uptake rate ( A). This reduced, acclimated, stimulation of A often occurs concomitantly with a reduction in the maximum carboxylation velocity ( Vc,max) of Rubisco. To investigate this relationship we used the Farquhar model of C 3 photosynthesis to predict the minimum Vc,max capable of supporting the acclimated stimulation in A observed at elevated pCO 2. For a wide range of species grown at elevated pCO 2 under contrasting conditions we found a strong correlation between observed and predicted values of Vc,max. This exercise mechanistically and quantitatively demonstrated that the observed acclimated stimulation of A and the simultaneous decrease in Vc,max observed at elevated pCO 2 is mechanistically consistent. With the exception of plants grown at a high elevated pCO 2 (> 90 Pa), which show evidence of an excess investment in Rubisco, the failure to maintain the initial stimulation of A is almost entirely attributable to the decrease in Vc,max and investment in Rubisco is coupled to requirements. 相似文献
18.
The limiting step of photosynthesis changes depending on CO 2 concentration and, in theory, photosynthetic nitrogen use efficiency at a respective CO 2 concentration is maximized if nitrogen is redistributed from non‐limiting to limiting processes. It has been shown that some plants increase the capacity of ribulose‐1,5‐bisphoshate (RuBP) regeneration (evaluated as J max) relative to the RuBP carboxylation capacity (evaluated as V cmax) at elevated CO 2, which is in accord with the theory. However, there is no study that tests whether this change is accompanied by redistribution of nitrogen in the photosynthetic apparatus. We raised a perennial plant, Polygonum sachalinense, at two nutrient availabilities under two CO 2 concentrations. The J max to V cmax ratio significantly changed with CO 2 increment but the nitrogen allocation among the photosynthetic apparatus did not respond to growth CO 2. Enzymes involved in RuBP regeneration might be more activated at elevated CO 2, leading to the higher J max to V cmax ratio. Our result suggests that nitrogen partitioning is not responsive to elevated CO 2 even in species that alters the balance between RuBP regeneration and carboxylation. Nitrogen partitioning seems to be conservative against changes in growth CO 2 concentration. 相似文献
19.
The aims of this paper was to modify the photosynthesis model of Farquhar, von Caemmerer and Berry (FvCB) to be able to predict light dependency of the carboxylation capacity ( Vc) and to improve the prediction of temperature dependency of the maximum carboxylation capacity ( Vcmax) and the maximum electron transport rate ( Jmax). The FvCB model was modified by adding a sub-model for Ribulose-1,5-bisphosphate carboxylase (Rubisco) activation and validating the parameters for temperature dependency of Vcmax and Jmax. Values of parameters for temperature dependency of Vcmax and Jmax were validated and adjusted based on data of the photosynthesis response to temperature. Parameter estimation was based on measurements under a wide range of environmental conditions, providing parameters with broad validity. The simultaneous estimation method and the nonlinear mixed effects model were applied to ensure the accuracy of the parameter estimation. The FvCB parameters, Vcmax, Jmax, α (the efficiency of light energy conversion), θ (the curvature of light response of electron transport), and Rd (the non-photorespiratory CO 2 release) were estimated and validated on a dataset from two other years. Observations and predictions matched well ( R2 = 0.94). We conclude that incorporating a sub-model of Rubisco activation improved the FvCB model through predicting light dependency of carboxylation rate; and that estimating Vcmax, Jmax, α, θ, and Rd requires data sets of both CO 2 and light response curves. 相似文献
20.
The photosynthetic enzyme ribulose bisphosphate carboxylase-oxygenase [EC 4.1.1.39] (RuBPCase) plays a key role in the carbon reduction system of plants. In this study, we determined the kinetic variability of RuBPCase among 46 varieties of Hordeum vulgare L. at two ages. The Vmax CO 2 and Km CO 2 of RuBPCase was determined for each cultivar. Varietal differences were found in Km CO 2 and Vmax CO 2 for one and four genotypes, respectively. One variety exhibited atypical behavior in both Km and Vmax. A comparison of varieties and age showed a significant interaction between these factors for Km but not for Vmax. These data indicate the presence of kinetic variability in RuBPCase within the H. vulgare population and perhaps between plant ages. 相似文献
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