The rate-limiting step for CO(2) assimilation at different temperatures is influenced by the leaf nitrogen content in several C(3) crop species

Effects of nitrogen (N) supply on the limiting step of CO(2) assimilation rate (A) at 380 μmol mol(-1) CO(2) concentration (A(380) ) at several leaf temperatures were studied in several crops, since N nutrition alters N allocation between photosynthetic components. Contents of leaf N, ribulose 1·5-bisphosphate carboxylase/oxygenase (Rubisco) and cytochrome f (cyt f) increased with increasing N supply, but the cyt f/Rubisco ratio decreased. Large leaf N content was linked to a high stomatal (g(s) ) and mesophyll conductance (g(m) ), but resulted in a lower intercellular (C(i) ) and chloroplast CO(2) concentration (C(c) ) because the increase in g(s) and g(m) was insufficient to compensate for change in A(380) . The A-C(c) response was used to estimate the maximum rate of RuBP carboxylation (V(cmax) ) and chloroplast electron transport (J(max) ). The J(max) /V(cmax) ratio decreased with reductions in leaf N content, which was consistent with the results of the cyt f/Rubisco ratio. Analysis using the C(3) photosynthesis model indicated that A(380) tended to be limited by RuBP carboxylation in plants grown at low N concentration, whereas it was limited by RuBP regeneration in plants grown at high N concentration. We conclude that the limiting step of A(380) depends on leaf N content and is mainly determined by N partitioning between Rubisco and electron transport components.     

施氮和大气CO2浓度升高对小麦旗叶光合电子传递和分配的影响

采用开顶式气室盆栽培养小麦,设计2个大气CO2浓度(正常:400 μmol.mol-1;高:760 μmol·mol-1)、2个氮素水平(0和200 mg·kg-1土)的组合处理,通过测定小麦抽穗期旗叶氮素和叶绿素浓度、光合速率(Pn)-胞间CO2浓度(C1)响应曲线及荧光动力学参数,来测算小麦叶片光合电子传递速率等,研究了高大气CO2浓度下施氮对小麦旗叶光合能量分配的影响.结果表明:与正常大气CO2浓度相比,高大气CO2浓度下小麦叶片氮浓度和叶绿素浓度降低,高氮处理的小麦叶片叶绿素a/b升高.施氮后小麦叶片PSⅡ最大光化学效率(Fv/Fm)、PSⅡ反应中心最大量子产额(Fv'/Fm')、PSⅡ反应中心的开放比例(qr)和PSⅡ反应中心实际光化学效率(φPSⅡ)在大气CO2浓度升高后无明显变化,虽然叶片非光化学猝灭系数(NPQ)显著降低,但PSⅡ总电子传递速率(JF)无明显增加;不施氮处理的Fv'/Fm'、φPSⅡ和NPQ在高大气CO2浓度下显著降低,尽管Fv/Fm和qp无明显变化,JF仍显著下降.施氮后小麦叶片JF增加,参与光化学反应的非环式电子流传递速率(Jc)明显升高.大气CO2浓度升高使参与光呼吸的非环式电子流传递速率(J0)、Rubisco氧化速率(V0)、光合电子的光呼吸/光化学传递速率比(J0/Jc)和Rubisco氧化/羧化比(V0/Vc)降低,但使Jc和Rubisco羧化速率(Vc)增加.因此,高大气CO2浓度下小麦叶片氮浓度和叶绿素浓度降低,而增施氮素使通过PSⅡ反应中心的电子流速率显著增加,促进了光合电子流向光化学方向的传递,使更多的电子进入Rubisco羧化过程,Pn显著升高.     

Determining Photosynthetic Parameters from Leaf CO2 Exchange and Chlorophyll Fluorescence (Ribulose-1,5-Bisphosphate Carboxylase/Oxygenase Specificity Factor,Dark Respiration in the Light,Excitation Distribution between Photosystems,Alternative Electron Transport Rate,and Mesophyll Diffusion Resistance

Using simultaneous measurements of leaf gas exchange and chlorophyll fluorescence, we determined the excitation partitioning to photosystem II (PSII), the CO2/O2 specificity of ribulose-1,5-bisphosphate carboxylase/oxygenase, the dark respiration in the light, and the alternative electron transport rate to acceptors other than bisphosphoglycerate, and the transport resistance for CO2 in the mesophyll cells for individual leaves of herbaceous and tree species. The specificity of ribulose-1,5-bisphosphate carboxylase/oxygenase for CO2 was determined from the slope of the O2 dependence of the CO2 compensation point between 1.5 and 21% O2. Its value, on the basis of dissolved CO2 and O2 concentrations at 25.5[deg]C, varied between 86 and 89. Dark respiration in the light, estimated from the difference between the CO2 compensation point and the CO2 photocompensation point, was about 20 to 50% of the respiration rate in the dark. The excitation distribution to PSII was estimated from the extrapolation of the dependence of the PSII quantum yield on F/Fm to F = 0, where F is steady-state and Fm is pulse-satuarated fluorescence, and varied between 0.45 and 0.6. The alternative electron transport rate was found as the difference between the electron transport rates calculated from fluorescence and from gas exchange, and at low CO2 concentrations and 10 to 21% O2, it was 25 to 30% of the maximum electron transport. The calculated mesophyll diffusion resistance accounted for about 20 to 30% of the total mesophyll resistance, which also includes carboxylation resistance. Whole-leaf photosynthesis is limited by gas phase, mesophyll diffusion, and carboxylation resistances in nearly the same proportion in both herbaceous species and trees.     

空气 NH3增高和不同氮源供应下大叶相思叶片光合参数的变化

生长在空气 NH3增高下 45 d的 NOˉ3- N大叶相思植株 ,其光饱和光合速率较对照的植株高 ;而生长在空气 NH3增高下的 NH 4- N和 NH4 NO3- N的大叶相思 ,当光强在 70 0 μmol·m- 2 ·s- 1左右时 Pn 达到最大值 ,较对照植株的要高。而当光强 >70 0 μmol·m- 2·s- 1时 ,Pn 降低 ,且较生长在对照条件下的低。表明在空气 NH3增高下生长的 NH 4- N和 NH4 NO3- N植株 ,其净光合速率 Pn会受到强光抑制。空气 NH3增高并不明显改变光呼吸 ( Rd)和无光呼吸下的 CO2 补充点 (Γ* )。无论生长在何种氮源下的大叶相思 ,其最大Ru BP饱和羧化速率 ( Vcmax)和最大电子传递速率 ( Jmax)均较生长在对照植株的高 ( P<0 .0 5 ) ,其叶氮含量亦较高 ( P<0 .0 5 ) ,其碳氮比较对照的低。在空气 NH3增高下 ,无论何种氮源生长的大叶相思 ,其 PR和 PB明显高于对照的植株 ,表明大叶相思能从空气 NH3中摄取和同化氮 ,增加氮积累和有利于 Rubisco和电子传递组分的合成 ,增高光合速率。空气 NH3增高可能有利于 Rubisco和电子传递组分的合成 ,在较低光强下能增高光合速率。空气 NH3增高可能有利于退化生态系统的生态恢复过程中的氮积累和先锋植物的早期生长。     

What does optimization theory actually predict about crown profiles of photosynthetic capacity when models incorporate greater realism?

Measured profiles of photosynthetic capacity in plant crowns typically do not match those of average irradiance: the ratio of capacity to irradiance decreases as irradiance increases. This differs from optimal profiles inferred from simple models. To determine whether this could be explained by omission of physiological or physical details from such models, we performed a series of thought experiments using a new model that included more realism than previous models. We used ray‐tracing to simulate irradiance for 8000 leaves in a horizontally uniform canopy. For a subsample of 500 leaves, we simultaneously optimized both nitrogen allocation (among pools representing carboxylation, electron transport and light capture) and stomatal conductance using a transdermally explicit photosynthesis model. Few model features caused the capacity/irradiance ratio to vary systematically with irradiance. However, when leaf absorptance varied as needed to optimize distribution of light‐capture N, the capacity/irradiance ratio increased up through the crown – that is, opposite to the observed pattern. This tendency was counteracted by constraints on stomatal or mesophyll conductance, which caused chloroplastic CO₂ concentration to decline systematically with increasing irradiance. Our results suggest that height‐related constraints on stomatal conductance can help to reconcile observations with the hypothesis that photosynthetic N is allocated optimally.     

Photosynthetic performance along a light gradient as related to leaf characteristics of a naturally occurring <Emphasis Type="Italic">Cypripedium flavum</Emphasis>

Photosynthesis, leaf structure, nitrogen content and nitrogen allocation in photosynthetic functions of Cypripedium flavum were studied in a naturally varying light regime. Light-saturated leaf net photosynthetic rate (A (max)) was strongly correlated with leaf dry mass per area (LMA), mesophyll conductance (g (m)) and area-based leaf nitrogen content (N(area)), with all variables increasing with increasing irradiance. Such coordinate variation of all these parameters illustrates the plastic response of leaf structure to high light (HL). Leaf N(area) was greater under HL than in low light (LL). The fractions of leaf nitrogen partitioning in carboxylation (P (R)) and bioenergetics (P (B)) were positively related to LMA. In contrast, P (R) and P (B) decreased with increasing mass-based leaf nitrogen content (N(mass)). However, no correlation was found between leaf nitrogen investment in light harvesting (P (L)) and either LMA or N(mass). Like maximum rate of carboxylation (V (cmax)) and electron transport (J (max)), the J (max)/V (cmax) ratio, which was strongly correlated to LMA, also increased significantly with irradiance. Under HL, leaf maximum photosynthetic nitrogen efficiency (ANUE) and intrinsic water use efficiency (WUE) were greater than in LL conditions, despite a small difference in WUE. This suggests that a functional balance in the photosynthetic machinery favors leaf photosynthetic plasticity of C. flavum in response to different light conditions. Given an ample soil nitrogen supply, C. flavum may offset its susceptibility to HL by efficient nitrogen use and higher stomatal and mesophyll conductance against photoinhibition so as to keep leaf photosynthesis positive.     

Nitrogen partitioning in the photosynthetic apparatus of Plantago asiatica leaves grown under different temperature and light conditions: similarities and differences between temperature and light acclimation

Effects of growth temperature and irradiance on nitrogen partitioning among photosynthetic components were studied. Plantago asiatica was grown under different temperature and light conditions. Growth conditions were regulated such that the Chl a/b ratio in leaves grown at a low temperature with a low irradiance was similar to that in leaves grown at a high temperature with a high irradiance, suggesting that the balance between acquisition and utilization of light energy in the photosynthetic apparatus was similar between the two growth conditions. When plotted against the leaf nitrogen content, the RuBP (ribulose-1,5-bisphosphate) carboxylase content did not significantly differ depending on growth conditions. Both high irradiance and low temperature decreased nitrogen partitioning to Chl-protein complexes. Low temperature increased nitrogen allocation to stroma FBPase (fructose-1,6-phosphatase) irrespective of growth irradiance. Gas exchange measurement indicated that the ratio of the electron transport (J(max)) to the maximum carboxylation rate (V(cmax)) was not affected by growth irradiance but by growth temperature. It is concluded that nitrogen partitioning between acquisition and utilization of light energy responds to both growth temperature and irradiance, while nitrogen partitioning between carboxylation and regeneration of RuBP responds only to growth temperature.     

不同光照条件下喜阴植物谢君魔芋对稳态和动态光源的响应特征

谢君魔芋(Amorphophallus xiei)是起源于云南西南地区热带雨林的典型喜阴植物,近年来得到了广泛种植和推广,在种植过程中,谢君魔芋需要采用遮荫栽培模式。为了揭示谢君魔芋对光照强度的适应策略,该研究探讨了生长在不同光照强度下(透光率为50%、29%、17%、7%)谢君魔芋叶片的光合作用特征、光合诱导特征、光合色素含量以及叶片氮素(N)含量和N分配。结果表明:随着生长环境光照强度的降低,单位叶面积和单位叶质量最大净光合速率、光合色素含量、最大羧化速率、最大电子传递速率及比叶面积均增大,而暗呼吸和光补偿点均减小。在光合诱导过程中,生长在透光率为17%光环境中的谢君魔芋完成50%光合诱导所需的时间最短,约为81.4 s;在光诱导进行10 min时,诱导状态最高,为87.3%。完成50%和90%光合诱导所需的时间与低光下初始气孔导度呈负相关关系。随着生长光照强度降低,叶片中的N分配到羧化组分和生物能转化组分中的比例先增大后减小,在透光率为17%的光环境下具有最大值;而叶片中的N分配到捕光色素组分中的比例随着生长环境光照强度降低而增加。该研究结果表明,喜阴植物谢君魔芋通过加强对低光和动态光源的利用能力及有效的N资源分配策略来适应低光照环境。     

Adaptive radiation of photosynthetic physiology in the Hawaiian lobeliads: light regimes, static light responses, and whole-plant compensation points

Six endemic genera/sections of lobeliads (Campanulaceae) occupy nearly the full range of light regimes on moist sites in the Hawaiian Islands, from open alpine bogs and seacliffs to densely shaded rainforest interiors. To determine whether this clade has undergone a corresponding adaptive radiation in photosynthetic adaptations, we studied the natural light habitats and physiological characteristics of 11 species representing each sublineage. Across species in the field, average photon flux density (PFD) varies from 2.3 to 30.0 mol · m(-2) · d(-1), and maximum assimilation rate (A(max)) ranges from 0.17 to 0.35 μmol CO(2) · g(-1) · s(-1). Across species, A(max), dark respiration rate (R), Michaelis-Menten constant (k), light compensation point, specific leaf area (SLA), maximum carboxylation rate (V(cmax)), maximum rate of electron transport (J(max)), photosynthesis at saturating CO(2) (A(satCO(2))), and carboxylation efficiency (α) all increase significantly and in tightly coupled fashion with PFD, in accord with classical economic theory. Area-based rates have a higher degree of physiological integration with each other and tighter coupling to PFD than the corresponding mass-based rates, despite the energetic importance of the latter. Area-based rates frequently show adaptive cross-over: high-light species outperform low-light species at high PFD and vice versa at low PFD. A(max)-mass has little relationship to leaf mass per unit area (LMA), leaf N content, or leaf lifespan individually, but a multiple regression explains 96% of the variance in A(max)-mass across species in terms of SLA, leaf N content, and average PFD. Instantaneous leaf compensation points range from 0.1 to 1.2% full sunlight, far lower than the ecological (whole-plant) compensation points (ECPs) of 1.1 to 29.0% sunlight calculated based on photosynthetic parameters, leaf longevity, and allocation to leaf vs. nonleaf tissue. The ECPs are much closer to the lower limits of PFD actually experienced by lobeliads, suggesting they may play an important role in restricting species distributions. Taken together, these data provide evidence for an adaptive radiation in photosynthetic traits that is strongly correlated with-and indeed may help determine-the light regime that each species inhabits.     

不同氮营养水平下草莓叶片光合作用对高CO2浓度的适应

研究了不同氮素水平（12mmol／L,4mmol／L,0、4mmol／L）下生长的‘丰香’草莓在富C02（700μL/L）和大气CO（390μL/L）下的光合作用。结果表明,高氮（12mmol／L）下,在富CO2环境中生长的‘丰香’草莓叶片未出现光合作用下调,富CO2下草莓叶片的净光合速率、最大羧化速率（Vc.max）、最大电子传递速率（Jmax）、碳同化的电子传递速率（Jc）和光化学猝灭系数（qp）等均显著提高;而在中氮（4mmol／L）、低氮（0．4mmol／L）下,富CO2下生长的草莓叶片的上述参数均出现不同程度的下降。富CO2下,无论氮素水平如何,草莓叶片的光呼吸电子传递速率（Jo）均降低高氮草莓叶片的非光化学猝灭系数（qN或NPQ）降低,光抑制降低,而低氮则相反。上述结果说明,氮素供应不足时草莓叶片在富CO2下光合作用出现下调,因此生产上进行CO2施肥时应适度增加氮素的供应。     

大气CO2浓度升高对香蕉光合作用及光合碳循环过程中叶氮分配的影响

生长在高CC2浓度(700±56μl     

Leaf photosynthesis and respiration of three bioenergy crops in relation to temperature and leaf nitrogen: how conserved are biochemical model parameters among crop species?

Given the need for parallel increases in food and energy production from crops in the context of global change, crop simulation models and data sets to feed these models with photosynthesis and respiration parameters are increasingly important. This study provides information on photosynthesis and respiration for three energy crops (sunflower, kenaf, and cynara), reviews relevant information for five other crops (wheat, barley, cotton, tobacco, and grape), and assesses how conserved photosynthesis parameters are among crops. Using large data sets and optimization techniques, the C(3) leaf photosynthesis model of Farquhar, von Caemmerer, and Berry (FvCB) and an empirical night respiration model for tested energy crops accounting for effects of temperature and leaf nitrogen were parameterized. Instead of the common approach of using information on net photosynthesis response to CO(2) at the stomatal cavity (A(n)-C(i)), the model was parameterized by analysing the photosynthesis response to incident light intensity (A(n)-I(inc)). Convincing evidence is provided that the maximum Rubisco carboxylation rate or the maximum electron transport rate was very similar whether derived from A(n)-C(i) or from A(n)-I(inc) data sets. Parameters characterizing Rubisco limitation, electron transport limitation, the degree to which light inhibits leaf respiration, night respiration, and the minimum leaf nitrogen required for photosynthesis were then determined. Model predictions were validated against independent sets. Only a few FvCB parameters were conserved among crop species, thus species-specific FvCB model parameters are needed for crop modelling. Therefore, information from readily available but underexplored A(n)-I(inc) data should be re-analysed, thereby expanding the potential of combining classical photosynthetic data and the biochemical model.     

Seasonal changes in temperature dependence of photosynthetic rate in rice under a free-air CO(2) enrichment

BACKGROUND AND AIMS: Influences of rising global CO(2) concentration and temperature on plant growth and ecosystem function have become major concerns, but how photosynthesis changes with CO(2) and temperature in the field is poorly understood. Therefore, studies were made of the effect of elevated CO(2) on temperature dependence of photosynthetic rates in rice (Oryza sativa) grown in a paddy field, in relation to seasons in two years. METHODS: Photosynthetic rates were determined monthly for rice grown under free-air CO(2) enrichment (FACE) compared to the normal atmosphere (570 vs 370 micromol mol(-1)). Temperature dependence of the maximum rate of RuBP (ribulose-1,5-bisphosphate) carboxylation (V(cmax)) and the maximum rate of electron transport (J(max)) were analysed with the Arrhenius equation. The photosynthesis-temperature response was reconstructed to determine the optimal temperature (T(opt)) that maximizes the photosynthetic rate. KEY RESULTS AND CONCLUSIONS: There was both an increase in the absolute value of the light-saturated photosynthetic rate at growth CO(2) (P(growth)) and an increase in T(opt) for P(growth) caused by elevated CO(2) in FACE conditions. Seasonal decrease in P(growth) was associated with a decrease in nitrogen content per unit leaf area (N(area)) and thus in the maximum rate of electron transport (J(max)) and the maximum rate of RuBP carboxylation (V(cmax)). At ambient CO(2), T(opt) increased with increasing growth temperature due mainly to increasing activation energy of V(cmax). At elevated CO(2), T(opt) did not show a clear seasonal trend. Temperature dependence of photosynthesis was changed by seasonal climate and plant nitrogen status, which differed between ambient and elevated CO(2).     

空气CO2增高条件下荔枝叶片光合作用和超氧自由基产率

研究结果表明,生长在77±5PaCO2分压下30d的荔枝幼树,其光合速率较大气CO2分压（39.3Pa）下的低23％,光下线粒体呼吸速率和不包含光下呼吸的CO2补偿点亦略有降低。空气CO2增高使叶片最大羧化速率（Vcmax）和最大电子传递速率（Jmax）降低,表明大气增高CO2分压下叶片的光I(PSI)能量水平较低,呈片超氧自由基产率亦降低39％,叶片感染荔枝霜疫霉病率则从生长在大气CO2分压下的1.8％增至9.5％,可能较低光合和呼吸代谢诱致较低的超氧自由基产率,而使叶片易受病害侵染。叶片受病害侵染后表现为超氧自由基的激增。在全球大气CO2分压增高趋势下须加强对荔枝霜疫霉病的控制。     

Low stomatal and internal conductance to CO2 versus Rubisco deactivation as determinants of the photosynthetic decline of ageing evergreen leaves

A novel A-Ci curve (net CO2 assimilation rate of a leaf -An- as a function of its intercellular CO2 concentration -Ci) analysis method (Plant, Cell & Environment 27, 137-153, 2004) was used to estimate the CO2 transfer conductance (gi) and the maximal carboxylation (Vcmax) and electron transport (Jmax) potentials of ageing, non-senescing Pseudotsuga menziesii leaves in relation to their nitrogen (N) content and protein and pigment composition. Both gi and the stomatal conductance (gsc) of leaves were closely coupled to Vcmax, Jmax and An with all variables decreasing with increasing leaf age. Consequently, both Ci and Cc (chloroplastic CO2 concentration) remained largely conserved through successive growing seasons. The N content of leaves, as well as the amount of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) and other sodium dodecyl sulfate-soluble proteins, increased during the first three growing seasons, then stabilized or decreased only slightly afterwards. Thus, the age-related photosynthetic nitrogen use efficiency (PNUE) decline of leaves was not a consequence of decreased allocation of N towards Rubisco and other proteins involved in bioenergetics and light harvesting. Rather, loss of photosynthetic capacity was the result of the decreased activation state of Rubisco and proportional down-regulation of electron transport towards the photosynthetic carbon reduction (PCR) and photorespiratory (PCO) cycles in response to a reduction of CO2 supply to the chloroplasts' stroma. This study emphasizes the regulatory potential and homeostaticity of Cc- rather than photosynthetic metabolites or Ci- in relation to the commonly observed correlation between photosynthesis and gsc.     

三种高山杜鹃的光合生理生态研究

对大白花杜鹃（Rhododendron decorum）、云南杜鹃（R.yunnanense）和红棕杜鹃（R.rubiginosum）进行了气体交换、叶片性状等研究,以期了解三种杜鹃的光合生理特性及其对环境的适应。结果表明,三种杜鹃的光饱和光合速率（Pmax）与RuBP饱和最大羧化速率（Vc max）、光饱和最大电子传递速率（Jmax）和气孔导度（gs）呈极显著正相关（P≤0.01）,但仅Vc max存在显著的种间差异,说明三种杜鹃的光合能力主要受Vc max影响。叶氮含量、叶片氮在电子传递和在Rubisco中的分配均显著影响Vc max和Jmax。大白花杜鹃的LSP最低,LCP较高,对强光和弱光利用能力都不强,光适应范围较窄。云南杜鹃LCP最低,LSP和Pmax相对较高,对弱光或较强的光照均能利用,光照适应范围相对最广,光合适应能力最强;红棕杜鹃LSP和LCP均为最高,对强光环境的适应性最强。     

Invasive <Emphasis Type="Italic">Buddleja davidii</Emphasis> allocates more nitrogen to its photosynthetic machinery than five native woody species

The general-purpose genotype hypothesis and the hypothesis of the evolution of invasiveness predict that invasive species are characterized by particular traits that confer invasiveness. However, these traits are still not well-defined. In this study, ecophysiological traits of eight populations of the invasive shrub Buddleja davidii from a wide range of European locations and five co-occurring native woody species in Germany were compared in a common garden experiment. We hypothesized that the invader has higher resource capture ability and utilization efficiency than the natives. No differences were detected among the eight populations of B. davidii in any of the traits evaluated, indicating that the invader did not evolve during range expansion, thus providing support to the general-purpose genotype hypothesis. The invader showed significantly higher maximum electron transport rate, maximum carboxylation rate, carboxylation efficiency, light-saturated photosynthetic rate (P _max) and photosynthetic nitrogen utilization efficiency (PNUE) than the five natives. Leaf nitrogen content was not significantly different between the invader and the natives, but the invader allocated more nitrogen to the photosynthetic machinery than the natives. The increased nitrogen content in the photosynthetic machinery resulted in a higher resource capture ability and utilization efficiency in the invader. At the same intercellular CO₂ concentration, P _max was significantly higher in the invader than in the natives, again confirming the importance of the higher nitrogen allocation to photosynthesis. The invader reduced metabolic cost by increasing the ratio of P _max to dark respiration rate (R _d), but it did not reduce carbon cost by increasing the specific leaf area and decreasing leaf construction cost. The higher nitrogen allocation to the photosynthetic machinery, P _max, PNUE and P _max/R _d may facilitate B. davidii invasion, although studies involving a wide range of invasive species are needed to understand the generality of this pattern and to fully assess the ecological advantages afforded by these features.     

生长光强对六个橡胶树品种幼苗光合特性的影响

研究了6个橡胶树品种幼苗(适应1年后)在不同生长光强(100%、50%、25%和5%自然光)下的叶片光合系统对光强和CO2浓度的响应特性。结果表明,6个橡胶树品种对不同的光环境均表现出较强的适应性。在不同生长光强下,橡胶树幼苗叶片的最大光合速率(Pmax)、光补偿点(LCP)、暗呼吸速率(Rd)、磷酸丙糖利用速率(TPU)、最大羧化速率(Vcmax)和最大电子传递速率(Jmax)以及叶绿素含量(Chl)均有显著差异(P<0.05),而光饱和点(LSP)和AQY(表观量子效率)则无显著差异。相同生长光强下,6个橡胶树品种间叶片的最大光合速率(Pmax)、暗呼吸速率(Rd)、磷酸丙糖利用速率(TPU)、最大电子传递速率(Jmax)和叶绿素含量(Chl)有显著差异(P<0.05),其光补偿点(LCP)、最大羧化速率(Vcmax)和表观量子效率(AQY)则无显著差异。综合比较各参数,RRIM600、云研77-4和PR107适宜于相对光强为100%~50%的植胶环境,而云研77-2、GT1和热研523适宜于相对光强为50%~25%的植胶环境。     

内蒙古温带草原大针茅叶片光合生理特性对氮添加的响应

大气氮沉降增加生态系统氮有效性,优势种植物对不同水平氮输入的响应影响草原生态系统结构和功能。研究设置4个氮添加水平,分析内蒙古温带草原优势种大针茅（Stipa grandis）光合生理特性对不同梯度氮添加的响应。结果表明：低氮（0-2 g m^-2 a^-1）处理时,大针茅叶片氮含量较低,叶绿素含量和1,5-二磷酸核酮糖羧化/加氧酶的活性不高,光能利用效率低,导致光系统II出现过剩激发能,光合器官受到抑制,净光合速率相对较低。适量氮添加（5-10 g m^-2 a^-1）提高了大针茅叶片羧化系统和电子传递系统的氮分配,进而提高了1,5-二磷酸核酮糖羧化/加氧酶的活性以及电子传递速率,净光合速率增大。高氮（25 g m^-2 a^-1）处理时,叶片氮含量较高,但光合氮分配比例下降,降低了光合氮利用效率。大针茅光抑制程度增大,叶绿素含量、1,5-二磷酸核酮糖羧化/加氧酶的活性下降,不利于生物量积累。研究结果有助于进一步了解全球变化背景下草原生态系统优势种的生理响应机制,并为草原的可持续发展提供一定的理论依据。