作 者 ：周玉梅,韩士杰,胡艳玲,张海森,郑俊强
期 刊 ：生态学报 2008年 28卷 1期 页码：423~429
Keywords:elevated CO2 concentration, photosynthesis, photosynthetic parameters, long-term,
摘 要 ：以开顶箱内经过6个生长季高浓度CO2处理的原位土壤种植的红松幼树为实验对象，研究了500μmolmol-1CO2对针叶光合作用及相应光合参数的影响。实地条件下测定了净光合速率（PN）对光合有效辐射（PAR）及胞间CO2浓度（Ci）的响应曲线，根据光合作用的生化模型，推算出了Rubisco活性或数量限制的最大羧化速率（VCmax）和光饱和条件下由RuBP再生能力限制的最大电子传递速率（Jmax），以及表观量子产量（AQY）和最大净光合速率（Pmax）等。500μmolmol-1CO2使红松针叶的VCmax降低了4%，Jmax和Jmax/VCmax比分别增加了27%和18%，均与对照差异不显著，所以红松针叶经过6个生长季高浓度CO2处理仍未发生光合驯化。在各自生长条件下测定的PN-PAR响应曲线表明，500μmolmol-1CO2使Pmax增加了94%，AQY增加了21%，Pmax增长高于AQY和Jmax的增加比例，说明500μmolmol-1CO2使红松针叶对光的利用效率增强。500μmolmol-1CO2下的最大气孔导度（gsmax）和最大蒸腾速率（Emax）与对照比增加了一倍，与Pmax增加的幅度接近。500μmol mol-1CO2下和对照条件下的Ci/Ca比均随环境CO2浓度（Ca）增加呈非线性下降趋势，在较低Ca处（Ca≤200μmol mol-1），500μmol mol-1CO2使Ci/Ca比下降了1%~7%，较高Ca处（Ca≥300μmol mol-1），500μmol mol-1CO2使Ci/Ca比增加了5%~20%。CO2浓度变化会改变Ci/Ca比，由于气孔的调节作用，Ci/Ca比最终还是要维持在一恒定范围，且气孔对较低的CO2浓度更敏感。
Abstract:Photosynthesis and photosynthetic parameters of Pinus koraiensis saplings were determined after these saplings have been exposed to 500 molmol-1CO2 for six growing seasons. The response curves of net photosynthetic rate (PN) versus photosynthetically active radiation (PAR) and intercellular CO2 concentration (Ci) were measured in situ. These response curves were then analysed using a biochemical model which described the limitations imposed by the amount and activity of ribulose-1,5-bisphosphate carboxylase/oxygenase (VCmax) and by the rate of ribulose-1,5-bisphosphate (RuBP) regeneration mediated by electron transport (Jmax). In addition, apparent quantum yield (AQY) and light-saturated photosynthetic rate (Pmax) were calculated. VCmax of needles under 500μmol mol-1CO2 decreased by 4% compared with that in the control chamber. Jmax and Jmax/VCmax ratio of plants grown at the elevated CO2 concentration were 27% and 18% greater than those in the control chamber, respectively, but the differences in Jmax and Jmax/VCmax between the two treatments were not significant. There was no evidence of photosynthetic acclimation for needles of Pinus koraiensis after six growing seasons’ exposure to 500μmol mol-1CO2. Pmax and AQY increased by 94% and 21% for plants grown at 500μmol mol-1CO2 according to PN-PAR response curves, respectively, compared with the plants in the control chamber. The proportionately greater increase in Pmax than AQY or Jmax indicates that saplings of Pinus koraiensis grown under 500μmol mol-1CO2 make more efficient use of light. Light-saturated stomatal conductance (gsmax) and transpiration rate (Emax) doubled for plants grown and measured at elevated CO2 concentration. The magnitudes of increase in gsmax and Emax were close to that in Pmax. Ci/Ca ratio declined non-linearly with increased CO2 concentration for plants grown at 500μmol mol-1CO2 and in the control chamber. Ci/Ca ratio decreased by 1% to 7% at low Ca (Ca≤200μmol mol-1), but increased by 5% to 20% at high Ca（Ca≥300μmol mol-1）for plants at elevated CO2. CO2 concentration could change Ci/Ca ratio, but Ci/Ca ratio ultimately remained at a constant range as a result of stomatal adjustment. The response of Ci/Ca ratio to Ca suggested that stomatal sensitivity to CO2 was greater at low CO2 concentration than at high CO2 concentration.
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