【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。更多还原

【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.更多还原