为探讨CO2浓度升高对叶片光能转换效率和光合固碳能力的影响,以亚热带地区阔叶林代表树种苦槠〔Castanopsis sclerophylla (Lindl.) Schottky〕、青冈(Quercus glauca Thunb.)和乌桕〔Triadica sebifera (Linn.) Small〕为研究对象,在生长季对3种树种进行4个CO2浓度短期处理,同步测量叶片气体交换和叶绿素荧光参数,并采用直角双曲线修正模型和Farquhar-von Caemmerer-Berry(FvCB)模型拟合光合生理参数。结果表明:在不同CO2浓度下,3种树种叶片的净光合速率、气孔导度及PSⅡ电子传递速率随着光合有效辐射的增加逐步升高,且增幅逐渐变缓；而胞间CO2浓度和Rubisco羧化位点CO2浓度则逐渐降低并趋于稳定。总体上看,CO2浓度升高明显提高了3种树种叶片的净光合速率、胞间CO2浓度、初始量子效率、最大净光合速率、最大电子传递速率和Rubisco羧化位点CO2浓度,明显降低了气孔导度、叶肉导度和暗呼吸速率。综上所述,随着CO2浓度的升高,3种典型亚热带树种通过调节多个光合相关参数,明显提高了光合效率和碳同化潜力,展现出较强的适应潜力。

To explore the effects of elevated CO2 concentration on leaf light energy conversion efficiency and photosynthetic carbon fixation capacity, three representative tree species of broad-leaved forest in subtropical area, namely Castanopsis sclerophylla (Lindl.) Schottky, Quercus glauca Thunb., and Triadica sebifera (Linn.) Small, were taken as research objects, three tree species were subjected to four short-term CO2 concentration treatments during the growing season. Simultaneous measurements of gas exchange and chlorophyll fluorescence parameters in leaves were conducted, and the photosynthetic physiological parameters were fitted by using the modified rectangular hyperbola model and Farquhar-von Caemmerer-Berry (FvCB) model. The results show that under different CO2 concentrations, the net photosynthetic rate, stomatal conductance, and PSⅡ electron transport rate in leaves of three tree species gradually increase with the increase of photosynthetically active radiation, and the increments gradually slow down; intercellular CO2 concentration and CO2 concentration at Rubisco carboxylation site gradually decrease and tend to be stable. Overall, elevated CO2 concentration evidently enhances the net photosynthetic rate, intercellular CO2 concentration, initial quantum efficiency, maximum net photosynthetic rate, maximum electron transport rate, and CO2 concentration at Rubisco carboxylation site in leaves of three tree species, but evidently reduces stomatal conductance, mesophyll conductance, and dark respiration rate. In conclusion, with the increase of CO2 concentrations, three typical subtropical tree species obviously enhance photosynthetic efficiency and carbon assimilation potential by regulating multiple photosynthetically related parameters, exhibiting strong adaptive potential.