东北红豆杉枝叶对不同CO2浓度的光合生理响应

Photosynthetic Physiological Response of Leaves and Shoots of Taxus cuspidata to Instantaneous Changes of CO2 Concentrations

利用LI-COR 6400测定了不同CO2浓度条件下的东北红豆杉净光合速率（PN）、蒸腾速率（E）、气孔导度（Cond）、胞间CO2浓度（Ci）及叶面饱和蒸气压亏缺（VPD）．结果表明：1a生枝和2a生枝条叶片的PN及E均随CO2浓度升高而增大．但PN增加幅度较大，E增加幅度较小；在高CO2浓度（物质的量比为1400×10^-6）争件下。1a生枝叶片最大PN（6．95μmol／（m^2·s））大于2a生枝（6．87μmol／（m^2·s））．1a生枝的E略大于2a生枝，但差异性不大；1a生枝与2a生枝水分利用效率（WUE=PN／E）均随CO2浓度升高而增大，1a生枝WUE略高于2a生枝，但差异未达到显著水平．可见，光合速率的显著增加是导致东北红豆杉水分利用效率随CO2浓度升高而增加的主要影响因素．

Net photosynthetic rate（PN）, transpiration rate（E）, stomatal conductance（ Cond ）, intercellular CO2 concentration（Ci）, vapor pressure deficit at the leaf surface（VPD） and water use efficiency（ WUE = PN/E） of Taxus cuspidata leaves were investigated by Li-COR 6 400 portable photosynthesis system under a series of CO2 concentrations. For the annual shoot and the biennial shoot, both PN and E increased with CO2 concentration increasing, but the increase in PN was larger than that in E. The maximal PN of the annual shoots （ 6.95/amol/（m2.s） ） was larger than that of the biennial shoots （6.87 μtmol/（m^2·s） ） at elevated CO2 concentration of 1 400×10^-6, E of the annual shoot was larger than that of the biennial shoot, but the increment of E of the annual shoot in response to increasing in CO2 enrichment was not significantly higher than that of the biennial shoot. Under elevated CO2 concentrations, WUE values for two types of shoots were both increased. The increase in WUE was primarily due to an increase in PN and not to a decrease in E.