干旱胁迫对杨树光合生理指标的影响

采用PEG模拟干旱胁迫的方法，利用气体交换法和叶绿素荧光技术，研究了干旱胁迫下小青杨（Populus pseudo-simonii）的光合生理变化.结果表明,干旱胁迫初期，小青杨的净光合速率(P_n)、蒸腾速率(T_r)、气孔导度(g_s)和胞间CO₂浓度(C_i)值均随干旱胁迫增强而下降，杨树P_n的下降主要是由于g_s下降引起的；干旱胁迫后期,C_i值逐渐升高，非气孔限制成为光合作用的主要限制因子.干旱胁迫后期,PSⅡ原初光能转化效率(F_v/F_m)和PSⅡ潜在活性(F_v/F_o)明显下降，光抑制增强，光合电子传递受阻.POD酶的活性在胁迫初期升高，后期降低，说明干旱胁迫初期对保护系统酶活性升高有诱导作用，随着胁迫时间的延长，F_v/F_m和F_v/F_o降低，活性氧清除酶活性下降，活性氧代谢的平衡被打破，导致光合器官的伤害.由此表明,干旱胁迫后期P_n的降低与PSⅡ荧光参数及POD酶活性下降有关.

Effects of drought stress on photosynthesis physiology of Populus pseudo-simonii

In this paper, the effects of drought stress simulated by PEG on the photosynthesis of Populus pseudo-simonii were monitored by gas exchange and chlorophyll fluorescence techniques. The results showed that in the early phase of drought stress, net photosynthetic rate (P(n)), transpiration rate (T(r)), stomata conductance (g(s)) , and intercellular CO2 concentration (C(i)) decreased with increasing stress, and the decrease of P(n) was mainly related to the decreased g(s). In the late phase, C(i) increased gradually, while F(v)/F(m) and F(v)/F(o) decreased significantly. POD activity increased in the early phase, but decreased in the late phase. All of these indicated that in the early phase of drought stress, stomata closure was the main factor limiting P. pseudo-simonii photosynthesis, while in the late phase, the main limiting factor was non-stomatal. A short period of drought stress induced the increase of protective enzyme activity, but a longer exposure to the stress resulted in the decrease of PS II efficiency and POD activity.