5种不同杨树光合指标日变化分析

对5种杨树中辽1号、辽宁杨、DM-9-18、小青杨和小叶杨的光合生理特性进行对比分析，结果表明：5种杨树日平均净光合速率排序是辽宁杨＞DM-9-18＞小叶杨＞中辽1号＞小青杨，小青杨净光合速率的整体水平低于其余4种杨树；中辽1号净光合速率日变化呈双峰型曲线，表现出明显的光合“午休”现象，主要是由气孔限制因素引起，其余4种杨树均为单峰型曲线；5种杨树在10：00—14：00，气孔导度和胞间CO2浓度降低，气孔限制是净光合速率降低的主要原因，而在14：00—18：00，气孔限制值减小，净光合速率下降主要受非气孔因素限制；5种杨树的净光合速率与蒸腾速率及气孔导度均呈显著或极显著正相关，与胞间CO2浓度均呈显著或极显著负相关，外界环境因子中光合有效辐射对净光合速率变化的影响最大，均达到极显著正相关。

Studies on Diurnal Variation of Photosynthesis on Five Species of Poplars

Photosynthetic physiological characteristics of Populus ×canadensis ‘zhongliao1’, PopulusבLiaoninensis’,DM-9-18, P.pseudo simonii and P.simonii were compared in this study. The results showed that：The order of daily average net photosynthetic rate from high to low was P.בLiaoninensis’,DM-9-18,P. simonii, Populus×canadensis‘zhongliao1’ and P. pseudo simonii. The P.pseudo simonii was the lowest in overall level of net photosynthetic rate. The diurnal course of Populus×canadensis‘zhongliao1’ had bimodal curve, showing obvious “midday depression” phenomenon, which mainly caused by stomatal limitation. The others were single peak curve. Stomatal conductance and intercellular CO2 concentration on five species of poplars reduced in the period from 10:00 to 14:00. Reduction of net photosynthetic rate was mainly due to stomatal limitation. Net photosynthetic rate decreased mainly due to non stomatal limitation from 14：00 to 18：00. Net photosynthetic rate on five species of poplars had significantly and extremely significantly positive correlation with transpiration rate and stomatal conductance.PAR of environmental factors had great influence upon on net photosynthesis rate, and showed significant positive correlation.