相对湿度对黄瓜叶片光合特性的影响

以黄瓜“津优1号”为试材，于2011年4月在南京信息工程大学进行人工环境控制试验，设计8个相对湿度梯度，用LI 6400进行光合参数的测定，系统研究不同相对湿度处理对黄瓜叶片光合特性的影响。结果表明：黄瓜叶片的净光合速率和胞间CO2浓度随着相对湿度的减小而降低；气孔导度、蒸腾速率和叶片的水分利用效率在相对湿度为75%时达到最大；而气孔限制值在相对湿度为75%时降到最低；黄瓜叶片最大光合作用速率（Pmax）与空气相对湿度呈指数关系：Pmax=22375e189085fRH；随空气相对湿度的减小，黄瓜叶片的表观量子效率、光饱和点均降低，而光补偿点增加；相关分析表明，净光合速率与叶面水汽压差呈负相关，而与气孔导度、胞间CO2浓度、相对湿度、蒸腾速率均呈正相关，且相关性均达到极显著水平。

Effects of Different Relative Humidity on Cucumber Leaf Photosynthesis Characteristic

In order to study the effects of different relative humidity on the leaf photosynthesis characteristic in a greenhouse, an experiment was conducted with eight models of relative humidity on cucumber Jinyou 1, which was chosen as the trail material. The photosynthetic physiology parameters of cucumber leaves were measured with the LI 6400 portable photosynthesis system. The results show that the net photosynthetic rate and intercellular CO2 concentration reduced with the decreasing relative humidity; the stomata conductance, transpiration rate, and the leaf water use efficiency reached the maximum when relative humidity was 75%, while the stomatal limitation value reached the minimum when relative humidity was 75%. The relationship of maximum photosynthetic rate and air relative humidity conforms to the exponent equation： 〖WTBX〗P〖WTBZ〗max=223753e189085fRH. Through the light response curves, it can be learned that the apparent photosynthetic quantum yield and light saturation decrease with deceasing relative humidity, and the light compensation point increases with the decreasing relative humidity. In addition, the correlative analysis indicates that a negative correlation between the vapor pressure deficit of leaves and relative humidity, and a positive correlation exists between intercellular CO2 concentration, stomata conductance transpiration rate, relative humidity, and photosynthetic rate.