豆科复叶和单叶树种的光合-水分关系分析

以豆科（Fabaceae）11个复叶树种和6个单叶树种为材料，测定他们的气孔导度、叶片水力导度、水势、相对含水量等指标，分析叶型对枝叶光合水分关系的影响。结果显示，复叶树种正午叶轴水势（-0.91 MPa）与单叶树种正午枝条水势（-0.88 MPa）间无显著差异，但正午枝条水势（-0.60 MPa）显著高于单叶树种。复叶树种正午气孔导度降低的百分比（55.3%）显著高于单叶树种（34.1%）。叶片、叶轴和枝条正午水势两两之间均显著正相关，但与正午气孔导度之间均不存在相关性。本研究中，17个树种的正午叶片水力导度与气孔导度间显著正相关（r=0.79，P<0.001），但他们与气孔导度降低百分比间呈负相关（r=-0.81，P<0.001），说明叶片导水率对日间气孔导度的维持具有重要作用。研究结果表明单叶和复叶树种在光合水分关系上存在明显差异，说明他们对环境条件具有不同的适应策略。

Analysis of photosynthesis-water relationship between simple- and compound-leafed leguminous trees

To investigate the influence of leaf form on the relationship between water and photosynthesis of leaves and branches, we measured the stomatal conductance, leaf water conductance, water potential, and relative water content of 11 compound-leafed species and six simple-leafed species in Fabaceae. Results showed no significant differences in midday water potential between leaf rachises (-0.91 MPa) of compound-leafed trees and branches of simple-leafed trees (-0.88 MPa). However, the midday water potential of the branches of compound-leafed trees (-0.60 MPa) was significantly higher than that of simple-leafed trees. The percent decrease in midday stomatal conductance of compound-leafed trees was significantly higher than that of simple-leafed trees (55.3% vs. 34.1%). We found significantly positive correlations between leaf and stem midday water potentials in all 17 species, and between the rachis and stem midday water potentials in the 11 compound-leafed species. There was no correlation between midday water potential of leaflets, leaf rachises, and branches and midday stomatal conductance. There was a significant positive correlation between leaf hydraulic conductance and midday stomatal conductance across the 17 species (r=0.79, P<0.001), and a significant negative correlation between leaf hydraulic conductance and percent decrease in midday stomatal conductance (r=-0.81, P<0.001), indicating the important role of leaf hydraulic conductance in maintaining diurnal stomatal conductance. There were significant differences in the photosynthesis-water relationship among simple-and compound-leafed tree species, reflecting their different adaptive strategies to environmental conditions.