With the one year old seedlings of the double cross hybrid clones of white poplar as the experimental meaterials,the major physiological properties of the clones were analyzed under four water stress conditions.The result shows that under the condition of soil drought stress,photosynthesis ( Pn ),transpiration ( Tr ),stomatal conduces ( Gs ),intercellular CO 2 concentration ( Ci ),and difference of leaf temperature and air temperature ( Lt ) were all influenced significantly. The sensitivity ...