The Research On The Photosynthesis And Water Eco-physiological Characteristics Of Platycladus Orientalis, Juniperus Rigida And Populus Alba Var.

The eco-physiological characteristics of drought endurance of Platycladus orientalis (Linn.) Franco [Biota orientalis (Linn.) Endl] , Juniperus rigida Sieb.et Zucc . and Populus alba var. pyramidalis Bunge [P.bolleana Lauche] were studied under different climatic regions and leaf water condition. The below showed the results.1 The research on the effect of the water characteristics of trees under water stree showed that the capability of absorbing water of trees under initial loss turgor state was not affected by lost water. That means the capability of absorbing water of trees would decline when the water deficit of trees was bigger than that of initial loss turgor point. The osmotic potentials at the initial loss turgor may be regarded as a critical index of the normal life activities. When the water condition of trees is equal to the osmotic potentials at the initial loss turgor, they can be on normal life activity by ameliorating the water condition of environment.2 The relationship between morning leaf water potential of little trees and soil moisture content showed that when soil moisture content was higher than"critical value", morning leaf water potential hardly was affected by the transformation of soil moisture content. When soil moisture content was lower than"critical value", the minuscule transformation of soil moisture content would lead to the big transformation of morning leaf water potential. It can know if soil moisture content is congruence by morning leaf water potential.3 The research on the relationship between photosynthetic rate , transpiration rate and the leaf water potential under the different water condition on Juniperus rigida Sieb.et Zucc. and Populus alba var. pyramidalis Bunge [P.bolleana Lauche] showed that the relative total photosynthetic rate declined with the increment of water deficit of trees. The transpiration of trees was mainly cuticle transformation under initial loss turgor point. The dimensions of cuticle transformation is an index of the water compatibility of trees. If it is small, the capability of preserving water of trees is big. And the capability of resisting water intimidation of trees is big, too.