Abstract: The P-V Curve water Parameters(WPs) of 12 trees are measured in field condition during tree growth season in 1996. The pattern of Wps' seasonal changes and trees' drought resistance and relationship between them are studied. We present the definition of osmotic adjustment ability(OAA) of trees using the parameter Ψ_i^sat and Ψ_i^tlp under water stress. The seasonal change pattern of OAA and the relation to the climate factors are studied. The synthetic evaluation of the trees' drought resistance has been done by using the method of quantitative analysis. Meanwhile the order of trees' drought resistance has also been done.

Key words: Water parameter, Drought resistance, Quantitative analysis