Abstract: Photosynthesis,photorespiration and carbon dioxode compensation point of six seed sources in two-year-old seedlings and the effects of water potential of PEG substrate from 16 seed sources on germination have been studied. Net photosynthetic rate showed significant difference in six seed sources and biomass is closely correlated with green tissue weight and net photo synthetic rate. Significant reduction of germination percentage and rate of germination were already observed at -2 bars,the behaviour of sixteen provenances under water stress was differentiated:the seed sources from arid region have lower reduction of germination percentage and rate of germination than other seed sources.These patterns were believed to have resulted from adaption to environmental factors.