Abstract: On the basis of the calculation models of crop water deficit index (CWDI) and canopy net photosynthesis rate (P_n), field observation items were chosen according to the parameters used in models. Comparisons of the conditions of water deficit,stomata activities,net photosynthesis rate and matter production were made between two typical experiment plots, one plot was well watered while the other was never watered artificially. Results indicated that: (1) Stomata activity was the key link relating to water deficit and net photosynthesis. The stomata under dry treatment responded to water deficit more sensitively. Increase of stomata resistance caused by water deficit could markedly reduce net photosynthesis rate . (2) There was a positive linear correlation between the crop water deficit index (CWDI) and the crop hunger index (CHI). According to this, the influenced degree of net photosynthesis rate can be estimated. (3) Water deficit influenced on crop photosynthesis frequently and complexly. The final results of water deficit was to obviously reduce the leaf area, number of stem (or spike) and economic yield of the wheat.

Key words: ecological stoichiometry, nitrogen, phosphorus, potassium, ecosystem restoration, arid-hot valley in Jinsha River, Southwest China.