Abstract: Plant’s ability to synthesize and store carbohydrate in terrestrial environment and the tolerance mechanism to flooding are important theoretical basis for vegetation restoration and reconstruction of hydro-fluctuation belt. Cynodon dactylon is one of the adaptive plants of hydrofluctuation belt of Three Gorges Reservoir. In order to understand the photosynthetic physiology of C. dactylon after flooding, the photosynthetic physiology of C. dactylon was measured under deep water (22-27 m), shallow water (2-7 m) and nonflooded conditions along an elevation gradient in Three Gorges Reservoir region. The results showed that (1) the net photosynthetic rates (P_n) of C. dactylon growing in deep water and shallow water were higher than that in nonflooded area, and P_n of C. dactylon growing in shallow water was the highest. (2) The P_n, apparent light use efficiency and apparent CO₂ use efficiency increased with the time extension of C. dactylon in terrestrial environment, indicating that the ability to synthesize and store carbohydrate of C. dactylon was enhanced after flooding. (3) The maximum photosynthetic rate and apparent quantum yield of C. dactylon growing in deep water and shallow water were higher than that growing in nonflooded area, while light compensation point significantly decreased, which suggested that the ability of C. dactylon to use low light improved. (4) P_n of C. dactylon was affected by the combination of both stomatal and nonstomatal factors and the flooding had a stimulating effect on C. dactylon photosynthetic potential. The positive selfadjustment ability and the photosynthetic compensation mechanism of C. dactylon after flooding and drought stress may be important reasons for its adaptation to floodingdrying habitat changes in hydrofluctuation belt of Three Gorges Reservoir.

Key words: resource, sustainable development, metabolism