| With the help of the method of a pot-cultivation experiment and the reference of different soil content with 70%～75%WHC(CK), 55%～60%WHC(LD), 40%～45%WHC(MD), 25%～30%WHC(VD) and with FMS-2 and Li-6400 photosynthetic apparatus, choosing seedling leaves of Pugionium cornutum(L.) Gaertn as the experimental materials, this paper studies the change laws of hlorophyll fluorescence parameters of Pugionium cornutum(L.) Gaertn under the drought stress, and the effects of drought stress on its photosynthetic index. The purpose of this paper is to reveal the mechanism of Pugionium cornutum(L.) Gaertn dealing with the drought stress, and to illustrate its drought resistance. The results showed that: (1) With intensifying drought stress, by contrast, the content of Pugionium cornutum leaf chlorophyll a, chlorophyll b in P. cornutum(L.) Gaertn decreased by 1.30%～7.04% and 19.47%～42.37% respectively, carotene content by 2.06%～9.88%; the value of chlorophyll a/b and Car/Chl increased by 33.49%～74.27% and 1.33%～15.73% respectively. (2) With intensifying the drought stress, there were distinct decrease trends of the net photosynthetic rate(Pn), transpiration rate(Tr), stomatal conductance(Gs) and water use efficiency(WUE) of P. cornutum(L.) Gaertn leaves, and the carbon dioxide concentration decrease at first and then increase and the stomatal limitation(Ls) decrease, which showed that Pn decrease of P. cornutum(L.) Gaertn leaves under light stress was mainly induced by stomatal factors, and Pn decrease under moderate and severe stress was mainly induced by non-stomatal factors. (3) Under drought stress, there were decrease trends of Fv/Fm, Fv/Fo,ΦPSⅡ, qP, ETR of Pugionium cornutum(L.) Gaertn leaf, and increase trends of qN. |