Effect of Drought Stress on Photosynthetic Properties of Leaves of Osmanthus fragrans "Chenghongdangui"

Effects of drought stress on photosynthetic properties of 3-year potted Osmanthus fragrans "Chenghongdangui" seedlings were investigated.The seedlings were treated with different soil water regime at five levels.Using LI-6400 portable photosynthesis system,the net photosynthetic rate(Pn),stomatal conductance(Gs),intercellular CO2 concentrations(Ci) and transpiration rate(Tr) were measured on 7th、14th、21th、28th day after treatments,and the light response curves and the CO2 response curves of the net photosynthetic rate were measured on the 15th day after treatments.The results showed that soil moisture content had significant effect on the photosynthetic parameters of O.fragrans "Chenghongdangui".Increasing of drought stress could significantly reduce Pn,Gs,Ci and Tr,but enhance WUE.The test indicated that the plant could adapt to a wide range of high light intensity(photosynthetically active radiation being 1000 ~ 2000 μmol?m-2s-1),and had a high efficiency in transforming and using lower light intensity(photosynthetically active radiation being 0 ~ 400 μmol?m-2s-1).In addition,drought also had an obvious impact on the light compensation point(LCP),light saturation point(LSP),apparent quantum yield(AQY),the CO2 compensation point(CCP) and apparent carboxyl efficiency(ACE).In general,AQY,LSP and ACE decreased,but LCP and CCP increased with drought stress increasing.