Abstract: Growth,leaf water potential,stomatal conductance,leaf photosynthesis(photosynthetic light response curve),and contents of flavonol glycoside,terpene lactone,starch and soluble sugar were investigated in saplings of two-year-old Ginkgo biloba subjected to drought,high night temperature(30 ℃)and drought*high night temperature,in order to determine effects of drought,high temperature and their interaction on these parameters.The results show that compared to saplings free from drought and high temperature in CK,the saplings under high temperature decreased in maximum net photosynthetic rate,leaf water potential and root/shoot ratio,but increased in stomatal conductance and light compensation point,and changes in light saturation point,flavonol glycoside and terpene lactone were not significant.Saplings subjected to drought got lower in maximum net photosynthetic rate,stomatal conductance and leaf water potential,but higher in light compensation,and remained almost unchanged in root/shoot ratio,apparent quantum yield and light saturation point.Under the interaction of high temperature and drought,the saplings rose in light compensation point and dark respiration rate,but fell markedly in light saturation point,and contents of flavonol glycoside and terpene lactone.Although there was no significant change in root/shoot ratio,the total dry weight per plant decreased.The findings suggest that drought and high temperature not only decreased the adaptability to light,light use efficiency,and stomatal conductance of the saplings,but increased dark respiration rate,thus resulting in inhibited growth.High temperature had greater impact on secondary metabolites than drought.

Key words: Ginkgo biloba, high temperature, drought, photosynthesis, growth, flavonol glycoside, terpene lactone