Comparison of Photosynthetic Characteristics of Four Geographical Provenances of Stephania tetrandra in Summer

Taking 2-year-old Stephania tetrandra as material,the photosynthetic characteristics of four provenances of Stephania tetrandra,which were from Yongfeng(YF),Suichuan(SC),Leping(LP)and Gaoan(GA)were studied.Li-6400 portable photosynthesis analyzer were used to measure the photosynthetic characteristics of the provenances in summer.The results showed that the net photosynthetic rate(Pn),stomatal conductance(Gs),and transpiration rate(Tr)of the four provenances changed as bimodal peak curve;the intercellular CO2(Ci)appeared to vary in a W-shaped curve.The photosynthetic characteristics between the four provenances were different;the order of average Pn of them taken as YFSCLPGA.The average values of Pn,LUE,Gs,Tr and WUE had decreased substantially in the afternoon while the average values of Ci increased slightly.The results of correlation analysis showed that Tr,Gs,Ci were the main influencing factors on Pn;and that Tr closely related with Gs,Ci,PAR.