The diurnal variations of net photosynthetic rate(Pn) of four different provenances of Zelkova schneideriana Hand-Mazz were conducted by using Li-6400 portable photosynthesis system under natural condition,the photoresponse curves(Pn-RPAR) and Pn-Ci curves were drawn.The results show that:(1) The diurnal variations of Pnof different provenances revealed different changing tendency,and the Huaihua provenance showed a single-peak curve,while the other three provenances all demonstrated double-peak curves,and ...