Analysis on Photosynthesis Rate and Transpiration Rate of Alnus crematogyme

Using Li-6400 portable photosynthesis system,the photosynthesis rate,transpiration rate and the growth of four Alnus crematogyme varieties were measured from April to October,2007.The results showed as following:(1) as far as net photosynthesis rate(Pn) and transpiration rate(Tr) were concerned,there were highly significant differences in different varieties,months and crown positions.While water use efficiency(WUE) only showed highly significant difference in different months.(2) Pn and Tr of these varieties showed similar changing trend,and the order is June April July August November September October.(3) Pn of the upper and lower crown showed double-peak curves,in which the peak value occurred in 12:00 and 15:00,respectively.And Pn of the lower crown was lower 23.38%～36.60% than that of the upper one.(4) There was highly significant difference among different varieties in Chlorophyll content.(5) Pn showed significant positive correlation to the biomass.This indicated that Pn could be used as important index for early selection of Alnus crematogym.