Photosynthesis characteristics of rare and endangered plant Hopea chinensis

The photosynthetic characteristics of rare and endangered plant Hopea chinensis with the Li-6400 portable photosynthesis system on clear days in the first ten days of August 2007.The results showed that the light saturation and compensation efficiency of H.chinensis were about 1 366.67 and 5.62 μmol·m-2·s-1.The curve of diurnal variations of photosynthetic rate(Pn) had two peaks,and changed positively with the variations of transpiration rate(Tr) and stomatal conductance(Gs),but negatively with internal CO2 concentration(Ci).The mid-depress of Pn was principally caused by environment factors.Correlation analysis among photosynthetic parameters showed that photosynthetically active radiation(PAR) were the primary direct factors affecting Pn,Tr,that light deficiency and low water use efficiency(WUE) was the main reason resulting in the plant grew slowly.