Diurnal Dynamics of Photosynthetic Characteristics of Betula microphylla under Different Temperature and Air Humidity Applications

By a Li-6400 portable photosynthesis system,the diurnal dynamics of the photosynthetic characteristics of Betula microphylla was investigated under different temperature and air humidity(RH)conditions.The results indicated that the photosynthesis of B.microphylla leaf treatet with 20～35 ℃,RH 50% and 25～30 ℃,RH 60%,showed a single-peak curve diurnal change,and the appropriate temperature and humidity can enhance photosynthesis of B.microphyllaleaf.But high temperature and humidity(30～40 ℃,RH 70%)condition can inhibit the speed of photosynthesis,which might be due to the non-stomatal factors combined with stomatal closure.