Diurnal Course of Photosynthetic Characteristics of Pinus yunnanensis and Its Correlation with Leaf Surface Micro-meteorological Factors

Diurnal changes of photosynthesis of Pinus yunnanensis and its influencing factors were studied in dry season.The results indicated that in the dry season,the diurnal course of photosynthesis of P.yunnanensis occurred regularly with the environmental factors change.The curve of net photosynthetic rate(Pn) and transpiration rate(Tr) had a diurnal change with one-peak curve,the peak of Pn occurred at 14:00 and the peak of Tr appeared at 15:00.There was no midday depression of photosynthesis.The different meteorological factors influencing the photosynthesis were different.The photosynthetic active radiation(PAR) was the ecological factor directly effecting on the Pn and stomatal conductance(Cond) of P.yunnanensis,the main factors affecting Tr were temperature leaf(Tl) and CO2.The course of air humidity on the dry season were lower,and its effects on photosynthesis was not significant,which showes that the P.yunnanensis has a strong physiological adaptability on dry season.