Photosynthesis characteristics of Juglans mandshurica Maxim in Taiyue Mountain region,Shanxi Province.
Ma Qinyan;Lin Chen;Han Hairong; Chen Xialin; Cao Wenqiang;Wang Zhizhong;Wang Zhanqin;Zhang Baoxiang.School of Resources and Environment, Beijing For. Univ.,100083,P.R.China.
By measuring the photosynthesis rate of Juglans mandshurica Maxim under nature and controlled conditions by Li 6400 portable photosynthesis system as well as logging the photosynthesis active radiation (PAR), CO 2 concentration, air temperature,leaf temperature etc. at the same time, it is showed that: ①the diurnal variation of photosynthesis rate is a midday depression pattern,the two peaks have nearly the same height,the peak occurred in morning lasts longer than the afternoon one.The stomatal conductance is strongly related to photosynthesis,and it changes the intercellar CO 2 concentration (Ci) and transpiration rate to some degree. ②Control the PAR at low level (0～50 μmol/(m 2·s),the photosynthesis rate will drop with the increasing of the CO 2 concentration. When the PAR is higher than 50 μmol/(m 2·s), the photosynthesis rate CO 2 concentration curve is a parabola,the peak is the CO 2 concentration saturation point (CSP) and the CSPs increased with the PARs.When the PAR changes between 0 and 1 200μmol/(m 2·s), the stomatal conductance keeps same change trend with PAR and opposite trend with CO 2 concentration.When the PAR is more than 1 200μmol/(m 2·s). the stomatal conductance reduces with the increase of both the PAR and CO 2 concentration. The transpiration rate changes with the stomatal conductance all the time.