摘要
本文研究了典型草原地带两个主要建群种,羊草和大针茅在没有土壤水分胁迫情况下的光合作用日进程,并分析了光合午间降低的原因。光合作用日进程为午前高峰型;午间,光合速率有所下降。光合午间降低的主要原因是大气湿度减小,引起叶片含水量和气孔传导率下降所致。午间温度和光强升高,导致光呼吸速率增大是次要原因。CO_2浓度降低和光合产物积累对光合午间降低也起一定作用。而生物节律与光合午间降低没有关系。
This paper deals with the characteristic of diurnal courses of pnoto-synthesis and the reasons of midday photosynthetic depression without lackof moisture in soil for two main community-forming species, A. chinenseand S. grandis in a typical steppe zone. The results of research show thatthe diurnal courses of photosynthesis of these two species are of the high-peak type before noon and their photosynthetic rate at midday decreasescertainly. The main reasons for the depressing photosynthesis are the de-crease of leaf water content and the stomatal conductance caused by thefall of atmospheric humidity. A secondary effect is the increment of lightrespiration resulting from the rise of air temperature and lightintensity in the midday period. The reduction of CO_2, concentration, andthe accumulation of photosynthetic product also contribute to photo-synthetic depression at midday. Biorhythm has no effect on photosyntheticdepression during the midday period.
关键词
光合作用
午间降低
羊草
大针茅
Photosynthetic depression during midday period
Atmospheric humidity
Water content of leaf
Stomatai conductance
