摘 要 ：在上午10时和下午2时,荷树(Schima Superba Gardn and Champ)叶子的田间光合速率分别为8.43和6.82mg·m(-2)·s(-1)。生长在温室的荷树,在叶温26℃时,最大光合速率为10μmol·m(-2)·s(-1)。光饱和点为0.7mmol·m(-2)·s(-1),在光强0—0.16mmol·m(-2)·s(-1)时,光合量子产率0.037±0.004。气孔对水分传导率随入射量子通量增高而增大。光合作用最适叶温为25—27℃,这表明夏季气温较高会限制荷树的田间光合强度。光合速率随细胞间CO2浓度增高而加大。CO2补偿点为35μl·1(-1)。荷树叶片气体交换对叶子/空气水蒸汽压陡度变化敏感。当叶子/空气水蒸汽压陡度从12增至33毫巴·巴(-1)时,叶子传导率从0.12降至0.05mol·m(-2)·s(-1),光合速率从10降至6μmol·m(-2)·s(-1)。光合速率的降低可能是细胞间CO2浓度降低所致。荷树叶片气体交换对叶子/空气水蒸汽压陡度变化的反应敏感,它可能表明在热带或亚热带树种中亦相当普遍。
Abstract:Schima superba was grown in greenhouse. The rate of photosynthesis and leaf conductance appeared to change in parallel in response to change of light intensity in lower photon quantum flux intensity. A photosynthetic rate of 10 μmol m-2s-1 was measured at 24 to 26℃ and leaves were light saturated by 0.7mmol m-2s-1. The photosynthetic optimum temperature was 24 to 27℃ and photosynthesis decreased more rapidly at leaf temperature above 30℃, which suggests that photosynthesis under field condition may be limited by the high temperature observed in summer.The rate of photosynthesis increases with increasing intercellular CO2 concentration and the CO2 compensation point of photosynthesis was with a value 35μl·l-1.CO2 exchange in Schima superba was sensitive to change in leaf to air water vapor gradient. The rate of photosynthesis and leaf conductance decreased from 10 to 6.1μmol m-2s-1 and 0.12 to 0.05 mol m-2s-1, respectively. The decrease in photosynthesis rate was attributable to a decrease in intercellular CO2 concentration.These results showed that Schima superba is a tropical species with humidity sensitive stomates and this phenomenon is quite common in tropical plants.