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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CO_2浓度增高而加大。CO_2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CO_2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。
At 10 a.m. and 2 p.m., the field photosynthetic rate of leaves of Schima superba Gardn and Champ were 8.43 and 6.82 mg · m -2 · s -1, respectively. When the leaf temperature was 26 ℃, the maximum photosynthetic rate was 10μmol · m ~ (-2) · s -1. The light saturation point was 0.7 mmol · m -2 s -1, and the photosynthetic quantum yield was 0.037 ± (-1) at the light intensity of 0-0.16 mmol · m -2 · s -1. 0.004. Stomatal conductance increases with incident quantum flux. The optimum leaf temperature for photosynthesis is 25-27 ℃, which indicates that the higher summer temperatures will limit the field photosynthesis of the tree. The photosynthetic rate increased with the increase of intercellular CO2 concentration. The CO2 compensation point is 35μl · 1 ~ (-1). Leaf gas exchange is sensitive to leaf / air steepness changes in water vapor pressure. When leaf / air steepness increased from 12 to 33 mbar · bar -1, leaf conductivity decreased from 0.12 to 0.05 mol · m -2 · s -1, photosynthesis The rate decreased from 10 to 6 μmol · m -2 · s -1. The decrease of photosynthetic rate may be caused by the decrease of intercellular CO 2 concentration. Leaf gas exchange is sensitive to changes in the leaf / air steepness of the water vapor pressure and may indicate that it is quite common in tropical or subtropical species.