Effects of water and light environment on photosynthesis of trees distributed in temperate forest at different insertion levels

水光环境对不同插入水平温带森林树木光合作用的影响

• 批准号: 10640617
• 负责人: FURUKAWA Akio
• 金额: $ 1.54万
• 依托单位: Nara Women's University
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (C)
• 财政年份: 1998
• 资助国家: 日本
• 起止时间: 1998 至 2000
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-10640617/
• 关键词: Viburnum awabuki; Photosynthesis; Midday depression; Stomatal conductance; 温帯林; 樹冠; 稚樹

The diurnal changes in net photosynthetic rates, stomatal conductance and the environmental factors were determined in Viburnum awabuki K.Koch using a portable photosynthetic system (LI-COR, LI-6400). The rates of net photosynthesis thus obtained were plotted against PAR (Photosynthetically Active Radiation) and the forenoon photosynthetic rates were higher than the rates obtained in the afternoon. The tree height was ca.3 m, so the water supply from roots to leaves might not be limited, though the highest resistance for water supply is in the root surface. To confirm this hypothesis, we measured the photosynthetic rates of cut stems and got the results that photosynthetic rates were not reduced in the afternoon. If the reduction of net photosynthetic rates in the afternoon is caused by the stomatal closure by high water saturation deficit and/or lowered water potential of leaves, the enrichment of CO_2 concentration might overcome the deficiency of CO_2 supply to chloroplasts. Then, we measured the diurnal changes in net photosynthetic rates at 1500 μmol CO_2 mol^<-1>. The depression of photosynthetic rates in the afternoon was not observed but the rates were higher than the rates detected in the forenoon. These results suggest that the stomatal closure and the limitation of CO_2 supply to chloroplasts should be the main factor causing the depression of photosyntheis in the afternoon. Furthermore, by highering the CO_2 concentration inhibits the photorespiration rates and enhanced the photosynthetic rates while leaf temperature was high in the afternoon.

利用LI-6400型便携式光合作用测定系统，测定了珊瑚树叶片净光合速率、气孔导度及环境因子的日变化。由此获得的净光合速率对PAR（光合有效辐射）作图，上午的光合速率高于下午获得的速率。树高约3 m，根系向叶片的供水可能不受限制，但根表供水阻力最大。为了证实这一假设，我们测定了切茎的光合速率，结果表明，光合速率在下午没有降低。如果午后净光合速率的降低是由于叶片水分饱和亏缺和/或水势降低导致气孔关闭所致，则CO_2浓度的增加可能克服了叶绿体CO_2供应的不足。在1500 μ molCO_2·mol ~（-1）浓度下，测定了叶片净光合速率的日变化<-1>。光合速率在下午没有受到抑制，但下午的光合速率高于上午。这些结果表明，气孔关闭和叶绿体CO_2供应的限制是造成下午光合作用下降的主要原因。在午后叶温较高时，CO_2浓度的升高抑制了光呼吸速率，提高了光合速率。