西南喀斯特地区黄荆叶片光合作用日变化的研究

Diurnal variation of photosynthesis of Vitex negundo leaves in the Southwest Karst Region

选取桂林丫吉岩溶试验场优势植物黄荆(Vitex negundoL.)作为研究对象,对相同条件下黄荆叶片净光合速率(Pn)、气孔导度(Gs)、胞间二氧化碳浓度(C i)和蒸腾速率(Tr)等光合作用特性的日变化进行了比较研究。结果表明:净光合速率(Pn)的日变化呈不对称的"双峰型"曲线,具有明显的光合"午休"现象;气孔导度曲线总体呈下降趋势;胞间CO2浓度日变化表现出单峰曲线;蒸腾速率(Tr)日变化呈不对称的双峰曲线,与净光合速率日变化基本一致,但主峰较净光合速率Pn主峰滞后1 h,也出现了"午休"现象。

Taking Vitex negundo as an object of study in Yaji Karst Proving Ground in Guilin. We studied Vitex negundo leaves in the diurnal variation of photosynthesis： net photosynthesis （Pn）, stomatal conductance （Gs）, intercellular CO2 concentration （Ci）, and transpiration（Tr）. The result shows that Pn can be described as an unsymmetrical dual-peaked curve with an obvious midday depression of the photosynthetic efficiency; the diurnal variation of intercellular CO2 concentration （Ci） presents single-peaked curves; the increase of Ci at midday indicates that the midday depression of the photosynthetic efficiency was mainly influ- enced by the non-stomatal limited elements; and the curve of （Tr） is unsymmetrical and dual-peaked which is consistent with Pn. In a word, great differences of diurnal variation of photosynthesis are observed from the leaves which belong to different ages and different places of the same Vitex negundo.