“三大硬阔”叶片气体交换过程的时间动态

Temporal Dynamics in Leaf Gas Exchange Processes of “Three Hardwood Species”

水曲柳、胡桃楸和黄波罗是东北东部山区天然次生林的主要组成树种。采用红外气体交换分析仪，分别在叶片生长初期、中期和末期，同步测定了净光合速率（Ａ）、气孔导度（ＧＳ）、蒸腾速率（Ｅ）及其相关的外界环境因子的日变化。三大硬阔的Ａ和Ｅ的日变化格局随树种、生长季节和天气状况而表现为单峰、双峰和多峰曲线等三种类型。水曲柳、胡桃楸和黄波罗单位面积叶片的最大净光合速率（Ａｍａｘ）分别为１５１１、２１５４和２３０３μｍｏｌ·ｍ－２·ｓ－１；但测得的日平均净光合速率峰值（Ａｍｅａｎ）以胡桃楸最大，为１１０７μｍｏｌ·ｍ－２·ｓ－１，水曲柳和黄波罗分别为８５１和８６５μｍｏｌ·ｍ－２·ｓ－１。在所测定的日期中，三大硬阔的光合作用变化主要是由非气孔限制引起的。三个树种的蒸腾速率的差异及其变化均不大，平均Ｅｍｅａｎ为２０ｍｏｌ·ｍ－２·ｓ－１左右。

Fraxinus mandshurica, Juglans mandshurica and Phellodendron amurense are the major components of the natural secondary forests in northeast China. Diurnal changes in net photosynthetic rate (A), stomatal conductance (G S), transpiration rate (E) and related environmental factors, using IRGA, were measured in 3 different dates. The diurnal patterns of A and E of the three hardwood species showed three types, i.e. mono-peak, bi-peak and multi-peak curves, depending on species, growing season, and weather conditions. The maximum net photosynthetic rate (A max ) of F. mandshurica, J. mandshurica and P. amurense were 15.11, 21.54, and 23.03 μ mol·m -2 ·s -1 respectively; the measured maximum daily mean net photosynthetic rate (A mean ) were 8.51, 11.07 and 8.65 μ mol·m -2 ·s -1 respectively. The change in A was mainly caused by nonstomatal inhibition. The differences and change in transpiration rates were not significant, with a mean transpiration rate (E mean ) of 2.0 mol·m -2 ·s -1 or so.