不同遮荫下多脉青冈和金叶含笑幼苗叶片的气体交换日变化

Diurnal variation of leaf gas exchange in Cyclobalanopsis multinervis and Michelia foveolata seedlings under different shadings

运用生理生态研究方法,选取多脉青冈Cyclobalanopsis multinervis和金叶含笑Micheliafoveolata的幼苗为研究对象,在全光照、1层遮荫和2层遮荫3种不同遮荫处理下,对其叶片气体交换日变化进行了测试分析。结果表明:遮荫处理改变了多脉青冈和金叶含笑的叶片气体交换日变化曲线,表现为遮荫处理下多脉青冈的净光合速率在1 d之内明显降低;金叶含笑的净光合速率在中午前随遮荫程度的加大而下降,但11:00时1层遮荫处理下的净光合速率最高,中午以后全光照和1层遮荫处理下的净光合速率相差不大。遮荫处理同时明显降低了1 d之内叶片的蒸腾速率和气孔导度,细胞间隙CO2体积分数日变化与净光合速率的日变化基本相反。多脉青冈和金叶含笑的净光合速率在13:00左右出现了明显的降低,发生了光合“午休”现象。

leaf gas exchange of photosynthesis in Cyclobalanopsis studied by ecophysiological techniques under full light, one-layer muhinervis and Micheliafoveolata seedlings were shading and two-layer shading. The curves of leaf gas exchange diurnal variation in C. muhinervis and M. foveoha were changed by shading. Photosynthetic rate of C. multinervis decreased obviously during daytime. With the increasing of shading, photosynthetic rate of M. foveolta decreased before noon, its photosynthetic rate was the highest at 11：00 am under one layer shading Moreover there was no significant difference of photosynthetic rates under full light and two-layer shading treatments after noon. Transpiration rate and stomatal conductance were decreased obviously by shading during daytime, but photosynthetic diurnal variation of intercellular CO2 concentration was contrary to that of photosynthetic rate. Photosynthetic rates of C. muhinervis and M. foveolta decreased obviously at 1：00 pm, which led to ＇midday depression of photosynthetic rate＇. This study showed the diurnal variation of leaf gas exchange in C. muhinervis and M. foveolata seedlings under different shadings and provided the scientific foundations for taking measures of scientific planting and management. [ Ch, 9 fig. 12 ref. ]