珊瑚树阳生和阴生叶片光合特性和状态转换的比较

Comparison of Photosynthetic Characteristics and State Transitions Between Sun and Shade Leaves of Viburnum odoratissimum

珊瑚树阳生和阴生叶片是在不同光照环境中长期生长的 ,它们的光合特性有一些明显的差异。与阳生叶片相比 ,阴生叶片单位干重的叶绿素含量较多 ,类囊体膜垛叠程度较高 (即每个基粒的类囊体膜垛叠层数较多 ,基粒类囊体的直径较大 ) ,而叶绿素a/b比值、光合作用的饱和光强和最大净光合速率等较低。用弱红光诱导阳生和阴生叶片向状态 2转换时 ,叶绿素荧光Fm/Fo 和F685/F73 5先迅速下降再逐渐回升 ,这表明两种叶片都先后通过满溢和LHCⅡ转移调节激发能在PSⅡ和PSⅠ之间的分配 ,改善光能利用 ,但阳生叶片Fm/Fo 和F685/F73

After adapting to different light environment for a long period, sun and shade leaves have many significant differences in photosynthetic characteristics. Compared with those of sun leaves, the shade leaves have a higher chlorophyll content per unit dry weight (Table 1), a higher extent of thylakoid stacking (including more thylakoids per grana stack, and a larger diameter of the stacked granum) (Fig.1), but a lower ratio of chlorophyll a/b (Table 1) and F 685 / F 735 (Figs.4 and 5), saturated light intensity for photosynthesis and maximal net photosynthetic rate (Fig.2). In the transition to state 2 induced by weak red light pre illumination, the chlorophyll fluorescence parameters F m/ F o and F 685 / F 735 in both the sun and shade leaves decreased promptly and then increased a little (Figs.3 and 5). These results suggested that both excited energy spillover and the lateral migration of light harvesting chlorophyll a/b complex of photosytem II (LHC II) involved the redistribution of absorbed light energy between photosystems II and I (PS II and PS I) in the two kinds of leaf. However, the magnitude of the prompt decrease of F m/ F o and F 685 / F 735 in sun leaves was larger than that in shade leaves ( Figs.3 and 5).