小麦叶片的状态转换涉及PSⅡ向PSⅠ激发能满溢的变化

The Involvement of Change in Excitation Energy Spillover from PS Ⅱ to PS Ⅰ During State Transitions in Wheat Leaves

叶片照远红光后，其叶绿素荧先参数Fm／Fo和两个光系统低温荧光产量比值F685／F735升高，照红先后，其Fm／Fo和F685／F735降低；在照远红光或红先过程中，与F685／F735的变化相比，Fm／Fo的变化幅度在较短的时间内达到最大；NaF预处理的叶片经远红光照射时，其Fm／Fo和F685／F735不增加；DCMU预处理的叶片经红光照射时，其Fm／Fo和F685／F735降低的幅度比对照小。这些结果表明，小麦叶片状态转换过程中两个先系统间能量分配的变化至少部分地与激发能满溢变化有关。这种满溢的变化与捕光色素蛋白复合体LHCⅡ的磷酸化相联，并且，与光吸收截面变化相比，满溢的变化是对两个光系统不平衡光吸收的较快响应。

The red light-or far red light induced chances in chlorophyll fluorescence Parameters and fluorescence spectrum at low temperature were oborved in wheat leaves to investigate whether the change in excitahon energy distribution between the two photosystems during state transihons involves the change in excitahon energy spillover from PS Ⅱ to PS Ⅰ. The chlorophyll fluorescence Parameter, Fm/Fo, and the raho of fluorescence yield of the two Photosysterns at low temperatUre, F685/F735, increased when leaves were expoSured to light I (far red light), while they decrease when leaves were exPOSured to light H (red light, Fial. 1-3). During illundnahon by light I or light Ⅱ, the chance in Fm/Fo attained to a maximum extent in a shorter bine as compared with the chance in F685/F735 (FigS. 2, 3). In the leaves fed with NaF through its cut end, Fm/FO and F685/F735 did not increase on exposure to light I (Fig. 4). The extent of decrease of Fm/Fo and F685/F735 in the leaves fed with DCMU also through the cut end of leaf was less than that in control without feeding of DCMU on exposure to light n (Fig. 5).arsed on the results above, the following conclusions are made: a) the change in excitahon energy distribuhon betWeen the tWO photosystems during Salts transihons is, at least panly, related to chance in excitahon energy spillover from PS n tO PS I; b) the chance in the spillover is associated with phOSPhorylahon of LHC E, and it is a quicker response to the inbalant light aborphon of the two Photosystems as compared with the change in light absorption cross-section.