Heber U, Bukhov N G, Shuvalov V A, Kobayashi Y, Lange O L
Julius-von-Sachs-Institut, Universität Würzburg, D-97082 Würzburg, Germany.
J Exp Bot. 2001 Oct;52(363):1999-2006. doi: 10.1093/jexbot/52.363.1999.
Experimental work on the control of photosystem II in the photosynthetic apparatus of higher plants, mosses and lichens is reviewed on a background of current literature. Transmembrane proton transport during photoassimilatory and photorespiratory electron flows is considered insufficient for producing the intrathylakoid acidification necessary for control of photosystem II activity under excessive illumination. Oxygen reduction during the Mehler reaction is slow. Together with associated reactions (the water-water cycle), it poises the electron transport chain for coupled cyclic electron transport rather than acting as an efficient electron sink. Coupled electron transport not accompanied by ATP consumption in associated reactions provides the additional thylakoid acidification needed for the binding of zeaxanthin to a chlorophyll-containing thylakoid protein. This results in the formation of energy-dissipating traps in the antennae of photosystem II. Competition for energy capture decreases the activity of photosystem II. In hydrated mosses and lichens, but not in leaves of higher plants, protein protonation and zeaxanthin availability are fully sufficient for effective energy dissipation even when photosystem II reaction centres are open. In leaves, an additional light reaction is required, and energy dissipation occurs not only in the antennae but also in reaction centres. Loss of chlorophyll fluorescence during the drying of predarkened poikilohydric mosses and lichens indicates energy dissipation in the dry state which is unrelated to protonation and zeaxanthin availability. Excitation of photosystem II by sunlight is not destructive in these dry organisms, whereas photosystem II activity of dried leaves is rapidly lost under strong illumination.
在当前文献的背景下，综述了关于高等植物、苔藓和地衣光合装置中光系统II调控的实验工作。光同化和光呼吸电子流过程中的跨膜质子运输被认为不足以在光照过强时产生控制光系统II活性所需的类囊体腔内酸化。梅勒反应中的氧还原速度很慢。它与相关反应（水-水循环）一起，使电子传递链为耦合循环电子传递做好准备，而不是作为一个有效的电子汇。相关反应中不伴随ATP消耗的耦合电子传递提供了将玉米黄质与含叶绿素的类囊体蛋白结合所需的额外类囊体酸化。这导致在光系统II的天线中形成能量耗散陷阱。对能量捕获的竞争降低了光系统II的活性。在水合的苔藓和地衣中，即使光系统II反应中心开放，蛋白质质子化和玉米黄质可用性也足以实现有效的能量耗散，但在高等植物的叶子中并非如此。在叶子中，需要额外的光反应，能量耗散不仅发生在天线中，也发生在反应中心。预暗处理的变水苔藓和地衣干燥过程中叶绿素荧光的丧失表明在干燥状态下存在与质子化和玉米黄质可用性无关的能量耗散。在这些干燥的生物体中，阳光对光系统II的激发不会造成破坏，而干燥叶片的光系统II活性在强光下会迅速丧失。
