Ley A C, Babcock G T, Sauer K
Biochim Biophys Acta. 1975 May 15;387(2):379-87. doi: 10.1016/0005-2728(75)90117-6.
Patterns of oxygen evolution in flashing light for the glue-green alga Anacystis nidulans are compared with those for broken spinach chloroplasts and whole cells of the green alga Chlorella pyrenoidosa. The oscillations of oxygen yield with flash number that occur in both Anacystis and Chlorella, display a greater degree of damping than do those of isolated spinach chloroplasts. The increase in damping results from a two- to threefold increase in the fraction (alpha) of reaction centers "missed" by a flash. The increase in alpha cannot be explained by non-saturing flash intensities or by the dark reduction of the oxidized intermediates formed by the flash. Anaerobic conditions markedly increase alpha in Anacystis and Chlorella but have no effect on alpha in broken spinach chloroplasts. The results signify that the mechanism of charge separation and water oxidation involved in all three orgainsms is the same, but that the pool of secondary electron acceptors between Photosystem II and Photosystem I is more reduced in the dark, in the algal cells, than in the isolated spinach chloroplasts. Oxygen evolution in flashing light for Anacystis and Chlorella show light saturation curves for the oxygen yield of the third flash (Y3) that differ markedly from those of the steady-state flashes(YS). In experiments in which all flashes are uniformly attenuated, Y3 requires nearly twice as much light as YS to reach half-saturation. Under these conditions Y3 has a sigmoidal dependence on intensity, while that of YS is hyperbolic. These differences depend on the number of flashes attenuated. When any one of the first three flashes is attenuated, the variation of Y3 with intensity resembles that of YS. When two of the first three flashes are attenuated, Y3 is intermediate in shape between the two extremes. A quantitative interpretation of these results based on the model of Kok et al. (Kik, B., Forbush, B.and McGloin, M. (1970) Photochem. Photobiol. 14, 307-321) fits the experimental data.
将蓝绿藻集胞藻6803在闪光下的放氧模式与破碎的菠菜叶绿体以及绿藻蛋白核小球藻的完整细胞的放氧模式进行了比较。集胞藻和小球藻中随着闪光次数出现的氧气产量振荡，相较于分离的菠菜叶绿体，显示出更大程度的衰减。衰减的增加源于闪光“错过”的反应中心比例（α）增加了两到三倍。α的增加无法用不饱和闪光强度或闪光形成的氧化中间体的暗还原作用来解释。厌氧条件显著增加了集胞藻和小球藻中的α，但对破碎的菠菜叶绿体中的α没有影响。结果表明，这三种生物体中涉及的电荷分离和水氧化机制是相同的，但在黑暗中，藻类细胞中光系统II和光系统I之间的次级电子受体池比分离的菠菜叶绿体中还原程度更高。集胞藻和小球藻在闪光下的放氧显示出第三次闪光（Y3）的氧气产量的光饱和曲线与稳态闪光（YS）的光饱和曲线明显不同。在所有闪光都均匀衰减的实验中，Y3达到半饱和所需的光量几乎是YS的两倍。在这些条件下，Y3对强度呈S形依赖关系，而YS则呈双曲线依赖关系。这些差异取决于衰减的闪光次数。当前三次闪光中的任何一次被衰减时，Y3随强度的变化类似于YS。当前三次闪光中的两次被衰减时，Y3的形状介于两个极端之间。基于Kok等人（Kok, B., Forbush, B.和McGloin, M. (1970) Photochem. Photobiol. 14, 307 - 321）的模型对这些结果进行的定量解释符合实验数据。
