PARALLEL TIME COURSES OF OXYGEN EVOLUTION AND CHLOROPHYLL FLUORESCENCE
PARALLEL TIME COURSES OF OXYGEN EVOLUTION AND CHLOROPHYLL FLUORESCENCE
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DOI：
10.1016/0005-2728(68)90063-7
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发表时间：
1968-01-01
期刊：
影响因子：
--
通讯作者：
RICE, G
中科院分区：
文献类型：
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作者：
BANNISTER, TT;RICE, G
在强光下，黑暗几分钟后，绿色藻类的荧光诱导曲线表现出以下特征：低初始电平O，在约15毫秒处的第一峰值P1，在约50毫秒处的最小值M1，持续约0.2至约1秒的高第二峰值P2，在约30秒处的最小值M2，在60至120秒处的第三峰值P3，并且在几分钟后达到稳态水平S。同时测得的释氧速率诱导曲线表明，在100毫秒以下达到最大值，当荧光处于高P2水平时，释氧速率为零，第一阶段a1为与荧光P2-M2下降互补的加速速率，第二阶段a2为与荧光M2-P3爬升平行的缓慢释氧速率上升。P1、M1和P2荧光水平显著提高。然而，稳态水平没有变化，从P2到S的荧光过程不再经过最小值，也没有表现出M2-P3的上升。此外，在光脉冲中，氧的释放量增加，a2相的氧释放速度更快，动力学与a1相相似。黑暗后和预光照后的荧光和氧诱导特征可以通过假设系统II单位的缓慢激活来解释。在黑暗之后，也许有一半的单位最初是活跃的，能够发出荧光。因此，P1、M1和P2水平以及尖峰中的O2量相对较低。在约30秒至约120秒的诱导过程中，最初无活性的非荧光单位缓慢转化为活性形式。M_2-P_3上升和α_2相O_2析出的平行加速是这种激活的表现。在预照明之后，所有的系统-II单元将被激活。结果表明，P1、M1和P2水平升高，M2-P3升高消失，O2释放速率加快，且与a1期的释放速率接近。野生型和System II突变体的M2-P3荧光升高，而System I突变体的M2-P3荧光没有升高。此外，对于单色预照明，708 nm在保持系统II单元的活性形式方面比650 nm有效约三倍。这些事实意味着系统I使系统II单位的缓慢激活敏感化。在黑暗中，失活的单位发生约4分钟的一半时间。总之，三种不同的激活似乎是诱导的基础。一个是由Joliotand发现的系统II的快速激活，解释了在最初的10-20毫秒期间荧光和O2释放活性的平行上升。第二个是暗步骤的激活，其允许系统II氧化剂的再生，并且表现在a1期期间P2-M2和O2演变期间荧光的互补过程中。第三个是系统II单位的缓慢激活，导致荧光（M2-P2）和O2释放（a2相）的平行上升。这三种激活似乎提供了对光合诱导的前2分钟的一般理解的基础。
In strong light, after several minutes darkness, fluorescence induction curves for green algae exhibit the following features: a low initial level O, a first peak P1at about 15 msec, a minimum M1at about 50 msec, a high second peak P2lasting from about 0.2 to about 1 sec, a minimum M2at about 30 sec, a third peak P3at 60 to 120 sec, and a steady-state level S reached after several minutes. Simultaneously measured induction curves of rate of O2evolution indicate a maximum reached in well under 100 msec, a zero rate while fluorescence is at the high P2level, a first phase a1of accelerating rate complementary to the P2-M2decline of fluorescence, and a slower second phase a2during which oxygen evolution rises in parallel with the M2-P3fluorescence climb.When strong light is given after a preillumination, the P1, M1, and P2fluorescence levels are substantially heightened. However, the steady-state level is unchanged, and the course of fluorescence from P2to S no longer passes through a minimum nor exhibits the M2-P3rise. In addition, the amount of oxygen evolved in the spike is increased, and the acceleration of O2evolution during the a2phase is faster and kinetically similar to that of the a1phase.The characteristics of fluorescence and O2induction, both after darkness and after preillumination, can be explained by assuming a slow activation of System-II units. After darkness, perhaps half of the units would be initially active and capable of fluorescence. As a result, the P1, M1, and P2levels, and the amount of O2in the spike, are relatively low. During the about 30th to about 120th sec of induction, the initially inactive, nonfluorescent units are slowly converted to the active form. The M2-P3rise and the parallel acceleration of O2evolution of the a2phase are manifestations of this activation. After preillumination, all System-II units would be active. In consequence, the P1, M1and P2levels are higher, the M2-P3rise is abolished, and the rate of O2evolution rises faster and more nearly continuously with that of the a1phase.The M2-P3fluorescence rise occurs in wild type and System II, but not System-I mutants, and in the presence, as well as the absence of 3-(3,4-dichlorophenyl)-1,1-dimethylurea. Furthermore, with monochromatic preilluminations, 708 nm is about three times more effective than 650 nm in maintaining the active form of System-II units. These facts imply that System I sensitizes the slow activation of System-II units. In darkness, inactivation of the units occurs with a half time of about 4 min.Altogether, three different activations appear to underly induction. One is the fast activation of System II discovered byJoliotand accounting for the parallel rises of fluorescence and O2-evolving activity during the first 10–20 msec. The second is the activation of a dark step which permits regeneration of System II oxidant, and which is manifested in the complementary courses of fluorescence during P2-M2and O2evolution during the a1phase. The third is the slow activation of System-II units underlying the parallel rises of fluorescence (M2-P2) and O2evolution (a2phase). These three activations appear to provide the basis for a general understanding of the first 2 min of photosynthetic induction.