Division of Biological Sciences, State University of New York, Stony Brook, New York 11790.
Plant Physiol. 1973 Feb;51(2):250-8. doi: 10.1104/pp.51.2.250.
Synchronous cell division in Euglena gracilis (strain Z) was obtained in 24-hour light cycles consisting of 10 hours of light and 14 hours of darkness; cell division was restricted to the dark period. Photosynthetic capacity was found to vary in a cyclic manner during the cell cycle, reaching a peak 2 hours before the onset of darkness. Light reactions were investigated during the cell cycle to determine what role they played in the control of the observed rhythmic changes in capacity. Light-saturation curves showed no major change in the light-limited region. No fluctuations were found in Hill reaction activity or photoreduction of methyl red during the cell cycle. These results imply that the reactions comprising photosystems I and II do not generate the capacity rhythm.Some of the photosynthetic dark reactions were also followed during the cell cycle in an attempt to determine their possible role in the control of the rhythm of photosynthetic capacity. The activity of ribulose-1, 5-diphosphate carboxylase showed no correlation with the rhythm. On the other hand, the activity of glyceraldehyde-3-phosphate dehydrogenase was found to parallel the change in photosynthetic rate under various growth conditions. The rhythm in photosynthetic capacity could be effectively divorced from the cell cycle itself by placing cultures in high frequency light cycles (LD: 2,4) or in stationary growth-phase conditions. If synchronously dividing cultures previously grown in LD: 10, 14 were released into continuous dim illumination and constant temperature, the rhythm of capacity persisted for only one full cycle.
在由 10 小时光照和 14 小时黑暗组成的 24 小时光周期中，可获得绿色巴夫藻（Z 株）的同步细胞分裂；细胞分裂仅限于黑暗期。在细胞周期中发现光合能力以周期性方式变化，在黑暗开始前 2 小时达到峰值。研究了细胞周期中的光反应，以确定它们在控制观察到的能力节律性变化中所起的作用。光饱和曲线在光限制区域没有重大变化。在细胞周期中，希尔反应活性或甲臜的光还原没有波动。这些结果表明，组成光系统 I 和 II 的反应不会产生能力节律。在细胞周期中还跟踪了一些光合作用暗反应，以试图确定它们在控制光合能力节律中的可能作用。核酮糖-1,5-二磷酸羧化酶的活性与节律没有相关性。另一方面，发现甘油醛-3-磷酸脱氢酶的活性与各种生长条件下光合速率的变化平行。通过将培养物置于高频光周期（LD：2,4）或静止生长阶段条件下，可以有效地将光合能力节律与细胞周期本身分离。如果先前在 LD：10、14 中生长的同步分裂培养物被释放到连续的弱光照明和恒温条件下，那么能力的节律仅持续一个完整周期。
