Development of the Primary Photochemical Apparatus of Photosynthesis during Greening of Etiolated Bean Leaves.

Seven-day-old dark-grown bean leaves were greened under continuous light. The amount of chlorophyll, the ratio of chlorophyll a to chlorophyll b, the O(2) evolving capacity and the primary photochemical activities of Photosystem I and Photosystem II were measured on the leaves after various times of greening. The primary photochemical activities were measured as the photo-oxidation of P(700), the photoreduction of C-550, and the photo-oxidation of cytochrome b(559) in intact leaves frozen to -196 C. The results indicate that the reaction centers of Photosystem I and Photosystem II begin to appear within the first few minutes and that Photosystem II reaction centers accumulate more rapidly than Photosystem I reaction centers during the first few hours of greening. The very early appearances of the primary photochemical activity of Photosystem II was also confirmed by light-induced fluorescence yield measurements at -196 C.