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

Abstract

Seven day old dark-grown bean [Phaseolus vulgaris] leaves were greened under continuous light. The amount of chlorophyll, the ratio of chlorophyll a to chlorophyll b, the O2 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[pigment]760, the photoreduction of C-550 [a Photosystem II pigment], and the photo-oxidation of cytochrome b559 in intact leaves frozen to -196.degree. C. The results indicate that the reaction centers of Photosystem I and Photosystem II begin to appear within the 1st few min and that Photosystem II reaction centers accumulate more rapidly than Photosystem I reaction centers during the 1st few hours of greening. The early appearances of the primary photochemical activity of Photosystem II was also confirmed by light-induced fluorescence yield measurements at -196.degree. C.