Biogenesis of chloroplast membranes X. Changes in the photosynthetic specific activity and the relationship between the light harvesting system and photosynthetic electron transfer chain during greening of Chlamydomonas reinhardi y-1 cells

Specific activities of photophosphorylation and light-dependent pH rise at different stages of the greening process, have been measured as a function of the illumination intensity. During the early phase of greening, the specific activity of cyclic photophosphorylation increases rapidly. Transfer of greening cells to the dark causes a marked decrease in the specific activity after 2 h incubation. Such an effect is not obtained if the greening cells are transferred to the dark at a later stage of the greening process. High illumination intensities (10⁶ erg·cm^-2·sec^-1) are required for maximal activity during the early phase of the normal greening process or the initial phase of repair of inactive membranes formed in the presence of chloramphenicol. The requirement for high illumination decreases during the late phase of the greening process (3·10⁵ erg·cm^-2·sec^-1) or during repair of inactive membranes if additional chlorophyll is synthesized. Saturation could not be obtained at 5·10⁵ erg·cm^-2·sec^-1, during repair of inactive membranes in absence of chlorophyll synthesis over a period of 6 h of incubation. Based on these and additional data, it is concluded that the photosynthetic membranes are built stepwise and that the quantitative and organizational relationships between the light harvesting and electron transfer systems can be modulated within wide limits.