EFFECT OF OXYGEN AND PENTACHLOROPHENOL ON THE INDUCTION LAG OF PHOTOSYNTHESIS IN CHLAMYDOMONAS-REINHARDI

Following dark anaerobic incubation Chlamydomonas reinhardi exhibit a pronounced induction lag in photosynthesis; in contrast, dark aerobic incubation caused only a minimal induction lag. Addition of a low concentration of the uncoupler, pentachlorophenol (PCP), to respiring cells in darkness extended the induction period. Far red light preillumination partially overcame the induction lag resulting from dark anaerobic treatment or uncoupling with PCP in aerobic medium. The induction lag in photosynthesis is explained in terms of intracellular energy reserve and its effects on the level of phosphorylated intermediates of the Calvin cycle e.g., RuDP, in the dark. Further, evidence is presented which demonstrates that: (a) PCP, at concentrations below 10 μm, preferentially uncouples oxidative phosphorylation in vivo and (b) photophosphorylation, both in in vivo and in vitro, is much more resistant. © 1979.