Energy‐dependent Processes in Chara Corallina: Absence of Light Stimulation When Only Photo‐system One Is Operative

Summary Light‐stimulated active chloride influx in Chara corallina, like that in other giant algal cells, requires the operation of photo‐system two of photosynthesis. Active phosphate influx and glucose influx also require photo‐system two for light‐stimulation, and are not stimulated by light under anaerobic conditions. This contrasts with the situation in Nitella and Hydrodictyon where influx of phosphate and glucose can be supported by photo‐system one, i.e. by cyclic photophosphorylation alone. None of the other metabolic processes in Chara tested in this work (acetate uptake and oxidation, starch synthesis, and passive Rb+ influx), or described elsewhere in the literature, are light‐stimulated when photo‐system two is inoperative. Possible explanations of this apparent inability of cyclic photophosphorylation to act as a source of metabolic energy in Chara are suggested. Their significance is discussed in relation to hypotheses of the light reactions of photosynthesis and mechanisms of light‐dependent solute transport.