Larkum, AWD & Boardman, NK 1974, 'The effect of nigericin and valinomycin on CO
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The energy source for active phosphate influx in Hydrodictyon Africanum has been investigated using gas mixtures with and without O2 and CO2, light of various wavelengths, and metabolic inhibitors selective for respiratory or photosynthetic electron transport and phosphorylation. It is concluded that, as in the other green algae studied, active phosphate transport requires ATP. In the dark this is supplied by oxidative phosphorylation; in the light the influx is much less sensitive to inhibition of oxidative phosphorylation, and photophosphorylation (including cyclic photophosphorylation) can act as energy source. This situation is more like that for active K influx (coupled to active Na efflux) than to active Cl influx in H. Africanum, except that the active dark influx is relatively greater for phosphate influx. The significance of these results for the mechanism of regulation of light-stimulated ATP-requiring processes, and for the role of photosynthetic and oxidative phosphorylation in the energy metabolism of green cells, is discussed. © 1974 Oxford University Press.