The Action of Phlorizin on Photosynthesis and Light-stimulated Ion Transport inHydrodictyon africanum

Abstract

Phlorizin at 1 mM inhibits the coupled active influx of K and efflux of Na in Hydrodictyon africanum in the light. It does not inhibit the coupled influx of Cl and monovalent cations, nor the passive ion fluxes. Photosynthesis can be stimulated up to 30 per cent under light-saturated conditions. It is concluded that the effects of phlorizin cannot be solely due to an inhibition of the membrane ATPase, and that photophosphorylation must in some way be affected. The nature of this effect is discussed in the light of the effects of phlorizin on photophosphorylation in isolated chloroplasts.