DEMONSTRATION OF LIGHT-INDUCED POTENTIAL CHANGE IN CHARA CELLS LACKING TONOPLAST

Chara cells without tonoplasts, prepared by replacing the cell sap with EGTA-containing media, showed essentially the same pattern of light-induced changes in membrane potential and membrane resistance as normal cells although the concentrations of ions and ATP in the cytoplasm decreased considerably (1/3-1/10) after loss of the tonoplast. Removal of the tonoplast reduced the rate of photosynthetic O2 evolution to about 50% of that of normal cells but did not affect the magnitude of light-induced potential change. Not a full but a certain level of electron flow seems necessary to activate the putative electrogenic H+-pump. © 1979 Oxford University Press.