Photosynthetic Electron Flow and Associated Changes in Electrical Potential and Resistance of Cytoplasmic Membranes in Green Plant Cells

Abstract

The electrical potential of the cytoplasmic membranes of Nitella translucens (VREDENBERG 1969) and various other algal and green plant cells (NISHIZAKI 1968, SCHILDE 1966, ANDRIANOV et al. 1968, SADDLER 1970, JESCHKE 1970, THROM 1970, GRADMAN & BENTRUP 1970, LÜTTGE & PALLAGHY 1969) has been observed to respond to light absorbed and converted by the photosynthetic apparatus. It has been evidenced that the initial 1ight-induced membrane depolarisation at the plasmalemma, which usually occurs during the first 10 to 60 seconds of illumination, is associated with an efficient primary photochemical process (VREDENBERG 1970). An association with the electron transport coupled proton transfer reactions at the chloroplast membrane has been suggested (VREDENBERG 1969). There are at least three alternative possibilities to explain the potential changes in association with these primary reactions at the chloroplast membrane, a. Changes in proton concentration (or of another ion primarily involved) in the cytoplasm cause hanges in the membrane potential, if the membrane is mainly a diffusion barrier for the protons, or for another ion that is primarily involved (VREDENBERG 1969, LÜTTGE & PALLAGHY 1969 VREDENBERG 1970). b. Change in the rate of pumping of an electrogenic pump which contributes to the membrane potential (SADDLER 1970, JESCHKE 1970). c.