Demonstration of Voltage Dependency of Light-induced Potential Change in Chara

概要

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The electromotive force (E_m) of the plasma membrane of the tonoplast-free cell of Chara australis decreased when the electrogenic pump was stopped by removing ATP or Mg^<2+> from the cell. Such a cell showed a rapid light-induced potential change (rLPC). Three factors were considered to be responsible for the generation of rLPC; removal of Mg・ATP, stoppage of the electrogenic pump and membrane depolarization per se. Tonoplast-free cells having enough Mg・ATP occasionally showed small E_m (-87-116 mV) due to stoppage of the electrogenic pump. Since the rLPC was induced in such cells, removal of Mg・ATP cannot be the factor. Cells having large E_m due to active pump activity also showed rLPC when the potential difference across the plasma membrane (V_m) was depolarized by an outward electric current; evidence that not the stoppage of the pump but membrane depolarization is a necessary condition for the generation of rLPC. In the rLPC V_m always changed in the negative direction. However, calculation of E_m revealed the existence of a reversal potential [(E_m)_<rev>] toward which E_m converged from either more negative or more positive values. The (E_m)_<rev> approximately coincided with the equilibrium potential for K^+ across the plasma membrane. Intracellular anions occupying lower positions in the lyotropic series inhibited rLPC.
日本植物生理学会の論文