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

元データ 日本植物生理学会


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.


Shimmen Teruo Departtnent Of Botany Faculty Of Science University Of Tokyo
Shimmen Teruo Department Of Biology Faculty Of Science Osaka University:(present)department Of Botany Faculty Of S
Tazawa Masashi Departlnent Of Biology Faculty Of Science Osaka University
Tazawa Masashi Departtnent Of Botany Faculty Of Science University Of Tokyo