Effect of intracellular pH on the light-induced potential change and electrogenic activity in tonoplast-free cells of Chara australis

元データ 日本植物生理学会

概要

Effects of the intracellular H^+ concentration on the membrane potential and membrane resistance of tonoplast-free cells of Chara australis were examined under light and dark conditions. Cells were made tonoplast-free by perfusing the vacuole with media containing 5 mM EGTA and 30 mM buffers of various pH values. The electrogenic pump was stopped by removing the intracellular ATP. The ATP-dependent part of the membrane potential was large at pH_i 6.2 and 6.9, but decreased in both the acidic (pH_i 5.1, 5.7) and alkaline (pH_i 7.9, 8.7) ranges. Assuming that the putative electrogenic H^+ pump acts solely as a current source, we estimated the current and the work done by the pump. Both the current and the work were at a maximum at pH_i 6.9, but decreased to some extent at pH_i 7.9-8.7 and decreased greatly at pH_i 5.7-5.1. Light caused a significant membrane hyperpolarization at pH_i 6.2-7.9, but only a slight hyperpolarization at pH_i 5.1, 5.7 and 8.7. The presence of light-induced hyperpolarization at pH_i lower than 6.2 suggests that acidification of the cytoplasm upon illumination does not cause activation of the putative H^+ pump. Membrane resistance was very high at pH_i 5.1 and 5.7 and very low at pH_i 8.7. The very high R_m values at pH_i 5.1 and 5.6 are believed to be related to inhibition of the activity of the pump.

著者

Shimmen Teruo Department Of Biology Faculty Of Science University Of Tokyo
Shimmen Teruo Department Of Botany Faculty Of Science University Of Tokyo
Tazawa Masashi Department Of Applied Physics And Chemistry Fukui University Of Technology
Tazawa Masashi Department Of Botany Faculty Of Science University Of Tokyo
Fujii Sumiko Department Of Biology Faculty Of Science Osaka University
Fujii Sumiko Department Of Biology Faculty Of Science Osaka University:(present)department Of Agricultural Chemis
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

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