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

概要

論文の詳細を見る
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.
日本植物生理学会の論文