Light-Induced Changes in Cytosolic pH in Leaf Cells of Egeria densa : Measurements with pH-Sensitive Microelectrodes : ENVIRONMENTAL AND STRESS RESPONSES : MEMBRANES AND BIOENERGETICS

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Light-induced changes of cytosolic pH (pH_c) and the plasmalemma potential (E_m) in dark-adapted leaf cells of the aquatic plant, Egeria densa were measured simultaneously with double-barreled pH_c sensitive microelectrodes. Upon illumination, pH_c increased transiently and then decreased to a level that was lower than the original value, while the plasmalemma was greatly hyperpolarized after an initial small depolarization. DCMU inhibited the light-induced changes in both pH_c and E_m. DCMU acted without directly inhibiting the electrogenic proton pump in the plasmalemma since a decrease in pH_c caused by treatment with butyrate (H^+-loading) hyperpolarized the plasmalemma in DCMU-pretreated cells. N.N'-Dicyclohexylcarbodiimide (DCCD) also inhibited the light-induced changes in both pH_c and E~. This result may be explained by direct inhibition of the proton pump in the plasmalemma by DCCD since the decrease in pH_c caused by butyrate did not induce membrane hyperpolarization in DCCD-treated leaf cells. Fusicoccin induced membrane hyperpolarization and slight acidification of the cytosol. DCCD inhibited the fusicoccin-induced changes in both pH_c and E_m. The mechamjsm of the light-induced changes in pH_c is discussed in relation to activities of the proton pump in the plasmalemma and photosynthesis.
日本植物生理学会の論文