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KMID : 0368419900330020135
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Journal of Plant Biology
1990 Volume.33 No. 2 p.135 ~ p.140
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Characterization of the Membrane Potential Relevant to Permeability Changes in the Plasmalemma of Lemna gibba G3
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Abstract
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The membrane potential in the subepidermal cells of Lemma gibba G3 fronds was measured in the dark with glass capillary microelectrodes. At pH 7, the membrane potential, approximately-215mV, could be depolarized to -82~-88mV by 0.1 mM dicyclohexylcarbodiimide (DCCD) or by KCN at 0.3 mM or higher concentrations. When the pH of the medium was altered the potential showed reversible changes, while it revealed no response to the external pH changes when energy transduction across the membrane was being blocked by 0.1 mM DCCD. The results support an assumption that the active component of the membrane potential of Lemma subepidermal cells is generated by electrogenic H+-pump. By the addition of 0.10~5.00mM salicylic acid (SA) to the bathing medium the membrane potential was depolarized to a great extent, and the removal of SA from the medium repolarized the potential showing almost complete recovery, 92.3~97.6% to the initial levels. Although the potential was greatly depolarized by 5.0% or higher concentrations of dimethylsulfoxide (DMSO), the recovery rate by DMSO removal was decreased as the pretreatment concentration had increased. Twenty percent DMSO pretreatment limited the recovery at only 47.1%. The presence of SA in the bathing medium could reversibly increase the permeability of the plasmalemma. DMSO at its concentration of 5.0% or higher increased the permeability of the membrane by irrevesibly impairing the membrane component involved in the membrane permeability.
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