The Water-Film Electrode : A New Device for Measuring the Characean Electro-Potential and -Conductance Distributions along the Length of the Internode

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A "water-film electrode" has been developed to study time dependencies of the distributions of electrical potential (Vm) and conductance (Gm) as a function of position along the length of asingle Characean internode. The water-film is formed by dipping a ring-shaped Ag/AgCl wire covered with an agar block into detergent-containing artificial pond water. The use of uncalcified internodes produced the following results: (1) Both Vm and Gm were relatively uniform along the internode in darkness. (2) Illumination induced hyperpolarization and increased Gm along the entire length of the internode within few minutes. During this period, small electro-potential differentiation of as much as 20 mV was sometimes observed. Thereafter, several depolarized regions (D-regions) with high Gm values appeared; as much as 100 mV of depolarization. (3) The positions of the D-regions in light remained unchanged for several days even when the light was turned off for a period of more than 1 h. (4) When the internode was partially exposed to light, the D-region appeared, or formed, only in the illuminated part. In calcified internodes electro-differentiation was induced by illumination as it was in uncalcified ones. Slightly depolarized regions, however, remained even in darkness. Unlike noncalcified internodes, the conductance of the depolarized region was generally less than that of the neighboring hyperpolarized regions (H-regions).
日本植物生理学会の論文