Distribution of electric potential and ion transport in the hypocotyl of Vigna sesquipedalis V. Electrogenic activity of the parenchyma cells in hypocotyl segments

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Intracellular potential of parenchyma cells (V_<ps>) in the hypocotyl segment of Vigna sesquipedalis was initially low after excision, then gradually increased to a more negative level. Thereafter V_<ps> could be remarkably reduced under anoxia then recovered with reaeration, accompanied by several cycles of damped oscillations. Both the rapidity of the decrease of V_<ps> caused by anoxia and its temperature dependency suggest an electrogenic mechanism. No marked spatial differences along the germ axis and the radius of hypocotyl were observed in the V_<ps> level and its electrogenic component when the reference electrode was placed on the surface of the hypocotyl segment. V_<ps> also decreased rapidly in an atmosphere containing 80% CO+20% O_2 m the dark, then was recovered immediately in the light or spontaneously but very slowly in the dark. The extent of the decrease of V_<ps> caused by CO depended on the growth activity of the cell and the time lapse after excision. These results suggest the possible conversion or replacement of the terminal oxidase. Sometimes phenomena resembling those of action potentials occurred spontaneously or during the reduction of V_<ps> due to inhibition of the energy metabolism. V_<ps> in the elongating region varied transiently with the change in illumination. Interrelationship between V_<ps> and the surface resting potential is discussed.
日本植物生理学会の論文