Electrophysiological study on ethylene induction in fruit and vegetables.

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Electrophysiological studies on ethylene biosynthesis was conducted with application of direct current to cucumber (Cucumis sativus L.) fruit.1) Direct current of 1 to 3mA induced ethylene synthesis with a sharp peak at 1h. This abrupt induction of ethylene synthesis was accompained by an equally abrupt activations of 1-aminocyclopropane-1-carboxylate (ACC) synthase and ACC oxidase.2) At least six different cDNAs for ACC synthase were obtained from cucumber fruit. By northerm blotting, five ACC synthase mRNAs were expressed withdirect current in cucumber fruit.3) Electrical impedance analysis of tissue properties was conducted in order to understand the relationship between impedance components and ethylene biosynthesis induced by direct current in cucumber fruit.Impedances were calculated from five components ; capacitances representing plasma membrane and organelle membranes, and resistances representing extracellular space, cytoplasm, and organelle interior. With direct current of 3 mA,capacitance of organelle membranes and resistances of extracellular space and cytoplasm were increased abruptly.Diazocyclopentadiene, an inhibitor of ethylene action, eliminated the direct current induction of resistance of extracellular space, but no effect on the increase in capacitance of organelle membranes and resistance of cytoplasm. The results indicate that an extemally applied current may generate signal (s) by altering the functions of organelle membranes and/or cytoplasmic pH to induce ACC synthase.