Activity of the Ethylene-forming Enzyme Measured in vivo at Different Cell potentials

Abstract

Summary Activity of the ethylene-forming enzyme (EFE) has been determined in hypocotyl segments of mung bean ( Vigna radiata L.) and in discs of red beet ( Beta vulgaris L.) at the same time as the plasma membrane potential difference, measured with a microelectrode, has been progressively reduced by titration with the protonophores 2,4-dinitrophenol and carbonyl cyanide m-chloropheny1hydrazone and with KCl. Treatment with the protonophores affected EFE activity in both the mung bean hypocotyls and in the beet discs, although in different ways in the two tissues, while the depolarisation resulting from KCl treatment did not affect the EFE activity of either tissue. The results obtained are not consistent with the proposal of John (1983, FEBS Letters 152, 141) that a potential-dependent EFE activity is located at the plasma membrane of plant cells.