Electrochemical Evidence of Specific Action of Indole Acetic Acid on Membranes in Mnium Leaves

Abstract

Indole acetic acid (IAA), membranes, electrochemical potential, ion uptake, membrane potentialThe effect of 5-10~7 and 5-10-«M IAA on K + , Cl" and S04"" uptake by young and old Mnium gametophytes from 0.2 MM or 10 MM salt solutions has been investigated. These IAA concentrations selectively enhance K + uptake from 0.2 MM KCl or K2S04 in old gametophytes. IAA up to 10 -5 M does not affect the membrane potential (P.D.). At 0.2 MM KCl the observed P.D. of -200 to -220 mV is more negative than the calculated Nernst potential of +84 to +107 mV for Cl~ and -136 to -157 mV for K 1 ". These results are discussed in relation to a recent model of IAA regulation of cell elongation involving a proton extrusion pump.In an earlier investigation 1 it was shown that the ion uptake isotherm of young Mnium leaves in the concentration range of 1 -10 MM salt was linear, while old Mnium leaves showed a typical saturating system 2 2 isotherm. This finding was related to differences in ultrastructure between young and old Requests for reprints should be sent to Prof. Dr. U. LÜTTGE, Mnium

Role of the plasma membrane H + -ATPase in auxin-induced elongation growth: historical and new aspects

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Indole-3-acetic acid and fusicoccin cause cytosolic acidification of corn coleoptile cells

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