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

Abstract

The effect of 5·10^-7 and 5·10^-6Μ IAA on K⁺, Cl^- and SO₄ ^-- 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 K₂SO₄ 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⁺. These results are discussed in relation to a recent model of IAA regulation of cell elongation involving a proton extrusion pump.