Electrochemical evidence of specific action of indole acetic acid on membranes in Mnium leeaves.

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.