Rapid Hormone-induced Hyperpolarization of the Oat Coleoptile Transmembrane Potential

Abstract
The effects of the plant growth substances indoleacetic acid (IAA) and fusicoccin on the transmembrane potential of Avena coleoptile cells (at 27-29 C) were studied. Fusicoccin caused hyperpolarization of the membrane potential which started after a lag of less than 20 seconds, and which on average reached −49 mv at an external K+ concentration of 1 mm and −75 mv at 0.1 mm K+. IAA caused a hyperpolarization of −25 mv starting after a lag of 7 to 8 minutes. These results suggest that fusicoccin and IAA both activate electrogenic H+ extrusion.