Net Proton Transport in Sunflower Hypocotyls: Comparative Studies of Inhibitors

Net H⁺-transport was continuously monitored by means of a computer assisted pH stat. Application of cycloheximide leads rapidly to a transient proton influx, followed by a periode of uncomplete recovery. This occurs even when net H⁺-efflux is stimulated before with indolacetic acid or dilute concentrations of the fungal toxin fusicoccin. The uncomplete recovery of proton secretion is unaffected by repeated treatment with CHI but it is markedly reduced by sulfhydril-blockers. The inhibition of proton secretion induced by sulfhydril-blockers is only reversed transiently by dithioerythritol. The results give no clear evidence for the existence of different pumps or a different mode of action between auxin and fusicoccin in their stimulation of net H⁺-transport.