Relationship between ATP Level and Activity of Fusicoccin-stimulated H+/K+-Exchange System in Plant Tissues

Abstract

The treatment with fusicoccin causes a slight but significant decrease (about 15%) in the ATP level in pea-internode and maize-coleoptile [maize Zea mays L. cv. Dekalb XL 640 seeds and pea (Pisum sativum cv. Alaska)]. This decrease is detectable within 15 min and is accompanied by a parallel increase in O2 uptake. Sodium azide inhibits O2 uptake and completely blocks the stimulation of O2 uptake by fusicoccin in both pea and coleoptile segments. Benzohydroxamic acid does not affect either basal or fusicoccin-induced O2 uptake in maize-coleoptile sections. The drop of ATP level induced by various treatments (sodium arsenate, 2-deoxyglucose, limiting O2 and anaerobiosis) is accompanied by a parallel inhibition of K+ uptake in maize coleoptiles treated with or without fusicoccin. Apparently, ATP is the energy source for the fusicoccin-activated H+/K+-exchange system.