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

The treatment with fusicoccin causes a slight but significant decrease (about 15%) in the ATP level in pea-internode and maize-coleoptile segments. This decrease is detectable within 15 minutes and is accompanied by a parallel increase in O(2) uptake. Sodium azide inhibits O(2) uptake and completely blocks the stimulation of O(2) uptake by fusicoccin in both pea and coleoptile segments. Benzohydroxamic acid does not affect either basal or fusicoccin-induced O(2) uptake in maize-coleoptile sections. The drop of ATP level induced by various treatments (sodium arsenate, 2-deoxyglucose, limiting O(2), and anaerobiosis) is accompanied by a parallel inhibition of K(+) uptake in maize coleoptiles treated with or without fusicoccin. These results are consistent with the hypothesis that ATP is the energy source for the fusicoccin-activated H(+)/K(+)-exchange system.