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Proton Efflux from Corn Roots Induced by Tripropyltin ¹

Department of Botany, University of Illinois, Urbana, Illinois 61801, Department of Agronomy, University of Illinois, Urbana, Illinois 61801

Tripropyltin restores medium acidification by washed corn root tissue in which electrogenic H⁺ efflux has been blocked by ATPase inhibitors or injury. However, the restored H⁺ efflux is not electrogenic and will not drive K⁺ influx, and, by itself, tripropyltin is inhibitory to K⁺ influx. Tripropyltin elicits a 5-fold increase in endogenous chloride efflux, and Cl^–/OH^– exchange can, thus, account for the observed acidification of the medium. This explanation cannot be applied equally to the acidification produced by the K⁺/H⁺ exchanging ionophore nigericin.