AbstractDissociation of active H+extrusion (−ΔH+) from K+uptake in pea and maize root segments was attempted by substituting K+in the incubation medium with lipophilic cations assumed to enter the cell by passive, non‐specific, permeation through the lipid component of the plasmalemma. Among the compounds tested, tributylbenzylammonium significantly stimulated −ΔH+in the absence of other monovalent cations in the medium. This effect was much more evident when the experiment was carried out in the presence of fusicoccin, which strongly stimulates proton extrusion and monovalent cation uptake, and hyperpolarizes the trans‐membrane electric potential in these materials. Also the lipophilic cations tetraphenylphosphonium, dimethyldibenzylammonium and hexylguanidine markedly stimulated FC‐promoted −ΔH+. Octylguanidine at a low concentration induced an early stimulation followed by a strong inhibition of −ΔH+. A complete lack of additivity was observed between the effects of lipophilic cations and that of K+on H+extrusion. Lipophilic cations severely inhibited K+uptake.These data are interpreted as supporting the view of an electric, rather than a chemical, (namely, involving the same carrier system) nature of the coupling of active H+extrus