Abstract
The effects of various ATPase inhibitors and ionophores on both H^+-K^+ exchange by excised rice roots, ATPase activity, and formation of pH gradient in the reconstituted plasma membrane vesicles were investigated. The inhibitors and the ionophores completely inhibited H^+-K^+ exchange, but partially both ATPase activity and formation of pH gradient. In some cases, these reagents resulted in reverse H^+-K^+ exchange that mediated influx of H^+ and efflux of K^+. These results suggest that the electrochemical gradient across the plasma membrane controls the H^+-K^+ exchange in point of the rate and the direction. Rb^+ and NH_4^+ were also effective for the exchange K^+, while Na^+, Li^+ and Cs^+ were ineffective.
