The effect of rishitin on potato tonoplast vesicle and vacuole proton transport.

Rishitin, a known potato phytoalexin, was tested for its effects on proton transport. Like the pterocarpan phytoalexins, glyceollin and phaseollin, rishitin was found to inhibit proton transport. At 100 microM rishitin, proton transport in potato tonoplast vesicles was inhibited by > 95%. This inhibition appears to be due to an increase in proton conductance and not to inhibition of the tonoplast ATPase. Potato vacuoles were also shown to have increased proton leakage in the presence of rishitin.