EFFECT OF RISHITIN ON POTATO TONOPLAST VESICLE AND VACUOLE PROTON TRANSPORT

Rishitin, a known potato phytoalexin, was tested for its effects on pr oton transport. Like the pterocarpan phytoalexins, glyceollin and phas eollin, rishitin was found to inhibit proton transport. At 100 mu M ri shitin, proton transport in potato tonoplast vesicles was inhibited by > 95%. This inhibition appears to be due to an increase in proton con ductance and not to inhibition of the tonoplast ATPase. Potato vacuole s were also shown to have increased proton leakage in the presence of rishitin.