INHIBITION OF OXYGEN EVOLUTION BY IVALIN

The inhibition of ATP synthesis, proton uptake, and electron transport (basal, phosphorylating, and uncoupled) from water to methylviologen by ivalin (a naturally occurring sesquiterpene lactone in Zaluzania tr iloba and Iva microcephala) indicates that it acts as electron transpo rt inhibitor. Since photosystem I and electron transport from DPC to e , were not affected, while the electron flow of uncoupled photosystem II from H2O to DAD and from water to silicomolybdate was inhibited, we concluded that the site of inhibition of ivalin is located at the oxy gen evolution level.