1,3,4(2H)-ISOQUINOLINETRIONE HERBICIDES - NOVEL REDOX MEDIATORS OF PHOTOSYSTEM-I

A series of 1,3,4(2H)-isoquinolinetriones have been found to be fast-a cting post-emergence herbicides, producing symptoms of desiccation. Th ese redox-active compounds are very potent stimulators of the light-de pendent consumption of oxygen at photosystem I in isolated chloroplast s. Pulse radiolysis studies on 2-ethyl-1,3,4(2H)-isoquinolinetrione ha ve shown it to have free-radical properties which could enhance the ge neration of superoxide radicals in plants. Electrochemical studies fur ther support a redox mediator mode of action for the series. The compo unds were found to be unstable towards hydrolysis, and this was consid ered to be a major factor limiting the overall herbicidal effects. Oth er parameters, related to uptake and/or translocation, which may limit the full expression of the herbicidal activity of certain compounds, are discussed.