DCMU-induced fluorescence changes and photodestruction of pigments associated with an inhibition of photosystem I cyclic electron flow

Abstract

Diuron (DCMU) induces the photodestruction of pigments, which is the initial herbicidal symptom. As a working hypothesis, it is proposed that this sym ptom can only be produced when the herbicide dose is sufficiently high to inhibit not only photosystem II electron transport almost completely, but also inhibit (through over oxidation) the natural cyclic electron flow associated with photosystem I as well. Using freshly prepared chloroplasts, studies of DCMU-induced fluorescence changes, and dose responses for inhibition of electron transport, have been com pared with a dose response for the photodestruction of pigm ents in chloroplasts during 24 h illumination. Photodestruction of pigments coincides with the inhibition of cyclic flow. © 1984, Walter de Gruyter. All rights reserved.