Photodestruction of pigments in higher plants by herbicide action. I. The effect of DCMU (diuron) on isolated chloroplasts
1990
Barry, P. | Young, AJ. | Britton, G.
3-(3',4'-Dichlorophenyl)-1',1'-dimethyl urea (DCMU) induced the photobleaching of chlorophylls and carotenoids in isolated chloroplasts of Hordeum vulgare. In chloroplasts illuminated in both the absence and presence of DCMU (5.0 mmol m-3), the destruction of carotenoid preceded that of the chlorophylls. The rate of photodestruction was accelerated by the presence of DCMU. After only 2 h illumination the rates of loss of beta-carotene and of the epoxyxanthophylls, neoxanthin and violaxanthin, were similar (approximately 40-50% loss in the presence of 5.0 mmol m-3 DCMU) but were much greater than that of lutein (25% loss). Analysis of the individual pigment-protein complexes, isolated from chloroplasts following such treatment, showed that whilst pigment destruction had occurred in all complexes, the relative content of the LHCP2/CPa complexes (containing the PSII core) had fallen to the greatest extent. Further illumination of the chloroplasts, for up to 22 h, resulted in far greater bleaching but showed a similar pattern of pigment loss, with DCMU again accelerating the rate at which this loss occurred. Carotene-5,6-epoxide was identified as a product of such photo-oxidative conditions.
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