The Bleaching Effect of the Diphenyl Ether Oxyfluorfen

Abstract

The diphenyl ether, oxyfluorfen [2-chloro-1-(3-ethoxy-4-nitrophenoxy)-4-(trifluoromethyl)benzene], exerts a very strong and rapid bleaching effect upon intact microalgae such as Scenedesmus acutus. Carotenoids, and subsequently chlorophylls, are destroyed concurrently with ethane formation and inhibition of photosynthetic oxygen evolution. These herbicidal effects are not observed before an activation time of approximately 2 h, during which photosynthetic electron transport is necessary. Diuron [3-(3,4-dichlorophenyl)-1,1-dimethylurea] inhibits oxyfluorfen activity during this activation time, but not thereafter. Isolated spinach chloroplasts (Spinacia oleracea ‘Atlanta’) evolve ethane after a light-incubation phase in the presence of oxyfluorfen as well as paraquat (methylviologen, 1,1′-dimethyl-4,4′-bipyridinium ion). Depending on their chemical constitution, diphenyl ethers apparently act differently and multifunctionally. The effects described for oxyfluorfen are believed to represent the primary mode of action of bleaching diphenyl ethers.