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RESEARCH PRODUCT

Photoreceptors and respiratory electron flow involvement in the activity of acifluorfen-methyl and LS 82-556 on nonchlorophyllous soybean cells

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Abstract The diphenyl ether acifluorfen-methyl [AFM; methyl 5-[2-chloro-4-(trifluoromethyl)phenoxy]-2-nitrobenzoate] and the pyridine derivative LS 82-556 [( S )-3- N -(methylbenzyl)carbamoyl-5-propionyl-2,6-lutidine] induce light-dependent polyunsaturated fatty acid peroxidation, leading to general membrane disruption. Although devoid of functional chloroplasts, cultured soybean cells are sensitive to AFM and LS 82-556 only in the light. The possible involvement of carotenoids and respiratory electron flow was examined by monitoring ethane evolution, fluorescein release, and dry weight/fresh weight ratio alteration. Herbicide effects on cells exposed to white light or blue light (380–540 nm) remain unchanged when the cells are deprived of carotenoids by treatment with norflurazon [4-chloro-5-(methylamino)-2-(α,α,α-trifluoro- m -tolyl)-3(2H)-pyridazinone]. Treatment with antimycin A reduced sensitivity to AFM and LS 82-556. In nonchlorophyllous cells, chromophores, other than carotenoids, absorbing between 380 and 540 nm are involved as photoreceptors. Furthermore, respiratory electron flow also participates in the toxic process.