Radical Formation and Peroxidative Activity of Phytotoxic Diphenyl Ethers

ESR Signals, Spin-Trapping, N itro/N on-N itro Diphenyl Ethers, Chloroplasts, Electron Transport Phenyl-/-butylnitrone can be used to trap light-induced radicals with isolated chloroplasts, measurable by ESR technique. The radical signals are dramatically am plified and their lifetim e prolonged in the presence of peroxidizing diphenyl ethers. A pora-substitution with —N 0 2, —Cl or I is necessary, as well as an operating photosynthetic electron transport. The nature o f radicals is not yet clear; they may be alkyl or linolenic-acid radicals, but their presence indicates peroxida­ tion. Furthermore, the ESR measurements presented strengthen our hypothesis that peroxidative activity o f paraquat and diphenyl ethers are not caused by the same mechanism.