Diphenylether-like physiological and biochemical actions of S-23142, a novel N-phenyl imide herbicide

Abstract Several physiological and biochemical actions of a new experimental herbicide, S-23142 [ N -(4-chloro-2-fluoro-5-propargyloxyphenyl)-3,4,5,6-tetrahydrophthalimide], have been investigated. S-23142 was active under the presence of light and oxygen. Photosynthetic CO 2 fixation in soybean began to decrease 4–5 hr after the foliar treatment of S-23142, being accompanied by the appearance of visible bleaching and wilting of the plants. A large amount of ethane, the products of peroxidation of unsaturated fatty acids, was produced from the cotyledon discs of cucumber ( Cucumis sativus L.) treated with S-23142. Leakage of ATP was also observed. S-23142 did not inhibit photosynthetic oxygen evolution of the discs just after the application; however, the oxygen evolution rate decreased as the treated discs produced ethane. The results suggest that cell membrane and chloroplast membrane were deteriorated by the membrane lipid peroxidation. S-23142 also induced ethylene production and a high level of phenylalanine-ammonia lyase activity in cucumber cotyledon, which was regarded as the phenomena of stress response. Only the ethylene production was inhibited by aminoethoxyvinylglycine and cycloheximide, while the ethane production was not affected. All of these actions of S-23142 were essentially the same as those of acifluorfen ethyl except that the activity of S-23142 was more than 10 times higher than that of acifluorfen ethyl. These data strongly suggest that S-23142 belongs to the same group as diphenylethers in its mechanisms of action despite the difference in chemical structure.