Disturbance in Vicia faba metabolism from exposure to imazethapyr and chlorimuron-ethyl

Disturbance in broad bean(Vicia faba L.) metabolism without lethal effect h as been ascertained following exposure to imidazolinone, imazethapyr (Im) a nd sulfonylurea chlorimuron-ethyl (Ch). During a period of 16 days followin g treatment with the herbicides at three dosages (field dose, half and twic e field dose), an inhibition of acetolactate-synthase (AHAS) accompanied by decreases of valine, leucine and isoleucine was found. Inhibition coincide d with decreases in protein and starch content. The relationship between th e inhibition of the above enzymes and herbicide dosage suggested that the p rotein decrease was an indirect effect of AHAS inhibition whilst the starch decrease was a consequence of sucrose accumulation. A comparative evaluati on shows that Lm was more active in the depression of starch while Ch cause d greater depression of proteins.