INVITRO AND INVIVO EFFECTS OF CHLORSULFURON IN SENSITIVE AND TOLERANT PLANTS

Differences in sensitivity to chlorsulfuron from 100 up to 1000-fold were observed between wheat and maize plants. Free amino acid content was analyzed in wheat and maize embryos and plants after 24 h and 10 days of chlorsulfuron treatment, respectively. Accumulation of free amino acids and increase in relative proportion of some of them were observed even when decreases in branched amino acid content could hardly be measured. Acetolactate synthase extracted from chlorsulfuron treated plants showed the same levels of extractable enzyme as from untreated plants. An effect of chlorsulfuron on acetolactate synthase in vivo could not be detected in wheat or maize at any time of plant treatment; this strongly suggests that the enzyme-inhibitor complex does not remain bound throughout the enzyme extraction procedure. Moreover, the extractable enzyme had the same properties as acetolactate synthase of untreated plants, showing that the enzyme in vivo is not irreversibly damaged by chlorsulfuron. This result is further supported by the growth recovery found in treated plants after removing the herbicide.