Mode of action of the dichloroacetamide antidote BAS 145-138 in corn. II. Effects on metabolism, absorption, and mobility of metazachlor
1992
Fuerst, E.P. | Lamoureux, G.L.
The first study in this series demonstrated that the dichloroacetamide antidote BAS 145-138 (BAS) decreased the concentration of metazachlor present in growing tissues, especially in the developing leaves, of corn seedlings. This decrease was attributed to enhanced metabolism, decreased mobility, and decreased absorption of metazachlor. The effects of BAS on metabolism, mobility, and absorption of [14C]metazachlor were investigated further. [14C]Metazachlor was metabolized rapidly in unantidoted corn seedling tissues but metabolism was even more rapid in BAS-treated corn tissues, including the coleoptile, developing leaves, mesocotyl, and roots. Metabolites of [14C]metazachlor were less mobile than the parent. Thus. the previously observed decrease in mobility of 14C in BAS-treated corn was probably the consequence of enhanced metabolism of [14C]metazachlor to a less mobile form. Metazachlor soil treatments increased subsequent absorption of [14C]metazachlor applied to corn possibly by inhibiting the normal development of cuticular wax. Thus, the previously observed slight decrease in absorption of [14C]metazachlor in BAS-treated corn could have been the consequence of enhanced metabolism of [14C]metazachlor to a form that did not inhibit the development of cuticular waxes. Wheat was not protected by BAS and also did not show an increased rate of metazachlor metabolism in response to BAS treatment. BAS did not affect glutathione levels but did increase glutathione S-transferase (EC 2.5.1.18) activity in corn. Evidence is consistent with the hypothesis that BAS protects corn from metazachlor by accelerating enzymatic glutathione conjugation of metazachlor.
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