Effects of Chlorimuron-ethyl, Imazethapyr, and Propachlor on Free Amino Acids and Protein Formation in <i>Vicia faba </i>L.

Abstract

Decreases in protein and changes in the free amino acid profile were ascertained in Vicia faba L. treated with chlorimuron-ethyl, imazethapyr, or propachlor. Valine, leucine, isoleucine, and total N were decreased by chlorimuron-ethyl and imazethapyr, while total soluble N was increased by all treatments. These changes were accompanied by decreases of the activities of acetohydroxy acid synthase (AHAS; EC 4.1.3.18), nitrite reductase (NiR; EC 1.7.7.1), glutamine synthetase (GS; EC 6.3.1.2), and glutamate synthase (NADH-GOGAT; EC 1.4.1.14). During the experimental period, the inhibition of GS activity preceded that of NiR and followed that of AHAS in samples treated with chlorimuron-ethyl or imazethapyr, while a reverse sequence was apparent in samples treated with propachlor. Therefore, the reduction in protein formation and the disturbance in free amino acid profile appears to be due to inhibition of AHAS following treatment with chlorimuron-ethyl or imazethapyr and to inhibition of NiR following treatment with propachlor. Keywords: Herbicides; acetohydroxy acid synthase; nitrate reductase; nitrite reductase; glutamine synthetase; glutamate synthase