EFFECTS OF CHLORIMURON-ETHYL, IMAZETHAPYR, AND PROPACHLOR ON FREE AMINO-ACIDS AND PROTEIN-FORMATION IN VICIA-FABA L

Decreases in protein and changes in the free amino acid profile were a scertained in Vicia faba L. treated with chlorimuron-ethyl, imazethapy r, or propachlor. Valine, leucine, isoleucine, and total N were decrea sed by chlorimuron-ethyl and imazethapyr, while total soluble N was in creased 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 exp erimental period, the inhibition of GS activity preceded that of NiR a nd 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 inhibitio n of AHAS following treatment with chlorimuron-ethyl or imazethapyr an d to inhibition of NiR following treatment with propachlor.