RESUMEN
Common vetch (Vicia sativa L.) is a forage and grain legume, widely distributed throughout the world. Alterations induced by the herbicide imazamox on plant growth, acetohydroxyacid synthase activity, total free amino acids, as well as concentrations of valine, leucine, isoleucine and imazamox in young and mature leaves were investigated at 2 and 7 days after the herbicide application. Plant growth decreased significantly after 7 days of imazamox treatment. The herbicide was detected in both young and mature leaves inducing an inhibition of acetohydroxyacid synthase activity in the former and consequently decreasing valine and leucine contents in this organ. At the same time, the treatment caused an increase of total free amino acids in young leaves, presumably as result of proteolysis stimulation in such conditions. Given that these effects were not observed in mature leaves, we suggest a different sensitivity of the acetohydroxyacid synthase activity to imazamox depending on leaf age. Common vetch seems not to degrade imazamox since the herbicide was accumulated in shoot with increasing treatment time. To our knowledge, no physiological and biochemical studies of common vetch responses to imazamox have been previously reported.