Alterations induced by imazamox on acetohydroxyacid synthase activity of common bean (Phaseolus vulgaris) depend on leaf position

Abstract

Imazamox is a selective herbicide applied in a wide spectrum of crops which belongs to the imidazolinone family, which mode of action is related to the inhibition of acetohydroxyacid synthase activity. The effect of this herbicide on plant growth, amino acids balance as well as the rate of inhibition of acetohydroxyacid synthase activity in different organs of common bean was studied. Our results indicated that total plant dry weight was not significantly affected two and seven days after herbicide application. Acetohydroxyacid synthase activity decreased in young tissues in response to imazamox treatments, whereas in mature organs the herbicide reversed the natural decrease of activity linked to ripeness. In shoot apical meristem and fully expanded leaves isoleucine content increased, while valine and leucine decreased less than expected considering the decline of acetohydroxyacid synthase activity, at less in young tissues. The results suggest that the herbicide is transported primarily to the growing areas where exerts its action by inhibiting the acetohydroxyacid synthase. Results found here allow to progress in the knowledge about legumes responses to imazamox herbicide.