ABSTRACT
This chapter describes the physiological responses of plants to inhibition of acetohydroxyacid synthase (AHAS) by the imidazolinones and how these responses may eventually result in plant death. Interference with the hormonal status of the plant may be responsible for the decrease in transpiration and disruption of plant growth after treatment with an imidazolinone. Plants treated with imazaquin show leaf epinasty, proliferation of axillary buds, and loss of apical dominance, chlorosis, and shortening of internodes. Treatment with the imidazolinones causes many different physiological changes in the plant: growth ceases because cell division and DNA synthesis are inhibited; transpiration and ethylene release decrease; and sugars and amino acids accumulate because protein synthesis and photosynthate transport are disrupted. Researchers have found that some of these changes relate in some way to the disruption of the synthesis of the branched-chain amino acids. These changes may also indicate a site of action of the imidazolinones other than AHAS inhibition.
