CHANGES IN FREE AMINO-ACID POOLS CAN PREDICT THE MODE OF ACTION OF HERBICIDES

Studies were conducted to determine the short-term changes in free ami no acid levels in the meristematic zone of maize after treatment with various herbicides with different modes of action. These herbicides in cluded inhibitors of various amino acid biosynthetic pathways, photosy nthesis, and fatty acids biosynthesis. Inhibitors of various amino aci d biosynthetic pathways caused specific reduction in the pools of amin o acids being produced by the particular pathway. Inhibitors of other metabolic pathways also caused significant changes in pools of various amino acids. Very similar changes in the pools of amino acids were se en in plants treated with different chemical classes of inhibitors aff ecting a certain metabolic pathway. However, the changes were quite di fferent between inhibitors of different metabolic processes. The data generated from these studies could be used as a diagnostic tool to det ermine the mode of action of novel herbicides.