Effects of Glyphosate N-(phosphonomethyl)-glycine on Water Potential, and Activities of Nitrate and Nitrite Reductase and Aspartate Aminotransferase in Lucerne and Clover

Summary Nitrate and nitrite reductase activities, water potential, and aspartate transaminase were measured in Medicago sativa (cv. Aragon) and Trifolium pratense (cv. Violeta) subjected to various glyphosate (N-[phosphonomethyl]-glycina) concentrations. Water potential was reduced by the herbicide at 0.15 mM, 1.5mM and 15 mM. The effect was greater in clover than lucerne. In both species an increase of water potential was observed at the end of the treatment. The activities of all three of the above enzymes were reduced by glyphosate. The results suggest that glyphosate affects water status and inhibits transamination reactions and consequently disturbs normal nitrate metabolism of these leguminous plants. In general, clover appears to be more sensitive to glyphosate.