Effects of aspartate and other compounds on glyphosate uptake and growth inhibition in cultured carrot cells.

The strong correlation between glyphosate uptake and growth inhibition of cultured carrot (Daucus carota L. cv Danvers) cells incubated in the presence of aspartate suggests that aspartate reverses glyphosate inhibition of growth primarily by reducing intracellular glyphosate concentration. Other compounds which reverse glyphosate inhibition of cell growth gave a range of effects on glyphosate uptake: succinate, alpha-ketoglutarate, glutamate, pyruvate, and malate at 10 millimolar and phenylalanine at 2 millimolar reduced uptake by 0, 8, 11, 16, 27, and 34%, respectively. These results suggest that more than one mechanism of reversal may operate in these cells.Glyphosate and aspartate produced only minor effects on intracellular ammonia, media pH, and cell viability. This suggests that ammonia toxicity may not be an important mechanism of action of glyphosate in this system.