Effects of Calcium, Magnesium, and Phosphate on Glyphosate Absorption by Cultured Plant Cells

Abstract

Effects of several inorganic ions on short-term glyphosate absorption by cultured plant cells were determined by measuring the glyphosate content of cells exposed to inorganic salts in a 0.01-mM glyphosate solution buffered at pH 5.7. Within 10 min, glyphosate absorption by potato and velvetleaf cells was stimulated about equally by 1.5 mM CaCl2or 1.5 mM MgCl2but was not affected by 1.5 mM KCl. Glyphosate absorption by both species increased linearly with log10CaCl2concentration; for velvetleaf cells, the response was greatest for CaCl2concentrations greater than 0.2 mM. Over time of absorption, glyphosate concentration within velvetleaf cells approached an asymptote. Addition of 0.1 mM KH2PO4inhibited glyphosate absorption by potato cells in the presence or absence of Ca2+and Mg2+salts; all other K+salts tested had no effect. Glyphosate absorption by potato, velvetleaf, soybean, corn, and rice cells was stimulated by 5.0 mM CaCl2but was inhibited by 0.1 mM KH2PO4in the presence of 0.05 or 5.0 mM CaCl2.