Glyphosate Uptake by Suspension-Cultured Potato (Solanum tuberosumandS. brevidens) Cells

Abstract

Characteristics of glyphosate [N-(phosphonomethyl)glycine] uptake for as long as 3 days by plant cells were studied using suspension-cultured potato (Solanum tuberosumL. cv. ‘Red Pontiac’ andS. brevidensPhil.) cells. An experimental system was developed wherein uptake was assayed in a reduced salt medium that minimized cell growth yet maintained cell viability. Glyphosate uptake was nonlinear over time; an immediate rapid uptake phase was followed by uptake at a decreased rate that continued through 72 h. Glyphosate uptake was the same in both an experimental uptake medium (reduced salt and sucrose, no hormones) and in the complete growth medium used for routine cell growth. The pattern of glyphosate uptake was similar with both Red Pontiac andS. brevidenscells, though uptake was greater in Red Pontiac cells. Glyphosate uptake was not inhibited by 1 mM CaSO4, MgSO4, MnSO4, or ZnSO4. Rather, uptake was inhibited by the absence of salts at 8 h, and ZnSO4and MnSO4increased uptake. Similarly, increasing concentrations (0 to 5 mM) of CaSO4and CaCl2did not inhibit uptake, whereas the absence of either salt of Ca2+decreased uptake. Increasing concentrations of (NH4)2SO4(0 to 150 mM) did not affect glyphosate uptake, but (NH4)2SO4at 50 mM and above was toxic to the cells.