Energy Facilitated Na+ Uptake in Excised Corn Roots via 31P and 23Na NMR

Abstract
The uptake of sodium ions by excised corn root tips (Zea mays L. cv FRB-73) was monitored by 23Na nuclear magnetic resonance (NMR) methods in the presence of a membrane impermeable shift reagent under different metabolic conditions. In addition, for the first time, the energy status as well as the intracellular pH associated with this influx was concurrently evaluated by 31P NMR. The rate of sodium ion uptake decreased (in order) as the normal metabolic state was changed by the addition of cyanide, anaerobic condition, and carbonyl cyanide trifluoromethoxy phenyl-hydrazone treatment. The results suggest that the proton electrochemical potential of the plasma membrane may facilitate the influx of Na+.