In vitro effect of different Na+/K+ ratios on plasma membrane H+-ATPase activity in maize and sugar beet shoot

► Determination of hydrolytic and H+-pumping activity of plasma membrane (PM) H+ pump. ► In vitro effect of Na on the activity H+ pumps in maize and sugar beet plants. ► Effect of pH (in assay) on the hydrolytic activity of PM-H+ pumps in both plants. ► PM-H+-ATPases in sugar beet are more resistant to elevated Na concentration.