Effect of K+ Nutrition on Plasma Membrane H+-ATPase of Suaeda salsa under Salt Stress

Suaeda salsa seedlings grown in Hoagland nutrient solution were treated with different concentrations of NaCl combined with two levels of K+ (0 and 6 mmol/L) to study the effect of K+ nutrition on the growth and activity of leaf plasma membrane proton-translocating adenosine triphosphatase (PM H(+)ATPase). The leaf PM H+-ATPase activity was significantly increased with increasing NaCl concentration under high K+ application (6 mmol/L) but little changed under K+ starvation (0 mmol/L). Western blot analysis showed that the subunit of leaf PM H+-ATPase and its protein amount were not affected by NaCl treatments under K+ starvation (0 mmol/L) but increased under high K+ application (6 mmol/L). There was a positive correlation between activity of PM H+-ATPase and the protein amount of PM H+-ATPase. The results suggest that K+ nutrition played an important role in the salt tolerance of S. salsa and that enhancement of PM H+-ATPase activity under salt stress was K+-dependent.