Amiloride inhibition of vacuolar Na+/H+ antiporter enhance salt stress in Zea mays L. seedlings.

The aim of this study to show the importance of salt intracellular compartmentation as a tolerance mechanism by inhibition of Na+/H+ antiporter system. In this research 4 day/old Zea mays L. seedlings (var. single cross 704) were exposed to 200 and 300 mM NaCl with and without 100 and 200 micromolar amiloride. After 48 h, the roots and shoots of seedlings were harvested separately. The changes of total Na+ absorption, the amount of malondialdehyde and the activity of antioxidant enzymes such as guaiacol peroxidase, ascorbate peroxidase and catalase were analysed. The results indicated that Na+ absorption has been increased by salt stress but was not influenced by amiloride. Malondialdehyde content and the activity of antioxidant enzymes such as guaiacol peroxidase, ascorbate peroxidase and catalase were increased in salt stressed plants specially in plants treated with salt and amiloride. Therefore salt stress has caused osmotic and oxidative stress in plants and amiloride as inhibitor of vacuolar Na+/H+ antiporter has been increased salt stress. Therefore we concluded that Na+ compartmentation in the cell is very important to reduce its damage in the cytosol and vacuolar Na+/H+ antiporter has an essential role in Na+ homeostasis in the cell by exporting excess Na+ to the vacuole.

Salt pretreatment enhance salt tolerance in Zea mays L. seedlings.

Recent molecular studies show that genetic factors of salt tolerance in halophytes exist in glycophytes too, but they are not active. If these plants expose to low level salt stress these factors may become active and cause plants acclimation to higher salt stresses. So because of the importance of these findings in this research the effect of salt pretreatment has been examined in Zea mays seedlings. To do the experiment four day old Zea mays seedlings (Var. single cross 704) pretreated with 50 mM NaCl for the period of 20 h. Then they were transferred to 200 and 300 mM NaCl for 48 h. At the end of treatment roots and shoots of seedlings were harvested separately. The changes of K+ -leakage, the amount of malondialdehyde, proline, soluble sugars and the Hill reaction rate were analyzed. The results indicated that the amount of K+ -leakage and malondialdehyde (MDA) have been increased because of salt-induced lipid peroxidation and membrane unstability. Soluble sugars and proline as osmoregulators has been increased in stress condition and in pretreated plants with NaCl were the highest. The rate of Hill reaction was reduced significantly in stressed plants. Therefore we concluded that salt stress causes serious physiological and biochemical damages in plants and salt pretreatment enhances tolerance mechanisms of plants and help them to tolerate salt stress and grow on salty environments.