Effect of salinity on organic solutes contents in barley.

Salinity (NaCl stress) was applied with 50, 100, 200, 300 and 400 mM NaCl. The shoot and root water content and organic solutes contents of two barley varieties (Hordeum vulgare L. var. Afzal and var. EMB82-12) were determined in various concentrations of NaCl. Soluble sugar and proline contents were increased in two barley varieties in response to increased salt concentration, but this increase in Afzal var. were higher than EMB82-12. Soluble protein content was decreased in two barley varieties in response to different salt regimes and this decrease in Afzal var. was lower than EMB82-12 var. RWC decreased with increasing NaCl concentrations. Decrease of water content in EMB82-12 plants was higher than Afzal plants.

Growth and inorganic solute accumulation of two barley varieties in salinity.

Salinity (NaCl stress) was applied with 50, 100, 200, 300 and 400 mM NaCl. The shoot and root length, fresh and dry weight, sodium and potassium content of two barley varieties (Hordeum vulgare L. var. Afzal and var. EMB82-12) were determined in various concentrations of NaCl. Root and shoot length, fresh and dry weight were decreased in two barley varieties in response to increased salt concentration, but the decrease was more significant in the root. Sodium content was increased and potassium content was decreased in two barley varieties in response to different salt regimes, but in general, these changes were more significant in the root.

Antioxidant responses of two barley varieties to saline stress.

In this study, we investigated antioxidant responses of activities of Superoxide Dismutase (SOD), Catalase (CAT), Ascorbate Peroxidase (APX) and Guaiacol Peroxidase (GPX) to saline stress in two barley varieties named Hordeum vulgare L. var. Afzal and var. EMB82-12 treated with 50, 100, 200, 300 and 400 mM NaCl for 3 days. The MDA content of Afzal plants grown under different salt regimes remained nearly constant but it largely increased in EMB82-12 plants under the same conditions. There was a linear and significant correlation in CAT, APX, SOD, GPX activities in Afzal plants in response to increased salt concentration. The strong and positive correlation between antioxidant enzymes and salt concentrations, may account for the MDA level of Afzal plants remaining constant in response to different salt regimes. In general, the activities of antioxidant enzymes were increased in the root and shoot under saline stress. But the increase was more significant and consistent in the root. Among the antioxidant enzymes, CAT activity was increased the most drastically.

Effects of salinity on photosynthetic pigments, respiration, and water content in two barley varieties.

Salinity (NaCl Stress) was applied with 50, 100, 200, 300 and 400 mM NaCl. The shoot and root respiration of two barley cultivars (Hordeum vulgare L. variety Afzal and variety EMB82-12) were determined in various concentrations ofNaCl. Chlorophyll a, b and total chlorophyll content were significantly decreased, but carotenoids content increased under salinity. Decrease of chlorophyll content in EMB82-12 was higher than Afzal, but carotenoids content in Afzal variety was higher than EMB82-12. Relative Water Content (RWC) was used to indicate the degree of stress. Oxygen uptake declined in shoot and root with increasing NaCl concentrations. Decrease of oxygen uptake in shoot and root of EMB82-12 variety was higher than Afzal variety. RWC decreased with increasing NaCl concentrations. Lowering of RWC reduced growth and increased shoot/root ratio. Decrease of water content in EMB82-12 plants was higher than Afzal plants. Shoot/root ratio in EMB82-12 variety was higher than Afzal.

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.