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.

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.

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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.

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