Biochemical and Physiological Changes in Response to Salinity in Two Durum Wheat (Triticum turgidum L.) Genotypes

The effects of salt stress on the activity of antioxidative enzymes, some oxidative stress indices and Na+ and K+ content were studied in leaves of two durum wheat cultivars, Egypt 449 (salt-tolerant) and Syria 371 (salt-sensitive), grown under control (nutrient solution) or salt stress (nutrient solution containing 200 mM NaCl) conditions. Leaves of control and salt-stressed plants were harvested from 10 days old plants beyond salt treatment. The results showed significant increase for activities of antioxidant enzymes such as ascorbate peroxidase (APX) and guaiacol peroxidase (GPX), in Egypt 449 under salinity. At the same time, in cultivar Egypt 449, activity of SOD and CAT were not changed. Meanwhile, under salinity condition the activities of antioxidant enzymes such as superoxide dismutase (SOD), catalase (CAT) and GPX in cultivar Syria 371 was lower than control. There was no significant difference between salinity situation and control ones regarding APX activity. Salt stress elevated the amounts of malondialdehyde (MDA) in both cultivars. However, the increasing rate in Syria 371 was more than (four times) that of Egypt 449. Membrane stability index (MSI) of both cultivars negatively influenced by salinity. This negative impact on Syria 371 was highlighted than on Egypt 449. Hydrogen peroxide (H2O2) content of salinity faced Syria 371 was higher than control. Both cultivars displayed increasing and decreasing trend for Na+ and K+ content, respectively. Moreover, K+/Na+ ratio was decreased in both cultivars due to salinity. The studied parameters elucidated that salt resistance of Egypt 449 might be due to increased activity of antioxidant enzymes, low lipid peroxidation, assumingly lower changes in membrane stability index and avoidance of Na+ absorption.