Unraveling Salinity Tolerance Mechanisms in Cultivated Barley and Its Wild Relative Hordeum marinum : Insights Into Antioxidant Defense and Physiological Adaptation

Sea barley ( Hordeum marinum ), a halophyte among the largely glycophytic Hordeum species, is a valuable genetic resource for elucidating salt tolerance mechanisms in cereals. This study assessed the physiological, biochemical, and antioxidant responses of two H. marinum genotypes (AR and SH) and the salt‐tolerant Hordeum vulgare L. cv. Rihane (RH) under 400 mM NaCl for 3 weeks. Results revealed a marked growth reduction in RH, correlating with higher accumulation of Na and Cl in leaves (six‐ and four‐fold, respectively) and roots (2.29‐ and 1.67‐fold, respectively) compared to AR and SH. In contrast, SH and AR maintained higher leaf osmotic potential (−1.96 and −2.11 MPa, respectively) and better root K acquisition under salinity. Despite an increase in leaf proline content and antioxidant enzyme activities, RH displayed elevated hydrogen peroxide (H ₂ O ₂ ) and malondialdehyde (MDA) accumulation compared to SH and AR, indicating insufficient antioxidant defenses against salt‐induced oxidative stress. Correlation analysis revealed positive associations between Cl, Na, H ₂ O ₂ , and MDA, while negative correlations emerged with K, osmotic potential, and antioxidant enzyme activities. The superior salt tolerance of AR and SH was closely linked to their ability to maintain osmotic balance, regulate ion homeostasis, and mitigate oxidative stress. These traits offer promising targets for improving salt tolerance in cultivated barley and other cereals.