Impact of Salinity Duration on Growth, Photosynthesis, Water Relations, and Recovery Capacity Reveals Adaptive...

Although the physiological mechanisms underlying salt tolerance in wild barley (Hordeum maritimum) are relatively well understood, its recovery after salt stress remains poorly characterized. In this pot experiment, plants were exposed to 200 mM NaCl for 0, 15, 30, 45, or 60 days to evaluate changes in growth and water status. Wild barley exhibited high tolerance during the early stages of salt exposure, maintaining normal growth and water balance for up to 30 days. However, longer exposure reduced plant growth and leaf water content, indicating that prolonged salinity eventually compromises plant performance. To cope with salt stress, plants accumulate soluble sugars, proline, and mineral ions, helping maintain water uptake and cell hydration. Mineral ions, particularly sodium (Na⁺) and chloride (Cl^-), contributed most to osmotic adjustment, accounting for up to 87% of the total osmotic adjustment after 60 days of treatment. Salt stress also induced structural modifications in leaf tissues that enhanced water retention and maintained cell function under saline conditions. Importantly, unlike cultivated barley, H. maritimum fully recovered after the salt treatment ended, restoring both growth and water relations. This strong recovery capacity demonstrates remarkable physiological flexibility and adaptation to changing environmental conditions. These findings highlight the adaptive advantage of wild barley in fluctuating saline environments, where efficient osmotic adjustment, flexible cell wall dynamics, and rapid recovery are key adaptive traits. From both physiological and ecological perspectives, H. maritimum represents a valuable model for studying salt tolerance mechanisms and a promising genetic resource for improving crop salinity resilience.