Physiological and Biochemical Mechanisms Behind Enhanced Salinity Tolerance in Limonium irtaense Seedlings Following Recovery from Salt Stress

<i>Limonium irtaense</i> is an endangered halophyte endemic to coastal Castellón (Spain). This study aimed to support its conservation by assessing the effects of salinity on seed germination and seedling performance, as well as plants' physiological and biochemical responses to salt stress during early vegetative growth. Seed germination was tested in the presence of 0 to 300 mM NaCl, followed by recovery assays for non-germinated seeds. Seedlings were grown under three salinity levels, by irrigation with water (control), 300 mM NaCl or 600 mM NaCl. Growth parameters, photosynthetic pigments, osmolytes, ion contents, oxidative stress markers and antioxidant compounds were determined in plants derived from the initial germination tests and the recovery of germination assays and subjected to the different salt treatments. Germination was highest in distilled water and declined with increasing salinity; however, salt-inhibited seeds germinated rapidly and efficiently in the recovery assays. Seedlings from salt-primed seeds showed higher survival rates and biomass than those from control germination tests. Salt treatments significantly reduced growth, with plants derived from salt-treated seeds generally showing higher tolerance, probably because of enhanced proline accumulation, more efficient transport and sequestration of toxic ions in leaf vacuoles, and potassium retention. These findings provide insights into <i>L. irtaense</i> adaptation mechanisms and support using salt-priming to improve conservation and translocation efforts for this endangered species.