Salinity tolerance in the halophyte species Cakile maritima from the Apulia region, southern Italy.

Introduction: Cakile maritima is a succulent halophyte from the Brassicaceae family, commonly found along sandy coasts. Understanding its response mechanisms to sodium excess is crucial for its exploitation under sustainable biosaline farming. Methods: For the first time, this research investigated the pinnatifid C. maritima population from the Apulia region (Italy) grown under varying levels of NaCl (0 -T0, 100 -T100 and 400 -T400 mM NaCl). Results: The T100 plants showed higher leaf area (LA) and specific leaf area (SLA) compared to T0, with a slight reduction in succulence index (SI). In T400 plants, a reduction in shoot and root fresh weight, water content (WC), leaf dry weight, LA, and SLA was observed, alongside an increase in SI and dry matter concentration. No changes were detected in leaf Na and Cl concentrations, whereas T400 stems accumulated Na. Leaf K, Mg, and Ca concentrations remained stable. The operating efficiency of PSII (FPSII) was similar across treatments. In salt-exposed plants, the decrease of Fv’/Fm’ was counteracted by an improvement of qP, with carotenoids and anthocyanins appearing to be involved in photoprotection. Saltexposed plants maintained stomatal opening (gs), allowing a higher CO2 assimilation rate (An), especially in T100. Despite unimpaired An, T400 plants exhibited reduced canopy-level photosynthesis due to lower LA, leading to reduced shoot biomass. Among antioxidants, ascorbic acid and anthocyanins were effective in improving the antioxidative defence of T400 plants. Discussion: The results indicate that C. maritima employs a complex protective strategy involving morphological adjustments, selective ion accumulation, efficient photoprotection, maintained gas exchange, and a potent antioxidant system to mitigate salinity stress, demonstrating its strong potential for biosaline agriculture.