Salt stress responses and tolerance mechanisms in native desert plants of the UAE: growth, biochemical, and antioxidant perspectives

Soil salinization threatens productivity and ecosystem stability in arid regions, yet salinity-tolerance mechanisms of native UAE desert shrubs remain poorly resolved under field-like conditions. This study aimed to identify tolerance strategies and rank salinity resilience among <i>Lycium shawii</i>, <i>Salvadora persica</i>, <i>Calligonum comosum</i>, and <i>Haloxylon salicornicum</i>. Plants were grown in an outdoor pot trial under ambient desert conditions and irrigated with three salinity levels (ECw = 1.5, 10, and 25 dS m^-¹). Severe salinity (25 dS m^-¹) revealed clear interspecific divergence: <i>S. persica</i> and <i>L. shawii</i> maintained 100% survival, relatively stable water status and photosynthetic performance, and reduced membrane injury and lipid peroxidation. Their tolerance was associated with stronger osmotic adjustment (higher proline and soluble sugars), improved ion homeostasis (lower shoot Na⁺ accumulation and more stable K⁺ status relative to <i>H. salicornicum</i>), and enhanced antioxidant capacity (higher enzyme activities and radical scavenging). In contrast, <i>C. comosum</i> showed reduced survival (83.3%), marked dehydration, strong photosynthetic inhibition, weak antioxidant activation, and pronounced membrane damage, indicating limited high-salinity tolerance. <i>H. salicornicum</i> displayed intermediate performance, consistent with ion-handling-based tolerance but with higher physiological costs. Overall tolerance ranked <i>S. persica</i> > <i>L. shawii</i> > <i>H. salicornicum</i> > <i>C. comosum</i>. Correlation analysis and PCA supported coordinated contributions of water status, ion regulation, and oxidative protection to tolerance. These findings provide field-relevant mechanistic evidence to guide species selection for biosaline agriculture and saline-land rehabilitation in arid environments.