Abstract
Drought stress is one of the most dangerous consequences of climate change, threatening plants and ecosystem stability worldwide. Most available studies have focused on drought tolerance in crops, while many desert native plant species remain poorly studied, despite their exceptional ability to tolerate drought. This research gap limits our ability to harness these plants in climate change-resilient agriculture, ecological restoration, food and forage innovation, and genetic improvement programs. This study aims to evaluate and compare the drought tolerance mechanisms of four native species, including Lycium shawii, Salvadora persica, Calligonum comosum, and Haloxylon salicornicum, under three irrigation regimes: control (100% field capacity), moderate drought (40% FC), and severe drought (25% FC), and to identify the traits responsible for tolerance to use them in future agricultural achievements. Morphological parameters, photosynthetic pigments, relative water content (RWC), gas exchange parameters (A, gs, E, VPD), osmolyte accumulation, lipid peroxidation (MDA), antioxidant enzyme activities (CAT, POD, SOD, PPO), and membrane stability (EC, EL) were assessed. Drought reduced biomass and plant height in all species, with L. shawii and H. salicornicum showing high root-to-shoot ratios due to adaptive root investment. L. shawii had stable chlorophyll and carotenoid levels, while C. comosum showed a sharp decline. Photosynthetic efficiency and water use parameters remained stable in L. shawii and S. persica, while they declined under severe drought in the remaining species. L. shawii had higher proline and sugar accumulation, reflecting effective osmotic adjustment. L. shawii and S. persica had strong antioxidant responses, and lower MDA and electrolyte leakage confirmed better oxidative stress defense. In contrast, C. comosum showed weak membrane stability. These results showed that L. shawii and S. persica have superior drought tolerance through physiological, biochemical, and structural adaptations. This research helps in selecting drought-tolerant species for desert rehabilitation, land restoration, and future breeding programs.