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The selection and introduction of drought tolerant species is a common method of restoring degraded grasslands in and environments. This study investigated the effects of water stress on growth, water relations, Na+ and K+ accumulation, and stomatal development in the native plant species Zygophyllum xanthoxylum (Bunge) Maxim., and an introduced species, Caragana korshinskii Kom., under three watering regimes. Moderate drought significantly reduced pre-dawn water potential, leaf relative water content, total biomass, total leaf area, above-ground biomass, total number of leaves and specific leaf area, but it increased the root/total weight ratio (0.23 versus 0.33) in C. korshinskii. Only severe drought significantly affected water status and growth in Z. xanthoxylum. In any given watering regime, a significantly higher total biomass was observed in Z xanthoxylum (1.14 g) compared to C. korshinskii (0.19 g). Moderate drought significantly increased Na+ ccumulation in all parts of Z xanthoxylum, e.g., moderate drought increased leaf Na+ concentration from 1.14 to 2.03 g/100 g DW, however, there was no change in Na+ (0.11 versus 0.12) in the leaf of C. korshinskii when subjected to moderate drought. Stomatal density increased as water availability was reduced in both C. korshinskii and Z xanthoxylum, but there was no difference in stomatal index of either species. Stomatal length and width, and pore width were significantly reduced by moderate water stress in Z xanthoxylum, but severe drought was required to produce a significant effect in C. korshinskii. These results indicated that C. korshinskii is more responsive to water stress and exhibits strong phenotypic plasticity especially in above-ground/below-ground biomass allocation. In contrast, Z xanthoxylum was more tolerant to water deficit, with a lower specific leaf area and a strong ability to maintain water status through osmotic adjustment and stomatal closure, thereby providing an effective strategy to cope with local extreme and environments.