Calligonum mongolicum employs a variety of physiological and biochemical strategies to acclimatize to hyperarid saline deserts

Key message

The shift in tolerance mechanisms from antioxidant to osmotic adjustments in Calligonum mongolicum, resulting in high seedling survival rates under progressively increasing saline stress, indicates the plant’s suitability for desert restoration and revegetation programs.

Abstract

Salinity is a significant barrier to vegetation renewal in the nutrient-limited saline and hyperarid Taklamakan desert. Using a pot experiment, we evaluated the growth and physiological responses of Calligonum mongolicum seedlings to saline stress (0, 50, 150, and 300 mM). The survival rate, root length, shoot length, and chlorophyll a content significantly reduced under 150 mM and 300 mM salinity compared with the control. Additionally, plant height, total biomass, and chlorophyll b content showed significant reductions across all salinity stress levels. Conversely, the chlorophyll a/b ratio increased with increasing salinity concentrations, indicating that salinity may adversely affect Chl b more than Chl a (p < 0.05). Furthermore, significant increases were observed in Na⁺, H₂O₂, and TBARS, whereas K⁺/Na⁺, K⁺, NO₃⁻, and NH₄⁺ decreased with increased stress levels. Under all treatments, superoxide dismutase, catalase, and peroxidase activities were upregulated, whereas glutamate synthase was decreased, and glutamine synthase was unaffected. Nitrate reductase activity was significantly reduced under 300 mM salinity. Moreover, significant increases were observed in proline under medium and high stress and in soluble protein under all stress levels, while soluble sugars were only increased under high stress. Our findings suggest Calligonum seedlings may sacrifice biomass production to maintain their anti-stress mechanisms. Increasing salinity concentrations may cause an increase in energy expenditure for antioxidant enzymes (at 50–150 mM) and osmotic adjustment (at 150–300 mM). Based on univariate and multivariate analyses, Calligonum seedlings subjected to low salinity can grow and survive without substantial changes in their functionality. Consequently, Calligonum seedlings may be utilized in vegetation renewal efforts in the Taklamakan desert to combat desertification under climate change scenarios.