Integrated physiological and metabolic reprogramming enables saline irrigation adaptation of Tamarix ramosissima in an arid coal-mining restoration landscape of Hami, Xinjiang

Field-based information on how established woody plants partition physiological responses between roots and shoots under sustained saline irrigation remains limited, particularly in arid coal-mining restoration landscapes. Here, we investigated field-established Tamarix ramosissima Ledeb. under freshwater and saline irrigation to characterize organ-specific changes in osmotic adjustment, oxidative status, antioxidant regulation, nitrogen metabolism, phytohormonal responses, and lipid status. Plants were exposed to freshwater irrigation or saline irrigation containing 8 or 12 g L⁻¹ total dissolved solids, with irrigation-water electrical conductivity monitored before application. The nine independently irrigated plots, with three plots per treatment, served as experimental units, while tissues from five plants within each plot were pooled to generate one plot-level biological replicate. Moderate salinity (8 g L⁻¹) was associated with increased soluble sugars and proline and with changes in antioxidant-related proteins, whereas 12 g L⁻¹ caused stronger pigment loss, oxidative imbalance, and suppression of nitrogen-assimilation-related proteins. At 12 g L⁻¹ , shoot chlorophyll decreased by 46.1% and carotenoids by 33.9% relative to the control, while H₂O₂ increased by 47% in roots and 96% in shoots, and MDA increased by 105% and 40%, respectively. Salinity was also associated with oxidation of the ascorbate-glutathione redox pools and reductions in nitrate reductase, glutamine synthetase, glutamate synthase, IAA, GA, and CTK, together with increases in ABA, JA, SA, and SL. Triglyceride accumulation further indicated altered lipid status under increasing salinity. Overall, increasing salinity shifted the physiological profile from osmotic and antioxidant adjustment at 8 g L⁻¹ toward stronger oxidative, pigment, redox, nitrogen-assimilation, and hormonal disturbances at 12 g L⁻¹ , with distinct response patterns between roots and shoots. These findings provide physiological evidence relevant to evaluating saline irrigation conditions for T. ramosissima in salt-affected arid restoration landscapes.