<p>Understanding the tissue-specific physiological strategies for salt resilience is critical for crop improvement. This study characterized the differential responses of two spring wheat varieties, XC43 (tolerant) and XC40 (non-tolerant), to varying NaCl concentrations. Our results demonstrated that salinity suppressed plant growth in both varieties, XC43 effectively mitigated salt-induced growth inhibition through optimizing root morphology and sustaining photosynthetic efficiency. Mechanistically, XC43 maintained favorable ion homeostasis by restricting Na⁺ translocation to shoots while actively enhancing root K⁺ retention, thereby preserving high K⁺/Na⁺ ratios. Furthermore, XC43 deployed a root-dominant antioxidant defense system. Compared to XC40, XC43 exhibited significantly lower reactive oxygen species (ROS) accumulation and lipid peroxidation in roots. The maintenance of higher ascorbate peroxidase (APX), glutathione reductase (GR), dehydroascorbate reductase (DHAR) activities, and more favorable ascorbic acid/dehydroascorbic acid (AsA/DHA) and reduced glutathione/glutathione disulfide (GSH/GSSG) ratios provided superior redox protection in XC43 roots under moderate and high salinity. Principal component analysis validated that the salt resilience of XC43 was primarily driven by root-specific functional traits. Our findings revealed that the synergistic coordination between root K⁺ retention and the AsA-GSH cycle was a core determinant of salt tolerance, identifying root-mediated physiological integration as a pivotal target for breeding salt-resilient spring wheat varieties.</p>