Coordinated maintenance of deeper roots and anatomical remodeling enhances salt tolerance in spring wheat

Background Salt stress is an important abiotic factor limiting yield formation and quality improvement in spring wheat. However, there is still a lack of systematic understanding of how root architectural maintenance and anatomical remodeling coordinately influence shoot growth maintenance during the development of salt tolerance in spring wheat. Methods To address this gap, a high-throughput paper-based cultivation platform was used to assess the shoot phenotypes, root architectural traits, and root anatomical characteristics of 28 spring wheat genotypes under control and Salt treatments. Principal component analysis, membership function analysis, and cluster analysis were combined to establish an integrated salt-tolerance evaluation system, and genotypes with contrasting salt tolerance were further selected to investigate differences in layered root architecture and anatomical responses. Results The results showed that salt stress significantly inhibited both shoot and root growth in spring wheat. The first five principal components explained 81.37% of the total variation, and the integrated evaluation system effectively distinguished salt-tolerance differences among genotypes and identified plant height, total root length, average root length, cortex/stele area ratio, and lacunar/cortex area ratio as key phenotypic indicators. Further analyses showed that root architectural maintenance and anatomical adjustment were significantly associated with shoot growth. Particularly in the deeper root system, salt-tolerant genotypes exhibited more stable salt tolerance, with root surface area reduced by only 18.68%–38.61%, whereas the corresponding reductions in salt-sensitive genotypes ranged from 28.57%–90.00%. Meanwhile, salt-tolerant genotypes showed more coordinated cortical contraction, stele maintenance, and lacunar adjustment, indicating that the key root adaptive basis of salt tolerance in spring wheat does not lie in any single structural trait, but rather in the coordinated optimization between sustained deeper-root maintenance and anatomical remodeling. Conclusion This study reveals the root basis of salt adaptation in spring wheat seedlings from the perspective of root architecture–anatomical coordination, provides new evidence for understanding the phenotypic–structural coupling mechanism underlying wheat salt tolerance, and offers operational indicators for salt-tolerant germplasm screening and targeted improvement of root traits.