Compensatory growth and ion balance adaptation mechanisms of Salix matsudana Koidz under heterogeneous salinity stress

Investigating plant responses to both homogeneous and heterogeneous salt concentrations is essential for the development and effective utilization of saline-alkali land. This study employs a split-root experiment to examine the growth characteristics, photosynthesis, ion distribution, root vigor, and water uptake of Salix matsudana under salt stress. The results indicate that root vigor in low-salinity zones significantly surpasses that in high-salinity zones under heterogeneous salt treatment, thereby enhancing moisture absorption in low-salinity areas. This mitigates the suppressive effects of salt concentration on the aboveground growth and stomatal limitations of Salix matsudana, while maintaining a high net photosynthetic rate and elevated levels of K⁺, Ca²⁺, and Mg²⁺, along with reducing Na⁺ content in the leaves. Additionally, micro X-ray fluorescence imaging reveals that Na⁺ is uniformly distributed in the leaves, while K⁺ is primarily concentrated in the main veins and redistributed to the root system in low-salinity areas under heterogeneous salt stress, further promoting ion balance in Salix matsudana. Compensatory growth is also observed in the roots of low-salinity zones, supporting normal plant development. In conclusion, compared to homogeneous salt stress, heterogeneous salt stress significantly alleviates the growth and physiological damage in Salix matsudana. Reducing salt concentrations in localized areas of saline-alkali soils may help mitigate the inhibitory effects of salt stress, providing a theoretical foundation for adaptive cultivation in saline-alkali regions.