Comparative Analysis of Salt Tolerance and Its Underlying Physiological Mechanisms between Wild and Cultivated Barley at Seedling Stage

Background Soil salinity poses a significant threat to global agricultural production. As the direct progenitor of cultivated barley, wild barley ( H. spontaneum ) harbors rich genetic diversity, which is crucial for stress adaptation. To systematically compared their salt tolerance, the study performed a comprehensive evaluation among six barley varieties (two wild barley, two salt - tolerant and two salt - sensitive cultivated barley), employing analysis of root / shoot growth and physiological traits under salt stress conditions. Results To evaluate the physiological performance differences between wild and cultivated barley, this study used tissue staining to assess the degree of damage to barley tissues, fluorescence staining techniques to observe the distribution patterns of sodium ions (Na ⁺ ) and potassium ions (K ⁺ ), and electron microscopy scanning to analyze stomatal aperture. The results demonstrated that although salt stress negatively affected plant growth in all the barley varieties, wild barley exhibited higher salt tolerance. Specifically, in terms of physiological indicators, the wild varieties maintained significantly lower accumulations of hydrogen peroxide (H ₂ O ₂ ) and malondialdehyde (MDA), lower cytoplasmic Na ⁺ contents, less cellular damage, smaller stomatal apertures, higher photosynthetic rates, and stronger antioxidant enzyme activities than all cultivated varieties. Conclusion In summary, under salt stress conditions, wild barley exhibits superior physiological performance to cultivated barley regarding ion homeostasis, reactive oxygen species (ROS) homeostasis, and stomatal regulation. These findings enhance our understanding of the divergence in salt tolerance between wild and cultivated barley and provide valuable insights for breeding more salt-tolerant crops.