Unraveling saline-alkali stress tolerance: Contrasting morpho-physiological, biochemical, and ionic responses in...

Saline-alkali stress inhibits the normal growth and development of plants, severely restricting crop yields. Maize is one of the most important staple crops worldwide. However, germplasm resources with strong saline-alkali tolerance that are suitable for large-scale field production remain scarce. Therefore, the objective of this study was to identify saline-alkali-tolerant maize inbred lines using a mixed saline-alkali solution and to investigate the associated changes in plant growth and physiological characteristics under stress conditions. In this study, 150 maize inbred lines were evaluated for their tolerance to saline-alkali stress at the germination stage. Based on principal component analysis, Pearson correlation analysis, and comprehensive D-value evaluation of germination parameters, all materials were classified into four distinct saline-alkali tolerance levels. Growth performance and physiological-biochemical measurements of representative extreme lines indicated that H23146 was a saline-alkali-sensitive inbred line, H23072 exhibited saline-alkali tolerance, and 22KN3894 was identified as a highly saline-alkali-tolerant inbred line. Compared with H23146 and H23072, 22KN3894 exhibited significantly higher activities of antioxidant enzymes and greater contents of soluble osmolytes, K⁺, Ca²⁺ and abscisic acid (ABA). It also showed lower levels of malondialdehyde (MDA) and Na+, a reduced Na⁺/K⁺ ratio, and decreased electrolyte leakage, indicating reduced cell membrane damage. Further analyses of phenotypic, physiological, and biochemical responses following exogenous ABA application revealed that ABA alleviated the damage caused by saline-alkali stress. This study provides valuable germplasm resources for the breeding of saline-alkali-tolerant and high-yielding maize varieties. Furthermore, it offers new insights into the role of ABA in saline-alkali tolerance in maize, laying a foundation for future research on the underlying molecular mechanisms.