Abstract: Aims The objective of this study is to elucidate the response mechanism of amino acids and their derivatives secreted by the roots of salt-tolerant plants under salt stress. Methods This study selected Elytrigia elongata as the research subject. Four levels of salt stress (control, mild, moderate, and severe) were established by adding varying concentrations of NaCl. Non-targeted metabolomics analysis based on liquid chromatography-mass spectrometry (LC-MS) was employed to investigate the changing trends of root-secreted amino acids and derivatives in response to increasing salt stress intensity, as well as their relationships with root characteristics and the rhizosphere soil properties. Important findings The results indicated that with escalating salt stress, the secretion of L-Arginine, L-Dopachrome, 2,3,4,5-tetrahydrodipicolinic acid, N-Acetylaspartic acid, L-Phenylalanine, L-Methionine, Trans-3-hydroxy-L-proline, and N-Acetyl-L-phenylalanine significantly decreased. In contrast, Betaine and N-Jasmonic acid isoleucine exhibited significant increases, although no significant differences were observed in the mild, moderate, and severe salt stress treatments. The secretion amounts of the other amino acids and derivatives showed no significant changes. These findings suggest that Elytrigia elongata adapts to salt-stressed environments by modulating the secretion of specific amino acids and derivatives. Soil salinity, electrical conductivity, volumetric water content, total root volume, and total root surface are keys factors influencing the upregulation of betaine and N-jasmonic acid isoleucine. Soil electrical conductivity serves as a key influencing factor for the secretion of eight down-regulated amino acids and their derivatives. Path analysis indicates that both the up-regulated and down-regulated groups of ten amino acids and their derivatives are regulated by soil electrical conductivity and pH.Collectively, these results provide a scientific foundation for understanding the physiological mechanisms underlying how plants adapt to salt stress.

Key words: Elytrigia elongata, salt stress, root exudates, amino acids and their derivatives