Abstract: Due to global climate change and the limitations of land resources, the cultivation and growth of Medicago sativa are influenced by multiple stresses. In this study, M. sativa cv. Aohan was subjected to various single and multifactorial stressors. The treatments included stressors of alkaline salt (A, 100 mmol·L^-1 NaHCO₃), neutral salt (S, 100 mmol·L^-1 NaCl), phosphorus deficiency (P, 10% KH₂PO₄ in HoagLand nutrient solution), heavy metal (Cd, 5 μmol·L^-1 CdCl₂), and drought (D, 30% water supply), along with unstressed control (CK, Hoagland nutrient solution). This setup allowed for a comprehensive evaluation of the eco-physiological responses of M. sativa cv. Aohan seedlings to diverse abiotic stressors. The results showed that the inhibitory effects of multifactorial stresses on plants were significantly higher than those of single stress, with the alkaline salt stress playing a dominant role in all combinations. Taking A+D+P stress as an example, aboveground growth and photosynthetic capacity were severely impaired, with plant height reduced by 43.05% and significant decline in relative chlorophyll content. The morphogenesis of root system underwent adaptive reshaping, showing reductions in total root length, surface area, and volume by 83.74%, 81.44%, and 78.92%, respectively, while the average root diameter increased by 16.22%. In addition, to counteract oxidative damage, the superoxide dismutase activity in leaves increased by 136.36%. Our results indicate that M. sativa cv. Aohan seedlings can mitigate adverse effects of multiple stresses through synergistic responses involving root morphological reshaping and antioxidant regulation.

Key words: multifactorial stress combination, root system architecture, antioxidase enzyme activity