This study investigated the effects of Pb stress on the physiology of seed germination and the antioxidant system and Pb accumulation in seedlings of alfalfa （Medicago sativa）. Six Pb stress concentrations were set to evaluate seed germination physiology， and three Pb stress concentrations were established to assess the activity of the antioxidant system and Pb content in seedlings. The results showed that： （1）Pb stress inhibited seed imbibition and germination， reduced the activities of amylase and protease， and decreased the levels of soluble sugars， reducing sugars， free proline， and free amino acids. （2）The suitable concentration for Pb during seed germination of alfalfa was ≤1.84 mmol·L^-1， with a half lethal concentration and a limit concentration of 3.93 mmol·L^-1 and 7.29 mmol·L^-1， respectively. （3）Under 2.0 mmol·L^-1 Pb stress， the antioxidant system activity in seedling leaves initially increased and then decreased. At 4.0 mmol·L^-1 Pb stress， the antioxidant system collapsed， and oxidative damage intensified. （4）Under Pb stress， Pb content in seedlings significantly increased， with the highest levels in roots， followed by stems and leaves. Only a small amount of Pb translocated from underground to aboveground parts. This indicates that Pb stress inhibited seed germination， exacerbated oxidative damage in seedlings， led to the collapse of the antioxidant system， and caused substantial Pb accumulation in seedling roots. The study provides a theoretical basis for using alfalfa to remediate Pb-contaminated soils.

Alfalfa  /  Pb Stress  /  Germination physiology  /  Antioxidant system  /  Enrichment effect