Seed soaking with salicylic acid improves alfalfa (Medicago sativa L.) germination by involving the antioxidation system

Cultivation of alfalfa (Medicago sativa L.), one of the most extensive forages around the world, is important for animal feeding and ecological conservation in Northwest China. Seed soaking with salicylic acid (SA) facilitates germination and improves morphological and physiological traits. Thus, it is necessary to investigate the effect of SA on alfalfa seed germination, as it may be beneficial for seedling establishment and field production. In this study, the influence of SA at different concentrations (C: 0, 0.4, 0.8, and 1.2 mM) and seed soaking times (ST: 8, 16, 24, and 32 h) on alfalfa cultivars (CV: Eureka + , WL525HQ, Central, Kehan) was investigated using an orthogonal experimental design. The results showed that the effect was dependent on C, CV, and ST. In addition, SA enhanced seed germination by improving seed vigor, reducing lipid peroxidation, promoting osmotic regulation, and enhancing antioxidant levels. More importantly, model analysis revealed that 0.77 mM SA and 25.5 h ST were the optimal seed soaking conditions.