Effects of exogenous glycine betaine on isoflavone accumulation in germinated soybeans under <scp>UV</scp> ‐B irradiation

BACKGROUND: Isoflavones, the key phenolic compounds in soybeans, can help scavenge free radicals and reduce oxidative damage in humans. Germination can promote isoflavone accumulation in soybeans, and UV-B irradiation during germination further enhances this effect. However, UV-B also induces oxidative stress and inhibits the growth of germinated soybeans. Here we report the effects of glycine betaine (GB), a plant growth regulator on growth, isoflavone content, and antioxidant defense systems of germinated soybeans under UV-B irradiation. This study explored the effects of glycine betaine (GB) on the growth, isoflavone content and antioxidant system of germinated soybeans under UV-B irradiation. RESULTS: , and enhanced isoflavone biosynthetic key enzyme activities (PAL, C4H and 4CL by 88.81%, 47.51% and 70.76%) and gene expression (PAL, C4H and 4CL by 56.22%, 110.43% and 75.23%). UV-B + GB also enhanced the activities of antioxidant enzymes (superoxide dismutase (SOD), peroxidase (POD), catalase (CAT) and ascorbate peroxidase (APX) increased by 14.68%, 60.95%, 49.59% and 52.21%, respectively) and up-regulated the expression of their corresponding genes (SOD, POD, CAT and APX increased by 15.72%, 48.14%, 50.35% and 46.91%, respectively). Meanwhile, UV-B + GB significantly reduced the levels of oxidative stress. Hydrogen peroxide, malondialdehyde and electrolyte leakage decreased by 16.52%, 19.62% and 8.47%, respectively. CONCLUSION: These results demonstrate that GB enhances isoflavone accumulation and antioxidant defense, alleviates oxidative damage, and promotes the growth of germinated soybeans under UV-B stress. © 2026 Society of Chemical Industry.