Abstract: Under low temperature conditions (7 ℃), seed soaking treatment with GA₃ solution (GA₃ concentration was 5 mg·L^-1 for ZD 958, 20 mg·L^-1 for FH 1) was carried out to investigate the effects of GA₃ on protective enzyme activity, MDA content and endogenous hormone content in seed embryos during seed germination of two maize varieties, ZD 958 (cold resistant type) and FH 1 (low temperature sensitive type), aiming to provide theoretical basis for chemical regulation of seed germination and low temperature tolerance processing before sowing in cold regions. The results showed that under low temperature stress, after soaking seeds in a GA3 solution at an appropriate concentration, the activities of two antioxidant enzymes (SOD, POD) in the embryos were significantly increased; the contents of endogenous hormones IAA, GA, and ZR were increased, while the contents of monochrome display adapter (MDA) and endogenous hormone ABA were significantly reduced. Under low temperature stress during seed germination, GA3 seed soaking could effectively enhance the activities of protective enzymes and increase seed metabolism. The increases of endogenous IAA and GA content promoted seed germination under low temperature, which resulted in stronger resistance to low temperature stress during seed germination.

Key words: GA₃, low temperature stress, maize seed, endogenous hormone.