| To explore the response mechanism of exogenous glycine betaine (GB) on improving the cold resistance in maize and to compare the cold mitigation effect of exogenous GB at germination and seedling stages, six different maize inbred lines were conducted under different concentrations of exogenous GB, and the effects of exogenous GB on seed germination and seedling physiological trait across 10℃ low temperature stress were analysed. It showed that maize seeds germinations were significantly inhibited and the seedlings were clearly hurt under low temperature stress, thus, the germination potential, germination rate, plumula length, radical length, shoot fresh weight and root fresh weight were decreased 55.2%, 45.4%, 64.6%, 61.3%, 57.7% ，and 71.0%, respectively, and relative conductivity, malondiadehyde content, proline content, soluble sugar content, SOD activity, POD activity and CAT activity were increased 282.7%, 150.1%, 140.6%, 124.7%, 374.4%, 209.7%, and 211.3%, respectively. 20 μmol·L-1 and 10 μmol·L-1 GB had the largest cold mitigation effect at germination and seedling stages, respectively, which increased seed germination and decreased seedling physiological injury, excluding relative conductivity (42.4%) and malondiadehyde content (30.5%) were significant decreased, the content of proline，soluble suger and the activity of antioxidant enzyme were significantly increased(12.6%~324.9%). Under the optimal exogenous GB concentration, the GB cold ease index (EI) of corresponding traits as evaluation indexes, then using the membership function method to comprehensively evaluate cold mitigation effect of different inbred lines at two stages, and the cold mitigation effect of exogenous GB at germination stage (0.585) that were better than seedling stage (0.454). |