Abstract: A field plot experiment was conducted to study the effects of seed dressing with imidacloprid at the pesticide / seed mass ratios of 6:10000，9:10000, and 12:10000 on the seedlings growth and protective enzyme activities of high-yielding summer maize. Seed dressing with an imidacloprid / seed mass ratio of 6:10000 increased the seedlings height, primary root length, secondary root number, aboveground fresh mass, and underground fresh mass by 2.81 cm, 2.31 cm, 1.71, 0.30 g, and 8.28 g, respectively, as compared to the control, and had better effect than the treatments 9:10000 and 12:10000. Comparing with the control, treatment 6:10000 increased the leaf- and root soluble protein content by 12.6% and 27.9% and catalase (CAT) activity by 2.5% and 11.5%, decreased malondialdehyde (MDA) content by 26.3% and 60.9%, improved superoxide dismutase (SOD) activity by 19.7% and 5.6%, enhanced glutathione-S-transferase (GSTs) activity by 11.5% and 13.2%, respectively, and increased the root peroxidase (POD) activity by 31.8%. Seed dressing with imidacloprid at the pesticide / seed mass ratio of 6:10000 could markedly improve maize seedlings protective enzyme activities, but had no promotion effect on leaf peroxidase (POD) activity.

Key words: GSTs, MDA, imidacloprid, high-yielding summer maize, seedling growth, protective enzyme