Abstract: 【Objective】Lodging is an important factor limiting grain yield of summer maize. This study was conducted to investigate the effects of waterlogging on the lodging resistance of summer maize under field conditions. 【Method】Two summer maize cultivars, Denghai605(DH605) and Zhengdan958(ZD958), were used as experimental materials. The field experiment was performed to explore the effects of waterlogging in different durations (3 and 6 days) on the morphology, rind penetration strength, bending property and microscopic structures of summer maize stalk at three-leaf stage (V3), six-leaf stage (V6), and ten days after the tasseling stage (10VT). 【Result】Results showed that the third internodes width and stalk rind penetration strength reduced significantly after waterlogging, and the decrease of the stalk rind penetration strength of two cultivars was the most in the treatment of waterlogging at V3 for 6 days, with 32.53% in DH605 and 42.73% in ZD958. Waterlogging at V3 and V6 decreased the stalk cortex thickness, the vascular bundle sheath thickness and vascular bundle number much more than waterlogging at 10VT, with the increase of waterlogging duration. Furthermore, waterlogging increased barrenness, and decreased grain yield, kernel number per ear and 1000-grain weight, and the response to different waterlogging treatments was waterlogging at V3>waterlogging at V6>waterlogging at 10VT and waterlogging for 6 days>waterlogging for 3 days.【Conclusion】Waterlogging had significant effects on grain yield and plant morphology. Waterlogging reduced the third internodes width, stalk rind penetration strength and bending property, the stalk cortex thickness, the vascular bundle sheath thickness and vascular bundle number, resulted in the decrease of the lodging resistance. It was most susceptible to be waterlogged at V3, followed by V6 and 10VT, and the effects decreased with the increase of waterlogging duration.

Key words: summer maize , waterlogging , stalk microscopic structures , lodging , grain yield