Abstract: 【Objective】 With the decreasing of the solar radiation in China, effects of shading (low light stress) on stalk morphology and microstructure of summer maize were studied to provide a theoretical basis for summer maize to adapt the current climatic condition of insufficient illumination. 【Method】 Summer maize was grown under the shading condition with a shading degree of 60%. Three shading treatments were designed in growing season ranged from tasseling to maturity (S1), from jointing to tasseling stage (S2) and whole growing period (S3), respectively. Two summer maize cultivars Denghai605 (DH605) and Zhengdan958 (ZD958) were used as experimental materials. Effects of shading in different growing seasons on stem characters and lodging property of summer maize were investigated. 【Result】 Results showed that plant height, ear height, leaf area index, the third internodes length, cross sectional area of stem, and stalk rind penetration strength reduced significantly after shading, and the response to different shading stages showed: S1＜S2＜S3. Compared to CK, stalk rind penetration strength of DH605 and ZD958 reduced by 22.23% and 24.41%, respectively. Stem rind thickness, vascular bundle number, the area of the central vascular bundle, xylem and phloem reduced significantly. Lodging property in fields increased significantly, and the lodging rate of DH605 and ZD958 in S3 were 36.5% and 24.7%, respectively. Furthermore, grain yield, kernel number per ear and harvest ear number reduced significantly. Barrenness increased and grain yield of S3 reduced. 【Conclusion】Shading had significant effects on stem form. Stem lodging resistance was also reduced by decreased basal internode length, diameter, puncture strength, hard skin tissue thickness and vascular bundle number, thus influencing yield formation. Shading before anthesis had a great influence on the lodging rate.

Key words: summer maize, shading, stalks, lodging, microstructure