Hybrids and planting density are the main factors affecting maize lodging resistance. Here, we aimed to elucidate the mechanism of the regulation of maize lodging resistance by comparing two hybrids at various planting densities from the perspective of lignin metabolism. Our results showed that compared to lodging-susceptible hybrid Xundan 20 (XD20), lodging-resistant hybrid Denghai 605 (DH605) showed a lower center of gravity and culm morphological characteristics that contributed to the higher lodging resistance of this hybrid. Lignin content, activities of key lignin synthesis-related enzymes and G-, S- and H-type monomer contents were significantly higher in hybrid DH605 than in hybrid XD20. Stalk mechanical strength, lignin accumulation and enzyme activity decreased significantly with increasing planting density in the two hybrids. While G-type monomers first decreased with increasing planting density but then remained stable, S-type monomers showed a decreasing trend, and H-type monomers showed an increasing trend. Correlation analysis showed that lodging rate was significantly correlated with plant traits and lignin metabolism. Therefore, maize hybrids characterized by high lignin accumulation, high lignin synthesis-related activities, high S-type monomer content, low center of gravity, high stem puncture strength, high cortical thickness, and small vascular bundle area are more resistant to lodging. High planting densities reduce stalk lignin accumulation, relevant enzyme activities and mechanical strength, thereby, ultimately increasing the lodging rate significantly.

杂交种和种植密度是影响玉米抗倒伏性的主要因素。在这里，我们旨在从木质素代谢的角度，通过比较不同种植密度的两个杂交种来阐明玉米抗倒伏的调控机制。我们的结果表明，与抗倒伏杂种荀单20（XD20）相比，抗倒伏杂种登海605（DH605）表现出较低的重心和秆形态特征，这有助于该杂种具有较高的抗倒性。杂交DH605的木质素含量、关键木质素合成相关酶的活性以及G-、S-和H-型单体含量显着高于杂交XD20。随着种植密度的增加，两个杂种的茎秆机械强度、木质素积累和酶活性显着降低。G型单体随着种植密度的增加先下降后保持稳定，S型单体呈下降趋势，H型单体呈上升趋势。相关分析表明，倒伏率与植物性状和木质素代谢显着相关。因此，具有高木质素积累、高木质素合成相关活性、高S型单体含量、低重心、高茎穿刺强度、高皮质厚度和小维管束面积的玉米杂种更耐倒伏。高种植密度会降低茎秆木质素积累、相关酶活性和机械强度，从而最终显着提高倒伏率。S型单体呈下降趋势，H型单体呈上升趋势。相关分析表明，倒伏率与植物性状和木质素代谢显着相关。因此，具有高木质素积累、高木质素合成相关活性、高S型单体含量、低重心、高茎穿刺强度、高皮质厚度和小维管束面积的玉米杂种更耐倒伏。高种植密度会降低茎秆木质素积累、相关酶活性和机械强度，从而最终显着提高倒伏率。S型单体呈下降趋势，H型单体呈上升趋势。相关分析表明，倒伏率与植物性状和木质素代谢显着相关。因此，具有高木质素积累、高木质素合成相关活性、高S型单体含量、低重心、高茎穿刺强度、高皮质厚度和小维管束面积的玉米杂种更耐倒伏。高种植密度会降低茎秆木质素积累、相关酶活性和机械强度，从而最终显着提高倒伏率。具有木质素积累高、木质素合成相关活性高、S型单体含量高、重心低、茎穿刺强度高、皮层厚度高、维管束面积小等特点的玉米杂交种更耐倒伏。高种植密度会降低茎秆木质素积累、相关酶活性和机械强度，从而最终显着提高倒伏率。具有木质素积累高、木质素合成相关活性高、S型单体含量高、重心低、茎穿刺强度高、皮层厚度高、维管束面积小等特点的玉米杂交种更耐倒伏。高种植密度会降低茎秆木质素积累、相关酶活性和机械强度，从而最终显着提高倒伏率。