Elucidating the mechanistic link: how silicon enhances lodging resistance in oat via targeted regulation of lignin biosynthesis in the second stem internode

Introduction Oat production is constrained by lodging, and silicon input has been shown to promote lignin accumulation in basal internodes and enhance stem mechanical strength and lodging resistance. However, the physiological mechanisms by which silicon input regulates lignin biosynthesis in the second basal internode of oat stems and its effects on lodging-related traits remain unclear. Method A split-plot field experiment was conducted in 2024 and 2025, with Mengyan 1 (MY1, lodging-resistant) and Dingyan 2 (DY2, lodging-susceptible) assigned to the main plots and five silicon inputs (0, 30, 60, 90, and 120 kg ha -1 ) to the subplots. Lodging-related and physiological traits were analyzed at the grain-filling and milk stages, and the dynamic patterns of lignin-biosynthetic enzyme activities were investigated. Results MY1 exhibited the highest lodging resistance at a silicon input of 60 kg ha -1 , and its lignin content increased by 12.5% and 14.6% at the grain-filling and milk stages, respectively, compared to no silicon input. In contrast, DY2 achieved the strongest lodging resistance at an input of 90 kg ha -1 , with lignin content increasing by 12.4% and 17.0% at the two stages, on average in two years. Notably, stem lodging resistance was closely associated with lignin content of the second basal internode in grain-filling ( R 2 = 0.80) and milk ( R 2 = 0.64) stages. Silicon primarily enhances stem lodging resistance in oat by promoting lignin accumulation. This effect is achieved through the stimulation of lignin-biosynthetic enzyme activities and the accumulation of key mineral elements in the second basal internode, thereby markedly increasing stem lignin content. Random forest analysis indicated that cinnamyl alcohol dehydrogenase activity at 30 days after jointing made the greatest contribution to lignin biosynthesis, whereas magnesium content at the grain-filling stage was the most influential mineral factor. Conclusions Silicon inputs of 60 and 90 kg ha -1 are recommended for lodging resistant and susceptible oat cultivars respectively, and it enhances lodging resistance by the promotion of lignin accumulation through upregulating enzyme activities and increasing mineral content in the stems.