Delaying wheat sowing date and increasing sowing rate promotes lignin synthesis and reduces lodging

Population size plays a crucial role in determining wheat yields. Altered carbohydrate accumulation resulting from increased competition between populations and individuals leads to poor-quality stems. The sowing date can mitigate competition in densely planted populations. However, the underlying mechanism by which it confers resistance to wheat lodging remains elusive. In this study, Zimai 28 (lodging-sensitive variety) and Shannong 28 (lodging-resistant variety) were used with three sowing treatments on October 22 (S1), October 28 (S2), and November 3 (S3). The sowing rate was adjusted to ensure adequate population size and consistency in the overwintering populations across sowing dates (300 plant m⁻² for S1, 375 plant m⁻² for S2, and 525 plant m⁻² for S3). The lodging resistance in winter wheat was increased by delayed sowing and increased sowing rate, which led to a reduction in tiller numbers and fostered primary stem development. A reduction in the overwinter cumulative temperature from 500 to 450 °C, coupled with an elevation in sowing rates from 300 to 375 plant m⁻² (transition from S1 to S2), corresponded with a notable increase in structural carbohydrates (lignin, cellulose, hemicellulose, and pectin) by 175.07 mg g⁻¹. Additionally, there was a moderate increase in non-structural carbohydrates, including soluble sugars and starch, by 15.54 mg g⁻¹. Delayed sowing and increased sowing rate elevated the precursor contents of lignin synthesis. Enhanced metabolic activity of related pathways ultimately increased dimer/trimer content. In summary, this study highlights the pivotal role of lignin metabolites and cross-linked structures in determining the stem stiffness breaking strength.