EDAH increases bleeding sap intensity and grain yield of maize under high-density cultivation on saline-alkali soils in Xinjiang.

High-density maize planting compromises stalk strength and increases susceptibility to lodging. While growth regulators enhance lodging resistance and yield by optimizing stalk mechanical properties, their specific effects on the vascular structure, bleeding sap characteristics, and dry matter accumulation of ear internodes and peduncles under high plant densities remain unclear. Field experiments (2023-2024) were performed to evaluate two maize cultivars (Denghai 618, DH618; MC670) under three planting densities (90,000 plants ha-1 (D1), 135,000 plants ha-1 (D2), and 180,000 plants ha-1 (D3)) combined with foliar-applied EDAH or a water control (CK). In 2023, under the D2 planting density, EDAH treatment significantly increased theoretical yields, with DH618 achieving a peak theoretical yield of 18.85 t ha-1, a 16.2% increase compared with the control. EDAH modified vascular bundle traits by increasing the number and cross-sectional area of both pith and rind vascular bundles in ear internodes, while thickening mechanical tissues. EDAH enhanced the quantity of bleeding sap in the ear and peduncle by 11.5%-81.5% and 12.4%-70.1%, respectively, and increased bleeding sap intensity by 5.3%-24.0% and 2.8%-14.2%,while significant effects occurred in specific comparisons. Plant dry matter accumulation and its allocation to the ear also increased following EDAH application. Correlation analysis revealed significant positive associations between theoretical yield and peduncle bleeding sap intensity. Regression modeling indicated that the peduncle bleeding sap intensity and peduncle vascular bundle area contributed 54.0% to the proportion of theoretical yield variation explained in Model 2. Therefore, under high-density conditions, EDAH application improves vascular structure in ear internodes and peduncles, and modifies bleeding sap characteristics, ultimately increasing theoretical yield.