Multi‐Scale Mechanisms of Zn‐Se Antagonism in Wheat After Spray: From Subcellular Sequestration to Transcriptional Regulation

Foliar Zn-Se application is a promising strategy to alleviate human micronutrient deficiencies, yet their interaction during co-application remains unclear. Through field and pot experiments, we investigated Zn-Se antagonism in wheat across organ allocation, subcellular distribution, and transcriptomic regulation. Co-application decreased grain Se concentration while increasing Se allocation to leaves and reversed the positive correlation between grain Se and leaf-to-sheath translocation factor. Zn enhanced Se sequestration in leaf cell walls and soluble fractions. Transcriptomic analysis revealed that altered expression of key genes in related metabolic pathways, including SULTR3;4 and PHT2, leads to Se compartmentalization in leaves and restricts Se transfer to grains and accumulation. Despite antagonism, co-application produced grains meeting Zn and Se Recommended Nutrient Intake, enhanced antioxidant capacity, and posed low ecological risk upon straw return. These results elucidate a mechanistic framework for Zn inhibiting Se remobilization to grains and provide molecular targets for optimizing Zn-Se co-biofortification in wheat.