Soil–plant interactions regulating the mobility and acquisition of Zn, Fe, Se, and I: implications for crop biofortification strategies

Micronutrient deficiencies, particularly those involving zinc (Zn), iron (Fe), selenium (Se), and iodine (I), remain major constraints to human nutrition and food security. Crop biofortification offers a sustainable approach to increasing the concentration and bioavailability of these elements in staple foods. Still, its effectiveness depends on the processes regulating their behavior across the soil–plantsoil–plant continuum. This structured narrative review synthesizes current evidence on the edaphic, rhizospheric, physiological, and molecular mechanisms controlling Zn, Fe, Se, and I mobility, acquisition, transport, redistribution, storage, and accumulation in edible plant organs. Literature searches were conducted in Scopus, Web of Science, PubMed, and Google Scholar, focusing primarily on studies published between 2021 and 18 March 2026, while retaining foundational research required to explain key mechanisms. The evidence indicates that parent material, texture, cation exchange capacity, pH, redox potential, organic matter, and nutrient interactions govern micronutrient speciation and availability. Plants respond through rhizosphere acidification, chelator and organic acid release, microbial associations, and coordinated transporter networks. Zinc and Fe homeostasis involves ZIP/IRT, HMA, YSL, NRAMP, MTP, VIT, and related transport systems. In contrast, Se largely shares sulfate and phosphate pathways, and iodine appears to use anion transport systems associated with chloride. Agronomic fertilization can rapidly increase micronutrient concentrations, while breeding, biotechnology, and gene editing can improve uptake, remobilization, and storage. The most promising strategies integrate soil diagnosis, appropriate nutrient sources and application methods, genotype selection, microbial processes, bioavailability, and food-system considerations. Such integration is essential for producing nutritionally improved crops without compromising yield, environmental sustainability, or consumer acceptance.