Environmental Heavy Metal Pollution Disrupts Heading in Major Cereal Crops: Mechanisms and Implications for Food Security.

Heavy-metal contamination threatens cereal food security through a dual pathway: it destabilizes reproductive development around heading and increases toxic-element transfer into edible grain. This review synthesizes evidence for rice, wheat, maize, and selected secondary cereals, with maize tasseling/silking treated as the functional analogue of heading. Across cadmium, arsenic, lead, chromium, nickel, and copper exposure scenarios, the strongest mechanistic convergence occurs at redox imbalance, transporter-mediated redistribution, sulfur and hormone metabolism, source-sink misallocation, and reproductive-organ injury. Primary studies show that yield penalties near heading are frequently coupled to stronger sterility, poorer spikelet or kernel set, and higher grain contaminant loading, but the magnitude of injury is strongly modulated by genotype, water regime, nutrient antagonism, and amendment strategy. The literature is now sufficient to support cross-crop synthesis, yet it remains fragmented by inconsistent stage definitions, weak reporting of metal speciation, limited field validation, and poor integration of reproductive phenotyping with grain-safety endpoints. Mitigation evidence indicates that silicon, selenium, biochar, organic amendments, beneficial microbes, water management, and transporter-informed breeding can reduce risk when they specifically limit toxic flux to reproductive sinks. A future Food Analytics 4.0 agenda should therefore integrate stage-aware sensing, soil-plant transfer analytics, machine-learning risk prediction, and reproductive phenotyping so that intervention can occur before irreversible heading-stage damage is translated into unsafe grain and reduced cereal supply.