Temporal dynamics of lead uptake in wheat: Identifying key growth stages for mitigation

Given that atmospheric Pb has become the primary source of Pb in wheat grains, scientifically managing atmospheric Pb pollution is a notable global challenge. Identifying the critical periods for Pb absorption in straw and accumulation in grains was essential for developing targeted mitigation strategies, as the varying nutrient demands of wheat across different growth stages might have influenced Pb accumulation. To investigate this, a pot experiment using Pb exposure and isotope tracing was conducted. The results showed that wheat directly absorbed Pb through its aerial parts, with Pb content in both the straw and grains increasing with exposure duration. A clear coupling relationship was observed between Pb absorption in straw and its accumulation in grains. Grain filling stage (FS) is a critical period for Pb accumulation and pollution control in wheat straw and grains, contributing approximately 41.14–41.87 % to Pb absorption in straw and 56.21–58.16 % to Pb accumulation in grains. Furthermore, Pb accumulation during the greening, jointing, and booting stages contributed 40.62–42.61 % to the total Pb in grains, which reflects the redistribution of Pb stored in the shoots before FS to the grains. Further isotope tracing also revealed that FS contributed 51.06 % of Pb accumulation in the grains, whereas the redistribution of Pb absorbed by the straw before FS contributed approximately 44.33 % to grain Pb content. This study highlights the FS as a critical period for Pb accumulation in both wheat straw and grains, despite it accounting for only 13.89 % of the total growth period. This highlights the importance of enhancing atmospheric Pb contamination control at this this stage to ensure the quality and safety of wheat production.