Deciphering Cadmium Accumulation in Peanut Kernels through Growth Stages and Source Organs: A Multi-Stable Isotope Labeling Study

The mechanisms of cadmium (Cd) uptake and redistribution throughout the peanut lifecycle remain unclear. This study employed multi-isotope labeling techniques in hydroponic and soil-foliar systems, revealing that Cd uptake during podding (Cd_p) constituted 73.7% of kernel Cd content, whereas contributions from the flowering (Cd_f) and seedling (Cd_s) stages were 22.2 and 4.1%, respectively. Stem-stored Cd (Cd_stem) contributes 53.2% to kernel Cd accumulation, while leaf-stored Cd (Cd_leaf) contributes 46.8%. Prestored Cd_f in shoots demonstrated the most efficient transport to pods, approximately twice that of Cd_s and Cd_p. Cd_s and Cd_f were predominantly stored in leaves (51.0%), while Cd_p mainly in stems (46.3%), 2.8 times its presence in leaves (16.5%), indicating distinct root-stem-kernel translocation. In the transfer of shoot Cd from stems to pods, 29.3% of Cd_leaf and 25.0% of Cd_stem were exported. This study provides novel insights into Cd dynamics in peanuts, establishing a foundation for future Cd regulation strategies.