Trade-off of phosphate mediated iron plaque formation and cell chemical remodeling on cadmium uptake and...

Phosphorus (P) plays a complex role in modulating cadmium (Cd) accumulation of rice, yet the effect of phosphorus on cadmium dynamics in rice remains unclear. Here, a hydroponic experiment was performed to investigate the trade-off of P mediated iron plaque and cell chemical remodeling on Cd uptake and translocation in rice. Results showed that P deficiency significantly enhanced Fe concentration in amorphous iron plaque (AIP), up to 4.0 mg g^-1, to increase Cd fixation, while elevated P supply decreased Fe concentration in AIP to 2.5 mg g^-1, resulting in the release of Fe and Cd into the solution and enhancing root Cd uptake. However, P starvation enhanced Cd transport from root to shoot of rice by improving transport factor (TF) from 0.07 to 0.09 under + IP and 0.078 to 0.11 under -IP treatment, respectively. The lack of P increased pectin methylesterase (PME) activity and promoted Cd bind to cell wall, while P addition obviously declined Cd in pectin, from 7.23 to 4.99 μg g^-1, and increased Cd-phosphate complex from 2.89 to 7.14 μg g^-1 under + IP, shifting chemical form of Cd from pectin-bound to insoluble phosphates due to potential absorption sites occupying by released Fe. Moreover, P deprivation downregulated phospholipids on the plasma membrane, altering its dynamics and potentially influencing Cd uptake. Therefore, P reduced Cd translocation from roots to shoots by promoting vacuolar Cd-phosphate complexes and cytosolic retention, despite weakening cell wall Cd immobilization. These findings emphasize the importance of Fe-P crosstalk on Cd uptake and translocation in rice, providing a novel insight for P management strategies to mitigate Cd contamination in paddy field.