Development of a process-based model for revealing role of silicon in regulating metal stress in roots

Abstract

Abstract Soil contamination by heavy metals has become a severe threat to the global food security. To mitigate metal toxicity in plants, the use of Si has been widely studied. Despite its ability to reduce the accumulation of metal in leaves, the mechanism by which Si influences the entry of metals into roots remains incompletely understood. To address this issue and explain the conflicting results observed in Si supplementation experiments, a process-based model was proposed to depict metal diffusion and adsorption in root cell wall. Using trivalent chromium (Cr[III]) as an example metal, the model was applied to explain the observed relation between Cr(III) and Si in rice roots considering Cr(III) concentration, stress duration, and Si concentration. Furthermore, we designed a device to simulate cell walls and protoplasts to analyze the switch of dual role of Si from increasing adsorption to blocking diffusion. The adsorption–diffusion model fitted well (R2 > 0.9) with the experimental results. The model revealed that Si increased metal adsorption onto cell walls but blocked diffusion into protoplasts, which was also confirmed by simulations in the device. The results deepen our understanding of the role of Si in mitigating metal stress in roots, broaden our knowledge about how Si influences plant growth, and provide a theoretical reference for future research on and applications of Si intervention.