Effects of Silicon Application on Arsenic Sequestration in Iron Plaque and Arsenic Translocation in Rice

Abstract

The As sequestration by iron plaque and the As translocation in rice significantly affect the As accumulation in brown rice, and silicon (Si) application inhibits the As accumulation in rice plants. However, little information is available concerning the effect of Si application on As sequestration by iron plaque and translocation in rice. In this study, a pot experiment using As-contaminated paddy soil with different Si supply levels was conducted to investigate the effects of Si application on the As sequestration by iron plaque on the root surface and the As translocation from different tissues to brown rice. The results showed that the Si2 (0.66 g·kg-1) treatment significantly increased the activities of CAT (1.81 times), SOD (7.98 times), and POD (1.25 times) in the roots, increased the DCB-extractable Fe concentration (44.35%), and promoted the roughness of iron plaque (108.91%), resulting in a significant increase in the DCB-extractable As concentration of iron plaque (88.32%). Moreover, the Si2 treatment significantly promoted the As accumulation in the roots and inhibited the As translocation from the roots and leaves to the brown rice, leading to a significant decrease in the brown rice As concentration (53.12%). The increase in As sequestration by iron plaque with Si application was attributed to the enhancement of iron plaque formation and the promotion of surface roughness of iron plaque, whereas the inhibition of As translocation from the roots and leaves to the brown rice in the Si application treatment was closely related to the competition between Si with As for transporters and the promotion of As-thiol complex formation and As compartmentalization in vacuolar. These findings provide more insight into the mechanisms of As translocation in rice and will be helpful for exploring strategies to reduce rice grain As through Si supply in As-contaminated paddy fields in South China.