Silicon-mediated control of cadmium contamination in rice: mechanisms and advances (2000-2024).

Many studies have explored silicon's (Si) impact on cadmium (Cd) accumulation in rice, but a comprehensive assessment of Si's remediation efficacy and its molecular mechanisms is lacking. This review synthesizes 25 years of research on Si's role in mitigating Cd stress, focusing on how Si application affects Cd absorption, transport, and accumulation to provide theoretical support and technical guidance for using Si in the remediation of Cd-contaminated soils and safe rice production. Both soil and foliar applications of Si fertilizers reduce Cd accumulation in rice grains, with Si showing significant effects in controlling Cd within the plant by improving rice's physiological condition under Cd stress, adjusting hormone levels, enhancing antioxidant enzyme activity, and promoting Cd chelation to the cell wall, reducing cellular damage. Si also regulates the expression of Cd transport proteins, with ten identified, five of which are particularly crucial: OsHMA2, OsNramp1, OsNramp5, OsZIP6, and OsZIP7. Six other proteins' relationship with Si remains unconfirmed and requires further investigation. Research on how Si coordinates interactions among various factors such as Cd transport proteins, antioxidant defence systems, and plant hormones to comprehensively enhance rice's resistance to Cd stress is still limited. It was revealed that foliar application of Si is more effective in reducing Cd levels in rice, while in heavily Cd-contaminated soils, soil application of Si is more effective. Future in-depth understanding of Si's role in this network will not only help reveal its multifaceted protective mechanisms but also provide new perspectives for developing more effective strategies to mitigate heavy metal pollution.