Distribution and status of silicon in rice plant

The content, distribution and existing form of silicon in tissues of rice plant were analyzed by UV-Vis spectrophotometer, X-ray analytical microscope and scanning electron microscope (SEM), and the chemical properties of silicic acid were investigated, which will provide a scientific basis for comprehensive utilization of silicon in rice plant. The results showed that silicic acid in soil was absorbed by rice plant in the form of monosilicic acid and transferred to different organs. The contents of the silicic acid varied with the growing periods, reaching 912 mg/L (expressed as SiO²) in maturity. The . comparison of silicic acid concentrations in xylem sap and in soil solution showed that the silicic acid was selectively absorbed and concentrated during the transportation from soil to xylem, and the concentration ratio of silicic acid was considerably high being 85 fold at maximum. X-ray characteristic images of silicon showed that silicon existed widely in each tissue and its content was higher in the rigid parts. SEM image suggested that the silicon colloid deposited in different organs had specific shapes and was insoluble in strong acid. The content of silicic acid in each tissue was determined after decomposition of organic material with mixed acids, indicating that the highest content of silicic acid of 13.3% was observed in rice hull. As a result, the rice hull is one of the most potential nature resources to produce elemental silicon and silicon carbide materials.