| Rice(Oryza sativa)is a typical Silicon(Si)-accumulating plant.Application of Si can not only promote the growth of rice but also effectively reduce the accumulation of cadmium(Cd)in rice.However,the chemical mechanism by which Si affecting the migration and transformation of Cd in rice is still unclear.In order to reveal the chemical mechanism of the migration and transformation of Cd in rice by exogenous mineral Si,and provide a scientific basis for the application of Si affects the reduction of Cd in rice.Therefore,in this paper,a pot experiment is carried out to research the influence of exogenous mineral Si in rice(high-accumulation of Cd in rice—HHZ;and low-accumulation of Cd in rice—XWX12)growth and exogenous mineral Si affects the Cd subcellular distribution and chemical form of Cd in roots,stems,and leaves cells of rice.And based on SEM,FTIR,and XRD to analysis the form and combination of Si and Cd in rice.The main research conclusions are as follows:(1)The application of exogenous mineral Si can increase the total biomass of rice and the production.The best effect is when the application amount of exogenous mineral Si is 2%;however,the application of Si does not affect the plant height of rice.Other factors vary.(2)With the increase of the amount of exogenous mineral Si,the Si content in the roots,stems and leaves of the two rice species also gradually increased,and reached the highest when the amount of exogenous mineral Si was 5%.The Si content in HHZ’s organs was higher than that in XWX12’s,and the increase of Si content in the roots of was significantly higher than that in stems and leaves.(3)The application of exogenous mineral Si can reduce the Cd content in various organs of rice.The decrease is most significant when the application amount of exogenous mineral Si is 2%.The Cd content in different organs and different growth stages of rice is:root>stem>leaf>husk>brown rice,tillering stage>filling stage>maturity stage.When the application of exogenous mineral Si was 1%to 5%,the Cd content in brown rice was lower than the national food safety standard,the Cd content in brown rice in HHZ decreased by 63.70%,and XWX12 decreased by 56.81%.Exogenous mineral Si can also increase the root enrichment coefficient of rice,reduce its transfer coefficient,and inhibit the ability of Cd to migrate and transport above ground.(4)With the increase of the application of exogenous mineral Si,the content of Cd in the cell wall of rice gradually increased,and the content of Cd in the soluble components gradually decreased.The proportion of Cd in the cell wall in HHZ and XXW was higher than 50%,followed by the Cd content of the soluble components in the cells was between 25.55%～39.77%,and the organelles were the least distributed,only 9.90%～13.10%.The exogenous mineral Si can reduce the ratio of the more active deionized water and ethanol extracted states in the roots,stems and leaves of rice,and increase the proportion of weakly migrated acetic acid extracted and hydrochloric acid extracted states,thereby reducing the Migration capacity and cumulative effects.(5)SEM analysis showed that exogenous mineral Si can effectively protect the integrity of plant cell walls,reduce the entry of Cd into the cells,and alleviate the harm of Cd to plants.FTIR analysis showed that exogenous mineral Si can promote the production of more lignin,hemicellulose,pectin and other substances in rice organs,enhance the ability of rice to secrete organic acids,and chelate with Cd on the cell wall.The synthesis of carbohydrates increases the complexation of Si and Cd,thereby reducing the biological activity of Cd and its ability to migrate and accumulate in rice.XRD analysis shows that the exogenous mineral Si can shift the diffraction angle of each characteristic peak to the right and enhance its diffraction peak intensity,peak height and increase the crystallinity,grain size and crystal content of various parts of rice,thereby alleviating the harm of Cd to rice. |
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