Effect Of Si On Absorption And Accumulation Of Cd In Different Rice Varieties

In recent years,the problem of Cd pollution in paddy soil in China was very serious.Liaoning Province,as the core based of the old industry in northeast China,was also experiencing serious Cd pollution in paddy soil dued to sewage irrigation and industrial solid waste.Rice was one of the most important food crops in China.Soil Cd pollution not only damaged the growth of rice,but also accumulated in the grains,and harmed human health through the food chain.Therefore,alleviating the toxic effect of Cd on the growth of rice and reducing the content of Cd in grains was one of the urgent environmental issues in China.Rice was a silicon like plant.Exogenous application of Si could effectively alleviate the harmful effects of heavy metals on rice.Simultaneously,Si inhibited the expression of Cd transporter genes,which in turn affected the uptake and accumulation of Cd.A large number of indoor and field trialed have recently proved that there were huge differences in Cd absorption and accumulation among different rice varieties.Screening low-Cd rice accumulation had become an important method for Cd-contaminated soil to reduce Cd accumulation.Different rice may caused differences in Cd absorption and accumulation dued to their different ability to absorb Si.Therefore,this study intended to use rice varieties commonly used in Shenyang area?Shendao 47,Beijing 1,Shendao 529.Liaojing 9?To explored the effect of Si on the absorption,migration,and accumulation of Cd in rice plants as a test material,in order to provide reasonable management of fertilizers for rice production and to further reduce the accumulation of Cd in low-accumulation rice to provide scientific in accordance with.The results of the study were as follows:1.Effects of Si on the chemical forms of different Cd riceThe chemical forms of Cd in roots,stems and leaves of rice show the following trended:Sodium chloride extract(F_NaCl)>Acetic acid extract(F_HAc)>Deionized water extracted state?F_W?>Ethanol extraction state?F_E?>Hydrochloric acid extract(F_HCl).Applying Si reduced the proportion of sodium chloride?stronger activity?and ethanol extracting state?strong migration ability?of Cd in the root system.Applying Si reduced the proportion of Cd de-ionized water extracted from the stems and leaves?strong migration ability?and the proportion of sodium chloride extracted?poor migration ability?.Among the four cultivars,the effect of Si on Liaojing 9 and Shendao 529 in suppressing Cd toxicity was better than Shendao 47 and Beijing 1.2.Effects of Si on uptake and accumulation of Cd in different rice at tillering stageCompared with the control,under the treatment with Cd concentration of 5 mg·kg^-1 in the soil,the Si content and biomass in rice plants were reduced,and the Cd content and accumulation in rice were increased.There were a negative correlation between Si and Cd contents in rice plants.It showed that the application of Si reduced the poisoning effect of Cd on rice.When the amount of Si applied was 1.2 g·kg^-1,the effect was best.The accumulation of Cd in roots of four varieties of rice was:Liaojing 9>Shendao 529>Beijing 1>Shendao 47;The order of Cd migration is:Shendao 47>Beijing 1>Shendao 529>Liaojing 9.3.Effect of Si Application on Si Gene Expression in Different Rice under Cd StressCompared with the control,under the treatment with soil Cd concentration of 5 mg·kg^-1,the expression of Si-binding protein gene and Lsi2 gene in the roots of the four varieties of rice leaves were reduced.Under the same concentration of Cd,the expression of Si-binding protein gene and Lsi2 gene in roots increased with the increase of Si application amount.Comparing the four varieties,the expression levels of the two genes were significantly different,indicating that the ability of different species to absorb and accumulate Si was different.4.Correlation of Si Gene Expression and Cd Content in RiceThe expression of Si-binding protein gene and the expression of Lsi2 gene in roots were negatively correlated with Cd content in the four varieties of rice.With the increase of gene expression,the content of Cd in rice plants decreased,indicating that rice had reduced the absorption and accumulation of Cd due to its increase in the absorption and accumulation of Si.5.Effect of Si on Cd content and yield of different rice at mature stageWith the increase of Si application amount,the Cd content in rice increased significantly,the proportion of Cd content in roots increased gradually,and the proportion of Cd content in stems and leaves and grains gradually decreased.Under Cd stress,the yield of all varieties of rice decreased significantly,and the yield was:Liaojing 9>Shendao 529>Shendao 47>Beijing 1.As the amount of applied Si increased,the yield increased,indicating that Si can reduce the Cd content in rice and increase grain yield.6.Effect of Si on Cd accumulation and translocation coefficient in different rice at mature stageUnder Cd stress,the accumulation of Cd in rice plants increased significantly,and decreased with the increase of Si application.The order of Cd accumulation in four varieties of rice grain was:Liaojing 9<Shendao 529<Beijing 1<Shendao 47.Si reduced the ability of Cd to migrate and transport part of the earth,and it could effectively alleviate the poisoning effect of Cd on rice,and it also had different relieving effects on different species.