Research On The Barrier Effect Of Zinc And Selenium On Mercury Uptake In Oryza Sativa

Mercury has been paid close attention to at home and abroad,which can be absorbed by crops and do harm to people’s health.Oryza sativa has a strong ability to accumulate mercury,and eating rice containing mercury will increase the exposure risk of mercury in the population.At present,the research on the barrier effect of mercury in rice has become one of the research hotspots.Zinc and selenium are essential trace elements for plant growth,which have important physiological functions and functions in plants.Appropriate amounts of zinc and selenium can improve the ability of plants to resist stress to a certain extent,and selenium can also antagonize heavy metals and block heavy metals from entering plants,so as to alleviate the toxicity of heavy metals to plants.In this paper,the barrier effect of zinc and selenium on mercury in rice was discussed.The changes of growth,absorption and transport of mercury in rice seedlings treated with zinc,selenium and mercury,and the changes of growth and physiological indexes of rice seedlings after mercury stress were studied by hydroponic experiment.A pot experiment was conducted to study the effects of zinc and selenium application on rice growth,mercury uptake and transport,and zinc and selenium contents in Oryza sativa organs.At the same time,the effects of zinc and selenium on p H,available mercury,available zinc and available selenium in mercury-contaminated soil after rice growth cycle were clarified.The main results are as follows:（1）Under the treatment of low concentration of mercury,the addition of zinc and selenium could promote the growth of Oryza sativa seedlings.With the increase of zinc and selenium treatment time,the promoting effect of zinc and selenium on Oryza sativa growth was more obvious.Under the treatment of low concentration of mercury,the addition of zinc and selenium could significantly reduce the content of mercury in the underground part and aboveground part of Oryza sativa,and the appropriate concentration of zinc and selenium could inhibit the transport of mercury from the underground part of rice to the aboveground part of Oryza sativa.（2）Under mercury stress,the application of appropriate concentration of zinc and selenium could alleviate the inhibition of mercury on rice growth.Under mercury stress,zinc and selenium could decrease SOD activities and CAT activities and MDA content,while proper concentration of zinc and selenium could increase chlorophyll content,POD activities and GSH activities in Oryza sativa seedlings.Among them,repeated application of Se(0.002mmol·L^-1)and Zn(10mg·L^-1,20mg·L^-1,40mg·L^-1and 60mg·L^-1)had better effects on the physiological mechanism of Oryza sativa under mercury stress.（3）Zinc and selenium could significantly reduce the content of available Hg in mercury contaminated soil.Among them,repeated application of Zn(50 mg·kg^-1)and Se(10 mg·kg^-1)had better effect on reducing soil available mercury.Single application of zinc or selenium and combined application of zinc and selenium could increase the content of available Zn and available Se in mercury contaminated soil,and the effect of proper concentration of zinc and selenium on the content of available Zn and available Se in mercury contaminated soil was even better than that of zinc or selenium alone.（4）The application of zinc and selenium in mercury-contaminated soil could affect the growth of rice in varying degrees;the application of zinc and selenium in mercury-contaminated soil could reduce the content of mercury in Oryza sativa organs;the application of zinc and selenium in mercury-contaminated soil could affect the transport of mercury in Oryza sativa,and the transport coefficient of mercury in Oryza sativa was as follows:TF _root-stem>TF _root-leaf>TF _root-husk>TF _root-grain.The effect of zinc and selenium on Oryza sativa in mercury contaminated soil was better than that of zinc and selenium alone.Among them,single application of 40mg·kg^-1Se and multiple application of Zn(10mg·kg^-1,50mg·kg^-1and 100mg·kg^-1)and Se(5 mg·kg^-1,10 mg·kg^-1,20mg·kg^-1and40 mg·kg^-1)in mercury contaminated soil had better blocking effect on mercury uptake and transport by Oryza sativa.（5）The application of zinc and selenium in mercury-contaminated soil could affect the contents of zinc and selenium in Oryza sativa organs.The application of zinc and selenium to mercury-contaminated soil could not only promote the absorption of zinc by Oryza sativa roots,but also promote the absorption of selenium by rice stems.In mercury contaminated soil,the effect of combined application of selenium and high concentration of zinc on zinc uptake of rice grain was better than that of high concentration of zinc,and the effect of combined application of zinc and high concentration of selenium on selenium uptake of Oryza sativa grain was better than that of high concentration selenium.（6）After the application of zinc and selenium in soil,the content of mercury in Oryza sativa root and stem was negatively correlated with the content of available selenium in soil,and the content of mercury in Oryza sativa organs was not significantly correlated with the content of available mercury in soil.The relationship between the content of mercury in Oryza sativa root,leaf,rice husk and grain and the content of available zinc in soil was not significant.In summary,multiple application of zinc and selenium had a significant blocking effect on mercury uptake by Oryza sativa.