Effects Of Brassinolide On Iron Plaque And Its Influence About The Absorbtion Of Arsenic And Cadmium

Heavy metal pollution is a global environmental problem.Most of all arsenic and cadmium pollution in farmland especially in rice land could influence agriculture production.So it is urgent to explore the effective methods to reduce the migration and accumulation of arsenic and cadmium in rice.In decades brassinosteroid（Brs）has been reported to promote plant growth,improve photosynthesis and reduce heavy metal toxicity.Meanwhile it also reported that the action of iron plaque promotion about the absorbtion and transshipment of arsenic and cadmium.However whether Brs could influence the promotion of iron plaque and the absorbtion of arsenic and cadmium is still not clear.Therefore in this study we set up two hyrdroponic experiments to test the effect of different kind（Br24:24 Epi-brassinolide,Br28:28 homobrassinolide）and concentration（10-6、10-7、10-8、10-9、10-10、0 mol L-1）of Brs on the promotion of iron plaque and accumulation of arsenic and cadmium.We set up another soil culture experiment to study the formation of iron plaque and the absorption of arsenic and cadmium by Brs spraying and application of exogenous FeSO4.The main results were as follows:In order to exploring the influence causing by Brs and FeSO₄ acting on the arsenic and cadmium absorbtion in rice,we use hydroponics and soil culture experiment to research the influence given by adding different concentration and kind of Brs and FeSO₄ acting on the biomass,the content of arsenic,cadmium and iron in rice.Finally we discussed how did Brs influence the absorbtion of arsenic and cadmium in rice.Main results were shown as follows:1.Under different concentrations of Br24（10-6,10-7,10-8,10-9,10-1,0 mol L-1）,10-6 mol L-1 Br24 could inhibit the growth of rice.The optimum concentration of Br24 was 10-8 rrmol L-1.The application of 10-8 mol L-1 Br24 alone significantly increased the As and Cd contents in iron o plaque and decreased the As content in rice shoot.The combined treatment of 10"8 mol L-1 Br24 and iron plaque induced significantly increased the As contents in iron plaque and significantly decreased the As content in rice shoot,but had no significant effect on the Cd content.2.Based on the first hydroponic experiment,we found that Br24 could promote rice growth better than Br28.Although the absorption of As and Cd by different parts of rice was not significantly affected by the application of Brs,the absorption and accumulation of As in rice were significantly reduced by the combined action of Brs and iron plaque induction.3.In soil culture experiments,we found that the application of exogenous FeSO₄ could effectively poison rice with As and Cd,while the application of exogenous FeSO₄ increased the Fe content in rice roots and iron plaque,but it had no significant effect on the Fe content in other parts of rice.Therefore,we inferred that the application of exogenous FeSO₄ in the environment would not cause Fe toxicity,and the application of exogenous FeSO₄ significantly improved the As content in iron plaque.4.FeSO₄ application and its combined effect with Brs reduced the migration of As and Cd to grains;Two Br24 concentrations（10-10 and 10-8 mol L-1）reduced As and Cd content in rice grains significantly;FeSO₄ application and the combined of FeSO₄ and Brs reduced As and Cd content in grains,which could be reduced by 73.2%and 67.0%and reduced Cd content in grains to national regulations below 0.2 mg kg-1.