Effects Of Selenium And Sulfur On The Physiological And Biochemical Characteristics And Cadmium Absorption And Distribution In Rice Seedling Under Cadmium Stress

In this experiment the No.6Huai rice was selected as experimental material and cultured in solution conditions by foliar application of selenium and at the meantime cadmium and sulfur is applied in root.Three cadmium concentration(mg/LCdCl2) is set as O(CdO),1(Cdl),10(Cd10), three sulfur concentration(mg/LMgSO4) is set as0(SO),48(S48),720(S720).At the same time spraying sodium selenite solution in rice foliar and setting two selenium concentration as0(SeO),500mg/L(Se500),where SeO means spraying of distilled water in rice shoot foliar as a control. The main findings are about the followings,1) From the perspective of growth condition,physiological and biochemical indexes,with the increase of time the increasing Cd level will inhibit root and shoot length growth, resulting in rice seedling biomass accumulation decline.The increasing Cd level contribute to rice seedling with the promotion of Cd and Se element absorption effect and the content of MDA,while decreasing chlorophyll content and root activity;The rice seedlings sprayed with Se500will be reduced in shoot and root biomass and length for different degree.Contrasting with the control of SeO,which can reduce Cd content and the chlorophyll content in rice seedlings while increasing the content of MDA, and the impact on root activity is not significant; High sulfur S720and non-sulfur condition SO relative to the moderate sulfur conditions S48in each sampling time produced the accumulation inhibitionof shoot and root biomassand length,Cd content to a certain extent.High S condition relative to the moderate S condition can inhibit the absorption and transfer of Se.Non-sulfur condition relative to the moderate S condition will promote Se absorption and transfer.Three S levels of S720, S48, SOeffect on chlorophyll content accumulation with the performance of S720>S48>S0.The increasing S level in the corresponding conditions can reduce the MDA content and increase the corresponding root activity.2) From the perspective of antioxidant enzymes system and sulfhydryl compounds, the increasing Cd level can increase SOD, POD and CAT activity,which measns raisingthe extent of response in rice seedlings antioxidant system.The effects of spraying Se on antioxidation system is complex, which cause SOD and POD activity in the corresponding conditions elevated, but may cause the decrease of CAT activity.S level can affect SOD and POD expression,non-sulfurcondition following on Cd stress with higher SOD and POD activity, at the same time the antioxidant system in response to a higher degree. High S condition S720can better antioxidant, anti stress and with the performance for decreasing activity of SOD and POD. The effect of S levels on SOD and POD activity influence in roots higher than shoots; As the S level from SO up to S48and S720,the CAT activity increase correspondingly, but the perfonnance is maximum under the S48condition in upper part;The trend has great consistency of GST and GSH influenced by different factors,the increasing Cd level can increase GSH and GST content.A higher level of S and Se significantly increased GSH content. Under the condition of Cdl the MT generation is higher than under CdO and Cd10.The spraying of Se500can obviously promote the MT and PCs content to some extent, the increase of S level is in favor of MT and PCs generation, but in high S condition S720and Se500, S and Se can form competitive inhibition, which is disadvantageous to the formation of MT and PCs.3) From the perspective of subcelluar distribution and chemical forms of cadmium.since the vacuole compartmentaliztion and the cell wall binding act as the main tolenrance mechnism for Cd in rice seedlings which suggests that sulfur and selenium relieves the Cd stress to some extent. Unfer different S, Se, Cd condition, FNacl and FE were the dominant form of Cd extraction.FNaClacts as the states of matter for extraction of proteins and other molecules,its level can reflect the degree of binding to heavy metals.So it means S and Se could promote certain proteins binding to Cd to reduce Cd stress,and this is the important mechanism of resistance to Cd in rice seedling.