Preliminary Mechanism Of Heavy Metal Thallium Uptake In Rice Roots(Oryza Sativa L.)

Thallium is a non-essential,highly toxic heavy metal element.The major sources of natural thallium are deposits of sulphide ores.Thallium adsorbed by plants and living organisms to the food chain can cause serious toxicity problems.At present,the mechanism of root absorption by plant roots is not yet clear.In this study,a variety of plant samples were cultured and screened in a hydroponics manner.Finally,rice plants with higher Tl uptake capacity were used as experimental materials.Potassium ion channel inhibitors,anion channel inhibitors,and ATPase inhibitors were added to compare groups.The Tl uptake ability of rice was different from that of the control(not added);at the same time,it was relatively easy for rice to absorb Tl and K under the condition of potassium and potassium coexistence.The related approaches of thallium to plant root system were preliminarily clarified.The factors affecting Tl(?)stability were also studied through the addition of exogenous organic acids and DTPA.The results are as follows:1.In the hydroponics experiment,the absorption of Tl in different plants was compared: the Tl absorption of rice was larger,higher than that of fern kidney fern,the aquatic plant Myriophyllum,the kale and the Chinese cabbage;the absorption and accumulation site,hydroponics rice roots absorption accounted for 84.8% of the absorption of whole plant,while the absorption of shoots in the stems and leaves of kale accounted for about 55% of the whole plant;under the soil culture mode,the absorption of rice plant roots accounted for 78.93% of the whole plant;the kale cabbage stems and leaves The absorbed volume of the department accounted for61.07%.Accumulation of Tl by rice is mainly concentrated in the roots,while the pods of kale are mainly accumulated in stems and leaves.The rules of absorption of Tl were basically the same for both plants under soil and water culture conditions.2.The effects of adding organic acids on the uptake of rice under thallium stress indicated that the addition of three organic acids(malic acid,citric acid,and oxalicacid)all inhibited the uptake of rice.The ability of exogenous oxalic acid to inhibit Tl absorption is higher than malic acid and citric acid.Oxalic acid was a specific root exudated organic acid in Tl-treated rice,and at 25 ?M concentration,Tl stress had an inhibition on the type and content of organic acid secretion in rice rhizosphere compared to the control.3.Inhibitors have been shown to influence the uptake of thallium in rice roots.Experiments have shown that in the treatment of K ion channel inhibitors,anion channel inhibitors and ATPase inhibitors,comparative inhibitors affect the uptake of potassium ions,indirectly indicating the uptake of rice roots.The K ion channel pathway exists and there is an active absorption process,and the anion channel has an influence on the absorption of Tl.The absorption of potassium ions is competitive.The presence of potassium ions can promote the inhibitory effect of a single inhibitor on Tl uptake,but under different conditions of inhibitors interaction,it will have different effects on Tl uptake.4.Thallium occurs in the environment in two redox states,namely Tl(?)and Tl(?).Tl(?)is thermodynamically more stable and less reactive compared to Tl(?)and is the dominant form in the environment.However,when Tl(?)coexists with plants,it is more likely to be converted to Tl(?),and what kind of substance promotes Tl(?)transformation has not been reported.Exogenous organic acids can lead to Tl(?)instability and promote the reduction of Tl(?)to Tl(?).Low molecular weight organic acids in plant cells or root exudates are important causes of T1(III)reduction.Tl(?)can form a stable and strong complex Tl(?)-DTPA with DTPA,which maintains the stability of Tl(?)in a hydroponic system.