| Cadmium, whose pernicious effect is just lower than lead in our body, is a heavy metal with obvious toxicity. Selenium, who has many effects on the plant growth and development as well as stress alleviation,too, is an essential microelement for animals and humans. There have been many studies on the effect of inorganic selenium on the output and quality, selenium accumulation and cadmium toxicosis mitigation of plants.A great portion of selenium in soil exists as the organic forms whose assmilation and transfer ratio in plants are higher than the inorganic species. However, the influcnce of organic selenium on plants is still not clear until now. Selenium and cadmium are associated elements in the geochemical cycles. It’s easy to get selenosis in seleferous soils and cadmium levels in the food chain exceed the criterion in the same region. Sulfur, which can be used to inhibit the selenium uptake and applied to reduce the cadmium accumulation by plants, is located in the same main group with selenium. Hence, it’s necessary to the study the impact of sulfur on the high cadmium seleniferous soil. Therefore, What included in this paper were about the characteristic of different selenium speciations on the edible rape growth, selenium accumulation and cadmium antagonism and in regard to the role of different sulfur varieties played in the growth, selenium/cadmium accumulation, stress poisoning amelioration by plants and the change of selenium/cadmium forms in the soil. The main results are as follows:1.Edible rape growth were improved by the three selenium species and the most obvious role was played by Se(IV)(sodium selenite). The edible rape, which were treated with Se(O)(selenomethionine)or Se(IV)(sodium selenate), was suitable for eat, but plants, which were treated with Se(VI), contained 6.8 fold selenium as the poisoning threshold. Nitrogen, phosphorus, potassium, calcium and magnesium contents were decreased by Se(O). Nitrogen, phosphorus concentration were increased by Se(IV) or Se(VI), while the potassium, calcium and magnesium contents were reduced by them. The MDA content in the plants which were declined by Se(O) significantly, were increased by Se(IV) slightly and promoted by Se(VI) remarkably. Besides, The SOD(superoxide dismutase), POD(peroxidase) and CAT(catalase) activities as well as the AsA(Ascorbic acid) and GSH(Reduced glutathione) contents were significantly decreased by all of the three selenium. Therefore, when carrying through biofortification at selenium deficiency place and judging the selenium pollution in seleniferous area, selenite and high-Se plant residues were recommended.2.The pernicious effects of cadmium on plants were intensified by cadmium concentration. Plant growth were significantly suppressed by cadmium. The effect of cadmium on the selenium accumulation in shoots depended on the cadmium concentrition and selenium speciation in soil. Plant selenium accumulation of CK and Se(O) treatments were increased by the 2.0 mg kg-1 Cd and CK, Se(O) and Se(IV) were intensified by the 5.0 mg kg-1 Cd. Nitrogen, phosphorus, potassium, calcium and magnesium content in the shoots of the edible rape were remarkably decreased with the increaing of cadmium. The MDA contents were prominently increased by Cd while the SOD, POD and CAT activities were induced by it.3. The growth inhibition of Cd were ameliorated by 1.0 mg kg-1 Se and the most obvious role was played by the Se(O). Cd accumulation in plants, which exceeded the food criterion, were inhibited by Se(O) or Se(IV) but promoted by Se(VI). Nitrogen, phosphorus concentration in plants were aggrandized by Se(O) or Se(IV), while furthur inhibited by Se(VI) under Cd stress. The SOD, POD and CAT activities as well as the AsA and GSH contents of Cd stressing plants were augmented by Se(O) or Se(IV), but the effect of Se(VI) was just on the contrary.4.Plant growth were significantly promoted, chlorophyll a and b content were increased and carotenoid concentration were decreased by sulfur. Selenium accumulation were lessened and cadmium as well as macroelements in plants were aggrandized at the meantime. The abilities of resisting cadmium stress by plants were remarktably augmented, which showed as the obvious increase of antioxidase activities, the apparent augment of reducing substances content and significant decrease of MDA. What can be seen in the results was that the toixicity of high cadmium seleniferous soil on plants can be ameliorated by sulfur, but the selenium accumulation were remarktably reduced and cadmium which is noxious were fortified by it.5.Soil pH, which was significantly reduced by S, conspicuously aggrandized by Na2SO3, while no obvious impact existed on it by Na2SO4. The acid soluble and oxidizable selenium/cadmium were evidently augmented by S, improving the bioavailability of soil selenium/cadmium. The reducible and oxidizable selenium/cadmium were increased by Na2SO3, lowering the migration of them slightly. The influence of Na2SO4 on were just on the contrary. The acid soluble, reducible and oxidizable selenium species were significantly increased while the corresponding cadmium forms were reduced remarkably. Therefore, sulfur speciation should be taken into account when sulfur fertilisation applied in high cadmium seleniferous soils. According to the influence of different sulfur on the effectiveness of selenium/cadmium, sulfide is the best sulfur fertilisation choice. |
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