Study On Interaction Of Molybdenum And Selenium And Its Mechanism Of Chinese Cabbage

Molybdenum and selenium are both essential trace elements for human health. A low intake of Mo and Se may increase the risk of many diseases, and intake of a certain amount of Mo and Se can also improve the body’s antioxidant capacity. There are many similar chemical properties of Mo and Se in the soil. In low soil pH, bioavailability of Mo and Se both trend to decrease. Large areas of soil are Mo deficiency, and most of those areas go with Se deficiency. In China, a large area of the land is Se and Mo deficiency and often results in the lack of Se and Mo in human body in this area. Therefore, co-application of Mo and Se not only has significance of human nutrition but also has significance of practical. Previous studies has focused more on Se-S, Mo-S, Se-P and Mo-P interactions in soil and solution culture, but little has been paid to the possible interactions of Mo-Se. Mo and Se are both absorbed by plants in form of anion, and they were both transported via sulphate and phosphate transporters. Therefore, the study of the relationship between Mo and Se also has a strong theoretical significance. On the basis of previous studies, soil and hydroponics trials were conducted to investigate the interactive effects of Mo and Se and its mechanism of Chinese cabbage. The Main results as follows:1. A pot experiment was conducted to determine the effects of co-application of Mo and Se on yield and quality of Chinese cabbage. The results showed that co-application of Mo and Se could increase yield, contents of vitamin C, soluble sugar, soluble protein, crude protein, organic acids and amino acids, as well as decrease nitrate content of Chinese cabbage. The effect of application of Mo is better than the effect of application of Se in improving quality of Chinese cabbage.2. A solution culture experiment was conducted to determine the effects of co-application of Mo and Se on nutrition uptake of Chinese cabbage. The results showed that Se decreased Mo concentration and inhibited translocation of excess Mo from roots to shoots in Chinese cabbage. When Se concentration reaches a certain level in the outside, root Se content did not increase with an increasing solution Se concentration, and application of Mo had no significant effect on plant uptake of Se and the capacity of Chinese cabbage uptake of Se depended only on the ability of translocation of Se from root to shoot. When root Se concentration was not saturated, application of Mo significantly decreased Se concentration. Although, there had a strong antagonism between Mo and Se on nutrition uptake, results showed that both Mo and Se could be easily translocated from solution to plants and from roots to edible parts. Therefore, co-application of Mo and Se could meet the need of producing Mo-enriched and Se-enriched crops.3. A short-term solution culture experiment was conducted to determine the effects of co-application of Mo and Se on Mo and Se absorption dynamics of Chinese cabbage. The results showed that there had a strong antagonism between Mo and Se on nutrition uptake, especially when Mo and Se deficiency persisted for long periods. Although the solution Se level can make root Se reach saturate, application of Mo decreased Se concentration. However, with the treatment time increasing, the antagonism between Mo and Se will become smaller and smaller. When the root Se concentration was saturated, application of Mo had no effect on Se uptake in Chinese cabbage. The performance characteristics of subcellular structures were similar, there has an antagonism between Mo and Se in subcellular structures. The effect of application of Se on the absorption kinetics parameters of Mo had a trend that it was not conducive to the absorption of Mo. The effects of application of Mo on the absorption kinetics parameters of Se had complex two sides. Due to the positive role of Mo on Chinese cabbage, both Km and Cmin had a trend that it was conducive to the absorption of Se. But due to competition between Mo and Se, Vmax had a slightly decreasing trend.4. A solution culture experiment was conducted to determine the effects of co-application of Mo and Se on chemical forms of them. The results showed that application of Se increased alcohol soluble and water soluble Mo concentrations of roots and shoots and decreased salt soluble and acetic acid Mo concentrations of roots and shoots in Chinese cabbage. Application of Se had no significant effect on shoot hydrochloric acid Mo concentration, but application of Se increased root hydrochloric acid Mo concentration. Application of Mo had no significant effects on shoot alcohol soluble and water soluble Se concentrations, application of Mo increased salt soluble and hydrochloric acid Se concentrations and decreased acetate acid Se concentration. Application of Mo had no significant effect on root alcohol soluble Se concentration, and application of Mo decreased water soluble Se concentration and increased salt soluble, acetate acid and hydrochloric acid Se concentrations. Application of tetravalent Se was conducive to the conversion of inorganic Se to organic Se, and application of Mo can promote the transformation of inorganic Se to organic Se in high Se level.5. A pot experiment was conducted to determine the effects of application of Mo and Se on soil available Mo and Se contents during two successive planting periods. The results revealed that yield was significantly increased by application of Mo and Se in the first harvest, which was not significantly increased by application of Mo and Se in the second harvest. Both application of Mo and Se could prompt Chinese cabbage uptake of Mo during the two successive planting periods; Soil available Mo maintained high level during the two successive planting periods, and application of Mo could meet the needs of producing Mo-riched cabbage during the two successive planting periods; Though both application of Mo and Se could prompt Chinese cabbage uptake of Se during the two successive planting periods, water souble Se and exchangeable Se were decreased after the first harvest and application of Se could only meet the need of producing Se-riched cabbage in the first harvest.6. Soil and solution culture experiments were conducted to determine the effects of application of Mo and Se on Mo and Se nutrition uptake in Chinese cabbage. The results showed that there had a strong antagonism between Mo and Se in solution culture experiment and had synergies between Mo and Se in soil experiment. Mo is an essential micronutrient for plants, and appropriate application of Mo can promote plant growth and then stimulate the absorption of selenium in Mo deficiency soil. Application of Mo had no obvious effect in promoting plant growth in Mo rich soil, and the antagonism between Mo and Se will be dominate. The beneficial and harmful boundaries of Se for plants are very narrow. When plants suffer from Se toxicity or potentially toxicity, Se would decrease Mo uptake. In our experiment, application of Mo and Se in Mo and Se deficiency soil, there had synergies between Mo and Se. In solution culture experiment, both Mo and Se had a very high effectiveness. The contents of Mo and Se of Chinese in the lowest solution Mo and Se levels are few times than the contents of Mo and Se of Chinese cabbage in soil experiment, and the transporters competition between Mo and Se will be dominate.7. A pot experiment was conducted to determine the effects of Mo and Se on the growth of Chinese cabbage under salt stress. The results showed that application of Mo and Se increased yield of Chinese cabbage, and the best treatments were combination of Mo and Se. The contents of Mo in Chinese cabbage were increased by application of Mo and combination of Mo and Se, especially when soil Mo deficiency. Mo and combination of Mo and Se increased activities of antioxidant enzymes and the contents of non-enzymatic antioxidants and then increased the capacity to eliminate active oxygen. Application of Mo, Se and combination of them increased osmotic-adjustment products contents and then increased the ability of osmotic-adjustment. Application of Mo and combination of Mo and Se increased photosynthesis rate in varying degrees. Application of Mo increased photosynthesis rate by non-stomatal factors, and combination of Mo and Se increased photosynthesis rate by stomatal factors. Mo and combination of Mo and Se were the best treatments in resisting salt stress of Chinese cabbage. Application of Se played a very small role in enhancing salt stress tolerance in Chinese cabbage.