| Radish(Raphanus sativus L.)is an important annual or biennial root vegetable crop of Brassicaceae family.The annual planting area of radish ranks in the top three of vegetable crops in China.Selenium(Se)is one of the essential nutrients for human body.Se deficiency can cause disorders of human physiological function and lead to many diseases.Se content in soil is seriously insufficient in about two-thirds of China’s land area.It is of great significance to improve the Se nutrition deficiency of Se-deficient population and study the Se enrichment technology in Se-deficient areas.Nowdays,several studies were focused on exploring the effects of different Se concentration on Se content,yield and nutritional quality of radish.However,no systematic study had been performed on the effects of exogenous Se types,treatment methods and genotype differences on Se uptake and transport in radish.The effects of leaf Se application,synergists and genotype differences on Se content and quality remain to be clarified in radish.The effects of exogenous Se concentration and synergist on Se uptake,transformation and nutritional quality of radish plants and sprouts were studied by pot and plot experiments.The main results are as follows:1.Different concentrations of sodium selenite solution were sprayed on the leaves of radish variety’NAU-SeYH’.It was found that the Se content in different radish tissues were increased with the increasing exogenous Se concentration.As expected,the low Se concentration(<10 mg/L)could promote the growth of radish plants,while high Se concentration(>20 mg/L)inhibited the growth of radish.The treatment effect reached the maximum at spraying 5 mg/L sodium selenite solution,indicating that this concentration is suitable to be further used for producing Se-rich radish.2.The leaves of 36 radish genotypes were sprayed with 5 mg/L sodium selenite solution in Se-deficient soil.The results showed that the Se content in the above-ground part was 0.120-0.301 mg/kg and that in the underground part was 0.079-0.197 mg/kg when the leaves were not sprayed with Se,which indicated that the Se-enriching ability of radish was strong.The Se content of the radish developmental stages was significantly increased after spraying Se on the leaves.However,the significant differences of Se uptake and accumulation were observed among different genotypes,and the’NAU-Se03’ was the top Se-enriched genotype because of its strong ability to enrich soil Se and leaf Se.Spraying Se on the leaves has a great effect on the yield and quality of radish.Different genotypes have different responses to exogenous Se.Spraying sodium selenite on the leaves can increase the fleshy root weight and increase contents of soluble solids,soluble protein and soluble sugar in fleshy roots except the Vc content.3.Field block experiments were conducted to study the effects of compound sodium nitrophenolate,diethyl aminoethyl hexanoate and polyaspartic acid combined with sodium selenite on Se uptake,transport and nutritional quality in seven radish genotypes.The results showed that the three synergists could significantly improve the growth and Se absorption efficiency on leaf surface of radish.The application of sodium selenite reduced the Vc content in fleshy roots,whereas it could increase the content of soluble solids,soluble protein,soluble sugar and Vc when combined with synergists.Taken together,the sodium dinitrophenol showed the most obvious effect to increase the Se content in radish,and aminophenol ester was not suitable for direct application with sodium selenite.4.Using the ’NAU-SeYH’,’NAU-SeSJQ’and’NAU-SeZDC’ as materials,the effects of different treatments and concentrations on germination rate and Se enrichment of radish genotypes were studied by soaking seeds in different concentrations of sodium selenite solution and spraying radish sprouts,respectively.The results showed that seed soaking with low Se concentration(<0.5 mg/L)could improve the germination rate and potential of radish seeds,but the optimum seed soaking concentration of different genotypes was different.Seed soaking and spraying with low Se concentration could increase the hypocotyl length and diameter,seedling length,and the content of soluble protein,Vc and soluble sugar of radish sprouts.Seed soaking treatment(0.1 mg/L)or spraying treatment(0.5 mg/L)was suitable for the production of Se-enriched sprouts.The average Se content of sprouts was 0.83 mg/kg and 2.77 mg/kg(DW),respectively.The effect of low Se concentration on the Se-enriched seedlings is not strong,and high Se concentration can inhibit seed germination.Taken together,the combination of low Se solution soaking and spraying could be further used to produce Se-enriched radish sprouts. |
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