| Selenium (Se) is an essential trace element of human body. Selenium deficiencyis a major cause of cancer, cardiovascular and cerebrovascular diseases, diabetes,gastrointestinal disease, cataracts and other diseases for human being in recent yearsalong with the research of selenium and health in depth step by step and improved thepeople’s health consciousness. Functional food and drugs with selenium has been paidmore and more attention. In general, inorganic selenium, suach as sodium selenateand sodium selenite is added in food or drugs with Se. Inorganic selenium is moretoxic than organic Se and can not easily be absorbed by human body. However,organic selenium in plants is beneficial to the human body and eaily absorbed.Research shows that selenium can improve the quality of Chinese herbal medicines,which are good for human health. So, it is important to do some research onselenium-rich herbal plants for the supplement for human body. Astragalus has thecharacteristics of strong enrichment of selenium, but we do not know whetherAstragalus membranaceus (Huangqi), one species of Astragalus can accumulate highlevel of Se. At present study on accumulation and translocation of Se in Astragalusmembranaceus (A. membranaceus) is few. Therefore, a survey of Se concentrations insome types of Chinese medicines herbs (CMHs) was conducted in the fields of Anguoor pharmacys in Baoding city firstly. Then, the uptake by and translocation of Se inAstragalus membranaceus were investigated in hydroponics culture and soilexperiments, resepectively.The main results are as follows:(1) A preliminary survey of selenium concentrations in Chinese herbal medicinesand Se enrichment characteristics of A. membranaceusThe three types of Chinese Herbal Medicines which act as medicines fromdifferent parts: A. membranaceus (Huangqi: roots as medicine), D. morifolium (Juhua:flowers as medicine) and S. Coicis (Yimi: fruits as medicine) were collected fromfield and pharmacies to explore selenium (Se) concentrations in herbal medicinesusing the high pressure and airtight vessels combined with Inductively CoupledPlasma Mass Spectrometry (ICP-MS). The results showed that there were significant differences in Se concentrations in three types of herbal medicines from pharmacies.The average Se concentrations in D. morifolium is the highest at1032±78ng/g,followed by S. Coicis at17.8±2.5ng/g. The average concentration of Se in A.membranaceus is the lowest at12.9±1.3ng/g. However, The Se level in A.membranaceus collected from the fields is46.7ng/g, which is significantly higherthan that from pharmacies. Moreover, the average level of Se in D. morifolium fromthe fields96.1ng/g, which is significantly lower than that from pharmaciess. Theresults also showed that the Se concentrations in S. Coicis from Yasukuni andGuangxi are higher than that from Guizhou. The Se level in A. membranaceus fromAnguo is higher than it from other regions. This is to provide the data basis for thescreening of selenium-enriched herbal medicines.Moreover, the bioaccumulation factors of Se in the roots and shoots of A.membranaceus are less than1.0from the fields, whereas Se concentrations in shootsare higher than those in roots, which indicate that Se could be translocted easily fromroots to shoots in A. membranaceus.(2) The study of uptake by and translocation of Se in Astragalus membranaceususing hydroponicsWhether applying sodium selenite or sodium selenate in nutrient solution, the dryweights of roots and shoots for Se treatments are higher than that of control, whichindicated that Se addition can enhance the growth of A. membranaceus. In addition,there was no significant difference between selenate and selenite with the same levelin dry weights. Se concentrations in roots and shoots of A. membranaceus increasedwith the increasing of Se levels in nutrient solution when selenate supplied. However,Se concentrations in shoots increased and decreased in roots with the increasing Selevels in nutrient solution when selenite supplied. Se concentration got the peak when5μmol/L~10μmol/L selemium supplied as selenite. The translocation factorsenhanced when selenate or selenite was supplied in nutrient solution, which indicatedthat Se addition accelated Se tranlocation in A. membranaceus.Se levels in roots and shoots of A. membranaceus growing in nutrient solutionwith selenate or selenite were higher than that of plants supplied Se in shoots, whichshowed that it is better to supply Se for A. membranaceus in nutrient solution.（3）The study of uptake by and translocation of Se in Astragalus membranaceususing soil experimentThe dry weights of plants with Se addition at2mg/kg,4mg/kg,6mg/kg,8mg/kg in soil with selenate or selenite were significantly lower than those of control（P<0.01）. The dry matter reduced gradually with the increase of selenate applicationrates and showed the trend of increase firstly and then decrease with the increasing ofselenite application rates, and was the maximum at4mg/kg~6mg/kg. Moreover, the dry weights of roots and shoots both were higher in selenite treatments than that inselenate treatments for the same application rate.Shoot-Se in treatments with selenate or selenite was higher than that in controland increased with the increasing of selenate or selenite application rates. For selenatetreatments, there was no significant difference in Se concentrations of shoots amongthe three treatments of4mg/kg,6mg/kg,8mg/kg, which were higher than that of2mg/kg application rate (P<0.05). For selenite treatments, Se concentrations in shootsfollowed the rank of8mg/kg>4mg/kg and6mg/kg>2mg/kg. These resultsillustrated that the application of selenate and selenite enhanced Se accumulation inthe shoots of A. membranaceus. Se levels in roots followed the similar trend to that inshoots.Se concentrations in roots or in shoots were much higher for selenate treatmentscompared to selenite treatments at the same each application rate（P<0.01）. However,selenate is very active in soil normally and much high level of available selenate insoil could inhibite the growth of A. membranaceus, which agreed with the results ofdry matter of A. membranaceus supplied with selenate or selenite. Therefore, it isbetter to supply selenite to plants of A. membranaceus. |
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