Effects Of Selenium Treatment On Growth Of Seedlings And Nut Quality In Pecan

Selenium（Se）is considered as a beneficial element in higher plants and one of the trace elements necessary for human health,such as preventing and curing various diseases,delaying aging,fighting heavy metals,and promoting metabolism.However,72%of our country’s soil has selenium deficiency or even low selenium.The resulting selenium deficiency seriously affects people’s health.The use of plant selenium for exogenous selenium supplementation is a convenient,effective and safe way to enrich selenium,and is a key way for food selenium supplementation.It can not only increase the selenium content of plants,but also increase the yield of fruit trees,improve fruit quality,and increase the antioxidant capacity of plants.In this experiment,pecan seedlings and fruits were used as research materials to study the response of different selenium levels to the growth of the seedlings of pecan,and the effects of different selenium application methods on the fruit quality of pecan Ci SULTR2.1 of thin-shell pecans is analyzed.The main findings are as follows:1.The study on the growth of pecan seedlings by different selenium concentrations showed that low concentration of selenium promoted the growth and biomass accumulation of pecan seedlings,while high-concentration selenium inhibited seedling growth and dry matter.Accumulation,photosynthetic rate,and the higher the concentration of selenium,the more obvious the inhibition.The root length after treatment with 80μmol·L^-1selenium was significantly lower than that of the control by 55.36%（P<0.05）.Selenium application significantly increased the selenium content in the seedlings,and the roots were>leaves.With the increase of selenium concentration,the selenium content in leaves and roots increased first and then decreased.When the concentration of selenium was≥0.5μmol·L^-1,other treatments were significantly different from the control group.The selenium content in leaves and roots of 40μmol·L^-1selenium treatment was significantly increased by1682 times and 482 times compared with the control group.2.The study on the quality of pecans by different selenium application methods showed that under the condition of 160 mg·kg^-1sodium selenite,both the exocarp and the compound leaves could promote the growth and development of the fruit.The selenium content of selenium and selenium applied to the exocarp was 49 times and 101 times that of the control treatment,respectively.The order of the mean value of unsaturated fatty acids was as follows:Selenium treatment on exocarp>Selenium application in complex leaves>Control treatment.Compared with the control group,the selenium treatment increased the average amino acid content of the kernel by about 11.04%.The order of the average value of each amino acid component was as follows:Selenium treatment on exocarp>Selenium application in complex leaves>Control treatment.It shows that the application of selenium can improve the nutritional quality of the pecan,and the effect of applying selenium on the outer peel is better.3.In terms of gene function,a 1902 bp pecan gene sequence was cloned by RT-PCR and PCR.This sequence belongs to the full-length open reading frame（ORF）of the sulfur transporter gene Ci SULTR2.1,encoding 633 amino acids with a molecular mass of 68 943.37 Da.The gene-encoded protein comprises a Sulfate-transp domain（PF00916）and a STAS domain（PF01740）,which are typical of sulfur transporters.It is a hydrophobic non-secretory protein,has no signal peptide,is structurally stable,and has eight transmembrane domains.The tertiary structure is a channel structure formed by theα-helix,which is related to the transport function of the protein.