Effects Of Selenium On Seedling Growth Of Perilla Frutescens And Soil Microbial Community Structure Under Cadmium Stress

With the rapid development of industry and agriculture in China,farmland soil pollution has been widely concerned,Cadmium(Cd)pollution is one of them.Cd in the soil and the environment is easily absorbed and utilized by plants.Excessive Cd will not only affect the growth and development of plants,but also affect human health through the food chain.Selenium(Se)can promote plant growth and play an important role in plant response to heavy metal stress.Using Perilla(Perilla frutescens(L.)Britt.)as the research material,this paper studied the effects of spraying and soil application of Se on the growth and development of Perilla seedlings under Cd stress by measuring the dry and fresh weight,root length,SPAD,photosynthetic parameters,fluorescence parameters and leaf antioxidant enzymes of Perilla.The contents of pectin and hemicellulose in root cell wall of Perilla seedlings were determined to investigate the effects of soil Se application on the cell wall components of Perilla seedlings under Cd stress.On this basis,high-throughput sequencing technology was used to explore the effects of soil Se application on microbial community structure and diversity in rhizosphere and non-rhizosphere soil of Perilla under Cd stress.The main research results are as follows:(1)Under 10 mg/kg Cd stress,leaf spraying of 5 μM Se and soil application of 0.6 and 1.2 mg/kg Se had no significant effect on the growth of Perilla.(2)Under 10 mg/kg Cd stress,photosynthetic pigment content and photosynthesis of Perilla seedlings were decreased.Under Cd stress,spraying on the leaf Se and soil Se seedlings were relatively higher chlorophyll content,Ci,NPQ,L(PFD)are reduced,the Ls,Fv’/Fm’,ΦPSⅡ,ETR are increased,the proportion of Hd is reduced.(3)Compared with the control,the activities of SOD and POD in leaves of Perilla seedlings increased and the activities of CAT decreased under the treatment of Cd alone,while the activities of SOD,POD and CAT in leaves were decreased under the treatment of Se on leaf surface.The changes of the three enzyme activities under soil application Se treatment were consistent with those of Cd treatment alone.Compared with Cd treatment alone,leaf spraying Se reduced the activities of SOD and POD,and increased the activities of CAT,while soil Se reduced the activities of SOD,POD and CAT.(4)Cd treatment affected the cell wall composition of root of Perilla.Compared with the control,root hemicellulose content increased under Cd treatment alone.The hemicellulose content of soil roots was also increased when soil applied Se.Compared with Cd alone,the contents of hemicellulosic 1 and hemicellulosic 2 in roots were significantly increased by 13.60% and 39.11%,respectively,while the pectin content was not significantly changed.(5)The results of soil microbial diversity analysis showed that the application of Se and Cd had no significant effect on the diversity of soil bacterial community.The results of community structure analysis showed that the dominant bacteria phylum of rhizosphere soil were Proteobacteria,Actinobacteria,Firmicutes and Acidobacteria,etc.Soil application of Se increased the relative abundance of Proteobacteria,Bacteroidetes,Fibrobacteres,Sphingomonas and Nitrosospira in Cd-contaminated soil,while decreased the relative abundance of Actinobacteria.