Effects Of Exogenous Abscisic Acid On Drought Resistance Of Silybum Marianum Under Drought Stress

Silymarin is an annual or biennial herb in the Asteraceae family.It is cold,drought,salinity and infertile resistant,and has wide adaptability and low soil requirements.Its active ingredients have various effects such as antioxidant,immune regulation,liver protection,etc.It is a good medicine for treating acute and chronic hepatitis and liver cirrhosis;meanwhile,its seeds can be used to extract oil and seed meal can be fed to livestock,which is a medicinal plant with various functions such as medicinal use,oil use and forage use,and is also a special economic crop suitable for large-scale cultivation.Studies have shown that drought stress can be mitigated by spraying plant growth hormones such as exogenous abscisic acid(ABA)to reduce the damage to plants during growth.Therefore,this thesis investigates the effects of different concentrations of exogenous ABA treatment on seed germination and seedling growth and development of water hyacinth,laying the foundation for revealing the response mechanism of exogenous ABA to alleviate drought stress in water hyacinth and providing theoretical basis for future water hyacinth in drought breeding and practical cultivation.1.Drought gradients were simulated by different concentrations of polyethylene glycol(ck,5%,10%,15%,20%).ABA(a1,a2,a3,a4,a5)immersion treatments were carried out under different levels of drought stress to study the effect of exogenous ABA on seed germination of water hyacinth under drought stress.The results showed that the growth and development of water hyacinth seeds under 5% PEG and 10% PEG simulated drought stress were better under a4 treatment;the growth and development of water hyacinth seeds under 15% PEG simulated drought stress were better under a2 treatment,and the seeds of water hyacinth no longer germinated under 20% PEG simulated drought stress.2.The leaves were sprayed with different concentrations of ABA(ck,200 mg/L,400mg/L,800 mg/L),and samples were taken at 0,3,5 and 10 d of drought to determine the physiological and biochemical parameters.The results showed that the chlorophyll content,soluble sugars and antioxidant enzyme system activities of water hyacinth seedlings were significantly increased after 400 mg/LABA treatment.At the same time,malondialdehyde(MDA)content decreased under this treatment.3.A total of 238 differentially expressed genes of S?C vs S?D were detected by DESeq analysis,of which 129 genes were up-regulated,and the number of up-regulation was 20 more than the number of down-regulation;a total of 641 differentially expressed genes of S?D vs S?DA were detected,of which 286 genes were up-regulated,and the number of down-regulation was 69 more than the number of up-regulation;a total of 983 differentially expressed genes of S?C vs S?DA were detected,of which 505 genes were down-regulated,and the number of down-regulation was 27 more than the number of upregulation.4.The GO enrichment and KEGG enrichment studies of differentially expressed genes revealed that biological processes were enriched after intercomparison between S?C vs S?D,S?D vs S?DA and S?C vs S?DA groups and were significantly annotated on the phytohormone transduction and MAPK signaling pathways.KEGG enrichment analysis of S?D vs S?DA and S?C vs S?D showed that the transcriptional activities of the differential genes annotated to the first five enrichment pathways: SAUR gene,GH3 gene,TGL gene and TPS gene were repressed and GPAT gene transcriptional activity was increased after ABA application.