Study On The Allelopathic Effect Of Aqueous Extracts Of Ambrosia Artemisiifolia L.and Ambrosia Trifida L.on Maize

Ambrosia artemisiifolia L.and Ambrosia trifida L.belong to the Ambrosia L.of Compositae are annual herbs and are recognized as malignant invasive weeds all over the world.Allelopathy is one of the important factors for the successful invasion of Ambrosia artemisiifolia L.and Ambrosia trifida L.In order to explore the mechanism of their allel opathy,this study used Ambrosia artemisiifolia L.and Ambrosia trifida L.in different growth periods as experimental materials,selected maize as experimental plants,and studies were carried out from the aspect s of seed germination,root morphology and transcriptome sequencing(RNA-Sequencing,RNA-seq)to analyze the seed germination,seedling growth and genomic transcription of the tested plants after stress,analyze and identify the allelochemicals in the aqueous extracts of Ambrosia artemisiifolia L.and Ambrosia trifida L.by gas chromatography-mass spectrometry(GC-MS).The purpose of this study is to provide theoretical and scientific basis for studying the harm mechanism,effective control methods,discove ry and resource utilization of maize resistance genes of Ambrosia artemisiifolia L.and Ambrosia trifida L.to agricultural production.The main r esults are as follows:(1)The aqueous extracts of Ambrosia artemisiifolia L.and Ambrosia trifida L.in different growth periods showed allelopathic inhibition on seed germination and seedling growth of maize.When maize seeds were treated with aqueous extracts with mass concentrations of 0.05 g/m L,0.10 g/m L,0.15 g/m L and 0.20 g/m L,the allelopathic comprehensive effect indexes of Ambrosia artemisiifolia L.at seedling stage,flowering stage and fruiting stage were-0.540,-0.459 and-0.555,respectively.The allelopathic comprehensive effect indexes of Ambrosia trifida L.at seedling stage,flowering stage and fruiting stage were-0.557,-0.533 and-0.330,respectively.The results showed that when the concentration of aqueous extract was 0.05～0.20g/m L,the allelopathic effect of aqueous extract of Ambrosia artemisiifolia L.at different growth stages on maize was from strong to weak: Ambrosia artemisiifolia L.at fruiting stage >Ambrosia artemisiifolia L.at seedling stage > Ambrosia artemisiifolia L.at flowering stage.The allelopathic effect of aqueous extract of Ambrosia trifida L.on maize in different growth stages was from strong to weak: Ambrosia trifida L.at seedling stage > Ambrosia trifida L.at flowering stage > Ambrosia trifida L.at fruiting stage.(2)When the concentration of water extract was 0.05～0.20 g/m L,the root morphology of maize seedlings changed significantly under the stress of aqueous extract of Ambrosia artemisiifolia L.and Ambrosia trifida L.compared with the control group,t he root hairs of maize seedlings in the treatment group were underdeveloped,short er and harder,more twisted,and the color was yellowish brown.Furthermore,the length of cells in the root maturation zone of maize seedlings became shorter after stress compared with the control group.(3)With distilled water(CK)as control,maize seedlings treated with0.1 0 g/ m L aqueous extract of Ambrosia artemisiifolia L.(TC)and Ambrosia trifida L.(SLY)were sequenced by transcriptome.The results showed that4 92 7 differentially expressed genes were identified in TC＿vs＿CK control group,including 14 7 5 up-regulated genes and 34 5 2 down-regulated genes.A total of 7377 differentially expressed genes were identified in SLY＿vs＿CK control group,including 2869 up-regulated genes and 4508down-regulated genes.GO functional enric hment analysis showed that in TC＿vs＿CK control group,DEGs was mainly enriched in GO terms,such as defense response,response to oxygen-containing compound,monooxygenase activity,terpene synthase a ctivity and transmembrane transporter activity.In the S LY＿vs＿CK control group,DEGs was mainly enriched in photosynthesis,secondary metabolite biosynthetic process,photosystem,oxidoreductase activity and monooxygenase activity,etc.GO terms.KEGG pathway enrichment analysis showed that in TC＿vs＿CK control group,the KEGG pathways significantly enriched by DEGs included histidine metabolism,photosynthesis,Metabolism of xenobiotics by cytochrome P450,starch and sucrose metabolism and oxidative phosphorylation.In the SLY＿vs＿CK control group,the KEGG pathw ays significantly enriched by DEGs were mainly the metabolism of xenobiotics by cytochrome P450,tryptophan metabolism,ascorbate and aldarate metabolism,photosynthesis and ABC transporters.In addit ion,39 genes related to plant antioxidation were screen ed in TC＿vs＿CK control group,and 61 genes related to plant antioxidation were screened in SLY＿vs＿CK control group.It was further explained at the molecular level that the stress of aqueous extracts of Ambrosia artemisiifolia L.and Ambrosia trifida L.broke the balance of protective enzyme system during the growth and development of maize seedlings.(4)Through the analysis of gas chromatography-mass spectrometry(GC-MS),it was found that the main c hemical substances in the aqueous extracts of Ambrosia artemisiifolia L.and Ambrosia trifida L.were diethyl phthalate.