Study On The Allelopathic Effects And Mechanism Of Borreria Latifolia On Eleusine Indica

Chemical herbicides are one of the most effective means to control weeds in farmland,but frequent use of herbicides also brings problems such as weed resistance and farmland ecological environment pollution.In order to explore the allelopathic mechanism of effective control of malignant weeds in orchard based on Borreria latifolia,this study used the Eleusine indica as a test plant to analyze the allelopathic potential of B.latifolia.Then,the main allelochemical of B.latifolia and its acting mechanisms were performed.The main results are as follows:1.Compared with the separate cultivation,plant dry weight,plant height,root dry weight and root length of E.indica were significantly inhibited in the mixed cultivation with B.latifolia.The aqueous extracts of root,stem and leaf in B.latifolia can significant reduce germination percentage,germination potential,germination index and radicle length in E.indica.The order of synthetic inhibitory effect of the aqueous extracts from different parts of B.latifolia was as follows:leaf>stem>root.Moreover,the analysis of the 7 allelochemicals contents in leaf aqueous extract and their inhibitory activities on seed germination of E.indica were performed.And the result found that coumarin had the strongest inhibitory activity on seed germination in E.indica among the 7 allelochemicals,and the ratio of coumarin concentration in leaf aqueous extract to its EC₅₀ value was higher than that of other 6 allelochemicals.These results indicated that coumarin was one of the main allelochemical in B.latifolia.2.The effect of coumarin on seed germination of E.indica was studied.Under 10-100 mg/L coumarin treatment,seed germination percentage,radicle and hypocotyl grow in E.indica were significantly inhibited.Under 50-100 mg/L coumarin treatment,the conversion between starch and soluble sugar was significantly inhibited,the contents of IAA,Z and SA were significantly increased,and the content of JA was significantly decreased,which interferes with endogenous hormone regulation.Under 100 mg/L coumarin treatment,SOD and CAT activities were significantly inhibited,and O₂^-and H₂O₂ accumulation was induced,resulting in membrane lipid peroxidation,and MDA content significantly increased.In addition,after 100 mg/L coumarin treatment for 48 h,the contents of 2 amino acids were significantly up-regulated and 15 amino acids were significantly down-regulated,indicating that coumarin significantly affected the amino acid metabolism during seed germination of E.indica.3.The effect of coumarin on plantt growth of E.indica was studied.By adding 100-500 mg/kg coumarin in soil,the plant height,plant dry weight and plant fresh weight of E.indica were significantly inhibited.The contents of Chl a,Chl b and total Chl were significantly decreased,and P_n,G_s and T_r were significantly inhibited.On the 5th day after treatment,500 mg/kg coumarin significantly inhibited Fv/Fm,Y（Ⅱ）,ETR（Ⅱ）,Pm,Y（Ⅰ）values,and significantly increased 1-q P values.The results showed that coumarin significantly inhibited the photosynthetic activity during the plant growth.Metabolomics analysis showed that after 500 mg/kg coumarin treatment,a total of 143 differential metabolites were found,of which 52 metabolites were down-regulated and 91 metabolites were up-regulated.These differential metabolites were significantly enriched in the pathways associated with carbon metabolism,biosynthesis and metabolism of amino acids and biosynthesis of plant secondary metabolite.Most of the 24 metabolites enriched in the first 5 pathways were amino acids,which indicated that coumarin significantly affected amino acid metabolism during the growth process of E.indica.4.50 mg/L coumarin significantly inhibited the seed germination rate,plant height,root total length and number of root tips of S,R-Gly and R-Glu of E.indica.The inhibition rate of R-Gly and R-Glu was higher than that of S.In conclusion,the water extract from the leaves of B.latifolia has strong allelopathic potential for seed germination of E.indica,and coumarin is one of the main allelochemicals.Coumarin inhibits seed germination and plant growth by affecting carbohydrate metabolism,amino acid metabolism,endogenous hormone signal transduction,reactive oxygen species balance and photosynthesis.In addition,Coumarin can inhibit seed germination and plant growth of R-Gly and R-Glu.