Study On Allelopathy Of (the Aqueous Extracts From) Conyza Canadensis

Conyza canadensis (L.)Cronq.(C. canadensis),an. invasive plant of genus Conyza, Compositae,is one of the regional weeds which is serious harm to.The allelopathy of C. canadensis is the important mechanisms of it successful invasion,its research is still in preliminary stages.In this paper, determined the allelopathic effect of the aqueous extracts from C. canadensis on several receptor plants of different families and genus;determined the changes in physiological and biochemical indexes of Raphanus sativus's seeding which was dealed with the aqueous extracts;through step extraction method and column chromatography,combined with biometrics,preliminarily analysed the allelochemical in the aqueous extracts from C. canadensis.The main results were as follows:1.The aqueous extracts from C. canadensis had strong allelopathic effects and concentration effect,with the increaseding of its concentration,the allelopathic activity is also increaseding gradually.The aqueous extracts from C. canadensis could inhibit the germination of receptor plants'seeds,such the RI values of 0.20g/mL aqueous extracts from the Stems and leaves of C. canadensis on the germination rate and germination index of Acalypha hainanensis's seed were-0.822 and-0.892.In addition,the aqueous extracts from C. canadensis on the growth of receptor plants'seedling showed significant inhibition. When the concentration of the aqueous extracts from the roots of C. canadensis was 0.10g/mL,the roots of tylosanthes guianensias and Amaranthus mangostanus these tow receptor plants'seedlings have been significantly inhibited,the RI values were-0.622 and-0.667.2.Comprehensived analysis of the indicators show that,the difference between the allelopathy of different parts of C. canadensis'plant did not exist.However,the allelopathy of C. canadensis on different plants shown significant differences in size,which allelopathic effects on Amaranthus mangostanus were the strongest,followed by Stylosanthes guianensias.3.Researched results showed that,relative high concentrations of aqueous extracts inhibited the activity of SOD and POD of Raphanus sativus'seedlings,chlorophyll content and soluble protein content decreased,inhibited the growth of stems,increased MDA,and inhibit the growth of root,ultimately leading to reduced plant fresh weight.But after the treatment of the relatively low concentration, the activity of SOD,POD and chlorophyll content in leaves of Raphanus sativus' seedlings significantly increased,soluble protein content increased,so the stem became longer,the final plant fresh weight increased,but the other three indicators increase in the degree is not obvious.4.There were a large number of components can be dissolved in ethyl acetate which have allelopathic activity in the aqueous extracts from C. canadensis.In. the treatment solution of ethyl acetate extract,the inhibition rates of the germination rate and germination index of Raphanus sativus' seed and the root length of its seedlings were 98.37%,98.87% and 93.09%.Ethyl acetate extract and petroleum ether extract has high antibacterial activity,and the EC50 of ethyl acetate extract on Colletotrichum musae only is 0.6103mg/mL.5.Used column chromatography to separate ethyl acetate extracts of C. canadensis,obtained 18 sets of fractions,and the biological activity of Fr10-14 and Fr 19-30 these two groups is the strongest,the inhibition rate of 1.0mg/mL solution on the germination of Stylosanthes guianensias'Seed reached 69.87%and 65.81%,and the inhibition rate of 0.5mg/mL solution on the growth of Colletotrichum musae reached 94.24% and 94.60%.Obtained by GC-MS analysis,some of the substances in Fr19-30 contains have allelopathic activity,such as ketones and esters,and the content of 7,7-DIMETHYL-4-[(Z)-ETHOXYMETHYLIDENE]-BICYCLO[3.2.0]HEPT-2-EN-6-ONE is the highest in it, reaching 37.70%.Study on allelopathy of the aqueous extracts from C. canadensis would supply theory foundations for systematic review to the characteristics of C. canadensis'allelopathy and inqriry preliminarily the mechanisms of C. canadensis'allelopathy and establish basis for studying the allelochemical of C. canadensis in futher.