Allelopathic Effect Of Humulus Scandens Root Extracts On The Growth Of Invasive Plant Alternanthera Philoxeroides

The invasion of alien plants has had a serious impact on the global ecology,economy, human and animal health.Among them,Alternanthera philoxeroides?Mart.?Griseb.)has become one of the most widely distributed and most important invasive weeds in the world.Harm to 32 different countries and regions including South America,Australia,Asia and North America.And also facing severe challenges in the control and management of invasive weeds.This article focuses on the allelopathy among plants and evaluates the allelopathy potential of the root extract of Humulus scandens?Lour.?Merr.on the invasive plant Alternanthera philoxeroides.The composition of allelopathy substances is analyzed,and the allelopathy mechanism of some allelopathy substances is discussed.In order to expand the breadth and depth of allelopathy in the field of intrusion prevention and control.Provide a certain theoretical basis for ecological control of invasive plants.?1?Allelopathy potential of the three chemical extracts of H.scandens root on the growth of invasive plant A.philoxeroidesIn order to study the allelopathy potential of Humulus scandens?Lour.?Merr.root extracts to invasive plant A.philoxeroides.Results showed that the allelopathy effects of a native plant,H.scandens,on a typical invasive species A.philoxeroides,was investigated by exposing A.philoxeroides seedlings to three chemical solvent extracts?i.e.,petroleum ether extract?PE?,ethyl acetate extract?EE?,and n-butanol extract?NE??of Humulus scandens root?HR?.The results showed that the three root extracts had significant allelopathy inhibiting the growth of small plants of invasive plant A.philoxeroides,and ethyl acetate extract had the strongest allelopathy inhibiting the growth of A.philoxeroides?SE=-0.539?.Compared with the control treatment,the stem length,node number,leaf number,leaf area and root number of A.philoxeroides decreased by 41.45%?39.68%?54.69%?63.81%?60%respectively.Under the condition of EE treatment,the total biomass,belowground biomass and aboveground biomass of A.philoxeroides reached the lowest,decreased by 67.63%,66.87%and 72.05%respectively compared with the control treatment,while the content of MDA increased 84.82%.?2?Identify allelochemicals from H.scandens root extractsIn order to study the kinds and relative contents of allelochemicals in H.scandens root extracts.Gas Chromatography-Mass Spectrometry?GC-MS?was used for analysis.Results showed that 55 compounds were identified from the three extracts of HR,among which 6compounds were isolated from them for the first time,which were dibutyl phthalate?1?,stigmasta-3,5-diene?2?,phenol,2,6-bis?1,1-dimethylethyl?-?3?,campesterol?4?,and neophytadiene?5?,docosanoic acid,methyl ester?6?.?3?Effects of 10 exogenous compounds on the growth of invasive plant A.philoxeroidesIn order to screen the allelochemicals which have stronger allelopathic effect on the rhizome of A.philoxeroides,10 kinds of exogenous compounds with relative content?1%were selected from the ethyl acetate extract,and the concentration gradients of 0.1,0.5 and1mmol/L were set.The results showed that 10 exogenous compounds had significant allelopathic inhibition on the growth of the clones.Among them,hexadecanoic acid,methyl ester,and 9,12,15-Octadecatrienoic acid,methyl ester,?Z,Z,Z?-,and Octadecanoic acid,and campesterol,and docosanoic acid showed significant concentration effect on the stem length,node number,leaf number,leaf area and biomass of the clones of A.philoxeroides.That is to say,with the increase of the concentration of the compounds,each index decreased significantly.The comprehensive allelopathy evaluation of morphological indexes of A.philoxeroides showed a significant concentration effect of allelochemicals on the number of nodes and above-ground biomass of the invasive plant clone of A.philoxeroides.When the concentration of the three exogenous compounds is 1mmol/L,the evaluation of the allelopathy effect on the morphological indicators of A.philoxeroides shows that the inhibitory effect is 9,12,15-Octadecatrienoic acid,methyl ester,?Z,Z,Z?-?SE=-0.62?>Hexadecanoic acid,methyl ester?SE=-0.49?>Campesterol?SE=-0.4?.When treated with Hexadecanoic acid,9,12,15-Octadecatrienoic acid,methyl ester,?Z,Z,Z?-and Stearic acid,the production rate of H₂O₂content and SOD activity in the leaves of the small plants of the invasive plant A.philoxeroides clone increased under compound stress,while the activity of POD enzyme decreased,and the dynamic balance of active oxygen was destroyed;the content of MDA increased significantly,and the membrane lipid peroxidation increased under chemical stress Inhibit plant growth.