The Effect Of Parasitism By Procecidochares Utilis Stone On Allelochemicals And Anti-herbivore Substance Of Ageratina Adenophora Sprengel

Ageratina adenophora Sprengel,a worldwide noxious invasive plant,has been widely introduced into more than 30 countries and regions,and has caused serious economic loss and ecological disaster and even posed a threat to the health of human beings and animals.It introduced into Yunnan Province from Burma in the 1940s,now it occurs in much of Southwest China and Taiwan Province and other places,has caused significant damage to agriculture,forestry,animal husbandry and fishery.Recent studies have confirmed that A.adenophorum has a significant allelopathic effect on surounding plants in invasived areas.During the interaction with local species,invasive plants often improve their biological and ecological characteristics to adapt to the new environment.It has been proved that the invasive plants can reallocate their defense and growth resources,that is,they tend to reduce the resistance to the specialist herbivores,and free more resources for its development or strengthening its invasive weapons:allelochemicals.It has recently been found that the invasice population of A.adenophora,compared with original population,could allocate more nitrogen from cell walls to photosynthetic apparatus.As a parasitical natural enemy,Procecidochares utilis Stone was introduced in the 1980s to control A.adenophora.This insect has established natural populations in many areas,but which have shown a poor control effect.In order to carry out the mechanism of the resource changes between the adaptability to enemies and allelopathy of alien invasive plants,the contents of allelochemicals and anti-herbivore substances between invasive and native populations of A.adenophora under the parasitical stress of P.utilis were examined.The results are as follows:1.The populations of A.adenophora from its native ranges(Mexico,2 populations)and invasived ranges(China,3 populations)were selected,and the contents of 6 anti-herbivore substances(Tannin:tannic acid,catechin,ellagic acid;Flavonoid:quercetin,isoquercetin,kaempferol)between invasive and native populations of A.adenophora were investigated.The morphological characteristics were also observed as well as the ratios of C/N were also detected.The results showed that,the shoot tips of A.adenophora from all investigated populations were covered with simple trichomes,and there were no significant differences of sclerenchyma and cortex cell layer numbers between invasive populations and native populations.The ratios of carbon and nitrogenin of invasive populations were all significantly lower than that those native populations,especially from the stems of the plants.The contents of anti-herbivore substances from invasive populations were significantly lower than that in native populations,especially the contents of tannic acid and catechin in shoot tip,which were 32.3%and 26.4%lower than that of the native populations,respectively.The contents of anti-herbivore substances also changed to some extent;A.adenophora produced more anti-herbivore substances,especially the tannins,after being parasitised by P.utilis.The content of catechin from M1 population was 163.2%higher than that of non-parasitic plants.To sum up,A.adenophora in invasive ranges has an adaptive change in anti-herbivore substances and C/N ratio,which confirmed that the invasive populations of alien species produced lower anti-herbivore substances than the populations in native range.And,the contents of anti-herbivore substances were enhanced when treated with P.utilis;the parasitism induced enhancement of anti-herbivore substances in native population was more profound than that in invasive population.2.With the methods of single plant cultured in cups with nutrient solution and vestured with gauze,changes of the contents of 2 allelochemicals(DTD,HHO)from A.adenophora in different origins under the parasitical stress of P.utilis were examined.We found that,the contents allelochemicals DTD in invasive populations was significantly higher than native populations,but there was no obvious difference in HHO.The contents of the two allelochemicals that produced from introduced populations after being parasited by P.utilis was significantly changed.P.utilis treatments enhanced the contents of allelochemicals at the beginning stage of parasitism,e.g.the content of HHO of C2 population increased by 77.6%.Thus,it is indicated that the allelopathic effect on native plants of invasive populations of A adenophora is more obvious than that of native populations,and which could be strengthened under the parasitism of P.utilis.