| Semanotus bifasciatus(Motschulsky) is one of the most destructive borers of Platycladus orientalis(L.) Franco.The ecological environment and forest resources have been threaten seriously by S.bifasciatus in China.The dissertation has emphasized on extracting and analyzing active ingredient of P. orientalis,bioassay and field tests of S.bifasciatus for filter plant attractants,as well as the new method for volatiles analysis by using Purge & Trap Injection combined with GC/MS (PTI-GC/MS),the changes of secondary metabolites and some related physiological indicators of the weak P.orientalis,which can be taken as a theoretical basis for an effective management of S.bifasciatus and may lay the foundation in understanding the mechanism of insects hurts weak host-plant.The chemical compounds of P.orientalis were extracted by four kinds of methods respectively,Modified simple distillation(MSD),Supercritical fluid extraction(SFE), Soxhlet extraction(SE) and Simultaneous distillation extraction(SDE).The results indicated that monoterpenes,sesquiterpene and oxygenated compounds of larger molecule were the dominant contents in P.orientalis.The relative contents of thujopsene and cedrol were higher in P.orientalis extracted by SFE and MSD methods.No monoterpenes was found in the compounds extracted by SFE and SDE,and the wood resin acids were the major compounds in the compounds extracted by SE.The analytial conditions of PTI-GC/MS were optimized for the analysis of volatiles: sample 0.2g,purge time 5 min and pre-back flashing 2 min.The results of monoterpenes analysis by PTI-GC/MS were better than by TCT-GC/MS.The EAG results showed that no significant difference between female and male S.bifasciatus.The EAG responses of S.bifasciatus to 3-Carene,Limonene,Terpinene and Thujopsene were increased with the concentration respecitively within the range of 1/1000-1/10.The results of "Y" tube olfactory bioassay showed the pests can be attracted by 1/100 Limonene,3-Carene and Thujopsene.Original and 1/10 Terpinene was the best. In addition,the extracts of A2(by MSD) and D1(by SFE) also caused positive attraction to S.bifasciatus,while the extracts by SE and SDE were non-attractive.Above results were proved further by field tests.Extract(A2) mixed with monoterpenes with a certain ratio (α-Pinene:β-pinene:3-Carene:Limonene:Thujopsene:α-Terpinene=1:1:10:1:1:1) was the best attractant which could trap S.bifasciatus and lasted for more than ten days.Moreover, the effect in cross-trapping was better than in triangle-trapping.The volatiles emitted from P.orientalis in different physiological state were analyzed by PTI-GC/MS.The results indicated that there were 9 kinds of monoterpenes and 3 kinds of sesquiterpenes were identified both in healthy and weak trees.The components included Thujene,α-Pinene,β-Phellandrene,β-Pinene,Camphene,3-Carene,Limonene, Terpinene,p-Mentha-1,4(8)-diene,Cedrene,Thujopsene andα-Caryophyllene.Compared with the control,the relative contents of 3-Carene and thujopsene increased significantly and that ofα-Pinene,β-phellandrene,β-Pinene and Limonene decreased in weak trees.The differences between healthy and weak tree only related to the relative contents of above volatiles.The contents of lignin,phenolic acid and two amino acids(Phe and Arg) decreased, Comparing with the control,whereas some other amino acids(Leu,Ser and Pro) increased in weak trees.This indicated that the plant resistance reduced when they suffered from environmental stress or biological damage.These changes were more beneficial to the insects to feed,grow and develop.This is one of the main evidences for insects damage weak P.oriental.Furthermore,the moisture content of weak P.orientalis was lower than that of healthy one.The temperature of weak tree body fluctuated frequently within one day.It was lower in the morning and night and was higher during 11:00 to 14:00 than the control.The result of chlorophyⅡfluorescence kinetics showed that photosystemⅡin weak P.orientalis was destroyed seriously and the transport rates of antenna system and reaction centers were reduced considerably.The correlation between them not only indicates the mechanism which caused insects damage weak tree,but also indicates the different physiological status of the tree as indicators.
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