| During the co-evolution of plants and pathogens, plants have developed to respond to pathogen by elaborating a vast array of secondary metabolites. Many of these compounds have evolved to confer selective advantage against microbial attack. VOCs(volatile organic compounds)of plants are mixture of fatty acide derivative, aromatic compounds, monoterpenoids and sesquiterpenoids. Others constituents include specific compounds containing sulphur or nitrogen. VOCs of many plants have antimicrobial activity. Since spores from pathogenic fungi may come in contact with volatiles from wounded or damaged leaves, this activity could play a potential role of chemical defence against plant pathogen. Some of the VOCs are plant-produced signals that activate plant defence genes after pathogen attack. Some of these roles may include long-distance signal within and perhaps between plants. VOCs of plants often undulate when plants experience various environmental abiotic or biotic factors.In our work, undulation rules of VOCs in the leaves of Lycopersicon esculentum, and its antipathogenic activity after induction by a known elicitor, chitosan oligomer were studied. The correlation between the change of quantity and quality of VOCs and its inhibitory activity against pathogen fungi, further the plant disease after elicitation was established. The response characteristic of VOCs was also examined when L. esculentum was exposed to different degree drought stress. Further, the induction of VOCs and its relation to AOS metabolite by several potential elicitors(burdock oligosaccharide, Nd 3+and multifunctional agent "Duoba2")were also investigated. The results are as followed.1. VOCs in the leaves of L.esculentum collected by solvents extraction, steam distillation and gas adsorption, and subjested to GC/MS analysis. The results demonstrated that 19 compounds were obtained according to these three methods, while there were 14 in common, most of which were main components. However, the absolute and relative amount of each component was different. The most abundant VOCs was obtained by steam distillation, 27.13μg/g, followed by gas adsorption, 23.38μg/g and solvents extraction, 12.40μg/g. VOCs collected with GDX-101 by gas adsorption method could closely reflect its naturally states in L. esculentum, and it was chosen for further research.2. The effect of VOCs and several compounds of L. esculentum on Botrytis cinerea and Fusarium oxysporum was examined by using the method of inverted culture of conidial suspensions. The results demonstrated that VOCs released from leaves was inhibitory, the inhibitory ratio of spore germination of B. cinerea and F oxysporum were 34.5% and 26.1%, respectively. And the the inhibitory ratio of hyphal growth was 75.3% and 63.2%, respectively. All the compounds tested were inhibitory against the pathogenic fungi, fatty acide derivative showed strongest activity, followed by aromatic compounds and terpene hydrocarbons. At the level of 10μmol/L, (E)-2-hexenal and nonenal could completely inhibited both of the fungi. While hyphal of B. cinerea grew abnormally when exposed to Eugenol (4umol/L) and Methy Salicylate (10~20umol/L). The results suggested that Lesculentum plants might defend against pathogen attack through the synergistic effect of the VOCs.3. Induction of VOCs in the leaves of L esculentum, and its antipathogenic activity after treatment with a known elicitor, chitosan oligomer were studied. The result demonastred that VOCs released from elicited leaves led spore germination reduced by 16.9% as compared with that of control 48h after treatment by 1.0% chitosan oligomer. Total VOCs was increased in chitosan oligomer(0.6%, 120h) -treated leaves, with 1.59-fold as compared with that of the control. Additionally, Phenols, Aldehydes, Ketones, Esters, Monoterpene were increased by 43%, 84%, 23%, 52%, and 51% , respectively as compared with that of control , after treatment. In our study, the level of PAL and LOX showed a similar trend with Methyl salicylate , Eugenol and (E)-2-hexenal, respe...
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