白木香响应真菌侵染与机械损伤胁迫的生理机制

Physiological Mechanism of Aquilaria sinensis in Response to Fungi and Mechanical Damage Stress

[目的]为研究白木香受到胁迫的生长与防御过程,探明其结香过程的生理响应机制。[方法]以3年生白木香为对象,应用注射真菌菌剂与机械钻孔2种诱导结香方法对白木香进行制香,通过分析其调控生长与防御的激素含量、抗氧化酶活性、防御物质总酚与总萜含量以及光合与叶绿素荧光特性,研究白木香对真菌侵染与机械损伤胁迫的生理响应机制。[结果]在胁迫初期,与防御反应相关的激素茉莉酸、水杨酸、乙烯前体含量在胁迫处理组中显著升高,而与生长相关的激素赤霉素与生长素含量降低;在胁迫后期,茉莉酸、水杨酸与乙烯前体含量逐步降低,而赤霉素与生长素的含量逐渐增加。胁迫处理初期的抗氧化酶活性与总酚、总萜的含量显著高于对照组;抗氧化酶活性增幅随处理时间的延长而减小,总酚和总萜含量随处理时间的延长而增加,但增幅速率降低。胁迫处理1~3个月的光合作用与叶绿素荧光受到抑制,而胁迫处理第6个月时,光合与荧光得到恢复。[结论]当白木香受到真菌侵染与机械损伤胁迫时,激活防御反应的激素含量显著升高,抗氧化酶活性增加,同时次生代谢防御产物酚类与萜类增加,光合作用受到抑制;随着时间的延长,白木香生长获得恢复,胁迫得到缓解。说明白木香结香过程是防御反应加强,产生沉香物质,且是生长与防御的动态平衡过程。

[Objective]To investigate the process between growth and defense of Aquilaria sinensis,and reveal physiological mechanism of agarwood formation in response to fungi and mechanical damage stress.[Method]Two methods including injection of fungal agent and drilling with mechanical damage were used to induce agarwood formation with the three-year-old Aquilaria sinensis trees.Subsequently,hormone content,antioxidant enzyme activity,total phenols and terpenoids content,and photosynthesis and chlorophyll fluorescence characteristics were periodically analyzed during agarwood formation.[Result]At the initial stress stage,the contents of defense related hormones,jasmonic acid,salicylic acid and ethylene increased significantly,while the contents of growth related hormones,gibberellin,and auxin decreased.At the later stress stage,the contents of jasmonic acid,salicylic acid,and ethylene gradually decreased,while the contents of gibberellin and auxin gradually increased.The activities of antioxidant enzymes and the contents of phenols and terpenes were significantly higher in the stress groups than those of the control group.The contents of phenols and terpenoids increased with the increase of treatment duration,and the rate of increase decreased.Three months after treatments,the photosynthesis and chlorophyll fluorescence were inhibited,while inhibition was alleviated after six months.[Conclusion]In response to the stress of fungus and mechanical damage,defense related hormones increase significantly,as well as the activities of antioxidant enzymes.In addition,the secondary metabolic defense products such as phenols and terpenes increase and photosynthesis is inhibited.The strength of defense response decrease with the increase of treatment duration and trees recover the growth.Thus,agarwood formation is the process to that Aquilaria sinensis trees produce secondary metabolites by strengthening the defense response,which is a trade-off between growth and defense.