摘  要  【目的】 植物的诱导防御反应在植物应对植食性昆虫取食时发挥重要作用。在自然界中，植物会频繁遭受植食性昆虫的取食，然而，植物遭受昆虫多次取食时是否会产生警备防御，进而诱导更强烈的防御反应尚未阐明。本研究旨在深入探究植物对昆虫的警备防御。【方法】 以烟草-斜纹夜蛾为体系，通过生测实验研究烟草植物警备防御对昆虫生长发育的影响；通过检测单次取食和多次取食的烟草植株茉莉酸、水杨酸和脱落酸，在激素水平分析烟草警备防御的调控途径；通过检测单次取食和多次取食的烟草叶片次生代谢物质，在代谢水平分析烟草警备防御的作用方式。【结果】 斜纹夜蛾Spodoptera litura诱导导致烟草植株对斜纹夜蛾的防御能力增强。与取食对照烟草植株相比，遭受斜纹夜蛾多次取食和单次取食的烟草植株使斜纹夜蛾的体重分别下降了30.3%和14.6%，二次诱导后的烟草植株比一次诱导后的烟草植株对斜纹夜蛾的防御作用更强。与对照相比，二次诱导导致烟草植株体内茉莉酸含量的显著升高，二次诱导后烟草植株茉莉酸的含量比一次诱导的烟草植株增加78.9%。斜纹夜蛾取食对烟草植株水杨酸和脱落酸的含量无显著影响。斜纹夜蛾取食诱导导致烟草植株中尼古丁、绿原酸和胰蛋白酶抑制剂的含量均显著升高，且二次诱导的增加量显著高于一次诱导的增加量。【结论】 烟草对植食性昆虫斜纹夜蛾存在警备防御，植物的警备防御使植物对植食性昆虫的诱导防御反应更强。

Abstract  [Objectives]  Herbivore induced plant defenses play a key role in protecting plants against herbivore damage. Plants suffer herbivore damage frequently in nature, however, it is unclear if damaged plant have primed defensive mechanisms that allow them to mount a stronger defense against repeated herbivore attacks. [Methods]  Experiments were conducted on tobacco plants Nicotiana tabacum to see if there was a difference in the plant defenses induced by single, or repeated, episodes of attack by Spodoptera litura larvae. Concentrations of jasmonic acid (JA), salicylic acid (SA) and abscisic acid (ABA) were measured to monitor hormone levels. Secondary metabolites were also measured to reveal the key metabolites involved in defense against herbivores. [Results]  Caterpillar damage induced a defensive response from tobacco plants and repeated damage induced a stronger defensive response than a single episode of damage. Compared to healthy plants, plants subject to repeated herbivore damage had significantly higher concentrations of JA (78.9%), but similar levels of SA and ABA. Herbivore damage significantly increased the concentration of nicotine, chlorogenic acid and trypsin inhibitors; plants subject to repeated herbivore attacks had higher concentrations of all three metabolites than those subject to an isolated attack. [Conclusion]  Tobacco plants have evolved primed defense against herbivores which allows them to mount a stronger defensive response to repeated herbivore attacks.