Turlings T C, Loughrin J H, McCall P J, Röse U S, Lewis W J, Tumlinson J H
Insect Attractants, Behavior, and Basic Biology Research Laboratory, U.S. Department of Agriculture, Gainesville, FL 32604, USA.
Proc Natl Acad Sci U S A. 1995 May 9;92(10):4169-74. doi: 10.1073/pnas.92.10.4169.
Parasitic and predatory arthropods often prevent plants from being severely damaged by killing herbivores as they feed on the plants. Recent studies show that a variety of plants, when injured by herbivores, emit chemical signals that guide natural enemies to the herbivores. It is unlikely that herbivore-damaged plants initiate the production of chemicals solely to attract parasitoids and predators. The signaling role probably evolved secondarily from plant responses that produce toxins and deterrents against herbivores and antibiotics against pathogens. To effectively function as signals for natural enemies, the emitted volatiles should be clearly distinguishable from background odors, specific for prey or host species that feed on the plant, and emitted at times when the natural enemies forage. Our studies on the phenomena of herbivore-induced emissions of volatiles in corn and cotton plants and studies conducted by others indicate that (i) the clarity of the volatile signals is high, as they are unique for herbivore damage, produced in relatively large amounts, and easily distinguishable from background odors; (ii) specificity is limited when different herbivores feed on the same plant species but high as far as odors emitted by different plant species and genotypes are concerned; (iii) the signals are timed so that they are mainly released during the daytime, when natural enemies tend to forage, and they wane slowly after herbivory stops.
寄生性和捕食性节肢动物在取食植食性动物时，常常通过杀死它们来防止植物受到严重损害。最近的研究表明，多种植物在受到植食性动物侵害时，会发出化学信号，引导天敌找到这些植食性动物。食草动物受损的植物不太可能仅仅为了吸引寄生蜂和捕食者而启动化学物质的产生。这种信号作用可能是从植物产生针对食草动物的毒素和威慑物以及针对病原体的抗生素的反应中次生演化而来的。为了有效地作为天敌的信号发挥作用，所释放的挥发物应该与背景气味有明显区别，对以该植物为食的猎物或寄主物种具有特异性，并且在天敌觅食时释放。我们对玉米和棉花植株中食草动物诱导挥发物现象的研究以及其他人进行的研究表明：（i）挥发物信号的清晰度很高，因为它们对于食草动物的损害具有独特性，产生量相对较大，并且很容易与背景气味区分开来；（ii）当不同的食草动物取食同一植物物种时，特异性有限，但就不同植物物种和基因型所释放的气味而言，特异性较高；（iii）信号的释放时间经过调整，以便它们主要在白天释放，此时天敌往往会觅食，并且在食草行为停止后会缓慢减弱。
