原文：Susanne Wurst, Sander van Beersum, Roel Wagenaar, Tanja Bakx-Schotman, Barbara Drigo, Ingar Janzik, Arnaud Lanoue, Wim H. van der Putten. Plant defence against nematodes is not mediated by changes in the soil microbial community. Functional Ecology, 2009, 23 (3):  488-495.

1.  Indirect plant defence, the recruitment of antagonists of herbivores, is well-known above the ground. In spite of various soil microorganisms acting as antagonists to root herbivores, it is still largely unknown whether plants can promote antagonistic microorganisms as an indirect defence mechanism.

2.  In a greenhouse study we examined whether soil microorganisms could mediate plant defence against plant-feeding nematodes. Growth, nutrient contents and root exudation of three plant species (Plantago lanceolata, Holcus lanatus, Lotus corniculatus) and the performance of nematodes and fungal communities in the rhizospheres were measured.

3.  The plant species differed in their effects on plant-feeding nematodes; however, the addition of soil microorganisms did not enhance nematode control. Nematode addition changed root exudation patterns and rhizosphere fungal community structure in a plant species-specific manner. Glucose levels in the root exudates of all three examined plant species were enhanced, and P. lanceolata root exudates contained higher levels of fumaric acid when nematodes had been added.

4.  We conclude that nematodes have plant species-specific effects on root exudate chemistry and rhizosphere fungal community composition, but these effects do not necessarily enhance indirect control of nematodes by antagonistic microorganisms. More studies on below-ground plant defence are definitely needed.

注：传统上地下生态学过程往往被处理为一个黑箱，随着研究方法的发展以及地下生态过程的揭示，不得不让我们重新反思或重新认识各种生态过程，特别是营养级相互关系，top-down和bottom-up效应。特定种类的食根线虫会改变植物根际分泌物的组分，进一步影响根际微生物群落组成和结构；而微生物群落的改变，是否也改变了作为植食者天敌的间接效应，这些都还有待于进一步的研究。

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