Scheublin Tanja R, van der Heijden Marcel G A
Institute of Ecological Science, Vrije Universiteit, de Boelelaan 1085, NL-1081HV Amsterdam, the Netherlands.
New Phytol. 2006;172(4):732-8. doi: 10.1111/j.1469-8137.2006.01858.x.
Many legumes form tripartite symbiotic associations with rhizobia and arbuscular mycorrhizal fungi (AMF). Rhizobia are located in root nodules and provide the plant with fixed atmospheric nitrogen, while AMF colonize plant roots and deliver several essential nutrients to the plant. Recent studies showed that AMF are also associated with root nodules. This might point to interactions between AMF and rhizobia inside root nodules. Here, we test whether AMF colonize root nodules in various plant-AMF combinations. We also test whether nodules that are colonized by AMF fix nitrogen. Using microscopy, we observed that AMF colonized the root nodules of three different legume species. The AMF colonization of the nodules ranged from 5% to 74% and depended on plant species, AMF identity and nutrient availability. However, AMF-colonized nodules were not active, that is, they did not fix nitrogen. The results suggest that AMF colonize old senescent nodules after nitrogen fixation has stopped, although it is also possible that AMF colonization of nodules inhibits nitrogen fixation.
许多豆科植物与根瘤菌和丛枝菌根真菌（AMF）形成三方共生关系。根瘤菌位于根瘤中，为植物提供固定的大气氮，而AMF定殖于植物根系，为植物提供几种必需营养元素。最近的研究表明，AMF也与根瘤有关。这可能表明根瘤内AMF与根瘤菌之间存在相互作用。在此，我们测试了在各种植物-AMF组合中，AMF是否定殖于根瘤。我们还测试了被AMF定殖的根瘤是否固氮。通过显微镜观察，我们发现AMF定殖于三种不同豆科植物的根瘤。根瘤中AMF的定殖率在5%至74%之间，这取决于植物种类、AMF种类和养分有效性。然而，被AMF定殖的根瘤并不活跃，也就是说，它们不固氮。结果表明，AMF在固氮停止后定殖于衰老的根瘤，尽管也有可能是AMF对根瘤的定殖抑制了固氮作用。
