Bonkowski Michael
Rhizosphere Ecology Group, Institut für Zoologie, Technische Universität Darmstadt, Schnittspahnstr. 3, D-64287 Darmstadt, Germany.
New Phytol. 2004 Jun;162(3):617-631. doi: 10.1111/j.1469-8137.2004.01066.x.
All nutrients that plants absorb have to pass a region of intense interactions between roots, microorganisms and animals, termed the rhizosphere. Plants allocate a great portion of their photosynthetically fixed carbon to root-infecting symbionts, such asmycorrhizal fungi; another part is released as exudates fuelling mainly free-living rhizobacteria. Rhizobacteria are strongly top-down regulated by microfaunal grazers, particularly protozoa. Consequently, beneficial effects of protozoa on plant growth have been assigned to nutrients released from consumed bacterial biomass, that is, the 'microbial loop'. In recent years however, the recognition of bacterial communication networks, the common exchange of microbial signals with roots and the fact that these signals are used to enhance the efflux of carbon from roots have revolutionized our view of rhizosphere processes. Most importantly, effects of rhizobacteria on root architecture seem to be driven in large by protozoan grazers. Protozoan effects on plant root systems stand in sharp contrast to effects of mycorrhizal fungi. Because the regulation of root architecture is a key determinant of nutrient- and water-use efficiency in plants, protozoa provide a model system that may considerably advance our understanding of the mechanisms underlying plant growth and community composition.
植物吸收的所有养分都必须经过一个根、微生物和动物之间强烈相互作用的区域，即根际。植物将其光合作用固定碳的很大一部分分配给感染根部的共生体，如菌根真菌；另一部分则以渗出物的形式释放，主要为自由生活的根际细菌提供养分。根际细菌受到小型动物食草者，特别是原生动物的强烈自上而下的调控。因此，原生动物对植物生长的有益作用被归因于从被消耗的细菌生物量中释放的养分，即“微生物循环”。然而，近年来，对细菌通讯网络的认识、微生物信号与根的共同交换以及这些信号被用于增强碳从根中的流出这一事实，彻底改变了我们对根际过程的看法。最重要的是，根际细菌对根系结构的影响似乎在很大程度上是由原生动物食草者驱动的。原生动物对植物根系的影响与菌根真菌的影响形成鲜明对比。由于根系结构的调控是植物养分和水分利用效率的关键决定因素，原生动物提供了一个模型系统，可能会极大地推进我们对植物生长和群落组成潜在机制的理解。
