Multifaceted roles of root exudates in light of plant-microbe interaction

Root exudates are high- or low-molecular-weight secondary metabolites of plants secreted as a consequence of root pressure and/or plant-microbe interactions, which have a direct influence on rhizosphere ecology. They are utilized as nutrients by soil microbes. Root exudates are responsible for modifying soil physicochemical properties, manipulating microbial communities in the close vicinity of the rhizosphere, controlling pests, regulating the carbon cycle, and also for the bioremediation of soil contaminants. The chemical composition of root exudates is diverse. In addition, root exudates mediate nodulation, mycorrhizal association, plant growth-promoting rhizobacterial consortia, endophytic associations, antimicrobial activity, biofilm inhibition, quorum-sensing mimicking, and tri-trophic interactions involving nematodes. This chapter will provide useful information on the current advancements in the chemical diversity of root exudate components, the mechanism of exudation, the factors affecting root secretions, several positive and negative interactions in the context of plant-soil-microorganisms, and the role of root exudates in shaping microbial community structure.