Root exudates mediated interactions belowground

The root exudate composition reflects the contradictory-concomitantly attractive and repulsive-behaviour of plants towards soil microorganisms. Plants produce antimicrobial, insecticide and nematicide compounds to repel pathogens and invaders. They also produce border cells that detach from roots and play an important role as biological and physical barrier against aggressors. Plants produce also metabolites used as carbon source resulting in the attraction of phytobeneficial soil microorganisms that help plants in controlling diseases directly via the production of antimicrobial compounds or indirectly via the induction of plant systemic resistance. The root exudates may have a direct impact on carbon and nitrogen cycling, as they exhibit a rhizosphere priming effect towards soil organic matter degraders, and may inhibit nitrification process by soil nitrifying microorganisms. They also contain signalling molecules required for the establishment of 'plant-microorganisms' interactions. The composition of root exudates is therefore broad ranging, consisting of feeding, antimicrobial and signalling molecules. We thus focused this review on current research concerning the role of the root exudate composition in 'plant-microorganisms' interactions and functioning of the rhizosphere.