ABSTRACT
The rhizosphere is conceptualized as a small volume of soil clinging to root segments. As plant roots grow through soil, they release various compounds such as amino acids, sugars, and organic acids which supply food for the microorganisms. The exudates act as messengers stimulating biological and physical interactions between roots and soil organisms. Both biotic and abiotic processes influence the exudation of organic compounds from roots. Root border cells act as chemical and physical barriers towards pathogens by secreting antipathogenic metabolites. Functions of root exudates are diverse and play important roles in biological processes. Components in root exudates assist plants in accessing nutrients by acidifying or changing the redox conditions within the rhizosphere, or directly chelating with the nutrient. Roots are exposed to a range of biotic and abiotic stresses at the root–soil interface, they respond to these stresses by secreting a different blend of chemicals to protect against negative influences and encourage positive interactions. Root exudates regulate plant and microbial communities in the rhizosphere. Understanding the biology of root exudation processes may contribute to devising novel strategies for improving plant fitness, and the isolation of novel value-added compounds found in the root exudates.
