Summary
The roots of higher plants comprise a metabolically active and largely unexplored biological frontier. Some of their prime features include the ability to synthesize a remarkably diverse group of secondary metabolites, and to adjust their metabolic activities in response to different abiotic and biotic stresses. This adjustment includes the ability to exude a wide array of micro- and macromolecules into the rhizosphere and to phytoremediate toxic metals, with the potential to affect and alter the relationships between plants and both beneficial and deleterious soil-borne pathogens. In the past, research on root biology has been hampered by the underground nature of roots and the lack of suitable experimental systems to study root-root and root-microbe communications. However, recent progress in growing roots in isolation with other elements of the rhizosphere has greatly facilitated the study of root-specific metabolism and contributed to our understanding of this organ.