ABSTRACT
Plants support various forms of life on earth. Their ability to adapt to various environments defines their survival, and in turn, has an impact on crop productivity. This adaptation is largely manifested by the three-way interactions between the roots as well as the biotic abiotic components of the soil. The interactions are governed typically by plant root secretions that can lead to symbiotic or defense outcomes for the plant. Studies on such interactions focus primarily on those occurring in the aerial parts of the plants or the
phyllosphere
(microenvironment region surrounding the leaves). Several of these processes involving root-soil interactions (via plant secretions) are confined to a narrow region surrounding the root tissue. This region is termed the
rhizosphere
. In this microenvironment, there is a constant exchange of energy, nutrients, and molecular signals between the plant roots and microbes that affect their mutual interactions (Mathesius et al., 2003; Walker et al., 2003a; Pinton, Varanini, and Nannipieri, 2001), rendering the rhizosphere a highly dynamic, yet less understood, soil environment due to its poor accessibility (Figure 4.1).
