exudates and can be coined as a fertile zone of the soil. Due to this immense fertility
of the soil, microbes are attracted and helpful for the growth and reproduction.
Among the microbial population, bacterial population is found to be huge and
have the symbiotic or nonsymbiotic relationships, and this microbial community
differs based on the texture of soil (Raynaud et al. 2007; Bulgarelli et al. 2013).
Since root exudate composition changes along the root system, according to
stages of plant development and plant genotypes, the rhizomicrobiome composition
differs accordingly (Bouffaud et al. 2012). In the rhizospheric region, the growth of
plants and microorganisms is mutually influenced by the secreted molecules.
The rhizodeposits referred as exudates of plant roots which include amino acids,
fatty acids, organic acids, plant growth regulators, carbohydrates, putrescine, nucleotides, sterols, phenolics, polypeptides, polysaccharides, water soluble sugars, sugar
phosphate esters and vitamins (Uren 2000). Some of the root exudates act as
repellents to microbes and other insects; hence, the nature of exudates depends on
the plant species from which it exuded (Kamilova et al. 2008). Several distinct
groups of microorganisms are found in the rhizosphere, and these were inducing the
growth of plants through the liberation of the above-said chemicals into the rhizosphere (Kundan et al. 2015). Plant growth–promoting rhizobacteria termed as PGPR
also dwell in the rhizospheric environment and promote the activity of plants
through continuous supply of nutrients to crops (Davison 1988), release of phytohormones to manage or reduce the activity of plant pathogens, to improve soil
texture, bioaccumulation, etc. (Ehrlich 1990). As rhizosphere is an exceptionally
nutrient dense region compared to nonrhizosphere, it not only is flourished with root
exudates but also have dead tissues of plants, animals, proteinaceous mucilage
secretions, carbonaceous compounds that obtained from plant roots, etc.
1.2 Niche for Rejuvenation of Soil Microorganisms
As the rhizosphere is the bowl full of essential and important storehouse of organic
nutrients, microbes are invigorated and growing under continuous supply of nutrients. They multiply in an exponential rate and releasing primary and secondary
metabolite that are an added advantage for the plant growth. In addition to the
secreted organic compounds, the organic and inorganic amendments added to the
soil for crop growth also influences the growth of microbes in the rhizosphere region.
Quite interestingly, microbes that lives in the nonrhizosphere region when it faces
deprival of nutrients can sense the availability of nutrients in the rhizosphere and
move towards the rhizospheric region through quorum sensing. These signalling
processes help the Rhizobia to move towards the root tip of leguminous plants (via
detection of the flavonoid signal produced by the plant system), to initiate the
nodulation process in the soil that has low nitrogen concentration.
1 Rhizosphere: Niche for Microbial Rejuvenation and Biodegradation of Pollutants
3
of the soil, microbes are attracted and helpful for the growth and reproduction.
Among the microbial population, bacterial population is found to be huge and
have the symbiotic or nonsymbiotic relationships, and this microbial community
differs based on the texture of soil (Raynaud et al. 2007; Bulgarelli et al. 2013).
Since root exudate composition changes along the root system, according to
stages of plant development and plant genotypes, the rhizomicrobiome composition
differs accordingly (Bouffaud et al. 2012). In the rhizospheric region, the growth of
plants and microorganisms is mutually influenced by the secreted molecules.
The rhizodeposits referred as exudates of plant roots which include amino acids,
fatty acids, organic acids, plant growth regulators, carbohydrates, putrescine, nucleotides, sterols, phenolics, polypeptides, polysaccharides, water soluble sugars, sugar
phosphate esters and vitamins (Uren 2000). Some of the root exudates act as
repellents to microbes and other insects; hence, the nature of exudates depends on
the plant species from which it exuded (Kamilova et al. 2008). Several distinct
groups of microorganisms are found in the rhizosphere, and these were inducing the
growth of plants through the liberation of the above-said chemicals into the rhizosphere (Kundan et al. 2015). Plant growth–promoting rhizobacteria termed as PGPR
also dwell in the rhizospheric environment and promote the activity of plants
through continuous supply of nutrients to crops (Davison 1988), release of phytohormones to manage or reduce the activity of plant pathogens, to improve soil
texture, bioaccumulation, etc. (Ehrlich 1990). As rhizosphere is an exceptionally
nutrient dense region compared to nonrhizosphere, it not only is flourished with root
exudates but also have dead tissues of plants, animals, proteinaceous mucilage
secretions, carbonaceous compounds that obtained from plant roots, etc.
1.2 Niche for Rejuvenation of Soil Microorganisms
As the rhizosphere is the bowl full of essential and important storehouse of organic
nutrients, microbes are invigorated and growing under continuous supply of nutrients. They multiply in an exponential rate and releasing primary and secondary
metabolite that are an added advantage for the plant growth. In addition to the
secreted organic compounds, the organic and inorganic amendments added to the
soil for crop growth also influences the growth of microbes in the rhizosphere region.
Quite interestingly, microbes that lives in the nonrhizosphere region when it faces
deprival of nutrients can sense the availability of nutrients in the rhizosphere and
move towards the rhizospheric region through quorum sensing. These signalling
processes help the Rhizobia to move towards the root tip of leguminous plants (via
detection of the flavonoid signal produced by the plant system), to initiate the
nodulation process in the soil that has low nitrogen concentration.
1 Rhizosphere: Niche for Microbial Rejuvenation and Biodegradation of Pollutants
3