How does the rhizosphere differ from other soil layers and importance of the rhizosphere to the root system of a plant?
Rhizosphere soil is biologically more active soil than the bulk soil. It contain higher and diverse microbial population. Mostly plant growth promoting bacteria reside in rhizosphere.
The rhizosphere is a very dynamic environment where plants, soil, microorganisms, nutrients and water meet and interact. The rhizosphere differs from the bulk soil because of the activities of plant roots and their effect on soil organisms. However, it is now appreciated that the rhizosphere is different to the bulk soil due to a range of biological, biochemical, chemical and physical processes that occur as a consequence of root growth, water and nutrient uptake, respiration and rhizodeposition. It was suggested that the remediation role of rhizosphere was the main part of phytoremediation, and one of the main basic theories to remedy contaminated soils by the activity of green plants and other organisms. The rhizosphere is a nutrient-rich region of the soil immediately surrounding the plant root. This region is highly dynamic and supports a dense and diverse fauna. The rhizosphere, the volume of soil directly affected by root activity, comprises an important hot spot for a multitude of biotic and abiotic processes in soils. While enabling plant growth by the uptake of water and nutrients, roots also shape a unique physical and biogeochemical environment for microbiota. Rhizosphere organisms that have been well studied for their beneficial effects on plant growth and health are the nitrogen-fixing bacteria, mycorrhizal fungi, plant growth-promoting rhizobacteria (PGPR), biocontrol microorganisms, mycoparasitic fungi, and protozoa. The rhizosphere is the zone of soil surrounding a plant root where the biology and chemistry of the soil are influenced by the root. As plant roots grow through soil they mostly release water soluble compounds such as amino acids, sugars and organic acids that supply food for the microorganisms. These rhizobacteria also indirectly improve plant growth by inducing plant resistance to various biotic and abiotic stresses, such as pathogen attack and heavy metal contamination, using such mechanisms as the production of antibiotics, induction of induced systemic resistance and rhizosphere competence. The rhizosphere as the area around a plant root that is inhabited by a unique population of microorganisms influenced, he postulated, by the chemicals released from plant roots.
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