What is the importance of rhizosphere to root system and positive interaction in the rhizosphere and use of plant growth promoting rhizobacteria?
Well, this is a bit like asking what is the importance of the gut microflora to human health, a veeeeeery broad topic, if not larger. :) Just to summarize in a few words, beneficial rhizobacteria can fix nitrogen, solubilize elements such as phosphorus or potassium, regulate and stimulate plant growth through phytohormones, produce useful compounds such as siderophores, control pathogenic bacteria, etc. This topic also overlaps with the concept of holobiont, as plants and associated microbiome (that of the rhizosphere but not only) can form a complex interwoven relationship with microorganisms being an integral part not only for plant health but for its continuity as well.
We can find a lot of literature about this argument that many people will surely enjoy, like these:
1) Article The rhizosphere microbiome: functions, dynamics, and role in...
2) Chapter Plant Growth-Promoting Bacterial Consortia Render Biological...
3) Chapter Endophytic Bacteria
4) Article Plant growth-promoting rhizobacteria: a potential bio-asset ...
5) Article An Insight into Plant Growth-Promoting Rhizobacteria-Mediate...
6) Article Cell-Free Supernatants of Plant Growth-Promoting Bacteria: A...
7) Article Engineering rhizobacteria for sustainable agriculture
8) Article Understanding the holobiont: the interdependence of plants a...
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. Plant growth promoting rhizobacteria after being inoculated on seeds, could successfully colonize plant roots and positively enhance plant growth. To date, there have been over two dozen genera of nonpathogenic rhizobacteria identified. First, they provide the anchor needed to keep a plant in place. More importantly, roots are the lifeline of a plant, taking up air, water, and nutrients from the soil and moving them up into the leaves, where they can interact with sunlight to produce sugars, flavors, and energy for the plant. Beneficial rhizobacteria have been utilized to improve water and nutrient uptake, abiotic and biotic stress tolerance. Even though numerous soil bacteria have been reported to promote plant growth and development, the mode(s) of action by which the bacteria exhibit beneficial activities are often not well understood.PGPR has the ability to increase the availability of nutrient concentration in the rhizosphere by fixing nutrients, thus preventing them from leaching out. As, nitrogen, which is needed for the synthesis of amino acids and proteins, is the most limiting nutrient for plants. The rhizosphere is an ecological niche, in which beneficial bacteria compete with other microbiota for organic carbon compounds and interact with plants through root colonization activity to the soil. Some of these root-colonizing beneficial rhizobacteria also colonize endophytically and multiply inside plant roots. Plant growth promoting rhizobacteria are the soil bacteria inhabiting around/on the root surface and are directly or indirectly involved in promoting plant growth and development via production and secretion of various regulatory chemicals in the vicinity of rhizosphere.
This is a topic of great interest to contribute to improving production systems, especially in soils whose characteristics inhibit the biodisposition of nutrients such as phosphorus and nitrogen. Our contributions indicate significant yield increases compared to chemically synthesized fertilizers in conservation tillage systems. There is a direct relationship between rhizobacteria and the improvement of the morphological characteristics of leguminous plants, but there is also an open space to investigate how strains of foreign commercial products respond to native rhizobacteria.
In the rhizosphere, plant roots secrete a number of exudates that act as attractants for microbes, which eventually improve the physicochemical properties of the surrounding soil. On the other hand, these exudates maintain the function and structure of microbial communities near plant roots. 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. Beneficial rhizosphere bacteria can benefit the plant directly or indirectly by 1) assisting plants to acquire nutrients from the soil, 2) suppression of plant pathogens, and 3) enhancing plant immunity through induced systemic resistance (ISR), which involves activation of plant resistance against a broad spectrum. The rhizosphere has a key role in mitigating root–root interactions. Both the rhizobiome and root exudation affect root–root interactions either directly or via modification of resource availability to the plants. Plant–microbe interactions have been utilized to improve plant growth for the production of food, fibre, biofuels and key metabolites. The mutualistic interaction can be beneficial in directly providing nutrients to the plant (biofertilizer) or increasing the availability of compounds such as iron or phosphate. Plant growth promoting rhizobacteria are the soil bacteria inhabiting around/on the root surface and are directly or indirectly involved in promoting plant growth and development via production and secretion of various regulatory chemicals in the vicinity of rhizosphere. Rhizosphere microorganisms increase P uptake by solubilising or mineralising more P than they require and by stimulating root growth. They can also indirectly enhance plant P uptake by releasing plant growth regulators that stimulate root or root hair growth or mycorrhizal colonization. Rhizobium is a nonspore-forming rod-shaped, motile, aerobic, gram-negative soil bacterium able to colonize in the rhizospheric region of leguminous plants and symbiotically fixes atmospheric nitrogen. 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.
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