What is the rhizosphere in nutrient dynamics and role of Endomycorrhiza in plant growth and development?
Rhizosphere nutrient dynamics
The rhizosphere is the region of soil directly influenced by plant roots. It is a dynamic zone where plant roots, soil microorganisms, and nutrients interact closely. Plant roots release exudates, which are a variety of organic and inorganic compounds that can influence the rhizosphere environment. These exudates can attract beneficial microbes, such as mycorrhizae, and provide them with carbon and energy.
Mycorrhizae are symbiotic fungi that form associations with the roots of most plants. They extend their hyphae (fungal threads) into the soil, where they can access nutrients that are unavailable or less available to plant roots on their own. Mycorrhizal hyphae can also help to improve soil structure and suppress pathogens.
Other microbes in the rhizosphere can also play important roles in nutrient dynamics. For example, some bacteria can solubilize phosphorus from mineral forms that are unavailable to plants. Other bacteria can fix nitrogen from the atmosphere, making it available to plants.
The complex interactions between plant roots, microbes, and nutrients in the rhizosphere play a vital role in plant growth and development.
Role of Endomycorrhiza in plant growth and development
Endomycorrhizae are the most common type of mycorrhiza, and they form symbiotic relationships with the roots of over 80% of all plant species. Endomycorrhizae penetrate the root cells of the plant, where they form specialized structures called arbuscules. Arbuscules are the sites of nutrient exchange between the fungus and the plant.
Endomycorrhizae can provide plants with a variety of benefits, including:
- Increased access to nutrients, especially phosphorus and nitrogen
- Improved water uptake
- Increased tolerance to drought and salinity
- Suppression of pathogens
- Improved soil structure
Studies have shown that endomycorrhizal plants can grow larger and produce more biomass than non-mycorrhizal plants. Endomycorrhizae can also help plants to survive in stressful environments, such as those with low nutrient availability or high salinity.
Overall, endomycorrhizae play a significant role in plant growth and development. They help plants to access nutrients, improve water uptake, and tolerate stress.
Here are some specific examples of how endomycorrhizae can promote plant growth and development:
- In a study of maize plants, endomycorrhizal plants were found to have 50% more phosphorus and 20% more nitrogen than non-mycorrhizal plants.
- In a study of soybean plants, endomycorrhizal plants were found to produce 20% more biomass than non-mycorrhizal plants.
- In a study of tomato plants, endomycorrhizal plants were found to be more tolerant to drought and salinity than non-mycorrhizal plants.
Endomycorrhizae are a valuable tool for sustainable agriculture and can help to improve crop yields and reduce the need for fertilizer inputs.
Mycorrhiza association makes the plant drought resistance and improves the availability of phosphorus for plant uptake. The VAM in the rhizosphere is affected by soil abiotic factors such as pH, electrical conductivity (EC), moisture, organic matter, and temperature. Radical colonisation by endomycorrhizal fungi initiates with the exchange of carbon from the host plant to the fungus, and in turn, establishes by exploring the soil through mycelium the transport of nutrients to the root, such as phosphorus, water and other nutrients to the plant. Rhizosphere plays a vital role in the nutrient cycling process and also protects plants against different environmental stresses such as salinity, flooding, pathogens, temperature, contaminants, etc. The rhizosphere selects microorganisms from bulk soil to function as a seed bank, reducing microbial diversity. The rhizosphere is enriched in Bacteroidetes, Proteobacteria, and other copiotrophs. Rhizospheric bacteria participate in the geochemical cycling of nutrients especially nitrogen, phosphorus and micronutrients as iron, manganese, zinc and copper, and determine their availability for plants and soil microbial community. Endomycorrhizae facilitate the exchange of nutrients between the host plant and the soil. Mycorrhizae aid in the uptake of water, inorganic phosphorus, mineral or organic nitrogen, and amino acids. In exchange for the mycorrhizae providing all of these nutrients, the plant in turn provides the mycorrhizae with carbon.
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