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Nitrogen fixation is a chemical process by which molecular nitrogen (N
2), which has a strong triple covalent bond, is converted into ammonia (NH
3) or related nitrogenous compounds, typically in soil or aquatic systems but also in industry. The nitrogen in air is molecular dinitrogen, a relatively nonreactive molecule that is metabolically useless to all but a few microorganisms. Biological nitrogen fixation or diazotrophy is an important microbe-mediated process that converts dinitrogen (N2) gas to ammonia (NH3) using the nitrogenase protein complex (Nif).
Companion planting in gardening and agriculture is the planting of different crops in proximity for any of a number of different reasons, including weed suppression, pest control, pollination, providing habitat for beneficial insects, maximizing use of space, and to otherwise increase crop productivity. Companion planting is a form of polyculture.
Klebsiella is a genus of Gram-negative, oxidase-negative, rod-shaped bacteria with a prominent polysaccharide-based capsule.
Nitrogen assimilation is the formation of organic nitrogen compounds like amino acids from inorganic nitrogen compounds present in the environment. Organisms like plants, fungi and certain bacteria that can fix nitrogen gas (N2) depend on the ability to assimilate nitrate or ammonia for their needs. Other organisms, like animals, depend entirely on organic nitrogen from their food.
Ensifer meliloti are an aerobic, Gram-negative, and diazotrophic species of bacteria. S. meliloti are motile and possess a cluster of peritrichous flagella. S. meliloti fix atmospheric nitrogen into ammonia for their legume hosts, such as alfalfa. S. meliloti forms a symbiotic relationship with legumes from the genera Medicago, Melilotus and Trigonella, including the model legume Medicago truncatula. This symbiosis promotes the development of a plant organ, termed a root nodule. Because soil often contains a limited amount of nitrogen for plant use, the symbiotic relationship between S. meliloti and their legume hosts has agricultural applications. These techniques reduce the need for inorganic nitrogenous fertilizers.
Agroforestry is a land use management system in which combinations of trees or shrubs are grown around or among crops or pastureland. Agroforestry combines agricultural and forestry technologies to create more diverse, productive, profitable, healthy, and sustainable land-use systems. There are many benefits to agroforestry such as increasing farm profitability. In addition, agroforestry helps to preserve and protect natural resources such as controlling soil erosions, creating habitat for the wildlife, and managing animal waste. Benefits also include increased biodiversity, improved soil structure and health, reduced erosion, and carbon sequestration.
The rhizosphere is the narrow region of soil or substrate that is directly influenced by root secretions and associated soil microorganisms known as the root microbiome. Soil pores in the rhizosphere can contain many bacteria and other microorganisms that feed on sloughed-off plant cells, termed rhizodeposition, and the proteins and sugars released by roots, termed root exudates. This symbiosis leads to more complex interactions, influencing plant growth and competition for resources. Much of the nutrient cycling and disease suppression by antibiotics required by plants, occurs immediately adjacent to roots due to root exudates and metabolic products of symbiotic and pathogenic communities of microorganisms. The rhizosphere also provides space to produce allelochemicals to control neighbours and relatives.
Rhizobacteria are root-associated bacteria that can have a detrimental, neutral or beneficial effect on plant growth. The name comes from the Greek rhiza, meaning root. The term usually refers to bacteria that form symbiotic relationships with many plants (mutualism). Rhizobacteria are often referred to as plant growth-promoting rhizobacteria, or PGPRs. The term PGPRs was first used by Joseph W. Kloepper in the late 1970s and has become commonly used in scientific literature.
Microbial inoculants also known as soil inoculants or bioinoculants are agricultural amendments that use beneficial rhizosphericic or endophytic microbes to promote plant health. Many of the microbes involved form symbiotic relationships with the target crops where both parties benefit (mutualism). While microbial inoculants are applied to improve plant nutrition, they can also be used to promote plant growth by stimulating plant hormone production. Although bacterial and fungal inoculants are common, inoculation with archaea to promote plant growth is being increasingly studied.
A biofertilizer is a substance which contains living micro-organisms which, when applied to seeds, plant surfaces, or soil, colonize the rhizosphere or the interior of the plant and promotes growth by increasing the supply or availability of primary nutrients to the host plant. Biofertilizers add nutrients through the natural processes of nitrogen fixation, solubilizing phosphorus, and stimulating plant growth through the synthesis of growth-promoting substances. The micro-organisms in biofertilizers restore the soil's natural nutrient cycle and build soil organic matter. Through the use of biofertilizers, healthy plants can be grown, while enhancing the sustainability and the health of the soil. Biofertilizers can be expected to reduce the use of synthetic fertilizers and pesticides, but they are not yet able to replace their use. Since they play several roles, a preferred scientific term for such beneficial bacteria is "plant-growth promoting rhizobacteria" (PGPR).
Agricultural microbiology is a branch of microbiology dealing with plant-associated microbes and plant and animal diseases. It also deals with the microbiology of soil fertility, such as microbial degradation of organic matter and soil nutrient transformations.
Azospirillum brasilense is a very well studied, nitrogen-fixing (diazotroph), genetically tractable, Gram-negative, alpha-proteobacterium bacterium, first described in Brazil by the group of Johanna Döbereiner and then receiving the name "brasilense". A. brasilense is able to fix nitrogen in the presence of low oxygen levels, making it a microaerobic diazotroph. An isolate from the genus Azospirillum was isolated from nitrogen poor soils in the Netherlands in 1925, however the species A. brasilense was first described in 1978 in Brazil, since this genus is widely found in the rhizospheres of grasses around the world where it confers plant growth promotion. Whether growth promotion occurs through direct nitrogen flux from the bacteria to the plant or through hormone regulation is debated. The two most commonly studied strains are Sp7 and Sp245, both are Brazilian isolates isolated from Tropical grasses from Seropedica, Brazil.
Azospirillum halopraeferens is a species of nitrogen-fixing bacteria associated with the roots of Diplachne fusca and black mangrove. It is microaerophilic and its type strain is Au 4.
Azospirillum doebereinerae is a species of nitrogen-fixing bacteria associated with the roots of Miscanthus species. Its type strain is GSF71T.
The root microbiome is the dynamic community of microorganisms associated with plant roots. Because they are rich in a variety of carbon compounds, plant roots provide unique environments for a diverse assemblage of soil microorganisms, including bacteria, fungi, and archaea. The microbial communities inside the root and in the rhizosphere are distinct from each other, and from the microbial communities of bulk soil, although there is some overlap in species composition.
Azospirillum oryzae is a species of nitrogen-fixing bacteria associated with the roots of Oryza sativa. Its type strain is COC8T.
Azospirillum is a Gram-negative, microaerophilic, non-fermentative and nitrogen-fixing bacterial genus from the family of Rhodospirillaceae. Azospirillum bacteria can promote plant growth.
Paraburkholderia is a genus of Pseudomonadota that are gram negative, slightly curved rods that are motile by means of flagella. They have been reported to colonize endophytic tissues of hybrid spruce and lodgepole pine with a strong potential to perform biological nitrogen fixation and plant growth promotion. Unlike Burkholderia species, Paraburkholderia members are not commonly associated with human infection. Paraburkholderia members form a monophyletic clade within the Burkholderiaceae family, which is what prompted their distinction as a genus independent from Burkholderia species, in combination with the finding of robust conserved signature indels which are unique to Paraburkholderia species, and are lacking in members of the genus Burkholderia. These CSIs distinguish the genus from all other bacteria. Additionally, the CSIs that were found to be shared by Burkholderia species are absent in Paraburkholderia, providing evidence of separate lineages.
Gluconacetobacter diazotrophicus is a bacterium with a rod-like shape, has rounded ends and belongs to Gram-negative bacteria. The bacterium is known for stimulating plant growth and being tolerant to acetic acid. With one to three lateral flagella, and known to be found on sugarcane, Gluconacetobacter diazotrophicus was discovered in Brazil by Vladimir A. Cavalcante and Johanna Dobereiner.
The flora of Nepal is one of the richest in the world due to the diverse climate, topology and geography of the country. Research undertaken in the late 1970s and early 1980s documented 5067 species of which 5041 were angiosperms and the remaining 26 species were gymnosperms. The Terai area has hardwood, bamboo, palm, and sal trees. Notable plants include the garden angelica, Luculia gratissima, Meconopsis villosa, and Persicaria affinis. However, according to ICOMOS checklist, in the protected sites, there are 2,532 species of vascular plants under 1,034 genera and 199 families. The variation in figures is attributed to inadequate floral coverage filed studies. Some of the plants contain medicinal values. It contains certain chemical which is used to heal wound by There are 400 species of vascular plants which are endemic to Nepal. Of these, two in particular are orchids Pleione coronaria and Oreorchis porphyranthes. The most popular endemic plant of Nepal is rhododendron (arboreum) which in Nepali language is called lali guras.
References
- 1 2 Tarrand JJ, Krieg NR, Dobereiner J (1978). "A taxonomic study of the Spirillum lipoferum group, with descriptions of a new genus, Azospirillum gen. nov. and two species, Azospirillum lipoferum (Beijerinck) comb. nov. and Azospirillum brasilense sp. nov". Can J Microbiol. 24 (8): 967–980. doi:10.1139/m78-160. hdl: 10919/54873 . PMID 356945.
- ↑ Euzéby JP, Parte AC. "Azospirillum lipoferum". List of Prokaryotic names with Standing in Nomenclature (LPSN). Retrieved June 7, 2021.
- ↑ Steenhoudt, O.; Vanderleyden, J. (October 2000). "Azospirillum, a free-living nitrogen-fixing bacterium closely associated with grasses: genetic, biochemical and ecological aspects". FEMS Microbiology Reviews. 24 (4): 487–506. doi: 10.1111/j.1574-6976.2000.tb00552.x . ISSN 0168-6445. PMID 10978548.
- ↑ Rozier, Camille; Gerin, Florence; Czarnes, Sonia; Legendre, Laurent (2019-06-01). "Biopriming of maize germination by the plant growth-promoting rhizobacterium Azospirillum lipoferum CRT1". Journal of Plant Physiology. 237: 111–119. doi: 10.1016/j.jplph.2019.04.011 . ISSN 0176-1617. PMID 31071544. S2CID 149443862.
- ↑ Mehmood, Tahir; Li, Guihua; Anjum, Tehmina; Akram, Waheed (2021-01-01). "Azospirillum lipoferum strain AL-3 reduces early blight disease of potato and enhance yield". Crop Protection. 139: 105349. doi: 10.1016/j.cropro.2020.105349 . ISSN 0261-2194. S2CID 224998617.
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