Nitrogen fixation
Some plants (e.g. beans, clover) have evolved to have a symbiotic relationship with bacteria trapped in root nodules in the plant root. They trap nitrogen from air and convert it to a compound. The plant can then use this as a nutrient for growth protein. The bacteria benefit from gaining food from the plant.
Plants in nature always grow amidst soil microorganisms, and some become intimately associated with plants to form mutualistic symbioses. Examples of such symbiotic micro–organisms include mycorrhizal fungi of various types and N2–fixing prokaryotes, especially Rhizobia.
All of these symbioses may affect rates of growth and eventually reproduction of plants compared with growth in the absence of such associations. A symbiotic association is therefore a potential selection pressure that can influence the evolutionary success of vascular plants and hence the composition of plant communities.
Nitrogen fixation: Nitrogen is a critical limiting element for plant growth and production. It is a major component of chlorophyll, the most important pigment needed for photosynthesis, as well as amino acids, the key building blocks of proteins. It is also found in other important biomolecules, such as ATP and nucleic acids. Even though it is one of the most abundant elements (predominately in the form of nitrogen gas (N2) in the Earth's atmosphere), plants can only utilize reduced forms of this element.
It is interesting to note that such binding occurs between compatible (bacteria – host) partners.
Nitrogen is a critical limiting element for plant growth and production. It is a major component of chlorophyll, the most important pigment needed for photosynthesis, as well as amino acids, the key building blocks of proteins. It is also found in other important biomolecules, such as ATP and nucleic acids. Even though it is one of the most abundant elements (predominately in the form of nitrogen gas (N2) in the Earth's atmosphere), plants can only utilize reduced forms of this element.
Biological nitrogen fixation (BNF), discovered by Beijerinck in 1901 (Beijerinck 1901), is carried out by a specialized group of prokaryotes. These organisms utilize the enzyme nitrogenase to catalyze the conversion of atmospheric nitrogen (N2) to ammonia (NH3). Plants can readily assimilate NH3 to produce the aforementioned nitrogenous biomolecules (proteins, nucleic acids). These prokaryotes include aquatic organisms, such as cyanobacteria, free–living soil bacteria, such as Azotobacter, bacteria that form associative relationships with plants, such as Azospirillum, and most importantly, bacteria, such as Rhizobium and Bradyrhizobium, that form symbioses with legumes and other plants.