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The host plant provides the bacteria with amino acids so they do not need to assimilate ammonia. [5] The amino acids are then shuttled back to the plant with newly fixed nitrogen. Nitrogenase is an enzyme involved in nitrogen fixation and requires anaerobic conditions. Membranes within root nodules are able to provide these conditions.
To express genes for nitrogen fixation, rhizobia require a plant host; they cannot independently fix nitrogen. [1] In general, they are gram negative , motile , non- sporulating rods. Rhizobia are a "group of soil bacteria that infect the roots of legumes to form root nodules ". [ 2 ]
Rhizobium is a genus of Gram-negative soil bacteria that fix nitrogen. Rhizobium species form an endosymbiotic nitrogen-fixing association with roots of (primarily) legumes and other flowering plants. The bacteria colonize plant cells to form root nodules, where they convert atmospheric nitrogen into ammonia using the enzyme nitrogenase.
Diazotroph fertilizer is a kind of biofertilizer that can use nitrogen-fixing microorganisms to convert molecular nitrogen (N 2) into ammonia (which is the formation of nitrogen available for the crops to use). These nitrogen nutrients then can be used in the process of protein synthesis for the plants.
Some nitrogen-fixing bacteria have symbiotic relationships with plants, especially legumes, mosses and aquatic ferns such as Azolla. [4] Looser non-symbiotic relationships between diazotrophs and plants are often referred to as associative, as seen in nitrogen fixation on rice roots. Nitrogen fixation occurs between some termites and fungi. [5]
Plants that contribute to N2 fixation include the legume family – Fabaceae – with taxa such as kudzu, clovers, soybeans, alfalfa, lupines, peanuts, and rooibos.They contain symbiotic bacteria called rhizobia within the nodules, producing nitrogen compounds that help the plant to grow and compete with other plants.
Nod factor cause the fragmentation and rearrangement of actin network, which coupled with the reinstitution of cell growth lead to the curling of the root hair around the bacteria. This is followed by the localized breakdown of the cell wall and the invagination of the plant cell membrane, allowing the bacterium to form an infection thread.
In turn, plants provide the bacteria with a carbon source to energize the nitrogen fixation. [29] [30] In addition to nitrogen fixation, Azospirillum species promote plant growth through the production of growth phytohormones (auxins, cytokinins, gibberellins). Due to these phytohormones, root hairs expand to occupy a larger area and better ...