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Root nodules are found on the roots of plants, primarily legumes, that form a symbiosis with nitrogen-fixing bacteria. [1] Under nitrogen -limiting conditions, capable plants form a symbiotic relationship with a host-specific strain of bacteria known as rhizobia. [2] This process has evolved multiple times within the legumes, as well as in ...
As in legumes, nodulation is favored by nitrogen deprivation and is inhibited by high nitrogen concentrations. Depending on the plant species, two mechanisms of infection have been described: The first is observed in casuarinas or alders and is called root hair infection.
Rhizobia are a "group of soil bacteria that infect the roots of legumes to form root nodules ". [2] Rhizobia are found in the soil and, after infection, produce nodules in the legume where they fix nitrogen gas (N 2) from the atmosphere, turning it into a more readily useful form of nitrogen. From here, the nitrogen is exported from the nodules ...
An alder root nodule. Frankia is a genus of nitrogen-fixing bacteria that live in symbiosis with actinorhizal plants, similar to the Rhizobium bacteria found in the root nodules of legumes in the family Fabaceae. Frankia also initiate the forming of root nodules .
The rhizobia penetrate the root hair cells with an infection thread that grows through the root hair into the main root. This causes the infected cells to divide and form a nodule. The rhizobia can now begin nitrogen fixation. Nod genes. Over 55 genes are known to be associated with nodulation.
Arbuscular mycorrhiza is a type of endomycorrhiza along with ericoid mycorrhiza and orchid mycorrhiza (not to be confused with ectomycorrhiza ). They are characterized by the formation of unique tree-like structures, the arbuscules. [1] In addition, globular storage structures called vesicles are often encountered.
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.
Plants that contribute to nitrogen fixation include those of the legume family—Fabaceae— with taxa such as kudzu, clover, soybean, alfalfa, lupin, peanut and rooibos. They contain symbiotic rhizobia bacteria within nodules in their root systems, producing nitrogen compounds that help the plant to grow and compete with other plants.