Legumes (Fabaceae or Leguminosae) are unique among cultivated plants for their ability to carry out endosymbiotic nitrogen fixation with rhizobial bacteria, a process that takes place in a specialized structure known as the nodule.
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Geurts, R.; Mitani, S.; Bisseling, T.; Franken, C.; Hartog, M.V.; Lang, C. (2011)
The Medicago genome provides insight into the evolution of rhizobial symbioses
Nature 480 . - p. 520 - 524.