legume

(noun)

Any of a large family (Leguminosae syn. Fabaceae) of dicotyledonous herbs, shrubs, and trees having fruits that are legumes or loments, bearing nodules on the roots that contain nitrogen-fixing bacteria, and including important food and forage plants (as peas, beans, or clovers).

Related Terms

Examples of legume in the following topics:

  • The Legume-Root Nodule Symbiosis

    • Legumes have a symbiotic relationship with bacteria called rhizobia, which create ammonia from atmospheric nitrogen and help the plant.
    • Many legumes have root nodules that provide a home for symbiotic nitrogen-fixing bacteria called rhizobia.
    • The relationship between a host legume and the rhizobia is symbiotic, providing benefits to both participants.
    • Used properly some legumes can even serve as fertilizer for later crops, binding nitrogen in the plant remains in the soil .
    • Soy beans are a type of legume crop that rely on rhizobia

  • Early Discoveries in Nitrogen Fixation

    • For thousands of years farmers were aware that plants belonging to the legume family, such as peas and soy beans, promoted crop growth when planted with other non-legumes such as wheat.
    • Growing a legume crop in a field could also result in the next year's crop of non-legume plants giving a far greater yield.
    • Later people knew legumes did replenish nitrogen in the soil, but did not know how atmospheric (N2) was converted into ammonium (NH3) by legumes until research done in the 19th century.
    • He found that the nodules on the roots of legumes are the location where nitrogen fixation takes place.
    • Work done by Martinus Beijerinck was key to the discovery of rhizobia, symbiotic bacteria found on the roots of legumes and responsible for nitrogen fixation.

  • Anaerobiosis and N2 Fixation

    • Many rhizobia, nitrogen fixing bacteria, live in a symbiotic relationship with plants known as legumes.
    • In plants infected with Rhizobium, (legumes such as alfalfa or soybeans), the presence of oxygen in the root nodules would reduce the activity of the oxygen-sensitive nitrogenase.
    • Leghemoglobin is produced by legumes in response to the roots being infected by rhizobia, as part of the symbiotic interaction between the plant and these nitrogen-fixing bacterium.

  • The Nitrogen Cycle

    • Some nitrogen fixing bacteria live in the root nodules of legumes where they produce ammonia in exchange for sugars.

  • Gas Requirements

    • Examples of those diazotrophs include: rhizobia that associate with legumes, plants of the Fabaceae family, frankias, and cyanobacteria that associate with fungi as lichens, with liverworts, with a fern, and with a cycad.

  • Endophytes and Plants

  • Nitrate Reduction and Denitrification

    • Rhizobia are soil bacteria with the unique ability to establish a N2-fixing symbiosis on legume roots.