Legume
Legumes are nitrogen-fixing plants vital for food and soil fertility.
Legumes belong to the pea family, known scientifically as Fabaceae or Leguminosae. The term can refer to the plants themselves or to their fruits and seeds. When the seeds are harvested dry for people to eat, they are called pulses. Farmers grow legumes mainly for food, but also for animal feed, silage, and as green manure to improve soil. The fruit of a legume is botanically distinctive: a simple, dry structure that grows from a single carpel and typically splits open along two seams. Most legumes host symbiotic bacteria called Rhizobia in their root nodules. These bacteria fix nitrogen, and some of that nitrogen becomes available to later crops, making legumes important in crop rotation.
The United Nations' Food and Agriculture Organization (FAO) uses the term "pulse" specifically for legume crops harvested only for their dry seeds. This excludes green beans and green peas, which are considered vegetables. It also excludes seeds grown mainly for oil, like soybeans and peanuts, and seeds used only for sowing forage, such as clovers and alfalfa. In everyday language, these distinctions are often blurred, and many varieties used for dried pulses are also eaten as green vegetables when the pods are young. The FAO recognizes 11 primary pulses, leaving out green vegetable legumes, oilseed legumes, and forage legumes.
Common dry beans include kidney, navy, pinto, black turtle, and haricot beans (Phaseolus vulgaris); lima and butter beans (Phaseolus lunatus); adzuki beans (Vigna angularis); mung beans (Vigna radiata); black gram (Vigna mungo); scarlet runner beans (Phaseolus coccineus); ricebeans (Vigna umbellata); moth beans (Vigna aconitifolia); and tepary beans (Phaseolus acutifolius). Dry broad beans include horse, broad, and field beans (Vicia faba). Dry peas include garden peas (Pisum sativum var. sativum) and protein peas (Pisum sativum var. arvense). Other pulses are chickpeas, dry cowpeas (including black-eyed peas), pigeon peas, lentils, Bambara groundnuts, common vetch, and lupins. Additional pulses not elsewhere specified include lablab or hyacinth beans, jack and sword beans, winged beans, velvet beans, and yam beans.
Legumes are the third-largest land plant family by number of species, after orchids and daisies. They include about 751 genera and roughly 19,000 known species, making up about seven percent of all flowering plants.
Many legumes host
- family
- Fabaceae (Leguminosae)
- number_of_species
- about 19,000 known species
- number_of_genera
- about 751
- primary_use
- human consumption, livestock forage, green manure
- key_trait
- nitrogen fixation via Rhizobia bacteria
- recognized_pulses_by_FAO
- 11 primary pulses
Lore & Background
Legumes are the third-largest land plant family by species, behind Orchidaceae and Asteraceae, with about 751 genera and 19,000 known species, constituting about seven percent of flowering plant species. They are widely distributed and cultivated for their seeds, which are called pulses when harvested dry for human consumption. The United Nations' Food and Agriculture Organization recognizes 11 primary pulses, excluding green vegetable legumes and those used mainly for oil extraction or as seed for forage.
Reader's Guide
Legumes are significant for their role in agriculture and human nutrition. They host symbiotic Rhizobia bacteria in root nodules that fix atmospheric nitrogen into ammonia, which is converted to ammonium usable by plants. When legume plants die, the nitrogen is released into the soil, serving as natural fertilizer. This makes legumes essential in crop rotation and polyculture, reducing the need for synthetic nitrogen fertilizers. Nutritionally, legumes are a significant source of protein, dietary fiber, carbohydrates, and minerals; for example, cooked chickpeas provide 18% of the daily value for protein and 30% for dietary fiber. They are also an excellent source of resistant starch, which produces short-chain fatty acids beneficial for intestinal health. Legumes are increasingly used in vegan meat and dairy substitutes, with products containing legumes growing by 39% in Europe between 2013 and 2017. Their versatility spans forage, grain, flowering, pharmaceutical, and green manure categories.
Did You Know?
- Legumes produce a simple dry fruit that develops from a simple carpel and usually opens along a seam on two sides.
- The FAO excludes green beans, green peas, soybeans, peanuts, clover, and alfalfa from its definition of pulses.
- A common pest of grain legumes in tropical and subtropical regions is the bean fly, which can destroy an entire crop early in growth.
- Seed viability for vetch, broad beans, and peas lasts about 5 years in storage, with temperature and humidity affecting germination.
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