The Fabaceae (legume family) are the third largest plant family in the world after the Asteraceae (daisy family) and Orchidaceae (orchids). More than 700 genera belong to this family, including Astragalus, possibly the most species-rich genus of the plant kingdom with more than 2000 species described.
The Fabaceae occur in all habitats and all continents except Antarctica, from the coast to the highest mountains. In our region, the Fabaceae are herbaceous plants such as clover (Trifolium) and Vicia or shrubs such as gorse (Ulex europaeus); in tropical regions, they are also often trees and lianas. Composite leaves occur very often but are not exclusive of the family. Typical for the Fabaceae is on the one hand the fruit, called legume or pulse, which always has the same structure. On the other hand, the symmetrical flower is also a typical characteristic, composed of five petals differentiated into a lower keel (two fused petals), an upper banner or standard, and two wings on the sides in-between; this is however only valid in temperate regions and/or for certain subgroups of the family.
Despite the typical fruit, which all legumes share, the flower structure is more variable. There are three subfamilies within the Fabaceae which are sometimes treated as separated families: the tropical Mimosoideae (e.g. sensitive plant, Mimosa pudica) with small radially symmetric flowers and very long stamina; the equally tropical Caesalpinioideae (e.g. peacock flower, Caesalpinia pulcherrima), with always symmetrical but a somewhat more open flowers; and the worldwide distributed Papilionoideae, also named Faboideae, also represented in the European flora and whose flower structure is described above.
This family is very important for mankind since many legumes are cultivated throughout the world as a food source, for instance peanuts (Arachis hypogaea), chickpeas (Cicer arietinum), soybean (Glycine max), lentils (Lens culinaris), beans (Phaseolus vulgaris), peas (Pisum sativum). In comparison with other edible plants, legumes are a rich source of proteins and nitrogen due to the commonly found association between the plant roots and bacteria in the soil. In regions, cultures, life philosophies in which animal products such as meat are not available, too expensive, or are simply avoided, legumes form a healthy alternative and as such are omnipresent in the vegetarian and vegan cuisine.
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