Legumes

Legumes (Leguminosae), a family (according to others, an order) of dicotyledonous plants, one of the most significant both in terms of the number of species (about 12,000) and in practical application. Herbs, trees, shrubs, and lianas of very diverse appearance, for the most part, with pinnate leaves. Their most characteristic common feature is the fruit—a legume (pod), formed by a single carpel, mostly multi-seeded, unilocular, and opening with two valves. According to the structure of the flower, Legumes are divided into three subfamilies (according to others, families): 1) Papilionaceae—pea-flowered; flower with an irregular, so-called papilionaceous corolla (e.g., sweet pea); for the most part, herbs distributed throughout the earth; 2) Caesalpinioideae; flower also irregular, not of the papilionaceous type; tropical and subtropical shrubs and trees; 3) Mimosoideae; flower regular with numerous stamens; for the most part, tropical shrubs and lianas. The most important physiological feature of apparently all Legumes is their symbiosis with nitrogen-assimilating bacteria (Bact. radicicola). This leads to the formation of characteristic nodules on their roots and enables them to develop well even in soils poor in nitrogenous compounds (see Nitrogen-fixing bacteria). Thanks to this feature, Legumes have gained exceptionally important significance in agriculture as a necessary member of crop rotation. The seeds of many Legumes are used for food (peas, beans, lentils). Unlike most other plant food products, they are rich in proteins (20% and more), which gives them special nutritional significance. Others, such as soy (Glycine hispida), peanut (Arachis hypogaea), are rich in fat and serve for the technical extraction of it. The most important forage plants are: clover (Trifolium), vetch (Vicia sativa), alfalfa (Medicago sativa), lupine (Lupinus luteus), sainfoin (Onobrychis sativa), and others. Many tropical woody Legumes provide valuable colored wood—rosewood (Dalbergia nigra and species of Machaerium), red sandalwood (Pterocarpus santalinus), logwood (Haematoxylon campechianum), from which the well-known dye hematoxylin is extracted (see). Many Legumes provide products important in technology or medicine: indigo dye (Indigofera tinctoria), tanning extract catechu (Acacia catechu), gum arabic (Acacia Senegal and others), tragacanth (Astragalus gummifer and others), Peruvian balsam (Toluifera Pereirae). Specifically medicinal are the following legumes: Alexandrian senna (Cassia acutifolia) and licorice, or licorice root (Glycyrrhiza glabra). Among the poisonous, potent agents is the Calabar bean (seed of the plant Physostigma venenosum); also poisonous are Abrus precatorius, species of broom (Cytisus), and many others.

L. Kursanov.