Agriculture Reference
In-Depth Information
Legumes
FABACEAE
Legumes are the third-largest plant family in the world, after the composites (Asteraceae)
and the orchids (Orchidaceae). The family is found the world over and consists of over
17,000 species. There are three subfamilies: the Mimosoideae and Caesalpinioideae contain
many perennial and woody species; most vegetable legumes are found in the Faboideae. In
practically all agricultural societies, legumes are an important plant source for protein.
Legumes have a symbiotic relationship to certain bacteria ( Rhizobium spp.) in which nitro-
gen gas from the air is “fixed” in root nodules, thus making nitrogen available to the plant in
a usable form (ammonium or nitrate); and the plant, in turn, leaves nitrogen behind in the soil
when it dies.
BOTANICAL CHARACTERISTICS The pods that develop on legumes are fruits. Legume flowers attract
many insects and are mostly outcrossers. For certain species, like common beans and soybeans, self-
pollination is the rule. Many species are climbing vines. People have also selected for non-climbing
varieties, e.g., bush beans ( Phaseolus vulgaris var. nanus ).
Not all legume pods are “green beans.”
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