Astragalus (plant) in the context of Vicia

Fabaceae (/fəˈbeɪsi.iː, -ˌaɪ/) or Leguminosae, commonly known as the legume, pea, or bean family, is a large and agriculturally important family of flowering plants. It includes trees, shrubs, and perennial or annual herbaceous plants, which are easily recognized by their fruit (legume) and their compound, stipulate leaves. The family is widely distributed, and is the third-largest land plant family in number of species, behind only the Orchidaceae and Asteraceae, with about 765 genera and nearly 20,000 known species.

The five largest genera of the family are Astragalus (over 3,000 species), Acacia (over 1,000 species), Indigofera (around 700 species), Crotalaria (around 700 species), and Mimosa (around 400 species), which constitute about a quarter of all legume species. The c. 19,000 known legume species amount to about 7% of flowering plant species. Fabaceae is the most common family found in tropical rainforests and dry forests of the Americas and Africa.

Acacia s.l. (pronounced /əˈkeɪʃə/ or /əˈkeɪsiə/), known commonly as mimosa, acacia, thorntree or wattle, is a polyphyletic genus of shrubs and trees belonging to the subfamily Mimosoideae of the family Fabaceae. It was described by the Swedish botanist Carl Linnaeus in 1773 based on the African species Acacia nilotica, now classified as Vachellia nilotica. Many non-Australian species tend to be thorny. Most Australian acacias are not. All species are pod-bearing, with sap and leaves often bearing large amounts of tannins and condensed tannins that historically found use as pharmaceuticals and preservatives.

The genus Acacia constitutes, in its traditional circumspection, the second largest genus in Fabaceae (Astragalus being the largest), with roughly 1,300 species, about 960 of them native to Australia, with the remainder spread around the tropical to warm-temperate regions of both hemispheres, including Europe, Africa, southern Asia, and the Americas (see List of Acacia species). The genus was divided into five separate genera under "Mimosoideae". The genus now called Acacia represents the majority of the Australian species and a few native to Southeast Asia, Réunion, and the Pacific Islands. Most of the species outside Australia, and a small number of Australian species, are classified into Vachellia and Senegalia. The two final genera, Acaciella and Mariosousa, each contain about a dozen species from the Americas (but see "Classification" below for the ongoing debate concerning their taxonomy).

There are over 80 genera of flowering plants estimated to contain at least 500 described species. The largest of these is currently the legume genus Astragalus (milk-vetches), with over 3,000 species.

The sizes of plant genera vary widely from those containing a single species to genera containing thousands of species, and this disparity became clear early in the history of plant classification. The largest genus in Carl Linnaeus' seminal Species Plantarum was Euphorbia, with 56 species; Linnaeus believed that no genus should contain more than 100 species.

The selenium cycle is a biological cycle of selenium similar to the cycles of carbon, nitrogen, and sulfur. Within the cycle, there are organisms which reduce the most oxidized form of the element and different organisms complete the cycle by oxidizing the reduced element to the initial state.

In the selenium cycle it has been found that bacteria, fungi, and plants, especially species of Astragalus, metabolize the most oxidized forms of selenium, selenate or selenite, to selenide. It is also thought that microorganisms may be able to oxidize selenium of valence zero to selenium of valence +6.