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Concept
Senna (genre)
Résumé
Senna, the sennas, is a large genus of flowering plants in the legume family (Fabaceae, subfamily Caesalpinioideae, tribe Cassieae ser. Aphyllae ). This diverse genus is native throughout the tropics, with a small number of species in temperate regions. The number of species is estimated to be from about 260 to 350. The type species for the genus is Senna alexandrina. About 50 species of Senna are known in cultivation. Plants in the Senna genus are vastly studied for their beneficial effects arising from the abundance of numerous phytochemicals, bioactive components and antioxidant and antimicrobial properties.
Plants in the genus Senna are shrubs, sometimes small trees or perennial herbs. The leaves are arranged alternately, paripinnate with up to 25 pairs of leaflets, each leaf with a stipule at the base, but that often falls off as the leaves mature. The flowers are arranged in racemes in leaf axils with bracts at the base. The flower has five egg-shaped green or yellowish sepals and five usually yellow, usually glabrous petals. There are usually ten stamens that are free from each other, the filaments of different lengths, and some are staminodes. The fruit is a leathery pod containing several seeds.
Chamaecrista, Cassia, and Senna form a monophyletic group which some authors have called Cassia sensu lato. In 1982, the group was named Cassiinae and classified as a subtribe of the tribe Cassieae. The tribe Cassieae contains 21 genera and is now known to be polyphyletic, but the classification is still accepted because a revision of Fabaceae has yet to be published.
The genus Senna has had a complex taxonomic history. What is now known as Senna was included by Linnaeus in his concept of Cassia in Species Plantarum in 1753. Philip Miller segregated Senna from Cassia in 1754 in the fourth edition of The Gardeners Dictionary. Until 1982, many authors, following Linnaeus, did not recognize Senna and Chamaecrista, but included them in a broadly circumscribed Cassia sensu lato.
Source officielle
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