Senna (plant)

Senna
Senna alexandrina
Scientific classification
Kingdom:	Plantae
Clade:	Angiosperms
Clade:	Eudicots
Clade:	Rosids
Order:	Fabales
Family:	Fabaceae
Tribe:	Cassieae
Genus:	Senna Mill.
Type species
Senna alexandrina Mill.
Species
Over 300; see text
Synonyms[1]
Adipera Raf. 1838 Cassia (Mill.) Benth. 1871 Cassia sect. Senna (Tournefort) DC. ex Colladon 1816 Cassia sect. Senna sensu Benth. 1865 Cassia subgen. Senna Benth. 1870 Cathartocarpus (partim) Chamaefistula (DC.) G. Don Chamaesenna (DC.) Raf. ex Pittier Desmodiocassia Britton & Rose Diallobus Earleocassia Britton Echinocassia Britton & Rose Gaumerocassia Britton Herpetica (DC.) Raf. Isandrina Leonocassia Britton Palmerocassia Britton Peiranisia Raf. Phragmocassia Britton & Rose Pseudocassia Britton & Rose Pterocassia Britton & Rose Sciacassia Britton Senna sensu Gaertn. 1791 Senna sensu Link 1831 Senna sensu Roxb. 1832 Sericeocassia Britton Tharpia Britton & Rose Vogelocassia Britton Xerocassia Britton & Rose

Senna (from Arabic sanā), the sennas, is a large genus of flowering plants in the legume family Fabaceae, and the subfamily Caesalpinioideae^[2] and the tribe Cassieae. 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^[3] to 350.^[4] The type species for the genus is Senna alexandrina. About 50 species of Senna are known in cultivation.^[5]

Description

Senna includes herbs, shrubs, and trees. The leaves are pinnate with opposite paired leaflets. The inflorescences are racemes at the ends of branches or emerging from the leaf axils. The flower has five sepals and five usually yellow petals. There are ten straight stamens. The stamens may be different sizes, and some are staminodes. The fruit is a legume pod containing several seeds.^[6]

Systematics

Chamaecrista, Cassia, and Senna form a monophyletic group which some authors have called Cassia sensu lato.^[7] In 1982, the group was named Cassiinae and classified as a subtribe of the tribe Cassieae.^[8] The tribe Cassieae contains 21 genera and is now known to be polyphyletic,^[7] but the classification is still accepted because a revision of Fabaceae has yet to be published.^[7]

The genus Senna has had a complex taxonomic history.^[9] What is now known as Senna was included by Linnaeus in his concept of Cassia in Species Plantarum in 1753.^[10] Philip Miller segregated Senna from Cassia in 1754 in the fourth edition of The Gardeners Dictionary.^[11] Until 1982, many authors, following Linnaeus, did not recognize Senna and Chamaecrista, but included them in a broadly circumscribed Cassia sensu lato. Phylogenetic analyses of DNA have shown that Chamaecrista, Cassia, and Senna are all monophyletic, but the relationships between these three genera have not been resolved.^[3] They are therefore shown in phylogenetic trees as a tritomy.

Ecology

Bark of Senna siamea

The caterpillars of many Lepidoptera species feed on Senna plants. The black witch (Ascalapha odorata), two-barred flasher (Astraptes fulgerator), common emigrant (Catopsilia pomona), and mottled emigrant (C. pyranthe) have all been recorded on candle bush (S. alata), for example.

Senna species are pollinated by a variety of bees, especially large female bees in genera such as Xylocopa.^[3] Some species also have extrafloral nectaries on the leaves or flower stalks, which attract ants, but do not benefit pollinators. The ants probably deter herbivores.^[3]

Uses

Some Senna species are used as ornamental plants in landscaping. The species is adapted to many climate types.

Cassia gum, an extract of the seeds of Chinese senna (S. obtusifolia), is used as a thickening agent. The leaves and flowers of Siamese cassia (S. siamea) are used in some Southeast Asian cuisines, such as Thai and Lao cuisines. They are known as khi-lek in Thai, and are used in curries.^[12]

Fossil record

A fossil seed pod of Senna sp. from the middle Eocene epoch has been described from the Rancho clay pit in Henry County, Tennessee(United States).^[19]

Species gallery

• 
  Senna alexandrina
• 
  Senna artemisioides
• 
  Senna aversiflora
• 
  Senna didymobotrya
• 
  Senna glutinosa
• 
  Senna hirsuta
• 
  Senna italic
• 
  Senna lindheimeriana
• 
  Senna macranthera
• 
  Senna multiglandulosa
• 
  Senna occidentalis
• 
  Senna pendula
• 
  Senna pinheiroi
• 
  Senna spectabilis
• 
  Senna surattensis

List of species

Senna comprises the following species:^[20][21][22]

Species names with uncertain taxonomic status

The status of the following species is unresolved:^[22]

References

External links

Wikimedia Commons has media related to Senna.

Look up senna (plant) in Wiktionary, the free dictionary.

Wikispecies has information related to Senna

• Senna US Department of Agriculture