Rheum australe

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Rheum australe
Rheum australe Oulu 03.jpg
Scientific classification edit
Kingdom: Plantae
Clade: Angiosperms
Clade: Eudicots
Order: Caryophyllales
Family: Polygonaceae
Genus: Rheum
Species:
R. australe
Binomial name
Rheum australe
Synonyms[1]
  • Rheum emodi Wall. ex Meisn.

Rheum australe, synonym Rheum emodi, is a flowering plant in the family Polygonaceae.[1] It commonly known as Himalayan rhubarb,[2][3], Indian rhubarb[2] and Red-veined pie plant.[2] It is a medicinal herb used in the Indian Unani system of medicine, and formerly in the European system of medicine where it was traded as Indian rhubarb.[4] The plant is found in the sub-alpine and alpine Himalayas at an altitude of 4000 m.[citation needed]

Description[edit]

The plant has a 1.5-2m high stem.[2][3] Its stem is stout, red, and streaked green and brown.[2][3] The large leaves are heart-shaped[3] or roundish with a heart-shaped base,[2] and greenish-red in colour.[3] The basal leaves can be up to 60cm wide.[2]

It has dark reddish-purple[2] or yellow flowers in late spring to summer,[3] in densely-branched clusters, in a inflorescence up to 30cm long. The inflorescence enlarges greatly when in fruit.[2]

Similar species[edit]

According to the 2003 key in the Flora of China, this species is distinguished from other entire-leaved rhubarbs in China with leaves having a wavy or crisped margin; R. wittrockii, R. rhabarbarum, R. webbianum and R. hotaoense, by having less than 1cm-sized fruit, purple-red flowers, and the surface of the rachis of panicle being densely pubescent. It is the only rhubarb in this group to have purple-red flowers as opposed to various shades of white.[5]

Developing inflorescence of Rheum australe in the Oulu University Botanical Gardens, Finland, in early June.

Karyotypy[edit]

A 1947 study found plants of R. emodi a chromosome count of 2n=22, but the same study found plants labelled as R. australe to be 2n=44. It is possible that this karyotypic diversity indicates the existence of one or more cryptic species, because the polyploid forms would essentially be reproductively isolated.[6]

Distribution[edit]

Native to India, Myanmar, Nepal, Pakistan and Sikkim.[2]

Ecology[edit]

It grows with Impatiens glandulifera in the Valley of Flowers, Uttarakhand, India.[2]

Cultivation[edit]

It is said to be quite hardy and readily propagated.[3]

Chemical constituents[edit]

Hydroxyanthracene derivatives are mainly emodin, chrysophanol and their glycosides.[7] Other hydroxyanthracene derivatives are rhein, aloe emodin and physcion and their glycosides.[8]

References[edit]

  1. ^ a b c "Rheum australe D.Don". Plants of the World Online. Royal Botanic Gardens, Kew. Retrieved 2019-03-10.
  2. ^ a b c d e f g h i j k "Rheum australe - Himalayan Rhubarb". Flowers of India. Retrieved 2 April 2019.
  3. ^ a b c d e f g Eisenreich, Dan (1996–2010). "Rhubarb Botanical Information". The Rhubarb Compendium. Retrieved 2 April 2019.CS1 maint: date format (link)
  4. ^ Alam, Shamshad; Khan, Naeem A. (2015). "Rhubarb (Rewand), A Review" (PDF). Hamdard Medicus. 58 (1): 84–96. Retrieved 13 March 2019.
  5. ^ Bojian (包伯坚), Bao; Grabovskaya-Borodina, Alisa E. (2003). "Rheum". In Zhengyi (吴征镒), Wu; Raven, Peter H.; Deyuan (洪德元), Hong (eds.). Flora of China, Vol. 5. Beijing: Science Press. p. 341.
  6. ^ Ruirui, Liu; Wang, Ailan; Tian, Xinmin; Wang, Dongshi; Liu, Jianquan (2010). "Uniformity of karyotypes in Rheum (Polygonaceae), a species-rich genus in the Qinghai-Tibetan Plateau and adjacent regions". Caryologia Firenze. 63 (1): 82–90. doi:10.1080/00087114.2010.10589711. Retrieved 26 March 2019.
  7. ^ Indian Herbal Pharmacopia Vol. II, Page-123
  8. ^ Shah C.S., Quadry J.S., and Bhatt J.G., Planta Med., 22, 103(1972).