Rheum australe

Rheum australe, synonym Rheum emodi, is a flowering plant in the family Polygonaceae.[1] It is 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.[5]

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

Description

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]

Developing inflorescence in the Oulu University Botanical Gardens, Finland, in early June.
Inflorescence

Similar species

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.[6]

Karyotypy

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.[7]

Distribution

Native to India, Myanmar, Nepal, Pakistan, Bhutan, and Sikkim.[2][8]

Ecology

It grows on grassy or rocky slopes, crevices and moraines, forest margins, near streams and between boulders in specific zones[9]. Impatiens glandulifera in the Valley of Flowers, Uttarakhand, India.[2]

Cultivation

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

Chemical constituents

Hydroxyanthracene derivatives are mainly emodin, chrysophanol and their glycosides.[10] Other hydroxyanthracene derivatives are rhein, aloe emodin and physcion and their glycosides.[11]

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gollark: They just defined Planck's constant as a fixed value, and the only other units used in it are metres and seconds, which have a definition.
gollark: kg.
gollark: I don't know what the thing is, but that's your problem.
gollark: So if you just divide Planck's constant by something in m^2 s^-1, you get kilograms out!

References
  1. "Rheum australe D.Don". Plants of the World Online. Royal Botanic Gardens, Kew. Retrieved 2019-03-10.
  2. "Rheum australe - Himalayan Rhubarb". Flowers of India. Retrieved 2 April 2019.
  3. Eisenreich, Dan (1996–2010). "Rhubarb Botanical Information". The Rhubarb Compendium. Retrieved 2 April 2019.
  4. Alam, Shamshad; Khan, Naeem A. (2015). "Rhubarb (Rewand), A Review" (PDF). Hamdard Medicus. 58 (1): 84–96. Retrieved 13 March 2019.
  5. Pandith, Shahzad A.; Dar, Riyaz Ahmad; Lattoo, Surrinder K.; Shah, Manzoor A.; Reshi, Zafar A. (2018-06-01). "Rheum australe, an endangered high-value medicinal herb of North Western Himalayas: a review of its botany, ethnomedical uses, phytochemistry and pharmacology". Phytochemistry Reviews. 17 (3): 573–609. doi:10.1007/s11101-018-9551-7. ISSN 1572-980X. PMC 7088705.
  6. 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.
  7. 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.
  8. Pandith, Shahzad A.; Dar, Riyaz Ahmad; Lattoo, Surrinder K.; Shah, Manzoor A.; Reshi, Zafar A. (2018-06-01). "Rheum australe, an endangered high-value medicinal herb of North Western Himalayas: a review of its botany, ethnomedical uses, phytochemistry and pharmacology". Phytochemistry Reviews. 17 (3): 573–609. doi:10.1007/s11101-018-9551-7. ISSN 1572-980X. PMC 7088705.
  9. Pandith, Shahzad A.; Dar, Riyaz Ahmad; Lattoo, Surrinder K.; Shah, Manzoor A.; Reshi, Zafar A. (2018-06-01). "Rheum australe, an endangered high-value medicinal herb of North Western Himalayas: a review of its botany, ethnomedical uses, phytochemistry and pharmacology". Phytochemistry Reviews. 17 (3): 573–609. doi:10.1007/s11101-018-9551-7. ISSN 1572-980X. PMC 7088705.
  10. Indian Herbal Pharmacopia Vol. II, Page-123
  11. Shah C.S., Quadry J.S., and Bhatt J.G., Planta Med., 22, 103(1972).
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