''Rheum rhabarbarum'' is a

species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...

flowering plant Flowering plants are plants that bear flowers and fruits, and form the clade Angiospermae (). The term angiosperm is derived from the Ancient Greek, Greek words (; 'container, vessel') and (; 'seed'), meaning that the seeds are enclosed with ...

in the family

Polygonaceae The Polygonaceae are a Family (biology), family of flowering plants known Common name, informally as the knotweed family or smartweed—buckwheat family in the United States. The Botanical name, name is Basionym, based on the genus ''Polygonum'', ...

, native to a region stretching from southern

Siberia Siberia ( ; , ) is an extensive geographical region comprising all of North Asia, from the Ural Mountains in the west to the Pacific Ocean in the east. It has formed a part of the sovereign territory of Russia and its predecessor states ...

to north and central China. It has been harvested from the wild for centuries for its root, which was harvested for use as a popular medicine in Europe and Asia. It was later cultivated for its root in England and Russia. It is considered to be one of the species involved in the development of culinary

rhubarb Rhubarb is the fleshy, edible stalks ( petioles) of species and hybrids (culinary rhubarb) of ''Rheum'' in the family Polygonaceae, which are cooked and used for food. The plant is a herbaceous perennial that grows from short, thick rhizomes. ...

, for which the scientific name ''R. rhabarbarum'' is sometimes (erroneously) used.

Taxonomy

''Rheum rhabarbarum'' was first described by

Carl Linnaeus Carl Linnaeus (23 May 1707 – 10 January 1778), also known after ennoblement in 1761 as Carl von Linné,#Blunt, Blunt (2004), p. 171. was a Swedish biologist and physician who formalised binomial nomenclature, the modern system of naming o ...

in 1753. Linnaeus also described ''R. undulatum'', but this is now considered to be the same species. The name ''rha barbarum'',

Latin Latin ( or ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken by the Latins (Italic tribe), Latins in Latium (now known as Lazio), the lower Tiber area aroun ...

for 'foreign rha', was first used in the writings of

Celsus Celsus (; , ''Kélsos''; ) was a 2nd-century Greek philosopher and opponent of early Christianity. His literary work '' The True Word'' (also ''Account'', ''Doctrine'' or ''Discourse''; Greek: )Hoffmann p.29 survives exclusively via quotati ...

, who uses the word to describe a valued medicinal root imported from the east.

Description

Similar species

According to the 2003 key in the ''

Flora of China The flora of China consists of a diverse range of plant species including over 39,000 vascular plants, 27,000 species of fungi and 3000 species of bryophytes.Wu, Z. Y., P. H. Raven & D. Y. Hong, eds. 2006. Flora of China. Vol. 22 (Poaceae). Sci ...

'', this species is distinguished from other entire-leaved rhubarbs in China with leaves having a wavy or crisped margin; ''R. wittrockii'', ''R. webbianum'', ''R. australe'' and ''R. hotaoense'', by having less than 1 cm-sized fruit, yellow-white to greenish-white flowers, and the surface of the rachis of

panicle In botany, a panicle is a much-branched inflorescence. (softcover ). Some authors distinguish it from a compound spike inflorescence, by requiring that the flowers (and fruit) be pedicellate (having a single stem per flower). The branches of a p ...

covered in

papilla Papilla (Latin, 'nipple') or papillae may refer to: In animals * Papilla (fish anatomy), in the mouth of fish * Papilla (worms), small bumps on the surface of certain worms * Basilar papilla, a sensory organ of lizards, amphibians and fish * ...

. In many characters it is most similar to ''R. webbianum'', and somewhat less so ''R. hotaoense''.

Karyotypy

There have been at least two studies investigating the karyotypy of this species, both studies focussing on the synonym ''R. undulatum''. Both 2''n''=22 and 2''n''=44 have been found. It is possible that this karyotypic diversity indicates the existence of one or more

cryptic species In biology, a species complex is a group of closely related organisms that are so similar in appearance and other features that the boundaries between them are often unclear. The taxa in the complex may be able to hybridize readily with each oth ...

, because the

polyploid Polyploidy is a condition in which the biological cell, cells of an organism have more than two paired sets of (Homologous chromosome, homologous) chromosomes. Most species whose cells have Cell nucleus, nuclei (eukaryotes) are diploid, meaning ...

forms would essentially be reproductively isolated.

Distribution

It is native to an area of southeastern

in the Daurian region around and stretching east from

Lake Baikal Lake Baikal is a rift lake and the deepest lake in the world. It is situated in southern Siberia, Russia between the Federal subjects of Russia, federal subjects of Irkutsk Oblast, Irkutsk Oblasts of Russia, Oblast to the northwest and the Repu ...

Russia Russia, or the Russian Federation, is a country spanning Eastern Europe and North Asia. It is the list of countries and dependencies by area, largest country in the world, and extends across Time in Russia, eleven time zones, sharing Borders ...

, and in northern

Mongolia Mongolia is a landlocked country in East Asia, bordered by Russia to the north and China to the south and southeast. It covers an area of , with a population of 3.5 million, making it the world's List of countries and dependencies by po ...

. In China, it occurs in the northern provinces of

Hebei Hebei is a Provinces of China, province in North China. It is China's List of Chinese administrative divisions by population, sixth-most populous province, with a population of over 75 million people. Shijiazhuang is the capital city. It bor ...

Heilongjiang Heilongjiang is a province in northeast China. It is the northernmost and easternmost province of the country and contains China's northernmost point (in Mohe City along the Amur) and easternmost point (at the confluence of the Amur and Us ...

Henan Henan; alternatively Honan is a province in Central China. Henan is home to many heritage sites, including Yinxu, the ruins of the final capital of the Shang dynasty () and the Shaolin Temple. Four of the historical capitals of China, Lu ...

Hubei Hubei is a province of China, province in Central China. It has the List of Chinese provincial-level divisions by GDP, seventh-largest economy among Chinese provinces, the second-largest within Central China, and the third-largest among inland ...

Jilin ) , image_skyline = Changbaishan Tianchi from western rim.jpg , image_alt = , image_caption = View of Heaven Lake , image_map = Jilin in China (+all claims hatched).svg , mapsize = 275px , map_al ...

Inner Mongolia Inner Mongolia, officially the Inner Mongolia Autonomous Region, is an Autonomous regions of China, autonomous region of China. Its border includes two-thirds of the length of China's China–Mongolia border, border with the country of Mongolia. ...

Shanxi Shanxi; Chinese postal romanization, formerly romanised as Shansi is a Provinces of China, province in North China. Its capital and largest city of the province is Taiyuan, while its next most populated prefecture-level cities are Changzhi a ...

and

Shaanxi Shaanxi is a Provinces of China, province in north Northwestern China. It borders the province-level divisions of Inner Mongolia to the north; Shanxi and Henan to the east; Hubei, Chongqing, and Sichuan to the south; and Gansu and Ningxia to t ...

Habitat & ecology

In China, it is known as a species growing on mountain slopes at 1,000–1,600 m elevation. In Russia it occurs in sandy ground along field edges, on the steppes, and in the regionally uncommon copses of woodland. In China, it flowers in June, and has fruit after July. Most documented insect relationships with this species are muddied by the misapplication of the name ''R. rhabarbarum'' to plants of ''R.'' × ''hybridum''. As such, most of the insects which are said to use this species as a food plant are generalists from Europe or North America which did not actually eat this species nor are native to the region where this species occurs. An exception is the butterfly '' Lycaena violacea'', whose caterpillars are only known to feed on ''R. rhabarbarum'' and whose range is concurrent with that of its host plant (most ''

Lycaena ''Lycaena'' is a genus of butterflies. The genus range is Holarctic, with the exception of four species found in New Zealand, two in South Africa, one in New Guinea and one in Java. It is commonly divided into several subgenera, such as ''Antipod ...

'' spp. are specialised on

). '' Cosmia trapezina'' var. ''exigua'' is roughly native to some of the same areas, and its European variety has been found to have eaten rhubarb in Finland (it usually feeds on various tree species). Other species found to eat (garden) rhubarb which occur in the native range of this plant are '' Arctia caja'', '' Hydraecia micacea'', '' Spilarctia luteum'' and '' Xestia baja''. Rheum undulatum g1

Cultivation

''Rheum rhabarbarum'' (syn. ''R. undulatum'') was one of a number of distinct species grown in Europe before the beginning of the 18th century. Initially the roots of a related species, possibly '' R. rhaponticum'', were used for medicinal purposes. A putative hybrid of unknown origin, ''Rheum'' × ''hybridum'', was also grown. The three taxa were grown as vegetable crops in England and Scandinavia by the early 18th century. They readily hybridize, and culinary

was developed by selecting open-pollinated seed, so that its precise origin is almost impossible to determine. In appearance, culinary rhubarb varies continuously between ''R. rhabarbarum'' and ''R. rhaponticum''. Modern rhubarb cultivars are

tetraploid Polyploidy is a condition in which the cells of an organism have more than two paired sets of ( homologous) chromosomes. Most species whose cells have nuclei (eukaryotes) are diploid, meaning they have two complete sets of chromosomes, one fro ...

s with 2''n'' = 44, in contrast to 2''n''=22 for the wild species such as ''R. rhaponticum''.

References

{{Taxonbar, from=Q720108 rhabarbarum Plants described in 1753 Taxa named by Carl Linnaeus Flora of temperate Asia