Polygonaceae

Polygonaceae
Polygonum persicaria
Scientific classification
Kingdom:	Plantae
Division:	Magnoliophyta
Class:	Magnoliopsida
Order:	Caryophyllales
Family:	Polygonaceae Juss.
Subfamilies
Polygonoideae Eriogonoideae

Persicaria capitata or Pink Knotweed

Polygonum plebeium or Small Knotweed

Polygonaceae is a family of flowering plants also known as the "knotweed family" or "smartweed family". The name is based on the genus Polygonum. Some well known members include Fagopyrum (buckwheat), Rumex (sorrel), Rheum (rhubarb), and Polygonum (knotweed). The family is named for the many swollen node joints that some species have; poly means many and goni means knee or joint.

According to the database of the Royal Botanic Gardens, Kew, the family consists of 43 genera, totalling about 1100 species. Numerically the most important are Eriogonum (250 species), Polygonum (200 species), Rumex (200 species), Coccoloba (120 species), and Calligonum (80 species).

The family is present worldwide, but are most differentiated in temperate regions.

Taxonomy

This family is very well-defined and is universally recognised, but its position has been less clear. For example, in the Cronquist system, it was given its own order (Polygonales), but newer systems such as APG treat them as part of the Caryophyllales.

Polygonaceae can be divided in two subfamilies:

• Polygonoideae, comprising about 28 genera and 800 species, are characterised by the lack of an involucre and the presence of ocreae. Important members are Polygonum, Rumex and Calligonum.

• Eriogonoideae, with about 330 species, are exclusive to the New World, cymose inflorescence and lack of ocreae. Eriogonum is an important member.

Description

Ochrea of Persicaria maculosa

Most Polygonaceae are perennial herbaceous plants with swollen nodes, but small shrubs (e.g. Coccoloba) and climbers (e.g. Antigonon) are also present.

Leaves of Polygonoideae are simple, arranged alternately on the stems and have a peculiar pair of sheathing stipules known as ocreae. Those species that do not have the nodal ocrea can be identified by having involucrate flower heads. The perianth is petaloid, often in two rows. The flowers are normally bisexual, small in size, actinomorphic with perianth of 3-6 sepals. After flowering the sepals often become membranous and enlarge around the developing fruit. Flowers lack a corolla and the sepals are petal-like and colorful. The androecium is composed of 3 to 8 stamens that are normally free or united at the base. Flowers with compound pistils composed of three united carpels with one locule - producing a single ovule. The ovary is superior with basal placentation, and 2 to 4 stigmas are produced.^[1]

Selected genera

• Afrobrunnichia
• Antigonon
• Aristocapsa
• Atraphaxis
• Bistorta
• Brunnichia
• Calligonum
• Centrostegia
• Chorizanthe
• Coccoloba
• Dedeckera
• Dodecahema
• Emex
• Eriogonum
• Fagopyrum
• Fallopia
• Gilmania
• Goodmania
• Gymnopodium
• Harfordia
• Hollisteria
• Knorringia
• Koenigia
• Lastarriaea
• Leptogonum
• Mucronea
• Muehlenbeckia
• Nemacaulis
• Neomillspaughia
• Oxygonum
• Oxyria
• Oxytheca
• Parapteropyrum
• Persicaria
• Podopterus
• Polygonella
• Polygonum or Knotweed
• Pteropyrum
• Pterostegia
• Rheum
• Rumex
• Ruprechtia
• Stenogonum
• Symmeria
• Systenotheca
• Triplaris

External links

Wikimedia Commons has media related to: Polygonaceae

• Polygonaceae in L. Watson and M.J. Dallwitz (1992 onwards). The families of flowering plants: descriptions, illustrations, identification, information retrieval. http://delta-intkey.com
• Family Polygonaceae Flowers in Israel
• Polygonaceae of Mongolia in FloraGREIF

References

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