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Polygonaceae plants are herbaceous or shrubby, rarely climbing plants or trees are met with; stem usually with swollen nodes. Leaves of Polygonaceae is simple, alternate, entire, stipulate; stipules ochreate. Inflorescence is usually a raceme often forming a panicle, rarely the inflorescence is cymose or the flowers are in clusters.
Flowers of Polygonaceae is usually bisexual, regular, usually with 2 whorls of perianth, hypogynous or perigynous; bracts and bracteoles usually present. Perianth members 3 or 2 in each whorl or rarely 5 and more or less spirally arranged, persistent, free and imbricate or connate; usually sepaloid and similar or rarely with distinct calyx and corolla.
Stamens of Polygonaceae is 6-9 or less, in 2 whorls or in 1 whorl due to the suppression of the inner whorl, each of the outer whorl of stamens often doubles itself; stamens free or united; nectaries often present. Carpels of Polygonaceae is 2-3, uniting to form a syncarpous, superior, 1-celled ovary with a single basal orthotropous ovule; ovary biconvex or triangular; styles 2-3, free; stigma capitate or fringed.
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Fruit a trigonous or ovoid nutlet enclosed by the persistent and often enlarged perianth; seed with copious starchy endosperm and a laterally placed straight or curved embryo; endosperm often ruminate.
The plants of Polygonaceae family show great variation in vegetative as well as floristic characters. Most plants are herbs or shrubs but Coccoloba are trees; Antigonon leptopus Endl. and a few species of Polygonum are climbers or twiners.
In Antigonon the upper, branches of the panicle are bare of flowers and act as tendrils. Muehlenbeckia platycados Meissn is a shrub having stem and branches transformed into flat phylloclade’s bearing small leaves. Ochreate stipules are present in many genera but absent in Erigonum, Antigonon etc.
Flowers of Polygonaceae are bisexual but in Triplaris and some species of Rumex these are unisexual. Usually the flowers are trimerous but dimerous in Oxyria and Rumex. Doubling of the outer whorl of stamens takes place in many species while partial or complete suppression of stamens of the inner whorl is also noticed.
Perianth is in 2 whorls but in Koenigia the inner whorl is absent. Fagopyrum has dimorphic flowers with long stamens and short styles and short stamens and long styles. Endosperm is ruminate in the seeds of Goccoloba, Muehlenbeckia, etc. but usually it is not ruminate in other genera.
In Polygonaceae, pollination is usually done by insects that come in search of nectar and also by wind where the stigma is brush-like.
The Polygonaceae family consists of about 40 genera and about 750 species occurring mostly in the temperate region of Northern Hemisphere while a quite fair number occurs also in the tropical countries and some reaching north as far as the Arctic regions.
In India many species of Polygonum are found in the plains, e.g., P. orientale Linn., P. barbatum Linn., P. plebeium R. Br. etc. and P. molle D. Don., P. chinensis, P. runcinatum Buch. Ham. etc. are in the hills. Fagopyrum, Rumex, Rheum, Calligonum are other genera having Indian species. Antigonon leptopus Endl. is commonly cultivated in gardens for its pink or white flowers.
Plants of economic importance in this family are few. Rheum species are the Rhubarb, the long succulent petioles of which are taken as vegetables. R. emodi Wall, of the Himalayas, R. officinalis Baill, R. rhaponticum Linn, of Europe, R. palmatum of Central Asia have medicinal properties.
Rumex vesicarius Linn, is cultivated in India for the acid leaves which are used as pot:herbs. Coccoloba uvifera Linn, produces edible fruits. Besides Antigonon, Muchlenbeckia platyclados Meiss. is cultivated in gardens as a curiosity. Fagopyrum esculentum Moench. is the Buck-wheat cultivated for the starchy seeds.
Polygonaceae is allied to the families Amaranthaceae, Chenopodiaceae, Catyophyllaceae, etc. of Caryophyllales or Centrospermae. Hutchinson considers that Polygonaceae and the families under Caryophyllales were derived from a common ancestor which originated from Ranales.
Most taxonomists agree that Polygonales and Caryophyllales are closely related and Bessey and Hallier included Polygonaceae under Caryophyllales.
