Rheum (genus)
| Rhubarb | |
|---|---|
 |
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| Scientific classification | |
| Kingdom: | Plantae |
| (unranked): | Angiosperms |
| (unranked): | Eudicots |
| (unranked): | Core eudicots |
| Order: | Caryophyllales |
| Family: | Polygonaceae |
| Genus: |
Rheum L. |
Rheum is a genus of about 60 perennial plants in the family Polygonaceae. The genus includes the vegetablerhubarb (Rheum rhabarbarum or Rheum x hybridum.) The species have large somewhat triangular shaped leaves with long, fleshy petioles. The flowers are small, greenish-white to rose-red, and grouped in large compound leafy inflorescences. A number of varieties of rhubarb have been domesticated both as medicinal plants and for human consumption. While the leaves are toxic, the stalks are used in pies and other foods for their tart flavor.
Rheum species are herbaceous perennials growing from fleshy roots. They have upright growing stems and mostly basal, deciduous leaves growing from short, thick rhizomes. They have persistent or deciduous ocrea. The inflorescences are terminal and panicle-like with pedicels. The hermaphrodite flowers consist of a whitish green to pinkish green, hairless and campanulate perianth, composed of six tepals. The outer three tepals are narrower than the inner three and all are sepal-like in appearance. The flowers have nine (sometimes six) stamina inserted on the torus at the base of the peranthium, they are free or subconnatent at their base. The anthers are yellow or pinkish green, elliptic in shape. The ovary is simple and triangular shaped with three erect or deflexed styles. The stigmas are head-like. The fruits are a three-sided achene with winged sides, and the seeds are albuminous with a straight or curved embryo.
The name has its origin in the Ancient Greek word rheon, which was used by Dioscorides, possibly for a plant in this genus.
Many rheum species have food and medicinal uses. Some of these uses originated in Asia more than 2,000 years ago. Rheum rhabarbarum is used to make pies, jellies, jams, and wine. All parts of the plant contain slightly poisonous oxalic acid, but its concentration in the leaf stems or petioles used in food preparation is very low, and their tart flavor instead is caused by nontoxic malic acid. The plants also produce other compounds, including citric acid and anthraquinone glycosides, and the raw or cooked leaf blades are poisonous to humans and livestock if consumed in large enough amounts. Plants in cultivation are propagated by cutting up the crowns of larger plants and by seeds.
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Wikipedia