rheum


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rheum

a watery discharge from the eyes or nose

Rheum

 

(rhubarb), a genus of plants of the family Polygonaceae. Rhubarbs are large perennial herbs. The flower stalk is solid or hollow and reaches a height of 1.5–2 m. The radical leaves, which have long, succulent petioles, form a rosette and are very large and usually entire. (R. palmatum var. tanguticum has five- to seven-lobed leaves.) The inflorescence is panicled or spicate. The flowers are bisexual; male flowers sometimes occur. The fruit is a brown, three-angled, winged achene.

Rhubarb is native to Southeast Asia, northern Mongolia, northern China, the Altai region, and Siberia. Of the approximately 30 known species (according to other data, 49), 22 are found in the USSR. Some species are cultivated as vegetable, medicinal, and tannin-yielding plants. The most commonly cultivated species are R. undulatum, R. compactum, and the garden rhubarb (R. rhaponticum).

Rhubarb, a cold-resistant plant, can tolerate spring frosts of - 10°C. Its growth is triggered by the thawing of the soil. The plant grows well at a temperature of 8°-10°C and requires little light. The soil must be fertile and damp, but there should be no standing water.

The leaf stalks, which are edible, contain as much as 2.5 percent sugars and approximately 3.5 percent organic acids (primarily malic, citric, oxalic, and succinic acids). They also contain potassium, calcium, phosphorus, and magnesium salts. Rhubarb is used to make compote, jelly, jam, and wine. The roots of R. palmatum var. tanguticum contain the laxatives emodin, chrysophanic acid, and anthracene glycosides; they are used medicinally in the form of powders, tablets, alcohol tinctures, and syrups.

Rhubarb is propagated from seeds, seedlings, or pieces of rhizome. The first crop is obtained two years after planting. The stalks, which measure 25–70 cm long and 1.5–4 cm thick, are gathered (by breaking, cutting, or mowing) from early May through the first ten days of June. The yield in the sixth or seventh year is 250–300 quintals per hectare. An early harvest (by ten to 15 days), with twice the normal yield, may be obtained by covering the plants with a synthetic film. Rhubarb can also be raised in hothouses from three- or four-year-old rhizomes.

Z. S. LEZHANKINA and N. I. OSINA

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