Polygonum aviculare (PROSEA)
- Protologue: Sp. pl. 1: 362 (1753).
- Family: Polygonaceae
- Chromosome number: 2n= 20 (22), 40, 60
- Knot grass, prostrate knot weed, wire weed (En). Renouée des oiseaux (Fr)
- Vietnam: biền súc, rau dắng.
Origin and geographic distribution
Native to Europe and northern Asia, now widely distributed in temperate, subtropical and tropical regions, including Vietnam and Malesia.
P. aviculare possesses astringent, tonic, antipyretic, antiseptic, diuretic, haemostatic and vermifuge properties. It contains tannins, and is therefore used for cicatrization of wounds. In Vietnam, it is prescribed in the treatment of oliguria, dysuria, urinary stones and jaundice. In China, the aerial parts are also used as a vermifuge and for skin diseases including eczema and stubborn itch. In India, the juice or a decoction is taken as a tonic, and used in the treatment of diabetes, rheumatism, fever and external and internal ulcers. A decoction of the whole plant is given in dysentery, diarrhoea, bronchitis and bleeding piles, and to check profuse menstruation. The seeds are aromatic and are considered a powerful emetic and cathartic.
P. aviculare is used as fodder for cattle, sheep and goats. In Australia, however, cases of dermatitis and gastric disturbances have been observed among sheep and horses feeding on it. Also, milk of animals fed P. aviculare acquires a bitter taste. The herb yields a blue dye, similar to indigo.
Production and international trade
P. aviculare is mainly locally used. In Vietnam and Malesia, the dried plant is found in Chinese pharmacies.
The aerial parts contain about 4% total tannins, of both gallotannin and catechin type. Also, several organic acids are recorded, like gallic-, chlorogenic-, cinnamic- and coumaric acid, as well as several flavonoids: avicularine (= quercetin-3-arabinofuranoside, 0.2%), astragalin, kaempferitrine (kaempferol-3,7-dirhamnoside), hyperoside, quercitrine and luteoline. In addition, the herb contains about 0.2% soluble and 1% insoluble silicic acids.
Pharmacological effects of P. aviculare extracts include lowering of blood pressure in cats, rabbits and dogs, an anticoagulant activity on sheep-blood by aqueous and alcohol extracts, and anti-inflammatory and hepato-protective activity. In mice, the aqueous extract showed immunomodulatory effects by stimulation of the production of anti-sheep red blood cells (IgG) antibodies.
The alcohol extract is moderately active in vitro against fungi causing leaf-spot disease in potato: Alternaria alternata , A. solani , Cladosporium herbarum , Colletotrichum coccodes , Phytophthora infestans and Verticillium lycopersici . The alcohol extract of the aerial parts exhibited insect repellent and insecticidal activities.
Finally, P. aviculare has been found to be phytotoxic in the United States and Australia, where it shows allelopathic activity in crop, pasture and weed species.
An annual, very variable, procumbent or ascending herb, 10-80 cm tall; stems much branched, grooved, glabrous. Leaves alternate, simple, oblanceolate to elliptical, 0.7-1.5 cm × 0.2-0.5 cm, base cuneate, apex acuminate to acute, both surfaces glabrous, papillose, subsessile, ocrea 2-5 mm long, glabrous, conspicuously veined, upper margin lacerate. Inflorescence an axillary, 3-6-flowered fascicle, often hidden in ocrea, bracts lacerate, glabrous. Flowers with short, jointed pedicel, actinomorphic, bisexual, small, perianth segments 5, elliptical, 2-3 mm long, apex acute, 1 main vein per tepal, sometimes branched, white to pink; stamens 8, filaments flattened, base swollen, dilated, anthers ovate, small; interstaminal nectaries absent; ovary superior, 1-ovulate, styles 3-partite. Fruit a trigonous nutlet, 2-3 mm long, puncticulate, dark brown, dull. Seedling with epigeal germination.
Growth and development
P. aviculare can be found flowering and fruiting throughout the year when enough water is available. The flavonoid content is highest at the start of flowering. Self-pollination in the open flower is the main pollination type. If this fails, pollination occurs as the perianth is closing. The flowers stay open for 1-5 days. Self-pollination in flower buds mainly takes place after a week of hot, sunny weather. Outbreeding seems to be extremely rare, and emasculation in flower buds precluds fruit formation.
Other botanical information
Polygonum s.l. has been a major challenge for taxonomists since Linnaeus established the genus as a large and loosely knit unit. After a major revision, 2 tribes within subfamily Polygonoideae were established. Tribe Persicarieae comprises the large genus Persicaria Miller, in which 4 sections are recognized, and 3 more small genera. Tribe Polygoneae comprises Polygonum , with about 20 species, and 6 small genera, one of which is Fallopia . In Polygonum , two sections are distinguished, Polygonum and Tephis , although their boundaries are not clear due to the high level of variability within the genus.
P. aviculare is a successful weedy species complex, due to the genetic polymorphism it shows, as well as the ploidy levels, and high phenotypic plasticity.
P. aviculare occurs in tropical regions in meadows and river banks, but in the temperate zone it is a weedy species. It is found from sea-level up to 3600 m altitude.
Propagation and planting
P. aviculare is a noxious weed in temperate regions because it germinates rapidly in spring and seeds may remain viable for up to 60 years. Emergence of seedlings declines with increasing depth of burial. The germination rate decreases at temperatures higher than 15C and under saline conditions. The salinity induced dormancy is alleviated by gibberellic acid.
In China, from May to July, whole plants are cut off above ground, tied in small bundles and dried in the sun.
Genetic resources and breeding
P. aviculare is a widespread weed with large genetic variation, and thus does not seem to be liable to genetic erosion. No substantial germplasm collections exist for P. aviculare .
Only general and preliminary information on the phytochemistry and pharmacology of P. aviculare is known, therefore more research is needed to explore its potential as a medicinal plant.
- Khan, M.A. & Ungar, I.A., 1998. Seed germination and dormancy of Polygonum aviculare L. as influenced by salinity, temperature and giberellic acid. Seed Science and Technology 26(1): 107-117.
- Meerts, P., 1995. Phenotypic plasticity in the annual weed Polygonum aviculare. Botanica Acta 108(5): 295-424.
- Nguyen Van Duong, 1993. Medicinal plants of Vietnam, Cambodia and Laos. Mekong Printing, Santa Ana, California, United States. p. 341.
- Ronse Decraene, L.-P. & Akeroyd, J.R., 1988. Generic limits in Polygonum and related genera (Polygonaceae) on the basis of floral characters. Botanical Journal of the Linnean Society 98: 321-371.
- Sas-Piotrowska, B., Piotrowski, W. & Misiak, M., 1996. The growth and development of potato pathogens on media with extracts of Polygonaceae plants. I. Pathogens causing dry leaf-spot disease. Phytopathologia Polonica 11: 103-109.
- Yurtseva, O.V., 1998. Self-pollination in species of Polygonum subsection Polygonum. Byulleten’ Moskovskogo Obshchestva Ispytatelei Prirody Otdel Biologicheskii 103(5): 61-67. (in Russian)
Other selected sources
- Council of Scientific and Industrial Research, 1948-1976. The wealth of India: a dictionary of Indian raw materials & industrial products. 11 volumes. Publications and Information Directorate, New Delhi, India.273, 455, 786, 788, 967.
Rina R.P. Irwanto