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Trianthema portulacastrum L.

Protologue
Sp. pl. 1: 223 (1753).
Family
Aizoaceae
Chromosome number
2n = 26, 36
Synonyms
Trianthema monogyna L. (1767).
Vernacular names
Horse purslane, carpetweed, giant pigweed (En). Pourpier courant (Fr).
Origin and geographic distribution
Trianthema portulacastrum is distributed pantropically, including in tropical Africa, where it is widespread.
Uses
In Africa the young tops and leaves of Trianthema portulacastrum are eaten as a cooked vegetable or in soups; there are records of such use from Ghana, Cameroon and Tanzania. In India and South-East Asia it is similarly used. However, the plant may cause diarrhoea or paralysis, particularly when older leaves are eaten. When used as a fodder, it can produce similar effects and most domestic animals refuse to eat it. The seeds are harmful contaminants in food grains and other crop seeds. The plant has a potential value as a source of organic matter. The roots have cathartic and stomachic properties and in Africa, the Philippines, Thailand and India they are used to relieve obstructions of the liver and to relieve asthma. In Asia they are given as an emmenagogue, and in large doses as an abortifacient. The leaves are diuretic and are applied in the treatment of oedema, jaundice, painful discharge of urine and dropsy. A decoction of the herb is used as a vermifuge and is useful in rheumatism; it is considered an antidote to alcoholic poisoning. The fleshy nature of the leaves makes them suitable for use as a wound-dressing or poultice. In Nigeria the old leaves are used in a treatment against gonorrhoea. In Gabon a decoction of the powdered root is taken to treat venereal discharge. Dried plants are occasionally traded in local markets and by herbalists.
Properties
Trianthema portulacastrum contains the alkaloid trianthemine and the steroid ecdysterone. The flavonoid C-methylflavone has been isolated from the dichloromethane extract of the herb. The seeds contain 12.5% of a fatty oil, and the leaves contain carotene and oxalates. Pharmacological investigations of extracts of Trianthema portulacastrum revealed effects on the liver. An ethanol extract of the aerial parts showed a significant reduction of CCl4-induced chronic hepatocellular damage of Swiss albino mice. A chloroform extract showed a significant reduction of diethylnitrosoamine-induced hepatocarcinogenesis in Sprague-Dawley rats. In particular the incidence, numerical preponderance, multiplicity and size distribution of visible pre-neoplastic nodules were reduced. An ethanol extract of the plant has also shown some effects on blood pressure of guinea pigs and on their ileum. Ecdysterone is a potential chemosterilant, and possesses moulting hormone activity, giving a full pupation-response for larvae of the housefly. Trianthema portulacastrum shows allelopathic effects on other weeds and crops including sorghum, pumpkin, eggplant, radish, several pulses and wheat, by inhibiting seed germination and vigour of seedlings. Interestingly, it is also autotoxic as plant extracts reduce its seed germination, shoot length and vigour.
Botany
An annual, prostrate or ascending, succulent herb up to 60 cm tall, often much branched, glabrous or finely pubescent, with a firm taproot. Leaves opposite, simple, those of the same pair very unequal in size; stipules small; petiole 0.5–3 cm long, dilated and sheathing at the base, pairwise connate into a funnel-shaped sheath; blade ovate-obovate to obcordate-oblong, 1–5 cm Χ 0.5–4.5 cm, entire, purple or green. Flowers solitary, axillary, the lower part hidden by the sheath, bisexual, regular, pale pink, rarely white; perianth 5-lobed, 4–5 mm long, tube fused with the petiolar sheath, with the 2 pointed bracteoles, and with the stem, lobes obtuse with a long dorsal but almost apical mucro; stamens 10–25, filaments white, glabrous; ovary superior, turbinate, truncate, 1-celled, style c. 1.5 mm long, unilaterally stigmatose throughout its length. Fruit a circumscissile capsule 5 mm Χ 3 mm, partly exserted from the persistent perianth, 2–8 -seeded. Seeds reniform, 1.5–2.5 mm long, with faint wavy ribs, black. Seedling with epigeal germination.
Trianthema comprises about 17 species and is closely related to Sesuvium and Cypselea. These 3 genera are thought to link the Aizoaceae to the Portulacaceae.
The production of flowers and seeds of Trianthema portulacastrum starts 20–30 days after germination of the seeds.
Ecology
Trianthema portulacastrum is a common weed in fields and in open, sunny localities such as roadsides; it is often found on clayey soils near the sea, up to 200 m altitude.
Management
Seeds of Trianthema portulacastrum germinate between 20°C and 45°C, with an optimum at 35°C. More than 50% of fresh seeds germinate within 4–8 days of incubation. When stored under field conditions, germination increases during 7–8 months. Optimum sowing depth is 1 cm.
Trianthema portulacastrum is often an aggressive weed. It can be controlled either by uprooting the plants before flowering, or by spraying e.g. the mycoherbicide Gibbago trianthemae or the herbicide Fernoxone. It is a host for aubergine mosaic virus, tobacco mosaic virus, rice tungro bacilliform virus, rice tungro spherical virus, cucumber mosaic virus and watermelon mosaic virus. It is attacked by trianthema mosaic virus, which causes distinct necrotic lesions on the leaves; this virus may also attack several other weeds and tobacco. It is also attacked by fungi such as Macrophomina phaseolina, causing dry root rot, and by Colletotrichum capsici, Fusarium semitectum, Drechslera spp. and Stemphylium spp., all of which cause leaf spot diseases.
Genetic resources and breeding
Trianthema portulacastrum is extremely widespread and occurs in anthropogenic habitats, which means that there is no risk of genetic erosion. Much effort is made to eradicate it as a noxious weed, but it seems well able to survive since it is resistant to many herbicides.
Prospects
The nutritive aspects (and possible toxicity) of Trianthema portulacastrum need more investigation before its value as a vegetable can be determined. The anti-hepatotoxic effects of its extracts in cases of jaundice and alcohol poisoning are interesting. These effects merit further research, as do those of the isolated ecdysterone as a chemosterilant in pest control.
Major references
• Aguilar, N.O., 2001. Trianthema portulacastrum L. In: van Valkenburg, J.L.C.H. & Bunyapraphatsara, N. (Editors). Plant Resources of South-East Asia No 12(2): Medicinal and poisonous plants 2. Backhuys Publishers, Leiden, Netherlands. pp. 555–557.
• Burkill, H.M., 1985. The useful plants of West Tropical Africa. 2nd Edition. Volume 1, Families A–D. Royal Botanic Gardens, Kew, United Kingdom. 960 pp.
• Jeffrey, C., 1960. Notes on tropical African Aizoaceae. Kew Bulletin 14: 235–238.
• Jeffrey, C., 1961. Aizoaceae (including Molluginaceae and Tetragoniaceae). In: Hubbard, O.B.E. & Milne-Redhead, E. (Editors). Flora of Tropical East Africa. Crown Agents for Oversea Governments and Administrations, London, United Kingdom. 37 pp.
Other references
• Adamson, R.S., 1962. The South African species of Aizoaceae. 12. Sesuvium, Trianthema, Zaleya. Journal of South African Botany 28: 243–253.
• Aneja, K.R., Khan, S.A. & Kaushal, S., 2000. Management of horse purslane (Trianthema portulacastrum L.) with Gibbago trianthemae Simmons in India. In: Spencer, N.R. (Editor). Proceedings of the 10th International Symposium on Biological Control of Weeds, 4–14 July 1999, Montana State University, Bozeman, Montana, United States. pp. 27–33.
• Balyan, R.S. & Bhan, V.M., 1986. Germination of horse purslane (Trianthema portulacastrum) in relation to temperature, storage conditions, and seeding depth. Weed Science 34(4): 513–515.
• Bogle, A.L., 1970. The genera of Molluginaceae and Aizoaceae in the southeastern United States. Journal of the Arnold Arboretum 51(4): 431–462.
• Mandal, A., Karmakar, R., Bandyopadhyay, S. & Chatterjee, M., 1998. Antihepatotoxic potential of Trianthema portulacastrum in carbon tetrachloride-induced chronic hepatocellular injury in mice: reflexion in haematological, histological and biochemical characteristics. Archives of Pharmacological Research 21(3): 223–230.
• Raponda-Walker, A. & Sillans, R., 1961. Les plantes utiles du Gabon. Paul Lechevalier, Paris, France. 614 pp.
• Ravishankar, G.A. & Mehta, A.R., 1979. Control of ecdysterone biogenesis in tissue cultures of Trianthema portulacastrum (bioassay on the larvae of house-fly Musca domestica). Journal of Natural Products 42(2): 152–158.
• van den Bergh, M.H., 1993. Minor vegetables. In: Siemonsma, J.S. & Kasem Piluek (Editors). Plant Resources of South-East Asia No 8. Vegetables. Pudoc Scientific Publishers, Wageningen, Netherlands. pp. 280–310.
Sources of illustration
• Aguilar, N.O., 2001. Trianthema portulacastrum L. In: van Valkenburg, J.L.C.H. & Bunyapraphatsara, N. (Editors). Plant Resources of South-East Asia No 12(2): Medicinal and poisonous plants 2. Backhuys Publishers, Leiden, Netherlands. pp. 555–557.
Author(s)
• P.C.M. Jansen
PROTA Network Office Europe, Wageningen University, P.O. Box 341, 6700 AH Wageningen, Netherlands


Editors
• G.J.H. Grubben
Prins Hendriklaan 24, 1401 AT Bussum, Netherlands
• O.A. Denton
National Horticultural Research Institute, P.M.B. 5432, Idi-Ishin, Ibadan, Nigeria
Associate Editors
• C.-M. Messiaen
Bat. B 3, Rιsidence La Guirlande, 75, rue de Fontcarrade, 34070 Montpellier, France
• R.R. Schippers
De Boeier 7, 3742 GD Baarn, Netherlands
General editors
• R.H.M.J. Lemmens
PROTA Network Office Europe, Wageningen University, P.O. Box 341, 6700 AH Wageningen, Netherlands
• L.P.A. Oyen
PROTA Network Office Europe, Wageningen University, P.O. Box 341, 6700 AH Wageningen, Netherlands
Illustrator
• PROSEA
PROSEA Network Office, Herbarium Bogoriense, P.O. Box 234, Bogor 16122, Indonesia

Correct citation of this article:
Jansen, P.C.M., 2004. Trianthema portulacastrum L. In: Grubben, G.J.H. & Denton, O.A. (Editors). PROTA 2: Vegetables/Lιgumes. [CD-Rom]. PROTA, Wageningen, Netherlands.
1, plant habit; 2, node with flower; 3, fruit, floral tube removed; 4, seed.
Source: PROSEA