Portulaca oleracea (PROTA)

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Plant Resources of Tropical Africa
Introduction
List of species


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Portulaca oleracea L.




Protologue: Sp. pl. 1: 445 (1753).
Family: Portulacaceae
Chromosome number: 2n = 18, 36, 54

Synonyms

Vernacular names

Purslane, garden purslane, pigweed (En). Pourpier, pourpier potager (Fr). Beldroega, bredo fêmea (Po).

Origin and geographic distribution

Portulaca oleracea is a cosmopolitan weed occurring especially in warm areas; it occurs throughout tropical Africa. The origin of its cultivation is uncertain, possibly western Asia or India. It is one of the oldest leafy vegetables, used from Europe to Japan, Australia and the Americas. It is eaten in many African countries, e.g. Côte d’Ivoire, Benin, Cameroon, Kenya, Uganda, Angola and South Africa. It is especially popular in Sudan and Egypt, where it is known in Arabic as ‘rigla’.

Uses

The succulent stems and leaves of purslane have a mildly acidulous pleasant flavour and are eaten in green salads or as a cooked vegetable. It is occasionally pickled like gherkins or capers. The seed is also edible and is made into flour and porridge in Kenya.

Purslane has been used in folk medicine since ancient times and is included in the World Health Organization’s list of most widely used medicinal plants. It is used as a diuretic, to treat rheumatism and gynaecological diseases, as a sedative, analgesic and cardiotonic, to treat fever, disorders of the urinary tract, intestinal worm infestation, as a tonic and choleretic, to treat dysentery, and as an external treatment for ulcers, eczema and dermatitis. Ash of purslane mixed with salt is taken to treat heart diseases. Purslane is also a source of livestock fodder.

Production and international trade

Purslane is mainly collected from the wild or grown for home comsumption or local markets. Statistics on its production are rare; in Sudan it is grown on about 3000 ha.

Properties

Per 100 g edible portion (76%) purslane contains: water 93.9 g, energy 67 kJ (16 kcal), protein 1.3 g, fat 0.1 g, carbohydrate 3.4 g, Ca 65 mg, Mg 68 mg, P 44 mg, Fe 2.0 mg, Zn 0.2 mg, vitamin A 1320 IU, thiamin 0.05 mg, riboflavin 0.11 mg, niacin 0.48 mg, folate 12 μg, ascorbic acid 21 mg (USDA, 2002). The fat in the stems, leaves and seed is rich in the polyunsaturated linolenic acid. Purslane is reportedly rich in antioxidants. Oxalate and nitrate poisoning may occur if used in large quantities and people with a history of kidney stones should use it with caution. Purslane may even contain oxalates in quantities toxic to livestock. Goats given mainly or only purslane for food died within weeks. The entire plant contains the alkaloid norepinephrine. The red pigments in purslane are acylated betacyanins.

Aqueous extracts of purslane showed muscle-relaxing effects in chicken, rats and goats. Ethanolic extracts showed significant analgesic and anti-inflammatory effects. In tests with mice, a crude extract of purslane accelerated wound healing when applied topically. An ethanolic extract showed antifungal activity against Trichophyton dermatophytes. Extracts of the plant have shown antityrosinase activity and are being tested for their skin-whitening activity.

Adulterations and substitutes

Single-flowered purslane (Portulaca quadrifida L.) and waterleaf (Talinum triangulare (Jacq.) Willd.) are used as substitutes for purslane.

Description

Succulent, copiously branched, erect or prostrate annual herb; stem up to 50 cm long, glabrous but with hairs at the nodes when young, green to reddish or brownish. Leaves alternate to more or less opposite or in whorls on branchlets, simple; stipules absent; petiole 1–3 mm long; blade obovate to spatulate, 0.5–4 cm × 0.1–2 cm, cuneate at base, rounded at apex, entire. Inflorescence a sessile cluster at the branch tips, up to 8-flowered, often overtopped by branches growing from leaf axils. Flowers bisexual, regular; sepals 2, connate at base, ovate-triangular, 3–5 mm long, keeled; petals 5, adnate at base to sepals, broadly obovate, 3–8 mm long, yellow, emarginate; stamens 7–12, connate at base; ovary half-inferior, 1-celled, style with 3–6 arms. Fruit an ovoid capsule c. 4 mm long, circumscissile just below the middle, many-seeded. Seeds orbicular-reniform, 0.5–1 mm in diameter, black, smooth to tuberculate. Seedling with epigeal germination; hypocotyl 1–1.5 cm long, epicotyl absent; cotyledons elliptical-lanceolate, 5–7 mm long, succulent.

Other botanical information

Portulaca comprises about 150 species, of which about 30 occur in tropical Africa, but opinions on species delimitation differ considerably. Portulaca oleracea is variable, with diploid, tetraploid and hexaploid populations. Several subspecies have been distinguished, mainly based on seed size and seed-coat morphology. Cultivated plants have been distinguished as subsp. sativa (Haw.) Schübl. & Mart., being hexaploid (2n = 54) and having a robust, erect habit and large seeds. These can best be distinguished as a cultivar group.

Growth and development

Purslane completes its life cycle in the tropics in 2–4 months. Early growth is slow, but growth accelerates after 2 weeks. Shoots root readily at the nodes. Development seems not to be influenced by photoperiod. Flowering occurs early and year-round. Self-pollination in the bud is the rule. Fruits ripen in 7–12 days from flowering. The seed is easily dispersed by water and wind, with crop seeds or through bird droppings. Portulaca oleracea is characterized by the C4-cycle photosynthetic pathway, which means it has a high rate of photosynthesis at high light intensity and temperatures.

Ecology

Purslane is a weed of fields and disturbed localities, and occurs also in open grassland and bushland, from sea-level up to 2400 m altitude. It is usually grown as a summer crop, requiring temperatures of 15–40°C with an optimum in some cultivars as high as 35°C. Frost is not tolerated. Near the equator it is grown up to an elevation of 1800(–2400) m. Purslane requires an ample supply of water from rainfall or irrigation. It is tolerant of a wide range of soils, but prefers sand or sandy loams. It is salt tolerant.

Propagation and planting

Under natural conditions, purslane generally perpetuates itself by reseeding, but stem fragments also root easily after being cut. In cultivation, propagation is generally by seed. The seeds are very small, the 1000-seed weight being (0.1–)0.4–0.5 g, and the seed rate is about 20 kg/ha. Fresh seeds need light for germination, but this requirement disappears in older seeds. The depth of sowing markedly affects seed germination, planting at a depth over 6 cm inhibiting germination. It is recommended that the seed be sprinkled on the ground and covered lightly with compost. Planting is done in a seedbed with light soil.

Management

Because purslane is shallowly rooted and grown as a densely planted, short-duration crop, the topsoil should be of good fertility. Organic manure is recommended at a rate of 20–30 t/ha at land preparation. As topdressing 40 kg/ha of urea may be added 3 weeks after planting. Purslane requires regular watering at short intervals, 3–4 days in dry warm weather. It tolerates irrigation with saline drainage water. In Indonesia it is sometimes transplanted to a spacing of 30 cm × 30 cm and grown for a longer duration.

Purslane is often listed as one of the world’s worst weeds, although others consider it not very harmful because of its shallow rooting. It is, however, an important host plant for root-knot nematodes. When controlling it in other crops, sprayed herbicides such as glyphosate and 2,4-D can be effective, but seeds may mature in the time it takes for a herbicide to kill the plant. It can also be controlled with the more environmentally friendly corn gluten meal. Purslane rarely develops in mulched areas, and mulch placed over purslane will usually smother it.

Diseases and pests

No serious pests or diseases occur, but white rust (Albugo spp.) is common during the rainy season in Sudan. A common pest is the rigla gall weevil (Baris lanata) causing conspicuous galls. The lesser army worm (Spodoptera exigua) may attack new unfolding leaves. Whiteflies and aphids may also affect purslane.

Harvesting

Harvesting can start 3–4 weeks after sowing, and 2–3 cuts at 2–3 week intervals are possible in commercial production. Cutting should be done low to stimulate new growth. Once-over harvesting by uprooting is also done. After 6–8 weeks flowering reduces the quality of the crop.

Yield

In the tropics yields of 12–17 t/ha per crop have been reported; maximum yields reported are as high as 50 t/ha.

Handling after harvest

Purslane can be stored in plastic boxes for 2–5 days at 0–1°C and high relative humidity.

Genetic resources

The wide distribution of purslane indicates great genetic variability and flexibility, but few germplasm collections exist. In 1985 indigenous germplasm of Portulaca oleracea was collected in north-eastern Sudan.

Breeding

Usually local landraces are cultivated in Africa, but some improved cultivars with larger leaves have been selected, e.g. ‘Rumi’ grown in Sudan. In Europe types with green leaves and yellow leaves are marketed.

Prospects

Purslane is a nutritious leafy vegetable, and more attention should be given to improving production and marketing practices, e.g. production of clean rootless seedlings 6–8 cm long and packaged in trays covered with plastic film. Attention should also be given to collecting its germplasm.

Major references

  • Phillips, S.M., 2002. Portulacaceae. In: Beentje, H.J. (Editor). Flora of Tropical East Africa. A.A. Balkema, Rotterdam, Netherlands. 40 pp.
  • Rubatzky, V.E. & Yamaguchi, M., 1997. World vegetables: principles, production and nutritive values. 2nd Edition. Chapman & Hall, New York, United States. 843 pp.
  • Schippers, R.R., 2002. African indigenous vegetables, an overview of the cultivated species 2002. Revised edition on CD-ROM. National Resources International Limited, Aylesford, United Kingdom.
  • Susiarti, S., 1993. Portulaca L. In: Siemonsma, J.S. & Kasem Piluek (Editors). Plant Resources of South-East Asia No 8. Vegetables. Pudoc Scientific Publishers, Wageningen, Netherlands. pp. 227–229.
  • USDA, 2002. USDA nutrient database for standard reference, release 15. [Internet] U.S. Department of Agriculture, Beltsville Human Nutrition Research Center, Beltsville Md, United States. http://www.nal.usda.gov/fnic/foodcomp. June 2003.

Other references

  • Andrews, F.W., 1950. The flowering plants of the Anglo-Egyptian Sudan. Volume 1. Buncle, Arbroath, United Kingdom. 237 pp.
  • Benvenuti, S., Macchia, M. & Miele, J., 2001. Quantitative analysis of emergence of seedlings from burried weed seeds with increasing soil depth. Weed Sciences 49(4): 528–535.
  • Chan, K., Islam, M.W., Kamil, M., Radhakrishnan, R., Zakaria, M.N.M., Habibullah, M. & Attas, A., 2000. The analgesic and anti-inflammatory effects of Portulaca oleracea L. subsp. sativa (Haw.) Celak. Journal of Ethnopharmacology 73: 445–451.
  • Duke, J.A., Bogenschutz-Godwin, M.J., duCellier, J. & Duke, P.K., 2002. Handbook of medicinal herbs. 2nd Edition. CRC Press, Boca Raton, United States. 870 pp.
  • Ellis, D.R., Guillard, K. & Adam, R.C., 2000. Purslane as a living mulch in broccoli production. American Journal of Alternative Agriculture 15: 50–59.
  • Gbile, Z.O., 1983. Indigenous and adapted African vegetables. Acta Horticulturae 123: 71–80.
  • Grieve, C.M. & Suarez, D.L., 1997. Purslane (Portulaca oleracea L.): a halophytic crop for drainage water reuse systems. Plant and Soil 192(2): 277–283.
  • Hernández Bermejo, J.E. & León, J. (Editors), 1994. Neglected crops: 1492 from a different perspective. FAO Plant Production and Protection Series No 26. Rome, Italy. 341 pp.
  • Keay, R.W.J., 1954. Portulacaceae. In: Keay, R.W.J. (Editor). Flora of West Tropical Africa. Volume 1, part 1. 2nd Edition. Crown Agents for Oversea Governments and Administrations, London, United Kingdom. pp. 136–137.
  • Maundu, P.M., Ngugi, G.W. & Kabuye, C.H.S., 1999. Traditional food plants of Kenya. Kenya Resource Centre for Indigenous Knowledge (KENRIK), Nairobi, Kenya. 270 pp.
  • Ochse, J.J. & Bakhuizen van den Brink, R.C., 1980. Vegetables of the Dutch East Indies. 3rd English edition. Asher & Co., Amsterdam, Netherlands. 1016 pp.
  • Palaniswamy, U.R., McAvoy, R.J. & Bible, B., 2000. Leaf yield and fatty acid composition of purslane (Portulaca oleracea L.) at different growth stages. Journal of Tropical Agriculture 38: 1–4.
  • Stevels, J.M.C., 1990. Légumes traditionnels du Cameroun: une étude agrobotanique. Wageningen Agricultural University Papers 90–1. Wageningen Agricultural University, Wageningen, Netherlands. 262 pp.

Sources of illustration

  • Susiarti, S., 1993. Portulaca L. In: Siemonsma, J.S. & Kasem Piluek (Editors). Plant Resources of South-East Asia No 8. Vegetables. Pudoc Scientific Publishers, Wageningen, Netherlands. pp. 227–229.

Author(s)

  • A.E. El Jack

Department of Horticulture, Faculty of Agricultural Sciences, University of Gezira, P.O. Box 20, Wad Medani, Sudan

Correct citation of this article

El Jack, A.E., 2004. Portulaca oleracea L. [Internet] Record from PROTA4U. Grubben, G.J.H. & Denton, O.A. (Editors). PROTA (Plant Resources of Tropical Africa / Ressources végétales de l’Afrique tropicale), Wageningen, Netherlands. <http://www.prota4u.org/search.asp>.

Accessed 8 July 2021.