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Schouwia purpurea (Forssk.) Schweinf.

Protologue
Bull. Herb. Boiss. 4, append. 2: 183 (1896).
Family
Brassicaceae (Cruciferae)
Chromosome number
2n = 36
Synonyms
Schouwia schimperi Jaub. & Spach (1847), Schouwia thebaica Webb (1847).
Vernacular names
Alouât (Fr).
Origin and geographic distribution
Schouwia purpurea is distributed from Mauritania, throughout the Sahel, Sahara and northern Africa to Djibouti and Somalia; also in Arabia.
Uses
The Touareg people collect the leaves of Schouwia purpurea from the wild and eat them either cooked or dried without salt. The young leaves add an agreeable flavour to a salad, similar to that of garden rocket (Eruca vesicaria (L.) Cav.). The plant is relished by camels, green or dry, less by other livestock, and when fresh it appears to reduce the camels’ need for water. Dry plants serve as fuel.
Properties
The composition of fresh leaves and flowering tops of Schouwia purpurea as animal feed is per kg: fat 13 g, protein 70 g, mineral content 62 g (of which 17 g insoluble in HCl), P 1.8 g, N 11.3 g, C/N ratio 23.7 (Adam, J.G., 1966).
Botany
Erect, glabrous, annual herb up to 1 m tall; stem becoming woody at base, branched in upper part. Leaves alternate, simple, sessile and clasping the stem at base, rather fleshy; blade ovate, 2–6 cm × 1.5–4 cm, upper leaves gradually becoming smaller, margin sinuate-dentate to almost entire. Inflorescence corymbose when flowering, in fruit elongating to a lax raceme. Flowers bisexual, regular, 4-merous; pedicel up to 7 mm long in fruit; sepals slightly saccate at base, 5–10 mm long; petals obovate-oblong to spatulate, 7.5–15 mm × 3–5 mm, purple-violet to white; stamens 6, filaments linear, anthers mucronate at apex; ovary superior, 2-celled, stigma conical, 2-lobed. Fruit a circular silique, flattened and winged, 1.5–3.5 cm in diameter with an up to 1 cm long beak, dehiscing with 2 valves, many-seeded. Seeds globose, c. 2 mm in diameter, red-brown, rather smooth.
Schouwia comprises only one variable species. In the past 2 species were distinguished: Schouwia purpurea occurring in the western part (less woody, with smaller flowers and fruits) and Schouwia thebaica occurring in the eastern part (more woody, larger flowers and fruits). In the literature, these are sometimes distinguished as subspecies of Schouwia purpurea.
Schouwia purpurea is of entomological importance since it provides feed and shelter for the desert locust Schistocerca gregaria, which sometimes develops migrating populations of plague size and may destroy crops completely.
Ecology
Schouwia purpurea is a desert and savanna plant. It may occur in large stands after rains, from sea-level up to 1500 m altitude.
Genetic resources and breeding
Schouwia purpurea is widespread and not in danger of genetic erosion.
Prospects
Schouwia purpurea will remain a minor vegetable, which may, however, be important as a source of food and fodder in the Sahel and Sahara.
Major references
• 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.
• El Naggar, S.M. & Soliman, M.A., 1999. Biosystematic studies on Schouwia DC. (Brassicaceae) in Egypt. Flora Mediterranea 9: 175–183.
• Jafri, S.M.H., 1977. Brassicaceae. In: Ali, S.I. & Jafri, S.M.H. (Editors). Flora of Libya. Volume 23. Al Faateh University, Faculty of Science, Department of Botany, Tripoli, Libya. 205 pp.
• Jonsell, B., 1993. Brassicaceae (Cruciferae). In: Thulin, M. (Editor). Flora of Somalia. Volume 1. Pteridophyta; Gymnospermae; Angiospermae (Annonaceae-Fabaceae). Royal Botanic Gardens, Kew, United Kingdom. pp. 62–73.
Other references
• Adam, J.G., 1966. Composition chimique de quelques herbes mauritaniennes pour dromadaires. Journal d’Agriculture Tropicale et de Botanique Appliquée 13(6–7): 337–342.
• Jonsell, B., 2000. Brassicaceae (Cruciferae). In: Edwards, S., Mesfin Tadesse, Demissew Sebsebe & Hedberg, I. (Editors). Flora of Ethiopia and Eritrea. Volume 2, part 1. Magnoliaceae to Flacourtiaceae. The National Herbarium, Addis Ababa University, Addis Ababa, Ethiopia and Department of Systematic Botany, Uppsala University, Uppsala, Sweden. pp. 121–154.
• Maire, R., 1967. Dicotyledonae: Rhoedales : Cruciferae p.p. Flore de l'Afrique du Nord. Volume 13. Éditions Paul Lechevalier, Paris, France. 365 pp.
• Moggi, G., 1967. Note di floristica Africana 4. Il genere Schouwia in Africa orientale. Webbia 22: 531–538.
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, Résidence 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

Correct citation of this article:
Jansen, P.C.M., 2004. Schouwia purpurea (Forssk.) Schweinf. In: Grubben, G.J.H. & Denton, O.A. (Editors). PROTA 2: Vegetables/Légumes. [CD-Rom]. PROTA, Wageningen, Netherlands.