Prota 3: Dyes and tannins/Colorants et tanins
Revis. gen. pl. 2: 458 (1891).
Scrophulariaceae (APG: Orobanchaceae)
Origin and geographic distribution
Alectra sessiliflora is widespread and found all over tropical Africa and subtropical southern Africa, through the Indian Ocean islands to tropical Asia.
The yellow to orange flowers and roots (haustoria) of Alectra sessiliflora have been used by rural people in South Africa to dye cloths and other textiles. In DR Congo a golden yellow dye is extracted which is used for colouring wood. In traditional medicine in Tanzania leaf sap is taken to hasten childbirth and plant ash mixed with castor oil is rubbed onto scars caused by leprosy. A root decoction is used as a mouthwash against toothache and given to small children to treat diarrhoea. In DR Congo macerated fresh plants are eaten by pregnant women as a galactagogue, and a leaf decoction is used against kwashiorkor (severe malnutrition in children resulting from a diet excessively high in carbohydrates and low in protein).
Erect, annual herb up to 60 cm tall, with straight, simple or branched, hairy stem. Leaves opposite, simple; stipules absent; petiole up to 3 mm long; blade circular to ovate or lanceolate, 1.55.5 cm Χ 13 cm, base cuneate, rounded or cordate, apex acute or obtuse, margin almost entire to coarsely toothed, rigid-hairy to almost glabrous. Flowers solitary in axils of upper leaves, bisexual, slightly zygomorphic, sessile or with pedicel up to 0.5(1.5) mm long; bracteoles linear to filiform; calyx campanulate, 68 mm long, 10-veined, 5-lobed with triangular lobes 35 mm long; corolla campanulate, slightly longer than calyx, pale yellow to dull orange, sometimes with reddish veins, withering but not falling off; stamens 4, 2 longer ones with long-hairy filaments; ovary superior, glabrous, 2-celled, style clavate above the middle, recurved, included with stamens in corolla. Fruit a globose capsule c. 5.5 mm in diameter, glabrous, many-seeded. Seeds linear to clavate, small.
Alectra comprises 3040 species and is distributed pantropically, with about 30 species in tropical Africa. Alectra sessiliflora is very variable and might turn out to be a complex of species. Three varieties have been distinguished, mainly based on differences in leaves and in degree of pubescence of several parts.
Alectra sessiliflora is a hemiparasitic weed on the roots of Asteraceae, grasses and a number of crops (e.g. groundnut, maize, sugar cane). Seeds require a chemical stimulant from the host roots in order to germinate. The temperature also plays an important role for successful germination. Alectra sessiliflora is at least partly dependent on the host for minerals and water, and it can become a serious pest in crops.
Alectra sessiliflora is found in grassland and cultivation areas, from sea-level up to 2500 m altitude.
Genetic resources and breeding
Alectra sessiliflora is very widespread and not in danger of genetic erosion.
Most probably Alectra sessiliflora will remain only very locally of some importance as a dye source. Its medicinal properties need further investigation for evaluation.
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Correct citation of this article:
Jansen, P.C.M., 2005. Alectra sessiliflora (Vahl) Kuntze In: Jansen, P.C.M. & Cardon, D. (Editors). PROTA 3: Dyes and tannins/Colorants et tanins. [CD-Rom]. PROTA, Wageningen, Netherlands.