Prota 3: Dyes and tannins/Colorants et tanins
Suppl. carp. 2(2): 209, pl. 217 (1807).
White mangrove (En). Palétuvier blanc, palétuvier gris, mangle blanc, mangle gris (Fr). Mangue branco (Po).
Origin and geographic distribution
Laguncularia racemosa is found in mangrove vegetations along the Atlantic Ocean in Africa and along the coasts of the Atlantic as well as Pacific Ocean in Central and South America. In Africa it is found from Senegal to Angola.
The bark and leaves of Laguncularia racemosa produce a tannin and a brown dye of good quality, but not in quantities that are economically interesting. The bark is used to treat fishing nets for longer preservation. In experiments with bark from Caribbean samples, the bark was found to contain 12–24% tannin and the leather prepared from it was of excellent quality. Though the leaves contain 10–20% tannin they are browsed by camels. The flowers are said to be useful in honey production and in Guinea Bissau the fruits are eaten. The wood is heavy, hard, strong and close-grained; it is mainly used as firewood, rarely for construction and wooden utensils. A bark infusion is used as an astringent, tonic and folk remedy for dysentery, aphthae, fever and scurvy. It is also attributed some antitumour activity.
Neither the tannin, nor the dye appear to have been investigated and characterized. Untreated poles of Laguncularia racemosa in contact with the ground served for only 2–3 years. If treated with preservatives the service time is 10 years or more. Gum exudate from the bark contains sugars (galactose, arabinose and rhamnose), galacturonic acid, glucuronic acid and its 4-O-methyl ether. The gum is similar to that of many Combretum species, giving acidic solutions, with low nitrogen content and high rhamnose content after acidic hydrolysis. The gum has been used in combination with agar as a cheap substrate for in vitro fungi cultures.
Shrub up to 3 m tall, or occasionally tree up to 25 m tall with bole up to 70 cm in diameter, irregularly branched, sometimes with pneumatophores, with rough, fissured, grey bark exuding a gum when wounded. Leaves decussately opposite, simple and entire, somewhat fleshy, glabrous; stipules absent; petiole 1–2 cm long, slightly grooved above, bearing 2 circular glands near the apex; blade elliptical to obovate, 5–10 cm × 3–6 cm, base truncate, apex rounded to slightly emarginate, usually with small glandular dots below. Inflorescence a spike aggregated into a loose terminal panicle. Flowers unisexual or bisexual, regular, 5-merous, 4–5 mm in diameter; receptacle cup-shaped with small acute calyx lobes, hairy; petals free, circular, c. 1 mm in diameter, whitish green, early falling, hairy outside; stamens 10; disk conspicuous; ovary inferior, 1-celled, style simple, 1–2 mm long. Fruit a ribbed, 1-seeded nut c. 2 cm long, hairy, with the persistent remains of the calyx at apex. Seed with spongy seed coat. Seedling with epigeal germination.
Laguncularia racemosa is the only species of the genus and can be recognized by its opposite, bluntly obovate, somewhat fleshy leaves with a pair of conspicuous glands on the petiole just below the blade. It is much branched, but many branches are aborted resulting in numerous dead or dying branches. It is predominantly dioecious, but bisexual individuals are also found. Flowering starts when plants are about 2 years old and occurs all year round; pollination is by insects. Fruiting is abundant and usually a carpet of seedlings is produced but most seedlings die in the first year. The fruits are dispersed by water. Most glands on the leaf blade function as salt glands and the salt solution may crystallize so rapidly that crystals are extruded in chains from the mouth of the gland.
Laguncularia racemosa is typically restricted to the landward fringe of mangrove vegetations, and it is also a pioneer on disturbed sites where it can form pure stands. For good growth it needs full light.
Laguncularia racemosa can be propagated by seed and rooted cuttings. Vegetative propagation is important in reforestation programmes in mangrove-suitable areas. The most important factor for survival of cuttings is rooting of the shoots prior to cutting from the parent trees. Under natural conditions rooting occurs often after flooding. Rooted cuttings can even be planted in salt water and they start flowering within a year.
Genetic resources and breeding
Laguncularia racemosa is widespread and does not seem to be in danger of genetic erosion. However, in many areas mangrove vegetations, of which Laguncularia racemosa is an element, are under pressure caused by human activities.
Laguncularia racemosa will remain of minor importance as source of tannin. Its use as a fuel plant is possibly of more economic importance.
• Burkill, H.M., 1985. The useful plants of West Tropical Africa. 2nd Edition. Volume 1, Families A–D. Royal Botanic Gardens, Kew, Richmond, United Kingdom. 960 pp.
• Irvine, F.R., 1961. Woody plants of Ghana, with special reference to their uses. Oxford University Press, London, United Kingdom. 868 pp.
• Jiménez, J.A., 1985. Laguncularia racemosa (L.) Gaertn.f. White mangrove. United States Department of Agriculture, Forest Service, Southern Forest Experiment Station. SO-ITF-SM-3, New Orleans, United States. 64 pp.
• Tomlinson, P.B., 1986. The botany of mangroves. Cambridge University Press, Cambridge, United Kingdom. 413 pp.
• Académie de la Martinique, undated. La flore de la mangrove. [Internet] http://www-peda.ac-martinique.fr/svt/flor5.shtml. Accessed September 2004.
• De Pinto, G.L., Nava, M., Martinez, M. & Rivas, C., 1993. Gum polysaccharides of nine specimens of Laguncularia racemosa. Biochemical Systematics and Ecology 21(4): 463–466.
• Elster, C. & Perdomo, L., 1999. Rooting and vegetative propagation in Laguncularia racemosa. Aquatic Botany 63(2): 83–93.
• Jongkind, C.C.H., 1999. Combretaceae. Flore du Gabon. Volume 35. Muséum National d’Histoire Naturelle, Paris, France. 115 pp.
• Liben, L., 1983. Combretaceae. Flore du Cameroun. Volume 25. Muséum National d’Histoire Naturelle, Paris, France. 97 pp.
Correct citation of this article:
Jansen, P.C.M., 2005. Laguncularia racemosa (L.) C.F.Gaertn. In: Jansen, P.C.M. & Cardon, D. (Editors). PROTA 3: Dyes and tannins/Colorants et tanins. [CD-Rom]. PROTA, Wageningen, Netherlands.