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Pterocarpus santalinoides DC.

Protologue
Prodr. 2: 419 (1825).
Family
Papilionaceae (Leguminosae - Papilionoideae, Fabaceae)
Chromosome number
n = 9, 2n = 22
Origin and geographic distribution
Pterocarpus santalinoides occurs from Senegal east to the Central African Republic and DR Congo, and is also widespread in South America.
Uses
The wood is locally used for temporary construction, carpentry, sculpturing, fences and boxboard. It is also used as firewood.
Roasted seeds are edible, tasting slightly like groundnut, but raw seeds are toxic. Cooked young leaves are eaten as a vegetable; they are also added to soup. The foliage is an important forage for many kinds of livestock. The bark is locally used for dyeing textiles brownish, while the bark. exudate is occasionally used to give them a reddish colour. Pterocarpus santalinoides is occasionally planted as a shade tree for crops and to improve the soil by fixing nitrogen and litter production. It is also planted as a windbreak. The bark, roots and leaves are commonly used in medicinal preparations. Decoctions are administered externally to wounds to promote healing, and to treat haemorrhoids and fever. They are taken internally to treat bronchial complaints, amoebic dysentery, stomach-ache and sleeping sickness, to prevent abortion and ease childbirth, and as a tonic.
Properties
The heartwood is creamy white to yellowish and indistinctly demarcated from the sapwood. The texture is moderately fine. The wood is moderately lightweight, moderately soft and easy to work. It is not durable and is liable to attacks by fungi and borers.
Tannin is present in the bark and the wood. Stem extracts showed slight antimalarial activity against Plasmodium falciparum strains. The fat content of the seeds is low: less than 1%. In tests with West-African dwarf goats fed with Pterocarpus santalinoides foliage, weight gains were low, only about 8.5 g/day. The litter production is relatively low: in tests in southern Nigeria 7.3–8.1 t/ha.
Botany
Usually evergreen small tree up to 15 m tall; bole usually short, straight or more or less twisted, up to 50 cm in diameter; bark thin, bark surface greyish brown, scaly and flaking in small patches, inner bark yellowish white to pinkish with red stripes, exuding a little reddish gum on slashing; crown dense, with more or less drooping branches; twigs glabrous, with lenticels. Leaves alternate, imparipinnately compound with (5–)6–8(–9) leaflets; stipules often curved, up to 2(–3) cm long, slightly hairy; petiole (2–)3–4(–5.5) cm long, rachis (4.5–)8–11(–15.5) cm long, sparsely hairy, glabrescent; petiolules 2–5 mm long; leaflets alternate to almost opposite, ovate to elliptical, (4–)6.5–12(–14.5) cm ื (2–)3–5.5(–7) cm, base rounded to obtuse, apex shortly acuminate, papery to thinly leathery, sparsely hairy below when young but soon glabrescent, with 7–10(–15) pairs of lateral veins. Inflorescence an axillary raceme (4–)6–14(–20) cm long, short-hairy. Flowers bisexual, papilionaceous; pedicel 2–4(–5) mm long; calyx campanulate, 8.5–9.5 mm long, densely brownish hairy, with 5 triangular teeth 1.5–2.5 mm long, lower 3 teeth smaller than upper 2; corolla with clawed petals, bright yellow to orange-yellow, standard almost circular, up to 13 mm ื 15.5 mm, wings up to 15 mm long, keel up to 12 mm long; stamens 10, fused into a sheath up to 10 mm long, the upper stamen sometimes partially free; ovary superior, whitish hairy, style up to 11.5 mm long, glabrous towards the top. Fruit an almost orbicular, flattened, indehiscent pod 2.5–4.5(–6) cm in diameter, wrinkled or warty, brownish hairy, beige to pale brown, with a keel-like wing, 1(–2)-seeded. Seed kidney-shaped, 1.5–2 cm ื c. 1 cm, dark brown.
Pterocarpus santalinoides grows fast. In trials in southern Cameroon the fastest growing trees reached a height of 6.4 m and a diameter of 10.3 cm 20 months after planting. Trees flower towards the end of the dry season. Bees commonly visit the flowers and probably act as pollinators. Fruits mature 2–3 months after flowering in the rainy season. They float in water. The roots have nodules containing nitrogen-fixing bacteria, but in tests in south-eastern Nigeria nodules did not develop in seedlings.
Pterocarpus is a pantropical genus belonging to the tribe Dalbergieae; it comprises approximately 30 species of which about 15 occur in Africa, 10 in America and 5 in Asia.
Ecology
Pterocarpus santalinoides is typically found on river banks, usually on sandy and moist soils, up to 500 m altitude. It occurs in regions with an annual rainfall of about 1600 mm, and may survive dry periods of over 5 months provided that the roots can reach the ground water. It tolerates shade and seasonal waterlogging. It is locally common, and sometimes even occurs gregariously. In central C๔te d’Ivoire about 60 adult trees per km have been recorded along the Bandama river. In southern Cameroon planted trees performed well on highly acidic and aluminium toxic soils.
Management
Pterocarpus santalinoides can be propagated by seeds, stem cuttings and root cuttings. Dry seeds can be stored for longer periods. Scarification or soaking in water is recommended prior to sowing. Germination starts after 7–14 days, and the germination rate is about 70%. Trees can be managed by pollarding, coppicing and lopping.
Tests in Nigeria and Cameroon showed that Pterocarpus santalinoides has significant potential for alley cropping. Hedgerows were established using 2-month-old seedlings planted at 4 m ื 0.25 m. The hedgerows were pruned after one year at 50 cm height, in subsequent years twice a year, and interplanted with maize.
Fruits are often collected from the water surface. They are heated over a fire until the seeds appear, which are eaten roasted.
Pterocarpus santalinoides is a host plant for the bean pod borer Maruca vitrata, which is a pest of e.g. cowpea; it is a key relay host during the long dry season.
Genetic resources and breeding
There are no indications yet that Pterocarpus santalinoides is threatened by genetic erosion. However, its characteristic habitat, i.e. riparian forests, is under pressure in many regions because of transformation into agricultural land, especially for rice cultivation.
Prospects
Like several other Pterocarpus species, Pterocarpus santalinoides is a multipurpose tree that deserves more attention. It will not gain importance as a timber tree because it is too small and provides wood of moderate quality, but it has prospects for agroforestry programmes as it improves soil fertility and outcompetes weeds, as well as providing forage and fuelwood. It is an important species for soil conservation in water catchment areas. Moreover, Pterocarpus santalinoides is suitable as an ornamental tree, having showy flowers and shiny leaves.
Major references
• Burkill, H.M., 1995. The useful plants of West Tropical Africa. 2nd Edition. Volume 3, Families J–L. Royal Botanic Gardens, Kew, Richmond, United Kingdom. 857 pp.
• CAB International, 2005. Forestry Compendium. Pterocarpus santalinoides. [Internet] http://www.cabicompendium.org/ fc/datasheet.asp?ccode=ptc1sa. Accessed June 2007.
• Gautier-B้guin, D., 1992. Plantes de cueillette เ utilisation alimentaire en C๔te d’Ivoire Centrale. Boissiera 46. 341 pp.
• Rojo, J.P., 1972. Pterocarpus (Leguminosae-Papilionaceae) revised for the world. Phanerogamarum Monographiae. Volume 5. J. Cramer, Lehre, Germany. 119 pp.
• World Agroforestry Centre, undated. Agroforestree Database. [Internet] World Agroforestry Centre (ICRAF), Nairobi, Kenya. http://www.worldagroforestry.org/ Sites/TreeDBS/ aft.asp. Accessed June 2007.
Other references
• Anegbeh, P. & Tchoundjeu, Z., 2002. Nodulation in some agroforestry tree and shrub legumes grown on acid soils in Southeast Nigeria. NFT News 5(1): 2–3.
• Arbonnier, M., 2004. Trees, shrubs and lianas of West African dry zones. CIRAD, Margraf Publishers Gmbh, MNHN, Paris, France. 573 pp.
• Arigbede, O.M., Bamikole, M.A. & Babayemi, O.J., 2003. Evaluation of three forms of two indigenous multi-purpose tree species fed to West African dwarf goats. ASSET Series A: Agriculture and Environment 3(1): 33–41.
• Arodokoun, D.Y., Tamo, M., Cloutier, C. & Adeoti, R., 2003. Importance of alternative host plants for the annual cycle of the legume pod borer, Maruca vitrata Fabricius (Lepidoptera: Pyralidae), in Southern and Central Benin. Insect Science and its Application 23(2): 103–113.
• Egbe, E.A., Lapido, D.O., Nwoboshi, L.C., Swift, M.J. & Duguma, B., 1998. Potentials of Millettia thonningii and Pterocarpus santalinoides for alley cropping in humid lowlands of West Africa. Agroforestry Systems 40(3): 309–321.
• Ezeagu, I.E., Petzke, K.J., Lange, E. & Metges, C.C., 1998. Fat content and fatty acid composition of oils extracted from selected wild-gathered tropical plant seeds from Nigeria. Journal of the American Oil Chemists’ Society 75(8): 1031–1035.
• Kanmegne, J., Bayomock, L.A., Duguma, B. & Ladipo, D.O., 2000. Screening of 18 agroforestry species for highly acid and aluminium toxic soils of the humid tropics. Agroforestry Systems 49(1): 31–39.
• Keay, R.W.J., 1989. Trees of Nigeria. A revised version of Nigerian trees (1960, 1964) by R.W.J. Keay, C.F.A. Onochie and D.P. Stanfield. Clarendon Press, Oxford, United Kingdom. 476 pp.
• Neuwinger, H.D., 2000. African traditional medicine: a dictionary of plant use and applications. Medpharm Scientific, Stuttgart, Germany. 589 pp.
• Salako, F.K. & Tian, G., 2005. Litter production and soil condition under agroforestry trees in two agroecological zones of Southern Nigeria. Journal of Sustainable Agriculture 26(2): 5–21.
Author(s)
• R.H.M.J. Lemmens
PROTA Network Office Europe, Wageningen University, P.O. Box 341, 6700 AH Wageningen, Netherlands


Editors
• D. Louppe
CIRAD, D้partement Environnements et Soci้t้s, Cirad es-dir, Campus international de Baillarguet, TA C-DIR / B (Bโt. C, Bur. 113), 34398 Montpellier Cedex 5, France
• A.A. Oteng-Amoako
Forestry Research Institute of Ghana (FORIG), University P.O. Box 63, KNUST, Kumasi, Ghana
• M. Brink
PROTA Network Office Europe, Wageningen University, P.O. Box 341, 6700 AH Wageningen, 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
• J.R. Cobbinah
Forestry Research Institute of Ghana (FORIG), University P.O. Box 63, KNUST, Kumasi, Ghana
Photo editor
• G.H. Schmelzer
PROTA Network Office Europe, Wageningen University, P.O. Box 341, 6700 AH Wageningen, Netherlands

Correct citation of this article:
Lemmens, R.H.M.J., 2008. Pterocarpus santalinoides DC. In: Louppe, D., Oteng-Amoako, A.A. & Brink, M. (Editors). Prota 7(1): Timbers/Bois d’œuvre 1. [CD-Rom]. PROTA, Wageningen, Netherlands.
flowering branch
obtained from
P. Ekpe NSBP


part of flowering branch
obtained from
P. Ekpe NSBP


various parts of the tree
obtained from
The Virtual Field Herbarium


wood in transverse section


wood in tangential section