Schinziophyton rautanenii (PROTA)

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Plant Resources of Tropical Africa
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Schinziophyton rautanenii (Schinz) Radcl.-Sm.




Protologue: Kew Bull. 45: 157 (1990).
Family: Euphorbiaceae

Synonyms

Ricinodendron rautanenii Schinz (1898).

Vernacular names

Mogongo, mongongo, mangetti, manketti (En). Mugongo (Fr). Omunkhete, mungomo (Po).

Origin and geographic distribution

Schinziophyton rautanenii occurs from southern DR Congo, southern Tanzania and Angola south to Namibia, Botswana and northern South Africa. It is dominant or codominant in the vegetation of sand dune crests in the border area of Namibia and Angola extending eastwards to the Victoria Falls, Zambia and Zimbabwe. It is sometimes planted in southern DR Congo and Zambia. It has been planted on a trial basis in Israel, but productivity there seems to be very low.

Uses

The fruit stones (‘nuts’) were, and locally still are the staple food for a number of hunter-gatherer peoples, particularly the San Bushmen in Namibia. After removal of the fruit pulp and hard shell of the stone, the kernels are boiled in water to extract oil. Traditionally the oil is spooned off the surface of the water and kept for later use in soups. Alternatively, the kernel may be roasted on live coals or pulped. The fruit pulp, which tastes like dates but is less sweet, is eaten raw or cooked, or it is used to produce a rather strong alcoholic brew as it has a high sugar content. The remains of the kernel after oil extraction are also eaten. In some southern African countries including Namibia, the trees are cut for wood (called ‘mugongo’ in trade) for the carving industry or for cabinet making. Since the wood is very light, it is also used for fishing floats, dart- and drawing boards, as an insulating material, and for the construction of crates and coffins. In Namibia the wood is also used for the construction of ox-drawn sledges that are used to transport goods in sandy areas. In Zambia the wood is used for carpentry and to make musical instruments, curios and toys, while the seeds are used in board games. The fruit is eaten by cattle. The inner bark is used to make strings, e.g. for nets. In traditional medicine the roots have been used to treat stomach-ache.

Production and international trade

In the early 20th century fruit stones of Schinziophyton rautanenii were exported from Namibia to Great Britain and Germany, but this trade lasted for only a few years. No statistical data on production or trade of fruits, oil or timber are available.

Properties

The pulp makes up about 26% of the fresh fruit, the kernel about 9%. The nutritional composition of the fruit pulp per 100 g edible portion is: water 13.4 g, energy 1307 kJ (312 kcal), protein 6.6 g, fat 0.6 g, carbohydrate 70.2 g, fibre 3.5 g, Ca 89.6 mg, Mg 195 mg, P 46.0 mg, Fe 0.7 mg, Zn 1.4 mg, thiamin 0.28 mg, riboflavin 0.11 mg, niacin 0.12 mg, ascorbic acid 8.5 mg. The nutritional composition of the kernel per 100 g is: water 4.8 g, energy 2685 kJ (641 kcal), protein 28.8 g, fat 57.3 g, carbohydrate 2.4 g, fibre 2.7 g, Ca 452 mg, Mg 432 mg, P 839 mg, Fe 2.3 mg, Zn 3.1 mg, thiamin 0.22 mg, riboflavin 0.13 mg, niacin 0.42 mg (Wehmeier, Lee & Whiting, 1969).

Fatty acids in the oil include linoleic acid (38%), oleic acid (15%) and α-eleostearic acid (29%). In cosmetics the oil is used for its hydrating, regenerating and restructuring properties and UV protection for hair and skin. The heartwood is pale yellow to straw-coloured and indistinctly demarcated from the sapwood. The grain is straight or wavy, texture coarse. The wood air-dries rapidly with little distortion. It tends to become woolly on sawing, and sharp tools are needed to obtain a good surface. The nailing properties are good. The wood is not durable and susceptible to termite and Lyctus attack. It is permeable to impregnation with preservatives.

Description

Dioecious shrub or small to medium-sized tree up to 20 m tall; bole up to 100 cm in diameter; bark up to 5 cm thick, whitish, pale grey or pale brown, smooth at first, later flaking; crown spreading, but rounded in denser stands; twigs thick, rusty stellate pubescent when young, exuding a white gum. Leaves alternate, digitately compound, (3–)5–7-foliolate; stipules fan-shaped, 3–5 mm × 2–3 mm, early caducous, glandular; petiole 6–25 cm long, with 2–4 prominent, usually apical glands; petiolules 0.5–1.5 cm long; leaflets elliptical-ovate to oblanceolate, rarely 3-lobed, median one 5–18 cm × 2–9 cm, lateral ones slightly smaller, base rounded to cuneate, apex obtuse to acute or shortly acuminate, entire, with glandular dots along edges, densely rusty stellate pubescent above but glabrescent, paler and longer hairy below, lateral veins in 6–16 pairs. Inflorescence a terminal panicle; bracts bristle-like or awl-shaped, 3–10 mm long; male inflorescence 10–22 cm × 4–8 cm; female inflorescence 5–6 cm × 2–3 cm. Flowers unisexual, regular, 5-merous, pale yellow to white; male flowers with pedicel 2–5 mm long, calyx lobes elliptical-oblong, c. 5 mm × 2–3 mm, stellate pubescent on both sides, petals elliptical-oblong, 6–7 mm × 2–3 mm, emarginate at apex, glabrous except at base inside, stamens 13–21, united at base; female flowers with pedicel 7–10 mm long, calyx lobes broadly ovate, 8–9 mm × 5–6 mm, stellate pubescent on both sides, petals elliptical-oblong, c. 9 mm × 4 mm, emarginate at apex, glabrous, disk shallowly cup-shaped, c. 4 mm in diameter, ovary superior, densely stellate pubescent, 1(–2)-celled, style c. 5 mm long, bifid. Fruit an ovoid-ellipsoid drupe up to 7 cm × 5 cm, green, turning grey-yellow, glabrescent, 1(–2)-seeded; wall of stone (endocarp) thick and hard, pitted. Seed compressed-ellipsoid, 2–2.5 cm × 1.5–2 cm, ridged.

Other botanical information

Schinziophyton consists of only a single species. It is related to Ricinodendron heudelotii (Baill.) Pierre ex Heckel, which differs in its sessile leaflets or slightly fused at base, larger, persistent stipules and fruits containing 2 or 3 thin-walled stones.

Growth and development

When the seed has germinated, the radicle grows slowly. When it is 5–10 cm long, 5–12 secondary roots emerge in a ring from immediately above the root-tip, resembling a Medusa’s head. When these roots are 20–50 mm long the plumule starts to emerge. The growth from seedling to sapling stage depends very much on the fire regime prevailing in the area. Fires reduce young saplings back to ground level as long as their bark is too thin to protect them. Trees may start flowering and fruiting when about 20 years old, and can live up to 100 years. Regular watering may speed up their development. Trees are leafless from March–May to October–November and flower in September–December, just before the onset of the rains. Fruits drop from April–May onwards when still green and ripen on the ground, turning rusty brown. Most stones contain a single seed, but around 5% of the nuts contain 2 seeds and 10% no seed. Strong winds often cause immature fruits to drop. Fruits are eaten by elephant and ostrich, and they may disperse the seeds. Due to the high sugar contents of the flesh, the fruits are often picked up and chewed by antelope and porcupine who will carry them shorter distances.

Ecology

Schinziophyton rautanenii occurs in deciduous woodland and grassland with scattered trees, sometimes in pure stands. In the area where it occurs the mean annual temperatures are about 20°C, and the maximum daily temperatures often exceed 30°C; the plant tolerates light frost, but temperatures below 7°C kill seedlings. Schinziophyton rautanenii occurs at 200–1500 m altitude and grows well when the annual rainfall is 200–1000 mm. It is always found on deep sands with a 94–99% fine sand component. In the Namib desert it commonly occurs on crests of sand dunes; it is rarely found on calcareous soils and does not occur on poorly drained or waterlogged soils. Its habitat is subject to frequent fires.

Propagation and planting

Seeds remain viable for up to 2 years when stored at 10°C. Artificial germination of the seed is difficult and has been the focus of several studies. The natural trigger is still not known, although some improvement in germination rate has been noted when the seed has passed through the digestive system of an elephant. In nursery conditions seeds need to be scarified. Treatment with ethylene or ethephon has given ambiguous results. Seedlings seem to grow slightly faster under moderate shade. It is not clear if this is a result of low light requirement or of reduced evaporation. Under natural conditions many seedlings are found under adult trees. Here it is not clear if this is because of an accumulation of seed, or because of better growing conditions. The plants coppice well when young. Older trees that have succumbed to fire generally do not produce coppice shoots, although saplings and even seedlings will produce new shoots when the above-ground parts are damaged. Truncheons root readily and are used for propagation. A number of cases were reported where fence posts made from freshly cut posts grew into large trees.

Management

Trees of Schinziophyton rautanenii, even those from which fruit is regularly collected, receive very little care.

Harvesting

Since the fruit ripens on the ground they are simply picked up from under the trees. Harvesting starts at the end of the rainy season when fresh fruits have fallen. Gathering continues until the end of the dry season (September–November) when half of the fruits have already lost their pulp to insects. During the rainy season (November–March), when drinking water is found more easily, nuts are collected from more remote groves.

Yield

Fruit production is very closely linked to the amount of rain of the previous season, with crop yields higher in years following heavy rains. High rainfall after flowering has been found to damage the developing fruits, as do fires late in the dry season. Limited data are available on yields, although some estimates indicate yields of 200–1000 kg/ha in northern Namibia, and about 300 kg/ha in Angola.

Handling after harvest

Collected fruits are mostly cooked in an iron pot. This softens the skin and makes them easy to peel. After peeling the fruits are cooked again to separate the flesh from the stones and to turn the flesh into a rich maroon pulp ready for eating. The stones are roasted in hot embers mixed with sand to facilitate cracking; excessive heat should be avoided as it spoils the taste of the kernels. After roasting the stones are cracked between two stones and are then ready for eating. The seed coat is easily removed by hand. The kernels may also be pounded and mixed with other foods, e.g. vegetables.

Logs felled for timber should be converted and dried quickly to prevent discoloration.

Genetic resources

The Tree Seed Centre of the Directorate of Forestry, Windhoek, Namibia has accumulated a comprehensive seed collection. As Schinziophyton rautanenii is widespread and is not damaged by the collection of fruits, it does not seem to be in danger of genetic erosion.

Prospects

Because of their local abundance, reliability of supply, ease of collection and good nutritional value, the kernels of Schinziophyton rautanenii remain an important traditional source of food in the Namib desert. The fruits are only collected from wild stands and it is unlikely that they will become important outside the area where they are used traditionally.

Major references

  • Bolza, E. & Keating, W.G., 1972. African timbers: the properties, uses and characteristics of 700 species. Division of Building Research, CSIRO, Melbourne, Australia. 710 pp.
  • Graz, F.P., 2002. Description and ecology of Schinziophyton rautanenii (Schinz) Radcl.-Sm. in Namibia. Dinteria 27: 19–35.
  • Lee, R.B., 1973. Mogongo: the ethnography of a major wild food resource. Ecology of Food and Nutrition 2: 307–321.
  • Peters, C.R., 1987. Ricinodendron rautanenii (Euphorbiaceae): Zambezian wild food plant for all seasons. Economic Botany 41: 494–502.
  • Radcliffe-Smith, A., 1996. Euphorbiaceae, subfamilies Phyllantoideae, Oldfieldioideae, Acalyphoideae, Crotonoideae and Euphorbioideae, tribe Hippomaneae. In: Pope, G.V. (Editor). Flora Zambesiaca. Volume 9, part 4. Royal Botanic Gardens, Kew, Richmond, United Kingdom. pp. 1–337.
  • Wehmeyer, A.S., 1976. Ricinodendron rautanenii Schinz, Addendum 1: The nutrient composition of manketti fruit. Southern African Plants, No 4463,000–0010. Government Printer, Pretoria, South Africa.
  • Wehmeyer, A.S., Lee, R.B. & Whiting, G., 1969. The nutrient composition and dietary importance of some vegetable foods eaten by the !Kung Bushman. South African Medical Journal 43: 1528–1532.
  • World Agroforestry Centre, undated. Agroforestree Database. [Internet] World Agroforestry Centre (ICRAF), Nairobi, Kenya. http://www.worldagroforestry.org/ Sites/TreeDBS/ aft.asp. March 2005.

Other references

  • Bonifacio, E., Santonoi, S. & Zanini, E., 2000. Soil properties required by some southern Africa fruit trees as assessed by discriminant analysis. Arid Soil Research and Rehabilitation 14: 253–263.
  • Léonard, J., 1962. Euphorbiaceae. In: Robyns, W., Staner, P., Demaret, F., Germain, R., Gilbert, G., Hauman, L., Homès, M., Jurion, F., Lebrun, J., Vanden Abeele, M. & Boutique, R. (Editors). Flore du Congo belge et du Ruanda-Urundi. Spermatophytes. Volume 8, 1. Institut National pour l’Étude Agronomique du Congo belge, Brussels, Belgium. 214 pp.

Sources of illustration

  • Radcliffe-Smith, A., 1996. Euphorbiaceae, subfamilies Phyllantoideae, Oldfieldioideae, Acalyphoideae, Crotonoideae and Euphorbioideae, tribe Hippomaneae. In: Pope, G.V. (Editor). Flora Zambesiaca. Volume 9, part 4. Royal Botanic Gardens, Kew, Richmond, United Kingdom. pp. 1–337.

Author(s)

  • F.P. Graz

Polytechnic of Namibia, Private Bag 13388, Windhoek, Namibia

Correct citation of this article

Graz, F.P., 2007. Schinziophyton rautanenii (Schinz) Radcl.-Sm. [Internet] Record from PROTA4U. van der Vossen, H.A.M. & Mkamilo, G.S. (Editors). PROTA (Plant Resources of Tropical Africa / Ressources végétales de l’Afrique tropicale), Wageningen, Netherlands. <http://www.prota4u.org/search.asp>.

Accessed 24 January 2019.