Acacia seyal Del.

Uses

According to some Biblical scholars, the Shittah tree is mentioned in the Bible only once (I will plant in the wilderness... the Shittah tree. Isaiah 41), but its wood is referred to many times as shittium, which is the plural of shittah in Hebrew. Some even speculate that it was only natural that Moses should turn to shittium when he came to build the Ark of the Covenant and the Tabernacle and needed beams and timber. No one can really be sure which species of Acacia was meant. Wood is white to yellow-brown, finely-striated with dark lines, coarse-grained, soft, easy to work, polishes well, but discolors eastly with mold and is susceptible to insect attack. Ancient Egyptians made coffins, some still intact, from the wood. Nigerians used sapling stems, or also the roots for spear shafts. Tree also yields a gum of good quality, inferior to that of A. senegal. Systematic tapping has produced a product of better color and taste. Bark contains tannin and yields a red liquid extract. The gum is said to be edible. The leaves are important for forage and the wood for fuel where the trees are abundant. In parts of Africa the tree is important for livestock, natives driving their animals to where it is common and lopping off branches for them, both leaves and young pods being eaten. The pods are sold, especially for fattening sheep. The tree is believed to provide the best firewood in Chad, and the best fodder in Sahelian savannas (NAS, 1980a; Duke, 1983a).

Folk Medicine

The gum is believed to be aphrodisiac. The bark decoction Is used for dysentery and leprosy. Tanganyikans use the bark as a stimulant in tropical Africa. The gum is used as emollient and astringent for colds, diarrhea, hemorrhage and ophhthalmia. Mixed with Acacia sieberana DC, it is used for intestinal ailments on the Ivory Coast. Wood used as a fumigant for rheumatic pains, and to protect puerperal mothers from colds and fevers. Eating the gum is supposed to afford some protection against bronchitis and rheumatism (Duke, 1983a).

Chemistry

This species has been reported to contain 18–20% tannin.

Description

Tree 3–12 m tall, crown flat-topped; bark powdery, white to greenish-yellow or orange-red; sparsely branched, the branches horizontal or ascending; young branchlets with sparse hairs or almost glabrous, with numerous reddish sessile glands; epidermis of twigs becoming reddish and shed annually; leaves often with a large gland on petiole and between the top 1–2 pairs of pinnae; stipules spinescent, up to 8 cm long, ant-galls present or absent; pinnae usually 3–7 pairs, the leaflets in 11–20 pairs, 3–8 cm long, 0.75–1 mm wide, sparingly ciliolate or glabrous; lateral veins invisible beneath; flowers bright yellow, in axillary, pedunculate heads 10–13 mm across, borne on terminal or short lateral shoots of current season; involucel in lower half of peduncle 2–4 mm long; apex of bracteoles rounded to elliptic, sometimes pointed; calyx 2–2.5 mm long, puberulous in upper part; corolla 3.5–4 mm long, glabrous outside; pods 7–20 cm long, 0.5–0.9 cm in diameter, dehiscent, falcate, constricted between seeds, glabrous except for sessile glands, 6–9-seeded; seeds elliptic, 7–9 mm long, 4.5–5 mm wide, compressed, minutely wrinkled, olive-brown to olive; areole 5–6 mm long, 2.5–3.5 mm wide.

Germplasm

Species has several botanical varieties. The two main ones are: A. seyal var. fistula (Schweinf.) Oliv. (A. fistula Schweinf.), is white-barked with some pairs of spines fused at base into 'ant-galls', 0.8–3 cm in diameter, grayish or whitish, often marked with sienna-red and with longitudinal furrows down center, more or less 2-lobed. Found in Zambia, Malawi, and Mozambique. A. seyal var. multijuga Schweinf. ex Baker f. (A. stenocarpa Oliv., pro partem), a shrub or tree, usually less than 5 m tall, sometimes up to 13 m, flattened crown; bark on main stem greenish-brown, peeling in papery rolls; bark on branchlets red-brown, thorns straight, weak, usually less than 2.5 cm long, sometimes absent; pinnae 4–12 pairs, leaflets 10–20 pairs; flowers golden-yellow; pod narrow-linear, strongly curved, up to 10 cm long, 0.6 cm wide, dehiscing on tree. Common in overgrazed pastures and widely distributed in East Africa. Hybrids, A. seyal var. fistula X A. xanthophloea Benth., are known from woodlands on black clay loams on flood plains in Malawi. Pods are conspicuously irregular, 4–11 cm long, 6–10 mm wide, ill-formed and curved. Assigned to the Africa Center of Diversity, shittim wood or cultivars thereof is reported to exhibit tolerance to high pH, heavy soil, insects, mycobacteria, poor soil, salt, savanna, slope, and waterlogging. (2n= 26.)

Distribution

Native to the Sahelian Zone from Senegal to Sudan, it also occurs in Egypt and eastern and southern Africa, from Somalia to Mozambique and Namibia (NAS, 1980a).

Ecology

Trees thrive in Sclerocarya caffra woodlands, wooded grasslands and especially on seasonally flooded black-cotton soils along water courses. Requires a heavy clay-alluvium, but will grow on stony ground at base of hills. Grows at 20–2,100 m altitude. A gregarious savanna tree, ranging from Subtropical Desert to Dry through Tropical Desert to Very Dry Forest Life Zones, shittim wood is reported to tolerate annual precipitation of 8.7–22.8 dm (mean of 7 cases = 15.0 dm), annual mean temperature of 18.7–27.8°C (mean of 7 cases = 24.0°C) and pH of 5.0–8.0 (mean of 5 cases = 6.9).

Cultivation

Propagated from scarified seed. large cuttings are said to strike root readity in moist soils.

Harvesting

Pods, bark or wood are harvested in season from trees or shrubs in native habitats. Gum also obtained from native plantings, in manner similar to that for other gum arabic plants.

Yields and Economics

Gum and other products of some local importance in East Africa, but do not enter international trade.

Energy

The dense wood is highly prized for firewood, in areas where few other plants survive. Considered one of the best firewoods in Chad, it is used in the Sudan to make fragrant fires over which women perfume themselves.

Biotic Factors

Following fungi reported on this plant: Fomes rimosus, Ganoderma lucidum, Leveillula taurica, Ravenelia volkensii, Trametes meyenii, and Uromyces schweinfurthii. Although the plant is reportedly resistant to insect attacks, felled logs may be severely damaged by wood borers.

References

  • Duke, J.A. 1983a. Medicinal plants of the Bible. Trado-Medic Books, Owerri, NY.
  • N.A.S. 1980a. Firewood crops. Shrub and tree species for energy production. National Academy of Sciences, Washington, DC.

No comments: