Acacia tortilis (Forsk.) Hayne

Syn.: Acacia raddiana Savi,
Acacia spirocarpa Hochst. ex A. Rich
Acacia heteracantha Burch.
Mimosaceae
Umbrella Thorn, Israeli Babool

Source: James A। Duke. 1983. Handbook of Energy Crops. unpublished.

Uses

Since this is one of the few timber species of the Arabian deserts, it is suspected as being the wood from which the Biblical Ark of the Tabernacle was made. Kaplan (1979) says rather emphatically it is the Shittim of the Bible, which provided the Israelites with the large-size timbers for the Ark. The timber is also used for fenceposts, firewood, furniture, and wagonwheels. The prolific pods made good fodder for desert grazers and the foliage is also palatable, being one of the major dry season fodder trees for the Sahara-Sahelian belt. Bark, used for string in Tanganyika. Gum used as a poor man's gum arabic, said to be edible. It is the tree most recommended for reclaiming dunes in India and Africa (Roy et al, 1973). The thorny branches are used to erect temporary cages and pens. Bark said to be a good source of tannin (Roy et al, 1973). Africans once strung the pods into necklaces. Senegalese use the roots for spear shafts, Lake Chad natives use the stems for fish spears. African nomads often use the flexible roots for frameworks of their temporary shelters.

Folk Medicine

While I find few data specific to this species, I suspect that the gum is used like that of gum arabics in folk remedies. In French Guinea, the bark is used as a vermifuge and dusted onto skin ailments (Dalziel, 1937).

Chemistry

Pods contain close to 19% protein (Palmer and Pitman, 1972). NAS (1979) reports unconfirmed allegations that the foliage can be toxic to livestock. Certainly HCN has been reported in several Acacias. The following tables are reproduced, with permission, from FAO's Tropical Feeds (1981):

Nutritive tables (Gohl, 1981)

		As % of dry matter
	DM	CP	CF	Ash	EE	NFE	Ca	P	Ref.
Fresh leaves, South Africa		19.2	11.6	8.7	6.1	54.4	2.27	0.17	213
Pods, South Africa		17.3	24.8	5.7	3.1	49.1	0.79	0.34	213
Seeds, South Africa		37.8	10.9	5.9	6.0	39.7	0.56	0.73	213
Pod husks, South Africa		8.7	34.3	6.2	1.6	49.2	1.10	0.14	213

Acacia tortilis (Forsk.) Hayne subsp. heteracantha (Burch.) Brenan

		As % of dry matter
	DM	CP	CF	Ash	EE	NFE	Ca	P	Ref.
Fresh leaves, Sudan	90.9	13.3	9.4	9.6	8.3	59.4	4.00	0.15	64
Pods, Tanzania		12.3	22.4	5.6	1.8	57.9	0.98	0.24	166
Pods, Kenya		17.8	17.5	8.4	1.7	54.6	1.34	0.36	129

		Digestibility (%)
	Animal	CP	CF	EE	NFE	ME	Ref
Pods	Cattle	46.2	42.0	74.0	76.6	2.30	166

Acacia tortilis (Forsk.) Hayne subsp. spirocarpa (Hochst. ex A. Rich) Brenan

Description

Medium umbrella-shaped tree 4–15 m tall, often with several trunks, reduced to a small wiry shrub less than 1 m tall under extremely arid conditions. Two types of thorns abound (1) long, straight, and white, and (2) small, hooked, and brownish. Leaves up to 2.5 cm long with 4–10 pairs of pinnae, each with ca 15 pairs of minute leaflets. Flowers white, aromatic, in small clusters. Pods flat, glabrose, coiled into a spring-like array.

Germplasm

Reported from North African and Middle Eastern Centers of Diversity, Umbrella Thorn, or cvs thereof, is reported to tolerate alkalinity, drought, heat, sand, slope, and stony soils. It seems to be more frost tolerant than Prosopis juliflora, still plants less than 2 years old are easily damaged by frost. Four subspecies are known in different ecological zones: subspecies tortilis—Sahel, Middle East; subspecies raddiana—Sudan, Middle East, Sahel(2n=104); subspecies spirocarpa—Eastern Africa, Sudan; and subspecies heteracantha—Southern Africa (2n= 52). The different subspecies seem to have different ecological tolerances, which is important to consider when choosing a subspecies for plantations. (2n= 52, 104)

Distribution

Native to much of Africa and the Middle East, this species has been introduced in many arid parts of the world. Ironically, it grows faster in the Rajastan Desert of India, where used for charcoal, firewood, and fodder, than in its native Israel (Kaplan, 1979). In Malawi, this species is already scorned by the rural public because it is thorny and difficult to work with. It is being tried for fencings (Nkaonja, 1980).

Ecology

Deemed the most promising of 56 Acacia species tried at Jodhpur, India. Probably ranging from Subtropical Desert to Dry through Tropical Desert Scrub to Very Dry Forest Life Zones, umbrella tree is reported to tolerate annual precipitation of 1 to 10 dm, estimated annual temperature of 18 to 28°C, and pH of 6.5 to 8.5. This species tolerates hot, arid climates with temperatures as high as 50°C subspecies raddiana grows where minimum temperatures are close to 0°C. It is best adapted to the lowlands. It thrives where rainfall is up to 1,000 mm. However, it is also extremely drought resistant and can survive in climates with less than 100 mm annual rainfall with long, erratic dry seasons. The tree favors alkaline soils. It grows fairly well in shallow soil, less than 0.25 m deep, though it develops long lateral roots that can become a nuisance in nearby fields, paths, and roadways. In shallow soil, the plants remain shrubby and must be widely spaced to allow for their lateral root growth.

Cultivation

For good seed germination, seeds should be treated with concentrated sulphuric acid for 30 minutes (Roy et al, 1973). Artificial regeneration aiming at large-scale nursery production requires full use of the germination capacity of the available seeds. This may be achieved by sulfuric acid pretreatment, which brings about the germination of all viable seeds. Treatment with boiling water is selective and mainly breaks the dormancy of bruchid-infested seeds, some of which are no longer able to germinate. Sowing of unripe seeds without pretreatment may be called for as an emergency measure in case of very severe infestation, to achieve at least partial success. Prior to storage, seeds should be fumigated to arrest progressing deterioration of seed viability by bruchids (Karschon, 1975). NAS (1980a) recommends dipping the seed in hot water to soak overnight. Seedlings require initial weeding to facilitate faster growth. Plantations can be spaced at 3 x 3 m.

Harvesting

Firewood harvested as needed, but 10-year rotations are suggested. In Jodhupr, flower initiation is ca May-June in 3-year old trees, fruits forming in July but ripening from November through February. Since the tree coppices well, there is no need to replant after every harvest.

Yields and Economics

Eleven-year old trees in deep sandy soils at Jodhpur averaged 6.4 m tall and 14 cm DBH. In shallow sandy loams over hardpan at Pali, India, 7-year old trees (98% survival) averaged 4.8 m tall, and 10 cm DBH. In sanddunes at Barmer, India, 5-year old trees averaged 3 m tall, 7 cm DBH. An average tree yields 6 kg pods of which 2.6 kg is clean seed. One tree is said to yield 14–18 kg pods and leaves per year in India (Muthana and Arora, 1980). Acacia tortilis has been reported to yield giraffe forage at 5 MT/ha/yr.

Energy

A 12-year-old plantation in India yielded 54 MT fuel , suggest, annual returns of 4.5 MT, not a bad return for the desert (NAS, 1980a). The heartwood has calorific value of 4,400 kcals/kg, making superior firewood and charcoal. It is one of the main firewood and charcoal sources in parts of Africa, e.g. around Khartoum. Nitrogen-fixing nodules are reported in South Africa and Zimbabwe.

Biotic Factors

Bruchids often damage or destroy the seeds, on the tree or after collecting. Herbivores, tame and wild alike, are liable to graze seedlings and innovations. Trees attacked by beetles, mimosoid blights, and caterpillars. The wood is susceptible to termites. In Tanzania, elephants which eat the bark are wiping out some park populations. In Israel, the native Acacias host several species (>40) of mostly monophagous insects, whereas on one exotic, Australian Acacia saligna, only a few polyphagous species occur (Halperin, 1980). Only Microcerotermes diversus and Kalotermes flavicollis, which feed on woody parts of both Acacias and Apate monachus (a beetle which tunnels the stems and branches, causing them to collapse in windblow), may seriously damage the tree. In nature, regeneration and spread of Acacias are probably limited by bruchids destroying much of the seed crop. Seedlings from natural regeneration may come from damaged seeds with a still intact embryo axis, since seedcoat dormancy is removed by the effect of exit holes permitting rapid water absorption and germination. Intact seeds with hard impermeable seedcoats may require a long time to germinate, and probably function as a reserve to ensure the survival of the species (Karschon, 1975).

References

• Dalziel, J.M. 1937. The useful plants of west tropical Africa. The Whitefriars Press, Ltd., London and Tonbridge.
  
• Gohl, B. 1981. Tropical feeds. Feed information summaries and nutritive values. FAO Animal Production and Health Series 12. FAO, Rome.
  
• Halperin, J. 1980. Forest insects and protection in the arid zones of Israel. J. Israel For. Assoc. 30(3/4):68–72.
  
• Kaplan, J. 1979. Some examples of successful use of Acacia for afforestation. J. Israel For. Assoc. 29(3/4):63–64.
  
• Karschon, R. 1975. Seed germination of Acacia raddiana Savi and A. tortilis Rayne as related to infestation by bruchids. Ag. Res. Org. Leaflet 52. Bet Dagan.
  
• Muthana, K.D. and Arora, G.D. 1980. Performance of Acacia tortilis (Forsk) under different habitats of the Indian arid zone. Ann. Arid Zone 19(1/2):110–118.
  
• N.A.S. 1979. Tropical legumes: resources for the future. National Academy of Sciences, Washington, DC.
  
• N.A.S. 1980a. Firewood crops. Shrub and tree species for energy production. National Academy of Sciences, Washington, DC.
  
• Nkaonja, R.S.W. 1980. Dryland afforestation problems in Malawi. J. Israel For. Assoc. 30(3/4):100–105.
  
• Palmer, E. and Pitman, N. 1972. Trees of Southern Africa. 3 vols. A.A. Balkemia, Cape Town.
  
• Roy, A.D., Kaul, R.N., and Gyanchand. 1973. Israeli babool a promising tree for arid and semiarid lands.

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.

Acacia tortilis (Forsk.) Hayne

Syn.: Acacia raddiana Savi,
Acacia spirocarpa Hochst. ex A. Rich
Acacia heteracantha Burch.
Mimosaceae
Umbrella Thorn, Israeli Babool

Source: James A। Duke. 1983. Handbook of Energy Crops. unpublished.

Uses

Since this is one of the few timber species of the Arabian deserts, it is suspected as being the wood from which the Biblical Ark of the Tabernacle was made. Kaplan (1979) says rather emphatically it is the Shittim of the Bible, which provided the Israelites with the large-size timbers for the Ark. The timber is also used for fenceposts, firewood, furniture, and wagonwheels. The prolific pods made good fodder for desert grazers and the foliage is also palatable, being one of the major dry season fodder trees for the Sahara-Sahelian belt. Bark, used for string in Tanganyika. Gum used as a poor man's gum arabic, said to be edible. It is the tree most recommended for reclaiming dunes in India and Africa (Roy et al, 1973). The thorny branches are used to erect temporary cages and pens. Bark said to be a good source of tannin (Roy et al, 1973). Africans once strung the pods into necklaces. Senegalese use the roots for spear shafts, Lake Chad natives use the stems for fish spears. African nomads often use the flexible roots for frameworks of their temporary shelters.

Folk Medicine

While I find few data specific to this species, I suspect that the gum is used like that of gum arabics in folk remedies. In French Guinea, the bark is used as a vermifuge and dusted onto skin ailments (Dalziel, 1937).

Chemistry

Pods contain close to 19% protein (Palmer and Pitman, 1972). NAS (1979) reports unconfirmed allegations that the foliage can be toxic to livestock. Certainly HCN has been reported in several Acacias. The following tables are reproduced, with permission, from FAO's Tropical Feeds (1981):

Nutritive tables (Gohl, 1981)

		As % of dry matter
	DM	CP	CF	Ash	EE	NFE	Ca	P	Ref.
Fresh leaves, South Africa		19.2	11.6	8.7	6.1	54.4	2.27	0.17	213
Pods, South Africa		17.3	24.8	5.7	3.1	49.1	0.79	0.34	213
Seeds, South Africa		37.8	10.9	5.9	6.0	39.7	0.56	0.73	213
Pod husks, South Africa		8.7	34.3	6.2	1.6	49.2	1.10	0.14	213

Acacia tortilis (Forsk.) Hayne subsp. heteracantha (Burch.) Brenan

		As % of dry matter
	DM	CP	CF	Ash	EE	NFE	Ca	P	Ref.
Fresh leaves, Sudan	90.9	13.3	9.4	9.6	8.3	59.4	4.00	0.15	64
Pods, Tanzania		12.3	22.4	5.6	1.8	57.9	0.98	0.24	166
Pods, Kenya		17.8	17.5	8.4	1.7	54.6	1.34	0.36	129

		Digestibility (%)
	Animal	CP	CF	EE	NFE	ME	Ref
Pods	Cattle	46.2	42.0	74.0	76.6	2.30	166

Acacia tortilis (Forsk.) Hayne subsp. spirocarpa (Hochst. ex A. Rich) Brenan

Description

Medium umbrella-shaped tree 4–15 m tall, often with several trunks, reduced to a small wiry shrub less than 1 m tall under extremely arid conditions. Two types of thorns abound (1) long, straight, and white, and (2) small, hooked, and brownish. Leaves up to 2.5 cm long with 4–10 pairs of pinnae, each with ca 15 pairs of minute leaflets. Flowers white, aromatic, in small clusters. Pods flat, glabrose, coiled into a spring-like array.

Germplasm

Reported from North African and Middle Eastern Centers of Diversity, Umbrella Thorn, or cvs thereof, is reported to tolerate alkalinity, drought, heat, sand, slope, and stony soils. It seems to be more frost tolerant than Prosopis juliflora, still plants less than 2 years old are easily damaged by frost. Four subspecies are known in different ecological zones: subspecies tortilis—Sahel, Middle East; subspecies raddiana—Sudan, Middle East, Sahel(2n=104); subspecies spirocarpa—Eastern Africa, Sudan; and subspecies heteracantha—Southern Africa (2n= 52). The different subspecies seem to have different ecological tolerances, which is important to consider when choosing a subspecies for plantations. (2n= 52, 104)

Distribution

Native to much of Africa and the Middle East, this species has been introduced in many arid parts of the world. Ironically, it grows faster in the Rajastan Desert of India, where used for charcoal, firewood, and fodder, than in its native Israel (Kaplan, 1979). In Malawi, this species is already scorned by the rural public because it is thorny and difficult to work with. It is being tried for fencings (Nkaonja, 1980).

Ecology

Deemed the most promising of 56 Acacia species tried at Jodhpur, India. Probably ranging from Subtropical Desert to Dry through Tropical Desert Scrub to Very Dry Forest Life Zones, umbrella tree is reported to tolerate annual precipitation of 1 to 10 dm, estimated annual temperature of 18 to 28°C, and pH of 6.5 to 8.5. This species tolerates hot, arid climates with temperatures as high as 50°C subspecies raddiana grows where minimum temperatures are close to 0°C. It is best adapted to the lowlands. It thrives where rainfall is up to 1,000 mm. However, it is also extremely drought resistant and can survive in climates with less than 100 mm annual rainfall with long, erratic dry seasons. The tree favors alkaline soils. It grows fairly well in shallow soil, less than 0.25 m deep, though it develops long lateral roots that can become a nuisance in nearby fields, paths, and roadways. In shallow soil, the plants remain shrubby and must be widely spaced to allow for their lateral root growth.

Cultivation

For good seed germination, seeds should be treated with concentrated sulphuric acid for 30 minutes (Roy et al, 1973). Artificial regeneration aiming at large-scale nursery production requires full use of the germination capacity of the available seeds. This may be achieved by sulfuric acid pretreatment, which brings about the germination of all viable seeds. Treatment with boiling water is selective and mainly breaks the dormancy of bruchid-infested seeds, some of which are no longer able to germinate. Sowing of unripe seeds without pretreatment may be called for as an emergency measure in case of very severe infestation, to achieve at least partial success. Prior to storage, seeds should be fumigated to arrest progressing deterioration of seed viability by bruchids (Karschon, 1975). NAS (1980a) recommends dipping the seed in hot water to soak overnight. Seedlings require initial weeding to facilitate faster growth. Plantations can be spaced at 3 x 3 m.

Harvesting

Firewood harvested as needed, but 10-year rotations are suggested. In Jodhupr, flower initiation is ca May-June in 3-year old trees, fruits forming in July but ripening from November through February. Since the tree coppices well, there is no need to replant after every harvest.

Yields and Economics

Eleven-year old trees in deep sandy soils at Jodhpur averaged 6.4 m tall and 14 cm DBH. In shallow sandy loams over hardpan at Pali, India, 7-year old trees (98% survival) averaged 4.8 m tall, and 10 cm DBH. In sanddunes at Barmer, India, 5-year old trees averaged 3 m tall, 7 cm DBH. An average tree yields 6 kg pods of which 2.6 kg is clean seed. One tree is said to yield 14–18 kg pods and leaves per year in India (Muthana and Arora, 1980). Acacia tortilis has been reported to yield giraffe forage at 5 MT/ha/yr.

Energy

A 12-year-old plantation in India yielded 54 MT fuel , suggest, annual returns of 4.5 MT, not a bad return for the desert (NAS, 1980a). The heartwood has calorific value of 4,400 kcals/kg, making superior firewood and charcoal. It is one of the main firewood and charcoal sources in parts of Africa, e.g. around Khartoum. Nitrogen-fixing nodules are reported in South Africa and Zimbabwe.

Biotic Factors

Bruchids often damage or destroy the seeds, on the tree or after collecting. Herbivores, tame and wild alike, are liable to graze seedlings and innovations. Trees attacked by beetles, mimosoid blights, and caterpillars. The wood is susceptible to termites. In Tanzania, elephants which eat the bark are wiping out some park populations. In Israel, the native Acacias host several species (>40) of mostly monophagous insects, whereas on one exotic, Australian Acacia saligna, only a few polyphagous species occur (Halperin, 1980). Only Microcerotermes diversus and Kalotermes flavicollis, which feed on woody parts of both Acacias and Apate monachus (a beetle which tunnels the stems and branches, causing them to collapse in windblow), may seriously damage the tree. In nature, regeneration and spread of Acacias are probably limited by bruchids destroying much of the seed crop. Seedlings from natural regeneration may come from damaged seeds with a still intact embryo axis, since seedcoat dormancy is removed by the effect of exit holes permitting rapid water absorption and germination. Intact seeds with hard impermeable seedcoats may require a long time to germinate, and probably function as a reserve to ensure the survival of the species (Karschon, 1975).

References

• Dalziel, J.M. 1937. The useful plants of west tropical Africa. The Whitefriars Press, Ltd., London and Tonbridge.
  
• Gohl, B. 1981. Tropical feeds. Feed information summaries and nutritive values. FAO Animal Production and Health Series 12. FAO, Rome.
  
• Halperin, J. 1980. Forest insects and protection in the arid zones of Israel. J. Israel For. Assoc. 30(3/4):68–72.
  
• Kaplan, J. 1979. Some examples of successful use of Acacia for afforestation. J. Israel For. Assoc. 29(3/4):63–64.
  
• Karschon, R. 1975. Seed germination of Acacia raddiana Savi and A. tortilis Rayne as related to infestation by bruchids. Ag. Res. Org. Leaflet 52. Bet Dagan.
  
• Muthana, K.D. and Arora, G.D. 1980. Performance of Acacia tortilis (Forsk) under different habitats of the Indian arid zone. Ann. Arid Zone 19(1/2):110–118.
  
• N.A.S. 1979. Tropical legumes: resources for the future. National Academy of Sciences, Washington, DC.
  
• N.A.S. 1980a. Firewood crops. Shrub and tree species for energy production. National Academy of Sciences, Washington, DC.
  
• Nkaonja, R.S.W. 1980. Dryland afforestation problems in Malawi. J. Israel For. Assoc. 30(3/4):100–105.
  
• Palmer, E. and Pitman, N. 1972. Trees of Southern Africa. 3 vols. A.A. Balkemia, Cape Town.
  
• Roy, A.D., Kaul, R.N., and Gyanchand. 1973. Israeli babool a promising tree for arid and semiarid lands.

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.

Acacia senegal (L.) Willd.

Syn.: Acacia verek Guill. et Perr.
Mimosaceae
Gum Arabic, Senegal Gum, Sudan Gum Arabic, Kher, Kumta

Source: James A। Duke. 1983. Handbook of Energy Crops. unpublished.

Uses

Tree yields commercial gum arabic, used extensively in pharmaceutical preparations, inks, pottery pigments, water-colors, wax polishes, and liquid gum; for dressing fabrics, giving lustre to silk and crepe; for thickening colors and mordants in calico-printing; in confections and sweetmeats. Causing partial destruction of many alkaloids including atropine, hyoscyamine, scopolamine, homatropine, morphine, apomorphine, cocaine, and physostigmine, gum arabic might be viewed as a possible antidote. Pharmaceutically used mainly in the manufacture of emulsions and in making pills and troches (as an excipient); as demulcent for inflammations of the throat or stomach and as masking agent for acrid tasting substances such as capsicum; also as a film-forming agent in peel-off masks. Its major use is in foods, for example, as suspending or emulsifying agent, stabilizer, adhesive, flavor fixative, and to prevent crystallization of sugar, etc. Used in practically all categories of processed foods (candy, snack foods, alcoholic and nonalcoholic beverages, baked goods, frozen dairy desserts, gelatins, and puddings, imitation dairy products, breakfast cereals, and fats and oils). Use levels range from less than 0.004% (40 ppm) in soups and milk products, 0.7 to 2.9% in nonalcoholic beverages, imitation dairy, and snack foods, to as high as 45% in candy products (Leung, 1980). Strong rope made from bark fibers. White wood used for tool handles, black heartwood for weaver's shuttles. The long flexible strands of surface roots provide one of the strongest of local fibers, used for cordage, well-ropes, fishing nets, horsegirdles, footropes, etc. Seeds are dried and preserved for human consumption (NAS, 1980). Young foliage makes good forage. Plants useful for afforestation of arid tracts, soil reclamation, and windbreaks (Duke, 1981a). In modern pharmacy, it is commonly employed as a demulcent in preparations designed to treat diarrhea, dysentery, coughs, throat irritation, and fevers. It serves as an emulsifying agent and gives viscosity to powdered drug materials; is used as a binding agent in making pills and tablets and particularly cough drops and lozenges. Because of its enzyme, the gum is not suitable for use in products having readily oxidizable ingredients. For example, it reduces the vitamin A content of cod liver oil by 54% within three weeks. It is incompatible with aminopyrine, morphine, vanillin, phenol, thymol, a- and b-naphthol, guiacol, cresols, creosol, eugenol, apomorphine, eserine, epinephrine, isobarbaloin, gallic acid, and tannin; also with strongly alcoholic liquids, solutions of ferric chloride and lead subacetate and strong solutions of sodium borate. It was formerly given intravenously to counteract low blood pressure after hemorrhages and surgery and to treat edema associated with nephrosis, but such practices caused kidney and liver damage and allergic reactions and have been abandoned (Morton, 1977).

Folk Medicine

The demulcent, emollient gum is used internally in inflammation of intestinal mucosa, and externally to cover inflamed surfaces, as burns, sore nipples and nodular leprosy. Also said to be used for antitussive, astringent, catarrh, colds, coughs, diarrhea, dysentery, expectorant, gonorrhea, hemorrhage, sore throat, typhoid, urinary tract (Duke and Wain, 1981).

Chemistry

Gum acacia contains neutral sugars (rhamnose, arabinose, and galactose), acids (glucuronic acid and 4-methoxyglucuronic acid), calcium, magnesium, potassium, and sodium. Its complex structure is still not completely known. Its backbone chain consists of D-galactose units, and its side chains are composed of D-glucuronic acid units with l-rhamnose or l-arabinose as end units. The molecular weight has been reported to be between 200,000 to 300,000 and as high as 600,000 (Leung, 1980).

Toxicity

Ingested orally, acacia is nontoxic. However, some people are allergic to its dust and develop skin lesions and severe asthmatic attacks when in contact with it. Acacia can be digested by rats to an extent of 71%; guinea pigs and rabbits also seem to utilize it for energy, as does man to a certain extent. Gum arabic may actually elevate serum or tissue cholesterol levels in rats (Leung, 1980).

Description

Savanna shrub or tree, up to 20 m tall, over 1.3 m in girth, spiny; bark gray to brown or blackish, scaly, rough; young branchlets densely to sparsely pubescent, soon glabrescent, crown dense; stipules not spinescent; prickles just below the nodes, either in threes up to 7 mm long, with the middle one hooked downwards and the lateral ones curved upwards, or solitary with the laterals absent; leaves bioinnate, up to 2.5 cm long; leaf-axis finely downy with 2 glands; pinnae 6–20 pairs; leaflets small, 7–25 pairs, rigid, leathery, glabrous, linear to elliptic-oblong, ciliate on margins, pale glaucous-green, apex obtuse to subacute; flowers in spikes 5–10 cm long, not very dense, on peduncles 0.7–2 cm long, normally produced with the leaves; calyx bell-shaped, glabrous, deeply toothed; corolla white to yellowish, fragrant, sessile; pod straight or slightly curved, retrap-shaped, 7.5–18 cm long, 2.5 cm wide, thin, light brown or gray, papery or woody, firm, indehiscent, glabrous, 5–6-(-15) seeded; seeds greenish-brown. Fl. Jan.–Mar.; fr. Jan.–Apr., July, Aug. or Oct. (Duke, 1981a).

Germplasm

Tree with a single central stem and a dense flat-topped crown, bark without any papery peel, rough, gray or brown, with pubescent, rarely glabrous inflorescence, and pods variable in size, rounded to somewhat pointed but not rostrate or acuminate at apex. Variety rostrata Brenan is a shrub, branching at or close to base, or a small tree, with a single stem, 1–6 m tall, with dense flattened crown, bark normally with a flaking papery peel, creamy-yellow to yellow-green or gray-brown, inflorescence axis always pubescent and pods 2–3.5 times as long as wide, rostrate or acuminate at apex. Variety leiorhachis Brenan, is always a tree with central stem, and rounded or irregular with straggling branches; bark with conspicuous yellow papery peel, and inflorescence axis always glabrous. Variety pseudoglaucophylla occurs on fixed sand duned in Africa. Assigned to the African Center of Diversity, gum arabic is reported to exhibit tolerance to alkali, drought, fire, high pH, poor soil, sand, slope, and wind. (2n=26) (Duke, 1981a)

Distribution

Widespread in tropical Africa from Mozambique, Zambia to Somalia, Sudan, Ethiopia, Kenya, and Tanzania. Cultivated in India, Nigeria, and Pakistan.

Ecology

Thrives on dry rocky hills, in low-lying dry savannas, and areas where annual rainfall is 25–36 cm. This hardy species survives many adverse conditions, and seems to be favored by low rainfall and absence of frost. Ranging from Warm Temperate Thorn through Tropical Thorn to Tropical Dry Forest Life Zones, gum arabic is reported to tolerate annual precipitation of 3.8–22.8 dm (mean of 9 cases = 12.4 dm), annual mean temperature of 16.2–27.8°C (mean of 9 cases 23.8°C), and pH of 5.0–7.7 (mean of 7 cases = 6.4), but Cheema and Qadir (1973) report 7.4–8.2.

Cultivation

In Sudan, trees are cultivated over a very large area. Best propagated from seeds which are produced once every few years, grown in Sudan, in special "gum gardens." Elsewhere, it is collected from wild trees. In Pakistan, the best period for afforestation is the early monsoon season (Apr.–Jun.). Surface sowing is recommended in mildly alkaline sandy soils. Plants can also be reproduced by shoot cuttings. Trees coppice well (NAS, 1980).

Harvesting

Gum exudes froin cracks in bark of wild trees, mostly in the dry season, with little or none in the rainy season when flowers are out. In some areas, a long strip of bark is torn off and the gum allowed to exude. In Africa, it is regularly tapped from trees which are about 6 years old by making narrow transverse incisions in bark in February and March. In about a month, tears of gum form on surface and are gathered. Trees begin to bear between 4–18 years of age and are said to yield only when they are in unhealthy state due to poor soil, lack of moisture or damaged. Attempts to improve conditions tend to reduce yield. Gum from wild trees is variable and somewhat darker colored than that from cultivated plants. Collected gum is carefully freed of extraneous matter, sorted and sometimes ripened in sun before export. Gum arabic is oderless with a bland taste, yellowish and some tears are vermiform in shape. Ripened or bleached gum occurs in rounded or ovoid tears over 2.5 cm in diameter, and in broken fragments. Tears are nearly white or pale yellow and break readily with a glassy fracture. Gum is almost completely soluble in an equal volume of water and gives a translucent, viscous, slightly acid solution, but is insoluble in 90% alcohol. Kordofan (Sudan) Gum is yellow or pinkish, has fewer cracks and is more transparent (Duke, 1981a).

Yields and Economics

Annual yields from young trees may range from 188 to 2856 g (avg. 900 g), from older trees, 379 to 6754 g (avg. 2,000 g). Gum arabic is important export product for some areas in tropical Africa and Mauritania. From Africa some genuine gum is shipped to India then to Europe and America. Between 1940 and 1950, United States imports range from 3,179–8,989 MT (Duke, 1981a) Morton (1977) reports >11,000 MT more recently.

Energy

Considered the best firewood in Mauritius and Senegal, this is not a big yielder, annual running 0.5–5 m³/ha wood, with an energy value of ca 3,500 kcal/kg. A nitrogen,fixing species, it can be used to reestablish vegetation cover in degraded areas, as well as for sand-dune fixation and wind erosion control (NAS, 1980a).

Biotic Factors

Fungi reported on this crop are Cladosporium herbarum, Fusarum sp., Ravenelia acaciae-senegalae and R. acaciocola. Many insect visitors mimic the plant, the buffalo treehopper, Stictocephala bisonia, being a good example. Spiders (Cyclops sp.) may completely cover the young growing apex. Seedlings are often grazed by gazelles, goats, and pigs (Morton, 1977).

References

• Cheema, M.S.Z.A. and Qadir, S.A. 1973. Autecology of Acacia senegal (L.) Willd. Vegetatio Vol. 27(1–3):131–162.
  
• Duke, J.A. 1981a. Handbook of legumes of world economic importance. Plenum Press. NewYork.
  
• Duke, J.A. and Wain, K.K. 1981. Medicinal plants of the world. Computer index with more than 85,000 entries. 3 vols.
  
• Leung, A.Y. 1980. Encyclopedia of common natural ingredients used in food, drugs, and cosmetics. John Wiley & Sons. New York.
  
• Morton, J.F. 1977. Major medicinal plants. C.C. Thomas, Springfield, IL.
  
• N.A.S. 1980a. Firewood crops. Shrub and tree species for energy production. National Academy of Sciences, Washington, DC.

Acacia saligna (Labill.) H.Wendl

Uses

Orange wattle is an extremely rugged tree, adaptable to barren slopes, derelict land, and exceptionally arid conditions in Australia and North Africa. It grows rapidly and is used for reclaiming eroded hillsides and wastelands and for stabilizing drift sands as well as for fuel. This is one of the best woody species for binding moving sand. It is useful for windbreaks, amenity plantings, beautification projects, and roadside stabilization in semiarid regions. The leaves, or phyllodes, are palatable to livestock when fresh or dried into hay, especially used as supplementary feed for sheep and goats. Crushed seeds have been fed to sheep without ill effects. Regrowth of established bushes is so good that Acacia saligna can be completely grazed off without harming the plants. The damaged bark exudes copious amounts of a very acidic gum that seems to show promise for use in pickles and other acidic foodstuffs (NAS, 1980).

Folk Medicine

No data observed.

Chemistry

Natal-grown bark contains up to 30.3% tannin compared to 19.1–23.0 at the Cape. The plant has given negative test for HCN.

Description

Dense, bushy shrub, usually 2–5 m tall; may grow treelike to 8 m tall with a single main stem (diameter to 30 cm). In spring its usually drooping branches are clad in beautiful and abundant yellow flowers (NAS, 1980a).

Germplasm

Reported from the Australian Center of Diversity, orange wattle, or cvs thereof, is reported to tolerate alkalinity, drought, heavy soil, poor soil, salinity, salt spray, sand, shade, slope, waterlogging, and weeds. (2n = 26)

Distribution

Acacia saligna is native to the southwestern corner of western Australia. It was introduced to South Africa in the 1840s in an attempt to stabilize the shifting sand dunes. It has also been planted in Uruguay, Mexico Israel, Iran, Iraq, Jordan, Syria, Greece, Cyprus, and North African countries (NAS, 1980a).

Ecology

Acacia saligna can grow throughout the tropical and the warm temperate regions of the world (NAS, 1980a). In its native habitat, the summer temperature ranges from about 23°–36°C, winter temperatures from 4°–9°C. The plant does not withstand frost and grows best where the winter and summer means are between 13° and 30°C respectively. Grows from near sea level to about 300 m, with isolated occurrences at higher elevations. Particularly drought hardy, it grows where annual rainfall is as low as 250 mm, though it probably does better with 350–600 mm. It grows well where annual rainfall is as high as 1,000 mm. Grows mainly on sandy, coastal plains, but is found from swampy sites and riverbanks to small, rocky hills (often granitic) and coastal slopes. It occurs on poor acid or calcareous sands, under the most dry and adverse soil conditions, in moderately heavy clays and a range of podzols (NAS, 1980a).

Cultivation

Seeds germinate readily; young plants can often be found under mature trees in the hundreds. Seedlings are easily raised in a nursery and established in the field. This species develops root suckers and coppices freely. Seeds are normally treated with boiling water, but nicking the seed coat, soaking in sulfuric acid, and exposing the seeds to dry heat are also effective (NAS, 1980a).

Harvesting

In Mediterranean countries, the fuelwood from this species is harvested on a coppice rotation system of 5–10 years (NAS, 1980).

Yields and Economics

Acacia saligna grows quickly, often reaching up to 8 m tall with a spread as great as its height in just 4 or 5 years. In very dry situations, growth rate is slower. Annual yields vary from 1.5 to 10 m³ per ha, depending on site. Because of its hardiness and profuse reproductive abilities, Acacia saligna has become a serious menace in parts of South Africa by invading and displacing indigenous vegetation. It infests water courses (sometimes decreasing the water available for irrigation), and has proved difficult to eradicate (NAS, 1980a).

Energy

Plantations for fuel have been established in some Mediterranean countries. But, according to one report from South Africa, the wood is "sappy, light, and not a popular fuelwood." The plant can withstand some shade and can be grown as an understory beneath pines or eucalypts in energy plantations or village fuel and fodder areas (NAS, 1980a). The annual litterfall of four Acacia species naturalized in the South African Cape, comprising 60% foliage and 30% reproductive structures, averages 7 MT/ha, double the value expected in evergreen scrub communities in winter rainfall regions.

Biotic Factors

Acacia saligna supports a diverse and abundant range of herbivores that cause damage to the plant. Among pests cited are Icerya purchasi (Hemiptera) and Euproctis fasciata (Lepidoptera) (NAS, 1980a) and Meloidgogyne sp. (Nematoda)

References

• N.A.S. 1980a. Firewood crops. Shrub and tree species for energy production. National Academy of Sciences, Washington, DC.

Acacia senegal (L.) Willd.

Syn.: Acacia verek Guill. et Perr.
Mimosaceae
Gum Arabic, Senegal Gum, Sudan Gum Arabic, Kher, Kumta

Source: James A। Duke. 1983. Handbook of Energy Crops. unpublished.

Uses

Tree yields commercial gum arabic, used extensively in pharmaceutical preparations, inks, pottery pigments, water-colors, wax polishes, and liquid gum; for dressing fabrics, giving lustre to silk and crepe; for thickening colors and mordants in calico-printing; in confections and sweetmeats. Causing partial destruction of many alkaloids including atropine, hyoscyamine, scopolamine, homatropine, morphine, apomorphine, cocaine, and physostigmine, gum arabic might be viewed as a possible antidote. Pharmaceutically used mainly in the manufacture of emulsions and in making pills and troches (as an excipient); as demulcent for inflammations of the throat or stomach and as masking agent for acrid tasting substances such as capsicum; also as a film-forming agent in peel-off masks. Its major use is in foods, for example, as suspending or emulsifying agent, stabilizer, adhesive, flavor fixative, and to prevent crystallization of sugar, etc. Used in practically all categories of processed foods (candy, snack foods, alcoholic and nonalcoholic beverages, baked goods, frozen dairy desserts, gelatins, and puddings, imitation dairy products, breakfast cereals, and fats and oils). Use levels range from less than 0.004% (40 ppm) in soups and milk products, 0.7 to 2.9% in nonalcoholic beverages, imitation dairy, and snack foods, to as high as 45% in candy products (Leung, 1980). Strong rope made from bark fibers. White wood used for tool handles, black heartwood for weaver's shuttles. The long flexible strands of surface roots provide one of the strongest of local fibers, used for cordage, well-ropes, fishing nets, horsegirdles, footropes, etc. Seeds are dried and preserved for human consumption (NAS, 1980). Young foliage makes good forage. Plants useful for afforestation of arid tracts, soil reclamation, and windbreaks (Duke, 1981a). In modern pharmacy, it is commonly employed as a demulcent in preparations designed to treat diarrhea, dysentery, coughs, throat irritation, and fevers. It serves as an emulsifying agent and gives viscosity to powdered drug materials; is used as a binding agent in making pills and tablets and particularly cough drops and lozenges. Because of its enzyme, the gum is not suitable for use in products having readily oxidizable ingredients. For example, it reduces the vitamin A content of cod liver oil by 54% within three weeks. It is incompatible with aminopyrine, morphine, vanillin, phenol, thymol, a- and b-naphthol, guiacol, cresols, creosol, eugenol, apomorphine, eserine, epinephrine, isobarbaloin, gallic acid, and tannin; also with strongly alcoholic liquids, solutions of ferric chloride and lead subacetate and strong solutions of sodium borate. It was formerly given intravenously to counteract low blood pressure after hemorrhages and surgery and to treat edema associated with nephrosis, but such practices caused kidney and liver damage and allergic reactions and have been abandoned (Morton, 1977).

Folk Medicine

The demulcent, emollient gum is used internally in inflammation of intestinal mucosa, and externally to cover inflamed surfaces, as burns, sore nipples and nodular leprosy. Also said to be used for antitussive, astringent, catarrh, colds, coughs, diarrhea, dysentery, expectorant, gonorrhea, hemorrhage, sore throat, typhoid, urinary tract (Duke and Wain, 1981).

Chemistry

Gum acacia contains neutral sugars (rhamnose, arabinose, and galactose), acids (glucuronic acid and 4-methoxyglucuronic acid), calcium, magnesium, potassium, and sodium. Its complex structure is still not completely known. Its backbone chain consists of D-galactose units, and its side chains are composed of D-glucuronic acid units with l-rhamnose or l-arabinose as end units. The molecular weight has been reported to be between 200,000 to 300,000 and as high as 600,000 (Leung, 1980).

Toxicity

Ingested orally, acacia is nontoxic. However, some people are allergic to its dust and develop skin lesions and severe asthmatic attacks when in contact with it. Acacia can be digested by rats to an extent of 71%; guinea pigs and rabbits also seem to utilize it for energy, as does man to a certain extent. Gum arabic may actually elevate serum or tissue cholesterol levels in rats (Leung, 1980).

Description

Savanna shrub or tree, up to 20 m tall, over 1.3 m in girth, spiny; bark gray to brown or blackish, scaly, rough; young branchlets densely to sparsely pubescent, soon glabrescent, crown dense; stipules not spinescent; prickles just below the nodes, either in threes up to 7 mm long, with the middle one hooked downwards and the lateral ones curved upwards, or solitary with the laterals absent; leaves bioinnate, up to 2.5 cm long; leaf-axis finely downy with 2 glands; pinnae 6–20 pairs; leaflets small, 7–25 pairs, rigid, leathery, glabrous, linear to elliptic-oblong, ciliate on margins, pale glaucous-green, apex obtuse to subacute; flowers in spikes 5–10 cm long, not very dense, on peduncles 0.7–2 cm long, normally produced with the leaves; calyx bell-shaped, glabrous, deeply toothed; corolla white to yellowish, fragrant, sessile; pod straight or slightly curved, retrap-shaped, 7.5–18 cm long, 2.5 cm wide, thin, light brown or gray, papery or woody, firm, indehiscent, glabrous, 5–6-(-15) seeded; seeds greenish-brown. Fl. Jan.–Mar.; fr. Jan.–Apr., July, Aug. or Oct. (Duke, 1981a).

Germplasm

Tree with a single central stem and a dense flat-topped crown, bark without any papery peel, rough, gray or brown, with pubescent, rarely glabrous inflorescence, and pods variable in size, rounded to somewhat pointed but not rostrate or acuminate at apex. Variety rostrata Brenan is a shrub, branching at or close to base, or a small tree, with a single stem, 1–6 m tall, with dense flattened crown, bark normally with a flaking papery peel, creamy-yellow to yellow-green or gray-brown, inflorescence axis always pubescent and pods 2–3.5 times as long as wide, rostrate or acuminate at apex. Variety leiorhachis Brenan, is always a tree with central stem, and rounded or irregular with straggling branches; bark with conspicuous yellow papery peel, and inflorescence axis always glabrous. Variety pseudoglaucophylla occurs on fixed sand duned in Africa. Assigned to the African Center of Diversity, gum arabic is reported to exhibit tolerance to alkali, drought, fire, high pH, poor soil, sand, slope, and wind. (2n=26) (Duke, 1981a)

Distribution

Widespread in tropical Africa from Mozambique, Zambia to Somalia, Sudan, Ethiopia, Kenya, and Tanzania. Cultivated in India, Nigeria, and Pakistan.

Ecology

Thrives on dry rocky hills, in low-lying dry savannas, and areas where annual rainfall is 25–36 cm. This hardy species survives many adverse conditions, and seems to be favored by low rainfall and absence of frost. Ranging from Warm Temperate Thorn through Tropical Thorn to Tropical Dry Forest Life Zones, gum arabic is reported to tolerate annual precipitation of 3.8–22.8 dm (mean of 9 cases = 12.4 dm), annual mean temperature of 16.2–27.8°C (mean of 9 cases 23.8°C), and pH of 5.0–7.7 (mean of 7 cases = 6.4), but Cheema and Qadir (1973) report 7.4–8.2.

Cultivation

In Sudan, trees are cultivated over a very large area. Best propagated from seeds which are produced once every few years, grown in Sudan, in special "gum gardens." Elsewhere, it is collected from wild trees. In Pakistan, the best period for afforestation is the early monsoon season (Apr.–Jun.). Surface sowing is recommended in mildly alkaline sandy soils. Plants can also be reproduced by shoot cuttings. Trees coppice well (NAS, 1980).

Harvesting

Gum exudes froin cracks in bark of wild trees, mostly in the dry season, with little or none in the rainy season when flowers are out. In some areas, a long strip of bark is torn off and the gum allowed to exude. In Africa, it is regularly tapped from trees which are about 6 years old by making narrow transverse incisions in bark in February and March. In about a month, tears of gum form on surface and are gathered. Trees begin to bear between 4–18 years of age and are said to yield only when they are in unhealthy state due to poor soil, lack of moisture or damaged. Attempts to improve conditions tend to reduce yield. Gum from wild trees is variable and somewhat darker colored than that from cultivated plants. Collected gum is carefully freed of extraneous matter, sorted and sometimes ripened in sun before export. Gum arabic is oderless with a bland taste, yellowish and some tears are vermiform in shape. Ripened or bleached gum occurs in rounded or ovoid tears over 2.5 cm in diameter, and in broken fragments. Tears are nearly white or pale yellow and break readily with a glassy fracture. Gum is almost completely soluble in an equal volume of water and gives a translucent, viscous, slightly acid solution, but is insoluble in 90% alcohol. Kordofan (Sudan) Gum is yellow or pinkish, has fewer cracks and is more transparent (Duke, 1981a).

Yields and Economics

Annual yields from young trees may range from 188 to 2856 g (avg. 900 g), from older trees, 379 to 6754 g (avg. 2,000 g). Gum arabic is important export product for some areas in tropical Africa and Mauritania. From Africa some genuine gum is shipped to India then to Europe and America. Between 1940 and 1950, United States imports range from 3,179–8,989 MT (Duke, 1981a) Morton (1977) reports >11,000 MT more recently.

Energy

Considered the best firewood in Mauritius and Senegal, this is not a big yielder, annual running 0.5–5 m³/ha wood, with an energy value of ca 3,500 kcal/kg. A nitrogen,fixing species, it can be used to reestablish vegetation cover in degraded areas, as well as for sand-dune fixation and wind erosion control (NAS, 1980a).

Biotic Factors

Fungi reported on this crop are Cladosporium herbarum, Fusarum sp., Ravenelia acaciae-senegalae and R. acaciocola. Many insect visitors mimic the plant, the buffalo treehopper, Stictocephala bisonia, being a good example. Spiders (Cyclops sp.) may completely cover the young growing apex. Seedlings are often grazed by gazelles, goats, and pigs (Morton, 1977).

References

• Cheema, M.S.Z.A. and Qadir, S.A. 1973. Autecology of Acacia senegal (L.) Willd. Vegetatio Vol. 27(1–3):131–162.
  
• Duke, J.A. 1981a. Handbook of legumes of world economic importance. Plenum Press. NewYork.
  
• Duke, J.A. and Wain, K.K. 1981. Medicinal plants of the world. Computer index with more than 85,000 entries. 3 vols.
  
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