Abroma augusta (PROSEA)
Abroma augusta (L.) L.f.
- Protologue: Suppl. pl.: 341 (1782) (" Ambroma , 1781").
- Family: Sterculiaceae
- Chromosome number: 2n= 16, 20, 22.
Abroma fastuosum Jacq. (1776, nom. illeg.), Theobroma augusta L. (1776), Abroma mollis DC. (1824).
- Devil's cotton, perennial Indian hemp, abroma (En). Abrome, abrome royal (Fr)
- Indonesia: kapasan (Javanese), kaworo (Sundanese), rebong pengayoh (Lampung)
- Malaysia: rami sengat
- Philippines: anabo (Ibanag, Ilokano, Tinggian, Tagalog, Bisaya), ambong (Tagalog), pakalkal (Pampango)
- Thailand: thian dam (central), thian dam luang (Chiang Mai)
- Vietnam: chi tai mèo, bông vàng.
Origin and geographic distribution
A. augusta is distributed from India throughout South-East Asia to southern China, the Solomon Islands and northern Australia. It is sometimes cultivated in India and New Guinea and experimental plantings have been set up in the Philippines and Africa (Uganda, Democratic Republic of Congo).
In the Philippines the strong bast fibre from A. augusta serves for making rope, twine, fishing lines, pouches and the like. Rope made of it is valued for its strength and is used for clotheslines, since it does not stain. In the Philippines A. augusta is also considered a substitute for rattan, and bark splits are made into products such as potholders, hampers, baskets and trays. In New Guinea the fibre is utilized for clothing, bags, hunting-nets and for lashing. Dyed, very fine fibres are used as false hair in Sumatra (Lampung). In Bali the inner bark is split into threads, yielding a fine, white yarn, which is made into lines and rope. In the Minahassa Peninsula (Sulawesi) the fibre is utilized for making nets.
The leaves are eaten as a supplementary source of food in New Guinea and India. In the Philippines and India the fresh or dried root bark is considered an emmenagogue and in Indonesia the root is used against scabies. A. augusta has been recommended for soil reclamation.
Production and international trade
In the Philippines considerable quantities of A. augusta fibre have been traded on the local market, but no export market has developed. Statistics on production and trade are not available.
The fibre obtained from A. augusta is located in the secondary phloem. The fibre content of fresh, defoliated stems is (4-)5-6.5(-8)%. The ultimate fibre cells are (1.4-)2-3(-6.4) mm long and (6-)12-20(-39) μm wide, with the lumen diameter being about one third of the total diameter. The ends of the ultimate fibre cells are tapered and sometimes forked. The cellulose content of the fibre is 75-78%. The extracted fibres, consisting of connected ultimate fibre cells, are 0.5-2.5 m long. Properly prepared fibre is fine, creamy white to golden brown, lustrous, rather silky in appearance, strong and supple. However, the fibre bundles are irregular and coarse and it is difficult to separate the bundles into individual strands. A. augusta fibre is difficult to spin, but can be used mixed with jute in the manufacture of hessian. On its own it is considered suitable for making twines and yarn for sack-cloth and it can serve as a substitute for jute ( Corchorus spp.) and hemp ( Cannabis sativa L.) fibre. The tensile strength of rope made of crude bast strips of A. augusta in the Philippines was 545 kg/cm2, whereas that of rope made of fibres that had been retted in water for about 10 days was 645 kg/cm2. The breaking length of these ropes was 5.8 and 7.7 km, respectively. When the rope made of crude strips was wetted, the tensile strength decreased by almost 50%. An important obstacle to the use of A. augusta as a source of fibre is that the plants are covered with irritating hairs, making handling very unpleasant and causing dermatitis in sensitive persons.
The seed of A. augusta yields 20% oil containing linoleic acid (72%), palmitic acid (14%), oleic acid (9.4%) and stearic acid (4%). The oil does not contain cyclopropenoid acids. Methanol extracts of leaves, stem bark and root bark of A. augusta have shown antibacterial activity.
An erect shrub or small tree, 2-4 m tall, normally branching at 1-2 m height but due to coppicing often multistemmed from the base, stem and branches with tenacious bark, smooth or armed with prickles, all parts often with prickly-pointed, irritating, stellate hairs and sometimes also with glandular hairs; orthotropic branches usually remain vegetative, flowering branches are usually plagiotropic. Leaves alternate, simple, highly variable but two main forms exist (heterophylly), lobed (often on plagiotropic branches) or unlobed (often on orthotropic branches); unlobed form with petiole up to 1.5 cm long, blade lanceolate, 16-23 cm × 9-12 cm, cordate at base, margin denticulate, palmate-pinnately veined; lobed form with petiole 10-40 cm long, blade 3-5-lobed, cordate-ovate in outline, up to 30-40 cm × 30-40 cm, base palmately 3-5-7-veined, margin irregularly dentate. Inflorescence a leaf-opposed or terminal 1-4-flowered cyme (usually only 1 flower develops); flowers pendent, 3-5 cm in diameter, bisexual, 5-merous; peduncle and pedicel 1-3 cm long each, slightly enlarging in fruit; calyx deeply divided, 5 lobes entire, triangular, about 15-20 mm × 6 mm, greenish; petals 5, spoon-shaped, 2-3.5 cm × 1 cm, base concave and white, blade dark purple, red or yellow, and ciliate; staminal tube short, apically with 5 fascicles of anthers alternating with 5 petal-like staminodes, each fascicle with 3(-4) anthers; pistil with 5-lobed, 5-celled ovary 2-3 mm long, containing numerous ovules, and 5 stigmatic style-branches 1-2.5 mm long. Fruit an obconical capsule, about 4-5 cm × 3-4 cm, base rounded, top truncate, 5-winged and angled, sometimes beaked, enveloped by the slightly enlarged calyx, densely prickly hairy, apical portion loculicidal, lateral parts septicidally dehiscent, with numerous seeds. Seed cylindrical to obovoid, 3-4 mm × 2 mm, without wings or aril, black.
Growth and development
In Java A. augusta flowers year-round. It is protogynous and allogamous, with pollination by wind and insects. The flowers fall off at the latest a day after opening. A. augusta normally spreads by seed, but when the stems are cut, new shoots may emerge from the buds in the axils of the leaf scars at the base of the plant. Suckers may also develop from lateral roots running parallel to the soil surface.
Other botanical information
The correct name for A. augusta has always been disputed. Linnaeus described this species as Theobroma augusta L. in 1776. Jacquin, also in 1776, did not agree with Linnaeus and described the plant as Abroma fastuosum Jacq., quoting Linnaeus' name as a synonym. In 1782 Linnaeus' son (L.f.) published this plant as Ambroma augusta L.f., quoting Linnaeus's and Jacquin's names as synonyms. Later many more names became involved, but most probably only these 3 names play a role in the correct naming. Most authors agree that this species is not a Theobroma L., so Abroma Jacq. or Ambroma L.f. remain. According to botanical nomenclatural rules Jacquin should have used Linnaeus' specific name " augusta " and L.f. should have used Jacquin's genus name "Abroma ". The view followed here is that the correct name is Abroma augusta (L.) L.f., assuming that L.f. made an orthographic error writing " Abroma " as " Ambroma ".
Another continuing dispute is the number of species in Abroma . Based on the presence or absence of prickles on the stems and branches, the colour of the flowers and the number of seeds in the capsules up to 3 species have been distinguished: A. augusta , unarmed, flowers red, capsule with more than 200 seeds; A. mollis DC., unarmed, flowers yellow, capsule with more than 200 seeds; A. fastuosa R.Br., armed, capsules with 50-60 seeds, only occurring on Madagascar. Here we accept the view that there is only one widespread, highly variable species, but a critical revision is needed.
The English vernacular name devil's cotton stems from the fact that Abroma fruits have the shape of cotton fruits but, due to the belief of the influence of the devil, they do not contain fibres like a cotton fruit.
The distribution area of A. augusta is characterized by mean daily temperatures of 27-30°C in the hottest months, an average annual rainfall of at least 1500 mm, and a high relative humidity. It is not suitable for areas with a marked dry season. A. augusta is not frost-hardy and it is not found at altitudes above 1100 m. It is a short-day plant. The best soils for A. augusta are fertile alluvials with a good structure and good drainage, as it does not tolerate waterlogging for a long period. However, it will also survive and grow when soil conditions are less favourable. When occurring naturally, A. augusta is found in thickets or tufts, secondary forest, waste places and village borders and along railways and roads, seemingly preferring forest edges and the banks of clearings or watercourses. As a light-loving plant, it does not occur in primary forest. In the Moluccas it occurs in dry valleys on poor, sandy locations or in fallow fields.
Propagation and planting
A. augusta can be propagated by seed, stem cuttings or suckers emerging from lateral roots. For seed propagation fresh material should be used, as seeds show low germination rates and lose viability rather quickly. Soaking may be necessary, e.g. in water for 15 minutes at 28°C. At a temperature of 33°C germination is more rapid and the final germination percentage higher than at 20-25°C. Seeds can be sown directly in the field or in nurseries for transplanting. Soil preparation before sowing is desirable, and farm manure or green manure may be incorporated. Spacings of 0.4 m × 0.4 m or 1 m × 0.2 m gave the highest yields in spacing trials in Africa, but wider spacings have been advocated in South-East Asia.
In cultivated A. augusta normally only 2 weedings are necessary, the first at about 20-30 days after sowing, the second about 1 month later.
Diseases and pests
No information exists on diseases and pests affecting A. augusta in Asia. In Uganda, however, it is very susceptible to Verticillium wilt.
A. augusta stems are harvested at flowering, 3-4 months after sowing, when fibre quality is optimal. However, if only coarse fibre suitable for cordage is to be obtained, harvesting may be done later, resulting in higher yields but a more lignified product. In the Philippines 7-8 months is considered the proper harvesting age for cordage. In the Moluccas 6-8 month-old stems are cut. The stems are coppiced at about 25 cm above the ground, as cutting at a lower height may endanger regrowth. Vigorous regrowth normally occurs, with 2-3(-5) new shoots per plant. Up to 4 harvests per year may be possible, but 1-2 harvests is most common. On good soils the plants may be harvested for 3 years, but on poor soils yields decrease sooner.
Fibre yields of A. augusta depend on a number of factors including climate, soil and whether wild or cultivated plants are involved. The average dry fibre yield for the whole economic life of a planted crop has been estimated at 700-–1000 kg/ha. A. augusta can yield 250 kg/ha seed per year.
Handling after harvest
The fibre bundles of A. augusta can be extracted by retting the whole stems (fresh or dried) or only the bark (fresh or dried). Where only the bark is retted, it is manually removed from the stems immediately after the harvest, when the bark is easiest to remove. Drying of stems or bark may be done in the open field or under shelters. Properly dried bark can be stored for several months. The required retting period depends on prevailing conditions, especially temperature, with older stems needing a longer retting period than young ones. After retting, the fibre is usually washed, dried and rubbed or beaten to make it supple and to separate the strands. Over-drying makes the fibre brittle. In South-East Asia processing practices vary. In southern Mindanao (the Philippines), for instance, harvested plants are left on the ground for about 2 days for the leaves and bristles to fall off. Then the bark is stripped from the stem and placed in water for 4-6 days, after which the fibre is washed and freed from adhering materials, dried and bundled. In the Philippines material to be used for weaving is prepared by splitting the bark in the same way as rattan and drying the strips in the sun. In Lampung (Sumatra) stems are retted for 10-15 days, after which the outer bark is washed off and the fibres are pulled off the wood. After drying, the fibre ribbons are divided into strips of the desired width. In Bali stems and thick branches are buried in mud for 2-3 days after which the outer bark is scraped off. In Buru (Moluccas) the stems are soaked and the bast is pulled off, retted in water until the outer bark starts to rot, cleaned, washed and dried. In North Sulawesi the stems are laid in the mud until the bast comes loose, usually after about 3 days, after which it is retted in running water and cleaned. In Central Sulawesi the green bark is scraped off the stems with a knife and the white fibre layer is pulled off the wood, dried in the sun, and twisted into rope.
Genetic resources and breeding
No germplasm collections or breeding programmes of A. augusta are known to exist. Priorities in any future breeding programme should be higher yields and the development of cultivars without irritating hairs.
A. augusta yields a strong fibre suitable for cordage and will remain useful for this purpose locally. It has been proposed from time to time as a promising perennial source of bast fibre, avoiding the labour and costs involved in growing annual bast fibre crops. However, the presence of irritating hairs all over the plant and the relatively low yields make an increase in the importance of its fibre very unlikely.
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N.O. Aguilar, P.C.M. Jansen & M. Brink