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3: Dye and tannin-producing plants

Bruguiera gymnorhiza (L.) Savigny

Lamk, Encycl. Méth. Bot. 4: 696 (1798).

RHIZOPHORACEAE

2n = 36 (+ 1B)

Bruguiera rheedii Blume (1827), Bruguiera cylindrica (non Blume) Hance (1879), Bruguiera conjugata Merr. (1914).

Black mangrove, Burma mangrove (En). Indonesia: tanjang (Java), putut (Sumatra). Malaysia: tumu, bakau besar (Peninsular), putut (Sarawak). Papua New Guinea: mangoro (Pidgin). Philippines: pototan (Tagalog, Bisaya), bakauan (Tagalog), siap (Ilokano). Singapore: tumu merah. Cambodia: prâsâk' nhii, prâsâk' tôôch. Thailand: pasak, pang kâ hûa sum. Vietnam: vet dzù, vet den, du'óc' hông.

Black mangrove is distributed from tropical southern and East Africa and Madagascar, through South and South-East Asia (throughout Malesia), to north-eastern Australia, Micronesia, Polynesia and the Ryukyu Islands. The South and South-East Asia area probably represents the centre of origin.

The bark is suitable for tanning leather and fishing nets as it contains up to 35% tanning substance in air-dry bark. A phlobaphene colouring matter from the bark is sometimes used as a dye in Malaysia and Vietnam for black or dark-brown colour, but this use is considered as minor.
Planks up to 7 m long can be obtained from the bole of this species, but the wood will withstand attacks by termites and teredos only up to 8 years. The timber is used for firewood and charcoal, less so for piles, house posts, rafters, fishing stakes, and telegraph poles. Poles have a life of about 10 years. The wood can be used for the paper industry, but the paper is of poor quality.
The bark is used also as condiment and adhesive, and as an astringent medicine against diarrhoea and sometimes malaria. The fruits are sometimes used as an astringent in betel quid when nothing better is available and they are suitable as an eye medicine, too. The leaves and peeled hypocotyls are eaten in times of scarcity in the Moluccas after having been soaked in water and boiled. In Jakarta, formerly the starchy central part of the hypocotyl was treated with sugar for food.

The main countries producing tannin from black mangrove are East African countries, Indonesia (Kalimantan), Papua New Guinea and the Philippines. At present Borneo accounts for an important proportion of world supplies. However, no figures are available because bark and tannin from Bruguiera gymnorhiza are sold together with bark and tannin from other mangrove trees such as Rhizophora and Ceriops species, collectively called 'mangrove cutch'. In Malaysia the production of tanbark is only a secondary consideration; charcoal and fuel are more important.

As in other mangrove species, the percentage of tannin in the bark varies largely from 20% to 43% on dry weight basis, depending on age, season, and habitat. The bark of the trunk of large, aged trees is richest in tannin. The tannin belongs to the proanthocyanidins. Ellagic acid and di- and tri-o-methylellagic acid have been demonstrated in the bark. The tannin imparts a reddish colour to leather, and is often mixed with other tannins in the tanning industry. It is suitable for tanning heavy hides into sole leather.
The bark contains about 11% mucilaginous sap, which is mainly composed of arabinose, rhamnose and galactose, and also 0.05% of a mixture (5:1) of bruguierol and isobruguierol.
The wood is red-brown, heavy (about 980 kg/m³), fine-grained, and hard, but it is a refractory timber. Sapwood and heartwood are distinct. The vessels are moderately small, rays up to 10 cells wide, often more than 3 mm high, almost homogeneous.

A moderate-sized, evergreen tree up to 36 m tall; bole 40—65 cm in diameter, buttressed and with kneed pneumatophores. Bark grey to almost black, roughly fissured, usually with large corky lenticels on buttresses and base of stem. Branching mostly sympodial. Leaves decussately opposite, simple and entire, coriaceous, elliptic to oblong, 8.5—22 cm x 5—7(—9) cm; base cuneate, rarely obtuse, apex acute; nerves 9—10 pairs; petiole 2—4.5 cm long, often reddish; stipules about 4 cm long, often reddish. Flowers solitary, 3—3.5 cm long, generally nodding, with 1—2.5 cm long pedicels, which are bright red on the outside curve; calyx red to pink-red, lobes (10—)12—14(—16), tube usually ribbed at the upper part; petals 13—15 mm long, 2-lobed with acute lobes, each with 3—4 long bristles, outer margins fringed with white silky hairs especially at the base; stamens 8—11 mm long, with linear anthers, embraced by the petals, and twice the number of the petals; ovary inferior, style about 15 mm long with filiform stigma. Fruit a campanulate berry enclosed by the calyx tube, 2—2.5 cm long, 1-celled and 1(—2)-seeded. Hypocotyl cigar-shaped, slightly angular, with a blunt narrowed apex, perforating the apex of the fruit and falling with it, 15—25 cm x 1.5—2 cm.
This species belongs to Aubréville's model of architecture.

Like red mangrove (Rhizophora mucronata Poiret), black mangrove is viviparous, i.e. the seeds germinate while still attached to the tree. After the seedlings are released they fall vertically into the mud and immediately become established. It is one of the largest trees of the mangrove, and probably the longest living. In Cambodia and Vietnam it flowers abundantly in the rainy season from May to November.

Other species of the genus Bruguiera Lamk, which has 6 species altogether, are used in the same way as Bruguiera gymnorhiza. Three species are also common in mangroves in South-East Asia.
Bruguiera cylindrica (L.) Blume is extremely slow-growing. The tannin content of the thin bark is comparatively low.
The bark of Bruguiera sexangula (Lour.) Poiret is reported to contain somewhat less tannin than that of Bruguiera gymnorhiza.
Bruguiera parviflora (Roxb.) Wight & Arn. ex Griffith is not of much use for timber because of its small dimensions, and its bark is deficient in tannin.

Black mangrove is characteristic of the landward side of mangroves, usually growing on somewhat dry, well-aerated soil. It often ascends tidal parts of rivers. Sometimes it forms pure stands, but often it is associated with Rhizophora species, especially Rhizophora apiculata Blume, but also Ceriops tagal (Perr.) C.B. Robinson and Xylocarpus moluccensis (Lamk) M. Roemer. It marks the climax vegetation of littoral forests (mangroves), before the transition to land forest. It is a shade tolerant species, and able to establish itself even in pure stands of Rhizophora L. The regeneration after felling is usually scant or even absent.
Black mangrove has proved to be able to grow, flower, fruit and even regenerate in artificial fresh water swamps, as in the botanical garden in Bogor (Indonesia). In fact, it is sensitive to high salt concentrations, dying soon at concentrations above 3% NaCl.

Seedlings can be collected either from the trees or from the ground. They are equally viable. They can be planted in a nursery, and transferred to the field 3—4 months later, spacing 3 m x 1 m. This is how the tree is propagated in Cilacap (Indonesia). Seedlings develop best where the tidal range is only about 0.35 m and the salinity is 1—2.5%. Seedlings can remain alive, floating in the water, for 5—6 months, which possibly explains the large area of distribution.

The natural and artificial regeneration has never been extensively investigated. Some authors have proposed a 10-year rotation but in Malaysia a 20-year rotation has long been practised. The liana Derris trifoliata Lour. is a common weed associated with this species. Usually this weed is controlled manually, because herbicides may affect the fauna living around the trees.

Seedlings may be attacked by mangrove crabs like Scylla serrata, Sesarma meinerti, and Sesarma smithii. In Cilacap (Indonesia), plantations have suffered from caterpillars of the genus Acanthopsyche, but these pests have been controlled successfully by using Dimercon 100 at concentrations of 0.1%.

There is no particular season for harvesting. After the trees have been felled, the bark is separated from the wood and air-dried.

Chopped bark may be used directly in the tannery. The tannin can be extracted by boiling the bark in large vessels and evaporating down to a solid.

Experiments in Indonesia have shown that black mangrove can easily be planted and grown. This species might be successfully used for reafforestation in areas where mangroves have been destroyed.

Hou, D., 1958. Rhizophoraceae. In: van Steenis, C.G.G.J. (Editor): Flora Malesiana, Series 1, Vol. 5. pp. 429—493.
Pratiwi et al., 1986. Perkembangan regenerasi alam dan buatan hutan mangrove di Cilacap [The development of natural and artificial regeneration of mangrove forests in Cilacap]. Buletin Penelitian Hutan 482: 1—9.
Tomlinson, P.B., 1986. The botany of mangroves. Cambridge University Press, Cambridge. xii + 413 pp.
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Watson, J.G., 1928. Mangrove forests of the Malay Peninsula. Malayan Forest Records 6: 1—275.

Rudjiman

Rudjiman, 1991. Bruguiera gymnorhiza (L.) Savigny. In: Lemmens, R.H.M.J. and Wulijarni-Soetjipto, N. (Editors): Plant Resources of South-East Asia No 3: Dye and tannin-producing plants. PROSEA Foundation, Bogor, Indonesia. Database record: prota4u.org/prosea