Bruguiera sexangula (PROSEA)

Plant Resources of South-East Asia Introduction

List of species

Bruguiera sexangula (Lour.) Poiret

Protologue: Lamk, Encycl. Suppl. 4: 262 (1816).

Family: Rhizophoraceae

Chromosome number: 2n= unknown

Synonyms

• Rhizophora sexangula Lour. (1790),
• Bruguiera eriopetala Wight & Arnott ex Arnott (1838).

Vernacular names

• Black mangrove (En)
• Indonesia: bakau tampusing (Kalimantan), busing, mata buaya (Sumatra)
• Malaysia: berus putut (Sarawak), mata buaya (Sabah), tumu putih (Peninsular)
• Philippines: pototan (general), busain, tagasa (Tagalog)
• Burma (Myanmar): saung
• Cambodia: plaông prâsak'
• Thailand: khlak, phangka hua sum, phangahuasum-dokkhao (peninsular), prasak, prasak-nu, prasak daeng (south-eastern)
• Vietnam: vẹt, vẹt den, vẹt dù

Origin and geographic distribution

B. sexangula occurs naturally from India and Sri Lanka throughout South-East Asia to New Guinea and New Britain. It has been introduced into Hawaii, where it is now naturalized.

Uses

Fuelwood, directly or after conversion to charcoal, is probably the main use of B. sexangula, especially at the local level. Wood from immature plants and branches is usually used for this purpose. The timber of well-grown trees is moderately durable and suitable for poles and house construction. It is traditionally also used for fishing stakes. The bark is used as a source of tannin; although it is thinner than the bark of Rhizophora spp., it contains more tannin. The bark also yields a flavouring and an adhesive. In Malaysia and Indonesia the fruit is sometimes used in the betel quid. B. sexangula can be used medicinally, the fruit is applied against shingles, the roots and leaves against burns. In Sulawesi the fruit is cooked, then soaked overnight and eaten, although it is very astringent.

Production and international trade

No statistics are available on production or trade. Wood is mainly cut from wild stands.

Properties

The wood of a full-grown tree is heavy, 820-1010 kg/m³ at 15% moisture content and may have a very attractive colour. It is straightly grained and finely textured, and very strong. The wood is very hard, difficult to saw and work, and finishes well. It is non-durable when exposed to weather or in contact with the ground. Logs shrink and check excessively in seasoning. In the trade it is not distinguished from Rhizophora wood. The energy value of the wood is about 20 200 kJ/kg.

Botany

• Tree up to 33 m tall, trunk diameter up to 65-80 cm; buttresses up to 1 m high, tending to develop into plank-like non-arching stilt roots; pneumatophores knee-shaped, up to 45 cm long, forming horizontal and anchor roots.
• Bark smooth, greyish to pale brown with a few, large, corky lenticels, especially on the buttresses.
• Branching mostly sympodial.
• Leaves decussately opposite, elliptical to elliptical-oblong, rarely oblanceolate, 8-16 cm × 3-6 cm, pale green, entire, acute at both ends; petiole 1.5-5 cm long; stipules in pairs, 3.5-4 cm long, early caducous, green or yellowish.
• Flowers solitary, generally nodding, at anthesis 2.7-4 cm long; pedicel 6-12 mm long, green, yellow or brownish; calyx tubular with 10-12 lobes, yellow, yellow-brown or reddish, never bright red, tube 1-1.5 cm long and distinctly ridged to the base; petals 10-12, 1.5 cm long, 2-lobed, whitish turning yellowish-brown, densely fringed with hairs along the outer margins, lobes half the length of the petal, each with a reflexed and obtuse apex bearing 1-3 bristles, up to 1.2 mm long and a distinct bristle in the sinus between the lobes; each petal embraces a pair of stamens; stamens 7-14 mm long; style filiform, 1.5-2.2 cm long, with 3-4 short branches.
• Fruit a berry, more or less distinctly ribbed, enclosed in calyx, 1.5-1.8 cm long; hypocotyl cigar-shaped, rather angular, 6-8 cm × 1.5 cm, with narrow blunt end.

In common with other members of the Rhizophoraceae, the fruits of this species are viviparous. The seedling, still attached to the fruit, drops from the tree, embedding itself in the mud or floating to where it is washed up on the beach.

B. sexangula is the only Bruguiera species which sometimes forms stilt roots. The twigs and petioles lack the white, waxy covering, often characteristic of the closely related B. gymnorhiza (L.) Savigny that grows more towards the centre of mangrove communities.

Ecology

B. sexangula occupies the inland parts of the mangrove forests which are not frequently submerged, and may be found along river banks. Occasionally, it is found on sandy shores. It occurs in soils with water that is less saline than seawater, and prefers easily drained soils. In India it is common along the outer fringes of mangrove swamps and sporadic along newly formed canals in their interior.

Husbandry

In a trial in the Philippines seed germinated 5-10 days after sowing. Harvesting is done manually with axes or matchets, which minimizes disturbance to the mangrove. Young trees from short-term rotations are preferred.

Prospects

B. sexangula is one of the less important mangrove species. It has some economic importance in mangrove vegetation close to the mainland.

Literature

• Backer, C.A. & Bakhuizen van den Brink, R.C., 1963. Flora of Java, Vol. 1. Noordhoff, Groningen, the Netherlands. pp. 380-381.
• Burkill, I.H., 1966. A dictionary of the economic products of the Malay Peninsula, 2nd edition. Vol 1. Ministry of Agriculture and Co-operatives, Kuala Lumpur, Malaysia. pp. 379-380.
• Hou, D., 1958. Rhizophoraceae. In: van Steenis, C.G.G.J. (Editor): Flora Malesiana, Series 1, Vol. 5. Noordhoff-Kolff, Djakarta, Indonesia. pp. 457-568.
• Hou, D., 1970. Rhizophoraceae. In: Smitinand, T. & Larsen, K. (Editors): Flora of Thailand, Vol. 2(1). The Forest Herbarium, Royal Forest Department, Bangkok, Thailand. pp. 5-10.
• Melana, D.M., Melana, E.E. & Arroyo, C.A., 1980. Germination study of selected mangrove species. Sylvatrop 5: 207-211.
• Tomlinson, P.B., 1986. The botany of mangroves. Cambridge University Press, Cambridge, United Kingdom. pp. 163-170, 349.

Authors

• H.T. Chan & T. Boonkerd
• Saberi Othman