Acmena (PROSEA)

Plant Resources of South-East Asia Introduction

List of species

Acmena DC.

Protologue: Prodr. 3: 262 (1828).

Family: Myrtaceae

Chromosome number: x= unknown; 2n= unknown

Vernacular names

• Kelat (trade name, generally used for Syzygium species).

Origin and geographic distribution

Acmena comprises about 15 species which occur from southern Burma (Myanmar), southern China and Thailand, throughout Malesia to the Solomon Islands and Australia. A. acuminatissima is the most widespread species.

Uses

The wood of Acmena is used for construction (ships, bridges and wharfs), building framework, flooring, window-sills and sidings, furniture, joinery, panelling, agricultural and household implements, turnery, plywood and musical instruments.

The bark of A. acuminatissima has been used in Indonesia to dye cotton black; its fruits are edible but sour and slightly bitter. A. hemilampra is used in Australia as an ornamental.

In Australia several Acmena species produce useful structural and joinery timbers traded as "satin ash" under various descriptive epithets, e.g. blush, cassowary, red eungella, lillipilli, and southern.

Production and international trade

On the rare occasions that Acmena timber is traded in Malesia it is sold as "kelat" together with Syzygium timber, or as "mixed medium hardwood".

Properties

Acmena yields a medium-weight to heavy hardwood with a density of 720-940 kg/m³at 15% moisture content. Heartwood pale brown to dark brown or pink to red-brown, not sharply demarcated from the pale brown or greyish-yellow sapwood; grain straight or interlocked, sometimes slightly wavy; texture fine to medium and even. Growth rings indistinct, boundaries marked by fewer or no vessels; vessels moderately small to medium-sized, solitary and in radial multiples of 2-4, tyloses and white deposits present; parenchyma narrow aliform or confluent to banded, not visible to the naked eye; rays fine, not visible to the naked eye, tending to 2 distinct widths; ripple marks absent.

The wood seasons well but slowly and needs careful seasoning to avoid checking and warping. It is hard, fairly strong and rather difficult to work, but finishes fairly well. The wood is very durable under cover and moderately resistant to decay when exposed to the weather, clear of the ground and well drained with free air circulation; it is not recommended in contact with the ground. The wood is resistant to dry-wood termites, the sapwood is susceptible to Lyctus .

See also the table on microscopic wood anatomy.

Botany

Shrubs or small to fairly large trees up to 35(-40) m tall; bole up to 150(-200) cm in diameter, often buttressed in older trees, sometimes with stilt roots; bark surface cracking to scaly or flaky, pinkish-brown to reddish-brown, inner bark pinkish-brown. Leaves opposite or subopposite, simple, entire, dotted with oil glands, secondary veins confluent near the leaf margin to form an intramarginal vein; stipules absent. Flowers in a terminal or axillary panicle, bisexual, 4-5-merous; calyx lobes minute or obsolete; petals free, distinct but caducous; stamens numerous; ovary inferior, 2-locular, with 1 long style. Fruit drupaceous, 1-seeded, globose or depressed globose, with subwoody endocarp. Seed lacking a testa, with ruminate cotyledons enclosing an intrusive ramifying mass of tissue. Seedling with hypogeal or semi-hypogeal germination; cotyledons remaining together; first 2-3(-4) pairs of leaves scale-like.

The fruits are eaten by birds, including cassowaries and pigeons which thus disperse the seeds; the thickened endocarp probably prevents digestion of the seed.

Acmena differs from the very large genus Syzygium in the globose or subglobose, divaricate anther sacs (more elongate and parallel in Syzygium ), and particularly in its peculiar seed structure with ruminate cotyledons enclosing a branching mass of tissue which is probably of placental origin. However, one species of Syzygium ( S. claviflorum (Roxb.) A.M. Cowan & J.M. Cowan) shows the same seed structure as Acmena . As the anther sacs of this species are similar to those of Syzygium it is intermediate between Acmena and Syzygium . It is sometimes placed in a separate genus Acmenosperma .

A. triphlebia has also been treated under Syzygium (as S. triphlebium Diels) in Prosea Vol. 5(2).

Ecology

Acmena usually occurs in primary and secondary lowland rain forest. A. acuminatissima is occasionally found up to 2600 m altitude in New Guinea, A. triphlebia up to 2000 m.

Genetic resources and breeding

Although A. acuminatissima is widespread and common, several Acmena species are known from only a few collections and might be vulnerable. On the other hand, Acmena trees are not sought after for their timber or other products.

Prospects

Very little is known about the wood and silvicultural aspects of Acmena in South-East Asia. More research is desirable, as the timber is considered a useful structural timber in Australia.

Literature

163, 235, 416, 436, 461, 464, 780, 787, 861, 934, 1221.