Acronychia (PROSEA)

Plant Resources of South-East Asia Introduction

List of species

Acronychia J.R. Forster & J.G. Forster

Protologue: Charact. gen. pl.: 27 (1775).

Family: Rutaceae

Chromosome number: x= 18;A. pedunculata: 2n= 36

Origin and geographic distribution

Acronychia comprises 47 species occurring from Sri Lanka and India to Indo-China, south-western China, Taiwan, Thailand, the whole of the Malesian archipelago, east to the Solomon Islands, New Caledonia and Lord Howe Island, and south to eastern and southern Australia. The majority of the species are endemic to New Guinea and Australia.

Uses

The wood of Acronychia is used for house building, utility furniture, flooring, lining, panelling, mouldings, turnery, carving and tool handles. It also produces a good quality charcoal and has been used as firewood.

In Indo-China an extract from the roots of A. pedunculata has been applied to the skin against rheumatism, and an extract from the bark against itch. Roots have also been used as a fish poison; the bark for caulking boats and toughening fishing nets. The leaves contain a volatile, aromatic oil used in stimulating baths. Young leaves are sometimes eaten as a condiment and applied to promote digestion.

Production and international trade

As supplies and the size of the timber of Acronychia are generally small, utilization is on a local scale only.

Properties

Acronychia yields a medium-weight hardwood with a density of 490-830 kg/m³at 15% moisture content. The following description is based on the Australian species A. laevis J.R. Forster & J.G. Forster. Wood whitish, darkening to pale brown or pale yellow on exposure; grain interlocked; texture fine and even. Growth rings indistinct; vessels very small to small, just visible with a hand lens, some solitary but mostly in radial multiples of up to 4, with yellowish deposits; parenchyma paratracheal vasicentric and apotracheal in irregularly spaced bands; rays very fine, only visible with a hand lens; ripple marks absent.

Shrinkage of the wood upon air drying is moderate. The wood of South-East Asian species is not very strong and is not durable. The sapwood is susceptible to Lyctus .

Leaves contain 0.06% of an aromatic oil. Several species contain alkaloids.

See also the table on microscopic wood anatomy.

Botany

Aromatic shrubs or small to medium-sized trees up to 27(-35) m tall, rarely climbers; bole sometimes straight but more often crooked, branchless for up to 23 m, up to 60 cm in diameter, without buttresses; bark surface smooth to finely cracked, greyish, inner bark pale brown to cream-coloured. Leaves opposite, 1-foliolate or 3-foliolate, leaflets entire, with pellucid dots; stipules absent. Inflorescence axillary, paniculate, subcorymbose or reduced to 1 or a few flowers. Flowers bisexual, 4-merous; sepals free or connate at base; petals valvate, deciduous or rarely persistent, white; stamens 8, filaments usually densely ciliate at base; disk intrastaminal; ovary superior, 4(-8)-carpellate, with or without septicidal fissures, with 2 axillary ovules in each cell, style twisted. Fruit a 4(-8)-locular drupe with (1-)2 seeds per cell.

Annual height increment can be 0.5-0.6 m. In Java A. pedunculata flowers and fruits throughout the year whereas A. trifoliolata has been observed flowering in September to November.

A. trifoliolata is very variable and has been subdivided into 3 varieties. Two of these, var. ampla T.G. Hartley and var. microcarpa T.G. Hartley, are confined to New Guinea. A. pedunculata is also highly variable, especially in the size of the fruit and the pubescence of the disk.

Ecology

Within Malesia Acronychia species are often found scattered in evergreen, primary or sometimes secondary, upper or lower montane forest. Sometimes they are even present in alpine habitats (e.g. A. murina and A. pullei ), although some are fairly common in lowland forest as well. A. pedunculata is found in primary and secondary rain forest and in coastal scrub, up to 2200 m altitude. A. trifoliolata is also found in monsoon forest and along the margins of Casuarina forest, up to 2400 m altitude.

Silviculture Acronychia can be propagated by seed, which germinates easily.

Genetic resources and breeding

There are no records of in situ conservation of Acronychia . Many narrow-endemic species from New Guinea and Australia may easily become endangered by destruction of their habitat.

Prospects

The timber of Acronychia appears to be hardly used in South-East Asia. This situation is unlikely to change in the near future.

Literature

70, 163, 221, 413, 436, 464, 497, 568, 595, 672, 861, 883, 974, 1038, 1048, 1170, 1221.