Polyalthia (PROSEA Timbers)

Plant Resources of South-East Asia
Introduction

Protologue: Fl. Javae Anonac.: 68 (1830).

Family: Annonaceae

Chromosome number: x= 9; P. affinis Teijsm. & Binnend.: 2n= 16, P. glauca, P. lateriflora, P. longifolia, P. micrantha(Hassk.) Boerl., P. rumphii: 2n= 18, P. littoralis(Blume) Boerl.: 2n= 36

Vernacular names

Mempisang, polyalthia (trade names)
Brunei: karai
Indonesia: tepis (general)
Malaysia: karai (Sarawak), pisang-pisang (Peninsular, Sabah)
Philippines: lanutan (Filipino)
Vietnam: nhọc, nóc, quần dầu.

Origin and geographic distribution

Polyalthia comprises about 150 species and is distributed in the Asian tropics from India to Indo-China, China, Taiwan, Thailand, throughout the Malesian region, Australia, the Solomon Islands and Fiji. The largest number of species is found in South-East Asia, especially in Malesia.

Uses

The generally tough and flexible wood of Polyalthia is used for temporary construction, house building, furniture, interior trim, mouldings, light framing, decorative wall panelling, masts, oars, wooden shoes, tool handles, sporting goods, novelties, toys, match splints, packing cases and boxes. It is also suitable for the production of veneer and plywood and is used as firewood (especially P. glauca). The wood of several species including that of P. cauliflora is often decoratively figured.

The fibrous bark of several species, but notably of P. sumatrana and P. hypoleuca, is used to make rope. A poultice of crushed leaves of P. cauliflora is used locally in Indonesia to treat skin diseases. P. longifolia is planted in Peninsular Malaysia as an ornamental; an extract of its leaves shows antibacterial and antifungal activities; its seeds yield an oil and in India its bark is used as a febrifuge.

Production and international trade

"Mempisang" is a general trade name comprising most of the genera of Annonaceae , and Polyalthia comprises an important part of the timber traded under this name. In 1992 the export of mempisang wood from Sabah amounted to 25 000 m³of sawn timber and 42 500 m³of logs with a total value of about US$ 7.2 million. Most of the small amounts of mempisang imported by Japan comes from Sabah, Sarawak and Papua New Guinea. In 1996 Papua New Guinea exported 1845 m³of Polyalthia logs at an average free-on-board (FOB) price of US$ 103/m³.

Properties

Polyalthia yields a medium-weight hardwood with a density of (555-)645-900 kg/m³at 15% moisture content; wood of P. glauca and P. oblongifolia are lightweight to medium-weight with a density of 390-730 kg/m³at 15% moisture content. Heartwood yellow to yellowish-brown with a pink or green tinge, not clearly differentiated from the pale yellow sapwood; grain straight; texture moderately coarse to fine and even; wood with silver grain; occasionally dark, hard core present. Growth rings rather distinct, sometimes indistinct, boundaries indicated by denser tissue; vessels moderately small to medium-sized, mostly in radial multiples of 2-4, rarely in clusters, occasional white deposits present; parenchyma abundant, apotracheal in regular, narrow bands (scalariform); rays moderately broad or rarely fine, distinct; ripple marks absent.

Shrinkage of the wood during seasoning is very low to moderate. The wood is moderately soft to hard and fairly weak to strong and tough with a wide variation between species. The wood is non-durable and needs chemical treatment to prevent stain immediately after sawing. In a graveyard test in the Philippines the average service life of test stakes (probably of P. rumphii ) was about 21 months. The wood of P. flava is resistant to dry-wood termites and the sapwood is non-susceptible to Lyctus . The sapwood of most other species is susceptible to Lyctus . The wood is fairly resistant to pressure preservative treatment.

Leaves of P. cauliflora and other species contain alkaloids.

See also the tables on microscopic wood anatomy and wood properties.

Botany

Evergreen or briefly deciduous, small to medium-sized or occasionally large trees up to 40(-50) m tall; bole straight, cylindrical, up to 60(-90) cm in diameter, occasionally fluted at base or with small buttresses, sometimes with pneumatophores (P. glauca); bark surface smooth to cracking or scaly to papery flaky, sometimes with hoop marks and/or lenticels, light grey to yellowish-white or brown, inner bark fibrous, pale yellow or yellow-brown with red spots or entirely pinkish.
Leaves alternate, simple, entire, often narrowly elliptical, exstipulate.
Flowers axillary or leaf-opposed, sometimes cauliflorous, solitary or in fascicles, bisexual; sepals 3, valvate or imbricate, free or connate; petals 6, valvate or imbricate, in 2 rows, subequal, often large and red, orange, yellow, greenish or white; stamens many, with flat-topped or convex connective; carpels few to many, free, each with 1-5 ovules in 1 row, style often absent.
Fruit apocarpous, with 1-50(-80) monocarps, each monocarp sessile or stalked, oblong or ovoid to transversely broadly elliptical.
Seed with a papery to woody wall; endosperm ruminate.
Seedling with epigeal or hypogeal germination; cotyledons emergent and leafy or not emergent; hypocotyl may or may not be elongated; leaves arranged spirally on the orthotropic leader, distichous on the branches.

Early growth is reputed to be slow, becoming more rapid afterwards. A 19-year-old P. sclerophylla Hook. f. & Thomson tree in the Arboretum of the Forest Research Institute Malaysia, Kepong was 14 m tall and 13 cm in diameter. Growth is rhythmic with suspension of the terminal bud of the vertical shoot, followed by plagiotropic branch growth, after which the vertical shoot resumes growth. Polyalthia develops according to Roux's architectural tree model, characterized by a monopodial orthotropic trunk with plagiotropic branches inserted continuously and with distichous leaf arrangement, flowering not influencing the architecture. Flowering can occur twice a year and flowers appear just before the new leaves. P. flava flowers from February to April. In Peninsular Malaysia the flowering-to-fruiting period of P. jenkensii is about 19 weeks. In general, Annonaceae fruits are eaten and dispersed by birds, mainly pigeons; fruits of P. longifolia are eaten and dispersed by bats.

Many of the individual Polyalthia species are rather poorly known botanically and in need of a thorough taxonomic revision. Polyalthia species reported for Africa and Madagascar probably all belong to Greenwayodendron, rendering Polyalthia in the present sense purely Asian.

Ecology

Polyalthia species occur scattered as understorey or main canopy trees in primary or secondary, lowland to lower montane rain forest, up to 1200(-1800) m altitude. They are found in evergreen and monsoon forest, both on well-drained hills and poorly drained level sites. Individual Polyalthia species may occur as common elements of peat-swamp forest, occasionally also in kerangas.

Silviculture

Polyalthia can be propagated by seed. Germination experiments in Peninsular Malaysia, however, showed that germination is unpredictable. The best results were obtained for P. cinnamomea, the seeds of which were sown with pulp and had about 95% germination in 1-2 months. Seeds of several other species showed 10-35% germination in 1-10 months. Sowing of fruits of P. sumatrana yielded a very low germination. P. cauliflora and P. cinnamomea are highly vulnerable in the nursery, as the cotyledons and epicotyl are easily trapped in the testa and then rot. Sufficient watering and manual removal of the testa may resolve the problem. In natural forest the regeneration of Polyalthia is generally profuse.

Genetic resources and breeding

Some Polyalthia species have a rather narrow geographical distribution and face the risk of genetic erosion by deforestation.

Prospects

Polyalthia is considered to be rather fast-growing and may be promising in timber plantations. However, only little silvicultural information is available and it seems justifiable to increase the research on propagation and planting, and on growth and yield.

Literature

40, 70, 125, 151, 162, 163, 209, 238, 267, 300, 304, 348, 358, 402, 436, 438, 464, 468, 496, 507, 526, 547, 632, 672, 673, 707, 800, 825, 827, 829, 831, 832, 836, 837, 861, 863, 883, 934, 955, 957, 974, 1017, 1038, 1098, 1123, 1126, 1134, 1221, 1242.