Palaquium (PROSEA Exudates)
- Protologue: Fl. Filip.: 403 (1837).
- Family: Sapotaceae
- Chromosome number: x= unknown
Major species and synonyms
Palaquium calophyllum (Teijsm. & Binnend.) Pierre, Ann. Jard. bot. Buitenz. 5: 28 (1886), synonym:
- Isonandra calophylla Teijsm. & Binnend. (1864).
Palaquium gutta (Hook.f.) Baill. - see separate article.
Palaquium leiocarpum Boerl., Bull. Inst. bot. Buitenzorg 5: 24 (1900), synonyms:
- Palaquium molle Pierre (1902),
- Croixia leiocarpa (Boerl.) Baehni (1965).
Palaquium luzoniense (Fern.-Vill.) S.Vidal, Revis. pl. vasc. Filip.: 176 (1886), synonyms:
- Palaquium ahernianum Merr. (1903),
- Croixia luzoniensis (Fern.-Vill.) Baehni (1965).
Palaquium obovatum (Griff.) Engl., Bot. Jahrb. Syst. 12: 511 (1890), synonyms:
- Isonandra obovata Griff. (1854),
- Palaquium theoideum Elmer (1910; "theoidea").
- gutta-percha (also used for other Sapotaceae species whose latex is used), nyatoh, bitis.
- Indonesia: nyatoh jankar merah, nyatoh tunjung, karikip (Kalimantan)
- Malaysia: getah tunjung, hangkang karikit, getah tewe (Sarawak)
- Philippines: natong-ganda.
- Indonesia: jongkang, hangkang (Kalimantan)
- Malaysia: nyatoh jangkar, jangkai (Sarawak).
- Philippines: kalipaya, nato (general), dolitan (Tagalog).
- Indonesia: mayang katapong, balam terupuh (Sumatra), siki putih (Ambon)
- Malaysia: nyatoh puteh (Peninsular)
- Philippines: lahas (Subanon). Burma (Myanmar): pinle-byin
- Cambodia: sang das, chor ny, chlôr
- Thailand: khanun-nok, saang (south-eastern), yue-raa-toh (peninsular)
- Vietnam: chây.
Origin and geographic distribution
Palaquium consists of about 110 species distributed from western India and Sri Lanka to southern China and east to Polynesia (Samoa). The centre of diversity is western Malesia and most species are found in the Philippines (about 30) and Borneo (about 35), many of them endemic. Peninsular Malaysia and Sumatra have comparatively fewer species (about 20). New Guinea is considered an important secondary centre of diversity, with about 13 species. P. calophyllum occurs in Borneo and in the Philippines (Mindoro). Its occurrence in Sulawesi and New Guinea is doubtful. P. leiocarpum is found in Borneo and Sulawesi, possibly also in Peninsular Malaysia. P. luzoniense has its natural distribution throughout the Philippines, but probably not in Palawan. P. obovatum is widespread and found in India, Burma (Myanmar), Indo-China, Thailand, Peninsular Malaysia, Sumatra, Lingga, the Riau Archipelago, Bangka, Borneo (Sarawak), Sulawesi, Flores, the Moluccas and the Philippines (Luzon, Mindoro, Sibuyan, Samar).
Gutta-percha, the coagulated latex from the bark or leaves of several Sapotaceae species including Palaquium, has been used extensively for submarine and underground cables due to its non-conductivity for electricity and heat, and imperviousness to water. Golf balls used to be manufactured with an outer cover of gutta-percha. This was the only significant end-use in the 1960s and 1970s. It has also been used for medical and chemical instruments, in dentistry, transmission belts, acid-resistant receptacles, as adhesives, waterproofing agents and as an ingredient of chewing gum. The advent of synthetic resins and other petroleum-based polymeric materials led to the rapid decline in the use of the natural material. At present its main application is for protecting wounds and in dental clinics, where it is proving to be useful for people allergic to synthetic fillers. Locally the gutta-percha is used for fixing tool handles.
The timber of Palaquium is of major importance. Species are traded as "nyatoh" containing the lightweight to medium-weight Sapotaceae species (e.g. P. leiocarpum, P. luzoniense, P. obovatum) or as "bitis" comprising the heavy hardwoods.
Production and international trade
Indonesia is probably the largest producer and exporter of gutta-percha. Annual exports during the period 1988-1993 varied considerably from 3-366 t, but these figures may not be reliable. In 1963-1972 the average annual import in the United States from Indonesia was 1140 t. The products of Palaquium gutta and Payena leerii (Teijsm. & Binnend.) Kurz are included in these figures. Early in the 20th Century the average annual world consumption of gutta-percha was 850 t, but an average annual export of 14 000 t over the period 1900-1920 from Singapore has also been reported. Exports of "getah hangkang", the gutta-percha of P. leiocarpum from Indonesia in the period 1928-1938 were 670-1260 t/year. International trade in gutta-percha, in particular to Europe, started in the second half of the 19th Century, with Singapore as the centre. After the trees around Singapore had been felled the search for gutta-percha quickly extended northward into Peninsular Malaysia, and south and east into Indonesia, through the Riau Archipelago to Kalimantan, to Sarawak and Sabah and eventually to the Philippines.
The Palaquium species yielding gutta-percha only account for a minor part of the amount of nyatoh timber traded.
Gutta-percha is non-elastic, but becomes plastic when heated and retains any form given while cooling. It is generally a white substance, which turns pink to dark red upon exposure due to oxidation and formation of resins. Moreover, it acquires a pungent odour when oxidation sets in. It resists concentrated alkalies and dilute acids (even hydrofluoric acid). It consists mainly of trans-polyisoprene, very little rubber (cis-polyisoprene) and a varying amount of resins but never less than 10%. The higher the resin content the lower the quality of the gutta-percha, as at lower temperatures it becomes more brittle and becomes plastic. Getah hangkang consists of about 75% resin. Refining raw gutta-percha lowers the resin content. The resins found in the latex are albane and fluavile.
The more important Palaquium species yielding gutta-percha are lightweight to medium-weight hardwoods with a density of 440-790 kg/m3at 15% moisture content.
- Small to very large trees, with latex in all tissues, sometimes up to 60 m tall, usually with columnar buttressed bole up to 130(-250) cm in diameter, often branchless for a considerable length; outer bark smooth, cracked or fissured, usually brown to reddish-brown, inner bark soft and fibrous, pinkish-yellow, pink, red or reddish-brown; twigs usually slender, often hairy or scurfy at least at tips, often with distinctly developed terminal cone-like buds.
- Leaves arranged spirally, usually densely to loosely clustered at ends of twigs; stipules small to large, usually early caducous, rarely absent; petiole usually of even thickness throughout its length; blade simple and entire, usually obovate, generally glabrous above and more or less hairy beneath when mature; secondary veins straight, curving towards apex and often joined near leaf margin, tertiary veins transverse or parallel to secondary ones or reticulate.
- Inflorescence an axillary or rarely terminal fascicle, 1-many-flowered.
- Flowers bisexual or rarely unisexual; sepals (4-)6(-7), generally in two whorls of 3, ovate or triangular; corolla (5-)6-lobed, with usually short tube and imbricate, often contort lobes, white to yellowish or greenish; stamens (10-)12-18(-36), inserted at the throat of the corolla tube, with acute anthers; pistil 1, with (5-)6(-10)-celled ovary and usually long style.
- Fruit a berry with fleshy pericarp, 1-3-seeded.
- Seed with a crustaceous to coriaceous testa and a large hilum often covering up to two-thirds of the surface of the seed; endosperm usually absent and cotyledons thick and fleshy.
- Seedling usually with epigeal germination and strongly developed taproot; first pair of leaves opposite or subopposite, subsequent leaves arranged spirally and soon similar to leaves of adult trees.
- a small tree up to 15 m tall.
- Leaves evenly distributed, obovate, rarely elliptical, 3.5-9 cm × 7-19 cm, tomentose or velvety beneath, tertiary veins transverse to secondary ones.
- Flowers in 2-11-flowered clusters; pedicel 10-25 mm long (in fruit up to 30 mm), rust- or golden-coloured tomentose.
- Fruit depressed globose, 2 cm × 2.5 cm, densely red-brown tomentose.
- a small to fairly large tree up to 35 m tall.
- Leaves evenly distributed or loosely clustered at tip of twigs, ovate, obovate or elliptical, 5-27 cm × 4-10 cm, with few transverse tertiary veins almost parallel to secondary veins and with a reticulate venation in between, velvety beneath.
- Flowers whitish in 3-6-flowered clusters; pedicel 8-15 mm long (in fruit up to 30 mm).
- Fruit globose to ellipsoidal, 15-25 mm long, glabrous.
- a small to medium-sized tree up to 25 m tall, with bole up to 50 cm in diameter, but sometimes attaining 120 cm, lacking buttresses.
- Leaves clustered at tip of twigs, obovate, oblong or elliptical, 11-20 cm × 2-10 cm, with transverse to reticulate tertiary venation, minutely hairy beneath.
- Flowers yellowish-green or whitish, in 1-4-flowered clusters; pedicel slender, 20-65 mm long.
- Fruit ellipsoidal, 3.5-4 cm long, initially minutely hairy but glabrescent, dull green.
- a medium-sized to large tree up to 45 m tall, with columnar bole up to 80(-110) cm in diameter.
- Leaves usually densely clustered at tip of branches, obovate to oblong, 6-45 cm × 3-17 cm, with distinct, transverse tertiary venation, puberulous or glabrous and glaucous beneath.
- Flowers greenish-yellow or greenish-white, in 4-12-flowered clusters; pedicel up to 2 cm long.
- Fruit globose, ellipsoidal to obpyriform, 2-3 cm long, glabrous; germination hypogeal.
Growth and development
In many cases Palaquium flowers do not reach maturity because of attack by insects and/or unfavourable weather conditions. Flowers may remain closed for a long time (up to 18 months), probably waiting for favourable weather conditions for opening. A regular periodicity of flowering and fruiting seasons does not exist but in certain years there is a general and heavy seed crop. Ripe fruits are eaten by animals who thus disperse the seeds. The average annual increment of P. obovatum trees as observed in transformed natural forest in Peninsular Malaysia was 1.3 cm.
Other botanical information
Other Palaquium species whose latex has been collected are: P. hexandrum (Griff.) Baill., P. hispidum H.J.Lam, P. maingayi (C.B.Clarke) King & Gamble, P. mindanaense Merr., P. oxleyanum Pierre, P. philippense (Perr.) C.B.Rob. and P. quercifolium (de Vriese) Burck. Their gutta-percha was usually mixed with gutta-percha of higher quality.
In P. obovatum two varieties have been distinguished: var. obovatum found from India to Sumatra and Borneo, and var. orientale H.J.Lam found in the Philippines, Sulawesi and the Moluccas. The latter variety differs particularly in having more oblong leaves with more acuminate apex, and shorter pedicels.
Most Palaquium species grow in lowland forest, where trees usually occur scattered. Many species are common in freshwater swamp forest, some grow commonly in peat swamp. P. calophyllum is common along rivers, up to 200 m altitude. In Borneo, P. leiocarpum is found in primary forest at low altitudes, but sometimes up to 1000 m. P. luzoniense and P. obovatum are fairly common in lowland forest, but the latter may ascend up to 1300 m altitude.
Propagation and planting
No Palaquium species apart from P. gutta are known to be planted for the production of gutta-percha.
In Peninsular Malaysia early in the 20th Century 3000 ha of natural forest were transformed to almost pure gutta-percha forest (containing P. gutta and P. obovatum). This type of forest management was abandoned in the 1960s.
Diseases and pests
Tapping wounds often start rotting or are attacked by termites.
Traditionally the latex is harvested by felling the tree, lopping off the branches and by cutting a number of rings in the bark at a spacing of 30-60(-100) cm. The exuding latex is collected in containers placed under the tree. This destructive method had already been abandoned in the first half of the 20th Century in several countries because resources had depleted rapidly. Various methods have been developed for tapping the living trees. Usually a series of V-shaped cuts 20-30 cm apart at an angle of 45°to the vertical are made and these cuts are joined by a vertical cut. The cuts are made on two sides of the tree, leaving a strip of untapped bark 10 cm wide. Most of the latex coagulates in the cuts and exuding latex is collected in a small cup attached to the bark. The coagulated latex is scraped off and formed into a ball, which is then pressed into the cuts and rolled along them. Each time the ball is rolled along a cut, the removal of the coagulated latex re-opens the cut ends of the latex cavities and the flow recommences. A rest period of at least 2 years was reported to be necessary before trees could be tapped again, to maintain the economic productivity. Palaquium trees contain irregular latex cavities in the bark which are not connected, so they cannot be tapped continuously like para rubber (Hevea brasiliensis (Willd. ex Juss.) Müll.Arg.). Cloudy, moist conditions allow the latex to flow more easily than during hot, sunny periods, when there is some loss of water by evaporation.
Yields of gutta-percha per tree are very variable, 0.45-3.6 kg has been reported for destructively harvested trees leaving an estimated 6-40 times of the latex unharvested. The latex yield obtained by tapping is much lower. Higher yields are obtained when tapping the upper portion of the trunk and branches than when tapping the lower part. In P. obovatum the latex flows more easily than in other species and latex yield is higher.
Handling after harvest
The latex of P. leiocarpum, which does not coagulate on the tree, is heated over a fire while stirred continuously until coagulation is completed and water has evaporated. Primary processing of other partially coagulated latex is done in a similar manner. The coagulum is then pressed into blocks after first softening it in hot water and removing larger pieces of foreign matter. The blocks are then transported to the factory for further processing. The blocks can best be stored under water, to avoid spoilage by aerial oxidation. In former days gutta-percha was deliberately adulterated with chopped bark, wood and even stones to increase its weight. Purified gutta-percha can be prepared by dissolving the resinous fraction in cold petroleum spirit, and then dissolving the remaining, separated gutta fraction in hot petroleum spirit. The hot extract is drained from any insoluble foreign matter and then allowed to cool, whereupon the purified gutta-percha separates out. After separation and distillation of residual solvent the hot, plasticized gutta is rolled into sheets and stored, either in the dark in well-sealed tins, or in water. This chemical method yields the "white gutta-percha", which has a resin content of 1% and hardly any foreign matter. The problem is that the natural anti-oxidants in the gutta-percha are also extracted, hence, the gutta-percha becomes susceptible to deterioration through oxidation. However, chemical anti-oxidants may be added. The mechanical method involves processing the raw gutta-percha by treatment with hot water to remove impurities, and collecting and pressing it into blocks. This yields "yellow gutta-percha" with about 9% resin and 3% impurities.
As Palaquium trees are harvested for timber and hardly for gutta-percha, timber exploitation is the main determinant of the risk of genetic erosion. Germplasm collections do not exist.
It is unlikely that the present use of gutta-percha from wild Palaquium trees will increase, as many synthetic products are available. Its special and local applications will remain of limited economic importance.
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