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18: Plants producing exudates

Palaquium gutta (Hook.f.) Baill.

Traité bot. méd. phan., Add.: 1500 (1884).

SAPOTACEAE

n = 24

Palaquium acuminatum Burck (1886), Palaquium oblongifolium (Burck) Burck (1886), Palaquium optimum Becc. (1902).

Gutta-percha tree (En). Indonesia: balam merah (Sumatra), getah merah, getah sambun (Kalimantan). Malaysia: taban merah, nyatoh taban merah (Peninsular), (nyatoh) rian (Sarawak). Thailand: chik-nom, saeo (peninsular).

Palaquium gutta occurs naturally in Peninsular Malaysia, Singapore, Sumatra and Borneo; it is cultivated elsewhere, e.g. in Java.

From the latex of the leaves of Palaquium gutta the best grade of gutta-percha is produced. Gutta-percha is the coagulum of the latex; it is scarcely elastic but on exposure it sets to a substance possessing the property of softening with heat and hardening again when allowed to cool. Gutta-percha 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. By the 1960s and 1970s, golf ball manufacture was the only significant end use for gutta-percha. It has also been used for medical and chemical instruments, in dentistry, for transmission belts and acid-resistant receptacles, as an adhesive, as a water-proofing agent and as an ingredient of chewing gum. The advent of synthetic resins and other petroleum-based polymeric materials led to the rapid decline in use of the natural material. At present its main application is for protecting wounds and in dental clinics (as 'dental points'), where it is proving to be useful for people allergic to synthetic fillers. Locally, gutta-percha is used for fixing tools in their handles.
The timber is used as 'nyatoh', for planks (not exposed to the weather or ground), panelling, and for the manufacture of fine furniture, decorative doors and veneers. The seeds contain a fat used for the manufacture of soap and candles, and sometimes for cooking.

Indonesia is probably the largest producer and exporter of gutta- percha. Annual exports were (3-)195(-366) t in 1988-1993, but these figures may not be reliable. In 1963-1972 average annual imports in the United States from Indonesia were 1140 t. Average annual gutta- percha exports from Singapore in 1961-1980 were 225 t. These figures include gutta-percha from other Palaquium species and Payena leerii (Teijsm. & Binnend.) Kurz. Early in the 20th Century the average annual world consumption of gutta-percha was 850 t, but average annual exports over the period 1900-1920 from Singapore of 14 000 t have also been reported. Exports of 'getah merah' (only gutta-percha from Palaquium gutta) from Kalimantan and Sumatra were 4-51 t/year in the period 1928-1938. Exports of gutta-percha from plantations in Java were 35-230 t/year in 1927-1940.

Gutta-percha is the coagulum of the latex of several species of Sapotaceae. It is non-elastic, but becomes plastic when heated at temperatures over 50°C 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 the formation of resins. Moreover, it acquires a pungent odour when oxidation sets in. It resists concentrated alkalies, dilute acids and even hydrofluoric acid. It consists mainly of trans-polyisoprene with a molecular weight of about 30 000, very little rubber (cis-polyisoprene) and a varying amount of resins, ranging from 20-30%. The higher the resin content the lower the quality of the gutta-percha, as it becomes more brittle and plastic at a lower temperature. Refining raw gutta-percha lowers the resin content, and the final product of Palaquium gutta contains 87-99% gutta, 1-9% resin and 0.2-3.3% foreign matter. The resins found in the latex are albane and fluavile. The gutta-percha content of leaves increases with age, from about 3% in young leaves and 8% in medium-aged leaves to 10% in old leaves. The reaction with sulphur is utilized to vulcanize gutta-percha, rendering it non-plastic and insoluble. The seeds contain 58-63% fat.

A medium-sized to large tree up to 45 m tall, but generally much shorter (about 25 m) with columnar bole, up to 60 cm in diameter and with usually small buttresses; twigs usually slender, often hairy or scurfy at least at tips, with 1 cm long terminal cone-like buds. Leaves alternate, clustered at tip of twigs or evenly distributed; stipules up to 3 mm long, falling off early; petiole 1-6 cm long; blade obovate, ovate, elliptical or narrowly elliptical, (8-)12-17(-50) cm x 2-6(-12) cm, with transverse or reticulate tertiary veins (sometimes parallel to secondary veins), distinct or inconspicuous, golden-brownish velvety beneath. Inflorescence an axillary fascicle with 2-7(-10) flowers; flowers bisexual; pedicel 2-9(-12) mm long; sepals (4-)6(-7), generally in two whorls of 3, ovate or triangular, about 4 mm long; corolla tubular, up to 9 mm long, (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 globose, ellipsoidal or ovoid, 2-3.5 cm long, finely hairy and green. Seedling with semi-hypogeal germination, cotyledons emergent, with strongly developed taproot; first pair of leaves opposite or subopposite, subsequent leaves arranged spirally and soon similar to leaves of adult trees.

In northern Peninsular Malaysia (Penang) trees of Palaquium gutta flower from January-April and in the central part of Peninsular Malaysia from July-September. In Java flowering occurs in the months of June-August and fruits reach maturity in January-March. In many cases flowers do not reach maturity because of attack by insects or unfavourable weather conditions. There are, however, certain years when there is a generally heavy seed crop. The ripe fruit, but not the seeds, is eaten by fruit bats. There are often numerous ripe seeds on the ground underneath bat roosts. Fallen fruits are quickly consumed by squirrels, birds, insects and other animals, so only a small proportion of the seeds survives. In Peninsular Malaysia, Palaquium gutta has a mean annual diameter increment of 1.2 cm and attains about 8 m tall in 7 years, 17 m in 23 years and a diameter of about 50 cm in 50 years.

Although Palaquium gutta is a rather variable species, the many existing subclassifications in the literature are not justified because they are often based on small differences, e.g. on the shape and size of the leaf, the apex of the leaf, the number and shape of secondary and tertiary veins, the lengths of the petiole and of the pedicel, all of which fall within the normal variability of a species.
Palaquium acuminatum Burck, Palaquium selendit Burck and Palaquium treubii Burck used to be considered as separate species because they produced an inferior quality gutta-percha. At present, however, they are considered as synonyms because morphologically they fall within the normal variability of Palaquium gutta.

Palaquium gutta occurs scattered in lowland forest, but sometimes occurs up to 1600 m altitude (Sabah). Plantations thrive in areas with precipitation over 2500 mm annually and without pronounced dry season. Palaquium gutta requires a loose and well aerated soil rich in organic matter.

Trial plantings of Palaquium gutta were made in Singapore as early as 1845. In 1885 important plantations for gutta-percha production by tapping were established in Cipetir (West Java) at 550 m altitude and with 3000 mm annual rainfall. Seed production of Palaquium gutta is unreliable and depends on the weather during flowering. Seed loses its viability in 2(-8) weeks, but fresh seed has a germination rate of 75-85%. Seed should be sown in deep nursery beds, as the seedlings develop a taproot. A minimum spacing of 15 cm is required. Young plants need shade and plenty of water, and when sown in February (West Java) they measure about 25 cm at the beginning of the rainy season in December when they are ready for planting out. Seedlings can be planted either as bare-rooted stock or as containerized planting stock, but mortality after planting is usually high: up to 35%. Older seedlings may be planted as stumps. In Cipetir seedlings used to be planted at 1.2 m x 1.2 m, whereas in Peninsular Malaysia the spacing applied was 1.5 m x 1.8 m.

Young plantations of Palaquium gutta require shade. This has been successfully supplied by Paraserianthes falcataria (L.) Nielsen, Derris microphylla (Miq.) B.D.Jacks. and Adenanthera microsperma Teijsm. & Binnend. Competition from grasses should be eliminated and green manure species should be planted to ameliorate the soil. In Cipetir, Sesbania sesban (L.) Merr. has proved to be very successful both for shade and in improving the soil. When it became possible to extract latex from leaves, planted trees needed to be managed as shrubs, for easy harvesting of leaves, instead of allowed to develop tappable stems. To achieve this, selective thinning is done to eliminate individuals with too few branches, stems are cut when they reach 60-75 cm tall, and branches are cut back to encourage leafing. Pruning should not be done before a dry period or on poor growing sites. Normally, pruning is done every 2.5-3.5 years. In Peninsular Malaysia, a 1000 ha plantation was established in 1905 with seed from Cipetir. In 1900-1910 many small plantations were established in Java and eastern Sumatra, but these were all abandoned when para rubber (Hevea brasiliensis (Willd. ex Juss.) Müll.Arg.) became profitable. In Peninsular Malaysia, 6000 ha of natural forest were transformed early in the 20th Century to almost pure gutta-percha forest (containing Palaquium gutta and Palaquium obovatum (Griff.) Engl.). Commercial plantations in Peninsular Malaysia ceased exploitation in 1967. In Cipetir, one commercial gutta-percha plantation of about 4000 ha was still active at the time of writing. In Singapore, a small plantation can be found in the foothills of Bukit Timah Nature Reserve.

A severe attack of Palaquium gutta by a leaf roller, Rhodoneura myrthea, has been observed in Java. This leaf roller spins younger leaves together, often causing the growing apex to rot. In severe cases loss in leaf production has been estimated to be about 20%.

Traditionally the latex of Palaquium gutta is harvested by felling the tree, lopping off the branches and cutting a number of rings in the bark at 30-60(-100) cm intervals. The exuding latex is collected in containers placed under the tree. This destructive method was prohibited in the first half of the 20th Century in several countries, as resources were dwindling rapidly. Various methods have been developed for tapping the living trees. A rest period of at least 2 years was thought to be necessary between successive tappings to keep the tree economically productive. Palaquium trees contain irregular latex cavities in the bark which are not connected, and tapping cannot be done repeatedly as in the case of para rubber. Cloudy, moist conditions allow the latex to flow more easily than hot, sunny periods, when there is some loss of water by evaporation.
In plantations, extraction of gutta-percha from the leaves of the trees is more productive than collection of latex by tapping. This type of exploitation started early in the 1900s when a process was developed to extract gutta- percha from the leaves. Harvesting is done partly by plucking twigs with 4-6 leaves (about every 40 days) and partly by collecting prunings which comprise leaves, twigs and small branches. Old leaves or even fallen leaves are harvested preferentially, as their gutta content is higher.

Higher latex yields are obtained by tapping the upper portion of the trunk and branches of Palaquium gutta than by tapping the lower part. Yields of gutta-percha per tree are also very variable. About 1.5 kg was reported to be a good average yield for destructive harvesting. The latex yield obtained by tapping living trees is much lower. The average annual yield of leaves is 3000-4000 kg/ha when leaves have a moisture content of 30%. Wide variations occur, however. The approximate gutta-percha yield per ha was 450 kg (2.3% from treated leaves) in 1920; a recent estimate from the company exploiting the Cipetir plantation was only 20 kg/ha annually, probably because of the extensive way of exploitation nowadays.

A factory for gutta-percha extraction was established in Cipetir in 1930 and is still functional. The present method of processing involves digesting of pulverized leaf material in hot water having a temperature of 70°C, and then rinsing with cold water. The coagulated latex then separates from the leaf pulp residue, which sinks in water. Purified gutta-percha can be prepared by dissolving the resinous fraction from the coagulated latex in cold petroleum spirit, and then dissolving the remaining, separated gutta fraction in hot petroleum spirit.
Bleaching earth is added to the hot mixture to remove unwanted leaf pigments. The hot extract is separated 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 pressed into round blocks of about 1.5 kg. These blocks are packed in round well- sealed containers for shipping. This chemical method yields the 'white gutta-percha', which has a resin content of 1% and almost no foreign matter. The problem is that the natural anti-oxidants in the gutta- percha are also extracted and that makes gutta-percha susceptible to deterioration through oxidation. However, chemical anti-oxidants may be added by the manufacturer of end-products, and the choice of anti- oxidants differs with the type of end-product.
Leaves have also been processed mechanically. This involves collecting the coagulated latex after the hot water treatment of the pulverized leaves, and pressing it into blocks. This method yields about 3% gutta. The leaves contain about 3.5% gutta.
Latex obtained by tapping the trees used to be processed by pressing the partially formed coagulum into blocks after first softening it in hot water and removing larger pieces of foreign matter. The blocks were then transported to the factory for further processing. These blocks were stored under water to avoid spoilage by aerial oxidation. The gutta-percha blocks were deliberately adulterated with chopped bark, wood and even stones to increase weight. The crude gutta-percha was processed in the factory either mechanically or chemically. The mechanical method consisted of processing the raw gutta-percha by treatment with hot water to remove impurities, and collecting and pressing it into blocks. This yielded the 'yellow gutta-percha' with about 9% resin and 3% impurities. Chemical treatment by solvent extraction of the chopped crude gutta-percha followed the same principles as those mentioned earlier for processing gutta-percha obtained from leaves.

Although several Palaquium species have been planted in Cipetir, the quality of the gutta-percha from Palaquium gutta proved to be superior to that of other species, so the existing plantation is currently a monoculture of Palaquium gutta. There are no known germplasm collections.

At the end of the 19th Century, best-yielding trees were selected in their natural habitat for the establishment of the plantation of Palaquium gutta in Cipetir. No later selection and breeding programmes are known of.

Although the market is currently very small with only one enterprise producing gutta-percha from Palaquium gutta, it is expected that gutta-percha as a product of natural origin will maintain its market share.

Coppen, J.J.W., 1995. Gums, resins and latexes of plant origin. Non-wood forest products 6. Food and Agriculture Organization of the United Nations, Rome, Italy. pp. 127-131.
Franke, G., 1983. Bemerkungen zur Produktion von Guttapercha [Remarks on the production of gutta-percha]. Beiträge zur tropischen Landwirtschaft und Veterinärmedizin 21(4): 431-436.
Kartasubrata, J., Tonanon, N., Lemmens, R.H.M.J. & Klaassen, R., 1993. Palaquium Blanco. In: Soerianegara, I. & Lemmens, R.H.M.J. (Editors): Plant resources of South-East Asia No 5(1). Timber trees: major commercial timbers. Pudoc Scientific Publishers, Wageningen, the Netherlands. pp. 303-319.
Meijer Drees, E., 1939. Herkomst, gebruik en bestemming der voornaamste boschbijprodukten van Nederlands-Indië [Origin, use and destination of the major non-timber forest products of the Dutch East Indies]. Tectona 32: 920-1017.
Reader, D.E., 1953. Gutta-percha. Colonial Plant and Animal Products 3(1): 33-45.
van Gelder, A., 1950. Guttapercha [Gutta-percha]. In: van Hall, C.J.J. & van de Koppel, C. (Editors): De landbouw in de Indische archipel. Deel 3: Industriële gewassen - register. W. van Hoeve, 's- Gravenhage, the Netherlands. pp. 476-520.
van Royen, P., 1960. Revision of the Sapotaceae of the Malaysian area in a wider sense. 23. Palaquium Blanco. Blumea 10(2): 432-606.
Williams, L., 1964. Laticiferous plants of economic importance V. Resources of gutta-percha - Palaquium species (Sapotaceae). Economic Botany 18: 5-26.

N.O. Aguilar

Aguilar, N.O., 2000. Palaquium gutta (Hook.f.) Baill.. In: Boer, E. and Ella, A.B. (Editors): Plant Resources of South-East Asia No 18: Plants producing exudates. PROSEA Foundation, Bogor, Indonesia. Database record: prota4u.org/prosea