90

16: Stimulants

Areca catechu L.

Sp. pl.: 1189 (1753) ('cathecu').

PALMAE

2n = 32

Areca palm, areca nut palm, betel palm, betel nut palm (En). Ar‚quier (plant), noix d'arec (fruit) (Fr). Indonesia: pinang (Indonesian), jambe (Javanese, Sundanese), pua (Lesser Sunda Islands, the Moluccas). Malaysia: pinang. Papua New Guinea: buai. Philippines: bunga (Tagalog, Bisayas), takotob (Bikol), boa (Iloko). Cambodia: sla, daëm sla. Laos: kôk hma:k. Thailand: mak (general). Vietnam: cau, binh lang, t[aa]n lang.

The exact origin of Areca catechu is not known, but most probably it originated from central Malesia where it is known to be of very ancient cultivation and where variability of the genus Areca L. is greatest. Areca catechu is only known from cultivation. Seemingly wild plants have always turned out to have been planted or distributed by humans. The cultivation of areca palm had spread from Malesia to the Indian subcontinent in pre-historic times and this spread was to continue later, although slower. At present areca palm is cultivated pantropically but is of greatest importance in South and South-East Asia, where it is grown in almost every village garden.

Throughout Asia and the Central Pacific the fresh or dried endosperm of ripe and unripe seeds ('nuts') of areca palm is chewed as a stimulant, alone or in combination with a leaf of betel pepper (Piper betle L.) and some slaked lime. In South-East Asia, the usual practice is to wrap pieces or slices of the nut in fresh betel pepper leaves that are sprinkled or smeared with lime. Other ingredients may be added to the betel quid, including gambier (Uncaria gambir (Hunter) Roxb.), tobacco, palm sugar and various spices, such as cardamom (Elettaria cardamomum (L.) Maton) and clove (Syzygium aromaticum (L.) Merrill & Perry). Very important is that the quid is spat out, not swallowed. The mixture is also taken after meals to sweeten the breath. Chewing the quid is said to increase the production of saliva (which is blood-red in colour) and gastric juices and thus to aid digestion. It is also an appetizer. However, excessive chewing may result in loss of appetite, continuous salivation and general deterioration of health. After years of chewing, teeth may become nearly black. In parts of India, Thailand and Malaysia, the offering and chewing of areca nuts fulfils an important religious and social function. Some 200 million people throughout the western Pacific basin and southern Asia chew betel regularly.
The nut of areca palm is widely used in Asian medicine, e.g. as a vermifuge for humans and animals, as an emmenagogue, as a cure for diarrhoea, urinary disorders, edema and lumbago. It is credited with, among others, astringent, tonic, digestive and bechic properties. The nut is applied externally to ulcers, sores, wounds, swellings and skin diseases. The husks, young shoots, buds, leaves, and roots also have medicinal uses. Tender shoots (the upper part or 'cabbage' of the young stem) are edible and are cooked in a syrup. The central bud or palm cabbage is sometimes eaten, though it may be rather bitter. In Java, the cabbage is eaten as 'lalab' or made into pickles as a vegetable. In the Philippines, it is eaten raw as a salad or cooked, whereas the flowers are also added to salads. Tannins are obtained as a by-product from the process of preparing masticatories from immature nuts. The nuts have also been used to obtain dyes, and their fat is used as an extender of cocoa butter. Husks are used as domestic fuel. In the Philippines, they have been used to make toothbrushes. Industrial uses of husk components and leaves as raw material for fibres, hardboard and plastics have been reported from India. Areca palm stems provide useful building material. The leaf sheaths and spathes are used as wrapping material.
The spathes have also been used to make containers and hats. In South-East Asia the fragrant flowers are used in ceremonies, such as weddings and funerals. In Florida and many parts of the tropics areca palm is grown as an ornamental.

In India, the most important areca palm growing country, the production of areca nuts rose from 75 000 t around 1955 to 250 000 t around 1990. The increase in production was a combination of increase in area under cultivation and in yield per ha. In Indonesia, the total production was 21 800 t in 1993, of which most was exported. Thailand exported about 5 200 t in 1991, with a value of 4.5 million US$. Neither production figures for other areas nor more recent information on domestic and international trade are available.

The main chemical constituents of ripe areca nuts per 100 g fresh weight are approximately: water 21-30 g, protein 5-8 g, carbohydrates 35-40 g, fat 5-10 g, fibre 11-15 g, polyphenols 11-18 g. Alkaloids are present as a minor but significant constituent. Eight related alkaloids have been identified, the most important one being arecoline; they generally range from 0.1-0.2%, but higher values of the order of 0.7% are also given. The largest amounts of alkaloids are found in the unripe nuts. Arecoline is known to act on the central and peripheral nervous systems. It promotes heart rate and blood pressure, increases the glucose utilization of the brain, and improves the cognitive function in people affected with Alzheimer's disease.
Betel quid use is associated with diseases such as oral leucoplakia, submucous fibrosis and oral squamous cell carcinoma. The possible carcinogenic effects may be due to cytotoxic and teratogenic N-nitrosamines formed from the alkaloids in areca nuts. The formation of N-nitrosamines may be enhanced by the phenolic compounds of the nuts. It has also been suggested that oral squamous cell cancer is caused by lime-induced cell proliferation and by reactive oxygen compounds generated in response to the combination of polyphenols and lime.
The 1000-seed weight is 10-20 kg.

The seeds of many other palms are used as inferior substitutes for the true areca nut, e.g. Areca caliso Becc. (the Philippines), Areca glandiformis Lamk (Indonesia, New Guinea), Areca ipot Becc. (the Philippines), Areca laosensis Becc. (Indochina), Areca latiloba Ridley (Indonesia), Areca macrocalyx Zipp. ex Blume (Indonesia, New Guinea), Areca triandra Roxb. (Indonesia, Indochina), Areca whitfordii Becc. (the Philippines), Calyptrocalyx spicatus (Lamk) Blume (Indonesia) and Pinanga spp. (Indonesia).

An erect, slender, unarmed, unbranched, solitary, pleonanthic, monoecious palm, up to 30 m tall with a terminal crown of 8-12 leaves. Root system dense but superficial, most roots within a 1 m radius from the trunk in the top 60 cm of soil. Trunk cylindrical, 15-30 m tall, 10-15(-40) cm in diameter, grey-brown, densely and regularly ringed with leaf scars. Leaves arranged spirally (phyllotaxy 2/5), crowded at the trunk top, 1-1.5 m long, paripinnate, sheathing; sheath completely encircling the stem like a tube, 0.5-1 m long; pinnae 30-50, subopposite, linear to lanceolate, 30-75 cm x 3-7 cm, longest in the centre of the blade, longitudinally plaited, apex dentate or irregularly incised, dark green, upper ones often partly cohering. Inflorescence erect, appearing on the trunk below the crown leaves (infrafoliar), 30-60 cm long, branched broomlike to 3 orders basally, tertiary branches filiform, spicate, 15-25 cm long, very fragrant; before opening, inflorescence enclosed by a double boat-shaped bract which opens longitudinally along the upper surface; male flowers numerous, borne above the female flowers, arranged in pairs in 2 rows, sessile, about 6 mm x 3 mm, creamy, deciduous, sepals 3, small, petals 3, lanceolate, larger, stamens 6 in 2 whorls; female flowers borne on the thickened bases of secondary and tertiary branches, 1-3 per branch, 1-2 cm x 1 cm, sessile, with persistent perianth of 3 sepals and 3 longer, creamy-white petals, ovary trilocular (2 carpels usually aborting), ovoid, stigmas 3, triangular, fleshy. Fruit an ovoid drupe, 3-6(-10) cm x 2-5 cm, orange to reddish, usually 1-seeded; pericarp fibrous, about 6 mm thick. Seed (so-called nut) ovoid, globose or ellipsoidal, 3-4 cm x 2-4 cm; endosperm ruminate with hard reddish tissue from inner integument running horizontally for some distance into pale brown endosperm.

Mature seeds of areca palm are sown as whole fruits, directly after harvesting or after a few days of drying in semi-shade. Germination is completed about 90 days after sowing when the first bifid leaf and five roots have developed. An adult palm bears 8-12 leaves and produces 6 new leaves per year. Flowering starts at the age of 4-6 years. In Malesia flowering is year-round, in India from November- February. Male flowers begin to open as the spadix frees itself from the spathe. Each flower lasts only a few hours. It takes 2-4 weeks for all the male flowers to open. After all the male flowers have been shed, the petals of the female flowers turn yellowish white, open slightly and the stigma becomes receptive for 3-4 days, with maximum receptivity between the first and third day. The duration of the female phase ranges from 5-8 days. As a rule there is no overlap between the male and female phase but exceptions (overlap of two days) have been observed. The palm is thus cross-pollinated and most of the pollination takes place by wind. The percentage of fruits set varies widely, not all female flowers set fruit. Fruits produced per spadix range from 50-400. Development from pollination to ripe fruit takes about 8 months. Yields are variable but gradually increasing until the palms reach full maturity at 12-15 years. Production continues until the palms are 40 years old and stop producing fruits. The life span of an areca palm is 60-100 years.

Although Linnaeus originally wrote 'cathecu' as specific epithet, most authors consider this an orthographic error for catechu. As Areca catechu is cross-fertilized its variability is great. Several varieties have been distinguished, mainly on the basis of fruit morphology. In South-East Asia and India the different forms, sizes, colours and tastes of the nuts have been given different vernacular names, but there is no formal classification of cultivars.

Areca palm grows well in humid tropical lowland. At altitudes above 900 m fruit quality and germination are adversely affected. It requires a high, well-distributed annual rainfall of 1500-5000 mm. In areas with dry spells irrigation is needed. Areca palm can be grown on a wide range of soils. It thrives on fertile, well-drained and deep clay loams.

Areca palm is exclusively propagated by seed. Criteria for mother-tree selection are early and regular bearing, a large number of leaves on the crown, short internodes and high fruit set. As to fruit selection, fully mature heavy fruits, floating vertically in water with the calyx end upward, give a high germination percentage and vigorous seedlings. As sprouts of the seedlings are damaged by direct exposure to the sun, nurseries should be shaded. At the age of 12-24 months, plants with five or more leaves are selected and, with a ball of earth adhering to the roots, planted in the field. In well-drained soils, deep planting - at a depth of about 90 cm - allows for gradual earthing up the fresh nodes above the bole. The covered nodes throw out fresh roots, resulting in firm anchorage and a larger rooting volume. In Indonesia, villagers often collect seedlings from fruits dropped by bats and squirrels and raise them into mature palms near their homes.
Selection criteria for areca palm gardens include protection against wind and sun-scorch, adequate drainage and preferably a clay-loam texture. Spacing depends on soil depth and fertility. In a trial in Kerala, India, a spacing of 2.7 m x 2.7 m was found to give the highest cumulative yield. After planting out in the field, seedlings may be protected against direct sun exposure by shading them with coconut palm leaves or planting a banana intercrop. Permanent intercropping takes place, using, among other, banana, cocoa, fruit trees, cardamom, and guinea grass as a fodder. In India pepper and betel pepper may be grown with the palm as support. If interplanted with banana the distance between plants may be 4-5 m x 2-2.5 m. Areca palm is often temporarily intercropped with annuals and biennials. The practice increases the per unit area yield through better use of land and light and provides revenue while the palms are still immature, without reducing their future yields. In many areas young seedlings are planted among 20-year old palms to replace older ones that have ceased bearing. This may be repeated and, unless thinned, an old garden may contain as many as 2500 palms per ha.

In young areca palm plantings regular weeding, mulching and sometimes intercultivation by hoe- digging are practised for weed control and water conservation. In India annual fertilizer applications of 100 g N, 40 g P₂O₅ and 140 g K₂O per palm are recommended, together with 12 kg each of green leaf and compost or cattle manure. Irrigation is used in some of the drier areas. In Indonesia areca palms are usually cultivated around homesteads and along the borders of upland fields. Larger plantations of areca palm are mostly found in India only.

The most important diseases of areca palm in India are yellow leaf disease, fruit rot, foot rot and inflorescence dieback and button shedding. Yellow leaf disease causes yellowing of leaves and shedding of both mature and immature fruits. It does not kill the palm outright but debilitates it. The nature of the disease and remedial measures are unknown. Fruit rot, i.e. rotting and shedding of immature fruits caused by Phytophthora arecae is a serious disease in areas of high rainfall. The fruit stalk and the rachis of the inflorescence are affected, but the fungus may also cause rotting of the growing bud, eventually killing the palm. Protective spraying with Bordeaux mixture and other copper fungicides is effective, and fallen plant material must be removed. Foot rot is a soilborne fungal disease caused by Ganoderma spp. destroying the xylem and thereby impeding the water supply and killing the palm. Removal of dead tree stumps and digging of trenches around affected palms limits the spread of the disease. Inflorescence dieback and button shedding is a serious problem in some states of India. Nutritional and physiological factors are probably involved and several fungi have been found to be associated with infected inflorescences.
The following pests, though not highly host specific, cause substantial damage in India: mites, spindle bugs, inflorescence caterpillars, and root or white grubs. The mites recorded on the crop are Oligonychus biharensis, Oligonychus indicus, Raoiella indica and Tetranychus fijiensis. They suck sap from the leaves, causing yellowish speckles which later coalesce; severely infested leaves wither away. Control measures are cutting and burning of infested leaves and spraying with insecticides. Spindle bugs (Carvalhoia arecae) suck on the tender spindle and leaves, causing necrotic lesions. Severely infested spindles fail to open and leaves are shredded, resulting in stunted growth. Various systemic insecticides have been found to give control. The moth of the inflorescence caterpillar (Tirathaba mundella) deposits eggs into the spadix. The emerging caterpillars bore into the interior of the spathe and feed on the tender rachillae and female flowers and may also bore into the young buttons. To control this pest, infected inflorescences are removed and burnt. The root grubs affecting the areca palm are larvae of Leucopholis burmeisteri and Leucopholis lepidophora. They feed on the roots and may cause the palms to topple over. Visual symptoms are the drooping and the drying of leaves. Soil insecticides give effective control.

The stage of harvesting of areca palm depends on the product wanted. Immature fruits to supply 'kalipak' (an important form of processed areca nut in India) can best be harvested when 6-7 months old. For the mature nut product, fruits should be harvested fully ripe. In Indonesia, unripe fruits are harvested for home consumption, whereas fruits intended for trade are usually harvested ripe, because ripe fruits keep better. In closely and regularly spaced plantings harvesters climb the palms, cut the bunches, lower them down on a rope and move from one crown to the other. Another method is to harvest bunches with a knife mounted on a bamboo pole.

In India mean annual yields of areca palm were of the order of 800 kg dry nuts per ha around 1955 and 1200 kg per ha around 1990. Calculated mean yield of ripe nuts is about 2.5 kg per palm per year, but some farmers obtain yields of 8 kg per palm. The highest yield ever recorded is 30 kg per palm per year.

The fruits are husked, either fresh or after drying, the embryos are removed, and the whole or sliced nuts are dried in the sun or with artificial heat; sometimes they are smoked. Ripe or almost ripe nuts, whole or sliced, may be boiled in water to which some of the concentrated liquid from previous boilings may be added; they are then dried. Boiling reduces the tannin content of the nuts. The product is graded on the basis of the ripeness at harvesting and on the colour, shape and size of the nuts. The most popular trade type is the dried, ripe, whole nut ('chali'). In Malaysia the nuts are not boiled. Here, the unripe or ripe fruits are usually split in two and dried in the sun or over an oven. Sometimes the fruits are dried without splitting, a slow process which gives an inferior product. In Taiwan the unripe fresh areca nut is directly used as an ingredient of the betel quid.

The Regional Station of the Central Plantation Crops Institute, Vittal, India, maintains a germplasm collection of Areca catechu and related species from within the country as well as from Sri Lanka, southern China, Thailand, Malaysia, Singapore, Indonesia, the Philippines, Fiji, Solomon Islands and Mauritius. Sixteen exotic accessions have been evaluated for yield in a long-term comparative trial, from which three accessions with high yield potential were released. None of the available cultivars has shown tolerance to yellow leaf disease, which makes identification of disease-tolerant genotypes a priority.

Procedures for mother-tree and seedling selection in areca palm are well established. It has been found that early-bearing palms were constantly better yielders and that selection of seedlings at the appropriate time for number of leaves, girth at collar and number of nodes totally eliminated the late-bearing palms and so increased the yield of the population. However, it did not prove effective to implement these criteria in a mass pedigree selection programme. Hybridization programmes involving selected exotic and local types were started in the early 70's, but so far no hybrids for commercial use have resulted. Interspecific hybrids between Areca catechu and Areca triandra showed hybrid vigour for a number of characteristics. However, these hybrids are sterile and efforts to develop progenies combining the desired traits of both species have failed.

Yields of areca per palm and per ha can be greatly increased by mother-tree and seedling selection and adequate crop husbandry. However, there is unlikely to be a substantial increase in total consumption, although consumption is increasing in Burma (Myanmar), Borneo, some Polynesian Islands and the highlands of Papua New Guinea. In the rest of Asia chewing of betel quid is not popular with the younger generation. Because of the link between betel quid use and oral cancer, betel quid consumption should not be encouraged.

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S. Brotonegoro, M. Wessel & M. Brink

Brotonegoro, S., Wessel, M. & Brink, M., 2000. Areca catechu L.. In: van der Vossen, H.A.M. and Wessel, M. (Editors): Plant Resources of South-East Asia No 16: Stimulants. PROSEA Foundation, Bogor, Indonesia. Database record: prota4u.org/prosea