Ethnobotany

Areca catechu

Introduction

Areca, also known as betel palm, consists in family Palmae (Arecaceae). About 54 spp. of monoecious palms from Indo-Malaysia to the Solomon Islands and northern Australia. The seeds of betel palm, Areca catechu, are widely used as a masticatory throughout the Indo-Malaysian region; other species of Areca, of which the commonest is A. triandra Roxb., are sometimes used as substitutes, but are usually inferior. The hard dried endosperm of ripe and unripe seeds, miscalled ‘nuts’, is chewed as a narcotic by some 400 million people from Zanzibar to India and the central Pacific, thus outrivaling chewing gum as a masticatory in popularity on a world basis.

Ecology

The areca palm flourishes in maritime climates of the tropics and is grown from sea level to 900 m; conditions in Malesia are particularly suitable for its growth. It requires an ample supply of soil moisture and a plentiful rainfall throughout the year of 1500 – 5000 mm. It is very sensitive to drought and in areas with under 1250 mm of rainfall per annum irrigation is usually necessary. It can be grown on a variety of soils, but clay loams seem to be preferred.

Origin & Distribution

Various centres of origin have been suggested, including the Sunda Islands by von Martius, the Philippines by Beccari (1919), and Malesia by Burkill (1966). However, Corner (1966) states that the ‘wild plant in primary forest has never been found’, but that it may have originated in central Malesia in the region of the Celebes, where its section of Areca occurs. Sangal (1963) states that A. catechu occurs naturally on the Nicobar Islands. It is certainly of very ancient cultivation in Malesia and was taken to India before the Christian era. The first record in European literature was by Herodotus in 340 BC (Before Christ). It was taken eastwards to the central Pacific and reached Zanzibar before AD (Latin anno domini) 1500.

Morphological Characters

A slender erect monoecious palm living for 60 – 100 years.

1) Leaves : Borne in terminal crown, about 2.5 m in diameter in mature palm, with phyllotaxy of 2/5. Adult leaves paripinnate, 1.0 – 1.5 m long, with long smooth sheathing base, completely encircling stem and forming crown-shaft, about 55 x 15 cm; pinnae 30 – 50, lanceolate, longest in centre of leaf, 30 – 70 x 3 – 7 cm; upper pinnae often partly confluent; stomata confined to lower surface. First leaves bifurcate; one-year-old seedling produces 4 - 5 leaves; number of mature leaves on adult palm 8 – 12; unfurled leaves retained for about two years before falling and approximately 6 new leaves produced per year.

Leaves

2) Inflorescence and Flowers : Flowering begins when 4 – 6 years old. Single inflorescence produced in axil of each leaf sheath which closely covers it until a few days before opening; abortion of some primordia occurs and 3 – 4 inflorescences are usually produced per year. Spadix enclosed by double boat-shaped spathe, about 60 x 18 cm, opening longitudinally along upper surface and later falling. Rachis of spadix 30 – 60 cm long, with 20 – 25 secondary branches, on which are filiform tertiary branches, 15 – 25 cm long. Male flowers very numerous, deciduous, minute, borne above female flowers, arranged in pairs two rows, ebracteate, sessile, about 3 mm long, cream-coloured; outer perianth 3, longer, lanceolate; stamens 6 in 2 whorls; anthers sagitate, pollen colourless; ovary rudimentary, slightly longer than stamens. Female flowers 250 – 500 per spadix, borne on thickened bases of secondary and tertiary branches, 1 – 3 per branch, 1.2 – 2 cm long, sessile; perianth persistent; outer perianth 3, green, broadly imbricate; inner perianth 3, longer, creamy-white; staminodes 6, small; ovary trilocular with 2 carpels usually aborting, ovoid; stigma triangular, with 3 triangular stylar projections.

3) Fruits : Take about 8 months to ripen from pollination; not all female flowers set fruit and 50 – 400 fruits produced per spadix. A fibrous ovoid drupe, variable in size and shape, sometimes beaked, 5 – 10 x 3 – 5 cm, usually 1-seeded, yellow to orange when ripe; pericarp fibrous, about 6 mm thick. Seed, so-called ‘nut’, above base of fruit, 3 – 4 x 2 – 4 cm, ovoid, globose, or ellipsoidal, sometimes flattened at base, weighing 10 – 20 g; endosperm ruminate with hard reddish tissue from inner integument running horizontally for some distance into pale brown endosperm; embryo conical at base of seed.
Fruits





Seeds

4) Stem : Not produced until third year. Mature stem single, unbranched (except very occasionally), straight, cylindrical, to 30 m tall and 25 – 40 cm in diameter, green when young, becoming greyish brown with age, ringed with leaf scars, internodal distance reduced as palm ascends.

Stem

5) Roots : The radical soon dies and adventitious roots are produced from the basal bole. Primary roots about 1.4 cm in diameter, turning dark brown with age, branching to give secondary and tertiary roots. Maximum concentration of roots within a radius of 1 m from bole and usually in the top 60 cm of soil. Root-hairs absent, absorption taking place through thin-walled cells behind root-cap; top-shaped pneumathodes present. Aerial roots occasionally produced from base of stem.

Anatomical Characters

1) Lamina : Hairs frequent above and below veins on both surfaces but most numerous abaxially. Epidermis with outer wall slightly thickened, cutinized layers thin, walls not sinuous. Adaxial epidermis uniform, cells more or less rhombohedral and obliquely extended. Abaxial epidermis with somewhat smaller cells and indistinct infrequent costal regions. Stomata restricted to abaxial intercostal regions, not in distinct files; rather remote from each other. Each guard-cell with 2 prominent cutinized ledges, walls scarcely thickened. Fibres rather few, mostly solitary or in groups of 2 – 3 scattered in the mesophyll but frequently adjacent to adaxial epidermis.

2) Stem : Either solitary, tall, slender, with well-marked, smooth internodes, or tufted and rather small. Hairs absent. Epidermis composed of more or less isodiametric cells and frequent stomata. Cortex narrow, including numerous fibrous bundles and vascular bundles. Central vascular bundles not congested, each with a fibrous phloem-sheath but xylem sheathed only by parenchyma. Ground parenchyma cells secondarily expanded, enclosing large air-lacunae.

Anatomy of stem

Vascular bundles

3) Root : Exodermis conspicuous. Cortex including radially-extended lacunae. Cortical fibres numerous, either solitary in outer cortex or in irregular lignified groups nearer stele. Stele with an irregular fibrous medulla; complex and polystelic in the wide roots.

Anatomy of root

Cultivars

Various types of areca nuts have been described in Malaya and India, differing in the size and shape of the fruits and in the blandness and astringency of the endosperm. As the palm is cross-pollinated and grown from seeds, the population is very heterogeneous.

Chemical Composition

The endosperm of the areca nut contains a number of alkaloids with a total of 0.2 – 0.7 per cent, of which the most active and important is arecoline, C₈H₁₃O₂N, with 0.1 – 0.5 per cent. Other alkaloids include arecaidine, arecolidine, guvacine and guvacoline. It also contains 11–26 per cent of catechol tannins, which is reduced during ripening. Other constituents include approximately: water 30 per cent; protein 5 per cent; fat 5 per cent; carbohydrate 47 per cent.

Pollination

The male flowers begin to open at the tips of the branches as soon as the spadix frees itself from the spathe. Each flower lasts but a few hours, and the maximum dispersal of pollen takes place between 9.0 and 12.0 a.m. It takes 2 – 4 weeks for all the male flowers to open to the base of the branches and most pollen is produced from the eighth or tenth days. After all the male flowers have been shed, the petals of the female flowers become yellowish white, open slightly at the tip, and the trifid stigma becomes receptive, remaining so for 3 – 4 days. Thus, as there is no overlap between the male and female phases, the palm is obligatorily cross-pollinated. The male flowers are sweet-scented and are visited by bees and other insects for pollen, but they have not been observed visiting the female flowers. It is considered that most of the pollination is by wind. The first inflorescences on young palms may produce only male flowers.

Germination

The embryo grows and emerges into the pericarp about 30 days after sowing. The lower end of the cotyledon grows into the endosperm between the ruminations to form the haustorial organ. Scale leaves are first produced on the developing shoot and adventitious roots are formed. The first bifid leaf is produced about 90 days after sowing, by which time five roots will have been produced. Average germination is usually over 90 per cent.

Propagation

Areca palms are always propagated by seeds. Fully ripe fruits, which have been dried for a few days, are planted in shallow pits 2.5 cm apart and just covered with sand. After three months, when they have sprouted, they are transferred to nursery beds at a spacing of 30 cm apart. The beds may be shaded by interplanted bananas. They are transplanted into the field at 1 – 2 years old. Seedlings should be selected for quick germination and vigour.

Husbandry

The nursery seedlings are transplanted in the field at approximately 2.5 x 2.5 m; if interplanted with bananas the distance may be 4 – 5 x 2 – 2.5 m. They are often grown in mixed cultivation with other fruit trees. In India black pepper, Piper nigrum L., and betel-pepper, P. Betle L., may be grown up the trunks. The areca palm comes into bearing at 7 – 8 years old, reaches full bearing at 10 – 15 years, continues to yield until about 40 years old, and then may persist in a sterile state until it dies. In many areas it is customary to interplant new seedlings among 20-year old palms, so that the new generation will replace the older palms as they go out of bearing. This may be repeated and, unless thinning is done, an old garden may contain as many as 2500 palms per hectare. Farmyard manure and leafy twigs may be incorporated in the soil from time to time.

The fruit bunches are harvested by climbing the palms or cutting them with a curved knife on the end of a long pole. A palm produces 2 – 6 bunches of fruits per year, each with 50 – 400 fruits, depending upon their size and the productivity of the individual palm. The fruits are husked, either fresh or after drying, the embryos are removed, and the nuts, whole or sliced are dried in the sun or with artificial heat; sometimes they may be smoked. The ripe or three-quarters ripe nuts, entire or sliced, may be boiled in water to which some of the concentrated liquid from previous boiling may be added, and are then dried. The boiling reduces the tannin content of nuts. The finished product is graded on the stage at which the nuts have been harvested and on the colour, shape and size of the nuts.

Utilizations

Areca catechu, the Betel-nut palm, is cultivated extensively in the eastern Tropics and East Africa where the seeds, after removal of the husk, are chewed as a masticatory; it may be chewed alone or with other ingredients, such as coconut shavings, sweetener, clove, cardamom, fennel, tobacco and other spices, wrapped in a fresh or processed pepper (Piper betle) leaves, lime, as well as Areca nuts. ‘Kossa’ is the Catechu of Areca extracted by boiling the nuts with lime until a red-brown paste is obtained, and it is used to intensify the flavour of inferior nuts of other Areca species or even other genera (such as Actinorhytis, Calyptrocalyx, Heterospathe, Oncosperma, Pinanga and Veitchia) which may be used as substitutes for Areca catechu. The palm is grown as an ornamental in many parts of the tropics and in Florida.

Medicinal Uses

The betel-nut and other parts of the palm have a number of medicinal uses in the Far East. The alkaloid arecaine (or arecoline) is an effective vermifuge. The central bud or cabbage is sometimes eaten, but may be rather bitter and its timber may have some local use.

Major Diseases and Pests

The most serious disease is a fruit rot caused by Phytophthora arecae (Col.) Pethy. It attacks the young fruits, causing them to shed; later it attacks the palm crown and may cause the death of the tree in 2 – 3 years. A foot rot, of which Ganoderma lucidum (Leys.) Karst. is the causal fungus, may result in serious losses. No serious pests have been reported.

References

Kochhar, S.L. 1986. Tropical Crops. Macmillan Publishers Ltd.

Purseglove, J.W. 1975. Tropical Crops Monocotyledons. Longman Group. Ltd.

Tomlinson, P.B. 1961. Anatomy of the Monocotyledons II Palmae. Oxford: Clarendon Press.