4.1 Cocos nucifera Coconut Valerie Hocher, [ean-Luc Verdeil and Bernard Malaurie IRD/CIRAD Coconut Program, UMR 1098 BEPC, IRD, BP 64501-911 Av. Agropolis, 34394 Montpellier, Cedex 5, France 1. Introduction length and 30-120 cm deep and continu­ ously generate adventitious roots (Reynolds, 1.1. Botany and history 1988; Persley, 1992). Nutrients and water are absorbed by the rootlets. The coconut palm (Cocos nucifera L.) is a rela­ The coconut palm 'trunk' is a stem with tively slow growing woody perennial species. no true bark, no branches and no cambium. It is the only species in the genus Cocos. All Secondary growth (increased stem diameter) forms known to date are diploid (2n = 2x = is by secondary enlargement meristem 32). No closely related species with even par­ located below the shoot meristem. Growth tial interfertility has been reported (Bourdeix depends on age, ecotype and edaphic condi­ et al., 2001). The lifespan of a coconut palm tions, but is generally between 30 and 100 cm can be > 60 years under favourable ecological per annum. The stem is surmounted by a conditions. Coconuts can grow to a height of crown of approx. 30 compound leaves, approx. 25 m (Ohler, 1999). which protect the terminal vegetative bud Optimum growing conditions for coconut and whose destruction causes the death of are in the lowland humid tropics at altitudes the palm. An adult coconut has virtually as < 1000 m near coastal areas in sandy, weII­ many unopened (20-30) as opened leaves. drained soils (Persley, 1992); however, Leaves are produced continuously at approx. coconuts are adaptable to other soil types 1 month intervals. including coral atolls and soils with moder­ The coconut palm is a monoic species. ate salinity (Batugal, 1999). Coconuts are also Flowering may begin between 3 and 10 years commonly cultivated several hundred kilo­ after planting. Each leaf bears an inflores­ metres inland, e.g. surrounding Lakes cence primordium in its axil. The coconut Victoria, Tanganyika and Malawi in Africa inflorescence is a spadix, which develops (Lombard, 2001). Coconuts cannot tolerate within a double sheath referred to as a temperatures < O°C and ideal growing tem­ spathe. When mature, the spadix breaks peratures range between 24 and 30°C through the spathe and 30-35 spikelets (Woodroof, 1979; Persley, 1992). emerge, each bearing a large number of male Coconuts do not form a tap root, but flowers (200-300) with one or two female develop a fasciculated root system, consist­ flowers at the base of each spikelet. Flowers ing of adventitious roots at the base of the are sessile and follow the trinary organiza­ stem, which typically grow laterally to 2-3 m tion of monocotyledons (Menon and 90 Cocos nucifera Coconut 91 Pandalai, 1958). Male flowers have three Histological studies have demonstrated digi­ short sepals, three petais, six stamens and tations in the epidermallayer in contact with one rudimentary pistil. Female flowers are the nutrient reserves, and the existence of approx. 3 cm in diameter, and are enveloped vascular bundles converging towards the by small scaly bracteoles endosing three embryonic axis. This villosity displays sepals and three petaIs, which overlap each numerous structural similarities to stomach other and surround the spherical pistil. The villi in the digestive system of animaIs ovary is tricarpous and each carpel has a sin­ (Verdeil and Hocher, 2002). gle ovule. After fertilization, a single ovule Fossil nuts > 15 million years old and develops and the two others abort or degen­ very similar to present-day coconuts have erate. The inflorescence can be either self- or been discovered in New Zealand and India cross-pollinated (Bourdeix et al., 2001). (Sauer, 1967, cited by Harries, 1978; De Pollination is by wind or insects. Taffin, 1998); however, the exact geographic The appearance of the fruit (size, shape origin of this species is uncertain. In aIl prob­ and colour) varies according to the ecotype ability, the coconut tree was first cultivated (Bourdeix et al., 2001). The coconut is a either in India or in South-east Asia. The drupe, whose development requires approx. coconut has attained its highest development 1 year. Only 25 to 40% of the female flowers in terms of variability and number of local develop into mature nuts and a tree pro­ names in South-east Asia. duces < 100 fruits per annum. After fertiliza­ tion, the husk and shell increase in size and the cavity of the embryo sac enlarges consid­ 1.2. Importance erably (Menon and Pandalai, 1958). The cav­ ity is filled with a liquid endosperm. After 6 The coconut palm has been referred to as the months, the solid endosperm develops as a 'tree of life', because of its importance as a thin and gelatinous layer against the inner subsistence crop in most tropical areas of the wall of the nut cavity (Ohler, 1999). After 8 world. It is grown on > 11 million ha, 94% of months and towards the later stages of which are in Asia and the South Pacifie ripening, the endosperm becomes hard and (Blake, 1990). World production of coconut white and is surrounded by a hard, brown has been estimated to be 52,940,408 t testa (Ohler, 1984). The immature endosperm (FAOSTAT, 2004). The leading producers are is composed of 95% water and < 1% oil, and Indonesia and the Philippines (> 13,000,000 t), 50% water and 30-40% oil at maturity India (9,500,000 t), Brazil (2,833,910 t), Sri (Ohler, 1984). When ripe, the nut generally Lanka (1,850,000 t), Thailand (1,400,000 t), falls. The seed, which is one of the largest in Papua New Guinea (570,000 t), Vietnam the plant kingdom, is characterized by lack (920,000 t) and Mexico (959,000 t). Many of dormancy and the time necessary for coconut-producing countries are small development from embryo to plantlets islands in the South Pacifie and Indian (Blake, 1990; Verdeil, 1993). Oceans and the Caribbean region (Daviron, Four months are generally required for 1995), where coconut can be grown in harsh the first leaf to emerge from the husk. A char­ environments, such as atolls, and can acteristic of coconut zygotic embryos is the tolerate swampy and water-deficient areas substantial development of the haustorium and poor soils. Coconut is an important (distal part of the cotyledon) within the nut attribute of the rural economy (Punchihewa, cavity during germination (Menon and 1999), and is cultivated by many farmers on Pandalai, 1958). This organ invades the nut smaIl landholdings « 4 ha) often in associ­ cavity and establishes intimate contact with ation with other crops (root crops, vegetables, the endosperm. It enables the hydrolysis of cacao, etc.) (Barrant, 1978; Reynolds, 1988; the endosperm and the mobilization of nutri­ Freud and Daviron, 1994). Only 10% of the ents required for embryo germination. planted areas constitute commercial planta­ Lipase, protease and saccharase activity have tions. Coconut palm is cultivated mainly for even been detected (Bertrand, 1994). copra (dried endosperm) production, from 92 V. Hochet et al. which oil is extracted and provides income therefore widely used in food products (mar­ for smallholders in the tropies and subtropies. garine, confectionery, ete.) (Ohler, 1984). The coconut has been a primary source of With only 4% of the world oil production, food, drink and shelter for millions of people coconut ranks seventh among oil-bearing from the earliest days of humankind crops. In the competitive international world (Batugal, 1999; Punchihewa, 1999). Coconut oil market, the coconut paIm is gradually farmers are deeply attached to the various being replaced by other oil-seed plants such products (Punchihewa, 1999), and have con­ as soya and oil palm (Freud and Daviron, tributed to its adaptation to a wide range of 1994). The coconut palm is therefore reverting environmental conditions. Although signifi­ to a multipurpose crop, especially for its fruit. cant achievements have been made with Several reasons can explain this graduai respect to the release of high copra-yielding decline: (i) low productivity due to old age of hybrids (Bourdeix et al., 2001), this progress coconut plantations (two-thirds of the indi­ has yet to reach most coconut producers. viduals are > 60 years old) and insufficient The coconut is mainly a subsistence crop, replanting; (ii) use of unimproved material e.g. 70% of the production is consumed and marginal culture practiees; (iii) several locally in Asia. Every part of the plant can be pests and diseases, e.g. lethal yellowing (LY) used. Oïl from the fresh nuts is used for food and Cadang-Cadang; (iv) production in areas preparation in many countries of Asia and often subjected to natural calamities, e.g. the Pacifie. The kernel can be oven- or sun­ typhoons or volcanic eruptions; and (v) low dried to a moisture content of 6% (copra), prices for coconut oil despite its high quality and can be conserved for months before oil and lower production (Freud and Daviron, extraction. Coconut water is a very refresh­ 1994). In addition, rapeseed oil, whieh has ing drink. Endosperm of mature nuts is been genetically modified to produce oil grated and used in pastries. The woody stem (Laurical®), with a higher content of laurie is used as a building material and in joinery. acid (37%), has had a significant impact on The leaves can serve for local handicrafts production. Despite these difficulties and and as roofing materia1. The processed sap stagnant production for 20 years, coconut oil provides sugar, syrup and vinegar. The fibres is still important, and there continues to be from the husk surrounding the nut can be demand for lauric oil for the soap industry used to manufacture esparto-type goods.