Section I - The plant and the environment
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History and origin
3. Pollination and fruit setting
1. History and origin
According to Groome (1970), the first planted nutmeg was introduced to Grenada by the Hon. Frank Gurney, with seeds brought from Banda in 1843. The supposed site for this first planting was Belvidere Estate in the parish of St. John's.
The nutmeg is indigenous to the eastern islands of the Moluccas, viz, Amboina and Ternate hut seldom found growing truly wild.
Ironically, nutmeg was first planted in the West Indies, on the island of St. Vincent as early as 1802 probably taken from Kew. By 1824 some plants were introduced from St. Vincent to Port-of-Spain Botanical Gardens, Trinidad.
In Grenada the first commercial plantations were established just about the 1 850's with the associated estate being Belle Vue and Capitol located in the St. Andrew's parish between Soubise point and Birchgrove. It was not until the year 1865 that nutmeg from Grenada had influence on the world market.
Nutmeg plants have been introduced in most tropical countries where suitable climatic and soil conditions exist and in the West Indies along with St. Vincent and Trinidad, other countries where nutmegs have been introduced include St. Lucia, Dominica, Jamaica, Montserrat, Martinique and Guadeloupe.
Grenada by far is the largest cultivator of nutmeg and producer of the spices, nutmeg and mace in the West Indies and is only surpassed internationally by Indonesia.
2.1 Systematics - Taxonomy and Phylogeny
The nutmeg plant, Myristica fragrans Houtt., is a member of the small primitive family Myristicaceae, taxonomically placed between the Annonaceae and Lauraceae (Joseph,1980). The family Myristicaceae contains only 18 genera and about 300 species. Myristica is the largest genus for which has been listed 72 species, spreading from India and Sri Lanka eastwards through Malaysia to North-Eastern Australia, Taiwan and the Pacific, including the Solomon Islands, Fiji and Samoa (Purseglove et al., 1981). Since 40 known species of Myristica -of which 34 endemics- are found in New Guinea (Indonesia) representing an area of concentration, this location has been designated the centre of origin and distribution of this genus.
Most of the species in the genus Myristica are tropical evergreen trees found growing mainly in the lowland tropical rain forest, but some mountain species also occur.
The principal synonyms of M.fragrans are M.officinalis L.f., M. moschata Thunb., M. aromatica Swartz, and M. ambeinensis Gandoger.
The cultivated species is mainly the Banda - nutmeg, Myristica fragrans Houtt., but in Indonesia there is some cultivation of the Papuan nutmeg, Myristica argentea Warb. In Grenada however, cultivation is of Banda nutmeg exclusively.
According to Groome (1970) another species found growing locally of the Myristicaceae family is Virola surinamensis (Rol). Warb. and with the common names wild nutmeg or wild cedar.
Genetically the somatic number of chromosomes in Myristica Fragrans is 2n=42, and the basic chromosome number for the genus is suggested to be 7 (Purseglove, et al., 1981).
2.3 The Plant and its Parts
The nutmeg is a medium-sized, spreading or conical, thickly-leaved evergreen tree that attains the average height of 4 - 10 m but sometimes may reach heights of 20 m and over. Trees grown from seedlings are usually singlestemmed and taller than those from vegetative propagation which are usually multi-stemmed. For single-stemmed trees over 30 years the average trunk circumference is 150 180 cm. However, some trees on Plaisance estate, St.John's which were pointed out to be over 80 years, (and possibly over 100) averaged 200 - 250 cm in girth. This is duplicated on other estate or plots where very old trees still exist (photograph 3).
Photo. 1. Field of nutmeg
interplanted with banana
Photo. 2. Young and mature fruits of nutmeg
Photo. 3. Stem over 200cm in girth of aged, bearing nutmeg tree
Photo. 4. Exposed shallow roots of toppled nutmeg tree
Trees are usually uniformly covered with leaves but older trees may show some protruding naked branches and in heavy wind swept areas there may be lateral tree deformation.
The tree is usually dioecious but sometimes there is the occurrence of male and female flowers on the same tree. Large, aged male trees are virtually nonexistent since these are systematically removed at an early age (4 - IS years) from nutmeg fields. All parts of the plant are aromatic. The structure and habit of the nutmeg tree has caused it to be used as a forest tree on some hillsides of Grenada and thus to a certain extent has prevented hillside erosion.
The root system is shallow but extensive, one tap root and a spreading mat of lateral feeder roots branching into rootless. This mat may extend beyond the spread of the stem branches and has measured as much as 3.5 - 5 m from the stem base. As the plant grows and ages the tap root proportionally shortens. Nutmeg rootless investigated showed the significant absence of root hairs. Absorption is predominantly at the rootlet tips.
Because of the shallow root system the tree could be easily uprooted or blown down by high winds (photograph 4). Thus hurricane Janet in Grenada in 1955 resulted in the destruction of about 80% of the nutmeg tree population (Muller et al., 1980).
Usually on the lower trunk of older trees may be seen lateral brown protuberances extending to as much as 0.5m. These are aerial adventitious roots. They emerge as a single lateral cylindrical root about 1.5 - 2 cm in circumference and the tip portion being softer in texture and a lighter brown than the tougher, woody, fibrous portion adjacent to the stem. The single branch, which may be sometimes hallow, extends, becoming a multi-branched root cluster, stouter (46cm) tougher and darker brown in colour, and orientated earthwards. They are observed on both male and female trees, trees propagated from seedlings or marcots and also on the plants of the later introduced MALAYAN plants. They are also seen on young as well as on old plants and on trees growing at high altitude, hillsides, or in valleys (photographs 5a and 5b).
Their function or usefulness to the plant is not clear. However, it is speculated that they may be a physiological and anatomical response to certain changes in the environment.
Depending on the origin of the plant from seedling or vegetative propagation, the stem may be a single woody trunk or multi-stemmed respectively (photograph 6). However, on some occasions it has been observed that marcots take on the profile of seedling plants. The single stemmed trunk is cylindrical sometimes furrowed and showing very slight decrease in girth from ground level to 1/3 up the plant. In older mature plants the bark is rough, a dark brownish grey and showing longitudinal fissures. Depending on the growing locale it may be spotted with greenish silvery lichens or may be host to some saprophytic climbing plants. The trunk bark of younger plants is smooth and a light-brownish grey. The average stem girth from various locations in Grenada show the ranges, seedlings (24 cm), in field 3 year old (8-12 cm), 5 years (18-25 cm), 8 years (35 - 45 cm) and 12 years (60-80 cm).
Profuse fairly spreading lateral branches arise from the main stem with a slight whorled, spiral arrangement. In some cases these emerge fairly low down on the trunk forming an acute angle to the main stem so that they tend to be turned upwards (photograph 7). Smaller branches then fan out laterally from these main branches. This arrangement affords maximum leaf display for photosynthesis. There may also be seen vertically oriented branches emerging from main branches particularly evident in unpruned trees. Extending from the trunk outwards the branches reduce in girth to slender twigs and the bark changes from a dark, grayishbrown, rough and fissured, to lighter grayish brown twigs terminating in smooth green tips. On wounding both stem and branches reddish sap is produced.
These are simple, persistent, alternate, glabrous and exstipulate, elliptic or oblong lanceolate with an apex acute or slightly acuminate and an acute base tapering into a short petiole slightly flattened adaxially and about 1-1.5 cm long. The lamina, 5-15 cm long and 2-7 cm broad, is coriaceous, medium to dark green above and shining, light silvery-green or subglaucous beneath (photograph 8).
In young leaves the upper surface is yellowish green. From the prominent lower mid-rib emerge 8-12 pairs of pinnatelateral veins slightly tapering to the apex and forming a network reticulation visible on the lower surface but not so from above. When crushed the leaves emit a characteristic nutmeg like aroma.
Photo. 5a. Aerial adventitious
Photo. 5b. Aerial adventitious roots
Photo. 6. Multi-stemmed trees from marcotting
Photo. 7. Arrangement of branches on single-stemmed nutmeg tree
The typical tree is unisexual- dioecious with male and female flowers on different trees. On occasion both male and female flowers may occur on the same tree and even rare hermorphrodite flowers may be encountered. From field observations in Grenada it has been reported that male trees progressively change to female with aging and bear fruits (personal communication, Reynold Benjamin). Locally, flowers and fruits occur on the trees all the year round, the months of April and May and November and December are the periods when flowers are in greatest abundance. It must be noted that there are slight variations in different parts of the island.
There is still no satisfactory method for distinguishing the sex of a young plant until it has declared, flowered. The calorimetric test published by Phadnis and Choudhari (1971) using 0.1g leaf sample and ammonium molybdate reagent was investigated locally by the author who found no significant difference in test for young leaves from male and female plants. Lawrence (1978) reported on a number of other tried methods.
1. Myristica fragrans
(a) male flower with part of calyx removed (x 4.5)
(b) female flower with part of calyx removed (x 3)
Flowers tend to occur on the outermost branches. The inflorescences with male and female flowers are structurally similar and are axillary and glabrous, bearing flowers in umbellate cymes with the male 1-10 usually outnumbering the female 1-3. It is quite common to find in the male inflorescence flowers in various stages of development. The pedicels, 1-1.5 cm long, are pale green with a minute caducous bracteole at the base of the flower.
The flowers are creamish-yellow in appearance, waxy and fleshy, fragrant and may measure up to 1 cm in length. Petals are absent so the dominant calyx is bellshaped, nectiferous at the base, with 3-reflexed triangular lobes. The female flowers, up to I cm long, exhibit a puberulous, superior, sessile, one celled ovary about 7 mm long and topped by a very short, white two lipped stigma. The male flowers consist of an androecium I cm long, glabrous, with a 2 mm stalk, with 8-12 stamens, with anthers adnate to a central column and attached to each other by their sides (Fig.1) and (photographs 9a,b,10a,b).
The fruit is a fleshy, pendulous, one seeded drupe suspended by a greenishbrown fruit stalk about 1.5 cm long. It is broadly pyriform, yellow, smooth, 6-9 cm long and almost as broad. Some fruits are obviously bell shaped, longer than there are broad, and in rare cases observed locally some rees may bear joined double fruits.
For the regular fruit there is a circumferential longitudinal groove which divides the fruit in halves including the persistent remains of the stigma and terminating at the fruit stalk. When ripe, the thick succulent, yellow (on the outside) pod 1-1.5 cm thick, dehisces into two halves along the length of the groove revealing a thin epicarp and two faces of whitish mesocarp which shows immediate browning on exposure to air and bright red net-like aril partially surrounding a dark brown to black shiny testa (endocarp) with a prominent seed base scar. The aril is attached to the base of the seed and its network is impressed as grooves on the testa (photographs 11 a,b and c).
2. Myristica fragrans kernel
(b) longitudinal section
(c) cross section
Photo. 8. Leaves showing upper and
Photo. 9a. Male inflorescences with flowers at various stages of maturity
Photo. 9b. Male inflorescences - also note young yellowish green leaves
Photo. 10a. Female inflorescences - few persistent flowers
Photo. 10b. Flowers. Female (upper) and male (lower)
Photo. 11a. Flower to mature fruit.
Photo. 11b. Flower to mature fruit. Longitudinal section through some stages of fruit.
Photo. 11c. Fruit, seed, aril, kernel and shell.
Within the hard, stout, brittle testa is a broadly ovoid, light brown kernel about 2-3.5 cm long and 1.5 - 2.0 cm broad. The outside of the kernel has broken longitudinal wrinkles and a prominent creamish brown base scar with a smaller dark brown "scar" at the other end. Internally, there is a convoluted pattern of dark brown perisperm, a light coloured endosperm and a small embryo (Fig. 2 and photograph 19d). All parts of the fruit are aromatic.
3. Pollination and fruit setting
The issue of pollination and fruit set in the nutmeg is still not fully clarified. Many local farmers believe that male trees should be in the fields as a source of pollen, while others are of the opinion that these are not obligatory. It has also been suggested locally by many that the local wasp "mibone" plays a role in pollination. The flowers are known to be fragrant and to produce nectar.
The literature presents various views. According to Cruickshank (1973), Deinum wrote that pollination was effected by a moth, Peryl concluded that M. fragrans may be able to produce seeds without pollination, while Flach is of the view that cross pollination is obligatory and the team of Duncan and Ferguson suggested a cross-pollination mechanism.
Cruickshank (1973) reported on a bagging experiment carried out on a marcotted flowering tree in Grenada. Although the results seem to suggest that the stimulation of pollination may be necessary for fruit set, the issue of pollination still requires further investigation.
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