- Related Topics:
- saw palmetto
- Euterpe
- Colpothrinax
- Ceroxylon
- Acrocomia
The palms with the greatest importance in world commerce are the coconut and the African oil palm (Elaeis guineensis); both are prime sources of vegetable oil and fat. Few plants are as versatile as the coconut. The husk of the fruit is the source of coir, used for ropes and mats; the hard inner fruit layer (endocarp) is used as fuel and to make charcoal, cups, bottles, and trinkets; coconut “juice” or “water” (liquid endosperm) is a tasty beverage; the flesh (solid endosperm) is eaten raw or dried to form copra, a source of oil (widely used for food preparation and industrial purposes) and oil cake (cattle feed); the flesh may also be grated, mixed with water, and pressed to obtain coconut milk, used in food preparation and as a substitute for cow’s milk. The sap obtained from tapping the inflorescence, or flower stalk, is drunk unfermented or fermented (toddy) and is a source of sugar, alcohol, and vinegar. Trunks are used in construction and furniture making, and leaves are used in a variety of ways in domestic economies. The African oil palm is important chiefly for the palm oil obtained from the fruit coat and for kernel oil from the seed.
Other palms are used extensively in both the Old and New worlds. Sugar and alcohol are obtained by tapping inflorescences of the sugar palm (Arenga pinnata), the palmyra palm (Borassus flabellifer), the wild date (Phoenix sylvestris), the toddy palm (Caryota urens), the nipa palm, and the gebang and talipot palms (Corypha elata and C. umbraculifera). Wine is made from species of the raffia palm in Africa and from the gru gru palm (Acrocomia) and the coquito palm (Jubaea) in America. The sago palm and, to a lesser extent, the sugar palm and the gebang palm are sources of starch obtained from the pith. The fruit of the date palm (Phoenix dactylifera) is a staple in parts of Asia Minor, the Arabian Peninsula, and North Africa and is also an article of commerce. Fruits are also widely used fresh, as sources of oil, and in the preparation of refreshing drinks and ice cream. Throughout much of the Asian tropics and even in parts of East Africa, the seed of the betel palm (Areca catechu) is used, with lime and the leaf of the betel pepper (Piper betle), as a chewing substance. Trunks and leaves serve in local construction, in the making of weapons, and as sources of wax (the wax palm, Ceroxylon; the carnauba wax palm). Leaves of the gebang palm are made into umbrellas and books; others provide material for rain capes, baskets, raffia (Raphia farinifera), hats, hammocks, and the fibre known as piassava.
Palms seem destined to continue to be extremely valuable economically, but in increasingly different ways. For centuries they have provided most of the necessities of life for humans in the tropics. Within rainforests and along their borders, whole communities have depended on palms for their livelihood. Except for the pantropical coconut, different genera have served in different tropical areas. The number of uses is legion. The sugar palm is used in more than 40 ways in Asia; the babassu palm (Attalea; see ) in Brazil yields 28 products of edible and chemical value. Native palm products are now contributing substantially to local economies. In 1979 the value of the harvest from six native palm genera (the black palm, Astrocaryum; the piassava palm, Attalea; the carnauba wax palm, Copernicia; Euterpe; Mauritia; and the babassu palm) was more than $100 million. Entrepreneurs recognized during the 1980s that several genera that have been utilized only from natural stands might be enhanced by the selection, cultivation, and mechanical harvesting that could be afforded them as major plantation crops. Certain neotropical palms, which are reported to have several times the potential yield of the traditional oil seeds such as peanuts and soybeans, are a good example. Perhaps 200 species of palms are potential oil producers, but only about 20 have been exploited, and, except for the oil palm (Elaeis), which is a plantation crop, oil has been extracted from wild specimens. The oil from the seeds of one species, Jessenia bataua, is physically and chemically much like olive oil, and the mesocarp pulp from the fruits of Jessenia and the closely related Oenocarpus is reported to have a protein content similar to that of meat. Large-scale production of such genera has been advocated.
Several genera show excellent potential for silviculture and agroforestry in land use systems where they are mixed with other species, sometimes also with animal components. A further advantage is that some useful palms grow on land not suitable for other crops, such as Mauritia flexuosa in waterlogged soils, the black palm in seasonally inundated areas, and Euterpe chaunostachys in swamps. Many palms, such as the sugar palm, the palmyra palm, and the sago palm, are multipurpose trees. In tropical America, the peach palm (Bactris gasipaes) is widely grown for hearts of palm and fruits, both in plantations and on small farms. The wood is valuable, and the peach palm also is grown as shade for several crops, such as coffee (Coffea arabica), citrus (Citrus), and breadfruit (Artocarpus altilis); it is especially successful with cacao (Theobroma cacao). In Ecuador, palms that are grown by the agroforestry industry include the peach palm; the tagua, or ivory, palm (Phytelephas aequatorialis) grown for vegetable ivory; and a fibre palm (Aphandra natalia). In Southeast Asia the production of rattan from species of Calamus (C. caesius, C. manan, and C. trachycoleus) is a promising industry. Commercial production of sago from trunks of Metroxylon has been investigated. Palms are sources of many products; indeed, no other plant family provides such a diversity. Their use in agroforestry may help conserve rainforests while providing an income for small farmers. The potential for their development is enormous.
Apart from commercial or local uses, palms are extensively planted for ornament in warm regions or indoors when a tropical effect is desired. Several hundred species are used as ornamentals in outdoor gardens as well.
Ecology
Palms have adapted to many habitats within their geographic limits. To the dweller in temperate regions, they tend to be associated with jungle or with tropical shores, where the coconut is often a prominent feature of the landscape. Most palms are inhabitants of tropical forests. There they thrive on well-drained acid soils in regions of high though often seasonal rainfall. They range from the lowlands to mountain and cloud forests up to altitudes of 1,800 metres. Rarely, as in the wax palm and some species of Geonoma, they grow at elevations as high as 3,000 metres in the Andes. There are exceptions, however, for palms are also found in swamps or poorly drained areas (bussu palm, Mauritia, date palm, sago palm, raffia palm) or brackish estuaries and lagoons (nipa palm) or areas subject to alternate flooding and drying (carnauba wax palm). They also occur in deserts or on seashores when underground water is present (doum palm, Washingtonia, coconut palm), or in open savanna, grassland, or gallery forest, or restricted to such special habitats as limestone outcrops (Maxburretia rupicola), serpentine soils (Gulubia hombronii), or river margins (Astrocaryum jauari, Leopoldinia pulchra) where competition is limited.
Palms were long assumed to be wind-pollinated, but recent studies are showing that, while some (the thatch palm, Thrinax) are indeed anemophilous, wind is only one of a diversity of mechanisms of pollination. Some genera, such as the coconut and babassu palms, are pollinated by both insects and wind. Beetles are implicated in Astrocaryum mexicanum, Bactris, Cryosophila albida, Rhapidophyllum hystrix, and Socratea exorrhiza. Syrphus flies apparently pollinate Asterogyne martiana in Costa Rica, and drosophila flies are thought to pollinate the nipa palm in New Guinea. Bees pollinate several species (Sabal palmetto and Iriartea deltoidea). Studies of pollination are difficult because of the large number of insects that are associated in some way with most palms. Few modern studies have been done, but obvious adaptations for insect pollination can be found in many palms. Bats have been found to pollinate Calyptrogyne in Costa Rica.
In most palm fruits only one ovule matures into a seed, although a few genera are known to have 2- or 3-seeded fruits and up to 10 seeds may develop in Phytelephas. The black or brightly coloured fruits are dispersed by many different animals. The African elephant feeds on fruits and is important in dispersing Phoenix reclinata, Borassus aethiopum, and species of Hyphaene. Shrikes feed on fruits of the date palm, and in northeastern Queensland, Australia, the cassowary ingests fruits and disperses seeds of several rainforest palms (Calamus and Linospadix). The black bear (Ursus americanus) disperses Sabal, Rhapidophyllum hystrix, and Serenoa repens in Florida, U.S. Fruits of Euterpe in northern South America are sought by fish and by the electric eel (Electrophorus electricus). Wild dogs (family Canidae) and palm civets (Paradoxurus) devour fruits of Arenga and Caryota in Asia. Studies of fruit dispersal are in their infancy, but a large number of interesting associations have been noted.
In tropical forest ecosystems palms are important in many ways. Breathing roots help aerate waterlogged soils. Orbignya cohune is known to be important in the development of the soil profile—stems are initially geotropic and buried to depths of one metre during establishment growth. The large cavities that are formed when palms in a population die result in considerable soil turnover. Many palms accumulate leaf litter in their crowns (Asterogyne martiana, Eugeissona minor, Pinanga ridleyana, and Daemonorops verticillaris), presumably trapping important nutrients. Some palms (Orbignya phalerata) contribute large amounts of dry matter, which, when recycled, adds to soil fertility.
During the 1980s the value of palms in demographic studies was realized. Palms are easily identified within the forest. Their age can be estimated by determining the length of time needed to produce a leaf and counting the leaf scars. This method, however, must be used with considerable caution since studies are beginning to show that the rate of leaf production can vary with environmental factors. Some palms have very long lives; life spans of 50 to 100 years are common. In the Seychelles, specimens of the double coconut, Lodoicea maldivica, have lived for up to 350 years, and Livistona eastonii in Australia has lived to be as old as 720 years.
Palms are important in determining the composition of the forest community. Forest understories are sometimes dominated by a single species, as is the case with Astrocaryum mexicanum in Veracruz, Mexico. Competition between young palms and ultimate canopy components may be an important factor in forest regeneration. Some palms that grow near the forest floor (Asterogyne martiana and Geonoma cuneata, for example) are being used to study light relationships, especially as regards simple versus dissected leaves. These studies are promising but in their preliminary stages.
