TheArecaceae (/ˌærəˈkeɪsi.iː,-ˌaɪ/) is afamily ofperennial,flowering plants in themonocot orderArecales. Their growth form can beclimbers,shrubs,tree-like and stemless plants, all commonly known aspalms. Those having a tree-like form are colloquially calledpalm trees.[4] Currently, 181genera with around 2,600species are known,[5][6] most of which are restricted totropical andsubtropical climates. Most palms are distinguished by their large, compound,evergreen leaves, known asfronds, arranged at the top of an unbranched stem, except for theHyphaene genus, who has branched palms. However, palms exhibit an enormous diversity in physical characteristics and inhabit nearly every type ofhabitat within their range, fromrainforests todeserts.
Palms are among the best known and most extensivelycultivated plant families. They have been important to humans throughout much of history, especially in regions like the Middle East and North Africa. A wide range of common products and foods are derived from palms. In contemporary times, palms are also widely used in landscaping. In many historical cultures, because of their importance as food, palms weresymbols for such ideas as victory, peace, and fertility.
The wordArecaceae is derived from the wordareca with the suffix "-aceae".Areca is derived fromPortuguese, viaMalayalam അടയ്ക്ക (aṭaykka), which is fromDravidian*aṭ-ay-kkāy ("areca nut"). The suffix-aceae is the feminine plural of the Latin-āceus ("resembling").[citation needed]
Palm originates fromLatinpalma semantically overlapping with sense of "hand front" (due to similar splayed shape) ultimately fromProto-Indo-European *pl̥h₂meh₂, a direct descendantfolm once existed in Old English.[7]
Whether as shrubs, tree-like, or vines, palms have two methods of growth: solitary or clustered. The common representation is that of a solitary shoot ending in a crown of leaves. Thismonopodial character may be exhibited by prostrate, trunkless, and trunk-forming members. Some common palms restricted to solitary growth includeWashingtonia andRoystonea. Palms may instead grow in sparse though dense clusters. The trunk develops an axillary bud at a leaf node, usually near the base, from which a new shoot emerges. The new shoot, in turn, produces an axillary bud and a clustering habit results. Exclusivelysympodial genera include many of therattans,Guihaia, andRhapis. Several palm genera have both solitary and clustering members. Palms which are usually solitary may grow in clusters and vice versa.[8]
Palms have large, evergreen leaves that are either palmately ('fan-leaved') or pinnately ('feather-leaved') compound and spirally (-alternately) arranged at the top of the stem, with the sole exception of the King Raphia (Raphia viniferavariety nigerica) which has opposite pairs of fronds). The leaves have a tubular sheath at the base that usually splits open on one side at maturity.[9] Theinflorescence is aspadix orspike surrounded by one or morebracts orspathes that become woody at maturity. Theflowers are generally small and white, radially symmetric, and can be either uni- or bisexual. The sepals and petals usually number three each and may be distinct or joined at the base. The stamens generally number six, with filaments that may be separate, attached to each other, or attached to the pistil at the base. Thefruit is usually a single-seededdrupe (sometimes berry-like)[10] but some genera (e.g.,Salacca) may contain two or more seeds in each fruit.
Sawn palm stem: Palms do not form annualtree rings.
Like allmonocots, palms do not have the ability to increase the width of a stem (secondary growth) via the same kind ofvascular cambium found in non-monocotwoody plants.[11] This explains the cylindrical shape of the trunk (almost constant diameter) that is often seen in palms, unlike inring-forming trees. However, many palms, like some other monocots, do have secondary growth, although because it does not arise from a single vascular cambium producingxylem inwards and phloem outwards, it is often called "anomalous secondary growth".[12]
The Arecaceae are notable among monocots for their height and for the size of their seeds, leaves, and inflorescences.Ceroxylon quindiuense, Colombia's national "tree", is the tallest monocot in the world, reaching up to 60 metres (197 ft) tall.[13] Thecoco de mer (Lodoicea maldivica) has the largest seeds of any plant, 40–50 centimetres (16–20 in) in diameter and weighing 15–30 kilograms (33–66 lb) each (coconuts are the second largest). Raffia palms (Raphia spp.) have the largest leaves of any plant, up to 25 metres (82 ft) long and 3 metres (10 ft) wide. TheCorypha species have the largest inflorescence of any plant, up to 7.5 metres (25 ft) tall and containing millions of small flowers.Calamus stems can reach 200 metres (656 ft) in length.
Most palms are native to tropical and subtropical climates. Palms thrive in moist and hot climates but can be found in a variety of different habitats. Their diversity is highest in wet, lowland forests.South America, theCaribbean, and areas of theSouth Pacific and southern Asia are regions of concentration.Colombia may have the highest number of palm species in one country. There are some palms that are also native to desert areas such as the Arabian Peninsula and parts of northwestern Mexico. Only about 130 palm species naturally grow entirely beyond the tropics, mostly in humid lowland subtropical climates, in highlands in southern Asia, and along the rim lands of theMediterranean Sea. The northernmost native palm isChamaerops humilis, which reaches44°N latitude along the coast ofLiguria,Italy.[14] In the southern hemisphere, the southernmost palm is theRhopalostylis sapida, which reaches44°S on theChatham Islands where anoceanic climate prevails.[15] Cultivation of palms is possible north of subtropical climates, and some higher latitude locales such as Ireland, Scotland, England, and thePacific Northwest feature a few palms in protected locations andmicroclimates. In theUnited States, there are at least 12 native palm species, mostly occurring in the states of theDeep South andFlorida.[16]
Palms inhabit a variety of ecosystems. More than two-thirds of palm species live in humid moist forests, where some species grow tall enough to form part of thecanopy and shorter ones form part of theunderstory.[17] Some species form pure stands in areas with poor drainage or regular flooding, includingRaphia hookeri which is common in coastal freshwater swamps in West Africa. Other palms live in tropical mountain habitats above 1 thousand metres (3 thousand feet), such as those in the genusCeroxylon native to theAndes. Palms may also live in grasslands and scrublands, usually associated with a water source, and in desertoases such as thedate palm. A few palms are adapted to extremelybasiclime soils, while others are similarly adapted to extremepotassium deficiency and toxicity of heavy metals inserpentine soils.[15]
TwoRoystonea regia specimens. The characteristic crownshaft and apex shoot, or 'spear', are visible.
Palms are amonophyletic group of plants, meaning the group consists of a common ancestor and all its descendants.[17] Extensive taxonomic research on palms began with botanistH.E. Moore, who organized palms into 15 major groups based mostly on general morphological characteristics. The following classification, proposed by N.W. Uhl and J. Dransfield in 1987, is a revision of Moore's classification that organizes palms into 6 subfamilies.[18] A few general traits of each subfamily are listed below.
SubfamilyArecoideae are the largest subfamily with14 tribes and containing over 100 genera. All tribes have pinnate or bipinnate leaves and flowers arranged in groups of three, with a central pistillate and two staminate flowers.
SubfamilyCalamoideae includes the climbing palms, such as rattans. The leaves are usually pinnate; derived characters (synapomorphies) include spines on various organs, organs specialized for climbing, an extension of the main stem of the leaf-bearing reflexed spines, and overlapping scales covering the fruit and ovary.
SubfamilyCeroxyloideae has small to medium-sized flowers, spirally arranged, with agynoecium of three joined carpels.
SubfamilyCoryphoideae are the second-largest subfamily with8 tribes. Most palms in this subfamily have palmately lobed leaves and solitary flowers with three, or sometimes fourcarpels. The fruit normally develops from only one carpel.
SubfamilyNypoideae contains only one species,Nypa fruticans,[19] which has large, pinnate leaves. The fruit is unusual in that it floats, and the stem is underground and dichotomously branched, also unusual in palms.
ThePhytelephantoideae is the sixth subfamily of Arecaceae in N.W. Uhl and J. Dransfield's 1987 classification. Members of this group have distinct monopodial flower clusters. Other distinct features include a gynoecium with five to 10 joined carpels, and flowers with more than three parts per whorl. Fruits are multiple-seeded and have multiple parts. From the modern phylogenomic data, the Phytelephantoideae are tribe in theCeroxyloideae subfamily.[20]
Currently, few extensive phylogenetic studies of the Arecaceae exist. In 1997, Bakeret al. explored subfamily and tribe relationships using chloroplastDNA from 60 genera from all subfamilies and tribes. The results strongly showed the Calamoideae are monophyletic, and Ceroxyloideae and Coryphoideae are paraphyletic. The relationships of Arecoideae are uncertain, but they are possibly related to the Ceroxyloideae and Phytelephantoideae. Studies have suggested the lack of a fully resolved hypothesis for the relationships within the family is due to a variety of factors, including difficulties in selecting appropriate outgroups,homoplasy in morphological character states, slow rates of molecular evolution important for the use of standardDNA markers, and character polarization.[21] However, hybridization has been observed amongOrbignya andPhoenix species, and using chloroplast DNA in cladistic studies may produce inaccurate results due to maternal inheritance of the chloroplast DNA. Chemical and molecular data from non-organelle DNA, for example, could be more effective for studying palm phylogeny.[20]
Recently, nuclear genomes and transcriptomes have been used to reconstruct the phylogeny of palms. This has revealed, for example, that a whole-genome duplication event occurred early in the evolution of the Arecaceae lineage, that was not experienced by its sister clade, theDasypogonaceae.[22]
The Arecaceae were the first modern family of monocots to appear in the fossil record around 80 million years ago (Mya), during the lateCretaceous period. The first modern species, such asNypa fruticans andAcrocomia aculeata, appeared 69 Mya, as evidenced by fossilNypa pollen. Palms appear to have undergone an early period ofadaptive radiation. By 60 Mya, many of the modern, specialized genera of palms appeared and became widespread and common, much more widespread than their range today. Because palms separated from the monocots earlier than other families, they developed more intrafamilial specialization and diversity. By tracing back these diverse characteristics of palms to the basic structures of monocots, palms may be valuable in studying monocot evolution.[23] Several species of palms have been identified from flowers preserved in amber, includingPalaeoraphe dominicana andRoystonea palaea.[24] Fossil evidence[clarification needed] of them can also be found in samples ofpetrified palmwood.[citation needed]
The relationship between the subfamilies is shown in the following cladogram:[citation needed]
Arecaceae are common in Saudi ArabiaPalmyra palm fruit atGuntur,India
Evidence for cultivation of the date palm byMesopotamians and other Middle Eastern peoples exists from more than 5,000 years ago,[25] in the form of date wood, pits for storing dates, and other remains of the date palm in Mesopotamian sites.[26][27] The date palm had a significant effect on the history of the Middle East and North Africa.[28] In the text "Date Palm Products" (1993), W.H. Barreveld wrote:[29]
One could go as far as to say that, had the date palm not existed, the expansion of the human race into the hot and barren parts of the "old" world would have been much more restricted. The date palm not only provided a concentrated energy food, which could be easily stored and carried along on long journeys across the deserts, it also created a more amenable habitat for the people to live in by providing shade and protection from the desert winds.[25]
An indication of the importance of palms in ancient times is that they are mentioned more than 30 times in theBible,[30] and at least 22 times in theQuran.[31] TheTorah also references the "70 date palm trees", which symbolize the 70 aspects of Torah that are revealed to those who "eat of its fruit."[32]
Arecaceae have great economic importance, including coconut products, oils, dates,palm syrup, ivory nuts, carnauba wax, rattan cane, raffia, andpalm wood. This family supplies a large amount of the human diet and several other human uses, both by absolute amount produced and by number ofspecies domesticated.[33] This is far higher than almost any other plant family, sixth out of domesticated crops in the human diet, and first in total economic value produced – sharing the top spot with thePoaceae andFabaceae.[33] These human uses have also spread many Arecaceae species around the world.[33]
Along with dates mentioned above, members of the palm family with human uses are numerous:
The type member of Arecaceae is the areca palm (Areca catechu), the fruit of which, theareca nut, is chewed with thebetel leaf for intoxicating effects.
Carnauba wax is harvested from the leaves of South American palms of the genusCopernicia.
Several species are harvested forheart of palm, a vegetable eaten in salads.[35]
Sap of the nipa palm,Nypa fruticans, is used to make vinegar.
Palmsap is sometimesfermented to producepalm wine or toddy, analcoholic beverage common in parts of Africa, India, and thePhilippines. The sap may be drunk fresh, but fermentation is rapid, reaching up to 4% alcohol content within an hour, and turning vinegary in a day.[36]
Palmyra and date palm sap is harvested in Bengal, India, to process intogur andjaggery.
Coconut is the partially edible seed of the fruit of the coconut palm (Cocos nucifera).[37]
Coir is a coarse, water-resistant fiber extracted from the outer shell of coconuts, used in doormats, brushes, mattresses, and ropes.[38]
Some indigenous groups living in palm-rich areas use palms to make many of their necessary items and food.Sago, for example, astarch made from the pith of the trunk of the sago palmMetroxylon sagu, is a majorstaple food for lowland peoples ofNew Guinea and theMoluccas.
Palm wine is made fromJubaea also called Chilean wine palm, or coquito palm.
Recently, the fruit of the açaí palmEuterpe has been used for its reputed health benefits.
Saw palmetto (Serenoa repens) is being investigated as a drug for treating enlarged prostates.[39]
Palm leaves are also valuable to some peoples as a material for thatching, basketry, clothing, and in religious ceremonies (see "Symbolism" below).[15]
The southeastern U.S. state ofSouth Carolina is nicknamed the Palmetto State after thesabal palmetto (cabbage palmetto), logs from which were used to build the fort atFort Moultrie. During theAmerican Revolutionary War, they were invaluable to those defending the fort, because their spongy wood absorbed or deflected the British cannonballs.[40]
OnAsh Wednesday, Catholics receive a cross on their forehead made of palm ashes as a reminder of theCatholic belief that everyone and everything eventually returns to where it came from, commonly expressed by the saying "ashes to ashes and dust to dust."[43]
Lately the Fujairah Research Centre reported the use of date palm leaves to help restore coral reefs as it merged ancientEmerati techniques with modern science.[44]
Like many other plants, palms have been threatened byhuman intervention andexploitation. The greatest risk to palms isdestruction of habitat, especially in thetropical forests, due tourbanization,wood-chipping,mining, andconversion to farmland. Palms rarely reproduce after such great changes in the habitat, and those with small habitat ranges are most vulnerable to them. The harvesting of heart of palm, a delicacy in salads, also poses a threat because it is derived from the palm'sapical meristem, a vital part of the palm that cannot be regrown (except in domesticated varieties, e.g. ofpeach palm).[45] The use ofrattan palms in furniture has caused a major population decrease in these species that has negatively affected local and international markets, as well as biodiversity in the area.[46] The sale of seeds to nurseries and collectors is another threat, as the seeds of popular palms are sometimes harvested directly from the wild. In 2006, at least 100 palm species were considered endangered, and nine species have been reported as recently extinct.[17]
However, several factors make palm conservation more difficult. Palms live in almost every type of warm habitat and have tremendous morphological diversity. Most palm seeds lose viability quickly, and they cannot be preserved in low temperatures because the cold kills the embryo. Using botanical gardens for conservation also presents problems, since they can rarely house more than a few plants of any species or truly imitate the natural setting.[47] There is also the risk that cross-pollination can lead to hybrid species.
The Palm Specialist Group of theWorld Conservation Union (IUCN) began in 1984, and has performed a series of three studies to find basic information on the status of palms in the wild, use of wild palms, and palms under cultivation. Two projects on palm conservation and use supported by theWorld Wildlife Fund took place from 1985 to 1990 and 1986–1991, in the American tropics and southeast Asia, respectively. Both studies produced copious new data and publications on palms. Preparation of a global action plan for palm conservation began in 1991, supported by the IUCN, and was published in 1996.[47]
The rarest palm known isHyophorbe amaricaulis. The only living individual remains at the Botanic Gardens of Curepipe inMauritius.
Edward Hitchcock's fold-out paleontological chart in his 1840Elementary Geology, showing the Palms as the crown of the planttree of life, alongside Man as the crown of the animal tree of life.
The palm branch was a symbol of triumph and victory inclassical antiquity. TheRomans rewarded champions of the games and celebrated military successes with palm branches. EarlyChristians used the palm branch to symbolize the victory of the faithful over enemies of the soul, as in thePalm Sunday festival celebrating the triumphal entry ofJesus Christ intoJerusalem. InJudaism, the palm represents peace and plenty, and is one of theFour Species ofSukkot; the palm may also symbolize theTree of Life inKabbalah.
The canopies of the Rathayatra carts which carry the deities of Krishna and his family members in the cart festival of Jagganath Puri in India are marked with the emblem of a palm tree. Specifically it is the symbol of Krishna's brother, Baladeva.[citation needed]
In 1840, the American geologistEdward Hitchcock (1793–1864) published the first tree-like paleontology chart in hisElementary Geology, with two separatetrees of life for the plants and the animals. These are crowned (graphically) with the Palms and with Man.[53]
Today, the palm, especially the coconut palm, remains a symbol of the tropical islandparadise.[17]Palms appear on the flags and seals of several places where they are native, including those ofHaiti,Guam,Saudi Arabia,Florida, andSouth Carolina.
^The name "Palmaceae" is not accepted because the name Arecaceae (and its acceptable alternative Palmae,ICBN Art. 18.5Archived 2006-05-24 at theWayback Machine) are conserved over other names for the palm family.
^Mallory, James P.; Adams, Douglas Q. (1997).Encyclopedia of Indo-European culture. Chicago: Fitzroy Dearborn. p. 255.ISBN1-884964-98-2.
^Uhl, Natalie W.; Dransfield, John (1987).Genera Palmarum – A classification of palms based on the work of Harold E. Moore. Lawrence, Kansas:Allen Press.ISBN978-0-935868-30-2.
Palmpedia—A wiki-based site dedicated to high quality images and information on palm trees.
Fairchild Guide to Palms—A collection of palm images, scientific data, and horticultural information hosted by Fairchild Tropical Botanic Garden, Miami.
