''Socratea exorrhiza'', the walking palm or cashapona, is a

palm Palm most commonly refers to: * Palm of the hand, the central region of the front of the hand * Palm plants, of family Arecaceae ** List of Arecaceae genera **Palm oil * Several other plants known as "palm" Palm or Palms may also refer to: Music ...

native to

rainforest Rainforests are forests characterized by a closed and continuous tree Canopy (biology), canopy, moisture-dependent vegetation, the presence of epiphytes and lianas and the absence of wildfire. Rainforests can be generally classified as tropi ...

s in tropical Central and

South America South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a considerably smaller portion in the Northern Hemisphere. It can also be described as the southern Subregion#Americas, subregion o ...

. It can grow to 25 metres in height, with a stem diameter of up to 16 cm, but is more typically 15–20 m tall and 12 cm in diameter. It has unusual stilt roots, the function of which has been debated. Many species of

epiphyte An epiphyte is a plant or plant-like organism that grows on the surface of another plant and derives its moisture and nutrients from the air, rain, water (in marine environments) or from debris accumulating around it. The plants on which epiphyt ...

have been found growing on the palms. The palm is pollinated by beetles, and various organisms eat its seeds or seedlings.

Function of stilt roots

E. J. H. Corner in 1961 hypothesised that the unusual stilt roots of ''S. exorrhiza'' were an adaptation to allow the palm to grow in

swamp A swamp is a forested wetland.Keddy, P.A. 2010. Wetland Ecology: Principles and Conservation (2nd edition). Cambridge University Press, Cambridge, UK. 497 p. Swamps are considered to be transition zones because both land and water play a role in ...

y areas of forest. No evidence exists that stilt roots are in fact an adaptation to flooding, and alternative functions for them have been suggested. John H. Bodley suggested in 1980 that they in fact allow the palm to "walk" away from the point of germination if another tree falls on the seedling and knocks it over. If such an event occurs then the palm produces new vertical stilt roots and can then right itself, the original roots rotting away. Radford writes in the ''

Skeptical Inquirer ''Skeptical Inquirer'' (S.I.) is a bimonthly American general-audience magazine published by the Committee for Skeptical Inquiry (CSI) with the subtitle "The Magazine for Science and Reason". The magazine initially focused on investigating clai ...

'' in December 2009 that "As interesting as it would be to think that when no one is around trees walk the rainforest floor, it is a mere myth", and cites two detailed studies that came to this conclusion. Other advantages of stilt roots over normal roots have since been proposed. Swaine proposed in 1983 that they allow the palm to colonise areas where there is much debris (for example, dead logs) as they can avoid it by moving their roots. Hartshorn suggested in 1983 that stilt roots allow the palm to grow upwards to reach light without having to increase the diameter of the stem. It was also thought that the roots may confer an advantage when the palm is growing on a slope, but no evidence has been found that this is the case. These very thick (8 to ten cm) roots grow as much as 28 inches (70 cm) longer in a month. ''

Iriartea ''Iriartea'' is a genus in the palm family ''Arecaceae''. It is native to Central and South America. The best-known species – and probably the only one – is ''Iriartea deltoidea'', which is found from Nicaragua, south into Bolivia an ...

'' has similar stilt roots to ''S. exorrhiza''.

Epiphytes

Many different species of

have been found to grow on ''S. exorrhiza''. A study of 118 individual trees in

Panama Panama, officially the Republic of Panama, is a country in Latin America at the southern end of Central America, bordering South America. It is bordered by Costa Rica to the west, Colombia to the southeast, the Caribbean Sea to the north, and ...

found 66 species from 15 families on them.

Bryophytes Bryophytes () are a group of land plants ( embryophytes), sometimes treated as a taxonomic division referred to as Bryophyta '' sensu lato'', that contains three groups of non-vascular land plants: the liverworts, hornworts, and mosses. In t ...

covered up to 30% of the stems, and the relative coverage increased as the stem diameter increased. Around half of the trees studied had

vascular Vascular can refer to: * blood vessels, the vascular system in animals * vascular tissue Vascular tissue is a complex transporting tissue, formed of more than one cell type, found in vascular plants. The primary components of vascular tissue ...

epiphytes growing on them. Up to 85 individuals from 12 different species were found on one palm, and another tree was colonised by a total of 16 different species. The most common epiphytes were three species of fern, '' Ananthacorus angustifolius'', '' Elaphoglossum sporadolepis'' and '' Dicranoglossum panamense'', altogether accounting for 30% of all the individuals recorded. Other common species, representing more than 5% of the individuals found, included '' Scaphyglottis longicaulis'' (

Orchidaceae Orchids are plants that belong to the family (biology), family Orchidaceae (), a diverse and widespread group of flowering plants with blooms that are often colourful and fragrant. Orchids are cosmopolitan distribution, cosmopolitan plants that ...

), '' Philodendron schottianum'' (

Araceae The Araceae are a family of monocotyledonous flowering plants in which flowers are borne on a type of inflorescence called a spadix. The spadix is usually accompanied by, and sometimes partially enclosed in, a spathe (or leaf-like bract). Also ...

) and '' Guzmania subcorymbosa'' (

Bromeliaceae The Bromeliaceae (the bromeliads) are a family of monocot flowering plants of about 80 genera and 3700 known species, native mainly to the tropical Americas, with several species found in the American subtropics and one in tropical west Africa, ...

). Almost half of the species recorded were rare, however, with only between 1 and 3 individuals being recorded on all of the palms. A clear vertical distribution was found between different species: some grew in the understory, other in the midstory and others in the canopy. Trees with epiphytes were found to be significantly larger than those without. This suggests that the palms must reach a certain age before they are colonised; for example, it is estimated that palms must be 20 years old before they are colonised by vascular epiphytes.

Leaf morphology

Leaves of ''S. exorrhiza'' that grow in the sun are thicker, have more

trichome Trichomes (; ) are fine outgrowths or appendages on plants, algae, lichens, and certain protists. They are of diverse structure and function. Examples are hairs, glandular hairs, scales, and papillae. A covering of any kind of hair on a plant ...

s and more

stoma In botany, a stoma (: stomata, from Greek language, Greek ''στόμα'', "mouth"), also called a stomate (: stomates), is a pore found in the Epidermis (botany), epidermis of leaves, stems, and other organs, that controls the rate of gas exc ...

ta than those that grow in the shade. Among the younger trees the leaflets are all arranged along a single plane, as with ''

Howea ''Howea'' is a genus of two palms, '' H. belmoreana'' and '' H. forsteriana'', both endemic to Lord Howe Island, Australia. ''H. forsteriana'' in particular is commonly grown as an indoor plant in the Northern Hemisphere, and the two species for ...

'', but in older individuals the leaflets are scattered among many planes as in the queen palm.

Predators

White-lipped peccaries consume a large proportion of the seeds of ''S. exorrhiza'' and play an important role in limiting their population.

Reproduction

''Socratea exorrhiza'' flowers mostly during the dry season and is considered to be

beetle Beetles are insects that form the Taxonomic rank, order Coleoptera (), in the superorder Holometabola. Their front pair of wings are hardened into wing-cases, elytra, distinguishing them from most other insects. The Coleoptera, with about 40 ...

pollinated Pollination is the transfer of pollen from an anther of a plant to the stigma of a plant, later enabling fertilisation and the production of seeds. Pollinating agents can be animals such as insects, for example bees, beetles or butterflies; bird ...

, being frequently visited by species of '' Phyllotrox'' ( Derelomini) and ''

Mystrops ''Mystrops'' is a genus of beetles belonging to the family Nitidulidae The sap beetles, also known as Nitidulidae, are a family of beetles. They are small (2–6 mm) ovoid, usually dull-coloured beetles, with knobbed antennae. Some ha ...

'' (

Nitidulidae The sap beetles, also known as Nitidulidae, are a family of beetles. They are small (2–6 mm) ovoid, usually dull-coloured beetles, with knobbed antennae. Some have red or yellow spots or bands. They feed mainly on decaying vegetable ma ...

). Seeds weigh around 3.5 g and are around 2 cm long and 1.5 cm wide, only around 45% of them germinate and around one quarter of these die.

Uses

The trunk is used in the construction of houses and other structures, as well as hunting spears. It is usually split lengthwise before it is used, but it can also be hollowed out and used as a tube. The inner parts of the stilt roots are used as a male

aphrodisiac An aphrodisiac is a substance that increases libido, sexual desire, sexual attraction, sexual pleasure, or sexual behavior. These substances range from a variety of plants, spices, and foods to synthetic chemicals. Natural aphrodisiacs, such as ...

. The yellow fruits are edible. The leaves may be used to build a temporary shelter or more permanent hut roofs. A harpoon foreshaft identified as wood of the palm was found with a large flaked lithic projectile point in an underwater preceramic site the middle Xingu.A. Roosevelt et al. 2009

References

External links

La Selva digital flora (Spanish)
{{Taxonbar, from=Q140538 Iriarteeae Trees of the Amazon rainforest Trees of Brazil Flora of Panama Taxa named by Carl Friedrich Philipp von Martius