Dendrosicyos

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Dendrosicyos
Cucumber tree (6407165121).jpg
Thiselton-Dyer Dendrosicyos-socotrana-2.jpg
Scientific classification OOjs UI icon edit-ltr.svg
Kingdom: Plantae
Clade: Tracheophytes
Clade: Angiosperms
Clade: Eudicots
Clade: Rosids
Order: Cucurbitales
Family: Cucurbitaceae
Subfamily: Cucurbitoideae
Tribe: Coniandreae
Genus: Dendrosicyos
Balf.f.
Species:
D. socotranus
Binomial name
Dendrosicyos socotranus

Dendrosicyos is a monotypic genus in the plant family Cucurbitaceae. The only species is Dendrosicyos socotranus, the cucumber tree. The species is endemic to the island of Socotra in Yemen, and is the only species in the Cucurbitaceae to grow in a tree form. The species name was originally spelled D. socotrana, [2] but this is corrected to masculine grammatical gender according to the International Code of Nomenclature for algae, fungi, and plants. [3] [4]

Contents

Features

It has a bulbous trunk and a small crown. [5] It was first described by Isaac Bayley Balfour in 1882. [1] A recent molecular phylogenetic analysis of the family Cucurbitaceae found that the Dendrosicyos lineage is about twice as old as the island, and thus seems to be an island relic of a progenitor lineage that became extinct on the mainland. [6]

The leaves are nearly round, covered with fine bristles, and slightly toothed. The yellow flowers (3 cm), males and females are present on the same plant for cross pollination. It reproduces only by seed. Fruits (3 x 5 cm) are green, turning brick-red when ripe.

Seedlings subjected to overgrazing and regeneration may be compromised over time, except for seedlings protected from goats by Cissus subaphylla . The species is considered endangered. In Soqotri, its name is qamhiyn.

Contrary to what its region of origin would suggest, Dendrosicyos socotranus responds well to being drenched and fertilized, if the temperature is greater than 20 °C. Individuals in their natural habitat can attain 3 meters (10 feet) in height. Trunks are succulent, but not bottle-shaped when young. The plant produces flowers when five years old. [7]

D. socotranus has a bottle-shaped base of fibrous wood (pachycaul). The trunk reaches a diameter of up to one meter. Numerous small twigs and branches grow from the stem, the bottle tree growth form making it distinctive.

The base consists largely of parenchyma. In it are embedded small xylem strands that are linked to each other (anastomosis). These xylem strands have a cambium, and a secondary phloem forms. There is not a consistently active cambium - it will always be sequentially formed on the periphery of a new cambium (cambium successively). Dendrosicyos is the first member of the Cucurbitaceae in which such meristem has been demonstrated.

The leaves are about 25 cm long and wide, its leaf edge being slightly thorny. On the underside of the leaves are trichomes of from two to seven cells, the cells often containing two cystoliths. The epidermal cells are lignified.

The flowers occur in the leaf axils. The species is monoecious - male and female flowers on one plant. The flowers are yellowish-orange with long petals and the fruits are ovate. The seeds are about 6 mm.

The plant contains dendrosycin, an iso-cucurbitacin with an unusual ring formation. [8]

Proliferation and locations

Described in 1882 by Isaac Bayley Balfour, the species is generally described as endemic to the island of Socotra, although some sources (1887) state that it was present on the African continent in Djibouti. It is quite abundant on the dry parts of the island of Socotra, associated with Croton socotranus in the plains, and on calcareous soils to 500 m elevation. The species is well-adapted to dry sites. It is widely distributed in several vegetation types but has a rather fragmented distribution; over large areas there are only isolated trees or small relict populations, whilst in other areas it is relatively abundant. There are a few trees on the island of Samhah, but none on Darsah or Abd al Kuri.

Conservation status

In times of severe drought trees are cut down, pulped and fed to livestock. In some areas (Kilissan) this has resulted in its almost total eradication. On the plains, seedlings germinate and grow protected from livestock in the cover of dense vegetation such as provided by the spiny shrub Lycium sokotranum or by colonies of the succulent shrub Cissus subaphylla . Where there is no Cissus or Lycium, there is little if any regeneration. Thus, along the southern region of Socotra and on Samhah the recovery of populations of Dendrosicyos after drought is dependent on the presence of colonies of Cissus.

Nomenclature

The genus is in the pumpkin subfamily Cucurbitoideae and in the tribe Coniandreae. Dendrosicyos is the basal taxon within the tribe, all other genera of the tribe being a sister group. [9]

The name Dendrosicyos socotranus means 'cucumber tree of Socotra'.

Related Research Articles

<span class="mw-page-title-main">Cucurbitales</span> Order of flowering plants

The Cucurbitales are an order of flowering plants, included in the rosid group of dicotyledons. This order mostly belongs to tropical areas, with limited presence in subtropical and temperate regions. The order includes shrubs and trees, together with many herbs and climbers. One major characteristic of the Cucurbitales is the presence of unisexual flowers, mostly pentacyclic, with thick pointed petals. The pollination is usually performed by insects, but wind pollination is also present.

<span class="mw-page-title-main">Cucurbitaceae</span> Family of plants

The Cucurbitaceae, also called cucurbits or the gourd family, are a plant family consisting of about 965 species in 101 genera. Those most important to humans are the following:

<span class="mw-page-title-main">Gourd</span> Type of fruit

Gourds include the fruits of some flowering plant species in the family Cucurbitaceae, particularly Cucurbita and Lagenaria. The term refers to a number of species and subspecies, many with hard shells, and some without. One of the earliest domesticated types of plants, subspecies of the bottle gourd, Lagenaria siceraria, have been discovered in archaeological sites dating from as early as 13,000 BCE. Gourds have had numerous uses throughout history, including as tools, musical instruments, objects of art, film, and food.

<span class="mw-page-title-main">Socotra</span> Largest of four islands of the Socotra Archipelago, Yemen

Socotra or Saqatri is an island of Yemen in the Indian Ocean. Lying between the Guardafui Channel and the Arabian Sea and near major shipping routes, Socotra is the largest of the four islands in the Socotra archipelago. Since 2013, the archipelago has constituted the Socotra Governorate.

<i>Adenium obesum</i> Species of plant

Adenium obesum, more commonly known as a desert rose, is a poisonous species of flowering plant belonging to the tribe Nerieae of the subfamily Apocynoideae of the dogbane family, Apocynaceae. It is native to the Sahel regions south of the Sahara, tropical and subtropical eastern and southern Africa, as well as the Arabian Peninsula. Other names for the flower include Sabi star, kudu, mock azalea, and impala lily. Adenium obesum is a popular houseplant and bonsai in temperate regions.

<span class="mw-page-title-main">Pachycaul</span>

Pachycauls are plants with a disproportionately thick trunk, for their height, and relatively few branches. With certain pachycaul species, particularly the more succulent varieties, they are commonly referred to as "caudiciformes", a reference to their trunk development of a moisture-filled caudex for periods of drought.

Boswellia nana is a species of plant in the Burseraceae family endemic to the Yemeni island of Socotra. They are small trees or shrubs, sometimes so bent that they are lying nearly horizontal to the ground.

<i>Euphorbia arbuscula</i> Species of plant

Euphorbia arbuscula is a species of plant in the spurge family (Euphorbiaceae). It is endemic to the archipelago of Socotra in Yemen. Its natural habitats are subtropical or tropical dry forests and subtropical or tropical dry shrubland.

Cucumber tree is a common name for several unrelated trees and may refer to:

Secamone socotrana is a species of plant in the family Apocynaceae. It is endemic to the Socotra Islands in the Republic of Yemen. Its natural habitats are subtropical or tropical dry forests and subtropical or tropical dry shrubland.

<span class="mw-page-title-main">Socotra Island xeric shrublands</span>

The Socotra Island xeric shrublands is a terrestrial ecoregion that covers the large island of Socotra and several smaller islands that constitute the Socotra Archipelago. The archipelago is in the western Indian Ocean, east of the Horn of Africa and south of the Arabian Peninsula. Politically the archipelago is part of Yemen, and lies south of the Yemeni mainland.

<span class="mw-page-title-main">Woody plant</span> Plant that produces wood and has a hard stem

A woody plant is a plant that produces wood as its structural tissue and thus has a hard stem. In cold climates, woody plants further survive winter or dry season above ground, as opposed to herbaceous plants that die back to the ground until spring.

<span class="mw-page-title-main">Plant stem</span> Structural axis of a vascular plant

A stem is on of two main structural axes of a vascular plant, the other being the root. It supports leaves, flowers and fruits, transports water and dissolved substances between the roots and the shoots in the xylem and phloem, photosynthesis takes place here, stores nutrients, and produces new living tissue. The stem can also be called halm or haulm or culms.

<i>Dracaena cinnabari</i> Species of plant

Dracaena cinnabari, the Socotra dragon tree or dragon blood tree, is a dragon tree native to the Socotra archipelago, part of Yemen, located in the Arabian Sea. It is named after the blood-like color of the red sap that the trees produce. It is considered the national tree of Yemen.

<i>Cissus trifoliata</i> Species of grapevine

Cissus trifoliata, known variously as possum-grape, sorrelvine, vine-sorrel, or hierba del buey is a New World plant species in the grape family. It is native to the southern United States, Mexico, Venezuela, Colombia and perhaps Ecuador (Loja). It is also dispersed among some islands in the Caribbean.

<i>Senna sophera</i> Species of legume

Senna sophera is a shrub or tree in the bean family Fabaceae. It is now widespread in tropical and subtropical regions of the world, but is believed to be native to tropical America. Originally described by Carl Linnaeus in 1753 as Cassia sophera, it has acquired a large number of synonyms. Vernacular names include algarrobilla, baner, kasunda, kasaundi (Hindi) and kolkasunda (Bengali).. This tree is called Gnazhar tree in Tamil. The flower of this tree has been extensively referred in poems of Sangam Tamil litterature.

<i>Cucurbita okeechobeensis</i> Species of vine

Cucurbita okeechobeensis, the Okeechobee gourd, is a species of gourd in the family Cucurbitaceae, native to Mexico and the United States. There are two subspecies; one is endemic to Florida, primarily in the region around Lake Okeechobee, the other to the State of Veracruz in eastern Mexico. Once abundant, it has state and federal listing as an endangered species. One of its peculiarities is the yellow corolla not so common in other Cucurbita species.

<i>Cissus subaphylla</i> Species of plant

Cissus subaphylla is a low shrub in the grape family Vitaceae. It is endemic to the Yemeni island of Socotra. The plant grows mainly in dry, low-lying areas on alluvial fans or on limestone slopes, and is rarely found above elevations of 300 metres (980 ft), where it is replaced by C. hamaderohensis. It does not have the climbing habit of other Cissus species, and its stems are flattened and gray-green in colour, with relatively small leaves and flowers. The tangled mats of C. subaphylla stems act as a protective covering for plants regularly eaten by goats and other browsing animals; the plant is thus important in the rehabilitation of species such as Dendrosicyos, Maerua and Commiphora.

Begonia samhaensis is a species in the family Begoniaceae. Similar to Begonia socotrana but separated by the asymmetrically ovate leaves and the unequal tepals in the male flowers; outer tepals broadly orbicular, 1.5–2.2 × 1.7–2.5 cm; inner obovate elliptic, 1.4–2.0 × 0.8 × 1.4 cm.

<span class="mw-page-title-main">Gordon Rowley</span> British botanist and writer (1921–2019)

Gordon Douglas Rowley (1921–2019) was a British botanist and writer specialising in cacti and succulents.

References

  1. 1 2 Miller, A. (2004). "Dendrosicyos socotrana". IUCN Red List of Threatened Species . 2004: e.T33691A9797777. doi: 10.2305/IUCN.UK.2004.RLTS.T33691A9797777.en .
  2. ↑ Isaac Bayley Balfour (1882), "Diagnoses Plantarum novarum et imperfecte descriptarum Phanerogamarum Socotrensium", Proceedings of the Royal Society of Edinburgh, 11: 498–514
  3. ↑ The International Plant Names Index , retrieved 23 January 2016
  4. ↑ McNeill, J.; Barrie, F.R.; Buck, W.R.; Demoulin, V.; Greuter, W.; Hawksworth, D.L.; Herendeen, P.S.; Knapp, S.; Marhold, K.; Prado, J.; Prud'homme Van Reine, W.F.; Smith, G.F.; Wiersema, J.H.; Turland, N.J. (2012), International Code of Nomenclature for algae, fungi, and plants (Melbourne Code) adopted by the Eighteenth International Botanical Congress Melbourne, Australia, July 2011, vol. Regnum Vegetabile 154, A.R.G. Gantner Verlag KG, ISBN   978-3-87429-425-6 . Article 62, Ex 1, specifies that the noun Sicyos is treated as masculine.
  5. ↑ Kingdon, Jonathan (1989). Island Africa: The Evolution of Africa's Rare Plants and Animals. Princeton, New Jersey: Princeton University Press. pp.  40–41. ISBN   0-691-08560-9.
  6. ↑ Schaefer, H.; Heibl, C; Renner, S (2009). "Gourds afloat: a dated phylogeny reveals an Asian origin of the gourd family (Cucurbitaceae) and numerous oversea dispersal events". Proceedings of the Royal Society B. 276 (1658): 843–851. doi:10.1098/rspb.2008.1447. PMC   2664369 . PMID   19033142.
  7. ↑ Dendrosicyos socotrana: A tree squash extraordinaire
  8. ↑ HA Hussein, O.B. Abdel-Halim, S.M. Marwan, A.A. El-Gamal, R. Mosana. Dendrocyin: an isocucurbitacin with novel cyclic side chain from Dendrosicyos socotrana Phytochemistry, Volume 65(18), 2004, p. 2551-2556. doi:10.1016/j.phytochem.2004.07.016
  9. ↑ Kocyan Alexander, Li-Bing Zhang, Hanno Schaefer, Susanne S. Renner. A multi-locus chloroplast phylogeny for the Cucurbitaceae and its implications for character evolution and classification. Molecular Phylogenetics and Evolution, Volume 44(2), August 2007, pp. 553-577 doi:10.1016/j.ympev.2006.12.022
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