Epidendroideae

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Epidendroid orchids
Epidendrum schomburgkii - 1.jpg
Epidendrum schomburgkii
Scientific classification Red Pencil Icon.png
Kingdom: Plantae
Clade: Tracheophytes
Clade: Angiosperms
Clade: Monocots
Order: Asparagales
Family: Orchidaceae
Subfamily: Epidendroideae
Tribes

See text.

Epidendroideae.png
Synonyms

Vandoideae

In plant systematics, Epidendroideae is a subfamily of the orchid family, Orchidaceae. Epidendroideae is larger than all the other orchid subfamilies together, comprising more than 15,000 species in 576 genera. Most epidendroid orchids are tropical epiphytes, typically with pseudobulbs. There are, however, some terrestrials such as Epipactis and even a few myco-heterotrophs, which are parasitic upon mycorrhizal fungi.

Contents

They typically contain the remaining orchids with a single, fertile anther ( = monandrous), which is also fully incumbent ( = strongly convex) to suberect (= ascending towards the edges). The anther form arises from column elongation or, as in the vandoids, from early anther bending. The incumbent anther forms a right angle with the column axis or is pointed backward in many genera. Most have hard pollinia, i.e. a mass of waxy pollen or of coherent pollen grains. The pollinia are with caudicle and viscidium or without. The stigma are entire or three-lobed; a beak is present. The apical part of the middle stigma lobe forms a stipe ( = pollinium stalk). The ovary is unilocular. The leaves are distichous or spiraling, growing on thickened stems.

The Epidendroideae are difficult to classify. They have been divided in “lower epidendroids” and “higher epidendroids”.

Description

Epiphytes are plants which grow above the ground, on top of other plants. They are not planted in the soil and are not parasitic (i.e. they do not feed on other plants; however, some types still damage their host in various ways). By growing on other plants, the epiphytes can reach to the light better or where they can avoid struggling for light. Many mosses and lichens are epiphytes, as are approximately 10 per cent of all seed plants and ferns. Epiphytes are common in some groups of plants, such as ferns, mosses, lichens, and algae. Over half of the 20,000 species of orchids are epiphytes.

Habitat

Most epiphytic seed plants and ferns are found in tropical and subtropical rainforests because they need high humidity to survive. The areas which most epiphytes grow are the montane rainforests. Epiphytic orchids are found on many positions of the host tree, depending on species requirements and size, some large species will grow in a fork, whereas some small species scramble through thin branches, other species will climb up the trunk etc. etc. The trees provide many habitats with different conditions of temperature, contact and light. In temperate places, epiphytes are most common in moist forests, such as the rainforests in Queensland.

Adaptation

Epiphytes are not adapted to droughts in the same way are other flora, because they don’t have access to the ground, but they still have some mechanisms to help them survive. Some become completely dormant for months at a time; many epiphytes show crassulacean acid metabolism (CAM), which involves taking in CO2 at night, and photo-fixing it during the day with closed stomata to reduce water loss by transpiration. They also contain absorptive plants that are capable at quickly taking up water when it is available and preventing drought when water is scarcer. CAM can be impeded by higher night-time temperatures, dehydrated tissues, and high saturation deficits in the surrounding air, which lower the "stomata conductance" of the epiphytes, reducing the CO2 uptake, which in turn reduces growth and reproduction and even induces carbon loss. Higher temperatures, strain on evaporation, and contact to light cause CAM-idling, which is the epiphyte closing its stomata when it becomes stressed, that brings down the range of habitats a species can inhabit. Epiphyte species work biomasses are much more sensitive to different relative moisture levels than other plants.

Tribe classification

The subfamily Epidendroideae is divided into two clades or subgroups known as the higher epidendroids (vandoids) and the lower epidendroids. The lower epidendroids contain polyphyletic tribes, particularly the Arethuseae and Epidendreae. The tribes are listed below:

This classification has a rather ephemeral nature and is prone to frequent revision. Changes are likely to occur as new morphological and genetic data become available. [1] [2] [3]

Related Research Articles

Orchidaceae The orchid family of flowering plants

The Orchidaceae are a diverse and widespread family of flowering plants, with blooms that are often colourful and fragrant, commonly known as the orchid family.

Epiphyte Non-parasitic organism that grows upon another plant but is not nourished by it

An epiphyte is an organism that grows on the surface of a plant and derives its moisture and nutrients from the air, rain, water or from debris accumulating around it. Epiphytes take part in nutrient cycles and add to both the diversity and biomass of the ecosystem in which they occur, like any other organism. They are an important source of food for many species. Typically, the older parts of a plant will have more epiphytes growing on them. Epiphytes differ from parasites in that they grow on other plants for physical support and do not necessarily affect the host negatively. An organism that grows on another organism that is not a plant may be called an epibiont. Epiphytes are usually found in the temperate zone or in the tropics. Epiphyte species make good houseplants due to their minimal water and soil requirements. Epiphytes provide a rich and diverse habitat for other organisms including animals, fungi, bacteria, and myxomycetes.

<i>Bulbophyllum</i> Genus of orchids

Bulbophyllum is a genus of mostly epiphytic and lithophytic orchids in the family Orchidaceae. It is the largest genus in the orchid family and one of the largest genera of flowering plants with more than 2,000 species, exceeded in number only by Astragalus. These orchids are found in diverse habitats throughout most of the warmer parts of the world including Africa, southern Asia, Latin America, the West Indies, and various islands in the Indian and Pacific Oceans. Orchids in this genus have thread-like or fibrous roots that creep over the surface of trees or rocks or hang from branches. The stem is divided into a rhizome and a pseudobulb, a feature that distinguished this genus from Dendrobium. There is usually only a single leaf at the top of the pseudobulb and from one to many flowers are arranged along an unbranched flowering stem that arises from the base of the pseudobulb. Several attempts have been made to separate Bulbophyllum into smaller genera, but most have not been accepted by the World Checklist of Selected Plant Families.

Cypripedioideae

Cypripedioideae is a subfamily of orchids commonly known as lady's slipper orchids, lady slipper orchids or slipper orchids. Cypripedioideae includes the genera Cypripedium, Mexipedium, Paphiopedilum, Phragmipedium and Selenipedium. They are characterised by the slipper-shaped pouches of the flowers – the pouch traps insects so they are forced to climb up past the staminode, behind which they collect or deposit pollinia, thus fertilizing the flower. There are approximately 165 species in the subfamily.

<i>Aerides</i>

Aerides, known commonly as cat's-tail orchids and fox brush orchids, is a genus belonging to the orchid family. It is a group of tropical epiphyte orchids that grow mainly in the warm lowlands of tropical Asia from India to southern China to New Guinea. They are valued in horticulture for their racemes of showy, fragrant, colorful flowers.

Tasmanian temperate rainforests

The Tasmanian temperate rain forests are a temperate broadleaf and mixed forests ecoregion in western Tasmania. The ecoregion is part of the Australasian realm, which includes Tasmania and Australia, New Zealand, New Guinea, New Caledonia, and adjacent islands.

<i>Trichocentrum</i>

Trichocentrum, often abbreviated Trctm in horticulture, is a genus in the orchid family, Orchidaceae. Dancinglady orchid is a common name for plants in this genus. It was described by Stephan Ladislaus Endlicher and Eduard Friedrich Poeppig in 1836. This genus alone makes up the monogeneric Trichocentrum alliance, a quite distinct lineage of the subtribe Oncidiinae.

<i>Laelia</i>

Laelia is a small genus of 25 species in the orchid family (Orchidaceae). Laelia species are found in areas of subtropical or temperate climate in Central and South America, but mostly in Mexico. Laelia is abbreviated L. in the horticultural trade.

The taxonomy of the Orchidaceae has evolved slowly during the last 250 years, starting with Carl Linnaeus who in 1753 recognized eight genera. De Jussieu recognized the Orchidaceae as a separate family in his Genera Plantarum in 1789. Olof Swartz recognized 25 genera in 1800. Louis Claude Richard provided us in 1817 with the descriptive terminology of the orchids.. The next step was taken in 1830-1840 by John Lindley, who recognized four subfamilies. He is generally recognized as the father of orchid taxonomy. The next important step was taken by George Bentham with a new classification, recognizing subtribes for the first time. This classification was first presented in a paper that Bentham read to the Royal Society in 1881. Then it was published in 1883 in the final volume of Genera Plantarum. The next great contributors were Pfitzer (1887), Schlechter (1926), Mansfeld (1937), Dressler and Dodson (1960), Garay, Vermeulen (1966), again Dressler (1981). and Burns-Balogh and Funk (1986). Dressler's 1993 book had considerable influence on later work.

Vanilloideae

Vanilloideae is one of the subfamilies of orchids belonging to the large family Orchidaceae.

<i>Xerorchis</i>

Xerorchis is an orchid genus in the subfamily Epidendroideae, and the sole representative of tribe Xerorchideae. This is a very primitive genus consisting of terrestrial orchids. Xerorchis thrives in South America.

<i>Dendrophylax lindenii</i> Species of perennial epiphyte from the orchid family

Dendrophylax lindenii, the ghost orchid is a perennial epiphyte from the orchid family (Orchidaceae). It is native to Florida and Cuba. Other common names include palm polly and white frog orchid.

Vandeae Tribe of orchids

The Vandeae is a large monophyletic tribe within the family of orchids.

<i>Cattleya maxima</i> Species of plant

Cattleya maxima is a species of orchid in subfamily Epidendroideae found from Venezuela to Peru.

<i>Cattleya walkeriana</i>

Cattleya walkeriana is a species of orchid. It differs from most species of Cattleya by having inflorescences which arise from the rhizome instead of from the apex of the pseudobulb. In its native habitat it grows as either an epiphyte or a lithophyte, sometimes in full sun. Pseudobulbs are relatively short, bulbous or fusiform, with one or two ovate leaves at the apex. Inflorescence is one- or few-flowered, about 8" (20 cm) tall. Flowers are 4-5" (9-12 cm) across.

Eriinae

The Eriinae form a subtribe of Podochileae, a tribe of the orchid family (Orchidaceae). The name is derived from the genus Eria.

Dendrobieae Tribe of orchids

Dendrobieae is a tribe in the subfamily Epidendroideae, in the family Orchidaceae.

<i>Rhinerrhizopsis</i>

Rhinerrhizopsis, commonly known as freckle orchids, is a genus of three species from the orchid family, Orchidaceae. Plants in this genus are epiphytes with smooth, thin roots, fleshy or leathery leaves and a large number of small, round, short-lived flowers with a three-lobed labellum. These orchids are found in the Bismarck Archipelago, the Solomon Islands, New Guinea and tropical North Queensland, Australia.

<i>Trachoma</i> (plant)

Trachoma, commonly known as spectral orchids, is a genus of flowering plants in the family Orchidaceae. Orchids in this genus are epiphytic plants with leafy stems, crowded, leathery leaves arranged in two ranks and a large number of relatively small, short-lived flowers that often open in successive clusters. The sepals and petals are free from and more or less similar to each other, except that the petals are often smaller. The labellum is rigidly fixed to the column and is more or less sac-shaped. There are about 17 species distributed from Assam to the Western Pacific Ocean. Most species grow in rainforests, often on emergent trees such as hoop pine.

Canopy soils, also known as arboreal soils, exist in areas of the canopy in a forests where branches, crevices, or some other physical feature on a tree can accumulate organic matter, such as leaves or fine branches. Eventually, this organic matter weathers into some semblance of a soil, and can reach depths of 30 cm in some temperate rainforests. Epiphytes can take root in this thin soil, which accelerates the development of the soil by adding organic material and physically breaking up material with their root system. Common epiphytes in the canopy soils in temperate rainforests include mosses, ferns, and lichens. Epiphytes on trees in the temperate zone are often ubiquitous and can cover entire trees. Some host trees house up to 6.5 tons dry weight of epiphytic biomass, which can equate to more than 4x of its own foliar mass. This massive presence means their dynamics need to be better understood in order to fully understand forest dynamics. The nutrients that become stored within canopy soils can then be utilized by the epiphytes that grow in them, and even the tree that the canopy soil is accumulating in through the growth of canopy roots. This storage allows nutrients to be more closely cycled through an ecosystem, and prevents nutrients from being washed out of the system.

References

  1. Cameron, Kenneth M. et al. American Journal of Botany. 1999. (86):p. 208–224. "A phylogenetic analysis of the Orchidaceae: evidence from rbcL nucleotide sequences".
  2. A diagram showing higher and lower epidendroids and their phylogenetic relationships
  3. John V. Freudenstein, Mark W. Chase. Annals of Botany. 2015. (115):p. s 665–681. Phylogenetic relationships in Epidendroideae (Orchidaceae), one of the great flowering plant radiations: progressive specialization and diversification. https://doi.org/10.1093/aob/mcu253