In plant systematics Epidendroideae is a subfamily of the orchid family, Orchidaceae

Orchidaceae

The Orchidaceae, commonly referred to as the orchid family, is a morphologically diverse and widespread family of monocots in the order Asparagales. Along with the Asteraceae, it is one of the two largest families of flowering plants, with between 21,950 and 26,049 currently accepted species,...

. Epidendroideae is larger than all the other orchid subfamilies together, comprising more than 15,000 species

Species

In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...

 in 576 genera

Genera

Genera is a commercial operating system and development environment for Lisp machines developed by Symbolics. It is essentially a fork of an earlier operating system originating on the MIT AI Lab's Lisp machines which Symbolics had used in common with LMI and Texas Instruments...

. Most Epidendroid orchids are tropical epiphyte

Epiphyte

An epiphyte is a plant that grows upon another plant non-parasitically or sometimes upon some other object , derives its moisture and nutrients from the air and rain and sometimes from debris accumulating around it, and is found in the temperate zone and in the...

s, typically with pseudobulb

Pseudobulb

The pseudobulb is a storage organ derived from the part of a stem between two leaf nodes.It applies to the orchid family , specifically certain groups of epiphytic orchids, and may be single or composed of several internodes with evergreen or deciduous leaves along its length.In some species, it is...

s. There are, however a few terrestrial

Terrestrial plant

A terrestrial plant is one that grows on land. Other types of plants are aquatic , epiphytic , lithophytes and aerial ....

s and even a few myco-heterotrophs, which are parasitic upon mycorrhizal fungi.

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

Column (botany)

The column, or technically the gynostemium, is a reproductive structure that can be found in several plant families: Aristolochiaceae, Orchidaceae, and Stylidiaceae....

 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

Pollinium

Pollinium, or plural pollinia, is a coherent mass of pollen grains in a plant.They are the product of only one anther, but are transferred, during pollination, as a single unit. This is regularly seen in plants such as orchids and many species of milkweeds .Most orchids have waxy pollinia...

, i.e. a mass of waxy pollen

Pollen

Pollen is a fine to coarse powder containing the microgametophytes of seed plants, which produce the male gametes . Pollen grains have a hard coat that protects the sperm cells during the process of their movement from the stamens to the pistil of flowering plants or from the male cone to the...

 or of coherent pollen grains. The pollinia are with caudicle and viscidium or without. The stigma are entire or 3-lobed; a beak

Rostellum

The rostellum is a projecting part of the column in Orchidaceae flowers, and separates the male stamen from the female gynoecium, commonly preventing self-fertilisation...

 is present. The apical part of the muiddle stigma lobe forms a stipe

Stipe (botany)

In botany, a stipe is a stalk that supports some other structure. The precise meaning is different depending on which taxonomic group is being described....

 ( = pollinium stalk). The ovary

Ovary (plants)

In the flowering plants, an ovary is a part of the female reproductive organ of the flower or gynoecium. Specifically, it is the part of the pistil which holds the ovule and is located above or below or at the point of connection with the base of the petals and sepals...

 is 1-locular. The leaves

Leaf

A leaf is an organ of a vascular plant, as defined in botanical terms, and in particular in plant morphology. Foliage is a mass noun that refers to leaves as a feature of plants....

 are distichous or spiraling, growing on thickened stems

Plant stem

A stem is one of two main structural axes of a vascular plant. The stem is normally divided into nodes and internodes, the nodes hold buds which grow into one or more leaves, inflorescence , conifer cones, roots, other stems etc. The internodes distance one node from another...

.

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, that grow 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, Strangler fig

Strangler Fig

Strangler fig is the common name for a number of tropical and subtropical plant species, including some banyans and unrelated vines, including among many other species:* Ficus aurea, also known as the Florida Strangler Fig...

s 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, where as 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 as 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 CAM (crassulacean acid metabolism), 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 Epidendroideae subfamily is divided into two clades or subgroups known as the Higher Epidendroids and the Lower Epidendroids. The higher epidendroids are partly monophyletic and partly polyphyletic (tribes Arethuseae

Arethuseae

Arethuseae is a mid-sized tribe of orchids in the subfamily Epidendroideae. This tribe was initially categorized by John Lindley in 1840. Its largest subtribes at Arethusinae and Bletiinae, in addition to the smaller subtribes Sobraliinae and Thuniinae....

 and Epidendreae

Epidendreae

The tribe Epidendreae of the Orchidaceae comprises six subtribes:* Bletiinae sensu MMIV, which contains only the genera Basiphyllaea, Bletia, and Hexalectris* Chysinae* Coeliinae* Laeliinae* Pleurothallidinae* Ponerinae...

). The Tribes are listed below: