Epiphyte

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Epiphytic tillandsia and mammillaries
Epiphytes on a jungle tree in Costa Rica (Atlantic area)
Epiphytes (Santa Elena Rainforest, Costa Rica)
Feather-leaved random epiphyte (mountain ash?) On a cherry tree.

As epiphytes ( Alt Gr. Ἐπί epi on ',' on 'and φυτόν phyton , plant') or epiphytes plants are referred growing on other plants. This term is applied to both land plants and aquatic plants. On land, trees are mostly used as a substrate for epiphytes, while aquatic epiphytes such as algae grow on higher aquatic plants (e.g. sea ​​grasses ). The plant that carries the epiphyte is called a phorophyte (Greek phoron , carrier).

The advantage of this way of life is the better availability of light, which is a limiting factor for plant growth on the forest floor (or sea floor). The disadvantage of the atmospheric epiphytic way of life, however, is that a continuous supply of water and nutrients is not always guaranteed due to the lack of connection to the ground. In the course of evolution, the epiphytes have developed different morphological and physiological adaptations in order to become independent of the water and nutrient supply of the soil. According to the existing doctrine, the epiphytic way of life has developed independently several times.

In the classic sense, epiphytes are not parasites because they do not tap into the phloem of their host plant. Some authors count the real parasites (e.g. mistletoe ) among the epiphytes because of their atmospheric way of life.

Types

Ontogenetically , there are two types of epiphytes: holoepiphytes, or true epiphytes, germinate and grow on another plant throughout their life. Hemiepiphytes, on the other hand, only spend part of their life on another plant. In the latter, a distinction is made between primary and secondary hemiepiphytes. Primary hemi-epiphytes begin their life cycle as an epiphyte and in a later phase develop roots that enable a connection to the soil. Secondary hemiepiphytes initially grow terrestrially and lose their connection to the ground in a later phase of life.

Geographical distribution

Epiphytic vascular plants occur almost exclusively in the subtropics and tropics. Lower plants such as algae , mosses , lichens and ferns can also appear as epiphylls here in regions with continuous water availability .

In the temperate latitudes, depending on the amount of rain, only lower plants (e.g. Europe), but also vascular plants (e.g. New Zealand or the southern Himalayas) occur epiphytically. Occasionally one also finds other terrestrial plants that find a suitable growth environment in the humus accumulations of tree branches (random epiphytes). Apart from rare individual cases, there are no other epiphytic vascular plants in Europe. The reason given in the literature is frost, which prevents the plants from being supplied with water for a longer period of time.

Systematic dissemination

Viewed worldwide, around 10 percent of all vascular plant species are epiphytic. In tropical mountain rainforests, however , the proportion of epiphytes can exceed the number of terrestrial vascular plants.

Epiphytic species occur in many plant families. Particularly rich in epiphytic species are:

Morphological adjustments

Bromeliads have small, sealed openings on their leaves, called suction scales , which they use to absorb rainwater and the nutrients it contains. The roots of most epiphytic bromeliads have largely lost the function of carrying water and nutrients and are mostly only used to attach to the substrate.

Many bromeliads form rosettes from stiff leaves. These leaves are so close together at the bottom that water can collect there. Falling parts of plants and dead animals can get into such a cistern (botany) and they are broken down there by microorganisms. The water and the nutrients released in it are channeled through the suction scales into the interior of the rosette leaves. The cistern water is partly supplemented by precipitation but also partly (as in a dew pond ) by fog condensation .

A large number of orchid species have pseudobulbs , which serve as water and nutrient storage organs. These stocks are used in the event of a prolonged dry period or during the formation of fruits.

Many orchids and some macaws have developed an adaptation to the rapid uptake of water and nutrients. The Velamen radicum is a root-enveloping tissue with a sponge-like structure, which quickly absorbs water and the nutrients it contains and transfers them to the roots.

Epiphytic ferns growing often form a bird's nest-like root system of collecting in which absorbent humus and water and provide the plant for a certain period without rain.

Many epiphytes have succulent leaves that offer some protection against evaporation.

Physiological adjustments

The CAM mechanism allows a plant to close its stomata during the day and thus evaporate less water than with an open one. The uptake of carbon dioxide, which is important for photosynthesis, is shifted to the night when the ambient temperature is lower and the humidity is higher.

When it rains, epiphytic mosses and lichens absorb large amounts of water in their often matted, spongy mass. During longer dry periods, they shrink and reduce their metabolism until the next rainy season.

literature

  • AFW Schimper: The epiphytic vegetation of America . Fischer, Jena 1888 ( digitized version ).
  • Alwyn H. Gentry, CH Dodson: Diversity and Biogeography of Neotropical Vascular Epiphytes . In: Annals of the Missouri Botanical Garden . tape 74 , no. 2 , 1987, pp. 205-233 ( abstract ).

Web links

Commons : Epiphytes  - collection of images, videos and audio files
Wiktionary: Epiphyte  - explanations of meanings, word origins, synonyms, translations

Individual evidence

  1. a b c D. H. Benzing: Vascular epiphytes. General biology and related biota . Cambridge University Press, Cambridge 1990 (354 pages).
  2. ^ WRB Oliver: New Zealand epiphytes . In: Journal of Ecology . tape 18 , 1930, p. 1-50 .
  3. VDL Gurung: Ecological observations on the pteridophyte flora of Langtang National Park, Central Nepal . In: Fern Gazette . tape 13 , 1985, pp. 25-32 .
  4. Gerhard Zotz : Gefässepiphyten in temperate forests . In: Bauhinia . tape 16 , 2002, pp. 13-22 .
  5. ^ AH Gentry, CH Dodson: Diversity and Biogeography of Neotropical Vascular Epiphytes . In: Annals of the Missouri Botanical Garden . tape 24 , no. 2 , 1987, pp. 205-233 .
  6. D. Kelly et al .: The epiphyte communities of a montane rain forest in the Andes of Venezuela: patterns in the distribution of the flora . In: Journal of Tropical Ecology . tape 20 , 2004, pp. 643-666 .