Rhizanthella
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Rhizanthella gardneri |
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Rhizanthella is a genus of the family of orchids . The three known species of the genus are native to Australia and are the only orchids to live completely underground.
features
All species of the genus are leafless and rootless, underground plants. They have completely given up photosynthesis and accordingly no longer form chlorophyll , instead they live myco-heterotrophic . As so-called mykoheterotrophe plant feeds rhizanthella gardneri doing of arbuscular mycorrhizal fungi that turn into a symbiosis life with surrounding plants.
The rhizome of the plants, 5 to 15 millimeters thick and 3 to 15 centimeters long, is weakly branched, white and fleshy. A so-called capitulum , an upright flower head with a diameter of 15 to 25 millimeters, which is bordered by fleshy bracts , the tips of which occasionally break through the surface of the earth, grows from the rhizome to just below the surface of the earth. The 8 to 90 short, tubular single flowers are arranged in a spiral in the flattened capitulum and are red-brown, reddish or dark purple in color. Small flies are thought to serve as pollinators.
Even after flowering, the stem does not elongate and the seeds mature underground. The seeds are probably distributed by bag mammals , which eat the fleshy seed capsules and excrete the seeds with the feces.
Occurrence / botanical history
In 1928, the first plants of the genus Rhizanthella were discovered near the western Australian city of Perth . It was Rhizanthella gardneri , which was found in seven other growing locations in Western Australia by 1960.
In 1931 the second species of this genus was found in a eucalyptus forest on the border between New South Wales and Queensland . It was described by Herman Montague Rucker Rupp in 1932 as Crypthanthemis slateri and assigned to the genus Rhizanthella in 1984 as Rhizanthella slateri .
In 2006 , the third species of the genus, Rhizanthella omissa , was described on the basis of two specimens collected in 1958 in Lamington National Park . A fourth species was first described in 2018.
Due to their rarity, all species are classified as vulnerable (= endangered).
Systematics
- Rhizanthella gardneri R. S. Rogers - type species : It occurs in southwestern Australia.
- Rhizanthella johnstonii K.W.Dixon & Christenh. : The species first described in 2018 occurs in Western Australia.
- Rhizanthella omissa D.L. Jones & MAClem. : It occurs in Queensland.
- Rhizanthella slateri (Rupp) MAClem. & PJCribb (Syn .: Cryptanthemis slateri Rupp ): It occurs from south-eastern Queensland to eastern New South Wales.
proof
- David L. Jones: A complete guide to native orchids of Australia: including the island territories. , Frenchs Forest, 2006, ISBN 1-8770-6912-4 .
- R. Schlechter: The orchids. 4 vol. & Reg. Revised K. Senghas. Blackwell-Wiss.-Verl., Berlin / Vienna 2003 (3rd edition). ISBN 3-8263-3410-8 .
Individual evidence
- ^ David L. Jones: Native Orchids of Australia. Reed Publishing Australia 1988, ISBN 0-7301-0189-4
- ↑ a b c d Rafaël Govaerts (Ed.): Rhizanthella. In: World Checklist of Selected Plant Families (WCSP) - The Board of Trustees of the Royal Botanic Gardens, Kew . Retrieved April 10, 2020.
