Takakia
Takakia | |
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Takakia lepidoziodes on a damp slope above Takakia Lake, Haida Gwaii | |
Scientific classification | |
Kingdom: | Plantae |
Division: | Bryophyta |
Subdivision: | Takakiophytina |
Class: | Takakiopsida W. Frey[2]
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Order: | Takakiales Stech & W. Frey[2] |
Family: | Takakiaceae Stech & W. Frey[2] |
Genus: | Takakia Inoue[1]
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Species | |
Takakia is a genus of two species of mosses known from western North America and central and eastern Asia. The genus is placed as a separate family, order and class among the mosses. It has had a history of uncertain placement, but the discovery of sporophytes clearly of the moss-type firmly supports placement with the mosses.
Discovery
Takakia was discovered in the Himalayas and described by William Mitten in 1861. It was originally described simply as a new liverwort species (Lepidozia ceratophylla)[3] within an existing genus, and it was thus long overlooked. The discovery of similar odd plants in the mid-20th century by Dr. Noriwo Takaki (1915–2006) in Japan sparked more interest. The many unusual features of these plants led to the establishment in 1958 of the species Takakia lepidozioides, in a new genus Takakia, named to honor the man who rediscovered it and recognized its unique characteristics.[1] The species originally described by Mitten was subsequently recognized by Grolle as belonging to this new genus, and accordingly renamed Takakia ceratophylla.
All of the plants originally collected lacked any reproductive structures; they were sterile gametophyte plants. Eventually, plants with archegonia were found, which resembled the archegonia found in mosses. Fertile plants bearing antheridia and sporophytes were first reported in 1993 from the Aleutian Islands,[4] and both structures were clearly of the form found in primitive mosses. This discovery established Takakia as a genus of moss, albeit an unusual one.
In
Description
Takakia is the oldest known extant genus of land plants. They secrete a microbe-harboring mucilage to establish a diverse microbiome containing microbes associated with nitrogen fixation and mycorrhiza.[7] The plant's Japanese name (nanjamonja-goke) "impossible moss" reflects this.[6] It was believed to have the lowest known chromosome count (n=4) per cell of any land plant,[8] but some plants of the small Australian daisy Brachyscome dichromosomatica are now known to have a count of n=2.[9]
From a distance, Takakia looks like a typical layer of moss or
Unlike in other bryophytes, the egg-producing archegonia and sperm-producing antheridia are not surrounded by perichaetial leaves or other protective tissues. Instead, the gametangia are naked in the angle formed between the stem and the vegetative leaves.[10] The sporophyte develops a long stalk ending in an elongated spore capsule. The capsule contains a central columella over and around which the spores are produced. When the sporophyte is mature, the capsule ruptures along a single spiral slit to release the spores.
In the year 2023 the complete genome sequence of Takakia lepidozioides from Tibet was deciphered. It faces extinction due to climate change.[11]
Classification
family Takakiaceae
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The classification of Takakia, and its phylogenetic position among the mosses.[12][13] |
References
- ^ a b Hattori, S.; Inoue, H. (1958). "Preliminary report on Takakia lepidozioides". Journal of the Hattori Botanical Laboratory. 18: 133–137.
- ^ .
- PMID 21708543.
- ^ Smith, D. K. & P. G. Davison. 1993. Antheridia and sporophytes in Takakia ceratophylla (Mitt.) Grolle: evidence for reclassification among the mosses. Journal of the Hattori Botanical Laboratory 73: 263–271.
- JSTOR 3243096.
- ^ ISBN 0-02-949660-8.
- PMID 35443766.
- ^ Schuster, Rudolf M. 1966. The Hepaticae and Anthocerotae of North America, volume I, pages 262–263. (New York: Columbia University Press).
- .
- ^ ISBN 0-521-66097-1.
- ISBN 978-0-521-87225-6.
- ISBN 1-930723-38-5.
External links
- J. R. Spence & W. B. Schofield. 2005. Bryophyte Flora of North America: Takakiaceae