Evolution and Systematics
Plants in calcareous peatlands photosynthesize in low CO2 levels by taking up bicarbonate and converting it to CO2.
"Some plant species live entirely submerged. The leaves are often very thin, with a large surface area, and lack stomata. Some of these plants are rooted in the bottom, but others have no roots at all (for instance Utricularia spp.). Waters around these plants can be still, slowly moving, or rapidly mixing as in case of rivers and lakes with peatland margins. Such plants take up carbon dioxide (C02) and nutrients directly into the leaves from the water, just in the way that bryophytes do. Carbon dioxide is rarely limiting, but in waters with very high pH (as in calcareous fens) the availability of C02 is much reduced, and some plants have the ability to take up bicarbonate (HC03 -), which is then converted to C02 in the cell and used in photosynthesis. Examples are the stoneworts (Characeae), which are characteristic species in calcareous waters, and several species of Myriophyllum and Ceratophyllum (Hutchinson 1975). Given that there are enough plants, they can produce the oxygen required for respiration themselves." (Rydin and Jeglum 2006:46-47)
Learn more about this functional adaptation.
- Rydin, H.; Jeglum, J. K. 2006. The Biology of Peatlands. Oxford University Press. 343 p.
- Hutchinson, GE. 1975. A treatise on limnology. III Limnological botany. New York: John Wiley & Sons. 660 p.
Molecular Biology and Genetics
Statistics of barcoding coverage
Specimen Records: 31
Specimens with Sequences: 42
Specimens with Barcodes: 37
Species With Barcodes: 3
Public Records: 12
Public Species: 2
Ceratophyllum is a cosmopolitan genus of flowering plants, commonly found in ponds, marshes, and quiet streams in tropical and in temperate regions. They are usually called hornworts, although this name is also used for unrelated plants of the division Anthocerotophyta.
Ceratophyllum grows completely submerged, usually, though not always, floating on the surface, and does not tolerate drought. The plant stems can reach 1–3 m in length. At intervals along nodes of the stem they produce rings of bright green leaves, which are narrow and often much-branched. The forked leaves are brittle and stiff to the touch in some species, softer in others. The plants have no roots at all, but sometimes they develop modified leaves with a rootlike appearance, which anchor the plant to the bottom. The flowers are small and inconspicuous, with the male and female flowers on the same plant. In ponds it forms thick buds (turions) in the autumn that sink to the bottom which give the impression that it has been killed by the frost but come spring these will grow back into the long stems slowly filling up the pond.
Hornwort plants float in great numbers just under the surface. They offer excellent protection to fish-spawn, but also to snails, infected with bilharzia. Because of their appearance and their high oxygen production, they are often used in freshwater aquaria.
Relationships and classification
Ceratophyllum is considered unique enough to warrant its own family, Ceratophyllaceae, and its precise relationship to other angiosperms remains unclear. It was considered a relative of Nymphaeaceae and included in Nymphaeales in the Cronquist system but recent research has shown that it is not closely related to Nymphaeaceae or any other extant plant family. Some early molecular phylogenies suggested it was the sister group to all other angiosperms, but more recent ones have suggested that it is the sister group to either the monocots or the eudicots. The APG III system places the family in its own order, the Ceratophyllales.
|The phylogeny of the flowering plants, as of APG III (2009).|
- Ceratophyllum demersum L. (Rigid Hornwort or Common Hornwort) - cosmopolitan
- Ceratophyllum muricatum Cham. (Prickly Hornwort) - widespread in many places though not all countries
- Ceratophyllum platyacanthum Cham. - Scattered locations in Germany, Hungary, France, Russia, China, Japan, Korea
- Ceratophyllum submersum L. (Soft Hornwort or Tropical Hornwort) - Europe, Central Asia, northern Africa, scattered places in tropical Africa, Turkey, Oman, Florida, Dominican Republic
Of these, Ceratophyllum demersum is widespread, with a global distribution; the others all have more restricted ranges.
- Angiosperm Phylogeny Group (2009). "An update of the Angiosperm Phylogeny Group classification for the orders and families of flowering plants: APG III" (PDF). Botanical Journal of the Linnean Society 161 (2): 105–121. doi:10.1111/j.1095-8339.2009.00996.x. Retrieved 2013-06-26.
- Kew World Checklist of Selected Plant Families
- Flora of China: Ceratophyllum
- Flora of North America: Ceratophyllum
- Blamey, M. & Grey-Wilson, C. (1989). Flora of Britain and Northern Europe. ISBN 0-340-40170-2
- Huxley, A., ed. (1992). New RHS Dictionary of Gardening. Macmillan ISBN 0-333-47494-5.
- Angiosperm Phylogeny Web: Ceratophyllales
- Germplasm Resources Information Network: Ceratophyllum
- Australian Plant Name Index: Ceratophyllum
- Flora Europaea: Ceratophyllum
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