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Isoetales

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Isoetales, sometimes also written Isoëtales, is an order of plants in the class Lycopodiopsida.

There are about 140-150 living species, all of which are classified in the genus Isoetes (quillworts), with a cosmopolitan distribution, but often scarce to rare. Living species are mostly aquatic or semi-aquatic, and are found in clear ponds and slowly moving streams. Each leaf is slender and broadens downward to a swollen base up to 5 mm wide where the leaves attach in clusters to a bulb-like, underground corm characteristic of most quillworts. This swollen base also contains male and female sporangia, protected by a thin, transparent covering (velum), which is used diagnostically to help identify quillwort species. Quillwort species are very difficult to distinguish by general appearance. The best way to identify them is by examining the megaspores under a microscope.

Isoetes are the only living pteridophytes capable of secondary growth.[1]

Fossils

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Whole plant reconstruction of Pleuromeia sternbergii from the Triassic of Germany

Fossilised specimens of Isoetes beestonii have been found in rocks dating to the latest Permian.[2][3]

All quillworts and their extinct relatives are heterosporous. Some fossil species are very well known, with many stages of development and the life cycle preserved. Two of the best known are the Carboniferous Chaloneria and Cretaceous Nathorstiana.

During the Early Triassic, the long-stemmed Isoetales genus Pleuromeia was dominant over large areas of the globe.[4]

References

  1. ^ Karrfalt, Eric E. (1982-12-01). "Secondary Development in the Cortex of Isoetes". Botanical Gazette. 143 (4): 439–445. doi:10.1086/337319. ISSN 0006-8071. S2CID 84969975.
  2. ^ Retallack, Gregory J. (1997). "Earliest Triassic origin of Isoetes and quillwort evolutionary radiation". Journal of Paleontology. 7 (3): 500–521. doi:10.1017/S0022336000039524.
  3. ^ Retallack, Gregory J. (2013). "Permian and Triassic greenhouse crises". Gondwana Research. 24 (1): 90–103. Bibcode:2013GondR..24...90R. doi:10.1016/j.gr.2012.03.003.
  4. ^ Looy, Cindy V.; van Konijnenburg-van Cittert, Johanna H. A.; Duijnstee, Ivo A. P. (2021). "Proliferation of Isoëtalean Lycophytes During the Permo-Triassic Biotic Crises: A Proxy for the State of the Terrestrial Biosphere". Frontiers in Earth Science. 9: 55. Bibcode:2021FrEaS...9...55L. doi:10.3389/feart.2021.615370. ISSN 2296-6463.

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Isoetales: Brief Summary

provided by wikipedia EN

Isoetales, sometimes also written Isoëtales, is an order of plants in the class Lycopodiopsida.

There are about 140-150 living species, all of which are classified in the genus Isoetes (quillworts), with a cosmopolitan distribution, but often scarce to rare. Living species are mostly aquatic or semi-aquatic, and are found in clear ponds and slowly moving streams. Each leaf is slender and broadens downward to a swollen base up to 5 mm wide where the leaves attach in clusters to a bulb-like, underground corm characteristic of most quillworts. This swollen base also contains male and female sporangia, protected by a thin, transparent covering (velum), which is used diagnostically to help identify quillwort species. Quillwort species are very difficult to distinguish by general appearance. The best way to identify them is by examining the megaspores under a microscope.

Isoetes are the only living pteridophytes capable of secondary growth.

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cc-by-sa-3.0
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Wikipedia authors and editors
original
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