Zygnematales: Difference between revisions
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{{Taxobox |
{{Taxobox |
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| image = Spyrogyra-bgiu.jpg |
| image = Spyrogyra-bgiu.jpg |
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| image_caption= ''[[Spirogyra]]'' green algae |
| image_caption= ''[[Spirogyra]]'' green algae |
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| regnum = [[Plantae]] |
| regnum = [[Plantae]] |
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| divisio = [[Charophyta]] |
| divisio = [[Charophyta]] |
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| classis = [[Zygnematophyceae]] |
| classis = [[Zygnematophyceae]] |
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| ordo = '''Zygnematales''' |
| ordo = '''Zygnematales''' |
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| subdivision_ranks = Families |
| subdivision_ranks = Families |
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| subdivision = |
| subdivision = |
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*[[Mesotaeniaceae]] |
*[[Mesotaeniaceae]] |
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*[[Zygnemataceae]] |
*[[Zygnemataceae]] |
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*[[Desmidiaceae]] |
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[[Sexual reproduction]] in Zygnematales takes place through a process called ''[[Isogamy|conjugation]]''.<ref name="pmid17272304">{{cite journal |author=Kapraun DF |title=Nuclear DNA Content Estimates in Green Algal Lineages: Chlorophyta and Streptophyta |journal=Ann. Bot. |volume=99 |issue=4 |pages=677–701 |date=April 2007 |pmid=17272304 |doi=10.1093/aob/mcl294 |url=http://aob.oxfordjournals.org/cgi/pmidlookup?view=long&pmid=17272304 |pmc=2802934}}</ref> Here filaments of opposite gender line up, and tubes form between corresponding cells. The male cells then become amoeboid and crawl across, or sometimes both cells crawl into the tube. The cells then meet and fuse to form a [[zygote]], which later undergoes [[meiosis]] to produce new filaments. As in plants, only the female passes [[chloroplast]]s on to the offspring.{{citation needed|date=April 2014}} |
[[Sexual reproduction]] in Zygnematales takes place through a process called ''[[Isogamy|conjugation]]''.<ref name="pmid17272304">{{cite journal |author=Kapraun DF |title=Nuclear DNA Content Estimates in Green Algal Lineages: Chlorophyta and Streptophyta |journal=Ann. Bot. |volume=99 |issue=4 |pages=677–701 |date=April 2007 |pmid=17272304 |doi=10.1093/aob/mcl294 |url=http://aob.oxfordjournals.org/cgi/pmidlookup?view=long&pmid=17272304 |pmc=2802934}}</ref> Here filaments of opposite gender line up, and tubes form between corresponding cells. The male cells then become amoeboid and crawl across, or sometimes both cells crawl into the tube. The cells then meet and fuse to form a [[zygote]], which later undergoes [[meiosis]] to produce new filaments. As in plants, only the female passes [[chloroplast]]s on to the offspring.{{citation needed|date=April 2014}} |
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The [[Desmidiales]]/[[Desmidiaceae]] have emerged within the Zygnematales.<ref>{{Cite journal|last=Lemieux|first=Claude|last2=Otis|first2=Christian|last3=Turmel|first3=Monique|date=2016|title=Comparative Chloroplast Genome Analyses of Streptophyte Green Algae Uncover Major Structural Alterations in the Klebsormidiophyceae, Coleochaetophyceae and Zygnematophyceae|url=http://journal.frontiersin.org/Article/10.3389/fpls.2016.00697/abstract|journal=Frontiers in Plant Science|language=English|volume=7|doi=10.3389/fpls.2016.00697|issn=1664-462X}}</ref> |
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The only other group of conjugating algae are the [[desmid]]s, which live as individual cells often with a striking symmetrical appearance. The desmids are sometimes placed in a separate order Desmidiales, which is closely related to Zygnematales, and the two are placed together in the [[class (biology)|class]] [[Zygnematophyceae]]. |
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==Gallery== |
==Gallery== |
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Revision as of 12:51, 9 September 2017
| Zygnematales | |
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| Spirogyra green algae | |
| Scientific classification | |
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| Order: | Zygnematales C.E.Bessey, 1907
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| Synonyms[citation needed] | |
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Zygnematales Borge and Pascher, 1913 | |
The Zygnematales (Greek: ζυγός (zygós) and νῆμα (nḗma) (nom.), νήματος (nḗmatos) (gen.)), also called the Conjugatales, are an order of green algae,[1] comprising several thousand different species in two families. The larger family Zygnemataceae, with well-known genera such as Zygnema and Spirogyra, includes members that grow as unbranched filaments, which grow longer through normal cell division. The smaller family Mesotaeniaceae includes the saccoderm "desmids", a group of unicellular species that were formerly classified with the "true" desmids. Most members of both families live in freshwater, and form an important component of the algal scum that grows on or near plants, rocks, and various debris.[clarification needed]
Systematically they fall within the division Charophyta, which includes the groups of algae that are most closely related to the higher plants. Charophyta are included with land plants (Embryophyta) in the clade Streptophyta.[2]
Sexual reproduction in Zygnematales takes place through a process called conjugation.[3] Here filaments of opposite gender line up, and tubes form between corresponding cells. The male cells then become amoeboid and crawl across, or sometimes both cells crawl into the tube. The cells then meet and fuse to form a zygote, which later undergoes meiosis to produce new filaments. As in plants, only the female passes chloroplasts on to the offspring.[citation needed]
The Desmidiales/Desmidiaceae have emerged within the Zygnematales.[4]
Gallery
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Netrium oblongum. A saccoderm "desmid" -
Spirotaenia condensata. A saccoderm "desmid" -
Single Spirogyra cell -
Spirogyra. Each numbered tick = 122 µM -
Spirogyra. Each numbered tick = 20 µM -
Microscopic view of Spirogyra conjugation -
Zygnema. Each numbered tick = 122 µM -
Zygnema. Each numbered tick = 20 µM
References
- ^ Turmel M, Otis C, Lemieux C (2005). "The complete chloroplast DNA sequences of the charophycean green algae Staurastrum and Zygnema reveal that the chloroplast genome underwent extensive changes during the evolution of the Zygnematales". BMC Biol. 3: 22. doi:10.1186/1741-7007-3-22. PMC 1277820. PMID 16236178.
{{cite journal}}: CS1 maint: unflagged free DOI (link) - ^ http://esciencenews.com/articles/2011/04/17/ancestors.land.plants.revealed
- ^ Kapraun DF (April 2007). "Nuclear DNA Content Estimates in Green Algal Lineages: Chlorophyta and Streptophyta". Ann. Bot. 99 (4): 677–701. doi:10.1093/aob/mcl294. PMC 2802934. PMID 17272304.
- ^ Lemieux, Claude; Otis, Christian; Turmel, Monique (2016). "Comparative Chloroplast Genome Analyses of Streptophyte Green Algae Uncover Major Structural Alterations in the Klebsormidiophyceae, Coleochaetophyceae and Zygnematophyceae". Frontiers in Plant Science. 7. doi:10.3389/fpls.2016.00697. ISSN 1664-462X.
{{cite journal}}: CS1 maint: unflagged free DOI (link)
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