View source for Pennales

{{Taxobox
| color = #FA7B62
| name = Diatoms
| image = Diatoms through the microscope.jpg
| image_width = 200px
| image_caption = Marine diatoms
| domain = [[Eukaryote|Eukaryota]]
| regnum = [[Chromalveolata]]
| phylum = [[Heterokont]]ophyta
| classis = [[Diatom|Bacillariophyceae]]
| ordo = '''Pennales'''
}}

'''Order Pennales''' is a traditional subdivision of the [[heterokont]] [[algae]] known as [[diatom]]s<ref name=hoek95>Hoek, C. van den, Mann, D. G. and Jahns, H. M. (1995).  ''Algae : An introduction to phycology'', Cambridge University Press, UK.</ref><ref name=round90>Round, F. E. and Crawford, R. M. (1990).  ''The Diatoms.  Biology and Morphology of the Genera'', Cambridge University Press, UK.</ref>.  The order is named for the shape of the [[cell wall#Diatom cell walls|cell walls]] (or valves or frustules) of '''pennate''' diatoms, which are elongated in valve view.  The valves may be linear or oval in shape, and usually bear [[Symmetry (biology)|bilaterally symmetrical]] ornamental patterns.  These patterns are composed of a series of transverse lines (known as striae) that can appear as rows of dots when viewed with an [[optical microscope]].  Some pennate diatoms also exhibit a fissure along their longitudinal axis.  This is known as a raphe, and is involved in gliding movements made by diatom cells.

In terms of [[cell cycle]], [[vegetative reproduction|vegetative]] cells are [[diploid]] and undergo [[mitosis]] during normal [[cell division]].  Periodically, [[meiosis]] produces [[morphology (biology)|morphologically]]-identical [[haploid]] [[gamete]]s (isogametes), which fuse to produce a (sometimes [[cell nucleus|binucleate]]) [[zygote]] that develops into an [[auxospore]] (from which full-size vegetative cells are produced).  

In some [[taxonomy|taxonomic]] schemes<ref name=round90/>, the pennate diatoms are divided into two groups: pennate diatoms without a [[raphe]] ('''Order Fragilariophyceae'''), and pennate diatoms with a raphe ('''Order Bacillariophyceae''').

==See also==
* [[Centrales]]

==References==
{{reflist|2}}


[[Category:Algae]]
[[Category:Biological oceanography]]
[[Category:Diatoms]]
[[Category:Heterokonts]]
[[Category:Planktology]]

[[fr:Fragilariophyceae]]
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