Chlorophyceae

(botany) A class of microscopic or macroscopic green algae, division Chlorophyta, composed of fresh- or salt-water, unicellular or multicellular, colonial, filamentous or sheetlike forms.

A large and diverse class of plants, commonly called green algae, in the chlorophyll a-b phyletic line (Chlorophycota). Estimated number of taxa varies widely; 560 genera and 8600 species are conservative estimates. See also Chlorophycota.

The green algae exhibit great morphological diversity while sharing fundamental biochemical and ultrastructural features. Their photosynthetic pigments are similar to those in higher plants and include chlorophyll a and b, α-, β-, and γ-carotene, and various xanthophylls. Chloroplasts vary in number and shape, but always have two membranes, two to five thylakoids per lamella, and usually one or more pyrenoids. A cell wall, which may be calcified, is usually present, often contains cellulose, hydroxyproline glycosides, xylan, and mannan. The chief food reserve is starch, stored in the chloroplast as granules which often sheathe a pyrenoid. Motile cells usually have two or four apically inserted smooth flagella of approximately equal length. See also Cell plastids; Chlorophyll; Photosynthesis.

Almost all somatic cell types known for algae occur among the Chlorophyceae, the exceptions being rhizopodial unicells and complex multicellular thalli differentiated into macroscopic organs. Ultrastructural studies have revealed differences in details of nuclear and cell division, cell coverings, plasmodesmata, pyrenoids, and flagellar structure that are correlated among themselves and with certain traditional characters to a degree that strongly suggests that the ulotrichine line is polyphyletic, with desmoschisis having evolved at least four times. Moreover, these studies suggest that the ultimate ancestral green flagellate was prasinophycean (asymmetrical and covered with scales) rather than Chlamydomonas-like. Integration of these studies and inferences suggests four phyletic lines: chlorophycean, ulvophycean, charophycean, and pleurastrophycean.

In addition to the four phyletic lines, each of which includes monads as well as multicellular algae, there is a residual group of primitive green flagellates for which the name Micromonadophyceae has been proposed. These monads are scaly or secondarily naked and have one to four flagella arising from an apical pit or lateral depression. The interzonal mitotic spindle persists during cytokinesis. This group corresponds to the class Prasinophyceae in the present classification. For the sake of consistency, however, Prasinophyceae and Charophyceae are treated elsewhere in this work as separate classes. See also Algae; Charophyceae; Prasinophyceae.

The noun has one meaning:

Meaning #1: algae distinguished chiefly by having flagella and a clear green color, their chlorophyll being masked little if at all by other pigments
  Synonym: class Chlorophyceae

Chlorophyceae
Scientific classification
Domain:	Eukaryota
Kingdom:	Plantae
Division:	Chlorophyta
Class:	Chlorophyceae Wille in Warming, 1884
Orders[1]
Chaetopeltidales Chaetophorales Chlorococcales Chlorocystidales Microsporales Oedogoniales Phaeophilales Tetrasporales Volvocales

The Chlorophyceae are one of the classes of green algae, distinguished mainly on the basis of ultrastructural morphology. For example the chlorophycean CW clade, and chlorophycean DO clade, are defined by the arrangement of their flagella. Members of the CW clade have flagella that are displaced in a "clockwise" (CW, 1–7 o'clock) direction eg. Chlamydomonadales. Members of the DO clade have flagella that are "directly opposed" (DO, 12–6 o'clock) eg. Sphaeropleales.

They share many similarities with the higher plants, including the presence of asymmetrical flagellated cells, the breakdown of the nuclear envelope at mitosis, and the presence of phytochromes, flavonoids, and the chemical precursors to the cuticle.^[2]

The following orders are typically recognised:

• Dunaliellales (e.g. Dunaliella)
• Volvocales (e.g. Volvox, Chlamydomonas)
• Chlorococcales (e.g. Chlorella, Nannochloris)
• Oedogoniales (e.g. Oedogonium)
• Sphaeropleales
• Chaetophorales
• Microsporales
• Tetrasporales (e.g. Tetraspora)

In older classifications, the term Chlorophyceae is sometimes used to apply to all the green algae except the Charales, and the internal division is considerably different.

The Orders of the Chlorophyceae as listed by: in Hoek, Mann and Jahns (1995)^[3]

• Volvocales
• Chlorococcales
• Chaetophoroales
• Oedogoniales

Ulvophyceae by Hoek, Mann and Jahns (1995)

• Codiolales
• Ulvales

References

1. ^ Guiry, M.D. & Guiry, G.M. (2007). "Class: Chlorophyceae taxonomy browser". AlgaeBase version 4.2 World-wide electronic publication, National University of Ireland, Galway. http://www.algaebase.org/browse/taxonomy/?id=4355. Retrieved 2007-09-23. 
2. ^ Raven, Evert and Eichhorn. The Biology of Plants 7th edition, pg. 335. W. H. Freeman and Company, New York, 2005.
3. ^ Hoek,C.van den, Mann, D.G. and Jahns, H.M. 1995. Algae An Introduction to Phycology. Cambridge University Press, Cambridge

See also

• Clade
• Cladistics

v • d • e Classification of Archaeplastida / Plantae sensu lato Rhodophyta Rhodophyceae · Bangiophyceae · Florideophyceae · Goniotrichales · Stylonematophyceae Glaucocystophyceae Glaucocystis · Cyanophora · Gloeochaete Viridiplantae/ Plantae sensu stricto Chlorophyta/GA Prasinophyceae UTC clade: Ulvophyceae · Trebouxiophyceae · Chlorophyceae Streptophyta Charophyta/GA Chlorokybophyceae Chlorokybales Klebsormidiophyceae Klebsormidiales Zygnematophyceae Desmidiales · Zygnematales Charophyceae Charales Coleochaetophyceae Coleochaetales Embryophyta/ Plantae sensu strictissimo Bryophytes (non-vascular) Marchantiophyta · Anthocerotophyta · Bryophyta "Moss" · Horneophytopsida Tracheophyta Lycopodiophyta Isoetopsida (Isoetales, Selaginellales) · Lycopodiopsida (Lycopodiales) Euphyllophyta Moniliformopses (Equisetopsida, Filicopsida, Psilotopsida) Spermatophyta: Gymnosperm (Pinophyta, Cycadophyta, Ginkgophyta, Gnetophyta) · Magnoliophyta See also: list of plant orders

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