Charophytes
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Embryophyta (Cladistically included but traditionally excluded) |
Mesostigmatophyceae
Klebsormidiophyceae
Zygnematophyceae
Chlorokybophyceae
Coleochaetales
Embryophyta (Cladistically included but traditionally excluded)
Charophyta is a division of freshwater green algae. The terrestrial plants, the Embryophyta emerged within Charophyta, with the class Zygnematophyceae as a sister group. In some charophyte groups, such as Zygnematophyceae or conjugating green algae, flagella are absent and sexual reproduction does not involve free-swimming flagellate sperm. Flagellate sperm, however, are found in stoneworts (Charales) and Coleochaetales, orders of parenchymatous charophytes that are the closest relatives of the land plants, where flagellate sperm are also present in all except the conifers and flowering plants. Fossil stoneworts of Devonian age that are similar to those of the present day have been described from the Rhynie chert of Scotland.
Charophyta are complex green algae that form a sister group to the Chlorophyta and within which the Embryophyta emerged. The chlorophyte and charophyte green algae and the embryophytes or land plants form a clade called the green plants or Viridiplantae, that is united among other things by the absence of phycobilins, the presence of chlorophyll b and chlorophyll a, cellulose in the cell wall and the use of starch, stored in the plastids, as a storage polysaccharide. Unlike chlorophytes, the charophytes and embryophytes share several traits, such as the presence of certain enzymes (class I aldolase, Cu/Zn Superoxide dismutase, Glycolate Oxidase, flagellar peroxidase), lateral flagella (when present), and, in many species, the use of phragmoplasts in mitosis. Thus Charophyta and Embryophyta together form the clade Streptophyta, excluding the Chlorophyta. The Charophyta sensu lato does not include all the descendents of their common ancestor with the embryophytes and as such they form a paraphyletic group i.e. the classes Chlorokybophyceae; Mesostigmatophyceae; Klebsormidiophyceae; Zygnematophyceae; Coleochaetophyceae and Chaetosphaeridiales are removed from the division.
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