Viridiplantae (literally "green plants") are a clade of

eukaryotic Eukaryotes () are organisms whose Cell (biology), cells have a cell nucleus, nucleus. All animals, plants, fungi, and many unicellular organisms, are Eukaryotes. They belong to the group of organisms Eukaryota or Eukarya, which is one of the ...

organisms that comprise approximately 450,000–500,000 species and play important roles in both terrestrial and aquatic ecosystems. They are made up of the green algae, which are primarily aquatic, and the land plants ( embryophytes), which emerged from within them. Green algae traditionally excludes the land plants, rendering them a paraphyletic group. However it is accurate to think of land plants as a kind of algae. Since the realization that the embryophytes emerged from within the green algae, some authors are starting to include them. They have cells with

cellulose Cellulose is an organic compound with the formula , a polysaccharide consisting of a linear chain of several hundred to many thousands of β(1→4) linked D-glucose units. Cellulose is an important structural component of the primary cell w ...

in their cell walls, and primary chloroplasts derived from

endosymbiosis An ''endosymbiont'' or ''endobiont'' is any organism that lives within the body or cells of another organism most often, though not always, in a mutualistic relationship. (The term endosymbiosis is from the Greek: ἔνδον ''endon'' "within ...

with cyanobacteria that contain chlorophylls a and b and lack phycobilins. In some classification systems, the group has been treated as a

kingdom Kingdom commonly refers to: * A monarchy ruled by a king or queen * Kingdom (biology), a category in biological taxonomy Kingdom may also refer to: Arts and media Television * ''Kingdom'' (British TV series), a 2007 British television drama s ...

, under various names, e.g. Viridiplantae, Chlorobionta, or simply

Plant Plants are predominantly photosynthetic eukaryotes of the kingdom Plantae. Historically, the plant kingdom encompassed all living things that were not animals, and included algae and fungi; however, all current definitions of Plantae exclu ...

ae, the latter expanding the traditional plant kingdom to include the green algae. Adl'' et al.'', who produced a classification for all eukaryotes in 2005, introduced the name Chloroplastida for this group, reflecting the group having primary chloroplasts with green chlorophyll. They rejected the name Viridiplantae on the grounds that some of the species are not plants, as understood traditionally. The Viridiplantae are made up of two clades:

Chlorophyta Chlorophyta or Prasinophyta is a taxon of green algae informally called chlorophytes. The name is used in two very different senses, so care is needed to determine the use by a particular author. In older classification systems, it refers to a ...

and

Streptophyta Streptophyta (), informally the streptophytes (, from the Greek ''strepto'' 'twisted', for the morphology of the sperm of some members), is a clade of plants. The composition of the clade varies considerably between authors, but the definition e ...

as well as the basal

Mesostigmatophyceae The Mesostigmatophyceae are a class of basal green algae found in freshwater. In a narrow circumscription, the class contains a single genus, ''Mesostigma''. AlgaeBase then places the order within its circumscription of Charophyta. A clade co ...

and

Chlorokybophyceae ''Chlorokybus'' is a multicellular (sarcinoid) genus of basal green algae or Charophyta, charophyte, a soil algae, alga. It has been classified as the sole member of the family Chlorokybaceae, which is the sole member of the order Chlorokybales, ...

. Together with Rhodophyta and

glaucophyte The glaucophytes, also known as glaucocystophytes or glaucocystids, are a small group of unicellular algae found in freshwater and moist terrestrial environments, less common today than they were during the Proterozoic. The stated number of speci ...

s, Viridiplantae are thought to belong to a larger clade called

Archaeplastida The Archaeplastida (or kingdom Plantae '' sensu lato'' "in a broad sense"; pronounced /ɑːrkɪ'plastɪdə/) are a major group of eukaryotes, comprising the photoautotrophic red algae (Rhodophyta), green algae, land plants, and the minor gr ...

or Primoplantae. A taxonomic evaluation of eukaryotes based on myosin distribution showed the Viridiplantae lost class-I myosins.

Phylogeny and classification

Simplified phylogeny of the Viridiplantae, according to Leliaert ''et al''. 2012. * Viridiplantae **

***core chlorophytes ****

Ulvophyceae The Ulvophyceae or ulvophytes are a class of green algae, distinguished mainly on the basis of ultrastructural morphology, life cycle and molecular phylogenetic data.Graham LE, Graham JM, Wilcox LW (2009) ''Algae''. 2nd Edition. Benjamin Cumming ...

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Cladophorales Cladophorales are an order of green algae, in the class Ulvophyceae The Ulvophyceae or ulvophytes are a class of green algae, distinguished mainly on the basis of ultrastructural morphology, life cycle and molecular phylogenetic data.Graham L ...

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Dasycladales Dasycladales is an order of large unicellular green algae in the class Ulvophyceae. It contains two families, the Dasycladaceae and the Polyphysaceae. These single celled algae are from 2 mm to 200 mm long. They live on substrates ...

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Bryopsidales Bryopsidales is an order of green algae, in the class Ulvophyceae. Characteristics The thallus is filamentous and much branched and may be packed into a mass. It is coenocytic, having multi-nucleate cells consisting of cytoplasm contained withi ...

***** Trentepohliales *****

Ulvales Ulvales is an order of green alga The green algae (singular: green alga) are a group consisting of the Prasinodermophyta and its unnamed sister which contains the Chlorophyta and Charophyta/Streptophyta. The land plants (Embryophytes) have e ...

- Ulotrichales ***** Oltmannsiellopsidales **** Chlorophyceae ***** Oedogoniales ***** Chaetophorales ***** Chaetopeltidales *****

Chlamydomonadales Chlamydomonadales, also known as Volvocales, are an order of flagellated or pseudociliated green algae, specifically of the Chlorophyceae.See the NCBIbr>webpage on Chlamydomonadales Data extracted from the Chlamydomonadales can form planar or ...

***** Sphaeropleales ****

Trebouxiophyceae The Trebouxiophyceae are a class of green algae, in the division Chlorophyta. Their circumscription within the green algae is not well established due to the need for more genetic studies at higher levels within the group. Genera without interve ...

***** Chlorellales ***** Oocystaceae ***** Microthamniales ***** Trebouxiales *****''

Prasiola ''Prasiola'' is a genus of fresh water and marine green algae. Each individual plant is small but they usually grow side by side to form a green turf on rock surfaces. The genus has a cosmopolitan distribution. Occurrence Freshwater species ...

'' clade **** Chlorodendrophyceae ***** Chlorodendrales **** Pedinophyceae *** prasinophytes (paraphyletic) ****

Pyramimonadales Pyramimonadales are an order of green algae in the Chlorophyta. The chloroplasts of phototrophic euglenids probably came from endosymbiosis with a member of this order. Taxonomy * Family Polyblepharidaceae Dangeard 1888 ** Genus '' Amphoraemon ...

**** Mamiellophyceae **** Pycnococcaceae **** Nephroselmidophyceae **** Prasinococcales **** Palmophyllales **

*** Charophytes (paraphyletic assemblage of freshwater algae). ****

Klebsormidiophyceae Klebsormidiales is an order of charophyte algae. It is the only order in the class Klebsormidiophyceae, sister of the Phragmoplastophyta. , AlgaeBase AlgaeBase is a global species database of information on all groups of algae, both marine an ...

**** Phragmoplastophyta ****

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***** Charophyceae *****

Zygnematophyceae Zygnematophyceae (or Conjugatophyceae) is a class of green algae in the paraphylum streptophyte algae, also referred to as Charophyta, consisting of more than 4000 described species. It contains five orders: the Spirogloeales, the Serritaeniales ...

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Coleochaetophyceae Coleochaetophyceae are a class of charophyte algae that includes some of the closest multicellular relatives of land plants The Embryophyta (), or land plants, are the most familiar group of green plants that comprise vegetation on Earth. Embr ...

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Embryophyta The Embryophyta (), or land plants, are the most familiar group of green plants that comprise vegetation on Earth. Embryophytes () have a common ancestor with green algae, having emerged within the Phragmoplastophyta clade of green algae as siste ...

(land plants)

Cladogram

Below is a consensus reconstruction of green algal relationships, mainly based on molecular data. Ancestrally, the green algae were flagellates.

References

{{Taxonbar, from=Q11973077 Biological classification Subkingdoms Taxa named by Thomas Cavalier-Smith