Viridiplantae (literally "green plants") are a clade of eukaryotic 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.
Since the realization that the embryophytes emerged from within the green algae, some authors are starting to include them.
They have cells with cellulose in their cell walls, and primary chloroplasts derived from endosymbiosis with cyanobacteria that contain chlorophylls a and b and lack phycobilins.
In some classification systems, the group has been treated as a kingdom, under various names, e.g. Viridiplantae, Chlorobionta, or simply Plantae, 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 and Streptophyta as well as the basal Mesostigmatophyceae and Chlorokybophyceae.
Together with Rhodophyta and glaucophytes, Viridiplantae are thought to belong to a larger clade called Archaeplastida 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
Chlorophyta
core chlorophytes
Ulvophyceae
Cladophorales
Dasycladales
Bryopsidales
Trentepohliales
Ulvales-Ulotrichales
Oltmannsiellopsidales
Chlorophyceae
Oedogoniales
Chaetophorales
Chaetopeltidales
Chlamydomonadales
Sphaeropleales
Trebouxiophyceae
Chlorellales
Oocystaceae
Microthamniales
Trebouxiales
Prasiola clade
Chlorodendrophyceae
Pedinophyceae
prasinophytes (paraphyletic)
Pyramimonadales
Mamiellophyceae
Pycnococcaceae
Nephroselmidophyceae
Prasinococcales
Palmophyllales
Streptophyta
Charophytes (paraphyletic assemblage of freshwater algae).
Klebsormidiophyceae
Phragmoplastophyta
Mesostigmatophyceae
Chlorokybophyceae
Charophyceae
Zygnematophyceae
Coleochaetophyceae
Embryophyta (land plants)
Cladogram
Below is a consensus reconstruction of green algal relationships, mainly based on molecular data.
More conventionally, Mesostigmatophyceae, Spirotaenia, and Cholokybophyceae are basal Streptophyta.
Ancestrally, the green algae were flagellates.
References
