# Viridiplantae

Viridiplantae (lit. 'green plants'; kingdom Plantae sensu stricto) is a clade of around 450,000–500,000 species of eukaryotic organisms, most of which obtain their energy by photosynthesis. The green plants are chloroplast-bearing autotrophs that play important primary production roles in both terrestrial and aquatic ecosystems. They include green algae, which are primarily aquatic, and the land plants (embryophytes, Plantae sensu strictissimo), which emerged within freshwater green algae. Green algae traditionally excludes the land plants, rendering them a paraphyletic group, however it is cladistically accurate to think of land plants as a special clade of green algae that evolved to thrive on dry land. Since the realization that the embryophytes emerged from within the green algae, some authors are starting to include them.
Viridiplantae species all 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. Corroborating this, a basal phagotroph Archaeplastida group has been found in the Rhodelphydia. 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 of embryophytes 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. They rejected the name Viridiplantae on the grounds that some of the species are not plants as understood traditionally. Together with Rhodophyta, glaucophytes and other basal groups, Viridiplantae belong to a larger clade called Archaeplastida which in itself is sometimes described as Plantae sensu lato.

## Evolution
### Taxonomy

Leliaert et al, 2012 propose the following simplified taxonomy of the Viridiplantae.
* 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
***** Chlorodendrales
**** Pedinophyceae
*** prasinophytes (paraphyletic)
**** Pyramimonadales
**** Mamiellophyceae
**** Pycnococcaceae
**** Nephroselmidophyceae
**** Prasinococcales
**** Palmophyllales
** Streptophyta
*** Charophytes
**** Mesostigmatophyceae
***** Mesostigmatales
***** Chlorokybales
**** Klebsormidiophyceae
**** Phragmoplastophyta
***** Charophyceae
***** Coleochaetophyceae
***** Zygnematophyceae
***** Embryophyta (land plants)

### Phylogeny

In 2019, a phylogeny based on genomes and transcriptomes from 1,153 plant species was proposed. The placing of algal groups is supported by phylogenies based on genomes from the Mesostigmatophyceae and Chlorokybophyceae that have since been sequenced. Both the "chlorophyte algae" and the "streptophyte algae" are treated as paraphyletic (vertical bars beside phylogenetic tree diagram) in this analysis. The classification of Bryophyta is supported both by Puttick et al. 2018, and by phylogenies involving the hornwort genomes that have also since been sequenced.
Ancestrally, the green algae were flagellates.