Green plants include all organisms commonly known as green algae and land plants, including liverworts, mosses, ferns and other nonseed plants, and seed plants.
IntroductionGreen plants as defined here includes a broad assemblage of photosynthetic organisms that all contain chlorophylls a and b, store their photosynthetic products as starch inside the double-membrane-bounded chloroplasts in which it is produced, and have cell walls made of cellulose (Raven et al., 1992). In this group are several thousand species of what are classically considered green algae, plus several hundred thousand land plants.
Discussion of Phylogenetic RelationshipsThere are two major lineages of green plants. One consists of most of what have been classically considered "green algae"--mostly microscopic freshwater forms and large seaweeds. The other lineage contains several groups of "green algae" that are more closely related to land plants. Because these two lineages are monophyletic, they have been placed in a single monophyletic group called green plants, or, in technical parlance, the subkingdom Chlorobionta (Bremer, 1985).
The groups of the primary "green algal" lineage included here (Prasinophytes, Chlorophyceae, Trebouxiophyceae, and Ulvophyceae) represent a synthesis of the most recent classifications based primarily on ultrastructure of motile cells (when present) and analysis of molecular data (small subunit rDNA) Melkonian and Surek, 1995; Friedl, 1995). The groups represent classes of green algae, except for the "Prasinophytes," which, although erected as a class (Prasinophyceae), is apparently a paraphyletic, basal radiation within the "green algal" lineage (Melkonian, 1990; Friedl, 1995; Melkonian and Surek, 1995). The name for the sister taxon to the Chlorophyceae used here (class Trebouxiophyceae) is has also been referred to as the order Microthmaniales (Melkonian and Surek, 1995); recent studies of small-subunit rDNA sequences led Friedl (1995) to raise the group to class level.
The other main lineage of green plants has been called the Streptophytes (Bremer, 1985), which consists of some organisms traditionally considered green algae plus the more familiar green plants found mostly on land. This lineage contains green algae that most textbooks include in the Class Charophyceae, but some members of this class are in fact more closely related to higher plants than to other members of the class (Mattox and Stewart, 1984; Mishler and Churchill, 1985; McCourt, 1995; Melkonian and Surek, 1995). Specifically, Chara and related algae (Order Charales) and Coleochaete and related algae (Order Coleochaetales) are probably the closest living "green algal" relatives of land plants. Ultrastructural and morphological studies were the first to support the relationship of these ordersof green algae to land plants (embryophytes) (Pickett-Heaps, 1975; Mishler and Churchill, 1985; Graham et al., 1991). The orders were all placed in the class Charophyceae (Mattox and Stewart,1984) and retained within the green algae (Division Chlorophyta in the classical sense [Bold andWynne, 1985]. Recent analyses suggest that the Charophyceae is a paraphyletic group, and therefore the orders originally circumscribed within it have been placed within the Streptophyta (Bremer, 1985).
Later molecular studies (reviews in McCourt, 1995 and Melkonian and Surek, 1995) largelyconfirmed this close relationship, and confirmed what the ultrastructural and morphological data had first suggested: that the Charophyceae is a paraphyletic assemblage. Specifically, the Charales and Coleochaetales are most closely related to land plants (Chapman and Buchheim, 1991; Ragan et al. 1993; Surek et al., 1993; Bhattacharya et al., 1994). The Charales/Coleochaetales/Embryophyte clade is shown as unresolved because morphological and molecular studies to date have not fully resolved which of the green algae is the sister taxon ofland plants (McCourt 1995; Melkonian and Surek, 1995).
Bhattacharya, D., Surek, B., Rüsing, M., Damberger, S., and Melkonian, M. (1994) Group I introns are inherited through common ancestry in the nuclear-encoded rRNA of Zygnematales (Charophyceae). Proc. Natl. Acad. Sci. USA 91: 9916-20.
Bold, H. C. & Wynne, M. J. (1985) Introduction to the Algae. 2nd ed., Prentice-Hall, Inc., Englewood Cliffs, New Jersey, 720 pp.
Bremer, K. (1985) Summary of green plant phylogeny and classification. Cladistics 1:369-385.
Friedl, T. (1995) Inferring taxonomic positions and testing genus level assignments in coccoid green lichen algae: A phylogenetic analysis of 18S ribosomal RNA sequences from Dictyochloropsis reticulata and from members of the genus Myrmecia (Chlorophyta, Trebouxiophyceae Cl. Nov.). J. Phycol. 31:632-639.
Graham, L. E., Delwiche, C. F. & Mishler, B. D. 1991. Phylogenetic connections between the 'Green Algae' and the 'Bryophytes.' Adv. Bryol., 4, 213-244.
Mattox, K. R. & Stewart, K. D. (1984) Classification of the green algae: A concept based on comparative cytology. In: Systematics of the Green Algae. Irvine, D.E.G. & John, D.M. [Eds.] Academic Press, London, pp. 29-72.
McCourt, R. M. (1995) Green algal phylogeny. Trends in Ecology and Evolution 10:159-163.
Melkonian, M. (1990) Phylum Chlorophyta: Introduction to the Chlorophyta. In: Handbook of Protoctista. Margulis, L., Corliss, J. O., Melkonian, M., and Chapman, D. J., eds. pp. 597-599. Jones and Bartlett Publishers, Boston. [Note: This chapter is followed by several others on the "green algae."]
Melkonian, M. and Surek, B. (1995) Phylogeny of the Chlorophyta: Congruence between ultrastructural and molecular evidence. Bull. Soc. Zool. Fr. 120: 191-208.
Mishler, B. D. & Churchill, S. P. (1985) Transition to a land flora: phylogenetic relationships of the green algae and bryophytes. Cladistics 1:305-28.
Pickett-Heaps, J. D. (1975) Green Algae: Structure, Reproduction and Evolution in Selected Genera. Sinauer Associates, Inc., Sunderland, Massachusetts, 606 pp.
Raven, P. H., Evert, R. H., Eichhorn, S. E. (1992) Biology of Plants. 5th Edition. Worth Publishers, New York.
Surek, B., Beemelmanns, U., Melkonian, M. & Bhattacharya, D. 1993. Ribosomal RNA sequence comparisons demonstrate an evolutionary relationship between Zygnematales and charophytes. Pl. Syst. Evol., 191, 171-81.
About This Page
Academy of Natural Sciences of Drexel University
R. L. Chapman
Louisiana State University, Baton Rouge, Louisiana, USA
University of Tulsa, Oklahoma, USA
Brent D. Mishler
University of California, Berkeley, California, USA
Correspondence regarding this page should be directed to Richard M. McCourt at
Page copyright © 2009
Citing this page:
McCourt, Richard M., R. L. Chapman, Mark Buchheim, and Brent D. Mishler. 1996. Green plants. Version 01 January 1996 (under construction). http://tolweb.org/Green_plants/2382/1996.01.01in The Tree of Life Web Project, http://tolweb.org/
For an explanation of very similar terms, see plant and green algae.
|An assortment of thallophyte Viridiplantae in a rock pool, Taiwan|
Viridiplantae (literally "green plants") are a clade of eukaryotic organisms made up of the green algae, which are primarily aquatic, and the land plants (embryophytes), which emerged within them. Green algae traditionally excludes the land plants, rendering them a paraphyletic group. 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. More than 350,000 species of Viridiplantae exist.
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. 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
Leliaert et al. 2012
Simplified phylogeny of the Viridiplantae, according to Leliaert et al. 2012.
Below is a consensus reconstruction of green algal relationships, mainly based on molecular data.
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