Globally distributed, in freshwater, marine, and terrestrial environments
Land plants (Kingdom Plantae, or the embryophyta) are specialized green algae adapted to life on land
An ancient group according to the fossil record, green algae are extremely diverse.
Often dominant algae in freshwater environment.
Structure & metabolism
Structurally diverse, the ancestral condition is thought to be a unicellular flagellate with two identical flagella, perhaps resembling a member of the modern Prasinophyceae
Derived conditions include
Coccoid, sessile cells
Siphons and coenocytes
Coenocyte - multiple nuclei, without transverse walls
Siphon - very large cells with multiple nuclei
Siphonocladous - multiple cells, each of which is siphonous
Pseudoparenchyma and Parenchyma
Flagellate stages (if present) are isokont, typically with two or four similar flagella
Hairs and scales may be present on the flagella, but mastigonemes are absent
Stellate transition zone on flagellum
Chloroplast is primary
Bound by two membranes
Thylakoids are stacked into lamellae, pseudograna, or grana; girdle lamellae are not present
Pyrenoids are often (but not always) present, are not stalked, and often have thylakoids passing through them.
Chlorophylls a and b (but chlorophyll c has been reported in some prasinophyceae)
Xanthophylls are principal accessory pigments
Most common are lutein, zeaxanthin, violaxanthin, antheraxanthin, and neoxanthin
Bryopsidales have siphonein and siphonoxanthin (the latter is also found outside of the Bryopsidales)
Reserve polysaccharide is starch, which is deposited inside of the chloroplast
Sometimes chloroplasts are differentiated to specialize in starch storage; these are called amyloplasts
DNA is scattered through chloropast in small nucleoids
Many life histories are known
Chlorophyta sensu stricto
Unicellular, typically scaly flagellates
Not a natural group; either paraphyletic or polyphyletic assemblage of lineages near the base of green algal diversity.
Equivalent to the Pleurastrophyceae of Mattox and Stewart (1984), but does not include Pleurastrum insigne
Centrioles to side of spindle at mitosis
Directly Opposed (DO) clade
Clockwise (CW) clade
Ulvophyceae sensu stricto
(= Cladophorales, Cladophorophyceae)
Van den Hoek et al., 1995 elevates several orders often placed in the Ulvophyceae to the class level; this is probably justified.
Charophyta sensu Karol et al., 2001
This group corresponds to the Charophyceae sensu Mattox and Stewart, 1984 but with the addition of embryophytes (land plants), which were arbitrarily exluded by Mattox and Stewart.
Both freshwater and marine.
Chlorophyceae are primarily freshwater
Ulvophyceae, Dasycladophyceae, Bryopsidophyceae, and Cladophorophyceae are primarily marine
Charophyceae are primarily freshwater
Important members of freshwater phytoplankton
Minor members of marine temperate intertidal communities
Important members of tropical (reef) intertidal communities
Dasycladales and Bryopsidales are important reef-building organisms
Complex life cycles in some
Plants are of profound economic importance
Required Reading: VdH Chapter 19 (actually, chapters 19-31)
KR Mattox and KD Stewart. 1984. Classification of the green algae: a concept based on comparative cytology. Pp. 29-72 in DEG Irvine and DM John, "Systematics of the Green Algae", Systematics Association Special Volume #27, Academic Press, London and Orlando.
Pickett-Heaps, J.D. 1975. Green Algae. Sinauer, Sunderland, MA.