Charales in the context of Chara (alga)

Charophyta (UK: /kəˈrɒfɪtə, ˌkærəˈfaɪtə/) is a paraphyletic group of freshwater green algae, called charophytes (/ˈkærəˌfaɪts/), sometimes treated as a division, yet also as a superdivision. The terrestrial plants, the Embryophyta emerged deep within Charophyta, possibly from terrestrial unicellular charophytes, with the class Zygnematophyceae as a sister group.

With the Embryophyta now cladistically placed in the Charophyta, it is a synonym of Streptophyta. The sister group of the charophytes are the Chlorophyta. In some charophyte groups, such as the Zygnematophyceae or conjugating green algae, flagella are absent and sexual reproduction does not involve free-swimming flagellate sperm. Flagellate sperm, however, are found in stoneworts (Charales) and Coleochaetales, orders of parenchymatous charophytes that are the closest relatives of the land plants, where flagellate sperm are also present in all except the conifers and flowering plants. Fossil stoneworts of early Devonian age that are similar to those of the present day have been described from the Rhynie chert of Scotland. Somewhat different charophytes have also been collected from the Late Devonian (Famennian) Waterloo Farm lagerstätte of South Africa. These include two species each of Octochara and Hexachara, which are the oldest fossils of Charophyte axes bearing in situ oogonia.

Charophyceae is a class of charophyte green algae. AlgaeBase places it in division Charophyta. Extant (living) species are placed in a single order Charales, commonly known as "stoneworts" and "brittleworts". Fossil members of the class may be placed in separate orders, e.g. Sycidiales and Trochiliscales.

Charophyceae is basal in the Phragmoplastophyta clade which contains the embryophytes (land plants). In 2018, the first nuclear genome sequence from a species belonging to the Charophyceae was published: that of Chara braunii.

Octochara is a genus of fossil charophyte (aquatic green alga) from the Famennian (Late Devonian). It is one of two genera of charophyte described from the Waterloo Farm lagerstätte in southern Africa. It and Hexachara, from the same locality provide the oldest record of reconstruct able charophytes with in situ oogonia.

Octochara is derived from a Greek word "octo", meaning eight, a reference to the octoradial symmetry, and "chara", referring to membership of the Charales. In Octochara, a whorl of eight laterals are borne at each node. Each lateral is branched to produce four secondary branches and bears an oogonium.

Characeae is a family of freshwater green algae in the order Charales, commonly known as stoneworts. They are also known as brittleworts or skunkweed, from the fragility of their lime-encrusted stems, and from the foul odor these produce when stepped on.

In some treatments, the Characeae includes all the living (extant) species of Charales; this circumscription is followed here. In other treatments, the genus Nitellopsis, which has both extant and extinct species, is placed in a separate family, Feistiellaceae.

Feistiellaceae is a family of freshwater green algae in the order Charales.

Plasmodesmata (singular: plasmodesma) are microscopic channels which traverse the cell walls of plant cells and some algal cells, enabling transport and communication between them. Plasmodesmata evolved independently in several lineages, and species that have these structures include members of the Charophyceae, Charales, Coleochaetales and Phaeophyceae (which are all algae), as well as all embryophytes, better known as land plants. Unlike animal cells, almost every plant cell is surrounded by a polysaccharide cell wall. Neighbouring plant cells are therefore separated by a pair of cell walls and the intervening middle lamella, forming an extracellular domain known as the apoplast. Although cell walls are permeable to small soluble proteins and other solutes, plasmodesmata enable direct, regulated, symplastic transport of substances between cells. There are two forms of plasmodesmata: primary plasmodesmata, which are formed during cell division, and secondary plasmodesmata, which can form between mature cells.

Similar structures, called gap junctions and membrane nanotubes, interconnect animal cells and stromules form between plastids in plant cells.