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Diagram of the plant cell, with the cell wall in green. Cell walls serve similar purposes in those organisms that possess them. They may give cells rigidity and strength, offering protection against mechanical stress. The chemical composition and mechanical properties of the cell wall are linked with plant cell growth and morphogenesis. [11]
The structure of these algae is unicellular, and lacks flagella.Although most desmid species are unicellular, some genera form chains of cells, called filaments. A few genera form non-filamentous colonies, with individual cells connected by threads or remnants of parent cell walls.
Green algae have chloroplasts that contain chlorophyll a and b, giving them a bright green colour, as well as the accessory pigments beta carotene (red-orange) and xanthophylls (yellow) in stacked thylakoids. [12] [13] The cell walls of green algae usually contain cellulose, and they store carbohydrate in the form of starch. [14]
Chara is a genus of charophyte green algae in the family Characeae. They are multicellular and superficially resemble land plants because of stem -like and leaf -like structures. They are found in freshwater, particularly in limestone areas throughout the northern temperate zone, where they grow submerged, attached to the muddy bottom.
The content of the cell divides into 2,4 (B), 8(C) sometimes daughter protoplasts. Each daughter protoplast rounds off to form a non-motile spore. These autospores (spores having the same distinctive shape as the parent cell) are liberated by the rupture of the parent cell wall (D). On release each autospore grows to become a new individual.
Desmodesmus species usually produce colonies of more than one cell, but single cells (unicells) may be found as well. [5] These single cells may be confused with Lagerheimia, a genus of single-celled algae. [6] The cell wall of Desmodesmus consists of an outer layer with a net-like structure, with "rosettes" of tubes underneath. [7]
A median constriction of the cells may appear either as distinct or faint. Desmidium cell walls are smooth with multiple side-by-side or scattered pores. Every semicell contains one stellate chloroplast. Typically cells are oval in shape or have a three to five angle. Angles of the cell are often off-balance on each semicell.
The chlorophyte and charophyte green algae and the embryophytes or land plants form a clade called the green plants or Viridiplantae, that is united among other things by the absence of phycobilins, the presence of chlorophyll a and chlorophyll b, cellulose in the cell wall and the use of starch, stored in the plastids, as a storage polysaccharide.