The periplast is one of three types of cell-covering of three classes of

algae Algae (; singular alga ) is an informal term for a large and diverse group of photosynthetic eukaryotic organisms. It is a polyphyletic grouping that includes species from multiple distinct clades. Included organisms range from unicellular mic ...

. The ''

Cryptomonad The cryptomonads (or cryptophytes) are a group of algae, most of which have plastids. They are common in freshwater, and also occur in marine and brackish habitats. Each cell is around 10–50 μm in size and flattened in shape, with an anterio ...

s'' have the periplast covering. The ''

Dinophyceae Dinophyceae is a class of dinoflagellates. Taxonomy * Class Dinophyceae Pascher 1914 eridinea Ehrenberg 1830 stat. nov. Wettstein; Blastodiniphyceae Fensome et al. 1993 orthog. emend.** Order Haplozoonales aplozooidea Poche 1913*** Family Ha ...

'' have a type called the

amphiesma Amphiesma is a genus of snakes in the family Colubridae. They are found across Asia. Species * '' Amphiesma stolatum'' (Linnaeus, 1758) – buff striped keelback * ''Amphiesma monticola ''Amphiesma monticola'', also known as the Wynad keel ...

, and the ''

Euglena ''Euglena'' is a genus of Unicellular organism, single cell flagellate eukaryotes. It is the best known and most widely studied member of the class Euglenoidea, a diverse group containing some 54 genera and at least 200 species. Species of ''Eug ...

'' covering is the pellicle.

Structure

The periplast is a proteinaceous covering. It can be subdivided into an inner periplast and an outer periplast. Both of these components are variable in their composition. The inner periplast may be formed as a single sheet as in the

Chilomonas paramecium ''Chilomonas'' is a genus of cryptophytes, including the species '' Chilomonas paramecium''. Chilomonas is a protozoa (heterotroph). Chilomonas is golden brown and has two flagella A flagellum (; ) is a hairlike appendage that protrudes fr ...

, or as multiple plates of varying shape. The outer periplast surrounds the plasma membrane. The inner periplast below the plasma membrane may sometimes as in ''

Komma caudata ''Komma caudata'' is a cryptomonad The cryptomonads (or cryptophytes) are a group of algae, most of which have plastids. They are common in freshwater, and also occur in marine and brackish habitats. Each cell is around 10–50 μm in size ...

'' have a hexagonal arrangement of superficial periplast plates, and these are made up of sub-units. The superficial plates are lined up exactly with the inner plate and are surrounded by crystalline borders with the occasional rosette scale on the surface of the plates. A number of different periplast arrangements have been described in cryptomonads. On the inner periplast part there may be seen intermembrane particles that penetrate the plasma membrane into the protoplasm. These intermembrane particles are larger around the plate boundaries. The Dinophyceae has a cell covering called the amphiesma–cisternae-like vesicles in a thecal form structure. Many of the dinoflagellates have thicker thecal plates giving them the name of ''armoured dinoflagellates''. The covering of the

Euglenid Euglenids (euglenoids, or euglenophytes, formally Euglenida/Euglenoida, ICZN, or Euglenophyceae, ICBN) are one of the best-known groups of flagellates, which are excavate eukaryotes of the phylum Euglenophyta and their cell structure is typical ...

s is called the pellicle.

References

{{Reflist Algal anatomy