image:Phycoplast.png, Schematic representation of types of cytokinesis in the green algae: 1) Phycoplast formation with cleavage furrow (e.g. ''Chlamydomonas''); 2) Cleavage furrow and persistent telophase spindle (e.g. ''Klebsormidium''); 3) Phycoplast and cell plate formation (e.g. ''Fritschiella''); 4) Persistent telophase spindle/phragmoplast with cell plate formation (e.g. ''Coleochaete'') The phycoplast is a microtubule structure observed during

cytokinesis Cytokinesis () is the part of the cell division process during which the cytoplasm of a single eukaryotic cell divides into two daughter cells. Cytoplasmic division begins during or after the late stages of nuclear division in mitosis and mei ...

in members of the '' Chlorophytina'', the largest and most well known subphylum of chlorophyte green algae. Cytokinesis in green algae occurs via a diverse range of mechanisms, including

cleavage furrow In cell biology, the cleavage furrow is the indentation of the cell's surface that begins the progression of cleavage, by which animal and some algal cells undergo cytokinesis, the final splitting of the membrane, in the process of cell division. ...

s in some algae and

cell plate image:Phragmoplast.png, 300px, Phragmoplast and cell plate formation in a plant cell during cytokinesis. Left side: Phragmoplast forms and cell plate starts to assemble in the center of the cell. Towards the right: Phragmoplast enlarges in a donut ...

s in others. Plants (=

Chloroplastida Viridiplantae (literally "green plants") are a clade of eukaryotic organisms that comprise approximately 450,000–500,000 species and play important roles in both terrestrial and aquatic ecosystems. They are made up of the green algae, which ar ...

) of the clade ''

Phragmoplastophyta The Phragmoplastophyta (Lecointre & Guyader 2006) are a proposed sister clade of the Klebsormidiaceae in the Streptophyte/Charophyte clade. The Phragmoplastophyta consist of the Charophycaea and another unnamed clade which contains the Coleocha ...

'' (a subgroup of charophytes which includes the land plants, desmids, water silk,

stoneworts Charales is an order of freshwater green algae in the division Charophyta, class Charophyceae, commonly known as stoneworts. Depending on the treatment of the genus '' Nitellopsis'', living (extant) species are placed into either one family (Ch ...

etc.) use structures called

phragmoplast image:Phragmoplast.png, 300px, Phragmoplast and cell plate formation in a plant cell during cytokinesis. Left side: Phragmoplast forms and cell plate starts to assemble in the center of the cell. Towards the right: Phragmoplast enlarges in a donut- ...

s to organize and guide the growing cell plate. In these plants, the microtubules of the

telophase Telophase () is the final stage in both meiosis and mitosis in a eukaryotic cell. During telophase, the effects of prophase and prometaphase (the nucleolus and nuclear membrane disintegrating) are reversed. As chromosomes reach the cell poles, ...

spindle give rise to the phragmoplast and are oriented perpendicular to the plane of cell division and the forming cell plate. The growth of the cell plate eventually disrupts the telophase spindle (see case 4 in picture). In the '' Chlorophyceae'', the most common form of cell division occurs via a phycoplast. In these algae, the spindle collapses and a new system of microtubules forms that is oriented in parallel to the plane of cell division. This phycoplast can be observed in algae undergoing cytokinesis via cleavage furrow (case 1 in picture) as well as algae utilizing a cell plate (case 3 in picture). The phycoplast may play a role in assuring that the plane of cell division will pass between the two daughter nuclei. Typically, these algae undergo "closed" mitosis where the nuclear envelope persists throughout mitosis.

References

*P.H. Raven, R.F. Evert, S.E. Eichhorn (2005): ''Biology of Plants'', 7th Edition, W.H. Freeman and Company Publishers, New York, {{Protist structures Cell cycle Mitosis Plant cells