In mitosis of higher plant cells, basically two differences can be highlighted compared to what occurs in animal cell mitosis:
- Mitosis occurs without centrioles. From certain places, corresponding to the centrosomes, the spindle fibers radiate. Since there are no centrioles, then there is no aster. For this reason, mitosis in plant cells is said to be anastral (from Greek, an = negative);
- Cytokinesis is centrifugal, occurs from the center to the periphery of the cell. At the beginning of telophase fragmoplasm forms, a set of protein microtubules similar to those of the division spindle. The microtubules of the fragmoplast function as scaffolds that guide the deposition of a median disk-like cell plate, originated from fused vesicles of the Golgi system. Progressively, the cell plate grows towards the periphery and, at the same time, inside the gallbladder, the deposition of some substances, including pectin and hemicellulose, both polysaccharides. On either side of the cell plate, the fused membranes contribute to the formation in this region of the plasma membranes of the two new cells that eventually connect with the plasma membrane of the mother cell. Following the formation of this middle lamella, each daughter cell deposits a primary cellulosic wall outside the plasma membrane. The primary wall eventually spans the entire perimeter of the cell. At the same time the primary cellulosic wall of the mother cell is progressively undone, allowing the growth of each daughter cell, each now endowed with a new primary wall. So if we could look at this median region of one of the cells from the cytoplasm outward, we would initially see the plasma membrane, then the primary cellulosic wall and then the middle lamella. Eventually, a secondary wall may be deposited between the plasma membrane and the primary wall.
Mitosis serves to…
Mitosis is a type of division that is very common among today's earth organisms. In single cells, it serves the asexual reproduction and the multiplication of organisms. In the multicellular she repairs damaged tissuesrepairs cells that usually die and is also involved in growth.
In men, the skin, bone marrow and intestinal lining are places where mitosis is frequent. Not all human cells, however, are capable of mitosis. Neurons and muscle cells are two highly specialized cell types in which this type of division does not occur (occurs only in the embryonic phase). In plants, mitosis occurs in places where there are tissues responsible for growth, such as root tips, stem tips and lateral buds. It also serves to produce gametes, unlike in animals, where meiosis is the process of division most directly associated with the production of gametic cells.