Tag: growth and development

The cells derived from root apical and shoot apical meristems and cambium differentiate and mature to perform specific functions. This process leading to maturation of cells is termed as differentiation. During differentiation, cells undergo few to major structural changes both in their cell walls and protoplasm e.g., to form a tracheary element the cells would lose their protoplasm, they also develop strong, elastic, lignocellulosic secondary cell walls, to carry water to long distances even under extreme tension. So, the correct answer is 'All of the above'.

The living differentiated cells, that have lost the capacity to divide can regain the power of division under certain conditions, this phenomenon is termed as de-differentiation. E.g.,formation of meristerns-interfascicular cambium (Formed from medullary rays) and cork cambium (formed from outer layer of cortex) from fully differentiated parenchyma cells. While doing so, such meristems/tissues are able to divide and produce cells that once again lose the capacity to deride but mature to perform specific functions, i.e., get redifferentiated. E.g., cells of secondary xylem, secondary phloem, periderm. Thus rediffrentiation can be defined as maturation or differentiation of dedifferentiated tissues. So, the correct answer is 'Redifferentiation'.

The portion of pith taken as an explant comprises of parenchymatous cells (i.e., simple permanent tissue which have lost the capacity to divide). When such cells are cultured on solid culture media, the parenchymatous cells of pith become meristematic and start dividing resulting in a mass of undifferentiated cells called callus. This is an example of dedifferentiation. 

Interfascicular cambium is the cambium formed by dedifferentiation of cells forming the ground tissue (parenchyma) that lie in line to the vascular cambium, since these strips of cambium originate between two vascular bundles or connect two vascular cambia together they are referred to as the interfascicular cambia. They are responsible for producing medullary rays during secondary growth.

Redifferentiation is the formation of new or differentiated tissue from a already differentiated tissue. During this process cells of parenchymatous tissue undergo dedifferentiation to meristematic tissue. The cells cut off by the meristematic tissue based on the location and function get modified to respective tissues like secondary cortex, secondary xylem and secondary phloem in roots, monocot stem, cork cells etc

Phytochrome is blue colored pigment present in the plants. It is a photoreceptor chromoprotein. It is mainly found in flowering plants. These are responsible for flowering. It mainly absorbs red and far-red radiation in plants and induces flowering process.

Phytochromes are photoreceptor found in plants that detects light. The different phytochromes are involved in different biological responses to red light. P$ _r$ is inactive form whereas P$ _{fr}$ is active form of phytochrome. When exposed to red light,  P$ _r$ is converted to P$ _{fr}$. This active form then initiate many biological processes in plants.