Question

Discuss the concept of radial patterning and its application to epidermal and vascular development.

Answer 1

Concept of radial patterning

All the plants have two types of pattern of growth in cell organisation and development from embryonic stage. One is axial pattern of organisation of cells which is along the axial length of the plant i.e. apical-basal axis. The other one is radial pattern which is organisation of cells in few concentric layers in either root or shoot system.

Briefly on discussing in root, there are 3 layers of concentric layers of cells, namely layer 1, layer 2 and layer 3. The layer 1 cells develops into epidermis cells and lateral root cap initials. The layer 2 cells give rise to corticol initials and/or endodermal one. Same way, the layer 3 cells give rise to vasculature and pith cells. Similarly, the shoot system also has radial pattern with a similar set of concentric cell layers.

Its application to epidermal and vascular development

There are specific set of genes are reponsible for development of each layer of initial cells into its specific functioning cell according to their cell fate. If the radial pattern of the specific plant is known and the genes reponsible for them are studied and they can be mutated to increase the development of its specific functional tissues such as epidermal and vascular tissues. Defects in development of these tissues can also be restored genetically by knowing the radial patterning of the cells. For example, Altered Phloem Development mutant -APL mutant of A.thaliana encodes a transcription factor that promotes pholem differentiation apart from repressing xylem differentiation during the development of vascualar tissue.