28. Explain in 2-3 lines each of the following terms with the help of examples taken from different plant tissues.
(a) Differentiation is permanent in size, structure, composition and function of cells, tissue or organs. For example the meristematic tissues in plants gives rise to new cells which mature and get differentiated into special tissue or an organ of the plant, e.g., cells, distal to root apical meristem form root cap, cell of the periphery form epiblema, followed by cortex, endodermis, pericycle and vascular.
(b) De-differentiation is the process of despecialisation of differentiated cells so that they again become differentiated and able to divide. e.g., in dicot stem, the cortical cells get de-differentiated and become meristematic to form cambium (interfascicular cambium, and fascicular cambiums).
(c) Re-differentiation The cambium cells thus formed, again re-differentiate to form secondary cortex cells secondary xylem and phloem elements and phelloderm in case of secondary growth of woodydicotplants.