Question

In a growing plant, the first phase during the process of growth is

• A. cell division
• B. cell enlargement
• C. cell differentiation
• D. cell maturation

Answer 1

The correct option is A cell division

All plant cells arise from the zygote. Development of a mature plant from a zygote (fertilized egg) follows a precise and highly ordered succession of events. Plant growth takes place in 3 steps or phases.

First phase is formative phase, also called the phase of cell formation or cell division. It occurs in root apex, shoot apex and other regions having meristematic tissues. New cells are produced by mitotic divisions of the meristematic cells.

In the 2nd phase i.e enlargement phase, the newly formed cells produced in the formative phase undergo enlargement. The cell walls of the enlarging cells show plastic extension through enzymatic loosening of microfibrils and deposition of new materials (intussusception). The enlarging cell also develops a central vacuole.

In the 3rd phase i.e phase of differentiation or maturation, the enlarged cells develop into special or particular types of cells by undergoing structural and physiological differentiation. Through structural differentiation, a cell attains a particular shape, size, thickens and remodels its internal constitution. In physiological differentiation, a cell takes up a particular function eg:- absorption of water by cells in the root hair, transfer of metabolites by transfer cells, photosynthesis by mesophyll cells, conduction by sieve tube cells, tracheids and vessels. Both structural and physiological differentiation produce various tissues and cell types.