1. Lag phase-Growth is slow in this phase.

2. Exponential phase-shows rapid growth and maintains maximum growth for sometime.

3. Stationany phase-Growth diminishes and ultimately stops in this phase.

Growth is the main character which distinguish living organisms from non-living. All living organism grow in number and then accumulate biomass and grow in size as well. The growth is exhibited by all living organisms in terms of increase in number of cells as well as increase in size and length of each cell. In unicelluar organism, show growth and the growth is synchronous with reproduction. Unicellular organism when divide they produce offsprings (reproduction) i.e., each cell accumulate (synthesise) protoplasm and increase in size but up to a limit and divide to from two cells.

The fungus Gibberella fuijkuroi when infects rice plant, it causes increase in internodal area of rice so, that the rice plant become foolishly tall as compored to normal ones. This is because this fungi produces GA in considerably higher amounts which causes over growth of rice plants thus, causing foolish disease.

Short day plants are those plants that flower only when the photoperiod (exposure to duration of light) is below critical period. Tobacco, being a short day plant is unable to show flowering when exposed to light above than the critical period.

(a) Meristematic cells near root tip the cells of this region are called Root Apical Meristems (RAM) and are in active state of division, thus their number increases continuously. The cells of this region are thin walled with dense cytoplasm and large nucleus. They have the ability to divide and self perpetuate.

(b) The Cells in the Elongation Zone of the Root This region is situated just above the meristematic zone. In the cells of this zone, a large number of small vacuoles develop and later these vacuoles fuse to form one large central vacuole filled with cell sap. The cells are elongated in this region.