The growth pattern of cells, organisms is uniform under favourable conditions & a typical growth curve in plants is sigmoidal. Thus following phases of growth are recognized.

(i) Lag phase: In the lag period the growth is slow. It represents the formative or cell division phase.

(ii) Log phase: Also called as exponential phase. During this phase, growth is maximum & most rapid. It represents the cell elongation phase.

(iii) Steady or stationary phase: It represents the cell maturation phase.

Time taken in growth phases (mainly log phase) is called a grand period of growth.