Exponential growth can be expressed by

Exponential growth: When the growth takes place rapidly at a very high rate.

It is also called the log phase, in exponential growth phase the cells divide mitotically and keep on dividing, therefore it is known as the exponential phase. It is expressed as:
W₁ = W₀e^rt, where W₁ is the final size and W₀ is the initial size of the plant, r is the growth rate, t is the time of growth and e is the base of logarithms.