Growth curve is the graphical representation of growth against time, thus it is also called sigmoid curve.
A typical S-shaped grand period of growth curve
It has three phases :
(1) Lag phase: It is in the beginning of the growth and represents the time in which minimum growth occurs. The growth is very slow in this phase.
(2) Log/Exponential phase : It represents the phase of maximum growth. If log phase persists for longer time then growth is linear. Both the progeny cells following mitotic cell division retain the ability to divide and continue to do so.
(3) Stationary phase : It is the phase in which no growth occurs. The limited nutrient supply, the growth slows down leading to a stationary phase.
Auxin was isolated by F.W. Went from tips of coleoptiles of oat seedling.