Question

What is sigmoid growth curve? Why is it so called?

Answer 1

Plant growth rate be termed as the increase in growth per unit time.

The rate of growth of a plant or plant part is not always uniform during its lifespan. Sometimes it is slow and at other times rapid. If we plot the increase in cell number (growth rate) against time, a typical S-shaped curve is obtained. This has been called as the growth curve or sigmoid growth curve by Sachs (1873) as the shape of the curve obtained was sigmoid.

The growth curve has three phases of growth:

(i) Lag Phase- This is the initial phase of growth where the rate of growth is very slow.

(ii) Log or Exponential Phase- Rate of growth rapidly increases during this phase.

(iii) Stationary Phase- The rate of growth starts decreasing and finally stops.