Typical growth curve in plants is Parabolic, Linear, Sigmoid, or Stair-steps shaped?

The growth curve is a S-shaped curve obtained when we plot growth against time. It is also called sigmoid curve. This curve mainly shows four phases of growth - 1. initial slow growth (Lag phase), 2. the rapid period of growth (log phase / exponential phase) where maximum growth is seen in a short period and 3. the diminishing phase where growth will be slow and 4. stationary / steady phase where finally growth stops.