Describe briefly: (a) Arithmetic growth (b) Geometric growth (c) Sigmoid growth curve (d) Absolute and relative growth rates

Arithmetic growth
In this mode, each mitotic division produces one cell that continues to divide and another that differentiates; plotted as a straight line vs. time, e.g., root elongation at a constant rate

Geometric (exponential) growth
Here both daughter cells retain the ability to divide, resulting in multiplicative increase; initial lag, then rapid log phase displayed by an exponential curve

Sigmoid growth curve
Represents real‑world plant growth in an S‑shaped curve:
• lag phase – slow initial growth
• log (exponential) phase – rapid increase
• stationary phase – rate slows due to limiting factors

Absolute growth rate (AGR)
The actual increase in a growth parameter per unit time; e.g., cm/day or g/week

Relative growth rate (RGR)
The growth rate per unit of existing size, often expressed per time; mathematically RGR = (1/S)(dS/dt), or ln(S₂/S₁)/(t₂–t₁)