what is exactly relative growth rate? how we can explain to students?

 Relative growth rate (RGR) is a measure used in plant physiology to quantify the speed of plant growth. It is measured as the mass increase per aboveground biomass per day, for example as g g^-1d^-1. It is considered to be the most widely used way of estimating plant growth, but has been criticised as calculations typically involve the destructive harvest of plants.^[1]

RGR is calculated using the following equation:^[1]

RGR = (ln W2 - ln W1)/(t2-t1)

Where:

ln = natural logarithm

t1 = time one (in days)

t2 = time two (in days)

W1 = Dry weight of plant at time one (in grams)

W2 = Dry weight of plant at time two (in grams)