Arithmetic Growth Rate The expression of arithmetic growth is exemplified by roots (or organ) elongating at constant rate. On plotting the length of an organ against time, a linear curve is obtained. Mathematically it is expressed as [image:15_image13.emf] Constant linear growth, a plot of length L against time $L_{t} = L_{0} + rt$ $L_{t}$ = Length of time ‘$t$’ $L_{0}$ = Length of time to $r$ = Growth rate or elongation per unit time