The correct option is C efficiency index
The measure of the ability of the plant to produce new plant material is called the efficiency index.
The growth rate of a plant shows an increase that may be arithmetic or geometrical.
In arithmetic growth, after mitosis, only one daughter cell continues to divide while the other differentiates and matures. A linear curve is obtained in the case of arithmetic growth.
In geometric growth, the rate of growth increases exponentially. It can be found in initial multiplication of unicellular organisms and growth of very early embryos.
The total growth per unit time is called absolute growth rate.