Efficiency index in the exponential phase of geometrical growth is the ability of plants to produce
a)	Cell wall	b)	New enzyme
c)	New plant material	d)	Young ones through mitosis

(c)

Ability of the plants to produce new plant material is called efficiency index.

The exponential growth or phase of geometrical growth of the plant can be expressed as

, where

 Initial size at the beginning of the period

 Final size at the beginning of the period

 Growth rate

 Time of growth

 Base of natural logarithms

Here, the relative growth rate is also the measure of the ability of the plant to produce new plant material, which is referred to as efficiency index. Hence, the final size,  depends on the initial size,