Why is not any one parameter good enough to demonstrate growth through the life of a flowering plant?

A plant has many different parts like leaves, stem, roots, flowers, fruits etc. which grow differently during different stages of life cycle. Different parameters are required to measure the growth of different plant parts. For stem and roots, increase in length and diameter are the parameters for measuring growth whereas for leaves, increase in surface area is a parameter for measuring growth.  Measuring the growth of plants using only one parameter does not provide sufficient information and hence, it is not good enough to demonstrate growth.