Which of the following is an example of secondary growth?

a. increase in length

b. increase in thickness or girth

c. increase in root hairs

d. increase in leaf number

Growth is usually associated with the development of new organs and tissues and reproduction that results in the formation of new individuals. The growth is possible in various dimensions such as latitudinal and longitudinal.

Lateral meristem is a type of meristematic tissue that is responsible for the secondary growth and development of some plants. The increase in stem thickness is a type of secondary growth that is contributed by the activity of the lateral meristems. Lateral meristems are absent in herbaceous plants. Lateral meristems include the vascular cambium that gives rise to the thickness of root and shoot. Another type is cork cambium that gives rise to the bark in the stem.

Increase in length is he significance of primary growth that results from the cell division in apical meristematic tissue.

Increase in root hairs also due to the function of apical meristems. The root cap has apical meristems that lead to the formation of smaller hair like extension from the root.

The increase in leaf number in plants are due to the amount of light, water, and minerals the plant is getting.

Therefore, option ‘b’ is the correct answer.

Secondary growth is responsible for the increase in girth or diameter of the stem that increases the thickness.