Question

How many of the following are true regarding secondary growth in root?
A. All cambium are secondary in orgin
B. Lenticels are not formed
C. Bark is formed
D. Cork cambium is originated from outer layer of cortex

• A. Two
• B. Three
• C. One
• D. Four

Answer 1

Answer: (B)

Three

In dicotyledonous plants, roots undergo secondary growth to increase in thickness by the formation of the secondary meristem. In roots, vascular bundles are radial, primary cambium is absent. During secondary growth, some of the parenchyma cells beneath each phloem group become meristematic and thus form cambium strips, which is secondary in origin.

Lenticels can be developed by the activity of phellogen or cork cambium as transversely elongated outer cortex regions.

In stems and roots of the woody dicots, all the cork layers together with cortical and dry secondary phloem tissue external to the innermost phellogen are called outer bark; while all the tissues external to the vascular cambium (secondary phloem, primary phloem, cortex, periderm, and tissues outside the periderm are termed bark.

In dicot roots, cork cambium or phellogen arises in the outer cells of the pericycle.

Hence, the except D all other options are correct.

So, the correct answer is option B, Three.