Question

Which tissue of the dicot root is involved in the formation of vascular cambium?
A. Pericycle part above primary phloem
B. Whole pericycle
C. Thick walled parenchymatous cell of pith
D. Portion of pericycle above the protoxylem

Answer 1

Hint: The vascular cambium produces the vascular system's xylem and phloem, which are responsible for transport and support. During the transition from primary to secondary growth, a single layer of meristematic cells expands. The axial and radial xylem and phloem derivatives are generated by the two cell types, fusiform initials and ray initials.

Complete answer:
Let us analyse each of the given options to determine their presence in the vascular cambium of the dicot root.
Option:A – Pericycle part above primary phloem is not involved in secondary growth and is thus not involved in the formation of vascular cambium.
Thus, Option:A is incorrect.
Option:B – The whole pericycle is not involved in formation of vascular cambium, however a part of it is involved in it.
Thus, Option:B is incorrect.
Option:C – In dicot roots, the pith is tiny and unnoticeable. So, thick walled parenchymatous cells of pith are not involved in the formation of vascular cambium in dicot roots.
Thus, Option:C is also incorrect.
Option:D – A portion of the pericycle located outside of the protoxylem transforms into a secondary meristem known as the vascular cambium during secondary growth.
Thus, Option:D is correct.

Hence, option D. Portion of the pericycle above the protoxylem is the correct answer

Note:
Secondary meristems allow woody plants to increase in diameter (secondary growth). Secondary growth does not occur in herbaceous plants. Both forms of secondary meristems are called cambium, which means "exchange" or "changing". Secondary xylem (towards the centre of the stem or root) and phloem (towards the exterior of the stem or root) are produced by the vascular cambium, which increases the diameter of the plant.