Question

Quiescent centre occurs in
A. Shoot apex
B. Root apex
C. Both A and B
D. Meristematic tissue

Answer 1

Hint: Quiescent centre is an inactive cell region present behind the root cap. They are used to replace the meristematic cells of the root cap.

Complete answer:
- Meristem is a type of tissue that is found in plants. It consists of undifferentiated meristematic cells capable of cell division. In a plant, we can see three types of meristematic tissues: apical meristem, intercalary meristem and lateral meristem.
- Apical meristem is found in the tips of roots and shoots. Intercalary meristem is located at the leaf blades and base of nods in stems. Lateral meristem is found in the woody part of the plants.

Fig: The longitudinal section of a shoot showing meristematic tissues

- The shoot apex of shoot apical meristem is a dome shaped region found in the tip of the shoots.
- The shoot apex is also known as the terminal bud of plants rising from 0.1-1.0 mm and consisting of apical meristem, forming leaves and the surrounding leaf primordial areas.
- The root apex is a small area at the root tip where all cells are able to divide in multiple divisions and from which all primary root tissues are produced.
- Quiescent centre is an area in the apical meristem of a root where cell division occurs very slowly. But the cells are able to resume meristematic activity if the tissue around them is damaged.

Fig: Organization of root apex

Thus, the correct answer is option B, i.e., Root apex.

Note: Quiescent centre serves as a stem cell reservoir to ensure the regeneration and persistence of apical meristem root. They are also important for organizing patterns of primary development in roots.