Lateral meristem
Explanation
Meristematic tissues in plants consist of actively dividing cells responsible for growth. Based on their location and function, they are classified into three types: apical, intercalary, and lateral meristems. While apical and intercalary meristems are associated with primary growth (increase in length), lateral meristems are responsible for secondary growth (increase in thickness or girth).
Option Analysis
- Apical meristem Apical meristem: This tissue is located at the growing tips of stems and roots. It is responsible for the elongation of the main axis of the plant, contributing to primary growth (increase in height or length). Therefore, this option is incorrect.
- Intercalary meristem Intercalary meristem: Found at the base of leaves or internodes (common in monocots like grasses), this meristem aids in the elongation of organs and the regeneration of parts removed by grazing herbivores. It contributes to length, not girth. Therefore, this option is incorrect.
- Lateral meristem Lateral meristem: These tissues occur along the longitudinal axis of the stem and root. Examples include the vascular cambium and cork cambium. They divide to produce new cells towards the periphery and the center, resulting in an increase in the diameter or girth of the plant axis. This process is known as secondary growth. Therefore, this option is correct.
- Epidermal tissue Epidermal tissue: This is a permanent tissue that forms the outer protective covering of the plant body. It is not a meristematic tissue and does not actively divide to increase the plant's dimensions. Therefore, this option is incorrect.
Key Takeaway
Lateral meristems (e.g., vascular cambium and cork cambium) are responsible for secondary growth, which increases the girth or thickness of the stem and root. In contrast, apical and intercalary meristems are responsible for primary growth (length).