Question

The girth of stem increases due to ---.
(a) Apical meristem
(b) Lateral meristem
(c) Intercalary meristem
(d) All of the above

Answer 1

Hint: The girth of an object, for instance, the body of a human or an animal, is its width or thickness, considered to be the measure around its circumference. Stem girth means stem thickening.

Complete answer:
Stem girth increases due to lateral meristematic tissues. They are found as thin layers under the bark (called the cork cambium) and in vascular bundles of dicot roots and stems (called the vascular change) . This increase in the plant's diameter and girth is termed secondary growth.
The apical meristem is located at the rising tip of the stems, the root, and also at the leaf apices. They cause elongation, i.e. increase in plant height. Located at the base of the leaf and the internode, intercalary meristem causes an increase in the length of an organ.

So, the correct answer is, ‘Lateral meristem’..

Additional Information:
- The lateral meristem occurs in the vascular bundles and the cork area.
- These meristematic regions possess cells capable of dividing and forming new cells for secondary development.
- The lateral meristematic tissue is responsible for an increase in plant diameter or girth.

Note: Meristem is undifferentiated plant tissue that is present in plant growth areas. Intercalary, apical, and lateral are the three types of meristematic tissue. The vascular change in plants is the principal route by which the stems and roots expand. The tissue consists of xylem to the outside and the internal phloem. Cork Cambium is found in mainly woody and some herbaceous plants, forming a cork or bark coating on the outside of the stem and secondary growth in the roots' epidermis.