Question

Which one increases girth of stem or root?
A.Xylem
B.Phloem
C.Cambium
D.Cortex

Answer 1

Hint: The increase in girth and diameter of the plant is particularly termed as secondary growth. The tissues that lead to the secondary growth are mainly found beneath the bark and in the vascular bundles of dicot roots and stems.

Complete answer:
Growth of plants associates two types of growth namely primary growth (increase in the length of stem and root) and secondary growth (increase in thickness). Primary growth takes place due to cell division in the apical meristem and secondary growth is due to cell division in the lateral meristem.

Lateral meristematic tissues are usually present as a thin layer in cork cambium and vascular cambium of dicot plants. That functions in the increase of girth of the plant.

Now let us find solution from given options:
A.Xylem: it is a kind of complex tissue that acts as main water conducting tissue. It does not perform any role in secondary growth but provides mineral and nutrition to plants parts.
B.Phloem: it is a kind of complex tissue that acts as the main Food conducting tissue. It does not perform any role in secondary growth but provides mineral and nutrition to plants parts.
C.Cambium: The girth of the stem or root increases due to the presence of ‘Cambium'. Cambiums are defined as the lateral meristems that participate in the secondary growth of dicots. Generally, secondary growth does not take place in monocots due to a lack of vascular cambium in them.
D.Cortex: outer layer is defined as the cortex or epidermis. This layer helps to protect the plant parts such as stem and root from the attack of outside and from the external environment. This does not play any role in secondary growth.

Hence, the correct answer is option (C)

Note: Annual rings or annual growth rings are particularly present in the trunk of a tree that provides the scientist with knowledge about the lifespan of a tree. This annual ring is formed as a result of the activity of the vascular cambium. The rate of lateral growth of the trunk gets increased in summer and decreases in winter, giving a characteristic ring for each year of growth. Thus, the count of growth rings in a tree trunk gives us the age of a tree.