Question

Besides phellem, phellogen, root epiderm comprises of
A. Secondary cortex
B. Phelloderm
C. Bark
D. More than one option is correct

Answer 1

Epidermal tissue serves as a boundary between the plant and the external environment. The epidermis performs several functions such as the protection against water loss, absorption of water and mineral nutrients and secretion of metabolic compounds. The epidermal cells of most leaves show dorsoventral anatomy.

Complete solution:
The information regarding the epidermis of different parts of plants is given below:
Epidermis is a single layer of flattened cells found at the surface. When in initial stages or say when they form for the first time, epidermal cells have extensions — the root hairs— which greatly increase the surface area responsible for the water-uptake and nutrients from the soil particles.
Root epidermal cells differentiate into hair and non-hair cells depending on the position and function.
The root hairs of the young epidermal cells increase the surface area quite well, through which movement of materials can occur.
The thread-like hairs are basically enlargements of the protoplast that extend outward into the soil. The wall material is thin and they are mostly fragile and can be easily broken.
The internal tissue produced by the phelloderm and phellogen, and consists of ordinary parenchymatous cells.
The extent of development of the phelloderm depends upon the origin of cells that is whether the phellogen has a superficial or a deep-seated origin.
The root epidermis comprises phellem, phellogen and phelloderm.
So, the correct answer is option (B) Phelloderm.

Note: Most woody eudicots and gymnosperms form a periderm in the root and the stem, and likewise, underground stems. In the stem of most trees, the first phellogen is formed in the sub‐epidermal layer, but in certain species it arises from the epidermis or the phloem. The formation of phellem, phellogen and phelloderm occurs during secondary growth which is the characteristic feature of dicots.