Question

Waxy coating on epidermis of young stem is called
A. Suberin
B. Periderm
C. Phellem
D. Cuticle

Answer 1

Hint: Epidermis is the outermost layer of cells in plants which are derived from the protoderm and covers the stem, roots, leaves, flowers, fruits and seed parts.

Complete Answer:
The epidermis forms a protective layer around the plant protecting it against mechanical injury, water loss and infection.

Now, let us look at each option one by one.
- Suberin is a lipophilic molecule found in specialized plant cell walls. It prevents water loss in cells, protects the plant against infection and plays a very important role in the wound healing process. Mostly, suberin forms the periderm which envelopes the secondary stem. The secondary stem is not a young stem, therefore, this option is incorrect.

- Periderm is the outer layer covering the secondary stem in older plants and is produced in response to injury or infection. Therefore, this option is incorrect.

- Phellem (or cork) is the secondary tissue that forms the outer layer of periderm and originates from the cork cambium. Therefore, this option is incorrect.

- Cuticle is a waxy lipid and hydrocarbon based material specially produced by the epidermal cells of aerial parts of the plant specially in plant parts lacking a periderm. This is the material which forms the waxy layer around young stems. Therefore, this option is correct.

Thus, the correct answer to this question is (D) Cuticle.

Note: The cuticle layer present in the leaves prevents the gases from entering the cells. When the stomata opens for the intake of carbon dioxide, the cuticle protects the mesophyll cells in which photosynthesis occurs by forming a transparent barrier over them.