Questions & Answers

Formation of periderm is function of
a. Vascular cambium
b. Cork cambium
c. Both A and B
d. None of these

Answer Verified Verified
Hint: A protecting tissue that substitutes the epidermis when the secondary growth dislocates the epidermis of the primary plant body and eventually kills it.

Complete answer:
> Option A is incorrect. The vascular cambium occurs between a young stem or root 's primary xylem and phloem. These parenchymatous cells are meristematic and begin to develop secondary xylem or wood outward to the inside of the cambium and secondary phloem. It is responsible for longitudinal growth and continuous development of new xylem and phloem; in woody plants, wood is made by the shooting vascular changes.

> Option B is correct. The periderm is the main protective tissue which replaces the epidermis in the thickness of stems and roots during development. The periderm is a multi-layered structure of tissue, the majority of which is usually the cork or phellem. Phellem (the cork) consists of dead cells at maturity, and its primary walls are protected from the inside by the secondary wall, consisting of parallel suberin lamellae alternating with wax layers. It covers the nucleus and is one cell layer thick that produces centrifugal periderm.

> Option C is incorrect. The vascular cambium and cork cambium are secondary meristems which are produced in stems and roots after separation of primary plant body tissues. The vascular cambium is responsible for the stem and root diameter and for the development of woody tissue. Some bark is produced by the cork cambium.

> Option D is incorrect. A cambium also known as the phellogen (cork cambium), is the source of the periderm, a defensive tissue that replaces the epidermis when the secondary growth displaces the epidermis of the primary plant body and eventually kills. It's among the plant's meristems – the collection of tissues consisting of (incompletely differentiated) embryonic disc cells from which the plant develops. Its function is to produce a tough protective material called cork.

Hence, The correct answer is option (B).

Note: The phellogen or cork cambium is a lateral meristem and is responsible for the secondary growth of roots and stems that replaces the epidermis. Some monocots (although there is no secondary growth for the monocots) and woody and many herbaceous dicots, gymnosperms develop cork cambium.