Question

ASSERTION: Phellogen is a couple of layers thick.
REASON: Phellogen is made up of thick-walled and nearly rectangular cells.
(a) Both assertion and reason are correct
(b) Both assertion and reason are correct but the reason is not the correct explanation for assertion
(c) Assertion is correct but the reason is incorrect
(d) Both assertion and reason are incorrect

Answer 1

This has many layers of meristematic cells and is mainly responsible for the growth of the peridermis. The cells that develop inward from these layers are referred to as phelloderm, and cells that develop outward are referred to as phellem or cork. It is also called cork cambium.

Complete answer:
Phellogen is classified as the layer of meristematic cells responsible for the growth of the peridermis. Phelloderm is named for cells that develop inward from the layers of phellogen, and phellem or cork is named for cells that develop outward the phellogen. The periderm is a three-part layered structure system:
(a) the phellogen, or cork cambium, is the meristematic tissue that forms the periderm's dividing activity;
(b) the phelloderm or cork is formed outside by the phellogen, and
(c) the phelloderm is broken inside by the phellogen. Phellogen has several layers and is mainly composed of rectangular cells with thick walls.

Additional information:
-Cork cambium (pl. cambia or cambiums) is a tissue used as a part of the epidermis in many vascular plants. It's one of the many bark layers between the cork and the main phloem.
-The cork cambium is the lateral meristem that is responsible for secondary growth in roots and stems and it also replaces the epidermis.
-Cork cambium is found in woody dicots, gymnosperms and some monocots (monocots typically lack secondary growth), and many herbal dicots.
-It is one of the meristems of the plant that is the collection of tissues from which the plant develops consisting of embryonic disc (incompletely distinguished) cells.
-The purpose of cork cambium is to produce cork which is a tough protective material.

So, the correct answer is ‘Both assertion and reason are correct but the reason is not the correct explanation for assertion’.

Note:
-Between different species, the growth and development of cork cambium vary greatly.
-Also among various species its growth is highly dependent on age and growing conditions, as can be seen from various bark surfaces that may be smooth, fissured, tessellated, scaly, or flaking off.