Question

Phelloderm is
A. Secondary cortex toward periphery with dead suberized cells
B Secondary cortex above xylem
C. Secondary cortex of monocots
D. Parenchymal cells of secondary cortex formed towards inside by phellogen

Answer 1

Hint: Phelloderm is a part of the periderm. Phelloderm is a layer of parenchyma produced inwardly by the cork cambium.

Complete answer
In this question we have asked what Phelloderm is.
In woody plants, the epidermis is replaced by a tougher, protective layer which we called bark.
The bark which is now the outermost layer, protects them from water loss, mechanical injuries and pathogen attacks.

It is made up of 3 parts: The periderm, the cortex, and the phloem.
The periderm consists of the outermost layer, cork, which we called phellem, the middle layer, cork cambium also known as the phellogen, and the inner layer, phelloderm. Now come to the options.

Our first option is a secondary cortex towards the periphery with a suberized cell. First of all, what is the secondary cortex? Secondary cortex is made up of cork and cambium and is derived from phelloderm. Suberized cells form by conversion of the cell walls into corky tissue by infiltration with suberin. As we already mentioned that phelloderm is the secondary cortex but it does not grow toward the periphery and is not suberized. So, this option is wrong.

Our 2nd option is the secondary cortex above xylem. As we already mentioned phelloderm is the secondary cortex but it is the inner layer of cork cambium. It doesn't present above xylem. So, this option is also wrong.

Option 3rd option is the secondary cortex of monocots. Phelloderm is the secondary cortex of dicotyledonous plants, not monocots. So, this option is also wrong.

Option 4th option is parenchymal cells of the secondary cortex formed towards inside by phellogen which is absolutely correct because phelloderm is made up of parenchymal cells of secondary cortex which is growing inside. So, this option is correct.

The correct option is D, the Parenchymal cell of the secondary cortex towards the inside by phellogen.

Note: Phelloderm is simply a layer of parenchyma produced inwardly by the cork cambium and it is an inner secondary cortex of the cork cambium.