Question

The cork cambium, cork and secondary cortex are collectively called:

• A. Phellem
• B. Phelloderm
• C. Phellogen
• D. Periderm

Answer 1

The correct option is D

Periderm

The correct option is D.

Explanation of the correct option:

1. Periderm is nothing but a group of secondary tissues forming a protective layer that replaces the epidermis of many plant stems, roots, and other parts.
2. Although it may also develop into leaves and fruit, its main function is to protect the stems and roots.
3. Phellem, Phelleogen, and Phellederm are the three distinct cell types that make up the periderm structurally.
4. It has three different layers:

Phellogen (Cork Cambium):

1. As the stem continues to increase in diameter due to the activity of vascular cambium, the outer cortical and epidermal layers gets broken down and need to be replaced by providing new protective layers.
2. So, another meristemic tissue called cork cambium develops, generally in the cortex region.
3. Cork cambium is generally couple of layer thick.
4. These are narrow cells, thin-walled nearly rectangular in shape.
5. Cork cambium cuts off cells on both sides.

Phellem (cork):

1. The outward cells divided by the cork cambium differentiate into cork or phellem.
2. The cork is impervious to water due to suberin deposition in the cell wall.

Phelloderm (secondary cortex):

1. Cork cambium divides on inward side and differentiate into secondary cortex or phelloderm.
2. The cells of secondary cortex are parenchymatous.

Final answer: The cork cambium, cork, and secondary cortex are collectively called periderm.