Question

The outer layer of Dicot root is called:

• A. Epidermis
• B. Endodermis
• C. Pericycle
• D. Cortex

Hint:

In root anatomy, the terms 'epidermis', 'epiblema', and 'piliferous layer' are used interchangeably.
Look for these synonyms when solving questions about root tissue systems.

Answer 1

The Correct Option is A

Step 1: Understanding the Question:
The question requires us to identify the outermost tissue layer of a dicotyledonous root.
This is a standard question from plant anatomy focusing on root tissue organization.

Step 2: Key Formula or Approach:
We examine the concentric arrangement of tissue layers in a typical dicot root from the outside to the inside.
The order of layers is: Epidermis (Epiblema) $\rightarrow$ Cortex $\rightarrow$ Endodermis $\rightarrow$ Pericycle $\rightarrow$ Vascular Bundles.

Step 3: Detailed Explanation:

• The outermost layer of a dicot root is called the epidermis, also commonly referred to as the epiblema or piliferous layer.

• It consists of a single layer of compactly arranged, thin-walled parenchymatous cells.

• Unlike the stem epidermis, the root epidermis typically lacks a thick cuticle and stomata to allow for efficient water absorption.

• Many of the epidermal cells protrude outwards to form unicellular root hairs, which significantly increase the surface area for absorption of water and minerals.

• The layer directly beneath the epidermis is the cortex, which consists of multiple layers of loosely packed parenchyma cells.

• The endodermis is the innermost layer of the cortex, characterized by barrel-shaped cells containing Casparian strips.

• The pericycle lies inward to the endodermis and gives rise to lateral roots.


Step 4: Final Answer:
Thus, the outermost layer of the dicot root is the epidermis (epiblema).