A.T.S. of dicot stem is stained with iodine with proper procedure. Which of the following structures are expected to show blue colour

Options

A. Endodermis
B. Cortex
C. Pericycle
D. Phloem

Answer

To solve the question regarding which structures in the A.T.S. (Anatomical Transverse Section) of a dicot stem will show blue color when stained with iodine, follow these steps:

### Step-by-Step Solution:

1. **Understand the Staining Process**: Iodine is used as a stain to identify the presence of starch in plant tissues. When starch is present, it reacts with iodine to produce a blue color.

2. **Identify Structures in Dicot Stem**: In a typical dicot stem, the following structures are present:
- Epidermis
- Cortex
- Endodermis
- Pericycle
- Phloem
- Xylem

3. **Focus on Starch Presence**: The key to answering the question is to identify which of these structures contain starch. The endodermis is known to contain starch grains, which is why it is often referred to as the "starch sheath."

4. **Evaluate Other Structures**:
- **Cortex**: Generally does not contain significant amounts of starch.
- **Pericycle**: Typically lacks starch.
- **Phloem**: Primarily involved in the transport of nutrients and does not store starch.

5. **Conclusion**: Since only the endodermis contains starch, it is the only structure that will show a blue color when stained with iodine.

### Final Answer:
The structure expected to show blue color when the A.T.S. of a dicot stem is stained with iodine is the **endodermis**.

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