External protective tissues of plants are (of dicot stem are)

Options

A. Cork and pericycle
B. Cortex and epidermis
C. Pericycle and cortex
D. Epidermis and cortex

Answer

To answer the question regarding the external protective tissues of dicot stems, we can break down the information step by step:

### Step-by-Step Solution:

1. **Understanding the Structure of Dicot Stems**:
- Dicot stems undergo secondary growth, which involves the formation of new tissues that increase the thickness of the stem.

2. **Role of Epidermis**:
- The epidermis is the outermost layer of the stem. It serves as the first line of defense against physical damage and pathogens.

3. **Formation of Cork**:
- During secondary growth, the epidermis is replaced by a protective layer known as cork. This cork is formed from the secondary cambium, which develops from the outer layers of the stem.

4. **Characteristics of Cork**:
- The cork cells lose their protoplasts (the living part of the cell) and become filled with suberin, a waxy substance that makes them impermeable to water and gases. This makes cork a very effective protective layer.

5. **Conclusion**:
- Therefore, the external protective tissues of dicot stems are primarily the epidermis and cork (also known as phellem).

### Final Answer:
The external protective tissues of dicot stems are the **epidermis and cork**.

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