Which of these terms have been paired correctly ?

Options

A. Bark-Periderm
B. Cork-Phellem
C. Cork cambium - phelloderm
D. Secondary cortex - phellogen

Answer

To determine which of the terms have been paired correctly, we need to analyze the terms related to plant growth and development, particularly focusing on the structures involved in secondary growth.

### Step-by-Step Solution:

1. **Understanding Plant Growth Types**:
- Plants undergo two types of growth: height increase (primary growth) and girth increase (secondary growth).

2. **Identifying Secondary Growth**:
- Secondary growth involves the formation of new tissues that contribute to the increase in girth. This process includes the formation of cork cambium.

3. **Cork Cambium**:
- Cork cambium, also known as phellogen, is a type of lateral meristem that produces cork (phellem) and secondary cortex (phelloderm).

4. **Layers Produced by Cork Cambium**:
- The cork cambium produces two layers:
- **Outer Layer**: Cork (Phellem)
- **Inner Layer**: Secondary Cortex (Phelloderm)

5. **Understanding Periderm**:
- The periderm is composed of the cork (phellem), cork cambium (phellogen), and secondary cortex (phelloderm).

6. **Evaluating the Given Options**:
- Now, we need to evaluate the pairs given in the question:
- **Bark - Periderm**: Incorrect. Bark refers to all tissues outside the vascular cambium, which includes the periderm but is not synonymous with it.
- **Cork - Phellem**: Correct. Cork is indeed the outer protective layer produced by the cork cambium.
- **Cork Cambium - Phelloderm**: Incorrect. Cork cambium is phellogen, not phelloderm.
- **Secondary Cortex - Phelloderm**: Incorrect. While phelloderm is a part of the secondary cortex, the term secondary cortex is broader.

7. **Conclusion**:
- The only correct pairing from the options provided is **Cork - Phellem**. Therefore, the correct answer is the second option.

### Final Answer:
The correct answer is **Option 2: Cork - Phellem**.