Which one is correct

Options

A. (a) Uneven thickening of cell wall is characteristic of sclerenchyma
B. (b) Periblem forms cortex of stem and root
C. (c) Tracheids are chief water conducting elements in gymnosperms
D. (d) Companion cell is devoid of nucleus at maturity

Answer

To solve the question "Which one is correct?", we need to evaluate the given statements related to plant anatomy and determine which ones are accurate.

### Step-by-Step Solution:

1. **Evaluate Statement A**: "Uneven thickening of cell wall is characteristic of sclerenchyma."
- Sclerenchyma is a type of supportive tissue in plants. It is characterized by having thickened cell walls, which can be uneven. This statement is correct.

2. **Evaluate Statement B**: "Periblem forms cortex of stem."
- According to histogen theory, the periblem is indeed the middle layer that gives rise to the cortex in stems. This statement is also correct.

3. **Evaluate Statement C**: "Tracheids are the chief water conducting element in gymnosperms."
- Tracheids are indeed the primary water-conducting cells in gymnosperms. This statement is correct as well.

4. **Evaluate Statement D**: "Companion cells devoid of nucleus at maturity."
- This statement is incorrect. Companion cells are living cells that retain their nucleus at maturity. It is the sieve tube elements that lack a nucleus at maturity.

### Conclusion:
- Statements A, B, and C are correct.
- Statement D is incorrect.

Thus, the correct statements are A, B, and C.

### Final Answer:
The correct options are A, B, and C.

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