All of the following are true about phloem except

Options

A. A nucleus is absent in the young sieve tube members
B. The central part of sieve tube member is occupied by a network of canals containing fibrils of p-protein.
C. Sieve tubers are absent in gymnospems
D. Phloem is also called bast.

Answer

To solve the question "All of the following are true about phloem except," we need to evaluate each option provided and identify the incorrect statement regarding phloem.

### Step-by-Step Solution:

1. **Understand the Structure of Phloem:**
- Phloem is a type of vascular tissue responsible for the transport of nutrients, particularly sugars produced by photosynthesis.

2. **Evaluate Option A:**
- **Statement:** A nucleus is absent in the young sieve tube members.
- **Analysis:** This statement is incorrect because young sieve tube members do have a nucleus. It is only in mature sieve tube members that the nucleus is absent.
- **Conclusion:** This statement is false.

3. **Evaluate Option B:**
- **Statement:** The central part of sieve tube member is occupied by a network of canals containing fibrils of P protein.
- **Analysis:** This statement is correct. Sieve tube members contain P protein, which plays a role in the functioning of the phloem.
- **Conclusion:** This statement is true.

4. **Evaluate Option C:**
- **Statement:** Sieve tubes are absent in gymnosperms.
- **Analysis:** This statement is correct. Gymnosperms have sieve cells instead of sieve tubes.
- **Conclusion:** This statement is true.

5. **Evaluate Option D:**
- **Statement:** Phloem is also called blast.
- **Analysis:** This statement is correct. Phloem is sometimes referred to as "blast" in certain contexts.
- **Conclusion:** This statement is true.

6. **Identify the Incorrect Statement:**
- After evaluating all options, we find that Option A is the only incorrect statement regarding phloem.

### Final Answer:
The correct answer is **Option A: A nucleus is absent in the young sieve tube members.**

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