A common structural feature of vessel elements and sieve tube elements is
(a) Enucleate condition
(b) Presence of p-protein
(c) Thick secondary wall
(d) Pores on lateral walls

Options

A. Enucleate condition
B. Presence of p-protein
C. Thick cecondary wall
D. Pores on lateral walls

Answer

To solve the question regarding the common structural feature of vessel elements and sieve tube elements, we will analyze each of the provided options step by step.

### Step-by-Step Solution:

1. **Understanding Vessel Elements and Sieve Tube Elements**:
- Vessel elements are part of the xylem and are responsible for water conduction. They are typically dead at maturity and lack a nucleus.
- Sieve tube elements are part of the phloem and are involved in the transport of nutrients. They also lack a nucleus at maturity.

2. **Analyzing Option (a): Enucleate condition**:
- The term "enucleate" refers to cells that do not have a nucleus. Both vessel elements and sieve tube elements are indeed enucleate at maturity. Therefore, this option is true.

3. **Analyzing Option (b): Presence of p-protein**:
- P-proteins are specific to sieve tube elements and are involved in the function of phloem transport. They are not found in vessel elements. Thus, this option is incorrect.

4. **Analyzing Option (c): Thick secondary wall**:
- Vessel elements have thick secondary walls that provide structural support and help in water conduction. However, sieve tube elements do not have thick secondary walls; they have thinner walls. Therefore, this option is also incorrect.

5. **Analyzing Option (d): Pores on lateral walls**:
- Vessel elements have perforation plates with pores that facilitate water movement. Sieve tube elements have sieve plates with pores, but these are not the same as the pores found in vessel elements. Thus, this option is incorrect as well.

6. **Conclusion**:
- The only common structural feature between vessel elements and sieve tube elements is the enucleate condition. Therefore, the correct answer is (a) Enucleate condition.

### Final Answer:
The common structural feature of vessel elements and sieve tube elements is (a) Enucleate condition.