How are sieve tubes different from sieve cells?
A. Being shorter
B. Being dead
C. Lacking Nuclei
D. Having sieve pores at end walls

Hint: Sieve tube elements are specialised cells that are important for the functioning of phloem as they take part in transportation of organic compounds prepared by the plant during photosynthesis. Sieve tube elements are the major conducting elements of the phloem.

Complete Answer:
Now, let us analyze each option to find the correct answer.
- Option A: Sieve tubes and Sieve cells both are elongated specialized cells that play a major part in the functioning of phloem. They are not short. So, option A is incorrect.
- Option B: Both sieve tubes and sieve cells are living cells that are specialized in food transport in plants. So, option B is incorrect.
- Option C: Both sieve tubes and sieve cells lack nucleus, they are elongated specialized cells that are the major conducting elements of the phloem. So, option C is incorrect.
- Option D: Sieve cells consist of sieve pores at end walls that are important for transport in many seedless vascular plants and gymnosperms. Sieve pores are absent in sieve tubes. So, option D is correct.

So, the correct option is option D) Having sieve pores at end walls.

Note: Sieve cells in gymnosperms lack of companion cells. Their narrow pores at the end walls are responsible for the transport. Gymnosperms lack sieve tube members and only have sieve cells to transport molecules to different parts of the plants.