Question

A mature sieve tube differs from a vessel in

• A. lacking a functional nucleus.
• B. absence of lignified walls.
• C. being nearly dead.
• D. lacking cytoplasm.

Answer 1

Answer: (B)

The vessel is a long cylindrical tube-like structure made up of many cells called vessel members, each with lignified walls and a large central cavity. The vessel cells are also devoid of protoplasm. Vessel members are interconnected through perforations in their common walls. The presence of vessels is a characteristic feature of angiosperms.
Sieve tube elements are also long, tube-like structures, arranged longitudinally and are associated with the companion cells. Their end walls are perforated in a sieve-like manner to form the sieve plates. A mature sieve element possesses a peripheral cytoplasm and a large vacuole but lacks a nucleus.