The correct option is (b).
Explanation
Phloem is a complex permanent tissue in vascular plants responsible for the translocation of organic nutrients (food). The main conducting elements of phloem are the sieve tube elements, which function in association with companion cells.- Statement 1 is Incorrect. Sieve tube elements are long, tube-like structures arranged longitudinally. Their walls are generally thin and cellulosic, not thick. Crucially, their end walls are perforated in a sieve-like manner to form sieve plates. These perforations allow for the flow of materials between cells.
- Statement 2 is Correct. Sieve tube elements are living cells at maturity. Although a mature sieve element possesses a peripheral cytoplasm and a large vacuole, it lacks a nucleus. The metabolic functions of the sieve tube are maintained and controlled by the nucleus of the adjacent companion cell.
- Statement 3 is Incorrect. Phloem is responsible for the transport of food materials (primarily sucrose) from leaves to other parts of the plant. The transport of water and minerals is the function of the Xylem tissue.
Key Takeaway: Sieve tubes are living, enucleated cells found in phloem that possess perforated end walls (sieve plates) and are responsible for the translocation of food, not water.