Question

From evolutionary point of view, tracheids and sieve cells are more primitive than xylem vessels and sieve tubes respectively. The angiosperms will posses:

• A. Vessels and sieve tubes
• B. Tracheids, vessel and sieve tubes
• C. Tracheids, sieve cells and sieve tubes
• D. Tracheids, vessels and sieve cells

Answer 1

The correct option is B Tracheids, vessel and sieve tubes

• Angiosperms are considered more advanced plant group than gymnosperms. Sieve cells and tracheids are also primitive structures which are present in gymnosperms.
• Angiosperms on the other hand being more advanced, developed vessels while also retaining small percentage of tracheids.
• Development of vessels in angiosperms greatly increases the water conducting efficiency due to presence of perforations, wider lumen etc.
• Sieve cells present in gymnosperms also changed to more advanced and efficient form called sieve tubes in angiosperms.
• Sieve cells remain separate and scattered in gymnosperms which decreases their efficiency, whereas in sieve tubes several cells join end to end. They contain pores which increases their efficiency.