Transport in Plants

Xylem

Xylem transports water and minerals from roots to leaves. Composed of tracheids, vessels, xylem parenchyma, and fibers.

Phloem

Phloem transports manufactured food (glucose) from leaves to other parts. Composed of sieve tubes, companion cells, phloem parenchyma, and fibers.

Mechanism of Water Transport

• Transpiration pull: Water evaporates from leaf surfaces, creating a suction force.
• Cohesion-tension: Water molecules stick together, forming a continuous column.
• Capillarity: Narrow xylem vessels assist water rise.

Mineral Uptake

• Minerals absorbed by root hairs through active transport.
• Minerals transported via xylem to leaves and other plant parts.

Adaptations

• Xylem vessels are hollow and lignified for easy water transport.
• Phloem has companion cells to assist sieve tubes.
• Transpiration creates continuous pull of water.
• Root hairs increase surface area for absorption.

Practice Questions

• Describe the structure and function of xylem and phloem. (6 marks)
• Explain the transpiration pull and cohesion-tension theory. (5 marks)
• How are minerals absorbed by roots and transported in plants? (4 marks)
• List four adaptations of xylem and phloem for efficient transport. (4 marks)
• Short answer: What is the role of companion cells in phloem? (1 mark)