What are the differences between the transport of materials in xylem and phloem?
The transport of materials in xylem and phloem differs in several ways:
Xylem transports water and minerals obtained from the soil. This transport occurs in upward direction only and can be largely explained by simple physical forces. The vessels and tracheids form a continuous system of water-conducting channels reaching all parts of the plant.
Phloem transports soluble products of photosynthesis (food), amino acids and other substances. This process, called translocation, occurs in both upward and downward directions. Unlike xylem, phloem transport is achieved by utilising energy from ATP. Material like sucrose is transferred into phloem using energy, which increases osmotic pressure and moves material according to the plant's needs.
Explanation
The textbook clearly distinguishes between xylem and phloem transport. Xylem moves water and minerals upward through physical forces, while phloem transports food (photosynthesis products) in both directions using energy. Key differences include: direction of transport (unidirectional vs bidirectional), substances transported (water/minerals vs food), and energy requirement (physical forces vs ATP utilization). Students should highlight these three main differences for full marks.