Xylem: The Water Transport System
Part of Plant Transport Systems — GCSE Biology
This deep dive covers Xylem: The Water Transport System within Plant Transport Systems for GCSE Biology. Xylem and phloem structure, water and sugar transport, root hair adaptations, translocation, and practical investigations It is section 3 of 17 in this topic. Use this deep dive to connect the idea to the wider topic before moving on to questions and flashcards.
Topic position
Section 3 of 17
Practice
19 questions
Recall
24 flashcards
Xylem: The Water Transport System
Structure of Xylem Tissue
Xylem tissue is made up of specialized cells called xylem vessels or tracheids. These have several key features:
- Hollow tubes: Xylem cells die and lose their cytoplasm, creating continuous hollow tubes for water flow
- Lignin reinforcement: Cell walls contain lignin, a strong polymer that prevents collapse under negative pressure
- No end walls: Adjacent xylem cells have their end walls broken down to form continuous vessels
- Pits and perforations: Allow water to move between vessels if one becomes blocked
How Water Moves Through Xylem
Water transport in xylem relies on the transpiration-cohesion-tension theory:
- Transpiration: Water evaporates from leaf surfaces through stomata
- Tension creation: This evaporation creates negative pressure (suction) in the xylem
- Cohesion: Water molecules stick together due to hydrogen bonding
- Adhesion: Water molecules also stick to xylem walls
- Mass flow: The entire water column is pulled up through the plant
This system can pull water up trees over 100 meters tall - imagine drinking through a straw that long!