Unit Overview
Transport in Plants
CIE IGCSE BiologyΒ· 5 min read π 8-10% of Paper 1/2 MCQ, 12-15% of structured questions in Paper 3/4
1. Unit at a Glance
The unit opens with a comparison of the two key vascular tissues in plants: xylem and phloem. It then explores how water and minerals move from root hair cells, through the root cortex, up the xylem to the leaves, and is lost as water vapor via transpiration, including practical skills for measuring transpiration rates with a potometer.
Core candidates complete their learning for this unit after mastering transpiration, while extended candidates proceed to study translocation: the active, bidirectional transport of dissolved sugars and amino acids around the plant body via phloem tissue.
Navigate to the sub-topics below to begin your learning:
Xylem, Phloem, Water Uptake and Transpiration
Covers vascular tissue structure, root hair cell adaptations, transpiration mechanism, factors affecting transpiration rate, and potometer practical skills for core and extended candidates.
β β β β± 12 min
Translocation (Extended Only)
Extended-only content covering the active mechanism of translocation in phloem, including sources and sinks of organic solutes in the plant.
β β β β β± 8 min
2. Common Pitfalls
Wrong move:
Confusing xylem and phloem transport direction and substance types
Why:
Both are vascular tissues but have opposite transport directions and carry different materials, a very common MCQ mistake
Correct move:
Remember: xylem carries water/minerals up only; phloem carries sugars up and down the plant
Wrong move:
Assuming transpiration is an active, energy-requiring process
Why:
Many students mix up passive transpiration flow with active translocation
Correct move:
Transpiration is a passive process driven by evaporation of water from leaf surfaces: no ATP is required
Wrong move:
Using transpiration and translocation interchangeably in responses
Why:
The terms sound similar and both relate to plant transport, leading to lost marks in structured questions
Correct move:
Label clearly: transpiration = water movement via xylem; translocation = sugar movement via phloem (extended only)
3. Quick Reference Cheatsheet
Concept | Key Detail | Associated Tissue |
|---|---|---|
Xylem function | Transport water + dissolved mineral ions from roots to shoots, provide structural support | Xylem |
Phloem function | Transport dissolved sucrose and amino acids to all parts of the plant | Phloem |
Transpiration definition | Loss of water vapor from plant leaves via evaporation and diffusion out of stomata | Xylem |
Transpiration rate drivers | Increased by high temperature, wind, light intensity; decreased by high humidity | Xylem |
Translocation (Extended) | Active movement of organic solutes from sources (e.g. leaves) to sinks (e.g. roots, fruits) | Phloem |
Root hair adaptation | Large surface area to maximise osmosis of water and active transport of minerals | Root epidermis |
What's Next
Start your study of plant transport with the first core sub-topic: Xylem, Phloem, Water Uptake and Transpiration, which covers all assessment content for core candidates, and foundational content for extended candidates. If you are sitting the extended exam, move on to the Translocation sub-topic once you have mastered the core content. After completing this unit, you will progress to the next unit on transport in humans.