This topic summary covers Knowledge Organiser 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 15 of 17 in this topic. Use this topic summary to connect the idea to the wider topic before moving on to questions and flashcards.
Topic position
Section 15 of 17
Practice
19 questions
Recall
24 flashcards
Knowledge Organiser
Key Terms
- Xylem — dead, hollow, lignified, water + minerals, one-way up
- Phloem — living, sieve plates, sugars + amino acids, two-way
- Translocation — sugar movement in phloem
- Transpiration — water loss through stomata
- Lignin — polymer strengthening xylem walls
- Companion cell — provides ATP to sieve tubes
- Root hair cell — large surface area for osmosis
- Cohesion — water molecules sticking together
- Tension — negative pressure in xylem from transpiration
Must-Know Facts
- Xylem cells die at maturity — lumen is hollow
- Xylem carries water AND mineral ions (not food)
- Phloem cells are living — maintain turgor and active loading
- Phloem carries sugars (as sucrose) and amino acids
- No pump needed for xylem — transpiration pull drives flow
- Active transport needed for phloem loading/unloading (ATP)
- Root hairs increase surface area by up to 1000x
- Lignin prevents xylem collapsing under tension
- Cohesion: hydrogen bonds between water molecules
Xylem vs Phloem — Quick Compare
- Dead vs Living
- Lignin walls vs Sieve plates
- Water + minerals vs Sugars + amino acids
- One-way up vs Two-way
- No energy needed vs ATP required
- Passive (osmosis/cohesion) vs Active loading
Required Practical Points
- Potometer measures water uptake (not transpiration directly)
- Cut shoot underwater — prevents air locks in xylem
- Rate = distance bubble moves / time
- Dye experiment proves water travels in xylem
- Phloroglucinol stain — xylem walls stain red