Mass Transport Plants

Question 1

Structure of xylem

Answer 1

• narrow, hollow vessels
• cell walls thickened with bands of lignin (strengthens + waterproofs)
• pits in lignified walls allow lateral movement of water
• end cell walls break down making a continuos water column

Question 2

How is xylem adapted for its function

Answer 2

• lignin - waterproof(prevents water loss), gives rigidity (prevent collapse), adhesion of water mols to side of tubes
• narrow - Inc capillary action

Question 3

Describe transpiration

Answer 3

1. Mass flow of water in xylem vessels (water moves up from roots where hydrostatic pressure due to active loading of mineral ions)
2. Osmosis of water through cells from xylem
3. Water vapour diffuses through leaf airspaces
4. Vapour diffuse through stomata
5. Capillary action (water mols attracted to xylem walls)

Question 4

Cohesion tension theory