Which substance strengthens and waterproofs xylem vessels?
Reveal answer
Lignin.
Key words: lignin
3(h) TRANSPORT · RECALL
3.4 Xylem
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Why is xylem good at carrying water?
Reveal answer
Dead, hollow, no end walls → continuous tube → water column flows freely.
Key words: hollow · end walls
What does xylem carry?
Reveal answer
Water and mineral ions, from roots to leaves.
Key words: water · mineral ions
What is meant by the term xylem?
Reveal answer
Vascular tissue transporting water and mineral ions and providing support.
Key words: xylem
What is meant by the term lignin?
Reveal answer
Waterproof strengthening material deposited in xylem walls.
Key words: lignin
What is meant by the term cohesion?
Reveal answer
Attraction between water molecules.
Key words: cohesion
What is meant by the term transpiration pull?
Reveal answer
Tension generated by evaporation that draws water through xylem.
Key words: transpiration pull
Xylem and phloem: for Main contents, give the xylem and the phloem.
Reveal answer
Xylem: Water and mineral ions. Phloem: Sucrose and amino acids.
Key words: Main contents
Xylem and phloem: for Direction, give the xylem and the phloem.
Reveal answer
Xylem: Mainly root to shoot. Phloem: Source to sink, either direction.
Key words: Direction
Xylem and phloem: for Conducting cells, give the xylem and the phloem.
Reveal answer
Xylem: Dead, hollow vessels. Phloem: Living sieve tubes.
Key words: Conducting cells
Xylem and phloem: for Wall/support, give the xylem and the phloem.
Reveal answer
Xylem: Lignified and supportive. Phloem: Not heavily lignified.
Key words: Wall/support
Xylem and phloem: for Driving process, give the xylem and the phloem.
Reveal answer
Xylem: Transpiration tension/pressure differences. Phloem: Source–sink pressure flow.
Key words: Driving process
True or false, and why? “Xylem pumps water using living cells.”
Reveal answer
False. Mature vessels are dead; evaporation-driven tension moves the water column.
True or false, and why? “Mineral ions travel in phloem only.”
Reveal answer
False. Dissolved mineral ions absorbed by roots travel mainly in xylem.
True or false, and why? “Water rises because it is lighter than air.”
Reveal answer
False. Pressure/tension gradients and cohesive water columns drive movement.