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B3.2.7—Water transport in plants

Plant water transport depends on root uptake, xylem vessels, transpiration pull, cohesion, adhesion and lignified support against strong internal tension.

Syllabus
First assessment 2025
Objective
B3.2.7
Level
SL

Exam analysis

Chance of appearing1%of analysed past papers
Latest appearanceNovember 2025
Most common paperPaper2
Typical marks3–7

Common command terms

  • Identify
  • Describe
  • Explain
  • Predict

Scoring notes

Common mistake
Explaining water movement as active transport through xylem rather than passive tension-driven flow.

Recent exam appearances

November 2025Paper2 ["SL"] · TZ37(c)[ 7 ]B3.2.7—Water transport in plants
May 2025Paper2 ["SL"] · TZ25(b)[ 3 ]B3.2.7—Water transport in plants

Coverage 2025–2025 · Updated 15 Jul 2026

Transpiration Pulls One Cohesive Water Column

Transpiration creates tension—a negative pressure potential—that pulls a continuous water column from roots to leaves through xylem.

Water evaporating from moist mesophyll cell walls draws replacement water through the wall by capillary action and out of nearby xylem. This lowers pressure in the leaf xylem and transmits tension down the vessel.

SL Summary: Flow Structures

Route Structural solution
artery elastic-muscular wall for high pressure
capillary one-cell wall + many branches for exchange
vein wide lumen + valves for low-pressure return
xylem hollow lignified tube for tension

Water transport in plants

[ 8 ]

Explain the process of water uptake and transport by plants.

Concept essentials

  • Transpiration pull creates tension that draws water upward through xylem.
  • Cohesion from hydrogen bonding keeps xylem water columns continuous.
  • Adhesion helps water move through cell walls and xylem surfaces.
  • Lignified xylem walls resist collapse under negative pressure.
  • Root uptake begins with osmosis into root tissues or xylem.