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B3.1.8—Leaf tissue distribution

Dicot leaf tissues are arranged so light capture, gas diffusion, water supply and sugar transport occur in coordinated epidermal, mesophyll and vascular layers.

Syllabus
First assessment 2025
Objective
B3.1.8
Level
SL

Exam analysis

Chance of appearing1%of analysed past papers
Latest appearanceNovember 2025
Most common paperPaper1A
Typical marks1

Common command terms

  • Draw
  • Explain

Scoring notes

Common mistake
Drawing individual cell detail when a plan diagram should show tissue distribution and relative positions.

Recent exam appearances

November 2025Paper1A ["SL"] · TZ114[ 1 ]B3.1.8—Leaf tissue distribution
May 2025Paper1A ["SL"] · TZ315[ 1 ]B3.1.8—Leaf tissue distribution

Coverage 2025–2025 · Updated 15 Jul 2026

Leaf Layers Coordinate Light, Gas and Transport

Leaf tissue distribution places palisade cells near light, spongy mesophyll beside interconnected air spaces, stomata in epidermis and vascular bundles within diffusion range of cells.

Clean labelled dicot leaf cross-section with cuticle, epidermis, palisade mesophyll, spongy mesophyll air spaces, stomata, xylem, and phloem, optimized for mobile reading.

upper epidermis/cuticle → light entry + water conservation
palisade → chloroplast-rich light capture
spongy mesophyll → moist exchange area + air spaces
xylem/phloem → water supply + assimilate export

SL Summary: One Diffusion Model

Feature Lung Leaf
area many alveoli broad blade + mesophyll walls
path thin barrier thin leaf + air spaces
gradient air + blood flow CO₂ use + stomata

Spirometry measures ventilation; a potometer estimates water uptake; a leaf cast measures stomatal density. Match each method to its direct measurement.

Leaf tissue distribution

[ 8 ]

Explain how the distribution of tissues in the leaf of a dicotyledonous plant is adapted to production and distribution of products of photosynthesis.

Drawing canvas

Concept essentials

  • Palisade mesophyll lies near the upper leaf surface and is rich in chloroplasts.
  • Spongy mesophyll contains air spaces for internal gas diffusion.
  • Xylem supplies water to leaf tissues, while phloem transports photosynthetic products.
  • A plan diagram shows tissue distribution and labels, not detailed organelles.