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Leaves and photosynthesis

Inside the leaf

You should be able to name and locate these parts of a leaf:

  • Cuticle
  • Upper and lower epidermis
  • Palisade and spongy mesophyll layers
  • Stomata and guard cells
  • Vascular bundle

The diagram shows a labelled cross-section through a leaf.

Shows the waxy cuticle on top of the upper epidermis.Under this is the palisade mesophyll layer and spongy mesophyll layer, which has air spaces in it. At the bottom, is the lower epidermis and wax cuticle. Gases are exchanged through the stoma. On each side of the stoma there is a guard cell with chloroplasts.

Inside the leaf - Higher tier

You should be able to explain how the cellular structure of a leaf is adapted for efficient photosynthesis. The table summarises some of these features.


Adaption of leafPurpose
Transparent epidermisAllows more light to reach the palisade cells
Palisade cell layer at top of the leaf and containing most of the chloroplastsTo absorb more light
Spongy layer with air spacesAllows carbon dioxide to diffuse from the stomata to the photosynthesising cells, and to provide a very large internal surface area to volume ratio

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