Gas exchange in the leaf of a plant

Waxy cuticle:

  • Transparent layer on top of the leaf
  • Waxy
  • Waterproof

Upper epidermis:

  • Single layer of flat cells covering the top surface of the leaf
  • no chloroplasts

Paliside cells:

  • Layer of long cylindrical cells just under the upper epidermis
  • Chloroplasts
  • Chlorophyll


  • Small structures within the cell where photosynthesis takes place

Spongy mesophyll:

  • Layer of cells with air-spaces between them


  • Contains the tissues that transport food and water
  • Xylem - carries water through the plant
  • Phloem - carries food through the plant

Lower epidermis:

  • Single layer of flat cells covering the bottom surface of the leaf

Guard cells:

  • Control the closing and opening of the stomatal pores


  • Pores on the underside of the leaf
  • Stomata = holes
  • Close at time where water loss would be excessive

Internal structure of a leaf:

  • The cuticle is a waxy layer on the surface that prevents water from evaporating from the leaf
  • Most photosynthesis occurs in the chloroplasts that are tightly packed inside the paliside cells
  • During photosynthesis, the gas C02 and water and combined together


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