Leaf structure

• Leaf


  • Large surface area to absorb a lot of light
  • Top surface protected from water loss, disease and weather damage by a waxy layer
• Palisade cell


  • Adapted to absorb a lot of light
  • Has lots of chloroplasts
  • Shaped like a tall box
• Plants get carbon dioxide

  1. Moves by diffusion through small holes in the underside of the leaf called stomata

  2. Guard cells control the size of the stomata
• Spongy mesophyll

  • Loose-fitting cells
  • Lets carbon dioxide reach the other cells
  • Lets oxygen produced in photosynthesis leave the leaf easily
• Root cells do not contain chloroplasts as they are normally in the dark and cannot carry out photosynthesis
• Diagram of the root hair cell

  • Long and thin
  • Water is absorbed from the soil
• Parts of leaf structure

  • Stomata
  • Guard cells
  • Waxy cuticle
  • Epidermis
  • Palisade cells
  • Vascular bundle
  • Xylem
  • Phloem
  • Spongy mesophyll
  • Chloroplasts
• Leaf features that aid photosynthesis

  • Flat thin leaves
  • Stomata
  • Veins
  • Chloroplasts
  • Waxy cuticle layer
• Upper epidermis


  Top side of a leaf
• Lower epidermis


  Lower side of a leaf
• Stomata


  Tiny holes that allow gases into and out of the leaf
• Guard cells


  Cells that control the opening and closing of the stomata
• For every one stomata there are two guard cells
• Respiration


  Happens in the mitochondria
• Photosynthesis


  Happens in the chloroplasts
• Respiration


  Glucose + oxygen → carbon dioxide + water + energy
• Photosynthesis


  Water + carbon dioxide → glucose + oxygen
• Photosynthesis happens in the chloroplasts, which are organelles inside plant cells
• Most photosynthesis happens in the palisade mesophyll layer where light intensity is highest
• Carbon dioxide needed for photosynthesis enters via stomata on the lower epidermis
• Test to see how light intensity affects the rate of photosynthesis

  1. Take a length piece of pondweed

  2. Use a paperclip to hold the pondweed at the bottom of a boiling tube

  3. Cover the pondweed with sodium hydrogen carbonate solution

  4. Place the boiling tube in a boiling tube rack

  5. Set up a lamp at different distances from the pondweed

  6. Switch on the lamp and leave the apparatus for 2 minutes

  7. Count the number of gas bubbles observed in one minute
• label the parts of the leaf

  A) waxy cuticle

  B) upper epidermis

  C) palisade cells

  D) vascular bundle

  E) lower epidermis

  F) spongy mesophyll

  G) stomata