Leaves

Leaves

1. Photosynthesis

   • Leaves make their own food using substances and energy from the sun, we call this photosynthesis
   • Photosynthesis takes place in the leaves of the plant
   • The equation for photosynthesis
     • carbon dioxide + water --> glucose + oxygen

2. A section through a small part of a leaf

3. Parts of a leaf

   • Palisade cells
     • Most photosynthesis occurs here
     • Large rectangular cells
     • Near the upper surface of the leaf
   • Air space
     • Source of carbon dioxide for photosynthesis
   • Stomata
     • Holes in the leaf's epidermis
     • Allows air to enter and leave the leaf
   • Cuticle
     • Waterproof layer
   • Spongy cell
     • Large cells that photosynthesise
     • Air spaces between them
   • Vein
     • Carry water and sugar to and from the leaf
   • Guard cells
     • Open and close the stomata
   • Epidermis
     • Outer covering that protects the leaf

4. Properties

   • Broad and flat
     • So they can absorb lots of light
   • Thin
     • So carbon dioxide can reach the cells easily
   • Many veins
     • To carry things around the cells

5. Testing a leaf for starch

   • Place the leaf in boiling water for 1 minute using forceps
     • Place the leaf in a boiling tube with ethanol and place in a water bath at 65degrees
       • After 5 minutes take the leaf out of the water bath and place back in the water
         • Place the leaf in the petri dish/white tile and add a few drops of iodine solution
           • If starch is present the leaf will turn blue/black
   • Uses of glucose
     • Used in respiration to release energy
     • Converted to fats/oils to store energy
     • Converted to amino acid to make proteins by combining glucose with nitrates taken in by the roots from the soil
     • Stored as starch
     • Used to make cellulose to construct cell walls

6. The vascular system

   • This is made of two types of long tubes used to transport substances around the plant
   • These tubes are made of cells lined up end to end
   • Xylem
     • Xylem tubes carry water around the plant
   • Phloem
     • Phloem tubes carry sugar around the plant

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