structure

• waxy cuticle - waxy layer on top of the leaf
• upper epidermis - transparent layer on top of the leaf
• palisade mesophyll - layer of long cylindrical cells where most photosynthesis happens
• spongy mesophyll - layer of cells with air-spaces between them

  gas exchange occurs here
• xylem - transports water and mineral ions
• phloem - transports dissolved sugars in the plant
• lower epidermis - thin underside layer of cells where the stomata is found
• stomata - controls how much water enters/exits the plant
• stomata opening:

  • potassium ions are moved into guard cells by active transport, to increases concentration
  • this lowers water potential and is followed by an osmotic influx of water
  • this causes guard cells to become turgid and open
• how does CO2 get into the leaf?

  • CO2 moves into the leaf through diffusion into the stomata
  • when guard cells become turgid and open, CO2 diffuses down a concentration gradient into the stomata, and enters the layer of spongy mesophyll