gas exchange in leaves and water loss

• gases are exchanged with the mesophyll layer of the leaf
• leaves are thin to reduce the diffusion distance
• waxy cuticle:

  • waxy layer at the top of the leaf
  • reduce water loss
• upper epidermis:

  • transparent layer at the top of the leaf
  • helps prevent water loss
  • transparent so sunlight can pass through
• palisade mesophyll:

  • layer of long cylindrical cells where most photosynthesis happens
  • contain chloroplasts
• spongy mesophyll:

  • layer of cells with air-spaces between them
  • Gas exchange happens here
• xylem:

  • transports water and mineral ions
  • made of dead cells
  • lignin strengthens the cells
• phloem:

  • transports dissolved sugars in the plant
• lower epidermis:

  • thin underside layer of cells where stomata are found
• transpiration is the loss of water from the plant, stomata can control how much water leaves.
• when plants have enough water guard cells are turgid which keeps pores open
• when plants are dehydrated the guard cells become flaccid causing the pores to close
• potassium ions move into the guard cell to decrease water concentration, water will then move into the cell due to osmosis