Structures and functions of gas exchange in plants

• Waxy cuticle


  • Thin layer atop the epidermis
  • Forms layers on the upper and lower surfaces of the leaf
  • Prevents water from getting out and stops unwanted substances/organisms from getting in
• Upper epidermis


  • Single layer of cells on the upper surface of the leaf
  • Aids water conservation
  • Few stomata and less number of chloroplast since it has less number of guard cells
• Lower epidermis


  • Single layer of cells on the lower surface of the leaf
  • Large number of stomata and guard cells
• Palisade mesophyll


  • Composed of closely packed photosynthetic cells
• Spongy mesophyll


  • Composed of spherical and loosely packed photosynthetic cells
  • Air spaces between these cells allow for gas exchange
• Stomata


  • Sites of gaseous exchange in the leaf
  • Regulate water loss (transpiration)
• Guard cells


  • Regulate the opening and closing of stomata
• Vascular bundle


  • Contains the xylem (transports water and minerals to the leaf) and phloem (in charge of the transport and distribution of the organic nutrients)
• Chloroplast


  • Organelle found only in plant cells
  • Allows the plant to go through photosynthesis