Internal Structures of a Leaf

• Internal features of the leaf

  • cuticle
  • upper epidermis
  • mesophyll (palisade mesophyll and spongy mesophyll)
  • lower epidermis
  • cuticle
  • stomatal pore (stoma)
  • guard cell

  
• upper epidermis


  • the leaf blade has an upper epidermis made up of a single layer of closely packed cells
  • covered in a waxy and transparent cuticle

  
• Mesophyll


  • lies between the upper epidermis and lower epidermis
  • main site of photosynthesis
  • consists of palisade mesophyll and spongy mesophyll

  
• Palisade Mesophyll


  • consists of one or two layers of closely packed, long and cylindrical cells
  • contains numerous chloroplasts
  • specialised for photosynthesis

  
• Spongy Mesophyll


  • contains cells with an irregular shape
  • has numerous large intercellular air spaces among loosely packed cells
  • carries out photosynthesis but contains fewer chloroplasts than palisade mesophyll
  • cells are covered with a thin film of moisture
  • contains transport tissues, the xylem and phloem, which are grouped together to form a vascular bundle

  
• Lower epidermis


  • beneath the mesophyll
  • consists of a single layer of closely packed cells
• Cuticle


  • covers cells of the leaf blade
  • reduces water loss through epidermal cells
  • transparent to allow light to enter the leaf

  
• Stomatal Pore (stoma)



  • the lower epidermis contains many minute openings called stomata (singular : stoma)

  
• Guard Cell


  • guard cells are found in the lower epidermis
  • a pair of guard cells surround each stoma
  • helps to regulate the rate of transpiration and the passage of gases into and out of the leaf by opening and closing the stoma
  • contain chlorophyll which are not present in other epidermal cells