xylem

• What are the functions of xylem tissue in a plant?

  
  

  • Vascular tissue that transports dissolved minerals and water around the plant
  • Structural support
  • Food storage
• Xylem tissue is made up of four cell types that function together, what are they?

  1. Tracheids (long, narrow tapered cells with pits)
  2. Vessel elements (large with thickened cell walls and no end plates when mature)
  3. Xylem parenchyma
  4. Sclerenchyma cells (fibres and sclereids) Most of the xylem tissue is made up of tracheids and vessel elements, which are both types of water-conducting cell
• What is the function of the lignified cell walls?

  to add extra strength to withstand the hydrostatic pressure so the vessels do not collapse

  impermeable to water - waterproofing

  improves adhesion of water molecules

  allows flexibility

  reduces loss of water
• Why do xylems have no end plates?

  allows the mass flow of water and dissolved solutes
• Why does the xylem have pits in the wall (non-lignified sections)?

  allows for the lateral movement of water

  allows for continual flow in case of air-bubbles forming in the vessels
• features of the xylem that enable water to pass?

  no cross walls thus continuous flow/ cells joined end to end

  hollow / no contents/ no cytoplasm

  bordered pits in wall
• How is the structure of the xylem related to its function?

  it's made up of long continuous columns composed of dead tissue, allowing transportation of water

  contains pits in the walls, allowing for the lateral movement of water between vessels

  the walls are thickened by lignin, providing structural support, flexibility and prevents water loss & waterproofs
• Describe a procedure by which you could observe the position of xylem vessels in leaf stalks of celery?

  put the leaf stalks in a dye/food colouring

  then cut a thin a cross section

  then add a stain e.g methylene blue

  observe with light microscope under low power
• features in a xylem tissue?

  vessel wall (NOT cell wall)

  vessel lumen (NOT vacuole)

  bordered pit (NOT plasmodesmata)
• how does the structure of the xylem relate to its function?


  long, continuous columns made of dead tissue, allowing transportation of water

  contain pits, allowing lateral movement of water between vessels

  thickened with lignin, providing structural support
• how are xylem vessels adapted to their function?

  • xylem vessels are very long, tube-like structures formed from cells joined end to end with no end walls, thus making an uniterrupted tube that allows water to pass up easily through the middle
  • the cells are dead (so contain no cytoplasm)
  • their walls are thickened with ligning, which helps to support the xylem vessels and stops them from collapsing inwards
• how can lignin be deposited in xylem walls?

  in a spiral or as distinct rings
• as the cell gets older, what happens to the amount of lignin?

  the amount of lignin increases