Transpiration and translocation

• Phloem tubes transport food:

  • made of columns of elongated living cells with small pores in the end walls to allow cell sal to flow through
  • transport food substances made in leaves to rest of plant
  • transport in both directions called translocation
• Xylem tubes take water up:

  • made of dead cells joined end to end with no end walls between them and a hole down the middle strengthened with lignin
  • they carry water and mineral ions from roots to the stem and leaves
  • movement of water from the roots through the xylem and out of the leaves is called transpiration stream
• Transpiration is the loss of water

  • caused by the evaporation and diffusion of water from plants surface
  • evaporation creates slight shortage of water in leaf so more water drawn up through xylem vessels
  • this means more water drawn from roots so there’s a constant transpiration stream of water through plant