Xylem and Phloem

• Functions of xylem tissue in a plant

  • Vascular Tissue that carries dissolved minerals and water up the plant
  • Structural support
  • Food storage
• Xylem tissue


  Found, along with phloem tissue and other tissues, in vascular bundles
• Location of vascular bundles in roots

  Vascular bundle is found in the center and the center core of this is xylem tissue. This helps the roots withstand the pulling strains they are subjected to as the plant transports water upwards and grows
• Location of vascular bundles in stems


  Vascular bundles are located around the outside and the xylem tissue is found on the inside (close to the centre of the stem to help support the plant
• Location of vascular bundles in leaves

  Vascular bundles form the midrib and veins and therefore spread from the centre of the leaf in a parallel line. The xylem tissue is found on the upper side of the bundles (close to the upper epidermis)
• Phloem tissue


  Transports organic compounds, particularly sucrose, from the source (eg. leaf) to the sink (eg. roots). The transport of these compounds can occur up and down the plant
• Phloem tissue


  • Complex tissue made up of various cell types; its bulk is made up of sieve tube elements which are the main conducting cells and the companion cells
  • Other cell types include parenchyma for storage and strengthening fibers
• Location of phloem tissue in roots

  Phloem tissue is found on the edges of the centre core
• Location of phloem tissue in stems

  Phloem tissue is found on the outside (close to the epidermis)
• Location of phloem tissue in leaves

  Phloem tissue is found on the lower side of the vascular bundles (close to the lower epidermis)
• Xylem vessel elements


  • Tracheids (long, narrow tapered cells with pits)
  • Vessel elements (large with thickened cell walls and no end plates when mature)
  • Xylem parenchyma
  • Sclerenchyma cells (fibres and sclereids)
• Xylem tissue


  Most of the xylem tissue is made up of tracheids and vessel elements, which are both types of water conducting cells
• Phloem sieve tube elements

  • Sieve tube elements line up end to end to form a continuous tube
• Companion cells


  • Each sieve tube element has a companion cell associated with it as companion cells control the metabolism of their associated sieve tube member
  • They also play a role in loading and unloading of sugars into the phloem
• Sieve tube elements


  • Allows for the continuous movement of the organic compounds
  • Strengthens the wall to withstand the hydrostatic pressure
  • Maximises the space for the translocation of the assimilates
  • Reduces friction to facilitate the movement of the assimilates