Xylem & Phloem (Cambridge (CIE) IGCSE Biology)

Transport in plants

What is the function of the xylem and phloem

• Plants contain two types of transport vessel:

  • Xylem vessels – transport water and minerals (pronounced: zi-lem) from the roots to the stem and leaves

  • Phloem vessels – transport food materials (mainly sucrose and amino acids) made by the plant from photosynthesising leaves to non-photosynthesising regions in the roots and stem (pronounced: flow-em)

• These vessels are arranged throughout the root, stem and leaves in groups called vascular bundles

Xylem and phloem diagram

Vascular tissue in a dicotyledonous plant

Xylem function

• Function: transport tissue for water and dissolved mineral ions

• Adaptations:

  • Cells joined end to end with no cross walls to form a long continuous tube

  • Cells are essentially dead, without cell contents, to allow free passage of water

  • Outer walls are thickened with a substance called lignin, strengthening the tubes, which helps support the plant

Xylem diagram

Xylem cells lose their top and bottom walls to form a continuous tube through which water moves through from the roots to the leaves