The stem of a plant functions to support and elevate the leaves, flowers and fruits (promoting photosynthesis and seed dispersal)

• Material is transported between the leaves and the roots via vascular bundles that traverse the length of the stem
  

Stems possess three main tissue layers that are organised to optimise the transport of water and nutrients between leaves and roots

• The epidermis covers the outer surface and functions to waterproof and protect the stem from damage
  

• The inner ground tissue (cortex and pith) assists in the storage of nutrients – it is also responsible for lateral growth
  

• In dicotyledons, the vascular tissue is arranged into concentric bundles around the outer edge of the stem
  

Stem Cross-Section

Stem Anatomy

The tissues in a stem are specifically distributed to support the weight of the plant and facilitate material transport

• Stems are normally divided into nodes that are capable of axillary growth (branching) and lateral growth (thickening)
  

• The epidermis in woody plants is eventually replaced by a secondary tissue (periderm) that forms bark
  

• The cells in the cortex typically have large, central vacuoles that allow the stem to store nutrients and regulate material transport
  

• The vascular bundles form a concentric ring near the outer edge of the stem to resist stem compression and bending 
  

  • The xylem is located to the interior side of the bundle and the phloem is on the exterior side (phloem = outside)
    

Stem Tissue Distribution