Plant Defence systems

• Plant defense systems


  • Physical responses
  • Chemical responses
  • Mechanical responses
• Physical responses


  • Cellulose cell wall difficult for microorganisms to penetrate
  • Waxy cuticle on leaves difficult for microorganisms to penetrate
  • Layers of dead cells (bark) around stems as a barrier to entry for microorganisms
• Chemical responses


  • Release of antibacterial chemicals to kill bacteria
  • Release of poisons to deter herbivores
• Mechanical defense system


  • Thorns or hairs to directly protect plants from herbivores
  • Leaves that droop or curl when touched, to scare herbivores
  • Mimicry - plants that look similar to stinging nettles to deter herbivores
• Plants can be attacked by microorganisms such as viruses and fungi (e.g. tobacco mosaic virus, rose black spot), and by insects and herbivores
• Plants have three main defense systems against attack: physical responses, chemical responses, and mechanical responses