Plant defences

• 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


  • Plants release antibacterial chemicals to kill bacteria and prevent them attacking the plant
  • Plants release poisons to deter herbivores from grazing on the plant
• Mechanical defense system


  • Thorns or hairs that directly protect plants from being eaten by herbivores
  • Leaves that droop or curl when touched, which may scare herbivores
  • Mimicry, where a plant looks similar to a stinging nettle but has no sting, deterring herbivores
• Plants have three main defense systems against attack: physical responses, chemical responses, and mechanical defense system