plant defences

• physical defences

  • waxy cuticle
  • bark on trees
  • cellulose cell walls
  • closed stomata
  • hypersensitivity= cell death
  • production of callose= deposited between cell wall and membrane in cell next to infected cell to act as a barrier preventing pathogens entering.
• chemical defences

  • resin= sticky to trap pathogens
  • phenols= antimicrobial
  • cyanide = toxic
  • tannins= enzyme inhibitor
  • citronella= insect repellent
  • chitinases+ glucanases= enzymes that break down cell wall in fungal pathogens.
• plant defences:

  • some molecules from pathogen recognised directly by receptors in cell membrane.
  • when pathogenic enzymes break down cell wall the breakdown products are recognised.
  • signal molecules alert the nucleus to attack
  • defence chemicals give alarm to other cells before they are attacked.