Plant diseases and defences

• 3 main causes of plant disease:

  • infection by microorganisms(fungi, bacteria or virus)
  • attack by insects
  • lack of essential minerals
• 6 symptoms of plant disease:

  • stunted growth
  • spots on leaves
  • areas of decay
  • growths
  • malformed stems
  • discolouration
• Plant disease can be identified by:

  • compare symptoms to a gardening manual
  • take infected plant to laboratory
  • use testing kits
  • test DNA of pathogens
  • use trial and error to test different treatments
• Nitrates->nitrogen->amino acids->proteins->growth
• Magnesium is required to produce chlorophyll, a lack of it could lead to chlorosis
• physical defences are defences that stop entry of pathogens
• 3 examples of physical defences:

  • cell walls
  • bark
  • waxy cuticle
• Chemical defences are chemicals that destroy pathogens
• examples of chemical defences:

  • antimicrobial substances
  • poisons that kill insects
• mechanical defences are structures that reduce the chance of being attacked
• examples of mechanical defences:

  • mimicking other organisms
  • leaves that curl or droop when insects land on them
  • hairs and thorns