Plant Disease

• Plant diseases can be detected by

  • Stunted growth
  • Spots on leaves
  • Areas of decay (rot)
  • Growths
  • Malformed stems or leaves
  • Discolouration
  • The presence of pests.
• Identification of plant diseases can be made by

  • Reference to a gardening manual or website
  • Taking infected plants to a laboratory to identify the pathogen
  • Using testing kits that contain monoclonal antibodies
• Plants can be infected by a range of viral, bacterial and fungal pathogens as well as by insects
• A nitrate deficiency in a plant can cause stunted growth because nitrate ions are needed for protein synthesis and therefore growth
• A magnesium deficiency in a plant leads to chlorosis (yellow leaves) as magnesium is needed to make chlorophyll which is needed for photosynthesis
• Physical defence responses to resist invasion of microorganisms and act as a barrier

  • Cellulose cell walls
  • Tough waxy cuticle on leaves
  • Layers of dead cells around stems (bark on trees) which fall off
• Chemical plant defence responses

  • Antibacterial chemicals to kill bacteria
  • Poisons to deter herbivores
• Mechanical adaptations

  • Thorns and hairs deter animals
  • Leaves which droop or curl when touched
  • Mimicry to trick animals