Plant Diseases and Defences

• Plants need minerals from soil. if there is not enough plants suffer from deficiency problems:

  • Nitrates are needed to make proteins for growth. a lack causes stunted growth
  • Magnesium ions are needed for making chlorophyll , which is needed for photosynthesis. plants with a lack suffer from chlorosis and have yellow leaves.
• When plants have a disease, common signs are:

  • Stunted growth
  • abnormal growth
  • spots on the leaves
  • malformed leaves or stems
  • patches of decay
  • discolouration
• When plants have a disease they can be identified by:

  • looking up symptoms in a gardening manual or website
  • Taking them to a laboratory to identify the pathogen
  • Using testing kits to identify the pathogen using monoclonal antibodies
• Physical defences:

  • Most plant have a waxy cuticle to provide a barrier between it and pathogens
  • Cell walls made of cellulose create a physical barrier against pathogens that make it past the waxy cuticle
  • Plants have layers of dead cells around their cells as a barrier
• Chemical defences:

  • plants produce antibacterial chemicals which kill bacteria
  • other plants have poisons to deter herbivores
• mechanical defences:

  • some plants have thorns and hairs to stop animals touching and eating them
  • some plant leaves droop and curl so insects get knocked off
  • some plants mimic other organisms