plant disease and defence

• direct contact in plants = pieces of infected tissue can infect an entire crop
• what is tmv?

  tobacco mosaic virus is a widespread plant pathogen affecting many species of plants including tomatoes. it gives a distinctive mosaic pattern of discolouration on the leaves which affects the growth the plant due to lack of photosynthesis.
• what is rose black spot?

  • fungal
  • causes purple of black spots to develop on leaves , affecting photosynthesis
  • spread by spores
  • prevented by burning effected leaves and stems using chemical fungicides
  • resistant strains can be bred
• what is TMV?


  • viral
  • causes distinctive mosaic pattern of discolouration on leaves - affecting photosynthesis
  • spread via direct contact and vectors
  • no treatment
• what is mineral deficiency?

  • plants need mineral ions form the soil or they become mineral deficient
  • when not enough magnesium ions are present, plants have chlorosis
• how can plant disease be detected?

  • stunted growth
  • abnormal growth
  • spots on leaves
  • malformation
  • patches of decay
  • discolouration
• how to identify plant disease?

  • test kits with monoclonal antibodies
  • taking infected plant to a lab
  • reading a manual
• what are plant physical barriers?

  • cellulose wall
  • tough waxy cuticle on leaves - bark on trees
  • leaf fall allows for infected leaves to be discarded
• what are chemical barriers for plants?

  • antibacterial chemicals - in some plants
  • others produce poisons which can deter herbivores
• stunted growth is caused by nitrate ion deficiency as they are needed for protein synthesis
• mechanical plant defences


  • thorns to deter animals from eating them
  • leaves drop or curl to startle animals
  • some mimic other organisms
  • hairy stems