Plant diseases and defences

• What happens if there aren’t enough mineral ions in the soil

  Plants suffer deficiency symptoms
• why do plants need nitrates

  to make protines
• what happens if plants don’t have enough nitrates

  proteins are needed for growth so a lack of nitrates causes stunted growth
• what do plants need magnesium ions for

  making chlorophyll
• what happens if plants don’t have enough magnesium ions

  they have chlorosis (yellow leaves) and can’t photosynthesise as well
• what are aphids

  an insect that infests and damages plants
• what are common signs of a plant disease

  -stunted growth

  -abnormal growth

  -spots on the leaves

  -malformed stems or leaves

  -patches of decay

  -discolouration
• how can plant diseases be identified

  -looking up signs in a gardening manual or website

  -taking the plant to a laboratory

  -using testing kits that identify the pathogen with monoclonal antibodies
• what are physical defences

  -waxy cuticle which provides a barrier to stop pathogens entering

  -plant cells have cell walls which form another physical barrier

  -layers of dead cells around the stems that acts as a barrier
• what are chemical defences

  -some plants produce antibacterial chemicals to kill bacterial e.g.mint and witch hazel

  -other plants produce poisons to stop herbivores eating them
• what are mechanical defences

  -thorns and hairs to stop animals touching/eating them
• What are other mechanical defences

  Leaves droop or curl when something ouches them ,they can knock insects off and move away from things

  some plants mimic other organisms