Plant Diseases and Defences

  • Created by: India.02
  • Created on: 06-05-19 18:29
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  • Plant Diseases and Defences
    • Defences
      • Physical
        • Plant leaves and stems have a axe cuticle - provides a barrier to stop pathogens from entering
        • Plant cells are surrounded by cell walls that are made of cellulose - physical barrier to stop pathogens that make it past the waxy cuticle
        • Layers of dead cells around their stems - bark on tress - stops pathogens from entering
      • Chemical
        • Antibacterial chemicals that kill bacteria - witch hazel from the mint plant
        • Other plants produce poisons - deter herbivores - tobacco plants, foxgloves, deadly nightshade
      • Mechanical
        • Thorns and hairs stop animals from touching and eating them
        • Other plants have leaves that droop or curl when touched - prevent themselves from being eaten by knocking insects off and moving away from things
        • Some plants mimic other organisms - several species of plant in the 'ice plant family' (southern Africa) look like stones and pebbles - tricks other organisms into not eating them
    • Diseases
      • Identified by...
        • Looking up the signs in a gardening manual or on a website
        • Taking infected plant to a lab - scientists can identify the pathogen
        • Testing kits that identify the pathogen using MA
        • Pest infestations can be seen on the plants
      • Signs and Symptoms
        • Stunted growth - spots on leaves - patches of decay - abnormal growths - malformed stems or leaves - discolouration
      • Plants can be infected by viral, bacterial and fungal pathogens - can also be infested and damaged by insects and pests - e.g. aphids
    • Mineral Ions from the Soil
      • Nitrates are needed to make proteins and for growth - lack of nitrates causes stunted growth
      • Magnesium ions needed for making chlorophyll - needed for photo-synthesis - lack of magnesium causes yellow leaves and chlorosis


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