AQA GCSE Biology

Revision Notes

3.3.1 Detection and Identification of Plant Diseases

Plant Pathogens

  • Plants can be infected with a range of bacterial and viral pathogens; such as the tobacco mosaic virus (TMV) and rose black spot fungus (see Viral Diseases & Fungal Diseases)
  • Plants can also be infested with insects such as aphids
    • Aphids have long sharp mouthpieces that pierce the surface of the stem and into the phloem so that they can feed on the sugar filled sap
    • They can infest a plant in large numbers and remove large quantities of the phloem sap. This can weaken the plant
    • Aphids can also act as a vector for the transfer of diseases
    • Biological pest control (using ladybirds, a natural predator of the aphid) to feed on them or using chemical pesticides are the best ways to control infestation with aphids
Higher Tier Only

Detecting Plant Diseases

  • Infections in plants as with all organisms are better when detected and treated quickly
  • Symptoms of diseases in plants include:

Plant diseases table

Detecting Plant Diseases table 1, downloadable IGCSE & GCSE Biology revision notes

Higher Tier Only

Identifying Plant Diseases

  • The symptoms of plant diseases can apply to more than one disease, which makes identifying them difficult
    • Diseases in the garden can be identified by comparing symptoms to those described in gardening manuals or online
    • Crop plants or forest trees, experts may visit the field/woodland to take samples which can then be taken to a lab to undergo DNA analysis. This would help to identify the specific pathogen causing the problem
    • Plant scientists, foresters, farmers and market gardeners can use testing kits which contain monoclonal antibodies to identify the presence of pathogens quickly and easily

Mineral Deficiencies

  • Plants like all organisms need the correct amount of nutrients to function properly
  • If plants are deficient in a mineral these can be replaced by fertilisers added to the soil
  • These fertilisers are often shown as NPK ratios depending on the need of the plant that is being grown

Mineral deficiencies table

Mineral Deficiencies table 2, downloadable IGCSE & GCSE Biology revision notes

Exam Tip

Exam questions about mineral deficiencies may ask you to recommend a fertilizer based on the symptoms that the plant has.

Author: Jenna

Jenna studied at Cardiff University before training to become a science teacher at the University of Bath specialising in Biology (although she loves teaching all three sciences at GCSE level!). Teaching is her passion, and with 10 years experience teaching across a wide range of specifications – from GCSE and A Level Biology in the UK to IGCSE and IB Biology internationally – she knows what is required to pass those Biology exams.

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