GCSE Biology · Edexcel 1BI0 · Topic 5B
Plant diseases and defences
Key points
- Plants can be infected by viruses, bacteria, fungi and insects; signs include stunted growth, spots, discoloured or rotting leaves, and visible pests.
- Physical defences: a waxy cuticle, cellulose cell walls and bark stop pathogens entering.
- Chemical defences: antimicrobial substances and poisons that deter herbivores. Some plant chemicals are used as medicines, e.g. aspirin came from willow and digitalis from foxgloves.
- Diagnosis: observe symptoms, look for pests, test in a lab, or use monoclonal antibody kits.
- Plants also need minerals; a lack of nitrate gives stunted growth and a lack of magnesium causes yellow leaves (chlorosis).
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Plants get diseases too, and because crops feed us, plant health matters for food security. This sub-topic covers the physical and chemical defences plants use, how plant diseases are recognised and identified, and the effect of missing…
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