Infection & ResponseTopic Summary
Knowledge Organiser
Part of Plant Diseases and Defenses — GCSE Biology
This topic summary covers Knowledge Organiser within Plant Diseases and Defenses for GCSE Biology. Plant pathogens, defense mechanisms, disease identification, crop protection It is section 17 of 17 in this topic. Use this topic summary to connect the idea to the wider topic before moving on to questions and flashcards.
Topic position
Section 17 of 17
Practice
18 questions
Recall
20 flashcards
Knowledge Organiser
Plant Pathogens
- Fungi — Rose black spot, potato blight
- Bacteria — fire blight, canker
- Viruses — TMV, cucumber mosaic virus
- Nematodes / protists / parasitic plants
Rose Black Spot
- Pathogen type: fungus
- Symptoms: black/purple spots, chlorosis, leaf drop
- Spread: spores via air and water
- Treatment: fungicide + remove infected leaves
TMV
- Pathogen type: virus
- Symptoms: mosaic pattern (light/dark patches)
- Mechanism: disrupts chloroplasts
- Effect: reduced photosynthesis, stunted growth
- Spread: aphid vectors, contact
Physical Defenses
- Waxy cuticle — hydrophobic barrier
- Cellulose cell walls — structural resistance
- Bark — dead cell outer layer
- Thorns/spines — deter herbivores
Chemical Defenses
- Antimicrobial proteins — kill bacteria/fungi
- Antifungal compounds — prevent spore germination
- Toxins — poison pathogens and herbivores
- Induced response — activated on infection
Disease Symptoms Summary
- Spots + surface growth = fungal
- Mosaic/mottling = viral
- Wilting + soft rot = bacterial
- Chlorosis = loss of chlorophyll (any cause)
- Stunted growth = reduced photosynthesis
Mineral Ion Deficiencies
- Nitrate — needed for amino acids/proteins; stunted growth, older leaves yellow first
- Magnesium — needed for chlorophyll; all-leaf chlorosis, reduced photosynthesis
- Potassium — needed for enzyme function; poor fruit/flower, leaf edge scorch
- Minerals absorbed by active transport via root hair cells