Physical Defenses
Waxy Cuticle
- Waterproof layer on leaves
- Prevents pathogen entry
- Reduces water loss
- Especially thick in desert plants
Cell Walls
- Made of tough cellulose
- Physical barrier to penetration
- Provide structural support
- Can thicken in response to attack
Bark
- Thick, protective outer layer
- Dead cells form barrier
- Protects inner living tissue
- Contains antimicrobial compounds
Thorns and Spines
- Deter herbivores
- Prevent physical damage
- Reduce pathogen transmission
- Modified leaves or stems
Chemical Defenses
Types of Chemical Compounds
- Antimicrobial proteins: Directly kill bacteria and fungi
- Antifungal compounds: Prevent fungal growth and spore germination
- Antiviral proteins: Interfere with virus replication
- Toxins: Poisonous to pathogens and herbivores
- Enzyme inhibitors: Block pathogen enzymes
Production and Response
- Constitutive: Always present as baseline protection
- Induced: Produced rapidly in response to attack
- Systemic: Warning signals sent throughout plant
- Local: Concentrated at site of infection
This deep dive covers Plant Defense Mechanisms within Plant Diseases and Defenses for GCSE Biology. Plant pathogens, defense mechanisms, disease identification, crop protection It is section 7 of 18 in this topic. Use this deep dive to connect the idea to the wider topic before moving on to questions and flashcards.
Practice questions for Plant Diseases and Defenses
What type of pathogen causes rose black spot disease?
Explain how rose black spot affects the growth of infected plants.
Quick recall flashcards
What is rose black spot?
A fungal disease that affects roses, causing black or purple spots on leaves, which turn yellow and drop off, reducing photosynthesis.
What is a plant pathogen?
A microorganism that causes disease in plants, such as fungi, bacteria, or viruses.