Plant defences

• What are passive defences in plants?

  Defences present before infection to prevent entry
• What are active defences in plants?

  Defences triggered after infection is detected
• How do tyloses protect plants from disease?

  They block xylem vessels to prevent pathogen spread
• What chemical defences do tyloses contain?

  Terpenes, which are toxic to pathogens
• How does callose help protect plants from disease?

  It reinforces barriers and blocks pathogen movement
• What happens to callose upon infection?

  It is deposited between cell wall and plasma membrane
• Why do plants produce protective chemicals only after infection?

  To conserve energy and resources
• How do chemicals toxic to insects help in plant defence?

  They prevent insect damage, reducing pathogen entry points
• What is the role of a cellulose cell wall in plant defence?

  Acts as a physical barrier against pathogens
• What is the function of waxy cuticles in plant defence?

  Prevents water accumulation and acts as a barrier
• What is lignin and its role in plant defence?

  Waterproofing substance that strengthens plant structures
• How does stomatal closure help defend plants?

  Prevents pathogen entry through stomata
• What are plasmodesmata?

  Gaps connecting neighbouring plant cells
• Why are plasmodesmata blocked during infection?

  To restrict pathogen movement between cells
• What are terpenes in plant defence?

  Chemical defences that are toxic to pathogens
• What are phenols and their role in plant defence?

  Anti-microbial chemicals that inhibit pathogen growth
• What are alkaloids and how do they contribute to plant defence?

  Bitter chemicals that deter herbivores
• What are hydrolytic enzymes and their function in plant defence?

  Enzymes that break down pathogen cell walls
• How do oxidative bursts defend plants?

  They produce reactive oxygen molecules damaging pathogens
• What is necrosis and its role in plant defence?

  Cell suicide to prevent pathogen spread
• How does necrosis help protect plants?

  It digests infected cells to limit spread
• What are the differences between passive and active defences in plants?

  • Passive defences: Present before infection, prevent entry.
  • Active defences: Triggered after infection, strengthen barriers.
• What are the two ways callose helps protect plants from disease?

  1. Reinforces physical barrier upon infection.
  2. Blocks phloem sieve tubes and plasmodesmata.
• What are the roles of antimicrobial chemicals in plant defence?

  • Inhibit growth of pathogens like fungi.
  • Destroy plasma membranes of fungal cells.
• What is the significance of tylose formation in plant defence?

  • Blocks xylem vessels to restrict pathogen spread.
  • Contains chemical defences against pathogens.
• What is the role of oxidative bursts in plant defence?

  • Produce reactive oxygen molecules.
  • Damage pathogen cells to limit infection.
• What is the process of necrosis in plant defence?

  • Deliberate "cell suicide" of infected cells.
  • Prevents pathogen spread to healthy tissues.