Plant Defenses

• What are the two categories of plant defence mechanisms?

  Passive and active
• What are passive defence mechanisms in plants?

  Always present mechanisms against pathogens
• What do physical barriers in plants do?


  Prevent pathogens from entering plants
• Name an example of a physical barrier in plants.

  Waxy cuticle
• How can viruses and bacteria penetrate the waxy cuticle?

  Through wounds on the leaf surface
• What is another example of a physical barrier in plants?

  Cellulose cell wall
• What role do closed stomata play in plant defence?

  They limit pathogen entry into plants
• What is the Casparian strip's role in plant defence?

  Prevents fungi from invading past endodermis
• How do chemical defences work in plants?

  They create acidic conditions to inhibit pathogens
• Give an example of a toxic compound in plant chemical defences.

  Catechol
• What is the function of sticky resin in plant defence?

  Traps pathogens to prevent their spread
• How do competing microorganisms help plants?

  They outcompete harmful pathogens
• What are enzyme inhibitors in plant defence?

  Compounds like tannins that inhibit pathogens
• What is the role of receptor molecules in plant defence?

  They detect pathogens and trigger defences
• What is hypersensitivity in plant defence?

  Rapid death of tissue around infection site
• How do plants create physical barriers during pathogen invasion?

  By reinforcing cell walls with callose and lignin
• What is callose?

  A polysaccharide that forms a matrix shape
• How does callose help in plant defence?

  It helps deposit antimicrobial compounds
• What happens to plasmodesmata during pathogen invasion?

  They narrow to reduce pathogen spread
• What are tyloses in plant defence?

  Ingrowths into xylem vessels to block pathogens
• How does callose affect phloem during pathogen invasion?

  It fills sieve pores to block sap transport
• What do pathogens produce that affects plant cell walls?

  Cellulase enzymes that digest cellulose
• What do phytoalexins do in plant defence?

  Disrupt pathogen metabolism and reproduction
• What is salicylic acid's role in plant defence?

  Activates defence mechanisms in uninfected areas
• What is systemic acquired resistance in plants?

  Long-term protection against pathogens
• How does ethylene function in plant defence?

  Stimulates reactions in leaves under attack
• What happens when ethylene vaporizes?

  It stimulates other leaves to react