Plant defences

• What do plants have to protect themselves against infection?

  Defence mechanisms
• How are plant defence mechanisms classified?

  Into passive and active categories
• What are passive defence mechanisms in plants?

  Always present defence mechanisms
• What do physical barriers in plants do?

  Prevent pathogens from entering
• How can viruses and bacteria penetrate the waxy cuticle?

  Only through wounds on the leaf surface
• What is the role of the cellulose cell wall in plant defence?

  Acts as a physical barrier
• What happens to stomata during pathogen invasion?

  They may close to prevent entry
• 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 prevent growth
• How does sticky resin help in plant defence?

  It traps pathogens to prevent spreading
• What role do competing microorganisms play in plant defence?

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

  Compounds that block pathogen enzymes
• What is the role of receptor molecules in plant defence?

  They detect pathogens and trigger responses
• What happens during hypersensitivity in plants?

  Tissue surrounding infection rapidly dies
• How do plants create physical barriers during pathogen invasion?

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

  A polysaccharide that forms a protective matrix
• What is the effect of narrowing plasmodesmata in plant defence?

  Reduces pathogen spread between cells
• What are tyloses in plant defence?

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

  Blocks phloem sap transport
• What role do cellulase enzymes play in plant defence?

  They digest cellulose in plant cell walls
• What are phytoalexins?

  Defence chemicals released by plants
• How do phytoalexins disrupt pathogen activity?

  By disrupting metabolism and reproduction
• What is the role of salicylic acid in plant defence?

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

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

  Stimulates reactions in other leaves and plants
• What do plants secrete when under pathogen attack?

  Ethylene
• What is the significance of ethylene vaporization?

  Stimulates defence reactions in nearby plants