12.4 plant defence against pathogens

Question 1

plants physical defences

Answer 1

• produce callose a polysacharide acts as a barrier to pathogen entering plant cells around sit of infection
• lignin is added as further mechanical barrier
• callose can seal of infected phloem to prevent spread
• and seals off healthy cells in the plasmodesmata

Question 2

plant chemical defences

Answer 2

• antimicrobials kill or inhibit pathogen growth eg. saponins destroy fungal cell membranes
• phytoalexins inhint growth of fungi
• toxins kill insects to prevent feeding