Plant defences against pathogens

Question 1

What physical barriers do plants have to defend against pathogens?

Answer 1

Waxy cuticle on plant leaves
Bark on trees
Cellulose cell walls
Produce high levels of callose which is then deposited between the cell wall and the cell membrane of neighbouring cells - preventing pathogens from entering plant cells around the site of infection
Lignin is added to the cell wall to make the barrier to invasion thicker and stronger
Callose blocks sieve plates in the phloem to prevent the spread of pathogens

Question 2

What chemical defences do plants have to defend against pathogens?

Answer 2

Produce chemicals that repel the insect vectors of disease or kill invading pathogens
Insecticides, antibiotics, antifungals, toxins (cyanide)