12.4 Plant Defences Against Pathogens

Question 1

How do plant cells recognise an attack?

Answer 1

1. RECEPTORS on plasma membrane respond to molecule either
   
   • produced by PATHOGEN
   • from BROKEN CELL WALLS.
2. Stimulates release of SIGNALLING MOLECULES which migrate to NUCLEUS.
3. Triggers RESPONSES to stop spread: production of…
   
   • molecules which ATTACK pathogen
   • proteins which ALERT other cells
   • CALLOSE to strengthen cell walls

Question 2

What is callose?

Answer 2

Polysaccharide important in plant’s response to pathogen.

Question 3

What are the 2 types of defences against pathogens which plants have?

Answer 3

physical + chemical

Question 4

What are the physical defences of plants?

Answer 4

Callose deposited in/between:

▪ CELL WALL + MEMBRANE - barriers stop spread

▪ CELL WALL ALONG WITH LIGNIN - strengthen

▪ PLASMODESMATA - block off routes of spread

Question 5

What are the chemical defences of plants?

Answer 5

▪ INSECT REPELLENTS + INSECTICIDES

▪ ANTIFUNGAL + ANTIBACTERIAL compounds + ANTI-OOMYCETES

▪ general TOXINS

Question 6

What do antifungal compounds do?

Answer 6

Interfere with CHITIN CELL WALLS of fungal cells

e.g use of chitinases

Question 7

What do antibacterial compounds do?

Answer 7

Interfere with PEPTIDOGLYCAN CELL WALLS of bacterial cells

Question 8

What are oomycetes?

Answer 8

A type of eukaryotic microorganism.

Many of which are plant pathogens.