12.4 Plant Defences Against Pathogens Flashcards
(15 cards)
How do plants recognise an attack? (Step by step process)
1- Receptors in cells respond to molecules from pathogens when the plant cell wall is attacked
2- Cell signalling molecules activate the defence genes
3- Causing production of defence molecules, that may also initiate cell death
4- Defence molecules communicate with other cells, and directly attack the pathogen
What does passive mean in terms of defence against pathogens?
Always present
What does active mean in terms of defence against pathogens?
Induced in response to an attack
List the types of active chemical defences that plants have.
-Insect repellants
-Insecticides
-General toxins
-Anti-oomycetes
-Tannin
-Antibacterial compounds containing antibiotics
-Antifungal compounds
Give examples of antifungal compounds.
Phenols, saponins
Give examples of antibacterial compounds including antibiotics
Phenols, defensins, lysosomes
Give examples of insect repellents.
Pine resin, citronella
Give examples of insecticides.
Pyrethrins, caffeine
Give examples of general toxins.
Cyanide
Give examples of anti-oomycetes
Glucanase
List some of the passive physical defences of plants.
-Cellulose cell wall
-Lignin thickening of cell walls
-Waxy cuticle
-Stomatal closure
What is the key active physical defence of plants?
Production of callose
What is callose?
A polysaccharide of beta glucose
What bonds are in callose?
Beta-1,3 and Beta-1,6 glycosidic bonds
What are the uses of callose?
-Callose deposited between cell wall and membrane of infected cells
-Callose deposited in plasmodesmata
-Callose blocks sieve plates in phloem
All done to prevent spread, and seal off infected areas.
