Plant Defences

Question 1

What happens when a pathogen enters a plant

Answer 1

Receptors of the cell responds to molecules from the pathogens or chemicals produced when cell wall attacked

Stimulates release of signalling molecules that appear to switch on genes in the nucleus- triggers cellular response which includes producing DEFENSIVE CHEMICALS, sending alarm signals to unaffected cells trigger their defenses and physically strengthening cell walls

Question 2

Physical barriers

Answer 2

Cellulose cell wall
Lignin thickening of cell walls - waterproof and indigestible
Bark- Chemical defenses
Stomatal closure
Waxy cuticle- prevents water collecting on surfaces

Question 3

Callose

Answer 3

PHYSICAL defennse
Polysacchardie
Beta 1,3 and 1,6 linkages between glucose
deposited between cell wals and cell membrane in cells next to infected
Papillae act as barriers, preventing pathogens entering the plant cells around the site of infection
Large amounts of callose deposited in cell walls after initial infection - lignin affected making barrier to invasion THICKER
Blocks sieve plates in phloem , preventing spread
Deposited in plasmodesmata between infected sells- seals them off

Question 4

Tylose

Answer 4

PHYSICAL defense
Baloon like swelling/projection that fills the xylem tissue
When fully formed, plugs vessel and h20 can no longer be carried
Blocking xylem prevents pathogen spread
Contains HIGH conc of chemicals toxic to pathogen

Question 5

Chemical defences

Answer 5

Insect repellents e.g. pine resin
Inseticides e.g. Pyrtherins
Antibacterial compounds e.g. phenols
Antioomyctes e..g gluanoses ( break down glucose)
anti fungal compounds e.g. chtinases( breka down chitin in fungus)
General toxins