CH12 plant defences against pathogens Flashcards
1
Q
How do plants recognise a pathogen attack
A
- receptors in plant cells respond to molecules from pathogens or to chemicals produced when plant cell wall is attacked
- stimulates the release of signalling molecules that appear to switch on genes in nucleus
- this triggers cellular responses
2
Q
What do plants produce when attacked by pathogens
A
- produce callose
3
Q
What is callose
A
- polysaccharide
- contains beta 1,3 and 1,6 linkages between glucose monomers
4
Q
Function of callose
A
- synthesised and deposited between cell walls and cell membrane in cells next to infected cells, preventing pathogens entering plant cells around site of infection
- continues to be deposited in large amounts and lignin added making barrier even thicker and stronger
- callose blocks sieve plates in phloem, sealing off infected part
- deposited in plasmodesmata between infected cells and neighbours, sealing them off
5
Q
Examples of insect repellents
A
- pine resin
- citronella
6
Q
Examples of insecticides
A
- pyrethrins from chrysanthemums acting as insect neurotoxins
- caffine toxic to insects and fungi
7
Q
Examples of antibacterial compounds
A
- phenols, antiseptics made in different plants
- antibacterial gossypol produced by cotton
- defensins, plant proteins that disrupt bacterial and fungal cell membranes
- lysosomes, organelles containing enzymes to break down bacterial cell walls
8
Q
Examples of antifungal compounds
A
- phenols, antifungals made in many different plants
- antifungal gossypol, produced by cotton
- caffine, toxic to fungi and insects
- saponins, chemicals in many plant cell membranes that interfere with fungal cell membranes
- chitinases, enzymes that break down chitin in fungal cell walls
9
Q
Examples of anti-oomycetes
A
- glucanases, enzymes made by some plants that break down glucans (polymers found in cell walls of oomycetes)
10
Q
general toxins
A
- some plants make chemicals that can be broken down to form cyanide compounds when plant cell attacked
- cyanide is toxic to most living things
