Plant Defences against Pathogens Flashcards
What are the physical barriers to prevent the entry of disease?
-Waxy cuticle
-Bark of tree
-Cellulose cell walls
What do plants do to to heal disease damaged tissues?
Section it off and sacrifice it.
What is the first step in recognising an attack after the pathogen has entered?
Some molecule from the pathogens are recognised directly by the plant cell.
What is the second step in recognising an attack?
When pathogenic enzymes break down the cell wall, the breakdown products are recognised.
What is the third step in recognising an attack?
Signalling molecules alert to an attack.
What is the fourth step in recognising an attack?
Polysaccharides (callose and lining) made to strengthen cell walls.
What is the fifth step in recognising an attack?
Defensive chemicals giver the alarm to other cells before they are attacked.
What is the sixth step in recognising an attack?
Some defensive molecules directly attack the pathogen.
What is the first physical defence in a plant?
Production of Callose
How does the production of callose work as a defence?
When a pathogen is detected the plants rapidly produces high levels of callose.
What is callose?
A polysaccharide substance deposited in sieve tube elements to prevent flow of back flow of pathogens
What is the first role of callose?
Is deposited between cell walls and membranes next to infected cells-this barrier prevents further spread.
What is the second role of callose?
Lignin is added to the callose to strengthen barrier.
What is the third role of callose?
Blocks the sieve cells of Phloem preventing the spread.
What is the fourth role of callose?
Deposited in the plasmodesmata.
In summary, what is the role does callose play?
Is deposited in the plasmodesmata between infected cells and their neighbours, sealing them off from healthy cells preventing spreading of pathogen
What is Tylose and what role does it play?
A balloon-like swelling that plugs the xylem and contains toxic chemical (terpenes) which prevents the spread of pathogens
What is the first chemical defence for?
Dealing with Fungi
How does this happen?
By antifungal compounds
-Gossypol; produced by cotton
-Caffeine; toxic to fungi and insects
–Saponins; chemicals in plant cell membranes which interfere with fungal membranes
What does the second chemical defence do?
Dealing with pathogens
How does this happen?
Antibacterial compounds containing antibiotics
-Phenols; antiseptic produced by cotton plants.
-Defensins; plant proteins that disrupt membranes of bacteria and fungi
What does the third chemical defence do?
Prevents Insects
How does this happen?
Insects can act as vector organisms for the spread of disease
-insect repellents (pine resin)
-insecticides (pyrethrin’s)
What is the fourth chemical defence?
Enzymes and Toxins
How does this happen?
-Chitinases; break down fungal cell walls
-Glucanase; break down glucans in oomycetes
-Cyanide; toxic to most living organisms
