Plant defences
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How do herbivores create disease?
They create wounds that allow access into plant tissue which allows it to be easily infected
What are the ways plants get infected?
Insects as vectors, spores blown through air, direct contact in soil or machinery and plants touching
What are physical plant defences against pathogens?
Bark, waxy cuticle, resins, closing stomata, endodermis around xylem (casparian strip) which prevents entry to xylem
What is the process of entrance of a pathogen?
• Recognition of the pathogen by the receptors in the cell surface membrane. • Biding to the receptor changes the shape which activates secondary messengers • Enzymes are activated and signal is passed to nucleus. • Active cell response with defence genes activated in nucleus and proteins are made. • Neighbouring cells altered through plasmodesmata • Callose produced which thickens cell wall and isolates cell. • Secondary metabolite defence molecules produced often using chloroplast genes
What is callose?
A polysaccharide with glucose monomers but beta 1-3 and beta 1-5 glycosidic bonds
What is lignin?
A large indigestible fibre
What happens if the first line of fence is breached?
The nucleus will signal for the cell to produce toxins and enzymes
What is an example of an enzyme from the secondary defence?
Enzymes that break down cell wall of bacteria or fungi
How are toxins made?
Reactions in the cell
What are chemical plant defences against pathogens?
Secrete compounds, secrete toxic compounds, secrete enzyme inhibitors, production of receptors and sticky resins
What is the purpose of compound secretion?
They promote the growth of competing micro-organisms
What is the purpose of secretion of enzyme inhibitors?
They stop the pathogen attaching by breaking down cell wall
What is the purpose of receptors?
They detect pathogens on cell surface
What is the purpose of sticky resins?
Stop spread of pathogens