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B5 Revision:Plant and body defences against pests and pathogens (Plants:…
B5 Revision:Plant and body defences against pests and pathogens
Plants:
Physical:
Cells walls made of cellulose
Barrier against pathogens that pass waxy cuticle
Waxy cuticle on leaves and stems, providing a barrier
Stop water collecting reducing risks of infection by pathogens that are transferred in water
Stops pathogens entering or pests damaging them
Chemical:
These chemicals used as a drug to treat human diseases or relieve symptoms of the disease
Aspirin used to relieve pain and fever, from chemical found in bark of willow tree
Quinine treats malaria and comes from the bark of the cinchona tree
Produce poison to deter pests from feeding on leaves
Foxgloves contain poison (digoxin)
Nicotine produced by tobacco plants act as an insecticide
Produce chemicals (antiseptics) which kill bacterial and fungal pathogens
Produce oil that acts as a natural fungicide, killing fungus
Produce chemicals to prevent damage from pathogens and pests, preventing infections however pathogens sometimes makes it past defences
Detecting plant diseases:
Lab:
Pathogens have unique molecules on surface (antigens) which from a are found in a plant infected by the pathogen
Pathogen's DNA will be in plant's tissue which it has infected, scientists use techniques to detect the DNA
Detected in plant tissue using monoclonal antibodies (proteins made to bind to a specific antibody
Field:
What they look for:
Observes plant's symptoms to see if plant diseased or if symptoms are due to something else
Symptoms of disease caused by environment (e.g. nutrient deficiency so can add more nutrients to soil to change)
Galls (abnormal growth) indicates crown gall disease
Detected by observations by plant pathologists.
Looks at distribution of diseased plants to see what pathogen involved as different pathogens spread in different ways
E.g. patches of diseased plant suggests disease spread through soil, random distribution suggests airborne pathogen
Body:
Chemical Barriers:
Body produces chemicals to destroy pathogens
Stomach produces hydrochloric acid to kill pathogens that makes it past the mouth
Produces enzymes called lysozymes that kill bacteria (e.g. in tears that kill bacteria on surface of eye
Physical barriers:
Block the entrance of pathogens into the body
Skin as a barrier, if damaged, blood clots quickly seal cuts to help keep microorganisms out of the body
Hair and mucus in nose traps particles that could contain pathogens
Cells in trachea and bronchi (lungs) secretes (makes) mucus to trap pathogens
Cells that line trachea and bronchi have cilia which push mucus to back on throat to be swallowed