transmission and plant defences Flashcards
what is direct transmission
transfer of pathogens from infected host to uninfected one
what do pathogens do to ensure transmission succesfull
large numbers to inc chance reach host
small infective stage to not waste energy
examples of how direct transmission
contact - between individuals eg TMV
spores eg black sig/late blight
body fluids eg HIV
ingestion - contaminated food/drink
animal bites eg rabies
what is indirect transmission
pathogen travels from one individual to another through intermediate
how can indirect trans occur
vectors eg malaria
droplets in air eg TB/ meningitis
fomites - inanimate objects
factors affecting direct
close proximity
high density monocultures
- close contact
factors affect indirect
climates
- change global temp
- mosquitoes can spread N/S of current breeding areas
factors affect human disease
poor housing/sanitation
contaminated water
travel - disease to place of no immunity
poverty - unhygenic
what is endemic
disease always present in population
eg malaria in tropical countries
how to prevent spread plant disease
crop rotations - die as no host
space between plants
wash machinery and hands
control vectors
what are passive defense mechanisms
present all time
what are the plant physical barriers
waxy cuticle
cellulose cell walls
casparian strip in endodermis of root
stomatal closure
barks
what are the plant chemical barriers
secrete toxic compounds
secrete enzyme inhibitors pathogens need to enter
eg cellulose used to break cell wall
sticky resin in bark
secrete compounds support growth of pathogen competitors
what is the point of physical barriers
reduces chance pathogen entering
what is point of chemical defenses
make conditions hostile for pathogens
