disease + defences in plants Flashcards
what are the 3 main ways disease spreads in plants
directly
indirectly
through vectors
what is direct transmission in plants
a pathogen spreads when a healthy plant touches part of an infected plant
what is indirect transmission in plants
pathogens spread through contaminated soil, infected plants leave pathogens in soil which spread to the next crop
what is vector transmission in plants
pathogens spread through wind, water, humans, or other animals from infected to healthy plants
what 4 factors can increase the rate of transmission in plants
changing temperatures
dampness or moisture
overcrowding crops
nourishment
give 4 examples of physical defences to pathogens in plants
cellulose cell wall
waxy cuticle
guard cells
callose deposits
how does a cellulose cell wall protect plants from pathogens
it is a physical barrier against pathogens
how does the waxy cuticle protect plants from pathogens
prevents water collecting on surface, pathogens need water to survive
how do guard cells protect plants from pathogens
closes the stomata which prevents pathogens from entering the plant
how do callose deposits protect plants from pathogens
it is synthesised and deposited between the cell wall, cell membrane, plasmodesmata, and in phloem sieve plates, which prevents pathogens from travelling inside the plant
what is callose
a carbohydrate polysaccharide molecule made of B-glucose attached with 1-3 and 1-6 glycosidic bonds to form a helical structure
outline the process of a plant cell responding to a pathogen attack
- pathogen releases chemicals / pathogenic enzymes to break down the cell wall
- plant cells can detect these enzymes or cell wall break down products through receptors in membrane
- signalling molecules alert nucleus
- the nucleus responds in 3 ways:
synthesising polysaccharides e.g. lignin and callose
producing signalling chemicals to alert other cells
producing defensive chemicals to attack the pathogen
