12.4 plant defences against pathogens

Physical protection against pathogens in plants (3)

-waxy cuticle in cell walls

-bark on trees

-cellulose cell walls

How do plants combat diseased tissue

They seal it off from the rest of the plant, let it die and then regrow and replace it through meristematic tissue

How do plants respond rapidly to pathogen attacks

-receptors in plant cells respond to pathogen molecules when the cell is attached, which stimulates the release of signalling molecules that switch on genes in the nucleus

-this then triggers cellular responses e.g. producing defensive chemicals

What do plants produce when they are attacked

-Callose (polysaccharide containing 1-3 and 1-6 beta glycosidic bonds)

Action of callose in plant cells? where does it act? 3x

-depositied between the cell walls/membrane in cells next to the infected cells, acting as a barrier and preventing pathogens from entering cells around the site of infection

-callose also blocks sieve plates in phloem and blocks the plasmodesmata between infected cells and healthy cells sealing off the infected part and preventing spread of pathogens

Example of plant chemicals (3)

-Insect repellents

anti-bacterial compounds

antifungal compounds

general toxins

what are antifungal compounds? and how do they damage fungi?

phenols,

produce chitinases which are enzymes that break the fungal wall

what are anti-oomcytes?

enzymes like glucanases that break down glucans (polymers found in the cell wall of oomycetes (fungi)