Plant defences

what are the primary defences of plants (3):

• waxy cuticle

• bark

• cellulose

what is the chemical in cell walls which is waterproof and nearly indigestible?

lignin

how does waxy cuticle and bark prevent pathogens from entering?

prevents water from collecting on surface of the plant and pathogens need water to survive and collect in water

what are 3 physical defences which happen once a pathogen has entered (3)?

• stomatal closure

• callose deposited

• tylose formation

where is callose deposited (3 places)?

• between the cell wall and cell membrane around infected cells

• sieve tubes in phloem

• plasmodesmata of connection cells

what is callose made out of?

it is a polysaccharides made of beta glucose monomers

what is tylose?

a balloon-like projections which fills the xylem vessels

what two ways does tylose prevent spread of infection?

• blocks off xylem vessels, preventing them from carrying water

• contains high concentrations of chemicals toxic to pathogens

what are some chemicals present before infection?

• terpenes in tylose

• tannins in bark

what are 3 antimicrobial chemicals:

• phenols

• defensins

• terpenoids

what properties do phenols have?

antibiotic and antifungal properties

what do defensins do?

they are defensive plant proteins that disrupt membranes of bacteria and fungi

what are terpenoids?

essential oils with antibacterial and antifungal properties

what are alkaloids?

nitrogen-containing compounds

what are some examples of alkakoids?

• caffeine

• nicotine

• cocaine

• morphine

what do alkaloids do?

• give a plant a bitter taste to prevent animals from grazing on it

• inhibits or active enzymes

what are hydrolytic enzymes found in plants (4)?

• chitinases

• glucanase

• lysozymes

• cyanide

what do lysozymes do?

break down bacterial cell walls

what do glucanases do?

break down glucans found in water mold

what do chitinases do?

break down fungal cell walls

what is an example of insect repellent?

pine resin

what a chemical defence against insects?

insecticides (eg. caffeine)

what is necrosis?

deliberate cell suicide

what happens in necrosis as a defense?

a few cells are sacrifices in order to prevent further spread of the pathogen to other parts, limiting supply of nutrients and water to the pathogen

what causes necrosis?

intra-cellular enzymes