Plant pathogens and defences

Question 1

what are examples of pathogens in plants?

Answer 1

Bacteria- Ring Rot (potatoes and tomatoes) in vascular tissue =blackening and death

virus- TMV =discolouration of leaves passed by touch

fungi, black, sigatoka in bananas, release, extracellular enzymes, e.g. cellulases

Protocista blight in potatoes, and tomatoes are spread by wind as spores in hot and wet conditions

Question 2

what physical defences against pathogens do plants have?

Answer 2

Waterproof, lignin
Waxy cuticle
Bark
Cell wall, Celulose
Callose:
blocks plasmodesmata
deposits between cell wall and plasma membrane
blocks sieve plates in phloem

Tylose causes balloon like swelling that plugs the xylem and contains toxic chemicals (terpenes)

Question 3

When will the plant produce chemical defences?

Answer 3

Only once pathogen is detected

Question 4

Give examples of chemical plant defences

Answer 4

antibiotics, an antifungal, methanol, tannins, binds and deactivates digestive enzymes

bitter taste to herbivores alkaloids

phenols prevent insects attacking

hydroleases hydrolytic enzymes

Examples of chemical defences:
Toxic compounds
E.g. Catechol

Sticky resin found in the bark
This traps the pathogens so they can’t spread

Compounds that encourage the growth of competing microorganisms
Microorganisms such as yeast found on the leaf surface are completely harmless to plants. They are strong competitors against harmful pathogens

Enzyme inhibitors
E.g. Tannins

Receptor molecules
They detect the presence of pathogens and trigger other defence mechanisms

Question 5

what is necrosis? How is it caused?

How does it prevent spread of pathogen?

Answer 5

deliberate cell suicide, destroys cells and produces brown spots

Caused by intracellular enzymes that are activated by injury

A pathogen is restricted access to nutrients and water

Question 6

what is canker and water she does it affect

Answer 6

sudden dead tissue

Cause she’s death to cambium tissue in the bark