B3: PLANT DISEASES AND DEFENCES

Question 1

What are plant diseases caused by?

Answer 1

-pathogens infecting plants
-insects (eg: aphids)
-mineral ion deficiency

Question 2

How does nitrate deficiency affect plants?

Answer 2

-causes stunted growth due to limited nitrate ions needed for protein synthesis
-reduced protein synthesis = stunted growth

Question 3

How does magnesium deficiency affect plants?

Answer 3

-causes chlorosis (lack of chlorophyll) due to limited magnesium ions needed to make chlorophyll
-reduced chlorophyll = limited photosynthesis

Question 4

How can plant diseases be detected?

Answer 4

-stunted growth
-spots on leaves
-areas of decay
-growths
-malformed stems/leaves
-discolouration
-presence of pests

Question 5

Cellulose cell walls
-physical/chemical/mechanical?
-defence against animal/pathogen?
-how does it work?

Answer 5

-physical
-pathogens
-physical barrier to resist invasion of microorganisms

Question 6

Tough waxy cuticle on leaves
-physical/chemical/mechanical?
-defence against animal/pathogen?
-how does it work?

Answer 6

-physical
-pathogens
-physical barrier to resist invasion of microorganisms

Question 7

Layers of dead cells around stems (eg: tree bark)
-physical/chemical/mechanical?
-defence against animal/pathogen?
-how does it work?

Answer 7

-physical
-pathogens
-physical barrier to resist invasion of microorganisms

Question 8

Antibacterial chemicals
-physical/chemical/mechanical?
-defence against animal/pathogen?
-how does it work?

Answer 8

-chemical
-pathogens
-chemicals kill bacteria (eg: mint plant, witch hazel)

Question 9

Poison to deter herbivores
-physical/chemical/mechanical?
-defence against animal/pathogen?
-how does it work?

Answer 9

-chemical
-animals (herbivores)
-prevent animals eating them (eg: foxgloves, deadly nightshade)

Question 10

Thorns and hairs deter animals
-physical/chemical/mechanical?
-defence against animal/pathogen?
-how does it work?

Answer 10

-mechanical
-animals (herbivores)
-prevent animals touching and eating them

Question 11

Leaves which droop/curl when touched
-physical/chemical/mechanical?
-defence against animal/pathogen?
-how does it work?

Answer 11

-mechanical
-animals (pests)
-prevent being eaten by insects by moving away causing insects to fall off

Question 12

Mimicry to trick animals
-physical/chemical/mechanical?
-defence against animal/pathogen?
-how does it work?

Answer 12

-mechanical
-animals (pests and herbivores)
-prevent being eaten as animals tricked into thinking they’re stones
-prevent pests laying eggs