b6.3.6 plant defences

Question 1

what is a physical defense

Answer 1

physical barriers that prevent the microorganisms from entering.

Question 2

what is a chemical defense

Answer 2

substances secreted by the plant

Question 3

cuticle

Answer 3

the leaves are covered in a waxy cuticle (above the epidermal cells) prevent water loss and also pathogens from coming inside. doesn’t allow water to remain on the leaves so that the bacteria can’t breed

Question 4

what is a palisade cell

Answer 4

it allows photosynthesis

Question 5

what does the spongy layer have

Answer 5

xylem and phloem

Question 6

cell wall

Answer 6

it provides a structural barrier. composed of cellulose fibers, providing strength and support. they also contain a chemical defense.

Question 7

examples of chemical defenses

Answer 7

• pine resin: insect repellant
• pyrethrins: insecticides
• phenols: antibacterial compounds to kill bacteria
• chitinases: antifungal compounds to kill fungi
• cyanide: some plants break down to form a sort of poison (apples and pear seeds)

Question 8

2 key techniques to diagnose a plant disease

Answer 8

observation

microscopy

Question 9

explain microscopy

Answer 9

they use a microscope to identify the pathogen.
they identify the species by their shapes.
sometimes electron microscopes may be needed

Question 10

how are plant disease identified in the laboratory

Answer 10

DNA analysis

Identification of antigens

Question 11

explain dna analysis

Answer 11

they compare an unknown plant’s pathogen genome to a known DNA profile. If it is a match, then an accurate diagnosis can be made.

Question 12

explain identification of antigens

Answer 12

antigens can be identified using chemical analysis.

there are diagnostic kits for farmers to identify pests.