Plant disease (3.3)

Question 1

7 needed

How can plant disease be detected?

Answer 1

• stunted growth
• spots on leaves
• areas of decay (rot)
• (abnormal) growths
• malformed stems or leaves
• discolouration
• the presence of pests.

Question 2

3 needed

How can plant disease be identified?

Answer 2

• reference to a gardening manual or website
• taking infected plants to a laboratory to identify the pathogen
• using testing kits that contain monoclonal antibodies.

Question 3

Which pathogens can infect plants and which organisms can infect/damage them?

Answer 3

Plants can be infected by a range of viral, bacterial and fungal pathogens as well as being infected/damaged by insects (aphids)

Question 4

3 diseases or organisms needed

What is knowledge of plant disease restricted to?

Answer 4

• tobacco mosaic virus as a viral disease
• (rose) black spot as a fungal disease
• aphids as insects

Question 5

2 needed with explanation

Plants can be damaged by a range of ion deficiency conditions such as…

Answer 5

• stunted growth caused by nitrate deficiency - nitrate ions needed for protein synthesis and therefore growth
• c_hlorosis (yellowing of leaves)_ caused by magnesium deficiency leading to less photosynthesis (may also lead to less growth as glucose can be used to make amino acids for protein synthesis and therefore growth) - magnesium ions needed to make chlorophyll

knowledge of ions limited to these two

Question 6

What are plants’ physical defence responses to resist invasion of microorganisms?

Answer 6

• Cellulose cell walls.
• Tough waxy cuticle on leaves.
• Layers of dead cells around stems (bark on trees) which fall off.

Question 7

What are plants’ chemical plant defence responses?

Answer 7

• Antibacterial chemicals.
• Poisons to deter herbivores.

Question 8

What are plants’ mechanical adaptations?

Answer 8

• Thorns and hairs deter herbivores.
• Leaves which droop or curl when touched.
• Mimicry to trick animals

Question 9

Why may plants infected with aphids showings of reduced growth?

Answer 9

Less amino acids produced (due to less sugars), so less protein synthesis

could also talk about glucose or cellulose

Question 10

Explain why the mouthpiece of the aphid contained a high concentration of dissolved sugars after feeding

Answer 10

mouthpiece had pierced/entered the phloem

or

(the aphid) had been feeding from the phloem