Plant diseases

Question 1

Signs of plant disease and what they show? (7)

Answer 1

• Stunted growth : nitrate deficiency
• Spots on leaves : black spot fungus on roses
• Decay : black spot fungus on roses
• Abnormal growths : bacterial infection
• Malformed stems/leaves : aphid infestation
• Discoloration : magnesium deficiency or TMV
• Pests

Question 2

How can someone identify the disease the plant has?

Answer 2

• Gardening manual/website
• Identifying the pathogen by sending the plant in a laboratory
• Using monoclonal antibodies in testing to identify the pathogen

Question 3

What can nitrate deficiency cause?

Answer 3

• Stunted growth
  Nitrated in the soil convert sugars made in photosynthesis into proteins.
  These proteins are used for growing

Question 4

What can magnesium deficiency cause?

Answer 4

Chlorosis -> yellow leaves
Magnesium is needed to make chlorophyll. This is pigmented green and is used in photosynthesis.
A lack of chlorophyll will decrease the rate of photosynthesis and cause stunted growth and cause the leaves to turn yellow

Question 5

What are examples of physical plant defenses?

3

Answer 5

• Tough waxy cuticle to stop microorganisms entry into leaves
• Cellulose cell walls form a physical barrier in to the cells
• Plants have layers of dead cells (bark) around stems to stop pathogens entering. Dead cells fall off with the pathogens

Question 6

What are examples of chemical plant defenses?

2

Answer 6

• Poisons deter herbivores

- Antibacterial compounds kill bacteria

Question 7

What are examples of mechanical plant defenses?

3

Answer 7

• Thorns and hairs make it difficult and painful for animals to eat them
• Some leaves can droop/curl when touched which allows them to move away and move insects off their leaves
• Mimicry (plants droop to look unhealthy so animals avoid them)
• Plants can have patterns on them to look like butterfly eggs, so butterflies do not lay their eggs there to avoid competitions