B5. TRIPLE ONLY. Plant communicable diseases

Question 1

How can plant communicable diseases be caused?

Answer 1

By pathogens - bacteria, viruses, fungi and protists.

Question 2

How could you detect that a plant has a disease?

Answer 2

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

Question 3

How could someone ‘diagnose’ a plant disease?

Answer 3

Identification can be made by:
• Use a reputable gardening manual or website
• taking infected plants to a laboratory to identify the pathogen
• using testing kits that contain monoclonal antibodies.

Question 4

Explain how a MAGNESIUM ion deficiency could affect a plant.

Answer 4

• Lack of magnesium: magnesium is needed to make chlorophyll. Lack of magnesium causes chlorosis.
• If there isn’t enough chlorophyll plants cannot trap sunlight energy therefore lack of magnesium affects the rate of photosynthesis.

Question 5

Explain how a NITROGEN ion deficiency could affect a plant.

Answer 5

• Lack of nitrogen: nitrogen (in the form of nitrates) are required by plants to make proteins.
• Lack of nitrogen causes poor plant growth.

Question 6

What are a 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 a plants CHEMICAL defence responses to resist invasion of microorganisms?

Answer 7

• Antibacterial chemicals.

* Poisons to deter herbivores.

Question 8

What are a plants MECHANICAL adaptations to resist invasion of microorganisms?

Answer 8

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