Paper 1: Topic 3 Infection & response - Plant disease and defence (IV form)

Question 1

List 3 mineral ions that plants need to maintain healthy growth

Answer 1

Potassium ions

Magnesium ions

Nitrate ions

Question 2

Explain why plants need potassium ions

Answer 2

To produce some enzymes

To produce fruits and flowers

Question 3

Explain why plants need nitrate ions

Answer 3

To produce amino acids to make new proteins

To produce nucleotides to make DNA

Question 4

Explain why plants needs magnesium ions

Answer 4

To produce chlorophyll to allow the plant to photosynthesise

Question 5

Describe and explain the signs of a lack of magnesium ions in plants

Answer 5

Description:

Yellowing of the leaves

Chlorosis occurs

Explanation:

Due to a lack of chlorophyll production the leaves do not have a green colour

Question 6

Describe the signs of a lack of potassium ions in plants

Answer 6

Lack of fruits and flowers

Stunted growth

Question 7

Describe and explain the signs of a lack of nitrate ions in plants

Answer 7

Description:

Stunted growth

Explanation:

Due to a lack of proteins for growth and repair of tissues and organs

Question 8

State 3 types of pathogens that can cause diseases in plants

Answer 8

Fungi

Bacteria

Viruses

Question 9

Define the term pathogen

Answer 9

A micro-organism that causes disease

Question 10

State reasons how a plant may be infested

Answer 10

Insect infestation

Aphid infestation

Question 11

State 7 general signs of disease in a plant

Answer 11

1. Stunted growth
2. Spots on leaves
3. Patches of decay (called rot)
4. Abnormal growths e.g. calluses
5. Malformed stems and leaves
6. Discolouration of stems and leaves
7. Presence of pests

Question 12

State 3 methods a gardener can use to identify a disease in his their plant(s)

Answer 12

1. Consult a gardening manual or gardening website
2. Take the infected plant to a specialised laboratory for testing
3. Use a testing kit that uses monoclonal antibodies to detect the presence of a specific antigen

Question 13

State the 3 types of defence a plant has

Answer 13

1. Chemical defence
2. Physical defence
3. Mechanical defence

Question 14

State 3 examples of physical defence mechanisms in plants

Answer 14

1. Tough waxy cuticle
2. Cellulose cell walls
3. Layers of dead cells around their stems e.g. bark

HINT: do not say these defences prevents PREADTORS eating them herbivores do not hunt plants :)

Question 15

State 2 examples of chemical defence mechanisms in plants

Answer 15

Production of antibacterial chemicals e.g. mint plant, witch hazel plant

Production of poisons e.g. tobacco plants, foxgloves and deadly nightshade plants

Question 16

State 3 examples of mechanical defence mechanisms by plants

Answer 16

1. Thorns and hairs
2. Drooping or curling their leaves when touched
3. Mimicry

HINT: do not say these defences prevent PREADTORS eating them herbivores do not hunt plants :)

Question 17

What type of defence mechanism does an ice plant use?

Answer 17

Mechanical defence – using mimicry the ice plants resemble stones and rocks and hence avoid being eaten by herbivores HINT: do not say these defences prevents PREADTORS eating them herbivores do not hunt plants 

Question 18

Explain how thorns and hairs act as a form of plant defence

Answer 18

Prevent herbivores touching and eating them e.g. cacti, rose bush

Form of mechanical defence

Question 19

Explain how drooping or curling their leaves when touched is a defence mechanism in plants

Answer 19

This is used to knock insects off their leaves to prevent the inset eating the leaves e.g. mimosa plant

Form of mechanical defence

Question 20

Exalpain how plant mimicry is a form of plant defence

Answer 20

The plant mimics certain characteristics e.g. passion flower has yellow spots on its leaves which look like butterfly eggs. Butterflies then avoid laying eggs on those leaves as they think there will be competition between the caterpillars for food!

This is a form of mechanical defence

HINT: do not say these defences prevent PREADTORS eating them herbivores do not hunt plants :)

Question 21

Explain how chemical defence mechanisms used in plants

Answer 21

Production of antibacterial chemicals kill any bacteria that penetrate the waxy cuticle and cell walls

Production of poisons deter herbivores from eating them e.g. tobacco plants, foxgloves and deadly nightshade plants

Question 22

Explain how plants use physical defnece mechanisms to protect themselves

Answer 22

Tough waxy cuticle – forms a barrier to prevent the entry of pathogens

Cellulose cell walls – surround every plant cell to form a physical barrier to any pathogen that may have passed through the waxy cuticle

Layers of dead cells around their stems e.g. bark – to form a physical barrier to prevent pathogens entering the plant

Question 23

Name a plant disease caused by a virus

Answer 23

Tobaco Mosaic

Question 24

Describe 2 symptoms of Tobacco Mosaic disease

Answer 24

• Discoloured leaves
• Stunted growth

Question 25

Explain why plants with tobacco mosaic virus often have stunted growth

Answer 25

• The discolouration of the leaves cuases there to be less chloroplhyll in the leaves
• This means the plant photosynthesise less
• This means they produce less glucose
• So there is less energy for the production of new cells and the production of new proteins
• So there is less growth

Question 26

Name a plant disease caused by a fungus

Answer 26

Rose black spot

Question 27

Describe the symptoms of rose black spot disease

Answer 27

• Black or purple spots on the leaves
• Leaves turn yellow
• Leaves fall of the plant early (called ‘early drop’)

Question 28

Explain the lack of growth that is often seen in roses with black spot disease

Answer 28

The yellowing of the leaves causes there to be less chloroplhyll in the leaves

This means the plant photosynthesise less

This means they produce less glucose

So there is less energy for the production of new cells and the production of new proteins

So there is less growth

This gets worse as leaves fall off the plant

Question 29

Describe how rose black spot disease is spread

Answer 29

• The fungus can spread through water
• The fungus can spread through the air

Question 30

Describe 3 actions gardeners can take to treat rose black spot disease

Answer 30

• Gardeners can apply fungicides to infected plants
• They should also strip off any affected leaves from the plant
• The infected leaves must then be dedtoyed to prevent further spread of the fungus