Download B1.41 Fact Sheet Plants

B1.41 Triple Science; Plant Disease and Hormones
Plant Disease; detection and identification
1. Give four examples of organisms that can
infect plants
2. Name a viral plant disease
3. Name a fungal plant disease
4. Name an insect that can infect plants
5. State two effects of ion deficiency conditions
in plant (include examples)
6. Explain why the above ion deficiencies cause
those effects
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Tobacco mosaic virus (TMV)
Rose black spot
Aphids
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A nitrate deficiency causes stunted growth
A magnesium deficiency causes chlorosis
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Nitrate ions are needed for protein synthesis and
therefore growth
Magnesium ions are needed to make chlorophyll,
without this leaves appear yellow rather than
green
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7. Describe how chlorosis affects plants
8. HT: Examples of symptoms of disease in
plants
9. HT: Describe the symptoms of black spot
fungus on roses
10. HT: Explain why identification of plant
diseases can be difficult
11. HT: Describe methods of identification
Yellowing of leaves due to lack of chlorophyll
 Stunted growth
 Spots on leaves
 Areas of decay or rotting
 Growths
 Malformed stems and leaves
 Discolouration
 Presence of visible pests e.g. aphids, caterpillars
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Spots on leaves and areas of decay/rotting
Because many plant diseases have very similar symptoms
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12. HT: Suggest why fast detection of diseases is
important
Defence responses in plants
13. Name four physical defence responses in
plants
Viral pathogens
Bacterial pathogens
Fungal pathogens
Insects
Using gardening manuals or websites to compare
symptoms in living plant with descriptions
Taking infected plants to a lab for DNA analysis
to identify pathogen causing the disease
Using testing kits that contain monoclonal
antibodies which can identify certain pathogens
Increases chance of effective treatment and helps to
reduce the spread of disease between plants
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Cellulose cell walls
Tough waxy cuticle on leaves
Bark on trees
Leaf fall
14. Explain how one of these physical defences
reduce invasion of pathogens
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15. State two chemical defence responses in
plants
16. Explain how one of these chemical defences
reduce invasion of pathogens
17. State three mechanical defence responses in
plants
18. Explain how one these mechanical defences
reduce invasion of pathogens
Cellulose cell walls: strengthens plant cells walls
to prevent microorganisms entering
Tough waxy cuticle on leaves: acts as a barrier to
the entry of pathogens
Bark on trees: acts as a protective layer that is
hard for pathogens to penetrate
Leaf fall: Happens in autumn, causes infected
pathogens in the leaves e.g. rose black spot, fall
off
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Antibacterial chemicals
Poisons
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Antibacterial chemicals: Protect plants against
invading bacterial pathogens by killing them
Poisons: Deter herbivores as the animals
remember plants that previously made them feel
ill and avoid eating them
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Thorns and hairs
Leaves which droop/curl when touched
Mimicry
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Thorns and hairs: Deter animals from eating the
plants and laying eggs on them
Leaves which droop/curl when touched: This
dislodges insects so they fall off or can frighten
animals
Mimicry: Some plants droop to mimic
unhealthy/wilting plants tricking animals not to
eat them and preventing insects from laying eggs
on/in them
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Plant Hormones
19. State three effects of plant hormones
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Coordinate and control growth
Cause plants to respond to light
Cause plants to respond to gravity
20. A response to light is called a…
Phototropism
21. A response to gravity is called…
Gravitropism/geotropism
22. Explain how auxin causes roots and shoots
to responds to gravity and light
23. Describe how auxin causes shoots to
respond to light
24. Describe how auxin causes roots to respond
to gravity
An uneven distribution of the hormone in the plant
causes an unequal growth rate
Shoots grow towards light
Roots grow downwards in the direction of gravity
25. Explain how auxin causes shoots to grow
towards light (3)
26. Explain how auxin causes new shoots to
respond to gravity (3)
27. Explain how auxin causes new roots to grow
downwards in response to gravity (3)
28. HT: State the plant hormone involved in
initiating seed germination
29. HT: Define germination
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There is an uneven distribution of auxin
Resulting in more on the shaded side
Cells here grow more causing the shoot to bend
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More auxin on the lower side of shoot
Shoot grows more on the side with more auxin
Shoot grows up away from the force of gravity
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More auxin on the lower side of root
Shoot grows less on the side with more auxin
Shoot grows down in response to the force of
gravity
(See diagram above)
Gibberellins
The process by which a plant grows from a seed.
30. HT: Give three uses of auxin in agriculture (3)
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As weed killers
As rooting powders
To promoting growth in tissue cultures
31. HT: Give three uses (with examples) of
ethene in the food industry
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To end seed dormancy e.g. barley seeds used in
brewing
To promote flowering e.g. pot plants such as
chrysanthemums
To increase fruit size e.g. seedless grapes
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32. HT: Suggest why auxins are used in
agriculture (2)
33. HT: Suggest why ethene is used in food
production (2)
34. HT: Give the name for chemicals that affect
one type of plant and now another
To control plant growth for more profit e.g. increase
growth of crops and decrease growth of weeds
To control ripening of fruit so it can be stored for long
periods and transported for long distances without going
over ripe
Selective Herbicides