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Science Quiz - Biology - Plant Sensitivity and Control (AQA) (Questions)

Plants detect light, gravity and touch. Special hormones control how shoots and roots grow towards or away from these stimuli, helping the plant survive in its environment.

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Fascinating Fact:

Gibberellins break seed dormancy and promote stem growth. Farmers use them to improve fruit set and size.

In GCSE Biology (AQA), you learn how plants sense their environment using receptors and respond with hormones such as auxins and gibberellins. These chemicals control tropisms, seed germination and coordinated growth.

Key Terms

  • Tropism: A directional growth response in a plant towards or away from a stimulus, such as light or gravity.
  • Auxin: A plant hormone that controls cell elongation, especially in shoot and root tips, affecting how they bend and grow.
  • Gibberellins: Plant hormones that help seeds germinate and stimulate stem growth after dormancy has been broken.

Frequently Asked Questions (Click to see answers)

What are plant hormones in GCSE Biology?

Plant hormones are chemical messengers that coordinate growth and responses to stimuli. Examples include auxins, gibberellins, cytokinin, ethene and abscisic acid.

What is phototropism and how does it work?

Phototropism is when a plant grows towards light. Auxins move to the shaded side of the shoot, causing those cells to elongate more so the shoot bends towards the light.

How do auxins affect roots and shoots differently?

In shoots, higher auxin levels increase cell elongation so the shoot bends towards light. In roots, higher auxin levels inhibit elongation, so the root bends in the opposite direction.

Try These Related Quizzes

1. Phototropism is caused by a hormone. What is phototropism?
[ ] When old photographs are ruined by bacteria
[ ] Skin darkening in response to sunlight
[ ] Plant leaves losing their green colour when there isn't much sunlight
[ ] Plants growing towards the light
2. Gravitropism (geotropism) is also caused by a hormone. What is gravitropism?
[ ] Roots growing downwards, shoots growing upwards
[ ] Shoots growing upwards only
[ ] A plant disease
[ ] Plants growing away from the light
3. Which of the following options applies to the plant hormones, auxins?
[ ] Auxins are found only in the leaf cells of plants
[ ] Auxins respond only to light
[ ] Auxins are made in the growing tips and spread throughout the plant
[ ] Auxins respond only to gravity
4. Which of these combinations describes the tropisms of shoots correctly?
[ ] Positively phototropic and positively geotropic
[ ] Negatively phototropic but positively geotropic
[ ] Positively phototropic but negatively geotropic
[ ] Negatively phototropic and negatively geotropic
5. Which of these combinations describes the tropisms of roots correctly?
[ ] Positively phototropic and positively geotropic
[ ] Negatively phototropic but positively geotropic
[ ] Positively phototropic but negatively geotropic
[ ] Negatively phototropic and negatively geotropic
6. What are the three main external stimuli to which plants respond?
[ ] Light, water, sound
[ ] Water, gravity, touch
[ ] Gravity, heat, light
[ ] Light, water, gravity
7. The ripening of fruit is a response to hormones. Certain hormones can be sprayed on plants to make the fruit all ripen at the same time. Which of the following is not a disadvantage with this?
[ ] There will be too much to pick all at once
[ ] It is easier for commercial fruit growing companies to pick fruit in one go
[ ] The fruits ripened in this way do not all have the same colour
[ ] The fruits will continue to ripen after they have ben picked
8. If a plant pot with a seedling is placed on its side with a bright light at 45 degrees to the pot and higher, what will happen?
[ ] The whole plant will continue to grow horizontally but the leaves will be at 45 degrees to the stem
[ ] The stem will grow downwards and the roots will continue to grow horizontally
[ ] The stem will grow upwards at 90 degrees and the roots will continue to grow horizontally
[ ] The stem will grow upwards at about 45 degrees and the roots will grow downwards
9. What happens in a plant shoot that makes it grow towards the light?
[ ] The warmth of the light attracts the hormone auxin so the shoot bends in the direction of the light
[ ] The auxin on the lit side of the plant shoot is destroyed by the light, making that side grow less than the other
[ ] There is less auxin on the shaded part of the plant shoot so that side grows more
[ ] The cells on the light side of the shoot shrivel up so that side gets shorter and the shoot bends over towards the light
10. Some students did an experiment on plant shoots. They cut off the tips of the shoots on 10 seedlings, covered the tips of 10 more with kitchen foil and left 10 seedlings as they were as a control. The seedlings were then placed in a large box with a hole cut in one side. Which of the following would describe their results?
[ ] All the seedlings died
[ ] The seedlings that had their tips covered with kitchen foil died; the others grew normally
[ ] The seedlings that had their tips cut off stayed the same; the ones covered in kitchen foil bent away from the hole in the side of the box and the other seedlings grew normally.
[ ] The seedlings that had their tips cut off stayed the same; the ones covered in kitchen foil grew taller than the others and stayed straight; the other seedlings grew towards the hole in the side of the box

You can find more about this topic by visiting BBC Bitesize - Plant organisation - AQA

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Science Quiz - Biology - Plant Sensitivity and Control (AQA) (Answers)
1. Phototropism is caused by a hormone. What is phototropism?
[ ] When old photographs are ruined by bacteria
[ ] Skin darkening in response to sunlight
[ ] Plant leaves losing their green colour when there isn't much sunlight
[x] Plants growing towards the light
Plants growing next to a window need to be turned round regularly otherwise their leaves will all lean towards the light
2. Gravitropism (geotropism) is also caused by a hormone. What is gravitropism?
[x] Roots growing downwards, shoots growing upwards
[ ] Shoots growing upwards only
[ ] A plant disease
[ ] Plants growing away from the light
If you plant a seed upside-down it doesn't matter. Gravitropism will ensure that the shoot and root grow the right way
3. Which of the following options applies to the plant hormones, auxins?
[ ] Auxins are found only in the leaf cells of plants
[ ] Auxins respond only to light
[x] Auxins are made in the growing tips and spread throughout the plant
[ ] Auxins respond only to gravity
Auxins are a group of plant hormones that control phototropism and geotropism
4. Which of these combinations describes the tropisms of shoots correctly?
[ ] Positively phototropic and positively geotropic
[ ] Negatively phototropic but positively geotropic
[x] Positively phototropic but negatively geotropic
[ ] Negatively phototropic and negatively geotropic
This ensures that they grow in the right direction and towards the light
5. Which of these combinations describes the tropisms of roots correctly?
[ ] Positively phototropic and positively geotropic
[x] Negatively phototropic but positively geotropic
[ ] Positively phototropic but negatively geotropic
[ ] Negatively phototropic and negatively geotropic
This ensures that they grow downwards, anchoring the plant in the soil and finding water and nutrients
6. What are the three main external stimuli to which plants respond?
[ ] Light, water, sound
[ ] Water, gravity, touch
[ ] Gravity, heat, light
[x] Light, water, gravity
Some carnivorous plants respond to touch
7. The ripening of fruit is a response to hormones. Certain hormones can be sprayed on plants to make the fruit all ripen at the same time. Which of the following is not a disadvantage with this?
[ ] There will be too much to pick all at once
[x] It is easier for commercial fruit growing companies to pick fruit in one go
[ ] The fruits ripened in this way do not all have the same colour
[ ] The fruits will continue to ripen after they have ben picked
In this type of question you are looking for an advantage. Picking all of the fruit in one short period of time makes the process cheaper for big companies
8. If a plant pot with a seedling is placed on its side with a bright light at 45 degrees to the pot and higher, what will happen?
[ ] The whole plant will continue to grow horizontally but the leaves will be at 45 degrees to the stem
[ ] The stem will grow downwards and the roots will continue to grow horizontally
[ ] The stem will grow upwards at 90 degrees and the roots will continue to grow horizontally
[x] The stem will grow upwards at about 45 degrees and the roots will grow downwards
The stems are positively phototropic and negatively geotropic so they will grow towards the bright light source as well as upwards. The roots are positively geotropic which is why they grow downwards
9. What happens in a plant shoot that makes it grow towards the light?
[ ] The warmth of the light attracts the hormone auxin so the shoot bends in the direction of the light
[x] The auxin on the lit side of the plant shoot is destroyed by the light, making that side grow less than the other
[ ] There is less auxin on the shaded part of the plant shoot so that side grows more
[ ] The cells on the light side of the shoot shrivel up so that side gets shorter and the shoot bends over towards the light
In the cells in plant shoots, the auxins are hormones that stimulate growth
10. Some students did an experiment on plant shoots. They cut off the tips of the shoots on 10 seedlings, covered the tips of 10 more with kitchen foil and left 10 seedlings as they were as a control. The seedlings were then placed in a large box with a hole cut in one side. Which of the following would describe their results?
[ ] All the seedlings died
[ ] The seedlings that had their tips covered with kitchen foil died; the others grew normally
[ ] The seedlings that had their tips cut off stayed the same; the ones covered in kitchen foil bent away from the hole in the side of the box and the other seedlings grew normally.
[x] The seedlings that had their tips cut off stayed the same; the ones covered in kitchen foil grew taller than the others and stayed straight; the other seedlings grew towards the hole in the side of the box
Auxins are made in the growing tips of plants - no tips, no growth. In the dark, auxin levels are higher so those seedlings grew taller. The control seedlings behaved normally and grew towards the light
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