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Year 11
Edexcel
Higher

Auxins, phototropism and gravitropism

I can explain how hormones called auxins cause plant shoots and roots to respond to light and gravity.

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New
New
Year 11
Edexcel
Higher

Auxins, phototropism and gravitropism

I can explain how hormones called auxins cause plant shoots and roots to respond to light and gravity.

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Share activities with pupils

Lesson details

Key learning points

  1. Hormones control growth and development in plants, and enable plants to respond to some environmental factors.
  2. Auxins are plant hormones that control tropisms, which are growth responses in plants that provide a survival advantage.
  3. Phototropism in a shoot: auxins build up on the shaded side and cause cell elongation, so it bends towards the light.
  4. Gravitropism in a shoot: auxins build up on the lower side and cause cell elongation, so it bends upwards.
  5. Gravitropism in a root: auxins build up on the lower side but this stops cell elongation, so it bends downwards.

Common misconception

Pupils may think that plants move towards the sun, rather than grow in that direction. Pupils may also think that plants are not living.

Plants grow in a certain direction through mitosis (in meristem) and elongation. Plants are living as they carry out the common processes of living organisms.

Keywords

  • Hormone - chemicals released by plants that regulate their growth

  • Auxins - control the growth of plants by promoting cell division and elongation in plant cells

  • Tropism - a plant growth response to a stimulus, it can be positive (towards) or negative (away from)

  • Phototropism - a plant growth response towards or away from light

  • Gravitropism - a plant growth response towards or opposite the direction of gravity

Show examples of plants that have grown towards the sunlight. Prepare some plants in advance that have been placed on their sides.
Teacher tip

Equipment

None required.

Licence

This content is © Oak National Academy Limited (2024), licensed on Open Government Licence version 3.0 except where otherwise stated. See Oak's terms & conditions (Collection 2).

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Starter quiz

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6 Questions

Q1.
True or false? Only animals have hormones.
true
Correct answer: false
Q2.
What is the process by which plants make their own food?
Correct Answer: photosynthesis
Q3.
Match the parts of this plant to their description.
An image in a quiz
Correct Answer:a,reproductive organ

reproductive organ

Correct Answer:b,provides support and contains tissues that transport sugars and water

provides support and contains tissues that transport sugars and water

Correct Answer:c,where most photosynthesis takes place

where most photosynthesis takes place

Correct Answer:d,where minerals and ions are absorbed

where minerals and ions are absorbed

Q4.
What is the name of the tissue in plants where cells grow and elongate?
An image in a quiz
Correct Answer: meristem, meristems, meristematic tissue, meristematic tissues
Q5.
Which of the following is true about hormones?
They are produced by photosynthesis.
Correct answer: They are chemicals.
They are used in reproduction only.
They are produced by respiration.
Q6.
How do plants grow in height and width?
photosynthesis
Correct answer: mitosis
light
Correct answer: elongation

Exit quiz

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6 Questions

Q1.
What do plant hormones do?
Correct answer: Control growth and development.
Prevent mitosis in shoots.
Deter predators.
Correct answer: Enable plants to respond to some environmental factors.
Q2.
are growth responses to stimuli in plants that provide a survival advantage.
Correct Answer: tropisms, tropism, a tropism
Q3.
When discussing tropisms, select the correct statements.
Auxins build up on the shaded side of roots, causing them to bend towards light.
Correct answer: Shoot cells are stimulated by auxins and so will elongate.
Correct answer: Auxins build up on the shaded side of shoots, causing them to bend towards light
Root cells are stimulated by auxins and so will elongate.
Q4.
Which tropism is the plant root below displaying?
An image in a quiz
positive phototropism
negative phototropism
Correct answer: positive gravitropism
negative gravitropism
Q5.
Which direction is light coming from and which side of the shoot is auxin most abundant?
An image in a quiz
Light coming from the left side and auxin on the left side of the shoot.
Light coming from the right side and auxin on the right side of the shoot.
Light coming from the top and auxin on the right side of the shoot.
Light coming from the left side and auxin on the right side of the shoot.
Correct answer: Light coming from the right side and auxin on the left side of the shoot.
Q6.
What happens if the tip of a shoot is covered with an opaque material?
Correct answer: It will grow upwards.
The plant will stop growing.
It will grow away from light.
It will grow towards light.