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Describe the function of auxin in regulating shoot growth, focusing on: (a) its production in the shoot tip, (b) its diffusion throughout the plant from the shoot tip, (c) its uneven distribution in response to light and gravity, and (d) its role in promoting cell elongation.

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Cambridge IGCSE BiologyCoordination and responseSupplement content

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Describe the function of auxin in regulating shoot growth, focusing on: (a) its production in the shoot tip, (b) its diffusion throughout the plant from the shoot tip, (c) its uneven distribution in response to light and gravity, and (d) its role in promoting cell elongation

  • This point belongs to Tropic responses, especially Tropic responses outcomes.
  • You need to be able to describe the function of auxin in regulating shoot growth, focusing on: (a) its production in the shoot tip, (b) its diffusion throughout the plant from the shoot tip, (c) its uneven distribution in response to light and gravity, and (d) its role in promoting cell elongation.
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Diagram Description

Auxin Distribution in a Plant Shoot

The diagram shows a plant shoot bending towards a light source. Auxin concentration is higher on the shaded side of the shoot than on the side facing the light.

Side of ShootAuxin Concentration
Light sideLow
Shaded sideHigh
  1. a

    State where auxin is produced in the plant shoot.

    Aim for approximately 1 distinct marking point.

    [1]
  2. b

    Explain how uneven auxin distribution causes the shoot to bend towards the light.

    Aim for approximately 3 distinct marking points.

    [3]
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