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Clarify how phototropism and gravitropism in shoots serve as examples of chemical regulation in plant growth.

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Cambridge IGCSE BiologyCoordination and responseSupplement content

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Clarify how phototropism and gravitropism in shoots serve as examples of chemical regulation in plant growth

This point belongs to Tropic responses, especially Tropic responses outcomes.
You need to be able to clarify how phototropism and gravitropism in shoots serve as examples of chemical regulation in plant growth.
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Paper 4 structured question: Tropic responses

Paper 4Theory (Extended)6 marks

Description

Phototropism and Gravitropism

Phototropism causes shoots to grow towards light, while gravitropism causes shoots to grow upwards against gravity. Both responses involve the redistribution of auxin, which promotes cell elongation on one side of the shoot, causing bending.

a
State the direction of shoot growth in phototropism and gravitropism.
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Aim for approximately 2 distinct marking points.
[2]
b
Explain how auxin causes shoots to bend during phototropism.
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Aim for approximately 4 distinct marking points.
[4]

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Related learning objectives

Explain gravitropism as a plant response where certain parts grow towards or away from gravitational pull.
Tropic responses outcomes
Explain phototropism as a plant response where certain parts grow towards or away from the light source.
Tropic responses outcomes
Conduct an investigation and describe the processes of gravitropism and phototropism in both shoots and roots.
Tropic responses outcomes
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.
Tropic responses outcomes

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