5. Auxins are plant hormones. (a) (i) Complete the sentence by putting a cross (✗) in the box next to your answer. Auxins cause the shoot of a plant to grow towards light in a process called ☐ A negative gravitropism ☐ B negative phototropism ☐ C positive gravitropism ☑ D positive phototropism (ii) Explain how auxins cause the shoot of a plant to grow towards light.

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5. Auxins are plant hormones - Edexcel - GCSE Biology - Question 5 - 2013 - Paper 1

Question 5

5. Auxins are plant hormones. (a) (i) Complete the sentence by putting a cross (✗) in the box next to your answer. Auxins cause the shoot of a plant to grow toward... show full transcript

Worked Solution & Example Answer:5. Auxins are plant hormones - Edexcel - GCSE Biology - Question 5 - 2013 - Paper 1

Step 1

Complete the sentence by putting a cross (✗) in the box next to your answer.

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Answer

The correct option is D, positive phototropism, which describes the growth of a plant shoot towards light.

Step 2

Explain how auxins cause the shoot of a plant to grow towards light.

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Answer

Auxins are hormones that play a crucial role in plant growth. When a plant is exposed to light, auxins redistribute towards the shaded side of the shoot. This uneven distribution causes the cells on the shaded side to elongate more than those on the light-exposed side. As a result, the shoot bends towards the light, allowing the plant to optimize light absorption for photosynthesis.

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