Photograph A shows the root of a plant when it was positioned horizontally. The root was kept in the dark and left in this position. Photograph B was taken three days later. (a) (i) Complete the sentence by putting a cross (X) in the box next to your answer. The process that resulted in the type of root growth shown in photograph B is A negative gravitropism B negative phototropism C positive gravitropism D positive phototropism (ii) Explain how this change in root growth has occurred.

GCSE Edexcel Biology Investigating plant growth responses: Photograph A shows the root of a

Photograph A shows the root of a plant when it was positioned horizontally - Edexcel - GCSE Biology - Question 3 - 2014 - Paper 1

Question 3

Photograph A shows the root of a plant when it was positioned horizontally. The root was kept in the dark and left in this position. Photograph B was taken three da... show full transcript

Worked Solution & Example Answer:Photograph A shows the root of a plant when it was positioned horizontally - Edexcel - GCSE Biology - Question 3 - 2014 - Paper 1

Step 1

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

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Answer

The correct answer is C) positive gravitropism. Positive gravitropism is the growth of plant roots downwards towards gravity.

Step 2

Explain how this change in root growth has occurred.

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Answer

The change in root growth can be explained through the following points:

Auxin Distribution: Auxin is a plant hormone that is distributed unevenly in response to gravity. In the case of the root, it accumulates on the lower side of the root.
Inhibition of Cell Elongation: When auxin is present on the lower side of the root, it inhibits the elongation of cells on that side, allowing the cells on the upper side to continue elongating.
Directional Growth: As a result, the upper side grows more than the lower side, causing the root to bend downwards. This behavior ensures that roots grow towards gravity, which is essential for the plant's stability and nutrient access.

Photograph A shows the root of a plant when it was positioned horizontally - Edexcel - GCSE Biology - Question 3 - 2014 - Paper 1

Worked Solution & Example Answer:Photograph A shows the root of a plant when it was positioned horizontally - Edexcel - GCSE Biology - Question 3 - 2014 - Paper 1

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

Explain how this change in root growth has occurred.

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