Edexcel GCSE Biology

Topic Questions

6.4 Plant Hormones

1a
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3 marks

Complete the sentence.

Choose the answer from the box

Towards         Decreases         Phototropism          Grow          Away from          Shade         Water         

Away from light     Geotropism         Towards light          Increases     Light Energy


__________ is beneficial for plants because it means that plant shoots can grow __________  __________ . This allows chloroplasts to absorb more __________ which __________ photosynthesis.

1b
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2 marks

Figure 1 shows different parts of the plant and a number of responses.

part-of-plants-responce

Figure 1

Draw one line from each plant part to the correct response.

1c
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2 marks

Figure 2 shows three different hormones and their potential functions within the plant.

plant-hormones-1

Figure 2
 

Draw one line from each hormone to its potential use.

1d
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1 mark

A scientist investigated the effects of gibberellins on flowering in plants.

The plants were grown in identical environmental conditions (light, temperature, water) but half the plants were treated with gibberellins.

The results are shown in Figure 3.

plant-treatment

Figure 3

What conclusion can the scientist make about gibberellins?

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2a
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1 mark

Name the plant hormone responsible for both phototropism and gravitropism.

2b
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1 mark

What effect do auxins have on plants?

  A Promotes growth in both the shoot and the root.
  B Inhibits growth in both the shoot and the root.
  C Promotes growth in the shoot but inhibits growth in the root.
  D Inhibits growth in the shoot and promotes growth in the root.

2c
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1 mark

A group of students set up an experiment to investigate plant growth.

They attached a plant pot to a machine called a clinostat so that it could be rotated slowly on its side as shown in Figure 1. The apparatus was then placed in a darkened room.

14--image-6---plant-1

Figure 1

Which of the following images would show the expected result of this experiment after two days?

14--image-7---plant-growth-1

2d
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1 mark

Figure 2 represents a plant shoot growing, it is illuminated from the side.

q6_9-3_growth_in_plants_ib_biology_hl_mcqq6_9-3_growth_in_plants_ib_biology_hl_mcq-1

Figure 2

Which of the following images best represents how auxins will start to accumulate in the shoot tip in response to light?

plants

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3a
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2 marks

A group of students wanted to investigate geotropism in bean seedling roots.

The set-up of their experiment is shown in the diagram below.

gravitropism-4agravitropism-4a

The students used the following method:

    • Measure the starting length of the roots of 5 bean seedlings
    • Pin the 5 bean seedlings to a cork mat as shown in Apparatus A
    • Place Apparatus A in a dark cupboard for 3 days
    • After 3 days, measure the length of the root in each seedling and make a drawing of each seedling

The students then set up Apparatus B in exactly the same way as Apparatus A, but used a clinostat to rotate the cork board constantly.

Explain the purpose of Apparatus B.

3b
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2 marks

The seedlings in the experiment in part (a) were placed in a dark room to remove the effect of light. This is a control variable.

State why this stage is necessary.

3c
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3 marks

The diagram below shows the appearance of the seedlings at the end of the 3 days.

seedlings-4d

Explain the appearance of the seedlings in the diagram.

3d
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2 marks

The students carried out their experiment using 10 bean seedlings split across two sets of apparatus; Apparatus A and Apparatus B (the control).

The results of the student’s investigation are shown in the table below.

  Apparatus A Apparatus B
Seedling number 1 2 3 4 5 1 2 3 4 5
Length of seedling on day 0 / mm 33 34 36 40 42 29 30 34 31 32
Length of seedling on day 2 / mm 45 35 48 53 56 41 43 44 44 43
Change in length / mm 12 1 12 13 14 12 13 10 13 11
Mean change in length / mm 12.75  

Calculate the mean change in length for the bean seedlings in Apparatus B.

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4a
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2 marks

Separate: Biology Only

Plants produce plant growth regulators similar to hormones in animals. 

State the role of auxins.

4b
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4 marks

Separate: Biology Only

Describe the coordination between phototropism and geotropism in guiding the growth of plant roots.

4c
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1 mark

Separate: Biology Only

Which of the following statements correctly defines the production of auxins in plants?

  A Auxins are produced only in response to external stimuli.
  B Auxins are continuously produced in the tips of shoots and roots as part of normal growth.
  C Auxins are exclusively produced in the presence of light.
  D Auxins are only produced when roots are exposed to gravity.
4d
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2 marks

Separate: Biology Only

Complete Table 1 by filling in the missing tropisms

Table 1

Tropism type Response to stimulus
Phototropism Bending towards light
Chemotropism  
  Bending towards/away from gravity

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5a
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1 mark

Separate: Biology Only

State one important factor that contributes to the successful development of clones after dipping plant tips in auxins (rooting powders). 

5b
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2 marks

Separate: Biology Only

(i)
Identify the hormone used for selective weed killers.

(1)

(ii)
List one potential challenge in the precise application of selective weedkillers in agriculture.

(1)

5c
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1 mark

Which of the following statements best describes the role of ethene in fruit ripening and its advantage for the fruit industry?

  A Ethene inhibits fruit ripening, preserving freshness
  B Ethene triggers enzyme release, promoting starch breakdown and ripening
  C Ethene accelerates fruit decay, reducing shelf life
  D Ethene has no impact on fruit ripening processes
5d
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2 marks

Separate: Biology Only

Identify two uses of gibberellins in agriculture.

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1a
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5 marks

Gravitropism is a plant growth response that causes roots to grow down towards the pull of gravity. Figure 1 shows two images of the same plant root, before and after it was left in the dark for three days. 

rOFKhSqj_1

Figure 1

(i)

Explain how this change in root growth has occurred. 

(3)

(ii)

Suggest the advantages of this response for the plant. 

(2)

1b
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3 marks

The same germinating seed produced a shoot. Complete the "after" diagram below showing how the shoot would respond to the stimulus of gravity if placed in the same position. 

Explain your answer. 

LutCHyg__2

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2a
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3 marks

Plants can respond to the stimulus of light and produce a growth response called phototropism. 

Explain how phototropism is controlled in plant shoots.

2b
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5 marks

Two students wanted to investigate the mechanism of phototropism in plants. They set up their investigation as shown in Figure 1

q2b_plant-hormones_edexcel_gcse_biology_sqFigure 1

(i)

State why it was necessary for the students to set up a control experiment.

(1)

(ii)

Explain the results of experiments 2-4 shown in Figure 1.

(4)

2c
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2 marks

Explain why this growth response is beneficial to plants. 

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3a
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3 marks

Higher Tier Only

Ethene is a plant hormone that stimulates the ripening of fruit. Figure 1 shows the effect of ethene concentration on the ripening of bananas after three days.

q3a_plant-hormones_edexcel_gcse_biology_sqFigure 1

(i)

Describe the effect of ethene on the ripening of bananas. 

(1)

(ii)

A supermarket purchases 1420 bananas.

Calculate how many of these bananas are likely to be ripe upon arrival, before treating with ethene.

(2) 

3b
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2 marks

Identify and explain which concentration of ethene would be most cost-effective for a supermarket to use when ripening bananas. 

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4a
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3 marks

Higher Tier Only

A gardener wanted to investigate the effect of a plant hormone weed killer on the growth of nettles in his field. He set up a trial to see which concentration of hormone would kill the most nettles. He counted the number of nettle plants in six 1 m2 areas of the field. He made five different concentrations of hormone weed killer solution and kept one area as a control with no hormone. He applied the solutions to the six different areas. After two weeks he counted the number of nettles in each area.

The results are shown in Figure 1.

screenshot-2022-04-28-180100

Figure 1

(i)

Give one variable the gardener should control when completing this trial. 

(1)

(ii)

Calculate the percentage decrease in the number of nettles when the concentration of weed killer hormone solution was 60 %. 

(2)

4b
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3 marks

State and explain the conclusion that the gardener can make, based on his trial. 

4c
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3 marks

In this experiment, the gardener observed that the nettles died but the grass surrounding them did not. 

Explain how plant hormones can act as selective weed killers.

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5a
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3 marks

Higher Tier Only

A scientist investigated the role of gibberellins in seed germination. They placed 20 cress seeds on agar jelly containing gibberellins and counted the number of seeds that had germinated after 5 days. Figure 1 shows the results.

BrILcXTv_5

Figure 1

Explain how the scientist could use a control to improve this investigation.

5b
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3 marks

Suggest how the scientist could vary their experiment in order to investigate how the concentration of gibberellin solution affects the number of seeds germinated. 

5c
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2 marks

State two other commercial uses of gibberellins, not including their role in germination.

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65 marks

Figure 1 shows an investigation into the growth of plant shoots.

Experiment 1:

The tip of a shoot was removed from the plant.

There was no growth in the shoot after 3 days.

q10a-1bio-2h-june18-qp-gcse-bio

Experiment 2:

The tip of a shoot was cut off and then placed back onto the shoot.

The shoot had grown 6 mm after 3 days.

q10a-1-1bio-2h-june18-qp-gcse-bio

Figure 1

(i)

Give one variable that must have been controlled for the plant shoot to grow vertically, as shown in experiment 2.

(1)

(ii)

State one conclusion that could be made based on these two experiments.

(1)

(iii)

Which plant hormone causes growth in the plant shoot?

(1)

  A auxin
  B ethene
  C gibberellin
  D chlorophyll

(iv)

Explain one way that this investigation could be improved.

(2)

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7a
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2 marks

Higher Tier Only

Commercial growers can use plant hormones to artificially ripen fruit and produce seedless fruit.

(i)

What is the name of the plant hormone used in fruit ripening?

(1)

  A auxin
  B gibberellin
  C sucrose
  D ethene

(ii)


Which plant hormone can commercial growers spray fruit with to produce seedless fruit?

(1)

  A auxin
  B gibberellin
  C sucrose
  D ethene
7b
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3 marks

Higher Tier Only

The effect of applying weed killer containing plant hormones to fields of wheat was investigated.

In field A, the weed killer was applied each year for five years.

In field B, no weed killer was applied for five years.

Each field was 1000 m2 and all other conditions remained the same.

The results are shown in Figure 1.

field wheat yield in kg per 100 m2
2015 2016 2017 2018 2019
A 54 52 48 49 50
B 32 28 34 33 34

Figure 1

Comment on the effect of using weed killer containing plant hormones in this investigation.

7c
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6 marks

Figure 2 shows a pot plant before it fell over and the same pot plant two weeks after it fell over.

fig-15-1bio-2h-nov2021-qp-gcse-bio

Figure 2

Explain how hormones in the roots and shoots of plants caused this directional growth.

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