Plant Hormones (AQA GCSE Biology)

Exam Questions

2 hours14 questions
1a1 mark

Draw a ring around the correct answer to complete the sentence.

Plants grow in the right direction due to the action of

  enzymes.

  hormones.

  mitosis.

1b1 mark

What is phototropism in plants?

  • Growth due to photosynthesis

  • Growth inhibited by light

  • Growth stimulated by temperature

  • Growth stimulated by light

1c1 mark

Plant roots respond to gravity by growing downwards.

What is this response called?

  • Positive gravitropism

  • Negative geotropism

  • Positive phototropism

  • Negative gravitropism

1d1 mark

A plant is grown near a fixed light source.

The plant is then rotated by 180· as shown in Figure 1.

Figure 1

plant-growth

Predict the direction of growth of the plant shoots over the next 48 hours.

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2a1 mark

Name the plant hormone responsible for both phototropism and gravitropism.

2b1 mark

What effect would positive gravitropism have on a plant?

  • Roots would grow towards gravity

  • Roots would grow away from gravity

  • Shoots would grow away from gravity

  • Shoots would grow sideways

2c1 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 2. The apparatus was then placed in a darkened room.

Figure 2

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

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

14--image-7---plant-growth-1
  • Option A

  • Option B

  • Option C

  • Option D

2d1 mark

Figure 3 represents a plant shoot growing, it is illuminated from the side.

Figure 3

q6_9-3_growth_in_plants_ib_biology_hl_mcqq6_9-3_growth_in_plants_ib_biology_hl_mcq-1

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

plants
  • Option A

  • Option B

  • Option C

  • Option D

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3a1 mark

What happens to the cells in plant shoots in response to auxins?

  • The cell cycle is stopped.

  • Mitosis is increased. 

  • Shorten.

  • Elongate.

3b3 marks

Complete the sentence.

Choose the answer from the box

Towards         Decreases         Phototropism          Grow          Away from          Shade         Water         Light energy     Geotropism          Light          Increases

__________ is beneficial for plants because they can grow __________  the __________ and absorb more __________ which __________ photosynthesis.

3c2 marks

Figure 4 shows different parts of the plant and a number of responses.

Figure 4

part-of-plants-responce

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

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4a1 mark

Higher Tier Only

Which gas acts as a plant hormone?

  • Ethane

  • Methane

  • Carbon Dioxide

  • Ethene

4b2 marks

Higher Tier Only

Figure 6 shows three different hormones and their potential functions within the plant.

Figure 5

plant-hormones-1

Draw one line from each hormone to its potential use.

4c1 mark

Higher Tier Only

A gardener wishes to remove all the dandelions (a type of weed) from their lawn without damaging the grass. 

They started to pick the dandelions out by hand but it was taking too long, so they purchased a selective weedkiller which contained a synthetic plant hormone.

Which hormone would most likely be in the weedkiller?

  • Oestrogen

  • Auxin

  • Gibberellin

  • Ethene

4d1 mark

Higher Tier Only

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 6.

Figure 6

plant-treatment

What conclusion can the scientist make about gibberellins?

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1a1 mark

Plants respond to stimuli such as light and gravity.

What is the name of a plant growth response to light?

1b3 marks

Describe the biological mechanism that results in the shoot bending towards the light.

1c2 marks

Higher Tier Only

Auxins have multiple uses amongst gardeners, including use as a naturally derived weedkiller.

Give one other use gardeners might have for auxins

1d4 marks

Higher Tier Only

Some gardeners use synthetic plant hormones as weedkillers.

Synthetic plant hormones behave in a similar way to auxins.

Evaluate the use of these hormones as weedkillers.

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2a2 marks

A group of students investigated control and coordination of growth in plants.

They planted a bean seed in a box filled with moist soil. After the seed germinated, the box was turned onto its side and placed in a dark room.

Figure 1 illustrates their experiment.

Figure 1

FLJM3riR_tropisms-in-plants-2a

Describe the expected appearance of the seed 3 days later.

2b5 marks

Explain the role of auxins in coordinating the response of seeds in this experiment.

2c2 marks

Suggest a suitable control for the investigation detailed in 2(a) and explain why it is necessary.

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3a1 mark

When a seed germinates, the developing root grows downwards towards gravity and the developing shoot grows away from gravity.

These effects are controlled plant hormones called auxins.

Name this type of plant response to gravity.

3b3 marks

Suggest why this growth response in developing roots and shoots is important.

3c4 marks

Higher Tier Only

Another important plant hormone is ethene.

Ethene is the most widely produced organic compound in the world. It is used in the manufacture of plastics and by the food industry.

Explain why ethene is widely used in the food industry.

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4a4 marks

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

Figure 1 shows part of the set-up of their experiment.

Figure 1

gravitropism-4agravitropism-4a

This is part of the method they planned to use:

  • Measure the length of the root 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' teacher told them that their method was incomplete and that they needed to set up a control experiment (Apparatus B) for comparison.

Describe how a suitable control could be set up so that the students could improve their investigation.

4b3 marks

Why was it important that the seedlings in the experiment were placed into a dark room?

4c4 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 Table 1 below. The table is incomplete.

Complete the table to calculate the mean change in length for the bean seedlings in Apparatus A and Apparatus B.

Table 1

seedlings-q4c
4d4 marks

Figure 2 shows the appearance of the seedlings at the end of the 3 days.

Figure 2

seedlings-4d

A plant hormone, made in the tip of the root, diffuses from the tip into the tissues of the root.

Explain how the hormone causes the appearance of the seedlings in Figure 2. 

You should refer to both seedlings A and B in your answer.

4e2 marks

Higher Tier Only

Plant hormones are used in horticulture to control plant growth.

Draw one line from each plant hormone to its correct use.

plant-hormones-4e

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5a6 marks

A group of students were given a number of young plant shoots and some powdered auxin.

Describe how the students could use these items to demonstrate how auxins cause shoots to grow towards a light stimulus.

5b2 marks

Figure 1 shows a developing seedling.

Figure 1

tropisms-in-plants-5b

Identify which letter represents the region which shows positive geotropism and explain why this is important for a developing seedling.

5c3 marks

Higher Tier Only

Describe three commercial uses of gibberellins for the food industry.

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1a6 marks

Explain the effect that auxins have on the cells in shoot tips.

1b3 marks

Explain why hormonal effects on the cells in shoot tips is beneficial for the plant.

1c2 marks

A young seedling, growing in a forest was knocked over by animal activity.

Figure 1 shows how the plant grew after being knocked over.

Figure 1

plant-in-soil

Identify the stimulus and the response in Figure 1 (including its direction).

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2a3 marks

Describe the effect phototropism has on the growth of plant roots.

2b6 marks

In the late 1800s, Charles Darwin performed an experiment where he grew maize seedlings in the dark, in a horizontal orientation. Half of the seedlings had the root tip removed (A), the other half of the seedlings were left intact (B). The results of his investigation are shown in Figure 2.

Figure 2

roots

Explain what these results demonstrate for each experiment.

2c4 marks

Figure 3 represents a plant shoot growing, it is illuminated from the side.

Figure 3

q6_9-3_growth_in_plants_ib_biology_hl_mcqq6_9-3_growth_in_plants_ib_biology_hl_mcq-1

Draw an annotated diagram showing accumulation of auxins in response to light and how the shoot tip will grow.

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3a1 mark

Which method of movement most likely explains how auxins travel to other parts of the plant shoot or root?

  • Osmosis

  • Active transport

  • Diffusion

  • Mass flow in the phloem

3b4 marks

Higher Tier Only

In UK supermarkets, bananas are usually in perfect condition even though they have been imported via ships from countries with tropical climates.

Describe how plant hormones can be used to ensure bananas arrive in perfect condition.

3c6 marks

Higher Tier Only

Read the following two statements:

During the Vietnam war, the U.S. military used a selective herbicide commonly known as called Agent Orange to destroy agricultural crops and jungle foliage in order to limit the areas of cover of their opponents. Agent Orange contained a synthetic plant auxin in addition to dioxin, a highly toxic compound, which is believed to have caused major health problems for exposed individuals.

In agriculture, auxins are used to promote root development, flowering, and fruit development and generally increase yields. Other uses for auxins in agriculture include preventing pre-harvest dropping of fruits. 

Evaluate the use of artificial auxins.

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4a
Sme Calculator
4 marks

Higher Tier Only

A company called SME agrochemicals were trailing a novel plant hormone selective herbicide in order to be able to register the product for commercial use. The agrochemical, named SME roundup ®, showed broad spectrum efficacy against dicot weeds in cereal crops. During a trial, winter wheat was grown alongside the broad leafed 'Yellow hawkweed' Hieracium pratense over four testing plots of 1 m2 in size and different concentrations of SME roundup were applied. The only data captured was the number of weeds, two weeks post application. The results, are shown in Table 1.

Table 1

Application rate of SME roundup (mg/m2)

Average number of Hieracium pratense plants per plot

Total Efficacy (%)

0

100

 

100

63

 

500

3

 

1000

2

  1.  

Calculate the total percentage efficacy for each application rate.

Use the following equation:

percent sign space E f f i c a c y space equals space fraction numerator M subscript 1 minus M subscript 2 over denominator M subscript 1 end fraction cross times space 100

Where 

M= Weed number on untreated plot

M= Weed number on treated plot

4b3 marks

Higher Tier Only

During early lab-based trials, SME Agrochemicals suggested that the recommended application rate for the herbicide SME roundup ®  should be 1000 mg/m2 Explain why this was an incorrect assumption (Use the information from part a to support your answer).

4c4 marks

Higher Tier Only

SME Roundup ® is marketed as a selective herbicide that can be used for cereal crops such as wheat and barley.

Explain how this product acts as a selective herbicide

4d6 marks

Higher Tier Only

When applying for regulatory approval to be able to distribute and sell SME roundup ® , the regulatory authorities initially rejected the application stating that the trials were not sufficient. 

Suggest how the trials could be improved.

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5a3 marks

Higher Tier Only

In addition to auxins, gibberellins, and ethene, there are a number of other groups of plant hormones that control many aspects of plant growth. When plant roots sense a water shortage in the soil, the plant hormone abscisic acid is released and binds to receptor proteins in guard cells.  Suggest how abscisic acid may help plants in drought conditions. 

5b3 marks

A student wanted to investigate the mechanism of phototropism in plants. They set up their investigation as shown in Figure 4.

Figure 4

shoot-tips

In experiment A - the shoot tip was left untreated (as a control).

In experiment B - 2mm was removed from the growing end of the shoot tip.

In experiment C - The shoot tips were covered with caps of aluminium foil.

The shoot tips were initially measured and left for 48 hours next to a unidirectional light source.

Predict what differences in growth occurred in each experiment after 48 hours.

5c6 marks

Explain why the plant shoots grow differently in experiments B and C.

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