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Chemical control in plants: Edexcel A‑Level Biology B questions

Every Edexcel A-Level Biology B exam question on 9.3 Chemical control in plants, 2016–2025, with its mark scheme and examiner’s report.

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1,826 questions

  1. Q5(a)

    June 2025 · Paper 2

    1 mark9.3 Chemical control in plants
    The whole paper ↗
    June 2025 Paper 2, question 5(a): Which of the following are functions of auxin? 1. inhibiting lateral shoot growth 2. stimulating the elongation of cells in plant stems 3. stimulating flowering

  2. Q5(b)(i)

    June 2025 · Paper 2

    1 mark9.3 Chemical control in plants
    The whole paper ↗
    June 2025 Paper 2, question 5(b)(i): Calculate the percentage increase in mean root length when given an auxin concentration of 10–4 μmol dm–3 compared with no auxin. Give your answer to the neares

  3. Q5(b)(ii)

    June 2025 · Paper 2

    4 marks9.3 Chemical control in plants
    The whole paper ↗
    June 2025 Paper 2, question 5(b)(ii): Analyse the data to discuss the effects of auxin on the growth of wheat seedlings. (4)

  4. Q2(b)

    June 2024 · Paper 2

    1 mark9.3 Chemical control in plants
    The whole paper ↗
    June 2024 Paper 2, question 2(b): Cereal grains, such as barley, start to germinate after exposure to water. Which growth substance is released by the embryo during germination to stimulate enzy

  5. Q4(a)(i)

    June 2023 · Paper 3

    2 marks9.3 Chemical control in plants
    The whole paper ↗
    June 2023 Paper 3, question 4(a)(i): The stock solution of gibberellin has a concentration of 1 g per dm3. Describe how you would dilute this stock solution to give a test solution of 300 µg per dm

  6. Q4(a)(ii)

    June 2023 · Paper 3

    2 marks9.3 Chemical control in plants
    The whole paper ↗
    June 2023 Paper 3, question 4(a)(ii): State one reason for each of the following steps in the method. (2) Step 2 Step 3

  7. Q4(b)(i)

    June 2023 · Paper 3

    2 marks9.3 Chemical control in plants
    The whole paper ↗
    June 2023 Paper 3, question 4(b)(i): Describe how you would control one named abiotic variable and one named biotic variable. (2) Abiotic Biotic

  8. Q4(b)(ii)

    June 2023 · Paper 3

    3 marks9.3 Chemical control in plants
    The whole paper ↗
    June 2023 Paper 3, question 4(b)(ii): Describe three further improvements to the method outlined in parts (a) and (b) that would improve the validity of the results. (3)

  9. Q2(a)(i)

    June 2022 · Paper 2

    1 mark9.3 Chemical control in plants
    The whole paper ↗
    June 2022 Paper 2, question 2(a)(i): Which row of the table shows the concentrations required for the fastest growth of lateral buds? (1) Auxin concentration Cytokinin concentration A high high B h

  10. Q2(b)

    June 2022 · Paper 2

    4 marks9.3 Chemical control in plants
    The whole paper ↗
    June 2022 Paper 2, question 2(b): Phytochrome is involved in the germination of seeds. The effect of red (R) light and far-red (FR) light on the germination of lettuce seeds was investigated. A

  11. Q9(a)

    November 2021 · Paper 2

    3 marks9.3 Chemical control in plants
    The whole paper ↗
    November 2021 Paper 2, question 9(a): Explain how auxins and cytokinins control the growth of lateral buds. (3)

  12. Q9(c)(i)

    November 2021 · Paper 2

    2 marks9.3 Chemical control in plants
    The whole paper ↗
    November 2021 Paper 2, question 9(c)(i): Calculate the maximum rate of elongation of the cell. (2) Answer

  13. Q9(c)(ii)

    November 2021 · Paper 2

    3 marks9.3 Chemical control in plants
    The whole paper ↗
    November 2021 Paper 2, question 9(c)(ii): Expansin is a protein located in cell walls. Expansin disrupts hydrogen bonds and ionic bonds of molecules in the cell wall. Deduce a mechanism by which auxin a

  14. Q5(c)

    October 2020 · Paper 3

    5 marks9.3 Chemical control in plants
    The whole paper ↗
    October 2020 Paper 3, question 5(c): Global warming may cause sea levels to rise and salty seawater to flood land used for growing crops. A student read that salt (NaCl) inhibits gibberellin synthe

  15. Q5(a)

    June 2019 · Paper 2

    1 mark9.3 Chemical control in plants
    Mark scheme (PDF)
    The whole paper ↗
    June 2019 Paper 2, question 5(a): Which of the following effects are caused by auxin? (1) 1 cell elongation 2 suppression of lateral bud growth 3 photomorphogenesis A 1 and 2 B 1 and 3 C 2 and 3

  16. Q5(b)

    June 2019 · Paper 2

    6 marks9.3 Chemical control in plants
    The whole paper ↗
    June 2019 Paper 2, question 5(b): The effect of day length on flowering in two species of plants, Kalanchoe and Sedum, was investigated. The effect of different periods of light and darkness and

  17. Q1(b)

    June 2017 · Paper 2

    3 marks9.3 Chemical control in plants
    The whole paper ↗
    June 2017 Paper 2, question 1(b): A scientist investigated apical dominance in plants. In experiment 1, the shoot tips were cut off and the growth of lateral shoots assessed. This was repeated i

  18. Q9(d)(ii)

    June 2017 · Paper 3

    2 marks9.3 Chemical control in plants
    The whole paper ↗
    June 2017 Paper 3, question 9(d)(ii): Explain why plants grown from these germinating seeds may not flower at the same time of year as they would have done in their country of origin. (2)
All 18 questions on Chemical control in plants, as a list
  1. June 2025, Paper 2, Q5(a) (1 mark): Which of the following are functions of auxin? 1. inhibiting lateral shoot growth 2. stimulating the elongation of cells in plant stems 3. stimulating flowering
  2. June 2025, Paper 2, Q5(b)(i) (1 mark): Calculate the percentage increase in mean root length when given an auxin concentration of 10–4 μmol dm–3 compared with no auxin. Give your answer to the neares
  3. June 2025, Paper 2, Q5(b)(ii) (4 marks): Analyse the data to discuss the effects of auxin on the growth of wheat seedlings. (4)
  4. June 2024, Paper 2, Q2(b) (1 mark): Cereal grains, such as barley, start to germinate after exposure to water. Which growth substance is released by the embryo during germination to stimulate enzy
  5. June 2023, Paper 3, Q4(a)(i) (2 marks): The stock solution of gibberellin has a concentration of 1 g per dm3. Describe how you would dilute this stock solution to give a test solution of 300 µg per dm
  6. June 2023, Paper 3, Q4(a)(ii) (2 marks): State one reason for each of the following steps in the method. (2) Step 2 Step 3
  7. June 2023, Paper 3, Q4(b)(i) (2 marks): Describe how you would control one named abiotic variable and one named biotic variable. (2) Abiotic Biotic
  8. June 2023, Paper 3, Q4(b)(ii) (3 marks): Describe three further improvements to the method outlined in parts (a) and (b) that would improve the validity of the results. (3)
  9. June 2022, Paper 2, Q2(a)(i) (1 mark): Which row of the table shows the concentrations required for the fastest growth of lateral buds? (1) Auxin concentration Cytokinin concentration A high high B h
  10. June 2022, Paper 2, Q2(b) (4 marks): Phytochrome is involved in the germination of seeds. The effect of red (R) light and far-red (FR) light on the germination of lettuce seeds was investigated. A
  11. November 2021, Paper 2, Q9(a) (3 marks): Explain how auxins and cytokinins control the growth of lateral buds. (3)
  12. November 2021, Paper 2, Q9(c)(i) (2 marks): Calculate the maximum rate of elongation of the cell. (2) Answer
  13. November 2021, Paper 2, Q9(c)(ii) (3 marks): Expansin is a protein located in cell walls. Expansin disrupts hydrogen bonds and ionic bonds of molecules in the cell wall. Deduce a mechanism by which auxin a
  14. October 2020, Paper 3, Q5(c) (5 marks): Global warming may cause sea levels to rise and salty seawater to flood land used for growing crops. A student read that salt (NaCl) inhibits gibberellin synthe
  15. June 2019, Paper 2, Q5(a) (1 mark): Which of the following effects are caused by auxin? (1) 1 cell elongation 2 suppression of lateral bud growth 3 photomorphogenesis A 1 and 2 B 1 and 3 C 2 and 3
  16. June 2019, Paper 2, Q5(b) (6 marks): The effect of day length on flowering in two species of plants, Kalanchoe and Sedum, was investigated. The effect of different periods of light and darkness and
  17. June 2017, Paper 2, Q1(b) (3 marks): A scientist investigated apical dominance in plants. In experiment 1, the shoot tips were cut off and the growth of lateral shoots assessed. This was repeated i
  18. June 2017, Paper 3, Q9(d)(ii) (2 marks): Explain why plants grown from these germinating seeds may not flower at the same time of year as they would have done in their country of origin. (2)

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