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5.4 Plant hormones

5.4 Plant hormones

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Question 11

A group of students investigates the effect of different concentrations of indole-3-acetic acid (IAA) on the elongation of oat coleoptile segments. They set up three experimental treatments:

  • Treatment P: Coleoptiles incubated in a 10−6 mol dm−310^{-6}\text{ mol dm}^{-3}10−6 mol dm−3 IAA solution. This treatment contains 8 coleoptile segments with an initial length of 10 mm, incubated at 25∘C25^\circ\text{C}25∘C in a shaking water bath for 24 hours.
  • Treatment Q: Coleoptiles incubated in distilled water (0 mol dm-3 IAA). This treatment contains 8 coleoptile segments with an initial length of 10 mm, incubated at 15∘C15^\circ\text{C}15∘C on a static lab bench for 24 hours.
  • Treatment R: Coleoptiles incubated in a 10−2 mol dm−310^{-2}\text{ mol dm}^{-3}10−2 mol dm−3 IAA solution. This treatment contains 3 coleoptile segments with an initial length of 15 mm, incubated at 25∘C25^\circ\text{C}25∘C in a shaking water bath for 12 hours.

Which two of the following modifications should the students make to ensure a valid comparison of the effect of IAA concentration on coleoptile elongation?

  • A: Use the same initial length (10 mm), the same number of segments (8), and the same incubation time (24 hours) for all three treatments.
  • B: Keep all three treatments at the same constant temperature of 25∘C25^\circ\text{C}25∘C in shaking water baths.
  • C: Use a different species of cereal crop for each treatment to increase the reliability of the study.
  • D: Increase the volume of IAA solution in Treatment R to compensate for the longer starting length of the coleoptiles.
  • E: Add a gibberellin solution to Treatment Q to stimulate elongation in the absence of IAA.
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Markscheme

5.4 Plant hormones Questions

  1. GCSE
  2. /Biology
  3. /5.4 Plant hormones

59 exam-style questions on AQA GCSE Biology 5.4 Plant hormones, covering 5.4.1 Control and coordination and 5.4.2 Use of plant hormones (HT only). Each one has a worked solution and a mark scheme showing where the marks go.

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