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5.4 Plant hormones

5.4 Plant hormones

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Question 13

A student investigates the effect of auxin (indole-3-acetic acid, or IAA) concentration on the elongation of plant coleoptile segments. They prepare three test tubes with different concentrations of IAA and place a set of young wheat coleoptiles in each:

  • Tube 1: Placed in a shaking water bath at 25 °C. This tube contains 15 coleoptile segments in a 10 ppm IAA solution.
  • Tube 2: Placed in a refrigerator at 4 °C. This tube contains 5 coleoptile segments in a 1 ppm IAA solution.
  • Tube 3: Placed on a cold laboratory windowsill (approximately 15 °C). This tube contains 15 coleoptile segments in distilled water (0 ppm IAA).

Which two of the following improvements should the student make to ensure a valid comparison of the effect of IAA concentration?

  • A: Use the same number of coleoptile segments of identical initial length in each test tube.
  • B: Add nutrient solution only to Tube 2 to help the segments grow at the lower hormone concentration.
  • C: Ensure all three test tubes are incubated at the same constant temperature.
  • D: Use a different species of cereal crop for each test tube to test the generalizability of the response.
  • E: Add more volume of solution to Tube 1 because it has the highest concentration 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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