Question 1
Unit 5 style
A seed that needs light to germinate is exposed to a brief flash of red light, followed immediately by a brief flash of far-red light. What happens to the phytochrome and to germination?
- Pr is converted to Pfr and the seed germinates
- Pfr is converted to Pr and the seed does not germinate
- Pr remains unchanged and the seed does not germinate
- Pfr remains unchanged and the seed germinates
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Question 2
Unit 5 style
The table shows the results of an investigation into flowering in a short-day plant kept in a 16-hour night. Explain the results for treatments 2 and 3.
| Treatment | Light given in the night | Flowering |
|---|---|---|
| 1 | None (continuous darkness) | Yes |
| 2 | 5-minute flash of red light | No |
| 3 | 5-minute flash of red light, then 5-minute flash of far-red light | Yes |
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Question 3
Unit 5 style
Explain how auxin causes a shoot to grow towards the light.
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Question 4
Unit 5 style
Explain how gibberellin affects transcription in a germinating barley grain.
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Question 5
Unit 6 style
Describe how you would investigate the production of amylase in germinating barley grains, including the controls you would use.
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Question 6
Unit 6 style
In core practical 18, the diameters of the clear zones around three embryo halves were measured. Calculate the mean area of the clear zone, in mm², to 3 significant figures.
| Grain half | Diameter of clear zone / mm |
|---|---|
| 1 | 10 |
| 2 | 12 |
| 3 | 14 |
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Question 7
Unit 6 style
A student placed boiled embryo halves on a starch agar plate as a control. Explain why this control was needed and what result would be expected.
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Question 8
Unit 5 style
Explain how a root grows downwards in response to gravity.