CAIE A Level Biology 9700 · Control and coordination
Table 1 shows the effect of auxin on the elongation of stem segments incubated in buffer at pH 7 for 2 hours.
Table 1
| Treatment | Mean increase in length / mm |
|---|---|
| Control (buffer only) | 0.3 |
| Buffer + 1 µM auxin | 1.2 |
(a) Outline the mechanism by which auxin stimulates cell elongation in stems, using the data in Table 1 to support your answer.
(b) Outline the mechanism of the rapid closure of the Venus fly trap.
(c) Outline the role of gibberellin in the germination of barley.
7 marks, so the mark scheme is looking for about 7 separate creditworthy points. Making the same point twice in different words earns it once.
Outline means: Give the main points briefly. Less detail than describe, but every key step has to be there. One short line per step, in order. The marks are for coverage, not depth.
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