CAIE A Level Biology 9700 · Control and coordination
The table below shows the increase in length of coleoptile segments incubated in different conditions for 2 hours.
| Condition | Increase in length / mm |
|---|---|
| pH 7, no auxin | 2.0 |
| pH 7, auxin (10⁻⁶ M) | 4.5 |
| pH 5, no auxin | 8.0 |
| pH 5, auxin (10⁻⁶ M) | 8.5 |
Using the information in the table, outline the acid growth hypothesis of auxin action.
4 marks, so the mark scheme is looking for about 4 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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