A researcher germinated mustard seeds on damp cotton wool. When the shoots had started to grow, two Petri dishes were placed inside identical light-proof boxes.
Dish P remained stationary with the shoots initially horizontal. Dish Q was attached to a clinostat that slowly rotated the dish.
The researcher marked sections of equal length just behind the tip of one shoot in each dish. The results are shown in the table.
| Dish | Movement | Side measured | Length at start / mm | Length after 18 hours / mm |
|---|---|---|---|---|
| P | stationary | upper | 10.0 | 13.2 |
| P | stationary | lower | 10.0 | 18.6 |
| Q | slowly rotating | A | 10.0 | 15.9 |
| Q | slowly rotating | B | 10.0 | 16.0 |
Calculate the difference between the increases in length of the lower and upper sides of the shoot in dish P.
Explain why the shoot in dish P bends upwards.
Explain why the shoot in dish Q grows almost straight.
87 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.