A scientist fitted split collars around the growing regions of intact young shoots and roots. Each collar supplied a separate auxin solution to the left and right sides of the organ.
Before each collar was fitted, the scientist marked a 10.0 mm region on each side of the organ. The organs were held vertically and kept in darkness.
The table shows the mean final length of each marked region after 18 hours.
| Collar treatment | Auxin concentration supplied to left side in arbitrary units | Auxin concentration supplied to right side in arbitrary units | Final length of left side of shoot in mm\text{mm}mm | Final length of right side of shoot in mm\text{mm}mm | Final length of left side of root in mm\text{mm}mm | Final length of right side of root in mm\text{mm}mm |
|---|---|---|---|---|---|---|
| 1 | 0.5 | 0.5 | 11.4 | 11.4 | 10.9 | 10.9 |
| 2 | 1.0 | 0.5 | 11.9 | 11.4 | 10.6 | 10.9 |
| 3 | 2.0 | 0.5 | 12.4 | 11.4 | 10.2 | 10.9 |
Calculate the percentage increase in the length of the left side of the shoot in collar treatment 3.
Describe how increasing the auxin concentration supplied to the left side affected the difference between the final lengths of the two sides of the shoots and roots.
Use data from the table in your answer.
The scientist left the collars for treatment 3 in position for longer.
Explain why the shoot and the root would curve in opposite directions and predict the direction in which each organ would curve.
105 exam-style questions on Edexcel GCSE Biology 6.3 Plant hormones, covering 6.3.1 Plant hormones and tropisms and 6.3.2 Commercial uses of plant hormones. Each one has a worked solution and a mark scheme showing where the marks go.