A seed germinates inside a fallen hollow log. At first, both the shoot and the root grow horizontally along the length of the log. Very little light reaches the plant, so light does not provide a directional stimulus.
A scientist measures the mean length of cells on the upper and lower sides of the shoot and root.
| Organ | Side | Mean cell length at 0 hours / µm | Mean cell length at 8 hours / µm |
|---|---|---|---|
| shoot | upper | 120 | 150 |
| shoot | lower | 120 | 190 |
| root | upper | 120 | 175 |
| root | lower | 120 | 135 |
Explain how auxin caused the results shown in the table and predict the direction of growth of the shoot and the root.
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.