A scientist investigated which region of a shoot detects the direction of light.
Narrow beams of light were directed separately at the shoot tip and the growing region immediately behind the tip. Black screens prevented light intended for one region from reaching the other region. The screens did not touch the shoots or restrict growth, and all shoot tips remained attached throughout the investigation.
Each region received the same total light intensity in every group. Light reached a region from the left, from the right, or equally from both sides.
A positive angle shows bending towards the left. A negative angle shows bending towards the right.
| Group | Direction of light reaching the shoot tip | Direction of light reaching the growing region | Mean change in angle after 12 hours |
|---|---|---|---|
| A | from the left | equally from both sides | +17° |
| B | from the right | equally from both sides | −16° |
| C | equally from both sides | from the left | +1° |
| D | equally from both sides | from the right | −1° |
Which conclusion is best supported by the results?
the growing region detects the direction of light, even when the shoot tip receives light equally from both sides
either the shoot tip or the growing region can detect the direction of light independently
both the shoot tip and the growing region must receive one-sided light for the shoot to bend
the shoot tip detects the direction of light, even when the growing region receives light equally from both sides
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.