A grower uses transparent plant-growth chambers. Each chamber has a water outlet in its left-hand wall. New roots that enter the outlet may block it.
Light panels can shine through the walls onto the roots. The shoots are separated from the light panels by an opaque cover.
The grower tested three positions for a light panel.
| Position of light panel | Mean percentage of new roots entering the outlet |
|---|---|
| No side light | 46 |
| Left-hand side, beside the outlet | 9 |
| Right-hand side, opposite the outlet | 78 |
Calculate the percentage decrease in roots entering the outlet when a light panel was placed beside the outlet, compared with no side light.
Give your answer to 3 significant figures.
The grower concluded:
‘Putting a light panel beside the outlet makes roots grow away from the outlet and prevents every root from entering it.’
Evaluate the grower’s conclusion.
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.