Plant responses

The seedlings are a model. The bend angles (0–32°), the lengths (20–30 mm) and the curves of the mustard seedlings are typical values, not one class’s measurements.

Each pot has five seedlings, and only the marked one in the middle (the red tie) is measured. In a real investigation you would measure all five and work out a mean.

The box and the light-proof cover are drawn with their fronts cut away, so that you can see inside. Real ones are closed, apart from the slit in the box.

Each day is sped up into a few seconds.

(Supplement) The orange dots in the lens show where the auxin is: a picture of its concentration, not molecules. Auxin cannot be seen.

With reduced motion each process is shown at one moment and then at its end.