Seedlings growing on a windowsill will often bend towards the window as they respond to light - phototropism. But what exactly are the seedlings responding to? Which wavelengths of light stimulate the phototropic response?

The technique for this experiment helps students design an investigation to find out more about this tropic response. Students germinate seedlings in enclosed containers, with a coloured filter over the small hole allowing light in. Students predict which seedlings will demonstrate phototropism, and which will remain unaffected.

The students' sheet contains a number of suggestions for further experiments, while the  worksheet outlines the basic technique.

Download the student sheets and teachers' notes from the links on the right.