Thigmotropism is an adaptive growth response shown by plants to mechanical stimuli, such as being touched. These responses involve biochemical, physiological and anatomical changes. Gardeners often say that plants grown entirely in a greenhouse can develop weak, floppy stems, while plants grown in the open air are tougher and less damaged by wind. These effects are a result of thigmotropism.

This project starter gives some ideas of ways that structural responses can be explored, suitable for Advanced Higher biology investigations or extended projects.