Thigmomorphogenesis

Thigmomorphogenesis is the response by plants to mechanical sensation (touch) by altering their growth patterns. In the wild, these patterns can be evinced by wind, raindrops, and rubbing by passing animals.

M.J. Jaffe discovered in the 1970s that regular rubbing of bending of stems inhibits their elongation and stimulates their radial expansion, resulting in shorter, stockier plants.

Growth responses are caused by changes in gene expression. This is likely related to the calcium-binding protein calmodulin, suggesting Ca^{2+ involvement in mediating growth responses.}