In case you’ve ever wondered, thigmomorphogenesis is a good thing. The only reason it hasn’t caught on is because nobody can say it.
If you touch your seedlings, they’ll get stronger. In nature, seedlings are touched by rain, wind, passing animals, etc. It encourages them to toughen up, thicken up, and not be tall and spindly. That’s thigmomorphogenesis.
That’s probably more than you ever wanted to know about thigmomorphogenesis, but just in case you need more: Growth responses are caused by changes in gene expression. This is likely related to the calcium-binding protein calmodulin, suggesting Ca2+ involvement in mediating growth responses.