Thigmotropism

In plant biology, thigmotropism is a directional growth movement which occurs as a mechanosensory response to a touch stimulus.

[2] Since growth is a complex developmental procedure, there are indeed many requirements (both biotic and abiotic) that are needed for both touch perception and a thigmotropic response to occur.

This triggers voltage-gated chloride and potassium channels to open and leads to an action potential that signals the perception of touch.

[5] Ethylene, another plant hormone, has also been shown to be an important regulator to the thigmotropic response in Arabidopsis thaliana roots.

While thigmotropic responses were historically thought to explain how lichen-forming fungi interact with algal cells during symbiosis formation, research has demonstrated this is not the case.

In a 2009 study with the lichen fungus Cladonia grayi, it was found that the fungus displays a distinctive growth response involving increased lateral branching only when encountering its compatible algal partner Asterochloris sp., but not when encountering glass beads of similar size or other photosynthetic organisms.

The fungus did adhere to and grow over various surfaces including glass beads, but without exhibiting the specialized branching pattern seen in successful lichen partnerships.