Seismonasty

Seismonasty is a non-directional plant movement triggered by mechanical stimulation, especially vibrations transmitted through the growing medium such as ground-borne seismic waves. It is a form of nastic movement, meaning the response is not oriented toward or away from the stimulus, but rather occurs in a more or less uniform way regardless of direction.

Physiologically, seismonastic movements are produced by rapid changes in turgor pressure within specialized motor tissues at the base of leaves, known as pulvini. This involves swift ion fluxes, osmotic water shifts, and coordinated electrical signals that cause leaves or leaflets to fold, droop, or reorient. The response is typically reversible, developing within seconds to minutes and relaxing after the disturbance ends.

Occurrences and scope vary among plant species. Seismonasty is discussed in the context of mechanoresponsive behavior in several plants with active pulvini, including some sensitive legumes, where vibrations from sources such as footsteps, wind, or earthquakes can induce leaf movements even in the absence of direct touch.

Relation to related concepts: seismonasty is often distinguished from thigmonasty, which is the movement in response to direct contact or touch. Both are mechanical nastic responses, but seismonasty emphasizes vibration-based stimuli rather than tactile stimulation.

Ecological significance is not fully resolved. Proposed roles include reducing damage from abrupt mechanical disturbance, altering leaf exposure after disturbance, or serving as a general mechanosensory response. Ongoing research aims to clarify the sensory pathways and ecological function of seismonastic movements.