Elater

An elater is a cell that is hygroscopic, and therefore will change shape in response to changes in moisture in the environment. Elaters come in a variety of forms, but are always associated with plant spores. In many plants that do not have seeds, they function in dispersing the spores to a new location. Mosses do not have elaters, but peristomes which change shape with changes in humidity or moisture to allow for a gradual release of spores.

This keyword could refer to multiple things. Here are some suggestions: