Definition of nastic in English:

nastic

adjective

Botany
  • (of the movement of plant parts) caused by an external stimulus but unaffected in direction by it.

    • ‘They may have a role in turgor regulation in response to salt and hyper-osmotic stresses, in nastic and gravitropic movements, in stomatal closure and in pollen tube elongation.’
    • ‘In biology, nastic refers to the natural movement of plants in response to changes in their environment, such as plants that track sunlight or that stiffen when watered.’

Origin

Early 20th century: from Greek nastos squeezed together (from nassein to press) + -ic.

Pronunciation:

nastic

/ˈnastɪk/