nastic movements

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nastic movements Movements of plant organs in response to external stimuli that are independent of the direction of the stimuli. Examples are the opening of crocus and tulip flowers in response to a rise in temperature (thermonasty), the opening of evening primrose flowers at night (photonasty), and the folding up and drooping of leaves of the sensitive plant (Mimosa pudica) when lightly touched (haptonasty). Compare tropism. See also nyctinasty.