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Plants don't always keep their leaves in exactly the same position. Certain plants display nyctinastic movements, in which leaves or leaflets change position in response to the day-night cycle.
The movement is controlled by changes in cells at specialized areas called pulvini. A familiar example is the prayer plant, whose leaves can appear differently positioned during the day and night.
These movements don't require muscles or a nervous system. Plants can therefore produce visible daily movements using changes in water pressure and cell expansion.
© Missouri Botanical Garden