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Here’s one from my volunteering on the Mary Gillham Archive Project. According to the Oxford Dictionary, nyctinasty is ‘the periodic movement of flowers or leaves caused by nightly changes in light intensity or temperature’, though I have also read that these movements, particularly the opening and closing of flowers, don’t always occur at night. When the weather is very dull due to thick cloud, or when the weather changes dramatically, as with the onset of a sudden storm, from a bright sunny day to a dark, grey, heavily cloudy sky, some flowers react by closing up. The word nyctinasty comes from the Greek and is a combination of nux or nukt meaning night and nastos meaning press or squeeze together.

171025 nyctinasty