Nyctitropism

Part of speech: noun

Definitions

1. The tendency of certain plant leaves or petals to fold or move downward at night and reopen during the day in response to light changes
2. The adaptive behavior in some plants to close their leaves or flowers during the evening and open them again at sunrise based on light conditions
3. The phenomenon whereby specific plants exhibit movement by closing leaves or flowers at night and re-opening during daylight in reaction to light variation

Etymology: Nyctitropism is a technical coinage, built in the modern scientific era from Greek parts rather than handed down from antiquity. Its first element, "nyct-", comes from the Greek "nyx", meaning "night", the same root that gives English "nocturnal" its sense of night activity. The middle element is a connecting vowel, and the ending "-tropism" comes from the Greek "tropos", "turning", which botanists use for a plant's growth or movement in response to a stimulus. Joined together, the word describes a plant that turns or moves in response to night. The word therefore names a movement rather than a thing: the folding of leaves or petals as light fades, and their reopening at dawn. The ancient Greeks had the root "nyx" and the root "tropos" as ordinary words, but they never combined them into this term. Its meaning comes entirely from the way the two parts were assembled by later scientists to describe a plant behaviour they had observed and needed to name.