from The American Heritage® Dictionary of the English Language, 4th Edition

  • n. The tendency of the leaves of some plants to change their position at nightfall.

from Wiktionary, Creative Commons Attribution/Share-Alike License

  • n. Alternative term for nyctinasty

from the GNU version of the Collaborative International Dictionary of English

  • n. The tendency of certain plant organs, as leaves, to assume special “sleeping” positions or make curvatures under the influence of darkness. It is well illustrated in the leaflets of clover and other leguminous plants.

from The Century Dictionary and Cyclopedia

  • n. In botany, the habit of certain plants or parts of plants whereby they assume at nightfall, or just before, certain positions unlike those which they have maintained during the day; the “sleep” of plants.


Greek nux, nukt-, night; see nekw-t- in Indo-European roots + -tropism.
(American Heritage® Dictionary of the English Language, Fourth Edition)


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