You searched for: “nastic
nastic (adjective)
1. Plant movements in response to diffuse stimuli and to structural curvatures resulting from differential growth of opposite surfaces.
2. Relating to a response of a plant part; such as, growth or a loss of turgidity; to external stimuli that is independent of the direction of origin of such stimuli.
3. The movement or growth of cellular tissue on one surface more than on another one, as in the opening of petal or young leaves.

Movements are rapid, reversible responses to stimuli; such as, water, temperature, humidity, light, etc. Nastic movements occur as a result of changes in water pressure within specialized cells or differing rates of growth in parts of the plant.

Nastic movements are among a plant's more beautiful motions: a typical example is the opening of a flower. They are the result of differing responses of different parts of the plant structure to the same external stimulus (Scientific American).
The American Heritage Dictionary of Science by Robert K. Barnhart, Houghton Mifflin Company, Boston, 1986.
This entry is located in the following unit: nastic, -nastic; nasty, -nasty; -nastism + (page 1)
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(Greek: nastos, pressed close, crammed full; firm, solid)
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nastic movement
Movement of a flat plant part, oriented relative to the plant body and produced by a variety of stimuli that cause disproportioinate growth or increased turgor pressure in the tissues of one surface.

The opening and closing movements of many flowers, and the responses of leaves to changes of temperature and light, are externally directed, or paratonic, nastic movements. Specialized plants, such as the insectivorous sundew, move in response to the touch and chemical stimuli of captured insects.

Nastic movements are responses to stimuli that uniformly affect the plant or else elicit a uniform response regardless of the direction they come from, whereas tropisms are movements in response to stimuli coming from one direction; geotropism, for example, is the response to gravity. The distinction between nasticisms and tropisms is sometimes unclear.

—Modified excerpts from The Columbia Electronic Encyclopedia