phototonusn.
/fəʊˈtɒtənəs/, U.S. /foʊˈtɑdənəs/ Biology. Now rare or disused.
A state of mobility or responsiveness induced or maintained in a plant, plant organ, or a cell by exposure to light.
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the world > plants > by nutrition or respiration > [noun] > sensitivity to stimuli
sensibility1784
sensitiveness1825
phototonus1875
tonotaxis1900
1875 A. W. Bennett & W. T. T. Dyer tr. J. von Sachs Text-bk. Bot. 678 The power of movement in plants is lost when they have remained in the dark for a considerable time..; in other words, they become rigid by long exposure to darkness..; the exposure to light must continue for a considerable time..before the motile condition which I have termed ‘Phototonus’ is restored.
1898 Science 11 Feb. 200/2 The remarkably delicate condition of phototonus [in Amoeba proteus] is..dependent upon a favorable quality of light and an optimum temperature.
1920 Webster's New Internat. Dict. Eng. Lang. Phototonus, 1. State of sensitiveness to light; the capability of performing curvatures under the tonic influence of light... 2. Irritable condition of protoplasm, resulting in movement, due to a certain intensity of light.
1936 Amer. Jrnl. Bot. 23 46/1 Sachs..called the normal motile condition in Mimosa..resulting from the alternation of day and night phototonus.
This entry has been updated (OED Third Edition, March 2006; most recently modified version published online March 2022).
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n.1875