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The Collaborative International Dictionary
Phototonic

Phototonus \Pho*tot"o*nus\, n. [NL. See Photo-, and Tone.]

  1. (Bot.) A motile condition in plants resulting from exposure to light. -- Pho`to*ton"ic, a.

  2. (Physiol.) An irritable condition of protoplasm, resulting in movement, due to a certain intensity of light. -- Pho`to*ton"ic, a.

Wiktionary
phototonic

a. Relating to phototonus.