\Pho*tot"o*nus\, n. (Physiol.)
An irritable condition of protoplasm, resulting in movement,
due to a certain intensity of light. -- {Pho`to*ton"ic}, a.

\Pho*tot"o*nus\, n. [NL. See {Photo-}, and {Tone}.]
(Bot.)
A motile condition in plants resulting from exposure to
light. -- {Pho`to*ton"ic}, a.