'Phototonus' definitions:

Definition of 'Phototonus'

From: GCIDE

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. [1913 Webster]
2. (Physiol.) An irritable condition of protoplasm, resulting in movement, due to a certain intensity of light. -- {Pho`to*ton"ic}, a. [Webster 1913 Suppl.]