- botany (of a plant movement) occurring in response to an external stimulus
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
Examples from the Web for paratonic
They are mostly reflex or paratonic, and due to external stimuli.The Wonders of Life
The change in torsion is, moreover, determined in reference to the paratonic action of incident geotropic stimulus.
I find that this autonomous movement becomes modified or even arrested by the paratonic effect of light.
I have already referred to the distinction that is made between nastic and paratonic movements.