Definition of: paraheliotropism

(par′ə·hē′lē·ot′rə·piz′əm) noun Bot.
A manifestation of irritability in motile leaves when exposed to bright sunlight, whereby they assume such a position that their surfaces are parallel to the direction of the incident rays; diurnal sleep of leaves.
—par′a·he′li·o·trop′ic (-ə·trop′ik) adjective