'Heliotropism' definitions:

Definition of 'heliotropism'

(from WordNet)
noun
An orienting response to the sun

Definition of 'Heliotropism'

From: GCIDE
  • Heliotropism \He`li*ot"ro*pism\, n. [Helio- + Gr. ? to turn.] (Bot.) The phenomenon of turning toward the light, seen in many leaves and flowers. [1913 Webster]