Phototropism \Pho*tot"ro*pism\, n. [Photo- + Gr. ? to turn.]
1. (Plant Physiol.) The tendency of growing plant organs to
move or curve under the influence of light. In ordinary
use the term is practically synonymous with
{heliotropism}.
[Webster 1913 Suppl.]
2. (Microbiology) exhibiting movement in a direction toward
({positive phototropism}) or away from ({negative
phototropism}) a source of light.
[PJC]