Phototropism /(?)/

Pho·tot·ro·pism

Phototropism

n.
  1. 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. (Plant Physiol.)
  2. exhibiting movement in a direction toward (positive phototropism) or away from (negative phototropism) a source of light. (Microbiology)