trophotropism

from The Century Dictionary.

• noun In biology, the growth or movement of organisms in relation to a source or supply of food; a form of chemotropism.
• noun In botany, the phenomena induced in a growing organ by the influence of the chemical nature of its environment, as when plasmodia that are spread out on surfaces which yield little or no nutriment move toward bodies which contain nutrient substances.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun an orienting response to food