  Quantum gravitational corrections to the effective potential, at one-loop
level and in the leading-log approximation, for scalar quantum electrodynamics
with higher-derivative gravity ---which is taken as an effective theory for
quantum gravity (QG)--- are calculated. We point out the appearence of relevant
phenomena caused by quantum gravity, like dimensional transmutation, QG-driven
instabilities of the potential, QG corrrections to scalar-to-vector mass
ratios, and curvature-induced phase transitions, whose existence is shown by
means of analytical and numerical study.
