  Very large anisotropies in transport quantities have been observed in the
presence of very small in-plane structural anisotropy in many strongly
correlated electron materials. By studying the two-dimensional Hubbard model
with dynamical-mean-field theory for clusters, we show that such large
anisotropies can be induced without static stripe order if the interaction is
large enough to yield a Mott transition. Anisotropy decreases at large
frequency. The maximum effect on conductivity anisotropy occurs in the
underdoped regime, as observed in high temperature superconductors.
