  Recent experimental developments in the iron pnictides have unambiguously
demonstrated the existence of in-plane electronic anisotropy in the absence of
the long-range magnetic order. Such anisotropy can arise from orbital ordering,
which is described by an energy splitting between the two otherwise degenerate
$d_{xz}$ and $d_{yz}$ orbitals. By including this phenomenological orbital
order into a five-orbital Hubbard model, we obtain the mean-field solutions
where the magnetic order is determined self-consistently. Despite sensitivity
of the resulting states to the input parameters, we find that a weak orbital
order that places the $d_{yz}$ orbital slightly higher in energy than the
$d_{xz}$ orbital, combined with intermediate on-site interactions, produces
band dispersions that are compatible with the photoemission results. In this
regime, the stripe antiferromagnetic order is further stabilized and the
resistivity displays the observed anisotropy. We also calculate the optical
conductivity and show that it agrees with the temperature evolution of the
anisotropy seen experimentally.
