  Applying the recently developed spin-charge gauge theory for the pseudogap
phase in cuprates, we propose a self-consistent explanation of several peculiar
features of the far-infrared in-plane AC conductivity, including a broad peak
as a function of frequency and significant anisotropy at low temperatures,
along with a similar temperature-dependent in-plane anisotropy of DC
conductivity in lightly doped cuprates. The anisotropy of the metal-insulator
crossover scale is considered to be responsible for these phenomena. The
obtained results are in good agreement with experiments. An explicit proposal
is made to further check the theory.
