We study Fourier transforms
of Lp-functions (1 < p ≤ 2) on nilpotent Lie groups and affine automorphism groups
of Siegel domains. We get an estimate for the norm of the Lp-Fourier transform for
certain classes of nilpotent Lie groups. For affine automorphism groups, which are
nonunimodular, we give an explicit definition of Lp-Fourier transform, and obtain an
estimate for the norm.