A sample of S0 galaxies belonging to southern clusters of galaxies will be investigated;
a range of S0 luminosities from $M_B=-18$ to $M_B=-20.5$ will be covered.
We plan to obtain long-slit spectra to investigate the age and
metallicity of the stellar populations up to the optical borders of the galaxies,
as well as the alpha-element (magnesium)-to-iron ratio in stars of their disks.
Our aim is to fix the moment  when star formation was quenched in the large-scale disks
of S0s under the influence of dense environment and the time scale of the quenching,
and to check the hypothesis that morphological transformation of S0 galaxies
was provoked by their accretion onto the clusters in the moment of their
accumulation, e.g. at the redshift of z~0.5-1 according to LCDM simulations.
