  In-medium effects of transverse-mass distributions of quarks and gluons are
considered assuming a possible local equilibrium for colorless quark objects
like mesons and baryons created in central A+A collisions. It is shown that the
average square of the transverse momentum for these partons grows and then
saturates when the initial energy increases. Within the quark-gluon string
model it leads to the energy dependence of hadron transverse mass spectra which
is similar to that observed in heavy ion collisions. Comparison with other
scenarios is given.
