We test whether the universal initial mass function (UIMF) or the integrated
galaxial IMF (IGIMF) can be employed to explain the metallicity distribution
(MD) of giants in the Galactic bulge. We make use of a single-zone chemical
evolution model developed for the Milky Way bulge in the context of an
inside-out model for the formation of the Galaxy. We checked whether it is
possible to constrain the yields above 80 M_{\sun} by forcing the UIMF and
required that the resulting MD matches the observed ones. We also extended the
analysis to the bulge of M31 to investigate a possible variation of the IMF
among galactic bulges. Several parameters that have an impact on stellar
evolution (star-formation efficiency, gas infall timescale) are varied. We show
that it is not possible to satisfactorily reproduce the observed metallicity
distribution in the two galactic bulges unless assuming a flatter IMF (x≤1.1) than the universal one. We conlude that it is necessary to assume a
variation in the IMF among the various environments.Comment: 9 pages, 4 figures, accepted for publication in A&