Metallicity gradients as a function of stellar mass for the analysed disc galaxies at z ~ 0 (upper panels). The normalised gradients are displayed in the lower panels. Observational results for the metallicity gradients of the stellar discs in the CALIFA survey by Sánchez-Blázquez et al. (2014; black diamonds) and González Delgado et al. (2015; yellow crosses, lower panel) are also displayed at z ~ 0 for comparison. Mean estimations and their standard dispersion in both radial intervals: [ 0.5,1.5 ] r_eff (blue shades and lines) and [ 0.5,1.0 ] r_eff (pink shades and lines) are included for comparison.