Top-left panel: distribution of the slopes of the abundance gradients as a function of the interaction stage of the galaxies, when the galactocentric distances are normalized to the effective radius derived by a growth curve analysis. The colors of the symbols and the corresponding histograms indicate three types of galaxies based on the interaction: (i) no signatures of interaction (red); (ii) galaxies with close companions and/or in an early interaction stage (green); and (iii) galaxies under clear collision or evolved mergers (blue). Top-right panel: similar distribution of slopes as a function of the morphological classification of the galaxies. The colors of the symbols and the corresponding histograms indicate three types of galaxies based on their morphology: (i) early spirals, SO-Sa (red); (ii) intermediate spirals, Sab-Sb (green) and (iii) late spirals, Sc-Sm (blue). Bottom-left panel: similar distribution of slopes as a function of the presence or absence of bars. The colors of the symbols and the corresponding histograms indicate three types of galaxies: (i) clearly unbarred (red); (ii) not clear if there is a bar or not (green) and (iii) clearly barred galaxies (blue). Bottom-right panel: similar distribution of slopes as a function of the absolute magnitude of the galaxies. The colors of the symbols and the corresponding histograms indicate three types of galaxies based on the luminosity: (i) luminous galaxies, M_g−SDSS < −20.25 mag (red); (ii) intermediate galaxies −19.5 < M_g−SDSS < −20.25 mag (green) and (iii) faint galaxies M_g−SDSS > −19.5 mag (blue). The size of the symbols are inversely proportional to the derived error in the slope for all the panels.