Comparison of the metallicity gradients obtained for the gaseous and stellar components in the bar region of our sample galaxies. They are normalized to R₂₅ (i.e. the gradients have been obtained from linear fits to the 12 + log (O/H) versus R/R₂₅ representation for each galaxy). Circles are those estimated with the R₂₃ (M91) or N2 methods, squares are the mean value of gradients calculated with all methods (the error bar covers the range of these gradients), and stars are the gradient [Z/H] for the stellar component (Paper II). Order indicated along the abscissas is that of Tables 6 and 7. Filled symbols represent star-forming galaxies.