Comparative histograms of (from top to bottom and from left to right): the Balmer extinction at the Hβ emission line, c(Hβ), R₂₃, N2, logarithm of the ionisation parameter, logarithm of the SFR per unit area, the [S ii]λ6717/[S ii]λ6731 line ratio, logarithm of the ionisation parameter, N/O abundance ratio, and oxygen abundance for barred (yellow, hatched) and unbarred (purple) galaxies separately for non-AGN galaxies with bulge mass lower than 10^9.7 M_⊙ and for galaxies with heavier bulges (≳10^9.7 M_⊙).