Panel a: [Mg/Ne] – O₃₂ relations for all Mg II emitters depicted as in Fig. 1. The dots inside green circles represent low-metallicity (12 + log O/H < 8.0) low-mass (log(M_⋆/M_⊙) < 9.0) galaxies with high EW(Hβ) > 150 Å. Linear regression to all the galaxies is shown by a purple line and average values in bins of O₃₂ are shown by blue lines for all galaxies and by green lines for galaxies of low metallicity, low mass, and high EW(Hβ). Panel b: same as in panel a, but only for galaxies with abundance determination by the direct T_e method and accuracy better than 40% (more than 2.5σ) for weak but important Mg IIλ2797Å and [O III]λ4363Å emission lines. Galaxies with flux ratios I[O III]λ4959/I(Hβ) less than 0.7 were also excluded, resulting in a significantly reduced number of galaxies N = 433 (red dots). A linear regression to the T_e data is shown by a purple line and average values in bins of O₃₂ are represented by blue lines. As in panel a the galaxies with stellar masses log(M_⋆/M_⊙) < 9.0, oxygen abundances 12 + log O/H < 8.0, and EW(Hβ) > 150 Å are represented by dots inside green circles. Average values of these galaxies in O₃₂ bins are shown by green lines. Long red and green horizontal lines are average values belonging to samples of corresponding colours.