Top panel: C/O vs. Mg/Si. Red circles refer to single stars (400 stars), and green dots refer to stars harbouring planets (99 stars). Middle panel: same as the top panel but only for stars with T_eff < 6100 K (312 single stars, 19 low-mass planet hosts and 65 high-mass planet hosts). Bottom panel: same as top panel but for solar analogues, with T_eff = T_eff,⊙± 300 K, log g = logg_⊙± 0.2 dex and [Fe/H] = [Fe/H]_⊙± 0.2 K (58 single stars, 2 low-mass planet hosts and 9 high-mass planet hosts). In all panels, an orange star represents solar values.