12+log(O/H) and 12+log(N/H) vs. surface gravity in the field and cluster stars. The circles represent single measurements, while the squares represent the results binned in log g bins of 0.5. The curves indicate the model of Lagarde et al. (2012) for 1 M _⊙ (red dashed indicates ST, red continuous indicates TCR), 2 M_⊙ (black dashed indicates ST, black continuous indicates TCR) and 3 M_⊙ (blue continuous indicates TCR).