Observations of ¹²C/¹³C in evolved stars of Galactic open clusters by Smiljanic et al. (2009, open symbols), Gilroy (1989), Gilroy & Brown (1991), and Mikolaitis et al. (2010) as a function of the turnoff mass of the corresponding host cluster that can be identified thanks to the colours of the symbols (see text and Table 4). Squares, circles, and asteriscs are for RGB, clump, and early-AGB stars respectively, while diamonds are for stars from Gilroy (1989) sample with doubtful evolutionary status; triangles are for lower limits. A typical error bar is indicated. Theoretical predictions are shown at the tip of the RGB and after completion of the second dredge-up (black and blue lines respectively). Standard models (no thermohaline nor rotation-induced mixing) are shown as dotted lines, models with thermohaline mixing only (V_ZAMS = 0) as solid lines, and models with thermohaline and rotation-induced mixing for different initial rotation velocities as indicated as long-dashed, dot-dashed, and dashed lines.