Micro-turbulent velocity of the sample stars, separated by spectral luminosity (Gr. 1 to 4), and by SpT and LC as a function of T_eff (same symbols and colours as in Fig. 3). Overplotted in gray are the adopted v_mac data with solid and open circles representing LC V/IV and LC III/I objects, respectively. The mean value of the upper detectability limit to v_mac averaged ’by eye’ and the corresponding ${\overline{v}}_{\text{mic}}$ are also provided to guide the eye (horizontal solid and dashed lines, respectively). In the bottom panel the solid curved line indicates the v_mac–T_eff calibration provided by Gray (1984). For more information, see the text.