Li and Na abundances for TO and SGB stars in NGC 6397 (data from Paper I, with improved non-LTE derivation). The initial [Na/Fe], shown on the abscissa, has been estimated by correcting A(Na) for atomic diffusion by  + 0.2 dex and assuming  [Fe/H]  =  −2.1 for all stars. The red bullets represent turn-off stars and the blue stars subgiants. Superimposed are the theoretical predictions for the chemical composition of the matter out of which second generation low-mass stars are expected to form in the WFRMS scenario. The tracks shown correspond to the cases of 20 M_⊙ and 120 M_⊙ polluter stars (dashed and full lines, respectively) assuming different values (0.2, 0.4, 0.6, 0.8) for the minimum dilution coefficient. See text for more details.