Validity domain of the radiative opacity tables (OPAL and F05, shaded area) and of the conductive ones (solid box). As in Fig. 1 we superimposed the time evolution of the bottom of the atmosphere (τ_ph = 10) and the stellar centre for Z = 0.03 (thick solid line) and Z = 0.0002 (thick dashed line), and the whole structure for the first model on the Hayashi track (dotted line) and for the ZAMS (dot-dashed line) for Z = 0.0002.