  The sensitivity of stellar spectra to alpha/Fe abundance changes is
investigated with the aim to be detected photometricly and employed for
scientific goals of the GAIA mission. A grid of plane parallel, line blanketed,
flux constant, LTE model atmospheres with different [alpha/Fe] ratios was
calculated. As a first step, the modelled stellar energy fluxes for solar-type
stars and giants were computed and intercompared. The spectral sensitivity
talpha/Fe abundance changes is noticeable and has to be taken into account when
selecting photometric filters for GAIA. The Ca II H and K lines and Mg I b
triplet are the most sensitive direct indicators of alpha/Fe abundance changes.
