Is the FIP effect present inside solar photospheric magnetic flux tubes?

The first determination of the elemental composition in the photospheric la yers of solar magnetic flux tubes is described. Stokes I and V profiles of 13 elements observed in solar active region plage and in the network are an alysed. The abundances are obtained for elements with high (C, O) and low ( Al, Ca, er, Na, Ni, Sc, Si, Ti, Y, Zn) first ionization potential (FIP) in order to investigate to what extent the abundance anomalies observed in the upper solar atmosphere (FIP-effect) are already present in the photospheri c layers of flux tubes, which are the source of much of the gas in the uppe r atmosphere. Various sources of error are considered and the uncertainties introduced by them are estimated. There are hints of a weak FIP-effect in the flux tubes, corresponding to an overabundance of a factor of 1.1-1.2 of the low-FIP elements relative to high-FIP elements, as compared to the qui et photosphere. However, our data set a firm upper limit of 1.3-1.6 on this factor, which is well below the enhancement seen in many parts of the uppe r solar atmosphere.