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In a recent study, based on homogeneous barium abundance measurements in openclusters, a trend of increasing [Ba/Fe] ratios for decreasing cluster age wasreported. We present here further abundance determinations, relative to fourother elements hav- ing important s-process contributions, with the aim ofinvestigating whether the growth found for [Ba/Fe] is or not indicative of ageneral property, shared also by the other heavy elements formed by slowneutron captures. In particular, we derived abundances for yttrium, zirconium,lanthanum and cerium, using equivalent widths measurements and the MOOG code.Our sample includes 19 open clusters of different ages, for which the spectrawere obtained at the ESO VLT telescope, using the UVES spectrometer. The growthpreviously suggested for Ba is confirmed for all the elements analyzed in ourstudy. This fact implies significant changes in our views of the Galacticchemical evolution for elements beyond iron. Our results necessarily requirethat very low-mass AGB stars (M < 1.5M\odot) produce larger amounts ofs-process elements (hence acti- vate the 13 C-neutron source more effectively)than previously expected. Their role in producing neutron-rich elements in theGalactic disk has been so far underestimated and their evolution andneutron-capture nucleosynthesis should now be reconsidered.

s-Processing in the Galactic Disk. I. Super-Solar Abundances of Y, Zr, La, Ce in Young Open Clusters