  Aims. A global O-Na abundance anti-correlation is observed in globular
clusters, which is not present in the Galactic field population. Open clusters
are thought to be chemically homogeneous internally. We aim to explore the O
and Na abundance pattern among the open cluster population of the Galactic
disk.
  Methods. We combine open cluster abundance ratios of O and Na from
high-resolution spectroscopic studies in the literature and normalize them to a
common solar scale. We compare the open cluster abundances against the globular
clusters and disk field.
  Results. We find that the different environments show different abundance
patterns. The open clusters do not show the O-Na anti-correlation at the
extreme O-depletion / Na-enhancement as observed in globular clusters.
Furthermore, the high Na abundances in open clusters do not match the disk
field stars. If real, it may be suggesting that the dissolution of present-day
open clusters is not a significant contribution to building the Galactic disk.
Large-scale homogeneous studies of clusters and field will further confirm the
reality of the Na enhancement.
