We discuss three effects of axial rotation at low metallicity. The first one
is the mixing of the chemical species which is predicted to be more efficient
in low metallicity environments. A consequence is the production of important
quantities of primary 14N, 13C, 22Ne and a strong impact on the
nucleosynthesis of the {\it s}-process elements. The second effect is a
consequence of the first. Strong mixing makes possible the apparition at the
surface of important quantities of CNO elements. This increases the opacity of
the outer layers and may trigger important mass loss by line driven winds. The
third effect is the fact that, during the main-sequence phase, stars, at very
low metallicity, reach more easily than their more metal rich counterparts, the
critical velocity\footnote{The critical velocity is the surface equatorial
velocity such that the centrifugal acceleration compensates for the local
gravity.}. We discuss the respective importance of these three effects as a
function of the metallicity. We show the consequences for the early chemical
evolution of the galactic halo and for explaining the CEMP stars. We conclude
that rotation is probably a key feature which contributes in an important way
to shape the evolution of the first stellar generations in the Universe.Comment: 8 pages, 4 figures, 2 tables, Review at IAU Symposium 265, Chemical
Abundances in the Universe: Connecting First Stars to Planets, K. Cunha, M.
Spite & B. Barbuy, ed
