Abstract
We have computed chemical evolution models considering: a) mass loss and He production in intermediate mass stars based on models of asymptotic giant branch evolution; b) several rates of mass loss for massive stars; c) various initial mass functions, including that by Serrano (1978), and d) evolution with and without instantaneous recycling. From these models we have derived the AY/AZ abundance ratio and concluded that the observed AY/AZ ratio provides strong restrictions for galactic and stellar evolution model& In particular, we discuss constraints for asymptotic giant branch stellar evolution models, for the initial mass function, for the distance scale to planetary nebulae, for mass loss in massive stars and for the standard theory.
