Yields (solar masses, see the definition in Sect. 5) of the chemical species involved in CNO cycling are shown as a function of the initial mass of the star for the metallicities Z = 3 × 10⁻⁵ (black points) and Z = 3 × 10⁻⁷ (green squares). The corresponding yields from GP21, Karakas (2010), and Doherty et al. (2014) are indicated with blue triangles, red diamonds, and orange crosses, respectively. Shaded areas on the right side of the panels indicate the values covered by the yields from Limongi & Chieffi (2018) for different initial rotation velocities. The values of the mass for which the points or the shadowing is missing indicate that the corresponding yields are negative.