log(N/O) versus [Fe/H] with open clusters shown as large filled circle (in green clusters with R_GC > 7 kpc and in orange clusters with R_GC ≤ 7 kpc), individual measurements of thin and thick disc stars are represented with cyan and pink triangles, respectively. In the top panel, we present the grid of models in which we vary the SFE; in the central panel, the infall timescale is changed, while in the bottom panel, the outflow loading factor is varied. In each panel, the reference model is identified with a solid line.