<p>The D” seismic discontinuity is one of the most prominent and enigmatic seismic anomalies in Earth’s lower mantle, and its origin remains unclear. Since the discovery of the post-perovskite phase, seismic anisotropy observed in the D” layer has been attributed to the texturing of this phase. However, no substantial seismic velocity jump has been observed across the isotropic post-perovskite phase transition boundary, revealing a critical gap in experimental data linking the discontinuity to phase texture. Here we present in situ high-pressure acoustic velocity and synchrotron X-ray diffraction data on both textured and randomly-oriented MgGeO₃ post-perovskite, an analogue for MgSiO₃ component, up to 115 gigapascals. The results show that texturing with a (001) slip plane reproduces the shear wave velocity jump at the D” discontinuity, while randomly oriented samples do not. These findings indicate that the texture of the post-perovskite phase can explain most of the key features of the D” discontinuity.</p>