The objective of this research is to characterize the positive impact in pre-service science teachers when applying one innovation in the Practicum, asking for an authentic interaction between the student future teacher, the university teacher, and the mentor teacher in the school of practices. The innovation consisted of developing in science class, didactic units based on scientific inquiry using the Gowin diagram as an instrument to support the argumentation and dialogue processes that are typical of scientific activity. Within the framework of this didactic proposal, a climate of dialogue and reflection was generated in the formative triad. It allowed us to reach some conclusions about the role of the mentor teachers of practices from a discourse analysis of the participants, through the use of systemic networks. As a result of the reflection on the action, the characterization of the role of the mentor teachers of practices in aspects as providing emotional, pedagogical-didactic support and feedback, also the perceived limitations due to the scarce relationship between the School and the University. For this reason, was provided data evidencing the necessity of mentor teachers should include transformative professional conversations leading to a "reflexive mentoring".