This study presents a framework for integrating meaningful learning into a mobile learning context to enhance the learning achievement of natural science students through the utilization of advanced technologies and outdoor learning. An experiment was conducted on elementary school students to examine the effect of an Augmented Reality-based Meaningful Mobile Learning System (ARMMLS) on enhancing students' botanical learning ability. The ARMMLS incorporated key features such as 3D augmented reality (AR) visualizations of aquatic plants, enabling students to explore plant structures in depth. Additionally, outdoor learning activities facilitated real-world plant identification and collaborative group work through interactive matching exercises. Following the system's implementation, a usability survey assessed students' perceptions of the mobile application. Results indicated that the experimental group, using ARMMLS, scored significantly higher with an effect size of 0.73 in improving students' botanical learning skills than the control group. This study contributes to the mobile learning literature by identifying essential usability evaluation features and an empirical model for meaningful mobile learning. The findings provide valuable insights for future research and instructional practice design.