<p>The harsh climate of Tunisia's arid regions, characterized by high temperatures and little precipitation, exacerbates desertification due to unsustainable farming practices and climate change. <i>Oloptum miliaceum</i> shows promise in strengthening the resistance of rural communities and ecosystems to these threats. This research investigates the response of two <i>Oloptum miliaceum</i> accessions from different climatic zones to drought simulated by four water treatments. The accessions, A1 and A2, are from northern and southern Tunisia, respectively. The experiment measured various morphological traits, such as plant height, number and length of leaves, number of tillers, number of spikes, and chlorophyll content. It also followed various gas exchange parameters, including net photosynthesis, stomatal conductance, transpiration rate, and internal CO₂ concentration. In addition, this study measured predawn and minimum leaf water potentials, efficient water use, and dry biomass product weight. The findings showed that as water stress increases, all evaluated attributes decline significantly. Compared to A2, A1's morphological and ecophysiological characteristics were more severely impacted by extreme water stress. A1 accession has an avoidance strategy that combines leaf entanglement and stomatal closure to stop water loss. A2 accession, on the other hand, exhibits a tolerance mechanism that allows it to flourish in low water potential and change from a vegetative to a reproductive stage as a means of escape. A2 would therefore be appropriate for restoration projects in arid and semi-arid areas.</p>