The Persian oak (Quercus brantii) is a keystone species in Iran’s Zagros forests, but its natural regeneration is severely challenged by soil moisture depletion in the arid and semi-arid climate. This research evaluated the efficacy of a superabsorbent polymer (SAP) in enhancing the growth and survival of one-year-old Persian oak seedlings under controlled drought stress. A factorial experiment was conducted in a completely randomized block design employing 16 treatments, 3 replications, and 2 controls. The treatments consisted of four SAP levels (0%, 3%, 5%, and 7% by weight) and four irrigation regimes (full irrigation, and mild, moderate, and severe stress at 75%, 55%, and 35% of field capacity, respectively). After a four-month drought period, a comprehensive set of growth, physiological, and biochemical parameters were measured. The application of SAP significantly influenced most morphological and physiological traits. A critical finding was the severely reduced seedling survival (down to 34% under severe drought) at the 7% SAP dose, likely due to physical impedance and disrupted root aeration. In contrast, the 3% and 5% SAP treatments yielded the best results, maintaining approximately 70% seedling health under moderate and severe stress, whereas control seedlings perished under these conditions. These moderate SAP doses significantly improved root volume, leaf area, plant height, and relative water content while reducing electrolyte leakage. The findings demonstrate that moderate concentrations (3–5%) of superabsorbent polymer can serve as an effective strategy to bolster drought resilience, improve physiological performance, and increase the survival rate of Persian oak seedlings in water-limited environments.
