Abstarct: This study examined how temperature and water potential influence quinoa germination and estimated the plant’s cardinal temperatures. A factorial experiment was conducted in a completely randomized design, testing eight temperature levels (ranging from 5 to 40°C) and four water potential levels (0 to -12 bars) in a laboratory setting. Additionally, a field experiment was conducted in two locations, Dibaj and Damghan, where the treatments included three levels of deficit irrigation (supplying 100%, 70%, and 40% of the plant's water needs) and three levels of sodium nitrophenolate foliar application (control, application at stem elongation, and application at flowering). Results indicated that the Hydrothermal Time to Event (HTTE) model effectively captured the combined influence of temperature and water potential on quinoa germination (R²=0.95). According to the model, the estimated cardinal temperatures were 2.2°C for the baxse, 31.86°C for the optimum, and 44.33°C for the ceiling temperature. While water potential increased the baxse temperature and lowered the ceiling temperature, it did not affect the optimum temperature. The relationship between biochemical traits such as carotenoids, catalase, ascorbate peroxidase, and anthocyanins with drought resistance followed a nonlinear, quadratic pattern. Proline and catalase had a synergistic role in enhancing drought resistance, whereas a simultaneous rise in soluble sugars and proline showed an antagonistic effect. The impact of sodium nitrophenolate varied, boosting antioxidant enzyme activity in some cases but negatively influencing traits like soluble sugar content and anthocyanin levels, particularly when applied during flowering stage. In both locations, foliar application of sodium nitrophenolate, especially at stem elongation, helped alleviate the adverse effects of severe drought stress on grain yield. Overall, Dibaj provided better conditions for plant growth and yield than Damghan, where water deficit had a more pronounced negative impact.