Among the variety of physiological criteria, seed vigor and metabolic efficiency are the most closely related to the overall resistance of plants to stress. Moreover, the methodological accessibility of their determination makes it possible to evaluate quickly the resistance of plants, in particular, to the influence of non-optimal temperatures. Purpose of this study was to determine the resistance potential of the Porumbeni 374 (P374) maize hybrid to temperatures of 48, 50 and 52ºC. Hybrid P374 is triline hybrid, semi-early maturation (FAO 290), dentate seed, weight of 1000 seeds 290-300 g, the production potential 11- 12 t/ha. The total germination of intact seeds and seeds exposed to temperature, as well as roots and shoots length and biomass of individual components (roots, shoots and seeds) of germinated seeds were determined. Moreover, shoot vigor I, root vigor II and metabolic efficiency were calculated. Vigor I and vigor II of intact seeds were 428.81 and 823.91, respectively. The vigor of seeds exposed to heat significantly decreased at 48ºC by 42.7 - 47.5% and at 52ºС by 62.2 -72.9% compared to intact seeds. Thus, the increase in temperature greatly affected the shoot and root vigor of maize seeds. Physiological differences between intact and heat-treated seeds were expressed in the quantitative use of reserve substances for the growth of roots and shoots, which depended on the effect of temperature. After heat stress at temperature of 48ºC, the amount of reserve substances used for the growth of roots and shoots did not change. When the temperature increased to 50ºC, this index increased by 7%. The temperature of 52ºС contributed to the rise of reserve substances using by 9.81%. The hybrid was characterized by a significantly increased metabolic efficiency after the heat stress at 52ºC by 42.5% compared to the intact seeds, which indicates an increase in the intensity of the growth processes of the seeds that survived after the heat treatment. The intensity of growth responses of maize seeds to temperature increase was studied. Based on the determined indices, the resistance degree of the P374 maize hybrid to such an unfavorable abiotic factor as a temperature exceeding the optimum was reliably assessed.