This study aimed to evaluate changes in the metabolic efficiency of germinated maize seeds immediately after harvest or after storage for five months. We also tested the influence of genistifolioside, a plant's growth regulator, on the corn hybrid Porumbeni 427 seeds' metabolic efficiency. Their germination after storage for five months leads to a decrease of the unused seed mass for growth, accumulation of the biomass in plantlets, and respiration. Together, these data suggest that during storage, the vigor of the seeds decreased. The treatment with genistifolioside of stored for five months maize seeds did not significantly influence the level of accumulated biomass in plantlets, but a considerable increase in the respiration rate of seeds treated before exposition for germination with detected. These data suggest that under the influence of the genistifolioside, maize seeds' germination and seedling growth require increasing the energy allocated from the endosperm. The beneficial effect of genistifolioside on seeds' metabolic efficiency was more pronounced in seeds stored for five months than in those incubated for germination immediately after harvest.