The impact of repeated droughts over time is often catastrophic for the rural economy. There is almost no data on the effect of repeated over time ecological stress on the functional processes of the most crop plants. In experiments with Glycine max (Merr.) L cultivars with different drought resistance potential, exposed to moderate water stress at the phase "first trifoliate leaf" and at the phase "button formation - the beginning of flowering", data on the argumentation of the concept of the existence of stress-memory in plants - as an attribute to memorize the response mechanisms to the incidents induced by previous stress and to react more quickly and adequately to repeated stress over time were obtained. The memory of the response to environmental incidents is provided by protection mechanisms accessed at different levels of organization, particularly, by the signal changes in water status parameters, in special, hydrostatic pressure and water retention capacity. At the molecular, cell and organ level, stress-memory and drought tolerance is ensured by increasing the water retention ability of the macromolecules and the degree of hydration and maintenance of the tissue turgor pressure. The implications of changes in the content of reactive oxygen species (ROS) and activation of enzymatic and non-enzymatic antioxidant protection systems in the plants stress-memory formation to the humidity fluctuation and repeated drought conditions have been demonstrated. The degree of increase ROS formation induced by the lack of moisture during the formation of the button and flowering phase is significantly lower in the plants, which have undergone a moderate water stress to the phase of the first trifoliate leaves in comparison with the plants exposed to the first cycle of drought during critical period. It is also remarkable that the same intensity and duration of drought induces the appearance of stronger oxidative stress in plants with less potential for selfregulation of the water status.The content of malondialdehyde is higher, and the activity of antioxidant enzymes is lower at cv. Enigma, sensitive to drought, compared to drought-tolerant cv. Indra. The formation of stress memory depends on the constitutive resistance of the plants: plants with a higher resistance potential, in particular with a higher constitutive tolerance, are more easily adapted to the repeated water stress. In summary: any process of adaptation is aimed at maintaining the homeostasis of organism at a constant level. The water homeostatic capacity of tissues, as well as the ability to prevent excessive formation of ROS, and to activate antioxidant protection, is important nonspecific mechanisms that ensure the adaptation of plants to the stress repeated in time trough formation a memory about the mechanisms induced by incidents caused by moderate adverse conditions at the initial stages of ontogenesis. This phenomenon ensures an adequate response to the repeated occurrence of unfavourable conditions and increased resistance to drought.