The objective of the thesis is to research the physiological differences between picked genotypes of Capsicum annuum and the effect of lower temperatures in the beginning of ontogeny. Another objective is to find out how Capsicum annuum plants react to application of anti-stress agent Atonic and to determine the most appropriate physiological indicators of resistence to low temperatures. Capsicum annuum ranks among thermophilic crops for which the temperature optimum is of 22 - 25 °C during the day and 18 - 20 °C overnight. They are planted at the field station at the time when ground frost may occur. These can cause physiological changes in the plant or even cause her death. Three varieties were chosen for the experiment: Amy, Eva a Lydia. Plants were divided into a control group and treatment group. Both groups were further divided into two additional groups - with and without the application of Atonic in the beginning of vegetative growth (6th day of exposure to stress). Control group plants were grown at 20 °C and stressed plants were moved into a klimabox with temperature of 5 °C throughout the entire day. Such temperature may occur after planting the plants into an outdoor habitat. Proline content in leaves of Capsicum annuum and relative discharge of electrolyte was studied in two - day intervals. From the obtained results it can be concluded that the accumulation of proline was the highest for Lydia variety in a stressed scenario with the application of Atonic and the lowest proline content was found in in the Amy variety in a control group. Furthermore, it was discovered that the ontogeny of plants has an effect on the accumulation of proline and relative discharge of electrolyte from the beginning of the measurement. The absolute highest electrolyte discharge was measured in the Lydia variety in a stressed scenario and the lowest one was present in the Amy variety in a control group. These results confirm the hypothesis.