The heat resistance of the boxwood leaf (Buxus sempervirens L.) taken for analysis in the summer season by the changes in the intensity of photosynthesis and the activity of oxidation-reduction processes after exposure to different doses of heat shock was studied was studied. On the basis of the dynamics of the relative activity of the FS II, the distribution of the response to the heat shock temperatures can be divided into three zones. Studies can assess the viability of plants and predict their adaptation and survival in the face of the threat of a global increase in the environmental temperatures.