The resistance of annual and biennial leaves of boxwood to the effects of negative temperatures has been studied. The parameters of PS II activity and the parameters of the redox potential were deter-mined in different periods after exposure to shock at temperatures of -5°C, -10°C , -15°C and -20°C. It was shown that the stability and ability to recover from damage caused by shock at different temperatures, were higher in annual leaves compared to biennial leaves.