Impact of negative temperatures on the state of the photosynthetic apparatus of evergreen species of Osmanthus Lour. genus

Abstract

The results of studies of photosynthetic processes in annual leaves of two species of the genus Osmanthus - Osmanthus x fortunei and O. fragrans in the cold period on the Southern coast of the Crimea and under the controlled action of negative temperatures are presented. It is shown that the main parameters of chlorophyll fluorescence induction (CFI) in annual leaves of O. x fortunei was relatively more stable during the winter months compared to O. fragrans . The effect of temperature -8,0°C for 8 hours on the leaves of the species in O. fragrans caused a decrease in the fluorescence decay coefficient to the lower limit of the norm of vitality and a significant increase in the processes of thermal dissociation of light energy. It is established that the temperature is -10°C is critical for the leaves of O. fragrans , which indicates its lower frost resistance. Changes in the state of PSII depend on both the duration and intensity of low-temperature exposure. It was found that for the more resistant species of O. x fortunei a relatively long-term effect of -10,0°C and a short one of -8,0°C temperature have a similar effect on the state of the photosynthetic apparatus, which is probably due to the activation of protective mechanisms.