The effect of negative air temperatures and humidity on the photosynthetic apparatus functioning in some species of Oleaceae family

Abstract

The characteristics of the photosynthetic apparatus functioning in the leaves of some evergreen species of Oleaceae family depending on the cold periods` weather conditions on the southern coast of Crimea are presented in this work. It has been revealed that changes in PSII are species-specific. Low air humidity in combination with negative air temperature promotes a significant decrease in frost resistance in the studied Olea and Osmantus genotypes. However, in Olea europea genotypes, changes in the PSII parameters under the simulation of winter desiccation approximated sublethal limits. The photosynthetic apparatus in L. lucidum species was more sensitive to a decrease in air temperature under conditions of relatively high air humidity. The development of the stress state in this species was accompanied by an increase in energy losses in the process of energy transfer from light-harvesting complexes. With the onset of frosty weather, a significant decrease in the chlorophyll a/b ratio was noted in all the studied genotypes. After the stress pressure, Olea europea cultivars and Osmantus spp. showed an increase in chlorophyll amount, in contrast to L. lucidum, in which the ratio of photosynthetic pigments remained low.