Assessment of the functioning of the photosynthetic apparatus of Olea europaea L. under freezing temperatures

Background. Olive (O. europaea) is a popular fruit crop, and is the second in the world by area after coffee. The main limiting factor for olive cultivation in regions located on the northern border of the subtropical zone, as well as in temperate climates, is their low frost resistance. So, the aim of the present study was to evaluate the degree of influence of low negative temperatures on the functional state of leaves of different O. europaea genotypes. Materials and methods. The functioning of pigment apparatus, stability of chlorophyll-protein complex and membrane damage under freezing temperatures were evaluated on leaves of the following cultivars of olive: ‘Aglandau’, ‘Coreggiolo’, ‘Obilnaya’, ‘Tiflis’, ‘Dalmatica’, ‘Nikitskaya 2’, ‘Ascolano’, ‘Tossijskaya’, ‘Leccino’, ‘Razzo’. The studies were carried out under native conditions (control) and after exposure to low temperatures (immediately and after 24 hours of the stress factor influence). Four temperature effects were analyzed: -7°C, -10°C, -12°C and -14°C. Results and conclusion. Exposure to sub-zero temperatures induced a different response both in the manifestation of visual lesions on leaves and in changes in their physiological parameters. At a low gradient of temperature exposure (-7... - 10°C), leaf tissues of the European selection varieties ‘Coreggiolo’, ‘Ascolano’, ‘Leccino’ and ‘Razzo’ were damaged: electrical conductivity reached 15%, chlorophyll stability index decreased, variable fluorescence and photosynthetic activity coefficients decreased, uncontrolled photon quenching was significantly higher than the effective photochemical quantum yield and non-photochemical quenching. Cultivars of crimean and caucasian breeding are characterised by increased frost resistance. Cultivars ‘Nikitskaya 2’, ‘Tossijskaya’ and ‘Tiflis’ demonstrate integrity of leaf cell membranes, preservation of stability of photosynthetic pigments content and work of photosystems at different levels of their organization at –14°C. EDN: WTGVZM