Physiological and Biochemical Aspects of Frost Resistance in Оlea europaea L.

Abstract

The results of studies on the frost resistance of Olea europaea L. varieties and its subspecies O. europaea subsp. cuspidata (Wall. and G. Don) Cif. under the conditions of the Southern Coast of Crimea (SCC), as well as the influence of temperature close to the absolute minimum value (–15°С) on the state of the photosynthetic apparatus, catalase activity, polyphenol oxidase, and the content of proline and phenolic compounds, are shown. It was established that a relatively high frost resistance is characteristic of the Nikitskaya variety under the conditions of the SCC. Varieties Ascoliano, Coregiolo, and Razzo turned out to be slightly frost-resistant. Minimum resistance was detected in the subspecies O. europaea subsp. cuspidata. The temperature of –15°C led to irreversible disruptions in the photosynthetic apparatus of weak varieties Razzo, Coregiolo and O. europaea subsp. cuspidata, which manifested in a significant decrease in photosynthetic activity immediately after the end of low-temperature exposure (by 80.19, 50.0, and 89.78%, respectively) as well as a fluorescence decay coefficient below the vital norm. After 24 h, a slowdown in the decrease in the parameters of chlorophyll fluorescence induction (CFI) was noted in the Ascoliano and Nikitskaya varieties. It was revealed that negative temperatures contribute to a decrease in the activity of catalase in weakly resistant O. europaea genotypes (by 40–60% on average) in contrast to the frost-resistant variety Nikitskaya, in which the activity of this enzyme remained almost unchanged. The change in polyphenol oxidase activity was multidirectional. In the Razzo and Coregiolo varieties, an increase in polyphenol oxidase activity was noted (19 and 24%, respectively). A decrease (by 8 and 37%, respectively) was noted in the subspecies O. europaea subsp. cuspidata and Nikitskaya variety. It was shown that, under the influence of negative temperatures, representatives of O. europaea decrease proline concentration in leaf tissues (by 17–55%). The most significant changes were detected in the variety Coregiolo (by 45.09%). The total content of phenolic compounds decreased in all weakly frost-resistant varieties and O. europaea subsp. cuspidata by 7–42% and remained unchanged in the frost-resistant variety Nikitskaya. It has been established that negative temperatures cause irreversible changes in the photosynthetic apparatus in weakly resistant representatives of O. europaea. The correlation of the degree of frost resistance of the studied genotypes with the activity of catalase and with the content of proline and phenolic compounds in leaf tissues was revealed.