Impact of chronic radiation exposure on phytohormonal status of pine trees in the Chernobyl exclusion zone

The paper presents results of the study of impacts of chronic radiation exposure on the hormonal system of the Scots pine in the Chernobyl exclusion zone. Pine needles taken from three experimental plots with a contrasting level of radioactive contamination: the Polesie State Radioecological Reserve, the Kozeluzh’ye forestry and the Khoiniki forestry in June 2021 were used in the study. Artificial stands of the Scots pine were planted in the experimental plots in 1982, few years before the Chernobyl accident. When radiation impact on pine trees was assessed the content of Cs-137, Sr-90, Am-241, Pu-238 и Pu-239+240 in soil and pine needles was taken into account. The absorbed dose rates in the needles taken from contaminated sites varied in the range of 1.5-24.6 µGy/h, the control dose rate was 0.58-0.6 µGy/h. The content of main classes of phytohormones: indol-3-acetic acid, indolyl-3-butyric acid, zeatin and abscisic acid in needles was estimated with the use of high-performance liquid chromatography. No significant changes in the phytohormonal status of pines from the contaminated plots of the Chernobyl exclusion zone were found. No relationship between statistically significant difference in phytohormones content in the pine needles and irradiation exposure is found. The difference may be caused by great biological variability in natural populations or other nonradiation factors.