Siberian Federal University

A comparative study of lignins isolated from woody plants of Sorbus aucuparia, which grew for three decades on the territory of the former radium mining enterprise, was carried out. It was found that radiation stress led to a decrease in the degree of lignification of mountain ash wood. Using methods of chemical analysis, NMR, IR and EPR spectroscopy, the peculiarities of the chemical structure of stress lignins were revealed. The quantitative ratios of guaiacyl, syringyl, and p- coumarin structural units, as well as the number of carboxyl groups and phenolic hydroxyls, have been established. The paramagnetic properties of lignins were investigated, and the concentration of stable radicals was determined, which varied in different samples in the range of 2.4–5.1 × 1017 spins/g. As a result of the study, it was concluded that radiation stress did not significantly affect the monomeric composition of lignins. However, an increase in the concentration of phenoxyl radicals was detected, which correlated with an increase in the number of phenolic hydroxyl groups. Information on the chemical structure and properties of stress lignins is necessary to predict the long- term effects of chronic radiation exposure on plants, as well as for their rational use in scenarios of environmental changes in territories.