FEATURES OF THE BIOCHEMICAL COMPOSITION OF SILVER BIRCH (<i>BETULA PENDULA</i> ROTH.) IN A TECHNOGENIC ENVIRONMENT
The results of studies of the peculiarities of the biochemical composition of silver birch, taking into account the exposure of the crown of a tree in the conditions of a large industrial centre of Naberezhnye Chelny (Republic of Tatarstan) are presented. The multivariate variance analysis of the research results showed that the studied parameters in the leaves of silver birch were significantly influenced by a complex of growing conditions, the growing season, exposure of the location of leaves and the interaction of these factors. In the main plantations in the leaves of the northern exposure, a higher concentration of ascorbic acid was noted during the entire period of active vegetation of plants, while the activity of ascorbate oxidase, on the contrary, was higher in the leaves of the southern exposure in June and July. In the plantations of sanitary protection zones of industrial enterprises and main plantations (July, August), a higher content of tannins in the leaves of the northern exposure was noted, compared to the leaves of the southern exposure. The activity of polyphenol oxidase in June in Sanzone plants in the leaves of northern exposure was the highest; in other cases, no significant differences were found. The investigated substances are important elements of the network of metabolic reactions of the antioxidant plant defense system aimed at compensating for the negative impact of the aggregate of air pollutants.