STABILITY EVALUATION OF PHOTOSYNTHETIC APPARATUS OF TILIA CORDATA MILL. IN THE GRADIENT OF TECHNOGENIC POLLUTION IN VLADIKAVKAZ

The study of the quantitative content of pigments in the leaves of small-leaved linden growing in linear plantings along roads was carried out on 10 sections of the transport network of the capital of the Republic of North Ossetia in Vladikavkaz. The sites are located in the industrial zone of the city, at different distances from stationary sources of air pollution. The complex impact of all sources of pollution with the level of the atmospheric pollution index (API) from 2.0 to 6.4 was assessed. The choice of research objects and sampling for analysis were carried out by the methods of E.V. Nikolaevskaya, N.P. Krasinsky, A.K. Frolova. The content of pigments (chlorophylls "a", "b"; carotenoids) in linden leaves was determined by the photometric method of V.F. Gavrilenko et al. The concentration of pigments was determined on a FEK-56 photocalorimeter. Statistical data processing was carried out using the methods of biological statistics by V.F. Lakin. The amount of green pigments in the leaves of small-leaved linden is not the same, the level of their concentration increases under conditions of the highest level of air pollution. The leading role in the work of the photosynthetic apparatus is played by chlorophyll "a", the content of which determines the overall picture of their joint content with chlorophyll "b". Changes in chlorophylls and their total amount are similar to changes in the content of carotenoids. An analysis of the obtained materials showed that in areas with a high API, the quantitative content of pigments increases, which is consistent with the results of some researchers (Tarabrin, Rachkovskaya, Kim), but not confirmed by others (Aksenova, Kazantseva, Tsandekova Neverova), which may be caused by an individual species reaction plants. The thickness of the leaf tissue decreases with increasing pollution, the ratio of columnar and spongy mesophyll shifts towards spongy, which will negatively affect the process of photosynthesis