EFFECT OF EMISSIONS FROM ALUMINUM PRODUCTION ON PHOTOSYNTHETIC APPARATUS OF SIBERIAN LARCH

The article presents data on the effect of emissions from the Bratsk Aluminum Plant (BrAZ) on the photosynthetic apparatus of Siberian larch ( Larix sibirica Ledeb.). On the basis of data on the content of elements-pollutants (fluorine, sulphur, heavy, light metals and metalloids) in needle trees using cluster analysis the trees of critical, strong, moderate, low level of contamination, as well as background stands were identified in the surveyed area. It has been established that in the needles of trees with an increase in the level of pollution, the content of pigments decreases: chlorophyll a - by 68 %, chlorophyll b - by 72 %, carotenoids - by 67 % compared to the background level. The morphometric parameters of the assimilation organs of polluted trees (the length of auxiblasts of the second year of life, the mass of needles on them, and the length of needles) are reduced by 45-65 % compared to the background values; their minimum values are found at a critical level of pollution (on the territory of the BrAZ industrial zone). The presence of functional disorders of the photosynthetic apparatus of needles in conditions of pollution by emissions from an aluminum plant is evidenced by a change in the parameters of chlorophyll fluorescence: a decrease in the photochemical activity of photosystem II (Fv/Fm) by 7 %, the electron transport flow rate (ETR) - by 26 %, the quantum yield of photosystem II (Y(II) - by 35 %, as well as an increase in background fluorescence of chlorophyll F0 by 26-35 % and non-photochemical quenching of chlorophyll fluorescence (NPQ) by 27 % compared to background values. The maximum negative impact of emissions on the photochemical processes of larch needles was recorded at the critical level of trees pollution.