The content of photosynthetic pigments in the leaves of «healthy» and «weakened» balsam poplar trees (<i>Populus balsamifera</i> L.) growing under conditions of industrial pollution (Republic of Bashkortostan, Sterlitamak industrial center)

Abstract

The paper presents the results of studies on the assessment of the relative vitality of balsam poplar ( Populus balsamifera L.) plantations under the conditions of polymetallic pollution of the Sterlitamak Industrial Center (SIC). Poplar plantations of the sanitary protection zone of the SPC are classified as weakened. External signs of oppression are manifested in a decrease in crown density, an increase in the number of dead branches, damage to the assimilation apparatus by chlorosis and necrosis. Trees belonging to the healthy category grow in the plantations. It was shown that the average content of chlorophylls ( a + b ) in the leaves of healthy poplar trees varied from 25,0 to 28,0 g/cm of fresh weight, while in weakened trees it was relatively low and amounted to 17,2-22,6 g/cm wet weight. The decrease in the total content of chlorophylls and the deterioration in the relative vitality of trees are interrelated. It has been established that during the period of active leaf growth (in June and early July), a high content of chlorophylls and nitrogen balance index (NBI) is noted in the leaves of both healthy and weakened balsam poplar trees. The relationship of the indicators under consideration is confirmed by the regression equations of the polynomial function ( y = -2,15x + 8,05x + 23,2 ; y = -2,35x + 8,75x + 19,9 for the leaves of healthy trees; y = -3,1x + 11,1x +13,4 ; y = -3,9x + 14,1x + 10 for the leaves of weakened trees), as well as determination coefficients (R = 1 for the leaves of healthy trees; R = 1 for the leaves of weakened trees). The maximum differences in the ratio of chlorophyll content ( a + b ) and nitrogen balance in the leaves of healthy and weakened poplar trees were noted at the end of August. During the growing season, in the leaves of weakened trees, compared with the leaves of healthy poplar trees, a decrease in the values NBI and the content of chlorophylls is observed. At the same time, there are no significant changes in the content of chlorophylls on the adaxial and abaxial sides of the leaves of healthy and weakened balsam poplar trees during the growing season.