Reaction of photosynthetic apparatus of a representative of extrazonal steppe plants Quercus robur to air pollution by motor vehicle emissions

Abstract

We examined the vital condition of the common oak (Quercus robur L.) in plantations of different categories in Dnipro-city. In the investigated plantations, differences in the individual resistance of plants were recorded. The patterns of changes in the pigmented complex of leaves exposed to atmospheric pollution from motor vehicle emissions were studied in connection with the life state of oak trees. The content of chlorophyll a had, in all variants of the experiment, significantly higher values than chlorophyll b. Chlorophyll a accounted for 52.4–75.0% of the total content of chlorophylls, and chlorophyll b (25.0–47.6%). Regardless of the level of air pollution, relatively healthy oak plants were characterized by a high content of pigments activity in the photosynthetic apparatus of the leaves. A chronic moderate influence of motor vehicle emissions had a positive effect on the content of green pigments and carotenoids. Increase in the intensity of transport emissions resulted in a significant reduction in the accumulation of chlorophylls and to an increase in carotenoids. The stability of the chlorophyll a / chlorophyll b ratio under the influence of motor vehicle emissions was been registered. Only severely damaged common oak trees showed a decrease of this parameter by 29.3% compared with healthy and moderately weakened specimens of oak. The values of the coefficients of variation in the content of chlorophylls, their amounts and ratios, as well as carotenoids were low and represent less than 19.0%, while the amplitude of the variability of the studied parameters of the pigment complex, depending on the life state of plants and the intensity of transport emissions, was quite significant: the highest fluctuations in the сontent indexes were recorded for chlorophyll a, the sum of chlorophylls a + b in trees from the park area and the area with a medium level of pollution, chlorophyll b only in oaks from the street with an average level of air pollution by transport emissions. The smallest variability was a characteristic of the ratio of chlorophylls a / b and the content of carotenoids. Low values of the ratio of the sum of chlorophylls a + b to carotenoids (4.3–5.2) indicate the stress state of oak plants in urban environments.