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The effect of vehicle exhaust emissions on morphometric and physiological characteristics of Rhus typhina

Rhus typhina L. (Staghorn Sumac) is fast-growing woody species that reproduces by rhizomes and seeds. Because of its biological benefits, this deciduous member of the Anacardiaceae family has been introduced from its native habitats in the east of North America to urbanized landscapes of Ukraine. In this study we anаlyse changes in morphometric and physiological indicators of 12-year plants of this species in artificial phytocenoses near highways in Pavlograd, Ukraine. Experimental plots were placed at a distance from 25 to 130 meters from the road. The control group of plants was at a distance of 1500 m from the highways. We measured the length and thickness of the annual sprout, number of leaves on it, the content of chlorophyll in the leaves and accumulation of cadmium and lead in the leaf tissues. It was found that, compared to the plants in the relatively clean area, the greatest decreases in the length of the annual shoots of the trees in the plantations were for those which were at a distance of twenty five metres and forty meters from the traffic lanes of the highways. The thickness of the annual shoots of the trees in the plantations did not differ from plants in the clean zone. The number of leaves on a one-year annual sprout at a distance of twenty five meters and forty meters from the path of moving sources of pollution was significantly lower compared to control. We evaluated the impact of vehicle exhaust emissions on the assimilatory organs. We identified a negative effect of the anthropogenic pollutants on photosynthetic pigment content in leaves. The amount of chlorophyll a and chlorophyll b decreased with decreasing distance from the plantation to the road. Changes in the content of chlorophyll b had a clear pattern. The concentration of this pigment and the amount of chlorophyll a + b decreased compared with control in the 130 meter area. The amount of toxic heavy metals (lead and cadmium) in the tissues of the leaf was significantly higher than the control values on all plots. The strongest negative effects of phytotoxicants on susceptible plants occurred in plantations in the twenty-five-meter zone, which led to deterioration of the decorative quality of the plants.