ACCUMULATION OF HEAVY METALS AND ANTIOXIDANT DEFENCE SYSTEM IN THE GAMETOPHYTE OF DIDYMODON RIGIDULUS HEDW. IN AREAS WITH HIGH TRAFFIC LOADS

Abstract

Background. Various modes of transport are among the main sources of environmental pollution with heavy metals and other pollutants. Bryophytes are known to accumulate heavy metals; however, metabolic changes in mosses under conditions of metal accumulation have not been extensively studied. The aim of this article was to analyze the accumulation of heavy metals, the process of lipid peroxidation (LPO) and the activity of enzymes of the antioxidant system in Didymodon rigidulus Hedw. moss collected in urban areas with an intense load created by road and railway transport.
Materials and Methods. Gametophyte shoots were collected at three sampling sites in the city of Lviv (Ukraine). Site 1 was selected in a park zone, which was considered a control one; sites 2 and 3 were selected in areas with heavy road and rail traffic, respectively. Concentrations of chromium (Cr), nickel (Ni), lead (Pb), and zinc (Zn) in the moss material were determined by atomic absorption spectrophotometry. The levels of LPO products, namely lipid hydroperoxides and thiobarbituric acid reactive substances (TBARS), as well as superoxide dismutase (SOD) and catalase activities, were determined by standard methods. The results were processed using the methods of variation statistics.
Results. Moss D. rigidulus growing in the park area (site 1) accumulated metals in the following order of decreasing concentration: Zn> Cr> Ni> Pb. Gametophyte shoots of D. rigidulus collected at site 2 accumulated higher levels of Pb, Zn and Ni (by 2.27, 1.78 and 1.45 times, respectively), and at site 3, higher levels of Pb and Zn (by 1.8 and 1.67 times, respectively) compared to gametophytes collected in the park zone. In the moss samples from these sites, no significant differences in the Cr content were found as compared to the control. Concentration of lipid hydroperoxides in the moss sampled at sites 2 and 3 was 4.26 and 3.75 times higher, respectively, compared to the control, and TBARS production was more intense in plant material from site 2 than from the control site. SOD and catalase activities were considerably increased in D. rigidulus moss from site 2 compared with those from the control area; however, the activity of both enzymes in the moss samples from site 3 did not significantly exceed the control levels.
Conclusions. Both road and rail traffic loads contribute to the accumulation of heavy metals, especially Zn and Pb, in D. rigidulus moss growing in the surrounding areas. Under such conditions, LPO process is stimulated, which is more pronounced in moss growing in area with heavy road traffic. The increased activity of antioxidant enzymes (SOD and catalase) in moss growing in this area can play an important role in protecting bryophyte cells against metal-induced oxidative stress under conditions of intense metal accumulation.