Impact of heavy metals on photosynthetic pigment content in roadside plant communities

The research is dedicated to the study of the impact of heavy metals (As, Cr, Cu, Mо, Ni, Pb, Sr, Zn) found in plant samples on photosynthetic pigments in anthropogenic roadside plant communities. In the process of research, the anthropogenic load intensity for the selected sites (1 < 6 < 5 < 4 < 2 < 3) was determined. The analysis of the results showed that the impact of heavy metals on photosynthetic pigment content depends not only on metal toxicity but also on its concentration. A high level was noted for Pb (7.2-10.6), Cr (2.6-4.5), As (0.1-0.9) and Sr (9.4-12.1) mg/kg. The inverse relation between the heavy metal and photosynthetic pigment concentrations was revealed. The research showed that the concentration of chlorophyll a, b and carotenoids changes depending on the growing conditions. Carotenoids are less vulnerable to the negative impact of heavy metals as compared to chlorophylls. A higher concentration of carotenoids is noted in stressing environment. On the one hand, it decreases stress effect; on the other hand, it performs a protective function by preventing destruction of chlorophyll molecules and other organic substances. The obtained data may be used to forecast dynamics of plant populations and communities in the polluted areas and to monitor conditions of natural ecosystems.