The Butterfly Effect: Mild Soil Pollution with Heavy Metals Elicits Major Biological Consequences in Cobalt-Sensitized Broad Bean Model Plants

Among the heavy metals (HMs), only cobalt induces a polymorphic response in Vicia faba plants, manifesting as chlorophyll morphoses and a ‘break-through’ effect resulting in the elevated accumulation of other HMs, which makes Co-pretreated broad bean plants an attractive model for investigating soil pollution by HMs. In this study, Co-sensitized V. faba plants were used to evaluate the long-term effect of residual industrial pollution by examining biochemical (H2O2, ascorbic acid, malondialdehyde, free proline, flavonoid, polyphenols, chlorophylls, carotenoids, superoxide dismutase) and molecular (conserved DNA-derived polymorphism and transcript-derived polymorphic fragments) markers after long-term exposure. HM-polluted soil induced a significantly higher frequency of chlorophyll morphoses and lower levels of nonenzymatic antioxidants in Co-pretreated V. faba plants. Both molecular markers effectively differentiated plants from polluted and control soils into distinct clusters, showing that HMs in mildly polluted soil are capable of inducing changes in DNA coding regions. These findings illustrate that strong background abiotic stressors (pretreatment with Co) can aid investigations of mild stressors (slight levels of soil pollution) by complementing each other in antioxidant content reduction and induction of DNA changes

Soil genotoxicity biomonitoring in recultivated factory area using the cytogenetic and molecular assays in two plant test-systems

Soil pollution with industrial leftovers is of real danger to living organisms since harmful effects can arise after exposure to the contaminants in the soil. In our study, we applied a plant bioassay battery to monitor soil genotoxicity after short-term exposure to the soil. The soil was collected in 3 rounds: at the central part of the brownfield before (S-I) and after (S-III) topsoil removal, and at the brownfield periphery (S-II). The permissible value of the total contamination index is <16 and the corresponding values were 780 in S-I, 69 in S-II and 133 in S-III soil showing that whole brownfield territory is extremely polluted with heavy metals. Cytogenetic markers were recorded in Allium and Tradescantia test-systems and two types of molecular markers, RAPD and ISSR, were analysed in Allium. Our results revealed that the most polluted soil sample has induced an alarming increase of apoptotic cells in onion roots. Chromosome aberration and micronuclei frequency in Allium decreased inconsistently along with the pollution reduction in the soil. Increased frequencies of all cytogenetic markers were revealed in Tradescantia cuttings after exposure to the S-I soil extracts. Cluster analysis of Allium RAPD and ISSR markers showed that the most polluted soil samples induced genetic changes in onions different from those induced by the least polluted soil. Both plant test-systems in this study confirm that soil from the brownfield is harmful to plants and is potentially hazardous to humans