Assessment of oxidative stress markers and concentrations of selected elements in the leaves of Cassia occidentalis growing wild on a coal fly ash basin.

Assessment of oxidative stress levels and tissue concentrations of elements in plants growing wild on fly ash basins is critical for realistic hazard identification of fly ash disposal areas. Hitherto, levels of oxidative stress markers in plants growing wild on fly ash basins have not been adequately investigated. We report here concentrations of selected metal and metalloid elements and levels of oxidative stress markers in leaves of Cassia occidentalis growing wild on a fly ash basin (Badarpur Thermal Power Station site) and a reference site (Garhi Mandu Van site). Plants growing on the fly ash basin had significantly high foliar concentration of As, Ni, Pb and Se and low foliar concentration of Mn and Fe compared to the plants growing on the reference site. The plants inhabiting the fly ash basin showed signs of oxidative stress and had elevated levels of lipid peroxidation, electrolyte leakage from cells and low levels of chlorophyll a and total carotenoids compared to plants growing at the reference site. The levels of both protein thiols and nonprotein thiols were elevated in plants growing on the fly ash basin compared to plants growing on the reference site. However, no differences were observed in the levels of cysteine, reduced glutathione and oxidized glutathione in plants growing at both the sites. Our study suggests that: (1) fly ash triggers oxidative stress responses in plants growing wild on fly ash basin, and (2) elevated levels of protein thiols and nonprotein thiols may have a role in protecting the plants from environmental stress.

Variability in foliar essential oils among different morphotypes of Lantana species complexes, and its taxonomic and ecological significance.

The genus Lantana has many species complexes, and L. camara is one of the aggressive alien weedy species complexes; species delimitation in these complexes is a nightmare for taxonomists. We examined the diversity in the chemical composition of foliar essential oils among morphotypes of Lantana species complexes inhabiting the same ecological gradient, and its taxonomic and ecological significance. The yields of essential oils varied from 0.1 to 0.79% in foliar hydrodistillates of eleven morphotypes, and a total of 39 chemical constituents were detected by GC/MS. The quantitative and qualitative variability in the composition of essential oils among morphotypes was very high, and hence they represent chemotypes. The diversity observed in the composition of essential oils appears to be of genetic origin and thus of taxonomic value. The formation of distinct clusters and sub-clusters at high distance cluster combine values also substantiates that the patterns of distribution of chemical constituents among morphotypes can be used in delimiting species and infraspecific taxa within the species complexes. The presence of beta-caryophyllene and other such compounds, which are known to prevent herbivory, in morphotypes of Lantana species complexes suggest that these compounds may provide selective advantage to Lantana over native species in the invasion of new and disturbed habitats.

Comparative study on elemental composition and DNA damage in leaves of a weedy plant species, Cassia occidentalis, growing wild on weathered fly ash and soil.

Open dumping of fly ash in fly ash basins has significant adverse environmental impacts due to its elevated trace element content. In situ biomonitoring of genotoxicity is of practical value in realistic hazard identification of fly ash. Genotoxicity of openly disposed fly ash to natural plant populations inhabiting fly ash basins has not been investigated. DNA damage, and concentrations of As, Co, Cr, Cu and Ni in the leaves of natural populations of Cassia occidentalis growing at two contrasting sites-one having weathered fly ash (fly ash basin) and the other having soil (reference site) as plant growth substrates-were assessed. The foliar concentrations of As, Ni and Cr were two to eight fold higher in plants growing on fly ash as compared to the plants growing on soil, whereas foliar concentrations of Cu and Co were similar. We report, for the first time, based upon comet assay results, higher levels of DNA damage in leaf tissues of Cassia occidentalis growing wild on fly ash basin compared to C. occidentalis growing on soil. Correlation analysis between foliar DNA damage and foliar concentrations of trace elements suggests that DNA damage may perhaps be associated with foliar concentrations of As and Ni. Our observations suggest that (1) fly ash triggers genotoxic responses in plants growing naturally on fly ash basins; and (2) plant comet assay is useful for in situ biomonitoring of genotoxicity of fly ash.