Nuclear alterations of maize plants grown in soil contaminated with coal fly ash

Abstract

Maize seedlings were grown in soil mixed with coal fly ash at rates of 35 t/ha, 70 t/ha, and 500 t/ha. Nuclei were isolated from the seedlings and analyzed by flow cytometry. Nuclei from seedlings grown in 70 t/ha and 500 t/ha fly ash had significantly higher fluorescence intensities when stained with propidium iodide and analyzed by flow cytometry than control plants. This increase in fluorescence intensity is correlated with alterations of the plant nucleus. Mean coefficients of variation of the G1 peaks were also increased in the fly ash treatments relative to controls. The high concentration of fly ash disrupted the cell cycle of seedlings, resulting in a higher frequency of G2 nuclei. Additionally, three triploid plants were found in the fly ash treatments. Despite the nuclear alterations, plants grown at 70 t/ha of fly ash appeared healthy. Thus, nuclear damage was evident at levels that do not significantly alter the phenotype. Because fly ash was revealed to induce nuclear changes in maize plants, its environmental safety should be carefully evaluated. Short-term field observation studies are inadequate for predicting the long-term consequences of large scale land application of this coal combustion product. In addition, the maize line used in this study has the potential to be used as a bioassay in monitoring potential contamination of land surrounding fly ash landfills and disposal ponds.