Bioaccumulation and oxidative stress impact of Pb, Ni, Cu, and Cr heavy metals in two bryophyte species, Pleurochaete squarrosa and Timmiella barbuloides


Abstract: This study was conducted to evaluate the bioaccumulation and oxidative stress impact of lead (Pb), nickel (Ni), copper (Cu), and chromium (Cr) in bryophyte species Pleurochaete squarrosa and Timmiella barbuloides exposed to Pb, Ni, Cu, and Cr at 1 mM concentration for 48 h. Bioaccumulation ratios in the non-Fenton metals Ni and Pb were found to be higher than in Fenton metals Cu and Cr for both moss species. Except for Cu, high levels of heavy metal accumulation caused a slight increase in dry weights of both species. Total chlorophyll and carotenoid contents of both species showed variations under Ni, Pb, and Cr stress; however, a Cu-induced decrease in the chl a/b ratio revealed prominent toxicity of the metal in both species. Copper and chromium provoked hydrogen peroxide (H2O2) increase in both species, but it was more prominent in P. squarrosa. Ni treatment also induced H2O2 accumulation in the species, but membrane damage was only observed in Cu-exposed samples of both species. Ni-, Pb-, Cu-, and Cr-induced oxidative stress was alleviated by different metal- and species-specific antioxidant components in both species. These findings indicate that both species are sensitive to Cu, and induced antioxidant components are not enough to overcome the phytotoxic effect of the metal. Accumulated Ni-, Pb-, and Cr-driven toxicity seems to be tolerated by reducing heavy metal access to the cytoplasm of the cells, as well as by stimulating different components of antioxidant defense in the cells of both species; however, this was more prominent in T. barbuloides than P. squarrosa.

Keywords: Pleurochaete squarrosa, Timmiella barbuloides, lead, nickel, copper, chromium, antioxidant, oxidative stress, bioaccumulation

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