Toxic Responses of Palladium Accumulation in Duckweed (Lemna minor): Determination of Biomarkers

Abstract

Palladium (Pd) is a trace metal of the platinum group elements, representing an emerging contaminant for the environment. It is of great interest to characterize the bioaccumulation and toxicity of Pd to improve our toxicological knowledge for this contaminant. Under standardized toxicity testing conditions, we analyzed Pd accumulation and toxicity effects on the duckweed Lemna minor exposed to nominal concentrations from 2 to 50 µM. The inhibitory effect was significant (p < 0.05) from 8 µM of Pd, starting with 9.5% of growth inhibition and a decrease of 1 cm for the root size. Under 12.5 μM of Pd, the bioaccumulated Pd of 63.93 µg/g fresh weight inhibited plant growth by 37.4%, which was caused by a strong oxidative stress in the cytosol and organelles containing DNA. Under 25 and 50 μM of Pd, bioaccumulated Pd was able to deteriorate the entire plant physiology including chlorophyll synthesis, the photosystem II antenna complex, and the photochemical reactions of photosynthesis. In fact, plants treated with 50 μM Pd accumulated Pd up to 255.95 µg/g fresh weight, causing a strong decrease in total biomass and root elongation process. Therefore, we showed several growth, physiological, and biochemical alterations which were correlated with the bioaccumulation of Pd. These alterations constituted toxicity biomarkers of Pd with different lowest-observed-effect dose, following this order: root size = growth inhibition < catalase activity = carotenoid content = reactive oxygen species production = total thiols < chlorophyll a/b = variable fluorescence to maximal fluorescence intensity ratio = absorbed-light energy transfer from the chlorophyll a antenna to the photosystem II reaction center = performance index of photosystem II activity < V J . Therefore, the present study provides insight into the toxicity mechanism of Pd in L. minor plants under standardized testing conditions.

Assessment of ecotoxicological effects of Fojo coal mine waste elutriate in aquatic species (Douro Coalfield, North Portugal)

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Environmental impacts of landfills: perspectives on bio-monitoring

“…Respond to subcellular biochemical, immunological and genetic changes (DNA modifications) with no visible morphological and physiological changes (Dunham et al, 2019;Jmii and Dewez, 2021;Jaskulak and Grobelak, 2019) Reaction biomarkers Physiognomic degree of damage depending on the acting factor physiological reaction of plants to the action of the given factor shows in functional disorders such as restricted flowering, dieback of some organs, reduction of overall life or limitation of the most important life processes (Fränzle, 2006;Khalid et al, 2019;Veskoukis et al, 2019;Martínez and Barrera, 2021).…”