Many contaminated soils contain several toxic elements (TEs) in elevated contents, and plant-TE interactions can differ from single TE contamination. Therefore, this study investigated the impact of combined contamination (As, Cd, Pb, Zn) on the physiological and metabolic processes of lettuce. After 45 days of exposure, TE excess in soil resulted in the inhibition of root and leaf biomass by 40 and 48%, respectively. Oxidative stress by TE accumulation was indicated by markers-malondialdehyde and 5-methylcytosine-and visible symptoms of toxicity (leaf chlorosis, root browning) and morpho-anatomical changes, which were related to the change in water regime (water potential decrease). An analysis of free amino acids (AAs) indicated that TEs disturbed N and C metabolism, especially in leaves, increasing the total content of free AAs and their families. Stress-induced senescence by TEs suggested changes in gas exchange parameters (increase in transpiration rate, stomatal conductance, and intercellular CO2 concentration), photosynthetic pigments (decrease in chlorophylls and carotenoids), a decrease in water use efficiency, and the maximum quantum yield of photosystem II. These results confirmed that the toxicity of combined contamination significantly affected the processes of lettuce by damaging the antioxidant system and expressing higher leaf sensitivity to TE multicontamination.

• Keywords
• anthropogenic contamination, bioaccumulation, metals/metalloids, nitrogen metabolism, oxidative stress, stress response,
• Publication type
• Journal Article MeSH

A pot experiment was undertaken to investigate the effect of Cd, Pb and Zn multi-contamination on the physiological and metabolic response of carrot (Daucus carota L.) after 98 days of growth under greenhouse conditions. Multi-contamination had a higher negative influence on leaves (the highest Cd and Zn accumulation) compared to the roots, which showed no visible change in terms of anatomy and morphology. The results showed the following: (i) significantly higher accumulation of Cd, Zn, and Pb in the multi-contaminated variant (Multi) compared to the control; (ii) significant metabolic responses-an increase in the malondialdehyde content of the Multi variant compared to the control in the roots (by 20%), as well as in the leaves (by 53%); carotenoid content in roots decreased by 31% in the Multi variant compared with the control; and changes in free amino acids, especially those related to plant stress responses. The determination of hydroxyproline and sarcosine may reflect the higher sensitivity of carrot leaves to multi-contamination in comparison to roots. A similar trend was observed for the content of free methionine (significant increase of 31% only in leaves); (iii) physiological responses (significant decreases in biomass, changes in gas-exchange parameters and chlorophyll a); and (iv) significant changes in enzymatic activities (chitinase, alanine aminopeptidase, acid phosphatase) in the root zone.

• Keywords
• cadmium, free amino acids, lead, malondialdehyde, photosynthesis, root vegetable, soil enzymes, zinc,
• MeSH
• Chlorophyll A metabolism   MeSH
• Cadmium * metabolism   MeSH
• Daucus carota * metabolism   MeSH
• Lead metabolism   MeSH
• Soil MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Chlorophyll A MeSH
• Cadmium * MeSH
• Lead MeSH
• Soil MeSH

The effect of toxic element multicontamination on photosynthetic responses was observed in a greenhouse hydroponic culture of lettuce plants (Lactuca sativa var. capitata). The experiment focused only on the combined effect of selected toxic elements without the influence of soil, due to the hydroponic conditions. Pre-cultivated (six-true-leaf stage) plants were grown in control and contaminated hydroponic culture for 14 d. The mix of toxic elements (As, Cd, Pb, and Zn) in the contaminated solution corresponded to the water-soluble fraction of soil from the anthropogenically contaminated Litavka River area, Czech Republic. The plant response was measured by determining the toxic element contents, dry biomass, and gas-exchange parameters. Lettuce accumulated toxic elements predominantly in the roots, with low translocation to the leaves. The uptake of toxic elements harmed photosynthesis and caused a decrease in net photosynthetic rate, transpiration rate, and stomatal conductance. Consequently, the whole dry biomass of the plants decreased. The results show that contamination in hydroponic conditions had an irreversible effect on plant fitness due to direct contact between the roots and contaminated solutions.

• Keywords
• solution, stress, toxic element, translocation factor, transpiration rate,
• Publication type
• Journal Article MeSH

We investigated the genera, trophic groups, and functional guilds of soil nematodes at five alluvial meadows along the Litavka River in the Czech Republic to assess their usefulness as indicators of heavy metal pollution in soils. The Litavka River flows around the waste-sedimentation pond of a smelter in the city of Příbram in the Central Bohemian Region. Lead, zinc, and arsenic are the main pollutants in the soils in the vicinity of the smelter. The alluvial meadows closest to the pond and mine waste were the most heavily polluted sites, and contamination decreased downstream along the river with increasing distance from the sources of pollution. The nematode communities were sensitive to pollution, with the most contaminated sites having considerably fewer nematode individuals, fewer genera, and a less diverse and more degraded food web with less nematode biomass. Arsenic, lead, and zinc contents were significantly negatively correlated with the numbers of bacterivores, predators, omnivores, plant parasites, and fungivores, which were significantly less abundant at highly polluted sites. This correlation suggests that nematode groups with higher c-p values, and those with c-p 1 and 2 designations, can be useful indicators of high heavy-metal contamination in areas polluted for a long time. In contrast, the abundance of c-p 3 plant parasitic nematodes was positively correlated with copper, nickel, and zinc contents and with soil-moisture content in the alluvial meadows. Maturity index (MI) and MI2-5 were the most sensitive indices of the degree of disturbance of the soil ecosystem, with enrichment index, structure index, and basal index indicating the altered decomposition channels and diminished structure of the food web.

• Keywords
• bioindicators, ecology, environmental impact, heavy metals, interaction, pollution, soil nematodes,
• Publication type
• Journal Article MeSH