Antioxidant system activation by mercury in Pfaffia glomerata plantlets

Exploring the origins and cleanup of mercury contamination: a comprehensive review

Mercury is a global pollutant that poses significant risks to human health and the environment. Natural sources of mercury include volcanic eruptions, while anthropogenic sources include industrial processes, artisanal and small-scale gold mining, and fossil fuel combustion. Contamination can arise through various pathways, such as atmospheric deposition, water and soil contamination, bioaccumulation, and biomagnification in food chains. Various remediation strategies, including phytoremediation, bioremediation, chemical oxidation/reduction, and adsorption, have been developed to address mercury pollution, including physical, chemical, and biological approaches. The effectiveness of remediation techniques depends on the nature and extent of contamination and site-specific conditions. This review discusses the challenges associated with mercury pollution and remediation, including the need for effective monitoring and management strategies. Overall, this review offers a comprehensive understanding of mercury contamination and the range of remediation techniques available to mitigate its adverse impacts.

Cardamine violifolia as a potential Hg hyperaccumulator and the cellular responses

Cardamine violifolia belongs to the Brassicaceae family and is a selenium (Se) hyperaccumulator found in Enshi, China. In this study, C. violifolia was found to accumulate mercury (Hg) in its roots and aboveground parts at concentrations up to 6000 μg/g. In the seedling and mature stages, the bioaccumulation factors (BAFS) of Hg reached 1.8-223, while the translocation factor (TF) for Hg reached 1.5. We observed a significant positive correlation between THg concentrations in plant tissues and those in the soil (r2 = 0.71-0.84). Synchrotron radiation X-ray fluorescence with focused X-ray (μ-SRXRF) showed that Hg was translocated from the roots to shoots through the vascular bundle and was transported through the leaf veins in leaves. Transmission electron microscopy showed that root cells were more tolerant to Hg than leaf cells. These findings provide insights into the mechanisms of Hg hyperaccumulation in C. violifolia. Overall, we demonstrated that C. violifolia is a promising Hg hyperaccumulator that may be used for phytoremediating Hg-contaminated farmlands.

Pfaffia glomerata is a hyperaccumulator candidate: Cd and Zn tolerance, absorption, transfer, and distribution

Pfaffia glomerata is a candidate for phytoremediation due to its high biomass and high bioaccumulation efficiency of multiple heavy metals. It is essential to further evaluate its tolerance, absorption, transfer, and distribution to multiple heavy metals. In the current study, we evaluated the tolerance, absorption, transfer, and distribution of P. glomerata in a Cd/Pb/Cu/Zn combined-contaminated environment by two hydroponic experiments. The results demonstrated that P. glomerata was not affected by Cd/Pb/Cu/Zn exposure, except for the 50 μM Cd/Pb/Cu/Zn treatment, which significantly decreased the stem biomass. In a single Cd, Pb, Cu, and Zn exposure, the root of P. glomerata absorbed Cd/Pb/Cu/Zn in the order of Cd > Zn > Pb > Cu. Almost all Pb and Cu accumulated in the plant roots and were hardly transferred to the aboveground parts. Therefore, the order of total Cd/Pb/Cu/Zn extraction of a single plant in multiple Cd/Pb/Cu/Zn exposures at the same concentration was Cd > Zn > Pb > Cu. The bioconcentration factor (BCF) of Cd and Zn in roots, stems, and leaves increased with the concentration of Cd and Zn in the solution, and was > 1. In contrast with Cd and Zn, the BCFs of Cu and Pb in the stems and leaves were < 1. The element distribution of Pb, Cu, Zn, and Mn in the stem of P. glomerata was dispersed, indicating that the stem of P. glomerata does not have a detoxification mechanism for distributing metals to the area of low biological activity. The total amount of tartaric acid, critic acid, and DOC secreted by P. glomerata roots decreased with the increase in Cd/Pb/Cu/Zn exposure. However, further investigation is needed to unravel the interaction between the LMWOAs secreted by the root of P. glomerata and heavy metals.

Heavy metal induced stress on wheat: phytotoxicity and microbiological management

Among many soil problems, heavy metal accumulation is one of the major agronomic challenges that has seriously threatened food safety. Due to these problems, soil biologists/agronomists in recent times have also raised concerns over heavy metal pollution, which indeed are unpleasantly affecting agro-ecosystems and crop production. The toxic heavy metals once deposited beyond certain permissible limits, obnoxiously affect the density, composition and physiological activities of microbiota, dynamics and fertility of soil leading eventually to reduction in wheat production and via food chain, human and animal health. Therefore, the metal induced phytotoxicity problems warrant urgent and immediate attention so that the physiological activities of microbes, nutrient pool of soils and concurrently the production of wheat are preserved and maintained in a constantly deteriorating environment. To mitigate the magnitude of metal induced changes, certain microorganisms have been identified, especially those belonging to the plant growth promoting rhizobacteria (PGPR) group endowed with the distinctive property of heavy metal tolerance and exhibiting unique plant growth promoting potentials. When applied, such metal-tolerant PGPR have shown variable positive impact on wheat production, even in soils contaminated with metals, by supplying macro and micro nutrients and secreting active biomolecules like EPS, melanins and metallothionein (MTs). Despite some reports here and there, the phytotoxicity of metals to wheat and how wheat production in metal-stressed soil can be enhanced is poorly explained. Thus, an attempt is made in this review to better understand the mechanistic basis of metal toxicity to wheat, and how such phytotoxicity can be mitigated by incorporating microbiological remediation strategies in wheat cultivation practices. The information provided here is likely to benefit wheat growers and consequently optimize wheat production inexpensively under stressed soils.

Among many soil problems, heavy metal accumulation is one of the major agronomic challenges that has seriously threatened food safety.

Critical mercury concentration in tropical soils: Impact on plants and soil biological attributes

Mercury is a toxic element that becomes a problem when present at high concentrations in soils. Mercury toxicity in soils varies depending on chemical species, concentration, exposure routes, and organism vulnerability. There is little information regarding the toxicity of Hg in tropical soils, especially for establishing safe levels of this pollutant. The purpose of this study was to investigate Hg concentrations in two tropical soils and their effect on oats and common beans, as well as on soil biological attributes. The experiment was carried out in a greenhouse, following ISO 11.269-2 and OECD-208 guidelines. Oat and common bean were cultivated in a Typic Hapludox (TyHpx) and Rhodic Acrudox (RhAcx) contaminated with HgCl₂ at the following concentrations: 0, 2.5, 5.0, 10.0, 20.0, 40.0, and 80.0 mg of Hg kg^-1 of dry soil. The biological variables analyzed were seedling emergence, vegetative growth, chlorophyll content (SPAD index), gas exchange (photosynthetic rate, internal CO₂ concentration, transpiration rate, and stomatal conductance), and Hg concentration and accumulation in shoot dry matter. Microbial biomass carbon, soil basal respiration, and metabolic quotient (qCO₂) were also analyzed. Due to the sorptive characteristics of TyHpx, it had higher Hg concentrations than RhAcx. Mercury showed toxic effects on both oat and common bean species. However, common bean was affected only at concentrations higher than 20 mg kg^-1. The microbial community showed high sensitivity to soil Hg concentrations, but external factors, such as the plant species cultivated, influenced the sensitivity of the community. The microbiota was most sensitive in pots with common bean, and this effect was more pronounced at low clay and low organic matter contents (TyHpx). In this study, the concentration of 0.36 mg kg^-1 was critical for Hg in these soils, based on its deleterious effects on oat and common bean and on biological soil attributes.

Mechanisms of metal toxicity in plants

Metal toxicity in plants is still a global problem for the environment, agriculture and ultimately human health.

Impact assessment of mercury accumulation and biochemical and molecular response of Mentha arvensis: a potential hyperaccumulator plant

The present study was focused on examining the effect of Hg oxidative stress induced physiochemical and genetic changes in M. arvensis seedlings. The growth rate of Hg treated seedlings was decreased to 56.1% and 41.5% in roots and shoots, respectively, compared to the control. Accumulation of Hg level in both roots and shoots was increased with increasing the concentration of Hg. Superoxide dismutase (SOD), catalase (CAT), and ascorbate peroxidase (APX) activities were found to be increased with increasing the Hg concentration up to 20 mg/L; however, it was decreased at 25 mg/L Hg concentration. The POX enzyme activity was positively correlated with Hg dose. The changes occurring in the random amplification of ploymorphic DNA (RAPD) profiles generated from Hg treated seedlings included variations in band intensity, disappearance of bands, and appearance of new bands compared with the control seedlings. It was concluded that DNA polymorphisms observed with RAPD profile could be used as molecular marker for the evaluation of heavy metal induced genotoxic effects in plant species. The present results strongly suggested that Mentha arvensis could be used as a potential phytoremediator plant in mercury polluted environment.

Phosphorus improves arsenic phytoremediation by Anadenanthera peregrina by alleviating induced oxidative stress

Due to similarities in their chemical behaviors, studies examining interactions between arsenic (As)--in special arsenate--and phosphorus (P) are important for better understanding arsenate uptake, toxicity, and accumulation in plants. We evaluated the effects of phosphate addition on plant biomass and on arsenate and phosphate uptake by Anadenanthera peregrina, an important Brazilian savanna legume. Plants were grown for 35 days in substrates that received combinations of 0, 10, 50, and 100 mg kg(-1) arsenate and 0, 200, and 400 mg kg(-1) phosphate. The addition of P increased the arsenic-phytoremediation capacity of A. peregrina by increasing As accumulation, while also alleviating As-induced oxidative stress. Arsenate phytotoxicity in A. peregrina is due to lipid peroxidation, but not hydrogen peroxide accumulation. Added P also increased the activity of important reactive oxygen species-scavenging enzymes (catalase and ascorbate peroxidase) that help prevent lipid peroxidation in leaves. Our findings suggest that applying P represents a feasible strategy for more efficient As phytoremediation using A. peregrina.

In vitro antiviral activity of Brazilian plants (Maytenus ilicifolia and Aniba rosaeodora) against bovine herpesvirus type 5 and avian metapneumovirus

CONTEXT

Medicinal plants are well known for their use in traditional folk medicine as treatments for many diseases including infectious diseases.

OBJECTIVE

Six Brazilian medicinal plant species were subjected to an antiviral screening bioassay to investigate and evaluate their biological activities against five viruses: bovine herpesvirus type 5 (BHV-5), avian metapneumovirus (aMPV), murine hepatitis virus type 3, porcine parvovirus and bovine respiratory syncytial virus.

MATERIALS AND METHODS

The antiviral activity was determined by a titration technique that depends on the ability of plant extract dilutions (25 or 2.5 µg/mL) to inhibit the viral induced cytopathic effect and the extracts' inhibition percentage (IP).

RESULTS

Two medicinal plant species showed potential antiviral activity. The Aniba rosaeodora Ducke (Lauraceae) extract had the best results, with 90% inhibition of viral growth at 2.5 µg/mL when the extract was added during the replication period of the aMPV infection cycle. The Maytenus ilicifolia (Schrad.) Planch. (Celastraceae) extracts at a concentration of 2.5 µg/mL exhibited antiviral activity during the attachment phase of BHV-5 (IP = 100%).

DISCUSSION AND CONCLUSION

The biomonitored fractionation of the active extracts from M. ilicifolia and A. rosaeodora could be a potential tool for identifying their active compounds and determining the exact mechanism of action.

Effects of lead on the growth, lead accumulation and physiological responses of Pluchea sagittalis

This work aimed to study the process of stress adaptation in root and leaves of different developmental stages (apex, middle and basal regions) of Pluchea sagittalis (Lam.) Cabrera plants grown under exposure to five Pb levels (0, 200, 400, 600 and 1000 μM) for 30 days. Pb concentration and content in roots, stems, and leaves of different developmental stages increased with external Pb level. Consumption of nutrient solution, transpiration ratio, leaf fresh weight, leaf area, and shoot length decreased upon addition of Pb treatments. However, dry weight of shoot parts and roots did not decrease upon addition of Pb treatments. Based on index of tolerance, the roots were much more tolerant to Pb than shoots. δ-aminolevulinic acid dehydratase activity was decreased by Pb treatments, whereas carotenoid and chlorophyll concentrations were not affected. Lipid peroxidation and hydrogen peroxide concentration both in roots and leaves increased with increasing Pb levels. Pb treatments increased ascorbate peroxidase activity in all plant parts, while superoxide dismutase activity increased in leaves and did not change in roots. Catalase activity in leaves from the apex shoot was not affected by Pb, but in other plant parts it was increased. Pb toxicity caused increase in non-protein thiol groups concentration in shoot parts, whereas no significant difference was observed in roots. Both root and shoot ascorbic acid concentration increased with increasing Pb level. Therefore, it seems that Pb stress triggered an efficient defense mechanism against oxidative stress in P. sagittalis but its magnitude was depending on the plant organ and of their physiological status. In addition, these results suggest that P. sagittalis is Pb-tolerant. In conclusion, P. sagittalis is able to accumulate on average 6730 and 550 μg Pb g(-1) dry weight, respectively, in the roots and shoot, a physiological trait which may be exploited for the phytoremediation of contaminated soils and waters.