Cadmium Hyperaccumulation and Translocation in Impatiens Glandulifera: From Foe to Friend?

Effects of particle size on toxicity, bioaccumulation, and translocation of zinc oxide nanoparticles to bok choy (Brassica chinensis L.) in garden soil

The indiscriminate use of zinc oxide nanoparticles (ZnO NPs) in daily life can lead to their release into soil environment. These ZnO NPs can be taken up by crops and translocated to their edible part, potentially causing risks to the ecosystem and human health. In this study, we conducted pot experiments to determine phytotoxicity, bioaccumulation and translocation depending on the size (10 - 30 nm, 80 - 200 nm and 300 nm diameter) and concentration (0, 100, 500 and 1000 mg Zn/kg) of ZnO NPs and Zn ion (Zn2+) in bok choy, a leafy green vegetable crop. After 14 days of exposure, our results showed that large-sized ZnO NPs (i.e., 300 nm) at the highest concentration exhibited greater phytotoxicity, including obstruction of leaf and root weight (42.5 % and 33.8 %, respectively) and reduction of chlorophyll a and b content (50.2 % and 85.2 %, respectively), as well as changes in the activities of oxidative stress responses compared to those of small-sized ZnO NPs, although their translocation ability was relatively lower than that of smaller ones. The translocation factor (TF) values decreased as the size of ZnO NPs increased, with TF values of 0.68 for 10 - 30 nm, 0.55 for 80 - 200 nm, and 0.27 for 300 nm ZnO NPs, all at the highest exposure concentration. Both the results of micro X-ray fluorescence (μ-XRF) spectrometer and bio-transmission electron microscopy (bio-TEM) showed that the Zn elements were mainly localized at the edges of leaves exposed to small-sized ZnO NPs. However, the Zn elements upon exposure to large-sized ZnO NP were primarily observed in the primary veins of leaves in the μ-XRF data, indicating a limitation in their ability to translocate from roots to leaves. This study not only advances our comprehension of the environmental impact of nanotechnology but also holds considerable implications for the future of sustainable agriculture and food safety.

Phytoremediation potential of invasive plant species for potentially toxic elements along the Sava River upstream

Invasive plant species (IPS) have many characteristics that are necessary for successful phytoremediation and the accumulation of large amounts of potentially toxic elements (PTEs). The most common IPS from the source of the Sava River are Reynoutria japonica, Solidago canadensis and Impatiens glandulifera. Considering that the riparian soils of the Sava River are classified as moderately polluted, this study investigated their enrichment with PTEs (As, B, Cd, Cr, Cu, Ni, Pb, Zn) and the potential for accumulation of these elements in roots and leaves of the most common IPS. The soil and plant samples were prepared using the wet digestion method in CEM Mars 6 microwave oven. The content of PTEs in soil and plant samples was determined by ICP-OES. The results showed a moderate to very high enrichment of Cu in the soils. Impatiens glandulifera has the highest uptake capacity in leaves and phytoextraction ability of B, Cd, Cu and Zn. Reynoutria japonica has some potential for phytoextraction of Pb, Zn and especially B, while Solidago canadensis has potential for phytoextraction of B and Zn, while excluding Cr and Cu. The analyzes have shown that the studied species are not suitable for bioindication of PTEs in the riparian soils of the Sava River. Considering the enrichment of soils with Cu, Impatiens glandulifera is the most suitable species for phytoremediation of these elements among the studied species.

The effects of cadmium on selected oxidative stress parameters and the content of photosynthetic pigments in cucumber Cucumis sativus L

BACKGROUND

Environmental pollution by cadmium (Cd) is currently a common problem in many countries, especially in highly industrialised areas. Cd present in the soil can be absorbed by plants through the root system.

AIM

The aim of the present study was to investigate the effects of cadmium on the metabolic activity of cucumber plants (Cucumis sativus L.) and the accumulation and distribution of Cd in the organs of the plants.

METHODS

Cucumber seeds (3 g) were exposed to 0.76, 1.58 or 4.17 mg Cd/L (applied as CdCl2 solutions). The activity of selected antioxidant enzymes - glutathione peroxidase (GSH-Px), superoxide dismutase (SOD) and catalase (CAT), lipid peroxidation and the content of photosynthetic pigments were determined in 6-week-old cucumber plants. In addition, intake of Cd has been determined by flame atomic absorption spectrometry (F-AAS).

RESULTS

The results show that the applied cadmium concentrations affected the activity of antioxidant enzymes. An increase in CAT activity and a decrease in SOD activity were observed in all cucumber organs analysed. GSH-Px activity increased in the roots and stems. Surprisingly, GSH-Px activity decreased in the leaves. The level of lipid peroxidation was usually unchanged (the only one statistically significant change was a decrease in the concentration of malondialdehyde in the leaves which was observed after exposure to the highest Cd concentration). The applied Cd concentrations had no effect on the content of photosynthetic pigments. The highest cadmium content was found in the roots of cucumber plants. Cd tends to accumulate in the roots and a small amount was translocated to the stems and leaves, which was confirmed with the translocation factor (TF).

CONCLUSIONS

The results indicate that the range of cadmium concentrations used, corresponding to the level of environmental pollution recorded in Europe, effectively activates the antioxidant enzyme system, without intensifying lipid peroxidation or reducing the content of photosynthetic pigments.

Multiomics and biotechnologies for understanding and influencing cadmium accumulation and stress response in plants

Cadmium (Cd) is one of the most toxic heavy metals faced by plants and, additionally, via the food chain, threatens human health. It is principally dispersed through agro-ecosystems via anthropogenic activities and geogenic sources. Given its high mobility and persistence, Cd, although not required, can be readily assimilated by plants thereby posing a threat to plant growth and productivity as well as animal and human health. Thus, breeding crop plants in which the edible parts contain low to zero Cd as safe food stuffs and harvesting shoots of high Cd-containing plants as a route for decontaminating soils are vital strategies to cope with this problem. Recently, multiomics approaches have been employed to considerably enhance our understanding of the mechanisms underlying (i) Cd toxicity, (ii) Cd accumulation, (iii) Cd detoxification and (iv) Cd acquisition tolerance in plants. This information can be deployed in the development of the biotechnological tools for developing plants with modulated Cd tolerance and detoxification to safeguard cellular and genetic integrity as well as to minimize food chain contamination. The aim of this review is to provide a current update about the mechanisms involved in Cd uptake by plants and the recent developments in the area of multiomics approach in terms of Cd stress responses, as well as in the development of Cd tolerant and low Cd accumulating crops.

Nitric oxide induces antioxidant machinery, PSII functioning and artemisinin biosynthesis in Artemisia annua under cadmium stress

Soil contamination by heavy metals poses a significant environmental challenge, as the practical implementation of existing remediation technologies in the field has encountered numerous obstacles. This has necessitated the requirement of finding alternate solutions to reduce the harm caused to plants. In this study, nitric oxide (NO) was investigated for its potential to reduce cadmium (Cd) toxicity in A. annua plants. Although NO plays a vital role in the growth and development of plants, information on its role in reducing abiotic stress in plants is limited. A. annua plants were exposed to 20 and 40 mg/kg Cd regardless of the addition of exogenous sodium nitroprusside (SNP), a NO donor, at 200 µM concentration. Results showed that SNP treatment improved plant growth, photosynthesis, chlorophyll fluorescence, pigment content, and artemisinin production while reducing Cd accumulation and improving membrane stability in A. annua during Cd stress. The results demonstrated that NO can effectively reverse Cd-induced damage in A. annua by modulating the antioxidant system, maintaining redox homeostasis, and improving photosynthetic performance and different fluorescence parameters such as Fv/Fm, ФPSII, and ETR. The supplementation of SNP caused a substantial improvement in chloroplast ultrastructure, stomatal behavior, and different attributes relate to glandular secretory trichomes, which in turn increased artemisinin production; 14.11 % in plants exposed to Cd stress of 20 mg/kg. Our findings highlight that NO could be useful in mediating the repair of Cd-induced damage to A. annua, and suggest that it may play a critical role in plant signaling networks, improving plant adaptability to Cd stress. The results have important implications for developing new strategies to mitigate the negative impacts of environmental contaminants on plant health, and ultimately, the ecosystem.

Alleviation of cadmium toxicity in wheat by strigolactone: Regulating cadmium uptake, nitric oxide signaling, and genes encoding antioxidant defense system

Cadmium (Cd) in the food system poses a serious threat to human health. The evidence on strigolactones-mediated alleviation of abiotic stress signaling and eliciting physiological modifications in plants is scarce. Therefore, this experiment was conducted to explore the role of exogenous applied strigolactone (SL) in alleviating the toxic effects of Cd and to unravel its physiological, biochemical, and molecular mechanisms in wheat. Excessive accumulation of Cd drastically reduces growth attributes (-15%), nitric oxide signaling, and photosynthetic pigments by increasing oxidative stress biomarkers. Foliar applied SL (4 μM) decreased the Cd-induced growth inhibition (+10%), lessened plant Cd contents (-38% and -36%), shielded chlorophyll pigments (+25%), and considerably decreased Cd-induced oxidative stress in wheat. Moreover, SL applied on wheat foliage remarkably enhanced shoot and root nitric oxide content (+122% and +156%) and nitric oxide synthase activity (104% and 92%) in wheat, efficiently mitigating the Cd-induced suppression of superoxide dismutase and peroxidase, elevating the expression of genes encoding antioxidant defense system. The results of the current research exhibit that SL (GR24) could be a potential candidate for detoxification of Cd by reducing Cd contents, elevating the expression of genes encoding antioxidant defense system, and protecting wheat plants from oxidative stress by indirectly reducing oxidative stress biomarkers andsubsequently contributing to decreasing the possible risk of Cd contamination.

Strigolactone decreases cadmium concentrations by regulating cadmium localization and glyoxalase defense system: Effects on nodules organic acids and soybean yield

To decrease environmental and human health risks associated with crop and soil contamination, alternative solutions are still needed. The information on strigolactones (SLs)-mediated elicitation of abiotic stress signaling and triggering physiological alterations is scarce in the plant. To unravel the same, soybean plants were subjected to cadmium (Cd) stress (20 mg kg^-1), presence or absence of foliar applied SL (GR24) at the concentration of 10 μM. Excess Cd accumulation causes reduced growth (-52% shoot and +24% root), yield (-35%), physio-biochemical markers, organic acid production, and genes encoding heavy metal resilience in soybean. SL exogenous application decreased the growth and yield suppression (-12%), shielded chlorophyll (+3%), and prominently declined Cd-induced oxidative stress biomarkers accumulation in soybean. Moreover, SL effectively alleviates Cd-induced suppression in organic acids, superoxide dismutase (+73%), catalase activities (+117%), and increments ascorbate glutathione (ASA-GSH) cycle activities comprising ascorbate peroxidase, glutathione peroxidase, glutathione reductase, dehydroascorbate reductase, and monodehydroascorbate reductase. SL-mediated upregulation of genes encoding heavy metals tolerance and glyoxalase defense system in Cd stressed plants. The results of this work point out that SL could be a promising player in mitigating Cd-induced injuries effectively in soybean. It acts through the antioxidant system modulation for redox homeostasis, shielding chloroplasts, enhancing photosynthetic apparatus, and elevating organic acid production in soybean plants.

Cadmium Uptake From Soil by Ornamental Metallophytes: A Meta-analytical Approach

Soil pollution by cadmium (Cd) is a serious issue worldwide affecting environmental and human health. Conventional chemical and physical methods of treating contaminated soil are costly, time-consuming, and less effective. Phytoremediation using ornamental plants is a safe and effective method for the treatment of heavy metal-polluted soil due to their rapid growth and accumulation of biomass, high heavy metal tolerance, and non-edible nature. The present study is the first attempt for the meta-analysis of existing literature on Cd accumulation and translocation by ornamental plants. The uptake and transfer capacity of ornamental plants was measured using the bio-concentration factor (BCF) and translocation factor (TF). The results indicate that ornamental plants have varying Cd-absorption capacities. Among the 49 plant species identified from 31 articles, Helianthus annuus (BCF = 5.785), Impatiens glandulifera (BCF = 4.722), and Crassocephalum crepidioides (BCF = 3.623) represented higher accumulation capacity, whereas Rorippa globosa (TF = 1.653) and Sedum spectabile Boreau (TF = 1.579) represented significantly higher translocation capacity for Cd. The contribution of various environmental factors in influencing BCF was obtained through multiple linear regression analysis. Results showed that soil pH was the major factor influencing the BCF. To further explain the influence of four main factors that are soil pH, soil organic matter (SOM), cation exchange capacity (CEC), and soil Cd concentration on the accumulation efficiency of ornamental plants, a subgroup meta-analysis was performed. Results of the subgroup meta-analysis revealed that the BCF is negatively correlated with the soil pH and SOM, while the estimated limit of soil Cd concentration for growing ornamental plants was up to 50 mg/kg. Results of this study indicate that choosing a native hyperaccumulator is not the sole key to the success of a phytoremediation design, rather the conditions of the pedosphere will determine the regulating factor for efficient removal. In order to overcome the issue of recirculation and gradual release in the rhizosphere, it is important to match the type of hyperaccumulators to the soil environment (pH, CEC, SOM, etc.) to achieve maximum translocation and desired removal. This study will help researchers to pair the right plant with environmental conditions and customize more efficient phytoremediation systems.

Evaluation of phytoremediation potential and resistance of Gladiolus grandiflora L. against cadmium stress

Although irrigation water is a fundamental need for plant growth, it is also a source of pollutants if contaminated with harmful materials like cadmium (Cd). Irrigation water possessing abundant Cd causes damage to soil, plants, animals and ultimately human beings through the food chain. A pot experiment was conducted to evaluate the gladiolus (Gladiolus grandiflora L.) potential of Cd accumulation and the capability of the plant to be an economically beneficial choice in presence of high Cd irrigation water supply. Artificially prepared four levels of Cd irrigation water were applied to the plants viz., 30, 60, 90 and 120 mg L^-1. The results revealed that 30 mg L^-1 Cd had no difference in all growth-related parameters when compared to the control. Photosynthesis rate, stomatal conductance and transpiration rate along with plant height and spike length were reduced with high accumulation levels of Cd in plants. The main plant portion for Cd storage found in Gladiolus grandiflora L was corm where the amount of Cd was 10-12 times higher than the amount found in leaves, and 2-4 times more than the stem. This deportment was further established by the translocation factor (TF). In corm to shoot TF and corm to stem TF, the factor reduced with increasing Cd levels, while, in corm to leaves TF, Cd levels were statistically non-significant. From corm to shoot TF value of 0.68 and 0.43 in case of 30 and 60 mg L^-1, Cd treatments indicates good phytoremediation potential of Gladiolus in low and moderate Cd-polluted environments. Conclusively, the study reveals the good capability of Gladiolus grandiflora L. to harvest Cd from the soil and water in reasonably good amount with sufficient potential to grow under irrigation-based Cd stress. Under revelations of the study, Gladiolus grandiflora L appeared as a Cd accumulator which could potentially be used as a sustainable approach for phytoremediation of Cd.

Insights into strigolactone (GR24) mediated regulation of cadmium-induced changes and ROS metabolism in Artemisia annua

Agricultural soil contamination and subsequently crops still require alternative solutions to reduce associated environmental risks. The effects of strigolactones (SLs) in alleviating cadmium (Cd) phytotoxicity in Artemisia annua plants were investigated during this study. Strigolactones play a vital role during plant growth and development due to their complex interplay during a plethora of biochemical processes. However, information on the potential of SLs to elicit abiotic stress signaling and trigger physiological modifications in plants is limited. In order to decipher the same, A. annua plants were exposed to different concentrations of Cd (20 and 40 mg kg^-1), with or without the supplementation of exogenous SL (GR24, a SL analogue) at 4 µM concentration. Under Cd stress, excess Cd accumulation resulted in reduced growth, physio-biochemical traits, and artemisinin content. However, the follow-up treatment of GR24 maintained a steady state equilibrium between reactive oxygen species and antioxidant enzymes, improved chlorophyll fluorescence parameters such as Fv/Fm, Ф_PSII, and ETR for improved photosynthesis, enhanced chlorophyll content, maintained chloroplast ultrastructure, improved the glandular trichome (GT) attributes and artemisinin production in A. annua. Moreover, it also resulted in improved membrane stability, reduced Cd accumulation, and regulated the behaviour of stomatal apertures for better stomatal conductance under Cd stress. The results of our study suggest that GR24 could be highly effective in alleviating Cd-induced damages in A. annua. It acts via the modulation of the antioxidant enzyme system for redox homeostasis, protection of the chloroplasts and pigments for improved photosynthetic performance, and improved GT attributes for enhanced artemisinin production in A. annua.

Improving capacity for phytoremediation of Vetiver grass and Indian mustard in heavy metal (Al and Mn) contaminated water through the application of clay minerals

One of the consequences of mining is the release of heavy metals into the environment, especially water bodies. Phytoremediation of areas contaminated by heavy metals using Vetiver grass and Indian mustard is cost-effective and environmentally friendly. This study aimed at enhancing remediation of heavy metal contaminated water through the simultaneous hybrid application of clay minerals (attapulgite and bentonite) and Vetiver grass or Indian mustard. A 21-day greenhouse experiment was carried out to investigate the effectiveness of the clay minerals to improve heavy metal phytoremediation. The highest accumulation of aluminium (Al) by Vetiver grass was 371.8 mg/kg in the BT2.5VT treatment, while for Mn, the highest accumulation of 34.71 mg/kg was observed in the AT1VT treatment. However, Indian mustard showed no significant uptake of heavy metals, but suffered heavy metal toxicity despite the addition of clay minerals. From this study, it was evident that bentonite added at 2.5% (w/v) could improve the phytoremediation capacity of Vetiver grass for Al and Mn polluted water. The current laboratory-scale findings provided a basis for field trials earmarked for remediation in a post-mining coal environment in South Africa. This remediation approach can also be adopted in other places.

Comparative bioaccumulation, translocation, and phytotoxicity of metal oxide nanoparticles and metal ions in soil-crop system

Exposure of the soil environment to metal nanoparticles (MNPs) has been extensive because of their indiscriminate use and the disposal of MNP products in various applications. In MNP-amended soil, various crops can absorb the nanoparticles, and accumulation of the MNPs in farm products has potential risks for bioconcentration in humans and livestock. Here, we evaluated the comparative bioaccumulation, translocation, and phytotoxicity of MNPs (ZnO and CuO NPs) and metal ions (Zn(NO3)2 and Cu(NO3)2) in four different crops, namely lettuce, radish, bok choy, and tomato. We carried out pot experiments to evaluate the phytotoxicity in the crops from the presence of MNPs and metal ions. Phytotoxicity from different treatments differed depending on the plant species, and metal types. In addition, exposure to Zn and Cu showed positive dose-dependent effects on their bioaccumulation in each crop. However, there were no significant differences in metal bioaccumulation depending on whether the crops were exposed to MNPs or metal ions. By calculating the bioconcentration factor (BCF) and translocation factor (TF), we were able to estimate the biological uptake and translocation abilities of MNPs and metal ions for each crop. It was found that lettuce and radish had greater BCFs than bok choy and tomato, while bok choy and tomato had higher TFs. Also, the uptake and translocation of Zn were better than those of Cu. However, the values for BCF and TF for each crop showed no significant differences between MNP and metal ion exposure. A micro X-ray fluorescence (μ-XRF) spectrometer analysis demonstrated that only Zn elements appeared in the primary veins and edges of all leaves and the storage root of radish. Our study aims to estimate bioaccumulation, translocation, and the implied potential risks from MNPs accumulated in different plant species.

Salinity and Heavy Metal Tolerance, and Phytoextraction Potential of Ranunculus sceleratus Plants from a Sandy Coastal Beach

The aim of the present study was to evaluate tolerance to salinity and different heavy metals as well as the phytoextraction potential of Ranunculus sceleratus plants from a brackish coastal sandy beach habitat. Four separate experiments were performed with R. sceleratus plants in controlled conditions: (1) the effect of NaCl gradient on growth and ion accumulation, (2) the effect of different Na⁺ and K⁺ salts on growth and ion accumulation, (3) heavy metal tolerance and metal accumulation potential, (4) the effect of different forms of Pb salts (nitrate and acetate) on plant growth and Pb accumulation. A negative effect of NaCl on plant biomass was evident at 0.5 g L^-1 Na⁺ and growth was inhibited by 44% at 10 g L^-1 Na⁺, and this was associated with changes in biomass allocation. The maximum Na⁺ accumulation (90.8 g kg^-1) was found in the stems of plants treated with 10 g kg^-1 Na⁺. The type of anion determined the salinity tolerance of R. sceleratus plants, as Na⁺ and K⁺ salts with an identical anion component had a comparable effect on plant growth: nitrates strongly stimulated plant growth, and chloride treatment resulted in slight but significant growth reduction, but plants treated with nitrites and carbonates died within 4 and 5 weeks after the full treatment, respectively. The shoot growth of R. sceleratus plants was relatively insensitive to treatment with Mn, Cd and Zn in the form of sulphate salts, but Pb nitrate increased it. Hyperaccumulation threshold concentration values in the leaves of R. sceleratus were reached for Cd, Pb and Zn. R. sceleratus can be characterized as a shoot accumulator of heavy metals and a hyperaccumulator of Na⁺. A relatively short life cycle together with a high biomass accumulation rate makes R. sceleratus useful for dynamic constructed wetland systems aiming for the purification of concentrated wastewaters.

Effect of Cadmium on Macro and Micronutrient Uptake and Translocation by Leucaena leucocephala

Environmental contamination with Cadmium (Cd) is of great concern due to its hazardous effects on living organisms.Query In the present research, Leucaena leucocephala plants were exposed to Cd concentrations of 5, 10, and 15 mg/L to determine their potential use in Cd remediation. Different parameters including Cd uptake, macro/micronutrient content, chlorophyl, and catalase production were determined. Results indicated that Cd uptake by L. leucocephala roots did not show a significant difference between treatments. However, a significant increase in Cd content (Tukey´s HSD) was observed in stems as Cd levels in the media augmented. The highest Cd content (830 ± 20 mg/kg) was determined in stems of plants exposed to 15 mg/L Cd, and no Cd was detected in leaves. Data showed that as Cd concentration increased in the media, Ca, Mg, K, Zn, and Mn decreased. Moreover, while the presence of Cd reduced catalase activity in roots, chlorophyll production was not affected.

Biodegradable chelant-metal complexes enhance cadmium phytoextraction efficiency of Solanum americanum

Toxic contaminants (metals and metal-containing compounds) are accumulating in the environment at an astonishing rate and jeopardize human health. Remarkable industrial revolution and the spectacular economic growth are the prime causes for the release of such toxic contaminants in the environment. Cadmium (Cd) is ranked the 7th most toxic compound by the Agency for Toxic Substances and Disease Registry (USA), owing to its high carcinogenicity and non-biodegradability even at miniscule concentration. The present study assessed the efficiency of four biodegradable chelants [nitrilotriacetic acid (NTA), ethylenediamine disuccinate (EDDS), ethylene glycol tetraacetic acid (EGTA), and citric acid (CA)] and their dose (5 mM and 10 mM) in enhancing metal accumulation in Solanum americanum Mill. (grown under 24 mg Cd kg^-1 soil) through morpho-physiological and metal extraction parameters. Significant variations were observed for most of the studied parameters in response to chelants and their doses. However, ratio of root and shoot length, and plant height stress tolerance index differed non-significantly. The potential of chelants to enhance Cd removal efficiency was in the order - EGTA (7.44%) > EDDS (6.05%) > NTA (4.12%) > CA (2.75%). EGTA and EDDS exhibited dose-dependent behavior for Cd extraction with 10 mM dose being more efficient than 5 mM dose. Structural equation model (SEM) depicted strong positive interaction of metal extraction parameters with chelants (Z-value = 11.61, p = 0.001). This study provides insights into the importance of selecting appropriate dose of biodegradable chelants for Cd extraction, as high chelant concentration might also result in phytotoxicity. In the future, phytoextraction potential of these chelants needs to be examined through field studies under natural environmental conditions.

Organic amendment additions to cadmium-contaminated soils for phytostabilization of three bioenergy crops

The effects of organic amendments on the phytoremediation of cadmium (Cd) in acacia (Acacia mangium), jatropha (Jatropha curcas), and cassava (Manihot esculenta) were investigated. The bone meal/bat manure and leonardite/bat manure amendments resulted in better growth performance in both acacia and cassava (growth rate in dry biomass; GRDB 24.2 and 22.2, respectively), while bone meal (GRDB 17.2) was best for jatropha. The lower root/shoot ratio values of jatropha and acacia suggest that these species were better suited than cassava on Cd-contaminated soil. Cassava experienced toxicity symptoms after harvest (3 months). Acacia root accumulated somewhat greater Cd concentrations (up to 5.1 mg kg^-1) than cassava and jatropha roots (2.2-3.9 and 2.7-4.1 mg kg^-1, respectively). The bone meal and chicken manure (BMCM) treatment for jatropha had the highest bioconcentration factor for root (1.3) and the lowest translocation factor (0.7). Despite the fact that this treatment had substantial Cd concentrations in the soil (3.1 mg kg^-1), low Cd accumulation value (3.2 mg kg^-1) and the lowest Cd uptake value (127.8 mg plant^-1) were observed, clearly indicating that this amendment reduced Cd bioavailability. When growth performance of the study plants is considered, jatropha and acacia may be suitable for phytomanagement of Cd-contaminated soil.

Metal Removal Kinetics, Bio-Accumulation and Plant Response to Nutrient Availability in Floating Treatment Wetland for Stormwater Treatment

Floating treatment wetland (FTW) is a recent innovation to remove nutrients from stormwater, but little is known about its effectiveness for metal removal. This study aims to test the hypothesis that the metal removal performance of FTWs will be affected by nutrient (NH3-N, NO3-N, and PO4-P) availability in stormwater. Two experiments were carried out in nutrient-deficient tap water, and two experiments were carried out in nutrient-rich lake water using four native Australian plants, namely Carex fascicularis, Juncus kraussii, Eleocharis acuta, and Baumea preissii. Up to 81% Cu and 44.9% Zn removal were achieved by the plants in 16 days in tap water. A reduction in Cu and Zn removal of 28.4–57.3% and 1.0–19.7%, respectively, was observed in lake water compared with tap water for the same duration. The kinetic analysis also confirmed that plant metal uptake rates slowed down in lake water (0.018–0.088 L/mg/day for Cu and 0.005–0.018 L/mg/day for Zn) compared to tap water (0.586–0.825 L/mg/day for Cu and 0.025–0.052 L/mg/day for Zn). A plant tissue analysis revealed that E. acuta and B. preissii bioaccumulated more than 1000 mg/kg of both metals in their tissue, indicating high metal accumulation capacities. To overcome the slower metal uptake rate problem due to nutrient availability, future studies can investigate multi-species plantations with nutrient stripping plants and metal hyper-accumulator plants.

Cadmium Uptake and Growth Responses of Seven Urban Flowering Plants: Hyperaccumulator or Bioindicator?

The application of flowering plants is the basis of urban forest construction. A newly-found flowering hyperaccumulator is crucial for remediating urban contaminated soil sustainably by cadmium (Cd). This study evaluated growth responses, Cd uptake and bioaccumulation characteristics of seven urban flowering plants. Based on growth responses of these plants, Calendula officinalis L. showed high tolerance to at least 100 mg kg−1 Cd, in terms of significant increase in biomass and with no obvious changes in height. After 60 d exposure to 100 mg kg−1 Cd, the accumulated Cd in shoots of the plant reached 279.51 ± 13.67 μg g−1 DW, which is above the critical value defined for a hyperaccumulator (100 μg g−1 DW for Cd). Meanwhile, the plant could accumulate Cd to as much as 926.68 ± 29.11 μg g−1 DW in root and 1206.19 ± 23.06 μg g−1 DW in plant, and had higher Cd uptake and bioaccumulation values. According to these traits, it is shown that Calendula officinalis L. can become a potential Cd-hyperaccumulator for phytoremediation. By contrast, Dianthus caryophyllus L. is very sensitive to Cd stress in terms of significantly decreased biomass, height and Cd uptake, indicating the plant is considered as a Cd-bioindicator.

Endophytic bacteria promote biomass production and mercury-bioaccumulation of Bermuda grass and Indian goosegrass

Plant growth-promoting endophytic bacteria can potentially improve the biomass production of Hg-accumulating grasses, resulting in improved Hg extraction from contaminated soils. This study aimed to analyze the effect of inoculation of Hg-resistant endophytic bacteria (i) Jeotgalicoccus huakuii (B1) and (ii) Bacillus amyloliquefaciens (B2), as single and consortium inoculant, on biomass production and Hg bioaccumulation of Bermuda grass (R1) and Indian goosegrass (R2) planted as monoculture and mixed cropping. The grass seeds were surface-sterilized before the inoculation. Both inoculated seeds with B1 and B2 (treatments) and uninoculated seeds were sown separately in sterilized sand. Grass seedlings of both treatments and control were replanted in the washed and sterilized sand medium, spiked with HgCl₂ (100 mg kg^-1). A subset of grass was harvested at 0, 4, 6, and 10 weeks after planting to measure biomass production and Hg bioaccumulation. The results showed that bacterial inoculation enhanced the grass biomass by 52.68% and Hg bioaccumulation by 47.76%. Mercury residue of Hg-spiked sand treated with the bacterial consortium was reduced by 80%. This suggests that endophytic bacteria can improve grass biomass production and enhance Hg bioaccumulation in grass biomass.

Hemarthria compressa—Aspergillus niger—Trichoderma pseudokoningii Mediated Trilateral Perspective for Bioremediation and Detoxification of Industrial Paper Sludge

The present study was carried out to evaluate the effects of different fungal species on the metal uptake from paper sludge by Hemarthria compressa L. Paper sludge (PS) in various concentrations (0, 30% and 60%) were used with four treatments of two fungal species (F0 = Control, F1 = Aspergillus niger, F2 = Trichoderma pseudokoningii, F3 = A. niger + T. pseudokoningii). Paper sludge as rooting medium steadily influenced growth and physio-biochemical attributes of H. compressa in F0. Results revealed discrete variations in growth attributes with different PS concentrations and each fungal treatment. The maximum damages in ionic homeostasis (Na+, K+, Ca2+, Mg2+) due to PS toxicity were evident in parallel with declined chlorophyll concentration. The highest growth, total chlorophyll and biomass of the plants were observed when PS was treated with combined fungal strains (F3). Translocation factor decreased with F3 that is indicative of changes in Cd, Pb, and Cu movement to shoot from root. The plants with combined fungal treatment also showed greater catalase (CAT), superoxide dismutase (SOD), and peroxidase (POD) activity. Ions, such as Ca, Mg, and Na, also increased gradually with combined fungal treatment. The correlation matrix displayed a close association among diverse fungal and PS levels with multiple plant attributes. PCA-Biplot confirmed the outcome of correlational analyses among different characters of H. compressa. The combined fungal mediate the extraction of heavy metals from the paper sludge by H. compressa recommends the high accumulation of heavy metal (HM) and possible reutilization of metal free sludge as a fertilizer, for application in cultivated fields. Furthermore, the effects of fungal species on HM attenuation in PS are linear and can be used in different habitats. Advancement in such research work will also be helpful in understanding the mechanisms and enhancing the ability of other native microbes to remediate metals.

Heavy metal phytoremediation potential of the roadside forage Chloris barbata Sw. (swollen windmill grass) and the risk assessment of the forage-cattle-human food system

This study presents the assessment of the risks incidental to the growth of the common tropical grass species Chloris barbata Sw. (swollen windmill grass) on road margins contaminated with Pb and Cd. Pot experiments were first carried out to quantify the Pb and Cd accumulation potential of the plant species in various plant parts as a function of the metal concentration in soil. C. barbata was found to be a hyperaccumulator for Cd (BCF>1, for aerial parts) and an excluder of Pb (BCF<1, for aerial parts). As the plant was found to accumulate Pb in its roots with TF<1, it can be considered a phytostabilizer of Pb. The mathematical relationship developed between soil concentrations of Pb and Cd and their corresponding concentrations in aerial parts were used in combination with the concentrations of these heavy metals reported in roadside soils to obtain estimates of their accumulation in the forage and consequently in the animal organs. Risk to the consumers of offal was estimated. It was found that the consumption of kidney meat was riskier than the consumption of liver meat. Furthermore, it was seen that despite the nearly two order less concentrations of Cd in roadside soils compared to Pb, it was posing a higher risk. For the median concentrations of Pb reported in roadside soils and cattle feeding exclusively on C. barbata growing on roadside soils, the HQ exceeded 1 for weekly consumption of kidney meat above 650 g. For median Cd concentrations, consumption of kidney meat above 230 g/week resulted in HQ>1. The scenario considered for risk assessment is significant for India, where stray grazing of cattle on road margins is common and offal offers a cheap source of animal protein for the economically poor.

Impacts of the Invasive Impatiens glandulifera: Lessons Learned from One of Europe's Top Invasive Species

Simple Summary

Plants and animals are a part of a larger system, commonly referred to as an ecosystem. This generally implies a balance existing between prey and predators. The unintentional introduction of a species in a new environment can lead to a significant alteration of the ecosystem(s) and the uncontrolled spread of the species. When this takes place, the introduced species is referred to as invasive. Invasives can affect the ecosystem in profound ways, and generally, negatively impacting on the native species. This manuscript reviewed the current knowledge of one of Europe’s top invasives, the Himalayan balsam (Impatiens glandulifera). It provides insights on the species and what have we learned from this invasive species.

Abstract

Biological invasions are renowned for their negative ecological and economic implications, however from studying invasions invaluable insights can be gained in the fields of ecology and evolution- potentially contributing towards conservation plans to deal, not only with biological invasion, but with other concerning issues, such as climate change. Impatiens glandulifera, or Himalayan balsam, is widely considered to be a highly problematic invasive, having spread across more than thirty countries during the past century. This paper will examine the findings which have arose from studying I. glandulifera and its impacts on the invaded ecosystem.

Potential of ornamental monocot plants for rhizofiltration of cadmium and zinc in hydroponic systems

Cadmium (Cd) and zinc (Zn) accumulation and uptake ability have been investigated in three ornamental monocot plants (Heliconia psittacorum x H. spathocircinata, Echinodorus cordifolius, and Pontederia cordata) grown in hydroponic systems. All study plants in the highest heavy metal treatments were found to be excluders for Cd and Zn with translocation factor values < 1 and bioconcentration factor (BCF) values > 100. The highest Cd and Zn accumulations were found in roots of E. cordifolius (4766.6 mg Zn kg^-1 and 6141.6 mg Cd kg^-1), followed by H. psittacorum x H. spathocircinata (4313.5 mg Zn kg^-1) and P. cordata (3673.3 mg Cd kg^-1), respectively, whereas shoots had lower performances. However, P. cordata had the lowest dry biomass production compared to the other two plant species in this study. As a result of dilution effects, heavy metal accumulation for all study plants was lower in the combined heavy metal treatments than in solely Cd and Zn only treatments. At the end of experiments, the highest uptakes of Cd and Zn were found in H. psittacorum x H. spathocircinata (62.1% Zn²⁺ from 10 mg Zn L^-1 solution) and E. cordifolius (27.3% Cd²⁺ from 2 mg Cd L^-1 solution). Low percentage metal uptakes were found in P. cordata; therefore, E. cordifolius and H. psittacorum x H. spathocircinata are clearly better suited for removing Cd and/or Zn from contaminated waters and hydroponic systems.

Soil Sulfur Sources Differentially Enhance Cadmium Tolerance in Indian Mustard (Brassica juncea L.)

The effect of four soil-applied sulfur (100 mg S kg−1 soil (100S) and 200 mg S kg−1 soil (200S)) in different sources (elemental S, ammonium sulfate, gypsum or magnesium sulfate) in protecting mustard (Brassica juncea L. (Czern & Coss.)) from cadmium effects was studied. Based on the observed reduction in growth and photosynthesis in plants subjected to 100 and 200 mg Cd kg−1 soil, B. juncea cv. Giriraj was selected as the most Cd-tolerant among five cultivars (namely, Giriraj, RH-0749, Pusa Agrani, RH-406, and Pusa Tarak). Sulfur applied to soil mitigated the negative impact of Cd on sulfur assimilation, cell viability, and photosynthetic functions, with a lower lipid peroxidation, electrolyte leakage, and contents of reactive oxygen species (ROS: hydrogen peroxide, H2O2, and superoxide anion, O2•−). Generally, added S caused higher activity of antioxidant enzymes (ascorbate peroxidase, catalase and superoxide dismutase), contents of ascorbate (AsA) and reduced glutathione (GSH); increases in the activities of their regenerating enzymes (dehydroascorbate reductase and glutathione reductase); as well as rises in S assimilation, biosynthesis of non-protein thiols (NPTs), and phytochelatins (PCs). Compared to the other S-sources tested, elemental S more prominently protected B. juncea cv. Giriraj against Cd-impacts by minimizing Cd-accumulation and its root-to-shoot translocation; decreasing cellular ROS and membrane damage, and improving Cd-chelation (NPTs and PCs), so strengthening the defense machinery against Cd. The results suggest the use of elemental S for favoring the growth and development of cultivated plants also in Cd-contaminated agricultural soils.

Assessing of growth, antioxidant enzymes, and phytohormone regulation in Cucurbita pepo under cadmium stress

One of the major problems worldwide is soil pollution by trace metal elements, which limits plant productivity and threatens human health. In this work, we have studied the effect of different concentrations of cadmium on Cucurbita pepo plants, evaluating different physiological and biochemical parameters: hormone signaling, metabolite concentration (malondialdehyde and hydrogen peroxide) and, in addition, the antioxidant enzyme activities of catalase and superoxide dismutase were evaluated. The production of biomass decreased under the Cd-stress. The results showed that C. pepo accumulates higher amounts of Cd2+ in roots than in shoots and fruits. Cd2+ differently affected the content of endogenous phytohormones. Furthermore, data suggest an essential involvement of roots in the regulation of tolerance to trace elements. As a result, indole acetic acid content increased in roots of treated plants, indicating that this phytohormone can stimulate root promotion and growth under Cd-stress. Similarly, salicylic acid content in roots and shoots increased in response to Cd2+, as well as abscisic acid levels in roots and fruits. In roots, the rambling accumulation pattern observed for jasmonic acid and salicylic acid suggests the lack of a specific regulation role against trace element toxicity. The activity of catalase and superoxide dismutase decreased, disrupted by the metal stress. However, the proline, malondialdehyde and hydrogen peroxide content significantly increased in Cd2+in all the analyzed tissues of the stressed plants. All these data suggest that C. pepo plants are equipped with an effective antioxidant mechanism against oxidative stress induced by cadmium up to a concentration of 500 μM.

Enzymatic response to cadmium by Impatiens glandulifera: A preliminary investigation

This paper aims to develop our understanding of the effect of cadmium (Cd) on Impatiens glandulifera, a recently identified potential Cd hyperaccumulator. Impatiens glandulifera plants were exposed to three concentrations of Cd (20, 60 and 90 mg/kg) and were sampled at two timepoints (one and seven days) to investigate the stress response of I. glandulifera to Cd. Cd can induce oxidative stress in plants, triggering overproduction of reactive oxygen species (ROS). The level of activity of catalase (CAT) and ascorbate peroxidase (APX), two crucial antioxidant enzymes responsible for detoxifying ROS, were found to increase in a concentration dependent manner. Though there was no change observed in the level of superoxide dismutase (SOD) activity, the activity of glutathione S-transferase (GST), involved in detoxifying and sequestering Cd, increased after exposure to Cd. Cd did not appear to impact the levels of proline and photosynthetic pigments, indicating the plants weren't stressed by the presence of Cd. These results suggest that the rapid response observed in enzyme activity aid the efficacious mitigation of the toxic effects of Cd, preventing significant physiological stress in I. glandulifera.

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Impatiens glandulifera display an enhance tolerance to Cadmium.

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An early response in a Catalase and Peroxidase ascorbate mediates Cadmium tolerance.

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No impact on stress indicators were shown by Impatiens glandulifera even after 7 days.

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SOD was found to be not involved in the early response to Cadmium.

Phytoremediation potential of Chromolaena odorata, Impatiens patula, and Gynura pseudochina grown in cadmium-polluted soils

To assess the cadmium (Cd) phytoremediation of three native plant species from Padeang zinc (Zn) mine area (Chromolaena odorata, Impatiens patula, and Gynura pseudochina), a hydroponic experiment was performed in nutrient solutions containing various concentrations of Cd (0, 5, 10, 20, and 50 mg L^-1) for 15 days. In the hydroponic experiment, C. odorata showed significantly higher total Cd content than those grown in 50 mg L^-1 Cd solutions. Only C. odorata and I. patula were chosen for the pot experiment. The plants were grown in spiked Cd-contaminated soils for 90 days, with different concentrations of Cd (0, 20, 40, 60, and 80 mg kg^-1). The results from the pot experiment revealed that both species accumulated more Cd in their root parts, with translocation factor values < 1. C. odorata exhibited the highest biomass production, relative growth rate, and Cd uptake or removal. The findings of the study clearly demonstrate the best uptake of C. odorata in Cd phytoremediation. Novelty statementEven though Chromolaena odorata, Impatiens patula, and Gynura pseudochina have been reported as a Cd accumulator but the assessment of these species by nutrient medium and the soil was not undertaken so far. The discovery of new Cd-accumulator plants has been hindered by the lack of efficient assessing. To assess the suitability of specific species of tropical plants that are able to uptake high amounts of Cd without risk of toxicity under conditions similar to the actual field study, is a novelty.

Response of Corchorus olitorius Leafy Vegetable to Cadmium in the Soil

Corchorus olitorius, a leafy vegetable with high nutrient content, is normally collected from the wild, in areas that are prone to cadmium (Cd) toxicity. However, studies on how Cd accumulation affects vegetative and reproductive traits of leafy vegetables in South Africa are limited. Therefore, this study tested the effect of Cd accumulation on C. olitorius morphological traits. Plants were grown under various Cd concentrations and studied for variation in vegetative and reproductive traits as well as accumulation in roots and shoots. Plants exposed to 5 mg/kg Cd had longer roots with higher moisture content, heavier fresh and dried stems, as well as dried leaves, which indicated a hormetic effect in C. olitorius after exposure to low Cd concentration in the soil. Again, plants treated with 5–10 mg/kg Cd, accumulated toxic (>10 mg/kg dry weight) Cd within shoots and roots, with minor morphological alterations. Plants could survive, with some morphological defects, Cd toxicity up to 20 mg/kg in soil. Only plants exposed to 5 mg/kg could reproduce. Cd accumulation increased with an increase in the soil, with higher accumulation in shoots. The translocation factor was high (>1) in all Cd concentrations. In conclusion, C. olitorius can accumulate toxic Cd, and yet grow and reproduce either normally or better than the control. The proposed dose of Cd that induces hormesis in C. olitorius is 5 mg/kg in the soil. Therefore, C. olitorius is suitable for phytoremediation of Cd contaminated soils, but unsafe for consumption when it grows in such areas.