Cadmium effects on mineral nutrition of the Cd-hyperaccumulator Pfaffia glomerata

Salicylic acid alleviates the effects of cadmium and drought stress by regulating water status, ions, and antioxidant defense in Pterocarya fraxinifolia

Introduction

Pterocarya fraxinifolia (Poiret) Spach (Caucasian wingnut, Juglandaceae) is a relict tree species, and little is known about its tolerance to abiotic stress factors, including drought stress and heavy metal toxicity. In addition, salicylic acid (SA) has been shown to have a pivotal role in plant responses to biotic and abiotic stresses.

Methods

The current study is focused on evaluating the impact of foliar application of SA in mediating Caucasian wingnut physiological and biochemical responses, including growth, relative water content (RWC), osmotic potential (Ψs), quantum yield (Fv/Fm), electrolyte leakage, lipid peroxidation, hydrogen peroxide, and antioxidant enzymes, to cadmium (Cd; 100 µM) and drought stress, as well as their interaction. Moreover, the antioxidant activity (e.g., ascorbate peroxidase, catalase, glutathione reductase, peroxidase, and superoxide dismutase activities) of the stressed trees was investigated. The study was conducted on 6-month-old seedlings under controlled environmental conditions in a greenhouse for 3 weeks.

Results and discussion

Leaf length, RWC, Ψs, and Fv/Fm were decreased under all treatments, although the effect of drought stress was the most pronounced. An efficient antioxidant defense mechanism was detected in Caucasian wingnut. Moreover, SA-treated Caucasian wingnut plants had lower lipid peroxidation, as one of the indicators of oxidative stress, when compared to non-SA-treated groups, suggesting the tolerance of this plant to Cd stress, drought stress, and their combination. Cadmium and drought stress also changed the ion concentrations in Caucasian wingnut, causing excessive accumulation of Cd in leaves. These results highlight the beneficial function of SA in reducing the negative effects of Cd and drought stress on Caucasian wingnut plants.

Assessing lead and cadmium tolerance of Chenopodium ambrosioides during micropropagation: an in-depth qualitative and quantitative analysis

The tolerance of Chenopodium ambrosioides to some heavy metals under in vitro environment was thoroughly investigated. A micropropagation protocol was developed to facilitate the mass production of plants and to identify metals-tolerant species for potential use in the restoration of polluted areas. Nodal explants exhibited callus formation when treated with N6-benzyladenin (BA) (1.5 mg/l) and a combination of BA/α-naphthalene acetic acid (NAA) at concentrations of 1.5/1.0 mg/l on the Murashige and Skoog (MS) medium. The optimal shoot formation was achieved with the callus grown on a medium enriched with 1.5/1.0 mg/l BA/NAA, resulting in an impressive number (21.89) and length (11.79 cm) of shoots. The in vitro shoots were rooted using NAA (1.0 and 1.5 mg/l) and were acclimatized in pots with 71% survival rate. After standardizing micropropagation protocol, the in vitro shoots were subjected to various doses of lead nitrate (Pb(NO3)2 and cadmium chloride (CdCl2). Pb(NO3)2 and CdCl2 in the media let to a reduction in shoot multiplication, decreasing from 18.73 in the control group to 11.31 for Pb(NO3)2 and 13.89 for CdCl2 containing medium. However, Pb(NO3)2 and CdCl2 promoted shoot length from 5.61 in the control to 9.86 on Pb(NO3)2 and 12.51 on CdCl2 containing medium. In the case of Pb(NO3)2 treated shoots, the growth tolerance index (GTI) ranged from117.64% to 194.11%, whereas for CdCl2 treated shoots, the GTI ranged from 188.23% to 264.70%. Shoots treated with high level of Pb(NO3)2induced reddish-purple shoots, while a low level of Pb(NO3)2 induced shoots displayed both green and reddish-purple colors in the same explants. In CdCl2 treated culture, the toxic effects were narrow leaf lamina, elongated petiole and a dark reddish purple coloration. These findings highlight the remarkable potential of C. ambrosioides to maintain growth and organogenesis even in the presence Pb(NO3)2 and CdCl2 on the MS medium, indicating a high degree of metal tolerance.

Effects of resource availability on the growth, Cd accumulation, and photosynthetic efficiency of three hyperaccumulator plant species

Plants that hyperaccumulate heavy metals such as cadmium (Cd) are important agents of phytoremediation. Availability of resources such as light, nutrients, and water can affect heavy metal accumulation by plants, but the responses of hyperaccumulators to different levels of resource availability remain little studied. To test such responses, three Cd hyperaccumulators, Solanum nigrum, Bidens pilosa, and Taraxacum mongolicum, were grown in Cd-contaminated soil; subjected to three levels of light, nutrient, or water availability; and measured for growth, Cd accumulation, and photosynthetic efficiency. All three species accumulated more total biomass and grew taller if given high than low water or light (each P < 0.001). Species accumulated four to eight times more Cd (190-309 versus 24-68 μg Cd g-1 mass) under high than low light. High water availability increased Cd accumulation by 89% in B. pilosa but decreased it by 31% and 40% in S. nigrum and B. pilosa, respectively. Effects of nutrients on both growth and accumulation varied between species; Cd accumulation by S. nigrum and T. mongolicum was respectively 14% and 54% lower at high than low nutrients, while it was 130% higher in B. pilosa. Light but not water or nutrient availability affected effective and maximum quantum yields and electron transport rate. Findings from this study suggest that low levels of light may constrain phytoremediation of Cd in soil and that testing species of Cd hyperaccumulators individually for responses to levels of water and nutrients will inform selection of species for phytoremediation.

Dose optimization of silicon for boosting arbuscular mycorrhizal fungi colonization and cadmium stress mitigation in maize (Zea mays L.)

The foliar applied silicon (Si) has the potential to ameliorate heavy metals, especially cadmium (Cd) toxicity; however, Si dose optimization is strategically important for boosting the growth of soil microbes and Cd stress mitigation. Thus, the current research was performed to assess the Si-induced physiochemical and antioxidant trait alterations along with Vesicular Arbuscular Mycorrhiza (VAM) status in maize roots under Cd stress. The trial included foliar Si application at the rate of 0, 5, 10, 15, and 20 ppm while Cd stress (at the rate of 20 ppm) was induced after full germination of maize seed. The response variables included various physiochemical traits such as leaf pigments, protein, and sugar contents along with VAM alterations under induced Cd stress. The results revealed that exogenous application of Si in higher doses remained effective in improving the leaf pigments, proline, soluble sugar, total proteins, and all free amino acids. Additionally, the same treatment remained unmatched in terms of antioxidant activity compared to lower doses of foliar-applied Si. Moreover, VAM was recorded to be at peak under 20 ppm Si treatment. Thus, these encouraging findings may serve as a baseline to develop Si foliar application as a biologically viable mitigation strategy for maize grown in Cd toxicity soils. Overall, the exogenous application of Si helpful for reducing the uptake of Cd in maize and also improving the mycorrhizal association as well as the philological mechanism and antioxidant activities in plant under cadmium stress conditions. Also, future studies must test more doses concerning to varying Cd stress levels along with determining the most responsive crop stage for Si foliar application.

Characteristics of cadmium translocation and isotope fractionation in Ricinus communis seedlings: Effects from split/cut-root and limited nutrients

Studying cadmium (Cd) transport in plants will improve the current understanding of Cd tolerance mechanisms. Due to the influence of analytical techniques, the application of Cd isotopes in plants is still in its early stages. Therefore, the relationships between Cd isotope fractionation and Cd translocation in plants remain unclear. In this study, we cultured Ricinus communis in hydroponic solutions during split/cut-root experiments and limited and infinite nutrient experiments. To understand the Cd transport process, the Cd²⁺ and other ion concentrations in different tissues (i.e., roots, stems, and leaves) and nutrient solutions, Cd isotope composition and the soluble protein in tissues were measured. The results showed that although significant effects were evident in the top leaves, the principal roots had less pronounced effects on Cd²⁺ translocation in the stems. Moreover, Cd underwent homolateral transport before it was translocated from the principal roots to the leaves on the side without Cd. It was apparent that the stems were responsible for translocating Cd²⁺ in plants. In addition, the continuous supply of high Cd²⁺ concentrations inhibited the growth of the top leaves, while in low Cd²⁺ concentrations, it was gradually transferred to the top leaves. Moreover, the tissues of R. communis were enriched with lighter Cd isotopes compared with the solutions. The clear differences between the Cd isotope fractionation of leaves under infinite and limited nutrient experiments may be attributed to plant growth and Cd uptake rates. This study provides important information for understanding Cd²⁺ translocation in R. communis and furthers our understanding of its tolerance and hyperaccumulation.

Effects of plant growth regulator and chelating agent on the phytoextraction of heavy metals by Pfaffia glomerata and on the soil microbial community

Pfaffia glomerata is a candidate for the remediation of heavy metal-contaminated soil, but phytoremediation efficiency requires enhancement. In this study, we evaluated how application of DA-6, EDTA, or CA affected the growth and heavy metal accumulation of P. glomerata and soil microorganisms. We found that P. glomerata removed more Cd and Zn than Pb or Cu from contaminated soil. When compared to the control, application of DA-6, CA, or CA + DA-6 increased plant biomass and increased stem Cd concentration by 1.28-, 1.20-, and 1.31-fold respectively; increased leaf Cd concentration by 1.25-, 1.28-, and 1.20-fold, respectively; and increased the total quantity of Cd extracted by 1.37-, 1.37-, and 1.38-fold, respectively. When compared to the control, application EDTA or EDTA + DA-6 significantly increased the soil available metal and Na concentrations, which harmed plant growth. Application of EDTA or EDTA + DA-6 also significantly decreased the Cd concentration in roots and stems. 16S rRNA high-throughput sequencing analysis revealed that application of EDTA or CA alone to soil significantly reduced the richness and diversity of soil bacteria, while foliar spraying of DA-6 combined with EDTA or CA slightly alleviated this reduction. EDTA or CA addition significantly changed the proportion of Actinobacteria and Proteobacteria. In addition, EDTA or CA addition caused changes in soil properties (e.g. heavy metal availability, K concentration, Na concentration, soil pH, soil CEC, and soil DOC concentration) that were associated with changes in the bacterial community. EDTA addition mainly affected the soil bacterial community by changing soil DOC concentration, the soil available Pb and Na concentration, and CA addition mainly affected the soil bacterial community by changing the soil available Ca concentration.

Effect of Cadmium Chloride and Cadmium Nitrate on Growth and Mineral Nutrient Content in the Root of Fava Bean (Vicia faba L.)

The present study aimed to analyze the differences in the tolerance of fava bean (Vicia faba cv. Aštar) roots to cadmium in nitrate-Cd(NO₃)₂-and chloride-CdCl₂-solutions. The physiological and biochemical parameters were assessed. The tested doses of Cd (50, 100, 150 and 300 mg/L) did not influence the germination of seeds. However, considerable growth inhibition and dehydration were observed after 96 h incubation. The thickness of roots and rupture of cell membranes increased along with the increasing concentration of the metal in the solution. At a Cd dose of 300 mg/L, irrespective of the solution used, increased nitrogen concentration and no change in sodium content were observed. The content of magnesium increased due to the dose of 100 mg/L (cadmium nitrate) and the content of calcium increased due to the dose of 300 mg/L (in either nitrate or chloride). The correlation analyses pointed to a possible effect of nitrates in the applied solutions on the accumulation of Cd and some minerals in the roots of the given variety of fava bean. This may be important for both research and agricultural practice. The identification of crops with high tolerance to cadmium, as well as knowledge about the mechanisms of ion interactions at the soil solution-plant level, is important in terms of such crops' use in the process of the remediation of cadmium-contaminated soils coupled with food production.

Effect of Cadmium Toxicity on Growth, Oxidative Damage, Antioxidant Defense System and Cadmium Accumulation in Two Sorghum Cultivars

Heavy metal stress is a leading environmental issue reducing crop growth and productivity, particularly in arid and semi-arid agro-ecological zones. Cadmium (Cd), a non-redox heavy metal, can indirectly increase the production of reactive oxygen species (ROS), inducing cell death. A pot experiment was conducted to investigate the effects of different concentrations of Cd (0, 5, 25, 50, 100 µM) on physiological and biochemical parameters in two sorghum (Sorghum bicolor L.) cultivars: JS-2002 and Chakwal Sorghum. The results showed that various concentrations of Cd significantly increased the Cd uptake in both cultivars; however, the uptake was higher in JS-2002 compared to Chakwal Sorghum in leaf, stem and root. Regardless of the cultivars, there was a higher accumulation of the Cd in roots than in shoots. The Cd stress significantly reduced the growth and increased the electrolyte leakage (EL), hydrogen peroxide (H₂O₂) concentration and malondialdehyde (MDA) content in both cultivars, but the Chakwal Sorghum showed more pronounced oxidative damage than the JS-2002, as reflected by higher H₂O₂, MDA and EL. Moreover, Cd stress, particularly 50 µM and 100 µM, decreased the activity of different antioxidant enzymes, including superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT). However, the JS-2002 exhibited higher SOD, POD and CAT activities than the Chakwal Sorghum under different Cd-levels. These findings revealed that JS-2002 had a stronger Cd enrichment capacity and also exhibited a better tolerance to Cd stress due to its efficient antioxidant defense system than Chakwal Sorghum. The present study provides the available information about Cd enrichment and tolerance in S. bicolor, which is used as an important agricultural crop for livestock feed in arid and semi-arid regions.

Influences of rice straw biochar and organic manure on forage soybean nutrient and Cd uptake

This pot experiment aimed to investigate the influence of rice straw biochar (BC 0, 1, and 3%, w/w) and organic manure (OM 0, 1, and 2%, w/w) addition on the growth, nutrient and cadmium (Cd) uptake of forage soybean in 10 mg Cd kg-1 contaminated soils. Compared with non-biochar treatments, biochar decreased shoot biomass, height and nitrogen (N) contents. Organic manure markedly increased the shoot biomass, shoot phosphorus (P), potassium (K), calcium (Ca) and magnesium (Mg) concentration, and root N, P, Ca contents without biochar addition treatments, while in the case of 3% biochar, there were no significant effects on N, K, Ca, and Mg contents of shoot and root among organic manure treatments. In comparison with other treatments, the minimum Cd content of shoots and roots both occurred in the treatment of BC3%+OM2%, while shoot Cd content reached the maximum value in OM2% treatment. Thus, these results suggested that organic manure addition can elevate forage soybean yield and nutrient content, while biochar had no positive effects. High biochar (3%) addition in combination with highest dose of organic manure (2%) can decline the Cd content of soybean and contribute to the agricultural product safety.

The Recovery of Soybean Plants after Short-Term Cadmium Stress

BACKGROUND

Cadmium is a non-essential heavy metal, which is toxic even in relatively low concentrations. Although the mechanisms of Cd toxicity are well documented, there is limited information concerning the recovery of plants after exposure to this metal.

METHODS

The present study describes the recovery of soybean plants treated for 48 h with Cd at two concentrations: 10 and 25 mg/L. In the frame of the study the growth, cell viability, level of membrane damage makers, mineral content, photosynthesis parameters, and global methylation level have been assessed directly after Cd treatment and/or after 7 days of growth in optimal conditions.

RESULTS

The results show that exposure to Cd leads to the development of toxicity symptoms such as growth inhibition, increased cell mortality, and membrane damage. After a recovery period of 7 days, the exposed plants showed no differences in relation to the control in all analyzed parameters, with an exception of a slight reduction in root length and changed content of potassium, magnesium, and manganese.

CONCLUSIONS

The results indicate that soybean plants are able to efficiently recover even after relatively severe Cd stress. On the other hand, previous exposure to Cd stress modulated their mineral uptake.

Effects of EDTA, citric acid, and tartaric acid application on growth, phytoremediation potential, and antioxidant response of Calendula officinalis L. in a cadmium-spiked calcareous soil

The improved efficiency of cadmium (Cd) phytoextraction potential of Calendula officinalis L. was evaluated in Cd-spiked calcareous soil, using various chelating agents. In a greenhouse study, three chelating agents, including EDTA, citric acid (CA), and tartaric acid (TA), were applied to Cd-spiked soils (50 and 100 mg kg^-1) under C. officinalis L. cultivation. According to the results, C. officinalis grew normally without any toxicity signs at various Cd levels of the soil; however, with increasing the Cd levels, the plant dry weight biomass decreased, and activities of antioxidant enzymes (AOEs) increased. The application of CA and TA in Cd-spiked soils improved the physiologic traits of plants and mitigated the Cd stress since the activities of AOEs decreased. Oppositely, due to increasing the Cd excessive permeability to the root of the plant, EDTA application diminished the physiologic traits and increased the activities of AOEs. The results also showed that all the chelators, especially EDTA, markedly increased the Cd mobility factor (from 58.80% to 65.20-89.60%) in Cd-spiked soils. The bioconcentration factor (BCF = 1.3-2.90) and translocation factor (TF = 1.28-1.58) of Cd, which were >1 in all treated and untreated plant samples, as well as the accumulated Cd >100 mg kg^-1, demonstrated that C. officinalis is a Cd-hyperaccumulator plant which could remediate Cd by the phytoextraction process. Regarding the biodegradation of CA, as well as the increased TF efficiency of Cd and plant biomass of CA treatments (by decreasing oxidative stress), compared to EDTA and TA treatments, it is recommended that CA be used as a superior chelating agent to enhance the efficiency of Cd phytoremediation in C. officinalis.

Characteristics of cadmium accumulation and isotope fractionation in higher plants

Cadmium (Cd) pollution of the soil is an important global environmental issue owing to its great toxicity. The study of metal isotope fractionation is a novel technique that could be used to identify and quantify metal uptake and transport mechanisms in plant. In this study, cadmium tolerant Ricinus communis and hyperaccumulator Solanum nigrum have been cultured in different Cd concentration nutrient solutions. The Cd isotope values, metal elements concentrations in the organs (root, stem and leaf) in the two plant species have been measured during the growth periods (10d, 15d, 20d, 25d, and 30d). The results indicate that the organs of S. nigrum could be enriched with lighter Cd isotopes compared with R. communis. In addition, the Cd isotope fractionation become smaller when the plants were subjected to high Cd toxicity, which indicates that Cd isotope fractionation reflected the extent of Cd toxicity to plants. This study advances our current view of Cd translocation machination in plants.

Sulfur nutrition level modifies the growth, micronutrient status, and cadmium distribution in cadmium-exposed spring wheat

The effect of S nutrition level (standard-2 and intensive-6 or 9 mmol S L-1) on the growth, micronutrient status, and Cd concentration of Cd-exposed (0, 0.0002, 0.02, and 0.04 mmol Cd L-1) Triticum aestivum L. 'Zebra' was examined. The hypothesis that Cd-induced micronutrient imbalance in this species is alleviated by enhanced S-sulfate (S-SO4) nutrition was tested. The intensive S nutrition, especially the dose of 6 mmol L-1, to some extent alleviated Cd-induced stress by improving the adverse changes in micronutrient status and increase of the biomass. The root and shoot Fe, Cu, Mn, and Zn concentrations of Cd-exposed wheat rose at 6 and remained unaltered at 9 mmol S L-1. Particularly noteworthy is the substantial increase of Fe bioconcentration found in Cd-stressed plants at 6 mmol S L-1. The root Cu concentration increased at 6 and decreased at 9 mmol S L-1, but did not change in shoots. Simultaneously, both the high S levels elevated the shoot Cl concentration but had no effect on the root Cl concentration. There were no substantial changes in the Mo concentration. The intensive S nutrition of the Cd-treated wheat did not affect the translocation factor (TF) of Fe and B. In turn, root-to-shoot translocation of Mo and Zn was enhanced at 6 and remained unchanged at 9 mmol S L-1. The changes in TF of Cl, Cu, and Mn varied greatly, depending on the S and Cd concentrations. Intensive S nutrition of Cd-stressed wheat, as a rule, dropped the root and increased the shoot Cd concentration as well as reduced Cd bioconcentration/bioaccumulation factor enhancing root-to-shoot Cd translocation.

Effect of Cadmium Accumulation on the Performance of Plants and of Herbivores That Cope Differently With Organic Defenses

Some plants are able to accumulate in their shoots metals at levels that are toxic to most other organisms. This ability may serve as a defence against herbivores. Therefore, both metal-based and organic defences may affect herbivores. However, how metal accumulation affects the interaction between herbivores and organic plant defences remains overlooked. To fill this gap, we studied the interactions between tomato (Solanum lycopersicum), a model plant that accumulates cadmium, and two spider-mite species, Tetranychus urticae and Tetranychus evansi that, respectively, induce and suppress organic plant defences, measurable via the activity of trypsin inhibitors. We exposed plants to different concentrations of cadmium and measured its effects on mites and plants. In the plant, despite clear evidence for cadmium accumulation, we did not detect any cadmium effects on traits that reflect the general response of the plant, such as biomass, water content, and carbon/nitrogen ratio. Still, we found effects of cadmium upon the quantity of soluble sugars and on leaf reflectance, where it may indicate structural modifications in the cells. These changes in plant traits affected the performance of spider mites feeding on those plants. Indeed, the oviposition of both spider mite species was higher on plants exposed to low concentrations of cadmium than on control plants, but decreased at concentrations above 0.5 mM. Therefore, herbivores with contrasting responses to organic defences showed a similar hormetic response to metal accumulation by the plants. Additionally, we show that the induction and suppression of plant defences by these spider-mite species was not affected by the amount of cadmium supplied to the plants. Furthermore, the effect of cadmium on the performance of spider mites was not altered by infestation with T. urticae or T. evansi. Together, our results suggest no interaction between cadmium-based and organic plant defences, in our system. This may be useful for plants living in heterogeneous environments, as they may use one or the other defence mechanism, depending on their relative performance in each environment.

Exogenous application of nitric oxide modulates osmolyte metabolism, antioxidants, enzymes of ascorbate-glutathione cycle and promotes growth under cadmium stress in tomato

Experiments were carried out to investigate the role of nitric oxide (NO) in ameliorating the negative effects of cadmium stress in tomato seedlings. Plants treated with cadmium (CdCl₂, 150 μM) showed reduced growth, biomass yield, pigment content, chlorophyll fluorescence, and gas exchange parameters. Exogenous application of NO donor (sodium nitroprusside) with nutrient solution protected chlorophyll pigments, restored chlorophyll fluorescence and gas exchange parameters, and caused significant enhancements in growth and biomass yield. Cadmium triggered the synthesis of proline and glycine betaine; however, application of NO caused further enhancement of their accumulation, reflecting an obvious amelioration of the cadmium-induced decline in relative water content. Activities of the antioxidant enzymes superoxide dismutase, catalase, ascorbate peroxidase, and glutathione reductase, monodehydroascorbate reductase, dehydroascorbate reductase, and other enzymatic activities of ascorbate-glutathione cycle were enhanced following the application of NO, as compared with those in untreated seedlings under control and cadmium stress conditions. NO increased the flavonoid and total phenol content in Cd-stressed tomato plants. Moreover, NO application restricted the uptake of cadmium and enhanced the accumulation of nutrients in different parts of tomato plants. On the basis of the findings of the present study, we propose that NO has a potential role as a growth promoter for tomato under cadmium stress.

Comparative Assessment of Response to Cadmium in Heavy Metal-Tolerant Shrubs Cultured In Vitro

Two species of Pb-adapted shrubs, Alyssum montanum and Daphne jasminea, were evaluated in vitro for their tolerance to elevated concentrations of cadmium. Shoot cultures were treated with 0.5, 2.5, and 5.0 μM CdCl₂ for 16 weeks and analyzed for their organogenic response, biomass accretion, pigment content, and macronutrient status. Cadmium accumulation and its root-to-shoot translocation were also determined. In both species, rooted microplantlets, suitable for acclimatization, were obtained in the presence of Cd applied as selection agent. In A. montanum, low and moderate dose of Cd stimulated multiplication, rooting, and biomass production. Growth tolerance index (GTI) in Cd-treated shoots ranged from 120 to 215%, while in the roots 51-202%. In turn, in Cd-treated D. jasminea proliferation and rooting were inhibited, and GTI for shoots decreased with increasing doses of Cd. However, roots exposed to Cd had higher biomass accretion. Both species accumulated Cd in developed organs, and its content increased with increasing CdCl₂ dose. Interestingly, D. jasminea accumulated higher amounts of Cd in the roots than A. montanum and immobilized this metal in the root system. On the contrary, A. montanum translocated some part of accumulated Cd to the shoots, but with low efficiency. In the presence of Cd, A. montanum maintained macronutrient homeostasis and synthesized higher amounts of phytosynthetic pigments in the shoots. D. jasminea accumulated root biomass, immobilized Cd, and restricted its translocation at the expense of nutrient balance. Considering remediation potential, A. montanum could be exploited in phytoextraction, while D. jasminea in phytostabilization of polluted substrate.

Toxic metal interactions affect the bioaccumulation and dietary intake of macro- and micro-nutrients

The present study was conducted to evaluate the effects of heavy metals (cadmium (Cd), lead (Pb) and Cd-Pb mix) on bioaccumulation of different nutrients. Three plant species including potato, tomato and lettuce were grown in pots containing soil contaminated with Cd, Pb and Cd-Pb mix at four different levels. The edible portions of each plant were analysed for Cd, Pb and different macro- and micro-nutrients including protein, vitamin C, nitrogen (N), phosphorous (P), potassium (K), iron (Fe), manganese (Mn), calcium (Ca) and magnesium (Mg). Results indicated significant variations in selected elemental concentrations in all the three plants grown in different treatments. The projected daily dietary intake values of selected metals were significant (P < 0.001) for Fe, Mn, Ca and Mg but not significant for protein, vitamin C, N and P. The elemental contribution to Recommended Dietary Allowance (RDA) was significant for Mn. Similarly, Fe and Mg also showed substantial contribution to RDA, while Ca, N, P, K, protein and vitamin C showed the minimal contribution for different age groups. This study suggests that vegetables cultivated on Cd and Pb contaminated soil may significantly affect their quality, and the consumption of such vegetables may result in substantial negative effects on nutritional composition of the consumer body. Long term and continuous use of contaminated vegetables may result in malnutrition.

Modulatory role of mineral nutrients on cadmium accumulation and stress tolerance in Oryza sativa L. seedlings

Cadmium (Cd)-contaminated rice is a serious health concern. In the present study, Cd accumulation and stress responses in Oryza sativa L. cv MTU 7029 seedlings were characterized under varying concentrations of plant nutrients in Hoagland media. It has been found that nutrient supplement modulates Cd accumulation and related stress tolerance while efficacy of each nutrient varies. Supplementation of Fe, Mn, N, Ca, and S were found to reduce Cd accumulation in leaf whereas Mn and Fe supply effect was also observed in roots. Analysis of maximum quantum efficiency of photosynthesis indicated that Fe and S supplements confer highest Cd stress tolerance. The present study highlighted the potential of plant nutrients for minimizing Cd accumulation and its toxicity in rice seedlings.

Phytoextraction of metals by Erigeron canadensis L. from fly ash landfill of power plant "Kolubara"

The objectives of this study were to determine the concentrations of Pb, Cd, As, Cr, Cu, Co, Ni, Zn, Ba, Fe, Al and Ag in Erigeron canadensis L. growing on fly ash landfill of power plant "Kolubara", Serbia. The content of each element was determined in every part of plant separately (root, stalk and inflorescence) and correlated with the content of elements in each phase of sequential extraction of fly ash. In order to ambiguously select the factors that are able to decidedly characterize the particular part of plant, principal component analysis (PCA) and partial least squares discriminant analysis (PLS-DA) were performed. The bioconcentration factors and translocation factors for each metal were calculated in order to determine the feasibility of the use of plant E. canadensis L. for phytoremediation purpose. There were strong positive correlations between metals in every part of plant samples, and metals from pseudo total form of sequential extraction indicate that the bioavailability of elements in fly ash is similarly correlated with total form. Retained Al, Fe, Cr and Co in the root indicate its suitability for phytostabilization. This plant takes up Cd and Zn from the soil (bioconcentration factors (BCFs) greater than 1), transporting them through the stalk into the inflorescence (translocation factors (TFs) higher than 1). Regarding its dominance in vegetation cover and abundance, E. canadensis L. can be considered adequate for phytoextraction of Cd and Zn from coal ash landfills at Kolubara.

Effect of cadmium on the growth and antioxidant enzymes in two varieties of Brassica juncea

Increasing contamination and higher enrichment ratio of non-essential heavy metal cadmium (Cd) induce various toxic responses in plants when accumulated above the threshold level. These effects and growth responses are genotype and Cd level dependent. An experiment was conducted to analyze the effect of Cd toxicity in Brassica juncea [L] Czern and Coss by selecting its two varieties Varuna and RH-30. Cadmium (0, 25, 50 or 100 mg CdCl2 kg(-1) of soil) fed to soil decreased the values of growth characteristics, activity of nitrate reductase and leaf water potential, whereas activities of antioxidant enzymes and proline content increased with the increasing concentration of Cd, observed at 30 and 60 day stages of growth, in both the varieties. Moreover, Cd uptake by the roots was higher in RH-30 than Varuna. Also the activity of antioxidant enzymes and proline accumulation were higher in Varuna with increasing soil level of Cd. Out of the two varieties, Varuna was more tolerant than RH-30 to Cd stress.