Cd Accumulation In Shoots Research Articles

Interactions between cadmium and zinc in uptake, accumulation and bioavailability for Salix integra with respect to phytoremediation

The willow (Salix spp.) is a potential accumulator of cadmium (Cd)/zinc (Zn), and the interaction between Cd and Zn is an important factor influencing their phytoextraction potentials. In this study, interactions between Cd and Zn in uptake, accumulation and bioavailability for Salix integra clone SI63 were investigated through nutrient solution and soil culture methods. The result of the soil culture showed that Cd had additive effects for Zn-caused biomass reduction. The result from nutrient solution indicated that added Zn showed antagonistic (low Cd level) or synergistic (moderate and high Cd levels) effects on shoot Cd accumulation and antagonistic effects on root Cd accumulation. Irrespective of nutrient solution or soil culture experiment, Cd addition always had antagonistic effects on Zn accumulation in both shoots and roots. Under Cd10Zn50 condition, the clone accumulated higher Cd and Zn concentrations (95 μg g−1 Cd and 165 μg g−1 Zn) in shoots. Cd slightly increased bioavailable Zn in the rhizosphere, and EDTA well predicted bioavailable Cd and Zn in the rhizosphere. Interactions of Cd–Zn markedly changed their respective phytoextraction potentials, especially for Zn. This result will provide a new insight into improving phytoextraction potentials of both Cd and Zn using willows through applying metal interactions.

Physiological response of Conyza Canadensis to cadmium stress monitored by Fourier transform infrared spectroscopy and cadmium accumulation.

The cadmium(Cd) pollution of soil causes serious environmental problems. Cd is a high toxic and high water soluble element without biological function, and it is easily taken in by plants owing to its high bioavailability. Thus it easily entered the food chain and threaten people's health. Here，different concentrations of Cd solutions were used to study the physiological response and Cd accumulation characteristics of Conyza Canadensis (L.) Cronq. The physiological response was characterized by Fourier Transform Infrared (FTIR) spectroscopy, and Cd accumulation in plant and distribution were tested by Atomic absorption spectroscopy (AAS) under different concentrations Cd stress. When Cd concentrations toxicity <3mg·L-1, the C. Canadensis (L.) Cronq. could grow normally without any symptoms, and the Cd concentrations increased to 7mg·L-1, the C. Canadensis (L.) Cronq. had a little lower biomass, but there was no significant difference in the biomass among treatment concentrations. The peak shape of each component remained unchanged before and after Cd treatment. Only the absorption peak of some functional groups involved in Cd adsorption shifted with different degrees, such as hydroxy groups (3417-3429cm-1), carboxyl groups (1380-1386cm-1), and acid amide groups (1631-1637cm -1). The characteristic peak absorption intensity of root, stem and leaf was different with the increase of heavy metal concentration. The absorbance of the roots with high Cd concentration was higher than that with medium-low Cd concentration. This shows that high concentration of Cd could induce C. Canadensis (L.) Cronq. seedlings to produce a large number of protein, amino acid and other substances, and through osmotic regulation to enhance stress resistance, provide nitrogen source, reduce heavy metal toxicity, and stabilize the internal environment. After Cd treatment, the characteristic peaks of stem and leaf were higher than or close to the control. This is due to the high tolerance of C. Canadensis (L.) Cronq. seedlings to heavy metals. The Cd accumulation in the shoots (stems and leaves) of C. Canadensis (L.) Cronq. was obviously lower than that in roots and the Cd content in the shoots usually increased with increasing Cd concentration. The maximum accumulation of Cd in shoots was 1898.07mg·kg-1 after 11days grown in the water spiked with 7mg·L-1 Cd concentration. The study suggests that C. Canadensis (L.) Cronq. has some remediation effect and endurance ability against heavy metal polluted contaminated soil and has potential utilization value in the technical field of phytoremediation of Cd polluted soil.

Melatonin and nitric oxide enhance cadmium tolerance and phytoremediation efficiency in Catharanthus roseus (L.) G. Don.

In this study, a pot experiment was performed to evaluate the effects of foliar spray with sodium nitroprusside (200 μM SNP) and melatonin (100 μM) singly and in combination on tolerance and accumulation of cadmium (Cd) in Catharanthus roseus (L.) G. Don plants exposed to different levels of cadmium (0, 50, 100, and 200 mg Cd kg-1 soil). The results showed that 50 mg kg-1 Cd had no significant effect on the fresh and dry weight of roots and shoots and content of chlorophyll (Chl) a and b, but the higher levels of Cd (100 and 200 mg kg-1) significantly reduced these attributes and induced an increase in the level of leaf electrolyte leakage and disrupted nutrient homeostasis. The activities of catalase (CAT) and peroxidase (POD) in leaves were increased under lower Cd concentrations (50 and 100 mg kg-1) but decreased under 200 mg kg-1 Cd. However, foliar spray with melatonin and/or SNP increased shoot biomass and the content of Chl a and b, augmented activities of POD and CAT, lowered electrolyte leakage (EL), and improved essential cations homeostasis in leaves. Cadmium content in shoots of C. roseus was less than roots and TF (transfer factor) was < 1. Interestingly, foliar spray with SNP and/or melatonin increased Cd accumulation and bioconcentration factor (BCF) in both roots and shoots and elevated the Cd transport from roots to shoot, as TF values increased in these treatments. The co-application of melatonin and SNP further than their separate usage augmented Cd tolerance through increasing activities of antioxidant enzymes and regulating mineral homeostasis in C. roseus. Furthermore, co-treatment of SNP and melatonin increased Cd phytoremediation efficiency in C. roseus through increasing biomass and elevating uptake and translocation of Cd from root to shoot.

The compound effects of biochar and iron on watercress in a Cd/Pb-contaminated soil.

Pot experiment was conducted to evaluate the effect of two types of biochar (2% (w/w)), Pennisetum sinese Roxb biochar (PB) and coffee grounds biochar (CB), combined with iron fertilizer (1.3gkg-1 Fe) on the growth, quality, Cd/Pb accumulation in watercress, soil physicochemical properties, soil fertility, soil enzyme activities, and fraction distribution of Cd/Pb in soil. The results showed that the two types of biochar combined with iron fertilizer (BC-Fe) amendments could increase the shoot height, root length, plant biomass, soluble sugar and soluble protein of watercress, soil pH value, soil organic matter (SOM), ammonium nitrogen (NH4+-N), available phosphorus, and available potassium. CB-Fe amendment enhanced soil urease, sucrose, and catalase activities, while PB-Fe amendment only enhanced soil urease activity among the three enzymes. The two BC-Fe amendments decreased exchangeable-Cd/Pb and reducible-Cd/Pb concentrations, while enhanced oxidizable-Cd/Pb and residual-Cd/Pb concentrations. Furthermore, the two BC-Fe amendments decreased significantly Cd and Pb accumulation in watercress root and shoot. The reduction rate for Cd and Pb in shoot by 42.9%, 20.0%, and 68.2%, 58.4% under PB-Fe and by 38.1%, 20%, and 62.5%, 48.8% under CB-Fe, respectively, for the first crop and the second crop. In conclusion, BC-Fe amendment could improve soil physicochemical properties and soil fertility, promote Cd and Pb transfer to the stable form, thus, reduce the bioavailability and mobility of Cd and Pb, and further, decrease Cd and Pb ecotoxicity and its accumulation in watercress and improve watercress quality.

Simultaneous reduction of arsenic (As) and cadmium (Cd) accumulation in rice by zinc oxide nanoparticles

Accumulation of arsenic (As) and cadmium (Cd) in rice grains is a serious food safety concern for populations consuming rice as a staple food worldwide. Some agricultural practices such as water and nutrient management strategies can exhibit significant impact on their fate and bioavailability in rice paddies due to the profound impact of these activities on paddy soil properties. However, due to the unique biogeochemistry of As and Cd in rice paddies, their bioavailability often goes opposite directions and thus simultaneous control of both As and Cd in rice grains has not been achieved. Several previous studies have showed that some engineered nanoparticles (ENPs) can substantially lower the accumulation of either As or Cd in rice grains. The primary goal of this study was to evaluate whether zinc oxide nanoparticles, a popular nanofertilizer, can simultaneous lower both As and Cd in rice tissues using a greenhouse setup. The results suggested that both zinc oxide nanoparticles (ZnONPs) and zinc ions (Zn2+) significantly reduced the total As in rice roots (−39.5% and −83.3%) and shoots (−60.2% and −80.0%) and the reduction was primarily due to the lowered inorganic As(III) and organic As species. However, only ZnONPs reduced the Cd accumulation in rice shoots. Zn2+ significantly increased Cd content in rice shoot by 26.8%, suggesting the differential impact of ZnONPs and Zn2+ on As and Cd accumulation in rice tissues. Only ZnONPs holds the potential to simultaneously reduce both As and Cd in rice grains in As and Cd co-contaminated rice paddies. The results provide new insights into the sustainable applications of nanotechnology in agriculture.

Accumulation and distribution of cadmium and lead in 28 oilseed rape cultivars grown in a contaminated field.

Heavy metal pollution in soils has become an important concern for human health. Therefore, it is vital to develop suitable remediation strategies for contaminated soils. Oilseed rape tolerates high concentrations of heavy metals and is a promising candidate for the phytoextraction of cadmium (Cd) and lead (Pb) from metal-contaminated soils. A field experiment was conducted to evaluate 28 oilseed rape cultivars including Brassica napus L. and Brassica juncea L. for their ability to accumulate Cd and Pb. These cultivars were grown in a field co-contaminated with Cd (0.78 mg kg-1) and Pb (330 mg kg-1). The results showed that concentrations in shoots ranged from 1.22 to 3.01 mg kg-1 for Cd and from 10.8 to 29.5 mg kg-1 for Pb. Cadmium and Pb accumulations in shoots could reach 83.4 and 799 μg plant-1, respectively. The majority of translocation factors (TFs) for Cd (> 1.0) were higher than for Pb (≤ 1.0). However, concentrations of Cd and Pb in seeds were much lower, in the range of 0.04 to 0.21 mg kg-1 and 0.04 to 0.51 mg kg-1, respectively. The seed yields of oilseed rape varied from 1238 to 2904 kg ha-1, with a mean value of 2289 kg ha-1. Among the cultivars, three (OS-9, OS-12, and OS-15) were selected as Cd and Pb potential accumulators, with Cd accumulation in shoots being 2.74-3.70 times higher and Pb accumulation in shoots being 3.37-5.23 times higher as compared with the lowest accumulating cultivar. These selected cultivars (B. napus) have application potential for phytoextraction of Cd and Pb from polluted soils without stopping agricultural activities and accompanying food safety issues.

Efficiency of various silicon rich amendments on growth and cadmium accumulation in field grown cereals and health risk assessment.

Cadmium (Cd) contamination of arable soils and its subsequent accumulation in food is one of the global issues which needs urgent attention. Field experiments were conducted to explore the impacts of ten silicon (Si) rich amendments on Cd bioavailability and accumulation by maize and wheat irrigated with sewage effluents. Results depicted that applied amendments decreased the total Cd accumulation in shoots and grains of both crops with and the maximum decrease was observed in rice husk biochar (RHB) treatment. The RHB was able to significantly decrease the translocation factor, Cd harvest and health risk indexes. All amendments differentially affected the soil pH, EC, CaCl2-extractable Si, and decreased the AB-DTPA-extractable soil Cd. Overall, suitable Si rich amendments (like RHB and CSB etc.) can be employed to mitigate the health risks associated with dietary Cd in untreated sewage irrigated fields. However, the cost-benefit analysis such Si rich amendments should be considered before final recommendations.

Screening of the proteins related to the cultivar-dependent cadmium accumulation of Brassica parachinensis L.

Cultivar-dependent cadmium (Cd) accumulation was principal in developing Cd-pollution safe cultivars (PSCs). Proteins related to different Cd accumulations of the low-Cd-accumulating (SJ19) and high-Cd-accumulating (CX4) cultivars were investigated by iTRAQ analysis. Higher Cd bioaccumulation factors and translocation factor in CX4 than in SJ19 were consistent with the cultivar-dependent Cd accumulations. The Cd uptake was promoted in CX4 due to its higher expression of Cd-binding proteins and the lower expression of Cd-efflux proteins in roots. What's more, significantly elevated thiol groups (PC2 and PC3) in CX4 under Cd stress might contribute to the high Cd accumulation in roots and the root-to-shoot translocation of Cd-PC complex. Up-regulated proteins involved in cellulose biosynthesis and pectin de-esterification in SJ19 enhanced the Cd sequestration of root cell walls, which was considered as the predominant strategy for reducing Cd accumulation in shoots. The present study provided novel insights in the cultivar-dependent Cd accumulation in shoots of B. parachinensis.

Cd accumulation, biomass and yield of rice are varied with silicon application at different growth phases under high concentration cadmium-contaminated soil.

Many reports suggest that exogenous Si addition could reduce Cd translocation to aerial part and make grain safe for rice production. But it remains unclear whether its supplementation during different growth phases can differentially impact Cd uptake in rice. Here, Positive effects of Si applied at different growth phases on biomass and yield of rice were observed. Dry weight of shoot including stem, leaf and grain was enhanced significantly by 15% when Si added at transplanting stage. Grain-yields supplied with Si at transplanting, jointing and heading stages were increased obviously by 14%, 11% and 12%, respectively. Higher percentage of filled spikelet and lower unfilled spikelet number per panicle were found when Si supplied at jointing stage. The increases of Cd accumulation in rice plants by Si application were mainly manifested in roots. Compared to CK, Cd accumulation in root when Si applied at transplanting and tillering stages were elevated by 75% and 64%, respectively. While Cd accumulation in aboveground tissues were all declined by Si addition. Bioconcentration and translocation factors were decreased significantly when Si added at jointing stage. In addition, higher soil pH, lowest available Cd-concentration in soil and Cd2+ concentration in xylem sap at 15d after flowering were found when the Si was applied at jointing stage. Overall, Si application at transplanting would be more beneficial to the growth of rice and increased Cd content in root, while Si supplied at jointing would be more favorable for grain filling and reducing Cd accumulation in shoot.

Accumulation efficiency of sunflower for lead and cadmium along with sustainable crop productivity under soil stress

By nature coastal saline soils having several constraints in crop production in addition to that of heavy metals contamination deteriorate the soil productivity. To restore these contaminated soils, various remediation techniques in practices must be revamped. The present study was conducted to enhance the accumulation of heavy metals lead and cadmium in sunflower and improve the crop productivity using organic and inorganic soil amendments along with NPK fertilizers in completely randomized design. Soil samples were admitted to estimating soil physico chemical properties and DTPA extractable lead (Pb) and cadmium (Cd) and plant samples analyzed for DTPA extractable Pb and Cd concentrations under ICP-OES. The physico-chemical properties and DTPA extractable Pb and Cd concentrations were significantly influenced by amendments. Sunflower exhibited significant differences concerning accumulation of Pb and Cd against amendments tested along with higher biomass production. Higher shoot and root concentration of Pb(0.72,0.81 and 0.94,0.97 mg kg-1) and Cd (1.78, 2.32 and 0.35,0.32 mg kg-1)were recorded in the treatment RDF + EDTA, which was followed by RDF + Potassium humate and RDF + Zeolite application at 45 DAS and at harvest. Remediation efficiency of sunflower increased by application of RDF + EDTA through enhanced solubility of Pb and Cd in soil and thus increased Pb and Cd accumulation in root and shoot of sunflower. Whereas, the application of RDF+ FYM or press mud reduced the bioavailability of Pb and Cd in soil and thus restricted the accumulation of Pb and Cd by sunflower. Further, application of NPK fertilizers maintained the availability of nutrients and enhanced the yield of sunflower. The application of EDTA along with NPK fertilizer enhanced the bioaccumulation of lead and cadmium by sunflower without yield loss. Since, there is a possibility to cause leaching of HMs to ground water by EDTA. Hence, RDF plus Potassium humate or Zeolite can be recommended for lead and cadmium removal by sunflower in coastal saline soils with no loss in crop productivity.

Biochar alleviates Cd phytotoxicity by minimizing bioavailability and oxidative stress in pak choi (Brassica chinensis L.) cultivated in Cd-polluted soil

The production of leafy vegetables such as Brassica chinensis L. in cadmium (Cd)-polluted soil causes serious threats to human health and food safety around the globe. A pot culture was established to examine the efficacy of rice-straw induced biochar (applied to soil at the rate of 0%, 2.5% and 5%, w/w) on growth, gaseous exchange attributes, antioxidative capacities and Cd uptake in pak choi (Brassica chinensis L.), when soil was spiked with Cd (CdCl2) at 0, 5, 10 and 20 mg kg−1 soil. The results revealed that Cd stress significantly (P < 0.05) reduced plant biomass and physiological attributes, and accumulated higher Cd concentrations in plant tissues with the increasing rate of Cd concentration in the soil. However, incorporation of biochar at 5% application rate prominently increased the shoot (98.27%) and root (85.96%) dry biomass, net photosynthesis (45.52%), transpiration rate (161.34%), stomatal activity (111.76%) and intracellular CO2 concentration (32.25%) when Cd was added at 20 mg kg−1 soil, relative to the respective treatment without biochar. Whereas, incorporation of biochar at 5% significantly reduced the bioavailable Cd by 16.64% under 20 mg kg-1 soil, compared to respective Cd treatment without biochar.Similarly, Cd accumulation in shoots and roots was decreased by 42.49% and 29.23%, and thereby reduced leaf MDA and H2O2 contents by 21.45% and 31.28%, respectively, at 20 mg Cd kg−1 spiked soil relative to without biochar amended soil. An increment was noticed in the activities of guaiacol peroxidase (POD), superoxide dismutase (SOD), ascorbate peroxidase (APX), catalase (CAT) and glutathione (GSH) by 37.31%, 66.35%, 115.94%, 122.72% and 59.96%, respectively, with 5% biochar addition in 20 mg kg−1 Cd spiked soil. Moreover, biochar induced a synergistic impact on plants by increasing soil alkalinization and thereby reducing Cd phytotoxicity throughimmobilization. Overall, results proposed that rice-straw biochar has an ability to restore Cd polluted soil and increased pak choi production and thereby reduced food security risks in polluted soil.

Plant uptake and leaching potential upon application of amendments in soils spiked with heavy metals (Cd and Pb)

The aim of this study was to assess the effects of soil amendments (organic and inorganic) on phytoavailability and leaching of cadmium (Cd) and lead (Pb) during enhanced phytoextraction. The vertical column study was carried out to investigate the metal leaching meanwhile studying plant biomass and metals uptake for phytoextraction by Pelargonium hortroum. For this purpose, soil amendments at several concentration levels, such as ethylene diaminetetraacetic acid (EDTA 0, 4, 5 mmol kg−1), ammonium nitrate (0, 8, 10 mmol kg−1), citric acid (0, 8, 10 mmol kg−1), compost (0, 8%, 10%) and titanium dioxide nanoparticles (TNPs, 0, 80, 100 mg kg−1) were used. Results revealed that EDTA efficiently improved Cd and Pb accumulation (mg kg−1) in shoots and roots. Cd accumulation was significantly increased by 270%, 44%, 145%, and 6.4% in shoot and 94%, 19%, 48% and 14% in root upon EDTA, ammonium nitrate, citric acid and TNPs application, respectively compared to the control without amendment (WA). Similarly, Pb accumulation was significantly increased by 71%, 58% and 52% in shoot and 88.8%, 70.6% and 64.6% in root upon exposure to higher levels of EDTA, citric acid and ammonium nitrate, respectively when compared to the WA control. Application of TNPs reduced the Pb-accumulation in shoots and roots by 33% and 28%, respectively. Similarly, the Pb-accumulation in shoots and roots was decreased by 39% and 35%, respectively upon compost addition. Plant biomass was significantly increased upon application of soil amendments, with the exception of EDTA. The maximum Cd and Pb uptake was found in citric acid amended soil. Leachate analysis revealed that the concentrations of Cd and Pb were increased by 109% and 101% in leachates upon EDTA application as compared to other amendments. In comparison with other amendments, citric acid may be recommended as an environmentally friendly alternative for non-biodegradable EDTA for enhanced phytoextraction of Cd and Pb.

Comparative efficacy of organic and inorganic silicon fertilizers on antioxidant response, Cd/Pb accumulation and health risk assessment in wheat (Triticum aestivum L.)

In wheat production areas of China, soil lead (Pb) pollution is generally accompanied by cadmium (Cd) pollution and it is of considerable significance in repairing the Cd and Pb co-contaminated soils for safe agronomic production. Organosilicon fertilizer (OSiF) is a new type of silicon (Si) fertilizer that can effectively alleviate heavy metal toxicity in plants, but the mechanisms on its heavy metal detoxification are poorly understood. A soil pot experiment was conducted to evaluate and compare the effects of two OSiFs (OSiFA and OSiFB) and an inorganic silicon fertilizer (InOSiF) on wheat heavy metal uptake and biochemical parameters in a Cd and Pb co-contaminated soil. The results demonstrated that OSiFA, OSiFB and InOSiF could alleviate the Cd and Pb toxicity of wheat, as indicated by increasing wheat grain yield by 65%, 45% and 22%, respectively. The Si fertilizers enhanced leaf gas exchange attributes and chlorophyll content, whereas diminished the oxidative damage, as indicated by a lower level of hydrogen peroxide (H2O2) and malondialdehyde (MDA) content, and lower activity of superoxide dismutase (SOD) and catalase (CAT) activity, as compared with control. Adding OSiFA, OSiFB and InOSiF increased Si uptake in roots and shoots, thus reducing Cd and Pb accumulation in the wheat shoot, bran and flour, especially, flour Cd contents by 17%, 10% and 31% respectively, flour Pb contents by 74%, 53% and 48% respectively. Also, Si fertilizers application decreased the health risk index (HRI) of both Cd and Pb. The grey correlation degrees of OSiFA, OSiFB and InOSiF are 0.72, 0.77 and 0.61, respectively, indicating that the effects of OSiFs on detoxifying Cd and Pb could be better than that of InOSiF in wheat. Thus, the use of OSiFs might be a feasible approach to reduce Cd and Pb entry into the human body through crops.

Nicotianamine Synthase Gene 1 from the hyperaccumulator Sedum alfredii Hance is associated with Cd/Zn tolerance and accumulation in plants

Sedum alfredii Hance is a hyperaccumulator of cadmium (Cd) and zinc (Zn) that exhibits extraordinary accumulation of these metals in various tissues. The Nicotianamine synthase (NAS) genes play key roles in regulating the production of nicotianamine, a non-protein amino acid that facilitates metal homeostasis in plants, but the functions of these genes in S. alfredii remain unknown. The aims of this study were to identify and characterize the NAS gene from S. alfredii (SaNAS1) and explore NAS roles in Cd or Zn tolerance and accumulation. One Cd-induced NAS gene from S. alfredii (SaNAS1) was cloned. We determined the subcellular localization of the encoded protein and evaluated SaNAS1 expression. We also assessed SaNAS1 function by conducting a complementary assay with yeast mutants Δzrc1 exposed to Cd or Zn. Finally, transgenic Arabidopsis plants expressing SaNAS1 were produced, and SaNAS1 function was further examined in these plants. SaNAS1 was highly expressed in response to Cd or Zn exposure, and the encoded protein was distributed throughout the cytoplasm and nucleus. Furthermore, yeast expressing SaNAS1 exhibited increased tolerance to Cd or Zn. Finally, expression of SaNAS1 in Arabidopsis increased nicotianamine production and promoted Cd or Zn accumulation in roots and shoots. SaNAS1-expressing transgenic Arabidopsis lines showed improved seedling growth under Cd or Zn stress compared with wild type, indicating that SaNAS1 enhances tolerance to both Cd and Zn. SaNAS1 may play a critical role in Cd or Zn tolerance and hyperaccumulation by regulating nicotianamine level in S. alfredii.

Mechanisms and uncertainties of Zn supply on regulating rice Cd uptake

Application of Zinc (Zn) is considered an effective measure to reduce Cadmium (Cd) uptake and toxicity in Cd-contaminated soils for many plant species. However, interaction between Zn and Cd in rice plant is complex and uncertain. In this study, four indica rice cultivars were selected to evaluate the effect of Zn exposure in an EGTA-buffered nutrient solution under varying Zn activities and a field level of Cd activity to characterize the interaction between Zn and Cd in rice. Severe depression in shoots’ biomass, tiller number, and SPAD (Soil and Plant Analyzer Development) value were found at both Zn deficiency and Zn phytotoxicity levels among four tested rice cultivars. There existed a strong antagonism interaction between Zn and Cd in both shoot and root from Zn deficiency to Zn phytotoxicity. The reduction of Cd accumulation in roots and shoots could be explained by the competition between Zn and Cd as well as the dilution effect of increasing biomass. The conflicting effect of Zn supply on Cd uptake may be attributed to the increasing transfer ratio of Cd from root to shoot with the increasing Zn2+ activities and the strong depression of Fe and Mn in shoots with the increasing Zn2+ activities as well as the variation of genotypes. Balance between Zn and Cd should be considered in field application.

Nitrogen fertilizer enhances zinc and cadmium uptake by hyperaccumulator Sedum alfredii Hance

Nitrogen (N) fertilization is known to have a substantial effect on heavy metal uptake in plants. However, the impact of N fertilization on plant growth and heavy metal uptake of hyperaccumulator plants remains unclear. This study examined the effect of N fertilization on growth and uptake of zinc (Zn) and cadmium (Cd) in Zn/Cd-hyperaccumulating plants species, Sedum alfredii (S. alfredii) Hance (Crassulaceae). Plants of S. alfredii were grown for 60 days in nutrient solution with 100 μmol Cd L−1 and 0–10 mmol N L−1, and in a Cd-contaminated soil receiving N fertilizer and composted pig manure amendment. Biomass production, nutrient uptake, and concentrations and accumulation of Zn and Cd in plant parts were measured. In the hydroponic experiment, both low ( 5 mmol L−1) N supply decreased the growth and Zn and Cd accumulation in the whole plants. The 2.5 mmol N L−1 is an optimal N dosage for shoot biomass production and Zn accumulation in shoots, while the 1.0 mmol N L−1 is an optimal N dosage for Cd accumulation in shoots, which was 68.1% higher than the control. The N doses of 1 to 2.5 mmol L−1 N represented optimal conditions for Zn and Cd accumulation in the shoots of S. alfredii seedlings. In the soil pot experiment, shoot dry weight decreased with increasing N fertilization rate, while composted pig manure decreased biomass production. Both Zn and Cd accumulation in the shoots of S. alfredii decreased along with the addition of higher N fertilization rate. However, the composted pig manure amendment increased the accumulation of Zn, but not Cd in the shoots. The application of N at appropriate amount enhanced the phytoremediation efficiency by S. alfredii in Zn/Cd-polluted fields, but the effectiveness of phytoextraction technology needs to be validated in the field trials.

Residual effects of tobacco biochar along with different fixing agents on stabilization of trace elements in multi-metal contaminated soils

The residual effect of tobacco biochar (TB ≥ 500°C) mono and co-application with Ca-hydroxide (CH), Ca-bentonite (CB) and natural zeolite (NZ) on the bio-availability of trace elements TE(s) in alkaline soils has not been deeply studied yet. A pot study that had earlier been investigated TB mono and blended with CH, CB and NZ on the immobilization of Pb, Cu Cd, and Zn by Chinese cabbage. Maize crop in the rotation was selected as test plant to assess the residual impact of amendments on stabilization of Pb, Cu Cd, and Zn in mine polluted (M-P), smelter heavily and low polluted (S-HP and S-LP, respectively) soils. The obtained results showed that stabilization of Pb, Cd, Cu and Zn reached 63.84% with TB + CB, 61.19% with TB + CH, 83.31% with TB + CH and 35.27% with TB + CH for M-P soil, 36.46% with TB + NZ, 38.46% with TB + NZ, 19.40% with TB + CH and 62.43% with TB + CH for S-LP soil, 52.94% TB + NZ, 57.65% with TB + NZ, 52.94% with TB + NZ, and 28.44% with TB + CH for S-LP soil. Conversely, TB + CH and TB alone had mobilized Pb and Zn up to 19.29% and 34.96% in M-P soil. The mobility of Zn reached 8.38% with TB + CB and 66.03% with TB for S-HP and S-LP soils. The uptake and accumulation of Pb, Cd, Cu and Zn in shoot and root were reduced in three polluted soils. Overall, the combination of TB along with CH, CB and NZ has been proven to be effective in Pb, Cd, Cu and Zn polluted mine/smelter soils restoration.

EDTA reduces cadmium toxicity in mustard (Brassica juncea L.) by enhancing metal chelation, antioxidant defense and glyoxalase systems

To investigate the possible role of EDTA in mitigating cadmium (Cd) toxicity, we treated mustard (&lt;em&gt;Brassica juncea&lt;/em&gt; L.) seedlings with CdCl&lt;sub&gt;2&lt;/sub&gt; (0.5 mM and 1.0 mM, 3 days) alone and in combination with 0.5 mM EDTA in a semihydroponic medium. In the absence of EDTA, mustard seedlings accumulated Cd in their roots and shoots in a concentration dependent manner. Overaccumulation of Cd boosted generation of hydrogen peroxide (H&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;2&lt;/sub&gt;) and superoxide anions (O&lt;sub&gt;2&lt;/sub&gt;&lt;sup&gt;•−&lt;/sup&gt;), increased lipoxygenase (LOX) activity, lipid peroxidation, and cytotoxic methylglyoxal (MG) content. It also disturbed components of the antioxidant defense and glyoxalase systems. Furthermore, Cd stress decreased growth, leaf relative water content (RWC) and chlorophyll (chl) content but augmented the proline (Pro) content. On the other hand, EDTA supplemented Cd-stressed seedlings improved the constituents of the AsA-GSH cycle with the upregulated activities of ascorbate peroxidase (APX), monodehydroascorbate reductase (MDHAR), dehydroascorbate reductase (DHAR), glutathione reductase (GR), glutathione peroxidase (GPX), superoxide dismutase (SOD), and catalase (CAT). Moreover, addition of EDTA to the Cd-stressed seedlings notably enhanced Gly I activity in contrast to the stress treatment. Ethylenediaminetetraacetic acid decreased Cd accumulation in the both shoots and roots, as well as increased other nonprotein thiols (NPTs) in leaves, including the phytochelatin (PC) content. It also decreased H&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;2&lt;/sub&gt; and O&lt;sub&gt;2&lt;/sub&gt;&lt;sup&gt;•−&lt;/sup&gt; generation, lipid peroxidation and MG content but enhanced RWC, chl and Pro contents in the leaves, which confirmed the improved growth of seedlings. The findings of the study suggest that exogenous application of EDTA to the Cd-treated seedlings reduces Cd-induced oxidative injuries by restricting Cd uptake, increasing NPTs concentration and upregulating most of the components of their antioxidant defense and glyoxalase systems.

Potential of indigenous plant species for phytoremediation of metal(loid)-contaminated soil in the Baoshan mining area, China.

A field survey was conducted to investigate metal(loid) concentration in soils and native plants in the Baoshan mining area for potential application in phytoremediation. Total concentrations of arsenic (As), cadmium (Cd), lead (Pb), and zinc (Zn) in soil varied from 125 to 6656, 5.10 to 1061, 568 to 49294, and 241 to 17296 mg kg-1, respectively, showing severe contamination. Among 20 species native to this area, Pteris ensiformis accumulated 1091 mg kg-1 As in the shoot, and its translocation factor (TF) was greater than 1, suggesting potential capacity for As phytoextraction. Boehmeria nivea, Aster prorerus, and Hydrocotyle sibthorpioides showed potential for phytoextraction of Cd due to their high accumulation of Cd in shoots (490.3, 175.4, and 128.5 mg kg-1, respectively) and high TFs (92.0, 22.1, and 6.7, respectively). Eleusine indica and P. ensiformis were found to contain high concentrations of Pb (7474 mg kg-1) and Zn (1662 mg kg-1) in roots, but with low TFs for Pb (0.4) and Zn (0.2), suggesting potential capability for phytostabilization. There was a positive correlation (p < 0.01, N = 25) of TFs between the metal(loid)s, indicating a synergic interaction in the uptake of metal(loid)s by these plants. According to metal(loid) concentrations in shoots, bioconcentration factors (BFs), and TFs, as well as the botanical features such as wide occurrence, high biomass yield, and rapid growth of the plants, the five native species identified above have the potential for phytoremediation in the Baoshan mining area.

Gene identification and transcriptome analysis of low cadmium accumulation rice mutant (lcd1) in response to cadmium stress using MutMap and RNA-seq

BackgroundCadmium (Cd) is a widespread toxic heavy metal pollutant in agricultural soil, and Cd accumulation in rice grains is a major intake source of Cd for Asian populations that adversely affect human health. However, the molecular mechanism underlying Cd uptake, translocation and accumulation has not been fully understood in rice plants.ResultsIn this study, a mutant displaying extremely low Cd accumulation (lcd1) in rice plant and grain was generated by EMS mutagenesis from indica rice cultivar 9311 seeds. The candidate SNPs associated with low Cd accumulation phenotype in the lcd1 mutant were identified by MutMap and the transcriptome changes between lcd1 and WT under Cd exposure were analyzed by RNA-seq. The lcd1 mutant had lower Cd uptake and accumulation in rice root and shoot, as well as less growth inhibition compared with WT in the presence of 5 μM Cd. Genetic analysis showed that lcd1 was a single locus recessive mutation. The SNP responsible for low Cd accumulation in the lcd1 mutant located at position 8,887,787 on chromosome 7, corresponding to the seventh exon of OsNRAMP5. This SNP led to a Pro236Leu amino acid substitution in the highly conserved region of OsNRAMP5 in the lcd1 mutant. A total of 1208 genes were differentially expressed between lcd1 and WT roots under Cd exposure, and DEGs were enriched in transmembrane transport process GO term. Increased OsHMA3 expression probably adds to the effect of OsNRAMP5 mutation to account for the significant decreases in Cd accumulation in rice plant and grain of the lcd1 mutant.ConclusionsAn extremely low Cd mutant lcd1 was isolated and identified using MutMap and RNA-seq. A Pro236Leu amino acid substitution in the highly conserved region of OsNRAMP5 is likely responsible for low Cd accumulation in the lcd1 mutant. This work provides more insight into the mechanism of Cd uptake and accumulation in rice, and will be helpful for developing low Cd accumulation rice by marker-assisted breeding.