Cd In Wheat Research Articles

Comparative effects of Tagetes patula L. extraction, mercapto-palygorskite immobilisation, and the combination thereof on Cd accumulation by wheat in Cd-contaminated soil

Phytoextraction and in situ immobilisation are two of the most commonly used remediation techniques for Cd-contaminated farmland. In theory, phytoextraction followed by immobilisation can reduce the total Cd and available Cd contents of the soil, making it suitable for the remediation of heavily Cd-contaminated alkaline soil. However, the real remediation efficiency is uncertain, and it is also unknown whether phytoextraction affects subsequent wheat Cd accumulation. In this study, two seasonal pot experiments were conducted to determine the effects of S,S-ethylenediamine disuccinic acid (EDDS)-assisted Tagetes patula L. (T. patula) extraction, mercapto-palygorskite (MPAL) immobilisation, and the combination thereof on subsequent Cd accumulation in wheat. EDDS application significantly increased the Cd content in the subsequent-soil solution, but the EDDS-activated Cd could not be absorbed by wheat roots. T. patula extraction decreased the subsequent soil pH value by 0.1–0.2 pH units, increased the available Cd content by 0.19 mg/kg, but had no effect on subsequent wheat Cd accumulation. The Cd absorption capacity of wheat roots and the Cd translocation capacity of wheat stems to grains of high-Cd wheat were higher than that of low-Cd wheat cultivar. The application of MPAL had no effect on soil pH value, but significantly decreased soil available Cd and exchangeable Cd contents by 17.78–36.76% and 21.13–52.63%; it also increased the Fe/Mn oxide-bound Cd fraction by 14.02–64.00%. MPAL application decreased the wheat grain Cd concentrations from 0.51 to 0.13 mg/kg (high-Cd wheat) and 0.35 to 0.05 mg/kg (low-Cd wheat), but had no negative effect on Fe, Mn, Cu, and Zn elements. Compared with the single MPAL application treatments, the combination treatments had no inhibition effect on Cd accumulation in wheat. MPAL is an efficient amendment, and considering the remediation efficiency, stability, and time of these methods, the combination of MPAL application with a low-Cd accumulation wheat cultivar represents a suitable proposal to ensure the safe production of wheat in Cd-contaminated alkaline soil.

Ionomics analysis provides new insights into the co-enrichment of cadmium and zinc in wheat grains

Cadmium (Cd) is present in many soils and, when enter a food chain, represents a major health threat to humans. The existent large variation in grain Cd content amongst wheat genotypes opens prospects for genetic improvement for reduced Cd uptake in this species. However, selecting low-Cd-accumulating varieties comes with a possible caveat of affecting uptake other essential nutrients. In this work, we screened 134 wheat varieties in 3 various field studies and selected 15 high- and 15 low-Cd accumulating varieties in grains for ionomics analysis. Our results showed that high-Cd accumulating varieties also possessed an ability to accumulate mineral elements of calcium, magnesium, manganese, iron and zinc, while varieties with low Cd content were deficient in many essential nutrients and, especially, zinc (Zn). The above data was confirmed in an independent trail involving another 97 wheat varieties. Thus, selecting plants for high Zn accumulation (as a part of biofortification programs) resulted in an inadvertent increase in accumulation of the toxic Cd in wheat. Vice versa, selecting low Cd-accumulating varieties comes with a danger of reducing their Zn content, with major consequences to food quality and human health. We suggest that the above conundrum can be resolved by understanding the structure-function relations of various transporters isoforms involved in Zn and Cd transport and issue-specific mode of their operation, via cell-based phenotyping followed by molecular breeding.

Polyamine-producing bacterium Bacillus megaterium N3 reduced Cd accumulation in wheat and increased the expression of DNA repair- and plant hormone- related proteins in wheat roots

Metal-immobilizing bacteria play an important role in reducing the metal uptake of plants. However, little research has characterized the effects of polyamine-producing bacteria on the inhibition of Cd uptake in wheat. Herein, the effects of Bacillus megaterium N3 on wheat Cd uptake and the differentially expressed proteins in wheat roots were studied using hydroponic experiments. The results showed that under 3 mg L-1 Cd stress, strain N3 reduced the Cd content in wheat roots (33.59%) and leaves (82.83%) compared with no inoculation. Strain N3 significantly reduced (24.19%-31.02%) the proportion of Cd in the organelles and the soluble fraction and increased (74.91%) the proportion of Cd in the cell walls of wheat roots. Moreover, the contents of abscisic acid and polyamines in the wheat roots and leaves also increased (22.64%-372.8%) in the presence of strain N3 under 3 mg L-1 Cd. Label-free proteomics showed that 127 and 85 proteins were up- and downregulated in the N3+Cd treatment compared with the Cd treatment. The significantly enriched items were identified as a protein-DNA complex, DNA packaging complex, intercellular transport, peroxidase activity, and transferase activity. Moreover, the expression of DNA replication, plant hormone, and Fe-Zn transporter related proteins in wheat roots was increased in the presence of strain N3 compared with uninoculated roots under Cd stress. These results provide new insights and a theoretical basis for applying polyamine-producing bacteria to safe wheat production.

Interactive Effects of Lanthanum and Calcium on Cadmium Accumulation in Wheat with Special Reference to TaNramp5 Expression Regulated by Calmodulin.

Lanthanum (La), calcium (Ca), and cadmium (Cd) have similar physical and chemical properties because of their similar ionic radius. Although the interactions between La, Ca, and Cd have been frequently reported in plants, few studies have investigated the interactive effects of La and Ca on the growth and Cd accumulation in plants. Therefore, we investigated the interactive effects of La and Ca on the growth and Cd accumulation in wheat under Cd exposure by a hydroponic experiment. The results indicated that wheat growth was significantly affected by La-Cd and La-Ca interactions. The accumulation of Cd in wheat was significantly affected by La-Ca and La-Cd interactions and La-Ca-Cd interplay. Correlation analysis indicated that Ca deficiency stimulated La to promote wheat growth and mitigate Cd toxicity. Simultaneously, a low Ca supply stimulated La to decrease Cd accumulation in wheat and induce TaNramp5 expression. In addition, Cd accumulation in wheat was significantly affected by the W7-La interaction and W7-La-Ca interplay. All of the results suggested that La, Ca, and Cd probably share the same binding sites in calmodulin (TaCaM) and La could affect Cd accumulation in wheat by interacting with TaCaM and then downregulating the expression of TaNramp5.

A newly-isolated Cd-loving Purpureocillium sp. strain YZ1 substantially alleviates Cd toxicity to wheat

Environmental approaches for minimizing wheat grain Cd are urgently in need in many parts of the world. While metal-removing strategies like phytoextraction or soil-washing are not suitable to the scenario of farmland Cd pollution, rhizoremediation which aims to reduce crops’ Cd uptake by using microbial technology has shown great potentials. In this study, a filamentous fungus strain YZ1 was isolated from wheat farmland soil, which is affiliated to Purpureocillium sp. based on morphological and phylogenetical evidence. The strain YZ1 had a minimum inhibitory concentration of 1 mM Cd and was able to survive at 100 mM Cd, with maximum biomass at 0.4 mM Cd. Comparative transcriptomics showed that little changes in cellular transcriptional patterns occurred at 0.4 mM Cd relative to the control, and substantial transcriptional changes could be detected mainly in substance metabolism/transport genes at 2 mM Cd. Pot culture experiments showed that YZ1 rhizo-inoculation ameliorated Cd stress to wheat substantially, leading to a significant reduction by 23.3% to 26.0% in Cd concentration of wheat seedlings. Further, molecular evidence indicated that YZ1 may colonize the wheat root and impact wheat Cd response by modulating wheat’s Cd-associated genes, mainly TaEXPA2, TaVP1, TaMRP3, TaPCS1 and TaTM20, while no effect of YZ1 on culture medium pH or Cd bioavailability was observed. A fungal strain YZ1 showing Cd-loving nature was isolated. The strain YZ1 can be a promising candidate for rhizoremediation of Cd-contaminated farmland in wheat-production areas.

Soil application of manganese sulfate could reduce wheat Cd accumulation in Cd contaminated soil by the modulation of the key tissues and ionomic of wheat

Wheat is one of the main sources of dietary Cd in northern China, and the reduction of Cd accumulation in wheat is of great significance for human health. This study explored and highlighted the effects of soil application of manganese sulfate (MnSO4) on the distribution and transport of Cd in two wheat cultivars, and identified the key tissues and elements during the Cd translocation in wheat by measuring the concentrations of eight elements in 17 parts of wheat under MnSO4 treatment. The bioaccumulation factor of Cd in the roots and the translocation factor of Cd in node1 (connected to the panicle) of the high-Cd wheat cultivar were found to be higher than that of the low-Cd wheat cultivar. Soil application of MnSO4 (0.05–0.2%) significantly reduced the Cd concentration in high- and low-Cd wheat grains by 24.16–57.52% and 25.90–63.44%, respectively, and decreased the Cd concentrations in all wheat tissues. MnSO4 application had no effect on wheat growth, and the inhibition effects on wheat Cd accumulation were more pronounced at wheat-seeding stage. MnSO4 application inhibited Cd uptake by the ion antagonism between Mn/Zn/Fe and Cd in the wheat roots and reduced Cd upward transport by reducing the Cd transport from node1 to internode1 and from panicle to wheat grain. Nodes 2–4 can restrict the transport of both Cd and Mn, whereas node1 and the panicle can inhibit Cd transport but have no effect on Mn transport. The ionomic results show that the overall spatial distribution of different tissues is consistent with the growth morphology of wheat plants. MnSO4 application significantly changed the ionomes of the roots, nodes, glumes, and wheat grains; meanwhile, the differences in the ionomic responses among the roots are the most remarkable. The results of this study show that soil application of MnSO4 is efficient for reducing the Cd accumulation in wheat grown in Cd-contaminated soil, demonstrating wide application potential.

Effects of Heavy Metal-immobilizing Bacteria on Reducing Wheat Uptake Cd by Regulation Soil Iron Oxides

Iron oxides are widely distributed in soils and have large specific surface areas and strong affinities with heavy metals, and thus play a significant role in the transformation of heavy metals in soils. Pot experiments were conducted to study the effects of heavy metal-immobilizing bacteria Bacillus megaterium N3, Serratia liquefaciens H12, and strain N3 combination with H12 on the absorption of Cd by ZM-3 (Triticum aestivum L.). The effects of different treatments on soil pH, iron oxide content, and relative abundance of iron oxide bacteria, clay particle mineral composition, and aggregates in wheat rhizosphere were also measured. The results showed that strains N3, H12, and N3+H12 significantly (P<0.05) increased the dry weight (36.5%-75.3%) of wheat grains, and significantly (P<0.05) decreased the content of Cd (30.2%-84.9%) in wheat grains. Furthermore, compared with the single application of strain N3 or H12, the application of strain N3 combined with H12 had a stronger ability to reduce the absorption of Cd by ZM-3. The results suggested that strain N3, combined with H12, decreased the uptake of Cd in wheat by:①increasing the pH (from 6.74 to 7.08) of wheat rhizosphere soil; ② increasing the Fe oxide (67.9%) and goethite contents of wheat rhizosphere soil; ③ increasing the relative abundance of iron-oxidizing bacteria (Leptothrix spp. and Gallionella spp.), and ④ increasing the content of small particle size (<0.25 mm) aggregates. The results provide a theoretical basis and technical support for the use of heavy metal-immobilizing bacteria to repair farmland contaminated by heavy metals.

Wheat-associated Pseudomonas taiwanensis WRS8 reduces cadmium uptake by increasing root surface cadmium adsorption and decreasing cadmium uptake and transport related gene expression in wheat.

Metal-resistant bacteria can reduce Cd accumulation in plants, but mechanisms underlying this effect are poorly understood. In this study, a highly effective Cd-resistant WRS8 strain was obtained from the rhizoshere soil of Triticum aestivum L. Yangmai-13 and identified as Pseudomonas taiwanensis based on 16S rRNA gene sequence analysis. Strain WRS8 was investigated for its effects on Cd availability and wheat tissue Cd contents and the related mechanisms using a hydroponic culture experiment. In strain WRS8-inoculated solution, the Cd concentration reduced and the pH and cell-adsorbed Cd increased with time. Strain WRS8 increased the wheat root and above-ground tissue dry weights by 11-36% compared to the controls. In strain WRS8-inoculated wheat plants, the Cd contents of the roots and above-ground tissues decreased by 78-85% and 88-94% and the Cd bioconcentration and translocation factors decreased by 78-85% and 46-58% at days 3 and 10, respectively, compared with the controls. The root surface-adsorbed Cd contents increased by 99-121% in the WRS8 strain-inoculated wheat plants at days 3 and 10 compared to the controls. Furthermore, strain WRS8 colonized the wheat root surfaces and interiors and reduced the expression levels of the LCT1 and HMA2 genes involved in Cd accumulation and transport in wheat roots by 46% and 30%, respectively, compared to the controls. In the Cd-contaminated soils, strain WRS8 significantly reduced the available Cd content by 20-24% and increased the pH compared to the controls. These findings showed the important role of strain WRS8 in reducing solution and soil Cd availability and suggested that strain WRS8 reduced the wheat tissue Cd accumulation by increasing root surface Cd adsorption and decreasing wheat root Cd uptake and transport-related gene expression and may provide a new and effective wheat rhizobacteria-enhanced approach for reducing wheat Cd uptake in Cd-polluted environments.

Effect of Wheat-Solanum nigrum L. intercropping on Cd accumulation by plants and soil bacterial community under Cd contaminated soil

Using accumulators for intercropping in agricultural production can change the heavy metal concentration in the target plants. This study aims to investigate how intercropping wheat (Triticum aestivum L.) and Solanum nigrum L. affects soil bacterial community and cadmium (Cd) absorption in response to Cd-contaminated soil. We compared the concentrations and accumulations of Cd by plants, the activities of soil enzymes and the bacterial community structures of rhizosphere soil in monoculture and intercropping system. Principal component analysis (PCA) ordinations showed that soil bacterial communities were significantly separated by MW and IW, which illustrated intercropping with Solanum nigrum L. impacted the bacterial community structure of wheat. Firstly, the results showed that the biomass of shoots and roots in intercropped wheat (IW) were significantly decreased by 16.19% and 29.38% compared with monoculture wheat (MW) after 60 days after transplanting (DAT). Secondly, the Cd concentration and accumulation of shoots in IW was higher than MW. The Cd accumulation of IW shoots and roots were increased 12.87% and 0.98%, respectively after 60 days DAT. Besides, the enzymes activity [catalase (CAT), urease (UA) and alkaline phosphatase (ALP)] of IW were decreased 35%, 6% and 21%, respectively after 60 days DAT. Finally, the diversity indexes [Abundance-based Coverage Estimator (ACE), Chao and InvSimpson] of IW were lower than MW. These results indicated that intercropping with Solanum nigrum L. inhibited the wheat growth and decreased the bacterial community diversity in wheat rhizosphere, increased the Cd concentration and accumulation in plant tissues of wheat. Therefore, intercropping Solanum nigrum L. and wheat with Cd-contaminated soil might increase the risk of excessive Cd in wheat.

Effects of biochars combined with ferrous sulfate and pig manure on the bioavailability of Cd and potential phytotoxicity for wheat in an alkaline contaminated soil

Reducing the content of Cd in wheat grains is necessary for human health, especially in alkaline farmland in northern China where a large area of soils is heavily polluted with Cd. A field experiment was conducted to investigate the effects of wheat straw biochar (WB) and maize straw biochar (MB) combined solely with ferrous sulfate (FeSO4) or combined with FeSO4 and pig manure (PFWB and PFMB) on Cd bioavailability in soil and the phytotoxicity of Cd in wheat in an alkaline contaminated soil. The results showed that the application of these treatments decreased the concentrations of CaCl2-extractable Cd by 32.8–60.5% and increased the soil organic matter by 36.8–106.7% compared with those of the control treatment. The acid-soluble fraction of Cd was decreased by 3.7–16.8% but the residual fraction was increased by 1.7–13.7%. Furthermore, the addition of WB and MB increased the soil pH by 0.29 and 0.16 units, respectively, while the other treatments decreased the soil pH by 0.16–0.37 units. The concentrations of Cd in different wheat tissues were decreased in amended soils, and these decreases were positively correlated with CaCl2-extractable Cd and the acid-soluble fraction of Cd. The ability to accumulate Cd was in the order of root>straw>grain. In addition, there was a downward trend in the bio-concentration and translocation factors under different amendments. The amendments of PFWB and PFMB had better efficiency in the immobilization of Cd in soil and the inhibition of Cd uptake of wheat than WB and MB. In addition, the treatments of PFWB and PFMB increased the wheat yield by 14.3–16.2%, and thus have a great application prospect based on the cost-benefit analysis.

Heavy metal-immobilizing bacteria combined with calcium polypeptides reduced the uptake of Cd in wheat and shifted the rhizosphere bacterial communities

In situ stabilization techniques for the “remediation” of heavy metal-contaminated soil are a novel and inexpensive technology. However, the mechanisms underlying the interaction of exogenous passivators with the bacterial community in wheat rhizosphere soil remain unclear. Soil static culture and pot experiments were conducted to evaluate the effects and mechanisms of the heavy metal-immobilizing bacterium Enterobacter bugandensis TJ6 and calcium polypeptides (CPPs) and their association with Cd uptake in wheat, soil quality and the rhizobacterial community structure. The results showed that compared with the control treatment (CK), the TJ6, CPP, and TJ6+CPP treatments significantly decreased the diethylenetriaminepentaacetic acid (DTPA)-extractable Cd (25.2%–60.1%) content and increased the pH, organic matter content and urease activity in the wheat rhizosphere soil, which resulted in decreases in the Cd (21.5%–77.8%) content in wheat tissues (grain, straw, and roots). In particular, the TJ6+CPP treatment was more effective at decreasing Cd accumulation in grains. Furthermore, the TJ6+CPP treatment improved the diversity of the soil bacterial community in the wheat rhizosphere, and the relative abundances of Proteobacteria, Firmicutes, Arthrobacter, Microvirga, Ensifer, Brevundimonas, Devosia and Pedobacter were enriched. These results suggest that the TJ6+CPP treatment decreased the uptake of Cd in wheat by i) providing essential elements (N and C sources), ii) increasing the pH and reducing the bioavailable Cd content in wheat rhizosphere soil, iii) allowing colonization to promote plant growth and Cd-resistant bacteria, and iv) increasing the abundance of genes associated with ABC transporters, carbon metabolism and oxidative phosphorylation in the rhizosphere bacterial community. Our results showed that the heavy metal-immobilizing bacterium TJ6 combined with CPPs decreased the Cd content and increased the bacterial community diversity of wheat rhizosphere soil. Our results also highlight the potential of using heavy metal-immobilizing bacteria and CPPs to ensure the safe production of crops growing on heavy metal-polluted soils.

Cadmium Uptake by Wheat (Triticum aestivum L.): An Overview.

Cadmium is a toxic heavy metal that may be detected in soils and plants. Wheat, as a food consumed by 60% of the world’s population, may uptake a high quantity of Cd through its roots and translocate Cd to the shoots and grains thus posing risks to human health. Therefore, we tried to explore the journey of Cd in wheat via a review of several papers. Cadmium may reach the root cells by some transporters (such as zinc-regulated transporter/iron-regulated transporter-like protein, low-affinity calcium transporters, and natural resistance-associated macrophages), and some cation channels or Cd chelates via yellow stripe 1-like proteins. In addition, some of the effective factors regarding Cd uptake into wheat, such as pH, organic matter, cation exchange capacity (CEC), Fe and Mn oxide content, and soil texture (clay content), were investigated in this paper. Increasing Fe and Mn oxide content and clay minerals may decrease the Cd uptake by plants, whereas reducing pH and CEC may increase it. In addition, the feasibility of methods to diminish Cd accumulation in wheat was studied. Amongst agronomic approaches for decreasing the uptake of Cd by wheat, using organic amendments is most effective. Using biochar might reduce the Cd accumulation in wheat grains by up to 97.8%.

Do polystyrene nanoplastics affect the toxicity of cadmium to wheat (Triticum aestivum L.)?

There has been an increase on the research of microplastics (<5 mm in diameter) as carriers for toxic chemicals to evaluate their risks for human health and environment, but only few works focused on nanoplastics (1 nm–1000 nm in diameter) interacting with pre-existing contaminants such as heavy metals. It is still unclear whether polystyrene nanoplastics (PSNPs) could affect the toxicity of cadmium to wheat (Triticum aestivum L.). Here, we assessed the impact of polystyrene nanoplastics (0, 10 mg/L) on the Cd (0, 20 μM) toxicity to wheat grown in 25% Hoagland solution for three weeks. We found that the presence of PSNPs could partially reduce Cd contents in leaves and alleviate Cd toxicity to wheat, which might be due to weakened adsorption capacity of PSNPs affected by ionic strength. In addition, PSNPs have little effect on catalase (CAT), peroxidase (POD) activities, except for decreasing superoxide dismutase (SOD) activity, which suggested that antioxidant defense systems might not be the main mechanism to reduce the oxidative damage induced by Cd in wheat. Electron paramagnetic resonance (EPR) analysis showed that PSNPs could accelerate the formation of long-lived radicals in leaves after exposure to Cd. Notably, our metabolomics profiling further indicated that the simultaneously elevated carbohydrate and amino acid metabolisms induced by PSNPs could partly alleviate Cd toxicity to wheat. Nevertheless, the present study provides important implications for the toxicological interaction and future risk assessment of co-contamination of nanoplastics and heavy metals in the environment.

Characteristics of Heavy Metal Absorption by Winter Wheat and Its Quantitative Relationship with Influencing Factors

Winter wheat is one of the main food crops in China, and ensuring the quality and safety of agricultural products is an important component in agricultural production. The absorption of heavy metals by winter wheat is affected by many factors. To clarify the characteristics of heavy metal absorption by winter wheat under field conditions, and the quantitative relationship between the content of heavy metals in wheat grains and the physical and chemical properties of soil and its content of heavy metals, point-to-point sampling was carried out from 50 fields with different levels of heavy metal pollution in the main wheat-producing areas of North China. The pH, organic matter (OM), cation exchange capacity (CEC), and contents of heavy metals in soil, wheat grain, and straw were analyzed. In addition, the characteristics of heavy metals absorbed by wheat and the effects of the physical and chemical properties of soil on the absorption of heavy metals by wheat were studied, and the quantitative relationship between heavy metals and physical and chemical properties of soil and heavy metals in wheat grain was studied by multivariate regression analysis. The results showed that the Cd content in soil in the wheat field ranged from 0.150 to 2.66 mg·kg-1, and the Cd content of the corresponding wheat grain ranged from 0.033 to 0.39 mg·kg-1. The range of Pb content in soil was 4.68-371 mg·kg-1, and the corresponding wheat Pb content range was 0.27-2.4 mg·kg-1. The soil As content range was 3.00-21.3 mg·kg-1, and the corresponding wheat grain As content range was 0.044-0.18 mg·kg-1. The over-standard rates of wheat Cd, Pb, and As were 55%, 100%, and 0, respectively, and those of soil Cd, Pb, and As were 52%, 13%, and 0, respectively. Soil Cd content was positively correlated with wheat grain Cd content (P<0.01), with correlation coefficient r=0.663 (n=50). There was a significant positive correlation between soil Pb content and wheat Pb content (P<0.05), with correlation coefficient r=0.348 (n=50). There was no significant correlation between soil As content and wheat As content. The mean enrichment coefficients of wheat grains on Cd, Pb, and As were 0.17, 0.027, and 0.0089, respectively, and the mean transfer coefficients were 0.52, 0.27, and 0.22, respectively. The enrichment and transfer coefficients of heavy metals in wheat were Cd > Pb > As. The content of heavy metals in wheat straw was 2-5 times higher than that in corresponding grains. Soil pH, OM, and CEC also affect Cd content in wheat grains. Soil Cd content, soil pH, OM, CEC, and wheat grain Cd content were analyzed by multiple regression analysis, and four prediction equations of wheat grain Cd content were obtained. The correlation coefficient r reached a very significant level (P<0.01), and the correlation coefficient of the prediction equation including all variables was highest at r=0.810 (n=50), showing that it could predict the Cd content in wheat grains well.

Cadmium foliar application affects wheat Cd, Cu, Pb and Zn accumulation

Cadmium is toxic to plants, easily reaching unsafe levels for animal and human consumption. A greenhouse experiment investigated the effect of foliar-applied Cd on the accumulation and distribution of Cd, Zn, Cu and Pb in wheat (Triticum aestivum) grown in heavy metal-contaminated soil. Cadmium solutions (0, 10, 20, 30 and 40 mg L−1) were repeatedly sprayed on entire aboveground wheat plants during heading stage to medium milk development stage. Plant sample analyses after harvest indicated that both the biomass yield and grain yield were negatively affected by Cd application (p < 0.05); compared to controls, leaf and grain Cd concentrations increased 187–547% and 26.3–91.8%, respectively. However, grain Cd accumulation (concentration × yield) was not affected by Cd treatments (p > 0.05). Stem, leaf and glume Zn concentrations increased by less than 31%, while grain Zn concentrations were negatively affected by Cd treatments (3.4–34.4% lower than the control). Grain Cu concentrations were also negatively affected by Cd treatments, while grain Pb concentrations were similar between treatments. The antagonistic effect of Cd on grain Zn accumulation may mainly be due to competition for transporters and binding compounds in wheat leaves and stems. Preventing excess Cd from entering aboveground plant tissues should lessen negative plant and potentially animal/human health effects.

Field survey study on the difference in Cd accumulation capacity of rice and wheat in rice-wheat rotation area

In the rice-wheat rotation area, Cd contamination affects food safety of rice and wheat. However, there have been conflicting results and different conclusions on the difference in Cd accumulation capacity of rice and wheat, and the factors that led to the difference were not clear. A field survey study was conducted by collecting 60 soil and grain samples in pairs during rice and wheat harvest in 30 long-term rice-wheat rotation areas with clean and mild Cd contamination in Jiangsu Province, China. The soil physicochemical properties, total Cd, soil available Cd, and grain Cd were determined, and the factors affecting Cd accumulation in rice and wheat were analyzed. The soil pH during wheat season (22 sampling points) was slightly higher than that during rice season; thus, soil available Cd in wheat was generally lower (with an average three times lower) than that in rice soil. The mean Cd content in rice grain was only half of that in wheat grain, and the Cd concentration in rice and bioconcentration factor of rice at 26 sampling points (86.7% of total samples) were lower than those of wheat, indicating that Cd accumulation capacity of wheat was stronger than that of rice. Pearson correlation coefficient and multivariate linear regression models revealed that the main factors affecting the difference of Cd accumulation in rice and wheat were soil pH and available Cd content in soil. The Cd accumulation capacity of wheat was higher than that of rice, especially in neutral and alkaline soil, and the Cd contents in rice and wheat grain depended on the soil pH and available Cd content. The food security risk of wheat was more noteworthy than rice in rice-wheat rotation area.

Effects of sulfate on cadmium uptake in wheat grown in paddy soil - pot experiment

Rice-wheat rotation is common in China. Cadmium (Cd) and sulfur (S) are added to rice fields through various activities. The sulfur amendment has been recommended to control the uptake of Cd in rice. However, the effect of S on Cd uptake in winter wheat cultivated in paddy soil is rarely reported. A greenhouse pot experiment including two Cd levels (0, 10 mg Cd/kg, as CdCl&lt;sub&gt;2&lt;/sub&gt;) combined with three S rates (0, 30, 60 mg S/kg, as Na&lt;sub&gt;2&lt;/sub&gt;SO&lt;sub&gt;4&lt;/sub&gt;) was performed to investigate the effect of S application on uptake and allocation of Cd in wheat cultivated in paddy soil. Cadmium concentrations in wheat grain significantly (P &amp;lt; 0.05) increased by 37% at 30 mg S/kg, and the percentage of Cd allocation to grain significantly (P &amp;lt; 0.05) increased by 7% at 60 mg S/kg compared with non-S addition treatment when wheat was grown in Cd-added soil. For the low Cd soil, a similar trend was seen, but Cd increases were insignificant for grain while significant (P &amp;lt; 0.05) for root at 60 mg S/kg. In conclusion, S fertiliser may promote Cd accumulation in wheat grain and should be considered when it is used for wheat in paddy soils.

Effects of carbon nanotubes on growth of wheat seedlings and Cd uptake

Carbon nanotubes (CNTs) have been widely used in many scientific fields including plant sciences due to their unique physical and chemical properties. However, little is known about the toxic effects of CNTs combined with cadmium (Cd) on wheat. The aim of this study was to investigate the effects of single-walled carbon nanotubes (SW) and multi-walled carbon nanotubes (MW) on the phytotoxicity of Cd in wheat. A hydroponic culture was carried out to study wheat seedling growth in six treatments, namely Cd only (Cd); MW only (MW); SW only (SW); SW combined with Cd (SWCd); MW combined with Cd (MWCd); and a control (neither Cd nor carbon nanotubes). Compared with the Cd, SW/MW alone, CNTsCd treatments induced a reduction in total root length, root surface area, average root diameter, number of root hairs, and the dry weight of shoots and roots, which indicated that wheat growth and development was significantly inhibited. In addition, an obvious decrease in tubulins in the roots was observed. However, SW/MWCd induced a significant increase in glutathione S-transferase and cyochrome P450 in the shoots and roots, which indicated that the defense ability of wheat seedlings had improved, thus alleviating Cd stress. Moreover, Cd content increased significantly in shoot and root tissues with an increase in SW/MW content, compared to the Cd treatment. According to the transmission electron microscopy, CNTs alone destroyed the cell structure, and this devastating phenomenon was deepened after combining Cd and CNTs due to CNTs carrying Cd to attack cells. Compared with MW, SW had a greater effect on wheat seedlings. To conclude, CNTs increase the toxicity of Cd to wheat seedlings. These results are significant as they evaluate indirect phytotoxicity of CNTs for adsorbing heavy metals and plant growth regulators. In view of the widespread exposure of agricultural crops to Cd, the nanotoxicity of CNTs should be seriously considered in relation to food security in the future.

Simultaneous in-situ remediation and fertilization of Cd-contaminated weak-alkaline farmland for wheat production

In-situ remediation of heavy metal-contaminated farmland mainly focuses on acidic soil, however, weak-alkaline farmland widely exists in north China. Meanwhile, fertilization is usually ignored, but it may influence remediation efficiency as well as grain production. In this paper, field experiments were carried out to investigate in-situ simultaneous remediation and fertilization of Cd-contaminated weak-alkaline soil by microbial agent mixed with fulvic acid (MFA), wheat straw biochar, sepiolite and their mixture. Results showed that addition of these conditioners decreased the soil available Cd by 39.86%–71.33% and the wheat Cd by 41.94%–87.10%. The decrease order of soil available Cd followed sepiolite > mixture > biochar > MFA, while the decrease order of wheat Cd was mixture > sepiolite > biochar > MFA. With addition of mixture, the wheat Cd reduced to 0.08 mg/kg, lower than the Cd limit of 0.1 mg/kg in Contaminant Limit in Food of National Food Safety Standards (GB2762-2017), and the highest wheat yield reached 7590 kg/hm2. The MFA had significant effects on improvement of soil organic matters, nutrients and rhizosphere microbes; the biochar was prominent in improving soil organic matters, inhibiting wheat Cd and soil available Cd; the sepiolite had obvious advantages in reducing wheat Cd and soil available Cd; and the mixture had a more balanced effect on soil remediation and fertilization. Correlation study showed that soil available Cd significantly affected the uptake of Cd by wheat, and wheat yield was significantly positively correlated with soil organic matters, available N. Therefore, reducing soil available Cd, increasing soil organic matters and nutrients are the keys to simultaneous remediation and fertilization of Cd-contaminated weak-alkaline soil for wheat production.

Concentration, Source, and Total Health Risks of Cadmium in Multiple Media in Densely Populated Areas, China.

Cadmium (Cd) is a non-essential and harmful element to humans. Cadmium contamination is a serious issue for human health, especially in densely populated agroecology areas. In this study, the investigation of an agroecology area was conducted to gain insight into the relationship between Cd in wheat and soil and then evaluate the Cd total risk for human health. The soil samples and their matching wheat samples, underground water samples, and atmospheric deposition (air) samples were collected from a wheat-growing area in an agroecology plain. The cadmium concentration in the four types of media, in order, was air > soil > wheat > water. The mean concentration of the geoaccumulation index (Igeo) showed that the total Cd in soil (Cd-T) and Cdair reached a mild and moderate pollution level. The results of the correlation and principal component analysis (PCA) showed that the majority of Cdwheat originated from Cd-2 (exchangeable), Cd-4 (humic acid-bound), and Cd-7 (residual). Furthermore, the results of the stepwise multiple linear regression (SMLR) showed that three fractions were primarily controlled by Cd-T: clay, cation exchange capacity (CeC), and total organic carbon (TOC). In addition, the total cancer risk (CR) of Cd in multiple media was, in the order wheat > water > soil > air. It is noteworthy that the Cd content in underground water and wheat by the ingestion pathway posed cancer risks to the local residents and provided a comprehensive insight into multiple media environment management. Furthermore, it provides a very significant basic study for detailed research into the mobility and transformation for factions.