Total Cd Uptake Research Articles

Roles of shoots and roots in cadmium uptake and distribution in tubers of potato (Solanum tuberosum L)

Potato cultivars vary in biomass production and Cd concentration. Differences in growth can lead to differences in tuber cadmium (Cd) concentration through growth dilution and/or limited uptake of Cd from the soil. The aims of this study were to investigate the relative importance of shoot (above ground plant parts) and root in dry weight (DW) accumulation, total Cd uptake and Cd distribution between organs and how this affects tuber Cd concentration. Three experiments were carried out, two with reciprocal grafting between high and low tuber Cd accumulating cultivars under two soil Cd conditions, and the other was involving the evaluation of F1 genotypes, from a cross between these high and low tuber Cd accumulating cultivars. These experiments were carried out under controlled greenhouse conditions. The results showed that the root system is important for total Cd uptake but less important for growth and Cd distribution between organs. On the other hand, the shoot system is important for regulating growth of shoot and roots, and for determining Cd distribution between organs. The data suggest that tuber Cd concentration was mainly regulated by shoot source and to a lesser extent by total uptake of Cd.

Farmyard manure alone and combined with immobilizing amendments reduced cadmium accumulation in wheat and rice grains grown in field irrigated with raw effluents

Cadmium (Cd) stress is a serious concern in agricultural soils worldwide whereas little is known about the impact of farmyard manure (FYM) alone or combined with limestone, lignite and biochar on Cd concentrations in plants. Wheat was grown in Cd-contaminated field amended with control (T1), FYM @ 0.1% (T2), FYM + limestone @ 0.05% each (T3), FYM + lignite @ 0.05% each (T4), FYM + biochar @ 0.05% each (T5) and subsequent rice was grown without additional use of amendments. Soil application of amendments increased straw and grain yield and thousand grain weight being maximum in FYM + limestone treatment. Wheat and rice straw yield increased by 19% and 10% in T3 than control respectively. Photosynthetic pigments increased with the supply of amendments than control. Amendments decreased Cd concentration, total Cd uptake in straw and grains and Cd harvest index of both crops and the maximum reduction in these parameters was recorded with where FYM + limestone (T3). Cd concentration in wheat and rice straw decreased by 78.5% and 65% in T3 than control, respectively. The highest benefit to cost ratio was obtained in FYM + limestone (T3). Ammonium bicarbonate - diethylenetriamine penta acetic acid (AB-DTPA) extractable Cd of the post-harvest soil reduced whereas Cd immobilization index and soil pH increased with the supply of all treatments than control being maximum in T3. The present study revealed that field management with FYM + limestone increased plant yield and reduced Cd concentrations in grains.

Soil geochemical factors regulate Cd accumulation by metal hyperaccumulating Noccaea caerulescens (J. Presl & C. Presl) F.K. Mey in field-contaminated soils

Cadmium contamination in soil is a substantial global problem, and of significant concern due to high food-chain transfer. Cadmium hyperaccumulators are of particular interest because of their ability to tolerate and take up significant amounts of heavy metal pollution from soils. One particular plant, Noccaea caerulescens (formerly, Thlaspi caerulescens), has been extensively studied in terms of its capacity to accumulate heavy metals (specifically Zn and Cd), though these studies have primarily utilized hydroponic and metal-spiked model soil systems. We studied Cd and nutrient uptake by two N. caerulescens ecotypes, Prayon (Zn-only hyperaccumulator) and Ganges (Zn- and Cd-hyperaccumulator) in four long-term field-contaminated soils. Our data suggest that individual soil properties such as total soil Cd, Zn:Cd molar ratio, or soil pH do not accurately predict Cd uptake by hyperaccumulating plants. Additionally, total Cd uptake by the hyperaccumulating Ganges ecotype was substantially less than its physiological capacity, which is likely due to Cd-containing solid phases (primarily iron oxides) and pH that play an important role in regulating and limiting Cd solubility. Increased P accumulation in the Ganges leaves, and greater plant Fe accumulation from Cd-containing soils suggests that rhizosphere alterations via proton, and potentially organic acid, secretion may also play a role in nutrient and Cd acquisition by the plant roots. The current study highlights the role that soil geochemical factors play in influencing Cd uptake by hyperaccumulating plants. While these plants may have high physiological potential to accumulate metals from contaminated soils, individual soil geochemical factors and the plant-soil interactions in that soil will dictate the actual amount of phytoextractable metal. This underlines the need for site-specific understanding of metal-containing solid phases and geochemical properties of soils before undertaking phytoextraction efforts.

Cadmium uptake and partitioning in potato (Solanum tuberosum L.) cultivars with different tuber-Cd concentration.

Potatoes grown in soil with high Cd concentrations can accumulate high levels of Cd in the tubers. Although there is significant environmental variation involved in the trait of crop uptake of Cd, there are also distinctive cultivar differences. In order to understand this differential Cd accumulation mechanism, two potato cultivars were chosen that accumulate high and low levels of Cd in tubers. The patterns of Cd concentration, Cd content and dry weight accumulation of the two cultivars were examined at different stages of plant growth. The data suggest that differences in total Cd uptake and in Cd partitioning among organs are the mechanisms governing differential Cd-tuber accumulation in the two cultivars. The low tuber-Cd accumulator exhibited lower root-to-shoot and shoot-to-tuber translocation driven by higher root and shoot biomass that retained more Cd in roots and shoots, respectively, reducing its movement to the tubers. Higher remobilization and more efficient tuber loading was observed in the high tuber-Cd accumulator, indicating that remobilization of Cd from leaves to tubers was a major factor, not only in tuber-Cd loading, but also in the establishment of differential tuber-Cd levels. Regardless of cultivar differences, the concentration of Cd in the tuber was very low compared to that in other organs suggesting that, despite its high phloem mobility, Cd tends to be sequestered in the shoots.

Role of Rhizophagus irregularis in alleviating cadmium toxicity via improving the growth, micro- and macroelements uptake in Phragmites australis.

Arbuscular mycorrhizal (AM) fungi have been used to alleviate heavy metal stress on plant growth and uptake of micro- and macroelements. A greenhouse pot experiment was conducted to verify the effects of AM fungus Rhizophagus irregularis on the growth, physiological characteristics, total Cd, and element uptake of Phragmites australis under different Cd stress (in the range of 0-20mgL-1). The results showed that the symbiosis could effectively alleviate Cd toxicity with greater root biomass, higher photosynthesis rate, and lower levels of malonaldehyde (MDA) and proline than non-mycorrhizal plants could. However, reduced transpiration rate (Tr) and stomatal conductance (g s) indicated R. irregularis protected host plants from Cd stress (≥5mgL-1) via the stomatal closure. Although micro- and macroelements displayed differently in the presence of Cd, higher concentrations were still detected in mycorrhizal plants in contrast to non-mycorrhizal plants. Moreover, step multiple regression significantly demonstrated Pnmax, stem diameter (Sd), and g s were the important factors with regard to total Cd uptake in the symbiosis, but Mn affected to non-mycorrhizal plants. These results suggested R. irregularis could alleviate the competition between Mn and Cd by altering plant physiology. This work clearly demonstrated that R. irregularis can be able to support P. australis growth better even though under high Cd stress (>1mgL-1), suggesting its good potential for practical use in high Cd-contaminated areas.

Inoculation with endophytic Bacillus megaterium H3 increases Cd phytostabilization and alleviates Cd toxicity to hybrid pennisetum in Cd-contaminated aquatic environments.

A hydroponic culture experiment was performed to investigate the effects of endophytic Bacillus megaterium H3 on the plant biomass, Cd accumulation and tolerance of hybrid pennisetum, and the mechanisms involved in the different levels of Cd-contaminated aquatic environments. Strain H3 significantly increased the plant growth (ranging from 13 to 71%) and total Cd uptake (ranging from 41 to 160%) but decreased Cd translocation factors of hybrid pennisetum treated with 0-20μM Cd compared with the controls. Furthermore, most of Cd (71-77%) was accumulated in the roots of the bacterial-inoculated hybrid pennisetum. Notably, strain H3 could significantly increase the production of oxalic and propanedioic acids (ranging from 18 to 188%) but decrease the production of phytochelatins of hybrid pennisetum compared to the controls under different levels of Cd stress. The live bacterial-induced increase in organic acid production and decrease in phytochelatins production by hybrid pennisetum might be responsible for the increased plant growth, root Cd accumulation, and Cd toxicity alleviation of the plant under different levels of Cd stress. The results highlight that hybrid pennisetum plus endophytic B. megaterium H3 may be utilized for biomass production and Cd phytostabilization of the plant in the different levels of Cd-contaminated aquatic environments.

Increased biomass and reduced heavy metal accumulation of edible tissues of vegetable crops in the presence of plant growth-promoting Neorhizobium huautlense T1-17 and biochar

The effects of a plant growth-promoting Neorhizobium huautlense T1-17, biochar, and their combination on the biomass and Cd and Pb accumulation of Chinese cabbages and radishes and the mechanisms involved were characterized. T1-17 increased the biomass and reduced the above-ground tissue (Chinese cabbages) or root (radishes) Cd and Pb contents of the seedlings compared to the control. T1-17 and biochar+T1-17 significantly increased the edible tissue biomass (ranging from 56% to 112%) of the two vegetables compared to the control. T1-17, biochar, and their combination significantly reduced the edible tissue Cd and Pb contents (ranging from 46% to 86%) and total Cd and Pb uptake (ranging from 16% to 78%) of the two vegetables compared to the controls. Biochar+T1-17 had higher ability to increase the biomass and decrease the edible tissue Cd (Chinese cabbages) and Pb (radishes) contents than T1-17 or biochar. Furthermore, T1-17, biochar, and their combination significantly decreased the water-soluble (ranging from 32% to 88%) and DTPA-extractable (ranging from 14% to 51%) Cd and Pb contents in the rhizosphere soils compared to the controls. Notably, biochar+T1-17 had higher ability to decrease the water-soluble Cd and Pb contents of the rhizosphere soils than T1-17 or biochar. T1-17 and biochar+T1-17 significantly increased the ratios of small soil aggregate particles (<0.25mm) of the rhizosphere soils of the two vegetables and negative correlation between the ratios of small soil aggregate particles and the DTPA-extractable Cd and Pb contents was observed. Furthermore, T1-17 and biochar+T1-17 significantly increased the ratio of IAA-producing bacteria in the rhizosphere soils of the two vegetables. The results showed the synergistic effects of T1-17 and biochar on the increased edible tissue biomass and decreased available Cd and Pb in the soils and Cd and Pb uptake of the vegetables. The results also suggested that T1-17 and biochar+T1-17 increased the edible tissue growth and reduced the edible tissue Cd and Pb uptake of the vegetables through increasing the proportions of plant growth-promoting bacteria and small soil aggregates in the rhizosphere soils.

Cadmium Removal Potential from Contaminated Soil by Tagetes erecta L. and Panicum maximum: Influence of Soil pH

ABSTRACTThe potential for cadmium (Cd) removal from contaminated soil by two species—marigold (Tagetes erecta L.) and Guinea grass (Panicum maximum)—was investigated in pot culture experiments in a greenhouse in triplicate. The concentration of Cd was varied from 50 to 200 mg kg−1 and the pH was varied from 5.0 to 7.5 to investigate the effect of pH on Cd uptake. The results showed that total biomass of Guinea grass was around nine and seven times higher than that of marigold for Cd treatments of 50 and 100 mg kg−1 at pH 5.0, respectively. Total cadmium uptake at Cd treatments of 50 and 100 mg kg−1 at pH 5.0 by Guinea grass was 19.28 ± 3.14 and 36.06 ± 4.28 mg kg−1, respectively, and for marigold was 15.66 ± 4.17 and 20.38 ± 3.24 mg kg−1, respectively. The total Cd uptake by Guinea grass was 1.23 and 1.77 higher than that of marigold at Cd treatments of 50 and 100 mg kg−1, respectively, at pH 5.0 due to higher biomass. The maximum Cd uptake by marigold and Guinea grass occurred at pH 5.0 at Cd treatment of 100 mg kg−1. The results clearly show that the two species behave very differently for Cd uptake. Guinea grass is easy to grow, drought tolerant and, due to its higher biomass, it can be used for remediation of Cd-contaminated soil.

Silicon alleviates Cd stress of wheat seedlings (Triticum turgidum L. cv. Claudio) grown in hydroponics.

We investigated the potential role of silicon in improving tolerance and decreasing cadmium (Cd) toxicity in durum wheat (Triticum turgidum L. durum) either through a reduced Cd uptake or exclusion/sequestration in non-metabolic tissues. For this, plants were grown in hydroponic conditions for 10days either in presence or absence of 1mM Si and for 11 additional days in various Cd concentrations (0, 0.5, 5.0 and 50μM). After harvesting, morphological and physiological parameters as well as elemental concentrations were recorded. Cadmium caused reduction in growth parameters, photosynthetic pigments and mineral nutrient concentrations both in shoots and roots. Shoot and root contents of malate, citrate and aconitate increased, while contents of phosphate, nitrate and sulphate decreased with increasing Cd concentrations in plants. Addition of Si to the nutrient solution mitigated these adverse effects: Cd concentration in shoots decreased while concentration of Cd adsorbed at the root cell apoplasmic level increased together with Zn uptake by roots. Overall, total Cd uptake decreased in presence of Si. There was no co-localisation of Cd and Si either at the shoot or at the root levels. No Cd was detected in leaf phytoliths. In roots, Cd was mainly detected in the cortical parenchyma and Si at the endodermis level, while analysis of the outer thin root surface of the plants grown in the 50μM Cd + 1mM Si treatment highlighted non-homogeneous Cd and Si enrichments. These data strongly suggest the existence of a root localised protection mechanism consisting in armoring the root surface by Si- and Cd-bearing compounds and in limiting root-shoot translocation.

Combined effects of elevated CO2 and Cd-contaminated soil on the growth, gas exchange, antioxidant defense, and Cd accumulation of poplars and willows

Few studies have explored the combined effects of elevated CO2 (EC) and Cd treatments on poplars and willows. The objective of this study is to determine how growth and phytoremediation efficiency are enhanced by EC. For this purpose, this study investigated the combined effects of EC and Cd treatments on the growth, gas exchange, antioxidant defense, and Cd accumulation in one poplar genotype (Populus×euramericana (Dode) cv. ‘Nanlin-95’ (NL95)) and one willow genotype (Salix jiangsuensis CL. ‘172’ (J172)), which were grown on three Cd-contaminated soil in six open-top chambers. Under Cd treatment, plant growth was decreased, Cd accumulation was increased, and the photosynthesis and malondialdehyde concentration were unchanged in leaves of two tree species. At EC levels for both species, plant growth, total Cd uptake, CO2 assimilation rate, and intrinsic water use efficiency were increased; stomatal conductance and transpiration rate were decreased; and Cd concentrations were unchanged. EC also decreased malondialdehyde content in two species grown in Cd-contaminated soil and increased antioxidant enzymatic activities in J172 grown in high Cd-contaminated soil. At EC, plant growth and total Cd uptake exhibited greater increase in high Cd-contaminated soil than in low Cd-contaminated soil. These findings suggest that EC stimulated plant growth by increasing leaf photosynthesis and enhanced phytoremediation efficiency, particularly at high levels of Cd exposure. EC decreased oxidative damage by stimulating photosynthesis and increasing antioxidant enzyme activities. Cd treatment inhibited the growth of two tree species, and this suppression was unrelated to photosynthesis. Under Cd treatment, the well-maintained photosynthesis is assumed responsible for decreasing reactive oxygen species accumulation and avoiding membrane lipid peroxidation.

Effect of elevated CO2 concentration on photosynthetic characteristics of hyperaccumulator Sedum alfredii under cadmium stress.

The combined effects of elevated CO2 and cadmium (Cd) on photosynthetic rate, chlorophyll fluorescence and Cd accumulation in hyperaccumulator Sedum alfredii Hance were investigated to predict plant growth under Cd stress with rising atmospheric CO2 concentration. Both pot and hydroponic experiments were conducted and the plants were grown under ambient (350 µL L(-1)) or elevated (800 µL L(-1)) CO2 . Elevated CO2 significantly (P < 0.05) increased Pn (105%-149%), Pnmax (38.8%-63.0%) and AQY (20.0%-34.8%) of S. alfredii in all the Cd treatments, but reduced chlorophyll concentration, dark respiration and photorespiration. After 10 days growth in medium with 50 µM Cd under elevated CO2 , PSII activities were significantly enhanced (P < 0.05) with Pm, Fv/Fm, Φ(II) and qP increased by 66.1%, 7.5%, 19.5% and 16.4%, respectively, as compared with ambient-grown plants. Total Cd uptake in shoot of S. alfredii grown under elevated CO2 was increased by 44.1%-48.5%, which was positively correlated with the increase in Pn. These results indicate that elevated CO2 promoted the growth of S. alfredii due to increased photosynthetic carbon uptake rate and photosynthetic light-use efficiency, and showed great potential to improve the phytoextraction of Cd by S. alfredii.

Dry Matter Yield of Sunflower as Affected by EDTA and EDDS Application in Soil Remediation from Ibadan, Metropolis, Nigeria

Phytoremediation has been found to be cost effective in removing heavy metals (HM) from polluted soils. Enhanced phytoextraction with the use of chelating agents for solubility of metal in soils and their uptake in the aerial parts of plants had also been employed. Phytoextraction efficiency of plants will depend on the metal accumulated in the dry matter yield of plant. An attempt was made to study the influence of Ethylene diamine tetra acetic acid (EDTA) and ethylene diamine disuccinic acid (EDDS) on the growth and dry matter yield content of sunflower planted in heavy metal polluted soils in a greenhouse pot experiment. Total heavy metal contents of five metals (Cu, Cd, Cr, Pb and Zn) were determined by acid digestion with aqua regia solution. A greenhouse experiment was conducted to assess the phytoextraction potential of sunflower with EDDS and EDTA applied at seven weeks after planting. Treatments were laid out in a completely randomized design with four replicates. Data were collected on metal accumulation in root and shoot, Total metal uptake, shoot and root dry matter yield and analyzed using descriptive statistics and ANOVA at α0.05. Original Research Article Thomas and Omueti; IJPSS, 7(1): 67-79, 2015; Article no.IJPSS.2015.132 68 The result shows a significant increase in the overall accumulation of metals in the root and shoot of sunflower and dry matter yield with EDDS except for Zn. However, Zinc only recorded significant increase in shoot uptake at 3 mmol/kg EDDS. The application of EDDS at 3 and 9 mmol/kg did better in total uptake of Cu, Pb and Cd. Ethylene diamine disuccinic acid (EDDS) was more efficient than EDTA in mobilizing metal uptake in sunflower root and shoot and also in increasing total dry matter yield. Translocation factor of Cd, Pb and Cu were enhanced by the addition of EDDS than EDTA application.

Phytoextraction of Cadmium and Zinc By Sedum plumbizincicola Using Different Nitrogen Fertilizers, a Nitrification Inhibitor and a Urease Inhibitor

Cadmium (Cd) and zinc (Zn) phytoavailability and their phytoextraction by Sedum plumbizincicola using different nitrogen fertilizers, nitrification inhibitor (dicyandiamide, DCD) and urease inhibitor (N-(n-Butyl) thiophosphoric triamide, NBPT) were investigated in pot experiments where the soil was contaminated with 0.99 mg kg−1 of Cd and 241 mg kg−1 Zn. The soil solution pH varied between 7.30 and 8.25 during plant growth which was little affected by the type of N fertilizer. The (NH4)2SO4+DCD treatment produced higher NH4+−N concentrations in soil solution than the (NH4)2SO4 and NaNO3 treatment which indicated that DCD addition inhibited the nitrification process. Shoot Cd and Zn concentrations across all treatments showed ranges of 52.9–88.3 and 2691–4276 mg kg−1, respectively. The (NH4)2SO4+DCD treatment produced slightly higher but not significant Cd and Zn concentrations in the xylem sap than the NaNO3 treatment. Plant shoots grown with NaNO3 had higher Cd concentrations than (NH4)2SO4+DCD treatment at 24.0 and 15.4 mg kg−1, respectively. N fertilizer application had no significant effect on shoot dry biomass. Total Cd uptake in the urea+DCD treatment was higher than in the control, urea+NBPT, urea+NBPT+DCD, or urea treatments, by about 17.5, 23.3, 10.7, and 25.1%, respectively.

Simultaneous determination of heavy metals in biological samples by a multiple-template imprinting technique: an electrochemical study

In order to make people aware of the contamination of heavy metals in our daily life by inappropriate food intake, we have studied the contents of copper, cadmium, and lead in various components of our biota (soil, water, and plants, i.e. fruits and vegetables), collected from different areas (normal, industrial, coal-mine, river, and hill areas). For the accurate and rapid sensing of these metal ions, a multi-template imprinted nanowire modified electrochemical sensor was reported. The imprinted nanowire was synthesized using multiwalled carbon nanotubes as a core, on which a layer of conducting polyarginine is cast using an electro-polymerization technique. To study the total uptake of food-borne Cu(II), Cd(II), and Pb(II) ions in the human body, blood samples of six people were taken based on their different diets in their daily routine. Moreover, during the soil, water and plant analysis, it was observed that plants growing in a contaminated environment have a large accumulation of metal ions in their leaves and fruits. One more study was performed to explore ‘how much heavy metal we are taking in from our regular diet?’ and it was perceived that some of the food, which has lower concentrations of copper ions, can release a bigger amount of metal ions after digestion.

The significant contribution of mycorrhizal fungi and earthworms to maize protection and phytoremediation in Cd-polluted soils

Abstract Mycorrhizal fungi and earthworms can individually or interactively influence plant growth and heavy metal uptake. The influence of earthworms and arbuscular mycorrhizal (AM) fungi either alone or in combination on maize (Zea mays L.) growth and cadmium (Cd) uptake was investigated in a calcareous soil artificially spiked with Cd. Soils were contaminated with Cd (10 and 20 mg Cd kg−1), inoculated or un-inoculated with the epigeic earthworm Lumbricus rubellus and two AM fungal species (Rhizophagus irregularis and Funneliformis mosseae) for two months of growth under greenhouse conditions. Generally, earthworms alone increased both shoot P uptake and biomass but decreased shoot Cd concentration and root Cd uptake. AM fungi individually often increased total maize P uptake, declined shoot Cd concentration, and consequently produced higher total biomass. However, R. irregularis enhanced shoot Cd uptake at low Cd level and root Cd uptake at high Cd level. In plants inoculated with F. mosseae species, earthworms increased shoot biomass and Cd uptake, decreased root biomass and Cd uptake at all Cd levels, and increased shoot Cd concentration at low Cd level. In plants colonized by R. irregularis species, however, earthworm addition decreased maize biomass only at high Cd level and root Cd concentration and total maize Cd uptake at both Cd levels. Earthworm activity decreased Cd transfer from the soil to maize roots at low Cd level, but this was counterbalanced in the presence of F. mosseae. Mycorrhizal symbiosis significantly reduced the transfer of Cd from roots to shoots, independence of earthworm effect. Overall, it is concluded that L. rubellus and AM fungi, in particular F. mosseae isolate, improved maize tolerance to Cd toxicity both individually and interactively by increasing plant growth and P nutrition, and restricting Cd transfer to the aboveground biomass. Consequently, the single and interactive effects of the two soil organisms might potentially be important not only in protecting maize plants against Cd toxicity, but also in Cd phytostabilization in soils polluted by this highly toxic metal.

Elevated ambient carbon dioxide and Trichoderma inoculum could enhance cadmium uptake of Lolium perenne explained by changes of soil pH, cadmium availability and microbial biomass

Trichoderma inoculum may mediate plant growth and uptake of heavy metals, but the combined effects and the mechanisms of Trichoderma sp. and elevated ambient carbon dioxide (CO2) on the cadmium (Cd) availability and plant uptake are far less investigated. A pot experiment was conducted to investigate plant growth, Cd uptake, and chemical and microbial biomass characteristics of the rhizosphere of Lolium perenne grown on three Cd-contaminated soils under combined effects of elevated ambient CO2 and Trichoderma virens strain F7 inoculum. Rhizosphere soil samples were analyzed for pH, concentrations of available Cd measured by diffusive gradients in thin-films (DGT-Cd) and microbial biomass carbon and nitrogen. It was found that the elevated ambient CO2 and Trichoderma inoculation, in combination or alone, significantly promoted plant biomass and total Cd uptake by plants with decreased soil pH (by 0.08–0.32 units) and increased microbial biomass carbon (by 21.54–121.21%) and nitrogen (by 21.88–112.95%) in the rhizosphere. Also, the concentration of DGT-Cd in the rhizosphere under elevated ambient CO2 and Trichoderma inoculum treatments was increased by 15.45–152.48%, indicating that there was more available Cd for plant uptake under effects of elevated ambient CO2 and Trichoderma inoculum. Results suggested that the acidulated rhizosphere, enhanced microbial activities and increased Cd availability may have contributed to the efficiency of plants in Cd accumulation under effects of elevated ambient CO2 and Trichoderma inoculum.

Comparative Effect of Two Different Types of Phosphate on Cadmium Uptake by Radish (Raphanus sativa L.) Grown in Arable Soil Affected by Mine Activity

To evaluate the effect of type of phosphate (P) material on reducing soil cadmium (Cd) extractability and radish Cd uptake in the field, two different P materials, fused superphosphate (FSP) and dipotassium phosphate (K2HPO4), were applied at rates of 0, 33.5, 100.5, and 167.5 kg P ha−1 before seeding radish (Raphanus sativa L.) in a Cd-contaminated soil. Plant-available Cd concentration in soil and total Cd uptake by radish increased with increasing FSP application but decreased with K2HPO4. The significant decrease in soil pH and negative charge of soil by FSP application led to an increase in bioavailable Cd fraction in soil and in Cd uptake by radish. However, K2HPO4 increased soil pH and negative charge of soil and decreased bioavailable Cd fractions. Soil pH and negative charge of soil played an important role in controlling Cd uptake by radish in soil to which phosphate was applied.

Phytoextraction by high-Cd-accumulating rice to reduce Cd in wheat grains grown in Cd-polluted fields

Phytoextraction using indica rice plants (Indian Rice Oryza ssp.) is a promising technique for remediating cadmium (Cd)-polluted paddy fields. Because this technique has only been established for paddy fields, we decided to examine phytoextraction in upland fields that have been converted from paddy fields. Although “CHOKOUKOKU” shows a shattering habit and lodging, its Cd uptake was significantly higher than that of other indica rice varieties. On the other hand, “IR8”, which was able to accumulate only moderate levels of Cd in its shoots, has a lodging tolerance, making it an optimal variety for southwest Japan, which experiences several typhoons each year. Therefore, both “CHOKOUKOKU” and “IR8” were useful in estimating practical phytoextraction in upland fields. A practical phytoextraction examination showed that the total Cd uptake of “CHOKOUKOKU” and “IR8” was 822 and 545 g ha−1, respectively, after a 4-year period. After phytoextraction by planting high Cd-accumulating rice plants, the Cd concentration of the plot soil decreased by approximately 35%, compared to the initial Cd concentration. To evaluate phytoextraction efficiency in the upland field, wheat (Triticum aestivum) was subsequently grown in the remediation field. The Cd concentration in the grains of “SHIROGANEKOMUGI” grown in the phytoextraction plot was lower than that grown in a non-phytoextraction plot; regrettably, it exceeded the Codex Alimentarius Commission standard, whereas the grain Cd concentrations of “CHUGOKU165” planted in phytoextraction plots complied with the Codex standard for wheat grain. These results suggest that phytoextraction using high Cd-accumulating rice varieties is a practical remediation system for low Cd-polluted upland fields. Moreover, we determined the end point of the phytoextraction process, which occurs when the soil Cd concentration of the phytoextraction fields is less than 0.6 mg kg−1 if “CHUGOKU165” is cultivated in this area.

Effects of Soil Type and Genotype on Cadmium Accumulation by Rootstalk Crops: Implications for Phytomanagement

The variations of Cd accumulation in three rootstalk crop species (radish, carrot and potato) were investigated by using twelve cultivars grown in acidic Ferralsols and neutral Cambisols under two Cd treatments (0.3 and 0.6 mg kg−1) in a pot experiment. The result showed that the total Cd uptake was significantly affected by genotype, soil type and interaction between them, suggesting the importance of selecting proper cultivars for phytoextraction in a given soil type. Among the cultivars tested, potato cultivar Luyin No.1 in Ferralsols and radish cultivar Zhedachang in Cambisols exhibited the highest Cd phytoextraction efficiency in aerial parts (4.45% and 0.59%, respectively) under 0.6 mg kg−1Cd treatment. Furthermore, the Cd concentrations in their edible parts were below the National Food Hygiene Standard of China (0.1 mg kg−1, fresh weight). Therefore, phytomanagement of slightly Cd-contaminated soils using rootstalk crops for safe food production combined with long-term phytoextraction was feasible, and potato cultivar Luyin No.1 for Ferralsols and radish cultivar Zhedachang for Cambisols were promising candidates for this approach.

Cadmium uptake and translocation in durum wheat varieties differing in grain-Cd accumulation

Wheat grain products are the primary source of dietary Cd-intake for humans. Since varieties differ markedly in grain-Cd accumulation, efforts are needed to find traits associated with low, or high, accumulation. Two durum wheat varieties, selected in a field screening as low (Creso) and high (Svevo) grain-Cd accumulating, were grown on soil spiked with 1.5, 3 and 4.5 mg Cd/kg. Growth patterns, Cd uptake and translocation were investigated at heading and maturity. Cadmium did not affect plant growth and grain yield, but grain-Cd concentration always exceeded the permissible limit of 0.2 mg Cd/kg, and was approximately double in Svevo than in Creso. At maturity, total Cd-uptake increased linearly with supply in Creso, from 13 to 23 &amp;micro;g/plant, and was approximately 18 &amp;micro;g/plant, irrespective of Cd level, in Svevo. Partitioning to shoot was higher in Svevo than in Creso, both at heading and maturity. We suggest that reduced plant height, high root to shoot biomass ratio during vegetative growth and elevated post-heading dry matter accumulation promoted Cd accumulation into grain. Since these traits are common to modern wheat varieties, risks of grain Cd-contamination can increase in the future.