Differences In Cd Accumulation Research Articles

Transport of cadmium from soil to grain in cereal crops: A review

Due to rapid urbanization and industrialization, many soils for crop production are contaminated by cadmium (Cd), a heavy metal highly toxic to many organisms. Cereal crops such as rice, wheat, maize, and barley are the primary dietary source of Cd for humans, and reducing Cd transfer from soil to their grains is therefore an important issue for food safety. During the last decade, great progress has been made in elucidating the molecular mechanisms of Cd transport, particularly in rice. Inter- and intraspecific variations in Cd accumulation have been observed in cereal crops. Transporters for Cd have been identified in rice and other cereal crops using genotypic differences in Cd accumulation and mutant approaches. These transporters belong to different transporter families and are involved in the uptake, vacuolar sequestration, root-to-shoot translocation, and distribution of Cd. Attempts have been made to reduce Cd accumulation in grains by manipulating these transporters through overexpression or knockout of the transporter genes, as well as through marker-assisted selection breeding based on genotypic differences in Cd accumulation in the grains. In this review, we describe recent progress on molecular mechanisms of Cd accumulation in cereal crops and compare different molecular strategies for minimizing Cd accumulation in grains.

Effects of Waterborne Cadmium Exposure on Its Internal Distribution in Meretrix meretrix and Detoxification by Metallothionein and Antioxidant Enzymes

Cadmium (Cd), one of the most toxic metals found in inshore sediments of China, is a persistent environmental contaminant capable of exerting irreversible toxic effect on aquatic organisms and their associated ecosystems. Although Cd is known to be toxic to marine animals, the underlying mechanism of this toxicity is not clear. In this study, Meretrix meretrix, a commercially and ecologically important species of clam, was exposed to different concentrations of cadmium chloride (0, 1.5, 3, 6, 12 mg L-1) for 5 days, and the levels of Cd accumulation, antioxidant enzyme activity and expression of metallothionein (MT) in the hepatopancreas, gill, foot and mantle were evaluated. The results revealed a sharp increase in Cd accumulation in the tissues in response to increased Cd2+ concentrations in the water, and significant differences in Cd accumulation were observed among the different tissues. Increased Cd2+ level in the tissues also led to a significant increase in malonaldehyde (MDA) content, caused by increased lipid peroxidation. The activities of superoxide dismutase (SOD) and catalase (CAT) also increased, peaking at different Cd2+ concentrations, depending on the tissue. Glutathione peroxidases (GPx) activity in the gill and mantle initially increased, but then decreased with increasing external Cd2+ concentration. In the hepatopancreas and foot, GPx activity was inhibited by Cd2+, even at low concentrations. Furthermore, Cd2+ also stimulated the expression of MT in all four tissues. However, the levels of reduced glutathione (GSH) andoxidized glutathione (GSSG) in the gill and mantle, as well as the GSH/GSSG ratios in all four tissues decreased with increasing external Cd2+ concentrations. Taken together, the results suggested that in M. meretrix, response to the toxic effect of Cd2+ might occur through a combination of mechanisms, which involve both enhanced antioxidant enzyme activities and the ability to bind and sequester Cd2+ via cysteine-rich molecules such as GSH and MT, both of which would eventually lead to the reduction of heavy metal-induced oxidative stress.

Nutrient allocation might affect the cadmium accumulation of Bermuda grass (Cynodon dactylon)

Hydroponic experiments with different cadmium (Cd) concentrations were conducted to explore the impacts of nutrient allocation on the Cd enrichment of Bermuda grass. The results demonstrated with the Cd concentration increase, the accumulation of nitrogen (N), phosphorus (P) and potassium (K) in roots, stems and leaves increased first and then decreased, while the accumulation of Cd had no significant difference. The biomass and N, P and K accumulation of CD1 and CD2 were significantly different from those of CD3 and CD4, but there was no significant difference in Cd accumulation. The root N, P and K distribution ratio of CD4 increased by 47.9%, 114.3% and 64.3% compared with those of CD2 treatment, the values of stem decreased by 29.4%, 22.4% and 17.2%, and the values of leaves increased by 15.8%, 19.8% and 23.6% respectively. The K ratio of root and leaf increased and that of stem decreased. Cd reduced N and K distribution ratio of stem and increased N and K distribution ratio of root and leaf. Pearson correlation analysis showed that the accumulation of N, P and K in stems was positively correlated with the accumulation of Cd in stems, and the accumulation of N, P and K in roots, stems and leaves were positively correlated with the Cd accumulation in leaves. Bermuda grass can schedule the nutrient allocation to adapt to the Cd absorption and enrichment in different organs under different Cd concentrations. In conclusion, nutrient allocation might affect the Cd accumulation of Bermuda grass.

Tolerance Mechanism and Cadmium Enrichment Abilities in Two Brassica napus L. Cultivars

A hydroponic experiment was conducted to explore the differences in growth status and Cd accumulation characteristics of two Brassica napus L. cultivars (QY-1 and SYH) under different concentrations of cadmium (Cd) stress (0, 2, and 5 mg·L-1). The Cd subcellular compartmentalization and antioxidant enzyme activities were determined to elucidate the intrinsic mechanism of the differences in the Cd accumulation capacity between the two cultivars of Brassica napus L. Furthermore, field trials were conducted to further verify the differences in phytoremediation of the two cultivars. Results show that neither of the cultivars exhibited obvious growth inhibition under Cd stress. Under the 2 mg·L-1 Cd condition, there were no significant differences in shoot Cd concentrations between the two cultivars. Under 5 mg·L-1 Cd condition, however, the Cd concentrations in both shoot and root of SYH were significantly higher than that of QY-1, which increased by 32.05% and 99.57%, respectively. In addition, the bioconcentration factor (BCF) of the root in SYH is significantly higher than that of QY-1. The subcellular Cd distribution in leaves of the two cultivars of Brassica napus L. showed that, with an increase of Cd stress, Cd concentrations of heat stable protein (HSP) and metal-rich granule (MRG) fractions in leaves significantly increased by 143.69% and 118.91% for QY-1, and by 63.34% and 118.91% for SYH. Thus, the segregation of Cd in HSP and MRG, which was reported to be biological detoxified metal fractions (BDM), might play an important role in the detoxification of Brassica napus L. at a subcellular level under Cd stress. Moreover, the distribution of Cd in the cellular debris fraction might be another important factor contributing to the differences in Cd accumulation of the two Brassica napus L. cultivars, which was 4.41 times higher in SYH than in QY-1 under Cd stress. The results of the antioxidant enzyme activities of two Brassica napus L. cultivars showed that, under the 5 mg·L-1 Cd condition, the antioxidant enzyme system may represent an important detoxification mechanism for QY-1 to cope with stress induced by high concentrations of Cd, while SYH is more effective in reducing the toxicity of Cd by separation of Cd into BDM fractions. The results of the field trial confirmed that the Cd concentrations in the above- and underground parts of SYH were 2.34 and 1.43 times higher than in QY-1, respectively. Therefore, SYH possess a higher Cd phytoextraction capacity than QY-1, and might be a good candidate for the remediation of moderate and mildly Cd-contaminated farmland.

Cadmium-Induced Structure Change of Pigment Glands and the Reduction of the Gossypol Content in Cottonseed Kernels

The risk of cotton production on arable land contaminated with heavy metals has increased in recent years. Cotton shows stronger and more extensive resistance to heavy metals, such as cadmium (Cd) than that of other major crops. Here, a potted plant experiment was performed to study Cd-induced alterations in the cottonseed kernel gossypol content and pigment gland structure at maturity in two transgenic cotton cultivars (ZD-90 and SGK3) and an upland cotton standard genotype (TM-1). The results showed that Cd accumulation in cottonseed kernels increased with increasing Cd levels in the soil. The seed kernel Cd content in plants grown on Cd-treated soils was 10-20 times greater than the amount in the corresponding controls. There was a significant difference in Cd accumulation in cottonseed kernels at the 400 and 600 μM Cd levels. Cd accumulation was higher in SGK3 and ZD-90 than in TM-1. However, the gossypol content in cottonseed kernels was lower in SGK3 and ZD-90 than in TM-1. There was a negative correlation (r = 0.550) between Cd accumulation and the gossypol content in cottonseed kernels. The density of cottonseed kernel pigment glands decreased under Cd stress. This is consistent with the change in gossypol content, which decreased under Cd stress. The damage of the cultivars ZD-90 and SGK3 from Cd poisoning was relatively low under Cd stress, while TM-1 was seriously affected and exhibited Cd sensitivity. Further studies are necessary to understand the cause of the reduced gossypol content in cotton seeds under Cd stress.

Differences in cadmium accumulation between indica and japonica rice cultivars in the reproductive stage

Excessive cadmium (Cd) in rice grains is of great concern worldwide, particularly in southern China where heavy metal pollution in the soil is widespread. Much work has been done regarding the key genes responsible for Cd absorption, transport, and accumulation in rice, but little is known about the differences of Cd accumulation between indica and japonica rice cultivars during the reproductive stage. Furthermore, physiological parameters, such as nonstructural carbohydrate content, involved in Cd accumulation have not been fully elucidated. We studied several indica and japonica cultivars under three different Cd treatment levels and harvested them at different periods after heading. Differences in Cd accumulation between subspecies mainly were generated during the reproductive stage. An increase in the Cd pollution level caused the average absorption rate of Cd in the aerial parts of the indica cultivars in the reproductive stage to be 6.17, 4.52, and 3.89 times greater than that of the japonica cultivars across the three Cd treatments. The contribution of Cd absorption by shoots to Cd accumulation at the pre- or postheading stages was 33.8% and 66.2% in indica, and 44.9% and 55.1% in japonica. We found a significant negative correlation between Cd content in the rice grains and the content of nonstructural carbohydrates in the sheath (P < 0.05). Cd translocation from sheath to grain occurred along with sugar transfer in the indica cultivars. The Cd content of the indica cultivar grain was 1.84–4.14 times higher than that of the japonica cultivars (P < 0.05). The japonica cultivars thus met the cereal Cd limits of China (0.2 mg kg−1) under low and moderate soil Cd pollution. These findings are helpful for the selection of proper cultivars and field management practices to alleviate Cd exposure risk in rice production.

Comparative transcriptome analysis revealed key factors for differential cadmium transport and retention in roots of two contrasting peanut cultivars

BackgroundPeanut is the world’s fourth largest oilseed crop that exhibits wide cultivar variations in cadmium (Cd) accumulation. To establish the mechanisms of Cd distribution and accumulation in peanut plants, eight cDNA libraries from the roots of two contrasting cultivars, Fenghua 1 (low-Cd cultivar) and Silihong (high-Cd cultivar), were constructed and sequenced by RNA-sequencing. The expression patterns of 16 candidate DEGs were validated by RT-qPCR analysis.ResultsA total of 75,634 genes including 71,349 known genes and 4484 novel genes were identified in eight cDNA libraries, among which 6798 genes were found to be Cd-responsive DEGs and/or DEGs between these two cultivars. Interestingly, 183 DEGs encoding ion transport related proteins and 260 DEGs encoding cell wall related proteins were identified. Among these DEGs, nine metal transporter genes (PDR1, ABCC4 and ABCC15, IRT1, ZIP1, ZIP11, YSL7, DTX43 and MTP4) and nine cell wall related genes (PEs, PGIPs, GTs, XYT12 CYP450s, LACs, 4CL2, C4H and CASP5) showed higher expression in Fenghua 1 than in Silihong.ConclusionsBoth the metal transporters and cell wall modification might be responsible for the difference in Cd accumulation and translocation between Fenghua 1 and Silihong. These findings would be useful for further functional analysis, and reveal the molecular mechanism responsible for genotype difference in Cd accumulation.

Differences in Cd Accumulation in Typical Soils Under the Double Rice System

Pot experiments were used to study the differences of Cd uptake and accumulation in double-cropping rice in typical soil types. To analyze the soil availability of Cd (DTPA-Cd) in soils and the Cd accumulation in double-cropping rice at different growth stages of the rice, we conducted pot experiments that selected the yellow clayey soil (paddy soil developed from plate shaley parent materials) and the granitic sandy soil (paddy soil developed from granitic parent materials). Exogenous Cd was added with gradients of 0, 0.5, 1.0, 2.0, 5.0, and 10.0 mg·kg-1. Results showed that, during the rice growth period, the available Cd in the yellow clayey soil was higher than that in the granitic sandy soil, and the difference was significant (P<0.01). This showed that the content of Cd in rice (roots, shoots, leaves, rice shells, and brown rice) increased along with the treatment level and with the extension of the rice growth period. The accumulation characteristics of Cd in rice grains and other tissues of rice indicated differences between two seasons and two soil types, that is, late rice was higher in Cd than was early rice, and reddish yellow clayey soil was higher in Cd than granitic sandy soil. Significant positive linear correlations were found between the effective contents of Cd in soils and those in rice tissues (roots, shoots, leaves, and brown rice). The prediction model of Cd in rice and the characteristic equation for rice accumulation of Cd were applied to calculate the critical values of Cd:0.98 mg·kg-1 for early rice and 0.83 mg·kg-1 for late rice in reddish yellow clayey soil, and 0.86 mg·kg-1 for early rice and 0.56 mg·kg-1 for late rice in granitic sandy soil. These threshold values are higher than the National Standards given in "farmland environmental quality evaluation standards for edible agricultural products (HJ 332-2006)." The soil security threshold values and the soil environmental capacities of the two different parent materials varied greatly; therefore, different environmental quality standards may be formulated and different measures may be needed to control Cd pollution in different parent materials.

Heavy metal accumulation in leaves and beans of cacao (Theobroma cacao L.) in major cacao growing regions in Peru

Peru is one of the leading exporters of organic cacao beans in the world. However, the accumulation of heavy metals in cacao beans represents a problem for cocoa bean export and chocolate quality. The aim of this study was to investigate the distribution and accumulation of heavy metals in cacao leaves and cocoa beans in three major cacao growing regions of Peru. The study was conducted in cacao plantations of 10 to 15years old in three regions of Peru: North (Regions of Tumbes, Piura, Cajamarca, and Amazonas); Center (Regions of Huánuco and San Martin) and South (Junin and Cuzco). Samples of leaf and cacao beans were collected from 70 cacao plantations, and the nature of cacao clone or genotype sampled was recorded. The concentrations of heavy metals such as Cd, Cr, Cu, Fe, Mn, Ni, Pb and Zn in leaves and beans were determined using atomic absorption spectrophotometer. Overall, concentrations of heavy metals were below the critical limits; however, the presence of high levels of Cd in cacao grown in Amazonas, Piura, and Tumbes regions is of primary concern. Plantations of cacao with different cacao clones show differences in Cd accumulation both in leaves and cocoa beans. Therefore, it is promising to screen low Cd accumulator cacao genotypes for safe production of cacao on lightly to moderately Cd contaminated soils. Also, synergism between Zn and Cd present both in plant and soil suggests that Zn has a direct effect on Cd accumulation in cacao.

Screening for Cd-Safe Cultivars of Chinese Cabbage and a Preliminary Study on the Mechanisms of Cd Accumulation.

With the rapid progress of industrialization, the effects of environmental contamination on plant toxicity, and subsequently on human health, is a growing concern. For example, the heavy metal pollution of soil such as that caused by cadmium (Cd) is a serious threat. Therefore, screening for pollution-safe edible plants is an essential approach for growing plants under heavy metal-contaminated soils. In the current study, 35 Chinese cabbage (Brassica pekinensis L.) cultivars were selected with the aim of screening for Cd-safe cultivars (CSCs), analyzing their safety, and exploring the mechanism of Cd accumulation. Our field-culture experiments revealed that the Cd content in the edible parts of the cultivars were varied and were determined to possibly be CSCs. Hydroponics experiments were used to simulate six different degrees of soil contamination (high and low Cd concentrations) on possible CSCs. The results indicated a significant difference (p < 0.05) in Cd concentration in the cultivars, and verified the safety of these possible CSCs. The analyses of the transport coefficient and expression levels showed that the differences in Cd accumulation among the Chinese cabbage cultivars were related to the expression of genes involved in absorption and transport rather than a root-to-shoot translocation limitation.

Uptake, sequestration and tolerance of cadmium at cellular levels in the hyperaccumulator plant species Sedum alfredii.

Sedum alfredii is one of a few plant species known to hyperaccumulate cadmium (Cd). Uptake, localization, and tolerance of Cd at cellular levels in shoots were compared in hyperaccumulating (HE) and non-hyperaccumulating (NHE) ecotypes of Sedum alfredii. X-ray fluorescence images of Cd in stems and leaves showed only a slight Cd signal restricted within vascular bundles in the NHEs, while enhanced localization of Cd, with significant tissue- and age-dependent variations, was detected in HEs. In contrast to the vascular-enriched Cd in young stems, parenchyma cells in leaf mesophyll, stem pith and cortex tissues served as terminal storage sites for Cd sequestration in HEs. Kinetics of Cd transport into individual leaf protoplasts of the two ecotypes showed little difference in Cd accumulation. However, far more efficient storage of Cd in vacuoles was apparent in HEs. Subsequent analysis of cell viability and hydrogen peroxide levels suggested that HE protoplasts exhibited higher resistance to Cd than those of NHE protoplasts. These results suggest that efficient sequestration into vacuoles, as opposed to rapid transport into parenchyma cells, is a pivotal process in Cd accumulation and homeostasis in shoots of HE S. alfredii. This is in addition to its efficient root-to-shoot translocation of Cd.

Impact of osmoregulation on the differences in Cd accumulation between two contrasting edible amaranth cultivars grown on Cd-polluted saline soils

This study aimed to investigate the difference of osmoregulation between two edible amaranth cultivars, Liuye (high Cd accumulator) and Quanhong (low Cd accumulator), under salinity stress and determine the effects of such difference on Cd accumulation. A pot experiment was conducted to expose the plants to sewage-irrigated garden soil (mean 2.28 mg kg−1 Cd) pretreated at three salinity levels. Under salinity stress, the concentrations of Cd in the two cultivars were significantly elevated compared with those in the controls, and the Cd concentration in Liuye was statistically higher than that in Quanhong (p < 0.05). Salinity-induced osmoregulation triggered different biogeochemical processes involved in Cd mobilization in the rhizosphere soil, Cd absorption, and translocation by the two cultivars. Rhizosphere acidification induced by an imbalance of cation over anion uptake was more serious in Liuye than in Quanhong, which obviously increased soil Cd bioavailability. Salinity-induced injuries in the cell wall pectin and membrane structure were worse in Liuye than in Quanhong, increasing the risk of Cd entering the protoplasts. The chelation of more cytoplasmic Cd2+ with Cl− ions in the roots of Liuye promoted Cd translocation into the shoots. Furthermore, the less organic solutes in the root sap of Liuye than in that of Quanhong also favored Cd translocation into the shoots. Hence, osmoregulation processes can be regarded as important factors in reducing Cd accumulation in crop cultivars grown on saline soils.

The difference of cadmium accumulation between the indica and japonica subspecies and the mechanism of it

Many studies have shown genotypic differences in Cadmium (Cd) accumulation among rice cultivars, and concentrations in shoots and grains are generally higher in indica rice cultivars than in japonica rice cultivars, but the mechanism remains unknown. The main objective of this study was to investigate differences in heavy metal accumulation between rice subspecies through the analysis of 46 indica cultivars and 30 japonica cultivars. At the seedling stage, the mean Cd concentrations in the shoots of indica subspecies were significantly higher than those in japonica subspecies (1.22-fold), but this pattern was not observed in the roots. At the filling stage, the mean Cd concentrations in the shoots and spikes of indica subspecies were 1.66- and 2.14-fold higher than the respective concentrations in japonica subspecies. At the harvest stage, the mean Cd concentrations in the shoots and brown rice of indica subspecies were 1.61- and 2.27-fold higher than the respective concentrations in japonica subspecies. These results indicate that root-to-shoot and shoot-to-grain translocation, rather than Cd absorption in the roots, may be the key processes that determine the differences in Cd accumulation among rice subspecies. Gene expression analysis revealed that overall, the expression levels of the Cd transporter gene OsNramp1 notably increased (22.46-fold), but the expression levels of OsHMA2, OsHMA3 and OsNRAMP5 were not significantly changed at the seedling stage in the 76 cultivars exposed to Cd; the expression levels of OsNramp1 were positively correlated with the Cd concentrations in spikes at the filling stage. In addition, a significant difference was observed in the expression levels of OsNramp1 between the indica and japonica subspecies, which may explain the higher Cd concentrations in roots but lower Cd concentrations in spikes and brown rice for the japonica subspecies. Together, these results demonstrate that OsNramp1 may be the most important gene among the four selected genes in the promotion of Cd uptake by roots and transfer of Cd into spikes and eventually into brown rice.

Functional components of the bacterial CzcCBA efflux system reduce cadmium uptake and accumulation in transgenic tobacco plants

Cadmium (Cd) is a toxic trace element released into the environment by industrial and agricultural practices, threatening the health of plants and contaminating the food/feed chain. Biotechnology can be used to develop plant varieties with a higher capacity for Cd accumulation (for use in phytoremediation programs) or a lower capacity for Cd accumulation (to reduce Cd levels in food and feed). Here we generated transgenic tobacco plants expressing components of the Pseudomonas putida CzcCBA efflux system. Plants were transformed with combinations of the CzcC, CzcB and CzcA genes, and the impact on Cd mobilization was analysed. Plants expressing PpCzcC showed no differences in Cd accumulation, whereas those expressing PpCzcB or PpCzcA accumulated less Cd in the shoots, but more Cd in the roots. Plants expressing both PpCzcB and PpCzcA accumulated less Cd in the shoots and roots compared to controls, whereas plants expressing all three genes showed a significant reduction in Cd levels only in shoots. These results show that components of the CzcCBA system can be expressed in plants and may be useful for developing plants with a reduced capacity to accumulate Cd in the shoots, potentially reducing the toxicity of food/feed crops cultivated in Cd-contaminated soils.

Effects of phosphorus on chemical forms of Cd in plants of four spinach (Spinacia oleracea L.) cultivars differing in Cd accumulation.

In order to clarify how cadmium (Cd) chemical forms in planta relate to the genotype difference in Cd accumulation of spinach (Spinacia oleracea L.), two low-Cd and two high-Cd cultivars were compared under a hydroponic experiment with two concentrations of Cd (8.98 or 44.71 μmol Cd L(-1)). The concentrations of phosphorus in the hydroponic system were also adjusted to two levels (0.5 and 1.0 mmol L(-1)) to investigate the influence of phosphorus on the forms and accumulation of Cd in the tested cultivars. Average Cd concentrations in shoots were 8.50-10.06 mg kg(-1) for high-Cd cultivars and 6.11-6.64 mg kg(-1) for low-Cd cultivars a under lower Cd treatment and were as high as 24.41-31.35 mg kg(-1) and 19.65-25.76 mg kg(-1), respectively, under a higher treatment. Phosphorus significantly decreased Cd accumulation in the tested cultivars, and the effect had superiority over the cultivar alternation under higher Cd stress. Cadmium in the NaCl-extractable fraction of the plant tissues showed the greatest relationship to genotype difference of Cd accumulation. The difference in the capacity to binding Cd into F HAc, F HCl, or F Residue was another important mechanism involving in the genotype difference in Cd accumulation of spinach. Among them, average proportion of Cd in F HAc in low-Cd cultivars was higher than that in high-Cd cultivars in association with the effect of phosphorus.

DNA microarray revealed and RNAi plants confirmed key genes conferring low Cd accumulation in barley grains.

BackgroundUnderstanding the mechanism of low Cd accumulation in crops is crucial for sustainable safe food production in Cd-contaminated soils.ResultsConfocal microscopy, atomic absorption spectrometry, gas exchange and chlorophyll fluorescence analyses revealed a distinct difference in Cd accumulation and tolerance between the two contrasting barley genotypes: W6nk2 (a low-grain-Cd-accumulating and Cd-sensitive genotype) and Zhenong8 (a high-grain-Cd-accumulating and tolerant genotype). A DNA microarray analysis detected large-scale changes of gene expression in response to Cd stress with a substantial difference between the two genotypes. Cd stress led to higher expression of genes involved in transport, carbohydrate metabolism and signal transduction in the low-grain-Cd-accumulating genotype. Novel transporter genes such as zinc transporter genes were identified as being associated with low Cd accumulation. Quantitative RT-PCR confirmed our microarray data. Furthermore, suppression of the zinc transporter genes HvZIP3 and HvZIP8 by RNAi silencing showed increased Cd accumulation and reduced Zn and Mn concentrations in barley grains. Thus, HvZIP3 and HvZIP8 could be candidate genes related to low-grain-Cd-accumulation.ConclusionNovel transporter genes such as HvZIP3 and HvZIP8 were identified as being associated with low-grain-Cd-accumulation. In addition to advancing academic knowledge, our findings may also result in potential economic benefits for molecular breeding of low Cd accumulating barley and other crops.Electronic supplementary materialThe online version of this article (doi:10.1186/s12870-015-0648-5) contains supplementary material, which is available to authorized users.

Subcellular cadmium distribution and antioxidant enzymatic activities in the leaves of two castor (Ricinus communis L.) cultivars exhibit differences in Cd accumulation

The aims of this study were: (1) the study of cadmium (Cd) accumulation and toxicity in different castor cultivars (Ricinus communis L.); (2) to investigate changes in antioxidant enzymatic activities and the subcellular distribution of Cd in young and old leaves from two different castor cultivars, after exposure to two different Cd concentrations, and explore the underlying mechanism of Cd detoxification focusing on antioxidant enzymes and subcellular compartmentalization. The Cd concentration, toxicity, and subcellular distribution, as well as superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD) activities were measured in Zibo-3 and Zibo-9 cultivars after exposure to two different concentrations of Cd (2mg/L and 5mg/L) for 10 days. This research revealed Cd accumulation characteristics in castor are root>stem>young leaf>old leaf. Castor tolerance was Cd dose exposure and the cultivars themselves dependent. Investigation of subcellular Cd partitioning showed that Cd accumulated mainly in the heat stable protein (HSP) and cellular debris fractions, followed by the Cd rich granule (MRG), heat denatured protein (HDP), and organelle fractions. With increasing Cd concentration in nutrient solution, the decreased detoxified fractions (BDM) and the increased Cd-sensitive fractions (MSF) in young leaves may indicate the increased Cd toxicity in castor cultivars. The BDM-Cd fractions or MSF-Cd in old leaves may be linked with Cd tolerance of different cultivars of castor. The antioxidant enzymes that govern Cd detoxification were not found to be active in leaves. Taken together, these results indicate Cd tolerance and toxicity in castor can be explained by subcellular partitioning.

Effects of cultivars and water management on cadmium accumulation in water spinach (Ipomoea aquatica Forsk.)

Water spinach is a common leafy vegetable in Asia, with a strong ability to accumulate cadmium (Cd) in its edible parts. The aims of this study were to investigate the effects of cultivar variation and water management on Cd accumulation in this plant. Three experiments were conducted: a soil pot trial with 32 cultivars, a rhizobox trial with 4 cultivars under flooded and non-flooded conditions and an uptake kinetics trial with 2 cultivars. There were significant differences in Cd accumulation between the different cultivars, and Cd concentrations in shoots were significantly lower in the flooded (0.25–1.4, mean 0.90 mg kg−1 DW) than in the non-flooded (1.9–4.7, 3.2 mg kg−1) treatments. Cultivars with a low Cd accumulation had a lower Cd bioavailability and mobility in the rhizosphere soil, higher Cd combined with Fe plaque on roots, lower Cd uptake capacity by roots, and lower Cd transfer factors than those with a high Cd accumulation. Water spinach grown under anaerobic conditions effectively reduces Cd accumulation in edible parts. Low Cd-accumulating cultivars tend to possess a high ability to reduce Cd bioavailability in rhizosphere soil, as well as decrease Cd uptake, and translocation from root to shoot.

Accumulation of cadmium in and its effect on the midgut gland of terrestrial snail Helix pomatia L. from urban areas in Poland.

The objectives of this study were (1) to determine cadmium (Cd) accumulation in the midgut gland of a land snail Helix pomatia L. inhabiting residential areas of the 14 largest cities in Poland, and (2) to examine whether the accumulated Cd exerted any toxic effects. The average accumulation of Cd in the midgut gland of snails, weighing 16–18 g, ranged from 7.00 to 87.3 µg/g dry weight (0.06–0.77 µmol/g) and differed significantly among animals from the various urban areas. This difference in Cd accumulation was not related to city population, but was associated with the topsoil Cd (R2 = 0.868, p < 0.0001). The tissue Cd was not found to produce toxicity (histopathology, programmed cell death, lipofuscin formation or lipid peroxidation), probably due to the induction of sufficiently high quantities of metallothionein and glutathione, well-known protective molecules.

Vertisol prevent cadmium accumulation in rice: Analysis by ecophysiological toxicity markers

Alfisol and vertisol cover more than fifty percent of rice fields in Asia. Rice cultivated in these soils is found to be contaminated with cadmium (Cd). Influence of physiochemical properties of these soils on Cd accumulation and ecophysiological functions of Oryza sativa L. cv MTU 7029 and MO 16 were analyzed. Plants grown in vertisol accumulated lower amount of Cd compare with those in alfisol. Soil properties such as cation exchange capacity and alkalinity played major role in decrease in Cd accumulation. Difference in Cd accumulation also reflected as more decrease in ecophysiological components such as biomass, relative water content and non-photochemical quenching among plants grown in alfisol. Plants grown in vertisol produced more flavanols, chlorophyll, anthocyanin, sugar, and protein than those in alfisol under Cd stress. But phenolic content was higher in plants grown in alfisol. Quantum efficiency of PSII, thiols, and silicon was increased while carotenes and calcium were decreased upon Cd accumulation. These changes were irrespective of soil type. Among the varieties chosen for the study, MTU 7029 accumulated more Cd compare with MO 16. It was concluded that soil properties caused difference in Cd accumulation among the plants grown in soils chosen and this would differentially reflect on specific ecophysiological markers.