Does radial oxygen loss and iron plaque formation on roots alter Cd and Pb uptake and distribution in rice plant tissues?

Background and Aims

Metal (e.g. Cd and Pb) pollution in agricultural soils and crops have aroused considerable attention in recent years. This study aimed to evaluate the effects of ROL and Fe plaque on Cd and Pb accumulation and distribution in the rice plant.

Methods

A rhizobag experiment was employed to investigate the correlations among radial oxygen loss (ROL), Fe plaque formation and uptake and distribution of Cd and Pb in 25 rice cultivars.

Results

Large differences between the cultivars were found in rates of ROL (1.55 to 6.88 mmol O₂ kg^?1 root d.w. h^?1), Fe plaque formation (Fe: 6,117–48,167 mg kg^?1; Mn: 127–1,089 mg kg^?1), heavy metals in shoot (Cd: 0.13–0.35 mg kg^?1; Pb: 4.8–8.1 mg kg^?1) and root tissues (Cd: 1.1–3.5 mg kg^?1; Pb: 45–199 mg kg^?1), and in Fe plaque (Cd: 0.54–2.6 mg kg^?1; Pb: 102–708 mg kg^?1). Rates of ROL were positively correlated with Fe plaque formation and metal deposition on root surfaces, but negatively correlated with metal transfer factors of root/plaque and distributions in shoot and root tissues.

Conclusions

ROL-induced Fe plaque promotes metal deposition on to root surfaces, leading to a limitation of Cd and Pb transfer and distribution in rice plant tissues.     

Phytoremediation Potential and Nutrient Status of Barringtonia acutangula Gaerth. Tree Seedlings Grown Under Different Chromium (CrVI) Treatments

To investigate the effect of different chromium (CrVI) treatments on seedlings of semi-aquatic plant Barringtonia acutangula, hydroponic experiments were conducted. Results revealed that B. acutangula could tolerate much higher CrVI concentration accumulated about 751–2,703 mg kg^?1 dry weight in roots and 50–1,101 mg kg^?1 dry weight in shoots, respectively, under 1.0, 2.0, 3.0, 4.0, and 5.0 mM chromium treatments. CrVI exposure at 1.0–4.0 mM does not exhibit toxicity signs; however, up to 4.0 mM CrVI exposure causes significant decline in growth parameters. Content of macronutrients such as Ca and K decreased under different Cr treatments in roots and shoots, while Mg content of roots and shoots did not influence at the range of 1.0–4.0 mM Cr; however, significant decrease at 5.0 mM Cr, besides P content, significantly shows increasing trends, respectively. Interestingly, sulfur content of roots and shoots show increasing trends at 1.0–2.0 mM Cr; however, severe decrease of up to 3.0–5.0 mM is shown in CrVI treatments. Furthermore, micronutrients content were enhanced under CrVI treatments excluding Cu and Fe since they show significant reduction in shoots as well as in roots. Bioaccumulation factor were also calculated on the basis of results obtained which shows the value of >1 without viewing chromium toxicity symptoms. This study demonstrated that B. acutangula could tolerate CrVI concentrations up to 1.0–4.0 mM Cr which may be useful in chromium phytoremediation programs.     

Metal-Dependent Root Iron Plaque Effects on Distribution and Translocation of Chromium and Nickel in Yellow Flag (Iris pseudacorus L.)

Iris pseudacorus L. (yellow flag) is a wide-use wetland plant for constructed wetlands for removing metals from wastewater. This study aims to understand effects of root iron plaque on sequestration and translocation of Cr and Ni in yellow flag seedlings using a hydroponic experiment. Yellow flag seedlings (4-week-old seedlings with 4–6 leaves) with or without iron plaque induction (at 50 mg Fe²⁺ L^?1 for 72 hours) were spiked for 6 days in the Hoagland solution with Cr or Ni at 0.5, 5, and 50 mg L^?1, equivalent to 1, 10, 100 times of thresholds of surface water quality, respectively. Results indicated that root iron plaque significantly reduced translocation of Cr and Ni to root but increased from root to shoot. Root iron plaque formation counteracted Cr toxicity to yellow flag seedlings while the control showed Cr toxicity to root at 5 mg L^?1and to shoot at 50 mg L^?1 with significant biomass loss. Neither Ni exposures caused significant biomass loss nor root iron plaque formation significantly changed Ni distribution among plant parts. Our study suggests that root iron plaque effects on metal sequestration and translocation in yellow flag seedlings were metal-dependent.     

Induced anti-oxidant activity in soybean alleviates oxidative stress under moderate boron toxicity

The effect of B toxicity on antioxidant responses of soybean (Glycine max) cv. Athow was investigated by growing plants for 43 days at 0.2 (control), 2 and 12 mg B kg^?1. At the end of the treatment period, shoot growth, lipid peroxidation level, the activities of antioxidant enzymes including superoxide dismutase (SOD), peroxidase (POX), catalase (CAT), ascorbate peroxidase (APX) and glutathione reductase (GR), and their isoenzymes in leaves were measured. Boron concentration in leaves was significantly increased by the increasing levels of B treatment from 43 to 522 mg kg^?1, and shoot dry matter was depressed at 12 mg B kg^?1. Significant increases in SOD, CAT, and APX activities were determined in leaves under 12 mg B kg^?1; however, GR activities were decreased while POX activity was unchanged. Increased enzymic antioxidant activity arose from a combination of newly formed isoenzymes and activation of existing isoenzymes. By contrast, SOD and GR activities were decreased by 2 mg B kg^?1 concentration as compared to the control groups while POX activity was increased and the activity of CAT did not change. Malondialdehyde content increased under 2 mg B kg^?1 but decreased under 12 mg B kg^?1. These results suggest that higher antioxidant activity observed under 12 than at 2 mg B kg^?1 provided higher free radical-scavenging capacity, and thus a lower level of lipid peroxidation in Athow. While the induction of increased antioxidant activity was related to internal boron levels, the signaling and coordination of responses remain unclear.     

Co-occurrence of five Fusarium toxins in corn-Dried Distiller’s Grains with Solubles in Thailand and comparison of ELISA and LC-MS/MS for fumonisin analysis

Dried Distiller’s Grains with Solubles (DDGS), a by-product of bio-ethanol production from maize and other cereals, is increasingly used as a feed additive. In this study, five Fusarium toxins, including fumonisin B₁ (FB₁), fumonisin B₂ (FB₂), deoxynivalenol (DON), zearalenone (ZEN) and beauvericin (BEA) were quantified by LC-MS/MS in 59 corn-DDGS samples. In addition, the fumonisin level in 30 randomly selected-samples was compared using an ELISA detection technique. No sample was free from mycotoxin contamination, and 50.8 % of the samples were co-contaminated with all five mycotoxins. Moreover, toxin levels were generally high, with mean levels of 9 mg kg^?1 FB₁, 6 mg kg^?1 FB₂, 1.2 mg kg^?1 DON, 0.9 mg kg^?1 ZEN, and 0.35 mg kg^?1 BEA. Maximum levels for FB₁ (143 mg kg^?1) and FB₂ (125 mg kg^?1) are of acute toxicological relevance. The ELISA method had a tendency to underestimate the fumonisin content when compared with LC-MS/MS. Finally, this is the first reported beauvericin contamination in corn-DDGS.     

Arsenic affects mineral nutrients in grains of various Indian rice (Oryza sativa L.) genotypes grown on arsenic-contaminated soils of West Bengal

The exposure of paddy fields to arsenic (As) through groundwater irrigation is a serious concern that may not only lead to As accumulation to unacceptable levels but also interfere with mineral nutrients in rice grains. In the present field study, profiling of the mineral nutrients (iron (Fe), phosphorous, zinc, and selenium (Se)) was done in various rice genotypes with respect to As accumulation. A significant genotypic variation was observed in elemental retention on root Fe plaque and their accumulation in various plant parts including grains, specific As uptake (29–167 mg kg^?1 dw), as well as As transfer factor (4–45%). Grains retained the least level of As (0.7–3%) with inorganic As species being the dominant forms, while organic As species, viz., dimethylarsinic acid and monomethylarsonic acid, were non-detectable. In all tested varieties, the level of Se was low (0.05–0.12 mg kg^?1 dw), whereas that of As was high (0.4–1.68 mg kg^?1 dw), considering their safe/recommended daily intake limits, which may not warrant their human consumption. Hence, their utilization may increase the risk of arsenicosis, when grown in As-contaminated areas.     

The influence of redox conditions in soils on extraplasmatic Fe-loading of plant roots

Loading of extraplasmatic Fe, as a potential storage pool for Fe nutrition, was studied in roots of maize grown under hypoxic conditions in soil culture. Extraplasmatic Fe loading was investigated depending on (i) duration of flooding (0, 1, 2 or 4 days) and (ii) microbial activity as affected by graduated addition of carbon sources (0, 2 or 10 g each starch and cellulose kg^?1 soil). Maize plants were grown in a soil culture system with root systems enclosed in membrane bags to avoid Fe contamination of the root surface by soil particles. Due to the high redox buffer capacity of the Haplic Luvisol employed for the experiments, flooding treatments induced only moderately reducing conditions (～?300 mV) and a slight increase of extraplasmatic Fe loading (41\to165 mg kg^?1 d.m.). Strongly reducing conditions (?100 mV) associated with a high Fe²⁺ concentration in the soil solution and a significant increase of extraplasmatic Fe (1190 mg kg^?1 d.m.) were obtained only after application of high amounts of organic carbon (10 g starch and 10 g cellulose kg^?1 soil), which accompanied by unrealistic reducing conditions due to intense stimulation of microbial growth. The expression of effects only under extremely high application level of organic carbon (～?33 t C ha^?1) suggest that similar to aerobic conditions, extraplasmatic Fe-loading under transient hypoxia is probably of limited ecological significance for the iron nutrition of higher plants, at least in soils with a high redox buffer capacity as employed in the present study. Abbreviations: DHA – dehydrogenase activity; d.m. – dry matter; DOC – dissolved organic carbon; Eh – redox potential; PIXE – proton-induced X-ray emission; STIM – scanning transmission ion microscopy.     

Interactive effects of cadmium and carbon nanotubes on the growth and metal accumulation in a halophyte Spartina alterniflora (Poaceae)

A study quantifying the interactive effects of cadmium (Cd) and carbon nanotubes (CNTs) on plant growth and Cd accumulation of pot-cultured Spartina alterniflora was conducted. The experiment consisted of two Cd levels (50, 200 mg kg^?1) as well as two CNTs levels (800, 2,400 mg kg^?1). As expected, CNTs alleviated higher Cd stress (200 mg kg^?1) due to restored shoot growth reduction, retrieved water content and resumed plant height. Furthermore, CNTs mitigated the deleterious effects of Cd stress through improving K⁺ and Ca²⁺ contents, while reducing Na⁺/K⁺ and Na⁺/Ca²⁺ ratios, regardless of the level of Cd stress. The proline contents in combined Cd and CNTs treatments were lower than Cd alone, suggesting that CNTs could reduce production of organic solutes under Cd stress. The results also showed higher Cd accumulation in roots than shoots, and both were improved by CNTs, except inhibition in roots under higher Cd stress (200 mg kg^?1). It appears that CNTs may not significantly affect negative Cd effects on growth of S. alterniflora, but improve total Cd accumulation under lower Cd stress (50 mg kg^?1). However, under higher Cd stress (200 mg kg^?1), CNTs restored the reduced plant growth, improved and reduced Cd accumulation in shoots and roots, respectively. Therefore, the effects of CNTs on plant growth and Cd accumulation are different, and levels of Cd stress should be considered when evaluating the combined application of CNTs and S. alterniflora on phytoremediation of Cd pollution.     

Sulfur and molybdenum fractionation in marine and riverine alluvium paddy soils

Intermittently submergence and drainage status of paddy fields can cause alterations in morphological and chemical characteristics of soils. We conducted a sequential fractionation study to provide an insight into solubility of Sulfur (S) and Molybdenum (Mo) in flooded alluvial paddy soils. The samples (0–15 and 15–30 cm) were taken from marine and riverine alluvial soils in Kedah and Kelantan areas, respectively, and were sequentially extracted with NaHCO₃, NaOH, HCl, and HClO₄–HNO₃. Total S in upper and lower layers of Kedah and Kelantan ranged between 273 and 1121 mg kg^?1, and 177 to 1509 mg kg^?1, respectively. In upper layers and subsoil of Kedah, average total Mo were 0.34 and 0.27 mg kg^?1, respectively. Average total Mo in Kelantan were 0.25 mg kg^?1 (surface layer) and 0.28 mg kg^?1 (subsoil). Cation exchange capacity (CEC) was positively correlated with plant available amounts of Mo in upper layers of Kedah area. Also, total and medium-term plant-available S was correlated with total carbon (C) at lower layers of Kelantan soil series. But in surface layers of Kelantan soil series, CEC was strongly correlated with total and medium-term plant-available S. Our results indicates that the influence of flooding conditions on soil S and Mo contents in paddy fields may cause long-term changes in S and Mo chemical reactivities.     

A novel <Emphasis Type="Italic">Trichoderma</Emphasis> fusant for enhancing nutritional value and defence activity in chickpea

In recent years, due to the rise in food consumption, much of the attention has been focused to increase the yield of the agricultural crops which resulted in compromised nutritional quality. Efforts have to be undertaken to enhance the nutritional attributes of legumes, cereals and staple food crops by increasing amino acids and mineral content. In the present study, we evaluated a protoplast fusant (H. lixii MTCC 5659) for its ability to enhance nutritional value and defence activity in chickpea. Essential amino acids; methionine (9.82 mg kg^?1 dw), cysteine (2.61 mg kg^?1 dw), glycine (11.34 mg kg^?1 dw), valine (9.26 mg kg^?1 dw), and non-essential amino acids; aspartic acid (39.19 mg kg^?1 dw) and serine (17.53 mg kg^?1 dw) were significantly higher in seeds of fusant inoculated chickpea. Fusant significantly improved accumulation of mineral nutrients i.e. Cu (157.73 mg kg^?1 dw), Co (0.06 mg kg^?1 dw), Ni (1.85 mg kg^?1 dw), Zn (157.73 mg kg^?1 dw) and S (16.29 mg kg^?1 dw) in seeds. Biocontrol and defence activities of chickpea increased from 20 to 35% in fusant inoculated plants suggesting its potential to ameliorate biotic stress. To the best of our knowledge, this is the first report of an increase in amino acids and mineral content of chickpea by fusant inoculation.     

Dietary Supplementation of Zinc Nanoparticles and Its Influence on Biology,Physiology and Immune Responses of the Freshwater Prawn,Macrobrachium rosenbergii

The present study was conducted to assess the influence of dietary zinc nanoparticles (size 50 nm) on the growth, biochemical constituents, enzymatic antioxidant levels and the nonspecific immune response of the freshwater prawn, Macrobrachium rosenbergii post larvae (PL). The concentrations of dietary supplement zinc nanoparticles (ZnNPs) were 0, 10, 20, 40, 60 and 80 mg kg^?1 with the basal diet, and the level of Zn in ZnNP-supplemented diets were 0.71, 10.61, 20.73, 40.73, 60.61 and 80.60 mg kg^?1, respectively. ZnNP-incorporated diets were fed to M. rosenbergii PL (initial body weight, 0.18?±?0.02 g) in a triplicate experimental setup for a period of 90 days. ZnNP supplemented feed fed PL up to 60 mg kg^?1 showed significantly (P?<?0.05) improved performance in survival, growth and activities of digestive enzymes (protease, amylase and lipase). The concentrations of biochemical constituents (total protein, total amino acid, total carbohydrate and total lipid), total haemocyte count and differential haemocyte count were elevated in 10–60 mg kg^?1 ZnNP supplemented feed fed PL. However, the PL fed with 80 mg ZnNPs kg^?1 showed negative results. Activities of enzymatic antioxidants [superoxide dismutase (SOD) and catalase (CAT)], metabolic enzymes [glutamate–oxaloacetate transaminase (GOT) and glutamate–pyruvate transaminase (GPT)] and the process of lipid peroxidation (LPO) in the hepatopancreas and muscle showed no significant alterations in 10–60 mg kg^?1 ZnNP supplemented feed fed PL. Whereas, 80 mg ZnNPs kg^?1 supplemented feed fed PL showed significant elevations in SOD, CAT, LPO, GOT and GPT. Therefore, 80 mg ZnNPs kg^?1 was found to be toxic to M. rosenbergii PL. Thus, the study suggests that up to 60 mg ZnNPs kg^?1 can be supplemented for regulating survival, growth and immunity of M. rosenbergii.     

Compartmentalization and ultrastructural alterations induced by chromium in aquatic macrophytes

The aim of the present study was to identify the sites of accumulation of Cr in the species of macrophytes that are abundant in the Cachoeira river, namely, Alternanthera philoxeroides, Borreria scabiosoides, Polygonum ferrugineum and Eichhornia crassipes. Plants were grown in nutritive solution supplemented with 0.25 and 50 mg l^?1 of CrCl₃·6H₂O. Samples of plant tissues were digested with HNO₃/HCl in a closed-vessel microwave system and the concentrations of Cr determined using inductively-coupled plasma mass spectrometry (ICP-MS). The ultrastructure of root, stem and leaf tissue was examined using transmission electron microscopy (TEM) and secondary ion mass spectrometry (SIMS) in order to determine the sites of accumulation of Cr and to detect possible alterations in cell organelles induced by the presence of the metal. Chromium accumulated principally in the roots of the four macrophytes (8.6?C30 mg kg^?1 dw), with much lower concentrations present in the stems and leaves (3.8?C8.6 and 0.01?C9.0 mg kg^?1 dw, respectively). Within root tissue, Cr was present mainly in the vacuoles of parenchyma cells and cell walls of xylem and parenchyma. Alterations in the shape of the chloroplasts and nuclei were detected in A. philoxeroides and B. scabiosoides, suggesting a possible application of these aquatic plants as biomarkers from Cr contamination.     

Temporal-spatial distribution,environmental significance and release risks of phosphorus in the sediments of a tropical mountain’s deep drinking water reservoir in southeastern China

In this study, the fractionation and distribution of phosphorus (P) in the core sediments of the Shanmei reservoir were investigated by using the chemical extraction method in directions for the first time in order to understand its bio-availability, adsorption characteristics, potential release and environmental significance. The results of the study showed that P in the sediments mainly consisted of inorganic phosphorus (IP) and that IP mainly consisted of non-apatite phosphorus (NAIP). The horizontal and temporal distributions of the P fractions were different from each other, but the vertical distribution was similar, which indicated a trend of stabilization after falling. The content of total phosphorus (TP), IP, organic phosphorus (OP), NAIP, apatite phosphorus (AP), and bio-available phosphorus (BAP) in the sediments during the three seasons ranged from 193.85 to 1664.05 mg·kg^?1, 126.90 to 1127.70 mg·kg^?1, 43.74 to 669.29 mg·kg^?1, 57.62 to 937.07 mg·kg^?1, 32.58 to 250.71 mg·kg^?1, and 41.06 to 871.82 mg·kg^?1, respectively. NAIP contents in the sediments accounted for more than 50% of TP. Using an analysis from three aspects, the eutrophication risk index (ERI) could be used to assess the potential release of P in the sediments, and there was a high release risk of P in the sediments in the Shanmei reservoir.     

The critical soil P levels for crop yield, soil fertility and environmental safety in different soil types

Background and aims

Sufficient soil phosphorus (P) is important for achieving optimal crop production, but excessive soil P levels may create a risk of P losses and associated eutrophication of surface waters. The aim of this study was to determine critical soil P levels for achieving optimal crop yields and minimal P losses in common soil types and dominant cropping systems in China.

Methods

Four long-term experiment sites were selected in China. The critical level of soil Olsen-P for crop yield was determined using the linear-plateau model. The relationships between the soil total P, Olsen-P and CaCl₂-P were evaluated using two-segment linear model to determine the soil P fertility rate and leaching change-point.

Results

The critical levels of soil Olsen-P for optimal crop yield ranged from 10.9 mg kg^?1 to 21.4 mg kg^?1, above which crop yield response less to the increasing of soil Olsen-P. The P leaching change-points of Olsen-P ranged from 39.9 mg kg^?1 to 90.2 mg kg^?1, above which soil CaCl₂-P greatly increasing with increasing soil Olsen-P. Similar change-point was found between soil total P and Olsen-P. Overall, the change-point ranged from 4.6 mg kg^?1 to 71.8 mg kg^?1 among all the four sites. These change-points were highly affected by crop specie, soil type, pH and soil organic matter content.

Conclusions

The three response curves could be used to access the soil Olsen-P status for crop yield, soil P fertility rate and soil P leaching risk for a sustainable soil P management in field.     

Healthy Response from Chromium Survived Pteridophytic Plant-Ampelopteris prolifera with the Interaction of Mycorrhizal Fungus-Glomus deserticola

Interaction between arbuscular mycorrhizal fungus Glomus deserticola and pteridophytic member Ampelopteris prolifera was found abundant on entire growth level based on elemental composition and gaseous exchange as a potential remediation system for phytoextraction of chromium. Inoculated A. prolifera (AM) and non-inoculated A. prolifera (Non-AM) were supplied with two Cr species: 12 mmol of trivalent cation (Cr⁺³) [Cr(III)] and 0.1 mmol of divalent dichromate anion (Cr₂O₇ ^?2) [Cr(VI)]. Both Cr species were found to be depressed in overall growth and inefficient stomatal conductance (g_s) and net photosynthesis (NP). Mycorrhizal association was found to be natural scavenger of Cr toxicity as indicated by greater growth in plants exposed to Cr species, and increased gas exchange of Cr(III) treated plants. Though, chromium reduction resulted lower level of nitrogen (N), phosphorus (P), and potassium (K) but interestingly elevated the level of aluminum (Al), iron (Fe), and zinc (Zn) uptake in many folds which is the significance of sustainable growth of plant.     

Extraction of sterols in brown macroalgae from Antarctica and their identification by liquid chromatography coupled with tandem mass spectrometry

This study reports for the first time the extraction and quantification of sterols in six species of brown macroalgae from Antarctica: Adenocystis utricularis, Ascoseira mirabilis, Cystosphaera jacquinotii, Desmarestia anceps, Desmarestia antarctica, and Himantothallus grandifolius. Ultrasound irradiation was used as a promotor to extract sterols from algal biomass. The extracts were analyzed by high-performance liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) for sterol quantization (ergosterol, brassicasterol, fucosterol, β-sitosterol, campesterol, cholesterol, and stigmasterol). In general, fucosterol was the most abundant (6.60 to 48.13 mg kg^?1), followed by β-sitosterol (5.29 to 16.49 mg kg^?1), stigmasterol (2.69 to 14.84 mg kg^?1) in five of the six examined algae. The sterol campesterol was found in lower concentrations (0.07 to 0.15 mg kg^?1) in all studied samples.     

Plant regeneration of the arsenic hyperaccumulator <Emphasis Type="Italic">Pteris vittata</Emphasis> L<Emphasis Type="Italic">.</Emphasis> from spores and identification of its tolerance and accumulation of arsenic and copper

An in vitro plant regeneration system was established from the spores of Pteris vittata and identification of its tolerance, and accumulation of gametophytes and callous, to arsenic (As) and copper (Cu) was investigated. The highest frequency (100%) of callus formation was achieved from gametophyte explants treated with 0.5 mg l^?1 6-benzylaminopurine (6-BA) + 0.5 mg l^?1 gibberellin acid (GA). Furthermore, sporophytes were differentiated from the callus tissue derived from gametophyte explants on MS medium supplemented with 0.5 mg l^?1 6-BA, 0.5–1.0 mg l^?1 GA and additional 300 mg l^?1 lactalbumin hydrolysate (LH) for 4 weeks. The optimum combination of ½ MS + 1.0 mg l^?1 GA + 0.5 mg l^?1 6-BA + 300 mg l^?1 LH promoted sporophyte formation on 75 ± 10% of the callus. Every callus derived from gametophyte explants could achieve 3–4 sporophytes. The in vitro growth of gametophyte and callus was accelerated in the medium containing Na₃AsO₄ lower than 0.5 mM, but this growth was inhibited with 2 mM Na₃AsO₄. And with the increase of Na₃AsO₄ in the culture medium from 0 to 2 mM, the As accumulation in gametophytes and callus increased and achieved a level of 763.3 and 315.4 mg kg^?1, respectively. Gametophytes and calluses transplanted to culture medium, supplemented with different concentrations of CuSO₄, are similar to those in Na₃AsO₄, and the Cu accumulation in gametophytes could achieve 7,940 mg kg^?1 when gametophytes were subcultured in medium containing 3 mM CuSO₄. These results suggested that the high efficiency propagation system could be a useful and rapid means to identify other heavy metal tolerance and accumulation. Further, the regeneration ability of callus made it possible for genetic transformation of this fern.     

Tolerance of Ricinus communis L. to Cd and screening of high Cd accumulation varieties for remediation of Cd contaminated soils

Response of castor (Ricinus communis L.) to cadmium (Cd) was assessed by a seed-suspending seedbed approach. Length of total radicle was the most sensitive indicator of Cd tolerance among the tested germination and growth characters. The ED₅₀ value for Cd was 11.87 mg L^?1, indicating high Cd tolerance in castor. A pot experiment was conducted by growing 46 varieties of castor under CK (without Cd) and Cd1 (10 mg kg^?1 of Cd) and Cd2 (50 mg kg^?1 of Cd) treatments to investigate genotype variations in growth response and Cd accumulation of castor under different Cd exposures. Castor possessed high Cd accumulation ability; average shoot and root Cd concentrations of the 46 tested varieties were 21.83 and 185.43 mg kg^?1, and 174.99 and 1181.96 mg kg^?1 under Cd1 and Cd2, respectively. Great variation in Cd accumulation was observed among varieties, and Cd concentration of castor was genotype dependent. The correlation between biomass and Cd accumulation was significantly positive, while no significant correlation was observed between Cd concentration and Cd accumulation, which indicated that biomass performance is the dominant factor in determining Cd accumulation ability.     

Growth and physiological responses to copper stress in a halophyte Spartina alterniflora (Poaceae)

A study quantifying the effects of different copper (Cu) concentrations (50, 200, 800 and 1,000 mg kg^?1 Cu) on Cu bioaccumulation and physiological responses of Spartina alterniflora was conducted. Plant biomass and Cu accumulation were determined. Plant height, tiller number, chlorophyll, leaf electrolyte leakage rate (ELR), malondialdehyde (MDA), proline, soluble sugar, and organic acids were also measured. The results showed that S. alterniflora mainly accumulated Cu in fine roots. No significant changes of biomass of fine roots were detected except for obvious reduction under 1,000 mg kg^?1 Cu. In leaves, rhizomes and fine roots, the highest Cu accumulations were detected under 800 mg kg^?1 Cu. The highest Cu accumulation in stem was revealed under 200 mg kg^?1 Cu. Plant height decreased under 1,000 mg kg^?1 Cu; chlorophyll content reduced under >50 mg kg^?1 Cu; levels of ELR and MDA increased under >200 mg kg^?1 Cu. However, osmotic components such as proline and soluble sugar were accumulated to cope with higher Cu stresses (800 and 1,000 mg kg^?1). Further, oxalic and citric acids were positively related with Cu contents in leaves and stems, suggesting that oxalic and citric acids may be related to Cu detoxification in aboveground parts of S. alterniflora. However, in above and belowground parts, no detoxification function of ascorbic and fumaric acids was observed due to unchanged or decreased trend under Cu stress.     

Heavy Metals Bioconcentration from Soil to Vegetables and Assessment of Health Risk Caused by Their Ingestion

The present study was undertaken to assess the non-carcinogenic human health risk of heavy metals through the ingestion of locally grown and commonly used vegetables viz. Raphanus sativus (root vegetable), Daucus carota (root vegetable), Benincasa hispida (fruit vegetable) and Brassica campestris leaves (leafy vegetable) in a semi-urbanized area of Haryana state, India. Heavy metal quantification of soil and vegetable samples was done using flame atomic absorption spectrophotometer. Lead, cadmium and nickel concentration in vegetable samples varied in range of 0.12–6.54 mg kg^?1, 0.02–0.67 mg kg^?1 and <0.05–0.41 mg kg^?1, respectively. Cadmium and lead concentration in some vegetable samples exceeded maximum permissible limit given by World Health Organization/Food and Agriculture Organization and Indian standards. Much higher concentrations of Pb (40–190.5 mg kg^?1), Cd (0.56–9.85 mg kg^-1) and Ni (3.21–45.87 mg kg^?1) were reported in corresponding vegetable fields’ soils. Correlation analysis revealed the formation of three primary clusters, i.e. Cu–Cd, Cd–Pb and Ni–Zn in vegetable fields’ soils further supported by cluster analysis and principal component analysis. Bioconcentration factor revealed that heavy metals’ uptake was more by leafy vegetable than root and fruit vegetables. Hazard index of all the vegetables was less than unity; thus, the ingestion of these vegetables is unlikely to pose health risks to the target population.