The effect of EDTA and EDDS on lead uptake and localization in hydroponically grown Pisum sativum L.

Pisum sativum plants were treated for 3 days with an aqueous solution of 100 μM Pb(NO₃)₂ or with a mixture of lead nitrate and ethylenediaminetetraacetic acid (EDTA) or [S,S]-ethylenediaminedisuccinic acid (EDDS) at equimolar concentrations. Lead decline from the incubation media and its accumulation and localization at the morphological and ultrastructural levels as well as plant growth parameters (root growth, root and shoot dry weight) were estimated after 1 and 3 days of treatment. The tested chelators, especially EDTA, significantly diminished Pb uptake by plants as compared to the lead nitrate-treated material. Simultaneously, EDTA significantly enhanced Pb translocation from roots to shoots. In the presence of both chelates, plant growth parameters remained considerably higher than in the case of uncomplexed Pb. Considerable differences between the tested chelators were visible in Pb localization both at the morphological and ultrastructural level. In Pb+EDTA-treated roots, lead was mainly located in the apical parts, while in Pb+EDDS-exposed material Pb was evenly distributed along the whole root length. Transmission electron microscopy and EDS analysis revealed that in meristematic cells of the roots incubated in Pb+EDTA, large electron-dense lead deposits were located in vacuoles and small granules were rarely noticed in cell walls or cytoplasm, while after Pb+EDDS treatment metal deposits were restricted to the border between plasmalemma and cell wall. Such results imply different ways of transport of those complexed Pb forms.     

Improvement of element uptake and antioxidative defense in Brassica napus under lead stress by application of hydrogen sulfide

Heavy metal pollution is one of the major constraints in oilseed rape (Brassica napus L.) production. In this study, protective role of hydrogen sulfide (H₂S) on plant growth under lead (Pb) stress was studied in B. napus. Plants were grown hydroponically in greenhouse conditions under three levels (0, 100, and 400 μM) of Pb and three levels (0, 100 and 200 μM) of H₂S donor sodium hydrosulfide. Outcomes demonstrated that Pb stress significantly reduced the plant biomass, leaf chlorophyll contents, nutrients uptake in the leaves and roots of B. napus plants. Exogenous application of H₂S significantly improved the plant biomass, chlorophyll contents and concentration of macro- and micronutrients in the leaves and roots of B. napus plants under Pb-toxicity conditions. The data indicated that application of Pb alone significantly increased the reactive oxygen species (ROS) as well as malondialdehyde (MDA) in the leaves and roots of plants. Meanwhile, application of H₂S decreased the production of MDA and ROS in the leaves and roots by increasing antioxidant activities under Pb stress. Moreover, this study also revealed that plants treated with H₂S at different concentrations enhanced the contents of total glutathione and glutathione reduced/glutathione oxidized ratio in leaves and roots under different levels of Pb. The results depicted that H₂S improved the plant biomass, uptake of nutrients in the leaves and roots of B. napus plants and enhanced the performance of antioxidant defense system due to its ameliorative potential under Pb stress conditions.     

Red cabbage extract limits copper stress injury in meristematic cells of <Emphasis Type="Italic">Vicia faba</Emphasis>

Natural phenolic compounds (phenolic acids, flavonoids, tannins, lignans) present in food of plant origin are in the focus of interest due to their prevalence, properties and biological activity. The aim of the presented work was to investigate antioxidant and antigenotoxic effects of the anthocyanin-rich extract from red cabbage leaves (Brassica oleracea rubrum) on the changes induced by toxic Cu²⁺ concentrations. MeOH extract from red cabbage containing anthocyanin (ATH) and phenolic acid derivatives exhibited strong antioxidant properties. Cu²⁺ decreased mitotic index (MI) and inhibited proliferative activity of Vicia faba root meristematic cells. The morphology of mitotic chromosomes was changed; “erosion” and pulverization might result from Cu²⁺ high-cytotoxicity. Numerous micronuclei, chromatid bridges and lagging/lost chromosomes were found in the meristematic cells of V. faba, which indicate the clastogenic effect of Cu²⁺. The application of the ATH-rich extract lowered the number of disturbances induced by Cu²⁺. The positive role of the ATH-rich red cabbage extract will be discussed.     

The effect of Achyranthes japonica extract on larval survival and development and oviposition behavior of Plutella xylostella L. (Lepidoptera: Plutellidae)

The extract of Achyranthes japonica was tested for effects on larval survival and development and the oviposition behavior of the diamondback moth, Plutella xylostella L. Chinese cabbage dipped in A. japonica extract solution showed 51–80% antifeedant activity for 5 days against P. xylostella larvae, and more larvae were also on untreated cabbage leaves 24 h after release. The mortality of P. xylostella larvae increased proportionally to the duration of dipping time in the extract, and both pupation and emergence rates of larvae feeding only on treated cabbage were lower than those for larvae raised on untreated or with a choice of cabbage. The 20-hydroxyecdysone (20E) concentration in leaves was approximately 549, 1232, 1275, and 1426 μg/g at 6, 12, 24, and 48 h after dipping treatment, respectively. Notably, naive females laid more eggs on untreated cabbage than on treated cabbage, and females from larvae raised on treated Chinese cabbage also preferred the non-treated leaves. Our results are in contrast to those from earlier studies using various insect models that confirmed most females prefer to lay eggs on the host type that was eaten in the larval stage (Hopkins host selection principle). Cabbage dipped in the A. japonica solution for 24 h caused 59% larval mortality and inhibited both pupation and emergence rates of the larvae when exposed to plants 15 and 22 days after planting in the field, with the 20E concentration in the treated cabbage leaves at 1600.9 ± 122.36 and 1386.8 ± 24.69 μg/g, respectively. Therefore, the biological effectiveness could be attributed to the 20E in the treated cabbage leaves.     

Red cabbage anthocyanins may protect blood plasma proteins and lipids

The present in vitro study was designed to examine the antioxidative activity of red cabbage anthocyanins (ATH) in the protection of blood plasma proteins and lipids against damage induced by oxidative stress. Fresh leaves of red cabbage were extracted with a mixture of methanol/distilled water/0.01% HCl (MeOH/H₂O/HCl, 50/50/1, v/v/w). Total ATH concentration [μM] was determined with cyanidin 3-glucoside as a standard. Phenolic profiles in the crude red cabbage extract were determined using the HPLC method. Plasma samples were exposed to 100 μM peroxynitrite (ONOO⁻) or 2 mM hydrogen peroxide (H₂O₂) in the presence/absence of ATH extract (5–15 μM); oxidative alterations were then assessed. Pre-incubation of plasma with ATH extract partly reduced oxidative stress in plasma proteins and lipids. Dose-dependent reduction of both ONOO⁻ and H₂O₂-mediated plasma protein carbonylation was observed. ATH extract partly inhibited the nitrative action of ONOO⁻, and significantly decreased plasma lipid peroxidation caused by ONOO⁻ or H₂O₂. Our results demonstrate that anthocyanins present in red cabbage have inhibitory effects on ONOO⁻ and H₂O₂-induced oxidative stress in blood plasma components. We suggest that red cabbage ATH, as dietary antioxidants, should be considered as potentially usable nutraceuticals in the prevention of oxidative stress-related diseases.     

Differences in Zn and Pb resistance of two ecotypes of the microalga Eustigmatos sp. inhabiting metal loaded calamine mine spoils

Soil-dwelling microalgae as pioneer organisms may play an essential role in degraded post-industrial areas. Zn and Pb resistance of two morphologically identical strains (E120, E5) of the soil microalga Eustigmatos sp. (Eustigmatophyceae) inhabiting two extremely metal polluted calamine mine spoils and Eustigmatos vischeri (Ev) from algal collection was compared. To compare Zn and Pb resistance of algal strains, toxicity parameters (72/96 h-EC₅₀) were determined during their exposure to high Zn (50–800 μM) and Pb (5–80 μM) concentrations. Both Zn- and Pb-EC₅₀ values increased as follows: Ev < E5 < E120. The E120 strain from the mine spoil with the highest metal contents appeared to be two times more Zn and Pb resistant (96 h-EC₅₀?=?416 μM Zn, 39.8 μM Pb) than E5 strain from the less metal polluted site and 4.7–8.8 times more than Ev. Differences in Zn and Pb accumulation as well as in metal-induced membrane lipid peroxidation were also observed. The present study highlights the evolution of algal ecotypes of high but various Zn and Pb resistance as a result of natural exposure to different metal concentrations in their habitats. The algae of high heavy metal resistance could have a practical application in remediation of contaminated soils of anthropogenic origin.     

Cadmium and lead interactive effects on oxidative stress and antioxidative responses in rice seedlings

Interactive effects of two heavy metal pollutants Cd and Pb in the growth medium were examined on their uptake, production of reactive oxygen species (ROS), induction of oxidative stress and antioxidative defence responses in Indica rice (Oryza sativa L.) seedlings. When rice seedlings in sand culture were exposed to 150 μM Cd (NO₃)₂ or 600 μM Pb (CH₃COO)₂ individually or in combination for 8–16 days, a significant reduction in root/shoot length, fresh weight, relative water content, photosynthetic pigments and increased production of ROS (O₂˙^? and H₂O₂) was observed. Both Cd and Pb were readily taken up by rice roots and localisation of absorbed metals was greater in roots than in shoots. When present together in the growth medium, uptake of both the metals Cd and Pb declined by 25–40 %. Scanning electron microscope (SEM) imaging of leaf stomata revealed that Pb caused more distortion in the shape of guard cells than Cd. Dithizone staining of roots showed localisation of absorbed Cd on root hairs and epidermal cells. Both Cd and Pb caused increased lipid peroxidation, protein carbonylation, decline in protein thiol and increase in non-protein thiol. The level of reduced forms of non-enzymic antioxidants glutathione (GSH) and ascorbate (AsA) and their redox ratios (GSH/AsA) declined, whereas the activities of antioxidative enzymes superoxide dismutase (SOD) and guaiacol peroxidase (GPX) increased in metal treated seedlings compared to controls. In-gel activity staining also revealed increased intensities of SOD and GPX isoforms with metal treatments. Catalase (CAT) activity increased during early days (8 days) of metal exposure and declined by 16 days. Results suggest that oxidative stress is an important component in expression of Cd and Pb toxicities in rice, though uptake of both metals gets reduced considerably when present together in the medium.     

Contents of Heavy Metals in Chinese Edible Herbs: Evidence from a Case Study of Epimedii Folium

Toxic heavy metal contamination in Chinese edible herbs has raised a worldwide concern. In this study, heavy metals in Epimedii Folium, an edible medicinal plant in China, were quantitatively analyzed. Variations of heavy metals in different species, in various organs (i.e., leaves, stems, and roots), in wild-growing and cultivated plants, and in 35 market samples of Epimedii Folium, were systematically investigated. In all of Epimedium samples, Hg (mercury) was not detectable (0.00 μg/g). Four species, Epimedium pubescens, Epimedium sagittatum, Epimedium brevicornu, and Epimedium wushanense, were found to contain Cu (copper) and Pb (lead). And contents of Cu and Pb in E. brevicornu were significantly higher than those in other species (P < 0.01). In wild-growing and cultivated Epimedium plants, Cd (cadmium) and As (arsenic) were not detectable, and concentrations of Cu and Pb in wild-growing plants were significantly higher than those in cultivated plants (P < 0.01). Cd was not detectable in leaves, roots, and stems, while organ specificity was apparent in the distribution of Cu, As, and Pb. And the highest levels of Cu and Pb were observed in roots and leaves, respectively. In Chinese markets, several samples of Epimedii Folium contained excessive Cu, Cd, As, and Pb beyond the national permissible limits. In summary, there was a large variation of heavy metals among Epimedii Folium samples, and Cu and Pb were the most important heavy metals contaminating the edible medicinal plant. Application of Epimedii Folium to drug and food industries will need to focus more on toxic heavy metal contamination.     

Ecophysiological responses of the mangrove Avicennia marina to trace metal contamination

Growth responses of Avicennia marina seedlings to contamination by different concentrations of two essential (Cu, Zn) and two non-essential (Pb, Hg) trace metals were studied under glasshouse conditions. We tested the hypothesis that soil retention and root ultrafiltration would exclude most of the trace metals, and that those that are absorbed and translocated to the shoots would interfere with plant performance and be excreted via leaf salt glands. One-month-old seedlings were subjected to Cu, Zn, Pb and Hg at concentrations of 0, 40, 80, 120 and 160 μg g⁻¹ sediment for 12 months in a randomized complete block design (n = 6). Photosynthesis was measured at the end of 12 months of trace metal exposure with a portable gas exchange system and chlorophyll fluorescence with a pulse-modulated fluorometer. After morphometric measurements, plants were harvested and analyzed for Cu, Zn, Pb and Hg by atomic absorption spectroscopy. Total dry biomass decreased with increasing trace metal concentration for all metals. In the 160 μg g⁻¹ Cu, Zn, Hg and Pb treatments, total biomass was significantly lower than the control value by 43%, 37%, 42% and 40%, respectively. Decreases in plant height and number of leaves followed trends similar to those for total biomass and ranged from 37% to 60%, compared to the controls. Decreases in chlorophyll content in the trace metal treatments ranged from 50% to 58% compared to the control. Carbon dioxide exchange, quantum yield of photosystem II (PSII), electron transport rate (ETR) through PSII and photosynthetic efficiency of PSII (F_v/F_m) were highest in the control treatment and decreased with increasing trace metal concentrations. Decreases in CO₂ exchange in the 160 μg g⁻¹ treatments for all trace metals ranged from 50% to 60%. Concentrations of all trace metals in plant organs increased with increasing metal concentrations and were higher in roots than in shoots, with concentrations of Cu and Zn being considerably higher than those of Hg and Pb. Qualitative elemental analyses and X-ray mapping of crystalline deposits over the glands at the leaf surfaces indicated that Cu and Zn were excreted from the salt glands, while Hg and Pb were absent, at least being below the limits of detection. These results demonstrate that growth processes are sensitive to trace metals and therefore can be considered as a cost of metal tolerance, but salt glands of this mangrove species do contribute eliminating at least part of physiologically essential trace metals if taken up in excess.     

Biological activities of plant extracts from Ficus elastica and Selaginella vogelli: An antimalarial,antitrypanosomal and cytotoxity evaluation

The cytotoxic, antiplasmodial, and antitrypanosomal activities of two medicinal plants traditionally used in Cameroon were evaluated. Wood of Ficus elastica Roxb. ex Hornem. aerial roots (Moraceae) and Selaginella vogelii Spring (Selaginellaceae) leaves were collected from two different sites in Cameroon. In vitro cell-growth inhibition activities were assessed on methanol extract of plant materials against Plasmodium falciparum strain 3D7 and Trypanosoma brucei brucei, as well as against HeLa human cervical carcinoma cells. Criteria for activity were an IC₅₀ value < 10 μg/mL. The extract of S. vogelii did not significantly reduce the viability of P. falciparum at a concentration of 25 μg/mL but dramatically affected the trypanosome growth with an IC₅₀ of 2.4 μg/mL. In contrast, at the same concentration, the extract of F. elastica exhibited plasmodiacidal activity (IC₅₀ value of 9.5 μg/mL) and trypanocidal (IC₅₀ value of 0.9 μg/mL) activity. Both extracts presented low cytotoxic effects on HeLa cancer cell line. These results indicate that the selected medicinal plants could be further investigated for identifying compounds that may be responsible for the observed activities and that may represent new leads in parasitical drug discovery.     

An evaluation of phycoremediation potential of cyanobacterium Nostoc muscorum: characterization of heavy metal removal efficiency

The present study relates to the use of cyanobacterium Nostoc muscorum as a model system for removal of heavy metals such as Pb and Cd from aquatic systems. The effects of various physicochemical factors on the surface binding and intracellular uptake of Pb and Cd were studied to optimize the metal removal efficiency of the living cells of N. muscorum. Results demonstrated that a significant proportion of Pb and Cd removal was mediated by surface binding of metals (85 % Pb and 79 % Cd), rather than by intracellular accumulation (5 % Pb and 4 % Cd) at the optimum level of cyanobacterial biomass (2.8 g L^?1), metal concentration (80 μg mL^?1), pH (pH 5.0–6.0), time (15–30 min), and temperature (30–40 °C). N. muscorum has maximum amounts of metal removal (q _max) capacity of 833 and 666.7 mg g^?1 protein for Pb and Cd, respectively. The kinetic parameters of metal binding revealed that adsorption of Pb and Cd by N. muscorum followed pseudo-second-order kinetics, and the adsorption behavior was better explained by both Langmuir and Freundlich isotherm models. The surface binding of both the metals was apparently facilitated by the carboxylic, hydroxyl, and amino groups as evident from Fourier transform infrared spectra.     

Cadmium-induced biochemical responses of Vallisneria spiralis

The following study was carried out to investigate the cadmium (Cd) accumulating potential of Vallisneria. After subjecting plants to different concentrations of Cd, it was observed that plants are able to accumulate ample amount of metal in their roots (5,542 μg g^?1 dw) and leaves (4,368 μg g^?1 dw) in a concentration- and duration-dependent manner. Thus, it is evident that the accumulation in roots was 1.3 times higher than the shoots. It was also noted that with increasing Cd accumulation, roots of the plant appeared darker in color and harder in texture. In response to metal exposure, amount of low molecular weight antioxidants such as cysteine and nonprotein thiols (NP-SH) and activity of enzymes such as APX and GPX were significantly enhanced at lower concentrations of Cd, followed by decline at higher doses. It was also observed that in exposed plants, activity of APX enzyme was higher in roots (ca. 3 times) as compared to leaves. However, chlorophyll and protein content was found to decline significantly in a dose-dependent manner. Results suggested that due to its high accumulation potential, Vallisneria may be effectively grown in water bodies moderately contaminated with Cd.     

Role of glutathione and glutathione S-transferase in lead tolerance and bioaccumulation by Dodonaea viscosa (L.) Jacq

Glutathione (GSH) plays a central role in the plant tolerance against the toxic effects of metals. It is a key antioxidant and acts as a cofactor for glutathione S-transferase (GST). The main objective of this study was to determine the Pb tolerance and bioaccumulation by Dodonaea viscosa (L.) Jacq. and their relation to GSH production and GST activity. The relationship between the Pb tolerance and bioaccumulation by D. viscosa and the effect of the exposure time on the GSH production or the GST activity was assessed in trials with perlite under different Pb treatments. D. viscosa showed a remarkable tolerance to Pb [half-inhibitory concentration (IC₅₀) = 2,797 mg kg^?1] and accumulated up to 11,428 mg Pb kg^?1 in dry roots with a limited translocation to shoots without any signs of phytotoxicity after 105 days of exposure. The stress caused by the fast Pb uptake rate (489 mg kg^?1 day^?1) during the first 10 days of exposure was strongly correlated to increased GSH contents (~1.3-fold) and GST activities (~3.6-fold) in both shoots and roots. The results indicate that the Pb stress triggered a defense mechanism that involved increased contents of GSH and GST activities, suggesting that both variables are involved in the tolerance of D. viscosa against Pb toxicity.     

Diversity of low-molecular weight organic acids synthesized by <Emphasis Type="Italic">Salix</Emphasis> growing in soils characterized by different Cu,Pb and Zn concentrations

The aim of the study was to evaluate the biosynthesis and exudation of 10 low-molecular weight organic acids (LMWOAs) into the rhizosphere with a simultaneous analysis of the acid contents in the roots and leaves of 9 Salix taxa growing on two experimental areas, differing in their concentrations of copper (Cu), lead (Pb) and zinc (Zn) in the soil (Area 1—low, Area 2—high concentration). The obtained results reveal a significant difference in the phytoextraction of the tested Salix taxa for the analysed metals in both areas. The highest contents of Cu, Pb and Zn were observed for all Salix collected from Area 2, especially in S. × smithiana roots (116 ± 8.76, 87.84 ± 7.30 and 203.42 ± 14.62 mg kg^?1 DW, respectively). The results obtained in Area 2 also revealed acidification of the rhizosphere and a higher concentration of acids, mainly oxalic, malic, malonic, acetic and citric acids. Contents of oxalic, malic, acetic and citric acids increased in the roots of Salix taxa from Area 2, while in the leaves formic and succinic acids were also present. S. × smithiana was the taxon with the highest concentration of acids in the rhizosphere and roots (73.48 ± 6.77 and 49.79 ± 2.65 μM 100 g^?1 DW, respectively), while in leaves a higher content was observed for S. alba and S. viminalis ‘PR’ taxa (78.12 ± 3.95 and 71.12 ± 3.75 μM 100 g^?1 DW, respectively).     

Milk and Dairy Products Intake Is Associated with Low Levels of Lead (Pb) in Workers highly Exposed to the Metal

Lead (Pb) is a toxic metal, frequently associated with occupational exposure, due to its widespread use in industry and several studies have shown high Pb levels in workers occupationally exposed to the metal. The aim of this study was to evaluate the influence of milk and dairy products (MDP) on Pb levels in blood (B-Pb), plasma (P-Pb), and urine (U-Pb), in workers from automotive battery industries in Brazil. The study included 237 male workers; information concerning diet and lifestyle were gathered through a questionnaire, and B-Pb, P-Pb, and U-Pb were determined by ICP-MS. Mean B-Pb, P-Pb, and U-Pb were 21 ± 12, 0.62 ± 0.73 μg/dL, and 39 ± 47 μg/g creatinine, respectively. Forty three percent of participants declared consuming ≤3 portions/week of MDP (classified as low-MDP intake), while 57% of individuals had >3portions/week of MDP (high-MDP intake). B-Pb and P-Pb were correlated with working time (r _s  = 0.21; r _s  = 0.20; p < 0.010). Multivariable linear regressions showed a significant influence of MDP intake on B-Pb (β = ?0.10; p = 0.012) and P-Pb (β = ?0.16; p < 0.010), while no significance was seen on U-Pb. Our results suggest that MDP consumption may modulate Pb levels in individuals highly exposed to the metal; these findings may be due to the Pb-Ca interactions, since the adverse effects of Pb are partially based on its interference with Ca metabolism and proper Ca supplementation may help to reduce the adverse health effects induced by Pb exposure.     

Secondary metabolites produced by Propionicimonas sp. (ENT-18) induce histological abnormalities in the sclerotia of Sclerotinia sclerotiorum

Sclerotinia sclerotiorum is a highly aggressive pathogen that causes great economic losses, especially in temperate climates. Several biological control agents are available, but actinobacteria have seldom been used to control this fungus. Our objective was to evaluate the efficiency and ultrastructural effects of the secondary metabolites produced by the ant-associated actinobacterium Propionicimonas sp. ENT-18 in controlling the sclerotia of S. sclerotiorum. We demonstrated total inhibition of sclerotia treated with 62.5 μg/10 μl of an ethyl acetate extract of compounds produced by ENT-18, and calculated an LC₅₀ of 1.69 μg/sclerotia. Histological and ultrastructural analysis indicated that the cells of the treated sclerotia were severely damaged, suggesting direct action of the biomolecule(s) produced by the actinobacterium ENT-18 on the cell structure of the medullae and rind cell wall. This is the first report demonstrating a novel property of Propionicimonas sp.—antifungal activity against S. sclerotiorum.     

Lead (Pb)-induced biochemical and ultrastructural changes in wheat (Triticum aestivum) roots

The focus of the present study was to explore lead (Pb)-induced metabolic alterations vis-à-vis ultrastructural changes in wheat roots to establish Pb toxicity syndrome at a structural level. Pb (50–500 μM) enhanced malondialdehyde (an indicator of lipid peroxidation) and hydrogen peroxide content, and electrolyte leakage, thereby suggesting reactive oxygen species-induced disruption of membrane integrity and oxidative stress in wheat roots. The activities of superoxide dismutases and catalases enhanced upon Pb exposure, whereas those of ascorbate and guaiacol peroxidases declined. Pb-induced metabolic disruption was manifested in significant alterations in wheat root ultrastructure as analyzed by transmission electron microscopy. Pb caused thinning of cell wall (at 50 μM), formation of amoeboid protrusions and folds and intercellular spaces, and appearance of lesions and nicks/breaks (at ≥250 μM Pb). Pb was deposited along the cell walls as dark precipitates. At ≤250 μM Pb, the number of mitochondria increased significantly, whereas structural damage in terms of change of shape and disintegration was observed at ≥ 250 μM Pb. Pb reduced the size of nucleoli and induced puff formation (at 250 μM), resulting in complete disintegration/disappearance of nucleolus at 500 μM. The study concludes that Pb inhibited wheat root growth involving an ROS-mediated oxidative damage vis-à-vis the ultrastructural alterations in cell membrane and disruption of mitochondrial and nuclear integrity.     

EDTA-enhanced lead phytoremediation in sunflower (Helianthus annuus L.) hydroponic culture

The aim of the present study was to investigate the capability of Sunflower (Helianthus annuus L.) to tolerate and accumulate high amount of lead (Pb) and propose it for soil phytoremediation. To this regard, plants were grown in hydroponics and treated with different Pb concentrations (10 to 160 ??M) and a fixed concentration (500 ??M) EDTA (ethylene diamine tetra acetic acid) for 14 and 28 days (d). Effects on total biomass production, photosynthetic pigments and protein contents as well as the quantities of non protein thiols (NP-SH), glutathione (GSH), phytochelatins (PCs) and activity of glutathione reductase (GR) were estimated. Results revealed that roots (575 ??g g^?1 DW) and shoots (135 ??g g^?1 DW) accumulated Pb after 28 d of exposure, however, addition of EDTA enhanced the Pb accumulation in roots (645 ??g g^?1 DW) and shoots (255 ??g g^?1 DW ). Exposure of Pb (28 d) registered a significant (P?<?0.05) reduction in growth parameters and induction of phytochelatins (P?<?0.05; r?=?0.26) plus some of the important antioxidants (P?<?0.05; r?=?0.42), which were positively correlated to metal accumulation. Sunflower exposed at 40 ??M of Pb for 28 d synthesized higher quantity of PC₂ (18.5 fold) and PC₃ (10.5 fold), as compared to control. However, the results showed that addition of EDTA resulted in low toxicity compared to Pb alone. These data support the capability of H. annuus L. to accumulate and tolerate significant quantity of Pb and its utility for phytoremediation. This is because of the plant has the capacity to combat metal induced oxidative stress via significant synthesis of NP-SH, GSH and high activity of GR, as it would provide sufficient GSH not only for PCs synthesis but also for antioxidant function.     

Nitrate signals determine the sensing of nitrogen through differential expression of genes involved in nitrogen uptake and assimilation in finger millet

In order to understand the molecular basis of high nitrogen use efficiency of finger millet, five genes (EcHNRT2, EcLNRT1, EcNADH-NR, EcGS, and EcFd-GOGAT) involved in nitrate uptake and assimilation were isolated using conserved primer approaches. Expression profiles of these five genes along with the previously isolated EcDof1 was studied under increased KNO₃ concentrations (0.15 to 1,500 μM) for 2 h as well as at 1.5 μM for 24 h in the roots and shoots of 25 days old nitrogen deprived two contrasting finger millet genotypes (GE-3885 and GE-1437) differing in grain protein content (13.76 and 6.15 %, respectively). Time kinetics experiment revealed that, all the five genes except EcHNRT2 in the leaves of GE-3885 were induced within 30 min of nitrate exposure indicating that there might be a greater nitrogen deficit in leaves and therefore quick transportation of nitrate signals to the leaves. Exposing the plants to increasing nitrate concentrations for 2 h showed that in roots of GE-3885, NR was strongly induced while GS was repressed; however, the pattern was found to be reversed in leaves of GE-1437 indicating that in GE-3885, most of the nitrate might be reduced in the roots but assimilated in leaves and vice-versa. Furthermore, compared with the low-protein genotype, expression of HNRT2 was strongly induced in both roots and shoots of high-protein genotype at the least nitrate concentration supplied. This further indicates that GE-3885 is a quick sensor of nitrogen compared with the low-protein genotype. Furthermore, expression of EcDof1 was also found to overlap the expression of NR, GS, and GOGAT indicating that Dof1 probably regulates the expression of these genes under different conditions by sensing the nitrogen fluctuations around the root zone.     

Strategies for lead distribution in organs of <Emphasis Type="Italic">Phragmites australis</Emphasis> (Cav.) Trin. ex Steud. (Common reed) subjected to Pb pollution in flood and drought environments

Heavy metal allocation in clonal organs, stems, leaves, and roots has not been systematically studied for rhizomatous perennial plants. Here, pot experiments have been designed to investigate lead (Pb) distribution in different organs of Phragmites australis (Cav.) Trin. ex Steud. Common reed subjected to 0–4500 mg Pb kg^?1 under both flood and drought conditions. In either water treatment, Pb concentrations in offspring shoots were lower than in parent shoots; however, the opposite response was observed for biomass allocation for which parent shoots protected offspring shoots. Lower allocation of Pb to leaves rather than stems in offspring shoots could be a protective strategy of leaves under flood conditions. Lower Pb allocation to rhizomes is better for rhizome growth. This further provides energy for the growth of buds and offspring shoots, because the rhizome biomass and the number of buds and offspring shoots were not significantly inhibited by Pb levels of?≤?3000 mg kg^?1 in the flooded environment. These Pb allocation strategies could enhance the resistance capacity of reeds to Pb contamination by stabilizing population propagation and productivity, especially at Pb levels of?≤?3000 mg kg^?1 under flood conditions.