Cu Concentrations In Roots Research Articles

Macronutrients dynamics in copper-contaminated soils: Implications for hemp growth and its phytoremediation potential

Fibrous plants with higher biomass, particularly industrial hemp, have ability to withstand and accumulate significant quantities of heavy metals from contaminated environments. The present study aimed to evaluate the dynamics of different levels (ratios) of macronutrients nitrogen, phosphorus and potassium (NPK) viz., NPK1NPK (1:1:1); NPK2NPK (2:1:1); NPK3NPK (3:1:2); NPK4NPK (4:1:2) on hemp growth and Cu contents under various levels of Cu stress (100, 400 and 800 mg kg−1 on dry soil basis using CuSO4·5H2O). Results revealed that by increasing the Cu stress, growth and biomass decreased linearly and lipid per oxidation and enzymatic antioxidants increased. Balanced application of NPK improved the biomass and decreased the membrane damage by the modulation of malonaldehyde contents. Maximum concentration of Cu in roots (377.47 ± 4.90 mg kg−1), shoots (137.45 ± 5.60 mg kg−1) and (150.07 ± 3.57 mg kg−1) was recorded at Cu3NPK2 treatment as compared to control. Maximum translocation factor (TF) and bioaccumulation coefficients (BAC) in the shoots and leaves of hemp plant were noticed where Cu stress was applied at the rate of 100 mg kg−1. However, BAC and TF were below 1. The NPK2 treatment enhanced biomass and increase Cu content both in leaves and stems, rather than the roots. Our study suggests that balanced application of NPK is a practicable approach to alleviate Cu stress and improve biomass production of industrial hemp plant. These findings indicate that optimum nutrient supply, under Cu stress, can maximize the growth potential and overall health of industrial hemp, making it a viable option for phytoremediation and sustainable agriculture on contaminated soils.

Arbuscular mycorrhizal fungi on the development and copper content in corn and sorghum plants.

The concentration of copper in the soil increased with the intensification of agricultural activities, mainly in grape production areas and orchards as a result of the application of pesticides. Arbuscular mycorrhizal fungi make up the microbial biomass of the soil and appear as an alternative to be researched for the development of plants in an environment contaminated with copper. The purpose of this pot study was to analyze the influence of arbuscular mycorrhizal fungi on the development and content of copper in corn and sorghum plants. Soil treatments were: without inoculum (control) and two arbuscular mycorrhizal (Acaulospora scrobiculata and Rhizoglomus clarum) and five doses of copper (0, 100, 200, 300, and 400 mg Cu kg-1 soil); with seven repetitions. Plant height, stem diameter, number of tillers, root volume, shoot and root dry weight yields, shoot, root and grain Cu concentrations, pseudo-total soil Cu, percentage of mycorrhizal colonization and relative mycorrhizal efficiency index in reducing Cu concentration in root and shoot of corn and sorgum were evaluated. Morphological parameters of sorghum and corn were reduced with at high Cu doses in the soil, and the inoculation with Acaulospora scrobiculata and Rhizoglomus clarum resulted in greater development and lower Cu concentration in the dry mass of the shoot and root parts sorghum and corn plants.

Photosynthesis governed by nanoparticulate titanium dioxide. The Pisum sativum L. case study

Wide availability of anthropogenic TiO2 nanoparticles facilitates their penetration into environment and prompts interactions with plants. They alter plants growth and change their nutritional status. In particular, metabolic processes are affected. In this work the effect of nanometric TiO2 on photosynthesis efficiency in green pea (Pisum sativum L.) was studied. Hydroponic cultivations with three Ti levels (10; 50 and 100 mg L−1) were applied. At all concentrations nanoparticles penetrated into plant tissues and were detected by the single particle ICP-MS/MS method. Nanoparticles altered the CO2 assimilation rate and gas exchange parameters (i.e. transpiration, stomatal conductance, sub-stomatal CO2 concentration). The most pronounced effects were observed for Ti 50 mg L−1 cultivation where photosynthesis efficiency, transpiration and stomatal conductance were increased by 14.69%, 4.58% and 8.92%, respectively. They were further confirmed by high maximum ribulose 1,5-bisphosphate carboxylation rate (27.40% increase), maximum electron transport rate (21.51% increase) and the lowest CO2 compensation point (45.19% decrease). Furthermore, concentrations of Cu, Mn, Zn, Fe, Mg, Ca, K and P were examined with the most pronounced changes observed for elements directly involved in photosynthesis (Cu, Zn, Mn, and Fe). The Cu concentrations in roots, stems and leaves for Ti 50 mg L−1 cultivation were below the control by 33.15%, 38.28% and 10.76%, respectively. The Zn content in analogous treatment and organs decreased by 30.24%, 26.69% and 13.35%. The Mn and Fe levels in leaves were increased by 72.22% and 50.32%, respectively. Our results indicated that plant defence mechanisms which restrain the water uptake have been overcome in pea by photocatalytic activity of nanoparticulate TiO2 which stimulated photosynthesis. On the contrary to the substantial stomatal conductance, the transpiration has been reduced because exceptional part of water flow was already consumed in chloroplasts and could not have been freed to the atmosphere.

Identification of plant cadmium resistance gene family in Brassica napus and functional analysis of BnPCR10.1 involved in cadmium and copper tolerance

The plant cadmium resistance (PCR) family proteins play important roles in maintaining metal homeostasis and detoxification. However, few functional PCR genes have been well-characterized in plants. In this study, we identified and cloned 26 BnPCR genes from the rapeseed (Brassica napus) genome. They were divided into four groups (I-IV) based on their phylogenetic relationship. Yeast functional complementation experiments showed that BnPCRs can transport copper (Cu) and cadmium (Cd) in yeast. The expression levels of the BnPCRs were variable among different organs. Moreover, most of the genes were induced by Cu2+ and Cd2+ stress. Among these genes, BnPCR10.1 was highly expressed in various organs and induced by Cu2+ and Cd2+. Therefore, we studied the function of BnPCR10.1 in more detail. BnPCR10.1 was localized to the plasma membrane (PM), and expression in yeast enhanced yeast cells to export Cu and Cd. Furthermore, overexpression of BnPCR10.1 transgenic lines pro35S::BnPCR10.1;athma5 had lower concentration of Cu in roots than athma5 mutants. In addition, transgenic plants pro35S::BnPCR10.1;atpdr8 had lower concentration of Cd in shoots and roots than atpdr8 mutants. Net Cu2+ and Cd2+ efflux assay showed that there was decreased absorption of Cu2+ and Cd2+ in the transgenic Arabidopsis elongation zone of roots than in athma5 and atpdr8 mutants, respectively. These results provide new information on BnPCRs and their roles in response to heavy metals and reveal the mechanism used by BnPCR10.1 to detoxify Cu and Cd. Our findings facilitate a theoretical basis for the genetic improvement of Cu–Cd tolerance in rapeseed.

A new technique for reducing accumulation, transport, and toxicity of heavy metals in wheat (Triticum aestivum L.) by bio-filtration of river wastewater

The occurrence of contaminants such as heavy metals in an aqueous environment has become a global concern. In the present study, a bio-filter was designed to eliminate heavy metals from river wastewater contaminated with industrial effluents. Moreover, we analyzed simple tap water, bio-filtered water, and unfiltered river wastewater and measured the concentrations of different heavy metals in the samples, such as cadmium (Cd), nickel (Ni), lead (Pb), and copper (Cu). The current experiment explored irrigation effects of three water regimes (tap water, bio-filtered water, and wastewater) on two wheat (Triticum aestivum L.) varieties (NARC-2009 and NARC-2011). Results of the present study indicated that wastewater negatively influenced the growth parameters and photosynthetic contents along with a significant increase in oxidative damage in terms of electrolyte leakage (EL) (50 and 61%), hydrogen peroxide (H2O2) (52 and 61 μmol/g), and malondialdehyde (MDA) (16 and 17.7 μmol/g) contents in NARC-2009 and NARC-2011 respectively. However, bio-filtered water positively regulated the growth profile, activities of antioxidants such as superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), total soluble sugars, amino acids, total protein, and proline contents in wheat as compared with untreated wastewater. In addition, bio-filtered water had significant impacts on the reduction of Cd, Ni, Pb, and Cu concentrations in roots, shoots, and grains of both wheat varieties as compared to wastewater. The concentrations (mg/kg) of Cd (15 and 18), Ni (35 and 57), Pb (5 and 7), and Cu (69 and 72) in roots, Cd (5 and 6), Ni (24 and 43), Pb (3 and 4), and Cu (16 and 19) in shoots, and Cd (0.7 and 1.0), Ni (11 and 26), Pb (2 and 3), and Cu (1.6 and 1.5) in grains of NARC-2009 and NARC-2011 were found under river wastewater treatment. Overall, wastewater treatment through bio-filtration process is an effective strategy for the reduction of toxic elements in bio-filtered water and their accumulation by plants.

Increased pH-mediated alleviation of copper-toxicity and growth response function in Citrus sinensis seedlings

Little is known about pH-mediated alleviation of copper (Cu)-toxicity in plants. ‘Xuegan’ [Citrus sinensis (L.) Osbeck] seedlings were irrigated with nutrient solution at a pH 3.0, 4.0 or 4.8 and a concentration of 0.5 (control) and 300 (Cu-toxicity) μM CuCl2 for 17 weeks. Thereafter, a total of 125 physiological parameters including biomass, nutrient elements in roots, stems and leaves, relative water content (RWC) in roots and leaves, and pigments, gas exchange, chlorophyll (Chl) a fluorescence (OJIP) transients and related fluorescence parameters in leaves were investigated in order to understand the physiological mechanisms for increased pH-mediated alleviation of Cu-toxicity. Our results clearly demonstrated that both pH 3.0 (at a concentration of 0.5 or 300 μM Cu) and 300 μM Cu (at a pH of 3.0, 4.0 or 4.8) were toxic to C. sinensis seedlings, as indicated by decreased biomass and/or CO2 assimilation. Raised pH decreased Cu uptake per plant (root dry weight) and Cu concentration in roots, stems and leaves and mitigated Cu-toxic damage to root growth and function, thus improving the uptake of water (root and leaf RWC) and some nutrients (nitrogen, potassium, phosphorus, magnesium, calcium, sulfur and iron), as well as the distribution of some nutrient elements (potassium, sulfur and zinc) in leaves, hence mitigating Cu-toxic impairment on the whole electron transport chain and increasing plant growth, leaf pigment level and CO2 assimilation. Principal component analysis (PCA) indicated that Cu-toxic-effects on all these physiological parameters as a whole decreased with increase of pH. Low pH (pH 3.0) effects on OJIP transients and most of physiological parameters were less pronounced in control than in Cu-toxic seedlings. Interactive effects of pHCu were significant on 84 physiological parameters. To conclude, low pH intensified Cu-toxic effects on C. sinensis seedlings; Cu-toxicity aggravated low-pH effects on C. sinensis seedlings.

Gibberellic acid application on biomass, oxidative stress response, and photosynthesis in spinach (Spinacia oleracea L.) seedlings under copper stress.

The mechanism of Cu tolerance in plants and its control measures are of considerable significance for the remediation of Cu-contaminated soils. Gibberellic acid (GA3) is involved in plant growth and development and in the response to heavy metal stress. In the present study, changes in the biomass, oxidative stress response responses, and photosynthesis of spinach seedlings were examined under Cu stress with exogenous GA3 applied at concentrations of 0, 3, 5, 10, 20, 40, 60, or 80 mg L-1. Under Cu stress, the plant Cu concentration and oxidative damage were greater, photosynthetic parameters and biomass declined, and antioxidant enzyme activities and the proline concentration increased. However, spinach growth did not terminate, indicating that spinach seedlings had strong Cu tolerance. When low concentrations of GA3 (3-5 mg L-1) were added to Cu-stressed spinach seedlings, the damage caused by Cu stress to spinach seedlings was reduced, and the Cu tolerance of spinach seedlings was enhanced, which mainly manifested as reduced oxidation damage, an increased proline concentration, elevated antioxidant enzyme activities, decreased Cu concentration in leaves, and increased Cu concentration in roots, increased photosynthetic parameters, and an increased in the total biomass. In contrast, additions of GA3 at concentrations higher than 40 mg L-1 intensified oxidative damage and decreased the activities of antioxidant enzymes, photosynthetic parameters, and biomass. Additionally, the Cu concentration increased in leaves and decreased Cu concentration in roots, indicating that high concentrations of GA3 aggravated stress damage and severely influenced physiological functions in spinach seedlings. In summary, the application of 3-5 mg L-1 GA3 to spinach seedlings in Cu-contaminated soil can be used to reduce Cu toxicity to plants and increase Cu tolerance.

Exogenous jasmonic acid decreased Cu accumulation by alfalfa and improved its photosynthetic pigments and antioxidant system.

Jasmonic acid (JA) is an important phytohormone, which among others may be involved in the regulation of plant accumulating heavy metal. This experiment was designed to explore the effects of exogenous JA on the responses of alfalfa to Cu stress (100μM) in Hoagland solution. When 1, 5 or 10mM JA was added to the treatment with Cu addition, Cu concentrations in roots and leaves of alfalfa were significantly decreased (p<0.05) to some extents compared to the treatment without JA addition. The biomasses of roots and leaves of alfalfa in treatments of JA additions were significantly increased (p<0.05) compared to the Cu stress treatment. Similarly, the concentrations of Chlorophyll, antioxidant enzyme activities, MDA and H2O2 were improved accordingly. But these factors of JA were not improved further when its concentration added in media was the highest (10mM), indicating its improvement roles were limited. These results suggested that there were positive roles of exogenous JA on alfalfa decreased its Cu accumulation and toxicities might via reduced oxidative stress.

Exogenous of Indole-3-Acetic Acid Application Alleviates Copper Toxicity in Spinach Seedlings by Enhancing Antioxidant Systems and Nitrogen Metabolism.

Indole-3-acetic acid (IAA) is a potential mediator in the protection of plants from copper (Cu) toxicity and the enhancement of Cu tolerance. In this paper, spinach (Spinacia oleracea L.) seedlings were cultivated in soil containing 700 mg kg−1 Cu and the leaves of seedlings were sprayed with different concentrations of IAA. Exogenous IAA treatment reduced the malondialdehyde (MDA) concentrations in Cu-stressed seedlings and increased biomass, proline content, and the activities of antioxidant enzymes. Exogenous IAA treatment also increased the levels of nitrogen (N) assimilation compounds and the activities of N-metabolizing enzymes, but reduced NH4+ content. Notably, lower concentrations of IAA (10–40 mg L−1) increased the Cu concentrations in roots and reduced the Cu concentrations in leaves, while higher concentrations of IAA (50 mg L−1) reduced the Cu concentrations in both roots and leaves to the lowest levels. The findings indicated that the application of IAA reduced Cu accumulation, alleviated Cu toxicity, and enhanced Cu tolerance in spinach seedlings. IAA application could be used as an alternative strategy for reducing Cu accumulation in vegetable crops and for remediating Cu-contaminated soil, in turn reducing the hazardous effects of heavy metal contamination on human health and the environment.

Copper pre-exposure reduces AgNP bioavailability to wheat

Heavy metals in contaminated sites can affect plant responses to emerging contaminates such as engineered silver nanoparticles (AgNPs), but the underlying mechanisms are poorly understood. After 4-day exposure to 0–2.5 mg Cu L−1 hydroponically, Cu concentrations in roots of wheat seedlings (Triticum aestivum L.) increased from 20 ± 3 to 325 ± 58 mg kg−1. Meanwhile, the cell death in root tips, as measured by the uptake of Evans blue stain, increased 1.8–2.8 times in response to Cu exposure. Total thiol contents in roots (including glutathione, cysteine and phytochelatins), as measured by high performance liquid chromatography, increased 1.4 times upon low Cu exposure but decreased 2.2 times upon high Cu exposure. After those wheats were exposed to 10 mg L−1 AgNPs for 8 h, the Ag influx rates decreased 1.3–3.9 times in Cu pre-exposed plants. Together, the cell death in root tips and thiol levels in roots could explain the decreased Ag influx rates of Cu pre-exposed plants. These findings indicate that the bioavailability of AgNPs without consideration of pre-existing metals could be over-estimated.

Concentration-dependent Accumulation and Translocation of PFASs by Wetland Plant Alisma orientale

This study investigated the concentration-dependent accumulation and translocation of perfluoroalkyl substances (PFASs) by wetland plant Alisma orientale. The concentrations of PFASs in nutrient solution were 0, 5, 10, 50, 100, 200, 500, and 1000 μg·L-1. The electrolytic leakage of roots, Cu concentration in roots and stems, and Ca concentration in stems and leaves decreased with an increase in PFASs concentration in external solution, while the plants were growing well. The removal mass of PFASs by plants increased (0.87-116.50 μg) with an increase in PFASs concentration, while the removal efficiency decreased (20.1%-2.9%). The PFASs concentration in plant roots, stems, and leaves increased linearly with that in nutrient solution, and fitted the Langmuir adsorption isotherm and Michaelis-Menten equation well, which indicated PFASs were uptaken through passive diffusion. The root concentration factor, stem concentration factor, transpiration stream concentration factor, and partition limited quasi-equilibrium factor αpt decreased with that of PFASs in nutrient solution, probably due to the increase in the volume of transpiration water and the longer time to reach equilibrium.

Copper and Zinc in Rhizosphere Soil and Toxicity Potential in White Oats (Avena sativa) Grown in Soil with Long-Term Pig Manure Application

Successive applications of pig manure increase Cu and Zn contents in soils and may cause toxicity to plants. However, plants may have defense strategies that reduce Cu and Zn availability in rhizosphere soil. The study aimed to evaluate growth of white oats (Avena sativa) and Cu and Zn availability in rhizosphere soil subjected to long-term applications of pig slurry (PS) and pig deep litter (PL). The study was carried out with samples of a Typic Hapludalf soil from an 11-year experiment with annual fertilization of 180 kg N ha−1 as pig slurry (PS180) and pig deep litter (PL180) and a control (C) treatment. White oats were grown in pots with soil collected at 0.0–0.10 m depth. Thirty-five and 70 days after emergence (DAE), rhizosphere (RS) and bulk soil (BS) were analyzed to determine Cu and Zn availability. Plant growth, tissue Cu and Zn concentration, and content (concentration X dry weight) were measured. The application of pig manure for 11 years increased available soil Cu and Zn, as well as tissue concentration and content. Dry matter yield and plant height in PL180 were similar to those found in plants grown in the control treatment, while plants grown in PS180 had higher dry matter than in C. We found few differences in soil chemical characteristics and Cu and Zn contents between RS and BS. The high Cu concentrations in roots, especially in soil treated with PL180, show that Cu retention in the roots prevents excess Cu transport to white oat shoots.

Linking phytotechnologies to bioeconomy; varietal screening of high biomass and energy crops for phytoremediation of Cr and Cu contaminated soils

Enerbiochem was a project devoted to study new strategies of industrial valorisation of high biomass crops grown on brownfields or contaminated soils not suitable for food production. Chromium and copper accumulation and toxicity were examined in different species of agronomic interest. Cultivars of Brassica carinata A. Braun (7), Brassica juncea (L.) Czern. (4), Brassica napus L. (4), Raphanus sativus L. (4), inbred lines of Helianthus annuus L. (6) and cultivars of Nicotiana tabacum L. (3) were screened for the best genetic materials to be used with the aims: i) to produce the highest biomass in contaminated soils; and ii) possibly to phytoremediate them. Cr and Cu accumulation in shoots were evaluated on 16 days old plants grown for additional 5 days in the presence of either Cr (60 μM) or Cu (2 μM) in hydroponic. They were characterised for Cr and Cu concentrations in roots and shoots, shoot biomass, and total chlorophyll as well. Shoot biomass was significantly lower in Brassica species than in R. sativus, H. annuus and N. tabacum under Cr treatments. On the contrary, under Cu treatments, N. tabacum produced the lowest biomass in respect to other species. Potentially toxic element concentrations varied among genetic material and some genetic material resulted less affected (higher chlorophyll content and shoot biomass) even under higher Cu or Cr concentrations in shoot. Potential candidates within each species, to be used for coupling phytoremediation and biomass production on slightly Cr-Cu potentially contaminated soils are listed.

Screening of native tropical trees for phytoremediation in copper-polluted soils

Due to the limited number of studies on phytoremediation using native tree species in tropical soils, the aim was to identify new phytoremediator species from tropical climate with the purpose of promoting an increase in the diversity of tropical native trees used in phytoremediation projects. Seven native tree species from Brazil were selected: Cedrela fissilis, Handroanthus serratifolius, Copaifera langsdorffii, Hymenaea courbaril, Mimosa caesalpiniifolia, Cecropia sp. and Myracrodruon urundeuva. Seedlings of these species were planted in pots with an unpolluted Arenosol, and then spiked with 60, 100 and 500 mg kg−1 Cu. Height and stem diameters were measured over 60 days. Biomass and total Cu concentration were determined in leaves, stem and roots. Copper in bulk soils and rhizospheres was analyzed by a sequential extraction method. All species accumulated high concentration of Cu in roots (>300 mg kg−1), so they could be used as phytostabilizators for this metal. Copper mobilization increased in the rhizospheres, but it was mostly absorbed by roots. Cecropia sp., M. urundeuva and C. langsdorffii are hyperaccumulators of Cu (>300 mg kg−1 in shoots), so they are potential phytoextractor species. This study evidence the potential of seven tree species native from tropical regions for phytostabilizing copper-polluted soils.

OsATX1 Interacts with Heavy Metal P1B-Type ATPases and Affects Copper Transport and Distribution.

Copper (Cu) is an essential micronutrient for plant growth. However, the molecular mechanisms underlying Cu trafficking and distribution to different organs in rice (Oryza sativa) are poorly understood. Here, we report the function and role of Antioxidant Protein1 (OsATX1), a Cu chaperone in rice. Knocking out OsATX1 resulted in increased Cu concentrations in roots, whereas OsATX1 overexpression reduced root Cu concentrations but increased Cu accumulation in the shoots. At the reproductive stage, the concentrations of Cu in developing tissues, including panicles, upper nodes and internodes, younger leaf blades, and leaf sheaths of the main tiller, were increased significantly in OsATX1-overexpressing plants and decreased in osatx1 mutants compared with the wild type. The osatx1 mutants also showed a higher Cu concentration in older leaves. Yeast two-hybrid and bimolecular fluorescence complementation assays showed that OsATX1 interacts with the rice heavy metal P1B-ATPases HMA4, HMA5, HMA6, and HMA9. These results suggest that OsATX1 may function to deliver Cu to heavy metal P1B-ATPases for Cu trafficking and distribution in order to maintain Cu homeostasis in different rice tissues. In addition, heterologous expression of OsATX1 in the yeast (Saccharomyces cerevisiae) cadmium-sensitive mutant Δycf1 increased the tolerance to Cu and cadmium by decreasing their respective concentrations in the transformed yeast cells. Taken together, our results indicate that OsATX1 plays an important role in facilitating root-to-shoot Cu translocation and the redistribution of Cu from old leaves to developing tissues and seeds in rice.

Tolerance and bioaccumulation of Cd and Cu in Sesuvium portulacastrum

In order to investigate the tolerance and bioaccumulation of Cd and Cu in the halophyte Sesuvium portulacastrum, seedlings were hydroponically cultured for 30 days using the modified 1/2 Hoagland nutrient solution with different concentrations of Cd (0, 5, 10, 15, and 20mgL−1) and Cu (0, 2.5, 5, 7.5, and 10mgL−1). Afterwards, the seedling height, leaf area, biomass, and mineral element contents (Fe, Mg, Cu, and Zn) in the roots, stems and leaves were measured, and the tolerance index, bioconcentration factor (BCF), transportation index, and removal rate were calculated. The effects of salinity (0‰–30‰) on the growth and bioaccumulation ability of S. portulacastrum under combined Cu/Cd (5mgL−1) exposure were also determined. The results showed that, with an increasing Cd concentration, the biomass and seedling height of S. portulacastrum initially increased and then decreased. The highest leaf biomass and seedlings height was observed in the 10mgL−1 and 5mgL−1 Cd treatment group, respectively. Salinity did not affect the biomass of S. portulacastrum but decreased Cd concentration in roots and aboveground tissues and Cu concentration in roots of S. portulacastrum. Cu treatment significantly facilitated the absorption of Mg, Cu, and Zn in roots. With an increasing Cu concentration, the Mg and Fe contents increased in the leaves of S. portulacastrum. In comparison to the above-ground portions, the root showed a higher bioaccumulation ability of Cd and Cu, with the BCF of 341.5 and 211.9, respectively. The BCF and translocation factor (TF) values indicated that S. portulacastrum was not a hyperaccumulator for Cd and Cu, but could be used as a phytostablization plant in heavy metal contaminated coastal environments.

Influence of phosphorous fertilization on copper phytoextraction and antioxidant defenses in castor bean (Ricinus communis L.).

Application of fertilizers to supply appropriate nutrients has become an essential agricultural strategy for enhancing the efficiency of phytoremediation in heavy metal contaminated soils. The present study was conducted to investigate the beneficial effects of three types of phosphate fertilizers (i.e., oxalic acid-activated phosphate rock (APR), Ca(H2PO4)2, and NaH2PO4) in the range of 0-600mg Pkg-1 soil, on castor bean growth, antioxidants [antioxidative enzymes and glutathione (GSH)], and Cu uptake. Results showed that with the addition of phosphorus fertilizers, the dry weight of castor bean and the Cu concentration in roots increased significantly, resulting in increased Cu extraction. The phosphorus concentration in both shoots and roots was increased as compared with the control, and the Ca(H2PO4)2 treatment had the greatest effect. Application of APR, NaH2PO4, and Ca(H2PO4)2 reduced the malondialdehyde (MDA) content, and the activity of the two antioxidant enzymes superoxide dismustase (SOD, EC 1.15.1.1) and catalase (CAT, EC 1.11.1.6) in the leaves of castor bean. GSH concentration in leaves increased with the increasing levels of phosphorus applied to soil as well as the accumulation of phosphorus in shoots, compared to the control. These results demonstrated that the addition of phosphorus fertilizers can enhance the resistance of castor bean to Cu and increase the Cu extraction efficiency of the plant from contaminated soils.

Influence of biochar and seaweed extract applications on growth, yield and mineral composition of wheat (Triticum aestivum L.) under sandy soil conditions

Two pot experiments were conducted during 2013/2014 and 2014/2015 winter seasons to study the effect of biochar (BC) as soil amendments at two rates 2% and 5%, seaweed extract (SWE) as foliar applications at 1 and 2g/l and the combination between BC 2% and SWE treatments on growth, yield attributes and some macro- and micronutrients concentration in roots, leaves and grains of wheat (Triticum aestivum L.) cultivar Sakha 93. Two samples were taken at 105 and 150 days after sowing. At the first sample date, plant height, leaves number per main tiller, number of tillers/plant, shoot fresh weight, root length, root fresh weight, chlorophyll reading, spikes number per plant, main spike length and N, P, K, Mg, Ca, Fe, Mn, Zn and Cu concentrations in roots and leaves were determined. At the second sample date (harvesting time), spike weight, number of grains per spike, weight of grains/spike and weight of 100 grains were recorded and nutrients concentrations in grains were determined. Obtained results revealed that, adding biochar, sprayed seaweed extract treatments individually or in combination have stimulating effect on the most of morphological characters and yield components as compared with control plants in both seasons. Generally, using the low level of BC at 2% individually or in combination with SWE treatments has more promotion effect on the most of growth parameters and yield components and achieved the highest concentrations on the most of macro- and micronutrients in roots, leaves and grains as compared with the control in both seasons.

Integration of copper subcellular distribution and chemical forms to understand copper toxicity in apple trees

Little information is known about the tolerance mechanisms of apple trees growing in soils with excess Cu. This study investigated not only the accumulation and translocation of Cu in the organs of two apple tree cultivars (Fuji and Ralls), but also the detoxification mechanisms of their roots at the cell level. Most accumulated Cu was within apple tree root, especially in the fibrous root, for both cultivars. Compared with Fuji, Ralls had significantly higher Cu concentrations in roots, especially for fibrous roots, while lower concentrations in the aboveground parts. Combining the results from subcellular distribution and chemical forms in the fibrous roots of two apple tree cultivars, more Cu amounts were sequestrated in cell wall and vacuole for Ralls and Cu accumulated in the fibrous root of Fuji had higher in vivo mobility. The results of this study implied that different apple tree cultivars differ in the accumulation, transportation and tolerance to toxic levels of soil Cu, and the chemical forms and subcellular partitioning of Cu in the fibrous roots can elucidate some of the variation of apple trees in Cu sensitivity.

Organic acids, amino acids compositions in the root exudates and Cu-accumulation in castor (Ricinus communis L.) Under Cu stress

abstractRicinus communis L. is a hyperaccumulation plant newly discovered in an abandoned land of Cu mine in China. A hydroponic experiment was then carried out to determine the root exudates in the Cu-tolerant castor (Ricinus communis L.). Plants were grown in nutrient solution with increasing level of Cu doses (0, 100, 250, 500, and 750 μmol/L Cu) in the form of CuSO4. Cu accumulation in the roots and shoots of castor, and root exudates collected from the castor were measured. The results indicated that the castor had a high Cu accumulation capacity and the Cu concentrations in the shoots and roots of the castor treated with 750 μmol/L Cu were 177.1, 14586.7 mg/kg, respectively. Tartaric was the largest in the root exudates in terms of concentrations, which reached up to 329.13 μmol/g (dry plant) in the level of 750 μmol/L Cu. There was a significantly positive linear relationship between the Cu concentration in root and the concentration of succinic (R = 0.92, P < 0.05), tartaric (R = 0.96, P < 0.01), and citric (R = 0.89, P < 0.05). These results indicated that the difference in root exudation from castor could affect their Cu tolerance. What is more, significant is that the high tartaric and citric, the low oxalic and cysteine in the root exudation of castor contributed to toleration of high Cu concentrations.