Cu In Plants Research Articles

Mechanism study of sulfur fertilization mediating copper translocation and biotransformation in rice (Oryza sativa L.) plants

Metabolism of sulfur (S) is suggested to be an important factor for the homeostasis and detoxification of Cu in plants. We investigated the effects of S fertilizers (S0, Na2SO4) on Cu translocation and biotransformation in rice plants by using multiple synchrotron-based techniques. Fertilization of S increased the biomass and yield of rice plants, as well as the translocation factor of Cu from root to shoot and shoot to grain, resulting in enhanced Cu in grain. Sulfur K-edge X-ray near edge structure (XANES) analysis showed that fertilization of S increased the concentration of glutathione in different rice tissues, especially in rice stem and leaf. Copper K-edge XANES results indicated that a much higher proportion of Cu (I) species existed in rice grain than husk and leaf, which was further confirmed by soft X-ray scanning transmission microscopy results. Sulfur increased the proportion of Cu (I) species in rice grain, husk and leaf, suggesting the inducing of Cu (II) reduction in rice tissues by S fertilization. These results suggested that fertilization of S in paddy soils increased the accumulation of Cu in rice grain, possibly due to the reduction of Cu (II) to Cu (I) by enhancing glutathione synthesis and increasing the translocation of Cu from shoot to grain.

Response of Pumpkin and Chinese Cabbage to Increasing Copper and Cobalt Levels in Irrigation Water on Sandy and Clay Loam Soils

<p>A study where Chinese cabbage and pumpkin crops were grown on sandy loam and clay loam soils and irrigated with water contaminated with five levels of contamination from 0 (control), 25, 50, 75 and 100% of smelter water was carried out in a greenhouse. Copper concentration in Chinese cabbage ranged from 4.0 mg/kg in control treatments to 539.0 mg/kg in 100% contaminated water. In pumpkin, Cu ranged from 9.0 mg/kg in control to 142.0 mg/kg when irrigate with 100% contaminated water. Mean Cu in plants grown on sandy loam soil was 217.4 mg/kg dry and 79.3 mg/kg when grown on clay loam. Co in plants grown on sandy loam soil was 86.6 mg/kg and 47.0 mg/kg on clay loam soil. Increasing above ground tissue Cu in Chinese cabbage results in biomass yield decrease according to the equation Y = 7.624e<sup>-0.0016x</sup>, (R<sup>2</sup> = 0.74) and in pumpkin decreased according to the equation Y = 8.4895e<sup>-0.004x</sup> (R<sup>2</sup> = 0.58).This study suggests that Chinese cabbage tends to accumulate higher amounts of Cu and Co than pumpkin. It can be concluded from this study that irrigating crops with contaminated results in higher uptake of contaminants and reduced biomass on sandy loam than clay loam soils.</p>

Acumulación de metales pesados y la evaluación bioquímica de las lombrices de tierra de los aserraderos en Abeokuta, Sur-Occidental Nigeria

<p>A través de los años, la industria de aserraderos ha mostrado un alto crecimiento en las áreas de bosque tropical de Nigeria, lanzando varios residuos al ambiente. Este estudio tiene como objetivo utilizar lombrices (<em>Eudrilus eugeniae</em>, <em>Libyodrilus violaceous</em> y <em>Hyperiodrilus africanus</em>) de origen aserradero como bioindicadores de contaminación por metales en los aserraderos. Se utilizaron cuatro grandes aserraderos ubicados en Abeokuta (7<sup>o</sup>9'11''44" N - 3<sup>o</sup>19'35'' E), a saber: Lafenwa, Sapon, Isale-Ake y Kotopo, para este estudio. El arboreto de la Universidad Federal de Agricultura, Abeokuta fue utilizado como sitio de control. Las lombrices de tierra, plantas y muestras de suelo se recogieron cada mes durante tres meses (marzo a mayo 2013), al azar en diferentes puntos en cada una de las localidades. El análisis de proteínas se llevó a cabo en las lombrices de tierra utilizando electroforesis en gel, mientras que las actividades de la superóxido dismutasa (SOD), catalasa (CAT) y glutatión peroxidasa (GPx) se realizaron espectrofotométricamente. Análisis de metales pesados también se llevaron a cabo en muestras de suelo, plantas y lombrices de tierra utilizando espectrofotómetro de absorción atómica. Resultados de la electroforesis del gel reveló la presencia de nueve bandas de proteínas de <em>E. eugeniae</em> en los aserraderos de Sapon y Kotopo, en comparación con seis bandas de proteínas de <em>E. eugeniae</em> de el sitio control. Se observaron siete bandas de proteínas de <em>L. violaceous</em> de Lafenwa y <em>H. africanus </em>en los aserraderos Isale-Ake. Los niveles de SOD, GPx y actividades CAT fueron significativamente mayores (P <0.05) en <em>E. eugeniae</em> del aserradero Sapon que las del aserradero Kotopo y el sitio control. El estudio también reveló que las concentraciones de Pb y Cd fueron mayores en las lombrices de tierra, plantas y el suelo de los aserraderos que los del sitio control. El aserradero Sapon mostró niveles significativamente mayores (P <0.05) de Cd y Cu en las plantas, así como Pb y Cd en muestras de suelo que las de los otros lugares. Las concentraciones de Cu, Co y Ni fueron mayores en el suelo del sitio de control que en los suelos de los aserraderos. Existe relación más fuerte en las concentraciones de metales entre las lombrices de tierra y los suelos (R = 0.602) que entre las plantas y el suelo (R = 0.405). Por lo tanto, la actividad en los aserraderos posee riesgos potenciales en el suelo y su fauna, especialmente las especies de lombrices.</p>

Effects of humic acid, compost and phosphorus on growth characteristics of basil herb and concentration of micro elements in plant and soil

Organic matters are important soil components which have considerable effects on phytoavailability of nutrients and improvement of soil physical, chemical and biological properties. The increasing demand for medicinal plants necessitates extensive research on them for sustainable agricultural development. In order to assess the effects of different levels of humic acid, compost and phosphorus (P) on growth traits and some micronutrients’ uptake by basil medicinal plant (Ocimum basiilicum L.) a factorial experiment was conducted in 2011 using a completely randomized design with three replications. Treatments consisted of three levels of humic acid (0, 10 and 20 mg/kg of soil; H1, H2 and H3, respectively), three levels of urban waste compost (0, 5 and 10 ton/ha; C1, C2 and C3, respectively) and three levels of P (0, 10 and 20 mg/kg of soil, as triple super phosphate, P1, P2 and P3, respectively). After harvesting the plants, parameters such as dry weight of aerial parts, number of lateral branches, plant height and concentration and uptake of Fe, Mn, Cu and Zn in aerial parts were measured. Results showed that the effects of humic acid (at H2 and H3 levels) and compost (at C2 and C3 levels) were significant on height, number of lateral branches and shoot dry weight, as compared to control; but these two levels did not have significant difference. Interaction of humic acid and compost, along with P, on plant height, number of lateral branches and dry weight of shoots was not significant. Application of humic acid and compost increased significantly the concentration of Fe, Mn, Zn and Cu in plant shoots, and availability of Fe, Mn, Zn and Cu in soil was increased with the application of organic fertilizers. Interaction of humic acid and compost on concentration of Fe, Mn, Zn and Cu in plant and soil was significant. In interaction of humic acid and compost with P, the application of P reduced concentration of Fe, Mn, Zn and Cu in plant and their availability in soil. But, study of these interactions showed that application of organic fertilizers can somehow improve the negative effects of P on availability of these elements, and therefore, application of these fertilizers is recommended for improving soil chemical conditions and enhancement of growth traits of basil plant.

Copper Accumulations in Soils, Coffee, Banana, and Bean Plants Following Copper-Based Fungicides in Coffee Farms in Arusha and Kilimanjaro Regions, Tanzania

This study was carried out to investigate the levels of copper (Cu) contamination in coffee fields in Kilimanjaro and Arusha regions, Tanzania, to increase the database on the contamination of soils by Cu-based fungicides in coffee fields. Surface (0–20 cm deep) soil samples were collected from different farms in Kilimanjaro and Arusha regions. Coffee, banana, and bean plant samples were collected from the locations of soil sampling. Soil and plant samples were analyzed at the Department of Soil Science, Sokoine University of Agriculture, Morogoro, Tanzania. It was found that the calcium chloride (CaCl2)–extractable Cu was less than the detection limit of flame atomic absorption spectrometry. Diethylenetriaminepentaacetic acid (DTPA)–extractable (24 to 366 mg Cu kg−1 soil) and aqua regia–extractable (80 to 806 mg Cu kg−1 soil) Cu levels were high enough to raise environmental alarm (based on European Union guidelines) in the Cu fungicide–treated soils as compared with natural Cu levels in untreated soils (1 to 12 mg Cu kg−1 soil for DTPA and 22 to 32 mg Cu kg−1 soil for aqua regia–extractable Cu). Coffee, banana, and bean plants grown on soils contaminated by Cu fungicides had varied concentrations of Cu that were greater than the concentrations of Cu in the plants collected from the uncontaminated soils. Stepwise regression analysis carried out to investigate the relationships between the soil properties and the concentrations of Cu in plants revealed a significant (P = 0.01) positive relationship (R2 = 0.4) between organic carbon and the concentration of Cu in banana leaves. Aqua regia–extractable Cu was positively correlated (P = 0.03, R2 = 0.4) with the concentrations of Cu in banana leaves. For bean leaves, electrical conductivity (EC) had a positive significant (P = 0.01) relationship (R2 = 0.56) with the concentrations of Cu in the plants. It is recommended that further research be carried out to investigate the dynamics and bioavailability of Cu for the different crops interplanted in the coffee fields.

Impact of sewage and mining activities on distribution of heavy metals in the water-soil-vegetation system

Several samples of groundwater and soils and plants have been collected from Sohar (Batina region, NE Oman), which is affected by various activities such as mining, agriculture, and sewage. To characterize quality of groundwater, As and Cu concentrations have been investigated in waters collected from different wells. Comparison of data with local and international standard values revealed that groundwater in Sohar region is characterized by lower concentrations in Cu and As compared with standards. In soils collected from the same area, concentrations of heavy metals have been measured in different fractions in order to investigate the mobility of such elements and risk of vulnerability in this area. A sequential extraction procedure has been applied to surface sediments to determine the partitioning of Zn, Cu, Co, Mn, Fe, Pb, Cr, Cd and Ni among (1) exchangeable and acid-soluble phases, (2) Fe–Mn oxides, (3) organic matter and sulphides and (4) resistant phases. The results showed that the mobile fraction in the sewage area accounts only for 10 % of the total concentration in sediments while in the Cu mining area, the contribution of the mobile fraction may exceed 10 %, especially for Pb, Mn, Cd, Cu and Co. Investigation of concentrations in As and Cu in plants collected from mining and sewage areas revealed an important accumulation of these elements in leaves and may explain enrichment of As in shallow groundwater relative to deep groundwater. This investigation also showed that Cu is more available in sewage area than in mining zone, as opposed to As.

Metal Uptake and Distribution in Cultured Seedlings of Nerium oleander L. (Apocynaceae) from the Río Tinto (Huelva, Spain)

Nerium oleander L. (Apocynaceae) is a micro-nano phanerophyte that grows in the riverbanks of the Río Tinto basin (Southwest Iberian Peninsula). The waters and soils of the Río Tinto area are highly acidic and have high concentrations of heavy metals. In this environment, N. oleander naturally grows in both extreme acidic (EA) and less extreme acidic (LEA) water courses, excluding, and bioindicating certain metals. In this work, we compared and evaluated the accumulation preferences and capacities, the distribution and processes of biomineralization of metals (Fe, Cu, Zn, Mn, Mg, Ca) in the first stages of growth of EA and LEA oleanders by means of inductively coupled plasma-mass spectrometry, scanning electron microscopy, and energy dispersive X-ray analyzer analysis. Seeds from both environments were grown and treated with a self-made solution simulating the most extreme red waters from the Río Tinto. LEA plants drastically reduces the metal uptake at the beginning, but later reactivates the uptake reaching concentration values in the same range as the EA plants. The results showed high Mn, Zn and Mg concentrations, accumulation of Fe and Cu in plants from both environments, differing from the metal concentrations of field-grown oleanders. Iron bioformations with traces of other metals were present inside and over epidermal cells and inside vascular cells of stems and roots. They were absent of leaves. The accumulation properties of N. oleander in its early stages of development make it a species to take in consideration in phytoremediation processes but optimized conditions are needed to ensure enough biomass production.

Effects of sewage sludge on the accumula-tion of heavy metals in soil and in mixtures of lawn grasses

The study was conducted on three specially prepared test areas along main streets of Bialystok. The experimental plots were sown with two lawn grass mixtures: Eko and Roadside, and three doses of sewage sludge 0.0 (control), 7.5 kg/m 2 and 15.0 kg/m 2 were used. The calculated bioconcentration factor made possible to determine the mobility of the various metals from the soil solution to the aerial parts of plants. The obtained results showed that the plants absorbed Cd, Zn, Cu easier than Pb and Ni suggesting a high mobility, in particular of Cd, Zn, Cu, and reflects the easiness extraction of those metals by plants. Significant correlations between concentrations of metals in soil and grass were observed, nickel in soil was significantly correlated with Cd, Zn and Cu in plants, while the Zn content in soil with the level of Cu in plants.

ROOT FERRIC CHELATE REDUCTASE IS REGULATED BY IRON AND COPPER IN STRAWBERRY PLANTS

In the present experiment, we studied the interaction between copper (Cu) and iron (Fe) in strawberry plants grown in nutrient solutions containing different concentrations of Fe. Plants grown in the absence of iron (Fe0) had the characteristic symptoms of Fe deficiency, with smaller chlorotic leaves, less biomass, acidification of the nutrient solution, and roots that were smaller and less ramified, while no symptoms of Fe deficiency were observed in plants grown with Fe. A greater amount of Cu was found in roots of chlorotic plants than in those grown with Fe, while plants grown with 20 μM of Fe (Fe20) in the nutrient solution had a greater amount of Fe compared with plants from the other treatments. Chlorotic plants (Fe0) and plants grown with the greatest level of Fe (Fe20) had a greater root ferric chelate reductase (FC-R; EC 1.16.1.17) activity compared with the other treatments with 5 or 10 μM Fe in the nutrient solution. The same pattern was obtained for relative FC-R mRNA concentration and for the sum of Fe and Cu contents in shoots (leaves plus crowns). The DNA obtained from amplification of the FC-R mRNA was cloned and several of the inserts analysed by single strand confirmation polymorphism (SSCP). Although there were different SSCP patterns in the Fe20 treatment, all the inserts that were sequenced were very similar, excluding the hypothesis of more than one FC-R mRNA species being present. The results suggest that Cu as well as Fe is involved in FC-R expression and activity, although the mechanism involved in this regulation is unknown so far. Both small contents of Fe and Cu in plants led to an over-expression of the FC-R gene and enhanced FC-R activity in strawberry roots.

Chemical analysis of Teucrium species (Lamiaceae) growing on serpentine soils in Bulgaria

AbstractTrace elemental concentrations (Fe, Ni, Mn, Cr, Co, Cu, Zn, Pb, Cd, and As) in aerial biomass (stems, leaves, and flowers) of the medicinal plants Teucrium chamaedrys, T. montanum, and T. polium growing on serpentine soils in Bulgaria were examined in relation to the total element contents in their respective rhizospheric soils. The objectives of the study were to evaluate: (1) elemental concentrations in plant tissues and associated soil samples together with the plants ability to tolerate/accumulate metal concentrations; (2) correlations between total metal concentrations in plants and their rhizospheric soils. Metal concentrations varied across species and sites. Their levels in plant tissues from nonserpentine sites were always lower compared to those from serpentine ones. The highest concentrations for Fe, Ni, Mn, Cr, As, Cu, and Pb were found in T. polium. Positive correlation coefficients were established between Ni, Cr, Fe, Co, and Cu in plants and Ca in the soil. None of the species tested hyperaccumulated metals although the metal concentration in some of them exceeded the range naturally found in plants. The Teucrium species can be considered as “excluders”, containing relatively low metal concentrations in their aerial parts (stems, leaves, and flowers) even in cases of high elemental concentrations in the rhizospheric soil. In all three medicinal plants, metal concentrations for toxic elements were above the permissible limits for pharmaceutical purposes. Therefore, plants found on serpentine bedrock are not recommended to be collected for pharmaceutical purposes.

Response of maize (Zea mays L.) to soil contamination with copper depending on applied contamination neutralizing substances

Copper is an essential trace element in living organisms, but its excess interferes with metabolic transformations in plant, animal and human cells. The uptake of copper from contaminated soils can be regulated, for example, by soil liming or application of other substances which enhance soil adsorption capacity and Cu binding in the substrate. The purpose of this study has been to assess the response of maize to soil contamination with copper depending on the applied neutralizing substances. The tested factors were increasing concentrations of Cu in soil: 0, 200, 400 and 600 mg Cu kg –1 dm, and soil application of mineral (lime, loam and zeolite) and organic (manure, peat and bark) neutralizing substances. Soil contamination with copper within the range of 200 to 600 mg kg –1 of soil caused reduction in maize yields. Positive influence such as alleviation of the harmful effect of copper contamination was demonstrated by lime and manure, which enhanced yields of maize, especially in the series polluted with 200 and 400 mg Cu kg –1 . The other soil amending substances, especially peat added in amounts of 400 and 600 mg kg –1 of soil, caused a considerable depression in maize yields. A linear dependence has been demonstrated between the concentration of Cu in maize plants and the content of Cu in the substrate, with the root content of Cu being on average six-fold higher than in aerial organs. Mineral soil amendments significantly decreased the BTC index in maize compared to organic substances, and lime as well as pine bark decreased the BCF index to 2.33 and 1.67 versus the value of 4.21 found in the control treatment without any neutralizing substances. The uptake of copper depended on the volume of yield and – to a lesser degree – on the concentration of Cu in plants. The uptake of copper by plants was the highest in treatments

Growth Responses and Metal Accumulation in an Ornamental Plant (Osmanthus fragrans var. thunbergii) Submitted to Different Cd Levels

To characterize the effects of Cd supplies on the accumulation efficiency of Cd, Pb, Zn, and Cu in an ornamental plant (osmanthus, Osmanthus fragrans var. thunbergii), a pot experiment using current-year osmanthus in field was carried out in western China. Biomass and its components showed a decreasing tendency as Cd supply increased, though insignificant differences were observed between treatments with a low and no Cd supply. Cd supplies increased the concentrations of Cd and Pb in plants, but the concentrations of Zn and Cu in plant showed a decreasing tendency with the increase of Cd supplies. Cd supplies also increased Cd accumulation for the plant, although the highest Cd accumulation was observed at a low Cd supply (T1). A higher Pb accumulation in the osmanthus was also detected in T1 than the other treatments. However, Zn and Cu accumulations decreased with the increase of Cd supplies. The examined osmanthus showed relative higher Cd and Pb transfer efficiencies in the presence of Cd supplies, but Cd supplies can limit the transfer of Zn and Cu. The results suggested that the examined osmanthus has potential for use in metal-contaminated environments due to phytoremediation application in the soil.

Isotopic fractionation of Cu in plants

Knowledge of the copper cycle in the plant–soil–water system is needed in order to better constrain proper plant micronutrient nutrition, control pollution, and determine sustainable soil management practices. Here, we report the Cu isotopic compositions of different components (seeds, germinated seeds, leaves, and stems) of the dicot, lentil ( Lens culinaris), and of two monocots, Virginia wild rye ( Elymus virginicus) and hairy-leaved sedge ( Carex hirsutella). According to our data, the isotopic compositions of these plants are systematically enriched in the lighter isotope of Cu ( 63Cu) in comparison to the soil in which they grow. Furthermore, different components within the plants themselves are isotopically fractionated. The shoots (stems, leaves and seeds) are systematically lighter than the germinated seeds of the plants and the Cu isotopic compositions of individual leaves correlate with their heights on the plant. These results are similar to what has been observed for Zn isotopes, which are assumed to be transported through plants by means of diffusion and kinetic fractionation across cell membranes. Because of this similarity, we suggest that the same transport mechanisms are also responsible for the observed isotopic fractionation of Cu. As a side-note, the Cu isotopic variations measured in plants are similar in magnitude to the differences previously measured in various soils, and therefore should not be neglected while interpreting the isotopic composition of soils.

مقایسه دو نوع کود آلی همراه با عناصر بر و روی بر برخی خصوصیات رشدی، غلظت و جذب عناصر غذایی ارزن معمولی (Panicum miliaceum L.)

A field experiment was conducted to study the effect of two organic fertilizers along with zinc and boron elements on some growth parameters, concentration and uptake of nutrients in millet (Panicum miliaceum L.) by using factorial based on randomized completely block design with three replications in Qaen region, Iran. The main treatments were municipal solid waste compost and cow manure (each at 0 and 25 t.ha-1) and sub treatments were elements of Zn (0, 50 kg.ha-1) and B (0, 10 kg.ha-1) using their respective ZnSO4 and H3BO3 salts. Results showed that treatments interaction had significant effects on total dry matter yield, number of tillers per plant and plant height of Millet. The highest total dry matter production was achieved by interaction of cow manure along with Zn and B elements. Concentrations of N, Fe, Zn, B and Cu in plant were increased significantly by treatments interaction effects compared to control. Interaction effect of organic fertilizers with B (in the absence of Zn) enhanced plant B concentration significantly, whereas, interaction of organic fertilizers with Zn (in the absence of B) decreased B concentration in plant. The highest plant uptake of N, P, K, Zn, and B was observed in plots with cow manure and Zn and B elements.

Diagnosis of Micronutrient Imbalance in Lime Crop in Semi-arid Region of Rajasthan, India

Low and unstable fruit yield, poor quality of fruits, and excessive fruit dropping are major problems in a lime crop and are due to either micronutrient deficiencies or nutrient imbalance. A study was conducted to assess the micronutrient status in a lime orchard at the Central Soil and Water Conservation Research and Training Institute (CSWCRTI)’s research farm in Kota, Rajasthan, India. Plant and soil samples were collected during September and October in 2006–2007. The micronutrients extracted with diethylenetriaminepentaacetic acid (DTPA) in soils were in the order of manganese (Mn) > iron (Fe) > zinc (Zn) > copper (Cu). The mean values of DTPA Mn, Fe, Zn, and Cu in surface soils varied from 13.98 to 22.70, 2.48 to 8.66, 0.79 to 1.19, and 0.14 to 0.46 mg kg−1, respectively, whereas in subsurface soils they varied from 12.94 to 23.06, 4.84 to 6.52, 0.51 to 0.83, and 0.07 to 0.20 mg kg−1, respectively. Results reveal that except for Fe, the other DTPA-extractable micronutrients decreased with depth. Total Mn, Fe, Zn, and Cu in plant leaves varied from 22 to 83, 70 to 630, 40 to 932, and 37 to 3057 mg kg−1, respectively, indicating greater or toxic concentrations of total micronutrient in leaf samples. Total Mn, Fe, Zn, and Cu in petiole samples varied from 7 to 60, 235 to 574, 70 to 827, and 101 to 2623 mg kg−1, respectively. High concentration of Cu and Zn in leaves resulted in Fe and Mn deficiencies (exhibited as leaf chlorosis) in lime plants. Results of the study indicated that Fe and Mn deficiencies are major disorders in lime plantation. Similarly, the measure of DTPA-extractable micronutrients showed the low statuses of Fe and Cu and marginal status of Zn in soils along the Chambal region.

Copper homeostasis

SummaryCopper (Cu) is a cofactor in proteins that are involved in electron transfer reactions and is an essential micronutrient for plants. Copper delivery is accomplished by the concerted action of a set of evolutionarily conserved transporters and metallochaperones. As a result of regulation of transporters in the root and the rarity of natural soils with high Cu levels, very few plants in nature will experience Cu in toxic excess in their tissues. However, low Cu bioavailability can limit plant productivity and plants have an interesting response to impending Cu deficiency, which is regulated by an evolutionarily conserved master switch. When Cu supply is insufficient, systems to increase uptake are activated and the available Cu is utilized with economy. A number of Cu‐regulated small RNA molecules, the Cu‐microRNAs, are used to downregulate Cu proteins that are seemingly not essential. On low Cu, the Cu‐microRNAs are upregulated by the master Cu‐responsive transcription factor SPL7, which also activates expression of genes involved in Cu assimilation. This regulation allows the most important proteins, which are required for photo‐autotrophic growth, to remain active over a wide range of Cu concentrations and this should broaden the range where plants can thrive. Contents Summary 799 I. Introduction 800 II. The origins of Cu homeostasis 800 III. Copper homeostasis in unicellular photosynthetic model organisms 801 IV. Functions of Cu in plants 802 V. Typical levels of Cu in plants, deficiency and toxicity 802 VI. Copper abundance in soils and appropriate Cu concentrations in media 804 VII. Uptake in the root and distribution to aerial tissues 804 VIII. Uptake in the shoot symplast, redistribution of Cu during flowering, seed set and senescence 806 IX. Cu delivery inside the cell 806 X. Regulation of Cu homeostasis 809 XI. Conclusions and outlook 811 Acknowledgements 811

Soil factors controlling the expression of copper toxicity to plants in a wide range of European soils

The impact of soil properties on metal bioavailability to plants is well recognized. However, the effect of soil bioavailability parameters on toxicity threshold values for Cu in plants needs quantification. Eighteen European soils varying widely in soil properties were amended with CuCl2 to obtain a range of seven concentrations including an unamended control. Two plant toxicity assays, barley root elongation (4 d) and tomato shoot growth (21 d after emergence), were performed on each soil under controlled environment conditions. The effective concentration of added Cu causing 50% inhibition (EC50) ranged from 36 to 536 mg/kg soil and from 22 to 851 mg/kg soil for barley root elongation and tomato shoot growth, respectively, representing variation in EC50 among soils of 15- and 39-fold. Single regressions carried out between Cu toxicity threshold values and various soil properties showed that exchangeable calcium and soil cation exchange capacity (CEC; measured at soil pH) were the best single predictors for toxicity values from both plant tests. The inclusion of other soil properties, such as iron oxide concentration, soil pH, clay, or organic carbon content, further improved predictions. For risk assessment, we suggest that Cu toxicity threshold values (EC50) be normalized on the key soil property of CEC. If available, soil exchangeable calcium and iron oxide concentration would improve the normalization.

Laboratory and Greenhouse Evaluation of Five Chemical Extractants for Estimating Available Copper in Selected Calcareous Soils of Iran

Documented plant responses to copper (Cu) are rare and consequently Cu soil tests have not received much individual effort. However, soil extraction techniques to measure the status of available Cu for plants are important in the diagnosis of deficiency or toxicity. In the present study, DTPA-CaCl2, EDTA-NH4OAc, EDTA-(NH4)2CO3, DTPA-NH4HCO3, and EDTA were evaluated for their relative efficiency to extract Cu from 26 soil series with a wide range of chemical properties. Wheat (Triticum aestivum L.) was used as a test crop. The results showed that Cu extractability decreased in the order: EDTA-(NH4)2CO3, DTPA-NH4HCO3, EDTA, EDTA-NH4OAc, and DTPA-CaCl2. Significant positive correlations were found between extractable Cu among the five extractions. Stepwise multiple regression equations showed that organic matter (OM) and clay content followed by cation exchange capacity (CEC) and calcium carbonate equivalent (CCE) were the most influential soil characteristics affecting extractable Cu. Mean top dry weight, Cu concentration and Cu uptake were significantly higher in Cu-treated plants than those in untreated plants. Significant correlations were found between Cu extracted with DTPA-CaCl2 and EDTA-(NH4)2CO3 and Cu uptake by wheat. However, the two extractants were not adequately efficient to predict Cu uptake with each accounting for only about 30% of the variation. Among soil properties tested, clay, pH, OM, and CCE correlated negatively and CEC positively with wheat top dry weight, whereas, pH, CEC, and CCE related positively and clay, and OM negatively with Cu uptake. In conclusion, it appears that none of the five test procedures in view of their relatively low coefficient of determinations with plant response proved to be a promising extractant for the determination of available Cu in the soils tested.

Loading beans with sublethal levels of copper enhances conditioning to oxidative stress

The relationship between Cu2+-overloading and oxidative stress in plant cells was studied. The involvement of Cu2+ in the reduction of superoxide O2− and hydrogen peroxide (H2O2) to hydroxyl radical (OH.), suggest that excess Cu in plants leads to oxidative stress. Cu excess was induced in Phaseolus vulgaris (cv. Pinto) plants by soaking the roots in a 1 mmol/L Cu(NO3)2 solution for 24 hours. As a result, Cu content in bean leaves increased from 12 to 23 mg Cu kg−1 DW. Indications for oxidative stress response were detected by monitoring changes in the activities and contents of some components of the antioxidative mechanism. The Cu treatment resulted in doubled activity of ascorbate peroxidase (APX, EC 1.11.1.11) and catalase (EC 1.11.1.6). Excess of copper inhibited glutathione reductase (GR, EC 1.6.4.2) to 60 % of control activity. No differences were found in CuZn-SOD (SOD, EC 1.15.11) and Mn-SOD activity, and glutathione and ascorbate content. Copper overloading affected also, primary reactions of photosynthesis and electron transport as probed by the photochemical energy storage in far-red light. Cu treatment of bean plants resulted in enhanced conditioning to successive methyl viologen and SO2 treatments as compared to non-treated control.

Evaluation of lipid peroxidation as a toxicity bioassay for plants exposed to copper

Agricultural soils may contain toxic levels of copper (Cu) due to sewage sludge spreading or industrial pollution but chemical analyses may not be representative of Cu bioavailability, defined as the soil Cu fraction that plants can actually absorb (i.e. Cu fraction which is not strongly adsorbed to soil components). Lipid peroxidation caused by Cu in plants was investigated as a relevant bioassay of toxicity. Seven-day-old rapeseed plantlets were grown on Cu-supplemented medium in controlled conditions. Lipid-peroxidation was assessed by measuring: (1) the 2-thiobarbituric acid (TBA)-reactive substances; (2) the hydroperoxy acids by HPLC analysis; and (3) the alkane outputs by gas chromatography. We first verified the correlation between the results obtained by each method and then discussed their advantages and disadvantages within the context of a bioassay, showing that the volatile alkane output measurement is the most precise and easy to perform method for this purpose.