Roberta Corrêa Nogueirol

Use of non-hyperaccumulator plant species for the phytoextraction of heavy metals using chelating agents

Soil contamination by heavy metals is a challenge faced by many countries, and engineering technologies to solve this problem are expensive and can cause negative impacts on the environment. One way to minimise the levels of heavy metals in the soil is to use plants that can absorb and accumulate heavy metals into harvestable parts, a process called phytoextraction. Typical plant species used in research involving phytoextraction are heavy metal hyperaccumulators, but plants from this group are not good biomass producers and grow more slowly than most species; thus, they have an important role in helping scientists understand the mechanisms involved in accumulating high amounts of heavy metals without developing symptoms or dying. However, because of their slow growth, it is not practical to use these species for phytoextraction. An alternative approach is to use non-hyperaccumulator plants assisted by chelating agents, which may improve the ability of plants to accumulate more heavy metals than they would naturally. Chelating agents can be synthetic or organic acids, and the advantages and disadvantages of their use in improving the phytoextraction potential of non-hyperaccumulator plants are discussed in this article. We hope to draw attention to ways to improve the phytoextraction potential of non-hyperaccumulator plants that produce a large amount of biomass and to stimulate more research on phytoextraction-inducing substances.

Sequential extraction and availability of copper in Cu fungicide-amended vineyard soils from Southern Brazil

The continuous use of cupric fungicides in vineyards, mainly copper sulfate (as a component of the bordeaux mixture), has increased Cu concentration in soils to levels near or even above the maximum established by the Commission of Soil Chemistry and Fertility of the States of Santa Catarina and Rio Grande do Sul, Brazil. Besides the total content, the fractions of the element along the soil profile must be known, because the total content of Cu in the soil is not sufficient to express its environmental impact. The objective of this study was to evaluate the variation of Cu contentes along the soil profile and its speciation and partitioning in 29 soil samples from vineyards in the state of Rio Grande do Sul, Brazil. Samples were collected in areas cropped with vineyards older than 15 years that had been frequently treated with the bordeaux mixture. These samples were from Nitosols, Acrisols, Cambisols and Leptosols and were analysed by sequential extractions and several chemical extractors. Soils had diverse chemical and physical attributes: clay content in the plowed layer (0-0.2 m) ranged from 120 to 610 g kg(-1), pH ranged from 5.3 to 7.3 and organic carbon contents varied from 2.9 to 51 g dm(-3). Among the 29 samples, 16 had the total Cu above the maximum limit allowed by the European Community regulations (140 mg kg(-1)). The average amount of Cu bonded to the oxide fraction accounted for 49.5% of the total Cu.

Tropical soils with high aluminum concentrations cause oxidative stress in two tomato genotypes

Tropical and subtropical soils are usually acidic and have high concentrations of aluminum (Al). Aluminum toxicity in plants is caused by the high affinity of the Al cation for cell walls, membranes, and metabolites. In this study, the response of the antioxidant-enzymatic system to Al was examined in two tomato genotypes: Solanum lycopersicum var. esculentum (Calabash Rouge) and Solanum lycopersicum var. cerasiforme (CNPH 0082) grown in tropical soils with varying levels of Al. Plant growth; activities of superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), guaiacol peroxidase (GPOX), and glutathione reductase (GR) enzymes; stress-indicating compounds (malondialdehyde (MDA) and hydrogen peroxide); and morphology (root length and surface area) were analyzed. Increased levels of Al in soils were correlated with reduced shoot and root biomass and with reduced root length and surface area. Calabash Rouge exhibited low Al concentrations and increased growth in soils with the highest levels of Al. Plants grown in soils with high availability of Al exhibited higher levels of stress indicators (MDA and hydrogen peroxide) and higher enzyme activity (CAT, APX, GPOX, and GR). Calabash Rouge absorbed less Al from soils than CNPH 0082, which suggests that the genotype may possess mechanisms for Al tolerance.

Concentrations of Cu, Fe, Mn, and Zn in tropical soils amended with sewage sludge and composted sewage sludge

Sewage sludge may be used as an agricultural fertilizer, but the practice has been criticized because sludge may contain trace elements and pathogens. The aim of this study was to compare the effectiveness of total and pseudototal extractants of Cu, Fe, Mn, and Zn, and to compare the results with the bioavailable concentrations of these elements to maize and sugarcane in a soil that was amended with sewage sludge for 13 consecutive years and in a separate soil that was amended a single time with sewage sludge and composted sewage sludge. The 13-year amendment experiment involved 3 rates of sludge (5, 10, and 20xa0txa0ha−1). The one-time amendment experiment involved treatments reflecting 50, 100, and 200xa0% of values stipulated by current legislation. The metal concentrations extracted by aqua regia (AR) were more similar to those obtained by Environmental Protection Agency (EPA) 3052 than to those obtained by EPA3051, and the strongest correlation was observed between pseudo(total) concentrations extracted by AR and EPA3052 and bioavailable concentrations obtained by Mehlich III. An effect of sewage sludge amendment on the concentrations of heavy metals was only observed in samples from the 13-year experiment.

Effect of Barium on Growth and Macronutrient Nutrition in Tanzania Guineagrass Grown in Nutrient Solution

Barium has been identified as a toxic element to most plants, although for grasses the toxicity has not been determined. A greenhouse experiment was performed to evaluate the effect of barium on growth parameters, barium accumulation, and macronutrient concentration in Tanzania guineagrass (Panicum maximum Jacq.), cultivated in nutrient solution. Five barium rates and a control were set in a complete randomized block design, with four replications. Forage yield, leaf area, barium, and macronutrient concentrations and accumulation were measured. Leaf area and yield sharply decreased with increase of barium concentration in the nutrient solution. The greatest barium concentration and accumulation were found in culms and sheaths. Toxic barium concentrations were estimated to be 1.24 mmol L−1 (170 mg L−1) in nutrient solution and 225 mg kg−1 in the diagnostic leaf, and the main symptoms of toxicity were interveinal chlorosis followed by necrotic spots in the leaf laminae of the grass.

Copper concentration of vineyard soils as a function of pH variation and addition of poultry litter

Copper (Cu) concentration was evaluated as a function of pH variation and addition of poultry litter to a Dystrophic Lithic Udorthent and a Humic Dystrudept from the state of Rio Grande do Sul, Brazil, cultivated with vines treated with successive applications of Cu-based product. Samples were collected from the surface layer (0 to 10 cm). Soluble Cu concentration was determined using DTPA and Mehlich III as extractants, and exchangeable Cu was determined in CaCl2. The availability of Cu was mainly affected by the soil pH. CaCl2 extractant had the best correlation with Cu concentration in contaminated soils, according to treatments applied. The addition of poultry litter did not reduce Cu availability in these soils. Total soil Cu content varied between 1,300 and 1,400 mg kg-1 in both soils. Copper available fractions, extracted by DTPA, CaCl2 and Mehlich III, averaged 35, 0.2 and 63%, respectively, of the total Cu present in the soil.

Cadmium Application in Tomato: Nutritional Imbalance and Oxidative Stress

Over the last few decades, the concentration of cadmium (Cd) in the environment has increased considerably in many countries due to anthropogenic activities. Cd is one of the most toxic pollutants in the environment and affects many metabolic processes in plants. The main objective of this study was to evaluate the response of the production, nutritional, and enzymatic antioxidant system of two tomato genotypes (Calabash Rouge and CNPH 0082) grown in tropical soils that were treated with doses of Cd. Soil samples were collected from the layer of earth at a depth of 0–0.2xa0m in areas subjected to a minimum of human disturbance. The concentrations of Cd applied to the soil samples were 0, 1, 2, and 4 times (0, 3, 6, and 12xa0mgxa0kg−1 of Cd) the agricultural intervention value adopted by current environmental legislation in the state of São Paulo, Brazil. Analysis of superoxide dismutase, catalase, glutathione reductase, guaiacol peroxidase, and ascorbate peroxidase activities, formation of stress indicator compound (malondialdehyde—MDA and hydrogen peroxide), parameters of production—dry mass of the shoot and root system (here in after “shoots” and “roots”), as well as nutrition, and both the bioavailable and total levels of this metal in the soil were performed. When the bioavailable content and total levels of Cd in the soil increased as a result of this metal doses applied, the biomass of both shoots and roots decreased in both genotypes (with the exception of the CNPH 0082 grown in clay soil) and displayed lower SPAD (relative chlorophyll index) values when exposed to contaminated environments with Cd concentrations. Cadmium treatment resulted in nutritional imbalances, mainly in terms of N, P, and Mn metabolism. Plants subjected to an elevated available content of metal in the soil exhibited increases in content of MDA and hydrogen peroxide and increased activity of catalase, ascorbate peroxidase, and guaiacol peroxidase in plant tissues when grown in both clay soil and sandy soil. Cadmium was phytotoxic to the plants causing a nutritional imbalance, especially on the metabolisms of N, P, and Mn. An oxidative stress condition was established in response to the Cd treatments applied, which led to changes in peroxidase activity.

The Role of Sulfur in Increasing Guinea Grass Tolerance of Copper Phytotoxicity

Soil pollution with trace elements is a growing problem with serious environmental impacts and developing strategies to reduce those impacts is a high priority. The objectives of this study were to assess the role of sulfur (S) in reducing the phytotoxic effects of copper (Cu) and the appearance of oxidative stress due to excess Cu in the growth medium and to assess the potential of guinea grass for Cu phytoremediation. The experiment was carried out in a greenhouse, where the forage grass Panicum maximum cv. Tanzânia was grown with a nutrient solution containing combinations of three S concentrations (0.1, 2, and 4xa0mmolxa0L−1) and four Cu concentrations (0.3, 100, 500, and 1,000xa0μmolxa0L−1) using a 3u2009×u20094 factorial design in complete randomized blocks with four replicates. The following variables were measured: shoot and root dry mass production, leaf and tiller number, S and Cu concentrations in diagnostic leaves and roots, H2O2, lipid peroxidation, and proline levels in the diagnostic leaves. Very high Cu availability (1,000xa0μmolxa0L−1) that resulted in Cu concentration higher than 60xa0mgxa0kg−1 in diagnostic leaves caused more than 50xa0% reduction in shoot and root dry mass production about 30–40xa0% in the number of leaves and tillers around 20xa0% increase in lipid peroxidation and more than 10 times increase in proline production. Plants properly fed with S showed mitigation to Cu toxicity. Guinea grass showed promise as an agent in the phytoremediation of Cu-polluted areas.

Extração seqüencial de Mn e Zn em solos em função do pH e adição de cama-de-frango

The availability of cationic micronutrients and their distribution in different soil fractions are affected by many soil attributes, such as pH and organic matter (OM) contents. Available Zn and Mn contents, obtained with three extractors, and Zn and Mn fractionation were evaluated in samples from surface layers (0 to 10 cm) of a distrophic Lithic Udorthent and a Typic Haplumbrept, as a function of pH variation and addition of poultry litter. Both soils are cultivated with vines, in Rio Grande do Sul highlands (Serra Gaucha), Brazil. As the pH decreased from 6.8 to 3.8, Zn and Mn available and exchangeable (by sequential extraction) contents increased. On the other hand, Zn and Mn contents bound to OM fraction decreased. The addition of poultry litter promoted an increase in the contents of both available and exchangeable Zn and Mn. The largest proportion of Mn was bound to OM (35%) and to residual fraction (30%), while the largest amount of Zn was in the residual fraction (55%). Zn and Mn extracted by DTPA, CaCl2 0.01 mol L-1, Mehlich III had a linear correlation with the exchangeable and with the OM-bound contents.

Tropical soils cultivated with tomato: fractionation and speciation of Al

Soil acidity and the associated problems of aluminum (Al) toxicity and scarce exchangeable bases are typically the most important limiting factors of agricultural yield in wet tropical regions. The goals of this study were to test how soil lime rates affect the forms and distribution of Al in the soil fractions and how different levels of bioavailable Al affect two tomato genotypes grown in wet tropical soils. The tomato genotypes CNPH 0082 and Calabash Rouge were grown in two wet tropical soils in a greenhouse. Soil lime rates of 0, 560, and 2240xa0mgxa0kg−1 soil (clay soil) and 0, 280, and 1120xa0mgxa0kg−1 soil (sandy soil) were applied to modify Al concentrations. Dry mass production and Al concentrations were determined in shoots and roots. Al was fractionated in the soil, and the soil solution was speciated after cultivation. The Calabash Rouge genotype possesses mechanisms to tolerate Al3+, absorbed less Al, exhibited smaller reduction in growth, and lower Al concentrations in plant parts than the CNPH 0082. Increased soil pH reduced the exchangeable Al fraction and increased the fraction mainly linked to organic matter. Al in the soil in the form of complexes with organic compounds and Al(SO4)+ (at the highest lime rate) did not affect plant development. Soil acidity can be easily neutralized by liming the soil, which transforms toxic Al3+ in the soil into forms that do not harm tomato plants, thereby avoiding oxidative stress in the plants. Al-induced stress in tomatoes varies with genotypes and soil type.