Triggered antioxidant defense mechanism in maize grown in soil with accumulation of Cu and Zn due to intensive application of pig slurry

1H-NMR Metabolomics Study after Foliar and Endo-Therapy Treatments of Xylella fastidiosa subsp. pauca Infected Olive Trees: Medium Time Monitoring of Field Experiments

Here we report the medium-term effects of foliar spray and endo-therapy treatments with different doses of a Cu/Zn citric acid biocomplex (Dentamet®) in Xylella fastidiosa infected olive trees of Salento, Apulia region (South-east Italy). Leaf extract samples from field-treated 150 years old olive trees cvs Ogliarola salentina and Cellina di Nardò were studied by 1H NMR-based metabolomics. The result of different applications of Dentamet® endo-therapy after 60, 120 and 180 days in comparison with traditional foliar spray treatment and water injection as a control have been investigated. The metabolic profile analyses, performed by 1H NMR-based metabolomic approach, indicated plant metabolites variations connected to the disease progression such as mannitol, quinic acid, and oleuropein related compounds. The best results, in terms of discrimination of the metabolic profiles with respect to water injection, were found for monthly endo-therapy treatments. Dentamet® foliar application demonstrated more specific time related progressive effectiveness with respect to intravascular treatments. Therefore, besides a possible more effective performance of endo-therapy with respect to foliar treatments, the need of further doses/frequencies trimming to obtain long-term results was also assessed. The present field studies confirmed the indication of Dentamet® effectiveness in metabolic variation induction, potentially linked with reducing the X. fastidiosa subspecies pauca related Olive Quick Decline Syndrome (OQDS) symptoms development.

Physiological responses of beet and cabbage plants exposed to copper and their potential insertion in human food chain

Copper (Cu) can be toxic to vegetables when it is absorbed and accumulated at large concentrations, a fact that increases the risk of excessive addition of this metal to the human food chain. The aims of the current study are (1) to determine the Cu concentrations that have critical toxic effects on beet and cabbage plants, and the potential of these plants to enter the human food chain, as well as (2) to assess the physiological and biochemical responses of representatives of these vegetables grown in nutrient solution presenting increasing Cu concentrations. Beet and cabbage plants were grown for 75 days in pots filled with sand added with nutrient solution presenting six Cu concentrations: 0.00, 0.52, 1.02, 1.52, 2.02 and 2.52 mg Cu L^-1. Dry matter yield and Cu accumulation in different plant organs were evaluated. Photosynthetic pigment contents, lipid peroxidation levels (TBARs), superoxide dismutase (SOD) and peroxidase (POD) activity and hydrogen peroxide (H₂O₂) concentrations in leaves were evaluated. Critical Cu concentrations that led to toxicity in plant organs such as beetroot and cabbage head, which are often found in human diets, corresponded to 1.43 mg Cu L^-1 and 1.59 mg Cu L^-1, respectively. High Cu concentrations in the nutrient solution have increased Cu concentrations and accumulation in plant tissues. This outcome justified the increased POD and SOD enzyme activity in the leaves of beet and cabbage plants, respectively, and was the cause of reduced plant growth in both crops. Cabbage plants presented higher tolerance to increased Cu levels in the growing environment than beet plants. However, it is necessary being careful at the time to consume both vegetables, when they are grown in Cu-enriched environments.

Soil tillage affects soybean growth and promotes heavy metal accumulation in seeds

When soybean is grown in soils with high heavy metal concentrations, it may introduce those contaminants into the human food chain, posing risks to human health. This study evaluated the effect of tilling the soil with high Cu, Zn, and Mn levels on soybean physiology and metal accumulation in seeds. Disturbed and undisturbed soil samples were collected in two different sites: a vineyard with high heavy metal concentration and a grassland area, containing natural vegetation. Two soybean cultivars were sown and grown in the greenhouse. Photosynthetic parameters and biochemical analysis of oxidative stress were performed. Cu, Zn, and Mn in leaves and seeds, dry mass, and weight of seeds were evaluated. Soil structure had a high influence on plant growth and physiology, while soil site had a high impact on heavy metal accumulation in leaves and seeds. Soybean plants that grown in vineyard soils with high heavy metal concentrations, accumulated 50% more Zn in leaves and seeds, 70% more Cu in leaves, and 90% more Cu in seeds, than those plants grown in grassland soils. Besides, Zn concentration in seeds was higher than the permissible limit. Moreover, the disturbance of both vineyard soil and grassland soil was not good for plant growth and physiology, which have increased TBARS and H2O2 concentration in plants, transpiration rate, metal concentration in leaves and seeds. Soil disturbance may have caused organic matter oxidation and changes in the composition and quantity of soil microorganisms and it affects the availability of other nutrients in the soil.

Potential of Eucalyptus globulus for the phytoremediation of metals in a Moroccan iron mine soil-a case study

The contamination left by abandoned mines demands sustainable mitigation measures. Hence, the aim of this study was to examine the phytoremediator ability of Eucalyptus globulus Labill. to be used for cleaning up metal-contaminated soils from an African abandoned iron (Fe) mine (Ait Ammar, Oued Zem, Morocco). Plantlets of this species were exposed to a control (CTL), a reference (REF), and a mine-contaminated soil (CS). Morphological (growth, leaf area) and physiological stress biomarkers (photosynthetic efficiency, pigments content, leaf relative water, and malondialdehyde (MDA) levels) and metal bioaccumulation were assessed. The growth and leaf area of E. globulus increased overtime in all soils, although at a lower rate in the CS. Its photosynthetic efficiency was not markedly impaired, as well as MDA levels decreased throughout the experiment in CS. In this soil, higher metal contents were detected in E. globulus roots than in leaves, especially Fe (roots: 15.98-213.99 μg g^-1; leaves: 5.97-15.98 μg g^-1) and Zn (roots: 1.64-1.99 μg g^-1; leaves: 0.67-1.19 μg g^-1), indicating their reduced translocation. Additionally, though at low extent, the plants bioaccumulated some metals (Pb > Zn > Cu) from CS. Overall, E. globulus may be potentially used for the phytoremediation of metals in metal-contaminated soils.

Antioxidant and defense genetic expressions in corn at early-developmental stage are differentially modulated by copper form exposure (nano, bulk, ionic): Nutrient and physiological effects

In the present study, Zea mays seedlings grown under nano Cu(OH)₂ (nCu), bulk Cu(OH)₂ (bCu), and ionic CuSO₄ (iCu) compound exposure were harvested after six days. The nutritional profile was determined to be significantly disrupted in the roots by 1000 ppm bCu treatment, resulting in a 58.7% reduction in potassium compared to the control. In the shoots, a significant decrease of manganese was observed for 10 and 1000 ppm iCu treatments with 55.7% and 64.2% reductions, respectively. The overall protein content and catalase (CAT) enzymatic activity, however, remained unaffected in either roots or shoots, while an absence of polyphenol oxidase (PPO) activity was observed for all samples. The genetic expression of defense-related genes, metallothionein (MT), CAT, ascorbate peroxidase (APX), and PPO was assessed. The genetic expression of MT was upregulated 50-fold in roots treated with 1000 ppm bCu. There were no significant differences in CAT transcripts among the various treatments, while APX was upregulated 28 and 19-fold in shoots treated with 10 ppm bCu and 10 ppm nCu, respectively. Meanwhile, APX mRNA levels were downregulated five-fold in shoots treated with 1000 ppm iCu. Thus, indicating that the role of APX in plant defense was reinforced in seedlings exposed to low concentration of particulate Cu compounds. Remarkably, no PPO expression was found in any of the treatments and controls, which suggests this enzyme is expressed only under specific external factors or seedlings have an "immature" cascade signaling activation of the PPO system. Taken together, these results show that bCu and nCu treatments at a low concentration do not compromise vital cell machinery but rather elicit the enhancement of defense responses as observed through the increase in APX expression. Furthermore, under optimal concentrations, these Cu treatments show promise in enhancing corn defense responses, which can ultimately lead to increases in future global crop yields.

Swine manure valorization in fabrication of nutrition and energy

Renewable energy can boost the growing population's need and rapid budgetary development. To reduce fossil fuel consumption is the initial purpose of renewable and sustainable energy, producing valuable bio-based products. The fermenters, using for pretreatment of swine manure, and involvement of swine carcasses are reported to enhance organic loading rate followed by improved biogas yield on household digesters. The compositions such as animal residues, pathogenic microbes, pharmaceutical residues and nutrient compositions including undigested feed are still confused. Therefore, it is mandatory to optimize and stabilize anaerobic practice and digestate filtration purification for consequential fertilizer consumption. The effective bio-methane recovery from energy-rich compounds is challenging due to slow degradation procedures. The pretreatment procedure could enhance lipid depolymerization and improve anaerobic fermentation. This article deeply focuses on biodegradation of swine manure. The components of this manure were evaluated and established several approaches to improve biogas production. Furthermore, recycling of co-digestates was discussed in detail as fertilizer consumption including hygienic aspects of manure and pretreatment strategies of biomass residues. KEY POINTS: • Co-digestion of manure and carcasses enhance bio-methane production. • Removel of ammonia from biogas digester may improve bio-methane gas. • A strong antimicrobial influence has been reported on biogas production.

Copper and Zn distribution in humic substances of soil after 10 years of pig manure application in south of Santa Catarina, Brazil

This study aims to evaluate available Cu and Zn levels in soil and related in soil organic matter (SOM) fractions (fulvic acids-FA, humic acids-HA, and humins-HU) after 10 years of application of pig slurry (PS) and pig deep litter (PL). Soil samples were collected from an experiment with black oat/corn succession under no-tillage in southern Brazil. The treatments consisted of fertilization of 90 and 180 kg N ha^-1 applied as PS and PL from 2002 to 2012 and a control treatment without any fertilization. SOM chemical fractionation was performed in air-dried samples. Copper and Zn concentrations were analyzed in soil (total, EDTA- and CaCl₂-extracted) and in SOM fractions. The amount of Cu and Zn (in mol) related to each fraction of SOM (Cu/C and Zn/C molar ratios) was established. The applications of PS and PL promoted the accumulation of total and available Cu and Zn, especially in the PL180 treatment. The highest amount of Zn was found with HU, while for Cu both HA and HU were important retention compartments. The highest Cu/C_FA, Cu/C_HA and Cu/C_HU ratios were found with the addition of PL. Increases in Zn/C ratio were found mainly in FA fraction. The high levels of Cu and Zn obtained in the HCl-extracted SOM fraction suggest that a considerable part is bound to SOM and clay minerals with low energy. However, the SOM is an important source of metal adsorption in soils with swine manure application.

Plants' genetic variation approach applied to zinc contamination: secondary metabolites and enzymes of the antioxidant system in Pfaffia glomerata accessions

Zinc (Zn) is a micronutrient, but its excessive concentration can impair plant growth and development. Fertilizers, liming materials, pesticides and fungicides containing Zn have contributed to increase its concentration in agricultural soils. The aim of the present study is to evaluate the effect of Zn excess on the non-enzymatic (anthocyanin and β-ecdysone) and enzymatic (superoxide dismutase-SOD and guaiacol peroxidase-GPX) antioxidant system of two P. glomerata accessions (JB and GD) grown in hydroponic system and soil, under short- and long-term exposure times. Three Zn levels (2, 100 and 200 μM) and two short-term exposure times (7 and 14 d) were tested in the hydroponic experiment. Three Zn levels (2, 100 and 200 mg kg^-1) and two long-term exposure times (34 and 74 d) were tested in the soil experiment. The effects of Zn excess on P. glomerata accessions depended on the growth system and exposure time. Zinc excess in both tested growth systems resulted in significant change in the tissue oxidative process (MDA concentration) in both accessions, as well as broadened the antioxidant system response, which was based on antioxidant enzymes (SOD and GPX) and secondary metabolites (anthocyanins and β-ecdysone). The highest anthocyanin concentration was observed in accession JB, which was grown in hydroponics, but tissue anthocyanin concentration increased in both accessions, regardless of growth medium and exposure time. The β-ecdysone concentration in the roots increased in both accessions, but accession GD was more responsive to Zn excess. There was significant physiological variation in P.glomerata accessions in response to Zn excess.

Fate of 4-bromodiphenyl ether (BDE3) in soil and the effects of co-existed copper

The quantitative fate of polybrominated diphenyl ethers (PBDEs) in soil is unknown. Furthermore, the effects of co-contamination by toxic copper on the behavior of PBDEs have not been investigated. Using a ¹⁴C-tracer, we studied mineralization, metabolism, and formation of non-extractable residues (NERs) of one PBDE congener, i.e., the 4-bromodiphenyl ether (BDE3) in oxic soil for 50 days, without and with amendment of Cu (400 mg kg^-1 soil dw). BDE3 rapidly dissipated with a half-life of 5.5 days and large amounts of CO₂ (38.8 ± 0.3% of initial applied amount at the end of incubation) and NERs (42.5 ± 0.4%) were rapidly produced. One hydroxylated metabolite (4'-HO-BDE3) was formed (8.1 ± 0.6%) at the beginning of the incubation, but then decreased to 2.2 ± 0.4%. Only BDE3 occurred in physico-chemically entrapped NERs, amounting to 9.2 ± 0.7%, while only 4'-HO-BDE3 in ester-linked NERs (10.9 ± 0.7%). The addition of Cu strongly reduced the kinetics constants of the transformations (including dissipation, mineralization, and NER-formation), the predicted maximal amounts of mineralization, as well as covalent binding of 4'-HO-BDE3 to soil. The results provide first quantitative insights into the fate of low-brominated congeners of PBDEs in soil and indicate that co-contamination by Cu may increase the environmental risks of biodegradable PBDEs in soil by increasing their persistence.

Nutritional, Energy and Sanitary Aspects of Swine Manure and Carcass Co-digestion

Renewable energy can assist the management of the effects of population growth and rapid economic development on the sustainability of animal husbandry. The primary aim of renewable energy is to minimize the use of fossil fuels via the creation of environmentally friendly energy products from depleted fossil fuels. Digesters that treat swine manure are extensively used in treatment systems; and inclusion of swine carcasses can increase the organic loading rate (OLR) thereby improving biogas yield and productivity on farms. However, the characteristics of the components including animal residues, proteins, lipids, remains of undigested feed items, antimicrobial drug residues, pathogenic microorganisms and nutrient contents, are complex and diverse. It is therefore necessary to manage the anaerobic process stability and digestate purification for subsequent use as fertilizer. Efficient methane recovery from residues rich in lipids is difficult because such residues are only slowly biodegradable. Pretreatment can promote solubilization of lipids and accelerate anaerobic digestion, and pretreatments can process the swine carcass before its introduction onto biodigesters. This review presents an overview of the anaerobic digestion of swine manure and carcasses. We analyze the characteristics of these residues, and we identify strategies to enhance biogas yield and process stability. We consider energy potential, co-digestion of swine manure and carcasses, physical, chemical, and biological pretreatment of biomass, sanitary aspects of swine manure and co-digestates and their recycling as fertilizers.

Physiological responses of soybean (Glycine max (L.) Merrill) cultivars to copper excess

Successive applications of copper fungicides on vines have resulted in increased copper content in vineyard soils over the years. This high copper content has affected the growth of young vines in eradicated vineyards. Thus, the cultivation of annual species for a few years is an alternative to copper phytostabilization, because it would be a good way to decrease copper availability to plants. The aim of this study was to evaluate the physiological responses of different soybean cultivars to copper concentration increase. Four different soybean cultivars were grown under three copper concentrations: 0.5, 20 and 40 μM in nutrient solution. The main outcomes of this study were: i) Cultivar M 6410 IPRO recorded the highest photosynthetic rate when plants were exposed to 40 μM of copper in the nutrient solution; ii) plants in cultivar M 6410 IPRO accumulated large copper concentrations in their roots although did not decrease the root dry mass, possibly due to the higher superoxide dismutase activity; iii) cultivar DM 5958 RSF IPRO recorded drastically reduced photosynthetic rate and dry mass production due to copper excess. We conclude that each cultivar responded differently to the excess of copper, but none of them showed tolerance to it.

Transcriptome profiling analysis of the seagrass, Zostera muelleri under copper stress

Copper (Cu) in an essential trace metal but it can also contaminate coastal waters at high concentrations mainly from agricultural run-off and mining activities which are detrimental to marine organisms including seagrasses. The molecular mechanisms driving Cu toxicity in seagrasses are not clearly understood yet. Here, we investigated the molecular responses of the Australian seagrass, Z. muelleri at the whole transcriptomic level after 7 days of exposure to 250 μg Cu L^-1 and 500 μg Cu L^-1. The leaf-specific whole transcriptome results showed a concentration-dependent disturbance in chloroplast function, regulatory stress responses and defense mechanisms. This study provided new insights into the responses of seagrasses to trace metal stress and reports possible candidate genes which can be considered as biomarkers to improve conservation and management of seagrass meadows.

Degradation of 2,2',4,4'-tetrabromodiphenyl ether by Pycnoporus sanguineus in the presence of copper ions

The degradation of 2,2',4,4'-tetrabromodiphenyl ether (BDE-47) by Pycnoporus sanguineus was investigated in order to explore the impact of the heavy metal Cu²⁺ on BDE-47 decomposition and the subsequent formation of metabolites, as well as to further elucidate the degradation mechanism of BDE-47. An increase in degradation rate from 18.63% to 49.76% in the first four days and its stabilization at (51.26 ± 0.08)% in the following days of BDE-47 incubation were observed. The presence of Cu²⁺ at 1 and 2 mg/L was found to promote the degradation rate to 56.41% and 60.79%, respectively, whereas higher level of Cu²⁺ (≥5 mg/L) inhibited the removal of BDE-47. The similar concentration effects of Cu²⁺ was also found on contents of fungal protein and amounts of metabolites. Both intracellular and extracellular enzymes played certain roles in BDE-47 transportation with the best degradation rate at 27.90% and 27.67% on the fourth and third day, individually. During the degradation of BDE-47, four types of hydroxylated polybrominated diphenyl ethers (OH-PBDEs), i.e., 6'-OH-BDE-47, 5'-OH-BDE-47, 4'-OH-BDE-17, 2'-OH-BDE-28, and two bromophenols, i.e., 2,4-DBP and 4-BP were detected and considered as degradation products. These metabolites were further removed by P. sanguineus at rates of 22.42%, 23.01%, 27.04%, 27.96%, 64.21%, and 40.62%, respectively.

Bioconcentration, Potential Health Risks, and a Receptor Prediction Model of Metal(loid)s in a Particular Agro-Ecological Area

To investigate the bioconcentration and potential health risks of metal(loid)s in a particular agro-ecological area, 230 pairs of soil and corresponding crop grain samples were collected from typical corn and wheat plants. The geo-accumulation index (Igeo), bioconcentration factors (BCF), health risk assessment (the target hazard quotient), and Receptor Prediction Model (PCS-SMLR) analysis were adopted to study the spatial distribution, assess the health risks, and predict the relationship between metal(loid)s and soil properties. It was found that the mean concentrations of Cu, Zn, Pb, Hg, and Cd in the study area’s agricultural soils exceeded the background soil concentrations, especially for Cd (0.2 mg/kg), Meanwhile, the corresponding Cd concentration in wheat samples was higher than the food quality limit. The results of the Igeo showed that the samples with a value higher than 0 for Cd and Hg accounted for 47.83% and 33.48%, respectively. The results of BCF of Cu, Zn, Cd, and As were higher in wheat than in corn, except for Ni. The target hazard quotient (TTHQ) of health risk of wheat, corn, and soil were higher for children (2.48) than adults (1.78), showing a potential health risk for individuals who mostly consume wheat. In addition, the PCS-SMLR analysis of the BCF prediction model for Cu, Zn, As, and soil properties showed differences in terms of the influences from wheat and corn. These results provide valuable information that not only can help local residents improve the staple food structure, but also can get provide a reference metal(loid)s concentration level for agricultural soils in the study area and restore a sustainable agro-ecological environment.

Physiological and nutritional status of black oat (Avena strigosa Schreb.) grown in soil with interaction of high doses of copper and zinc

Vineyard sandy acid soils from South Brazil have experienced heavy metal contamination due to replacement of copper (Cu)-based by zinc (Zn)-based products to control foliar diseases. Thus, we evaluate physiological and nutritional status of black oat (Avena strigosa Schreb.), a common interrow crop in vineyards from this region. Soil was collected in a natural field from Santana do Livramento, in Rio Grande do Sul, the southernmost state of Brazil. Black oat was cultivated for 30 days in a greenhouse with application of 0, 30, and 60 mg Cu kg(-1) combined with 0, 15, 30, 60, 120, and 180 mg Zn kg(-1). After the trial period, dry matter accumulation of roots and shoots, Cu and Zn contents in roots and shoots, chlorophyll a fluorescence, photosynthetic pigments and catalase (CAT, EC 1.11.1.6) and peroxidase (POD, EC 1.11.1.7) activity were determined. Cu and Zn toxicity was evidenced by the decrease in plant growth of black oat as well as by the decrease of photochemical efficiency associated with the decrease in photosynthetic pigment content, especially with the highest doses of Cu and Zn. Furthermore, the activity of antioxidant enzymes (CAT and POD) was increased in intermediate doses of Zn, indicating the activation of the antioxidant system, but the stress condition in treatments with high levels of Cu and Zn was not reversed.

Effects of zinc addition to a copper-contaminated vineyard soil on sorption of Zn by soil and plant physiological responses

The occurrence of high levels of Cu in vineyard soils is often the result of intensive use of fungicides for the preventive control of foliar diseases and can cause toxicity to plants. Nowadays many grape growers in Southern Brazil have replaced Cu-based with Zn-based products. The aim of the study was to evaluate whether the increase in Zn concentration in a soil with high Cu contents can interfere with the dynamics of these elements, and if this increase in Zn may cause toxicity to maize (Zea mays L.). Soil samples were collected in two areas, one in a vineyard with more than 30 years of cultivation and high concentration of Cu and the other on a natural grassland area adjacent to the vineyard. Different doses of Cu and Zn were added to the soil, and the adsorption isotherms were built following the Langmuir's model. In a second experiment, the vineyard soil was spiked with different Zn concentrations (0, 30, 60, 90, 180, and 270mg Zn kg(-1)) in 3kg pots where maize was grown in a greenhouse for 35 days. When Cu and Zn were added together, there was a reduction in the quantities adsorbed, especially for Zn. Zn addition decreased the total plant dry matter and specific leaf mass. Furthermore, with the increase in the activity of catalase, an activation of the antioxidant system was observed. However, the system was not sufficiently effective to reverse the stress levels imposed on soil, especially in plants grown in the highest doses of Zn. At doses higher than 90Znmgkg(-1) in the Cu-contaminated vineyard soil, maize plants were no longer able to activate the protection mechanism and suffered from metal stress, resulting in suppressed dry matter yields due to impaired functioning of the photosynthetic apparatus and changes in the enzymatic activity of plants. Replacement of Cu- by Zn-based fungicides to avoid Cu toxicity has resulted in soil vineyards contaminated with these metals and damaging of plant photosynthetic apparatus and enzyme activity.

Influence of Zn-contaminated soils in the antioxidative defence system of wheat (Triticum aestivum) and maize (Zea mays) at different exposure times: potential use as biomarkers

In this study, we evaluated the antioxidant responses of wheat and maize growing in Zn-treated soils (200, 450 and 900 mg kg(-1)) at different exposure times (7, 14, 21 and 35 days). The Zn concentration in the plants increased with an increase in the Zn concentration in the soil, thereby causing an increase in the accumulation of Mg and Mn. The emergence of wheat and the growth of maize were inhibited by Zn. The chlorophyll levels increased in wheat, whereas the opposite effect was observed in maize. Regarding enzymatic activities, Zn only provoked pronounced increases in the ascorbate peroxidase activity in maize at the early exposure times and occasionally in the superoxide dismutase (14 days) and catalase (7 and 35 days) activities in wheat. The most notable effect of the exposure of plants to Zn was an inhibition of antioxidative activities after 35 days in both plant species. The reduced glutathione levels increased in wheat and maize after 35 days and the protein levels in wheat after 7 and 35 days. The only significant alteration of lipid peroxidation was a decrease in the malondialdehyde level in wheat after 35 days. Results of this work suggest that Zn may generate oxidative stress by interfering with the plant antioxidant defence system (peroxidases, catalases and superoxide dismutase) responsible for free radical detoxification. The enzymatic activities, particularly ascorbate peroxidase, and the content of reduced glutathione could be considered good biomarkers of serious stress by Zn in soils.