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Mercury (Hg) is a global environmental concern due to its toxicity (especially high in methylated form) and the long-range distribution of its gaseous elemental form (GEM). Hg-contaminated areas, such as abandoned mining sites, pose intrinsic difficulties for their management and heavy monitoring costs. In these environments, plant-based solutions may play a key role in the ecosystem quality assessment and support remediation strategies, combining reliability and costeffectiveness. In this study, we adopted a biomonitoring approach by using tree rings of four different species collected in the proximity of the miningmetallurgical area of Abbadia San Salvatore, central Italy, a major former Hg mining district whose reclamation is currently in progress. Our dendrochemical analysis was aimed at identifying the historical changes of local atmospheric Hg contamination and at singling out, for the first time in the study area, other potentially toxic elements (PTEs) associated with the past mining activity. Collected cores dated back to early as 1940 and provided the temporal patterns of atmospheric Hg emission vs the produced liquid quantities, so reconstructing the historical impact of the mining site on nearby terrestrial ecosystems and resident human population. Current GEM contamination was found about twenty times lower than that of the fully operational mine periods. From a first survey on other PTEs, thallium (Tl) and lead (Pb) appeared to be potentially associated with the mining activity, thus suggesting new working assumptions for further dendrochemical analyses and for the inclusion of Pb in human biomonitoring surveys of the Mt. Amiata area, actually not present in the control list. The results prompt a more thorough assessment by tracking for a longer time span a critical site that is an ideal open-field lab to study the ecophysiology of different tree species in relation to environmental behavior of PTEs for better-assessing wildlife and human exposures. [ABSTRACT FROM AUTHOR]

Reductions in industrial pollutant loads and the introduction and modernization of wastewater treatment facilities have improved the quality of inland waters in Europe and elsewhere, but climatic change, changes in runoff and the legacy of mine wastes may increase pressures on many aquatic environments. In the present study, data obtained by monitoring the French–German river are collated to visualize long-term trends in the pollution, river discharges and temperatures of Moselle waters. While air temperatures and accumulated heat sums in the catchment area showed an upward trend, precipitation and discharge levels as well as river temperatures were less affected by the ongoing climatic change. At the same time, the electric conductivity, i.e., the total suspended solids, did not show the anticipated reductions, while oxygen levels and pH values have showed upward trends since the 1990s. Despite the improvements in classical water quality parameters, the flooding of abandoned mines, increased water abstraction for cooling and agriculture and untreated old and emerging pollutants may aggravate environmental problems in the future. Climatic change will probably modify the runoff of pollutant loads by increasing the severity of flash floods and by concentrating water pollutants in drought spells. [ABSTRACT FROM AUTHOR]

The bioconcentration factors and two methods for estimating the bioavailable fraction of Cd and Zn were evaluated to their concentrations in young silage maize under different phosphate and crop management. The DGT technique and the extraction method with NH4NO3 indicated a moderate correlation to Cd levels in maize. After the first crop rotation, Cd bioavailability increased under high-banded P fertilization, indicating a potential accumulation of labile Cd in arable soil in a short period of time. This effect was not visible in the Cd uptake by the following maize crop. P placement strongly affected Zn concentration in maize. A previous legume crop enhanced Cd bioavailability and Cd uptake compared with a wheat crop rotation. Particular attention should be paid to interactions between essential and toxic elements (P, Zn, and Cd), P overfertilization, and high Cd contents in P fertilizers even in the short term to prevent accumulation of labile Cd in soil-maize systems. [ABSTRACT FROM AUTHOR]

Background and aims: Given that environmental factors like atmospheric CO2, temperature, and water availability will likely change simultaneously, it is difficult to make accurate predictions about future crop production. Effects of elevated CO2 or drought on aboveground plant growth are relatively well studied, while effects on the rhizosphere are rarely dealt with. The present work investigates the root exudation pattern of different osmotic protectants such as ions and sugars of two cultivars of barley grown under different water and CO2 levels. Methods: Barley (Hordeum vulgare L.) plants were grown in plant containers in climate chambers with an optimal and reduced water supply and two CO2 concentrations (380 and 550 ppm) and harvested at the stem elongation growth stage and when the inflorescences emerged. Results: The responses of root exudation to CO2 enrichment, watering level, and cultivar and their interactions varied with the developmental stage. While K+/Na+ ratio in root exudates remained stable at the stem elongation stage (DC30), it was higher at the booting stage (DC49) in the cv. "Bambina" than in cv. "Golden Promise". At DC30, in general the exudation of sugars, dissolved organic carbon (DOC) and their ratio (SUG/DOC) were lower at e[CO2] compared to ambient CO2 at normal watering conditions. Under reduced watering conditions, plants exuded on average 55% more sucrose than under well-watered conditions. The modern cv. BA exuded on average 53% more fructose than the older cv.GP. In contrast, at DC49, sucrose, DOC and SUG/DOC exudation were not affected by any factor. At e[CO2] plants exuded on average 39% less fructose than under ambient CO2. A water and CO2 interaction on glucose exudation was found at this stage. Under reduced water conditions, plants growing at ambient CO2 exuded less glucose but at e[CO2] exuded similar (GP) or even higher (BA) glucose levels than under normal water supply. Although drought and cultivar factors affected the root exudation of barley, the strongest effects in the exudation pattern were caused by CO2. Conclusions: This study presents a non-destructive percolation method for the collection of root exudates which can be used to give an insight into the complex interaction between global warming-associated environmental factors that cause yield losses and changes in crop quality and components of the belowground plant metabolism. [ABSTRACT FROM AUTHOR]

BACKGROUND Cadmium (Cd) is a mobile heavy metal and soybeans accumulate more of this element compared to other grain crops. Because vegan and vegetarian lifestyles are increasingly popular, plant‐based diets should be free from contaminants. Cd minimization has recently been identified as a breeding aim in addition to protein and oil levels. It is also important to consider the regional variability of Cd in crops. RESULTS: A large sample collection (n = 602) was subjected to Cd analyses. Soybeans were grown using a standard protocol by private gardeners in a citizen science program. Some 12.5% of samples exceeded European Union limits, although Cd concentrations and exceedances showed regional variation around the national mean (0.13 mg kg−1). Contamination was higher in densely populated regions, possibly as a result of the long‐term emissions of heavy metal loaded dusts from industry, traffic and energy production. Cd concentrations were also elevated in regions once characterized by mining and heavy industry. Values were low overall in rural areas and agricultural regions despite potential inputs via phosphate fertilizers. CONCLUSION: Grain Cd levels are highly variable across Germany. Soybean farming may be problematic in regions with a long history of mining and heavy metal deposition. © 2018 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Background and aims: Given that environmental factors like atmospheric CO2, temperature, and water availability will likely change simultaneously, it is difficult to make accurate predictions about future crop production. Effects of elevated CO2 or drought on aboveground plant growth are relatively well studied, while effects on the rhizosphere are rarely dealt with. The present work investigates the root exudation pattern of different osmotic protectants such as ions and sugars of two cultivars of barley grown under different water and CO2 levels. Methods: Barley (Hordeum vulgare L.) plants were grown in plant containers in climate chambers with an optimal and reduced water supply and two CO2 concentrations (380 and 550 ppm) and harvested at the stem elongation growth stage and when the inflorescences emerged. Results: The responses of root exudation to CO2 enrichment, watering level, and cultivar and their interactions varied with the developmental stage. While K+/Na+ ratio in root exudates remained stable at the stem elongation stage (DC30), it was higher at the booting stage (DC49) in the cv. "Bambina" than in cv. "Golden Promise". At DC30, in general the exudation of sugars, dissolved organic carbon (DOC) and their ratio (SUG/DOC) were lower at e[CO2] compared to ambient CO2 at normal watering conditions. Under reduced watering conditions, plants exuded on average 55% more sucrose than under well-watered conditions. The modern cv. BA exuded on average 53% more fructose than the older cv.GP. In contrast, at DC49, sucrose, DOC and SUG/DOC exudation were not affected by any factor. At e[CO2] plants exuded on average 39% less fructose than under ambient CO2. A water and CO2 interaction on glucose exudation was found at this stage. Under reduced water conditions, plants growing at ambient CO2 exuded less glucose but at e[CO2] exuded similar (GP) or even higher (BA) glucose levels than under normal water supply. Although drought and cultivar factors affected the root exudation of barley, the strongest effects in the exudation pattern were caused by CO2. Conclusions: This study presents a non-destructive percolation method for the collection of root exudates which can be used to give an insight into the complex interaction between global warming-associated environmental factors that cause yield losses and changes in crop quality and components of the belowground plant metabolism. [ABSTRACT FROM AUTHOR]

Extraction and processing of cassiterite (SnO2) left large tailings with high concentrations of tin, tungsten, molybdenum and lithium. Information on the phytotoxicity of mine waste is important with regard to ecological hazards. Exposure studies help to identify plants useful for the stabilization of waste tips and the phytomining of metals. A greenhouse study was performed using a dilution series of mine waste and four crops, a halophytic and a metallophytic species to derive dose response curves. Based on effective doses for growth reductions, sensitivity increased in the following order: maize > common buckwheat > quinoa > garden bean. Element analyses in different species and compartments of common buckwheat grown in a mixture of standard soil and 25% of the mine waste showed that only low levels of the metals were taken up and that transfer to seed tissues was negligible. As indicated by soil metal levels prior to and after the experiment, only lithium and arsenic proved to be plant available and reached high levels in green tissues while seed levels were low. The experiment confirmed differences in the uptake of metals with regard to elements and species. Common buckwheat is a suited candidate for cultivation on metal polluted soils. [ABSTRACT FROM AUTHOR]

In the spring oilseed rape (OSR) cultivar 'Mozart' grown under optimal N supply (NO) or mild N deficiency (NL) the transcriptome changes associated with progressing age until early senescence in developmentally old lower canopy leaves (leaf #4) and younger higher canopy leaves (leaf #8) were investigated. Twelve weeks old NO and NL plants appeared phenotypically and transcriptomically identical, but thereafter distinct nutritiondependent differences in gene expression patterns in lower and upper canopy leaves emerged. In NO leaves #4 of 14-week-old compared to 13-week-old plants, ~600 genes were up- or downregulated, whereas in NL leaves #4 ~3000 genes were upor downregulated. In contrast, in 15-week-old compared to 13-week-old upper canopy leaves #8 more genes were up- or downregulated in optimally N-supplied plants (~2000 genes) than in N-depleted plants (~750 genes). This opposing effect of N depletion on gene regulation was even more prominent among photosynthesis-related genes (PSGs). Between week 13 and 14 in leaves #4, 99 of 110 PSGs were downregulated in NL plants, but none in NO plants. In contrast, from weeks 13 to 16 in leaves #8 of NL plants only 11 PSGs were downregulated in comparison to 66 PSGs in NO plants. Different effects of N depletion in lower versus upper canopy leaves were also apparent in upregulation of autophagy genes and NAC transcription factors. More than half of the regulated NAC and WRKY transcription factor, autophagy and protease genes were specifically regulated in NL leaves #4 or NO leaves #8 and thus may contribute to differences in senescence and nutrient mobilization in these leaves. We suggest that in N-deficient plants the upper leaves retain their N resources longer than in amply fertilized plants and remobilize them only after shedding of the lower leaves. [ABSTRACT FROM AUTHOR]

Rising CO2 concentrations associated with drought stress is likely to influence not only aboveground growth, but also belowground plant processes. Little is known about root exudation being influenced by elements of climate change. Therefore, this study wanted to clarify whether barley root exudation responds to drought and CO2 enrichment and whether this reaction differs between an old and a recently released malting barley cultivar. Barley plants were grown in pots filled with sand in controlled climate chambers at ambient (380 ppm) or elevated (550 ppm) atmospheric [ CO2] and a normal or reduced water supply. Root exudation patterns were examined at the stem elongation growth stage and when the inflorescences emerged. At both dates, root exudates were analyzed for different compounds such as total free amino acids, proline, potassium, and some phytohormones. Elevated [ CO2] decreased the concentrations in root exudates of some compounds such as total free amino acids, proline, and abscisic acid. Moreover, reduced water supply increased proline, potassium, electric conductivity, and hormone concentrations. In general, the modern cultivar showed higher concentrations of proline and abscisic acid than the old one, but the cultivars responded differentially under elevated CO2. Plant developmental stage had also an impact on the root exudation patterns of barley. Generally, we observed significant effects of CO2 enrichment, watering levels, and, to a lesser extent, cultivar on root exudation. However, we did not find any mitigation of the adverse effects of drought by elevated CO2. Understanding the multitude of relationships within the rhizosphere is an important aspect that has to be taken into consideration in the context of crop performance and carbon balance under conditions of climate change. [ABSTRACT FROM AUTHOR]

The growing use of lithium (Li) in industrial and energetic applications and the inability to completely recycle the alkali metal will most likely increase anthropogenic emissions and environmental concentrations in the future. Although non-essential to plants, Li + is an important ultra-trace element in the animal and human diet and is also used in the treatment of e.g. mental disorders. Most of the lithium is consumed with the drinking water and vegetables, but concentrations in foodstuffs vary with the geochemistry of the element. In order to identify potential risks and to avoid an overmedication due to consumption of Li rich or Li contaminated foods it is advisable to identify background levels and to derive recommended Daily Allowances (RDAs) for the element. Although Germany does not possess large amounts of primary or secondary resources of lithium, geochemical investigations (mineral and ground waters and soils) in this country confirm a wide variation of environmental concentrations with generally higher levels in the southwest. Despite the large number of soil and water data, only very few data exist on lithium concentrations in plants and its phytotoxicity. Within the scope of present study common grassland plant species were sampled in regions of SW-Germany with reportedly high geogenic levels of Li. The data are discussed with regard to literature surveys and existing reference values. Since lithium has phytotoxic effects a greenhouse experiment was performed with different Li salts (LiCl and Li 2 CO 3 ) and plant species (maize, bean and buckwheat) to derive dose-response relationships for the endpoint shoot growth. While corn growth was not reduced significantly by soil concentrations of 118 ppm, EC50 values in buckwheat were 47 and 16 ppm for lithium derived from LiCl and Li 2 CO 3 , respectively. [ABSTRACT FROM AUTHOR]

Studies of soil Cd and Zn are often performed on sites that are contaminated or have deficient Zn conditions. Soil characteristics and crop management could impact the soil mobility and uptake of Cd and Zn, even when considering unpolluted Cd soils and adequate soil Zn levels. The concentrations of these two metals were assessed in soil and silage maize under five P fertilization treatments at two growth stages under low Cd and sufficient Zn conditions. Pearson correlation coefficients and stepwise linear regressions were calculated to investigate the soil characteristics influencing the bioavailable metal fraction in soil and the metal concentration in silage maize. P treatments did not impact Cd accumulation in maize; however, the Zn uptake was affected by P placement at the leaf development stage. From early development to maturity, the Cd level in maize decreased to 10% of the initial uptake, while the Zn level decreased to 50% of the initial uptake. This reduction in both metals may be attributed to a dilution effect derived from high biomass production. Silage maize could alleviate the initial Cd uptake while diminishing the depressant effect of P fertilizer on Zn concentration. Further research is required to understand the effect of P fertilizer on Cd uptake and its relation to Zn under field conditions at early and mature stages. [ABSTRACT FROM AUTHOR]

In general, yield and fruit quality strongly rely on efficient nutrient remobilization during plant development and senescence. Transcriptome changes associated with senescence in spring oilseed rape grown under optimal nitrogen supply or mild nitrogen deficiency revealed differences in senescence and nutrient mobilization in old lower canopy leaves and younger higher canopy leaves. Having a closer look at this transcriptome analyses, we identified the major classes of seed storage proteins (SSP) to be expressed in vegetative tissue, namely leaf and stem tissue. Expression of SSPs was not only dependent on the nitrogen supply but transcripts appeared to correlate with intracellular H2O2 contents, which functions as well-known signaling molecule in developmental senescence. The abundance of SSPs in leaf material transiently progressed from the oldest leaves to the youngest. Moreover, stems also exhibited short-term production of SSPs, which hints at an interim storage function. In order to decipher whether hydrogen peroxide also functions as a signaling molecule in nitrogen deficiency-induced senescence, we analyzed hydrogen peroxide contents after complete nitrogen depletion in oilseed rape and Arabidopsis plants. In both cases, hydrogen peroxide contents were lower in nitrogen deficient plants, indicating that at least parts of the developmental senescence program appear to be suppressed under nitrogen deficiency. [ABSTRACT FROM AUTHOR]

• Cadmium soil pollution and crop accumulation are detectable on national level in China. • Mining activities and sewage irrigation dominate to Cd pollution in China. • Cd pollution in Southwest of China, Middle Yellow River region and North China plain should be taken more seriously. • Cd enrichment models differ with investigated sites and are influenced by pollution sources. Cadmium (Cd) pollution of agricultural soil is of public concern due to its high potential toxicity and mobility. This study aimed to reveal the risk of Cd accumulation in soil and wheat/maize systems, with a specific focus on the source-specific ecological risk, human health risk and Cd enrichment model. For this we investigated more than 6100 paired soil and grain samples with 216 datasets including soil Cd contents, soil pH and grain Cd contents of 85 sites from China. The results showed that mining activities, sewage irrigation, industrial activities and agricultural practices were the critical factors causing Cd accumulation in wheat and maize cultivated sites. Thereinto, mining activities contributed to a higher Cd accumulation risk in the southwest China and Middle Yellow River regions; sewage irrigation influenced the Cd accumulation in the North China Plain. In addition, the investigated sites were classified into different categories by comparing their soil and grain Cd contents with the Chinese soil screening values and food safety values, respectively. Cd enrichment models were developed to predict the Cd levels in wheat and maize grains. The results showed that the models exhibited a good performance for predicting the grain Cd contents among safe and warning sites of wheat (R2 = 0.61 and 0.72, respectively); while the well-fitted model for maize was prone to the overestimated sites (R2 = 0.77). This study will provide national viewpoints for the risk assessments and prediction of Cd accumulation in soil and wheat/maize systems. [Display omitted] [ABSTRACT FROM AUTHOR]

Current atmospheric CO 2 levels are unprecedented for the last 800,000 years and require assessments of their potential effects. Free Air Carbon dioxide Enrichment (FACE) is regarded as the most appropriate exposure system for experimental field investigations. While the early FACE technology involved fans for pre-dilution of CO 2 , now systems both with fans and without fans operating with pure CO 2 are employed. The most often used construction in FACE technology involves peripheral injection from a circular or octagonal plenum with CO 2 release pipes and jet holes surrounding the experimental plot which can create [CO 2 ] gradients across the plot. Here, we present a new FACE design for short vegetation (crops and grassland) that does not involve peripheral injection but distributes CO 2 directly within the plot canopy. The system involves numerous CO 2 release holes in porous tubes that hang down from the upper canopy surface and stretch into the canopy. They can be adjusted in height according to crop growth. Plot size was 2 m × 2 m which allows for a high number of replicates at low CO 2 consumption costs (6.5 tons CO 2 in one season at five replicate plots = 3.5 kg CO 2 per m 2 usable plot area and day during 24hr operation). System performance in terms of CO 2 control was very good both in time and space, with 93% of all instantaneous readings during daylight hours matching ±20% deviation from the set point, and low variation of [CO 2 ] at a given moment within the exposed canopy. Some shading (c. 4% at full canopy development) resulted from the FACE structure at the plots but hardly any other microclimatic artifacts were observed. The FACE system is of modular construction and highly flexible and adaptable to various types of short vegetation. [ABSTRACT FROM AUTHOR]

Leaf nutrient composition and stoichiometry reflect complex interactions of the plant with its environment and are useful traits to explore ecological processes and relationships. In the present study, the foliar elemental compositions of two common Mediterranean woody species, the evergreen broad-leaved Quercus ilex and the coniferous Pinus pinaster growing in an area of Central Italy known for geochemical and geothermal anomalies, were investigated. To assess the site-specific and age-dependent pattern of foliar composition and stoichiometry, macronutrients (C, N, P, K, Mg, S) and trace elements (Al, As, Ba, Cd, Cr, Cu, Fe, Hg, Ni, Pb, Sb, V, Zn) were determined in leaves and needles of three different ages (6-, 12- and 24-month-old) collected from metalliferous (geothermal, mining) and rural areas. Leaves of Q. ilex showed comparatively high concentrations of micronutrients (i.e., Cu, Fe and Zn), while needles of P. pinaster accumulated significantly high concentrations of potentially toxic elements (i.e., As, Pb and S). No significant trend was found in elemental concentrations in relation to the age of leaves and needles. Multi-element stoichiometry of P. pinaster was driven by the geochemical heterogeneity of the sites, suggesting plastic adaptation at the sites with the most selective edaphoclimatic conditions (i.e., patches with nutrient poor and metalliferous soils). On the other hand, the content of both nutrients and potentially toxic elements in Q. ilex leaves varied little across the study area, reflecting stoichiometric stability; this is consistent with the ecophysiological features of Q. ilex as a late-successional species with a dominant role in the ecosystems of the Mediterranean area. Our findings demonstrate the value of foliar stoichiometric traits for understanding plant adaptation in a heterogeneous environment and also the consequences of biotic interactions during succession. [Display omitted] • Needles of P. pinaster accumulate potentially toxic elements, such as As, Pb and S. • Nutritional plasticity distinguishes P. pinaster colonizing mining and geothermal sites. • Invariant nutritional status (homeostasis) characterizes the late-successional Q. ilex. • Multi-elemental foliar composition reveals pine-ecosystem interactions. [ABSTRACT FROM AUTHOR]

Rising CO 2 concentrations associated with drought stress is likely to influence not only aboveground growth, but also belowground plant processes. Little is known about root exudation being influenced by elements of climate change. Therefore, this study wanted to clarify whether barley root exudation responds to drought and CO 2 enrichment and whether this reaction differs between an old and a recently released malting barley cultivar. Barley plants were grown in pots filled with sand in controlled climate chambers at ambient (380 ppm) or elevated (550 ppm) atmospheric [CO 2 ] and a normal or reduced water supply. Root exudation patterns were examined at the stem elongation growth stage and when the inflorescences emerged. At both dates, root exudates were analyzed for different compounds such as total free amino acids, proline, potassium, and some phytohormones. Elevated [CO 2 ] decreased the concentrations in root exudates of some compounds such as total free amino acids, proline, and abscisic acid. Moreover, reduced water supply increased proline, potassium, electric conductivity, and hormone concentrations. In general, the modern cultivar showed higher concentrations of proline and abscisic acid than the old one, but the cultivars responded differentially under elevated CO 2 . Plant developmental stage had also an impact on the root exudation patterns of barley. Generally, we observed significant effects of CO 2 enrichment, watering levels, and, to a lesser extent, cultivar on root exudation. However, we did not find any mitigation of the adverse effects of drought by elevated CO 2 . Understanding the multitude of relationships within the rhizosphere is an important aspect that has to be taken into consideration in the context of crop performance and carbon balance under conditions of climate change., (© 2016 John Wiley & Sons Ltd.)