Heavy Metal Resistance and Accumulation Characteristics in Willows

The resistance of Salix to Cu, Cd, Ni, and Zn was investigated in hydroponic culture, with phytoextraction potential evaluated for Cu. Root elongation (indicative of resistance level) was significantly affected, with considerable variation between and within individual clones. Resistance appeared to be clone- or hybrid-specific, rather than species-specific. S. caprea clones (and hybrids) were among the most resistant, but a secondary S. caprea clone from a different provenance was much less tolerant. S. viminalis and S. triandra clones were the most sensitive. Highest resistance was found in response to Cd, while Cu and Ni were extremely toxic. A resistant S. caprea ecotype originating from a metalliferous mine spoil was identified using this technique. Copper concentration reached a maximum of 2000, 400, and 82 μg g^-1 (d.wt) in roots, wood, and foliage, respectively, after 1 month in hydroponic culture. The level of variation in the response of Salix to metals may cause difficulties in phytoremediation screening programs, but may be essential in providing genetic variation for selection of metal resistance traits, where the contaminant profile is heterogeneous, mixed, or subject to change. Clone selection for metal phytoextraction is feasible, but a longer field-scale study on metal-contaminated soils is needed before their role in phytoremediation can be confirmed.     

基因工程改良植物重金属抗性与富集能力的研究进展

基于分子水平上对植物吸收、解毒、忍耐以及超富集重金属的几个关键步骤的认识,以及一些功能基因相继在细菌、酵母、植物和动物中被分离、鉴定,近年来,人们利用转基因技术提高植物重金属抗性和富集能力方面已获得进展, 一些功能基因（如gsh1, MerA和ArsC)及其工程植物已显示出植物修复产业化潜力。特别对转基因技术所采取的分子生物学途径、达到的效果以及存在的问题进行了详述,对今后研究的重点和策略进行了探讨。     

Photosynthetic Carbon Metabolism in Photoautotrophic Cell Suspension Cultures Grown at Low and High CO(2)

Photosynthetic carbon metabolism was characterized in four photoautotrophic cell suspension cultures. There was no apparent difference between two soybean (Glycine max) and one cotton (Gossypium hirsutum) cell line which required 5% CO₂ for growth, and a unique cotton cell line that grows at ambient CO₂ (660 microliters per liter). Photosynthetic characteristics in all four lines were more like C₃ mesophyll leaf cells than the cell suspension cultures previously studied. The pattern of ¹⁴C-labeling reflected the high ratio of ribulosebisphosphate carboxylase to phosphoenolpyruvate carboxylase activity and showed that CO₂ fixation occurred primarily by the C₃ pathway. Photorespiration occurred at 330 microliters per liter CO₂, 21% O₂ as indicated by the synthesis of high levels of ¹⁴C-labeled glycine and serine in a pulse-chase experiment and by oxygen inhibition of CO₂ fixation. Short-term CO₂ fixation in the presence and absence of carbonic anhydrase showed CO₂, not HCO₃⁻, to be the main source of inorganic carbon taken up by the low CO₂-requiring cotton cells. The cells did not have a CO₂-concentrating mechanism as indicated by silicone oil centrifugation experiments. Carbonic anhydrase was absent in the low CO₂-requiring cotton cells, present in the high CO₂-requiring soybean cell lines, and absent in other high CO₂ cell lines examined. Thus, the presence of carbonic anhydrase is not an essential requirement for photoautotrophy in cell suspension cultures which grow at either high or low CO₂ concentrations.     

Photosynthetic Carbon Metabolism in Leaves and Isolated Chloroplasts from Spinach Plants Grown under Short and Intermediate Photosynthetic Periods

Responses of foliar and isolated intact chloroplast photosynthetic carbon metabolism observed in spinach (Spinacia oleracea cv Wisconsin Bloomsdale) plants exposed to a shortened photosynthetic period (7-hour light/17-hour dark cycle), were used as probes to examine in vivo metabolic factors that exerted rate determination on photosynthesis (PS) and on starch synthesis. Compared with control plants propagated continuously on a 12-hour light/12-hour dark cycle, 14 to 15 days were required, subsequent to a shift from 12 to 7 hours daylength, for 7-hour plants to begin to grow at rates comparable to those of 12-hour daylength plants. Because of shorter daily durations of PS, daily demand for photosynthate by growth processes appeared to be greater in the 7-hour than in the 12-hour plants. The result was that 7-hour plants established a 1.5- to 2.0-fold higher total PS rate than 12-hour plants.

Intact chloroplasts isolated from the leaves of 7-hour plants (7-h PLD) displayed 1.5- to 2.0-fold higher PS rates than plastids isolated from 12-hour plants (12-h PLD). Plastid lamellae prepared from 7- and 12-h PLD isolates displayed equivalent rates of ferredoxin-dependent ATP and NADPH photoformation indicating that electron transport processes were not factors in the establishment of higher 7-h PLD PS rates. Analyses, both in leaves as well as intact PLD isolates, of dark to light transitional increases in Calvin cycle intermediates, e.g., ribulose-1,5-bisphosphate (RuBP) and 3-phosphoglycerate (3-PGA), as well as estimations of activities of RuBP carboxylase and fructose-1,6-bisphosphate phosphatase, indicated that 7-hour plant leaves displayed higher PS rates (than 12-hour plants), because there was a higher magnitude of activity of the Calvin cycle.

Although both the foliar level of starch and sucrose, as well as starch synthesis rate, often was higher in 7-hour compared with 12-hour plant foliage, the higher 7-hour plant total PS rates indicated that maximal sucrose and starch levels did not mediate any `feedback' inhibition of PS. The higher 7-hour plant foliar and PLD PS rates resulted in higher glucose-1-P levels as well as a higher ratio of 3-PGA:Pi, both factors of which would enhance the activity of chloroplast ADP-glucose pyrophosphorylase, and which were attributed to be causal to the higher starch synthesis rates observed in 7-hour plant foliage and PLD isolates.

     

鄱阳湖北段白鹭和苍鹭重金属富集特征比较

水鸟对重金属的富集水平及特征是了解湿地生态系统健康状况、水鸟生境安全的重要渠道。2016年通过非损伤取样方式采集了鄱阳湖北段白鹭Egretta garzetta和苍鹭Ardea cinerea各20个卵壳样品,并收集了2种鹭鸟觅食地的土壤样品9份,利用电感耦合等离子体质谱仪对卵壳和土样中铬(Cr)、铜(Cu)、镍(Ni)、锌(Zn)、砷(As)、铅(Pb)、镉(Cd)、汞(Hg)8种重金属的残留量进行了测量,分析了重金属在2种鹭鸟卵壳中的残留量,在此基础上分析了该区域2种鹭鸟对土壤重金属富集特征。研究结果表明,8种重金属中,白鹭和苍鹭卵壳重金属残留量均以Zn最高、Cd最低。苍鹭的Pb残留量极显著高于白鹭(P<0.01)。白鹭和苍鹭卵壳对Hg的生物富集系数最高,As的最低,而苍鹭对Pb的生物富集系数极显著高于白鹭(P<0.01)。     

Characteristics of Naturally Grown Biofilms in Deep Groundwaters and Their Heavy Metal Sorption Property in a Deep Subsurface Environment

Two biofilm samples were collected from anaerobic groundwater in the depth range of 158.8–199.4 m in a borehole drilled in the Tono area, Japan, to understand their effects on the migration behavior of heavy metals in subsurface environments. The depth range is featured geologically by the lignite formation of sedimentary rocks that bear a uranium ore and the underlying granitic formation. Microbiomes of the derived biofilms, as well as of the ambient bacterioplankton, were characterized based on 16S rRNA gene sequences (clones) or phylotypes, and their heavy metal sorption properties were examined with reference to geochemical features of groundwaters. Phylotypic compositions of the four microbiomes, i.e., of biofilm vs. planktonic bacteria as well as in granitic vs. sedimentary rock groundwaters showed significant differences. In addition, each microbiome was dominated by one or two distinctive phylotypes. In bacterioplankton, the phylotype related to a betaproteobacterial environmental clone dominated 54% of the sequenced clones derived from sedimentary rock groundwater, whereas those related to Denitratisoma oestradiolicum and Clostridium sp. dominated 45% and 37%, respectively, of the clones derived from granitic groundwater. In biofilms, the phylotypes related to Methylobacillus flagellatus and Ignavibacterium album accounted for 77% and 78% of the clones of the biofilms derived from the sedimentary rock and granitic groundwaters, respectively. Chemical and mineralogical analyses demonstrated that high amounts of heavy metals such as Fe, Ni, Cu, Zn, As, Cd, Pb, Th and U accumulated in the biofilms; and their sorption properties varied between biofilms presumably with influences of co-occurring Fe-hydroxides and sulfide minerals under the redox conditions of approximately ?360 to 0 mV in subsurface environments. The biofilm-mineral interaction provides an implication for possible retardation of radionuclide migration in subsurface hydrology, which is of practical interest in geological disposal systems for high-level radioactive waste.     

Heavy Metal Contamination in Roadside Soil and Their Mobility in Relations to pH and Organic Carbon

Concentrations of Pb, Zn, Cd, Ni, Cu, Cr, and Mn were determined to assess the impact of automobiles on heavy metal contamination of roadside soil. Soil samples at four polluted sites and a control site were collected at a depth of 0, 2, 5, 10, 15, 20, 30?cm. A comparison of elemental levels between polluted and control sites exhibited exceptionally higher concentrations at the former sites. The Pb levels in polluted sites varied from 70 to 280.5?µgg^?1and it rapidly decreased with depth. Similarly, mean concentrations of Zn, Cd, Ni, Cu, Cr, and Mn were significantly higher at polluted sites and followed a decreasing trend with the increase in depth. Correlation coefficients between heavy metals and traffic density were positively significant except for nickel. Profile samples showed that Pb, Zn, Cd, Cu, and Mn were largely concentrated in the top 5?cm confirming airborne contamination. The vertical movement and partitioning of metals, except Ni and Cr, exhibited predominant association with soil pH and organic carbon. The results have been presented using Heavy Metal Index.     

陕西省主要蔬菜产区蔬菜重金属污染状况分析与评价

以GB18406．1-2001无公害蔬菜标准为评价依据．对陕西省8个蔬菜主产区的127个蔬菜样品中汞、砷、铅、镉和铬5种重金属污染状况进行分析评价。结果表明,陕西省主要蔬菜产区蔬菜重金属污染以铅污染为主。茄果类和瓜菜类蔬菜铅污染严重,绿叶类蔬菜铅污染相对较轻．其它4种重金属污染未超过国家标准,其中各产区均未检出镉。铅污染程度的大小顺序足成阳秦都〉宝鸡岐山蔡家坡〉汉中汉台〉渭南临渭。成阳泾阳、宝鸡太白、汉中城固、渭南大荔蔬菜产区5种蓖金瞒均未超标．具备发展无公害蔬菜生产基地条件。     

Double Knockout Mutants of Arabidopsis Grown under Normal Conditions Reveal that the Plastidial Phosphorylase Isozyme Participates in Transitory Starch Metabolism

In leaves of two starch-related single-knockout lines lacking either the cytosolic transglucosidase (also designated as disproportionating enzyme 2, DPE2) or the maltose transporter (MEX1), the activity of the plastidial phosphorylase isozyme (PHS1) is increased. In both mutants, metabolism of starch-derived maltose is impaired but inhibition is effective at different subcellular sites. Two constitutive double knockout mutants were generated (designated as dpe2-1 × phs1a and mex1 × phs1b) both lacking functional PHS1. They reveal that in normally grown plants, the plastidial phosphorylase isozyme participates in transitory starch degradation and that the central carbon metabolism is closely integrated into the entire cell biology. All plants were grown either under continuous illumination or in a light-dark regime. Both double mutants were compromised in growth and, compared with the single knockout plants, possess less average leaf starch when grown in a light-dark regime. Starch and chlorophyll contents decline with leaf age. As revealed by transmission electron microscopy, mesophyll cells degrade chloroplasts, but degradation is not observed in plants grown under continuous illumination. The two double mutants possess similar but not identical phenotypes. When grown in a light-dark regime, mesophyll chloroplasts of dpe2-1 × phs1a contain a single starch granule but under continuous illumination more granules per chloroplast are formed. The other double mutant synthesizes more granules under either growth condition. In continuous light, growth of both double mutants is similar to that of the parental single knockout lines. Metabolite profiles and oligoglucan patterns differ largely in the two double mutants.During the last two decades, biochemical analyses of starch metabolism in higher plants have been favored by the availability of large sets of insertion mutants deficient in a single starch-related gene product. Based on phenotypical characterization of these mutants followed by the identification of the respective locus in the genome, novel starch-related proteins were discovered that reside inside the plastid, in the cytosol, in the nucleus, and in the plastidial envelope membranes. Taken together, these results have largely altered the current view on starch metabolism (Zeeman et al., 2010; Fettke et al., 2012a; Smith, 2012).Despite this progress, phenotypical analyses of starch-related mutants are complex and, under certain circumstances, yield misleading conclusions. Loss of function of metabolic steps may cause the entire starch synthesizing or degrading process to become nonfunctional. In this case, mutants are expected to have starch levels that are significantly altered. If, however, single knockout mutants are capable of partially or fully compensating the loss of function by other routes, the resulting phenotypes are less obvious and more difficult to predict. Carbon fluxes through existing paths may be enhanced, or novel metabolic routes may be established that compensate the lost function. As an example, leaves of Arabidopsis (Arabidopsis thaliana) mutants constitutively lacking the plastidial hexose-phosphate isomerase strongly express a distinct plastidial Glc-6-P/orthophosphate antiporter isoform that in wild-type plants is found only in heterotrophic tissues (Kunz et al., 2010). In mesophyll cells of the mutant, the reductive pentose phosphate cycle cannot drive assimilatory starch biosynthesis, as chloroplasts are unable to convert Fru-6-P to Glc-6-P. However, their capacity of transporting Glc-6-P between the cytosolic and the chloroplastic compartment is strongly increased. Furthermore, nonfunctionality of some starch-related proteins can lead to enlarged or diminished metabolite pools that via sensing processes, lead to cellular alterations distant from central carbon metabolism. This complexity is evidenced by several starch-related Arabidopsis mutants that possess a largely altered plastidial ultrastructure and exhibit premature degradation of the entire chloroplast (Stettler et al., 2009; Cho et al., 2011).Furthermore, several starch-related enzymes are capable of forming homomeric or heteromeric complexes that are functionally relevant but, to some extent, variable (Delatte et al., 2005; Utsumi and Nakamura, 2006; Kubo et al., 2010; Emes and Tetlow, 2012; Nakamura et al., 2012; Streb et al., 2012).In starch or glycogen storing prokaryotic and eukaryotic cells, α-glucan phosphorylase (EC 2.4.1.1) is common. Initially, this enzyme was considered to be the main starch synthesizing activity (Hanes, 1940). Later, both starch and glycogen synthases have been discovered that utilize either ADPglucose or UDPglucose (or both; Deschamps et al., 2006) as hexosyl donor. Ample evidence has been presented that these enzymes are essential biosynthetic enzymes (Ballicora et al., 2003; Zeeman et al., 2010; Roach et al., 2012; Palm et al., 2013). Furthermore, it is widely accepted that in glycogen-storing cells, phosphorylase is indispensible for the degradation of the storage polysaccharide (Hwang et al., 1989; Alonso-Casajús et al., 2006; Wilson et al., 2010; Roach et al., 2012; Gazzerro et al., 2013).In plant cells, the metabolic function of phosphorylase is more complex and far from being clear. In lower and higher plants, two distinct phosphorylase types exist as plastid- and cytosol-specific isozymes and are designated as Pho1 (or, in Arabidopsis, PHS1) and Pho2 (PHS2), respectively. Based on the large differences in the affinities for glycogen, the plastidial and the cytosolic phosphorylases are also named as low-affinity (L-type) and high-affinity (H-type) isozymes, respectively. As starch is restricted to the plastids, only the Pho1 (PHS1) type appears to possess direct access to native starch and/or plastidial starch-derived α-glucans.Conflicting phenotypical features have been reported for several mutants possessing altered levels of the plastidial phosphorylase isozyme(s). In the starch-related mutant4 of the unicellular green alga Chlamydomonas reinhardtii, the lack of one plastidial Pho1 isozyme (designated as PhoB) was associated with a lower cellular starch content, abnormally shaped granules, a modified amylopectin structure, and an elevated amylose-to-amylopectin ratio when the cells were kept under nitrogen limitation (Dauvillée et al., 2006). These phenotypical features suggest an involvement of the plastidial phosphorylase PhoB in the biosynthesis of a storage polysaccharide resembling the reserve starch of higher plants. Similarly, a rapid incorporation of ¹⁴C into starch was observed when tuber discs from various transgenic potato lines were incubated with [U-¹⁴C]Glc-1-P. The rate of starch labeling was found to reflect the activity of the plastidial phosphorylase isozyme Pho1 (Fettke et al., 2010, 2012b). By contrast, transgenic potato (Solanum tuberosum) lines have been generated that due to expression of an antisense construct, possess a largely diminished total Pho1 activity in leaves. Leaf starch content is essentially unchanged compared with that of the wild-type plants, suggesting that under normal growth conditions, the plastidial phosphorylase is not necessarily involved in starch metabolism or, alternatively, can easily be replaced by other enzymes (Sonnewald et al., 1995). Likewise, the phenotype (including leaf starch content) of an Arabidopsis mutant lacking functional PHS1 has been reported not to differ from the wild type when the plants were grown under normal conditions. However, under water stress conditions, significantly more local leaf lesions have been reported to occur (Zeeman et al., 2004).When leaf discs from bean (Phaseolus vulgaris) or Arabidopsis plants were exposed to conditions favoring photorespiration (i.e. an atmosphere consisting of 30% [v/v] O₂ and 70% [v/v] N₂ but lacking CO₂), transitory starch was degraded in the light at a high rate and the plastidial Glc-6-P pool increased. In Arabidopsis mutants deficient in PHS1, the Glc monophosphate pool did not respond to photorespiratory conditions (Weise et al., 2006). These data lead to the conclusion that in illuminated leaves with very high rates of photorespiration, PHS1 is involved in the conversion of starch to Glc monophosphates but does not to participate in the nocturnal starch degradation.When studying several starch-related Arabidopsis mutants, we noticed that two single knockout mutations that both affect the maltose metabolism but differ in the subcellular location of the target protein possess a significantly increased PHS1 activity (Malinova et al., 2011a, 2011b). One mutant constitutively lacks the functional cytosolic transglucosidase (also designated as disproportionating enzyme2; DPE2) and, therefore, the cytosolic route of starch-derived maltose metabolism is impaired (Chia et al., 2004; Lu and Sharkey, 2004). The other mutant does not express the plastidial maltose transporter MEX1, resulting in a massively enlarged maltose pool (Niittylä et al., 2004). Thus, in the two mutants, the metabolism of starch-derived maltose is blocked at different subcellular sites, i.e. the cytosol and the chloroplast. The enhanced PHS1 activity as observed for the two mutants is difficult to explain unless a more general function of the phosphorylase isozyme in starch metabolism is assumed.For a detailed functional analysis of PHS1-related processes, we generated two types of constitutive PHS1-deficient double knockout mutants (DPE2 plus PHS1 or MEX1 plus PHS1) and studied their phenotypes in more detail under various experimental conditions. Shoot growth and leaf chlorophyll content are reduced when the plants are grown under a light-dark regime, but under continuous illumination, both effects are far less pronounced. Based on these data, we propose that the plastidial phosphorylase participates in both the turnover of transitory starch and in the maintenance of intact chloroplasts.     

Health Risks Assessment of Heavy Metal Pollution in the Soil-Crop System from an E-Waste Dismantling Area

Soil is an essential resource for agricultural production. In order to investigate the pollution situation of heavy metals in the soil-crop system in the e-waste dismantling area, the crop and soil samples (226 pairs, including leaf vegetables, solanaceous vegetables, root vegetables, and fruits) around the e-waste dismantling area in southeastern Zhejiang Province were collected. The concentrations of Cd, Cu, Pb, and Cr were determined. The average concentrations of Cd, Cu, Pb, and Cr in soils were 0.94, 107.79, 80.28, and 78.14 mg kg^-1, respectively, and their corresponding concentrations in crops were 0.024, 0.7, 0.041, and 0.06 mg kg^-1, respectively. The transfer capacity of leaf vegetables was significantly higher than that of non-leaf vegetables, and the accumulation of four heavy metals in crops tended to be Cd > Cu > Cr/Pb. The pollution index’s results revealed that the soil pollution degree under different land uses ranked as root vegetables soil > leaf vegetables soil > solanaceous vegetables soil > fruit soil. The carcinogenic and non-carcinogenic risks of heavy metal exposure were ranked as food intake > accidental ingestion > dermal contact > inhalation. The comprehensive non-carcinogenic risk was ranked as Cr > Cd > Pb/Cu. Our results could be used to provide useful information for further crop cultivation layout in the study area, which can guarantee the local residents’ health and food safety.

     

Aspects of Growth and Metabolism in a Suspension Culture of Acer pseudoplatanus (L. ) Grown on a Glycerol Carbon Source

A suspension culture of Acer pseudoplatanus cells was transferredfrom medium containing 2% (w/v) glucose to an identical onecontaining glycerol at 2% (w/v) as the sole carbon source. Thepatterns of cell number increase, dry weight increase, and changesin packed cell volume showed marked differences as a resultof this transfer. The glucose-grown cultures contained a small proportion of cellsof exceptionally large diameter, and transfer to the glycerolcarbon source appeared to bring about a considerable increasein their number. These larger cells, in both glucose- and glycerol-containingcultures, exhibited considerable differences in cell wall architecturewhen compared with their smaller counterparts. They appearedmore irregular, and had much looser cellulose microfibril arrangementin their outer layers     

Characterization of Plant-Growth-Promoting Effects and Concurrent Promotion of Heavy Metal Accumulation in the Tissues of the Plants Grown in The Polluted Soil by Burkholderia Strain LD-11

Plant-growth-promoting (PGP) bacteria especially with the resistance to multiple heavy metals are helpful to phytoremediation. Further development of PGP bacteria is very necessary because of the extreme diversity of plants, soils, and heavy metal pollution. A Burkholderia sp. strain, numbered LD-11, was isolated, which showed resistances to multiple heavy metals and antibiotics. It can produce indole-3-acetic acid, 1-aminocyclopropane-1-carboxylic acid deaminase and siderophores. Inoculation with the LD-11 improved germination of seeds of the investigated vegetable plants in the presence of Cu, promoted elongation of roots and hypocotyledonary axes, enhanced the dry weights of the plants grown in the soils polluted with Cu and/or Pb, and increased activity of the soil urease and the rhizobacteria diversity. Inoculation with the LD-11 significantly enhanced Cu and/or Pb accumulation especially in the roots of the plants grown in the polluted soils. Notably, LD-11 could produce siderophores in the presence of Cu. Conclusively, the PGP effects and concurrent heavy metal accumulation in the plant tissues results from combined effects of the above-mentioned multiple factors. Cu is an important element that represses production of the siderophore by the bacteria. Phytoremediation by synergistic use of the investigated plants and the bacterial strain LD-11 is a phytoextraction process.     

Focus on Metabolism: Changes in Whole-Plant Metabolism during the Grain-Filling Stage in Sorghum Grown under Elevated CO2 and Drought

Projections indicate an elevation of the atmospheric CO₂ concentration ([CO₂]) concomitant with an intensification of drought for this century, increasing the challenges to food security. On the one hand, drought is a main environmental factor responsible for decreasing crop productivity and grain quality, especially when occurring during the grain-filling stage. On the other hand, elevated [CO₂] is predicted to mitigate some of the negative effects of drought. Sorghum (Sorghum bicolor) is a C₄ grass that has important economical and nutritional values in many parts of the world. Although the impact of elevated [CO₂] and drought in photosynthesis and growth has been well documented for sorghum, the effects of the combination of these two environmental factors on plant metabolism have yet to be determined. To address this question, sorghum plants (cv BRS 330) were grown and monitored at ambient (400 µmol mol⁻¹) or elevated (800 µmol mol⁻¹) [CO₂] for 120 d and subjected to drought during the grain-filling stage. Leaf photosynthesis, respiration, and stomatal conductance were measured at 90 and 120 d after planting, and plant organs (leaves, culm, roots, prop roots, and grains) were harvested. Finally, biochemical composition and intracellular metabolites were assessed for each organ. As expected, elevated [CO₂] reduced the stomatal conductance, which preserved soil moisture and plant fitness under drought. Interestingly, the whole-plant metabolism was adjusted and protein content in grains was improved by 60% in sorghum grown under elevated [CO₂].Global food demand is projected to increase up to 110% by the middle of this century (Tilman et al., 2011; Alexandratos and Bruinsma, 2012), particularly due to a rise in world population that is likely to plateau at about 9 billion people (Godfray et al., 2010). Additionally, the average concentration of atmospheric CO₂ ([CO₂]) has increased 1.75 µmol mol⁻¹ per year between 1975 and today, reaching 400 µmol mol⁻¹ in April 2015 (NOAA, 2015). According to the A2 emission scenario from the U.S. Environmental Protection Agency, in the absence of explicit climate change policy, atmospheric CO₂ concentrations will reach 800 µmol mol⁻¹ by the end of this century. The increasing atmospheric [CO₂] is resulting in global climate changes, such as reduction in water availability and elevation in temperature. These factors are expected to heavily influence food production in the next years (Godfray and Garnett, 2014; Magrin et al., 2014).Sorghum (Sorghum bicolor) is a C₄ grass, considered a staple food grain for millions of the poorest and most food-insecure people in the semiarid tropics of Africa, Asia, and Central America, serving as an important source of energy, proteins, vitamins, and minerals (Taylor et al., 2006). Moreover, this crop is used for animal feed and as industrial raw material in developed countries such as the United States, which is the main world producer (FAO, 2015). With a fully sequenced genome (Paterson et al., 2009) and over 45,000 accessions representing a large geographic and genetic diversity, sorghum is a good model system in which to study the impact of global climate changes in C₄ grasses.The increase in [CO₂] in the atmosphere, which is the main driver of global climate changes (Meehl et al., 2007), is predicted to boost photosynthesis rates and productivity in a series of C₃ legumes and cereals, mainly due to a decrease in the photorespiration process (Grashoff et al., 1995; Long et al., 2006). On the contrary, due to their capacity to concentrate CO₂ in bundle sheath cells and reduce photorespiration to virtually zero, C₄ plants are unlikely to respond to the elevation of atmospheric [CO₂] (Leakey, 2009). However, even for C₄ plants, elevated [CO₂] can ameliorate the effects caused by drought, maintaining higher photosynthetic rates. This is due to an improvement in the efficiency of water use that is achieved by the reduction in stomatal conductance (Leakey et al., 2004; Markelz et al., 2011).The rate of photosynthesis as well as the redistribution of photoassimilates accumulated in different plant tissues during the day and/or during vegetative growth are crucial to grain development, and later, to its filling (Schnyder, 1993). Due to this relationship, any environmental stress such as drought occurring during the reproductive phase has the potential to result in poor grain filling and losses in yield (Blum et al., 1997). For instance, postanthesis drought can cause up to 30% decrease in yield (Borrell et al., 2000). It is also known that elevated [CO₂], drought, high temperature, and any combinations of these stresses can lead to significant changes in grain composition (Taub et al., 2008; Da Matta et al., 2010; Uprety et al., 2010; Madan et al., 2012), suggesting diverse metabolic alterations and/or adaptations that occur in the plant when it is cultivated in such conditions.Although the impacts of elevated [CO₂] and drought on photosynthesis and the growth of sorghum have been well documented (Conley et al., 2001; Ottman et al., 2001; Wall et al., 2001), no attention has been given to the impact of the combination of these two environmental changes on plant metabolism and composition. Regarding physiology, studies on the growth of sorghum under elevated [CO₂] and drought showed an increase of the net assimilation rate of 23% due to a decrease of 32% in stomatal conductance (Wall et al., 2001). This resulted in sorghum’s ability to use water 17% more efficiently (Conley et al., 2001). An improvement in the final overall biomass under elevated [CO₂] and drought has also been described (Ottman et al., 2001), but without a significant effect in grain yield (Wall et al., 2001).Few studies have been monitoring metabolic pathways in plants under elevated [CO₂] (Li et al., 2008; Aranjuelo et al., 2013) and drought (Silvente et al., 2012; Nam et al., 2015; Wenzel et al., 2015). Furthermore, to our knowledge, there are only two reports in which metabolite profiles or metabolic pathways were investigated under the combination of these two environmental conditions (Sicher and Barnaby, 2012; Zinta et al., 2014). Although it is widely accepted that whole-plant metabolism and composition can impact grain filling and yield, metabolic studies conducted so far have focused on a specific plant organ. For instance, Sicher and Barnaby (2012) analyzed the metabolite profile of leaves from maize (Zea mays) plants that were grown under elevated [CO₂] and drought, but they did not show how those environmental changes could have affected the metabolism of other tissues (e.g. culm and roots) or how they might have influenced the biomass or grain composition.In order to address how the combination of elevated [CO₂] and drought can modify whole-plant metabolism as well as biomass composition in sorghum, this study aimed to (1) evaluate photosynthesis, growth, and yield; (2) underline the differences in biomass composition and primary metabolite profiles among leaves, culm, roots, prop roots, and grains; and (3) determine the effect of elevated [CO₂] and drought on the primary metabolism of each organ.     

Assessment of Heavy Metal Pollution in Water and Sediments from the Ghalechay River,Baychebagh Copper Mine Area,Iran

The concentrations of selected heavy metals in sediments and waters in Baychebagh copper mine were determined using ICP-OES. Except for Co, the average concentrations of Cd, Cu, Pb, and Zn in sediments from the Ghalechay River in the district exceed the world-average shale and continental upper crust value. Enrichment factors for Pb, Cu, and Cd were significantly enriched in sediments, indicating environmental contamination. Geoaccumulation index calculated for different sampling stations indicates that the sediments are unpolluted with respect to Co and Zn while unpolluted to moderately polluted with Cu and highly polluted with Pb and Cd. The Sediment Quality Guidelines (SQGs) suggest that Cd and Pb may pose the highest risk for the environment. Sequential extraction analyses of sediments revealed that Cu, Co, Pb, and Zn bound to extractable, carbonate, reducible and oxidizable fractions are lower than residual fraction. About 10% of the total Pb was associated with the exchangeable fraction, indicating remobilization, while Cd (89%), Pb (73%) Co (58%), Cu (76%), and Zn (68%) closely associated with the residual and oxidizable fractions, resulting in their environmental immobility. The residual forms are not expected to be released under normal conditions in the river and could be considered an inert phase.     

营养杯对长喙田菁在铅锌尾矿上的生长、固氮和重金属积累的影响

设置移栽时营养杯的有无及其大小作试验,研究长喙田菁在乐昌铅锌矿强酸化尾矿上的生长、固氮和积累重金属情况。结果表明,强酸性(pH<3)是限制植物定植的主要因素,在pH=5-7情况下,长喙田菁能在该尾矿库中定植、生长和固氮,表现出良好的适应性。未带营养杯移栽的长喙田菁在尾矿上生长84d,其株高117cm、茎基部直径1.35cm、单株生物量(干物质)20.2g、单位面积生物量(干物质)2828kghm-2、氮素积累量40kghm-2;带营养杯移栽的上述各指标分别达到140-144cm、1.59-1.68cm、36.6-38.8g、5124-5432kghm-2和77-107kghm-2,均显著高于未带营养杯处理的。长喙田菁根部铅、锌、铜、镉含量均最高,其次为茎,叶中最低;长喙田菁的4种重金属积累量为锌(186-221mgkg-1)>铅(96-145mgkg-1)>铜(17-30mgkg-1)>镉(3-4mgkg-1)。带营养杯移栽能有效提高长喙田菁的产量和氮积累量,且明显降低其体内的重金属含量。试验证明长喙田菁是较理想的铅锌矿尾矿废弃地植被重建的先锋植物。     

Environmental Monitoring of Heavy Metal Status and Human Health Risk Assessment in the Agricultural Soils of the Jinxi River Area,China

Soil contamination with heavy metals is one of the main environmental concerns in China, mainly owing to rapid industrialization and mining activities in certain areas. The current study aimed at monitoring the levels of heavy metals in soils of the industrial areas along the Jinxi River and surrounding Lake Qingshan. In addition, a health risk assessment for humans in contact with these soils was also conducted. The results revealed that the soils of the studied areas were contaminated with Cr, Cu, As, Se, Cd, Pb, and Zn and that the industrial activities were the main source of soil contamination therein. Furthermore, soils of the sites adjacent to Lin’an city exhibited higher levels of heavy metals than the upstream and Lake Qingshan sites. Most of the studied heavy metals tended to concentrate in the fine soil fractions (PM100, PM10, and PM2.5). Calculation of the hazard index (HI) revealed that humans, especially children, have potential health risks. Moreover, As was found to contribute to more magnitude of cancer risks. Thus, we concluded that the unmanaged development negatively affects the Chinese environment and human health. Furthermore, fine fractions of soil particles should be considered for risk assessment.     

Metal Resistance and Lithoautotrophy in the Extreme Thermoacidophile Metallosphaera sedula

Archaea such as Metallosphaera sedula are thermophilic lithoautotrophs that occupy unusually acidic and metal-rich environments. These traits are thought to underlie their industrial importance for bioleaching of base and precious metals. In this study, a genetic approach was taken to investigate the specific relationship between metal resistance and lithoautotrophy during biotransformation of the primary copper ore, chalcopyrite (CuFeS₂). In this study, a genetic system was developed for M. sedula to investigate parameters that limit bioleaching of chalcopyrite. The functional role of the M. sedula copRTA operon was demonstrated by cross-species complementation of a copper-sensitive Sulfolobus solfataricus copR mutant. Inactivation of the gene encoding the M. sedula copper efflux protein, copA, using targeted recombination compromised metal resistance and eliminated chalcopyrite bioleaching. In contrast, a spontaneous M. sedula mutant (CuR1) with elevated metal resistance transformed chalcopyrite at an accelerated rate without affecting chemoheterotrophic growth. Proteomic analysis of CuR1 identified pleiotropic changes, including altered abundance of transport proteins having AAA-ATPase motifs. Addition of the insoluble carbonate mineral witherite (BaCO₃) further stimulated chalcopyrite lithotrophy, indicating that carbon was a limiting factor. Since both mineral types were actively colonized, enhanced metal leaching may arise from the cooperative exchange of energy and carbon between surface-adhered populations. Genetic approaches provide a new means of improving the efficiency of metal bioleaching by enhancing the mechanistic understanding of thermophilic lithoautotrophy.