Energy deprivation affects nitrogen assimilation and fatty acid biosynthesis leading to leaf chlorosis under waterlogging stress in the endangered Abies koreana.

Energy deprivation triggers various physiological, biochemical and molecular changes in plants under abiotic stress. We investigated the oxidative damages in the high altitude grown conifer Korean fir (Abies koreana) exposed to waterlogging stress. Our experimental results showed that waterlogging stress led to leaf chlorosis, 35 days after treatment. A significant decrease in leaf fresh weight, chlorophyll and sugar content supported this phenotypic change. Biochemical analysis showed a significant increase in leaf proline, lipid peroxidase and 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical content of waterlogged plants. To elucidate the molecular mechanisms, we conducted RNA-sequencing (RNA-seq) and de novo assembly. Using RNA-seq analysis approach and filtering (P < 0.05 and false discovery rate <0.001), we obtained 134 unigenes upregulated and 574 unigenes downregulated. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis placed the obtained differentially expressed unigenes in α-linoleic pathway, fatty acid degradation, glycosis, glycolipid metabolism and oligosaccharide biosynthesis process. Mapping of unigenes with Arabidopsis using basic local alignment search tool for nucleotides showed several critical genes in photosynthesis and carbon metabolism downregulated. Following this, we found the repression of multiple nitrogen (N) assimilation and nucleotide biosynthesis genes including purine metabolism. In addition, waterlogging stress reduced the levels of polyunsaturated fatty acids with a concomitant increase only in myristic acid. Together, our results indicate that the prolonged snowmelt may cause inability of A. koreana seedlings to lead the photosynthesis normally due to the lack of root intercellular oxygen and emphasizes a detrimental effect on the N metabolic pathway, compromising this endangered tree's ability to be fully functional under waterlogging stress.

Analysis of micro(nano)plastics based on automated data interpretation and modeling: A review.

The widespread presence of micro(nano)plastics (MNPs) in the environment threatens ecosystem integrity, and thus, it is necessary to determine and assess the occurrence, characteristics, and transport of MNPs between ecological components. However, most analytical approaches are cost- and time-inefficient in providing quantitative information with sufficient detail, and interpreting results can be difficult. Alternative analyses integrating novel measurements by imaging or proximal sensing with signal processing and machine learning may supplement these approaches. In this review, we examined published research on methods used for the automated data interpretation of MNPs found in the environment or those artificially prepared by fragmenting bulk plastics. We critically reviewed the primary areas of the integrated analytical process, which include sampling, data acquisition, processing, and modeling, applied in identifying, classifying, and quantifying MNPs in soil, sediment, water, and biological samples. We also provide a comprehensive discussion regarding model uncertainties related to estimating MNPs in the environment. In the future, the development of routinely applicable and efficient methods is expected to significantly contribute to the successful establishment of automated MNP monitoring systems.

Effects of different sizes of polystyrene micro(nano)plastics on soil microbial communities.

Micro(nano)plastic (MNP) pollution in soil environments is a major concern, but the effects of different sizes of MNPs on soil microbial communities, which are crucial in nutrient cycling, has not been well investigated. In this study, we aimed to determine the effects of polystyrene (PS) MNPs of different sizes (0.05-, 0.5-, and 5-µm) on soil microbial activity and community composition. Changes in inorganic N concentration, microbial biomass, and extracellular enzyme activities were determined in soils treated with 100 and 1000 µg PS MNPs g-1 soil during a 40-d incubation experiment. Soil microbial biomass was significantly lowered when soils were treated with 0.5- or 5-µm MNPs at 100 and 1000 µg PS MNPs g-1 soil. NH4+ concentration was higher in soils treated with 5-µm MNPs at 100 and 1000 µg g-1 soil than in the control soils at day 1, suggesting that MNPs inhibited the soil nitrification in short term. In contrast, extracellular enzyme activity was not altered by MNPs. The composition of microbial communities analyzed by Illumina MiSeq sequencing changed; particularly, the relative abundance of several bacteria related to N cycling, such as the genus Rhizomicrobium belonging to Alphaproteobacteria was decreased by 0.5- and 5-µm MNPs. Our study shows that the size of MNPs is an important factor that can determine their effects on soil microbial communities. Therefore, the size effects need to be considered in assessing the environmental impacts of MNPs.

Application of colorimetric sensor in monitoring dissolved CO2 in natural waters.

Dissolved CO2 originating from underground structures at high concentrations may pose a threat to public and environmental health. Therefore, a convenient monitoring technique that allows fast detection of dissolved CO2 needs to be developed. In this study, a low-cost colorimetric CO2 sensor was applied for monitoring dissolved CO2. The sensor is composed of an acrylic reactor, cresol red pH indicator solution, and a gas-permeable membrane, and the performance of the sensor was tested for the detection of dissolved CO2 at the range of 2-800 mg CO2 L-1. Color change of the detection solution within the sensor was mainly dependent on CO2 dissolved in the water sample. This was analyzed using an RGB program that extracts the red, green, and blue intensity of a target color on a scale of 0-255. ΔGB, an index of CO2 concentration corresponding to the change in intensity of green (G) and blue (B) extracted by the RGB program, exhibited a linear relationship with dissolved CO2 concentrations (r2 > 0.95, p < 0.005). In the field, the sensor was able to measure dissolved CO2 between 10 and 411 mg CO2 L-1 within 1 min. Overall, our CO2 sensor has high potential to be used in detection of dissolved CO2 in groundwater and surface waters.

Effects of Graphene Oxide on Germination and Early Growth of Plants.

Owing to its excellent material properties such as large surface area and superb mechanical and thermal characteristics, graphene oxide (GO) is likely to be applied in a variety of environmental fields. These applications may lead to the entrance of GO in terrestrial ecosystems, but there is little research regarding the impact of GO on plants upon such entrances. To analyze the effects of GO on the germination and growth of various plants, the changes in lettuce, radish, perennial ryegrass, alfalfa, and cucumber seeds under GO treatment was studied. Germination rate and growth were analyzed after the seeds were exposed to GO at 0, 0.2, 0.4, 0.8, and 1.6 mg ml-1. For lettuce, the germination rate decreased with GO concentration. However, no significant effects were observed on the germination rate of other plants. On the other hand, the growth of lettuce, alfalfa, and radish decreased under GO treatment. For example, at 1.6 mg ml-1 of GO, the length of shoot and root of lettuce was shortened by 87% and 86%, respectively. Such results indicate that the germination and early growth of plants can be negatively affected in a species-specific manner under high concentrations of GO. Hence, we anticipate that our results may assist in supplementing the legal regulations for the proper disposal of nanomaterials.

Highly efficient colorimetric CO2 sensors for monitoring CO2 leakage from carbon capture and storage sites.

Carbon capture and storage (CCS) technology used for reducing anthropogenic CO2 emissions involves the capture of CO2 from industrial sources and its injection into geological sinks, such as oil reservoirs and abandoned gas fields. To ensure environmental and public safety in implementing CCS technology, efficient CO2-monitoring technology must be developed to detect potential CO2 leakage from CCS sites. Conventional CO2 sensors used for monitoring CCS sites are typically high in cost and require professional staff for maintenance. In this study, we developed a portable and low-cost colorimetric CO2 sensor with high soil CO2 detection efficiency for CCS sites. The sensor consists of a detection solution that contains the pH indicator cresol red encapsulated with a gas-permeable membrane. When CO2 enters the sensor through the membrane, the color of the pH indicator changes and this was quantified using an RGB (red, green, blue) application (app), an app that measures the RGB values of a given color. The change in G and B values of the detection solution showed a significant linear relationship with soil CO2 concentration determined via non-dispersive infra-red (NDIR) CO2 sensor (r2 = 0.98, p = 0.001), and thus these values were used for quantification of CO2 concentration. Tests using CO2-injection chamber showed that the optical CO2 sensors can detect soil CO2 concentration of 0.1 to 30% within a few minutes. Field studies conducted at a natural CO2 vent and an artificial CO2 leakage site showed that the optical CO2 sensors can be applied in analyzing surficial CO2 leakage patterns. The advantage of this optical CO2 sensor when applied to field monitoring is that it is inexpensive and has few installation restrictions. Therefore, this optical CO2 sensor has a strong potential for use in monitoring CO2 leakages from CCS sites.

Effects of silver-graphene oxide on seed germination and early growth of crop species.

Due to its excellent material properties, silver-graphene oxide (Ag-GO) is being studied for diverse applications, such as antimicrobial agents, catalysts and absorbents. Such use of Ag-GO may lead to its release into terrestrial ecosystems, but little is known about the impact of Ag-GO on plants. In the present study, we determined the effects of Ag-GO on seed germination and early growth of crop species by analyzing the germination rate, growth of roots and shoots, hydrogen peroxide (H2O2) accumulation, and the uptake of Ag in alfalfa, radish and cucumber treated with 0.2-1.6 mg mL-1 of Ag-GO. Ag-GO treatment increased the shoot growth of radish at 0.2-1.6 mg mL-1 but decreased that of cucumber at 0.8 mg mL-1. In addition, Ag-GO enhanced the root elongation of radish at 0.2 mg mL-1 but inhibited that of alfalfa at 0.2, 0.8 and 1.6 mg mL-1. Ag-GO treatment induced H2O2 production in alfalfa, radish and cucumber in a concentration-dependent manner. Larger amounts of Ag accumulated in the seedlings as the concentration of Ag-GO increased, and such accumulation suggests that Ag may be transferred to higher trophic levels when plants are exposed to Ag-GO in ecosystems. Our study can, thus, serve as an important basis for setting guidelines for the release of nanomaterials into the environment.

Effects of graphene oxides and silver-graphene oxides on aquatic microbial activity.

Graphene oxide (GO) and silver-graphene oxide (Ag-GO) are used in various fields, such as biotechnology and environmental engineering, due to their unique material properties, including hydrophilicity, high surface area, mechanical strength, and antibacterial activity. With the increase in the usage of such nanomaterials, they are likely to enter the aquatic environment during the manufacturing process, product use, and disposal. However, the effects of GO and Ag-GO on aquatic microbial activities are not well understood. In this study, we aimed to determine the effects of GO and Ag-GO on the aquatic microbial communities inhabiting a river and a lake located in Seoul, South Korea. Unfiltered natural surface water samples were exposed to GO and Ag-GO at a final concentration of 10 to 100 mg L-1 for 48 h. The activity of leucine aminopeptidase was significantly lowered within 1 h of GO and Ag-GO treatments and nitrification rate was significantly lowered. An increase in intracellular lactate dehydrogenase levels of up to 5% was observed in natural waters under GO and Ag-GO treatments compared to the control (0%), indicating cell membrane damage. In addition, generation of intracellular reactive oxygen species increased up to 184% under 100 mg GO L-1 and 102% under 100 mg Ag-GO L-1 treatment compared to the control (0%). Our results indicate that the activities of microorganisms inhabiting natural surface waters may have been inhibited by oxidative stress and cell membrane damage induced by GO and Ag-GO. We believe that our results may contribute to the development of regulatory guidelines on the release of emerging engineered nanomaterials to the environment.

Effects of silver-graphene oxide nanocomposites on soil microbial communities.

Due to the application of silver-graphene oxide (Ag-GO) in diverse fields, it is important to investigate its potential impacts on the environment including soils. In this study, the response of microbial communities in soils treated with Ag-GO synthesized by glucose reduction was determined by analyzing enzyme activities, biomass, and inorganic N concentrations and by pyrosequencing. In soils treated with 0.1-1 mg Ag-GO g-1 soil, the activities of ß-glucosidase, cellobiohydrolase, and xylosidase decreased up to 80% and NO3- concentration decreased up to 82% indicating inhibited nitrification. Within the bacterial community, the relative abundance of Acidobacteria and Cyanobacteria in soils treated with Ag-GO were lower than that in control soil. Meanwhile, the relative abundance of AD3 and Firmicutes tended to increase under Ag-GO treatments. These changes in bacterial community composition reflected lowered activities associated with C and N cycling. On the other hand, microbial biomass showed no distinct change in response to Ag-GO treatment. Our study can serve as important basis in establishing guidelines for regulating the release of nanocomposites such as Ag-GO to the soil environment.

Corrigendum: High-throughput screening of metal-porphyrin-like graphenes for selective capture of carbon dioxide.

This corrects the article DOI: 10.1038/srep21788.

Increased N2O emission by inhibited plant growth in the CO2 leaked soil environment: Simulation of CO2 leakage from carbon capture and storage (CCS) site.

Atmospheric carbon dioxide (CO2) concentrations is continuing to increase due to anthropogenic activity, and geological CO2 storage via carbon capture and storage (CCS) technology can be an effective way to mitigate global warming due to CO2 emission. However, the possibility of CO2 leakage from reservoirs and pipelines exists, and such leakage could negatively affect organisms in the soil environment. Therefore, to determine the impacts of geological CO2 leakage on plant and soil processes, we conducted a greenhouse study in which plants and soils were exposed to high levels of soil CO2. Cabbage, which has been reported to be vulnerable to high soil CO2, was grown under BI (no injection), NI (99.99% N2 injection), and CI (99.99% CO2 injection). Mean soil CO2 concentration for CI was 66.8-76.9% and the mean O2 concentrations in NI and CI were 6.6-12.7%, which could be observed in the CO2 leaked soil from the pipelines connected to the CCS sites. The soil N2O emission was increased by 286% in the CI, where NO3--N concentration was 160% higher compared to that in the control. This indicates that higher N2O emission from CO2 leakage could be due to enhanced nitrification process. Higher NO3--N content in soil was related to inhibited plant metabolism. In the CI treatment, chlorophyll content decreased and chlorosis appeared after 8th day of injection. Due to the inhibited root growth, leaf water and nitrogen contents were consistently lowered by 15% under CI treatment. Our results imply that N2O emission could be increased by the secondary effects of CO2 leakage on plant metabolism. Hence, monitoring the environmental changes in rhizosphere would be very useful for impact assessment of CCS technology.

High-throughput screening of metal-porphyrin-like graphenes for selective capture of carbon dioxide.

Nanostructured materials, such as zeolites and metal-organic frameworks, have been considered to capture CO2. However, their application has been limited largely because they exhibit poor selectivity for flue gases and low capture capacity under low pressures. We perform a high-throughput screening for selective CO2 capture from flue gases by using first principles thermodynamics. We find that elements with empty d orbitals selectively attract CO2 from gaseous mixtures under low CO2 pressures (~10(-3) bar) at 300 K and release it at ~450 K. CO2 binding to elements involves hybridization of the metal d orbitals with the CO2 π orbitals and CO2-transition metal complexes were observed in experiments. This result allows us to perform high-throughput screening to discover novel promising CO2 capture materials with empty d orbitals (e.g., Sc- or V-porphyrin-like graphene) and predict their capture performance under various conditions. Moreover, these findings provide physical insights into selective CO2 capture and open a new path to explore CO2 capture materials.

Effects of graphene oxides on soil enzyme activity and microbial biomass.

Due to recent developments in nanotechnology, nanomaterials (NMs) such as graphene oxide (GO) may enter the soil environment with mostly unknown consequences. We investigated the effects of GO on soil microbial activity in a 59-day soil incubation study. For this, high-purity GO was prepared and characterized. Soils were treated with up to 1 mg GO g(-1) soil, and the changes in the activities of 1,4-ß-glucosidase, cellobiohydrolase, xylosidase, 1,4-ß-N-acetyl glucosaminidase, and phosphatase and microbial biomass were determined. 0.5-1 mg GO g(-1) soil lowered the activity of xylosidase, 1,4-ß-N-acetyl glucosaminidase, and phosphatase by up to 50% when compared to that in the control soils up to 21 days of incubation. Microbial biomass in soils treated with GO was not significantly different from that in control soils throughout the incubation period, and the soil enzyme activity and microbial biomass were not significantly correlated in this study. Our results indicate that soil enzyme activity can be lowered by the entry of GO into soils in short term but it can be recovered afterwards.

Energy-density enhancement of carbon-nanotube-based supercapacitors with redox couple in organic electrolyte.

We demonstrate for the first time that the incorporation of a redox-active molecule in an organic electrolyte can increase the cell voltage of a supercapacitor. The redox molecule also contributes to increasing the cell capacitance by a faradaic redox reaction, and therefore the energy density of the supercapacitor can be significantly increased. More specifically, the addition of redox-active decamethylferrocene in an organic electrolyte results in an approximately 27-fold increase in the energy density of carbon-nanotube-based supercapacitors. The resulting high energy density (36.8 Wh/kg) stems from the increased cell voltage (1.1 V→2.1 V) and cell capacitance (8.3 F/g→61.3 F/g) resulting from decamethylferrocene addition. We found that the voltage increase is associated with the potential of the redox species relative to the electrochemical stability window of the supporting electrolyte. These results will be useful in identifying new electrolytes for high-energy-density supercapacitors.

Large-scale solvothermal synthesis of fluorescent carbon nanoparticles.

The large-scale production of high-quality carbon nanomaterials is highly desirable for a variety of applications. We demonstrate a novel synthetic route to the production of fluorescent carbon nanoparticles (CNPs) in large quantities via a single-step reaction. The simple heating of a mixture of benzaldehyde, ethanol and graphite oxide (GO) with residual sulfuric acid in an autoclave produced 7 g of CNPs with a quantum yield of 20%. The CNPs can be dispersed in various organic solvents; hence, they are easily incorporated into polymer composites in forms such as nanofibers and thin films. Additionally, we observed that the GO present during the CNP synthesis was reduced. The reduced GO (RGO) was sufficiently conductive (σ ≈ 282 S m(-1)) such that it could be used as an electrode material in a supercapacitor; in addition, it can provide excellent capacitive behavior and high-rate capability. This work will contribute greatly to the development of efficient synthetic routes to diverse carbon nanomaterials, including CNPs and RGO, that are suitable for a wide range of applications.

Single-walled carbon nanotubes alter soil microbial community composition.

Recent developments in nanotechnology may lead to the release of nanomaterials into the natural environment, such as soils, with largely unknown consequences. We investigated the effects of single-walled carbon nanotubes (SWCNTs), one of the most widely used nanomaterials, on soil microbial communities by incubation of soils to which powder or suspended forms of SWCNTs were added (0.03 to 1 mg g(-1) soil). To determine changes in soil microbial community composition, phospholipid fatty acid (PLFA) profiles were analyzed at 25th day of the incubation experiment. The biomass of major microbial groups including Gram-positive and Gram-negative bacteria, and fungi showed a significant negative relationship with SWCNT concentration, while the relative abundance of bacteria showed a positive relationship with SWCNT concentration. Furthermore, soils under distinct concentrations of SWCNT treatments had PLFA profiles that were significantly different from one another. Our results indicate that the biomass of a broad range of soil microbial groups is negatively related with SWCNT concentration and upon entry into soils, SWCNTs may alter microbial community composition. Our results may serve as foundation for scientific guideline on regulating the discharge of nanomaterials such as SWCNTs to the soil ecosystem.

Experimental warming studies on tree species and forest ecosystems: a literature review.

Temperature affects a cascade of ecological processes and functions of forests. With future higher global temperatures being inevitable it is critical to understand and predict how forest ecosystems and tree species will respond. This paper reviews experimental warming studies in boreal and temperate forests or tree species beyond the direct effects of higher temperature on plant ecophysiology by scaling up to forest level responses and considering the indirect effects of higher temperature. In direct response to higher temperature (1) leaves emerged earlier and senesced later, resulting in a longer growing season (2) the abundance of herbivorous insects increased and their performance was enhanced and (3) soil nitrogen mineralization and leaf litter decomposition were accelerated. Besides these generalizations across species, plant ecophysiological traits were highly species-specific. Moreover, we showed that the effect of temperature on photosynthesis is strongly dependent on the position of the leaf or plant within the forest (canopy or understory) and the time of the year. Indirect effects of higher temperature included among others higher carbon storage in trees due to increased soil nitrogen availability and changes in insect performance due to alterations in plant ecophysiological traits. Unfortunately only a few studies extrapolated results to forest ecosystem level and considered the indirect effects of higher temperature. Thus more intensive, long-term studies are needed to further confirm the emerging trends shown in this review. Experimental warming studies provide us with a useful tool to examine the cascade of ecological processes in forest ecosystems that will change with future higher temperature.

Synthesis of monoclinic potassium niobate nanowires that are stable at room temperature.

We report the synthesis of KNbO(3) nanowires (NWs) with a monoclinic phase, a phase not observed in bulk KNbO(3) materials. The monoclinic NWs can be synthesized via a hydrothermal method using metallic Nb as a precursor. The NWs are metastable, and thermal treatment at ∼450 °C changed the monoclinic phase into the orthorhombic phase, which is the most stable phase of KNbO(3) at room temperature. Furthermore, we fabricated energy-harvesting nanogenerators by vertically aligning the NWs on SrTiO(3) substrates. The monoclinic NWs showed significantly better energy conversion characteristics than orthorhombic NWs. Moreover, the frequency-doubling efficiency of the monoclinic NWs was ∼3 times higher than that of orthorhombic NWs. This work may contribute to the synthesis of materials with new crystalline structures and hence improve the properties of the materials for various applications.

High concentrations of single-walled carbon nanotubes lower soil enzyme activity and microbial biomass.

Nanomaterials such as single-walled carbon nanotubes (SWCNTs) may enter the soil environment with unknown consequences resulting from the development of nanotechnology for a variety of applications. We determined the effects of SWCNTs on soil enzyme activity and microbial biomass through a 3-week incubation of urban soils treated with different concentrations of SWCNTs ranging from 0 to 1000 µg g(-1) soil. The activities of cellobiohydrolase, ß-1,4-glucosidase, ß-1,4-xylosidase, ß-1,4-N-acetylglucosaminidase, L-leucine aminopeptidase, and acid phosphatase and microbial biomass were measured in soils treated with powder and suspended forms of SWCNTs. SWCNTs of concentrations at 300-1000 µg g(-1) soil significantly lowered activities of most enzymes and microbial biomass. It is noteworthy that the SWCNTs showed similar effects to that of multi-walled carbon nanotubes (MWCNTs), but at a concentration approximately 5 times lower; we suggest that this is mainly due to the higher surface area of SWCNTs than that of MWCNTs. Indeed, our results show that surface area of CNTs has significant negative relationship with relative enzyme activity and biomass, which suggests that greater microorganism-CNT interactions could increase the negative effect of CNTs on microorganisms. Current work may contribute to the preparation of a regulatory guideline for the release of CNTs to the soil environment.

All-solid-state flexible supercapacitors fabricated with bacterial nanocellulose papers, carbon nanotubes, and triblock-copolymer ion gels.

We demonstrate all-solid-state flexible supercapacitors with high physical flexibility, desirable electrochemical properties, and excellent mechanical integrity, which were realized by rationally exploiting unique properties of bacterial nanocellulose, carbon nanotubes, and ionic liquid based polymer gel electrolytes. This deliberate choice and design of main components led to excellent supercapacitor performance such as high tolerance against bending cycles and high capacitance retention over charge/discharge cycles. More specifically, the performance of our supercapacitors was highly retained through 200 bending cycles to a radius of 3 mm. In addition, the supercapacitors showed excellent cyclability with C(sp) (~20 mF/cm(2)) reduction of only <0.5% over 5000 charge/discharge cycles at the current density of 10 A/g. Our demonstration could be an important basis for material design and development of flexible supercapacitors.