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Dynamics of non-structural carbohydrates in terrestrial plants: a global synthesis
Plants store large amounts of non-structural carbohydrates (NSC). While multiple functions of NSC have long been recognized, the interpretation of NSC seasonal dynamics is often based on the idea that stored NSC is a reservoir of carbon that fluctuates depending on the balance between supply via photosynthesis and demand for growth and respiration (the source–sink dynamics concept). Consequently, relatively high NSC concentrations in some plants have been interpreted to reflect excess supply relative to demand. An alternative view, however, is that NSC accumulation reflects the relatively high NSC levels required for plant survival; an important issue that remains highly controversial. Here, we assembled a new global database to examine broad patterns of seasonal NSC variation across organs (leaves, stems, and belowground), plant functional types (coniferous, drought-deciduous angiosperms, winter deciduous angiosperms, evergreen angiosperms, and herbaceous) and biomes (boreal, temperate, Mediterranean, and tropical). We compiled data from 121 studies, including seasonal measurements for 177 species under natural conditions. Our results showed that, on average, NSC account for ~10% of dry plant biomass and are highest in leaves and lowest in stems, whereas belowground organs show intermediate concentrations. Total NSC, starch, and soluble sugars (SS) varied seasonally, with a strong depletion of starch during the growing season and a general increase during winter months, particularly in boreal and temperate biomes. Across functional types, NSC concentrations were highest and most variable in herbaceous species and in conifer needles. Conifers showed the lowest stem and belowground NSC concentrations. Minimum NSC values were relatively high (46% of seasonal maximums on average for total NSC) and, in contrast to average values, were similar among biomes and functional types. Overall, although starch depletion was relatively common, seasonal depletion of total NSC or SS was rare. These results are consistent with a dual view of NSC function: whereas starch acts mostly as a reservoir for future use, soluble sugars perform immediate functions (e.g., osmoregulation) and are kept above some critical threshold. If confirmed, this dual function of NSC will have important implications for the way we understand and model plant carbon allocation and survival under stress.
Journal Article
Recent progress in metabolic engineering of microbial formate assimilation
Formate can be efficiently produced via electrochemical or photochemical catalytic conversion of CO2, and it can be directly used as an organic carbon source by microorganisms. In theory, formate can be used as the sole carbon source for the microbial production of high-value-added chemicals. Consequently, the construction of efficient formate-assimilation pathways in microorganisms is essential for the utilization of cheap, renewable one-carbon compounds. This paper summarizes new methods of formate synthesis, as well as the natural formate utilization pathways of microorganisms with their advantages and disadvantages. Furthermore, it reviews recent progress in the design of utilization pathways for formate in microbial cells through metabolic engineering and synthetic biology. Besides, we also use the pathway-prediction algorithm comb-FBA to rationally design completely new one-carbon compounds utilization pathways. The pathway with the highest efficiency, named GAA, was corroborated by the in vitro experiments showing a carbon molar yield up to 88%. Finally, it discusses the main problems and challenges presently existing in the pathway design and strain improvement for microbial utilization of formate.Key points• Natural and artificial design pathways of formate-assimilation was summarized.• Recent progresses in different hosts and approaches of using one-carbon compounds was reviewed.• Metabolic engineering and synthetic biology methods to improve formate utilization were discussed.
Journal Article
Carbons for Electrochemical Energy Storage and Conversion Systems
As carbons are widely used in energy storage and conversion systems, there is a rapidly growing need for an updated book that describes their physical, chemical, and electrochemical properties. Edited by those responsible for initiating the most progressive conference on Carbon for Energy Storage and Environment Protection (CESEP), this book undoubtedly fills this need. Written in collaboration with prominent scientists in carbon science and its energy-related applications, Carbons for Electrochemical Energy Storage and Conversion Systems provides the most complete and up-to-date coverage available on carbon materials for application in electrochemical energy storage and conversion. The text studies different carbon materials and their detailed physicochemical properties and provides an in-depth review of their wide-ranging applications-including lithium-ion batteries, supercapacitors, fuel cells, and primary cells.
eBook
Sources of carbon supporting the fast growth of developing immature moso bamboo (Phyllostachys edulis) culms: inference from carbon isotopes and anatomy
Abstract
Phyllostachys edulis is a spectacularly fast-growing species that completes its height growth within 2 months after the shoot emerges without producing leaves (fast-growing period, FGP). This phase was considered heterotrophic, with the carbon necessary for the growth being transferred from the mature culms via the rhizomes, although previous studies observed key enzymes and anatomical features related to C4-carbon fixation in developing culms. We tested whether C4-photosynthesis or dark-CO2 fixation through anaplerotic reactions significantly contributes to the FGP, resulting in differences in the natural abundance of δ13C in bulk organic matter and organic compounds. Further, pulse-13CO2-labelling was performed on developing culms, either from the surface or from the internal hollow, to ascertain whether significant CO2 fixation occurs in developing culms. δ13C of young shoots and developing culms were higher (−26.3 to −26.9 ‰) compared to all organs of mature bamboos (−28.4 to −30.1 ‰). Developing culms contained chlorophylls, most observed in the skin tissues. After pulse-13CO2-labelling, the polar fraction extracted from the skin tissues was slightly enriched in 13C, and only a weak 13C enrichment was observed in inner tissues. Main carbon source sustaining the FGP was not assimilated by the developing culm, while a limited anaplerotic fixation of respired CO2 cannot be excluded and is more likely than C4-photosynthetic carbon fixation.
Phyllostachys edulis , a fast-growing bamboo species, undergoes a rapid growth phase without producing leaves. We found that the carbon needed for growth is mainly transferred from mature bamboos via rhizomes. We also observed the Kranz anatomical feature in developing culms as the same as in previous studies. However, our results suggest that the main carbon source for the rapid growth phase is not assimilated by the developing culm, indicating a limited role of C4 photosynthesis. Instead, a minor contribution from anaplerotic fixation of respired CO2 is more likely.
Journal Article
In Vivo Risk Evaluation of Carbon-Coated Iron Carbide Nanoparticles Based on Short- and Long-Term Exposure Scenarios
While carbon-encapsulated iron carbide nanoparticles exhibit strong magnetic properties appealing for biomedical applications, potential side effects of such materials remain comparatively poorly understood. Here, we assess the effects of iron-based nanoparticles in an in vivo long-term study in mice with observation windows between 1 week and 1 year.
Functionalized (PEG or IgG) carbon-encapsulated platinum-spiked iron carbide nanoparticles were injected intravenously in mice (single or repeated dose administration).
One week after administration, magnetic nanoparticles were predominantly localized in organs of the reticuloendothelial system, particularly the lung and liver. After 1 year, particles were still present in these organs, however, without any evident tissue alterations, such as inflammation, fibrosis, necrosis or carcinogenesis. Importantly, reticuloendothelial system organs presented with normal function.
This long-term exposure study shows high in vivo compatibility of intravenously applied carbon-encapsulated iron nanoparticles suggesting continuing investigations on such materials for biomedical applications.
Journal Article
Site- and alignment-controlled growth of graphene nanoribbons from nickel nanobars
Graphene nanoribbons combine the unique electronic and spin properties of graphene
1
,
2
with a transport gap that arises from quantum confinement and edge effects
3
,
4
,
5
,
6
. This makes them an attractive candidate material for the channels of next-generation transistors. Nanoribbons can be made in a variety of ways, including lithographic
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,
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,
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, chemical
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,
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,
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and sonochemical
6
approaches, the unzipping of carbon nanotubes
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,
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,
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,
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,
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, the thermal decomposition of SiC
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and organic synthesis
19
. However, the reliable site and alignment control of nanoribbons with high on/off current ratios
20
remains a challenge. Here we control the site and alignment of narrow (∼23 nm) graphene nanoribbons by directly converting a nickel nanobar into a graphene nanoribbon using rapid-heating plasma chemical vapour deposition. The nanoribbons grow directly between the source and drain electrodes of a field-effect transistor without transfer, lithography and other postgrowth treatments, and exhibit a clear transport gap (58.5 meV), a high on/off ratio (>10
4
) and no hysteresis. Complex architectures, including parallel and radial arrays of supported and suspended ribbons, are demonstrated. The process is scalable and completely compatible with existing semiconductor processes, and is expected to allow integration of graphene nanoribbons with silicon technology.
Graphene nanoribbons with a clear transport gap and high on/off ratio are grown directly into complex architectures using plasma chemical vapour deposition onto lithographically defined nickel nanobar substrates.
Journal Article
Non-linear temperature sensitivity of litter component decomposition under warming gradient with precipitation addition on the Tibetan plateau
Background and aims
Interactive effect of warming and precipitation addition on litter decomposition is still scarce. Moreover, nonlinear response of its temperature sensitivity to warming is not demonstrated due to lack of warming gradient experiment in situ.
Methods
we performed a warming gradient experiment (0, ~0.25–0.5, ~1, ~2, and ~4 °C, respectively) using infrared heaters and a precipitation addition treatment in a fully-factorial design for 2-years on the Tibetan Plateau. The responses of mass loss of litter components (i.e. organic matter (OM), soluble cell content (SCC), lignin, cellulose (Ce), hemi-cellulose (Hce), total organic carbon (OC)) and nutrients (total nitrogen (TN) and total phosphorus (TP)) to warming and precipitation addition were determined over 2-years.
Results
We found that warming significantly increased annual mass losses of all litter components in both treatment years. Precipitation addition significantly increased annual mass losses of OM, SCC, OC, TN and TP only in the first year due to drought. There were no interactive effects between warming and precipitation addition on litter component decomposition in the semi-arid alpine region. Temperature sensitivities were lowest when soil temperature increased by a mean of about 2.3 °C. There was an inverse relationship between the temperature sensitivity of organic matter decomposition and quality of litter carbon compounds.
Conclusions
Our results suggest that soil temperature effects may override soil moisture effects on litter decomposition in the alpine region, and the nonlinear temperature sensitivity of litter decomposition should be estimated using warming gradients. Lower quality of litter carbon compounds had higher temperature sensitivity of organic matter decomposition.
Journal Article
Can new energy demonstration city policy reduce carbon emissions? A quasi-natural experiment from China
Against achieving carbon peaking by 2030 and carbon neutrality by 2060 context in China, the new energy demonstration city policy (NEDCP) has a crucial function to perform in promoting resource utilization efficiency, building the green development policy system, and facilitating carbon emission reduction. However, existing research has rarely investigated the contribution of NEDCP on carbon reduction. To investigate the policy effect of NEDCP, the differences-in-differences (DID) model is introduced to quantify the influence of NEDCP on carbon reduction, taking a statistical sample of 285 Chinese cities over the period 2005–2017 on the basis of exploring the intrinsic mechanism of NEDCP on carbon emissions. The statistical results reveal that NEDCP significantly inhibits carbon emissions. NEDCP’s dampening impact on carbon reduction is more pronounced in the eastern area but not in other areas. City size and resource endowment heterogeneity results suggest that NEDCP significantly inhibits the output of carbon emissions in non-resource-based and large cities but insignificantly in resource-based and small- and medium-sized cities. Finally, we conclude that policy-makers should not only broaden the scope of NEDCP implementation continuously but also design relevant policy combination tools following the basic characteristics of each city to provide institutional guarantees for achieving carbon emission reduction.
Journal Article
Biocompatibility between Silicon or Silicon Carbide surface and Neural Stem Cells
Silicon has been widely used as a material for microelectronic for more than 60 years, attracting considerable scientific interest as a promising tool for the manufacture of implantable medical devices in the context of neurodegenerative diseases. However, the use of such material involves responsibilities due to its toxicity, and researchers are pushing towards the generation of new classes of composite semiconductors, including the Silicon Carbide (3C-SiC). In the present work, we tested the biocompatibility of Silicon and 3C-SiC using an
in vitro
model of human neuronal stem cells derived from dental pulp (DP-NSCs) and mouse Olfactory Ensheathing Cells (OECs), a particular glial cell type showing stem cell characteristics. Specifically, we investigated the effects of 3C-SiC on neural cell morphology, viability and mitochondrial membrane potential. Data showed that both DP-NSCs and OECs, cultured on 3C-SiC, did not undergo consistent oxidative stress events and did not exhibit morphological modifications or adverse reactions in mitochondrial membrane potential. Our findings highlight the possibility to use Neural Stem Cells plated on 3C-SiC substrate as clinical tool for lesioned neural areas, paving the way for future perspectives in novel cell therapies for neuro-degenerated patients.
Journal Article