Although fine roots are important components of the global carbon cycle, there is limited understanding of root structure–function relationships among species. We determined whether root respiration ...rate and decomposability, two key processes driving carbon cycling but always studied separately, varied with root morphological and chemical traits, in a coordinated way that would demonstrate the existence of a root economics spectrum (RES).
Twelve traits were measured on fine roots (diameter ≤ 2 mm) of 74 species (31 graminoids and 43 herbaceous and dwarf shrub eudicots) collected in three biomes.
The findings of this study support the existence of a RES representing an axis of trait variation in which root respiration was positively correlated to nitrogen concentration and specific root length and negatively correlated to the root dry matter content, lignin : nitrogen ratio and the remaining mass after decomposition. This pattern of traits was highly consistent within graminoids but less consistent within eudicots, as a result of an uncoupling between decomposability and morphology, and of heterogeneity of individual roots of eudicots within the fine-root pool.
The positive relationship found between root respiration and decomposability is essential for a better understanding of vegetation–soil feedbacks and for improving terrestrial biosphere models predicting the consequences of plant community changes for carbon cycling.
This study presents one of the first long term datasets including a statistical summary of PM2.5 concentrations obtained from one-year monitoring in 190 cities in China. We found only 25 out of 190 ...cities could meet the National Ambient Air Quality Standards of China, and the population-weighted mean of PM2.5 in Chinese cities are 61 μg/m(3), ~3 times as high as global population-weighted mean, highlighting a high health risk. PM2.5 concentrations are generally higher in north than in south regions due to relative large PM emissions and unfavorable meteorological conditions for pollution dispersion. A remarkable seasonal variability of PM2.5 is observed with the highest during the winter and the lowest during the summer. Due to the enhanced contributions from dust particles and open biomass burning, high PM2.5 abundances are also found in the spring (in Northwest and West Central China) and autumn (in East China), respectively. In addition, we found the lowest and highest PM2.5 often occurs in the afternoon and evening hours, respectively, associated with daily variation of the boundary layer depth and anthropogenic emissions. The diurnal distribution of the PM2.5-to-CO ratio consistently displays a pronounced peak during the afternoon periods, reflecting a significant contribution of secondary PM formation.
Embolism spreading in dehydrating angiosperm xylem is driven by gas movement between embolized and sap‐filled conduits. Here we examine how the proximity to pre‐existing embolism and hydraulic ...segmentation affect embolism propagation. Based on the optical method, we compare xylem embolism resistance between detached leaves and leaves attached to branches, and between intact leaves and leaves with cut minor veins, for six species. Embolism resistance of detached leaves was significantly lower than that of leaves attached to stems, except for two species, with all vessels ending in their petioles. Cutting of minor veins showed limited embolism spreading in minor veins near the cuts prior to major veins. Moreover, despite strong agreement in the overall embolism resistance of detached leaves between the optical and pneumatic method, minor differences were observed during early stages of embolism formation. We conclude that embolism resistance may represent a relative trait due to an open‐xylem artefact, with embolism spreading possibly affected by the proximity and connectivity to pre‐existing embolism as a gas source, while hydraulic segmentation prevents such artefact. Since embolism formation may not rely on a certain pressure difference threshold between functional and embolized conduits, we speculate that embolism is facilitated by pressure‐driven gas diffusion across pit membranes.
Application of the optical and pneumatic method shows that embolism spreading across xylem conduits may occur under different water potentials, depending on the proximity and interconduit connectivity to pre‐existing embolism. Hydraulic segmentation, however, may reduce this artefact considerably.
Spatiotemporal organization of distinct biological processes in cytomimetic compartments is a crucial step towards engineering functional artificial cells. Mimicking controlled bi‐directional ...molecular communication inside artificial cells remains a considerable challenge. Here we present photoswitchable molecular transport between programmable membraneless organelle‐like DNA coacervates in a synthetic microcompartment. We use droplet microfluidics to fabricate membraneless non‐fusing DNA coacervates by liquid‐liquid phase separation in a water‐in‐oil droplet, and employ the interior DNA coacervates as artificial organelles to imitate intracellular communication via photo‐regulated uni‐ and bi‐directional transfer of biomolecules. Our results highlight a promising new route to assembly of multicompartment artificial cells with functional networks.
Photoswitchable bi‐directional trafficking of biomolecules between programmable DNA‐based artificial membraneless organelles in a cell‐like microcompartment has been achieved to imitate intracellular communication towards construction of advanced functional artificial cells.
Lianas exhibit peak abundance in tropical forests with strong seasonal droughts, the eco‐physiological mechanisms associated with lianas coping with water deficits are poorly understood. We examined ...soil water partitioning, sap flow, and canopy eco‐physiological properties for 99 individuals of 15 liana and 34 co‐occurring tree species in three tropical forests that differed in soil water availability. In the dry season, lianas used a higher proportion of deep soil water in the karst forest (KF; an area with severe seasonal soil water deficit (SSWD)) and in the tropical seasonal forest (TSF, moderate SSWD), permitting them to maintain a comparable leaf water status than trees in the TSF or a better status than trees in the KF. Lianas exhibited strong stomatal control to maximize carbon fixation while minimizing dry season water loss. During the dry period, lianas significantly decreased water consumption in the TSF and the KF. Additionally, lianas had a much higher maximum photosynthetic rates and sap flux density in the wet season and a lower proportional decline in photosynthesis in the dry season compared with those of trees. Our results indicated that access to deep soil water and strong physiological adjustments in the dry season together with active wet‐season photosynthesis may explain the high abundance of lianas in seasonally dry forests.
The evolution of lignified xylem allowed for the efficient transport of water under tension, but also exposed the vascular network to the risk of gas emboli and the spread of gas between xylem ...conduits, thus impeding sap transport to the leaves. A well‐known hypothesis proposes that the safety of xylem (its ability to resist embolism formation and spread) should trade off against xylem efficiency (its capacity to transport water). We tested this safety–efficiency hypothesis in branch xylem across 335 angiosperm and 89 gymnosperm species. Safety was considered at three levels: the xylem water potentials where 12%, 50% and 88% of maximal conductivity are lost. Although correlations between safety and efficiency were weak (r² < 0.086), no species had high efficiency and high safety, supporting the idea for a safety–efficiency tradeoff. However, many species had low efficiency and low safety. Species with low efficiency and low safety were weakly associated (r² < 0.02 in most cases) with higher wood density, lower leaf‐ to sapwood‐area and shorter stature. There appears to be no persuasive explanation for the considerable number of species with both low efficiency and low safety. These species represent a real challenge for understanding the evolution of xylem.
The as-cast Mg-4Zn-2Gd-0.5Ca alloy mainly contained I phase and W phase, while the I phase dissolved into Mg substrate after homogenization treatment which improved the alloy’s corrosion resistance. ...After the application of multidirectional forging (MDF), the grains were refined obviously accompanied with the precipitation of I phase. With the increasing pass of MDF, both the size of dynamic recrystallized grains and the amount of precipitated I phase increased. The corrosion resistance of Mg-4Zn-2Gd-0.5Ca alloy became worse after 1 pass of MDF as compared with the as-homogenizated condition because of the precipitation of I phase. Neverthless, the corrosion resistance of the as-MDFed Mg-4Zn-2Gd-0.5Ca alloy deteriorated with the increasing pass of MDF. As compared with grain refinement, the precipitated I phase is thought to play a main role on the corrosion behavior of Mg-4Zn-0.5Ca alloy.
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•Dissolution of I phase lead to the improved corrosion resistance of as-HTed alloy.•MDF results in the grain refinement and precipitated I phase of Mg-4Zn-2Gd-0.5Ca alloy.•The influence of precipitated I phase on corrosion resistance is larger than grain refinement.
Summary
The evolution of angiosperms was accompanied by the segregation and specialisation of their xylem tissues. This study aimed to determine whether the fraction and arrangement of parenchyma ...tissue influence the hydraulic efficiency–safety trade‐off in the basal angiosperms.
We examined xylem anatomical structure and hydraulic functioning of 28 woody species of Magnoliids in a tropical rainforest of Madagascar and reported, for the first time, quantitative measurements that support the relationship between vessel‐to‐xylem parenchyma connectivity and the hydraulic efficiency–safety trade‐off. We also introduced a new measurement – the distance of species from the trade‐off limit – to quantify the co‐optimisation of hydraulic efficiency and safety.
Although the basal angiosperms in this study had low hydraulic conductivity and safety, species with higher axial parenchyma fraction (APf) had significantly higher hydraulic conductivity. Hydraulic efficiency–safety optimisation was accompanied by higher APf and vessel‐to‐axial parenchyma connectivity. Conversely, species exhibiting high ray parenchyma fraction and high vessel‐to‐ray connectivity had lower Ks and were further away from the hydraulic trade‐off limit line.
Our results provide evidence that axial parenchyma fraction and paratracheal arrangement are associated with both enhanced hydraulic efficiency and safety.
Fetal metabolic programming caused by the adverse intrauterine environment can induce metabolic syndrome in adult offspring. Adverse intrauterine environment introduces fetal long-term relatively ...irreversible changes in organs and metabolism, and thus causes fetal metabolic programming leading metabolic syndrome in adult offspring. Fetal metabolic programming of obesity and insulin resistance plays a key role in this process. The mechanism of fetal metabolic programming is still not very clear. It is suggested that epigenetic programming, also induced by the adverse intrauterine environment, is a critical underlying mechanism of fetal metabolic programming. Fetal epigenetic programming affects gene expression changes and cellular function through epigenetic modifications without DNA nucleotide sequence changes. Epigenetic modifications can be relatively stably retained and transmitted through mitosis and generations, and thereby induce the development of metabolic syndrome in adult offspring. This manuscript provides an overview of the critical role of epigenetic programming in fetal metabolic programming.
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