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51.
H. B. A. PRINS J. F. H. SNEL P. E. ZANSTRA R. J. HELDER 《Plant, cell & environment》1982,5(3):207-214
Abstract. Photosynthetic utilization of HCO, in leaves of Poiamogeton and Elodea occurs at the lower leaf side, with subsequent OH∼ release at the upper side. It is accompanied by transport of cations, in the present experiment K +, across the leaf. The resulting pH and K+ concentration changes near the leaf surface were recorded with miniature electrodes. From the pH and K+ concentration the concentrations of the different inorganic carbon species were calculated and compared with photosynthetic O, production. HCO− 3 utilization is accompanied by a drastic increase in the free CO2 concentration near the lower epidermis. Experiments with CO2 − and HCO3 − free solutions showed an oscillating acidification near the lower epidermis and alkalinization near the upper epidermis. It is concluded that the acidification results from the activity of light-dependent H+ pumps. The finding that an increase in pH at the upper side always coincided with a decrease at the lower in these experiments shows that the H+ pumps and the OH− extruding mechanism are coupled although occurring in different cell layers. Previously we have suggested that the first step in the process of photosynthetic HCO3 − utilization is external conversion of HCO3 − " by acidification caused by light-dependent H+ pumps. The present results strongly support this hypothesis. Two possible pathways for the accompanying K + transport are discussed. The model presented here explains the known inhibiting effects of buffers and high pH on photosynlhetic HCO3 − utilization. 相似文献
52.
53.
Studies of starvation survival in non-differentiating bacteria have largely focused on physiological changes and regulatory
aspects of a few master regulators such as the signal molecule ppGpp and the stationary phase alternative sigma factor, sigma
S. Recent findings have implicated a series of novel key events for the entry as well as exit from starvation. The importance
of alternative sigma factors other than sigma S is emerging. In addition, low molecular weight extracellular signals have
been demonstrated to be essential for the induction and mediation of several adaptive responses. The importance of mRNA modification
and stability for starvation survival as well as outgrowth is receiving renewedinterest. In this paper, we present the results
obtained from studies of starvation survival and recovery ofVibrio sp. strain S14. 相似文献
54.
Dan Zhu;Yilong Wang;Philippe Ciais;Frédéric Chevallier;Shushi Peng;Yao Zhang;Xuhui Wang; 《Global Change Biology》2024,30(1):e17043
In the northern high latitudes, warmer spring temperatures generally lead to earlier leaf onsets, higher vegetation production, and enhanced spring carbon uptake. Yet, whether this positive linkage has diminished under climate change remains debated. Here, we used atmospheric CO2 measurements at Barrow (Alaska) during 1979–2020 to investigate the strength of temperature dependence of spring carbon uptake reflected by two indicators, spring zero-crossing date (SZC) and CO2 drawdown (SCC). We found a fall and rise in the interannual correlation of temperature with SZC and SCC (RSZC-T and RSCC-T), showing a recent reversal of the previously reported weakening trend of RSZC-T and RSCC-T. We used a terrestrial biosphere model coupled with an atmospheric transport model to reproduce this fall and rise phenomenon and conducted factorial simulations to explore its potential causes. We found that a strong–weak–strong spatial synchrony of spring temperature anomalies per se has contributed to the fall and rise trend in RSZC-T and RSCC-T, despite an overall unbroken temperature control on net ecosystem CO2 fluxes at local scale. Our results provide an alternative explanation for the apparent drop of RSZC-T and RSCC-T during the late 1990s and 2000s, and suggest a continued positive linkage between spring carbon uptake and temperature during the past four decades. We thus caution the interpretation of apparent climate sensitivities of carbon cycle retrieved from spatially aggregated signals. 相似文献
55.
Xiankun Li;Ainara Leizeaga;Johannes Rousk;Siyuan Zhou;Gustaf Hugelius;Stefano Manzoni; 《Global Change Biology》2024,30(10):e17522
Climate change is causing an intensification of soil drying and rewetting events, altering microbial functioning and potentially destabilizing soil organic carbon. After rewetting, changes in microbial community carbon use efficiency (CUE), investment in life history strategies, and fungal to bacterial dominance co-occur. Still, we have yet to generalize what drives these dynamic responses. Here, we collated 123 time series of microbial community growth (G, sum of fungal and bacterial growth, evaluated by leucine and acetate incorporation, respectively) and respiration (R) after rewetting and calculated CUE = G/(G + R). First, we characterized CUE recovery by two metrics: maximum CUE and time to maximum CUE. Second, we translated microbial growth and respiration data into microbial investments in life history strategies (high yield (Y), resource acquisition (A), and stress tolerance (S)). Third, we characterized the temporal change in fungal to bacterial dominance. Finally, the metrics describing the CUE recovery, investment in life history strategies, and fungal to bacterial dominance after rewetting were explained by environmental factors and microbial properties. CUE increased after rewetting as fungal dominance declined, but the maximum CUE was explained by the CUE under moist conditions, rather than specific environmental factors. In contrast, higher soil pH and carbon availability accelerated the decline of microbial investment in stress tolerance and fungal dominance. We conclude that microbial CUE recovery is mostly driven by the shifting microbial community composition and the metabolic capacity of the community, whereas changes in microbial investment in life history strategies and fungal versus bacterial dominance depend on soil pH and carbon availability. 相似文献
56.
Hanshuang Zhao;Zenghu Zhang;Shailesh Nair;Hongmei Li;Chen He;Quan Shi;Qiang Zheng;Ruanhong Cai;Genming Luo;Shucheng Xie;Nianzhi Jiao;Yongyu Zhang; 《Global Change Biology》2024,30(11):e17570
Long-term carbon sequestration by the ocean's recalcitrant dissolved organic carbon (RDOC) pool regulates global climate. Algae and bacteria interactively underpin RDOC formation. However, on the long-term scales, the influence of their persistent interactions close to in situ state on ocean RDOC dynamics and accumulation remains unclear, limiting our understanding of the oceanic RDOC pool formation and future trends under global change. We show that a Synechococcus-bacteria interaction model system viable over 720 days gradually accumulated high DOC concentrations up to 84 mg L−1. Concurrently, the DOC inertness increased with the RDOC ratio reaching > 50%. The identified Synechococcus-bacteria-driven RDOC molecules shared similarity with over half of those from pelagic ocean DOC. Importantly, we provide direct genetic and metabolite evidence that alongside the continuous transformation of algal carbon by bacteria to generate RDOC, Synechococcus itself also directly synthesized and released RDOC molecules, representing a neglected RDOC source with ~0.2–1 Gt y−1 in the ocean. However, we found that although ocean warming (+4°C) can promote algal and bacterial growth and DOC release, it destabilizes and reduces RDOC reservoirs, jeopardizing the ocean's carbon sequestration capacity. This study unveils the previously underestimated yet significant role of algae and long-term algae-bacteria interactions in ocean carbon sequestration and its vulnerability to ocean warming. 相似文献
57.
M. Francesca Cotrufo;Michelle L. Haddix;Jack L. Mullen;Yao Zhang;John K. McKay; 《Global Change Biology》2024,30(11):e17591
Breeding annual crops for enhanced root depth and biomass is considered a promising intervention to accrue soil organic carbon (SOC) in croplands, with benefits for climate change mitigation and soil health. In annual crops, genetic technology (seed) is replaced every year as part of a farmer's fixed costs, making breeding solutions to climate change more scalable and affordable than management approaches. However, mechanistic understanding and quantitative estimates of SOC accrual potentials from crops with enhanced root phenotypes are lacking. Maize is the highest acreage and yielding crop in the US, characterized by relatively low root biomass confined to the topsoil, making it a suitable candidate for improvement that could be rapidly scaled. We ran a 2-year field experiment to quantify the formation and composition (i.e., particulate (POM), coarse and fine mineral–associated organic matter (chaOM and MAOM, respectively) of new SOC to a depth of 90 cm from the decomposition of isotopically labeled maize roots and exudates. Additionally, we used the process-based MEMS 2 model to simulate the SOC accrual potential of maize root ideotypes enhanced to either shift root production to deeper depths or increase root biomass allocation, assuming no change in overall productivity. In our field experiment, maize root decomposition preferentially formed POM, with doubled efficiency below 50 cm, while root exudates preferentially formed MAOM. Modeling showed that shifting root inputs to deeper layer or increasing allocation to roots resulted in a deterministic increase in SOC, ranging from 0.05 to 0.15 Mg C ha−1 per year, which are at the low end of the range of published SOC per hectare annual accrual estimates from adoption of a variety of crop management practices. Our analysis indicates that for maize, breeding for increasing root inputs as a strategy for SOC accrual has limited impact on a per-hectare basis, although given that globally maize is produced on hundreds of millions of hectares each year, there is potential for this technology and its effect to scale. For maize–soy system that dominates US acres, changes in the overall cropping system are needed for sizable greenhouse gas reductions and SOC accrual. This study demonstrated a modeling and experimental framework to quantify and forecast SOC changes created by changing crop root inputs. 相似文献
58.
Junmin Pei;Changming Fang;Bo Li;Ming Nie;Jinquan Li; 《Global Change Biology》2024,30(11):e17565
Global warming is generally predicted to increase aridity in drylands, while the effects of aridity changes on microbial carbon use efficiency (CUE) and its linkage to soil organic carbon (SOC) storage remain unresolved, limiting the accuracy of soil carbon dynamic predictions under changing climates. Here, by employing large-scale soil sampling from 50 sites along an ~6000 km aridity gradient in northern China, we report a significant decreasing trend in microbial CUE (ranging from approximately 0.07 to 0.59 across the aridity gradient) with increasing aridity. The negative effect of aridity on microbial CUE was further verified by an independent moisture manipulation experiment, which revealed that CUE was lower under lower moisture levels than under higher moisture levels. Aridity-induced increases in physicochemical protection or decreases in microbial diversity primarily mediated the decrease in CUE with increasing aridity. Moreover, we found a highly positive microbial CUE–SOC relationship, and incorporating CUE improved the explanatory power of SOC variations along the aridity gradient. Our findings provide empirical evidence for aridity-induced reductions in microbial CUE over a broad geographic scale and highlight that increasing aridity may be a crucial mechanism underlying SOC loss by suppressing the ability of soil microorganisms to sequester carbon. 相似文献
59.
Baptiste J. Wijas;Mike Letnic;William K. Cornwell; 《Austral ecology》2024,49(7):e13555
Drylands are characterized by high spatial variability in resource availability due to sporadic rainfall, topography of the landscape and important effects of animals. Resource availability gradients may trigger patterns in decomposer population abundances and activity, which could affect ecosystem functions such as decomposition. Here, we examined the influence of resource availability gradients on the importance of termites in the decomposition of wood and grass litter. We placed wood blocks and grass litter baits in bags accessible and inaccessible to termites across wood and grass resource gradients as determined by the presence or absence of a top mammalian predator and across topographic gradients during a 9-month period in arid Australia. We hypothesized that grass-eating termite activity would track grass abundance and wood-eating termite activity would track wood abundance. Termites were the predominant decomposition agent at these sites. Termites contributed to 99.5% of wood decomposition and 83.9% of grass decomposition during our study period. For wood, the termite effect was spatially variable and increased with habitat wood availability, which was greatest on dunes and where top predators were absent. However, the contribution of termites to grass litter decomposition did not track grass availability or termite abundance. The highest effects of termites on grass decomposition rates were found in habitats where the absence of top predators led to low grass availability. Our findings highlight how spatial variability in resources in addition to other factors that we do not document but are known to be influenced by the presence of top predators, such as insectivore predation rates, across the landscape could affect ecosystem functions such as decomposition. 相似文献
60.
Lei Qin Yu Lei Huwei Wang Jiahui Dong Yiying Wu Dengyun Zhai Feiyu Kang Ying Tao Quan‐Hong Yang 《Liver Transplantation》2019,9(29)
Metallic potassium (K) is a desirable anode for potassium secondary batteries due to its low electrode potential in nonaqueous electrolytes and high theoretical capacity. Nevertheless, instability caused by dendritic growth, large volume changes, and parasitic side reactions hamper its practical application. Here, an anode containing metallic K is fabricated by infiltrating an aligned carbon nanotube membrane (ACM) with molten K because of its good wettability to molten K due to the strong capillary forces. The K metal is spatially distributed on the 3D ACM framework, which offers sufficient electrode/electrolyte contact for charge transfer. The robust ACM host provides a large number of K nucleation sites and physically confines the K deposited there, thus mitigating dimensional changes during cycling. The pathways for electrons and ions in the anode are associated to form a mixed conducting network, which is beneficial for the electrochemical redox. Consequently, the anode shows stable plating/stripping profiles with low polarization in symmetric cells using conventional carbonate‐based electrolytes. In addition, dendrite growth is suppressed, and the anode demonstrates excellent suitability when paired with a Prussian blue cathode in a full cell. This design strategy is expected to provide a way to address the problems with using metallic K anodes. 相似文献
