Search Results (11)

The apparent respiratory quotient (ARQ) of tree stems, defined as the ratio of net stem CO₂ efflux (E_{S_CO2}) to net stem O₂ influx (E_{S_O2}), offers insights into the balance between local respiratory CO₂ production and CO₂ transported via the xylem. Traditional static chamber methods for measuring ARQ can introduce artifacts and obscure natural diurnal variations. Here, we employed an open flow-through stem chamber with ambient air coupled with cavity ring-down spectrometry, which uses the molecular properties of CO₂ and O₂ molecules to continuously measure E_{S_CO2}, E_{S_O2}, and ARQ, at the base of a California cherry tree (Prunus ilicifolia) during the 2024 growing season. Measurements across three stem chambers over 3–11-day periods revealed strong correlations between E_{S_CO2} and E_{S_O2} and mean ARQ values ranging from 1.3 to 2.9, far exceeding previous reports. Two distinct diurnal ARQ patterns were observed: daytime suppression with nighttime recovery, and a morning peak followed by gradual decline. Partitioning E_{S_CO2} into local respiration and xylem-transported CO₂ indicated that the latter can dominate when ARQ exceeds 2.0. Furthermore, transported CO₂ exhibited a higher temperature sensitivity than local respiration, with both processes showing declining temperature sensitivity above 20 °C. These findings underscore the need to differentiate stem CO₂ flux components to improve our understanding of whole-tree carbon cycling. Full article

The carbon source/sink nature and the water balance of a drip-irrigated and mulched watermelon cultivated under a semi-arid climate were investigated. Biodegradable films, plants and some fruits were left on the soil as green manure. The study spanned from watermelon planting to the subsequent crop (June–November 2023). The eddy covariance technique was employed to monitor water vapor (H₂O) and carbon dioxide (CO₂) fluxes, which were partitioned into transpiration, evaporation, photosynthesis and respiration, respectively, using the flux variance similarity method.This method utilizesthe Monin–Obukhov similarity theory to separate stomatal (photosynthesis and transpiration) from non-stomatal (respiration and evaporation) processes. The results indicate that mulching films contribute to carbon sequestration in the soil (+19.3 g C m⁻²). However, the mulched watermelon crop presented in this study functions as a net carbon source, with a net biome exchange, representing the net rate of C accumulation in or loss from ecosystems, equal to +230 g C m⁻². This is primarily due to the substantial amount of carbon exported through marketable fruits. Fixed water scheduling led to water waste through deep percolation (approximately 1/6 of the water supplied), which also contributed to the loss of organic carbon via leaching (−4.3 g C m⁻²). These findings recommend further research to enhance the sustainability of this crop in terms of both water and carbon balances. Full article

Through photosynthesis, forests absorb annually large amounts of atmospheric CO₂. However, they also release CO₂ back through respiration. These two, opposite in sign, large fluxes determine how much of the carbon is stored or released back into the atmosphere. The mean seasonal cycle (MSC) is an interesting metric that associates phenology and carbon (C) partitioning/allocation analysis within forest stands. Here, we applied the 3D-CMCC-FEM model and analyzed its capability to represent the main C-fluxes, by validating the model against observed data, questioning if the sink/source mean seasonality is influenced under two scenarios of climate change, in five contrasting European forest sites. We found the model has, under current climate conditions, robust predictive abilities in estimating NEE. Model results also predict a consistent reduction in the forest’s capabilities to act as a C-sink under climate change and stand-aging at all sites. Such a reduction is predicted despite the number of annual days as a C-sink in evergreen forests increasing over the years, indicating a consistent downward trend. Similarly, deciduous forests, despite maintaining a relatively stable number of C-sink days throughout the year and over the century, show a reduction in their overall annual C-sink capacity. Overall, both types of forests at all sites show a consistent reduction in their future mitigating potential. Full article

Aripiprazole has fewer metabolic side effects than other antipsychotics; however, there are some severe ones in the liver, leading to drug-induced liver injury. Repeated treatment with aripiprazole affects cell division. Since this process requires a lot of energy, we decided to investigate the impact of aripiprazole on rat liver cells and mitochondria as the main source of cellular energy production by measuring the mitochondrial membrane potential, respiration, adenosine triphosphate (ATP) production, oxidative stress, antioxidative response, and human blood haemolysis. Here, we report that mitochondrial hyperpolarisation from aripiprazole treatment is accompanied by higher reactive oxygen species (ROS) production and increased antioxidative response. Lower mitochondrial and increased glycolytic ATP synthesis demand more glucose through glycolysis for equal ATP production and may change the partition between the glycolysis and pentose phosphate pathway in the liver. The uniform low amounts of the haemolysis of erythrocytes in the presence of aripiprazole in 25 individuals indicate lower quantities of the reduced form of nicotinamide adenine dinucleotide phosphate (NADPH+H⁺), which is in accordance with a decreased activity of glucose 6-phosphate dehydrogenase and the lower dehydrogenase activity upon aripiprazole treatment. The lower activity of glucose 6-phosphate dehydrogenase supports a shift to glycolysis, thus rescuing the decreased mitochondrial ATP synthesis. The putative reduction in NADPH+H⁺ did not seem to affect the oxidised-to-reduced glutathione ratio, as it remained equal to that in the untreated cells. The effect of aripiprazole on glutathione reduction is likely through direct binding, thus reducing its total amount. As a consequence, the low haemolysis of human erythrocytes was observed. Aripiprazole causes moderate perturbations in metabolism, possibly with one defect rescuing the other. The result of the increased antioxidant enzyme activity upon treatment with aripiprazole is increased resilience to oxidative stress, which makes it an effective drug for schizophrenia in which oxidative stress is constantly present because of disease and treatment. Full article

Expanding the use of environmentally friendly materials to protect the environment is one of the key factors in maintaining a sustainable ecological balance. Poly(butylene succinate-co-adipate) (PBSA) is considered among the most promising bio-based and biodegradable plastics for the future with a high number of applications in soil and agriculture. Therefore, the decomposition process of PBSA and its consequences for the carbon stored in soil require careful monitoring. For the first time, the stable isotope technique was applied in the current study to partitioning plastic- and soil-originated C in the CO₂ released during 80 days of PBSA decomposition in a Haplic Chernozem soil as dependent on nitrogen availability. The decomposition of the plastic was accompanied by the C loss from soil organic matter (SOM) through priming, which in turn was dependent on added N. Nitrogen facilitated PBSA decomposition and reduced the priming effect during the first 6 weeks of the experiment. During the 80 days of plastic decomposition, 30% and 49% of the released CO₂ were PBSA-derived, while the amount of SOM-derived CO₂ exceeded the corresponding controls by 100.2 and 132.3% in PBSA-amended soil without and with N fertilization, respectively. Finally, only 4.1% and 5.4% of the PBSA added into the soil was mineralized to CO₂, in the treatments without and with N amendment, respectively. Full article

Most cultivated potatoes are tetraploid, and the tuber is the main economic part that is consumed due to its calorific and nutritional values. Recent trends in climate change led to the frequent occurrence of heat and drought stress in major potato-growing regions worldwide. The optimum temperature for tuber production is 15–20 °C. High-temperature and water-deficient conditions during the growing season result in several morphological, physiological, biochemical, and molecular alterations. The morphological changes under stress conditions may affect the process of stolon formation, tuberization, and bulking, ultimately affecting the tuber yield. This condition also affects the physiological responses, including an imbalance in the allocation of photoassimilates, respiration, water use efficiency, transpiration, carbon partitioning, and the source–sink relationship. The biochemical responses under stress conditions involve maintaining ionic homeostasis, synthesizing heat shock proteins, achieving osmolyte balance, and generating reactive oxygen species, ultimately affecting various biochemical pathways. Different networks that include both gene regulation and transcription factors are involved at the molecular level due to the combination of hot and water-deficient conditions. This article attempts to present an integrative content of physio-biochemical and molecular responses under the combined effects of heat and drought, prominent factors in climate change. Taking into account all of these aspects and responses, there is an immediate need for comprehensive screening of germplasm and the application of appropriate approaches and tactics to produce potato cultivars that perform well under drought and in heat-affected areas. Full article

Bioenergy is one of the most considered alternatives to fossil fuels. Short-rotation woody crops (SRWCs) as bioenergy sources are capable of alleviating energy constraints and sequestering atmospheric CO₂. However, studies investigating soil carbon (C) dynamics at SWRC plantations are scarce. We studied American sycamore (Platanus occidentalis) as a model tree species for SRWC at different planting densities ((1) 0.5 × 2.0 m (10,000 trees·ha⁻¹ or tph), (2) 1.0 × 2.0 m (5000 tph), and (3) 2.0 × 2.0 m (2500 tph)) to examine seasonal variation in total soil respiration (R_total), partitioned into heterotrophic (R_h) and autotrophic (R_a) respiration, and we evaluated climatic and biological controls on soil respiration. R_total and R_h exhibited larger seasonal variation than R_a (p < 0.05). During the nongrowing seasons, the average R_total was 0.60 ± 0.21 g·C·m⁻²·day⁻¹ in winter and 1.41 ± 0.73 g·C·m⁻²·day⁻¹ in fall. During the growing season, R_total was 2–7 times higher in spring (3.49 ± 1.44 g·C·m⁻²·day⁻¹) and summer (4.01 ± 1.17 g·C·m⁻²·day⁻¹) than winter. Average R_total was 2.30 ± 0.63 g·C·m⁻²·day⁻¹ in 2500 tph, 2.43 ± 0.64 g·C·m⁻²·day⁻¹ in 5000 tph, and 2.41 ± 0.75 g·C·m⁻²·day⁻¹ in 10,000 tph treatments. Average R_h was 1.72 ± 0.40 g·C·m⁻²·day⁻¹ in 2500 tph, 1.57 ± 0.39 g·C·m⁻²·day⁻¹ in 5000 tph, and 1.93 ± 0.64 g·C·m⁻²·day⁻¹ in 10,000 tph, whereas R_a had the lowest rates, with 0.59 ± 0.53 g·C·m⁻²·day⁻¹ in 2500 tph, 0.86 ± 0.51 g·C·m⁻²·d⁻¹ in 5000 tph, and 0.48 ± 0.34 g·C·m⁻²·day⁻¹ in 10,000 tph treatments. R_h had a greater contribution to R_total (63%–80%) compared to R_a (20%–37%). Soil temperature was highly correlated to R_total (R² = 0.92) and R_h (R² = 0.77), while the correlation to R_a was weak (R² = 0.21). R_total, R_h, and R_a significantly declined with soil water content extremes (e.g., <20% or >50%). Total root biomass in winter (469 ± 127 g·C·m⁻²) was smaller than in summer (616 ± 161 g·C·m⁻²), and the relationship of total root biomass to R_total, R_h, and R_a was only significant during the growing seasons (R² = 0.12 to 0.50). The litterfall in 5000 tph (121 ± 16 g DW·m⁻²) did not differ (p > 0.05) from the 2500 tph (108 ± 16 g DW·m⁻²) or 10,000 tph (132 ± 16 g DW·m⁻²) treatments. In no circumstances were R_total, R_h, and R_a significantly correlated with litterfall amount across planting densities and seasons (p > 0.05). Overall, our results show that R_total in American sycamore SRWC is dominated by the heterotrophic component (R_h), is strongly correlated to soil environmental conditions, and can be minimized by planting at a certain tree density (5000 tph). Full article

Returning crop residues to agricultural fields can accelerate nutrient turnover and increase N₂O and NO emissions. Increased microbial respiration may lead to formation of local hotspots with anoxic or microoxic conditions promoting denitrification. To investigate the effect of litter quality on CO₂, NO, N₂O, and N₂ emissions, we conducted a laboratory incubation study in a controlled atmosphere (He/O₂, or pure He) with different maize litter types (Zea mays L., young leaves and roots, straw). We applied the N₂O isotopocule mapping approach to distinguish between N₂O emitting processes and partitioned the CO₂ efflux into litter- and soil organic matter (SOM)-derived CO₂ based on the natural ¹³C isotope abundances. Maize litter increased total and SOM derived CO₂ emissions leading to a positive priming effect. Although C turnover was high, NO and N₂O fluxes were low under oxic conditions as high O₂ diffusivity limited denitrification. In the first week, nitrification contributed to NO emissions, which increased with increasing net N mineralization. Isotopocule mapping indicated that bacterial processes dominated N₂O formation in litter-amended soil in the beginning of the incubation experiment with a subsequent shift towards fungal denitrification. With onset of anoxic incubation conditions after 47 days, N fluxes strongly increased, and heterotrophic bacterial denitrification became the main source of N₂O. The N₂O/(N₂O+N₂) ratio decreased with increasing litter C:N ratio and C_org:NO₃⁻ ratio in soil, confirming that the ratio of available C:N is a major control of denitrification product stoichiometry. Full article

Cultivation of winter wheat under reduced tillage systems is increasing in the U.S. Southern Great Plains. Likewise, there is revived interest for including summer legumes in monocultures of winter wheat as green sources of nitrogen (N). This study investigated the influence of tillage systems (no- and conventional tillage), and source and rates of N fertilizer (0, 45 and 90 kg N ha⁻¹ yr⁻¹ in inorganic N fertilizer, and cowpea as green manure) on emissions of carbon dioxide (CO₂) and nitrous oxide (N₂O) from winter wheat cultivation. The study was conducted within a long-term field experiment initiated in 2011, at upland and bottomland sites near El Reno, Oklahoma during the 2016–2017 growing season of winter wheat. The experiment was conducted site-wise as split-plots in a completely randomized design, with N treatment as main plots and tillage system as subplots. Thus, there were a total of eight treatment combinations with three replicated plots (4 m × 10 m) in each combination in both sites. Net ecosystem exchange (NEE) of CO₂ was measured by a closed chamber connected to an infra-red gas analyzer, and fluxes were partitioned to gross primary production (GPP) and ecosystem respiration (ER). Heterotrophic soil respiration (SR) was measured on bare soil spots. Fluxes of N₂O were measured with an opaque closed chamber system with a portable gas analyzer. Dynamics of canopy CO₂ fluxes (NEE, GPP and ER) were similar between tillage systems, while canopy CO₂ fluxes increased with rate of N fertilization. Canopy CO₂ fluxes from cowpea and an unfertilized control were similar, and the lowest, due to poor growth of winter wheat compared to the N fertilized treatments. Fluxes of N₂O approximated zero from all treatments throughout the study and no response of N fertilizer or tillage system was seen. In conclusion, the results from this study indicated that canopy fluxes of CO₂ from winter wheat are controlled by forms and rates of N fertilizers rather than tillage systems. Full article

Starting from the universal concept of entropy production, a large number of new results are obtained and a wealth of novel thermodynamic, kinetic, and molecular mechanistic insights are provided into the coupling of oxidation and ATP synthesis in the vital process of oxidative phosphorylation (OX PHOS). The total dissipation, $\Phi$ , in OX PHOS with succinate as respiratory substrate is quantified from measurements, and the partitioning of $\Phi$ into the elementary components of ATP synthesis, leak, slip, and other losses is evaluated for the first time. The thermodynamic efficiency, $\eta$ , of the coupled process is calculated from the data on $\Phi$ and shown to agree well with linear nonequilibrium thermodynamic calculations. Equations for the P/O ratio based on total oxygen consumed and extra oxygen consumed are derived from first principles and the source of basal (state 4) mitochondrial respiration is postulated from molecular mechanistic considerations based on Nath’s two-ion theory of energy coupling within the torsional mechanism of energy transduction and ATP synthesis. The degree of coupling, $q$ , between oxidation and ATP synthesis is determined from the experimental data and the irreversible thermodynamics analysis. The optimality of biological free energy converters is explored in considerable detail based on (i) the standard biothermodynamic approach, and (ii) a new biothermokinetic approach developed in this work, and an effective solution that is shown to arise from consideration of the molecular aspects in Nath’s theory is formulated. New experimental data in state 4 with uncouplers and redox inhibitors of OX PHOS and on respiratory control in the physiological state 3 with ADP and uncouplers are presented. These experimental observations are shown to be incompatible with Mitchell’s chemiosmotic theory. A novel scheme of coupling based on Nath’s two-ion theory of energy coupling within the torsional mechanism is proposed and shown to explain the data and also pass the test of consistency with the thermodynamics, taking us beyond the chemiosmotic theory. It is concluded that, twenty years since its first proposal, Nath’s torsional mechanism of energy transduction and ATP synthesis is now well poised to catalyze the progress of experimental and theoretical research in this interdisciplinary field. Full article

Northern peatlands store globally significant amounts of soil carbon that could be released to the atmosphere under drier conditions induced by climate change. We measured forest floor respiration (RFF) at hummocks and hollows in a treed boreal bog in Alberta, Canada and partitioned the flux into aboveground forest floor autotrophic, belowground forest floor autotrophic, belowground tree respiration, and heterotrophic respiration using a series of clipping and trenching experiments. These fluxes were compared to those measured at sites within the same bog where water‐table (WT) was drawn down for 2 and 12 years. Experimental WT drawdown significantly increased RFF with greater increases at hummocks than hollows. Greater RFF was largely driven by increased autotrophic respiration driven by increased growth of trees and shrubs in response to drier conditions; heterotrophic respiration accounted for a declining proportion of RFF with time since drainage. Heterotrophic respiration was increased at hollows, suggesting that soil carbon may be lost from these sites in response to climate change induced drying. Overall, although WT drawdown increased RFF, the substantial contribution of autotrophic respiration to RFF suggests that peat carbon stocks are unlikely to be rapidly destabilized by drying conditions. Full article