Compensation Point Research Articles

In situ estimates of kelp forest productivity in macro‐tidal environments

AbstractAccurately quantifying primary productivity of marine macrophytes is essential to further understanding of coastal ecosystem functioning and will allow its inclusion within marine ecosystem models. Traditional quantification of carbon standing stock and biomass accumulation only allow rough estimates of net primary production whereas incubations that measure photosynthesis in the laboratory lack realism and underestimate true photosynthetic rates. We developed in situ photorespirometry methods to estimate productivity of Laminaria hyperborea, the dominant forest‐building kelp species in Northeast Atlantic. We show that sub‐canopy individuals are better adapted to low light levels with higher photosynthetic efficiency and lower compensation point than larger canopy individuals. Laboratory incubations of L. hyperborea stipes revealed that productivity rates could be positive or negative, even at saturating irradiances, depending on whether they were dominated by autotrophic or heterotrophic communities, respectively. Scaling up productivity estimates based on local population demographics resulted in mean daily net productivity rates of 13.3 and −30.1 g C m−2 d−1, for shallow L. hyperborea forest during late summer and autumn, respectively. At saturating irradiances in the late summer–autumn study period, estimates of net and gross productivity reached 9.4 and 12 g C m−2 h−1, respectively. Sub‐canopy individuals were responsible for 12% of estimated daily productivity during summer, but 20% in autumn. We conclude that in situ photorespirometry provides a more direct measurement of production, unaffected by exudation of dissolved carbon or tissue loss, that can account for sub‐canopy and stipe components of the kelp forest, commonly excluded from traditional studies.

Do corm seeding rate and planting depth influence growth indicators of saffron (Crocus sativus L.)?

Saffron, the primary in the market now, is a food spice by far the world’s most expensive. In order to study the effects of different corm seeding rates and sowing depth on physiological indices of saffron, an experiment was conducted as a factorial layout based on randomized complete block design with three replications at the research farm of the Ferdowsi University of Mashhad during 2015–2017 years. The experimental treatments were all combinations of different corms seeding rates in four levels (7, 8, 9, and 10 Mg ha−1) and sowing depth in three levels (10, 15, and 20 cm). The studied traits were the dry weight of mother and daughter corms, cumulative dry matter, and some growth indices such as leaf area index (LAI), crop growth rates (CGR), relative growth rate (RGR), and Leaf Area Ratio (LAR). The results showed 8 Mg ha−1 corm seeding rate and 10 cm sowing depth increased total crop dry weight, CGR, and RGR in saffron. Based on obtained results at the beginning of the vegetative growth period, CGR declined for a short time. So that by continuing the vegetative growth, the plant reached on growth compensation point, and then CGR increased. From 180 days after the sowing date and in the late stages of vegetative growth, the growth rates trend decreased again. The results also showed that the LAR trend decreased from the early vegetative growth period, which can be explained by the faster growth of the daughter corms and other underground parts of the plant than the leaves during the early vegetative growth period. According to the results and the natural trend of mother corm breakup during the growing season, increasing density due to increasing competition between mother corms caused intensification in a weight reduction of mother corms in the late stages of the growing season. Also, in the first three months after sowing, daughter corms did not grow anymore, and the beginning of their growth coincided with the end of the saffron flowering period.

The Effect of Low Irradiance on Leaf Nitrogen Allocation and Mesophyll Conductance to CO2 in Seedlings of Four Tree Species in Subtropical China.

Low light intensity can lead to a decrease in photosynthetic capacity. However, could N-fixing species with higher leaf N contents mitigate the effects of low light? Here, we exposed seedlings of Dalbergia odorifera and Erythrophleum fordii (N-fixing trees), and Castanopsis hystrix and Betula alnoides (non-N-fixing trees) to three irradiance treatments (100%, 40%, and 10% sunlight) to investigate the effects of low irradiance on leaf structure, leaf N allocation strategy, and photosynthetic physiological parameters in the seedlings. Low irradiance decreased the leaf mass per unit area, leaf N content per unit area (Narea), maximum carboxylation rate (Vcmax), maximum electron transport rate (Jmax), light compensation point, and light saturation point, and increased the N allocation proportion of light-harvesting components in all species. The studied tree seedlings changed their leaf structures, leaf N allocation strategy, and photosynthetic physiological parameters to adapt to low-light environments. N-fixing plants had a higher photosynthesis rate, Narea, Vcmax, and Jmax than non-N-fixing species under low irradiance and had a greater advantage in maintaining their photosynthetic rate under low-radiation conditions, such as under an understory canopy, in a forest gap, or when mixed with other species.

Development of a battery management system with flying capacitor‐type multiport converter in the discontinuous current mode

AbstractThis paper proposes a multiport converter based on a flying capacitor converter (FCC) topology for use in a battery management system. The proposed circuit operates in discontinuous current mode (DCM) and pulse frequency modulation (PFM) in order to reduce inductor volume. The circuit achieves load fluctuation compensation and maximum power point tracking (MPPT) of the photovoltaic (PV) system by deciding duty ratio based on load current and PV output current. According to the experimental results, an efficiency of more than 95.8% was achieved under all operation conditions. In addition, the maximum efficiency reached 98.8% at the rated load (750 W). Furthermore, the inductor volume reduced by 85.5% compared to that of the conventional circuit (CCM) using two inductors.

Exogenous nitric oxide alleviates manganese toxicity in bean plants by modulating photosynthesis in relation to leaf lipid composition.

Nitric oxide (NO) is a signaling molecule controlling several steps of plant development and defense process under stress conditions. NO-induced alleviation of manganese (Mn) toxicity was investigated on bean plants submitted for 28days to 500µM MnCl2. Manganese excess decreased plant dry weight and elongation and increased levels of reactive oxygen species and lipid peroxidation leading to up-regulation of superoxide dismutase, catalase, and ascorbate peroxidase activities. The inhibitory effects of Mn on plant growth were associated to reduction of light-saturated carbon assimilation (Amax), stomatal conductance (gs), and transpiration (E). By contrast, Mn induced significant increase in the apparent quantum yield (ɸ) and light compensation point (LCP). Interestingly, intracellular CO2 (Ci) remains stable under Mn stress. Concomitantly, leaf membrane lipids have drastically reduced under high Mn concentration. After Mn exposition, leaf fatty acids exhibited a significant loss of linolenic acid, accompanied by an accumulation of palmitoleic, stearic, and linoleic acids leading to alteration of lipid desaturation. NO supply reversed Mn toxicity as evidenced by enhancement of growth biomass and recovery of Amax, E, ɸ, and LCP. Similarly, NO addition has positive effects on leaf lipid content and composition leading to restoration of lipid unsaturation. The modulation of fatty acid composition can be a way to reduce leaf membrane damages and maintain optimal photosynthesis and plant growth. Despite the absence of enough evidences in how NO is involved in lipid and photosynthesis recovery under Mn stress conditions, it is assumed that NO beneficial effects are attributable to NO/Mn cross-talk.

Commercially available carbohydrate drink with menthol fails to improve thermal perception or cycling exercise capacity in males

ABSTRACT The purpose of this double-blinded, crossover randomized and counterbalanced study was to compare the effects of ingesting a tepid commercially available carbohydrate–menthol-containing sports drink (menthol) and an isocaloric carbohydrate-containing sports drink (placebo) on thermal perception and cycling endurance capacity “in a simulated home virtual cycling environment”. It was hypothesized that the addition of menthol would improve indicators of thermal perception and improve endurance exercise capacity. Twelve healthy, endurance-trained males (age 29 ± 5 years, height 181 ± 6 cm, body mass 79 ± 2 kg and V̇O2max 57.3 ± 6.4 mL kg−1 min−1) completed two experimental trials on a stationary bicycle without external air flow. Each trial consisted of (1) cycling for 60 min at 90% of the first ventilatory threshold while receiving a fixed amount of menthol or placebo every 10 min followed immediately by (2) cycling until volitional exhaustion (TTE) at 105% of the intensity corresponding to the respiratory compensation point. TTE did not differ between both conditions (541 ± 177 and 566 ± 150 s for menthol and placebo; p > 0.05) and neither did ratings of perceived thermal comfort or thermal sensation (p > 0.05). Also, the rectal temperature at the end of TTE was comparable between menthol and placebo trials (38.7 ± 0.2°C and 38.7 ± 0.3°C, respectively; p > 0.05). The present results demonstrate that the addition of menthol to commercially available sports drink does not improve thermal comfort or endurance exercise capacity during ∼65 min of intense virtual cycling. Highlights Ingestion of a commercially available carbohydrate–menthol beverage at high exercise intensity and without air flow does not improve endurance exercise capacity. When ingested with carbohydrates, it appears that a combination of carbohydrates and menthol does not improve thermal discomfort caused by intense exercise and a lack of air flow. A menthol concentration higher than 0.01% might be required to induce the reduction in thermal discomfort when ingested in combination with carbohydrates.

Photosynthesis, Growth and Dry Biomass Production in Euglena gracilis Klebs as Affected by Three Growth Irradiance Levels

Aims: The research aimed to investigate the shade response of E. gracilis Klebs while making the irradiance a crucial factor for photosynthesis based physiological activities and its applicability for industrial level culture conditions.
 Study Design: Euglena was cultured at three different light intensities of 30, 90, and 210 mol m-2s-1 photoautotrophically and axenically in modified Cramer-Meyer medium at 25 ˚C as batch cultures.
 Methodology: The photosynthesis O2 evaluation of Euglena cultures was measured under exponential (EP), transitional (TP), and stationary phases (SP). The light compensation point (LCP), light saturation point (LSP), and dark respiration rate (DRR) were obtained. Cell volume and cell number in each culture were measured simultaneously. Cells were collected and obtained dry mass (DM) after drying aliquots at 80˚C. Specific growth rate (SGR) and relative growth rate (RGR) were calculated. Tests for homogeneity of variance were performed on all parameters and LSDs were used for the mean separation.
 Results: In the TP, the lowest LCP was achieved in the higher light culture. The values of both the DRR and the LSP were the same as in EP. The DRR, LCP and LSP are lower in lower PFD cultures and decreased with increasing cell titers. The cellular growth levels were lower in lower light culture and decreased as each culture grew. Cellular DM was maintained constant in the EP, where SGR almost equaled RGR. In the EP, SGR was maintained constant in each culture, SGR displayed a saturation phenomenon. In the later TP, SGR became equal to RGR and all the cultures revealed constant DM.
 Conclusion: Euglena photoautotrophic cultures can tolerate low light intensities. With the SGR and RGR behavior under the shade conditions, they can maintain the constant photosynthesis rate and constant dry matter level.

Photosynthetic and morphological traits control aquatic plant distribution according to light stress

The eutrophication of aquatic systems resulting from human activities frequently leads to phytoplankton blooms, which decrease water transparency and therefore limit light availability for aquatic plants. However, several submerged macrophytes are able to grow despite the light competition pressure exerted by phytoplankton. Photosynthetic performance and plant morphology may be key traits allowing plant species to tolerate phytoplankton-induced light limitation in eutrophic systems. The aim of this study was to explore how morphological and photosynthetic traits allow submerged macrophytes to withstand the stress induced by decreased light in eutrophic systems. Morphological and photosynthetic traits were measured in 7 species of submerged macrophytes collected from mesotrophic to hypertrophic shallow lakes (Dombes, Ain, France). Then, we determined whether these traits were related to species occurrence in lakes according to depth and water turbidity. This study highlighted 2 strategies potentially resulting in a trade-off between morphological and photosynthetic traits. The first strategy was tolerance to reduced light and was characterized by a higher investment in leaf area and photosynthetic efficiency (initial slope of photosynthetic activity measured at low light intensities), allowing plants to use low amounts of light energy. The second strategy was to avoid the regions of reduced light and was characterized by a greater investment in vertical growth and maximum photosynthesis at high light intensities. The morphological and physiological traits favoured in turbid lakes corresponded to the avoidance strategy with a low compensation point, allowing plants to grow to the photic zone to reach the water areas where light is at a maximum. Small species exhibiting a light stress tolerance strategy may be maintained in turbid lakes subjected to disturbances, offering a window of opportunity for successful recruitment and reproduction.

Monte Carlo calculations of Curie temperatures of Y[formula omitted]Gd[formula omitted](Fe[formula omitted]Co[formula omitted])[formula omitted] pseudobinary system

The close-packed AB2 structures called Laves phases constitute the largest group of intermetallic compounds. In this paper we computationally investigated the pseudo-binary Laves phase system Y1−xGdx(Fe1−yCoy)2 spanning between the YFe2, YCo2, GdFe2, and GdCo2 vertices. While the vast majority of the Y1−xGdx(Fe1−yCoy)2 phase diagram is the ferrimagnetic phase, YCo2 along with a narrow range of concentrations around it is the paramagnetic phase. We presented results obtained by Monte Carlo simulations of the Heisenberg model with parameters derived from first-principles calculations. For calculations we used the Uppsala atomistic spin dynamics (UppASD) code together with the spin-polarized relativistic Korringa–Kohn–Rostoker (SPR-KKR) code. From first principles we calculated the magnetic moments and exchange integrals for the considered pseudo-binary system, together with spin-polarized densities of states for boundary compositions. Furthermore, we showed how the compensation point with the effective zero total moment depends on the concentration in the considered ferrimagnetic phases. However, the main result of our study was the determination of the Curie temperature dependence for the system Y1−xGdx(Fe1−yCoy)2. Except for the paramagnetic region around YCo2, the predicted temperatures were in good qualitative and quantitative agreement with experimental results, which confirmed the ability of the method to predict magnetic transition temperatures for systems containing up to three different magnetic elements (Fe, Co, and Gd) simultaneously. For the Y(Fe1−yCoy)2 and Gd(Fe1−yCoy)2 systems our calculations matched the experimentally-confirmed Slater–Pauling-like behavior of TC dependence on the Co concentration. For the Y1−xGdxFe2 system we obtained, also in agreement with the experiment, a linear dependence of TC on the Gd concentration. In addition, on the example of Y0.8Gd0.2Co2 ferrimagnet, we showed the possibility of predicting the non-trivial behavior of the temperature dependence of magnetization, confirmed by comparison with previous measurement results.

Spin compensation, critical and discontinuous transitions behaviors in a ferrimagnet of spins 5/2 and 7/2

We apply Monte Carlo simulation techniques to study the magnetic behavior of a mixed ferrimagnetic Ising model on sites of a square lattice of LxL size, with L = 120, where 5/2 spins are alternated with 7/2 spins. We consider an antiferromagnetic interaction next-neighbor, ferromagnetic interactions next-nearest-neighbor, and an external magnetic field in the Hamiltonian that defines the model. We characterize the effects of an external magnetic field on the behavior of the system through the analysis of spin compensation points, discontinuous transitions, and hysteresis loops at various temperatures in the total magnetization and magnetic susceptibility. At the end, we study the phase diagrams of the critical, compensation and discontinuous transition temperatures. The physical phenomena experienced by the system under study are relevant to the application in magneto-optical recordings, in the synthesis and construction of molecular-based magnets and have technological applications in the manipulation and storage of magnetic information. We found some phenomena not reported in previous works on the same system.

Characteristic Features of Magnetization Reversal of Exchange Coupled Tb–Co/FeNi Film Structures in a Temperature Range Including the Compensation Point of the Ferrimagnetic Layer

Characteristic Features of Magnetization Reversal of Exchange Coupled Tb–Co/FeNi Film Structures in a Temperature Range Including the Compensation Point of the Ferrimagnetic Layer

Plasma-Derived microRNAs Are Influenced by Acute and Chronic Exercise in Patients With Heart Failure With Reduced Ejection Fraction.

Background: Exercise training improves VO2peak in heart failure with reduced ejection fraction (HFrEF), but the effect is highly variable as it is dependent on peripheral adaptations. We evaluated changes in plasma-derived miRNAs by acute and chronic exercise to investigate whether these can mechanistically be involved in the variability of exercise-induced adaptations.Methods: Twenty-five male HFrEF patients (left ventricular ejection fraction < 40%, New York Heart Association class ≥ II) participated in a 15-week combined strength and aerobic training program. The effect of training on plasma miRNA levels was compared to 21 male age-matched sedentary HFrEF controls. Additionally, the effect of a single acute exercise bout on plasma miRNA levels was assessed. Levels of 5 miRNAs involved in pathways relevant for exercise adaptation (miR-23a, miR-140, miR-146a, miR-191, and miR-210) were quantified using RT-qPCR and correlated with cardiopulmonary exercise test (CPET), echocardiographic, vascular function, and muscle strength variables.Results: Expression levels of miR-146a decreased with training compared to controls. Acute exercise resulted in a decrease in miR-191 before, but not after training. Baseline miR-23a predicted change in VO2peak independent of age and left ventricular ejection fraction (LVEF). Baseline miR-140 was independently correlated with change in load at the respiratory compensation point and change in body mass index, and baseline miR-146a with change in left ventricular mass index.Conclusion: Plasma-derived miRNAs may reflect the underlying mechanisms of exercise-induced adaptation. In HFrEF patients, baseline miR-23a predicted VO2peak response to training. Several miRNAs were influenced by acute or repeated exercise. These findings warrant exploration in larger patient populations and further mechanistic in vitro studies on their molecular involvement.

Comparisons of photosynthesis-related traits among understory lichens, mosses and vascular plant leaves in a high-elevation subalpine forest

AbstractMany mosses and lichens thrive in high-elevation subalpine forests and even become dominant species on the forest floor. Although they play an irreplaceable ecological role in the forest, less is known about their eco-physiological status, and how their photosynthesis-related functional traits differ from those of co-occurring vascular plants. We determined the carbon, nitrogen and phosphorus concentrations and stoichiometric ratios, tissue mass per area, chlorophyll concentrations and photosynthetic light–response curves of three lichens, three mosses and four vascular plants in a subalpine forest in the eastern Tibetan Plateau of China. Trait values were compared among and within each group. The lichens possessed a higher nitrogen concentration than that of mosses. In addition, the two poikilohydric groups exhibited lower concentrations of nitrogen, phosphorus and chlorophyll, light-saturated assimilation rates and photosynthetic nutrient use efficiencies, and higher light compensation points than those of vascular plant leaves. Furthermore, variations in photosynthesis-related traits for lichen species reflect their different adaptation strategies to their corresponding environments. In contrast, the differences were weak among the three forest-floor mosses and the three herb species. These results demonstrate that the high abundance of understory lichens and mosses in the high-elevation subalpine forest cannot be explained by the photosynthesis-related traits.

Robust finite-temperature magnetization dynamics in ferrimagnetic Gdx(FeCo)1−x (x = 0 ∼ 0.44) nanospheres across angular-momentum and magnetization compensation points: An atomistic model simulation

We explored robust magnetization dynamics in ferrimagnetic Gdx(FeCo)1−x nanospheres of Gd compositions ranging from x = 0 to 0.44 at finite T = 0 – 1200 K temperatures using two-sublattice atomistic simulations based on the stochastic Landau-Lifshitz-Gilbert equation. It was found that the magnetization compensation and angular-momentum compensation temperatures vary remarkably with x and that the former temperature is always lower than the latter. Also, it was found that neither compensation temperature exists below a specific Gd composition of x = 0.22, but above which, both exist and increase with x. The ferromagnetic resonance (FMR) frequency remarkably increases at the angular momentum compensation composition, whereas the FMR frequency does not reach zero at the magnetization compensation composition. The significant difference in the FMR frequency between the two characteristic compensation points is ascribed to the contrasting effective gyromagnetic ratios of Gd and FeCo. Our present atomistic simulation study well reproduced the earlier experimental observations of such dynamic behaviors at both the angular-momentum and magnetization compensation points, which observations cannot be explained by the existing Kittel and Wangsness models. This work provides a better understanding of robust dynamic behaviors of ferrimagnetic nanospheres as functions of temperature and constituent sublattice composition, especially at and near the characteristic compensation points.

What Is Moderate to Vigorous Exercise Intensity?

A variety of health benefits associated with physical activity depends upon the frequency, intensity, duration, and type of exercise. Intensity of exercise is the most elusive of these elements and yet has important implications for the health benefits and particularly cardiovascular outcomes elicited by regular physical activity. Authorities recommend that we obtain 150min of moderate to vigorous intensity physical activity (MVPA) each week. The current descriptions of moderate to vigorous intensity are not sufficient, and we wish to enhance understanding of MVPA by recognition of important boundaries that define these intensities. There are two key thresholds identified in incremental tests: ventilatory and lactate thresholds 1 and 2, which reflect boundaries related to individualized disturbance to homeostasis that are appropriate for prescribing exercise. VT2 and LT2 correspond with critical power/speed and respiratory compensation point. Moderate intensity physical activity approaches VT1 and LT1 and vigorous intensity physical activity is between the two thresholds (1 and 2). The common practice of prescribing exercise at a fixed metabolic rate (# of METs) or percentage of maximal heart rate or of maximal oxygen uptake (V̇O2max) does not acknowledge the individual variability of these metabolic boundaries. As training adaptations occur, these boundaries will change in absolute and relative terms. Reassessment is necessary to maintain regular exercise in the moderate to vigorous intensity domains. Future research should consider using these metabolic boundaries for exercise prescription, so we will gain a better understanding of the specific physical activity induced health benefits.

Severe Reduction of Energy Availability in Controlled Conditions Causes Poor Endurance Performance, Impairs Explosive Power and Affects Hormonal Status in Trained Male Endurance Athletes

The aim of this study was to severely reduce energy availability (EA) in controlled conditions in trained male endurance athletes to observe any effects on health, performance, and psychological and energy markers. EA was reduced by 50% over 14 days in athletes by maintaining identical energy intake and increasing exercise energy expenditure. Blood was drawn, performance was measured by three specific tests (endurance, explosive power and agility) and two psychological questionnaires were used. Reduced EA (17.3 ± 5.0 kcal/kg FFM/day) resulted in lower body fat% (t(12) = 3.36, p = 0.006), lower power output and relative power output (t(12) = 2.69, p = 0.021 t(12) = 2.34, p = 0.036), explosive power was reduced (t(12) = 6.41, p = 0.000), lactate metabolism was altered (p = 0.001). EA was negatively correlated with haemoglobin and testosterone (r = −0.557, p = 0.30 and r = −0.532, p = 0.037), anaerobic threshold (r = −0.597, p = 0.02) and respiratory compensation point (r = −0.575, p = 0.025). There were significant differences in Well-being (t(12) = 4.11, p = 0.002) and the Three Factor Eating Questionnaire (t(12) = −2.71, p = 0.020). This is the first study to demonstrate that endurance performance and explosive power can be affected before detrimental health effects occur in male athletes. Drastic reductions of EA could lead to poor eating behaviours. The two psychological questionnaires seem to be more sensitive to EA changes than blood markers.

Effects of growth temperature and nitrogen nutrition on expression of C3-C4 intermediate traits in Chenopodium album.

Proto-Kranz plants represent an initial phase in the evolution from C3 to C3-C4 intermediate to C4 plants. The ecological and adaptive aspects of C3-C4 plants would provide an important clue to understand the evolution of C3-C4 plants. We investigated whether growth temperature and nitrogen (N) nutrition influence the expression of C3-C4 traits in Chenopodium album (proto-Kranz) in comparison with Chenopodium quinoa (C3). Plants were grown during 5weeks at 20 or 30°C under standard or low N supply levels (referred to as 20SN, 20LN, 30SN, and 30LN). Net photosynthetic rate and leaf N content were higher in 20SN and 30SN plants than in 20LN and 30LN plants of C. album but did not differ among growth conditions in C. quinoa. The CO2 compensation point (Γ) of C. album was lowest in 30LN plants (36µmolmol-1), highest in 20SN plants (51µmolmol-1), and intermediate in 20LN and 30SN plants, whereas Γ of C. quinoa did not differ among the growth conditions (51-52µmolmol-1). The anatomical structure of leaves was not considerably affected by growth conditions in either species. However, ultrastructural observations in C. album showed that the number of mitochondria per mesophyll or bundle sheath (BS) cell was lower in 20LN and 30LN plants than in 20SN and 30SN plants. Immunohistochemical observations revealed that lower accumulation level of P-protein of glycine decarboxylase (GDC-P) in mesophyll mitochondria than in BS mitochondria is the major factor causing the decrease in Γ values in C. album plants grown under low N supply and high temperature. These results suggest that high growth temperature and low N supply lead to the expression of C3-C4 traits (the reduction of Γ) in the proto-Kranz plants of C. album through the regulation of GDC-P expression.

Photosynthetic Physiology Comparisons between No Tillage and Sod Culture of Citrus Farming in Different Seasons under Various Light Intensities

Sod culture (SC) and no tillage (NT) are modern orchard management systems, and are two different bases for the sustainable development and production of citrus orchards in Taiwan. However, there is no information about the efficiency of either NT or SC on the photosynthetic physiology of farmed citrus under different seasons and varying light intensities. The objective of this study was to clarify the impacts of SC and NT under eco-friendly farming management on the photosynthetic apparatus of an important plantation citrus species in response to varying light intensities over the seasons. The results showed that Rd (dark respiration rate of CO2), Qy (light quantum yield of CO2), LCP (light compensation point), Amax (maximum net assimilation of CO2), and Fv/Fm values of citrus plants under SC were somewhat higher under NT in the same season, particularly in the fall and in winter. As light intensity increased from 200 to 2000 μmol photon m−2 s−1 PPFD, higher Pn (net photosynthesis rate), Gs (stomatal conductance), ETR (electron transport rate), NPQ (non-photochemical quenching), and Fv/Fm (potential quantum efficiency of PSII) values were observed in spring and summer compared to the fall and winter, and increasing NPQ and decreasing Fv/Fm values were observed in all seasons. Positive and significant correlations were shown between the Pn and Gs under NT and SC in all seasons with all light illuminations, whereas significant and negative relationships were observed between the ETR and NPQ under NT in fall and winter at 1200~2000 PPFD. In short, ETR was useful for non-destructive estimations of Pn and NPQ since these indices were significantly and positively correlated with ETR in citrus leaves exposed to 0~1200 PPFD in all seasons and 1200~2000 PPFD in spring, the fall, and winter, providing a quick means to identify the physiological condition of plants under various seasons and tillages. The precise management of photosynthetic parameters such as ETR in response to light irradiances under varied seasons also provides implications for sustainable citrus production for tillage cropping systems in future higher CO2 and potentially wetter or drier environments. The tillages may hold promise for maximizing the economic efficiency of the growth and development of citrus plants grown in the field.

Intracanopy CO2 and light interactions on Humulus lupulus L. net canopy carbon gain under current and future atmospheric CO2 concentrations

Photosynthetic light response curves were measured in four cultivars of Humulus lupulus L. (hop) at CO2 concentrations of 415, 500, 600, and 700 μmol CO2 mol−1. Short-term elevated CO2 increased net photosynthesis (An), light-saturated rates of photosynthesis, and quantum yield and decreased the light compensation point and leaf respiration. To illustrate the effects on canopy carbon gain, we used a rigorously validated physiologically-explicit canopy process model (MAESTRA). The cultivar-specific leaf-level physiological response parameters at 415, 500, 600, and 700 μmol CO2 mol−1 were extrapolated throughout the canopy to reproduce the cultivar-specific carbon gain under current and future atmospheric CO2 conditions. Under sub optimal light conditions, the initial CO2 increase of 415 to 500 μmol CO2 mol−1 resulted in the highest relative carbon gain increase (∼18%), whereas enrichment from 500 to 600 and 600 to 700 μmol CO2 mol−1 resulted in an additional carbon uptake of ∼16% and ∼12%. Ratios of An to increased CO2 indicated that shaded leaves benefit more from elevated CO2 than light saturated leaves. Estimated daily canopy carbon uptake increased ∼24% from 415 to 500 µmol mol−1 CO2. Daily carbon uptake increased by ∼17% from 500 to 600 µmol mol−1 CO2 and ∼18% from 600 to 700 µmol mol−1. Thus, in comparison to leaves exposed to direct sunlight, hop canopy carbon gain in shaded diffuse light lower canopy layers may contribute a greater proportion of total canopy carbon in future atmospheric CO2 conditions.

Structure and magnetic properties of ferrimagnetic [Gd/Fe]n multilayer and GdxFe100−x thin films

The structural and magnetic properties of two series of [Gd(2, 4 nm)/Fe(t)]n multilayer films with varying Fe thickness were investigated and compared to those of amorphous ferrimagnetic GdFe alloys of the same corresponding composition. Transmission electron microscopy studies confirmed the high interface quality of both multilayer series. Furthermore, the microstructure was analyzed, revealing polycrystallinity in both Gd and Fe layers with strong (101̄0)-oriented textured growth of Gd particularly for the multilayer series with 2 nm Gd. Magnetic measurements confirm an out-of-plane magnetic easy axis in the alloy samples and an in-plane magnetic easy axis in all multilayer samples. Twisted spin states in samples with a low remanent magnetization were identified. Magnetic compensation points of both multilayer series are compared to those of the alloy samples. It was found that the dependence of the magnetic compensation point on effective Gd concentration in the series with 2 nm Gd closely resembles the strong dependence observed in the alloy counterparts. In contrast, a weaker dependence is revealed for the multilayer series with 4 nm Gd, which makes this system more robust against variations in composition required for applications.