RATE OF O2 PRODUCTION DERIVED FROM PULSE‐AMPLITUDE‐MODULATED FLUORESCENCE: TESTING THREE BIOOPTICAL APPROACHES AGAINST MEASURED O2‐PRODUCTION RATE1

Light absorption by phytoplankton is both species specific and affected by photoacclimational status. To estimate oxygenic photosynthesis from pulse‐amplitude‐modulated (PAM) fluorescence, the amount of quanta absorbed by PSII needs to be quantified. We present here three different biooptical approaches to estimate the fraction of light absorbed by PSII: (1) the factor 0.5, which implies that absorbed light is equally distributed among PSI and PSII; (2) the fraction of chl a in PSII, determined as the ratio between the scaled red‐peak fluorescence excitation and the red absorption peak; and (3) the measure of light absorbed by PSII, determined from the scaling of the fluorescence excitation spectra to the absorption spectra by the “no‐overshoot” procedure. Three marine phytoplankton species were used as test organisms: Prorocentrum minimum (Pavill.) J. Schiller (Dinophyceae), Prymnesium parvum cf. patelliferum (J. C. Green, D. J. Hibberd et Pienaar) A. Larsen (Haptophyceae), and Phaeodactylum tricornutum Bohlin (Bacillariophyceae). Photosynthesis versus irradiance (P vs. E) parameters calculated using the three approaches were compared with P versus E parameters obtained from simultaneously measured rates of oxygen production. Generally, approach 1 underestimated, while approach 2 overestimated the gross O₂‐production rate calculated from PAM fluorescence. Approach 3, in principle the best approach to estimate quanta absorbed by PSII, was also superior according to observations. Hence, we recommend approach 3 for estimation of gross O₂‐production rates based on PAM fluorescence measurements.     

Temperature response of photosynthetic light‐ and carbon‐use characteristics in the red seaweed Gracilariopsis lemaneiformis (Gracilariales,Rhodophyta)

The red seaweed Gracilariopsis is an important crop extensively cultivated in China for high‐quality raw agar. In the cultivation site at Nanao Island, Shantou, China, G. lemaneiformis experiences high variability in environmental conditions like seawater temperature. In this study, G. lemaneiformis was cultured at 12, 19, or 26°C for 3 weeks, to examine its photosynthetic acclimation to changing temperature. Growth rates were highest in G. lemaneiformis thalli grown at 19°C, and were reduced with either decreased or increased temperature. The irradiance‐saturated rate of photosynthesis (P_max) decreased with decreasing temperature, but increased significantly with prolonged cultivation at lower temperatures, indicating the potential for photosynthesis acclimation to lower temperature. Moreover, P_max increased with increasing temperature (~30 μmol O₂ · g^?1FW · h^?1 at 12°C to 70 μmol O₂ · g^?1FW · h^?1 at 26°C). The irradiance compensation point for photosynthesis (I_c) decreased significantly with increasing temperature (28 μmol photons · m^?2 · s^?1 at high temperature vs. 38 μmol photons · m^?2 · s^?1 at low temperature). Both the photosynthetic light‐ and carbon‐use efficiencies increased with increasing growth or temperatures (from 12°C to 26°C). The results suggested that the thermal acclimation of photosynthetic performance of G. lemaneiformis would have important ecophysiological implications in sea cultivation for improving photosynthesis at low temperature and maintaining high standing biomass during summer. Ongoing climate change (increasing atmospheric CO₂ and global warming) may enhance biomass production in G. lemaneiformis mariculture through the improved photosynthetic performances in response to increasing temperature.     

Growth energetics of juvenile herring,Clupea harengus L.: food conversion efficiency and temperature dependency of metabolic rate

The relationship between rates of food consumption (C) and somatic growth (G) and the effect of temperature (T) on rates of mass lost during food deprivation were examined in 9–10 cm total length (TL) [1.0–1.5 g dry mass (DM)] juvenile Atlantic herring (Clupea harengus L.) in the laboratory. One feeding‐growth trial was conducted at 16°C using groups of herring feeding on known rations of brine shrimp (Artemia spp.) nauplii to quantify gross and net growth efficiency. Rates of mass lost by groups of herring (a proxy for metabolic rate, M) were measured in trials conducted at 9.7, 14.2 and 17.9°C. Gross growth efficiency (GGE = 100*G*C^?1) at 16°C was 25% at the highest rations (5.8–6.6% DM). The maintenance ration (C_main = C at zero G) was equal to 432 J*fish^?1*d^?1 or 2.0% DM*d^?1. At 16°C, net growth efficiency (100*G*(C?C_main)^?1) was 42%. The nucleic acid content (RNA‐DNA ratio, RD) in herring muscle tissue was strongly related to somatic growth (G, % DM*d^?1 = ?0.36*RD² + 3.21*RD ?3.92, r² = 0.90, P < 0.05, n = 8 groups). The effect of T (9.7–17.9°C) on M was described by a second order polynomial equation M = ?1.24*T + 38.2*T ? 218 (J*g DM^?1*d^?1) and M = ?10*T + 310*T ? 1815 (J*fish^?1*d^?1). This was the first study to investigate the influence of temperature on the metabolic rate of juvenile Atlantic herring under stress‐free conditions in the laboratory and provides the first estimates of gross and net growth efficiency for this species feeding on live prey.     

Grafting Benzenediazonium Tetrafluoroborate onto LiNixCoyMnzO2 Materials Achieves Subzero‐Temperature High‐Capacity Lithium‐Ion Storage via a Diazonium Soft‐Chemistry Method

Subzero‐temperature Li‐ion batteries (LIBs) are highly important for specific energy storage applications. Although the nickel‐rich layered lithium transition metal oxides(LiNi_xCo_yMn_zO₂) (LNCM) (x > 0.5, x + y +z = 1) are promising cathode materials for LIBs, their very slow Li‐ion diffusion is a main hurdle on the way to achieve high‐performance subzero‐temperature LIBs. Here, a class of low‐temperature organic/inorganic hybrid cathode materials for LIBs, prepared by grafting a conducting polymer coating on the surface of 3 µm sized LiNi_0.6Co_0.2Mn_0.2O₂ (LNCM‐3) material particles via a greener diazonium soft‐chemistry method is reported. Specifically, LNCM‐3 particles are uniformly coated with a thin polyphenylene film via the spontaneous reaction between LNCM‐3 and C₆H₅N₂⁺BF₄^?. Compared with the uncoated one, the polyphenylene‐coated LNCM‐3 (polyphenylene/LNCM‐3) has shown much improved low‐temperature discharge capacity (≈148 mAh g^?1 at 0.1 C, ?20 °C), outstanding rate capability (≈105 mAh g^?1 at 1 C, ?20 °C), and superior low‐temperature long‐term cycling stability (capacity retention is up to 90% at 0.5 C over 1150 cycles). The low‐temperature performance of polyphenylene/LNCM‐3 is the best among the reported state‐of‐the art cathode materials for LIBs. The present strategy opens up a new avenue to construct advanced cathode materials for wider range applications.     

Fluctuating water levels control water chemistry and metabolism of a charophyte‐dominated pond

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Photosynthetic responses to photosynthetically active radiation and temperature including chilling‐light stress on the heteromorphic life history stages of a brown alga,Cladosiphon okamuranus (Chordariaceae) from Ryukyu Islands,Japan

Photosynthetic responses to temperature and photosynthetically active radiation (PAR) were investigated on the heteromorphic life history stages (macroscopic and microscopic stages) of an edible Japanese brown alga, Cladosiphon okamuranus from the Ryukyu Islands. Measurements were carried out by using optical dissolved oxygen sensors and a pulse‐amplitude modulated fluorometer. Maximum net photosynthetic rates and other parameters of the Photosynthesis – PAR curves at 28°C were somewhat similar in both life history stages, without characteristic photoinhibition at 1000 μmol photons m^?2 s^?1. Results of oxygenic gross photosynthesis and dark respiration experiments over a temperature range of 8–40°C revealed similar temperature optima for both stages (29.7°C, macroscopic stage; 30.3°C, microscopic stage), which support their observed occurrences in the habitat during summer. Maximum quantum yields of photosystem II (PSII ) (F _v /F _m ) were relatively stable at low temperatures with the highest at 15.1°C for the macroscopic stage and at 16.5°C for the microscopic stage; but dropped at higher temperatures especially above 28°C. Continuous exposures (6 h) to 200 and 1000 μmol photons m^?2 s^?1 at 8, 16, and 28°C revealed greater depressions in effective quantum yields of PSII (Φ _PSII ) of the microscopic stage at 8°C, as well as its F _v /F _m that barely increased after 6 h of dark acclimation. Whereas post‐dark acclimation F _v /F _m of both stages exposed to low PAR fairly recovered at 28°C, suggesting their photosynthetic tolerance to such high temperature. Under natural conditions, both heteromorphic stages of C. okamuranus may persist throughout the year in this region. Beyond its northern limit of distribution, the microscopic stage of this species may suffer from photodamage, as enhanced by low winter temperatures; hence, its restricted occurrence.     

Evidence of temperature‐independent metabolic rates in diurnal Namib Desert tenebrionid beetles

To investigate whether the sensitivity to environmental temperature varies between nocturnal and diurnal species of tenebrionid beetle, the metabolic rates of three diurnal species (Onymacris plana Peringuey, Onymacris rugatipennis Haag and Physadesmia globosa Haag) and three nocturnal species (Epiphysa arenicola Penrith, Gonopus sp. and Stips sp.) of beetles from the Namib Desert are measured over a range of temperatures (15–40 °C) that are experienced by these beetles in their natural habitat. The diurnal species O. plana, O. rugatipennis and P. globosa exhibit temperature‐independent metabolic rates (mean Q₁₀ = 1.2) within temperature ranges that are ecologically relevant for diurnal desert beetles (30–40 °C). Onymacris plana, in particular, has a 20–40 °C rate–temperature slope (0.007 log₁₀ mL O₂ h^?1 g^?1 °C^?1; Q₁₀ = 1.1) that is less than half that of the other five beetle species (0.022–0.063 log₁₀ mL O₂ h^?1 g^?1 °C^?1; Q₁₀ ranges from 1.3–1.9), suggesting that O. plana is more metabolically independent of temperature than the other nocturnal and diurnal tenebrionids being investigated. Animals with metabolic rates that are decoupled from body temperature (or ambient temperature) may have an ecological advantage that allows them to exploit thermal and spatial niches during extreme temperature conditions.     

EFFECTS OF LOWERING TEMPERATURE DURING CULTURE ON THE PRODUCTION OF POLYUNSATURATED FATTY ACIDS IN THE MARINE DIATOM PHAEODACTYLUM TRICORNUTUM (BACILLARIOPHYCEAE)1

The composition of fatty acids and contents of eicosapentaenoic acid (EPA) and polyunsaturated fatty acids (PUFAs) of the economically important marine diatom, Phaeodactylum tricornutum (Bohlin), were investigated to see whether reducing the culture temperature enhances the production of EPA and PUFAs. The contents of EPA and PUFAs of P. tricornutum were found to be higher at lower temperature when cultured at 10, 15, 20, or 25°C. When the cells grown at 25°C were shifted to 20, 15, or 10°C, the contents per dry mass of PUFAs and EPA increased to the maximal values in 48, 24, and 12 h, respectively. The highest yields of PUFAs and EPA per unit dry mass (per unit volume of culture) were 4.9% and 2.6% (12.4 and 6.6 mg·L^?1), respectively, when temperature was shifted from 25 to 10°C for 12 h, both being raised by 120% compared with the control. The representative fatty acids in the total fatty acids, when temperature was lowered from 25 to 10°C, decreased proportionally by about 30% in C_16:0 and 20% in C_16:1(n?7) but increased about 85% in EPA. It was concluded that lowering culture temperature of P. tricornutum could significantly raise the yields of EPA and PUFAs.     

Hemp (Cannabis sativa L.) leaf photosynthesis in relation to nitrogen content and temperature: implications for hemp as a bio‐economically sustainable crop

Hemp (Cannabis sativa L.) may be a suitable crop for the bio‐economy as it requires low inputs while producing a high and valuable biomass yield. With the aim of understanding the physiological basis of hemp's high resource‐use efficiency and yield potential, photosynthesis was analysed on leaves exposed to a range of nitrogen and temperature levels. Light‐saturated net photosynthesis rate (A_max) increased with an increase in leaf nitrogen up to 31.2 ± 1.9 μmol m^?2 s^?1 at 25 °C. The A_max initially increased with an increase in leaf temperature (T_L), levelled off at 25–35 °C and decreased when T_L became higher than 35 °C. Based on a C₃ leaf photosynthesis model, we estimated mesophyll conductance (g_m), efficiency of converting incident irradiance into linear electron transport under limiting light (κ_2LL), linear electron transport capacity (J_max), Rubisco carboxylation capacity (V_cmax), triose phosphate utilization capacity (T_p) and day respiration (R_d), using data obtained from gas exchange and chlorophyll fluorescence measurements at different leaf positions and various levels of incident irradiance, CO₂ and O₂. The effects of leaf nitrogen and temperature on photosynthesis parameters were consistent at different leaf positions and among different growth environments except for κ_2LL, which was higher for plants grown in the glasshouse than for those grown outdoors. Model analysis showed that compared with cotton and kenaf, hemp has higher photosynthetic capacity when leaf nitrogen is <2.0 g N m^?2. The high photosynthetic capacity measured in this study, especially at low nitrogen level, provides additional evidence that hemp can be grown as a sustainable bioenergy crop over a wide range of climatic and agronomic conditions.     

Effect of various environmental factors on the viability of Cryptosporidium parvum oocysts

Aims: To evaluate individual and combined effects of temperature (4, 18 and 25°C), pH (7 and 10), ammonia (5 and 50 mg l^?1) and exposure time (1, 2, 4 and 6 days) on the viability of Cryptosporidium parvum oocysts in water. Methods and Results: The viability of oocysts was evaluated using the fluorogenic vital dyes assay (4′,6‐diamidino‐2‐phenylindole and propidium iodide). All the factors analysed (temperature, pH, ammonia and exposure time) and their interaction were statistically significant (P < 0·005). Exposure of oocysts to pH 10 for 6 days at 25°C reduced oocyst viability from ～80% to 51%. Similarly, the exposure of C. parvum oocysts to 5 mg NH₃ l^?1 and 50 mg NH₃ l^?1 for 4 days reduced their viability from between ～80% to 41·5% and 14·8%, respectively. Conclusions: The interaction between pH, temperature and exposure time may have adverse effects on the survival of C. parvum oocysts in water. Low concentrations of ammonia, as commonly found in alga‐based wastewater systems, over a long period of time can produce high C. parvum oocyst inactivation rates. Significance and Impact of the Study: This study provides relevant data on the inactivation of C. parvum oocysts in alga‐based wastewater‐treatment systems in the northwest of Spain.     

Long‐term elevated air [CO2] strengthens photosynthetic functioning and mitigates the impact of supra‐optimal temperatures in tropical Coffea arabica and C. canephora species

The tropical coffee crop has been predicted to be threatened by future climate changes and global warming. However, the real biological effects of such changes remain unknown. Therefore, this work aims to link the physiological and biochemical responses of photosynthesis to elevated air [CO₂] and temperature in cultivated genotypes of Coffea arabica L. (cv. Icatu and IPR108) and Coffea canephora cv. Conilon CL153. Plants were grown for ca. 10 months at 25/20 °C (day/night) and 380 or 700 μl CO₂ l^?1 and then subjected to temperature increase (0.5 °C day^?1) to 42/34 °C. Leaf impacts related to stomatal traits, gas exchanges, C isotope composition, fluorescence parameters, thylakoid electron transport and enzyme activities were assessed at 25/20, 31/25, 37/30 and 42/34 °C. The results showed that (1) both species were remarkably heat tolerant up to 37/30 °C, but at 42/34 °C a threshold for irreversible nonstomatal deleterious effects was reached. Impairments were greater in C. arabica (especially in Icatu) and under normal [CO₂]. Photosystems and thylakoid electron transport were shown to be quite heat tolerant, contrasting to the enzymes related to energy metabolism, including RuBisCO, which were the most sensitive components. (2) Significant stomatal trait modifications were promoted almost exclusively by temperature and were species dependent. Elevated [CO₂], (3) strongly mitigated the impact of temperature on both species, particularly at 42/34 °C, modifying the response to supra‐optimal temperatures, (4) promoted higher water‐use efficiency under moderately higher temperature (31/25 °C) and (5) did not provoke photosynthetic downregulation. Instead, enhancements in [CO₂] strengthened photosynthetic photochemical efficiency, energy use and biochemical functioning at all temperatures. Our novel findings demonstrate a relevant heat resilience of coffee species and that elevated [CO₂] remarkably mitigated the impact of heat on coffee physiology, therefore playing a key role in this crop sustainability under future climate change scenarios.     

Advanced Electrolytes for Fast‐Charging High‐Voltage Lithium‐Ion Batteries in Wide‐Temperature Range

LiNi_xMn_yCo_1?x?yO₂ (NMC) cathode materials with Ni ≥ 0.8 have attracted great interest for high energy‐density lithium‐ion batteries (LIBs) but their practical applications under high charge voltages (e.g., 4.4 V and above) still face significant challenges due to severe capacity fading by the unstable cathode/electrolyte interface. Here, an advanced electrolyte is developed that has a high oxidation potential over 4.9 V and enables NMC811‐based LIBs to achieve excellent cycling stability in 2.5–4.4 V at room temperature and 60 °C, good rate capabilities under fast charging and discharging up to 3C rate (1C = 2.8 mA cm^?2), and superior low‐temperature discharge performance down to ?30 °C with a capacity retention of 85.6% at C/5 rate. It is also demonstrated that the electrode/electrolyte interfaces, not the electrolyte conductivity and viscosity, govern the LIB performance. This work sheds light on a very promising strategy to develop new electrolytes for fast‐charging high‐energy LIBs in a wide‐temperature range.     

Structural,morphological and steady state photoluminescence spectroscopy studies of red Eu3+‐doped Y2O3 nanophosphors prepared by the sol‐gel method

Europium trivalent (Eu³⁺)‐doped Y₂O₃ nanopowders of different concentrations (0.5, 2.5, 5 or 7 at.%) were synthesized by the sol‐gel method, at different pH values (pH 2, 5 or 8) and annealing temperatures (600°C, 800°C or 1000°C). The nanopowders samples were characterized by X‐ray diffraction (XRD), field emission scanning electron microscopy (FE‐SEM), Fourier transform infrared spectroscopy (FT‐IR) and steady state photoluminescence spectroscopy. The effect of pH of solution and annealing temperatures on structural, morphological and photoluminescence properties of Eu³⁺‐doped Y₂O₃ were studied and are discussed. It was found that the average crystallite size of the nanopowders increased with increasing pH and annealing temperature values. The Y₂O₃:Eu³⁺ material presented different morphology and its evolution depended on the pH value and the annealing temperature. Activation energies at different pH values were determined and are discussed. Under ultraviolet (UV) light excitation, Y₂O₃:Eu³⁺ showed narrow emission peaks corresponding to the ⁵D_0–⁷F_J (J = 0, 1, 2 and 3) transitions of the Eu³⁺ ion, with the most intense red emission at 611 assigned to forced electric dipole ⁵D₀→⁷F₂. The emission intensity became more intense with increasing annealing temperature and pH values, related to the improvement of crystalline quality. For the 1000°C annealing temperature, the emission intensity presented a maximum at pH 5 related to the uniform cubic‐shaped particles. It was found that for lower annealing temperatures (small crystallite size) the CTB (charge transfer band) position presented a red shift. Copyright © 2015 John Wiley & Sons, Ltd.     

Optimized 4‐V Spinel Cathode Material with High Energy Density for Li‐Ion Cells Operating at 60 °C

Spinel cathodes comprising 16‐μm, AlPO₄‐coated Li_1.09Mn_1.83Al_0.08O₄ with a high energy density of 1.2 W h cm^‐3 are synthesized via a conventional solid‐state reaction using MnO₂ and Li₂CO₃ at 770 °C for 10 h and using a solution‐based coating method in bulk scale (>20 kg). The cathodes are coated by aluminum phosphate at a thickness of <10 nm. The coated cathodes exhibit a first discharge capacity of 108 mA·h g^‐1 and a coulombic efficiency of >99.8%, and their capacity retention is 78% after 200 cycles at a 0.5C rate in a Li‐ion cell under 60 °C. More importantly, a Li‐ion cell containing the coated cathode does not exhibit a swelling problem after 200 cycles at 60 °C. Transmission and scanning electron microscopy suggest that the uniformly distributed AlPO₄ coating and the possible formation of a solid solution phase along the surface play key roles in enhancing the electrochemical performance of the LiMn₂O₄ spinel at 60 °C.     

Isotopic biosignatures in carbonate‐rich,cyanobacteria‐dominated microbial mats of the Cariboo Plateau,B.C.

Photosynthetic activity in carbonate‐rich benthic microbial mats located in saline, alkaline lakes on the Cariboo Plateau, B.C. resulted in pCO₂ below equilibrium and δ¹³C_DIC values up to +6.0‰ above predicted carbon dioxide (CO₂) equilibrium values, representing a biosignature of photosynthesis. Mat‐associated δ¹³C_carb values ranged from ~4 to 8‰ within any individual lake, with observations of both enrichments (up to 3.8‰) and depletions (up to 11.6‰) relative to the concurrent dissolved inorganic carbon (DIC). Seasonal and annual variations in δ¹³C values reflected the balance between photosynthetic ¹³C‐enrichment and heterotrophic inputs of ¹³C‐depleted DIC. Mat microelectrode profiles identified oxic zones where δ¹³C_carb was within 0.2‰ of surface DIC overlying anoxic zones associated with sulphate reduction where δ¹³C_carb was depleted by up to 5‰ relative to surface DIC reflecting inputs of ¹³C‐depleted DIC. δ¹³C values of sulphate reducing bacteria biomarker phospholipid fatty acids (PLFA) were depleted relative to the bulk organic matter by ~4‰, consistent with heterotrophic synthesis, while the majority of PLFA had larger offsets consistent with autotrophy. Mean δ¹³C_org values ranged from ?18.7 ± 0.1 to ?25.3 ± 1.0‰ with mean Δ¹³C_inorg‐org values ranging from 21.1 to 24.2‰, consistent with non‐CO₂‐limited photosynthesis, suggesting that Precambrian δ¹³C_org values of ~?26‰ do not necessitate higher atmospheric CO₂ concentrations. Rather, it is likely that the high DIC and carbonate content of these systems provide a non‐limiting carbon source allowing for expression of large photosynthetic offsets, in contrast to the smaller offsets observed in saline, organic‐rich and hot spring microbial mats.     

Low‐Temperature Micro‐Solid Oxide Fuel Cells with Partially Amorphous La0.6Sr0.4CoO3‐δ Cathodes

Partially amorphous La_0.6Sr_0.4CoO_3‐δ (LSC) thin‐film cathodes are fabricated using pulsed laser deposition and are integrated in free‐standing micro‐solid oxide fuel cells (micro‐SOFC) with a 3YSZ electrolyte and a Pt anode. A low degree of crystallinity of the LSC layers is achieved by taking advantage of the miniaturization of the cells, which permits low‐temperature operation (300–450 °C). Thermomechanically stable micro‐SOFC are obtained with strongly buckled electrolyte membranes. The nanoporous columnar microstructure of the LSC layers provides a large surface area for oxygen incorporation and is also believed to reduce the amount of stress at the cathode/electrolyte interface. With a high rate of failure‐free micro‐SOFC membranes, it is possible to avoid gas cross‐over and open‐circuit voltages of 1.06 V are attained. First power densities as high as 200–262 mW cm^?2 at 400–450 °C are achieved. The area‐specific resistance of the oxygen reduction reaction is lower than 0.3 Ω cm² at 400 °C around the peak power density. These outstanding findings demonstrate that partially amorphous oxides are promising electrode candidates for the next‐generation of solid oxide fuel cells working at low‐temperatures.     

Photosynthetic activity including the thermal‐ and chilling‐light sensitivities of a temperate Japanese brown alga Sargassum macrocarpum

The effects of irradiance, temperature, thermal‐ and chilling‐light sensitivities on the photosynthesis of a temperate alga, Sargassum macrocarpum (Fucales) were determined by a pulse amplitude modulation (PAM)‐chlorophyll fluorometer and dissolved oxygen sensors. Oxygenic photosynthesis–irradiance curves at 8, 20, and 28°C revealed that the maximum net photosynthetic rates (NP _max) and saturation irradiance were highest at 28°C, and lowest at 8°C. Gross photosynthesis and dark respiration determined over a range of temperatures (8–36°C) at 300 μmol photons m^?2 s^?1 revealed that the maximum gross photosynthetic rate (GP_max) occurred at 27.8°C, which is consistent with the highest seawater temperature in the southern distributional limit of this species in Japan. Additionally, the maximum quantum yields of photosystem II (F _v/F _m) during the 72‐h temperature exposures were stable at 8–28°C, but suddenly dropped to zero at higher temperatures, indicative of PSII deactivation. Continuous exposure (12 h) to irradiance of 200 (low) and 1000 (high) μmol photons m^?2 s^?1 at 8, 20, and 28°C revealed greater declines in their effective quantum yields (Φ _PSII) under high irradiance. While Φ _PSII under low irradiance were very similar with the initial F _v/F _m under 20 and 28°C, values rapidly decreased with exposure duration at 8°C. At this temperature, F _v/F _m did not recover to initial values even after 12 h of dark acclimation. Final F _v/F _m of alga at 28°C under high irradiance treatment also did not recover, suggesting its sensitivity to photoinhibition at both low and high temperatures. These photosynthetic characteristics reflect both the adaptation of the species to the general environmental conditions, and its ability to acclimate to seasonal changes in seawater temperature within their geographical range of distribution.     

Three physiological parameters capture variation in leaf respiration of Eucalyptus grandis,as elicited by short‐term changes in ambient temperature,and differing nitrogen supply

We used instantaneous temperature responses of CO₂‐respiration to explore temperature acclimation dynamics for Eucalyptus grandis grown with differing nitrogen supply. A reduction in ambient temperature from 23 to 19 °C reduced light‐saturated photosynthesis by 25% but increased respiratory capacity by 30%. Changes in respiratory capacity were not reversed after temperatures were subsequently increased to 27 °C. Temperature sensitivity of respiration measured at prevalent ambient temperature varied little between temperature treatments but was significantly reduced from ~105 kJ mol^?1 when supply of N was weak, to ~70 kJ mol^?1 when it was strong. Temperature sensitivity of respiration measured across a broader temperature range (20–40 °C) could be fully described by 2 exponent parameters of an Arrhenius‐type model (i.e., activation energy of respiration at low reference temperature and a parameter describing the temperature dependence of activation energy). These 2 parameters were strongly correlated, statistically explaining 74% of observed variation. Residual variation was linked to treatment‐induced changes in respiration at low reference temperature or respiratory capacity. Leaf contents of starch and soluble sugars suggest that respiratory capacity varies with source‐sink imbalances in carbohydrate utilization, which in combination with shifts in carbon‐flux mode, serve to maintain homeostasis of respiratory temperature sensitivity at prevalent growth temperature.     

Low-temperature photosynthetic performance of a C4 grass and a co-occurring C3 grass native to high latitudes

The photosynthetic performance of C₄ plants is generally inferior to that of C₃ species at low temperatures, but the reasons for this are unclear. The present study investigated the hypothesis that the capacity of Rubisco, which largely reflects Rubisco content, limits C₄ photosynthesis at suboptimal temperatures. Photosynthetic gas exchange, chlorophyll a fluorescence, and the in vitro activity of Rubisco between 5 and 35 °C were measured to examine the nature of the low‐temperature photosynthetic performance of the co‐occurring high latitude grasses, Muhlenbergia glomerata (C₄) and Calamogrostis canadensis (C₃). Plants were grown under cool (14/10 °C) and warm (26/22 °C) temperature regimes to examine whether acclimation to cool temperature alters patterns of photosynthetic limitation. Low‐temperature acclimation reduced photosynthetic rates in both species. The catalytic site concentration of Rubisco was approximately 5.0 and 20 µmol m^?2 in M. glomerata and C. canadensis, respectively, regardless of growth temperature. In both species, in vivo electron transport rates below the thermal optimum exceeded what was necessary to support photosynthesis. In warm‐grown C. canadensis, the photosynthesis rate below 15 °C was unaffected by a 90% reduction in O₂ content, indicating photosynthetic capacity was limited by the capacity of P_i‐regeneration. By contrast, the rate of photosynthesis in C. canadensis plants grown at the cooler temperatures was stimulated 20–30% by O₂ reduction, indicating the P_i‐regeneration limitation was removed during low‐temperature acclimation. In M. glomerata, in vitro Rubisco activity and gross CO₂ assimilation rate were equivalent below 25 °C, indicating that the capacity of the enzyme is a major rate limiting step during C₄ photosynthesis at cool temperatures.     

A surface plasmon resonance assay for characterisation and epitope mapping of anti‐GLP‐1 antibodies

The incretin hormone glucagon‐like peptide‐1 (GLP‐1) has been subject to substantial pharmaceutical research regarding the treatment of type 2 diabetes mellitus. However, quantification of GLP‐1 levels remains complicated due to the low circulation concentration and concurrent existence of numerous metabolites, homologous peptides, and potentially introduced GLP‐1 receptor agonists. Surface plasmon resonance (SPR) facilitates real‐time monitoring allowing a more detailed characterisation of the interaction compared with conventional enzyme‐linked immunosorbent assays (ELISA). In this paper, we describe the development of the first SPR assays for characterisation of anti‐GLP‐1 antibodies for ELISA purposes. Binding responses were obtained on covalently immobilised anti‐GLP‐1 antibodies at 12°C, 25°C, and 40°C and fitted to a biomolecular (1:1) interaction model showing association rates of 1.01 × 10³ to 4.54 × 10³ M^?1 s^?1 and dissociation rates of 3.56 × 10^?5 to 1.56 × 10^?3 s^?1 leading to affinities of 35.2 to 344 nM, depending on the temperature. Determination of thermodynamic properties revealed an enthalpy driven interaction (ΔH < ΔS < 0) with higher affinities at lower temperatures due to the formation and stabilisation of hydrogen bonds within the binding site primarily composed of polar amino acids (ΔC_p < 0). Pair‐wise epitope mapping was performed on captured anti‐GLP‐1 antibodies followed by subsequent interaction with GLP‐1 (7‐36) and other anti‐GLP‐1 antibodies. A global evaluation of every binding response led to an epitope map elucidating the potential of various anti‐GLP‐1 antibody pairs for sandwich ELISA and hence pinpointing the optimal antibody combinations. The SPR assays proved capable of providing vital information for ELISA development endorsing it as a useful optimisation tool.