Gas exchange and carbon isotope composition of Ananas comosus in response to elevated CO2 and temperature

Ananas comosus L. (Merr.) (pineapple) was grown at three day/night temperatures and 350 (ambient) and 700 (elevated) μ mol mol^–1 CO₂ to examine the interactive effects of these factors on leaf gas exchange and stable carbon isotope discrimination ( Δ ,‰). All data were collected on the youngest mature leaf for 24 h every 6 weeks. CO₂ uptake (mmol m^–2 d^–1) at ambient and elevated CO₂, respectively, were 306 and 352 at 30/20 °C, 175 and 346 at 30/25 °C and 187 and 343 at 35/25 °C. CO₂ enrichment enhanced CO₂ uptake substantially in the day in all environments. Uptake at night at elevated CO₂, relative to that at ambient CO₂, was unchanged at 30/20 °C, but was 80% higher at 30/25 °C and 44% higher at 35/25 °C suggesting that phosphoenolpyruvate carboxylase was not CO₂-saturated at ambient CO₂ levels and a 25 °C night temperature. Photosynthetic water use efficiency (WUE) was higher at elevated than at ambient CO₂. Leaf Δ -values were higher at elevated than at ambient CO₂ due to relatively higher assimilation in the light. Leaf Δ was significantly and linearly related to the fraction of total CO₂ assimilated at night. The data suggest that a simultaneous increase in CO₂ level and temperature associated with global warming would enhance carbon assimilation, increase WUE, and reduce the temperature dependence of CO₂ uptake by A. comosus .     

The effects of temperature and hyperoxia on arterial PO2 and acid-base status in Piaractus mesopotamicus

The effects of hyperoxia and change of temperature (range 20–30° C) on blood gases were studied in the teleost fish Piaractus mesopotamicus , native to several major river systems in Brazil. Large hyperoxia-induced increases of arterial P o₂ ( P _ao₂) indicated that true branchial blood shunts are negligible in relation to total gill perfusion. This implies that blood gases will be influenced by ventilation rather than by shunts. Acute variations of temperature ( t ) were accompanied by changes of arterial blood pH (on the average Δ p H_aΔt⁻¹ of — 0·015 units °C⁻¹), due mainly to alterations of P _aco₂: 2·4 mmHg at 20° C, 5·0 mmHg at 30° C. Concomitantly, P _ao₂ declined from 116 mmHg (20° C) to 89 mmHg (30° C). The data suggest that temperature-induced changes of acid-base status depend mainly on gill ventilation and that the decrease of P _ao₂ with higher temperature is a result of this regulation.     

The Role of SwrA,DegU and PD3 in fla/che Expression in B. subtilis

In B. subtilis swarming and robust swimming motility require the positive trigger of SwrA on fla/che operon expression. Despite having an essential and specific activity, how SwrA executes this task has remained elusive thus far. We demonstrate here that SwrA acts at the main σ^A-dependent fla/che promoter P_A(fla/che) through DegU. Electrophoretic mobility shift assays (EMSA) reveal that SwrA forms a complex with the phosphorylated form of DegU (DegU~P) at P_A(fla/che) while it is unable to do so with either unphosphorylated DegU or the DegU32(Hy) mutant protein. Motility assays show that a highly phosphorylated DegU is not detrimental for flagellar motility provided that SwrA is present; however, DegU~P represses P_A(fla/che) in the absence of SwrA. Overall, our data support a model in which DegU~P is a dual regulator, acting either as a repressor when alone or as a positive regulator of P_A(fla/che) when combined with SwrA. Finally, we demonstrate that the σ^D-dependent P_D3(fla/che) promoter plays an important role in motility, representing a contingent feedback loop necessary to maintain basal motility when swrA is switched to the non-functional swrA ^- status.     

Characterization of Immunoreactive Thyrotropin Releasing Hormone in Human Fetal Cerebellum

Abstract— High concentrations (411 ± 30 pg/mg protein; mean ± S.E., n = 12) of immunoreactive TRH (TRH_i) were detected in extracts of human fetal cerebellum (13-26 weeks gestation). The TRH_i in the cerebellar extracts, when subjected to gel filtration and high performance liquid chromatography (HPLC), co-migrated with synthetic TRH. In each instance, no TRHⁱ was detected which did not share identical chromatographic mobilities with synthetic TRH. Like synthetic TRH, the TRH_i in extracts of fetal cerebellum and hypothalamus was insoluble in diethyl ether and was efficiently degraded when incubated at 37°C with adult rat serum. No significant degradation of TRH_i occurred when the incubation was conducted at 0°C or when the extracts were incubated with rat serum that had been preheated at 60°C for 20 min. Neither synthetic TRH nor TRH_i in extracts of fetal cerebellum or hypothalamus was degraded when incubated with human umbilical cord serum at 37°C or 0°C. The results of this study are supportive of the view that the TRHⁱ in extracts of human fetal cerebellum is identical to TRH.     

Effects of gaseous environment and temperature on the storage behaviour of Listeria monocytogenes on chicken breast meat

Portions of skinless chicken breast meat (pH 5·8) were inoculated with a strain of Listeria monocytogenes and stored at 1, 6 or 15°C in (1) aerobic conditions; (2) 30% CO₂+ air; (3) 30% CO₂+ N₂; and (4) 100% CO₂. When samples were held at 1°C the organism failed to grow under any of the test conditions, despite marked differences between treatments in spoilage rate and ultimate microflora. At 6°C counts of L. monocytogenes increased ca 10-fold in aerobic conditions before spoilage of the meat, but only when the inoculum culture was incubated at 1°C rather than 37°C. In CO₂ atmospheres growth of L. monocytogenes was inhibited on meat held at 6°C, especially under 100% CO₂. By contrast, storage at 15°C led to spoilage of the meat within 2 d, in all gaseous environments, and listeria levels increased up to 100-fold. Differences in the behaviour of L. monocytogenes on poultry and red meats are discussed.     

Thermal tolerance of a northern population of striped bass Morone saxatilis

Thermal tolerance of age 0+ year Shubenacadie River (Nova Scotia, Canada) striped bass Morone saxatilis juveniles (mean ± s . e . fork length, L _F, 19·2 ± 0·2 cm) acclimated in fresh water to six temperatures from 5 to 30° C was measured by both the incipient lethal technique (72 h assay), and the critical thermal method ( C _m). The lower incipient lethal temperature ranged from 2·4 to 11·3° C, and the upper incipient lethal temperature ( I _U) from 24·4 to 33·9° C. The area of thermal tolerance was 618° C². In a separate experiment, the I _U of large age 2+ year fish (34·4 ± 0·5 cm L _F) was 1·2 and 0·6° C lower ( P < 0·01) than smaller age 1+ year fish (21·8 ± 0·5 cm L _F) at acclimation temperatures of 16 and 23° C. Using the C _m, loss of equilibrium occurred at 27·4–37·7° C, loss of righting response at 28·1–38·4° C and onset of spasms at 28·5–38·8° C, depending on acclimation temperature. The linear regression slopes for these three responses were statistically similar (0·41; P > 0·05), but the intercepts differed (25·3, 26·0 and 26·5° C; P < 0·01). The thermal tolerance of this northern population appears to be broader than southern populations.     

The influence of thermal parameters on the acclimation responses of pinfish Lagodon rhomboides exposed to static and decreasing low temperatures

Pinfish Lagodon rhomboides acclimation rates were determined by modelling changes in critical thermal minimum ( T _{crit min}, ° C) estimates at set intervals following a temperature decrease of 3–4° C. The results showed that pinfish gained a total of 3·7° C of cold tolerance over a range of acclimation temperatures ( T _acc, ° C) from (23–12° C), that cold tolerance increased with exposure time to the reduced temperature at all T _acc, but that the rate of cold tolerance accruement (mean 0·14° C day⁻¹) was independent of T _acc. A highly significant ( P < 0·001) multivariate predictive model was generated that described the acclimation rates and thermal tolerance of pinfish exposed to reduction in water temperature: log₁₀ T _{crit min}= 0·41597 − 0·01704 T _acc+ 0·04320 T _plunge− 0·08376[log₁₀ ( t + 1)], where T _plunge is plunge temperature (° C) and t is the time (days). A comparison of the present data, with acclimation rate data for other species, suggests that factors such as latitude or geographic range may play a more important role than ambient temperature in determining cold acclimation rates in fishes.     

Processes contributing to photoprotection of grapevine leaves illuminated at low temperature

Photoinactivation of photosystem II (PSII) and energy dissipation at low leaf temperatures were investigated in leaves of glasshouse-grown grapevine ( Vitis vinifera L. cv. Riesling). At low temperatures (< 15°C), photosynthetic rates of CO₂ assimilation were reduced. However, despite a significant increase in the amount of light excessive to that required by photosynthesis, grapevine leaves maintained high intrinsic quantum efficiencies of PSII ( F _v/ F _m) and were highly resistant to photoinactivation compared to other species. Non-photochemical energy dissipation involving xanthophylls and fast D1 repair were the main protective processes reducing the 'gross' rate of photoinactivation and the 'net' rate of photoinactivation, respectively. We developed an improved method of energy dissipation analysis that revealed up to 75% of absorbed light is dissipated thermally via pH- and xanthophyll-mediated non-photochemical quenching at low temperatures (5–15°C) and moderate (800 µmol quanta m⁻² s⁻¹) light. Up to 20% of the energy flux contributing to electron transport was dissipated via photorespiration when taking into account temperature-dependent mesophyll conductance; however, this flux used in photorespiration was only a relatively small amount of the total absorbed light energy. Photoreduction of O₂ at photosystem I (PSI) and subsequent superoxide detoxification (water-water cycle) was more sensitive to inhibition by low temperature than photorespiration. Therefore the water-water cycle represents a negligibly small energy sink below 15°C, irrespective of mesophyll conductance.     

Differences in the nature of thermodormancy and far-red dormancy in lettuce seeds

Lettuce seeds cv. Noran germinate at 23°C in light as well as in darkness. However dormancy can be induced either by a long exposure (24 h) to far-red radiation or by an exposure of 48–72 h to a temperature of 37°C. The difference in response of these two types of dormant seeds to conditions inducing germination indicate that in both types P_fr is inactivated, but that a dark process required for immediate action of P_fr does not proceed at 37°C as it does during far-red radiation.     

NONPARAMETRIC MODELS FOR DISCRIMINATION METHODS AND SENSITIVITY ANALYSIS FOR TRIADS

Nonparametric models for sensory discrimination methods are developed. In these models, the relationship between the probability of a correct response, P_c, and the measures for sensory discriminability or sensory difference, p₁ and p₂ are given. On the basis of the models, different sensitivities for triadic tests were compared including 3-AFC and triangle methods with the strong stimulus as the odd sample and with the weak stimulus as the odd sample. Predictions were made which can be tested experimentally.     

Influence of ambient and thoracic temperatures upon sexual behaviour of the gypsy moth, Lymantria dispar

ABSTRACT. In an ambient temperature ( T _a) range of 18–28°C, thoracic temperatures ( T _th) of individual male Lymantria dispar (L.), caught at flight in the field, ranged from 21 to 36.5°C, with a correlation coefficient of 0.63 between T _th and ambient temperature ( T _a). Ambient temperature (and insolation) altered the insect's body temperature and the probabilities, latencies, and durations of preflight responses to pheromone. In a wind tunnel at 16 and 20°C, quiescent males exposed to pheromone raised their T _th by sustained wing fanning from 17 and 21°C, respectively, to c. 24°C before takeoff. At 24 and 28°C ambient, T _th rose by takeoff to 28 and 31°C, respectively. The latencies of male wing fanning in response to pheromone decreased from 1.44 min at 16°C ambient, to 0.58 min at 20°C, to 0.26 min at 24°C, and to 0.16min at 28°C. The components of behaviour (antennal twitch, body jerk, step and wing tremor) that occurred between quiescence and wing fanning were more frequent at ambients of 16 and 20°C than at 24 and 28°C.     

Rhodopseudomonas cryptolactis, sp. nov., a new thermotolerant species of budding phototrophic purple bacteria

Abstract A proton motive force (Δp) generated by oxidation of CO in membrane vesicles of Clostridium thermoautotrophicum drove active transport of l -alanine, glycine and l -serine. The maximum rate ( V _max) for l -alanine transport was 12 × higher at 50°C than at 25°C. The apparent transport constant ( K _t) for l -alanine uptake was 30–40 μM and independent of the temperature. Glycine was a substrate for the l -alanine transport system as demonstrated by the competitive inhibition of l -alanine uptake by glycine ( K _i= 6 μ M), by the kinetics of glycine uptake ( K _t= 7 μ M) and by the inhibiton of glycine uptake by l -alanine. The uptake kinetics of glycine was biphasic. l -Serine inhibited competitively also l -alanine and glycine transport but it was taken up by a separate transport system. The rate of amino acid transport, but not the K _t, was dependent on the value of the proton motive force.     

Physicochemical surface properties of five Listeria monocytogenes strains from a pork-processing environment in relation to serotypes, genotypes and growth temperature

Physicochemical surface properties, related to electrostatic, van der Waals and Lewis acid–base interactions, of five Listeria monocytogenes strains isolated from pork-processing environments were determined after two subcultures at 37 °C and a final culture at three temperatures: 37, 10 and 4 °C. Three strains (Lm1, Lm114 and Lm191) were genetically related while two were unrelated (Lm25 and Lm74) according to Apa I-macrorestriction and pulsed-field gel electrophoresis (PFGE) typing.
Listeria monocytogenes cell surfaces were generally negatively charged regardless of pH and tended to be hydrophilic due to a basic character. However, variable physicochemical surface properties of the five Listeria monocytogenes isolates were observed after growth at 37 °C. After growth at 10 °C, the three genetically related isolates exhibited similar surface properties and were slightly more hydrophilic and basic than the others. After growth at 4 °C, the five isolates displayed the same weak affinity for all kinds of solvents and low electrophoretic mobility values.
A sharp decrease of temperature and subsequent growth of various Listeria monocytogenes strains resulted in loss of the physicochemical surface property variability, which may suggest the role of common chill adaptation mechanisms affecting surface properties.