Interaction of temperature and irradiance effects on photosynthetic acclimation in two accessions of Arabidopsis thaliana

The effect of temperature and irradiance during growth on photosynthetic traits of two accessions of Arabidopsis thaliana was investigated. Plants were grown at 10 and 22 °C, and at 50 and 300 μmol photons m(−2) s(−1) in a factorial design. As known from other cold-tolerant herbaceous species, growth of Arabidopsis at low temperature resulted in increases in photosynthetic capacity per unit leaf area and chlorophyll. Growth at high irradiance had a similar effect. However, the growth temperature and irradiance showed interacting effects for several capacity-related variables. Temperature effects on the ratio between electron transport capacity and carboxylation capacity were also different in low compared to high irradiance grown Arabidopsis. The carboxylation capacity per unit Rubisco, a measure for the in vivo Rubisco activity, was low in low irradiance grown plants but there was no clear growth temperature effect. The limitation of photosynthesis by the utilization of triose-phosphate in high temperature grown plants was less when grown at low compared to high irradiance. Several of these traits contribute to reduced efficiency of the utilization of resources for photosynthesis of Arabidopsis at low irradiance. The two accessions from contrasting climates showed remarkably similar capabilities of developmental acclimation to the two environmental factors. Hence, no evidence was found for photosynthetic adaptation of the photosynthetic apparatus to specific climatic conditions

Метод коррекции для параллелизации численных моделей гидродинамики водоемов со свободной поверхностью

В роботi запропоновано метод перетворення послiдовних алгоритмiв моделей гiдродинамiки резервуарiв з вiльною поверхнею в паралельнi, використовуючи MPI та розбивку розрахункової областi на пiдобластi, перевагою якого є відносна простота реалізації, обумовлена потребою тільки у додаткових процедурах корекції замість значних перетворень існуючих програм послідовного розрахунку. Дослiджується вплив рiзноманiтних факторiв на ефективнiсть методу в термінах зменшення тривалості розрахунків зі збільшенням числа застосованих процесорів.В работе предложен метод преобразования последовательных алгоритмов моделей гидродинамики резервуаров со свободной поверхностью в параллельные, используя MPI и разбивку расчётной области на подобласти, преимуществом метода является относительная простота реализации, обусловленная потребностью только в дополнительных процедурах коррекции вместо значительных преобразований существующих программ последовательного расчёта. Исследуется влияние различных факторов на эффективность метода в терминах уменьшения длительности параллельных расчётов с увеличением числа используемых процессоров.This paper proposes a technique using MPI and domain decomposition to transform serial algorithms of numerical models for hydrodynamics simulations in the water reservoirs with free surface into parallel algorithms. The advantage of the proposed technique is a comparatively simple realization due to the necessity of only additional correction procedures instead of significant transformations of existing serial program code. The impacts of various factors on the method of efficiency are studied in terms of the speedup of computations with the increase of number of utilized processors

Privacy enhanced recommender system

Recommender systems are widely used in online applications since they enable personalized service to the users. The underlying collaborative filtering techniques work on user’s data which are mostly privacy sensitive and can be misused by the service provider. To protect the privacy of the users, we propose to encrypt the privacy sensitive data and generate recommendations by processing them under encryption. With this approach, the service provider learns no information on any user’s preferences or the recommendations made. The proposed method is based on homomorphic encryption schemes and secure multiparty computation (MPC) techniques. The overhead of working in the encrypted domain is minimized by packing data as shown in the complexity analysis

Audio-visual speech in noise perception in dyslexia

Individuals with developmental dyslexia (DD) may experience, besides reading problems, other speech-related processing deficits. Here, we examined the influence of visual articulatory information (lip-read speech) at various levels of background noise on auditory word recognition in children and adults with DD. We found that children with a documented history of DD have deficits in their ability to gain benefit from lip-read information that disambiguates noise-masked speech. We show with another group of adult individuals with DD that these deficits persist into adulthood. These deficits could not be attributed to impairments in unisensory auditory word recognition. Rather, the results indicate a specific deficit in audio-visual speech processing and suggest that impaired multisensory integration might be an important aspect of DD

Switching Intentions of Service Providers and Cultural Orientation

This study performs a cross-cultural comparison to understand how the drivers of switching intentions differ between countries that vary in their long-term orientation (LTO). The authors hypothesize how LTO moderates the influence of the drivers of switching intentions for a mobile phone subscription service. Structural invariance tests between consumer samples of the United States (low LTO) and the Netherlands (high LTO) reveal that, consumers from high LTO nation attribute more importance to relational quality but care less about service recovery in their formation of switching intentions. The theoretical and managerial implications of how differences in time orientation affect the pathways to loyalty are discussed

Exploring the potential of Δ¹⁷O in CO₂ for determining mesophyll conductance

Mesophyll conductance to CO2 from the intercellular air space to the CO2–H2O exchange site has been estimated using δ18O measurements (gm18). However, the gm18 estimates are affected by the uncertainties in the δ18O of leaf water where the CO2–H2O exchange takes place and the degree of equilibration between CO2 and H2O. We show that measurements of Δ17O (i.e. Δ17O = δ17O − 0.528 × δ18O) can provide independent constraints on gm (gmΔ17) and that these gm estimates are less affected by fractionation processes during gas exchange. The gm calculations are applied to combined measurements of δ18O and Δ17O, and gas exchange in two C3 species, sunflower (Helianthus annuus L. cv. ‘sunny’) and ivy (Hedera hibernica L.), and the C4 species maize (Zea mays). The gm18 and gmΔ17 estimates agree within the combined errors (P-value, 0.876). Both approaches are associated with large errors when the isotopic composition in the intercellular air space becomes close to the CO2–H2O exchange site. Although variations in Δ17O are low, it can be measured with much higher precision compared with δ18O. Measuring gmΔ17 has a few advantages compared with gm18: (i) it is less sensitive to uncertainty in the isotopic composition of leaf water at the isotope exchange site and (ii) the relative change in the gm due to an assumed error in the equilibration fraction θeq is lower for gmΔ17 compared with gm18. Thus, using Δ17O can complement and improve the gm estimates in settings where the δ18O of leaf water varies strongly, affecting the δ18O (CO2) difference between the intercellular air space and the CO2–H2O exchange site.</p

Leaf-scale quantification of the effect of photosynthetic gas exchange on δ ¹⁷O of atmospheric CO ₂

Understanding the processes that affect the triple oxygen isotope composition of atmospheric CO2during gas exchange can help constrain the interaction and fluxes between the atmosphere and the biosphere. We conducted leaf cuvette experiments under controlled conditions using three plant species. The experiments were conducted at two different light intensities and using CO2with different δ17O. We directly quantify the effect of photosynthesis on δ17O of atmospheric CO2for the first time. Our results demonstrate the established theory for δ18O is applicable to δ17O.CO2/at leaf level, and we confirm that the following two key factors determine the effect of photosynthetic gas exchange on the δ17O of atmospheric CO2. The relative difference between δ17O of the CO2entering the leaf and the CO2in equilibrium with leaf water and the back-diffusion flux of CO2from the leaf to the atmosphere, which can be quantified by the cm=ca ratio, where ca is the CO2mole fraction in the surrounding air and cm is the one at the site of oxygen isotope exchange between CO2and H2O. At low cm=ca ratios the discrimination is governed mainly by diffusion into the leaf, and at high cm=ca ratios it is governed by back-diffusion of CO2that has equilibrated with the leaf water. Plants with a higher cm=ca ratio modify the 117O of atmospheric CO2more strongly than plants with a lower cm=ca ratio. Based on the leaf cuvette experiments, the global value for discrimination against δ17O of atmospheric CO2during photosynthetic gas exchange is estimated to be-0:57±0:14% using cm=ca values of 0.3 and 0.7 for C4and C3plants, respectively. The main uncertainties in this global estimate arise from variation in cm=ca ratios among plants and growth conditions.</p

Fluorescence resonance energy transfer sensors for quantitative monitoring of pentose and disaccharide accumulation in bacteria

<p>Abstract</p> <p>Background</p> <p>Engineering microorganisms to improve metabolite flux requires detailed knowledge of the concentrations and flux rates of metabolites and metabolic intermediates <it>in vivo</it>. Fluorescence resonance energy transfer sensors represent a promising technology for measuring metabolite levels and corresponding rate changes in live cells. These sensors have been applied successfully in mammalian and plant cells but potentially could also be used to monitor steady-state levels of metabolites in microorganisms using fluorimetric assays. Sensors for hexose and pentose carbohydrates could help in the development of fermentative microorganisms, for example, for biofuels applications. Arabinose is one of the carbohydrates to be monitored during biofuels production from lignocellulose, while maltose is an important degradation product of starch that is relevant for starch-derived biofuels production.</p> <p>Results</p> <p>An <it>Escherichia coli </it>expression vector compatible with phage λ recombination technology was constructed to facilitate sensor construction and was used to generate a novel fluorescence resonance energy transfer sensor for arabinose. In parallel, a strategy for improving the sensor signal was applied to construct an improved maltose sensor. Both sensors were expressed in the cytosol of <it>E. coli </it>and sugar accumulation was monitored using a simple fluorimetric assay of <it>E. coli </it>cultures in microtiter plates. In the case of both nanosensors, the addition of the respective ligand led to concentration-dependent fluorescence resonance energy transfer responses allowing quantitative analysis of the intracellular sugar levels at given extracellular supply levels as well as accumulation rates.</p> <p>Conclusion</p> <p>The nanosensor destination vector combined with the optimization strategy for sensor responses should help to accelerate the development of metabolite sensors. The new carbohydrate fluorescence resonance energy transfer sensors can be used for <it>in vivo </it>monitoring of sugar levels in prokaryotes, demonstrating the potential of such sensors as reporter tools in the development of metabolically engineered microbial strains or for real-time monitoring of intracellular metabolite during fermentation.</p

Exploring the potential of Δ17O in CO2 for determining mesophyll conductance

Mesophyll conductance to CO2 from the intercellular air space to the CO2–H2O exchange site has been estimated using δ18O measurements (gm18). However, the gm18 estimates are affected by the uncertainties in the δ18O of leaf water where the CO2–H2O exchange takes place and the degree of equilibration between CO2 and H2O. We show that measurements of Δ17O (i.e. Δ17O = δ17O − 0.528 × δ18O) can provide independent constraints on gm (gmΔ17) and that these gm estimates are less affected by fractionation processes during gas exchange. The gm calculations are applied to combined measurements of δ18O and Δ17O, and gas exchange in two C3 species, sunflower (Helianthus annuus L. cv. ‘sunny’) and ivy (Hedera hibernica L.), and the C4 species maize (Zea mays). The gm18 and gmΔ17 estimates agree within the combined errors (P-value, 0.876). Both approaches are associated with large errors when the isotopic composition in the intercellular air space becomes close to the CO2–H2O exchange site. Although variations in Δ17O are low, it can be measured with much higher precision compared with δ18O. Measuring gmΔ17 has a few advantages compared with gm18: (i) it is less sensitive to uncertainty in the isotopic composition of leaf water at the isotope exchange site and (ii) the relative change in the gm due to an assumed error in the equilibration fraction θeq is lower for gmΔ17 compared with gm18. Thus, using Δ17O can complement and improve the gm estimates in settings where the δ18O of leaf water varies strongly, affecting the δ18O (CO2) difference between the intercellular air space and the CO2–H2O exchange site

Interactions between chytrids cause variable infection strategies on harmful algal bloom forming species

Cyanobacteria have a great diversity of natural enemies, such as herbivores and pathogens, including fungal pathogens within the Chytridiomycota (chytrids). While these pathogens have been previously described on a select number of cyanobacterial hosts and are suspected to play a significant ecological role, little is understood about species interactions and how competition between parasites can affect epidemic development and bloom formation. Here, three Planktothrix agardhii isolates from Sandusky Bay, Lake Erie (OH, USA) were challenged in monoculture and polyculture against infection by three isolates (C1, C2, C10) of their obligate chytrid fungal pathogen, Rhizophydiales sp. The chytrid isolates were inoculated as single isolates or a mixture of up to three different isolates. In monoculture, host isolates were characterized as highly susceptible (P. agardhii 1030), moderately susceptible (P. agardhii 1808) or mostly resistant (P. agardhii 1801). Co-infection of chytrid isolates on the highly susceptible host isolate had an additive effect on chytrid prevalence, leading to a culture crash where 2 or 3 chytrid isolates were present. Co-infection of chytrid isolates on the moderately susceptible and mostly resistant isolates had no effect on chytrid infection outcome or prevalence compared to infection with a single isolate. In polyculture, the effect on host growth was most significant in the single chytrid isolate treatment, which was attenuated with the addition of mixed chytrid treatments. Genetic analysis of the resulting population after the experimental period showed a tendency for the chytrid isolate C1 and P. agardhii 1801 to dominate in mixed population samples. Two different interspecific interactions seem to be in play; varied parasite infection strategies allow for the amplification of infection prevalence due to mixed chytrids in a susceptible monoculture, or competition allows for the dominance of a single chytrid isolate in monoculture and the reduction of infection prevalence in a host polyculture. This work thus highlights how interactions between chytrid infections can change the course of epidemic development and harmful algal bloom formation