Reduced Light Conditions Research Articles

RhLHY-RhTPPF-Tre6P Inhibits Flowering in Rosa hybrida Under Insufficient Light by Regulating Sugar Distribution.

Light is crucial for flower bud development in plants, serving as both signal and energy source. However, the mechanisms by which daylength and light intensity regulate flowering in modern roses remain unclear. In Rosa hybrida 'Carola', insufficient light delays flowering and reduces the sugar content in terminal buds. RNA sequencing identified the Trehalose-6-phosphate phosphatase F (RhTPPF) gene as a key responder to insufficient light, modulating Tre6P metabolism. Overexpression of RhTPPF in rose calli enhanced sugar accumulation and suppressed the synthesis of RhCO/FT. In tobacco, overexpression of RhTPPF delayed the transition from vegetative growth to flowering, while silencing RhTPPF in roses accelerated flowering. Silencing RhTPPF in roses elevated trehalose-6-phosphate (Tre6P) levels and decreased trehalose. Transcriptome data showed that the expression level of RhTPPF was highly correlated with the circadian rhythm gene LATE ELONGATED HYPOCOTYL (RhLHY). Yeast one-hybrid assays, dual luciferase assays and EMSA revealed that RhLHY directly binds to the RhTPPF promoters. Overexpression of RhLHY suppressed flowering, while silencing RhLHY promoted flowering. Furthermore, altering the expression of RhLHY influenced Tre6P synthesis and the expression of sucrose-related transport genes. These findings suggest a RhLHY-RhTPPF-Tre6P regulatory module that maintains sugar balance and inhibits flower formation under reduced light conditions by modulating sugar distribution.

Effect of Attenuated Light Through Translucent Zirconia on the Interfacial Adaptation and Polymerization of Resin Cements.

The first objective was to determine if dual-curing of resin cement with reduced light could affect interfacial adaptations of zirconia restoration. The second objective was to examine whether cement type and pretreatment method of universal adhesive affected interfacial adaptation. The final objective was to compare the polymerization degree of cement under different reduced-light conditions. Inlay cavities were prepared on extracted third molars. Translucent zirconia restorations were milled using Katana UTML (Kuraray Noritake) in three groups with restoration thicknesses of 1, 2, and 3 mm, respectively. Each group had three subgroups using different cementation methods. For subgroup 1, restorations were cemented with self-adhesive cement. For subgroup 2, universal adhesive was applied and light cured. After the restoration was seated with conventional resin cement, light curing was performed. For subgroup 3, after adhesive was applied, the restoration was seated with conventional resin cement. Light curing was performed for the adhesive and cement simultaneously. After thermocycling, interfacial adaptation at the restoration-tooth interface was investigated using swept-source optical coherence tomography imaging. Finally, polymerization shrinkage of the cement was measured using a linometer and compared under the conditions of different zirconia thicknesses and light-curing durations. Interfacial adaptation varied signficantly depending on the zirconia thickness, pretreatment, polymerization mode and cements used (p < 0.05). The effects of the adhesive and polymerization shrinkage differed signficantly, depending on the reduced light under the zirconia (p < 0.05). Lower curing-light irradiance may lead to inferior adaptation and lower polymerization of the cement. Polymerization of resin cement can differ depending on the light irradiance and exposure duration.

Generation of High-Value Genomic Resource in Rice: A “Subgenomic Library” of Low-Light Tolerant Rice Cultivar Swarnaprabha

Rice is the major staple food crop for more than 50% of the world's total population, and its production is of immense importance for global food security. As a photophilic plant, its yield is governed by the quality and duration of light. Like all photosynthesizing plants, rice perceives the changes in the intensity of environmental light using phytochromes as photoreceptors, and it initiates a morphological response that is termed as the shade-avoidance response (SAR). Phytochromes (PHYs) are the most important photoreceptor family, and they are primarily responsible for the absorption of the red (R) and far-red (FR) spectra of light. In our endeavor, we identified the morphological differences between two contrasting cultivars of rice: IR-64 (low-light susceptible) and Swarnaprabha (low-light tolerant), and we observed the phenological differences in their growth in response to the reduced light conditions. In order to create genomic resources for low-light tolerant rice, we constructed a subgenomic library of Swarnaprabha that expedited our efforts to isolate light-responsive photoreceptors. The titer of the library was found to be 3.22 × 105 cfu/mL, and the constructed library comprised clones of 4-9 kb in length. The library was found to be highly efficient as per the number of recombinant clones. The subgenomic library will serve as a genomic resource for the Gramineae community to isolate photoreceptors and other genes from rice.

Photo-acclimatory thresholds anticipate sudden shifts in seagrass ecosystem state under reduced light conditions

Seagrass ecosystems usually respond in a nonlinear fashion to increasing pressures and environmental changes. Feedback mechanisms operating at the ecosystem level and involving multiple interactions among the seagrass meadow, its associated community and the physical environment are known to play a major role in such nonlinear responses. Phenotypic plasticity may also be important for buffering these ecological thresholds (i.e., regime shifts) as many physiological processes show nonlinear responses to gradual environmental changes, conferring the appearance of resistance before the effects at the organism and population levels are visible. However, the potential involvement of plant plasticity in driving catastrophic shifts in seagrass ecosystems has not yet been assessed. In this study, we conducted a manipulative 6-month light-gradient experiment in the field to capture nonlinearities of the physiological and population responses of the seagrass Cymodocea nodosa to gradual light reduction. The aim was to explore if and how the photo-acclimatory responses of shaded plants are translated to the population level and, hence, to the ecosystem level. Results showed that the seagrass population was rather stable under increasing shading levels through the activation of multilevel photo-acclimative responses, which are initiated with light reduction and modulated in proportion to shading intensity. The activation of photo-physiological and metabolic compensatory responses allowed shaded plants to sustain nearly constant plant productivity (metabolic carbon balance) along a range of shading levels before losing linearity and starting to decline. The species then activated plant- and meadow-scale photo-acclimative responses and drew on its energy reserves (rhizome carbohydrates) to confer additional population resilience. However, when the integration of all these buffering mechanisms failed to counterbalance the effects of extreme light limitation, the population collapsed, giving place to a phase shift from vegetated to bare sediments with catastrophic ecosystem outcomes. Our findings evidence that ecological thresholds in seagrass ecosystems under light limitation can be explained by the role of species’ compensatory responses in modulating population-level responses. The thresholds of these plastic responses anticipate the sudden loss of seagrass meadows with the potential to be used as early warning indicators signalling the imminent collapse of the ecosystem, which is of great value for the real-world management of seagrass ecosystems.

Cognitive Distractions During Sonographic Procedures: Reducing Noise-Based and Light-Based Interruptions in Hospital Rooms

Sonographers experience a high cognitive load in hospital-based care. High ambient noise and frequent noise-based interruptions include knocking on the room door, questions from others in the room or through communication technology, alarms, alerts from personal devices, and carts and people passing in the hallway. In addition, other providers turning on the overhead light is distracting for exams that need to be conducted in reduced lighting conditions. This article suggests strategies to improve working conditions for sonographers conducting exams on a patient in the hospital room. Our strategies emerge from human factors methods and principles, which derive from communication principles and theory. These strategies are organized by reducing noise-based and light-based interruptions in the hospital room and hallway, primarily through changes to the built environment and communication technology settings and reducing the use of speech during cognitively challenging time periods through training. Most of the strategies are low-cost and can be implemented within the current built environment and communication technology infrastructure. We anticipate that these strategies could enhance patient outcomes, increase patient satisfaction, improve sonographers’ job satisfaction, protect provider health, and increase procedural efficiency.

Examining the influence of regional‐scale variability in temperature and light availability on the depth distribution of subtidal kelp forests

AbstractFoundation species play a disproportionate role in maintaining biodiversity and ecosystem functioning. Improved understanding of how environmental factors influence the distribution and population structure of foundation species therefore contributes to management and conservation of entire ecosystems. We surveyed subtidal kelp forests within four regions of the U.K., distributed over 9° of latitude and a mean sea temperature gradient of ~ 2.5°C. Our aims were: (1) to examine relationships between light availability and the structure and depth distribution of Laminaria hyperborea populations and (2) to determine whether depth‐related patterns were consistent across regions with different temperature regimes. We recorded marked depth‐related shifts in structure with decreasing light levels strongly correlated with declines in kelp density, cover, plant biomass, standing biomass, plant length, and age. We also recorded an effect of latitude; populations at our two colder, northernmost regions exhibited greater wet weight and length and higher standing biomass than populations in the warmer southern regions when under similar or even reduced light conditions, indicating an interactive effect of latitude, most likely related to temperature variability. We show that shifts in kelp population structure along depth gradients are strongly driven by light availability, although regional variability in the strength and nature of these relationships may be promoted by other factors such as temperature. Maximum depth penetration, standing biomass, plant density, and plant weight are useful indicators of light availability and, over time, could be monitored to detect changes in the quality of the overlying water column.

Factors that Influence Drivers’ Responses to Slower-Moving or Stopped Lead Vehicles

&lt;div class="section abstract"&gt;&lt;div class="htmlview paragraph"&gt;Rear-end crashes account for more than one in five fatal crashes in the U.S. The rear-end crash scenario most commonly associated with fatal crashes involves a following vehicle traveling 40 to 70 mph closing on a lead vehicle at a rate greater than 30 mph. The current research compiled an analysis of the literature to identify the kinematic factors, environmental factors, traffic-related factors and individual differences that are likely to influence drivers’ responses when closing on a slower-moving or stopped lead vehicle [LV].&lt;/div&gt;&lt;div class="htmlview paragraph"&gt;In Part 1, several primarily kinematic-based methods for modeling drivers’ responses to a LV were compared for high-speed closing events. Methods utilizing looming (angular growth rate) equations were shown to predict drivers’ responses and time-to-contact methods (Inverse Tau) were conditionally accurate when applied to specific crash scenarios. However, the ratio or nominal response time methods did not predict drivers’ responses in most crash scenarios. Overall, with few exceptions, drivers responded in ways that could best be described when using the looming equation.&lt;/div&gt;&lt;div class="htmlview paragraph"&gt;In Part 2, the influence of the environment, traffic in the area, and individual differences were evaluated. Drivers responded much earlier than the looming equation suggested when in congested traffic, when following closely behind the lead vehicle, when the LV was parked on the shoulder, and when the lead vehicle was sideways across the road. In reduced lighting conditions, drivers responded significantly later when the lead vehicle had narrowed taillights, when the distances between the taillights was narrowed from the normal width, and when the lights on the lead vehicle were dimmer than normal. Interchanges, work zones, and inclines (or elevated roadways) were identified as locations where rear-end crash rate increased significantly. Drivers commonly responded 0.2 to 0.35 second faster when the lead vehicle displayed emergency flashing lights. Lastly, many drivers, whether a crash occurred or not, were found to make mirror glances in the moments before reaching the looming threshold. Hence, unbeknownst to a following driver, he/she may be looking away from the forward roadway at a critical moment while closing at a dangerous speed.&lt;/div&gt;&lt;/div&gt;

Adult pedestrian and cyclist injuries in Lilongwe, Malawi: a cross-sectional study.

Pedestrian and cyclist injuries are a major concern globally, but especially in low-income countries. Locally conducted research is needed to measure the size of the problem and advise policy on road safety interventions. We wanted to investigate the precise circumstances of these injuries in Lilongwe, Malawi and to identify risk factors for severe injuries. Cross-sectional study of all adult pedestrian and cyclist injuries presenting to a large central hospital. This was a sub-study of a larger study with all types of road users included. All patients provided detailed information about the incidents leading to injury and were tested for alcohol. There were 222 pedestrians, 183 bicycle riders and 42 bicycle passengers among the 1259 adult road traffic injury victims that were treated at Kamuzu Central Hospital during a 90-day period in 2019. Of these injuries, 60.2% occurred while the victim was walking/cycling along the road and 22.3% when the victim was trying to cross the road. The majority of the victims were men (89.1%). Helmet use for bicyclists was almost non-existent. Only 1 patient had used reflective devices when injured in the dark, despite 44.7% of these injuries occurring in reduced light conditions. There was an increased risk for serious and fatal injuries for pedestrians compared with bicyclists, and also compared with all types of road users. Patients injured in rural areas and those hit by lorries were more severely injured. Consuming alcohol before being injured was associated with more severe injuries in bicyclists. Being injured while crossing the road at painted zebra crossings was associated with an increased risk of serious and potentially fatal injuries. This study identified important risk factors for severe injuries in pedestrians and cyclists. Implications for preventive measures are presented in a Haddon Matrix.

Complex Interactions of Temperature, Light and Tissue Damage on Seagrass Wasting Disease in Zostera marina

The temperate seagrass species eelgrass Zostera marina can be infected by the wasting disease pathogen Labyrinthula zosterae, which is believed to have killed about 90% of the seagrass in the Atlantic Ocean in the 1930s. It is not known why this opportunistic pathogen sometimes becomes virulent, but the recurrent outbreaks may be due to a weakening of the Z. marina plants from adverse environmental changes. This study investigated the individual and interactive effects of multiple extrinsic factors (temperature, light, and tissue damage) on the host-pathogen interaction between Z. marina and L. zosterae in a fully crossed infection experiment. The degree of infection was measured as both lesion coverage and L. zosterae cell concentration. We also investigated if the treatment factors affect the chemical defense of the host, measured as the inhibitory capacity of seagrass extracts in bioassays with L. zosterae. Finally, gene expression of a set of targeted genes was quantified in order to investigate how the treatments change Z. marina’s response to infection. Light had a pronounced effect on L. zosterae infection measured as lesion coverage, where reduced light conditions increased lesions by 35%. The response to light on L. zosterae cell concentration was more complex and showed significant interaction with the temperature treatment. Cell concentration was also significantly affected by physical damage, where damage surprisingly resulted in a reduced cell concentration of the pathogen. No treatment factor caused detectable decrease in the inhibitory capacity of the seagrass extracts. There were several interactive effects between L. zosterae infection and the treatment factors on Z. marina growth, and on the expression of genes associated with immune defense, phenol synthesis and primary metabolism, showing that the molecular reaction towards L. zosterae infection depends on prevailing environmental conditions. Our study shows that individual or interactive effects of light, temperature and tissue damage can affect multiple aspects of host-pathogen interactions in seagrass. These results highlights the complexity of marine host-pathogen systems, showing that more multi-factorial investigations are needed to gain a better understanding of disease in marine plants under different environmental conditions.

Differential impact of heat stress on reef-building corals under different light conditions

Heat stress is an environmental factor that regularly challenges the well-being of living organisms. This study aims to examine the physiological changes happening in two reef-building coral species exposed to thermal stress under various light conditions. The two ecologically relevant heatwave scenarios were applied under ambient lights (high irradiance) and reduced light conditions (250 and < 10 μmol photons m−2 s−1). Corals were exposed to elevated temperatures of 32°C (plus 6°) for a period of 1 up to 5 days corresponding to heatwaves reported on the Great Barrier Reef (GBR) that were associated with coral bleaching. We monitored changes in the physiological performance of these two coral species by measuring symbionts and corals’ physiological parameters including symbiont density, levels of multiple algal pigments (chlorophyll a and peridinin), as well as the changes in the host protein concentration. During the short-term heat stress, both species were with stable physiological performance with the only exception of Stylophora pistillata under ambient lights. These results show that S. pistillata was negatively influenced by a synergistic effect of temperature and high irradiance resulting in the first signs of bleaching after only 24h of thermal stress. Exposure to prolonged thermal stress, characterised with a slower rate of temperature increase, affected both coral species investigated and resulted in bleaching mainly by day 5. Interestingly, severe light reduction (<10 μmol photons m−2 s−1) made Acropora millepora corals more thermally sensitive and resulted in earlier signs of bleaching (on day 3). These findings indicate that there was a synergistic effect of very low lights and thermal stress that caused higher levels of bleaching in A. millepora. Our results revealed differential thermal sensitivity for two branching corals exposed to different thermal stress scenarios under various light irradiance conditions, naturally found in their existing habitats. Consequently, global warming may have a differential impact on coral reef biodiversity depending on light availability.

Quantitative Multiparameter Evaluation of Vacuoles in Intraocular Lenses Employing a High-Magnification Digital Microscopy Method.

As small imperfections with micrometric sizes, fluid-filled vacuoles, also referred to as glistenings, in intraocular lenses (IOLs) have been known to induce significant unwanted light scattering that in several cases presumably cause complaints and sometimes lead to IOL explantation and replacement. This unwanted scatter is of particular concern for patients viewing bright light in reduced-light conditions such as when driving at night, as the scattered light toward the retina can cause temporary blindness. In this study, we have developed and implemented an accurate test methodology based on a high-magnification digital microscopy approach for quantitative multiparameter evaluation and classification of IOL vacuoles depending on their critical optical characteristics including vacuole size, density, shape, and orientation within the IOL material. Using the multiparameter database developed by evaluating vacuole characteristics, we established a classification grading system that can be used to evaluate vacuole effects on light scattering.

A Systematic Review of How Multiple Stressors From an Extreme Event Drove Ecosystem-Wide Loss of Resilience in an Iconic Seagrass Community

A central question in contemporary ecology is how climate change will alter ecosystem structure and function across scales of space and time. Climate change has been shown to alter ecological patterns from individuals to ecosystems, often with negative implications for ecosystem functions and services. Furthermore, as climate change fuels more frequent and severe extreme climate events (ECEs) like marine heatwaves (MHWs), such acute events become increasingly important drivers of rapid ecosystem change. However, our understanding of ECE impacts is hampered by limited collection of broad scale in situ data where such events occur. In 2011, a MHW known as the Ningaloo Nino bathed the west coast of Australia in waters up to 4°C warmer than normal summer temperatures for almost 2 months over 1000s of kilometres of coastline. We revisit published and unpublished data on the effects of the Ningaloo Nino in the seagrass ecosystem of Shark Bay, Western Australia (24.6 – 26.6o S), at the transition zone between temperate and tropical seagrasses. Therein we focus on resilience, including resistance to and recovery from disturbance across local, regional and ecosystem-wide spatial scales and over the past 8 yearsThermal effects on temperate seagrass health were severe and exacerbated by simultaneous reduced light conditions associated with sediment inputs from record floods in the south-eastern embayment and from increased detrital loads and sediment destabilisation. Initial extensive defoliation of Amphibolis antarctica, the dominant seagrass, was followed by rhizome death that occurred in 60-80% of the bay’s meadows, equating to decline of over 1000 km2 of meadows. This loss, driven by direct abiotic forcing, has persisted, while indirect biotic effects (e.g. dominant seagrass loss) have allowed colonisation of some areas by small fast-growing tropical species (e.g. Halodule uninervis). Those biotic effects also impacted multiple consumer populations including turtles and dugongs, with implications for species dynamics, food web structure, and ecosystem recovery. We show multiple stressors can combine to evoke extreme ecological responses by pushing ecosystems beyond their tolerance. Finally, both direct abiotic and indirect biotic effects need to be explicitly considered when attempting to understand and predict how ECEs will alter marine ecosystem dynamics.

39 General motility and mitochondrial cytochemical activity of post-thawed semen of pasture-fed Nelore bulls supplemented with palm and soybean oils

This study aimed to evaluate general motility and mitochondrial cytochemical activity of post-thawed semen of pasture-fed Nelore bulls supplemented with palm and soybean oils (protected by calcium salts). Twenty-four young male Nellore bulls were randomly assigned to 2 groups: control (CO; corn supplement and distillery grains without the addition of protected fat) and palm and soybean oils association (OP+OS; control supplement+145g of protected soybean oil+145g of protected palm). The experiment lasted 84 days, and semen was collected for cryopreservation. Post-thawed general sperm motility was assessed by computer-assisted sperm analysis using a computerized analyser (HTR Ivos II; Hamilton Thorne, Beverly, MA, USA). Motility (%), progressive motility (%), velocity average path (μm s−1), linearity (%), and lateral displacement of sperm head (μm) were analysed. Additionally, mitochondrial cytochemical activity was evaluated by co-incubation with 3,3′-diaminobenzidine (DAB; 1mg mL−1 of PBS) at 37°C (water bath) for 1h under reduced lighting conditions. Sperm cells were classified based on the mitochondrial activity of their midpiece in a 4-class scale: class 1 (DAB 1; all mitochondria are active; sperm cells with midpiece completely stained), class 2 (DAB 2; sperm cells with active and inactive segments but with prevalence of active stained segments, indicating average to high mitochondrial activity), class 3 (DAB 3; spermatozoa with less than half of the mitochondrial sheath active), and class 4 (DAB 4; spermatozoa totally inactive, with midpiece completely discolored). Data were analysed using SAS statistical program (SAS 9.3, SAS Institute Inc., Cary, NC, USA), and Tukey’s test was used to identify treatments. Study design was completely randomized, and effects were declared significant at P&amp;lt;0.05. Increased percentage of sperm motility (CO: 30.27±5.44v. OP+OS: 38.90±4.68) and progressive motility (CO: 17.27±3.84v. OP+OS: 22.90±3.88) were noticed in post-thawed samples after supplementation. Nevertheless, the addition of palm and soybean oils to the feed promoted a decrease in the percentage of DAB 3 sperm cells (CO: 4.77±1.03v. OP+OS: 2.06±0.51; P=0.0267). Therefore, supplementation with palm and soybean oils improves sperm kinetics in post-thawed semen of grazing Nellore bulls.

A fine tuned tracking of vehicles under different video degradations

Estimating the tracking efficacy of vehicles in traffic videos is one of the most desirable analysis specially in the presence of a challenging weather conditions. In this paper, a fine-tuning Kalman filter based tracking system has been proposed so that it will work robustly on the traffic videos. Such tracking efficacy has been tested and tuned by integrating a system that calculates the distance between adjacent vehicles as a case study. The integrated system could provide some sort of traffic warning system according to the allowable traffic safety standards. Analysis has been utilized in two phases; phase (1): by changing the performance indices of Kalman filter parameters (initial estimation error, motion noise, and measurement noise). We have measured both average number of assigned tracks and processing time of interest in order to acquire best tuning decision. From observations, changing values of initial estimation error has no effect on the performance of the tracking efficacy however increasing both motion noise and measurement noise has an adverse impact on the tracking performance. Phase (2) by applying the integrated system on a degraded version of a captured urban traffic video to measure performance of the tracking procedure according to the existence of salt and pepper, Gaussian, and Speckle video degradations. Such video disturbances could perform an evaluation for some sort of challenging weather conditions (e.g., rain, fog, and reduced light conditions). It is obviously that average number of assigned tracks has been degraded in the presence of video disturbance with respect to percentage of occurrence and the appropriate statistical features (mean, and variance) of such degradation. Twelve different types of filtering mask have been applied in order to measure average number of assigned tracks (correct predictions) after the cleaning process. We have measured the deviation between both the no noise and the with noise traffic video to study effect of each filter mask within each noise type of video disturbance. Such deviation measurements introduce a decision making criteria for best tuning that increases the efficacy of the vehicular tracking.

Efficient long-term conservation of Taraxacum pieninicum synthetic seeds in slow growth conditions

The aim of this paper was to develop a protocol for efficient storage of artificial seeds of Taraxacum pieninicum, critically endangered Asteraceae species. Storage under reduced light conditions or in the darkness was tested on a basis of synthetic seeds ability to conversion and post-storage regrowth of shoot tips. The results indicated that synseeds obtained from shoot tips of T. pieninicum can be stored at 4 °C even for 12 months without subculture. The light is a stress factor during storage what was manifested by numerous necrosis and decreased shoots ability to proliferate in optimal growth conditions in 1st subculture. Additionally our results showed that the storage does not produce genetic variation at the resolution provided by the flow cytometry and RAPD analysis.

Removing Leakage and Surface Recombination in Planar Perovskite Solar Cells

Thin-film solar cells suffer from various types of recombination, of which leakage current usually dominates at lower voltages. Herein, we demonstrate first a three-order reduction of the shunt loss mechanism in planar methylammonium lead iodide perovskite solar cells by replacing the commonly used hole transport layer poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) with a better hole-selective polyarylamine. As a result, these cells exhibit superior operation under reduced light conditions, which we demonstrate for the extreme case of moonlight irradiance, at which open-circuit voltages of 530 mV can still be obtained. By the shunt removal we also observe the VOC to drop to zero after as long as 2 h after the light has been switched off. Second, at higher illumination intensities the dominant losses in the PEDOT:PSS-based cell are ascribed to surface recombination and are also proven to be substantially minimized by instead employing the polyarylamine. We attribute the reduced shunt a...

Efficient Monolithic Perovskite/Perovskite Tandem Solar Cells

Thin-film solar cells suffer from various types of recombination, of which leakage current usually dominates at lower voltages. Herein, we demonstrate first a three-order reduction of the shunt loss mechanism in planar methylammonium lead iodide perovskite solar cells by replacing the commonly used hole transport layer poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) with a better hole-selective polyarylamine. As a result, these cells exhibit superior operation under reduced light conditions, which we demonstrate for the extreme case of moonlight irradiance, at which open-circuit voltages of 530 mV can still be obtained. By the shunt removal we also observe the VOC to drop to zero after as long as 2 h after the light has been switched off. Second, at higher illumination intensities the dominant losses in the PEDOT:PSS-based cell are ascribed to surface recombination and are also proven to be substantially minimized by instead employing the polyarylamine. We attribute the reduced shunt and surface recombination to the far better suited semiconductor character of the polyarylamine, compared to that of PEDOT:PSS, efficiently blocking electrons from recombining at this electrode.

Photoprotection and recovery of photosystem II in the Southern Ocean phytoplankton

The future shoaling of surface mixed layer depth due to global warming will expose natural assemblages of phytoplankton to increased mean light. Under these conditions, photoprotective acclimation against high light can determine ecological success. We investigated photoprotective responses to sunlight and recovery from photodamage of photosystem II (PSII) in natural assemblages north and south of the Polar Front (PF). The decrease in the maximum quantum yield (Fv/Fm) of PSII during direct sunlight exposure for 2 h was moderated progressively by the enhancement of diatoxanthin synthesis. When the light-exposed cells were incubated under three reduced light conditions, Fv/Fm recovered to more than the initial values north of the PF but did not reach initial values south of the PF. Temperatures higher in the north than the south of the PF could have induced the faster recovery from photodamage of PSII in assemblages north of the PF. These northern assemblages may be able to acclimate to fast-changing light conditions.

Functional Plant Types Drive Plant Interactions in a Mediterranean Mountain Range.

Shrubs have positive (facilitation) and negative (competition) effects on understory plants, the net interaction effect being modulated by abiotic conditions. Overall shrubs influence to great extent the structure of plant communities where they have significant presence. Interactions in a plant community are quite diverse but little is known about their variability and effects at community level. Here we checked the effects of co-occurring shrub species from different functional types on a focal understory species, determining mechanisms driving interaction outcome, and tested whether effects measured on the focal species were a proxy for effects measured at the community level. Growth, physiological, and reproductive traits of Euphorbia nicaeensis, our focal species, were recorded on individuals growing in association with four dominant shrub species and in adjacent open areas. We also recorded community composition and environmental conditions in each microhabitat. Shrubs provided environmental conditions for plant growth, which contrasted with open areas, including moister soil, greater N content, higher air temperatures, and lower radiation. Shrub-associated individuals showed lower reproductive effort and greater allocation to growth, while most physiological traits remained unaffected. Euphorbia individuals were bigger and had more leaf N under N-fixing than under non-fixing species. Soil moisture was also higher under N-fixing shrubs; therefore soil conditions in the understory may counter reduced light conditions. There was a significant effect of species identity and functional types in the outcome of plant interactions with consistent effects at individual and community levels. The contrasting allocation strategies to reproduction and growth in Euphorbia plants, either associated or not with shrubs, showed high phenotypic plasticity and evidence its ability to cope with contrasting environmental conditions.

SChlorophyll a fluorescence of perennial ryegrass (Lolium perenne L.) varieties under long term exposure to shade

The perennial ryegrass is the species widely used in Europe as forage as well as for creating lawns in urban areas. Unfavourable light conditions in cities are the principal reason of improper growth and functioning of grass communities. The aim of our work was to answer the following questions: what is the adaptive ability of photosynthetic apparatus of perennial ryegrass varieties to long-term reduction of solar radiation and which of the tested varieties has the best properties to be used for grassland establishment under reduced light conditions. A two-factor experiment was conducted with three varieties and three shading variants. Measurements of chlorophyll a fluorescence were provided, and the basic assessed parameters were: minimal fluorescence (F 0 ), maximal fluorescence (F m ), variable fluorescence (F v ) and maximal photosynthetic efficiency of photosystem II (F v /F m ). Gas exchange was also measured. We explored the differences between the selected varieties in terms of their photosynthetic apparatus adaptation to light conditions. During May, all varieties were characterized by increase in minimal and maximal fluorescence levels under reduced light. The most significant changes were noticed for variety ‘Taya’. During following months, a trend of decline in photosynthetic efficiency was observed for this variety. For this variety the most significant changes of CO 2 were also noted. The stomatal conductance was not affected by shading. On the basis of our results, we have assumed that each variety is unique in terms of threshold values and demand for light.