Light Requirements Research Articles

Desalination effects on macroalgae (part A): Laboratory-controlled experiments with Dictyota spp. from the Pacific Ocean and Mediterranean Sea

Desalination brines from direct seawater intake that get discharged to coastal areas may produce stress responses on benthic marine communities, mostly due to its excess salinity, and especially on sessile organisms; in this context, macroalgae have been understudied in desalination ecotoxicological investigations. In this study, we assessed the short- and long-term cellular tolerance responses in two brown species of the macroalgae genus Dictyota through controlled laboratory conditions. Dictyota kunthii was collected from the eastern Pacific Ocean (average salinity, ~34 psu), whereas Dictyota dichotoma was from the Mediterranean Sea (average salinity, ~37 psu). Each macroalgae species was exposed for up to 7 days to two conditions with increased salinity values: +2 and +7 psu above their natural average salinity. Photosynthetic parameters and oxidative stress measurements were determined. The results showed that, in both Dictyota species, high salinity values induced reduced photoinhibition (Fv/Fm) but increased the primary productivity (ETRmax) and light requirement (EkETR) especially after 7 days. Conversely, the photosynthetic efficiency (αETR) decreased in hypersalinity treatments in D. dichotoma, while there were no changes in D. kunthii. The reactive oxygen species hydrogen peroxide (H2O2) was greater at high salinity values at 3 days for D. dichotoma and after 7 days in D. kunthii, while lipid peroxidation decreases under hypersalinity with time in both species. Despite the evident H2O2 accumulation in both species against hypersalinity, it did not produce oxidative damage and important impairment in the photosynthetic apparatus. These results contribute to understanding the tolerance strategies at the cellular level of Dictyota spp., which may be considered as potential candidates for biomonitoring of desalination impacts in the field.

Desalination effects on macroalgae (part b): Transplantation experiments at brine-impacted sites with Dictyota spp. from the Pacific Ocean and Mediterranean Sea

Desalination residual brines are mostly discharged to marine environments, which can produce osmotic stress on sensitive benthic organisms. In this investigation, we performed transplantation experiments nearby desalination plants using two brown macroalgae species from a cosmopolitan genus: Dictyota kunthii (Chile) and Dictyota dichotoma (Spain). Parameters related to photosynthetic activity and oxidative stress were evaluated at 3 and 7 days for D. kunthii, and 3 and 6 days for D. dichotoma; each at 2 different impacted sites and 1 control. We observed that brine exposition at both impacted sites in Chile generated a marked stress response on D. kunthii, reflected in a decrease of primary productivity (ETRmax), light requirement (EkETR), and an excessive thermal dissipation (NPQmax), especially at 7 days. In D. dichotoma, similar impaired photosynthetic activity was recorded but only at the highest brine influence site during day 3. Regarding oxidative stress, both species displayed high levels of H2O2 when exposed to brine-influenced sites. Although in D. kunthii H2O2 content together with lipid peroxidation was higher after 3 days, these returned to baseline values towards day 7; instead, D. dichotoma H2O2 levels increased only at day 6. This easy and practical approach has proven to provide valuable data to address potential impacts of brine discharges at global scale coastal ecosystems.

Feasibility of Solar Thermal and Photovoltaic Integrated With Building Facade, a Case Study in Thimphu

Based on energy simulations, the annual energy demand of the DHI office is estimated to be 3,739 kWh. The total energy includes heating, lighting, and equipment energy requirements. The thermal energy demand of the office is 2,240 kWh and the combined lighting and equipment energy is 1,499 kWh. A radiation analysis of the front of the office is carried out to determine which facade received the most solar radiation. The annual global solar radiation received on building facade are 2.6 kWh/m^2, 2.4 kWh/m^2 and 2.3 kWh/m^2 on south, west and east facing facade respectively. Accordingly, the radiation results concluded that the south-facing facade is the most promising facade, followed by the west-facing facade and the east-facing facade. The proposed STC system, designed to maintain hot water temperature of 55°C, and simulations indicate that it would generate 2,440 kilowatt-hours of heating energy per year. This thermal energy would be sufficient to meet the space heating energy needs of the DHI office. Finally, the possibility of installing photovoltaic (PV) panels on the west-facing facade area 26 m^2 was simulated, suggesting the potential of 2,016 kWh of energy, which could replace the total lighting loads of 1,499 kWh currently received from grid supply.

A Plausible Model for the Galactic Extended Red Emission: Graphene Exposed to Far-ultraviolet Light

Extended red emission (ERE) is a broad feature in the spectral region of 500–900 nm commonly observed in a wide range of circumstellar and interstellar environments. Although the observational constraints for ERE are well established, definitive identifications of the carriers and associated processes complying with these constraints remain unanswered. We report a plausible two-step model involving far-ultraviolet (UV)-irradiated single-layer graphene (SLG), considered as large polycyclic aromatic hydrocarbons, to meet these constraints and supported by laboratory experiments. The far-UV-treated SLG, producing structural defects and graphene quantum dots, showed photoluminescence excitation spectrum extending from the far-UV to UV–visible region, hence meeting the requirements of far-UV light and high photon conversion efficiency. Furthermore, a photoluminescence band shifted from ∼585 to ∼750 nm for high-dose-exposed SLG agrees with the observed redshift of the ERE band in regions under a greater far-UV radiation density.

Respiratory Monitoring after Opioid-Sparing Bariatric Surgery in Patients with Obstructive Sleep Apnea (OSA)

Introduction with Aim: Postoperative respiratory depression can complicate a patient’s recovery after surgery. A predictive score (PRODIGY) was recently proposed to evaluate the risk of opioid-induced postoperative respiratory depression. For the first time, we applied this score to a cohort of patients receiving bariatric surgery, stratified by Obstructive Sleep Apnea (OSA) status. In addition, we recorded continuous postoperative capnography to evaluate respiratory depression and apnea episodes (Respiratory Events, RE). Materials and Methods: The present study was approved by our IRB and comprised continuous surveillance of respiratory variables during postoperative recovery (in PACU) after robotic bariatric surgery. We utilized continuous capnography and pulse oximetry (Capnostream 35, Medtronic Inc., and Profox Respiratory Oximetry software). Preoperative preparation included OSA evaluation for all bariatric patients, additional sleep studies for severe OSA grades, and evaluation of risk for respiratory depression (low, intermediate, or high) using the published PRODIGY score. In addition, we evaluated patients by OSA status. All patients received multimodal intraoperative non-opioid anesthesia from the same team. After surgery, all patients received continuous respiratory surveillance in PACU (average duration exceeding 140 min). Respiratory depression events were scored using a modified list of the five standard published categories. Events were measured according to analysis of continuously recorded tracing of the compiled respiratory variables by observers kept blind from the study patient’s group. Results: Of the 80 patients evaluated (18 male), 56 had obstructive sleep apnea and were using CPAP at home (OSA); 24 did not. OSA patients received CPAP via an oronasal mask or a nasal pillow pressure support immediately after arriving in PACU, utilizing their at-home settings. We encountered 115 respiratory depression events across 48 patients. The most frequent respiratory event recorded was a transient desaturation (as low as 85%), which usually lasted 20–30 sec and resolved spontaneously in 3 to 5 min; most episodes followed small boluses of IV opioid analgesia administered during recovery, on demand. All episodes resolved spontaneously without any nursing or medical intervention. OSA patients had significantly more events than non-OSA patients (1.84 (1.78–1.9) mean events vs. 0.50 (0.43–0.57) for non-OSA, p = 0.0002). The level of PRODIGY score (low, intermediate, or high), instead, was not predictive of the number of events when we treated this variable as continuous (p = 0.39) or categorical (high vs. low, p = 0.65, and intermediate vs. low, p = 0.17). Conclusions: We attribute these novel results, showing a lack of respiratory events requiring intervention, to opioid-free anesthesia, early CPAP utilization, and head-up positioning on admission to PACU. Furthermore, all these patients had light postoperative narcotic requirements. Finally, an elevated PRODIGY score in our patients did not sufficiently predict respiratory events, but OSA status alone did. Key Points Summary: We investigated the incidence of Respiratory Events (RE) in Obstructive Sleep Apnea patients after surgery (56 patients) and compared them to similar patients without OSA (24 patients). All patients received identical robotic-assisted surgery and low- or no-opiate anesthesia. Patients were pre-screened with the standard published PRODIGY scores and were monitored after PACU arrival with continuous oximetry and capnography (Capnostream 35 and Profox analysis). OSA patients showed more RE than non-OSA (1.8 vs. 0.5, p = −0.0002). However, patients with elevated PRODIGY scores did not develop more frequent RE compared to patients with low scores. We attribute these novel results to opioid-sparing anesthesia/analgesia and immediate CPAP utilization on admission to PACU.

Light induction of somatic embryogenesis in Arabidopsis is regulated by PHYTOCHROME E

The requirement of light on somatic embryogenesis (SE) has been documented in many species; however, no mechanism of action has been elucidated. Using Arabidopsis SE as a model, the effect of red light (660 nm) during the induction phase corresponding to the formation of the embryogenic tissue was examined. Analyses of several phytochrome mutants revealed that red light signaling, conducive to SE, was mediated by PHYTOCHROME E (PHYE). Both phyE and darkness were sufficient to repress the formation of somatic embryos and reduced the expression of CONSTITUTIVE PHOTOMORPHIC DWARF 3 (CPD3), a rate limiting step in brassinosteroid (BR) biosynthesis, as well as AGAMOUS LIKE 15 (AGL15), a key inducer of many SE genes. We further integrated BR signaling and nitric oxide (NO) with PHYE by demonstrating that applications of both compounds to phyE explants and WT explants cultured in the dark partially restored AGL15 expression. These results demonstrate that SE induction by red light operates via PHYE through BR signaling and NO required to induce AGL15.

Phylogeny of Saxifraga section Saxifraga subsection Arachnoideae (Saxifragaceae) and the origin of low elevation shade-dwelling species.

Saxifraga section Saxifraga subsection Arachnoideae is a lineage of 12 species distributed mainly in the European Alps. It is unusual in terms of ecological diversification by containing both high elevation species from exposed alpine habitats and low elevation species from shady habitats such as overhanging rocks and cave entrances. Our aims are to explore which of these habitat types is ancestral, and to identify the possible drivers of this remarkable ecological diversification. Using a Hybseq DNA-sequencing approach and a complete species sample we reconstructed and dated the phylogeny of subsection Arachnoideae. Using Landolt indicator values, this phylogenetic tree was used for the reconstruction of the evolution of temperature, light and soil pH requirements in this lineage. Diversification of subsection Arachnoideae started in the late Pliocene and continued through the Pleistocene. Both diversification among and within clades was largely allopatric, and species from shady habitats with low light requirements are distributed in well-known refugia. We hypothesize that low light requirements evolved when species persisting in cold-stage refugia were forced into marginal habitats by more competitive warm-stage vegetation. While we do not claim that such competition resulted in speciation, it very likely resulted in adaptive evolution.

Sunlight and red to far-red ratio impact germination of tropical montane cloud forest species

Context Australia’s tropical montane cloud forests (TMCF) exhibit exceptional species richness and endemism. Determinants of regeneration via seed of these species are next to unknown, limiting our ability to quantify and project their vulnerability to climate change. The ratio of red to far-red light (R:FR) has been shown to influence seed germination of many tropical species. Aims We investigated germination of six previously unstudied TMCF species in relation to the presence or absence of light (light/dark) and light quality (R:FR). We hypothesised that increased R:FR would lead to increased germination and that small-seeded species would be more likely to have a light requirement and be less sensitive to R:FR compared to larger-seeded species. Methods Sunlight and polyester filters were used to create a gradient of R:FR ranging from 0.1 to 1.14. Seeds were also sown in constant darkness. Key results Across species we saw varying germination responses. Three of the four smallest-seeded species exhibited an absolute light requirement for germination and did not discriminate between different R:FR. Germination of the small-seeded TMCF endemic Dracophyllum increased exponentially with increasing R:FR. Germination of the largest-seeded species was inhibited by both low and high R:FR, and germination was higher in constant darkness than diurnal light/dark. All six species were able to germinate at remarkably low R:FR values. Conclusions Light affects seed germination of Australia’s TMCF plant species in a variety of ways. Implications The findings of this study provide insights into plant recruitment in situ, and the acclimation potential of these species under reduced R:FR predicted for the future.

Changing the direction of the luminaire: A strategy to improve lighting energy efficiency in offices

Light environment’s non-visual effects influence people’s health and work efficiency. However, considering non-visual requirements in addition to traditional visual requirements may significantly increase lighting energy consumption. This study utilized simulation software to explore energy saving potential of changing the direction of the luminaire. A model of a single-person office with the luminaire attached to the ceiling right above the workstation was built in ECOTECT. Vertical eye-level illuminance and horizontal work-plane illuminance were calculated with luminaires of different luminous fluxes and elevation angles from downward vertical (0°-180° at an interval of 10° on both sides) using RADIANCE. Furthermore, six cases of different lighting requirements and light correlated color temperatures were considered. Based on the illuminance-versus-luminous flux coefficients obtained from simulation results, luminous fluxes were calculated to fulfill both visual and non-visual requirements under different elevation angles in all cases. It was found that compared to traditional lighting design with the luminaire facing vertically downwards, turning the luminaire at an elevation angle of 50° reduced the required luminous flux by up to 22.7%, which would benefit energy savings. Therefore, changing the direction of the luminaire has the potential to improve office lighting energy efficiency when considering both visual and non-visual requirements.

Nitrogen-doped carbon dots enhanced seedling growth and salt tolerance with distinct requirements of excitation light.

Numerous nanomaterials with optical properties have demonstrated excellent capacities to enhance plant growth and stress tolerance. However, the corresponding mechanisms have only been partially characterized, especially the excitation-light dependencies of different actions. Here, nitrogen-doped carbon dots (N-CDs) were developed to explore the excitation-light dependence in N-CD-induced growth enhancement and salt tolerance. Compared to the control, N-CDs induced significant enhancements in Arabidopsis thaliana growth under excitation light, including fresh/dry weight of shoot (21.07% and 16.87%), chlorophyll content (9.17%), soluble sugar content (23.41%), leaf area (28.68%), total root length (34.07%) and root tip number (46.69%). In the absence of excitation light, N-CD-treated seedlings exhibited little differences in these parameters, except the enhancements in root length (24.51%) and root tip number (10.24%). On the other hand, N-CD-treatment could improve seedling salt tolerance with or without excitation light. Under salt stress (150 mM NaCl), in the presence of excitation light, the N-CDs treatment significantly increased shoot/root fresh weight and chlorophyll content by 43.29%, 50.66% and 22.59%, and reduced malondialdehyde (MDA) content and relative conductivity by 17.59% and 32.58% compared to the control group. In the absence of excitation light, significant enhancements in shoot/root fresh weight (34.22%, 32.60%) and chlorophyll content (10.45%), and obvious decreases in MDA content (28.84%) and relative conductivity (16.13%) were also found. These results indicated that N-CDs only induced growth enhancement under excitation light, but they improved salt tolerance with and without excitation light, suggesting that the two effects occurred via distinct signaling pathways. This study revealed the excitation-light dependencies of nanomaterial-involved agriculture applications, providing insight into designing more efficient nanomaterials in the future.

Interactions between light and temperature during the in vitro as well as in situ modulation of phosphoenolpyruvate carboxylase in leaves of a C3 plant Pisum sativum L.

The C4 phosphoenolpyruvate carboxylase (PEPC) is well known for its modulation by light and temperature. We have attempted to address such coordinated effects of light and temperature on C3 PEPC in leaves of Pisum sativum. Experiments were done with dark-adapted leaf discs as well as with leaves collected at different times during the day and in each month during the year. The modulation of C3 PEPC by temperature was much stronger than that by light. The optimum temperature for in vitro activity of C3 PEPC was 25°C while 20°C was sub-optimal and 30°C to 45°C were supra-optimal. The photo-activation of PEPC was more at 25°C than at 45°C. The activation of C3 PEPC by temperature was more in the dark than in the light. In in situ conditions, a diurnal rhythm in the activity and regulatory properties of C3 PEPC was more prominent at colder than at warm temperatures. However, no consistent trends in the seasonal changes in PEPC activity/ regulatory properties were observed. Scatter plots suggested that light had a greater influence on PEPC activity while temperature exerted a much greater effect on its regulatory properties. Thus, C3 PEPC was also modulated by a natural variation in light and temperature under in situ conditions. These observations correlated well with the light and temperature requirements of C3 plants.

Edge Detection Method Driven by Knowledge-Based Neighborhood Rules

Edge detection is a fundamental process, and therefore there are still demands to improve its efficiency and computational complexity. This study proposes a knowledge-based edge detection method to meet this requirement by introducing a set of knowledge-based rules. The methodology to derive the rules is based on the observed continuity properties and the neighborhood characteristics of the edge pixels, which are expressed as simple arithmetical operations to improve computational complexity. The results show that the method has an advantage over the gradient-based methods in terms of performance and computational load. It is appropriately four times faster than Canny method and shows superior performance compared to the gradient-based methods in general. Furthermore, the proposed method provides robustness to effectively identify edges at the corners. Due to its light computational requirement and inherent parallelization properties, the method would be also suitable for hardware implementation on field-programmable gate arrays (FPGA).

A proposal on residential lighting design considering visual requirements, circadian factors and energy performance of lighting

ABSTRACT This study assesses residential areas which have been converted into workplaces and are still used after the Covid-19 in terms of visual, non-visual, and energy performance requirements of lighting. We proposed a lighting design using LED systems with dimmable and tuneable features. Circadian factors in WELL Building Standard are analyzed for compatibility with the current visual requirements. The impact of various design parameters on lighting energy consumption, including daylight availability, lighting schedules, lighting control strategies, and light reflectance value of walls is evaluated through a case study in Turkey. Although the annual lighting energy consumption is higher than it was before the pandemic, building energy simulation results show that the application of LED systems with lighting energy measures can improve lighting energy performance by up to 38%. From the non-visual dimension of light, our data indicate that higher melanopic illuminance and/or colour temperature of light sources are necessary to entrain and sustain the circadian rhythm under overcast sky conditions in winter months. On the other hand, an increase in luminous intensity can lead to glare and higher energy consumption while a higher colour temperature may affect the physiology and psychology of occupants negatively.

Water clarity monitoring in complex coastal environments: Leveraging seagrass light requirement toward more functional satellite ocean color algorithms

Florida's Big Bend region is home to the second largest contiguous seagrass bed in the continental United States, but the extent and integrity of this seagrass bed is declining as a result of degraded water clarity. Seagrass beds provide important ecological services and support high levels of biodiversity, thus monitoring the spatial and temporal variability of water clarity in the Big Bend region, particularly during the seagrass growth season (April to October), is of vital importance. Satellite remote sensing of coastal water clarity is often challenging due to the optical complexity and heterogeneity of coastal regions as well as frequent clouds and sun glint in the satellite imagery. As such, we developed machine learning (ML) approaches to derive the diffuse attenuation coefficient at 490 nm [Kd(490)] from satellite data with partial atmospheric correction. Traditionally, such algorithms would be developed to capture the full range and variation of the parameter of interest. Here, we demonstrate deficiencies in this method, and instead advocate for an alternate approach which leverages seagrass light requirements to improve the algorithm design. Specifically, we developed and implemented a 2-stage ML approach, which first classifies the coastal water into two types, then retrieves Kd(490) for the water type within which measurable changes in water clarity may impact seagrass health. We developed and compared the traditional ML approach and the proposed 2-stage ML approach based on data from MODIS/Aqua, OLCI/Sentinel-3A, and VIIRS/SNPP. Given the outperformance of the 2-stage ML approach, we applied it to the MODIS/Aqua data archive (2003−2020) to generate time-series Kd(490) maps and analyzed how often different areas across the Northern Big Bend region are suitable for seagrass growth each year. The derived information is important toward understanding how the spatial and temporal variation in light availability impacts seagrass growth and distribution in the study region, while the 2-stage ML approach appears applicable to other coastal regions with similar optical complexity.

A new predictive model for the design and evaluation of bifacial photovoltaic plants under the influence of vegetation soils

The rapid expansion of photovoltaics within the global energy market requires increasing use of land, a limited resource where different uses compete. In this respect, photovoltaic systems that combine electricity generation with land use for crops are becoming increasingly important. This article proposes an analytical model validated in an operating bifacial photovoltaic plant during the summer months. This analytical model considers view factors and heat transfer calculations, as well as an electrical model of the photovoltaic modules. A study was carried out on a commercial solar power plant (11.24 MWp) in Seville, southern Spain, where different vegetal species were planted in two strings, and string performance was monitored. Nine crop species with different irrigation and light requirements, offering different albedo parameters and thermal characteristics. The results show advantages from the point of view of module temperature and power gain. This paper provides regressions for the characterisation of the photovoltaic agricultural plant, with R2 higher than 85%, both for module temperature and energy exported in the string with crops.

Design of a Hybrid Refractive/Diffractive Lens System for Broadband UV.

Traditional broadband UV optical designs often have complex structural problems and cannot meet the current requirements of light and miniaturization. In this study, we first design the substrate material of double-layer diffractive optical elements (DOEs) in the 0.23-0.8 μm band, optimize the diffraction efficiency and analyze the effect of the angle of incidence on the diffraction efficiency of double-layer DOEs. Second, we design a refractive lens system and a refractive/diffractive hybrid lens system with double-layer DOEs designed for a wide UV wavelength range of 0.23-0.8 μm, a half field of view of 15 mm, an objective aperture of 0.1 and a magnification of 1. The refractive/diffractive hybrid lens system designed with seven lenses produces a higher image quality than the refractive lens system. The novel design is an effective solution to the problem of the low transmission rate of traditional UV refractive lens systems.

Stereolithography 3D printing of transparent resin lens for high-power phosphor-coated WLEDs packaging

Advanced lens fabricating techniques are urgently required for the development of white light-emitting diodes (WLEDs) packaging, due to the traditional LED lenses molding possesses presents many disadvantages like high cost, long-fabrication period, less compactness and low accuracy. The current study demonstrated the fabrication of lenses with transparent resin utilizing stereolithography (SLA) 3D printing. The SLA 3D printing parameters were optimized to accurately regulate the spheric and ellipsoidal lenses with the smooth surface and the acceptable transmittance. The illuminances, lighting efficiency (LE) and lighting distribution curves of the SLA-fabricated lens packaged WLEDs highly depended on the lens structure. The WLEDs with lower lens height exhibited more intense lighting energy density, higher LE and wider light output angle. SLA 3D printing offers a flexible approach of fabricating WLED lens, which provides a novel technical route for WLEDs to meet different lighting requirements.

Powder synthesis and luminescence of a novel yellow-emitting Ba5Si11Al7N25: Eu2+ phosphor discovered by a single-particle-diagnosis approach for warm w-LEDs

White LEDs combined by blue LED chip and yellow YAG: Ce phosphor are the mainstream of the lighting industry. However, due to the lack of red light component, it is difficult to meet the requirements of warm white lighting. The novel needle-like Ba5Si11Al7N25:Eu2+ particle discovered by the single-particle-diagnosis method shows a broad yellow emission band centered at ∼570 nm and a FWHM of 98 nm. Compared with YAG: Ce phosphor, the novel Ba5Si11Al7N25:Eu2+ phosphor exhibits longer emission wavelength, indicating potential application in warm white LEDs. In this work, the phase-pure powder of Ba5Si11Al7N25:Eu2+ is obtained in a non-stoichiometric ratio by the double-crucible method, and it shows similar luminescent properties as the single particle. Upon excitation with violet light (400 nm), the maximum emission wavelength of the as-prepared Ba5(1-x)Si11Al7N25: 5xEu2+ phosphors shift from 558 nm to 591 nm with Eu2+ ions concentration increasing, and the full width at half-maximum (FWHM) increase from 87 nm to 100 nm. The broad emission band is attributed to three luminescent centers corresponding to three different Ba2+ ions sites Ba5Si11Al7N25:Eu2+ phosphor, which is demonstrated by time-resolved emission spectra and the decomposition of the emission spectrum at 4 K. The Ba5Si11Al7N25:Eu2+ phosphor shows a small thermal quenching with a quenching temperature as high as 700 K. The as-prepared phosphor can absorb both of UV and blue light effectively and exhibits similar quantum efficiency under the excitation of 400 nm (58.5 %) and 450 nm (54.5 %). The fabricated white LED lamp emitted a warm white light with CIE coordinates of (0.3838, 0.3252) and CCT = 3412 K, implying the potential applications in warm w-LEDs.

Tagging active neurons by soma-targeted Cal-Light

Verifying causal effects of neural circuits is essential for proving a direct circuit-behavior relationship. However, techniques for tagging only active neurons with high spatiotemporal precision remain at the beginning stages. Here we develop the soma-targeted Cal-Light (ST-Cal-Light) which selectively converts somatic calcium rise triggered by action potentials into gene expression. Such modification simultaneously increases the signal-to-noise ratio of reporter gene expression and reduces the light requirement for successful labeling. Because of the enhanced efficacy, the ST-Cal-Light enables the tagging of functionally engaged neurons in various forms of behaviors, including context-dependent fear conditioning, lever-pressing choice behavior, and social interaction behaviors. We also target kainic acid-sensitive neuronal populations in the hippocampus which subsequently suppress seizure symptoms, suggesting ST-Cal-Light’s applicability in controlling disease-related neurons. Furthermore, the generation of a conditional ST-Cal-Light knock-in mouse provides an opportunity to tag active neurons in a region- or cell-type specific manner via crossing with other Cre-driver lines. Thus, the versatile ST-Cal-Light system links somatic action potentials to behaviors with high temporal precision, and ultimately allows functional circuit dissection at a single cell resolution.

Weed community shifts during the aging of perennial intermediate wheatgrass crops harvested for grain in arable fields

The development of a perennial grain offers opportunities to diversify annual crop rotations, with potential benefits in terms of soil protection. Perennials could also reduce weed development over time through year-round soil cover and longer growing seasons. However, whether weeds would actually decrease remains mainly theoretical, with field data on perennial grains remaining sparse. Qualitative changes might also have an effect, because disturbance and modifications to resource regimes drive shifts in weed communities. Here, we analyzed weed abundance, composition, and traits in three arable fields containing perennial grain over a 4-year period. Specifically, intermediate wheatgrass (IWG) perennial grain (Kernza) was cultivated. IWG grain production was maximal during the first and second growing seasons (899 and 854 kg.ha-1 respectively), with total biomass production peaking in the second year (mean: 11.9 t DM.ha-1). However, reproductive effort noticeably dropped in the third and fourth years. Weed biomass also gradually reduced during the fall of all years (mean: ∼0.4–∼0.03 t DM.ha-1), but remained constant in spring (mean: 1–2 t DM.ha-1). During spring, the community composition of weeds shifted from broadleaves to grass species and, to a lesser extent, from annuals to perennials, with weed species having an earlier phenology than IWG. Thus, relative fitness appeared to be the strongest driver of weed community composition in aging IWG stands. Weed species richness systematically declined over the years. Specific leaf area, height, light, and nitrogen requirement index of weed communities provided poor descriptors of community shifts; however, all weed species with high light requirements were excluded from aging IWG stands. IWG capacity to compete with weeds might have been undermined by its late growing cycle, absence of forage harvest during the growing season, and substantial initial weed development during establishment (first year of growth). Thus, before IWG establishment, initial site conditions and land use history should be considered to implement the best management strategies for each field. Important weed development in perennial grain fields could lead to high weeding requirement, either mechanical or chemical, in conflict with the initial principle of increasing sustainability and reducing inputs.