Dark Treatment Research Articles

Effects of UV-A/B/C on flavonoids and related synthetic enzymes in Tetrastigma hemsleyanum

IntroductionTetrastigma hemsleyanum is a folk and rare medicinal plant, and specifically, it is distributed in the south, China. To investigate the cumulative properties of its medicinal components, we examined the effect of UV light on flavonoid content and related enzyme activity changes in T. hemsleyanum.MethodsThe leaves and tubers were treated with UV-A, UV-B and UV-C for 1 h, 1L/23D h, 3 h and 3L/21D h (D represents darkness treatment). High-performance liquid chromatography (HPLC) analysis showed that the content of many flavonoids decreased significantly during UV-A treatment, increased after UV-B and UV-C irradiation and accumulated again after darkness treatment.ResultsIn the root tubers of the UV-A group, naringin content in the 3L/21D h group (0.069 μg/g) was 16.30 times higher than that of 3 h group (0.0042 μg/g). The rutin content was elevated after UV irradiation but was not detected in the CK group. The test results of the enzyme-linked kit indicated that the activities of many enzymes were higher in the UV-A and UV-B irradiation groups than those in the CK group, but the results were reversed in the UV-C treatment. After darkness treatment, the activities of most enzymes were higher than those with UV irradiation alone; F3’5’H activity in the 3L/21D h group (97.25 U/L) was 1.24 times higher than that in the 3 h group (78.12 U/L) in the UV-A-treated group.DiscussionThe study results suggest that appropriate UV-B and UV-C irradiation, as well as darkness supplementation, had a promotive effect on flavonoids in the leaves and root tubers of T. hemsleyanum. Additionally, UV irradiation and darkness treatment enhanced the activity of most enzymes.

Characterization and functional analysis of novel α-bisabolol synthase (MrBAS) promoter from Matricaria recutita

Matricaria recutita is widely used in industry and as a medicinal plant because it contains α-bisabolol. Alpha-bisabolol has broad application prospects due to its healthy function and medical value. The activity of the α-bisabolol synthase (MrBAS) promoter determines the expression of the MrBAS gene, which in turn influences the synthesis and accumulation of α-bisabolol. However, the activity and tissue specificity of the MrBAS promoter have not yet been characterized. In this study, a 1327-base pair (bp) region upstream of the MrBAS of the translation start site was cloned from the genome of M. recutita. MrBAS promoter sequence analysis revealed multiple light-responsive elements, and further dark treatment reduced α-bisabolol content in flowers. The α-bisabolol content and MrBAS expression levels in various flower tissues showed a strong correlation. The 5′ deletion analysis revealed that the MrBAS promoter sequence could drive β-glucuronidase (GUS) gene expression in Nicotiana benthamiana leaves, with activity decreasing as the fragment shortened. Transgenic experiments demonstrated that the MrBAS promoter could specifically drive GUS gene expression in Arabidopsis anthers, pollen tubes, and petals. Thus, the MrBAS promoter has the potential to be a tool for directing transgene expression specifically in flower organs, offering new research avenues for cultivar development.

BpTCP19 targets BpWRKY53 to negatively regulate jasmonic acid- and dark-induced leaf senescence in Betula platyphylla

TCP (TEOSINTE-LIKE1, CYCLOIDEA, and PROLIFERATING CELL FACTOR1) is a plant-specific transcription factor that has garnered significant attention due to its wide-ranging involvement in the regulation of plant growth or developmental processes. However, the molecular mechanisms through which TCP genes orchestrate leaf senescence have not been extensively elucidated. BpTCP19, a member of the PCF subfamily in Betula platyphylla, and has high homology to AtTCP19. BpTCP19 displayed pronounced downregulation in response to methyl jasmonate (MeJA) and dark treatment. Overexpressing BpTCP19 in Betula platyphylla led to a delay in leaf senescence, resulting in prolonged leaf greenness under both MeJA and dark conditions. Transcriptome analysis revealed that overexpression of BpTCP19 induced alterations in the expression levels of genes linked to cell proliferation, hormone signaling transduction, and leaf senescence, including the early responsive factor BpWRKY53. Furthermore, through Yeast one-hybrid assays and GUS analysis, BpTCP19 was shown to bind to the promoter region of BpWRKY53, suppressing its expression and thereby retarding leaf senescence. This study elucidates the physiological and molecular functions of BpTCP19 as a central transcriptional regulatory module in leaf senescence and provides a potential target gene for delaying leaf senescence by mitigating sensitivity to external aging signals such as Jasmonic acid (JA) and darkness.

Effects of turfgrass canopy shade levels and quantum spectrum on the germination and development of smooth crabgrass (Digitaria ischaemum)

AbstractSmooth crabgrass [Digitaria ischaemum (Schreb.) Schreb. ex Muhl.] is one of the most troublesome summer annual weeds in cool‐season turfgrass. Field experiments demonstrated a strong relationship between spring photosynthetic active radiation reaching the soil surface and the resulting smooth crabgrass cover in Kentucky bluegrass (Poa pratensis L.) 2/3 months later in summer. Both smooth crabgrass and canopy penetrating light were consistently reduced by higher mowing heights. Follow‐up experiments in controlled environments were initiated to improve our understanding of how light quality and quantity influence smooth crabgrass germination and growth. Smooth crabgrass germination was ≥99% following exposure to blue, red (R), far red (FR), both R and FR light pulses, or complete darkness treatments. A second germination experiment examined six levels of turfgrass canopy shade (0%, 24%, 44%, 77%, 90%, and 100% photosynthetic photon flux density [PPFD] reduction) and found that smooth crabgrass germination was ≥99% for all treatments. These experiments indicate that light quality and quantity do not affect smooth crabgrass germination. A greenhouse experiment examined five levels of turfgrass canopy shade (0%, 44%, 59%, 81%, and 91% PPFD reduction). Smooth crabgrass quantum and PSII (Photosystem II) operating efficiency increased in response to shade, while leaf number and thickness, specific leaf weight, tillering, mass, electron transport rate, and stomatal conductance decreased with increasing shade. Overall, the results demonstrate that smooth crabgrass is able to germinate regardless of canopy density, but seedling growth, development, and plant function are diminished in a dense turfgrass canopy shade.

Capsaicin‐mediated repair of circadian disruption‐induced Intestinal barrier damage via the gut microbiota

AbstractCircadian clock serves as a regulator of gastrointestinal health, and the disruption of circadian rhythm may trigger the dysregulation of the intestinal barrier functions. This study investigated the effectiveness of capsaicin (CAP) in mitigating intestinal barrier dysfunction induced by circadian disruption in male SPF C57BL/6J mice. Our findings indicated that CAP supplementation attenuated abnormal weight gain, alterations in serum lipid levels, and misalignment in hepatic and colonic circadian clock gene expressions in mice caused by constant darkness (CD) treatment. The restoration of the intestinal barrier integrity was also observed through the increase in mucosal thickness and goblet cell numbers. Both the diversity and the circadian rhythm of gut microbiota were improved in CAP‐treated group. Correlation analysis indicated that CAP could modulate the gut microbiota by affecting intestinal barrier function and systemic metabolism in CD‐treated mice. These results highlight the potential of CAP as a functional food component in maintaining the intestinal barrier homeostasis through regulating gut microbiota.

High-Throughput Transcriptomic Analysis of Circadian Rhythm of Chlorophyll Metabolism under Different Photoperiods in Tea Plants.

Tea plants are a perennial crop with significant economic value. Chlorophyll, a key factor in tea leaf color and photosynthetic efficiency, is affected by the photoperiod and usually exhibits diurnal and seasonal variations. In this study, high-throughput transcriptomic analysis was used to study the chlorophyll metabolism, under different photoperiods, of tea plants. We conducted a time-series sampling under a skeleton photoperiod (6L6D) and continuous light conditions (24 L), measuring the chlorophyll and carotenoid content at a photoperiod interval of 3 h (24 h). Transcriptome sequencing was performed at six time points across two light cycles, followed by bioinformatics analysis to identify and annotate the differentially expressed genes (DEGs) involved in chlorophyll metabolism. The results revealed distinct expression patterns of key genes in the chlorophyll biosynthetic pathway. The expression levels of CHLE (magnesium-protoporphyrin IX monomethyl ester cyclase gene), CHLP (geranylgeranyl reductase gene), CLH (chlorophyllase gene), and POR (cytochrome P450 oxidoreductase gene), encoding enzymes in chlorophyll synthesis, were increased under continuous light conditions (24 L). At 6L6D, the expression levels of CHLP1.1, POR1.1, and POR1.2 showed an oscillating trend. The expression levels of CHLP1.2 and CLH1.1 showed the same trend, they both decreased under light treatment and increased under dark treatment. Our findings provide potential insights into the molecular basis of how photoperiods regulate chlorophyll metabolism in tea plants.

Enhancement of In Vitro Seed Germination, Growth, and Root Development in Two Sideritis Species through GA3 Application and Diverse LED Light Conditions

The Sideritis genus includes over 150 species primarily found in the Mediterranean basin, including the S. clandestina subsp. pelopponesiaca from the Peloponnese and S. scardica from North and Central Greece. In vitro seed germination has proven effective for conserving and amplifying the genetic diversity of endangered species such as Sideritis. This study aimed to optimize in vitro germination and seedling growth of S. scardica and S. clandestina subsp. pelopponesiaca under different lighting conditions at 22 °C, including white fluorescent lamps (WFL-BG-40) and LEDs (LED-BGYOR-40, LED-BR-40, LED-BR-80, LED-BR-120) all under a 16-h light/8-h dark photoperiod (WFL: white fluorescent light, B:blue, G:green, Y:yellow, O:orange, R:red, 40–80–120 μmol m−2 s−1), along with a 24-h dark treatment. The results indicated that LED-BR-80 combined with 250 mg L−1 GA3 in the MS medium promoted best germination (40%, day 55) and shoot proliferation in S. clandestina subsp. pelopponesiaca. Conversely, 5-year-old cold stratified S. scardica seeds showed higher germination rates (80%) and robust seedling growth under LED-BGYOR-40 with 250 mg L−1 GA3, particularly thriving in LED-BR-120 for increased shoot height and root number. This is the first report of the efficacy of LED technology in optimizing in vitro conditions for Sideritis species, crucial for their conservation and sustainable commercial cultivation.

A transcription factor of SHI family AaSHI1 activates artemisinin biosynthesis genes in Artemisia annua

BackgroundTranscription factors (TFs) of plant-specific SHORT INTERNODES (SHI) family play a significant role in regulating development and metabolism in plants. In Artemisia annua, various TFs from different families have been discovered to regulate the accumulation of artemisinin. However, specific members of the SHI family in A. annua (AaSHIs) have not been identified to regulate the biosynthesis of artemisinin.ResultsWe found five AaSHI genes (AaSHI1 to AaSHI5) in the A. annua genome. The expression levels of AaSHI1, AaSHI2, AaSHI3 and AaSHI4 genes were higher in trichomes and young leaves, also induced by light and decreased when the plants were subjected to dark treatment. The expression pattern of these four AaSHI genes was consistent with the expression pattern of four structural genes of artemisinin biosynthesis and their specific regulatory factors. Dual-luciferase reporter assays, yeast one-hybrid assays, and transient transformation in A. annua provided the evidence that AaSHI1 could directly bind to the promoters of structural genes AaADS and AaCYP71AV1, and positively regulate their expressions. This study has presented candidate genes, with AaSHI1 in particular, that can be considered for the metabolic engineering of artemisinin biosynthesis in A. annua.ConclusionsOverall, a genome-wide analysis of the AaSHI TF family of A. annua was conducted. Five AaSHIs were identified in A. annua genome. Among the identified AaSHIs, AaSHI1 was found to be localized to the nucleus and activate the expression of structural genes of artemisinin biosynthesis including AaADS and AaCYP71AV1. These results indicated that AaSHI1 had positive roles in modulating artemisinin biosynthesis, providing candidate genes for obtaining high-quality new A. annua germplasms.

The natural variance of Arabidopsis secondary metabolism on extended darkness

In plants due to their sessile nature, secondary metabolites are important components against different abiotic and biotic stress, such as extended darkness. For this reason, the variation of secondary metabolite content of the Arabidopsis thaliana HapMap natural population following 0-and 6-d darkness treatment were detected and the raw data of different accessions at two timepoints were deposited in the Zenodo database. Moreover, the annotated secondary metabolites of these samples are presented in this data descriptor, which we believe will be a usefully re-usable resource for future integrative analysis with dark-treated transcripts, proteins or other phenotypic data in order to comprehensively illustrate the multiomic landscape of Arabidopsis in response to the stresses exerted by extended darkness.

The Complex FtBBX22 and FtHY5 Positively Regulates Light-Induced Anthocyanin Accumulation by Activating FtMYB42 in Tartary Buckwheat Sprouts.

Anthocyanin is one important nutrition composition in Tartary buckwheat (Fagopyrum tataricum) sprouts, a component missing in its seeds. Although anthocyanin biosynthesis requires light, the mechanism of light-induced anthocyanin accumulation in Tartary buckwheat is unclear. Here, comparative transcriptome analysis of Tartary buckwheat sprouts under light and dark treatments and biochemical approaches were performed to identify the roles of one B-box protein BBX22 and ELONGATED HYPOCOTYL 5 (HY5). The overexpression assay showed that FtHY5 and FtBBX22 could both promote anthocyanin synthesis in red-flower tobacco. Additionally, FtBBX22 associated with FtHY5 to form a complex that activates the transcription of MYB transcription factor genes FtMYB42 and FtDFR, leading to anthocyanin accumulation. These findings revealed the regulation mechanism of light-induced anthocyanin synthesis and provide excellent gene resources for breeding high-quality Tartary buckwheat.

Green light mediates atypical photomorphogenesis by dual modulation of Arabidopsis phytochromes B and A.

Although green light (GL) is located in the middle of the visible light spectrum and regulates a series of plant developmental processes, the mechanism by which it regulates seedling development is largely unknown. In this study, we demonstrated that GL promotes atypical photomorphogenesis in Arabidopsis thaliana via the dual regulations of phytochrome B (phyB) and phyA. Although the Pr-to-Pfr conversion rates of phyB and phyA under GL were lower than those under red light (RL) in a fluence rate-dependent and time-dependent manner, long-term treatment with GL induced high Pfr/Pr ratios of phyB and phyA. Moreover, GL induced the formation of numerous small phyB photobodies in the nucleus, resulting in atypical photomorphogenesis, with smaller cotyledon opening angles and longer hypocotyls in seedlings compared to RL. The abundance of phyA significantly decreased after short- and long-term GL treatments. We determined that four major PHYTOCHROME-INTERACTING FACTORs (PIFs: PIF1, PIF3, PIF4, and PIF5) act downstream of phyB in GL-mediated cotyledon opening. In addition, GL plays opposite roles in regulating different PIFs. For example, under continuous GL, the protein levels of all PIFs decreased, whereas the transcript levels of PIF4 and PIF5 strongly increased compared with dark treatment. Taken together, our work provides a detailed molecular framework for understanding the role of the antagonistic regulations of phyB and phyA in GL-mediated atypical photomorphogenesis.

Benzoxazinoids Biosynthetic Gene Cluster Identification and Expression Analysis in Maize under Biotic and Abiotic Stresses.

Benzoxazinoids (BXs) are unique bioactive metabolites with protective and allelopathic properties in maize in response to diverse stresses. The production of BXs involves the fine regulations of BXs biosynthetic gene cluster (BGC). However, little is known about whether and how the expression pattern of BGC members is impacted by biotic and abiotic stresses. Here, maize BGC was systemically investigated and 26 BGC gene members were identified on seven chromosomes, for which Bin 4.00-4.01/4.03-4.04/7.02 were the most enriched regions. All BX proteins were clearly divided into three classes and seven subclasses, and ten conserved motifs were further identified among these proteins. These proteins were localized in the subcellular compartments of chloroplast, endoplasmic reticulum, or cytoplasmic, where their catalytic activities were specifically executed. Three independent RNA-sequencing (RNA-Seq) analyses revealed that the expression profiles of the majority of BGC gene members were distinctly affected by multiple treatments, including light spectral quality, low-temperature, 24-epibrassinolide induction, and Asian corn borer infestation. Thirteen differentially expressed genes (DEGs) with high and specific expression levels were commonly detected among three RNA-Seq, as core conserved BGC members for regulating BXs biosynthesis under multiple abiotic/biotic stimulates. Moreover, the quantitative real-time PCR (qRT-PCR) verified that six core conserved genes in BGC were significantly differentially expressed in leaves of seedlings upon four treatments, which caused significant increases in 2,4-dihydroxy-7-methoxy-1,4-benzoxazin-3-one (DIMBOA) content under darkness and wound treatments, whereas a clear decrease in DIMBOA content was observed under low-temperature treatment. In conclusion, the changes in BX metabolites in maize were regulated by BGC gene members in multiple stress presences. Therefore, the identification of key genes associated with BX accumulation under biotic/abiotic stresses will provide valuable gene resources for breeding maize varieties with enhanced capability to adapt to environmental stresses.

Synergistic enhancement of NC-GCN/Ag2O photocatalytic reduction of uranium by D-A and p-n junction structures

Recently, how to improve the photocatalytic uranium removal performance of Graphite-phase carbon nitride (GCN) has always been a hot research topic. In this paper, a new strategy based on p-n junction and D-A structure is proposed to improve the photocatalytic performance. And as a result, a novel cyano modified photocatalytic material NC-GCN/Ag2O was designed and prepared for the reduction of U(VI). Interestingly, the material shows better adsorption performance for U(VI) in the dark treatment stage, and its removal of U(VI) is close to 70 % under the initial U(VI) concentration of 20 ppm and the solid–liquid ratio of 0.2 g/L. And the adsorption is in accordance with the Langmuir model and Pseudo second order model. After 30 min of illumination, the removal rate of U(VI) can reach 93.2 %, significantly higher than that of GCN (13.6 %) and NC-GCN10(37.7 %). It’s worth mentioning that photocatalytic reduction dominated the adsorption-reduction process for U(VI) removal after light exposure. In addition, after four cycles, the removal of U(VI) from the composite material decreased by only 5 % with no change in the crystal structure, i.e., it has good reusability and stability. Meanwhile, there was no significant interference with other ions except for Cu2+ and V5+, which had a weak interference. Finally, a new mechanism for U(Ⅵ) reduction was proposed.

The use of LEDs for the stomatal response, light compensation points, and storage of spinach and kale

The spectral composition of some light-emitting diodes (LEDs) reportedly results in higher crop yield, prevents wilting, and reduces thermal damage to plants. The use of LEDs for postharvest storage and shelf-life extension has been limited, but the potential of this technology will allow for greater applications in horticulture and the food industry. In this experiment, ‘Winterbor’ kale (Brassica oleracea) and ‘Melody’ spinach (Spinacia oleracea) plants were measured for the light compensation point and stomatal response under 14 different wavelengths of light ranging from 405 to 661 nm. Data collected from these measurements were used to select two different wavelengths of LEDs and determine the proper irradiance levels for an LED irradiance storage test on spinach and kale. Treatments comprising blue, red, and amber lights were effective at increasing the stomatal opening, while the green light resulted in reduced stomatal opening. For spinach, the light response curve showed that light compensation points at 500 nm and 560 nm were 65.3 and 64.7 μmol m−2 s−1, respectively. For kale, the light compensation points at 500 nm and 560 nm were 50.8 and 44.1 μmol m−2 s−1, respectively. For the storage test experiment at room temperature, kale and spinach were stored under four different treatments: dark treatment (control), standard white fluorescent light, 500 nm, and 560 nm LED wavelengths. For spinach, the moisture content was 70.1% at 560 nm and 53.7% for dark, moisture losses of 41.5% under the 560-nm treatment and 52.0% for the dark treatment. The fresh basis moisture content was 74.6% at 560 nm and 59.3% in the dark. Moisture loss under the 560 nm treatment was 39.6% while the dark treatment had a 54.0% moisture loss. A visual assessment scale was monitored, 560 nm resulted in the top visual quality for kale compared to the other treatments with the lowest visual quality under the dark treatment at day 4. For spinach, the visual quality for 560 nm treatment was statistically the standard white fluorescent light and 500 nm, with poor-quality product occurring by day 4 and the lowest-quality product occurring at day 5. The LED treatments improved the shelf life of spinach and kale, likely as a result of stomatal aperture closure, photosynthetic rate near the light compensation point and stability of the atmospheric moisture content. This study provides valuable information on the extension of the shelf life of leafy greens during storage. Reducing fresh produce waste in grocery stores will increase revenue, thereby benefiting the Canadian economy while providing social and environmental benefits that entail increased food security and reduced food waste.

The Characteristics and Expression Analysis of the Tomato SlRBOH Gene Family under Exogenous Phytohormone Treatments and Abiotic Stresses.

Respiratory burst oxidase homologs (RBOHs), also known as NADPH oxidases, contribute significantly to the production of ROS in plants, alongside other major sources such as photosynthesis and electron transport in chloroplasts. It has been shown that plant RBOHs play an active role in plant adversity response and electron transport. However, the phylogenetic analysis and characterization of the SlRBOH gene family in tomatoes have not been systematically studied. This study identified 11 SlRBOH genes in the tomato genome using a genome-wide search approach. The physicochemical properties, chromosomal localization, subcellular localization, secondary structure, conserved motifs, gene structure, phylogenetics, collinear relationships, cis-acting elements, evolutionary selection pressures, tissue expressions, and expression patterns under exogenous phytohormones (ABA and MeJA) and different abiotic stresses were also analyzed. We found that the SlRBOHs are distributed across seven chromosomes, collinearity reflecting their evolutionary relationships with corresponding genes in Arabidopsis thaliana and rice. Additionally, all the SlRBOH members have five conserved domains and 10 conserved motifs and have similar gene structures. In addition, the results of an evolutionary selection pressure analysis showed that SlRBOH family members evolved mainly by purifying selection, making them more structurally stable. Cis-acting element analyses showed that SlRBOHs were responsive to light, hormone, and abiotic stresses. Tissue expression analysis showed that SlRBOH family members were expressed in all tissues of tomato to varying degrees, and most of the SlRBOHs with the strongest expression were found in the roots. In addition, the expressions of tomato SlRBOH genes were changed by ABA, MeJA, dark period extension, NaCl, PEG, UV, cold, heat, and H2O2 treatments. Specifically, SlRBOH4 was highly expressed under NaCl, PEG, heat, and UV treatments, while SlRBOH2 was highly expressed under cold stress. These results provide a basis for further studies on the function of SlRBOHs in tomato.

Impact of dichromatic lighted incubation on hatching result and post-hatch performance of broiler chickens.

This study was planned to evaluate the impact of dichromatic lights during incubation on the hatching and post-hatch performance of broiler chickens. A total of 500 eggs of broiler breeder (Ross 308; Age 44 weeks) were evenly divided according to a completely randomized design into 4 treatments having 5 replicates and 25 eggs each. Treatments consisted of dichromatic lights Blue + Red (BR), Green + Red (GR) and Green + Blue (GB) provided at an intensity of 250lx for 12h a day along with a Dark (D) environment. After hatching 200 chicks (50 from each respective light group) were divided into 4 treatments with 5 replicates each having 10 chicks. Results indicated a higher embryo index (13.12%) in the GR group on the 12th day of incubation; while an ideal hatch window was observed in GR and GB (98.18% and 96.00% hatched chicks) lighting groups. In hatching traits, higher hatchability (86.15) and hatch of fertile (93.85) percentages were observed in GR lighting followed by GB, BR and Dark treatment groups; while dead-in shell embryos were lowest in the GR group. In growth performance, higher feed intake (513.20g) and body weight (479.20g) were observed in the GB group followed by GR, BR and dark group; and feed conversion ratio (FCR) was better in the GR group (1.06). In welfare parameters, improved physical asymmetry (0.90mm) and tonic immobility (54.40s) were measured in the GR group followed by GB, BR and the dark group. It was concluded that under experimental conditions when broiler breeder eggs are provided with GR lighting during incubation, it can help to improve hatchability, growth performance and welfare traits in chicks.

Daubenton’s bats maintain stereotypical echolocation behaviour and a lombard response during target interception in light

Most bats hunt insects on the wing at night using echolocation as their primary sensory modality, but nevertheless maintain complex eye anatomy and functional vision. This raises the question of how and when insectivorous bats use vision during their largely nocturnal lifestyle. Here, we test the hypothesis that the small insectivorous bat, Myotis daubentonii, relies less on echolocation, or dispenses with it entirely, as visual cues become available during challenging acoustic noise conditions. We trained five wild-caught bats to land on a spherical target in both silence and when exposed to broad-band noise to decrease echo detectability, while light conditions were manipulated in both spectrum and intensity. We show that during noise exposure, the bats were almost three times more likely to use multiple attempts to solve the task compared to in silent controls. Furthermore, the bats exhibited a Lombard response of 0.18 dB/dBnoise and decreased call intervals earlier in their flight during masking noise exposures compared to in silent controls. Importantly, however, these adjustments in movement and echolocation behaviour did not differ between light and dark control treatments showing that small insectivorous bats maintain the same echolocation behaviour when provided with visual cues under challenging conditions for echolocation. We therefore conclude that bat echolocation is a hard-wired sensory system with stereotyped compensation strategies to both target range and masking noise (i.e. Lombard response) irrespective of light conditions. In contrast, the adjustments of call intervals and movement strategies during noise exposure varied substantially between individuals indicating a degree of flexibility that likely requires higher order processing and perhaps vocal learning.

Effects of Dark Treatment on Lignin and Cellulose Synthesis in Celery

To clarify the impact of continuous dark stress on lignin and cellulose synthesis in celery, shade-tolerant celery varieties were screened. Yellow celery variety ‘Qianhuang No.1’ and green celery variety ‘Qianlv No.1’ were separately grown in vegetable greenhouses. Dark treatments were applied using PVC shading sleeves for 4, 8, 12, and 16 d after celery had grown 10–13 true leaf blades. This study aimed to investigate the impact of varying periods of dark treatment on the morphological characteristics, lignin accumulation, and cellulose accumulation in celery. The results showed that dark treatment led to celery yellowing, a reduced stem thickness, and an increased plant height. Analysis of lignin and cellulose contents, as well as the expression of related genes, showed that dark treatment caused down-regulation of AgLAC, AgC3′H, AgCCR, AgPOD and AgCAD genes, leading to changes in lignin accumulation. Dark treatment inhibited the expression of the AgCesA6 gene, thus affecting cellulose synthesis. Under dark conditions, the expression of AgF5H and AgHCT genes had little effect on lignin content in celery, and the expression of the AgCslD3 gene had little effect on cellulose content. Analysis of morphological characteristics, lignin accumulation and cellulose accumulation after different lengths of dark treatment demonstrated that ‘Qianlv No.1’ is a shade-tolerant variety in contrast to ‘Qianhuang No.1’.

Testing the influence of light on nitrite cycling in the eastern tropical North Pacific

Abstract. Light is considered a strong controlling factor of nitrification rates in the surface ocean. Previous work has shown that ammonia oxidation and nitrite oxidation may be inhibited by high light levels, yet active nitrification has been measured in the sunlit surface ocean. While it is known that photosynthetically active radiation (PAR) influences microbial nitrite production and consumption, the level of inhibition of nitrification is variable across datasets. Additionally, phytoplankton have light-dependent mechanisms for nitrite production and consumption that co-occur with nitrification around the depths of the primary nitrite maximum (PNM). In this work, we experimentally determined the direct influence of light level on net nitrite production, including all major nitrite cycling processes (ammonia oxidation, nitrite oxidation, nitrate reduction and nitrite uptake) in microbial communities collected from the base of the euphotic zone. We found that although ammonia oxidation was inhibited at the depth of the PNM and was further inhibited by increasing light at all stations, it remained the dominant nitrite production process at most stations and treatments, even up to 25 % surface PAR. Nitrate addition did not enhance ammonia oxidation in our experiments but may have increased nitrate and nitrite uptake at a coastal station. In contrast to ammonia oxidation, nitrite oxidation was not clearly inhibited by light and sometimes even increased at higher light levels. Thus, accumulation of nitrite at the PNM may be modulated by changes in light, but light perturbations did not exclude nitrification from the surface ocean. Nitrite uptake and nitrate reduction were both enhanced in high-light treatments relative to low light and in some cases showed high rates in the dark. Overall, net nitrite production rates of PNM communities were highest in the dark treatments.

Antibacterial Properties of an Experimental Dental Resin Loaded with Gold Nanoshells for Photothermal Therapy Applications.

This study explored the chemical and antibacterial properties of a dental resin loaded with gold nanoshells (AuNPs) in conjunction with photothermal therapy (PTT) as a novel method against Streptococcus mutans (S. mutans) to prevent secondary caries. First, a 20-h minimum inhibitory concentration (MIC) assay was performed on solutions of AuNPs with planktonic S. mutans under an LED device and laser at 660 nm. Next, resin blends containing 0, 1 × 1010, or 2 × 1010 AuNPs/mL were fabricated, and the degree of conversion (DC) was measured using an FTIR spectroscopy. Lastly, a colony forming unit (CFU) count was performed following 24 h growth of S. mutans on 6 mm diameter resin disks with different light treatments of an LED device and a laser at 660 nm. The MIC results only showed a reduction in S. mutans at AuNP concentrations less than 3.12 µg/mL under a laser illumination level of 95.5 J/cm2 compared to the dark treatment (p < 0.010 for each). CFU and DC results showed no significant dependence on any light treatment studied. The AuNPs expressed antibacterial effects following PPT against planktonic S. mutans but not in a polymerized dental adhesive resin. Future studies should focus on different shapes, structure, and concentrations of AuNPs loaded in a resin blend.