Search Results (26)

Salt stress severely impairs photosynthesis and development in tomato seedlings. This study investigated the regulatory role of exogenous melatonin (MT) on photosynthetic performance under salt stress by determining chlorophyll content, chlorophyll a fluorescence parameters, Calvin cycle enzyme activities, and related gene expression. Results showed that salt stress significantly reduced chlorophyll content and impaired photosystem II (PSII) functionality, as evidenced by the increased minimum fluorescence (F_o) and decreased maximum quantum efficiency of PSII (F_v/F_m) and effective PSII quantum yield (Φ_PSII). MT application mitigated these negative effects, as reflected by higher F_v/F_m, increased chlorophyll content, and lower non-photochemical quenching (NPQ). In addition, MT-treated plants exhibited improved PSII electron transport and more efficient use of absorbed light energy, as shown by elevated Φ_PSII and qP values. These changes suggest improved PSII functional stability and reduced excess thermal energy dissipation. Furthermore, MT significantly enhanced both the activity and expression of key enzymes involved in the Calvin cycle, including ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco), Rubisco activase (RCA), phosphoglycerate kinase (PGK), glyceraldehyde-3-phosphate dehydrogenase (GAPDH), fructose-1,6-bisphosphatase (FBPase), fructose-bisphosphate aldolase (FBA), transketolase (TK), and sedoheptulose-1,7-bisphosphatase (SBPase), thereby promoting carbon fixation and ribulose-1,5-bisphosphate (RuBP) regeneration under salt stress. Conversely, inhibition of endogenous MT synthesis by p-CPA exacerbated salt stress damage, further confirming MT’s crucial role in salt tolerance. These findings demonstrate that exogenous MT enhances salt tolerance in tomato seedlings by simultaneously improving photosynthetic electron transport efficiency and upregulating the activity and gene expression of key Calvin cycle enzymes, thereby promoting the coordination between light reactions and carbon fixation processes. This study provides valuable insights into the comprehensive regulatory role of MT in maintaining photosynthetic performance under saline conditions. Full article

This study elucidates the structural determinants and optogenetic potential of Archaerhodopsin HeAR, a proton pump from Halorubrum sp. Ejinoor isolated from Inner Mongolian salt lakes. Through heterologous expression in E. coli BL21 (DE3) and integrative biophysical analyses, we demonstrate that HeAR adopts a stable trimeric architecture (129 kDa) with detergent-binding characteristics mirroring bacteriorhodopsin (BR); however, it exhibits a 10 nm bathochromic spectral shift (λmax = 550 nm) and elevated proton affinity (Asp-95 pKa = 3.5 vs. BR Asp-85 pKa = 2.6), indicative of evolutionary optimization in its retinal-binding electrostatic microenvironment. Kinetic profiling reveals HeAR’s prolonged photocycle (100 ms vs. BR’s 11 ms), marked by rapid M-state decay (3.3 ms) and extended dark-adaptation half-life (160 min), a bistable behavior attributed to enhanced hydrogen bond persistence (80%) and reduced conformational entropy (RMSD = 2.0 Å). Functional assays confirm light-driven proton extrusion (0.1 ng H⁺/mg·s) with DCCD-amplified flux (0.3 ng H⁺/mg·s) and ATP synthesis (0.3 nmol/mg·s), underscoring its synergy with H⁺-ATPase. Phylogenetic and structural analyses reveal 95% homology with Halorubrum AR4 and conservation of 11 proton-wire residues, despite divergent Trp/Tyr/Ser networks that redefine chromophore stabilization. AlphaFold-predicted models (TM-score > 0.92) and molecular docking identify superior retinoid-binding affinity (ΔG = −12.27 kcal/mol), while spectral specificity (550–560 nm) and acid-stable photoresponse highlight its adaptability for low-irradiance neuromodulation. These findings position HeAR as a precision optogenetic tool, circumventing spectral overlap with excitatory opsins and enabling sustained hyperpolarization with minimized phototoxicity. By bridging microbial energetics and optobioengineering, this work expands the archaeal rhodopsin toolkit and provides a blueprint for designing wavelength-optimized photoregulatory systems. Full article

The emissions of reactive nitrogen (Nr) from cropland links the pedosphere and atmosphere, playing a crucial role in the Earth’s nitrogen cycle while significantly impacting regional climate change, air quality, and human health. Among various Nr species, nitrogen oxide (NO) and nitrous acid (HONO) have garnered increasing attention as critical precursors to surface ozone (O₃) formation due to their participation in photochemical reactions. While most studies focus on Nr emissions from soils, the specific contributions of cropland Nr emissions considering planting activities to regional O₃ pollution remain insufficiently investigated. This study applied the enhanced process-based agroecological model (FEST-C*) coupled with the air quality (CMAQ) model to quantify cropland Nr emissions and assess their contributions to regional O₃ formation across China in June 2020. The simulated results indicated that the fertilizer-induced total Nr emission was estimated at 1.26 Tg in China, with NO emissions accounting for 0.66 Tg and HONO emissions for 0.60 Tg. North China was identified as a hotspot for cropland Nr emissions, contributing 43% of the national total. The peak emissions of cropland NO and HONO occurred in June, with emissions of 169 and 192 Gg, respectively. Cropland Nr emissions contributed approximately 8% to the national monthly mean MDA8 O₃ concentration, with localized enhancements exceeding 9% in agricultural hotspots in summer. North China experienced the largest MDA8 O₃ increase, reaching 11.71 μg m⁻³, primarily due to intensive fertilizer application and favorable climatic conditions. Conversely, reductions in nighttime hourly O₃ concentrations were observed in southern North China and northern Southeast China due to the rapid titration of O₃ via NO. In this study, the contributions of cropland Nr emissions to MDA8 O₃ concentrations across different regions of China have been further constrained. Incorporating cropland Nr emissions into the CMAQ model improved simulation accuracy and reduced mean biases in MDA8 O₃ predictions. This study offers a detailed quantification of the contribution of cropland Nr emissions in regional ozone formation across China and highlights the critical need to address cropland NO and HONO emissions in air quality management strategies. Full article

Photosynthesis is a vital process for seed productivity. It occurs in the leaves and provides developing seeds with the necessary nutrients. Moreover, many crops require photochemical reactions inside the seeds for proper development. The present study aimed to investigate Pisum sativum L. seeds at the middle stage of maturation, which is characterized by the active synthesis of nutrient reserves. Embryonic photosynthesis represents a crucial process to produce cells’ NADP(H) and ATP, which are necessary to convert sucrose into reserve biopolymers. However, it remains unclear how the pea embryo, covered by a coat and pericarp, receives sufficient light to provide energy for photochemical reactions. Recent studies have demonstrated that the photosynthetically active radiation reaching the developing pea embryo has a high proportion of green light. In addition, green light can be utilized in foliar photosynthesis by plants cultivated in shaded conditions. Here, we addressed the role of green light in seed development. Pea plants were cultivated under red and blue (RB) LEDs or red, green, and blue (RGB) LEDs. A Chl a fluorescence transient based on OJIP kinetics was detected at the periphery of the cotyledons isolated from developing seeds. Our findings showed that the addition of green light resulted in an increase in photochemical activity. Furthermore, the mature seeds that developed in the RGB module had a significantly higher weight and more storage proteins. Using a metabolomics approach, we also detected significant differences in the levels of organic acids, carbohydrates, nucleotide monophosphates, and nitrogenous substances between the RB and RGB conditions. Under RGB light, the cotyledons contained more ornithine, tryptophan, arginine, and aspartic acid. These changes indicate an impact of green light on the ornithine–urea cycle and polyamine biosynthesis. These results allow for a deeper understanding of the photochemical processes in embryos of developing seeds grown under a low light intensity. The photosynthetic system in the embryo cell adapts to the shade conditions by using green light. Full article

Understanding the dynamics of physiological changes involved in the acclimation responses of plants after their exposure to repeated cycles of water stress is crucial to selecting resilient genotypes for regions with recurrent drought episodes. Under such background, we tried to respond to questions as: (1) Are there differences in the stomatal-related and non-stomatal responses during water stress cycles in different clones of Coffea canephora Pierre ex A. Froehner? (2) Do these C. canephora clones show a different response in each of the two sequential water stress events? (3) Is one previous drought stress event sufficient to induce a kind of “memory” in C. canephora? Seven-month-old plants of two clones (’3V’ and ‘A1’, previously characterized as deeper and lesser deep root growth, respectively) were maintained well-watered (WW) or fully withholding the irrigation, inducing soil water stress (WS) until the soil matric water potential (Ψ_msoil) reached ≅ −0.5 MPa (−500 kPa) at a soil depth of 500 mm. Two sequential drought events (drought-1 and drought-2) attained this Ψ_msoil after 19 days and were followed by soil rewatering until a complete recovery of leaf net CO₂ assimilation rate (A_net) during the recovery-1 and recovery-2 events. The leaf gas exchange, chlorophyll a fluorescence, and leaf reflectance parameters were measured in six-day frequency, while the leaf anatomy was examined only at the end of the second drought cycle. In both drought events, the WS plants showed reduction in stomatal conductance and leaf transpiration. The reduction in internal CO₂ diffusion was observed in the second drought cycle, expressed by increased thickness of spongy parenchyma in both clones. Those stomatal and anatomical traits impacted decreasing the A_net in both drought events. The ‘3V’ was less influenced by water stress than the ‘A1’ genotype in A_net, effective quantum yield in PSII photochemistry, photochemical quenching, linear electron transport rate, and photochemical reflectance index during the drought-1, but during the drought-2 event such an advantage disappeared. Such physiological genotype differences were supported by the medium xylem vessel area diminished only in ‘3V’ under WS. In both drought cycles, the recovery of all observed stomatal and non-stomatal responses was usually complete after 12 days of rewatering. The absence of photochemical impacts, namely in the maximum quantum yield of primary photochemical reactions, photosynthetic performance index, and density of reaction centers capable of Q_A reduction during the drought-2 event, might result from an acclimation response of the clones to WS. In the second drought cycle, the plants showed some improved responses to stress, suggesting “memory” effects as drought acclimation at a recurrent drought. Full article

Cytochrome P450s (P450s), a superfamily of heme-containing enzymes, existed in animals, plants, and microorganisms. P450s can catalyze various regional and stereoselective oxidation reactions, which are widely used in natural product biosynthesis, drug metabolism, and biotechnology. In a typical catalytic cycle, P450s use redox proteins or domains to mediate electron transfer from NAD(P)H to heme iron. Therefore, the main factors determining the catalytic efficiency of P450s include not only the P450s themselves but also their redox-partners and electron transfer pathways. In this review, the electron transfer pathway engineering strategies of the P450s catalytic system are reviewed from four aspects: cofactor regeneration, selection of redox-partners, P450s and redox-partner engineering, and electrochemically or photochemically driven electron transfer. Full article

Naturally occurring Fe(III) films with rainbow reflection iridescence have been observed floating on the water surface of various spots covered with shallow water (e.g., edges of wetlands and creeks, standing water over soils). This natural phenomenon has become a scenic attraction and stimulated much curiosity. We pursued an experimental inquiry aimed at probing this interesting, curious natural wonder. As the first critical task, floating Fe(III) films were successfully generated in an assessable, controllable setting in our laboratory. This enabled us to establish this phenomenon reproducibly under controlled conditions and characterize the phenomenon over the entire span of the formation and transformation of the Fe(III) films. Our film generation method requires a few things: fresh soil (source for Fe(III) and microbes), glucose (energy source), and water in a container. The floating Fe(III) films as observed in the field occurred in ~1–3 day(s) on the water surface of the inundated soil mixed with the sugar. The Fe(III) films then grew from initial very thin, colorless, somewhat transparent films with rainbow reflection iridescence to colored thicker films and then to orange/orange-red/red crusts over the time. A comprehensive mechanistic picture was formulated to depict the formation of the Fe(III) films. Several sequential processes are operative. First, the Fe(III) (oxides, oxyhydroxides) in the soil is reduced to Fe(II) by the Fe(III)-reducing microbes during their anerobic respiration with Fe(III) as the electron (e⁻) acceptor after depletion of dissolved O₂ in the water as a result of aerobic microbial respiration with O₂ as the e⁻ acceptor. The Fe(II), being soluble, then diffuses to the water surface where it is oxidized to Fe(III). Subsequently, the Fe(III) hydrolyzes and various Fe(III) hydrolysis products polymerize to stabilize. A polymeric model was created to account for the Fe(III) film transformation. The Fe(III) films are considered to transform from the dimers and trimers and linear polymers of Fe(OH)₃ to Fe(III) polymer sheets (e.g., Fe(OH)₃, FeOOH), to 3D Fe(III) polymers, and eventually to Fe₂O₃ colloid particles. This floating Fe(III) film phenomenon boasts an environmental chemical drama of redox cycling of Fe(III)/Fe(II) at soil/water and water/air interfaces coupled with Fe(II) transport from the inundated soil to the water surface followed by ultimate mineralization of the Fe(III) polymers. Our Fe(III) film generation method can be readily scaled up to supply Fe(III) films of rich varieties in thickness, size, morphology, and structure over the entire span of various stages of their formation and transformation as desired for various uses. This setup offers a platform needed for further controlled studies on the kinetics, mechanism, and process of abiotic and biotic nature involved in the Fe(III) film phenomenon and for exploration of versatile roles of the Fe(III) films as nanofilms in Fe(III)/Fe(II)-surface catalyzed chemical and photochemical reactions involving various natural and synthetic compounds. Full article

The preparation of electrocatalysts with high performance for the ethanol oxidation reaction is vital for the large-scale commercialization of direct ethanol fuel cells. Here, we successfully synthesized a high-performance electrocatalyst of a AuPd alloy with a decreased alloying degree via pulsed laser irradiation in liquids. As indicated by the experimental results, the photochemical effect-induced surficial deposition of Pd atoms, combined with the photothermal effect-induced interdiffusion of Au and Pd atoms, resulted in the formation of AuPd alloys with a decreased alloying degree. Structural characterization reveals that L-AuPd exhibits a lower degree of alloying compared to C-AuPd prepared via the conventional co-reduction method. This distinct structure endows L-AuPd with outstanding catalytic activity and stability in EOR, achieving mass and specific activities as high as 16.01 A mg_Pd⁻¹ and 20.69 mA cm⁻², 9.1 and 5.2 times than that of the commercial Pd/C respectively. Furthermore, L-AuPd retains 90.1% of its initial mass activity after 300 cycles. This work offers guidance for laser-assisted fabrication of efficient Pd-based catalysts in EOR. Full article

Nitrogen oxides (NO_X) in the atmosphere cause oxidation reactions with photochemical radicals and volatile organic compounds, leading to the accumulation of ozone (O₃). NO_X constitutes a significant portion of the NO_y composition, with nitrous acid (HONO) and nitric acid (HNO₃) following. HONO plays a crucial role in the reaction cycle of NO_X and hydrogen oxides. The majority of HNO₃ reduction mechanisms result from aerosolization through heterogeneous reactions, having adverse effects on humans and plants by increasing secondary aerosol concentrations in the atmosphere. The investigation of the formation and conversion mechanisms of HONO and HNO₃ is important; however, research in this area is currently lacking. In this study, we observed HONO, HNO₃, and their precursor gases were observed in the atmosphere using parallel-plate diffusion scrubber-ion chromatography. A 0-D box model simulated the compositional distribution of NO_y in the atmosphere. The formation reactions and conversion mechanisms of HONO and HNO₃ were quantified using reaction equations and reaction coefficients. Among the various mechanisms, dominant mechanisms were identified, suggesting their importance. According to the calculation results, the produce of HONO was predominantly attributed to heterogeneous reactions, excluding an unknown source. The sink processes were mainly governed by photolysis during daytime and reactions with OH radicals during nighttime. HNO₃ showed dominance in its production from N₂O₅, and in its conversion mechanisms primarily involving aerosolization and deposition. Full article

In this study, the author improved and modified g-C₃N₄ by doping it with the metals Ag and Cu, which changed the photochemical properties of g-C₃N₄, narrowed the band gap, and improved the photocatalytic performance regarding quantum efficiency. Organic hydrocarbons such as 1,2-dichloroethane (DCE) are very stable prepared materials produced as intermediates to obtain polyvinyl chloride, and the prepared photo-catalyst is an innovative method for extreme decomposition of chlorinated hydrocarbons. However, some significant results were obtained using different analysis techniques. X-ray diffraction (XRD) and Fourier-transform infrared spectroscopy (FTIR) showed that the addition of Ag and Cu-NPS partially altered the structure of pure graphitic carbon nitride (g-C₃N₄-Pure). Scanning electron microscopy (TEM) analysis revealed that the morphological features of Ag-Cu/g-C₃N₄ contain quantum dots of Ag and Cu nanoparticles in addition to 2d-g-C₃N₄. The better separation of the photo-generated charge carriers is attributed to better photoactivity in the case of 0.3 g Ag-Cu/g-C₃N₄ with a reaction time of less than 30 min. Furthermore, the Ag-Cu/g-C₃N₄ recycling experiment showed that the catalyst remained stable after three stages of the pyrolysis experimental cycle. Another clear indicator of DCE degradation is the measurement using the titration of the Cl ions released by the decomposition. Full article

The production of crops is severely limited by water scarcity. We still do not fully understand the underlying mechanism of exogenous melatonin (MT)-mediated water stress tolerance in barley. This study is the first of its kind to show how MT can potentially mitigate changes in barley’s physio-biochemical parameters caused by water deficiency. Barley was grown under three irrigation levels (100%, 70%, and 30% of field capacity) and was foliar sprayed with 70 μM MT. The results showed that exogenously applied MT protected the photosynthetic apparatus by improving photosynthetic pigment content, photochemical reactions of photosynthesis, Calvin cycle enzyme activity, gas exchange capacity, chlorophyll fluorescence system, and membrane stability index. Furthermore, the increased levels of salicylic acid, gibberellins, cytokinins, melatonin, and indole-3-acetic acid, as well as a decrease in abscisic acid, indicated that foliar-applied MT greatly improved barley water stress tolerance. Additionally, by increasing the activity of antioxidant enzymes such as superoxide dismutase, catalase, ascorbate peroxidase, monodehydroascorbate reductase, dehydroascorbate reductase, and glutathione reductase and decreasing hydrogen peroxide content, lipid peroxidation, and electrolyte leakage, MT application lessened water stress-induced oxidative stress. According to the newly discovered data, MT application improves barley water stress tolerance by reprogramming endogenous plant hormone production and antioxidant activity, which enhances membrane stability and photosynthesis. This study unraveled MT’s crucial role in water deficiency mitigation, which can thus be applied to water stress management. Full article

Photosynthesis is the largest mass- and energy-conversion process on Earth, and it is the material basis for almost all biological activities. The efficiency of converting absorbed light energy into energy substances during photosynthesis is very low compared to theoretical values. Based on the importance of photosynthesis, this article summarizes the latest progress in improving photosynthesis efficiency from various perspectives. The main way to improve photosynthetic efficiency is to optimize the light reactions, including increasing light absorption and conversion, accelerating the recovery of non-photochemical quenching, modifying enzymes in the Calvin cycle, introducing carbon concentration mechanisms into C₃ plants, rebuilding the photorespiration pathway, de novo synthesis, and changing stomatal conductance. These developments indicate that there is significant room for improvement in photosynthesis, providing support for improving crop yields and mitigating changes in climate conditions. Full article

To assess the best measures for the improvement of air quality, it is crucial to investigate in situ and columnar pollution levels. In this study, ground-based measurements of nitrogen dioxide (NO₂) and ozone (O₃) collected in Rome (Italy) between 2017 and 2022 are analyzed. Pandora sun-spectrometers provided the time series of the NO₂ vertical column density (VC-NO₂), tropospheric column density (TC-NO₂), near-surface concentration (SC-NO₂), and the O₃ vertical column density (VC-O₃). In situ concentrations of NO₂ and O₃ are provided by an urban background air quality station. The results show a clear reduction of NO₂ over the years, thanks to the recent ecological transition policies, with marked seasonal variability, observable both by columnar and in situ data. Otherwise, O₃ does not show inter-annual variations, although a clear seasonal cycle is detectable. The results suggest that the variation of in situ O₃ is mainly imputable to photochemical reactions while, in the VC-O₃, it is triggered by the predominant contribution of stratospheric O₃. The outcomes highlight the importance of co-located in situ and columnar measurements in urban environments to investigate physical and chemical processes driving air pollution and to design tailored climate change adaptation strategies. Full article

Photosynthetic capacity is usually affected by light intensity in the field. In this study, photosynthetic characteristics of four different Triticeae crops (wheat, triticale, barley, and highland barley) were investigated based on chlorophyll fluorescence and the level of photosynthetic proteins under high light. Compared with wheat, three cereals (triticale, barley, and highland barley) presented higher photochemical efficiency and heat dissipation under normal light and high light for 3 h, especially highland barley. In contrast, lower photoinhibition was observed in barley and highland barley relative to wheat and triticale. In addition, barley and highland barley showed a lower decline in D1 and higher increase in Lhcb6 than wheat and triticale under high light. Furthermore, compared with the control, the results obtained from PSII protein phosphorylation showed that the phosphorylation level of PSII reaction center proteins (D1 and D2) was higher in barley and highland barley than that of wheat and triticale. Therefore, we speculated that highland barley can effectively alleviate photodamages to photosynthetic apparatus by high photoprotective dissipation, strong phosphorylation of PSII reaction center proteins, and rapid PSII repair cycle under high light. Full article

The photoprotective role of anthocyanin remains controversial. In this study, we explored the effects of anthocyanin on photosynthesis and photoprotection using transgenic ‘Galaxy Gala’ apple plants overexpressing MdMYB10 under high light stress. The overexpression of MdMYB10 dramatically enhanced leaf anthocyanin accumulation, allowing more visible light to be absorbed, particularly in the green region. However, through post-transcriptional regulation, anthocyanin accumulation lowered leaf photosynthesis in both photochemical reaction and CO₂ fixation capacities. Anthocyanin accumulation also led to a decreased de-epoxidation state of the xanthophyll cycle and antioxidant capacities, but this is most likely a response to the light-shielding effect of anthocyanin, as indicated by a higher chlorophyll concentration and lower chlorophyll a/b ratio. Under laboratory conditions when detached leaves lost carbon fixation capacity due to the limitation of CO₂ supply, the photoinhibition of detached transgenic red leaves was less severe under strong white, green, or blue light, but it became more severe in response to strong red light compared with that of the wild type. In field conditions when photosynthesis was performed normally in both green and transgenic red leaves, the degree of photoinhibition was comparable between transgenic red leaves and wild type leaves, but it was less severe in transgenic young shoot bark compared with the wild type. Taken together, these data show that anthocyanin protects plants from high light stress by absorbing excessive visible light despite reducing photosynthesis. Full article