Electron Transport Rate Research Articles

Removal of heavy metal ions from wastewater using two-dimensional transition metal carbides

Water is an indispensable material for human life. Unfortunately, the development of industrial activities has reduced the quality of water resources in the world. Meantime, heavy metals are an important factor in water pollution due to their toxicity. This study highlights the method for the capture of heavy metal ions from wastewater using the procedure of adsorption. The adsorption of toxic heavy metal ions (Pb2+, Hg2+, and Cd2+) on Ca2C as well as Cr2C carbide-nitride MXene monolayers is investigated using the density functional theory. We have carried out the optimization of the considered MXenes by nine DFT functionals: PBE, TPSS, BP86, B3LYP, TPSSh, PBE0, CAM-B3LYP, M11, and LC-WPBE. Our results have shown a good agreement with previously measured electronic properties of the Ca2C and Cr2C MXene layers and the PBE DFT method. The calculated cohesive energy for the Ca2C and Cr2C MXene monolayers are −4.12 eV and −4.20 eV, respectively, which are in agreement with the previous studies. The results reveal that the adsorbed heavy metal ions have a substantial effect on the electronic properties of the considered MXene monolayers. Besides, our calculations show that the metal/MXene structures with higher electron transport rates display higher binding energy as well as charge transfers between the metal and Ca2C and Cr2C layers. Time-dependent density functional analysis also displayed “ligand to metal charge transfer” excitations for the metal/MXene systems. The larger Ebin for the Pb@Ca2C as well as Pb@Cr2C are according to larger redshifts which are expected (Δλ = 45 nm and 71 nm, respectively). Our results might be helpful for future research toward the application of carbide-nitride MXene materials for removing wastewater pollutants.

Physiology and Development of Soybean under Light Supplementation Treated with Herbicides in the Field

Soy is Brazil’s main commodity, and due to its importance, farmers have adopted several technological innovations, such as light supplementation, to increase grain productivity and quality. However, the use of artificial light can interfere with weed dynamics and herbicide efficiency. The objective of this work was to evaluate the effect of herbicides on weed control and qualitative and quantitative attributes of soybeans grown under light supplementation. A field experiment was set up in the city of Monte Carmelo, MG, Brazil. The treatments were distributed in plots mounted under a central pivot in two environments: with light supplementation (LED panels) and without light supplementation. The treatments were distributed across four blocks, and plots were subdivided in space. The herbicides used were glyphosate, diclosulam and glyphosate, s-metolachlor and glyphosate, fomesafen + clethodim, flumioxazin + clethodim. The variables analyzed were the number of weeds, biomass, and control; chlorophyll levels; initial fluorescence; ratio of variable fluorescence to maximum fluorescence; and soybean electron transport rate—indicators of soybean yield. Light supplementation increases the density and biomass of weeds and impairs the effectiveness of herbicides. However, light supplementation with LED panels installed on the central irrigation pivot promotes increased productivity and improvements in the quantitative and qualitative parameters of soybeans. Due to these benefits, light supplementation can be considered advantageous for irrigated soybean production.

Effect of Secondary Paper Sludge on Physiological Traits of Lactuca sativa L. under Heavy-Metal Stress.

To eliminate the negative effect of soil contamination with heavy metals on plant growth and crop yield, different methods and techniques are the subject of discussion and study. In this study, we aimed to evaluate the effect of secondary pulp and paper-mill sludge application to soil on the response of the main physiological processes such as the growth, photosynthesis, and respiration of lettuce (Lactuca sativa L.) plants to soil contamination with Pb. For the pot experiment, Pb was added to sandy loam soil at concentrations of 0, 50, and 250 mg Pb(NO3)2 per kg of the soil, and secondary sludge was added to a 0, 20, or 40% sludge solution during each plant watering. The Pb-mediated change in plant biomass allocation, decrease in the photosynthetic rate, increase in leaf respiration rate, and the degree of light inhibition of respiration were closely associated with increases in both root and shoot Pb content. For the Pb-free soil condition, secondary sludge application contributed to the allocation of plant biomass towards a greater accumulation in the shoots than in the roots. Although stomatal opening was not affected by either Pb or sludge, sludge application increased photosynthetic CO2 assimilation regardless of soil Pb content, which was associated with an increase in the electron-transport rate and carboxylase activity of Rubisco. Soil contamination with Pb significantly increased the ratio of respiration to photosynthesis, reflecting a shift in the carbon balance toward carbon losses in the leaves, but sludge application modified the coupling between the processes with a decrease in the proportion of respiratory carbon losses. The sludge-mediated recovery of the physiological processes of L. sativa reflected an increase in plant tolerance to soil contamination with heavy metals, the formation of which is associated with plant and soil adjustments initiated by secondary sludge application.

Effects of foliar iron oxide nanoparticles (Fe3O4) application on photosynthetic parameters, distribution of mineral elements, magnetic behaviour, and photosynthetic genes in tomato (Solanum lycopersicum var. cerasiforme) plants

This study aims to examine the effect of foliar magnetic iron oxide (Fe3O4) nanoparticles (IONP) application on the physiology, photosynthetic parameters, magnetic character, and mineral element distribution of cherry tomatoes (Solanum lycopersicum var. cerasiforme). The IONP suspension (500 mg L−1) was sprayed once (S1), twice (S2), thrice (S3), and four times (S4) a week on seedlings. Upon 21 days of the treatments, photosynthetic parameters (chlorophyll, carotenoids, photosynthetic yield, electron transport rate) were elucidated. Inductively-coupled plasma-optical emission spectrometer (ICP-OES) and vibrating sample magnetometer (VSM) were used to determine the mineral elements and abundance of magnetic power in the seedlings. In addition, the RT-qPCR method was performed to quantify the expressions of photosystem-related (PsaC, PsbP6, and PsbQ) and ferritin-coding (Fer-1 and Fer-2) genes. Results revealed that the physiological and photosynthetic indices were improved upon S1 treatment. The optimal dosage of IONP spraying enhances chlorophyll, carotenoid, electron transport rate (ETR), and effective photochemical quantum yield of photosystem II (Y(II)) but substantially diminishes non-photochemical quenching (NPQ). However, frequent IONP applications (S2, S3, and S4) caused growth retardation and suppressed the photosynthetic parameters, suggesting a toxic effect of IONP in recurrent treatments. Fer-1 and Fer-2 expressions were strikingly increased by IONP applications, suggesting an attempt to neutralize the excess amount of Fe ions by ferritin. Nevertheless, frequent IONP treatment fluctuated the mineral distribution and caused growth inhibition. Although low-repeat foliar applications of IONP (S1 in this study) may help improve plant growth, consecutive applications (S2, S3, and S4) should be avoided.

Toward More Accurate Modeling of Canopy Radiative Transfer and Leaf Electron Transport in Land Surface Modeling

AbstractModeling leaf photosynthesis is essential for quantifying the carbon, water, and energy fluxes of the terrestrial biosphere. However, due to the lack of simultaneous measurements of leaf light absorption and gas exchange, canopy radiative transfer (RT) and photosynthesis modeling often rely on simplified assumptions about light absorption and electron transport. These assumptions ignore variations in leaf biophysical traits and environmental conditions. In this study, we utilized a next‐generation land surface model (LSM)—CliMA Land, which incorporates hyperspectral canopy RT and provides a more accurate representation of trait variations. We evaluated the potential bias in electron transport estimates introduced by the broadband RT schemes used in traditional LSMs. Additionally, we explored the impact of different leaf electron transport parameterization schemes on global‐scale photosynthesis and fluorescence modeling. We showed that (a) traditional LSMs that disregard the impacts of leaf temperature and leaf traits on electron transport tend to overestimate electron transport rates. (b) Photosynthesis and fluorescence within a grid can exhibit biases exceeding 20%, with these biases demonstrating contrasting seasonality. (c) Global estimates of integrated photosynthesis and fluorescence differ by 8.1% and 8.8%, respectively. These results underscore the importance of adopting more sophisticated and accurate modeling schemes, such as hyperspectral canopy RT, in future LSMs and Earth system modeling to enhance the reliability of modeling outcomes.

Kinetic, electrochemical and spectral characterization of bacterial and archaeal rusticyanins; unexpected stability issues and consequences for applications in biotechnology

Motivated by the ambition to establish an enzyme-driven bioleaching pathway for copper extraction, properties of the Type-1 copper protein rusticyanin from Acidithiobacillus ferrooxidans (AfR) were compared with those from an ancestral form of this enzyme (N0) and an archaeal enzyme identified in Ferroplasma acidiphilum (FaR). While both N0 and FaR show redox potentials similar to that of AfR their electron transport rates were significantly slower. The lack of a correlation between the redox potentials and electron transfer rates indicates that AfR and its associated electron transfer chain evolved to specifically facilitate the efficient conversion of the energy of iron oxidation to ATP formation. In F. acidiphilum this pathway is not as efficient unless it is up-regulated by an as of yet unknown mechanism. In addition, while the electrochemical properties of AfR were consistent with previous data, previously unreported behavior was found leading to a form that is associated with a partially unfolded form of the protein. The cyclic voltammetry (CV) response of AfR immobilized onto an electrode showed limited stability, which may be connected to the presence of the partially unfolded state of this protein. Insights gained in this study may thus inform the engineering of optimized rusticyanin variants for bioleaching processes as well as enzyme-catalyzed solubilization of copper-containing ores such as chalcopyrite.

Toxic effect of ciprofloxacin on the photosynthesis reactions in microalga Scenedesmus quadricauda (Turp.) Bréb.

Ciprofloxacin (CIP) is widely used broad-spectrum antimicrobial drug of fluoroquinolone family. The widespread use of ciprofloxacin increases its release into the environment. Ciprofloxacin is detected in aquatic ecosystems potentially harming aquatic organisms. The CIP effect on photosynthetic organisms is not fully studied. In this study we examined the CIP effect on green freshwater microalgae Scenedesmus quadricauda (Turp.) Bréb. using chlorophyll fluorescence methods (JIP test parameters and rapid light curves). A significant decrease in the cell number was observed at ≥10 mg/L of сiprofloxacin in comparison with control. Analysis of chlorophyll fluorescence parameters obtained from OJIP transients revealed the changes in photosynthetic reactions in сiprofloxacin treatment. Ciprofloxacin was found to inhibit electron transport rate in photosystem II (PSII). The decrease in the quantum yield of electron transport in photosystem II (φEo) was accompanied by the decrease in performance index (PIABS) and an increase in energy dissipation (DI0/RC). Ciprofloxacin enhanced the photosensitivity of microalgae but did not inhibit the recovery of photosynthetic activity after the photooxidative stress. In this regard the effect of CIP differs from that of the well-known antibiotic chloramphenicol that inhibits the resynthesis of plastid proteins and, accordingly, the recovery of photosynthetic activity associated with the resynthesis of PSII protein D1. Among the fluorescence parameters, PIABS was found to be the most stress-specific; therefore it can be proposed to detect an early toxic CIP effect in microalgae.

Gas exchange and chlorophyll fluorescence responses of Camellia sinensis grown under various cultivations in different seasons

Sod culture (SC) and conventional agriculture (CA) represent two distinct field management approaches utilized in the cultivation of tea plants in Taiwan. In this study, we employed gas exchange and chlorophyll fluorescence techniques to assess the impact of SC and CA methods on the photosynthetic machinery of Camellia sinensis cv. TTES No.12 (Jhinhsuan) in response to variable light intensities across different seasons. In spring, at photosynthetic photon flux densities (PPFD) ranging from 800 to 2,000 μmol photon m-2 s-1, the net photosynthesis rate (Pn, 10.43 μmol CO2 m-2 s-1), stomatal conductance (Gs, 126.11 mmol H2O m-2 s-1), electron transport rate (ETR, 137.94), and ΔF/Fm’ and Fv/Fm (50.37) values for plants grown using SC were comparatively higher than those cultivated under CA. Conversely, the non-photochemical quenching (NPQ) values for SC-grown plants were relatively lower (3.11) compared to those grown under CA at 800 to 2,000 PPFD in spring. Additionally, when tea plants were exposed to PPFD levels below 1,500 μmol photon m− 2 s− 1, there was a concurrent increase in Pn, Gs, ETR, and NPQ. These photosynthetic parameters are crucial for devising models that optimize cultivation practices across varying seasons and specific tillage requirements, and for predicting photosynthetic and respiratory responses of tea plants to seasonally or artificially altered light irradiances. The observed positive impacts of SC on maximum photosynthetic rate (Amax), Fv/Fm, Gs, water-use efficiency (WUE), and ETR suggest that SC is advantageous for enhancing the productivity of tea plants, thereby offering a more adaptable management model for tea gardens.

Physiological and transcriptomic analysis of tomato in response to sub-optimal temperature stress

ABSTRACT Tomato (Solanum lycopersicum L.) is one of the most important economic crops in China. However, its quality and yield are susceptible to the adverse effects of low temperatures. In our study, two tomato cultivars, showing different tolerance to low temperatures, namely the cold-sensitive tomato cultivar (S708) and cold-tolerant tomato cultivar (T722), were grown at optimal (25/18°C) and sub-optimal (15/10°C) temperature conditions for 5 days. Our study aimed to explore the effect of sub-optimal temperature on fresh weight, chlorophyll content and chlorophyll fluorescence, soluble sugars and proline content of two tomato cultivars. Moreover, we employed RNA-Seq to analyze the transcriptomic response of tomato roots to sub-optimal temperature. The results revealed that S708 showed a more significant reduction in fresh weight, chlorophyll content, photochemical efficiency of PSII (YII), maximum quantum yield of PSII (Fv/Fm), photochemical quenching (qP) and electron transport rate (ETR) compared to T722 under the sub-optimal temperature condition. Notably, T722 maintained higher level of soluble sugars and proline in comparison to S708 uner sub-optimal temperature. RNA-seq data showed that up-regulated DEGs in both tomato cultivars were involved in “plant-pathogen interaction”, “MAPK signaling pathway”, “plant hormone signal transduction”, and “phosphatidylinositol signaling system”. Furthermore, “Amino sugar and nucleotide sugar metabolism” pathway was enriched only in T722. Moreover, under sub-optimal temperature, transcription factor genes and osmoregulation genes showed varying degrees of response in both tomato cultivars. Conclusion: In summary, our results offer detailed insights into the response characteristics of tomato to sub-optimal temperature, providing valuable references for the practical management of tomato crops under sub-optimal temperature condition.

Effects of Warming and Elevated CO2 on Stomatal Conductance and Chlorophyll Fluorescence of C3 and C4 Coastal Wetland Species

Coastal wetland communities provide valuable ecosystem services such as erosion prevention, soil accretion, and essential habitat for coastal wildlife, but are some of the most vulnerable to the threats of climate change. This work investigates the combined effects of two climate stressors, elevated temperature (ambient, + 1.7 °C, + 3.4 °C, and 5.1 °C) and elevated CO2 (eCO2), on leaf physiological traits of dominant salt marsh plant species. The research took place at the Salt Marsh Accretion Response to Temperature eXperiment (SMARTX) at the Smithsonian Environmental Research Center, which includes two plant communities: a C3 sedge community and a C4 grass community. Here we present data collected over five years on rates of stomatal conductance (gs), quantum efficiency of PSII photochemistry (Fv/Fm), and rates of electron transport (ETRmax). We found that both warming and eCO2 caused declines in all traits, but the warming effects were greater for the C3 sedge. This species showed a strong negative stomatal response to warming in 2017 and 2018 (28% and 17% reduction, respectively in + 5.1 °C). However, in later years the negative response to warming was dampened to < 7%, indicating that S. americanus was able to partially acclimate to the warming over time. In 2022, we found that sedges growing in the combined + 5.1 °C eCO2 plots exhibited more significant declines in gs, Fv/Fm, and ETRmax than in either treatment individually. These results are important for predicting future trends in growth of wetland species, which serve as a large carbon sink that may help mitigate the effects of climate change.

Variability of Primary Productivity as an Initial Link in Carbon Flux Under the Influence of Hydrological Conditions in the Baltic Sea

Investigating variability in phytoplankton primary productivity as a key component of the “biological pump” is critical to quantifying flux in the marine environment. We hypothesized that under certain hydrological conditions, changes in phytoplankton productivity are greater with changes in photosynthetic efficiency (the ratio of primary production (P P ) to the rate of electron transport in the phytoplankton photosystem, P P /ETR) than with changes in chlorophyll content. This study showed that increase of P P during sharp changes in hydrological parameters in the temporary frontal South-East Baltic (SEB) is achieved by increasing the efficiency of photosynthesis, i.e., the degree of use of light energy captured by chlorophyll a (Chl a). In the Gulf of Finland (GF), an increase in P P followed an increase in salinity from the Neva mouth to the sea and controls chlorophyll contents with low variability in photosynthetic efficiency. For SEB and GF, measurements of parameters of phytoplankton productivity and chlorophyll a content in late autumn (November) are carried out. The first stage of carbon flow (in biological pump), expressed in terms of primary production, was higher in the SEB than in the GF

Impacts of Compound Hot–Dry Events on Vegetation Productivity over Northern East Asia

Climate extremes, such as heatwaves and droughts, significantly impact terrestrial ecosystems. This study investigates the influence of compound hot–dry (CHD) events on vegetation productivity in northern East Asia. Four of the most widespread CHD events occurring during the summer from 2003 to 2019 were selected as the focus of this research. We first verified the performance of the Community Land Model version 5 (CLM5) in the region and then conducted factor-controlled experiments using CLM5 to assess the effects of different climate factors on gross primary productivity (GPP) changes during CHD events. Our results show that vegetation productivity exhibits greater sensitivity to CHD events within the transitional climatic zone (TCZ) than in other affected areas. In grassland areas within the TCZ, precipitation deficit is the primary factor leading to the decrease in GPP (explaining 56%–90% of GPP anomalies), while high temperatures serve as a secondary detrimental factor (explaining 13%–32% of GPP anomalies). In high-latitude forests outside the TCZ, high temperature has a more significant impact on suppressing GPP, while the decrease in soil moisture has a synchronously negligible impact on GPP. There are differences in the effects of high solar radiation on grasslands and woodlands during CHD events. It was observed that high radiation benefits trees by increasing the maximum carboxylation rate (Vcmax) and maximum electron transport rate (Jmax), as well as enhancing photosynthesis, but has a negligible impact on grasses. Furthermore, this study highlights the potential for compound events to impact vegetation productivity more than expected from individual events due to confounding nonlinear effects between meteorological factors. More than 10% of the negative anomalies in GPP during two CHD events in 2017 and 2010 were attributed to these nonlinear effects. These research findings are significant for understanding ecosystem responses to climate extremes and their influence on carbon cycling in terrestrial ecosystems. They can also contribute to more precisely evaluating and predicting carbon dynamics in these regions.

Photosystem II Tolerance to Excess Zinc Exposure and High Light Stress in Salvia sclarea L.

High light (HL) intensity has a substantial impact on light energy flow and partitioning within photosynthetic apparatus. To realize the impact of HL intensity on zinc (Zn) tolerance mechanisms in clary sage (Salvia sclarea L., Lamiaceae) plants, we examined the effect of the altered chlorophyll and nutrient uptake under excess Zn supply on the response mechanism of photosystem II (PSII) photochemistry. Eight-week-old clary sage plants were treated with 5 μM Zn (control) or 900 μM Zn in Hoagland nutrient solution. Leaf elemental analysis for Zn, Mn, Mg, and Fe was performed by inductively coupled plasma mass spectrometry (ICP-MS), whereas PSII functioning under HL was evaluated by chlorophyll fluorescence imaging analysis. Exposure of S. sclarea plants to 900 μM Zn increased leaf Zn accumulation and decreased leaf Mg and chlorophyll. The decreased non-photochemical quenching (NPQ) provided evidence of the photoprotection offered by the smaller light-harvesting antennae due to the reduced chlorophyll. The increased Mn after Zn exposure corresponded with higher efficiency of the oxygen-evolving complex (OEC) that was significantly correlated with the maximum efficiency of photosystem II (PSII) photochemistry (Fv/Fm). An increased electron transport rate (ETR) coincided with increased leaf Fe, which is known to play a vital role in the enzymes engaged in ETR. The decreased (32%) NPQ after an 8-day exposure to Zn caused an increased (10%) quantum yield of non-regulated energy loss in PSII (ΦNO), indicative of an increased singlet oxygen (1O2) production. It is suggested that the decreased NPQ induced acclimation responses of clary sage plants to HL and excess Zn by increasing 1O2 production. The reduced (18%) excess excitation energy (EXC) at PSII and the increased (24%) quantum yield of PSII photochemistry (ΦPSII) and ETR indicated improved photosynthetic efficiency under excess Zn and HL intensity. Therefore, the exposure of medicinal plants to excess Zn not only boosts their photosynthetic efficiency, enhancing crop yields, but can also improve Fe and Zn content, ameliorating the human health deficiency of these two essential micronutrients.

Differential photosynthetic plasticity of Amazonian tree species in response to light environments.

To investigate how and to what extent there are differences in the photosynthetic plasticity of trees in response to different light environments, six species from three successional groups (late successional, mid-successional, and pioneers) were exposed to three different light environments [deep shade - DS (5% full sunlight - FS), moderate shade - MS (35% FS) and full sunlight - FS]. Maximum net photosynthesis (Amax), leaf N partitioning, stomatal, mesophile, and biochemical limitations (SL, ML, and BL, respectively), carboxylation velocity (Vcmax), and electron transport (Jmax) rates, and the state of photosynthetic induction (IS) were evaluated. Higher values of Amax, Vcmax, and Jmax in FS were observed for pioneer species, which invested the largest amount of leaf N in Rubisco. The lower IS for pioneer species reveals its reduced ability to take advantage of sunflecks. In general, the main photosynthetic limitations are diffusive, with SL and ML having equal importance under FS, and ML decreasing along with irradiance. The leaf traits, which are more determinant of the photosynthetic process, respond independently in relation to the successional group, especially with low light availability. An effective partitioning of leaf N between photosynthetic and structural components played a crucial role in the acclimation process and determined the increase or decrease of photosynthesis in response to the light conditions.

Improving nitrogen content in the carboxylation and electron transfer component can boost the reproductive biomass of filmless cotton in arid areas

AbstractDeep drip irrigation combined with high‐density planting is one of the most economical and effective ways to address residual film pollution. This study aimed to explore the photosynthetic potential of and achieve water‐saving and high‐yielding filmless cotton (Gossypium hirsutum L.) by optimizing the irrigation amount. We analyzed the effect of source leaf activity on leaf nitrogen allocation and photosynthetic nitrogen utilization efficiency (PNUE) under different irrigation amounts (mm, 375 (W5), 348 (W4), 320 (W3), 293 (W2), and 265 (W1)) in a 2‐year field experiment under this planting mode. The photosynthetic pigment content, leaf mass per area, and light compensation point all decreased with increasing amounts of irrigation, while the apparent quantum yield of photosynthesis, light saturation point, maximum carboxylation rate (Vcmax), maximum electron transport rate (Jmax), triose phosphate utilization rate (VTPU), nitrogen content in the electron transfer component (NB), and nitrogen content in the carboxylation component (NC) showed opposite trends. At the later full boll stage, the W3 and W4 treatments increased the leaf area of a whole plant (LA) by 10.4% and 19.4%, respectively, compared to that in the W1 treatment, while the PNUE increased by 20.2% and 20.8%, respectively, compared to that in the W5 treatment. In addition, principal component analysis found that the factor variables total nitrogen content in the photosynthetic apparatus (NT), net photosynthetic rate (Pn), stomatal conductance (Gs), light‐saturated net photosynthetic rate (Amax), NC, and Vcmax had higher loadings and were all positively correlated with PNUE; LA had a higher loading and was positively correlated with reproductive organ biomass. Therefore, we recommend using an irrigation rate of 320 mm in this cultivation system to increase nitrogen in carboxylation and electron transport components, enhance photosynthetic capacity, and thereby improve PNUE to increase reproductive organ biomass and reduce the irrigation amount in arid areas.

Mechanisms Underlying the Differential Sensitivity to Mesotrione in Sweet Corn

Mesotrione is a widely used post-emergence herbicide for maize. The toxicity of mesotrione to maize (especially sweet corn) has been widely reported, and some sweet corn varieties are highly sensitive to mesotrione, which affects subsequent plant growth periods. However, the molecular mechanisms responsible for the differences in susceptibility to mesotrione are not known. By comparing changes in the transcriptome of mesotrione-tolerant line 301 and mesotrione-sensitive line 276 after mesotrione treatment, we found that the genes coding light-harvesting chlorophyll protein complex were induced in 301, and the genes coding loosening cell walls were overrepresented in 276. The net photosynthetic rate, maximum photochemical efficiency of leaf PSII, photochemical quenching of chlorophyll fluorescence, and the electron transport rate were significantly higher in 301 than in 276 after mesotrione treatment, and these effects became more severe as time passed. In addition, oxidative balance was also affected by mesotrione. Compared with 301, SOD, POD, and CAT activities were significantly reduced with longer exposure time in 276. The results suggested that sweet corn can mitigate herbicide mesotrione toxicity by improving photosynthesis, ROS scavenging, and cell wall synthesis.

Strong Lewis acid-induced self-healing of loose FeOOH for alkaline oxygen evolution

The fast leaching of the Fe catalytic center and low conductivity of FeOOH have hindered the optimal stability and activity of Fe-based electrocatalysts for oxygen evolution reactions (OER). Here, Zn2+ is introduced into FeOOH with a looser nanosheet structure by regulating electric double layer (EDL) repulsion during electrodeposition. Meanwhile, as strong Lewis acids, Zn2+ in ZnxFeOOH could act as an electron acceptor, accepting electrons from FeOOH. The doping of Zn2+ shortens the bond length of Fe-O and enhances the covalency of Fe-O to improve electron transport rate and stability. The faster catalytic kinetics also been obtained by facilitating O* to form OOH* intermediates. At 100 mA cm−2, Zn0.5FeOOH requires overpotential of only 250 mV and maintains initial activity in 1 M KOH after 120 h. Notably, Zn-induced self-healing is achieved when the leaching and redeposition of Fe reach dynamic equilibrium. In 1 M KOH seawater, Zn0.5FeOOH requires overpotentials of 286 mV to produce current density of 100 mA cm−2. At 2.0 V, Zn0.5FeOOH can achieve 1000 mA cm−2 in anion exchange membrane (AEM) water electrolyzer at room temperature. This work provides an effective Zn-induced strategy for designing efficient and stable OER catalysts for industrial development.

Mitigating Salinity Stress in Pomegranate: Effects of Pseudomonas fluorescens and Glomus mosseae on Stress Responses of Red Angel and Wonderful Cultivars

Salinity stress is a major challenge in modern pomegranate orchards. The application of biofertilizers is a promising strategy to mitigate the adverse effects of salinity stress and enhance the performance in pomegranates. This experiment was conducted in 2021 to investigate the effects of salinity stress (control, 4, and 8 dS/m) and inoculation with Pseudomonas fluorescens and Glomus mosseae, either individually or in combination (Pf+Gm), on Red Angel and Wonderful pomegranate cultivars. The results revealed a significant difference in the percentage of symbiosis and colonization among the biofertilizer treatments. Pf+Gm exhibited the highest percentages of symbiosis and colonization, followed by P. fluorescens. While salinity levels did not significantly affect symbiosis percentage, they had a detrimental effect on colonization percentage. Furthermore, biofertilizer treatments significantly increased leaf density, stem growth, total chlorophyll, and total anthocyanin, while reducing ion leakage and salinity damage index. In comparison to the non-inoculated control, the Pf+Gm treatment resulted in a 53.2 % decrease in ion leakage for the Red Angel cultivar and a 39.9 % decrease for the Wonderful cultivar. Salinity had a significant effect on proline production, with the Red Angel cultivar exhibiting the highest proline content (2.09 µmol/g) in response to salinity stress of 8 ds/m. However, biofertilizer treatments increased proline content in both cultivars. In Red Angel, the Pf+Gm treatment resulted in the highest proline production in the leaves (5.82 µmol/g), which was 123 % higher than that of the non-inoculated control. Additionally, the transpiration rate decreased with increasing salinity levels, and biofertilizer treatments had varying effects on photosynthetic gas exchange and electron transport rate. The interaction effect of biofertilizer treatments and salinity on CO2 absorption was highly significant, with Pf+Gm treatment exhibiting the highest absorption (8.51 and 8.61 µmol/m2/s in Red Angel and Wonderful, respectively). These findings suggest that applied biofertilizer treatments, especially Pf+Gm, can be an effective strategy for alleviating the negative effects of salinity stress on pomegranate cultivation.

Physiological and photochemical profiling of soybean plant using biological and chemical methods of treatment against biotic stress management

Phyto-pathogenic fungal species is a leading biotic stress factor to agri-food production and ecosystem of globe. Chemical (Systemic fungicides) and biological treatment (micro-organism) are globally accepted methods that are being used against biotic stress (disease) management. Plant Growth-Promoting Microbes are being used as an alternative to ease chemical dependency as their overdoses have generated injurious effects on plants and environment. Therefore, present study performs to evaluate the photochemical and physiological profiling of plants exposed to chemical and biological treatment in biotic stress (disease) environment. Two concentrations of each chemical treatment i.e. Topsin-M 70 (Dimethyl 4,4′-o-phenylene bis 3-thioallaphanate, MF1 = 3 g kg−1 and MF2 = 6 g kg−1 seeds) and biological treatment i.e. Trichoderma harzianum strain Th-6 (MT1 = 106 spores mL−1and MT2 = 107 spores mL−1) were used in this experiment. Macrophomina phaseolina (MP) were used as biotic stress factor causing root rot disease in soybean plants. Morpho-physiological assessments and light harvesting efficiency of photosystem II were conducted after 52 days of treatment. Maximum quantum yield (Fv/Fm), number and size of active reaction center (Fv/Fo), photochemical quenching (qP), efficiency of photosystem II (ΦPSII), electron transport rate (ETR), chlorophyll content index (CCI), relative water content (RWC) and stomatal conductance (SC) were increased in MT2 and MF1 treatments as compared to stress plants (MP). Biological (MT2) and chemical (MF1) treatment lessen the production of stress markers showing −48.0 to −54.3% decline in malondialdehyde (MDA) and −42.0 to −53.7% in hydrogen peroxide (H2O2) as compared to stress plant (MP). Biological treatment in both concentration (MF1 & MF2) while chemical treatment at low dose effectively mitigates biotic stress and eases the magnitude of disease. Increasing doses of chemical treatment persuaded deleterious effects on the physiology and light harvesting efficiency of stressed plant suggesting the role of biological treatment (T. harzianum) against biotic stress management in future of crop protection.

Diffusional and Biochemical Limitations to Photosynthesis Under Water Deficit for Field-Grown Cotton.

Water deficit stress limits net photosynthetic rate (AN), but the relative sensitivities of underlying processes such as thylakoid reactions, ATP production, carbon fixation reactions, and carbon loss processes to water deficit stress in field-grown upland cotton require further exploration. Therefore, the objective of the present study was to assess (1) the diffusional and biochemical mechanisms associated with water deficit-induced declines in AN and (2) associations between water deficit-induced variation in oxidative stress and energy dissipation for field-grown cotton. Water deficit stress was imposed for three weeks during the peak bloom stage of cotton development, causing significant reductions in leaf water potential and AN. Among diffusional limitations, mesophyll conductance was the major contributor to the AN decline. Several biochemical processes were adversely impacted by water deficit. Among these, electron transport rate and RuBP regeneration were most sensitive to AN-limiting water deficit. Carbon loss processes (photorespiration and dark respiration) were less sensitive than carbon assimilation, contributing to the water deficit-induced declines in AN. Increased energy dissipation via non-photochemical quenching or maintenance of electron flux to photorespiration prevented oxidative stress. Declines in AN were not associated with water deficit-induced variation in ATP production. It was concluded that diffusional limitations followed by biochemical limitations (ETR and RuBP regeneration) contributed to declines in AN, carbon loss processes partially contributed to the decline in AN, and increased energy dissipation prevented oxidative stress under water deficit in field-grown cotton.