Photoinhibition Research Articles

Sub-diffraction optical beam lithography based on a center-non-zero depletion laser.

Photoinhibition (PI) mechanisms have been introduced in nanofabrication which allows breaking the diffraction limit by large factors. Donut-shaped laser is usually selected as a depletion beam to reduce linewidth, but the parasitic process has made the results of the experiment less than expected. As a result, the linewidth is difficult to achieve below 50 nm with 780 nm femtosecond and 532 nm continuous-wave lasers. Here, we propose a new, to the best of our knowledge, method based on a center-non-zero (CNZ) depletion laser to further reduce linewidth. By constructing a smaller zone of action under the condition of keeping the maximum depletion intensity constant, a minimum linewidth of 30 nm (λ / 26) was achieved. Two ways to construct CNZ spots were discussed and experimented, and the results show the advantages of our method to reduce the parasitic process to further improve the writing resolution.

Effect of Light Intensity on Photosynthesis in Aquatic Plants in Australia

Purpose: The aim of the study was to investigate the Effect of Light Intensity on Photosynthesis in Aquatic Plants in Australia.
 Methodology: The study adopted a desktop methodology. Desk research refers to secondary data or that which can be collected without fieldwork. Desk research is basically involved in collecting data from existing resources hence it is often considered a low cost technique as compared to field research, as the main cost is involved in executive’s time, telephone charges and directories. Thus, the study relied on already published studies, reports and statistics. This secondary data was easily accessed through the online journals and library
 Findings: In the study examining the impact of light intensity on photosynthesis in Australian aquatic plants, key findings emerged. It was evident that light intensity played a crucial role, with higher light levels in shallower waters leading to increased photosynthesis rates. This underscored the significance of light as a primary determinant of photosynthesis in these ecosystems. Additionally, the study highlighted the impressive adaptability of Australian aquatic plants, some of which employed unique photo protective mechanisms to prevent photo inhibition under varying light conditions.
 Unique Contribution to Theory, Practice and Policy: Theory of Liebig's Law of the Minimum, Theory of The Beer-Lambert Law and Optimal Foraging Theory may be used to anchor future studies on the Effect of Light Intensity on Photosynthesis in Aquatic Plants in Australia. Develop practical guidelines for growers to optimize light conditions for maximum photosynthetic efficiency. Advocate for policies that recognize the significance of aquatic plants in maintaining healthy aquatic ecosystems. Promote the conservation and restoration of natural habitats for aquatic plants, especially in areas threatened by pollution or habitat destruction.

Rapid photodegradation of toxic organic compounds and photo inhibition of bacteria in the presence of novel hydrothermally synthesized Ag/Mn–ZnO nanomaterial

Purified water is the most concerning issue these days, and utmost conventional practices are allied with various downsides. Therefore, an ecologically benign and easily amicable therapeutic approach is the requirement. In this wonder, nanometer phenomena bring an innovative change to the material world. It has the potential to produce nanosized materials for wide-ranging applications. The subsequent research highlights the synthesis of Ag/Mn–ZnO nanomaterial via a one-pot hydrothermal route with an efficient photocatalytic activity against organic dyes and bacteria. The outcomes revealed that the size of the particle (4–5 nm) and dispersion of spherically shaped silver nanoparticles intensely affected by employing Mn–ZnO as a support material. Use of silver NPs as a dopant activates the active sites of the support medium and provides a higher surface area to upsurge the degradation rate. The synthesized nanomaterial was evaluated against photocatalytic activity using Methyl orange and alizarin red as model dyes and confided that more than 70% of both the dyes degraded under 100 min duration. It is well recognize that the modified nanomaterial recreates an essential role in every light-based reaction, and virtually produced highly reactive oxygen species. The synthesized nanomaterial was also evaluated against E. coli bacterium both in light and dark. The zone of inhibition in the presence of Ag/Mn–ZnO was observed both in light (18 ± 0.2 mm) and dark (12 ± 0.4 mm). The hemolytic activity shows that Ag/Mn–ZnO has very low toxicity. Hence, the prepared Ag/Mn–ZnO nanomaterial might be an effective tool against the depletion of further harmful environmental pollutants and microbes.

Synthesis of Zr–Fe2O3/In2O3 photocatalyst by novel hydrothermal method for highly selective photo inhibition of pathogens, pollutant degradation and DPPH stabilization

Researchers are continuously in searching of inspecting new and exclusive technique and materials to manipulate with environmental circumstances and human life. In the present work Zr–Fe2O3@In2O3 porous nanomatrials were synthesized by new eco-friendly method. The Triton X-100 and green surfactants were utilized as reducing and structure directing agents. Firstly Zr–Fe2O3 was synthesized at different optimized conditions i.e. pH, Temperature and extract concentrations. The results show that the spherical shape and small size of Zr–Fe2O3 was obtained at pH = 9, 50 °C temperature and 20 mL plant extract. The porous nanocomposite was obtained by the treatment of Zr–Fe2O3 with indium oxide. The results also indicated that Zr–Fe2O3@In2O3 nanomaterial is crystalline in nature and have high surface area. The synthesized Zr–Fe2O3@In2O3 nanomaterial was used as a photocatalyst against methylene blue. The irradiation time analysis showed that photo degradation of MB was a rapid process and decomposed 98% in 40 min. The said nanocomposite was also worked as good antibacterial agent and inhibits E. coli and S. aureus. The inhibition zone of the said porous composite in light was 17 (±0.4) against E. coli and 22 (±0.2) against S. aureus. The detail mechanism of action of the synthesized nanomaterial was also studied. The Zr–Fe2O3@In2O3 also shows promising DPPH scavenging activity.

Facile synthesis of copper oxide nanoparticles (CuONPs) using green method to promote photocatalytic and biocidal applications

• Novel method was applied for the synthesis of CuO. • Cirsium arvense plant extract was used as a reducing and stabilizing agent. • The said nanostructure was applied for the photo inhibition of Bacteria. • Detail mechanism was studied. • Degradation of Rhodamine B was studied. As the overuse and misuse of hazardous chemical substance contribute to environmental pollution, it is imperative to explore facile and eco-friendly method for the synthesis of nanostructures. In this regard, a novel hydrothermal assisted green synthetic protocol was adopted for the synthesis of CuONPs, using purified Cirsium arvense plant extract and ascorbic acid. The synthesized nanoparticles were systematically characterized by UV–vis, FTIR, XRD, SEM, HRTEM, XPS and EDS. The biogenic CuONPs are utilized efficiently for important applications, such as antibacterial and photocatalytic activities. It is revealed that the CuONPs displays enhanced photocatalytic action, where complete degradation of Rhodamine B (RhB) was observed within 30 min in the presence of visible light irradiation. Moreover, the results demonstrate that biogenic CuONPs has shown best antibacterial action by inhibiting the growth of S. aureus and E. coli with zone of inhibition 18(±0.3) mm and 21(±0.4) mm respectively. The best photocatalytic and biomedical response of CuONPs seem to be the result of high potential reducing and capping property of plant phytochemicals. More importantly, the synthesized CuONPs are not only active for ROS generation but also show no hemolytic activity. Based on the above results, the silent features of CuONPs can be deemed for multifunctional applications.

Plant Responses to Water Deficit and Photo Inhibition

Plant Responses to Water Deficit and Photo Inhibition

Photo Inhibition Aided Vat Photopolymerization Additive Manufacturing (Pinpam): A Potential Pathway to Tackle Over-Curing for Printing Three-Dimensional High-Fidelity Parts

Photo Inhibition Aided Vat Photopolymerization Additive Manufacturing (Pinpam): A Potential Pathway to Tackle Over-Curing for Printing Three-Dimensional High-Fidelity Parts

Morpho-physiological and biochemical attributes of Chili (Capsicum annum L.) genotypes grown under varying salinity levels.

Climate change is causing soil salinization, resulting in huge crop losses throughout the world. Multiple physiological and biochemical pathways determine the ability of plants to tolerate salt stress. Chili (Capsicum annum L.) is a salt-susceptible crop; therefore, its growth and yield is negatively impacted by salinity. Irreversible damage at cell level and photo inhibition due to high production of reactive oxygen species (ROS) and less CO2 availability caused by water stress is directly linked with salinity. A pot experiment was conducted to determine the impact of five NaCl salinity levels, i.e., 0,1.5, 3.0, 5.0 and 7.0 dS m-1 on growth, biochemical attributes and yield of two chili genotypes (‘Plahi’ and ‘A-120’). Salinity stress significantly reduced fresh and dry weight, relative water contents, water use efficiency, leaf osmotic potential, glycine betaine (GB) contents, photosynthetic rate (A), transpiration rate (E), stomatal conductance (Ci), and chlorophyll contents of tested genotypes. Salinity stress significantly enhanced malondialdehyde (MDA) contents and activities of the enzymatic antioxidants such as superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD). In addition, increasing salinity levels significantly reduced the tissue phosphorus and potassium concentrations, while enhanced the tissue sodium and chloride concentrations. Genotype ‘Plahi’ had better growth and biochemical attributes compared to ‘A-120’. Therefore, ‘Plahi’ is recommended for saline areas to improve chili production.

Combined chlorophyll fluorescence techniques to study environmental impact on the mountain moss Polytrichum commune

Two chlorophyll fluorescence (ChlF) methods were used to study the effects of high light (photoinhibition) and dehydration, common stressors of the alpine environment, on primary photosynthetic processes in the moss Polytrichum commune from the Czech Republic, the Jeseníky Mountains. Photoinhibition (PI) was studied in fully hydrated thalli of P. commune and during the period of spontaneous desiccation. Time courses of Kautsky kinetics (KK) of ChlF and derived parameters: maximum quantum yield (FV/FM), effective quantum yeld (ΦPSII), and non-photochemical quenching parameters, were measured before and after the samples were treated with high light (1500 µmol m-2 s-1 PAR) for 60 min. Dehydration effects were tested in two sets of experiments with a Pulse-Amplitude-Modulation fluorometry (PAM) and Fast Chlorophyll Fluorescence induction curve (OJIP) techniques. In PAM tests, the desiccating samples were exposed to saturating light pulses every 10 min. in order to obtain ΦPSII and non-photochemical quenching (NPQ). In the second dehydration experiment, OJIP transients of ChlF were repeatedly recorded, OJIP-derived ChlF parameters were plotted against relative water content (RWC) monitored during desiccation. Combined ChF techniques provided insights into the mechanisms activated during P. commune desiccation, such as dissipation of excess absorbed energy through heat dissipation, and conformational changes or destructions of the light harvesting complexes. Combination of stressors resulted in amplified interference with the photosynthetic machinery, even when the added stressor (dehydration) was applied in low dose.

Photoinhibition of primary photosynthetic processes in hydrated Polytrichum commune: Analysis of non-photochemical quenching affecting species resistance

A moss from the alpine environment of the Jeseníky mountains, Polytrichum commune, was studied under lab-induced light stress to analyse photoinhibition (PI) stress response; three PI doses were used: PAR 1500 µmol m-2 s-1 for 60 min., 1200 µmol m-2 s-1 for 60 min. and 1200 µmol m-2 s-1 for 30 min.; in the last one the added component of slight desiccation stress was added. Chlorophyll fluorescence parameters were plotted as time series, immediately before and after the PI treatments, then every 20 minutes for three hours (recovery period). FV/FM, ΦPSII and NPQ parameters and quenching components were analysed. Decreasing courses and final values of FV/FM and ΦPSII parameters along with increased values of NPQ clearly indicated PI stress response, although not very severe. Quenching parameters analysis showed a dominant role played by xanthophyll pigments along with changes in PS II in the non-photochemical energy quenching. Dehydration contributed additional value to NPQ. All these factors are consistent with the adaptation of the species to harsh conditions of alpine environments.

Effect of drought stress in jointing stage on the photosynthetic light response of spring maize in Northeast China

The field experiments of drought stress and rewatering for spring maize were carried out in jointing stage in Northeast China. The effects of drought stress on the photosynthetic light response of maize and rewatering compensation recovery were analyzed. The results were showed as followed: Under moderate drought stress condition in jointing stage, drought stress affected the photosynthesis of maize leaves and led to the decrease of the values of photosynthetic light response parameters such as the transpiration rate, photosynthesis rate, stomatal conductance and intercellular CO2 concentration. The longer time of the drought stress, the more severe the damage of the photosynthesis, the more obvious photo inhibition occurred, and the more difficult to recover. The compensation recovery of photosynthetic rate after 10 days of rewatering was better than that of stomatal conductance, transpiration rate, and intercellular CO2 concentration. Therefore, there needed to be moderate water supply in the jointing stage of maize to ensure the photosynthetic structure not to be damaged.

Two-Wavelength, Photo-Initiation and Photo-Inhibition Competing for Selective Photo-Patterning of Hydrogel Porous Microstructures

Ever since its development, tissue engineering has played a significant role in the medical arena with an ever-growing demand for various tissue donations. One crucial factor in conducting in vitro tissue engineering study is the construction of a desirable artificial three-dimensional (3D) hydrogel tissue scaffold to act as the extracellular matrix (ECM), meeting the complex requirements for specific cell cultures. Existing hydrogel scaffold fabrication techniques and systems utilized in constructing ECM are either twodimensionally limiting, hard to control the pattern morphologies or expensive and time consuming. In the present study, we introduce a simple, inexpensive method for selective patterning 3D porous microstructures. This technique-'two wavelength photo-initiation and photo inhibition competes’ is an extension of conventional photo-patterning method. Integrating with shadow mask, photo inhibition radicals were introduced to couple with the polymerization chains and terminate the photo crosslinking behavior at designed region, making 3D selectively patterning hydrogel feasible. High aspect ratio ridge with selectively inhibited porous structures and selectively patterned micro pillar were fabricated using this method within 1 minute. The in vitro cell test results indicate the patterned structures' good biocompatibility.

Photo-inhibition and photo-protective mechanisms of shaded peanut leaves after re-exposure to natural light

Photo-inhibition and photo-protective mechanisms of shaded peanut leaves after re-exposure to natural light

Adaptation of Arabidopsis Plants to Tropical Aeroponics Using Cool Root Zone Temperatures

Arabidopsis thaliana (L.) Heyhn. is a well known model plant in plant research. However, its growth conditions and diminutive stature associated with low biomass at maturity make it a challenging species for physiological studies. While in the tropical countries, it can only be grown either by tissue cultures or in growth chambers under controlled conditions. An aeroponic technique with 20°C ± 2°C and 30°C ± 2°C root-zone temperatures (RZT) was used to grow Arabidopsis (Columbia ecotype) in a tropical greenhouse with natural irradiance and high ambient temperature (38°C/28°C day/night). Seedlings germinated in growth chambers at 20°C or 30°C. At 6 to 8 leaf stage, they were transferred to the aeroponic troughs with their roots exposed to constant temperature of 20°C ± 2°C and 30°C ± 2°C while their aerial parts were subjected to fluctuating ambient temperature from 28°C to 38°C. After a week, plants have acclimatised to both RZTs and started developing normal rosettes, bolted and yielded viable seeds. However, 20°C ± 2°C RZT allowed them to recover from turgor pressure despite of wilting, and significantly increased biomass. Mature plants grown in each RZTs were compared morphologically and physiologically to the plants grown in growth chamber (GC) at 20°C (root and shoot) temperature with 60% relative humidity. Aeroponically grown plants did not experience photoinhibition, and also exhibited higher photosynthetic light usage efficiency and higher capacities of heat dissipation, compared to GC plants. This aeroponics with cool RZTs can allow the use of Arabidopsis as a model plant even under tropical climate.

Chlorophyll fluorescence and excitation energy dissipation of pot-grown Phyllostachys rivalis leaves after long-term flooding.

To determine the physiological and biochemical responses and adaptive mechanisms of Phyllostachys rivalis to long-term soil flooding, two-year-old potted seedlings of Ph. rivalis were subjected to different flooding depths. The flooding treatment was set with water levels of 5 cm (TreatmentⅠ) and 10 cm (TreatmentⅡ) higher than the soil surface and normal water supply (ck). Then the chlorophyll fluorescence parameters in leaves were determined after continuous flooding for 30, 90, 180, 270, and 360 d. Responses to the continuous flooding stress for light energy absorption and transformation, energy transfer and distribution, reaction center activity, and excitation energy dissipation in leaves of three leaves per seedlings and three seedlings were measured and analyzed. A one-way analysis of variance with duncan's test was conducted at a significant level of 0.05. Results showed that the chlorophyll fluorescence parameters varied with different flooding levels. When flooding for 30 d and 90 d, minimal fluorescence (Fo), maximum fluorescence (Fm), photochemical maximum efficiency of PS Ⅱ (Fv/Fm), photochemical quenching coefficient (qP), and electron transport rate(RET) of Treatment Ⅰ were not significantly different (P > 0.05) compared with ck; however, Treatment Ⅱ when flooding for 90 d compared with ck was significantly increased for Fo while significantly decreased for Fm, Fv/Fm and RET (P 0.05). The amount of absorbed light in photochemistry (P) and excess energy (E) increased first and then decreased (P < 0.05), but the energy of dissipation of the antenna heat dissipation (D) observed were opposite. Taken together, Ph. rivalis could maintain a relatively high RET, qP, and P in the early stages of flooding, and enhance qN to regulate their energy metabolism, dissipate excess light energy via heat dissipation, thereby alleviating the light photoinhibition and photooxidation; however, continuous long-term soil flooding could damage photosystem Ⅱ (PS Ⅱ) even though there was minimal adverse effect on the functional center of PS Ⅱ (P < 0.05). It can be inferred that Ph. rivalis can tolerate a short term flooding which facilitate its possible application in plantation restoration of riparion zone.

Towards improving the agronomic performance, chlorophyll fluorescence parameters and pigments in fenugreek using zeolite and vermicompost under deficit water stress

A comprehensive study has not been carried out so far to determine the outcome and impact of chlorophyll (Chl) fluorescence parameters and photosynthetic pigments in relation to qualitative and quantitative properties in fenugreek, especially in regions with limited water availability. Fenugreek (Trigonella foenum-graecum) is one of the most important medicinal plants in the world. To determine the effects of water deficit stress, nitrogen fertilization and zeolite on Chl fluorescence, pigments, trigonelline concentration and seed yield of fenugreek, a split factorial experiment was laid out in a randomized complete block design with three replications in a semi-arid region of Iran in 2014 and 2015. Five irrigation regimes (unstress control, irrigation at 60% available soil water (ASW); mild stress, irrigation at 40% ASW during the vegetative and reproductive stages; severe stress, irrigation at 20% ASW during the vegetative and reproductive stages) were randomized to the main plots. Subplots consisted of a factorial combination of three nitrogen treatments (untreated plots, vermicompost @ 2.7tha−1 and urea @ 11kgha−1) and two zeolite treatments (@ 0 and 9tha−1). The results demonstrated that water deficit stress decreased maximum Chl fluorescence (Fm), variable Chl fluorescence (Fv), the photochemical efficiency of PSII (Fv/Fm), Chl (a, b and a+b), leaf area index (LAI), biological yield and seed yield but minimum fluorescence (F0), carotenoids, Anthocyanin and trigonelline concentration increased under water deficit stress. There were negative and significant correlations between Fo and LAI, biological and seed yield and on the other side, positive and significant correlations between total Chl. and the above mentioned traits. Water deficit stress led to the photo inhibition of photosynthesis. In most treatments, both vermicompost and zeolite application increased LAI, biological yield, seed yield and trigonelline concentration in fenugreek. Greater concentration of trigonelline in fenugreek under mild water deficit stress conditions may not necessarily supply give economic benefits, as higher concentration is often compensated by lower seed yield.

The comparison of light responses among four species of Calligonum L. in early autumn

The photosynthetic characteristics of 4 species from different Calligonum sections were examined in autumn. Light response curves were measured in the field and fitted by the nonrectangular hyperbola model and modified rectangular hyperbola model. Modified rectangular hyperbola model was found greater when the fitting effects of two models were analyzed by relative errors. The comparison of the photosynthesis among four species revealed that C. pumilum had the maximum net photosynthetic rate (Pmax) with high utilization of light. The lowest light saturation point (LSP) and apparent quantum yield (AQY) were observed in C. Calliphysa which seemed to be the low utilization of light. C. densum had the highest photo inhibition coefficient and smallest photo saturation coefficient; in contrast, C. leucocladum had the smallest photo inhibition coefficient and highest photo saturation coefficient. Present study revealed that there were differences of photosynthetic characteristics between four species in the genus Calligonum. Further studies are needed to elucidate this conclusion with more species and data collected in other season.

Catalytic reduction of 4-nitrophenol and photo inhibition of Pseudomonas aeruginosa using gold nanoparticles as photocatalyst

A simple, green method is described for the synthesis of Gold (Au) nanoparticles (NPs) using Cotoneaster horizontalis extract as a phyto-reducer and capping agent with superior photo inhibition activity against Pseudomonas aeruginosa. Different from the other methods used elevated temperatures for nanoparticles synthesis, the novelty of our method lies in its energy saving process and fast synthesis rates (~5min for AuNPs), and its potential to tune the nanoparticles size and afterward their catalytic activity. The starch, fatty acid and reducing sugars present in the extract are mostly responsible for repaid reduction rate Au+3 ions to AuNPs. Strong Plasmon resonance (SPR) of AuNPs was observed at 560nm, which indicates the formation of gold nanoparticles. Uv-visible spectroscopy, high resolution transmission electron microscope (HRTEM) and energy dispersion X-ray diffraction (XRD) were preformed to find out the formation of AuNPs. Proficient reduction of 4-nitrophenol (4-NP) into 4-aminophenol (4-AP) in the presence of AuNPs and NaBH4 was observed and was found to depend upon the nanoparticle size or the extract concentration. The AuNPs was also evaluated for antibacterial against P. aeruginosa. Before transferred it into antibacterial activity, it placed under visible light for 120min. The same experiment was performed in dark as control medium. The photo irradiated AuNPs was observed to be more effective against P. aeruginosa. The result showed that diameter of zone of inhibition of visible light irradiated AuNPs against P. aeruginosa was 17 (±0.5) and in dark was 8 (±0.4) mm.

Growth, phenology and chlorophyll fluorescence of Habanero pepper (Capsicum chinense Jacq.) under water stress conditions.

The irrigation methods offer a good alternative for increasing water use efficiency. The main purpose of this study was to identify the best irrigation level for Habanero pepper (Capsicum chinense Jacq.) plants based on available water capacity (AWC) of substrate. An experiment carried out with three irrigation levels (20, 40 and 60% of AWC) and five genotypes (H225, H241, H244, H226 and Jaguar). The irrigation level of 20% decreased the soil water potential to cause water stress in plants. At an irrigation level of 40%, average jaguar plant height (92 cm) and H241 (79 cm), genotypes were greater than under the other treatments. Average leaf area of H225, H241 and H244 plants was at least 48% greater than Jaguar plants. Average total dry matter of H241 and Jaguar plants, were 30 and 28% greater than H226 plants; and values of maximum photochemical quantum yield (Fv/Fm), relative electron transport rate and effective photochemical quantum yield of photosystem II were higher in H241, H244 and H226 plants; i.e. they are less probably due to photo inhibition damage. However, flowering time was earlier in plants with an irrigation level (IL) of 20% than plants with an IL of 40%, this was a consequence of stress due to water deficit. The 60% irrigation treatment caused flooding and all genotypes died before the inflorescence stage. These results suggest the enforcement of a suitable irrigation level based in available water capacity of substrate coupled with a vigorous genotype can encourage healthy plants and high water use efficiency.

Lumostatic operation controlled by the optimum light intensity per dry weight for the effective production of Chlorella zofingiensis in the high cell density continuous culture

To maximize the production rate of Chlorella zofingiensis, a lumostatic continuous culture was operated under light intensities of 250–1510μEm−2s−1. The cell density and volumetric biomass production rate were increased without photo inhibition and reached 13.5g-dry weight (dw)L−1 on day 21.5 and 2.41g-dwL−1day−1 on day 10.5, respectively. These maximum values were higher than any previous photoautotrophic culture study with C. zofingiensis. The specific growth rate was maintained at a high level>0.5day−1 until the light intensity per dry weight decreased below 28μEg-dw−1s−1, which coincided with the value estimated in our previous study, verifying the reliability of this estimated value. There was a strong relationship between the photosynthetic efficiency and light intensity per dry weight for C. zofingiensis. This relationship may be useful for evaluating species-specific productivity to select productive species.