Increase In Light Intensity Research Articles

Molecular Dynamics Simulations of Photo-Induced Free Radical Polymerization.

Curing kinetic models provide insight into how design parameters affect the kinetics of photopolymerization. However, they do not provide insight into how networks form or how they influence the process. This article describes a molecular dynamics simulation framework for simulating photoinitiated, chain growth, free radical polymerization. The framework was applied to simulate the photo-induced polymerization of bisphenol A (EO)10 diacrylate under varying conditions of curing light intensity and photoinitiator concentration. Results from the simulations agree very well with curing kinetic curves and gelation points derived from experiments. The simulations also reveal that: (1) gelation is highly correlated with the formation of giant molecules, (2) differences in the number of free radicals generated at the beginning of polymerization significantly affect polymer network formation at low to intermediate conversion, and thus affect the gelation point, and (3) increasing light intensity or photoinitiator concentration tends to delay the gelation point, but does not affect the ultimate polymer network structure near the latter stages of photopolymerization.

Microbial community composition in the rhizosphere of Larix decidua under different light regimes with additional focus on methane cycling microorganisms

Microbial community and diversity in the rhizosphere is strongly influenced by biotic and/or abiotic factors, like root exudates, nutrient availability, edaphon and climate. Here we report on the microbial diversity within the rhizosphere of Larix decidua, a dominant tree species in the Alps, as compared with the microbiome within the surrounding soil. We describe how increased light intensity influenced the rhizobiome and put emphasize on methane cycling microorganisms. Microbial taxa were classified into 26 bacterial, 4 archaeal and 6 fungal phyla revealing significant differences between bulk and rhizosphere soils. The dominant prokaryotic phyla were Proteobacteria, Acidobacteria, Actinobacteria (both, rhizosphere and bulk soil) and Bacteroidetes (rhizosphere soil only) and dominant fungal phyla in both fractions included Ascomycota and Basidiomycota. The rhizosphere community was indicated by Suillus sp., plant growth-promoting bacteria and Candidatus Saccharibacteria. Predicted genes in membrane transport and carbohydrate metabolism were significantly more abundant in rhizosphere soils while genes connected with energy metabolisms and cell motility increased in bulk soils. Dominant methanotrophic microorganisms were Upland Soil Cluster (USC) α methanotrophs, Methylogaea spp. and Methylosinus spp., while most methanogens belonged to Methanomassiliicoccales. The overall abundance of methanotrophs distinctly increased in the rhizosphere but to a very different species-specific extent. The increased light intensity only led to minor changes in the rhizobiome, nevertheless a couple of indicator species (e.g. Pseudomonas sp.) for intensified light conditions were established.

Limits of UV-light acceleration on the photooxidation of low-density polyethylene

Lifetime prediction of polymers requires accelerated ageing based on an increase in UV light intensity and temperature. However, the representativeness of artificial ageing is still an issue. The relevance of highly accelerated UV-induced weathering raises the question of reciprocity failure depending on the polymer. The influences of irradiance and temperature on the photooxidation kinetics of polyethylene were studied to determine the extent to which increasing light intensity leads to accelerated photooxidation of polyethylene. Polyethylene films were subjected to accelerated photooxidative experiments at various UV light intensities and different temperatures, and the amounts of carbonylated photoproducts were monitored by IR spectroscopy. The results show reciprocity failure for polyethylene photooxidation and the limits of acceleration by UV light.

Investigation on UV Photoresponsivity of main electrical properties of Au/CuO-PVA/n-Si MPS type Schottky Barrier Diodes (SBDs)

In this study, (CuO doped PVA) composite material was deposited using spin coating technique on n-Si and the Au/CuO-PVA/n-Si Metal/Polymer/Semiconductor type Schottky Barrier Diodes (MPS type SBDs) were fabricated. The electrical measurements of Au/CuO-PVA/n-Si SBDs were realized in the dark and under various UV (365 nm) light intensities ranging from 50 to 250 mW/cm2. The basic parameters of the MPS type SBDs such as leakage current (I0), zero bias barrier height (ΦB0), barrier height (ΦB), ideality factor (n), series resistance (Rs), shunt resistance (Rsh), rectification rate (RR), photocurrent (Ipc) and surface states (Nss) were obtained Current-Voltage (I–V) plot based on Thermionic Emission (TE) theory, and Norde function depending on the UV light intensity. As the light intensity increases, RR, Rsh, ΦB0, and ΦB decreased but the n and I0 increased. In addition, the increase of UV light intensity caused the increase of photocurrent in MPS type SBDs and thus MPS type SBDs exhibited more ohmic behavior.

The Light Dependence of Mesophyll Conductance and Relative Limitations on Photosynthesis in Evergreen Sclerophyllous Rhododendron Species.

Mesophyll conductance (gm) limits CO2 diffusion from sub-stomatal internal cavities to the sites of RuBP carboxylation. However, the response of gm to light intensity remains controversial. Furthermore, little is known about the light response of relative mesophyll conductance limitation (lm) and its effect on photosynthesis. In this study, we measured chlorophyll fluorescence and gas exchange in nine evergreen sclerophyllous Rhododendron species. gm was maintained stable across light intensities from 300 to 1500 μmol photons m−2 s−1 in all these species, indicating that gm did not respond to the change in illumination in them. With an increase in light intensity, lm gradually increased, making gm the major limiting factor for area-based photosynthesis (AN) under saturating light. A strong negative relationship between lm and AN was found at 300 μmol photons m−2 s−1 but disappeared at 1500 μmol photons m−2 s−1, suggesting an important role for lm in determining AN at sub-saturating light. Furthermore, the light-dependent increase in lm led to a decrease in chloroplast CO2 concentration (Cc), inducing the gradual increase of photorespiration. A higher lm under saturating light made AN more limited by RuBP carboxylation. These results indicate that the light response of lm plays significant roles in determining Cc, photorespiration, and the rate-limiting step of AN.

Identification and Characterization of DlGI Promoter Involved in Photoperiod, Light Intensity, Hormone, and DlELF4 Response from Longan

In fruit trees, flowering is a key event followed by fruit development and seed production. Gigentea (GI), a clock-associated gene, is known to contribute to photoperiodic flowering and circadian clock control in Arabidopsis thaliana. However, its functions in woody fruit trees remain unclear. In this study, a 2000 bp promoter fragment of the longan (Dimocarpous longan) DlGI gene was isolated from the genomic DNA of longan ‘Honghezi’ by polymerase chain reaction amplification. The DlGI promoter contained two main types of potential cis-acting elements: light-responsive and hormone-responsive elements. The promoter was fused with the β-glucuronidase (GUS) reporter gene of pBI121 to generate the pDlGI:GUS construct. GUS histochemical staining of transgenic A. thaliana revealed that DlGI might play a role in different developmental phases of longan. Exposure of transgenic A. thaliana to varying light intensities showed that the GUS activity increases with increased light intensity. Transient expression of pDlGI::GUS in Nicotiana benthamiana showed that the GUS activity was higher and reached peak a few hours earlier under short-day (SD) than long-day conditions. Exposure to different hormonal treatments revealed that the transcript level of GUS was activated by gibberellin (GA3) and indoleacetic acid (IAA) but suppressed by abscisic acid and methyl jasmonate treatment. In addition, N. benthamiana transient assay and dual-luciferase assay revealed that the presence of early flowering 4 (ELF4) homologs of longan (DlELF4-1 and DlELF4-2) significantly activated the DlGI promoter. The positive response of DlGI promoter to high light-intensity, SD photoperiod, GA3 and IAA signals, and DlELF4 transcription factor suggest that DlGI may function as a circadian clock and play a role in responding to SD conditions and other signals in flower initiation of longan.

P.803Motor speed and subjective alertness in healthy female participants following one week of escitalopram

In this study, (CuO doped PVA) composite material was deposited using spin coating technique on n-Si and the Au/CuO-PVA/n-Si Metal/Polymer/Semiconductor type Schottky Barrier Diodes (MPS type SBDs) were fabricated. The electrical measurements of Au/CuO-PVA/n-Si SBDs were realized in the dark and under various UV (365 nm) light intensities ranging from 50 to 250 mW/cm2. The basic parameters of the MPS type SBDs such as leakage current (I0), zero bias barrier height (ΦB0), barrier height (ΦB), ideality factor (n), series resistance (Rs), shunt resistance (Rsh), rectification rate (RR), photocurrent (Ipc) and surface states (Nss) were obtained Current-Voltage (I–V) plot based on Thermionic Emission (TE) theory, and Norde function depending on the UV light intensity. As the light intensity increases, RR, Rsh, ΦB0, and ΦB decreased but the n and I0 increased. In addition, the increase of UV light intensity caused the increase of photocurrent in MPS type SBDs and thus MPS type SBDs exhibited more ohmic behavior.

Application of batch system ultraviolet light on the surface of kashar cheese, a kind of pasta-filata cheese: effects on mould inactivation, lipid oxidation, colour, hardness and sensory properties.

This research paper addresses the hypothesis that the application of ultraviolet (UV) light before packaging of pasta-filata cheese has the potential to eliminate or control post-processing contamination whilst maintaining chemical and sensorial quality. The surfaces of kashar cheese were treated at different doses of UV light (0.32-9.63 kJ/m2) in a batch UV cabinet system to determine effects on physicochemical and sensorial quality as well as mould inactivation. Untreated cheese samples were also used for comparison. Kashar cheese was naturally contaminated in a mouldy environment to provide the desired mould numbers before UV treatments. Log reductions of 0.34, 0.69 and 2.49 were achieved in samples treated at doses of 0.32, 0.96 and 1.93 kJ/m2, respectively and the mould count of sample treated at 9.63 kJ/m2 was below the detection limit. We found no significant differences in composition and hardness values between any of the treated or control cheeses. Although some individual colour values increased as the UV doses increased, this change was not observed visually in sensory analysis. Increased light intensity accelerated the lipid oxidation causing a perception of off-flavour. The results of this study show that it is necessary to examine the relationship between the oxidative and sensory interactions while determining the effective doses applied to cheese surface for microbial inactivation.

Impact of Physical Attributes on Proficient Phytosynthesis of Silver Nanoparticles Using Extract of Fresh Mulberry Leaves: Characterization, Stability and Bioactivity Assessment

Application of green chemistry towards phytosynthesis of nanoparticles has gained attention of environment friendly world due to its simple, rapid, stable, eco-friendly and cost-effective property. But there are limitations to this growing interest, as the dimension and geometry of nanoparticles produced through phytosynthesis often varies greatly. To overcome the problem, current study deals with the assessment of reducing effect of the plant extract at different light intensity, pH and temperatures. Current study reports that the optimal condition for phytosynthesis of silver nanoparticles was neutral pH (pH 7), 25 °C and diffuse light (230 lx). It was observed that rapid synthesis of silver nanoparticles takes place with increase in light intensity, alkalinity and temperature, as revealed by quick appearance of dark brown colouration on addition of extract. But rapid synthesis leads to the formation of large size particles with increase in polydispersity as revealed from TEM analysis and were found to be instable through zeta potential analysis. It was observed that at acidic pH nanosilver formation does not takes place, while at low temperature it takes more time for nanosilver formation, but both conditions were found to be unstable. Nanosilver formed at neutral pH and 25 °C under diffuse light gives the size dimension of 18.11 ± 2.55 and 18.94 ± 5.30 nm with zeta potential of + 36.4 and + 37.4 mV respectively indicating stability, besides that they were found to be stable under long storage condition as revealed by UV–Visible spectrophotometric analysis. Silver nanoparticles formed under optimized condition of pH 7 and at 25 °C were found to be bioactive as it showed potentiality to extend the shelf life of post harvest mulberry leaves by 7 days.

Methylation Pattern and Expression Dynamics of Methylase and Photosystem Genes Under varying light Intensities in Fugacium kawagutii (Symbiodiniaceae).

Previous studies have documented extensive methylation of CpG islands and abundant methyltransferase gene (DNMT) in Fugacium kawagutii (formerly Symbiodinium kawagutii) genome. However, whether DNA methylation plays a role in regulating gene expression in this and other dinoflagellates remains unclear. Here, we characterized gene body methylation levels using methylation-specific PCR (MS-PCR) and bisulfite sequencing PCR (BSP) and measured transcriptional levels for three photosystem genes in F. kawagutii under different light conditions (20, 100, and 600µE·m-2 ·s-1 ). To explore the association of methylation with DNA methylase, the expression of DNA methyltransferase (Symbio-DIRS-Dnmt3) was also measured. Our results showed that peridinin-chlorophyll a-binding protein (PCP), light-harvesting complex (LHC), and chlorophyll a-c-binding protein complex (acpPC) gene expression was all significantly up-regulated under low light in which their methylation level was down-regulated, constant, and elevated, respectively. Symbio-DIRS-Dnmt3 exhibited elevated transcriptional level under increased light intensity. The results led us to hypothesize that DNA methylation level can be modulated by environmental conditions such as irradiance, probably through the regulation of Symbio-DIRS-Dnmt3 transcription level, and in turn may regulate the expression of genes in F. kawagutii. Further study is needed to determine whether the same gene methylation and expression characteristics reported here occur in other dinoflagellates and to explore their ecological implications.

Synechococcus elongatus BDU 130192, an Attractive Cyanobacterium for Feedstock Applications: Response to Culture Conditions

Marine cyanobacteria are attractive organisms as feedstock for bioethanol and biotechnological applications. Previously, a marine cyanobacterial strain Synechococcus elongatus BDU 130192 was identified which can accumulate high polyglucan levels without the need to resort to N-deprivation. In this study, among the three different temperatures (30, 34, and 38 °C) tested, the highest biomass accumulation and total carbohydrate occur at 34 °C. The biomass and total carbohydrate increased with increasing light intensities, while protein, chlorophyll, and carotenoid contents were reduced. The best growth occurred at 1.8% NaCl concentration, even though the strain could grow well until 5.8% NaCl. Among the different concentrations of CO2 tested, the best growth occurred at 5% CO2 in the air. NaNO3 gave the best growth, though the cells were able to grow well on urea and NH4Cl too. Tripling the concentration of either N or P in the medium led to a significant increase in growth rate. The strain does not require the addition of vitamin B12 for growth, and about 90% flocculation could be achieved in an hour with the addition of chitosan. High productivities of 0.5 g/L/day of biomass and 0.23 g/L/day of carbohydrates could be reached in a 3-L photobioreactor (PBR) bubbled with air. This work shows many unique properties of this strain such as high carbohydrate productivity, ability to tolerate high light intensities and high concentrations of salt and CO2, and efficient flocculation. These properties make Synechococcus elongatus BDU 130192 an attractive candidate as a feedstock for bioethanol and biotechnological applications.

Analysis of β-d-glucan biosynthetic genes in oat reveals glucan synthesis regulation by light.

Oat (Avena sativa) has human health benefits when consumed as a whole-grain food, attributed to the high content of (1,3;1,4)-β-d-glucan (mixed-linkage glucan [MLG]), but little is known about the synthase genes and synthesis mechanism of MLG polysaccharides in this species. The concentration of oat MLGs under different light intensities was measured by a standard enzymatic approach and further verified by immunoelectron microscopy. The effect of light intensity on MLG synthase genes was examined by RT-qPCR and western blot analyses. The pattern of expression directed by the promoter of the oat MLG synthase gene was also investigated by histochemical β-glucuronidase (GUS) analysis. The oat orthologues of genes implicated in the synthesis of MLG in other cereals, including cellulose synthase-like (Csl) F, H and J gene families, were defined. Transcript profiling of these genes across oat tissues indicated that AsCslF6 transcripts dominated. Under high light intensities, the expression of AsCslF6, a major isoform of the MLG synthase genes, increased to >30 % of the dark growth control. The amount of MLG in oat rose from 0.07 to 1.06 % with increased light intensity. Histochemical tests showed that the AsCslF6 gene promoter preferentially directs GUS expression under high light intensity conditions. Oat MLG synthesis is regulated by light. High light intensity upregulates the expression of the MLG synthase AsCslF6 gene, leading to an increase in the amount of MLG in oat leaves.

Transversally travelling ultrasound for light guiding deep into scattering media

The application of optical methods for tissue diagnosis, activation, and treatment suffers dramatically from the low accessible depths due to strong light scattering in tissues. Here we demonstrate a method to address this issue by utilizing transient ultrasound waves, travelling transversally to the light propagation direction, to guide light into deeper tissue regions. We study the formation of the ultrasound-induced refractive index structures and waveguides using simple ultrasound field configurations and analyze their effects on the propagation of short light pulses. As a proof of concept, we demonstrate using 5 ns pulses of 532 nm light and Intralipid-20%-based phantoms with mu _{mathrm{s}}^prime up to 4.5 cm−1 a waveguide supported light intensity increase up to the depths of at least 90 mean free paths.

Growth of cucumber seedlings in different varieties as affected by light environment

High-quality cucumber seedlings are a prerequisite for ensuring high yield of cucumbers. With the continuous increase of cucumber planting area in China, the demand for high-quality cucumber seedlings is also increasing. One of the important ways to improve the quality of cucumber seedlings is to improve the light environment by using artificial light source. In this study, three cucumber seedlings (cv. Jintong, cv. Yunv and cv. Xiazhiguang) were grown for 23 d under eight levels of daily light integral (DLI) at 4.3 mol/(m2·d), 8.6 mol/(m2·d), 10.1 mol/(m2·d), 13.0 mol/(m2·d), 5.8 mol/(m2·d), 11.5 mol/(m2·d), 14.4 mol/(m2·d) and 17.3 mol/(m2·d), respectively. The results showed that when DLI was 14.4 mol/(m2·d), the seedling height, stem diameter, total leaf area and shoot dry/fresh weight of all three cucumber cultivars reached the maximum, while hypocotyl length decreased with the increase of light intensity. When DLI was 14.4 mol/(m2·d), Jintong and Xiazhiguang had the highest health index, which were 49.29 and 28.56, respectively, while that of Yunv was 81.59 (DLI = 14.4 mol/(m2·d)). With the increase of DLI, the photosynthetic capacity of cucumber increases gradually. The highest net photosynthetic rate was shown at DLI of 14.4 mol/(m2·d), while the chlorophyll content of cucumber seedlings of all three cultivars were less affected by DLI. Jintong and Yunv had the highest chlorophyll content when DLI was 8.6 mol/(m2·d) because they were adapted to low-light environment. In conclusion, the DLI of 14.4 mol/(m2·d) for Jintong and Xiazhiguang, while that of 17.3 mol/(m2·d) for Yunv are suggested for the light environment design of factory-cultivated seedling for cucumber. Keywords: cucumber seedling, daily light integral (DLI), growth, photosynthesis DOI: 10.25165/j.ijabe.20201305.5566 Citation: Ji F, Wei S Q, Liu N, Xu L J, Yang P. Growth of cucumber seedlings in different varieties as affected by light environment. Int J Agric & Biol Eng, 2020; 13(5): 73–78.

Detection of City Integration Processes in Rapidly Urbanizing Areas Based on Remote Sensing Imagery

Since China’s reform and development commenced, in the context of rapid urbanization and coordinated regional development, Chinese cities with a close geographic proximity and social ties have gradually formed an integrated city development model. As a new phenomenon in China’s urbanization process, existing research on China’s integrated cities mainly focuses on typical case studies, and most research has been limited to literature reviews and theoretical analyses. The growing application of remote sensing technology in urbanization research in recent years has provided new opportunities for the analysis of city integration. Therefore, based on multi-spectral Landsat-8 and nighttime light images (SNPP/VIIRS, Suomi National Polar-orbiting Platform/Visible Infrared Imaging Radiometer Suite), this paper selects four of the most representative integrated cities with different backgrounds in China to analyze the land-use conversion, plot light fluctuation, and light gravity center shift in the boundary zone between cities. The results show that (1) Guangfo has the highest level of integration and urban expansion is mainly concentrated in the south-central part of the boundary area; (2) Guanshen’s level of integration is second to Guangfo’s and is mainly concentrated in the west; (3) HuSu’s integration is still in the initial stage and its increase in light intensity lags behind the expansion of building land during the study period; (4) although the light intensity and building land area increased significantly during the study period in Xixian, the overall development level of Xixian still lagged behind coastal cities due to the restriction of its geographical location. Our application results expand the data sources for integrated city research and the obtained results can potentially support decision-making and planning in the process of urban development.

Astaxanthin accumulation in the green microalga Haematococcus pluvialis: Effect of initial phosphate concentration and stepwise/continuous light stress

Nutrient composition and light stress significantly affect the productivity of astaxanthin in Haemotococcus pluvialis. Hence, the present study aimed to investigate the effect of initial phosphate concentration and two distinct light regimes on astaxanthin accumulation in H. pluvialis.In the green stage, microalgae were cultivated in different initial phosphate concentrations under 2000 lx and a 12:12 h photoperiod. To initiate astaxanthin accumulation, an increased light intensity of 5000 lx was provided using two methods; (i) stepwise light stress, where a 12:12 h photoperiod was provided for 14 days, followed by 14 days of continuous illumination, and (ii) continuous illumination for 28 days.Phosphate limitation and continuous light stress were favourable to enhance cellular astaxanthin accumulation, which reached 7% by weight. The highest astaxanthin concentration of 27.0 ± 1.9 mg/L and lowest specific light energy consumption of 32.9 ± 2.3 kW h/g astaxanthin were reported in cultures grown in 41 mg/L phosphate under continuous light stress.

The Effect of Light Intensity on the Expression of Leucoanthocyanidin Reductase in Grapevine Calluses and Analysis of Its Promoter Activity.

To investigate the effect of light intensity on flavonoid biosynthesis, grapevine calluses were subjected to high light (HL, 250 μmol m−2 s−1) and dark (0 μmol m−2 s−1) in comparison to 125 μmol m−2 s−1 under controlled conditions (NL). The alteration of flavonoid profiles was determined and was integrated with RNA sequencing (RNA-seq)-based transcriptional changes of the flavonoid pathway genes. Results revealed that dark conditions inhibited flavonoid biosynthesis. Increasing light intensity affected flavonoids differently—the concentrations of flavonols and anthocyanins as well as the expressions of corresponding genes were less affected, whereas flavan-3-ol concentrations were predominantly increased, which caused enhanced trans-flavan-3-ol concentrations. Moreover, genes encoding leucoanthocyanidin reductase (LAR) exhibited different response patterns to light intensity changes—VviLAR1 expression increased with an increased light intensity, whereas VviLAR2 expression was insensitive. We further confirmed that the known transcription factors (TFs) involved in regulating flavan-3-ol biosynthesis utilized VviLAR1 as a target gene in grapevine calluses. In addition, VviLAR1 promoter activity was more sensitive to light intensity changes than that of VviLAR2 as determined using a transgenic Arabidopsis leaf system. These results suggested that light intensity had the most prominent effect on trans-flavan-3-ols in grapevine calluses and demonstrated that the two LAR genes had different response patterns to light intensity changes.

Carbon and nitrogen isotopic records of effects of urbanization and hydrology on particulate and sedimentary organic matter in the highly urbanized Pearl River Delta, China

The deltaic and coastal region is an important area for transportation, production and transformation of organic matter (OM). However, the high degree of urbanization and seasonal variability of runoff in this region significantly impact source apportionments and biogeochemical processes of the OM. In this study, stable isotopes of carbon (C) and nitrogen (N) in both suspended particulate matter (SPM) and sedimentary organic matter (SOM) were measured in the highly urbanized Pearl River Delta (PRD), China. The results revealed that source apportionments exhibited spatial variations due to different degrees of urbanization and seasonal variations due to seasonal changes in runoff. High urbanization could increase the contribution of sewage-derived OM in the SPM and decrease the proportion of soil OM in the SOM. Increased precipitation and runoff during wet season could result in a greater contribution of sewage-derived OM (55%), and decreased runoff during the dry season resulted in an increased proportion of phytoplankton (51%) in the SPM. Urbanization and runoff also affected C and N transformation processes of OM. An increased volume of sewage discharge due to urbanization provided nutrients for phytoplankton growth, promoting photosynthesis and assimilation processes. Increased light intensity due to decreased precipitation and runoff during the dry season could facilitate photosynthesis by phytoplankton. This study suggested that OM could record the impacts of urbanization and hydrology on C and N transformation processes in the rivers, further improving knowledge on the C and N cycling processes in highly urbanized river ecosystems.

Upregulation of mitochondrial alternative oxidase pathway protects photosynthetic apparatus against photodamage under chilling stress in Rumex K-1 leaves

This study aimed to clarify the role of mitochondrial alternative oxidase (AOX) pathway upregulation in photoprotection under chilling stress in Rumex K-1 leaves. Malate-oxaloacetate shuttleꞌs activity and AOX pathwayꞌs capacity were synchronously enhanced with light intensity increase both in control and chilling-treated leaves. Besides, the AOX pathway was upregulated more significantly when irradiated by light in chilling-treated leaves than that of control. These results suggested that excess reducing equivalents generated by photosynthesis were exported from chloroplasts and oxidized by the AOX pathway at a potentially higher rate in chilling-treated leaves than in control, which avoided the overaccumulation of excess reducing equivalents under light conditions. Also, inhibition of the AOX pathway led to more severe accumulation of hydrogen peroxide in chilling-treated leaves than that in control. Therefore, the mitochondrial AOX pathway was specifically upregulated and employed for sinking excess reducing equivalents produced by photosynthesis, which protected photosynthetic apparatus from photodamage under chilling stress in Rumex K-1 leaves.

Effect of light intensity and wavelengths on ascorbic acid content and the antioxidant system in tomato fruit grown in vitro

The ascorbic acid (ASA) content of tomatoes is regulated by culture practices and environmental conditions such as light. However, in tomatoes, little is known about the direct effect of lighting conditions on ASA content in the absence of natural environmental fluctuations. The aim of this study was to determine the direct light regulation of ASA and dehydroascorbic acid (DHA) contents and the antioxidant system in tomato fruits grown in vitro using two different cultivars (high- and low-ASA cultivars), different light intensities [darkness, low light (∼249 μmol m−2 s−1), and high light (∼961 μmol m−2 s−1)], and different light spectra light emitting diodes (LEDs) under the same light intensity (226–249 μmol m−2 s−1): control (eight-peak LED), red LED light (peaks at 625 and 660 nm), and blue LED light (peaks at 420 and 450 nm). Results indicate that the effect of light on ASA and DHA content may be universal regardless of whether the cultivar is designated as a high- or low-ASA cultivar. ASA content was enhanced by an increase in light intensity and by blue (but not red) LED light. Our results also indicate that stimulation of the antioxidant system (ascorbate peroxidase and dehydroascorbate reductase activity) enhances ASA content under high light intensity, and underlying differences in mechanisms in response to blue and red LED light were observed. Therefore, we conclude that the direct light regulation of ASA content and the antioxidant system occurs in tomato fruits grown in vitro. In addition, our findings provide useful information for improving agricultural techniques to develop high-ASA tomatoes by controlling lighting conditions and by applying LED light.