Effects Of High-intensity Light Research Articles

The Adaptive Role of Carotenoids and Anthocyanins in Solanum lycopersicum Pigment Mutants under High Irradiance.

The effects of high-intensity light on the pigment content, photosynthetic rate, and fluorescence parameters of photosystem II in high-pigment tomato mutants (hp 3005) and low-pigment mutants (lp 3617) were investigated. This study also evaluated the dry weight percentage of low molecular weight antioxidant capacity, expression patterns of some photoreceptor-regulated genes, and structural aspects of leaf mesophyll cells. The 3005 mutant displayed increased levels of photosynthetic pigments and anthocyanins, whereas the 3617 mutant demonstrated a heightened content of ultraviolet-absorbing pigments. The photosynthetic rate, photosystem II activity, antioxidant capacity, and carotenoid content were most pronounced in the high-pigment mutant after 72 h exposure to intense light. This mutant also exhibited an increase in leaf thickness and water content when exposed to high-intensity light, suggesting superior physiological adaptability and reduced photoinhibition. Our findings indicate that the enhanced adaptability of the high-pigment mutant might be attributed to increased flavonoid and carotenoid contents, leading to augmented expression of key genes associated with pigment synthesis and light regulation.

Effect of high-intensity light on the photosynthetic activity, pigment content and expression of light-dependent genes of photomorphogenetic Solanum lycopersicum hp mutants

The relationship between photosynthesis, pigment accumulation, and the expression of key light-regulated genes in Solanum lycopersicum hp-1, hp-2 and hp-1.2 photomorphogenetic mutants under conditions of high-intensity light (2000 μm (photons) m−2s−1) was studied.The hp-2 mutant (LA3006) and the hp-1 mutants (LA4012 and LA3538) are deficient in DET1 (De-etiolated 1 and DDB1 (DNA DAMAGE-BINDING PROTEIN 1), respectively, which are components of the CDD complex (COP10, DDB1, DET1). HP mutants are superproducers of various pigments and are sensitive to light. We have shown that HIL (high-intensity light) causes a decrease in PSII activity after 24 and 72 h of irradiation, which was partially restored after 72 h in the WT. The photosynthetic rate noticeably decreased only in LA4012 and LA3538 after 24 h of irradiation. After 72 h, the photosynthetic rate decreased in all mutants, with the exception of hp-1.2 LA0279, but the decrease was most noticeable in LA4012, yet significant changes in the respiration rate were absent. The LA0279 mutant was more capable of accumulating anthocyanin in the cells of the subepidermal parenchyma and chlorenchyma, as well as in the cells at the base of large multicellular glandular trichomes and in the mesophyll. Another important difference was the accumulation of increased amounts of antheraxanthin and phenolic compounds in the leaves of LA0279 after 72 h of HIL irradiation. Unlike LA4012, LA3006, LA0279, and LA3538 sowed a significantincrease in the expression levels of CHS, HY5, and FLS genes after 24 h, which may be one of the reasons for the higher adaptive potential of those three mutants. In addition to that in LA3538, strong light-induced stress led to an increased level of flavonol synthase (FLS) expression in the LA3006, LA0279, and LA4012 mutants.We hypothesize that the photosynthetic apparatus (PA) of the LA0279 mutant, which is deficient in the DET1 and DDB1 genes, is most adapted to prolonged HIL. Most likely, the resistance of PA mutants to HIL is due to a variety of factors, which, in addition to the redistribution of carotenoids, may include morphological features associated with the accumulation of anthocyanin in the epidermis, subepidermal layer, mesophyll and trichomes of leaves and with an increase in leaf thickness.

Effect of high-intensity light and UV-B on photosynthetic activity and the expression of certain light-responsive genes in A. thaliana phyA and phyB mutants

The effects of high-intensity light (HIL, 4 and 24 h) and UV-B (1 h) on the net photosynthesis rate, activity of photosystem II (PSII), content of photosynthetic pigments, anthocyanin and UV-absorbing pigments as well as the expression of certain light-responsive genes (HY5,CAB1) chalcone synthase (CHS) and main antioxidants enzyme genes (APX1, GPX and GR) in the leaves of phyB and phyA mutant A. thaliana plants were studied. Both UV-B and 4 and 24 h HIL decreased the PSII maximum quantum yield (Fv/Fm), PSII performance index (PIABS), photosynthesis and respiration rates in plants. Moreover, all stress treatments increased the dissipation of the absorbed energy (DI0/RC) as well as the flux of absorbed energy per RC (ABS/RC). The maximal changes in photosynthesis and chlorophyll fluorescence parameters were observed in the phyB mutant. The WT and the phyA mutant showed similar responses. In addition, the phyB mutant exhibited decreases in the expression of genes encoding enzyme CHS, the transcription factor HY5 and the antioxidant enzymes APX1 and GPX. One of the possible mechanisms protecting the photosynthetic apparatus from light excess or UV radiation is the elevated content of various pigments that can act as antioxidants or optical filters. We assume that the greater decrease in photosynthetic activity in the phyB mutant under HIL and UV-B conditions was due to the decreased content of carotenoids and UV-absorbing pigments in this mutant.

Deficiencies in phytochromes A and B and cryptochrome 1 affect the resistance of the photosynthetic apparatus to high-intensity light in Solanum lycopersicum

The effects of high-intensity light (HIL) on the activity of photosystem II (PSII) and photosynthesis in wild-type (WT) and single (phyB2, phyB1, phyA and cry1), double (phyB1B2, phyAB2 and phyAB1) and triple (phyAB1B2 and cry1phyAB1) mutants of Solanum lycopersicum were studied. In addition, changes in the activity of the antioxidant enzymes ascorbate peroxidase, glutathione reductase and guaiacol peroxidase as well as the photosynthetic pigment and anthocyanin contents in the leaves of phyB2 and cry1phAB1 mutants under HIL were examined. When plants were irradiated with HIL (2 h), the PSII resistance of the cry1phyAB1 mutant was the lowest, while the resistance of WT and single mutants excluding cry1 was the highest. The effect of HIL on PSII activity in all double mutants and the phyAB1B2 mutant was intermediate between the effects on the WT and the cry1phyAB1 mutant. The intensity of oxidative processes in the cry1phyAB1 mutant was higher than that in WT and phyB2, but in cry1phyAB1, the activity of antioxidant enzymes and the anthocyanin content were lower. The low resistance of the cry1phyAB1 mutant to HIL may be due to the low antioxidant activity of key enzymes and the reduced pigment content, which are consistent with the reduced expression of CHS and sAPX genes in the cry1phyAB1 mutant.

Effect of high-intensity light on the retinal pigment epithelium of zebrafish - An induced retinal damage study model

Background: Natural light sources emit light with two physical properties namely, spectrum and intensity. However, the electronic light sources these days were adjusted in their parameters of color and the intensity without the consumer being aware of these. These lights become potential harm to its users both in household and handheld digital devices. Aims and Objectives: In this study, we have tried to estimate the changes in the morphology of the retinal pigment epithelium of zebrafish when exposed to high-intensity light. Materials and Methods: Institutional Animal Ethics Committee clearance was obtained. Two groups of zebrafish with an average bodyweight (690 ± 50 mg) and length (26.75 ± 1.39 mm) were taken for the study. Group I (n = 6) control group: Housing was in a glass tank in the common working area exposed to the sunlight for the light source. Group II (n = 6) study group: Housing was done in a dark room with the custom-built electrical light source with an adjustable setting for a uniform light intensity of 15,000 lux. Experimental study period was for 15 days with maintained 12 hrs light and 12 hrs dark cycle. Fishes were euthanized by exposing them to cold water with ice and the eyeballs removed and stored in 4% formalin. Whole eye histological staining was done with hematoxylin and eosin stain. The histological slides were photographed in a digital microscope and the distribution of neurons in the selected layer of the retinal epithelium was estimated and compared among the groups using a software. Results: The study results are conclusive with zebrafish animal models and further suggest that even under the water when exposed to high intensity of light there is a potential risk of damaging the retinal epithelium. Conclusion: An experimental damage of the retinal epithelium of zebrafish was established to be used for further research.

Effect of high-intensity light on the properties and structure of ceramic Nb2O5

This paper examines the effect of exposure to high-intensity light on the structure, thermal expansion, mechanical properties, and Raman spectrum of ceramic Nb2O5. We demonstrate that such exposure creates fractal micro- and nanostructures in ceramic Nb2O5, has a significant effect on its thermal expansion, increases its elastic moduli and the anisotropy in its mechanical properties, and produces isolated polyhedra in its crystal structure.

Effect of high-intensity light on the micro- and nanostructuring and thermal expansion of Ta2O5 and Nb2O5 ceramics

This paper examines the effect of exposure to high-intensity light on the formation of fractal micro- and nanostructures and the thermal expansion of tantalum pentoxide and niobium pentoxide ceramics. After such processing, the thermal expansion curve of Ta2O5 shows anomalous regions of zero or negative expansion, whereas the thermal expansion of Nb2O5 ceramics decreases in magnitude in the region of negative values, and their thermal expansion curve becomes more symmetrical.

Effects of High-Intensity Curing Lights on Microleakage under Bonded Lingual Retainers

To evaluate the effects of high-intensity light curing units (light-emitting diode [LED] and plasma arc curing [PAC]) on the microleakage of flexible spiral wire retainers (FSWRs) at the composite/enamel and composite/wire interfaces. Forty-five human mandibular incisor teeth were separated into three groups of 15 teeth. Multistranded PentaOne wire of .0215 inch diameter was bonded to enamel and was cured with three different light curing units: a quartz-tungsten-halogen (QTH) unit and two high-intensity units (ie, LED and PAC). A conventional halogen light served as the control. Samples were sealed with nail varnish, stained with 0.5% basic fuchsine, and sectioned. Transverse sections were evaluated under a stereomicroscope and were scored for microleakage for the composite/enamel and composite/wire interfaces. Statistical analysis was performed by Kruskal-Wallis and Mann-Whitney U-tests with Bonferroni correction. Little or no microleakage was detected at the composite/enamel interface of the FSWR cured with three different light sources. However, at the composite/wire interface, statistically significant differences were found between the QTH (mean, 1.10 +/- 1.05 mm) and high-intensity curing units. The PAC resulted in the greatest amount of microleakage (mean, 2.63 +/- 1.49 mm), whereas no statistically significant difference was noted between the PAC and the LED (mean, 2.35 +/- 1.28 mm). High-intensity light curing units show statistically significant microleakage at the composite/wire interface and therefore may not be safe for use in bonding FSWRs.

Photoinhibition Induced Alterations in Energy Transfer Process in Phycobilisomes of PS II in the Cyanobacterium, Spirulina platensis

Exposure of algae or plants to irradiance from above the light saturation point of photosynthesis is known as high light stress. This high light stress induces various responses including photoinhibition of the photosynthetic apparatus. The degree of photoinhibition could be clearly determined by measuring the parameters such as absorption and fluorescence of chromoproteins. In cyanobacteria and red algae, most of the photosystem (PS) II associated light harvesting is performed by a membrane attached complex called the phycobilisome (PBS). The effects of high intensity light (1000-4000 micromol photons m(-2) s(-1)) on excitation energy transfer from PBSs to PS II in a cyanobacterium Spirulina platensis were studied by measuring room temperature PC fluorescence emission spectra. High light (3000 micromol photons m(-2) s(-1)) stress had a significant effect on PC fluorescence emission spectra. On the other hand, light stress induced an increase in the ratio of PC fluorescence intensity of PBS indicating that light stress inhibits excitation energy transfer from PBS to PS II. The high light treatment to 3000 micromol photons m(-2) s(-1) caused disappearance of 31.5 kDa linker polypeptide which is known to link PC discs together. In addition we observed the similar decrease in the other polypeptide contents. Our data concludes that the Spirulina cells upon light treatment causes alterations in the phycobiliproteins (PBPs) and affects the energy transfer process within the PBSs.

Effects of high intensity light on ultraviolet-irradiated and non-irradiated fish pathogenic bacteria

The viability of the fish pathogenic bacterium Aeromonas salmonicida was rapidly reduced when exposed to sunlight at about 10 5 lx in river water. A 99.9% inactivation was observed after 2 h exposure. Artificial light at 28,000 lx induced inactivation at a lowered rate. If pre-exposed to disinfecting doses of ultraviolet C irradiation in the river water, sunlight illumination induced rapid initial photorecovery followed by inactivation as outlined above. After reducing the number of colony-forming units to 0.08% of the initial count in an experimental UV system, a 160-fold recovery within 20 min of sunlight exposure was observed. However, after 2 h of sunlight exposure, the viable count was down again to 0.07% of the initial value. The presence of humic acid accelerated the photoinactivating effect while sodium chloride at 0.9% concentration increased survivability of both light-stressed and dark-incubated bacteria. The marine bacterium Vibrio anguillarum showed a slower response than A. salmonicida, both with respect to sunlight-induced inactivation and photorepair. In non-irradiated cells, the viable count was reduced by 97.5% after 3 h, while 1 h was needed to obtain a maximum of 19-fold photorecovery in sunlight after UV-C irradiation. It is concluded that sunlight induced processes should be taken into consideration when assessing the survival of fish pathogens in surface waters and the UV disinfection efficiency towards inlet and effluent water of aquacultural installations.

Effect of High-intensity Light Given Prior to Low-temperature Treatment on the Long-day Flowering of Pharbitis nil

Effect of High-intensity Light Given Prior to Low-temperature Treatment on the Long-day Flowering of Pharbitis nil

Blindness in Roses: Effects of High Intensity Light and Blind Shoot Prediction Techniques1

Abstract ‘Tropicana’ rose plants (Rosa hybrida L.) were exposed to increasing periods of high intensity light (640 W/m2) beginning immediately after flower removal, in the fall and winter of 1975 and spring and summer of 1976. Flowers were also removed from ‘Forever Yours’ and ‘Cara Mia’ plants in the summer of 1976 and shoot length, stem diameter and bud diameter were evaluated as morphological indicators of blind shoot development. Plants were transferred to a growth chamber (300 W/m2) following the high intensity lighting treatment. Plants grown in the growth chamber without supplemental lighting had the highest percentage of blind shoots. Maximum blindness occurred during the winter months regardless of lighting treatments. Blind shoot production decreased with increased duration of supplemental lighting. Shoot length proved to be an effective indicator of blind shoots as early as 10 days following lateral bud initiation on all cultivars. The value of bud diameter and stem diameter as indicators of blindness was dependent on cultivars.

The Effect of High Intensity Light on Choroidal Circulation

The Effect of High Intensity Light on Choroidal Circulation