The Effects of UV‐B Radiation Intensity on Biochemical Parameters and Active Ingredients in Flowers of Qi Chrysanthemum and Huai Chrysanthemum

The article studied UV‐B effects on biochemical parameters and active ingredients in flowers of Qi chrysanthemum and Huai chrysanthemum during the bud stage. The experiment included four UV‐B radiation levels (CK, ambient UV‐B; T1, T2 and T3 indicated a 5%, 10% and 15% increase in ambient UV‐B_BE, respectively) to determine the optimal UV‐B radiation intensity in regulating active ingredients level in flowers of two chrysanthemum varieties. Flower dry weight of two cultivars was not affected by UV‐B radiation under experimental conditions reported here. UV‐B treatments significantly increased the rate of superoxide radical production, hydrogen peroxide (H₂O₂) (except for T1) and malondialdehyde concentration in flowers of Huai chrysanthemum and H₂O₂ concentration in flowers of Qi chrysanthemum. T2 and T3 treatments induced a significant increase in phenylalanine ammonia lyase enzyme (PAL) activity, anthocyanins, proline, ascorbic acid, chlorogenic acid and flavone content in flowers of two chrysanthemum varieties, and there were no significant differences in PAL activity, ascorbic acid, flavone and chlorogenic acid content between the two treatments. These results indicated that appropriate UV‐B radiation intensity did not result in the decrease in flower yield, and could regulate PAL activity and increase active ingredients content in flowers of two chrysanthemum varieties.     

Enhanced UV‐B Radiation Increases Glyphosate Resistance in Velvetleaf (Abutilon theophrasti)

Depletion of the ozone layer leads to increasing UV‐B radiation on the earth's surface, which may affect weeds and their responses to herbicides. However, the effect of increased UV‐B radiation on weeds and the interaction of weeds and herbicides are still obscure. The objective of this study was to compare glyphosate efficacy on velvetleaf that was grown under with and without increased UV‐B radiation. Leaf area, dry weight and net photosynthesis of velvetleaf seedlings were adversely affected by increased UV‐B radiation. Leaf cuticle wax significantly increased by 28% under increased UV‐B radiation. Glyphosate efficacy on velvetleaf, evaluated by shoot dry weight, was significantly decreased by increased UV‐B radiation. Exposure to increased UV‐B radiation significantly decreased ¹⁴C‐glyphosate absorption from 49% to 43%, and also resulted in less ¹⁴C‐glyphosate translocation out of treated leaves and less glyphosate accumulation in newly expanded leaves. The decrease in glyphosate efficacy was due to changes in absorption and distribution, which were attributed to increased cuticle wax and decreased photosynthesis caused by increased UV‐B radiation. These results suggest that the responses of weeds to herbicides may be affected by increased UV‐B radiation, to the extent that higher rates may be required to achieve the desired effects.     

Effects of PAR and UV‐B Radiation on Herbal Yield,Bioactive Compounds and Their Antioxidant Capacity of Some Medicinal Plants Under Controlled Environmental Conditions

Photosynthetically active radiation (PAR) and Ultraviolet B (UV‐B) radiation are among the main environmental factors acting on herbal yield and biosynthesis of bioactive compounds in medicinal plants. The objective of this study was to evaluate the influence of biologically effective UV‐B light (280–315 nm) and PAR (400–700 nm) on herbal yield, content and composition, as well as antioxidant capacity of essential oils and polyphenols of lemon catmint (Nepeta cataria L. f. citriodora), lemon balm (Melissa officinalis L.) and sage (Salvia officinalis L.) under controlled greenhouse cultivation. Intensive UV‐B radiation (2.5 kJ m^?2 d^?1) influenced positively the herbal yield. The essential oil content and composition of studied herbs were mainly affected by PAR and UV‐B radiation. In general, additional low‐dose UV‐B radiation (1 kJ m^?2d^?1) was most effective for biosynthesis of polyphenols in herbs. Analysis of major polyphenolic compounds provided differences in sensitivity of main polyphenols to PAR and UV‐B radiation. Essential oils and polyphenol‐rich extracts of radiated herbs showed essential differences in antioxidant capacity by the ABTS system. Information from this study can be useful for herbal biomass and secondary metabolite production with superior quality under controlled environment conditions.     

Effects of UV‐B Irradiation on a Marine Microecosystem¶

Purpose of this work was to study the effect of UV irradiation on a microecosystem consisting of several interacting species. The system chosen was of a hypersaline type, where all the species present live at high salt concentration; it comprises different bacteria; a producer, the photosynthetic green alga Dunaliella salina; and a consumer, the ciliated protozoan Fabrea salina, which form a complete food chain. We were able to establish the initial conditions that give rise to a selfsustaining microecosystem, stable for at least 3 weeks. We then determined the effect of UV irradiation on this microecosystem under laboratory‐controlled conditions, in particular by measuring the critical UV exposure for the two main components of the microecosystem (algae and protozoa) under UV‐B irradiances comparable to those of solar irradiation. In our experiments, we varied irradiance, total dose and spectral composition of the actinic light. The critical doses at irradiances of the order of 56 kJ/m² (typical average daily irradiance in a sunny summer day in Pisa), measured for each main component of the microecosystem (algae and ciliates), turned out to be around 70 kJ/m² for ciliates and 50 kJ/m² for D. salina. By exposing microecosystems to daily UV‐B irradiances of the order of 8 kJ/m² (typical average daily irradiance in a sunny winter day in Pisa), we found no effect at total doses of the order of the critical doses at high irradiances, showing that the reciprocity law does not hold. We have also measured a preliminary spectral‐sensitive curve of the UV effects, which shows an exponential decay with wavelength.     

Heteropogon contortus BL‐1 (Pilli Grass) and Elevated UV‐B Radiation: The Role of Growth,Physiological, and Biochemical Traits in Determining Forage Productivity and Quality

Exposure to elevated UV‐B (eUV‐B) is well known for its phytotoxicity, although studies made with UV‐B exposure and its impact on grasses are limited especially from tropical countries including India. In this study, responses of a valuable grass species, Heteropogon contortus BL‐1, were assessed under eUV‐B (over ambient UV‐B) at different growth stages. Damage caused by eUV‐B was observed in the form of membrane damage and loss of pigments at early stages of growth, whereas tannin, phenol, and protein contents showed their increments at all the growth stages, to overcome the imposed stress. Reducing sugar showed its decline at all the growth stages, whereas starch and sucrose contents were higher mostly at later ages of plant growth. eUV‐B caused a marked variations in anatomical structures with increase of mesophyll and spongy parenchymatous cells in leaves to reduce severity of irradiation, to maintain the growth and productivity. The study also highlights the significant negative influence of eUV‐B on the growth of H. contortus BL‐1 and its adaptive strategy to minimize the negative impacts. With the progression of age, plants although adopted to UV‐B stress with maintenance of productivity, but palatability of forage was affected due to increment of tannin content.     

Inactivation of Bacteriophage Infecting Bacteroides Strain GB124 Using UV‐B Radiation

Ultraviolet‐B radiation (280–320 nm) has long been associated with the inactivation of microorganisms in the natural environment. Determination of the environmental inactivation kinetics of specific indicator organisms [used as tools in the field of microbial source tracking (MST)] is fundamental to their successful deployment, particularly in geographic regions subject to high levels of solar radiation. Phage infecting Bacteroides fragilis host strain GB124 (B124 phage) have been demonstrated to be highly specific indicators of human fecal contamination, but to date, little is known about their susceptibility to UV‐B radiation. Therefore, B124 phage (n = 7) isolated from municipal wastewater effluent, were irradiated in a controlled laboratory environment using UV‐B collimated beam experiments. All B124 phage suspensions possessed highly similar first order log‐linear inactivation profiles and the mean fluence required to inactivate phage by 4 ? log¹⁰ was 320 mJ cm^?2. These findings suggest that phage infecting GB124 are likely to be inactivated when exposed to the levels of UV‐B solar radiation experienced in a variety of environmental settings. As such, this may limit the utility of such methods for determining more remote inputs of fecal contamination in areas subject to high levels of solar radiation.     

Intra‐strain Variability in the Effects of Temperature on UV‐B Sensitivity of Cyanobacteria

Stratospheric ozone depletion is mostly marked over the Antarctic and to a lesser extent over the Arctic, though recent reports have revealed that this also occurs at lower latitudes. Continued depletion of ozone in the lower stratosphere allows more UVR to reach the Earth's surface. Furthermore, it is projected that surface water temperatures will increase by between 0.2 and 2.0°C by the year 2060 and this will directly or indirectly influence algal growth. The interactions between environmental factors are complicated by the existence of different strains (ecotypes) of the same species that may respond differently. To understand the interactive effects of temperature and UV‐B on two strains of Anabaena circinalis, we investigated the damaging effects of UV‐B on cell numbers and photosynthetic characteristics and also examined the effect of temperature on the capacity of cells to recover from such stress. Both strains of A. circinalis responded differently in terms of survival, photosynthetic characteristics and recovery with interactions between temperature and UV‐B. This could be due to the variations in strain‐specific photoreactive mechanisms. This needs to be explored further including more strains and species before definitive conclusions can be reached about effects of global change on cyanobacteria generally.     

Environmental UV‐A and UV‐B Threshold Doses for Apoptosis and Necrosis in Humans Fibroblasts¶

Apoptosis involves a highly organized and programmed series of events aimed at maintaining genomic stability by eliminating defective host cells. The purpose of this study was to determine the threshold doses and environmental UV‐A and UV‐B exposure times necessary to produce apoptosis and necrosis in the normal cells of a human fibroblast cell line. Enviromental UV‐A and UV‐B doses were measured over a 6 year period with a four‐channel UV radiometer. The fibroblasts were irradiated once using an Oriel UV Solar Simulator with six doses of environmentally‐based UV. Doses corresponded to 0,11,19,23 and 45 min of average environmental UV‐A and UV‐B radiation at solar noon in Puerto Rico. The Annexin‐V binding method was used to differentiate between normal fibroblasts and apoptotic or necrotic fibroblasts. The threshold dose from apoptosis to necrosis was found between 24–28 kJ/m², which corresponded to 19 and 23 min of environmental UV‐A and UV‐B exposure. This study provides the first data that specify the environmental threshold doses of UV‐A and UV‐B at which human fibroblasts undergo apoptosis and necrosis. These results may provide valuable dose‐response thresholds for apoptosis and necrosis for future mechanistic studies and baseline data for skin cancer prevention programs.     

Effects of Ultraviolet Radiation (UV‐A+UV‐B) on the Antioxidant Metabolism of the Red Macroalga Species Acanthophora spicifera (Rhodophyta,Ceramiales) From Different Salinity and Nutrient Conditions

Acanthophora spicifera (M.Vahl) Børgesen is a macroalga of great economic importance. This study evaluated the antioxidant responses of two algal populations of A. spicifera adapted to different abiotic conditions when exposed to ultraviolet‐A+ultraviolet‐B radiation (UV‐A+UV‐B). Experiments were performed using the water at two collection points for 7 days of acclimatization and 7 days of exposure to UVR (3 h per day), followed by metabolic analyses. At point 1, water of 30 ± 1 practical salinity unit (psu) had concentrations of 1.06 ± 0.27 mm ${\text{NH}}_4^{+}$, 8.47 ± 0.01 mm ${\text{NO}}_3^{?}$, 0.17 ± 0.01 mm ${\text{PO}}_4^{?3}$ and pH 7.88. At point 2, water of 35 ± 1 psu had concentrations of 1.13 ± 0.05 mm ${\text{NH}}_4^{+}$, 3.73 ± 0.01 mm ${\text{NO}}_3^{?}$, 0.52 ± 0.01 mm ${\text{PO}}_4^{?3}$ and pH 8.55. Chlorophyll a, phycobiliproteins, carotenoids, mycosporins, polyphenolics and antioxidant enzymes (catalase, superoxide dismutase and guaiacol peroxidase) were evaluated. The present study demonstrates that ultraviolet radiation triggers antioxidant activity in the A. spicifera. However, such activation resulted in greater responses in samples of the point 1, with lower salinity and highest concentration of nutrients.     

Triplet–Triplet Energy Transfer from a UV‐A Absorber Butylmethoxydibenzoylmethane to UV‐B Absorbers

The phosphorescence decay of a UV‐A absorber, 4‐tert‐butyl‐4′‐methoxydibenzolymethane (BMDBM) has been observed following a 355 nm laser excitation in the absence and presence of UV‐B absorbers, 2‐ethylhexyl 4‐methoxycinnamate (octyl methoxycinnamate, OMC) and octocrylene (OCR) in ethanol at 77 K. The lifetime of the lowest excited triplet (T₁) state of BMDBM is significantly reduced in the presence of OMC and OCR. The observed quenching of BMDBM triplet by OMC and OCR suggests that the intermolecular triplet–triplet energy transfer occurs from BMDBM to OMC and OCR. The T₁ state of OCR is nonphosphorescent or very weakly phosphorescent. However, we have shown that the energy level of the T₁ state of OCR is lower than that of the enol form of BMDBM. Our methodology of energy‐donor phosphorescence decay measurements can be applied to the study of the triplet–triplet energy transfer between UV absorbers even if the energy acceptor is nonphosphorescent. In addition, the delayed fluorescence of BMDBM due to triplet–triplet annihilation was observed in the BMDBM–OMC and BMDBM–OCR mixtures in ethanol at 77 K. Delayed fluorescence is one of the deactivation processes of the excited states of BMDBM under our experimental conditions.     

Short‐term UV‐B Dose Stimulates Production of Protective Metabolites in Matricaria chamomilla Leaves

Physiological response of two cultivars of Matricaria chamomilla plants on UV irradiation was studied. The impact of used short‐time UV dose was evaluated in three time points; 2, 24 and 48 h after irradiation. Used UV irradiation immediately resulted in changes in plant oxidative status monitored as increased concentration of H₂O₂. Decrease in chlorophyll a and b indicated the impact on photosynthetic apparatus. For phenolic secondary metabolites, an increase in total soluble phenols and AlCl₃‐reactive flavonols was observed. The activity of main phenolic enzyme, phenylalanine ammonia‐lyase, increased with time after irradiation. Significant changes, mainly decreasing trends, in the content of free coumarins and their glycosidic precursors were observed. Enhanced accumulation in chlorogenic and 1,5‐dicaffeoylquinic acid and in (Z)‐isoform of dicycloethers was detected. From these results, the redirecting precursors of coumarin biosynthesis to biosynthesis of substances with higher antioxidative potential can be assumed. Different reactions in diploid and tetraploid plants were recorded, too.     

Growth under Visible Light Increases Conidia and Mucilage Production and Tolerance to UV‐B Radiation in the Plant Pathogenic Fungus Colletotrichum acutatum

Light conditions can influence fungal development. Some spectral wavebands can induce conidial production, whereas others can kill the conidia, reducing the population size and limiting dispersal. The plant pathogenic fungus Colletotrichum acutatum causes anthracnose in several crops. During the asexual stage on the host plant, Colletototrichum produces acervuli with abundant mucilage‐embedded conidia. These conidia are responsible for fungal dispersal and host infection. This study examined the effect of visible light during C. acutatum growth on the production of conidia and mucilage and also on the UV tolerance of these conidia. Conidial tolerance to an environmentally realistic UV irradiance was determined both in conidia surrounded by mucilage on sporulating colonies and in conidial suspension. Exposures to visible light during fungal growth increased production of conidia and mucilage as well as conidial tolerance to UV. Colonies exposed to light produced 1.7 times more conidia than colonies grown in continuous darkness. The UV tolerances of conidia produced under light were at least two times higher than conidia produced in the dark. Conidia embedded in the mucilage on sporulating colonies were more tolerant of UV than conidia in suspension that were washed free of mucilage. Conidial tolerance to UV radiation varied among five selected isolates.     

Chitosan‐capped sulfur microparticles grafted on UV‐treated PET surface

Antimicrobial materials with immobilized particles are of considerable interest. Sulfur, as one of the abundant elements on earth, is cheap and environmentally friendly; therefore, sulfur particles (SPs) can be used as an effective, nontoxic and low‐cost alternative to metal particles. SPs were prepared by precipitation method using sodium thiosulfate and hydrochloric acid in the presence of chitosan as a stabilizer. Further, SPs were grafted on polyethylene terephthalate (PET) foil activated by ultraviolet radiation. The changes in surface properties of modified foils were characterized by contact angle measurement, electrokinetic analysis and X‐ray photoelectron spectroscopy (XPS). The contact angle decreased on the UV‐treated sample, owing to the formation of oxidized groups. The presence of nitrogen and sulfur on the polymer surface, revealed by XPS, showed that chitosan‐capped SPs were bound to this surface. The surface morphology of samples and particle sizes were examined by scanning electron microscopy. The size of SPs increased after grafting on surface to a few micrometres. The antibacterial activity of the PET samples was tested against Staphylococcus epidermidis and Escherichia coli bacteria strains. UV‐treated samples grafted with one of the tested chitosan‐capped SPs demonstrated antibacterial effect against both of the bacteria strains. This new nanocomposite has potential to be used in medical applications as an antibacterial agent or in food processing as an antimicrobial food packaging material. Food spoilage caused by microorganisms such as E. coli during distribution and storage has a major impact on food quality and shelf life.     

Effects of UV‐C and Vacuum‐UV TiO2 Advanced Oxidation Processes on the Acute Mortality of Microalgae

Advanced oxidation processes/technologies (AOT) that combine a semiconductor, such as titanium dioxide (TiO₂), with a UV source have been used to eliminate microorganisms in various water treatment applications. To facilitate the applicability of this technique, the gain in efficiency from the semiconductor compared to the UV source alone with respect to different target organisms requires evaluation. The primary objective of this study was to determine the effects of TiO₂ and UV wavelength on a freshwater alga, Pseudokirchneriella subcapitata and a marine alga, Tetraselmis suecica. For each species, dose–response experiments were conducted to determine the median lethal dose (LC₅₀) of the following treatments: UV light emitted with a peak of 254 nm, UV light emitted with a peak of 254 nm in the presence of TiO₂ and UV light emitted with a peak of 254 and 185 nm in the presence of TiO₂. In both species, the presence of TiO₂ significantly increased mortality. Across all three treatments, P. subcapitata was more sensitive than T. suecica; moreover, the addition of the 185 nm wavelength significantly increased cell mortality in P. subcapitata but not in T. suecica.     

UV‐Light‐Induced Hydrogen Transfer in Guanosine–Guanosine Aggregates

Aggregates of a lipophilic guanine (G) derivative have been studied in n‐hexane by femtosecond‐to‐microsecond UV‐visible broadband transient absorption, stationary infrared and UV‐visible spectroscopy and by quantum chemical calculations. We report the first time‐resolved spectroscopic detection of hydrogen transfer in GG aggregates, which leads to (G?H) ^. radicals by means of G⁺G^? charge transfer followed by proton transfer. These radicals show a characteristic electronic spectrum in the range 300–550 nm. The calculated superimposed spectrum of the species that result from NH???N proton transfer agrees best with the experimental spectrum.     

Synthesis and characterization of UV‐curable ladder‐like polysilsesquioxane

Various ladder‐like structured poly(phenyl‐co‐methacryl silsesquioxane)s (LPMSQ)s with high molecular weight (M_w = 10,000 ～ 40,000) were synthesized by direct hydrolysis and polymerization in the presence of base catalyst at 25 °C. Synthesized LPMSQs mainly showed ladder‐like structure and photo‐cure reaction by 100 mW/cm² (360 nm) for 10 s without any photo‐cure initiators. Chemical composition and structural analysis of the obtained LPMSQs were characterized using ¹H NMR, ²⁹Si NMR, Fourier transform infrared spectroscopy (FTIR), gel permeation chromatography (GPC), and X‐ray diffraction (XRD). Physical properties of LPMSQs before and after photcuring were analyzed by Nanoindentation. Surface modulus increased to 8GPa and hardness of thin films increased from 100 to 400 MPa. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Molecular Regulation of UV‐Induced DNA Repair

Ultraviolet (UV) radiation from sunlight is a major etiologic factor for skin cancer, the most prevalent cancer in the United States, as well as premature skin aging. In particular, UVB radiation causes formation of specific DNA damage photoproducts between pyrimidine bases. These DNA damage photoproducts are repaired by a process called nucleotide excision repair, also known as UV‐induced DNA repair. When left unrepaired, UVB‐induced DNA damage leads to accumulation of mutations, predisposing people to carcinogenesis as well as to premature aging. Genetic loss of nucleotide excision repair leads to severe disorders, namely, xeroderma pigmentosum (XP), trichothiodystrophy (TTD) and Cockayne syndrome (CS), which are associated with predisposition to skin carcinogenesis at a young age as well as developmental and neurological conditions. Regulation of nucleotide excision repair is an attractive avenue to preventing or reversing these detrimental consequences of impaired nucleotide excision repair. Here, we review recent studies on molecular mechanisms regulating nucleotide excision repair by extracellular cues and intracellular signaling pathways, with a special focus on the molecular regulation of individual repair factors.     

Aligned carbon cones in free‐standing UV‐Curable polymer composite

A concept where an alternating electric field (dielectrophoresis) is used to assemble and align carbon nanocone particles (CNCs) into microscopic wires in self‐supporting polymer films is demonstrated. The particle fraction is kept low (one‐tenth of the percolation threshold of isotropic mixture), which allows uniform dispersion and efficient UV curing. The alignment leads to the conductivity enhancement of three to four orders of magnitude (from ～10^?7 to ～10^?3 S/m) in the alignment direction. It does not require passing current so the material can be isolated from the alignment electrodes. This prevents electrodes attaching to the film, if the film is adhesive in nature. The alignment can be done using either in‐plane or out‐of‐plane geometries. It is proposed that this concept could be applied in areas such as electrostatic discharge applications where inexpensive conductive or dissipative materials and macroscopic uniformity are prerequisites. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2011