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Laurencia brongniartii is usually found at depths below 4 m, but can be found in shallow subtidal areas in crevices and on the walls of a coral reef in Amami Oshima Island, Kagoshima Prefecture, Japan, where irradiances were significantly lower than those at similar depths in open water. In preparation for the possible cultivation of this species for its antibiotic compounds, the effects of temperature and irradiance on photosynthesis and growth were measured. Photosynthesis and growth rates of L. brongniartii explants were highest at 26 and 28 °C, which closely corresponded to temperatures found during August to late December when it was most abundant. The estimated maximum photosynthesis rate (Pmax) was 4.41 μmol photon m−2 s−1 at 26 °C and 4.07 μmol photon m−2 s−1 at 28 °C. Saturating irradiance occurred at 95 μmol photon m−2 s−1 at 26 °C and 65 μmol photon m−2 s−1 at 28 °C. In contrast, growth experiments at 41.7 μmol photon m−2 s−1 caused bleaching of explants and the maximum growth rate observed during the study was 3.02 ± 0.75% day−1 at 28 °C and 25 μmol photon m−2 s−1. The difference in the saturating irradiance for photosynthesis and the irradiance that caused bleaching in growth experiments suggests that long-term exposure to high irradiance was detrimental and should be addressed before the initiation of large scale cultivation.

Sensitometric and spectroscopic techniques are used to study the effect of 4-hydroxy-6-methyl-1,3,3a,7-tetraazaindene (TAI) during the sulphur sensitization of AgBr octahedra. TAI increased the speed of an oversensitized emulsion, causing it to have a speed comparable with the optimally sulphur-sensitized emulsion at high irradiance. TAI decreased the absorption by sulphide centres at 1.5 mmole concentration but not at 1 mmole. The long wavelength sensitivity (> 500 nm) increased at 1 mmole TAI concentration, but decreased at 1.5 mmole TAI concentration, whereas the activation energy for this response was reduced at both TAI levels. These results are interpreted using a model which assumes that TAI interacts with multiple-sulphide centres to lower their ground-state energy level, but not their electron-trapping energy level. This interaction reduces the degree of free-hole/trapped-electron recombination that occurs at these centres. The enhancement of this recombination channel by high levels of s...

Unicellular green algae of the genusDunaliella thrive in extreme environmental conditions such as high salinity, low pH, high irradiance and subzero temperatures. Species ofDunaliella are well known in the alga biotechnological industry and are employed widely for the production of valuable biochemicals, such as carotenoids. Some strains ofDunaliella are cultivated commercially in large outdoor ponds and are harvested to produce dry algal meals, such as polyunsaturated fatty acids and oils for the health food industry, and coloring agents for the food and cosmetic industries. During the past decade, the advances in molecular biology and biochemistry of microalgae, along with the advances in biotechnology of microalgal mass cultivation, enabled this microalga to become a staple of commercial exploitation. In particular, the advent of molecular biology and mutagenesis inDunaliella has permitted enhancements in the carotenoids content of this green alga, making it more attractive for biotechnological applications. Accordingly, the present review summarizes the recent developments and advances in biotechnology of carotenoid production inDunaliella.

Summary • We report the influence of a systemic irradiance signal, from mature leaves, on the anatomical characteristics of developing leaves. • A systemic signal of reduced irradiance was induced by growing tobacco (Nicotiana tabaccum) plants at high irradiance and then measuring the effect of shading mature leaves on the development of new leaves. The reverse, a systemic signal of increased irradiance was induced by growing plants at low irradiance and then measuring the effect of increasing the irradiance of mature leaves. • Stomatal pore length, stomatal density and index, epidermal cell shape, epidermal cell size and developing leaf size were all influenced by the irradiance signal. These responses were reversible with changing irradiance, except for stomatal pore length.

Attempts are being made to introduce C4 photosynthetic characteristics into C3 crop plants by genetic manipulation. This research has focused on engineering single-celled C4-type CO2 concentrating mechanisms into C3 plants such as rice. Herein the pros and cons of such approaches are discussed with a focus on CO2 diffusion, utilizing a mathematical model of single-cell C4 photosynthesis. It is shown that a high bundle sheath resistance to CO2 diffusion is an essential feature of energy-efficient C4 photosynthesis. The large chloroplast surface area appressed to the intercellular airspace in C3 leaves generates low internal resistance to CO2 diffusion, thereby limiting the energy efficiency of a single-cell C4 concentrating mechanism, which relies on concentrating CO2 within chloroplasts of C3 leaves. Nevertheless the model demonstrates that the drop in CO2 partial pressure, pCO2, that exists between intercellular airspace and chloroplasts in C3 leaves at high photosynthetic rates, can be reversed under high irradiance when energy is not limiting. The model shows that this is particularly effective at lower intercellular pCO2. Such a system may therefore be of benefit in water-limited conditions when stomata are closed and low intercellular pCO2 increases photorespiration.

【Two isolated Antarctic marine diatoms, Chaetoceros neogracile VanLandingham and Stellarima microtrias (Ehrenberg) Hasle and Sims were examined to show changes of growth and uptake rate of nitrate due to UV-B irradiance. Chlorophyll (chl) a concentration was regarded as the growth index of diatom. The diatoms were treated with UV-B radiation and cultured for 4 days under cool-white fluorescent light without UV-B radiation. Two levels of UV-B exposures were applies: 1 and 6 W $m^{-2}$ . Durations of UV-B treatment were 20, 40 and 60 minutes under 6 W $m^{-2}$ and 1, 2, 3, 4 and 5 hrs under 1 W $m^{-2}$ . The control groups were cultured at the same time without UV-B radiation. The growth rates of two diatoms decreased under 1 and 6 W $m^{-2}$ UV-B irradiances than that of control group. After 4 days, chl a concentrations of C. neogracile were increased more than 4 times from 133 μgo $l^{-1}$ to 632 μgo $l^{-1}$ in control group. However, the concentration of experimental groups under 1 W $m^{-2}$ UV-B were only increased from 139 μgo $l^{-1}$ to 421 μgo $l^{-1}$ during one hour and the chl a concentrations were decreased from 144 μgo $l^{-1}$ to 108 μgo $l^{-1}$ during five hour. Growth of diatom dramatically more decreased under 6 W $m^{-2}$ UV-B than 1 W $m^{-2}$ UV-B. The chl a concentration of experimental groups under 6 W $m^{-2}$ UV-B for one hour was only increased from 111 μgo $l^{-1}$ to 122 μgo $l^{-1}$ . In the case of S. microtrias showed also similar pattern to C. neogracile by UV-B radiation. The uptake rates of nitrate by the two strains were decreased abruptly under 6 W $m^{-2}$ UV-B irradiances. When two strains were treated under 1 and 6 W $m^{-2}$ UV-B during one hour, the strains were only continued growth and uptake of nitrate under 1 W $m^{-2}$ UV-B. This experimental evidence shows that exposure to UV-B radiation especially to high irradiance of UV-B decreases diatom survival and causes lower decrease of nutrient concentrations by microalgae in Antarctic water. Furthermore, evidence suggests that microalgal communities confined to near-surface waters in Antarctica will be harmed by increased UV-B radiation, thereby altering the dynamics of Antarctic marine ecosystems】

Rumohra adiantiformis (Forst.) Ching is a fern (Dryopteridaceae) which is used to compose floral arrangements. Fertile fronds were harvested in the "Permanently Protected Area" of Ilha Comprida, Sao Paulo, Brazil. Sterilized spores were germinated in Mohr liquid medium modified by Dyer. The effect of 72%, 54%, 17% and 9% of total irradiance on germination under field conditions, was analyzed. Experiments were carried out in March (I), April (II) and August of 2000 (III). Under 54% and 72% of total irradiance in Experiment I (March) the germination was completely inhibited and partially inhibited under 72% of total irradiance in Experiment II (April). The lowest mean germination time () was observed under 9% of total irradiance in Experiments II (11.62 days) and III (8.80 days) respectively, followed by 17% in Experiment III (10.12 days) and 9% of total irradiance in the Experiment I (11.62 days ). The effect of temperatures of 15 ± 1, 20 ± 1, 25 ± 1 and 30 ± 1 oC on germination was also analyzed. The lowest mean germination time (7.93 days) was observed at 25 ± 1 °C followed by 20 ± 1 °C. The highest mean germination time was observed at 15 ± 1 °C (12.10 days) followed by 30 ± 1 °C (10.63 days), which inhibited germination. The germination of R. adiantiformis was photoinhibited by high irradiance and partially inhibited by the highest temperature tested.

Maximum light-saturated photosynthetic rate (Pmax) and stomatal conductance (gs) of field-grown cocksfoot (Dactylis glomerata L.) leaves in a silvopastoral system were measured at different times under moderate (850-950 mol m-2 s-1 photosynthetic photon flux density, PPFD) and severe shade (85-95 μmol m-2 s-1 PPFD). Also Pmax and gs were measured after 30, 60 and 180 min of severe shade to determine the lag in the rise of photosynthesis rate from low to high irradiance levels (induction state). The highest Pmax and gs values obtained were 26.5 μmol CO2 m-2 s-1 and 0.41 mol H2O m-2 s-1 in non-limiting conditions with full sunlight (1900 μmol m-2 s-1 PPFD). These values were defined as standardized dimensionless Pmaxs = 1 and gss = 1 for comparison of treatment effects. The Pmaxs under severe shade decreased by 0.004 units per minute from 1 to 180 min and reached a steady-state of 0.37 units after 140 min. Under moderate shade, Pmaxs decreased by 0.002 units per minute from 1 to 120 min and reached a steady-state of 0.76 units. The time required to reach full induction on return to full sun (Pmaxs = 1) was 15 min after 30 min of severe shade and 37 min after 180 min of shade. Mathematical equations were derived to describe the changes in Pmaxs and gss under severe and moderate shade and during induction. The rate of change of gss was slower than for Pmaxs on entering shade and also slower during the subsequent induction process. This indicated other factors in addition to gs were operating in the reduction and increment of Pmax and a two-step model to explain this is proposed. The defined photosynthetic responses of cocksfoot leaves to fluctuating light regimes could be used to develop quantitative predictions of Pmax for inclusion in a canopy photosynthesis model of silvopastoral systems.

Photoinhibition, defined as the inhibition of photosynthesis caused by excessive radiance, affects field production to a great extent. This phenomenon is particularly relevant in reforestation practices, when one deals with forests of rapid growth such asEucalyptus. The imposition of additional stress factors during exposure to high radiance increases the potential for photoinhibitory effects, so the inhibition of photosynthesis indicates that the plant is submitted to stressful conditions. Photoinhibition can be reversible, playing a protective role for the photosynthetic systems, but it can also reflect damage that has already occurred in the photosynthetic apparatus, being irreversible in this case. In this review, we present the physiological and molecular mechanisms of photoinhibition and discuss the interaction between light and other stress factors and its effects on plants destined for reforestation. In addition, the present work analyzes some of the features and strategies that help plants avoid or restrict the occurrence of photoinhibition. For instance, pigments and enzymes which naturally occur in plants can prevent photoinhibition, while preadaptation to nonideal conditions can enhance tolerance to a certain stress factor. Most of these morphological, metabolic, and biochemical mechanisms of defense are related to the dissipation of excessive energy such as heat. Understanding these mechanisms can help improve cultivation procedures, avoid the plants’ death, and increase productivity in the field.

Vegetal Production Department/Horticulture Section Agronomical Sciences College Universidade Estadual Paulista, Botucatu, Sao Paulo

Summary This study represents the first genome-wide transcriptomic and lipidomic analysis of H. pluvialis to reveal the regulation of astaxanthin biosynthesis and lipid metabolism during the encystment process under high irradiation., Haematococcus pluvialis cells predominantly remain in the macrozooid stage under favourable environmental conditions but are rapidly differentiated into haematocysts upon exposure to various environmental stresses. Haematocysts are characterized by massive accumulations of astaxanthin sequestered in cytosolic oil globules. Lipidomic analyses revealed that synthesis of the storage lipid triacylglycerol (TAG) was substantially stimulated under high irradiance. Simultaneously, remodelling of membrane glycerolipids occurred as a result of dramatic reductions in chloroplast membrane glycolipids but remained unchanged or declined slightly in extraplastidic membrane glycerolipids. De novo assembly of transcriptomes revealed the genomic and metabolic features of this unsequenced microalga. Comparative transcriptomic analysis showed that so-called resting cells (haematocysts) may be more active than fast-growing vegetative cells (macrozooids) regarding metabolic pathways and functions. Comparative transcriptomic analyses of astaxanthin biosynthesis suggested that the non-mevalonate pathway mediated the synthesis of isopentenyl diphosphate, as the majority of genes involved in subsequent astaxanthin biosynthesis were substantially up-regulated under high irradiance, with the genes encoding phytoene synthase, phytoene desaturase, and β-carotene hydroxylase identified as the most prominent regulatory components. Accumulation of TAG under high irradiance was attributed to moderate up-regulation of de novo fatty acid biosynthesis at the gene level as well as to moderate elevation of the TAG assembly pathways. Additionally, inferred from transcriptomic differentiation, an increase in reactive oxygen species (ROS) scavenging activity, a decrease in ROS production, and the relaxation of over-reduction of the photosynthetic electron transport chain will work together to protect against photooxidative stress in H. pluvialis under high irradiance.

In this paper, a polarization recycling method is proposed for a light-pipe-based liquid crystal on silicon (LCoS) pico-optical engine. The method is based on making use of the virtual light sources array forming at the light pipe’s input surface. With traditional imaging optics, the virtual light sources array can be imaged to a plane after the light pipe, where the separated beams array can be obtained. By applying the polarization conversion system to the separated beams, the incoming unpolarized light can be converted to polarized light. The polarized light is then collected and transferred to the LCoS panel through the relay system. This new polarization recycling method can highly improve the light efficiency. A design example of a 0.29 in. (7.366 mm) color-filter LCoS pico-optical engine with 852×480 resolution is listed. High light efficiency of about 10.5 lm per LED Watt and high irradiance uniformity of about 95% has been achieved. The thickness of the optical engine is 8 mm.

PURPOSE New corneal cross-linking (CXL) devices are capable of using higher UV-A light irradiances than used in original CXL protocols. The Bunsen-Roscoe law states that a photochemical reaction should stay constant if the delivered total energy is kept constant; however, little clinical data are available to support this hypothesis. METHODS We investigated the biomechanical properties of four groups (n = 50 each) of porcine corneas. Three groups were exposed to riboflavin 0.1 % and UV-A irradiation of equal total energy (3 mW/cm(2) for 30 minutes, 9 mW/cm(2) for 10 minutes, and 18 mW/cm(2) for 5 minutes). Controls were exposed to riboflavin 0.1% without irradiation. Young's modulus of 5-mm wide corneal strips was used as an indicator of corneal stiffness. RESULTS We observed a decreased stiffening effect with increasing UV-A intensity. Young's modulus at 10% strain showed significant differences between 3 mW/cm(2) and 9 mW/cm(2) (P = 0.002), 3 mW/cm(2) and 18 mW/cm(2) (P = 0.0002), 3 mW/cm(2) and the control group (P < 0.0001), and 9 mW/cm(2) and the control group (P = 0.015). There was no difference between 18 mW/cm(2) and the control group (P = 0.064) and between 9 mW/cm(2) and 18 mW/cm(2) (P = 0.503). CONCLUSIONS The biomechanical effect of CXL decreased significantly when using high irradiance/short irradiation time settings. Intrastromal oxygen diffusion capacity and increased oxygen consumption associated with higher irradiances may be a limiting factor leading to reduced treatment efficiency. Our results regarding the efficiency of high-irradiance collagen cross-linking (CXL) raise concerns about the clinical efficiency of the new high-irradiance CXL devices already used in clinical practice without proper validation.

High-irradiance damage in two epiphytic lichens was recorded as reduction in predawn photosystem II quantum yield (Fv/Fm) measured at the end of a night with full hydration. Measurements were repeated during a 29-day transplantation in early summer at defined aspects (north, east, south, west, perpendicular to the sun at noon, and shade) in an open site at 60°N. These treatments included the contrasts that remaining lichens adjacent to clear-cut areas could experience subsequent to logging. The Fv/Fmvalues declined linearly with the mean irradiance during the previous day, with the old-forest epiphyte Lobaria pulmonaria (L.) Hoffm. being consistently more severely photoinhibited than the ubiquitous Parmelia sulcata Taylor. Both irradiance levels and predawn Fv/Fmvalues decreased in the following direction: shaded controls > transplants facing north > south, east, west > transplants perpendicular to the sun. Since the transplantation period happened to be very rainy with favorable conditions for recovery, all transplants survived. Nevertheless, photoinhibition was sustained from one day to the other, especially in the old-forest species L. pulmonaria, implying a long-lasting strain, which could affect long-term performance and survival of thalli. The results are discussed in a wider context including confounding effects of irradiance in forests, with implications to facilitate lichen conservation in managed forests.

Ta2O5/SiO2 high reflection (HR) interference coatings for λ∼1 μm offer superior performance at high irradiance conditions. However, these coatings are not good candidates for high peak power conditions in comparison to HfO2/SiO2 multilayer stacks. Here we show that the modification of the top layers design of a quarter wave Ta2O5/SiO2 high reflector leads to 4-5 fold increase in the laser damage fluence compared to a quarter wave (Ta2O5/SiO2)15 when tested at λ=1.03 μm using pulse durations of 0.19 and 4 ns and peak power densities of 43.5 and 216 GW/cm2. One of the designs achieved a laser damage threshold fluence of 174 J/cm2 at 4 ns, which is 10% higher than that of a HfO2/SiO2 quarter wave design.

Various flowering responses in Petunia × hybrida Vilm. 'Garden Party White' and 'Snow Cloud White' were studied under different photoperiods and irradiance levels. In particular, leaf number below the first flower bud (LNBFB) on the main stem, time to macroscopic flower bud visibility (MFBV), time to anthesis, time to flower bud development, and the percentage of flower bud abortion were examined. LNBFB increased significantly (P

Objective Exposure reciprocity suggests that, as long as the same radiant exposure is delivered, different combinations of irradiance and exposure time will achieve the same degree of resin polymerization. This study examined the validity of exposure reciprocity using real time degree of conversion results from one commercial flowable dental resin. Additionally a new fitting function to describe the polymerization kinetics is proposed. Methods A Plasma Arc Light Curing Unit (LCU) was used to deliver 0.75, 1.2, 1.5, 3.7 or 7.5 W/cm 2 to 2 mm thick samples of Tetric EvoFlow (Ivoclar Vivadent). The irradiances and radiant exposures received by the resin were determined using an integrating sphere connected to a fiber-optic spectrometer. The degree of conversion (DC) was recorded at a rate of 8.5 measurements a second at the bottom of the resin using attenuated total reflectance Fourier Transform mid-infrared spectroscopy (FT-MIR). Five specimens were exposed at each irradiance level. The DC reached after 170 s and after 5, 10 and 15 J/cm 2 had been delivered was compared using analysis of variance and Fisher's PLSD post hoc multiple comparison tests (alpha = 0.05). Results The same DC values were not reached after the same radiant exposures of 5, 10 and 15 J/cm 2 had been delivered at an irradiance of 3.7 and 7.5 W/cm 2 . Thus exposure reciprocity was not supported for Tetric EvoFlow ( p Significance For Tetric EvoFlow, there was no significant difference in the DC when 5, 10 and 15 J/cm 2 were delivered at irradiance levels of 0.75, 1.2 and 1.5 W/cm 2 . The optimum combination of irradiance and exposure time for this commercial dental resin may be close to 1.5 W/cm 2 for 12 s.

Previous investigations have suggested that the phototactic behaviour of diatoms, as observed by the accumulation of diatoms in low/moderate intensity light spots and avoidance of high intensity light, is primarily due to a change in cell direction at light/dark boundaries. In order to better determine the nature of this direction reversal and the manner in which it is generated, we used a high energy microbeam coupled to a monochrometer to irradiate specific areas of moving diatoms. When the leading end of moving Craticula cuspidata (Kutzing) D.G. Mann cells were irradiated with a 1–3 s exposure of high irradiance (about 500 to 2000 μmol photons m−2 s−1), they quickly reversed their direction (100% of cells tested), while unirradiated control cells rarely changed direction. Similar irradiation of the trailing half of the cell caused no change in direction, but greatly reduced the effect of a subsequent irradiation of the leading half. Using a monochrometer to vary the wavelength of irradiation and a shut...

Using numerical modeling, the voltage drop on the base of the photocells with a base length approximately equal to the minority carrier diffusion path is shown to be non-Ohmic under high irradiance levels; this should be taken into account when calculating the volt-ampere characteristics.

Leaf chlorophyll content may be used as an indirect indicator of crop nitrogen status. Chlorophyll meter values (SPAD values) taken with the Minolta SPAD-502 chlorophyll meter in the shade plantOxalis acetosellaL. and in winter wheat (Triticum aestivumL.) varied by 15 and 8%, respectively, with variation in irradiance. The lowest SPAD-values were measured at high irradiance. During a natural night-day-night cycle SPAD values for winter wheat were lowest in the middle of the day, highest at low irradiance at dusk and dawn and intermediate in darkness before dawn and after dusk. The results indicate that irradiance during measurement should be considered when using the Minolta SPAD-502 chlorophyll meter for the estimation of crop N-status.

Changes in fluorescence parameters observed during irradiation of the Scenedesmus cells showed that photosystem 2 (PS2) photoinactivation in cells treated with phenolic PS2 inhibitor 2-bromo-3-methyl-6-isopropyl-4-nitrophenol (BNT) was significantly accelerated in comparison with control and DCMU-treated cells. Moreover, a negligible difference in the rate of PS2 photoinactivation in the absence and presence of chloramphenicol indicated that both DCMU and BNT blocked the PS2 repair process.

Violaxanthin cycle activity in Nannochloropsis gaditana has been investigated using high-performance liquid chromatography (HPLC) to determine the changes in pigment content on exposure to high irradiance (2000 μmol m−2 s−1). Within the range 20–40°C, the effects of exposure time and temperature on the activity of the cycle have also been ascertained. Violaxanthin cycle activity was clearly shown by changes in pigment content accompanied by a concurrent decrease in the epoxidation state (EPS). From the de-epoxidation time course, the de-epoxidation rate was found to be slower than in other plant systems. In addition, the extent of de-epoxidation was dependent on both exposure time and temperature. De-epoxidation occurred faster and more extensively at 20°C (the temperature at which the experimental cultures were grown) than at 25°C (optimal growth temperature) or 35°C. Thus, after exposure to excess light for 240 min at these temperatures, violaxanthin decreased by about 28%, 6%, and 21 % of the ...

Several studies show that the high irradiance response (HIR) of plants is probably due to two photoreceptors. One of the photoreceptors is phytochrome, and the other is an unidentified pigment provisionally named heliochrome. One of the functions of heliochrome is the synthesis of phytochrome, using far-red and blue radiations of high intensities, to replace the phytochrome destroyed by light. Another possible function could be an interaction of heliochrome with a substance produced by phytochrome. The data presented show that heliochrome is a pigment with different properties from phytochrome. It shows a far-red/green reversibility. Heliochrome has been shown to participate with phytochrome in such HIRs as leaf movement in Albizzia and flowering in a long-day plant. The first event initiated by phytochrome and by heliochrome could be the generation of a strong positive, electrostatic charge in the cell membrane.

The photoinhibition of photosynthesis was investigated on intact attached leaves and isolated thylakoid membranes of Populus deltoides.Our studies demonstrate that in intact leaves photoinhibition takes place under high irradiance which is more pronounced at higher temperatures. No net loss of Dl and other proteins associated with photosystem II (PSII) were observed even after 64 % photoinhibition suggesting that the degradation of polypeptides associated with PSII is not the only key step responsible for photoinhibition as observed by other workers. Electron transport studies in isolated thylakoid membranes suggested water oxidation complex as one of the damaged site during high light exposure. The possible mechanisms of photoinhibition without net loss of D1 protein are discussed.

Photosystem II plays a central role not only in energy transduction, but also in monitoring the molecular redox mechanisms involved in signal transduction for acclimation to environmental stresses. Central to the regulation of photosystem II (PSII) function as a light-driven molecular machine in higher plant leaves, is an inevitable photoinactivation of one PSII after 10 6 -10 7 photons have been delivered to the leaf, although the act of photoinactivation per se requires only one photon. PSII function in acclimated pea leaves shows a reciprocity between irradiance and the time of illumination, demonstrating that the photoinactivation of PSII is a light dosage effect, depending on the number of photons absorbed rather than the rate of photon absorption. Hence, PSII photoinactivation will occur at low as well as high irradiance. There is a heterogeneity of PSII functional stability, possibly with less stable PSII monomers being located in grana margins and more stable PSII dimers in appressed granal domains. Matching the inevitable photoinactivation of PSII, green plants have an intrinsic capacity for D1 protein synthesis to restore PSII function which is saturated at very low light. Photoinhibition of PSII in vivo is often a photoprotective strategy rather than a damaging process.

The occurrence of very-low-fluence responses (VLFR), low-fluence responses (LFR) and high-irradiance responses (HIR) of phytochrome was investigated for the expression of the gene of β-glucuronidase (gusA) under the control of the tobacco Lhcb1*2 promoter, in etiolated transgenic tobacco seedlings. The activity of β-glucuronidase (GUS) showed biphasic responses to the calculated proportion of Pfr provided by light pulses. The first phase (i.e. the VLFR) showed a maximum for Pfr levels characteristic of far-red light. The second phase (i.e. the LFR) was observed at higher Pfr levels and was reversible by far-red light pulses. The strong effect of continuous far-red light (i.e. HIR) was fluence-rate-dependent and could not be replaced either by hourly pulses of the same spectral composition and total fluence or by very low fluences of red light. Deletion Lhcb1*2 promoter to -453 caused little loss of GUS activity. The -453 to -31, -270 to -31 and -176 to -31 fragments of the Lhcb1*2 promoter conferred proportionally normal VLFR, LFR and HIR to a truncated (-46 to +8) CaMV 35S minimal promoter. This is the first demonstration of the presence of three phytochrome action modes in the control of the transcriptional activity of a single gene. The cis-acting regulatory elements necessary for VLFR, LFR and HIR are present in a 146 bp fragment of the tobacco Lhcb1*2 promoter.

High irradiance blue light (HIBL), but not red light, diminished anti-tubulin indirect immunofluorescence of cortical microtubules in the green alga Mougeotia. Quantitation of MT-specific immunofluorescence by digital image analysis revealed taxol to counteract the HIBL-elicited decrease in immunolabelling. Taxol caused no significant increase of immunofluorescence in red light.

We demonstrate that core/graded-shell CdSe/CdSe1-xSx/CdS giant semiconductor nanocrystals (g-NCs) have robust photoluminescence (PL) temperature response. At a size of 10.2 nm in diameter, these g-NCs undergo a PL drop of only 30% at 355 K relative to their PL intensity at 85 K. In comparison, the core/step-shell CdSe/CdS g-NCs at the same diameter exhibit 80% PL drop at 355 K. Spectral shifting and broadening were found to be, respectively, 5-10 times and 2-4 times smaller than those observed in standard CdSe core and CdSe/CdS core/shell NCs. These core/graded-shell g-NCs are largely blinking suppressed and have insignificant photoluminescence decay even after excitation at very high irradiance (44 kW cm(-2)) for over an hour. These types of g-NC have potential applications as the active medium for thermally robust laser devices (in the visible range) or as temperature-insensitive bioprobes for biomedical imaging.

Laser micro-fabrication and micro-structuring of materials is usually carried out at the conditions close to the dielectric breakdown. Interplay between multi-photon and avalanche generation of electrons and thermal relaxation become critically important at those conditions in photo-polymerization, waveguide writing in glasses and for creation of new materials at the focal region. Relevant mechanisms of structuring are reviewed and discussed.

To evaluate the effectiveness of accelerated corneal collagen crosslinking (CXL) with riboflavin for keratoconus by the change in dioptric power and corneal topography.Private practice, Tokyo, Japan.Case series.The accelerated CXL treatments (KXL system) were performed using a 10-minute riboflavin 0.1% (Vibex Rapid) soak and a 3-minute ultraviolet-A (UVA) irradiance at a level of 30 mW/cm(2). This corresponds to a total radiant exposure of 5.4 J/cm(2). Preoperative and 1, 3, and 6 months postoperative examinations were performed.The study enrolled 39 eyes of 22 patients. The mean uncorrected distance visual acuity showed a statistically significant improvement, from 1.11 ± 0.42 logMAR preoperatively to 0.89 ± 0.53 logMAR 6 months postoperatively (P.01). The mean maximum keratometry readings also changed significantly, from 49.95 ± 6.11 diopters (D) preoperatively to 49.19 ± 5.82 D at 6 months (P.01). There were no statistically significant changes in the endothelial cell density between preoperatively and postoperatively.The changes after accelerated CXL were similar to those after conventional CXL. Thus, accelerated CXL has the potential to efficiently treat and halt the progression of keratoconus and may be an effective, efficient therapeutic option for treating corneal ectatic disease.No author has a financial or proprietary interest in any material or method mentioned.

This article is a highlight of the study by Stamenkovic and Hanelt in this issue of Photochemistry and Photobiology describing the high-irradiance photophysiology of several strains of freshwater chlorophyte microalgal genus, Cosmarium. These strains exhibit distinct differences in how combined thermal- high irradiance stress is managed which can be related to the temperature and irradiance conditions of their native habitat.

The effect of light during desiccation of the resurrection plant Haberlea rhodopensis on the photosynthetic activity and some morphological parameters was evaluated using plants growing at low or high irradiance in natural habitat. Chlorophyll content was not only lower in sun plants compared to shade plants, but it declined to a higher extent when desiccation was carried out at high light irradiance. Regardless of lower chlorophyll content in sun plants their photosynthetic activity (PN) was about 30% higher compared to shade plants. However, during dehydration PN declined more rapidly in sun plants. The mean leaf thickness of fully hydrated leaves from sun plants was larger when compared with shade plants, which was due to higher thickness of the mesophyll. Following rehydration plants rapidly recovered and PN was higher by about 70% in sun than in shade plants. The results showed that the sun-exposed Haberlea plants exhibited good adaptation to desiccation under high irradiance.

In addition to driving photosynthesis, light acts as an important signal that modulates plant growth and development in response to the environment. Far-red (FR) high-irradiance responses (HIRs), which are triggered by prolonged exposure to FR light and have various effects, such as enabling plants

The overheating protection of walls equipped with transparent insulation (TI) usually requires cost intensive, often unreliable mechanical shading devices. An effective way to avoid overheating and simultaneously increase the solar gains is the direct cooling of the outer wall surface (absorber). For this purpose, water is pumped through a system of pipes that is attached to the outer wall surface. The heat transferred to the fluid can be used for hot-water production and/or space heating. Thus, the passive solar TI system is extended to an active/passive solar system, called the transparently insulated hybrid wall (TIHW). In this paper the results of experimental investigations of a laboratory model (aperture 1 m2) are presented: more than 75% of the absorbed heat could be removed by the fluid. The surface temperature at the inner wall remains moderate even after a long period of high irradiance. Already with small flow rates an effective cooling is achieved. Finally the fast reaction of the system after turning on the fluid pump enhances the control of the TI system in order to avoid overheating in adjacent rooms.

Leaves of 2-year-old seedlings of longan (Dimocarpus longan Lour.) and mango (Mangifera indica L.) were exposed to high irradiance (2000 μmol m-2•S-1) provided by metal halide lamps and to 70 ± 5 % of relative humidity. Temperature was raised by incre ments of 3 °C each, at every 1.5 hr interval, from 30 °C till 36 °C. Net assimilation rates decreased for both species as the temperature was increased, but the decline in net assimilation rates was more in longan than in mango. As the temperature increased, stomatal conductance decreased and intercellular CO2 concentration increased for both species especially in longan. A positively significant correlation (r=0.91**) was found in longan between stomatal conductance and net assimilation rate at 30 °C and 33 °C, but r = 0.27NS at 36 °C. In mango, however, the correlation coefficient was consistently significant, r ranging from 0.79 ** to 0.92**, at the three temperatures. Intercellular CO2 concentration and net assimilation rate were not closely related at 30 °C and 33 °C, but a strong negative association was found at 36 °C in both longan (r= --0.89**) and mangc (-0.70**). These results indicate that the decline in net assimilation rate was caused by nonstomatal limitations at high temperatures. The extent of decline in the chlorophyll fluorescence ratio [variable (Fv) to maximum fluorescence (Fm)] by high temperature treatment in the dark was greater in longan than in mango, suggesting that mango leaves are more tolerant of high temperatures than are longan leaves.

— The mixed epidermal cell lymphocyte reaction (MECLR) is a commonly used method to study the effects of ultraviolet B (UVB) radiation on the skin immune system. In UVB experiments dosimetry is very important. The influence of irradiance on the MECLR was studied in vitro using Philips FS40 lamps with variable UV intensities. Irradiation of isolated epidermal cells with high irradiance impaired the alloactivating capacity more than irradiation with low irradiance. In vivo, the influence of long-term UVB exposure on the MECLR was studied by treating normal healthy volunteers with suberythemagenic doses of UVB thrice weekly during 4 weeks. The first set of experiments, using low irradiance Sylvania UV-21 F75/85 W lamps, resulted in a decrease of MECLR responses of 83.1%. In the second set of experiments performed a year later, employing an identical protocol except for the use of high irradiance Waldmann UV-21 F85/100 W lamps, an increase of MECLR responses of 99.7% was observed. Volunteers of both sets of experiments received equal doses of UVB. In conclusion, this study shows that in vitro UVB-induced suppression of the MECLR is critically dependent on irradiance and therefore might explain contradictory results described in the literature. The in vivo data suggest that, comparable to the in vitro experiments, irradiance may influence the effects of UVB irradiation in vivo. Further experiments should prove whether this is indeed the case.

We examined if higher plant water use efficiency is related to a higher investment of nitrogen in components of the photosynthetic apparatus and if this is associated with a less efficient use of nitrogen for photosynthesis or for growth. We also assessed the influence of a reduced supply of water and nitrogen on these relationships. For this purpose we used two Triticum aestivum cultivars, differing in whole plant water use efficiency. Differences in leaf water use efficiency (A/E) between cultivars or treatments were associated with differences in Rubisco activity or rate of electron transport and, in general, with differences in plant water use efficiency. They were not invariably related to a low photosynthetic nitrogen use efficiency (PNUE). A high A/E was associated with a low PNUE, e.g. when we compared cultivars at high irradiance. In this case, a high A/E and a high leaf nitrogen concentration were associated with a low stornatal conductance and an equal rate of photosynthesis. A high A/E was not associated with a low PNUE when differences in A/E were mainly caused by higher rates of photosynthesis associated with higher nitrogen concentrations, e.g. when we compared cultivars at low irradiance and high water and nitrogen supply. An increase in the proportion of total leaf nitrogen associated with the photosynthetic apparatus at low soil-nitrogen increased PNUE, without affecting A/E in the opposite way. We conclude that whole plant nitrogen use efficiency was low for the cultivars with a high plant water use efficiency.

PURPOSE: To evaluate the safety and efficacy of intrastromally applied collagen cross-linking (CXL) in a comparative contralateral eye study of topography-guided femtosecond laser–assisted hyperopic LASIK. METHODS: Thirty-four consecutive patients with hyperopia and hyperopic astigmatism elected to have bilateral topography-guided LASIK and were randomized to receive a single drop of 0.1% sodium phosphate riboflavin solution under the flap followed by 3-minute exposure of 10 mW/cm 2 ultraviolet A (UVA) light with the flap realigned in one eye (CXL group) and no intrastromal CXL in the contralateral eye (no CXL group). All eyes were treated with the WaveLight FS200 femtosecond laser and WaveLight EX500 excimer laser (Alcon Laboratories Inc). Refractive error and keratometric, topographic, and tomographic measurements were evaluated over mean follow-up of 23 months. RESULTS: Preoperatively, mean spherical equivalent refraction was +3.15±1.46 diopters (D) and +3.40±1.78 D with a mean cylinder of 1.20±1.18 D and 1.40±1.80 D and mean uncorrected distance visual acuity (UDVA) (decimal) of 0.1±0.26 and 0.1±0.25 in the CXL and no CXL groups, respectively. At 2 years postoperatively, mean spherical equivalent refraction was −0.20±0.56 D and +0.20±0.40 D with mean cylinder of 0.65±0.56 D and 0.76±0.72 D and mean UDVA of 0.95±0.15 and 0.85±0.23 in the CXL and no CXL groups, respectively. Eyes with CXL demonstrated a mean regression from treatment of +0.22±0.31 D, whereas eyes without CXL showed a statistically significant greater regression of +0.72±0.19 D ( P =.0001). CONCLUSIONS: Topography-guided hyperopic LASIK with or without intrastromal CXL is safe and effective, with greater long-term efficacy (less regression) in eyes with CXL. Our data suggest that the regression seen with hyperopic LASIK may be related to biomechanical changes in corneal shape over time.

The main goal of this study was to increase the hydrogen production rate improving the culture technique and the photobioreactor performances. Experiments were carried out at a constant culture temperature of 30°C and at an average irradiance of 480 W m−2using a cylindrical photobioreactor (4.0 cm, internal diameter). The culture technique, namely, the semicontinuous regime for growingRhodopseudomonas palustris42OL made it possible to achieve a very high daily hydrogen production rate of 594 ± 61 mL (H2) L−1 d−1. This value, never reported for this strain, corresponds to about 25 mL (H2) L−1 h−1, and it was obtained when the hydraulic retention time (HRT) was of 225 hours. Under the same growth conditions, a very high biomass production rate (496 ± 45 mg (dw) L−1 d−1) was also achieved. Higher or lower HRTs caused a reduction in both the hydrogen and the biomass production rates. The malic-acid removal efficiency (MAre) was always higher than 90%. The maximal hydrogen yield was 3.03 mol H2mol MA−1at the HRT of 360 hours. The highest total energy conversion efficiency was achieved at the HRT of 225 hours.

The Solar Probe Plus (SPP) spacecraft will fly further into the Sun's corona than any previous mission, reaching a minimum perihelion at 9.5 solar radii from the center of the Sun. The solar arrays powering the spacecraft will operate under unusually high irradiances and temperatures. The array design, material choices, and necessary test facilities for SPP are therefore quite different from those used on traditional space panels. This paper gives an overview of the high-irradiance high-temperature vacuum (HIHT-Vac) reliability testing completed to date at Emcore on three small-scale coupons representing two competing SPP-array technologies. Both technologies successfully passed the HIHT-Vac test with no measurable performance, visual or mechanical degradation, reaching a key milestone in the development of the SPP array.

UV curing is a green technology that is largely underutilized because UV radiation sources like Hg Lamps are unreliable and difficult to use. High Power UV LEDs are now efficient enough to replace Hg Lamps, and offer significantly improved performance relative to Hg Lamps. In this study, a modular, scalable high power UV LED curing system was designed and tested, performing well in industrial coating evaluations. In order to achieve mechanical form factors similar to commercial Hg Lamp systems, a new patent pending design was employed enabling high irradiance at long working distances. While high power UV LEDs are currently only available at longer UVA wavelengths, rapid progress on UVC LEDs and the development of new formulations designed specifically for use with UV LED sources will converge to drive more rapid adoption of UV curing technology. An assessment of the environmental impact of replacing Hg Lamp systems with UV LED systems was performed. Since UV curing is used in only a small portion of the industrial printing, painting and coating markets, the ease of use of UV LED systems should increase the use of UV curing technology. Even a small penetration of the significant number of industrial applications still using more » oven curing and drying will lead to significant reductions in energy consumption and reductions in the emission of green house gases and solvent emissions. « less

Microalgae are considered a promising source of high-value products (carotenoids, omega-3, DHA) as well as feedstocks for feed/food, bulk chemicals, cosmetics/pharmaceutics and biofuels. Moreover, they can be used in bioremediation tasks of polluted environments, as part of the CO2 gas mitigation process or in wastewater treatment. Light is the main substrate for the production of microalgae. Therefore, areas with high irradiances and moderated temperatures along the year are considered to be optimal for the production of microalgal biomass. However, the photosynthetic process is not a perfect process and the low efficiencies obtained in outdoor cultivation processes, especially when cultures are exposed to high irradiance conditions, are limiting the development of feasible production systems at industrial scale. Considering the excess of light hinders the photosynthetic efficiency outdoors, more knowledge on the effect of photo-saturation over the complete photosynthetic process is needed with the aim of enhancing the microalgal productivities. In this sense, simulation experiments at laboratory scale where real outdoor irradiance conditions can be simulated while keeping the rest of operational parameters optimal might result in a better understanding of the microalgal cultivation process. In this Thesis Dissertation, irradiance conditions typical from the Summer and Winter period in Huelva (south-west of Spain), geographical area with a high annual irradiance, were simulated. Different cultivation strategies leading to avoid/reduce the effects of photo-saturation and/or photo-inhibition over the microalgal cultures were evaluated and their effect over the final production of the microalgae Chlorella sorokiniana was discussed. Obtained results show the potential of such microalgae to be cultivated in a high irradiance area as Huelva, the study site, for the obtainment of biomass and high-value molecules as lutein. Moreover, the positive effect of light dilution over the photosynthetic efficiency was confirmed., Las microalgas son consideradas una fuente alternativa de productos de alto valor añadido (carotenoides, omega-3, DHA), son utilizadas en alimentación animal y humana, en el sector cosmético y farmacéutico así como en la industria química, pudiendo además ser substrato para la producción de biocombustibles o usadas en tareas de biorremediación o depuración de efluentes. La luz es el principal substrato para la producción de microalgas. Regiones con alta irradiancia y temperaturas moderadas a lo largo de todo el año son, por lo tanto, consideradas idóneas para la producción de biomasa de microalgas. Sin embargo, la fotosíntesis no es un proceso perfecto, y las bajas eficiencias fotosintéticas alcanzadas en cultivos en el exterior, especialmente bajo condiciones de alta irradiancia, limitan el desarrollo de sistemas de producción de microalgas a escala comercial. Por tanto, debido a que el exceso de luz reduce la eficiencia fotosintética en el exterior, se requiere un mayor conocimiento sobre el efecto de la foto-saturación en el proceso fotosintético con objeto de mejorar la productividad de los cultivos. En este sentido, experimentos a nivel de laboratorio donde pueden simularse condiciones reales de irradiancia, a la vez que se mantienen el resto de parámetros operacionales en sus valores óptimos, proporcionan una mejor comprensión sobre el cultivo de microalgas. En esta Tesis se simulan condiciones de irradiancia propias del periodo estival, así como del invierno, en la región de Huelva, zona geográfica de alta irradiancia anual. Se evalúan diferentes estrategias para minimizar y/o evitar los efectos de la foto-saturación y de la fotoinhibición y se discute la producción de biomasa de la microalga Chlorella sorokiniana en el lugar geográfico de estudio. Los resultados obtenidos ponen en valor el potencial de dicha microalga para ser producida en una región de alta irradiancia como Huelva (Andalucía, España) para la obtención de biomasa y de moléculas de valor añadido –luteína-, confirmando además el positivo efecto de la dilución de la luz incidente sobre la eficiencia fotosintética.

Microalgae are considered a promising source of high-value products (carotenoids, omega-3, DHA) as well as feedstocks for feed/food, bulk chemicals, cosmetics/pharmaceutics and biofuels. Moreover, they can be used in bioremediation tasks of polluted environments, as part of the CO2 gas mitigation process or in wastewater treatment. Light is the main substrate for the production of microalgae. Therefore, areas with high irradiances and moderated temperatures along the year are considered to be optimal for the production of microalgal biomass. However, the photosynthetic process is not a perfect process and the low efficiencies obtained in outdoor cultivation processes, especially when cultures are exposed to high irradiance conditions, are limiting the development of feasible production systems at industrial scale. Considering the excess of light hinders the photosynthetic efficiency outdoors, more knowledge on the effect of photo-saturation over the complete photosynthetic process is needed with the aim of enhancing the microalgal productivities. In this sense, simulation experiments at laboratory scale where real outdoor irradiance conditions can be simulated while keeping the rest of operational parameters optimal might result in a better understanding of the microalgal cultivation process. In this Thesis Dissertation, irradiance conditions typical from the Summer and Winter period in Huelva (south-west of Spain), geographical area with a high annual irradiance, were simulated. Different cultivation strategies leading to avoid/reduce the effects of photo-saturation and/or photo-inhibition over the microalgal cultures were evaluated and their effect over the final production of the microalgae Chlorella sorokiniana was discussed. Obtained results show the potential of such microalgae to be cultivated in a high irradiance area as Huelva, the study site, for the obtainment of biomass and high-value molecules as lutein. Moreover, the positive effect of light dilution over the photosynthetic efficiency was confirmed. Las microalgas son consideradas una fuente alternativa de productos de alto valor añadido (carotenoides, omega-3, DHA), son utilizadas en alimentación animal y humana, en el sector cosmético y farmacéutico así como en la industria química, pudiendo además ser substrato para la producción de biocombustibles o usadas en tareas de biorremediación o depuración de efluentes. La luz es el principal substrato para la producción de microalgas. Regiones con alta irradiancia y temperaturas moderadas a lo largo de todo el año son, por lo tanto, consideradas idóneas para la producción de biomasa de microalgas. Sin embargo, la fotosíntesis no es un proceso perfecto, y las bajas eficiencias fotosintéticas alcanzadas en cultivos en el exterior, especialmente bajo condiciones de alta irradiancia, limitan el desarrollo de sistemas de producción de microalgas a escala comercial. Por tanto, debido a que el exceso de luz reduce la eficiencia fotosintética en el exterior, se requiere un mayor conocimiento sobre el efecto de la foto-saturación en el proceso fotosintético con objeto de mejorar la productividad de los cultivos. En este sentido, experimentos a nivel de laboratorio donde pueden simularse condiciones reales de irradiancia, a la vez que se mantienen el resto de parámetros operacionales en sus valores óptimos, proporcionan una mejor comprensión sobre el cultivo de microalgas. En esta Tesis se simulan condiciones de irradiancia propias del periodo estival, así como del invierno, en la región de Huelva, zona geográfica de alta irradiancia anual. Se evalúan diferentes estrategias para minimizar y/o evitar los efectos de la foto-saturación y de la fotoinhibición y se discute la producción de biomasa de la microalga Chlorella sorokiniana en el lugar geográfico de estudio. Los resultados obtenidos ponen en valor el potencial de dicha microalga para ser producida en una región de alta irradiancia como Huelva (Andalucía, España) para la obtención de biomasa y de moléculas de valor añadido –luteína-, confirmando además el positivo efecto de la dilución de la luz incidente sobre la eficiencia fotosintética.