LIGHT REQUIREMENTS FOR THE ENHANCED SYNTHESIS OF A PLASTID mRNA DURING SPIRODELA GREENING

A plastid mRNA (5 × 10⁵ mol wt) appears as a burst 3 h after white light greening of steady state dark grown plants of Spirodela oligorrhiza. In this species, chlorophyll synthesis begins after 12 h. The light requirement is different from the pulse of far-red reversible red light required to abolish the lag of chlorophyll synthesis in many species, including Spirodela. Continuous high energy far-red is not stimulatory. When the illumination is not continued throughout the time of incorporation, the stimulation is minimal. Low energy blue and red light are stimulatory, and green and far-red light are ineffectual. Blue light was > 5 times as effective as red light at many dose levels. Illumination with 3 × 10¹⁷ quanta/m²/s (50pEm/cm²/s) blue light at 476 nm gave about half maximum stimulation.     

RELATIONSHIP BETWEEN LIGHT QUALITY DEPENDENCE AND IRRADIANCE ADAPTATION OF PHOTOSYNTHESIS IN Acetabularia mediterranea*

Characteristic differences in the light intensity curves of photosynthesis after growth of cells of Acetabularia mediterranea Lamour. (A. acetabulum (L.) Silva) in weak and strong white light were similar to those for red and blue light-treated cells, respectively. This indicated that responses to white light quantity and those to light quality might be causally related. Small differences in the thylakoid polypeptide composition of cells grown in high and low intensities of white light were not significant and thus did not help to clarify whether the adaptations to blue or red light, respectively, were the same. When the red to blue-light ratio was varied, keeping the total photon fluence rate constant, the photosynthetic capacity (red light saturated O₂-production) was dependent on blue light irradiance in a logarithmic fashion. The specific influence of red light was not detectable, indicating that only blue light was effective for light irradiance adaptation in Acetabularia. The situation was different, at least for a transient period, when adaptation to light irradiance was allowed to proceed from a low photosynthetic activity after preirradiation of the cells with prolonged red light. The effect of low white light irradiances was pronounced, causing a maximum increase of photosynthetic activity within 3 days. The response to blue light was enhanced as well, and a very low photon irradiance added to continuous red light caused a change of the same order as that produced by high irradiances of blue light alone. This elevated action of low intensity white and blue light is most likely due to increased metabolite supply derived from the degradation of starch enhanced by this light quality. Therefore, photosynthetic effectiveness in Acetabularia is regulated by the irradiance of blue light and by feedback via photosynthetic products.     

IDENTITY OF THE PHOTORECEPTORS FOR THE PERCEPTION OF IRRADIANCE IN PHOTOSYNTHETIC LIGHT ACCLIMATION IN TOMATO*

The photoreceptors involved in the photosynthetic acclimation of tomato (Lycopersicon esculentum Mill.) to increased irradiance were investigated. Plants were transferred from 100 p.mol m^?2 s^?1 cool white fluorescent light to higher irradiances of white light or white light supplemented with blue, red, green or yellow light. In these experiements light of all wavelengths tested was capable of causing acclimation as measured by the rate of light-saturated photosynthesis. It was concluded that the photosynthetic system rather than the blue-absorbing photoreceptor or phytochrome system acts as the photoreceptor for increased irradiance. No acclimation was observed in response to increased CO₂ levels, but increasing light integral at a constant irradiance was effective in bringing about acclimation. We conclude that acclimation is a response to increased photosynthetic light capture rather than increased photosynthetic carbon fixation, and involves a photon counting mechanism.     

STUDIES ON THE RED AND BLUE FORMS OF THE PIGMENT OF BLEPHARISMA*

Abstract— –The intracellular pigment of the ciliate protozoan Blepharisma in the presence of oxygen sensitizes the cells to bright visible light (2700 foot candles (fc)). Illumination of the cells with dim visible light (200 fc) changes the color of the pigment to blue-gray; such cells are no longer sensitive to bright visible light. The pigment which exists in granules can be extruded by cold treatment and is slowly regenerated. The suspension of red cells, the extruded pigment from them and an ethanol extract of the pigment all have very similar absorption spectra. Illumination of the red pigment in ethanol converts it to the blue form of the pigment but only if oxygen is present, indicating a photooxidation. The pigment can be oxidized in darkness to the blue form by ozonation. A suspension of blue cells, the extruded pigment from them and an ethanol extract from them, all have similar absorption spectra. The pigments in red and blue form are very similar spectrophotometrically and in solubility in three species of Blepharisma studies: B. americanum, B. intermedium and B. japonicum. The purified pigment has strong absorption in the far (200–300 nm) ultraviolet (u.v.) and may serve as a screen against damaging U.V. radiation, especially as Blepharisma shows poor photoreactivation.     

Effect of light quality on the accumulation of photosynthetic pigments, proteins and mycosporine-like amino acids in the red alga Porphyra leucosticta (Bangiales, Rhodophyta)

The effect of different light qualities (white, blue, green, yellow and red light) on photosynthesis, measured as chlorophyll fluorescence, and the accumulation of photosynthetic pigments, proteins and the UV-absorbing mycosporine-like amino acids (MAAs) was studied in the red alga Porphyra leucosticta. Blue light promoted the highest accumulation of nitrogen metabolism derived compounds i.e., MAAs, phycoerythrin and proteins in previously N-starved algae after seven days culture in ammonium enriched medium. Similar results were observed in the culture under white light. In contrast, the lowest photosynthetic capacity i.e., lowest electron transport rate and lowest photosynthetic efficiency as well as the growth rate were found under blue light, while higher values were found in red and white lights. Blue light favored the accumulation of the MAAs porphyra-334, palythine and asterina-330 in P. leucosticta. However, white, green, yellow and red lights favored the accumulation of shinorine. The increase of porphyra-334, palythine and asterina-330 occurred in blue light simultaneous to a decrease in shinorine. The accumulation of MAAs and other nitrogenous compounds in P. leucosticta under blue light could not be attributed to photosynthesis and the action of a non-photosynthetic blue light photoreceptor is suggested. A non-photosynthetic photoreceptor could be also involved in the MAAs interconversion pathways in P. leucosticta.     

Efficient Nondoped Pure Blue Organic Light‐Emitting Diodes Based on an Anthracene and 9,9‐Diphenyl‐9,10‐dihydroacridine Derivative

Organic light‐emitting diodes (OLEDs) have been greatly developed in recent years owing to their abundant advantages for full‐color displays and general‐purpose lightings. Blue emitters not only provide one of the primary colors of the RGB (red, green and blue) display system to reduce the power consumption of OLEDs, but are able able to generate light of all colors, including blue, green, red, and white by energy transfer processes in devices. However, it remains a challenge to achieve high‐performance blue electroluminescence, especially for nondoped devices. In this paper, we report a blue light emitting molecule, DPAC‐AnPCN, which consists of 9,9‐diphenyl‐9,10‐dihydroacridine and p‐benzonitrile substituted anthracene moieties. The asymmetrically decoration on anthracene with different groups on its 9 and 10 positions combines the merits of the respective constructing units and endows DPAC‐AnPCN with pure blue emission, high solid‐state efficiency, good thermal stability and appropriate HOMO and LUMO energy levels. Furthermore, DPAC‐AnPCN can be applied in a nondoped device to effectively reduce the fabrication complexity and cost. The nondoped device exhibits pure blue electroluminescence (EL) locating at 464 nm with CIE coordinates of (0.15, 0.15). Moreover, it maintains high efficiency at relatively high luminescence. The maximum external quantum efficiency (EQE) reaches 6.04 % and still remains 5.31 % at the luminance of 1000 cd m^?2 showing a very small efficiency roll‐off.     

RED LIGHT-INDUCED REDUCTION OF A PARTICLE-ASSOCIATED b-TYPE CYTOCHROME FROM CORN IN THE PRESENCE OF METHYLENE BLUE*

Abstract— In the presence of methylene blue, red light causes the reduction of a h-type cytochrome in particulate fractions from corn coleoptiles. Two types of difference spectra for the cytochromes in these fractions are presented: (a) red light-minus-dark in the presence of methylene blue, and (b) dithionite-reduced-minus-oxidized. Comparison of these spectra shows that photoexcited methylene blue selectively reduces a b-type cytochrome which constitutes at most only 30% of the total dithionite-reducible cytochrome present in the most active fractions. The photoreducible cytochrome has an alpha band at room temperature near 557 nm. Bleaching of methylene blue precedes cytochrome reduction under appropriate conditions, suggesting that the photoreduced dye is donating an electron to the cytochrome. This electron transfer does not involve a flavin, at least as judged by the absence of light-induced spectral changes attributable to flavins. Preliminary kinetic studies suggest that EDTA provides the pool of electrons for the reaction. The cytochrome cannot be assigned exclusively either to mitochondria or to endoplasmic reticulum, as judged by its sedimentation properties. These results and the current literature are discussed in the context of the hypothesis that this b-type cytochrome may be involved in the photoreception mechanism for blue and uv light in vivo.     

Peri-Anthracenethioindigo: A Scaffold for Efficient All-Red-Light and Near-Infrared Molecular Photoswitching**

Molecular photoswitching with red light is greatly desired to evade photodamage and achieve specific photoresponses. In virtually all reported cases however, only one switching direction uses red light while for the reverse switching, UV or visible light is needed. All-red-light photoswitching brings with it the clear advantage of pushing photoswitching to the limit of the low-energy spectrum, but no viable system is available currently. Here we report on peri-anthracenethioindigo (PAT) as molecular scaffold for highly efficient all-red-light photoswitching with an outstanding performance and property profile. The PAT photoswitch provides near-infrared (NIR) absorption up to 850 nm, large negative photochromism with more than 140 nm maxima shifts and changes color from green to blue upon irradiation with two shades of red light. Thermal stability of the metastable Z isomer is high with a corresponding half-life of days at 20 °C. Application in red-light responsive polymers undergoing pronounced and reversible green to blue color changes demonstrate spatially resolved photoswitching. The PAT photoswitch thus offers unique responsiveness to very low energy light together with predictable and large geometrical changes within a rigid molecular scaffold. We expect a plethora of applications for PAT in the near future, e.g. in materials, molecular machines or biological context.     

REDOX DYES AS ARTIFICIAL PHOTORECEPTORS IN LIGHT-DEPENDENT CAROTENOID SYNTHESIS*

Abstract— The photodynamically active dyes methylene blue, toluidine blue, and neutral red act as artificial photoreceptors in light-dependent carotenoid synthesis in Fusarium aquaeductuum. Normally, carotenoid production is only induced by light of wavelengths shorter than 520 nm, but when mycelia are incubated with neutral red, methylene blue, and toluidine blue, red light is also effective in inducing carotenogenesis. Experiments with methylene blue and red light showed that pigments induced under these conditions are qualitatively the same as those induced with white light, and also that, in accord with the results found for photoinduction with white light, the amount of pigment synthesized was proportional to the logarithm of illumination time. In addition to their role in photoinduction, the dyes were also shown to interfere with the biosynthesis of carotenoids, whereas addition after irradiation caused an increase in pigment production that involves a quantitative change in the more unsaturated components.     

ACTION SPECTRA FOR LIGHT-INDUCED DE-EPOXIDATION AND EPOXIDATION OF XANTHOPHYLLS IN SPINACH LEAF*

Abstract— The action spectra for violaxanthin de-epoxidation and zeaxanthin epoxidation in New Zealand spinach leaf segments, Tetragonia expansa, were determined at equal incident quanta of 2·0 × 10¹⁵ quanta cm^-2 sec^-1. Precise action spectra were not obtained due to variable leaf activity. The de-epoxidation action spectrum had major peaks at approximately 480 and 648 nm. Blue light was slightly more effective than red light and little activity was observed beyond 700 nm. The epoxidation action spectrum showed major peaks at around 440 and 670 nm. Blue light was more effective than red light and light beyond 700 nm showed definite activity. The net result of de-epoxidation and epoxidation is a cyclic scheme, the violaxanthin cycle, which consumes O₂ and photoproducts. The action spectra indicate that the violaxanthin cycle is more active in blue than in red light and therefore could account for O₂ uptake stimulated by blue light. However, the violaxanthin cycle is not the pathway for O₂ uptake by photosynthetic system 1. It was suggested that the violaxanthin cycle may function as a pathway for the consumption of excess photoproducts generated in blue light or the conversion of these photo-products to other forms of energy.     

Light quality influences indigo precursors production and seed germination in Isatis tinctoria L. and Isatis indigotica Fort

Isatis tinctoria L. and Isatis indigotica Fort. are biennial herbaceous plants belonging to the family of Cruciferae that are used as a source of natural indigo and show several morphological and genetic differences. Production of indigo (indigotin) precursors, indican (indoxyl beta-D glucoside) and isatan B (indoxyl ketogluconate), together with seed germination ability were compared in Isatis tinctoria and Isatis indigotica grown under six different light conditions (darkness, white, red, far red, blue, yellow light) at 25 degrees C. Light quality influenced both germination and production of indigo precursors in the two Isatis species. Different responsiveness to far red and blue light was observed. Indeed, a detrimental effect on germination by blue and far red light was found in I. tinctoria only. Different amounts of isatan B were produced under red and far red light in the two Isatis species. In I. tinctoria, the level of main indigo precursor isatan B was maximal under red light and minimal under far red light. Whereas in I. indigotica far red light promoted a large accumulation of isatan B. The photon fluence rate dependency for white and yellow light responses showed that the accumulation of indigo precursors was differently influenced in the two Isatis species. In particular, both white and yellow light enhanced above 40 micromol m(-2) s(-1) the production of isatan B in I. indigotica while only white light showed a photon fluence dependency in I. tinctoria. These results suggest a different role played by the labile and stable phytochrome species (phyA and phyB) in the isatan B production in I. tinctoria and I. indigotica. I. indigotica, whose germination percentage was not influenced by light quality, demonstrated higher germination capability compared with I. tinctoria. In fact, I. tinctoria showed high frequency of germination in darkness and under light sources that establish high phytochrome photoequilibrium (red, white and yellow light). Germination in I. tinctoria was negatively affected by far red and blue light. I. indigotica seeds appear to be indifferent to canopy-like light (far red). Our results provide further insights on the distinct behaviour of I. tinctoria and I. indigotica that belong to two different genetic clusters and different original environments.     

PHYSIOLOGICAL CHARACTERIZATION OF A HIGH-PIGMENT MUTANT OF TOMATO

Abstract— A high-pigment (hp) mutant, which shows exaggerated phytochrome responses and three other genotypes of Lycopersicon esculenrum Mill. cv. Ailsa Craig: the aurea (au) mutant deficient in the bulk light-labile phytochrome (PI) pool, the au, hp double mutant, and their isogenic wild type, were used in this study. Measurements of phytochrome destruction in red light (R) revealed that the exaggerated responses of the hp mutant are not caused by a higher absolute phytochrome level or a reduced rate of phytochrome destruction. Fluence-response relationships for anthocyanin synthesis after a blue-light pretreatment were studied to test if the hp mutant conveys hypersensitivity to the far-red light (FR)-absorbing form of phytochrome (Pfr), i.e. the threshold of Pfr required to initiate the response is lower. The response range for the hp mutant and wild type was identical, although the former exhibited a 6-fold larger response. Moreover, the kinetics of anthocyanin accumulation in continuous R were similar in the wild-type and hp-mutant seedlings, despite the latter accumulating 9-fold more anthocyanin. Since the properties of phytochrome are the same, the hp mutation appears to affect the state of responsiveness amplification, i.e. the same amount of Pfr leads to a higher response in the hp mutant. We therefore propose that the hp mutation is associated with an amplification step in the phytochrome transduction chain. Escape experiments showed that the anthocyanin synthesis after different light pretreatments terminated with a R pulse was still 50% FR reversible after 4–6 h darkness, indicating that the Pfr pool regulating this response must be relatively stable. However, fluence-rate response relationships for anthocyanin synthesis and hypocotyl growth induced by a 24-h irradiation with 451, 539, 649, 693, 704 and 729 nm light showed no or a severely reduced response in the au and au, hp mutants, suggesting the importance of PI in these responses. We therefore propose that the capacity for anthocyanin synthesis (state of responsiveness amplification) could be established by PI, while the anthocyanin synthesis is actually photoregulated via a stable Pfr pool. The Hp gene product is proposed to be an inhibitor of the state of responsiveness amplification for responses controlled by this relatively stable Pfr species.     

RESPONSES OF LIGHT-GROWN WILD-TYPE and LONG-HYPOCOTYL MUTANT CUCUMBER SEEDLINGS TO NATURAL and SIMULATED SHADE LIGHT*

The photomorphogenic control of hypocotyl extension growth was characterized in wild type (WT) and long hypocotyl (Ih) mutant seedlings of cucumber (Cucumis sativus L.) grown under natural radiation in outdoor and glasshouse experiments. Hypocotyl extension growth of WT plants was promoted by supplementing sunlight with far-red light during the photoperiod, by reducing the amount of blue light reaching either the whole shoot or the hypocotyl, and by reducing the amount of UV reaching the whole shoot.The Ih seedlings only responded to a reduction in UV-B levels. Both WT and Ih seedlings showed phototropic responses to the direction of blue light. Increasing degrees of vegetational shade promoted hypocotyl growth of WT plants. The Ih mutant showed no hypocotyl growth promotion by natural shade in glasshouse experiments (no UV-B, low water demand) and a reduced response (10-23% of the WT response, according to pretreatment conditions) in outdoor experiments (UV-B, high water demand).     

CONTROL BY PHYTOCHROME OF CHLOROPHYLL SYNTHESIS IN SEEDLINGS OF SORGHUM VULGARE

The strong effect of light pretreatments on the synthesis of chlorophyll-a and-b in the shoot of Sorghum vulgare (kept under saturating white light) can be attributed to phytochrome only. No specific blue light effect was found. The phytochrome system appears to function perfectly normally under these conditions. Escape from reversibility is not detectable up to approximately 40 min after the onset of an inductive red light pulse. Thereafter, escape is fast, being completed at approximately 2.5 h after the inductive light pulse.     

ACTION SPECTRA FOR INHIBITION OF HYPOCOTYL GROWTH OF WILD-TYPE PLANTS AND OF THE hy2 LONG-HYPOCOTYL MUTANT OF Arabidopsis thaliana L.

Abstract— An analysis was made by action spectroscopy, using the Okazaki Large Spectrograph, of the inhibition of hypocotyl elongation of wild-type plants and the hy2 mutant of Arabidopsis thaliana. Two day old etiolated seedlings were irradiated for 8 h with monochromatic light and left in the dark for 16 h before measurement of hypocotyl length. Spectrophotometric measurement showed that levels of phytochrome in the etiolated tissue of the hy2 mutant were less than 9% of those in the wild type. The action spectra of the wild type looked like those of high irradiance response and showed peaks at 375, 450, 625 and 725 nm, whereas the action spectra of hy2 showed only the peaks at 375 and 450 nm. Monochromatic light of wavelengths longer than 500 nm had no significant inhibitory effects on hy2 plants. Blue and UV-A light were about five times more effective in the wild type than in hy2 plants. Severe inhibitory effects were observed with UV-B light. It is concluded that inhibition of the growth of the hypocotyl involves combined actions of phytochrome and a putative blue/UV-A photoreceptor(s).     

THE PHOTOSYNTHETIC APPARATUS OF Acetabularia mediterranea GROWN UNDER RED OR BLUE LIGHT. BIOPHYSICAL QUANTIFICATION and CHARACTERIZATION OF PHOTOSYSTEM II and ITS CORE COMPONENTS

Abstract— The photosynthetic activity of white light-grown Acetabularia mediterranea Lamouroux (= A. acetabulum (L.) Silva) decreases under continuous red light to less than 20% within 3 weeks. Subsequent blue light reactivates photosynthesis within a relatively short period of 3 days. In a former publication (Wennicke and Schmid, Plant Physiol. 84 ,1252–1256, 1987) we have shown that the regulated rate limiting step, which is an immediate light driven reaction, is part of photosystem II (PS II). The following biophysical properties of PS II were analyzed in thylakoids isolated from algae grown 3 weeks under either blue or red light with or without subsequent 3 days of blue light illumination: (a) fluorescence induction in the short time domain dominated by Q_A reduction, (b) the slow fluorescence decline reflecting pheophytin photoaccumulation, (c) absorption changes at 320 and 830 nm under repetitive flash excitation as indicator for the turnover of Q_A and P₆₈₀, respectively, (d) oscillation pattern of the oxygen yield by a flash train in dark adapted samples and (e) the binding capacity for atrazine. None of these PS II functions were severely affected, but a minor impairment of20–30% was observed in the thylakoids from algae grown for 3 weeks in red irradiation. The changes do not fully account for the drastic reduction of the electron transport through PS II which was 80% after red light treatment. Therefore, the regulated rate-limiting step appears to not be mainly located in the PS II core complex itself. It seems likely that the regulation process predominantly comprises the antenna system.     

FLAVIN TYPE ACTION SPECTRUM OF NITRATE UTILIZATION BY Monoraphidium braunii

The light-dependent utilization of nitrate by the green alga Monoraphidium braunii, coming from nocturnal dark periods, shows an action spectrum of flavin type with two main bands: one in the blue, peaking at 450 and 480 nm, and the other in the near-UV region with a maximum at 365 nm. Other results indicate that cells growing on nitrate as the only nitrogen source resynthesize nitrate reductase daily, which implies the nocturnal loss of this enzyme. The biosynthesis of nitrate reductase at the beginning of the light periods can proceed under red light. In addition, blue or near-UV light is required for the activation of the previously formed nitrate reductase.     

彩色不锈钢与氧化着色

通过化学或电化学手段与技术促使不锈钢表面发生氧化生成的钝化膜,不仅能够保护金属免受腐蚀,还能产生光干涉效应,使不锈钢不再是单一的银白色,而是呈现红橙黄绿蓝靛紫等不同的颜色,扩展了不锈钢的应用范围.     

MODE OF COACTION OF PHYTOCHROME AND BLUE LIGHT PHOTORECEPTOR IN CONTROL OF HYPOCOTYL ELONGATION

Abstract The rate of hypocotyl longitudinal growth in seedlings of Sesamum indicum L. is strongly inhibited by continuous blue light (cBL)† and slightly by continuous far-red light while continuous red light (cRL) or red light pulses are hardly effective from 60 h after sowing onwards. Between 36 and 60 h after sowing the growth rate responds to red light pulses the effect of which is fully reversible by long wavelength far-red light. When seedlings are kept in cBL for 3 days and then treated with red light hypocotyl growth rate responds strongly. However, RL effectiveness decreases with time after transfer from BL to RL. BL → darkness transfer experiments with different levels of P_fr established at the beginning of darkness show that after a BL pretreatment phytochrome (P_fr) alone is capable of fully controlling growth rate. When white light (WL) is given no BL effect is detectable in weak WL. Only high light fluxes maintain a typical BL growth rate. At medium WL fluxes elongation rate returns gradually to the dark rate. The simplest explanation of the data is that light absorbed by a separate BL photoreceptor is necessary to maintain responsivity to P_fr. With increasing age of the seedlings the requirement for BL increases strongly. On the other hand, brief light pulses—given to demonstrate photoreversibility of phytochrome—remain equally effective provided that responsivity to P_fr exists.