Development of heterodyne detection of dynamic light scattering enhanced by the Talbot effect for the size measurement of nanoparticles.

A new type of dynamic light scattering method for the size measurement of nanoparticles was developed using a transmission grating. A sample cell was located behind the grating, and light was incident from the grating side. The scattered light by a solution with nanopariticles was mixed with diffracted light by the grating, and the mixed signal was detected; namely, the diffracted light was used as reference light for heterodyne detection. It was confirmed that the S/N ratio of the autocorrelation curve was 26-times improved by heterodyne detection. Furthermore, the S/N ratio was improved by setting the sample cell at the sample grating distance where the electromagnetic field is maximum due to the Talbot effect. Size measurements for several kinds of nanoparticles were demonstrated by this new method.     

REGULATION OF PROTEIN PHOSPHORYLATION BY PHYTOCHROME IN Sorghum bicolor

Abstract— In vitro phosphorylation of some polypeptides was affected in extracts obtained from 5-and 6-day-old plants irradiated with 5 min of red light. The phosphorylation of 55 kDa polypeptide in both 5- and 6-day-old plants, a 60 kDa, and 76 kDa polypeptide in 6-day-old plants and 70 kDa, 67 kDa polypeptide in 5-day-old plants was stimulated by red light. This effect was reversible by far-red light. The extent of stimulation by red light and reversal by far-red light varied for different polypeptides. No differential effect of red and far-red light was seen on the phosphorylation of 94 and 40 kDa polypeptides. In fact, phosphorylation of 94 kDa polypeptide in 6-day-old plants decreased on red light irradiation. These results show that the phosphorylation or dephosphorylation of some proteins is affected by phytochrome and the effect of light is also dependent on the age of the plant.     

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.     

BLUE and NEAR ULTRAVIOLET REVERSIBLE PHOTOREACTION IN THE INDUCTION OF FUNGAL CONIDIATION

Abstract— The effects of blue light and near UV light on the induction of conidiation in the fungus, Aliernuriu tomato, were investigated. Induction of conidiation was repeatedly controlled by alternating doses of near UV light and blue light. When the final light was near UV, conidiation was induced and conidia developed in the following darkness; when it was blue, the induction of conidiation was suppressed. When conidiation was induced by irradiation with a light mixed with near UV and blue, not only the time lag for inducing conidiation but also the amount of conidia formed were regulated by the fluence rates of both those lights.
Thus, 'mycochrome' is considered to function as a photoreceptor system in the induction of conidiation of this fungus.     

SIMILARITIES IN THE INDUCTION OF SYNTHESIS OF A CELL-SURFACE POLYPEPTIDE IN Arthrobacter sp. BY NEAR-UV IRRADIATION and PHOTODYNAMIC CONDITIONS

Irradiation of aerobic suspensions of Arthrobacter sp. with near-UV light (310-400 nm) induced synthesis of a 21 000 dalton, cell-surface polypeptide. Synthesis of this polypeptide also was induced by visible light in the presence of photodynamic dyes, as shown previously (Hoober, 1978). Induction of the polypeptide in near-UV light and with visible light plus dyes was inhibited by histidine. Hemin inhibited induction in near-UV light and in visible light with methylene blue, neutral red and acrifiavin, which are cationic dyes, but failed to inhibit induction in visible light with rose bengal, an anionic dye. These results suggested that inhibition by hemin required electrostatically favored interaction between the anionic porphyrin and the sensitizer, and that the near-UV light effect was mediated by a cationic or neutral endogenous sensitizer. The similarities in the responses of the cells to near-UV irradiation and visible light plus dyes suggested that the mechanism of induction under the two conditions was the same.     

A POSSIBLE CONTROL BY A PHYTOCHROME-LIKE PHOTORECEPTOR OF CHLOROPHYLL SYNTHESIS IN THE GREEN ALGA Ulva rigida

Chlorophyll synthesis is stimulated by red light pulses in the green alga Ulva rigida C. Aghard. Chlorophyll synthesis in darkness is greater after longer red light pulses (30 min) than after shorter red light pulses (5 min). Chlorophyll synthesis was higher after red light pulses of 14 Wm_-2 fluence rate than after those of 7 Wm_-2. The effect of red light showed some far-red reversibility. The reversion by far-red light was higher after red light pulses of 4 min than after those of 30 min. These results indicate the existence of a rapid induction of chlorophyll synthesis during the red light pulses and a fast escape from photoreversibility. The percentage of reversion is also affected by the fluence rate of the light pulses. The reversion was reduced by about 15% when the photon fluence rate was increased from 7 to 14 Wm_-2. Reversion was also observed when red and far-red light pulses were applied successively. Thus, phytochrome or a phytochrome-like photoreceptor could be involved in the induction of chlorophyll synthesis in Ulva rigida.     

Sterilization system using microwave and UV light

We constructed a novel microwave–UV light sterilization system and investigated its sterilization effect. This sterilization system can emit UV light by irradiation of microwave without other power. When irradiating UV light with and/or without microwave on aqueous DMPO solution, active oxygen species such as hydroxyl radical or superoxide were generated in the solution. The amount of active oxygen species generated by irradiation of microwave and UV light was larger than that by irradiation of UV light alone. This would be due to the promotion of emission of UV light photons by microwave and UV light irradiation. Moreover, microwave–UV light sterilization was highly effective to sterilize microorganisms. The generation of active oxygen species would play an important role in sterilization of the sterilization system.     

SPECTRAL DEPENDENCE OF A SINGLE AND A SUBSEQUENT SECOND LIGHT PULSE INDUCING BARLEY LEAF UNFOLDING

The unfolding of etiolated barley leaves was induced by two short pulses of light separated by a dark interval. For certain wavelengths of light the effect of the “second light pulse was enhanced when the pulse was given after a 300–2000 s dark interval as compared with its effect when the two light pulses were given simultaneously. We investigated the spectral dependence of the effect of the first, inducing light flash and of the effect of the second Light flash given after a 500 s dark interval. The spectral actinity for the effect of the first flash showed phytochrome involvement. The spectral actinity for the effect of the second light flash, however, was shifted towards shorter wavelengths and the inductive action of red and far red light was attenuated.     

PHOTOTACTIC BEHAVIOR OF INDIVIDUAL CELLS OF CRYPTOMONAS SP. IN RESPONSE TO CONTINUOUS AND INTERMITTENT LIGHT STIMULI

Abstract— The phototactic response of cells of Cryptomonas sp. to stimulation with continuous or intermittent lateral light was determined by an individual cell method using photomicrography and videomicrography. The cells showed positive phototaxis under the conditions studied. The phototactic orientation of individual cells was induced most effectively by irradiation with light of 570 nm; blue light was less effective, and no orientation was found in red light. An intermittent stimulus regime with a long dark interval (250 ms) elicited a weaker phototactic orientation than did a regime with a short dark interval (63 ms) irrespective of the duration of light pulses (16, 250 and 1000 ms). The swimming rate was ca. 240 ums ^-1 and the rotation period ca. 450 ms in the dark, neither of which was greatly affected by stimulation with continuous or intermittent light. Neither step-up nor step-down photophobic responses were observed at the time of onset or removal of the light stimulus under the experimental conditions. The swimming direction of individual cells became gradually oriented toward the light source. Phototactic response was detectable within 4 s after the onset of light stimulation, reaching a saturation level after more than 30 s.     

SOME EFFECTS OF LIGHT ON LEAF GROWTH IN PISUM SATIVUM AND TROPAEOLUM MAJUS

Abstract— The effect of wave-length of light on leaf expansion in Tropaeolum majus 'Double Orange Gleam' and Pisurn sativum 'Meteor' has been studied. In both species leaf growth is strongly promoted by light.
Increasing the daily duration of exposure to light increased leaf expansion in Tropueolum in both blue and red wave-bands over a range of light intensities. In Pisum a similar effect of ail increase in duration of irradiation was found over the whole range of intensities used for blue light but only at the highest intensity for red light: at the two lower intensities in red an increase in duration of the light treatment beyond 1 hr did not increase leaf expansion.
In both species a period of 4 hr of blue followed by 4 hr of red promoted leaf growth more than 4 hr of red followed by 4 hr of blue. The effect of a 4 hr period of red light was largely prevented when it was followed by far-red; the effect of 4 hr of blue light, on the other hand, was not affected by subsequent exposure to far-red.
It is concluded that leaf growth in Pisum and Tropaeolum is dependent not only on the 'low-energy' red/far-red reversible reaction but also on one or more 'high-enerFy' photo-reactions.     

EFFECT OF PHYTOCHROME ON THE BIOSYNTHESIS OF ACYCLIC AND CYCLIC CAROTENOIDS IN HIGHER PLANTS

Radish plants were grown in the presence of three different herbicides that interfere with the formation of the normal range of cyclic carotenoids, leading to an accumulation of acyclic biosynthetic intermediates, mainly phytoene (SAN 6706 and amitrole) and zeta-carotene (3852). Plants were then irradiated by four different light programs in order to gain more insight into the first steps of carotenoid biosynthesis and their control by light and phytochrome. In all cases, herbicide-treated and control, carotenoid biosynthesis was greatly enhanced by red light consistent with an effect of phytochrome on the early steps of the pathway. However, similar enhancement was also obtained after treatment with far-red light. Indeed with SAN 6706-treated plants synthesis of phytoene was stimulated to a much greater extent by far-red light given alone, than by red light. The involvement of phytochrome in the regulation of carotenoid biosynthesis appears not to be as simple as previously supposed.     

Phase transition of layer structure of poly(1,4-benzenedithiol-co-1,4-diethynylbenzene) by photon mode

The effect of light wavelength on the phase transition of the layer structure of poly(1,4-benzenedithiol-co-1,4-diethynylbenzene) was studied under an air atmosphere at 18–22°C. The thin layer polymer crystals were prepared by solid state polymerization, and the amount of the layer structure was evaluated by an X-ray diagram. A monochromatic light with a wavelength in the region of ca. 500–600 nm was used as a light source. The amount of the layer structure was found to be altered by light. There were three characteristic wavelengths at 545.6, 567.8 and 590.1 nm, inducing pronounced peak intensities in the X-ray diagram. On the other hand, at 501.1, 539.6, 571.8 and 588.1 nm the light made the peak intensity decrease steeply. The phase transition was induced by a photon mode, but not by a heat mode. The amount of the layer structure was altered linearly with increasing irradiation time up to 60 min. However, over 60 min the change became dull. The total energy given to the polymers during the irradiation was about 24 X 10^?3 J/cm². Accordingly, the phase transition occurs with a high sensitivity to the light. The polymers were irradiated alternately by the light of 545.6 nm and 571.8 nm at intervals of 60 min, respectively. The amount of the layer structure was controlled reversibly by the light.     

Light-induced starch degradation in non-dormant turions of Spirodela polyrhiza

Continuous red light controls starch degradation in turions of Spirodela polyrhiza[Dölger, K., U. K. Tirlapur and K.‐J. Appenroth [1997]Photochem. Photobiol. 66, 126–127 (1997)]. This light could be replaced by repeated red light pulses with the reciprocity law fulfilled over a large range of fluence rates. The effect of red light pulses repeated every 24 or 12 h for 6 days was reversible by subsequent far‐red light pulses. In contrast, hourly applied red pulses were irreversible by far‐red light. This discrepancy was explained by showing the starch degradation activity of far‐red pulses themselves. The investigated process was categorized as a phytochrome low fluence response with an unusual property: requirement of light treatment for several days. A partial fulfillment of this requirement was obtained with a red pulse followed by a dark period and a 24 h continuous irradiation. These results suggest the existence of two separate steps in the process of starch degradation in turions: formation of a sprout (=sink) during the pulse‐induced germination, and starch degradation in the storage tissue (=source) induced by the second light treatment.     

Red and blue pulse timing control for pulse width modulation light dimming of light emitting diodes for plant cultivation

A pulse width modulation (PWM) light dimming system containing red and blue light emitting diodes was designed and constructed. Cultivation of the plant Arabidopsis thaliana under various light dimming wave patterns was compared. Control of the pulse timing (phase of wave pattern) between red and blue light in PWM light dimming was examined. Different plant growth was obtained by changing the phase of red and blue pulses. Pulse timing control of PWM light dimming for plant cultivation has the potential to act as a method for probing photosynthesis.     

PHYTOCHROME-MEDIATED PHOTOTROPISM IN PROTONEMATA OF THE MOSS Ceratodon purpureus BRID

Abstract— Protonemata of the moss Ceratodon purpureus cultured in white light were transferred to darkness for 3 days and then used for phototropic experiments. Irradiation of the apical region of vertically position protonemata with small beams (0.2 mm) of red light induced a growth response towards the irradiated side (positive phototropism). The phototropic response showed irradiance dependence. The effect of red light was completely reversed by far-red light following red light irradiations, demonstrating that phytochrome was the photoreceptor pigment. Far-red light or UV-blue light had no influence on either bulging or phototropism. Experiments with linearly polarized red or far-red light showed a different dichroic distribution of phytochrome in its different forms, the red-absorbing form, P_r and the far-red-absorbing form, P_fr. Red light with a vibration plane parallel to the long axis of the filaments was most effective. The effectiveness of far-red light was expressed best when its vibration plane was 90° to the electrical vector of the inductive red light.     

Evidence for a circadian rhythm of susceptibility to retinal light damage

This study investigated a possible circadian rhythm of light damage susceptibility in photoreceptors of both cyclic light-reared and dark-reared rats. A single exposure to intense green light was administered, beginning either in the early light period, the late light period or the dark period. In some animals exposed in the dark period, the synthetic antioxidant dimethylthiourea was administered before or after the onset of intense light exposure. Retinas were examined either immediately after exposure or after 2 weeks of recovery in darkness. Rod outer segment length and outer nuclear layer thickness measurements were used to assess light damage, along with qualitative analysis of swelling and disruption of the outer retinal layers. In all animals, retinal light damage was the most severe when intense light exposure began during the dark period. However, this severe damage was significantly reduced by pretreatment with the antioxidant. In a separate set of unexposed animals, fluctuations in plasma adrenocorticotropic hormone (ACTH) and corticosterone concentrations followed the same time course, regardless of the light regime during rearing. Our data support the notion of a circadian rhythm of light damage susceptibility that peaks in the dark period and yet can be modulated by the exogenous administration of an antioxidant.     

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.     

PHOTORECEPTOR PIGMENT IN Blepharisma: H+ RELEASE FROM RED PIGMENT

In faded cells of Blepharisma kept in a standard saline solution containing bacteria which had been cultured on agar plates containing glucose and polypepton, threshold light intensity for step-up photophobic response elevated. This result suggests that red pigment (blepharismin) contained in Blepharisma cells is involved in the step-up photophobic response. The pH of the aqueous solution of the red pigment was found to decrease when light was applied, indicating that the pigment releases H⁺ in response to light stimulation. However, faded pigment preparation by light irradiation did not show pH decrease. In the living cells faded by light irradiation, threshold light intensity for the step-up photophobic response was raised. Results suggest that H⁺ release from the red pigment induced by light irradiation might be responsible for the step-up photophobic response of the cells.