Action Spectra for Stimulatory and Inhibitory Effects of UV and Blue Light on Fruit-Body Formation in Coprinus congregatus

Spectral sensitivity for stimulatory and inhibitory effectsof light on fruit-body formation in Coprinus congregatus wasdetermined between 250 and 730 nm using the Okazaki Large Spectrograph.Eight-day-old dark grown cultures were exposed to varying amountsof monochromatic photon fluences for 60 s. Primordial initiationwas strictly localized in the youngest hyphae of the culture.After a dark period of 24 h at 25C, the primordial initiationwas assayed by counting the number of primordia. The actionspectrum showed peaks of effectiveness at 260, 280, 370 and440 nm. The quantum effectiveness at 280 nm was 4 times higherthan that at 440 nm. The lethal effect of far UV (260–280nm) was demonstrated when using 100 times higher photon fluencesthan that inducing primordial formation. The primordia growing in continuous light required an uninterrupteddark period for 5 h at 25C to produce sporulating fruit-bodies.A brief exposure to light during the dark period inhibited thedevelopment of primordia. The action spectrum for this photoinhibitoryeffect showed maxima at 280, 350, 380, 440 and 460 nm. The quantumeffectiveness at 280 nm was Ca. 1.3 times higher than that ofblue light. The spectral sensitivities for primordial initiationand for inhibition of primordial development were quite similarand suggested a common photoreceptor during fruit-body morphogenesis. ⁴ Permanent address: Botany Department, Faculty of Science,University of Tokyo, Hongo, Tokyo 113, Japan.     

Adaptation of the Photosynthetic Apparatus of Chlorella and Ankistrodesmus to Blue and Red Light

The mode of adaptation of the photosynthetic apparatus of three unicellular green algae, Ankistrodesmus braunii, Chlorella fusca and Chlorella saccharophila to red and blue light are documented by the fluence-rate curves of photosynthetic oxygen evolution. For all three algae tested photosynthetic capacity, respiration and light compensation point were higher for cells grown under red light, while the chlorophyll content increased in blue light-grown cells. Blue light-adapted cells have a lower chlorophyll a to chlorophyll b ratio and more chlorophyll in the light-harvesting system than red light-adapted cells, as shown in the electrophoretic profile of the pigment-protein complexes. It is concluded that the action of red light resembles that of high levels of white light, while blue light causes the same effects as low levels of white light. In agreement with previous publications these findings indicate that the mode of adaptation to different light qualities is ubiquitous in unicellular green algae.     

Complementary Chromatic Adaptation in the Cyanobacterium, Tolypothrix tenuis: Location of Phycoerythrin Newly Synthesized by Green Illumination

Phycoerythrin (PE) formation in the dark induced by green preilluminationwas studied with the cyanobacterium Tolypothrix tenuis (IAMM29) with special attention to the localization of newly synthesizedPE. The initial synthesis of PE in the dark after preilluminationwas much faster than the formation of thylakoids indicated byChi increase. However, the amount of PE synthesized in thedark was far less than that needed for a complete change ofall phycobilisomes (PBS's) to the PBS containing PE at the maximumamount. These features give rise to questions as to whetherthe PE synthesized in the dark is located uniformly in everyPBS of every cell, or het-erogeneously in limited number ofcells, or PBS's newly divided or formed during the initial periodof the dark incubation. To solve the question, PE formationin individual cells was followed by a microscopic fluorometry,and at the same time, PE content in fractionated PBS was determined.Results indicated that (1) PE synthesis was induced uniformlyin every cell even by a limited dose of green light, and (2)PE was found in almost all PBS's. These results are interpretedas that newly synthesized PE is assembled in existing PBS, andthus, formation of PE-PBS induced by green light does not necessarilyrequire a new assembly of PBS. However exchange between PE andphycocyanin in peripheral rods of existing PBS probably occursat least in the initial phase of PE synthesis induced by greenlight. (Received August 16, 1990; Accepted February 27, 1991)     

Inhibitory Action of Blue and Far-Red Light in the Flowering of Lemna paucicostata

In a new strain of short-day duckweed (Lemna paucicostata T-101), blue and far-red light-induced inhibition of flowering was investigated. Flowering of this strain failed to be induced under a short-day photoperiod of blue and far-red light, although it responded as a typical short-day plant in red and white light. When the short-day photoperiod of blue or far-red light was terminated by a 15 min red light pulse, flowering recovered completely. This inducing effect of red light was reversed by subsequent exposure to far-red light. Furthermore, it could be demonstrated that 30 min of blue light completely reversed the flowering inductive effect of 5 min red light and vice versa. Evidence is presented suggesting that the inhibitory action of blue and far red light may be due to the lowering of phytochrome P_fr levels below those required to start the dark reactions which lead to flowering. These results are discussed in relation to the time measurement system of photoperiodism.     

Effects of Light on Chlorophyll Formation in Cultured Tobacco Cells II. Blue Light Effect on 5-Aminolevulinic Acid Formation

5-Aminolevulinic acid (ALA) accumulation in dark-grown tobaccocallus cells in the presence of levulinic acid (LA) was followedunder blue or red light or in continuous darkness. Significantformation of ALA continued in the dark. The protochlorophyll-(ide) (Pchl) content of dark-incubated cells remained low becauseof its turnover. We inferred that the feedback inhibition ofALA synthesis by Pchl would not occur in darkincubated calluscells. ALA formation was enhanced by blue light, and this effectreached saturation at an intensity of about 800 mW.m^–2.Neither weak nor strong red light affected ALA formation. Fullenhancement of ALA formation by blue light was attained afterfairly long continuous illumination of the callus cells. Thisblue lightenhanced activity of ALA synthesis declined very slowlyduring the subsequent dark incubation. The blue light enhancement of ALA formation was observed incallus cells supplied with sucrose over a wide range of concentrations.Pchl regeneration in carbon-starved callus cells, supplied withglutamate at various concentrations, was also markedly enhancedby blue light. Respiration of the callus cells was not enhancedby blue light. A possible role of blue light in regulating ALAformation in callus cells is discussed. ¹Dedicated to the late Professor Joji Ashida. (Received September 3, 1982; Accepted April 5, 1983)     

Photocontrol of the Functional Coupling between Photosynthesis and Stomatal Conductance in the Intact Leaf : Blue Light and Par-Dependent Photosystems in Guard Cells

The photocontrol of the functional coupling between photosynthesis and stomatal conductance in the leaf was investigated in gas exchange experiments using monochromatic light provided by lasers. Net photosynthesis and stomatal conductance were measured in attached leaves of Malva parviflora L. as a function of photon irradiance at 457.9 and 640.0 nanometers.

Photosynthetic rates and quantum yields of photosynthesis were higher under red light than under blue, on an absorbed or incident basis.

Stomatal conductance was higher under blue than under red light at all intensities. Based on a calculated apparent photon efficiency of conductance, blue and red light had similar effects on conductance at intensities higher than 0.02 millimoles per square meter per second, but blue light was several-fold more efficient at very low photon irradiances. Red light had no effect on conductance at photon irradiances below 0.02 millimoles per square meter per second. These observations support the hypothesis that stomatal conductance is modulated by two photosystems: a blue light-dependent one, driving stomatal opening at low light intensities and a photosynthetically active radiation (PAR)-dependent one operating at higher irradiances.

When low intensity blue light was used to illuminate a leaf already irradiated with high intensity, 640 nanometers light, the leaf exhibited substantial increases in stomatal conductance. Net photosynthesis changed only slightly. Additional far-red light increased net photosynthesis without affecting stomatal conductance. These observations indicate that under conditions where the PAR-dependent system is driven by high intensity red light, the blue light-dependent system has an additive effect on stomatal conductance.

The wavelength dependence of photosynthesis and stomatal conductance demonstrates that these processes are not obligatorily coupled and can be controlled by light, independent of prevailing levels of intercellular CO₂. The blue light-dependent system in the guard cells may function as a specific light sensor while the PAR-dependent system supplies a CO₂-modulated energy source providing functional coupling between the guard cells and the photosynthesizing mesophyll.

     

蓝光对绿豆下胚轴愈伤组织形成和生长过程中蛋白质代谢的影响

蓝光、白光和黑暗对绿豆下胚轴愈伤组织形成和生长过程中蛋白质代谢的影响不同。培养后３～１８ ｄ ,蓝光处理材料的可溶性蛋白质含量明显高于白光处理,更高于黑暗培养的材料。蓝光和白光明显促进３Ｈ亮氨酸掺入蛋白质,而蓝光和白光处理后游离氨基酸含量与黑暗对照相比,下降时间早,幅度大。在培养过程中,蛋白酶活性的变化与游离氨基酸相似。蛋白质合成抑制剂环己酰亚胺（ＣＨＭ） 抑制愈伤组织生长,其中以蓝光最大,白光次之,黑暗最小。在培养基中加入ＣＨＭ 愈早,抑制程度愈大。实验表明,ＣＨＭ 抑制愈伤组织蛋白质合成,也是以蓝光最甚。由此可见,蓝光促进绿豆下胚轴愈伤组织的形成、生长和蛋白质合成。     

Effects of Chromatic Adaptation on the Photochemical Apparatus of Photosynthesis in Porphyridium cruentum

Cells of Porphyridium cruentum were grown in different colors of light which would be absorbed primarily by chlorophyll (Chl) (red and blue light) or by the phycobilisomes (green or two intensities of cool-white fluorescent light), and samples of these cells were frozen to −196 C for measurements of absorption and fluorescence emission spectra. Cells grown in the high intensity white light had least of all of the photosynthetic pigments, a higher ratio of carotenoid/Chl, but essentially the same ratio of phycobilin to Chl as cells grown in the low intensity white light. The ratio of photosystem II (PSII) to photosystem I (PSI) pigments was affected by light quality; the ratios of phycobilin to Chl and of short wavelength (PSII) Chl to long wavelength (PSI) Chl were both greater in the cells grown in red or blue light.     

A Kinetic Model for Adaptation and the Light Responses of Phycomyces

A kinetic model is described consisting of two sequential first order processes connected by two parallel reaction pathways, one of which is light-catalyzed. A change in light flux changes the rate constant of the light-dependent process, whereupon the levels of two chemical intermediaries readjust. The model's output duplicates all the main features of the cell's light-growth and dark-growth responses except their latent periods. An asymmetric modification of the model reproduces the two types of phototropic inversion discovered by Reichardt and Varjú and by Dennison. Simple exponential equations describe these responses of the model, as well as the theoretical course of its light and dark adaptation. It is concluded that adaptation in Phycomyces consist in the photocatalytic adjustment of the level of a metabolic reservoir.     

On the Relationship between Photocontrol of Phycoerythrin Formation and Photoreversible Pigment of Scheibe

Dose-response of photocontrolled phycobiliprotein formationwas studied with two types of Tolypothrix tenuis cells havingdifferent content of photoreversible pigment (PRP) of Scheibe[cf. Scheibe (1972) Science 176: 1037]. PRP was not detectablein cells grown in a medium rich in nitrogen source under weakred light (normal cells) while the content was much larger (morethan 10 times) in cells incubated in light under nitrogen-deficientconditions [nitrogen-deficient cells, cf. Ohki and Fujita (1979)Plant & Cell Physiol. 20: 1341]. Both cells were found toform phycoerythrin (PE) in the dark after a short green illumination,while red illumination suppressed its formation. The amount of PE formation depended on the dose of green orred preillumination. Despite a large difference in content ofPRP of Scheibe, the dose-response of PE formation induced bygreen light was almost the same in both types of cells. Suppressionby red light in normal cells required a dose larger than thatin nitrogen-deficient cells. The results indicate that PRP ofScheibe formed during the incubation under nitrogen-deficientconditions does not act as the photoreceptor in photocontrolof PE formation. (Received September 29, 1980; Accepted January 6, 1981)     

Growth and Chromatic Adaptation of Nostoc sp. Strain MAC and the Pigment Mutant R-MAC

A spontaneous, stable, pigmentation mutant of Nostoc sp. strain MAC was isolated. Under various growth conditions, this mutant, R-MAC, had similar phycoerythrin contents (relative to allophycocyanin) but significantly lower phycocyanin contents (relative to allophycocyanin) than the parent strain. In saturating white light, the mutant grew more slowly than the parent strain. In nonsaturating red light, MAC grew with a shorter generation time than the mutant; however, R-MAC grew more quickly in nonsaturating green light.

When the parental and mutant strains were grown in green light, the phycoerythrin contents, relative to allophycocyanin, were significantly higher than the phycoerythrin contents of cells grown in red light. For both strains, the relative phycocyanin contents were only slightly higher for cells grown in red light than for cells grown in green light. These changes characterize both MAC and R-MAC as belonging to chromatic adaptation group II: phycoerythrin synthesis alone photocontrolled.

A comparative analysis of the phycobilisomes, isolated from cultures of MAC and R-MAC grown in both red and green light, was performed by polyacrylamide gel electrophoresis in the presence of 8.0 molar urea or sodium dodecyl sulfate. Consistent with the assignment of MAC and R-MAC to chromatic adaptation group II, no evidence for the synthesis of red light-inducible phycocyanin subunits was found in either strain. Phycobilisomes isolated from MAC and R-MAC contained linker polypeptides with relative molecular masses of 95, 34.5, 34, 32, and 29 kilodaltons. When grown in red light, phycobilisomes of the mutant R-MAC appeared to contain a slightly higher amount of the 32-kilodalton linker polypeptide than did the phycobilisomes isolated from the parental strain under the same conditions. The 34.5-kilodalton linker polypeptide was totally absent from phycobilisomes isolated from cells of either MAC or R-MAC grown in green light.

     

Action Spectrum in Ultraviolet and Blue Light Region for the Inhibition of Red-Light-Induced Spore Germination in Adiantum capillus-veneris L.

The action spectrum for the inhibition of red-light-inducedgermination of spores in the fern Adiantum capillus-veneriswas determined between 250 and 500 nm using the Okazaki largespectrograph. When monochromatic lights were given after red-lightirradiation, two prominent peaks for inhibition of spore germinationwere observed at 275 and 440 nm and a minor peak at ca. 390nm. ² Permanent address: Department of Botany, Faculty of Science,University of Tokyo, Hongo, Tokyo 113, Japan.     

A Comparison of Blue Light and Caffeine Effects on Cognitive Function and Alertness in Humans

The alerting effects of both caffeine and short wavelength (blue) light have been consistently reported. The ability of blue light to enhance alertness and cognitive function via non-image forming neuropathways have been suggested as a non-pharmacological countermeasure for drowsiness across a range of occupational settings. Here we compare and contrast the alerting and psychomotor effects of 240 mg of caffeine and a 1-h dose of ~40 lx blue light in a non-athletic population. Twenty-one healthy subjects performed a computer-based psychomotor vigilance test before and after each of four randomly assigned trial conditions performed on different days: white light/placebo; white light/240 mg caffeine; blue light/placebo; blue light/240 mg caffeine. The Karolinska Sleepiness Scale was used to assess subjective measures of alertness. Both the caffeine only and blue light only conditions enhanced accuracy in a visual reaction test requiring a decision and an additive effect was observed with respect to the fastest reaction times. However, in a test of executive function, where a distraction was included, caffeine exerted a negative effect on accuracy. Furthermore, the blue light only condition consistently outperformed caffeine when both congruent and incongruent distractions were presented. The visual reactions in the absence of a decision or distraction were also enhanced in the blue light only condition and this effect was most prominent in the blue-eyed participants. Overall, blue light and caffeine demonstrated distinct effects on aspects of psychomotor function and have the potential to positively influence a range of settings where cognitive function and alertness are important. Specifically, despite the widespread use of caffeine in competitive sporting environments, the possible impact of blue light has received no research attention.     

A Numerical Simulation of the Diffusion of Near Infrared Light Through Brain Tissue

A numerical simulation of the transport of light energy in the near infrared region of the spectrum through human brain tissue is presented. This simulation models the use of near infrared spectroscopic techniques to quantify the levels of oxygen present in brain tissue. Successful application of the technique requires knowledge of the optical pathlength in the tissue, and it is the goal of this simulation to quantify the relationship of the optical pathlength and the oxygenation state of the tissue. Both implicit and explicit finite element schemes for unstructured grids are implemented and discussed. Several application simulations using three tissue grids of varying degrees of physiological accuracy are then conducted, and figures for the optical pathlength of light through the tissue at varying levels of oxygenation are computed. These results are then used to develop a quantitative relationship between the pathlength and the absorption parameter for the three tissue models which we explore.     

Effects of Light Adaptation on the Temporal Resolution of Deep-sea Crustaceans

The effects of light adaptation on flicker fusion frequencywere examined in the photoreceptors of 13 species of deep-seacrustaceans. Light adaptation produced a significant increasein the maximum critical flicker fusion frequency (CFF_max) in7 species—all 6 species of euphausiids in the study, and1 species of oplophorid (Group 1). This is the first exampleof an increase in temporal resolution due to light adaptationin a deep-sea species. In the other six species—2 oplophorids,1 pandalid, 1 pasiphaeid, 1 penaeid and 1 sergestid (Group 2)—lightadaptation had no effect, or resulted in a decrease in the flickerfusion frequency. The mean dark-adapted CFF_max of the Group1 species was significantly higher, and the mean response latencysignificantly lower, than those of the Group 2 species. Possibleexplanations for these differences include the activity andbioluminescence mode of preferred prey items, as well as theretention of larval/juvenile adaptations in adult eyes.     

Chromatic Adaptation of the Planktonic Blue-green Alga Oscillatoria redekei VAN GOOR and its Ecological Significance

Natural populations and culture strains of Oscillatoria redekei isolated from the same lakes exhibit a great variety of phycoerythrine/phycocyanine ratios even under the same growth conditions. Cytophotometric and spectrophotometric determinations of the phycoerythrine and phycocyanine contents of different strains after exposure to blue-green and orange-red light, respectively, suggested that chromatic adaptation of O. redekei takes place both at cellular and population level. This wide intraspecific diversity is considered at least one reason for competitiveness in highly eutrophic lakes.     

Photo-Inhibition of Red-Light-Induced Spore Germination in Pteris vittata: Cyanide, Azide and Ethanol Counteracts Restorable Inhibitory Action of Near UV and Blue-light but not That of Far UV

In Pteris vittata, red-light-induction of spore germinationwas completely inhibited by subsequent irradiation with farUV (260 nm), near UV (380 nm) or blue (440 nm) monochromaticlight produced at the Okazaki Large Spectrograph. Germinationbut recovered from these photo-inhibition after less than 48h of darkness. Near UV- and blue-light-induced inhibition werestrongly counteracted by addition of 1 mM KCN, 1 RIM NaN₃ or100 mM ethanol. Far UV- and far red light-induced inhibition,however, was not influenced by these chemicals. Consequentlythe heights of peaks of action spectrum for this photo-inhibitionof spore germination was changed by addition of these chemicalsin the blue and near UV region but not at 260 nm. The resultssuggest that either or both of the photoreceptor system andthe signal transduction chain of the photo-inhibition are qualitativelydifferent between the shorter (i.e. far UV) and the longer (i.e.near UV and blue) wavelength regions. (Received August 31, 1989; Accepted February 19, 1990)