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At least 109 records · Page 6Linked to original sources
PubMed2006

Effects of red, far-red and blue light in maintaining growth in latitudinal populations of Norway spruce (Picea abies).

Seedlings of trees with a free growth pattern cease growth when night-lengths become shorter than a critical value, and this critical night-length (CNL) decreases with increasing latitude of origin. In northern populations, the light quality also appears to play an important role and a clinal variation in requirement for far-red (FR) light has been documented. In this study we dissected the light quality requirements for maintaining growth in different latitudinal populations of Norway spruce (Picea abies (L.) H. Karst.) using light emitting diodes for red (R), FR and blue (B) light, as 12 h day extension to provide 24 h photoperiod. At equal spectral photon flux, FR light was more effective than R light in maintaining growth, and the requirement of both R and FR increased with northern latitude of origin. One-to-one mixtures of R and FR light were more effective in maintaining growth than either FR or R light alone, indicating a possible interaction between R and FR light maintaining growth. Using the blue light as day extension could not prevent growth cessation in any of the populations, but delayed the bud set slightly in all populations. Our results suggest that phytochrome(s) are the primary photoreceptors in high irradiance responses maintaining growth in Norway spruce seedlings.

Light↗
PubMed2001

Phenylheptatriyne variation in Bidens alba var. radiata leaves.

Variation of phenylheptatriyne (PHT) in leaves of Bidens alba (Linn.) var. radiata (Shultz-Bip.) was investigated across its Florida range, throughout the year, and in response to the photoenvironment. A survey of PHT in B. alba leaves was done at 13 sites in Florida and three sites throughout the year. PHT concentrations differed among populations (P < 0.001), but little of the variation was explained by latitude (R2 = 0.024) or longitude (R2 = 0.022). Leaf concentrations of PHT fluctuated throughout the year (P < 0.001); they were highest in October and lowest in January and April. Experimental manipulations of light quality and quantity caused increased PHT accumulation when UV wavelengths were filtered out and decreased accumulation under low R/FR treatments. Low light levels did not significantly influence the concentration of PHT on a dry weight basis, but did decrease leaf biomass and PHT levels on a leaf area basis. The results suggest that PHT in B. alba leaves varies in nature and that light quality affects PHT biosynthesis in situ.

Alkynes↗
PubMed1993

Sugar and Organic Acid Accumulation in Guard Cells of Vicia faba in Response to Red and Blue Light.

Changes in neutral sugar and organic acid content of guard cells were quantitated by high-performance liquid chromatography during stomatal opening in different light qualities. Sonicated Vicia faba epidermal peels were irradiated with 10 [mu]mol m-2 s-1 of blue light, a fluence rate insufficient for the activation of guard cell photosynthesis, or 125 [mu]mol m-2 s-1 of red light, in the presence of 1 mM KCl, 0.1 mM CaCl2. The low-fluence-rate blue light stimulated an average net stomatal opening of 4.7 [mu]m in 2 h, whereas the saturating fluence rate of red light stimulated an average net opening of 3.8 [mu]m in 2 h. Under blue light, the malate content of guard cells increased to 173% of the initial level during the first 30 min of opening and declined as opening continued. Sucrose levels continuously rose throughout the blue light-stimulated opening, reaching 215% of the initial level after 2 h. The starch hydrolysis products maltose and maltotriose remained elevated at all times. Under red light, guard cells showed very little increase in organic acid or maltose levels, whereas sucrose levels increased to 208% of the initial level after 2 h. Total measured organic metabolite concentrations were correlated with stomatal apertures in all cases except where substantial malate increases occurred. These results support the hypothesis that light quality modulates alternative mechanisms of osmotic accumulation in guard cells, including potassium uptake, photosynthetic sugar production, and starch breakdown.

Journal Article↗
PubMed2006

Genome-wide analysis of light sensing in Prochlorococcus.

Prochlorococcus MED4 has, with a total of only 1,716 annotated protein-coding genes, the most compact genome of a free-living photoautotroph. Although light quality and quantity play an important role in regulating the growth rate of this organism in its natural habitat, the majority of known light-sensing proteins are absent from its genome. To explore the potential for light sensing in this phototroph, we measured its global gene expression pattern in response to different light qualities and quantities by using high-density Affymetrix microarrays. Though seven different conditions were tested, only blue light elicited a strong response. In addition, hierarchical clustering revealed that the responses to high white light and blue light were very similar and different from that of the lower-intensity white light, suggesting that the actual sensing of high light is mediated via a blue-light receptor. Bacterial cryptochromes seem to be good candidates for the blue-light sensors. The existence of a signaling pathway for the redox state of the photosynthetic electron transport chain was suggested by the presence of genes that responded similarly to red and blue light as well as genes that responded to the addition of DCMU [3-(3,4-dichlorophenyl)-1,1-N-N'-dimethylurea], a specific inhibitor of photosystem II-mediated electron transport.

Bacterial Proteins↗
PubMed1988

Photoreversibility of the Effect of Red and Green Light Pulses on the Accumulation in Darkness of mRNAs Coding for Phycocyanin and Phycoerythrin in Fremyella diplosiphon.

DNA fragments encoding a red light-inducible phycocyanin gene and a green light-inducible phycoerythrin gene have been used to investigate the effect of red and green pulses on the accumulation of phycocyanin and phycoerythrin mRNA in subsequent darkness. A red pulse promotes phycocyanin and suppresses phycoerythrin mRNA accumulation while a green pulse has an opposite effect on both transcript levels. The effect of a saturating light pulse is canceled by a subsequently given pulse of the other light quality. For a given mRNA, the positive and negative effects require the same fluence for saturation, whereas to saturate the phycoerythrin mRNA response requires at least twice as much light as to saturate the phycocyanin mRNA response. Calculations of the apparent extinction coefficients for the pigments mediating the light-regulated mRNA increase and decrease are of the order of 2 x 10(4) for phycocyanin mRNA and less than 10(4) for phycoerythrin mRNA. The data are consistent with the hypothesis that the light-induced increase and decrease of a particular phycobiliprotein mRNA is controlled by a single red/green photoreversible photosystem, but that phycoerythrin and phycocyanin mRNA levels are either controlled by two distinct photoreversible systems or that marked differences occur in the chain of events leading from photoperception to gene activation. These system(s) differ from most phytochrome systems in several ways: First, they remain fully on or off depending upon the light quality of the terminal irradiation. Second, they can be completely reversed by light of the appropriate wavelength after several hours of darkness without diminution of the effectiveness of the reversing light pulse. These two features argue against the existence of dark reversion or dark destruction of the biologically active moiety. Third, signal transduction is rapid-measurable mRNA changes occur even during a 10 minute irradiation.

Journal Article↗
PubMed2004

The influence of some different factors on the accuracy of shade selection.

The purpose of this study was to elucidate some of the factors on which accurate shade taking depends. Custom shade tabs (0.5, 1.0 and 1.5 mm porcelain thickness) were fabricated from selected Vita and Shofu porcelains. Four main factors were investigated, namely, the difference between the two types of porcelain used, the effect of light quality, the effect of porcelain thickness and the experience of the observer. The chi-square test for independence at a probability level of P <0.05 was used to analyse the results. The results indicated that in ideal light there was no difference between the two porcelains (P=0.58). The experienced observers proved better than the novice observers in ideal light conditions (P=0.003). Thickness was also significant in the overall results (P=0.0001), in that thicker samples gave more accurate results. The results indicate that in adverse light, there was an overall difference between the two porcelains (P=0.046), but no difference between the experienced and novice observers. The thickness made no difference to the experienced or the novice observer in adverse light. These results indicate that the most influential factor on shade taking was the light quality (P <0.0001); better results were obtained overall for the ideal light situation. In ideal light thicker samples gave better results (P=0.0001).

Clinical Competence↗
PubMed1990

Adjustments of photosystem stoichiometry in chloroplasts improve the quantum efficiency of photosynthesis.

The efficiency of photosynthetic electron transport depends on the coordinated interaction of photosystem II (PSII) and photosystem I (PSI) in the electron-transport chain. Each photosystem contains distinct pigment-protein complexes that harvest light from different regions of the visible spectrum. The light energy is utilized in an endergonic electron-transport reaction at each photosystem. Recent evidence has shown a large variability in the PSII/PSI stoichiometry in plants grown under different environmental irradiance conditions. Results in this work are consistent with the notion of a dynamic, rather than static, thylakoid membrane in which the stoichiometry of the two photosystems is adjusted and optimized in response to different light quality conditions. Direct evidence is provided that photosystem stoichiometry adjustments in chloroplasts are a compensation strategy designed to correct unbalanced absorption of light by the two photosystems. Such adjustments allow the plant to maintain a high quantum efficiency of photosynthesis under diverse light quality conditions and constitute acclimation that confers to plants a significant evolutionary advantage over that of a fixed photosystem stoichiometry in thylakoid membranes.

Journal Article↗
PubMed1999

Dynamic properties of endogenous phytochrome A in Arabidopsis seedlings.

The dynamic behavior of phytochrome A (phyA) in seedlings of the model plant Arabidopsis was examined by in vivo spectroscopy and by western and northern blotting. Rapid accumulation of phyA was observed, reaching a steady state after 3 d. Both red and far-red light initiated a rapid destruction of the far-red-light-absorbing form of phytochrome (Pfr); the apparent half-life was only 4-fold longer in far-red than in red light. Furthermore, the Pfr-induced destruction of the red-light-absorbing form of phytochrome (Pr) of phyA occurred in darkness with a rate identical to that of Pfr destruction. A 2-fold decrease in mRNA abundance was observed after irradiation, irrespective of the applied light quality. However, reaccumulation occurred rapidly after far-red but slowly after red irradiation, indicating different modes of regulation of phytochrome expression after light-dark transitions depending on the light quality of the preceding irradiation. The wavelength dependency of the destruction rates was distinct from that of mustard, a close relative of Arabidopsis, and was explained on the basis of Pfr-induced Pr destruction and a simple kinetic two-step model. No dark reversion was detectable in the destruction kinetics after a red pulse. From these data we conclude that Arabidopsis phyA differs significantly in several aspects from other dicot phytochromes.

Arabidopsis↗
PubMed1996

Effects of blue, red, and blue/red lights of two different PPF levels on growth and morphogenesis of lettuce plants.

To clarify the possibility of plant production under red and blue monochrome light using light emitting diodes (LEDs), the effects of light quality and photosynthetic photon flux (PPF) on the growth and morphogenesis of lettuce plants were examined. Lettuce plants were hydroponically grown for 20 days, under 3 different light qualities (Red, Blue and Red/Blue) and 2 PPF levels (about 85 and 170 micromoles/m2/s) for a l6hr day and an 8hr night cycle, at a temperature range of 20 to 22 degrees C. Irrespective of the two different PPF levels, the plants grown under the red LEDs developed more leaves than the plants under the blue LEDs, but less leaves than the plants under blue/red light. The curvature rate of the leaf margin in the plants grown under the blue LEDs was less than that of the plants under red LEDs on both PPF levels. The inclination angle of the seventh leaf in the plants grown under the blue LEDs and the blue/red fluorescence lamps was greater than that of the plants under red LEDs on the high PPF level. The whole plant dry weight was greater in the plants grown under the high PPF level than the plants under a low PPF level.

Biomass↗
PubMed1999

Light quality-dependent nuclear import of the plant photoreceptors phytochrome A and B

The phytochrome (phy) family of plant photoreceptors controls various aspects of photomorphogenesis. Overexpression of rice phyA-green fluorescent protein (GFP) and tobacco phyB-GFP fusion proteins in tobacco results in functional photoreceptors. phyA-GFP and phyB-GFP are localized in the cytosol of dark-adapted plants. In our experiments, red light treatment led to nuclear translocation of phyA-GFP and phyB-GFP, albeit with different kinetics. Red light-induced nuclear import of phyB-GFP, but not that of phyA-GFP, was inhibited by far-red light. Far-red light alone only induced nuclear translocation of phyA-GFP. These observations indicate that nuclear import of phyA-GFP is controlled by a very low fluence response, whereas translocation of phyB-GFP is regulated by a low fluence response of phytochrome. Thus, light-regulated nucleocytoplasmic partitioning of phyA and phyB is a major step in phytochrome signaling.

Journal Article↗
PubMedDate not supplied

[Ergonomics in planning and reconstruction].

The state of well being of people is not represented only by any illness, but also by the satisfaction of all environmental components around him. For this reason, the hospitals demand new and more project attentions and in particular they demand specific attentions for all the environmental qualities (light, colours, indoor air qualities, and temperature), the equipment, the furniture and the privacy. This new attention to the requirements of people, during the phase of planning, needs the ergonomic studies. This kind of discipline, in fact, has got the objective of good relationships between men and context where they live. The study of ergonomic qualities needs different competence of multiple areas of acquaintance, that collaborate to analyse the requirements of sanitary structure, and in particular they analyse needs of different categories of people that work or stay in this place (the patients, visitors and sanitary staff). Moreover ergonomic studies concurs to analyse the various factors of complexity, of the buildings, that are very important for the project of hospital. From the scientific literature, we say that some physical environmental characteristics (light, colour, noise,) can influence the psychological conditions of people, and in particular they can generate three different categories of reactions: behavioural, neuropsychological, neuroendocrinal. For this reason the study of all the environmental factors, simple and composed, is a primary necessity in the hospital planning. In this way we can guarantee to the patient, a better sanitary service and a better comfort, and we can guarantee to all sanitary staff adequate conditions of security and functionality.

Ergonomics↗
PubMed2001

Patient information in the light of quality assurance.

The relationship between patients and doctors has markedly changed over the last century. While until the turn of the 19th/20th century the patient was considered an object upon whom the doctor had the right to exert his art, the patient was then thought to have an integrity which the doctor could only legally injure with the consent of the patient. This was reflected in many court rulings, e.g. in Germany in 1894, requesting a doctor to inform the patient about therapy before performing surgery or even before giving medication, but also before performing invasive diagnostic procedures. The intensity of information required by law/court to be given to the patient varies also over time. Details of the implications to today's medical treatments are discussed.

Documentation↗
PubMed1999

Spaceflight hardware allowing unilateral irradiation and chemical fixation in petri dishes.

To accommodate a spaceflight experiment with moss (SPM), experiment-unique equipment (EUE) was developed by engineers at Kennedy Space Center. The hardware allows sterile culture for an extended period of time in commercial petri dishes, lateral illumination of each culture with light of a specific wavelength (660 nm; other wavelengths are possible) and a range of intensities (0.05-5 micromoles photons m-2 s-1), incubation in complete darkness, and chemical fixation to terminate the experiment under conditions of microgravity. The use of a fixative required triple containment to protect the astronaut crew. An external panel on the experiment container allowed the timing of illumination and fixation to be controlled by the crew. Light quality is provided by light emitting diodes (LEDs) that are located in the lid of the outer container, the BRIC (Biological Research In Canisters)-LED. Each canister accommodates 6 Petri Dish Fixation Units (PDFUs), and each PDFU holds one 6 cm petri dish. All components are autoclavable. LED illumination is piped through a transparent glass rod. Each PDFU contains fixative in a reservoir that is released by the depression of an actuator. This hardware performed well during its first flight, the 16-day STS-87 mission in Nov./Dec., 1997 as part of the Collaborative USA and Ukrainian Experiment (CUE). It supported vigorous and sterile moss growth, cells were maintained in position and were well-fixed, and there was a vigorous and consistent response to light. Although here used for moss, in future flight experiments this unique new hardware can be used for many types of organisms normally grown in petri dishes, with or without a requirement for illumination.

Bryopsida↗
PubMed1999

Visual discrimination: Seeing the third quality of light.

Objects can differ in brightness and colour. At least that is what our own visual system tells us. It now seems that stomatopod shrimps, and possibly also cephalopod molluscs, can see the direction of the electric vector of light, in much the same way we see colour.

Animals↗
PubMed1986

Developmental regulation of two genes encoding ribulose-bisphosphate carboxylase small subunit in pea and transgenic petunia plants: Phytochrome response and blue-light induction.

We describe the effects of light quality on the light-induced expression of two genes (rbcS-3A and rbcS-3C) encoding the ribulose-1,5-bisphosphate carboxylase small subunit of pea plants. These two genes exhibit distinctive photoresponses depending on the developmental stages of the leaves. In etiolated primary leaves, changes in the rbcS-3A and rbcS-3C transcript levels are regulated by phytochrome. In mature green leaves, on the other hand, the transcript levels are modulated by a putative blue-light photoreceptor working in concert with phytochrome. We transferred the two pea rbcS genes into the petunia genome and found that their phytochrome (rbcS-3A and -3C) and blue-light responses (rbcS-3C) are recapitulated in the appropriate developmental stages of the transgenic plants. Moreover, the transgenic plants express the pea rbcS genes in leaves at levels close to those in pea leaves. Our results show that 0.4 kilobases of the rbcS-3A and 2 kilobases of the rbcS-3C upstream regions are sufficient for these photoresponses.

Journal Article↗
PubMed1995

Use of edible coatings to preserve quality of lightly (and slightly) processed products.

Lightly processed agricultural products present a special problem to the food industry and to scientists involved in postharvest and food technology research. Light or minimal processing includes cutting, slicing, coring, peeling, trimming, or sectioning of agricultural produce. These products have an active metabolism that can result in deteriorative changes, such as increased respiration and ethylene production. If not controlled, these changes can lead to rapid senescence and general deterioration of the product. In addition, the surface water activity of cut fruits and vegetables is generally quite high, inviting microbial attack, which further reduces product stability. Methods for control of these changes are numerous and can include the use of edible coatings. Also mentioned in this review are coating of nut products, and dried, dehydrated, and freeze-dried fruits. Technically, these are not considered to be minimally processed, but many of the problems and benefits of coating these products are similar to coating lightly processed products. Generally, the potential benefits of edible coatings for processed or lightly processed produce is to stabilize the product and thereby extend product shelf life. More specifically, coatings have the potential to reduce moisture loss, restrict oxygen entrance, lower respiration, retard ethylene production, seal in flavor volatiles, and carry additives that retard discoloration and microbial growth.

Food Handling↗