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Sample records for absorbed photosynthetic active

  1. Spectral estimators of absorbed photosynthetically active radiation in corn canopies

    NASA Technical Reports Server (NTRS)

    Gallo, K. P.; Daughtry, C. S. T.; Bauer, M. E.

    1984-01-01

    Most models of crop growth and yield require an estimate of canopy leaf area index (LAI) or absorption of radiation. Relationships between photosynthetically active radiation (PAR) absorbed by corn canopies and the spectral reflectance of the canopies were investigated. Reflectance factor data were acquired with a LANDSAT MSS band radiometer. From planting to silking, the three spectrally predicted vegetation indices examined were associated with more than 95% of the variability in absorbed PAR. The relationships developed between absorbed PAR and the three indices were evaluated with reflectance factor data acquired from corn canopies planted in 1979 through 1982. Seasonal cumulations of measured LAI and each of the three indices were associated with greater than 50% of the variation in final grain yields from the test years. Seasonal cumulations of daily absorbed PAR were associated with up to 73% of the variation in final grain yields. Absorbed PAR, cumulated through the growing season, is a better indicator of yield than cumulated leaf area index. Absorbed PAR may be estimated reliably from spectral reflectance data of crop canopies.

  2. Spectral estimators of absorbed photosynthetically active radiation in corn canopies

    NASA Technical Reports Server (NTRS)

    Gallo, K. P.; Daughtry, C. S. T.; Bauer, M. E.

    1985-01-01

    Most models of crop growth and yield require an estimate of canopy leaf area index (LAI) or absorption of radiation. Relationships between photosynthetically active radiation (PAR) absorbed by corn canopies and the spectral reflectance of the canopies were investigated. Reflectance factor data were acquired with a Landsat MSS band radiometer. From planting to silking, the three spectrally predicted vegetation indices examined were associated with more than 95 percent of the variability in absorbed PAR. The relationships developed between absorbed PAR and the three indices were evaluated with reflectance factor data acquired from corn canopies planted in 1979 through 1982. Seasonal cumulations of measured LAI and each of the three indices were associated with greater than 50 percent of the variation in final grain yields from the test years. Seasonal cumulations of daily absorbed PAR were associated with up to 73 percent of the variation in final grain yields. Absorbed PAR, cumulated through the growing season, is a better indicator of yield than cumulated leaf area index. Absorbed PAR may be estimated reliably from spectral reflectance data of crop canopies.

  3. Absorbed photosynthetically active radiation of steppe vegetation and sun-view geometry effects on APAR estimates

    NASA Technical Reports Server (NTRS)

    Walter-Shea, E. A.; Blad, B. L.; Mesarch, M. A.; Hays, C. J.; Deering, D. W.; Eck, T. F.

    1992-01-01

    Instantaneous fractions of absorbed photosynthetically active radiation (APAR) were measured at the Streletskaya Steppe Reserve in conjunction with canopy bidirectional-reflected radiation measured at solar zenith angles ranging between 37 and 74 deg during the Kursk experiment (KUREX-91). APAR values were higher for KUREX-91 than those for the first ISLSCP field experiment (FIFE-89) and the amount of APAR of a canopy was a function of solar zenith angle, decreasing as solar zenith angle increased at the resrve. Differences in absorption are attributed to leaf area index (LAI) and leaf angle distribution and subsequently transmitted radiation interactions. LAIs were considerably higher at the reserve than those at the FIFE site. Leaf angle distributions of the reserve approach a uniform distribution while distributions at the FIFE site more closely approximate erectophile distributions. Reflected photosynthetically active radiation (PAR) components at KUREX-91 and FIFE-89 were similar in magnitude and in their response to solar zenith angle. Transmitted PAR increased with increasing solar zenith angle at KUREX-91 and decreased with increasing solar zenith angle at FIFE-89. Transmitted PAR at FIFE-89 was considerably larger than those at KUREX-91.

  4. [Estimation of Fraction of Absorbed Photosynthetically Active Radiation for Winter Wheat Based on Hyperspectral Characteristic Parameters].

    PubMed

    Zhang, Chao; Cai, Huan-jie; Li, Zhi-jun

    2015-09-01

    Estimating fraction of absorbed photosynthetically active radiation (FPAR) precisely has great importance for detecting vegetation water content, energy and carbon cycle balance. Based on this, ASD FieldSpec 3 and SunScan canopy analyzer were applied to measure the canopy spectral reflectance and photosynthetically active radiation over whole growth stage of winter wheat. Canopy reflectance spectral data was used to build up 24 hyperspectral characteristic parameters and the correlation between FPAR and different spectral characteristic parameters were analyzed to establish the estimation model of FPAR for winter wheat. The results indicated that there were extremely significant correlations (p<0.01) between FPAR and hyperspectral characteristic parameters except the slope of blue edge (Db). The correlation coefficient between FPAR and the ratio of red edge area to blue edge area (VI4) was the highest, reaching at 0.836. Seven spectral parameters with higher correlation coefficient were selected to establish optimal linear and nonlinear estimation models of FPAR, and the best estimating models of FPAR were obtained by accuracy analysis. For the linear model, the inversin model between green edge and FPAR was the best, with R2, RMSE and RRMSE of predicted model reaching 0.679, 0.111 and 20.82% respectively. For the nonlinear model, the inversion model between VI2 (normalized ratio of green peak to red valley of reflectivity) and FPAR was the best, with R2, RMSE and RRMSE of predicted model reaching 0.724, 0.088 and 21.84% for. In order to further improve the precision of the model, the multiple linear regression and BP neural network methods were used to establish models with multiple high spectral parameters BP neural network model (R2=0.906, RMSE=0.08, RRMSE=16.57%) could significantly improve the inversion precision compared with the single variable model. The results show that using hyperspectral characteristic parameters to estimate FPAR of winter wheat is

  5. Inferring total canopy APAR from PAR bidirectional reflectances and vegetation indices in tallgrass prairie. [Absorbed Photosynthetically Active Radiation

    NASA Technical Reports Server (NTRS)

    Middleton, Elizabeth M.

    1992-01-01

    The fraction of photosynthetically active radiation (PAR) absorbed by a vegetated canopy (APARc) or landscape (APARs) is a critical parameter in climate processes. A grassland study examined: 1) whether APARs can be estimated from PAR bidirectional exitance fractions; and 2) whether APARs is correlated with spectral vegetation indices (SVIs). Data were acquired with a high resolution continuous spectroradiometer at 4 sun angles on grassland sites. APARs was computed from the scattered surface PAR exitance fractions. The nadir APARs value was the most variable diurnally; it provided a good estimate of the average surface APARs at 95 percent. APARc was best represented by exitance factors between 30-60* forward.

  6. Use of narrow-band spectra to estimate the fraction of absorbed photosynthetically active radiation

    NASA Technical Reports Server (NTRS)

    Hall, Forrest G.; Huemmrich, Karl F.; Goward, Samuel N.

    1990-01-01

    A novel approach is proposed for using high-spectral resolution imagers to estimate the fraction of photosynthetically active radiation adsorbed, f(apar), by vegetated land surfaces. In comparison to approaches using broad-band vegetation indices, the proposed method appears to be relatively insensitive to the reflectance of nonphotosynthetically active material beneath the canopy, such as leaf litter or soil. The method is based on a relationship between the second derivative of the reflectance vs wavelength function for terrestrial vegetation and f(apar). The relationship can be defined by the second derivatives in either of two windows, one in the visible region centered at 0.69 micron, another in the near-infrared region centered at 0.74 micron.

  7. Productivity, absorbed photosynthetically active radiation, and light use efficiency in crops: implications for remote sensing of crop primary production.

    PubMed

    Gitelson, Anatoly A; Peng, Yi; Arkebauer, Timothy J; Suyker, Andrew E

    2015-04-01

    Vegetation productivity metrics such as gross primary production (GPP) at the canopy scale are greatly affected by the efficiency of using absorbed radiation for photosynthesis, or light use efficiency (LUE). Thus, close investigation of the relationships between canopy GPP and photosynthetically active radiation absorbed by vegetation is the basis for quantification of LUE. We used multiyear observations over irrigated and rainfed contrasting C3 (soybean) and C4 (maize) crops having different physiology, leaf structure, and canopy architecture to establish the relationships between canopy GPP and radiation absorbed by vegetation and quantify LUE. Although multiple LUE definitions are reported in the literature, we used a definition of efficiency of light use by photosynthetically active "green" vegetation (LUE(green)) based on radiation absorbed by "green" photosynthetically active vegetation on a daily basis. We quantified, irreversible slowly changing seasonal (constitutive) and rapidly day-to-day changing (facultative) LUE(green), as well as sensitivity of LUE(green) to the magnitude of incident radiation and drought events. Large (2-3-fold) variation of daily LUE(green) over the course of a growing season that is governed by crop physiological and phenological status was observed. The day-to-day variations of LUE(green) oscillated with magnitude 10-15% around the seasonal LUE(green) trend and appeared to be closely related to day-to-day variations of magnitude and composition of incident radiation. Our results show the high variability of LUE(green) between C3 and C4 crop species (1.43 g C/MJ vs. 2.24 g C/MJ, respectively), as well as within single crop species (i.e., maize or soybean). This implies that assuming LUE(green) as a constant value in GPP models is not warranted for the crops studied, and brings unpredictable uncertainties of remote GPP estimation, which should be accounted for in LUE models. The uncertainty of GPP estimation due to facultative and

  8. Seasonal Variation in Fraction of Absorbed Photosynthetically Active Radiation and Vegetation Properties in Burned Forests in Interior Alaska

    NASA Astrophysics Data System (ADS)

    Iwata, H.; Harazono, Y.; Iwama, C.; Ueyama, M.

    2011-12-01

    Wildfire is a major disturbance in boreal forest ecosystems, and it significantly influences carbon exchange processes. It is important to explicitly incorporate burned areas in estimating regional carbon dioxide (CO2) exchange. A simple approach to quantify regional CO2 exchange is an application of a light-use efficiency model with satellite data. The model calculates CO2 uptake from light-use efficiency and absorbed photosynthetically active radiation (PAR). In the regional application, the fraction of absorbed PAR (FAPAR) provided from MODIS satellite data, together with incident PAR, is often used to calculate absorbed PAR. In spite of the importance of FAPAR in estimating CO2 uptake, an earlier study revealed that the MODIS FAPAR data are overestimated for a burned boreal forest. This study aims to provide ground truth data to validate MODIS FAPAR in other burned boreal forests. It also focuses on obtaining an empirical relationship to estimate seasonal and interannual variation in FAPAR from satellite data such as the normalized difference vegetation index (NDVI) in the early stage of recovery after wildfire. We observed incident, reflected, and transmitted PAR to obtain FAPAR in one- and six-year-old burned black spruce forests. Vegetation properties such as NDVI, leaf area index (LAI), and vegetation cover were also observed to explain seasonal variation of FAPAR. CO2 flux was also continuously monitored using the eddy covariance technique. The analysis showed that MODIS FAPAR was overestimated in the two burned forests, and the degree of overestimation was especially large for the younger burned forest. The relationship between FAPAR and NDVI was similar at the two burned forests, implying that this single relationship can be applied to estimate FAPAR from MODIS NDVI regardless of age after wildfire for the early stage of recovery.

  9. The 3D plant canopy radiative transfer analysis in an Alaskan black spruce forest: the characteristics of fraction of absorbed photosynthetically active radiation in the heterogeneous landscape

    NASA Astrophysics Data System (ADS)

    Kobayashi, H.; Suzuki, R.; Nagai, S.; Nakai, T.; Kim, Y.

    2012-12-01

    Over the last couple of decades, the three dimensional plant canopy radiative transfer models have been developed, improved and used for the retrievals of biophysical variables of vegetative surface. Fraction of absorbed photosynthetically active radiation (FAPAR) by plant canopy, a similar variable to heating rate in the atmosphere, is one of the important biophysical variables to infer the terrestrial plant canopy photosynthesis. FAPAR can be estimated by the radiative transfer model inversion or the empirical relationships between FAPAR and vegetation indices such as normalized difference vegetation index (NDVI). To date, some global FAPAR products are publicly available. These products are estimated from the moderate resolution satellites such as MODIS and SPOT-VEGETATION. One may apply the similar FAPAR algorithms to higher spatial resolution satellites if the ecosystem structures are horizontally homogeneous, which means that the adjacent satellite pixels have a similar spectral properties. If the vegetation surface is highly heterogeneous, "domain average FAPAR", which assumes no net horizontal radiation fluxes, can be unrealistically high (more than 1). In this presentation, we analyzed the characteristics of FAPAR in a heterogeneous landscape. As a case study, we selected our study site in a sparse black spruce forest in Alaska. We conducted the field campaigns to measure forest structural and optical properties that are used in the radiative transfer simulation. We used a 3D radiative transfer, FLiES (Kobayashi, H. and H. Iwabuchi (2008), A coupled 1-D atmosphere and 3-D canopy radiative transfer model for canopy reflectance, light environment, and photosynthesis simulation in a heterogeneous landscape, Remote Sensing of Environment, 112, 173-185) to create a high resolution simulated spectral reflectance and FAPAR images over the course of the growing season. From the analysis, we show (1) FAPAR with no net horizontal fluxes assumption can be higher than

  10. Phosphofructokinase Activities in Photosynthetic Organisms 1

    PubMed Central

    Carnal, Nancy Wieland; Black, Clanton C.

    1983-01-01

    A pyrophosphate-dependent phosphofructokinase (PPi-PFK) activity is detectable in extracts of a wide variety of primitive and advanced plants, the Charalean algae, and in the photosynthetic bacterium, Rhodospirillum rubrum. Angiosperms with extractable PPi-PFK activities 4- to 70-fold higher than the respective ATP-PFK activities tend to be succulent and to exhibit CAM. Even though PPi-PFK activity is not detected in crude extracts of some well known CAM plants, e.g. plants in the Crassulaceae, gel filtration of the extract and/or inclusion of the PPi-PFK activator, fructose 2,6-bisphosphate, in the assay reveals that a PPi-PFK activity is present in these species. Fructose 2,6-bisphosphate likewise activates PPi-PFK activities in extracts of C3 and C4 plants. C3 and C4 plant PPi-PFK activities are roughly equivalent to ATP-PFK activities in the same species. PPi-PFK activity is also detected in some bryophytes, lower vascular plants, ferns, and gymnosperms. The Charophytes, advanced algae presumed to be similar to species ancestral to vascular plants, exhibit at least 4-fold higher PPi-PFK than ATP-PFK activities. R. rubrum also exhibits a much higher PPi-PFK activity than ATP-PFK activity. These data indicate that PPi-PFK may serve as an alternate enzyme to ATP-PFK in glycolysis in a wide range of photosynthetic organisms. PMID:16662776

  11. Laser remote monitoring of plant photosynthetic activity

    NASA Astrophysics Data System (ADS)

    Barbini, Roberto; Colao, Francesco; Fantoni, Roberta; Palucci, Antonio; Ribezzo, Sergio

    1995-11-01

    Laboratory measurements of laser induced chlorophyll fluorescence kinetics (Kautsky effect) on dark-adapted vegetation targets (maize, pine-tree) have been performed with a lidar fluorosensor by superimposing probe pulses upon an actinic light. The collected induction curves (fast rise and slow decline) have been used to reveal the occurrence of stresses and the damage produced by a pine-tree parasite. A new two-pulse LIF (laser induced fluorescence) methodology has been investigated both theoretically and experimentally, in view of remotely monitoring the plant photosynthetic activity. This technique may yield information upon the in-vivo photosynthetic processes of plants, revealing a possible stress status (nutrients depletion, presence of herbicides, photoinhibition, etc.). The lidar apparatus used contains two laser sources in order to differentially measure the chlorophyll fluorescence by means of a laser pump-and-probe technique. In fact LIF signals in the red chlorophyll band 690 nm may provide in-vivo information upon photosynthesis process in high order plants and algae. Laser pump-and-probe experimental tests, with excitation 355 nm or 532 nm, already detect the presence of herbicides, and the effects of plant exposure to thermal stresses and to low levels of gaseous pollutants. Laser measured fluorescence yields (Y) have been found to be consistent with those obtained by an in-situ fluorimeter (PAM). With proper choices of experimental parameters (pump and probe laser intensities), Y approaches the theoretical value expected for a healthy dark-adapted plant.

  12. PAR (photosynthetically active radiation) conversion efficiencies of a tropical rain forest

    SciTech Connect

    Luxmoore, R.J.; Saldarriaga, J.G.

    1988-01-01

    The mean annual quantities of photosynthetically active radiation (PAR) absorbed during various stage of regeneration of a tropical rain forest in the upper Rio Negro region of Colombia and Venezuela were estimated for the intervals between clearcut and 1, 3, 10, 20, 35, 60, 80, and 200 years of growth. The forest phytomass and litterfall at each storage were from previous studies, and the data were used to calculate the mean annual quantity of net dry matter production per unit of absorbed PAR, the PAR conversion efficiency. 7 refs., 2 figs., 1 tab.

  13. Coral bleaching independent of photosynthetic activity.

    PubMed

    Tolleter, Dimitri; Seneca, François O; DeNofrio, Jan C; Krediet, Cory J; Palumbi, Stephen R; Pringle, John R; Grossman, Arthur R

    2013-09-23

    The global decline of reef-building corals is due in part to the loss of algal symbionts, or "bleaching," during the increasingly frequent periods of high seawater temperatures. During bleaching, endosymbiotic dinoflagellate algae (Symbiodinium spp.) either are lost from the animal tissue or lose their photosynthetic pigments, resulting in host mortality if the Symbiodinium populations fail to recover. The >1,000 studies of the causes of heat-induced bleaching have focused overwhelmingly on the consequences of damage to algal photosynthetic processes, and the prevailing model for bleaching invokes a light-dependent generation of toxic reactive oxygen species (ROS) by heat-damaged chloroplasts as the primary trigger. However, the precise mechanisms of bleaching remain unknown, and there is evidence for involvement of multiple cellular processes. In this study, we asked the simple question of whether bleaching can be triggered by heat in the dark, in the absence of photosynthetically derived ROS. We used both the sea anemone model system Aiptasia and several species of reef-building corals to demonstrate that symbiont loss can occur rapidly during heat stress in complete darkness. Furthermore, we observed damage to the photosynthetic apparatus under these conditions in both Aiptasia endosymbionts and cultured Symbiodinium. These results do not directly contradict the view that light-stimulated ROS production is important in bleaching, but they do show that there must be another pathway leading to bleaching. Elucidation of this pathway should help to clarify bleaching mechanisms under the more usual conditions of heat stress in the light.

  14. Optimum combinations of visible and near-infrared reflectances for estimating the fraction of photosynthetically available radiation absorbed by plants

    NASA Technical Reports Server (NTRS)

    Podaire, Alain; Deschamps, Pierre-Yves; Frouin, R.; Asrar, Ghassem

    1991-01-01

    A useful parameter to estimate terrestrial primary productivity, that can be sensed from space, is the daily averaged fraction of Photosynthetically Available Radiation (PAR) absorbed by plants. To evaluate this parameter, investigators have relied on the fact that the relative amount of radiation reflected by a vegetated surface in the visible and near infrared depends on the fraction of the surface covered by the vegetation and therefore, correlates with absorbed PAR. They have used vegetation indices, namely normalized difference and simple ratio, to derive absorbed PAR. The problem with normalized difference and simple ratio is first, they are non linear functions of radiance or reflectance and therefore, cannot be readily applied to heterogeneous targets, second, they are used in generally nonlinear relationships, which make time integrals of the indices not proportional to primary productivity, and third, the relationships depend strongly on the type of canopy and background. To remove these limitations, linear combinations of visible and near infrared reflectances at optimum (one or two) viewing zenith angles are proposed.

  15. Optimal active vibration absorber: Design and experimental results

    NASA Technical Reports Server (NTRS)

    Lee-Glauser, Gina; Juang, Jer-Nan; Sulla, Jeffrey L.

    1992-01-01

    An optimal active vibration absorber can provide guaranteed closed-loop stability and control for large flexible space structures with collocated sensors/actuators. The active vibration absorber is a second-order dynamic system which is designed to suppress any unwanted structural vibration. This can be designed with minimum knowledge of the controlled system. Two methods for optimizing the active vibration absorber parameters are illustrated: minimum resonant amplitude and frequency matched active controllers. The Controls-Structures Interaction Phase-1 Evolutionary Model at NASA LaRC is used to demonstrate the effectiveness of the active vibration absorber for vibration suppression. Performance is compared numerically and experimentally using acceleration feedback.

  16. Quantifying reflectance anisotropy of photosynthetically active radiation in grasslands

    NASA Technical Reports Server (NTRS)

    Middleton, Elizabeth M.

    1992-01-01

    Quantifying the vegetative surface's reflectance anisotropy was an important part of the First ISLSCP Field Experiment, as its major objectives focused on retrieval of surface parameters from satellite-derived reflectances. The explicit remote measurements for approximating the bidirectional reflectance distribution function (BRDF) of photosynthetically active radiation had not been previously undertaken. In this paper the proper expression of reflectance for BRDFs for retrieval of canopy parameters is assessed.

  17. Ferrochelatase activity in the photosynthetic alga Cyanidium caldarium. Development of the enzyme during biosynthesis of photosynthetic pigments.

    PubMed Central

    Brown, S B; Holroyd, J A; Vernon, D I; Jones, O T

    1984-01-01

    Dark-grown cells of the photosynthetic alga Cyanidium caldarium were shown to contain ferrochelatase activity, which increased markedly when the cells were induced to form pigments by exposure to light. Km values for the crude enzyme preparation were 14.8 microM and 6.5 microM for binding of Co2+ and deuteroporphyrin IX respectively. PMID:6466309

  18. [Pigment composition and photosynthetic activity of pea chlorophyll mutants].

    PubMed

    Ladygin, V G

    2003-01-01

    Pea chlorophyll mutants chlorotica 2004 and 2014 have been studied. The mutants differ from the initial form (pea cultivar Torsdag) in stem and leaf color (light green in the mutant 2004 and yellow-green in the mutant 2014), relative chlorophyll content (approximately 80 and 50%, respectively), and the composition of carotenoids: the mutant 2004 contains a significantly smaller amount of carotene but accumulates more lutein and violaxanthine; in the mutant 2014, the contents of all carotenoids are decreased proportionally to the decrease in chlorophyll content. It is shown that the rates of CO2 assimilation and oxygen production in the mutant chlorotica 2004 and 2014 plants are reduced. The quantum efficiency of photosynthesis in the mutants is 29-30% lower than in the control plants; in their hybrids, however, it is 1.5-2 higher. It is proposed that both the greater role of dark respiration in gas exchange and the reduced photosynthetic activity in chlorotica mutants are responsible for the decreased phytomass increment in these plants. On the basis of these results, the conclusion is drawn that the mutations chlorotica 2004 and 2014 affect the genes controlling the formation and functioning of various components of the photosynthetic apparatus.

  19. Quantifying reflectance anisotropy of photosynthetically active radiation in grasslands

    SciTech Connect

    Middleton, E.M. )

    1992-11-30

    This work is part of the First International Satellite Land Surface Climatology Project (ISLSCP) Field Experiment (FIFE), an international land-surface-atmosphere experiment aimed at improving the way climate models represent energy, water, heat, and carbon exchanges, and improving the utilization of satellite based remote sensing to monitor such parameters. This paper reports on a study to quantify the reflectance anisotropy of the photosynthetically active radiation (PAR) for grasslands. PAR falls in the wavelength range 0.4 to 0.7[mu]m. The study looks at the variation of PAR with illumination and vegetative canopy conditions. It uses bidirectional reflectance distribution function data, and measures of anisotropy derived from reflectance factor and reflectance fraction data to aid in the analysis. The data used for this analysis came from an intense effort mounted to measure diurnal changes in the anisotropy of surface reflectance from prairie grassland as a function of the vegetative canopy.

  20. Intercepted photosynthetically active radiation estimated by spectral reflectance

    NASA Technical Reports Server (NTRS)

    Hatfield, J. L.; Asrar, G.; Kanemasu, E. T.

    1984-01-01

    Interception of photosynthetically active radiation (PAR) was evaluated relative to greenness and normalized difference (MSS (7-5)/(7+5) for five planting dates of wheat for 1978-79 and 1979-80 at Phoenix, Arizona. Intercepted PAR was calculated from leaf area index and stage of growth. Linear relatinships were found with greeness and normalized difference with separate relatinships describing growth and senescence of the crop. Normalized difference was significantly better than greenness for all planting dates. For the leaf area growth portion of the season the relation between PAR interception and normalized difference was the same over years and planting dates. For the leaf senescence phase the relationships showed more variability due to the lack of data on light interception in sparse and senescing canopies. Normalized difference could be used to estimate PAR interception throughout a growing season.

  1. Photosynthetic response of Nodularia spumigena to UV and photosynthetically active radiation depends on nutrient (N and P) availability.

    PubMed

    Roleda, Michael Y; Mohlin, Malin; Pattanaik, Bagmi; Wulff, Angela

    2008-11-01

    Biomass of N. spumigena is distributed within the dynamic photic zone that changes in both light quantity and quality. This study was designed to determine whether nutrient status can mitigate the negative impacts of experimental radiation treatments on the photosynthetic performance of N. spumigena. Cyanobacterial suspensions were exposed to radiation consisting of photosynthetically active radiation (PAR=400-700 nm), PAR+UV-A (=PA, 320-700 nm), and PAR+UV-A+UV-B (=PAB, 280-700 nm) under different nutrient media either replete with external dissolved nitrate (N) and orthophosphate (P; designated as +N/+P), replete with P only (-N/+P), or replete with N only (+N/-P). Under low PAR (75 micromol photons m(-2) s(-1)), nutrient status had no significant effect on the photosynthetic performance of N. spumigena in terms of rETRmax, alpha, and E(k). Nodularia spumigena was able to acclimate to high PAR (300 micromol photons m(-2) s(-1)), with a corresponding increase in rETRmax and E(k). The photosynthetic performance of N. spumigena cultured with supplemental nitrogen was more susceptible to experimental PAR irradiance. Under UVR, P-enrichment in the absence of additional external N (-N/+P) induced lower photoinhibition of photosynthesis compared with +N/-P cultures. However, the induction of NPQ may have provided PSII protection under P-deplete and PAR+UVR conditions. Because N. spumigena are able to fix nitrogen, access to available P can render them less susceptible to photoinhibition, effectively promoting blooms. Under a P-deficient condition, N. spumigena were more susceptible to radiation but were capable of photosynthetic recovery immediately after removal of radiation stress. In the presence of an internal P pool in the Baltic Sea, which may be seasonally available to the diazotrophic cyanobacteria, summer blooms of the resilient N. spumigena will persist. PMID:18754779

  2. Energy transfer in light-adapted photosynthetic membranes: from active to saturated photosynthesis.

    PubMed

    Fassioli, Francesca; Olaya-Castro, Alexandra; Scheuring, Simon; Sturgis, James N; Johnson, Neil F

    2009-11-01

    In bacterial photosynthesis light-harvesting complexes, LH2 and LH1 absorb sunlight energy and deliver it to reaction centers (RCs) with extraordinarily high efficiency. Submolecular resolution images have revealed that both the LH2:LH1 ratio, and the architecture of the photosynthetic membrane itself, adapt to light intensity. We investigate the functional implications of structural adaptations in the energy transfer performance in natural in vivo low- and high-light-adapted membrane architectures of Rhodospirillum photometricum. A model is presented to describe excitation migration across the full range of light intensities that cover states from active photosynthesis, where all RCs are available for charge separation, to saturated photosynthesis where all RCs are unavailable. Our study outlines three key findings. First, there is a critical light-energy density, below which the low-light adapted membrane is more efficient at absorbing photons and generating a charge separation at RCs, than the high-light-adapted membrane. Second, connectivity of core complexes is similar in both membranes, suggesting that, despite different growth conditions, a preferred transfer pathway is through core-core contacts. Third, there may be minimal subareas on the membrane which, containing the same LH2:LH1 ratio, behave as minimal functional units as far as excitation transfer efficiency is concerned.

  3. Seasonal photosynthetic activity in evergreen conifer leaves monitored with spectral reflectance

    NASA Astrophysics Data System (ADS)

    Wong, C. Y.; Gamon, J. A.

    2013-12-01

    Boreal evergreen conifers must maintain photosynthetic systems in environments where temperatures vary greatly across seasons from high temperatures in the summer to freezing levels in the winter. This involves seasonal downregulation and photoprotection during periods of extreme temperatures. To better understand this downregulation, seasonal dynamics of photosynthesis of lodgepole (Pinus contorta D.) and ponderosa pine (Pinus ponderosa D.) were monitored in Edmonton, Canada over two years. Spectral reflectance at the leaf and stand scales was measured weekly and the Photochemical Reflectance Index (PRI), often used as a proxy for chlorophyll and carotenoid pigment levels and photosynthetic light-use efficiency (LUE), was used to track the seasonal dynamics of photosynthetic activity. Additional physiological measurements included leaf pigment content, chlorophyll fluorescence, and gas exchange. All the metrics indicate large seasonal changes in photosynthetic activity, with a sharp transition from winter downregulation to active photosynthesis in the spring and a more gradual fall transition into winter. The PRI was a good indicator of several other variables including seasonally changing photosynthetic activity, chlorophyll fluorescence, photosynthetic LUE, and pigment pool sizes. Over the two-year cycle, PRI was primarily driven by changes in constitutive (chlorophyll:carotenoid) pigment levels correlated with seasonal photosynthetic activity, with a much smaller variation caused by diurnal changes in xanthophyll cycle activity (conversion between violaxanthin & zeaxanthin). Leaf and canopy scale PRI measurements exhibited parallel responses during the winter-spring transition. Together, our findings indicate that evergreen conifers photosynthetic system possesses a remarkable degree of resilience in response to large temperature changes across seasons, and that optical remote sensing can be used to observe the seasonal effects on photosynthesis and

  4. PARduino: A Simple Device Measuring and Logging Photosynthetically Active Radiation

    NASA Astrophysics Data System (ADS)

    Barnard, H. R.; Findley, M. C.

    2013-12-01

    Photosynthetically Active Radiation (PAR, 400 to 700 nm) is one of the primary controls of forest carbon and water relations. In complex terrain, PAR has high spatial-variability. Given the high cost of commercial datalogging equipment, spatially-distributed measurements of PAR have been typically modeled using geographic coordinates and terrain indices. Here, we present a design for a low cost, field-deployable device for measuring and logging PAR built around an Arduino microcontroller (we named it PARduino). PARduino provides for widely distributed sensor arrays and tests the feasibility of using hobbyist-grade electronics for collecting scientific data. PARduino components include a LiCor quantum sensor, EME Systems signal converter/amplifier, and Sparkfun's Arduino Pro Mini microcontroller. Additional components include a real time clock, a microSD flash memory card, and a custom printed circuit board (PCB). We selected the components with an eye towards ease of assembly. Everything can be connected to the PCB using through-hole soldering techniques. Since the device will be deployed in remote research plots that lack easy access to line power, battery life was also a consideration in the design. Extended deployment is possible because PARduino's software keeps it in a low-power sleep mode until ready to make a measurement. PARduino will be open-source hardware for use and improvement by others.

  5. Photosynthetic Adaptation to Length of Day Is Dependent on S-Sulfocysteine Synthase Activity in the Thylakoid Lumen1[W

    PubMed Central

    Bermúdez, María Ángeles; Galmés, Jeroni; Moreno, Inmaculada; Mullineaux, Philip M.; Gotor, Cecilia; Romero, Luis C.

    2012-01-01

    Arabidopsis (Arabidopsis thaliana) chloroplasts contain two O-acetyl-serine(thiol)lyase (OASTL) homologs, OAS-B, which is an authentic OASTL, and CS26, which has S-sulfocysteine synthase activity. In contrast with OAS-B, the loss of CS26 function resulted in dramatic phenotypic changes, which were dependent on the light treatment. We have performed a detailed characterization of the photosynthetic and chlorophyll fluorescence parameters in cs26 plants compared with those of wild-type plants under short-day growth conditions (SD) and long-day growth conditions (LD). Under LD, the photosynthetic characterization, which was based on substomatal CO2 concentrations and CO2 concentration in the chloroplast curves, revealed significant reductions in most of the photosynthetic parameters for cs26, which were unchanged under SD. These parameters included net CO2 assimilation rate, mesophyll conductance, and mitochondrial respiration at darkness. The analysis also showed that cs26 under LD required more absorbed quanta per driven electron flux and fixed CO2. The nonphotochemical quenching values suggested that in cs26 plants, the excess electrons that are not used in photochemical reactions may form reactive oxygen species. A photoinhibitory effect was confirmed by the background fluorescence signal values under LD and SD, which were higher in young leaves compared with mature ones under SD. To hypothesize the role of CS26 in relation to the photosynthetic machinery, we addressed its location inside of the chloroplast. The activity determination and localization analyses that were performed using immunoblotting indicated the presence of an active CS26 enzyme exclusively in the thylakoid lumen. This finding was reinforced by the observation of marked alterations in many lumenal proteins in the cs26 mutant compared with the wild type. PMID:22829322

  6. A New Quantum Sensor for Measuring Photosynthetically Active Radiation

    NASA Astrophysics Data System (ADS)

    Johnson, D.; Thomas, T.; Heinicke, D.; Peterson, R.; Morgan, P.; McDermitt, D. K.; Burba, G. G.

    2015-12-01

    A quantum sensor measures photosynthetically active radiation (PAR, in μmol of photons m-2 s-1) in the 400 nm to 700 nm waveband. Plants utilize this radiation to drive photosynthesis, though individual plant responses to incident radiation may vary within this range. The new quantum sensor (model LI-190R, LI-COR Biosciences, Lincoln, NE), with an optical filter and silicon photodiode detector housed in a cosine-corrected head, is designed to provide a better response to incident radiation across the 400-700 nm range. The new design is expected to significantly improve spectral response due to uniformity across the PAR waveband, but particularly in the wavebands from 520 nm to 600 nm and 665 nm to 680 nm, and sharp cutoffs in the regions below and above the PAR waveband. Special care was taken to make sure that PAR sensor would not substantially respond to incident radiation above the 700 nm threshold because this can lead to errors when performing measurements in environments with a large proportion of near-infrared radiation, such as canopy understory. The physical housing of the sensor is designed to be weather-resistant, to effectively shed precipitation, provide protection at high temperature and high humidity conditions, and has a cosine-corrected response to 82° zenith angle. The latter is particularly important when measuring incident radiation at low elevation angles, diffuse light, or low light conditions. This presentation describes the principles of the new design, and shows the performance results from field experiments and laboratory tests.

  7. Dynamic response of UV-absorbing compounds, quantum yield and the xanthophyll cycle to diel changes in UV-B and photosynthetic radiations in an aquatic liverwort.

    PubMed

    Fabón, Gabriel; Monforte, Laura; Tomás-Las-Heras, Rafael; Núñez-Olivera, Encarnación; Martínez-Abaigar, Javier

    2012-01-01

    We studied the diel responses of the liverwort Jungermannia exsertifolia subsp. cordifolia to radiation changes under laboratory conditions. The samples were exposed to three radiation regimes: P (only PAR), PA (PAR+UV-A), and PAB (PAR+UV-A+UV-B). The day was divided in four periods: darkness, a first low-PAR period, the high-PAR plus UV period, and a second low-PAR period. After 15 days of culture, we measured photosynthetic pigments, chlorophyll fluorescence and UV-absorbing compounds in the four periods of the day on two consecutive days. With respect to UV-absorbing compounds, we analyzed their global amount (as the bulk UV absorbance of methanolic extracts) and the concentration of seven hydroxycinnamic acid derivatives, both in the soluble (mainly vacuolar) and insoluble (cell wall-bound) fractions of the plant extracts. PAB samples increased the bulk UV absorbance of the soluble and insoluble fractions, and the concentrations of p-coumaroylmalic acid in the soluble fraction and p-coumaric acid in the cell wall. Most of these variables showed significant diel changes and responded within a few hours to radiation changes (more strongly to UV-B), increasing at the end of the period of high-PAR plus UV. F(v)/F(m), Φ(PSII), NPQ and the components of the xanthophyll cycle showed significant and quick diel changes in response to high PAR, UV-A and UV-B radiation, indicating dynamic photoinhibition and protection of PSII from excess radiation through the xanthophyll cycle. Thus, the liverwort showed a dynamic protection and acclimation capacity to the irradiance level and spectral characteristics of the radiation received.

  8. Temporal variation in photosynthetic pigments and UV-absorbing compounds in shallow populations of two Hawaiian reef corals

    USGS Publications Warehouse

    Kuffner, I.B.

    2005-01-01

    As we seek to understand the physiological mechanisms of coral bleaching, it is important to understand the background temporal variation in photosynthetic pigments and photoprotective compounds that corals exhibit. In this study, reef flat populations of two hermatypic coral species, Montipora capitata (Dana, 1846) and Porites compressa Dana, 1846, were sampled monthly in Kane'ohe Bay, Hawai'i, from January 1998 to March 1999. Surface ultraviolet radiation (UVR) was measured continually during this time period at the same location. High-performance liquid chromatography (HPLC) analysis of photosynthetic pigments and mycosporine-like amino acids (MAAs) revealed temporal changes in concentrations and proportions of these compounds in tissues of both species of coral. Chlorophyll a (chl a), chlorophyll c2 (chl c2), peridinin, and diadinoxanthin concentrations changed on a skeletal weight (M. capitata) or surface area (P. compressa) basis, significantly correlating with seasonal changes in solar input (number of days from the winter solstice). In P. compressa, diadinoxanthin increased in proportion to the total pigment pool during summer months, suggesting an up-regulation of a xanthophyll cycle. In M. capitata, the ratio of chl a: chl c2 decreased during winter months, suggesting photoacclimation to lower light levels. It is surprising that there was not a clear seasonal pattern in total MAA concentration for either species, with the exception of shinorine in P. compressa. The relative stability of MAA concentrations over the course of the year despite a pronounced seasonal trend in UVR suggests either that MAAs are not performing a photoprotective role in these species or that concentrations are kept at a threshold level in the presence of a dynamic light environment. ?? 2005 by University of Hawai'i Press All rights reserved.

  9. Wireless device for activation of an underground shock wave absorber

    NASA Astrophysics Data System (ADS)

    Chikhradze, M.; Akhvlediani, I.; Bochorishvili, N.; Mataradze, E.

    2011-10-01

    The paper describes the mechanism and design of the wireless device for activation of energy absorber for localization of blast energy in underground openings. The statistics shows that the greatest share of accidents with fatal results associate with explosions in coal mines due to aero-methane and/or air-coal media explosion. The other significant problem is terrorist or accidental explosions in underground structures. At present there are different protective systems to reduce the blast energy. One of the main parts of protective Systems is blast Identification and Registration Module. The works conducted at G. Tsulukidze Mining Institute of Georgia enabled to construct the wireless system of explosion detection and mitigation of shock waves. The system is based on the constant control on overpressure. The experimental research continues to fulfill the system based on both threats, on the constant control on overpressure and flame parameters, especially in underground structures and coal mines. Reaching the threshold value of any of those parameters, the system immediately starts the activation. The absorber contains a pyrotechnic device ensuring the discharge of dispersed water. The operational parameters of wireless device and activation mechanisms of pyrotechnic element of shock wave absorber are discussed in the paper.

  10. Estimation of Evapotranspiration as a function of Photosynthetic Active Radiation

    NASA Astrophysics Data System (ADS)

    Wesley, E.; Migliaccio, K.; Judge, J.

    2012-12-01

    The purpose of this research project is to more accurately measure the water balance and energy movements to properly allocate water resources at the Snapper Creek Site in Miami-Dade County, FL, by quantifying and estimating evapotranspiration (ET). ET is generally estimated using weather based equations, this project focused on estimating ET as a function of Photosynthetic Active Radiation (PAR). The project objectives were first to compose a function of PAR and calculated coefficients that can accurately estimate daily ET values with the least amount of variables used in its estimation equation, and second, to compare the newly identified ET estimation PAR function to TURC estimations, in comparison to our actual Eddy Covariance (EC) ET data and determine the differences in ET values. PAR, volumetric water content (VWC), and temperature (T) data were quality checked and used in developing singular and multiple variable regression models fit with SigmaPlot software. Fifteen different ET estimation equations were evaluated against EC ET and TURC estimated ET using R2 and slope factors. The selected equation that best estimated EC ET was cross validated using a 5 month data set; its daily and monthly ET values and sums were compared against the commonly used TURC equation. Using a multiple variable regression model, an equation with three variables (i.e., VWC, T, and PAR) was identified that best fit EC ET daily data. However, a regression was also found that used only PAR and provided ET predictions of similar accuracy. The PAR based regression model predicted daily EC ET more accurately than the traditional TURC method. Using only PAR to estimate ET reduces the input variables as compared to using the TURC model which requires T and solar radiation. Thus, not only is the PAR approach more accurate but also more cost effective. The PAR-based ET estimation equation derived in this study may be over fit considering only 5 months of data were used to produce the PAR

  11. Sulfur Use Efficiency Is a Significant Determinant of Drought Stress Tolerance in Relation to Photosynthetic Activity in Brassica napus Cultivars.

    PubMed

    Lee, Bok-Rye; Zaman, Rashed; Avice, Jean-Christophe; Ourry, Alain; Kim, Tae-Hwan

    2016-01-01

    To investigate the varietal difference in sulfur use efficiency (SUE) and drought stress tolerance, Brassica napus 'Mosa' and 'Saturnin' were exposed to polyethylene glycol (PEG)-induced drought stress for 72 h. Direct quantification of S uptake, de novo synthesis of amino acids and proteins was performed by tracing (34)S. The responses of photosynthetic activity in relation to SUE were also examined. The total amount of newly absorbed S decreased with drought stress in both cultivars but the decrease rate was significantly higher in Mosa (-64%) than in Saturnin (-41%). Drought stress also decreased the amount of S assimilated into amino acids ((34)S-amino acids) and proteins ((34)S-proteins). The total amount of S incorporated into amino acids and proteins was generally higher in Saturnin (663.7 μg S per plant) than in Mosa (337.3 μg S per plant). The estimation of SUE based on S uptake (SUpE) and S assimilation (SUaE) showed that SUE was much higher in Saturnin than in Mosa. The inhibition of photosynthetic activity including Rubisco protein degradation caused by drought stress was much lower in the cultivar with higher SUE (Saturnin). The present study clearly indicates that the genotype with higher SUE is more tolerant to PEG-induced drought stress. PMID:27092167

  12. Sulfur Use Efficiency Is a Significant Determinant of Drought Stress Tolerance in Relation to Photosynthetic Activity in Brassica napus Cultivars

    PubMed Central

    Lee, Bok-Rye; Zaman, Rashed; Avice, Jean-Christophe; Ourry, Alain; Kim, Tae-Hwan

    2016-01-01

    To investigate the varietal difference in sulfur use efficiency (SUE) and drought stress tolerance, Brassica napus ‘Mosa’ and ‘Saturnin’ were exposed to polyethylene glycol (PEG)-induced drought stress for 72 h. Direct quantification of S uptake, de novo synthesis of amino acids and proteins was performed by tracing 34S. The responses of photosynthetic activity in relation to SUE were also examined. The total amount of newly absorbed S decreased with drought stress in both cultivars but the decrease rate was significantly higher in Mosa (-64%) than in Saturnin (-41%). Drought stress also decreased the amount of S assimilated into amino acids (34S-amino acids) and proteins (34S-proteins). The total amount of S incorporated into amino acids and proteins was generally higher in Saturnin (663.7 μg S per plant) than in Mosa (337.3 μg S per plant). The estimation of SUE based on S uptake (SUpE) and S assimilation (SUaE) showed that SUE was much higher in Saturnin than in Mosa. The inhibition of photosynthetic activity including Rubisco protein degradation caused by drought stress was much lower in the cultivar with higher SUE (Saturnin). The present study clearly indicates that the genotype with higher SUE is more tolerant to PEG-induced drought stress. PMID:27092167

  13. Comparison of ground and satellite based measurements of the fraction of photosynthetically active radiation intercepted by tall-grass prairie

    NASA Technical Reports Server (NTRS)

    Demetriades-Shah, T. H.; Kanemasu, E. T.; Flitcroft, I.; Su, H.

    1990-01-01

    The fraction, of photosynthetically active radiation absorbed by vegetation, F sub ipar, is an important requirement for estimating vegetation biomass productivity and related quantities. This was an integral part of a large international effort; the First ISLSCP Field Experiment (FIFE). The main objective of FIFE was to study the effects of vegetation on the land atmosphere interactions and to determine if these interactions can be assessed from satellite spectral measurements. The specific purpose of this experiment was to find out how well measurements of F sub ipar relate to ground, helicopter, and satellite based spectral reflectance measurements. Concurrent measurements of F sub ipar and ground, helicopter, and satellite based measurements were taken at 13 tall grass prairie sites in Kansas. The sites were subjected to various combinations of burning and grazing managements.

  14. The absorbed dose to blood from blood-borne activity

    NASA Astrophysics Data System (ADS)

    Hänscheid, H.; Fernández, M.; Lassmann, M.

    2015-01-01

    The radiation absorbed dose to blood and organs from activity in the blood is relevant for nuclear medicine dosimetry and for research in biodosimetry. The present study provides coefficients for the average absorbed dose rates to the blood from blood-borne activity for radionuclides frequently used in targeted radiotherapy and in PET diagnostics. The results were deduced from published data for vessel radius-dependent dose rate coefficients and reasonable assumptions on the blood-volume distribution as a function of the vessel radius. Different parts of the circulatory system were analyzed separately. Vessel size information for heart chambers, aorta, vena cava, pulmonary artery, and capillaries was taken from published results of morphometric measurements. The remaining blood not contained in the mentioned vessels was assumed to reside in fractal-like vascular trees, the smallest branches of which are the arterioles or venules. The applied vessel size distribution is consistent with recommendations of the ICRP on the blood-volume distribution in the human. The resulting average absorbed dose rates to the blood per nuclear disintegration per milliliter (ml) of blood are (in 10-11 Gy·s-1·Bq-1·ml) Y-90: 5.58, I-131: 2.49, Lu-177: 1.72, Sm-153: 2.97, Tc-99m: 0.366, C-11: 4.56, F-18: 3.61, Ga-68: 5.94, I-124: 2.55. Photon radiation contributes 1.1-1.2·10-11 Gy·s-1·Bq-1·ml to the total dose rate for positron emitters but significantly less for the other nuclides. Blood self-absorption of the energy emitted by ß-particles in the whole blood ranges from 37% for Y-90 to 80% for Tc-99m. The correspondent values in vascular trees, which are important for the absorbed dose to organs, range from 30% for Y-90 to 82% for Tc-99m.

  15. How absorbed hydrogen affects the catalytic activity of transition metals.

    PubMed

    Aleksandrov, Hristiyan A; Kozlov, Sergey M; Schauermann, Swetlana; Vayssilov, Georgi N; Neyman, Konstantin M

    2014-12-01

    Heterogeneous catalysis is commonly governed by surface active sites. Yet, areas just below the surface can also influence catalytic activity, for instance, when fragmentation products of catalytic feeds penetrate into catalysts. In particular, H absorbed below the surface is required for certain hydrogenation reactions on metals. Herein, we show that a sufficient concentration of subsurface hydrogen, H(sub) , may either significantly increase or decrease the bond energy and the reactivity of the adsorbed hydrogen, H(ad) , depending on the metal. We predict a representative reaction, ethyl hydrogenation, to speed up on Pd and Pt, but to slow down on Ni and Rh in the presence of H(sub) , especially on metal nanoparticles. The identified effects of subsurface H on surface reactivity are indispensable for an atomistic understanding of hydrogenation processes on transition metals and interactions of hydrogen with metals in general.

  16. Antioxidative activity of lactobacilli measured by oxygen radical absorbance capacity.

    PubMed

    Saide, J A O; Gilliland, S E

    2005-04-01

    The reducing ability and antioxidative activity of some species of Lactobacillus were compared under in vitro conditions. Cultures of Lactobacillus delbrueckii ssp. lactis, Lactobacillus delbrueckii ssp. bulgaricus, Lactobacillus acidophilus, and Lactobacillus casei were grown at 37 degrees C in de Man, Rogosa, Sharpe (MRS) broth supplemented with 0.5% 2,3,5 triphenyl tetrazolium chloride (TTC) to evaluate reducing activity. Reduced TTC was extracted from the cultures with acetone, and the intensity of the red color measured colorimetrically at 485 nm was an indication of reducing activity. The lactobacilli varied significantly in relative ability to reduce TTC when grown in MRS broth for 15 h. The relative amounts of growth as indicated by pH values at 18 h appeared to influence the amount of reduction. Antioxidative activity was evaluated by the ability of the whole cells or the cell-free extracts from cultures to protect a protein from being attacked by free radicals. These analyses were performed using the oxygen radical absorbance capacity method. All cultures tested exhibited some degree of antioxidative activity. Among the treatments, the cell-free extracts from cells grown in MRS broth exhibited significantly higher values than did whole cells. There was no apparent relationship between the reducing and antioxidative activities of the cultures evaluated. The results from this study show that these cultures can provide a source of dietary antioxidants. Furthermore, selection of cultures that produce antioxidants as starters could provide yet another health or nutritional benefit from cultured or culture-containing dairy products.

  17. Photosynthetic activity of spinach chloroplasts after isopycnic centrifugation in gradients of silica.

    PubMed

    Morgenthaler, J J; Price, C A

    1974-10-01

    Chloroplast suspensions from spinach (Spinacia oleracea L.) were clearly resolved into intact and stripped chloroplasts by isopycnic centrifugation in density gradients of silica sol ("Ludox") and polyethlene glycol. The intact chloroplasts fixed CO(2) and evolved O(2) more rapidly than the crude suspensions; the stripped chloroplasts were inactive. During the photosynthetic fixation of (14)CO(2) in the intact chloroplasts recovered from the gradient, the (14)C label was observed to spread through the photosynthetic intermediate pools, as well as into starch, which indicates that the purified chloroplasts are metabolically competent. This appears to be the first report of the retention of photosynthetic activity following the purification of chloroplasts in density gradients. PMID:16658922

  18. Enhanced photosynthetic activity in Spinacia oleracea by spectral modification with a photoluminescent light converting material.

    PubMed

    Xia, Qi; Batentschuk, Miroslaw; Osvet, Andres; Richter, Peter; Häder, Donat P; Schneider, Juergen; Brabec, Christoph J; Wondraczek, Lothar; Winnacker, Albrecht

    2013-11-01

    The spectral conversion of incident sunlight by appropriate photoluminescent materials has been a widely studied issue for improving the efficiency of photovoltaic solar energy harvesting. By using phosphors with suitable excitation/emission properties, also the light conditions for plants can be adjusted to match the absorption spectra of chlorophyll dyes, in this way increasing the photosynthetic activity of the plant. Here, we report on the application of this principle to a high plant, Spinacia oleracea. We employ a calcium strontium sulfide phosphor doped with divalent europium (Ca0.4Sr0.6S:Eu(2+), CSSE) on a backlight conversion foil in photosynthesis experiments. We show that this phosphor can be used to effectively convert green to red light, centering at a wavelength of ~650 nm which overlaps the absorption peaks of chlorophyll a/b pigments. A measurement system was developed to monitor the photosynthetic activity, expressed as the CO2 assimilation rate of spinach leaves under various controlled light conditions. Results show that under identical external light supply which is rich in green photons, the CO2 assimilation rate can be enhanced by more than 25% when the actinic light is modified by the CSSE conversion foil as compared to a purely reflecting reference foil. These results show that the phosphor could be potentially applied to modify the solar spectrum by converting the green photons into photosynthetically active red photons for improved photosynthetic activity.

  19. Solar PAR and UVR modify the community composition and photosynthetic activity of sea ice algae.

    PubMed

    Enberg, Sara; Piiparinen, Jonna; Majaneva, Markus; Vähätalo, Anssi V; Autio, Riitta; Rintala, Janne-Markus

    2015-10-01

    The effects of increased photosynthetically active radiation (PAR) and ultraviolet radiation (UVR) on species diversity, biomass and photosynthetic activity were studied in fast ice algal communities. The experimental set-up consisted of nine 1.44 m(2) squares with three treatments: untreated with natural snow cover (UNT), snow-free (PAR + UVR) and snow-free ice covered with a UV screen (PAR). The total algal biomass, dominated by diatoms and dinoflagellates, increased in all treatments during the experiment. However, the smaller biomass growth in the top 10-cm layer of the PAR + UVR treatment compared with the PAR treatment indicated the negative effect of UVR. Scrippsiella complex (mainly Scrippsiella hangoei, Biecheleria baltica and Gymnodinium corollarium) showed UV sensitivity in the top 5-cm layer, whereas Heterocapsa arctica ssp. frigida and green algae showed sensitivity to both PAR and UVR. The photosynthetic activity was highest in the top 5-cm layer of the PAR treatment, where the biomass of the pennate diatom Nitzschia frigida increased, indicating the UV sensitivity of this species. This study shows that UVR is one of the controlling factors of algal communities in Baltic Sea ice, and that increased availability of PAR together with UVR exclusion can cause changes in algal biomass, photosynthetic activity and community composition.

  20. Solar PAR and UVR modify the community composition and photosynthetic activity of sea ice algae.

    PubMed

    Enberg, Sara; Piiparinen, Jonna; Majaneva, Markus; Vähätalo, Anssi V; Autio, Riitta; Rintala, Janne-Markus

    2015-10-01

    The effects of increased photosynthetically active radiation (PAR) and ultraviolet radiation (UVR) on species diversity, biomass and photosynthetic activity were studied in fast ice algal communities. The experimental set-up consisted of nine 1.44 m(2) squares with three treatments: untreated with natural snow cover (UNT), snow-free (PAR + UVR) and snow-free ice covered with a UV screen (PAR). The total algal biomass, dominated by diatoms and dinoflagellates, increased in all treatments during the experiment. However, the smaller biomass growth in the top 10-cm layer of the PAR + UVR treatment compared with the PAR treatment indicated the negative effect of UVR. Scrippsiella complex (mainly Scrippsiella hangoei, Biecheleria baltica and Gymnodinium corollarium) showed UV sensitivity in the top 5-cm layer, whereas Heterocapsa arctica ssp. frigida and green algae showed sensitivity to both PAR and UVR. The photosynthetic activity was highest in the top 5-cm layer of the PAR treatment, where the biomass of the pennate diatom Nitzschia frigida increased, indicating the UV sensitivity of this species. This study shows that UVR is one of the controlling factors of algal communities in Baltic Sea ice, and that increased availability of PAR together with UVR exclusion can cause changes in algal biomass, photosynthetic activity and community composition. PMID:26310455

  1. Mapping high-resolution incident photosynthetically active radiation over land surfaces from MODIS and GOES satellite data

    NASA Astrophysics Data System (ADS)

    Liang, S.; Wang, K.; Wang, D.; Townshend, J.; Running, S.; Tsay, S.

    2008-05-01

    Incident photosynthetically active radiation (PAR) is a key variable required by almost all terrestrial ecosystem models. Many radiation efficiency models are linearly related canopy productivity to the absorbed PAR. Unfortunately, the current incident PAR products estimated from remotely sensed data or calculated by radiation models at spatial and temporal resolutions are not sufficient for carbon cycle modeling and various applications. In this study, we aim to develop incident PAR products at one kilometer scale from multiple satellite sensors, such as Moderate Resolution Imaging Spectrometer (MODIS) and Geostationary Operational Environmental Satellite (GOES) sensor. We first developed a look-up table approach to estimate instantanerous incident PAR product from MODIS (Liang et al., 2006). The temporal observations of each pixel are used to estimate land surface reflectance and look-up tables of both aerosol and cloud are searched, based on the top-of-atmosphere reflectance and surface reflectance for determining incident PAR. The incident PAR product includes both the direct and diffuse components. The calculation of a daily integrated PAR using two different methods has also been developed (Wang, et al., 2008a). The similar algorithm has been further extended to GOES data (Wang, et al., 2008b, Zheng, et al., 2008). Extensive validation activities are conducted to evaluate the algorithms and products using the ground measurements from FLUXNET and other networks. They are also compared with other satellite products. The results indicate that our approaches can produce reasonable PAR product at 1km resolution. We have generated 1km incident PAR products over North America for several years, which are freely available to the science community. Liang, S., T. Zheng, R. Liu, H. Fang, S. C. Tsay, S. Running, (2006), Estimation of incident Photosynthetically Active Radiation from MODIS Data, Journal of Geophysical Research ¡§CAtmosphere. 111, D15208,doi:10

  2. Biophysical properties affecting vegetative canopy reflectance and absorbed photosynthetically active radiation at the FIFE site

    NASA Technical Reports Server (NTRS)

    Walter-Shea, E. A.; Blad, B. L.; Hays, C. J.; Mesarch, M. A.; Deering, D. W.; Middleton, E. M.

    1992-01-01

    Leaves of the dominant grass species of the ISCLP FIFE site reflect and transmit radiation in a like manner to other healthy green leaves. Visible reflectance factors (RFs) and transmittance factors (TFs) were less for older leaves than younger leaves except during senescence, when RF and TF values were greater. NIR-RF values increased and TF values decreased with leaf age, with the reverse occurring as the leaf went through senescence.

  3. Biophysical properties affecting vegetative canopy reflectance and absorbed photosynthetically active radiation at the FIFE site

    SciTech Connect

    Walter-shea, E.A.; Blad, B.L.; Hays, C.J.; Mesarch, M.A.; Deering, D.W.; Middleton, E.M. NASA, Goddard Space Flight Center, Greenbelt, MD )

    1992-11-01

    Leaves of the dominant grass species of the ISCLP FIFE site reflect and transmit radiation in a like manner to other healthy green leaves. Visible reflectance factors (RFs) and transmittance factors (TFs) were less for older leaves than younger leaves except during senescence, when RF and TF values were greater. NIR-RF values increased and TF values decreased with leaf age, with the reverse occurring as the leaf went through senescence. 39 refs.

  4. [Photosynthetic activity of Gloiopeltis furcata (intertidal red macroalga) in response to desiccation].

    PubMed

    Liu, Hong-Liang; Liu, Hong-Liang; Li, Xue-Meng; Nan, Guo-Ning; Zhang, Quan-Sheng

    2014-05-01

    In this study, the diurnal change of photosynthesis activity in response to various tidal patterns, the relationship between photosynthetic activity and tissue water content, and the interactive effect of desiccation and irradiance on photosynthetic activity in Gloiopeltis furcata were investigated by using portable pulse amplitude modulated (PAM) fluorometer. Results showed that Fv/Fm decreased more rapidly during the noon low tide than during the morning- or evening low tide. F/Fm decreased slowly at the beginning of desiccation during the morning low tide, but decreased rapidly throughout the evening low tide. Fv/Fm recovered to the initial values on the same day no matter when the low tide occurred, suggesting the occurrence of dynamic photoinhibition. These features endowed G. furcata with an ability to adapt to the periodic desiccation on high intertidal rocks. The maximum (Fv/Fm) and effective (Phi(PSII)) quantum yield declined with the decrease of tissue water content (TWC). However, photosynthetic activity could recover completely when TWC exceeded 6%, showing a strong ability of G. furcata to tolerate desiccation. The relationships between TWC and Fv/Fm and Phi (PS II) as were as follows: F/Fm = 0.68 + (0.44-0.68)/[1 +(TWC/ 66.96)]5 , R2 = 0.99; Phi(PSII) = 0.585 + (0.004-0.585)/[1+(TWC/73)10], R2 = 0.99. ANOVA result further showed that the interactive effect of irradiance and desiccation on photosynthetic activity was significant, and that the photoinhibition degree increased with elevation of irradiation and duration of desiccation. The extreme condition (6 h desiccation at 1000 micromol photons x m(-2) x s(-1)) resulted in a serious photoinhibition, with the longest period of complete recovery for photosynthesis activity.

  5. Deactivation of photosynthetic activities is triggered by loss of a small amount of water in a desiccation-tolerant cyanobacterium, Nostoc commune.

    PubMed

    Hirai, Manabu; Yamakawa, Ruriko; Nishio, Junko; Yamaji, Takaharu; Kashino, Yasuhiro; Koike, Hiroyuki; Satoh, Kazuhiko

    2004-07-01

    Changes in photosynthetic activities under hypertonic conditions were studied in a terrestrial, highly desiccation-tolerant cyanobacterium, Nostoc commune, and in some desiccation-sensitive cyanobacteria. The amounts of water sustained in the colony matrix outside the N. commune cells and the cellular solute concentration were estimated by measuring the water potential, and the solute concentration was supposed to correspond to around 0.22 M sorbitol. Incubation of the colonies in 0.8 M sorbitol solution inhibited the energy transfer from the phycobilisome (PBS) anchor to PSII core complexes. At higher sorbitol concentrations, light energy absorbed by PSI, PSII, and PBS was dissipated to heat. PSI and cyclic electron flow around PSI was also deactivated by hypertonic treatment. Fv/Fm and (Fm'-F)/Fm' values started to decrease at 0.6 and 0.3 M sorbitol and reached zero at 1.0 and 0.8 M, respectively. Decreases in these two fluorescence parameters corresponded to the decreases in PSII fluorescence (F695) and photosynthetic CO2 fixation, respectively. The intensity of delayed light emission started to decrease at 1.0 M sorbitol and became negligible at 4.0 M. Comparing these changes in N. commune with those in desiccation-sensitive species, we found that N. commune cells actively deactivates photosynthetic systems on sensing water loss. PMID:15295070

  6. [Biological activity of lipids and photosynthetic pigments of Sargassum pallidum C. Agardh].

    PubMed

    Gerasimenko, N I; Martyias, E A; Logvinov, S V; Busarova, N G

    2014-01-01

    The biological activity of lipids and photosynthetic pigments of the kelp Sargassum pallidum (Turner) C. Agardh has been studied. Free fatty acids and their esters demonstrated considerable antimicrobial activity against bacteria (Staphylococcus aureus[ital] and Escherichia coli), yeast-like fungi (Candida albicans), and opportunistic pathogenic (Aspergilius niger) and phytopathogenic (Fusarium oxysporum, and Septoria glycines) fungi. Glyceroglycolipids and neutral lipids demonstrated moderate activity. Fucoxanthin and chlorophylls weakly suppressed the growth of microorganisms. None of the studied substances demonstrated activity against Ehrlich's carcinoma. It was shown that the season of weed harvesting affected both antimicrobial and hemolytic activities of different lipids due to changes in their fatty acid composition. PMID:25272757

  7. Survival potential and photosynthetic activity of lichens under Mars-like conditions: a laboratory study.

    PubMed

    de Vera, Jean-Pierre; Möhlmann, Diedrich; Butina, Frederike; Lorek, Andreas; Wernecke, Roland; Ott, Sieglinde

    2010-03-01

    Lichens were repetitively exposed over 22 days to thermophysical Mars-like conditions at low-and mid-latitudes. The simulated parameters and the experimental setup are described. Natural samples of the lichen Xanthoria elegans were used to investigate their ability to survive the applied Mars-like conditions. The effects of atmospheric pressure, CO(2) concentration, low temperature, water availability, and light on Mars were also studied. The results of these experiments indicate that no significant decrease in the vitality of the lichen occurred after exposure to simulated martian conditions, which was demonstrated by confocal laser scanning microscopy analysis, and a 95% CO(2) atmosphere with 100% humidity, low pressure (partial pressure of CO(2) was 600 Pa), and low temperature has a balancing effect on photosynthetic activity as a function of temperature. This means a starting low photosynthetic activity at high CO(2) concentrations with Earth-like pressure has a reduction of 60%. But, if the simulated atmospheric pressure is reduced to Mars-like conditions with the maintenance of the same Mars-like 95% CO(2) concentration, the photosynthetic activity increases and again reaches similar values as those exhibited under terrestrial atmospheric pressure and concentration. Based on these results, we presume that, in any region on Mars where liquid water might be available, even for short periods of time, a eukaryotic symbiotic organism would have the ability to survive, at least over weeks, and to temporarily photosynthesize.

  8. Effects of planting configuration and in-row plant spacing on photosynthetic active radiation interception for three irrigated potato cultivars

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Research studies have evaluated the production of potatoes (Solanum tuberosum L.) grown in conventional and bed planting configurations. However, intercepted photosynthetically active radiation (PAR) from these planting configurations has not been quantified. A study conducted in 2008 and 2009 quant...

  9. Synergistic Effect of Photosynthetic Bacteria and Isolated Bacteria in Their Antifungal Activities against Root Rot Fungi.

    PubMed

    Wei, Hongyi; Okunishi, Suguru; Yoshikawa, Takeshi; Kamei, Yuto; Dawwoda, Mahmoud A O; Santander-DE Leon, Sheila Mae S; Nuñal, Sharon Nonato; Maeda, Hiroto

    2016-01-01

    Antifungal bacteria (AB) in root rot fungus (RRF)-contaminated sweet potato farms were isolated, and seven strains were initially chosen as antagonistic candidates. An antagonistic test by using the mycelial disk placement method revealed that one AB strain by itself could inhibit the RRF growth. This AB strain was identified as Bacillus polyfermenticus based on phylogeny of 16S ribosomal RNA genes. Two AB strains (Bacillus aerophilus) displayed high levels of antifungal activity when paired with photosynthetic bacterial strain A (a purple nonsulfur photosynthetic bacterium Rhodopseudomonas faecalis). The results suggest the possible use of the isolates as agents for the biological control of the RRF infection of agricultural products in fields of cultivation. PMID:27667522

  10. Whiting events: biogenic origin due to the photosynthetic activity of cyanobacterial picoplankton

    NASA Technical Reports Server (NTRS)

    Thompson, J. B.; Schultze-Lam, S.; Beveridge, T. J.; Des Marais, D. J.

    1997-01-01

    An annual whiting event occurs each year in late May to early June in Fayetteville Green Lake, New York. The initiation of this event correlates with exponential growth of the Synechococcus population within the lake. Synechococcus is the dominant (by approximately 4 orders of magnitude) autotrophic organism owing to the oligotrophic condition of the lake. The delta 13C values of the dissolved inorganic C range seasonally from -9.5% in winter to -6.2% in summer due to photosynthetic activity. Calcite precipitates principally in the microenvironment surrounding Synechococcus because of a photosynthetically driven alkalization process and the availability of the cells as nucleation sites. This calcite has a heavier delta 13C value (>4%) than does the dissolved inorganic C of the lake water owing to the cells' preferential uptake of 12C. A conceptual model suggests that photosynthetic activity and cell surface chemistry, together with the substantial surface area that arises from the great abundance of micron-sized cells, allow Synechococcus to dominate the annual whiting events in Fayetteville Green Lake.

  11. Photosynthetic activity buffers ocean acidification in seagrass meadows

    NASA Astrophysics Data System (ADS)

    Hendriks, I. E.; Olsen, Y. S.; Ramajo, L.; Basso, L.; Steckbauer, A.; Moore, T. S.; Howard, J.; Duarte, C. M.

    2014-01-01

    Macrophytes growing in shallow coastal zones characterised by intense metabolic activity have the capacity to modify pH within their canopy and beyond. We observed diel pH changes in shallow (5-12 m) seagrass (Posidonia oceanica) meadows spanning 0.06 pH units in September to 0.24 units in June. The carbonate system (pH, DIC, and aragonite saturation state (ΩAr)) and O2 within the meadows displayed strong diel variability driven by primary productivity, and changes in chemistry were related to structural parameters of the meadow, in particular, the leaf surface area available for photosynthesis (LAI). LAI was positively correlated to mean, max and range pHNBS and max and range ΩAr. In June, vertical mixing (as Turbulent Kinetic Energy) influenced max and min ΩAr, while in September there was no effect of hydrodynamics on the carbonate system within the canopy. Max and range ΩAr within the meadow showed a positive trend with the calcium carbonate load of the leaves, pointing to a possible link between structural parameters, ΩAr and carbonate deposition. Calcifying organisms, e.g. epiphytes with carbonate skeletons, may benefit from the modification of the carbonate system by the meadow. There is, however, concern for the ability of seagrasses to provide modifications of similar importance in the future. The predicted decline of seagrass meadows may alter the scope for alteration of pH within a seagrass meadow and in the water column above the meadow, particularly if shoot density and biomass decline, on which LAI is based. Organisms associated with seagrass communities may therefore suffer from the loss of pH buffering capacity in degraded meadows.

  12. Reduced glutamine synthetase activity plays a role in control of photosynthetic responses to high light in barley leaves.

    PubMed

    Brestic, Marian; Zivcak, Marek; Olsovska, Katarina; Shao, Hong-Bo; Kalaji, Hazem M; Allakhverdiev, Suleyman I

    2014-08-01

    The chloroplastic glutamine synthetase (GS, EC 6.3.1.2) activity was previously shown to be the limiting step of photorespiratory pathway. In our experiment, we examined the photosynthetic high-light responses of the GS2-mutant of barley (Hordeum vulgare L.) with reduced GS activity, in comparison to wild type (WT). The biophysical methods based on slow and fast chlorophyll fluorescence induction, P700 absorbance, and gas exchange measurements were employed. Despite the GS2 plants had high basal fluorescence (F0) and low maximum quantum yield (Fv/Fm), the CO2 assimilation rate, the PSII and PSI actual quantum yields were normal. On the other hand, in high light conditions the GS2 had much higher non-photochemical quenching (NPQ), caused both by enhanced capacity of energy-dependent quenching and disconnection of PSII antennae from reaction centers (RC). GS2 leaves also maintained the PSII redox poise (QA(-)/QA total) at very low level; probably this was reason why the observed photoinhibitory damage was not significantly above WT. The analysis of fast chlorophyll fluorescence induction uncovered in GS2 leaves substantially lower RC to antenna ratio (RC/ABS), low PSII/PSI ratio (confirmed by P700 records) as well as low PSII excitonic connectivity.

  13. effects of natural flavonoids on photosynthetic activity and cell integrity in Microcystis aeruginosa.

    PubMed

    Huang, Haomin; Xiao, Xi; Ghadouani, Anas; Wu, Jiaping; Nie, Zeyu; Peng, Cheng; Xu, Xinhua; Shi, Jiyan

    2015-01-01

    Flavonoids are natural polyphenolic compounds produced by many aquatic plants and released in their environments. In this study, the effects of several aquatic flavonoids on cyanobacterial Microcystis aeruginosa, especially in relation to the cell growth, photosynthetic activity, cell morphology, and cell membrane integrity, were investigated. Significant growth inhibition was observed when the cyanobacteria were exposed to three flavonoids, namely, 5,4'-dihydroxyflavone (DHF), apigenin, and luteolin. Luteolin reduced the effective quantum yield, photosynthetic efficiency, and maximal electron transport rate by 70%, 59% and 44%, respectively, whereas 5,4'-DHF and apigenin slightly affected these parameters, which implies that luteolin disrupts the photosynthetic system. Moreover, 5,4'-DHF and apigenin compromised the membrane integrity, and induced membrane depolarization in 52% and 38%, and permeabilization in 30% and 44% of the cells, respectively. The 5,4'-DHF and apigenin showed more pronounced effects on M. aeruginosa morphology and membrane integrity, compared to the luteolin. These results suggest that flavonoids could have significant effects on growth and physiological functions in cyanobacterial species. PMID:25584428

  14. Study the effect of insecticide dimethoate on photosynthetic pigments and photosynthetic activity of pigeon pea: Laser-induced chlorophyll fluorescence spectroscopy.

    PubMed

    Pandey, Jitendra Kumar; Dubey, Gunjan; Gopal, R

    2015-10-01

    Pigeon pea is one of the most important legume crops in India and dimethoate is a widely used insecticide in various crop plants. We studied the effect of dimethoate on growth and photosynthetic activity of pigeon pea plants over a short and long term exposure. Plant growth parameters, photosynthetic pigment content and chlorophyll fluorescence response of pigeon pea (Cajanus cajan L.) plants treated with various concentrations of the insecticide dimethoate (10, 20, 40 and 80 ppm) have been compared for 30 days at regular intervals of 10 days each. Laser induced chlorophyll fluorescence spectra and fluorescence-induction kinetics (FIK) curve of dimethoate treated pigeon pea plants were recorded after 10, 20 and 30 days of treatment. Fluorescence intensity ratio at the two fluorescence maxima (F685/F730) was calculated by evaluating curve-fitted parameters. The variable chlorophyll fluorescence decrease ratio (Rfd) was determined from the FIK curves. Our study revealed that after 10 days of treatment, 10 ppm of dimethoate showed stimulatory response whereas 20, 40 and 80 ppm of dimethoate showed inhibitory response for growth and photosynthetic activity of pigeon pea plants, but after 20 and 30 days of treatment all the tested concentrations of dimethoate became inhibitory. This study clearly shows that dimethoate is highly toxic to the pigeon pea plant, even at very low concentration (10 ppm), if used for a prolonged duration. Our study may thus be helpful in determining the optimal dose of dimethoate in agricultural practices. PMID:25228224

  15. Study the effect of insecticide dimethoate on photosynthetic pigments and photosynthetic activity of pigeon pea: Laser-induced chlorophyll fluorescence spectroscopy.

    PubMed

    Pandey, Jitendra Kumar; Dubey, Gunjan; Gopal, R

    2015-10-01

    Pigeon pea is one of the most important legume crops in India and dimethoate is a widely used insecticide in various crop plants. We studied the effect of dimethoate on growth and photosynthetic activity of pigeon pea plants over a short and long term exposure. Plant growth parameters, photosynthetic pigment content and chlorophyll fluorescence response of pigeon pea (Cajanus cajan L.) plants treated with various concentrations of the insecticide dimethoate (10, 20, 40 and 80 ppm) have been compared for 30 days at regular intervals of 10 days each. Laser induced chlorophyll fluorescence spectra and fluorescence-induction kinetics (FIK) curve of dimethoate treated pigeon pea plants were recorded after 10, 20 and 30 days of treatment. Fluorescence intensity ratio at the two fluorescence maxima (F685/F730) was calculated by evaluating curve-fitted parameters. The variable chlorophyll fluorescence decrease ratio (Rfd) was determined from the FIK curves. Our study revealed that after 10 days of treatment, 10 ppm of dimethoate showed stimulatory response whereas 20, 40 and 80 ppm of dimethoate showed inhibitory response for growth and photosynthetic activity of pigeon pea plants, but after 20 and 30 days of treatment all the tested concentrations of dimethoate became inhibitory. This study clearly shows that dimethoate is highly toxic to the pigeon pea plant, even at very low concentration (10 ppm), if used for a prolonged duration. Our study may thus be helpful in determining the optimal dose of dimethoate in agricultural practices.

  16. Material Activation Benchmark Experiments at the NuMI Hadron Absorber Hall in Fermilab

    SciTech Connect

    Matsumura, H.; Matsuda, N.; Kasugai, Y.; Toyoda, A.; Yashima, H.; Sekimoto, S.; Iwase, H.; Oishi, K.; Sakamoto, Y.; Nakashima, H.; Leveling, A.; Boehnlein, D.; Lauten, G.; Mokhov, N.; Vaziri, K.

    2014-06-15

    In our previous study, double and mirror symmetric activation peaks found for Al and Au arranged spatially on the back of the Hadron absorber of the NuMI beamline in Fermilab were considerably higher than those expected purely from muon-induced reactions. From material activation bench-mark experiments, we conclude that this activation is due to hadrons with energy greater than 3 GeV that had passed downstream through small gaps in the hadron absorber.

  17. A method to determine photosynthetic activity from oxygen microsensor data in biofilms subjected to evaporation.

    PubMed

    Li, Tong; Podola, Björn; de Beer, Dirk; Melkonian, Michael

    2015-10-01

    Phototrophic biofilms are widely distributed in nature and their ecological importance is well recognized. More recently, there has been a growing interest in using artificial phototrophic biofilms in innovative photobioreactors for production of microalgal biomass in biotechnological applications. To study physiological processes within these biofilms, microsensors have been applied in several studies. Here, the 'light-dark shift method' relies on measurement of photosynthetic activity in terms of light-induced oxygen production. However, when applied to non-submerged biofilms that can be found in numerous locations in nature, as well as in some types of photobioreactors, limitations of this approach are obvious due to rapid removal of gaseous species at the biofilm surface. Here, we introduce a mathematical correction to recover the distribution of the actual photosynthetic activity along the depth gradient in the biofilm, based on a numerical solution of the inversed diffusion equation of oxygen. This method considers changes in mass transport during the measurement period as can found on biofilms possessing a thin flow/mass transfer boundary layer (e. g., non-submerged biofilms). Using both simulated and real microsensor data, the proposed method was shown to be much more accurate than the classical method, which leads to underestimations of rates near the biofilm surface. All test profiles could be recovered with a high fit. According to our simulated microsensor measurements, a depth resolution of ≤20 μm is recommended near the surface. We conclude that our method strongly improves the quality of data acquired from light-dark measurements of photosynthetic activity in biofilms.

  18. Winter photosynthetic activity of twenty temperate semi-desert sand grassland species.

    PubMed

    Tuba, Zoltán; Csintalan, Zsolt; Szente, Kálmán; Nagy, Zoltán; Fekete, Gábor; Larcher, Walter; Lichtenthaler, Hartmut K

    2008-09-29

    The winter photosynthetic activity (quantified by net CO(2) assimilation rates and chlorophyll (Chl) a fluorescence parameters) of 20 plant species (including two lichens and two mosses) of a Hungarian temperate semi-desert sand grassland was determined on one occasion per year in 1984, 1989 and 1994. Throughout winter, the overwintering green shoots, leaves or thalli were regularly exposed to below zero temperatures at night and daytime temperatures of 0-5 degrees C. In situ tissue temperature varied between -2.1 and +6.9 degrees C and the photosynthetic photon flux density (PPFD) between 137 and 351 micromol m(-2)s(-1). Under these conditions 18 of the grassland species exhibited photosynthetic CO(2) uptake (range: vascular plants ca. 0.2-3.8 micromol m(-2)s(-1), cryptogams 0.3-2.79 micromol kg(-1)s(-1)) and values of 0.9-5.1 of the Chl fluorescence decrease ratio R(Fd). In 1984, Festuca vaginata and Sedum sexangulare had net CO(2) assimilation at leaf temperatures of -0.85 to -1.2 degrees C. In 1989, all species except Cladonia furcata showed net CO(2) assimilation at tissue temperatures of 0 to +3.3 degrees C, with the highest rates observed in Poa bulbosa and F. vaginata. The latter showed a net CO(2) assimilation saturation at a PPFD of 600 micromol m(-2)s(-1) and a temperature optimum between +5 and +18 degrees C. At the 1994 measurements, the photosynthetic rates were higher at higher tissue water contents. The two mosses and lichens had a net photosynthesis (range: 1.1-2.79 micromol CO(2)kg(-1)s(-1)) at 2 degrees C tissue temperature and at 4-5 degrees C air temperature. Ca. 80% of the vascular grassland plant species maintained a positive C-balance during the coldest periods of winter, with photosynthetic rates of 1.5-3.8 micromol CO(2)m(-2)s(-1). In an extremely warm beginning March of the relatively warm winter of 2006/2007, the dicotyledonous plants had much higher CO(2) assimilation rates on a Chl (range 6-14.9 micromol g(-1)Chl s(-1)) and on a dry

  19. [Effects of high temperature on leaf photosynthetic characteristics and photosystem II photochemical activity of kernel-used apricot].

    PubMed

    Du, Guo-dong; Lü, De-guo; Zhao, Ling; Wang, Su-su; Cai, Qian

    2011-03-01

    In order to explore the photosynthetic adaption mechanisms of kernel-used apricot under high temperature stress, gas exchange technique and chlorophyll fluorescence transient technique (JIP-test) were adopted to study the leaf photosynthetic characteristics and photosystem II (PS II) photochemical activity of 4 year-old 'Chaoren' (Armeniaca vulgaris x sibirica) growing on Horqin sandy land at 25 degrees C, 30 degrees C, 40 degrees C, and 50 degrees C. Within a definite temperature range, and as the temperature increased, the 'Chaoren' could enhance its leaf photosynthetic pigments content and ratio to maintain the light absorption, transfer, and conversion, and thereby, to ensure the function of photosynthetic apparatus. However, when the temperature exceeded the physiological adjustment threshold of leaves, the chlorophyll began to be decomposed, net photosynthetic rate (Pn) declined obviously, and intercellular CO2 concentration (Ci) increased, indicating that the decline in photosynthesis was limited by mesophyll factor. At 40 degrees C, the density of PS II reaction centers per excited cross-section (RC/CS0) dropped distinctly; and at 50 degrees C, the K phase (Wk) and J phase (Vj) in the O-J-I-P chlorophyll fluorescence transients increased distinctly, indicating that high temperature damaged the oxygen-evolving complex (OEC), donor sides, and PS II reaction centers. In addition, the minimum chlorophyll fluorescence (F0) at 50 degrees C increased significantly by 1.26 times, compared with the control, and the maximum photochemical efficiency (Fv/Fm) and performance index (PI(ABS)) reduced to 37.9% and 10.3% of the control, respectively. High temperature injured the function of the donor and acceptor sides in the PS II of photosynthetic apparatus, leading to the decrease of photosynthetic efficiency, and being one of the main mechanisms for the damage of photosynthetic apparatus in kernel-used apricot leaves under high temperature stress.

  20. Evaluating a three dimensional model of diffuse photosynthetically active radiation in maize canopies

    NASA Astrophysics Data System (ADS)

    Wang, Xiping; Guo, Yan; Li, Baoguo; Wang, Xiyong; Ma, Yuntao

    2006-07-01

    Diffuse photosynthetically active radiation (DPAR) is important during overcast days and for plant parts shaded from the direct beam radiation. Simulation of DPAR interception by individual plant parts of a canopy, separately from direct beam photosynthetically active radiation (PAR), may give important insights into plant ecology. This paper presents a model to simulate the interception of DPAR in plant canopies. A sub-model of a virtual maize canopy was reconstructed. Plant surfaces were represented as small triangular facets positioned according to three-dimensionally (3D) digitized data collected in the field. Then a second sub-model to simulate the 3D DPAR distribution in the canopy was developed by dividing the sky hemisphere into a grid of fine cells that allowed for the anisotropic distribution of DPAR over the sky hemisphere. This model, DSHP (Dividing Sky Hemisphere with Projecting), simulates which DSH (Divided Sky Hemisphere) cells are directly visible from a facet in the virtual canopy, i.e. not obscured by other facets. The DPAR reaching the center of a facet was calculated by summing the amounts of DPAR present in every DSH cell. The distribution of DPAR in a canopy was obtained from the calculated DPARs intercepted by all facets in the canopy. This DSHP model was validated against DPAR measurements made in an actual maize ( Zea mays L.) canopy over selected days during the early filling stage. The simulated and measured DPAR at different canopy depths showed a good agreement with a R 2 equaling 0.78 ( n=120).

  1. Responses of epidermal cell turgor pressure and photosynthetic activity of leaves of the atmospheric epiphyte Tillandsia usneoides (Bromeliaceae) after exposure to high humidity.

    PubMed

    Martin, Craig E; Rux, Guido; Herppich, Werner B

    2013-01-01

    It has been well-established that many epiphytic bromeliads of the atmospheric-type morphology, i.e., with leaf surfaces completely covered by large, overlapping, multicellular trichomes, are capable of absorbing water vapor from the atmosphere when air humidity increases. It is much less clear, however, whether this absorption of water vapor can hydrate the living cells of the leaves and, as a consequence, enhance physiological processes in such cells. The goal of this research was to determine if the absorption of atmospheric water vapor by the atmospheric epiphyte Tillandsia usneoides results in an increase in turgor pressure in leaf epidermal cells that subtend the large trichomes, and, by using chlorophyll fluorescence techniques, to determine if the absorption of atmospheric water vapor by leaves of this epiphyte results in increased photosynthetic activity. Results of measurements on living cells of attached leaves of this epiphytic bromeliad, using a pressure probe and of whole-shoot fluorescence imaging analyses clearly illustrated that the turgor pressure of leaf epidermal cells did not increase, and the photosynthetic activity of leaves did not increase, following exposure of the leaves to high humidity air. These results experimentally demonstrate, for the first time, that the absorption of water vapor following increases in atmospheric humidity in atmospheric epiphytic bromeliads is mostly likely a physical phenomenon resulting from hydration of non-living leaf structures, e.g., trichomes, and has no physiological significance for the plant's living tissues.

  2. Responses of epidermal cell turgor pressure and photosynthetic activity of leaves of the atmospheric epiphyte Tillandsia usneoides (Bromeliaceae) after exposure to high humidity.

    PubMed

    Martin, Craig E; Rux, Guido; Herppich, Werner B

    2013-01-01

    It has been well-established that many epiphytic bromeliads of the atmospheric-type morphology, i.e., with leaf surfaces completely covered by large, overlapping, multicellular trichomes, are capable of absorbing water vapor from the atmosphere when air humidity increases. It is much less clear, however, whether this absorption of water vapor can hydrate the living cells of the leaves and, as a consequence, enhance physiological processes in such cells. The goal of this research was to determine if the absorption of atmospheric water vapor by the atmospheric epiphyte Tillandsia usneoides results in an increase in turgor pressure in leaf epidermal cells that subtend the large trichomes, and, by using chlorophyll fluorescence techniques, to determine if the absorption of atmospheric water vapor by leaves of this epiphyte results in increased photosynthetic activity. Results of measurements on living cells of attached leaves of this epiphytic bromeliad, using a pressure probe and of whole-shoot fluorescence imaging analyses clearly illustrated that the turgor pressure of leaf epidermal cells did not increase, and the photosynthetic activity of leaves did not increase, following exposure of the leaves to high humidity air. These results experimentally demonstrate, for the first time, that the absorption of water vapor following increases in atmospheric humidity in atmospheric epiphytic bromeliads is mostly likely a physical phenomenon resulting from hydration of non-living leaf structures, e.g., trichomes, and has no physiological significance for the plant's living tissues. PMID:23000465

  3. Application of a passive/active autoparametric cantilever beam absorber with PZT actuator for Duffing systems

    NASA Astrophysics Data System (ADS)

    Silva-Navarro, G.; Abundis-Fong, H. F.; Vazquez-Gonzalez, B.

    2013-04-01

    An experimental investigation is carried out on a cantilever-type passive/active autoparametric vibration absorber, with a PZT patch actuator, to be used in a primary damped Duffing system. The primary system consists of a mass, viscous damping and a cubic stiffness provided by a soft helical spring, over which is mounted a cantilever beam with a PZT patch actuator actively controlled to attenuate harmonic and resonant excitation forces. With the PZT actuator on the cantilever beam absorber, cemented to the base of the beam, the auto-parametric vibration absorber is made active, thus enabling the possibility to control the effective stiffness and damping associated to the passive absorber and, as a consequence, the implementation of an active vibration control scheme able to preserve, as possible, the autoparametric interaction as well as to compensate varying excitation frequencies and parametric uncertainty. This active vibration absorber employs feedback information from a high resolution optical encoder on the primary Duffing system and an accelerometer on the tip beam absorber, a strain gage on the base of the beam, feedforward information from the excitation force and on-line computations from the nonlinear approximate frequency response, parameterized in terms of a proportional gain provided by a voltage input to the PZT actuator, thus modifying the closed-loop dynamic stiffness and providing a mechanism to asymptotically track an optimal, robust and stable attenuation solution on the primary Duffing system. Experimental results are included to describe the dynamic and robust performance of the overall closed-loop system.

  4. A hybrid electromagnetic shock absorber for active vehicle suspension systems

    NASA Astrophysics Data System (ADS)

    Ebrahimi, Babak; Bolandhemmat, Hamidreza; Behrad Khamesee, Mir; Golnaraghi, Farid

    2011-02-01

    The use of electromagnetic dampers (ED) in vehicle active suspension systems has drawn considerable attention in the past few years, attributed to the fact that active suspension systems have shown superior performance in improving ride comfort and road handling of terrain vehicles, compared with their passive and semi-active counterparts. Although demonstrating superb performance, active suspensions still have some shortcomings that must be overcome. They have high energy consumption, weight, and cost and are not fail-safe in case of a power breakdown. The novel hybrid ED, which is proposed in this paper, is a potential solution to the above-mentioned drawbacks of conventional active suspension systems. The proposed hybrid ED is designed to inherit the high-performance characteristics of an active ED with the reliability of a passive damper in a single package. The eddy current damping effect is utilised as a source of the passive damping. First, a prototype ED is designed and fabricated. The prototype ED is then utilised to experimentally establish the design requirements for a real-size active ED. This is accomplished by comparing its vibration isolation performance in a 1-DOF quarter-car test rig with that of a same-class semi-active damper. Then, after a real-size active ED is designed, the concept of hybrid damper is introduced to the damper design to address the drawbacks of the active ED. Finally, the finite-element method is used to accurately model and analyse the designed hybrid damper. It is demonstrated that by introducing the eddy current damping effect to the active part, a passive damping of approximately 1570 Ns/m is achieved. This amount of passive damping guarantees that the damper is fail-safe and reduces the power consumption more than 70%, compared with an active ED in an automotive active suspension system.

  5. Extrinsic chirality: Tunable optically active reflectors and perfect absorbers

    NASA Astrophysics Data System (ADS)

    Plum, Eric

    2016-06-01

    Conventional three-dimensional (3D) chiral media can exhibit optical activity for transmitted waves, but optical activity for reflected waves is negligible. This work shows that mirror asymmetry of the experimental arrangement—extrinsic 3D chirality—leads to giant optical activity for reflected waves with fundamentally different characteristics. It is demonstrated experimentally that extrinsically 3D-chiral illumination of a lossy metasurface backed by a mirror enables tunable circular dichroism and circular birefringence as well as perfect absorption of circularly polarized waves. In contrast, such polarization phenomena vanish for conventional optically active media backed by a mirror.

  6. Ground level photosynthetically active radiation dynamics in stands of Acacia mearnsii De Wild.

    PubMed

    Péllico Netto, Sylvio; Sanquetta, Carlos R; Caron, Braulio O; Behling, Alexandre; Simon, Augusto A; Corte, Ana Paula D; Bamberg, Rogério

    2015-09-01

    The objective is to study the dynamics of photosynthetic radiation reaching the soil surface in stands of Acacia mearnsii De Wild and its influence on height growth in stands. This fact gives rise to the formulation of the following hypothesis for this study: "The reduction of the incidence of light inside the stand of black wattle will cause the inflection point in its height growth when this reaches 4 to 5 m in height, i.e. when the stand is between 2 and 3 years of age". The study was conducted in stands in the state of Rio Grande do Sul, Brazil, where diameters at breast height, total height and photosynthetically active radiation available at ground level were measured. The frequency tended to be more intense when the age of the stands increases. It was evident that a reduction of light incidence inside the forest occurred, caused by canopy closure. Consequently, closed canopy propitiated the competition of plants. This has affected the conditions for growth in diameter and height of this species, reason why it becomes possible to conceive the occurrence of an inflection point in the growth of these two variables, confirming the formulated hypothesis.

  7. The Effect of Kanamycin and Tetracycline on Growth and Photosynthetic Activity of Two Chlorophyte Algae

    PubMed Central

    2016-01-01

    Antibiotics are routinely used in microalgae culture screening, stock culture maintenance, and genetic transformation. By studying the effect of antibiotics on microalgae growth, we can estimate the least value to inhibit growth of undesired pathogens in algal culture. We studied the effect of kanamycin and tetracycline on the growth and photosynthetic activity of two chlorophyte microalgae, Dictyosphaerium pulchellum and Micractinium pusillum. We measured CFU mL−1 on agar plates, optical density, fluorescence yields, and photosynthetic inhibition. Our results showed a significant effect of kan and tet on the tested microalgae species except tet, which showed a minor effect on M. pusillum. Both antibiotics are believed to interact with the protein synthesis machinery; hence, the inhibitory effect of the tested antibiotics was further confirmed by isolation and quantification of the whole cell protein. A significant reduction in protein quantity was observed at concentrations more than 5 mg L−1, except M. pusillum, which showed only a slight reduction in protein quantity even at the maximum tested concentration of tet (30 mg L−1). This study can further aid in aquaculture industry, for the maintenance of the microalgae stock cultures and it can also help the microalgae genetic engineers in the construction of molecular markers. PMID:27747232

  8. Ground level photosynthetically active radiation dynamics in stands of Acacia mearnsii De Wild.

    PubMed

    Péllico Netto, Sylvio; Sanquetta, Carlos R; Caron, Braulio O; Behling, Alexandre; Simon, Augusto A; Corte, Ana Paula D; Bamberg, Rogério

    2015-09-01

    The objective is to study the dynamics of photosynthetic radiation reaching the soil surface in stands of Acacia mearnsii De Wild and its influence on height growth in stands. This fact gives rise to the formulation of the following hypothesis for this study: "The reduction of the incidence of light inside the stand of black wattle will cause the inflection point in its height growth when this reaches 4 to 5 m in height, i.e. when the stand is between 2 and 3 years of age". The study was conducted in stands in the state of Rio Grande do Sul, Brazil, where diameters at breast height, total height and photosynthetically active radiation available at ground level were measured. The frequency tended to be more intense when the age of the stands increases. It was evident that a reduction of light incidence inside the forest occurred, caused by canopy closure. Consequently, closed canopy propitiated the competition of plants. This has affected the conditions for growth in diameter and height of this species, reason why it becomes possible to conceive the occurrence of an inflection point in the growth of these two variables, confirming the formulated hypothesis. PMID:26375018

  9. Screening of photosynthetic pigments for herbicidal activity with a new computational molecular approach.

    PubMed

    Krishnaraj, R Navanietha; Chandran, Saravanan; Pal, Parimal; Berchmans, Sheela

    2013-12-01

    There is an immense interest among the researchers to identify new herbicides which are effective against the herbs without affecting the environment. In this work, photosynthetic pigments are used as the ligands to predict their herbicidal activity. The enzyme 5-enolpyruvylshikimate-3-phosphate (EPSP) synthase is a good target for the herbicides. Homology modeling of the target enzyme is done using Modeler 9.11 and the model is validated. Docking studies were performed with AutoDock Vina algorithm to predict the binding of the natural pigments such as β-carotene, chlorophyll a, chlorophyll b, phycoerythrin and phycocyanin to the target. β-carotene, phycoerythrin and phycocyanin have higher binding energies indicating the herbicidal activity of the pigments. This work reports a procedure to screen herbicides with computational molecular approach. These pigments will serve as potential bioherbicides in the future. PMID:24050696

  10. Analysis of photosynthetic activity in the most polluted stretch of river Ganga.

    PubMed

    Tare, Vinod; Yadav, Ajay Veer Singh; Bose, Purnendu

    2003-01-01

    As a result of the increasing anthropogenic activities in the gangetic plain, Ganga water quantity as well as quality has declined over the years. A major effort to clean Ganga, named Ganga Action Plan (GAP) was instituted by the Government of India in 1984. The emphasis in GAP was on the reduction of organic load on the river through interception, diversion and treatment of wastewater reaching the river, thus maintaining the biochemical oxygen demand (BOD) and dissolved oxygen (DO) levels of river within the acceptable limits. A major criticism of GAP is that the significance of river ecology has not been addressed adequately during its conception and implementation. One of the important aspects from this perspective is the photosynthetic activity in the river Ganga. It has been postulated that photosynthetic activity plays an important role in maintaining high levels of DO in Ganga, and as a result the river can assimilate high organic loads without appreciable depletion in dissolved oxygen levels. Objective of the present study was to assess the photosynthetic activity and oxygen production rates in the river and correlate these values with various water quality parameters. Most polluted stretch of Ganga, which is known as the Kannauj-Kanpur stretch was chosen for this study. Based on the results of the study, it was concluded that despite implementation of phase I of GAP, and consequent diversion and reduction of organic loading to the river, both BOD and DO levels in the river has increased in the entire Kannauj-Kanpur stretch, except at Jajmau, where anaerobically treated effluent is discharged to the river. The nitrogen levels have also increased in the entire Kannauj-Kanpur stretch. Dissolved oxygen (DO) and alkalinity in the river water vary diurnally at all sites. Chlorophyll-a levels and oxygen production rates due to photosynthesis appear to be positively influenced by phosphate levels in the river water. Chlorophyll-a levels appear to be negatively

  11. Integrated passive/active vibration absorber for multi-story buildings

    NASA Technical Reports Server (NTRS)

    Lee-Glauser, Gina J.; Ahmadi, Goodarz; Horta, Lucas G.

    1995-01-01

    Passive isolator, active vibration absorber, and an integrated passive/active (hybrid) control are studied for their effectiveness in reducing structural vibration under seismic excitations. For the passive isolator, a laminated rubber bearing base isolator which has been studied and used extensively by researchers and seismic designers is considered. An active vibration absorber concept, which can provide guaranteed closed-loop stability with minimum knowledge of the controlled system, is used to reduce the passive isolator displacement and to suppress the top floor vibration. A three-story building model is used for the numerical simulation. The performance of an active vibration absorber and a hybrid vibration controller in reducing peak structural responses is compared with the passively isolated structural response and with absence of vibration control systems under the N00W component of El Centro 1940 and N90W component of the Mexico City earthquake excitation records. The results show that the integrated passive/active vibration control system is most effective in suppressing the peak structural acceleration for the El Centro 1940 earthquake when compared with the passive or active vibration absorber alone. The active vibration absorber, however, is the only system that suppresses the peak acceleration of the structure for the Mexico City 1985 earthquake.

  12. Effect of smoke on the transmissivity of photosynthetically active radiation inside the canopy

    NASA Astrophysics Data System (ADS)

    Yamasoe, M.; von Randow, C.; Manzi, A.; Schafer, J.; Eck, T.; Holben, B.

    2005-08-01

    Biomass burning activities emit high concentrations of aerosol particles to the atmosphere. Such particles can interact with solar radiation, decreasing the amount of light reaching the surface and increasing the fraction of diffuse radiation through scattering processes. This work reports results from photosynthetic active radiation (PAR) and aerosol optical depth (AOD) measurements conducted simultaneously at Reserva Biológica do Jaru (Rondonia State, Brazil) during LBA/SMOCC (Large-Scale Biosphere-Atmosphere Experiment in Amazonia/ Smoke, Aerosols, Clouds, Rainfall, and Climate) and RaCCI (Radiation, Cloud, and Climate Interactions in the Amazon during the Dry-to-Wet Transition Season) field experiments from 15 September to 15 November 2002. AOD values were retrieved from an AERONET (Aerosol Robotic Network) radiometer, MODIS (Moderate Resolution Spectroradiometer) and a portable sunphotometer from the United States Department of Agriculture-Forest Service. Daily mean downward PAR irradiance at the top of canopy was reduced by up to 50% due to the smoke aerosol particles. This radiation reduction affected turbulent fluxes of sensible and latent heats at the surface, observed particularly for high values of aerosol optical depth. The increase of aerosol optical depth also enhanced the transmission of photosynthetic active radiation inside the canopy. This result was a consequence of enhanced availability of diffuse radiation due to light scattering by the aerosol particles. A complex relationship was identified between light availability inside the canopy and net ecosystem exchange (NEE). The results showed that the increase of aerosol optical depth corresponded to an increase on CO2 exchange, indicating more CO2 uptake by the vegetation. However, for a higher AOD value, the corresponding NEE was lower than for intermediate values. Further studies are needed to better understand these findings, which were reported for the first time for the Amazon region under

  13. Growth, photosynthetic activity and oxidative stress in wheat (Triticum aestivum) after exposure of lead to soil.

    PubMed

    Kaur, Gurpreet; Singh, Harminder Pal; Batish, Daizy R; Kohli, Ravinder Kumar

    2012-03-01

    The present study was conducted to assess quantitative information about lead (Pb) contamination in soil on the growth and physiology of wheat. Solutions with three different concentrations of Pb as [Pb(NO3)2 at 500, 1000 and 2500 microM] were incorporated into the soil to achieve Pb-stressed conditions in comparison to unstressed, water treated, control variant. Wheat growth measured in terms of root length, shoot length and dry weight exhibited a significant decline with increasing Pb concentrations in the soil. Root and shoot length and seedling weight declined in the range of -23-51, -17-44, and -21-44% in response to 500 to 2500 microM Pb. In addition, there was a significant reduction in the levels of photosynthetic pigments-chlorophyll a (16-66%) and b (10-24%) and total chlorophyll content (by 14-39%) in plants growing in Pb-contaminated soil. It indicated a negative effect on photosynthetic activity in wheat and was confirmed by reduced photochemical efficiency of PSII (Fv/Fm) in the range of - 3-37% in response to 500 to 2500 microM Pb. The reduction in wheat growth in Pb-contaminated soil was accompanied by induction of oxidative stress as indicated by enhanced lipid peroxidation ir. terms of malondialdehyde (MDA) content (by 18-40%) and hydrogen peroxide (H2O2) content (by 34-123%) and alterations in the activity of enzymes, superoxide dismutases (SOD) and guaiacol peroxidases (GPX) in wheat roots. The study concludes that Pb in soil inhibits growth and phototsynthetic activity in wheat through induction of oxidative stress.

  14. Salinity effects on growth, photosynthetic parameters, and nitrogenase activity in estuarine planktonic cyanobacteria.

    PubMed

    Moisander, P H; McClinton, E; Paerl, H W

    2002-05-01

    Salinity has been suggested as being a controlling factor for blooms of N2-fixing cyanobacteria in estuaries. We tested the effect of salinity on the growth, N2 fixation, and photosynthetic activities of estuarine and freshwater isolates of heterocystous bloom-forming cyanobacteria. Anabaena aphanizomenoides and Anabaenopsis sp. were isolated from the Neuse River Estuary, North Carolina, and Cylindrospermopsis raciborskii from Lakes Dora and Griffin, central Florida. Salinity tolerance of these cyanobacteria was compared with that of two Nodularia strains from the Baltic Sea. We measured growth rates, N2 fixation (nitrogenase activity), and CO2 fixation at salinities between 0 and 20 g L(-1) NaCl. We also examined photosynthesis-irradiance relation-ships in response to salinity. Anabaenopsis maintained similar growth rates in the full range of salinities from 2 to 20 g L(-1) NaCl. Anabaena grew at up to 15 g L-', but the maximum salinity 20 g L(-1) NaCl was inhibitory. The upper limit for salinity tolerance of Cylindrospermopsis was 4 g L(-1) NaCl. Nodularia spp. maintained similar growth rates in the full range of salinities from 0 to 20 g L(-1) . Between 0 and 10 g L(-1), the growth rate of Nodularia spumigena was slower than that of the Neuse Estuary strains. In most strains, the sensitivity of nitrogenase activity and CO2 fixation to salinity appeared similar. Anabaenopsis, Anabaena, and the two Nodularia strains rapidly responded to NaCl by increasing their maximum photosynthetic rates (Pmn). Overall, both Neuse River Estuary and Baltic Sea strains showed an ability to acclimate to salt stress over short-(24 h) and long-term (several days to weeks) exposures. The study suggested that direct effect of salinity (as NaCl in these experiments) on cyanobacterial physiology does not alone explain the low frequency and magnitude of blooms of N2-fixing cyanobacteria in estuaries. PMID:12043002

  15. Towards improved quantification of vegetation photosynthetic activity at global scale: the FLuorescence EXplorer (FLEX) mission

    NASA Astrophysics Data System (ADS)

    Moreno, Jose

    2014-05-01

    The fluorescence signal, originated from the core complexes of the photosynthetic machinery, is a sensitive indicator of the actual photosynthesis in both healthy and physiologically stressed vegetation, which can be used as a powerful non-invasive marker to track the status, resilience, and recovery of photochemical processes. This is of particular interest for the improvements in the predictive capability of global carbon cycle models through new parameterizations for canopy photosynthesis and the corresponding exchange processes of energy, water and carbon between the surface and the atmosphere. The shape of the fluorescence emission spectrum consists of two peaks having broad bands with maxima around 685 nm and 740 nm. The variations in amplitude and shape of the emission reflect the efficiency of photosynthetic electron transport. The integral of the overall fluorescence emission provides information about actual photosynthetic light conversion. The shape of the emission spectrum provides additional information about the vegetation health status. While most of the information that has been acquired by remote sensing of the Earth's surface about vegetation conditions and photosynthetic activity has come from "reflected" light in the solar domain, the ESA's Earth Explorer candidate FLEX (Fluorescence EXplorer) mission is the first space mission focused on the estimation of fluorescence emission by terrestrial vegetation on a global scale with high spatial resolution and resolving the spectral shape of fluorescence emission. The FLEX mission also includes explicit measurement of photochemical changes in reflectance (i.e., PRI), canopy temperature measurements and all the relevant variables (chlorophyll content, Leaf Area Index, etc.) needed to asses the actual physiological status of vegetation and to provide quantitative estimates of photosynthetic rates and gross primary production. FLEX is one of two candidate Earth Explorer-8 missions currently under Phase A

  16. Cytochrome c-553 is not required for photosynthetic activity in the cyanobacterium Synechococcus.

    PubMed Central

    Laudenbach, D E; Herbert, S K; McDowell, C; Fork, D C; Grossman, A R; Straus, N A

    1990-01-01

    In cyanobacteria, the water-soluble cytochrome c-553 functions as a mobile carrier of electrons between the membrane-bound cytochrome b6-f complex and P-700 reaction centers of Photosystem I. The structural gene for cytochrome c-553 (designated cytA) of the cyanobacterium Synechococcus sp. PCC 7942 was cloned, and the deduced amino acid sequence was shown to be similar to known cyanobacterial cytochrome c-553 proteins. A deletion mutant was constructed that had no detectable cytochrome c-553 based on spectral analyses and tetramethylbenzidine-hydrogen peroxide staining of proteins resolved by polyacrylamide gel electrophoresis. The mutant strain was not impaired in overall photosynthetic activity. However, this mutant exhibited a decreased efficiency of cytochrome f oxidation. These results indicate that cytochrome c-553 is not an absolute requirement for reducing Photosystem I reaction centers in Synechococcus sp. PCC 7942. PMID:1967057

  17. Intercepted photosynthetically active radiation in wheat canopies estimated by spectral reflectance. [Phoenix, Arizona

    NASA Technical Reports Server (NTRS)

    Hatfield, J. L.; Asrar, G.; Kanemasu, E. T.

    1982-01-01

    The interception of photosynthetically active radiation (PAR) was evaluated relative to greenness and normalized difference (MSS 7-5/7+5) for five planting dates of wheat for 1978-79 and 1979-80 in Phoenix. Intercepted PAR was calculated from a model driven by leaf area index and stage of growth. Linear relationships were found between greenness and normalized difference with a separate model representing growth and senescence of the crop. Normalized difference was a significantly better model and would be easier to apply than the empirically derived greenness parameter. For the leaf area growth portion of the season the model between PAR interception and normalized difference was the same over years, however, for the leaf senescence the models showed more variability due to the lack of data on measured interception in sparse canopies. Normalized difference could be used to estimate PAR interception directly for crop growth models.

  18. Regulation of rhizosphere acidification by photosynthetic activity in cowpea (Vigna unguiculata L. walp.) seedlings.

    PubMed

    Rao, Theertham P; Yano, Katsuya; Iijima, Morio; Yamauchi, Akira; Tatsumi, Jiro

    2002-02-01

    In contrast to cereals or other crops, legumes are known to acidify the rhizosphere even when supplied with nitrates. This phenomenon has been attributed to N2 fixation allowing excess uptake of cations over anions; however, as we have found previously, the exposure of the shoot to illumination can cause rhizosphere acidification in the absence of N2 fixation in cowpea (Vigna unguiculata L. Walp). In this study, we examined whether the light-induced acidification can relate to photosynthetic activity and corresponding alterations in cation-anion uptake ratios. The changes of rhizosphere pH along the root axis were visualized using a pH indicator agar gel. The intensity of pH changes (alkalization/acidification) in the rhizosphere was expressed in proton fluxes, which were obtained by processing the images of the pH indicator agar gel. The uptake of cations and anions was measured in nutrient solution. The rhizosphere was alkalinized in the dark but acidified with exposure of the shoots to light. The extent of light-induced acidification was increased with leaf size and intensity of illumination on the shoot, and completely stopped with the application of photosynthesis inhibitor. Although the uptake of cations was significantly lower than that of anions, the rhizosphere was acidified by light exposure. Proton pump inhibitors N,N'-dicyclohexyl carbodimide and vanadate could not stop the light-induced acidification. The results indicate that light-induced acidification in cowpea seedlings is regulated by photosynthetic activity, but is not due to excess uptake of cations. PMID:12099352

  19. Growth habit and photo-synthetic activity of shoot cultures of Medicago sativa L. transformed with the oryzacystatin II gene

    Technology Transfer Automated Retrieval System (TEKTRAN)

    In vitro maintained shoot cultures of alfalfa (Medicago sativa L. cv. Zajeÿarska 83) that were transformed with the oryzacystatin II (OCII) gene and propagated on growth regulator-free medium were subjected to analysis of morphological characteristics and photosynthetic activity. The most striking f...

  20. An ultra-thin broadband active frequency selective surface absorber for ultrahigh-frequency applications

    NASA Astrophysics Data System (ADS)

    Xu, Wenhua; He, Yun; Kong, Peng; Li, Jialin; Xu, Haibing; Miao, Ling; Bie, Shaowei; Jiang, Jianjun

    2015-11-01

    At frequencies below 2 GHz, conventional microwave absorbers are limited in application by their thickness or narrow absorption bandwidth. In this paper, we propose and fabricate an ultra-thin broadband active frequency selective surface (AFSS) absorber with a stretching transformation (ST) pattern for use in the ultrahigh-frequency (UHF) band. This absorber is loaded with resistors and varactors to produce its tunability. To expand the tunable bandwidth, we applied the ST with various coefficients x and y to the unit cell pattern. With ST coefficients of x = y = 1, the tunability and strong absorption are concisely demonstrated, based on a discussion of impedance matching. On analyzing the patterns with various ST coefficients, we found that a small x/y effectively expands the tunable bandwidth. After this analysis, we fabricated an AFSS absorber with ST coefficients of x = 0.7 and y = 1. Its measured reflectivity covered a broad band of 0.7-1.9 GHz below -10 dB at bias voltages of 10-48 V. The total thickness of this absorber, 7.8 mm, was only ˜λ/54 of the lower limit frequency, ˜λ/29 of the center frequency, and ˜λ/20 of the higher limit frequency. Our measurements and simulated results indicate that this AFSS absorber can be thin and achieve a broad bandwidth simultaneously.

  1. Active control of payload fairing noise using distributed active vibration absorbers

    NASA Astrophysics Data System (ADS)

    Charpentier, Arnaud; Johnson, Marty E.; Fuller, Chris R.

    2003-04-01

    High sound pressure inside a launch vehicle fairing during lift-off can damage the payload. Interior levels of up to 140 dB between 60 and 250 Hz are mostly due to exhaust plume noise combined with the limited transmission loss of lightweight composite fairings and little acoustic damping in the fairing volume. Past work using passive and hybrid passive/reactive noise control devices has shown that their limitations are mostly due to packaging volume and weight penalty. The objective of this work is to design a lightweight, compact, and low electrical power active noise control system to reduce the fairing interior sound level. Hybrid active/passive actuators such as Smart Foam (Couche and Fuller, Proceedings of Active 1999, Ft. Lauderdale, FL, pp. 609-620) and Distributed Active Vibration Absorbers (Marcotte, Fuller, and Johnson, Proceedings of Active 2002, ISVR, Southampton, England, pp. 535-546) are optimized for fairing noise control. The latter have been used to increase the transmission loss of the fairing. Active noise control test results on a sub-scale, sandwich composite fairing are presented. The global interior acoustic response due to airborne exterior excitation is minimized using an adaptive multiple-input, multiple-output feedforward controller. [Work supported by the Air Force Research Laboratory, Space Vehicles Directorate (AFRL).

  2. Microelectrode studies of interstitial water chemistry and photosynthetic activity in a hot spring microbial mat

    SciTech Connect

    Revsbech, N.P.; Ward, D.M.

    1984-08-01

    Microelectrodes were used to measure oxygen, pH, and oxygenic photosynthetic activity in a hot spring microbial mat (Octopus Spring, Yellowstone National Park), where the cyanobacterium Synechoccus lividus and the filamentous bacteria Chloroflexus aurantiacus are the only known phototrophs. The data showed very high biological activities in the topmost layers of the microbial mat, resulting in extreme values for oxygen and pH. At a 1-mm depth at a 55 C site, oxygen and pH reached 900 micro M and 9.4, respectively, just after solar noon, whereas anoxic conditions with pH of 7.2 were measured before sunrise. Although diurnal changes between these extremes occurred over hours during a diurnal cycle microbial activity was great enough to give the same response in 1 to 2 mm after artificial shading. Oxygenic photosynthesis was confined to a 0.5- to 1.1-mm layer at sites with temperatures at or above about 50 C, with maximum activities in the 55 to 60 C region. The data suggest that S. lividus is the dominant primary producer of the mat. 30 references, 5 figures.

  3. Techniques for measuring intercepted and absorbed PAR in corn canopies

    NASA Technical Reports Server (NTRS)

    Gallo, K. P.; Daughtry, C. S. T.

    1984-01-01

    The quantity of radiation potentially available for photosynthesis that is captured by the crop is best described as absorbed photosynthetically active radiation (PAR). Absorbed PAR (APAR) is the difference between descending and ascending fluxes. The four components of APAR were measured above and within two planting densities of corn (Zea mays L.) and several methods of measuring and estimating APAR were examined. A line quantum sensor that spatially averages the photosynthetic photon flux density provided a rapid and portable method of measuring APAR. PAR reflectance from the soil (Typic Argiaquoll) surface decreased from 10% to less than 1% of the incoming PAR as the canopy cover increased. PAR reflectance from the canopy decreased to less than 3% at maximum vegetative cover. Intercepted PAR (1 - transmitted PAR) generally overestimated absorbed PAR by less than 4% throughout most of the growing season. Thus intercepted PAR appears to be a reasonable estimate of absorbed PAR.

  4. Photosynthetic carbon reduction and carbon oxidation cycles are the main electron sinks for photosystem II activity during a mild drought.

    PubMed

    Cornic, Gabriel; Fresneau, Chantal

    2002-06-01

    Stomatal closure can explain the inhibition of net CO2 uptake by a leaf subjected to a mild drought: the photosynthetic apparatus appears resistant to lack of water. Changes in both the water content of leaves maintained in a constant environment and the ambient CO2 molar fraction during measurements on well-hydrated leaves lead to similar effects on net CO2 uptake and whole chain electron transport as estimated by leaf chlorophyll fluorescence measurements. In particular, it is shown that photosystem II (PSII) functioning and its regulation are not qualitatively changed during desiccation and that the variations in PSII photochemistry can simply be understood by changes in substrate availability in this condition. Moreover, an analysis of the literature shows that when inhibition of net CO2 uptake by C3 leaves under drought (Phaseolus vulgaris L., Helianthus annus L. and Solanum tuberosum L.) was lower than 80 %, elevated CO2 completely restored the photosynthetic capacity. The CO2 molar fraction in the chloroplasts declines as stomata close in drying leaves. As a consequence, in C3 plants, ribulose-1,5-bisphosphate oxygenation increases and becomes the main sink for photosynthetic electrons. Depending on the prevailing photon flux density, the O2 uptake through photorespiratory activity can entirely replace carbon dioxide as an electron acceptor, or not. The rate of the Mehler reaction remains low and unchanged during desiccation. However, drought could also involve CO2-sensitive modification of the photosynthetic metabolism depending on plant growth conditions and possibly also on plant species.

  5. Changes in SBPase activity influence photosynthetic capacity, growth, and tolerance to chilling stress in transgenic tomato plants.

    PubMed

    Ding, Fei; Wang, Meiling; Zhang, Shuoxin; Ai, Xizhen

    2016-01-01

    Sedoheptulose-1, 7-bisphosphatase (SBPase) is an important enzyme involved in photosynthetic carbon fixation in the Calvin cycle. Here, we report the impact of changes in SBPase activity on photosynthesis, growth and development, and chilling tolerance in SBPase antisense and sense transgenic tomato (Solanum lycopersicum) plants. In transgenic plants with increased SBPase activity, photosynthetic rates were increased and in parallel an increase in sucrose and starch accumulation was evident. Total biomass and leaf area were increased in SBPase sense plants, while they were reduced in SBPase antisense plants compared with equivalent wild-type tomato plants. Under chilling stress, when compared with plants with decreased SBPase activity, tomato plants with increased SBPase activity were found to be more chilling tolerant as indicated by reduced electrolyte leakage, increased photosynthetic capacity, and elevated RuBP regeneration rate and quantum efficiency of photosystem II. Collectively, our data suggest that higher level of SBPase activity gives an advantage to photosynthesis, growth and chilling tolerance in tomato plants. This work also provides a case study that an individual enzyme in the Calvin cycle may serve as a useful target for genetic engineering to improve production and stress tolerance in crops. PMID:27586456

  6. Changes in SBPase activity influence photosynthetic capacity, growth, and tolerance to chilling stress in transgenic tomato plants.

    PubMed

    Ding, Fei; Wang, Meiling; Zhang, Shuoxin; Ai, Xizhen

    2016-09-02

    Sedoheptulose-1, 7-bisphosphatase (SBPase) is an important enzyme involved in photosynthetic carbon fixation in the Calvin cycle. Here, we report the impact of changes in SBPase activity on photosynthesis, growth and development, and chilling tolerance in SBPase antisense and sense transgenic tomato (Solanum lycopersicum) plants. In transgenic plants with increased SBPase activity, photosynthetic rates were increased and in parallel an increase in sucrose and starch accumulation was evident. Total biomass and leaf area were increased in SBPase sense plants, while they were reduced in SBPase antisense plants compared with equivalent wild-type tomato plants. Under chilling stress, when compared with plants with decreased SBPase activity, tomato plants with increased SBPase activity were found to be more chilling tolerant as indicated by reduced electrolyte leakage, increased photosynthetic capacity, and elevated RuBP regeneration rate and quantum efficiency of photosystem II. Collectively, our data suggest that higher level of SBPase activity gives an advantage to photosynthesis, growth and chilling tolerance in tomato plants. This work also provides a case study that an individual enzyme in the Calvin cycle may serve as a useful target for genetic engineering to improve production and stress tolerance in crops.

  7. Changes in SBPase activity influence photosynthetic capacity, growth, and tolerance to chilling stress in transgenic tomato plants

    PubMed Central

    Ding, Fei; Wang, Meiling; Zhang, Shuoxin; Ai, Xizhen

    2016-01-01

    Sedoheptulose-1, 7-bisphosphatase (SBPase) is an important enzyme involved in photosynthetic carbon fixation in the Calvin cycle. Here, we report the impact of changes in SBPase activity on photosynthesis, growth and development, and chilling tolerance in SBPase antisense and sense transgenic tomato (Solanum lycopersicum) plants. In transgenic plants with increased SBPase activity, photosynthetic rates were increased and in parallel an increase in sucrose and starch accumulation was evident. Total biomass and leaf area were increased in SBPase sense plants, while they were reduced in SBPase antisense plants compared with equivalent wild-type tomato plants. Under chilling stress, when compared with plants with decreased SBPase activity, tomato plants with increased SBPase activity were found to be more chilling tolerant as indicated by reduced electrolyte leakage, increased photosynthetic capacity, and elevated RuBP regeneration rate and quantum efficiency of photosystem II. Collectively, our data suggest that higher level of SBPase activity gives an advantage to photosynthesis, growth and chilling tolerance in tomato plants. This work also provides a case study that an individual enzyme in the Calvin cycle may serve as a useful target for genetic engineering to improve production and stress tolerance in crops. PMID:27586456

  8. Solar spectral conversion for improving the photosynthetic activity in algae reactors.

    PubMed

    Wondraczek, Lothar; Batentschuk, Miroslaw; Schmidt, Markus A; Borchardt, Rudolf; Scheiner, Simon; Seemann, Benjamin; Schweizer, Peter; Brabec, Christoph J

    2013-01-01

    Sustainable biomass production is expected to be one of the major supporting pillars for future energy supply, as well as for renewable material provision. Algal beds represent an exciting resource for biomass/biofuel, fine chemicals and CO2 storage. Similar to other solar energy harvesting techniques, the efficiency of algal photosynthesis depends on the spectral overlap between solar irradiation and chloroplast absorption. Here we demonstrate that spectral conversion can be employed to significantly improve biomass growth and oxygen production rate in closed-cycle algae reactors. For this purpose, we adapt a photoluminescent phosphor of the type Ca0.59Sr0.40Eu0.01S, which enables efficient conversion of the green part of the incoming spectrum into red light to better match the Qy peak of chlorophyll b. Integration of a Ca0.59Sr0.40Eu0.01S backlight converter into a flat panel algae reactor filled with Haematococcus pluvialis as a model species results in significantly increased photosynthetic activity and algae reproduction rate.

  9. Photosynthetically active radiation and comparison of methods for its estimation in equatorial Singapore

    NASA Astrophysics Data System (ADS)

    Tan, Puay Yok; Ismail, Mirza Rifqi Bin

    2016-02-01

    Photosynthetically active radiation (PAR) is an important input variable for urban climate, crop modelling and ecosystem services studies. Despite its importance, only a few empirical studies have been conducted on PAR, its relationship to global solar radiation and sky conditions and its estimation in the tropics. We report in this study, the characterisation of PAR in Singapore through direct measurements and development of models for its estimation using input variables of global solar radiation ( H), photometric radiation ( L), clearness index ( k t ) and sky view factor (SVF). Daily PAR showed a good correlation with daily H and had a comparatively small seasonal variation in PAR due to Singapore's equatorial position. The ratio of PAR to H ( PAR/ H) showed a slight depression in midyear from May to August, which correlated well with seasonal patterns in rainfall over the study period. Hourly PAR/ H increased throughout the day. Three empirical models developed in this study were able to predict daily PAR satisfactorily, with the most accurate model being one which included both H and k t as independent variables. A regression model for estimation of PAR under shaded conditions using SVF produced satisfactory estimation of daily PAR but was prone to high mean percentage error at low PAR levels.

  10. Solar spectral conversion for improving the photosynthetic activity in algae reactors

    NASA Astrophysics Data System (ADS)

    Wondraczek, Lothar; Batentschuk, Miroslaw; Schmidt, Markus A.; Borchardt, Rudolf; Scheiner, Simon; Seemann, Benjamin; Schweizer, Peter; Brabec, Christoph J.

    2013-06-01

    Sustainable biomass production is expected to be one of the major supporting pillars for future energy supply, as well as for renewable material provision. Algal beds represent an exciting resource for biomass/biofuel, fine chemicals and CO2 storage. Similar to other solar energy harvesting techniques, the efficiency of algal photosynthesis depends on the spectral overlap between solar irradiation and chloroplast absorption. Here we demonstrate that spectral conversion can be employed to significantly improve biomass growth and oxygen production rate in closed-cycle algae reactors. For this purpose, we adapt a photoluminescent phosphor of the type Ca0.59Sr0.40Eu0.01S, which enables efficient conversion of the green part of the incoming spectrum into red light to better match the Qy peak of chlorophyll b. Integration of a Ca0.59Sr0.40Eu0.01S backlight converter into a flat panel algae reactor filled with Haematococcus pluvialis as a model species results in significantly increased photosynthetic activity and algae reproduction rate.

  11. A new function based on boltzmann statistisc to model the distribution of photosynthetically active radiation data

    NASA Astrophysics Data System (ADS)

    Tovar-Pescador, J.; Pozo-Vázquez, D.; Batlles, J.; López, G.; Rubio, M. A.

    2003-04-01

    To obtain simple correlations for the estimation of the performance of biological systems, which transform the solar energy by photosynthesis, and to generate synthetic data, it is necessary to know the frequency distributions of photosynthetically active radiation (PAR). In this work we carried out an analysis of the properties of hourly values of PAR data collected in southern Spain. Its dependence on the optical mass for all type of skies, including cloudy skies, is analyzed. Results show that, for a given value of the optical mass, the PAR density distributions are not symmetrical and have certain degree of bimodality. The increment in the optical mass value has two effects on the PAR distributions, the first one is a shift toward lower values of the maximum and the second one is a decrease in the range of PAR values. A model of the frequency distribution of PAR values, based on a new kind of functions related to the Boltzmann´s statistic, is proposed. The parameters of these functions depend just on the optical mass. Results show a very good agreement between the data and the model proposed

  12. Proposal of a function for modelling the hourly frequency distributions of photosynthetically active radiation

    NASA Astrophysics Data System (ADS)

    Tovar-Pescador, J.; Pozo-Vazquez, D.; Batlles, J.; López, G.; Muñoz-Vicente, D.

    2004-10-01

    Solar irradiance is a key factor in the physiological processes of living beings. To obtain simple correlations for the estimation of the performance of biological systems, which transform the solar energy by photosynthesis, and to generate synthetic data, it is necessary to know the frequency distributions of photosynthetically active radiation (PAR). In this work we carried out an analysis of the properties of hourly values of PAR data, using 9 years of data collected in southern Spain. In particularly, its dependence on the optical mass, for all type of skies including cloudy skies, is studied. Results shows that, for a given value of the optical mass, the PAR density distributions are not symmetrical and have a certain degree of bimodality. The increment in the optical mass value has two effects on the PAR distributions, the first one is a shift toward lower values of the maximum and the second one is a decrease in the range of PAR values. Finally, a model of the frequency distribution of PAR values, based on a new kind of functions related to the Boltzmann’s statistic, is proposed. The parameters of these functions depend just on the optical mass. Results show a very good agreement between the data and the model proposed.

  13. Solar spectral conversion for improving the photosynthetic activity in algae reactors.

    PubMed

    Wondraczek, Lothar; Batentschuk, Miroslaw; Schmidt, Markus A; Borchardt, Rudolf; Scheiner, Simon; Seemann, Benjamin; Schweizer, Peter; Brabec, Christoph J

    2013-01-01

    Sustainable biomass production is expected to be one of the major supporting pillars for future energy supply, as well as for renewable material provision. Algal beds represent an exciting resource for biomass/biofuel, fine chemicals and CO2 storage. Similar to other solar energy harvesting techniques, the efficiency of algal photosynthesis depends on the spectral overlap between solar irradiation and chloroplast absorption. Here we demonstrate that spectral conversion can be employed to significantly improve biomass growth and oxygen production rate in closed-cycle algae reactors. For this purpose, we adapt a photoluminescent phosphor of the type Ca0.59Sr0.40Eu0.01S, which enables efficient conversion of the green part of the incoming spectrum into red light to better match the Qy peak of chlorophyll b. Integration of a Ca0.59Sr0.40Eu0.01S backlight converter into a flat panel algae reactor filled with Haematococcus pluvialis as a model species results in significantly increased photosynthetic activity and algae reproduction rate. PMID:23797513

  14. Experimental studies on active control of a dynamic system via a time-delayed absorber

    NASA Astrophysics Data System (ADS)

    Xu, Jian; Sun, Yixia

    2015-04-01

    The traditional passive absorber is fully effective within a narrow and certain frequency band. To solve this problem, a time-delayed acceleration feedback is introduced to convert a passive absorber into an active one. Both the inherent and the intentional time delays are included. The former mainly comes from signal acquiring and processing, computing, and applying the actuation force, and its value is fixed. The latter is introduced in the controller, and its value is actively adjustable. Firstly, the mechanical model is established and the frequency response equations are obtained. The regions of stability are delineated in the plane of control parameters. Secondly, the design scheme of control para- meters is performed to help select the values of the feedback gain and time delay. Thirdly, the experimental studies are conducted. Effects of both negative and positive feedback control are investigated. Experimental results show that the proper choices of control parameters may broaden the effective frequency band of vibration absorption. Moreover, the time-delayed absorber greatly suppresses the resonant response of the primary system when the passive absorber totally fails. The experimental results are in good agreement with the theoretical predictions and numerical simulations.

  15. Skin Anti-Aging Activities of Bacteriochlorophyll a from Photosynthetic Bacteria, Rhodobacter sphaeroides.

    PubMed

    Kim, Nam Young; Yim, Tae Bin; Lee, Hyeon Yong

    2015-10-01

    In this work, the anti-aging skin effects of bacteriochlorophyll a isolated from Rhodobacter sphaeroides are first reported, with notably low cytotoxicity in the range of 1% to 14% in adding 0.00078 (% (w/w)) of the extracts, compared with the normal growth of both human dermal fibroblast and keratinocyte cells without any treatment as a control. The highest production of procollagen from human fibroblast cells (CCD-986sk) was observed as 221.7 ng/ml with 0.001 (% (w/w)) of bacteriochlorophyll a, whereas 150 and 200 ng/ml of procollagen production resulted from addition of 0.001 (% (w/w)) of the photosynthetic bacteria. The bacteriochlorophylla- induced TNF-α production increased to 63.8%, which was lower secretion from HaCaT cells than that from addition of 0.00005 (% (w/w)) of bacteriochlorophyll a. Additionally, bacteriochlorophyll a upregulated the expression of genes related to skin anti-aging (i.e., keratin 10, involucrin, transglutaminase-1, and MMPs), by up to 4-15 times those of the control. However, crude extracts from R. sphaeroides did not enhance the expression level of these genes. Bacteriochlorophyll a showed higher antioxidant activity of 63.8% in DPPH free radical scavenging than those of water, ethanol, and 70% ethanol extracts (14.0%, 57.2%, and 12.6%, respectively). It was also shown that the high antioxidant activity could be attributed to the skin anti-aging effect of bacteriochlorophyll a, although R. sphaeroides itself would not exhibit significant anti-aging activities.

  16. Effect of Chilling on Carbon Assimilation, Enzyme Activation, and Photosynthetic Electron Transport in the Absence of Photoinhibition in Maize Leaves.

    PubMed Central

    Kingston-Smith, A. H.; Harbinson, J.; Williams, J.; Foyer, C. H.

    1997-01-01

    The relationships between electron transport and photosynthetic carbon metabolism were measured in maize (Zea mays L.) leaves following exposure to suboptimal temperatures. The quantum efficiency for electron transport in unchilled leaves was similar to that previously observed in C3 plants, although maize has two types of chloroplasts, mesophyll and bundle sheath, with PSII being largely absent from the latter. The index of noncyclic electron transport was proportional to the CO2 assimilation rate. Chilled leaves showed decreased rates of CO2 assimilation relative to unchilled leaves, but the integral relationships between the quantum efficiency for electron transport or the index of noncyclic electron transport and CO2 fixation were unchanged and there was no photoinhibition. The maximum catalytic activities of the Benson-Calvin cycle enzymes, fructose-1,6-bisphosphatase and ribulose-1,5-bisphosphate carboxylase, were decreased following chilling, but activation was unaffected. Measurements of thiol-regulated enzymes, particularly NADP-malate dehydrogenase, indicated that chilling induced changes in the stromal redox state so that reducing equivalents were more plentiful. We conclude that chilling produces a decrease in photosynthetic capacity without changing the internal operational, regulatory or stoichiometric relationships between photosynthetic electron transport and carbon assimilation. The enzymes of carbon assimilation are particularly sensitive to chilling, but enhanced activation may compensate for decreases in maximal catalytic activity. PMID:12223758

  17. Effect of smoke and clouds on the transmissivity of photosynthetically active radiation inside the canopy

    NASA Astrophysics Data System (ADS)

    Yamasoe, M. A.; von Randow, C.; Manzi, A. O.; Schafer, J. S.; Eck, T. F.; Holben, B. N.

    2006-05-01

    Biomass burning activities emit high concentrations of aerosol particles to the atmosphere. Such particles can interact with solar radiation, decreasing the amount of light reaching the surface and increasing the fraction of diffuse radiation through scattering processes, and thus has implications for photosynthesis within plant canopies. This work reports results from photosynthetically active radiation (PAR) and aerosol optical depth (AOD) measurements conducted simultaneously at Reserva Biológica do Jaru (Rondonia State, Brazil) during LBA/SMOCC (Large-Scale Biosphere-Atmosphere Experiment in Amazonia/ Smoke, Aerosols, Clouds, Rainfall, and Climate) and RaCCI (Radiation, Cloud, and Climate Interactions in the Amazon during the Dry-to-Wet Transition Season) field experiments from 15 September to 15 November 2002. AOD values were retrieved from an AERONET (Aerosol Robotic Network) radiometer, MODIS (Moderate Resolution Spectroradiometer) and a portable sunphotometer from the United States Department of Agriculture - Forest Service. Significant reduction of PAR irradiance at the top of the canopy was observed due to the smoke aerosol particles layer. This radiation reduction affected turbulent fluxes of sensible and latent heats. The increase of AOD also enhanced the transmission of PAR inside the canopy. As a consequence, the availability of diffuse radiation was enhanced due to light scattering by the aerosol particles. A complex relationship was identified between light availability inside the canopy and net ecosystem exchange (NEE). The results showed that the increase of aerosol optical depth corresponded to an increase of CO2 uptake by the vegetation. However, for even higher AOD values, the corresponding NEE was lower than for intermediate values. As expected, water vapor pressure deficit (VPD), retrieved at 28m height inside the canopy, can also affect photosynthesis. A decrease in NEE was observed as VPD increased. Further studies are needed to better

  18. Moderate Thermal Stress Causes Active and Immediate Expulsion of Photosynthetically Damaged Zooxanthellae (Symbiodinium) from Corals

    PubMed Central

    Fujise, Lisa; Yamashita, Hiroshi; Suzuki, Go; Sasaki, Kengo; Liao, Lawrence M.; Koike, Kazuhiko

    2014-01-01

    The foundation of coral reef biology is the symbiosis between corals and zooxanthellae (dinoflagellate genus Symbiodinium). Recently, coral bleaching, which often results in mass mortality of corals and the collapse of coral reef ecosystems, has become an important issue around the world as coral reefs decrease in number year after year. To understand the mechanisms underlying coral bleaching, we maintained two species of scleractinian corals (Acroporidae) in aquaria under non-thermal stress (27°C) and moderate thermal stress conditions (30°C), and we compared the numbers and conditions of the expelled Symbiodinium from these corals. Under non-thermal stress conditions corals actively expel a degraded form of Symbiodinium, which are thought to be digested by their host coral. This response was also observed at 30°C. However, while the expulsion rates of Symbiodinium cells remained constant, the proportion of degraded cells significantly increased at 30°C. This result indicates that corals more actively digest and expel damaged Symbiodinium under thermal stress conditions, likely as a mechanism for coping with environmental change. However, the increase in digested Symbiodinium expulsion under thermal stress may not fully keep up with accumulation of the damaged cells. There are more photosynthetically damaged Symbiodinium upon prolonged exposure to thermal stress, and corals release them without digestion to prevent their accumulation. This response may be an adaptive strategy to moderate stress to ensure survival, but the accumulation of damaged Symbiodinium, which causes subsequent coral deterioration, may occur when the response cannot cope with the magnitude or duration of environmental stress, and this might be a possible mechanism underlying coral bleaching during prolonged moderate thermal stress. PMID:25493938

  19. Suppression of rotary unbalance spin-up vibration using passive and semi-active vibration absorbers

    NASA Astrophysics Data System (ADS)

    Begg, Colin Duncan

    Rotating machine unbalance can be the source of unwanted vibrations in many mechanical systems. One problematic form of unbalance force is generated by machine start-up or shut-down. Start-up/shut-down unbalance induces a harmonic excitation force with a varying frequency that is directly proportional to rotor speed, and an amplitude that is proportional to the square of the frequency. When the frequency of a start-up/shut-down unbalance approaches or passes a system resonant frequency, large amplitude vibrations can occur. These vibrations generate greater than normal system operating forces, which could accelerate cumulative part wear and damage internal components. Such degradation could significantly reduce a mechanical system's life. This thesis presents a passive and a semi-active control method for the suppression of vibrations caused by unbalance spin-up excitation (focusing on the start-up scenario) in a mechanical structure. Both methods employ dynamic vibration absorbers (DVAs). A passive control method using dual mechanical DVAs has been previously proposed (Bursal, 1995). As a basis for design, Bursal (1995) made a conjecture that shaping the system's frequency response function (FRF) by using DVAs to provide a low, flattened, FRF curve over the excitation spin-up frequency range, would minimize the structural vibration response for an unbalance spin-up event. Although the method has been shown to be effective for a few sets of conditions, the conjecture of using steady-state-based FRF-Shaping to suppress transient responses (spin-up unbalance generates a transient response) has not been substantiated. This thesis validates the dual absorber design conjecture and provides additional information regarding the optimal design of such a system. The parametric studies compare the performances between an optimal design (minimum peak response) and the FRF-Shaping design. It is shown that the performances of the two designs are similar for very slow spin

  20. Phytoplankton photosynthetic activity dynamics in a temperate macrotidal ecosystem (the Strait of Dover, eastern English Channel): Time scales of variability and environmental control

    NASA Astrophysics Data System (ADS)

    Houliez, Emilie; Lizon, Fabrice; Lefebvre, Sébastien; Artigas, Luis Felipe; Schmitt, François G.

    2015-07-01

    The temporal variability in phytoplankton photosynthetic activity was studied in the coastal waters of the Strait of Dover and related to environmental conditions. Phytoplankton photosynthetic activity data collected from October 2008 and August 2010 at different time scales (hourly to interannual) using a nested sampling design are presented. Photosynthetic parameters including the maximum quantum yield (Fv/Fm), maximal light utilization efficiency (α), maximum electron transport rate (ETRm) and light saturation coefficient (Ek) were measured using Pulse Amplitude Modulation (PAM) fluorometry. Information on the taxonomic composition of phytoplankton assemblages and physicochemical parameters were also collected. Marked changes in photosynthetic parameters were observed at the different time scales investigated. The variability of photosynthetic parameters at sub-seasonal scale (hourly to monthly) could be of the same order of magnitude as at seasonal scale. At short time scale (hour to week), there was no consistent pattern of diel periodicity in photosynthetic parameters. There was a decline of ETRm and α during the day as often as there was a peak at the maximum of irradiance. Light conditions were the main influencing factor on photosynthetic parameters at these time scales. The optimal use of incident irradiance seemed focused on between-day rather than within-day variability. At longer time scale (seasonal to interannual), close interplays between shifts in community taxonomic composition and changes in the physicochemical characteristics of the environment controlled the variability in photosynthetic parameters. Whatever the time scale and period of year considered, variability in photosynthetic parameters was "Ek-independent". In well-mixed macrotidal ecosystems, such as the Strait of Dover, a nested sampling design allowing to characterize the short- (intraday and daily) as well as long-term variability (within months, monthly, seasonal, annual and

  1. Active-to-absorbing-state phase transition in an evolving population with mutation

    NASA Astrophysics Data System (ADS)

    Sarkar, Niladri

    2015-10-01

    We study the active to absorbing phase transition (AAPT) in a simple two-component model system for a species and its mutant. We uncover the nontrivial critical scaling behavior and weak dynamic scaling near the AAPT that shows the significance of mutation and highlights the connection of this model with the well-known directed percolation universality class. Our model should be a useful starting point to study how mutation may affect extinction or survival of a species.

  2. Effect of Azospirillum brasilense and Burkholderia unamae Bacteria on Maize Photosynthetic Activity Evaluated Using the Photoacoustic Technique

    NASA Astrophysics Data System (ADS)

    Gordillo-Delgado, F.; Marín, E.; Calderón, A.

    2016-09-01

    In this work, the photosynthetic process of maize plants ( Zea mays), which were grown using seeds inoculated with plant growth promoting bacteria Azospirillum brasilense and Burkholderia unamae, was monitored. Photothermal and photobaric signals obtained by a time-resolved photoacoustic measurement configuration were used for measuring the oxygen evolution rate in situ. A frequency-resolved configuration of the method was utilized to determine the oxygen diffusion coefficient and the thermal diffusivity of the maize leaves. The latter parameters, which can be used as indicators of the photosynthetic activity of maize, are found to vary according to the plant-microbe interaction. Treatment with plant growth promoting bacteria induced a decrease in the oxygen diffusion coefficient of about 20 %.

  3. Using a simple apparatus to measure direct and diffuse photosynthetically active radiation at remote locations.

    PubMed

    Cruse, Michael J; Kucharik, Christopher J; Norman, John M

    2015-01-01

    Plant canopy interception of photosynthetically active radiation (PAR) drives carbon dioxide (CO2), water and energy cycling in the soil-plant-atmosphere system. Quantifying intercepted PAR requires accurate measurements of total incident PAR above canopies and direct beam and diffuse PAR components. While some regional data sets include these data, e.g. from Atmospheric Radiation Measurement (ARM) Program sites, they are not often applicable to local research sites because of the variable nature (spatial and temporal) of environmental variables that influence incoming PAR. Currently available instrumentation that measures diffuse and direct beam radiation separately can be cost prohibitive and require frequent adjustments. Alternatively, generalized empirical relationships that relate atmospheric variables and radiation components can be used but require assumptions that increase the potential for error. Our goal here was to construct and test a cheaper, highly portable instrument alternative that could be used at remote field sites to measure total, diffuse and direct beam PAR for extended time periods without supervision. The apparatus tested here uses a fabricated, solar powered rotating shadowband and other commercially available parts to collect continuous hourly PAR data. Measurements of total incident PAR had nearly a one-to-one relationship with total incident radiation measurements taken at the same research site by an unobstructed point quantum sensor. Additionally, measurements of diffuse PAR compared favorably with modeled estimates from previously published data, but displayed significant differences that were attributed to the important influence of rapidly changing local environmental conditions. The cost of the system is about 50% less than comparable commercially available systems that require periodic, but not continual adjustments. Overall, the data produced using this apparatus indicates that this instrumentation has the potential to support

  4. Analysis of photosynthetically active radiation under various sky conditions in Wuhan, Central China.

    PubMed

    Wang, Lunche; Gong, Wei; Lin, Aiwen; Hu, Bo

    2014-10-01

    Observations of photosynthetically active radiation (PAR) and global solar radiation (G) at Wuhan, Central China during 2005-2012 were first reported to investigate PAR variability at different time scales and its PAR fraction (F(p)) under different sky conditions. Both G irradiances (I(g)) and PAR irradiances (I(p)) showed similar seasonal features that peaked in values at noon during summer and reached their lower values in winter. F(p) reached higher values during either sunrise or sunset; lower values of F p appeared at local noon because of the absorption effects of water vapor and clouds on long-wave radiation. There was an inverse relationship between clearness index (K(t)) and F(p); the maximum I(p) decreased by 22.3 % (39.7 %) when sky conditions changed from overcast to cloudless in summer (winter); solar radiation was more affected by cloudiness than the seasonal variation in cloudy skies when compared with that in clear skies. The maximum daily PAR irradiation (R(p)) was 11.89 MJ m⁻² day⁻¹ with an annual average of 4.85 MJ m⁻² day⁻¹. F p was in the range of 29-61.5 % with annual daily average value being about 42 %. Meanwhile, hourly, daily, and monthly relationships between R p and G irradiation (R g) under different sky conditions were investigated. It was discovered that cloudy skies were the dominated sky condition in this region. Finally, a clear-sky PAR model was developed by analyzing the dependence of PAR irradiances on optical air mass under various sky conditions for the whole study period in Central China, which will lay foundations for ecological process study in the near future. PMID:24357490

  5. Analysis of photosynthetically active radiation under various sky conditions in Wuhan, Central China.

    PubMed

    Wang, Lunche; Gong, Wei; Lin, Aiwen; Hu, Bo

    2014-10-01

    Observations of photosynthetically active radiation (PAR) and global solar radiation (G) at Wuhan, Central China during 2005-2012 were first reported to investigate PAR variability at different time scales and its PAR fraction (F(p)) under different sky conditions. Both G irradiances (I(g)) and PAR irradiances (I(p)) showed similar seasonal features that peaked in values at noon during summer and reached their lower values in winter. F(p) reached higher values during either sunrise or sunset; lower values of F p appeared at local noon because of the absorption effects of water vapor and clouds on long-wave radiation. There was an inverse relationship between clearness index (K(t)) and F(p); the maximum I(p) decreased by 22.3 % (39.7 %) when sky conditions changed from overcast to cloudless in summer (winter); solar radiation was more affected by cloudiness than the seasonal variation in cloudy skies when compared with that in clear skies. The maximum daily PAR irradiation (R(p)) was 11.89 MJ m⁻² day⁻¹ with an annual average of 4.85 MJ m⁻² day⁻¹. F p was in the range of 29-61.5 % with annual daily average value being about 42 %. Meanwhile, hourly, daily, and monthly relationships between R p and G irradiation (R g) under different sky conditions were investigated. It was discovered that cloudy skies were the dominated sky condition in this region. Finally, a clear-sky PAR model was developed by analyzing the dependence of PAR irradiances on optical air mass under various sky conditions for the whole study period in Central China, which will lay foundations for ecological process study in the near future.

  6. PARduino: a simple and inexpensive device for logging photosynthetically active radiation.

    PubMed

    Barnard, Holly R; Findley, Matthew C; Csavina, Janae

    2014-06-01

    Photosynthetically active radiation (PAR, 400-700 nm) is one of the primary controls of forest carbon and water relations. In complex terrain, PAR has high spatial variability. Given the high cost of commercial datalogging equipment, spatially distributed measurements of PAR have been typically modeled using geographic coordinates and terrain indices. Here, we present a design for a low-cost, field-deployable device for measuring and recording PAR built around an Arduino microcontroller-named PARduino. PARduino provides for widely distributed sensor arrays and tests the feasibility of using open-source, hobbyist-grade electronics for collecting scientific data. PARduino components include a quantum sensor, an EME Systems signal converter/amplifier and an Arduino Pro Mini microcontroller. Additional components include a real-time clock, a microSD Flash memory card and a custom printed circuit board. The components were selected for ease of assembly. We found strong agreement between the PARduino datalogger system and National Institute of Standards and Technology traceable sensors logged by an industry standard datalogger (slope = 0.99, SE < 0.01, P < 0.01; intercept = - 14.84, SE = 0.78, P < 0.01). The average difference between the two systems was 22.0 µmol m(-2) s(-1) with PARduino typically underestimating PAR. The average percentage difference between systems was 3.49%. On average, PARduino performed within the factory absolute calibration of the PAR sensor; however, larger errors occurred at low PAR levels. Using open-source technologies such as this can make it possible to develop a spatially distributed sensor network within the constraints of a typical research budget. PMID:24935916

  7. PARduino: a simple and inexpensive device for logging photosynthetically active radiation.

    PubMed

    Barnard, Holly R; Findley, Matthew C; Csavina, Janae

    2014-06-01

    Photosynthetically active radiation (PAR, 400-700 nm) is one of the primary controls of forest carbon and water relations. In complex terrain, PAR has high spatial variability. Given the high cost of commercial datalogging equipment, spatially distributed measurements of PAR have been typically modeled using geographic coordinates and terrain indices. Here, we present a design for a low-cost, field-deployable device for measuring and recording PAR built around an Arduino microcontroller-named PARduino. PARduino provides for widely distributed sensor arrays and tests the feasibility of using open-source, hobbyist-grade electronics for collecting scientific data. PARduino components include a quantum sensor, an EME Systems signal converter/amplifier and an Arduino Pro Mini microcontroller. Additional components include a real-time clock, a microSD Flash memory card and a custom printed circuit board. The components were selected for ease of assembly. We found strong agreement between the PARduino datalogger system and National Institute of Standards and Technology traceable sensors logged by an industry standard datalogger (slope = 0.99, SE < 0.01, P < 0.01; intercept = - 14.84, SE = 0.78, P < 0.01). The average difference between the two systems was 22.0 µmol m(-2) s(-1) with PARduino typically underestimating PAR. The average percentage difference between systems was 3.49%. On average, PARduino performed within the factory absolute calibration of the PAR sensor; however, larger errors occurred at low PAR levels. Using open-source technologies such as this can make it possible to develop a spatially distributed sensor network within the constraints of a typical research budget.

  8. Using a Simple Apparatus to Measure Direct and Diffuse Photosynthetically Active Radiation at Remote Locations

    PubMed Central

    Cruse, Michael J.; Kucharik, Christopher J.; Norman, John M.

    2015-01-01

    Plant canopy interception of photosynthetically active radiation (PAR) drives carbon dioxide (CO2), water and energy cycling in the soil-plant-atmosphere system. Quantifying intercepted PAR requires accurate measurements of total incident PAR above canopies and direct beam and diffuse PAR components. While some regional data sets include these data, e.g. from Atmospheric Radiation Measurement (ARM) Program sites, they are not often applicable to local research sites because of the variable nature (spatial and temporal) of environmental variables that influence incoming PAR. Currently available instrumentation that measures diffuse and direct beam radiation separately can be cost prohibitive and require frequent adjustments. Alternatively, generalized empirical relationships that relate atmospheric variables and radiation components can be used but require assumptions that increase the potential for error. Our goal here was to construct and test a cheaper, highly portable instrument alternative that could be used at remote field sites to measure total, diffuse and direct beam PAR for extended time periods without supervision. The apparatus tested here uses a fabricated, solar powered rotating shadowband and other commercially available parts to collect continuous hourly PAR data. Measurements of total incident PAR had nearly a one-to-one relationship with total incident radiation measurements taken at the same research site by an unobstructed point quantum sensor. Additionally, measurements of diffuse PAR compared favorably with modeled estimates from previously published data, but displayed significant differences that were attributed to the important influence of rapidly changing local environmental conditions. The cost of the system is about 50% less than comparable commercially available systems that require periodic, but not continual adjustments. Overall, the data produced using this apparatus indicates that this instrumentation has the potential to support

  9. Photosynthetically active radiation and its relationship with global solar radiation in Central China.

    PubMed

    Wang, Lunche; Gong, Wei; Ma, Yingying; Hu, Bo; Zhang, Miao

    2014-08-01

    Photosynthetically active radiation (PAR) and other solar components were observed for a period of 3 years at Wuhan, China to determine for the first time the temporal variability of PAR fraction [PAR/G (G here stands for global solar radiation)] and its dependence on different sky conditions in Central China. PAR, G and PAR/G showed similar seasonal features that peaked in summer and reached their lowest values in winter. The seasonal PAR/G ranged from 1.70 E MJ(-1) (winter) to 2.01 E MJ(-1) (summer) with an annual mean value of 1.89 E MJ(-1). Hourly values of PAR/G increased from 1.78 to 2.11 E MJ(-1) on average as sky conditions changed from clear to cloudy. Monthly mean hourly PAR/G revealed a diurnal variation, with highest values observed around sunrise and sunset, slightly higher PAR fractions were also found around noon for most months. The effect of daylength on PAR/G was also studied and no significant impact was found. Three models were developed to estimate PAR from G. These models consisted of atmospheric parameters that were found to cause substantial changes of PAR/G, such as sky clearness, brightness, path length and the sky clearness index. The estimations obtained from different models were very close to the measured values with maximum relative errors below 8 % (hourly values) in Wuhan. The models were not only tested at seven radiation stations in Central China, but also verified in six stations with different climates in China. The models were found to estimate PAR accurately from commonly available G data in Central China; however, the results also implied that the models need to be modified to account for local climatic conditions when applied to the whole country.

  10. Brassinosteroids promote photosynthesis and growth by enhancing activation of Rubisco and expression of photosynthetic genes in Cucumis sativus.

    PubMed

    Xia, Xiao-Jian; Huang, Li-Feng; Zhou, Yan-Hong; Mao, Wei-Hua; Shi, Kai; Wu, Jian-Xiang; Asami, Tadao; Chen, Zhixiang; Yu, Jing-Quan

    2009-11-01

    Brassinosteroids (BRs) are a new group of plant growth substances that promote plant growth and productivity. We showed in this study that improved growth of cucumber (Cucumis sativus) plants after treatment with 24-epibrassinolide (EBR), an active BR, was associated with increased CO(2) assimilation and quantum yield of PSII (Phi(PSII)). Treatment of brassinazole (Brz), a specific inhibitor for BR biosynthesis, reduced plant growth and at the same time decreased CO(2) assimilation and Phi(PSII). Thus, the growth-promoting activity of BRs can be, at least partly, attributed to enhanced plant photosynthesis. To understand how BRs enhance photosynthesis, we have analyzed the effects of EBR and Brz on a number of photosynthetic parameters and their affecting factors, including the contents and activity of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco). Northern and Western blotting demonstrated that EBR upregulated, while Brz downregulated, the expressions of rbcL, rbcS and other photosynthetic genes. In addition, EBR had a positive effect on the activation of Rubisco based on increased maximum Rubisco carboxylation rates (V (c,max)), total Rubisco activity and, to a greater extent, initial Rubisco activity. The accumulation patterns of Rubisco activase (RCA) based on immunogold-labeling experiments suggested a role of RCA in BR-regulated activation state of Rubisco. Enhanced expression of genes encoding other Calvin cycle genes after EBR treatment may also play a positive role in RuBP regeneration (J (max)), thereby increasing maximum carboxylation rate of Rubisco (V (c,max)). Thus, BRs promote photosynthesis and growth by positively regulating synthesis and activation of a variety of photosynthetic enzymes including Rubisco in cucumber.

  11. Gender, season and habitat: Patterns of variation in photosynthetic activity, growth and fecundity in Thymelaea velutina

    NASA Astrophysics Data System (ADS)

    de la Bandera, Maria del Carmen; Traveset, Anna; Valladares, Fernando; Gulías, Javier

    2008-11-01

    Changes in the ecophysiological performance of a plant species due to different environmental conditions generally reflect adaptations to the habitat where the plant grows and are often related to its survival capacity in a particular place. We examined this with the dioecious shrub Thymelaea velutina, in two contrasting populations representing the extremes of the altitudinal gradient where the species lives (coastal dunes and mountain habitats over 1000 m). We measured net photosynthetic rates and stomatal conductance, estimated the level of plant stress by chlorophyll fluorescence, and assessed their correlations with growth rate, plant size, flower production and fruit set. We hypothesized that plants at high altitude were more photosynthetically stressed than at sea level and expected a gender × habitat interaction in performance as females need more resources than males. Plants in the mountain experienced chronic photoinhibition during winter and a reduced photosynthetic performance both in winter and spring compared to plants in coastal dunes. However, there was no association between any of the fluorescence variables and either plant growth or fecundity, suggesting that other factors are involved determining performance. Mountain plants showed also an apparent lower capacity of heat dissipation to excessive radiation than dune plants. In the dunes, the greater leaf area and mass can lead to a higher photosynthetic carbon gain by whole individuals compared to plants in the mountain. No effect of gender was detected on the ecophysiological performance of this species, which we partly attribute to the small size of fruits of the female plants.

  12. A Photosynthesis Lab. Response of Algal Suspensions to a Gradient of Photosynthetically Active Radiation (PAR).

    ERIC Educational Resources Information Center

    Zee, Delmar Vander

    1995-01-01

    This photosynthesis exercise is intended for introductory college biology or botany courses. It is based on the principle that a closed suspension of algal cells may be expected to produce more dissolved oxygen with a greater photon fluence rate, but within limits of the photosynthetic capacity of the system. Describes materials and methods. (LZ)

  13. Semi-active vibration absorber based on real-time controlled MR damper

    NASA Astrophysics Data System (ADS)

    Weber, F.

    2014-06-01

    A semi-active vibration absorber with real-time controlled magnetorheological damper (MR-SVA) for the mitigation of harmonic structural vibrations is presented. The MR damper force targets to realize the frequency and damping adaptations to the actual structural frequency according to the principle of the undamped vibration absorber. The relative motion constraint of the MR-SVA is taken into account by an adaptive nonlinear control of the internal damping of the MR-SVA. The MR-SVA is numerically and experimentally validated for harmonic excitation of the primary structure when the natural frequency of the passive mass spring system of the MR-SVA is correctly tuned to the targeted structural resonance frequency and when de-tuning is present. The results demonstrate that the MR-SVA outperforms the passive TMD at structural resonance frequency by at least 12.4% and up to 60.0%.

  14. Modified cotton gauze dressings that selectively absorb neutrophil elastase activity in solution.

    PubMed

    Edwards, J V; Yager, D R; Cohen, I K; Diegelmann, R F; Montante, S; Bertoniere, N; Bopp, A F

    2001-01-01

    Dressings for chronic human wounds have been aimed at protection, removal of exudate, and improved appearance. However since the time of ancient Greece wound care and dressing strategies have primarily relied on empiricism. Recent studies have shown that chronic wounds contain high levels of tissue and cytokine destroying proteases including collagenase and neutrophil elastase. Therefore we sought to develop an effective wound dressing that could absorb elastase through affinity sequestration. Cotton gauze was modified by oxidation, phosphorylation, and sulfonation to enhance elastase affinity by ionic or active site uptake. Type VII absorbent cotton gauze was oxidized to dialdehyde cotton which was subsequently converted in part to the bisulfite addition product. Gauze preparations were also phosphorylated and carboxymethylated. Modified cotton gauzes were compared with untreated gauze for reduction of elastase activity in buffered saline. Solutions of elastase that were soaked in oxidized, sulfonated, and phosphorylated cotton gauze showed reduced elastase activity. The initial velocities (v(o)) and turnover rates of elastase showed significant decreases compared with solutions taken from untreated gauze. The reduction in enzyme activity with dialdehyde cotton gauze was confirmed in solution by determining elastase inhibition with dialdehyde starch. The dialdehyde cotton gauze also decreased elastase activity in human wound fluid in a dose response relation based on weight of gauze per volume of wound fluid. Absorbency, pH, air permeability and strength properties of the modified gauze were also compared with untreated cotton gauze. This report shows the effect of reducing elastase activity in solution with cotton containing aldehydic or negatively charged cellulose fibers that may be applicable to treatment modalities in chronic wounds.

  15. Influence on photosynthesis of starlight, moonlight, planetlight, and light pollution (reflections on photosynthetically active radiation in the universe).

    PubMed

    Raven, J A; Cockell, C S

    2006-08-01

    Photosynthesis on Earth can occur in a diversity of organisms in the photosynthetically active radiation (PAR) range of 10 nmol of photons m(-2) s(-1) to 8 mmol of photons m(-2) s(-1). Similar considerations would probably apply to photosynthetic organisms on Earth-like planets (ELPs) in the continuously habitable zone of other stars. On Earth, starlight PAR is inadequate for photosynthetically supported growth. An increase in starlight even to reach the minimum theoretical levels to allow for photosynthesis would require a universe that was approximately ten million times older, or with a ten million times greater density of stars, than is the case for the present universe. Photosynthesis on an ELP using PAR reflected from a natural satellite with the same size as our Moon, but at the Roche limit, could support a low rate of photosynthesis at full Moon. Photosynthesis on an ELP-like satellite of a Jupiter-sized planet using light reflected from the planet could be almost 1% of the rate in full sunlight on Earth when the planet was full. These potential contributions to photosynthesis require that the contribution is compared with the rate of photosynthesis driven by direct radiation from the star. Light pollution on Earth only energizes photosynthesis by organisms that are very close to the light source. However, effects of light pollution on photosynthesis can be more widespread if the photosynthetic canopy is retained for more of the year, caused by effects on photoperiodism, with implications for the influence of civilizations on photosynthesis. PMID:16916290

  16. Holographically patterned activation using photo-absorber induced neural-thermal stimulation

    NASA Astrophysics Data System (ADS)

    Farah, Nairouz; Zoubi, Alaa; Matar, Suhail; Golan, Lior; Marom, Anat; Butson, Christopher R.; Brosh, Inbar; Shoham, Shy

    2013-10-01

    Objective. Patterned photo-stimulation offers a promising path towards the effective control of distributed neuronal circuits. Here, we demonstrate the feasibility and governing principles of spatiotemporally patterned microscopic photo-absorber induced neural-thermal stimulation (PAINTS) based on light absorption by exogenous extracellular photo-absorbers. Approach. We projected holographic light patterns from a green continuous-wave (CW) or an IR femtosecond laser onto exogenous photo-absorbing particles dispersed in the vicinity of cultured rat cortical cells. Experimental results are compared to predictions of a temperature-rate model (where membrane currents follow I ∝ dT/dt). Main results. The induced microscopic photo-thermal transients have sub-millisecond thermal relaxation times and stimulate adjacent cells. PAINTS activation thresholds for different laser pulse durations (0.02 to 1 ms) follow the Lapicque strength-duration formula, but with different chronaxies and minimal threshold energy levels for the two excitation lasers (an order of magnitude lower for the IR system <50 nJ). Moreover, the empirical thresholds for the CW system are found to be in good agreement with detailed simulations of the temperature-rate model, but are generally lower for the IR system, suggesting an auxiliary excitation mechanism. Significance. Holographically patterned PAINTS could potentially provide a means for minimally intrusive control over neuronal dynamics with a high level of spatial and temporal selectivity.

  17. Modeling the relationship between photosynthetically active radiation and global horizontal irradiance using singular spectrum analysis

    NASA Astrophysics Data System (ADS)

    Zempila, Melina-Maria; Taylor, Michael; Bais, Alkiviadis; Kazadzis, Stelios

    2016-10-01

    We report on the construction of generic models to calculate photosynthetically active radiation (PAR) from global horizontal irradiance (GHI), and vice versa. Our study took place at stations of the Greek UV network (UVNET) and the Hellenic solar energy network (HNSE) with measurements from NILU-UV multi-filter radiometers and CM pyranometers, chosen due to their long (≈1 M record/site) high temporal resolution (≈1 min) record that captures a broad range of atmospheric environments and cloudiness conditions. The uncertainty of the PAR measurements is quantified to be ±6.5% while the uncertainty involved in GHI measurements is up to ≈±7% according to the manufacturer. We show how multi-linear regression and nonlinear neural network (NN) models, trained at a calibration site (Thessaloniki) can be made generic provided that the input-output time series are processed with multi-channel singular spectrum analysis (M-SSA). Without M-SSA, both linear and nonlinear models perform well only locally. M-SSA with 50 time-lags is found to be sufficient for identification of trend, periodic and noise components in aerosol, cloud parameters and irradiance, and to construct regularized noise models of PAR from GHI irradiances. Reconstructed PAR and GHI time series capture ≈95% of the variance of the cross-validated target measurements and have median absolute percentage errors <2%. The intra-site median absolute error of M-SSA processed models were ≈8.2±1.7 W/m2 for PAR and ≈9.2±4.2 W/m2 for GHI. When applying the models trained at Thessaloniki to other stations, the average absolute mean bias between the model estimates and measured values was found to be ≈1.2 W/m2 for PAR and ≈0.8 W/m2 for GHI. For the models, percentage errors are well within the uncertainty of the measurements at all sites. Generic NN models were found to perform marginally better than their linear counterparts.

  18. Suppression of mechanical vibrations in a building-like structure using a passive/active autoparametric absorber

    NASA Astrophysics Data System (ADS)

    Abundis-Fong, H. F.; Silva-Navarro, G.

    2014-03-01

    An experimental investigation is carried out on a system consisting of a primary structure coupled with a passive/active autoparametric vibration absorber. The primary structure consists of a building-like mechanical structure, it has three rigid floors connected by flexible columns made from aluminium strips, while the absorber consists of a cantilever beam with a PZT patch actuator actively controlled through an acquisition card. The whole system, which is a coupled non-linear oscillator, is subjected to sinusoidal excitation obtained from an electromechanical shaker in the neighborhood of internal resonances. The natural frequency of the absorber is tuned to be one-half of any of the natural frequencies of the main system. With the addition of a PZT actuator, the autoparametric vibration absorber is made active, thus enabling the possibility to control the effective stiffness associated to the passive absorber and, as a consequence, the implementation of an active vibration control scheme able to preserve, as possible, the autoparametric interaction as well as to compensate varying excitation frequencies. This active vibration absorber employs feedback information from an accelerometer on the primary structure, an accelerometer on the tip of the beam absorber and a strain gage on the base of the beam, feedforward information from the excitation force and on-line computations from the nonlinear approximate frequency response, parameterized in terms of a proportional gain provided by a voltage input to the PZT actuator, thus providing a mechanism to asymptotically track an optimal, robust and stable attenuation solution on the primary system.

  19. Chlorophylls d and f and Their Role in Primary Photosynthetic Processes of Cyanobacteria.

    PubMed

    Allakhverdiev, S I; Kreslavski, V D; Zharmukhamedov, S K; Voloshin, R A; Korol'kova, D V; Tomo, T; Shen, J-R

    2016-03-01

    The finding of unique Chl d- and Chl f-containing cyanobacteria in the last decade was a discovery in the area of biology of oxygenic photosynthetic organisms. Chl b, Chl c, and Chl f are considered to be accessory pigments found in antennae systems of photosynthetic organisms. They absorb energy and transfer it to the photosynthetic reaction center (RC), but do not participate in electron transport by the photosynthetic electron transport chain. However, Chl d as well as Chl a can operate not only in the light-harvesting complex, but also in the photosynthetic RC. The long-wavelength (Qy) Chl d and Chl f absorption band is shifted to longer wavelength (to 750 nm) compared to Chl a, which suggests the possibility for oxygenic photosynthesis in this spectral range. Such expansion of the photosynthetically active light range is important for the survival of cyanobacteria when the intensity of light not exceeding 700 nm is attenuated due to absorption by Chl a and other pigments. At the same time, energy storage efficiency in photosystem 2 for cyanobacteria containing Chl d and Chl f is not lower than that of cyanobacteria containing Chl a. Despite great interest in these unique chlorophylls, many questions related to functioning of such pigments in primary photosynthetic processes are still not elucidated. This review describes the latest advances in the field of Chl d and Chl f research and their role in primary photosynthetic processes of cyanobacteria.

  20. Chlorophylls d and f and Their Role in Primary Photosynthetic Processes of Cyanobacteria.

    PubMed

    Allakhverdiev, S I; Kreslavski, V D; Zharmukhamedov, S K; Voloshin, R A; Korol'kova, D V; Tomo, T; Shen, J-R

    2016-03-01

    The finding of unique Chl d- and Chl f-containing cyanobacteria in the last decade was a discovery in the area of biology of oxygenic photosynthetic organisms. Chl b, Chl c, and Chl f are considered to be accessory pigments found in antennae systems of photosynthetic organisms. They absorb energy and transfer it to the photosynthetic reaction center (RC), but do not participate in electron transport by the photosynthetic electron transport chain. However, Chl d as well as Chl a can operate not only in the light-harvesting complex, but also in the photosynthetic RC. The long-wavelength (Qy) Chl d and Chl f absorption band is shifted to longer wavelength (to 750 nm) compared to Chl a, which suggests the possibility for oxygenic photosynthesis in this spectral range. Such expansion of the photosynthetically active light range is important for the survival of cyanobacteria when the intensity of light not exceeding 700 nm is attenuated due to absorption by Chl a and other pigments. At the same time, energy storage efficiency in photosystem 2 for cyanobacteria containing Chl d and Chl f is not lower than that of cyanobacteria containing Chl a. Despite great interest in these unique chlorophylls, many questions related to functioning of such pigments in primary photosynthetic processes are still not elucidated. This review describes the latest advances in the field of Chl d and Chl f research and their role in primary photosynthetic processes of cyanobacteria. PMID:27262189

  1. Active vibration absorber for the CSI evolutionary model - Design and experimental results. [Controls Structures Interaction

    NASA Technical Reports Server (NTRS)

    Bruner, Anne M.; Belvin, W. Keith; Horta, Lucas G.; Juang, Jer-Nan

    1991-01-01

    The development of control of large flexible structures technology must include practical demonstrations to aid in the understanding and characterization of controlled structures in space. To support this effort, a testbed facility has been developed to study practical implementation of new control technologies under realistic conditions. The paper discusses the design of a second order, acceleration feedback controller which acts as an active vibration absorber. This controller provides guaranteed stability margins for collocated sensor/actuator pairs in the absence of sensor/actuator dynamics and computational time delay. Experimental results in the presence of these factors are presented and discussed. The robustness of this design under model uncertainty is demonstrated.

  2. Effects of ocean acidification on the photosynthetic performance, carbonic anhydrase activity and growth of the giant kelp Macrocystis pyrifera.

    PubMed

    Fernández, Pamela A; Roleda, Michael Y; Hurd, Catriona L

    2015-06-01

    Under ocean acidification (OA), the 200 % increase in CO2(aq) and the reduction of pH by 0.3-0.4 units are predicted to affect the carbon physiology and growth of macroalgae. Here we examined how the physiology of the giant kelp Macrocystis pyrifera is affected by elevated pCO2/low pH. Growth and photosynthetic rates, external and internal carbonic anhydrase (CA) activity, HCO3 (-) versus CO2 use were determined over a 7-day incubation at ambient pCO2 400 µatm/pH 8.00 and a future OA treatment of pCO2 1200 µatm/pH 7.59. Neither the photosynthetic nor growth rates were changed by elevated CO2 supply in the OA treatment. These results were explained by the greater use of HCO3 (-) compared to CO2 as an inorganic carbon (Ci) source to support photosynthesis. Macrocystis is a mixed HCO3 (-) and CO2 user that exhibits two effective mechanisms for HCO3 (-) utilization; as predicted for species that possess carbon-concentrating mechanisms (CCMs), photosynthesis was not substantially affected by elevated pCO2. The internal CA activity was also unaffected by OA, and it remained high and active throughout the experiment; this suggests that HCO3 (-) uptake via an anion exchange protein was not affected by OA. Our results suggest that photosynthetic Ci uptake and growth of Macrocystis will not be affected by elevated pCO2/low pH predicted for the future, but the combined effects with other environmental factors like temperature and nutrient availability could change the physiological response of Macrocystis to OA. Therefore, further studies will be important to elucidate how this species might respond to the global environmental change predicted for the ocean.

  3. Effects of Heat Shock on Photosynthetic Properties, Antioxidant Enzyme Activity, and Downy Mildew of Cucumber (Cucumis sativus L.)

    PubMed Central

    Hao, Ting; Jin, Haijun; Zhang, Hongmei; He, Lizhong; Zhou, Qiang; Huang, Danfeng; Hui, Dafeng; Yu, Jizhu

    2016-01-01

    Heat shock is considered an abiotic stress for plant growth, but the effects of heat shock on physiological responses of cucumber plant leaves with and without downy mildew disease are still not clear. In this study, cucumber seedlings were exposed to heat shock in greenhouses, and the responses of photosynthetic properties, carbohydrate metabolism, antioxidant enzyme activity, osmolytes, and disease severity index of leaves with or without the downy mildew disease were measured. Results showed that heat shock significantly decreased the net photosynthetic rate, actual photochemical efficiency, photochemical quenching coefficient, and starch content. Heat shock caused an increase in the stomatal conductance, transpiration rate, antioxidant enzyme activities, total soluble sugar content, sucrose content, soluble protein content and proline content for both healthy leaves and downy mildew infected leaves. These results demonstrate that heat shock activated the transpiration pathway to protect the photosystem from damage due to excess energy in cucumber leaves. Potential resistance mechanisms of plants exposed to heat stress may involve higher osmotic regulation capacity related to an increase of total accumulations of soluble sugar, proline and soluble protein, as well as higher antioxidant enzymes activity in stressed leaves. Heat shock reduced downy mildew disease severity index by more than 50%, and clearly alleviated downy mildew development in the greenhouses. These findings indicate that cucumber may have a complex physiological change to resist short-term heat shock, and suppress the development of the downy mildew disease. PMID:27065102

  4. Effects of Heat Shock on Photosynthetic Properties, Antioxidant Enzyme Activity, and Downy Mildew of Cucumber (Cucumis sativus L.).

    PubMed

    Ding, Xiaotao; Jiang, Yuping; Hao, Ting; Jin, Haijun; Zhang, Hongmei; He, Lizhong; Zhou, Qiang; Huang, Danfeng; Hui, Dafeng; Yu, Jizhu

    2016-01-01

    Heat shock is considered an abiotic stress for plant growth, but the effects of heat shock on physiological responses of cucumber plant leaves with and without downy mildew disease are still not clear. In this study, cucumber seedlings were exposed to heat shock in greenhouses, and the responses of photosynthetic properties, carbohydrate metabolism, antioxidant enzyme activity, osmolytes, and disease severity index of leaves with or without the downy mildew disease were measured. Results showed that heat shock significantly decreased the net photosynthetic rate, actual photochemical efficiency, photochemical quenching coefficient, and starch content. Heat shock caused an increase in the stomatal conductance, transpiration rate, antioxidant enzyme activities, total soluble sugar content, sucrose content, soluble protein content and proline content for both healthy leaves and downy mildew infected leaves. These results demonstrate that heat shock activated the transpiration pathway to protect the photosystem from damage due to excess energy in cucumber leaves. Potential resistance mechanisms of plants exposed to heat stress may involve higher osmotic regulation capacity related to an increase of total accumulations of soluble sugar, proline and soluble protein, as well as higher antioxidant enzymes activity in stressed leaves. Heat shock reduced downy mildew disease severity index by more than 50%, and clearly alleviated downy mildew development in the greenhouses. These findings indicate that cucumber may have a complex physiological change to resist short-term heat shock, and suppress the development of the downy mildew disease.

  5. Effects of Heat Shock on Photosynthetic Properties, Antioxidant Enzyme Activity, and Downy Mildew of Cucumber (Cucumis sativus L.).

    PubMed

    Ding, Xiaotao; Jiang, Yuping; Hao, Ting; Jin, Haijun; Zhang, Hongmei; He, Lizhong; Zhou, Qiang; Huang, Danfeng; Hui, Dafeng; Yu, Jizhu

    2016-01-01

    Heat shock is considered an abiotic stress for plant growth, but the effects of heat shock on physiological responses of cucumber plant leaves with and without downy mildew disease are still not clear. In this study, cucumber seedlings were exposed to heat shock in greenhouses, and the responses of photosynthetic properties, carbohydrate metabolism, antioxidant enzyme activity, osmolytes, and disease severity index of leaves with or without the downy mildew disease were measured. Results showed that heat shock significantly decreased the net photosynthetic rate, actual photochemical efficiency, photochemical quenching coefficient, and starch content. Heat shock caused an increase in the stomatal conductance, transpiration rate, antioxidant enzyme activities, total soluble sugar content, sucrose content, soluble protein content and proline content for both healthy leaves and downy mildew infected leaves. These results demonstrate that heat shock activated the transpiration pathway to protect the photosystem from damage due to excess energy in cucumber leaves. Potential resistance mechanisms of plants exposed to heat stress may involve higher osmotic regulation capacity related to an increase of total accumulations of soluble sugar, proline and soluble protein, as well as higher antioxidant enzymes activity in stressed leaves. Heat shock reduced downy mildew disease severity index by more than 50%, and clearly alleviated downy mildew development in the greenhouses. These findings indicate that cucumber may have a complex physiological change to resist short-term heat shock, and suppress the development of the downy mildew disease. PMID:27065102

  6. Modeling photosynthetically active radiation in water of Tampa Bay, Florida, with emphasis on the geometry of incident irradiance

    USGS Publications Warehouse

    Miller, R.L.; McPherson, B.F.

    1995-01-01

    A model is developed that uses a simplified geometric description of incident direct solar beam and diffuse skylight. The model incorporates effects of solar elevation angle and cloudiness on the amount of in-air photosynthetically active radiation (PAR) that passes through the air-water interface and on K0 in waters of relatively low turbidity. The value of K0 was estimated to vary as much as 41% on a clear summer day due to changes in solar elevation angle. The model was used to make estimates of the depth to which sea-grasses might receive adequate light for survival for a range of values of K0. -from Authors

  7. Partial root zone drying: regulation of photosynthetic limitations and antioxidant enzymatic activities in young olive (Olea europaea) saplings.

    PubMed

    Aganchich, Badia; Wahbi, Said; Loreto, Francesco; Centritto, Mauro

    2009-05-01

    The effect of partial root drying (PRD) irrigation on split-root olive (Olea europaea L. cv Picholine marocaine) saplings was investigated. An irrigated control and two PRD regimes were applied (control: irrigation applied on both sides of the root system to keep the soil water content close to field capacity; PRD(50): irrigation applied at 50% of the control amount on one side of the root system and irrigation withheld from the other side, with irrigation regimes switched between the sides of the root system every 2 weeks; and PRD(100): irrigation applied at 100% of the control amount on one side and irrigation withheld on the other side, with irrigation regimes switched between the sides of the root system every 2 weeks. Only saplings in the PRD(50) regime were subjected to water-deficit irrigation. The PRD treatments significantly affected water relations and vegetative growth throughout the growing season. Predawn leaf water potential and relative water content differed significantly between the PRD(50) and PRD(100) saplings, leading to reduced stomatal conductance, carbon assimilation, shoot length and leaf number in PRD(50) saplings. However, the PRD(50) water-deficit treatment did not affect the capacity of the saplings to assimilate CO(2). Activities of superoxide dismutase, soluble and insoluble peroxidase (POX) and polyphenol oxidase were up-regulated by the PRD(50) and PRD(100) treatments compared with control values. The higher activities of both soluble and insoluble POX observed in PRD(50) saplings may reflect the greater inhibitory effect of this treatment on vegetative growth. Up-regulation of the detoxifying systems in the PRD(100) and PRD(50) saplings may have provided protection mechanisms against irreversible damage to the photosynthetic machinery, thereby allowing the photosynthetic apparatus to function and preventing the development of severe water stress. We also measured CO(2) assimilation rate/internal leaf CO(2) concentration (A

  8. Photosynthetic activity and protein overexpression found in Cr(III)-tolerant cells of the green algae Dictyosphaerium chlorelloides.

    PubMed

    Pereira, M; Bartolomé, C M; Sánchez-Fortún, S

    2014-08-01

    Chromium is an important constituent in effluents obtained from chromium plating industries. Due to the highly toxic nature of Cr(VI), attention has been shifted to less hazardous Cr(III) electroplating processes. This study evaluated aquatic toxicity of Cr(III)-containing laboratory samples representative of effluents from chromium electroplating industries, on the photosynthetic activity exhibited by both Cr(III)-sensitive (Dc1M(wt)) and tolerant (Dc1M(Cr(III)R30)) Dictyosphaerium chlorelloides strains. Additionally, selected de novo-determined peptide sequences, obtained from Dc1M(Cr(III)R30), have been analyzed to evidence the possible Cr(III) toxic mechanism involved in the resistance of these cells to high Cr(III) levels in aquatic environments. Dc1M(Cr(III)R30) strain exhibited a gross photosynthetic balance of about five times lower than that exhibited by Dc1M(wt) strain, demonstrating that Dc1M(Cr(III)R30) has a photosynthetic yield significantly lower than Dc1M(wt). SDS-PAGE of Dc1M(Cr(III)R30) samples showed the presence of at least two protein bands (23.05 and 153.46 KDa, respectively) absent in wild-type strain samples. Although it has achieved a low coincidence between the lower molecular weight band and a GTPase identified from genome of the green alga Chlamydomonas reinhardtii, none of de novo peptide sequences obtained showed a significant MS-BLAST score, so that further studies will be required. PMID:24556547

  9. [Time lag effect between stem sap flow and photosynthetically active radiation, vapor pressure deficit of Acacia mangium].

    PubMed

    Wang, Hua; Zhao, Ping; Cai, Xi-An; Ma, Ling; Rao, Xing-Quan; Zeng, Xiao-Ping

    2008-02-01

    Based on the measurement of the stem sap flow of Acacia mangium with Granier' s thermal dissipation probe, and the cross-correlation and time serial analysis of the sap flow and corresponding photosynthetically active radiation and vapor pressure deficit, this paper studied the time lag effect between the stem sap flow of A. mangium and the driving factors of the tree canopy transpiration. The results indicated that the main driving factors of the transpiration were photosynthetically active radiation (PAR) and vapor pressure deficit (VPD). Sap flux density (Js) was more dependent on PAR than on VPD, and the dependence was more significant in dry season than in wet season. Sap flow lagged behind PAR but advanced than VPD in both dry and wet seasons. The time lag did not show any significant variation across different size tree individuals, but showed significant variation in different seasons. Time lag effect was not correlated with tree height, diameter at the breast, and canopy size. The time lag between Js and VPD was significantly related to nighttime water recharge in dry season, but reversed in wet season.

  10. Electroacoustic absorbers: bridging the gap between shunt loudspeakers and active sound absorption.

    PubMed

    Lissek, Hervé; Boulandet, Romain; Fleury, Romain

    2011-05-01

    The acoustic impedance at the diaphragm of an electroacoustic transducer can be varied using a range of basic electrical control strategies, amongst which are electrical shunt circuits. These passive shunt techniques are compared to active acoustic feedback techniques for controlling the acoustic impedance of an electroacoustic transducer. The formulation of feedback-based acoustic impedance control reveals formal analogies with shunt strategies, and highlights an original method for synthesizing electric networks ("shunts") with positive or negative components, bridging the gap between passive and active acoustic impedance control. This paper describes the theory unifying all these passive and active acoustic impedance control strategies, introducing the concept of electroacoustic absorbers. The equivalence between shunts and active control is first formalized through the introduction of a one-degree-of-freedom acoustic resonator accounting for both electric shunts and acoustic feedbacks. Conversely, electric networks mimicking the performances of active feedback techniques are introduced, identifying shunts with active impedance control. Simulated acoustic performances are presented, with an emphasis on formal analogies between the different control techniques. Examples of electric shunts are proposed for active sound absorption. Experimental assessments are then presented, and the paper concludes with a general discussion on the concept and potential improvements.

  11. Electroacoustic absorbers: bridging the gap between shunt loudspeakers and active sound absorption.

    PubMed

    Lissek, Hervé; Boulandet, Romain; Fleury, Romain

    2011-05-01

    The acoustic impedance at the diaphragm of an electroacoustic transducer can be varied using a range of basic electrical control strategies, amongst which are electrical shunt circuits. These passive shunt techniques are compared to active acoustic feedback techniques for controlling the acoustic impedance of an electroacoustic transducer. The formulation of feedback-based acoustic impedance control reveals formal analogies with shunt strategies, and highlights an original method for synthesizing electric networks ("shunts") with positive or negative components, bridging the gap between passive and active acoustic impedance control. This paper describes the theory unifying all these passive and active acoustic impedance control strategies, introducing the concept of electroacoustic absorbers. The equivalence between shunts and active control is first formalized through the introduction of a one-degree-of-freedom acoustic resonator accounting for both electric shunts and acoustic feedbacks. Conversely, electric networks mimicking the performances of active feedback techniques are introduced, identifying shunts with active impedance control. Simulated acoustic performances are presented, with an emphasis on formal analogies between the different control techniques. Examples of electric shunts are proposed for active sound absorption. Experimental assessments are then presented, and the paper concludes with a general discussion on the concept and potential improvements. PMID:21568400

  12. Sunlight mediated seasonality in canopy structure and photosynthetic activity of Amazonian rainforests

    NASA Astrophysics Data System (ADS)

    Bi, Jian; Knyazikhin, Yuri; Choi, Sungho; Park, Taejin; Barichivich, Jonathan; Ciais, Philippe; Fu, Rong; Ganguly, Sangram; Hall, Forrest; Hilker, Thomas; Huete, Alfredo; Jones, Matthew; Kimball, John; Lyapustin, Alexei I.; Mõttus, Matti; Nemani, Ramakrishna R.; Piao, Shilong; Poulter, Benjamin; Saleska, Scott R.; Saatchi, Sassan S.; Xu, Liang; Zhou, Liming; Myneni, Ranga B.

    2015-06-01

    Resolving the debate surrounding the nature and controls of seasonal variation in the structure and metabolism of Amazonian rainforests is critical to understanding their response to climate change. In situ studies have observed higher photosynthetic and evapotranspiration rates, increased litterfall and leaf flushing during the Sunlight-rich dry season. Satellite data also indicated higher greenness level, a proven surrogate of photosynthetic carbon fixation, and leaf area during the dry season relative to the wet season. Some recent reports suggest that rainforests display no seasonal variations and the previous results were satellite measurement artefacts. Therefore, here we re-examine several years of data from three sensors on two satellites under a range of sun positions and satellite measurement geometries and document robust evidence for a seasonal cycle in structure and greenness of wet equatorial Amazonian rainforests. This seasonal cycle is concordant with independent observations of solar radiation. We attribute alternative conclusions to an incomplete study of the seasonal cycle, i.e. the dry season only, and to prognostications based on a biased radiative transfer model. Consequently, evidence of dry season greening in geometry corrected satellite data was ignored and the absence of evidence for seasonal variation in lidar data due to noisy and saturated signals was misinterpreted as evidence of the absence of changes during the dry season. Our results, grounded in the physics of radiative transfer, buttress previous reports of dry season increases in leaf flushing, litterfall, photosynthesis and evapotranspiration in well-hydrated Amazonian rainforests.

  13. Sunlight Mediated Seasonality in Canopy Structure and Photosynthetic Activity of Amazonian Rainforests

    NASA Astrophysics Data System (ADS)

    Bi, J.; Knyazikhin, Y.; CHOI, S.; Park, T.; Barichivich, J.; Ciais, P.; Fu, R.; Ganguly, S.; Hall, F. G.; Hilker, T.; Huete, A. R.; Jones, M. O.; Kimball, J. S.; Lyapustin, A.; Mottus, M.; Nemani, R. R.; Piao, S.; Poulter, B.; Saleska, S. R.; Saatchi, S. S.; Xu, L.; Zhou, L.; Myneni, R.

    2015-12-01

    Resolving the debate about the nature and controls of seasonal variation in structure and metabolism of Amazonian rainforests is critical to understanding their response to climate change. In situ studies have observed higher photosynthetic and evapotranspiration rates, increased litterfall and leaf flushing during the sunlight-rich dry season. Satellite data also indicated higher greenness level, a proven surrogate of photosynthetic carbon fixation, and leaf area during the dry season relative to the wet season. Some recent reports suggest that rainforests display no seasonal variations and the previous results were satellite measurement artefacts. Therefore, we re-examine here several years of data from three sensors on two satellites under a range of sun positions and satellite measurement geometries and document robust evidence for a seasonal cycle in structure and greenness of wet equatorial Amazonian rainforests. This seasonal cycle is concordant with independent observations of solar radiation. We attribute alternative conclusions to an incomplete study of the seasonal cycle, i.e. the dry season only, and to prognostications based on a biased radiative transfer model. Consequently, evidence of dry season greening in geometry corrected satellite data was ignored and the absence of evidence for seasonal variation in lidar data due to noisy and saturated signals was misinterpreted as evidence of absence of changes during the dry season. Our results, grounded in the physics of radiative transfer, buttress previous reports of dry season increases in leaf flushing, litterfall, photosynthesis and evapotranspiration in well-hydrated Amazonian rainforests.

  14. [Photosynthetic activity and components of the electron transport chain in the aerobic bacteriochlorophyll A-containing bacterium Roseinatronobacter thiooxidans].

    PubMed

    Stadnichuk, I N; Ianiushin, M F; Boĭchenko, V A; Lukashev, E P; Boldareva, E N; Solov'ev, A A; Gorlenko, V M

    2009-01-01

    Bioenergetics of the aerobic bacteriochlorophyll a-containing (BCl a) bacterium (ABC bacterium) Roseinatronobacter thiooxidans is a combination of photosynthesis, oxygen respiration, and oxidation of sulfur compounds under alkaliphilic conditions. The photosynthetic activity of Rna. thiooxidans cells was established by the photoinhibition of cell respiration and reversible photobleaching discoloration of the BCl a of reaction centers (RC), connected by the chain of electron transfer with cytochrome c551 oxidation. The species under study, like many purple bacteria and some of the known ABC bacteria, possesses a light-harvesting pigment-protein (LHI) complex with the average number of 30 molecules of antenna BCl a per one photosynthetic RC. Under microaerobic growth conditions, the cells contained bc1 complex and two terminal oxidases: cbb3-cytochrome oxidase and the alternative cytochrome oxidase of the a3 type. Besides, Rna. thiooxidans was shown to have several different soluble low- and high-potential cytochromes c, probably associated with the ability of utilizing sulfur compounds as additional electron donors.

  15. Active vibration absorber for CSI evolutionary model: Design and experimental results

    NASA Technical Reports Server (NTRS)

    Bruner, Anne M.; Belvin, W. Keith; Horta, Lucas G.; Juang, Jer-Nan

    1991-01-01

    The development of control of large flexible structures technology must include practical demonstration to aid in the understanding and characterization of controlled structures in space. To support this effort, a testbed facility was developed to study practical implementation of new control technologies under realistic conditions. The design is discussed of a second order, acceleration feedback controller which acts as an active vibration absorber. This controller provides guaranteed stability margins for collocated sensor/actuator pairs in the absence of sensor/actuator dynamics and computational time delay. The primary performance objective considered is damping augmentation of the first nine structural modes. Comparison of experimental and predicted closed loop damping is presented, including test and simulation time histories for open and closed loop cases. Although the simulation and test results are not in full agreement, robustness of this design under model uncertainty is demonstrated. The basic advantage of this second order controller design is that the stability of the controller is model independent.

  16. Photosynthetic units.

    PubMed

    Schmid, G H; Gaffron, H

    1968-08-01

    Leaf tissues of aurea mutants of tobacco and Lespedeza have been shown to have higher photosynthetic capacity per molecule of chlorophyll, a higher saturation intensity, a simpler lamellar structure, and the same quantum yield as their dark green parents. Here we report on the values of photosynthetic units for both types of plants and some algae. The unit has been assumed to be about as uniform and steady in the plant world as the quantum efficiency. The number on which all theoretical discussions have been based so far is 2400 per O(2) evolved or CO(2) reduced. With dark green plants and algae our determinations of units by means of 40 microsec flashes superimposed on a steady rate of background photosynthesis at 900 ergs cm(-2) sec(-1) of red light yielded mostly numbers between 2000 and 2700. However, the photosynthetic unit turned out to be very variable, even in these objects. In aurea mutants the unit was distinctly smaller, averaging 600 chl/CO(2). By choosing the right combination of colors for flash and background light, units as low as 300 chl/CO(2) or 40 chl/e(-) could be measured consistently. We found five well-defined groups of units composed of multiples of its smallest member. These new findings are discussed in terms of structural entities that double or divide under the influence of far-red light.

  17. Coupled Estimation of Surface Heat fluxes and Vegetation Dynamics From Remotely Sensed Land Surface Temperature and Fraction of Photosynthetically Active Radiation

    NASA Astrophysics Data System (ADS)

    Castelli, F.; Bateni, S.; Entekhabi, D.

    2011-12-01

    Remotely sensed Land Surface Temperature (LST) and Fraction of Photosynthetically Active Radiation absorbed by vegetation (FPAR) are assimilated respectively into the Surface Energy Balance (SEB) equation and a Vegetation Dynamics Model (VDM) in order to estimate surface fluxes and vegetation dynamics. The problem is posed in terms of three unknown and dimensionless parameters: (1) neutral bulk heat transfer coefficient that scales the sum of turbulent fluxes, (2) evaporative fractions for soil and canopy, which represent partitioning among the turbulent fluxes over soil and vegetation, and (3) specific leaf area, which captures seasonal phenology and vegetation dynamics. The model is applied over the Gourma site in Mali, the northern edge of the West African Monsoon (WAM) domain. The application of model over the Gourma site shows that remotely sensed FPAR observations can constrain the VDM and retrieve its main unknown parameter (specific leaf area) over large-scale domains without costly in situ measurements. The results indicate that the estimated specific leaf area values vary reasonably with the influential environmental variables such as precipitation, air temperature, and solar radiation. Assimilating FPAR observations into the VDM can also provide Leaf Area Index (LAI) dynamics. The retrieved LAI values are comparable in magnitude, spatial pattern and temporal evolution with observations. Moreover, it is demonstrated that the spatial patterns of estimated neutral bulk heat transfer coefficient resemble those of observed vegetation index even though no explicit information on vegetation phenology is used in the model. Furthermore, the day-to-day variations in the retrieved evaporative fraction values are consistent with wetting and drydown events. Finally, it is found that evaporative fraction is strongly correlated to LAI when soil surface is dry because in this condition soil evaporation is an insignificant component of latent heat flux, and therefore

  18. Hourly photosynthetically active radiation estimation in Midwestern United States from artificial neural networks and conventional regressions models

    NASA Astrophysics Data System (ADS)

    Yu, Xiaolei; Guo, Xulin

    2016-08-01

    The relationship between hourly photosynthetically active radiation (PAR) and the global solar radiation ( R s ) was analyzed from data gathered over 3 years at Bondville, IL, and Sioux Falls, SD, Midwestern USA. These data were used to determine temporal variability of the PAR fraction and its dependence on different sky conditions, which were defined by the clearness index. Meanwhile, models based on artificial neural networks (ANNs) were established for predicting hourly PAR. The performance of the proposed models was compared with four existing conventional regression models in terms of the normalized root mean square error (NRMSE), the coefficient of determination ( r 2), the mean percentage error (MPE), and the relative standard error (RSE). From the overall analysis, it shows that the ANN model can predict PAR accurately, especially for overcast sky and clear sky conditions. Meanwhile, the parameters related to water vapor do not improve the prediction result significantly.

  19. Effects of UVC254 nm on the photosynthetic activity of photobionts from the astrobiologically relevant lichens Buellia frigida and Circinaria gyrosa

    NASA Astrophysics Data System (ADS)

    Meeßen, J.; Backhaus, T.; Sadowsky, A.; Mrkalj, M.; Sánchez, F. J.; de la Torre, R.; Ott, S.

    2014-10-01

    In the past decade, various astrobiological studies on different lichen species investigated the impairment of viability and photosynthetic activity by exposure to simulated or real space parameters (as vacuum, polychromatic ultraviolet (UV)-radiation and monochromatic UVC) and consistently found high post-exposure viability as well as low rates of photosynthetic impairment (de Vera et al. 2003, 2004a; 2004b; de la Torre et al. 2010; Onofri et al. 2012; Sánchez et al. 2012, 2014; Brandt et al. 2014). To achieve a better understanding of the basic mechanisms of resistance, the present study subdued isolated and metabolically active photobionts of two astrobiologically relevant lichens to UVC254 nm, examined its effect on photosynthetic activity by chlorophyll a fluorescence and characterized the UVC-induced damages by quantum yield reduction and measurements of non-photochemical quenching. The results indicate a strong impairment of photosynthetic activity, photoprotective mechanisms and overall photobiont vitality when being irradiated in the isolated and metabolically active state. In conclusion, the present study stresses the higher susceptibility of photobionts towards extreme environmental conditions as UVC-exposure, a stressor that does not occur on the Earth. By comparison with previous studies, the present results highlight the importance of protective mechanisms in lichens, such as morphological-anatomical traits (Meeßen et al. 2013), secondary lichen compounds (Meeßen et al. 2014) and the symbiont's pivotal ability to pass into anhydrobiosis when desiccating.

  20. A Micro-Powered Underwater Logger For Recording Photosynthetically Active Radiation And Illumination

    NASA Astrophysics Data System (ADS)

    Zabloudil, Karel F.

    1984-09-01

    An underwater data logger is designed to use a micro-powered recording circuit. The in situ monitor can record up to eight signals from sensors onto an internally-housed, 32,000-word erasable programmable read-only memory (EPROM) unit. The very low energy requirements permit the logger to record hourly measurements for a monitoring period of up to six months without recharging the internal batteries. Equipped with underwater light sensors, the instrument can record photosynthetic photon flux density either through an instantaneous reading or as an integrated value for the period between sampling. In addition to these light measurements, other sensors can be used to simultaneously monitor further parameters such as: temperature, pressure, salinity, currents, etc.. Circuits diagrams depicting unit operation and data processing are described. Computer plots of sample survey data (irradiance between two depths, extinction coefficient, and temperature) are illustrated. This paper further describes such additional features of the underwater logger as the capability of the light sensors, designed for all types of measurements and/or manufactured by different companies, to be evaluated in situ at the same environmental conditions.

  1. Spectral Bio-indicator Simulations for Tracking Photosynthetic Activities in a Corn Field

    NASA Technical Reports Server (NTRS)

    Cheng, Yen-Ben; Middleton, Elizabeth M.; Huemmrich, K. Fred; Zhang, Qingyuan; Corp, Lawrence; Campbell, Petya; Kustas, William

    2011-01-01

    Accurate assessment of vegetation canopy optical properties plays a critical role in monitoring natural and managed ecosystems under environmental changes. In this context, radiative transfer (RT) models simulating vegetation canopy reflectance have been demonstrated to be a powerful tool for understanding and estimating spectral bio-indicators. In this study, two narrow band spectroradiometers were utilized to acquire observations over corn canopies for two summers. These in situ spectral data were then used to validate a two-layer Markov chain-based canopy reflectance model for simulating the Photochemical Reflectance Index (PRI), which has been widely used in recent vegetation photosynthetic light use efficiency (LUE) studies. The in situ PRI derived from narrow band hyperspectral reflectance exhibited clear responses to: 1) viewing geometry which affects the asset of light environment; and 2) seasonal variation corresponding to the growth stage. The RT model (ACRM) successfully simulated the responses to the variable viewing geometry. The best simulations were obtained when the model was set to run in the two layer mode using the sunlit leaves as the upper layer and shaded leaves as the lower layer. Simulated PRI values yielded much better correlations to in situ observations when the cornfield was dominated by green foliage during the early growth, vegetative and reproductive stages (r = 0.78 to 0.86) than in the later senescent stage (r = 0.65). Further sensitivity analyses were conducted to show the important influences of leaf area index (LAI) and the sunlit/shaded ratio on PRI observations.

  2. Spectral bio-indicator simulations for tracking photosynthetic activities in a corn field

    NASA Astrophysics Data System (ADS)

    Cheng, Yen-Ben; Middleton, Elizabeth M.; Huemmrich, K. Fred; Zhang, Qingyuan; Corp, Lawrence; Campbell, Petya; Kustas, William

    2011-09-01

    Accurate assessment of vegetation canopy optical properties plays a critical role in monitoring natural and managed ecosystems under environmental changes. In this context, radiative transfer (RT) models simulating vegetation canopy reflectance have been demonstrated to be a powerful tool for understanding and estimating spectral bio-indicators. In this study, two narrow band spectroradiometers were utilized to acquire observations over corn canopies for two summers. These in situ spectral data were then used to validate a two-layer Markov chain-based canopy reflectance model for simulating the Photochemical Reflectance Index (PRI), which has been widely used in recent vegetation photosynthetic light use efficiency (LUE) studies. The in situ PRI derived from narrow band hyperspectral reflectance exhibited clear responses to: 1) viewing geometry which affects the light environment; and 2) seasonal variation corresponding to the growth stage. The RT model (ACRM) successfully simulated the responses to the viewing geometry. The best simulations were obtained when the model was set to run in the two layer mode using the sunlit leaves as the upper layer and shaded leaves as the lower layer. Simulated PRI values yielded much better correlations to in situ observations when the cornfield was dominated by green foliage during the early growth, vegetative and reproductive stages (r = 0.78 to 0.86) than in the later senescent stage (r = 0.65). Further sensitivity analyses were conducted to show the important influences of leaf area index (LAI) and the sunlit/shaded ratio on PRI observations.

  3. Elevated temperature altered photosynthetic products in wheat seedlings and organic compounds and biological activity in rhizopshere soil under cadmium stress

    PubMed Central

    Jia, Xia; Zhao, YongHua; Wang, WenKe; He, Yunhua

    2015-01-01

    The objective of this study was to investigate the effects of slightly elevated atmospheric temperature in the spring on photosynthetic products in wheat seedlings and on organic compounds and biological activity in rhizosphere soil under cadmium (Cd) stress. Elevated temperature was associated with increased soluble sugars, reducing sugars, starch, and total sugars, and with decreased amino acids in wheat seedlings under Cd stress. Elevated temperature improved total soluble sugars, free amino acids, soluble phenolic acids, and organic acids in rhizosphere soil under Cd stress. The activity of amylase, phenol oxidase, invertase, β-glucosidase, and l-asparaginase in rhizosphere soil was significantly improved by elevated temperature under Cd stress; while cellulase, neutral phosphatase, and urease activity significantly decreased. Elevated temperature significantly improved bacteria, fungi, actinomycetes, and total microorganisms abundance and fluorescein diacetate activity under Cd stress. In conclusion, slightly elevated atmospheric temperature in the spring improved the carbohydrate levels in wheat seedlings and organic compounds and biological activity in rhizosphere soil under Cd stress in the short term. In addition, elevated atmospheric temperature in the spring stimulated available Cd by affecting pH, DOC, phenolic acids, and organic acids in rhizosphere soil, which resulted in the improvement of the Cd uptake by wheat seedlings. PMID:26395070

  4. Elevated temperature altered photosynthetic products in wheat seedlings and organic compounds and biological activity in rhizopshere soil under cadmium stress.

    PubMed

    Jia, Xia; Zhao, YongHua; Wang, WenKe; He, Yunhua

    2015-01-01

    The objective of this study was to investigate the effects of slightly elevated atmospheric temperature in the spring on photosynthetic products in wheat seedlings and on organic compounds and biological activity in rhizosphere soil under cadmium (Cd) stress. Elevated temperature was associated with increased soluble sugars, reducing sugars, starch, and total sugars, and with decreased amino acids in wheat seedlings under Cd stress. Elevated temperature improved total soluble sugars, free amino acids, soluble phenolic acids, and organic acids in rhizosphere soil under Cd stress. The activity of amylase, phenol oxidase, invertase, β-glucosidase, and l-asparaginase in rhizosphere soil was significantly improved by elevated temperature under Cd stress; while cellulase, neutral phosphatase, and urease activity significantly decreased. Elevated temperature significantly improved bacteria, fungi, actinomycetes, and total microorganisms abundance and fluorescein diacetate activity under Cd stress. In conclusion, slightly elevated atmospheric temperature in the spring improved the carbohydrate levels in wheat seedlings and organic compounds and biological activity in rhizosphere soil under Cd stress in the short term. In addition, elevated atmospheric temperature in the spring stimulated available Cd by affecting pH, DOC, phenolic acids, and organic acids in rhizosphere soil, which resulted in the improvement of the Cd uptake by wheat seedlings.

  5. Elevated temperature altered photosynthetic products in wheat seedlings and organic compounds and biological activity in rhizopshere soil under cadmium stress

    NASA Astrophysics Data System (ADS)

    Jia, Xia; Zhao, Yonghua; Wang, Wenke; He, Yunhua

    2015-09-01

    The objective of this study was to investigate the effects of slightly elevated atmospheric temperature in the spring on photosynthetic products in wheat seedlings and on organic compounds and biological activity in rhizosphere soil under cadmium (Cd) stress. Elevated temperature was associated with increased soluble sugars, reducing sugars, starch, and total sugars, and with decreased amino acids in wheat seedlings under Cd stress. Elevated temperature improved total soluble sugars, free amino acids, soluble phenolic acids, and organic acids in rhizosphere soil under Cd stress. The activity of amylase, phenol oxidase, invertase, β-glucosidase, and L-asparaginase in rhizosphere soil was significantly improved by elevated temperature under Cd stress; while cellulase, neutral phosphatase, and urease activity significantly decreased. Elevated temperature significantly improved bacteria, fungi, actinomycetes, and total microorganisms abundance and fluorescein diacetate activity under Cd stress. In conclusion, slightly elevated atmospheric temperature in the spring improved the carbohydrate levels in wheat seedlings and organic compounds and biological activity in rhizosphere soil under Cd stress in the short term. In addition, elevated atmospheric temperature in the spring stimulated available Cd by affecting pH, DOC, phenolic acids, and organic acids in rhizosphere soil, which resulted in the improvement of the Cd uptake by wheat seedlings.

  6. Elevated temperature altered photosynthetic products in wheat seedlings and organic compounds and biological activity in rhizopshere soil under cadmium stress.

    PubMed

    Jia, Xia; Zhao, YongHua; Wang, WenKe; He, Yunhua

    2015-01-01

    The objective of this study was to investigate the effects of slightly elevated atmospheric temperature in the spring on photosynthetic products in wheat seedlings and on organic compounds and biological activity in rhizosphere soil under cadmium (Cd) stress. Elevated temperature was associated with increased soluble sugars, reducing sugars, starch, and total sugars, and with decreased amino acids in wheat seedlings under Cd stress. Elevated temperature improved total soluble sugars, free amino acids, soluble phenolic acids, and organic acids in rhizosphere soil under Cd stress. The activity of amylase, phenol oxidase, invertase, β-glucosidase, and l-asparaginase in rhizosphere soil was significantly improved by elevated temperature under Cd stress; while cellulase, neutral phosphatase, and urease activity significantly decreased. Elevated temperature significantly improved bacteria, fungi, actinomycetes, and total microorganisms abundance and fluorescein diacetate activity under Cd stress. In conclusion, slightly elevated atmospheric temperature in the spring improved the carbohydrate levels in wheat seedlings and organic compounds and biological activity in rhizosphere soil under Cd stress in the short term. In addition, elevated atmospheric temperature in the spring stimulated available Cd by affecting pH, DOC, phenolic acids, and organic acids in rhizosphere soil, which resulted in the improvement of the Cd uptake by wheat seedlings. PMID:26395070

  7. High strength semi-active energy absorbers using shear- and mixedmode operation at high shear rates

    NASA Astrophysics Data System (ADS)

    Becnel, Andrew C.

    This body of research expands the design space of semi-active energy absorbers for shock isolation and crash safety by investigating and characterizing magnetorheological fluids (MRFs) at high shear rates ( > 25,000 1/s) under shear and mixed-mode operation. Magnetorheological energy absorbers (MREAs) work well as adaptive isolators due to their ability to quickly and controllably adjust to changes in system mass or impact speed while providing fail-safe operation. However, typical linear stroking MREAs using pressure-driven flows have been shown to exhibit reduced controllability as impact speed (shear rate) increases. The objective of this work is to develop MREAs that improve controllability at high shear rates by using pure shear and mixed shear-squeeze modes of operation, and to present the fundamental theory and models of MR fluids under these conditions. A proof of concept instrument verified that the MR effect persists in shear mode devices at shear rates corresponding to low speed impacts. This instrument, a concentric cylinder Searle cell magnetorheometer, was then used to characterize three commercially available MRFs across a wide range of shear rates, applied magnetic fields, and temperatures. Characterization results are presented both as flow curves according to established practice, and as an alternate nondimensionalized analysis based on Mason number. The Mason number plots show that, with appropriate correction coefficients for operating temperature, the varied flow curve data can be collapsed to a single master curve. This work represents the first shear mode characterization of MRFs at shear rates over 10 times greater than available with commercial rheometers, as well as the first validation of Mason number analysis to high shear rate flows in MRFs. Using the results from the magnetorheometer, a full scale rotary vane MREA was developed as part of the Lightweight Magnetorheological Energy Absorber System (LMEAS) for an SH-60 Seahawk helicopter

  8. Relationship Between Ecosystem Productivity and Photosynthetically Active Radiation for Northern Peatlands

    NASA Technical Reports Server (NTRS)

    Frolking, S. E.; Bubier, J. L.; Moore, T. R.; Ball, T.; Bellisario, L. M.; Bhardwaj, A.; Carroll, P.; Crill, P. M.; Lafleur, P. M.; McCaughey, J. H.; Roulet, N. T.; Suyker, A. E.; Verma, S. B.; Waddington, J. M.; Whiting, G. J.

    1998-01-01

    We analyzed the relationship between net ecosystem exchange of carbon dioxide (NEE) and irradiance (as photosynthetic photon flux density or PPFD), using published and unpublished data that have been collected during midgrowing season for carbon balance studies at seven peatlands in North America and Europe, NEE measurements included both eddy-correlation tower and clear, static chamber methods, which gave very similar results. Data were analyzed by site, as aggregated data sets by peatland type (bog, poor fen, rich fen, and all fens) and as a single aggregated data set for all peatlands. In all cases, a fit with a rectangular hyperbola (NEE = alpha PPFD P(sub max)/(alpha PPFD + P(sub max) + R) better described the NEE-PPFD relationship than did a linear fit (NEE = beta PPFD + R). Poor and rich fens generally had similar NEE-PPFD relationships, while bogs had lower respiration rates (R = -2.0 micro mol m(exp -2) s(exp -1) for bogs and -2.7 micro mol m(exp -2) s(exp -1)) for fens) and lower NEE at moderate and high light levels (P(sub max)= 5.2 micro mol m(exp -2) s(exp -1) for bogs and 10.8 micro mol m(exp -2) s(exp -1) for fens). As a single class, northern peatlands had much smaller ecosystem respiration (R = -2.4 micro mol m(exp -2) s(exp -1)) and NEE rates (alpha = 0.020 and P(sub max)= 9.2 micro mol m(exp -2) s(exp -1)) than the upland ecosystems (closed canopy forest, grassland, and cropland). Despite this low productivity, northern peatland soil carbon pools are generally 5-50 times larger than upland ecosystems because of slow rates of decomposition caused by litter quality and anaerobic, cold soils.

  9. Ferredoxin-thioredoxin reductase: a catalytically active dithiol group links photoreduced ferredoxin to thioredoxin functional in photosynthetic enzyme regulation

    SciTech Connect

    Droux, M.; Miginiac-Maslow, M.; Jacquot, J.P.; Gadal, P.; Crawford, N.A.; Kosower, N.S.; Buchanan, B.B.

    1987-07-01

    The mechanism by which the ferredoxin-thioredoxin system activates the target enzyme, NADP-malate dehydrogenase, was investigated by analyzing the sulfhydryl status of individual protein components with (/sup 14/C)iodoacetate and monobromobimane. The data indicate that ferredoxin-thioredoxin reductase (FTR)--an iron-sulfur enzyme present in oxygenic photosynthetic organisms--is the first member of a thiol chain that links light to enzyme regulation. FTR possesses a catalytically active dithiol group localized on the 13 kDa (similar) subunit, that occurs in all species investigated and accepts reducing equivalents from photoreduced ferredoxin and transfers them stoichiometrically to the disulfide form of thioredoxin m. The reduced thioredoxin m, in turn, reduces NADP-malate dehydrogenase, thereby converting it from an inactive (S-S) to an active (SH) form. The means by which FTR is able to combine electrons (from photoreduced ferredoxin) with protons (from the medium) to reduce its active disulfide group remains to be determined.

  10. Fe-, Co-, and Ni-Loaded Porous Activated Carbon Balls as Lightweight Microwave Absorbents.

    PubMed

    Li, Guomin; Wang, Liancheng; Li, Wanxi; Xu, Yao

    2015-11-16

    Porous activated carbon ball (PACB) composites impregnated with iron, cobalt, nickel and/or their oxides were synthesized through a wet chemistry method involving PACBs as the carrier to load Fe(3+), Co(2+), and Ni(2+) ions and a subsequent carbothermal reduction at different annealing temperatures. The results show that the pyrolysis products of nitrates and/or the products from the carbothermal reduction are embedded in the pores of the PACBs, with different distributions, resulting in different crystalline phases. The as-prepared PACB composites possessed high specific surface areas of 791.2-901.5 m(2)  g(-1) and low densities of 1.1-1.3 g cm(-3). Minimum reflection loss (RL) values of -50.1, -20.6, and -20.4 dB were achieved for Fe-PACB (annealed at 500 °C), Co-PACB (annealed at 800 °C), and Ni-PACB (annealed at 800 °C) composites, respectively. Moreover, the influence of the amount of the magnetic components in the PACB composites on the microwave-absorbing performances was investigated, further confirming that the dielectric loss was the primary contributor to microwave absorption. PMID:26373310

  11. Fractional absorption of active absorbable algal calcium (AAACa) and calcium carbonate measured by a dual stable-isotope method

    Technology Transfer Automated Retrieval System (TEKTRAN)

    With the use of stable isotopes, this study aimed to compare the bioavailability of active absorbable algal calcium (AAACa), obtained from oyster shell powder heated to a high temperature, with an additional heated seaweed component (Heated Algal Ingredient, HAI), with that of calcium carbonate. In ...

  12. Photosynthetic proteins for technological applications.

    PubMed

    Giardi, Maria Teresa; Pace, Emanuela

    2005-05-01

    Photosynthetic proteins are a source of biological material well-suited to technological applications. They exhibit light-induced electron transfer across lipid membranes that can be exploited for the construction of photo-optical electrical devices. The structure and function of photosynthetic proteins differ across the photosynthetic evolutionary scale, allowing for their application in a range of technologies. Here we provide a general description of the basic and technical research in this sector and an overview of biochips and biosensors based on photochemical activity that have been developed for the bioassay of pollutants.

  13. Light piping driven photosynthesis in the soil: Low-light adapted active photosynthetic apparatus in the under-soil hypocotyl segments of bean (Phaseolus vulgaris).

    PubMed

    Kakuszi, Andrea; Sárvári, Éva; Solti, Ádám; Czégény, Gyula; Hideg, Éva; Hunyadi-Gulyás, Éva; Bóka, Károly; Böddi, Béla

    2016-08-01

    Photosynthetic activity was identified in the under-soil hypocotyl part of 14-day-old soil-grown bean plants (Phaseolus vulgaris L. cv. Magnum) cultivated in pots under natural light-dark cycles. Electron microscopic, proteomic and fluorescence kinetic and imaging methods were used to study the photosynthetic apparatus and its activity. Under-soil shoots at 0-2cm soil depth featured chloroplasts with low grana and starch grains and with pigment-protein compositions similar to those of the above-soil green shoot parts. However, the relative amounts of photosystem II (PSII) supercomplexes were higher; in addition a PIP-type aquaporin protein was identified in the under-soil thylakoids. Chlorophyll-a fluorescence induction measurements showed that the above- and under-soil hypocotyl segments had similar photochemical yields at low (10-55μmolphotonsm(-2)s(-1)) light intensities. However, at higher photon flux densities the electron transport rate decreased in the under-soil shoot parts due to inactivation of the PSII reaction centers. These properties show the development of a low-light adapted photosynthetic apparatus driven by light piping of the above-soil shoot. The results of this paper demonstrate that the classic model assigning source and sink functions to above- and under-soil tissues is to be refined, and a low-light adapted photosynthetic apparatus in under-soil bean hypocotyls is capable of contributing to its own carbon supply.

  14. Light piping driven photosynthesis in the soil: Low-light adapted active photosynthetic apparatus in the under-soil hypocotyl segments of bean (Phaseolus vulgaris).

    PubMed

    Kakuszi, Andrea; Sárvári, Éva; Solti, Ádám; Czégény, Gyula; Hideg, Éva; Hunyadi-Gulyás, Éva; Bóka, Károly; Böddi, Béla

    2016-08-01

    Photosynthetic activity was identified in the under-soil hypocotyl part of 14-day-old soil-grown bean plants (Phaseolus vulgaris L. cv. Magnum) cultivated in pots under natural light-dark cycles. Electron microscopic, proteomic and fluorescence kinetic and imaging methods were used to study the photosynthetic apparatus and its activity. Under-soil shoots at 0-2cm soil depth featured chloroplasts with low grana and starch grains and with pigment-protein compositions similar to those of the above-soil green shoot parts. However, the relative amounts of photosystem II (PSII) supercomplexes were higher; in addition a PIP-type aquaporin protein was identified in the under-soil thylakoids. Chlorophyll-a fluorescence induction measurements showed that the above- and under-soil hypocotyl segments had similar photochemical yields at low (10-55μmolphotonsm(-2)s(-1)) light intensities. However, at higher photon flux densities the electron transport rate decreased in the under-soil shoot parts due to inactivation of the PSII reaction centers. These properties show the development of a low-light adapted photosynthetic apparatus driven by light piping of the above-soil shoot. The results of this paper demonstrate that the classic model assigning source and sink functions to above- and under-soil tissues is to be refined, and a low-light adapted photosynthetic apparatus in under-soil bean hypocotyls is capable of contributing to its own carbon supply. PMID:27318297

  15. Minimization of the mean square velocity response of dynamic structures using an active-passive dynamic vibration absorber.

    PubMed

    Cheung, Y L; Wong, W O; Cheng, L

    2012-07-01

    An optimal design of a hybrid vibration absorber (HVA) with a displacement and a velocity feedback for minimizing the velocity response of the structure based on the H(2) optimization criterion is proposed. The objective of the optimal design is to reduce the total vibration energy of the vibrating structure under wideband excitation, i.e., the total area under the velocity response spectrum is minimized in this criterion. One of the inherent limitations of the traditional passive vibration absorber is that its vibration suppression is low if the mass ratio between the absorber mass and the mass of the primary structure is low. The active element of the proposed HVA helps further reduce the vibration of the controlled structure, and it can provide very good vibration absorption performance even at a low mass ratio. Both the passive and active elements are optimized together for the minimization of the mean square velocity of the primary system as well as the active force required in the HVA. The proposed HVA was tested on single degree-of-freedom (SDOF) and continuous vibrating structures and compared to the traditional passive vibration absorber.

  16. Ion antiport accelerates photosynthetic acclimation in fluctuating light environments

    PubMed Central

    Armbruster, Ute; Carrillo, L. Ruby; Venema, Kees; Pavlovic, Lazar; Schmidtmann, Elisabeth; Kornfeld, Ari; Jahns, Peter; Berry, Joseph A.; Kramer, David M.; Jonikas, Martin C.

    2014-01-01

    Many photosynthetic organisms globally, including crops, forests and algae, must grow in environments where the availability of light energy fluctuates dramatically. How photosynthesis maintains high efficiency despite such fluctuations in its energy source remains poorly understood. Here we show that Arabidopsis thaliana K+ efflux antiporter (KEA3) is critical for high photosynthetic efficiency under fluctuating light. On a shift from dark to low light, or high to low light, kea3 mutants show prolonged dissipation of absorbed light energy as heat. KEA3 localizes to the thylakoid membrane, and allows proton efflux from the thylakoid lumen by proton/potassium antiport. KEA3’s activity accelerates the downregulation of pH-dependent energy dissipation after transitions to low light, leading to faster recovery of high photosystem II quantum efficiency and increased CO2 assimilation. Our results reveal a mechanism that increases the efficiency of photosynthesis under fluctuating light. PMID:25451040

  17. Ion antiport accelerates photosynthetic acclimation in fluctuating light environments.

    PubMed

    Armbruster, Ute; Carrillo, L Ruby; Venema, Kees; Pavlovic, Lazar; Schmidtmann, Elisabeth; Kornfeld, Ari; Jahns, Peter; Berry, Joseph A; Kramer, David M; Jonikas, Martin C

    2014-11-13

    Many photosynthetic organisms globally, including crops, forests and algae, must grow in environments where the availability of light energy fluctuates dramatically. How photosynthesis maintains high efficiency despite such fluctuations in its energy source remains poorly understood. Here we show that Arabidopsis thaliana K(+) efflux antiporter (KEA3) is critical for high photosynthetic efficiency under fluctuating light. On a shift from dark to low light, or high to low light, kea3 mutants show prolonged dissipation of absorbed light energy as heat. KEA3 localizes to the thylakoid membrane, and allows proton efflux from the thylakoid lumen by proton/potassium antiport. KEA3's activity accelerates the downregulation of pH-dependent energy dissipation after transitions to low light, leading to faster recovery of high photosystem II quantum efficiency and increased CO2 assimilation. Our results reveal a mechanism that increases the efficiency of photosynthesis under fluctuating light.

  18. Engineering photosynthetic organisms for the production of biohydrogen.

    PubMed

    Dubini, Alexandra; Ghirardi, Maria L

    2015-03-01

    Oxygenic photosynthetic organisms such as green algae are capable of absorbing sunlight and converting the chemical energy into hydrogen gas. This process takes advantage of the photosynthetic apparatus of these organisms which links water oxidation to H2 production. Biological H2 has therefore the potential to be an alternative fuel of the future and shows great promise for generating large scale sustainable energy. Microalgae are able to produce H2 under light anoxic or dark anoxic condition by activating 3 different pathways that utilize the hydrogenases as catalysts. In this review, we highlight the principal barriers that prevent hydrogen production in green algae and how those limitations are being addressed, through metabolic and genetic engineering.  We also discuss the major challenges and bottlenecks facing the development of future commercial algal photobiological systems for H2 production. Finally we provide suggestions for future strategies and potential new techniques to be developed towards an integrated system with optimized hydrogen production. PMID:24671643

  19. Ion antiport accelerates photosynthetic acclimation in fluctuating light environments.

    PubMed

    Armbruster, Ute; Carrillo, L Ruby; Venema, Kees; Pavlovic, Lazar; Schmidtmann, Elisabeth; Kornfeld, Ari; Jahns, Peter; Berry, Joseph A; Kramer, David M; Jonikas, Martin C

    2014-01-01

    Many photosynthetic organisms globally, including crops, forests and algae, must grow in environments where the availability of light energy fluctuates dramatically. How photosynthesis maintains high efficiency despite such fluctuations in its energy source remains poorly understood. Here we show that Arabidopsis thaliana K(+) efflux antiporter (KEA3) is critical for high photosynthetic efficiency under fluctuating light. On a shift from dark to low light, or high to low light, kea3 mutants show prolonged dissipation of absorbed light energy as heat. KEA3 localizes to the thylakoid membrane, and allows proton efflux from the thylakoid lumen by proton/potassium antiport. KEA3's activity accelerates the downregulation of pH-dependent energy dissipation after transitions to low light, leading to faster recovery of high photosystem II quantum efficiency and increased CO2 assimilation. Our results reveal a mechanism that increases the efficiency of photosynthesis under fluctuating light. PMID:25451040

  20. Effects of sediment and turbulence on alkaline phosphatase activity and photosynthetic activity of phytoplankton in the shallow hyper-eutrophic Lake Taihu, China.

    PubMed

    Ding, Yanqing; Qin, Boqiang; Xu, Hai; Wang, Xiaodong

    2016-08-01

    Sediments play important roles, as nutrient reservoir, especially in shallow lake ecosystem. The water column of large shallow lakes is often stable but also disturbed by turbulence causing resuspension of sediments. While considerable research has been carried out to investigate the influence of sediment resuspension on nutrient release, fewer studies have been done to understand the contribution of alkaline phosphatase activity (APA) in water as a response to the two conditions (turbulence and stability). Also, effects of the two lake conditions on photosynthetic efficiency of phytoplankton are still poorly understood. This study will evaluate the effect of these two conditions on photosynthetic efficiency and APA. Sediments used in the indoor experiments were collected from Zhushan Bay in Lake Taihu. Turbulence was generated by rotors to simulate the strong wind-induced disturbance in Lake Taihu. Results of the experiments showed that TN and TP in the stable and episodically turbulent conditions were not significantly different, with TN ranging from 1.34 to 1.90 mg/L and TP from 0.08 to 0.18 mg/L. Whereas, the soluble reactive phosphorus in the episodically turbulent condition was significantly higher than in the stable condition. Episodic turbulence could enhance P cycling by resuspending sediment-associated P, which alleviated algal P limitation. In stable conditions, P deficiency induced the production of high APA, which enhanced the availability of P. Although episodic turbulence could also cause increased algal biomass, photosynthetic efficiency of the algae was also affected not only by the nutrients but also by many other factors, especially light availability. Our results suggest that episodic turbulence is an important driver of biogeochemical cycling in large shallow hypertrophic lake ecosystem.

  1. Effects of sediment and turbulence on alkaline phosphatase activity and photosynthetic activity of phytoplankton in the shallow hyper-eutrophic Lake Taihu, China.

    PubMed

    Ding, Yanqing; Qin, Boqiang; Xu, Hai; Wang, Xiaodong

    2016-08-01

    Sediments play important roles, as nutrient reservoir, especially in shallow lake ecosystem. The water column of large shallow lakes is often stable but also disturbed by turbulence causing resuspension of sediments. While considerable research has been carried out to investigate the influence of sediment resuspension on nutrient release, fewer studies have been done to understand the contribution of alkaline phosphatase activity (APA) in water as a response to the two conditions (turbulence and stability). Also, effects of the two lake conditions on photosynthetic efficiency of phytoplankton are still poorly understood. This study will evaluate the effect of these two conditions on photosynthetic efficiency and APA. Sediments used in the indoor experiments were collected from Zhushan Bay in Lake Taihu. Turbulence was generated by rotors to simulate the strong wind-induced disturbance in Lake Taihu. Results of the experiments showed that TN and TP in the stable and episodically turbulent conditions were not significantly different, with TN ranging from 1.34 to 1.90 mg/L and TP from 0.08 to 0.18 mg/L. Whereas, the soluble reactive phosphorus in the episodically turbulent condition was significantly higher than in the stable condition. Episodic turbulence could enhance P cycling by resuspending sediment-associated P, which alleviated algal P limitation. In stable conditions, P deficiency induced the production of high APA, which enhanced the availability of P. Although episodic turbulence could also cause increased algal biomass, photosynthetic efficiency of the algae was also affected not only by the nutrients but also by many other factors, especially light availability. Our results suggest that episodic turbulence is an important driver of biogeochemical cycling in large shallow hypertrophic lake ecosystem. PMID:27151245

  2. Effects of fatty acid activation on photosynthetic production of fatty acid-based biofuels in Synechocystis sp. PCC6803

    PubMed Central

    2012-01-01

    Background Direct conversion of solar energy and carbon dioxide to drop in fuel molecules in a single biological system can be achieved from fatty acid-based biofuels such as fatty alcohols and alkanes. These molecules have similar properties to fossil fuels but can be produced by photosynthetic cyanobacteria. Results Synechocystis sp. PCC6803 mutant strains containing either overexpression or deletion of the slr1609 gene, which encodes an acyl-ACP synthetase (AAS), have been constructed. The complete segregation and deletion in all mutant strains was confirmed by PCR analysis. Blocking fatty acid activation by deleting slr1609 gene in wild-type Synechocystis sp. PCC6803 led to a doubling of the amount of free fatty acids and a decrease of alkane production by up to 90 percent. Overexpression of slr1609 gene in the wild-type Synechocystis sp. PCC6803 had no effect on the production of either free fatty acids or alkanes. Overexpression or deletion of slr1609 gene in the Synechocystis sp. PCC6803 mutant strain with the capability of making fatty alcohols by genetically introducing fatty acyl-CoA reductase respectively enhanced or reduced fatty alcohol production by 60 percent. Conclusions Fatty acid activation functionalized by the slr1609 gene is metabolically crucial for biosynthesis of fatty acid derivatives in Synechocystis sp. PCC6803. It is necessary but not sufficient for efficient production of alkanes. Fatty alcohol production can be significantly improved by the overexpression of slr1609 gene. PMID:22433663

  3. Enhanced photosynthetic performance and growth as a consequence of decreasing mitochondrial malate dehydrogenase activity in transgenic tomato plants.

    PubMed

    Nunes-Nesi, Adriano; Carrari, Fernando; Lytovchenko, Anna; Smith, Anna M O; Loureiro, Marcelo Ehlers; Ratcliffe, R George; Sweetlove, Lee J; Fernie, Alisdair R

    2005-02-01

    Transgenic tomato (Solanum lycopersicum) plants expressing a fragment of the mitochondrial malate dehydrogenase gene in the antisense orientation and exhibiting reduced activity of this isoform of malate dehydrogenase show enhanced photosynthetic activity and aerial growth under atmospheric conditions (360 ppm CO2). In comparison to wild-type plants, carbon dioxide assimilation rates and total plant dry matter were up to 11% and 19% enhanced in the transgenics, when assessed on a whole-plant basis. Accumulation of carbohydrates and redox-related compounds such as ascorbate was also markedly elevated in the transgenics. Also increased in the transgenic plants was the capacity to use L-galactono-lactone, the terminal precursor of ascorbate biosynthesis, as a respiratory substrate. Experiments in which ascorbate was fed to isolated leaf discs also resulted in increased rates of photosynthesis providing strong indication for an ascorbate-mediated link between the energy-generating processes of respiration and photosynthesis. This report thus shows that the repression of this mitochondrially localized enzyme improves both carbon assimilation and aerial growth in a crop species. PMID:15665243

  4. Predicting trace organic compound breakthrough in granular activated carbon using fluorescence and UV absorbance as surrogates.

    PubMed

    Anumol, Tarun; Sgroi, Massimiliano; Park, Minkyu; Roccaro, Paolo; Snyder, Shane A

    2015-06-01

    This study investigated the applicability of bulk organic parameters like dissolved organic carbon (DOC), UV absorbance at 254 nm (UV254), and total fluorescence (TF) to act as surrogates in predicting trace organic compound (TOrC) removal by granular activated carbon in water reuse applications. Using rapid small-scale column testing, empirical linear correlations for thirteen TOrCs were determined with DOC, UV254, and TF in four wastewater effluents. Linear correlations (R(2) > 0.7) were obtained for eight TOrCs in each water quality in the UV254 model, while ten TOrCs had R(2) > 0.7 in the TF model. Conversely, DOC was shown to be a poor surrogate for TOrC breakthrough prediction. When the data from all four water qualities was combined, good linear correlations were still obtained with TF having higher R(2) than UV254 especially for TOrCs with log Dow>1. Excellent linear relationship (R(2) > 0.9) between log Dow and the removal of TOrC at 0% surrogate removal (y-intercept) were obtained for the five neutral TOrCs tested in this study. Positively charged TOrCs had enhanced removals due to electrostatic interactions with negatively charged GAC that caused them to deviate from removals that would be expected with their log Dow. Application of the empirical linear correlation models to full-scale samples provided good results for six of seven TOrCs (except meprobamate) tested when comparing predicted TOrC removal by UV254 and TF with actual removals for GAC in all the five samples tested. Surrogate predictions using UV254 and TF provide valuable tools for rapid or on-line monitoring of GAC performance and can result in cost savings by extended GAC run times as compared to using DOC breakthrough to trigger regeneration or replacement.

  5. [Impacts of suboptimal temperature and low light intensity on the activities and gene expression of photosynthetic enzymes in cucumber seedling leaves].

    PubMed

    Bi, Huan-Gai; Wang, Mei-Ling; Jiang, Zhen-Sheng; Dong, Xu-Bing; Ai, Xi-Zhen

    2011-11-01

    Taking the cucumber cultivar 'Jinyou 3' as test material, this paper studied the variations of the mRNA expression and activities of ribulose-1, 5-bisphosphate carboxylase/oxygenase (Rubisco), fructose-1, 6-bisphosphatase (FBPase), glyceraldehydes-3-phosphate dehydrogenase (GAPDH), fructose-1, 6-bisphosphate aldolase (FBA), and transketolase (TK) in cucumber seedling leaves under suboptimal temperature and low light intensity (ST+LL). In the treatment of ST+LL, the leaf area and the dry mass per plant decreased remarkably, compared with the control. On the early days of ST+LL treatment, the gene expression of Rubisco rbcL and rbcS, FBPase, GAPDH, FBA, and TK declined markedly, the activities of the enzymes except TK obviously weakened, and the photosynthetic rate (P(n)) decreased rapidly. 3 days later, the gene expression of Rubisco rbcL and rbcS and the initial activity of Rubisco showed a continuous decrease but the decrement was obviously lesser, the total activity of Rubisco and the activities and gene expression of FBPase, GAPDH, FBA, and TK had an increasing trend, and the P(n) ascended simultaneously. When the treating time exceeded 6 days, the gene expression and the activities of Rubisco and FBPase tended to be constant, while those of the other enzymes as well as the P(n) presented a decreasing trend. These results suggested that the decline of the gene expression and activities of the photosynthetic enzymes in cucumber seedlings under suboptimal temperature and low light intensity was the important reason which led to the decrease of P(n). The adaptation of photosynthetic apparatus in cucumber seedlings to suboptimal temperature and low light intensity was related to the activation mechanisms of photosynthetic enzymes.

  6. Photosynthetic gene expression in higher plants.

    PubMed

    Berry, James O; Yerramsetty, Pradeep; Zielinski, Amy M; Mure, Christopher M

    2013-11-01

    Within the chloroplasts of higher plants and algae, photosynthesis converts light into biological energy, fueling the assimilation of atmospheric carbon dioxide into biologically useful molecules. Two major steps, photosynthetic electron transport and the Calvin-Benson cycle, require many gene products encoded from chloroplast as well as nuclear genomes. The expression of genes in both cellular compartments is highly dynamic and influenced by a diverse range of factors. Light is the primary environmental determinant of photosynthetic gene expression. Working through photoreceptors such as phytochrome, light regulates photosynthetic genes at transcriptional and posttranscriptional levels. Other processes that affect photosynthetic gene expression include photosynthetic activity, development, and biotic and abiotic stress. Anterograde (from nucleus to chloroplast) and retrograde (from chloroplast to nucleus) signaling insures the highly coordinated expression of the many photosynthetic genes between these different compartments. Anterograde signaling incorporates nuclear-encoded transcriptional and posttranscriptional regulators, such as sigma factors and RNA-binding proteins, respectively. Retrograde signaling utilizes photosynthetic processes such as photosynthetic electron transport and redox signaling to influence the expression of photosynthetic genes in the nucleus. The basic C3 photosynthetic pathway serves as the default form used by most of the plant species on earth. High temperature and water stress associated with arid environments have led to the development of specialized C4 and CAM photosynthesis, which evolved as modifications of the basic default expression program. The goal of this article is to explain and summarize the many gene expression and regulatory processes that work together to support photosynthetic function in plants.

  7. The design of an active-adaptive tuned vibration absorber based on magnetorheological elastomer and its vibration attenuation performance

    NASA Astrophysics Data System (ADS)

    Liao, G. J.; Gong, X. L.; Kang, C. J.; Xuan, S. H.

    2011-07-01

    This paper presents an active-adaptive tuned vibration absorber (AATVA) which is based on magnetorheological elastomer (MRE). A voice coil motor is attached to a conventional MRE adaptive tuned vibration absorber (ATVA) to improve its performance. In this study, two feedback types of the activation force were analyzed and the stability condition was obtained. In order to eliminate the time delay effect during the signal processing, a phase-lead compensator was incorporated. Based on the analysis, an MRE AATVA prototype was designed and its dynamic properties were experimentally investigated. The experimental results demonstrated that its resonant frequency could vary from 11 to 18 Hz and its damping ratio decreased to roughly 0.05 from 0.19 by adding the activation force. Besides, its vibration reduction abilities at the first two resonant frequencies of the experimental platform could reach 5.9 dB and 7.9 dB respectively.

  8. Elevated atmospheric CO2 affected photosynthetic products in wheat seedlings and biological activity in rhizosphere soil under cadmium stress.

    PubMed

    Jia, Xia; Liu, Tuo; Zhao, Yonghua; He, Yunhua; Yang, Mingyan

    2016-01-01

    The objective of this study was to investigate the effects of elevated CO2 (700 ± 23 μmol mol(-1)) on photosynthetic products in wheat seedlings and on organic compounds and biological activity in rhizosphere soil under cadmium (Cd) stress. Elevated CO2 was associated with decreased quantities of reducing sugars, starch, and soluble amino acids, and with increased quantities of soluble sugars, total sugars, and soluble proteins in wheat seedlings under Cd stress. The contents of total soluble sugars, total free amino acids, total soluble phenolic acids, and total organic acids in the rhizosphere soil under Cd stress were improved by elevated CO2. Compared to Cd stress alone, the activity of amylase, phenol oxidase, urease, L-asparaginase, β-glucosidase, neutral phosphatase, and fluorescein diacetate increased under elevated CO2 in combination with Cd stress; only cellulase activity decreased. Bacterial abundance in rhizosphere soil was stimulated by elevated CO2 at low Cd concentrations (1.31-5.31 mg Cd kg(-1) dry soil). Actinomycetes, total microbial abundance, and fungi decreased under the combined conditions at 5.31-10.31 mg Cd kg(-1) dry soil. In conclusion, increased production of soluble sugars, total sugars, and proteins in wheat seedlings under elevated CO2 + Cd stress led to greater quantities of organic compounds in the rhizosphere soil relative to seedlings grown under Cd stress only. Elevated CO2 concentrations could moderate the effects of heavy metal pollution on enzyme activity and microorganism abundance in rhizosphere soils, thus improving soil fertility and the microecological rhizosphere environment of wheat under Cd stress.

  9. Novel approach for computing photosynthetically active radiation for productivity modeling using remotely sensed images in the Great Plains, United States

    USGS Publications Warehouse

    Singh, Ramesh K.; Liu, Shu-Guang; Tieszen, Larry L.; Suyker, Andrew E.; Verma, Shashi B.

    2012-01-01

    Gross primary production (GPP) is a key indicator of ecosystem performance, and helps in many decision-making processes related to environment. We used the Eddy covariancelight use efficiency (EC-LUE) model for estimating GPP in the Great Plains, United States in order to evaluate the performance of this model. We developed a novel algorithm for computing the photosynthetically active radiation (PAR) based on net radiation. A strong correlation (R2=0.94,N=24) was found between daily PAR and Landsat-based mid-day instantaneous net radiation. Though the Moderate Resolution Spectroradiometer (MODIS) based instantaneous net radiation was in better agreement (R2=0.98,N=24) with the daily measured PAR, there was no statistical significant difference between Landsat based PAR and MODIS based PAR. The EC-LUE model validation also confirms the need to consider biological attributes (C3 versus C4 plants) for potential light use efficiency. A universal potential light use efficiency is unable to capture the spatial variation of GPP. It is necessary to use C3 versus C4 based land use/land cover map for using EC-LUE model for estimating spatiotemporal distribution of GPP.

  10. Global-scale pattern of peatland Sphagnum growth driven by photosynthetically active radiation and growing season length

    NASA Astrophysics Data System (ADS)

    Loisel, J.; Gallego-Sala, A. V.; Yu, Z.

    2012-02-01

    High-latitude peatlands contain about one third of the world's soil organic carbon, most of which is derived from partly decomposed Sphagnum (peat moss) plants. We conducted a meta-analysis based on a global dataset of Sphagnum growth measurements collected from published literature to investigate the effects of bioclimatic variables on Sphagnum growth. Analysis of variance and general linear models were used to relate Sphagnum magellanicum and S. fuscum growth rates to photosynthetically active radiation integrated over the growing season (PAR0) and a moisture index. We found that PAR0 was the main predictor of Sphagnum growth for the global dataset, and effective moisture was only correlated with moss growth at continental sites. The strong correlation between Sphagnum growth and PAR0 suggests the existence of a global pattern of growth, with slow rates under cool climate and short growing seasons, highlighting the important role of temperature and growing season length in explaining peatland biomass production. Large-scale patterns of cloudiness during the growing season might also limit moss growth. Although considerable uncertainty remains over the carbon balance of peatlands under a changing climate, our results suggest that increasing PAR0 as a result of global warming and lengthening growing seasons could promote Sphagnum growth. Assuming that production and decomposition have the same sensitivity to temperature, this enhanced growth could lead to greater peat-carbon sequestration, inducing a negative feedback to climate change.

  11. Global-scale pattern of peatland Sphagnum growth driven by photosynthetically active radiation and growing season length

    NASA Astrophysics Data System (ADS)

    Loisel, J.; Gallego-Sala, A. V.; Yu, Z.

    2012-07-01

    High-latitude peatlands contain about one third of the world's soil organic carbon, most of which is derived from partly decomposed Sphagnum (peat moss) plants. We conducted a meta-analysis based on a global data set of Sphagnum growth measurements collected from published literature to investigate the effects of bioclimatic variables on Sphagnum growth. Analysis of variance and general linear models were used to relate Sphagnum magellanicum and S. fuscum growth rates to photosynthetically active radiation integrated over the growing season (PAR0) and a moisture index. We found that PAR0 was the main predictor of Sphagnum growth for the global data set, and effective moisture was only correlated with moss growth at continental sites. The strong correlation between Sphagnum growth and PAR0 suggests the existence of a global pattern of growth, with slow rates under cool climate and short growing seasons, highlighting the important role of growing season length in explaining peatland biomass production. Large-scale patterns of cloudiness during the growing season might also limit moss growth. Although considerable uncertainty remains over the carbon balance of peatlands under a changing climate, our results suggest that increasing PAR0 as a result of global warming and lengthening growing seasons, without major change in cloudiness, could promote Sphagnum growth. Assuming that production and decomposition have the same sensitivity to temperature, this enhanced growth could lead to greater peat-carbon sequestration, inducing a negative feedback to climate change.

  12. Relating photosynthetic activity of BSCs from spectral indices: a first step to upscale BSC role on carbon fluxes

    NASA Astrophysics Data System (ADS)

    Rodriguez-Caballero, Emilio; Chamizo, Sonia; Miralles, Isabel; Ortega, Raul; Luna, Lourdes; Cantón, Yolanda

    2014-05-01

    Arid and semiarid ecosystems are water limited environments where water availability is the main limiting factor controlling vegetation cover, productivity and ecosystem function. However, bare areas of these systems are usually covered by a thin layer of photoautrophic communities of microorganisms comprising cyanobacteria, algae, microfungi, lichens or bryophytes, so called biological soil crusts (BSCs), which may cover up to 70 % of the soil surface in these areas. These BSCs are capable to survive long drought periods, during which their physiological activity ceases, and become active just after rainfall or even after dew or fog events, thus triggering their photosynthetic activity. So, they play an active role in C storage in arid ecosystems, where they are considered the main agent of nutrient input on bare areas. Moreover, the carbon (C) stored in soils covered by BSCs may constitute an important nutrient surplus for soil microbial communities or vegetation. Thus, having accurate continuous information about C stocks and C fluxes in soils covered by BSCs, at ecosystems scale, constitutes a relevant issue for scientists and researchers from many different disciplines, and is crucial for assessing the impacts of increasing atmospheric CO2 concentration on global environmental change. Remote sensing images and derived vegetation indices are presented as one of the most promising tools to achieve this goal, since they provide spatially explicit information with high temporal resolution. So that, quantifying the photosynthetic activity on BSC areas using remote sensing data constitutes an essential step to advance in the knowledge about the role of arid and semiarid regions in global C balance. In this study we analyzed the potential of the most widely used vegetation indices to estimate gross photosynthesis (GP) in BSCs. To achieve this objective, GP was calculated, after a rainfall event on different BSCs and on bare field plots, as the sum of net primary

  13. Optical activity and ultraviolet absorbance detection of dansyl L-amino acids separated by gradient liquid chromatography

    SciTech Connect

    Not Available

    1987-04-01

    Many scientific investigations (e.g., geochronology, pharmaceuticals) have the need to determine enantiometric ratios of amino acids and other compounds. It has been reported that OA/UV or OA/RI (refractive index) are ideal methods for the determination of enantiomeric ratios without the need for chiral columns, chiral eluents, or diasteromer preparation. Unfortunately, only three amino acids are naturally UV absorbing (254 nm), and RI sensitivity for amino acids is low. Derivatization by several methods (o-phthalaldehyde, dansyl, phenylisothiocyanate, fluorescamine, 2,4-dinitrofluorobenzene, and phenylthiohydantoin) renders all amino acids UV absorbing and makes UV or fluorescence viable techniques for amino acids determinations. A previously neglected aspect of derivatization is the effect on optical activity. These highly polar groups influence the chiral center of amino acids drastically (electronic and steric effects). The shifting of the absorption band to the proximity of the wavelength used for OA measurements further enhances the importance of the substituent. The authors report here the determination of 17 dansyl amino acids in a mixture by UV absorbance and optical activity. This involves gradient elution. Previously, the optical activity detector (OAD) has been used only with isocratic HPLC.

  14. Influence of Vertical Attenuation of Photosynthetically Active Radiation on the Growth of Submerged Aquatic Vegetation in Tropical Reservoir.

    NASA Astrophysics Data System (ADS)

    da Silva Rotta, L. H.; Mishra, D. R.; Alcântara, E. H.; Imai, N. N.

    2015-12-01

    Reservoir construction cause many changes in lotic ecosystems and can favor the aquatic macrophyte growth. Nova Avanhandava Reservoir (São Paulo, Brazil), is fully inhabited by submerged aquatic vegetation (SAV) which may cause serious problems to hydropower and irrigation systems. The goal of this study was to assess the radiation availability in the water column in Nova Avanhandava and analyze its influence on SAV development and growth. The measurements were carried out between 28th and 30th June, 2013, at 19 sampling stations. Water samples for analytical determination of the suspended solids and chlorophyll-a concentration were collected. Hyperspectral downwelling irradiance (Ed) data, at several depths, were measured using the TriOS/RAMSES optical sensor. Depths and SAV heights were collected through hydroacoustic measurements by transects using the scientific digital sonar BioSonics DT-X (Echosounder). The Ed data were normalized, than calculated the Kd PAR - downwelling diffuse attenuation coefficient of photosynthetically active radiation, and the euphotic zone depth (ZEZ). Results showed that SAV height values were lower at upstream (around P01) with highest TSS (Total Suspended Solids) and Kd, compared to areas downstream (around P19) (Figure). The maximum depth of SAV development, average SAV height, maximum SAV height, variability, and depth of occurrence of SAV were primarily influenced by Kd. A linear inverse relationship between the average SAV height and the Kd PAR (R2 = 0.56, p<0.001), and between maximum SAV height and Kd PAR (R²=0.5, p<0.001) demonstrated that the SAV heigth can be estimated by Kd PAR with significant accuracy. Therefore, studies on subaquatic radiation availability measured by the vertical attenuation of Ed PAR in the water column and the optically active components can be effiectivly linked to SAV growth and occurrence and aid in understanding SAV in tropical reservoirs, contributing to its management.

  15. The history of photosynthetic thermoluminescence.

    PubMed

    Vass, Imre

    2003-01-01

    A fundamental discovery of photosynthetis research in the 1950s was the detection of thermally stimulated light emission from preilluminated photosynthetic material [Arnold W and Sherwood H (1957) Proc Natl Acad Sci USA 43: 105-114]. This phenomenon, called thermoluminescence (TL), is characteristic of a wide range of materials (minerals, semiconductors, inorganic and organic crystals, and complex biological systems), which share the ability of storing radiant energy in thermally stabilized trap states. The original discovery of TL in dried chloroplasts later proved to be a phenomenon common to all photosynthetic organisms: photosynthetic bacteria, cyanobacteria, algae and higher plants, which can be observed in isolated membrane particles, intact chloroplasts and unicellular organisms, and whole leaves. Following the initial observations considerable effort has been devoted to the identification and characterization of photosynthetic TL components. This work has firmly established the participation of various oxidation states of the water-oxidizing complex, the redox-active tyrosines, and the quinone electron acceptors of Photosystem II (PS II) in the generation of photosynthetic glow curves. Since TL characteristics are very sensitive to subtle changes in the redox properties of the involved electron transport components, the TL method has become a powerful tool in probing a wide range of PS II redox reactions and their modifications by environmental stress effects. Here, the main milestones of research in photosynthetic TL are covered until the present day. PMID:16228589

  16. Phycobilisome-thylakoid topography on photosynthetically active vesicles of Porphyridium cruentum

    SciTech Connect

    Dilworth, M.F.; Gantt, E.

    1981-04-01

    Conditions are described for isolating functional phycobilisome-thylakoid vesicles from the red alga Porphyridium cruentum. They required ferricyanide as an oxidant and had O/sub 2/ evolution rates higher than whole cells. Energy transfer to photosystem II chlorophyll was evident from a high F695 nanometer (-196 C) emission peak. In electron micrographs of negatively stained material, the active thylakoid vesicles were found covered by closely spaced phycobilisomes on their external surface. The phycobilisome number in negatively stained vesicles was 450 per square micrometer, which was in the same range as the 400 per square micrometer observed in surface sections.

  17. Dark/Light Modulation of Ribulose Bisphosphate Carboxylase Activity in Plants from Different Photosynthetic Categories 1

    PubMed Central

    Vu, J. Cu V.; Allen, Leon H.; Bowes, George

    1984-01-01

    Ribulose bisphosphate carboxylase/oxygenase (RuBPCase) from several plants had substantially greater activity in extracts from lightexposed leaves than dark leaves, even when the extracts were incubated in vitro with saturating HCO3− and Mg2+ concentrations. This occurred in Glycine max, Lycopersicon esculentum, Nicotiana tabacum, Panicum bisulcatum, and P. hylaeicum (C3); P. maximum (C4 phosphoenolpyruvate carboxykinase); P. milioides (C3/C4); and Bromelia pinguin and Ananas comosus (Crassulacean acid metabolism). Little or no difference between light and dark leaf extracts of RuBPCase was observed in Triticum aestivum (C3); P. miliaceum (C4 NAD malic enzyme); Zea mays and Sorghum bicolor (C4 NADP malic enzyme); Moricandia arvensis (C3/C4); and Hydrilla verticillata (submersed aquatic macrophyte). It is concluded that, in many plants, especially Crassulacean acid metabolism and C3 species, a large fraction of ribulose-1,5-bisphosphate carboxylase/oxygenase in the dark is in an inactivatable state that cannot respond to CO2 and Mg2+ activation, but which can be converted to an activatable state upon exposure of the leaf to light. PMID:16663937

  18. Dark/Light modulation of ribulose bisphosphate carboxylase activity in plants from different photosynthetic categories.

    PubMed

    Vu, J C; Allen, L H; Bowes, G

    1984-11-01

    Ribulose bisphosphate carboxylase/oxygenase (RuBPCase) from several plants had substantially greater activity in extracts from lightexposed leaves than dark leaves, even when the extracts were incubated in vitro with saturating HCO(3) (-) and Mg(2+) concentrations. This occurred in Glycine max, Lycopersicon esculentum, Nicotiana tabacum, Panicum bisulcatum, and P. hylaeicum (C(3)); P. maximum (C(4) phosphoenolpyruvate carboxykinase); P. milioides (C(3)/C(4)); and Bromelia pinguin and Ananas comosus (Crassulacean acid metabolism). Little or no difference between light and dark leaf extracts of RuBPCase was observed in Triticum aestivum (C(3)); P. miliaceum (C(4) NAD malic enzyme); Zea mays and Sorghum bicolor (C(4) NADP malic enzyme); Moricandia arvensis (C(3)/C(4)); and Hydrilla verticillata (submersed aquatic macrophyte). It is concluded that, in many plants, especially Crassulacean acid metabolism and C(3) species, a large fraction of ribulose-1,5-bisphosphate carboxylase/oxygenase in the dark is in an inactivatable state that cannot respond to CO(2) and Mg(2+) activation, but which can be converted to an activatable state upon exposure of the leaf to light.

  19. Comparison of ground and satellite based measurements of the fraction of photosynthetically active radiation intercepted by tall-grass prairie

    SciTech Connect

    Demetriades-shah, T.H.; Kanemasu, E.T.; Flitcroft, I.D.; Su, H. Kansas State Univ., Manhattan )

    1992-11-01

    The fraction of photosynthetically active radiation intercepted by vegetation, F(sub ipar) is an important parameter for modeling the interactions between the land-surface and atmosphere and for estimating vegetation biomass productivity. This study was, therefore, an integral part of FIFE. The specific purpose of this experiment was to find out how well definitive measurements of F(sub ipar) on the ground relate to near-ground and satellite based spectral reflectance measurements. Concurrent measurements of F(sub ipar) and ground, helicopter, and satellite based reflectance measurements were taken at thirteen tall-grass prairie sites within the FIFE experimental area. The sites were subjected to various combinations of burning and grazing managements. The ground and helicopter based reflectance measurements were taken on the same day or few days from the time of the overpass of LANDSAT and SPOT satellites. Ground-based reflectance measurements and sun photometer readings taken at the times of the satellite overpasses were used to correct for atmospheric attenuation. Hand-held radiometer spectral indices were strongly correlated with helicopter and satellite based values (r = 0.94 for helicopter, 0.93 for LANDSAT Thematic Mapper, and 0.86 for SPOT). However, the ground, helicopter, and satellite based normalized difference spectral vegetation indices showed low sensitivity to changes in F(sub ipar). Reflectance measurements were only moderately well correlated with measurements of F(sub ipar) (r = 0.82 for hand-held radiometer, 0.84 for helicopter measurements, and 0.75 for the LANDSAT Thematic Mapper and SPOT). Improved spectral indices which can compensate for site differences are needed in order to monitor F(sub ipar) more reliably. 12 refs.

  20. Comparison of ground and satellite based measurements of the fraction of photosynthetically active radiation intercepted by tall-grass prairie

    NASA Technical Reports Server (NTRS)

    Demetriades-Shah, T. H.; Kanemasu, E. T.; Flitcroft, I. D.; Su, H.

    1992-01-01

    The fraction of photosynthetically active radiation intercepted by vegetation, F(sub ipar) is an important parameter for modeling the interactions between the land-surface and atmosphere and for estimating vegetation biomass productivity. This study was, therefore, an integral part of FIFE. The specific purpose of this experiment was to find out how well definitive measurements of F(sub ipar) on the ground relate to near-ground and satellite based spectral reflectance measurements. Concurrent measurements of F(sub ipar) and ground, helicopter, and satellite based reflectance measurements were taken at thirteen tall-grass prairie sites within the FIFE experimental area. The sites were subjected to various combinations of burning and grazing managements. The ground and helicopter based reflectance measurements were taken on the same day or few days from the time of the overpass of LANDSAT and SPOT satellites. Ground-based reflectance measurements and sun photometer readings taken at the times of the satellite overpasses were used to correct for atmospheric attenuation. Hand-held radiometer spectral indices were strongly correlated with helicopter and satellite based values (r = 0.94 for helicopter, 0.93 for LANDSAT Thematic Mapper, and 0.86 for SPOT). However, the ground, helicopter, and satellite based normalized difference spectral vegetation indices showed low sensitivity to changes in F(sub ipar). Reflectance measurements were only moderately well correlated with measurements of F(sub ipar) (r = 0.82 for hand-held radiometer, 0.84 for helicopter measurements, and 0.75 for the LANDSAT Thematic Mapper and SPOT). Improved spectral indices which can compensate for site differences are needed in order to monitor F(sub ipar) more reliably.

  1. A comparison of models to estimate in-canopy photosynthetically active radiation and their influence on canopy stomatal resistance

    NASA Astrophysics Data System (ADS)

    Zhang, Leiming; Moran, Michael D.; Brook, Jeffrey R.

    The models for photosynthetically active radiation (PAR) used in a multi-layer canopy stomatal resistance (CSR) model developed by Baldocchi et al. (Atmospheric Environment 21 (1987) 91-101) and in a two-big-leaf CSR model developed by Hicks et al. (Water, Air and Soil Pollution 36 (1987) 311) are investigated in this study. The PAR received by shaded leaves in Baldocchi et al. (1987) is found to be larger than that predicted by a canopy radiative-transfer model developed by Norman (in: Barfield, Gerber, (Eds.), Modification of the Aerial Environment of Crops. ASAE Monograph No. 2. American Society for Agricultural. Engineering, St. Joseph, MI, 1979, p. 249) by as much as 50% even though the Baldocchi et al. (1987) model is indirectly based on Norman's model. This larger value of PAR results in turn in a smaller CSR by as much as 30% for canopies with larger leaf area indexes. A new formula to predict vertical profiles for PAR received by shaded leaves inside a canopy is suggested in the present study based on Norman (1979) and agrees well with the original model of Norman (1979). The simple treatment used in Hicks et al. (1987) for canopy-average PAR received by shaded leaves is found to diverge for canopies with leaf area indexes not close to two A new empirical formula for canopy-average PAR is then suggested for use in a two-big-leaf model, and it is shown that under most conditions the modified two-big-leaf CSR model can predict reasonable values when compared with the more complex multi-layer CSR model. Both the modified multi-layer CSR model and the modified two-big-leaf CSR model are also shown to predict reasonable dry deposition velocities for O 3 when compared to several sets of measurements.

  2. Comparison of ground and satellite based measurements of the fraction of photosynthetically active radiation intercepted by tall-grass prairie

    NASA Technical Reports Server (NTRS)

    Demetriades-Shah, T. H.; Kanemasu, E. T.; Flitcroft, I.; Su, H.

    1991-01-01

    The fraction, of photosynthetically active radiation intercepted by vegetation, F(sub ipar) is an important parameter for modeling the interactions between the land-surface and atmosphere and for estimating vegetation biomass productivity. This study was; therefore, an integral part of FIFE. The specific purpose of this experiment was to find out how well definitive measurements of F(sub ipar) on the ground relate to near-ground and satellite based spectral reflectance measurements. Concurrent measurements of F(sub ipar) and ground, helicopter, and satellite based reflectance measurements were taken at thirteen tall-grass prairie sites within the FIFE experimental area. The sites were subjected to various combinations of burning and grazing managements. The ground and helicopter based reflectance measurements were taken on the same day or few days from the time of the overpass of LANDSAT and SPOT satellites. Ground-based reflectance measurements and sun photometer readings taken at the times of the satellite overpasses were used to correct for atmospheric attenuation. Hand-held radiometer spectral indices were strongly correlated with helicopter and satellite based values (r=0.94 for helicopter, 0.93 for LANDSAT Thematic Mapper, and 0.86 for SPOT). However, the ground, helicopter, and satellite based normalized difference spectral vegetation indices showed low sensitivity to changes in F(sub ipar). Reflectance measurements were only moderately well correlated with measurements of F(sub ipar) (r=0.82 for hand-held radiometer, 0.84 for helicopter measurements, and 0.75 for the LANDSAT Thematic Mapper and SPOT). Improved spectral indices which can compensate for site differences are needed in order to monitor F(sub ipar) more reliably.

  3. Ultraviolet and photosynthetically active radiation can both induce photoprotective capacity allowing barley to overcome high radiation stress.

    PubMed

    Klem, Karel; Holub, Petr; Štroch, Michal; Nezval, Jakub; Špunda, Vladimír; Tříska, Jan; Jansen, Marcel A K; Robson, T Matthew; Urban, Otmar

    2015-08-01

    The main objective of this study was to determine the effects of acclimation to ultraviolet (UV) and photosynthetically active radiation (PAR) on photoprotective mechanisms in barley leaves. Barley plants were acclimated for 7 days under three combinations of high or low UV and PAR treatments ([UV-PAR-], [UV-PAR+], [UV+PAR+]). Subsequently, plants were exposed to short-term high radiation stress (HRS; defined by high intensities of PAR - 1000 μmol m(-2) s(-1), UV-A - 10 W m(-2) and UV-B 2 W m(-2) for 4 h), to test their photoprotective capacity. The barley variety sensitive to photooxidative stress (Barke) had low constitutive flavonoid content compared to the resistant variety (Bonus) under low UV and PAR intensities. The accumulation of lutonarin and 3-feruloylquinic acid, but not of saponarin, was greatly enhanced by high PAR and further increased by UV exposure. Acclimation of plants to both high UV and PAR intensities also increased the total pool of xanthophyll-cycle pigments (VAZ). Subsequent exposure to HRS revealed that prior acclimation to UV and PAR was able to ameliorate the negative consequences of HRS on photosynthesis. Both total contents of epidermal flavonols and the total pool of VAZ were closely correlated with small reductions in light-saturated CO2 assimilation rate and maximum quantum yield of photosystem II photochemistry caused by HRS. Based on these results, we conclude that growth under high PAR can substantially increase the photoprotective capacity of barley plants compared with plants grown under low PAR. However, additional UV radiation is necessary to fully induce photoprotective mechanisms in the variety Barke. This study demonstrates that UV-exposure can lead to enhanced photoprotective capacity and can contribute to the induction of tolerance to high radiation stress in barley.

  4. Abatement of SO2-NOx binary gas mixtures using a ferruginous active absorbent: Part I. Synergistic effects and mechanism.

    PubMed

    Han, Yinghui; Li, Xiaolei; Fan, Maohong; Russell, Armistead G; Zhao, Yi; Cao, Chunmei; Zhang, Ning; Jiang, Genshan

    2015-04-01

    A novel ferruginous active absorbent, prepared by fly ash, industrial lime and the additive Fe(VI), was introduced for synchronous abatement of binary mixtures of SO2-NOx from simulated coal-fired flue gas. The synergistic action of various factors on the absorption of SO2 and NOx was investigated. The results show that a strong synergistic effect exists between Fe(VI) dose and reaction temperature for the desulfurization. It was observed that in the denitration process, the synergy of Fe(VI) dose and Ca/(S+N) had the most significant impact on the removal of NO, followed by the synergy of Fe(VI) and reaction temperature, and then the synergy of reaction temperature and flue gas humidity. A scanning electron microscope (SEM) and an accessory X-ray energy spectrometer (EDS) were used to observe the surface characteristics of the raw and spent absorbent as well as fly ash. A reaction mechanism was proposed based on chemical analysis of sulfur and nitrogen species concentrations in the spent absorbent. The Gibbs free energy, equilibrium constants and partial pressures of the SO2-NOx binary system were determined by thermodynamics.

  5. Abatement of SO2-NOx binary gas mixtures using a ferruginous active absorbent: Part I. Synergistic effects and mechanism.

    PubMed

    Han, Yinghui; Li, Xiaolei; Fan, Maohong; Russell, Armistead G; Zhao, Yi; Cao, Chunmei; Zhang, Ning; Jiang, Genshan

    2015-04-01

    A novel ferruginous active absorbent, prepared by fly ash, industrial lime and the additive Fe(VI), was introduced for synchronous abatement of binary mixtures of SO2-NOx from simulated coal-fired flue gas. The synergistic action of various factors on the absorption of SO2 and NOx was investigated. The results show that a strong synergistic effect exists between Fe(VI) dose and reaction temperature for the desulfurization. It was observed that in the denitration process, the synergy of Fe(VI) dose and Ca/(S+N) had the most significant impact on the removal of NO, followed by the synergy of Fe(VI) and reaction temperature, and then the synergy of reaction temperature and flue gas humidity. A scanning electron microscope (SEM) and an accessory X-ray energy spectrometer (EDS) were used to observe the surface characteristics of the raw and spent absorbent as well as fly ash. A reaction mechanism was proposed based on chemical analysis of sulfur and nitrogen species concentrations in the spent absorbent. The Gibbs free energy, equilibrium constants and partial pressures of the SO2-NOx binary system were determined by thermodynamics. PMID:25872709

  6. Influence of Green, Red and Blue Light Emitting Diodes on Multiprotein Complex Proteins and Photosynthetic Activity under Different Light Intensities in Lettuce Leaves (Lactuca sativa L.)

    PubMed Central

    Muneer, Sowbiya; Kim, Eun Jeong; Park, Jeong Suk; Lee, Jeong Hyun

    2014-01-01

    The objective of this study was to investigate the response of light emitting diodes (LEDs) at different light intensities (70 and 80 for green LEDs, 88 and 238 for red LEDs and 80 and 238 μmol m−2 s−1 for blue LEDs) at three wavelengths in lettuce leaves. Lettuce leaves were exposed to (522 nm), red (639 nm) and blue (470 nm) LEDs of different light intensities. Thylakoid multiprotein complex proteins and photosynthetic metabolism were then investigated. Biomass and photosynthetic parameters increased with an increasing light intensity under blue LED illumination and decreased when illuminated with red and green LEDs with decreased light intensity. The expression of multiprotein complex proteins including PSII-core dimer and PSII-core monomer using blue LEDs illumination was higher at higher light intensity (238 μmol m−2 s−1) and was lowered with decreased light intensity (70–80 μmol m−2 s−1). The responses of chloroplast sub-compartment proteins, including those active in stomatal opening and closing, and leaf physiological responses at different light intensities, indicated induced growth enhancement upon illumination with blue LEDs. High intensity blue LEDs promote plant growth by controlling the integrity of chloroplast proteins that optimize photosynthetic performance in the natural environment. PMID:24642884

  7. Downregulation of a putative plastid PDC E1α subunit impairs photosynthetic activity and triacylglycerol accumulation in nitrogen-starved photoautotrophic Chlamydomonas reinhardtii.

    PubMed

    Shtaida, Nastassia; Khozin-Goldberg, Inna; Solovchenko, Alexei; Chekanov, Konstantin; Didi-Cohen, Shoshana; Leu, Stefan; Cohen, Zvi; Boussiba, Sammy

    2014-12-01

    The chloroplast pyruvate dehydrogenase complex (cpPDC) catalyses the oxidative decarboxylation of pyruvate forming acetyl-CoA, an immediate primer for the initial reactions of de novo fatty acid (FA) synthesis. Little is known about the source of acetyl-CoA in the chloroplasts of photosynthetic microalgae, which are capable of producing high amounts of the storage lipid triacylglycerol (TAG) under conditions of nutrient stresses. We generated Chlamydomonas reinhardtii CC-1618 mutants with decreased expression of the PDC2_E1α gene, encoding the putative chloroplast pyruvate dehydrogenase subunit E1α, using artificial microRNA. A comparative study on the effects of PDC2_E1α silencing on FAs and TAG production in C. reinhardtii, grown photoautotrophically and mixotrophically, with and without a nitrogen source in the nutrient medium, was carried out. Reduced expression of PDC2 _E1α led to a severely hampered photoautotrophic growth phenotype with drastic impairment in TAG accumulation under nitrogen deprivation. In the presence of acetate, downregulation of PDC2_E1α exerted little to no effect on TAG production and photosynthetic activity. In contrast, under photoautotrophic conditions, especially in the absence of a nitrogen source, a dramatic decline in photosynthetic oxygen evolution and photosystem II quantum yield against a background of the apparent over-reduction of the photosynthetic electron chain was recorded. Our results suggest an essential role of cpPDC in the supply of carbon precursors for de novo FA synthesis in microalgae under conditions of photoautotrophy. A shortage of this supply is detrimental to the nitrogen-starvation-induced synthesis of storage TAG, an important carbon and energy sink in stressed Chlamydomonas cells, thereby impairing the acclimation ability of the microalga.

  8. Downregulation of a putative plastid PDC E1α subunit impairs photosynthetic activity and triacylglycerol accumulation in nitrogen-starved photoautotrophic Chlamydomonas reinhardtii.

    PubMed

    Shtaida, Nastassia; Khozin-Goldberg, Inna; Solovchenko, Alexei; Chekanov, Konstantin; Didi-Cohen, Shoshana; Leu, Stefan; Cohen, Zvi; Boussiba, Sammy

    2014-12-01

    The chloroplast pyruvate dehydrogenase complex (cpPDC) catalyses the oxidative decarboxylation of pyruvate forming acetyl-CoA, an immediate primer for the initial reactions of de novo fatty acid (FA) synthesis. Little is known about the source of acetyl-CoA in the chloroplasts of photosynthetic microalgae, which are capable of producing high amounts of the storage lipid triacylglycerol (TAG) under conditions of nutrient stresses. We generated Chlamydomonas reinhardtii CC-1618 mutants with decreased expression of the PDC2_E1α gene, encoding the putative chloroplast pyruvate dehydrogenase subunit E1α, using artificial microRNA. A comparative study on the effects of PDC2_E1α silencing on FAs and TAG production in C. reinhardtii, grown photoautotrophically and mixotrophically, with and without a nitrogen source in the nutrient medium, was carried out. Reduced expression of PDC2 _E1α led to a severely hampered photoautotrophic growth phenotype with drastic impairment in TAG accumulation under nitrogen deprivation. In the presence of acetate, downregulation of PDC2_E1α exerted little to no effect on TAG production and photosynthetic activity. In contrast, under photoautotrophic conditions, especially in the absence of a nitrogen source, a dramatic decline in photosynthetic oxygen evolution and photosystem II quantum yield against a background of the apparent over-reduction of the photosynthetic electron chain was recorded. Our results suggest an essential role of cpPDC in the supply of carbon precursors for de novo FA synthesis in microalgae under conditions of photoautotrophy. A shortage of this supply is detrimental to the nitrogen-starvation-induced synthesis of storage TAG, an important carbon and energy sink in stressed Chlamydomonas cells, thereby impairing the acclimation ability of the microalga. PMID:25210079

  9. Downregulation of a putative plastid PDC E1α subunit impairs photosynthetic activity and triacylglycerol accumulation in nitrogen-starved photoautotrophic Chlamydomonas reinhardtii

    PubMed Central

    Shtaida, Nastassia; Khozin-Goldberg, Inna; Solovchenko, Alexei; Chekanov, Konstantin; Didi-Cohen, Shoshana; Leu, Stefan; Cohen, Zvi; Boussiba, Sammy

    2014-01-01

    The chloroplast pyruvate dehydrogenase complex (cpPDC) catalyses the oxidative decarboxylation of pyruvate forming acetyl-CoA, an immediate primer for the initial reactions of de novo fatty acid (FA) synthesis. Little is known about the source of acetyl-CoA in the chloroplasts of photosynthetic microalgae, which are capable of producing high amounts of the storage lipid triacylglycerol (TAG) under conditions of nutrient stresses. We generated Chlamydomonas reinhardtii CC-1618 mutants with decreased expression of the PDC2_E1α gene, encoding the putative chloroplast pyruvate dehydrogenase subunit E1α, using artificial microRNA. A comparative study on the effects of PDC2_E1α silencing on FAs and TAG production in C. reinhardtii, grown photoautotrophically and mixotrophically, with and without a nitrogen source in the nutrient medium, was carried out. Reduced expression of PDC2 _E1α led to a severely hampered photoautotrophic growth phenotype with drastic impairment in TAG accumulation under nitrogen deprivation. In the presence of acetate, downregulation of PDC2_E1α exerted little to no effect on TAG production and photosynthetic activity. In contrast, under photoautotrophic conditions, especially in the absence of a nitrogen source, a dramatic decline in photosynthetic oxygen evolution and photosystem II quantum yield against a background of the apparent over-reduction of the photosynthetic electron chain was recorded. Our results suggest an essential role of cpPDC in the supply of carbon precursors for de novo FA synthesis in microalgae under conditions of photoautotrophy. A shortage of this supply is detrimental to the nitrogen-starvation-induced synthesis of storage TAG, an important carbon and energy sink in stressed Chlamydomonas cells, thereby impairing the acclimation ability of the microalga. PMID:25210079

  10. [Estimation of Diffuse Attenuation Coefficient of Photosynthetically Active Radiation in Xin'anjiang Reservoir Based on Landsat 8 Data].

    PubMed

    Zhang, Yi-bo; Zhang, Yun-lin; Zha, Yong; Shi, Kun; Zhou, Yong-qiang; Liu, Ming-liang

    2015-12-01

    Photosynthetically active radiation (PAR) is defined as the wavelength band of 400 to 700 nm, representing most of the visible solar radiation that could be used for photosynthesis. PAR is attenuated by the absorption and scattering of nonpigment suspended matter, chromophoric dissolved organic matter and phytoplankton, and it plays an important role in determining the density and distribution of aquatic organisms. This study developed an empirical model and presented the spatial-temporal distribution of PAR diffuse attenuation coefficient [Kd (PAR)] for the slightly turbid Xin'anjiang Reservoir based on the in situ ground data and the matching Landsat 8 data. The results showed that the three-hand combinational model of Kd ( PAR) using Band 2, Band 3 and Band 8 could give a reasonable and acceptable estimation accuracy with a determination coefficient of 0. 87. Independent dataset was used to validate the model with a mean relative error of 9.16% and a root mean square error of 0.06 m⁻¹. Therefore, the three-band combination using Landsat 8 data could be used to accurately estimate Kd (PAR) in the slightly turbid Xin'anjiang Reservoir. Kd (PAR) exhibited significant seasonal and spatial differences. Kd (PAR) was higher in autumn (September-November) and summer (June-August) with the average Kd (PAR) of (0.82 ± 0.60) m⁻¹ and (0.77 ± 0.41) m⁻¹, but lower in winter (December-February) and spring (March-May) with the average Kd (PAR) of (0.56 ± 0.50) m⁻¹ and (0.40 ± 0.45 ) m⁻¹, respectively. Spatially, Kd (PAR) ranged from 0.002 to 13.86 m⁻¹ with an average of (0.64 ± 0.49) m⁻¹. The temporal heterogeneity of Kd (PAR) was mainly caused by the seasonal rainfall and seasonal growth of phytoplankton. The spatial heterogeneity was mainly caused by suspended matter concentration derived from watershed inputs and human dredging activity. PMID:27011976

  11. Successful treatment of active haemorrhage from a duodenal diverticulum using surgicel (absorbable haemostat): a case report.

    PubMed

    Muguti, Gi; Gandhi, H; Ridgeway, D

    2007-01-01

    Haemorrhage is one of the rare but serious complications of duodenal diverticula. Current methods of treatment include: endoscopy with injection therapy or hemoclip application and diverticulectomy. In this paper we present the case of a 61 year old man with life threatening haemorrhage who was managed successfully with gentle packing of a bleeding duodenal diverticulum using SURGICEL (Absorbable Haemostat). This appears to be a simple and effective way of dealing with the problem especially in situations where other methods are ineffective or inapplicable. Early surgical intervention before the development of any coagulopathy increases the chances of a successful outcome. It has not been possible to find a similar report from a thorough literature search. PMID:20353131

  12. Exogenous proline mediates alleviation of cadmium stress by promoting photosynthetic activity, water status and antioxidative enzymes activities of young date palm (Phoenix dactylifera L.).

    PubMed

    Zouari, M; Ben Ahmed, Ch; Zorrig, W; Elloumi, N; Rabhi, M; Delmail, D; Ben Rouina, B; Labrousse, P; Ben Abdallah, F

    2016-06-01

    The ability of exogenous compatible solutes, such as proline, to counteract cadmium (Cd) inhibitory effects in young date palm plants (Phoenix dactylifera L. cv Deglet Nour) was investigated. Two-year-old date palm plants were subjected for five months at different Cd stress levels (0, 10 and 30 mg CdCl2 kg(-1) soil) whether supplied or not with exogenous proline (20mM) added through the irrigation water. Different levels of Cd stress altered plant growth, gas exchanges and chlorophyll content as well as water status, but at different extent among them. In contrast, an increase of antioxidant enzymes activities of Cd-treated plants in association with high amounts of proline content, hydrogen peroxide (H2O2), thiobarbituric acid reactive substances (TBARS) and electrolyte leakage (EL) were observed. Interestingly, exogenous proline mitigated the adverse effects of Cd on young date palm. Indeed, it alleviated the oxidative damage induced by Cd accumulation and established better levels of plant growth, water status and photosynthetic activity. Moreover, proline-treated plants showed high antioxidant enzymes activities (superoxide dismutase, catalase and glutathione peroxydase) in roots and leaves as compared to Cd-treated plants. PMID:26901506

  13. Activation of NADP-Malate Dehydrogenase, Pyruvate,Pi Dikinase, and Fructose 1,6-Bisphosphatase in Relation to Photosynthetic Rate in Maize 1

    PubMed Central

    Usuda, Hideaki; Ku, Maurice S. B.; Edwards, Gerald E.

    1984-01-01

    The activity and extent of light activation of three photosynthetic enzymes, pyruvate,Pi dikinase, NADP-malate dehydrogenase (NADP-MDH), and fructose 1,6-bisphosphatase (FBPase), were examined in maize (Zea mays var Royal Crest) leaves relative to the rate of photosynthesis during induction and under varying light intensities. There was a strong light activation of NADP-MDH and pyruvate,Pi dikinase, and light also activated FBPase 2- to 4-fold. During the induction period for whole leaf photosynthesis at 30°C under high light, the time required to reach half-maximum activation for all three enzymes was only 1 minute or less. After 2.5 minutes of illumination the enzymes were fully activated, while the photosynthetic rate was only at half-maximum activity, indicating that factors other than enzyme activation limit photosynthesis during the induction period in C4 plants. Under steady state conditions, the light intensity required to reach half-maximum activation of the three enzymes was similar (300-400 microEinsteins per square meter per second), while the light intensity required for half-maximum rates of photosynthesis was about 550 microEinsteins per square meter per second. The light activated levels of NADP-MDH and FBPase were well in excess of the in vivo activities which would be required during photosynthesis, while maximum activities of pyruvate,Pi dikinase were generally just sufficient to accommodate photosynthesis, suggesting the latter may be a rate limiting enzyme. There was a large (5-fold) light activation of FBPase in isolated bundle sheath strands of maize, whereas there was little light activation of the enzyme in isolated mesophyll protoplasts. In mesophyll protoplasts the enzyme was largely located in the cytoplasm, although there was a low amount of light-activated enzyme in the mesophyll chloroplasts. The results suggest the chloroplastic FBPase in maize is primarily located in the bundle sheath cells. PMID:16663806

  14. Absorbing Outflows in AGN

    NASA Technical Reports Server (NTRS)

    Mathur, Smita

    2002-01-01

    The goal of this program was a comprehensive multiwavelength study of absorption phenomena in active galactic nuclei (AGN). These include a variety of associated absorption systems: X-ray warm absorbers, X-ray cold absorbers. UV absorbers with high ionization lines, MgII absorbers, red quasars and BALQSOs. The aim is to determine the physical conditions in the absorbing outflows, study their inter-relations and their role in AGN. We designed several observing programs to achieve this goal: X-ray spectroscopy, UV spectroscopy, FLAY spectroscopy and X-ray imaging. We were very successful towards achieving the goal over the five year period as shown through following observing programs and papers. Copies of a few papers are attached with this report.

  15. Photosystem activity and state transitions of the photosynthetic apparatus in cyanobacterium Synechocystis PCC 6803 mutants with different redox state of the plastoquinone pool.

    PubMed

    Bolychevtseva, Y V; Kuzminov, F I; Elanskaya, I V; Gorbunov, M Y; Karapetyan, N V

    2015-01-01

    To better understand how photosystem (PS) activity is regulated during state transitions in cyanobacteria, we studied photosynthetic parameters of photosystem II (PSII) and photosystem I (PSI) in Synechocystis PCC 6803 wild type (WT) and its mutants deficient in oxidases (Ox(-)) or succinate dehydrogenase (SDH(-)). Dark-adapted Ox(-) mutant, lacking the oxidation agents, is expected to have a reduced PQ pool, while in SDH(-) mutant the PQ pool after dark adaptation will be more oxidized due to partial inhibition of the respiratory chain electron carriers. In this work, we tested the hypothesis that control of balance between linear and cyclic electron transport by the redox state of the PQ pool will affect PSII photosynthetic activity during state transition. We found that the PQ pool was reduced in Ox(-) mutant, but oxidized in SDH(-) mutant after prolonged dark adaptation, indicating different states of the photosynthetic apparatus in these mutants. Analysis of variable fluorescence and 77K fluorescence spectra revealed that the WT and SDH(-) mutant were in State 1 after dark adaptation, while the Ox(-) mutant was in State 2. State 2 was characterized by ~1.5 time lower photochemical activity of PSII, as well as high rate of P700 reduction and the low level of P700 oxidation, indicating high activity of cyclic electron transfer around PSI. Illumination with continuous light 1 (440 nm) along with flashes of light 2 (620 nm) allowed oxidation of the PQ pool in the Ox(-) mutant, thus promoting it to State 1, but it did not affect PSII activity in dark adapted WT and SDH(-) mutant. State 1 in the Ox(-) mutant was characterized by high variable fluorescence and P700(+) levels typical for WT and the SDH(-) mutant, indicating acceleration of linear electron transport. Thus, we show that PSII of cyanobacteria has a higher photosynthetic activity in State 1, while it is partially inactivated in State 2. This process is controlled by the redox state of PQ in

  16. Guard cells in albino leaf patches do not respond to photosynthetically active radiation, but are sensitive to blue light, CO2 and abscisic acid.

    PubMed

    Roelfsema, M Rob G; Konrad, Kai R; Marten, Holger; Psaras, George K; Hartung, Wolfram; Hedrich, Rainer

    2006-08-01

    Stomatal openings can be stimulated by light through two signalling pathways. The first pathway is blue light specific and involves phototropins, while the second pathway mediates a response to photosynthetically active radiation (PAR). This second pathway was studied with the use of albino Vicia faba plants and variegated leaves of Chlorophytum comosum. Treatment of V. faba with norflurazon (Nf) inhibits the synthesis of carotenoids and leads to albino leaves with guard cells that lack functional green chloroplasts. Guard cells in albino leaf patches of C. comosum, however, do contain photosynthetically active chloroplasts. Stomata in albino leaf patches of both plants did not respond to red light, although blue light could still induce stomatal opening. This shows that the response to PAR is not functioning in albino leaf patches, even though guard cells of C. comosum harbour chloroplasts. Stomata of Nf-treated plants still responded to CO2 and abscisic acid (ABA). The size of Nf-treated guard cells was increased, but impalement studies with double-barrelled microelectrodes revealed no changes in ion-transport properties at the plasma membrane of guard cells. Blue light could hyperpolarize albino guard cells by triggering outward currents with peak values of 37 pA in albino plants and 51 pA in green control cells. Because of the inhibition of carotenoid biosynthesis, Nf-treated V. faba plants contained only 4% of the ABA content found in green control plants. The ABA dose dependence of anion channel activation in guard cells was shifted in these plants, causing a reduced response to 10 microM ABA. These data show that despite the dramatic changes in physiology caused by Nf, the gross responsiveness of guard cells to blue light, CO2 and ABA remains unaltered. Stomata in albino leaf patches, however, do not respond to PAR, but require photosynthetically active mesophyll cells for this response.

  17. Chlorophyll fluorescence kinetics, photosynthetic activity, and pigment composition of blue-shade and half-shade leaves as compared to sun and shade leaves of different trees.

    PubMed

    Lichtenthaler, Hartmut K; Babani, Fatbardha; Navrátil, Martin; Buschmann, Claus

    2013-11-01

    The chlorophyll (Chl) fluorescence induction kinetics, net photosynthetic CO2 fixation rates P N, and composition of photosynthetic pigments of differently light exposed leaves of several trees were comparatively measured to determine the differences in photosynthetic activity and pigment adaptation of leaves. The functional measurements were carried out with sun, half-shade and shade leaves of seven different trees species. These were: Acer platanoides L., Ginkgo biloba L., Fagus sylvatica L., Platanus x acerifolia Willd., Populus nigra L., Quercus robur L., Tilia cordata Mill. In three cases (beech, ginkgo, and oak), we compared the Chl fluorescence kinetics and photosynthetic rates of blue-shade leaves of the north tree crown receiving only blue sky light but no direct sunlight with that of sun leaves. In these cases, we also determined in detail the pigment composition of all four leaf types. In addition, we determined the quantum irradiance and spectral irradiance of direct sunlight, blue skylight as well as the irradiance in half shade and full shade. The results indicate that sun leaves possess significantly higher mean values for the net CO2 fixation rates P N (7.8-10.7 μmol CO2 m(-2) s(-1) leaf area) and the Chl fluorescence ratio R Fd (3.85-4.46) as compared to shade leaves (mean P N of 2.6-3.8 μmol CO2 m(-2) s(-1) leaf area.; mean R Fd of 1.94-2.56). Sun leaves also exhibit higher mean values for the pigment ratio Chl a/b (3.14-3.31) and considerably lower values for the weight ratio total chlorophylls to total carotenoids, (a + b)/(x + c), (4.07-4.25) as compared to shade leaves (Chl a/b 2.62-2.72) and (a + b)/(x + c) of 5.18-5.54. Blue-shade and half-shade leaves have an intermediate position between sun and shade leaves in all investigated parameters including the ratio F v/F o (maximum quantum yield of PS2 photochemistry) and are significantly different from sun and shade leaves but could not be differentiated from each other. The

  18. Mycosporine-like amino acids (MAAs): chemical structure, biosynthesis and significance as UV-absorbing/screening compounds.

    PubMed

    Singh, Shailendra P; Kumari, Sunita; Rastogi, Rajesh P; Singh, Kanchan L; Sinha, Rajeshwar P

    2008-01-01

    Continuous depletion of the stratospheric ozone layer has resulted in an increase in ultraviolet-B (UV-B; 280-315 nm) radiation on the earth's surface which inhibits photochemical and photobiological processes. However, certain photosynthetic organisms have evolved mechanisms to counteract the toxicity of ultraviolet or high photosynthetically active radiation by synthesizing the UV-absorbing/screening compounds, such as mycosporine-like amino acids (MAAs) and scytonemin besides the repair of UV-induced damage of DNA and accumulation of carotenoids and detoxifying enzymes or radical quenchers and antioxidants. Chemical structure of various MAAs, their possible biochemical routes of synthesis and role as photoprotective compounds in various organisms are discussed.

  19. Sound Absorbers

    NASA Astrophysics Data System (ADS)

    Fuchs, H. V.; Möser, M.

    Sound absorption indicates the transformation of sound energy into heat. It is, for instance, employed to design the acoustics in rooms. The noise emitted by machinery and plants shall be reduced before arriving at a workplace; auditoria such as lecture rooms or concert halls require a certain reverberation time. Such design goals are realised by installing absorbing components at the walls with well-defined absorption characteristics, which are adjusted for corresponding demands. Sound absorbers also play an important role in acoustic capsules, ducts and screens to avoid sound immission from noise intensive environments into the neighbourhood.

  20. Photosynthetic Pigments in Diatoms

    PubMed Central

    Kuczynska, Paulina; Jemiola-Rzeminska, Malgorzata; Strzalka, Kazimierz

    2015-01-01

    Photosynthetic pigments are bioactive compounds of great importance for the food, cosmetic, and pharmaceutical industries. They are not only responsible for capturing solar energy to carry out photosynthesis, but also play a role in photoprotective processes and display antioxidant activity, all of which contribute to effective biomass and oxygen production. Diatoms are organisms of a distinct pigment composition, substantially different from that present in plants. Apart from light-harvesting pigments such as chlorophyll a, chlorophyll c, and fucoxanthin, there is a group of photoprotective carotenoids which includes β-carotene and the xanthophylls, diatoxanthin, diadinoxanthin, violaxanthin, antheraxanthin, and zeaxanthin, which are engaged in the xanthophyll cycle. Additionally, some intermediate products of biosynthetic pathways have been identified in diatoms as well as unusual pigments, e.g., marennine. Marine algae have become widely recognized as a source of unique bioactive compounds for potential industrial, pharmaceutical, and medical applications. In this review, we summarize current knowledge on diatom photosynthetic pigments complemented by some new insights regarding their physico-chemical properties, biological role, and biosynthetic pathways, as well as the regulation of pigment level in the cell, methods of purification, and significance in industries. PMID:26389924

  1. Induction of Photosynthetic Carbon Fixation in Anoxia Relies on Hydrogenase Activity and Proton-Gradient Regulation-Like1-Mediated Cyclic Electron Flow in Chlamydomonas reinhardtii1

    PubMed Central

    Bailleul, Benjamin; Berne, Nicolas

    2015-01-01

    The model green microalga Chlamydomonas reinhardtii is frequently subject to periods of dark and anoxia in its natural environment. Here, by resorting to mutants defective in the maturation of the chloroplastic oxygen-sensitive hydrogenases or in Proton-Gradient Regulation-Like1 (PGRL1)-dependent cyclic electron flow around photosystem I (PSI-CEF), we demonstrate the sequential contribution of these alternative electron flows (AEFs) in the reactivation of photosynthetic carbon fixation during a shift from dark anoxia to light. At light onset, hydrogenase activity sustains a linear electron flow from photosystem II, which is followed by a transient PSI-CEF in the wild type. By promoting ATP synthesis without net generation of photosynthetic reductants, the two AEF are critical for restoration of the capacity for carbon dioxide fixation in the light. Our data also suggest that the decrease in hydrogen evolution with time of illumination might be due to competition for reduced ferredoxins between ferredoxin-NADP+ oxidoreductase and hydrogenases, rather than due to the sensitivity of hydrogenase activity to oxygen. Finally, the absence of the two alternative pathways in a double mutant pgrl1 hydrogenase maturation factor G-2 is detrimental for photosynthesis and growth and cannot be compensated by any other AEF or anoxic metabolic responses. This highlights the role of hydrogenase activity and PSI-CEF in the ecological success of microalgae in low-oxygen environments. PMID:25931521

  2. Induction of Photosynthetic Carbon Fixation in Anoxia Relies on Hydrogenase Activity and Proton-Gradient Regulation-Like1-Mediated Cyclic Electron Flow in Chlamydomonas reinhardtii.

    PubMed

    Godaux, Damien; Bailleul, Benjamin; Berne, Nicolas; Cardol, Pierre

    2015-06-01

    The model green microalga Chlamydomonas reinhardtii is frequently subject to periods of dark and anoxia in its natural environment. Here, by resorting to mutants defective in the maturation of the chloroplastic oxygen-sensitive hydrogenases or in Proton-Gradient Regulation-Like1 (PGRL1)-dependent cyclic electron flow around photosystem I (PSI-CEF), we demonstrate the sequential contribution of these alternative electron flows (AEFs) in the reactivation of photosynthetic carbon fixation during a shift from dark anoxia to light. At light onset, hydrogenase activity sustains a linear electron flow from photosystem II, which is followed by a transient PSI-CEF in the wild type. By promoting ATP synthesis without net generation of photosynthetic reductants, the two AEF are critical for restoration of the capacity for carbon dioxide fixation in the light. Our data also suggest that the decrease in hydrogen evolution with time of illumination might be due to competition for reduced ferredoxins between ferredoxin-NADP(+) oxidoreductase and hydrogenases, rather than due to the sensitivity of hydrogenase activity to oxygen. Finally, the absence of the two alternative pathways in a double mutant pgrl1 hydrogenase maturation factor G-2 is detrimental for photosynthesis and growth and cannot be compensated by any other AEF or anoxic metabolic responses. This highlights the role of hydrogenase activity and PSI-CEF in the ecological success of microalgae in low-oxygen environments. PMID:25931521

  3. Recent drought induced increase of non-photosynthetically active vegetation cover in the aspen forests of southern Rocky Mountain

    NASA Astrophysics Data System (ADS)

    Huang, C.; Anderegg, W.

    2011-12-01

    Severe droughts in concert with rising temperatures have triggered widespread of forest mortality across multiple tree species worldwide. Tree die-off would produce a significant amount of additional non-photosynthetically active vegetation (NPV), which is the major source of carbon (C) emissions to ecosystems. Trembling aspen (Populus tremuloides) is the most widely distributed tree species in North America and arguably among the largest known organisms in the world, reaching 6000 Mg in a single clone and storing a substantial amount of C in the system. A recent widespread aspen forest mortality (known as sudden aspen decline [SAD]) occurred in the last decade and its ramifications on C cycles of aspen forests and the impact on regional C budgets are not well known. Here we carry out a landscape scale assessment of NPV dynamics across 1186 km2 of aspen forests in southwestern Colorado, USA, which suffered some of the most severe forest biomass loss of the continent. We compared time-series (2000 [the pre-drought condition], 2002 [the driest period] and 2009 [the current condition]) projected NPV derived from summer Landsat Thematic Mapper (TM) images using an automated, probability based spectral mixture analysis model (AutoMCU) with aid from contemporary in-situ field observations conducted in 2009 and 2010. We found that SAD produced 40.3% more of NPV cover comparing to the pre-drought condition (mean ± standard deviation = 23.0 ± 15.8% in 2000 and 32.3 ± 19.0% in 2002) due to the senescence of top canopy aspen leaves that equated to additional 110.3 km2 of NPV cover increase in the region during the driest period. This NPV "ramp-up" also resulted in 22% decrease of green vegetation (mean ± standard deviation = 65.7 ± 18.0% in 2000 and 50.1 ± 18.8% in 2002) and 9.7% increase of visible albedo (3.7 ± 2.4% in 2000 and 4.1 ± 2.3% in 2002), which were also computed from TM images using AutoMCU and a Landsat-based albedo model, respectively. These rapid

  4. Effect of the temperature, pH and irradiance on the photosynthetic activity by Scenedesmus obtusiusculus under nitrogen replete and deplete conditions.

    PubMed

    Cabello, Juan; Toledo-Cervantes, Alma; Sánchez, León; Revah, Sergio; Morales, Marcia

    2015-04-01

    This paper evaluates the effect of the irradiance, pH and temperature on the photosynthetic activity (PA) of Scenedesmus obtusiusculus under N-replete and N-deplete conditions through oxygen measurements. The highest PA values were 160 mgO2 gb(-1) h(-1) at 620 μmol m(-2) s(-1), 35 °C and pH of 8 under N-replete conditions and 3.3 mgO2 gb(-1) h(-1) at 100 μmol m(-2) s(-1), 28.5 °C and pH of 5.5 for N-deplete conditions. Those operation conditions were tested in a flat-panel photobioreactor. The biomass productivity was 0.97 gb L(-1) d(-1) under N-replete conditions with a photosynthetic efficiency (PE) of 4.4% yielding 0.85 gb mol photon(-1). Similar biomass productivity was obtained under N-deplete condition; and the lipid productivity was 0.34 gL L(-1) d(-1) with a PE of 7.8% yielding 0.39 gL mol photon(-1). The apparent activation and deactivation energies were 16.1 and 30 kcal mol(-1), and 11.9 and 15.3 kcal mol(-1), for N-replete and N-deplete conditions, respectively. PMID:25647022

  5. Photosynthetic activity in marine and brackish water strains of Fucus vesiculosus and Fucus radicans (Phaeophyceae) at different light qualities.

    PubMed

    Svahn, Carina; Maria Gylle, A; Ekelund, Nils G A

    2012-01-01

    This study investigates the effects of different light qualities on the photosynthetic capacity of the brown algae Fucus vesiculosus, from the Norwegian Sea, and Fucus radicans and F. vesiculosus, from the Bothnian Sea. The electron transport rates (ETR) obtained for F. vesiculosus from the Norwegian Sea showed significantly higher levels of light saturation compared with both species of algae from the Bothnian Sea. The maximum of ETR values for the Norwegian Sea strain showed no significant changes due to varying light quality compared with the initial values. For F. vesiculosus, from the Bothnian Sea, treatment with blue light showed an effect after 1 week of 30 and 90 μmol photons m(-2) s(-1) (P<0.01), and for F. radicans from the Bothnian Sea, at the irradiance of 90 μmol photons m(-2) s(-1) and 1 week (P<0.01). After 1 week in the Bothnian Sea species and after 2 weeks in F. vesiculosus from the Norwegian Sea, the photosynthetic efficiency (α) was significantly higher regardless of light quality and irradiance compared with the initial values. Variation in light quality and irradiance had minor effects on the F(v):F(m) values of the three algal strains studied. PMID:22697409

  6. Water-soluble two-photon absorbing nitrosyl complex for light-activated therapy through nitric oxide release.

    PubMed

    Zheng, Qingdong; Bonoiu, Adela; Ohulchanskyy, Tymish Y; He, Guang S; Prasad, Paras N

    2008-01-01

    A water-soluble nitrosyl complex with large two-photon absorption was synthesized by incorporating a two-photon absorbing chromophore with tetra(ethylene glycol) units, into the Roussin's red salt. The nitrosyl complex exhibits quenched emission due to energy transfer from the two-photon chromophore to the Roussin's red salt. The nitric oxide (NO) release induced by one- or two-photon irradiation was detected by EPR spectroscopy with a chemical probe, the Fe(II)- N-(dithiocarbamoyl)- N-methyl- d-glucamine (Fe-MGD) complex. Increased one- or two-photon excited fluorescence, with a concomitant photochemical release of NO, was observed upon one- or two-photon light irradiation. With the observed light-dependent cytotoxicity against cancer cells of the water-soluble nitrosyl complex, it was demonstrated that two-photon-functionalized nitrosyl complexes can be effective NO donors for light-activated treatment.

  7. Major temporal variations in shortening rate absorbed along a large active fold of the southeastern Tianshan piedmont (China)

    NASA Astrophysics Data System (ADS)

    Saint-Carlier, Dimitri; Charreau, Julien; Lavé, Jérôme; Blard, Pierre-Henri; Dominguez, Stéphane; Avouac, Jean-Philippe; Wang, Shengli

    2016-01-01

    The investigation of deformation rates on a mountain piedmont can provide key information for improving our understanding of the overall dynamics of a mountain range. Here, we estimate the shortening rate absorbed by a Quaternary emergent detachment fold on the southeastern piedmont of the Tianshan (China). Our work is primarily based on new 10Be cosmogenic exposure dating of deformed alluvial surfaces. The method we have developed combines depth profiling with sampling of surface cobbles, thereby allowing exposure time, erosion rate and inheritance to be simultaneously constrained. The exposure ages of the uppermost uplifted alluvial surfaces are around 140 ± 17 ka, 130 ± 9 ka and 47 ± 9 ka, from west to east. A terrace lying below the 140 ka surface is dated at 65 ± 5 ka. The ages of the uplifted and folded alluvial surfaces were then combined with estimates of shortening obtained using two distinct methods: (1) the excess area method, where sedimentation rates, extracted from magnetostratigraphic studies, are used to determine the amount of sedimentation after the abandonment of the river; and (2) a folding model derived from sandbox experiments. The late Pleistocene shortening rates are shown to be between 0.4 ± 0.1 mm /yr and 0.8 ± 0.5 mm /yr on the western part of the fold and 2.1 ± 0.4 mm /yr along its central part. The central part of the frontal Yakeng anticline therefore accommodates up to 25% of the total shortening currently absorbed across the whole Eastern Tianshan range (8 mm/yr). However, this situation seems to have prevailed for only the last 150 ka, as the shortening rate absorbed by this nascent fold was previously ten times slower. While the initiation of folding of the Yakeng anticline can be traced back to 5.5 Ma ago, the basinward migration of the active deformation front onto the Yakeng fold is a relatively recent phenomenon and appears to be diachronous from west to east, probably in relation to the tectonic activity of the folds in

  8. Accuracy and optimal timing of activity measurements in estimating the absorbed dose of radioiodine in the treatment of Graves' disease

    NASA Astrophysics Data System (ADS)

    Merrill, S.; Horowitz, J.; Traino, A. C.; Chipkin, S. R.; Hollot, C. V.; Chait, Y.

    2011-02-01

    Calculation of the therapeutic activity of radioiodine 131I for individualized dosimetry in the treatment of Graves' disease requires an accurate estimate of the thyroid absorbed radiation dose based on a tracer activity administration of 131I. Common approaches (Marinelli-Quimby formula, MIRD algorithm) use, respectively, the effective half-life of radioiodine in the thyroid and the time-integrated activity. Many physicians perform one, two, or at most three tracer dose activity measurements at various times and calculate the required therapeutic activity by ad hoc methods. In this paper, we study the accuracy of estimates of four 'target variables': time-integrated activity coefficient, time of maximum activity, maximum activity, and effective half-life in the gland. Clinical data from 41 patients who underwent 131I therapy for Graves' disease at the University Hospital in Pisa, Italy, are used for analysis. The radioiodine kinetics are described using a nonlinear mixed-effects model. The distributions of the target variables in the patient population are characterized. Using minimum root mean squared error as the criterion, optimal 1-, 2-, and 3-point sampling schedules are determined for estimation of the target variables, and probabilistic bounds are given for the errors under the optimal times. An algorithm is developed for computing the optimal 1-, 2-, and 3-point sampling schedules for the target variables. This algorithm is implemented in a freely available software tool. Taking into consideration 131I effective half-life in the thyroid and measurement noise, the optimal 1-point time for time-integrated activity coefficient is a measurement 1 week following the tracer dose. Additional measurements give only a slight improvement in accuracy.

  9. Preillumination of lettuce seedlings with red light enhances the resistance of photosynthetic apparatus to UV-A.

    PubMed

    Kreslavski, Vladimir D; Lyubimov, Valery Yu; Shirshikova, Galina N; Shmarev, Alexander N; Kosobryukhov, Anatoly A; Schmitt, Franz-Josef; Friedrich, Thomas; Allakhverdiev, Suleyman I

    2013-05-01

    Seedlings of 10-day-old lettuce (Lactuca sativa L., cultivar Berlin) were preilluminated by low intensity red light (λmax=660 nm, 10 min, 5 μmol quanta m(-2) s(-1)) and far-red light (λmax=730 nm, 10 min, 5 μmol quanta m(-2) s(-1)) to study the effect of pre-treatment on photosynthesis, photochemical activity of photosystem II (PSII), the contents of photosynthetic and UV-A-absorbing pigments (UAPs) and H2O2, as well as total and ascorbate peroxidase activities in cotyledonary leaves of seedlings exposed to UV-A. UV radiation reduced the photosynthetic rate (Pn), the activity of PSII, and the contents of Chl a and b, carotenoids and UAPs in the leaves, but increased the content of H2O2 and the total peroxidase activity. Preillumination with red light removed these effects of UV. In turn, the illumination with red light, then far-red light removed the effect of the red light. Illumination with red light alone increased the content of UAPs, as well as peroxidase activity. It is suggested that higher resistance of the lettuce photosynthetic apparatus to UV-A radiation is associated with involvement of the active form of phytochrome B, thereby increasing peroxidase activities as well as UAPs and saving preservation of photosynthetic pigment contents due to pre-illumination with red light.

  10. Effects of climate and lifeform on dry matter yield (epsilon) from simulations using BIOME BGC. [ecosystem process model for vegetation biomass production using daily absorbed photosynthetically active radiation

    NASA Technical Reports Server (NTRS)

    Hunt, E. R., Jr.; Running, Steven W.

    1992-01-01

    An ecosystem process simulation model, BIOME-BGC, is used in a sensitivity analysis to determine the factors that may cause the dry matter yield (epsilon) and annual net primary production to vary for different ecosystems. At continental scales, epsilon is strongly correlated with annual precipitation. At a single location, year-to-year variation in net primary production (NPP) and epsilon is correlated with either annual precipitation or minimum air temperatures. Simulations indicate that forests have lower epsilon than grasslands. The most sensitive parameter affecting forest epsilon is the total amount of living woody biomass, which affects NPP by increasing carbon loss by maintenance respiration. A global map of woody biomass should significantly improve estimates of global NPP using remote sensing.

  11. Influence of CO2 change during 90-day experiment on growth characteristics and photosynthetic activity in vegetables grown in Lunar Palace 1

    NASA Astrophysics Data System (ADS)

    Shao, Lingzhi; Liu, Hong; Wang, Minjuan; Fu, Yuming; Dong, Chen; Liu, Guanghui

    To establish bioregenerative life support system (BLSS) on lunar or Mars bases in the future, it is necessary to firstly conduct manned simulation experiments on the ground. For this purpose, Lunar palace 1 as an integrative experimental facility for permanent astrobase life support artificial closed ecosystem was set up, and 90-day experiment was carried out in this system. Vegtables as one of the important plant units, provide various nutrient content for crews in the system, such as vitamin, antioxidants and so on. However, it is not clear yet that how the CO _{2} change during 90-day experiment to affect on growth characteristics and photosynthetic activity in vegtables grown in the system. In this study, red lettuce, red rape, romaine lettuce, and bibb lettuce grown in the system were chosen as the subject investigated. Growth, expressed as dry weight, length of shoot and root, leaf area, was mearsured, and photosynthesis,expressed as net photosynthetic rate, intercellular CO _{2} concentration, chlorophyll contents and fluorescence was analyzed to detemind influence of CO _{2} change during 90-day experiment on growth in vegtables grown in the system.

  12. Enhanced metabolic and redox activity of vascular aquatic plant Lemna valdiviana under polarization in Direct Photosynthetic Plant Fuel Cell.

    PubMed

    Hubenova, Yolina; Mitov, Mario

    2015-12-01

    In this study, duckweed species Lemna valdiviana was investigated as a photoautotrophycally grown biocatalyst in recently developed Direct Photosynthetic Plant Fuel Cell. Stable current outputs, reaching maximum of 226±11 mА/m(2), were achieved during the operating period. The electricity production is associated with electrons generated through the light-dependent reactions in the chloroplasts as well as the respiratory processes in the mitochondria and transferred to the anode via endogenous electron shuttle, synthesized by the plants as a specific response to the polarization. In parallel, a considerable increase in the content of proteins (47%) and reserve carbohydrates (44%) of duckweeds grown under polarization conditions was established by means of biochemical analyses. This, combined with the electricity generation, makes the technology a feasible approach for the duckweed farming.

  13. Enhanced metabolic and redox activity of vascular aquatic plant Lemna valdiviana under polarization in Direct Photosynthetic Plant Fuel Cell.

    PubMed

    Hubenova, Yolina; Mitov, Mario

    2015-12-01

    In this study, duckweed species Lemna valdiviana was investigated as a photoautotrophycally grown biocatalyst in recently developed Direct Photosynthetic Plant Fuel Cell. Stable current outputs, reaching maximum of 226±11 mА/m(2), were achieved during the operating period. The electricity production is associated with electrons generated through the light-dependent reactions in the chloroplasts as well as the respiratory processes in the mitochondria and transferred to the anode via endogenous electron shuttle, synthesized by the plants as a specific response to the polarization. In parallel, a considerable increase in the content of proteins (47%) and reserve carbohydrates (44%) of duckweeds grown under polarization conditions was established by means of biochemical analyses. This, combined with the electricity generation, makes the technology a feasible approach for the duckweed farming. PMID:25129413

  14. Photosynthetic water splitting

    SciTech Connect

    Greenbaum, E.

    1981-01-01

    The photosynthetic unit of hydrogen evolution, the turnover time of photosynthetic hydrogen production, and hydrogenic photosynthesis are discussed in the section on previous work. Recent results are given on simultaneous photoproduction of hydrogen and oxygen, kinetic studies, microscopic marine algae-seaweeds, and oxygen profiles.

  15. The monitoring of transient regimes on machine tools based on speed, acceleration and active electric power absorbed by motors

    NASA Astrophysics Data System (ADS)

    Horodinca, M.

    2016-08-01

    This paper intend to propose some new results related with computer aided monitoring of transient regimes on machine-tools based on the evolution of active electrical power absorbed by the electric motor used to drive the main kinematic chains and the evolution of rotational speed and acceleration of the main shaft. The active power is calculated in numerical format using the evolution of instantaneous voltage and current delivered by electrical power system to the electric motor. The rotational speed and acceleration of the main shaft are calculated based on the signal delivered by a sensor. Three real-time analogic signals are acquired with a very simple computer assisted setup which contains a voltage transformer, a current transformer, an AC generator as rotational speed sensor, a data acquisition system and a personal computer. The data processing and analysis was done using Matlab software. Some different transient regimes were investigated; several important conclusions related with the advantages of this monitoring technique were formulated. Many others features of the experimental setup are also available: to supervise the mechanical loading of machine-tools during cutting processes or for diagnosis of machine-tools condition by active electrical power signal analysis in frequency domain.

  16. Ionized Absorbers in Active Galactic Nuclei and Very Steap Soft X-Ray Quasars

    NASA Technical Reports Server (NTRS)

    Fiore, Fabrizio; White, Nicholas (Technical Monitor)

    2000-01-01

    Steep soft X-ray (0.1-2 keV) quasars share several unusual properties: narrow Balmer lines, strong Fe II emission, large and fast X-ray variability, and a rather steep 2-10 keV spectrum. These intriguing objects have been suggested to be the analogues of Galactic black hole candidates in the high, soft state. We present here results from ASCA observations for two of these quasars: NAB 0205 + 024 and PG 1244 + 026. Both objects show similar variations (factor of approximately 2 in 10 ks), despite a factor of approximately 10 difference in the 0.5-10 keV luminosity (7.3 x 10(exp 43) erg/s for PG 1244 + 026 and 6.4 x 10(exp 44) erg/s for NAB 0205 + 024, assuming isotropic emission, H(sub 0) = 50.0 and q(sub 0) = 0.0). The X-ray continuum of the two quasars flattens by 0.5-1 going from the 0.1-2 keV band towards higher energies, strengthening recent results on another half-dozen steep soft X-ray active galactic nuclei. PG 1244 + 026 shows a significant feature in the '1-keV' region, which can be described either as a broad emission line centered at 0.95 keV (quasar frame) or as edge or line absorption at 1.17 (1.22) keV. The line emission could be a result of reflection from a highly ionized accretion disc, in line with the view that steep soft X-ray quasars are emitting close to the Eddington luminosity. Photoelectric edge absorption or resonant line absorption could be produced by gas outflowing at a large velocity (0.3-0.6 c).

  17. Modeling the ratio of photosynthetically active radiation to broadband global solar radiation using ground and satellite-based data in the tropics

    NASA Astrophysics Data System (ADS)

    Janjai, S.; Wattan, R.; Sripradit, A.

    2015-12-01

    Data from four stations in Thailand are used to model the ratio of photosynthetically active radiation (PAR) to broadband global solar radiation. The model expresses the ratio of PAR-to-broadband global solar radiation as a function of cloud index, aerosol optical depth, precipitable water, total ozone column and solar zenith angle. Data from the MTSAT-1R and OMI/AURA satellites are used to estimate the cloud index and total ozone column, respectively at each of the four stations, while aerosol optical depth and precipitable water are retrieved from Aerosol Robotic Network (AERONET) sunphotometer measurements, also available at each station. When tested against hourly measurements, the model exhibits a coefficient of variance (R2) equal to or better than 0.96, and root mean square difference (RMSD) in the range of 7.3-7.9% and mean bias difference (MBD) of -4.5% to 3.5%. The model compares favorably with other existing models.

  18. Time-dependent changes in antioxidative enzyme expression and photosynthetic activity of Chlamydomonas reinhardtii cells under acute exposure to cadmium and anthracene.

    PubMed

    Aksmann, Anna; Pokora, Wojciech; Baścik-Remisiewicz, Agnieszka; Dettlaff-Pokora, Agnieszka; Wielgomas, Bartosz; Dziadziuszko, Małgorzata; Tukaj, Zbigniew

    2014-12-01

    Heavy metals (HM) and polycyclic aromatic hydrocarbons (PAHs) are present in the freshwater environment at concentrations that can be hazardous to the biota. Among HMs and PAHs, cadmium (Cd) and anthracene (ANT) are the most prevalent and toxic ones. The response of Chlamydomonas cells to Cd and ANT at concentrations that markedly reduced the growth of algal population was investigated in this study. At such concentrations, both cadmium and anthracene were recognized as oxidative stress inducers, since high concentration of H2O2 in treated cultures was observed. Therefore, as a part of the "molecular phase" of the cell response to this stress, we examined the time-dependent expression of genes encoding the main antioxidative enzymes: superoxide dismutase (SOD), catalase (CAT) and ascorbate peroxidase (APX), as well as the activity of these enzymes in cells, with special attention paid to chloroplastic and mitochondrial isoforms of SOD. To characterize the cell response at the "physiological level", we examined the photosynthetic activity of stressed cells via analysis of chlorophyll a fluorescence in vivo. In contrast to standard ecotoxicity studies in which the growth end-points are usually determined, herein we present time-dependent changes in algal cell response to Cd- and ANT-induced stress. The most significant effect(s) of the toxicants on photosynthetic activity was observed in the 6th hour, when strong depression of PI parameter value, an over 50 percent reduction of the active reaction center fraction (RC0) and a 3-fold increase in non-photochemical energy dissipation (DI0/RC) were noted. At the same time, the increase (up to 2.5-fold) in mRNA transcript of SOD and CAT genes, followed by the enhancement in the enzyme activity was observed. The high expression of the Msd 3 gene in treated Chlamydomonas cells probably complements the partial loss of chloroplast Fe-SOD and APX activity, while catalase and Mn-SOD 5 seem to be the major enzymes responsible for

  19. Time-dependent changes in antioxidative enzyme expression and photosynthetic activity of Chlamydomonas reinhardtii cells under acute exposure to cadmium and anthracene.

    PubMed

    Aksmann, Anna; Pokora, Wojciech; Baścik-Remisiewicz, Agnieszka; Dettlaff-Pokora, Agnieszka; Wielgomas, Bartosz; Dziadziuszko, Małgorzata; Tukaj, Zbigniew

    2014-12-01

    Heavy metals (HM) and polycyclic aromatic hydrocarbons (PAHs) are present in the freshwater environment at concentrations that can be hazardous to the biota. Among HMs and PAHs, cadmium (Cd) and anthracene (ANT) are the most prevalent and toxic ones. The response of Chlamydomonas cells to Cd and ANT at concentrations that markedly reduced the growth of algal population was investigated in this study. At such concentrations, both cadmium and anthracene were recognized as oxidative stress inducers, since high concentration of H2O2 in treated cultures was observed. Therefore, as a part of the "molecular phase" of the cell response to this stress, we examined the time-dependent expression of genes encoding the main antioxidative enzymes: superoxide dismutase (SOD), catalase (CAT) and ascorbate peroxidase (APX), as well as the activity of these enzymes in cells, with special attention paid to chloroplastic and mitochondrial isoforms of SOD. To characterize the cell response at the "physiological level", we examined the photosynthetic activity of stressed cells via analysis of chlorophyll a fluorescence in vivo. In contrast to standard ecotoxicity studies in which the growth end-points are usually determined, herein we present time-dependent changes in algal cell response to Cd- and ANT-induced stress. The most significant effect(s) of the toxicants on photosynthetic activity was observed in the 6th hour, when strong depression of PI parameter value, an over 50 percent reduction of the active reaction center fraction (RC0) and a 3-fold increase in non-photochemical energy dissipation (DI0/RC) were noted. At the same time, the increase (up to 2.5-fold) in mRNA transcript of SOD and CAT genes, followed by the enhancement in the enzyme activity was observed. The high expression of the Msd 3 gene in treated Chlamydomonas cells probably complements the partial loss of chloroplast Fe-SOD and APX activity, while catalase and Mn-SOD 5 seem to be the major enzymes responsible for

  20. Engineering photosynthetic organisms for the production of biohydrogen

    DOE PAGES

    Dubini, Alexandra; Ghirardi, Maria L.

    2014-03-27

    Oxygenic photosynthetic organisms such as green algae are capable of absorbing sunlight and converting the chemical energy into hydrogen gas. This process takes advantage of the photosynthetic apparatus of these organisms which links water oxidation to H2 production. Biological H2 has therefore the potential to be an alternative fuel of the future and shows great promise for generating large scale sustainable energy. Microalgae are able to produce H2 under light anoxic or dark anoxic condition by activating 3 different pathways that utilize the hydrogenases as catalysts. In this review, we highlight the principal barriers that prevent hydrogen production in greenmore » algae and how those limitations are being addressed, through metabolic and genetic engineering. We also discuss the major challenges and bottlenecks facing the development of future commercial algal photobiological systems for H2 production. Lastly we provide suggestions for future strategies and potential new techniques to be developed towards an integrated system with optimized hydrogen production.« less

  1. Function and distribution of bilin biosynthesis enzymes in photosynthetic organisms.

    PubMed

    Dammeyer, Thorben; Frankenberg-Dinkel, Nicole

    2008-10-01

    Bilins are open-chain tetrapyrrole molecules essential for light-harvesting and/or sensing in many photosynthetic organisms. While they serve as chromophores in phytochrome-mediated light-sensing in plants, they additionally function in light-harvesting in cyanobacteria, red algae and cryptomonads. Associated to phycobiliproteins a variety of bile pigments is responsible for the specific light-absorbance properties of the organisms enabling efficient photosynthesis under different light conditions. The initial step of bilin biosynthesis is the cleavage of heme by heme oxygenases (HO) to afford the first linear molecule biliverdin. This reaction is ubiquitously found also in non-photosynthetic organisms. Biliverdin is then further reduced by site specific reductases most of them belonging to the interesting family of ferredoxin-dependent bilin reductases (FDBRs)-a new family of radical oxidoreductases. In recent years much progress has been made in the field of heme oxygenases but even more in the widespread family of FDBRs, revealing novel biochemical FDBR activities, new crystal structures and new ecological aspects, including the discovery of bilin biosynthesis genes in wild marine phage populations. The aim of this review is to summarize and discuss the recent progress in this field and to highlight the new and remaining questions.

  2. Engineering photosynthetic organisms for the production of biohydrogen

    SciTech Connect

    Dubini, Alexandra; Ghirardi, Maria L.

    2014-03-27

    Oxygenic photosynthetic organisms such as green algae are capable of absorbing sunlight and converting the chemical energy into hydrogen gas. This process takes advantage of the photosynthetic apparatus of these organisms which links water oxidation to H2 production. Biological H2 has therefore the potential to be an alternative fuel of the future and shows great promise for generating large scale sustainable energy. Microalgae are able to produce H2 under light anoxic or dark anoxic condition by activating 3 different pathways that utilize the hydrogenases as catalysts. In this review, we highlight the principal barriers that prevent hydrogen production in green algae and how those limitations are being addressed, through metabolic and genetic engineering. We also discuss the major challenges and bottlenecks facing the development of future commercial algal photobiological systems for H2 production. Lastly we provide suggestions for future strategies and potential new techniques to be developed towards an integrated system with optimized hydrogen production.

  3. Photosynthetic control of the plasma membrane H+-ATPase in Vallisneria leaves. I. Regulation of activity during light-induced membrane hyperpolarization.

    PubMed

    Harada, Akiko; Okazaki, Yoshiji; Takagi, Shingo

    2002-04-01

    In mesophyll cells of the aquatic angiosperm Vallisneria gigantea Graebner, red, blue, or blue plus far-red light induced a typical membrane hyperpolarization, whereas far-red light alone had little effect. Both N,N'-dicyclohexylcarbodiimide, a potent inhibitor of H+-ATPase, and carbonylcyanide m-chlorophenylhydrazone, an uncoupler, produced a considerable membrane depolarization in the dark-adapted cells and a complete suppression of the light-induced hyperpolarization. Although 3-(3',4'-dichlorophenyl)-1,1-dimethylurea (DCMU), an inhibitor of photosynthetic electron transport, did not affect the membrane potential in darkness, it completely inhibited the light-induced membrane hyperpolarization. In vivo illumination of the leaves with red light caused a substantial decrease in the Km for ATP, not only of the vanadate-sensitive ATP-hydrolyzing activity in leaf homogenate, but also of the ATP-dependent H+-transporting activity in plasma membrane (PM) vesicles isolated from the leaves by aqueous polymer two-phase partitioning methods. The effects of red light were negated by the presence of DCMU during illumination. In vivo illumination with far-red light had no effect on the Km for ATP of H+-transporting activity. These results strongly suggest that an electrogenic component in the membrane potential of the mesophyll cell is generated by the PM H+-ATPase, and that photosynthesis-dependent modulation of the enzymatic activity of the PM H+-ATPase is involved in the light-induced membrane hyperpolarization. PMID:11941462

  4. Changes of ribulose bisphosphate carboxylase/oxygenase content, ribulose bisphosphate concentration, and photosynthetic activity during adaptation of high-CO/sub 2/ grown cells to low-CO/sub 2/ conditions in Chlorella pyrenoidosa

    SciTech Connect

    Yokota, A.; Canvin, D.T.

    1986-02-01

    Changes of some photosynthetic properties of high-CO/sub 2/ grown cells of Chlorella pyrenoidosa during adaptation to low-CO/sub 2/ conditions have been investigated. The K/sub m/ value of photosynthesis of the high-CO/sub 2/ grown cells for dissolved inorganic carbon was 3.3 millimolar and decreased to 25 to 30 micromolar within 4 hours after transferring to air. In the presence of saturating CO/sub 2/ concentrations the photosynthetic activity of the high-CO/sub 2/ grown cells was 1.5 times as high as that of the low-CO/sub 2/ grown cells. There was a significant rise of the photosynthetic activity during adaptation of the high-CO/sub 2/ grown cells to air, followed by a steady decrease. The activity of ribulose 1,5-bisphosphate carboxylase/oxygenase in both the high and low-CO/sub 2/ grown cells was close to the photosynthetic activity of the cells. The concentration of ribulose 1,5-bisphosphate (RuBP) was higher in the low-CO/sub 2/ adapting and low-CO/sub 2/ grown celsl than in the high-CO/sub 2/ grown cells regardless of the photosynthetic rate. This seems to be due to an increased RuBP regeneration activity during adaptation followed by maintenance of the new higher concentration. The RuBP level always exceeded the concentration of ribulose 1,5-bisphosphate carboxylase/oxygenase RuBP binding sites in both the high- and low-CO/sub 2/ grown cells at any dissolved inorganic carbon concentration.

  5. Electrochemically regenerable carbon dioxide absorber

    NASA Technical Reports Server (NTRS)

    Woods, R. R.; Marshall, R. D.; Schubert, F. H.; Heppner, D. B.

    1979-01-01

    Preliminary designs were generated for two electrochemically regenerable carbon dioxide absorber concepts. Initially, an electrochemically regenerable absorption bed concept was designed. This concept incorporated the required electrochemical regeneration components in the absorber design, permitting the absorbent to be regenerated within the absorption bed. This hardware was identified as the electrochemical absorber hardware. The second hardware concept separated the functional components of the regeneration and absorption process. This design approach minimized the extravehicular activity component volume by eliminating regeneration hardware components within the absorber. The electrochemical absorber hardware was extensively characterized for major operating parameters such as inlet carbon dioxide partial pressure, process air flow rate, operational pressure, inlet relative humidity, regeneration current density and absorption/regeneration cycle endurance testing.

  6. [Photosynthetic characteristics of five arbor species in Shenyang urban area].

    PubMed

    Li, Hai-Me; He, Xing-Yuan; Wang, Kui-Ling; Chen, Wei

    2007-08-01

    By using LI-6400 infrared gas analyzer, this paper studied the diurnal and seasonal variations of the photosynthetic rate of main arbor species (Populus alba x P. berolinensis, Salix matsudana, Ulmus pumila, Robinia pseudoacacia and Prunus davidiana) in Shenyang urban area. The correlations between net photosynthetic rate and environmental factors (photosynthetic active radiation, temperature, and stomatal conductance) were assessed by multivariate regression analysis, and related equations were constructed. The results showed that for test arbor species, the diurnal variation of photosynthetic rate mainly presented a single peak curve, and the seasonal variation was in the order of summer > autumn > spring. The major factors affecting the photosynthetic rate were photosynthetic active radiation, stomatal conductance, and intercellular CO2 concentration.

  7. Nanophase iron oxides as a key ultraviolet sunscreen for ancient photosynthetic microbes

    NASA Astrophysics Data System (ADS)

    Bishop, Janice L.; Louris, Stephanie K.; Rogoff, Dana A.; Rothschild, Lynn J.

    2006-07-01

    We propose that nanophase iron-oxide-bearing materials provided important niches for ancient photosynthetic microbes on the Earth that ultimately led to the oxygenation of the Earth's atmosphere and the formation of iron-oxide deposits. Atmospheric oxygen and ozone attenuate ultraviolet radiation on the Earth today providing substantial protection for photosynthetic organisms. With ultraviolet radiation fluxes likely to have been even higher on the early Earth than today, accessing solar radiation was particularly risky for early organisms. Yet, we know that photosynthesis arose early and played a critical role in subsequent evolution. Of primary importance was protection below 290 nm, where peak nucleic acid (~260 nm) and protein (~280 nm) absorptions occur. Nanophase ferric oxide/oxyhydroxide minerals absorb, and thus block, the lethal ultraviolet radiation, while transmitting light through much of the visible and near-infrared regions of interest to photosynthesis (400 to 1100 nm). Furthermore, they were available in early environments, and are synthesized by many organisms. Based on experiments using nanophase ferric oxide/oxyhydroxide minerals as a sunscreen for photosynthetic microbes, we suggest that iron, an abundant element widely used in biological mechanisms, may have provided the protection that early organisms needed in order to be able to use photosynthetically active radiation while being protected from ultraviolet-induced damage. The results of this study are broadly applicable to astrobiology because of the abundance of iron in other potentially habitable bodies and the evolutionary pressure to utilize solar radiation when available as an energy source. This model could apply to a potential life form on Mars or other bodies where liquid water and ultraviolet radiation could have been present at significant levels. Based on ferric oxide/oxyhydroxide spectral properties, likely geologic processes, and the results of experiments with the

  8. Quantitative phosphoproteomics of tomato mounting a hypersensitive response reveals a swift suppression of photosynthetic activity and a differential role for hsp90 isoforms.

    PubMed

    Stulemeijer, Iris J E; Joosten, Matthieu H A J; Jensen, Ole N

    2009-03-01

    An important mechanism by which plants defend themselves against pathogens is the rapid execution of a hypersensitive response (HR). Tomato plants containing the Cf-4 resistance gene mount an HR that relies on the activation of phosphorylation cascades, when challenged with the Avr4 elicitor secreted by the pathogenic fungus Cladosporium fulvum. Phosphopeptides were isolated from tomato seedlings expressing both Cf-4 and Avr4 using titanium dioxide columns and LC-MS/MS analysis led to the identification of 50 phosphoproteins, most of which have not been described in tomato before. Phosphopeptides were quantified using a label-free approach based on the MS peak areas. We identified 12 phosphopeptides for which the abundance changed upon HR initiation, as compared to control seedlings. Our results suggest that photosynthetic activity is specifically suppressed in a phosphorylation-dependent way during the very early stages of HR development. In addition, phosphopeptides originating from four Hsp90 isoforms exhibited altered abundances in Cf-4/Avr4 seedlings compared to control seedlings, suggesting that the isoforms of this chaperone protein have a different function in defense signaling. We show that label-free relative quantification of the phosphoproteome of complex samples is feasible, allowing extension of our knowledge on the general physiology and defense signaling of plants mounting the HR. PMID:19178300

  9. Incorporation of Photosynthetic Reaction Centers in the Membrane of Human Cells: Toward a New Tool for Optical Control of Cell Activity

    SciTech Connect

    Pennisi, Cristian P.; Jensen, Poul Erik; Zachar, Vladimir; Greenbaum, Elias; Yoshida, Ken

    2009-01-01

    The Photosystem I (PSI) reaction center is a photosynthetic membrane complex in which light-induced charge separation is accompanied by the generation of an electric potential. It has been recently proposed as a means to confer light sensitivity to cells possessing voltage-activated ion channels, but the feasibility of heterologous incorporation has not been demonstrated. In this work, methods of delivery and detection of PSI in the membrane of human cells are presented. Purified fractions of PSI were reconstituted in proteoliposomes that were used as vehicles for the membrane incorporation. A fluorescent impermeable dye was entrapped in the vesicles to qualitatively analyze the nature of the vesicle cell interaction. After incorporation, the localization and orientation of the complexes in the membrane was studied using immuno-fluorescence microscopy. The results showed complexes oriented as in native membranes, which were randomly distributed in clusters over the entire surface of the cell. Additionally, analysis of cell viability showed that the incorporation process does not damage the cell membrane. Taken together, the results of this work suggest that the mammalian cellular membrane is a reasonable environment for the incorporation of PSI complexes, which opens the possibility of using these molecular photovoltaic structures for optical control of cell activity.

  10. Comparison of Photoacoustic Signals in Photosynthetic and Nonphotosynthetic Leaf Tissues of Variegated Pelargonium zonale

    NASA Astrophysics Data System (ADS)

    Veljović-Jovanović, S.; Vidović, M.; Morina, F.; Prokić, Lj.; Todorović, D. M.

    2016-09-01

    Green-white variegated leaves of Pelargonium zonale were studied using the photoacoustic method. Our aim was to characterize photosynthetically active green tissue and nonphotosynthetically active white tissue by the photoacoustic amplitude signals. We observed lower stomatal conductance and higher leaf temperature in white tissue than in green tissue. Besides these thermal differences, significantly higher absorbance in green tissue was based on chlorophyll and carotenoids which were absent in white tissue. However, optical properties of epidermal layers of both tissues were equal. The photoacoustic amplitude of white tissue was over four times higher compared to green tissue, which was correlated with lower stomatal conductance. In addition, at frequencies >700 Hz, the significant differences between the photoacoustic signals of green and white tissue were obtained. We identified the photoacoustic signal deriving from photosynthetic oxygen evolution in green tissue, using high intensity of red light modulated at 10 Hz. Moreover, the photoacoustic amplitude of green tissue increased progressively with time which corresponded to the period of induction of photosynthetic oxygen evolution. For the first time, very high frequencies (1 kHz to 5 kHz) were applied on leaf material.

  11. Microspectroscopy of the photosynthetic compartment of algae.

    PubMed

    Evangelista, Valtere; Frassanito, Anna Maria; Passarelli, Vincenzo; Barsanti, Laura; Gualtieri, Paolo

    2006-01-01

    We performed microspectroscopic evaluation of the pigment composition of the photosynthetic compartments of algae belonging to different taxonomic divisions and higher plants. The feasibility of microspectroscopy for discriminating among species and/or phylogenetic groups was tested on laboratory cultures. Gaussian bands decompositions and a fitting algorithm, together with fourth-derivative transformation of absorbance spectra, provided a reliable discrimination among chlorophylls a, b and c, phycobiliproteins and carotenoids. Comparative analysis of absorption spectra highlighted the evolutionary grouping of the algae into three main lineages in accordance with the most recent endosymbiotic theories.

  12. Characterisation of antioxidants in photosynthetic and non-photosynthetic leaf tissues of variegated Pelargonium zonale plants.

    PubMed

    Vidović, M; Morina, F; Milić-Komić, S; Vuleta, A; Zechmann, B; Prokić, Lj; Veljović Jovanović, S

    2016-07-01

    Hydrogen peroxide is an important signalling molecule, involved in regulation of numerous metabolic processes in plants. The most important sources of H2 O2 in photosynthetically active cells are chloroplasts and peroxisomes. Here we employed variegated Pelargonium zonale to characterise and compare enzymatic and non-enzymatic components of the antioxidative system in autotrophic and heterotrophic leaf tissues at (sub)cellular level under optimal growth conditions. The results revealed that both leaf tissues had specific strategies to regulate H2 O2 levels. In photosynthetic cells, the redox regulatory system was based on ascorbate, and on the activities of thylakoid-bound ascorbate peroxidase (tAPX) and catalase. In this leaf tissue, ascorbate was predominantly localised in the nucleus, peroxisomes, plastids and mitochondria. On the other hand, non-photosynthetic cells contained higher glutathione content, mostly located in mitochondria. The enzymatic antioxidative system in non-photosynthetic cells relied on the ascorbate-glutathione cycle and both Mn and Cu/Zn superoxide dismutase. Interestingly, higher content of ascorbate and glutathione, and higher activities of APX in the cytosol of non-photosynthetic leaf cells compared to the photosynthetic ones, suggest the importance of this compartment in H2 O2 regulation. Together, these results imply different regulation of processes linked with H2 O2 signalling at subcellular level. Thus, we propose green-white variegated leaves as an excellent system for examination of redox signal transduction and redox communication between two cell types, autotrophic and heterotrophic, within the same organ.

  13. A Mechanistic Understanding of the Role Drought-Induced Stress Play in Regulating Photosynthetic and Respiration Activities of the Sagebrush after a Precipitation Pulse Event

    NASA Astrophysics Data System (ADS)

    Mitra, B.; Mackay, D. S.; Pendall, E.; Ewers, B. E.

    2009-12-01

    Dryland ecosystems with low annual precipitation have been predicted to be susceptible to changes in precipitation pattern due to global climate change. A lot of uncertainty still remains with regard to the role soil moisture stress plays in regulating photosynthetic and soil respiration activities of the plants. Thus in order to have a better understanding of how plants in the dryland ecosystem physiologically respond to changes in water availability, an irrigation experiment was conducted in a sagebrush ecosystem in the months of July and August of 2009. Also, in order to separate heterotrophic and autotrophic respiration trench plots were established a few weeks prior to the irrigation experiment. The study site located near the town of Saratoga, Wyoming at an elevation of 2200m was dominated by Wyoming big sagebrush (Artemisia tridentata ssp. wyomingensis). A 20 mm rainfall was simulated over both the trench plots and the sagebrush plots, which were of 1 m2 dimension. We measured predawn water potential, gas exchange, soil respiration as well as del 13C of the roots and leaves of the sagebrush. All these measurements were conducted 1 day prior to and up to 7 days after the irrigation experiment. On day 7 soil samples were collected from all the plots in order to analyze for substrate induced respiration (SIR) in order to determine microbial biomass carbon in soils. Sagebrush responded to pulse event immediately after the irrigation experiment as indicated by the increase in carbon flux, and photosynthesis rate and decrease in predawn water potential, but by day 5 they returned to their pre-pulse status. A plausible explanation for this phenomenon can be attributed to the high degree of soil moisture stress which may have lead to its incomplete photosynthetic recovery from the pulse event. Heterotrophic respiration also displayed a similar response with the effect of pulse disappearing by day 5. Interestingly the irrigation experiment repeated again in August

  14. Spatial variability in photosynthetic and heterotrophic activity drives localized δ13C org fluctuations and carbonate precipitation in hypersaline microbial mats.

    PubMed

    Houghton, J; Fike, D; Druschel, G; Orphan, V; Hoehler, T M; Des Marais, D J

    2014-11-01

    Modern laminated photosynthetic microbial mats are ideal environments to study how microbial activity creates and modifies carbon and sulfur isotopic signatures prior to lithification. Laminated microbial mats from a hypersaline lagoon (Guerrero Negro, Baja California, Mexico) maintained in a flume in a greenhouse at NASA Ames Research Center were sampled for δ(13) C of organic material and carbonate to assess the impact of carbon fixation (e.g., photosynthesis) and decomposition (e.g., bacterial respiration) on δ(13) C signatures. In the photic zone, the δ(13) C org signature records a complex relationship between the activities of cyanobacteria under variable conditions of CO2 limitation with a significant contribution from green sulfur bacteria using the reductive TCA cycle for carbon fixation. Carbonate is present in some layers of the mat, associated with high concentrations of bacteriochlorophyll e (characteristic of green sulfur bacteria) and exhibits δ(13) C signatures similar to DIC in the overlying water column (-2.0‰), with small but variable decreases consistent with localized heterotrophic activity from sulfate-reducing bacteria (SRB). Model results indicate respiration rates in the upper 12 mm of the mat alter in situ pH and HCO3- concentrations to create both phototrophic CO2 limitation and carbonate supersaturation, leading to local precipitation of carbonate minerals. The measured activity of SRB with depth suggests they variably contribute to decomposition in the mat dependent on organic substrate concentrations. Millimeter-scale variability in the δ(13) C org signature beneath the photic zone in the mat is a result of shifting dominance between cyanobacteria and green sulfur bacteria with the aggregate signature overprinted by heterotrophic reworking by SRB and methanogens. These observations highlight the impact of sedimentary microbial processes on δ(13) C org signatures; these processes need to be considered when attempting to relate

  15. Spatial variability in photosynthetic and heterotrophic activity drives localized δ13C org fluctuations and carbonate precipitation in hypersaline microbial mats.

    PubMed

    Houghton, J; Fike, D; Druschel, G; Orphan, V; Hoehler, T M; Des Marais, D J

    2014-11-01

    Modern laminated photosynthetic microbial mats are ideal environments to study how microbial activity creates and modifies carbon and sulfur isotopic signatures prior to lithification. Laminated microbial mats from a hypersaline lagoon (Guerrero Negro, Baja California, Mexico) maintained in a flume in a greenhouse at NASA Ames Research Center were sampled for δ(13) C of organic material and carbonate to assess the impact of carbon fixation (e.g., photosynthesis) and decomposition (e.g., bacterial respiration) on δ(13) C signatures. In the photic zone, the δ(13) C org signature records a complex relationship between the activities of cyanobacteria under variable conditions of CO2 limitation with a significant contribution from green sulfur bacteria using the reductive TCA cycle for carbon fixation. Carbonate is present in some layers of the mat, associated with high concentrations of bacteriochlorophyll e (characteristic of green sulfur bacteria) and exhibits δ(13) C signatures similar to DIC in the overlying water column (-2.0‰), with small but variable decreases consistent with localized heterotrophic activity from sulfate-reducing bacteria (SRB). Model results indicate respiration rates in the upper 12 mm of the mat alter in situ pH and HCO3- concentrations to create both phototrophic CO2 limitation and carbonate supersaturation, leading to local precipitation of carbonate minerals. The measured activity of SRB with depth suggests they variably contribute to decomposition in the mat dependent on organic substrate concentrations. Millimeter-scale variability in the δ(13) C org signature beneath the photic zone in the mat is a result of shifting dominance between cyanobacteria and green sulfur bacteria with the aggregate signature overprinted by heterotrophic reworking by SRB and methanogens. These observations highlight the impact of sedimentary microbial processes on δ(13) C org signatures; these processes need to be considered when attempting to relate

  16. Modeling the reflection of Photosynthetically active radiation in a monodominant floodable forest in the Pantanal of Mato Grosso State using multivariate statistics and neural networks.

    PubMed

    Curado, Leone F A; Musis, Carlo R DE; Cunha, Cristiano R DA; Rodrigues, Thiago R; Pereira, Vinicius M R; Nogueira, José S; Sanches, Luciana

    2016-09-01

    The study of radiation entrance and exit dynamics and energy consumption in a system is important for understanding the environmental processes that rule the biosphere-atmosphere interactions of all ecosystems. This study provides an analysis of the interaction of energy in the form of photosynthetically active radiation (PAR) in the Pantanal, a Brazilian wetland forest, by studying the variation of PAR reflectance and its interaction with local rainfall. The study site is located in Private Reserve of Natural Heritage, Mato Grosso State, Brazil, where the vegetation is a monodominant forest of Vochysia divergens Phol. The results showed a high correlation between the reflection of visible radiation and rainfall; however, the behavior was not the same at the three heights studied. An analysis of the hourly variation of the reflected waves also showed the seasonality of these phenomena in relation to the dry and rainy seasons. A predictive model for PAR was developed with a neural network that has a hidden layer, and it showed a determination coefficient of 0.938. This model showed that the Julian day and time of measurements had an inverse association with the wind profile and a direct association with the relative humidity profile. PMID:27556220

  17. Ultraviolet-B and photosynthetically active radiation interactively affect yield and pattern of monoterpenes in leaves of peppermint (Mentha x piperita L.).

    PubMed

    Behn, Helen; Albert, Andreas; Marx, Friedhelm; Noga, Georg; Ulbrich, Andreas

    2010-06-23

    Solar radiation is a key environmental signal in regulation of plant secondary metabolism. Since metabolic responses to light and ultraviolet (UV) radiation exposure are known to depend on the ratio of spectral ranges (e.g., UV-B/PAR), we examined effects of different UV-B radiation (280-315 nm) and photosynthetically active radiation (PAR, 400-700 nm) levels and ratios on yield and pattern of monoterpenoid essential oil of peppermint. Experiments were performed in exposure chambers, technically equipped for realistic simulation of natural climate and radiation. The experimental design comprised four irradiation regimes created by the combination of two PAR levels including or excluding UV-B radiation. During flowering, the highest essential oil yield was achieved at high PAR (1150 micromol m(-2) s(-1)) and approximate ambient UV-B radiation (0.6 W m(-2)). Regarding the monoterpene pattern, low PAR (550 micromol m(-2) s(-1)) and the absence of UV-B radiation led to reduced menthol and increased menthone contents and thereby to a substantial decrease in oil quality. Essential oil yield could not be correlated with density or diameter of peltate glandular trichomes, the epidermal structures specialized on biosynthesis, and the accumulation of monoterpenes. The present results lead to the conclusion that production of high quality oils (fulfilling the requirements of the Pharmacopoeia Europaea) requires high levels of natural sunlight. In protected cultivation, the use of UV-B transmitting covering materials is therefore highly recommended.

  18. Integrating Map Algebra and Statistical Modeling for Spatio-Temporal Analysis of Monthly Mean Daily Incident Photosynthetically Active Radiation (PAR) over a Complex Terrain

    PubMed Central

    Evrendilek, Fatih

    2007-01-01

    This study aims at quantifying spatio-temporal dynamics of monthly mean daily incident photosynthetically active radiation (PAR) over a vast and complex terrain such as Turkey. The spatial interpolation method of universal kriging, and the combination of multiple linear regression (MLR) models and map algebra techniques were implemented to generate surface maps of PAR with a grid resolution of 500 × 500 m as a function of five geographical and 14 climatic variables. Performance of the geostatistical and MLR models was compared using mean prediction error (MPE), root-mean-square prediction error (RMSPE), average standard prediction error (ASE), mean standardized prediction error (MSPE), root-mean-square standardized prediction error (RMSSPE), and adjusted coefficient of determination (R2adj.). The best-fit MLR- and universal kriging-generated models of monthly mean daily PAR were validated against an independent 37-year observed dataset of 35 climate stations derived from 160 stations across Turkey by the Jackknifing method. The spatial variability patterns of monthly mean daily incident PAR were more accurately reflected in the surface maps created by the MLR-based models than in those created by the universal kriging method, in particular, for spring (May) and autumn (November). The MLR-based spatial interpolation algorithms of PAR described in this study indicated the significance of the multifactor approach to understanding and mapping spatio-temporal dynamics of PAR for a complex terrain over meso-scales.

  19. Phlorotannin production and lipid oxidation as a potential protective function against high photosynthetically active and UV radiation in gametophytes of Alaria esculenta (Alariales, Phaeophyceae).

    PubMed

    Steinhoff, Franciska S; Graeve, Martin; Bartoszek, Krzysztof; Bischof, Kai; Wiencke, Christian

    2012-01-01

    Radiation damage can inter alia result in lipid peroxidation of macroalgal cell membranes. To prevent photo-oxidation within the cells, photoprotective substances such as phlorotannins are synthesized. In the present study, changes in total fatty acids (FA), FA composition and intra/extracellular phlorotannin contents were determined by gas chromatography and the Folin-Ciocalteu method to investigate the photoprotective potential of phlorotannins to prevent lipid peroxidation. Alaria esculenta juveniles (Phaeophyceae) were exposed over 20 days to high/low photosynthetically active radiation (PAR) in combination with UV radiation (UVR) in the treatments: PAB (low/high PAR + UV-B + UV-A), PA (low/high PAR + UV-A) or low/high PAR only. While extracellular phlorotannins increased after 10 days, intracellular phlorotannins increased with exposure time and PA and decreased under PAB. Interactive effects of time:radiation wavebands, time:PAR dose as well as radiation wavebands:PAR dose were observed. Low FA contents were detected in the PA and PAB treatments; interactive effects were observed between time:high PAR and PAB:high PAR. Total FA contents were correlated to extra/intracellular phlorotannin contents. Our results suggest that phlorotannins might play a role in intra/extracellular protection by absorption and oxidation processes. Changes in FA content/composition upon UVR and high PAR might be considered as an adaptive mechanism of the A. esculenta juveniles subjected to variations in solar irradiance.

  20. Ultraviolet-B and photosynthetically active radiation interactively affect yield and pattern of monoterpenes in leaves of peppermint (Mentha x piperita L.).

    PubMed

    Behn, Helen; Albert, Andreas; Marx, Friedhelm; Noga, Georg; Ulbrich, Andreas

    2010-06-23

    Solar radiation is a key environmental signal in regulation of plant secondary metabolism. Since metabolic responses to light and ultraviolet (UV) radiation exposure are known to depend on the ratio of spectral ranges (e.g., UV-B/PAR), we examined effects of different UV-B radiation (280-315 nm) and photosynthetically active radiation (PAR, 400-700 nm) levels and ratios on yield and pattern of monoterpenoid essential oil of peppermint. Experiments were performed in exposure chambers, technically equipped for realistic simulation of natural climate and radiation. The experimental design comprised four irradiation regimes created by the combination of two PAR levels including or excluding UV-B radiation. During flowering, the highest essential oil yield was achieved at high PAR (1150 micromol m(-2) s(-1)) and approximate ambient UV-B radiation (0.6 W m(-2)). Regarding the monoterpene pattern, low PAR (550 micromol m(-2) s(-1)) and the absence of UV-B radiation led to reduced menthol and increased menthone contents and thereby to a substantial decrease in oil quality. Essential oil yield could not be correlated with density or diameter of peltate glandular trichomes, the epidermal structures specialized on biosynthesis, and the accumulation of monoterpenes. The present results lead to the conclusion that production of high quality oils (fulfilling the requirements of the Pharmacopoeia Europaea) requires high levels of natural sunlight. In protected cultivation, the use of UV-B transmitting covering materials is therefore highly recommended. PMID:20481601

  1. Interactive effects of salinity and phosphorus availability on growth, water relations, nutritional status and photosynthetic activity of barley (Hordeum vulgare L.).

    PubMed

    Talbi Zribi, O; Abdelly, C; Debez, A

    2011-11-01

    The interactive effects of salinity and phosphorus availability on growth, water relations, nutritional status and photosynthetic activity were investigated in barley (Hordeum vulgare L. cv. Manel). Seedlings were grown hydroponically under low or sufficient phosphorus (P) supply (5 or 180 μmol KH(2) PO(4) plant(-1) week(-1) , respectively), with or without 100 mm NaCl. Phosphorus deficiency or salinity significantly decreased whole plant growth, leaf water content, leaf osmotic potential and gas exchange parameters, with a more marked impact of P stress. The effect of both stresses was not additive since the response of plants to combined salinity and P deficiency was similar to that of plants grown under P deficiency alone. In addition, salt-treated plants exposed to P deficiency showed higher salt tolerance compared to plants grown with sufficient P supply. This was related to plant ability to significantly increase root:shoot DW ratio, root length, K(+)/Na(+) ratio, leaf proline and soluble sugar concentrations and total non-enzymatic antioxidant capacity, together with restricting Na(+) accumulation in the upper leaves. As a whole, our results indicate that under concomitant exposure to both salt and P deficiency, the impact of the latter constraint is pre-dominant.

  2. [Radiometers performance attenuation and data correction in long-term observation of total radiation and photosynthetically active radiation in typical forest ecosystems in China].

    PubMed

    Zhu, Zhi-Lin; Sun, Xiao-Min; Yu, Gui-Rui; Wen, Xue-Fa; Zhang, Yi-Ping; Han, Shi-Jie; Yan, Jun-Hua; Wang, Hui-Min

    2011-11-01

    Based on the total radiation and photosynthetically active radiation (PAR) observations with net radiometer (CNR1) and quantum sensor (Li-190SB) in 4 ChinaFLUX forest sites (Changbaishan, Qianyanzhou, Dinghushan, and Xishuangbanna) in 2003-2008, this paper analyzed the uncertainties and the radiometers performance changes in long-term and continuous field observation. The results showed that the 98% accuracy of the total radiation measured with CNR1 (Q(cNR1)) could satisfy the technical criterion for the sites except Xishuangbanna where the Q(CNR1) was averagely about 7% lower than Q(CM11), the radiation measured with high accuracy pyranometer CM11. For most sites, though the temperature had definite effects on the performance of CNR1, the effects were still within the allowable range of the accuracy of the instrument. Besides temperature, the seasonal fog often occurred in tropical rain forests in Xishuangbanna also had effects on the performance of CNR1. Based on the long-term variations of PAR, especially its ratio to total radiation in the 4 sites, it was found that quantum sensor (Li-190SB) had obvious performance attenuation, with the mean annual attenuation rate being about 4%. To correct the observation error caused by Li-190SB, an attempt was made to give a post-correction of the PAR observations, which could basically eliminate the quantum sensor's performance attenuation due to long-term field measurement.

  3. The ratio of transmitted near-infrared radiation to photosynthetically active radiation (PAR) increases in proportion to the adsorbed PAR in the canopy.

    PubMed

    Kume, Atsushi; Nasahara, Kenlo N; Nagai, Shin; Muraoka, Hiroyuki

    2011-01-01

    The daily total photosynthetically active radiation (400-700 nm, PAR) and near-infrared radiation (700-1000 nm, NIR) were measured in the understory beneath the canopy (PARt and NIRt) and above the canopy (PARi and NIRi) of a Japanese cool-temperate deciduous broad-leaved forest during the snow-free period (May to November). The integration of spectral radiation for NIR and that for PAR, and the daily integrations of instantaneous NIR and PAR, reduced the noises from the optical difference in spectrum and from canopy structure heterogeneity, sky condition and solar elevation. PARi/PARt was linearly related to NIRt/PARt (R² = 0.96). The effect of cloudiness was negligible, because the fluctuation of NIRi/PARi was quite small regardless of season and weather conditions compared with the range of NIRt/PARt in the forest. The ratio of NIRt/PARt beneath the canopy was log-linearly related to the in situ leaf area index (LAI) with a wide range from 0 to 5.25 (R² = 0.97). We conclude that seasonal changes in fAPAR (= 1 - PARt/PARi) and LAI of a canopy can be estimated with high accuracy by transmitted NIRt and PARt beneath the canopy.

  4. Leaf absorbance and photosynthesis

    NASA Technical Reports Server (NTRS)

    Schurer, Kees

    1994-01-01

    The absorption spectrum of a leaf is often thought to contain some clues to the photosynthetic action spectrum of chlorophyll. Of course, absorption of photons is needed for photosynthesis, but the reverse, photosynthesis when there is absorption, is not necessarily true. As a check on the existence of absorption limits we measured spectra for a few different leaves. Two techniques for measuring absorption have been used, viz. the separate determination of the diffuse reflectance and the diffuse transmittance with the leaf at a port of an integrating sphere and the direct determination of the non-absorbed fraction with the leaf in the sphere. In a cross-check both methods yielded the same results for the absorption spectrum. The spectrum of a Fuchsia leaf, covering the short-wave region from 350 to 2500 nm, shows a high absorption in UV, blue and red, the well known dip in the green and a steep fall-off at 700 nm. Absorption drops to virtually zero in the near infrared, with subsequent absorptions, corresponding to the water absorption bands. In more detailed spectra, taken at 5 nm intervals with a 5 nm bandwidth, differences in chlorophyll content show in the different depths of the dip around 550 nm and in a small shift of the absorption edge at 700 nm. Spectra for Geranium (Pelargonium zonale) and Hibiscus (with a higher chlorophyll content) show that the upper limit for photosynthesis can not be much above 700 nm. No evidence, however, is to be seen of a lower limit for photosynthesis and, in fact, some experiments down to 300 nm still did not show a decrease of the absorption although it is well recognized that no photosynthesis results with 300 nm wavelengths.

  5. Elevated CO2 enhances photosynthetic efficiency, ion uptake and antioxidant activity of Gynura bicolor DC. grown in a porous-tube nutrient delivery system under simulated microgravity.

    PubMed

    Wang, M; Liu, H; Dong, C; Fu, Y; Liu, H

    2016-05-01

    It is well known that plants can grow under space conditions, however, perturbations of many biological phenomena have been highlighted due to the effect of altered gravity and its possible interaction with other factors (e.g., CO2 , ion radiation, etc. Our aim was to test whether elevated CO2 could provide 'protection' to Gynura bicolor against the damaging effects of simulated microgravity (SM) on photosynthesis, ion uptake and antioxidant activity. As compared to G. bicolor grown in ambient CO2 with no SM (ACO2 ), growth and yield of the plants increased under elevated ambient CO2 with no SM (ECO2 ) and decreased under ACO2 +SM, whereas there was no significant effect on ECO2 +SM. Reductions in the content of Chl a, carotenoids and Chl a+b were 17.9%, 20.7% and 17.9% under ACO2 +SM, respectively, but under ECO2 there was a significant effect on all photosynthetic pigments except Chl b, compared to ACO2 . Photosynthesis was improved under ECO2 with SM and such an improvement was associated with improved water use efficiency and instantaneous carboxylation efficiency. Furthermore, SM caused a reduction in ion absorption rate, except for Ca(2+) , while ECO2 increased the uptake rate. Finally, the activity of SOD, POD and the content of MDA and H2 O2 were enhanced under SM treatments and were highest in ACO2 +SM. In contrast, T-AOC activity and GSH content significantly declined in ACO2 +SM compared to other treatments. These results suggest that ACO2 is not sufficient to counteract SM impact, but the increase is usually caused by improvement in CO2 nutrition in ECO2 +SM in comparison with ACO2 +SM.

  6. Direct extraction of photosynthetic electrons from single algal cells by nanoprobing system.

    PubMed

    Ryu, WonHyoung; Bai, Seoung-Jai; Park, Joong Sun; Huang, Zubin; Moseley, Jeffrey; Fabian, Tibor; Fasching, Rainer J; Grossman, Arthur R; Prinz, Fritz B

    2010-04-14

    There are numerous sources of bioenergy that are generated by photosynthetic processes, for example, lipids, alcohols, hydrogen, and polysaccharides. However, generally only a small fraction of solar energy absorbed by photosynthetic organisms is converted to a form of energy that can be readily exploited. To more efficiently use the solar energy harvested by photosynthetic organisms, we evaluated the feasibility of generating bioelectricity by directly extracting electrons from the photosynthetic electron transport chain before they are used to fix CO(2) into sugars and polysaccharides. From a living algal cell, Chlamydomonas reinhardtii, photosynthetic electrons (1.2 pA at 6000 mA/m(2)) were directly extracted without a mediator electron carrier by inserting a nanoelectrode into the algal chloroplast and applying an overvoltage. This result may represent an initial step in generating "high efficiency" bioelectricity by directly harvesting high energy photosynthetic electrons. PMID:20201533

  7. Abscisic acid and aldehyde oxidase activity in maize ear leaf and grain relative to post-flowering photosynthetic capacity and grain-filling rate under different water/nitrogen treatments.

    PubMed

    Qin, Shujun; Zhang, Zongzheng; Ning, Tangyuan; Ren, Shizhong; Su, Licheng; Li, Zengjia

    2013-09-01

    This study investigated changes in leaf abscisic acid (ABA) concentrations and grain ABA concentrations in two maize cultivars and analyzed the following relationships under different water/nitrogen treatments: leaf ABA concentrations and photosynthetic parameters; leaf ABA concentrations and grain ABA concentrations; leaf/grain ABA concentrations and grain-filling parameters; and aldehyde oxidase (AO, EC 1.2.3.1) activities and ABA concentrations. The ear leaf average AO activities and ABA concentrations were lower in the controlled release urea treatments compared with the conventional urea treatments. The average AO activities in the grains were higher in the controlled release urea treatments, and the ABA concentrations were significantly increased at 11-30 DAF. The Pn and ABA concentrations in ear leaves were negatively correlated. And the Gmean were positively correlated with the grain ABA concentrations at 11-30 DAF and negatively correlated with the leaf ABA concentrations at 20 and 40-50 DAF. The grain ABA concentrations and leaf ABA concentrations were positively correlated. Thus, the Gmean were closely related to the AO activities and to the ear leaf and grain ABA concentrations. As compared to other treatments, the subsoiling and controlled release urea treatment promoted the uptake of water and nitrogen by maize, increased the photosynthetic capacity of the ear leaves, increased the grain-filling rate, and improved the movement of photosynthetic assimilates toward the developing grains. In the cultivar Z958, higher ABA concentrations in grains at 11-30 DAF and lower ABA concentrations in ear leaves during the late grain-filling stage, resulted in higher grain-filling rate and increased accumulation of photosynthetic products (relative to the cultivar D3). PMID:23770596

  8. Abscisic acid and aldehyde oxidase activity in maize ear leaf and grain relative to post-flowering photosynthetic capacity and grain-filling rate under different water/nitrogen treatments.

    PubMed

    Qin, Shujun; Zhang, Zongzheng; Ning, Tangyuan; Ren, Shizhong; Su, Licheng; Li, Zengjia

    2013-09-01

    This study investigated changes in leaf abscisic acid (ABA) concentrations and grain ABA concentrations in two maize cultivars and analyzed the following relationships under different water/nitrogen treatments: leaf ABA concentrations and photosynthetic parameters; leaf ABA concentrations and grain ABA concentrations; leaf/grain ABA concentrations and grain-filling parameters; and aldehyde oxidase (AO, EC 1.2.3.1) activities and ABA concentrations. The ear leaf average AO activities and ABA concentrations were lower in the controlled release urea treatments compared with the conventional urea treatments. The average AO activities in the grains were higher in the controlled release urea treatments, and the ABA concentrations were significantly increased at 11-30 DAF. The Pn and ABA concentrations in ear leaves were negatively correlated. And the Gmean were positively correlated with the grain ABA concentrations at 11-30 DAF and negatively correlated with the leaf ABA concentrations at 20 and 40-50 DAF. The grain ABA concentrations and leaf ABA concentrations were positively correlated. Thus, the Gmean were closely related to the AO activities and to the ear leaf and grain ABA concentrations. As compared to other treatments, the subsoiling and controlled release urea treatment promoted the uptake of water and nitrogen by maize, increased the photosynthetic capacity of the ear leaves, increased the grain-filling rate, and improved the movement of photosynthetic assimilates toward the developing grains. In the cultivar Z958, higher ABA concentrations in grains at 11-30 DAF and lower ABA concentrations in ear leaves during the late grain-filling stage, resulted in higher grain-filling rate and increased accumulation of photosynthetic products (relative to the cultivar D3).

  9. C2-substituted aromatic cytokinin sugar conjugates delay the onset of senescence by maintaining the activity of the photosynthetic apparatus.

    PubMed

    Vylíčilová, Hana; Husičková, Alexandra; Spíchal, Lukáš; Srovnal, Josef; Doležal, Karel; Plíhal, Ondřej; Plíhalová, Lucie

    2016-02-01

    Cytokinins are plant hormones with biological functions ranging from coordination of plant growth and development to the regulation of senescence. A series of 2-chloro-N(6)-(halogenobenzylamino)purine ribosides was prepared and tested for cytokinin activity in detached wheat leaf senescence, tobacco callus and Amaranthus bioassays. The synthetic compounds showed significant activity, especially in delaying senescence in detached wheat leaves. They were also tested in bacterial receptor bioassays using both monocot and dicot members of the cytokinin receptor family. Most of the derivatives did not trigger cytokinin signaling via the AHK3 and AHK4 receptors from Arabidopsis thaliana in the bacterial assay, but some of them specifically activated the ZmHK1 receptor from Zea mays and were also more active than the aromatic cytokinin BAP in an ARR5::GUS cytokinin bioassay using transgenic Arabidopsis plants. Whole transcript expression analysis was performed using an Arabidopsis model to gather information about the reprogramming of gene transcription when senescent leaves were treated with selected C2-substituted aromatic cytokinin ribosides. Genome-wide expression profiling revealed that the synthetic halogenated derivatives induced the expression of genes related to cytokinin signaling and metabolism. They also prompted both up- and down-regulation of a unique combination of genes coding for components of the photosystem II (PSII) reaction center, light-harvesting complex II (LHCII), and the oxygen-evolving complex, as well as several stress factors responsible for regulating photosynthesis and chlorophyll degradation. Chlorophyll content and fluorescence analyses demonstrated that treatment with the halogenated derivatives increased the efficiency of PSII photochemistry and the abundance of LHCII relative to DMSO- and BAP-treated controls. These findings demonstrate that it is possible to manipulate and fine-tune leaf longevity using synthetic aromatic cytokinin

  10. Solar ultraviolet radiation affects the activity of ribulose-1,5-bisphosphate carboxylase-oxygenase and the composition of photosynthetic and xanthophyll cycle pigments in the intertidal green alga Ulva lactuca L.

    PubMed

    Bischof, Kai; Kräbs, Gudrun; Wiencke, Christian; Hanelt, Dieter

    2002-07-01

    The effect of solar UV radiation on the physiology of the intertidal green macroalga Ulva lactuca L. was investigated. A natural Ulva community at the shore of Helgoland was covered with screening foils, excluding UV-B or UV-B + UV-A from the solar spectrum. In the sampled material, changes in the activity and concentration of ribulose-1,5-bisphosphate carboxylase-oxygenase (Rubisco), and the concentration of photosynthetic and xanthophyll cycle pigments were determined. Exclusion of UV radiation from the natural solar spectrum resulted in an elevated overall activity of Rubisco, related to an increase in its cellular concentration. Among the photosynthetic pigments, lutein concentration was substantially elevated under UV exclusion. In addition, marked UV effects on the xanthophyll cycle were found: exclusion of solar UV radiation (and particularly UV-B) resulted in an increased ratio of zeaxanthin concentration to the total xanthophyll content, indicating adverse effects of UV-B on the efficiency of photoprotection under high irradiances of photosynthetically active radiation. The results confirm a marked impact of present UV-B levels on macroalgal physiology under field conditions.

  11. Accuracy of quantum sensors measuring yield photon flux and photosynthetic photon flux

    NASA Technical Reports Server (NTRS)

    Barnes, C.; Tibbitts, T.; Sager, J.; Deitzer, G.; Bubenheim, D.; Koerner, G.; Bugbee, B.; Knott, W. M. (Principal Investigator)

    1993-01-01

    Photosynthesis is fundamentally driven by photon flux rather than energy flux, but not all absorbed photons yield equal amounts of photosynthesis. Thus, two measures of photosynthetically active radiation have emerged: photosynthetic photon flux (PPF), which values all photons from 400 to 700 nm equally, and yield photon flux (YPF), which weights photons in the range from 360 to 760 nm according to plant photosynthetic response. We selected seven common radiation sources and measured YPF and PPF from each source with a spectroradiometer. We then compared these measurements with measurements from three quantum sensors designed to measure YPF, and from six quantum sensors designed to measure PPF. There were few differences among sensors within a group (usually <5%), but YPF values from sensors were consistently lower (3% to 20%) than YPF values calculated from spectroradiometric measurements. Quantum sensor measurements of PPF also were consistently lower than PPF values calculated from spectroradiometric measurements, but the differences were <7% for all sources, except red-light-emitting diodes. The sensors were most accurate for broad-band sources and least accurate for narrow-band sources. According to spectroradiometric measurements, YPF sensors were significantly less accurate (>9% difference) than PPF sensors under metal halide, high-pressure sodium, and low-pressure sodium lamps. Both sensor types were inaccurate (>18% error) under red-light-emitting diodes. Because both YPF and PPF sensors are imperfect integrators, and because spectroradiometers can measure photosynthetically active radiation much more accurately, researchers should consider developing calibration factors from spectroradiometric data for some specific radiation sources to improve the accuracy of integrating sensors.

  12. Accuracy of quantum sensors measuring yield photon flux and photosynthetic photon flux.

    PubMed

    Barnes, C; Tibbitts, T; Sager, J; Deitzer, G; Bubenheim, D; Koerner, G; Bugbee, B

    1993-12-01

    Photosynthesis is fundamentally driven by photon flux rather than energy flux, but not all absorbed photons yield equal amounts of photosynthesis. Thus, two measures of photosynthetically active radiation have emerged: photosynthetic photon flux (PPF), which values all photons from 400 to 700 nm equally, and yield photon flux (YPF), which weights photons in the range from 360 to 760 nm according to plant photosynthetic response. We selected seven common radiation sources and measured YPF and PPF from each source with a spectroradiometer. We then compared these measurements with measurements from three quantum sensors designed to measure YPF, and from six quantum sensors designed to measure PPF. There were few differences among sensors within a group (usually <5%), but YPF values from sensors were consistently lower (3% to 20%) than YPF values calculated from spectroradiometric measurements. Quantum sensor measurements of PPF also were consistently lower than PPF values calculated from spectroradiometric measurements, but the differences were <7% for all sources, except red-light-emitting diodes. The sensors were most accurate for broad-band sources and least accurate for narrow-band sources. According to spectroradiometric measurements, YPF sensors were significantly less accurate (>9% difference) than PPF sensors under metal halide, high-pressure sodium, and low-pressure sodium lamps. Both sensor types were inaccurate (>18% error) under red-light-emitting diodes. Because both YPF and PPF sensors are imperfect integrators, and because spectroradiometers can measure photosynthetically active radiation much more accurately, researchers should consider developing calibration factors from spectroradiometric data for some specific radiation sources to improve the accuracy of integrating sensors.

  13. Comparative Ni tolerance and accumulation potentials between Mesembryanthemum crystallinum (halophyte) and Brassica juncea: Metal accumulation, nutrient status and photosynthetic activity.

    PubMed

    Amari, Taoufik; Ghnaya, Tahar; Debez, Ahmed; Taamali, Manel; Ben Youssef, Nabil; Lucchini, Giorgio; Sacchi, Gian Attilio; Abdelly, Chedly

    2014-11-01

    Saline soils often constitute sites of accumulation of industrial and urban wastes contaminated by heavy metals. Halophytes, i.e. native salt-tolerant species, could be more suitable for heavy metal phytoextraction from saline areas than glycophytes, most frequently used so far. In the framework of this approach, we assess here the Ni phytoextraction potential in the halophyte Mesembryanthemum crystallinum compared with the model species Brassica juncea. Plants were hydroponically maintained for 21 days at 0, 25, 50, and 100μM NiCl2. Nickel addition significantly restricted the growth activity of both species, and to a higher extent in M. crystallinum, which did not, however, show Ni-related toxicity symptoms on leaves. Interestingly, photosynthesis activity, chlorophyll content and photosystem II integrity assessed by chlorophyll fluorescence were less impacted in Ni-treated M. crystallinum as compared to B. juncea. The plant mineral nutrition was differently affected by NiCl2 exposure depending on the element, the species investigated and even the organ. In both species, roots were the preferential sites of Ni(2+) accumulation, but the fraction translocated to shoots was higher in B. juncea than in M. crystallinum. The relatively good tolerance of M. crystallinum to Ni suggests that this halophyte species could be used in the phytoextraction of moderately polluted saline soils. PMID:25171515

  14. BOREAS TE-10 Photosynthetic Response Data

    NASA Technical Reports Server (NTRS)

    Hall, Forrest G. (Editor); Papagno, Andrea (Editor); Middleton, Elizabeth; Sullivan, Joseph

    2000-01-01

    The Boreal Ecosystem-Atmospheric Study (BOREAS) TE-10 (Terrestrial Ecology) team collected several data sets in support of its efforts to characterize and interpret information on the gas exchange, reflectance, transmittance, chlorophyll content, carbon content, hydrogen content, nitrogen content, and photosynthetic response of boreal vegetation. This data set contains measurements of quantitative parameters and leaf photosynthetic response to increases in light conducted in the SSA during the growing seasons of 1994 and 1996 using an oxygen electrode system. Leaf photosynthetic responses were not collected in 1996. The data are stored in tabular ASCII files. The data files are available on a CD-ROM (see document number 20010000884), or from the Oak Ridge National Laboratory (ORNL) Distributed Active Archive Center (DAAC).

  15. Visualization of water usage and photosynthetic activity of street trees exposed to 2 ppm of SO 2—A combined evaluation by cold neutron and chlorophyll fluorescence imaging

    NASA Astrophysics Data System (ADS)

    Matsushima, U.; Kardjilov, N.; Hilger, A.; Manke, I.; Shono, H.; Herppich, W. B.

    2009-06-01

    Photosynthetic efficacy and auto-exhaust-fume resistance of street trees were evaluated by cold neutron radiography (CNR) with D 2O tracer and chlorophyll fluorescence (CF) imaging. With these techniques, information on the responses of water usage and photosynthetic activity of plants exposed to simulate toxic auto-exhaust fumes (2 ppm SO 2 in air) were obtained. Branches of hibiscus trees were detached, placed into a tub with aerated water and used for the experiments after rooting. A CF image was taken before SO 2 was applied for 1 h. During the experiment, CNR and CF imaging were conduced. H 2O and D 2O in the plant container were exchanged every 30 min to observe water uptake. D 2O tracer clearly showed water uptake into the hibiscus stem during each treatment. When the atmosphere was changed from simulated auto-exhaust fumes to normal air again, the amount of D 2O and, hence, water uptake increased. CF imaging was well suited to evaluate the effects of SO 2 as simulated toxic auto-exhaust fumes on plants. The maximum photochemical efficiency ( Fv/ Fm), a sensitive indicator of the efficacy and the integrity of plants' photosynthesis, immediately dropped by 30% after supplying the simulated auto-exhaust fumes. This indicates that toxic auto-exhaust fumes negatively affected the photosynthetic activity of hibiscus leaves. Simultaneous CNR and CF imaging successfully visualized variations of photosynthetic activity and water uptake in the sample. Thus, this combination method was effective to non-destructive analyze the physiological status of plants.

  16. Reduced photosynthetic activity is directly correlated with 2-(3H)-benzoxazolinone accumulation in lettuce leaves.

    PubMed

    Sánchez-Moreiras, Adela M; Oliveros-Bastidas, Alberto; Reigosa, Manuel J

    2010-02-01

    2-(3H)-benzoxazolinone (BOA) is a secondary plant metabolite previously found to inhibit plant growth and development. The phytotoxic activity of BOA has been extensively demonstrated over the last years. However, the relation of BOA phytotoxicity with BOA accumulation in plant leaves has not been thoroughly investigated. In this work, BOA phytotoxicity on photosynthesis (PhiPSII and Pn) of lettuce (Lactuca sativa L. cv. Great Lakes) was studied, and these results were correlated with BOA quantities in the leaves. BOA-treated plants showed reduced photosynthesis rate 6 h after the beginning of the treatment, and the efficiency of photosystem II started to be affected 10 h after treatment. These results were correlated with an increasing concentration of BOA in leaves that starts 6 h after treatment and shows a maximum at 96 h.

  17. Hydrogen metabolism of photosynthetic bacteria and algae

    SciTech Connect

    Kumazawa, S.; Mitsui, A.

    1982-01-01

    The metabolism, metabolic pathways and biochemistry of hydrogen in photosynthetic bacteria and algae are reviewed. Detailed information on the occurrence and measurement of hydrogenase activity is presented. Hydrogen production rates for different species of algae and bacteria are presented. 173 references, 1 figure, 7 tables.

  18. Low and moderate photosynthetically active radiation affects the flavonol glycosides and hydroxycinnamic acid derivatives in kale (Brassica oleracea var. sabellica) dependent on two low temperatures.

    PubMed

    Neugart, Susanne; Fiol, Michaela; Schreiner, Monika; Rohn, Sascha; Zrenner, Rita; Kroh, Lothar W; Krumbein, Angelika

    2013-11-01

    Kale (Brassica oleracea var. sabellica) contains a large number of naturally occurring structurally different non-acylated and acylated flavonol glycosides as well as hydroxycinnamic acid derivatives. The objective of this study was to determine the effect of low and moderate photosynthetic active radiation (PAR) and how these levels interact with low temperature in these phenolic compounds. Juvenile kale plants were treated with PAR levels from 200 to 800 μmol m(-2) s(-1) at 5 and 10 °C under defined conditions in climate chambers. Of the investigated 20 compounds, 11 and 17 compounds were influenced by PAR and temperature, respectively. In addition, an interaction between PAR and temperature was found for eight compounds. The response of the phenolic compounds to PAR was structure-dependent. While quercetin triglycosides increased with higher PAR at 5 and 10 °C, the kaempferol triglycosides exhibited the highest concentrations at 400 μmol m(-2) s(-1). In contrast, kaempferol diglycosides exhibited the highest concentrations at increased PAR levels of 600 and 800 μmol m(-2) s(-1) at 10 °C. However, key genes of flavonol biosynthesis were influenced by temperature but remained unaffected by PAR. Furthermore, there was no interaction between the PAR level and the low temperature in the response of hydroxycinnamic acid derivatives in kale with the exception of caffeoylquinic acid, which decreased with higher PAR levels of 600 and 800 μmol m(-2) s(-1) and at a lower temperature. In conclusion, PAR and its interaction with temperature could be a suitable tool for modifying the profile of phenolic compounds.

  19. A simple optical model to estimate diffuse attenuation coefficient of photosynthetically active radiation in an extremely turbid lake from surface reflectance.

    PubMed

    Zhang, Yunlin; Liu, Xiaohan; Yin, Yan; Wang, Mingzhu; Qin, Boqiang

    2012-08-27

    Accurate estimation of the diffuse attenuation coefficient is critical for our understanding and modelling of key physical, chemical, and biological processes in water bodies. For extremely turbid, shallow, Lake Taihu in China, we synchronously monitored the diffuse attenuation coefficient of photosynthetically active radiation (Kd(PAR)) and the remote sensing reflectance at 134 sites. Kd(PAR)) varied greatly among different sites from 1.62 to 14.68 m(-1) with a mean value of 5.62 ± 2.99 m(-1). A simple optical model from near-infrared remote sensing reflectance of MODIS channels 2 (859 nm) and 15 (748 nm) was calibrated, and validated, to estimate Kd(PAR). With the simple optical model, the root mean square error and mean relative error were 0.95 m(-1) and 17.0% respectively at 748 nm, and 0.98 m(-1) and 17.6% at 859 nm, based on an independent validation data set. Our results showed a good precision of estimation for Kd(PAR) using the new simple optical model, contrasting with the poor estimations derived from existing empirical and semi-analytical models developed in clear, open ocean waters or slightly turbid coastal waters. Although at 748 nm the model had slightly higher precision than at 859 nm, the spatial resolution at 859 nm was four times that at 748 nm. Therefore, we propose a new model based on the MODIS-derived normalized water-leaving radiances at a wavelength of 859 nm, for accurate retrieval of Kd(PAR) in extremely turbid, shallow lakes with Kd(PAR) larger than 1.5 m(-1).

  20. Regulation of some carbohydrate metabolism-related genes, starch and soluble sugar contents, photosynthetic activities and yield attributes of two contrasting rice genotypes subjected to salt stress.

    PubMed

    Boriboonkaset, Thanaphol; Theerawitaya, Cattarin; Yamada, Nana; Pichakum, Aussanee; Supaibulwatana, Kanyaratt; Cha-Um, Suriyan; Takabe, Teruhiro; Kirdmanee, Chalermpol

    2013-10-01

    Soluble carbohydrates play a key role as osmolytes and significantly contribute in salt defence mechanism, especially in halophyte species. The objective of this study is to investigate the transcriptional expression of starch-related genes, sugar profile and physiological performances of two contrasting rice genotypes, Pokkali (salt tolerant) and IR29 (salt sensitive), in response to salt stress. Total soluble sugars, glucose and fructose levels in the flag leaf of salt-stressed Pokkali rice were enhanced relative to soluble starch accumulation in plants exposed to EC = 13.25 dS m(-1) (salt stress) for 3 days. In Pokkali, the net photosynthetic rate and starch metabolism may play a key role as energy resources under salt stress. In contrast, photosynthetic performance, indicated by photosynthetic pigment levels and chlorophyll fluorescence parameters, in salt-stressed IR29 was significantly reduced, leading to delayed starch biosynthesis. The reduction in photosynthetic ability and lack of defence mechanisms in IR29 caused growth inhibition and yield loss. Soluble starch and soluble sugar enrichment in Pokkali rice may function alternatively as osmotic adjustment in salt defence mechanism and strengthen carbon energy reserves, greater survival prospects under salt stress and enhanced productivity.

  1. Actively manipulation of operation states in passively pulsed fiber lasers by using graphene saturable absorber on microfiber.

    PubMed

    Sheng, Qiwen; Feng, Ming; Xin, Wei; Han, Tianyu; Liu, Yange; Liu, Zhibo; Tian, Jianguo

    2013-06-17

    We experimentally demonstrate an operation switchable Erbium-doped fiber laser by employing graphene saturable absorber (GSA) on microfiber. With the introducing of a polydimethylsiloxane layer, a graphene can be considered as a parallel plate on microfiber and induces different propagation losses to TE and TM modes. By the use of such polarization sensitive GSA on microfiber, Erbium doped fiber laser with switchable operation states such as continuous wave, stable Q-switching, Q-switched mode-locking, and continuous-wave mode-locking, can be achieved by simply tuning the polarization states in the laser cavity. Our results show that covering graphene on microfibers could be a promising method for fabricating all fiber SA, and may have high potential in wide applications.

  2. Absorber coatings' degradation

    SciTech Connect

    Moore, S.W.

    1984-01-01

    This report is intended to document some of the Los Alamos efforts that have been carried out under the Department of Energy (DOE) Active Heating and Cooling Materials Reliability, Maintainability, and Exposure Testing program. Funding for these activities is obtained directly from DOE although they represent a variety of projects and coordination with other agencies. Major limitations to the use of solar energy are the uncertain reliability and lifetimes of solar systems. This program is aimed at determining material operating limitations, durabilities, and failure modes such that materials improvements can be made and lifetimes can be extended. Although many active and passive materials and systems are being studied at Los Alamos, this paper will concentrate on absorber coatings and degradation of these coatings.

  3. Spatial Heterogeneity of Ice Cover Sediment and Thickness and Its Effects on Photosynthetically Active Radiation and Chlorophyll-a Distribution: Lake Bonney, Antarctica

    NASA Astrophysics Data System (ADS)

    Obryk, M.; Doran, P. T.; Priscu, J. C.; Morgan-Kiss, R. M.; Siebenaler, A. G.

    2012-12-01

    The perennially ice-covered lakes in the McMurdo Dry Valleys, Antarctica have been extensively studied under the Long Term Ecological Research project. But sampling has been spatially restricted due to the logistical difficulty of penetrating the 3-6 m of ice cover. The ice covers restrict wind-driven turbulence and its associated mixing of water, resulting in a unique thermal stratification and a strong vertical gradient of salinity. The permanent ice covers also shade the underlying water column, which, in turn, controls photosynthesis. Here, we present results of a three-dimensional record of lake processes obtained with an autonomous underwater vehicle (AUV). The AUV was deployed at West Lake Bonney, located in Taylor Valley, Dry Valleys, to further understand biogeochemical and physical properties of the Dry Valley lakes. The AUV was equipped with depth, conductivity, temperature, under water photosynthetically active radiation (PAR), turbidity, chlorophyll-and-DOM fluorescence, pH, and REDOX sensors. Measurements were taken over the course of two years in a 100 x 100 meter spaced horizontal sampling grid (and 0.2 m vertical resolution). In addition, the AUV measured ice thickness and collected 200 images looking up through the ice, which were used to quantify sediment distribution. Comparison with high-resolution satellite QuickBird imagery demonstrates a strong correlation between aerial sediment distribution and ice cover thickness. Our results are the first to show the spatial heterogeneity of lacustrine ecosystems in the McMurdo Dry Valleys, significantly improving our understanding of lake processes. Surface sediment is responsible for localized thinning of ice cover due to absorption of solar radiation, which in turn increases total available PAR in the water column. Higher PAR values are negatively correlated with chlorophyll-a, presenting a paradox; historically, long-term studies of PAR and chlorophyll-a have shown positive trends. We hypothesized

  4. Function of the Chloroplast Hydrogenase in the Microalga Chlamydomonas: The Role of Hydrogenase and State Transitions during Photosynthetic Activation in Anaerobiosis

    PubMed Central

    Ghysels, Bart; Godaux, Damien; Matagne, René F.; Cardol, Pierre; Franck, Fabrice

    2013-01-01

    Like a majority of photosynthetic microorganisms, the green unicellular alga Chlamydomonas reinhardtii may encounter O2 deprived conditions on a regular basis. In response to anaerobiosis or in a respiration defective context, the photosynthetic electron transport chain of Chlamydomonas is remodeled by a state transition process to a conformation that favours the photoproduction of ATP at the expense of reductant synthesis. In some unicellular green algae including Chlamydomonas, anoxia also triggers the induction of a chloroplast-located, oxygen sensitive hydrogenase, which accepts electrons from reduced ferredoxin to convert protons into molecular hydrogen. Although microalgal hydrogen evolution has received much interest for its biotechnological potential, its physiological role remains unclear. By using specific Chlamydomonas mutants, we demonstrate that the state transition ability and the hydrogenase function are both critical for induction of photosynthesis in anoxia. These two processes are thus important for survival of the cells when they are transiently placed in an anaerobic environment. PMID:23717558

  5. Function of the chloroplast hydrogenase in the microalga Chlamydomonas: the role of hydrogenase and state transitions during photosynthetic activation in anaerobiosis.

    PubMed

    Ghysels, Bart; Godaux, Damien; Matagne, René F; Cardol, Pierre; Franck, Fabrice

    2013-01-01

    Like a majority of photosynthetic microorganisms, the green unicellular alga Chlamydomonas reinhardtii may encounter O2 deprived conditions on a regular basis. In response to anaerobiosis or in a respiration defective context, the photosynthetic electron transport chain of Chlamydomonas is remodeled by a state transition process to a conformation that favours the photoproduction of ATP at the expense of reductant synthesis. In some unicellular green algae including Chlamydomonas, anoxia also triggers the induction of a chloroplast-located, oxygen sensitive hydrogenase, which accepts electrons from reduced ferredoxin to convert protons into molecular hydrogen. Although microalgal hydrogen evolution has received much interest for its biotechnological potential, its physiological role remains unclear. By using specific Chlamydomonas mutants, we demonstrate that the state transition ability and the hydrogenase function are both critical for induction of photosynthesis in anoxia. These two processes are thus important for survival of the cells when they are transiently placed in an anaerobic environment. PMID:23717558

  6. Principles of light harvesting from single photosynthetic complexes

    PubMed Central

    Schlau-Cohen, G. S.

    2015-01-01

    Photosynthetic systems harness sunlight to power most life on Earth. In the initial steps of photosynthetic light harvesting, absorbed energy is converted to chemical energy with near-unity quantum efficiency. This is achieved by an efficient, directional and regulated flow of energy through a network of proteins. Here, we discuss the following three key principles of this flow and of photosynthetic light harvesting: thermal fluctuations of the protein structure; intrinsic conformational switches with defined functional consequences; and environmentally triggered conformational switches. Through these principles, photosynthetic systems balance two types of operational costs: metabolic costs, or the cost of maintaining and running the molecular machinery, and opportunity costs, or the cost of losing any operational time. Understanding how the molecular machinery and dynamics are designed to balance these costs may provide a blueprint for improved artificial light-harvesting devices. With a multi-disciplinary approach combining knowledge of biology, this blueprint could lead to low-cost and more effective solar energy conversion. Photosynthetic systems achieve widespread light harvesting across the Earth's surface; in the face of our growing energy needs, this is functionality we need to replicate, and perhaps emulate. PMID:26052423

  7. Principles of light harvesting from single photosynthetic complexes.

    PubMed

    Schlau-Cohen, G S

    2015-06-01

    Photosynthetic systems harness sunlight to power most life on Earth. In the initial steps of photosynthetic light harvesting, absorbed energy is converted to chemical energy with near-unity quantum efficiency. This is achieved by an efficient, directional and regulated flow of energy through a network of proteins. Here, we discuss the following three key principles of this flow and of photosynthetic light harvesting: thermal fluctuations of the protein structure; intrinsic conformational switches with defined functional consequences; and environmentally triggered conformational switches. Through these principles, photosynthetic systems balance two types of operational costs: metabolic costs, or the cost of maintaining and running the molecular machinery, and opportunity costs, or the cost of losing any operational time. Understanding how the molecular machinery and dynamics are designed to balance these costs may provide a blueprint for improved artificial light-harvesting devices. With a multi-disciplinary approach combining knowledge of biology, this blueprint could lead to low-cost and more effective solar energy conversion. Photosynthetic systems achieve widespread light harvesting across the Earth's surface; in the face of our growing energy needs, this is functionality we need to replicate, and perhaps emulate. PMID:26052423

  8. Longitudinal photosynthetic gradient in crust lichens' thalli.

    PubMed

    Wu, Li; Zhang, Gaoke; Lan, Shubin; Zhang, Delu; Hu, Chunxiang

    2014-05-01

    In order to evaluate the self-shading protection for inner photobionts, the photosynthetic activities of three crust lichens were detected using Microscope-Imaging-PAM. The false color images showed that longitudinal photosynthetic gradient was found in both the green algal lichen Placidium sp. and the cyanolichen Peltula sp. In longitudinal direction, all the four chlorophyll fluorescence parameters Fv/Fm, Yield, qP, and rETR gradually decreased with depth in the thalli of both of these two lichens. In Placidium sp., qN values decreased with depth, whereas an opposite trend was found in Peltula sp. However, no such photosynthetic heterogeneity was found in the thalli of Collema sp. in longitudinal direction. Microscope observation showed that photobiont cells are compactly arranged in Placidium sp. and Peltula sp. while loosely distributed in Collema sp. It was considered that the longitudinal photosynthetic heterogeneity was ascribed to the result of gradual decrease of incidence caused by the compact arrangement of photobiont cells in the thalli. The results indicate a good protection from the self-shading for the inner photobionts against high radiation in crust lichens.

  9. The Photosynthetic Cycle

    DOE R&D Accomplishments Database

    Calvin, Melvin

    1955-03-21

    A cyclic sequence of transformations, including the carboxylation of RuDP (ribulose diphosphate) and its re-formation, has been deduced as the route for the creation of reduced carbon compounds in photosynthetic organisms. With the demonstration of RuDP as substrate for the carboxylation in a cell-free system, each of the reactions has now been carried out independently in vitro. Further purification of this last enzyme system has confirmed the deduction that the carboxylation of RuDP leads directly to the two molecules of PGA (phosphoglyceric acid) involving an internal dismutation and suggesting the name "carboxydismutase" for the enzyme. As a consequence of this knowledge of each of the steps in the photosynthetic CO{sub 2} reduction cycle, it is possible to define the reagent requirements to maintain it. The net requirement for the reduction of one molecule of CO{sub 2} is four equivalents of [H]and three molecules of ATP (adenine triphosphate). These must ultimately be supplied by the photochemical reaction. Some possible ways in which this may be accomplished are discussed.

  10. Characterisation of antioxidants in photosynthetic and non-photosynthetic leaf tissues of variegated Pelargonium zonale plants.

    PubMed

    Vidović, M; Morina, F; Milić-Komić, S; Vuleta, A; Zechmann, B; Prokić, Lj; Veljović Jovanović, S

    2016-07-01

    Hydrogen peroxide is an important signalling molecule, involved in regulation of numerous metabolic processes in plants. The most important sources of H2 O2 in photosynthetically active cells are chloroplasts and peroxisomes. Here we employed variegated Pelargonium zonale to characterise and compare enzymatic and non-enzymatic components of the antioxidative system in autotrophic and heterotrophic leaf tissues at (sub)cellular level under optimal growth conditions. The results revealed that both leaf tissues had specific strategies to regulate H2 O2 levels. In photosynthetic cells, the redox regulatory system was based on ascorbate, and on the activities of thylakoid-bound ascorbate peroxidase (tAPX) and catalase. In this leaf tissue, ascorbate was predominantly localised in the nucleus, peroxisomes, plastids and mitochondria. On the other hand, non-photosynthetic cells contained higher glutathione content, mostly located in mitochondria. The enzymatic antioxidative system in non-photosynthetic cells relied on the ascorbate-glutathione cycle and both Mn and Cu/Zn superoxide dismutase. Interestingly, higher content of ascorbate and glutathione, and higher activities of APX in the cytosol of non-photosynthetic leaf cells compared to the photosynthetic ones, suggest the importance of this compartment in H2 O2 regulation. Together, these results imply different regulation of processes linked with H2 O2 signalling at subcellular level. Thus, we propose green-white variegated leaves as an excellent system for examination of redox signal transduction and redox communication between two cell types, autotrophic and heterotrophic, within the same organ. PMID:26712503

  11. Composition for absorbing hydrogen

    DOEpatents

    Heung, Leung K.; Wicks, George G.; Enz, Glenn L.

    1995-01-01

    A hydrogen absorbing composition. The composition comprises a porous glass matrix, made by a sol-gel process, having a hydrogen-absorbing material dispersed throughout the matrix. A sol, made from tetraethyl orthosilicate, is mixed with a hydrogen-absorbing material and solidified to form a porous glass matrix with the hydrogen-absorbing material dispersed uniformly throughout the matrix. The glass matrix has pores large enough to allow gases having hydrogen to pass through the matrix, yet small enough to hold the particles dispersed within the matrix so that the hydrogen-absorbing particles are not released during repeated hydrogen absorption/desorption cycles.

  12. Composition for absorbing hydrogen

    DOEpatents

    Heung, L.K.; Wicks, G.G.; Enz, G.L.

    1995-05-02

    A hydrogen absorbing composition is described. The composition comprises a porous glass matrix, made by a sol-gel process, having a hydrogen-absorbing material dispersed throughout the matrix. A sol, made from tetraethyl orthosilicate, is mixed with a hydrogen-absorbing material and solidified to form a porous glass matrix with the hydrogen-absorbing material dispersed uniformly throughout the matrix. The glass matrix has pores large enough to allow gases having hydrogen to pass through the matrix, yet small enough to hold the particles dispersed within the matrix so that the hydrogen-absorbing particles are not released during repeated hydrogen absorption/desorption cycles.

  13. Structural and Functional Hierarchy in Photosynthetic Energy Conversion-from Molecules to Nanostructures.

    PubMed

    Szabó, Tibor; Magyar, Melinda; Hajdu, Kata; Dorogi, Márta; Nyerki, Emil; Tóth, Tünde; Lingvay, Mónika; Garab, Győző; Hernádi, Klára; Nagy, László

    2015-12-01

    Basic principles of structural and functional requirements of photosynthetic energy conversion in hierarchically organized machineries are reviewed. Blueprints of photosynthesis, the energetic basis of virtually all life on Earth, can serve the basis for constructing artificial light energy-converting molecular devices. In photosynthetic organisms, the conversion of light energy into chemical energy takes places in highly organized fine-tunable systems with structural and functional hierarchy. The incident photons are absorbed by light-harvesting complexes, which funnel the excitation energy into reaction centre (RC) protein complexes containing redox-active chlorophyll molecules; the primary charge separations in the RCs are followed by vectorial transport of charges (electrons and protons) in the photosynthetic membrane. RCs possess properties that make their use in solar energy-converting and integrated optoelectronic systems feasible. Therefore, there is a large interest in many laboratories and in the industry toward their use in molecular devices. RCs have been bound to different carrier matrices, with their photophysical and photochemical activities largely retained in the nano-systems and with electronic connection to conducting surfaces. We show examples of RCs bound to carbon-based materials (functionalized and non-functionalized single- and multiwalled carbon nanotubes), transitional metal oxides (ITO) and conducting polymers and porous silicon and characterize their photochemical activities. Recently, we adapted several physical and chemical methods for binding RCs to different nanomaterials. It is generally found that the P(+)(QAQB)(-) charge pair, which is formed after single saturating light excitation is stabilized after the attachment of the RCs to the nanostructures, which is followed by slow reorganization of the protein structure. Measuring the electric conductivity in a direct contact mode or in electrochemical cell indicates that there is an

  14. Structural and Functional Hierarchy in Photosynthetic Energy Conversion—from Molecules to Nanostructures

    NASA Astrophysics Data System (ADS)

    Szabó, Tibor; Magyar, Melinda; Hajdu, Kata; Dorogi, Márta; Nyerki, Emil; Tóth, Tünde; Lingvay, Mónika; Garab, Győző; Hernádi, Klára; Nagy, László

    2015-12-01

    Basic principles of structural and functional requirements of photosynthetic energy conversion in hierarchically organized machineries are reviewed. Blueprints of photosynthesis, the energetic basis of virtually all life on Earth, can serve the basis for constructing artificial light energy-converting molecular devices. In photosynthetic organisms, the conversion of light energy into chemical energy takes places in highly organized fine-tunable systems with structural and functional hierarchy. The incident photons are absorbed by light-harvesting complexes, which funnel the excitation energy into reaction centre (RC) protein complexes containing redox-active chlorophyll molecules; the primary charge separations in the RCs are followed by vectorial transport of charges (electrons and protons) in the photosynthetic membrane. RCs possess properties that make their use in solar energy-converting and integrated optoelectronic systems feasible. Therefore, there is a large interest in many laboratories and in the industry toward their use in molecular devices. RCs have been bound to different carrier matrices, with their photophysical and photochemical activities largely retained in the nano-systems and with electronic connection to conducting surfaces. We show examples of RCs bound to carbon-based materials (functionalized and non-functionalized single- and multiwalled carbon nanotubes), transitional metal oxides (ITO) and conducting polymers and porous silicon and characterize their photochemical activities. Recently, we adapted several physical and chemical methods for binding RCs to different nanomaterials. It is generally found that the P+(QAQB)- charge pair, which is formed after single saturating light excitation is stabilized after the attachment of the RCs to the nanostructures, which is followed by slow reorganization of the protein structure. Measuring the electric conductivity in a direct contact mode or in electrochemical cell indicates that there is an

  15. TPX/TFTR Neutral Beam energy absorbers

    SciTech Connect

    Dahlgren, F.; Wright, K.; Kamperschroer, J.; Grisham, L.; Lontai, L.; Peters, C.; VonHalle, A.

    1993-11-01

    The present beam energy absorbing surfaces on the TFTR Neutral Beams such as Ion Dumps, Calorimeters, beam defining apertures, and scrapers, are simple water cooled copper plates which wee designed to absorb (via their thermal inertia) the incident beam power for two seconds with a five minute coal down interval between pulses. These components are not capable of absorbing the anticipated beam power loading for 1000 second TPX pulses and will have to be replaced with an actively cooled design. While several actively cooled energy absorbing designs were considered,, the hypervapotron elements currently being used on the JET beamlines were chosen due to their lower cooling water demands and reliable performance on JET.

  16. BOREAS TE-9 NSA Photosynthetic Response Data

    NASA Technical Reports Server (NTRS)

    Hall, Forrest G.; Curd, Shelaine (Editor); Dang, Qinglai; Margolis, Hank; Coyea, Marie

    2000-01-01

    The Boreal Ecosystem-Atmospheric Study (BOREAS) TE-9 (Terrestrial Ecology) team collected several data sets related to chemical and photosynthetic properties of leaves. This data set describes: (1) the response of leaf and shoot-level photosynthesis to ambient and intercellular CO2 concentration, temperature, and incident photosynthetically active radiation (PAR) for black spruce, jack pine, and aspen during the three intensive field campaigns (IFCs) in 1994 in the Northern Study Area (NSA); (2) the response of stomatal conductance to vapor pressure difference throughout the growing season of 1994; and (3) a range of shoot water potentials (controlled in the laboratory) for black spruce and jack pine. The data are stored in tabular ASCII files. The data files are available on a CD-ROM (see document number 20010000884), or from the Oak Ridge National Laboratory (ORNL) Distributed Active Archive Center (DAAC).

  17. Photosynthesis, Growth, and Ultraviolet Irradiance Absorbance of Cucurbita pepo L. Leaves Exposed to Ultraviolet-B Radiation (280-315 nm) 1

    PubMed Central

    Sisson, William B.

    1981-01-01

    Net photosynthesis, growth, and ultraviolet (UV) radiation absorbance were determined for the first leaf of Cucurbita pepo L. exposed to two levels of UV-B irradiation and a UV-B radiation-free control treatment. Absorbance by extracted flavonoid pigments and other UV-B radiation-absorbing compounds from the first leaves increased with time and level of UV-B radiation impinging on leaf surfaces. Although absorbance of UV-B radiation by extracted pigments increased substantially, UV-B radiation attenuation apparently was insufficient to protect completely the photosynthetic apparatus or leaf growth processes. Leaf expansion was repressed by daily exposure to 1365 Joules per meter per day of biologically effective UV-B radiation but not by exposure to 660 Joules per meter per day. Photosynthesis measured through ontogenesis of the first leaf was depressed by both UV-B radiation treatments. Repression of photosynthesis by UV-B radiation was especially evident during the ontogenetic period of maximum photosynthetic activity. PMID:16661610

  18. Production and characterization of activated carbon prepared from safflower seed cake biochar and its ability to absorb reactive dyestuff

    NASA Astrophysics Data System (ADS)

    Angın, Dilek; Köse, T. Ennil; Selengil, Uğur

    2013-09-01

    The use of activated carbon obtained from biochar for the removal of reactive dyestuff from aqueous solutions at various contact times, pHs and temperatures was investigated. The biochar was chemically modified with potassium hydroxide. The surface area and micropore volume of activated carbon was 1277 m2/g and 0.4952 cm3/g, respectively. The surface characterization of both biochar and activated carbon was undertaken using by Fourier transform infrared spectroscopy and scanning electron microscopy. The experimental data indicated that the adsorption isotherms are well described by the Dubinin-Radushkevich (DR) isotherm equation. The adsorption kinetics of reactive dyestuff obeys the pseudo second-order kinetic model. The thermodynamic parameters such as ΔG̊, ΔH̊ and ΔS̊ were calculated to estimate the nature of adsorption. The activation energy of the system was calculated as 1.12 kJ/mol. According to these results, prepared activated carbon could be used as a low-cost adsorbent to compare with the commercial activated carbon for the removal reactive dyestuff from wastewater.

  19. Modification of carbon partitioning, photosynthetic capacity, and O{sub 2} sensitivity in Arabidopsis plants with low ADP-glucose pyrophosphorylase activity

    SciTech Connect

    Sun, J.; Okita, T.W.; Edwards, G.E.

    1999-01-01

    Wild-type Arabidopsis plants, the starch-deficient mutant TL46, and the near-starchless mutant TL25 were evaluated by noninvasive in situ methods for their capacity for net CO{sub 2} assimilation, true rates of photosynthetic O{sub 2} evolution (determined from chlorophyll fluorescence measurements of photosystem II), partitioning of photosynthate into sucrose and starch, and plant growth. Compared with wild-type plants, the starch mutants showed reduced photosynthetic capacity, with the largest reduction occurring in mutant TL25 subjected to high light and increased CO{sub 2} partial pressure. The extent of stimulation of CO{sub 2} assimilation by increasing CO{sub 2} or by reducing O{sub 2} partial pressure was significantly less for the starch mutants than for wild-type plants. Under high light and moderate to high levels of CO{sub 2}, the rates of CO{sub 2} assimilation and O{sub 2} evolution and the percentage inhibition of photosynthesis by low O{sub 2} were higher for the wild type than for the mutants. The relative rates of {sup 14}CO{sub 2} incorporation into starch under high light and high CO{sub 2} followed the patterns of photosynthetic capacity, with TL46 showing 31% to 40% of the starch-labeling rates of the wild type and TL25 showing less than 14% incorporation. Overall, there were significant correlations between the rates of starch synthesis and CO{sub 2} assimilation and between the rates of starch synthesis and cumulative leaf area. These results indicate that leaf starch plays an important role as a transient reserve, the synthesis of which can ameliorate any potential reduction in photosynthesis caused by feedback regulation.

  20. Modelling Absorbent Phenomena of Absorbent Structure

    NASA Astrophysics Data System (ADS)

    Sayeb, S.; Ladhari, N.; Ben Hassen, M.; Sakli, F.

    Absorption, retention and strike through time, as evaluating criteria of absorbent structures quality were studied. Determination of influent parameters on these criteria were realized by using the design method of experimental sets. In this study, the studied parameters are: Super absorbent polymer (SAP)/fluff ratio, compression and the porosity of the non woven used as a cover stock. Absorption capacity and retention are mostly influenced by SAP/fluff ratio. However, strike through time is affected by compression. Thus, a modelling of these characteristics in function of the important parameter was established.

  1. Methods for absorbing neutrons

    DOEpatents

    Guillen, Donna P.; Longhurst, Glen R.; Porter, Douglas L.; Parry, James R.

    2012-07-24

    A conduction cooled neutron absorber may include a metal matrix composite that comprises a metal having a thermal neutron cross-section of at least about 50 barns and a metal having a thermal conductivity of at least about 1 W/cmK. Apparatus for providing a neutron flux having a high fast-to-thermal neutron ratio may include a source of neutrons that produces fast neutrons and thermal neutrons. A neutron absorber positioned adjacent the neutron source absorbs at least some of the thermal neutrons so that a region adjacent the neutron absorber has a fast-to-thermal neutron ratio of at least about 15. A coolant in thermal contact with the neutron absorber removes heat from the neutron absorber.

  2. Externally tuned vibration absorber

    DOEpatents

    Vincent, Ronald J.

    1987-09-22

    A vibration absorber unit or units are mounted on the exterior housing of a hydraulic drive system of the type that is powered from a pressure wave generated, e.g., by a Stirling engine. The hydraulic drive system employs a piston which is hydraulically driven to oscillate in a direction perpendicular to the axis of the hydraulic drive system. The vibration absorbers each include a spring or other resilient member having one side affixed to the housing and another side to which an absorber mass is affixed. In a preferred embodiment, a pair of vibration absorbers is employed, each absorber being formed of a pair of leaf spring assemblies, between which the absorber mass is suspended.

  3. The stereochemistry of chlorophyll-c₃ from the haptophyte Emiliania huxleyi: the (13²R)-enantiomers of chlorophylls-c are exclusively selected as the photosynthetically active pigments in chromophyte algae.

    PubMed

    Mizoguchi, Tadashi; Kimura, Yuki; Yoshitomi, Taichi; Tamiaki, Hitoshi

    2011-11-01

    Chlorophyll(Chl)-c pigments in algae, diatoms and some prokaryotes are characterized by the fully conjugated porphyrin π-system as well as the acrylate residue at the 17-position. The precise structural characterization of Chl-c(3) from the haptophyte Emiliania huxleyi was performed. The conformations of the π-conjugated peripheral substituents, the 3-/8-vinyl, 7-methoxycarbonyl and 17-acrylate moieties were evaluated, in a solution, using nuclear Overhauser enhancement correlations and molecular modeling calculations. The rotation of the 17-acrylate residue was considerably restricted, whereas the other three substituents readily rotated at ambient temperature. Moreover, the stereochemistry at the 13²-position was determined by combination of chiral high-performance liquid chromatography (HPLC) with circular dichroism (CD) spectroscopy. Compared with the CD spectra of the structurally related, synthetic (13²R)- and (13²S)-protochlorophyllide(PChlide)-a, naturally occurring Chl-c₃ had exclusively the (13²R)-configuration. To elucidate this natural selection of a single enantiomer, we analyzed the three major Chl-c pigments (Chl-c₁, c₂ and c₃) in four phylogenetically distinct classes of Chl-c containing algae, i.e., heterokontophyta, dinophyta, cryptophyta and haptophyta using chiral HPLC. All the photosynthetic organisms contained only the (13²R)-enantiomerically pure Chls-c, and lacked the corresponding enantiomeric (13²S)-forms. Additionally, Chl-c₂ was found in all the organisms as the common Chl-c. These results throw a light on the biosynthesis as well as photosynthetic function of Chl-c pigments: Chl-c₂ is derived from 8-vinyl-PChlide-a by dehydrogenation of the 17-propionate to acrylate residues as generally proposed, and the (13²R)-enantiomers of Chls-c function as photosynthetically active, light-harvesting pigments together with the principal Chl-a and carotenoids. PMID:21806961

  4. Photosynthetic approaches to chemical biotechnology.

    PubMed

    Desai, Shuchi H; Atsumi, Shota

    2013-12-01

    National interest and environmental advocates encourage alternatives to petroleum-based products. Besides biofuels, many other valuable chemicals used in every-day life are petroleum derivatives or require petroleum for their production. A plausible alternative to production using petroleum for chemical production is to harvest the abundant carbon dioxide resources in the environment to produce valuable hydrocarbons. Currently, efforts are being made to utilize a natural biological system, photosynthetic microorganisms, to perform this task. Photosynthetic microorganisms are attractive to use for biochemical production because they utilize economical resources for survival: sunlight and carbon dioxide. This review examines the various compounds produced by photosynthetic microorganisms.

  5. Mannose-6-Phosphate Reductase, a Key Enzyme in Photoassimilate Partitioning, Is Abundant and Located in the Cytosol of Photosynthetically Active Cells of Celery (Apium graveolens L.) Source Leaves.

    PubMed

    Everard, J. D.; Franceschi, V. R.; Loescher, W. H.

    1993-06-01

    Mannitol, a major photosynthetic product and transport carbohydrate in many plants, accounts for approximately 50% of the carbon fixed by celery (Apium graveolens L.) leaves. Previous subfractionation studies of celery leaves indicated that the enzymes for mannitol synthesis were located in the cytosol, but these data are inconsistent with that published for the sites of sugar alcohol synthesis in other families and taxa, including apple (Malus) and a brown alga (Fucus). Using antibodies to a key synthetic enzyme, NADPH-dependent mannose-6-phosphate reductase (M6PR), and immunocytochemical techniques, we have resolved both the inter-cellular and intracellular sites of mannitol synthesis. In leaves, M6PR was found only in cells containing ribulose-1,5-bisphosphate carboxylase/oxygenase. M6PR was almost exclusively cytosolic in these cells, with the nucleus being the only organelle to show labeling. The key step in transport carbohydrate biosynthesis that is catalyzed by M6PR displays no apparent preferential association with vascular tissues or with the bundle sheath. These results show that M6PR and, thus, mannitol synthesis are closely associated with the distribution of photosynthetic carbon metabolism in celery leaves. The principal role of M6PR is, therefore, in the assimilation of carbon being exported from the chloroplast, and it seems unlikely that this enzyme plays even an indirect role in phloem loading of mannitol.

  6. The biodistribution and dosimetry of {sup 117m}Sn DTPA with special emphasis on active marrow absorbed doses

    SciTech Connect

    Stubbs, J.; Atkins, H.

    1999-01-01

    {sup 117m}Sn(4+) DTPA is a new radiopharmaceutical for the palliation of pain associated with metastatic bone cancer. Recently, the Phase 2 clinical trials involving 47 patients were completed. These patients received administered activities in the range 6.7--10.6 MBq/kg of body mass. Frequent collections of urine were acquired over the first several hours postadministration and daily cumulative collections were obtained for the next 4--10 days. Anterior/posterior gamma camera images were obtained frequently over the initial 10 days. Radiation dose estimates were calculated for 8 of these patients. Each patient`s biodistribution data were mathematically simulated using a multicompartmental model. The model consisted of the following compartments: central, bone, kidney, other tissues, and cumulative urine. The measured cumulative urine data were used as references for the cumulative urine excretion compartment. The total-body compartment (sum of the bone surfaces, central, kidney, and other tissues compartments) was reference to all activity not excreted in the urine.

  7. Structural dynamics of phenylisothiocyanate in the light-absorbing excited states: Resonance Raman and complete active space self-consistent field calculation study

    NASA Astrophysics Data System (ADS)

    Ouyang, Bing; Xue, Jia-Dan; Zheng, Xuming; Fang, Wei-Hai

    2014-05-01

    The excited state structural dynamics of phenyl isothiocyanate (PITC) after excitation to the light absorbing S2(A'), S6(A'), and S7(A') excited states were studied by using the resonance Raman spectroscopy and complete active space self-consistent field method calculations. The UV absorption bands of PITC were assigned. The vibrational assignments were done on the basis of the Fourier transform (FT)-Raman and FT-infrared measurements, the density-functional theory computations, and the normal mode analysis. The A-, B-, and C-bands resonance Raman spectra in cyclohexane, acetonitrile, and methanol solvents were, respectively, obtained at 299.1, 282.4, 266.0, 252.7, 228.7, 217.8, and 208.8 nm excitation wavelengths to probe the corresponding structural dynamics of PITC. The results indicated that the structural dynamics in the S2(A'), S6(A'), and S7(A') excited states were very different. The conical intersection point CI(S2/S1) were predicted to play important role in the low-lying excited state decay dynamics. Two major decay channels were predicted for PITC upon excitation to the S2(A') state: the radiative S2,min → S0 transition and the nonradiative S2 → S1 internal conversion via CI(S2/S1). The differences in the decay dynamics between methyl isothiocyanate and PITC in the first light absorbing excited state were discussed. The role of the intersystem crossing point ISC(S1/T1) in the excited state decay dynamics of PITC is evaluated.

  8. Structural dynamics of phenylisothiocyanate in the light-absorbing excited states: Resonance Raman and complete active space self-consistent field calculation study

    SciTech Connect

    Ouyang, Bing Xue, Jia-Dan Zheng, Xuming E-mail: zxm@zstu.edu.cn; Fang, Wei-Hai E-mail: fangwh@dnu.edu.cn

    2014-05-21

    The excited state structural dynamics of phenyl isothiocyanate (PITC) after excitation to the light absorbing S{sub 2}(A′), S{sub 6}(A′), and S{sub 7}(A′) excited states were studied by using the resonance Raman spectroscopy and complete active space self-consistent field method calculations. The UV absorption bands of PITC were assigned. The vibrational assignments were done on the basis of the Fourier transform (FT)-Raman and FT-infrared measurements, the density-functional theory computations, and the normal mode analysis. The A-, B-, and C-bands resonance Raman spectra in cyclohexane, acetonitrile, and methanol solvents were, respectively, obtained at 299.1, 282.4, 266.0, 252.7, 228.7, 217.8, and 208.8 nm excitation wavelengths to probe the corresponding structural dynamics of PITC. The results indicated that the structural dynamics in the S{sub 2}(A′), S{sub 6}(A′), and S{sub 7}(A′) excited states were very different. The conical intersection point CI(S{sub 2}/S{sub 1}) were predicted to play important role in the low-lying excited state decay dynamics. Two major decay channels were predicted for PITC upon excitation to the S{sub 2}(A′) state: the radiative S{sub 2,min} → S{sub 0} transition and the nonradiative S{sub 2} → S{sub 1} internal conversion via CI(S{sub 2}/S{sub 1}). The differences in the decay dynamics between methyl isothiocyanate and PITC in the first light absorbing excited state were discussed. The role of the intersystem crossing point ISC(S{sub 1}/T{sub 1}) in the excited state decay dynamics of PITC is evaluated.

  9. Absorbed in the task: Personality measures predict engagement during task performance as tracked by error negativity and asymmetrical frontal activity.

    PubMed

    Tops, Mattie; Boksem, Maarten A S

    2010-12-01

    We hypothesized that interactions between traits and context predict task engagement, as measured by the amplitude of the error-related negativity (ERN), performance, and relative frontal activity asymmetry (RFA). In Study 1, we found that drive for reward, absorption, and constraint independently predicted self-reported persistence. We hypothesized that, during a prolonged monotonous task, absorption would predict initial ERN amplitudes, constraint would delay declines in ERN amplitudes and deterioration of performance, and drive for reward would predict left RFA when a reward could be obtained. Study 2, employing EEG recordings, confirmed our predictions. The results showed that most traits that have in previous research been related to ERN amplitudes have a relationship with the motivational trait persistence in common. In addition, trait-context combinations that are likely associated with increased engagement predict larger ERN amplitudes and RFA. Together, these results support the hypothesis that engagement may be a common underlying factor predicting ERN amplitude.

  10. Advanced neutron absorber materials

    DOEpatents

    Branagan, Daniel J.; Smolik, Galen R.

    2000-01-01

    A neutron absorbing material and method utilizing rare earth elements such as gadolinium, europium and samarium to form metallic glasses and/or noble base nano/microcrystalline materials, the neutron absorbing material having a combination of superior neutron capture cross sections coupled with enhanced resistance to corrosion, oxidation and leaching.

  11. OL3, a novel low-absorbed TGR5 agonist with reduced side effects, lowered blood glucose via dual actions on TGR5 activation and DPP-4 inhibition

    PubMed Central

    Ma, Shan-yao; Ning, Meng-meng; Zou, Qing-an; Feng, Ying; Ye, Yang-liang; Shen, Jian-hua; Leng, Ying

    2016-01-01

    Aim: TGR5 agonists stimulate intestinal glucagon-like peptide-1 (GLP-1) release, but systemic exposure causes unwanted side effects, such as gallbladder filling. In the present study, linagliptin, a DPP-4 inhibitor with a large molecular weight and polarity, and MN6, a previously described TGR5 agonist, were linked to produce OL3, a novel low-absorbed TGR5 agonist with reduced side-effects and dual function in lowering blood glucose by activation of TGR5 and inhibition of DPP-4. Methods: TGR5 activation was assayed in HEK293 cells stably expressing human or mouse TGR5 and a CRE-driven luciferase gene. DPP-4 inhibition was assessed based on the rate of hydrolysis of a surrogate substrate. GLP-1 secretion was measured in human enteroendocrine NCI-H716 cells. OL3 permeability was tested in Caco-2 cells. Acute glucose-lowering effects of OL3 were evaluated in ICR and diabetic ob/ob mice. Results: OL3 activated human and mouse TGR5 with an EC50 of 86.24 and 17.36 nmol/L, respectively, and stimulated GLP-1 secretion in human enteroendocrine NCI-H716 cells (3–30 μmol/L). OL3 inhibited human and mouse DPP-4 with IC50 values of 18.44 and 69.98 μmol/L, respectively. Low permeability of OL3 was observed in Caco-2 cells. In ICR mice treated orally with OL3 (150 mg/kg), the serum OL3 concentration was 101.10 ng/mL at 1 h, and decreased to 13.38 ng/mL at 5.5 h post dose, confirming the low absorption of OL3 in vivo. In ICR mice and ob/ob mice, oral administration of OL3 significantly lowered the blood glucose levels, which was a synergic effect of activating TGR5 that stimulated GLP-1 secretion in the intestine and inhibiting DPP-4 that cleaved GLP-1 in the plasma. In ICR mice, oral administration of OL3 did not cause gallbladder filling. Conclusion: OL3 is a low-absorbed TGR5 agonist that lowers blood glucose without inducing gallbladder filling. This study presents a new strategy in the development of potent TGR5 agonists in treating type 2 diabetes, which target to the

  12. Electrochemical and optical studies of model photosynthetic systems

    SciTech Connect

    Not Available

    1992-01-15

    The objective of this research is to obtain a better understanding of the relationship between the structural organization of photosynthetic pigments and their spectroscopic and electrochemical properties. Defined model systems were studied first. These included the least ordered (solutions) through the most highly ordered (Langmuir-Blodgett (LB) monolayers and self-assembled monolayers) systems containing BChl, BPheo, and UQ. Molecules other than the photosynthetic pigments and quinones were also examined, including chromophores (i.e. surface active cyanine dyes and phtahlocyanines) an redox active compounds (methyl viologen (MV) and surfactant ferrocenes), in order to develop the techniques needed to study the photosynthetic components. Because the chlorophylls are photosensitive and labile, it was easier first to develop procedures using stable species. Three different techniques were used to characterize these model systems. These included electrochemical techniques for determining the standard oxidation and reduction potentials of the photosynthetic components as well as methods for determining the heterogeneous electron transfer rate constants for BChl and BPheo at metal electrodes (Pt and Au). Resonance Raman (RR) and surface enhanced resonance Raman (SERR) spectroscopy were used to determine the spectra of the photosynthetic pigments and model compounds. SERRS was also used to study several types of photosynthetic preparations.

  13. GlnD Is Essential for NifA Activation, NtrB/NtrC-Regulated Gene Expression, and Posttranslational Regulation of Nitrogenase Activity in the Photosynthetic, Nitrogen-Fixing Bacterium Rhodospirillum rubrum

    PubMed Central

    Zhang, Yaoping; Pohlmann, Edward L.; Roberts, Gary P.

    2005-01-01

    GlnD is a bifunctional uridylyltransferase/uridylyl-removing enzyme and is thought to be the primary sensor of nitrogen status in the cell. It plays an important role in nitrogen assimilation and metabolism by reversibly regulating the modification of PII proteins, which in turn regulate a variety of other proteins. We report here the characterization of glnD mutants from the photosynthetic, nitrogen-fixing bacterium Rhodospirillum rubrum and the analysis of the roles of GlnD in the regulation of nitrogen fixation. Unlike glnD mutations in Azotobacter vinelandii and some other bacteria, glnD deletion mutations are not lethal in R. rubrum. Such mutants grew well in minimal medium with glutamate as the sole nitrogen source, although they grew slowly with ammonium as the sole nitrogen source (MN medium) and were unable to fix N2. The slow growth in MN medium is apparently due to low glutamine synthetase activity, because a ΔglnD strain with an altered glutamine synthetase that cannot be adenylylated can grow well in MN medium. Various mutation and complementation studies were used to show that the critical uridylyltransferase activity of GlnD is localized to the N-terminal region. Mutants with intermediate levels of uridylyltransferase activity are differentially defective in nif gene expression, the posttranslational regulation of nitrogenase, and NtrB/NtrC function, indicating the complexity of the physiological role of GlnD. These results have implications for the interpretation of results obtained with GlnD in many other organisms. PMID:15687189

  14. Is It Beneficial for the Major Photosynthetic Antenna Complex of Plants To Form Trimers?

    PubMed

    Janik, Ewa; Bednarska, Joanna; Zubik, Monika; Sowinski, Karol; Luchowski, Rafal; Grudzinski, Wojciech; Gruszecki, Wieslaw I

    2015-07-01

    The process of primary electric charge separation in photosynthesis takes place in the reaction centers, but photosynthesis can operate efficiently and fluently due to the activity of several pigment-protein complexes called antenna, which absorb light quanta and transfer electronic excitations toward the reaction centers. LHCII is the major photosynthetic pigment-protein antenna complex of plants and appears in the trimeric form. Several recent reports point to trimeric organization of LHCII as a key factor responsible for the chloroplast architecture via stabilization of granal organization of the thylakoid membranes. In the present work, we address the question of whether such an organization could also directly influence the antenna properties of this pigment-protein complex. Chlorophyll fluorescence analysis reveals that excitation energy transfer in LHCII is substantially more efficient in trimers and dissipative energy losses are higher in monomers. It could be concluded that trimers are exceptionally well suited to perform the antenna function. Possibility of fine regulation of the photosynthetic antenna function via the LHCII trimer-monomer transition is also discussed, based on the fluorescence lifetime analysis in a single chloroplast. PMID:26085037

  15. Modeling the dynamic modulation of light energy in photosynthetic algae.

    PubMed

    Papadakis, Ioannis A; Kotzabasis, Kiriakos; Lika, Konstadia

    2012-05-01

    An integrated cell-based dynamic mathematical model that take into account the role of the photon absorbing process, the partition of excitation energy, and the photoinactivation and repair of photosynthetic units, under variable light and dissolved inorganic carbon (DIC) availability is proposed. The modeling of the photon energy absorption and the energy dissipation is based on the photoadaptive changes of the underlying mechanisms. The partition of the excitation energy is based on the relative availability of light and DIC to the cell. The modeling of the photoinactivation process is based on the common aspect that it occurs under any light intensity and the modeling of the repair process is based on the evidence that it is controlled by chloroplast and nuclear-encoded enzymes. The present model links the absorption of photons and the partitioning of excitation energy to the linear electron flow and other quenchers with chlorophyll fluorescence emission parameters, and the number of the functional photosynthetic units with the photosynthetic oxygen production rate. The energy allocation to the LEF increases as DIC availability increases and/or light intensity decreases. The rate of rejected energy increases with light intensity and with DIC availability. The resulting rate coefficient of photoinactivation increases as light intensity and/or as DIC concentration increases. We test the model against chlorophyll fluorescence induction and photosynthetic oxygen production rate measurements, obtained from cultures of the unicellular green alga Scenedesmus obliquus, and find a very close quantitative and qualitative correspondence between predictions and data.

  16. Differences in the Photosynthetic Activity of C3 and C4 Graminoids in Short-Hydroperiod Marl Prairies of the Florida Everglades: Responses to Seasonality and Water Management

    NASA Astrophysics Data System (ADS)

    Oberbauer, S. F.; Olivas, P. C.; Schedlbauer, J. L.; Moser, J.

    2011-12-01

    Short hydroperiod marsh of the Everglades is dominated by a mix of sawgrass (Cladium jamaicense, a C3 sedge) and Muhly grass (Muhlenbergia capillaris, a C4 grass). Although the Everglades are located in a subtropical region, the climate is classified as tropical with distinct annual rainy and dry seasons during the summer and winter, respectively. Water levels in marl prairies vary greatly over the year driven by seasonality of rainfall, but are modified strongly by water management practices. As a result, the rainy season and period of inundation generally do not completely coincide. Water tables fall as much as 80 cm below the surface for approximately 6-7 months starting about December/January and reach up to 40 cm above the surface during the inundation period. Eddy covariance studies from this habitat revealed strong reductions in CO2 uptake coinciding with water tables inundating the surface. Submersion of macrophyte leaf area accounts for some of the reduction. To test if changes in leaf physiology also contribute to this reduced ecosystem CO2 uptake, we measured maximum assimilation rates (Amax) of the dominant species during both seasons in the marsh and on a nearby levee that remains above water. Typical of C4 plants, Amax of Muhlenbergia were high, > 20 μmol m-2 s-1, during the dry season. However when plant crowns were submerged, photosynthetic rates of emergent leaves of Muhlenbergia were strongly reduced to near compensation in some cases. In contrast, Amax of Muhlenbergia measured from higher terrain within 30 m of the flooded sites maintained high rates. Rates of Cladium were lower overall but did not show strong seasonality at either site. This wetland represents an unusual situation in which one of the codominants is effectively photosynthetically inactive during wet season. Planned changes to increase water flow to the Everglades and predicted changes in rainfall with climate change will strongly affect the carbon balance of this habitat.

  17. UV254 absorbance as real-time monitoring and control parameter for micropollutant removal in advanced wastewater treatment with powdered activated carbon.

    PubMed

    Altmann, Johannes; Massa, Lukas; Sperlich, Alexander; Gnirss, Regina; Jekel, Martin

    2016-05-01

    This study investigates the applicability of UV absorbance measurements at 254 nm (UVA254) to serve as a simple and reliable surrogate parameter to monitor and control the removal of organic micropollutants (OMPs) in advanced wastewater treatment applying powdered activated carbon (PAC). Correlations between OMP removal and corresponding UVA254 reduction were determined in lab-scale adsorption batch tests and successfully applied to a pilot-scale PAC treatment stage to predict OMP removals in aggregate samples with good accuracy. Real-time UVA254 measurements were utilized to evaluate adapted PAC dosing strategies and proved to be effective for online monitoring of OMP removal. Furthermore, active PAC dosing control according to differential UVA254 measurements was implemented and tested. While precise removal predictions based on real-time measurements were not accurate for all OMPs, UVA254-controlled dynamic PAC dosing was capable of achieving stable OMP removals. UVA254 can serve as an effective surrogate parameter for OMP removal in technical PAC applications. Even though the applicability as control parameter to adjust PAC dosing to water quality changes might be limited to applications with fast response between PAC adjustment and adsorptive removal (e.g. direct filtration), UVA254 measurements can also be used to monitor the adsorption efficiency in more complex PAC applications. PMID:26963606

  18. Photosynthetic carbon metabolism in Enteromorpha compressa (Chlorophyta)

    SciTech Connect

    Beer, S.; Shragge, B.

    1987-12-01

    The intertidal macroalga Enteromorpha compressa showed the ability to use HCO/sub 3//sup -/, as an exogenous inorganic carbon (Ci) source for photosynthesis. However, although the natural sea water concentration of this carbon form was saturating, additional CO/sub 2/ above ambient Ci levels doubled net photosynthetic rates. Therefore, the productivity of this alga, when submerged, is likely to be limited by Ci. When plants were exposed to air, photosynthetic rates saturated at air-levels of CO/sub 2/ during mild desiccation. Based on carbon fixing enzyme activities and Ci pulse-chase incorporation patterns, it was found that Enteromorpha is a C/sub 3/ plant. However, this alga did not show O/sub 2/ inhibited photosynthetic rates at natural sea water Ci conditions. It is suggested that such a C/sub 4/-like gas exchange response is due to the HCO/sub 3//sup -/ utilization system concentrating CO/sub 2/ intracellularly, thus alleviating apparent photorespiration.

  19. Internal absorber solar collector

    DOEpatents

    Sletten, Carlyle J.; Herskovitz, Sheldon B.; Holt, F. S.; Sletten, E. J.

    1981-01-01

    Thin solar collecting panels are described made from arrays of small rod collectors consisting of a refracting dielectric rod lens with an absorber imbedded within it and a reflecting mirror coated on the back side of the dielectric rod. Non-tracking collector panels on vertical walls or roof tops receive approximately 90% of solar radiation within an acceptance zone 60.degree. in elevation angle by 120.degree. or more in the azimuth sectors with a collector concentration ratio of approximately 3.0. Miniaturized construction of the circular dielectric rods with internal absorbers reduces the weight per area of glass, plastic and metal used in the collector panels. No external parts or insulation are needed as heat losses are low due to partial vacuum or low conductivity gas surrounding heated portions of the collector. The miniature internal absorbers are generally made of solid copper with black selective surface and the collected solar heat is extracted at the collector ends by thermal conductivity along the absorber rods. Heat is removed from end fittings by use of liquid circulants. Several alternate constructions are provided for simplifying collector panel fabrication and for preventing the thermal expansion and contraction of the heated absorber or circulant tubes from damaging vacuum seals. In a modified version of the internal absorber collector, oil with temperature dependent viscosity is pumped through a segmented absorber which is now composed of closely spaced insulated metal tubes. In this way the circulant is automatically diverted through heated portions of the absorber giving higher collector concentration ratios than theoretically possible for an unsegmented absorber.

  20. Lipid-absorbing Polymers

    NASA Technical Reports Server (NTRS)

    Marsh, H. E., Jr.; Wallace, C. J.

    1973-01-01

    The removal of bile acids and cholesterol by polymeric absorption is discussed in terms of micelle-polymer interaction. The results obtained with a polymer composed of 75 parts PEO and 25 parts PB plus curing ingredients show an absorption of 305 to 309%, based on original polymer weight. Particle size effects on absorption rate are analyzed. It is concluded that crosslinked polyethylene oxide polymers will absorb water, crosslinked polybutadiene polymers will absorb lipids; neither polymer will absorb appreciable amounts of lipids from micellar solutions of lipids in water.

  1. Regulation of the photosynthetic apparatus under fluctuating growth light.

    PubMed

    Tikkanen, Mikko; Grieco, Michele; Nurmi, Markus; Rantala, Marjaana; Suorsa, Marjaana; Aro, Eva-Mari

    2012-12-19

    Safe and efficient conversion of solar energy to metabolic energy by plants is based on tightly inter-regulated transfer of excitation energy, electrons and protons in the photosynthetic machinery according to the availability of light energy, as well as the needs and restrictions of metabolism itself. Plants have mechanisms to enhance the capture of energy when light is limited for growth and development. Also, when energy is in excess, the photosynthetic machinery slows down the electron transfer reactions in order to prevent the production of reactive oxygen species and the consequent damage of the photosynthetic machinery. In this opinion paper, we present a partially hypothetical scheme describing how the photosynthetic machinery controls the flow of energy and electrons in order to enable the maintenance of photosynthetic activity in nature under continual fluctuations in white light intensity. We discuss the roles of light-harvesting II protein phosphorylation, thermal dissipation of excess energy and the control of electron transfer by cytochrome b(6)f, and the role of dynamically regulated turnover of photosystem II in the maintenance of the photosynthetic machinery. We present a new hypothesis suggesting that most of the regulation in the thylakoid membrane occurs in order to prevent oxidative damage of photosystem I.

  2. Pigment oligomers as natural and artificial photosynthetic antennas

    SciTech Connect

    Blankenship, R.E.

    1996-12-31

    Green photosynthetic bacteria contain antenna complexes known as chlorosomes. These complexes are appressed to the cytoplasmic side of the inner cell membrane and function to absorb light and transfer the energy to the photochemical reaction center, where photochemical energy storage takes place. Chlorosomes differ from all other known photosynthetic antenna complexes in that the geometrical arrangement of pigments is determined primarily by pigment-pigment interactions instead of pigment-protein interactions. The bacteriochlorophyll c, d or e pigments found in chlorosomes form large oligomers with characteristic spectral properties significantly perturbed from those exhibited by monomeric pigments. Because of their close spatial interaction, the pigments are thought to be strongly coupled electronically, and many of the optical properties result from exciton interactions. This presentation will summarize existing knowledge on the chemical composition and properties of chlorosomes, the evidence for the oligomeric nature of chlorosome pigment organization and proposed structures for the oligomers, and the kinetics and mechanisms of energy transfer in chlorosomes.

  3. Hydrogen production by photosynthetic microorganisms

    SciTech Connect

    Akano, T.; Fukatsu, K.; Miyasaka, H. |

    1996-12-31

    Hydrogen is a clean energy alternative to the fossil fuels, the main source of greenhouse gas emissions. We developed a stable system for the conversion of solar energy into hydrogen using photosynthetic microorganisms. Our system consists of the following three stages: (1) Photosynthetic starch accumulation in green microalgae (400 L x2); (2) Dark anaerobic fermentation of the algal starch biomass to produce hydrogen and organic compounds (155 L x2); and (3) Further conversion of the organic compounds to produce hydrogen using photosynthetic bacteria (three types of reactors, parallel plate, raceway, and tubular). We constructed a test plant of this process at Nankoh power plant of Kansai Electric Power Company in Osaka, Japan, and carried out a series of tests using CO{sub 2} obtained from a chemical absorption pilot-plant. The photobiological hydrogen production process used a combination of a marine alga, Chlamydomonas sp. MGA 161 and marine photosynthetic bacterium, Rhodopseudomonas sp. W-1S. The dark anaerobic fermentation of algal starch biomass was also investigated. Sustained and stable starch accumulation, starch degradation in the algal cell, and hydrogen production from algal fermentation and photosynthetic bacteria in the light were demonstrated during several experiments. 3 refs., 12 figs., 1 tab.

  4. Synthesis of eucalyptus/tea tree oil absorbed biphasic calcium phosphate-PVDF polymer nanocomposite films: a surface active antimicrobial system for biomedical application.

    PubMed

    Bagchi, Biswajoy; Banerjee, Somtirtha; Kool, Arpan; Thakur, Pradip; Bhandary, Suman; Hoque, Nur Amin; Das, Sukhen

    2016-06-22

    A biocompatible poly(vinylidene) difluoride (PVDF) based film has been prepared by in situ precipitation of calcium phosphate precursors. Such films were surface absorbed with two essential oils namely eucalyptus and tea tree oil. Physico-chemical characterization of the composite film revealed excellent stability of the film with 10% loading of oils in the PVDF matrix. XRD, FTIR and FESEM measurements confirmed the presence of hydroxyapatite and octacalcium phosphate in the PVDF matrix which showed predominantly β phase. Strong bactericidal activity was observed with very low minimum bactericidal concentration (MBC) values on both E. coli and S. aureus. The composite films also resisted biofilm formation as observed by FESEM. The release of essential oils from the film showed an initial burst followed by a very slow release over a period of 24 hours. Antibacterial action of the film was found to be primarily due to the action of essential oils which resulted in leakage of vital fluids from the microorganisms. Both necrotic and apoptotic morphologies were observed in bacterial cells. Biocompatibility studies with the composite films showed negligible cytotoxicity to mouse mesenchymal and myoblast cells at MBC concentration.

  5. Fall of blood ionized calcium on watching a provocative TV program and its prevention by active absorbable algal calcium (AAA Ca).

    PubMed

    Fujita, T; Ohgitani, S; Nomura, M

    1999-01-01

    In December 1997, more than 680 children developed convulsive seizures while watching a notorious audiovisually provocative TV program, "Pocket Monster." Emotional stimulation via hyperventilation may cause respiratory alkalosis, fall of blood ionized calcium (Ca), and sensitization of the nervous system to excessive emotional stress. A study was therefore undertaken to follow the changes of blood ionized Ca in eight healthy volunteers after watching the "Pocket Monster" and also a quiet program, "Classical Music," as a control for 20min from 4 P.M. Although neither marked hyperventilation nor convulsions developed in any of these adult volunteers, blood ionized Ca showed a significantly more pronounced fall during and after watching "Pocket Monster," and their plasma intact parathyroid hormone (iPTH) was significantly higher 120min after the beginning of "Pocket Monster" than the "Classical Music" program. Plasma total Ca, pH, and albumin were free of detectable changes. Ingestion of 600mg Ca as active absorbable algal Ca (AAA Ca) with high bioavailability completely prevented the fall of ionized Ca and suppressed iPTH. Plama osteocalcin was also significantly suppressed after ingestion of AAA Ca. It may be worthwhile to ingest AAA Ca before anticipated emotional stress such as watching a provocative TV program to prevent possible neuromuscular instability. PMID:10340641

  6. Synthesis of eucalyptus/tea tree oil absorbed biphasic calcium phosphate-PVDF polymer nanocomposite films: a surface active antimicrobial system for biomedical application.

    PubMed

    Bagchi, Biswajoy; Banerjee, Somtirtha; Kool, Arpan; Thakur, Pradip; Bhandary, Suman; Hoque, Nur Amin; Das, Sukhen

    2016-06-22

    A biocompatible poly(vinylidene) difluoride (PVDF) based film has been prepared by in situ precipitation of calcium phosphate precursors. Such films were surface absorbed with two essential oils namely eucalyptus and tea tree oil. Physico-chemical characterization of the composite film revealed excellent stability of the film with 10% loading of oils in the PVDF matrix. XRD, FTIR and FESEM measurements confirmed the presence of hydroxyapatite and octacalcium phosphate in the PVDF matrix which showed predominantly β phase. Strong bactericidal activity was observed with very low minimum bactericidal concentration (MBC) values on both E. coli and S. aureus. The composite films also resisted biofilm formation as observed by FESEM. The release of essential oils from the film showed an initial burst followed by a very slow release over a period of 24 hours. Antibacterial action of the film was found to be primarily due to the action of essential oils which resulted in leakage of vital fluids from the microorganisms. Both necrotic and apoptotic morphologies were observed in bacterial cells. Biocompatibility studies with the composite films showed negligible cytotoxicity to mouse mesenchymal and myoblast cells at MBC concentration. PMID:27271864

  7. Conformationally Constrained Macrocyclic Diporphyrin-Fullerene Artificial Photosynthetic Reaction Center

    SciTech Connect

    Garg, Vikas; Kodis, Gerdenis; Chachisvilis, Mirianas; Hambourger, Michael; Moore, Ana L.; Moore, Thomas A.; Gust, Devens

    2011-02-14

    Photosynthetic reaction centers convert excitation energy from absorbed sunlight into chemical potential energy in the form of a charge-separated state. The rates of the electron transfer reactions necessary to achieve long-lived, high-energy charge-separated states with high quantum yields are determined in part by precise control of the electronic coupling among the chromophores, donors, and acceptors and of the reaction energetics. Successful artificial photosynthetic reaction centers for solar energy conversion have similar requirements. Control of electronic coupling in particular necessitates chemical linkages between active component moieties that both mediate coupling and restrict conformational mobility so that only spatial arrangements that promote favorable coupling are populated. Toward this end, we report the synthesis, structure, and photochemical properties of an artificial reaction center containing two porphyrin electron donor moieties and a fullerene electron acceptor in a macrocyclic arrangement involving a ring of 42 atoms. The two porphyrins are closely spaced, in an arrangement reminiscent of that of the special pair in bacterial reaction centers. The molecule is produced by an unusual cyclization reaction that yields mainly a product with C2 symmetry and trans-2 disubstitution at the fullerene. The macrocycle maintains a rigid, highly constrained structure that was determined by UV-vis spectroscopy, NMR, mass spectrometry, and molecular modeling at the semiempirical PM6 and DFT (B3LYP/6-31G**) levels. Transient absorption results for the macrocycle in 2-methyltetrahydrofuran reveal photoinduced electron transfer from the porphyrin first excited singlet state to the fullerene to form a P•--C60•--P charge separated state with a time constant of 1.1 ps. Photoinduced electron transfer to the fullerene excited singlet state to form the same charge-separated state has a time constant of 15 ps. The

  8. System Responses to Equal Doses of Photosynthetically Usable Radiation of Blue, Green, and Red Light in the Marine Diatom Phaeodactylum tricornutum

    PubMed Central

    Valle, Kristin Collier; Nymark, Marianne; Aamot, Inga; Hancke, Kasper; Winge, Per; Andresen, Kjersti; Johnsen, Geir; Brembu, Tore; Bones, Atle M.

    2014-01-01

    Due to the selective attenuation of solar light and the absorption properties of seawater and seawater constituents, free-floating photosynthetic organisms have to cope with rapid and unpredictable changes in both intensity and spectral quality. We have studied the transcriptional, metabolic and photo-physiological responses to light of different spectral quality in the marine diatom Phaeodactylum tricornutum through time-series studies of cultures exposed to equal doses of photosynthetically usable radiation of blue, green and red light. The experiments showed that short-term differences in gene expression and profiles are mainly light quality-dependent. Transcription of photosynthesis-associated nuclear genes was activated mainly through a light quality-independent mechanism likely to rely on chloroplast-to-nucleus signaling. In contrast, genes encoding proteins important for photoprotection and PSII repair were highly dependent on a blue light receptor-mediated signal. Changes in energy transfer efficiency by light-harvesting pigments were spectrally dependent; furthermore, a declining trend in photosynthetic efficiency was observed in red light. The combined results suggest that diatoms possess a light quality-dependent ability to activate photoprotection and efficient repair of photodamaged PSII. In spite of approximately equal numbers of PSII-absorbed quanta in blue, green and red light, the spectral quality of light is important for diatom responses to ambient light conditions. PMID:25470731

  9. Arsenic biomethylation by photosynthetic organisms

    PubMed Central

    Ye, Jun; Rensing, Christopher; Rosen, Barry P.; Zhu, Yong-Guan

    2013-01-01

    Arsenic (As) is a ubiquitous element that is widespread in the environment and causes numerous health problems. Biomethylation of As has implications for its mobility and toxicity. Photosynthetic organisms may play a significant role in As geochemical cycling by methylating it to different As species, but little is known about the mechanisms of methylation. Methylated As species have been found in many photosynthetic organisms, and several arsenite S-adenosylmethionine (SAM) methyltransferases have been characterized in cyanobacteria and algae. However, higher plants may not have the ability to methylate As. Instead, methylated arsenicals in plants probably originate from microorganisms in soils and the rhizosphere. Here, we propose possible approaches for developing ‘smart’ photosynthetic organisms with an enhanced and sensitive biomethylation capacity for bioremediation and safer food. PMID:22257759

  10. Tectonics and the photosynthetic habitable zone (Invited)

    NASA Astrophysics Data System (ADS)

    Sleep, N. H.

    2009-12-01

    The traditional habitable zone lies between an inner stellar radius where the surface of the planet becomes too hot for liquid water carbon-based life and on outer radius, where the surface freezes. It is effectively the zone where photosynthesis is feasible. The concept extends to putative life on objects with liquid methane at the surface, like Titan. As a practical matter, photosynthesis leaves detectable biosignatures in the geological record; black shale on the Earth indicates that sulfide and probably FeO based photosynthesis existed by 3.8 Ga. The hard crustal rocks and the mantle sequester numerous photosynthetic biosignatures. Photosynthesis can produce detectable free oxygen with ozone in the atmosphere of extrasolar planets. In contrast, there is no outer limit for subsurface life in large silicate objects. Pre-photosynthetic niches are dependable but meager and not very detectable at great antiquity or great distance, with global productivity less than 1e-3 of the photosynthetic ones. Photosynthetic organisms have bountiful energy that modifies their surface environment and even tectonics. For example, metamorphic rocks formed at the expense of thick black shale are highly radioactive and hence self-fluxing. Active tectonics with volcanism and metamorphism prevents volatiles from being sequestered in the subsurface as on Mars. A heat-pipe object, like a larger Io, differs from the Earth in that the volatiles return to the deep interior distributed within massive volcanic deposits rather than concentrated in the shallow oceanic crust. One the Earth, the return of water to the surface by arc volcanoes controls its mantle abundance at the transition between behaving as a trace element and behaving as a major element that affects melting. The ocean accumulates the water that the mantle and crust do not take. The Earth has the “right” amount of water that erosion/deposition and tectonics both tend to maintain near sea level surfaces. The mantle contains

  11. Comparison of UV-absorbing nets in pepper crops: spectral properties, effects on plants and pest control.

    PubMed

    Legarrea, Saioa; Karnieli, Arnon; Fereres, Alberto; Weintraub, Phyllis G

    2010-01-01

    In horticultural crops, the use of screens to protect plants is the usual strategy in the Mediterranean area. Screen manufacturers offer a range of netting that vary in their UV-absorbing properties. We compared the photoeffects of seven different screens. Sweet pepper trials were conducted at the Gilat Research Center, Israel, where the spectral properties of the nets and their influence on pest infestation and crop development were evaluated. UV transmittance varied among the materials studied ranging from 40% to 70% of the incident radiation. BioNet white and P-Optinet, which absorbed and reflected the highest amount of UV radiation, performed the best protection against the main pepper pest (thrips, whiteflies and broad mites). Spectral measurements also showed that the photosynthetically active radiation differentially penetrated the nets, which together with the amount of UV absorbed by the screenings, resulted in a range of plant height and chlorophyll content. A global understanding of the UV-absorbing nets' effect on pepper crops and their pests was evaluated in this work because of the importance of these screens to integrated pest management and sustainable agriculture production.

  12. Spectropolarimetry of Photosynthetic Pigments as Global Surface Biosignatures

    NASA Astrophysics Data System (ADS)

    Sparks, W. B.; Parenteau, M. N.; Blankenship, R. E.; Germer, T. A.; Meadows, V. S.; Telesco, C. M.

    2015-12-01

    Photosynthesis is an ancient metabolic process on the early Earth. The most primitive phototrophs used reductants such as H2, H2S, and Fe(II) and were widespread in marine, intertidal, and likely continental habitats. These anoxygenic phototrophs were the key primary producers for the first ~1 billion years before the evolution of oxygenic photosynthesis at 2.7 Ga. The potential clearly exists for this type of primitive photosynthesis to operate on habitable exoplanets. Anoxygenic phototrophs are not known to emit gases that are uniquely biogenic in origin, so we focus on surface pigments signatures as having the strongest promise to offer identifiable biosignatures for a pre-oxygenic habitable exoplanet. Following our earlier work that showed photosynthetic cyanobacteria yield a polarization signature potentially useful in remote sensing, here we seek to characterize the remotely detectable polarization biosignatures associated with anoxygenic phototrophs. The six major pigments of anoxygenic phototrophs (bacteriochlorophylls [Bchls]) absorb in the near-infrared (NIR) from ~705 - 1040 nm. The lower symmetry of the pigment structure relative to chlorophylls shifts the energy absorption bands to longer wavelengths. As a result, Bchls are well suited to absorbing the relatively higher flux of red and NIR radiation of M dwarf stars, the most abundant type of star in the Galaxy, as well as the plentiful flux of typical main sequence stars. Homochirality is a powerful biosignature, and because of the optical activity of biological molecules, it can, in principle, be remotely observed on macroscopic scales using circular polarization spectroscopy. Bchls and Chls are optically active molecules with several chiral centers, strongly interacting with the incident light. We measured the reflectance and transmission full Stokes polarization spectra of pure cultures of anoxygenic phototrophs and environmental samples of microbial mats, and found strong correlations between

  13. Unidirectional perfect absorber

    PubMed Central

    Jin, L.; Wang, P.; Song, Z.

    2016-01-01

    This study proposes a unidirectional perfect absorber (UPA), which we realized with a two-arm Aharonov-Bohm interferometer, that consists of a dissipative resonator side-coupled to a uniform resonator array. The UPA has reflection-less full absorption on one direction, and reflectionless full transmission on the other, with an appropriate magnetic flux and coupling, detuning, and loss of the side-coupled resonator. The magnetic flux controls the transmission, the left transmission is larger for magnetic flux less than one-half flux quantum; and the right transmission is larger for magnetic flux between one-half and one flux quantum. Besides, a perfect absorber (PA) can be realized based on the UPA, in which light waves from both sides, with arbitrary superposition of the ampli- tude and phase, are perfectly absorbed. The UPA is expected to be useful in the design of novel optical devices. PMID:27615125

  14. Unidirectional perfect absorber

    NASA Astrophysics Data System (ADS)

    Jin, L.; Wang, P.; Song, Z.

    2016-09-01

    This study proposes a unidirectional perfect absorber (UPA), which we realized with a two-arm Aharonov-Bohm interferometer, that consists of a dissipative resonator side-coupled to a uniform resonator array. The UPA has reflection-less full absorption on one direction, and reflectionless full transmission on the other, with an appropriate magnetic flux and coupling, detuning, and loss of the side-coupled resonator. The magnetic flux controls the transmission, the left transmission is larger for magnetic flux less than one-half flux quantum; and the right transmission is larger for magnetic flux between one-half and one flux quantum. Besides, a perfect absorber (PA) can be realized based on the UPA, in which light waves from both sides, with arbitrary superposition of the ampli- tude and phase, are perfectly absorbed. The UPA is expected to be useful in the design of novel optical devices.

  15. Unidirectional perfect absorber.

    PubMed

    Jin, L; Wang, P; Song, Z

    2016-01-01

    This study proposes a unidirectional perfect absorber (UPA), which we realized with a two-arm Aharonov-Bohm interferometer, that consists of a dissipative resonator side-coupled to a uniform resonator array. The UPA has reflection-less full absorption on one direction, and reflectionless full transmission on the other, with an appropriate magnetic flux and coupling, detuning, and loss of the side-coupled resonator. The magnetic flux controls the transmission, the left transmission is larger for magnetic flux less than one-half flux quantum; and the right transmission is larger for magnetic flux between one-half and one flux quantum. Besides, a perfect absorber (PA) can be realized based on the UPA, in which light waves from both sides, with arbitrary superposition of the ampli- tude and phase, are perfectly absorbed. The UPA is expected to be useful in the design of novel optical devices. PMID:27615125

  16. Mechanical energy absorber

    NASA Technical Reports Server (NTRS)

    Wesselski, Clarence J. (Inventor)

    1993-01-01

    An energy absorbing system for controlling the force where a moving object engages a stationary stop and where the system utilized telescopic tubular members, energy absorbing diaphragm elements, force regulating disc springs, and a return spring to return the telescoping member to its start position after stroking is presented. The energy absorbing system has frusto-conical diaphragm elements frictionally engaging the shaft and are opposed by a force regulating set of disc springs. In principle, this force feedback mechanism serves to keep the stroking load at a reasonable level even if the friction coefficient increases greatly. This force feedback device also serves to desensitize the singular and combined effects of manufacturing tolerances, sliding surface wear, temperature changes, dynamic effects, and lubricity.

  17. Unidirectional perfect absorber.

    PubMed

    Jin, L; Wang, P; Song, Z

    2016-09-12

    This study proposes a unidirectional perfect absorber (UPA), which we realized with a two-arm Aharonov-Bohm interferometer, that consists of a dissipative resonator side-coupled to a uniform resonator array. The UPA has reflection-less full absorption on one direction, and reflectionless full transmission on the other, with an appropriate magnetic flux and coupling, detuning, and loss of the side-coupled resonator. The magnetic flux controls the transmission, the left transmission is larger for magnetic flux less than one-half flux quantum; and the right transmission is larger for magnetic flux between one-half and one flux quantum. Besides, a perfect absorber (PA) can be realized based on the UPA, in which light waves from both sides, with arbitrary superposition of the ampli- tude and phase, are perfectly absorbed. The UPA is expected to be useful in the design of novel optical devices.

  18. Long-term and short-term responses of the photosynthetic electron transport to fluctuating light.

    PubMed

    Kono, Masaru; Terashima, Ichiro

    2014-08-01

    Light energy absorbed by chloroplasts drives photosynthesis. When absorbed light is in excess, the thermal dissipation systems of excess energy are induced and the photosynthetic electron flow is regulated, both contributing to suppression of reactive oxygen species production and photodamages. Various regulation mechanisms of the photosynthetic electron flow and energy dissipation systems have been revealed. However, most of such knowledge has been obtained by the experiments conducted under controlled conditions with constant light, whereas natural light condition is drastically fluctuated. To understand photosynthesis in nature, we need to clarify not only the mechanisms that raise photosynthetic efficiency but those for photoprotection in fluctuating light. Although these mechanisms appear to be well balanced, regulatory mechanisms achieving the balance is little understood. Recently, some pioneering studies have provided new insight into the regulatory mechanisms in fluctuating light. In this review, firstly, the possible mechanisms involved in regulation of the photosynthetic electron flow in fluctuating light are presented. Next, we introduce some recent studies focusing on the photosynthetic electron flow in fluctuating light. Finally, we discuss how plants effectively cope with fluctuating light showing our recent results.

  19. Can a Satellite-Derived Estimate of the Fraction of PAR Absorbed by Chlorophyll (FAPAR(sub chl)) Improve Predictions of Light-Use Efficiency and Ecosystem Photosynthesis for a Boreal Aspen Forest?

    NASA Technical Reports Server (NTRS)

    Zhang, Qingyuan; Middleton, Elizabeth M.; Margolis, Hank A.; Drolet, Guillaume G.; Barr, Alan A.; Black, T. Andrew

    2009-01-01

    Gross primary production (GPP) is a key terrestrial ecophysiological process that links atmospheric composition and vegetation processes. Study of GPP is important to global carbon cycles and global warming. One of the most important of these processes, plant photosynthesis, requires solar radiation in the 0.4-0.7 micron range (also known as photosynthetically active radiation or PAR), water, carbon dioxide (CO2), and nutrients. A vegetation canopy is composed primarily of photosynthetically active vegetation (PAV) and non-photosynthetic vegetation (NPV; e.g., senescent foliage, branches and stems). A green leaf is composed of chlorophyll and various proportions of nonphotosynthetic components (e.g., other pigments in the leaf, primary/secondary/tertiary veins, and cell walls). The fraction of PAR absorbed by whole vegetation canopy (FAPAR(sub canopy)) has been widely used in satellite-based Production Efficiency Models to estimate GPP (as a product of FAPAR(sub canopy)x PAR x LUE(sub canopy), where LUE(sub canopy) is light use efficiency at canopy level). However, only the PAR absorbed by chlorophyll (a product of FAPAR(sub chl) x PAR) is used for photosynthesis. Therefore, remote sensing driven biogeochemical models that use FAPAR(sub chl) in estimating GPP (as a product of FAPAR(sub chl x PAR x LUE(sub chl) are more likely to be consistent with plant photosynthesis processes.

  20. Regulatory RNAs in photosynthetic cyanobacteria.

    PubMed

    Kopf, Matthias; Hess, Wolfgang R

    2015-05-01

    Regulatory RNAs play versatile roles in bacteria in the coordination of gene expression during various physiological processes, especially during stress adaptation. Photosynthetic bacteria use sunlight as their major energy source. Therefore, they are particularly vulnerable to the damaging effects of excess light or UV irradiation. In addition, like all bacteria, photosynthetic bacteria must adapt to limiting nutrient concentrations and abiotic and biotic stress factors. Transcriptome analyses have identified hundreds of potential regulatory small RNAs (sRNAs) in model cyanobacteria such as Synechocystis sp. PCC 6803 or Anabaena sp. PCC 7120, and in environmentally relevant genera such as Trichodesmium, Synechococcus and Prochlorococcus. Some sRNAs have been shown to actually contain μORFs and encode short proteins. Examples include the 40-amino-acid product of the sml0013 gene, which encodes the NdhP subunit of the NDH1 complex. In contrast, the functional characterization of the non-coding sRNA PsrR1 revealed that the 131 nt long sRNA controls photosynthetic functions by targeting multiple mRNAs, providing a paradigm for sRNA functions in photosynthetic bacteria. We suggest that actuatons comprise a new class of genetic elements in which an sRNA gene is inserted upstream of a coding region to modify or enable transcription of that region.

  1. Photosynthetic reaction centers in bacteria

    SciTech Connect

    Norris, J.R. Univ. of Chicago, IL ); Schiffer, M. )

    1990-07-30

    The photochemistry of photosynthesis begins in complexes called reaction centers. These have become model systems to study the fundamental process by which plants and bacteria convert and store solar energy as chemical free energy. In green plants, photosynthesis occurs in two systems, each of which contains a different reaction center, working in series. In one, known as photosystem 1, oxidized nicotinamide adenine dinucleotide phosphate (NADP[sup +]) is reduced to NADPH for use in a series of dark reactions called the Calvin cycle, named for Nobel Laureate Melvin Calvin, by which carbon dioxide is converted into useful fuels such as carbohydrates and sugars. In the other half of the photosynthetic machinery of green plants, called photosystem 2, water is oxidized to produce molecular oxygen. A different form of photosynthesis occurs in photosynthetic bacteria, which typically live at the bottom of ponds and feed on organic debris. Two main types of photosynthetic bacteria exist: purple and green. Neither type liberates oxygen from water. Instead, the bacteria feed on organic media or inorganic materials, such as sulfides, which are easier to reduce or oxidize than carbon dioxide or water. Perhaps in consequence, their photosynthetic machinery is simpler than that of green, oxygen-evolving plants and their primary photochemistry is better understood.

  2. Flash spectroscopic characterization of photosynthetic electron transport in isolated heterocysts

    SciTech Connect

    Houchins, J.P.; Hind, G.

    1983-07-01

    Electron transport was studied in heterocysts of the filamentous cyanobacterium Anabaena 7120 using spectral and kinetic analysis of absorbance transients elicited by single turnover flashes. Consistent photosynthetic turnovers were observed only in the presence of an exogenous source of reductant; therefore measurements were routinely made under a gas phase containing H2. Prominent absorbance changes corresponding to the oxidation of cytochrome c (554 nm) and the reduction of cytochrome b563 (563 nm) were observed. Under the most reducing conditions (99% H2/1% O2) cytochrome b563 was partially reduced between flashes in a slow, dark reaction. At 10-15% O2, the slow, dark reduction of cytochrome b563 was eliminated. Cytochrome turnover ceased entirely at high O2 concentrations (30%) but was restored by the addition of 25 microM KCN, demonstrating an interaction between the photosynthetic and respiratory electron transfer chains. Strobilurin A slowed the re-reduction of cytochrome c and eliminated the appearance of reduced cytochrome b563 by blocking electron transfer between reduced plastoquinone and the cytochrome b/f complex. Inhibition at a second site was apparent with 2-(n-heptyl)-4-hydroxyquinoline N-oxide, which blocked the reoxidation of cytochrome b563 but had little effect on cytochrome c relaxation. In uncoupled heterocysts, the rates of cytochrome c re-reduction and cytochrome b563 reduction were equal. Additional unassigned absorbance changes at 475 nm, 515 nm, and 572 nm were partially characterized. No absorbance change corresponding to an electrochromic shift was observed.

  3. Neutron Absorbing Alloys

    DOEpatents

    Mizia, Ronald E.; Shaber, Eric L.; DuPont, John N.; Robino, Charles V.; Williams, David B.

    2004-05-04

    The present invention is drawn to new classes of advanced neutron absorbing structural materials for use in spent nuclear fuel applications requiring structural strength, weldability, and long term corrosion resistance. Particularly, an austenitic stainless steel alloy containing gadolinium and less than 5% of a ferrite content is disclosed. Additionally, a nickel-based alloy containing gadolinium and greater than 50% nickel is also disclosed.

  4. Solar concentrator/absorber

    NASA Technical Reports Server (NTRS)

    Von Tiesenhausen, G. F.

    1976-01-01

    Collector/energy converter, consisting of dual-slope optical concentrator and counterflow thermal energy absorber, is attached to multiaxis support structure. Efficient over wide range of illumination levels, device may be used to generate high temperature steam, serve as solar powered dryer, or power absorption cycle cooler.

  5. Multiantenna artificial photosynthetic reaction center complex.

    PubMed

    Terazono, Yuichi; Kodis, Gerdenis; Liddell, Paul A; Garg, Vikas; Moore, Thomas A; Moore, Ana L; Gust, Devens

    2009-05-21

    In order to ensure efficient utilization of the solar spectrum, photosynthetic organisms use a variety of antenna chromophores to absorb light and transfer excitation to a reaction center, where photoinduced charge separation occurs. Reported here is a synthetic molecular heptad that features two bis(phenylethynyl)anthracene and two borondipyrromethene antennas linked to a hexaphenylbenzene core that also bears two zinc porphyrins. A fullerene electron acceptor self-assembles to both porhyrins via dative bonds. Excitation energy is transferred very efficiently from all four antennas to the porphyrins. Singlet-singlet energy transfer occurs both directly and by a stepwise funnel-like pathway wherein excitation moves down a thermodynamic gradient. The porphyrin excited states donate an electron to the fullerene with a time constant of 3 ps to generate a charge-separated state with a lifetime of 230 ps. The overall quantum yield is close to unity. In the absence of the fullerene, the porphyrin excited singlet state donates an electron to a borondipyrromethene on a slower time scale. This molecule demonstrates that by incorporating antennas, it is possible for a molecular system to harvest efficiently light throughout the visible from ultraviolet wavelengths out to approximately 650 nm.

  6. Photocurrent of a single photosynthetic protein

    NASA Astrophysics Data System (ADS)

    Gerster, Daniel; Reichert, Joachim; Bi, Hai; Barth, Johannes V.; Kaniber, Simone M.; Holleitner, Alexander W.; Visoly-Fisher, Iris; Sergani, Shlomi; Carmeli, Itai

    2012-10-01

    Photosynthesis is used by plants, algae and bacteria to convert solar energy into stable chemical energy. The initial stages of this process--where light is absorbed and energy and electrons are transferred--are mediated by reaction centres composed of chlorophyll and carotenoid complexes. It has been previously shown that single small molecules can be used as functional components in electric and optoelectronic circuits, but it has proved difficult to control and probe individual molecules for photovoltaic and photoelectrochemical applications. Here, we show that the photocurrent generated by a single photosynthetic protein--photosystem I--can be measured using a scanning near-field optical microscope set-up. One side of the protein is anchored to a gold surface that acts as an electrode, and the other is contacted by a gold-covered glass tip. The tip functions as both counter electrode and light source. A photocurrent of ~10 pA is recorded from the covalently bound single-protein junctions, which is in agreement with the internal electron transfer times of photosystem I.

  7. Computation studies into architecture and energy transfer properties of photosynthetic units from filamentous anoxygenic phototrophs

    SciTech Connect

    Linnanto, Juha Matti; Freiberg, Arvi

    2014-10-06

    We have used different computational methods to study structural architecture, and light-harvesting and energy transfer properties of the photosynthetic unit of filamentous anoxygenic phototrophs. Due to the huge number of atoms in the photosynthetic unit, a combination of atomistic and coarse methods was used for electronic structure calculations. The calculations reveal that the light energy absorbed by the peripheral chlorosome antenna complex transfers efficiently via the baseplate and the core B808–866 antenna complexes to the reaction center complex, in general agreement with the present understanding of this complex system.

  8. Photosynthetic biomaterials: a pathway towards autotrophic tissue engineering.

    PubMed

    Schenck, Thilo Ludwig; Hopfner, Ursula; Chávez, Myra Noemi; Machens, Hans-Günther; Somlai-Schweiger, Ian; Giunta, Riccardo Enzo; Bohne, Alexandra Viola; Nickelsen, Jörg; Allende, Miguel L; Egaña, José Tomás

    2015-03-01

    Engineered tissues are highly limited by poor vascularization in vivo, leading to hypoxia. In order to overcome this challenge, we propose the use of photosynthetic biomaterials to provide oxygen. Since photosynthesis is the original source of oxygen for living organisms, we suggest that this could be a novel approach to provide a constant source of oxygen supply independently of blood perfusion. In this study we demonstrate that bioartificial scaffolds can be loaded with a solution containing the photosynthetic microalgae Chlamydomonas reinhardtii, showing high biocompatibility and photosynthetic activity in vitro. Furthermore, when photosynthetic biomaterials were engrafted in a mouse full skin defect, we observed that the presence of the microalgae did not trigger a native immune response in the host. Moreover, the analyses showed that the algae survived for at least 5 days in vivo, generating chimeric tissues comprised of algae and murine cells. The results of this study represent a crucial step towards the establishment of autotrophic tissue engineering approaches and suggest the use of photosynthetic cells to treat a broad spectrum of hypoxic conditions. PMID:25536030

  9. Photoperiodic Regulation of the Seasonal Pattern of Photosynthetic Capacity and the Implications for Carbon Cycling

    SciTech Connect

    Bauerle, William L.; Oren, Ram; Way, Danielle A.; Qian, Song S.; Stoy, Paul C.; Thornton, Peter E; Bowden, Joseph D.; Hoffman, Forrest M; Reynolds, Robert F.

    2012-01-01

    Although temperature is an important driver of seasonal changes in photosynthetic physiology, photoperiod also regulates leaf activity. Climate change will extend growing seasons if temperature cues predominate, but photoperiod-controlled species will show limited responsiveness to warming. We show that photoperiod explains more seasonal variation in photosynthetic activity across 23 tree species than temperature. Although leaves remain green, photosynthetic capacity peaks just after summer solstice and declines with decreasing photoperiod, before air temperatures peak. In support of these findings, saplings grown at constant temperature but exposed to an extended photoperiod maintained high photosynthetic capacity, but photosynthetic activity declined in saplings experiencing a naturally shortening photoperiod; leaves remained equally green in both treatments. Incorporating a photoperiodic correction of photosynthetic physiology into a global-scale terrestrial carbon-cycle model significantly improves predictions of seasonal atmospheric CO{sub 2} cycling, demonstrating the benefit of such a function in coupled climate system models. Accounting for photoperiod-induced seasonality in photosynthetic parameters reduces modeled global gross primary production 2.5% ({approx}4 PgC y{sup -1}), resulting in a >3% ({approx}2 PgC y{sup -1}) decrease of net primary production. Such a correction is also needed in models estimating current carbon uptake based on remotely sensed greenness. Photoperiod-associated declines in photosynthetic capacity could limit autumn carbon gain in forests, even if warming delays leaf senescence.

  10. Energy transfer in the primary stages of the photosynthetic process investigated by picosecond time resolved fluorescence spectroscopy

    NASA Astrophysics Data System (ADS)

    Pellegrino, F.

    The fate of the absorbed light energy in the primary stages of the photosynthetic process was studied. In particular, the energy transfer in the accessory pigment complex consisting of carotenoids, Chl. a and Chl. b in higher green plants and phycobiliproteins in blue-green algae were investigated. These accessory pigments are responsible for the highly efficient transfer of the excitation energy to the photochemically active reaction center traps. The risetime, decay time, fluorescence depolarization, temperature and intensity dependence of the fluoresence emission from higher green plant and algal photosystems were directly measured. Excitation was provided by single picosecond laser pulses, as well as a train of pulses at 530 nm, within an intensity range of 10 to the 12th power to 10 to the 16th power photons/sq cm per pulse.

  11. Respiratory processes in non-photosynthetic plastids

    PubMed Central

    Renato, Marta; Boronat, Albert; Azcón-Bieto, Joaquín

    2015-01-01

    Chlororespiration is a respiratory process located in chloroplast thylakoids which consists in an electron transport chain from NAD(P)H to oxygen. This respiratory chain involves the NAD(P)H dehydrogenase complex, the plastoquinone pool and the plastid terminal oxidase (PTOX), and it probably acts as a safety valve to prevent the over-reduction of the photosynthetic machinery in stress conditions. The existence of a similar respiratory activity in non-photosynthetic plastids has been less studied. Recently, it has been reported that tomato fruit chromoplasts present an oxygen consumption activity linked to ATP synthesis. Etioplasts and amyloplasts contain several electron carriers and some subunits of the ATP synthase, so they could harbor a similar respiratory process. This review provides an update on the study about respiratory processes in chromoplasts, identifying the major gaps that need to be addressed in future research. It also reviews the proteomic data of etioplasts and amyloplasts, which suggest the presence of a respiratory electron transport chain in these plastids. PMID:26236317

  12. Respiratory processes in non-photosynthetic plastids.

    PubMed

    Renato, Marta; Boronat, Albert; Azcón-Bieto, Joaquín

    2015-01-01

    Chlororespiration is a respiratory process located in chloroplast thylakoids which consists in an electron transport chain from NAD(P)H to oxygen. This respiratory chain involves the NAD(P)H dehydrogenase complex, the plastoquinone pool and the plastid terminal oxidase (PTOX), and it probably acts as a safety valve to prevent the over-reduction of the photosynthetic machinery in stress conditions. The existence of a similar respiratory activity in non-photosynthetic plastids has been less studied. Recently, it has been reported that tomato fruit chromoplasts present an oxygen consumption activity linked to ATP synthesis. Etioplasts and amyloplasts contain several electron carriers and some subunits of the ATP synthase, so they could harbor a similar respiratory process. This review provides an update on the study about respiratory processes in chromoplasts, identifying the major gaps that need to be addressed in future research. It also reviews the proteomic data of etioplasts and amyloplasts, which suggest the presence of a respiratory electron transport chain in these plastids.

  13. Porphyrin Based Near Infrared-Absorbing Materials for Organic Photovoltaics

    NASA Astrophysics Data System (ADS)

    Zhong, Qiwen

    photosynthesis. Photosynthesis uses light from the sun to drive a series of chemical reactions. Most natural photosynthetic systems utilize chlorophylls to absorb light energy and carry out photochemical charge separation that stores energy in the form of chemical bonds. The sun produces a broad spectrum of light output that ranges from gamma rays to radio waves. The entire visible range of light (400-700 nm) and some wavelengths in the NIR (700-1000 nm), are highly active in driving photosynthesis. Although the most familiar chlorophyll-containing organisms, such as plants, algae and cyanobacteria, cannot use light longer than 700 nm, anoxygenic bacterium containing bacteriochlorophylls can use the NIR part of the solar spectrum. No organism is known to utilize light of wavelength longer than about 1000 nm for photosynthesis. NIR light has a very low-energy content in each photon, so that large numbers of these low-energy photons would have to be used to drive the chemical reactions of photosynthesis. This is thermodynamically possible but would require a fundamentally different molecular mechanism that is more akin to a heat engine than to photochemistry. Early work on developing light absorbing materials for OPVs was inspired by photosynthesis in which light is absorbed by chlorophyll. Structurally related to chlorophyll is the porphyrin family, which has accordingly drawn much interest as the potential light absorbing component in OPV applications. In this dissertation, the design and detail studies of several porphyrin-based NIR absorbing materials, including pi--extended perylenyl porphryins and pyrazole-containing carbaporphyrins, as well as porphyrin modified single-walled carbon nanotube hybrids, will be presented, dedicating efforts to develop novel and application-oriented materials for efficient utilization of sustainable solar energy.

  14. Science on a Roll. Part One: Absorbing Inquiry.

    ERIC Educational Resources Information Center

    Brendzel, Sharon

    2002-01-01

    Presents an activity that tests the absorbency of different brands of paper towels. Suggests making this activity into an open-ended inquiry type of activity. Includes sample questions to guide students, topics for class discussion, and sample methods of using the absorbency activity. (KHR)

  15. Photosynthetic water splitting

    NASA Astrophysics Data System (ADS)

    Greenbaum, E.

    It has been demonstrated that eukaryotic green algae (as represented by Chlamydomonas) are inherently rugged algae with respect to the biophotolysis of water. There also exists a potential for selecting subpropulations of wild-type algae with enhanced properties for hydrogen and oxygen production. Second, hydrogenase activity in macroscopic marine algae does not conform to the conventional dogma of the catalog of reactions that this enzyme is supposed to catalyze. A kinetic argument has been presented which suggests that, with respect to light activated reactions, hydrogenase in these organisms operates primarily in a hydrogen uptake mode. Third, the light saturation curves for the simultaneous photoproduction of hydrogen and oxygen do not have the same analytical shape. It is suggested that a Photosystem I-like hydrogen producing light reaction may be present in anaerobically adapted Scenedesmus which is uncoupled from the Z scheme.

  16. Phytochromes in photosynthetically competent plants

    SciTech Connect

    Pratt, L.H.

    1990-07-01

    Plants utilize light as a source of information in photomorphogenesis and of free energy in photosynthesis, two processes that are interrelated in that the former serves to increase the efficiency with which plants can perform the latter. Only one pigment involved in photomorphogenesis has been identified unequivocally, namely phytochrome. The thrust of this proposal is to investigate this pigment and its mode(s) of action in photosynthetically competent plants. Our long term objective is to characterize phytochrome and its functions in photosynthetically competent plants from molecular, biochemical and cellular perspectives. It is anticipated that others will continue to contribute indirectly to these efforts at the physiological level. The ultimate goal will be to develop this information from a comparative perspective in order to learn whether the different phytochromes have significantly different physicochemical properties, whether they fulfill independent functions and if so what these different functions are, and how each of the different phytochromes acts at primary molecular and cellular levels.

  17. Metasurface Broadband Solar Absorber

    PubMed Central

    Azad, Abul K.; Kort-Kamp, Wilton J. M.; Sykora, Milan; Weisse-Bernstein, Nina R.; Luk, Ting S.; Taylor, Antoinette J.; Dalvit, Diego A. R.; Chen, Hou-Tong

    2016-01-01

    We demonstrate a broadband, polarization independent, wide-angle absorber based on a metallic metasurface architecture, which accomplishes greater than 90% absorptance in the visible and near-infrared range of the solar spectrum, and exhibits low absorptivity (emissivity) at mid- and far-infrared wavelengths. The complex unit cell of the metasurface solar absorber consists of eight pairs of gold nano-resonators that are separated from a gold ground plane by a thin silicon dioxide spacer. Our experimental measurements reveal high-performance absorption over a wide range of incidence angles for both s- and p-polarizations. We also investigate numerically the frequency-dependent field and current distributions to elucidate how the absorption occurs within the metasurface structure. PMID:26828999

  18. Metasurface Broadband Solar Absorber.

    PubMed

    Azad, Abul K; Kort-Kamp, Wilton J M; Sykora, Milan; Weisse-Bernstein, Nina R; Luk, Ting S; Taylor, Antoinette J; Dalvit, Diego A R; Chen, Hou-Tong

    2016-01-01

    We demonstrate a broadband, polarization independent, wide-angle absorber based on a metallic metasurface architecture, which accomplishes greater than 90% absorptance in the visible and near-infrared range of the solar spectrum, and exhibits low absorptivity (emissivity) at mid- and far-infrared wavelengths. The complex unit cell of the metasurface solar absorber consists of eight pairs of gold nano-resonators that are separated from a gold ground plane by a thin silicon dioxide spacer. Our experimental measurements reveal high-performance absorption over a wide range of incidence angles for both s- and p-polarizations. We also investigate numerically the frequency-dependent field and current distributions to elucidate how the absorption occurs within the metasurface structure.

  19. Metasurface Broadband Solar Absorber

    DOE PAGES

    Azad, Abul K.; Kort-Kamp, Wilton J. M.; Sykora, Milan; Weisse-Bernstein, Nina R.; Luk, Ting S.; Taylor, Antoinette J.; Dalvit, Diego A. R.; Chen, Hou-Tong

    2016-02-01

    Here, we demonstrate a broadband, polarization independent, wide-angle absorber based on a metallic metasurface architecture, which accomplishes greater than 90% absorptance in the visible and near-infrared range of the solar spectrum, and exhibits low absorptivity (emissivity) at mid- and far-infrared wavelengths. The complex unit cell of the metasurface solar absorber consists of eight pairs of gold nano-resonators that are separated from a gold ground plane by a thin silicon dioxide spacer. Moreover, our experimental measurements reveal high-performance absorption over a wide range of incidence angles for both s- and p-polarizations. We also investigate numerically the frequency-dependent field and current distributionsmore » to elucidate how the absorption occurs within the metasurface structure.« less

  20. Metasurface Broadband Solar Absorber.

    PubMed

    Azad, Abul K; Kort-Kamp, Wilton J M; Sykora, Milan; Weisse-Bernstein, Nina R; Luk, Ting S; Taylor, Antoinette J; Dalvit, Diego A R; Chen, Hou-Tong

    2016-01-01

    We demonstrate a broadband, polarization independent, wide-angle absorber based on a metallic metasurface architecture, which accomplishes greater than 90% absorptance in the visible and near-infrared range of the solar spectrum, and exhibits low absorptivity (emissivity) at mid- and far-infrared wavelengths. The complex unit cell of the metasurface solar absorber consists of eight pairs of gold nano-resonators that are separated from a gold ground plane by a thin silicon dioxide spacer. Our experimental measurements reveal high-performance absorption over a wide range of incidence angles for both s- and p-polarizations. We also investigate numerically the frequency-dependent field and current distributions to elucidate how the absorption occurs within the metasurface structure. PMID:26828999

  1. Absorbed dose water calorimeter

    SciTech Connect

    Domen, S.R.

    1982-01-26

    An absorbed dose water calorimeter that takes advantage of the low thermal diffusivity of water and the water-imperviousness of polyethylene film. An ultra-small bead thermistor is sandwiched between two thin polyethylene films stretched between insulative supports in a water bath. The polyethylene films insulate the thermistor and its leads, the leads being run out from between the films in insulated sleeving and then to junctions to form a wheatstone bridge circuit. Convection barriers may be provided to reduce the effects of convection from the point of measurement. Controlled heating of different levels in the water bath is accomplished by electrical heater circuits provided for controlling temperature drift and providing adiabatic operation of the calorimeter. The absorbed dose is determined from the known specific heat of water and the measured temperature change.

  2. Ionized Absorbers in AGN

    NASA Technical Reports Server (NTRS)

    Mathur, S.

    1999-01-01

    As a part of this program, we observed three AGN:PKS2251 + 113, PG0043 = 039 and PLH909. Two objects show signatures of absorbtion in their UV spectra. Based on our earlier modeling of X-ray warm absorbents, we expected to observe X-ray observation in these objects. The third, PLH909, is known to have soft excess in EINSTEIN data. Attachment: "Exploratory ASCA observation of broad absorption line quasi-stellar objects".

  3. The making of a photosynthetic animal

    PubMed Central

    Rumpho, Mary E.; Pelletreau, Karen N.; Moustafa, Ahmed; Bhattacharya, Debashish

    2011-01-01

    Symbiotic animals containing green photobionts challenge the common perception that only plants are capable of capturing the sun's rays and converting them into biological energy through photoautotrophic CO2 fixation (photosynthesis). ‘Solar-powered’ sacoglossan molluscs, or sea slugs, have taken this type of symbiotic association one step further by solely harboring the photosynthetic organelle, the plastid (=chloroplast). One such sea slug, Elysia chlorotica, lives as a ‘plant’ when provided with only light and air as a result of acquiring plastids during feeding on its algal prey Vaucheria litorea. The captured plastids (kleptoplasts) are retained intracellularly in cells lining the digestive diverticula of the sea slug, a phenomenon sometimes referred to as kleptoplasty. Photosynthesis by the plastids provides E. chlorotica with energy and fixed carbon for its entire lifespan of ∼10 months. The plastids are not transmitted vertically (i.e. are absent in eggs) and do not undergo division in the sea slug. However, de novo protein synthesis continues, including plastid- and nuclear-encoded plastid-targeted proteins, despite the apparent absence of algal nuclei. Here we discuss current data and provide hypotheses to explain how long-term photosynthetic activity is maintained by the kleptoplasts. This fascinating ‘green animal’ provides a unique model to study the evolution of photosynthesis in a multicellular heterotrophic organism. PMID:21177950

  4. Photosynthetic water splitting: 1987 annual report

    SciTech Connect

    Greenbaum, E.

    1988-01-01

    This document is an annual report of photosynthetic water splitting for the production of hydrogen and oxygen. Unicellular green algae are capable of evolving molecular hydrogen in the presence of carbon dioxide. Controlling factors that determine hydrogen evolution are either temperature or light intensity. Also, mutants of the green alga Chlamydomonas are capable of evolving hydrogen in the presence of carbon dioxide. The significance of these discoveries is that the presence of carbon dioxide (or bicarbonate) is a key factor in determining the activity of the Photosystem II water splitting complex. Second, a new advance in oxygen sensor technology has been made that, for the first time, allows the absolute measurement of photosynthetically evolved oxygen from a single colony of microalgae growing on a solidified agar medium. The key aspect of this electrochemical sensor is the utilization of ultra-pure potassium hydroxide as the electrolyte and a recognition of the role that electrolyte impurities play in contributing to base line noise. 9 refs., 8 figs., 2 tabs.

  5. Micromachined microbial and photosynthetic fuel cells

    NASA Astrophysics Data System (ADS)

    Chiao, Mu; Lam, Kien B.; Lin, Liwei

    2006-12-01

    This paper presents two types of fuel cells: a miniature microbial fuel cell (µMFC) and a miniature photosynthetic electrochemical cell (µPEC). A bulk micromachining process is used to fabricate the fuel cells, and the prototype has an active proton exchange membrane area of 1 cm2. Two different micro-organisms are used as biocatalysts in the anode: (1) Saccharomyces cerevisiae (baker's yeast) is used to catalyze glucose and (2) Phylum Cyanophyta (blue-green algae) is used to produce electrons by a photosynthetic reaction under light. In the dark, the µPEC continues to generate power using the glucose produced under light. In the cathode, potassium ferricyanide is used to accept electrons and electric power is produced by the overall redox reactions. The bio-electrical responses of µMFCs and µPECs are characterized with the open-circuit potential measured at an average value of 300-500 mV. Under a 10 ohm load, the power density is measured as 2.3 nW cm-2 and 0.04 nW cm-2 for µMFCs and µPECs, respectively.

  6. Fusion of liposomones and chromatophores of Rhodopseudomonas capsulata: effect on photosynthetic energy transfer between B875 and reaction center complexes

    SciTech Connect

    Takemoto, J.Y.; Schonhardt, T.; Golecki, J.R.; Drews, G.

    1985-06-01

    The photosynthetic chromatophore membranes of Rhodopseudomonas capsulata were fused with liposomes to investigate the effects of lipid dilution on energy transfer between the bacteriochlorophyll-protein complexes of this membrane. Freeze-fracture electron microscopy revealed that the fractions contained closed vesicles formed by the fusion of liposomes to chromatophores. Particles with 9-nm diameters on the P fracture faces did not appear to change in size with increasing lipid content, but the number of particles per membrane area decreased proportionally with increases in the lipid-to-protein ratio. The bacteriochlorophyll-to-protein ratios, electrophoretic polypeptide profiles on sodium dodecyl sulfate-polyacrylamide gels, and light-induced absorbance changes at 595 nm caused by photosynthetic reaction centers were not altered by fusion. The relative fluorescence emission intensities due to the B875 light-harvesting complex increased significantly with increasing lipid content, but no increases in fluorescence due to the B800-B850 light-harvesting complex were observed. Electron transport rates, measured as succinate-cytochrome c reductase activities, decreased with increased lipid content. The results indicate an uncoupling of energy transfer between the B875 light-harvesting and reaction center complexes with lipid dilution of the chromatophore membrane.

  7. Airborne remote sensing of photosynthetic light use efficiency and carbon uptake along an Arctic transect in Finland

    NASA Astrophysics Data System (ADS)

    Atherton, J.; Hill, T. C.; Prieto-Blanco, A.; Wade, T.; Clement, R.; Moncrieff, J.; Williams, M. D.; Disney, M.; Nichol, C. J.

    2009-12-01

    It is critical to understand the dynamics of ecosystem carbon uptake through seasonal changes and in response to environmental drivers. In this study we utilised aircraft based remote sensing and CO2/H2O flux monitoring systems to quantify changes in photosynthesis along an Arctic transect. The University of Edinburgh's (UK) research aircraft (a Diamond HK 36 TTC-ECO Dimona) was deployed in the Arctic during summer 2008 to carry out a series of transect-flights over a birch-mire mosaic site near Kevo, Finland as part of the Arctic Biosphere Atmosphere Coupling at Multiple Scales (ABACUS) project. The aircraft is equipped with automated dual field-of-view (hyperspectral) radiometers and CO2/H2O flux and meteorological instrumentation. Vegetation indices known to be related to photosynthetic light use efficiency (LUE), including the well established Photochemical Reflectance Index (PRI) and Solar-induced Fluorescence (SiF) as well as the Normalized Difference Vegetation Index (NDVI) were calculated from the spectral data and matched in space to the CO2 flux measurements. We explored spatial relationships between NDVI and CO2 flux, LUE (CO2 flux / Absorbed Photosynthetically Active Radiation) and PRI and finally SiF (calculated using the Fraunhofer infilling method) and relevant environmental drivers. Our results highlight the unique ability of an airborne platform to quantify ecosystem physiology across a landscape and demonstrate how such measurements can bridge the spatial gap between ground and satellite-based observations.

  8. Accounting for non-photosynthetic vegetation in remote-sensing-based estimates of carbon flux in wetlands

    USGS Publications Warehouse

    Schile, Lisa M.; Byrd, Kristin B.; Windham-Myers, Lisamarie; Kelly, Maggi

    2013-01-01

    Monitoring productivity in coastal wetlands is important due to their high carbon sequestration rates and potential role in climate change mitigation. We tested agricultural- and forest-based methods for estimating the fraction of absorbed photosynthetically active radiation (f APAR), a key parameter for modelling gross primary productivity (GPP), in a restored, managed wetland with a dense litter layer of non-photosynthetic vegetation, and we compared the difference in canopy light transmission between a tidally influenced wetland and the managed wetland. The presence of litter reduced correlations between spectral vegetation indices and f APAR. In the managed wetland, a two-band vegetation index incorporating simulated World View-2 or Hyperion green and near-infrared bands, collected with a field spectroradiometer, significantly correlated with f APAR only when measured above the litter layer, not at the ground where measurements typically occur. Measures of GPP in these systems are difficult to capture via remote sensing, and require an investment of sampling effort, practical methods for measuring green leaf area and accounting for background effects of litter and water.

  9. Photosynthetic acclimation to drought stress in Agave salmiana Otto ex Salm-Dyck seedlings is largely dependent on thermal dissipation and enhanced electron flux to photosystem I.

    PubMed

    Campos, Huitziméngari; Trejo, Carlos; Peña-Valdivia, Cecilia B; García-Nava, Rodolfo; Conde-Martínez, F Víctor; Cruz-Ortega, Ma Del Rocío

    2014-10-01

    Agave salmiana Otto ex Salm-Dyck, a crassulacean acid metabolism plant that is adapted to water-limited environments, has great potential for bioenergy production. However, drought stress decreases the requirement for light energy, and if the amount of incident light exceeds energy consumption, the photosynthetic apparatus can be injured, thereby limiting plant growth. The objective of this study was to evaluate the effects of drought and re-watering on the photosynthetic efficiency of A. salmiana seedlings. The leaf relative water content and leaf water potential decreased to 39.6 % and -1.1 MPa, respectively, over 115 days of water withholding and recovered after re-watering. Drought caused a direct effect on photosystem II (PSII) photochemistry in light-acclimated leaves, as indicated by a decrease in the photosynthetic electron transport rate. Additionally, down-regulation of photochemical activity occurred mainly through the inactivation of PSII reaction centres and an increased thermal dissipation capacity of the leaves. Prompt fluorescence kinetics also showed a larger pool of terminal electron acceptors in photosystem I (PSI) as well as an increase in some JIP-test parameters compared to controls, reflecting an enhanced efficiency and specific fluxes for electron transport from the plastoquinone pool to the PSI terminal acceptors. All the above parameters showed similar levels after re-watering. These results suggest that the thermal dissipation of excess energy and the increased energy conservation from photons absorbed by PSII to the reduction of PSI end acceptors may be an important acclimation mechanism to protect the photosynthetic apparatus from over-excitation in Agave plants. PMID:24798124

  10. Photosynthetic acclimation to drought stress in Agave salmiana Otto ex Salm-Dyck seedlings is largely dependent on thermal dissipation and enhanced electron flux to photosystem I.

    PubMed

    Campos, Huitziméngari; Trejo, Carlos; Peña-Valdivia, Cecilia B; García-Nava, Rodolfo; Conde-Martínez, F Víctor; Cruz-Ortega, Ma Del Rocío

    2014-10-01

    Agave salmiana Otto ex Salm-Dyck, a crassulacean acid metabolism plant that is adapted to water-limited environments, has great potential for bioenergy production. However, drought stress decreases the requirement for light energy, and if the amount of incident light exceeds energy consumption, the photosynthetic apparatus can be injured, thereby limiting plant growth. The objective of this study was to evaluate the effects of drought and re-watering on the photosynthetic efficiency of A. salmiana seedlings. The leaf relative water content and leaf water potential decreased to 39.6 % and -1.1 MPa, respectively, over 115 days of water withholding and recovered after re-watering. Drought caused a direct effect on photosystem II (PSII) photochemistry in light-acclimated leaves, as indicated by a decrease in the photosynthetic electron transport rate. Additionally, down-regulation of photochemical activity occurred mainly through the inactivation of PSII reaction centres and an increased thermal dissipation capacity of the leaves. Prompt fluorescence kinetics also showed a larger pool of terminal electron acceptors in photosystem I (PSI) as well as an increase in some JIP-test parameters compared to controls, reflecting an enhanced efficiency and specific fluxes for electron transport from the plastoquinone pool to the PSI terminal acceptors. All the above parameters showed similar levels after re-watering. These results suggest that the thermal dissipation of excess energy and the increased energy conservation from photons absorbed by PSII to the reduction of PSI end acceptors may be an important acclimation mechanism to protect the photosynthetic apparatus from over-excitation in Agave plants.

  11. [Differences in the light-activation of NADP-dependent glyceraldehyde-3-phosphate dehydrogenase and of ribulose-5-phosphate kinase between plants containing the Calvin and those containing the C4-dicarboxylic acid pathway of photosynthetic carbon reduction].

    PubMed

    Steiger, E; Ziegler, I; Ziegler, H

    1971-06-01

    1. Preceding experiments had shown that irradiance of intact leaves or of isolated chloroplasts causes a reversible increase in the activity of NADP-GPD (Ziegler and Ziegler, 1965) as well as of ribulose-5-phosphate kinase (Latzko and Gibbs, 1969). Examination of several species which carry out the Calvin type of photosynthetic CO2 fixation (Vicia faba, Spinacia oleracea, Nicotiana tabacum, Avena sativa) now revealed that the dark level of NADP-GPD activity ranges between 300-400 μmol NADPH/mg chlorophyll·h; irradiance causes an activation to an turnover rate of 900-1600 μmol NADPH/mg chlorophyll·h. 2. The dark-level of ribulose-5-phosphate kinase in these Calvin type plants corresponds to about 400 \\gmmol PO4---/mg chlorophyll\\sdh. It rises to 900\\2-1300 \\gmmol PO4---/mg chlorophyll\\sdh after irradiance. 3. In all species examined which carry out the C4-dicarboxylic acid type of CO2 fixation (Zea mays, Cyperus rotundus, Portulacca oleracea, Saccharum officinarum) the dark-level of NADP-GPD as well as of ribulose-5-phosphate kinase is already as high as the light-level of Calvin type plants. In these species irradiance either activates both enzymes only to a small extent (Saccharum officinarum, Portulacea oleracea) or it activates only one of the two enzymes to an exceptional high activity (NADP-GPD in Zea mays, ribulose-5-phosphate kinase in Cyperus rotundus), while the activity of the other one remains nearly constant. 4. The dark-level of NADP-GPD in young Zea mays (2 leaves expanded) is as high as in adult plants; moreover its further activation by light corresponds to that in adult plants. In contrast, the dark-activity of ribulose-5-phosphate kinase in young Zea mays corresponds to the lower level found in Calvin type plants and is activated by irradiance in the same manner as it is in the latter plants. 5. The activity of ribose-5-phosphate isomerase is not influenced by light.

  12. cPPB-aE is discovered from photosynthetic benthic dinoflagellates.

    PubMed

    Yamada, Norico; Tanaka, Ayumi; Horiguchi, Takeo

    2014-02-01

    Although chlorophyll degradation pathways in higher plants have been well studied, little is known about the mechanisms of chlorophyll degradation in microalgae. In this article, we report the occurrence of a chlorophyll a derivative that has never been discovered in photosynthetic organisms. This chlorophyll derivative emits no fluorescence and has a peculiar absorbance peak at 425, 451, 625, and 685 nm. From these features, it was identified as 13(2) ,17(3) -cyclopheophorbide a enol (cPPB-aE), reported as a degradation product of chlorophyll a derived from prey algal cells in heterotrophic protists. We discovered cPPB-aE in six benthic photosynthetic dinoflagellates that are phylogenetically separated into four clades based on SSU rDNA molecular phylogeny. This is the first report of this chlorophyll derivative in photosynthetic organisms and we suggest that the derivative is used to quench excess light energy.

  13. An obligately photosynthetic bacterial anaerobe from a deep-sea hydrothermal vent.

    PubMed

    Beatty, J Thomas; Overmann, Jörg; Lince, Michael T; Manske, Ann K; Lang, Andrew S; Blankenship, Robert E; Van Dover, Cindy L; Martinson, Tracey A; Plumley, F Gerald

    2005-06-28

    The abundance of life on Earth is almost entirely due to biological photosynthesis, which depends on light energy. The source of light in natural habitats has heretofore been thought to be the sun, thus restricting photosynthesis to solar photic environments on the surface of the Earth. If photosynthesis could take place in geothermally illuminated environments, it would increase the diversity of photosynthetic habitats both on Earth and on other worlds that have been proposed to possibly harbor life. Green sulfur bacteria are anaerobes that require light for growth by the oxidation of sulfur compounds to reduce CO2 to organic carbon, and are capable of photosynthetic growth at extremely low light intensities. We describe the isolation and cultivation of a previously unknown green sulfur bacterial species from a deep-sea hydrothermal vent, where the only source of light is geothermal radiation that includes wavelengths absorbed by photosynthetic pigments of this organism.

  14. Growth, photosynthetic and respiratory responses to sub-lethal copper concentrations in Scenedesmus incrassatulus (Chlorophyceae).

    PubMed

    Perales-Vela, Hugo Virgilio; González-Moreno, Sergio; Montes-Horcasitas, Carmen; Cañizares-Villanueva, Rosa Olivia

    2007-05-01

    In the present paper we investigated the effects of sub-lethal concentrations of Cu2+ in the growth and metabolism of Scenedesmus incrassatulus. We found that the effect of Cu2+ on growth, photosynthetic pigments (chlorophylls and carotenoids) and metabolism do not follow the same pattern. Photosynthesis was more sensitive than respiration. The analysis of chlorophyll a fluorescence transient shows that the effect of sub-lethal Cu2+ concentration in vivo, causes a reduction of the active PSII reaction centers and the primary charge separation, decreasing the quantum yield of PSII, the electron transport rate and the photosynthetic O2 evolution. The order of sensitivity found was: Growth>photosynthetic pigments content=photosynthetic O2 evolution>photosynthetic electron transport>respiration. The uncoupled relationship between growth and metabolism is discussed.

  15. Growth, photosynthetic and respiratory responses to sub-lethal copper concentrations in Scenedesmus incrassatulus (Chlorophyceae).

    PubMed

    Perales-Vela, Hugo Virgilio; González-Moreno, Sergio; Montes-Horcasitas, Carmen; Cañizares-Villanueva, Rosa Olivia

    2007-05-01

    In the present paper we investigated the effects of sub-lethal concentrations of Cu2+ in the growth and metabolism of Scenedesmus incrassatulus. We found that the effect of Cu2+ on growth, photosynthetic pigments (chlorophylls and carotenoids) and metabolism do not follow the same pattern. Photosynthesis was more sensitive than respiration. The analysis of chlorophyll a fluorescence transient shows that the effect of sub-lethal Cu2+ concentration in vivo, causes a reduction of the active PSII reaction centers and the primary charge separation, decreasing the quantum yield of PSII, the electron transport rate and the photosynthetic O2 evolution. The order of sensitivity found was: Growth>photosynthetic pigments content=photosynthetic O2 evolution>photosynthetic electron transport>respiration. The uncoupled relationship between growth and metabolism is discussed. PMID:17267014

  16. Effect of CO sub 2 enrichment and high photosynthetic photon flux densities (PPFD) on rubisco and PEP-case activities of in vitro cultured strawberry plants

    SciTech Connect

    Desjardins, Y.; Beeson, R.; Gosselin, A. )

    1989-04-01

    Standard growing conditions in vitro (low light and CO{sub 2}) are not conducive to autotrophy. An experiment was conducted to improve photosynthesis in vitro in the hope of increasing survival in acclimatization. A factorial experiment was elaborated where CO{sub 2} and PPFD were supplied to in vitro cultured strawberry plants in the rooting stage. Activities of carboxylating enzymes were determined after 4 weeks of culture. The activities of non-activated and activated rubisco and PEP-Case were measured after extraction of the enzymes and a reaction with NaH{sup 14}CO{sub 3} followed by scintillation counting spectroscopy. High CO{sub 2} concentration significantly increased net assimilation rates (NAR) by 165% over the control for both 1650 and 3000 ppm CO{sub 2}. High PPFD only increased NAR by 12 and 35% for 150 and 250 {mu}mol{center dot}m{sup {minus}2}{center dot}s{sup {minus}1} respectively over the control. Plants grown at 3000 ppm CO{sub 2} had the highest level of chlorophyll/g FW with 97% more than the control. The activity of PEP-Case was the highest at high light levels and high CO{sub 2} with rates of 1.65 for 1650 ppm versus 1.22 mmol CO{sub 2} mg{sup {minus}1} chl. h{sup {minus}1} at 250 {mu}mol{center dot}m{sup {minus}2}{center dot}s{sup {minus}1}. There was no difference in PEP activity at low light levels. The rubisco activity was lower at 1650 and 3000 ppm CO{sub 2}. Increases in NAR correlate more closely to the PEP-Case than to Rubisco activity. Physiological significance of high activity of PEP-Case over rubisco will be discussed.

  17. Abscisic acid induced changes in production of primary and secondary metabolites, photosynthetic capacity, antioxidant capability, antioxidant enzymes and lipoxygenase inhibitory activity of Orthosiphon stamineus Benth.

    PubMed

    Ibrahim, Mohd Hafiz; Jaafar, Hawa Z E

    2013-01-01

    An experiment was conducted to investigate and distinguish the relationships in the production of total phenolics, total flavonoids, soluble sugars, H2O2, O2-, phenylalanine ammonia lyase (PAL) activity, leaf gas exchange, antioxidant activity, antioxidant enzyme activity [ascorbate peroxidase (APX), catalase (CAT), superoxide dismutase (SOD) and Lipoxygenase inhibitory activity (LOX)] under four levels of foliar abscisic acid (ABA) application (0, 2, 4, 6 µM) for 15 weeks in Orthosiphon stamineus Benth. It was found that the production of plant secondary metabolites, soluble sugars, antioxidant activity, PAL activity and LOX inhibitory activity was influenced by foliar application of ABA. As the concentration of ABA was increased from 0 to 6 µM the production of total phenolics, flavonoids, sucrose, H2O2, O2-, PAL activity and LOX inhibitory activity was enhanced. It was also observed that the antioxidant capabilities (DPPH and ORAC) were increased. This was followed by increases in production of antioxidant enzymes APX, CAT and SOD. Under high application rates of ABA the net photosynthesis and stomatal conductance was found to be reduced. The production of primary and secondary metabolites displayed a significant positive relationship with H2O2 (total phenolics, r2 = 0.877; total flavonoids, r2 = 0.812; p ≤ 0.05) and O2- (total phenolics, r2 = 0.778; total flavonoids, r2 = 0.912; p ≤ 0.05). This indicated that increased oxidative stress at high application rates of ABA, improved the production of phytochemicals. PMID:23884129

  18. Absorber for terahertz radiation management

    DOEpatents

    Biallas, George Herman; Apeldoorn, Cornelis; Williams, Gwyn P.; Benson, Stephen V.; Shinn, Michelle D.; Heckman, John D.

    2015-12-08

    A method and apparatus for minimizing the degradation of power in a free electron laser (FEL) generating terahertz (THz) radiation. The method includes inserting an absorber ring in the FEL beam path for absorbing any irregular THz radiation and thus minimizes the degradation of downstream optics and the resulting degradation of the FEL output power. The absorber ring includes an upstream side, a downstream side, and a plurality of wedges spaced radially around the absorber ring. The wedges form a scallop-like feature on the innermost edges of the absorber ring that acts as an apodizer, stopping diffractive focusing of the THz radiation that is not intercepted by the absorber. Spacing between the scallop-like features and the shape of the features approximates the Bartlett apodization function. The absorber ring provides a smooth intensity distribution, rather than one that is peaked on-center, thereby eliminating minor distortion downstream of the absorber.

  19. Allocation of Secondary Metabolites, Photosynthetic Capacity, and Antioxidant Activity of Kacip Fatimah (Labisia pumila Benth) in Response to CO2 and Light Intensity

    PubMed Central

    Jaafar, Hawa Z. E.; Karimi, Ehsan; Ghasemzadeh, Ali

    2014-01-01

    A split plot 3 by 4 experiment was designed to investigate and distinguish the relationships among production of secondary metabolites, soluble sugar, phenylalanine ammonia lyase (PAL; EC 4.3.1.5) activity, leaf gas exchange, chlorophyll content, antioxidant activity (DPPH), and lipid peroxidation under three levels of CO2 (400, 800, and 1200 μmol/mol) and four levels of light intensity (225, 500, 625, and 900 μmol/m2/s) over 15 weeks in Labisia pumila. The production of plant secondary metabolites, sugar, chlorophyll content, antioxidant activity, and malondialdehyde content was influenced by the interactions between CO2 and irradiance. The highest accumulation of secondary metabolites, sugar, maliondialdehyde, and DPPH activity was observed under CO2 at 1200 μmol/mol + light intensity at 225 μmol/m2/s. Meanwhile, at 400 μmol/mol CO2 + 900 μmol/m2/s light intensity the production of chlorophyll and maliondialdehyde content was the highest. As CO2 levels increased from 400 to 1200 μmol/mol the photosynthesis, stomatal conductance, fv/fm (maximum efficiency of photosystem II), and PAL activity were enhanced. The production of secondary metabolites displayed a significant negative relationship with maliondialdehyde indicating lowered oxidative stress under high CO2 and low irradiance improved the production of plant secondary metabolites that simultaneously enhanced the antioxidant activity (DPPH), thus improving the medicinal value of Labisia pumila under this condition. PMID:24683336

  20. Allocation of secondary metabolites, photosynthetic capacity, and antioxidant activity of Kacip Fatimah (Labisia pumila Benth) in response to CO2 and light intensity.

    PubMed

    Ibrahim, Mohd Hafiz; Jaafar, Hawa Z E; Karimi, Ehsan; Ghasemzadeh, Ali

    2014-01-01

    A split plot 3 by 4 experiment was designed to investigate and distinguish the relationships among production of secondary metabolites, soluble sugar, phenylalanine ammonia lyase (PAL; EC 4.3.1.5) activity, leaf gas exchange, chlorophyll content, antioxidant activity (DPPH), and lipid peroxidation under three levels of CO2 (400, 800, and 1200 μ mol/mol) and four levels of light intensity (225, 500, 625, and 900 μ mol/m(2)/s) over 15 weeks in Labisia pumila. The production of plant secondary metabolites, sugar, chlorophyll content, antioxidant activity, and malondialdehyde content was influenced by the interactions between CO2 and irradiance. The highest accumulation of secondary metabolites, sugar, maliondialdehyde, and DPPH activity was observed under CO2 at 1200 μ mol/mol + light intensity at 225 μ mol/m(2)/s. Meanwhile, at 400 μ mol/mol CO2 + 900 μ mol/m(2)/s light intensity the production of chlorophyll and maliondialdehyde content was the highest. As CO2 levels increased from 400 to 1200 μ mol/mol the photosynthesis, stomatal conductance, f v /f m (maximum efficiency of photosystem II), and PAL activity were enhanced. The production of secondary metabolites displayed a significant negative relationship with maliondialdehyde indicating lowered oxidative stress under high CO2 and low irradiance improved the production of plant secondary metabolites that simultaneously enhanced the antioxidant activity (DPPH), thus improving the medicinal value of Labisia pumila under this condition.

  1. Effects of ultraviolet radiation (UVA+UVB) on young gametophytes of Gelidium floridanum: growth rate, photosynthetic pigments, carotenoids, photosynthetic performance, and ultrastructure.

    PubMed

    Simioni, Carmen; Schmidt, Eder C; Felix, Marthiellen R de L; Polo, Luz Karime; Rover, Ticiane; Kreusch, Marianne; Pereira, Debora T; Chow, Fungyi; Ramlov, Fernanda; Maraschin, Marcelo; Bouzon, Zenilda L

    2014-01-01

    This study investigated the effects of radiation (PAR+UVA+UVB) on the development and growth rates (GRs) of young gametophytes of Gelidium floridanum. In addition, photosynthetic pigments were quantified, carotenoids identified, and photosynthetic performance assessed. Over a period of 3 days, young gametophytes were cultivated under laboratory conditions and exposed to photosynthetically active radiation (PAR) at 80 μmol photons m(-2) s(-1) and PAR+UVA (0.70 W m(-2))+UVB (0.35 W m(-2)) for 3 h per day. The samples were processed for light and electron microscopy to analyze the ultrastructure features, as well as carry out metabolic studies of GRs, quantify the content of photosynthetic pigments, identify carotenoids and assess photosynthetic performance. PAR+UVA+UVB promoted increase in cell wall thickness, accumulation of floridean starch grains in the cytoplasm and disruption of chloroplast internal organization. Algae exposed to PAR+UVA+UVB also showed a reduction in GR of 97%. Photosynthetic pigments, in particular, phycoerythrin and allophycocyanin contents, decreased significantly from UV radiation exposure. This result agrees with the decrease in photosynthetic performance observed after exposure to ultraviolet radiation, as measured by a decrease in the electron transport rate (ETR), where values of ETRmax declined approximately 44.71%. It can be concluded that radiation is a factor that affects the young gametophytes of G. floridanum at this stage of development.

  2. Corrosion resistant neutron absorbing coatings

    DOEpatents

    Choi, Jor-Shan; Farmer, Joseph C; Lee, Chuck K; Walker, Jeffrey; Russell, Paige; Kirkwood, Jon; Yang, Nancy; Champagne, Victor

    2013-11-12

    A method of forming a corrosion resistant neutron absorbing coating comprising the steps of spray or deposition or sputtering or welding processing to form a composite material made of a spray or deposition or sputtering or welding material, and a neutron absorbing material. Also a corrosion resistant neutron absorbing coating comprising a composite material made of a spray or deposition or sputtering or welding material, and a neutron absorbing material.

  3. Corrosion resistant neutron absorbing coatings

    DOEpatents

    Choi, Jor-Shan; Farmer, Joseph C.; Lee, Chuck K.; Walker, Jeffrey; Russell, Paige; Kirkwood, Jon; Yang, Nancy; Champagne, Victor

    2012-05-29

    A method of forming a corrosion resistant neutron absorbing coating comprising the steps of spray or deposition or sputtering or welding processing to form a composite material made of a spray or deposition or sputtering or welding material, and a neutron absorbing material. Also a corrosion resistant neutron absorbing coating comprising a composite material made of a spray or deposition or sputtering or welding material, and a neutron absorbing material.

  4. Functional Relationship Between Phytoplankton and Aerobic Anoxygenic Photosynthetic Bacteria: Modes of Coexistence

    NASA Astrophysics Data System (ADS)

    Kolber, Z. S.; Haffa, A.; Klimov, D.

    2006-12-01

    Aerobic Anoxygenic Photosynthetic Bacteria (AAPs) are ubiquitously distributed in the upper ocean. Although they contain bacteriochlorophyll a (BChla), the main absorption bands in the near UV (370 nm) and infrared (800-850 nm) make this pigment impractical in light harvesting below the first few meters of the water column. Instead, they utilize carotenoids as major light harvesting pigments. Since these carotenoids absorb in the 430-550 nm range, phytoplankton and AAPs utilize a similar portion of the available light spectrum. As AAPs cannot utilize water as the electron donor, they transfer electrons between a range of organic/inorganic electron donors and electron acceptors, thus significantly participating in the redox cycle in the upper ocean. We have measured the vertical distribution and photosynthetic properties of both phytoplankton and AAPs in a highly oligotrophic region 800 km SW of Monterey Bay (34N, 129W), and we have consistently observed the presence of a BChla maximum about 30 to 40 meters above the chlorophyll maximum, indicating that phytoplankton and AAPs occupy different ecological niches in the water column. However, the abundance of AAPs generally displayed a maximum at dawn and a minimum at the dusk, indicating a high level of mortality. This diel cycle was observed in 5 micron and 3 micron size fractions, indicating active grazing by small protists. Incubation experiments with natural, mixed population of AAPs and phytoplankton results in an unusually high accumulation of AAPs in DCMU-treated samples, indicating that pigmented protists do contribute significantly to AAP grazing in a tightly-controlled microbial loop. On the other hand, AAP incubations in pure cultures indicate that they biomineralize sulfur, thus affecting the sulfur cycle. All of these observations indicate that the role of AAPs in the upper ocean ecology is defined by their relationship with phototrophic and heterotrophic communities, rather than by their relative

  5. Tunable microwave metamaterial absorbers using varactor-loaded split loops

    NASA Astrophysics Data System (ADS)

    Zhu, Jinfeng; Li, Delong; Yan, Shuang; Cai, Yijun; Huo Liu, Qing; Lin, Timothy

    2015-12-01

    Currently, implementation of active circuit elements within metamaterials is an effective way to make them electrically tunable. We combine varactors with split copper loops in a metamaterial absorber in order to obtain an electrically tunable microwave response. This absorber has a compact planar structure and a simplified back feeding network. Flexible frequency tunability of the microwave reflection in the range of 5-6 GHz is experimentally achieved. The design, simulation, and experimental results are systematically presented. The proposed method is scalable for developing active metamaterial absorbers based on metal loops, and shows a promising potential of active metamaterial absorbers for extensive microwave applications.

  6. Underwater acoustic omnidirectional absorber

    NASA Astrophysics Data System (ADS)

    Naify, Christina J.; Martin, Theodore P.; Layman, Christopher N.; Nicholas, Michael; Thangawng, Abel L.; Calvo, David C.; Orris, Gregory J.

    2014-02-01

    Gradient index media, which are designed by varying local element properties in given geometry, have been utilized to manipulate acoustic waves for a variety of devices. This study presents a cylindrical, two-dimensional acoustic "black hole" design that functions as an omnidirectional absorber for underwater applications. The design features a metamaterial shell that focuses acoustic energy into the shell's core. Multiple scattering theory was used to design layers of rubber cylinders with varying filling fractions to produce a linearly graded sound speed profile through the structure. Measured pressure intensity agreed with predicted results over a range of frequencies within the homogenization limit.

  7. Solar radiation absorbing material

    DOEpatents

    Googin, John M.; Schmitt, Charles R.; Schreyer, James M.; Whitehead, Harlan D.

    1977-01-01

    Solar energy absorbing means in solar collectors are provided by a solar selective carbon surface. A solar selective carbon surface is a microporous carbon surface having pores within the range of 0.2 to 2 micrometers. Such a surface is provided in a microporous carbon article by controlling the pore size. A thermally conductive substrate is provided with a solar selective surface by adhering an array of carbon particles in a suitable binder to the substrate, a majority of said particles having diameters within the range of about 0.2-10 microns.

  8. Primary, Secondary Metabolites, Photosynthetic Capacity and Antioxidant Activity of the Malaysian Herb Kacip Fatimah (Labisia Pumila Benth) Exposed to Potassium Fertilization under Greenhouse Conditions

    PubMed Central

    Ibrahim, Mohd Hafiz; Jaafar, Hawa Z. E.; Karimi, Ehsan; Ghasemzadeh, Ali

    2012-01-01

    A randomized complete block design was used to characterize the relationship between production of total phenolics, flavonoids, ascorbic acid, carbohydrate content, leaf gas exchange, phenylalanine ammonia-lyase (PAL), soluble protein, invertase and antioxidant enzyme activities (ascorbate peroxidase (APX), catalase (CAT) and superoxide dismutase (SOD) in Labisia pumila Benth var. alata under four levels of potassium fertilization experiments (0, 90, 180 and 270 kg K/ha) conducted for 12 weeks. It was found that the production of total phenolics, flavonoids, ascorbic acid and carbohydrate content was affected by the interaction between potassium fertilization and plant parts. As the potassium fertilization levels increased from 0 to 270 kg K/ha, the production of soluble protein and PAL activity increased steadily. At the highest potassium fertilization (270 kg K/ha) L. pumila exhibited significantly higher net photosynthesis (A), stomatal conductance (gs), intercellular CO2 (Ci), apparent quantum yield (ξ) and lower dark respiration rates (Rd), compared to the other treatments. It was found that the production of total phenolics, flavonoids and ascorbic acid are also higher under 270 kg K/ha compared to 180, 90 and 0 kg K/ha. Furthermore, from the present study, the invertase activity was also found to be higher in 270 kg K/ha treatment. The antioxidant enzyme activities (APX, CAT and SOD) were lower under high potassium fertilization (270 kg K/ha) and have a significant negative correlation with total phenolics and flavonoid production. From this study, it was observed that the up-regulation of leaf gas exchange and downregulation of APX, CAT and SOD activities under high supplementation of potassium fertilizer enhanced the carbohydrate content that simultaneously increased the production of L. pumila secondary metabolites, thus increasing the health promoting effects of this plant. PMID:23203128

  9. Primary, secondary metabolites, photosynthetic capacity and antioxidant activity of the Malaysian Herb Kacip Fatimah (Labisia Pumila Benth) exposed to potassium fertilization under greenhouse conditions.

    PubMed

    Ibrahim, Mohd Hafiz; Jaafar, Hawa Z E; Karimi, Ehsan; Ghasemzadeh, Ali

    2012-11-20

    A randomized complete block design was used to characterize the relationship between production of total phenolics, flavonoids, ascorbic acid, carbohydrate content, leaf gas exchange, phenylalanine ammonia-lyase (PAL), soluble protein, invertase and antioxidant enzyme activities (ascorbate peroxidase (APX), catalase (CAT) and superoxide dismutase (SOD) in Labisia pumila Benth var. alata under four levels of potassium fertilization experiments (0, 90, 180 and 270 kg K/ha) conducted for 12 weeks. It was found that the production of total phenolics, flavonoids, ascorbic acid and carbohydrate content was affected by the interaction between potassium fertilization and plant parts. As the potassium fertilization levels increased from 0 to 270 kg K/ha, the production of soluble protein and PAL activity increased steadily. At the highest potassium fertilization (270 kg K/ha) L. pumila exhibited significantly higher net photosynthesis (A), stomatal conductance (g(s)), intercellular CO(2) (C(i)), apparent quantum yield (ξ) and lower dark respiration rates (R(d)), compared to the other treatments. It was found that the production of total phenolics, flavonoids and ascorbic acid are also higher under 270 kg K/ha compared to 180, 90 and 0 kg K/ha. Furthermore, from the present study, the invertase activity was also found to be higher in 270 kg K/ha treatment. The antioxidant enzyme activities (APX, CAT and SOD) were lower under high potassium fertilization (270 kg K/ha) and have a significant negative correlation with total phenolics and flavonoid production. From this study, it was observed that the up-regulation of leaf gas exchange and downregulation of APX, CAT and SOD activities under high supplementation of potassium fertilizer enhanced the carbohydrate content that simultaneously increased the production of L. pumila secondary metabolites, thus increasing the health promoting effects of this plant.

  10. [Influence of photosynthetic parameters on leaf longevity].

    PubMed

    Vasfilov, S P

    2015-01-01

    Higher plants show a wide range of leaf lifespan (LL) variability. LL is calculated as a sum of functional LL(f) (corresponding to the time of active photosynthesis and CO2 accumulation in the leaf) and nonfunctional LL(n) (the time of photosynthetic activity absence). For evergreen species of boreal zones, LL(n) corresponds to the period of winter rest. Photosynthetic potential of leaf (PPL), interpreted as the maximum possible amount of CO2 that can be fixed during its life, can be estimated on the basis of maximum photosynthesis rate (P(a)) dynamics during LL(f); the maximum (P(a max)) being achieved in mature leaf. Photosynthetic potential depends on LL(f) more strongly than on P(a max). The PPL/LL(f) ratio is indicative of the rate of PPL realization over leaf lifespan. As LL(f) shows strong positive correlation with LL, the latter parameter can also characterize the rate of PPL realization. Long LL(f) in evergreen species provides higher PPL, which is advantageous by comparison with deciduous ones. In evergreen species, the PPL itself is realized slower than in deciduous ones. The increase in LL(f) and LL is accompanied by the increase in leaf constructional cost (LCC(a)) as well as the decrease in photosynthesis rate. At that, photosynthesis rate per unit of dry weight (P(m)) decreases much faster than that per unit of leaf area (P(a)). Apparently, when considering dry leaf weight, the apoplast share seems to be much higher in long-living leaves of evergreen species than in short-living leaves of deciduous species. The leaf payback (LP) may be stabilized by unidirectional shifts in PPL and LCC(a). Species with short/long LL(f) and high/low PPL realization rate are typical for early/late succession stages and for habitats with the environmental conditions favorable/adverse for photosynthesis and growth. If the conditions for photosynthesis and growth are favorable, high PPL realization rate provides advantage in competition. The PPL realization rate is

  11. Nitrogen fixation by photosynthetic bacteria in lowland rice culture.

    PubMed

    Habte, M; Alexander, M

    1980-02-01

    Propanil (3',4'-dichloropropionanilide) was a potent inhibitor of the nitrogenase activity of blue-green algae (cyanobacteria) in flooded soil, but the herbicide at comparable concentrations was not toxic to rice, protozoa, and nitrogen-fixing bacteria. Ethanol-amended flooded soils treated with propanil exhibited higher rates of nitrogenase activity than those not treated with the herbicide. The enhanced nitrogenase activity in propanil-treated soils was associated with a rise in the population of purple sulfur bacteria, especially of cells resembling Chromatium and Thiospirillum. By employing propanil and a means of excluding light from the floodwater to prevent the development of phototrophs during rice growth under lowland conditions, the relative activities of blue-green algae, photosynthetic bacteria, and the rhizosphere microflora were determined. The results suggest that the potential contribution of photosynthetic bacteria may be quite high. PMID:16345507

  12. Nitrogen Fixation by Photosynthetic Bacteria in Lowland Rice Culture

    PubMed Central

    Habte, M.; Alexander, M.

    1980-01-01

    Propanil (3′,4′-dichloropropionanilide) was a potent inhibitor of the nitrogenase activity of blue-green algae (cyanobacteria) in flooded soil, but the herbicide at comparable concentrations was not toxic to rice, protozoa, and nitrogen-fixing bacteria. Ethanol-amended flooded soils treated with propanil exhibited higher rates of nitrogenase activity than those not treated with the herbicide. The enhanced nitrogenase activity in propanil-treated soils was associated with a rise in the population of purple sulfur bacteria, especially of cells resembling Chromatium and Thiospirillum. By employing propanil and a means of excluding light from the floodwater to prevent the development of phototrophs during rice growth under lowland conditions, the relative activities of blue-green algae, photosynthetic bacteria, and the rhizosphere microflora were determined. The results suggest that the potential contribution of photosynthetic bacteria may be quite high. PMID:16345507

  13. Calibration of the Odyssey Photosynthetic Irradiance Recorder for Absolute Irradiance Measures

    EPA Science Inventory

    Researchers are increasingly interested in measuring hotosynthetically active radiation (PAR) because of its importance in determining the structure and function of lotic ecosystems. The Odyssey Photosynthetic Irradiance Recorder is an affordable PAR meter gaining popularity am...

  14. Photosynthetic CO{sub 2} fixation and energy production - microalgae as a main subject

    SciTech Connect

    Asada, Yasuo

    1993-12-31

    Research activities for application of microalgal photosynthesis to CO{sub 2} fixation in Japan are overviewed. Presenter`s studies on energy (hydrogen gas) production by cyanobacteria (blue-green algae) and photosynthetic bacteria are also introduced.

  15. Simplicity in complexity: the photosynthetic reaction center performs as a simple 0.2 V battery.

    PubMed

    van Rotterdam, Bart J; Crielaard, Wim; van Stokkum, Ivo H M; Hellingwerf, Klaas J; Westerhoff, Hans V

    2002-01-01

    The photosynthetic reaction center is one of the most complicated molecular complexes. Transducing photon energy to a transmembrane electrochemical potential difference for protons, it is the direct or indirect energy source for virtually all life. We show here that it operates in a simple, battery-like manner, with a maximum potential of 0.20 V. Intriguingly this is only one fifth of the energy of the absorbed photon.

  16. Bioinspired hollow semiconductor nanospheres as photosynthetic nanoparticles

    NASA Astrophysics Data System (ADS)

    Sun, Jianhua; Zhang, Jinshui; Zhang, Mingwen; Antonietti, Markus; Fu, Xianzhi; Wang, Xinchen

    2012-10-01

    Natural photosynthesis occurs in the thylakoid membrane where functional proteins and electron carriers are precisely arranged to efficiently convert sunlight into a chemical potential between the two membrane sides, via charge separation and electron transport chains, for use in oxygen generation and CO2 fixation. These light-harvesting complexes and cofactors have been actively mimicked using dyes, semiconductors and catalytic nanoparticles. However, the photosynthetic scaffold that optimizes both the capture and distribution of light and separates both the oxidative and reductive species has been mimicked much less often, especially using polymer substances. Here we report the synthesis of hollow nanospheres sized in the optical range and made of a robust semiconductor, melon or carbon-nitride polymer. These hollow nanospheres are shown to function as both light-harvesting antennae and nanostructured scaffolds that improve photoredox catalysis, which was determined to have a 7.5% apparent quantum yield via a hydrogen-generation assay.

  17. Liquid Cryogen Absorber for MICE

    SciTech Connect

    Baynham, D.E.; Bish, P.; Bradshaw, T.W.; Cummings, M.A.; Green,M.A.; Ishimoto, S.; Ivaniouchenkov, I.; Lau, W.; Yang, S.Q.; Zisman, M.S.

    2005-08-20

    The Muon Ionization Cooling Experiment (MICE) will test ionization cooling of muons. In order to have effective ionization cooling, one must use an absorber that is made from a low-z material. The most effective low z materials for ionization cooling are hydrogen, helium, lithium hydride, lithium and beryllium, in that order. In order to measure the effect of material on cooling, several absorber materials must be used. This report describes a liquid-hydrogen absorber that is within a pair of superconducting focusing solenoids. The absorber must also be suitable for use with liquid helium. The following absorber components are discussed in this report; the absorber body, its heat exchanger, the hydrogen system, and the hydrogen safety. Absorber cooling and the thin windows are not discussed here.

  18. Photosynthetic carbon assimilation in the coccolithophorid Emiliania huxleyi (Haptophyta): Evidence for the predominant operation of the c3 cycle and the contribution of {beta}-carboxylases to the active anaplerotic reaction.

    PubMed

    Tsuji, Yoshinori; Suzuki, Iwane; Shiraiwa, Yoshihiro

    2009-02-01

    The coccolithophorid Emiliania huxleyi (Haptophyta) is a representative and unique marine phytoplankton species that fixes inorganic carbon by photosynthesis and calci-fication. We examined the initial process of photosynthetic carbon assimilation by analyses of metabolites, enzymes and genes. When the cells were incubated with a radioactive substrate (2.3 mM NaH(14)CO(3)) for 10 s under illumination, 70% of the (14)C was incorporated into the 80% methanol-soluble fraction. Eighty-five and 15% of (14)C in the soluble fraction was incorporated into phosphate esters (P-esters), including the C(3) cycle intermediates and a C(4) compound, aspartate, respectively. A pulse-chase experiment showed that (14)C in P-esters was mainly transferred into lipids, while [(14)C]aspartate, [(14)C]alanine and [(14)C]glutamate levels remained almost constant. These results indicate that the C(3) cycle functions as the initial pathway of carbon assimilation and that beta-carboxylation contributes to the production of amino acids in subsequent metabolism. Transcriptional analysis of beta-carboxylases such as pyruvate carboxylase (PYC), phosphoenolpyruvate carboxylase (PEPC) and phosphoenolpyruvate carboxykinase (PEPCK) revealed that PYC and PEPC transcripts were greatly increased under illumination, whereas the PEPCK transcript decreased remarkably. PEPC activity was higher in light-grown cells than in dark-adapted cells. PYC activity was detected in isolated chloroplasts of light-grown cells. According to analysis of their deduced N-terminal sequence, PYC and PEPC are predicted to be located in the chloroplasts and mitochondria, respectively. These results suggest that E. huxleyi possesses unique carbon assimila-tion mechanisms in which beta-carboxylation by both PYC and PEPC plays important roles in different organelles.

  19. Role of an elliptical structure in photosynthetic energy transfer: Collaboration between quantum entanglement and thermal fluctuation.

    PubMed

    Oka, Hisaki

    2016-05-13

    Recent experiments have revealed that the light-harvesting complex 1 (LH1) in purple photosynthetic bacteria has an elliptical structure. Generally, symmetry lowering in a structure leads to a decrease in quantum effects (quantum coherence and entanglement), which have recently been considered to play a role in photosynthetic energy transfer, and hence, elliptical structure seems to work against efficient photosynthetic energy transfer. Here we analyse the effect of an elliptical structure on energy transfer in a purple photosynthetic bacterium and reveal that the elliptical distortion rather enhances energy transfer from peripheral LH2 to LH1 at room temperature. Numerical results show that quantum entanglement between LH1 and LH2 is formed over a wider range of high energy levels than would have been the case with circular LH1. Light energy absorbed by LH2 is thermally pumped via thermal fluctuation and is effectively transferred to LH1 through the entangled states at room temperature rather than at low temperature. This result indicates the possibility that photosynthetic systems adopt an elliptical structure to effectively utilise both quantum entanglement and thermal fluctuation at physiological temperature.

  20. Role of an elliptical structure in photosynthetic energy transfer: Collaboration between quantum entanglement and thermal fluctuation

    NASA Astrophysics Data System (ADS)

    Oka, Hisaki

    2016-05-01

    Recent experiments have revealed that the light-harvesting complex 1 (LH1) in purple photosynthetic bacteria has an elliptical structure. Generally, symmetry lowering in a structure leads to a decrease in quantum effects (quantum coherence and entanglement), which have recently been considered to play a role in photosynthetic energy transfer, and hence, elliptical structure seems to work against efficient photosynthetic energy transfer. Here we analyse the effect of an elliptical structure on energy transfer in a purple photosynthetic bacterium and reveal that the elliptical distortion rather enhances energy transfer from peripheral LH2 to LH1 at room temperature. Numerical results show that quantum entanglement between LH1 and LH2 is formed over a wider range of high energy levels than would have been the case with circular LH1. Light energy absorbed by LH2 is thermally pumped via thermal fluctuation and is effectively transferred to LH1 through the entangled states at room temperature rather than at low temperature. This result indicates the possibility that photosynthetic systems adopt an elliptical structure to effectively utilise both quantum entanglement and thermal fluctuation at physiological temperature.

  1. Role of an elliptical structure in photosynthetic energy transfer: Collaboration between quantum entanglement and thermal fluctuation

    PubMed Central

    Oka, Hisaki

    2016-01-01

    Recent experiments have revealed that the light-harvesting complex 1 (LH1) in purple photosynthetic bacteria has an elliptical structure. Generally, symmetry lowering in a structure leads to a decrease in quantum effects (quantum coherence and entanglement), which have recently been considered to play a role in photosynthetic energy transfer, and hence, elliptical structure seems to work against efficient photosynthetic energy transfer. Here we analyse the effect of an elliptical structure on energy transfer in a purple photosynthetic bacterium and reveal that the elliptical distortion rather enhances energy transfer from peripheral LH2 to LH1 at room temperature. Numerical results show that quantum entanglement between LH1 and LH2 is formed over a wider range of high energy levels than would have been the case with circular LH1. Light energy absorbed by LH2 is thermally pumped via thermal fluctuation and is effectively transferred to LH1 through the entangled states at room temperature rather than at low temperature. This result indicates the possibility that photosynthetic systems adopt an elliptical structure to effectively utilise both quantum entanglement and thermal fluctuation at physiological temperature. PMID:27173144

  2. Relationship between leaf temperature and photosynthetic ratio of cherry tree

    NASA Astrophysics Data System (ADS)

    Nakashima, Atsushi; Ogura, Yasushi; Fujigaki, Motoharu; Tanikawa, Hiroki; Miwa, Masafumi

    2003-03-01

    We investigated the relations between leaf-air temperature and photosynthetic ratio of cherry trees in order to obtain the fundamental data for applying the biological information to the remote sensing system. Some branches of Prunus jamasakura were cut and put into the water pot prompt once per month from May to October 2001. We measured the surface temperature of ten leaves and photosynthetic ratio every five second for ten minutes every measurement air temperature condition at 20, 25, 30 and 35°C with 1000 PAR light intensity. Result as, there was recognized the small significantly relation between leaf temperature and photosynthetic ratio because leaf temperature is usually changed with air temperature. Although, there was recognized large significantly correlations between the difference of the leaf temperature and air temperature and photosynthetic ratio. It is thought that transpiring in healthy plants are active for absorption of water and it cause to drop the leaf temperature. This research showed that the health of cherry trees could be diagnosed for measurement of the difference of leaf and air temperature.

  3. Dual broadband metamaterial absorber.

    PubMed

    Kim, Young Ju; Yoo, Young Joon; Kim, Ki Won; Rhee, Joo Yull; Kim, Yong Hwan; Lee, YoungPak

    2015-02-23

    We propose polarization-independent and dual-broadband metamaterial absorbers at microwave frequencies. This is a periodic meta-atom array consisting of metal-dielectric-multilayer truncated cones. We demonstrate not only one broadband absorption from the fundamental magnetic resonances but additional broadband absorption in high-frequency range using the third-harmonic resonance, by both simulation and experiment. In simulation, the absorption was over 90% in 3.93-6.05 GHz, and 11.64-14.55 GHz. The corresponding experimental absorption bands over 90% were 3.88-6.08 GHz, 9.95-10.46 GHz and 11.86-13.84 GHz, respectively. The origin of absorption bands was elucidated. Furthermore, it is independent of polarization angle owing to the multilayered circular structures. The design is scalable to smaller size for the infrared and the visible ranges.

  4. Potassium deficiency affects water status and photosynthetic rate of the vegetative sink in green house tomato prior to its effects on source activity.

    PubMed

    Kanai, Synsuke; Moghaieb, Reda E; El-Shemy, Hany A; Panigrahi, R; Mohapatra, Pravat K; Ito, J; Nguyen, Nguyen T; Saneoka, Hirofumi; Fujita, Kounosuke

    2011-02-01

    The potassium requirement of green house tomatoes is very high for vegetative growth and fruit production. Potassium deficiency in plants takes long time for expression of visible symptoms. The objective of this study is to detect the deficiency early during the vegetative growth and define the roles of aquaporin and K-channel transporters in the process of regulation of water status and source-sink relationship. The tomato plants were grown hydroponically inside green house of Hiroshima University, Japan and subjected to different levels of K in the rooting medium. Potassium deficiency stress decreased photosynthesis, expansion and transport of ¹⁴C assimilates of the source leaf, but the effects became evident only after diameter expansion of the growing stem (sink) was down-regulated. The depression of stem diameter expansion is assumed to be associated with the suppression of water supply more than photosynthate supply to the organ. The stem diameter expansion is parameterized by root water uptake and leaf transpiration rates. The application of aquaporin inhibitor (AgNO₃) decreased leaf water potential, stem expansion and root hydraulic conductance within minutes of application. Similar results were obtained for application of the K-channel inhibitors. These observations suggested a close relationship between stem diameter expansion and activities of aquaporins and K-channel transporters in roots. The deficiency of potassium might have reduced aquaporin activity, consequently suppressing root hydraulic conductance and water supply to the growing stem for diameter expansion and leaf for transpiration. We conclude that close coupling between aquaporins and K-channel transporters in water uptake of roots is responsible for regulation of stem diameter dynamics of green house tomato plants. PMID:21421382

  5. Potassium deficiency affects water status and photosynthetic rate of the vegetative sink in green house tomato prior to its effects on source activity.

    PubMed

    Kanai, Synsuke; Moghaieb, Reda E; El-Shemy, Hany A; Panigrahi, R; Mohapatra, Pravat K; Ito, J; Nguyen, Nguyen T; Saneoka, Hirofumi; Fujita, Kounosuke

    2011-02-01

    The potassium requirement of green house tomatoes is very high for vegetative growth and fruit production. Potassium deficiency in plants takes long time for expression of visible symptoms. The objective of this study is to detect the deficiency early during the vegetative growth and define the roles of aquaporin and K-channel transporters in the process of regulation of water status and source-sink relationship. The tomato plants were grown hydroponically inside green house of Hiroshima University, Japan and subjected to different levels of K in the rooting medium. Potassium deficiency stress decreased photosynthesis, expansion and transport of ¹⁴C assimilates of the source leaf, but the effects became evident only after diameter expansion of the growing stem (sink) was down-regulated. The depression of stem diameter expansion is assumed to be associated with the suppression of water supply more than photosynthate supply to the organ. The stem diameter expansion is parameterized by root water uptake and leaf transpiration rates. The application of aquaporin inhibitor (AgNO₃) decreased leaf water potential, stem expansion and root hydraulic conductance within minutes of application. Similar results were obtained for application of the K-channel inhibitors. These observations suggested a close relationship between stem diameter expansion and activities of aquaporins and K-channel transporters in roots. The deficiency of potassium might have reduced aquaporin activity, consequently suppressing root hydraulic conductance and water supply to the growing stem for diameter expansion and leaf for transpiration. We conclude that close coupling between aquaporins and K-channel transporters in water uptake of roots is responsible for regulation of stem diameter dynamics of green house tomato plants.

  6. Photosynthetic and molecular markers of CO₂-mediated photosynthetic downregulation in nodulated alfalfa.

    PubMed

    Sanz-Sáez, Alvaro; Erice, Gorka; Aranjuelo, Iker; Aroca, Ricardo; Ruíz-Lozano, Juan Manuel; Aguirreolea, Jone; Irigoyen, Juan José; Sanchez-Diaz, Manuel

    2013-08-01

    Elevated CO₂ leads to a decrease in potential net photosynthesis in long-term experiments and thus to a reduction in potential growth. This process is known as photosynthetic downregulation. There is no agreement on the definition of which parameters are the most sensitive for detecting CO₂ acclimation. In order to investigate the most sensitive photosynthetic and molecular markers of CO₂ acclimation, the effects of elevated CO₂, and associated elevated temperature were analyzed in alfalfa plants inoculated with different Sinorhizobium meliloti strains. Plants (Medicago sativa L. cv. Aragón) were grown in summer or autumn in temperature gradient greenhouses (TGG). At the end of the experiment, all plants showed acclimation in both seasons, especially under elevated summer temperatures. This was probably due to the lower nitrogen (N) availability caused by decreased N₂-fixation under higher temperatures. Photosynthesis measured at growth CO₂ concentration, rubisco in vitro activity and maximum rate of carboxylation were the most sensitive parameters for detecting downregulation. Severe acclimation was also related with decreases in leaf nitrogen content associated with declines in rubisco content (large and small subunits) and activity that resulted in a drop in photosynthesis. Despite the sensitivity of rubisco content as a marker of acclimation, it was not coordinated with gene expression, possibly due to a lag between gene transcription and protein translation.

  7. [Photosynthetic characteristics of Gynostemma pentaphyllum under shade].

    PubMed

    Huang, Chenglin; Wu, Zemin; Yao, Yongkang; Xu, Xiaoniu

    2004-11-01

    The study showed that under summer shade condition, the diurnal variation of net photosynthetic rate of Gynostemma pentaphyllum presented nontypical double apex, the first apex being 13.8 micromol CO2 x m(-2) x s(-1) at 11:00, and the diurnal net photosynthetic rate was about 176.97 micromol CO2 x m(-2), 3.1 times of that under full sunlight. There was a positive correlation between net photosynthetic rate and photon flux density (PFD), and relative humidity had a small effect on net photosynthetic rate. Under full sunlight, the typical "midday depression" of photosynthesis was observed, and the diurnal variation of net photosynthetic rate presented double apex, with the first apex being 3.0 micromol CO2 x m(-2) x s(-1) at 10:00 and the second being 1.25 micromol CO2 x m(-2) x s(-1) at 14:00. There was a positive correlation between net photosynthetic rate and relative humidity, and the latter had a strong effect on net photosynthetic rate. When PFD was higher than 700 micromol CO2 x m(-2) x s(-1), it had a negative correlation with net photosynthetic rate. Stoma conductance was the main factor affecting the transpiration rate of Gynostemma pentaphyllum. Therefore, Gynostemma pentaphyllum was a typical sciophytic plant, and light factor should be considered firstly in its cultivation. PMID:15707321

  8. Anthropogenic impacts on photosynthetic activity: a multidisciplinary context for research training. Final report for period September 15, 1992 - September 14, 1998

    SciTech Connect

    Colin A. Wraight

    1999-01-01

    Under the federal agency initiative for Collaborative Research in Plant Biology, the intrinsic breadth of photosynthesis research at the University of Illinois was developed as a paradigm for training in modern biology. Research projects were developed to prepare students for understanding and contributing to the solution of pressing issues of plant biology, broadly defined as anthropogenic impacts on photosynthesis and plant productivity, and to provide students with an interdisciplinary outlook and multidisciplinary technical abilities. By coordinating the expertise of two or more faculty laboratories, the projects took and integrated and comparative approach to investigating the varied mechanisms adopted by plants for coping with environmental limitations and stresses, especially those that are at risk for increased impact due to human activities and technology. In addition to graduate and post-doctoral training, the program supported undergraduate involvement in hands-on research, through Summer Fellowships. A two week Summer workshop was also developed specifically for high school and community college science teachers. Offered each year, the Workshop provided perspectives on modern science, arming the participants with knowledge of societally important issues such as global climate change and prospects for biotechnology, and providing easily transferable techniques to take back to their own classrooms.

  9. Role of various hormones in photosynthetic responses of green plants under environmental stresses.

    PubMed

    Poonam; Bhardwaj, Renu; Kaur, Ravdeep; Bali, Shagun; Kaur, Parminder; Sirhindi, Geetika; Thukral, Ashwani K; Ohri, Puja; Vig, Adarsh P

    2015-01-01

    Environmental stress includes adverse factors like water deficit, high salinity, enhanced temperature and heavy metals etc. These stresses alter the normal growth and metabolic processes of plants including photosynthesis. Major photosynthetic responses under various stresses include inhibition of photosystems (I and II), changes in thylakoid complexes, decreased photosynthetic activity and modifications in structure and functions of chloroplasts etc. Various defense mechanisms are triggered inside the plants in response to these stresses that are regulated by plant hormones or plant growth regulators. These phytohormones include abscisic acid, auxins, cytokinins, ethylene, brassinosteroids, jasmonates and salicylic acid etc. The present review focuses on stress protective effects of plants hormones on the photosynthetic responses.

  10. Photosynthetic energy conversion efficiency: setting a baseline for gauging future improvements in important food and biofuel crops.

    PubMed

    Slattery, Rebecca A; Ort, Donald R

    2015-06-01

    The conversion efficiency (ε(c)) of absorbed radiation into biomass (MJ of dry matter per MJ of absorbed photosynthetically active radiation) is a component of yield potential that has been estimated at less than half the theoretical maximum. Various strategies have been proposed to improve ε(c), but a statistical analysis to establish baseline ε(c) levels across different crop functional types is lacking. Data from 164 published ε(c) studies conducted in relatively unstressed growth conditions were used to determine the means, greatest contributors to variation, and genetic trends in ε(c )across important food and biofuel crop species. ε(c) was greatest in biofuel crops (0.049-0.066), followed by C4 food crops (0.046-0.049), C3 nonlegumes (0.036-0.041), and finally C3 legumes (0.028-0.035). Despite confining our analysis to relatively unstressed growth conditions, total incident solar radiation and average growing season temperature most often accounted for the largest portion of ε(c) variability. Genetic improvements in ε(c), when present, were less than 0.7% per year, revealing the unrealized potential of improving ε(c) as a promising contributing strategy to meet projected future agricultural demand.

  11. Photosynthetic energy conversion efficiency: setting a baseline for gauging future improvements in important food and biofuel crops.

    PubMed

    Slattery, Rebecca A; Ort, Donald R

    2015-06-01

    The conversion efficiency (ε(c)) of absorbed radiation into biomass (MJ of dry matter per MJ of absorbed photosynthetically active radiation) is a component of yield potential that has been estimated at less than half the theoretical maximum. Various strategies have been proposed to improve ε(c), but a statistical analysis to establish baseline ε(c) levels across different crop functional types is lacking. Data from 164 published ε(c) studies conducted in relatively unstressed growth conditions were used to determine the means, greatest contributors to variation, and genetic trends in ε(c )across important food and biofuel crop species. ε(c) was greatest in biofuel crops (0.049-0.066), followed by C4 food crops (0.046-0.049), C3 nonlegumes (0.036-0.041), and finally C3 legumes (0.028-0.035). Despite confining our analysis to relatively unstressed growth conditions, total incident solar radiation and average growing season temperature most often accounted for the largest portion of ε(c) variability. Genetic improvements in ε(c), when present, were less than 0.7% per year, revealing the unrealized potential of improving ε(c) as a promising contributing strategy to meet projected future agricultural demand. PMID:25829463

  12. Design of a reusable kinetic energy absorber for an astronaut safety tether to be used during extravehicular activities on the Space Station

    NASA Technical Reports Server (NTRS)

    Borthwick, Dawn E.; Cronch, Daniel F.; Nixon, Glen R.

    1991-01-01

    The goal of this project is to design a reusable safety device for a waist tether which will absorb the kinetic energy of an astronaut drifting away from the Space Station. The safety device must limit the tension of the tether line in order to prevent damage to the astronaut's space suit or to the structure of the spacecraft. The tether currently used on shuttle missions must be replaced after the safety feature has been developed. A reusable tether for the Space Station would eliminate the need for replacement tethers, conserving space and mass. This report presents background information, scope and limitations, methods of research and development, alternative designs, a final design solution and its evaluation, and recommendations for further work.

  13. Broadband patterned magnetic microwave absorber

    SciTech Connect

    Li, Wei; Wu, Tianlong; Wang, Wei; Guan, Jianguo; Zhai, Pengcheng

    2014-07-28

    It is a tough task to greatly improve the working bandwidth for the traditional flat microwave absorbers because of the restriction of available material parameters. In this work, a simple patterning method is proposed to drastically broaden the absorption bandwidth of a conventional magnetic absorber. As a demonstration, an ultra-broadband microwave absorber with more than 90% absorption in the frequency range of 4–40 GHz is designed and experimentally realized, which has a thin thickness of 3.7 mm and a light weight equivalent to a 2-mm-thick flat absorber. In such a patterned absorber, the broadband strong absorption is mainly originated from the simultaneous incorporation of multiple λ/4 resonances and edge diffraction effects. This work provides a facile route to greatly extend the microwave absorption bandwidth for the currently available absorbing materials.

  14. Liquid Hydrogen Absorber for MICE

    SciTech Connect

    Ishimoto, S.; Suzuki, S.; Yoshida, M.; Green, Michael A.; Kuno, Y.; Lau, Wing

    2010-05-30

    Liquid hydrogen absorbers for the Muon Ionization Cooling Experiment (MICE) have been developed, and the first absorber has been tested at KEK. In the preliminary test at KEK we have successfully filled the absorber with {approx}2 liters of liquid hydrogen. The measured hydrogen condensation speed was 2.5 liters/day at 1.0 bar. No hydrogen leakage to vacuum was found between 300 K and 20 K. The MICE experiment includes three AFC (absorber focusing coil) modules, each containing a 21 liter liquid hydrogen absorber made of aluminum. The AFC module has safety windows to separate its vacuum from that of neighboring modules. Liquid hydrogen is supplied from a cryocooler with cooling power 1.5 W at 4.2 K. The first absorber will be assembled in the AFC module and installed in MICE at RAL.

  15. [Spatial heterogeneity of photosynthetic characteristics of Castanopsis fargesii canopy].

    PubMed

    Meng, Chen; Xu, Ming-Ce; Li, Jun-Xiang; Gao, San-Ping

    2007-09-01

    The vertical and horizontal differences in the energy transmission, photosynthetically active radiation, and micrometeorological characteristics of forest canopy can lead to a considerable heterogeneity, which should be analyzed when estimating forest primary productivity. With Castanopsis fargesii, the dominant species in the subtropical evergreen broad-leaved forest in Tiantong National Forest Park of Zhejiang Province as test object, this paper studied the vertical and horizontal variations of photosynthetic characteristics of its canopy. Vertically, the photosynthetic indices such as maximum photosynthetic rate (Amax), light saturation point (LSP), and carboxylation efficiency (CCE) of north-facing leaves in the canopy all declined in the sequence of top canopy > mid-canopy > bottom canopy. The mean values of light compensation point (LCP), respiration in light (Rd), and Amax from top canopy to bottom canopy reduced by 19.4% , 18.1% and 37.1% , respectively. The LSP and CCE of south-facing leaves followed the pattern of top canopy > bottom canopy > mid-canopy. These two indices decreased by 12.3% in bottom canopy and 71.4% in mid-canopy, compared with those in top canopy. The apparent quantum yield (AQY) of leaves followed the sequence of bottom canopy > top canopy > mid-canopy, being 1.1 and 1.3 times higher at bottom canopy than at top- and mid-canopy, respectively. Horizontally, the Amax, LSP and CCE of south-facing leaves at top- and bottom canopy were 0.9%-31.5% higher than those of north-facing leaves. In mid-canopy however, the values of test six indices of north-facing leaves were 9.6%-63.2% higher than those of south-facing leaves. It was suggested that in order to estimate and model forest primary productivity accurately, the vertical and horizontal heterogeneity of photosynthetic characteristics of forest canopy should be analyzed.

  16. Oxygen absorbers in food preservation: a review.

    PubMed

    Cichello, Simon Angelo

    2015-04-01

    The preservation of packaged food against oxidative degradation is essential to establish and improve food shelf life, customer acceptability, and increase food security. Oxygen absorbers have an important role in the removal of dissolved oxygen, preserving the colour, texture and aroma of different food products, and importantly inhibition of food spoilage microbes. Active packaging technology in food preservation has improved over decades mostly due to the sealing of foods in oxygen impermeable package material and the quality of oxygen absorber. Ferrous iron oxides are the most reliable and commonly used oxygen absorbers within the food industry. Oxygen absorbers have been transformed from sachets of dried iron-powder to simple self-adhesive patches to accommodate any custom size, capacity and application. Oxygen concentration can be effectively lowered to 100 ppm, with applications spanning a wide range of food products and beverages across the world (i.e. bread, meat, fish, fruit, and cheese). Newer molecules that preserve packaged food materials from all forms of degradation are being developed, however oxygen absorbers remain a staple product for the preservation of food and pharmaceutical products to reduce food wastage in developed nations and increased food security in the developing & third world. PMID:25829570

  17. Oxygen absorbers in food preservation: a review.

    PubMed

    Cichello, Simon Angelo

    2015-04-01

    The preservation of packaged food against oxidative degradation is essential to establish and improve food shelf life, customer acceptability, and increase food security. Oxygen absorbers have an important role in the removal of dissolved oxygen, preserving the colour, texture and aroma of different food products, and importantly inhibition of food spoilage microbes. Active packaging technology in food preservation has improved over decades mostly due to the sealing of foods in oxygen impermeable package material and the quality of oxygen absorber. Ferrous iron oxides are the most reliable and commonly used oxygen absorbers within the food industry. Oxygen absorbers have been transformed from sachets of dried iron-powder to simple self-adhesive patches to accommodate any custom size, capacity and application. Oxygen concentration can be effectively lowered to 100 ppm, with applications spanning a wide range of food products and beverages across the world (i.e. bread, meat, fish, fruit, and cheese). Newer molecules that preserve packaged food materials from all forms of degradation are being developed, however oxygen absorbers remain a staple product for the preservation of food and pharmaceutical products to reduce food wastage in developed nations and increased food security in the developing & third world.

  18. BIOGEOCHEMICAL STUDIES OF PHOTOSYNTHETIC MICROBIAL MATS AND THEIR BIOTA

    NASA Technical Reports Server (NTRS)

    DesMarais, David; Discipulo, M.; Turk, K.; Londry, K. L.

    2005-01-01

    Photosynthetic microbial mats offer an opportunity to define holistic functionality at the millimeter scale. At the same time. their biogeochemistry contributes to environmental processes on a planetary scale. These mats are possibly direct descendents of the most ancient biological communities; communities in which oxygenic photosynthesis might have been invented. Mats provide one of the best natural systems to study how microbial populations associate to control dynamic biogeochemical gradients. These are self- sustaining, complete ecosystems in which light energy absorbed over a dial (24 hour) cycle drives the synthesis of spatially-organized, diverse biomass. Tightly-coupled microorganisms in the mat have specialized metabolisms that catalyze transformations of carbon, nitrogen, sulfur, and a host of other elements.

  19. [Primary study on photosynthetic characteristics of Dendrobium nobile].

    PubMed

    Su, Wenhua; Zhang, Guangfei

    2003-03-01

    With LiCor-6400 Portable Photosynthesis System, carbon dioxide exchange pattern for leaves of Dendrobium nobile during 24 hours were studied in sunny day and rainy day, and the variation of CO2 exchange rate to light intensity was analysed. The results showed that in sunny day D. nobile absorbed CO2 in all day except at midday, at noon photorespiration took place. The CO2 exchange pattern was similar to Crassulacean Acid Metabolism(CAM). In rainy day CO2 uptake was in all day, at night CO2 uptake was monitored at 21:00, then CO2 released from 23:00 to dawn. Light saturation point was 1000 mumol/m2s. Over light saturation point photosynthesis, photoinhibition of photosynthesis will be induced by high-light. Exposed to high-light, the light saturation point and the CO2 uptake velocity would be decreased. With variation of environmental factors, photosynthetic pathway in D. nobile could change from CAM to C3 photosynthetic metabolism. It may be one of main reasons for D. nobile to adapt to the shade-requiring environment, the slow growth and rareness in nature. PMID:12856465

  20. [Primary study on photosynthetic characteristics of Dendrobium nobile].

    PubMed

    Su, Wenhua; Zhang, Guangfei

    2003-03-01

    With LiCor-6400 Portable Photosynthesis System, carbon dioxide exchange pattern for leaves of Dendrobium nobile during 24 hours were studied in sunny day and rainy day, and the variation of CO2 exchange rate to light intensity was analysed. The results showed that in sunny day D. nobile absorbed CO2 in all day except at midday, at noon photorespiration took place. The CO2 exchange pattern was similar to Crassulacean Acid Metabolism(CAM). In rainy day CO2 uptake was in all day, at night CO2 uptake was monitored at 21:00, then CO2 released from 23:00 to dawn. Light saturation point was 1000 mumol/m2s. Over light saturation point photosynthesis, photoinhibition of photosynthesis will be induced by high-light. Exposed to high-light, the light saturation point and the CO2 uptake velocity would be decreased. With variation of environmental factors, photosynthetic pathway in D. nobile could change from CAM to C3 photosynthetic metabolism. It may be one of main reasons for D. nobile to adapt to the shade-requiring environment, the slow growth and rareness in nature.

  1. Artificial photosynthetic reaction centers coupled to light-harvesting antennas.

    PubMed

    Ghosh, Pulak Kumar; Smirnov, Anatoly Yu; Nori, Franco

    2011-12-01

    We analyze a theoretical model for energy and electron transfer in an artificial photosynthetic system. The photosystem consists of a molecular triad (i.e., with a donor, a photosensitive unit, and an acceptor) coupled to four accessory light-harvesting-antenna pigments. The resonant energy transfer from the antennas to the artificial reaction center (the molecular triad) is described here by the Förster mechanism. We consider two different kinds of arrangements of the accessory light-harvesting pigments around the reaction center. The first arrangement allows direct excitation transfer to the reaction center from all the surrounding pigments. The second configuration transmits energy via a cascade mechanism along a chain of light-harvesting chromophores, where only one chromophore is connected to the reaction center. We show that the artificial photosynthetic system using the cascade energy transfer absorbs photons in a broader wavelength range and converts their energy into electricity with a higher efficiency than the system based on direct couplings between all the antenna chromophores and the reaction center.

  2. Diagnostic beam absorber in Mu2e beam line

    SciTech Connect

    Rakhno, Igor; /Fermilab

    2011-03-01

    Star density, hadron flux, and residual dose distributions are calculated around the {mu}2e diagnostic beam absorber. Corresponding surface and ground water activation, and air activation are presented as well.

  3. Violaxanthin Cycle Pigment Contents in Potato and Tobacco Plants with Genetically Reduced Photosynthetic Capacity.

    PubMed Central

    Bilger, W.; Fisahn, J.; Brummet, W.; Kossmann, J.; Willmitzer, L.

    1995-01-01

    The influence of photosynthetic activity on the light-dependent adaptation of the pool size of the violaxanthin cycle pigments (violaxanthin + antheraxanthin + zeaxanthin) was studied in leaves of wild-type and transgenic potato (Solanum tuberosum L.) and tobacco (Nicotiana tabacum L.) plants. The genetically manipulated plants expressed an antisense mRNA coding for the chloroplastic fructose-bisphosphatase. Chl fluorescence quenching analysis revealed that the transformed plants exhibited a greatly impaired electron transport capacity. Light-limited and light-saturated non-photochemical quenching was strongly enhanced in the mRNA antisense potato plants. After 7 d of adaptation at various high photosynthetic photon flux densities (PPFDs), the violaxanthin cycle pool size increased, with a progressive elevation in PPFD. The pool size was higher for transgenic potatoes than for wild-type plants at all PPFDs. This difference vanished when pool size was correlated with the PPFD in excess of photosynthesis, as indicated by the epoxidation state of the violaxanthin cycle. Contrasting results were obtained for tobacco; in this species, photosynthetic activity did not affect the pool size. We conclude that regulatory mechanisms exist in potato, by which photosynthetic activity can influence the violaxanthin cycle pool size. Furthermore, evidence is provided that this adaptation of the pool size may contribute to an improved photoprotection of the photosynthetic apparatus under high-light conditions. However, tobacco plants seem to regulate their pool size independently of photosynthetic activity. PMID:12228557

  4. Plants absorb heavy metals

    SciTech Connect

    Parry, J.

    1995-02-01

    Decontamination of heavy metals-polluted soils remains one of the most intractable problems of cleanup technology. Currently available techniques include extraction of the metals by physical and chemical means, such as acid leaching and electroosmosis, or immobilization by vitrification. There are presently no techniques for cleanup which are low cost and retain soil fertility after metals removal. But a solution to the problem could be on the horizon. A small but growing number of plants native to metalliferous soils are known to be capable of accumulating extremely high concentrations of metals in their aboveground portions. These hyperaccumulators, as they are called, contain up to 1,000 times larger metal concentrations in their aboveground parts than normal species. Their distribution is global, including many different families of flowering plants of varying growth forms, from herbaceous plants to trees. Hyperaccumulators absorb metals they do not need for their own nutrition. The metals are accumulated in the leaf and stem vacuoles, and to a lesser extent in the roots.

  5. Effects of Mg(2+)on spectral characteristics and photosynthetic functions of spinach photosystem II.

    PubMed

    Liang, Chen; Xiao, Wu; Hao, Huang; Xiaoqing, Liu; Chao, Liu; Lei, Zheng; Fashui, Hong

    2009-03-01

    In the present paper we report the results obtained with the photosystem II (PSII) isolated from spinach treated by MgCl(2), and studied the effect of Mg(2+) on spectral characteristics and photosynthetic functions of PSII. The results showed that Mg(2+) treatment at a suitable concentration could significantly increase the absorption intensity of PSII and the intensity ratio of Soret band to Q band of chlorophyll-a. The treatment also elevated the excited peak intensity at 230, 278 and 343 nm, and the emitted peak intensity at 304 and 682 nm, and the ratio of F(278)/F(230), respectively. The results implied that Mg(2+) increased absorbance for visible light, improving energy transfer among amino acids within PSII protein complex and accelerating energy transport from tyrosine residue to chlorophyll-a. The photochemical activity and oxygen evolving rate of PSII were also enhanced by Mg(2+). This is viewed as evidence that Mg(2+) can promote energy transfer and oxygen evolution in PSII of spinach.

  6. Effects of Mg 2+on spectral characteristics and photosynthetic functions of spinach photosystem II

    NASA Astrophysics Data System (ADS)

    Liang, Chen; Xiao, Wu; Hao, Huang; Xiaoqing, Liu; Chao, Liu; Lei, Zheng; Fashui, Hong

    2009-03-01

    In the present paper we report the results obtained with the photosystem II (PSII) isolated from spinach treated by MgCl 2, and studied the effect of Mg 2+ on spectral characteristics and photosynthetic functions of PSII. The results showed that Mg 2+ treatment at a suitable concentration could significantly increase the absorption intensity of PSII and the intensity ratio of Soret band to Q band of chlorophyll-a. The treatment also elevated the excited peak intensity at 230, 278 and 343 nm, and the emitted peak intensity at 304 and 682 nm, and the ratio of F278/ F230, respectively. The results implied that Mg 2+ increased absorbance for visible light, improving energy transfer among amino acids within PSII protein complex and accelerating energy transport from tyrosine residue to chlorophyll-a. The photochemical activity and oxygen evolving rate of PSII were also enhanced by Mg 2+. This is viewed as evidence that Mg 2+ can promote energy transfer and oxygen evolution in PSII of spinach.

  7. Warm Absorber Diagnostics of AGN Dynamics

    NASA Astrophysics Data System (ADS)

    Kallman, Timothy

    Warm absorbers and related phenomena are observable manifestations of outflows or winds from active galactic nuclei (AGN) that have great potential value. Understanding AGN outflows is important for explaining the mass budgets of the central accreting black hole, and also for understanding feedback and the apparent co-evolution of black holes and their host galaxies. In the X-ray band warm absorbers are observed as photoelectric absorption and resonance line scattering features in the 0.5-10 keV energy band; the UV band also shows resonance line absorption. Warm absorbers are common in low luminosity AGN and they have been extensively studied observationally. They may play an important role in AGN feedback, regulating the net accretion onto the black hole and providing mechanical energy to the surroundings. However, fundamental properties of the warm absorbers are not known: What is the mechanism which drives the outflow?; what is the gas density in the flow and the geometrical distribution of the outflow?; what is the explanation for the apparent relation between warm absorbers and the surprising quasi-relativistic 'ultrafast outflows' (UFOs)? We propose a focused set of model calculations that are aimed at synthesizing observable properties of warm absorber flows and associated quantities. These will be used to explore various scenarios for warm absorber dynamics in order to answer the questions in the previous paragraph. The guiding principle will be to examine as wide a range as possible of warm absorber driving mechanisms, geometry and other properties, but with as careful consideration as possible to physical consistency. We will build on our previous work, which was a systematic campaign for testing important class of scenarios for driving the outflows. We have developed a set of tools that are unique and well suited for dynamical calculations including radiation in this context. We also have state-of-the-art tools for generating synthetic spectra, which are

  8. Analysis of UV-absorbing photoprotectant mycosporine-like amino acid (MAA) in the cyanobacterium Arthrospira sp. CU2556.

    PubMed

    Rastogi, Rajesh P; Incharoensakdi, Aran

    2014-07-01

    Mycosporine-like amino acids (MAAs) are ecologically important biomolecules with great photoprotective potential. The present study aimed to investigate the biosynthesis of MAAs in the cyanobacterium Arthrospira sp. CU2556. High-performance liquid chromatography (HPLC) with photodiode-array detection studies revealed the presence of a UV-absorbing compound with an absorption maximum at 310 nm. Based on its UV absorption spectrum and ion trap liquid chromatography/mass spectrometry (LC/MS) analysis, the compound was identified as a primary MAA mycosporine-glycine (m/z: 246). To the best of our knowledge this is the first report on the occurrence of MAA mycosporine-glycine (M-Gly) in Arthrospira strains studied so far. In contrast to photosynthetic activity under UV-A radiation, the induction of the biosynthesis of M-Gly was significantly more prominent under UV-B radiation. The content of M-Gly was found to increase with the increase in exposure time under UV-B radiation. The MAA M-Gly was highly stable under UV radiation, heat, strongly acidic and alkaline conditions. It also exhibited good antioxidant activity and photoprotective ability by detoxifying the in vivo reactive oxygen species (ROS) generated by UV radiation. Our results indicate that the studied cyanobacterium may protect itself by synthesizing the UV-absorbing/screening compounds as important defense mechanisms, in their natural brightly-lit habitat with high solar UV-B fluxes.

  9. Atmospheric transmittance model for photosynthetically active radiation

    SciTech Connect

    Paulescu, Marius; Stefu, Nicoleta; Gravila, Paul; Paulescu, Eugenia; Boata, Remus; Pacurar, Angel; Mares, Oana; Pop, Nicolina; Calinoiu, Delia

    2013-11-13

    A parametric model of the atmospheric transmittance in the PAR band is presented. The model can be straightforwardly applied for calculating the beam, diffuse and global components of the PAR solar irradiance. The required inputs are: air pressure, ozone, water vapor and nitrogen dioxide column content, Ångström's turbidity coefficient and single scattering albedo. Comparison with other models and ground measured data shows a reasonable level of accuracy for this model, making it suitable for practical applications. From the computational point of view the calculus is condensed into simple algebra which is a noticeable advantage. For users interested in speed-intensive computation of the effective PAR solar irradiance, a PC program based on the parametric equations along with a user guide are available online at http://solar.physics.uvt.ro/srms.

  10. Hydraulic shock absorber

    SciTech Connect

    Tanaka, T.

    1987-03-03

    This patent describes a hydraulic shock absorber including a piston reciprocating in a cylinder, a piston upper chamber and a piston lower chamber which are oil-tightly separated by the piston, piston ports formed through the piston in a circle for communicating the piston upper chamber with the piston lower chamber, and return ports formed outside of the piston ports in a circle for communicating the piston upper chamber with the piston lower chamber. It also includes a sheet ring-like non-return valve provided above the piston and fitted to a piston rod, valve holes formed through the non-return valve in opposed relation with the piston ports. A ring-like non-return valve stopper fixed to the piston rod on an upper side of the non-return valve with a small spaced defined between the non-return valve and the non-return valve stopper, and a spring is interposed between the non-return valve and the non-return valve stopper for normally urging the non-return valve to an upper surface of the piston. Movement of the piston to the piston upper chamber allows oil to flow from the piston upper chamber through the piston ports to the piston lower chamber, while the return ports are closed by the non-return valve to generate a vibration damping force by resistance upon pass of the oil through the piston parts. The improvement described here comprises a groove formed in an upper surface of the piston facing the non-return valve and aligned with the valve holes, the groove being in the circle where the piston ports lie and being in communication with the piston ports.

  11. Metal-shearing energy absorber

    NASA Technical Reports Server (NTRS)

    Fay, R. J.; Wittrock, E. P.

    1971-01-01

    Device, consisting of tongue of thin aluminum alloy strip, pull tab, slotted steel plate which serves as cutter, and steel buckle, absorbs mechanical energy when its ends are subjected to tensile loading. Device is applicable as auxiliary shock absorbing anchor for automobile and airplane safety belts.

  12. The broadband dynamic vibration absorber

    NASA Astrophysics Data System (ADS)

    Hunt, J. B.; Nissen, J.-C.

    1982-08-01

    The limited effectiveness of the linear passive dynamic vibration absorber is described. This is followed by an analysis producing the response of a primary system when a non-linear softening Belleville spring is used in the absorber. It is shown that the suppression bandwidth can be doubled by this means.

  13. Photosynthetic responses to phytoplasma infection in Chinese jujube.

    PubMed

    Liu, Zhiguo; Zhao, Jin; Liu, Mengjun

    2016-08-01

    Phytoplasma is one of the most devastating plant pathogens. Jujube witches' broom (JWB) is a typical and highly fatal phytoplasma disease of Chinese jujube (Ziziphus jujuba Mill.), which is widely cultivated in Asia. To further elucidate the mechanism of plant-phytoplasma interaction, we first compared the effects of phytoplasma infection on photosynthetic pigments and activities between a JWB-resistant cultivar (Xingguang) and a susceptible cultivar (Pozao). Total chlorophyll and carotenoid levels were significantly decreased in the susceptible cultivar at later stages of infection, but were remarkably increased in the resistant cultivar at the earlier stages. Compared to uninfected plant, a significant decrease in the main photochemical parameters (Fv/Fm, ΦPSII and qP) was recorded at the initial stages of infection in the resistant cultivar, but occurred at later stages in the susceptible cultivar. Meanwhile, the qRT-PCR results of four key photosynthesis-related genes (ZjGluTR, ZjCBP, ZjRubisco and ZjRCA2) demonstrated that the expression patterns were similar in uninfected cultivars, but up-regulated in resistant cultivar and down-regulated in the susceptible one at 12 wks after grafting inoculation. Collectively, our data indicated that the resistant cultivar 'Xingguang' undergoes a decrease in initial stage (inhibiting phytoplasma multiplication) and then a rapid enhancement of photosynthetic activity (helping jujube recovery) in response to phytoplasma infection, while the susceptible cultivar 'Pozao' displays a later decrease in photosynthetic activity. The novel photosynthetic response pattern of the resistant cultivar may contribute to its stronger immunity to phytoplasma infection, which provides new insights into plant-phytoplasma interactions.

  14. Photosynthetic Characteristics of Photoautotrophically Grown Tobacco Callus Cells 1

    PubMed Central

    Berlyn, Mary B.; Zelitch, Israel; Beaudette, Pamela D.

    1978-01-01

    Haploid callus cells of tobacco (Nicotiana tabacum) were grown photoautotrophically on a solid agar medium in the absence of sucrose in Petri plates in an atmosphere of 1% or 3% CO2 in air. The averages of dry weight increases for four to five consecutive passages were 2.3- to 3.6-fold per 3-week passage for different subclones. Photosynthetic 14CO2 assimilation was maximum at about 1% CO2 with half-maximal rates obtained at 0.2% CO2. At saturating CO2 concentration the average rate of CO2 fixation was about 5 μmole per gram fresh weight per hour or about 125 μmole per mg of chlorophyll per hour. The existence of an active photorespiratory system in these tissues was established in a number of independent ways. The photosynthetic rate in 0.18% CO2 was inhibited 38 to 50% in 100% O2 compared with 21% O2. Glycolate accumulated at a constant rate in the presence of 5 mm α-hydroxy-2-pyridinemethanesulfonic acid for 20 minutes in light. This rate was rapid relative to the photosynthetic rate. Glycolate synthesis was three times faster in autotrophic than in heterotrophic cells. [1-14C]Glycolate was rapidly metabolized and the products included 14CO2, [14C]glycine, and [14C]serine, thus demonstrating an active glycolate pathway. Photorespiration was demonstrated directly by measurement of an O2-dependent release of 14CO2 in the light from callus that fixed 14CO2 for about 22 hours. Autotrophic growth in 60% O2 and 0.03% CO2 was slowed and ceased entirely after two or three passages, while heterotrophic growth was unaffected by 60% O2 in the atmosphere. The method of growing autotrophic callus which has an active photorespiratory system should facilitate the selection and analysis of photosynthetic mutants in which photorespiration is regulated. PMID:16660346

  15. [Effects of light quality on photosynthetic pigment contents and photosynthetic characteristics of peanut seedling leaves].

    PubMed

    Yan, Meng-Meng; Wang, Ming-Lun; Wang, Hong-Bo; Wang, Yue-Fu; Zhao, Chang-Xing

    2014-02-01

    This study explored the effects of different light quality on photosynthetic pigment contents and photosynthetic characteristics of peanut (Qinhua 6) seedling leaves. The results showed that, compared with natural light, blue light (445-470 nm) could significantly improve the specific leaf area (SLA), chlorophyll a/b value and carotenoid content of peanut seedlings. Meanwhile, the net photosynthetic rate, stomatal conductance, and transpiration rate were higher, the intercellular CO2 content was lower, and the photosynthetic efficiency was improved significantly under blue light. Red light (610-660 nm) could improve the chlorophyll content significantly, and reduce SLA, chlorophyll a/b value and carotenoid content, with a lower photosynthetic efficiency than natural light. Green light (515-520 nm) and yellow light (590-595 nm) were not conducive to photosynthetic pigment accumulation of leaves, and significantly inhibited leaf photosynthesis of peanut seedlings.

  16. BOREAS TE-9 NSA Photosynthetic Capacity and Foliage Nitrogen Data

    NASA Technical Reports Server (NTRS)

    Hall, Forrest G. (Editor); Curd, Shelaine (Editor); Dang, Qinglai; Margolis, Hank; Coyea, Marie

    2000-01-01

    The Boreal Ecosystem-Atmospheric Study (BOREAS) TE-9 (Terrestrial Ecology) team collected several data sets related to chemical and photosynthetic properties of leaves in boreal forest tree species. This data set describes the spatial and temporal relationship between foliage nitrogen concentration and photosynthetic capacity in the canopies of black spruce, jack pine, and aspen located within the Northern Study Area (NSA). The data were collected from June to September 1994 and are useful for modeling the vertical distribution of carbon fixation for different forest types in the boreal forest. The data are available in tabular ASCII files. The data files are available on a CD-ROM (see document number 20010000884), or from the Oak Ridge National Laboratory (ORNL) Distributed Active Archive Center (DAAC).

  17. Detecting extraterrestrial life with the Colossus telescope using photosynthetic biosignatures

    NASA Astrophysics Data System (ADS)

    Berdyugina, S.; Kuhn, J.; Harrington, D.; Moretto, G.; Langlois, M.; Halliday, D.; Harlingten, C.

    2014-03-01

    We propose to search for life on Earth-like planets in habitable zones using photosynthesis biosignatures. Many life forms on Earth process the solar light and utilize it to support their own activity and to provide a valuable energy source for other life forms. We expect therefore that photosynthesis is very likely to arise on another planet and can produce conspicuous biosignatures. We have recently identified biological polarization effects, e.g., selective light absorption or scattering by photosynthetic molecules which can be used for remote detection of extraterrestrial life. Here we present synthetic spectra and polarization of Earth-like planets with photosynthetic life and evaluate the sensitivity of the Colossus telescope for their remote detection in the solar neighborhood.

  18. Photosynthetic carbon reduction by seagrasses exposed to ultraviolet A radiation

    NASA Technical Reports Server (NTRS)

    1979-01-01

    The seagrasses Halophila engelmannii, Halodule wrightii, and Syringodium filiforme were examined for their intrinsic sensitivity to ultraviolet-A-UV-A and ultraviolet-B-UV-B radiation. The effect of UV-A on photosynthetically active radiation (PAR) was also determined. Ultraviolet-A and ultraviolet-B were studied with emphasis on the greater respective environmental consequence in terms of seagrass distribution and abundance. Results indicate that an intrinsic sensitivity to UV-A alone is apparent only in Halophila, while net photosynthesis in Halodule and Syringodium seems unaffected by the level of UV-A provided. The sensitivity of Halophila to UV-A in the absense of (PAR) indicates that the photosynthetic reaction does not need to be in operation for damage to occur. Other significant results are reported.

  19. An allosteric photoredox catalyst inspired by photosynthetic machinery.

    PubMed

    Lifschitz, Alejo M; Young, Ryan M; Mendez-Arroyo, Jose; Stern, Charlotte L; McGuirk, C Michael; Wasielewski, Michael R; Mirkin, Chad A

    2015-03-30

    Biological photosynthetic machinery allosterically regulate light harvesting via conformational and electronic changes at the antenna protein complexes as a response to specific chemical inputs. Fundamental limitations in current approaches to regulating inorganic light-harvesting mimics prevent their use in catalysis. Here we show that a light-harvesting antenna/reaction centre mimic can be regulated by utilizing a coordination framework incorporating antenna hemilabile ligands and assembled via a high-yielding, modular approach. As in nature, allosteric regulation is afforded by coupling the conformational changes to the disruptions in the electrochemical landscape of the framework upon recognition of specific coordinating analytes. The hemilabile ligands enable switching using remarkably mild and redox-inactive inputs, allowing one to regulate the photoredox catalytic activity of the photosynthetic mimic reversibly and in situ. Thus, we demonstrate that bioinspired regulatory mechanisms can be applied to inorganic light-harvesting arrays displaying switchable catalytic properties and with potential uses in solar energy conversion and photonic devices.

  20. Detection of circular polarization in light scattered from photosynthetic microbes

    PubMed Central

    Sparks, William B.; Hough, James; Germer, Thomas A.; Chen, Feng; DasSarma, Shiladitya; DasSarma, Priya; Robb, Frank T.; Manset, Nadine; Kolokolova, Ludmilla; Reid, Neill; Macchetto, F. Duccio; Martin, William

    2009-01-01

    The identification of a universal biosignature that could be sensed remotely is critical to the prospects for success in the search for life elsewhere in the universe. A candidate universal biosignature is homochirality, which is likely to be a generic property of all biochemical life. Because of the optical activity of chiral molecules, it has been hypothesized that this unique characteristic may provide a suitable remote sensing probe using circular polarization spectroscopy. Here, we report the detection of circular polarization in light scattered by photosynthetic microbes. We show that the circular polarization appears to arise from circular dichroism of the strong electronic transitions of photosynthetic absorption bands. We conclude that circular polarization spectroscopy could provide a powerful remote sensing technique for generic life searches. PMID:19416893

  1. [Diurnal change of photosynthetic characteristics of native Vetiveria zizanioides in western Guangdong].

    PubMed

    Lin, Baohua; Liu, Jinxiang; Xiao, Shenghong; Yang, Yunfei

    2006-11-01

    The determinations on the photosynthetic parameters of native Vetiveria zizanioides in Western Guangdong in autumn showed that the net photosynthetic rate (P(n)) of V. zizanioides had a diurnal change with two peaks, transpiration rate (T(r)) and stomatal conductance (G(s)) were similar with P(n), while intercellular CO2 concentration (C(i)) was in adverse. There was a significant positive correlation between P(n) and photosynthetic active radiation (PAR) (P < 0.01) , T(r) and PAR (P < 0.01), air temperature (T(a)) and relative humidity (RH) (P < 0.01), and G(s) and T(a) (P < 0.05). Same environmental factors had different effects on P(n), T(r) and G(s), and PAR had most intensive effect on the photosynthesis of V. zizanioides. Among the test photosynthetic parameters, T(r) was most sensitive to the environmental factors. PMID:17269323

  2. Automated systems to monitor space radiation effect on photosynthetic organisms

    NASA Astrophysics Data System (ADS)

    Esposito, D.; di Costa, F.; Faraloni, C.; Fasolo, F.; Pace, E.; Perosino, M.; Torzillo, G.; Touloupakis, E.; Zanini, A.; Giardi, M. T.

    We developed automated biodevices to obtain, automatically, measures about the space radiation effect on living photosynthetic organisms, which can be used as biomass and oxygen-producing system on shuttles or ISS. Vitality measurements were performed by optical devices (fluorimeters) measuring fluorescence emission. Fluorescence methodology is a well known applied technique for studying photosynthetic activity, and in particular the oxygen-evolving process of photosynthetic organisms. Different strains of unicellular green algae are properly immobilized on agar growth medium and kept under survial light. The biodevices are characterised by the sensibility and selectivity of the biological component response, together with easy use, versatility, miniature size and low cost. We performed experiments in some facilities, in order to understand separately the effect of radiation of different LET, on the biochemical activity (gamma rays at Joint Research Centre -Varese, Italy; fast neutrons at CERF -- SPS beam at CERN -Geneva, Switzerland). The exposure to different radiation beams of the automatic devices, allowed us to test them under stress condition. In one year, these instrument are expected to be sent to space, inside a spacecraft, in order to study the effect of ionising cosmic radiation during an ESA flight.

  3. Variation potential influence on photosynthetic cyclic electron flow in pea

    PubMed Central

    Sukhov, Vladimir; Surova, Lyubov; Sherstneva, Oksana; Katicheva, Lyubov; Vodeneev, Vladimir

    2015-01-01

    Cyclic electron flow is an important component of the total photosynthetic electron flow and participates in adaptation to the action of stressors. Local leaf stimulation induces electrical signals, including variation potential (VP), which inactivate photosynthesis; however, their influence on cyclic electron flow has not been investigated. The aim of this study was to investigate VP's influence on cyclic electron flow in pea (Pisum sativum L.). VP was induced in pea seedling leaves by local heating and measured in an adjacent, undamaged leaf by extracellular electrodes. CO2 assimilation was measured using a portable gas exchange measuring system. Photosystem I and II parameters were investigated using a measuring system for simultaneous assessment of P700 oxidation and chlorophyll fluorescence. Heating-induced VP reduced CO2 assimilation and electron flow through photosystem II. In response, cyclic electron flow rapidly decreased and subsequently slowly increased. Slow increases in cyclic flow were caused by decreased electron flow through photosystem II, which was mainly connected with VP-induced photosynthetic dark stage inactivation. However, direct influence by VP on photosystem I also participated in activation of cyclic electron flow. Thus, VP, induced by local leaf-heating, activated cyclic electron flow in undamaged leaves. This response was similar to photosynthetic changes observed under the direct action of stressors. Possible mechanisms of VP's influence on cyclic flow were discussed. PMID:25610447

  4. Photosynthetic hydrogen and oxygen production by green algae

    SciTech Connect

    Greenbaum, E.; Lee, J.W.

    1997-12-31

    An overview of photosynthetic hydrogen and oxygen production by green algae in the context of its potential as a renewable chemical feed stock and energy carrier is presented. Beginning with its discovery by Gaffron and Rubin in 1942, motivated by curiosity-driven laboratory research, studies were initiated in the early 1970s that focused on photosynthetic hydrogen production from an applied perspective. From a scientific and technical point of view, current research is focused on optimizing net thermodynamic conversion efficiencies represented by the Gibbs Free Energy of molecular hydrogen. The key research questions of maximizing hydrogen and oxygen production by light-activated water splitting in green algae are (1) removing the oxygen sensitivity of algal hydrogenases; (2) linearizing the light saturation curves of photosynthesis throughout the entire range of terrestrial solar irradiance--including the role of bicarbonate and carbon dioxide in optimization of photosynthetic electron transport and (3) the minimum number of light reactions that are required to split water to elemental hydrogen and oxygen. Each of these research topics is being actively addressed by the photobiological hydrogen research community.

  5. On the railway track dynamics with rail vibration absorber for noise reduction

    NASA Astrophysics Data System (ADS)

    Wu, T. X.

    2008-01-01

    A promising means to increase the decay rate of vibration along the rail is using a rail absorber for noise reduction. Compound track models with the tuned rail absorber are developed for investigation of the performance of the absorber on vibration reduction. Through analysis of the track dynamics with the rail absorber some guidelines are given on selection of the types and parameters for the rail absorber. It is found that a large active mass used in the absorber is beneficial to increase the decay rate of rail vibration. The effectiveness of the piecewise continuous absorber is moderate compared with the discrete absorber installed in the middle of sleeper span or at a sleeper. The most effective installation position for the discrete absorber is in the middle of sleeper span. Over high or over low loss factor of the damping material used in the absorber may degrade the performance on vibration reduction.

  6. Phosphorylation stoichiometry determination in plant photosynthetic membranes.

    PubMed

    Ingelsson, Björn; Fristedt, Rikard; Turkina, Maria V

    2015-01-01

    This chapter describes different strategies for the study of phosphorylation dynamics and stoichiometry in photosynthetic membranes. Detailed procedures for the detection, large-scale identification, and quantification of phosphorylated proteins optimized for plant thylakoid proteins are given. PMID:25930698

  7. Regulation of Carotenoid Biosynthesis in Photosynthetic Organs.

    PubMed

    Llorente, Briardo

    2016-01-01

    A substantial proportion of the dazzling diversity of colors displayed by living organisms throughout the tree of life is determined by the presence of carotenoids, which most often provide distinctive yellow, orange and red hues. These metabolites play fundamental roles in nature that extend far beyond their importance as pigments. In photosynthetic lineages, carotenoids are essential to sustain life, since they have been exploited to maximize light harvesting and protect the photosynthetic machinery from photooxidative stress. Consequently, photosynthetic organisms have evolved several mechanisms that adjust the carotenoid metabolism to efficiently cope with constantly fluctuating light environments. This chapter will focus on the current knowledge concerning the regulation of the carotenoid biosynthetic pathway in leaves, which are the primary photosynthetic organs of most land plants. PMID:27485221

  8. Hybrid system of semiconductor and photosynthetic protein.

    PubMed

    Kim, Younghye; Shin, Seon Ae; Lee, Jaehun; Yang, Ki Dong; Nam, Ki Tae

    2014-08-29

    Photosynthetic protein has the potential to be a new attractive material for solar energy absorption and conversion. The development of semiconductor/photosynthetic protein hybrids is an example of recent progress toward efficient, clean and nanostructured photoelectric systems. In the review, two biohybrid systems interacting through different communicating methods are addressed: (1) a photosynthetic protein immobilized semiconductor electrode operating via electron transfer and (2) a hybrid of semiconductor quantum dots and photosynthetic protein operating via energy transfer. The proper selection of materials and functional and structural modification of the components and optimal conjugation between them are the main issues discussed in the review. In conclusion, we propose the direction of future biohybrid systems for solar energy conversion systems, optical biosensors and photoelectric devices.

  9. Protection of the photosynthetic apparatus against dehydration stress in the resurrection plant Craterostigma pumilum.

    PubMed

    Zia, Ahmad; Walker, Berkley J; Oung, Hui Min Olivia; Charuvi, Dana; Jahns, Peter; Cousins, Asaph B; Farrant, Jill M; Reich, Ziv; Kirchhoff, Helmut

    2016-09-01

    The group of homoiochlorophyllous resurrection plants evolved the unique capability to survive severe drought stress without dismantling the photosynthetic machinery. This implies that they developed efficient strategies to protect the leaves from reactive oxygen species (ROS) generated by photosynthetic side reactions. These strategies, however, are poorly understood. Here, we performed a detailed study of the photosynthetic machinery in the homoiochlorophyllous resurrection plant Craterostigma pumilum during dehydration and upon recovery from desiccation. During dehydration and rehydration, C. pumilum deactivates and activates partial components of the photosynthetic machinery in a specific order, allowing for coordinated shutdown and subsequent reinstatement of photosynthesis. Early responses to dehydration are the closure of stomata and activation of electron transfer to oxygen accompanied by inactivation of the cytochrome b6 f complex leading to attenuation of the photosynthetic linear electron flux (LEF). The decline in LEF is paralleled by a gradual increase in cyclic electron transport to maintain ATP production. At low water contents, inactivation and supramolecular reorganization of photosystem II becomes apparent, accompanied by functional detachment of light-harvesting complexes and interrupted access to plastoquinone. This well-ordered sequence of alterations in the photosynthetic thylakoid membranes helps prepare the plant for the desiccated state and minimize ROS production.

  10. Protection of the photosynthetic apparatus against dehydration stress in the resurrection plant Craterostigma pumilum.

    PubMed

    Zia, Ahmad; Walker, Berkley J; Oung, Hui Min Olivia; Charuvi, Dana; Jahns, Peter; Cousins, Asaph B; Farrant, Jill M; Reich, Ziv; Kirchhoff, Helmut

    2016-09-01

    The group of homoiochlorophyllous resurrection plants evolved the unique capability to survive severe drought stress without dismantling the photosynthetic machinery. This implies that they developed efficient strategies to protect the leaves from reactive oxygen species (ROS) generated by photosynthetic side reactions. These strategies, however, are poorly understood. Here, we performed a detailed study of the photosynthetic machinery in the homoiochlorophyllous resurrection plant Craterostigma pumilum during dehydration and upon recovery from desiccation. During dehydration and rehydration, C. pumilum deactivates and activates partial components of the photosynthetic machinery in a specific order, allowing for coordinated shutdown and subsequent reinstatement of photosynthesis. Early responses to dehydration are the closure of stomata and activation of electron transfer to oxygen accompanied by inactivation of the cytochrome b6 f complex leading to attenuation of the photosynthetic linear electron flux (LEF). The decline in LEF is paralleled by a gradual increase in cyclic electron transport to maintain ATP production. At low water contents, inactivation and supramolecular reorganization of photosystem II becomes apparent, accompanied by functional detachment of light-harvesting complexes and interrupted access to plastoquinone. This well-ordered sequence of alterations in the photosynthetic thylakoid membranes helps prepare the plant for the desiccated state and minimize ROS production. PMID:27258321

  11. Radiative energy budget reveals high photosynthetic efficiency in symbiont-bearing corals

    PubMed Central

    Brodersen, Kasper Elgetti; Lichtenberg, Mads; Ralph, Peter J.; Kühl, Michael; Wangpraseurt, Daniel

    2014-01-01

    The light field on coral reefs varies in intensity and spectral composition, and is the key regulating factor for phototrophic reef organisms, for example scleractinian corals harbouring microalgal symbionts. However, the actual efficiency of light utilization in corals and the mechanisms affecting the radiative energy budget of corals are underexplored. We present the first balanced light energy budget for a symbiont-bearing coral based on a fine-scale study of the microenvironmental photobiology of the massive coral Montastrea curta. The majority (more than 96%) of the absorbed light energy was dissipated as heat, whereas the proportion of the absorbed light energy used in photosynthesis was approximately 4.0% under an irradiance of 640 µmol photons m−2 s−1. With increasing irradiance, the proportion of heat dissipation increased at the expense of photosynthesis. Despite such low energy efficiency, we found a high photosynthetic efficiency of the microalgal symbionts showing high gross photosynthesis rates and quantum efficiencies (QEs) of approximately 0.1 O2 photon−1 approaching theoretical limits under moderate irradiance levels. Corals thus appear as highly efficient light collectors with optical properties enabling light distribution over the corallite/tissue microstructural canopy that enables a high photosynthetic QE of their photosynthetic microalgae in hospite. PMID:24478282

  12. Absorbent product to absorb fluids. [for collection of human wastes

    NASA Technical Reports Server (NTRS)

    Dawn, F. S.; Correale, J. V. (Inventor)

    1982-01-01

    A multi-layer absorbent product for use in contact with the skin to absorb fluids is discussed. The product utilizes a water pervious facing layer for contacting the skin, overlayed by a first fibrous wicking layer, the wicking layer preferably being of the one-way variety in which fluid or liquid is moved away from the facing layer. The product further includes a first container section defined by inner and outer layer of a water pervious wicking material between which is disposed a first absorbent mass. A second container section defined by inner and outer layers between which is disposed a second absorbent mass and a liquid impermeable/gas permeable layer. Spacesuit applications are discussed.

  13. Process for photosynthetically splitting water

    SciTech Connect

    Greenbaum, E.

    1982-01-28

    In one form of the invention, hydrogen is produced by providing a reactor containing a body of water. The water contains photolytic material, i.e., photoactive material containing a hydrogen-catalyst. The interior of the reactor is isolated from atmosphere and includes a volume for receiving gases evolved from the body of water. The photolytic material is exposed to light to effect photosynthetic splitting of the water into gaseous hydrogen and oxygen. The gas-receiving volume is continuously evacuated by pumping to promote evolution of gaseous hydrogen and oxygen into that volume and to withdraw them therefrom. In another form of the invention, separation of the hydrogen and oxygen is effected by selectively diffusing the hydrogen through a heated semipermeable membrane in a separation zone while maintaining across the zone a magnetic field gradient biasing the oxygen away from the membrane. In a third form of the invention, the withdrawn gas is contacted with a membrane blocking flow of water vapor to the region for effecting recovery of the hydrogen. In a fourth embodiment, the invention comprises a process for selectively recovering hydrogen from a gas mixture comprising hydrogen and oxygen. The process is conducted in a separation zone and comprises contacting the mixture with a semipermeable membrane effecting selective diffusion of hydrogen while maintaining across the zone a magnetic field gradient effecting movement of oxygen in a direction away from the membrane.

  14. Self-Regulating Shock Absorber

    NASA Technical Reports Server (NTRS)

    Wesselski, Clarence J.

    1995-01-01

    Mechanical shock absorber keeps frictional damping force within tolerable limit. Its damping force does not increase with coefficient of friction between energy-absorbing components; rather, frictional damping force varies only slightly. Relatively insensitive to manufacturing variations and environmental conditions altering friction. Does not exhibit high breakaway friction and consequent sharp increase followed by sharp decrease in damping force at beginning of stroking. Damping force in absorber does not vary appreciably with speed of stroking. In addition, not vulnerable to leakage of hydraulic fluid.

  15. Photosynthetic reaction center complexes from heliobacteria

    NASA Technical Reports Server (NTRS)

    Trost, J. T.; Vermaas, W. F. J.; Blankenship, R. E.

    1991-01-01

    Photosynthetic reaction centers are pigment-protein complexes that are responsible for the transduction of light energy into chemical energy. Considerable evidence indicates that photosynthetic organisms were present very early in the evolution of life on Earth. The goal of this project is to understand the early evolutionary development of photosynthesis by examining the properties of reaction centers isolated from certain contemporary organisms that appear to contain the simplest photosynthetic reaction centers. The major focus is on the family of newly discovered strictly anaerobic photosynthetic organisms that are grouped with the gram-positive phylum of bacteria. The properties of these reactions centers suggest that they may be the descendants of an ancestor that also gave rise to Photosystem 1 found in oxygen-evolving photosynthetic organisms. Photoactive reaction center-core antenna complexes were isolated from the photosynthetic bacteria, Heliobacillus mobilis and Heliobacterium gestii, by extraction of membranes with Deriphat 160C followed by differential centrifugation and sucrose density gradient centrifugation. Other aspects of this investigation are briefly discussed.

  16. Forster Energy Transfer Theory as Reflected in the Structures of Photosynthetic Light-Harvesting Systems

    SciTech Connect

    Sener, Melih; Strumpfer, Johan; Hsin, Jen; Chandler, Danielle; Scheuring, Simon; Hunter, C. Neil; Schulten, Klaus

    2011-02-22

    Förster's theory of resonant energy transfer underlies a fundamental process in nature, namely the harvesting of sunlight by photosynthetic life forms. The theoretical framework developed by Förster and others describes how electronic excitation migrates in the photosynthetic apparatus of plants, algae, and bacteria from light absorbing pigments to reaction centers where light energy is utilized for the eventual conversion into chemical energy. The demand for highest possible efficiency of light harvesting appears to have shaped the evolution of photosynthetic species from bacteria to plants which, despite a great variation in architecture, display common structural themes founded on the quantum physics of energy transfer as described first by Förster. Herein, Förster’s theory of excitation transfer is summarized, including recent extensions, and the relevance of the theory to photosynthetic systems as evolved in purple bacteria, cyanobacteria, and plants is demonstrated. Förster's energy transfer formula, as used widely today in many fields of science, is also derived.

  17. Hydrogen Biogeochemistry in Anaerobic and Photosynthetic Ecosystems

    NASA Technical Reports Server (NTRS)

    Hoehler, Tori M.; DeVincenzi, Donald L. (Technical Monitor)

    2000-01-01

    culture studies. Our recent work has extended the study of hydrogen to cyanobacterial mat communities. The large amounts of reducing power generated during photosynthetic activity carry the potential to contribute a swamping term to the H2 economy of the anaerobic microbial populations within the mat - and thereby to alter the population structure and biogeochemical function of the mat as a whole. In hypersaline microbial mats, we observe a distinct diel cycle in H2 production and a substantial corresponding flux. On an early Earth dominated by microbial mats, this transmission of photosynthetic reducing power may have carried important implications for both biospheric and atmospheric evolution.

  18. Renewable hydrogen production by photosynthetic water splitting

    SciTech Connect

    Greenbaum, E.; Lee, J.W.

    1998-06-01

    This mission-oriented research project is focused on the production of renewable hydrogen. The authors have demonstrated that certain unicellular green algae are capable of sustained simultaneous photoproduction of hydrogen and oxygen by light-activated photosynthetic water splitting. It is the goal of this project to develop a practical chemical engineering system for the development of an economic process that can be used to produce renewable hydrogen. There are several fundamental problems that need to be solved before the application of this scientific knowledge can be applied to the development a practical process: (I) maximizing net thermodynamic conversion efficiency of light energy into hydrogen energy, (2) development of oxygen-sensitive hydrogenase-containing mutants, and (3) development of bioreactors that can be used in a real-world chemical engineering process. The authors are addressing each of these problems here at ORNL and in collaboration with their research colleagues at the National Renewable Energy Laboratory, the University of California, Berkeley, and the University of Hawaii. This year the authors have focused on item 1 above. In particular, they have focused on the question of how many light reactions are required to split water to molecular hydrogen and oxygen.

  19. Countercurrent flow absorber and desorber

    DOEpatents

    Wilkinson, William H.

    1984-01-01

    Countercurrent flow absorber and desorber devices are provided for use in absorption cycle refrigeration systems and thermal boosting systems. The devices have increased residence time and surface area resulting in improved heat and mass transfer characteristics. The apparatuses may be incorporated into open cycle thermal boosting systems in which steam serves both as the refrigerant vapor which is supplied to the absorber section and as the supply of heat to drive the desorber section of the system.

  20. Countercurrent flow absorber and desorber

    DOEpatents

    Wilkinson, W.H.

    1984-10-16

    Countercurrent flow absorber and desorber devices are provided for use in absorption cycle refrigeration systems and thermal boosting systems. The devices have increased residence time and surface area resulting in improved heat and mass transfer characteristics. The apparatuses may be incorporated into open cycle thermal boosting systems in which steam serves both as the refrigerant vapor which is supplied to the absorber section and as the supply of heat to drive the desorber section of the system. 9 figs.

  1. Counting Viruses and Bacteria in Photosynthetic Microbial Mats

    PubMed Central

    Staal, Marc; Middelboe, Mathias; Brussaard, Corina P. D.

    2015-01-01

    Viral abundances in benthic environments are the highest found in aquatic systems. Photosynthetic microbial mats represent benthic environments with high microbial activity and possibly high viral densities, yet viral abundances have not been examined in such systems. Existing extraction procedures typically used in benthic viral ecology were applied to the complex matrix of microbial mats but were found to inefficiently extract viruses. Here, we present a method for extraction and quantification of viruses from photosynthetic microbial mats using epifluorescence microscopy (EFM) and flow cytometry (FCM). A combination of EDTA addition, probe sonication, and enzyme treatment applied to a glutaraldehyde-fixed sample resulted in a substantially higher viral (5- to 33-fold) extraction efficiency and reduced background noise compared to previously published methods. Using this method, it was found that in general, intertidal photosynthetic microbial mats harbor very high viral abundances (2.8 × 1010 ± 0.3 × 1010 g−1) compared with benthic habitats (107 to 109 g−1). This procedure also showed 4.5- and 4-fold-increased efficacies of extraction of viruses and bacteria, respectively, from intertidal sediments, allowing a single method to be used for the microbial mat and underlying sediment. PMID:25595761

  2. The origin of cytosolic ATP in photosynthetic cells.

    PubMed

    Gardeström, Per; Igamberdiev, Abir U

    2016-07-01

    In photosynthetically active cells, both chloroplasts and mitochondria have the capacity to produce ATP via photophosphorylation and oxidative phosphorylation, respectively. Thus, theoretically, both organelles could provide ATP for the cytosol, but the extent, to which they actually do this, and how the process is regulated, both remain unclear. Most of the evidence discussed comes from experiments with rapid fractionation of isolated protoplasts subjected to different treatments in combination with application of specific inhibitors. The results obtained indicate that, under conditions where ATP demand for photosynthetic CO2 fixation is sufficiently high, the mitochondria supply the bulk of ATP for the cytosol. In contrast, under stress conditions where CO2 fixation is severely limited, ATP will build up in chloroplasts and it can then be exported to the cytosol, by metabolite shuttle mechanisms. Thus, depending on the conditions, either mitochondria or chloroplasts can supply the bulk of ATP for the cytosol. This supply of ATP is discussed in relation to the idea that mitochondrial functions may be tuned to provide an optimal environment for the chloroplast. By balancing cellular redox states, mitochondria can contribute to an optimal photosynthetic capacity. PMID:27087668

  3. Photosynthetic lesions can trigger accelerated senescence in Arabidopsis thaliana.

    PubMed

    Wang, Jing; Leister, Dario; Bolle, Cordelia

    2015-11-01

    Senescence is a highly regulated process characterized by the active breakdown of cells, which ultimately leads to the death of plant organs or whole plants. In annual plants such as Arabidopsis thaliana senescence can be observed in each individual leaf. Whether deficiencies in photosynthesis promote the induction of senescence was investigated by monitoring chlorophyll degradation, photosynthetic parameters, and reactive oxygen species accumulation in photosynthetic mutants. Several mutations affecting components of the photosynthetic apparatus, including psal-2, psan-2, and psbs, were found to lead to premature or faster senescence, as did simultaneous inactivation of the STN7 and STN8 kinases. Premature senescence is apparently not directly linked to an overall reduction in photosynthesis but to perturbations in specific aspects of the process. Dark-induced senescence is accelerated in mutants affected in linear electron flow, especially psad2-1, psan-2, and pete2-1, as well as in stn7 and stn8 mutants and STN7 and STN8 overexpressor lines. Interestingly, no direct link with ROS production could be observed. PMID:26272903

  4. Iron-mediated changes in phytoplankton photosynthetic competence during SOIREE

    NASA Astrophysics Data System (ADS)

    Boyd, P. W.; Abraham, E. R.

    Active fluorescence (fast repetition rate fluorometry, FRRF) was used to follow the photosynthetic response of the phytoplankton community during the 13-day Southern Ocean Iron RElease Experiment (SOIREE). This in situ iron enrichment was conducted in the polar waters of the Australasian-Pacific sector of the Southern Ocean in February 1999. Iron fertilisation of these high nitrate low chlorophyll (HNLC) waters resulted in an increase in the photosynthetic competence ( Fv/ Fm) of the resident cells from around 0.20 to greater than 0.60 (i.e. close to the theoretical maximum) by 10/11 days after the first enrichment. Although a significant iron-mediated response in Fv/ Fm was detected as early as 24 h after the initial fertilisation, the increase in Fv/ Fm to double ambient levels took 6 days. This response was five-fold slower than observed in iron enrichments (in situ and in vitro) in the HNLC waters of the subarctic and equatorial Pacific. Although little is known about the relationship between water temperature and Fv/ Fm, it is likely that low water temperatures — and possibly the deep mixed layer — were responsible for this slow response time. During SOIREE, the photosynthetic competence of the resident phytoplankton in iron-enriched waters increased at dissolved iron levels above 0.2 nM, suggesting that iron limitation was alleviated at this concentration. Increases in Fv/ Fm of cells within four algal size classes suggested that all taxa displayed a photosynthetic response to iron enrichment. Other physiological proxies of algal iron stress (such as flavodoxin levels in diatoms) exhibited different temporal trends to iron-enrichment than Fv/ Fm during the time-course of SOIREE. The relationship between Fv/ Fm, algal growth rate and such proxies in Southern Ocean waters is discussed.

  5. Photosynthetic Bradyrhizobia Are Natural Endophytes of the African Wild Rice Oryza breviligulata

    PubMed Central

    Chaintreuil, Clémence; Giraud, Eric; Prin, Yves; Lorquin, Jean; Bâ, Amadou; Gillis, Monique; de Lajudie, Philippe; Dreyfus, Bernard

    2000-01-01

    We investigated the presence of endophytic rhizobia within the roots of the wetland wild rice Oryza breviligulata, which is the ancestor of the African cultivated rice Oryza glaberrima. This primitive rice species grows in the same wetland sites as Aeschynomene sensitiva, an aquatic stem-nodulated legume associated with photosynthetic strains of Bradyrhizobium. Twenty endophytic and aquatic isolates were obtained at three different sites in West Africa (Senegal and Guinea) from nodal roots of O. breviligulata and surrounding water by using A. sensitiva as a trap legume. Most endophytic and aquatic isolates were photosynthetic and belonged to the same phylogenetic Bradyrhizobium/Blastobacter subgroup as the typical photosynthetic Bradyrhizobium strains previously isolated from Aeschynomene stem nodules. Nitrogen-fixing activity, measured by acetylene reduction, was detected in rice plants inoculated with endophytic isolates. A 20% increase in the shoot growth and grain yield of O. breviligulata grown in a greenhouse was also observed upon inoculation with one endophytic strain and one Aeschynomene photosynthetic strain. The photosynthetic Bradyrhizobium sp. strain ORS278 extensively colonized the root surface, followed by intercellular, and rarely intracellular, bacterial invasion of the rice roots, which was determined with a lacZ-tagged mutant of ORS278. The discovery that photosynthetic Bradyrhizobium strains, which are usually known to induce nitrogen-fixing nodules on stems of the legume Aeschynomene, are also natural true endophytes of the primitive rice O. breviligulata could significantly enhance cultivated rice production. PMID:11097925

  6. [Leaf photosynthetic potential in canopy layers of un-thinned and thinned apple orchards].

    PubMed

    Zhang, Ji-xiang; Wei, Qin-ping; Zhang, Jing; Wang, Lian-xin; Wang, Cui-ling; Sun, Xie-ping; Song, Kai

    2009-12-01

    Through the comparison of leaf photosynthetic potential and of photosynthetically active radiation (PAR), leaf nitrogen concentration (Nl), and mass per unit leaf area (Ml) in different canopy layers of un-thinned orchard (UOD) and thinned orchard (TOD), this paper studied the effects of UOD rebuilding on the use efficiencies of PAR and nitrogen, and their relationships to the fruit yield and quality. Thinning obviously improved the radiation environment in canopy. The radiation distribution in TOD canopy was more uniformly than that in UOD canopy, and the invalid space with relative PAR (PARr) less than 30% in TOD approached to zero, while the minimum mean PARr in UOD was 17%, and the space under 0. 3 of relative canopy height was invalid. The leaf photosynthetic efficiency in TOD was notably improved. Comparing with that in UOD, the photsynthetic rate (Pn) at the middle and bottom of the canopy in TOD was increased by 7.8% and 10.2%, respectively. Meanwhile, the photosynthetic potential parameters such as maximum carboxylation rate (Vmax) and maximum electron transfer rate (Jmax) also increased remarkably in TOD. The leaf photosynthetic potential had significant correlation with Nl, and the Nl was strongly correlated with PARr. As a result, leaf photosynthetic potential and PARr could be estimated according to the spatial distribution of relative leaf nitrogen concentration (Nlr).

  7. Irradiance heterogeneity within crown affects photosynthetic capacity and nitrogen distribution of leaves in Cedrela sinensis.

    PubMed

    Yoshimura, Kenichi

    2010-05-01

    Because light conditions in the forest understory are highly heterogeneous, photosynthetic acclimation to spatially variable irradiance within a crown is important for crown-level carbon assimilation. The effect of variation in irradiance within the crown on leaf nitrogen content and photosynthetic rate was examined for pinnate compound leaves in saplings of Cedrela sinensis, a pioneer deciduous tree. Five shading treatments, in which 0, 25, 50, 75 and 100% of leaves were shaded, were established by artificial heavy shading using shade screen umbrellas with 25% transmittance. Although the nitrogen content of leaves was constant regardless of shading treatment, ribulose 1.5-bisphosphate carboxylase/oxygenase (Rubisco) content and light-saturated photosynthetic capacity were lower in shade leaves within partially shaded crowns than within fully shaded crowns. Shade leaves within partially shaded crowns contained higher amount of amino acids. Most shade leaves died in partially shaded crowns, whereas more than half of shade leaves survived in totally shaded crowns. Assumptions on photosynthetic acclimation to local light conditions cannot explain why shade leaves have different photosynthetic capacities and survival rates in between partially and totally shaded crowns. Irradiance heterogeneity within the crown causes a distinct variation in photosynthetic activity between sun and shaded leaves within the crown.

  8. Mycorrhiza Symbiosis Increases the Surface for Sunlight Capture in Medicago truncatula for Better Photosynthetic Production

    PubMed Central

    Adolfsson, Lisa; Keresztes, Áron; Uddling, Johan; Schoefs, Benoît; Spetea, Cornelia

    2015-01-01

    Arbuscular mycorrhizal (AM) fungi play a prominent role in plant nutrition by supplying mineral nutrients, particularly inorganic phosphate (Pi), and also constitute an important carbon sink. AM stimulates plant growth and development, but the underlying mechanisms are not well understood. In this study, Medicago truncatula plants were grown with Rhizophagus irregularis BEG141 inoculum (AM), mock inoculum (control) or with Pi fertilization. We hypothesized that AM stimulates plant growth through either modifications of leaf anatomy or photosynthetic activity per leaf area. We investigated whether these effects are shared with Pi fertilization, and also assessed the relationship between levels of AM colonization and these effects. We found that increased Pi supply by either mycorrhization or fertilization led to improved shoot growth associated with increased nitrogen uptake and carbon assimilation. Both mycorrhized and Pi-fertilized plants had more and longer branches with larger and thicker leaves than the control plants, resulting in an increased photosynthetically active area. AM-specific effects were earlier appearance of the first growth axes and increased number of chloroplasts per cell section, since they were not induced by Pi fertilization. Photosynthetic activity per leaf area remained the same regardless of type of treatment. In conclusion, the increase in growth of mycorrhized and Pi-fertilized Medicago truncatula plants is linked to an increase in the surface for sunlight capture, hence increasing their photosynthetic production, rather than to an increase in the photosynthetic activity per leaf area. PMID:25615871

  9. Mycorrhiza symbiosis increases the surface for sunlight capture in Medicago truncatula for better photosynthetic production.

    PubMed

    Adolfsson, Lisa; Solymosi, Katalin; Andersson, Mats X; Keresztes, Áron; Uddling, Johan; Schoefs, Benoît; Spetea, Cornelia

    2015-01-01

    Arbuscular mycorrhizal (AM) fungi play a prominent role in plant nutrition by supplying mineral nutrients, particularly inorganic phosphate (Pi), and also constitute an important carbon sink. AM stimulates plant growth and development, but the underlying mechanisms are not well understood. In this study, Medicago truncatula plants were grown with Rhizophagus irregularis BEG141 inoculum (AM), mock inoculum (control) or with P(i) fertilization. We hypothesized that AM stimulates plant growth through either modifications of leaf anatomy or photosynthetic activity per leaf area. We investigated whether these effects are shared with P(i) fertilization, and also assessed the relationship between levels of AM colonization and these effects. We found that increased P(i) supply by either mycorrhization or fertilization led to improved shoot growth associated with increased nitrogen uptake and carbon assimilation. Both mycorrhized and P(i)-fertilized plants had more and longer branches with larger and thicker leaves than the control plants, resulting in an increased photosynthetically active area. AM-specific effects were earlier appearance of the first growth axes and increased number of chloroplasts per cell section, since they were not induced by P(i) fertilization. Photosynthetic activity per leaf area remained the same regardless of type of treatment. In conclusion, the increase in growth of mycorrhized and P(i)-fertilized Medicago truncatula plants is linked to an increase in the surface for sunlight capture, hence increasing their photosynthetic production, rather than to an increase in the photosynthetic activity per leaf area.

  10. Regulation of Photosynthetic Electron Transport and Photoinhibition

    PubMed Central

    Roach, Thomas; Krieger-Liszkay, Anja Krieger

    2014-01-01

    Photosynthetic organisms and isolated photosystems are of interest for technical applications. In nature, photosynthetic electron transport has to work efficiently in contrasting environments such as shade and full sunlight at noon. Photosynthetic electron transport is regulated on many levels, starting with the energy transfer processes in antenna and ending with how reducing power is ultimately partitioned. This review starts by explaining how light energy can be dissipated or distributed by the various mechanisms of non-photochemical quenching, including thermal dissipation and state transitions, and how these processes influence photoinhibition of photosystem II (PSII). Furthermore, we will highlight the importance of the various alternative electron transport pathways, including the use of oxygen as the terminal electron acceptor and cyclic flow around photosystem I (PSI), the latter which seem particularly relevant to preventing photoinhibition of photosystem I. The control of excitation pressure in combination with the partitioning of reducing power influences the light-dependent formation of reactive oxygen species in PSII and in PSI, which may be a very important consideration to any artificial photosynthetic system or technical device using photosynthetic organisms. PMID:24678670

  11. Oxygen concentration inside a functioning photosynthetic cell.

    PubMed

    Kihara, Shigeharu; Hartzler, Daniel A; Savikhin, Sergei

    2014-05-01

    The excess oxygen concentration in the photosynthetic membranes of functioning oxygenic photosynthetic cells was estimated using classical diffusion theory combined with experimental data on oxygen production rates of cyanobacterial cells. The excess oxygen concentration within the plesiomorphic cyanobacterium Gloeobactor violaceus is only 0.025 μM, or four orders of magnitude lower than the oxygen concentration in air-saturated water. Such a low concentration suggests that the first oxygenic photosynthetic bacteria in solitary form could have evolved ∼2.8 billion years ago without special mechanisms to protect them against reactive oxygen species. These mechanisms instead could have been developed during the following ∼500 million years while the oxygen level in the Earth's atmosphere was slowly rising. Excess oxygen concentrations within individual cells of the apomorphic cyanobacteria Synechocystis and Synechococcus are 0.064 and 0.25 μM, respectively. These numbers suggest that intramembrane and intracellular proteins in isolated oxygenic photosynthetic cells are not subjected to excessively high oxygen levels. The situation is different for closely packed colonies of photosynthetic cells. Calculations show that the excess concentration within colonies that are ∼40 μm or larger in diameter can be comparable to the oxygen concentration in air-saturated water, suggesting that species forming colonies require protection against reactive oxygen species even in the absence of oxygen in the surrounding atmosphere.

  12. Photosynthetic reaction center complexes from heliobacteria

    NASA Technical Reports Server (NTRS)

    Trost, J. T.; Vermaas, W. F. J.; Blankenship, R. E.

    1991-01-01

    The goal of this project is to understand the early evolutionary development of photosynthesis by examining the properties of reaction centers isolated from certain contemporary organisms that appear to contain the simplest photosynthetic reaction centers. The major focus of this project is the family of newly discovered strictly anaerobic photosynthetic organisms known as Heliobacteria. These organisms are the only known photosynthetic organisms that are grouped with the gram-positive phylum of bacteria. The properties of these reaction centers suggest that they might be the decendants of an ancestor that also gave rise to Photosystem 1 found in oxygen-evolving photosynthetic organisms. Photoactive reaction center-core antenna complexes have been isolated from the photosynthetic bacteria Heliobacillus mobilis and Heliobacterium gestii. The absorption and fluorescence properties of membranes and reaction centers are almost identical, suggesting that a single pigment-protein complex serves as both antenna and reaction center. Experiments in progress include sequence determination of the 48,000 Mr reaction center protein, and evolutionary comparisons with other reaction center proteins.

  13. ENHANCED PRACTICAL PHOTOSYNTHETIC CO2 MITIGATION

    SciTech Connect

    Dr. David J. Bayless; Dr. Morgan Vis; Dr. Gregory Kremer; Dr. Michael Prudich; Dr. Keith Cooksey; Dr. Jeff Muhs

    2001-04-16

    This quarterly report documents significant achievements in the Enhanced Practical Photosynthetic CO{sub 2} Mitigation project during the period from 1/03/2001 through 4/02/2001. Many of the activities and accomplishments are continuations of work initiated and reported in last quarter's status report. Major activities and accomplishments for this quarter include: Three sites in Yellowstone National Park have been identified that may contain suitable organisms for use in a bioreactor; Full-scale culturing of one thermophilic organism from Yellowstone has progressed to the point that there is a sufficient quantity to test this organism in the model-scale bioreactor; The effects of the additive monoethanolamine on the growth of one thermophilic organism from Yellowstone has been tested; Testing of growth surface adhesion and properties is continuing; Construction of a larger model-scale bioreactor to improve and expand testing capabilities is completed and the facility is undergoing proof tests; Model-scale bioreactor tests examining the effects of CO{sub 2} concentration levels and lighting levels on organism growth rates are continuing; Alternative fiber optic based deep-penetration light delivery systems for use in the pilot-scale bioreactor have been designed, constructed and tested; An existing slug flow reactor system has been modified for use in this project, and a proof-of-concept test plan has been developed for the slug flow reactor; Research and testing of water-jet harvesting techniques is continuing, and a harvesting system has been designed for use in the model-scale bioreactor; and The investigation of comparative digital image analysis as a means for determining the ''density'' of algae on a growth surface is continuing Plans for next quarter's work and an update on the project's web page are included in the conclusions.

  14. Toward understanding as photosynthetic biosignatures: light harvesting and energy transfer calculation

    NASA Astrophysics Data System (ADS)

    Komatsu, Y.; Umemura, M.; Shoji, M.; Shiraishi, K.; Kayanuma, M.; Yabana, K.

    2014-03-01

    Among several proposed biosignatures, red edge is a direct evidence of photosynthetic life if it is detected (Kiang et al 2007). Red edge is a sharp change in reflectance spectra of vegetation in NIR region (about 700-750 nm). The sign of red edge is observed by Earthshine or remote sensing (Wolstencroft & Raven 2002, Woolf et al 2002). But, why around 700-750 nm? The photosynthetic organisms on Earth have evolved to optimize the sunlight condition. However, if we consider about photosynthetic organism on extrasolar planets, they should have developed to utilize the spectra of its principal star. Thus, it is not strange even if it shows different vegetation spectra. In this study, we focused on the light absorption mechanism of photosynthetic organisms on Earth and investigated the fundamental properties of the light harvesting mechanisms, which is the first stage for the light absorption. Light harvesting complexes contain photosynthetic pigments like chlorophylls. Effective light absorption and the energy transfer are accomplished by the electronic excitations of collective photosynthetic pigments. In order to investigate this mechanism, we constructed an energy transfer model by using a dipole-dipole approximation for the interactions between electronic excitations. Transition moments and transition energies of each pigment are calculated at the time-dependent density functional theory (TDDFT) level (Marques & Gross 2004). Quantum dynamics simulation for the excitation energy transfer was calculated by the Liouvelle's equation. We adopted the model to purple bacteria, which has been studied experimentally and known to absorb lower energy. It is meaningful to focus on the mechanism of this bacteria, since in the future mission, M planets will become a important target. We calculated the oscillator strengths in one light harvesting complex and confirmed the validity by comparing to the experimental data. This complex is made of an inner and an outer ring. The

  15. Carbon Absorber Retrofit Equipment (CARE)

    SciTech Connect

    Klein, Eric

    2015-12-23

    During Project DE-FE0007528, CARE (Carbon Absorber Retrofit Equipment), Neumann Systems Group (NSG) designed, installed and tested a 0.5MW NeuStream® carbon dioxide (CO2) capture system using the patented NeuStream® absorber equipment and concentrated (6 molal) piperazine (PZ) as the solvent at Colorado Springs Utilities’ (CSU’s) Martin Drake pulverized coal (PC) power plant. The 36 month project included design, build and test phases. The 0.5MW NeuStream® CO2 capture system was successfully tested on flue gas from both coal and natural gas combustion sources and was shown to meet project objectives. Ninety percent CO2 removal was achieved with greater than 95% CO2product purity. The absorbers tested support a 90% reduction in absorber volume compared to packed towers and with an absorber parasitic power of less than 1% when configured for operation with a 550MW coal plant. The preliminary techno-economic analysis (TEA) performed by the Energy and Environmental Research Center (EERC) predicted an over-the-fence cost of $25.73/tonne of CO2 captured from a sub-critical PC plant.

  16. Mushroom plasmonic metamaterial infrared absorbers

    NASA Astrophysics Data System (ADS)

    Ogawa, Shinpei; Fujisawa, Daisuke; Hata, Hisatoshi; Uetsuki, Mitsuharu; Misaki, Koji; Kimata, Masafumi

    2015-01-01

    There has been a considerable amount of interest in the development of various types of electromagnetic wave absorbers for use in different wavelength ranges. In particular, infrared (IR) absorbers with wavelength selectivity can be applied to advanced uncooled IR sensors, which would be capable of identifying objects through their radiation spectrum. In the present study, mushroom plasmonic metamaterial absorbers (MPMAs) for the IR wavelength region were designed and fabricated. The MPMAs consist of a periodic array of thin metal micropatches connected to a thin metal plate with narrow silicon (Si) posts. A Si post height of 200 nm was achieved by isotropic XeF2 etching of a thin Si layer sandwiched between metal plates. This fabrication procedure is relatively simple and is consistent with complementary metal oxide semiconductor technology. The absorption spectra of the fabricated MPMAs were experimentally measured. In addition, theoretical calculations of their absorption properties were conducted using rigorous coupled wave analysis. Both the calculated and measured absorbance results demonstrated that these MPMAs can realize strong selective absorption at wavelengths beyond the period of the array by varying the micropatch width. Absorbance values greater than 90% were achieved. Dual- or single-mode absorption can also be selected by varying the width of the Si posts. Pixel structures using such MPMAs could be used as high responsivity, high resolution and fast uncooled IR sensors.

  17. Additive manufacturing of RF absorbers

    NASA Astrophysics Data System (ADS)

    Mills, Matthew S.

    The ability of additive manufacturing techniques to fabricate integrated electromagnetic absorbers tuned for specific radio frequency bands within structural composites allows for unique combinations of mechanical and electromagnetic properties. These composites and films can be used for RF shielding of sensitive electromagnetic components through in-plane and out-of-plane RF absorption. Structural composites are a common building block of many commercial platforms. These platforms may be placed in situations in which there is a need for embedded RF absorbing properties along with structural properties. Instead of adding radar absorbing treatments to the external surface of existing structures, which adds increased size, weight and cost; it could prove to be advantageous to integrate the microwave absorbing properties directly into the composite during the fabrication process. In this thesis, a method based on additive manufacturing techniques of composites structures with prescribed electromagnetic loss, within the frequency range 1 to 26GHz, is presented. This method utilizes screen printing and nScrypt micro dispensing to pattern a carbon based ink onto low loss substrates. The materials chosen for this study will be presented, and the fabrication technique that these materials went through to create RF absorbing structures will be described. The calibration methods used, the modeling of the RF structures, and the applications in which this technology can be utilized will also be presented.

  18. Mushroom plasmonic metamaterial infrared absorbers

    SciTech Connect

    Ogawa, Shinpei Fujisawa, Daisuke; Hata, Hisatoshi; Uetsuki, Mitsuharu; Misaki, Koji; Kimata, Masafumi

    2015-01-26

    There has been a considerable amount of interest in the development of various types of electromagnetic wave absorbers for use in different wavelength ranges. In particular, infrared (IR) absorbers with wavelength selectivity can be applied to advanced uncooled IR sensors, which would be capable of identifying objects through their radiation spectrum. In the present study, mushroom plasmonic metamaterial absorbers (MPMAs) for the IR wavelength region were designed and fabricated. The MPMAs consist of a periodic array of thin metal micropatches connected to a thin metal plate with narrow silicon (Si) posts. A Si post height of 200 nm was achieved by isotropic XeF{sub 2} etching of a thin Si layer sandwiched between metal plates. This fabrication procedure is relatively simple and is consistent with complementary metal oxide semiconductor technology. The absorption spectra of the fabricated MPMAs were experimentally measured. In addition, theoretical calculations of their absorption properties were conducted using rigorous coupled wave analysis. Both the calculated and measured absorbance results demonstrated that these MPMAs can realize strong selective absorption at wavelengths beyond the period of the array by varying the micropatch width. Absorbance values greater than 90% were achieved. Dual- or single-mode absorption can also be selected by varying the width of the Si posts. Pixel structures using such MPMAs could be used as high responsivity, high resolution and fast uncooled IR sensors.

  19. Nonventing, Regenerable, Lightweight Heat Absorber

    NASA Technical Reports Server (NTRS)

    Izenson, Michael G.; Chen, Weibo

    2008-01-01

    A lightweight, regenerable heat absorber (RHA), developed for rejecting metabolic heat from a space suit, may also be useful on Earth for short-term cooling of heavy protective garments. Unlike prior space-suit-cooling systems, a system that includes this RHA does not vent water. The closed system contains water reservoirs, tubes through which water is circulated to absorb heat, an evaporator, and an absorber/radiator. The radiator includes a solution of LiCl contained in a porous material in titanium tubes. The evaporator cools water that circulates through a liquid-cooled garment. Water vapor produced in the evaporator enters the radiator tubes where it is absorbed into the LiCl solution, releasing heat. Much of the heat of absorption is rejected to the environment via the radiator. After use, the RHA is regenerated by heating it to a temperature of 100 C for about 2 hours to drive the absorbed water back to the evaporator. A system including a prototype of the RHA was found to be capable of maintaining a temperature of 20 C while removing heat at a rate of 200 W for 6 hours.

  20. Photosynthetic O2 evolution and spectroscopy of hybrids and mutants undetached maize leaves studied by open photoacoustic cell

    NASA Astrophysics Data System (ADS)

    Vargas, H.; Alvarado-Gil, J. J.

    1995-08-01

    A new and highly sensitive method is described for in vivo and in situ studies of photosynthetic activity of undetached leaves based on the photoacoustic effect. The general utility of this simple photothermal method is illustrated by examining the spectroscopy and photosynthetic activity of green, striped, and albino plants of maize. The technique is also used to show that the oxygen evolution in hybrids is higher than in inbred lines of maize.

  1. Modification of physicochemical characteristics of active pharmaceutical ingredients and application of supersaturatable dosage forms for improving bioavailability of poorly absorbed drugs.

    PubMed

    Kawakami, Kohsaku

    2012-05-01

    New chemical entities are required to possess physicochemical characteristics that result in acceptable oral absorption. However, many promising candidates need physicochemical modification or application of special formulation technology. This review discusses strategies for overcoming physicochemical problems during the development at the preformulation and formulation stages with emphasis on overcoming the most typical problem, low solubility. Solubility of active pharmaceutical ingredients can be improved by employing metastable states, salt forms, or cocrystals. Since the usefulness of salt forms is well recognized, it is the normal strategy to select the most suitable salt form through extensive screening in the current developmental study. Promising formulation technologies used to overcome the low solubility problem include liquid-filled capsules, self-emulsifying formulations, solid dispersions, and nanosuspensions. Current knowledge for each formulation is discussed from both theoretical and practical viewpoints, and their advantages and disadvantages are presented.

  2. DHCAL with minimal absorber: measurements with positrons

    NASA Astrophysics Data System (ADS)

    Freund, B.; Neubüser, C.; Repond, J.; Schlereth, J.; Xia, L.; Dotti, A.; Grefe, C.; Ivantchenko, V.; Berenguer Antequera, J.; Calvo Alamillo, E.; Fouz, M.-C.; Marin, J.; Puerta-Pelayo, J.; Verdugo, A.; Brianne, E.; Ebrahimi, A.; Gadow, K.; Göttlicher, P.; Günter, C.; Hartbrich, O.; Hermberg, B.; Irles, A.; Krivan, F.; Krüger, K.; Kvasnicka, J.; Lu, S.; Lutz, B.; Morgunov, V.; Provenza, A.; Reinecke, M.; Sefkow, F.; Schuwalow, S.; Tran, H. L.; Garutti, E.; Laurien, S.; Matysek, M.; Ramilli, M.; Schroeder, S.; Bilki, B.; Norbeck, E.; Northacker, D.; Onel, Y.; Cvach, J.; Gallus, P.; Havranek, M.; Janata, M.; Kovalcuk, M.; Kvasnicka, J.; Lednicky, D.; Marcisovsky, M.; Polak, I.; Popule, J.; Tomasek, L.; Tomasek, M.; Sicho, P.; Smolik, J.; Vrba, V.; Zalesak, J.; van Doren, B.; Wilson, G. W.; Kawagoe, K.; Hirai, H.; Sudo, Y.; Suehara, T.; Sumida, H.; Takada, S.; Tomita, T.; Yoshioka, T.; Bilokin, S.; Bonis, J.; Cornebise, P.; Pöschl, R.; Richard, F.; Thiebault, A.; Zerwas, D.; Hostachy, J.-Y.; Morin, L.; Besson, D.; Chadeeva, M.; Danilov, M.; Markin, O.; Popova, E.; Gabriel, M.; Goecke, P.; Kiesling, C.; van der Kolk, N.; Simon, F.; Szalay, M.; Corriveau, F.; Blazey, G. C.; Dyshkant, A.; Francis, K.; Zutshi, V.; Kotera, K.; Ono, H.; Takeshita, T.; Ieki, S.; Kamiya, Y.; Ootani, W.; Shibata, N.; Jeans, D.; Komamiya, S.; Nakanishi, H.

    2016-05-01

    In special tests, the active layers of the CALICE Digital Hadron Calorimeter prototype, the DHCAL, were exposed to low energy particle beams, without being interleaved by absorber plates. The thickness of each layer corresponded approximately to 0.29 radiation lengths or 0.034 nuclear interaction lengths, defined mostly by the copper and steel skins of the detector cassettes. This paper reports on measurements performed with this device in the Fermilab test beam with positrons in the energy range of 1 to 10 GeV. The measurements are compared to simulations based on GEANT4 and a standalone program to emulate the detailed response of the active elements.

  3. Photosynthetic complex stoichiometry dynamics in higher plants: environmental acclimation and photosynthetic flux control

    PubMed Central

    Schöttler, Mark A.; Tóth, Szilvia Z.

    2014-01-01

    The composition of the photosynthetic apparatus of higher plants is dynamically adjusted to long-term changes in environmental conditions such as growth light intensity and light quality, and to changing metabolic demands for ATP and NADPH imposed by stresses and leaf aging. By changing photosynthetic complex stoichiometry, a long-term imbalance between the photosynthetic production of ATP and NADPH and their metabolic consumption is avoided, and cytotoxic side reactions are minimized. Otherwise, an excess capacity of the light reactions, relative to the demands of primary metabolism, could result in a disturbance of cellular redox homeostasis and an increased production of reactive oxygen species, leading to the destruction of the photosynthetic apparatus and the initiation of cell death programs. In this review, changes of the abundances of the different constituents of the photosynthetic apparatus in response to environmental conditions and during leaf ontogenesis are summarized. The contributions of the different photosynthetic complexes to photosynthetic flux control and the regulation of electron transport are discussed. PMID:24860580

  4. Absorption microspectroscopy, theory and applications in the case of the photosynthetic compartment.

    PubMed

    Barsanti, Laura; Evangelista, Valtere; Frassanito, Anna Maria; Vesentini, Nicoletta; Passarelli, Vincenzo; Gualtieri, Paolo

    2007-01-01

    We performed microspectroscopic evaluation of the pigment composition of the photosynthetic compartments of both algae and higher plants. The feasibility of microspectroscopy for discriminating among species and/or phylogenetic groups was tested on laboratory cultures. Gaussian bands decompositions, and a fitting algorithm, together with fourth-derivative transformation of absorbance spectra, provided a reliable discrimination among chlorophylls, phycobiliproteins and carotenoids. Comparative analysis of absorption spectra highlighted the evolutionary grouping of the algae into three main lineages in accordance with the most recent endosymbiotic theories.

  5. Damage tolerant light absorbing material

    DOEpatents

    Lauf, Robert J.; Hamby, Jr., Clyde; Akerman, M. Alfred; Seals, Roland D.

    1993-01-01

    A light absorbing article comprised of a composite of carbon-bonded carbon fibers, prepared by: blending carbon fibers with a carbonizable organic powder to form a mixture; dispersing the mixture into an aqueous slurry; vacuum molding the aqueous slurry to form a green article; drying and curing the green article to form a cured article; and, carbonizing the cured article at a temperature of at least about 1000.degree. C. to form a carbon-bonded carbon fiber light absorbing composite article having a bulk density less than 1 g/cm.sup.3.

  6. Damage tolerant light absorbing material

    DOEpatents

    Lauf, R.J.; Hamby, C. Jr.; Akerman, M.A.; Seals, R.D.

    1993-09-07

    A light absorbing article comprised of a composite of carbon-bonded carbon fibers, is prepared by: blending carbon fibers with a carbonizable organic powder to form a mixture; dispersing the mixture into an aqueous slurry; vacuum molding the aqueous slurry to form a green article; drying and curing the green article to form a cured article; and, carbonizing the cured article at a temperature of at least about 1000 C to form a carbon-bonded carbon fiber light absorbing composite article having a bulk density less than 1 g/cm[sup 3]. 9 figures.

  7. Waveform-Dependent Absorbing Metasurfaces

    NASA Astrophysics Data System (ADS)

    Wakatsuchi, Hiroki; Kim, Sanghoon; Rushton, Jeremiah J.; Sievenpiper, Daniel F.

    2013-12-01

    We present the first use of a waveform-dependent absorbing metasurface for high-power pulsed surface currents. The new type of nonlinear metasurface, composed of circuit elements including diodes, is capable of storing high-power pulse energy to dissipate it between pulses, while allowing propagation of small signals. Interestingly, the absorbing performance varies for high-power pulses but not for high-power continuous waves (CW’s), since the capacitors used are fully charged up. Thus, the waveform dependence enables us to distinguish various signal types (i.e., CW or pulse) even at the same frequency, which potentially creates new kinds of microwave technologies and applications.

  8. Enhanced practical photosynthetic CO2 mitigation

    DOEpatents

    Bayless, David J.; Vis-Chiasson, Morgan L.; Kremer, Gregory G.

    2003-12-23

    This process is unique in photosynthetic carbon sequestration. An on-site biological sequestration system directly decreases the concentration of carbon-containing compounds in the emissions of fossil generation units. In this process, photosynthetic microbes are attached to a growth surface arranged in a containment chamber that is lit by solar photons. A harvesting system ensures maximum organism growth and rate of CO.sub.2 uptake. Soluble carbon and nitrogen concentrations delivered to the cyanobacteria are enhanced, further increasing growth rate and carbon utilization.

  9. Design criteria for optimal photosynthetic energy conversion

    NASA Astrophysics Data System (ADS)

    Fingerhut, Benjamin P.; Zinth, Wolfgang; de Vivie-Riedle, Regina

    2008-12-01

    Photochemical solar energy conversion is considered as an alternative of clean energy. For future light converting nano-machines photosynthetic reaction centers are used as prototypes optimized during evolution. We introduce a reaction scheme for global optimization and simulate the ultrafast charge separation in photochemical energy conversion. Multiple molecular charge carriers are involved in this process and are linked by Marcus-type electron transfer. In combination with evolutionary algorithms, we unravel the biological strategies for high quantum efficiency in photosynthetic reaction centers and extend these concepts to the design of artificial photochemical devices for energy conversion.

  10. [Study on absorbing volatile oil with mesoporous carbon].

    PubMed

    Yan, Hong-mei; Jia, Xiao-bin; Zhang, Zhen-hai; Sun, E; Yang Nan

    2014-11-01

    Clove oil and turmeric oil were absorbed by mesoporous carbon. The absorption ratio of mesoporous carbon to volatile oil was optimized with the eugenol yield and curcumol yield as criteria Curing powder was characterized by scanning electron microscopy (SEM) and differential scanning calorietry (DSC). The effects of mesoporous carbon on dissolution in vitro and thermal stability of active components were studied. They reached high adsorption rate when the absorption ratio of mesoporous carbon to volatile oil was 1:1. When volatile oil was absorbed, dissolution rate of active components had a little improvement and their thermal stability improved after volatile oil was absorbed by the loss rate decreasing more than 50%. Absorbing herbal volatile oil with mesoporous carbon deserves further studying. PMID:25850263

  11. Contributions of Respiratory and Photosynthetic Pathways during Growth of a Facultative Photoautotrophic Cyanobacterium, Aphanocapsa 6714 1

    PubMed Central

    Der-Vartanian, Maurice; Joset-Espardellier, Francoise; Astier, Chantal

    1981-01-01

    Comparison of the growth parameters and photosynthetic capacities of cells of Aphanocapsa 6714 under various growth conditions led to the following conclusions: (a), no enzymic regulation of CO2/glucose assimilation takes place in this strain; (b), functioning of photodependent phosphorylating pathways turns off oxidative ATP synthesis; (c), no efficient regulation of pigment synthesis exists in these cells; (d), most modulations of photosynthetic activities probably occur through structural modifications of the photosynthetic membranes (a small proportion of the pigments might appear as a nonintegrated pool in the cell and be sensitive to synthesis regulation); and (e), photosystem II activity would be dependent on light intensity in a discontinuous way, the consequence of this property being the appearance of two successive exponential phases during phototrophic growth in adequate light conditions. PMID:16662036

  12. Satellite-observed photosynthetic trends across boreal North America associated with climate and fire disturbance

    PubMed Central

    Goetz, Scott J.; Bunn, Andrew G.; Fiske, Gregory J.; Houghton, R. A.

    2005-01-01

    We analyzed trends in a time series of photosynthetic activity across boreal North America over 22 years (1981 through 2003). Nearly 15% of the region displayed significant trends, of which just over half involved temperature-related increases in growing season length and photosynthetic intensity, mostly in tundra. In contrast, forest areas unaffected by fire during the study period declined in photosynthetic activity and showed no systematic change in growing season length. Stochastic changes across the time series were predominantly associated with a frequent and increasing fire disturbance regime. These trends have implications for the direction of feedbacks to the climate system and emphasize the importance of longer term synoptic observations of arctic and boreal biomes. PMID:16174745

  13. Oil and fat absorbing polymers

    NASA Technical Reports Server (NTRS)

    Marsh, H. E., Jr. (Inventor)

    1977-01-01

    A method is described for forming a solid network polymer having a minimal amount of crosslinking for use in absorbing fats and oils. The polymer remains solid at a swelling ratio in oil or fat of at least ten and provides an oil absorption greater than 900 weight percent.

  14. Counterflow absorber for an absorption refrigeration system

    DOEpatents

    Reimann, Robert C.

    1984-01-01

    An air-cooled, vertical tube absorber for an absorption refrigeration system is disclosed. Strong absorbent solution is supplied to the top of the absorber and refrigerant vapor is supplied to the bottom of the absorber to create a direct counterflow of refrigerant vapor and absorbent solution in the absorber. The refrigeration system is designed so that the volume flow rate of refrigerant vapor in the tubes of the absorber is sufficient to create a substantially direct counterflow along the entire length of each tube in the absorber. This provides several advantages for the absorber such as higher efficiency and improved heat transfer characteristics, and allows improved purging of non-condensibles from the absorber.

  15. The Relationship between Anatomy and Photosynthetic Performance of Heterobaric Leaves1

    PubMed Central

    Nikolopoulos, Dimosthenis; Liakopoulos, Georgios; Drossopoulos, Ioannis; Karabourniotis, George

    2002-01-01

    Heterobaric leaves show heterogeneous pigmentation due to the occurrence of a network of transparent areas that are created from the bundle sheaths extensions (BSEs). Image analysis showed that the percentage of photosynthetically active leaf area (Ap) of the heterobaric leaves of 31 plant species was species dependent, ranging from 91% in Malva sylvestris to only 48% in Gynerium sp. Although a significant portion of the leaf surface does not correspond to photosynthetic tissue, the photosynthetic capacity of these leaves, expressed per unit of projected area (Pmax), was not considerably affected by the size of their transparent leaf area (At). This means that the photosynthetic capacity expressed per Ap (P*max) should increase with At. Moreover, the expression of P*max could be allowing the interpretation of the photosynthetic performance in relation to some critical anatomical traits. The P*max, irrespective of plant species, correlated with the specific leaf transparent volume (λt), as well as with the transparent leaf area complexity factor (CFAt), parameters indicating the volume per unit leaf area and length/density of the transparent tissues, respectively. Moreover, both parameters increased exponentially with leaf thickness, suggesting an essential functional role of BSEs mainly in thick leaves. The results of the present study suggest that although the Ap of an heterobaric leaf is reduced, the photosynthetic performance of each areole is increased, possibly due to the light transferring capacity of BSEs. This mechanism may allow a significant increase in leaf thickness and a consequent increase of the photosynthetic capacity per unit (projected) area, offering adaptive advantages in xerothermic environments. PMID:12011354

  16. Light, temperature and nutrients as factors in photosynthetic adjustment to elevated carbon dioxide

    SciTech Connect

    Bunce, J.; Lee, D. )

    1991-05-01

    It has been noted many times that the short-term stimulation of photosynthesis by elevated carbon dioxide usually observed in C3 plants may not persist in the long-term. Experiments were designed to test the hypotheses that photosynthetic adjustment to elevated carbon dioxide is due to (a) feedback inhibition resulting from excess photosynthate production relative to use, and (b) nutrient deficiency resulting from more rapid growth. Soybeans and sugarbeets were grown in controlled environment chambers at 350 and 700 ppm carbon dioxide, at two temperatures, two levels of photosynthetically active radiation, and with three nutrient regimes in a factorial design. Net carbon dioxide uptake rates of individual leaves from all growth conditions were measured at both 350 and 700 ppm carbon dioxide to assay photosynthetic adjustment to the elevated carbon dioxide. Growth at elevated carbon dioxide reduced rates of photosynthesis measured at standard carbon dioxide levels in both species. Photosynthetic rates measured at 350 ppm were lower on average by 33% in sugarbeet and 23% in soybean after growth at elevated carbon dioxide. Photosynthetic adjustment to elevated carbon dioxide was not greater after growth at 1.0 than 0.5 mmol m{sup {minus}2}s{sup {minus}1} PPFD, was not greater at 20 than 25C growth temperature, and could not be overcome by high rates of nutrient application. These results do not support either the feedback inhibition nor nutrient deficiency hypotheses of photosynthetic adjustment to elevated carbon dioxide. In soybeans, complete photosynthetic adjustment could be induced by a single night at elevated carbon dioxide.

  17. Determination of neutron absorbed doses in lithium aluminates.

    PubMed

    Delfín Loya, A; Carrera, L M; Ureña-Núñez, F; Palacios, O; Bosch, P

    2003-04-01

    Lithium-based ceramics have been proposed as tritium breeders for fusion reactors. The lithium aluminate (gamma phase) seems to be thermally and structurally stable, the damages produced by neutron irradiation depend on the absorbed dose. A method based on the measurement of neutron activation of foils through neutron capture has been developed to obtain the neutron absorbed dose in lithium aluminates irradiated in the thermal column facility and in the fixed irradiation system of a Triga Mark III Nuclear Reactor. PMID:12672632

  18. Screening and identification of compounds with antiviral activity against hepatitis B virus using a safe compound library and novel real-time immune-absorbance PCR-based high throughput system.

    PubMed

    Lamontagne, Jason; Mills, Courtney; Mao, Richeng; Goddard, Cally; Cai, Dawei; Guo, Haitao; Cuconati, Andy; Block, Timothy; Lu, Xuanyong

    2013-04-01

    There are now seven nucleoside/tide analogues, along with interferon-α, that are approved by the FDA for the management of chronic hepatitis B virus (HBV) infection, a disease affecting hundreds of millions of people worldwide. These medications, however, are limited in usefulness, and significant side effects and the emergence of viral escape mutants make the development of novel and updated therapeutics a pressing need in the treatment of HBV. With this in mind, a library containing 2000 compounds already known to be safe in both humans and mice with known mechanisms of action in mammalian cells were tested for the possibility of either antiviral activity against HBV or selective toxicity in HBV producing cell lines. A modified real-time immune-absorbance-polymerase chain reaction (IA-PCR) assay was developed for this screen, utilizing cells that produce and secrete intact HBV virions. In this procedure, viral particles are first captured by an anti-HBs antibody immobilized on a plate. The viral load is subsequently assessed by real-time PCR directly on captured particles. Using this assay, eight compounds were shown to consistently reduce the amount of secreted HBV viral particles in the culture medium under conditions that had no detectable impact on cell viability. Two compounds, proparacaine and chlorophyllide, were shown to reduce HBV levels 4- to 6-fold with an IC₅₀ of 1 and 1.5 μM, respectively, and were selected for further study. The identification of these compounds as promising antiviral drug candidates against HBV, despite a lack of previous recognition of HBV antiviral activity, supports the validity and utility of testing known compounds for "off-pathogen target" activity against HBV, and also validates this IA-PCR assay as an important tool for the detection of anti-viral activity against enveloped viruses.

  19. Enhanced Practical Photosynthetic CO2 Mitigation

    SciTech Connect

    Gregory Kremer; David J. Bayless; Morgan Vis; Michael Prudich; Keith Cooksey; Jeff Muhs

    2004-07-15

    This report highlights significant achievements in the Enhanced Practical Photosynthetic CO{sub 2} Mitigation Project for the period ending 06/30/2004. The major accomplishment was the modification of the header and harvesting work, with a system designed to distribute algae at startup, sustain operations and harvest in one unit.

  20. Photosynthetic strategies of two Mojave Desert shrubs

    SciTech Connect

    Kleinkopf, G.E.; Hartsock, T.L.; Wallace, A.; Romney, E.M.

    1980-01-01

    Photosynthetic production of two Mojave Desert shrubs was measured under natural growing conditions. Measurements of photosynthesis, transpiration, resistances to water vapor flux, soil moisture potential, and tissue water potential were made. Atriplex canescens (Pursh) Nutt., a member of the C/sub 4/ biochemical carbon dioxide fixation group was highly competitive in growth rate and production during conditions of adequate soil moisture. As soil moisture conditions declined to minus 40 bars, the net photosynthetic rate of Atriplex decreased to zero. However, the C/sub 3/ shrub species Larrea tridentata (Sesse and Moc. ex DC.) Cov. was able to maintain positive net photosynthetic production during conditions of high temperature and extreme low soil moisture through the major part of the season. The comparative advantages of the C/sub 4/ versus the C/sub 3/ pathway of carbon fixation was lost between these two species as the soil moisture potential declined to minus 40 bars. Desert plants have diffferent strategies for survival, one of the strategies being the C/sub 4/ biochemical carbon fixation pathway. However, many of the plants are members of the C/sub 3/ group. In this instance, the C/sub 4/ fixation pathway does not confer an added advantage to the productivity of the species in the Mojave Desert. Species distribution based on comparative photosynthetic production is discussed

  1. On the evolution of the photosynthetic pigments.

    PubMed

    Evstigneev, V B

    1975-07-01

    During the course of terrestrial evolution, some organisms developed the capability of capturing and utilizing solar radiation. Colored compounds were undoubtedly incorporated within living forms from the earliest times, but during the transition from heterotrophic to a photoautotrophic metabolism only those pigments were selected that were components of the evolving photosynthetic apparatus and were able to catalyze reactions involving storage of light energy in chemical bonds. In this communication, some properties of tetrapyrroles with a closed porphyrin ring containing a metal ion in the center are discussed. These compounds are present in all principal contemporary photosynthetic pigments, and their synthesis has been demonstrated from simpler compounds under prebiotic conditions. It is probable that during intermediate stages in the evolution of photosynthesis, pigments with oxidizing potentials lower than that of chlorophyll were utilized to store light energy although they were not capable of removing electrons from water. The evolution and function of multiple forms of a given photosynthetic pigment in vivo are discussed. 'Accessory' pigments may be regarded as rudiments of the evolutionary development of the photosynthetic apparatus.

  2. ENHANCED PRACTICAL PHOTOSYNTHETIC CO2 MITIGATION

    SciTech Connect

    Dr. Gregory Kremer; Dr. David J. Bayless; Dr. Morgan Vis; Dr. Michael Prudich; Dr. Keith Cooksey; Dr. Jeff Muhs

    2002-10-15

    This report documents significant achievements in the Enhanced Practical Photosynthetic CO{sub 2} Mitigation project during the period from 10/2/2001 through 10/01/2002. This report marks the end of year 2 of a three-year project as well as the milestone date for completion of Phase I activities. This report includes our current status and defines the steps being taken to ensure that we meet the project goals by the end of year 3. As indicated in the list of accomplishments below our current efforts are focused on evaluating candidate organisms and growth surfaces, preparing to conduct long-term tests in the bench-scale bioreactor test systems, and scaling-up the test facilities from bench scale to pilot scale. Specific results and accomplishments for the third quarter of 2002 include: Organisms and Growth Surfaces: (1) Test results continue to indicate that thermophilic cyanobacteria have significant advantages as agents for practical photosynthetic CO{sub 2} mitigation before mesophilic forms. (2) Additional thermal features with developed cyanobacterial mats, which might be calcium resistant, were found in YNP. (3) Back to back tests show that there is no detectable difference in the growth of isolate 1.2 s.c. (2) in standard and Ca-modified BG-11 medium. The doubling time for both cases was about 12 hours. (4) The cultivation of cyanobacteria in Ca-BG medium should proceed in the pH range between 7 and 7.4, but this suggestion requires additional experiments. (5) Cyanobacteria can be grown in media where sodium is present at trace levels. (6) Ca{sup 2+} enriched medium can be used as a sink for CO{sub 2} under alkaline conditions. (7) Cyanobacteria are able to generate cones of filaments on travertine surfaces. [Travertine is a mixture of CaCO{sub 3} and CaSO{sub 4}]. We hypothesize that SO{sub 4}{sup 2-} stimulates the generation of such cones, because they are not almost generated on CaCO3 surface. On the other hand, we know that plant gas contains elevated

  3. In Silico and Biochemical Analysis of Physcomitrella patens Photosynthetic Antenna: Identification of Subunits which Evolved upon Land Adaptation

    PubMed Central

    Alboresi, Alessandro; Caffarri, Stefano; Nogue, Fabien; Bassi, Roberto; Morosinotto, Tomas

    2008-01-01

    Background In eukaryotes the photosynthetic antenna system is composed of subunits encoded by the light harvesting complex (Lhc) multigene family. These proteins play a key role in photosynthesis and are involved in both light harvesting and photoprotection. The moss Physcomitrella patens is a member of a lineage that diverged from seed plants early after land colonization and therefore by studying this organism, we may gain insight into adaptations to the aerial environment. Principal Findings In this study, we characterized the antenna protein multigene family in Physcomitrella patens, by sequence analysis as well as biochemical and functional investigations. Sequence identification and analysis showed that some antenna polypeptides, such as Lhcb3 and Lhcb6, are present only in land organisms, suggesting they play a role in adaptation to the sub-aerial environment. Our functional analysis which showed that photo-protective mechanisms in Physcomitrella patens are very similar to those in seed plants fits with this hypothesis. In particular, Physcomitrella patens also activates Non Photochemical Quenching upon illumination, consistent with the detection of an ortholog of the PsbS protein. As a further adaptation to terrestrial conditions, the content of Photosystem I low energy absorbing chlorophylls also increased, as demonstrated by differences in Lhca3 and Lhca4 polypeptide sequences, in vitro reconstitution experiments and low temperature fluorescence spectra. Conclusions This study highlights the role of Lhc family members in environmental adaptation and allowed proteins associated with mechanisms of stress resistance to be identified within this large family. PMID:18446222

  4. Comparative analysis of plastid genomes of non-photosynthetic Ericaceae and their photosynthetic relatives.

    PubMed

    Logacheva, Maria D; Schelkunov, Mikhail I; Shtratnikova, Victoria Y; Matveeva, Maria V; Penin, Aleksey A

    2016-07-25

    Although plastid genomes of flowering plants are typically highly conserved regarding their size, gene content and order, there are some exceptions. Ericaceae, a large and diverse family of flowering plants, warrants special attention within the context of plastid genome evolution because it includes both non-photosynthetic and photosynthetic species with rearranged plastomes and putative losses of "essential" genes. We characterized plastid genomes of three species of Ericaceae, non-photosynthetic Monotropa uniflora and Hypopitys monotropa and photosynthetic Pyrola rotundifolia, using high-throughput sequencing. As expected for non-photosynthetic plants, M. uniflora and H. monotropa have small plastid genomes (46 kb and 35 kb, respectively) lacking genes related to photosynthesis, whereas P. rotundifolia has a larger genome (169 kb) with a gene set similar to other photosynthetic plants. The examined genomes contain an unusually high number of repeats and translocations. Comparative analysis of the expanded set of Ericaceae plastomes suggests that the genes clpP and accD that are present in the plastid genomes of almost all plants have not been lost in this family (as was previously thought) but rather persist in these genomes in unusual forms. Also we found a new gene in P. rotundifolia that emerged as a result of duplication of rps4 gene.

  5. Comparative analysis of plastid genomes of non-photosynthetic Ericaceae and their photosynthetic relatives.

    PubMed

    Logacheva, Maria D; Schelkunov, Mikhail I; Shtratnikova, Victoria Y; Matveeva, Maria V; Penin, Aleksey A

    2016-01-01

    Although plastid genomes of flowering plants are typically highly conserved regarding their size, gene content and order, there are some exceptions. Ericaceae, a large and diverse family of flowering plants, warrants special attention within the context of plastid genome evolution because it includes both non-photosynthetic and photosynthetic species with rearranged plastomes and putative losses of "essential" genes. We characterized plastid genomes of three species of Ericaceae, non-photosynthetic Monotropa uniflora and Hypopitys monotropa and photosynthetic Pyrola rotundifolia, using high-throughput sequencing. As expected for non-photosynthetic plants, M. uniflora and H. monotropa have small plastid genomes (46 kb and 35 kb, respectively) lacking genes related to photosynthesis, whereas P. rotundifolia has a larger genome (169 kb) with a gene set similar to other photosynthetic plants. The examined genomes contain an unusually high number of repeats and translocations. Comparative analysis of the expanded set of Ericaceae plastomes suggests that the genes clpP and accD that are present in the plastid genomes of almost all plants have not been lost in this family (as was previously thought) but rather persist in these genomes in unusual forms. Also we found a new gene in P. rotundifolia that emerged as a result of duplication of rps4 gene. PMID:27452401

  6. Comparative analysis of plastid genomes of non-photosynthetic Ericaceae and their photosynthetic relatives

    PubMed Central

    Logacheva, Maria D.; Schelkunov, Mikhail I.; Shtratnikova, Victoria Y.; Matveeva, Maria V.; Penin, Aleksey A.

    2016-01-01

    Although plastid genomes of flowering plants are typically highly conserved regarding their size, gene content and order, there are some exceptions. Ericaceae, a large and diverse family of flowering plants, warrants special attention within the context of plastid genome evolution because it includes both non-photosynthetic and photosynthetic species with rearranged plastomes and putative losses of “essential” genes. We characterized plastid genomes of three species of Ericaceae, non-photosynthetic Monotropa uniflora and Hypopitys monotropa and photosynthetic Pyrola rotundifolia, using high-throughput sequencing. As expected for non-photosynthetic plants, M. uniflora and H. monotropa have small plastid genomes (46 kb and 35 kb, respectively) lacking genes related to photosynthesis, whereas P. rotundifolia has a larger genome (169 kb) with a gene set similar to other photosynthetic plants. The examined genomes contain an unusually high number of repeats and translocations. Comparative analysis of the expanded set of Ericaceae plastomes suggests that the genes clpP and accD that are present in the plastid genomes of almost all plants have not been lost in this family (as was previously thought) but rather persist in these genomes in unusual forms. Also we found a new gene in P. rotundifolia that emerged as a result of duplication of rps4 gene. PMID:27452401

  7. Mimicking the Role of the Antenna in Photosynthetic Photoprotection

    SciTech Connect

    Terazono, Yuichi; Kodis, Gerdenis; Bhushan, Kul; Zaks, Julia; Madden, Christopher; Moore, Ana L.; Moore, Thomas A.; Fleming, Graham R.; Gust, Devens

    2011-03-09

    One mechanism used by plants to protect against damage from excess sunlight is called nonphotochemical quenching (NPQ). Triggered by low pH in the thylakoid lumen, NPQ leads to conversion of excess excitation energy in the antenna system to heat before it can initiate production of harmful chemical species by photosynthetic reaction centers. Here we report a synthetic hexad molecule that functionally mimics the role of the antenna in NPQ. When the hexad is dissolved in an organic solvent, five zinc porphyrin antenna moieties absorb light, exchange excitation energy, and ultimately decay by normal photophysical processes. Their excited-state lifetimes are long enough to permit harvesting of the excitation energy for photoinduced charge separation or other work. However, when acid is added, a pH-sensitive dye moiety is converted to a form that rapidly quenches the first excited singlet states of all five porphyrins, converting the excitation energy to heat and rendering the porphyrins kinetically incompetent to readily perform useful photochemistry.

  8. Molecular basis of photoprotection and control of photosynthetic light-harvesting.

    PubMed

    Pascal, Andrew A; Liu, Zhenfeng; Broess, Koen; van Oort, Bart; van Amerongen, Herbert; Wang, Chao; Horton, Peter; Robert, Bruno; Chang, Wenrui; Ruban, Alexander

    2005-07-01

    In order to maximize their use of light energy in photosynthesis, plants have molecules that act as light-harvesting antennae, which collect light quanta and deliver them to the reaction centres, where energy conversion into a chemical form takes place. The functioning of the antenna responds to the extreme changes in the intensity of sunlight encountered in nature. In shade, light is efficiently harvested in photosynthesis. However, in full sunlight, much of the energy absorbed is not needed and there are vitally important switches to specific antenna states, which safely dissipate the excess energy as heat. This is essential for plant survival, because it provides protection against the potential photo-damage of the photosynthetic membrane. But whereas the features that establish high photosynthetic efficiency have been highlighted, almost nothing is known about the molecular nature of the dissipative states. Recently, the atomic structure of the major plant light-harvesting antenna protein, LHCII, has been determined by X-ray crystallography. Here we demonstrate that this is the structure of a dissipative state of LHCII. We present a spectroscopic analysis of this crystal form, and identify the specific changes in configuration of its pigment population that give LHCII the intrinsic capability to regulate energy flow. This provides a molecular basis for understanding t