Photosynthetic Action Spectra Research Articles

A Chloroplast-Localised Fluorescent Protein Enhances the Photosynthetic Action Spectrum in Green Algae

Green microalgae are important sources of natural products and are attractive cell factories for manufacturing high-value products such as recombinant proteins. Increasing scales of production must address the bottleneck of providing sufficient light energy for photosynthesis. Enhancing the photosynthetic action spectrum of green algae to improve the utilisation of yellow light would provide additional light energy for photosynthesis. Here, we evaluated the Katushka fluorescent protein, which converts yellow photons to red photons, to drive photosynthesis and growth when expressed in Chlamydomonas reinhardtii chloroplasts. Transplastomic algae expressing a codon-optimised Katushka gene accumulated the active Katushka protein, which was detected by excitation with yellow light. Removal of chlorophyll from cells, which captures red photons, led to increased Katushka fluorescence. In yellow light, emission of red photons by fluorescent Katushka increased oxygen evolution and photosynthetic growth. Utilisation of yellow photons increased photosynthetic growth of transplastomic cells expressing Katushka in light deficient in red photons. These results showed that Katushka was a simple and effective yellow light-capturing device that enhanced the photosynthetic action spectrum of C. reinhardtii.

Multi-site occupancies and dependent photoluminescence of Ca9Mg1.5(PO4)7:Eu2+ phosphors: A bifunctional platform for optical thermometer and plant growth lighting

Herein, we demonstrate an optical thermometer based on single Eu2+ doped Ca9Mg1.5(PO4)7 phosphors, which were prepared by traditional solid-state reaction technique under a reduction atmosphere. Considerations on the bond length obtained by the crystal structure refinement and the dependent photoluminescence performances allow to assign the two distinct emission bands to Eu2+ ions occupied Ca1–Ca3 and Mg2 sites. Moreover, the blue and red emitting bands perfectly match with the photosynthetic action spectrum, which can enhance the indoor plant photosynthesis. The optimal doping content of Eu2+ ions in this Ca9Mg1.5(PO4)7 system is 3 mol%. The corresponding concentration quenching effect is verified as dipole–dipole interaction with the critical distance of 3.315 nm. Furthermore, by exploiting the fluorescence intensity technique, the optical thermal resistance properties of Ca9Mg1.5(PO4)7:Eu2+ are identified based on the temperature dependent emission spectra in a range of 303–523 K. In detail, the maximum absolute and relative sensitivity Sa and Sr of Ca9Mg1.5(PO4)7:Eu2+ thermometer are as high as 0.637%/K and 0.3155 K–1, respectively. Consequently, the Eu2+ doped Ca9Mg1.5(PO4)7 phosphors establish a bifunctional platform for both optical thermometer and plant growth lighting via multi-site occupancies.

Spectral Design of Light-Emitting Diodes for Plant Photosynthesis Based on Quantum Dots

Light is one of the five indispensable factors for plant growth. Green houses and plant factories have advantages of growing vegetables off-season and high production. However, artificial lighting occupies most of the running cost during the operation of plant factories, and intelligent and programmable light-emitting diodes (LEDs) have been considered to be used as growing lamps to save energy. Taking both the photosynthetic and the visual performances into consideration, luminescent spectrum of LEDs based on quantum dot (QD) materials is designed and optimized according to the photosynthetic action spectrum (PAS) of plants. In our calculation, the three-band QD-based LEDs (QLEDs) show a highest photosynthetic action factor (PAF) of 8.088 and a highest induced photosynthetic index (IPI) of 4.012. The four-band QLEDs show a highest PAF of 7.689 and a highest IPI of 3.818. CdZnS/ZnS and CdZnS/ZnSe QDs are also synthesized for fabricating three- and four-band QLEDs. Investigations of the photosynthetic and the vison performances on these devices are consistent with those theoretical simulation results. Both the simulation and the experimental results show that either the three- or the four-band QLEDs has better photosynthetic parameters than those of the conventional light sources. The fabricated four-band QLED under different applied current exhibits a highest PAF of 2.6942 and a highest IPI of 1.3621. For the vison performances, the four-band device demonstrate a highest CRI of 93 and a highest CCT of 2053 K. Despite the visual performances of the four-band QLEDs show improvement than those of the three-band ones, they still need to be improved to offer better visual experience for human eyes. With further investigation on the synthesis of emission tunable QD materials and the optimization of the spectrum, highly efficient QLEDs with both good photosynthetic and visual performances are expected to be applied in the field of growing lamps.

Agrivoltaics—The Perfect Fit for the Future of Organic Photovoltaics

AbstractThis Essay presents a possible pathway for the advancement of organic photovoltaics toward broader commercial success and enlarged market size. This vision aims at broad scale applications in photovoltaic greenhouses and polytunnels, which harvest those portions of the solar spectrum that are not used or required by plants. Based on the assumptions of the Shockley–Queisser–Limit, respectively detailed balance, and the additional postulation of using no absorption in the visible part of the AM 1.5G solar spectrum a power conversion efficiency of ≈17% is theoretically predicted. The suggestion is supported by the existence of a number of organic compounds, which already exhibit a good spectral compatibility with the typical photosynthetic action spectrum of chloroplasts. It is hoped that more suitable materials development shall be triggered and fertilized as a result of this Essay.

Tunable spectrum resemblance of LED lights for improving the photosynthetic action of Chinese Cabbages

To increase efficiency, and reduce energy loss and waste, we propose to improve the photosynthetic action spectrum resemblance (SRPAS) of LED light with the absorption spectra of the fresh leaf, for accelerating the growth of Chinese Cabbages. Eight spectral LED lights were adopted to irradiate Chinese Cabbages under 150 μmol•m−2 s−1 for a 16 hd−1 photoperiod. Of these, under the irradiation of blue + broad red + more yellow (BRY2) light with high spectrum resemblance of 75%, the fresh weight and dry weight are 5.1times and 3.0 times, respectively, and the leaf area and leaf number are 1.7 times, as high as under the blue light. The results demonstrate that the optimized LED light can be presumed to have the highest spectrum resemblance (SRPAS) with the absorption spectra of Chinese Cabbages, and the highest energy-conversion efficiency. These conclusions may be of great benefit to further assess and find either an ideal light applied for plant growth or design of better light sources for growing different plants.

High-efficient and thermal-stable Ca19Zn2(PO4)14: Eu2+, Mn2+ blue-red dual-emitting phosphor for plant cultivation LEDs

A series of dual-emitting Eu2+, Mn2+ co-doped Ca19Zn2(PO4)14 (CZP) phosphors capable for plant cultivation LEDs are synthesized. As a sensitzer, Ca19Zn2(PO4)14: Eu2+ emits a dominant blue light with green shoulder by Eu2+ occupying CaO8 and CaO6 sites, respectively. Mn2+ was introduced into CZP: Eu2+ to obtain the red emission component. The as-synthesized CZP: Eu2+, Mn2+ phosphor shows a blue emission peaking at 415 nm and significantly enhanced deep-red emission peaking at 650 nm under single UV excitation, which should be attributed to the existence and energy transfer of Eu2+ and Mn2+, respectively. The emission spectra match well with the plants’ photosynthetic action spectra (PAS) for both red and blue lights simultaneously. Energy transfer from Eu2+ to Mn2+ enables a facile tune of emitting color from blue to red, and the corresponding mechanism is revealed to be the electric dipole-dipole interaction by analyzing Eu2+/Mn2+ decay lifetime variations. High quantum efficiency (93.3%) and favorable thermal stability (68% of RT intensity at 473 K) clearly verify the good properties of CZP: Eu2+, Mn2+ phosphor. Results confirmed that CZP: Eu2+, Mn2+ phosphor might have great applicational potential in plant growth LED lighting.

Analyses of multi-color plant-growth light sources in achieving maximum photosynthesis efficiencies with enhanced color qualities.

An optimal design of light-emitting diode (LED) lighting that benefits both the photosynthesis performance for plants and the visional health for human eyes has drawn considerable attention. In the present study, we have developed a multi-color driving algorithm that serves as a liaison between desired spectral power distributions and pulse-width-modulation duty cycles. With the aid of this algorithm, our multi-color plant-growth light sources can optimize correlated-color temperature (CCT) and color rendering index (CRI) such that photosynthetic luminous efficacy of radiation (PLER) is maximized regardless of the number of LEDs and the type of photosynthetic action spectrum (PAS). In order to illustrate the accuracies of the proposed algorithm and the practicalities of our plant-growth light sources, we choose six color LEDs and German PAS for experiments. Finally, our study can help provide a useful guide to improve light qualities in plant factories, in which long-term co-inhabitance of plants and human beings is required.

Dual-responsive Sr2SiO4:Eu2+-Ba3MgSi2O8:Eu2+, Mn2+ composite phosphor to human eyes and plant chlorophylls applications for general lighting and plant lighting

Herein, blue–red synchronous emitting Ba3MgSi2O8:Eu2+, Mn2+ nanocrystals matched well the photosynthetic action spectrum (PAS) of plant chlorophylls was fabricated on green emitting Sr2SiO4:Eu2+ emitter covered entirely the photopic vision function (PVF) of human eyes, to construct Sr2SiO4:Eu2+-Ba3MgSi2O8:Eu2+, Mn2+ dual-responsive composite phosphor. The micro-structure and blue–green–red tri-bands photoluminescence for the obtained composite phosphor were investigated in detail. White light emission with excellent dual-response characters to PAS of plant chlorophylls and PVF of human eyes was obtained, indicating the potential applications in both of general lighting and plant lighting.

Plant Growth Absorption Spectrum Mimicking Light Sources.

Plant factories have attracted increasing attention because they can produce fresh fruits and vegetables free from pesticides in all weather. However, the emission spectra from current light sources significantly mismatch the spectra absorbed by plants. We demonstrate a concept of using multiple broad-band as well as narrow-band solid-state lighting technologies to design plant-growth light sources. Take an organic light-emitting diode (OLED), for example; the resulting light source shows an 84% resemblance with the photosynthetic action spectrum as a twin-peak blue dye and a diffused mono-peak red dye are employed. This OLED can also show a greater than 90% resemblance as an additional deeper red emitter is added. For a typical LED, the resemblance can be improved to 91% if two additional blue and red LEDs are incorporated. The approach may facilitate either an ideal use of the energy applied for plant growth and/or the design of better light sources for growing different plants.

Enhancement of photosynthetic action spectrum for 660 nm-featured phase-pure (Ba,Sr)3MgSi2O8: Eu2+, Mn2+ phosphor by spray-combustion synthesis

Dual band emissions positioned at both 660 and 430 nm of (Ba, Sr)3MgSi2O8: Eu2+, Mn2+ phosphor was achieved via spray-combustion synthesis procedure. At a specific limited solid solubility composition Ba1.3Sr1.7MgSi2O8, the secondary green-emitting phases of (Ba, Sr)2SiO4 or (Ba, Sr)MgSiO4 were effectively suppressed to give out the desired 660 nm broad emission. An enhancement of photoluminescence (PL) intensity for 660 nm red emission originated from Mn transition was observed in combustion synthesis samples, indicating an intrinsic promotion of energy transfer from Eu2+ to Mn2+ in (Ba, Sr)3MgSi2O8 host. This PL enhancement to 660 nm emission is probably ascribed to an effective reduction of Mn ion in the combustion process with the aid of decomposed reductive radicals formed in situ upon fuel ignition. The crystallized particle size varies in the range from 5 to 20 μm depending on process parameters. A near ultraviolet LED illumination prototype packaged with as-prepared phosphor exhibits to be violet in color. This combustion synthesis process provides an effective means for PL enhancement of phase-pure (Ba,Sr)3MgSi2O8: Eu2+, Mn2+ phosphors to construct the photosynthetic action spectrum.

Luminescence properties of a solid solution typed (Ba,Ca)3MgSi2O8: Eu2+, Mn2+ phosphor with a 660 nmfeatured photosynthetic action spectrum

A solid-solution-phase Ba1.75Ca1.25MgSi2O8: Eu2+, Mn2+ phosphor in the photosynthetic action spectrum with dual band emissions at 438 nm and 660 nm is fabricated. X-ray diffraction (XRD) confirms the presence of the solid-solution phase. With the supporting information from the diffuse reflection spectrum, a feasible way to obtain higher energy-transfer (ET) efficiency is attained, and the ET efficiency of Eu2+-Mn2+ is enhanced to 76%. The mechanism of this enhancement is owing to variation of the solid solution composition of Ca3MgSi2O8 and Ba3MgSi2O8, which contributes to the extension of the critical distance. Temperature-dependent results show an enhancement which is attributed to Ca. These enhancements show great promise for improving eco-lighting devices.

Single-phased silicate-hosted phosphor with 660 nm-featured band emission for biological light-emitting diodes

A single-phased (Ba,Sr)3MgSi2O8:Eu2+, Mn2+ phosphor with 660 nm-featured dual band-emission is investigated upon optimizing composition to simulate the artificial photosynthetic action spectrum (PAS) for near-ultraviolet (NUV) biological light-emitting diodes (bio-LEDs). A specific composition range in Ba–Sr binary solid solution of (Ba,Sr)3MgSi2O8 is found to be capable of obtaining single-phased host in the absence of an easily formed orthosilicate impurity, leading to a 660 nm-featured red band emission of Mn2+ induced by an efficient energy transfer from a co-doped blue-emitting Eu2+ sensitizer. This dual broad band emission phosphor has a 72 nm full width at half maximum (FWHM) for red band that covers fairly well to the absorption spectrum of chlorophyll and PAS for most plants, enabling a flexible option in the application of bio-illumination for artificial photosynthesis.

Blue and Red Light‐Induced Germination of Resting Spores in the Red‐Tide Diatom Leptocylindrus danicus†

Photophysiological and pharmacological approaches were used to examine light-induced germination of resting spores in the red-tide diatom Leptocylindrus danicus. The equal-quantum action spectrum for photogermination had peaks at about 440 nm (blue light) and 680 nm (red light), which matched the absorption spectrum of the resting spore chloroplast, as well as photosynthetic action spectra reported for other diatoms. DCMU, an inhibitor of photosynthetic electron flow near photosystem II, completely blocked photogermination. These results suggest that the photosynthetic system is involved in the photoreception process of light-induced germination. Results of pharmacological studies of the downstream signal transduction pathway suggested that Ca(2+) influx is the closest downstream neighbor, followed by steps involving calmodulin, nitric oxide synthase, guanylyl cyclase, protein-tyrosine-phosphatase, protein kinase C and actin polymerization and translation.

Intensification of the Photosynthetic Action Spectrum of Ba3MgSi2O8:Eu2+, Mn2+ Phosphor with Metal-Enhanced Fluorescence

The simultaneous emission of 440 nm-peaked blue and 619 nm-peaked red of Ba3MgSi2O8:Eu2+, Mn2+ was enhanced by the metal-enhanced fluorescence (MEF) through assembling sliver island films for photosynthetic action spectrum (PAS). A 1.42-fold enhancement of blue emission was resulted from MEF-induced resonant coupling between the localized surface plasmon of Ag and the photons of blue emission from Eu2+. Sequentially, this enhanced photonic energy of blue emission was transferred to the co-activator of Mn2+, leading to a 1.47-fold intensification of red emission. The dual enhanced emission of PAS could be optimized to a maximum with an annealed 50-nm-thick silver film. © 2011 The Electrochemical Society. [DOI: 10.1149/2.014202esl] All rights reserved.

Photosynthesis Research in Canada from 1945 to the early 1970s

This history traces the development of photosynthesis research in Canada from 1945 to 1975, starting with the work of Gleb(1) Krotkov and his students, Paul Vittorio, Tony(1) Bidwell, Don(1) Nelson, Jim(1) Craigie, Bruce Tregunna, Andreas Hauschild, Geoff Lister and others in the Department of Biology at Queen's University, Kingston, Ontario. They focused on the influence of taxonomy and light quality on the path of carbon into early products, photorespiration and photosynthesis in young trees. During the same period, Ken(1) Clendenning and one of the authors (PRG) at the National Research Council of Canada (NRCC) laboratory in Ottawa began studies of chloroplast photoreduction and leaf carboxylases. They were joined by Don(1) Mortimer, who showed that the path of carbon varies with species of plant and by Morris Kates, who studied phospholipid enzymology in chloroplasts and leaves. Stan(1) Holt researched the chemistry and distribution of chlorophylls in different taxa. In 1952, Ralph Lewin joined NRCC's new Atlantic Regional Laboratory in Halifax, Nova Scotia, followed by Jim Craigie, Jack McLachlan and Tony Bidwell who mainly investigated the products of photosynthesis in marine algae. Tony Bidwell continued these studies in 1959 at the Department of Botany, University of Toronto. Dave(1) Canvin joined the staff at Queen's in 1965 and became involved in solving the mystery of photorespiration. Tony Bidwell returned to Queen's in 1969 and studied photosynthesis of algal chloroplasts using an 'artificial leaf.' In 1965, Don Nelson established a group at Simon Fraser University in Burnaby, British Columbia that included his former student, Geoff Lister who produced the first photosynthetic action spectra for trees, and Bill(1) Vidaver, who showed the useful relation between chlorophyll fluorescence and photosynthetic activity. In 1970, Mário Fragata headed a group at the Université du Québec à Trois Rivières, Québec, that began with studies of Photosystem II in chloroplasts and particles.

Effect of Mesodinium rubrum (= Myrionecta rubra) on the action and absorption spectra of phytoplankton in a coastal marine inlet

This study, carried out at a single station in the Bedford Basin (Nova Scotia, Canada), examined time-dependent changes in the physical and chemical conditions of the waters with associated changes in species composition and some photosynthesis properties of phytoplankton. The sampling period covered late summer months (August and September) and fall months (October to December). Changes in the water conditions were found to influence species composition, which in turn had an effect on the shapes and amplitudes of the action and absorption spectra of phytoplankton, and on the maximum quantum yield of photosynthesis. The most remarkable change was observed in October during a bloom of Mesodinium rubrum, a ciliate harbouring photosynthetic endosymbionts rich in phycobilins. The presence of M. rubrum yielded atypical shapes of the measured photosynthetic action spectra; furthermore, other photosynthesis properties changed significantly. These results demonstrate that the presence of certain pigments in the water column may be associated with a marked shift from what may be considered typical (representative) photosynthesis properties of phytoplankton.

Bio-optical properties of the subtropical North Atlantic. II. Relevance to models of primary production

. ABSTRACT: Based on measurements of phytoplankton biomass, absorption coefficients and photosynthetic performance obtained from samples collected in the subtropical Atlantic Ocean, standard sets of bio-optical parameters were selected and applied to a spectral model of primary production. Computed profiles of instantaneous production, integrated over the day, and spectral irradiance were compared with measurements of 12 h in situ production and in situ spectral irradiance to assess the model's performance. Although the model performed well for the stations located on the western side of the transect, at the eastern side of the basin the model overestimated both primary production and irradiance below the mixed layer. The modelled irradiance profile was then reconciled with the observations of irradiance by increasing the assumed contribution to absorption by yellow substances. When the production model was re-implemented with the new irradiance values below the mixed layer, the computed and measured production profiles of all the stations were in good agreement. In the spectral model used in this study, the shape of the absorption spectrum of phytoplankton was used as a proxy for the shape of the photosynthetic action spectrum. Because non-photosynthetic pigments (NPPs) were abundant in pigment samples collected in the study region, the influence of NPPs on the shape of the absorption spectrum was examined and its effect on computations of primary production was quantified. When total aPh(z, h) and photosynthetic a,,(z, h) phytoplankton absorption at wavelength h and depth z were used to quantify the error resulting from failure to correct for the influence of NPPs on the shape of the absorption spectra, the results showed small errors in the computation of production at depth (up to 20%) and integrated, water-column primary production (a maximum of 10 %).

Bio‐optical properties of the marine diazotrophic cyanobacteria Trichodesmium spp. I. Absorption and photosynthetic action spectra

The optical absorption, fluorescence excitation and emission, and photosynthetic action spectra were measured in vivo on intact colonies of Trichodesmium from the Caribbean Sea. The optical cross‐sections were dominated by ultraviolet‐A (UVA) absorption, which was a consequence of massive accumulations of mycosporinelike amino acids. The visible region of the spectrum was decomposed into several bands, among which chlorophyll a (Chl a), carotenoids, and individual phycobilipigments could be discerned. There was a clear diel periodicity in the ratio of the optical absorption cross‐sections of phycourobilin (PUB) to phycoerythrobilin (PEB), increasing from around 1.7 at night to 2.1 at midmorning. The diel cycle in PUB/PEB is consistent with a reversible interconversion of the two pigments. The ratio of PUB/PEB was inversely correlated with the transfer of excitation energy to photosystem II (PSII). Light absorbed by PUB was not transferred to PSII with a high efficiency, but rather, a significant fraction was reemitted at 565 nm as fluorescence. These observations suggest that the PUBs and PEBs in Trichodesmium act as a dynamic biophysical energy valve that modify the rate of excitation energy delivered to PSII in response to changes in ambient light regime. The low‐temperature (77 K) fluorescence emission spectra reveal an extremely weak 685‐nm emission signal in relation to that at 730 nm. Based on a simple model, these data suggest that the ratio of PSI/PSII reaction centers in Trichodesmium is about 24:1. Such an extraordinary bias against PSII may help minimize damage to nitrogenase from O2 production in PSII, but it also reduces the photosynthesis‐enhanced growth and makes Trichodesmium virtually undetectable by chlorophyll fluorescence. The unique bio‐optical properties of Trichodesmium can be used to develop algorithms to study its temporal and spatial distributions from remotely sensed information.

Estimation of the photosynthetic action spectrum:implication for primary production models

A slmple method for estimating the photosynthetic action spectrum is developed The method uses the shape ot the absorption spectrum of phytoplankton p~gmen t s , scaled to the magnitude of the initial slope of the photosynthesis-light curve as established for broad-band i l lun~~nat ion The method was tested by comparing the estimated action spectra with those measured dunng a crulse in the North Atlant~c In the fall of 1992 The agreement between the constructed and the measured spectra was good Both the measured and constructed action spectra were then used to compute daily water-column pnmary production (PZT) using a spectrally resolved model The results showed that, at most of the stations, the P Z T c ~ m p u t e d using the constructed action spectrum was not significantly different from PZ calculated using the measured spectrum Daily water-column pnmary production was also computed at each station uslng the average shape of the measured action spectra (spectra averaged over all stations), scaled to the m a g n ~ t u d e of broad-band initial slope at that station The results were s im~lar to the P Z T values computed using the action spectra constructed for individual stations The errors that may affect the constructed ac t~on spectrum are assessed through a sens~tivity analysis The analysis suggests that, for our data, the presence of photosynthet~cally inactive p~gmen t s causes negligible errors in the computed P,. An assessment of the effects of random errors in the action spectrum showed that the error in the computed primary production was on average 1 5% (under the conditions chosen for the computation), when random errors of up to k 2 0 % were introduced into the action spectrum However, given similar conditions, systematic errors of similar magnitude in the actlon spectrum cause an average error of about 6% in the computed water-column pnmary production

Spectral Efficiency of in vivo Photochemical Energy Storage in SO 2 Fumigated Sugar Maple Leaves

Photosynthetic action spectrum and quantum yield of photochemical energy storage were determined by recording photoacoustic spectra of sugar maple (Acer saccharum Marsh.) leaves at a modulation frequency of 80 Hz. At this low frequency, the difference between the intensity of spectra in the presence and in the absence of a non-modulated background light indicated the relative magnitude of the photochemical energy storage, which is generally measured at high frequencies. The amount of energy stored per unit absorbed light energy is low in blue, intermediate in green and high in red regions of the spectrum, indicating the excitation energy transfer efficiency of photosynthetic pigments. Similarly, the relative quantum yield of energy storage was low in blue and high in red regions showing the red-drop phenomenon. The energy storage spectrum per unit incident energy showed a similar profile except for a decline between 520 and 570 nm. In 2 µL L-1 SO2 fumigated leaves, the photochemical activity decreased relative to the control, confirming the SO2 inhibitory site on the electron transport chain.