Natural genetic variation for acclimation of photosynthetic light use efficiency to growth irradiance in Arabidopsis
Rooijen, R. van; Aarts, M.G.M. ; Harbinson, J. - \ 2015
Plant Physiology 167 (2015)4. - ISSN 0032-0889 - p. 1412 - 1429.
genome-wide association - chlorophyll fluorescence - photosystem-ii - supramolecular organization - protein-phosphorylation - plant photosynthesis - electron-transport - barley leaves - quantum yield - green plants
Plants are known to be able to acclimate their photosynthesis to the level of irradiance. Here we present the analysis of natural genetic variation for photosynthetic light use efficiency (FPSII) in response to five light environments among 12 genetically diverse Arabidopsis thaliana accessions. We measured acclimation of FPSII to constant growth irradiances of four different levels (100, 200, 400, and 600 µmol m-2 s-1) by imaging chlorophyll fluorescence after 24 days of growth, and compared these results to acclimation of FPSII to a step-wise change in irradiance where the growth irradiance was increased from 100 to 600 µmol m-2 s-1 after 24 days of growth. Genotypic variation for FPSII is shown by calculating heritability for short-term FPSII response to different irradiance levels, as well as for the relation of FPSII measured at light saturation (a measure of photosynthetic capacity) to growth irradiance level, and for the kinetics of the response to a step-wise increase in irradiance from 100 to 600 µmol m-2 s-1. A genome-wide association study for FPSII measured one hour after a step-wise increase in irradiance identified several new candidate genes controlling this trait. In conclusion, the different photosynthetic responses to a changing light environment displayed by different Arabidopsis are due to genetic differences and we have identified candidate genes for the photosynthetic response to an irradiance change. The genetic variation for photosynthetic acclimation to irradiance found in this study will allow future identification and analysis of the causal genes for the regulation of FPSII in plants
Exploring the Structure of the 100 Amino-Acid Residue Long N-Terminus of the Plant Antenna Protein CP29
Shabestari, M.H. ; Wolfs, C.J.A.M. ; Spruijt, R.B. ; Amerongen, H. van; Huber, M. - \ 2014
Biophysical Journal 106 (2014)6. - ISSN 0006-3495 - p. 1349 - 1358.
light-harvesting complex - electron-paramagnetic-resonance - comprehensive software package - labeled side-chains - photosystem-ii - distance measurements - conformational-changes - structure prediction - energy-transfer - t4 lysozyme
The structure of the unusually long (~100 amino-acid residues) N-terminal domain of the light-harvesting protein CP29 of plants is not defined in the crystal structure of this membrane protein. We studied the N-terminus using two electron paramagnetic resonance (EPR) approaches: the rotational diffusion of spin labels at 55 residues with continuous-wave EPR, and three sets of distances with a pulsed EPR method. The N-terminus is relatively structured. Five regions that differ considerably in their dynamics are identified. Two regions have low rotational diffusion, one of which shows a-helical character suggesting contact with the protein surface. This immobile part is flanked by two highly dynamic, unstructured regions (loops) that cover residues 10-22 and 82-91. These loops may be important for the interaction with other light-harvesting proteins. The region around residue 4 also has low rotational diffusion, presumably because it attaches noncovalently to the protein. This section is close to a phosphorylation site (Thr-6) in related proteins, such as those encoded by the Lhcb4.2 gene. Phosphorylation might influence the interaction with other antenna complexes, thereby regulating the supramolecular organization in the thylakoid membrane.
A single locus confers tolerance to continuous light and allows substantial yield increase in tomato
Vélez Ramírez, A.I. ; Ieperen, W. van; Vreugdenhil, D. ; Poppel, P.M.J.A. van; Heuvelink, E. ; Millenaar, F.F. - \ 2014
Nature Communications 5 (2014). - ISSN 2041-1723
differential expression analysis - photosystem-ii - lycopersicon-esculentum - greenhouse tomato - dependent phosphorylation - chlorophyll fluorescence - arabidopsis-thaliana - gene-expression - air humidity - plants
An important constraint for plant biomass production is the natural day length. Artificial light allows for longer photoperiods, but tomato plants develop a detrimental leaf injury when grown under continuous light—a still poorly understood phenomenon discovered in the 1920s. Here, we report a dominant locus on chromosome 7 of wild tomato species that confers continuous light tolerance. Genetic evidence, RNAseq data, silencing experiments and sequence analysis all point to the type III light harvesting ¿chlorophyll a/b binding protein 13 (¿CAB-13) gene as a major factor responsible for the tolerance. In Arabidopsis thaliana, this protein is thought to have a regulatory role balancing light harvesting by photosystems I and II. Introgressing the tolerance into modern tomato hybrid lines, results in up to 20% yield increase, showing that limitations for crop productivity, caused by the adaptation of plants to the terrestrial 24-h day/night cycle, can be overcome.
Fluorescence kinetics of PSII crystals containing Ca2+ or Si2+ in the oxygen evolving complex
Oort, B.F. van; Kargul, K. ; Barber, J. ; Amerongen, H. van - \ 2014
Biochimica et Biophysica Acta. B, Bioenergetics 1837 (2014)2. - ISSN 0005-2728 - p. 264 - 269.
ftir difference spectroscopy - x-ray crystallography - ii core particles - photosystem-ii - charge separation - thermosynechococcus-elongatus - picosecond fluorescence - angstrom resolution - ca2+/sr2+ exchange - manganese complex
Photosystem II (PSII) is the pigment–protein complex which converts sunlight energy into chemical energy by catalysing the process of light-driven oxidation of water into reducing equivalents in the form of protons and electrons. Three-dimensional structures from x-ray crystallography have been used extensively to model these processes. However, the crystal structures are not necessarily identical to those of the solubilised complexes. Here we compared picosecond fluorescence of solubilised and crystallised PSII core particles isolated from the thermophilic cyanobacterium Thermosynechococcus elongatus. The fluorescence of the crystals is sensitive to the presence of artificial electron acceptors (K3Fe(CN)3) and electron transport inhibitors (DCMU). In PSII with reaction centres in the open state, the picosecond fluorescence of PSII crystals and solubilised PSII is indistinguishable. Additionally we compared picosecond fluorescence of native PSII with PSII in which Ca2 in the oxygen evolving complex (OEC) is biosynthetically replaced by Sr2 +. With the Sr2 + replaced OEC the average fluorescence decay slows down slightly (81 ps to 85 ps), and reaction centres are less readily closed, indicating that both energy transfer/trapping and electron transfer are affected by the replacement.
Commentary: Improving the accuracy of chlorophyll fluorescence measurements
Harbinson, J. - \ 2013
Plant, Cell & Environment 36 (2013)10. - ISSN 0140-7791 - p. 1751 - 1754.
photosynthetic electron-transport - redox state - photosystem-ii - light - resolution - induction - leaves
Using additive modelling to quantify the effect of chemicals on phytoplankton diversuity and biomass
Viaene, K.P.J. ; Laender, F. de; Brink, P.J. van den; Janssen, C.R. - \ 2013
Science of the Total Environment 449 (2013). - ISSN 0048-9697 - p. 71 - 80.
ecological risk-assessment - fresh-water microcosms - herbicide linuron - primary producers - photosystem-ii - pond mesocosms - food-web - biodiversity - sensitivity - communities
Environmental authorities require the protection of biodiversity and other ecosystem properties such as biomass production. However, the endpoints listed in available ecotoxicological datasets generally do not contain these two ecosystem descriptors. Inferring the effects of chemicals on such descriptors from micro- or mesocosm experiments is often hampered by inherent differences in the initial biodiversity levels between experimental units or by delayed community responses. Here we introduce additive modelling to establish the effects of a chronic application of the herbicide linuron on 10 biodiversity indices and phytoplankton biomass in microcosms. We found that communities with a low (high) initial biodiversity subsequently became more (less) diverse, indicating an equilibrium biodiversity status in the communities considered here. Linuron adversely affected richness and evenness while dominance increased but no biodiversity indices were different from the control treatment at linuron concentrations below 2.4 µg/L. Richness-related indices changed at lower linuron concentrations (effects noticeable from 2.4 µg/L) than other biodiversity indices (effects noticeable from 14.4 µg/L) and, in contrast to the other indices, showed no signs of recovery following chronic exposure. Phytoplankton biomass was unaffected by linuron due to functional redundancy within the phytoplankton community. Comparing thresholds for biodiversity with conventional toxicity test results showed that standard ecological risk assessments also protect biodiversity in the case of linuron.
Light harvesting and Blue-Green light induced non-photochemical quenching in two different C-phycocyanin mutants of synechocytis PCC 6803
Tian, L. ; Stokkum, I.H.M. van; Koehorst, R.B.M. ; Amerongen, H. van - \ 2013
The Journal of Physical Chemistry Part B: Condensed Matter, Materials, Surfaces, Interfaces & Biophysical 117 (2013)38. - ISSN 1520-6106 - p. 11000 - 11006.
orange carotenoid protein - excitation-energy transfer - photosystem-ii - sp pcc-6803 - phycobilisome fluorescence - photoprotective mechanism - picosecond kinetics - wild-type - cyanobacterium - photosynthesis
Cyanobacteria are oxygen-evolving photosynthetic organisms that harvest sunlight and convert excitation energy into chemical energy. Most of the light is absorbed by large light harvesting complexes called phycobilisomes (PBs). In high-light conditions, cyanobacteria switch on a photoprotective mechanism called non-photochemical quenching (NPQ): During this process, absorption of blue-green light transforms the inactive orange form of the orange carotenoid protein OCP (OCPo) into the red active form OCPr that subsequently binds to the PB, resulting in a substantial loss of excitation energy and corresponding decrease of the fluorescence. In wild-type cells, the quenching site is a bilin chomophore that fluoresces at 660 nm and which is called APCQ660. In the present work, we studied NPQ in two different types of mutant cells (CB and CK) that possess significantly truncated PBs, using spectrally resolved picosecond fluorescence spectroscopy. The results are in very good agreement with earlier in vitro experiments on quenched and unquenched PBs, although the fraction of quenched PBs is far lower in vivo. It is also lower than the fraction of PBs that is quenched in wild-type cells, but the site, rate, and location of quenching appear to be very similar.
A model for customising biomass composition in continuous microalgae production
Klok, A.J. ; Verbaanderd, J.A. ; Lamers, P.P. ; Martens, D.E. ; Rinzema, A. ; Wijffels, R.H. - \ 2013
Bioresource Technology 146 (2013). - ISSN 0960-8524 - p. 89 - 100.
light-intensity - chlamydomonas-reinhardtii - neochloris-oleoabundans - lipid-accumulation - photosystem-ii - growth - metabolism - photosynthesis - phytoplankton - temperature
A kinetic model is presented that describes functional biomass, starch and storage lipid (TAG) synthesis in the microalga Neochloris oleoabundans as a function of nitrogen and light supply rates to a nitrogen-limited turbidostat cultivation system. The model is based on the measured electron distribution in N. oleoabundans, which showed that starch is the primary storage component, whereas TAG was only produced after an excess of electrons was generated, when growth was limited by nitrogen supply. A fixed 8.6% of the excess electrons ended up in TAG, suggesting close metabolic interactions between nitrogen assimilation and TAG accumulation, such as a shared electron pool. The proposed model shows that by manipulating the cultivation conditions in a light or nitrogen limited turbidostat, algal biomass composition can be customised and the volumetric productivities and yields of the major biomass constituents can be changed on demand.
Effect of oxygen at low and high light intensities on the growth of Neochloris oleoabundans
Sousa, C.A. ; Compadre, A. ; Vermuë, M.H. ; Wijffels, R.H. - \ 2013
Algal Research 2 (2013)2. - ISSN 2211-9264 - p. 122 - 126.
spirulina-platensis cyanobacteria - singlet oxygen - photosystem-ii - photoinhibition - photosynthesis - stress - plants - photobioreactor - temperature - microalgae
The effect of partial oxygen pressure on growth of Neochloris oleoabundans was studied at near-saturating light intensity in a fully-controlled photobioreactor. At the partial oxygen pressures tested (PO2=0.24; 0.42; 0.63; 0.84 bar), the specific growth rate was 1.36; 1.16; 0.93 and 0.68 day-1, respectively. An increase of the PCO2 from 0.007 to 0.02 bar at PO2 of 0.84 bar did not show any positive effect on the overall growth of the algae, contrary to what happens at sub-saturating light intensities. These results indicate that at near-saturating light intensity the inhibitory effect of oxygen by photorespiration cannot be overcome. The chlorophyll content of N. oleoabundans grown at 200 µmol m-2 s-1 is about 1.9 times higher than when cultivated at 500 µmol m-2 s-1, whereas the carotenoid contentwas about 1.5 lower, both demonstrating photoacclimation effects. The elevated oxygen concentration in the growth mediumdoes not affect the pigment content both at sub- and near-saturating light conditions. This indicates that elevated oxygen concentrations in the medium do not contribute to photooxidative damage at the light conditions that are predominantly experienced by algae in closed photobioreactors, but only inhibit the growth via photorespiration effects.
Variations in the first steps of photosynthesis for the diatom Cyclotella meneghiniana grown under different light conditions
Chukhutsina, V.U. ; Buchel, C. ; Amerongen, H. van - \ 2013
Biochimica et Biophysica Acta. B, Bioenergetics 1827 (2013)1. - ISSN 0005-2728 - p. 10 - 18.
fucoxanthin-chlorophyll proteins - excitation-energy transfer - (sub)-picosecond spectral evolution - streak-camera system - photosystem-ii - thylakoid membranes - harvesting complex - charge separation - marine diatoms - centric diatom
In this work we have applied picosecond and steady-state fluorescence measurements to study excitation energy transfer and trapping in intact Cyclotella meneghiniana diatom cells grown at different light intensities. Different excitation and detection wavelengths were used to discriminate between Photosystem I and II (PSI and PSII) kinetics and to study excitation energy transfer from the outer antenna to the core of PSI and PSII. It is found that the light-harvesting fucoxanthin chlorophyll proteins (FCPs) transfer their excitation energy predominantly to PSII. It is also observed that the PSII antenna is slightly richer in red-absorbing fucoxanthin than the FCPs associated with PSI. The average excitation trapping time in PSI is around 75 ps whereas this time is around 450 ps for PSII in cells grown in 20 µmol of photons per m2 per s. The latter time decreases to 425 ps for 50 µmol of photons and 360 ps for 140 µmol of photons. It is concluded that cells grown under higher photon flux densities have a smaller antenna size than the ones grown in low light. At the same time, the increase of growth light intensity leads to a decrease of the relative amount of PSI. This effect is accompanied by a substantial increase in the amount of chlorophyll a that is not active in excitation energy transfer and most probably attached to inactivated/disassembled PSII units.
Picosecond Kinetics of Light Harvesting and Photoprotective Quenching in Wild-Type and Mutant Phycobilisomes Isolated from the Cyanobacterium Synechocystis PCC 6803
Tian, L. ; Gwizdala, M. ; Stokkum, I.H.M. van; Koehorst, R.B.M. ; Kirilovsky, D. ; Amerongen, H. van - \ 2012
Biophysical Journal 102 (2012)7. - ISSN 0006-3495 - p. 1692 - 1700.
orange carotenoid protein - chlorophyll-binding protein - energy-dissipation - photosystem-ii - molecular architecture - higher-plants - fluorescence - mechanism - organization - photoinhibition
In high light conditions, cyanobacteria dissipate excess absorbed energy as heat in the light-harvesting phycobilisomes (PBs) to protect the photosynthetic system against photodamage. This process requires the binding of the red active form of the Orange Carotenoid Protein (OCPr), which can effectively quench the excited state of one of the allophycocyanin bilins. Recently, an in vitro reconstitution system was developed using isolated OCP and isolated PBs from Synechocystis PCC 6803. Here we have used spectrally resolved picosecond fluorescence to study wild-type and two mutated PBs. The results demonstrate that the quenching for all types of PBs takes place on an allophycocyanin bilin emitting at 660 nm (APCQ660) with a molecular quenching rate that is faster than (1 ps)-1. Moreover, it is concluded that both the mechanism and the site of quenching are the same in vitro and in vivo. Thus, utilization of the in vitro system should make it possible in the future to elucidate whether the quenching is caused by charge transfer between APCQ660 and OCP or by excitation energy transfer from APCQ660 to the S1 state of the carotenoid—a distinction that is very hard, if not impossible, to make in vivo.
Modeling the protection of photosynthesis
Harbinson, J. - \ 2012
Proceedings of the National Academy of Sciences of the United States of America 109 (2012)39. - ISSN 0027-8424 - p. 15533 - 15534.
photosystem-ii - energy-dissipation - electron - plants - light - fluorescence - leaves - identification - arabidopsis
It is hard to overstate the importance of photosynthesis for mankind and the biosphere. It produces the oxygen we breathe and the food we eat, and images of Earth from space show the green of terrestrial vegetation and swirls of marine phytoplankton. To meet our increasing demand for food and energy, it seems inevitable that we will need to increase the efficiency of photosynthesis in plants and algae. There is therefore some urgency in our drive to better understand the operation, regulation, and limitations of photosynthesis. This ambition is made particularly challenging because of the complexity of photosynthesis; it comprises many significant subprocesses that range in scale from quantum mechanics to ecosystems. Given the complexity of photosynthesis, mathematical models have proven to be a vital tool with which to encapsulate knowledge and to describe, analyze, and simulate the operation of photosynthesis in vivo (1). In PNAS, Zaks et al. (2) describe a comprehensive mathematical model for qE, a mechanism with a somewhat odd name that is essential for protecting a component of photosynthesis, photosystem II (PSII), from photodamage. In vivo, qE is a dynamic, actively controlled process whose regulation depends on the combined effects of photosynthetic electron and proton transport, and photosynthetic metabolism. To model qE, therefore, Zaks et al. needed to produce an impressive toolkit of models that will be useful for modeling much more than just qE. Photosynthesis uses the energy of absorbed photons to drive the otherwise endothermic reduction of CO2, and the importance of qE arises because leaves are often unable to use for CO2 fixation all the light absorbed by their photosynthetic pigments. Ideally, the light absorbed by the leaf would be used to fix carbon dioxide with a constant quantum efficiency across all natural light intensities, with the efficiency being determined
The proteome response of salt-resistant and salt-sensitive barley genotypes to long-term salinity stress
Fatehi, F. ; Hosseinzadeh, A. ; Alizadeh, H. ; Brimavandi, T. ; Struik, P.C. - \ 2012
Molecular Biology Reports 39 (2012)5. - ISSN 0301-4851 - p. 6387 - 6397.
two-dimensional electrophoresis - escherichia-coli ribosomes - oxalate oxidase activity - arabidopsis-thaliana - photosystem-ii - dehydroascorbate reductase - molecular characterization - ribulose 1,5-bisphosphate - translational regulation - diphosphate kinase
Responses of plants to salinity stress and the development of salt tolerance are extremely complex. Proteomics is a powerful technique to identify proteins associated with a particular environmental or developmental signal. We employed a proteomic approach to further understand the mechanism of plant responses to salinity in a salt-tolerant (Afzal) and a salt-sensitive (Line 527) genotype of barley. At the 4-leaf stage, plants were exposed to 0 (control) or 300 mM NaCl. Salt treatment was maintained for 3 weeks. Total proteins of leaf 4 were extracted and separated by two-dimensional gel electrophoresis. More than 500 protein spots were reproducibly detected. Of these, 44 spots showed significant changes to salt treatment compared to the control: 43 spots were upregulated and 1 spot was downregulated. Using MALDI-TOF-TOF MS, we identified 44 cellular proteins have been identified, which represented 18 different proteins and were classified into seven categories and a group with unknown biological function. These proteins were involved in various many cellular functions. Up regulation of proteins which involved in reactive oxygen species scavenging, signal transduction, protein processing and cell wall may increase plant adaptation to salt stress. The upregulation of the three of four antioxidant proteins (thioredoxin, methionine sulfoxide reductase and dehydroascorbate reductase) in susceptible genotype Line 527 suggesting a different tolerance mechanism (such as tissue tolerance) to tolerate a salinity condition in comparison with the salt sensitive genotype
Mathematical review of the energy transduction stoichiometries of C4 leaf photosynthesis under limiting light
Yin, X. ; Struik, P.C. - \ 2012
Plant, Cell & Environment 35 (2012)7. - ISSN 0140-7791 - p. 1299 - 1312.
alternative electron flow - bundle-sheath cells - chlorophyll fluorescence - c-3 photosynthesis - co2 assimilation - quantum yield - nitrate assimilation - biochemical-model - oxygen-exchange - photosystem-ii
A generalized model for electron (e-) transport limited C4 photosynthesis of NAD–malic enzyme and NADP–malic enzyme subtypes is presented. The model is used to review the thylakoid stoichiometries in vivo under strictly limiting light conditions, using published data on photosynthetic quantum yield and on photochemical efficiencies of photosystems (PS). Model review showed that cyclic e- transport (CET), rather than direct O2 photoreduction, most likely contributed significantly to the production of extra ATP required for the C4 cycle. Estimated CET, and non-cyclic e- transport supporting processes like nitrogen reduction, accounted for ca. 45 and 7% of total photosystem I (PSI) e- fluxes, respectively. The factor for excitation partitioning to photosystem II (PSII) was ca. 0.4. Further model analysis, in terms of the balanced NADPH : ATP ratio required for metabolism, indicated that: (1) the Q-cycle is obligatory; (2) the proton : ATP ratio is 4; and (3) the efficiency of proton pumping per e- transferred through the cytochrome b6/f complex is the same for CET and non-cyclic pathways. The analysis also gave an approach to theoretically assess CO2 leakiness from bundle-sheath cells, and projected a leakiness of 0.07–0.16. Compared with C3 photosynthesis, the most striking C4 stoichiometry is its high fraction of CET
The analysis of PS II photochemical activity using single and multi- turnover excitations
Vredenberg, W.J. ; Durchan, M. ; Prášil, O. - \ 2012
Journal of Photochemistry and Photobiology. B, Biology 107 (2012). - ISSN 1011-1344 - p. 45 - 54.
chlorophyll-a fluorescence - photosystem-ii - in-vivo - photoelectrochemical control - induction kinetics - electron-transfer - higher-plants - redox state - flash - yield
Paper describes chlorophyll a fluorescence measurements in algal cells, and intact plant leaves and isolated chloroplasts. It focuses on amplitude and 10 µs-resolved kinetics of variable fluorescence responses upon excitation with fluorescence-saturating pulses (SP) and with 25 µs saturating single turnover flashes (STF) which are exposed before, during and after a 100 s actinic illumination (AL) of low and high intensity. In addition to the amply documented suppression of the maximal variable fluorescence from Fm to F’m, the relative proportion of the distinguished O-J- , J-I and I-P-phases of an SP-induced response is shown to be distinctly different in dark- and light-adapted leaves. The O-J-phase in the 0.01 to 1 ms time range is much less sensitive to light adaptation than the other phases in the 1 – 200 ms range. In algae and chloroplasts, the amplitude FmSTF of the STF-induced response is hardly affected by a shift from the dark- to the light-activated steady state. The results support the hypothesis that the maximal variable fluorescence Fm induced by a multiple-turnover, fluorescence-saturating pulse (SP), is associated with the release of photochemical and photoelectrochemical quenching. It is argued that the OJIPMT- or Kautsky induction curve of variable chlorophyll fluorescence in the 0 – 100 s time range is the reflection of the release of photochemical quenching supplemented with a temporary Photosystem I (PSI)-dependent photoelectric stimulation and transient release of photoelectrochemical quenching of radiative energy loss in the Photosystem II (PSII) antennas, rather than solely of a decrease in PSII photochemical activity as is usually concluded.
Site, rate and mechanism of photoprotective quenching in cyanobacteria
Tian, L. ; Stokkum, I.H.M. van; Koehorst, R.B.M. ; Jongerius, A. ; Kirilovsky, D. ; Amerongen, H. van - \ 2011
Journal of the American Chemical Society 133 (2011)45. - ISSN 0002-7863 - p. 18304 - 18311.
orange carotenoid protein - light-harvesting complex - bacteriochlorophyll energy-transfer - synechocystis sp pcc-6803 - photosystem-ii - pcc 6803 - purple bacteria - s-1 state - phycobilisome fluorescence - 2-photon excitation
In cyanobacteria, activation of the Orange Carotenoid Protein (OCP) by intense blue-green light triggers photoprotective thermal dissipation of excess absorbed energy leading to a decrease (quenching) of fluorescence of the light harvesting phycobilisomes and, concomitantly, of the energy arriving to the reaction centers. Using spectrally resolved picosecond fluorescence, we have studied cells of wild-type Synechocystis sp. PCC 6803 and of mutants without and with extra OCP (¿OCP and OverOCP) both in the unquenched and quenched state. With the use of target analysis, we managed to spectrally resolve seven different pigment pools in the phycobilisomes and photosystems I and II, and to determine the rates of excitation energy transfer between them. In addition, the fraction of quenched phycobilisomes and the rates of charge separation and quenching were resolved. Under our illumination conditions, 72% of the phycobilisomes in OverOCP appeared to be substantially quenched. For wild-type cells, this number was only 29%. It is revealed that upon OCP activation, a bilin chromophore in the core of the phycobilisome, here called APCQ660, with fluorescence maximum at 660 nm becomes an effective quencher that prevents more than 80% of the excitations in the phycobilisome to reach Photosystems I and II. The quenching rate of its excited state is extremely fast, that is, at least (240 ± 60 fs)-1. It is concluded that the quenching is most likely caused by charge transfer between APCQ660 and the OCP carotenoid hECN in its activated form
Nitrogen and phosphorus removal from municipal wastewater effluent using microalgal biofilms
Boelee, N.C. ; Temmink, H. ; Janssen, M.G.J. ; Buisman, C.J.N. ; Wijffels, R.H. - \ 2011
Water Research 45 (2011)18. - ISSN 0043-1354 - p. 5925 - 5933.
afvalwaterbehandeling - biofilms - anaërobe afbraak - modellen - waste water treatment - biofilms - anaerobic digestion - models - nutrient removal - photosystem-ii - phytoplankton - growth - bioavailability - photosynthesis - plants - algae - ph
Microalgal biofilms have so far received little attention as post-treatment for municipal wastewater treatment plants, with the result that the removal capacity of microalgal biofilms in post-treatment systems is unknown. This study investigates the capacity of microalgal biofilms as a post-treatment step for the effluent of municipal wastewater treatment plants. Microalgal biofilms were grown in flow cells with different nutrient loads under continuous lighting of 230 µmol/m(2)/s (PAR photons, 400-700 nm). It was found that the maximum uptake capacity of the microalgal biofilm was reached at loading rates of 1.0 g/m(2)/day nitrogen and 0.13 g/m(2)/day phosphorus. These maximum uptake capacities were the highest loads at which the target effluent values of 2.2 mg/L nitrogen and 0.15 mg/L phosphorus were still achieved. Microalgal biomass analysis revealed an increasing nitrogen and phosphorus content with increasing loading rates until the maximum uptake capacities. The internal nitrogen to phosphorus ratio decreased from 23:1 to 11:1 when increasing the loading rate. This combination of findings demonstrates that microalgal biofilms can be used for removing both nitrogen and phosphorus from municipal wastewater effluent
Using a biochemical C4 photosynthesis model and combined gas exchange and chlorophyll fluorescence measurements to estimate bundle-sheath conductance of maize leaves differing in age and nitrogen content
Yin, X. ; Sun, Z. ; Struik, P.C. ; Putten, P.E.L. van der; Ieperen, W. van; Harbinson, J. - \ 2011
Plant, Cell & Environment 34 (2011)12. - ISSN 0140-7791 - p. 2183 - 2199.
carbon-isotope discrimination - co2 concentrating mechanism - flaveria-bidentis leads - zea-mays l. - c-4 photosynthesis - photosystem-ii - co2-concentrating mechanism - mesophyll conductance - electron-transport - quantum yield
Bundle-sheath conductance (gbs) affects CO2 leakiness, and, therefore, the efficiency of the CO2-concentrating mechanism (CCM) in C4 photosynthesis. Whether and how gbs varies with leaf age and nitrogen status is virtually unknown. We used a C4-photosynthesis model to estimate gbs, based on combined measurements of gas exchange and chlorophyll fluorescence on fully expanded leaves of three different ages of maize (Zea mays L.) plants grown under two contrasting nitrogen levels. Nitrogen was replenished weekly to maintain leaf nitrogen content (LNC) at a similar level across the three leaf ages. The estimated gbs values on leaf-area basis ranged from 1.4 to 10.3 mmol m-2 s-1 and were affected more by LNC than by leaf age, although gbs tended to decrease as leaves became older. When converted to resistance (rbs = 1/gbs), rbs decreased monotonically with LNC. The correlation was presumably associated with nitrogen effects on leaf anatomy such as on wall thickness of bundle-sheath cells. Despite higher gbs, meaning less efficient CCM, the calculated loss due to photorespiration was still low for high-nitrogen leaves. Under the condition of ambient CO2 and saturating irradiance, photorespiratory loss accounted for 3–5% of fixed carbon for the high-nitrogen, versus 1–2% for the low-nitrogen, leaves.
Different crystal morphologies lead to slightly different conformations of light-harvesting complex II as monitores by variations of the intrinsic fluorescence lifetime
Oort, B.F. van; Marechal, A. ; Ruban, A.V. ; Bruno, R. ; Pascal, A.A. ; Ruijter, N.C.A. de; Grondelle, R. van; Amerongen, H. van - \ 2011
Physical Chemistry Chemical Physics 13 (2011)27. - ISSN 1463-9076 - p. 12614 - 12622.
time-resolved fluorescence - photoprotective energy-dissipation - photosystem-ii - higher-plants - green plants - xanthophyll cycle - antenna proteins - cation formation - lhcii - photosynthesis
In 2005, it was found that the fluorescence of crystals of the major light-harvesting complex LHCII of green plants is significantly quenched when compared to the fluorescence of isolated LHCII (A. A. Pascal et al., Nature, 2005, 436, 134–137). The Raman spectrum of crystallized LHCII was also found to be different from that of isolated LHCII but very similar to that of aggregated LHCII, which has often been considered a good model system for studying nonphotochemical quenching (NPQ), the major protection mechanism of plants against photodamage in high light. It was proposed that in the crystal LHCII adopts a similar (quenching) conformation as during NPQ and indeed similar changes in the Raman spectrum were observed during NPQ in vivo (A. V. Ruban et al., Nature, 2007, 450, 575–579). We now compared the fluorescence of various types of crystals, differing in morphology and age. Each type gave rise to its own characteristic mono-exponential fluorescence lifetime, which was 5 to 10 times shorter than that of isolated LHCII. This indicates that fluorescence is not quenched by random impurities and packing defects (as proposed recently by T. Barros et al., EMBO Journal, 2009, 28, 298–306), but that LHCII adopts a particular structure in each crystal type, that leads to fluorescence quenching. Most interestingly, the extent of quenching appears to depend on the crystal morphology, indicating that also the crystal structure depends on this crystal morphology but at the moment no data are available to correlate the crystals' structural changes to changes in fluorescence lifetime
Blue light dose–responses of leaf photosynthesis, morphology, and chemical composition of Cucumis sativus grown under different combinations of red and blue light
Hogewoning, S.W. ; Trouwborst, G. ; Maljaars, H. ; Poorter, H. ; Ieperen, W. van; Harbinson, J. - \ 2010
Journal of Experimental Botany 61 (2010)11. - ISSN 0022-0957 - p. 3107 - 3117.
emitting-diodes leds - electron-transport - supplemental blue - acetabularia-mediterranea - chlorophyll fluorescence - photosystem-ii - co2 assimilation - quantum yield - leaves - plants
The blue part of the light spectrum has been associated with leaf characteristics which also develop under high irradiances. In this study blue light dose–response curves were made for the photosynthetic properties and related developmental characteristics of cucumber leaves that were grown at an equal irradiance under seven different combinations of red and blue light provided by light-emitting diodes. Only the leaves developed under red light alone (0% blue) displayed dysfunctional photosynthetic operation, characterized by a suboptimal and heterogeneously distributed dark-adapted Fv/Fm, a stomatal conductance unresponsive to irradiance, and a relatively low light-limited quantum yield for CO2 fixation. Only 7% blue light was sufficient to prevent any overt dysfunctional photosynthesis, which can be considered a qualitatively blue light effect. The photosynthetic capacity (Amax) was twice as high for leaves grown at 7% blue compared with 0% blue, and continued to increase with increasing blue percentage during growth measured up to 50% blue. At 100% blue, Amax was lower but photosynthetic functioning was normal. The increase in Amax with blue percentage (0–50%) was associated with an increase in leaf mass per unit leaf area (LMA), nitrogen (N) content per area, chlorophyll (Chl) content per area, and stomatal conductance. Above 15% blue, the parameters Amax, LMA, Chl content, photosynthetic N use efficiency, and the Chl:N ratio had a comparable relationship as reported for leaf responses to irradiance intensity. It is concluded that blue light during growth is qualitatively required for normal photosynthetic functioning and quantitatively mediates leaf responses resembling those to irradiance intensity