Modeling the relationship between CO2 assimilation and leaf anatomical properties in tomato leaves
Berghuijs, H.N.C. ; Yin, X. ; Ho, Q.T. ; Putten, P.E.L. van der; Verboven, P. ; Retta, M.A. ; Nicolai, B.M. ; Struik, P.C. - \ 2015
Plant Science 238 (2015). - ISSN 0168-9452 - p. 297 - 311.
mesophyll diffusion conductance - gas-exchange - chlorophyll fluorescence - carbonic-anhydrase - internal conductance - 3-dimensional model - transgenic tobacco - c-3 plants - photosynthesis - parameters
The CO2 concentration near Rubisco and, therefore, the rate of CO2 assimilation, is influenced by both leaf anatomical factors and biochemical processes. Leaf anatomical structures act as physical barriers for CO2 transport. Biochemical processes add or remove CO2 along its diffusion pathway through mesophyll. We combined a model that quantifies the diffusive resistance for CO2 using anatomical properties, a model that partitions this resistance and an extended version of the Farquhar–von Caemmerer–Berry model. We parametrized the model by gas exchange, chlorophyll fluorescence and leaf anatomical measurements from three tomato cultivars. There was generally a good agreement between the predicted and measured light and CO2 response curves. We did a sensitivity analysis to assess how the rate of CO2 assimilation responds to changes in various leaf anatomical properties. Next, we conducted a similar analysis for assumed diffusive properties and curvature factors. Some variables (diffusion pathway length in stroma, diffusion coefficient of the stroma, curvature factors) substantially affected the predicted CO2 assimilation. We recommend more research on the measurements of these variables and on the development of 2-D and 3-D gas diffusion models, since these do not require the diffusion pathway length in the stroma as predefined parameter.
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
Joint control of terrestrial gross primary productivity by plant phenology and physiology
Xia, J. ; Niu, S. ; Ciais, P. ; Janssens, I.A. ; Chen, J. ; Ammann, C. ; Arain, A. ; Blanken, P.D. ; Cescatti, A. ; Moors, E.J. - \ 2015
Proceedings of the National Academy of Sciences of the United States of America 112 (2015)9. - ISSN 0027-8424 - p. 2788 - 2793.
climate-change - chlorophyll fluorescence - ecosystem productivity - vegetation phenology - stomatal conductance - forest phenology - carbon uptake - models - photosynthesis - variability
Terrestrial gross primary productivity (GPP) varies greatly over time and space. A better understanding of this variability is necessary for more accurate predictions of the future climate–carbon cycle feedback. Recent studies have suggested that variability in GPP is driven by a broad range of biotic and abiotic factors operating mainly through changes in vegetation phenology and physiological processes. However, it is still unclear how plant phenology and physiology can be integrated to explain the spatiotemporal variability of terrestrial GPP. Based on analyses of eddy–covariance and satellite-derived data, we decomposed annual terrestrial GPP into the length of the CO2 uptake period (CUP) and the seasonal maximal capacity of CO2 uptake (GPPmax). The product of CUP and GPPmax explained >90% of the temporal GPP variability in most areas of North America during 2000–2010 and the spatial GPP variation among globally distributed eddy flux tower sites. It also explained GPP response to the European heatwave in 2003 (r2 = 0.90) and GPP recovery after a fire disturbance in South Dakota (r2 = 0.88). Additional analysis of the eddy–covariance flux data shows that the interbiome variation in annual GPP is better explained by that in GPPmax than CUP. These findings indicate that terrestrial GPP is jointly controlled by ecosystem-level plant phenology and photosynthetic capacity, and greater understanding of GPPmax and CUP responses to environmental and biological variations will, thus, improve predictions of GPP over time and space.
Identification of quantitative trait loci and a candidate locus for freezing tolerance in controlled and outdoor environments in the overwintering crucifer Boechera stricta.
Heo, J. ; Feng, D. ; Niu, X. ; Mitchell-Olds, T. ; Tienderen, P.H. van; Tomes, D. ; Schranz, M.E. - \ 2014
Plant, Cell & Environment 37 (2014)11. - ISSN 0140-7791 - p. 2459 - 2469.
cold-acclimation - arabidopsis-thaliana - chlorophyll fluorescence - transcription factor - natural variation - frost tolerance - genes - temperature - wheat - expression
Development of chilling and freezing tolerance is complex and can be affected by photoperiod, temperature and photosynthetic performance; however, there has been limited research on the interaction of these three factors. We evaluated 108 recombinant inbred lines of Boechera stricta, derived from a cross between lines originating from Montana and Colorado, under controlled long day (LD), short-day (SD) and in an outdoor environment (OE). We measured maximum quantum yield of photosystem II, lethal temperature for 50% survival and electrolyte leakage of leaves. Our results revealed significant variation for chilling and freezing tolerance and photosynthetic performance in different environments. Using both single- and multi-trait analyses, three main-effect quantitative trait loci (QTL) were identified. QTL on linkage group (LG)3 were SD specific, whereas QTL on LG4 were found under both LD and SD. Under all conditions, QTL on LG7 were identified, but were particularly predictive for the outdoor experiment. The co-localization of photosynthetic performance and freezing tolerance effects supports these traits being co-regulated. Finally, the major QTL on LG7 is syntenic to the Arabidopsis C-repeat binding factor locus, known regulators of chilling and freezing responses in Arabidopsis thaliana and other species.
Accounting for the decrease of photosystem photochemical efficiency with increasing irradiance to estimate quantum yield of leaf photosynthesis
Yin, X. ; Belay, D. ; Putten, P.E.L. van der; Struik, P.C. - \ 2014
Photosynthesis Research 122 (2014)3. - ISSN 0166-8595 - p. 323 - 335.
temperature response functions - chlorophyll fluorescence - co2 uptake - electron-transport - c-3 photosynthesis - biochemical-model - limited photosynthesis - mesophyll conductance - vascular plants - o-2 evolution
Maximum quantum yield for leaf CO2 assimilation under limiting light conditions (UCO2LL) is commonly estimated as the slope of the linear regression of net photosynthetic rate against absorbed irradiance over a range of low-irradiance conditions. Methodological errors associated with this estimation have often been attributed either to light absorptance by non-photosynthetic pigments or to some data points being beyond the linear range of the irradiance response, both causing an underestimation of UCO2LL. We demonstrate here that a decrease in photosystem (PS) photochemical efficiency with increasing irradiance, even at very low levels, is another source of error that causes a systematic underestimation of UCO2LL. A model method accounting for this error was developed, and was used to estimate UCO2LL from simultaneous measurements of gas exchange and chlorophyll fluorescence on leaves using various combinations of species, CO2, O2, or leaf temperature levels. The conventional linear regression method under-estimated UCO2LL by ca. 10–15 %. Differences in the estimated UCO2LL among measurement conditions were generally accounted for by different levels of photorespiration as described by the Farquhar-von Caemmerer–Berry model. However, our data revealed that the temperature dependence of PSII photochemical efficiency under low light was an additional factor that should be accounted for in the model.
Enhancement of crop photosynthesis by diffuse light: quantifying the contributing factors
Li, T. ; Heuvelink, E. ; Dueck, T.A. ; Janse, J. ; Gort, G. ; Marcelis, L.F.M. - \ 2014
Annals of Botany 114 (2014)1. - ISSN 0305-7364 - p. 145 - 156.
modeling canopy photosynthesis - net ecosystem exchange - structural plant-model - chlorophyll fluorescence - deciduous forest - global radiation - direct component - solar-radiation - leaf-area - leaves
Plants use diffuse light more efficiently than direct light. However, experimental comparisons between diffuse and direct light have been obscured by co-occurring differences in environmental conditions (e.g. light intensity). This study aims to analyse the factors that contribute to an increase in crop photosynthesis in diffuse light and to quantify their relative contribution under different levels of diffuseness at similar light intensities. The hypothesis is that the enhancement of crop photosynthesis in diffuse light results not only from the direct effects of more uniform vertical and horizontal light distribution in the crop canopy, but also from crop physiological and morphological acclimation. Tomato (Solanum lycopersicum) crops were grown in three greenhouse compartments that were covered by glass with different degrees of light diffuseness (0, 45 and 71 % of the direct light being converted into diffuse light) while maintaining similar light transmission. Measurements of horizontal and vertical photosynthetic photon flux density (PPFD) distribution in the crop, leaf photosynthesis light response curves and leaf area index (LAI) were used to quantify each factor's contribution to an increase in crop photosynthesis in diffuse light. In addition, leaf temperature, photoinhibition, and leaf biochemical and anatomical properties were studied. The highest degree of light diffuseness (71 %) increased the calculated crop photosynthesis by 7 center dot 2 %. This effect was mainly attributed to a more uniform horizontal (33 % of the total effect) and vertical PPFD distribution (21 %) in the crop. In addition, plants acclimated to the high level of diffuseness by gaining a higher photosynthetic capacity of leaves in the middle of the crop and a higher LAI, which contributed 23 and 13 %, respectively, to the total increase in crop photosynthesis in diffuse light. Moreover, diffuse light resulted in lower leaf temperatures and less photoinhibition at the top of the canopy when global irradiance was high. Diffuse light enhanced crop photosynthesis. A more uniform horizontal PPFD distribution played the most important role in this enhancement, and a more uniform vertical PPFD distribution and higher leaf photosynthetic capacity contributed more to the enhancement of crop photosynthesis than did higher values of LAI.
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.
Quantum yield of charge separation in photosystem II: functional effect of changes in the antenna size upon light acclimation
Wientjes, E. ; Amerongen, H. van; Croce, R. - \ 2013
The Journal of Physical Chemistry Part B: Condensed Matter, Materials, Surfaces, Interfaces & Biophysical 117 (2013)38. - ISSN 1520-6106 - p. 11200 - 11208.
excitation-energy transfer - arabidopsis-thaliana - chlorophyll fluorescence - supramolecular organization - harvesting antenna - green plants - chlamydomonas-reinhardtii - photosynthetic apparatus - thylakoid membrane - grana membranes
We have studied thylakoid membranes of Arabidopsis thaliana acclimated to different light conditions and have related protein composition to excitation energy transfer and trapping kinetics in Photosystem II (PSII). In high light: the plants have reduced amounts of the antenna complexes LHCII and CP24, the overall trapping time of PSII is only 180 ps, and the quantum efficiency reaches a value of 91%. In low light: LHCII is upregulated, the PSII lifetime becomes 310 ps, and the efficiency decreases to 84%. This difference is largely caused by slower excitation energy migration to the reaction centers in low-light plants due to the LHCII trimers that are not part of the C2S2M2 supercomplex. This pool of “extra” LHCII normally transfers energy to both photosystems, whereas it transfers only to PSII upon far-red light treatment (state 1). It is shown that in high light the reduction of LHCII mainly concerns the LHCII-M trimers, while the pool of “extra” LHCII remains intact and state transitions continue to occur. The obtained values for the efficiency of PSII are compared with the values of Fv/Fm, a parameter that is widely used to indicate the PSII quantum efficiency, and the observed differences are discussed.
Effects of far-red light on fluorescence induction in infiltrated pea leaves under diminished ¿pH and ¿f components of the proton motive force
Bulychev, A.A. ; Osipov, V.A. ; Matorin, D.N. ; Vredenberg, W.J. - \ 2013
Journal of Bioenergetics and Biomembranes 45 (2013)1-2. - ISSN 0145-479X - p. 37 - 45.
photoprotective energy-dissipation - electron-transport - chlorophyll fluorescence - delayed fluorescence - photosystem-i - photosynthetic control - charge separation - chloroplasts - kinetics - activation
Chlorophyll fluorescence induction curves induced by an actinic pulse of red light follow different kinetics in dark-adapted plant leaves and leaves preilluminated with far-red light. This influence of far-red light was abolished in leaves infiltrated with valinomycin known to eliminate the electrical (¿f) component of the proton-motive force and was strongly enhanced in leaves infiltrated with nigericin that abolishes the ¿pH component. The supposed influence of ionophores on different components of the proton motive force was supported by differential effects of these ionophores on the induction curves of the millisecond component of chlorophyll delayed fluorescence. Comparison of fluorescence induction curves with the kinetics of P700 oxidation in the absence and presence of ionophores suggests that valinomycin facilitates a build-up of a rate-limiting step for electron transport at the site of plastoquinone oxidation, whereas nigericin effectively removes limitations at this site. Far-red light was found to be a particularly effective modulator of electron flows in chloroplasts in the absence of ¿pH backpressure on operation of the electron-transport chain.
A microscale model for combined CO2 diffusion and photosynthesis in leaves
Ho, Q.T. ; Verboven, P. ; Yin, X. ; Struik, P.C. ; Nicolaï, B.M. - \ 2012
PLoS ONE 7 (2012)11. - ISSN 1932-6203 - 15 p.
mesophyll conductance - gas-exchange - chlorophyll fluorescence - internal conductance - carbon-dioxide - temperature response - leaf photosynthesis - electron-transport - biochemical-model - c-3 plants
Transport of CO2 in leaves was investigated by combining a 2-D, microscale CO2 transport model with photosynthesis kinetics in wheat (Triticum aestivum L.) leaves. The biophysical microscale model for gas exchange featured an accurate geometric representation of the actual 2-D leaf tissue microstructure and accounted for diffusive mass exchange of CO2. The resulting gas transport equations were coupled to the biochemical Farquhar-von Caemmerer-Berry model for photosynthesis. The combined model was evaluated using gas exchange and chlorophyll fluorescence measurements on wheat leaves. In general a good agreement between model predictions and measurements was obtained, but a discrepancy was observed for the mesophyll conductance at high CO2 levels and low irradiance levels. This may indicate that some physiological processes related to photosynthesis are not incorporated in the model. The model provided detailed insight into the mechanisms of gas exchange and the effects of changes in ambient CO2 concentration or photon flux density on stomatal and mesophyll conductance. It represents an important step forward to study CO2 diffusion coupled to photosynthesis at the leaf tissue level, taking into account the leaf's actual microstructure.
Genetic dissection of drought tolerance and recovery potential by quantitative trait locus mapping of a diploid potato population
Anithakumari, A.M. ; Nataraja, K.N. ; Visser, R.G.F. ; Linden, C.G. van der - \ 2012
Molecular Breeding 30 (2012)3. - ISSN 1380-3743 - p. 1413 - 1429.
carbon-isotope discrimination - water-use efficiency - chlorophyll fluorescence - solanum-tuberosum - transpiration efficiency - soil-water - arabidopsis-thaliana - arid conditions - winter-wheat - leaf growth
Potato is the third most important staple food crop in terms of consumption, yet it is relatively susceptible to yield loss because of drought. As a first step towards improving drought tolerance in this crop, we set out to identify the genetic basis for drought tolerance in a diploid potato mapping population. Experiments were carried out under greenhouse conditions in two successive years by recording four physiological, seven growth and three yield parameters under stress and recovery treatments. Genotypes showed significant variation for drought and recovery responses. The traits measured had low to moderately high heritabilities (ranging from 22 to 74 %). A total of 47 quantitative trait loci (QTL) were identified, of which 28 were drought-specific, 17 under recovery treatment and two under well-watered conditions. The majority of these growth and yield QTL co-localized with a QTL for maturity on chromosome 5. Four QTL for d13C, three for chlorophyll content and one for chlorophyll fluorescence (Fv/Fm) were found to co-localize with yield and other growth trait QTL identified on other chromosomes. Several multi-year and multi-treatment QTL were detected and QTL 9 environment interaction was found for d13C. To our knowledge, this is the first comprehensive QTL study on water deficit and recovery potential in potato.
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
Using chromosome introgression lines to map quantitative trait loci for photosynthesis parameters in rice (Oryza sativa L.) leaves under drought and well-watered field conditions
Gu, J. ; Yin, X. ; Struik, P.C. ; Stomph, T.J. ; Wang, J. - \ 2012
Journal of Experimental Botany 63 (2012)1. - ISSN 0022-0957 - p. 455 - 469.
qtl analysis - upland rice - chlorophyll fluorescence - reproductive-stage - genetic-variation - grain-yield - physiological traits - plant photosynthesis - carbon assimilation - advanced backcross
Photosynthesis is fundamental to biomass production, but sensitive to drought. To understand the genetics of leaf photosynthesis, especially under drought, upland rice cv. Haogelao, lowland rice cv. Shennong265, and 94 of their introgression lines (ILs) were studied at flowering and grain filling under drought and well-watered field conditions. Gas exchange and chlorophyll fluorescence measurements were conducted to evaluate eight photosynthetic traits. Since these traits are very sensitive to fluctuations in microclimate during measurements under field conditions, observations were adjusted for microclimatic differences through both a statistical covariant model and a physiological approach. Both approaches identified leaf-to-air vapour pressure difference as the variable influencing the traits most. Using the simple sequence repeat (SSR) linkage map for the IL population, 1–3 quantitative trait loci (QTLs) were detected per trait–stage–treatment combination, which explained between 7.0% and 30.4% of the phenotypic variance of each trait. The clustered QTLs near marker RM410 (the interval from 57.3¿cM to 68.4¿cM on chromosome 9) were consistent over both development stages and both drought and well-watered conditions. This QTL consistency was verified by a greenhouse experiment under a controlled environment. The alleles from the upland rice at this interval had positive effects on net photosynthetic rate, stomatal conductance, transpiration rate, quantum yield of photosystem II (PSII), and the maximum efficiency of light-adapted open PSII. However, the allele of another main QTL from upland rice was associated with increased drought sensitivity of photosynthesis. These results could potentially be used in breeding programmes through marker-assisted selection to improve drought tolerance and photosynthesis simultaneously
Metabolic modeling of Chlamydomonas reinhardtii: energy requirements for photoautotrophic growth and maintenance
Kliphuis, A.M.J. ; Klok, A.J. ; Martens, D.E. ; Lamers, P.P. ; Janssen, M.G.J. ; Wijffels, R.H. - \ 2012
Journal of Applied Phycology 24 (2012)2. - ISSN 0921-8971 - p. 253 - 266.
genome-scale reconstruction - escherichia-coli - chlorophyll fluorescence - chlorella-sorokiniana - quantum requirement - light - photosynthesis - microalgae - network - photobioreactor
In this study, a metabolic network describing the primary metabolism of Chlamydomonas reinhardtii was constructed. By performing chemostat experiments at different growth rates, energy parameters for maintenance and biomass formation were determined. The chemostats were run at low irradiances resulting in a high biomass yield on light of 1.25 g mol-1. The ATP requirement for biomass formation from biopolymers (Kx) was determined to be 109 mmol g-1 (18.9 mol mol-1) and the maintenance requirement (mATP) was determined to be 2.85 mmol g-1 h-1. With these energy requirements included in the metabolic network, the network accurately describes the primary metabolism of C. reinhardtii and can be used for modeling of C. reinhardtii growth and metabolism. Simulations confirmed that cultivating microalgae at low growth rates is unfavorable because of the high maintenance requirements which result in low biomass yields. At high light supply rates, biomass yields will decrease due to light saturation effects. Thus, to optimize biomass yield on light energy in photobioreactors, an optimum between low and high light supply rates should be found. These simulations show that metabolic flux analysis can be used as a tool to gain insight into the metabolism of algae and ultimately can be used for the maximization of algal biomass and product yield.
The water-water cycle in leaves is not a major alternative electron sink for dissipation of excess excitation energy when CO2 assimilation is restricted
Driever, S.M. ; Baker, N.R. - \ 2011
Plant, Cell & Environment 34 (2011)5. - ISSN 0140-7791 - p. 837 - 846.
carbon-isotope discrimination - bundle-sheath leakiness - photosynthetic oxygen-exchange - chlorophyll fluorescence - oxidative stress - mehler reaction - c-4 grasses - light - plants - o-2
Electron flux from water via photosystem II (PSII) and PSI to oxygen (water–water cycle) may provide a mechanism for dissipation of excess excitation energy in leaves when CO2 assimilation is restricted. Mass spectrometry was used to measure O2 uptake and evolution together with CO2 uptake in leaves of French bean and maize at CO2 concentrations saturating for photosynthesis and the CO2 compensation point. In French bean at high CO2 and low O2 concentrations no significant water–water cycle activity was observed. At the CO2 compensation point and 3% O2 a low rate of water–water cycle activity was observed, which accounted for 30% of the linear electron flux from water. In maize leaves negligible water–water cycle activity was detected at the compensation point. During induction of photosynthesis in maize linear electron flux was considerably greater than CO2 assimilation, but no significant water–water cycle activity was detected. Miscanthus × giganteus grown at chilling temperature also exhibited rates of linear electron transport considerably in excess of CO2 assimilation; however, no significant water–water cycle activity was detected. Clearly the water–water cycle can operate in leaves under some conditions, but it does not act as a major sink for excess excitation energy when CO2 assimilation is restricted.
Differential tomato transcriptomic responses induced by Pepino mosaic virus Isolates with differential aggressiveness
Hanssen, I.M. ; Esse, H.P. van; Ballester, A.R. ; Hogewoning, S.W. ; Parra, N.O. ; Paeleman, A. ; Lievens, B. ; Bovy, A.G. ; Thomma, B.P.H.J. - \ 2011
Plant Physiology 156 (2011)1. - ISSN 0032-0889 - p. 301 - 318.
gene-expression - chlorophyll fluorescence - molecular-biology - salicylic-acid - plant defense - genomic rna - arabidopsis - infection - protein - sequence
Pepino mosaic virus (PepMV) is a highly infectious potexvirus and a major disease of greenhouse tomato (Solanum lycopersicum) crops worldwide. Damage and economic losses caused by PepMV vary greatly and can be attributed to differential symptomatology caused by different PepMV isolates. Here, we used a custom-designed Affymetrix tomato GeneChip array with probe sets to interrogate over 22,000 tomato transcripts to study transcriptional changes in response to inoculation of tomato seedlings with a mild and an aggressive PepMV isolate that share 99.4% nucleotide sequence identity. The two isolates induced a different transcriptomic response, despite accumulating to similar viral titers. PepMV inoculation resulted in repression of photosynthesis. In addition, defense responses were stronger upon inoculation with the aggressive isolate, in both cases mediated by salicylic acid signaling rather than by jasmonate signaling. Our results furthermore show that PepMV differentially regulates the RNA silencing pathway, suggesting a role for a PepMV-encoded silencing suppressor. Finally, perturbation of pigment biosynthesis, as shown by differential regulation of the flavonoid and lycopene biosynthesis pathways, was monitored. Metabolite analyses on mature fruits of PepMV-infected tomato plants, which showed typical fruit marbling, revealed a decrease in carotenoids, likely responsible for the marbled phenotype, and an increase in alkaloids and phenylpropanoids that are associated with pathogen defense in the yellow sectors of the fruit.
Excitation energy transfer and trapping in higher plant photosystem II complexes with different antenna sizes
Caffarri, S. ; Broess, K. ; Croce, R. ; Amerongen, H. van - \ 2011
Biophysical Journal 100 (2011)9. - ISSN 0006-3495 - p. 2094 - 2103.
light-harvesting complex - green plants - chlorophyll fluorescence - charge separation - arabidopsis-thaliana - core complex - kinetics - organization - membranes - lhcii
We performed picosecond fluorescence measurements on well-defined Photosystem II (PSII) supercomplexes from Arabidopsis with largely varying antenna sizes. The average excited-state lifetime ranged from 109 ps for PSII core to 158 ps for the largest C2S2M2 complex in 0.01% a-DM. Excitation energy transfer and trapping were investigated by coarse-grained modeling of the fluorescence kinetics. The results reveal a large drop in free energy upon charge separation (>700 cm-1) and a slow relaxation of the radical pair to an irreversible state (150 ps). Somewhat unexpectedly, we had to reduce the energy-transfer and charge-separation rates in complexes with decreasing size to obtain optimal fits. This strongly suggests that the antenna system is important for plant PSII integrity and functionality, which is supported by biochemical results. Furthermore, we used the coarse-grained model to investigate several aspects of PSII functioning. The excitation trapping time appears to be independent of the presence/absence of most of the individual contacts between light-harvesting complexes in PSII supercomplexes, demonstrating the robustness of the light-harvesting process. We conclude that the efficiency of the nonphotochemical quenching process is hardly dependent on the exact location of a quencher within the supercomplexes
Natural genetic variation in plant photosynthesis
Flood, P.J. ; Harbinson, J. ; Aarts, M.G.M. - \ 2011
Trends in Plant Science 16 (2011)6. - ISSN 1360-1385 - p. 327 - 335.
quantitative trait loci - association mapping population - recurrent phenotypic selection - genome-wide association - wheat triticum-aestivum - rice oryza-sativa - chlorophyll fluorescence - qtl analysis - arabidopsis-thaliana - leaf photosynthesis
Natural genetic variation in plant photosynthesis is a largely unexplored and as a result an underused genetic resource for crop improvement. Numerous studies show genetic variation in photosynthetic traits in both crop and wild species, and there is an increasingly detailed knowledge base concerning the interaction of photosynthetic phenotypes with their environment. The genetic factors that cause this variation remain largely unknown. Investigations into natural genetic variation in photosynthesis will provide insights into the genetic regulation of this complex trait. Such insights can be used to understand evolutionary processes that affect primary production, allow greater understanding of the genetic regulation of photosynthesis and ultimately increase the productivity of our crops
Horizontal or vertical photobioreactors? How to improve microalgae photosynthetic efficiency
Cuaresma, M. ; Janssen, M.G.J. ; Vilchez, C. ; Wijffels, R.H. - \ 2011
Bioresource Technology 102 (2011)8. - ISSN 0960-8524 - p. 5129 - 5137.
outdoor mass cultivation - chlorophyll fluorescence - tubular photobioreactor - muriellopsis sp - chlorella - light - temperature - culture - productivity - irradiance
The productivity of a vertical outdoor photobioreactor was quantitatively assessed and compared to a horizontal reactor. Daily light cycles in southern Spain were simulated and applied to grow the microalgae Chlorella sorokiniana in a flat panel photobioreactor. The maximal irradiance around noon differs from 400µmolphotonsm(-2)s(-1) in the vertical position to 1800µmolphotonsm(-2)s(-1) in the horizontal position. The highest volumetric productivity was achieved in the simulated horizontal position, 4gkg culture(-1)d(-1). The highest photosynthetic efficiency was found for the vertical simulation, 1.3g of biomass produced per mol of PAR photons supplied, which compares favorably to the horizontal position (0.85gmol(-1)) and to the theoretical maximal yield (1.8gmol(-1)). These results prove that productivity per unit of ground area could be greatly enhanced by placing the photobioreactors vertically
Can the progressive increase of C4 bundle sheath leakiness at low PFD be explained by incomplete suppression of photorespiration?
Kromdijk, J. ; Griffiths, H. ; Schepers, H.E. - \ 2010
Plant, Cell & Environment 33 (2010). - ISSN 0140-7791 - p. 1935 - 1948.
carbon-isotope discrimination - chloroplast atp synthase - short-term changes - water-water cycle - gas-exchange - quantum yield - chlorophyll fluorescence - co2 assimilation - c4 grasses - co2-concentrating mechanism
The ability to concentrate CO2 around Rubisco allows C-4 crops to suppress photorespiration. However, as phosphoenolpyruvate regeneration requires ATP, the energetic efficiency of the C-4 pathway at low photosynthetic flux densities (PFD) becomes a balancing act between primary fixation and concentration of CO2 in mesophyll (M) cells, and CO2 reduction in bundle sheath (BS) cells. At low PFD, retro-diffusion of CO2 from BS cells, relative to the rate of bicarbonate fixation in M cells (termed leakiness phi), is known to increase. This paper investigates whether this increase in phi could be explained by incomplete inhibition of photorespiration. The PFD response of phi was measured at various O-2 partial pressures in young Zea mays plants grown at 250 (LL) and 750 mu mol m-2 s-1 PFD (HL). phi increased at low PFD and was positively correlated with O-2 partial pressure. Low PFD during growth caused BS conductance and interveinal distance to be lower in the LL plants, compared to the HL plants, which correlated with lower phi. Model analysis showed that incomplete inhibition of photorespiration, especially in the HL plants, and an increase in the relative contribution of mitochondrial respiration at low PFD could explain the observed increases in phi.