Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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    Growth under fluctuating light reveals large trait variation in a panel of arabidopsis accessions
    Kaiser, Elias ; Walther, Dirk ; Armbruster, Ute - \ 2020
    Plants 9 (2020)3. - ISSN 2223-7747
    Acclimation - Chlorophyll a fluorescence - Fluctuating light - Natural variation - Photosynthesis

    The capacity of photoautotrophs to fix carbon depends on the efficiency of the conversion of light energy into chemical potential by photosynthesis. In nature, light input into photosynthesis can change very rapidly and dramatically. To analyze how genetic variation in Arabidopsis thaliana affects photosynthesis and growth under dynamic light conditions, 36 randomly chosen natural accessions were grown under uniform and fluctuating light intensities. After 14 days of growth under uniform or fluctuating light regimes, maximum photosystem II quantum efficiency (Fv/Fm) was determined, photosystem II operating efficiency (ΦPSII) and non‐photochemical quenching (NPQ) were measured in low light, and projected leaf area (PLA) as well as the number of visible leaves were estimated. Our data show that ΦPSII and PLA were decreased and NPQ was increased, while Fv/Fm and number of visible leaves were unaffected, in most accessions grown under fluctuating compared to uniform light. There were large changes between accessions for most of these parameters, which, however, were not correlated with genomic variation. Fast growing accessions under uniform light showed the largest growth reductions under fluctuating light, which correlated strongly with a reduction in ΦPSII, suggesting that, under fluctuating light, photosynthesis controls growth and not vice versa.

    Warming and CO2 effects under oligotrophication on temperate phytoplankton communities
    Cabrerizo, Marco J. ; Álvarez-Manzaneda, Inmaculada M. ; León-Palmero, Elizabeth ; Guerrero-Jiménez, Gerardo ; Senerpont Domis, Lisette N. de; Teurlincx, Sven ; González-Olalla, Juan M. - \ 2020
    Water Research 173 (2020). - ISSN 0043-1354
    Cyanobacteria - Eukaryotes - Global change - Photosynthesis - Resource use efficiency - Shallow lakes

    Eutrophication, global warming, and rising carbon dioxide (CO2) levels are the three most prevalent pressures impacting the biosphere. Despite their individual effects are well-known, it remains untested how oligotrophication (i.e. nutrients reduction) can alter the planktonic community responses to warming and elevated CO2 levels. Here, we performed an indoor mesocosm experiment to investigate the warming × CO2 interaction under a nutrient reduction scenario (40%) mediated by an in-lake management strategy (i.e. addition of a commercial solid-phase phosphorus sorbent -Phoslock®) on a natural freshwater plankton community. Biomass production increased under warming × CO2 relative to present-day conditions; however, a Phoslock®-mediated oligotrophication reduced such values by 30–70%. Conversely, the warming × CO2 × oligotrophication interaction stimulated the photosynthesis by 20% compared to ambient nutrient conditions, and matched with higher resource use efficiency (RUE) and nutrient demand. Surprisingly, at a group level, we found that the multi-stressors scenario increased the photosynthesis in eukaryotes by 25%, but greatly impaired in cyanobacteria (ca. −25%). This higher cyanobacterial sensitivity was coupled with a reduced light harvesting efficiency and compensation point. Since Phoslock®-induced oligotrophication unmasked a strong negative warming × CO2 effect on cyanobacteria, it becomes crucial to understand how the interplay between climate change and nutrient abatement actions may alter the, ecosystems functioning. With an integrative understanding of these processes, policy makers will design more appropriate management strategies to improve the ecological status of aquatic ecosystems without compromising their ecological attributes and functioning.

    Flashing light does not improve photosynthetic performance and growth of green microalgae
    Schulze, Peter S.C. ; Brindley, Celeste ; Fernández, José M. ; Rautenberger, Ralf ; Pereira, Hugo ; Wijffels, René H. ; Kiron, Viswanath - \ 2020
    Bioresource Technology Reports 9 (2020). - ISSN 2589-014X
    Artificial light - Chlorella - Flashing light - Oxygen evolution - Photosynthesis - Tetraselmis

    Light attenuation in photobioreactors is a major bottleneck in microalgal production. A possible strategy for artificial light-based microalgal production to deliver light deep inside the culture is through the periodical emission of high intensity light flashes (so-called flashing light). However, our results did not show improved photosynthetic rates compared to continuous light for dilute and concentrated Tetraselmis chui cultures exposed to flashing light with various repetition rates (frequencies 0.01 Hz–1 MHz), light-dark ratios (duty cycles: 0.001–0.7) or time-averaged light intensity (50–1000 μmol s 1 m 2). Likewise, flashing light applied to Chlorella stigmatophora and T. chui batch cultures could not enhance growth. However, we observed flashing light effects at different duty cycles and frequencies, depending on cell acclimation, culture concentration, and light intensity. In conclusion, artificial flashing light does not improve microalgal biomass productivities in photobioreactors, but low frequencies (f < 50 Hz) may be still used to improve light harvesting-associated biomolecules production.

    The relevance of dynamic thylakoid organisation to photosynthetic regulation
    Johnson, Matthew P. ; Wientjes, Emilie - \ 2020
    Biochimica et Biophysica Acta. B, Bioenergetics 1861 (2020)4. - ISSN 0005-2728
    Electron transfer - Light harvesting - Macrostructure - Microscopy - Photosynthesis

    The higher plant chloroplast thylakoid membrane system performs the light-dependent reactions of photosynthesis. These provide the ATP and NADPH required for the fixation of CO2 into biomass by the Calvin-Benson cycle and a range of other metabolic reactions in the stroma. Land plants are frequently challenged by fluctuations in their environment, such as light, nutrient and water availability, which can create a mismatch between the amounts of ATP and NADPH produced and the amounts required by the downstream metabolism. Left unchecked, such imbalances can lead to the production of reactive oxygen species that damage the plant and harm productivity. Fortunately, plants have evolved a complex range of regulatory processes to avoid or minimize such deleterious effects by controlling the efficiency of light harvesting and electron transfer in the thylakoid membrane. Generally the regulation of the light reactions has been studied and conceptualised at the microscopic level of protein-protein and protein-ligand interactions, however in recent years dynamic changes in the thylakoid macrostructure itself have been recognised to play a significant role in regulating light harvesting and electron transfer. Here we review the evidence for the involvement of macrostructural changes in photosynthetic regulation and review the techniques that brought this evidence to light.

    Influence of foliar kaolin application and irrigation on photosynthetic activity of grape berries
    Garrido, Andreia ; Serôdio, João ; Vos, Ric De ; Conde, Artur ; Cunha, Ana - \ 2019
    Agronomy 9 (2019)11. - ISSN 2073-4395
    Grape berry tissues - Irrigation - Kaolin - Light micro-climates - Mitigation strategies - Photosynthesis - Photosynthetic pigments - Pulse amplitude modulated (PAM) fluorometry - Vitis vinifera L

    Climate changes may cause severe impacts both on grapevine and berry development. Foliar application of kaolin has been suggested as a mitigation strategy to cope with stress caused by excessive heat/radiation absorbed by leaves and grape berry clusters. However, its effect on the light micro-environment inside the canopy and clusters, as well as on the acclimation status and physiological responses of the grape berries, is unclear. The main objective of this work was to evaluate the effect of foliar kaolin application on the photosynthetic activity of the exocarp and seeds, which are the main photosynthetically active berry tissues. For this purpose, berries from high light (HL) and low light (LL) microclimates in the canopy, from kaolin-treated and non-treated, irrigated and non-irrigated plants, were collected at three developmental stages. Photochemical and non-photochemical efficiencies of both tissues were obtained by a pulse amplitude modulated chlorophyll fluorescence imaging analysis. The maximum quantum efficiency (Fv/Fm) data for green HL-grown berries suggest that kaolin application can protect the berry exocarp from light stress. At the mature stage, exocarps of LL grapes from irrigated plants treated with kaolin presented higher Fv/Fm and relative electron transport rates (rETR200) than those without kaolin. However, for the seeds, a negative interaction between kaolin and irrigation were observed especially in HL grapes. These results highlight the impact of foliar kaolin application on the photosynthetic performance of grape berries growing under different light microclimates and irrigation regimes, throughout the season. This provides insights for a more case-oriented application of this mitigation strategy on grapevines.

    Stomatal anatomy and closing ability is affected by supplementary light intensity in rose (Rosa hybrida L.)
    Fanourakis, Dimitrios ; Hyldgaard, Benita ; Giday, Habtamu ; Aulik, Isaac ; Bouranis, Dimitris ; Körner, Oliver ; Ottosen, Carl Otto - \ 2019
    Horticultural Science 46 (2019)2. - ISSN 0862-867X - p. 81 - 89.
    Cuticular water loss - Photosynthesis - Stomatal size - Transpiration

    Increasing the light level in protected cultivation of ornamental crops via supplementary lighting is critical to enhance both production and external quality especially during the periods of low light availability. Despite wide applications the effects of light intensities were not previously addressed on water loss pathways. In this study rose plants were cultivated at 100, 200 or 400 μmol/(m2 s) photosynthetic photon flux density (PPFD). The stomatal responsiveness to desiccation, stomatal anatomical features and cuticular transpiration were determined. Plant biomass as well as photosynthesis response to light and CO2 were also assessed. Increasing growth PPFD led to a considerable increase in plant biomass (85 and 57% for 100 to 200 and 200 to 400 μmol/(m2 s) respectively). Photosynthesis was marginally affected by increasing growth PPFD from 100 to 200 μmol/(m2 s) while a further rise to 400 μmol/(m2 s) considerably increased photosynthetic rate at high light intensities. Higher PPFD during cultivation generally led to larger stomata with bigger pores. A PPFD increase from 100 to 200 μmol/(m2 s) had a small negative effect on stomatal closing ability whereas a further rise to 400 μmol/(m2 s) had a substantial stimulatory effect. Cultivation at a PPFD higher than 100 μmol/(m2 s) led to lower rates of cuticular transpiration. In conclusion, high growth PPFD (> 200 μmol/(m2 s)) enchanced both photosynthetic and stomatal anatomical traits. High light intensity (> 200 μmol/(m2 s)) also led to a better control of water loss due to more responsive stomata and decreased cuticular permeability.

    Influences of light and humidity on carbonyl sulfide-based estimates of photosynthesis
    Kooijmans, Linda M.J. ; Sun, Wu ; Aalto, Juho ; Erkkilä, Kukka Maaria ; Maseyk, Kadmiel ; Seibt, Ulrike ; Vesala, Timo ; Mammarella, Ivan ; Chen, Huilin - \ 2019
    Proceedings of the National Academy of Sciences of the United States of America 116 (2019)7. - ISSN 0027-8424 - p. 2470 - 2475.
    Carbon cycle - Carbonyl sulfide - Photosynthesis - Stomatal conductance

    Understanding climate controls on gross primary productivity (GPP) is crucial for accurate projections of the future land carbon cycle. Major uncertainties exist due to the challenge in separating GPP and respiration from observations of the carbon dioxide (CO 2 ) flux. Carbonyl sulfide (COS) has a dominant vegetative sink, and plant COS uptake is used to infer GPP through the leaf relative uptake (LRU) ratio of COS to CO 2 fluxes. However, little is known about variations of LRU under changing environmental conditions and in different phenological stages. We present COS and CO 2 fluxes and LRU of Scots pine branches measured in a boreal forest in Finland during the spring recovery and summer. We find that the diurnal dynamics of COS uptake is mainly controlled by stomatal conductance, but the leaf internal conductance could significantly limit the COS uptake during the daytime and early in the season. LRU varies with light due to the differential light responses of COS and CO 2 uptake, and with vapor pressure deficit (VPD) in the peak growing season, indicating a humidity-induced stomatal control. Our COS-based GPP estimates show that it is essential to incorporate the variability of LRU with environmental variables for accurate estimation of GPP on ecosystem, regional, and global scales.

    Light regulation of vitamin C in tomato fruit is mediated through photosynthesis
    Ntagkas, Nikolaos ; Woltering, Ernst ; Nicole, Celine ; Labrie, Caroline ; Marcelis, Leo F.M. - \ 2019
    Environmental and Experimental Botany 158 (2019). - ISSN 0098-8472 - p. 180 - 188.
    Ascorbic acid - Irradiance - Photosynthesis - Respiration - Spectrum - Vitamin C

    Higher levels of irradiance result in higher accumulation of ascorbate in leaves and fruits. Photosynthesis and respiration are an integral part of the physiological mechanism of light regulation of ascorbate in leaves, but little is known about the light regulation of ascorbate in fruit. The aim of this study was to investigate whether fruit illumination alone is sufficient for ascorbate increase in tomato fruit and whether this light signal is mediated by respiration and photosynthesis. First the changes of ascorbate with the progress of fruit development were investigated and subsequently detached fruit of different tomato genotypes were exposed to different irradiances and spectra. Measurements were performed on ascorbate, respiration, photosynthesis and chlorophyll content of the fruit. When attached to the plant, there was no effect of development on ascorbate from the mature green to the red stage. Detached fruit stored in darkness did not accumulate ascorbate. However, when exposed to 300–600 μmol m−2 s-1 light detached mature green fruit (photosynthetically active) substantially accumulated ascorbate, while mature red fruit (non-photosynthetically active) did not respond to light. Photosynthesis correlated with this increase of ascorbate while no correlation between respiration and ascorbate was found. Spectral effects on ascorbate in detached tomato fruit were limited. These results indicate that the signal for light regulation of ascorbate is perceived locally in the fruit and that fruit illumination alone is sufficient for a considerable increase in ascorbate levels for as long as the fruit contains chlorophyll. It is shown that photosynthetic activity of the fruit is an integral part of the response of ascorbate to light in tomato fruit. The light induced increase in ascorbate levels occurred in a range of genotypes, indicating a universal effect of light to ascorbate in tomato fruit.

    Nitrate control using LED lights
    Nicole, C.C.S. ; Mooren, J. ; Stuks, A. ; Krijn, M.P.C.M. - \ 2018
    In: International Symposium on New Technologies for Environment Control, Energy-Saving and Crop Production in Greenhouse and Plant Factory - GreenSys 2017 / Yang, Q., Li, T., ISHS (Acta Horticulturae ) - ISBN 9789462612242 - p. 661 - 668.
    Controlled-environment agriculture - Greenhouse - Light-emitting diode - Nitrate - Photosynthesis - Phytochemicals - Plant factory - Shelf-life - Vertical farm

    Light emitting diodes (LEDs) have become very efficient light sources for application in horticulture. Light sources based on LEDs are relatively easy to control in intensity and spectrum. Light-source optimization allows growth efficiency and quality of leafy greens to be influenced, especially the nutrient content. Leafy green vegetables contain relatively high concentrations of nitrate compared with other foods, and constitute a significant source of dietary nitrate to the consumer. Because of health concerns, nitrate content is regulated in Europe. Nitrate levels in vegetables grown in plant factories or greenhouses can be reduced significantly with an appropriate light strategy. In this paper, we present such a strategy, as well as results that show that, with optimized light recipes, the level of nitrate at harvest can be controlled, while the growth efficiency can be kept high. When grown in a closed environment without daylight, we have found that the daily light integral has a strong influence on the final nitrate level. For an optimum daily light integral, we have found that using a continuous pre-harvest light treatment for 2-5 days before harvesting can significantly reduce the nitrate level in lettuce. Light composed of red and blue or red and white can achieve a similar reduction of the nitrate level for various cultivars of baby-leaf lettuce. We present several results on lettuce, spinach and rocket. We also discuss how to achieve extremely low nitrate levels (<500 mg kg-1) and how to find the optimum light sum and spectrum during growth or pre-harvest treatment in combination with an adapted irrigation strategy. Finally, we applied our findings in a greenhouse trial during winter and compare the results with those obtained under plant factory growth conditions.

    Survey of tools for measuring in vivo photosynthesis
    Walker, Berkley J. ; Busch, Florian A. ; Driever, Steven M. ; Kromdijk, Johannes ; Lawson, Tracy - \ 2018
    In: Photosynthesis / Covshoff, Sarah, New York : Humana Press Inc. (Methods in Molecular Biology ) - ISBN 9781493977857 - p. 3 - 24.
    Chlorophyll fluorescence - CO exchange - O exchange - Online mass spectrometry - Photosynthesis
    Measurements of in vivo photosynthesis are powerful tools that probe the largest fluxes of carbon and energy in an illuminated leaf, but often the specific techniques used are so varied and specialized that it is difficult for researchers outside the field to select and perform the most useful assays for their research questions. The goal of this chapter is to provide a broad overview of the current tools available for the study of in vivo photosynthesis so as to provide a foundation for selecting appropriate techniques, many of which are presented in detail in subsequent chapters. This chapter also organizes current methods into a comparative framework and provides examples of how they have been applied to research questions of broad agronomical, ecological, or biological importance. The chapter closes with an argument that the future of in vivo measurements of photosynthesis lies in the ability to use multiple methods simultaneously and discusses the benefits of this approach to currently open physiological questions. This chapter, combined with the relevant methods chapters, could serve as a laboratory course in methods in photosynthesis research or as part of a more comprehensive laboratory course in general plant physiology methods.
    Dynamic modelling of limitations on improving leaf CO2 assimilation under fluctuating irradiance
    Morales, Alejandro ; Kaiser, Elias ; Yin, Xinyou ; Harbinson, Jeremy ; Molenaar, Jaap ; Driever, Steven M. ; Struik, Paul C. - \ 2018
    Plant, Cell & Environment 41 (2018)3. - ISSN 0140-7791 - p. 589 - 604.
    Arabidopsis - Lightflecks - Photosynthesis - Rubisco - Rubisco activase - Stomatal conductance - Sunflecks
    A dynamic model of leaf CO2 assimilation was developed as an extension of the canonical steady-state model, by adding the effects of energy-dependent non-photochemical quenching (qE), chloroplast movement, photoinhibition, regulation of enzyme activity in the Calvin cycle, metabolite concentrations, and dynamic CO2 diffusion. The model was calibrated and tested successfully using published measurements of gas exchange and chlorophyll fluorescence on Arabidopsis thaliana ecotype Col-0 and several photosynthetic mutants and transformants affecting the regulation of Rubisco activity (rca-2 and rwt43), non-photochemical quenching (npq4-1 and npq1-2), and sucrose synthesis (spsa1). The potential improvements on CO2 assimilation under fluctuating irradiance that can be achieved by removing the kinetic limitations on the regulation of enzyme activities, electron transport, and stomatal conductance were calculated in silico for different scenarios. The model predicted that the rates of activation of enzymes in the Calvin cycle and stomatal opening were the most limiting (up to 17% improvement) and that effects varied with the frequency of fluctuations. On the other hand, relaxation of qE and chloroplast movement had a strong effect on average low-irradiance CO2 assimilation (up to 10% improvement). Strong synergies among processes were found, such that removing all kinetic limitations simultaneously resulted in improvements of up to 32%.
    Non-linear direct effects of acid rain on leaf photosynthetic rate of terrestrial plants
    Dong, Dan ; Du, Enzai ; Sun, Zhengzhong ; Zeng, Xuetong ; Vries, Wim de - \ 2017
    Environmental Pollution 231 (2017)2. - ISSN 0269-7491 - p. 1442 - 1445.
    Acid rain - Herbs - Non-linear effect - Photosynthesis - Woody plant
    Anthropogenic emissions of acid precursors have enhanced global occurrence of acid rain, especially in East Asia. Acid rain directly suppresses leaf function by eroding surface waxes and cuticle and leaching base cations from mesophyll cells, while the simultaneous foliar uptake of nitrates in rainwater may directly benefit leaf photosynthesis and plant growth, suggesting a non-linear direct effect of acid rain. By synthesizing data from literature on acid rain exposure experiments, we assessed the direct effects of acid rain on leaf photosynthesis across 49 terrestrial plants in China. Our results show a non-linear direct effect of acid rain on leaf photosynthetic rate, including a neutral to positive effect above pH 5.0 and a negative effect below that pH level. The acid rain sensitivity of leaf photosynthesis showed no significant difference between herbs and woody species below pH 5.0, but the impacts above that pH level were strongly different, resulting in a significant increase in leaf photosynthetic rate of woody species and an insignificant effect on herbs. Our analysis also indicates a positive effect of the molar ratio of nitric versus sulfuric acid in the acid solution on leaf photosynthetic rate. These findings imply that rainwater acidity and the composition of acids both affect the response of leaf photosynthesis and therefore result in a non-linear direct effect.
    Spatial configuration drives complementary capture of light of the understory cotton in young jujube plantations
    Wang, Qi ; Zhang, Dongsheng ; Zhang, Lizhen ; Han, Shuo ; Werf, Wopke van der; Evers, Jochem B. ; Su, Zhicheng ; Anten, Niels P.R. - \ 2017
    Field Crops Research 213 (2017). - ISSN 0378-4290 - p. 21 - 28.
    Inter-specific competition - Intercropping - Light interception fraction - Maximum growth rate - Photosynthesis
    In intercropping systems (growing >1 species in a field), interactions between species affect the performance of plants and the overall yield. These interactions lead to plastic responses in plant traits due to the specific environmental conditions typical for intercrops, especially in agroforestry in which the understory crop is strongly shaded by the trees. To quantify the extent to how physiological plasticity is driven by inter-specific competition, field experiments with mixtures of cotton and jujube trees grown in strips were conducted in 2012 and 2013 in Hetian, Xinjiang, China. Cotton was grown at three levels of inter-specific competition, represented by the distance between the adjacent cotton and tree rows without change in plant density. The highest cotton yield was attained farthest away from the trees, i.e. at the lowest level of inter-specific competition, with a higher proportion of fiber in the bolls as well as a higher boll density compared to plants grown at higher inter-specific competition. Low inter-specific competition also increased maximum leaf area index (LAI), total light interception and dry matter accumulation. However, light-use efficiency was higher at high levels of inter-specific competition especially in the rows close to the tree line, associated with a higher fraction of diffuse radiation. These results aid in the optimization of the spatial pattern of crops in agroforestry system.
    Can increased leaf photosynthesis be converted into higher crop mass production? A simulation study for rice using the crop model GECROS
    Yin, Xinyou ; Struik, Paul C. - \ 2017
    Journal of Experimental Botany 68 (2017)9. - ISSN 0022-0957 - p. 2345 - 2360.
    Crop modelling - Crop productivity - GECROS - Genetic transformation - Photosynthesis - Radiation use efficiency - Simulation - Water use efficiency - Yield potential

    Various genetic engineering routes to enhance C3 leaf photosynthesis have been proposed to improve crop productivity. However, their potential contribution to crop productivity needs to be assessed under realistic field conditions. Using 31 year weather data, we ran the crop model GECROS for rice in tropical, subtropical, and temperate environments, to evaluate the following routes: (1) improving mesophyll conductance (gm); (2) improving Rubisco specificity (Sc/o); (3) improving both gm and Sc/o; (4) introducing C4 biochemistry; (5) introducing C4 Kranz anatomy that effectively minimizes CO2 leakage; (6) engineering the complete C4 mechanism; (7) engineering cyanobacterial bicarbonate transporters; (8) engineering a more elaborate cyanobacterial CO2-concentrating mechanism (CCM) with the carboxysome in the chloroplast; and (9) a mechanism that combines the low ATP cost of the cyanobacterial CCM and the high photosynthetic capacity per unit leaf nitrogen. All routes improved crop mass production, but benefits from Routes 1, 2, and 7 were ≤10%. Benefits were higher in the presence than in the absence of drought, and under the present climate than for the climate predicted for 2050. Simulated crop mass differences resulted not only from the increased canopy photosynthesis competence but also from changes in traits such as light interception and crop senescence. The route combinations gave larger effects than the sum of the effects of the single routes, but only Route 9 could bring an advantage of ≥50% under any environmental conditions. To supercharge crop productivity, exploring a combination of routes in improving the CCM, photosynthetic capacity, and quantum efficiency is required.

    Interactive effects of oxygen, carbon dioxide and flow on photosynthesis and respiration in the scleractinian coral Galaxea fascicularis
    Osinga, Ronald ; Derksen-Hooijberg, Marlous ; Wijgerde, Tim ; Verreth, Johan A.J. - \ 2017
    Journal of Experimental Biology 220 (2017)12. - ISSN 0022-0949 - p. 2236 - 2242.
    Carbon dioxide - Coral - Flow - Oxygen - Photosynthesis - Respiration

    Rates of dark respiration and net photosynthesis were measured for six replicate clonal fragments of the stony coral Galaxea fascicularis (Linnaeus 1767), which were incubated under 12 different combinations of dissolved oxygen (20%, 100% and 150% saturation), dissolved carbon dioxide (9.5 and 19.1 μmol l-1) and water flow (1-1.6 versus 4-13 cm s-1) in a repeated measures design. Dark respiration was enhanced by increased flow and increased oxygen saturation in an interactive way, which relates to improved oxygen influx into the coral tissue. Oxygen saturation did not influence net photosynthesis: neither hypoxia nor hyperoxia affected net photosynthesis, irrespective of flow and pH, which suggests that hyperoxia does not induce high rates of photorespiration in this coral. Flow and pH had a synergistic effect on net photosynthesis: at high flow, a decrease in pH stimulated net photosynthesis by 14%. These results indicate that for this individual of G. fascicularis, increased uptake of carbon dioxide rather than increased efflux of oxygen explains the beneficial effect of water flow on photosynthesis. Rates of net photosynthesis measured in this study are among the highest ever recorded for scleractinian corals and confirm a strong scope for growth.

    Can the responses of photosynthesis and stomatal conductance to water and nitrogen stress combinations be modeled using a single set of parameters?
    Zhang, Ningyi ; Li, Gang ; Yu, Shanxiang ; An, Dongsheng ; Sun, Qian ; Luo, Weihong ; Yin, Xinyou - \ 2017
    Frontiers in Plant Science 8 (2017). - ISSN 1664-462X
    Mesophyll conductance - Model - Nitrogen - Photosynthesis - Stomatal conductance - Water
    Accurately predicting photosynthesis in response to water and nitrogen stress is the first step toward predicting crop growth, yield and many quality traits under fluctuating environmental conditions. While mechanistic models are capable of predicting photosynthesis under fluctuating environmental conditions, simplifying the parameterization procedure is important toward a wide range of model applications. In this study, the biochemical photosynthesis model of Farquhar, von Caemmerer and Berry (the FvCB model) and the stomatal conductance model of Ball, Woodrow and Berry which was revised by Leuning and Yin (the BWB-Leuning-Yin model) were parameterized for Lilium (L. auratum × speciosum "Sorbonne") grown under different water and nitrogen conditions. Linear relationships were found between biochemical parameters of the FvCB model and leaf nitrogen content per unit leaf area (Na), and between mesophyll conductance and Na under different water and nitrogen conditions. By incorporating these Na-dependent linear relationships, the FvCB model was able to predict the net photosynthetic rate (An) in response to all water and nitrogen conditions. In contrast, stomatal conductance (gs) can be accurately predicted if parameters in the BWB-Leuning-Yin model were adjusted specifically to water conditions; otherwise gs was underestimated by 9% under well-watered conditions and was overestimated by 13% under water-deficit conditions. However, the 13% overestimation of gs under water-deficit conditions led to only 9% overestimation of An by the coupled FvCB and BWB-Leuning-Yin model whereas the 9% underestimation of gs under well-watered conditions affected little the prediction of An. Our results indicate that to accurately predict An and gs under different water and nitrogen conditions, only a few parameters in the BWB-Leuning-Yin model need to be adjusted according to water conditions whereas all other parameters are either conservative or can be adjusted according to their linear relationships with Na. Our study exemplifies a simplified procedure of parameterizing the coupled FvCB and gs model that is widely used for various modeling purposes.
    Drought responses, phenotypic plasticity and survival of Mediterranean species in two different microclimatic sites
    Bongers, F.J. ; Olmo, M. ; Lopez-Iglesias, B. ; Anten, N.P.R. ; Villar, R. - \ 2017
    Plant Biology 19 (2017)3. - ISSN 1435-8603 - p. 386 - 395.
    Cistus - Leaf traits - Photosynthesis - Quercus - SLA - Slope orientations - Survival - Water potential

    Climate models predict a further drying of the Mediterranean summer. One way for plant species to persist during such climate changes is through acclimation. Here, we determine the extent to which trait plasticity in response to drought differs between species and between sites, and address the question whether there is a trade-off between drought survival and phenotypic plasticity. Throughout the summer we measured physiological traits (photosynthesis - Amax, stomatal conductance - gs, transpiration - E, leaf water potential - ψl) and structural traits (specific leaf area - SLA, leaf density - LD, leaf dry matter content - LDMC, leaf relative water content - LRWC) of leaves of eight woody species in two sites with slightly different microclimate (north- versus south-facing slopes) in southern Spain. Plant recovery and survival was estimated after the summer drought period. We found high trait variability between species. In most variables, phenotypic plasticity was lower in the drier site. Phenotypic plasticity of SLA and LDMC correlated negatively with drought survival, which suggests a trade-off between them. On the other hand, high phenotypic plasticity of SLA and LDMC was positively related to traits associated with rapid recovery and growth after the drought period. Although phenotypic plasticity is generally seen as favourable during stress conditions, here it seemed beneficial for favourable conditions. We propose that in environments with fluctuating drought periods there can be a trade-off between drought survival and growth during favourable conditions. When climate become drier, species with high drought survival but low phenotypic plasticity might be selected for.

    Increased sink strength offsets the inhibitory effect of sucrose on sugarcane photosynthesis
    Ribeiro, Rafael V. ; Machado, Eduardo C. ; Magalhães Filho, José R. ; Lobo, Ana K.M. ; Martins, Márcio O. ; Silveira, Joaquim A.G. ; Yin, Xinyou ; Struik, Paul C. - \ 2017
    Journal of Plant Physiology 208 (2017). - ISSN 0176-1617 - p. 61 - 69.
    Photosynthesis - Saccharum - Source-sink - Sucrose - Sugarcane

    Spraying sucrose inhibits photosynthesis by impairing Rubisco activity and stomatal conductance (gs), whereas increasing sink demand by partially darkening the plant stimulates sugarcane photosynthesis. We hypothesized that the stimulatory effect of darkness can offset the inhibitory effect of exogenous sucrose on photosynthesis. Source-sink relationship was perturbed in two sugarcane cultivars by imposing partial darkness, spraying a sucrose solution (50 mM) and their combination. Five days after the onset of the treatments, the maximum Rubisco carboxylation rate (Vcmax) and the initial slope of A-Ci curve (k) were estimated by measuring leaf gas exchange and chlorophyll fluorescence. Photosynthesis was inhibited by sucrose spraying in both genotypes, through decreases in Vcmax, k, gs and ATP production driven by electron transport (Jatp). Photosynthesis of plants subjected to the combination of partial darkness and sucrose spraying was similar to photosynthesis of reference plants for both genotypes. Significant increases in Vcmax, gs and Jatp and marginal increases in k were noticed when combining partial darkness and sucrose spraying compared with sucrose spraying alone. Our data also revealed that increases in sink strength due to partial darkness offset the inhibition of sugarcane photosynthesis caused by sucrose spraying, enhancing the knowledge on endogenous regulation of sugarcane photosynthesis through the source-sink relationship.

    Storage of fresh-cut lettuce at light levels below the light compensation point increases sugar levels and greatly prolongs the shelf-life
    Woltering, E.J. ; Wang, J.F. ; Seifu, Y.W. - \ 2016
    Acta Horticulturae 1141 (2016). - ISSN 0567-7572 - p. 357 - 364.
    Carbohydrate status - Fresh-cut - LED lighting - Lettuce quality - Photosynthesis - Shelf-life

    The quality of fresh-cut butterhead lettuce held at 12°C was greatly improved when the product was stored under low levels of light, provided by either fluorescent tubes, or red, blue or green LEDs. Although the applied light level (5 μmol m-2 s-1 photosynthetically active radiation) was well below the light compensation point, significant accumulation of carbohydrates (sugars and starch) was observed. The level of carbohydrates positively correlated with the shelf-life. Photosynthetic activity was low and net photosynthesis during storage was negative and cannot account for the observed accumulation of carbohydrates. Treating the leaf pieces with an inhibitor of photosynthetic electron transport, 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU), diminished the light-induced sugar accumulation and the beneficial effect of light on fresh-cut quality. Currently, it is not clear which processes are responsible for the sugar accumulation in light-stored samples. We hypothesize that, under low light conditions, sugars may be produced through the processing of chloroplast degradation products in the glyoxysome, subsequent production of malate and oxaloacetate and production of glucose through reversal of the glycolysis pathway (gluconeogenesis).

    Mesophyll conductance and reaction-diffusion models for CO2 transport in C3 leaves; needs, opportunities and challenges
    Berghuijs, Herman N.C. ; Yin, Xinyou ; Tri Ho, Q. ; Driever, Steven M. ; Retta, Moges A. ; Nicolaï, Bart M. ; Struik, Paul C. - \ 2016
    Plant Science 252 (2016). - ISSN 0168-9452 - p. 62 - 75.
    3D models - C plants - CO - Mesophyll conductance - Photosynthesis - Reaction-diffusion models

    One way to increase potential crop yield could be increasing mesophyll conductance gm. This variable determines the difference between the CO2 partial pressure in the intercellular air spaces (Ci) and that near Rubisco (Cc). Various methods can determine gm from gas exchange measurements, often combined with measurements of chlorophyll fluorescence or carbon isotope discrimination. gm lumps all biochemical and physical factors that cause the difference between Cc and Ci. gm appears to vary with Ci. This variability indicates that gm does not satisfy the physical definition of a conductance according to Fick's first law and is thus an apparent parameter. Uncertainty about the mechanisms that determine gm can be limited to some extent by using analytical models that partition gm into separate conductances. Such models are still only capable of describing the CO2 diffusion pathway to a limited extent, as they make implicit assumptions about the position of mitochondria in the cells, which affect the re-assimilation of (photo)respired CO2. Alternatively, reaction-diffusion models may be used. Rather than quantifying gm, these models explicitly account for factors that affect the efficiency of CO2 transport in the mesophyll. These models provide a better mechanistic description of the CO2 diffusion pathways than mesophyll conductance models. Therefore, we argue that reaction-diffusion models should be used as an alternative to mesophyll conductance models, in case the aim of such a study is to identify traits that can be improved to increase gm.

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