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Sample records for photosynthetic acclimation response

  1. Inter and intra-specific variation in photosynthetic acclimation response to long term exposure of elevated carbon dioxide

    SciTech Connect

    Wilkinson, M. |

    1996-08-01

    The response of intra and interspecific variation in photosynthetic acclimation to growth at elevated atmospheric CO{sub 2} concentration (600{micro}mol mol-l) in six important grassland species was investigated. Plants were grown in a background sward of Lolium perenne and measurements were made after four years of growth at elevated C{sub a}. Elevated CO{sub 2} was maintained using a FACE (Free-Air Carbon Enrichment) system. Significant intra and interspecific variation in acclimation response was demonstrated. The response of adaxial and abaxial stomatal conductance to elevated CO{sub 2} was also investigated. The stomatal conductance of both the adaxial and abaxial leaf surfaces was found to be reduced by elevated C{sub a}. Significant asymmetric responses in stomatal conductance was demonstrated in D. glomerata and T. pratense. Analysis of stomatal indices and densities indicated that the observed reductions in stomatal conductance were probably the result of changes in stomatal aperture.

  2. Molecular and photosynthetic responses to prolonged darkness and subsequent acclimation to re-illumination in the diatom Phaeodactylum tricornutum.

    PubMed

    Nymark, Marianne; Valle, Kristin C; Hancke, Kasper; Winge, Per; Andresen, Kjersti; Johnsen, Geir; Bones, Atle M; Brembu, Tore

    2013-01-01

    Photosynthetic diatoms that live suspended throughout the water column will constantly be swept up and down by vertical mixing. When returned to the photic zone after experiencing longer periods in darkness, mechanisms exist that enable the diatoms both to survive sudden light exposure and immediately utilize the available energy in photosynthesis and growth. We have investigated both the response to prolonged darkness and the re-acclimation to moderate intensity white irradiance (E = 100 µmol m(-2) s(-1)) in the diatom Phaeodactylum tricornutum, using an integrated approach involving global transcriptional profiling, pigment analyses, imaging and photo-physiological measurements. The responses were studied during continuous white light, after 48 h of dark treatment and after 0.5 h, 6 h, and 24 h of re-exposure to the initial irradiance. The analyses resulted in several intriguing findings. Dark treatment of the cells led to 1) significantly decreased nuclear transcriptional activity, 2) distinct intracellular changes, 3) fixed ratios of the light-harvesting pigments despite a decrease in the total cell pigment pool, and 4) only a minor drop in photosynthetic efficiency (Φ(PSII_max)). Re-introduction of the cells to the initial light conditions revealed 5) distinct expression profiles for nuclear genes involved in photosynthesis and those involved in photoprotection, 6) rapid rise in photosynthetic parameters (α and rETR(max)) within 0.5 h of re-exposure to light despite a very modest de novo synthesis of photosynthetic compounds, and 7) increasingly efficient resonance energy transfer from fucoxanthin chlorophyll a/c-binding protein complexes to photosystem II reaction centers during the first 0.5 h, supporting the observations stated in 6). In summary, the results show that despite extensive transcriptional, metabolic and intracellular changes, the ability of cells to perform photosynthesis was kept intact during the length of the experiment. We conclude

  3. Molecular and Photosynthetic Responses to Prolonged Darkness and Subsequent Acclimation to Re-Illumination in the Diatom Phaeodactylum tricornutum

    PubMed Central

    Nymark, Marianne; Valle, Kristin C.; Hancke, Kasper; Winge, Per; Andresen, Kjersti; Johnsen, Geir; Bones, Atle M.; Brembu, Tore

    2013-01-01

    Photosynthetic diatoms that live suspended throughout the water column will constantly be swept up and down by vertical mixing. When returned to the photic zone after experiencing longer periods in darkness, mechanisms exist that enable the diatoms both to survive sudden light exposure and immediately utilize the available energy in photosynthesis and growth. We have investigated both the response to prolonged darkness and the re-acclimation to moderate intensity white irradiance (E = 100 µmol m−2 s−1) in the diatom Phaeodactylum tricornutum, using an integrated approach involving global transcriptional profiling, pigment analyses, imaging and photo-physiological measurements. The responses were studied during continuous white light, after 48 h of dark treatment and after 0.5 h, 6 h, and 24 h of re-exposure to the initial irradiance. The analyses resulted in several intriguing findings. Dark treatment of the cells led to 1) significantly decreased nuclear transcriptional activity, 2) distinct intracellular changes, 3) fixed ratios of the light-harvesting pigments despite a decrease in the total cell pigment pool, and 4) only a minor drop in photosynthetic efficiency (ΦPSII_max). Re-introduction of the cells to the initial light conditions revealed 5) distinct expression profiles for nuclear genes involved in photosynthesis and those involved in photoprotection, 6) rapid rise in photosynthetic parameters (α and rETRmax) within 0.5 h of re-exposure to light despite a very modest de novo synthesis of photosynthetic compounds, and 7) increasingly efficient resonance energy transfer from fucoxanthin chlorophyll a/c-binding protein complexes to photosystem II reaction centers during the first 0.5 h, supporting the observations stated in 6). In summary, the results show that despite extensive transcriptional, metabolic and intracellular changes, the ability of cells to perform photosynthesis was kept intact during the length of the experiment. We conclude that

  4. Acclimation of photosynthetic temperature optima of temperate and boreal tree species in response to experimental forest warming.

    PubMed

    Sendall, Kerrie M; Reich, Peter B; Zhao, Changming; Jihua, Hou; Wei, Xiaorong; Stefanski, Artur; Rice, Karen; Rich, Roy L; Montgomery, Rebecca A

    2015-03-01

    Rising temperatures caused by climate change could negatively alter plant ecosystems if temperatures exceed optimal temperatures for carbon gain. Such changes may threaten temperature-sensitive species, causing local extinctions and range migrations. This study examined the optimal temperature of net photosynthesis (Topt ) of two boreal and four temperate deciduous tree species grown in the field in northern Minnesota, United States under two contrasting temperature regimes. We hypothesized that Topt would be higher in temperate than co-occurring boreal species, with temperate species exhibiting greater plasticity in Topt , resulting in better acclimation to elevated temperatures. The chamberless experiment, located at two sites in both open and understory conditions, continuously warmed plants and soils during three growing seasons. Results show a modest, but significant shift in Topt of 1.1 ± 0.21 °C on average for plants subjected to a mean 2.9 ± 0.01 °C warming during midday hours in summer, and shifts with warming were unrelated to species native ranges. The 1.1 °C shift in Topt with 2.9 °C warming might be interpreted as suggesting limited capacity to shift temperature response functions to better match changes in temperature. However, Topt of warmed plants was as well-matched with prior midday temperatures as Topt of plants in the ambient treatment, and Topt in both treatments was at a level where realized photosynthesis was within 90-95% of maximum. These results suggest that seedlings of all species were close to optimizing photosynthetic temperature responses, and equally so in both temperature treatments. Our study suggests that temperate and boreal species have considerable capacity to match their photosynthetic temperature response functions to prevailing growing season temperatures that occur today and to those that will likely occur in the coming decades under climate change. PMID:25354151

  5. Systems-wide analysis of acclimation responses to long-term heat stress and recovery in the photosynthetic model organism Chlamydomonas reinhardtii.

    PubMed

    Hemme, Dorothea; Veyel, Daniel; Mühlhaus, Timo; Sommer, Frederik; Jüppner, Jessica; Unger, Ann-Katrin; Sandmann, Michael; Fehrle, Ines; Schönfelder, Stephanie; Steup, Martin; Geimer, Stefan; Kopka, Joachim; Giavalisco, Patrick; Schroda, Michael

    2014-11-01

    We applied a top-down systems biology approach to understand how Chlamydomonas reinhardtii acclimates to long-term heat stress (HS) and recovers from it. For this, we shifted cells from 25 to 42°C for 24 h and back to 25°C for ≥8 h and monitored abundances of 1856 proteins/protein groups, 99 polar and 185 lipophilic metabolites, and cytological and photosynthesis parameters. Our data indicate that acclimation of Chlamydomonas to long-term HS consists of a temporally ordered, orchestrated implementation of response elements at various system levels. These comprise (1) cell cycle arrest; (2) catabolism of larger molecules to generate compounds with roles in stress protection; (3) accumulation of molecular chaperones to restore protein homeostasis together with compatible solutes; (4) redirection of photosynthetic energy and reducing power from the Calvin cycle to the de novo synthesis of saturated fatty acids to replace polyunsaturated ones in membrane lipids, which are deposited in lipid bodies; and (5) when sinks for photosynthetic energy and reducing power are depleted, resumption of Calvin cycle activity associated with increased photorespiration, accumulation of reactive oxygen species scavengers, and throttling of linear electron flow by antenna uncoupling. During recovery from HS, cells appear to focus on processes allowing rapid resumption of growth rather than restoring pre-HS conditions. PMID:25415976

  6. Systems-Wide Analysis of Acclimation Responses to Long-Term Heat Stress and Recovery in the Photosynthetic Model Organism Chlamydomonas reinhardtii[W][OPEN

    PubMed Central

    Hemme, Dorothea; Veyel, Daniel; Mühlhaus, Timo; Sommer, Frederik; Jüppner, Jessica; Unger, Ann-Katrin; Sandmann, Michael; Fehrle, Ines; Schönfelder, Stephanie; Steup, Martin; Geimer, Stefan; Kopka, Joachim; Giavalisco, Patrick; Schroda, Michael

    2014-01-01

    We applied a top-down systems biology approach to understand how Chlamydomonas reinhardtii acclimates to long-term heat stress (HS) and recovers from it. For this, we shifted cells from 25 to 42°C for 24 h and back to 25°C for ≥8 h and monitored abundances of 1856 proteins/protein groups, 99 polar and 185 lipophilic metabolites, and cytological and photosynthesis parameters. Our data indicate that acclimation of Chlamydomonas to long-term HS consists of a temporally ordered, orchestrated implementation of response elements at various system levels. These comprise (1) cell cycle arrest; (2) catabolism of larger molecules to generate compounds with roles in stress protection; (3) accumulation of molecular chaperones to restore protein homeostasis together with compatible solutes; (4) redirection of photosynthetic energy and reducing power from the Calvin cycle to the de novo synthesis of saturated fatty acids to replace polyunsaturated ones in membrane lipids, which are deposited in lipid bodies; and (5) when sinks for photosynthetic energy and reducing power are depleted, resumption of Calvin cycle activity associated with increased photorespiration, accumulation of reactive oxygen species scavengers, and throttling of linear electron flow by antenna uncoupling. During recovery from HS, cells appear to focus on processes allowing rapid resumption of growth rather than restoring pre-HS conditions. PMID:25415976

  7. The photosynthetic acclimation response of Lolium perenne to four years growth in a free-air CO{sub 2} enrichment (FACE) facility

    SciTech Connect

    Creasey, R.

    1996-11-01

    In this study, the photosynthetic responses of field grown Lolium perenne to ambient (354 {mu}mol mol{sup -1}) and elevated (600 {mu}mol mol{sup -1}) C{sub a} were measured. The experiment utilized the FACE facility at Eschikon, Switzerland; here the L. Perenne swards had been grown at two nitrogen treatments, with six cuts per year, for 4 years. The study revealed a significant decrease in Rubisco activity (Vcmax) in the low nitrogen FACE plots; this is consistent with the theories of source-sink imbalance resulting in feedback inhibition and down-regulation. Such negative acclimation was not wholly supported by diurnal investigations which revealed an average stimulation of 53.38% and 52.78% in the low and high nitrogen, respectively. However, light response curves and AI investigations also suggested down-regulation, especially in the low nitrogen. SI is expected to decrease in response to elevated C{sub a}, if any change is seen. This was indeed observed in the high nitrogen plots but for the low nitrogen a significant increase was found. Conclusions drawn from this project center around the implications of negative acclimation to future crop productivity. For instance, inter-specific differences in response to elevated C{sub a} may result in ecosystem changes and new management techniques may be necessary. However, real predictions cannot be made from leaf level studies alone as these may not represent the overall changes at the whole plant level.

  8. Photosynthetic acclimation in the context of structural constraints to carbon export from leaves.

    PubMed

    Adams, William W; Watson, Amy M; Mueh, Kristine E; Amiard, Véronique; Turgeon, Robert; Ebbert, Volker; Logan, Barry A; Combs, Andrew F; Demmig-Adams, Barbara

    2007-01-01

    The potential role of foliar carbon export features in the acclimation of photosynthetic capacity to differences and changes in light environment was evaluated. These features included apoplastic vs. symplastic phloem loading, density of loading veins, plasmodesmatal frequency in intermediary cells, and the ratio of loading cells to sieve elements. In initial studies, three apoplastic loaders (spinach, pea, Arabidopsis thaliana) exhibited a completely flexible photosynthetic response to changing light conditions, while two symplastic loaders (pumpkin, Verbascum phoeniceum), although able to adjust to different long-term growth conditions, were more limited in their response when transferred from low (LL) to high (HL) light. This suggested that constraints imposed by the completely physical pathway of sugar export might act as a bottleneck in the export of carbon from LL-acclimated leaves of symplastic loaders. While both symplastic loaders exhibited variable loading vein densities (low in LL and high in HL), none of the three apoplastic loaders initially characterized exhibited such differences. However, an additional apoplastic species (tomato) exhibited similar differences in vein density during continuous growth in different light environments. Furthermore, in contrast to the other apoplastic loaders, photosynthetic acclimation in tomato was not complete following a transfer from LL to HL. This suggests that loading vein density and loading cells per sieve element, and thus apparent loading surface capacity, play a major role in the potential for photosynthetic acclimation to changes in light environment. Photosynthetic acclimation and vein density acclimation were also characterized in the slow-growing, sclerophytic evergreen Monstera deliciosa. This evergreen possessed a lower vein density during growth in LL compared to HL and exhibited a more severely limited potential for photosynthetic acclimation to increases in light environment than the rapidly

  9. Exploiting heterogeneous environments: does photosynthetic acclimation optimize carbon gain in fluctuating light?

    PubMed Central

    Retkute, Renata; Smith-Unna, Stephanie E.; Smith, Robert W.; Burgess, Alexandra J.; Jensen, Oliver E.; Johnson, Giles N.; Preston, Simon P.; Murchie, Erik H.

    2015-01-01

    Plants have evolved complex mechanisms to balance the efficient use of absorbed light energy in photosynthesis with the capacity to use that energy in assimilation, so avoiding potential damage from excess light. This is particularly important under natural light, which can vary according to weather, solar movement and canopy movement. Photosynthetic acclimation is the means by which plants alter their leaf composition and structure over time to enhance photosynthetic efficiency and productivity. However there is no empirical or theoretical basis for understanding how leaves track historic light levels to determine acclimation status, or whether they do this accurately. We hypothesized that in fluctuating light (varying in both intensity and frequency), the light-response characteristics of a leaf should adjust (dynamically acclimate) to maximize daily carbon gain. Using a framework of mathematical modelling based on light-response curves, we have analysed carbon-gain dynamics under various light patterns. The objective was to develop new tools to quantify the precision with which photosynthesis acclimates according to the environment in which plants exist and to test this tool on existing data. We found an inverse relationship between the optimal maximum photosynthetic capacity and the frequency of low to high light transitions. Using experimental data from the literature we were able to show that the observed patterns for acclimation were consistent with a strategy towards maximizing daily carbon gain. Refinement of the model will further determine the precision of acclimation. PMID:25788730

  10. Low temperature acclimation of photosynthetic capacity and leaf morphology in the context of phloem loading type.

    PubMed

    Dumlao, Matthew R; Darehshouri, Anza; Cohu, Christopher M; Muller, Onno; Mathias, Jennifer; Adams, William W; Demmig-Adams, Barbara

    2012-09-01

    Carbon export from leaf mesophyll to sugar-transporting phloem occurs via either an apoplastic (across the cell membrane) or symplastic (through plasmodesmatal cell wall openings) pathway. Herbaceous apoplastic loaders generally exhibit an up-regulation of photosynthetic capacity in response to growth at lower temperature. However, acclimation of photosynthesis to temperature by symplastically loading species, whose geographic distribution is particularly strong in tropical and subtropical areas, has not been characterized. Photosynthetic and leaf anatomical acclimation to lower temperature was explored in two symplastic (Verbascum phoeniceum, Cucurbita pepo) and two apoplastic (Helianthus annuus, Spinacia oleracea) loaders, representing summer- and winter-active life histories for each loading type. Regardless of phloem loading type, the two summer-active species, C. pepo and H. annuus, exhibited neither foliar anatomical nor photosynthetic acclimation when grown under low temperature compared to moderate temperature. In contrast, and again irrespective of phloem loading type, the two winter-active mesophytes, V. phoeniceum and S. oleracea, exhibited both a greater number of palisade cell layers (and thus thicker leaves) and significantly higher maximal capacities of photosynthetic electron transport, as well as, in the case of V. phoeniceum, a greater foliar vein density in response to cool temperatures compared to growth at moderate temperature. It is therefore noteworthy that symplastic phloem loading per se does not prevent acclimation of intrinsic photosynthetic capacity to cooler growth temperatures. Given the vagaries of weather and climate, understanding the basis of plant acclimation to, and tolerance of, low temperature is critical to maintaining and increasing plant productivity for food, fuel, and fiber to meet the growing demands of a burgeoning human population. PMID:22791016

  11. Growth, photosynthetic acclimation and yield quality in legumes under climate change simulations: an updated survey.

    PubMed

    Irigoyen, J J; Goicoechea, N; Antolín, M C; Pascual, I; Sánchez-Díaz, M; Aguirreolea, J; Morales, F

    2014-09-01

    Continued emissions of CO2, derived from human activities, increase atmospheric CO2 concentration. The CO2 rise stimulates plant growth and affects yield quality. Effects of elevated CO2 on legume quality depend on interactions with N2-fixing bacteria and mycorrhizal fungi. Growth at elevated CO2 increases photosynthesis under short-term exposures in C3 species. Under long-term exposures, however, plants generally acclimate to elevated CO2 decreasing their photosynthetic capacity. An updated survey of the literature indicates that a key factor, perhaps the most important, that characteristically influences this phenomenon, its occurrence and extent, is the plant source-sink balance. In legumes, the ability of exchanging C for N at nodule level with the N2-fixing symbionts creates an extra C sink that avoids the occurrence of photosynthetic acclimation. Arbuscular mycorrhizal fungi colonizing roots may also result in increased C sink, preventing photosynthetic acclimation. Defoliation (Anthyllis vulneraria, simulated grazing) or shoot cutting (alfalfa, usual management as forage) largely increases root/shoot ratio. During re-growth at elevated CO2, new shoots growth and nodule respiration function as strong C sinks that counteracts photosynthetic acclimation. In the presence of some limiting factor, the legumes response to elevated CO2 is weakened showing photosynthetic acclimation. This survey has identified limiting factors that include an insufficient N supply from bacterial strains, nutrient-poor soils, low P supply, excess temperature affecting photosynthesis and/or nodule activity, a genetically determined low nodulation capacity, an inability of species or varieties to increase growth (and therefore C sink) at elevated CO2 and a plant phenological state or season when plant growth is stopped. PMID:25113447

  12. Redundant roles of photoreceptors and cytokinins in regulating photosynthetic acclimation to canopy density.

    PubMed

    Boonman, A; Prinsen, E; Voesenek, L A C J; Pons, T L

    2009-01-01

    The regulation of photosynthetic acclimation to canopy density was investigated in tobacco canopies and in tobacco and Arabidopsis plants with part of their foliage experimentally shaded. Both species acclimated to canopy light gradients and partial shading by allocating photosynthetic capacity to leaves in high light and adjusting chloroplast organization to the local light conditions. An investigation was carried out to determine whether signalling mediated by photoreceptors, sugars, cytokinin, and nitrate is involved in and necessary for proper photosynthetic acclimation. No evidence was found for a role for sugars, or for nitrate. The distribution of cytokinins in tobacco stands of contrasting density could be explained in part by irradiance-dependent delivery of cytokinins through the transpiration stream. Functional studies using a comprehensive selection of Arabidopsis mutants and transgenics showed that normal wild-type responses to partial shading were retained when signalling mediated by photoreceptors or cytokinins was disrupted. This indicates that these pathways probably operate in a redundant manner. However, the reduction of the chlorophyll a/b ratio in response to local shade was completely absent in the Arabidopsis Ws-2 accession mutated in PHYTOCHROME D and in the triple phyAphyCphyD mutant. Moreover, cytokinin receptor mutants also showed a reduced response, suggesting a previously unrecognized function of phyD and cytokinins. PMID:19240103

  13. Redundant roles of photoreceptors and cytokinins in regulating photosynthetic acclimation to canopy density

    PubMed Central

    Boonman, A.; Prinsen, E.; Voesenek, L. A. C. J.; Pons, T. L.

    2009-01-01

    The regulation of photosynthetic acclimation to canopy density was investigated in tobacco canopies and in tobacco and Arabidopsis plants with part of their foliage experimentally shaded. Both species acclimated to canopy light gradients and partial shading by allocating photosynthetic capacity to leaves in high light and adjusting chloroplast organization to the local light conditions. An investigation was carried out to determine whether signalling mediated by photoreceptors, sugars, cytokinin, and nitrate is involved in and necessary for proper photosynthetic acclimation. No evidence was found for a role for sugars, or for nitrate. The distribution of cytokinins in tobacco stands of contrasting density could be explained in part by irradiance-dependent delivery of cytokinins through the transpiration stream. Functional studies using a comprehensive selection of Arabidopsis mutants and transgenics showed that normal wild-type responses to partial shading were retained when signalling mediated by photoreceptors or cytokinins was disrupted. This indicates that these pathways probably operate in a redundant manner. However, the reduction of the chlorophyll a/b ratio in response to local shade was completely absent in the Arabidopsis Ws-2 accession mutated in PHYTOCHROME D and in the triple phyAphyCphyD mutant. Moreover, cytokinin receptor mutants also showed a reduced response, suggesting a previously unrecognized function of phyD and cytokinins. PMID:19240103

  14. The influence of photosynthetic acclimation to rising CO2 and warmer temperatures on leaf and canopy photosynthesis models

    NASA Astrophysics Data System (ADS)

    Bagley, Justin; Rosenthal, David M.; Ruiz-Vera, Ursula M.; Siebers, Matthew H.; Kumar, Praveen; Ort, Donald R.; Bernacchi, Carl J.

    2015-02-01

    There is an increasing necessity to understand how climate change factors, particularly increasing atmospheric concentrations of CO2 ([CO2]) and rising temperature, will influence photosynthetic carbon assimilation (A). Based on theory, an increased [CO2] concomitant with a rise in temperature will increase A in C3 plants beyond that of an increase in [CO2] alone. However, uncertainty surrounding the acclimation response of key photosynthetic parameters to these changes can influence this response. In this work, the acclimation responses of C3 photosynthesis for soybean measured at the SoyFACE Temperature by Free-Air CO2 Enrichment experiment are incorporated in a leaf biochemical and canopy photosynthesis model. The two key parameters used as model inputs, the maximum velocity for carboxylation (Vc,max) and maximum rate of electron transport (Jmax), were measured in a full factorial [CO2] by temperature experiment over two growing seasons and applied in leaf- and canopy-scale models to (1) reassess the theory of combined increases in [CO2] and temperature on A, (2) determine the role of photosynthetic acclimation to increased growth [CO2] and/or temperature in leaf and canopy predictions of A for these treatments, and (3) assess the diurnal and seasonal differences in leaf- and canopy-scale A associated with the imposed treatments. The results demonstrate that the theory behind combined increases in [CO2] and temperature is sound; however, incorporating more recent parameterizations into the photosynthesis model predicts greater increases in A when [CO2] and temperature are increased together. Photosynthetic acclimation is shown to decrease leaf-level A for all treatments; however, in elevated [CO2] the impact of acclimation does not result in any appreciable loss in photosynthetic potential at the canopy scale. In this analysis, neglecting photosynthetic acclimation in heated treatments, with or without concomitant rise in [CO2], leads to modeled overestimates of

  15. Adaptation and acclimation of photosynthetic microorganisms to permanently cold environments.

    PubMed

    Morgan-Kiss, Rachael M; Priscu, John C; Pocock, Tessa; Gudynaite-Savitch, Loreta; Huner, Norman P A

    2006-03-01

    Persistently cold environments constitute one of our world's largest ecosystems, and microorganisms dominate the biomass and metabolic activity in these extreme environments. The stress of low temperatures on life is exacerbated in organisms that rely on photoautrophic production of organic carbon and energy sources. Phototrophic organisms must coordinate temperature-independent reactions of light absorption and photochemistry with temperature-dependent processes of electron transport and utilization of energy sources through growth and metabolism. Despite this conundrum, phototrophic microorganisms thrive in all cold ecosystems described and (together with chemoautrophs) provide the base of autotrophic production in low-temperature food webs. Psychrophilic (organisms with a requirement for low growth temperatures) and psychrotolerant (organisms tolerant of low growth temperatures) photoautotrophs rely on low-temperature acclimative and adaptive strategies that have been described for other low-temperature-adapted heterotrophic organisms, such as cold-active proteins and maintenance of membrane fluidity. In addition, photoautrophic organisms possess other strategies to balance the absorption of light and the transduction of light energy to stored chemical energy products (NADPH and ATP) with downstream consumption of photosynthetically derived energy products at low temperatures. Lastly, differential adaptive and acclimative mechanisms exist in phototrophic microorganisms residing in low-temperature environments that are exposed to constant low-light environments versus high-light- and high-UV-exposed phototrophic assemblages. PMID:16524924

  16. Adaptation and Acclimation of Photosynthetic Microorganisms to Permanently Cold Environments

    PubMed Central

    Morgan-Kiss, Rachael M.; Priscu, John C.; Pocock, Tessa; Gudynaite-Savitch, Loreta; Huner, Norman P. A.

    2006-01-01

    Persistently cold environments constitute one of our world's largest ecosystems, and microorganisms dominate the biomass and metabolic activity in these extreme environments. The stress of low temperatures on life is exacerbated in organisms that rely on photoautrophic production of organic carbon and energy sources. Phototrophic organisms must coordinate temperature-independent reactions of light absorption and photochemistry with temperature-dependent processes of electron transport and utilization of energy sources through growth and metabolism. Despite this conundrum, phototrophic microorganisms thrive in all cold ecosystems described and (together with chemoautrophs) provide the base of autotrophic production in low-temperature food webs. Psychrophilic (organisms with a requirement for low growth temperatures) and psychrotolerant (organisms tolerant of low growth temperatures) photoautotrophs rely on low-temperature acclimative and adaptive strategies that have been described for other low-temperature-adapted heterotrophic organisms, such as cold-active proteins and maintenance of membrane fluidity. In addition, photoautrophic organisms possess other strategies to balance the absorption of light and the transduction of light energy to stored chemical energy products (NADPH and ATP) with downstream consumption of photosynthetically derived energy products at low temperatures. Lastly, differential adaptive and acclimative mechanisms exist in phototrophic microorganisms residing in low-temperature environments that are exposed to constant low-light environments versus high-light- and high-UV-exposed phototrophic assemblages. PMID:16524924

  17. Photosynthetic acclimation to enriched CO{sub 2} concentrations in Pinus Ponderosa

    SciTech Connect

    Torres, M.P.

    1995-11-01

    By the middle of the 21st century earth`s ambient CO{sub 2} level is expected to increase two-fold ({approximately}350 umol/L). Higher levels of CO{sub 2} are expected to cause major changes in the morphological, physiological, and biochemical traits of the world`s vegetation. Therefore, we constructed an experiment designed to measure the long-term acclimation processes of Pinus Ponderosa. As a prominent forest conifer, Pinus Ponderosa is useful when assessing a large scale global carbon budget. Eighteen genetically variable families were exposed to 3 different levels of CO{sub 2} (350 umol/L, 525 umol/L, 700 umol/L), for three years. Acclimation responses were quantified by assays of photosynthetic rate, chlorophyll fluorescence, and chlorophyll pigment concentrations.

  18. Daily photosynthetic and C-export patterns in winter wheat leaves during cold stress and acclimation.

    PubMed

    Leonardos, Evangelos D.; Savitch, Leonid V.; Huner, Norman P. A.; Oquist, Gunnar; Grodzinski, Bernard

    2003-04-01

    Diurnal patterns of whole-plant and leaf gas exchange and 14C-export of winter wheat acclimated at 20 and 5 degrees C were determined. The 5 degrees C-acclimated plants had lower relative growth rates, smaller biomass and leaf area, but larger specific leaf weight than 20 degrees C plants. Photosynthetic rates in 20 degrees C and 5 degrees C-acclimated leaves were similar; however, daytime export from 5 degrees C-acclimated leaves was 45% lower. Photosynthesis and export remained steady in 20 degrees C and 5 degrees C-acclimated leaves during the daytime. By comparison, photosynthesis in 5 degrees C-stressed leaves (20 degrees C-acclimated plants exposed to 5 degrees C 12 h before and during measurements) declined from 70 to 50% of the 20 degrees C-acclimated leaves during the daytime, while export remained constant at 35% of the 20 degrees C-acclimated and 60% of the 5 degrees C-acclimated leaves. At high light and CO2, photosynthesis and export increased in both 20 degrees C and 5 degrees C-acclimated leaves, but rates in 5 degrees C-stressed leaves remained unchanged. At all conditions daytime export was greater than nighttime export. Taken together, during cold acclimation photosynthesis was upregulated, whereas export was only partially increased. We suggest that this reflects a requirement of cold-acclimated plants to both sustain an increased leaf metabolic demand while concomitantly supporting translocation of photoassimilates to overwintering sinks. PMID:12675742

  19. Acclimation of photosynthetic tolerance to acute heat stress at elevated CO₂ and N.

    PubMed

    Wang, Dan; Fan, Jiazhi; Heckathorn, Scott A

    2014-09-01

    Determining interactive effects of pre-heat-stress, CO2 and N on photosynthetic thermotolerance is necessary for predicting plant responses to global change. We grew Hordeum vulgare (barley, C3) and Zea mays (corn, C4) at current or elevated CO2 (370 and 700 ppm) and limiting or optimal soil N (0.5 and 7.5mM). We assessed basal and inducible thermotolerance of net photosynthesis (Pn), photosystem II efficiency [Formula: see text] , photochemical quenching (qp), carboxylation efficiency (CE), and rubisco activase content. Inducible thermotolerance was measured on plants which were pre-heat-stressed (PHS) for 4h before heat stress. We also assayed content of several major heat-shock proteins (HSPs), as HSPs are primary adaptations to heat stress and affected by N. Acclimation of photosynthetic thermotolerance was dependent on species, CO2 and N treatment and the component in the photosynthetic processes. PHS had a positive effect on the production of HSP60 and sHSP in low-N barley and corn. These results indicate that stimulatory effects of elevated CO2 at normal temperatures on photosynthesis may be partly changed by the different interactive effects of CO2, heat stress and N for species with different photosynthetic pathways. Thus, PHS, CO2 and N effects on photosynthetic thermotolerance may contribute to changes in plant productivity, distribution, and diversity. PMID:25113461

  20. Natural Genetic Variation for Acclimation of Photosynthetic Light Use Efficiency to Growth Irradiance in Arabidopsis1[OPEN

    PubMed Central

    Harbinson, Jeremy

    2015-01-01

    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 (ΦPSII) in response to five light environments among 12 genetically diverse Arabidopsis (Arabidopsis thaliana) accessions. We measured the acclimation of ΦPSII to constant growth irradiances of four different levels (100, 200, 400, and 600 µmol m−2 s−1) by imaging chlorophyll fluorescence after 24 d of growth and compared these results with acclimation of ΦPSII to a step-wise change in irradiance where the growth irradiance was increased from 100 to 600 µmol m−2 s−1 after 24 d of growth. Genotypic variation for ΦPSII is shown by calculating heritability for the short-term ΦPSII response to different irradiance levels as well as for the relation of ΦPSII 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 ΦPSII measured 1 h 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 accessions 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 ΦPSII in plants. PMID:25670817

  1. Photosynthetic acclimation to temperature in the endemic Petrophytum cinerascens

    SciTech Connect

    Moore, D.J.; Nowak, R.S.

    1995-06-01

    Past research has shown that only some plants have the ability to acclimate to increased temperatures. Petrophytum cinerascens is a highly restricted endemic found on steep rocky outcrops and sandy soils. Our goal was to examine the plant`s ability to acclimate to increased temperature. Plants collected from the field were subjected to three sets of day/night temperatures and to two different watering regimes. Data were analyzed using a 3x2 split plot treatment with temperature as the main effect and watering treatment as a split plot factor. Leaf gas exchange was measured at step-intervals of leaf temperature. Data were fit to individual temperature response curves, and optimum assimilation rate (A{sub opt}), optimum temperature for assimilation (T{sub opt}) and high temperature intercept (T{sub high}) were calculated from the regressions. A{sub opt} for clones grown at 30/16 and 34/20 C was significantly greater than that for clones grown at 38/24 C, but the main effects of temperature on T{sub opt} and T{sub high} were not significant. The only significant effect of watering treatment was a significant temperature x water treatment interaction. The lack of change in T{sub opt} and T{sub high} suggests that p. cinerascens is not able to tolerate increased global temperature and therefore may serve as a sensitive indicator of climate change.

  2. Photosynthetic complex stoichiometry dynamics in higher plants: environmental acclimation and photosynthetic flux control

    PubMed Central

    Schöttler, Mark A.; Tóth, Szilvia Z.

    2014-01-01

    The composition of the photosynthetic apparatus of higher plants is dynamically adjusted to long-term changes in environmental conditions such as growth light intensity and light quality, and to changing metabolic demands for ATP and NADPH imposed by stresses and leaf aging. By changing photosynthetic complex stoichiometry, a long-term imbalance between the photosynthetic production of ATP and NADPH and their metabolic consumption is avoided, and cytotoxic side reactions are minimized. Otherwise, an excess capacity of the light reactions, relative to the demands of primary metabolism, could result in a disturbance of cellular redox homeostasis and an increased production of reactive oxygen species, leading to the destruction of the photosynthetic apparatus and the initiation of cell death programs. In this review, changes of the abundances of the different constituents of the photosynthetic apparatus in response to environmental conditions and during leaf ontogenesis are summarized. The contributions of the different photosynthetic complexes to photosynthetic flux control and the regulation of electron transport are discussed. PMID:24860580

  3. Effect of cold acclimation on the photosynthetic performance of two ecotypes of Colobanthus quitensis (Kunth) Bartl.

    PubMed

    Bravo, León A; Saavedra-Mella, Felipe A; Vera, Felipe; Guerra, Alexi; Cavieres, Lohengrin A; Ivanov, Alexander G; Huner, Norman P A; Corcuera, Luis J

    2007-01-01

    The effects of cold acclimation of two ecotypes (Antarctic and Andes) of Colobanthus quitensis (Kunth) Bartl. Caryophyllaceae on their photosynthetic characteristics and performance under high light (HL) were compared. Non-acclimated plants of the Antarctic ecotype exhibited a higher (34%) maximal rate of photosynthesis than the Andes ecotype. In cold-acclimated plants the light compensation point was increased. Dark respiration was significantly increased during the exposure to 4 degrees C in both ecotypes. Cold-acclimated Antarctic plants showed higher Phi(PSII) and qP compared with the Andes ecotype. In addition, the Antarctic ecotype exhibited higher heat dissipation (NPQ), especially in the cold-acclimated state, which was mainly associated with the fast relaxing component of non-photochemical quenching (NPQ(F)). By contrast, the Andes ecotype exhibited a lower NPQ(F) and a significant increase in the slowly relaxing component (NPQ(s)) at low temperature and HL, indicating higher sensitivity to low temperature-induced photoinhibition. Although the xanthophyll cycle was fully operational in both ecotypes, cold-acclimated Antarctic plants exposed to HL exhibited higher epoxidation state of the xanthophyll cycle pigments (EPS) compared with the cold-acclimated Andes ecotype. Thus, the photosynthetic apparatus of the Antarctic ecotype operates more efficiently than that of the Andes one, under a combination of low temperature and HL. The ecotype differences are discussed in relation to the different climatic conditions of the two Colobanthus. PMID:18057038

  4. Acclimation of photosynthetic parameters is not the icing on the cake. It is the cake.

    NASA Astrophysics Data System (ADS)

    Prentice, Iain Colin; Wang, Han; Togashi, Henrique; Keenan, Trevor; Davis, Tyler; Wright, Ian

    2015-04-01

    Photosynthesis and transpiration are tightly coupled through stomatal behaviour and therefore it is impossible to understand and parsimoniously model one without also considering the other. The ratio of leaf-internal to ambient carbon dioxide concentration (ci:ca ratio) is a measure of the "exchange rate" between water and carbon. We have shown that it is possible to predict the observed dependencies of ci:ca on environmental factors (temperature, vapour pressure deficit and atmospheric pressure) based on the "least-cost hypothesis", which states that plants minimize the sum of the unit costs (respiration per unit assimilation) of maintaining the capacities for carbon fixation (Vcmax) and water transport. Moreover, with the help of the "co-ordination hypothesis" (the long-accepted idea that Rubisco capacity and electron transport tend to co-limit photosynthesis) it is possible to predict not only how ci:ca should vary, but also how Vcmax and electron transport capacity (Jmax) should vary, in space and time. We will present empirical support for this idea based on both ecophysiological measurements at the leaf scale, and analysis of carbon dioxide flux measurements at the ecosystem scale. We conclude that acclimation of photosynthetic parameters is pervasive. This is fundamental because it predicts a quite different set of environmental responses than those that are usually applied in models that incorrectly assume constancy of parameter values with time and within plant functional types (PFTs). In addition, acclimation actually simplifies modelling because it describes universal relationships that apply across all PFTs with the C3 photosynthetic pathway, and it removes the need to specify parameters such as Vcmax and Jmax as if they were properties of PFTs.

  5. Protective effect of UV-A radiation during acclimation of the photosynthetic apparatus to UV-B treatment.

    PubMed

    Štroch, Michal; Materová, Zuzana; Vrábl, Daniel; Karlický, Václav; Šigut, Ladislav; Nezval, Jakub; Špunda, Vladimír

    2015-11-01

    We examined the acclimation response of the photosynthetic apparatus of barley (Hordeum vulgare L.) to a combination of UV-A and UV-B radiation (UVAB) and to UV-B radiation alone. Our aim was to evaluate whether UV-A radiation prevents UV-B-induced damage to the photosynthetic apparatus and whether UV-A pre-acclimation is required to mitigate the negative influence of UV-B radiation. Barley plants were grown from seeds under low photosynthetically active radiation (50 μmol m(-2) s(-1)) either in the absence or presence of UV-A radiation (UVA- and UVA+ plants, respectively). After 8 days of development, plants were exposed simultaneously to UV-A and UV-B radiation for the next 6 days. Additionally, UVA- plants were exposed to UV-B radiation alone. The UVA+ plants had a higher CO2 assimilation rate near the light-saturation region (A(N)) and a higher content of both total chlorophylls (Chls) and total carotenoids than the UVA- plants. Chls content, A(N), the potential quantum yield of photosystem II (PSII) photochemistry (F(V)/F(M)), the capacity of light-induced thermal energy dissipation and the efficiency of excitation energy transfer within PSII remained the same or even increased in both UVA+ and UVA- plants after UVAB treatment. On the contrary, exposure of UVA- plants to UV-B radiation itself led to a reduction in all these characteristics. We revealed that the presence of UV-A radiation during UVAB treatment not only mitigated but completely eliminated the negative effect of UV-B radiation on the functioning of the photosynthetic apparatus and that UV-A pre-acclimation was not crucial for development of this UV-A-induced resistance against UV-B irradiation. PMID:26233710

  6. UV-acclimation responses in natural populations of cyanobacteria (Calothrix sp.).

    PubMed

    Dillon, Jesse G; Miller, Scott R; Castenholz, Richard W

    2003-06-01

    Phenotypic acclimation to changing conditions is typically thought to be beneficial to organisms in the environment. UV radiation is an important parameter affecting photosynthetic organisms in natural environments. We measured the response of photosynthetic carbon fixation in populations of cyanobacteria inhabiting a hot spring following acclimation to different UV treatments. These two very closely related populations of cyanobacteria, differing in their content of the extracellular UV-screening pigment scytonemin, were acclimated in situ under natural solar irradiance modified by filters that excluded both UVA/B, only UVB or transmitted both UVA/B. Cells from each preacclimation treatment were subsequently assayed for photosynthetic performance under all UV conditions (incubation treatment) giving a two-factor experimental design for each population. No acclimation filter treatment effects were observed even after two months under different acclimation treatments. This suggests that UV photoacclimation does not occur in either of these populations, regardless of the presence of scytonemin. By contrast, cells showed significant UV-inhibition during 1 h incubations under full sun. The population with high levels of scytonemin usually had lower rates of photosynthetic carbon fixation than the scytonemin-lacking population. However, the degree of UV inhibition, especially UVA inhibition, was higher for the cells without scytonemin pigment. These results suggest that closely related natural cyanobacterial populations respond differently to natural irradiance conditions and may be adopting different strategies of UV tolerance. PMID:12755714

  7. Ion antiport accelerates photosynthetic acclimation in fluctuating light environments

    PubMed Central

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

    2014-01-01

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

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

    PubMed

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

    2014-01-01

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

  9. Influence of nutrient supply on shade-sun acclimation of Picea abies seedlings: effects on foliar morphology, photosynthetic performance and growth.

    PubMed

    Grassi, G.; Minotta, G.

    2000-05-01

    Norway spruce seedlings (Picea abies Karst.) were grown in low light for one year, under conditions of adequate and limiting nutrition, then transferred to high light. Three months after transfer we measured photosynthesis, leaf nitrogen concentration, leaf chlorophyll concentration and leaf mass per area (LMA) of current-year and 1-year-old shoots; silhouette area ratio (SAR, the ratio of shoot silhouette area to projected needle area) was also measured in current-year shoots. At the foliage level, the effects of light and nutrient treatments differed markedly. Light availability during foliage expansion primarily affected LMA and SAR (morphological acclimation at the needle and shoot level, respectively). By contrast, nutrient supply in high light affected photosynthetic capacity per unit of leaf tissue (physiological acclimation at the cellular level) but did not affect LMA and SAR. The capacity for shade-sun acclimation in foliage formed before transfer to high light differed greatly from that of foliage formed following the transfer. The morphological inflexibility of mature needles (measured by LMA) limited their shade-sun acclimation potential. In contrast, at high nutrient supply, shoots that developed just after the change in photosynthetic photon flux density largely acclimated, both morphologically and physiologically, to the new light environment. The acclimation response of both current- and 1-year-old shoots was prevented by nutrient limitation. Analysis of growth at the whole-plant level largely confirmed the conclusions drawn at the shoot level. We conclude that nutrient shortage subsequent to the opening of a canopy gap may strongly limit the acclimation response of Norway spruce seedlings. Successful acclimation was largely related to the plant's ability to produce sun foliage and adjust whole-plant biomass allocation rapidly. PMID:12651514

  10. The photosynthetic acclimation of Lolium perenne in response to three years growth in a free-air CO{sub 2} enrichment (FACE) system

    SciTech Connect

    Hymus, G.J. |

    1996-08-01

    Pure stands of Ryegrass were in their third year of growth in the field, exposed to either ambient (355 {mu}mol mol{sup -1}), or elevated (600 {mu}mol mol{sup -1}) atmospheric CO{sub 2} concentration. A Free-Air CO{sub 2} Enrichment (FACE) system was used to maintain the elevated CO{sub 2} concentration whilst limiting experimental constraints on the field conditions. The theoretically predicted increase in the net rates of CO{sub 2} uptake per unit leaf area (A {mu}mol mol{sup -1}) as a consequence, primarily, of the suppression of photorespiration by CO{sub 2} a competitive inhibitor of RubP oxygenation by Rubisco, was observed for the Lolium perenne studied. Also observed was a general decline in leaf evapotranspiration (E) consistent with observations of increased water use efficiency of crops grown in elevated CO{sub 2}. Enhancement of leaf A in the FACE grown L. perenne ranged from 26.5 1 % to 44.95% over the course of a diurnal set of measurements. Whilst reductions in leaf E reached a maximum of 16.61% over the same diurnal course of-measurements. The increase in A was reconciled with an absence of the commonly observed decline in V{sub c}{sub max} as a measure of the maximum in vivo carboxylation capacity of the primary carboxylasing enzyme Rubisco and J{sub max} a measure of the maximum rate of electron transport. The manipulation of the source sink balance of the crop, stage of canopy regrowth or height in the canopy had no effect on the observation of a lack of response. The findings of this study will be interpreted with respect to the long term implications of C{sub 3} crops being able to adapt physiologically to maximize the potential benefits conferred by growth in elevated CO{sub 2}.

  11. UV-B radiation and photosynthetic irradiance acclimate eggplant for outdoor exposure

    NASA Technical Reports Server (NTRS)

    Latimer, J. G.; Mitchell, C. A.; Mitchell, G. A.

    1987-01-01

    Treatment of greenhouse-grown eggplant (Solanum melongena L. var. esculentum Nees. 'Burpee's Black Beauty') seedlings with supplemental photosynthetically active radiation from cool-white fluorescent lamps increased growth of plants subsequently transferred outdoors relative to growth of plants that received no supplemental radiation or were shaded to 45% of solar irradiation in the greenhouse before transfer outdoors. Eggplant seedlings transferred outdoors were placed under plastic tarps either to provide relative protection from solar ultraviolet-B (UV-B) radiation (280-315 nm) using Mylar film or to allow exposure to UV-B using cellulose acetate. Protection of seedlings from UV-B radiation resulted in greater leaf expansion than for UV-B-exposed seedlings, but no change in leaf or shoot dry weight occurred after 9 days of treatment. Specific leaf weight increased in response to UV-B exposure outdoors. Exposure of eggplant to UV-B radiation from fluorescent sunlamps in the greenhouse also decreased leaf expansion and leaf and shoot dry weight gain after 5 days of treatment. However, there were no differences in leaf or shoot dry weight relative to control plants after 12 days of UV-B treatment, indicating that UV-B treated plants had acclimated to the treatment and actually had caught up with non-UV-B-irradiated plants in terms of growth.

  12. Photosynthetic acclimation of the filamentous cyanobacterium, Plectonema boryanum UTEX 485, to temperature and light.

    PubMed

    Miśkiewicz, E; Ivanov, A G; Williams, J P; Khan, M U; Falk, S; Huner, N P

    2000-06-01

    Photosynthetic acclimation to temperature and irradiance was studied in the filamentous, non-heterocystous cyanobacterium Plectonema boryanum UTEX 485. Growth rates of this cyanobacterium measured at ambient CO2 were primarily influenced by temperature with minimal effects of irradiance. Both growth temperature and irradiance affected linolenic (18:3) and linoleic acid (18:2) levels in the four major lipid classes in an independent but additive manner. In contrast, photosynthetic acclimation was not due to either growth temperature or irradiance per se, but rather, due to the interaction of these environmental factors. P. boryanum grown at low temperature and moderate irradiance mimicked cells grown at high light. Compared to cells grown at either 29 degrees C/150 micromol m(-2) s(-1) (29/150) or 15/10, P. boryanum grown at either 15/150 or 29/750 exhibited: (1) reduced cellular levels of Chl a and phycobilisomes (PBS), and concomitantly higher content of an orange-red carotenoid, myxoxanthophyll; (2) higher light saturated rates (Pmax) when expressed on a Chl a basis but lower apparent quantum yields of oxygen evolution and (3) enhanced resistance to high light stress. P. boryanum grown at 15/150 regained normal blue-green pigmentation within 16 h after a temperature shift to 29 degrees C at a constant irradiance of 150 micromol m(-2) s(-1). DBMIB and KCN but not DCMU and atrazine partially inhibited the change in myxoxanthophyll/Chl a ratio following the shift from 15 to 29 degrees C. We conclude that P. boryanum responds to either varying growth temperature or varying growth irradiance by adjusting the ability to absorb light through decreasing the cellular contents of Chl a and light-harvesting pigments and screening of excessive light by myxoxanthophyll predominantly localized in the cell wall/cell membrane to protect PSII from over-excitation. The possible role of redox sensing/signalling for photosynthetic acclimation of cyanobacteria to either temperature

  13. Thermal Plasticity of Photosynthesis: the Role of Acclimation in Forest Responses to a Warming Climate

    SciTech Connect

    Gunderson, Carla A; O'Hara, Keiran H; Campion, Christina M; Walker, Ashley V; Edwards, Nelson T

    2010-01-01

    The increasing air temperatures central to climate change predictions have the potential to alter forest ecosystem function and structure by exceeding temperatures optimal for carbon gain. Such changes are projected to threaten survival of sensitive species, leading to local extinctions, range migrations, and altered forest composition. This study investigated photosynthetic sensitivity to temperature and the potential for acclimation in relation to the climatic provenance of five species of deciduous trees, Liquidambar styraciflua, Quercus rubra, Quercus falcata, Betula alleghaniensis, and Populus grandidentata. Open-top chambers supplied three levels of warming (+0, +2, and +4 C above ambient) over 3 years, tracking natural temperature variability. Optimal temperature for CO2 assimilation was strongly correlated with daytime temperature in all treatments, but assimilation rates at those optima were comparable. Adjustment of thermal optima was confirmed in all species, whether temperatures varied with season or treatment, and regardless of climate in the species' range or provenance of the plant material. Temperature optima from 17 to 34 were observed. Across species, acclimation potentials varied from 0.55 C to 1.07 C per degree change in daytime temperature. Responses to the temperature manipulation were not different from the seasonal acclimation observed in mature indigenous trees, suggesting that photosynthetic responses should not be modeled using static temperature functions, but should incorporate an adjustment to account for acclimation. The high degree of homeostasis observed indicates that direct impacts of climatic warming on forest productivity, species survival, and range limits may be less than predicted by existing models.

  14. High-Temperature Sensitivity and Its Acclimation for Photosynthetic Electron Transport Reactions of Desert Succulents 1

    PubMed Central

    Chetti, Mahadev B.; Nobel, Park S.

    1987-01-01

    Photosynthetic electron transport reactions of succulent plants from hot deserts are able to tolerate extremely high temperatures and to acclimate to seasonal increases in temperature. In this study, we report the influence of relatively long, in vivo, high-temperature treatments on electron transport reactions for two desert succulents, Agave deserti and Opuntia ficus-indica, species which can tolerate 60°C. Whole chain electron transport averaged 3°C more sensitive to a 1-hour high-temperature treatment than did PSII (Photosystem II) which in turn averaged 3°C more sensitive than did PSI. For plants maintained at day/night air temperatures of 30°C/20°C, treatment at 50°C caused these reactions to be inhibited an average of 39% during the first hour, an additional 31% during the next 4 hours, and 100% by 12 hours. Upon shifting the plants from 30°C/20°C to 45°C/35°C, the high temperatures where activity was inhibited 50% increased 3°C to 8°C for the three electron transport reactions, the half-times for acclimation averaging 5 days for A. deserti and 4 days for O. ficus-indica. For the 45°C/35°C plants treated at 60°C for 1 hour, PSI activity was reduced by 54% for A. deserti and 36% for O. ficus-indica. Acclimation leads to a toleration of very high temperatures without substantial disruption of electron transport for these desert succulents, facilitating their survival in hot deserts. Indeed, the electron transport reactions of these species tolerate longer periods at higher temperatures than any other vascular plant so far reported. PMID:16665562

  15. Root Restriction as a Factor in Photosynthetic Acclimation of Cotton Seedlings Grown in Elevated Carbon Dioxide 1

    PubMed Central

    Thomas, Richard B.; Strain, Boyd R.

    1991-01-01

    Interactive effects of root restriction and atmospheric CO2 enrichment on plant growth, photosynthetic capacity, and carbohydrate partitioning were studied in cotton seedlings (Gossypium hirsutum L.) grown for 28 days in three atmospheric CO2 partial pressures (270, 350, and 650 microbars) and two pot sizes (0.38 and 1.75 liters). Some plants were transplanted from small pots into large pots after 20 days. Reduction of root biomass resulting from growth in small pots was accompanied by decreased shoot biomass and leaf area. When root growth was less restricted, plants exposed to higher CO2 partial pressures produced more shoot and root biomass than plants exposed to lower levels of CO2. In small pots, whole plant biomass and leaf area of plants grown in 270 and 350 microbars of CO2 were not significantly different. Plants grown in small pots in 650 microbars of CO2 produced greater total biomass than plants grown in 350 microbars, but the dry weight gain was found to be primarily an accumulation of leaf starch. Reduced photosynthetic capacity of plants grown at elevated levels of CO2 was clearly associated with inadequate rooting volume. Reductions in net photosynthesis were not associated with decreased stomatal conductance. Reduced carboxylation efficiency in response to CO2 enrichment occurred only when root growth was restricted suggesting that ribulose-1,5-bisphosphate carboxylase/oxygenase activity may be responsive to plant source-sink balance rather than to CO2 concentration as a single factor. When root-restricted plants were transplanted into large pots, carboxylation efficiency and ribulose-1,5-bisphosphate regeneration capacity increased indicating that acclimation of photosynthesis was reversible. Reductions in photosynthetic capacity as root growth was progressively restricted suggest sink-limited feedback inhibition as a possible mechanism for regulating net photosynthesis of plants grown in elevated CO2. PMID:16668232

  16. Sweating responses during heat acclimation and moderate conditioning

    NASA Technical Reports Server (NTRS)

    Shvartz, E.; Bhattacharya, A.; Sperinde, S. J.; Brock, P. J.; Sciaraffa, D.; Van Beaumont, W.

    1979-01-01

    Experiments were conducted on ten young male subjects to determine sweating onset, distribution, and patterns as well as the relationships of these responses to body temperature during heat acclimation and moderate conditioning performed in temperate (24 C) conditions. The subjects are randomly assigned to two groups of five subjects each. The experimental period consisted of eight successive days of either graded exercise to exhaustion on a bicycle ergometer in heat (acclimation group) or in a temperate environment (control group). Major conclusions are that (1) acclimation and conditioning result in relatively more sweat rate on the limbs than on the torso, but that these changes are less related to body temperature than torso sweat rate; and (2) sweating sensitivity increases during acclimation and conditioning, but its contribution to heat acclimation is minor.

  17. Biochemical acclimation, stomatal limitation and precipitation patterns underlie decreases in photosynthetic stimulation of soybean (Glycine max) at elevated [CO₂] and temperatures under fully open air field conditions.

    PubMed

    Rosenthal, David M; Ruiz-Vera, Ursula M; Siebers, Matthew H; Gray, Sharon B; Bernacchi, Carl J; Ort, Donald R

    2014-09-01

    The net effect of elevated [CO2] and temperature on photosynthetic acclimation and plant productivity is poorly resolved. We assessed the effects of canopy warming and fully open air [CO2] enrichment on (1) the acclimation of two biochemical parameters that frequently limit photosynthesis (A), the maximum carboxylation capacity of Rubisco (Vc,max) and the maximum potential linear electron flux through photosystem II (Jmax), (2) the associated responses of leaf structural and chemical properties related to A, as well as (3) the stomatal limitation (l) imposed on A, for soybean over two growing seasons in a conventionally managed agricultural field in Illinois, USA. Acclimation to elevated [CO2] was consistent over two growing seasons with respect to Vc,max and Jmax. However, elevated temperature significantly decreased Jmax contributing to lower photosynthetic stimulation by elevated CO2. Large seasonal differences in precipitation altered soil moisture availability modulating the complex effects of elevated temperature and CO2 on biochemical and structural properties related to A. Elevated temperature also reduced the benefit of elevated [CO2] by eliminating decreases in stomatal limitation at elevated [CO2]. These results highlight the critical importance of considering multiple environmental factors (i.e. temperature, moisture, [CO2]) when trying to predict plant productivity in the context of climate change. PMID:25113459

  18. Increased photosynthetic acclimation in alfalfa associated with arbuscular mycorrhizal fungi (AMF) and cultivated in greenhouse under elevated CO2.

    PubMed

    Goicoechea, Nieves; Baslam, Marouane; Erice, Gorka; Irigoyen, Juan José

    2014-11-15

    Medicago sativa L. (alfalfa) can exhibit photosynthetic down-regulation when grown in greenhouse conditions under elevated atmospheric CO2. This forage legume can establish a double symbiosis with nitrogen fixing bacteria and arbuscular mycorrhizal fungi (AMF), which may increase the carbon sink effect of roots. Our aim was to assess whether the association of alfalfa with AMF can avoid, diminish or delay the photosynthetic acclimation observed in previous studies performed with nodulated plants. The results, however, showed that mycorrhizal (M) alfalfa at the end of their vegetative period had lower carbon (C) discrimination than non-mycorrhizal (NM) controls, indicating photosynthetic acclimation under ECO2 in plants associated with AMF. Decreased C discrimination was due to the acclimation of conductance, since the amount of Rubisco and the expression of genes codifying both large and small subunits of Rubisco were similar or slightly higher in M than in NM plants. Moreover, M alfalfa accumulated a greater amount of soluble sugars in leaves than NM plants, thus favoring a down-regulation effect on photosynthetic rates. The enhanced contents of sugars in leaves coincided with a reduced percentage of arbuscules in roots, suggesting decreased sink of carbohydrates from shoots to roots in M plants. The shorter life cycle of alfalfa associated with AMF in comparison with the NM controls may also be related to the accelerated photosynthetic acclimation in M plants. Further research is needed to clarify to what extent this behavior could be extrapolated to alfalfa cultivated in the field and subjected to periodic cutting of shoots under climatic change scenarios. PMID:25240322

  19. Adaptive and acclimative responses of cyanobacteria to far-red light.

    PubMed

    Gan, Fei; Bryant, Donald A

    2015-10-01

    Cyanobacteria use three major photosynthetic complexes, photosystem (PS) I, PS II and phycobilisomes, to harvest and convert sunlight into chemical energy. Until recently, it was generally thought that cyanobacteria only used light between 400 nm and 700 nm to perform photosynthesis. However, the discovery of chlorophyll (Chl) d in Acaryochloris marina and Chl f in Halomicronema hongdechloris showed that some cyanobacteria could utilize far-red light. The synthesis of Chl f (and Chl d) is part of an extensive acclimation process, far-red light photoacclimation (FaRLiP), which occurs in many cyanobacteria. Organisms performing FaRLiP contain a conserved set of 17 genes encoding paralogous subunits of the three major photosynthetic complexes. Far-red light photoacclimation leads to substantial remodelling of the photosynthetic apparatus and other changes in cellular metabolism through extensive changes in transcription. Far-red light photoacclimation appears to be controlled by a red/far-red photoreceptor, RfpA, as well as two response regulators (RfpB and RfpC), one of which is a DNA-binding protein. The remodelled photosynthetic complexes, including novel phycobiliproteins, absorb light above 700 nm and enable cells to grow in far-red light. A much simpler acclimation response, low-light photoacclimation (LoLiP), occurs in some cyanobacteria that contain the apcD4-apcB3-isiX cluster, which allows cells to grow under low light conditions. PMID:26234306

  20. Photosynthetic Acclimation of Symbiodinium in hospite Depends on Vertical Position in the Tissue of the Scleractinian Coral Montastrea curta

    PubMed Central

    Lichtenberg, Mads; Larkum, Anthony W. D.; Kühl, Michael

    2016-01-01

    Coral photophysiology has been studied intensively from the colony scale down to the scale of single fluorescent pigment granules as light is one of the key determinants for coral health. We studied the photophysiology of the oral and aboral symbiont band of scleractinian coral Montastrea curta to investigate if different acclimation to light exist in hospite on a polyp scale. By combined use of electrochemical and fiber-optic microsensors for O2, scalar irradiance and variable chlorophyll fluorescence, we could characterize the physical and chemical microenvironment experienced by the symbionts and, for the first time, estimate effective quantum yields of PSII photochemistry and rates of electron transport at the position of the zooxanthellae corrected for the in-tissue gradient of scalar irradiance. The oral- and aboral Symbiodinium layers received ∼71% and ∼33% of surface scalar irradiance, respectively, and the two symbiont layers experience considerable differences in light exposure. Rates of gross photosynthesis did not differ markedly between the oral- and aboral layer and curves of PSII electron transport rates corrected for scalar irradiance in hospite, showed that the light use efficiency under sub-saturating light conditions were similar between the two layers. However, the aboral Symbiodinium band did not experience photosynthetic saturation, even at the highest investigated irradiance where the oral layer was clearly saturated. We thus found a different light acclimation response for the oral and aboral symbiont bands in hospite, and discuss whether such response could be shaped by spectral shifts caused by tissue gradients of scalar irradiance. Based on our experimental finding, combined with previous knowledge, we present a conceptual model on the photophysiology of Symbiodinium residing inside living coral tissue under natural gradients of light and chemical parameters. PMID:26955372

  1. Anatomical and photosynthetic acclimation to the light environment in species with differing mechanisms of phloem loading

    PubMed Central

    Amiard, Véronique; Mueh, Kristine E.; Demmig-Adams, Barbara; Ebbert, Volker; Turgeon, Robert; Adams, William W.

    2005-01-01

    Plants load sugars from photosynthesizing leaves into the phloem of exporting veins either “apoplastically” (by using H+/sucrose symporters) or “symplastically” (through plasmodesmata). The ability to regulate photosynthesis in response to the light environment was compared among apoplastic loaders (pea and spinach) and symplastic loaders (pumpkin and Verbascum phoeniceum). Plants were grown under low light (LL) or high light (HL) or transferred from LL to HL. Upon transfer, pea and spinach up-regulated photosynthesis to the level found in HL-acclimated plants, whereas up-regulation in pumpkin and V. phoeniceum was limited. The vein density of pea and spinach was the same in HL and LL. Although spinach did not exhibit anatomical or ultrastructural acclimation to the light environment, in pea, wall invaginations in minor vein companion (transfer) cells were more extensive in HL. Furthermore, upon transfer from LL to HL, these invaginations increased in mature pea leaves. Foliar starch levels in mature leaves of plants transferred from LL to HL were not greater than in HL-acclimated leaves of either apoplastically loading species. In the symplastic loaders, plasmodesmatal frequency per loading cell did not vary with treatment, but vein density and thus total plasmodesmatal frequency were higher in HL. Upon transfer of symplastic loaders, however, vein density remained low, and starch levels were higher than in HL; the incomplete acclimation of photosynthesis upon transfer is thus consistent with a carbon export capacity physically limited by an inability to increase vein and plasmodesmatal density in a mature leaf. PMID:16120679

  2. Biochemical acclimation, stomatal limitation and precipitation patterns underlie decreases in photosynthetic stimulation of Soybean (Glycine max) at elevated [CO2] and temperatures under fully open air field conditions

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The net effect of elevated [CO2] and temperature on photosynthetic acclimation and plant productivity is poorly resolved. We assessed the effects of canopy warming and fully open air [CO2] enrichment on 1) the acclimation of two biochemical parameters that frequently limit photosynthesis (A), the ma...

  3. Interaction of proline, sugars, and anthocyanins during photosynthetic acclimation of Arabidopsis thaliana to drought stress.

    PubMed

    Sperdouli, Ilektra; Moustakas, Michael

    2012-04-15

    The relationships among photosynthetic acclimation, proline (Pro), soluble sugar (SS), and anthocyanin (An) accumulation in Arabidopsis thaliana leaves to the onset of drought stress (OnDS), mild (MiDS) and moderate drought stress (MoDS), were evaluated. As leaf water content (LWC) decreased, metabolic concentrations (Pro, SS, and An) increased and were negatively and significantly correlated with LWC. Thus, these metabolites may have an important role in the acclimation process to drought stress (DS). No correlations among Pro, SS and An accumulation with the quantum efficiency of PSII photochemistry (Φ(PSII)) and the excitation pressure (1-q(P)) were observed under DS. This implies that, while metabolites increased in a drought-dependent way, PSII activity did not decrease in the same pattern. Our results indicated that, under MoDS, A. thaliana leaves were able to maintain oxidative compounds such as malondialdeyde, an end product of lipid peroxidation, within the range of control leaves, and to cope with oxidative damage, as was evident by the decreased excitation pressure (1-q(P)) and similar (ns difference) Φ(PSII) to that of control leaves. In addition, a statistically significant increased accumulation of Pro, SS and An was recorded only under MoDS compared to controls. The better PSII functioning of MoDS Arabidopsis leaves may reflect the greater capacity of these leaves to undertake key metabolic adjustments, including increased Pro, SS and An accumulation, to maintain a higher antioxidant protection and a better balance between light capture and energy use. PMID:22305050

  4. The photosynthetic acclimation of Lolium perenne growing in a free-air CO{sub 2} enrichment (FACE) system

    SciTech Connect

    Bryant, J.B. |

    1994-11-01

    Stands of Ryegrass (Lolium perenne L. cv. Bastion) were grown in the field at ambient or elevated (600{mu}mol/mol) CO{sub 2} concentration, high (560Kg/ha) or low (140Kg/ha) nitrogen addition and with a frequent (every 4 weeks) or infrequent (every 8 weeks) cutting regime. Plants were in the second year of a 3 year experiment. Exposure to elevated CO{sub 2} was carried out with a Free-Air CO{sub 2} Enrichment (FACE) system which provides the most {open_quote}realistic{close_quote} system of CO{sub 2} fumigation currently available. Elevated CO{sub 2} increased diurnal CO{sub 2} assimilation by between 34 and 88% whilst reducing rates of stomatal conductance by between 1 and 42%. However, analysis of the A vs. Ci response showed considerable acclimation of the photosynthetic apparatus in response to elevated CO{sub 2} - Vc{sub max} as an in vivo measure of RubisCO activity, decreased by between 29 and 35% in high CO{sub 2}, whilst J{sub max}, as a measure of the RubP regeneration capacity, showed no significant change. Two out of three additional perennial grassland species studied showed similar acclamatory behavior to Ryegrass. Diurnal assimilation rate, J{sub max} and, in most cases, Vc{sub max}, increased significantly directly after cutting of Ryegrass stands, but nitrogen treatment had little effect on any of these parameters. Neither stomatal density, stomatal index nor stomatal pore length of Ryegrass were significantly altered by growth in elevated CO{sub 2}. The results are discussed in terms of the limitation imposed on maximizing photosynthetic and growth responses of Ryegrass at elevated CO{sub 2}, by the ability of perennial species to increase long-term sink capacity under these conditions.

  5. Enhancement of photosynthetic O2 evolution in Chlorella vulgaris under high light and increased CO2 concentration as a sign of acclimation to phosphate deficiency.

    PubMed

    Kozłowska-Szerenos, Bozena; Bialuk, Izabela; Maleszewski, Stanisław

    2004-05-01

    The photosynthetic oxygen evolution of Chlorella vulgaris (Beijer.) cells taken from phosphate-deficient (-P) and control cultures was measured during 8 days of culture growth. Under inorganic carbon concentration (50 microM) in the measuring cell suspension and irradiance (150 micromol m(-2) s(-1)), the same as during culture growth, there were no marked differences in the photosynthetic O2 evolution rate between the -P cells and the controls. The much slower growth of -P cultures indicated that the utilization of absorbed photosynthetically active radiation (PAR) in the CO2 assimilation and biomass production were in -P cells less efficient than in the controls. Alga cells under the phosphorus stress utilized more of the absorbed PAR in the nitrate reduction than the control cells. However, under conditions of more efficient CO2 supply (inorganic carbon concentration 150 microM, introducing of exogenous carbonic anhydrase to the measuring cell suspension) and under increased irradiance (500 micromol m(-2) s(-1)), the photosynthetic O2 evolution in -P cells reached a higher rate than in the controls. The results suggest that in -P cells the restricted CO2 availability limits the total photosynthetic process. But under conditions more favorable for the CO2 uptake and under high irradiance, the -P cells may reveal a higher photosynthetic oxygen evolution rate than the controls. It is concluded that an increased potential activity of the photosynthetic light energy absorption and conversion in the C. vulgaris cells from -P cultures is a sign of acclimation to phosphorus stress by a sun-type like adaptation response of the photosynthetic apparatus. PMID:15191743

  6. Photosynthetic acclimation to high CO{sub 2} concentration varies with a plant`s capacity to adjust leaf thickness and nitrogen concentration

    SciTech Connect

    Sims, D.A.; Luo, Y.; Ball, J.T.

    1995-06-01

    Photosynthetic capacities (A{sub max}) of plants grown at high CO{sub 2} concentrations can increase, decrease or remain unchanged depending on the species and growth conditions. Increases in A{sub max} are associated with increases in leaf nitrogen concentration and/or leaf thickness. Leaf nitrogen concentration invariably decreases during growth at high CO{sub 2} while leaf thickness often increases. A{sub max} will increase during growth in high CO{sub 2} if the increase in leaf thickness outweighs the decrease in leaf nitrogen concentration. We will present a model that predicts the photosynthetic acclimation response to CO{sub 2} concentration from changes in leaf nitrogen concentration and thickness. The model was also used to predict the acclimation response under various environmental conditions. It is assumed that plants have a limited range of potential adjustment in leaf nitrogen concentration and thickness. Plants already near these limits, such as sun plants with thick leaves or low nitrogen grown plants with low leaf nitrogen concentration, may have limited potential for further adjustment in response to high CO{sub 2}. We predict that growth in high CO{sub 2} will result in upregulation of A{sub max} in low light and high nutrient environments and downregulation and low nutrient environments.

  7. Delayed flowering is associated with lack of photosynthetic acclimation in Pigeon pea (Cajanus cajan L.) grown under elevated CO₂.

    PubMed

    Sreeharsha, Rachapudi Venkata; Sekhar, Kalva Madhana; Reddy, Attipalli Ramachandra

    2015-02-01

    In the present study, we investigated the likely consequences of future atmospheric CO2 concentrations [CO2] on growth, physiology and reproductive phenology of Pigeonpea. A short duration Pigeonpea cultivar (ICPL 15011) was grown without N fertilizer from emergence to final harvest in CO2 enriched atmosphere (open top chambers; 550μmolmol(-1)) for two seasons. CO2 enrichment improved both net photosynthetic rates (Asat) and foliar carbohydrate content by 36 and 43%, respectively, which further reflected in dry biomass after harvest, showing an increment of 29% over the control plants. Greater carboxylation rates of Rubisco (Vcmax) and photosynthetic electron transport rates (Jmax) in elevated CO2 grown plants measured during different growth periods, clearly demonstrated lack of photosynthetic acclimation. Further, chlorophyll a fluorescence measurements as indicated by Fv/Fm and ΔF/Fm' ratios justified enhanced photosystem II efficiency. Mass and number of root nodules were significantly high in elevated CO2 grown plants showing 58% increase in nodule mass ratio (NMR) which directly correlated with Pn. Growth under high CO2 showed significant ontogenic changes including delayed flowering. In conclusion, our data demonstrate that the lack of photosynthetic acclimation and increased carbohydrate-nitrogen reserves modulate the vegetative and reproductive growth patterns in Pigeonpea grown under elevated CO2. PMID:25575994

  8. Paradoxical acclimation responses in the thermal performance of insect immunity.

    PubMed

    Ferguson, Laura V; Heinrichs, David E; Sinclair, Brent J

    2016-05-01

    Winter is accompanied by multiple stressors, and the interactions between cold and pathogen stress potentially determine the overwintering success of insects. Thus, it is necessary to explore the thermal performance of the insect immune system. We cold-acclimated spring field crickets, Gryllus veletis, to 6 °C for 7 days and measured the thermal performance of potential (lysozyme and phenoloxidase activity) and realised (bacterial clearance and melanisation) immune responses. Cold acclimation decreased the critical thermal minimum from -0.5 ± 0.25 to -2.1 ± 0.18 °C, and chill coma recovery time after 72 h at -2 °C from 16.8 ± 4.9 to 5.2 ± 2.0 min. Measures of both potential and realised immunity followed a typical thermal performance curve, decreasing with decreasing temperature. However, cold acclimation further decreased realised immunity at low, but not high, temperatures; effectively, immune activity became paradoxically specialised to higher temperatures. Thus, cold acclimation induced mismatched thermal responses between locomotor and immune systems, as well as within the immune system itself. We conclude that cold acclimation in insects appears to preferentially improve cold tolerance over whole-animal immune performance at low temperatures, and that the differential thermal performance of physiological responses to multiple pressures must be considered when predicting ectotherms' response to climate change. PMID:26846428

  9. Photosynthetic acclimation to elevated carbon dioxide: Basis for variability among plants. Final technical report, September 1, 1988--April 30, 1992

    SciTech Connect

    Cure, J.

    1998-03-30

    The objective of this research was to investigate the acclimation phenomena involved in plants as they adjust to a CO{sub 2} enriched atmosphere. Plants were grown under various CO{sub 2} concentrations in the controlled chambers of the Duke University Phytotron. Soil nutrients, irradiance, temperature, soil water, and atmospheric relative humidity were controlled. Photosynthesis, leaf structure, leaf biomass of photosynthetic leaves or leaflets and of growth points that are not assimilating CO{sub 2} were measured to determine contributions of carbon source tissues to sink tissues. Export and import rates following movement of plants into atmospheres of higher carbon dioxide concentration were specifically examined.

  10. The temporal and species dynamics of photosynthetic acclimation in flag leaves of rice (Oryza sativa L.) and wheat (Triticum aestivum L.) under elevated carbon dioxide

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Although initial exposure to higher atmospheric carbon dioxide can result in enhanced photosynthetic rates, temporal declines in photosynthesis associated with prolonged exposure to higher CO2 levels can also result in a down-regulation or acclimation of photosynthesis. In this study, we tested for...

  11. Cold acclimation of Arabidopsis thaliana results in incomplete recovery of photosynthetic capacity, associated with an increased reduction of the chloroplast stroma.

    PubMed

    Savitch, L V; Barker-Astrom, J; Ivanov, A G; Hurry, V; Oquist, G; Huner, N P; Gardeström, P

    2001-12-01

    The effects of short-term cold stress and long-term cold acclimation on the light reactions of photosynthesis were examined in vivo to assess their contributions to photosynthetic acclimation to low temperature in Arabidopsis thaliana (L.) Heynh.. All photosynthetic measurements were made at the temperature of exposure: 23 degrees C for non-acclimated plants and 5 degrees C for cold-stressed and cold-acclimated plants. Three-day cold-stress treatments at 5 degrees C inhibited light-saturated rates of CO2 assimilation and O2 evolution by approximately 75%. The 3-day exposure to 5 degrees C also increased the proportion of reduced QA by 50%, decreased the yield of PSII electron transport by 65% and decreased PSI activity by 31%. In contrast, long-term cold acclimation resulted in a strong but incomplete recovery of light-saturated photosynthesis at 5 degrees C. The rates of light-saturated CO2 and O2 gas exchange and the in vivo yield of PSII activity under light-saturating conditions were only 35-40% lower, and the relative redox state of QA only 20% lower, at 5 degrees C after cold acclimation than in controls at 23 degrees C. PSI activity showed full recovery during long-term cold acclimation. Neither short-term cold stress nor long-term cold acclimation of Arabidopsis was associated with a limitation in ATP, and both treatments resulted in an increase in the ATP/NADPH ratio. This increase in ATP/NADPH was associated with an inhibition of PSI cyclic electron transport but there was no apparent change in the Mehler reaction activity in either cold-stressed or cold-acclimated leaves. Cold acclimation also resulted in an increase in the reduction state of the stroma, as indicated by an increased total activity and activation state of NADP-dependent malate dehydrogenase, and increased light-dependent activities of the major regulatory enzymes of the oxidative pentose-phosphate pathway. We suggest that the photosynthetic capacity during cold stress as well as cold

  12. Acclimation of Photosynthetic Light Reactions during Induction of Inorganic Carbon Accumulation in the Green Alga Chlamydomonas reinhardtii12

    PubMed Central

    Palmqvist, Kristin; Sundblad, Lars-Göran; Wingsle, Gunnar; Samuelsson, Göran

    1990-01-01

    Cells of the unicellular green algae Chlamydomonas reinhardtii were grown in high dissolved inorganic carbon (DIC) concentrations (supplied with 50 milliliters per liter CO2[g]) and transferred to low DIC concentrations (supplied with ≤ 100 microliters per liter CO2[g]). Immediately after transfer from high to low DIC the emission of photosystem II related chlorophyll a fluorescence was substantially quenched. It is hypothesized that the suddenly induced inorganic carbon limitation of photosynthesis resulted in a phosphorylation of LHCII, leading to the subsequent state 1 to state 2 transition. After 2 hours of low-DIC acclimation, 77 K fluorescence measurements revealed an increase in the fluorescence emitted from photosystem I, due to direct excitation, suggesting a change in photosystem II/photosystem I stoichiometry or an increased light harvesting capacity of photosystem I. After 5 to 6 hours of acclimation a considerable increase in spillover from photosystem II to photosystem I was observed. These adjustments of the photosynthetic light reactions reached steady-state after about 12 hours of low DIC treatment. The quencher of fluorescence could be removed by 5 minutes of dark treatment followed by 5 minutes of weak light treatment, of any of four different light qualities. It is hypothesized that this restoration of fluorescence was due to a state 2 to state 1 transition in low-DIC acclimated cells. A decreased ratio of violaxanthin to zeaxanthin was also observed in 12 hour low DIC treated cells, compared with high DIC grown cells. This ratio was not coupled to the level of fluorescence quenching. The role of different processes during the induction of a DIC accumulating mechanism is discussed. PMID:16667710

  13. BOREAS TE-10 Photosynthetic Response Data

    NASA Technical Reports Server (NTRS)

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

    2000-01-01

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

  14. Leaf architectural, vascular and photosynthetic acclimation to temperature in two biennials.

    PubMed

    Muller, Onno; Stewart, Jared J; Cohu, Christopher M; Polutchko, Stephanie K; Demmig-Adams, Barbara; Adams, William W

    2014-12-01

    Acclimation of leaf features to growth temperature was investigated in two biennials (whose life cycle spans summer and winter seasons) using different mechanisms of sugar loading into exporting conduits, Verbascum phoeniceum (employs sugar-synthesizing enzymes driving symplastic loading through plasmodesmatal wall pores of phloem cells) and Malva neglecta (likely apoplastic loader transporting sugar via membrane transport proteins of phloem cells). In both species, acclimation to lower temperature involved greater maximal photosynthesis rates and vein density per leaf area in close correlation with modification of minor vein cellular features. While the symplastically loading biennial exhibited adjustments in the size of minor leaf vein cells (consistent with adjustment of the level of sugar-synthesizing enzymes), the putative apoplastic biennial exhibited adjustments in the number of cells (consistent with adjustment of cell membrane area for transporter placement). This upregulation of morphological and anatomical features at lower growth temperature likely contributes to the success of both the species during the winter. Furthermore, while acclimation to low temperature involved greater leaf mass per area in both species, this resulted from greater leaf thickness in V. phoeniceum vs a greater number of mesophyll cells per leaf area in M. neglecta. Both types of adjustments presumably accommodate more chloroplasts per leaf area contributing to photosynthesis. Both biennials exhibited high foliar vein densities (particularly the solar-tracking M. neglecta), which should aid both sugar export from and delivery of water to the leaves. PMID:24818515

  15. Integration of polyamines in the cold acclimation response.

    PubMed

    Alcázar, Rubén; Cuevas, Juan C; Planas, Joan; Zarza, Xavier; Bortolotti, Cristina; Carrasco, Pedro; Salinas, Julio; Tiburcio, Antonio F; Altabella, Teresa

    2011-01-01

    Temperature is one of the most important environmental factors limiting the geographical distribution of plants and accounts for significant reductions in the yield of agriculturally important crops. Low temperature damages many plant species, especially those adapted to tropical climates. In contrast, some species from temperate regions are able to develop freezing tolerance in response to low-non-freezing temperature, an adaptive process named cold acclimation. Numerous molecular, biochemical and physiological changes occur during cold acclimation, most of them being associated with significant changes in gene expression and metabolite profiles. During recent years, transcriptomic and metabolomic approaches have allowed the identification of cold-responsive genes and main metabolites which accumulate in plants exposed to cold. The obtained data support the previously held idea that polyamines (PAs) are involved in plant responses to cold, although their specific role is still not well understood. In this review, we synthesize published data regarding PA-responses to cold stress and integrate them with global transcriptional and metabolic changes. The potential of PA genetic engineering for the development of plants resistant to cold and freezing temperatures, and their plausible mechanisms of action are also discussed. PMID:21421344

  16. Growth of the C4 dicot Flaveria bidentis: photosynthetic acclimation to low light through shifts in leaf anatomy and biochemistry

    PubMed Central

    Pengelly, Jasper J. L.; Sirault, Xavier R. R.; Tazoe, Youshi; Evans, John R.; Furbank, Robert T.; von Caemmerer, Susanne

    2010-01-01

    In C4 plants, acclimation to growth at low irradiance by means of anatomical and biochemical changes to leaf tissue is considered to be limited by the need for a close interaction and coordination between bundle sheath and mesophyll cells. Here differences in relative growth rate (RGR), gas exchange, carbon isotope discrimination, photosynthetic enzyme activity, and leaf anatomy in the C4 dicot Flaveria bidentis grown at a low (LI; 150 μmol quanta m2 s−1) and medium (MI; 500 μmol quanta m2 s−1) irradiance and with a 12 h photoperiod over 36 d were examined. RGRs measured using a 3D non-destructive imaging technique were consistently higher in MI plants. Rates of CO2 assimilation per leaf area measured at 1500 μmmol quanta m2 s−1 were higher for MI than LI plants but did not differ on a mass basis. LI plants had lower Rubisco and phosphoenolpyruvate carboxylase activities and chlorophyll content on a leaf area basis. Bundle sheath leakiness of CO2 (ϕ) calculated from real-time carbon isotope discrimination was similar for MI and LI plants at high irradiance. ϕ increased at lower irradiances, but more so in MI plants, reflecting acclimation to low growth irradiance. Leaf thickness and vein density were greater in MI plants, and mesophyll surface area exposed to intercellular airspace (Sm) and bundle sheath surface area per unit leaf area (Sb) measured from leaf cross-sections were also both significantly greater in MI compared with LI leaves. Both mesophyll and bundle sheath conductance to CO2 diffusion were greater in MI compared with LI plants. Despite being a C4 species, F. bidentis is very plastic with respect to growth irradiance. PMID:20693408

  17. Host and parasite thermal acclimation responses depend on the stage of infection.

    PubMed

    Altman, Karie A; Paull, Sara H; Johnson, Pieter T J; Golembieski, Michelle N; Stephens, Jeffrey P; LaFonte, Bryan E; Raffel, Thomas R

    2016-07-01

    Global climate change is expected to alter patterns of temperature variability, which could influence species interactions including parasitism. Species interactions can be difficult to predict in variable-temperature environments because of thermal acclimation responses, i.e. physiological changes that allow organisms to adjust to a new temperature following a temperature shift. The goal of this study was to determine how thermal acclimation influences host resistance to infection and to test for parasite acclimation responses, which might differ from host responses in important ways. We tested predictions of three, non-mutually exclusive hypotheses regarding thermal acclimation effects on infection of green frog tadpoles (Lithobates clamitans) by the trematode parasite Ribeiroia ondatrae with fully replicated controlled-temperature experiments. Trematodes or tadpoles were independently acclimated to a range of 'acclimation temperatures' prior to shifting them to new 'performance temperatures' for experimental infections. Trematodes that were acclimated to intermediate temperatures (19-22 °C) had greater encystment success across temperatures than either cold- or warm-acclimated trematodes. However, host acclimation responses varied depending on the stage of infection (encystment vs. clearance): warm- (22-28 °C) and cold-acclimated (13-19 °C) tadpoles had fewer parasites encyst at warm and cold performance temperatures, respectively, whereas intermediate-acclimated tadpoles (19-25 °C) cleared the greatest proportion of parasites in the week following exposure. These results suggest that tadpoles use different immune mechanisms to resist different stages of trematode infection, and that each set of mechanisms has unique responses to temperature variability. Our results highlight the importance of considering thermal responses of both parasites and hosts when predicting disease patterns in variable-temperature environments. PMID:27040618

  18. BOREAS TE-9 NSA Photosynthetic Response Data

    NASA Technical Reports Server (NTRS)

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

    2000-01-01

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

  19. Deconditioning-induced exercise responses as influenced by heat acclimation

    NASA Technical Reports Server (NTRS)

    Shvartz, E.; Bhattacharya, A.; Sperinde, S. J.; Brock, P. J.; Sciaraffa, D.; Haines, R. F.; Greenleaf, J. E.

    1979-01-01

    A study to determine the effect of heat acclimation and physical training in temperate conditions on changes in exercise tolerance following water-immersion deconditioning is presented. Five young men were tested on a bicycle ergometer before and after heat acclimation and after water immersion. The subjects and the experimental procedure, heat acclimation and exercise training, water immersion, and exercise tolerance are discussed. Heat acclimation resulted in the usual decreases in exercise heart rate and rectal temperature and an increase in sweat rate. Water immersion resulted in substantial diuresis despite water consumed. The results show that heat acclimation provides an effective method of preventing the adverse effects of water-immersion deconditioning on exercise tolerance.

  20. The low temperature response pathways for cold acclimation and vernalization are independent.

    PubMed

    Bond, Donna M; Dennis, Elizabeth S; Finnegan, E Jean

    2011-10-01

    Vernalization is the promotion of flowering in response to the prolonged cold of winter. To survive sub-zero winter temperatures, plants must first acclimate to low, non-freezing temperatures (cold acclimation). Induction of VERNALIZATION INSENSITIVE 3 (VIN3), the first gene in the vernalization pathway, is initiated within the same time frame as the induction of genes in the cold acclimation pathway raising the question of whether there are common elements in the signal transduction pathways that activate these two responses to cold. We show that none of the signalling components required for cold acclimation, including the 'master regulator'INDUCTION OF CBF EXPRESSION1 (ICE1) or HIGH EXPRESSION OF OSMOTICALLY RESPONSIVE GENE1 (HOS1), which has been described as a link between cold acclimation and vernalization, play a role in VIN3 induction. We also show that the hormone abscisic acid (ABA) does not modulate VIN3 induction, consistent with earlier reports that ABA signalling plays no role in the vernalization response. The cold acclimation pathway is activated at 12 °C, at which temperature there is no induction of VIN3 expression. Taken together, our data demonstrate that the responses to low temperatures leading to cold acclimation and vernalization are controlled by distinct signalling pathways. PMID:21631537

  1. Temperature response of Antarctic cryptoendolithic photosynthetic microorganisms

    NASA Technical Reports Server (NTRS)

    Ocampo-Friedmann, R.; Meyer, M. A.; Chen, M.; Friedmann, E. I.

    1988-01-01

    Growth responses to temperatures between 12.5 [degrees] C and 25 degrees C were determined for five photosynthetic microorganisms isolated from the Ross Desert cryptoendolithic community. Among eukaryotic algae, two strains of Trebouxia sp. have an upper temperature limit of 20 degrees C, and two strains of Hemichloris antarctica of 25 degrees C. The cyanobacterium Chroococcidiopsis sp., in contrast, grows at temperatures above 25 degrees C. These and earlier studies suggest that the eukaryotic algae of the Antarctic cryptoendolithic community have an upper temperature limit near 25 degrees C.

  2. Balancing photosynthetic light-harvesting and light-utilization capacities in potato leaf tissue during acclimation to different growth temperatures

    NASA Technical Reports Server (NTRS)

    Steffen, K. L.; Wheeler, R. M.; Arora, R.; Palta, J. P.; Tibbitts, T. W.

    1995-01-01

    We investigated the effect of temperature during growth and development on the relationship between light-harvesting capacity, indicated by chlorophyll concentration, and light-utilization potential, indicated by light- and bicarbonate-saturated photosynthetic oxygen evolution, in Solanum tuberosum L. cv. Norland. Clonal plantlets were transplanted and grown at 20 degrees C for 2 weeks before transfer to 12, 16, 20, 24 and 28 degrees C for 6 weeks. After 4 weeks of the temperature treatments, leaf tissue fresh weights per area were one-third higher in plants grown at 12 degrees C vs those grown at 28 degrees C. Conversely, chlorophyll content per area in tissue grown at 12 degrees C was less than one-half of that of tissue grown at 28 degrees C at 4 weeks. Photosynthetic capacity measured at a common temperature of 20 degrees C and expressed on a chlorophyll basis was inversely proportional to growth temperature. Leaf tissue from plants grown at 12 degrees C for 4 weeks had photosynthetic rates that were 3-fold higher on a chlorophyll basis than comparable tissue from plants grown at 28 degrees C. These results suggest that the relationship between light-harvesting capacity and light-utilization potential varies 3-fold in response to the growth temperatures examined. The role of this response in avoidance of photoinhibition is discussed.

  3. Thermal responses of Symbiodinium photosynthetic carbon assimilation

    NASA Astrophysics Data System (ADS)

    Oakley, Clinton A.; Schmidt, Gregory W.; Hopkinson, Brian M.

    2014-06-01

    The symbiosis between hermatypic corals and their dinoflagellate endosymbionts, genus Symbiodinium, is based on carbon exchange. This symbiosis is disrupted by thermally induced coral bleaching, a stress response in which the coral host expels its algal symbionts as they become physiologically impaired. The disruption of the dissolved inorganic carbon (DIC) supply or the thermal inactivation of Rubisco have been proposed as sites of initial thermal damage that leads to the bleaching response. Symbiodinium possesses a highly unusual Form II ribulose bisphosphate carboxylase/oxygenase (Rubisco), which exhibits a lower CO2:O2 specificity and may be more thermally unstable than the Form I Rubiscos of other algae and land plants. Components of the CO2 concentrating mechanism (CCM), which supplies inorganic carbon for photosynthesis, may also be temperature sensitive. Here, we examine the ability of four cultured Symbiodinium strains to acquire and fix DIC across a temperature gradient. Surprisingly, the half-saturation constant of photosynthesis with respect to DIC concentration ( K P), an index of CCM function, declined with increasing temperature in three of the four strains, indicating a greater potential for photosynthetic carbon acquisition at elevated temperatures. In the fourth strain, there was no effect of temperature on K P. Finding no evidence for thermal inhibition of the CCM, we conclude that CCM components are not likely to be the primary sites of thermal damage. Reduced photosynthetic quantum yields, a hallmark of thermal bleaching, were observed at low DIC concentrations, leaving open the possibility that reduced inorganic carbon availability is involved in bleaching.

  4. Global transcriptome analyses provide evidence that chloroplast redox state contributes to intracellular as well as long-distance signalling in response to stress and acclimation in Arabidopsis.

    PubMed

    Bode, Rainer; Ivanov, Alexander G; Hüner, Norman P A

    2016-06-01

    Global transcriptome analyses were used to assess the interactive effects of short-term stress versus long-term acclimation to high light (HL), low temperature (LT) and excitation pressure in Arabidopsis. Microarray analyses indicated that exposure to stress resulted in two times as many modulated transcripts in both, high-light-treated and low-temperature-treated plants, compared to plants that were fully acclimated to either one of these conditions. We showed that 10.9 % of all transcripts were regulated in the same way by both stress conditions, and hence, were categorized as excitation pressure regulated, rather than regulated by either high-light or low-temperature stress per se. This group of chloroplast redox-sensitive genes included various photosynthetic genes as well as genes known to be associated with cold acclimation (cbf3, cor15A, cor15B) and gibberellic acid (GA) metabolism and signalling (ga2ox1, gai). Chemical inhibition of the photosynthetic electron transport by either DCMU or DBMIB indicated that although the plastoquinone pool contributes significantly to redox regulation of the transcriptome (8.6 %), it appears that PSI represents the major source of redox signals (89 %), whereas PSII appears to contribute only 3.1 %. A comparison of the gene expression profiles between stress and acclimated plants indicated that 10 % of the genes induced by a short, 1-h stress were also associated with long-term acclimation to high excitation pressure. This included the APETALA2/ETHYLENE-RESPONSIVE-BINDING PROTEIN family, the MYB domain- and MYB-related transcription factor family as well as the GRAS transcription factor family important in GA signalling confirming that acclimation to stress is a time-nested phenomenon. We suggest that acclimation to photosynthetic redox imbalance extends beyond the chloroplast and the leaf cell to systemic ROS signalling. This is discussed in terms of the control of plant phenotype through regulation of the nuclear

  5. Cotton growth and photosynthetic acclimation to phosphorus nutrition and CO2 enrichment

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Two experiments were conducted in 2011 to study cotton response to varying phosphorus (P) supply under current and projected atmospheric CO2 concentrations. Cotton (cultivar deltapine 555) plants were grown in six growth chambers with three levels of P supply (0.2 (optimum), 0.05 and 0.01 mM) and tw...

  6. Family origin and the response of threespine stickleback, Gasterosteus aculeatus, to thermal acclimation.

    PubMed

    Guderley, H; Leroy, P H

    2001-03-01

    To establish whether family origin affects the response of the threespine stickleback (Gasterosteus aculeatus) to thermal acclimation, we examined the rates of feeding, growth, and food conversion, relative tissue and organ masses and activities of a mitochondrial and a glycolytic enzyme in pectoral and axial muscle of individually housed fish from six families during acclimation to 8 degrees C and 23 degrees C. Feeding rates differed among families but were consistently higher in warm-acclimated than cold-acclimated fish. Growth rates differed among families. In four families growth was greater at 8 degrees C; these families generally had higher conversion efficiencies at 8 degrees C than 23 degrees C. For two families, growth was greater at 23 degrees C than 8 degrees C and conversion efficiencies did not differ between 8 degrees C and 23 degrees C. Relative tissue and organ masses (percent axial muscle, hepatosomatic, gut and kidney indices) differed with gender and among families (hepatosomatic, gut and kidney indices) but little with acclimation status. In all families and in both muscles, activities of the mitochondrial enzyme, citrate synthase (CS), were increased by cold acclimation. Axial muscle levels of the glycolytic enzyme, lactate dehydrogenase (LDH), were not affected by thermal acclimation or family origin, but were strongly correlated with the hepatosomatic index and axial muscle protein content. Pectoral muscle levels of LDH were affected by family origin which also influenced the response to thermal acclimation. Similar patterns were observed for specific activities and total muscle contents of these enzymes. Stickleback family origin influenced rates of feeding and growth and the thermal sensitivity of growth rates but not the compensatory increase in muscle CS levels with cold acclimation. The differing thermal sensitivities of growth could reflect distinct strategies for the timing of juvenile growth. PMID:11302536

  7. Photosynthetic acclimation to drought stress in Agave salmiana Otto ex Salm-Dyck seedlings is largely dependent on thermal dissipation and enhanced electron flux to photosystem I.

    PubMed

    Campos, Huitziméngari; Trejo, Carlos; Peña-Valdivia, Cecilia B; García-Nava, Rodolfo; Conde-Martínez, F Víctor; Cruz-Ortega, Ma Del Rocío

    2014-10-01

    Agave salmiana Otto ex Salm-Dyck, a crassulacean acid metabolism plant that is adapted to water-limited environments, has great potential for bioenergy production. However, drought stress decreases the requirement for light energy, and if the amount of incident light exceeds energy consumption, the photosynthetic apparatus can be injured, thereby limiting plant growth. The objective of this study was to evaluate the effects of drought and re-watering on the photosynthetic efficiency of A. salmiana seedlings. The leaf relative water content and leaf water potential decreased to 39.6 % and -1.1 MPa, respectively, over 115 days of water withholding and recovered after re-watering. Drought caused a direct effect on photosystem II (PSII) photochemistry in light-acclimated leaves, as indicated by a decrease in the photosynthetic electron transport rate. Additionally, down-regulation of photochemical activity occurred mainly through the inactivation of PSII reaction centres and an increased thermal dissipation capacity of the leaves. Prompt fluorescence kinetics also showed a larger pool of terminal electron acceptors in photosystem I (PSI) as well as an increase in some JIP-test parameters compared to controls, reflecting an enhanced efficiency and specific fluxes for electron transport from the plastoquinone pool to the PSI terminal acceptors. All the above parameters showed similar levels after re-watering. These results suggest that the thermal dissipation of excess energy and the increased energy conservation from photons absorbed by PSII to the reduction of PSI end acceptors may be an important acclimation mechanism to protect the photosynthetic apparatus from over-excitation in Agave plants. PMID:24798124

  8. Ecological Acclimation and Hydrologic Response: Problem Complexity and Modeling Challenges

    NASA Astrophysics Data System (ADS)

    Kumar, P.; Srinivasan, V.; Le, P. V. V.; Drewry, D.

    2012-04-01

    Elevated CO2 in the atmosphere leads to a number of acclimatory responses in different vegetation types. These may be characterized as structural such as vegetation height or foliage density, ecophysiological such as reduction in stomatal conductance, and biochemical such as photosynthetic down-regulation. Furthermore, the allocation of assimilated carbon to different vegetation parts such as leaves, roots, stem and seeds is also altered such that empirical allometric relations are no longer valid. The extent and nature of these acclimatory responses vary between C3 and C4 vegetation and across species. These acclimatory responses have significant impact on hydrologic fluxes both pertaining to water and energy with the possibility of large-scale hydrologic influence. Capturing the pathways of acclimatory response to provide accurate ecohydrologic response predictions requires incorporating subtle relationships that are accentuated under elevated CO2. The talk will discuss the challenges of modeling these as well as applications to soybean, maize and bioenergy crops such as switchgrass and miscanthus.

  9. Photosynthetic acclimation to photon irradiance and its relation to chlorophyll fluorescence and carbon assimilation in the halotolerant green alga Dunaliella viridis.

    PubMed

    Gordillo, F J; Jiménez, C; Chavarría, J; Xavier Niell, F

    2001-01-01

    This work describes the long-term acclimation of the halotolerant microalga Dunaliella viridis to different photon irradiance, ranging from darkness to 1500 mumol m(-2) s(-1). In order to assess the effects of long-term photoinhibition, changes in oxygen production rate, pigment composition, xanthophyll cycle and in vivo chlorophyll fluorescence using the saturating pulse method were measured. Growth rate was maximal at intermediate irradiance (250 and 700 mumol m(-2) s(-1)). The increase in growth irradiance from 700 to 1500 mumol m(-2) s(-1) did not lead to further significant changes in pigment composition or EPS, indicating saturation in the pigment response to high light. Changes in Photosystem II optimum quantum yield (F(v)/F(m)) evidenced photoinhibition at 700 and especially at 1500 mumol m(-2) s(-1). The relation between photosynthetic electron flow rate and photosyntetic O(2) evolution was linear for cultures in darkness shifting to curvilinear as growth irradiance increased, suggesting the interference of the energy dissipation processes in oxygen evolution. Carbon assimilation efficiencies were studied in relation to changes in growth rate, internal carbon and nitrogen composition, and organic carbon released to the external medium. All illuminated cultures showed a high capability to maintain a C:N ratio between 6 and 7. The percentage of organic carbon released to the external medium increased to its maximum under high irradiance (1500 mumol m(-2) s(-1)). These results suggest that the release of organic carbon could act as a secondary dissipation process when the xanthophyll cycle is saturated. PMID:16228345

  10. The Acclimation of Phaeodactylum tricornutum to Blue and Red Light Does Not Influence the Photosynthetic Light Reaction but Strongly Disturbs the Carbon Allocation Pattern

    PubMed Central

    Jungandreas, Anne; Schellenberger Costa, Benjamin; Jakob, Torsten; von Bergen, Martin; Baumann, Sven; Wilhelm, Christian

    2014-01-01

    Diatoms are major contributors to the aquatic primary productivity and show an efficient acclimation ability to changing light intensities. Here, we investigated the acclimation of Phaeodactylum tricornutum to different light quality with respect to growth rate, photosynthesis rate, macromolecular composition and the metabolic profile by shifting the light quality from red light (RL) to blue light (BL) and vice versa. Our results show that cultures pre-acclimated to BL and RL exhibited similar growth performance, photosynthesis rates and metabolite profiles. However, light shift experiments revealed rapid and severe changes in the metabolite profile within 15 min as the initial reaction of light acclimation. Thus, during the shift from RL to BL, increased concentrations of amino acids and TCA cycle intermediates were observed whereas during the BL to RL shift the levels of amino acids were decreased and intermediates of glycolysis accumulated. Accordingly, on the time scale of hours the RL to BL shift led to a redirection of carbon into the synthesis of proteins, whereas during the BL to RL shift an accumulation of carbohydrates occurred. Thus, a vast metabolic reorganization of the cells was observed as the initial reaction to changes in light quality. The results are discussed with respect to a putative direct regulation of cellular enzymes by light quality and by transcriptional regulation. Interestingly, the short-term changes in the metabolome were accompanied by changes in the degree of reduction of the plastoquinone pool. Surprisingly, the RL to BL shift led to a severe inhibition of growth within the first 48 h which was not observed during the BL to RL shift. Furthermore, during the phase of growth arrest the photosynthetic performance did not change. We propose arguments that the growth arrest could have been caused by the reorganization of intracellular carbon partitioning. PMID:25111046

  11. Orthostatic responses to dietary sodium restriction during heat acclimation

    NASA Technical Reports Server (NTRS)

    Szlyk, Patricia C.; Sils, Ingrid V.; Caretti, David M.; Moore, Robert J.; Armstrong, Lawrence E.; Tartarini, Kim A.; Francesconi, Ralph P.; Askew, Eldon W.; Hubbard, Roger W.

    1994-01-01

    Several studies have shown that individuals consuming low-salt diets and working in the heat have an increased risk or incidence of heat injury, suggestive of inadequate cardiovascular adjustment. Furthermore, others have shown that prolonged work in hot climates can precipitate orthostatic hypotension and syncope. This study was designed to evaluate the effects of moderate-salt (MS) and low-salt (LS) diets on the circulatory responses and incidence of presyncopal symptoms to an orthostatic test (OT) during successive days of heat acclimation (HA). Seventeen unacclimatized male soldiers (mean +/- SE: age 20+/-1 yrs) participated in this two-phase study. The first phase consisted of a seven day dietary stabilization period during which all subjects consumed similar diets of about 4000 kcal/day containing 8g NaCl and lived in a dormitory setting (21 C, 30% RH). The second phase commenced on day eight and consisted of dietary NaCl restriction and 10 days HA (days 8-17). Volunteers were randomly assigned to either the MS diet (n=9) providing 8g NaCl/day or the LS diet (n=8) furnishing just 4g NaCl/day. The acquisition of HA was manifested in both groups by reductions in exercising rectal temperature and heart rate (HR); these characteristics were similar in the MS and LS diets. The OT was performed at 21 C on day seven of the stabilization phase and on days 9, 11, 13, 15, and 17 of the HA phase, before and after 8.5 hr of intermittent treadmill walking in a hot environment. Blood pressure (BP) and HR responses at 1,2, and 4 min and any presyncopal symptoms were recorded after assuming an upright position from recumbency. All subjects completed the OT before and after prolonged exercise in the heat without incidence of either hypotension or presyncopal symptoms irrespective of dietary-salt intake and day of HA. The results indicate that the prolonged work in the heat can be performed without orthostatic hypotension or syncope while consuming 4g NaCl/day with adequate

  12. Cold acclimation is accompanied by complex responses of glycosylphosphatidylinositol (GPI)-anchored proteins in Arabidopsis

    PubMed Central

    Takahashi, Daisuke; Kawamura, Yukio; Uemura, Matsuo

    2016-01-01

    Cold acclimation results in changes of the plasma membrane (PM) composition. The PM is considered to contain specific lipid/protein-enriched microdomains which can be extracted as detergent-resistant plasma membrane (DRM). Previous studies in animal cells have demonstrated that glycosylphosphatidylinositol-anchored proteins (GPI-APs) can be targeted to microdomains and/or the apoplast. However, the functional significance of GPI-APs during cold acclimation in plants is not yet fully understood. In this study, we aimed to investigate the responsiveness of GPI-APs to cold acclimation treatment in Arabidopsis. We isolated the PM, DRM, and apoplast fractions separately and, in addition, GPI-AP-enriched fractions were prepared from the PM preparation. Label-free quantitative shotgun proteomics identified a number of GPI-APs (163 proteins). Among them, some GPI-APs such as fasciclin-like arabinogalactan proteins and glycerophosphoryldiester phosphodiesterase-like proteins predominantly increased in PM- and GPI-AP-enriched fractions while the changes of GPI-APs in the DRM and apoplast fractions during cold acclimation were considerably different from those of other fractions. These proteins are thought to be associated with cell wall structure and properties. Therefore, this study demonstrated that each GPI-AP responded to cold acclimation in a different manner, suggesting that these changes during cold acclimation are involved in rearrangement of the extracellular matrix including the cell wall towards acquisition of freezing tolerance. PMID:27471282

  13. Cold acclimation is accompanied by complex responses of glycosylphosphatidylinositol (GPI)-anchored proteins in Arabidopsis.

    PubMed

    Takahashi, Daisuke; Kawamura, Yukio; Uemura, Matsuo

    2016-09-01

    Cold acclimation results in changes of the plasma membrane (PM) composition. The PM is considered to contain specific lipid/protein-enriched microdomains which can be extracted as detergent-resistant plasma membrane (DRM). Previous studies in animal cells have demonstrated that glycosylphosphatidylinositol-anchored proteins (GPI-APs) can be targeted to microdomains and/or the apoplast. However, the functional significance of GPI-APs during cold acclimation in plants is not yet fully understood. In this study, we aimed to investigate the responsiveness of GPI-APs to cold acclimation treatment in Arabidopsis We isolated the PM, DRM, and apoplast fractions separately and, in addition, GPI-AP-enriched fractions were prepared from the PM preparation. Label-free quantitative shotgun proteomics identified a number of GPI-APs (163 proteins). Among them, some GPI-APs such as fasciclin-like arabinogalactan proteins and glycerophosphoryldiester phosphodiesterase-like proteins predominantly increased in PM- and GPI-AP-enriched fractions while the changes of GPI-APs in the DRM and apoplast fractions during cold acclimation were considerably different from those of other fractions. These proteins are thought to be associated with cell wall structure and properties. Therefore, this study demonstrated that each GPI-AP responded to cold acclimation in a different manner, suggesting that these changes during cold acclimation are involved in rearrangement of the extracellular matrix including the cell wall towards acquisition of freezing tolerance. PMID:27471282

  14. Acclimation of photosynthesis to temperature in Arabidopsis thaliana and Brassica oleracea

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Plants differ in how much the response of photosynthesis to temperature changes with the temperature during leaf development, and also in the biochemical basis of such changes in photosynthetic response. The amount of photosynthetic acclimation to temperature and the components of the photosyntheti...

  15. Physiological responses during short-term acclimation to increasing atmospheric CO2 concentration in Pinus nigra

    NASA Astrophysics Data System (ADS)

    Maseyk, K. S.; Biron, P.; Richard, P.; Canale, L.; Bariac, T.

    2010-12-01

    atmospheric CO2, but were still ~40% higher at 800 ppm compared to 380 ppm. Stomatal conductance varied little in response to leaf-level changes in CO2 concentration but decreased overall by about 30% with increasing ambient CO2. Consequently the acclimated intrinsic water-use efficiency (A/gs) increased by 125% with CO2, or 20% more than predicted from the instantaneous measurements. Measurements of the chamber air CO2 isotopic composition (13C/12C) also indicated decreasing photosynthetic discrimination against 13CO2, consistent with the increase in water use efficiency, and is being checked with analysis of the leaf sugar isotopic composition. Transpiration trends were consistent between leaf-level and total canopy measurements, but did not show a clear trend with CO2 due to concurrent increases in leaf temperature and leaf-atmosphere vapour pressure deficit. These results possibly indicate interactions with stomatal conductance that result in constant total plant water use, but increasing transpiration ratio (A/E), with increasing CO2. Likewise, there was little increase in the evaporative enrichment of leaf water isotopic composition (18O/16O), despite the changes in stomatal conductance.

  16. Heat Acclimation and Water-Immersion Deconditioning: Responses to Exercise

    NASA Technical Reports Server (NTRS)

    Shvartz, E.; Bhattacharya, A.; Sperinde, S. J.; Brock, P. J.; Sciaraffa, D.; Haines, R. F.; Greenleaf, J. E.

    1977-01-01

    Simulated subgravity conditions, such as bed rest and water immersion, cause a decrease in a acceleration tolerance (3, 4), tilt tolerance (3, 9, 10), work capacity (5, 7), and plasma volume (1, 8-10). Moderate exercise training performed during bed rest (4) and prior to water immersion (5) provides some protection against the adverse effects of deconditioning, but the relationship between exercise and changes due to deconditioning remains unclear. Heat acclimation increases plasma and interstitial volumes, total body water, stroke volume (11), and tilt tolerance (6) and may, therefore, be a more efficient method of ameliorating deconditioning than physical training alone. The present study was undertaken to determine the effects of heat acclimation and moderate physical training, performed in cool conditions, on water-immersion deconditioning.

  17. No effects of acclimation to heat on immune and hormonal responses to passive heating in healthy volunteers

    NASA Astrophysics Data System (ADS)

    Kanikowska, Dominika; Sato, Maki; Sugenoya, Junichi; Iwase, Satoshi; Shimizu, Yuuki; Nishimura, Naoki; Inukai, Yoko

    2012-01-01

    Heat acclimation results in whole body-adaptations that increase heat tolerance, and might also result in changed immune responses. We hypothesized that, after heat acclimation, tumor necrosis factor alpha, interleukin 6 and the lymphocyte count would be altered. Heat acclimation was induced in 6 healthy men by 100 min of heat exposure for 9 days. Heat exposure consisted of (1) 10 min of immersion up to chest-level in water at 42°C and (2) 90 min of passive heating by a warm blanket to maintain tympanic temperature at 37.5°C. The climatic chamber was maintained at 40°C and a relative humidity of 50%. Blood samples were analyzed before and after heat acclimation for natural killer (NK) cell activity, counts of lymphocytes B and T, before and after heat acclimation for peripheral blood morphology, interleukin 6, tumor necrosis factor alpha, and cortisol. A Japanese version of the profile of mood states questionnaire was also administered before and after acclimation. The concentrations of white blood cells, lymphocytes B and T, cortisol, interleukin 6, tumor necrosis factor alpha and NK cell activity showed no significant differences between pre- and post-acclimation, but there was a significantly lower platelet count after acclimation and, with the profile of mood states questionnaire, there was a significant rise in anger after acclimation. It is concluded that heat acclimation by passive heating does not induce alterations in immune or endocrine responses.

  18. Time course of the response of mitochondria from oxidative muscle during thermal acclimation of rainbow trout, Oncorhynchus mykiss.

    PubMed

    Bouchard, Patrice; Guderley, Helga

    2003-10-01

    The time course of changes in the properties of mitochondria from oxidative muscle of rainbow trout was examined during warm (15 degrees C) and cold (5 degrees C) acclimation. Mitochondrial oxidative capacities showed a biphasic response during thermal acclimation: at a given assay temperature, capacities first increased and then decreased during warm acclimation and showed the inverse pattern during cold acclimation. This was most apparent for maximal rates of state 3 oxygen consumption expressed per mg mitochondrial protein. Rates expressed per nmol ADP-ATP translocase (ANT) showed this pattern during cold acclimation. A biphasic pattern was also apparent for state 4 and oligomycin-inhibited (state 4(ol)) rates of oxygen uptake expressed per mg protein. Changes in states 4 and 4(ol) were smaller during cold than warm acclimation. Warm acclimation reduced the proportion of cytochrome c oxidase and citrate synthase needed during mitochondrial substrate oxidation. Phospholipid concentrations per mg mitochondrial protein changed little with thermal acclimation. Mitochondrial properties changed more quickly during warm than cold acclimation. While the biochemical modifications during thermal acclimation may eventually compensate for the thermal change, compensation did not occur at its onset. Rather, the initial changes of mitochondrial oxidative capacity in response to temperature change accentuated the functional impact of the thermal change, and prolonged exposure to the new temperature was required to attain a degree of thermal compensation. PMID:12939376

  19. Responses to iron limitation are impacted by light quality and regulated by RcaE in the chromatically acclimating cyanobacterium Fremyella diplosiphon.

    PubMed

    Pattanaik, Bagmi; Busch, Andrea W U; Hu, Pingsha; Chen, Jin; Montgomery, Beronda L

    2014-05-01

    Photosynthetic organisms adapt to environmental fluctuations of light and nutrient availability. Iron is critical for photosynthetic organismal growth, as many cellular processes depend upon iron cofactors. Whereas low iron levels can have deleterious effects, excess iron can lead to damage, as iron is a reactive metal that can result in the production of damaging radicals. Therefore, organisms regulate cellular iron levels to maintain optimal iron homeostasis. In particular, iron is an essential factor for the function of photosystems associated with photosynthetic light-harvesting complexes. Photosynthetic organisms, including cyanobacteria, generally respond to iron deficiency by reduced growth, degradation of non-essential proteins and in some cases alterations of cellular morphology. In response to fluctuations in ambient light quality, the cyanobacterium Fremyella diplosiphon undergoes complementary chromatic adaptation (CCA). During CCA, phycobiliprotein composition of light-harvesting antennae is altered in response to green light (GL) and red light (RL) for efficient utilization of light energy for photosynthesis. We observed light-regulated responses to iron limitation in F. diplosiphon. RL-grown cells exhibited significant reductions in growth and pigment levels, and alterations in iron-associated proteins, which impact the accumulation of reactive oxygen species under iron-limiting conditions, whereas GL-grown cells exhibited partial resistance to iron limitation. We investigated the roles of known CCA regulators RcaE, RcaF and RcaC in this light-dependent iron-acclimation response. Through comparative analyses of wild-type and CCA mutant strains, we determined that photoreceptor RcaE has a central role in light-induced oxidative stress associated with iron limitation, and impacts light-regulated iron-acclimation responses, physiologically and morphologically. PMID:24623652

  20. Temperature response of photosynthetic light- and carbon-use characteristics in the red seaweed Gracilariopsis lemaneiformis (Gracilariales, Rhodophyta).

    PubMed

    Zou, Dinghui; Gao, Kunshan

    2014-04-01

    The red seaweed Gracilariopsis is an important crop extensively cultivated in China for high-quality raw agar. In the cultivation site at Nanao Island, Shantou, China, G. lemaneiformis experiences high variability in environmental conditions like seawater temperature. In this study, G. lemaneiformis was cultured at 12, 19, or 26°C for 3 weeks, to examine its photosynthetic acclimation to changing temperature. Growth rates were highest in G. lemaneiformis thalli grown at 19°C, and were reduced with either decreased or increased temperature. The irradiance-saturated rate of photosynthesis (Pmax ) decreased with decreasing temperature, but increased significantly with prolonged cultivation at lower temperatures, indicating the potential for photosynthesis acclimation to lower temperature. Moreover, Pmax increased with increasing temperature (~30 μmol O2  · g(-1) FW · h(-1) at 12°C to 70 μmol O2  · g(-1) FW · h(-1) at 26°C). The irradiance compensation point for photosynthesis (Ic ) decreased significantly with increasing temperature (28 μmol photons · m(-2)  · s(-1) at high temperature vs. 38 μmol photons · m(-2)  · s(-1) at low temperature). Both the photosynthetic light- and carbon-use efficiencies increased with increasing growth or temperatures (from 12°C to 26°C). The results suggested that the thermal acclimation of photosynthetic performance of G. lemaneiformis would have important ecophysiological implications in sea cultivation for improving photosynthesis at low temperature and maintaining high standing biomass during summer. Ongoing climate change (increasing atmospheric CO2 and global warming) may enhance biomass production in G. lemaneiformis mariculture through the improved photosynthetic performances in response to increasing temperature. PMID:26988193

  1. Photosynthetic acclimation to elevated CO{sub 2} occurs in transformed tobacco with decreased ribulose-1,5-bisphosphate carboxylase/oxygenase content

    SciTech Connect

    Sicher, R.C.; Kremer, D.F.; Rodermel, S.R.

    1994-02-01

    Inhibition of net carbon assimilation rates during growth at elevated CO{sub 2} was studied in transgenic tobacco (Nicotiana tabacum L.) plants containing zero to two copies of antisense DNA sequences to the small subunit polypeptide (rbcS) gene of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco). High- and low-Rubisco tobacco plants were obtained from the selfed progeny of the original line 3 transformant. Assimilation rates of high- and low-Rubisco tobacco plants increased 22 and 71%, respectively, when transferred from 35- to 70-Pa CO{sub 2} chamber air at 900 {mu}mol m{sup -2} s{sup -1} photon flux density. However, CO{sub 2}-dependent increases of net carbon assimilation rates of high- and low-Rubisco plants virtually disappeared after 9 d of growth in elevated CO{sub 2} chamber air. Total above-ground dry matter production of high- and low-Rubisco plants was 28 and 53% greater, respectively, after 9 d of growth at 70 Pa compared with 35 Pa CO{sub 2}. Most of this dry weight gain was due to increased specific leaf weight. Rubisco activity, Rubisco protein, and total chlorophyll were lower in both high- and low-Rubisco plants grown in enriched compared with ambient CO{sub 2} chamber air. Soluble leaf protein also decreased in response to CO{sub 2} enrichment in high- but not in low-Rub tobacco plants. Decreased Rubisco activities in CO{sub 2}adapted high- and low-Rubisco plants were not attributable to changes in activation state of the enzyme. Carbonic anhydrase activities and subunit levels measured with specific antibodies were similar in high- and low-Rubisco tobacco plants and were unchanged by CO{sub 2} enrichment. Collectively, these findings suggested that photosynthetic acclimation to enriched CO{sub 2} occurred in tobacco plants either with or without transgenically decreased Rubisco in CO{sub 2}-adapted tobacco plants was related to decreased specific activity of this enzyme. 35 refs., 2 figs., 1 tab.

  2. Anatomic and metabolic responses to thermal acclimation in the ninespine stickleback, Pungitius pungitius.

    PubMed

    Guderley, H; Foley, L

    1990-11-01

    Male ninespine sticklebacks, Pungitius pungitius, acclimated to 3°C have higher activities of mitochondrial enzymes in their axial muscles than males acclimated to 20°C. Phosphofructokinase and pyruvate kinase activities tended to be higher in cold than warm acclimated males. For females, warm acclimation tended to decrease only mitochondrial enzyme activities. As thermal acclimation did not change the physical condition and most anatomic parameters of the sticklebacks, the enzymatic changes do not seem due to mobilization of somatic reserves. Field acclimatization to warm temperatures led to a marked decrease in physical condition in both males and females. This decrease in physical condition could largely be attributed to atrophy of the carcass mass. Spring males had higher activities of phosphofructokinase, citrate synthase and cytochrome oxidase in the axial muscle than summer males. Again, females showed a less marked response. These data suggest that environmental temperature is a major determinant of muscle aerobic capacity, at least for male ninespine sticklebacks. Thus, these northern temperate zone fish retain the capacity for thermal compensation, much like their temperate zone counterparts. PMID:24221033

  3. Carbon balance, partitioning and photosynthetic acclimation in fruit-bearing grapevine (Vitis vinifera L. cv. Tempranillo) grown under simulated climate change (elevated CO2, elevated temperature and moderate drought) scenarios in temperature gradient greenhouses.

    PubMed

    Salazar-Parra, Carolina; Aranjuelo, Iker; Pascual, Inmaculada; Erice, Gorka; Sanz-Sáez, Álvaro; Aguirreolea, Jone; Sánchez-Díaz, Manuel; Irigoyen, Juan José; Araus, José Luis; Morales, Fermín

    2015-02-01

    Although plant performance under elevated CO2 has been extensively studied in the past little is known about photosynthetic performance changing simultaneously CO2, water availability and temperature conditions. Moreover, despite of its relevancy in crop responsiveness to elevated CO2 conditions, plant level C balance is a topic that, comparatively, has received little attention. In order to test responsiveness of grapevine photosynthetic apparatus to predicted climate change conditions, grapevine (Vitis vinifera L. cv. Tempranillo) fruit-bearing cuttings were exposed to different CO2 (elevated, 700ppm vs. ambient, ca. 400ppm), temperature (ambient vs. elevated, ambient +4°C) and irrigation levels (partial vs. full irrigation). Carbon balance was followed monitoring net photosynthesis (AN, C gain), respiration (RD) and photorespiration (RL) (C losses). Modification of environment (13)C isotopic composition (δ(13)C) under elevated CO2 (from -10.30 to -24.93‰) enabled the further characterization of C partitioning into roots, cuttings, shoots, petioles, leaves, rachides and berries. Irrespective of irrigation level and temperature, exposure to elevated CO2 induced photosynthetic acclimation of plants. C/N imbalance reflected the inability of plants grown at 700ppm CO2 to develop strong C sinks. Partitioning of labeled C to storage organs (main stem and roots) did not avoid accumulation of labeled photoassimilates in leaves, affecting negatively Rubisco carboxylation activity. The study also revealed that, after 20 days of treatment, no oxidative damage to chlorophylls or carotenoids was observed, suggesting a protective role of CO2 either at current or elevated temperatures against the adverse effect of water stress. PMID:25462972

  4. Acclimation of Chlamydomonas reinhardtii to Different Growth Irradiances*

    PubMed Central

    Bonente, Giulia; Pippa, Sara; Castellano, Stefania; Bassi, Roberto; Ballottari, Matteo

    2012-01-01

    We report on the changes the photosynthetic apparatus of Chlamydomonas reinhardtii undergoes upon acclimation to different light intensity. When grown in high light, cells had a faster growth rate and higher biomass production compared with low and control light conditions. However, cells acclimated to low light intensity are indeed able to produce more biomass per photon available as compared with high light-acclimated cells, which dissipate as heat a large part of light absorbed, thus reducing their photosynthetic efficiency. This dissipative state is strictly dependent on the accumulation of LhcSR3, a protein related to light-harvesting complexes, responsible for nonphotochemical quenching in microalgae. Other changes induced in the composition of the photosynthetic apparatus upon high light acclimation consist of an increase of carotenoid content on a chlorophyll basis, particularly zeaxanthin, and a major down-regulation of light absorption capacity by decreasing the chlorophyll content per cell. Surprisingly, the antenna size of both photosystem I and II is not modulated by acclimation; rather, the regulation affects the PSI/PSII ratio. Major effects of the acclimation to low light consist of increased activity of state 1 and 2 transitions and increased contributions of cyclic electron flow. PMID:22205699

  5. Molecular, behavioral, and performance responses of juvenile largemouth bass acclimated to an elevated carbon dioxide environment.

    PubMed

    Dennis, Clark E; Adhikari, Shivani; Wright, Adam W; Suski, Cory D

    2016-04-01

    Aquatic hypercarbia, either naturally occurring or anthropogenically induced, can have extensive impacts on aquatic environments and resident organisms. While the impact of acute hypercarbia exposure on the behavior and physiology of fishes has been well studied, relatively little work has examined the physiological impact and acclimation capacity of fishes to chronic hypercarbia. To better understand the impacts of prolonged hypercarbia exposure, largemouth bass were held at ambient CO2 (13 mg L(-1)) and elevated CO2 (31 mg L(-1); ≈ 21,000 µatm) for 58 days. Following this acclimation period, fish were subjected to three separate, yet complementary, experiments: (1) acute hypercarbia challenge of 120 mg L(-1) CO2 for 1 h to quantify physiological and molecular responses; (2) hypercarbia avoidance challenge to compare CO2 agitation and avoidance responses; and (3) swim performance challenge to quantify burst swimming performance. Acclimation to 31 mg L(-1) CO2 resulted in a significant constitutive upregulation of c-fos expression in erythrocytes, combined with significant constitutive expression of hsp70 in both gill and erythrocytes, relative to controls. Largemouth bass acclimated to elevated CO2 also had a reduced glucose response (relative to controls) following an acute CO2 exposure, indicating a reduced stress response to CO2 stressors. In addition, largemouth bass acclimated to elevated CO2 conditions required 50 % higher CO2 concentrations to illicit agitation behaviors and displayed prolonged burst swimming abilities in high CO2 environments relative to controls. Together, results demonstrate that largemouth bass exposed to chronic hypercarbia may possess a physiological advantage during periods of elevated CO2 relative to naïve fish, which may permit increased performance in hypercarbia. PMID:26758610

  6. The effect of high versus low intensity heat acclimation on performance and neuromuscular responses.

    PubMed

    Wingfield, Georgia L; Gale, Rachel; Minett, Geoffrey M; Marino, Frank E; Skein, Melissa

    2016-05-01

    This study examined the effect of exercise intensity and duration during 5-day heat acclimation (HA) on cycling performance and neuromuscular responses. 20 recreationally trained males completed a 'baseline' trial followed by 5 consecutive days HA, and a 'post-acclimation' trial. Baseline and post-acclimation trials consisted of maximal voluntary contractions (MVC), a single and repeated countermovement jump protocol, 20km cycling time trial (TT) and 5×6s maximal sprints (SPR). Cycling trials were undertaken in 33.0 ± 0.8°C and 60 ± 3% relative humidity. Core (Tcore), and skin temperatures (Tskin), heart rate (HR), rating of perceived exertion (RPE) and thermal sensation were recorded throughout cycling trials. Participants were assigned to either 30min high-intensity (30HI) or 90min low-intensity (90LI) cohorts for HA, conducted in environmental conditions of 32.0 ± 1.6°C. Percentage change time to complete the 20km TT for the 90LI cohort was significantly improved post-acclimation (-5.9 ± 7.0%; P=0.04) compared to the 30HI cohort (-0.18 ± 3.9%; P<0.05). The 30HI cohort showed greatest improvements in power output (PO) during post-acclimation SPR 1 and 2 compared to 90LI (546 ± 128W and 517 ± 87W, respectively; P<0.02). No differences were evident for MVC within 30HI cohort, however, a reduced performance indicated by % change within the 90LI (P=0.04). Compared to baseline, mean Tcore was reduced post-acclimation within the 30HI cohort (P=0.05) while mean Tcore and HR were significantly reduced within the 90LI cohort (P=0.01 and 0.04, respectively). Greater physiological adaptations and performance improvements were noted within the 90LI cohort compared to the 30HI. However, 30HI did provide some benefit to anaerobic performance including sprint PO and MVC. These findings suggest specifying training duration and intensity during heat acclimation may be useful for specific post-acclimation performance. PMID:27157334

  7. Cardiorespiratory responses in an Antarctic fish suggest limited capacity for thermal acclimation.

    PubMed

    Egginton, Stuart; Campbell, Hamish A

    2016-05-01

    Polar fishes are at high risk from increasing seawater temperatures. Characterising the physiological responses to such changes may both clarify mechanisms that permit life under extreme conditions and identify limitations in the response to continued global warming. We hypothesised that Notothenia coriiceps would show physiological compensation after an acute exposure to 5°C, and following 6 weeks warm acclimation, compared with ambient temperature (0°C). However, initial tachycardia (22.4±2.8 versus 12.8±1.1 min(-1); P<0.01) was not reversed by acclimation (21.0±1.9 min(-1)). Hyperventilation (45.5±3.1 versus 21.4±2.4 breaths min(-1); P<0.001) showed a modest reduction following acclimation (38.0±2.9 min(-1); P<0.05), while resting oxygen consumption (0.52±0.08 mmol kg(-1) h(-1)) was acutely increased at 5°C (1.07±0.10 mmol kg(-1) h(-1); P<0.001) but unchanged with acclimation. Autonomic blockade showed initial responses were mainly of vagal origin, with little subsequent withdrawal or recovery in long-term heart rate variability after 6 weeks. Given the limited cardiorespiratory capacity to withstand sustained warming, effective physiological compensation probably requires a more prolonged acclimation period. PMID:26944499

  8. The influence of photosynthetic acclimation to rising CO2 and warmer temperatures on leaf and canopy photosynthesis models

    Technology Transfer Automated Retrieval System (TEKTRAN)

    There is an increasing necessity to understand how climate change factors, particularly increasing atmospheric concentrations of CO2 ([CO2]) and rising temperature, will influence photosynthetic carbon assimilation (A). Based on theory, an increased [CO2] concomitant with a rise in temperature will ...

  9. New estimates of temperature response of leaf photosynthesis in Amazon forest trees, its acclimation to mean temperature change and consequences for modelling climate response to rain forests.

    NASA Astrophysics Data System (ADS)

    Kruijt, B.; Jans, W.; Vasconcelos, S.; Tribuzy, E. S.; Felsemburgh, C.; Eliane, M.; Rowland, L.; da Costa, A. C. L.; Meir, P.

    2014-12-01

    In many dynamic vegetation models, degradation of the tropical forests is induced because they assume that productivity falls rapidly when temperatures rise in the region of 30-40°C. Apart plant respiration, this is due to the assumptions on the temperature optima of photosynthetic capacity, which are low and can differ widely between models, where in fact hardly any empirical information is available for tropical forests. Even less is known about the possibility that photosynthesis will acclimate to changing temperatures. The objective of this study to is to provide better estimates for optima, as well as to determine whether any acclimation to temperature change is to be expected. We present both new and hitherto unpublished data on the temperature response of photosynthesis of Amazon rainforest trees, encompassing three sites, several species and five field campaigns. Leaf photosynthesis and its parameters were determined at a range of temperatures. To study the long-term (seasonal) acclimation of this response, this was combined with an artificial, in situ, multi-season leaf heating experiment. The data show that, on average for all non-heated cases, the photosynthetic parameter Vcmax weakly peaks between 35 and 40 ˚C, while heating does not have a clearly significant effect. Results for Jmax are slightly different, with sharper peaks. Scatter was relatively high, which could indicate weak overall temperature dependence. The combined results were used to fit new parameters to the various temperature response curve functions in a range of DGVMs. The figure shows a typical example: while the default Jules model assumes a temperature optimum for Vcmax at around 33 ˚C, the data suggest that Vcmax keeps rising up to at least 40 ˚C. Of course, calculated photosynthesis, obtained by applying this Vcmax in the Farquhar model, peaks at lower temperature. Finally, the implication of these new model parameters for modelled climate change impact on modelled Amazon

  10. Thermal acclimation of interactions: differential responses to temperature change alter predator–prey relationship

    PubMed Central

    Grigaltchik, Veronica S.; Ward, Ashley J. W.; Seebacher, Frank

    2012-01-01

    Different species respond differently to environmental change so that species interactions cannot be predicted from single-species performance curves. We tested the hypothesis that interspecific difference in the capacity for thermal acclimation modulates predator–prey interactions. Acclimation of locomotor performance in a predator (Australian bass, Macquaria novemaculeata) was qualitatively different to that of its prey (eastern mosquitofish, Gambusia holbrooki). Warm (25°C) acclimated bass made more attacks than cold (15°C) acclimated fish regardless of acute test temperatures (10–30°C), and greater frequency of attacks was associated with increased prey capture success. However, the number of attacks declined at the highest test temperature (30°C). Interestingly, escape speeds of mosquitofish during predation trials were greater than burst speeds measured in a swimming arena, whereas attack speeds of bass were lower than burst speeds. As a result, escape speeds of mosquitofish were greater at warm temperatures (25°C and 30°C) than attack speeds of bass. The decline in the number of attacks and the increase in escape speed of prey means that predation pressure decreases at high temperatures. We show that differential thermal responses affect species interactions even at temperatures that are within thermal tolerance ranges. This thermal sensitivity of predator–prey interactions can be a mechanism by which global warming affects ecological communities. PMID:22859598

  11. Potential for increased photosynthetic performance and crop productivity in response to climate change: role of CBFs and gibberellic acid

    PubMed Central

    Hüner, Norman P. A.; Dahal, Keshav; Kurepin, Leonid V.; Savitch, Leonid; Singh, Jas; Ivanov, Alexander G.; Kane, Khalil; Sarhan, Fathey

    2014-01-01

    We propose that targeting the enhanced photosynthetic performance associated with the cold acclimation of winter cultivars of rye (Secale cereale L.), wheat (Triticum aestivum L.), and Brassica napus L. may provide a novel approach to improve crop productivity under abiotic as well as biotic stress conditions. In support of this hypothesis, we provide the physiological, biochemical, and molecular evidence that the dwarf phenotype induced by cold acclimation is coupled to significant enhancement in photosynthetic performance, resistance to photoinhibition, and a decreased dependence on photoprotection through non-photochemical quenching which result in enhanced biomass production and ultimately increased seed yield. These system-wide changes at the levels of phenotype, physiology, and biochemistry appear to be governed by the family of C-repeat/dehydration-responsive family of transcription factors (CBF/DREB1). We relate this phenomenon to the semi-dwarf, gibberellic acid insensitive (GAI), cereal varieties developed during the “green revolution” of the early 1960s and 1970s. We suggest that genetic manipulation of the family of C-repeat/dehydration-responsive element binding transcription factors (CBF/DREB1) may provide a novel approach for the maintenance and perhaps even the enhancement of plant productivity under conditions of sub-optimal growth conditions predicted for our future climate. PMID:24860799

  12. Potential for Increased Photosynthetic Performance and Crop Productivity in Response to Climate Change: role of CBFs and Gibberellic Acid

    NASA Astrophysics Data System (ADS)

    Huner, Norman; Dahal, Keshav; Kurepin, Leonid; Savitch, Leonid; Singh, Jas; Ivanov, Alexander; Kane, Khalil; Sarhan, Fathey

    2014-04-01

    We propose that targeting the dwarf phenotype, enhanced photosynthetic performance typically associated with the cold acclimation of winter cultivars of rye (Secale cereale L.), wheat (Triticum aestivum L.) and Brassica napus L. may provide a novel approach to improve crop yield and productivity under abiotic as well as biotic stress conditions. In support of this hypothesis, we provide the physiological, biochemical and molecular evidence that the dwarf phenotype induced by cold acclimation is coupled to significant enhancement in photosynthetic performance, resistance to photoinhibition and a decreased dependence on photoprotection through nonphotochemical quenching which result in enhanced biomass production and ultimately increased seed yield. These system-wide changes at the levels of phenotype, physiology and biochemistry appear to be governed by the family of C-repeat / dehydration-responsive family of transcription factors (CBF/DREB1). We relate this phenomenon to the semi-dwarf, gibberellic acid insensitive, cereal varieties developed during the “green revolution” of the early 1960s and 1970s. We suggest that genetic manipulation of the family of C-repeat / dehydration-responsive element binding transcription factors (CBF/DREB1) may provide a novel approach for the maintenance and perhaps even the enhancement of plant productivity under conditions of sub-optimal growth conditions predicted for our future climate.

  13. Potential for increased photosynthetic performance and crop productivity in response to climate change: role of CBFs and gibberellic acid.

    PubMed

    Hüner, Norman P A; Dahal, Keshav; Kurepin, Leonid V; Savitch, Leonid; Singh, Jas; Ivanov, Alexander G; Kane, Khalil; Sarhan, Fathey

    2014-01-01

    We propose that targeting the enhanced photosynthetic performance associated with the cold acclimation of winter cultivars of rye (Secale cereale L.), wheat (Triticum aestivum L.), and Brassica napus L. may provide a novel approach to improve crop productivity under abiotic as well as biotic stress conditions. In support of this hypothesis, we provide the physiological, biochemical, and molecular evidence that the dwarf phenotype induced by cold acclimation is coupled to significant enhancement in photosynthetic performance, resistance to photoinhibition, and a decreased dependence on photoprotection through non-photochemical quenching which result in enhanced biomass production and ultimately increased seed yield. These system-wide changes at the levels of phenotype, physiology, and biochemistry appear to be governed by the family of C-repeat/dehydration-responsive family of transcription factors (CBF/DREB1). We relate this phenomenon to the semi-dwarf, gibberellic acid insensitive (GAI), cereal varieties developed during the "green revolution" of the early 1960s and 1970s. We suggest that genetic manipulation of the family of C-repeat/dehydration-responsive element binding transcription factors (CBF/DREB1) may provide a novel approach for the maintenance and perhaps even the enhancement of plant productivity under conditions of sub-optimal growth conditions predicted for our future climate. PMID:24860799

  14. Cold acclimation and BnCBF17-over-expression enhance photosynthetic performance and energy conversion efficiency during long-term growth of Brassica napus under elevated CO2 conditions.

    PubMed

    Dahal, Keshav; Gadapati, Winona; Savitch, Leonid V; Singh, Jas; Hüner, Norman P A

    2012-11-01

    The effects of cold acclimation and long-term elevated CO(2) on photosynthetic performance of wild-type (WT) and BnCBF17-over-expressing line of Brassica napus cv. Westar (BnCBF17-OE) grown at either 20/16 °C (non-acclimated) or 5/5 °C (cold acclimated) and at either ambient (380 μmol C mol(-1)) or elevated (700 μmol C mol(-1)) CO(2) were studied. Compared with non-acclimated WT, the BnCBF17-OE grown at 20 °C mimicked the effects of cold acclimation on WT B. napus with respect to compact dwarf phenotype and increased rates of light-saturated CO(2) assimilation and photosynthetic electron transport. This was associated with enhanced energy conversion efficiency into biomass as assessed by decreased excitation pressure coupled to decreased dependence on non-photochemical energy dissipation for a given irradiance. Growth at elevated CO(2) decreased the light and CO(2)-saturated rates of photosynthesis by 30 % for non-acclimated WT relative to growth at ambient CO(2). This was associated with inhibition in electron transport rates (20 %), decrease in amount of rbcL (35 %) and cytosolic FBPase (70 %) and increased excitation pressure and non-photochemical quenching in elevated versus ambient CO(2)-grown non-acclimated WT. In contrast, light and CO(2)-saturated rates of photosynthesis, electron transport, excitation pressure, non-photochemical quenching and levels of rbcL, cytosolic FBPase and Lhcb1 were insensitive to growth under elevated CO(2) in BnCBF17-OE and cold-acclimated WT. Thus, BnCBF17-over-expression and cold acclimation maintain enhanced energy conversion efficiency and reduced sensitivity to feedback-limited photosynthesis during long-term growth of B. napus under elevated CO(2). Our results indicated that CBFs transcription factors regulate not only freezing tolerance but also has major whole plant effects. PMID:22847022

  15. Canopy warming caused photosynthetic acclimation and reduced seed yield in maize grown at ambient and elevated [CO2 ].

    PubMed

    Ruiz-Vera, Ursula M; Siebers, Matthew H; Drag, David W; Ort, Donald R; Bernacchi, Carl J

    2015-11-01

    Rising atmospheric CO2 concentration ([CO2 ]) and attendant increases in growing season temperature are expected to be the most important global change factors impacting production agriculture. Although maize is the most highly produced crop worldwide, few studies have evaluated the interactive effects of elevated [CO2 ] and temperature on its photosynthetic physiology, agronomic traits or biomass, and seed yield under open field conditions. This study investigates the effects of rising [CO2 ] and warmer temperature, independently and in combination, on maize grown in the field throughout a full growing season. Free-air CO2 enrichment (FACE) technology was used to target atmospheric [CO2 ] to 200 μmol mol(-1) above ambient [CO2 ] and infrared heaters to target a plant canopy increase of 3.5 °C, with actual season mean heating of ~2.7 °C, mimicking conditions predicted by the second half of this century. Photosynthetic gas-exchange parameters, leaf nitrogen and carbon content, leaf water potential components, and developmental measurements were collected throughout the season, and biomass and yield were measured at the end of the growing season. As predicted for a C4 plant, elevated [CO2 ] did not stimulate photosynthesis, biomass, or yield. Canopy warming caused a large shift in aboveground allocation by stimulating season-long vegetative biomass and decreasing reproductive biomass accumulation at both CO2 concentrations, resulting in decreased harvest index. Warming caused a reduction in photosynthesis due to down-regulation of photosynthetic biochemical parameters and the decrease in the electron transport rate. The reduction in seed yield with warming was driven by reduced photosynthetic capacity and by a shift in aboveground carbon allocation away from reproduction. This field study portends that future warming will reduce yield in maize, and this will not be mitigated by higher atmospheric [CO2 ] unless appropriate adaptation traits can be introduced

  16. Carbon Gain and Photosynthetic Response of Chrysanthemum to Photosynthetic Photon Flux Density Cycles 1

    PubMed Central

    Stoop, Johan M. H.; Willits, Dan H.; Peet, Mary M.; Nelson, Paul V.

    1991-01-01

    Most models of carbon gain as a function of photosynthetic irradiance assume an instantaneous response to increases and decreases in irradiance. High- and low-light-grown plants differ, however, in the time required to adjust to increases and decreases in irradiance. In this study the response to a series of increases and decreases in irradiance was observed in Chrysanthemum × morifolium Ramat. “Fiesta” and compared with calculated values assuming an instantaneous response. There were significant differences between high- and low-light-grown plants in their photosynthetic response to four sequential photosynthetic photon flux density (PPFD) cycles consisting of 5-minute exposures to 200 and 400 micromoles per square meter per second (μmol m−2s−1). The CO2 assimilation rate of high-light-grown plants at the cycle peak increased throughout the PPFD sequence, but the rate of increase was similar to the increase in CO2 assimilation rate observed under continuous high-light conditions. Low-light leaves showed more variability in their response to light cycles with no significant increase in CO2 assimilation rate at the cycle peak during sequential cycles. Carbon gain and deviations from actual values (percentage carbon gain over- or underestimation) based on assumptions of instantaneous response were compared under continuous and cyclic light conditions. The percentage carbon gain overestimation depended on the PPFD step size and growth light level of the leaf. When leaves were exposed to a large PPFD increase, the carbon gain was overestimated by 16 to 26%. The photosynthetic response to 100 μmol m−2 s−1 PPFD increases and decreases was rapid, and the small overestimation of the predicted carbon gain, observed during photosynthetic induction, was almost entirely negated by the carbon gain underestimation observed after a decrease. If the PPFD cycle was 200 or 400 μmol m−2 s−1, high- and low-light leaves showed a carbon gain overestimation of 25

  17. Identification of Mutants of Arabidopsis Defective in Acclimation of Photosynthesis to the Light Environment1

    PubMed Central

    Walters, Robin G.; Shephard, Freya; Rogers, Jennifer J.M.; Rolfe, Stephen A.; Horton, Peter

    2003-01-01

    In common with many other higher plant species, Arabidopsis undergoes photosynthetic acclimation, altering the composition of the photosynthetic apparatus in response to fluctuations in its growth environment. The changes in photosynthetic function that result from acclimation can be detected in a noninvasive manner by monitoring chlorophyll (Chl) fluorescence. This technique has been used to develop a screen that enables the rapid identification of plants defective at ACCLIMATION OF PHOTOSYNTHESIS TO THE ENVIRONMENT (APE) loci. The application of this screen to a population of T-DNA-transformed Arabidopsis has successfully led to the identification of a number of mutant lines with altered Chl fluorescence characteristics. Analysis of photosynthesis and pigment composition in leaves from three such mutants showed that they had altered acclimation responses to the growth light environment, each having a distinct acclimation-defective phenotype, demonstrating that screening for mutants using Chl fluorescence is a viable strategy for the investigation of acclimation. Sequencing of the genomic DNA flanking the T-DNA elements showed that in the ape1 mutant, a gene was disrupted that encodes a protein of unknown function but that appears to be specific to photosynthetic organisms, whereas the ape2 mutant carries an insertion in the region of the TPT gene encoding the chloroplast inner envelope triose phosphate/phosphate translocator. PMID:12586872

  18. Growth and photosynthetic responses of wheat plants grown in space

    NASA Technical Reports Server (NTRS)

    Tripathy, B. C.; Brown, C. S.; Levine, H. G.; Krikorian, A. D.

    1996-01-01

    Growth and photosynthesis of wheat (Triticum aestivum L. cv Super Dwarf) plants grown onboard the space shuttle Discovery for 10 d were examined. Compared to ground control plants, the shoot fresh weight of space-grown seedlings decreased by 25%. Postflight measurements of the O2 evolution/photosynthetic photon flux density response curves of leaf samples revealed that the CO2-saturated photosynthetic rate at saturating light intensities in space-grown plants declined 25% relative to the rate in ground control plants. The relative quantum yield of CO2-saturated photosynthetic O2 evolution measured at limiting light intensities was not significantly affected. In space-grown plants, the light compensation point of the leaves increased by 33%, which likely was due to an increase (27%) in leaf dark-respiration rates. Related experiments with thylakoids isolated from space-grown plants showed that the light-saturated photosynthetic electron transport rate from H2O through photosystems II and I was reduced by 28%. These results demonstrate that photosynthetic functions are affected by the microgravity environment.

  19. Uncoupling High Light Responses from Singlet Oxygen Retrograde Signaling and Spatial-Temporal Systemic Acquired Acclimation.

    PubMed

    Carmody, Melanie; Crisp, Peter A; d'Alessandro, Stefano; Ganguly, Diep; Gordon, Matthew; Havaux, Michel; Albrecht-Borth, Verónica; Pogson, Barry J

    2016-07-01

    Distinct ROS signaling pathways initiated by singlet oxygen ((1)O2) or superoxide and hydrogen peroxide have been attributed to either cell death or acclimation, respectively. Recent studies have revealed that more complex antagonistic and synergistic relationships exist within and between these pathways. As specific chloroplastic ROS signals are difficult to study, rapid systemic signaling experiments using localized high light (HL) stress or ROS treatments were used in this study to uncouple signals required for direct HL and ROS perception and distal systemic acquired acclimation (SAA). A qPCR approach was chosen to determine local perception and distal signal reception. Analysis of a thylakoidal ascorbate peroxidase mutant (tapx), the (1)O2-retrograde signaling double mutant (ex1/ex2), and an apoplastic signaling double mutant (rbohD/F) revealed that tAPX and EXECUTER 1 are required for both HL and systemic acclimation stress perception. Apoplastic membrane-localized RBOHs were required for systemic spread of the signal but not for local signal induction in directly stressed tissues. Endogenous ROS treatments revealed a very strong systemic response induced by a localized 1 h induction of (1)O2 using the conditional flu mutant. A qPCR time course of (1)O2 induced systemic marker genes in directly and indirectly connected leaves revealed a direct vascular connection component of both immediate and longer term SAA signaling responses. These results reveal the importance of an EXECUTER-dependent (1)O2 retrograde signal for both local and long distance RBOH-dependent acclimation signaling that is distinct from other HL signaling pathways, and that direct vascular connections have a role in spatial-temporal SAA induction. PMID:27288360

  20. Warm acclimation and oxygen depletion induce species-specific responses in salmonids.

    PubMed

    Anttila, Katja; Lewis, Mario; Prokkola, Jenni M; Kanerva, Mirella; Seppänen, Eila; Kolari, Irma; Nikinmaa, Mikko

    2015-05-15

    Anthropogenic activities are greatly altering the habitats of animals, whereby fish are already encountering several stressors simultaneously. The purpose of the current study was to investigate the capacity of fish to respond to two different environmental stressors (high temperature and overnight hypoxia) separately and together. We found that acclimation to increased temperature (from 7.7±0.02°C to 14.9±0.05°C) and overnight hypoxia (daily changes from normoxia to 63-67% oxygen saturation), simulating climate change and eutrophication, had both antagonistic and synergistic effects on the capacity of fish to tolerate these stressors. The thermal tolerance of Arctic char (Salvelinus alpinus) and landlocked salmon (Salmo salar m. sebago) increased with warm acclimation by 1.3 and 2.2°C, respectively, but decreased when warm temperature was combined with overnight hypoxia (by 0.2 and 0.4°C, respectively). In contrast, the combination of the stressors more than doubled hypoxia tolerance in salmon and also increased hypoxia tolerance in char by 22%. Salmon had 1.2°C higher thermal tolerance than char, but char tolerated much lower oxygen levels than salmon at a given temperature. The changes in hypoxia tolerance were connected to the responses of the oxygen supply and delivery system. The relative ventricle mass was higher in cold- than in warm-acclimated salmon but the thickness of the compact layer of the ventricle increased with the combination of warm and hypoxia acclimation in both species. Char had also significantly larger hearts and thicker compact layers than salmon. The results illustrate that while fish can have protective responses when encountering a single environmental stressor, the combination of stressors can have unexpected species-specific effects that will influence their survival capacity. PMID:25827840

  1. Mechanisms and fitness implications of photomorphogenesis during chromatic acclimation in cyanobacteria.

    PubMed

    Montgomery, Beronda L

    2016-07-01

    Photosynthetic organisms absorb photons and convert light energy to chemical energy through the process of photosynthesis. Photosynthetic efficiency is tuned in response to the availability of light, carbon dioxide and nutrients to promote maximal levels of carbon fixation, while simultaneously limiting the potential for light-associated damage or phototoxicity. Given the central dependence on light for energy production, photosynthetic organisms possess abilities to tune their growth, development and metabolism to external light cues in the process of photomorphogenesis. Photosynthetic organisms perceive light intensity and distinct wavelengths or colors of light to promote organismal acclimation. Cyanobacteria are oxygenic photosynthetic prokaryotes that exhibit abilities to alter specific aspects of growth, including photosynthetic pigment composition and morphology, in responses to changes in available wavelengths and intensity of light. This form of photomorphogenesis is known as chromatic acclimation and has been widely studied. Recent insights into the photosensory photoreceptors found in cyanobacteria and developments in our understanding of the molecular mechanisms initiated by light sensing to affect the changes characteristic of chromatic acclimation are discussed. I consider cyanobacterial responses to light, the broad diversity of photoreceptors encoded by these organisms, specific mechanisms of photomorphogenesis, and associated fitness implications in chromatically acclimating cyanobacteria. PMID:27217547

  2. Cold-responsive gene regulation during cold acclimation in plants.

    PubMed

    Lissarre, Mickael; Ohta, Masaru; Sato, Aiko; Miura, Kenji

    2010-08-01

    Regulation of the transcriptome is necessary for plants to acquire cold tolerance, and cold induces several genes via a cold signaling pathway. The transcription factors CBF/DREB1 (C-repeat binding factor/dehydration responsive element binding1) and ICE1 (inducer of CBF expression1) have important roles in the regulation of cold-responsive gene expression. ICE1 is post-translationally regulated by ubiquitylation-mediated proteolysis and sumoylation. This mini-review highlights some recent studies on plant cold signaling. The relationships among cold signaling, salicylic acid accumulation and stomatal development are also discussed. PMID:20699657

  3. The Role of Structural, Biochemical and Ecophysiological Plant Acclimation in the Eco-Hydrologic Response of Agro-Ecosystems to Global Change in the Central US

    NASA Astrophysics Data System (ADS)

    Drewry, D.; Kumar, P.; Long, S.; Sivapalan, M.; Bernacchi, C.; Liang, X.

    2009-12-01

    The acclimation of terrestrial vegetation to changes in ambient growth environment has significant implications for land-atmosphere exchange of carbon dioxide (CO2) and energy, as well as critical ecosystem services such as food production. Recent field campaigns at the SoyFACE Free Air Carbon Enrichment (FACE) facility in central Illinois have provided clear evidence of the modification of structural, biochemical and ecophysiological properties of key agricultural species at CO2 concentrations projected for the middle of this century. While these acclamatory responses have been linked to changes in leaf-level gas exchange and leaf states (ie. leaf temperature and stomatal conductance), determining the implications for these changes at the canopy-scale has remained a challenge. Here we present a simulation analysis that examines the role of observed plant acclimation in two key mid-west agricultural species, soy (C3 photosynthetic pathway) and corn (C4 photosynthetic pathway), in modifying future carbon uptake and surface energy partitioning, crop water use and resilience to water stress. The model canopies are divided into multiple layers, allowing for resolution of the shortwave and longwave radiation regimes that drive photosynthesis, stomatal conductance and leaf energy balance in each layer, along with the canopy microclimate. The canopy component of the model is coupled to a multi-layer soil-root model that computes soil moisture and root water uptake at each time period, accounting for the effects of moisture stress on canopy functioning. Model skill in capturing the sub-diurnal variability in canopy-atmosphere fluxes is demonstrated using multi-year records of eddy covariance CO2, water vapor and heat fluxes collected at the Bondville (Illinois) AmeriFlux site. An evaluation of the ability of the model to simulate observed changes in energy balance components, leaf-level photosynthetic assimilation, leaf temperature and stomatal conductance under elevated

  4. Ecohydrological responses of dense canopies to environmental variability: 2. Role of acclimation under elevated CO2

    NASA Astrophysics Data System (ADS)

    Drewry, D. T.; Kumar, P.; Long, S.; Bernacchi, C.; Liang, X.-Z.; Sivapalan, M.

    2010-12-01

    The ability to accurately predict land-atmosphere exchange of mass, energy, and momentum over the coming century requires the consideration of plant biochemical, ecophysiological, and structural acclimation to modifications of the ambient environment. Amongst the most important environmental changes experienced by terrestrial vegetation over the last century has been the increase in ambient carbon dioxide (CO2) concentrations, with a projected doubling in CO2 from preindustrial levels by the middle of this century. This change in atmospheric composition has been demonstrated to significantly alter a variety of leaf and plant properties across a range of species, with the potential to modify land-atmosphere interactions and their associated feedbacks. Free Air Carbon Enrichment (FACE) technology has provided significant insight into the functioning of vegetation in natural conditions under elevated CO2, but remains limited in its ability to quantify the exchange of CO2, water vapor, and energy at the canopy scale. This paper addresses the roles of ecophysiological, biochemical, and structural plant acclimation on canopy-scale exchange of CO2, water vapor, and energy through the application of a multilayer canopy-root-soil model (MLCan) capable of resolving changes induced by elevated CO2 through the canopy and soil systems. Previous validation of MLCan flux estimates were made for soybean and maize in the companion paper using a record of six growing seasons of eddy covariance data from the Bondville Ameriflux site. Observations of leaf-level photosynthesis, stomatal conductance, and surface temperature collected at the SoyFACE experimental facility in central Illinois provide a basis for examining the ability of MLCan to capture vegetation responses to an enriched CO2 environment. Simulations of control (370 [ppm]) and elevated (550 [ppm]) CO2 environments allow for an examination of the vertical variation and canopy-scale responses of vegetation states and fluxes

  5. Photosynthetic responses mediate the adaptation of two Lotus japonicus ecotypes to low temperature.

    PubMed

    Calzadilla, Pablo Ignacio; Signorelli, Santiago; Escaray, Francisco Jose; Menéndez, Ana Bernardina; Monza, Jorge; Ruiz, Oscar Adolfo; Maiale, Santiago Javier

    2016-09-01

    Lotus species are important forage legumes due to their high nutritional value and adaptability to marginal conditions. However, the dry matter production and regrowth rate of cultivable Lotus spp. is drastically reduced during colder seasons. In this work, we evaluated the chilling response of Lotus japonicus ecotypes MG-1 and MG-20. No significant increases were observed in reactive oxygen species and nitric oxide production or in lipid peroxidation, although a chilling-induced redox imbalance was suggested through NADPH/NADP(+) ratio alterations. Antioxidant enzyme catalase, ascorbate peroxidase, and superoxide dismutase activities were also measured. Superoxide dismutase, in particular the chloroplastic isoform, showed different activity for different ecotypes and treatments. Stress-induced photoinhibition also differentially influenced both ecotypes, with MG-1 more affected than MG-20. Data showed that the D2 PSII subunit was more affected than D1 after 1 d of low temperature exposure, although its protein levels recovered over the course of the experiment. Interestingly, D2 recovery was accompanied by improvements in photosynthetic parameters (Asat and Fv/Fm) and the NADPH/NADP(+) ratio. Our results suggest that the D2 protein is involved in the acclimation response of L. japonicus to low temperature. This may provide a deeper insight into the chilling tolerance mechanisms of the Lotus genus. PMID:27457984

  6. Linking the Salt Transcriptome with Physiological Responses of a Salt-Resistant Populus Species as a Strategy to Identify Genes Important for Stress Acclimation1[W][OA

    PubMed Central

    Brinker, Monika; Brosché, Mikael; Vinocur, Basia; Abo-Ogiala, Atef; Fayyaz, Payam; Janz, Dennis; Ottow, Eric A.; Cullmann, Andreas D.; Saborowski, Joachim; Kangasjärvi, Jaakko; Altman, Arie; Polle, Andrea

    2010-01-01

    To investigate early salt acclimation mechanisms in a salt-tolerant poplar species (Populus euphratica), the kinetics of molecular, metabolic, and physiological changes during a 24-h salt exposure were measured. Three distinct phases of salt stress were identified by analyses of the osmotic pressure and the shoot water potential: dehydration, salt accumulation, and osmotic restoration associated with ionic stress. The duration and intensity of these phases differed between leaves and roots. Transcriptome analysis using P. euphratica-specific microarrays revealed clusters of coexpressed genes in these phases, with only 3% overlapping salt-responsive genes in leaves and roots. Acclimation of cellular metabolism to high salt concentrations involved remodeling of amino acid and protein biosynthesis and increased expression of molecular chaperones (dehydrins, osmotin). Leaves suffered initially from dehydration, which resulted in changes in transcript levels of mitochondrial and photosynthetic genes, indicating adjustment of energy metabolism. Initially, decreases in stress-related genes were found, whereas increases occurred only when leaves had restored the osmotic balance by salt accumulation. Comparative in silico analysis of the poplar stress regulon with Arabidopsis (Arabidopsis thaliana) orthologs was used as a strategy to reduce the number of candidate genes for functional analysis. Analysis of Arabidopsis knockout lines identified a lipocalin-like gene (AtTIL) and a gene encoding a protein with previously unknown functions (AtSIS) to play roles in salt tolerance. In conclusion, by dissecting the stress transcriptome of tolerant species, novel genes important for salt endurance can be identified. PMID:20959419

  7. Thermal and metabolic responses of temperature-acclimated rats during cold and heat exposures.

    PubMed

    Kuroshima, A; Yahata, T; Doi, K; Ohno, T

    1982-01-01

    Some endocrine and metabolic responses to acute cold and heat exposures were observed in rats acclimated to cold, heat, or both cold and heat. Rats exposed to both cold (12 hr, 5 degrees C) and heat (12 hr, 34 degrees C) for 4 to 5 weeks (CHA) showed less fall of colonic temperature (Tc) in the cold (-5 degrees C) than heat-acclimated rats (34 degrees C, 4 to 5 weeks) (HA) and warm controls (WC), but a greater fall than cold-acclimated rats (5 degrees C, 4 to 5 weeks) (CA). CHA possessed a larger quantity of interscapular brown adipose tissue and showed greater cold-induced oxygen consumption (VO2) than WC and HA but less than CA. Blood glycerol levels rose similarly in all groups in the cold, while the increase in blood free fatty acids (FFA) levels was significantly greater in HA and smaller in CA than in WC and CHA. Acute cold exposure caused the elevation of plasma glucagon level in WC and HA, but not in CA and CHA. It lowered plasma insulin levels in HA, and the insulin/glucagon molar ratio (I/G) in WC, HA, and CHA. All groups showed the same increases in Tc during acute heat exposure (34 degrees C). However, the heat-induced increase in VO2 was greater in WC than in HA, CA, and CHA. Blood metabolite levels were not affected by acute heat exposure in all groups. Plasma glucagon levels decreased in CHA, while plasma insulin levels increased in WC and CA. I/G increased in WC and CHA. These results indicate that thermal and metabolic responses would be modified by previous exposures to cold, heat, and cold-heat. PMID:6757502

  8. Photosynthetic responses to phytoplasma infection in Chinese jujube.

    PubMed

    Liu, Zhiguo; Zhao, Jin; Liu, Mengjun

    2016-08-01

    Phytoplasma is one of the most devastating plant pathogens. Jujube witches' broom (JWB) is a typical and highly fatal phytoplasma disease of Chinese jujube (Ziziphus jujuba Mill.), which is widely cultivated in Asia. To further elucidate the mechanism of plant-phytoplasma interaction, we first compared the effects of phytoplasma infection on photosynthetic pigments and activities between a JWB-resistant cultivar (Xingguang) and a susceptible cultivar (Pozao). Total chlorophyll and carotenoid levels were significantly decreased in the susceptible cultivar at later stages of infection, but were remarkably increased in the resistant cultivar at the earlier stages. Compared to uninfected plant, a significant decrease in the main photochemical parameters (Fv/Fm, ΦPSII and qP) was recorded at the initial stages of infection in the resistant cultivar, but occurred at later stages in the susceptible cultivar. Meanwhile, the qRT-PCR results of four key photosynthesis-related genes (ZjGluTR, ZjCBP, ZjRubisco and ZjRCA2) demonstrated that the expression patterns were similar in uninfected cultivars, but up-regulated in resistant cultivar and down-regulated in the susceptible one at 12 wks after grafting inoculation. Collectively, our data indicated that the resistant cultivar 'Xingguang' undergoes a decrease in initial stage (inhibiting phytoplasma multiplication) and then a rapid enhancement of photosynthetic activity (helping jujube recovery) in response to phytoplasma infection, while the susceptible cultivar 'Pozao' displays a later decrease in photosynthetic activity. The novel photosynthetic response pattern of the resistant cultivar may contribute to its stronger immunity to phytoplasma infection, which provides new insights into plant-phytoplasma interactions. PMID:27064193

  9. Thermoregulatory responses during thermal acclimation in pigs divergently selected for residual feed intake

    NASA Astrophysics Data System (ADS)

    Campos, Paulo Henrique Reis Furtado; Noblet, Jean; Jaguelin-Peyraud, Yolande; Gilbert, Hélène; Mormède, Pierre; de Oliveira Donzele, Rita Flavia Miranda; Donzele, Juarez Lopes; Renaudeau, David

    2014-09-01

    The objective of this study was to evaluate the performance and thermoregulatory responses during acclimation to high ambient temperature (Ta) of pigs from two lines selected for high (RFI+) or low (RFI-) residual feed intake with the hypothesis that RFI- pigs producing less heat would better tolerate high Ta. Pigs (50 kg initial body weight; 17 per line among which 10 of them were catheterized) were individually housed in a climatic-controlled room where Ta was maintained at 24.2 ± 0.4 °C during 7 days and thereafter at 30.4 ± 0.7 °C during 14 days. Irrespective of Ta, RFI- pigs had lower feed intake (ADFI) and similar average daily gain (ADG) than RFI+ pigs. Whatever the line, ADFI, ADG, and feed efficiency decreased with increased Ta. Overall, the Ta increase resulted in an increase in rectal temperature (RT), skin temperature (ST), and respiratory rate (RR) within the first 24-48 h and, subsequently, in a decrease followed by stabilization. The RT decrease during acclimation occurred 24 h earlier in RFI- pigs than in RFI+. Thyroid hormones and cortisol decreased at high Ta and it was similar in both lines. Based on performance and RT, ST, and RR responses, it seems that selection for low RFI tends to ameliorate pigs' tolerance to high Ta. Nevertheless, this selection does not induce significant differences between lines in endocrine and metabolite responses during thermal stress.

  10. Functional significance of metabolic responses to thermal acclimation in fish muscle.

    PubMed

    Guderley, H

    1990-08-01

    Compensatory increases of the aerobic capacity of fish swimming muscle are frequently observed in response to cold acclimation. Such thermal compensation occurs both in fish that remain active in the cold and in fish that become dormant at cold temperatures. For cold-active fish, positive thermal compensation is best explained by conservation of the capacity for aerobic metabolic flux at low temperatures. The compensatory responses of cold-active species can be used to suggest the temperature range over which the activities of glycolytic and tricarboxylic acid cycle enzymes in a muscle, i.e., the muscle's "metabolic profile," can suffice. Analysis of the available data suggests that a 16 degrees C range of temperatures cannot be covered by one metabolic profile, even when the preferred temperatures are centered between the acclimation temperatures. For cold-inactive species that remain normoxic during winter dormancy, the compensatory metabolic modifications may facilitate lipid catabolism. Alternately, an increased aerobic capacity may be adaptive during the relatively cold periods that precede and follow winter dormancy. For goldfish and carp that encounter hypoxia and anoxia during winter dormancy, increased mitochondrial abundance could facilitate ethanol production during anoxia and the diffusion of oxygen to mitochondria during hypoxia. Finally, metabolic modifications during natural acclimatization indicate both thermal compensation and direct thermal effects and suggest that thermal compensation may be masked by reproductive and feeding activities. PMID:2201217

  11. Kinetics of photosynthetic response to ultraviolet and photosynthetically active radiation in Synechococcus WH8102 (cyanobacteria).

    PubMed

    Fragoso, Glaucia M; Neale, Patrick J; Kana, Todd M; Pritchard, Alicia L

    2014-01-01

    The picoplanktonic cyanobacteria, Synechococcus spp., (Nägeli) are important contributors to global ocean primary production that can be stressed by solar radiation, both in the photosynthetically active (PAR) and ultraviolet (UV) range. We studied the responses of PSII quantum yield (active fluorescence), carbon fixation ((14)C assimilation) and oxygen evolution (membrane inlet mass spectrometry) in Synechococcus WH8102 under moderate UV and PAR. PSII quantum yield decreased during exposure to moderate UV and UV+PAR, with response to the latter being faster (6.4 versus 2.8 min, respectively). Repair processes were also faster when UV+PAR exposure was followed by moderate PAR (1.68 min response time) than when UV was followed by very low PAR (10.5 min response time). For the UV+PAR treatment, the initial decrease in quantum yield was followed by a 50% increase ("rebound") after 7 min exposure, showing an apparent photoprotection induction. While oxygen uptake increased with PAR, it did not change under UV, suggesting that this oxygen-dependent mechanism of photoprotection, which may be acting as an electron sink, is not an important strategy against UV. We used propyl gallate, an antioxidant, to test for plastid terminal oxidase (ptox) or ptox-like enzymes activity, but it caused nonspecific and toxic effects on Synechococcus WH8102. PMID:24175996

  12. Ecohydrological responses of dense canopies to environmental variability: 1. Interplay between vertical structure and photosynthetic pathway

    NASA Astrophysics Data System (ADS)

    Drewry, D. T.; Kumar, P.; Long, S.; Bernacchi, C.; Liang, X.-Z.; Sivapalan, M.

    2010-12-01

    Vegetation acclimation to changing climate, in particular elevated atmospheric concentrations of carbon dioxide (CO2), has been observed to include modifications to the biochemical and ecophysiological functioning of leaves and the structural components of the canopy. These responses have the potential to significantly modify plant carbon uptake and surface energy partitioning, and have been attributed with large-scale changes in surface hydrology over recent decades. While the aggregated effects of vegetation acclimation can be pronounced, they often result from subtle changes in canopy properties that require the resolution of physical, biochemical and ecophysiological processes through the canopy for accurate estimation. In this paper, the first of two, a multilayer canopy-soil-root system model developed to capture the emergent vegetation responses to environmental change is presented. The model incorporates both C3 and C4 photosynthetic pathways, and resolves the vertical radiation, thermal, and environmental regimes within the canopy. The tight coupling between leaf ecophysiological functioning and energy balance determines vegetation responses to climate states and perturbations, which are modulated by soil moisture states through the depth of the root system. The model is validated for three growing seasons each for soybean (C3) and maize (C4) using eddy-covariance fluxes of CO2, latent, and sensible heat collected at the Bondville (Illinois) Ameriflux tower site. The data set provides an opportunity to examine the role of important environmental drivers and model skill in capturing variability in canopy-atmosphere exchange. Vertical variation in radiative states and scalar fluxes over a mean diurnal cycle are examined to understand the role of canopy structure on the patterns of absorbed radiation and scalar flux magnitudes and the consequent differences in sunlit and shaded source/sink locations through the canopies. An analysis is made of the impact of

  13. Copper and hypoxia modulate transcriptional and mitochondrial functional-biochemical responses in warm acclimated rainbow trout (Oncorhynchus mykiss).

    PubMed

    Sappal, Ravinder; Fast, Mark; Purcell, Sara; MacDonald, Nicole; Stevens, Don; Kibenge, Fred; Siah, Ahmed; Kamunde, Collins

    2016-04-01

    To survive in changing environments fish utilize a wide range of biological responses that require energy. We examined the effect of warm acclimation on the electron transport system (ETS) enzymes and transcriptional responses to hypoxia and copper (Cu) exposure in fish. Rainbow trout (Oncorhynchus mykiss) were acclimated to cold (11 °C; control) and warm (20 °C) temperatures for 3 weeks followed by exposure to Cu, hypoxia or both for 24 h. Activities of ETS enzyme complexes I-IV (CI-CIV) were measured in liver and gill mitochondria. Analyses of transcripts encoding for proteins involved in mitochondrial respiration (cytochrome c oxidase subunits 4-1 and 2: COX4-1 and COX4-2), metal detoxification/stress response (metallothioneins A and B: MT-A and MT-B) and energy sensing (AMP-activated protein kinase α1: AMPKα1) were done in liver mitochondria, and in whole liver and gill tissues by RT-qPCR. Warm acclimation inhibited activities of ETS enzymes while effects of Cu and hypoxia depended on the enzyme and thermal acclimation status. The genes encoding for COX4-1, COX4-2, MT-A, MT-B and AMPKα1 were strongly and tissue-dependently altered by warm acclimation. While Cu and hypoxia clearly increased MT-A and MT-B transcript levels in all tissues, their effects on COX4-1, COX4-2 and AMPKα1 mRNA levels were less pronounced. Importantly, warm acclimation differentially altered COX4-2/COX4-1 ratio in liver mitochondria and gill tissue. The three stressors showed both independent and joint actions on activities of ETS enzymes and transcription of genes involved in energy metabolism, stress response and metals homeostasis. Overall, we unveiled novel interactive effects that should not be overlooked in real world situations wherein fish normally encounter multiple stress factors. PMID:26774776

  14. Photosynthetic Enzyme Level and Distribution through Canopies in Relation to Canopy Photosynthesis and its Acclimation to Light, Temperature and CO2

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The distribution of photosynthetic enzymes through the canopy affects canopy photosynthesis, as well as plant quality and nitrogen demand. Most canopy photosynthesis models assume an exponential distribution of photosynthetic enzymes through the canopy, although this is rarely consistent with exper...

  15. Whole plant acclimation responses by finger millet to low nitrogen stress

    PubMed Central

    Goron, Travis L.; Bhosekar, Vijay K.; Shearer, Charles R.; Watts, Sophia; Raizada, Manish N.

    2015-01-01

    The small grain cereal, finger millet (FM, Eleusine coracana L. Gaertn), is valued by subsistence farmers in India and East Africa as a low-input crop. It is reported by farmers to require no added nitrogen (N), or only residual N, to produce grain. Exact mechanisms underlying the acclimation responses of FM to low N are largely unknown, both above and below ground. In particular, the responses of FM roots and root hairs to N or any other nutrient have not previously been reported. Given its low N requirement, FM also provides a rare opportunity to study long-term responses to N starvation in a cereal species. The objective of this study was to survey the shoot and root morphometric responses of FM, including root hairs, to low N stress. Plants were grown in pails in a semi-hydroponic system on clay containing extremely low background N, supplemented with N or no N. To our surprise, plants grown without deliberately added N grew to maturity, looked relatively normal and produced healthy seed heads. Plants responded to the low N treatment by decreasing shoot, root, and seed head biomass. These declines under low N were associated with decreased shoot tiller number, crown root number, total crown root length and total lateral root length, but with no consistent changes in root hair traits. Changes in tiller and crown root number appeared to coordinate the above and below ground acclimation responses to N. We discuss the remarkable ability of FM to grow to maturity without deliberately added N. The results suggest that FM should be further explored to understand this trait. Our observations are consistent with indigenous knowledge from subsistence farmers in Africa and Asia, where it is reported that this crop can survive extreme environments. PMID:26347768

  16. Photosynthetic responses of soybean to soybean aphid (Homoptera: Aphididae) injury.

    PubMed

    Macedo, T B; Bastos, C S; Higley, L G; Ostlie, K R; Madhavan, S

    2003-02-01

    The soybean aphid, Aphis glycines Matsumara, was discovered in the United States in the summer of 2000. Since that initial discovery, the aphid has spread across northern soybean production regions. In 2001, we examined the physiological responses of soybeans to low aphids densities (fewer than 50 aphids/leaf). In this study, we determined photosynthetic rates, leaf fluorescence responses, and photosynthetic responses to variable carbon dioxide and light levels. In addition, analyses for chlorophyll content and stable carbon isotope ratios were used to differentiate potential differences in stomatal versus mesophyll limitations to photosynthesis. We observed rate reductions of up to 50% on infested leaflets, including lealets with no apparent symptoms of aphid injury (such as chlorosis). Differences in fluorescence data indicated that photoelectron transport was not impaired. These results indicate that substantial physiological impact on soybean is possible even at low aphid densities. Also, the conventional view of aphid injury acting through reductions in chlorophyll content and light-harvesting reactions of photosynthesis is not supported by our findings in this system. PMID:12650361

  17. Foliar temperature acclimation reduces simulated carbon sensitivity to climate

    NASA Astrophysics Data System (ADS)

    Smith, Nicholas G.; Malyshev, Sergey L.; Shevliakova, Elena; Kattge, Jens; Dukes, Jeffrey S.

    2016-04-01

    Plant photosynthesis and respiration are the largest carbon fluxes between the terrestrial biosphere and the atmosphere, and their parameterizations represent large sources of uncertainty in projections of land carbon uptake in Earth system models (ESMs). The incorporation of temperature acclimation of photosynthesis and foliar respiration, commonly observed processes, into ESMs has been proposed as a way to reduce this uncertainty. Here we show that, across 15 flux tower sites spanning multiple biomes at various locations worldwide (10° S-67° N), acclimation parameterizations improve a model's ability to reproduce observed net ecosystem exchange of CO2. This improvement is most notable in tropical biomes, where photosynthetic acclimation increased model performance by 36%. The consequences of acclimation for simulated terrestrial carbon uptake depend on the process, region and time period evaluated. Globally, including acclimation has a net effect of increasing carbon assimilation and storage, an effect that diminishes with time, but persists well into the future. Our results suggest that land models omitting foliar temperature acclimation are likely to overestimate the temperature sensitivity of terrestrial carbon exchange, thus biasing projections of future carbon storage and estimates of policy indicators such as the transient climate response to cumulative carbon emissions.

  18. Photosynthetic responses to 30 years of atmospheric change

    NASA Astrophysics Data System (ADS)

    Lunch, C. K.

    2009-12-01

    Plant physiological studies of responses to atmospheric CO2 concentration most frequently involve artificially increasing local CO2 concentration. However, CO2 levels in the atmosphere have already risen by more than 100 ppm over pre-industrial levels, and the response to that increase should also be considered. I measured changes in leaf-level photosynthesis over the most recent 50-60 ppm rise in atmospheric CO2, using photosynthetic studies from the late 1970s and early 1980s as a baseline. The study encompassed 17 plant species at three sites in California. The sites covered a rainfall range of 40 to 1000 mm year-1, and a mean annual temperature range of 12 to 24 oC. Species included annual forbs, perennial shrubs, and trees. Over the 30 years since the previous studies were carried out, leaf-level photosynthesis at ambient CO2 has risen by an average of 0.8 μmol m-2 s-1, a nonsignificant change. Stomatal conductance has declined, such that water use efficiency has increased by an average of 12.7%. The largest changes in photosynthetic characteristics were observed at the desert site.

  19. Acclimation of metabolism to light in A rabidopsis thaliana: the glucose 6‐phosphate/phosphate translocator GPT2 directs metabolic acclimation

    PubMed Central

    DYSON, BETH C.; ALLWOOD, J. WILLIAM; FEIL, REGINA; XU, YUN; MILLER, MATTHEW; BOWSHER, CAROLINE G.; GOODACRE, ROYSTON; LUNN, JOHN E.

    2015-01-01

    Abstract Mature leaves of plants transferred from low to high light typically increase their photosynthetic capacity. In A rabidopsis thaliana, this dynamic acclimation requires expression of GPT2, a glucose 6‐phosphate/phosphate translocator. Here, we examine the impact of GPT2 on leaf metabolism and photosynthesis. Plants of wild type and of a GPT2 knockout (gpt2.2) grown under low light achieved the same photosynthetic rate despite having different metabolic and transcriptomic strategies. Immediately upon transfer to high light, gpt2.2 plants showed a higher rate of photosynthesis than wild‐type plants (35%); however, over subsequent days, wild‐type plants acclimated photosynthetic capacity, increasing the photosynthesis rate by 100% after 7 d. Wild‐type plants accumulated more starch than gpt2.2 plants throughout acclimation. We suggest that GPT2 activity results in the net import of glucose 6‐phosphate from cytosol to chloroplast, increasing starch synthesis. There was clear acclimation of metabolism, with short‐term changes typically being reversed as plants acclimated. Distinct responses to light were observed in wild‐type and gpt2.2 leaves. Significantly higher levels of sugar phosphates were observed in gpt2.2. We suggest that GPT2 alters the distribution of metabolites between compartments and that this plays an essential role in allowing the cell to interpret environmental signals. PMID:25474495

  20. Intraspecific variation in thermal acclimation of photosynthesis across a range of temperatures in a perennial crop

    PubMed Central

    Zaka, Serge; Frak, Ela; Julier, Bernadette; Gastal, François; Louarn, Gaëtan

    2016-01-01

    Interest in the thermal acclimation of photosynthesis has been stimulated by the increasing relevance of climate change. However, little is known about intra-specific variations in thermal acclimation and its potential for breeding. In this article, we examined the difference in thermal acclimation between alfalfa (Medicago sativa) cultivars originating from contrasting origins, and sought to analyze the mechanisms in play. A series of experiments was carried out at seven growth temperatures between 5 and 35 °C using four cultivars from temperate and Mediterranean origin. Leaf traits, the photosynthetic rate at 25 °C (A40025), the photosynthetic rate at optimal temperature (A400opt), the thermal optimum of photosynthesis (Topt), and the photosynthetic parameters from the Farqhuar model were determined. Irrespective of cultivar origin, a clear shift in the temperature responses of photosynthesis was observed as a function of growth temperature, affecting thermal optimum of photosynthesis, photosynthetic rate at optimal temperature and photosynthetic rate at 25 °C. For both cultivars, Topt values increased linearly in leaves grown between 5 and 35 °C. Relative homeostasis of A40025 and A400opt was found between 10 °C and 30 °C growth temperatures, but sharp declines were recorded at 5 and 35 °C. This homeostasis was achieved in part through modifications to leaf nitrogen content, which increased at extreme temperatures. Significant changes were also recorded regarding nitrogen partitioning in the photosynthetic apparatus and in the temperature dependence of photosynthetic parameters. The cultivars differed only in terms of the temperature response of photosynthetic parameters, with Mediterranean genotypes displaying a greater sensitivity of the maximum rate of Rubisco carboxylation to elevated temperatures. It was concluded that intra-specific variations in the temperature acclimation of photosynthesis exist among alfalfa cultivars, but that

  1. Intraspecific variation in thermal acclimation of photosynthesis across a range of temperatures in a perennial crop.

    PubMed

    Zaka, Serge; Frak, Ela; Julier, Bernadette; Gastal, François; Louarn, Gaëtan

    2016-01-01

    Interest in the thermal acclimation of photosynthesis has been stimulated by the increasing relevance of climate change. However, little is known about intra-specific variations in thermal acclimation and its potential for breeding. In this article, we examined the difference in thermal acclimation between alfalfa (Medicago sativa) cultivars originating from contrasting origins, and sought to analyze the mechanisms in play. A series of experiments was carried out at seven growth temperatures between 5 and 35 °C using four cultivars from temperate and Mediterranean origin. Leaf traits, the photosynthetic rate at 25 °C (A400 (25)), the photosynthetic rate at optimal temperature (A400 (opt)), the thermal optimum of photosynthesis (Topt), and the photosynthetic parameters from the Farqhuar model were determined. Irrespective of cultivar origin, a clear shift in the temperature responses of photosynthesis was observed as a function of growth temperature, affecting thermal optimum of photosynthesis, photosynthetic rate at optimal temperature and photosynthetic rate at 25 °C. For both cultivars, Topt values increased linearly in leaves grown between 5 and 35 °C. Relative homeostasis of A400 (25) and A400 (opt) was found between 10 °C and 30 °C growth temperatures, but sharp declines were recorded at 5 and 35 °C. This homeostasis was achieved in part through modifications to leaf nitrogen content, which increased at extreme temperatures. Significant changes were also recorded regarding nitrogen partitioning in the photosynthetic apparatus and in the temperature dependence of photosynthetic parameters. The cultivars differed only in terms of the temperature response of photosynthetic parameters, with Mediterranean genotypes displaying a greater sensitivity of the maximum rate of Rubisco carboxylation to elevated temperatures. It was concluded that intra-specific variations in the temperature acclimation of photosynthesis exist among alfalfa cultivars

  2. Photosynthetic responses and accumulation of mesotrione in two freshwater algae.

    PubMed

    Ni, Yan; Lai, Jinhu; Wan, Jinbao; Chen, Lianshui

    2014-01-01

    Mesotrione is a herbicide used for killing annual grasses and broad-leaved weeds in maize. A recent investigation has shown that mesotrione has been detected as an organic contaminant in aquatic environments and may have a negative impact on aquatic organisms. To evaluate the eco-toxicity of mesotrione to algae, experiments focusing on photosynthetic responses and mesotrione accumulation in Microcystis sp. and Scenedesmus quadricauda were carried out. Both algae treated with mesotrione at 0.05-10 mg L(-1) for 7 days reduced the photosynthetic capacity. The fluorescence of chlorophyll a, the maximal PSII activity (Fv/Fm), and the parameters (Ik, α and ETRmax) of rapid light curves (RLCs) in both algae were decreased under mesotrione exposure. The 96 h EC50 values for mesotrione on S. quadricauda and Microcystis sp. were 4.41 and 6.19 mg L(-1), respectively. The latter shows more tolerance to mesotrione. Mesotrione was shown to be readily accumulated by both species. Such uptake of mesotrione led to the rapid removal of mesotrione from the medium. Overall, this study represents the initial comprehensive analyses of Microcystis sp. and S. quadricauda in adaptation to the mesotrione contaminated aquatic ecosystems. PMID:25059419

  3. Fitting photosynthetic carbon dioxide response curves for C(3) leaves.

    PubMed

    Sharkey, Thomas D; Bernacchi, Carl J; Farquhar, Graham D; Singsaas, Eric L

    2007-09-01

    Photosynthetic responses to carbon dioxide concentration can provide data on a number of important parameters related to leaf physiology. Methods for fitting a model to such data are briefly described. The method will fit the following parameters: V(cmax), J, TPU, R(d) and g(m)[maximum carboxylation rate allowed by ribulose 1.5-bisphosphate carboxylase/oxygenase (Rubisco), rate of photosynthetic electron transport (based on NADPH requirement), triose phosphate use, day respiration and mesophyll conductance, respectively]. The method requires at least five data pairs of net CO(2) assimilation (A) and [CO(2)] in the intercellular airspaces of the leaf (C(i)) and requires users to indicate the presumed limiting factor. The output is (1) calculated CO(2) partial pressure at the sites of carboxylation, C(c), (2) values for the five parameters at the measurement temperature and (3) values adjusted to 25 degrees C to facilitate comparisons. Fitting this model is a way of exploring leaf level photosynthesis. However, interpreting leaf level photosynthesis in terms of underlying biochemistry and biophysics is subject to assumptions that hold to a greater or lesser degree, a major assumption being that all parts of the leaf are behaving in the same way at each instant. PMID:17661745

  4. Role of CBFs as integrators of chloroplast redox, phytochrome and plant hormone signaling during cold acclimation.

    PubMed

    Kurepin, Leonid V; Dahal, Keshav P; Savitch, Leonid V; Singh, Jas; Bode, Rainer; Ivanov, Alexander G; Hurry, Vaughan; Hüner, Norman P A

    2013-01-01

    Cold acclimation of winter cereals and other winter hardy species is a prerequisite to increase subsequent freezing tolerance. Low temperatures upregulate the expression of C-repeat/dehydration-responsive element binding transcription factors (CBF/DREB1) which in turn induce the expression of COLD-REGULATED (COR) genes. We summarize evidence which indicates that the integration of these interactions is responsible for the dwarf phenotype and enhanced photosynthetic performance associated with cold-acclimated and CBF-overexpressing plants. Plants overexpressing CBFs but grown at warm temperatures mimic the cold-tolerant, dwarf, compact phenotype; increased photosynthetic performance; and biomass accumulation typically associated with cold-acclimated plants. In this review, we propose a model whereby the cold acclimation signal is perceived by plants through an integration of low temperature and changes in light intensity, as well as changes in light quality. Such integration leads to the activation of the CBF-regulon and subsequent upregulation of COR gene and GA 2-oxidase (GA2ox) expression which results in a dwarf phenotype coupled with increased freezing tolerance and enhanced photosynthetic performance. We conclude that, due to their photoautotrophic nature, plants do not rely on a single low temperature sensor, but integrate changes in light intensity, light quality, and membrane viscosity in order to establish the cold-acclimated state. CBFs appear to act as master regulators of these interconnecting sensing/signaling pathways. PMID:23778089

  5. Role of CBFs as Integrators of Chloroplast Redox, Phytochrome and Plant Hormone Signaling during Cold Acclimation

    PubMed Central

    Kurepin, Leonid V.; Dahal, Keshav P.; Savitch, Leonid V.; Singh, Jas; Bode, Rainer; Ivanov, Alexander G.; Hurry, Vaughan; Hüner, Norman P. A.

    2013-01-01

    Cold acclimation of winter cereals and other winter hardy species is a prerequisite to increase subsequent freezing tolerance. Low temperatures upregulate the expression of C-repeat/dehydration-responsive element binding transcription factors (CBF/DREB1) which in turn induce the expression of COLD-REGULATED (COR) genes. We summarize evidence which indicates that the integration of these interactions is responsible for the dwarf phenotype and enhanced photosynthetic performance associated with cold-acclimated and CBF-overexpressing plants. Plants overexpressing CBFs but grown at warm temperatures mimic the cold-tolerant, dwarf, compact phenotype; increased photosynthetic performance; and biomass accumulation typically associated with cold-acclimated plants. In this review, we propose a model whereby the cold acclimation signal is perceived by plants through an integration of low temperature and changes in light intensity, as well as changes in light quality. Such integration leads to the activation of the CBF-regulon and subsequent upregulation of COR gene and GA 2-oxidase (GA2ox) expression which results in a dwarf phenotype coupled with increased freezing tolerance and enhanced photosynthetic performance. We conclude that, due to their photoautotrophic nature, plants do not rely on a single low temperature sensor, but integrate changes in light intensity, light quality, and membrane viscosity in order to establish the cold-acclimated state. CBFs appear to act as master regulators of these interconnecting sensing/signaling pathways. PMID:23778089

  6. Microtopographic hydrologic variability change resulting from vegetation acclimation response to elevated atmospheric CO2

    NASA Astrophysics Data System (ADS)

    Le, P. V.; Kumar, P.

    2015-12-01

    The elevated concentration of atmospheric CO2 increases the ratio of carbon fixation to water loss from plants or water use efficiency, which reduces transpiration. However, the magnitude of the effects of this vegetation acclimation on hydrologic dynamics, such as soil moisture content and surface runoff controlled by microtopographic variability on the land surface, remains unclear. Here we integrate a multi-layer canopy-root-soil model (MLCan) with a coupled surface-subsurface flow model (GCSFlow) to capture the acclimation responses of vegetation to climate change and predict how these changes affect hydrologic dynamics on landscapes at fine scales. The model is implemented on a hybrid CPU-GPU parallel computing environment to overcome challenges associated with the high density of computational grid and nonlinear solvers. The model is capable of simulating large-scale heterogeneities due to both microtopography and soils and lateral water fluxes at emerging lidar-scale resolutions (~1m). We demonstrate that hybrid computing is feasible for detailed, large-scale ecohydrologic modeling, which has been previously assumed to be an intractable computational problem. Simulations are performed for corn crop in the Goose Creek watershed in central Illinois, USA at present and projected higher concentrations of atmospheric CO2, 400 ppm and 550 ppm, respectively. The results show a net decrease of 11% for the average annual evapotranspiration of corn, which increases water content in the soil and at the land surface. These results highlight the critical role of a warming climate on atmospheric-soil-vegetation interactions and the need to understand other dynamics near the soil surface associated with water and vegetation.

  7. Infective Juveniles of the Entomopathogenic Nematode, Steinernema feltiae Produce Cryoprotectants in Response to Freezing and Cold Acclimation

    PubMed Central

    Ali, Farman; Wharton, David A.

    2015-01-01

    Steinernema feltiae is a moderately freeze-tolerant entomopathogenic nematode which survives intracellular freezing. We have detected by gas chromatography that infective juveniles of S. feltiae produce cryoprotectants in response to cold acclimation and to freezing. Since the survival of this nematode varies with temperature, we analyzed their cryoprotectant profiles under different acclimation and freezing regimes. The principal cryoprotectants detected were trehalose and glycerol with glucose being the minor component. The amount of cryoprotectants varied with the temperature and duration of exposure. Trehalose was accumulated in higher concentrations when nematodes were acclimated at 5°C for two weeks whereas glycerol level decreased from that of the non-acclimated controls. Nematodes were seeded with a small ice crystal and held at -1°C, a regime that does not produce freezing of the nematodes but their bodies lose water to the surrounding ice (cryoprotective dehydration). This increased the levels of both trehalose and glycerol, with glycerol reaching a higher concentration than trehalose. Nematodes frozen at -3°C, a regime that produces freezing of the nematodes and results in intracellular ice formation, had elevated glycerol levels while trehalose levels did not change. Steinernema feltiae thus has two strategies of cryoprotectant accumulation: one is an acclimation response to low temperature when the body fluids are in a cooled or supercooled state and the infective juveniles produce trehalose before freezing. During this process a portion of the glycerol is converted to trehalose. The second strategy is a rapid response to freezing which induces the production of glycerol but trehalose levels do not change. These low molecular weight compounds are surmised to act as cryoprotectants for this species and to play an important role in its freezing tolerance. PMID:26509788

  8. Exercise- and methylcholine-induced sweating responses in older and younger men: effect of heat acclimation and aerobic fitness

    NASA Astrophysics Data System (ADS)

    Inoue, Y.; Havenith, George; Kenney, W. Larry; Loomis, Joseph L.; Buskirk, Elsworth R.

    The purpose of this investigation was to examine the effects of aging and aerobic fitness on exercise- and methylcholine-induced sweating responses during heat acclimation. Five younger [Y group - age: 23+/-1 (SEM) years; maximal oxygen consumption (V.O2max): 47+/-3 ml.kg-1.min-1], four highly fit older (HO group - 63+/-3 years; 48+/-4 ml.kg-1.min-1) and five normally fit older men (NO group - 67+/-3 years; 30+/-1 ml.kg-1.min-1) who were matched for height, body mass and percentage fat, were heat acclimated by daily cycle exercise ( 35% V.O2max for 90 min) in a hot (43°C, 30% RH) environment for 8 days. The heat acclimation regimen increased performance time, lowered final rectal temperature (Tre) and percentage maximal heart rate (%HRmax), improved thermal comfort and decreased sweat sodium concentration similarly in all groups. Although total body sweating rates (M.sw) during acclimation were significantly greater in the Y and HO groups than in the NO group (P<0.01) (because of the lower absolute workload in the NO group), the M.sw did not change in all groups with the acclimation sessions. Neither were local sweating rates (m.sw) on chest, back, forearm and thigh changed in all groups by the acclimation. The HO group presented greater forearm m.sw (30-90 min) values and the Y group had greater back and thigh m.sw (early in exercise) values, compared to the other groups (P<0.001). In a methylcholine injection test on days immediately before and after the acclimation, the order of sweat output per gland (SGO) on chest, back and thigh was Y>HO>NO, and on the forearm Y=HO>NO. No group differences were observed for activated sweat gland density at any site. The SGO at the respective sites increased in the post-acclimation test regardless of group (P<0.01), but on the thigh the magnitude of the increase was lower in the NO (P<0.02) and HO (P=0.07) groups than in the Y group. These findings suggest that heat tolerance and the improvement with acclimation are little

  9. Comparative Transcriptomic Analysis of the Response to Cold Acclimation in Eucalyptus dunnii

    PubMed Central

    Liu, Yiqing; Jiang, Yusong; Lan, Jianbin; Zou, Yong; Gao, Junping

    2014-01-01

    Eucalyptus dunnii is an important macrophanerophyte with high economic value. However, low temperature stress limits its productivity and distribution. To study the cold response mechanisms of E. dunnii, 5 cDNA libraries were constructed from mRNA extracted from leaves exposed to cold stress for varying lengths of time and were evaluated by RNA-Seq analysis. The assembly of the Illumina datasets was optimized using various assembly programs and parameters. The final optimized assembly generated 205,325 transcripts with an average length of 1,701 bp and N50 of 2,627 bp, representing 349.38 Mb of the E. dunnii transcriptome. Among these transcripts, 134,358 transcripts (65.4%) were annotated in the Nr database. According to the differential analysis results, most transcripts were up-regulated as the cold stress prolonging, suggesting that these transcripts may be involved in the response to cold stress. In addition, the cold-relevant GO categories, such as ‘response to stress’ and ‘translational initiation’, were the markedly enriched GO terms. The assembly of the E. dunnii gene index and the GO classification performed in this study will serve as useful genomic resources for the genetic improvement of E. dunnii and also provide insights into the molecular mechanisms of cold acclimation in E. dunnii. PMID:25412179

  10. The effects on photosynthetic CO{sub 2} assimilation to long-term elevation of atmospheric CO{sub 2} concentration: An assessment of the response of Trifolium Repens L. cv. Blanca grown at F.A.C.E.

    SciTech Connect

    Lewis, C.E.

    1994-11-01

    Understanding how photosynthetic capacity acclimates to elevated CO{sub 2} concentrations is vital in predicting the response of important grassland species such as Trifolium repens. Previous studies of acclimatization have been carried out in artificial experimental conditions, such as acrylic greenhouses or controlled environment chambers. The advent of FACE technology has enabled a large area of crop to be fumigated in the field, providing more realistic growing conditions. Pure stands of Trifolium repens L. cv. Blanca grown at either 355 or 600{mu}mol mol{sup -1} CO{sub 2} were examined, and their photosynthetic response to elevated Ca determined via gas exchange studies. Rates of photosynthesis of young, fully expanded leaves were increased between 21 and 36% when grown and measured at elevated CO{sub 2}. This increase in A corresponded to a decrease in g{sub S} of between 18 and 52%. No acclimation effect was observed in the most frequently cut stands, whilst the response of stands clipped only 4 times per year was more variable. When down regulation of V{sub cmax} did occur, this was not nearly as marked as that which occurred in 3 other temperate species (Chrysanthemum leucanthemum, Ranunculus friesianus, Plantago lanceolata (L.) J. & C. Presl.), at similar growth regimes. No acclimation of stomatal frequency, SI or pore length was found to occur in the enriched clover stands.

  11. Temperature acclimation of photosynthesis and respiration: A key uncertainty in the carbon cycle-climate feedback

    NASA Astrophysics Data System (ADS)

    Lombardozzi, Danica L.; Bonan, Gordon B.; Smith, Nicholas G.; Dukes, Jeffrey S.; Fisher, Rosie A.

    2015-10-01

    Earth System Models typically use static responses to temperature to calculate photosynthesis and respiration, but experimental evidence suggests that many plants acclimate to prevailing temperatures. We incorporated representations of photosynthetic and leaf respiratory temperature acclimation into the Community Land Model, the terrestrial component of the Community Earth System Model. These processes increased terrestrial carbon pools by 20 Pg C (22%) at the end of the 21st century under a business-as-usual (Representative Concentration Pathway 8.5) climate scenario. Including the less certain estimates of stem and root respiration acclimation increased terrestrial carbon pools by an additional 17 Pg C (~40% overall increase). High latitudes gained the most carbon with acclimation, and tropical carbon pools increased least. However, results from both of these regions remain uncertain; few relevant data exist for tropical and boreal plants or for extreme temperatures. Constraining these uncertainties will produce more realistic estimates of land carbon feedbacks throughout the 21st century.

  12. Acyl-lipid desaturase 1 primes cold acclimation response in Arabidopsis.

    PubMed

    Chen, Mingjie; Thelen, Jay J

    2016-09-01

    Membrane fluidity change has long been suggested as the primary mechanism by which, plants adapt to cold stress, but the underlying molecular mechanisms are not completely established. In this study, we found that a knockout of acyl-lipid/CoA desaturase 1 gene (ADS1; EC 1.14.99) enhances freezing tolerance after cold acclimation (CA). Fatty acid composition analysis demonstrated that 18:1 content in ads1 mutant plants was 20% lower than in wild-type (WT) grown at 23°C. Lipidomics revealed that 34C-species of monogalactosyl diacylglycerol (MGDG) content in ads1 mutants were 3.3-14.9% lower than in WT. Lipid positional analysis identified 10% lower 18:1 fatty acid content at the sn-2 position of MGDG. The cytosolic calcium content in ads1 mutant plants was also approximately two-times higher than that of WT in response to cold shock. Each of these biochemical differences between WT and ads1 mutant disappeared after CA. Subcellular localization of C- and N-terminal enhanced-fluorescence-fusion proteins indicated that ADS1 localized exclusively to chloroplasts. These observations suggest that ADS1-mediated alteration of chloroplast membrane fluidity is required to prime a CA response, and is the upstream event of cytosolic calcium signaling. PMID:27062193

  13. Effects of acclimation to handling on performance, reproductive, and physiological responses of Brahman-crossbred heifers.

    PubMed

    Cooke, R F; Arthington, J D; Austin, B R; Yelich, J V

    2009-10-01

    The objective of this study was to evaluate the effects of acclimation to handling on growth, plasma concentrations of progesterone (P4) and cortisol, temperament, and reproductive performance of Brahman-crossbred heifers. Over 2 consecutive years, 37 Braford and 43 Brahman x Angus heifers were initially evaluated, within 30 d after weaning, for BW and puberty status via transrectal ultrasonography and plasma P4 concentrations (d 0 and 10), and for temperament by measurements of chute score, pen score, and exit velocity (d 10 only). On d 11, heifers were stratified by breed, puberty status, temperament score, BW, and age and randomly assigned to receive or not (control) the acclimation treatment. Acclimated heifers were exposed to a handling process 3 times weekly (Mondays, Wednesdays, and Fridays) for 4 wk (d 11 to 39 of the experiment). The acclimation treatment was applied individually to heifers by processing them through a handling facility, whereas control heifers remained undisturbed on pasture. Heifer puberty status, evaluated via plasma P4 concentrations and transrectal ultrasonography, and BW were assessed again on d 40 and 50, d 80 and 90, and d 120 and 130. Blood samples collected before (d 10) and at the end of the acclimation period (d 40) were also analyzed for plasma concentrations of cortisol. Heifer temperament was assessed again on d 40 of the study. No interactions containing the effects of treatment, breed, and year were detected. Acclimated heifers had reduced (P < 0.01) ADG compared with control heifers (0.50 vs. 0.58 kg/d, respectively). Attainment of puberty and pregnancy, however, was hastened (P = 0.02 and 0.04, respectively) in acclimated heifers compared with control. Acclimated heifers had reduced chute score (P < 0.01) and concentrations of cortisol (P < 0.01) and P4 (P = 0.03; prepubertal heifers only) compared with control heifers after the acclimation period (1.37 vs. 1.84 for chute score; 37.8 vs. 50.5 ng/mL of cortisol; 0.52 vs

  14. Acclimation-dependent expression of heat shock protein 70 in Pacific abalone ( Haliotis discus hannai Ino) and its acute response to thermal exposure

    NASA Astrophysics Data System (ADS)

    Li, Jiaqi; He, Qingguo; Sun, Hui; Liu, Xiao

    2012-01-01

    Heat shock protein 70 (Hsp70) is one important member of heat shock protein (Hsp) family that is responsible for various stresses, especially thermal stress. Here we examined the response of Hsp70 gene to both chronic and acute thermal exposure in Pacific abalone ( Haliotis discus hannai Ino). For the chronic exposure, abalones were maintained at 8, 12, 20, and 30°C for four months and their mRNA levels were measured. The highest mRNA level of Hsp70 gene relative to actin gene was detected in the 30°C-acclimated group, followed by the 8°C-acclimated group and then the 12°C- and 20°C-acclimated groups. After the long-term acclimation, gills from each of the above acclimation groups were dissected and exposed to different temperatures between 8°C and 38°C for 30 min. Hsp70 expression in gills acclimated to different temperatures responded differentially to the same temperature exposure. The incubation temperature that induced maximum Hsp70 mRNA expression was higher in the higher temperature acclimation groups than lower temperature groups. Pacific abalones could alter the expression pattern of Hsp70 gene according to environmental thermal conditions, through which they deal with the stress of thermal variations.

  15. Trait Acclimation Mitigates Mortality Risks of Tropical Canopy Trees under Global Warming

    PubMed Central

    Sterck, Frank; Anten, Niels P. R.; Schieving, Feike; Zuidema, Pieter A.

    2016-01-01

    There is a heated debate about the effect of global change on tropical forests. Many scientists predict large-scale tree mortality while others point to mitigating roles of CO2 fertilization and – the notoriously unknown – physiological trait acclimation of trees. In this opinion article we provided a first quantification of the potential of trait acclimation to mitigate the negative effects of warming on tropical canopy tree growth and survival. We applied a physiological tree growth model that incorporates trait acclimation through an optimization approach. Our model estimated the maximum effect of acclimation when trees optimize traits that are strongly plastic on a week to annual time scale (leaf photosynthetic capacity, total leaf area, stem sapwood area) to maximize carbon gain. We simulated tree carbon gain for temperatures (25–35°C) and ambient CO2 concentrations (390–800 ppm) predicted for the 21st century. Full trait acclimation increased simulated carbon gain by up to 10–20% and the maximum tolerated temperature by up to 2°C, thus reducing risks of tree death under predicted warming. Functional trait acclimation may thus increase the resilience of tropical trees to warming, but cannot prevent tree death during extremely hot and dry years at current CO2 levels. We call for incorporating trait acclimation in field and experimental studies of plant functional traits, and in models that predict responses of tropical forests to climate change. PMID:27242814

  16. Trait Acclimation Mitigates Mortality Risks of Tropical Canopy Trees under Global Warming.

    PubMed

    Sterck, Frank; Anten, Niels P R; Schieving, Feike; Zuidema, Pieter A

    2016-01-01

    There is a heated debate about the effect of global change on tropical forests. Many scientists predict large-scale tree mortality while others point to mitigating roles of CO2 fertilization and - the notoriously unknown - physiological trait acclimation of trees. In this opinion article we provided a first quantification of the potential of trait acclimation to mitigate the negative effects of warming on tropical canopy tree growth and survival. We applied a physiological tree growth model that incorporates trait acclimation through an optimization approach. Our model estimated the maximum effect of acclimation when trees optimize traits that are strongly plastic on a week to annual time scale (leaf photosynthetic capacity, total leaf area, stem sapwood area) to maximize carbon gain. We simulated tree carbon gain for temperatures (25-35°C) and ambient CO2 concentrations (390-800 ppm) predicted for the 21st century. Full trait acclimation increased simulated carbon gain by up to 10-20% and the maximum tolerated temperature by up to 2°C, thus reducing risks of tree death under predicted warming. Functional trait acclimation may thus increase the resilience of tropical trees to warming, but cannot prevent tree death during extremely hot and dry years at current CO2 levels. We call for incorporating trait acclimation in field and experimental studies of plant functional traits, and in models that predict responses of tropical forests to climate change. PMID:27242814

  17. Role of various hormones in photosynthetic responses of green plants under environmental stresses.

    PubMed

    Poonam; Bhardwaj, Renu; Kaur, Ravdeep; Bali, Shagun; Kaur, Parminder; Sirhindi, Geetika; Thukral, Ashwani K; Ohri, Puja; Vig, Adarsh P

    2015-01-01

    Environmental stress includes adverse factors like water deficit, high salinity, enhanced temperature and heavy metals etc. These stresses alter the normal growth and metabolic processes of plants including photosynthesis. Major photosynthetic responses under various stresses include inhibition of photosystems (I and II), changes in thylakoid complexes, decreased photosynthetic activity and modifications in structure and functions of chloroplasts etc. Various defense mechanisms are triggered inside the plants in response to these stresses that are regulated by plant hormones or plant growth regulators. These phytohormones include abscisic acid, auxins, cytokinins, ethylene, brassinosteroids, jasmonates and salicylic acid etc. The present review focuses on stress protective effects of plants hormones on the photosynthetic responses. PMID:25824389

  18. Response of mice to continuous 5-day passive hyperthermia resembles human heat acclimation.

    PubMed

    Sareh, Houtan; Tulapurkar, Mohan E; Shah, Nirav G; Singh, Ishwar S; Hasday, Jeffrey D

    2011-05-01

    Chronic repeated exposure to hyperthermia in humans results in heat acclimation (HA), an adaptive process that is attained in humans by repeated exposure to hyperthermia and is characterized by improved heat elimination and increased exercise capacity, and acquired thermal tolerance (ATT), a cellular response characterized by increased baseline heat shock protein (HSP) expression and blunting of the acute increase in HSP expression stimulated by re-exposure to thermal stress. Epidemiologic studies in military personnel operating in hot environments and elite athletes suggest that repeated exposure to hyperthermia may also exert long-term health effects. Animal models demonstrate that coincident exposure to mild hyperthermia or prior exposure to severe hyperthermia can profoundly affect the course of experimental infection and injury, but these models do not represent HA. In this study, we demonstrate that CD-1 mice continuously exposed to mild hyperthermia (ambient temperature ~37°C causing ~2°C increase in core temperature) for 5 days and then exposed to a thermal stress (42°C ambient temperature for 40 min) exhibited some of the salient features of human HA, including (1) slower warming during thermal stress and more rapid cooling during recovery and (2) increased activity during thermal stress, as well as some of the features of ATT, including (1) increased baseline expression of HSP72 and HSP90 in lung, heart, spleen, liver, and brain; and (2) blunted incremental increase in HSP72 expression following acute thermal stress. This study suggests that continuous 5-day exposure of CD-1 mice to mild hyperthermia induces a state that resembles the physiologic and cellular responses of human HA. This model may be useful for analyzing the molecular mechanisms of HA and its consequences on host responsiveness to subsequent stresses. PMID:21080137

  19. THE PHOTOSYNTHETIC RESPONSE OF THE PERENNIAL RYEGRASS (LOLIUM PERENNE) IN ITS FIFTH YEAR OF FREE-AIR CO{sub 2} ENRICHMENT (FACE) AT ESCHIKON, SWITZERLAND

    SciTech Connect

    ANDERSON,J.P.; LONG,STEPHEN,P.; WILLIAMS,J.

    1998-12-31

    Stands of Ryegrass (Lolium perenne L. cv.Bastion) were grown in the field at ambient or elevated (600 {micro}mol mol{sup {minus}1}) [CO{sub 2}], high (560 kg Ha{sup {minus}1} y{sup {minus}1}) or low (140 kg Ha{sup {minus}1} y{sup {minus}1}) nitrogen addition and were harvested five times a year during the growing season. The plants were sown during 1992, additional plots being sown during 1995. These were in their fifth year and second year of growth respectively. Exposure to elevated [CO{sub 2}] was carried out with a Free-Air CO{sub 2} Enrichment (FACE) system which provides the most realistic system of fumigation currently available. Elevated [CO{sub 2}] increased diurnal CO{sub 2} uptake by between 40 to 83% while reducing stomatal conductance by between 1 and 38% in all of the 1992 grown plants measured at high [CO{sub 2}]. Analysis of the A/c{sub i} response of 1992 grown plants showed no acclimation of the photosynthetic apparatus in response to elevated [CO{sub 2}]--both V{sub c,max} (a measure of the maximum in vivo rate of carboxylation) and J{sub max} (a measure of the maximum capacity for the regeneration of RuBP) showed no significant change during any of the periods of regrowth. In contrast the leaves of 1995 grown plants, appeared to be experiencing an acclimatory change in their photosynthetic apparatus in response to elevated [CO{sub 2}]. However, this negative response seemed to be removed directly after a harvest when the source:sink balance had increased. The apparent lack of an acclimatory response after almost 5 years of growth at elevated [CO{sub 2}], suggests that L. perenne may be close to achieving the appropriate photosynthetic adjustments which would allow it to attain a significantly higher photosynthetic potential.

  20. The photosynthetic response of the perennial ryegrass (Lolium perenne) in its fifth year of free-air CO(sub 2) enrichment (FACE) at Eschikon, Switzerland

    SciTech Connect

    Anderson, J.P.; Long, S.P.; Williams, J.

    1998-12-31

    Stands of Ryegrass (Lolium perenne L. cv.Bastion) were grown in the field at ambient or elevated (600 {micro}mol mol{sup {minus}1}) [CO{sub 2}], high (560 kg Ha{sup {minus}1} y{sup {minus}1}) or low (140 kg Ha{sup {minus}1} y{sup {minus}1}) nitrogen addition and were harvested five times a year during the growing season. The plants were sown during 1992, additional plots being sown during 1995. These were in their fifth year and second year of growth respectively. Exposure to elevated [CO{sub 2}] was carried out with a Free-Air CO{sub 2} Enrichment (FACE) system which provides the most realistic system of fumigation currently available. Elevated [CO{sub 2}] increased diurnal CO{sub 2} uptake by between 40 to 83% while reducing stomatal conductance by between 1 and 38% in all of the 1992 grown plants measured at high [CO{sub 2}]. Analysis of the A/c{sub i} response of 1992 grown plants showed no acclimation of the photosynthetic apparatus in response to elevated [CO{sub 2}] - both V{sub c,max} (a measure of the maximum in vivo rate of carboxylation) and J{sub max} (a measure of the maximum capacity for the regeneration of RuBP) showed no significant change during any of the periods of regrowth. In contrast the leaves of 1995 grown plants, appeared to be experiencing an acclimatory change in their photosynthetic apparatus in response to elevated [CO{sub 2}]. However, this negative response seemed to be removed directly after a harvest when the source:sink balance had increased. The apparent lack of an acclimatory response after almost 5 years of growth at elevated [CO{sub 2}], suggests that L. perenne may be close to achieving the appropriate photosynthetic adjustments which would allow it to attain a significantly higher photosynthetic potential.

  1. Growth response and acclimation of CO2 exchange characteristics to elevated temperatures in tropical tree seedlings.

    PubMed

    Cheesman, Alexander W; Winter, Klaus

    2013-09-01

    Predictions of how tropical forests will respond to future climate change are constrained by the paucity of data on the performance of tropical species under elevated growth temperatures. In particular, little is known about the potential of tropical species to acclimate physiologically to future increases in temperature. Seedlings of 10 neo-tropical tree species from different functional groups were cultivated in controlled-environment chambers under four day/night temperature regimes between 30/22 °C and 39/31 °C. Under well-watered conditions, all species showed optimal growth at temperatures above those currently found in their native range. While non-pioneer species experienced catastrophic failure or a substantially reduced growth rate under the highest temperature regime employed (i.e. daily average of 35 °C), growth in three lowland pioneers showed only a marginal reduction. In a subsequent experiment, three species (Ficus insipida, Ormosia macrocalyx, and Ochroma pyramidale) were cultivated at two temperatures determined as sub- and superoptimal for growth, but which resulted in similar biomass accumulation despite a 6°C difference in growth temperature. Through reciprocal transfer and temperature adjustment, the role of thermal acclimation in photosynthesis and respiration was investigated. Acclimation potential varied among species, with two distinct patterns of respiration acclimation identified. The study highlights the role of both inherent temperature tolerance and thermal acclimation in determining the ability of tropical tree species to cope with enhanced temperatures. PMID:23873999

  2. Growth response and acclimation of CO2 exchange characteristics to elevated temperatures in tropical tree seedlings

    PubMed Central

    Cheesman, Alexander W.; Winter, Klaus

    2013-01-01

    Predictions of how tropical forests will respond to future climate change are constrained by the paucity of data on the performance of tropical species under elevated growth temperatures. In particular, little is known about the potential of tropical species to acclimate physiologically to future increases in temperature. Seedlings of 10 neo-tropical tree species from different functional groups were cultivated in controlled-environment chambers under four day/night temperature regimes between 30/22 °C and 39/31 °C. Under well-watered conditions, all species showed optimal growth at temperatures above those currently found in their native range. While non-pioneer species experienced catastrophic failure or a substantially reduced growth rate under the highest temperature regime employed (i.e. daily average of 35 °C), growth in three lowland pioneers showed only a marginal reduction. In a subsequent experiment, three species (Ficus insipida, Ormosia macrocalyx, and Ochroma pyramidale) were cultivated at two temperatures determined as sub- and superoptimal for growth, but which resulted in similar biomass accumulation despite a 6°C difference in growth temperature. Through reciprocal transfer and temperature adjustment, the role of thermal acclimation in photosynthesis and respiration was investigated. Acclimation potential varied among species, with two distinct patterns of respiration acclimation identified. The study highlights the role of both inherent temperature tolerance and thermal acclimation in determining the ability of tropical tree species to cope with enhanced temperatures. PMID:23873999

  3. Uncoupling High Light Responses from Singlet Oxygen Retrograde Signaling and Spatial-Temporal Systemic Acquired Acclimation1[OPEN

    PubMed Central

    Gordon, Matthew; Havaux, Michel; Albrecht-Borth, Verónica

    2016-01-01

    Distinct ROS signaling pathways initiated by singlet oxygen (1O2) or superoxide and hydrogen peroxide have been attributed to either cell death or acclimation, respectively. Recent studies have revealed that more complex antagonistic and synergistic relationships exist within and between these pathways. As specific chloroplastic ROS signals are difficult to study, rapid systemic signaling experiments using localized high light (HL) stress or ROS treatments were used in this study to uncouple signals required for direct HL and ROS perception and distal systemic acquired acclimation (SAA). A qPCR approach was chosen to determine local perception and distal signal reception. Analysis of a thylakoidal ascorbate peroxidase mutant (tapx), the 1O2-retrograde signaling double mutant (ex1/ex2), and an apoplastic signaling double mutant (rbohD/F) revealed that tAPX and EXECUTER 1 are required for both HL and systemic acclimation stress perception. Apoplastic membrane-localized RBOHs were required for systemic spread of the signal but not for local signal induction in directly stressed tissues. Endogenous ROS treatments revealed a very strong systemic response induced by a localized 1 h induction of 1O2 using the conditional flu mutant. A qPCR time course of 1O2 induced systemic marker genes in directly and indirectly connected leaves revealed a direct vascular connection component of both immediate and longer term SAA signaling responses. These results reveal the importance of an EXECUTER-dependent 1O2 retrograde signal for both local and long distance RBOH-dependent acclimation signaling that is distinct from other HL signaling pathways, and that direct vascular connections have a role in spatial-temporal SAA induction. PMID:27288360

  4. The Metabolic Status Drives Acclimation of Iron Deficiency Responses in Chlamydomonas reinhardtii as Revealed by Proteomics Based Hierarchical Clustering and Reverse Genetics*

    PubMed Central

    Höhner, Ricarda; Barth, Johannes; Magneschi, Leonardo; Jaeger, Daniel; Niehues, Anna; Bald, Till; Grossman, Arthur; Fufezan, Christian; Hippler, Michael

    2013-01-01

    Iron is a crucial cofactor in numerous redox-active proteins operating in bioenergetic pathways including respiration and photosynthesis. Cellular iron management is essential to sustain sufficient energy production and minimize oxidative stress. To produce energy for cell growth, the green alga Chlamydomonas reinhardtii possesses the metabolic flexibility to use light and/or carbon sources such as acetate. To investigate the interplay between the iron-deficiency response and growth requirements under distinct trophic conditions, we took a quantitative proteomics approach coupled to innovative hierarchical clustering using different “distance-linkage combinations” and random noise injection. Protein co-expression analyses of the combined data sets revealed insights into cellular responses governing acclimation to iron deprivation and regulation associated with photosynthesis dependent growth. Photoautotrophic growth requirements as well as the iron deficiency induced specific metabolic enzymes and stress related proteins, and yet differences in the set of induced enzymes, proteases, and redox-related polypeptides were evident, implying the establishment of distinct response networks under the different conditions. Moreover, our data clearly support the notion that the iron deficiency response includes a hierarchy for iron allocation within organelles in C. reinhardtii. Importantly, deletion of a bifunctional alcohol and acetaldehyde dehydrogenase (ADH1), which is induced under low iron based on the proteomic data, attenuates the remodeling of the photosynthetic machinery in response to iron deficiency, and at the same time stimulates expression of stress-related proteins such as NDA2, LHCSR3, and PGRL1. This finding provides evidence that the coordinated regulation of bioenergetics pathways and iron deficiency response is sensitive to the cellular and chloroplast metabolic and/or redox status, consistent with systems approach data. PMID:23820728

  5. Oxidative stress and metabolic responses to copper in freshwater- and seawater-acclimated killifish, Fundulus heteroclitus.

    PubMed

    Ransberry, Victoria E; Morash, Andrea J; Blewett, Tamzin A; Wood, Chris M; McClelland, Grant B

    2015-04-01

    In freshwater (FW), many of the main mechanisms of copper (Cu) toxicity have been characterized; however, toxicity mechanisms in seawater (SW) are less well understood. We investigated the effects of salinity on Cu-induced oxidative stress and metabolic responses in adult killifish, Fundulus heteroclitus. We exposed FW and SW-acclimated killifish to either low Cu (LC, 50 μg/L) or high Cu (HC, 200 μg/L) for 96 h and compared them to controls (CTRL) under the same salinities without added Cu. Cu exerted minimal influence on tissue ion levels in either FW or SW. Salinity generally protected against Cu bioaccumulation in the gills and liver, but not in the carcass. Hematocrit (Hct) and hemoglobin (Hb) levels were increased by LC and HC in both FW and SW, and blood lactate was reduced in FW-killifish exposed to LC and HC. Rates of oxygen consumption were similar across treatments. Salinity reduced Cu load in gill, liver and intestine at LC but only in the gills at HC. In general, Cu increased gill, liver, and intestine catalase (CAT) activity, while superoxide dismutase (SOD) either decreased or remained unchanged depending on tissue-type. These changes did not directly correlate with levels of protein carbonyls, used as an index of oxidative stress. Cu-induced changes in carbohydrate metabolic enzymes were low across tissues and the effect of salinity was variable. Thus, while salinity clearly protects against Cu bioaccumulation in some tissues, it is unclear whether salinity protects against Cu-induced oxidative stress and metabolic responses. PMID:25731683

  6. Early and delayed long-term transcriptional changes and short-term transient responses during cold acclimation in olive leaves.

    PubMed

    Leyva-Pérez, María de la O; Valverde-Corredor, Antonio; Valderrama, Raquel; Jiménez-Ruiz, Jaime; Muñoz-Merida, Antonio; Trelles, Oswaldo; Barroso, Juan Bautista; Mercado-Blanco, Jesús; Luque, Francisco

    2015-02-01

    Low temperature severely affects plant growth and development. To overcome this constraint, several plant species from regions having a cool season have evolved an adaptive response, called cold acclimation. We have studied this response in olive tree (Olea europaea L.) cv. Picual. Biochemical stress markers and cold-stress symptoms were detected after the first 24 h as sagging leaves. After 5 days, the plants were found to have completely recovered. Control and cold-stressed plants were sequenced by Illumina HiSeq 1000 paired-end technique. We also assembled a new olive transcriptome comprising 157,799 unigenes and found 6,309 unigenes differentially expressed in response to cold. Three types of response that led to cold acclimation were found: short-term transient response, early long-term response, and late long-term response. These subsets of unigenes were related to different biological processes. Early responses involved many cold-stress-responsive genes coding for, among many other things, C-repeat binding factor transcription factors, fatty acid desaturases, wax synthesis, and oligosaccharide metabolism. After long-term exposure to cold, a large proportion of gene down-regulation was found, including photosynthesis and plant growth genes. Up-regulated genes after long-term cold exposure were related to organelle fusion, nucleus organization, and DNA integration, including retrotransposons. PMID:25324298

  7. Early and delayed long-term transcriptional changes and short-term transient responses during cold acclimation in olive leaves

    PubMed Central

    Leyva-Pérez, María de la O; Valverde-Corredor, Antonio; Valderrama, Raquel; Jiménez-Ruiz, Jaime; Muñoz-Merida, Antonio; Trelles, Oswaldo; Barroso, Juan Bautista; Mercado-Blanco, Jesús; Luque, Francisco

    2015-01-01

    Low temperature severely affects plant growth and development. To overcome this constraint, several plant species from regions having a cool season have evolved an adaptive response, called cold acclimation. We have studied this response in olive tree (Olea europaea L.) cv. Picual. Biochemical stress markers and cold-stress symptoms were detected after the first 24 h as sagging leaves. After 5 days, the plants were found to have completely recovered. Control and cold-stressed plants were sequenced by Illumina HiSeq 1000 paired-end technique. We also assembled a new olive transcriptome comprising 157,799 unigenes and found 6,309 unigenes differentially expressed in response to cold. Three types of response that led to cold acclimation were found: short-term transient response, early long-term response, and late long-term response. These subsets of unigenes were related to different biological processes. Early responses involved many cold-stress-responsive genes coding for, among many other things, C-repeat binding factor transcription factors, fatty acid desaturases, wax synthesis, and oligosaccharide metabolism. After long-term exposure to cold, a large proportion of gene down-regulation was found, including photosynthesis and plant growth genes. Up-regulated genes after long-term cold exposure were related to organelle fusion, nucleus organization, and DNA integration, including retrotransposons. PMID:25324298

  8. Human Monocyte Heat Shock Protein 72 Responses to Acute Hypoxic Exercise after 3 Days of Exercise Heat Acclimation

    PubMed Central

    Lee, Ben J.; Mackenzie, Richard W. A.; Cox, Valerie; James, Rob S.; Thake, Charles D.

    2015-01-01

    The aim of this study was to determine whether short-term heat acclimation (STHA) could confer increased cellular tolerance to acute hypoxic exercise in humans as determined via monocyte HSP72 (mHSP72) expression. Sixteen males were separated into two matched groups. The STHA group completed 3 days of exercise heat acclimation; 60 minutes cycling at 50% V˙O2peak in 40°C 20% relative humidity (RH). The control group (CON) completed 3 days of exercise training in 20°C, 40% RH. Each group completed a hypoxic stress test (HST) one week before and 48 hours following the final day of CON or STHA. Percentage changes in HSP72 concentrations were similar between STHA and CON following HST1 (P = 0.97). STHA induced an increase in basal HSP72 (P = 0.03) with no change observed in CON (P = 0.218). Basal mHSP72 remained elevated before HST2 for the STHA group (P < 0.05) and was unchanged from HST1 in CON (P > 0.05). Percent change in mHSP72 was lower after HST2 in STHA compared to CON (P = 0.02). The mHSP72 response to hypoxic exercise was attenuated following 3 days of heat acclimation. This is indicative of improved tolerance and ability to cope with the hypoxic insult, potentially mediated in part by increased basal reserves of HSP72. PMID:25874231

  9. Drought acclimation in wild and cultivated barley lines. [Hordeum spontaneum; Hordeum vulgare

    SciTech Connect

    Glinka, Z. ); Gunasekera, D.; Mane, S.; Berkowitz, G. )

    1991-05-01

    Wild barley (Hordeum spontaneum) seeds collected from arid and temperate regions in Israel were used, along with cultivated barley (H. vulgare) in a study to evaluate the range of acclimation responses to low leaf water potential ({Psi}w). Stress was imposed on plants by withholding water until {Psi}w was {minus}2 megapascals (MPa). Protoplast volume (PV) was measured at {minus}0.2 and {minus}2 MPa (imposed in vitro) in leaf tissue from well-watered and stressed plants. In well-watered plants, PV declined at {minus}2, as compared to {minus}0.2 MPa in all lines. With tissue from in situ stressed plants, PV reduction at {minus}2 MPa was not as great in some lines. The change in the extent of PV reduction occurring at {minus}2 MPa was used as an index of drought acclimation. The 13 wild barley lines were separated into high, medium, and low acclimation groups. Lines collected from arid regions scored in the high acclimation group. The cultivated barley lines scored in the medium and low groups. Relative water content decline at low leaf {Psi}w in situ was not a good indicator of acclimation; all lines responded similarly. Photosynthesis in situ was measured at high and low leaf {Psi}w in lines from the three groupings. Photosynthetic sensitivity to low {Psi}w was twice as great in low acclimation, as compared to high acclimation lines. It was concluded that PV response to low {Psi}w is a good indicator of drought acclimation in barley, and that wild lines offer a range of acclimation potential which could be used in breeding programs.

  10. Phenotypic flexibility of thermogenesis in the hwamei (Garrulax canorus): responses to cold acclimation.

    PubMed

    Zhou, Li-Meng; Xia, Su-Su; Chen, Qian; Wang, Run-Mei; Zheng, Wei-Hong; Liu, Jin-Song

    2016-02-15

    Cold acclimation in birds involves a comprehensive array of physiological and morphological adjustment ranging from changes in aerobic enzyme activity to metabolic rate and organ mass. In the present study, we investigated phenotypic variation in thermogenic activity in the hwamei (Garrulax canorus) under normal (35°C) or cold (15°C) ambient temperature conditions. Acclimation to an ambient temperature of 15°C for 4 wk significantly increased the body mass, basal metabolic rate (BMR), and energy intake, including both gross energy intake and digestible energy intake, compared with birds kept at 35°C. Furthermore, birds acclimated to 15°C increased the dry mass of their liver and kidneys, but not their heart and pectoral muscles, and displayed higher state-4 respiration in the liver, kidneys, heart, and pectoral muscles, and higher cytochrome-c oxidase (COX) activity in liver, kidney, and pectoral muscle, compared with those kept at 35°C. There was a positive correlation between BMR and state-4 respiration in all of the above organs except the liver, and between BMR and COX activity in all of the above organs. Taken together, these data illustrate the morphological, physiological, and enzymatic changes associated with cold acclimation, and support the notion that the hwamei is a bird species from temperate climates that exhibits high phenotypic flexibility of thermogenic capacity. PMID:26661097

  11. Gene expression responses in photosynthetic tissues to herbicides and pathogens

    Technology Transfer Automated Retrieval System (TEKTRAN)

    When plants are attacked by pathogens, the photosynthetic tissue is often dramatically affected. The chloroplasts within this tissue can participate in defense by being a source of many plant secondary metabolites that serve as defense signaling compounds, antioxidants, and phytoalexins. The chlorop...

  12. Thermal acclimation of leaf respiration of tropical trees and lianas: response to experimental canopy warming, and consequences for tropical forest carbon balance.

    PubMed

    Slot, Martijn; Rey-Sánchez, Camilo; Gerber, Stefan; Lichstein, Jeremy W; Winter, Klaus; Kitajima, Kaoru

    2014-09-01

    Climate warming is expected to increase respiration rates of tropical forest trees and lianas, which may negatively affect the carbon balance of tropical forests. Thermal acclimation could mitigate the expected respiration increase, but the thermal acclimation potential of tropical forests remains largely unknown. In a tropical forest in Panama, we experimentally increased nighttime temperatures of upper canopy leaves of three tree and two liana species by on average 3 °C for 1 week, and quantified temperature responses of leaf dark respiration. Respiration at 25 °C (R25 ) decreased with increasing leaf temperature, but acclimation did not result in perfect homeostasis of respiration across temperatures. In contrast, Q10 of treatment and control leaves exhibited similarly high values (range 2.5-3.0) without evidence of acclimation. The decrease in R25 was not caused by respiratory substrate depletion, as warming did not reduce leaf carbohydrate concentration. To evaluate the wider implications of our experimental results, we simulated the carbon cycle of tropical latitudes (24°S-24°N) from 2000 to 2100 using a dynamic global vegetation model (LM3VN) modified to account for acclimation. Acclimation reduced the degree to which respiration increases with climate warming in the model relative to a no-acclimation scenario, leading to 21% greater increase in net primary productivity and 18% greater increase in biomass carbon storage over the 21st century. We conclude that leaf respiration of tropical forest plants can acclimate to nighttime warming, thereby reducing the magnitude of the positive feedback between climate change and the carbon cycle. PMID:24604769

  13. UV-B Perception and Acclimation in Chlamydomonas reinhardtii.

    PubMed

    Tilbrook, Kimberley; Dubois, Marine; Crocco, Carlos D; Yin, Ruohe; Chappuis, Richard; Allorent, Guillaume; Schmid-Siegert, Emanuel; Goldschmidt-Clermont, Michel; Ulm, Roman

    2016-04-01

    Plants perceive UV-B, an intrinsic component of sunlight, via a signaling pathway that is mediated by the photoreceptor UV RESISTANCE LOCUS8 (UVR8) and induces UV-B acclimation. To test whether similar UV-B perception mechanisms exist in the evolutionarily distant green alga Chlamydomonas reinhardtii, we identified Chlamydomonas orthologs of UVR8 and the key signaling factor CONSTITUTIVELY PHOTOMORPHOGENIC1 (COP1). Cr-UVR8 shares sequence and structural similarity to Arabidopsis thaliana UVR8, has conserved tryptophan residues for UV-B photoreception, monomerizes upon UV-B exposure, and interacts with Cr-COP1 in a UV-B-dependent manner. Moreover, Cr-UVR8 can interact with At-COP1 and complement the Arabidopsis uvr8 mutant, demonstrating that it is a functional UV-B photoreceptor. Chlamydomonas shows apparent UV-B acclimation in colony survival and photosynthetic efficiency assays. UV-B exposure, at low levels that induce acclimation, led to broad changes in the Chlamydomonas transcriptome, including in genes related to photosynthesis. Impaired UV-B-induced activation in the Cr-COP1 mutant hit1 indicates that UVR8-COP1 signaling induces transcriptome changes in response to UV-B. Also, hit1 mutants are impaired in UV-B acclimation. Chlamydomonas UV-B acclimation preserved the photosystem II core proteins D1 and D2 under UV-B stress, which mitigated UV-B-induced photoinhibition. These findings highlight the early evolution of UVR8 photoreceptor signaling in the green lineage to induce UV-B acclimation and protection. PMID:27020958

  14. Growth and photosynthetic responses to copper in wild grapevine.

    PubMed

    Cambrollé, J; García, J L; Ocete, R; Figueroa, M E; Cantos, M

    2013-09-01

    The present study evaluates the tolerance and accumulation potential of Vitis vinifera ssp. sylvestris under moderate and high external Cu levels. A greenhouse experiment was conducted in order to investigate the effects of a range of external Cu concentrations (0-23mmolL(-1)) on growth and photosynthetic performance by measuring gas exchange, chlorophyll fluorescence parameters and photosynthetic pigments. We also measured the total copper, nitrogen, phosphorus, sulphur, calcium, magnesium, iron, potassium and sodium concentrations in the plant tissues. All the experimental plants survived even with external Cu concentrations as high as 23mmolL(-1) (1500mg Cu L(-1)), although the excess of metal resulted in a biomass reduction of 35%. The effects of Cu on growth were linked to a reduction in net photosynthesis, which may be related to the effect of the high concentration of the metal on photosynthetic electron transport. V. vinifera ssp. sylvestris survived with leaf Cu concentrations as high as 80mgkg(-1) DW and growth parameters were unaffected by leaf tissue concentrations of 35mg Cu kg(-1) DW. The results of our study indicate that plants of V. vinifera ssp. sylvestris from the studied population are more tolerant to Cu than the commercial varieties of grapevine that have been studied in the literature, and could constitute a basis for the genetic improvement of Cu tolerance in grapevine. PMID:23746388

  15. Photosynthetic consequences of phenotypic plasticity in response to submergence: Rumex palustris as a case study.

    PubMed

    Mommer, Liesje; Pons, Thÿs L; Visser, Eric J W

    2006-01-01

    Survival and growth of terrestrial plants is negatively affected by complete submergence. This is mainly the result of hampered gas exchange between plants and their environment, since gas diffusion is severely reduced in water compared with air, resulting in O2 deficits which limit aerobic respiration. The continuation of photosynthesis could probably alleviate submergence-stress in terrestrial plants, but its potential under water will be limited as the availability of CO2 is hampered. Several submerged terrestrial plant species, however, express plastic responses of the shoot which may reduce gas diffusion resistance and enhance benefits from underwater photosynthesis. In particular, the plasticity of the flooding-tolerant terrestrial species Rumex palustris turned out to be remarkable, making it a model species suitable for the study of these responses. During submergence, the morphology and anatomy of newly developed leaves changed: 'aquatic' leaves were thinner and had thinner cuticles. As a consequence, internal O2 concentrations and underwater CO2 assimilation rates were higher at the prevailing low CO2 concentrations in water. Compared with heterophyllous amphibious plant species, underwater photosynthesis rates of terrestrial plants may be very limited, but the effects of underwater photosynthesis on underwater survival are impressive. A combination of recently published data allowed quantification of the magnitude of the acclimation response in this species. Gas diffusion resistance in terrestrial leaves underwater was about 15,000 times higher than in air. Strikingly, acclimation to submergence reduced this factor to 400, indicating that acclimated leaves of R. palustris had an approximately 40 times lower gas diffusion resistance than non-acclimated ones. PMID:16291797

  16. Long-term growth of soybean at elevated [CO2] does not cause acclimation of stomatal conductance under fully open-air conditions

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Accurately predicting plant function and global biogeochemical cycles later this century will be complicated if stomatal conductance (gs) acclimates to growth at elevated [CO2], in the sense of a long-term alteration of the response of gs to [CO2], humidity (h) and/or photosynthetic rate (A). If so,...

  17. Light-exposed shoots of seven coexisting deciduous species show common photosynthetic responses to tree height.

    PubMed

    Miyata, Rie; Kohyama, Takashi S

    2016-10-01

    Functional traits of light-exposed leaves have been reported to show tree height-dependent change. However, it remains unknown how plastic response of leaf traits to tree height is linked with shoot-level carbon gain. To answer this question, we examined the photosynthetic properties of fully lit current-year shoots in crown tops with various heights for seven deciduous broad-leaved species dominated in a cool-temperate forest in northern Japan. We measured leaf mass, stomatal conductance, nitrogen content, light-saturated net photosynthetic rate (all per leaf lamina area), foliar stable carbon isotope ratio, and shoot mass allocation to leaf laminae. We employed hierarchical Bayesian models to simultaneously quantify inter-trait relationships for all species. We found that leaf and shoot traits were co-varied in association with height, and that there was no quantitative inter-specific difference in leaf- and shoot-level plastic responses to height. Nitrogen content increased and stomatal conductance decreased with height. Reflecting these antagonistic responses to height, photosynthetic rate was almost unchanged with height. Photosynthetic rate divided by stomatal conductance as a proxy of photosynthetic water use efficiency sufficiently explained the variation of foliar carbon isotope ratio. The increase in mass allocation to leaves in a shoot compensated for the height-dependent decline in photosynthetic rate per leaf lamina mass. Consequently, photosynthetic gain at the scale of current-year shoot mass was kept unchanged with tree height. We suggest that the convergent responses of shoot functional traits across species reflect common requirements for trees coexisting in a forest. PMID:27262582

  18. Two Cyanobacterial Photoreceptors Regulate Photosynthetic Light Harvesting by Sensing Teal, Green, Yellow, and Red Light

    PubMed Central

    Wiltbank, Lisa B.

    2016-01-01

    ABSTRACT The genomes of many photosynthetic and nonphotosynthetic bacteria encode numerous phytochrome superfamily photoreceptors whose functions and interactions are largely unknown. Cyanobacterial genomes encode particularly large numbers of phytochrome superfamily members called cyanobacteriochromes. These have diverse light color-sensing abilities, and their functions and interactions are just beginning to be understood. One of the best characterized of these functions is the regulation of photosynthetic light-harvesting antenna composition in the cyanobacterium Fremyella diplosiphon by the cyanobacteriochrome RcaE in response to red and green light, a process known as chromatic acclimation. We have identified a new cyanobacteriochrome named DpxA that maximally senses teal (absorption maximum, 494 nm) and yellow (absorption maximum, 568 nm) light and represses the accumulation of a key light-harvesting protein called phycoerythrin, which is also regulated by RcaE during chromatic acclimation. Like RcaE, DpxA is a two-component system kinase, although these two photoreceptors can influence phycoerythrin expression through different signaling pathways. The peak responsiveness of DpxA to teal and yellow light provides highly refined color discrimination in the green spectral region, which provides important wavelengths for photosynthetic light harvesting in cyanobacteria. These results redefine chromatic acclimation in cyanobacteria and demonstrate that cyanobacteriochromes can coordinately impart sophisticated light color sensing across the visible spectrum to regulate important photosynthetic acclimation processes. PMID:26861023

  19. Eleven days of moderate exercise and heat exposure induces acclimation without significant HSP70 and apoptosis responses of lymphocytes in college-aged males.

    PubMed

    Hom, Lindsay L; Lee, Elaine Choung-Hee; Apicella, Jenna M; Wallace, Sean D; Emmanuel, Holly; Klau, Jennifer F; Poh, Paula Y S; Marzano, Stefania; Armstrong, Lawrence E; Casa, Douglas J; Maresh, Carl M

    2012-01-01

    The purpose of this study was to assess whether a lymphocyte heat shock response and altered heat tolerance to ex vivo heat shock is evident during acclimation. We aimed to use flow cytometry to assess the CD3(+)CD4(+) T lymphocyte cell subset. We further aimed to induce acclimation using moderately stressful daily exercise-heat exposures to achieve acclimation. Eleven healthy males underwent 11 days of heat acclimation. Subjects walked for 90 min (50 ± 8% VO(2max)) on a treadmill (3.5 mph, 5% grade), in an environmental chamber (33°C, 30-50% relative humidity). Rectal temperature (°C), heart rate (in beats per minute), rating of perceived exertion , thermal ratings, hydration state, and sweat rate were measured during exercise and recovery. On days 1, 4, 7, 10, and 11, peripheral blood mononuclear cells were isolated from pre- and post-exercise blood samples. Intracellular and surface HSP70 (SPA-820PE, Stressgen, Assay Designs), and annexin V (ab14085, Abcam Inc.), as a marker of early apoptosis, were measured on CD3(+) and CD4(+) (sc-70624, sc-70670, Santa Cruz Biotechnology) gated lymphocytes. On day 10, subjects experienced 28 h of sleep loss. Heat acclimation was verified with decreased post-exercise rectal temperature, heart rate, and increased sweat rate on day 11, versus day 1. Heat acclimation was achieved in the absence of significant changes in intracellular HSP70 mean fluorescence intensity and percent of HSP70(+) lymphocytes during acclimation. Furthermore, there was no increased cellular heat tolerance during secondary ex vivo heat shock of the lymphocytes acquired from subjects during acclimation. There was no effect of a mild sleep loss on any variable. We conclude that our protocol successfully induced physiological acclimation without induction of cellular heat shock responses in lymphocytes and that added mild sleep loss is not sufficient to induce a heat shock response. PMID:21796498

  20. Thermal acclimation of photosynthesis: on the importance of adjusting our definitions and accounting for thermal acclimation of respiration.

    PubMed

    Way, Danielle A; Yamori, Wataru

    2014-02-01

    While interest in photosynthetic thermal acclimation has been stimulated by climate warming, comparing results across studies requires consistent terminology. We identify five types of photosynthetic adjustments in warming experiments: photosynthesis as measured at the high growth temperature, the growth temperature, and the thermal optimum; the photosynthetic thermal optimum; and leaf-level photosynthetic capacity. Adjustments of any one of these variables need not mean a concurrent adjustment in others, which may resolve apparently contradictory results in papers using different indicators of photosynthetic acclimation. We argue that photosynthetic thermal acclimation (i.e., that benefits a plant in its new growth environment) should include adjustments of both the photosynthetic thermal optimum (T opt) and photosynthetic rates at the growth temperature (A growth), a combination termed constructive adjustment. However, many species show reduced photosynthesis when grown at elevated temperatures, despite adjustment of some photosynthetic variables, a phenomenon we term detractive adjustment. An analysis of 70 studies on 103 species shows that adjustment of T opt and A growth are more common than adjustment of other photosynthetic variables, but only half of the data demonstrate constructive adjustment. No systematic differences in these patterns were found between different plant functional groups. We also discuss the importance of thermal acclimation of respiration for net photosynthesis measurements, as respiratory temperature acclimation can generate apparent acclimation of photosynthetic processes, even if photosynthesis is unaltered. We show that while dark respiration is often used to estimate light respiration, the ratio of light to dark respiration shifts in a non-predictable manner with a change in leaf temperature. PMID:23812760

  1. Thioredoxin f1 and NADPH-Dependent Thioredoxin Reductase C Have Overlapping Functions in Regulating Photosynthetic Metabolism and Plant Growth in Response to Varying Light Conditions1[OPEN

    PubMed Central

    Thormählen, Ina; Meitzel, Tobias; Groysman, Julia; Öchsner, Alexandra Bianca; von Roepenack-Lahaye, Edda; Naranjo, Belén; Cejudo, Francisco J.; Geigenberger, Peter

    2015-01-01

    Two different thiol redox systems exist in plant chloroplasts, the ferredoxin-thioredoxin (Trx) system, which depends on ferredoxin reduced by the photosynthetic electron transport chain and, thus, on light, and the NADPH-dependent Trx reductase C (NTRC) system, which relies on NADPH and thus may be linked to sugar metabolism in the dark. Previous studies suggested, therefore, that the two different systems may have different functions in plants. We now report that there is a previously unrecognized functional redundancy of Trx f1 and NTRC in regulating photosynthetic metabolism and growth. In Arabidopsis (Arabidopsis thaliana) mutants, combined, but not single, deficiencies of Trx f1 and NTRC led to severe growth inhibition and perturbed light acclimation, accompanied by strong impairments of Calvin-Benson cycle activity and starch accumulation. Light activation of key enzymes of these pathways, fructose-1,6-bisphosphatase and ADP-glucose pyrophosphorylase, was almost completely abolished. The subsequent increase in NADPH-NADP+ and ATP-ADP ratios led to increased nitrogen assimilation, NADP-malate dehydrogenase activation, and light vulnerability of photosystem I core proteins. In an additional approach, reporter studies show that Trx f1 and NTRC proteins are both colocalized in the same chloroplast substructure. Results provide genetic evidence that light- and NADPH-dependent thiol redox systems interact at the level of Trx f1 and NTRC to coordinately participate in the regulation of the Calvin-Benson cycle, starch metabolism, and growth in response to varying light conditions. PMID:26338951

  2. Thioredoxin f1 and NADPH-Dependent Thioredoxin Reductase C Have Overlapping Functions in Regulating Photosynthetic Metabolism and Plant Growth in Response to Varying Light Conditions.

    PubMed

    Thormählen, Ina; Meitzel, Tobias; Groysman, Julia; Öchsner, Alexandra Bianca; von Roepenack-Lahaye, Edda; Naranjo, Belén; Cejudo, Francisco J; Geigenberger, Peter

    2015-11-01

    Two different thiol redox systems exist in plant chloroplasts, the ferredoxin-thioredoxin (Trx) system, which depends on ferredoxin reduced by the photosynthetic electron transport chain and, thus, on light, and the NADPH-dependent Trx reductase C (NTRC) system, which relies on NADPH and thus may be linked to sugar metabolism in the dark. Previous studies suggested, therefore, that the two different systems may have different functions in plants. We now report that there is a previously unrecognized functional redundancy of Trx f1 and NTRC in regulating photosynthetic metabolism and growth. In Arabidopsis (Arabidopsis thaliana) mutants, combined, but not single, deficiencies of Trx f1 and NTRC led to severe growth inhibition and perturbed light acclimation, accompanied by strong impairments of Calvin-Benson cycle activity and starch accumulation. Light activation of key enzymes of these pathways, fructose-1,6-bisphosphatase and ADP-glucose pyrophosphorylase, was almost completely abolished. The subsequent increase in NADPH-NADP(+) and ATP-ADP ratios led to increased nitrogen assimilation, NADP-malate dehydrogenase activation, and light vulnerability of photosystem I core proteins. In an additional approach, reporter studies show that Trx f1 and NTRC proteins are both colocalized in the same chloroplast substructure. Results provide genetic evidence that light- and NADPH-dependent thiol redox systems interact at the level of Trx f1 and NTRC to coordinately participate in the regulation of the Calvin-Benson cycle, starch metabolism, and growth in response to varying light conditions. PMID:26338951

  3. Diatom Proteomics Reveals Unique Acclimation Strategies to Mitigate Fe Limitation

    PubMed Central

    Nunn, Brook L.; Faux, Jessica F.; Hippmann, Anna A.; Maldonado, Maria T.; Harvey, H. Rodger; Goodlett, David R.; Boyd, Philip W.; Strzepek, Robert F.

    2013-01-01

    Phytoplankton growth rates are limited by the supply of iron (Fe) in approximately one third of the open ocean, with major implications for carbon dioxide sequestration and carbon (C) biogeochemistry. To date, understanding how alteration of Fe supply changes phytoplankton physiology has focused on traditional metrics such as growth rate, elemental composition, and biophysical measurements such as photosynthetic competence (Fv/Fm). Researchers have subsequently employed transcriptomics to probe relationships between changes in Fe supply and phytoplankton physiology. Recently, studies have investigated longer-term (i.e. following acclimation) responses of phytoplankton to various Fe conditions. In the present study, the coastal diatom, Thalassiosira pseudonana, was acclimated (10 generations) to either low or high Fe conditions, i.e. Fe-limiting and Fe-replete. Quantitative proteomics and a newly developed proteomic profiling technique that identifies low abundance proteins were employed to examine the full complement of expressed proteins and consequently the metabolic pathways utilized by the diatom under the two Fe conditions. A total of 1850 proteins were confidently identified, nearly tripling previous identifications made from differential expression in diatoms. Given sufficient time to acclimate to Fe limitation, T. pseudonana up-regulates proteins involved in pathways associated with intracellular protein recycling, thereby decreasing dependence on extracellular nitrogen (N), C and Fe. The relative increase in the abundance of photorespiration and pentose phosphate pathway proteins reveal novel metabolic shifts, which create substrates that could support other well-established physiological responses, such as heavily silicified frustules observed for Fe-limited diatoms. Here, we discovered that proteins and hence pathways observed to be down-regulated in short-term Fe starvation studies are constitutively expressed when T. pseudonana is acclimated (i

  4. Leaf photosynthetic and water-relations responses for 'Valencia' orange trees exposed to oxidant air pollution

    SciTech Connect

    Olszyk, D.M.; Takemoto, B.K.; Poe, M.

    1991-01-01

    Leaf responses were measured to test a hypothesis that reduced photosynthetic capacity and/or altered water relations were associated with reductions in yield for 'Valencia' orange trees (Citrus sinensis (L.), Osbeck) exposed to ambient oxidant air pollution. Exposures were continuous for 4 years to three levels of oxidants (in charcoal-filtered, half-filtered, and non-filtered air). Oxidants had no effect on net leaf photosynthetic rates or on photosynthetic pigment concentrations. A single set of measurements indicated that oxidants increased leaf starch concentrations (24%) prior to flowering, suggesting a change in photosynthate allocation. Leaves exposed to oxidants had small, but consistent, changes in water relations over the summer growing season, compared to trees growing in filtered air. Other changes included decreased stomatal conductance (12%) and transpiration (9%) rates, and increased water pressure potentials (5%). While all responses were subtle, their cumulative impact over 4 years indicated that 'Valencia' orange trees were subject to increased ambient oxidant stress.

  5. Algal photosynthetic responses to toxic metals and herbicides assessed by chlorophyll a fluorescence.

    PubMed

    Kumar, K Suresh; Dahms, Hans-Uwe; Lee, Jae-Seong; Kim, Hyung Chul; Lee, Won Chan; Shin, Kyung-Hoon

    2014-06-01

    Chlorophyll a fluorescence is established as a rapid, non-intrusive technique to monitor photosynthetic performance of plants and algae, as well as to analyze their protective responses. Apart from its utility in determining the physiological status of photosynthesizers in the natural environment, chlorophyll a fluorescence-based methods are applied in ecophysiological and toxicological studies to examine the effect of environmental changes and pollutants on plants and algae (microalgae and seaweeds). Pollutants or environmental changes cause alteration of the photosynthetic capacity which could be evaluated by fluorescence kinetics. Hence, evaluating key fluorescence parameters and assessing photosynthetic performances would provide an insight regarding the probable causes of changes in photosynthetic performances. This technique quintessentially provides non-invasive determination of changes in the photosynthetic apparatus prior to the appearance of visible damage. It is reliable, economically feasible, time-saving, highly sensitive, versatile, accurate, non-invasive and portable; thereby comprising an excellent alternative for detecting pollution. The present review demonstrates the applicability of chlorophyll a fluorescence in determining photochemical responses of algae exposed to environmental toxicants (such as toxic metals and herbicides). PMID:24632123

  6. The Role of Light in Cold Acclimation of Hedera helix L. var. Thorndale 1

    PubMed Central

    Steponkus, Peter L.; Lanphear, F. O.

    1968-01-01

    The role of light in cold acclimation of Hedera helix L. var. Thorndale appears to differ from that reported for winter annuals. Although light greatly enhances the degree of hardiness attained, cold acclimation is not obligatorily linked to a light requirement. Photoperiods, varying from 8 to 24 hours, received during the cold acclimation period were equally effective in promoting maximum hardiness. Relatively low light intensities and short photoperiods stimulated maximum hardiness, and proportional increases in hardiness in response to increased photoperiods were demonstrated only in stems of prestarved plants. Exclusion of CO2 and high concentrations of photosynthetic inhibitors decreased hardiness, but in no instance was hardiness reduced to the level of the dark control. The data are only compatible with a photosynthetic role of light if it is assumed that only a small portion of the total photosynthates are required to elicit maximum hardiness. Alternatively, the light stimulation which was elicited by low light intensities, short photoperiods, in the absence of CO2, and in the presence of photosynthetic inhibitors, may be a light signal similar to a phytochrome response. PMID:16656748

  7. In High-Light-Acclimated Coffee Plants the Metabolic Machinery Is Adjusted to Avoid Oxidative Stress Rather than to Benefit from Extra Light Enhancement in Photosynthetic Yield

    PubMed Central

    Martins, Samuel C. V.; Araújo, Wagner L.; Tohge, Takayuki; Fernie, Alisdair R.; DaMatta, Fábio M.

    2014-01-01

    Coffee (Coffea arabica L.) has been traditionally considered as shade-demanding, although it performs well without shade and even out-yields shaded coffee. Here we investigated how coffee plants adjust their metabolic machinery to varying light supply and whether these adjustments are supported by a reprogramming of the primary and secondary metabolism. We demonstrate that coffee plants are able to adjust its metabolic machinery to high light conditions through marked increases in its antioxidant capacity associated with enhanced consumption of reducing equivalents. Photorespiration and alternative pathways are suggested to be key players in reductant-consumption under high light conditions. We also demonstrate that both primary and secondary metabolism undergo extensive reprogramming under high light supply, including depression of the levels of intermediates of the tricarboxylic acid cycle that were accompanied by an up-regulation of a range of amino acids, sugars and sugar alcohols, polyamines and flavonoids such as kaempferol and quercetin derivatives. When taken together, the entire dataset is consistent with these metabolic alterations being primarily associated with oxidative stress avoidance rather than representing adjustments in order to facilitate the plants from utilizing the additional light to improve their photosynthetic performance. PMID:24733284

  8. In high-light-acclimated coffee plants the metabolic machinery is adjusted to avoid oxidative stress rather than to benefit from extra light enhancement in photosynthetic yield.

    PubMed

    Martins, Samuel C V; Araújo, Wagner L; Tohge, Takayuki; Fernie, Alisdair R; DaMatta, Fábio M

    2014-01-01

    Coffee (Coffea arabica L.) has been traditionally considered as shade-demanding, although it performs well without shade and even out-yields shaded coffee. Here we investigated how coffee plants adjust their metabolic machinery to varying light supply and whether these adjustments are supported by a reprogramming of the primary and secondary metabolism. We demonstrate that coffee plants are able to adjust its metabolic machinery to high light conditions through marked increases in its antioxidant capacity associated with enhanced consumption of reducing equivalents. Photorespiration and alternative pathways are suggested to be key players in reductant-consumption under high light conditions. We also demonstrate that both primary and secondary metabolism undergo extensive reprogramming under high light supply, including depression of the levels of intermediates of the tricarboxylic acid cycle that were accompanied by an up-regulation of a range of amino acids, sugars and sugar alcohols, polyamines and flavonoids such as kaempferol and quercetin derivatives. When taken together, the entire dataset is consistent with these metabolic alterations being primarily associated with oxidative stress avoidance rather than representing adjustments in order to facilitate the plants from utilizing the additional light to improve their photosynthetic performance. PMID:24733284

  9. Photosynthetic response to fluctuating environments and photoprotective strategies under abiotic stress.

    PubMed

    Yamori, Wataru

    2016-05-01

    Plants in natural environments must cope with diverse, highly dynamic, and unpredictable conditions. They have mechanisms to enhance the capture of light energy when light intensity is low, but they can also slow down photosynthetic electron transport to prevent the production of reactive oxygen species and consequent damage to the photosynthetic machinery under excess light. Plants need a highly responsive regulatory system to balance the photosynthetic light reactions with downstream metabolism. Various mechanisms of regulation of photosynthetic electron transport under stress have been proposed, however the data have been obtained mainly under environmentally stable and controlled conditions. Thus, our understanding of dynamic modulation of photosynthesis under dramatically fluctuating natural environments remains limited. In this review, first I describe the magnitude of environmental fluctuations under natural conditions. Next, I examine the effects of fluctuations in light intensity, CO2 concentration, leaf temperature, and relative humidity on dynamic photosynthesis. Finally, I summarize photoprotective strategies that allow plants to maintain the photosynthesis under stressful fluctuating environments. The present work clearly showed that fluctuation in various environmental factors resulted in reductions in photosynthetic rate in a stepwise manner at every environmental fluctuation, leading to the conclusion that fluctuating environments would have a large impact on photosynthesis. PMID:27023791

  10. Photosynthetic Physiological Response of Radix Isatidis (Isatis indigotica Fort.) Seedlings to Nicosulfuron

    PubMed Central

    Ning, Na; Wen, Yinyuan; Dong, Shuqi; Yin, Meiqiang; Guo, Meijun; Wang, Binqiang; Feng, Lei; Guo, Pingyi

    2014-01-01

    Radix Isatidis (Isatis indigotica Fort.) is one of the most important traditional Chinese medicine plants. However, there is no suitable herbicide used for weed control in Radix Isatidis field during postemergence stage. To explore the safety of sulfonylurea herbicide nicosulfuron on Radix Isatidis (Isatis indigotica Fort.) seedlings and the photosynthetic physiological response of the plant to the herbicide, biological mass, leaf area, photosynthetic pigment content, photosynthetic rate, chlorophyll fluorescence characteristics, and P700 parameters of Radix Isatidis seedlings were analyzed 10 d after nicosulfuron treatment at 5th leaf stage in this greenhouse research. The results showed that biological mass, total chlorophyll, chlorophyll a, and carotenoids content, photosynthetic rate, stomatal conductance, PS II maximum quantum yield, PS II effective quantum yield, PS II electron transport rate, photochemical quenching, maximal P700 change, photochemical quantum yield of PS I, and PS I electron transport rate decreased with increasing herbicide concentrations, whereas initial fluorescence, quantum yield of non-regulated energy dissipation in PS II and quantum yield of non-photochemical energy dissipation due to acceptor side limitation in PS I increased. It suggests that nicosulfuron ≥1 mg L−1 causes the damage of chloroplast, PS II and PS I structure. Electron transport limitations in PS I receptor side, and blocked dark reaction process may be the main cause of the significantly inhibited growth and decreased photosynthetic rate of Radix Isatidis seedlings. PMID:25165819

  11. LEAF PHOTOSYNTHETIC AND WATER RELATIONS RESPONSES FOR "VALENCIA" ORANGE TREES EXPOSED TO OXIDANT AIR POLLUTION

    EPA Science Inventory

    Leaf responses were measured to test a hypothesis that reduced photosynthetic capacity and/or altered water relations were associated with reductions in yield for "Valencia" orange trees exposed to ambient oxidant air pollution. xposures were continuous for four years to three le...

  12. Field and controlled environment measurements show strong seasonal acclimation in photosynthesis and respiration potential in boreal Scots pine.

    PubMed

    Kolari, Pasi; Chan, Tommy; Porcar-Castell, Albert; Bäck, Jaana; Nikinmaa, Eero; Juurola, Eija

    2014-01-01

    Understanding the seasonality of photosynthesis in boreal evergreen trees and its control by the environment requires separation of the instantaneous and slow responses, as well as the dynamics of light reactions, carbon reactions, and respiration. We determined the seasonality of photosynthetic light response and respiration parameters of Scots pine (Pinus sylvestris L.) in the field in southern Finland and in controlled laboratory conditions. CO2 exchange and chlorophyll fluorescence were measured in the field using a continuously operated automated chamber setup and fluorescence monitoring systems. We also carried out monthly measurements of photosynthetic light, CO2 and temperature responses in standard conditions with a portable IRGA and fluorometer instrument. The field and response measurements indicated strong seasonal variability in the state of the photosynthetic machinery with a deep downregulation during winter. Despite the downregulation, the photosynthetic machinery retained a significant capacity during winter, which was not visible in the field measurements. Light-saturated photosynthesis (P sat) and the initial slope of the photosynthetic light response (α) obtained in standard conditions were up to 20% of their respective summertime values. Respiration also showed seasonal acclimation with peak values of respiration in standard temperature in spring and decline in autumn. Spring recovery of all photosynthetic parameters could be predicted with temperature history. On the other hand, the operating quantum yield of photosystem II and the initial slope of photosynthetic light response stayed almost at the summertime level until late autumn while at the same time P sat decreased following the prevailing temperature. Comparison of photosynthetic parameters with the environmental drivers suggests that light and minimum temperature are also decisive factors in the seasonal acclimation of photosynthesis in boreal evergreen trees. PMID:25566291

  13. Field and controlled environment measurements show strong seasonal acclimation in photosynthesis and respiration potential in boreal Scots pine

    PubMed Central

    Kolari, Pasi; Chan, Tommy; Porcar-Castell, Albert; Bäck, Jaana; Nikinmaa, Eero; Juurola, Eija

    2014-01-01

    Understanding the seasonality of photosynthesis in boreal evergreen trees and its control by the environment requires separation of the instantaneous and slow responses, as well as the dynamics of light reactions, carbon reactions, and respiration. We determined the seasonality of photosynthetic light response and respiration parameters of Scots pine (Pinus sylvestris L.) in the field in southern Finland and in controlled laboratory conditions. CO2 exchange and chlorophyll fluorescence were measured in the field using a continuously operated automated chamber setup and fluorescence monitoring systems. We also carried out monthly measurements of photosynthetic light, CO2 and temperature responses in standard conditions with a portable IRGA and fluorometer instrument. The field and response measurements indicated strong seasonal variability in the state of the photosynthetic machinery with a deep downregulation during winter. Despite the downregulation, the photosynthetic machinery retained a significant capacity during winter, which was not visible in the field measurements. Light-saturated photosynthesis (Psat) and the initial slope of the photosynthetic light response (α) obtained in standard conditions were up to 20% of their respective summertime values. Respiration also showed seasonal acclimation with peak values of respiration in standard temperature in spring and decline in autumn. Spring recovery of all photosynthetic parameters could be predicted with temperature history. On the other hand, the operating quantum yield of photosystem II and the initial slope of photosynthetic light response stayed almost at the summertime level until late autumn while at the same time Psat decreased following the prevailing temperature. Comparison of photosynthetic parameters with the environmental drivers suggests that light and minimum temperature are also decisive factors in the seasonal acclimation of photosynthesis in boreal evergreen trees. PMID:25566291

  14. Effects of exercise-heat acclimation on fluid, electrolyte, and endocrine responses during tilt and +Gz acceleration in women and men.

    PubMed

    Greenleaf, J E; Brock, P J; Sciaraffa, D; Polese, A; Elizondo, R

    1985-07-01

    Plasma fluid, electrolyte, protein, renin, and vasoactive hormone (epinephrine, norepinephrine, vasopressin) responses were measured in six women (21-23 yr) and four men (21-38 yr) before and immediately following an orthostatic tolerance test (70 degrees head-up tilt) and a +Gz (head-to-foot) acceleration tolerance test (0.5 G X min-1 linear ramp to grayout). These tests were conducted before and after 12 consecutive days of exercise-heat acclimation when the subjects exercised on a cycle ergometer at a relative oxygen uptake of 44% to 49% peak oxygen uptake in a hot environment (Ta = 40 degrees C, 42% rh). During acclimation plasma volume increased by 10.6% (p less than 0.05) in the women and by 11.9% (p less than 0.05) in the men; in both groups exercise heart rate decreased significantly. After acclimation, acceleration tolerance was unchanged in both groups (range 3.1 to 3.4 G); the women's tilt tolerance was unchanged (range 33.6 to 39.5 min), but the men's tilt tolerance increased from 30.4 min before to 58.3 min (delta = 91%, p less than 0.05) after acclimation. Since the pattern of fluid, electrolyte, and protein shifts and acceleration tolerances in the women and men were virtually the same, the hormone responses were highly variable, and the men's tilt tolerance increased significantly after acclimation, it is clear that responses to tilting cannot be used to predict responses to acceleration. Analysis of data from the present study and the literature suggests that current exercise training regimes should be unrestricted for astronauts who have not previously been highly endurance trained.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:4026752

  15. Photosynthetic response of Cannabis sativa L. to variations in photosynthetic photon flux densities, temperature and CO2 conditions.

    PubMed

    Chandra, Suman; Lata, Hemant; Khan, Ikhlas A; Elsohly, Mahmoud A

    2008-10-01

    Effect of different photosynthetic photon flux densities (0, 500, 1000, 1500 and 2000 μmol m(-2)s(-1)), temperatures (20, 25, 30, 35 and 40 °C) and CO2 concentrations (250, 350, 450, 550, 650 and 750 μmol mol(-1)) on gas and water vapour exchange characteristics of Cannabis sativa L. were studied to determine the suitable and efficient environmental conditions for its indoor mass cultivation for pharmaceutical uses. The rate of photosynthesis (PN) and water use efficiency (WUE) of Cannabis sativa increased with photosynthetic photon flux densities (PPFD) at the lower temperatures (20-25 °C). At 30 °C, PN and WUE increased only up to 1500 μmol m(-2)s(-1) PPFD and decreased at higher light levels. The maximum rate of photosynthesis (PN max) was observed at 30 °C and under 1500 μmol m(-2)s(-1) PPFD. The rate of transpiration (E) responded positively to increased PPFD and temperature up to the highest levels tested (2000 μmol m(-2)s(-1) and 40 °C). Similar to E, leaf stomatal conductance (gs) also increased with PPFD irrespective of temperature. However, gs increased with temperature up to 30 °C only. Temperature above 30 °C had an adverse effect on gs in this species. Overall, high temperature and high PPFD showed an adverse effect on PN and WUE. A continuous decrease in intercellular CO2 concentration (Ci) and therefore, in the ratio of intercellular CO2 to ambient CO2 concentration (Ci/Ca) was observed with the increase in temperature and PPFD. However, the decrease was less pronounced at light intensities above 1500 μmol m(-2)s(-1). In view of these results, temperature and light optima for photosynthesis was concluded to be at 25-30 °C and ∼1500 μmol m(-2)s(-1) respectively. Furthermore, plants were also exposed to different concentrations of CO2 (250, 350, 450, 550, 650 and 750 μmol mol(-1)) under optimum PPFD and temperature conditions to assess their photosynthetic response. Rate of photosynthesis, WUE and Ci decreased by 50 %, 53 % and 10

  16. Photosynthetic responses of subtidal seagrasses to a daily light cycle in Torres Strait: A comparative study

    NASA Astrophysics Data System (ADS)

    Campbell, Stuart J.; Kerville, Simon P.; Coles, Robert G.; Short, Fred

    2008-09-01

    In this study, we examined the photosynthetic responses of five common seagrass species from a typical mixed meadow in Torres Strait at a depth of 5-7 m using pulse amplitude modulated (PAM) fluorometry. The photosynthetic response of each species was measured every 2 h throughout a single daily light cycle from dawn (6 am) to dusk (6 pm). PAM fluorometry was used to generate rapid light curves from which measures of electron transport rate (ETR max), photosynthetic efficiency ( α), saturating irradiance ( E k) and light-adapted quantum yield (Δ F/ F' m) were derived for each species. The amount of light absorbed by leaves (absorption factor) was also determined for each species. Similar diurnal patterns were recorded among species with 3-4 fold increases in maximal electron rate from dawn to midday and a maintenance of ETR max in the afternoon that would allow an optimal use of low light by all species. Differences in photosynthetic responses to changes in the daily light regime were also evident with Syringodium isoetifolium showing the highest photosynthetic rates and saturating irradiances suggesting a competitive advantage over other species under conditions of high light. In contrast Halophila ovalis, Halophila decipiens and Halophila spinulosa were characterised by comparatively low photosynthetic rates and minimum light requirements (i.e. low E k) typical of shade adaptation. The structural makeup of each species may explain the observed differences with large, structurally complex species such as Syringodium isoetifolium and Cymodocea serrulata showing high photosynthetic effciciencies ( α) and therefore high-light-adapted traits (e.g. high ETR max and E k) compared with the smaller Halophila species positioned lower in the canopy. For the smaller Halophila species these shade-adapted traits are features that optimise their survival during low-light conditions. Knowledge of these characteristics and responses improves our understanding of the underlying

  17. Photosynthetic and Biochemical Changes in Response to Short Interval High ``g'' Exposure in Wheat

    NASA Astrophysics Data System (ADS)

    Dixit, Jyotsana; Vidyasagar, Pandit; Jagtap, Sagar; Kamble, Shailendra

    We have investigated the effect of short interval post imbibition high “g” exposure on wheat seeds (Triticum aestivum var.Lok-1) by evaluating the photosynthetic performance, chlorophyll “a” fluorescence biochemical indices and antioxidant response. Imbibed wheat seeds were exposed to high “g” ranging from 500 g to 2500 g for 10 min, allowed to germinate and grown for 5 days under normal gravity i.e. 1 g. Chlorophyll “a” fluorescence transient was examined in wheat seedling raised from hyper gravity treated seeds. Fv/Fm, PI, Fv/Fo decreased in high “g” treated seeds compared to control. Photosynthetic performance indices such as Transpiration rate, Stomatal conductance, Net photosynthetic rate, Intracellular CO2 concentration, Intrinsic water use efficiency also declined in wheat seedlings raised from High “g” treated seeds suggesting that high g reduces efficiency of photosynthesis in wheat seedlings. Results of Biochemical analysis showed reduced alpha- amylase activity in wheat seeds subjected to high “g” ranging from 500 g to 2500 g in a magnitude dependent manner. Decline in enzyme activity was positively correlated with higher starch content and lower reducing sugars in high “g” exposed wheat seeds. This possibly explains the reduced percent germination and growth in response to high “g”. Antioxidant enzyme activity (CAT and POX) significantly increased as a result of hypergravity exposure In conclusion, short interval high “g” exposure results in reduced growth and photosynthetic activity in wheat seedlings.

  18. Long-Term Growth of Soybean at Elevated [CO2] Does not Cause Acclimation of Stomatal Conductance Under Fully Open-air Conditions.

    NASA Astrophysics Data System (ADS)

    Leakey, A. D.; Bernacchi, C. J.; Ort, D. R.; Long, S. P.

    2008-12-01

    Accurately predicting plant function and global biogeochemical cycles later this century will be complicated if stomatal conductance (gs) acclimates to growth at elevated [CO2], in the sense of a long-term alteration of the response of gs to [CO2], humidity (h) and/or photosynthetic rate (A). If so, photosynthetic and stomatal models will require parameterization at each growth [CO2] of interest. Photosynthetic acclimation to long-term growth at elevated [CO2] occurs frequently. Acclimation of gs has rarely been examined, even though stomatal density commonly changes with growth [CO2]. Soybean was grown under field conditions at ambient [CO2] (378 μmol mol-1) and elevated [CO2] (552 μmol mol-1) using Free-Air [CO2] Enrichment (FACE). This study tested for stomatal acclimation by parameterizing and validating the widely used Ball et al. model (1987, Progress in Photosynthesis Research, Vol IV, 221-224) with measurements of leaf gas exchange. The dependence of gs on A, h and [CO2] at the leaf surface was unaltered by long-term growth at elevated [CO2]. This suggests that the commonly observed decrease in gs under elevated [CO2] is due entirely to the direct instantaneous effect of [CO2] on gs and that there is no longer-term acclimation of stomatal conductance independent of photosynthetic acclimation. The Ball et al. (1987) model accurately predicted gs for soybean growing under ambient and elevated [CO2] in the field. Model parameters under ambient and elevated [CO2] were indistinguishable, demonstrating that stomatal function under ambient and elevated [CO2] could be modeled without the need for parameterization at each growth [CO2].

  19. Long-term growth of soybean at elevated [CO2] does not cause acclimation of stomatal conductance under fully open-air conditions.

    PubMed

    Leakey, Andrew D B; Bernacchi, Carl J; Ort, Donald R; Long, Stephen P

    2006-09-01

    Accurately predicting plant function and global biogeochemical cycles later in this century will be complicated if stomatal conductance (g(s)) acclimates to growth at elevated [CO(2)], in the sense of a long-term alteration of the response of g(s) to [CO(2)], humidity (h) and/or photosynthetic rate (A). If so, photosynthetic and stomatal models will require parameterization at each growth [CO(2)] of interest. Photosynthetic acclimation to long-term growth at elevated [CO(2)] occurs frequently. Acclimation of g(s) has rarely been examined, even though stomatal density commonly changes with growth [CO(2)]. Soybean was grown under field conditions at ambient [CO(2)] (378 micromol mol(-1)) and elevated [CO(2)] (552 micromol mol(-1)) using free-air [CO(2)] enrichment (FACE). This study tested for stomatal acclimation by parameterizing and validating the widely used Ball et al. model (1987, Progress in Photosynthesis Research, vol IV, 221-224) with measurements of leaf gas exchange. The dependence of g(s) on A, h and [CO(2)] at the leaf surface was unaltered by long-term growth at elevated [CO(2)]. This suggests that the commonly observed decrease in g(s) under elevated [CO(2)] is due entirely to the direct instantaneous effect of [CO(2)] on g(s) and that there is no longer-term acclimation of g(s) independent of photosynthetic acclimation. The model accurately predicted g(s) for soybean growing under ambient and elevated [CO(2)] in the field. Model parameters under ambient and elevated [CO(2)] were indistinguishable, demonstrating that stomatal function under ambient and elevated [CO(2)] could be modelled without the need for parameterization at each growth [CO(2)]. PMID:16913868

  20. Variation in photosynthetic response to temperature in a guild of winter annual plants.

    PubMed

    Gremer, Jennifer R; Kimball, Sarah; Angert, Amy L; Venable, D Lawrence; Huxman, Travis E

    2012-12-01

    How species respond to environmental variation can have important consequences for population and community dynamics. Temperature, in particular, is one source of variation expected to strongly influence plant performance. Here, we compared photosynthetic responses to temperature across a guild of winter annual plants. Previous work in this system identified a trade-off between relative growth rate (RGR) and water-use efficiency (WUE) that predicts species differences in population dynamics over time, which then contribute to long-term species coexistence. Interestingly, species with high WUE invest in photosynthetic processes that appear to maximize carbon assimilation, while high-RGR species appear to maximize carbon gain by increasing leaf area for photosynthesis. In high-WUE species, higher rates of carbon acquisition were associated with increased investment into light-driven electron transport (J(max)). We tested whether such allocation allows these plants to have greater photosynthetic performance at lower temperatures by comparing the temperature sensitivity of photosynthesis across species in the community. Six species were grown in buried pots in the field, allowing them to experience natural changes in seasonal temperature. Plants were taken from the field and placed in growth chambers where photosynthetic performance was measured following short-term exposure to a wide range of temperatures. These measurements were repeated throughout the season. Our results suggest that high-WUE species are more efficient at processing incoming light, as measured by chlorophyll fluorescence, and exhibit higher net photosynthetic rates (A(net)) than high-RGR species, and these advantages are greatest at low temperatures. Sampling date differentially affected fluorescence across species, while species had similar seasonal changes in A(net). Our results suggest that species-specific responses to temperature contribute to the WUE-RGR trade-off that has been shown to

  1. Ecohydrological Responses of Dense Canopies to Environmental Variability Part 1: Interplay Between Vertical Structure and Photosynthetic Pathway

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Vegetation acclimation to changing climate, in particular elevated atmospheric concentrations of carbon dioxide (CO2), has been observed to include modifications to the biochemical and eco physiological functioning of leaves and the structural components of the canopy. These responses have the poten...

  2. Defects in a New Class of Sulfate/Anion Transporter Link Sulfur Acclimation Responses to Intracellular Glutathione Levels and Cell Cycle Control1[W][OPEN

    PubMed Central

    Fang, Su-Chiung; Chung, Chin-Lin; Chen, Chun-Han; Lopez-Paz, Cristina; Umen, James G.

    2014-01-01

    We previously identified a mutation, suppressor of mating type locus3 15-1 (smt15-1), that partially suppresses the cell cycle defects caused by loss of the retinoblastoma tumor suppressor-related protein encoded by the MAT3 gene in Chlamydomonas reinhardtii. smt15-1 single mutants were also found to have a cell cycle defect leading to a small-cell phenotype. SMT15 belongs to a previously uncharacterized subfamily of putative membrane-localized sulfate/anion transporters that contain a sulfate transporter domain and are found in a widely distributed subset of eukaryotes and bacteria. Although we observed that smt15-1 has a defect in acclimation to sulfur-limited growth conditions, sulfur acclimation (sac) mutants, which are more severely defective for acclimation to sulfur limitation, do not have cell cycle defects and cannot suppress mat3. Moreover, we found that smt15-1, but not sac mutants, overaccumulates glutathione. In wild-type cells, glutathione fluctuated during the cell cycle, with highest levels in mid G1 phase and lower levels during S and M phases, while in smt15-1, glutathione levels remained elevated during S and M. In addition to increased total glutathione levels, smt15-1 cells had an increased reduced-to-oxidized glutathione redox ratio throughout the cell cycle. These data suggest a role for SMT15 in maintaining glutathione homeostasis that impacts the cell cycle and sulfur acclimation responses. PMID:25361960

  3. Evidence for involvement of photosynthetic processes in the stomatal response to CO2.

    PubMed

    Messinger, Susanna M; Buckley, Thomas N; Mott, Keith A

    2006-02-01

    Stomatal conductance (gs) typically declines in response to increasing intercellular CO2 concentration (ci). However, the mechanisms underlying this response are not fully understood. Recent work suggests that stomatal responses to ci and red light (RL) are linked to photosynthetic electron transport. We investigated the role of photosynthetic electron transport in the stomatal response to ci in intact leaves of cocklebur (Xanthium strumarium) plants by examining the responses of gs and net CO2 assimilation rate to ci in light and darkness, in the presence and absence of the photosystem II inhibitor 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU), and at 2% and 21% ambient oxygen. Our results indicate that (1) gs and assimilation rate decline concurrently and with similar spatial patterns in response to DCMU; (2) the response of gs to ci changes slope in concert with the transition from Rubisco- to electron transport-limited photosynthesis at various irradiances and oxygen concentrations; (3) the response of gs to ci is similar in darkness and in DCMU-treated leaves, whereas the response in light in non-DCMU-treated leaves is much larger and has a different shape; (4) the response of gs to ci is insensitive to oxygen in DCMU-treated leaves or in darkness; and (5) stomata respond normally to RL when ci is held constant, indicating the RL response does not require a reduction in ci by mesophyll photosynthesis. Together, these results suggest that part of the stomatal response to ci involves the balance between photosynthetic electron transport and carbon reduction either in the mesophyll or in guard cell chloroplasts. PMID:16407445

  4. Putrescine is involved in Arabidopsis freezing tolerance and cold acclimation by regulating abscisic acid levels in response to low temperature.

    PubMed

    Cuevas, Juan C; López-Cobollo, Rosa; Alcázar, Rubén; Zarza, Xavier; Koncz, Csaba; Altabella, Teresa; Salinas, Julio; Tiburcio, Antonio F; Ferrando, Alejandro

    2008-10-01

    The levels of endogenous polyamines have been shown to increase in plant cells challenged with low temperature; however, the functions of polyamines in the regulation of cold stress responses are unknown. Here, we show that the accumulation of putrescine under cold stress is essential for proper cold acclimation and survival at freezing temperatures because Arabidopsis (Arabidopsis thaliana) mutants defective in putrescine biosynthesis (adc1, adc2) display reduced freezing tolerance compared to wild-type plants. Genes ADC1 and ADC2 show different transcriptional profiles upon cold treatment; however, they show similar and redundant contributions to cold responses in terms of putrescine accumulation kinetics and freezing sensitivity. Our data also demonstrate that detrimental consequences of putrescine depletion during cold stress are due, at least in part, to alterations in the levels of abscisic acid (ABA). Reduced expression of NCED3, a key gene involved in ABA biosynthesis, and down-regulation of ABA-regulated genes are detected in both adc1 and adc2 mutant plants under cold stress. Complementation analysis of adc mutants with ABA and reciprocal complementation tests of the aba2-3 mutant with putrescine support the conclusion that putrescine controls the levels of ABA in response to low temperature by modulating ABA biosynthesis and gene expression. PMID:18701673

  5. Response to cold acclimation in diapause pupae of Hyles euphorbiae (Lepidoptera: Sphingidae): candidate biomarker identification using proteomics.

    PubMed

    Stuckas, H; Mende, M B; Hundsdoerfer, A K

    2014-08-01

    The distribution range of Hyles euphorbiae covers distinct climates across the Palaearctic. Previous investigations showed a correlation between mitochondrial DNA identity of populations and climatic conditions related to winter; however, the lack of biomarkers hampers investigations to test whether geographically distinct populations do show specific molecular responses to low temperatures or whether they possess specific genetic identity at loci functionally related to cold response. The present study was designed to identify candidate protein biomarkers and biological processes that are associated with cold acclimation of overwintering H. euphorbiae diapause pupae. Specimens taken from a single central European population were gradually cooled from 20 °C to -2 °C over 36 days and 12 differentially abundant proteins were identified. In addition, DeepSuperSAGE sequencing technology was applied to study differentially regulated genes. There was incongruence between differentially abundant proteins and differentially expressed genes, but functional characteristics of regulated proteins and analyses of gene ontology term enrichment among differentially regulated genes pointed to activation of the same biological processes, e.g. oxidative stress response. As proteins represent biologically active molecules, candidate biomarkers derived from proteomics are considered well suited to explore intraspecific patterns of local adaptation to different climates. PMID:24628883

  6. Acclimation of marine phytoplankton to ultraviolet radiation

    SciTech Connect

    Hazzard, C.E.

    1993-01-01

    The ability of marine phytoplankton to acclimate to ultraviolet radiation (UVR) was examined. Monocultures of a subtropical diatom, Chaetoceros gracilis, were maintained under photosynthetically available radiation (PAR-only) and PAR plus UVR (PAR + UVR) for a 48 h exposure period. By 24 h, and for the remainder of the 48 h exposure period, growth rate, pigment concentrations, Rubisco activity and carbon fixation capability were not affected by PAR + UVR. After 48 h of UVR exposure turnover rates of the putative D1 protein of photosystem II (PSII) and Chlorophyll (Chl) a were higher than controls, suggesting continual damage by UVR. Maximum rate of oxygen evolution and the efficiency of PSII increased following acclimation to UVR. The maximum rate of carbon fixation was not affected on a per cell basis and decreased on a per Chl a basis following UVR acclimation. Chlorophyll a specific photosynthesis over a 5 h exposure period was equal between the two acclimation treatments (PAR-only and PAR + UV). Transfer of PAR-only acclimated cells to PAR + UVR for the same 5 h period lead to a reduction in Chl a specific photosynthesis, indicating acute inhibition of photosynthesis by UVR. Chlorophyll a specific photosynthesis of cells acclimated to PAR + UVR and transferred to PAR-only was 24% higher than cells maintained in PAR + UVR during the determination of photosynthesis, indicating enhancement of productivity following the removal of UVR. Effect of ambient subtropical UVR on natural phytoplankton populations was examined. Rates of primary production by assemblages Natural phytoplankton assemblages from Hawaii, exposed to PAR-only and PAR + UVR were equal. Assemblages acclimated to PAR + UVR and then transferred to PAR-only fixed 67% more carbon per Chl a than assemblages acclimated to PAR + UVR and maintained in PAR + UVR. Acclimation to ambient PAR + UVR resulted in a 171% increase in Chl a concentration compared to assemblages maintained under PAR-only conditions.

  7. Ecohydrological Responses of Dense Canopies to Environmental Variability Part 2: Role of Acclimation Under Elevated CO2

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The ability to accurately predict land-atmosphere exchange of mass, energy, and momentum over the coming century requires the consideration of plant biochemical, ecophysiological and structural acclimation to modifications of the ambient environment. Amongst the most important environmental changes ...

  8. Photosynthetic acclimation and decreased chlorophyll (a & b) concentrations occur in nitrogen sufficient tobacco leaves in response to carbon dioxide enrichment

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The effects of CO2 enrichment on plant growth and on nitrogen partitioning were examined using fully-expanded tobacco leaves (Nicotiana tabacum L. cv. Samsun). Plants were grown from single seeds in matching controlled environment chambers with continuous ambient CO2 partial pressures of 38 to 40 P...

  9. Incorporating temperature-sensitive Q10 and foliar respiration acclimation algorithms modifies modeled ecosystem responses to global change

    NASA Astrophysics Data System (ADS)

    Wythers, Kirk R.; Reich, Peter B.; Bradford, John B.

    2013-03-01

    Evidence suggests that respiration acclimation (RA) to temperature in plants can have a substantial influence on ecosystem carbon balance. To assess the influence of RA on ecosystem response variables in the presence of global change drivers, we incorporated a temperature-sensitive Q10 of respiration and foliar basal RA into the ecosystem model PnET-CN. We examined the new algorithms' effects on modeled net primary production (NPP), total canopy foliage mass, foliar nitrogen concentration, net ecosystem exchange (NEE), and ecosystem respiration/gross primary production ratios. This latter ratio more closely matched eddy covariance long-term data when RA was incorporated in the model than when not. Averaged across four boreal ecotone sites and three forest types at year 2100, the enhancement of NPP in response to the combination of rising [CO2] and warming was 9% greater when RA algorithms were used, relative to responses using fixed respiration parameters. The enhancement of NPP response to global change was associated with concomitant changes in foliar nitrogen and foliage mass. In addition, impacts of RA algorithms on modeled responses of NEE closely paralleled impacts on NPP. These results underscore the importance of incorporating temperature-sensitive Q10 and basal RA algorithms into ecosystem models. Given the current evidence that atmospheric [CO2] and surface temperature will continue to rise, and that ecosystem responses to those changes appear to be modified by RA, which is a common phenotypic adjustment, the potential for misleading results increases if models fail to incorporate RA into their carbon balance calculations.

  10. Effects of exercise-heat acclimation on fluid, electrolyte, and endocrine responses during tilt and +Gz acceleration in women and men

    NASA Technical Reports Server (NTRS)

    Greenleaf, J. E.; Brock, P. J.; Sciaraffa, D.; Polese, A.; Elizondo, R.

    1985-01-01

    Two aspects of prolonged endurance training were investigated: (1) the effects of exercise-heat acclimation (on a cycle ergometer at 40 C, 42 rh) on orthostatic tolerance (70 deg head-up tilt) and on a +Gz (head-to-foot) acceleration tolerance of male and female subjects; and (2) comparison of their fluid-electrolyte shifts and hormonal (plasma epinephdrine, norepinephrine, renin, and vasopressin) responses during tilting and centrifugation. The adaptive responses during the 12 d, 2-h acclimation did not alter acceleration tolerance of either men or women, or the women's tilt tolerance, but did increase men's tilt tolerance from 30.4 min before to 58.3 min after acclimation. The patterns of fluid, electrolyte, and protein shifts at tolerance in acceleration and tilting tests were virtually the same in men and women. On the other hand, the hormonal plasma epinephrine, norepinephrine, renin, and vasopressin resonses displayed different shift patterns during acceleration and tilting. It is concluded that the responses to tilting cannot be used to predict responses to acceleration. Future experiments for relating the orthostatic and the acceleration tolerances, and the practical questions of the training regimens for future astronauts are discussed.

  11. Seismic stress responses of soybean to different photosynthetic photon flux

    NASA Technical Reports Server (NTRS)

    Jones, R. S.; Coe, L. L.; Montgomery, L.; Mitchell, C. A.

    1990-01-01

    Physical agitation applied as periodic seismic stress (shaking) reduced stem elongation, leaf expansion, and biomass accumulation by vegetative soybeans. Level of photon flux (PPF) influenced the type and extent of plant response to mechanical stress. Plant parts responded differently as PPF varied between 135 and 592 micromoles m-2 s-1. Stem length was significantly reduced by seismic stress at 135 micromoles m-2 s-1 but this effect was insignificant at higher PPFs. Reduced stem length resulted from an inhibition of internode elongation. Stem diameter was unaffected by stress at the PPFs tested. In contrast to effects on stem elongation, leaf area was insensitive to stress treatments at 135 micromoles m-2 s-1 but was progressively inhibited by stress as PPF increased. Statistically significant reductions in shoot f. wt and d. wt by seismic stress occurred only at 295 micromoles m-2 s-1. Root biomass accumulation was not affected by seismic stress at any PPF used in this study.

  12. Development of photosynthetic response curves and their integration into a decision-support tool for floriculture growers

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Irradiance, CO2, and temperature are critical inputs for photosynthesis and crop growth. They are also environmental parameters which growers can control in protected horticulture production systems. We evaluated the photosynthetic response of 13 herbaceous ornamentals (Begonia × hiemalis, Begonia...

  13. Alterations in mitochondrial electron transport system activity in response to warm acclimation, hypoxia-reoxygenation and copper in rainbow trout, Oncorhynchus mykiss.

    PubMed

    Sappal, Ravinder; MacDougald, Michelle; Fast, Mark; Stevens, Don; Kibenge, Fred; Siah, Ahmed; Kamunde, Collins

    2015-08-01

    Fish expend significant amounts of energy to handle the numerous potentially stressful biotic and abiotic factors that they commonly encounter in aquatic environments. This universal requirement for energy singularizes mitochondria, the primary cellular energy transformers, as fundamental drivers of responses to environmental change. Our study probed the interacting effects of thermal stress, hypoxia-reoxygenation (HRO) and copper (Cu) exposure in rainbow trout to test the prediction that they act jointly to impair mitochondrial function. Rainbow trout were acclimated to 11 (controls) or 20°C for 2 months. Liver mitochondria were then isolated and their responses in vitro to Cu (0-20μM) without and with HRO were assessed. Sequential inhibition and activation of mitochondrial electron transport system (ETS) enzyme complexes permitted the measurement of respiratory activities supported by complex I-IV (CI-IV) in one run. The results showed that warm acclimation reduced fish and liver weights but increased mitochondrial protein indicating impairment of energy metabolism, increased synthesis of defense proteins and/or reduced liver water content. Whereas acute rise (11→20°C) in temperature increased mitochondrial oxidation rates supported by CI-IV, warm acclimation reduced the maximal (state 3) and increased the basal (state 4) respiration leading to global uncoupling of oxidative phosphorylation (OXPHOS). HRO profoundly inhibited both maximal and basal respiration rates supported by CI-IV, reduced RCR for all except CII and lowered CI:CII respiration ratio, an indication of decreased OXPHOS efficiency. The effects of Cu were less pronounced but more variable and included inhibition of CII-IV maximal respiration rates and stimulation of both CI and CIII basal respiration rates. Surprisingly, only CII and CIII indices exhibited significant 3-way interactions whereas 2-way interactions of acclimation either with Cu or HRO were portrayed mostly by CIV, and those of

  14. Leaf cold acclimation and freezing injury in C3 and C4 grasses of the Mongolian Plateau

    PubMed Central

    Liu, Mei-Zhen; Osborne, Colin P.

    2008-01-01

    The scarcity of C4 plants in cool climates is usually attributed to their lower photosynthetic efficiency than C3 species at low temperatures. However, a lower freezing resistance may also decrease the competitive advantage of C4 plants by reducing canopy duration, especially in continental steppe grasslands, where a short, hot growing season is bracketed by frost events. This paper reports an experimental test of the hypothesis that cold acclimation is negligible in C4 grasses, leading to greater frost damage than in C3 species. The experiments exposed six C3 and three C4 Mongolian steppe grasses to 20 d chilling or control pre-treatments, followed by a high-light freezing event. Leaf resistance to freezing injury was independent of photosynthetic type. Three C3 species showed constitutive freezing resistance characterized by <20% leaf mortality, associated with high photosynthetic carbon fixation and electron transport rates and low leaf osmotic potential. One freezing-sensitive C4 species showed the expected pattern of chilling-induced damage to photosynthesis and >95% leaf mortality after the freezing event. However, three C3 and two C4 species displayed a cold acclimation response, showing significant decreases in osmotic potential and photosynthesis after exposure to chilling, and a 30–72% reduction of leaf freezing injury. This result suggested that down-regulation of osmotic potential may be involved in the cold acclimation process, and demonstrated that there is no inherent barrier to the development of cold acclimation in C4 species from this ecosystem. Cold acclimation via osmoregulation represents a previously undescribed mechanism to explain the persistence of C4 plants in cool climates. PMID:18980952

  15. Species-specific photosynthetic responses of four coniferous seedlings to open-field experimental warming

    NASA Astrophysics Data System (ADS)

    Han, S.; Yoon, S. J.; Yoon, T. K.; Han, S. H.; Lee, J.; Lee, D.; Kim, S.; Hwang, J.; Cho, M.; Son, Y.

    2014-12-01

    Temperature increase under climate change is expected to affect photosynthesis of tree species. Biochemical models generally suggest that the elevated temperature increases the photosynthetic carbon fixation, however, many opposing results were reported as well. We aimed to examine the photosynthetic responses of four coniferous seedlings to projected future temperature increase, by conducting an open-field warming experiment. Experimental warming set-up using infra-red heater was built in 2011 and the temperature in warming plots has been regulated to be consistently 3oC higher than that of control plots. The seeds of Abies holophylla (AH), A. koreana (AK), Pinus densiflora (PD), and P. koraiensis (PK) were planted in each 1 m × 1 m plot (n=3) in April, 2012. Monthly net photosynthetic rates (Pn; μmol CO2 m-2 s-1) of 1-year-old seedlings (n=9) from June to November, 2013 were measured using CIRAS-2 (PP-Systems, UK) and photosynthetic parameters (the apparent quantum yield; ф; µmol CO2 mol-1, the dark respiration rate; Rd; µmol CO2 mol-1, and the light compensation point; LCP; µmol mol-1 s-1) were also calculated from the light-response curve of photosynthesis in August, 2013. Chlorophyll contents were measured using DMSO extraction method. Monthly Pn was generally higher for PD and decreased for AK in warmed plots than in control plots (Fig. 1). Pn of AK and PK did not show any significant difference, however, Pn of PK in October and November increased by experimental warming. Pn of PD also showed the highest increase in November and this distinct increase of Pn in autumn might be caused by delayed cessation of photosynthesis by temperature elevation. ф and Rd in warmed plots were higher for PD and lower for AK, while LCP did not significantly differ by treatments for all species. Because ф is considered to be related to the efficiency of harvesting and using light, the change in ф might have caused the response of Pn to warming in this study. Decreases

  16. Implications of plant acclimation for future climate-carbon cycle feedbacks

    NASA Astrophysics Data System (ADS)

    Mercado, Lina; Kattge, Jens; Cox, Peter; Sitch, Stephen; Knorr, Wolfgang; Lloyd, Jon; Huntingford, Chris

    2010-05-01

    The response of land ecosystems to climate change and associated feedbacks are a key uncertainty in future climate prediction (Friedlingstein et al. 2006). However global models generally do not account for the acclimation of plant physiological processes to increased temperatures. Here we conduct a first global sensitivity study whereby we modify the Joint UK land Environment Simulator (JULES) to account for temperature acclimation of two main photosynthetic parameters, Vcmax and Jmax (Kattge and Knorr 2007) and plant respiration (Atkin and Tjoelker 2003). The model is then applied over the 21st Century within the IMOGEN framework (Huntingford et al. 2004). Model simulations will provide new and improved projections of biogeochemical cycling, forest resilience, and thus more accurate projections of climate-carbon cycle feedbacks and the future evolution of the Earth System. Friedlingstein P, Cox PM, Betts R et al. (2006) Climate-carbon cycle feedback analysis, results from the C4MIP model intercomparison. Journal of Climate, 19, 3337-3353. Kattge J and Knorr W (2007): Temperature acclimation in a biochemical model of photosynthesis: a reanalysis of data from 36 species. Plant, Cell and Environment 30, 1176-1190 Atkin O.K and Tjoelker, M. G. (2003): Thermal acclimation and the dynamic response of plant respiration to temperature. Trends in Plant Science 8 (7), 343-351 Huntingford C, et al. (2004) Using a GCM analogue model to investigate the potential for Amazonian forest dieback. Theoretical and Applied Climatology, 78, 177-185.

  17. Changes in ultrastructure and responses of antioxidant systems of algae (Dunaliella salina) during acclimation to enhanced ultraviolet-B radiation.

    PubMed

    Tian, Jiyuan; Yu, Juan

    2009-12-01

    Because of depletion of the stratospheric ozone layer, levels of solar ultraviolet-B (UV-B) radiation (280-315 nm), which penetrates the water column to an ecologically-significant depth, are increasing. In order to assess changes in ultrastructure and responses of antioxidant systems of algae during acclimation to enhanced ultraviolet-B radiation, Dunaliella salina was treated with higher dose of UV-B radiation (13.2 kJm(-2) d(-1) dose) in this study. As compared to the control panel (8.8 kJm(-2) d(-1)), the treatment D. salina had many changes in ultrastructures: (1) thylakoids became swelled, and some of them penetrated into the pyrenoid; (2) lipid globules accumulated; (3) the amounts of starch grains increased; (4) cristae of mitochondria disintegrated; (5) inclusions in vacuoles reduced; and (6) cisternae of Golgi dictyosomes became loose and swollen. Enhanced UV-B irradiation also induced different responses of the antioxidant systems in D. salina: (1) contents of TBARS (thiobarbituric acid reacting substance) and H(2)O(2) increased significantly (p<0.05); (2) levels of MAAs (mycosporine-like amino acids) increased at the beginning and subsequently decreased, and finally they leveled off at lower values; (3) there were not apparent variations for carotenoid contents, and contents of chlorophyll a presented a trend of initial increase and ultimate decrease; (4) both ascorbate and glutathione contents increased significantly (p<0.05); and (5) for the enzyme activities, POD activities increased remarkably (p<0.05), and SOD activities declined apparently (p<0.05), and CAT activity in D. salina had slight variations (p>0.05). In addition, growth curve displayed that enhanced UV-B radiation prominently inhibited increase of cell concentration when compared with control panel (p<0.05). Our results indicated that enhanced UV-B radiation caused ultrastructural changes of D. salina and induced different responses of antioxidant systems in D. salina. PMID:19818642

  18. Involvement of ethylene in gibberellic acid-induced sulfur assimilation, photosynthetic responses, and alleviation of cadmium stress in mustard.

    PubMed

    Masood, Asim; Khan, M Iqbal R; Fatma, Mehar; Asgher, Mohd; Per, Tasir S; Khan, Nafees A

    2016-07-01

    The role of gibberellic acid (GA) or sulfur (S) in stimulation of photosynthesis is known. However, information on the involvement of ethylene in GA-induced photosynthetic responses and cadmium (Cd) tolerance is lacking. This work shows that ethylene is involved in S-assimilation, photosynthetic responses and alleviation of Cd stress by GA in mustard (Brassica juncea L.). Plants grown with 200 mg Cd kg(-1) soil were less responsive to ethylene despite high ethylene evolution and showed photosynthetic inhibition. Plants receiving 10 μM GA spraying plus 100 mg S kg(-1) soil supplementation exhibited increased S-assimilation and photosynthetic responses under Cd stress. Application of GA plus S decreased oxidative stress of plants grown with Cd and limited stress ethylene formation to the range suitable for promoting sulfur use efficiency (SUE), glutathione (GSH) production and photosynthesis. The role of ethylene in GA-induced S-assimilation and reversal of photosynthetic inhibition by Cd was substantiated by inhibiting ethylene biosynthesis with the use of aminoethoxyvinylglycine (AVG). The suppression of S-assimilation and photosynthetic responses by inhibiting ethylene in GA plus S treated plants under Cd stress indicated the involvement of ethylene in GA-induced S-assimilation and Cd stress alleviation. The outcome of the study is important to unravel the interaction between GA and ethylene and their role in Cd tolerance in plants. PMID:26998941

  19. Death-specific protein in a marine diatom regulates photosynthetic responses to iron and light availability.

    PubMed

    Thamatrakoln, Kimberlee; Bailleul, Benjamin; Brown, Christopher M; Gorbunov, Maxim Y; Kustka, Adam B; Frada, Miguel; Joliot, Pierre A; Falkowski, Paul G; Bidle, Kay D

    2013-12-10

    Diatoms, unicellular phytoplankton that account for ∼40% of marine primary productivity, often dominate coastal and open-ocean upwelling zones. Limitation of growth and productivity by iron at low light is attributed to an elevated cellular Fe requirement for the synthesis of Fe-rich photosynthetic proteins. In the dynamic coastal environment, Fe concentrations and daily surface irradiance levels can vary by two to three orders of magnitude on short spatial and temporal scales. Although genome-wide studies are beginning to provide insight into the molecular mechanisms used by diatoms to rapidly respond to such fluxes, their functional role in mediating the Fe stress response remains uncharacterized. Here, we show, using reverse genetics, that a death-specific protein (DSP; previously named for its apparent association with cell death) in the coastal diatom Thalassiosira pseudonana (TpDSP1) localizes to the plastid and enhances growth during acute Fe limitation at subsaturating light by increasing the photosynthetic efficiency of carbon fixation. Clone lines overexpressing TpDSP1 had a lower quantum requirement for growth, increased levels of photosynthetic and carbon fixation proteins, and increased cyclic electron flow around photosystem I. Cyclic electron flow is an ATP-producing pathway essential in higher plants and chlorophytes with a heretofore unappreciated role in diatoms. However, cells under replete conditions were characterized as having markedly reduced growth and photosynthetic rates at saturating light, thereby constraining the benefits afforded by overexpression. Widespread distribution of DSP-like sequences in environmental metagenomic and metatranscriptomic datasets highlights the presence and relevance of this protein in natural phytoplankton populations in diverse oceanic regimes. PMID:24277817

  20. Death-specific protein in a marine diatom regulates photosynthetic responses to iron and light availability

    PubMed Central

    Thamatrakoln, Kimberlee; Bailleul, Benjamin; Brown, Christopher M.; Gorbunov, Maxim Y.; Kustka, Adam B.; Frada, Miguel; Joliot, Pierre A.; Falkowski, Paul G.; Bidle, Kay D.

    2013-01-01

    Diatoms, unicellular phytoplankton that account for ∼40% of marine primary productivity, often dominate coastal and open-ocean upwelling zones. Limitation of growth and productivity by iron at low light is attributed to an elevated cellular Fe requirement for the synthesis of Fe-rich photosynthetic proteins. In the dynamic coastal environment, Fe concentrations and daily surface irradiance levels can vary by two to three orders of magnitude on short spatial and temporal scales. Although genome-wide studies are beginning to provide insight into the molecular mechanisms used by diatoms to rapidly respond to such fluxes, their functional role in mediating the Fe stress response remains uncharacterized. Here, we show, using reverse genetics, that a death-specific protein (DSP; previously named for its apparent association with cell death) in the coastal diatom Thalassiosira pseudonana (TpDSP1) localizes to the plastid and enhances growth during acute Fe limitation at subsaturating light by increasing the photosynthetic efficiency of carbon fixation. Clone lines overexpressing TpDSP1 had a lower quantum requirement for growth, increased levels of photosynthetic and carbon fixation proteins, and increased cyclic electron flow around photosystem I. Cyclic electron flow is an ATP-producing pathway essential in higher plants and chlorophytes with a heretofore unappreciated role in diatoms. However, cells under replete conditions were characterized as having markedly reduced growth and photosynthetic rates at saturating light, thereby constraining the benefits afforded by overexpression. Widespread distribution of DSP-like sequences in environmental metagenomic and metatranscriptomic datasets highlights the presence and relevance of this protein in natural phytoplankton populations in diverse oceanic regimes. PMID:24277817

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

    PubMed

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

    2014-05-01

    In this study, the diurnal change of photosynthesis activity in response to various tidal patterns, the relationship between photosynthetic activity and tissue water content, and the interactive effect of desiccation and irradiance on photosynthetic activity in Gloiopeltis furcata were investigated by using portable pulse amplitude modulated (PAM) fluorometer. Results showed that Fv/Fm decreased more rapidly during the noon low tide than during the morning- or evening low tide. F/Fm decreased slowly at the beginning of desiccation during the morning low tide, but decreased rapidly throughout the evening low tide. Fv/Fm recovered to the initial values on the same day no matter when the low tide occurred, suggesting the occurrence of dynamic photoinhibition. These features endowed G. furcata with an ability to adapt to the periodic desiccation on high intertidal rocks. The maximum (Fv/Fm) and effective (Phi(PSII)) quantum yield declined with the decrease of tissue water content (TWC). However, photosynthetic activity could recover completely when TWC exceeded 6%, showing a strong ability of G. furcata to tolerate desiccation. The relationships between TWC and Fv/Fm and Phi (PS II) as were as follows: F/Fm = 0.68 + (0.44-0.68)/[1 +(TWC/ 66.96)]5 , R2 = 0.99; Phi(PSII) = 0.585 + (0.004-0.585)/[1+(TWC/73)10], R2 = 0.99. ANOVA result further showed that the interactive effect of irradiance and desiccation on photosynthetic activity was significant, and that the photoinhibition degree increased with elevation of irradiation and duration of desiccation. The extreme condition (6 h desiccation at 1000 micromol photons x m(-2) x s(-1)) resulted in a serious photoinhibition, with the longest period of complete recovery for photosynthesis activity. PMID:25129953

  2. Geographic range predicts photosynthetic and growth response to warming in co-occurring tree species

    NASA Astrophysics Data System (ADS)

    Reich, Peter B.; Sendall, Kerrie M.; Rice, Karen; Rich, Roy L.; Stefanski, Artur; Hobbie, Sarah E.; Montgomery, Rebecca A.

    2015-02-01

    Populations near the warm edge of species ranges may be particularly sensitive to climate change, but lack of empirical data on responses to warming represents a key gap in understanding future range dynamics. Herein we document the impacts of experimental warming on the performance of 11 boreal and temperate forest species that co-occur at the ecotone between these biomes in North America. We measured in situ net photosynthetic carbon gain and growth of >4,100 juvenile trees from local seed sources exposed to a chamberless warming experiment that used infrared heat lamps and soil heating cables to elevate temperatures by +3.4 °C above- and belowground for three growing seasons across 48 plots at two sites. In these ecologically realistic field settings, species growing nearest their warm range limit exhibited reductions in net photosynthesis and growth, whereas species near their cold range limit responded positively to warming. Differences among species in their three-year growth responses to warming parallel their photosynthetic responses to warming, suggesting that leaf-level responses may scale to whole-plant performance. These responses are consistent with the hypothesis, from observational data and models, that warming will reduce the competitive ability of currently dominant southern boreal species compared with locally rarer co-occurring species that dominate warmer neighbouring regions.

  3. UV-B Perception and Acclimation in Chlamydomonas reinhardtii[OPEN

    PubMed Central

    Chappuis, Richard; Allorent, Guillaume

    2016-01-01

    Plants perceive UV-B, an intrinsic component of sunlight, via a signaling pathway that is mediated by the photoreceptor UV RESISTANCE LOCUS8 (UVR8) and induces UV-B acclimation. To test whether similar UV-B perception mechanisms exist in the evolutionarily distant green alga Chlamydomonas reinhardtii, we identified Chlamydomonas orthologs of UVR8 and the key signaling factor CONSTITUTIVELY PHOTOMORPHOGENIC1 (COP1). Cr-UVR8 shares sequence and structural similarity to Arabidopsis thaliana UVR8, has conserved tryptophan residues for UV-B photoreception, monomerizes upon UV-B exposure, and interacts with Cr-COP1 in a UV-B-dependent manner. Moreover, Cr-UVR8 can interact with At-COP1 and complement the Arabidopsis uvr8 mutant, demonstrating that it is a functional UV-B photoreceptor. Chlamydomonas shows apparent UV-B acclimation in colony survival and photosynthetic efficiency assays. UV-B exposure, at low levels that induce acclimation, led to broad changes in the Chlamydomonas transcriptome, including in genes related to photosynthesis. Impaired UV-B-induced activation in the Cr-COP1 mutant hit1 indicates that UVR8-COP1 signaling induces transcriptome changes in response to UV-B. Also, hit1 mutants are impaired in UV-B acclimation. Chlamydomonas UV-B acclimation preserved the photosystem II core proteins D1 and D2 under UV-B stress, which mitigated UV-B-induced photoinhibition. These findings highlight the early evolution of UVR8 photoreceptor signaling in the green lineage to induce UV-B acclimation and protection. PMID:27020958

  4. Biomass allocation and photosynthetic responses of lianas and pioneer tree seedlings to light

    NASA Astrophysics Data System (ADS)

    Toledo-Aceves, Tarin; Swaine, Michael D.

    2008-07-01

    Lianas are frequently considered as light demanding plants due to their proliferation in gaps and forest edges. Since lianas are exposed to a very heterogeneous light environment, they could be expected to express morphological and physiological plasticity in response to changes in the light environment, as high as that found in pioneer trees. We compared the biomass allocation and photosynthetic responses of seedlings of three species of lianas and two species of pioneer trees to increased light availability. Seedlings were transferred from medium (4-5 mol m -2 d -1) to high irradiance (12-15 mol m -2 d -1) in a controlled environment. In general the three liana species allocated fewer resources to the stem in comparison with the trees. The difference in the response between irradiance regimes was similar among the species, with no strong differences between trees and lianas probably due the early stage of the plants. With increase in irradiance plants accumulated more biomass, allocated more resources to the roots and less to the leaves, reduced the leaf area ratio (LAR) and specific leaf area (SLA). The photosynthetic rates recorded were not related to the rates of growth as measured by the increase in dry biomass (RGRm). Regardless of the life form, plants under higher irradiance increased their light compensation point (Lcp) and attained light saturation (Lsp) at higher levels of irradiance, while the saturated photosynthetic rate (A max) did not show a clear pattern, and dark respiration (R d) and quantum yield (Q) were not affected by the transference. The understanding of liana and tree seedlings responses to the light environment may have important implications in the dynamics of tropical forest regeneration.

  5. The acclimation of Chlorella to high-level nitrite for potential application in biological NOx removal from industrial flue gases.

    PubMed

    Li, Tianpei; Xu, Gang; Rong, Junfeng; Chen, Hui; He, Chenliu; Giordano, Mario; Wang, Qiang

    2016-05-20

    Nitrogen oxides (NOx) are the components of fossil flue gas that give rise to the greatest environmental concerns. This study evaluated the ability of the green algae Chlorella to acclimate to high level of NOx and the potential utilization of Chlorella strains in biological NOx removal (DeNOx) from industrial flue gases. Fifteen Chlorella strains were subject to high-level of nitrite (HN, 176.5 mmolL(-1) nitrite) to simulate exposure to high NOx. These strains were subsequently divided into four groups with respect to their ability to tolerate nitrite (excellent, good, fair, and poor). One strain from each group was selected to evaluate their photosynthetic response to HN condition, and the nitrite adaptability of the four Chlorella strains were further identified by using chlorophyll fluorescence. The outcome of our experiments shows that, although high concentrations of nitrite overall negatively affect growth and photosynthesis of Chlorella strains, the degree of nitrite tolerance is a strain-specific feature. Some Chlorella strains have an appreciably higher ability to acclimate to high-level of nitrite. Acclimation is achieved through a three-step process of restrict, acclimate, and thriving. Notably, Chlorella sp. C2 was found to have a high tolerance and to rapidly acclimate to high concentrations of nitrite; it is therefore a promising candidate for microalgae-based biological NOx removal. PMID:27010349

  6. Interplay between cold-responsive gene regulation, metabolism and RNA processing during plant cold acclimation.

    PubMed

    Zhu, Jianhua; Dong, Chun-Hai; Zhu, Jian-Kang

    2007-06-01

    Temperate plants are capable of developing freezing tolerance when they are exposed to low nonfreezing temperatures. Acquired freezing tolerance involves extensive reprogramming of gene expression and metabolism. Recent full-genome transcript profiling studies, in combination with mutational and transgenic plant analyses, have provided a snapshot of the complex transcriptional network that operates under cold stress. Ubiquitination-mediated proteosomal protein degradation has a crucial role in regulating one of the upstream transcription factors, INDUCER OF CBF EXPRESSION 1 (ICE1), and thus in controlling the cold-responsive transcriptome. The changes in expression of hundreds of genes in response to cold temperatures are followed by increases in the levels of hundreds of metabolites, some of which are known to have protective effects against the damaging effects of cold stress. Genetic analysis has revealed important roles for cellular metabolic signals, and for RNA splicing, export and secondary structure unwinding, in regulating cold-responsive gene expression and chilling and freezing tolerance. PMID:17468037

  7. Time course of physiological and psychological responses in humans during a 20-day severe-cold-acclimation programme.

    PubMed

    Brazaitis, Marius; Eimantas, Nerijus; Daniuseviciute, Laura; Baranauskiene, Neringa; Skrodeniene, Erika; Skurvydas, Albertas

    2014-01-01

    The time course of physiological and psychological markers during cold acclimation (CA) was explored. The experiment included 17 controlled (i.e., until the rectal temperature reached 35.5°C or 170 min had elapsed; for the CA-17 session, the subjects (n = 14) were immersed in water for the same amount of time as that used in the CA-1 session) head-out water immersions at a temperature of 14°C over 20 days. The data obtained in this study suggest that the subjects exhibited a thermoregulatory shift from peripheral-to-central to solely central input thermoregulation, as well as from shivering to non-shivering thermogenesis throughout the CA. In the first six CA sessions, a hypothermic type of acclimation was found; further CA (CA-7 to CA-16) led to a transitional shift to a hypothermic-insulative type of acclimation. Interestingly, when the subjects were immersed in water for the same time as that used in the CA-1 session (CA-17), the CA led to a hypothermic type of acclimation. The presence of a metabolic type of thermogenesis was evident only under thermoneutral conditions. Cold-water immersion decreased the concentration of cold-stress markers, reduced the activity of the innate immune system, suppressed specific immunity to a lesser degree and yielded less discomfort and cold sensation. We found a negative correlation between body mass index and Δ metabolic heat production before and after CA. PMID:24722189

  8. Time Course of Physiological and Psychological Responses in Humans during a 20-Day Severe-Cold–Acclimation Programme

    PubMed Central

    Brazaitis, Marius; Eimantas, Nerijus; Daniuseviciute, Laura; Baranauskiene, Neringa; Skrodeniene, Erika; Skurvydas, Albertas

    2014-01-01

    The time course of physiological and psychological markers during cold acclimation (CA) was explored. The experiment included 17 controlled (i.e., until the rectal temperature reached 35.5°C or 170 min had elapsed; for the CA-17 session, the subjects (n = 14) were immersed in water for the same amount of time as that used in the CA-1 session) head-out water immersions at a temperature of 14°C over 20 days. The data obtained in this study suggest that the subjects exhibited a thermoregulatory shift from peripheral-to-central to solely central input thermoregulation, as well as from shivering to non-shivering thermogenesis throughout the CA. In the first six CA sessions, a hypothermic type of acclimation was found; further CA (CA-7 to CA-16) led to a transitional shift to a hypothermic–insulative type of acclimation. Interestingly, when the subjects were immersed in water for the same time as that used in the CA-1 session (CA-17), the CA led to a hypothermic type of acclimation. The presence of a metabolic type of thermogenesis was evident only under thermoneutral conditions. Cold-water immersion decreased the concentration of cold-stress markers, reduced the activity of the innate immune system, suppressed specific immunity to a lesser degree and yielded less discomfort and cold sensation. We found a negative correlation between body mass index and Δ metabolic heat production before and after CA. PMID:24722189

  9. Photosynthetic and physiological responses of native and exotic tidal woody seedlings to simulated tidal immersion

    NASA Astrophysics Data System (ADS)

    Wu, Tonggui; Gu, Shenhua; Zhou, Hefeng; Wang, G. Geoff; Cheng, Xiangrong; Yu, Mukui

    2013-12-01

    Hibiscus hamabo, a native tidal woody species, and Myrica cerifera, an exotic tidal woody species, have been widely planted on coastal beaches in subtropical China. However, whether there are differences in physiological response and tolerance to immersion between the two tidal species is still unknown. Our objectives were to evaluate differences in the photosynthetic and physiological responses to tidal immersion for the two species in the context of sea level rise. With increasing immersion, net photosynthesis, stomatal conductance, intercellular CO2 concentration, and light saturation point declined progressively for both species, whereas dark respiration and light compensation point showed the reverse trend. Lower variation was observed in H. hamabo than in M. cerifera for each index in the same treatment. Photosynthetic ability and utilization of light, especially under high light intensity, decreased for both species. Leaf soluble sugar and protein contents, and glycolate oxidase activity first increased and then decreased with increasing of immersion degree, with the higher values observed in the W4 (4 h duration, 15 cm depth) and W6 (6 h duration, 25 cm depth) treatments for H. hamabo, and W2 (2 h duration, 5 cm depth) and W4 treatments for M. cerifera. These findings indicate that H. hamabo has a better ability to keep the reduction of photosynthesis at a minimum through soluble substance regulated osmotic potential and avoiding excess light damage to the photosynthetic system through increased photorespiration, heat dissipation, chlorophyll fluorescence. Our results suggest that H. hamabo is more tolerant to tidal immersion than M. cerifera, and therefore it is better adapted to the anticipated sea level rise in future.

  10. Longleaf pine photosynthetic response to soil resource availability and elevated atmospheric carbon dioxide

    SciTech Connect

    Runion, G.B.; Mitchell, R.J.; Green, T.H.; Prior, S.A.; Rogers, H.H.; Gjerstad, D.H.

    1999-05-01

    Gas exchange responses during a drought cycle were studied in longleaf pine (Pinus palustris Mill.) seedlings after prolonged exposure to varying levels of atmospheric CO{sub 2} soil N and water. Elevated atmospheric CO{sub 2} concentration increased photosynthesis, tended to decrease stomatal conductance, and increased water-use efficiency (WUE). Although soil resource availability influences gas exchange measurements, it generally did not affect the magnitude or direction of the response to CO{sub 2} concentration. However, significant interactions among treatment variables were observed for plant xylem pressure potential. In seedlings grown with high N, a positive growth response to elevated atmospheric CO{sub 2} increased whole-plant water use resulting in more severe plant water stress, despite increased leaf-level WUE; however, under low N conditions the lack of a growth response to elevated CO{sub 2} reduced whole-plant water use, decreased water stress severity, and increased WUE. Photosynthetic response to CO{sub 2} was greatest in the high N treatment at the beginning of the drought cycle, but diminished as water stress increased; however, plants grown with low N showed greater photosynthetic responses to CO{sub 2} later in the drought cycle. Therefore, plant gas exchange rates interact with growth response in determining the severity of water stress under drought and, thus, the ability of elevated atmospheric CO{sub 2} to ameliorate the effects of drought and allow plants to maintain increased rates of photosynthesis may be influenced by the availability of other resources, such as N and water.

  11. A graphical user interface for numerical modeling of acclimation responses of vegetation to climate change

    NASA Astrophysics Data System (ADS)

    Le, Phong V. V.; Kumar, Praveen; Drewry, Darren T.; Quijano, Juan C.

    2012-12-01

    Ecophysiological models that vertically resolve vegetation canopy states are becoming a powerful tool for studying the exchange of mass, energy, and momentum between the land surface and the atmosphere. A mechanistic multilayer canopy-soil-root system model (MLCan) developed by Drewry et al. (2010a) has been used to capture the emergent vegetation responses to elevated atmospheric CO2 for both C3 and C4 plants under various climate conditions. However, processing input data and setting up such a model can be time-consuming and error-prone. In this paper, a graphical user interface that has been developed for MLCan is presented. The design of this interface aims to provide visualization capabilities and interactive support for processing input meteorological forcing data and vegetation parameter values to facilitate the use of this model. In addition, the interface also provides graphical tools for analyzing the forcing data and simulated numerical results. The model and its interface are both written in the MATLAB programming language. Finally, an application of this model package for capturing the ecohydrological responses of three bioenergy crops (maize, miscanthus, and switchgrass) to local environmental drivers at two different sites in the Midwestern United States is presented.

  12. RESPONSE OF THE PHOTOSYNTHETIC APPARATUS OF PHAEODACTYLYM TRICORNUTUM (BACILLARIOPHYCEAE) TO NITRATE, PHOSPHATE OR IRON STARVATION

    EPA Science Inventory

    The effects of nitrate, phosphate, and iron starvation and resupply on photosynthetic pigments, selected photosynthetic proteins, and photosystem II (PSII) photochemistry were examined in the diatom Phaeodactylum tricornutum Bohlin (CCMP1327). lthough cell chlorophyll a (chl a) c...

  13. Flower Development under Drought Stress: Morphological and Transcriptomic Analyses Reveal Acute Responses and Long-Term Acclimation in Arabidopsis[C][W

    PubMed Central

    Su, Zhao; Ma, Xuan; Guo, Huihong; Sukiran, Noor Liyana; Guo, Bin; Assmann, Sarah M.; Ma, Hong

    2013-01-01

    Drought dramatically affects plant growth and crop yield, but previous studies primarily examined responses to drought during vegetative development. Here, to study responses to drought during reproductive development, we grew Arabidopsis thaliana plants with limited water, under conditions that allowed the plants to initiate and complete reproduction. Drought treatment from just after the onset of flowering to seed maturation caused an early arrest of floral development and sterility. After acclimation, plants showed reduced fertility that persisted throughout reproductive development. Floral defects included abnormal anther development, lower pollen viability, reduced filament elongation, ovule abortion, and failure of flowers to open. Drought also caused differential expression of 4153 genes, including flowering time genes FLOWERING LOCUS T, SUPPRESSOR OF OVEREXPRESSION OF CO1, and LEAFY, genes regulating anther and pistil development, and stress-related transcription factors. Mutant phenotypes of hypersensitivity to drought and fewer differentially expressed genes suggest that DEHYDRATION RESPONSE ELEMENT B1A may have an important function in drought response in flowers. A more severe filament elongation defect under drought in myb21 plants demonstrated that appropriate stamen development requires MYB DOMAIN PROTEIN 21 under drought conditions. Our study reveals a regulatory cascade in reproductive responses and acclimation under drought. PMID:24179129

  14. Comparison between NaCl tolerance response and acclimation to cold temperature in Shewanella putrefaciens.

    PubMed

    Leblanc, Laurence; Leboeuf, Céline; Leroi, Françoise; Hartke, Axel; Auffray, Yanick

    2003-03-01

    Two strains of the spoiling bacterium S. putrefaciens showed an adaptation capacity to hyperosmotic shock when they were pretreated with a sublethal concentration of NaCl. The maximal tolerance factor for the CIP 69.29 strain was obtained when cells were incubated for 1 h in the presence of 1.5% NaCl, whereas for the J13.1 strain, an incubation of 15 min in the presence of 1% NaCl seemed to be the optimal conditions to harden the cells against a subsequent lethal salt treatment. During NaCl adaptation and growth at low temperatures (2 degrees C), 37 and 32 polypeptides were induced respectively. Interestingly, 11 proteins were common between the two different stress responses. These proteins and the corresponding genes seem to play a key role in the observed cross-protection towards the NaCl challenge induced by growth of the cultures at 2 degrees C. One of the overlapping proteins has been identified to correspond to the alkyl hydroperoxide reductase (AhpC) of S. putrefaciens. Northern blot analysis showed that induction of this enzyme was accompanied by accumulation of the corresponding transcript under both conditions. PMID:12567236

  15. Photosynthetic Responses of Plant Communities to Sand Burial on the Machair Dune Systems of the Outer Hebrides, Scotland

    PubMed Central

    KENT, MARTIN; OWEN, NIA W.; DALE, M. PAMELA

    2005-01-01

    • Background and Aims The effects of both short-term (2 weeks) and long-term (6 weeks) burial on the photosynthetic efficiency of four typical plant sub-communities of the machair sand dunes of the Outer Hebrides are described. Previous studies have examined the photosynthetic responses on individual species rather than the response at the community level. • Methods Three replicate turves from four different sub-community types (foredune grassland, dune slack, three-year fallow and unploughed grassland) were subjected to short- and long-term burial treatments after acclimatisation in an unheated greenhouse for approximately 10 weeks. Three replicate control turves from each sub-community were left unburied. After treatment, photosynthetic rate was measured at 16–20 h and 40–44 h after re-exposure, using an infra-red gas analyser, with standardization by total leaf area for each turf. Effects of sub-community type, burial duration and time since re-exposure were analysed by 3-factor split-plot analysis of variance (ANOVA) with repeated measures for time since re-exposure in the subplots. • Key Results Buried turves were characterized by a low dark respiration rate, which may represent a maintenance response to burial. After removal of sand, each machair sub-community showed some capacity for an elastic photosynthetic response. There were no differences between the effects of short- and long-term burial on the photosynthetic efficiency of machair vegetation, although turves buried for 6 weeks generally attained photosynthetic rates approaching those of control rates sooner than turves buried for 2 weeks. Photosynthetic responses to burial varied between sub-communities, with the slack turves exhibiting the poorest capacity for recovery within the investigated 44-h period. • Conclusions In the machair environment, the ability to maintain photosynthetic equipment whilst buried, and the ability to bring about a relatively rapid reinstatement of

  16. Elevated carbon dioxide influences yield and photosynthetic responses of hydroponically-grown sweetpotato

    NASA Technical Reports Server (NTRS)

    Mortley, D.; Hill, J.; Loretan, P.; Bonsi, C.; Hill, W.; Hileman, D.; Terse, A.

    1996-01-01

    The response of 'TI-155' and 'Georgia Jet' sweetpotato cultivars to elevated CO2 concentrations of 400 (ambient), 750 and 1000 micromoles mol-1 were evaluated under controlled environment conditions using the nutrient film technique (NFT). Growth chamber conditions included photosynthetic photon flux (PPF) of 600 micromoles m-2 s-1, 14/10 light/dark period, and 70% +/- 5% RH. Plants were grown using a modified half-Hoagland nutrient solution with a pH range of 5.5-6.0 and an electrical conductivity of 0.12 S m-1. Gas exchange measurements were made using infrared gas analysis, an open-flow gas exchange system, and a controlled-climate cuvette. Photosynthetic (Pn) measurements were made at CO2 ranges of 50 to 1000 micromoles mol-1. Storage root yield/plant increased with CO2 up to 750 but declined at 1000 micromoles mol-1. Storage root dry matter (DM) and foliage dry weight increased with increasing CO2. Harvest index (HI) for both cultivars was highest at 750 micromoles mol-1. The PPF vs Pn curves were typical for C3 plants with saturation occurring at approximately 600 micromoles m-2 s-1. CO2 concentration did not significantly influence net Pn, transpiration, water-use-efficiency (WUE), and stomatal conductance. As measurement CO2 concentration increased, net Pn and WUE increased while transpiration and stomatal conductance decreased.

  17. Effects of Soil Water and Nitrogen on Growth and Photosynthetic Response of Manchurian Ash (Fraxinus mandshurica) Seedlings in Northeastern China

    PubMed Central

    Wang, Miao; Shi, Shuai; Lin, Fei; Hao, Zhanqing; Jiang, Ping; Dai, Guanhua

    2012-01-01

    Background Soil water and nitrogen (N) are considered to be the main environmental factors limiting plant growth and photosynthetic capacity. However, less is known about the interactive effects of soil water and N on tree growth and photosynthetic response in the temperate ecosystem. Methods/Principal Findings We applied N and water, alone and in combination, and investigated the combined effect of different water and N regimes on growth and photosynthetic responses of Fraxinus mandshurica seedlings. The seedlings were exposed to three water regimes including natural precipitation (CK), higher precipitation (HW) (CK +30%) and lower precipitation (LW) (CK −30%), and both with and without N addition for two growing seasons. We demonstrated that water and N supply led to a significant increase in the growth and biomass production of the seedlings. LW treatment significantly decreased biomass production and leaf N content, but they showed marked increases in N addition. N addition could enhance the photosynthetic capability under HW and CK conditions. Leaf chlorophyll content and the initial activity of Rubisco were dramatically increased by N addition regardless of soil water condition. The positive relationships were found between photosynthetic capacity, leaf N content, and SLA in response to water and N supply in the seedling. Rubisco expression was up-regulated by N addition with decreasing soil water content. Immunofluorescent staining showed that the labeling for Rubisco was relatively low in leaves of the seedlings under LW condition. The accumulation of Rubisco was increased in leaf tissues of LW by N addition. Conclusions/Significance Our study has presented better understanding of the interactions between soil water and N on the growth and photosynthetic response in F. mandschurica seedlings, which may provide novel insights on the potential responses of the forest ecosystem to climate change associated with increasing N deposition. PMID:22347401

  18. Lettuce irrigated with contaminated water: Photosynthetic effects, antioxidative response and bioaccumulation of microcystin congeners.

    PubMed

    Bittencourt-Oliveira, Maria do Carmo; Cordeiro-Araújo, Micheline Kézia; Chia, Mathias Ahii; Arruda-Neto, João Dias de Toledo; de Oliveira, Ênio Tiago; dos Santos, Flávio

    2016-06-01

    The use of microcystins (MCs) contaminated water to irrigate crop plants represents a human health risk due to their bioaccumulation potential. In addition, MCs cause oxidative stress and negatively influence photosynthetic activities in plants. The present study was aimed at investigating the effect of MCs on photosynthetic parameters and antioxidative response of lettuce. Furthermore, the bioaccumulation factor (BAF) of total MCs, MC-LR and MC-RR in the vegetable after irrigation with contaminated water was determined. Lettuce crops were irrigated for 15 days with water containing cyanobacterial crude extracts (Microcystis aeruginosa) with MC-LR (0.0, 0.5, 2.0, 5.0 and 10.0 µg L(-1)), MC-RR (0.0, 0.15, 0.5, 1.5 and 3.0 µg L(-1)) and total MCs (0.0, 0.65, 2.5, 6.5 and 13.0 µg L(-1)). Increased net photosynthetic rate, stomatal conductance, leaf tissue transpiration and intercellular CO2 concentration were recorded in lettuce exposed to different MCs concentrations. Antioxidant response showed that glutathione S-transferase activity was down-regulated in the presence of MCs. On the other hand, superoxide dismutase, catalase and peroxidase activities were upregulated with increasing MCs concentrations. The bioaccumulation factor (BAF) of total MCs and MC-LR was highest at 6.50 and 5.00 µg L(-1), respectively, while for MC-RR, the highest BAF was recorded at 1.50 µg L(-1) concentration. The amount of total MCs, MC-LR and MC-RR bioacumulated in lettuce was highest at the highest exposure concentrations. However, at the lowest exposure concentration, there were no detectable levels of MC-LR, MC-RR and total MCs in lettuce. Thus, the bioaccumulation of MCs in lettuce varies according to the exposure concentration. In addition, the extent of physiological response of lettuce to the toxins relies on exposure concentrations. PMID:26896895

  19. Photosynthetic Response to Long- and Short-Term Changes in Carbon Dioxide in Sweetpotatoes Grown Hydroponically with Enhanced Mineral Nutrition

    NASA Technical Reports Server (NTRS)

    Hamilton, Casey; Terse, Anita; Hileman, Douglas R.; Mortley, Desmond G.; Hill, Jill

    1998-01-01

    Sweetpotato [Ipomoea batatas L.(Lam.)] has been selected by NASA as a potential food for long-term space missions. In previous experiments, sweetpotato plants grown hydroponically under elevated levels of CO2 depleted the nitrogen in the nutrient solution between the hi-weekly solution replacements. In this experiment, the effect of enhanced nutrient replenishment on photosynthetic rates of sweetpotato was determined. CO2 response curves were determined for "TU-82-155" and "Georgia-Jet" sweetpotatoes grown hydroponically in growth chambers at three different CO2 concentrations (400, 750, and 1000 micro-mol/mol CO2). Gas exchange measurements were made using infrared gas analysis, an open-flow gas exchange system, and a controlled-climate cuvette. Photosynthetic measurements were made at CO2 concentrations from 50-1000 micro-mol/mol CO2. Net photosynthetic rates showed an increase with increasing measurement CO2 in all nutrient regimes, but the response of photosynthetic rates to the growth CO2 conditions varied among the experiments and between the two varieties. Enhanced mineral nutrition led to increased net photosynthetic rates in "Georgia Jet" plants, but not in "TU-82-155" plants. The results of this study will help to determine the CO2 requirements for growth of sweetpotato on proposed space missions.

  20. Contributions of photosynthetic and non-photosynthetic cell types to leaf respiration in Vicia faba L. and their responses to growth temperature.

    PubMed

    Long, Benedict M; Bahar, Nur H A; Atkin, Owen K

    2015-11-01

    In intact leaves, mitochondrial populations are highly heterogeneous among contrasting cell types; how such contrasting populations respond to sustained changes in the environment remains, however, unclear. Here, we examined respiratory rates, mitochondrial protein composition and response to growth temperature in photosynthetic (mesophyll) and non-photosynthetic (epidermal) cells from fully expanded leaves of warm-developed (WD) and cold-developed (CD) broad bean (Vicia faba L.). Rates of respiration were significantly higher in mesophyll cell protoplasts (MCPs) than epidermal cell protoplasts (ECPs), with both protoplast types exhibiting capacity for cytochrome and alternative oxidase activity. Compared with ECPs, MCPs contained greater relative quantities of porin, suggesting higher mitochondrial surface area in mesophyll cells. Nevertheless, the relative quantities of respiratory proteins (normalized to porin) were similar in MCPs and ECPs, suggesting that ECPs have lower numbers of mitochondria yet similar protein complement to MCP mitochondria (albeit with lower abundance serine hydroxymethyltransferase). Several mitochondrial proteins (both non-photorespiratory and photorespiratory) exhibited an increased abundance in response to cold in both protoplast types. Based on estimates of individual protoplast respiration rates, combined with leaf cell abundance data, epidermal cells make a small but significant (2%) contribution to overall leaf respiration which increases twofold in the cold. Taken together, our data highlight the heterogeneous nature of mitochondrial populations in leaves, both among contrasting cell types and in how those populations respond to growth temperature. PMID:25828647

  1. Cell-Wall Changes and Cell Tension in Response to Cold Acclimation and Exogenous Abscisic Acid in Leaves and Cell Cultures.

    PubMed Central

    Rajashekar, C. B.; Lafta, A.

    1996-01-01

    Freeze-induced cell tensions were determined by cell water relations in leaves of broadleaf evergreen species and cell cultures of grapes (Vitis spp.) and apple (Malus domestica). Cell tensions increased in response to cold acclimation in leaves of broadleaf evergreen species during extracellular freezing, indicating a higher resistance to cell volume changes during freezing in cold-hardened leaves than in unhardened leaves. Unhardened leaves, typically, did not develop tension greater than 3.67 MPa, whereas cold-hardened leaves attained tensions up to 12 MPa. With further freezing there was a rapid decline and a loss of tension in unhardened leaves of all the broadleaf evergreen species studied. Also, similar results were observed in cold-hardened leaves of all of the species except in those of inkberry (Ilex glabra) and Euonymus fortunei, in which negative pressures persisted below -40[deg]C. Abscisic acid treatment of inkberry and Euonymus kiautschovica resulted in increases in freeze-induced tensions in leaves, suggesting that both cold acclimation and abscisic acid have similar effects on freezing behavior[mdash] specifically on the ability of cell walls to undergo deformation. Decreases in peak tensions were generally associated with lethal freezing injury and may suggest cavitation of cellular water. However, in suspension-cultured cells of grapes and apple, no cell tension was observed during freezing. Cold acclimation of these cells resulted in an increase in the cell-wall strength and a decrease in the limiting cell-wall pore size from 35 to 22 A in grape cells and from 29 to 22 A in apple cells. PMID:12226314

  2. Long-term growth under elevated CO2 suppresses biotic stress genes in non-acclimated, but not cold-acclimated winter wheat.

    PubMed

    Kane, Khalil; Dahal, Keshav P; Badawi, Mohamed A; Houde, Mario; Hüner, Norman P A; Sarhan, Fathey

    2013-11-01

    This study compared the photosynthetic performance and the global gene expression of the winter hardy wheat Triticum aestivum cv Norstar grown under non-acclimated (NA) or cold-acclimated (CA) conditions at either ambient CO2 or elevated CO2. CA Norstar maintained comparable light-saturated and CO2-saturated rates of photosynthesis but lower quantum requirements for PSII and non-photochemical quenching relative to NA plants even at elevated CO2. Neither NA nor CA plants were sensitive to feedback inhibition of photosynthesis at elevated CO2. Global gene expression using microarray combined with bioinformatics analysis revealed that genes affected by elevated CO2 were three times higher in NA (1,022 genes) compared with CA (372 genes) Norstar. The most striking effect was the down-regulation of genes involved in the plant defense responses in NA Norstar. In contrast, cold acclimation reversed this down-regulation due to the cold induction of genes involved in plant pathogenesis resistance; and cellular and chloroplast protection. These results suggest that elevated CO2 has less impact on plant performance and productivity in cold-adapted winter hardy plants in the northern climates compared with warmer environments. Selection for cereal cultivars with constitutively higher expression of biotic stress defense genes may be necessary under elevated CO2 during the warm growth period and in warmer climates. PMID:23969557

  3. Temperature-dependent responses of the photosynthetic and chlorophyll fluorescence attributes of apple (Malus domestica) leaves during a sustained high temperature event.

    PubMed

    Greer, Dennis H

    2015-12-01

    The objective of this study was to follow changes in the temperature-dependent responses of photosynthesis and photosystem II performance in leaves of field-grown trees of Malus domestica (Borkh.) cv. 'Red Gala' before and after exposure to a long-term heat event occurring late in the growing season. Light-saturated photosynthesis was optimal at 25 °C before the heat event. The high temperatures caused a reduction in rates at low temperatures (15-20 °C) but increased rates at high temperatures (30-40 °C) and a shift in optimum to 30 °C. Rates at all temperatures increased after the heat event and the optimum shifted to 33 °C, indicative of some acclimation to the high temperatures occurring. Photosystem II attributes were all highly temperature-dependent. The operating quantum efficiency of PSII during the heat event declined, but mostly at high temperatures, partly because of decreased photochemical quenching but also from increased non-photochemical quenching. However, a further reduction in PSII operating efficiency occurred after the heat event subsided. Non-photochemical quenching had subsided, whereas photochemical quenching had increased in the post-heat event period and consistent with a greater fraction of open PSII reaction centres. What remained uncertain was why these effects on PSII performance appeared to have no effect on the process of light-saturated photosynthesis. However, the results provide an enhanced understanding of the impacts of sustained high temperatures on the photosynthetic process and its underlying reactions, notably photochemistry. PMID:26465670

  4. Impacts of thermal acclimation of photosynthesis on future land carbon storage

    NASA Astrophysics Data System (ADS)

    Mercado, L. M.; Medlyn, B. E.; Huntingford, C.; Sitch, S.; Zelazowsk, P.; Cox, P. M.

    2015-12-01

    Plants have the ability to adjust their photosynthetic characteristics in order to improve their performance at the prevailing thermal regimes, this is termed thermal acclimation of photosynthesis. The impacts of thermal acclimation of photosynthesis on future land sink and climate is unknown. In this study we estimate the impact of accounting for thermal acclimation of photosynthetic traits on future land carbon sink using 22 climate models and a global land surface model. We find an enhancement of land carbon storage of up to 70 % and 13 % in tropical and temperate regions in 2100 when accounting for thermal plasticity of photosynthetic capacity. The outcome of this study highlights the urgent need for more studies on thermal acclimation of photosynthesis, specifically in the tropical regions where there is a lack of data and ecosystem scale warming and elevated CO2 experiments.

  5. A better energy allocation of absorbed light in photosystem II and less photooxidative damage contribute to acclimation of Arabidopsis thaliana young leaves to water deficit.

    PubMed

    Sperdouli, Ilektra; Moustakas, Michael

    2014-05-01

    Water deficit stress promotes excitation pressure and photooxidative damage due to an imbalance between light capture and energy use. Young leaves (YL) of Arabidopsis thaliana plants acclimate better to the onset of water deficit (OnsWD) than do mature leaves (ML). To obtain a better understanding of this differential response, we evaluated whether YL and ML of A. thaliana exposed to the OnsWD, mild water deficit (MiWD) and moderate water deficit (MoWD), show differences in their photosynthetic performance, and whether photosynthetic acclimation correlates with leaf developmental stage. Water deficit (WD) resulted in greater photooxidative damage in ML compared to YL, but the latter could not be protected under the OnsWD or MiWD, but only under MoWD. YL of A. thaliana with signs of photosynthetic acclimation under MoWD retained higher maximum quantum yield (Fv/Fm) and decreased reactive oxygen species (ROS) formation. YL under MoWD, show a reduced excitation pressure and a better balance between light capture and photochemical energy use, which contributed to their photoprotection, but only under low light intensity (LL, 130μmolphotonsm(-2)s(-1)) and not under high light (HL, 1200μmolphotonsm(-2)s(-1)). In conclusion, leaf developmental stage was correlated with photo-oxidative damage and a differential allocation of absorbed light energy in photosystem II (PSII) of Arabidopsis leaves under WD. PMID:24709149

  6. Leaf photosynthetic and solar-tracking responses of mallow, Malva parviflora, to photon flux density.

    PubMed

    Greer, Dennis H; Thorpe, Michael R

    2009-10-01

    Malva parviflora L. (mallow) is a species that occupies high-light habitats as a weedy invader in orchards and vineyards. Species of the Malvaceae are known to solar track and anecdotal evidence suggests this species may also. How M. parviflora responds physiologically to light in comparison with other species within the Malvaceae remains unknown. Tracking and photosynthetic responses to photon flux density (PFD) were evaluated on plants grown in greenhouse conditions. Tracking ability was assessed in the growth conditions and by exposing leaves to specific light intensities and measuring changes in the angle of the leaf plane. Light responses were also determined by photosynthesis and chlorophyll fluorescence. Leaves followed a heliotropic response which was highly PFD-dependent, with tracking rates increasing in a curvilinear pattern. Maximum tracking rates were up to 20 degrees h(-1) and saturated for light above 1,300 micromol (photons) m(-2) s(-1). This high-light saturation, both for tracking (much higher than the other species), and for photosynthesis, confirmed mallow as a high-light demanding species. Further, because there was no photoinhibition, the leaves could capture the potential of an increased carbon gain in higher irradiance by resorting to solar tracking. Modelling suggested the tracking response could increase the annual carbon gain by as much as 25% compared with leaves that do not track the sun. The various leaf attributes associated with solar tracking, therefore, help to account for the success of this species as a weed in many locations worldwide. PMID:19576789

  7. Mutations in the Ca2+/H+ transporter CAX1 increase CBF/DREB1 expression and the cold-acclimation response in Arabidopsis.

    PubMed

    Catala, Rafael; Santos, Elisa; Alonso, Jose M; Ecker, Joseph R; Martinez-Zapater, Jose M; Salinas, Julio

    2003-12-01

    Transient increases in cytosolic free calcium concentration ([Ca2+]cyt) are essential for plant responses to a variety of environmental stimuli, including low temperature. Subsequent reestablishment of [Ca2+]cyt to resting levels by Ca2+ pumps and antiporters is required for the correct transduction of the signal [corrected]. C-repeat binding factor/dehydration responsive element binding factor 1 (Ca2+/H+) antiporters is required for the correct transduction of the signal. We have isolated a cDNA from Arabidopsis that corresponds to a new cold-inducible gene, rare cold inducible4 (RCI4), which was identical to calcium exchanger 1 (CAX1), a gene that encodes a vacuolar Ca2+/H+ antiporter involved in the regulation of intracellular Ca2+ levels. The expression of CAX1 was induced in response to low temperature through an abscisic acid-independent pathway. To determine the function of CAX1 in Arabidopsis stress tolerance, we identified two T-DNA insertion mutants, cax1-3 and cax1-4, that display reduced tonoplast Ca2+/H+ antiport activity. The mutants showed no significant differences with respect to the wild type when analyzed for dehydration, high-salt, chilling, or constitutive freezing tolerance. However, they exhibited increased freezing tolerance after cold acclimation, demonstrating that CAX1 plays an important role in this adaptive response. This phenotype correlates with the enhanced expression of CBF/DREB1 genes and their corresponding targets in response to low temperature. Our results indicate that CAX1 ensures the accurate development of the cold-acclimation response in Arabidopsis by controlling the induction of CBF/DREB1 and downstream genes. PMID:14630965

  8. A compendium of temperature responses of Rubisco kinetic traits: variability among and within photosynthetic groups and impacts on photosynthesis modeling

    PubMed Central

    Galmés, Jeroni; Hermida-Carrera, Carmen; Laanisto, Lauri; Niinemets, Ülo

    2016-01-01

    The present study provides a synthesis of the in vitro and in vivo temperature responses of Rubisco Michaelis–Menten constants for CO2 (Kc) and O2 (Ko), specificity factor (Sc,o) and maximum carboxylase turnover rate (kcatc) for 49 species from all the main photosynthetic kingdoms of life. Novel correction routines were developed for in vitro data to remove the effects of study-to-study differences in Rubisco assays. The compilation revealed differences in the energy of activation (∆Ha) of Rubisco kinetics between higher plants and other photosynthetic groups, although photosynthetic bacteria and algae were under-represented and very few species have been investigated so far. Within plants, the variation in Rubisco temperature responses was related to species’ climate and photosynthetic mechanism, with differences in ∆Ha for kcatc among C3 plants from cool and warm environments, and in ∆Ha for kcatc and Kc among C3 and C4 plants. A negative correlation was observed among ∆Ha for Sc/o and species’ growth temperature for all data pooled, supporting the convergent adjustment of the temperature sensitivity of Rubisco kinetics to species’ thermal history. Simulations of the influence of varying temperature dependences of Rubisco kinetics on Rubisco-limited photosynthesis suggested improved photosynthetic performance of C3 plants from cool habitats at lower temperatures, and C3 plants from warm habitats at higher temperatures, especially at higher CO2 concentration. Thus, variation in Rubisco kinetics for different groups of photosynthetic organisms might need consideration to improve prediction of photosynthesis in future climates. Comparisons between in vitro and in vivo data revealed common trends, but also highlighted a large variability among both types of Rubisco kinetics currently used to simulate photosynthesis, emphasizing the need for more experimental work to fill in the gaps in Rubisco datasets and improve scaling from enzyme kinetics to

  9. A compendium of temperature responses of Rubisco kinetic traits: variability among and within photosynthetic groups and impacts on photosynthesis modeling.

    PubMed

    Galmés, Jeroni; Hermida-Carrera, Carmen; Laanisto, Lauri; Niinemets, Ülo

    2016-09-01

    The present study provides a synthesis of the in vitro and in vivo temperature responses of Rubisco Michaelis-Menten constants for CO2 (Kc) and O2 (Ko), specificity factor (Sc,o) and maximum carboxylase turnover rate (kcatc) for 49 species from all the main photosynthetic kingdoms of life. Novel correction routines were developed for in vitro data to remove the effects of study-to-study differences in Rubisco assays. The compilation revealed differences in the energy of activation (∆Ha) of Rubisco kinetics between higher plants and other photosynthetic groups, although photosynthetic bacteria and algae were under-represented and very few species have been investigated so far. Within plants, the variation in Rubisco temperature responses was related to species' climate and photosynthetic mechanism, with differences in ∆Ha for kcatc among C3 plants from cool and warm environments, and in ∆Ha for kcatc and Kc among C3 and C4 plants. A negative correlation was observed among ∆Ha for Sc/o and species' growth temperature for all data pooled, supporting the convergent adjustment of the temperature sensitivity of Rubisco kinetics to species' thermal history. Simulations of the influence of varying temperature dependences of Rubisco kinetics on Rubisco-limited photosynthesis suggested improved photosynthetic performance of C3 plants from cool habitats at lower temperatures, and C3 plants from warm habitats at higher temperatures, especially at higher CO2 concentration. Thus, variation in Rubisco kinetics for different groups of photosynthetic organisms might need consideration to improve prediction of photosynthesis in future climates. Comparisons between in vitro and in vivo data revealed common trends, but also highlighted a large variability among both types of Rubisco kinetics currently used to simulate photosynthesis, emphasizing the need for more experimental work to fill in the gaps in Rubisco datasets and improve scaling from enzyme kinetics to realized

  10. Does physiological acclimation to climate warming stabilize the ratio of canopy respiration to photosynthesis?

    PubMed

    Drake, John E; Tjoelker, Mark G; Aspinwall, Michael J; Reich, Peter B; Barton, Craig V M; Medlyn, Belinda E; Duursma, Remko A

    2016-08-01

    Given the contrasting short-term temperature dependences of gross primary production (GPP) and autotrophic respiration, the fraction of GPP respired by trees is predicted to increase with warming, providing a positive feedback to climate change. However, physiological acclimation may dampen or eliminate this response. We measured the fluxes of aboveground respiration (Ra ), GPP and their ratio (Ra /GPP) in large, field-grown Eucalyptus tereticornis trees exposed to ambient or warmed air temperatures (+3°C). We report continuous measurements of whole-canopy CO2 exchange, direct temperature response curves of leaf and canopy respiration, leaf and branch wood respiration, and diurnal photosynthetic measurements. Warming reduced photosynthesis, whereas physiological acclimation prevented a coincident increase in Ra . Ambient and warmed trees had a common nonlinear relationship between the fraction of GPP that was respired above ground (Ra /GPP) and the mean daily temperature. Thus, warming significantly increased Ra /GPP by moving plants to higher positions on the shared Ra /GPP vs daily temperature relationship, but this effect was modest and only notable during hot conditions. Despite the physiological acclimation of autotrophic respiration to warming, increases in temperature and the frequency of heat waves may modestly increase tree Ra /GPP, contributing to a positive feedback between climate warming and atmospheric CO2 accumulation. PMID:27122489

  11. Photosynthetic response of Persian Gulf acroporid corals to summer versus winter temperature deviations

    PubMed Central

    Saleh, Abolfazl; Mehdinia, Ali; Shirvani, Arash; Kayal, Mohsen

    2015-01-01

    With on-going climate change, coral susceptibility to thermal stress constitutes a central concern in reefconservation. In the Persian Gulf, coral reefs are confronted with a high seasonal variability in water temperature, and both hot and cold extremes have been associated with episodes of coral bleaching and mortality. Using physiological performance as a measure of coral health, we investigated the thermal susceptibility of the common acroporid, Acropora downingi, near Hengam Island where the temperature oscillates seasonally in the range 20.2–34.2 °C. In a series of two short-term experiments comparing coral response in summer versus winter conditions, we exposed corals during each season (1) to the corresponding seasonal average and extreme temperature levels in a static thermal environment, and (2) to a progressive temperature deviation from the annual mean toward the corresponding extreme seasonal value and beyond in a dynamic thermal environment. We monitored four indictors of coral physiological performance: net photosynthesis (Pn), dark respiration (R), autotrophic capability (Pn/R), and survival. Corals exposed to warming during summer showed a decrease in net photosynthesis and ultimately died, while corals exposed to cooling during winter were not affected in their photosynthetic performance and survival. Coral autotrophic capability Pn/R was lower at the warmer thermal level within eachseason, and during summer compared to winter. Corals exposed to the maximum temperature of summer displayed Pn/R < 1, inferring that photosynthetic performance could not support basal metabolic needs under this environment. Our results suggest that the autotrophic performance of the Persian Gulf A. downingi is sensitive to the extreme temperatures endured in summer, and therefore its populations may be impacted by future increases in water temperature. PMID:26157627

  12. Photosynthetic response of Persian Gulf acroporid corals to summer versus winter temperature deviations.

    PubMed

    Vajed Samiei, Jahangir; Saleh, Abolfazl; Mehdinia, Ali; Shirvani, Arash; Kayal, Mohsen

    2015-01-01

    With on-going climate change, coral susceptibility to thermal stress constitutes a central concern in reefconservation. In the Persian Gulf, coral reefs are confronted with a high seasonal variability in water temperature, and both hot and cold extremes have been associated with episodes of coral bleaching and mortality. Using physiological performance as a measure of coral health, we investigated the thermal susceptibility of the common acroporid, Acropora downingi, near Hengam Island where the temperature oscillates seasonally in the range 20.2-34.2 °C. In a series of two short-term experiments comparing coral response in summer versus winter conditions, we exposed corals during each season (1) to the corresponding seasonal average and extreme temperature levels in a static thermal environment, and (2) to a progressive temperature deviation from the annual mean toward the corresponding extreme seasonal value and beyond in a dynamic thermal environment. We monitored four indictors of coral physiological performance: net photosynthesis (Pn), dark respiration (R), autotrophic capability (Pn/R), and survival. Corals exposed to warming during summer showed a decrease in net photosynthesis and ultimately died, while corals exposed to cooling during winter were not affected in their photosynthetic performance and survival. Coral autotrophic capability Pn/R was lower at the warmer thermal level within eachseason, and during summer compared to winter. Corals exposed to the maximum temperature of summer displayed Pn/R < 1, inferring that photosynthetic performance could not support basal metabolic needs under this environment. Our results suggest that the autotrophic performance of the Persian Gulf A. downingi is sensitive to the extreme temperatures endured in summer, and therefore its populations may be impacted by future increases in water temperature. PMID:26157627

  13. Photosynthetic electron transport and specific photoprotective responses in wheat leaves under drought stress.

    PubMed

    Zivcak, Marek; Brestic, Marian; Balatova, Zuzana; Drevenakova, Petra; Olsovska, Katarina; Kalaji, Hazem M; Yang, Xinghong; Allakhverdiev, Suleyman I

    2013-11-01

    The photosynthetic responses of wheat (Triticum aestivum L.) leaves to different levels of drought stress were analyzed in potted plants cultivated in growth chamber under moderate light. Low-to-medium drought stress was induced by limiting irrigation, maintaining 20 % of soil water holding capacity for 14 days followed by 3 days without water supply to induce severe stress. Measurements of CO2 exchange and photosystem II (PSII) yield (by chlorophyll fluorescence) were followed by simultaneous measurements of yield of PSI (by P700 absorbance changes) and that of PSII. Drought stress gradually decreased PSII electron transport, but the capacity for nonphotochemical quenching increased more slowly until there was a large decrease in leaf relative water content (where the photosynthetic rate had decreased by half or more). We identified a substantial part of PSII electron transport, which was not used by carbon assimilation or by photorespiration, which clearly indicates activities of alternative electron sinks. Decreasing the fraction of light absorbed by PSII and increasing the fraction absorbed by PSI with increasing drought stress (rather than assuming equal absorption by the two photosystems) support a proposed function of PSI cyclic electron flow to generate a proton-motive force to activate nonphotochemical dissipation of energy, and it is consistent with the observed accumulation of oxidized P700 which causes a decrease in PSI electron acceptors. Our results support the roles of alternative electron sinks (either from PSII or PSI) and cyclic electron flow in photoprotection of PSII and PSI in drought stress conditions. In future studies on plant stress, analyses of the partitioning of absorbed energy between photosystems are needed for interpreting flux through linear electron flow, PSI cyclic electron flow, along with alternative electron sinks. PMID:23860828

  14. Photosynthetic response to globally increasing CO2 of co-occurring temperate seagrass species.

    PubMed

    Borum, Jens; Pedersen, Ole; Kotula, Lukasz; Fraser, Matthew W; Statton, John; Colmer, Timothy D; Kendrick, Gary A

    2016-06-01

    Photosynthesis of most seagrass species seems to be limited by present concentrations of dissolved inorganic carbon (DIC). Therefore, the ongoing increase in atmospheric CO2 could enhance seagrass photosynthesis and internal O2 supply, and potentially change species competition through differential responses to increasing CO2 availability among species. We used short-term photosynthetic responses of nine seagrass species from the south-west of Australia to test species-specific responses to enhanced CO2 and changes in HCO3 (-) . Net photosynthesis of all species except Zostera polychlamys were limited at pre-industrial compared to saturating CO2 levels at light saturation, suggesting that enhanced CO2 availability will enhance seagrass performance. Seven out of the nine species were efficient HCO3 (-) users through acidification of diffusive boundary layers, production of extracellular carbonic anhydrase, or uptake and internal conversion of HCO3 (-) . Species responded differently to near saturating CO2 implying that increasing atmospheric CO2 may change competition among seagrass species if co-occurring in mixed beds. Increasing CO2 availability also enhanced internal aeration in the one species assessed. We expect that future increases in atmospheric CO2 will have the strongest impact on seagrass recruits and sparsely vegetated beds, because densely vegetated seagrass beds are most often limited by light and not by inorganic carbon. PMID:26476101

  15. Growth, photosynthetic and respiratory responses to sub-lethal copper concentrations in Scenedesmus incrassatulus (Chlorophyceae).

    PubMed

    Perales-Vela, Hugo Virgilio; González-Moreno, Sergio; Montes-Horcasitas, Carmen; Cañizares-Villanueva, Rosa Olivia

    2007-05-01

    In the present paper we investigated the effects of sub-lethal concentrations of Cu2+ in the growth and metabolism of Scenedesmus incrassatulus. We found that the effect of Cu2+ on growth, photosynthetic pigments (chlorophylls and carotenoids) and metabolism do not follow the same pattern. Photosynthesis was more sensitive than respiration. The analysis of chlorophyll a fluorescence transient shows that the effect of sub-lethal Cu2+ concentration in vivo, causes a reduction of the active PSII reaction centers and the primary charge separation, decreasing the quantum yield of PSII, the electron transport rate and the photosynthetic O2 evolution. The order of sensitivity found was: Growth>photosynthetic pigments content=photosynthetic O2 evolution>photosynthetic electron transport>respiration. The uncoupled relationship between growth and metabolism is discussed. PMID:17267014

  16. Vulnerability and acclimation to increased UVB radiation in three intertidal macroalgae of different morpho-functional groups.

    PubMed

    Figueroa, Félix L; Domínguez-González, Belén; Korbee, Nathalie

    2014-06-01

    The vulnerability and acclimation to increased UVB radiation in three macroalgae of different morpho-functional groups collected in the Mediterranean coastal waters were evaluated. The algae were submitted for 7 days to increased (PAB+) and decreased (PAB-) UVB radiation. The thickness and morphology influenced the response to increased UVB radiation, being Cystoseira tamariscifolia the less vulnerable algae followed by Ellisolandia elongata. The highest resistance to increased UVB radiation in C. tamariscifolia was related to the accumulation of polyphenols and high antioxidant activity, whereas E. elongata was due to its high reflectance. Finally, Ulva rigida suffered the highest photoinhibition under PAB+ culture. The latest species presented 10 times lower polyphenol content and antioxidant activity than C. tamariscifolia. The three species showed different acclimation patterns to the changes of UVB radiation related to the morphology, photosynthetic activity, accumulation of photoprotectors and antioxidant activities. The ecological implications of the UVB variations on macroalgae are discussed. PMID:24556033

  17. Elucidating cold acclimation pathway in blueberry by transcriptome profiling

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A fundamental goal of cold acclimation research is to understand the mechanisms responsible for the increase in freezing tolerance in response to environmental cues. Changes in gene expression underlie some of the biochemical and physiological changes that occur during cold acclimation. Detailed and...

  18. Synergic effect of salinity and CO2 enrichment on growth and photosynthetic responses of the invasive cordgrass Spartina densiflora

    PubMed Central

    Mateos-Naranjo, Enrique; Redondo-Gómez, Susana; Álvarez, Rosario; Cambrollé, Jesús; Gandullo, Jacinto; Figueroa, M. Enrique

    2010-01-01

    Spartina densiflora is a C4 halophytic species that has proved to have a high invasive potential which derives from its clonal growth and its physiological plasticity to environmental factors, such as salinity. A greenhouse experiment was designed to investigate the synergic effect of 380 and 700 ppm CO2 at 0, 171, and 510 mM NaCl on the growth and the photosynthetic apparatus of S. densiflora by measuring chlorophyll fluorescence parameters, gas exchange and photosynthetic pigment concentrations. PEPC activity and total ash, sodium, potassium, calcium, magnesium, and zinc concentrations were determined, as well as the C/N ratio. Elevated CO2 stimulated growth of S. densiflora at 0 and 171 mM NaCl external salinity after 90 d of treatment. This growth enhancement was associated with a greater leaf area and improved leaf water relations rather than with variations in net photosynthetic rate (A). Despite the fact that stomatal conductance decreased in response to 700 ppm CO2 after 30 d of treatment, A was not affected. This response of A to elevated CO2 concentration might be explained by an enhanced PEPC carboxylation capacity. On the whole, plant nutrient concentrations declined under elevated CO2, which can be ascribed to the dilution effect caused by an increase in biomass and the higher water content found at 700 ppm CO2. Finally, CO2 and salinity had a marked overall effect on the photochemical (PSII) apparatus and the synthesis of photosynthetic pigments. PMID:20194923

  19. Plant acclimation impacts carbon allocation to isoprene emissions: evidence from past to future CO2 levels

    NASA Astrophysics Data System (ADS)

    de Boer, Hugo J.; van der Laan, Annick; Dekker, Stefan C.; Holzinger, Rupert

    2016-04-01

    Isoprene (C5H8) is produced in plant leaves as a side product of photosynthesis, whereby approximately 0.1-2.0% of the photosynthetic carbon uptake is released back into the atmosphere via isoprene emissions. Isoprene biosynthesis is thought to alleviate oxidative stress, specifically in warm, dry and high-light environments. Moreover, isoprene biosynthesis is influenced by atmospheric CO2 concentrations in the short term (responses in the leaf interior CO2 concentration (Ci), and in the long term (>weeks) via acclimation in photosynthetic biochemistry. In order to understand the effects of CO2-induced climate change on carbon allocation in plants it is therefore important to quantify how isoprene biosynthesis and emissions are effected by both short-term responses and long-term acclimation to rising atmospheric CO2 levels. A promising development for modelling CO2-induced changes in isoprene emissions is the Leaf-Energetic-Status model (referred to as LES-model hereafter, see Harrison et al., 2013 and Morfopoulos et al., 2014). This model simulates isoprene emissions based on the hypothesis that isoprene biosynthesis depends on the imbalance between the photosynthetic electron supply of reducing power and the electron demands of carbon fixation. In addition to environmental conditions, this imbalance is determined by the photosynthetic electron transport capacity (Jmax) and the maximum carboxylation capacity of Rubisco (V cmax). Here we compare predictions of the LES-model with observed isoprene emission responses of Quercus robur (pedunculate oak) specimen that acclimated to CO2 levels representative of the last glacial, the present and the end of this century (200, 400 and 800 ppm, respectively) for two growing seasons. Plants were grown in walk-in growth chambers with tight control of light, temperature, humidity and CO2 concentrations. Photosynthetic biochemical parameters V cmax and Jmax were determined with a Licor LI-6400XT photosynthesis system

  20. A comparative study of the photosynthetic capacity in two green tide macroalgae using chlorophyll fluorescence.

    PubMed

    Wang, Ying; Qu, Tongfei; Zhao, Xinyu; Tang, Xianghai; Xiao, Hui; Tang, Xuexi

    2016-01-01

    Green tides have occurred in the Yellow Sea, China, every year from 2007 to 2015. The free-floating Ulva prolifera (Müller) J. Agardh was the causative macroalgal species. The co-occurring, attached U. intestinalis was also observed. Photosynthetic capacities were determined using chlorophyll fluorescence in situ and after 7 days lab acclimation, and a significant differences were noted. Pigment composition showed no obvious differences, but concentrations varied significantly, especially chlorophyll b in U. prolifera two times increase was observed after acclimation. The optimal photochemical efficiency of PS II (Fv/Fm) was significantly higher in U. prolifera. Photosynthetic rate (α), maximum relative electron transport rate (rETRmax), and minimum saturating irradiance (Ek), obtained from rapid light response curves (RLCs), showed almost the same photosynthetic physiological status as Fv/Fm. Quenching coefficients and low temperature (77 K) chlorophyll fluorescence emission spectra of thylakoid membranes analysis showed U. prolifera has a better recovery activity and plasticity of PSII than U. intestinalis. Furthermore, energy dissipation via non-photochemical quenching (NPQ) and state transitions showed efficacious photoprotection solution especially in U. prolifera suffered from the severe stresses. Results in the present study suggested that U. prolifera's higher photosynthetic capacity would contribute to its free-floating proliferation, and efficacious photoprotection in addition to favorable oceanographic conditions and high nutrient levels support its growth and aggregation. PMID:27386261

  1. Salinity induced changes in photosynthetic pigment and antioxidant responses in Sesuvium portulacastrum.

    PubMed

    Sivakumar, Thirumal; Panneerselvam, Rajaram

    2011-11-01

    The production of leaf and root antioxidant changes when exposed to saline conditions were investigated in the perennial halophyte Sesuvium portulacastrum L. Plants were grown with a nonsterilized soil and sterilized soil with 50 and 100% of sterilized seawater on 25, 55 and 85 Days After Planting (DAP). The plants were harvested on 30th, 60th and 90th DAP and used for analyzing the photosynthetic pigments, antioxidant enzyme activities viz., Superoxide dismutase (SOD; EC1.15.1.1) Ascorbate peroxidase (APX, EC 1.11.1.11) and non enzymatic antioxidant contents like ascorbic acid, alpha-tocopherol, reduced glutathione were determined. Plants exposed to salinity, either alone (SSW) sterilized seawater/unsterilized soil (USS) along with higher pigments, antioxidative enzymes and Na+ ions response. This tendency was generally more marked in SSW/USS plants when compared to SSW/SS plants. The concentration of SSW/SS was negatively correlated with the antioxidative capacity of the plant, either enzymatic or non enzymatic and K+ ions. These data suggest that the enhancement of the antioxidative response is of crucial significance for S. portulacastrum plants growing under saline conditions. PMID:22514886

  2. Ozone exposure and flux-based response functions for photosynthetic traits in wheat, maize and poplar.

    PubMed

    Bagard, Matthieu; Jolivet, Yves; Hasenfratz-Sauder, Marie-Paule; Gérard, Joëlle; Dizengremel, Pierre; Le Thiec, Didier

    2015-11-01

    Ozone exposure- and dose-response relationships based on photosynthetic leaf traits (CO2 assimilation, chlorophyll content, Rubisco and PEPc activities) were established for wheat, maize and poplar plants grown in identical controlled conditions, providing a comparison between crop and tree species, as well as between C3 and C4 plants. Intra-specific variability was addressed by comparing two wheat cultivars with contrasting ozone tolerance. Depending on plant models and ozone levels, first-order, second-order and segmented linear regression models were used to derive ozone response functions. Overall, flux-based functions appeared superior to exposure-based functions in describing the data, but the improvement remained modest. The best fit was obtained using the POD0.5 for maize and POD3 for poplar. The POD6 appeared relevant for wheat, although intervarietal differences were found. Our results suggest that taking into account the dynamics of leaf antioxidant capacity could improve current methods for ozone risk assessment for plants. PMID:26253315

  3. Needle age and season influence photosynthetic temperature response and total annual carbon uptake in mature Picea mariana trees

    SciTech Connect

    Jensen, Anna M.; Warren, Jeffrey; Hanson, Paul J.; Childs, Joanne; Wullschleger, Stan D.

    2015-01-01

    Using seasonal- and cohort-specific photosynthetic temperature response functions, we quantified the physiological significance of maintaining multiple foliar cohorts in mature (~40-45 year old) Picea mariana trees in an ombrotrophic Sphagnum-bog, northern Minnesota, USA. We measured photosynthetic capacity, foliar respiration (Rd), biochemistry and morphology to estimate annual carbon (C) uptake by cohort, season and canopy position. Temperature response of key photosynthetic parameters at 25 C (i.e., light-saturated rate of CO2 assimilation (Asat), light-saturated rate of Rubisco carboxylation (Vcmax), light-saturated electron transport rate (Jmax)) were clearly dependent on season and were generally less responsive in younger needles. Temperature optimums range between 18.7-23.7, 31.3-38.3 and 28.7-36.7 C for Asat, Vcmax and Jmax respectively. Current-year (Y0) foliage had lower photosynthetic capacities compared to one-year-old (Y1) and two-year-old (Y2) foliage. As Y0 needles matured, values of Asat, Vcmax, Jmax, foliar LMA and nitrogen increased. Values of Vcmax, Jmax and Rd were related to foliar nitrogen but only in the youngest (Y0) cohort. Foliar ontogeny affected photosynthetic capacity more than growth temperature. Morphological and physiological cohort differences were reflected by their annual contribution to modeled C uptake, with a ~36% lower estimated annual C uptake by Y0 needles (LAI 0.52 m2m-2) compared to Y1&2 cohorts (LAI 0.67 m2m-2). Collectively, these results illustrate the physiological and ecological significance of characterizing multiple foliar cohorts during bud break and throughout the growth season, and for cumulative C uptake model estimates.

  4. Needle age and season influence photosynthetic temperature response and total annual carbon uptake in mature Picea mariana trees

    DOE PAGESBeta

    Jensen, Anna M.; Warren, Jeffrey; Hanson, Paul J.; Childs, Joanne; Wullschleger, Stan D.

    2015-01-01

    Using seasonal- and cohort-specific photosynthetic temperature response functions, we quantified the physiological significance of maintaining multiple foliar cohorts in mature (~40-45 year old) Picea mariana trees in an ombrotrophic Sphagnum-bog, northern Minnesota, USA. We measured photosynthetic capacity, foliar respiration (Rd), biochemistry and morphology to estimate annual carbon (C) uptake by cohort, season and canopy position. Temperature response of key photosynthetic parameters at 25 C (i.e., light-saturated rate of CO2 assimilation (Asat), light-saturated rate of Rubisco carboxylation (Vcmax), light-saturated electron transport rate (Jmax)) were clearly dependent on season and were generally less responsive in younger needles. Temperature optimums range between 18.7-23.7,more » 31.3-38.3 and 28.7-36.7 C for Asat, Vcmax and Jmax respectively. Current-year (Y0) foliage had lower photosynthetic capacities compared to one-year-old (Y1) and two-year-old (Y2) foliage. As Y0 needles matured, values of Asat, Vcmax, Jmax, foliar LMA and nitrogen increased. Values of Vcmax, Jmax and Rd were related to foliar nitrogen but only in the youngest (Y0) cohort. Foliar ontogeny affected photosynthetic capacity more than growth temperature. Morphological and physiological cohort differences were reflected by their annual contribution to modeled C uptake, with a ~36% lower estimated annual C uptake by Y0 needles (LAI 0.52 m2m-2) compared to Y1&2 cohorts (LAI 0.67 m2m-2). Collectively, these results illustrate the physiological and ecological significance of characterizing multiple foliar cohorts during bud break and throughout the growth season, and for cumulative C uptake model estimates.« less

  5. Can leaf net carbon gain acclimate to keep up with global warming?

    NASA Astrophysics Data System (ADS)

    Vico, Giulia; Manzoni, Stefano; Way, Danielle; Hurry, Vaughan

    2016-04-01

    Plants are able to adjust their physiological activity to fluctuations and long-term changes in their growing environment. Nevertheless, projected increases in temperature will occur with unprecedented speed. Will global warming exceed the thermal acclimation capacity of leaves, thus reducing net CO2 assimilation? Such a reduction in net CO2 assimilation rate (Anet) in response to warming may deplete ecosystems' net primary productivity, with global impacts on the carbon cycling. Here we combine data on net photosynthetic thermal acclimation to changes in temperature with a probabilistic description of leaf temperature variability. We analytically obtain the probability distribution of the net CO2 assimilation rate as a function of species-specific leaf traits and growing conditions. Using this approach, we study the effects of mean leaf temperature and its variability on average Anet and the frequency of occurrence of sub-optimal thermal conditions. To maximize the net CO2 assimilation in warmer conditions, the thermal optimum for Anet (Topt) must track the growing temperature. Observations suggest that plants' thermal acclimation capacity is limited, so that growing temperatures cannot be tracked by the Topt. It is thus likely that net CO2 assimilation rates will decline in the future. Furthermore, for set leaf traits, large fluctuations in leaf temperature reduce average Anet and increase the frequency of occurrence of sub-optimal conditions for net CO2 assimilation.

  6. Induction of DREB2A pathway with repression of E2F, jasmonic acid biosynthetic and photosynthesis pathways in cold acclimation-specific freeze-resistant wheat crown.

    PubMed

    Karki, Amrit; Horvath, David P; Sutton, Fedora

    2013-03-01

    Winter wheat lines can achieve cold acclimation (development of tolerance to freezing temperatures) and vernalization (delay in transition from vegetative to reproductive phase) in response to low non-freezing temperatures. To describe cold-acclimation-specific processes and pathways, we utilized cold acclimation transcriptomic data from two lines varying in freeze survival but not vernalization. These lines, designated freeze-resistant (FR) and freeze-susceptible (FS), were the source of crown tissue RNA. Well-annotated differentially expressed genes (p ≤ 0.005 and fold change ≥ 2 in response to 4 weeks cold acclimation) were used for gene ontology and pathway analysis. "Abiotic stimuli" was identified as the most enriched and unique for FR. Unique to FS was "cytoplasmic components." Pathway analysis revealed the "triacylglycerol degradation" pathway as significantly downregulated and common to both FR and FS. The most enriched of FR pathways was "neighbors of DREB2A," with the highest positive median fold change. The "13-LOX and 13-HPL" and the "E2F" pathways were enriched in FR only with a negative median fold change. The "jasmonic acid biosynthesis" pathway and four "photosynthetic-associated" pathways were enriched in both FR and FS but with a more negative median fold change in FR than in FS. A pathway unique to FS was "binding partners of LHCA1," which was enriched only in FS with a significant negative median fold change. We propose that the DREB2A, E2F, jasmonic acid biosynthesis, and photosynthetic pathways are critical for discrimination between cold-acclimated lines varying in freeze survival. PMID:23262780

  7. Heat acclimation and cross tolerance to hypoxia

    PubMed Central

    Ely, Brett R; Lovering, Andrew T; Horowitz, Michal; Minson, Christopher T

    2014-01-01

    Recent research has suggested a potential for some of the physiological and cellular responses to heat acclimation to carry over to improved tolerance of the novel stresses of another environment. This cross-tolerance is evident in heat-acclimated animals that exhibit enhanced tolerance to either hypoxic or ischemic stress, and is primarily attributed to shared cellular stress response pathways. These pathways include Hypoxia-Inducible Factor-1 (HIF-1) and Heat Shock Proteins (HSP). Whether these shared cellular stress response pathways translate to systemic cross-tolerance (improved exercise tolerance, reduced risk of environment-associated illness) has not been clearly shown, particularly in humans. This review highlights the HIF-1 and HSP pathways and their relationship with systemic acclimation responses, and further examines the potential cellular and systemic adaptations that may result in cross-tolerance between hot and hypoxic environments.

  8. Convexity of the Photosynthetic Light-Response Curve in Relation to Intensity and Direction of Light during Growth.

    PubMed Central

    Ogren, E.

    1993-01-01

    Photosynthesis in the intermediate light range is most efficient when the convexity of the photosynthetic light-response curve is high. Factors determining the convexity were examined for intact leaves using Salix sp. and for a plant cell culture using the green microalga Coccomyxa sp. It was found that the leaf had lower convexity than diluted plant cells because the light gradient through the leaf was not fully matched by a corresponding gradient in photosynthetic capacity. The degree to which the leaf gradients were matched was quantified by measuring photosynthesis at both leaf surfaces using modulated fluorescence. Two principal growth conditions were identified as those causing mismatch of leaf gradients and lowering of the convexity relative to cells. The first was growth under low light, where leaves did not develop any noteworthy gradient in photosynthetic capacity. This led to decreased convexity, particularly in old leaves with high chlorophyll content and, hence, steep light gradients. Second and less conspicuous was growth under high light conditions when light was given bilaterally rather than unilaterally, which yielded leaves of high photosynthetic capacity at both surfaces. Two situations were also identified that caused the convexity to decrease at the chloroplast level: (a) increased light during growth, for both leaves and cells, and (b) increased CO2 concentration during measurement of high-light-grown leaves. These changes of the intrinsic convexity were interpreted to indicate that the convexity declines with increased capacity of ribulose-1,5-bisphosphate carboxylase/oxygenase relative to the capacity of electron transport. PMID:12231754

  9. Physiological and biochemical response of the photosynthetic apparatus of two marine diatoms to Fe stress

    SciTech Connect

    McKay, R.M.L.; LaRoche, J.; Geider, R.J.

    1997-06-01

    Flavodoxin is a small electron-transfer protein capable of replacing ferredoxin during periods of Fe deficiency. When evaluating the suitability of flavodoxin as a diagnostic indicator for Fe limitation of phytoplankton growth, we examined its expression in two marine diatoms we cultured using trace-metal-buffered medium. Thalassiosira weissflogii and Phaeodactylum tricornutum were cultured in ethylenediaminetetraacetic acid-buffered Sargasso Sea water containing from 10 to 1000 nm added Fe. Trace-metal-buffered cultures of each diatom maintained high growth rates across the entire range of Fe additions. Similarly, declines in chlorophyll/cell and in the ratio of photosystem II variable-to-maximum fluorescence were negligible (P. tricornutum) to moderate (T. weissflogii, 54% decline in chlorophyll/cell and 22% decrease in variable-to-maximum fluorescence). Moreover, only minor variations in photosynthetic parameters were observed across the range of additions. In contrast, flavodoxin was expressed to high levels in low-Fe cultures. Despite the inverse relationship between flavodoxin expression and Fe content of the medium, its expression was seemingly independent of any of the indicators of cell physiology that were assayed. It appears that flavodoxin is expressed as an early-stage response to Fe stress and that its accumulation need not be intimately connected to limitations imposed by Fe on the growth rate of these diatoms.

  10. Physiological and Biochemical Response of the Photosynthetic Apparatus of Two Marine Diatoms to Fe Stress.

    PubMed Central

    McKay, R. M. L.; Geider, R. J.; LaRoche, J.

    1997-01-01

    Flavodoxin is a small electron-transfer protein capable of replacing ferredoxin during periods of Fe deficiency. When evaluating the suitability of flavodoxin as a diagnostic indicator for Fe limitation of phytoplankton growth, we examined its expression in two marine diatoms we cultured using trace-metal-buffered medium. Thalassio-sira weissflogii and Phaeodactylum tricornutum were cultured in ethylenediaminetetraacetic acid-buffered Sargasso Sea water containing from 10 to 1000 nM added Fe. Trace-metal-buffered cultures of each diatom maintained high growth rates across the entire range of Fe additions. Similarly, declines in chlorophyll/cell and in the ratio of photosystem II variable-to-maximum fluorescence were negligible (P. tricornutum) to moderate (T. weissflogii; 54% decline in chlorophyll/cell and 22% decrease in variable-to-maximum fluorescence). Moreover, only minor variations in photosynthetic parameters were observed across the range of additions. In contrast, flavodoxin was expressed to high levels in low-Fe cultures. Despite the inverse relationship between flavodoxin expression and Fe content of the medium, its expression was seemingly independent of any of the indicators of cell physiology that were assayed. It appears that flavodoxin is expressed as an early-stage response to Fe stress and that its accumulation need not be intimately connected to limitations imposed by Fe on the growth rate of these diatoms. PMID:12223732

  11. Light history modulates antioxidant and photosynthetic responses of biofilms to both natural (light) and chemical (herbicides) stressors.

    PubMed

    Bonnineau, Chloé; Sague, Irene Gallardo; Urrea, Gemma; Guasch, Helena

    2012-05-01

    In multiple stress situations, the co-occurrence of environmental and chemical factors can influence organisms' ability to cope with toxicity. In this context, the influence of light adaptation on the response of freshwater biofilms to sudden light changes or to herbicides exposure was investigated by determining various parameters: diatom community composition, photosynthetic parameters, chlorophyll a content, antioxidant enzyme activities. Biofilms were grown in microcosms under sub-optimal, saturating, and high light intensities and showed already described characteristics of shade/light adaptation (community structure, photosynthetic adaptation, etc.). Light history modulated antioxidant and photosynthetic responses of biofilms to the stress caused by short-term exposure to sudden light changes or to herbicides. First biofilms adapted to sub-optimal light intensity (shade-adapted) were found to be more sensitive to an increase in light intensity than high-light adapted ones to a reduction in light intensity. Second, while light history influenced biofilms' response to glyphosate, it had little influence on biofilms' response to copper and none on its response to oxyfluorfen. Indeed glyphosate exposure led to a stronger decrease in photosynthetic efficiency of shade-adapted biofilms (EC(50) = 11.7 mg L(-1)) than of high-light adapted communities (EC(50) = 35.6 mg L(-1)). Copper exposure led to an activation of ascorbate peroxidase (APX) in biofilms adapted to sub-optimal and saturating light intensity while the protein content decreased in all biofilms exposed to copper. Oxyfluorfen toxicity was independent of light history provoking an increase in APX activity. In conclusion this study showed that both previous exposure to contaminants and physical habitat characteristics might influence community tolerance to disturbances strongly. PMID:22407402

  12. Higher thermal acclimation potential of respiration but not photosynthesis in two alpine Picea taxa in contrast to two lowland congeners.

    PubMed

    Zhang, Xiao Wei; Wang, Jing Ru; Ji, Ming Fei; Milne, Richard Ian; Wang, Ming Hao; Liu, Jian-Quan; Shi, Sheng; Yang, Shu-Li; Zhao, Chang-Ming

    2015-01-01

    The members of the genus Picea form a dominant component in many alpine and boreal forests which are the major sink for atmospheric CO2. However, little is known about the growth response and acclimation of CO2 exchange characteristics to high temperature stress in Picea taxa from different altitudes. Gas exchange parameters and growth characteristics were recorded from four year old seedlings of two alpine (Picea likiangensis vars. rubescens and linzhiensis) and two lowland (P. koraiensis and P. meyeri) taxa. Seedlings were grown at moderate (25°C/15°C) and high (35°C/25°C) day/night temperatures, for four months. The approximated biomass increment (ΔD2H) for all taxa decreased under high temperature stress, associated with decreased photosynthesis and increased respiration. However, the two alpine taxa exhibited lower photosynthetic acclimation and higher respiratory acclimation than either lowland taxon. Moreover, higher leaf dry mass per unit area (LMA) and leaf nitrogen content per unit area (Narea), and a smaller change in the nitrogen use efficiency of photosynthesis (PNUE) for lowland taxa indicated that these maintained higher homeostasis of photosynthesis than alpine taxa. The higher respiration rates produced more energy for repair and maintenance biomass, especially for higher photosynthetic activity for lowland taxa, which causes lower respiratory acclimation. Thus, the changes of ΔD2H for alpine spruces were larger than that for lowland spruces. These results indicate that long term heat stress negatively impact on the growth of Picea seedlings, and alpine taxa are more affected than low altitude ones by high temperature stress. Hence the altitude ranges of Picea taxa should be taken into account when predicting changes to carbon fluxes in warmer conditions. PMID:25874631

  13. Photosynthetic responses of field-grown Pinus radiata trees to artificial and aphid-induced defoliation.

    PubMed

    Eyles, Alieta; Smith, David; Pinkard, Elizabeth A; Smith, Ian; Corkrey, Ross; Elms, Stephen; Beadle, Chris; Mohammed, Caroline

    2011-06-01

    The phloem-feeding aphid Essigella californica represents a potential threat to the productivity of Pinus radiata plantations in south-eastern Australia. Five- and nine-year-old field trials were used to characterize the effects of artificial and natural aphid-induced (E. californica) defoliation, respectively, on shoot photosynthesis and growth. Photosynthetic capacity (A(max)) was significantly greater following a 25% (D25) (13.8 µmol m(-2) s(-1)) and a 50% (D50) (15.9 µmol m(-2) s(-1)) single-event upper-crown artificial defoliation, 3 weeks after defoliation than in undefoliated control trees (12.9 µmol m(-2) s(-1)). This response was consistently observed for up to 11 weeks after the defoliation event; by Week 16, there was no difference in A(max) between control and defoliated trees. In the D50 treatment, this increased A(max) was not sufficient to fully compensate for the foliage loss as evidenced by the reduced diameter increment (by 15%) in defoliated trees 36 weeks after defoliation. In contrast, diameter increment of trees in the D25 treatment was unaffected by defoliation. The A(max) of trees experiencing upper-crown defoliation by natural and repeated E. californica infestations varied, depending on host genotype. Despite clear differences in defoliation levels between resistant and susceptible genotypes (17 vs. 35% of tree crown defoliated, respectively), growth of susceptible genotypes was not significantly different from that of resistant genotypes. The observed increases in A(max) in the lower crown of the canopy following attack suggested that susceptible genotypes were able to partly compensate for the loss of foliage by compensatory photosynthesis. The capacity of P. radiata to regulate photosynthesis in response to natural aphid-induced defoliation provides evidence that the impact of E. californica attack on stem growth will be less than expected, at least for up to 35% defoliation. PMID:21697147

  14. Seagrass Canopy Photosynthetic Response Is a Function of Canopy Density and Light Environment: A Model for Amphibolis griffithii

    PubMed Central

    Hedley, John D.; McMahon, Kathryn; Fearns, Peter

    2014-01-01

    A three-dimensional computer model of canopies of the seagrass Amphibolis griffithii was used to investigate the consequences of variations in canopy structure and benthic light environment on leaf-level photosynthetic saturation state. The model was constructed using empirical data of plant morphometrics from a previously conducted shading experiment and validated well to in-situ data on light attenuation in canopies of different densities. Using published values of the leaf-level saturating irradiance for photosynthesis, results show that the interaction of canopy density and canopy-scale photosynthetic response is complex and non-linear, due to the combination of self-shading and the non-linearity of photosynthesis versus irradiance (P-I) curves near saturating irradiance. Therefore studies of light limitation in seagrasses should consider variation in canopy structure and density. Based on empirical work, we propose a number of possible measures for canopy scale photosynthetic response that can be plotted to yield isoclines in the space of canopy density and light environment. These plots can be used to interpret the significance of canopy changes induced as a response to decreases in the benthic light environment: in some cases canopy thinning can lead to an equivalent leaf level light environment, in others physiological changes may also be required but these alone may be inadequate for canopy survival. By providing insight to these processes the methods developed here could be a valuable management tool for seagrass conservation during dredging or other coastal developments. PMID:25347849

  15. Photosynthetic and molecular responses of the marine diatom Thalassiosira pseudonana to triphenyltin exposure.

    PubMed

    Yi, Andy Xianliang; Leung, Priscilla T Y; Leung, Kenneth M Y

    2014-09-01

    This study aimed to investigate the responses of the marine diatom Thalassiosira pseudonana upon waterborne exposure to triphenyltin chloride (TPTCl) through determining their photosynthetic response, growth performance, and expressions of genes and proteins. Based on the growth inhibition test, the 96-h IC50 (i.e., median inhibition concentration) was found to be 1.09 μg/L (95% confidence interval (CI): 0.89-1.34 μg/L). According to photosynthetic parameters, the 96-h EC50s (i.e., median effect concentrations) were estimated at 1.54 μg/L (95% CI: 1.40-1.69 μg/L) and 1.51 μg/L (95% CI: 1.44-1.58 μg/L) for the maximum quantum yield of photosystem II (PSII) photochemistry (ΦPo) and the effective quantum yield of photochemical energy conversion in PSII (Φ2), respectively. Non-photochemical quenching in the algae was increased at low concentrations of TPTCl (0.5-1.0 μg/L) but it decreased gradually when the TPTCl concentration further increased from 1.0 to 2.5 μg/L. Results of gene expressions showed that lipid metabolism related genes were not influenced by TPTCl at 0.5 or 1.0 μg/L, while silica shell formation genes were down-regulated at 0.5 μg/L. Photosynthesis related genes were up-regulated at 0.5 μg/L TPTCl but were down-regulated at 1.0 μg/L TPTCl. Proteomics analysis revealed that relatively less proteins could be detected after exposure to 1.0 μg/L TPTCl (only about 50-60 spots) compared with that observed in the 0.5μg/L TPTCl treatment and two control groups (each with about 290-300 protein spots). At 0.5 μg/L TPTCl, five proteins were differentially expressed when compared with the seawater control and solvent control, and most of these proteins are involved in defence function to protect the biological systems from reactive oxygen species that generated by TPTCl. These proteins include oxygen-evolving enhancer protein 1 precursor, fucoxanthin chlorophyll a/c protein - LI818 clade, and mitochondrial manganese superoxide dismutase, which can

  16. Comparative ventilatory strategies of acclimated rats and burrowing plateau pika (Ochotona curzoniae) in response to hypoxic-hypercapnia.

    PubMed

    Pichon, Aurélien; Voituron, Nicolas; Bai, Zhenzhong; Jeton, Florine; Tana, Wuren; Marchant, Dominique; Jin, Guoen; Richalet, Jean-Paul; Ge, Ri-Li

    2015-09-01

    The objective of this study was to compare the different ventilatory strategies that help in coping with hypoxic-hypercapnia environment among two species: use acclimated rats and plateau pikas (Ochotona curzoniae) that live in Tibetan plateaus, and have been well adjusted to high altitude. Arterial blood samples taken at 4100 m of elevation in acclimatized rats and adapted pikas revealed inter-species differences with lower hemoglobin and hematocrit and higher blood pH in pikas. A linear and significant increase in minute ventilation was observed in pikas, which help them to cope with hypoxic-hypercapnia. Pikas also displayed a high inspiratory drive and an invariant respiratory timing regardless of the conditions. Biochemical analysis revealed that N-methyl-D-aspartate receptor (NMDA) receptor gene and nNOS gene are highly conserved between rats and pikas, however pikas have higher expression of NMDA receptors and nNOS compared to rats at the brainstem level. Taken together, these results suggest that pikas have developed a specific ventilatory pattern supported by a modification of the NMDA/NO ventilatory central pathways to survive in extreme conditions imposed on the Tibetan plateaus. These physiological adaptive strategies help in maintaining a better blood oxygenation despite high CO2 concentration in burrows at high altitude. PMID:25988712

  17. Sea urchins in a high-CO2 world: the influence of acclimation on the immune response to ocean warming and acidification.

    PubMed

    Brothers, C J; Harianto, J; McClintock, J B; Byrne, M

    2016-08-31

    Climate-induced ocean warming and acidification may render marine organisms more vulnerable to infectious diseases. We investigated the effects of warming and acidification on the immune response of the sea urchin Heliocidaris erythrogramma Sea urchins were gradually introduced to four combinations of temperature and pHNIST (17°C/pH 8.15, 17°C/pH 7.6, 23°C/pH 8.15 and 23°C/pH 7.6) and then held in temperature-pH treatments for 1, 15 or 30 days to determine if the immune response would adjust to stressors over time. Coelomocyte concentration and type, phagocytic capacity and bactericidal activity were measured on day 1, 15 and 30 with different sea urchins used each time. At each time point, the coelomic fluid of individuals exposed to increased temperature and acidification had the lowest coelomocyte concentrations, exhibited lower phagocytic capacities and was least effective at inhibiting bacterial growth of the pathogen Vibrio anguillarum Over time, increased temperature alleviated the negative effects of acidification on phagocytic activity. Our results demonstrate the importance of incorporating acclimation time to multiple stressors when assessing potential responses to future ocean conditions and indicate that the immune response of H. erythrogramma may be compromised under near-future ocean warming and acidification. PMID:27559066

  18. Hydrogen Peroxide Alleviates Nickel-Inhibited Photosynthetic Responses through Increase in Use-Efficiency of Nitrogen and Sulfur, and Glutathione Production in Mustard.

    PubMed

    Khan, M I R; Khan, Nafees A; Masood, Asim; Per, Tasir S; Asgher, Mohd

    2016-01-01

    The response of two mustard (Brassica juncea L.) cultivars differing in photosynthetic capacity to different concentrations of hydrogen peroxide (H2O2) or nickel (Ni) was evaluated. Further, the effect of H2O2 on photosynthetic responses of the mustard cultivars grown with or without Ni stress was studied. Application of 50 μM H2O2 increased photosynthesis and growth more prominently in high photosynthetic capacity cultivar (Varuna) than low photosynthetic capacity cultivar (RH30) grown without Ni stress. The H2O2 application also resulted in alleviation of photosynthetic inhibition induced by 200 mg Ni kg(-1) soil through increased photosynthetic nitrogen-use efficiency (NUE), sulfur-use efficiency (SUE), and glutathione (GSH) reduced production together with decreased lipid peroxidation and electrolyte leakage in both the cultivars. However, the effect of H2O2 was more pronounced in Varuna than RH30. The greater increase in photosynthetic-NUE and SUE and GSH production with H2O2 in Varuna resulted from higher increase in activity of nitrogen (N) and sulfur (S) assimilation enzymes, nitrate reductase and ATP-sulfurylase, respectively resulting in enhanced N and S assimilation. The increased N and S content contributed to the higher activity of ribulose-1,5-bisphosphate carboxylase under Ni stress. Application of H2O2 also regulated PS II activity and stomatal movement under Ni stress for maintaining higher photosynthetic potential in Varuna. Thus, H2O2 may be considered as a potential signaling molecule for augmenting photosynthetic potential of mustard plants under optimal and Ni stress conditions. It alleviates Ni stress through the regulation of stomatal and non-stomotal limitations, and photosynthetic-NUE and -SUE and GSH production. PMID:26870064

  19. Hydrogen Peroxide Alleviates Nickel-Inhibited Photosynthetic Responses through Increase in Use-Efficiency of Nitrogen and Sulfur, and Glutathione Production in Mustard

    PubMed Central

    Khan, M. I. R.; Khan, Nafees A.; Masood, Asim; Per, Tasir S.; Asgher, Mohd

    2016-01-01

    The response of two mustard (Brassica juncea L.) cultivars differing in photosynthetic capacity to different concentrations of hydrogen peroxide (H2O2) or nickel (Ni) was evaluated. Further, the effect of H2O2 on photosynthetic responses of the mustard cultivars grown with or without Ni stress was studied. Application of 50 μM H2O2 increased photosynthesis and growth more prominently in high photosynthetic capacity cultivar (Varuna) than low photosynthetic capacity cultivar (RH30) grown without Ni stress. The H2O2 application also resulted in alleviation of photosynthetic inhibition induced by 200 mg Ni kg-1 soil through increased photosynthetic nitrogen-use efficiency (NUE), sulfur-use efficiency (SUE), and glutathione (GSH) reduced production together with decreased lipid peroxidation and electrolyte leakage in both the cultivars. However, the effect of H2O2 was more pronounced in Varuna than RH30. The greater increase in photosynthetic-NUE and SUE and GSH production with H2O2 in Varuna resulted from higher increase in activity of nitrogen (N) and sulfur (S) assimilation enzymes, nitrate reductase and ATP-sulfurylase, respectively resulting in enhanced N and S assimilation. The increased N and S content contributed to the higher activity of ribulose-1,5-bisphosphate carboxylase under Ni stress. Application of H2O2 also regulated PS II activity and stomatal movement under Ni stress for maintaining higher photosynthetic potential in Varuna. Thus, H2O2 may be considered as a potential signaling molecule for augmenting photosynthetic potential of mustard plants under optimal and Ni stress conditions. It alleviates Ni stress through the regulation of stomatal and non-stomotal limitations, and photosynthetic-NUE and -SUE and GSH production. PMID:26870064

  20. Dynamic balancing of isoprene carbon sources reflects photosynthetic and photorespiratory responses to temperature stress.

    PubMed

    Jardine, Kolby; Chambers, Jeffrey; Alves, Eliane G; Teixeira, Andrea; Garcia, Sabrina; Holm, Jennifer; Higuchi, Niro; Manzi, Antonio; Abrell, Leif; Fuentes, Jose D; Nielsen, Lars K; Torn, Margaret S; Vickers, Claudia E

    2014-12-01

    The volatile gas isoprene is emitted in teragrams per annum quantities from the terrestrial biosphere and exerts a large effect on atmospheric chemistry. Isoprene is made primarily from recently fixed photosynthate; however, alternate carbon sources play an important role, particularly when photosynthate is limiting. We examined the relative contribution of these alternate carbon sources under changes in light and temperature, the two environmental conditions that have the strongest influence over isoprene emission. Using a novel real-time analytical approach that allowed us to examine dynamic changes in carbon sources, we observed that relative contributions do not change as a function of light intensity. We found that the classical uncoupling of isoprene emission from net photosynthesis at elevated leaf temperatures is associated with an increased contribution of alternate carbon. We also observed a rapid compensatory response where alternate carbon sources compensated for transient decreases in recently fixed carbon during thermal ramping, thereby maintaining overall increases in isoprene production rates at high temperatures. Photorespiration is known to contribute to the decline in net photosynthesis at high leaf temperatures. A reduction in the temperature at which the contribution of alternate carbon sources increased was observed under photorespiratory conditions, while photosynthetic conditions increased this temperature. Feeding [2-(13)C]glycine (a photorespiratory intermediate) stimulated emissions of [(13)C1-5]isoprene and (13)CO2, supporting the possibility that photorespiration can provide an alternate source of carbon for isoprene synthesis. Our observations have important implications for establishing improved mechanistic predictions of isoprene emissions and primary carbon metabolism, particularly under the predicted increases in future global temperatures. PMID:25318937

  1. Effect of neonatal or adult heat acclimation on plasma fT3 level, testicular thyroid receptors expression in male rats and testicular steroidogenesis in vitro in response to triiodothyronine treatment.

    PubMed

    Kurowicka, B; Chrusciel, M; Zmijewska, A; Kotwica, G

    2016-01-01

    This study aimed to evaluate the effect of heat acclimation of neonatal and adult rats on their testes response to in vitro treatment with triiodothyronine (T3). Four groups of rats were housed from birth as: 1) control (CR) at 20°C for 90 days, 2) neonatal heat-acclimated (NHA) at 34°C for 90 days, 3) adult heat-acclimated (AHA) at 20°C for 45 days followed by 45 days at 34°C and 4) de-acclimated (DA) at 34°C for 45 days followed by 45 days at 20°C. Blood plasma and both testes were harvested from 90-day old rats. Testicular slices were then submitted to in vitro treatment with T3 (100 ng/ml) for 8 h. Plasma fT3 level was lower in AHA, NHA and DA groups than in CR group. Basal thyroid hormone receptor α1 (Thra1) expression was higher in testes of NHA and DA and β1 receptor (Thrb1) in DA rats vs. other groups. In the in vitro experiment, T3: 1) decreased Thra1 expression in all groups and Thrb1 in DA group, 2) increased Star expression in CR, NHA and DA groups, and Hsd17b3 expression in NHA group, 3) decreased the expression of Cyp11a1 in NHA and DA groups, and Cyp19a1 in all the groups, 4) did not affect the activity of steroidogenic enzymes and steroid secretion (A4, T, E2) in all the groups. These results indicate, that heat acclimation of rats, depending on their age, mainly affects the testicular expression of steroidogenic enzymes in response to short-lasting treatment with T3. PMID:27487513

  2. Putrescine Is Involved in Arabidopsis Freezing Tolerance and Cold Acclimation by Regulating Abscisic Acid Levels in Response to Low Temperature1

    PubMed Central

    Cuevas, Juan C.; López-Cobollo, Rosa; Alcázar, Rubén; Zarza, Xavier; Koncz, Csaba; Altabella, Teresa; Salinas, Julio; Tiburcio, Antonio F.; Ferrando, Alejandro

    2008-01-01

    The levels of endogenous polyamines have been shown to increase in plant cells challenged with low temperature; however, the functions of polyamines in the regulation of cold stress responses are unknown. Here, we show that the accumulation of putrescine under cold stress is essential for proper cold acclimation and survival at freezing temperatures because Arabidopsis (Arabidopsis thaliana) mutants defective in putrescine biosynthesis (adc1, adc2) display reduced freezing tolerance compared to wild-type plants. Genes ADC1 and ADC2 show different transcriptional profiles upon cold treatment; however, they show similar and redundant contributions to cold responses in terms of putrescine accumulation kinetics and freezing sensitivity. Our data also demonstrate that detrimental consequences of putrescine depletion during cold stress are due, at least in part, to alterations in the levels of abscisic acid (ABA). Reduced expression of NCED3, a key gene involved in ABA biosynthesis, and down-regulation of ABA-regulated genes are detected in both adc1 and adc2 mutant plants under cold stress. Complementation analysis of adc mutants with ABA and reciprocal complementation tests of the aba2-3 mutant with putrescine support the conclusion that putrescine controls the levels of ABA in response to low temperature by modulating ABA biosynthesis and gene expression. PMID:18701673

  3. Specific dynamic action in the shore crab, Carcinus maenas (L.), in relation to acclimation temperature and to the onset of the emersion response.

    PubMed

    Robertson, R F; Meagor, J; Taylor, E W

    2002-01-01

    The rate of oxygen uptake (MO(2)) of shore crabs following a period of fasting varied directly with acclimation temperature, with a Q(10) of 2.96 between 7 degrees and 15 degrees C and a Q(10) of 2.11 between 15 degrees and 22 degrees C. The factorial rise in MO(2) following a meal (specific dynamic action [SDA]) ranged between 1.9 and 3.1 and varied with temperature, being highest at 15 degrees C and significantly lower at both 7 degrees and 22 degrees C, despite similar ration sizes in all groups. At 7 degrees C, the SDA coefficient and magnitude were significantly lower than at 15 degrees C, possibly due in part to the inhibition of protein synthesis. Both the time to peak and the duration of the SDA response were inversely related to temperature. SDA coefficients were inversely related to the amount of food consumed. The critical oxygen tension of inspired water (P(I)O(2)), which evoked the emersion response in fasted animals, increased with temperature and further increased at each temperature when the animals were fed. Thus, the threshold P(I)O(2) evoking the emersion response is directly related to relative metabolic oxygen demand in Carcinus. PMID:12324891

  4. The tomato mutant ars1 (altered response to salt stress 1) identifies an R1-type MYB transcription factor involved in stomatal closure under salt acclimation.

    PubMed

    Campos, Juan F; Cara, Beatriz; Pérez-Martín, Fernando; Pineda, Benito; Egea, Isabel; Flores, Francisco B; Fernandez-Garcia, Nieves; Capel, Juan; Moreno, Vicente; Angosto, Trinidad; Lozano, Rafael; Bolarin, Maria C

    2016-06-01

    A screening under salt stress conditions of a T-DNA mutant collection of tomato (Solanum lycopersicum L.) led to the identification of the altered response to salt stress 1 (ars1) mutant, which showed a salt-sensitive phenotype. Genetic analysis of the ars1 mutation revealed that a single T-DNA insertion in the ARS1 gene was responsible of the mutant phenotype. ARS1 coded for an R1-MYB type transcription factor and its expression was induced by salinity in leaves. The mutant reduced fruit yield under salt acclimation while in the absence of stress the disruption of ARS1 did not affect this agronomic trait. The stomatal behaviour of ars1 mutant leaves induced higher Na(+) accumulation via the transpiration stream, as the decreases of stomatal conductance and transpiration rate induced by salt stress were markedly lower in the mutant plants. Moreover, the mutation affected stomatal closure in a response mediated by abscisic acid (ABA). The characterization of tomato transgenic lines silencing and overexpressing ARS1 corroborates the role of the gene in regulating the water loss via transpiration under salinity. Together, our results show that ARS1 tomato gene contributes to reduce transpirational water loss under salt stress. Finally, this gene could be interesting for tomato molecular breeding, because its manipulation could lead to improved stress tolerance without yield penalty under optimal culture conditions. PMID:26578112

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

    ERIC Educational Resources Information Center

    Zee, Delmar Vander

    1995-01-01

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

  6. Transcriptional responses indicate maintenance of photosynthetic proteins as key to the exceptional chilling tolerance of C4 photosynthesis in Miscanthus × giganteus

    PubMed Central

    Spence, Ashley K.; Boddu, Jay; Wang, Dafu; James, Brandon; Swaminathan, Kankshita; Moose, Stephen P.; Long, Stephen P.

    2014-01-01

    Miscanthus × giganteus is exceptional among C4 plants in its ability to acclimate to chilling (≤14 °C) and maintain a high photosynthetic capacity, in sharp contrast to maize, leading to very high productivity even in cool temperate climates. To identify the mechanisms that underlie this acclimation, RNA was isolated from M × giganteus leaves in chilling and nonchilling conditions and hybridized to microarrays developed for its close relative Zea mays. Among 21 000 array probes that yielded robust signals, 723 showed significant expression change under chilling. Approximately half of these were for annotated genes. Thirty genes associated with chloroplast membrane function were all upregulated. Increases in transcripts for the lhcb5 (chlorophyll a/b-binding protein CP26), ndhF (NADH dehydrogenase F, chloroplast), atpA (ATP synthase alpha subunit), psbA (D1), petA (cytochrome f), and lhcb4 (chlorophyll a/b-binding protein CP29), relative to housekeeping genes in M. × giganteus, were confirmed by quantitative reverse-transcription PCR. In contrast, psbo1, lhcb5, psbA, and lhcb4 were all significantly decreased in Z. mays after 14 days of chilling. Western blot analysis of the D1 protein and LHCII type II chlorophyll a/b-binding protein also showed significant increases in M. × giganteus during chilling and significant decreases in Z. mays. Compared to other C4 species, M. × giganteus grown in chilling conditions appears to counteract the loss of photosynthetic proteins and proteins protecting photosystem II typically observed in other species by increasing mRNA levels for their synthesis. PMID:24958895

  7. Epigenetics and cytoprotection with heat acclimation.

    PubMed

    Horowitz, Michal

    2016-03-15

    Studying "phenotypic plasticity" involves comparison of traits expressed in response to environmental fluctuations and aims to understand tolerance and survival in new settings. Reversible phenotypic changes that enable individuals to match their phenotype to environmental demands throughout life can be artificially induced, i.e., acclimation or occur naturally, i.e., acclimatization. The onset and achievement of acclimatory homeostasis are determined by molecular programs that induce the acclimated transcriptome. In heat acclimation, much evidence suggests that epigenetic mechanisms are powerful players in these processes. Epigenetic mechanisms affect the accessibility of the DNA to transcription factors, thereby regulating gene expression and controlling the phenotype. The heat-acclimated phenotype confers cytoprotection against novel stressors via cross-tolerance mechanisms, by attenuation of the initial damage and/or by accelerating spontaneous recovery through the release of help signals. This indispensable acclimatory feature has a memory and can be rapidly reestablished after the loss of acclimation and the return to the physiological preacclimated phenotype. The transcriptional landscape of the deacclimated phenotype includes constitutive transcriptional activation of epigenetic bookmarks. Heat shock protein (HSP) 70/HSP90/heat shock factor 1 memory protocol demonstrated constitutive histone H4 acetylation on hsp70 and hsp90 promotors. Novel players in the heat acclimation setup are poly(ADP-ribose)ribose polymerase 1 affecting chromatin condensation, DNA linker histones from the histone H1 cluster, and transcription factors associated with the P38 pathway. We suggest that these orchestrated responses maintain euchromatin and proteostasis during deacclimation and predispose to rapid reacclimation and cytoprotection. These mechanisms represent within-life epigenetic adaptations and cytoprotective memory. PMID:26472869

  8. Whole-plant versus leaf-level regulation of photosynthetic responses after partial defoliation in Eucalyptus globulus saplings.

    PubMed

    Eyles, Alieta; Pinkard, Elizabeth A; Davies, Noel W; Corkrey, Ross; Churchill, Keith; O'Grady, Anthony P; Sands, Peter; Mohammed, Caroline

    2013-04-01

    Increases in photosynthetic capacity (A1500) after defoliation have been attributed to changes in leaf-level biochemistry, water, and/or nutrient status. The hypothesis that transient photosynthetic responses to partial defoliation are regulated by whole-plant (e.g. source-sink relationships or changes in hydraulic conductance) rather than leaf-level mechanisms is tested here. Temporal variation in leaf-level gas exchange, chemistry, whole-plant soil-to-leaf hydraulic conductance (KP), and aboveground biomass partitioning were determined to evaluate mechanisms responsible for increases in A1500 of Eucalyptus globulus L. potted saplings. A1500 increased in response to debudding (B), partial defoliation (D), and combined B&D treatments by up to 36% at 5 weeks after treatment. Changes in leaf-level factors partly explained increases in A1500 of B and B&D treatments but not for D treatment. By week 5, saplings in B, B&D, and D treatments had similar leaf-specific KP to control trees by maintaining lower midday water potentials and higher transpiration rate per leaf area. Whole-plant source:sink ratios correlated strongly with A1500. Further, unlike KP, temporal changes in source:sink ratios tracked well with those observed for A1500. The results indicate that increases in A1500 after partial defoliation treatments were largely driven by an increased demand for assimilate by developing sinks rather than improvements in whole-plant water relations and changes in leaf-level factors. Three carbohydrates, galactional, stachyose, and, to a lesser extent, raffinose, correlated strongly with photosynthetic capacity, indicating that these sugars may function as signalling molecules in the regulation of longer term defoliation-induced gas exchange responses. PMID:23382548

  9. Sensitivity and Acclimation of Three Canopy-Forming Seaweeds to UVB Radiation and Warming.

    PubMed

    Xiao, Xi; de Bettignies, Thibaut; Olsen, Ylva S; Agusti, Susana; Duarte, Carlos M; Wernberg, Thomas

    2015-01-01

    Canopy-forming seaweeds, as primary producers and foundation species, provide key ecological services. Their responses to multiple stressors associated with climate change could therefore have important knock-on effects on the functioning of coastal ecosystems. We examined interactive effects of UVB radiation and warming on juveniles of three habitat-forming subtidal seaweeds from Western Australia-Ecklonia radiata, Scytothalia dorycarpa and Sargassum sp. Fronds were incubated for 14 days at 16-30°C with or without UVB radiation and growth, health status, photosynthetic performance, and light absorbance measured. Furthermore, we used empirical models from the metabolic theory of ecology to evaluate the sensitivity of these important seaweeds to ocean warming. Results indicated that responses to UVB and warming were species specific, with Sargassum showing highest tolerance to a broad range of temperatures. Scytothalia was most sensitive to elevated temperature based on the reduced maximum quantum yields of PSII; however, Ecklonia was most sensitive, according to the comparison of activation energy calculated from Arrhenius' model. UVB radiation caused reduction in the growth, physiological responses and thallus health in all three species. Our findings indicate that Scytothalia was capable of acclimating in response to UVB and increasing its light absorption efficiency in the UV bands, probably by up-regulating synthesis of photoprotective compounds. The other two species did not acclimate over the two weeks of exposure to UVB. Overall, UVB and warming would severely inhibit the growth and photosynthesis of these canopy-forming seaweeds and decrease their coverage. Differences in the sensitivity and acclimation of major seaweed species to temperature and UVB may alter the balance between species in future seaweed communities under climate change. PMID:26630025

  10. Sensitivity and Acclimation of Three Canopy-Forming Seaweeds to UVB Radiation and Warming

    PubMed Central

    Xiao, Xi; de Bettignies, Thibaut; Olsen, Ylva S.; Agusti, Susana; Duarte, Carlos M.; Wernberg, Thomas

    2015-01-01

    Canopy-forming seaweeds, as primary producers and foundation species, provide key ecological services. Their responses to multiple stressors associated with climate change could therefore have important knock-on effects on the functioning of coastal ecosystems. We examined interactive effects of UVB radiation and warming on juveniles of three habitat-forming subtidal seaweeds from Western Australia–Ecklonia radiata, Scytothalia dorycarpa and Sargassum sp. Fronds were incubated for 14 days at 16–30°C with or without UVB radiation and growth, health status, photosynthetic performance, and light absorbance measured. Furthermore, we used empirical models from the metabolic theory of ecology to evaluate the sensitivity of these important seaweeds to ocean warming. Results indicated that responses to UVB and warming were species specific, with Sargassum showing highest tolerance to a broad range of temperatures. Scytothalia was most sensitive to elevated temperature based on the reduced maximum quantum yields of PSII; however, Ecklonia was most sensitive, according to the comparison of activation energy calculated from Arrhenius’ model. UVB radiation caused reduction in the growth, physiological responses and thallus health in all three species. Our findings indicate that Scytothalia was capable of acclimating in response to UVB and increasing its light absorption efficiency in the UV bands, probably by up-regulating synthesis of photoprotective compounds. The other two species did not acclimate over the two weeks of exposure to UVB. Overall, UVB and warming would severely inhibit the growth and photosynthesis of these canopy-forming seaweeds and decrease their coverage. Differences in the sensitivity and acclimation of major seaweed species to temperature and UVB may alter the balance between species in future seaweed communities under climate change. PMID:26630025

  11. Cold acclimation of the Arabidopsis dgd1 mutant results in recovery from photosystem I-limited photosynthesis.

    PubMed

    Hendrickson, Luke; Vlcková, Alexandra; Selstam, Eva; Huner, Norman; Oquist, Gunnar; Hurry, Vaughan

    2006-09-01

    We compared the thylakoid membrane composition and photosynthetic properties of non- and cold-acclimated leaves from the dgd1 mutant (lacking >90% of digalactosyl-diacylglycerol; DGDG) and wild type (WT) Arabidopsis thaliana. In contrast to warm grown plants, cold-acclimated dgd1 leaves recovered pigment-protein pools and photosynthetic function equivalent to WT. Surprisingly, this recovery was not correlated with an increase in DGDG. When returned to warm temperatures the severe dgd1 mutant phenotype reappeared. We conclude that the relative recovery of photosynthetic activity at 5 degrees C resulted from a temperature/lipid interaction enabling the stable assembly of PSI complexes in the thylakoid. PMID:16930596

  12. Reduction of photosynthetic sensitivity in response to abiotic stress in tomato is mediated by a new generation plant activator

    PubMed Central

    2013-01-01

    Background Yield losses as a result of abiotic stress factors present a significant challenge for the future of global food production. While breeding technologies provide potential to combat negative stress-mediated outcomes over time, interventions which act to prime plant tolerance to stress, via the use of phytohormone-based elicitors for example, could act as a valuable tool for crop protection. However, the translation of fundamental biology into functioning solution is often constrained by knowledge-gaps. Results Photosynthetic and transcriptomic responses were characterised in young tomato (Solanum lycopersicum L.) seedlings in response to pre-treatment with a new plant health activator technology, ‘Alethea’, followed by a subsequent 100 mM salinity stress. Alethea is a novel proprietary technology composed of three key constituent compounds; the hitherto unexplored compound potassium dihydrojasmonate, an analogue of jasmonic acid; sodium benzoate, a carboxylic acid precursor to salicylic acid, and the α-amino acid L-arginine. Salinity treatment led to a maximal 47% reduction in net photosynthetic rate 8 d following NaCl treatment, yet in Alethea pre-treated seedlings, sensitivity to salinity stress was markedly reduced during the experimental period. Microarray analysis of leaf transcriptional responses showed that while salinity stress and Alethea individually impacted on largely non-overlapping, distinct groups of genes, Alethea pre-treatment substantially modified the response to salinity. Alethea affected the expression of genes related to biotic stress, ethylene signalling, cell wall synthesis, redox signalling and photosynthetic processes. Since Alethea had clear effects on photosynthesis/chloroplastic function at the physiological and molecular levels, we also investigated the ability of Alethea to protect various crop species against methyl viologen, a potent generator of oxidative stress in chloroplasts. Alethea pre-treatment produced

  13. NITROGEN INTERACTIONS AND PHOTOSYNTHETIC RESPONSES TO CO{sub 2}: WORK PLAN FOR BIOCON EXPERIMENT/PHYSIOLOGICAL MEASUREMENTS AT CEDAR CREEK

    SciTech Connect

    ELLSWORTH,D.

    1998-12-31

    Nitrogen plays a critical role in photosynthetic function, which in turn can affect many ecosystem processes through its effects on plant growth and ecosystem carbon cycles. As a result of its central role in photosynthetic enzymes, leaf N status can affect the magnitude of photosynthetic enhancement by elevated CO{sub 2}. It is now well-recognized that species responses to elevated CO{sub 2} may be different when species are grown in isolation vs. in a mixed community. Part of this effect may result from effects on leaf N itself as a result of species competition for N in N-limited ecosystems, and pad of the effect is simply a function of dilution of leaf nutrients in leaves with greater carbohydrates as a result of elevated CO{sub 2}, However, photosynthetic efficiency itself may be affected if N-limited plants reallocate N within leaves away from carboxylation functions under elevated CO{sub 2} compared to ambient plants (Drake et al. 1997). Thus while there is cause to believe that there are interactive effects of N and CO{sub 2} on species photosynthetic physiology, there is little experimental data to support or reject this idea, particularly in realistic ecosystems under field conditions. Biotic interactions, most notably the presence of N-fixing plants, can affect ecosystem N stocks and carbon cycling via effects of N on photosynthetic function (Chapin et al. 1997, Hooper and Vitousek 1997). If photosynthetic responses of leaves and ecosystems are largely mediated through canopy N, then biotic as well as inorganic N sources will affect the magnitude of these responses. Under elevated CO{sub 2} there is evidence from the Swiss FACE experiment that growth and photosynthetic function are most responsive to CO{sub 2} in species mixtures including N-fixers (Hebeisin et al. 1997, Liischer et al. 1998, S.P. Long, pers. comm.). However, in that experiment there were confounding management factors and species diversity effects per se could not be tested. Still

  14. Growth and photosynthetic pigments responses of two varieties of Catharanthus roseus to triadimefon treatment.

    PubMed

    Jaleel, Cheruth Abdul; Gopi, Ragupathi; Panneerselvam, Rajaram

    2008-04-01

    Triadimefon, potential fungicide cum plant-growth retardant was used in this study to investigate its effect on the growth and the photosynthetic pigment contents of two varieties of Catharanthus roseus (L.) G. Don. The plants of both varieties were subjected to 15 mg l(-1) triadimefon treatment by soil drenching 30, 45, 60, and 75 days after planting (DAP). Plants were uprooted on 90 DAP, and morphological parameters, like plant height, number of leaves, leaf area, root length and fresh and dry weights were determined. The photosynthetic pigments, like chlorophylls a and b, total chlorophyll, carotenoids, floral pigment, anthocyanin, were extracted and estimated. It was observed that plant height, number of leaves and leaf area were decreased and that root length, fresh and dry weights were increased under triadimefon treatment. The photosynthetic and floral pigments were increased under triadimefon treatment in both varieties. The results suggest that the application of this plant-growth retardant (triadimefon) has favourable effects on the reduction of plant height; it can thus be used for replacing manual hand pruning and for improving floral and vegetation colour in bedding plants like C. roseus. PMID:18355749

  15. Photosynthetic temperature responses of tree species in Rwanda: evidence of pronounced negative effects of high temperature in montane rainforest climax species

    NASA Astrophysics Data System (ADS)

    Vårhammar, Angelica; Wallin, Göran; McLean, Christopher M.; Dusenge, Mirindi Eric; Medlyn, Belinda E.; Hasper, Thomas B.; Nsabimana, Donat; Uddling, Johan

    2015-04-01

    The sensitivity of photosynthetic metabolism to temperature has been identified as a key uncertainty for projecting the magnitude of the terrestrial feedback on future climate change. While temperature responses of photosynthetic capacities have been comparatively well investigated in temperate species, the responses of tropical tree species remain unexplored. We compared the responses of seedlings of native cold-adapted tropical montane rainforest tree species to exotic warm-adapted plantation species, all growing in an intermediate temperature common garden in Rwanda. Leaf gas exchange responses to CO2 at different temperatures (20 - 40 C) were used to assess the temperature responses of biochemical photosynthetic capacities. Analyses revealed a lower optimum temperature for photosynthetic electron transport rates than for Rubisco carboxylation rates, along with lower electron transport optima in the native cold-adapted than in the exotic warm-adapted species. The photosynthetic optimum temperatures were generally exceeded by daytime peak leaf temperatures, in particular in the native montane rainforest climax species. This study thus provides evidence of pronounced negative effects of high temperature in tropical trees and indicates high susceptibility of montane rainforest climax species to future global warming. (Reference: New Phytologist, in press)

  16. Changes in Respiratory Mitochondrial Machinery and Cytochrome and Alternative Pathway Activities in Response to Energy Demand Underlie the Acclimation of Respiration to Elevated CO2 in the Invasive Opuntia ficus-indica1[OA

    PubMed Central

    Gomez-Casanovas, Nuria; Blanc-Betes, Elena; Gonzalez-Meler, Miquel A.; Azcon-Bieto, Joaquim

    2007-01-01

    Studies on long-term effects of plants grown at elevated CO2 are scarce and mechanisms of such responses are largely unknown. To gain mechanistic understanding on respiratory acclimation to elevated CO2, the Crassulacean acid metabolism Mediterranean invasive Opuntia ficus-indica Miller was grown at various CO2 concentrations. Respiration rates, maximum activity of cytochrome c oxidase, and active mitochondrial number consistently decreased in plants grown at elevated CO2 during the 9 months of the study when compared to ambient plants. Plant growth at elevated CO2 also reduced cytochrome pathway activity, but increased the activity of the alternative pathway. Despite all these effects seen in plants grown at high CO2, the specific oxygen uptake rate per unit of active mitochondria was the same for plants grown at ambient and elevated CO2. Although decreases in photorespiration activity have been pointed out as a factor contributing to the long-term acclimation of plant respiration to growth at elevated CO2, the homeostatic maintenance of specific respiratory rate per unit of mitochondria in response to high CO2 suggests that photorespiratory activity may play a small role on the long-term acclimation of respiration to elevated CO2. However, despite growth enhancement and as a result of the inhibition in cytochrome pathway activity by elevated CO2, total mitochondrial ATP production was decreased by plant growth at elevated CO2 when compared to ambient-grown plants. Because plant growth at elevated CO2 increased biomass but reduced respiratory machinery, activity, and ATP yields while maintaining O2 consumption rates per unit of mitochondria, we suggest that acclimation to elevated CO2 results from physiological adjustment of respiration to tissue ATP demand, which may not be entirely driven by nitrogen metabolism as previously suggested. PMID:17660349

  17. Unique role for translation initiation factor 3 in the light color regulation of photosynthetic gene expression.

    PubMed

    Gutu, Andrian; Nesbit, April D; Alverson, Andrew J; Palmer, Jeffrey D; Kehoe, David M

    2013-10-01

    Light-harvesting antennae are critical for collecting energy from sunlight and providing it to photosynthetic reaction centers. Their abundance and composition are tightly regulated to maintain efficient photosynthesis in changing light conditions. Many cyanobacteria alter their light-harvesting antennae in response to changes in ambient light-color conditions through the process of chromatic acclimation. The control of green light induction (Cgi) pathway is a light-color-sensing system that controls the expression of photosynthetic genes during chromatic acclimation, and while some evidence suggests that it operates via transcription attenuation, the components of this pathway have not been identified. We provide evidence that translation initiation factor 3 (IF3), an essential component of the prokaryotic translation initiation machinery that binds the 30S subunit and blocks premature association with the 50S subunit, is part of the control of green light induction pathway. Light regulation of gene expression has not been previously described for any translation initiation factor. Surprisingly, deletion of the IF3-encoding gene infCa was not lethal in the filamentous cyanobacterium Fremyella diplosiphon, and its genome was found to contain a second, redundant, highly divergent infC gene which, when deleted, had no effect on photosynthetic gene expression. Either gene could complement an Escherichia coli infC mutant and thus both encode bona fide IF3s. Analysis of prokaryotic and eukaryotic genome databases established that multiple infC genes are present in the genomes of diverse groups of bacteria and land plants, most of which do not undergo chromatic acclimation. This suggests that IF3 may have repeatedly evolved important roles in the regulation of gene expression in both prokaryotes and eukaryotes. PMID:24048028

  18. Bacteriophytochrome controls carotenoid-independent response to photodynamic stress in a non-photosynthetic rhizobacterium, Azospirillum brasilense Sp7

    PubMed Central

    Kumar, Santosh; Kateriya, Suneel; Singh, Vijay Shankar; Tanwar, Meenakshi; Agarwal, Shweta; Singh, Hina; Khurana, Jitendra Paul; Amla, Devinder Vijay; Tripathi, Anil Kumar

    2012-01-01

    Ever since the discovery of the role of bacteriophytochrome (BphP) in inducing carotenoid synthesis in Deinococcus radiodurans in response to light the role of BphPs in other non-photosynthetic bacteria is not clear yet. Azospirillum brasilense, a non-photosynthetic rhizobacterium, harbours a pair of BphPs out of which AbBphP1 is a homolog of AtBphP1 of Agrobacterium tumefaciens. By overexpression, purification, biochemical and spectral characterization we have shown that AbBphP1 is a photochromic bacteriophytochrome. Phenotypic study of the ΔAbBphP1 mutant showed that it is required for the survival of A. brasilense on minimal medium under red light. The mutant also showed reduced chemotaxis towards dicarboxylates and increased sensitivity to the photooxidative stress. Unlike D. radiodurans, AbBphP1 was not involved in controlling carotenoid synthesis. Proteome analysis of the ΔAbBphP1 indicated that AbBphP1 is involved in inducing a cellular response that enables A. brasilense in regenerating proteins that might be damaged due to photodynamic stress. PMID:23173079

  19. Photosynthetic responses of trees in high-elevation forests: comparing evergreen species along an elevation gradient in the Central Andes.

    PubMed

    García-Plazaola, José I; Rojas, Roke; Christie, Duncan A; Coopman, Rafael E

    2015-01-01

    Plant growth at extremely high elevations is constrained by high daily thermal amplitude, strong solar radiation and water scarcity. These conditions are particularly harsh in the tropics, where the highest elevation treelines occur. In this environment, the maintenance of a positive carbon balance involves protecting the photosynthetic apparatus and taking advantage of any climatically favourable periods. To characterize photoprotective mechanisms at such high elevations, and particularly to address the question of whether these mechanisms are the same as those previously described in woody plants along extratropical treelines, we have studied photosynthetic responses in Polylepis tarapacana Philippi in the central Andes (18°S) along an elevational gradient from 4300 to 4900 m. For comparative purposes, this gradient has been complemented with a lower elevation site (3700 m) where another Polylepis species (P. rugulosa Bitter) occurs. During the daily cycle, two periods of photosynthetic activity were observed: one during the morning when, despite low temperatures, assimilation was high; and the second starting at noon when the stomata closed because of a rise in the vapour pressure deficit and thermal dissipation is prevalent over photosynthesis. From dawn to noon there was a decrease in the content of antenna pigments (chlorophyll b and neoxanthin), together with an increase in the content of xanthophyll cycle carotenoids. These results could be caused by a reduction in the antenna size along with an increase in photoprotection. Additionally, photoprotection was enhanced by a partial overnight retention of de-epoxized xanthophylls. The unique combination of all of these mechanisms made possible the efficient use of the favourable conditions during the morning while still providing enough protection for the rest of the day. This strategy differs completely from that of extratropical mountain trees, which uncouple light-harvesting and energy-use during long

  20. Comparison of population growth and photosynthetic apparatus changes in response to different nutrient status in a diatom and a coccolithophore.

    PubMed

    Zhao, Yan; Wang, You; Quigg, Antonietta

    2015-10-01

    In many marine ecosystems, diatoms dominate in nutrient-rich coastal waters while coccolithiophores are found offshore in areas where nutrients may be limiting. In lab-controlled batch cultures, mixed-species competition between the diatom Phaeodactylum tricornutum and the coccolithophore Emiliana huxleyi and the response of each species were examined under nitrate (N) and phosphate (P) starvation. Based on the logistic growth model and the Lotka-Volterra competition model, E. huxleyi showed higher competitive abilities than P. tricornutum under N and P starvation. For both species, cell growth was more inhibited by P starvation, while photosynthetic functions (chl a fluorescence parameters) and cellular constituents (pigments) were impaired by N starvation. The decline of photosynthetic functions occurred later in E. huxleyi (day 12) than in P. tricornutum (day 9); this time difference was associated with greater damage of the photosynthetic apparatus in P. tricornutum compared with E. huxleyi. Xanthophyll cycle pigment accumulation and the transformation from diadinoxanthin to diatoxanthin was more active in E. huxleyi than P. tricornutum, under similar N and P starvation. We concluded that E. huxleyi and P. tricornutum have different mechanisms to allocate resources and energy under nutrient starvation. It appears that E. huxleyi has a more economic strategy to adapt to nutrient depleted environments than P. tricornutum. These findings provided additional evidence explaining how N versus P limitation differentially support diatom and coccolithophore blooms in natural environments. PMID:26986884

  1. Photosynthetic responses of trees in high-elevation forests: comparing evergreen species along an elevation gradient in the Central Andes

    PubMed Central

    García-Plazaola, José I.; Rojas, Roke; Christie, Duncan A.; Coopman, Rafael E.

    2015-01-01

    Plant growth at extremely high elevations is constrained by high daily thermal amplitude, strong solar radiation and water scarcity. These conditions are particularly harsh in the tropics, where the highest elevation treelines occur. In this environment, the maintenance of a positive carbon balance involves protecting the photosynthetic apparatus and taking advantage of any climatically favourable periods. To characterize photoprotective mechanisms at such high elevations, and particularly to address the question of whether these mechanisms are the same as those previously described in woody plants along extratropical treelines, we have studied photosynthetic responses in Polylepis tarapacana Philippi in the central Andes (18°S) along an elevational gradient from 4300 to 4900 m. For comparative purposes, this gradient has been complemented with a lower elevation site (3700 m) where another Polylepis species (P. rugulosa Bitter) occurs. During the daily cycle, two periods of photosynthetic activity were observed: one during the morning when, despite low temperatures, assimilation was high; and the second starting at noon when the stomata closed because of a rise in the vapour pressure deficit and thermal dissipation is prevalent over photosynthesis. From dawn to noon there was a decrease in the content of antenna pigments (chlorophyll b and neoxanthin), together with an increase in the content of xanthophyll cycle carotenoids. These results could be caused by a reduction in the antenna size along with an increase in photoprotection. Additionally, photoprotection was enhanced by a partial overnight retention of de-epoxized xanthophylls. The unique combination of all of these mechanisms made possible the efficient use of the favourable conditions during the morning while still providing enough protection for the rest of the day. This strategy differs completely from that of extratropical mountain trees, which uncouple light-harvesting and energy-use during long

  2. Rapid Acclimation Ability Mediated by Transcriptome Changes in Reef-Building Corals.

    PubMed

    Bay, Rachael A; Palumbi, Stephen R

    2015-06-01

    Population response to environmental variation involves adaptation, acclimation, or both. For long-lived organisms, acclimation likely generates a faster response but is only effective if the rates and limits of acclimation match the dynamics of local environmental variation. In coral reef habitats, heat stress from extreme ocean warming can occur over several weeks, resulting in symbiont expulsion and widespread coral death. However, transcriptome regulation during short-term acclimation is not well understood. We examined acclimation during a 11-day experiment in the coral Acropora nana. We acclimated colonies to three regimes: ambient temperature (29 °C), increased stable temperature (31 °C), and variable temperature (29-33 °C), mimicking local heat stress conditions. Within 7-11 days, individuals acclimated to increased temperatures had higher tolerance to acute heat stress. Despite physiological changes, no gene expression changes occurred during acclimation before acute heat stress. However, we found strikingly different transcriptional responses to heat stress between acclimation treatments across 893 contigs. Across these contigs, corals acclimated to higher temperatures (31 °C or 29-33 °C) exhibited a muted stress response--the magnitude of expression change before and after heat stress was less than in 29 °C acclimated corals. Our results show that corals have a rapid phase of acclimation that substantially increases their heat resilience within 7 days and that alters their transcriptional response to heat stress. This is in addition to a previously observed longer term response, distinguishable by its shift in baseline expression, under nonstressful conditions. Such rapid acclimation may provide some protection for this species of coral against slow onset of warming ocean temperatures. PMID:25979751

  3. Divergent Responses of Coastal and Oceanic Synechococcus to Iron Limitation

    NASA Astrophysics Data System (ADS)

    Mackey, K. R.; McIlvin, M.; Post, A.; Saito, M. A.

    2014-12-01

    Marine Synechococcus are some of the most diverse and ubiquitous phytoplankton in the ocean, and are major contributors to global primary productivity. Iron (Fe) is a micronutrient required for maintenance of the photosynthetic apparatus that limits productivity in many parts of the ocean. To investigate how marine Synechococcus strains adapt and acclimate to Fe availability, we compared the growth, photophysiology, and protein abundance in two Synechococcus strains over a range of Fe concentrations. Synechococcus strain WH8102, from the permanently stratified southern Sargasso Sea in a region that receives significant dust deposition, had few acclimation strategies under low Fe and showed impaired growth rates and photophysiology as Fe declined. Coastal isolate WH8020, from the dynamic, seasonally variable North Atlantic Ocean, displayed a range of acclimation responses, including changes in Fe acquisition, storage, and photosynthetic electron transport proteins, substitution of flavodoxin for ferredoxin, and modified photophysiology. Each of these acclimation responses occurred at different Fe threshold concentrations over which growth rate remained remarkably stable. This study demonstrates that genomic streamlining in waters with low nitrogen and phosphorus may favor the loss of Fe acclimation genes when the Fe supply is consistent over time, and expands the regions where Fe stress is thought to occur to most coastal environments.

  4. Chlorophyll Fluorescence Analysis of Cyanobacterial Photosynthesis and Acclimation

    PubMed Central

    Campbell, Douglas; Hurry, Vaughan; Clarke, Adrian K.; Gustafsson, Petter; Öquist, Gunnar

    1998-01-01

    Cyanobacteria are ecologically important photosynthetic prokaryotes that also serve as popular model organisms for studies of photosynthesis and gene regulation. Both molecular and ecological studies of cyanobacteria benefit from real-time information on photosynthesis and acclimation. Monitoring in vivo chlorophyll fluorescence can provide noninvasive measures of photosynthetic physiology in a wide range of cyanobacteria and cyanolichens and requires only small samples. Cyanobacterial fluorescence patterns are distinct from those of plants, because of key structural and functional properties of cyanobacteria. These include significant fluorescence emission from the light-harvesting phycobiliproteins; large and rapid changes in fluorescence yield (state transitions) which depend on metabolic and environmental conditions; and flexible, overlapping respiratory and photosynthetic electron transport chains. The fluorescence parameters FV/FM, FV′/FM′,qp,qN, NPQ, and φPS II were originally developed to extract information from the fluorescence signals of higher plants. In this review, we consider how the special properties of cyanobacteria can be accommodated and used to extract biologically useful information from cyanobacterial in vivo chlorophyll fluorescence signals. We describe how the pattern of fluorescence yield versus light intensity can be used to predict the acclimated light level for a cyanobacterial population, giving information valuable for both laboratory and field studies of acclimation processes. The size of the change in fluorescence yield during dark-to-light transitions can provide information on respiration and the iron status of the cyanobacteria. Finally, fluorescence parameters can be used to estimate the electron transport rate at the acclimated growth light intensity. PMID:9729605

  5. Responses of photosynthetic parameters to drought in subtropical forest ecosystem of China

    NASA Astrophysics Data System (ADS)

    Zhou, Lei; Wang, Shaoqiang; Chi, Yonggang; Li, Qingkang; Huang, Kun; Yu, Quanzhou

    2015-12-01

    The mechanism underlying the effect of drought on the photosynthetic traits of leaves in forest ecosystems in subtropical regions is unclear. In this study, three limiting processes (stomatal, mesophyll and biochemical limitations) that control the photosynthetic capacity and three resource use efficiencies (intrinsic water use efficiency (iWUE), nitrogen use efficiency (NUE) and light use efficiency (LUE)), which were characterized as the interactions between photosynthesis and environmental resources, were estimated in two species (Schima superba and Pinus massoniana) under drought conditions. A quantitative limitation analysis demonstrated that the drought-induced limitation of photosynthesis in Schima superba was primarily due to stomatal limitation, whereas for Pinus massoniana, both stomatal and non-stomatal limitations generally exhibited similar magnitudes. Although the mesophyll limitation represented only 1% of the total limitation in Schima superba, it accounted for 24% of the total limitations for Pinus massoniana. Furthermore, a positive relationship between the LUE and NUE and a marginally negative relationship or trade-off between the NUE and iWUE were observed in the control plots. However, drought disrupted the relationships between the resource use efficiencies. Our findings may have important implications for reducing the uncertainties in model simulations and advancing the understanding of the interactions between ecosystem functions and climate change.

  6. Responses of photosynthetic parameters to drought in subtropical forest ecosystem of China

    PubMed Central

    Zhou, Lei; Wang, Shaoqiang; Chi, Yonggang; Li, Qingkang; Huang, Kun; Yu, Quanzhou

    2015-01-01

    The mechanism underlying the effect of drought on the photosynthetic traits of leaves in forest ecosystems in subtropical regions is unclear. In this study, three limiting processes (stomatal, mesophyll and biochemical limitations) that control the photosynthetic capacity and three resource use efficiencies (intrinsic water use efficiency (iWUE), nitrogen use efficiency (NUE) and light use efficiency (LUE)), which were characterized as the interactions between photosynthesis and environmental resources, were estimated in two species (Schima superba and Pinus massoniana) under drought conditions. A quantitative limitation analysis demonstrated that the drought-induced limitation of photosynthesis in Schima superba was primarily due to stomatal limitation, whereas for Pinus massoniana, both stomatal and non-stomatal limitations generally exhibited similar magnitudes. Although the mesophyll limitation represented only 1% of the total limitation in Schima superba, it accounted for 24% of the total limitations for Pinus massoniana. Furthermore, a positive relationship between the LUE and NUE and a marginally negative relationship or trade-off between the NUE and iWUE were observed in the control plots. However, drought disrupted the relationships between the resource use efficiencies. Our findings may have important implications for reducing the uncertainties in model simulations and advancing the understanding of the interactions between ecosystem functions and climate change. PMID:26666469

  7. Responses of photosynthetic parameters to drought in subtropical forest ecosystem of China.

    PubMed

    Zhou, Lei; Wang, Shaoqiang; Chi, Yonggang; Li, Qingkang; Huang, Kun; Yu, Quanzhou

    2015-01-01

    The mechanism underlying the effect of drought on the photosynthetic traits of leaves in forest ecosystems in subtropical regions is unclear. In this study, three limiting processes (stomatal, mesophyll and biochemical limitations) that control the photosynthetic capacity and three resource use efficiencies (intrinsic water use efficiency (iWUE), nitrogen use efficiency (NUE) and light use efficiency (LUE)), which were characterized as the interactions between photosynthesis and environmental resources, were estimated in two species (Schima superba and Pinus massoniana) under drought conditions. A quantitative limitation analysis demonstrated that the drought-induced limitation of photosynthesis in Schima superba was primarily due to stomatal limitation, whereas for Pinus massoniana, both stomatal and non-stomatal limitations generally exhibited similar magnitudes. Although the mesophyll limitation represented only 1% of the total limitation in Schima superba, it accounted for 24% of the total limitations for Pinus massoniana. Furthermore, a positive relationship between the LUE and NUE and a marginally negative relationship or trade-off between the NUE and iWUE were observed in the control plots. However, drought disrupted the relationships between the resource use efficiencies. Our findings may have important implications for reducing the uncertainties in model simulations and advancing the understanding of the interactions between ecosystem functions and climate change. PMID:26666469

  8. Rapid Acclimation Ability Mediated by Transcriptome Changes in Reef-Building Corals

    PubMed Central

    Bay, Rachael A.; Palumbi, Stephen R.

    2015-01-01

    Population response to environmental variation involves adaptation, acclimation, or both. For long-lived organisms, acclimation likely generates a faster response but is only effective if the rates and limits of acclimation match the dynamics of local environmental variation. In coral reef habitats, heat stress from extreme ocean warming can occur over several weeks, resulting in symbiont expulsion and widespread coral death. However, transcriptome regulation during short-term acclimation is not well understood. We examined acclimation during a 11-day experiment in the coral Acropora nana. We acclimated colonies to three regimes: ambient temperature (29 °C), increased stable temperature (31 °C), and variable temperature (29–33 °C), mimicking local heat stress conditions. Within 7–11 days, individuals acclimated to increased temperatures had higher tolerance to acute heat stress. Despite physiological changes, no gene expression changes occurred during acclimation before acute heat stress. However, we found strikingly different transcriptional responses to heat stress between acclimation treatments across 893 contigs. Across these contigs, corals acclimated to higher temperatures (31 °C or 29–33 °C) exhibited a muted stress response—the magnitude of expression change before and after heat stress was less than in 29 °C acclimated corals. Our results show that corals have a rapid phase of acclimation that substantially increases their heat resilience within 7 days and that alters their transcriptional response to heat stress. This is in addition to a previously observed longer term response, distinguishable by its shift in baseline expression, under nonstressful conditions. Such rapid acclimation may provide some protection for this species of coral against slow onset of warming ocean temperatures. PMID:25979751

  9. Physiological and molecular evidence of heat acclimation memory: a lesson from thermal responses and ischemic cross-tolerance in the heart.

    PubMed

    Tetievsky, Anna; Cohen, Omer; Eli-Berchoer, Luba; Gerstenblith, Gary; Stern, Michael D; Wapinski, Ilan; Friedman, Nir; Horowitz, Michal

    2008-06-12

    Sporadic findings in humans suggest that reinduction of heat acclimation (AC) after its loss occurs markedly faster than that during the initial AC session. Animal studies substantiated that the underlying acclimatory processes are molecular. Here we test the hypothesis that faster reinduction of AC (ReAC) implicates "molecular memory." In vivo measurements of colonic temperature profiles during heat stress and ex vivo assessment of cross-tolerance to ischemia-reperfusion or anoxia insults in the heart demonstrated that ReAC only needs 2 days vs. the 30 days required for the initial development of AC. Stress gene profiling in the experimental groups highlighted clusters of transcriptionally activated genes (37%), which included heat shock protein (HSP) genes, antiapoptotic genes, and chromatin remodeling genes. Despite a return of the physiological phenotype to its preacclimation state, after a 1 mo deacclimation (DeAC) period, the gene transcripts did not resume their preacclimation levels, suggesting a dichotomy between genotype and phenotype in this system. Individual detection of hsp70 and hsf1 transcripts agreed with these findings. HSP72, HSF1/P-HSF1, and Bcl-xL protein profiles followed the observed dichotomized genomic response. In contrast, HSP90, an essential cytoprotective component mismatched transcriptional activation upon DeAC. The uniform activation of the similarly responding gene clusters upon De-/ReAC implies that reacclimatory phenotypic plasticity is associated with upstream denominators. During AC, DeAC, and ReAC, the maintenance of elevated/phosphorylated HSF1 protein levels and transcriptionally active chromatin remodeling genes implies that chromatin remodeling plays a pivotal role in the transcriptome profile and in preconditioning to rapid cytoprotective acclimatory memory. PMID:18430807

  10. Roles of sodium hydrosulfide and sodium nitroprusside as priming molecules during drought acclimation in citrus plants.

    PubMed

    Ziogas, Vasileios; Tanou, Georgia; Belghazi, Maya; Filippou, Panagiota; Fotopoulos, Vasileios; Grigorios, Diamantidis; Molassiotis, Athanassios

    2015-11-01

    Emerging evidence suggests that the gaseous molecules hydrogen sulfide (H2S) and nitric oxide (NO) enhances plant acclimation to stress; however, the underlying mechanism remains unclear. In this work, we explored if pretreatment of citrus roots with NaHS (a H2S donor) or sodium nitroprusside (SNP, a NO donor) for 2 days (d) could elicit long-lasting priming effects to subsequent exposure to PEG-associated drought stress for 21 d following a 5 d acclimation period. Detailed physiological study documented that both pretreatments primed plants against drought stress. Analysis of the level of nitrite, NOx, S-nitrosoglutahione reductase, Tyr-nitration and S-nitrosylation along with the expression of genes involved in NO-generation suggested that the nitrosative status of leaves and roots was altered by NaHS and SNP. Using a proteomic approach we characterized S-nitrosylated proteins in citrus leaves exposed to chemical treatments, including well known and novel S-nitrosylated targets. Mass spectrometry analysis also enabled the identification of 42 differentially expressed proteins in PEG alone-treated plants. Several PEG-responsive proteins were down-regulated, especially photosynthetic proteins. Finally, the identification of specific proteins that were regulated by NaHS and SNP under PEG conditions provides novel insight into long-term drought priming in plants and in a fruit crop such as citrus in particular. PMID:26404728

  11. FREEZING IN NON-ACCLIMATED OATS: A COMPARISON OF THERMAL RESPONSE AND HISTOLOGY OF RECOVERING CROWNS IN GRADUAL AND RAPIDLY FROZEN PLANTS.

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Freezing in winter cereals is a complex phenomenon that can affect various plant tissues differently. To better understand how freezing affects specific tissue in the over wintering organ (crown) of winter cereal crops, non acclimated oats were frozen to -3°C over an extended period and tissue dama...

  12. Morphological, Photosynthetic, and Physiological Responses of Rapeseed Leaf to Different Combinations of Red and Blue Lights at the Rosette Stage.

    PubMed

    Shengxin, Chang; Chunxia, Li; Xuyang, Yao; Song, Chen; Xuelei, Jiao; Xiaoying, Liu; Zhigang, Xu; Rongzhan, Guan

    2016-01-01

    Rapeseed (Brassica napus L.) is sensitive to light quality. The factory production of rapeseed seedlings for vegetable use and for transplanting in the field requires an investigation of the responses of rapeseed to light quality. This study evaluated the responses of the leaf of rapeseed (cv. "Zhongshuang 11") to different ratios of red-photonflux (RPF) and blue-photonflux (BPF) from light emitting diodes (LEDs). The treatments were set as monochromatic lights, including 100R:0B% and 0R:100B%, and compound lights (CLs), including 75R:25B%, 50R:50B%, and 25R:75B%. The total photonflux in all of the treatments was set as 550 μmolm(-2)s(-1). With an increase of BPF, the rapeseed leaves changed from wrinkled blades and down-rolled margins to flat blades and slightly up-rolled margins, and the compact degree of palisade tissue increased. One layer of the cells of palisade tissue was present under 100R:0B%, whereas two layers were present under the other treatments. Compared to 100R:0B%, 0R:100B% enhanced the indexes of leaf thickness, leaf mass per area (LMA), stomatal density, chlorophyll (Chl) content per weight and photosynthetic capacity (P max), and the CLs with high BPF ratios enhanced these indexes. However, the 100R:0B% and CLs with high RPF ratios enhanced the net photosynthetic rate (P n). The leaves under the CLs showed growth vigor, whereas the leaves under 100R:0B% or 0R:100B% were stressed with a low F v/F m (photosynthetic maximum quantum yield) and a high content of [Formula: see text] and H2O2. The top second leaves under 100R:0B% or 0R:100B% showed stress resistance responses with a high activity of antioxidase, but the top third leaves showed irreversible damage and inactivity of antioxidase. Our results showed that the rapeseed leaves grown under 0R:100B% or CLs with a high BPF ratio showed higher ability to utilize high photonflux, while the leaves grown under 100R:0B% or CLs with a low BPF ratio showed higher efficiency in utilizing low

  13. Morphological, Photosynthetic, and Physiological Responses of Rapeseed Leaf to Different Combinations of Red and Blue Lights at the Rosette Stage

    PubMed Central

    Shengxin, Chang; Chunxia, Li; Xuyang, Yao; Song, Chen; Xuelei, Jiao; Xiaoying, Liu; Zhigang, Xu; Rongzhan, Guan

    2016-01-01

    Rapeseed (Brassica napus L.) is sensitive to light quality. The factory production of rapeseed seedlings for vegetable use and for transplanting in the field requires an investigation of the responses of rapeseed to light quality. This study evaluated the responses of the leaf of rapeseed (cv. “Zhongshuang 11”) to different ratios of red-photonflux (RPF) and blue-photonflux (BPF) from light emitting diodes (LEDs). The treatments were set as monochromatic lights, including 100R:0B% and 0R:100B%, and compound lights (CLs), including 75R:25B%, 50R:50B%, and 25R:75B%. The total photonflux in all of the treatments was set as 550 μmolm−2s−1. With an increase of BPF, the rapeseed leaves changed from wrinkled blades and down-rolled margins to flat blades and slightly up-rolled margins, and the compact degree of palisade tissue increased. One layer of the cells of palisade tissue was present under 100R:0B%, whereas two layers were present under the other treatments. Compared to 100R:0B%, 0R:100B% enhanced the indexes of leaf thickness, leaf mass per area (LMA), stomatal density, chlorophyll (Chl) content per weight and photosynthetic capacity (Pmax), and the CLs with high BPF ratios enhanced these indexes. However, the 100R:0B% and CLs with high RPF ratios enhanced the net photosynthetic rate (Pn). The leaves under the CLs showed growth vigor, whereas the leaves under 100R:0B% or 0R:100B% were stressed with a low Fv/Fm (photosynthetic maximum quantum yield) and a high content of O2.- and H2O2. The top second leaves under 100R:0B% or 0R:100B% showed stress resistance responses with a high activity of antioxidase, but the top third leaves showed irreversible damage and inactivity of antioxidase. Our results showed that the rapeseed leaves grown under 0R:100B% or CLs with a high BPF ratio showed higher ability to utilize high photonflux, while the leaves grown under 100R:0B% or CLs with a low BPF ratio showed higher efficiency in utilizing low photonflux. Under

  14. Phycoerythrin-specific bilin lyase-isomerase controls blue-green chromatic acclimation in marine Synechococcus.

    PubMed

    Shukla, Animesh; Biswas, Avijit; Blot, Nicolas; Partensky, Frédéric; Karty, Jonathan A; Hammad, Loubna A; Garczarek, Laurence; Gutu, Andrian; Schluchter, Wendy M; Kehoe, David M

    2012-12-01

    The marine cyanobacterium Synechococcus is the second most abundant phytoplanktonic organism in the world's oceans. The ubiquity of this genus is in large part due to its use of a diverse set of photosynthetic light-harvesting pigments called phycobiliproteins, which allow it to efficiently exploit a wide range of light colors. Here we uncover a pivotal molecular mechanism underpinning a widespread response among marine Synechococcus cells known as "type IV chromatic acclimation" (CA4). During this process, the pigmentation of the two main phycobiliproteins of this organism, phycoerythrins I and II, is reversibly modified to match changes in the ambient light color so as to maximize photon capture for photosynthesis. CA4 involves the replacement of three molecules of the green light-absorbing chromophore phycoerythrobilin with an equivalent number of the blue light-absorbing chromophore phycourobilin when cells are shifted from green to blue light, and the reverse after a shift from blue to green light. We have identified and characterized MpeZ, an enzyme critical for CA4 in marine Synechococcus. MpeZ attaches phycoerythrobilin to cysteine-83 of the α-subunit of phycoerythrin II and isomerizes it to phycourobilin. mpeZ RNA is six times more abundant in blue light, suggesting that its proper regulation is critical for CA4. Furthermore, mpeZ mutants fail to normally acclimate in blue light. These findings provide insights into the molecular mechanisms controlling an ecologically important photosynthetic process and identify a unique class of phycoerythrin lyase/isomerases, which will further expand the already widespread use of phycoerythrin in biotechnology and cell biology applications. PMID:23161909

  15. Growth and photosynthetic response of a freshwater alga, Selenastrum capricornutum, to an oil shale by-product water

    SciTech Connect

    Delistraty, D.

    1986-01-01

    Several recent studies have focused on toxic effects of various oil shale waters to freshwater algae (e.g., Cleave et al. 1980; McKnight et al. 1983). Algal bioassays are ecologically significant, since algae are the dominant primary producers in most freshwater environments. Furthermore, algae have been shown to be more sensitive to complex wastes than fish or invertebrates. Using a standard algal species provides a systematic approach to toxicant evaluation. One such species is Selenastrum capricornutum Printz, a freshwater unicellular green alga. A strategy to assess the hazards of complex effluents should include a battery of rapid, easily conducted, predictive tests within the larger framework of tier testing. This approach is used in this study to compare the growth and photosynthetic response of S. capricornutum to an oil shale by-product water and its organophilic and hydrophilic subfractions.

  16. Photosynthetic Light Responses May Explain Vertical Distribution of Hymenophyllaceae Species in a Temperate Rainforest of Southern Chile.

    PubMed

    Parra, María José; Acuña, Karina I; Sierra-Almeida, Angela; Sanfuentes, Camila; Saldaña, Alfredo; Corcuera, Luis J; Bravo, León A

    2015-01-01

    Some epiphytic Hymenophyllaceae are restricted to lower parts of the host (< 60 cm; 10-100 μmol photons m(-2) s(-1)) in a secondary forest of Southern Chile; other species occupy the whole host height (≥ 10 m; max PPFD > 1000 μmol photons m(-2) s(-1)). Our aim was to study the photosynthetic light responses of two Hymenophyllaceae species in relation to their contrasting distribution. We determined light tolerance of Hymenoglossum cruentum and Hymenophyllum dentatum by measuring gas exchange, PSI and PSII light energy partitioning, NPQ components, and pigment contents. H. dentatum showed lower maximum photosynthesis rates (A max) than H. cruentum, but the former species kept its net rates (An) near Amax across a wide light range. In contrast, in the latter one, An declined at PPFDs > 60 μmol photons m(-2) s(-1). H. cruentum, the shadiest plant, showed higher chlorophyll contents than H. dentatum. Differences in energy partitioning at PSI and PSII were consistent with gas exchange results. H. dentatum exhibited a higher light compensation point of the partitioning of absorbed energy between photochemical Y(PSII) and non-photochemical Y(NPQ) processes. Hence, both species allocated energy mainly toward photochemistry instead of heat dissipation at their light saturation points. Above saturation, H. cruentum had higher heat dissipation than H. dentatum. PSI yield (YPSI) remained higher in H. dentatum than H. cruentum in a wider light range. In both species, the main cause of heat dissipation at PSI was a donor side limitation. An early dynamic photo-inhibition of PSII may have caused an over reduction of the Qa+ pool decreasing the efficiency of electron donation to PSI. In H. dentatum, a slight increase in heat dissipation due to acceptor side limitation of PSI was observed above 300 μmol photons m(-2)s(-1). Differences in photosynthetic responses to light suggest that light tolerance and species plasticity could explain their contrasting vertical distribution

  17. Photosynthetic Light Responses May Explain Vertical Distribution of Hymenophyllaceae Species in a Temperate Rainforest of Southern Chile

    PubMed Central

    Parra, María José; Acuña, Karina I.; Sierra-Almeida, Angela; Sanfuentes, Camila; Saldaña, Alfredo; Corcuera, Luis J.; Bravo, León A.

    2015-01-01

    Some epiphytic Hymenophyllaceae are restricted to lower parts of the host (<60 cm; 10–100 μmol photons m-2 s-1) in a secondary forest of Southern Chile; other species occupy the whole host height (≥10 m; max PPFD >1000 μmol photons m-2 s-1). Our aim was to study the photosynthetic light responses of two Hymenophyllaceae species in relation to their contrasting distribution. We determined light tolerance of Hymenoglossum cruentum and Hymenophyllum dentatum by measuring gas exchange, PSI and PSII light energy partitioning, NPQ components, and pigment contents. H. dentatum showed lower maximum photosynthesis rates (Amax) than H. cruentum, but the former species kept its net rates (An) near Amax across a wide light range. In contrast, in the latter one, An declined at PPFDs >60 μmol photons m-2 s-1. H. cruentum, the shadiest plant, showed higher chlorophyll contents than H. dentatum. Differences in energy partitioning at PSI and PSII were consistent with gas exchange results. H. dentatum exhibited a higher light compensation point of the partitioning of absorbed energy between photochemical Y(PSII) and non-photochemical Y(NPQ) processes. Hence, both species allocated energy mainly toward photochemistry instead of heat dissipation at their light saturation points. Above saturation, H. cruentum had higher heat dissipation than H. dentatum. PSI yield (YPSI) remained higher in H. dentatum than H. cruentum in a wider light range. In both species, the main cause of heat dissipation at PSI was a donor side limitation. An early dynamic photo-inhibition of PSII may have caused an over reduction of the Qa+ pool decreasing the efficiency of electron donation to PSI. In H. dentatum, a slight increase in heat dissipation due to acceptor side limitation of PSI was observed above 300 μmol photons m-2s-1. Differences in photosynthetic responses to light suggest that light tolerance and species plasticity could explain their contrasting vertical distribution. PMID:26699612

  18. Extensive Acclimation in Ectotherms Conceals Interspecific Variation in Thermal Tolerance Limits.

    PubMed

    Pintor, Anna F V; Schwarzkopf, Lin; Krockenberger, Andrew K

    2016-01-01

    Species' tolerance limits determine their capacity to tolerate climatic extremes and limit their potential distributions. Interspecific variation in thermal tolerances is often proposed to indicate climatic vulnerability and is, therefore, the subject of many recent meta-studies on differential capacities of species from climatically different habitats to deal with climate change. Most studies on thermal tolerances do not acclimate animals or use inconsistent, and insufficient, acclimation times, limiting our knowledge of the shape, duration and extent of acclimation responses. Consequently patterns in thermal tolerances observed in meta-analyses, based on data from the literature are based on inconsistent, partial acclimation and true trends may be obscured. In this study we describe time-course of complete acclimation of critical thermal minima in the tropical ectotherm Carlia longipes and compare it to the average acclimation response of other reptiles, estimated from published data, to assess how much acclimation time may contribute to observed differences in thermal limits. Carlia longipes decreased their lower critical thermal limits by 2.4°C and completed 95% of acclimation in 17 weeks. Wild populations did not mirror this acclimation process over the winter. Other reptiles appear to decrease cold tolerance more quickly (95% in 7 weeks) and to a greater extent, with an estimated average acclimation response of 6.1°C. However, without data on tolerances after longer acclimation times available, our capacity to estimate final acclimation state is very limited. Based on the subset of data available for meta-analysis, much of the variation in cold tolerance observed in the literature can be attributed to acclimation time. Our results indicate that (i) acclimation responses can be slow and substantial, even in tropical species, and (ii) interspecific differences in acclimation speed and extent may obscure trends assessed in some meta-studies. Cold tolerances of

  19. Extensive Acclimation in Ectotherms Conceals Interspecific Variation in Thermal Tolerance Limits

    PubMed Central

    Pintor, Anna F. V.; Schwarzkopf, Lin; Krockenberger, Andrew K.

    2016-01-01

    Species’ tolerance limits determine their capacity to tolerate climatic extremes and limit their potential distributions. Interspecific variation in thermal tolerances is often proposed to indicate climatic vulnerability and is, therefore, the subject of many recent meta-studies on differential capacities of species from climatically different habitats to deal with climate change. Most studies on thermal tolerances do not acclimate animals or use inconsistent, and insufficient, acclimation times, limiting our knowledge of the shape, duration and extent of acclimation responses. Consequently patterns in thermal tolerances observed in meta-analyses, based on data from the literature are based on inconsistent, partial acclimation and true trends may be obscured. In this study we describe time-course of complete acclimation of critical thermal minima in the tropical ectotherm Carlia longipes and compare it to the average acclimation response of other reptiles, estimated from published data, to assess how much acclimation time may contribute to observed differences in thermal limits. Carlia longipes decreased their lower critical thermal limits by 2.4°C and completed 95% of acclimation in 17 weeks. Wild populations did not mirror this acclimation process over the winter. Other reptiles appear to decrease cold tolerance more quickly (95% in 7 weeks) and to a greater extent, with an estimated average acclimation response of 6.1°C. However, without data on tolerances after longer acclimation times available, our capacity to estimate final acclimation state is very limited. Based on the subset of data available for meta-analysis, much of the variation in cold tolerance observed in the literature can be attributed to acclimation time. Our results indicate that (i) acclimation responses can be slow and substantial, even in tropical species, and (ii) interspecific differences in acclimation speed and extent may obscure trends assessed in some meta-studies. Cold tolerances

  20. Seasonal responses of photosynthetic electron transport in Scots pine (Pinus sylvestris L.) studied by thermoluminescence.

    PubMed

    Ivanov, A G; Sane, P V; Zeinalov, Y; Simidjiev, I; Huner, N P A; Oquist, G

    2002-07-01

    The potential of photosynthesis to recover from winter stress was studied by following the thermoluminescence (TL) and chlorophyll fluorescence changes of winter pine needles during the exposure to room temperature (20 degrees C) and an irradiance of 100 micromol m(-2) s(-1). TL measurements of photosystem II (PSII) revealed that the S(2)Q(B)(-) charge recombinations (the B-band) were shifted to lower temperatures in winter pine needles, while the S(2)Q(A)(-) recombinations (the Q-band) remained close to 0 degrees C. This was accompanied by a drastically reduced (65%) PSII photochemical efficiency measured as F(v)/ F(m,) and a 20-fold faster rate of the fluorescence transient from F(o) to F(m) as compared to summer pine. A strong positive correlation between the increase in the photochemical efficiency of PSII and the increase in the relative contribution of the B-band was found during the time course of the recovery process. The seasonal dynamics of TL in Scots pine needles studied under field conditions revealed that between November and April, the contribution of the Q- and B-bands to the overall TL emission was very low (less than 5%). During spring, the relative contribution of the Q- and B-bands, corresponding to charge recombination events between the acceptor and donor sides of PSII, rapidly increased, reaching maximal values in late July. A sharp decline of the B-band was observed in late summer, followed by a gradual decrease, reaching minimal values in November. Possible mechanisms of the seasonally induced changes in the redox properties of S(2)/S(3)Q(B)(-) recombinations are discussed. It is proposed that the lowered redox potential of Q(B) in winter needles increases the population of Q(A)(-), thus enhancing the probability for non-radiative P680(+)Q(A)(-) recombination. This is suggested to enhance the radiationless dissipation of excess light within the PSII reaction center during cold acclimation and during cold winter periods. PMID:12111228

  1. Growth and photosynthetic responses of ectomycorrhizal pine seedlings exposed to elevated Cu in soils.

    PubMed

    Chen, Yahua; Nara, Kazuhide; Wen, Zhugui; Shi, Liang; Xia, Yan; Shen, Zhenguo; Lian, Chunlan

    2015-10-01

    It is still controversial whether ectomycorrhizal (ECM) mycelia filter out toxic metals in nutrient absorption of host trees. In this study, pine (Pinus densiflora) seedlings colonized by Cu-sensitive and Cu-tolerant ECM species were exposed to a wide spectrum of soil Cu concentrations to investigate functions of ECM fungi under Cu stress. The photosynthetic rates of intact needles were monitored in situ periodically. The biomass and elements of plants were also measured after harvest. The ameliorating effect of ECM infection on host plants exposed to toxic stress was metal concentration specific. Under lower-level Cu stress, ECM fungi increased seedling performance, while ECM seedlings accumulated more Cu than nonmycorrhizal (NM) seedlings. Under higher-level Cu stress, photosynthesis decreased well before visible symptoms of Cu toxicity appeared. The reduced photosynthesis and biomass in ECM seedlings compared to NM seedlings under higher Cu conditions were also accompanied by lower phosphorus in needles. There was no marked difference between the two fungal species. Our results indicate that the two ECM fungi studied in our system may not have an ability to selectively eliminate Cu in nutrient absorption and may not act as effective barriers that decrease toxic metal uptake into host plants. PMID:25720735

  2. Response of photosynthetic systems to salinity stress in the desert cyanobacterium Scytonema javanicum

    NASA Astrophysics Data System (ADS)

    Hu, Jinlu; Jin, Liang; Wang, Xiaojuan; Cai, Wenkai; Liu, Yongding; Wang, Gaohong

    2014-01-01

    The present study investigated the physiological and biochemical characteristics of Scytonema javanicum, a pioneer species isolated from desert biological crusts, under salinity stress. Pigment analysis showed that salinity decreased chlorophyll a and phycocyanin content, while low salinity increased carotenoid concentration and high salinity decreased carotenoid concentration. Salinity also inhibited CO2 assimilation rate and photosynthetic oxygen evolution in this cyanobacterium. Chlorophyll a fluorescence transient parameters (φPo, φEo, ψO, RC/ABS, RC/CS, PIABS, and PICS) were decreased under salt stress, while dVo/dto(Mo), Vj and φDo were increased. The decrease of ETRmax and Yield and the change of chlorophyll a fluorescence transients showed that salt stress had an important influence on photosynthesis. These results indicated that the effects of salinity stress on photosynthesis in S. javanicum may depend on the inhibition of electron transport and the inactivation of the reaction centers, but this inhibition may occur in the electron transport pathway at the PSII donor and acceptor sites.

  3. AtFKBP16-1, a chloroplast lumenal immunophilin, mediates response to photosynthetic stress by regulating PsaL stability

    PubMed Central

    Seok, Min Sook; You, Young Nim; Park, Hyun Ji; Lee, Sang Sook; Aigen, Fu; Luan, Sheng; Ahn, Jun Cheul; Cho, Hye Sun

    2014-01-01

    Arabidopsis contains 16 putative chloroplast lumen-targeted immunophilins (IMMs). Proteomic analysis has enabled the subcellular localization of IMMs experimentally, but the exact biological and physiological roles of most luminal IMMs remain to be discovered. FK506-binding protein (FKBP) 16-1, one of the lumenal IMMs containing poorly conserved amino acid residues for peptidyl-prolyl isomerase (PPIase) activity, was shown to play a possible role in chloroplast biogenesis in Arabidopsis, and was also found to interact with PsaL in wheat. In this study, further evidence is provided for the notion that Arabidopsis FKBP16-1 (AtFKBP16-1) is transcriptionally and post-transcriptionally regulated by environmental stresses including high light (HL) intensity, and that overexpression of AtFKBP16-1 plants exhibited increased photosynthetic stress tolerance. A blue native-polyacrylamide gel electrophoresis/two-dimensional (BN-PAGE/2-D) analysis revealed that the increase of AtFKBP16-1 affected the levels of photosystem I (PSI)-light harvesting complex I (LHCI) and PSI-LHCI-light harvesting complex II (LHCII) supercomplex, and consequently enhanced tolerance under conditions of HL stress. In addition, plants overexpressing AtFKBP16-1 showed increased accumulation of PsaL protein and enhanced drought tolerance. Using a protease protection assay, AtFKBP16-1 protein was found to have a role in PsaL stability. The AtPsaL levels also responded to abiotic stresses derived from drought, and from methyl viologen stresses in wild-type plants. Taken together, these results suggest that AtFKBP16-1 plays a role in the acclimation of plants under photosynthetic stress conditions, probably by regulating PsaL stability. PMID:24124981

  4. Plasma aldosterone and sweat sodium concentrations after exercise and heat acclimation

    NASA Technical Reports Server (NTRS)

    Kirby, C. R.; Convertino, V. A.

    1986-01-01

    The relationship between plasma aldosterone levels and sweat sodium excretion after chronic exercise and heat acclimation was investigated, using subjects exercised, at 40 C and 45 percent humidity, for 2 h/day on ten consecutive days at 45 percent of their maximal oxygen uptake. The data indicate that, following heat acclimation, plasma aldosterone concentrations decrease, and that the eccrine gland responsiveness to aldosterone, as represented by sweat sodium reabsorption, may be augmented through exercise and heat acclimation.

  5. The photosynthetic response to a shift in the chlorophyll a to chlorophyll B ratio of chlorella.

    PubMed

    Reger, B J; Krauss, R W

    1970-10-01

    The chlorophyll a:b ratio was shifted in Chlorella vannielii by varying the illuminance under which the cells were cultured-the ratio increased from 2.9, 3.0, 4.0, and 4.8 to 6.2, respectively, at 100, 300, 900, 2,700 and 6,000 foot candles. The 6,000-foot candle cells retained an optimal growth rate at the chlorophyll a:b ratio of 6.2 which was the upper limit of normal growth. Comparisons were made between the 300-and 6,000-foot candle cultures to determine the significance to the photosynthetic mechanism of a shift in the chlorophyll a:b ratio.The high light cells (6,000 foot candles) contained only one-tenth the total amount of chlorophyll of the low light cells (300 foot candles) based on dry weight. The total chlorophyll per cell of the high light cells was one-fifth of that in the low light cells. Electron micrographs indicated differences in chloroplast structure. An average of five or six thylakoids composed a granum-like region of the low light chloroplasts, whereas only a pair of thylakoids at most was found in the high light chloroplasts. The high light chloroplasts had more starch. On a dry weight basis, the high light cells had a respiration rate 3 times that of the low light cells. Based on chlorophyll, the respiration rate of the high light cells was 26 times greater. Based on dry weight, the oxygen evolution for both cultures was essentially the same at 6,000 foot candles; however, at 300 foot candles the rate for the low light cells was about 5 times faster than that of the high light cells. With chlorophyll as the index, the rates of the high light cells were higher than those of the low light cells-7 times faster at 6,000 and 2 times faster at 300 foot candles. At 10,000 foot candles, the low light-grown cells underwent photooxidation, whereas the high light grown cells photosynthesized at a rate slightly higher than at 6,000 foot candles.Action spectra of system II (oxygen evolution) from a modulated polarograph indicated photochemical

  6. Evidence of higher photosynthetic plasticity in the early successional Guazuma ulmifolia Lam. compared to the late successional Hymenaea courbaril L. grown in contrasting light environments.

    PubMed

    Portes, M T; Damineli, D S C; Ribeiro, R V; Monteiro, J A F; Souza, G M

    2010-02-01

    The present study investigated changes in photosynthetic characteristics of Guazuma ulmifolia Lam. (early successional species) and Hymenaea courbaril L. (late successional species) grown in contrasting light conditions as a way of assessing photosynthetic plasticity. Early successional species typically inhabit gap environments being exposed to variability in multiple resources, hence it is expected that these species would show higher photosynthetic plasticity than late successional ones. In order to test this hypothesis, light and CO2 response curves and chlorophyll content (Chl) were measured in plants grown in high and low light environments. G. ulmifolia presented the highest amounts of both Chl a and b, especially in the low light, and both species presented higher Chl a than b in both light conditions. The Chl a/b ratio was higher in high light leaves of both species and greater in G. ulmifolia. Taken together, these results evidence the acclimation potential of both species, reflecting the capacity to modulate light harvesting complexes according to the light environment. However, G. ulmifolia showed evidence of higher photosynthetic plasticity, as indicated by the greater amplitude of variation on photosynthetic characteristics between environments shown by more significant shade adjusted parameters (SAC) and principal component analysis (PCA). Thus, the results obtained were coherent with the hypothesis that the early successional species G. ulmifolia exhibits higher photosynthetic plasticity than the late successional species H. courbaril. PMID:20231962

  7. Effects of acclimation temperature and cadmium exposure on cellular energy budgets in the marine mollusk Crassostrea virginica: linking cellular and mitochondrial responses.

    PubMed

    Cherkasov, Anton S; Biswas, Pradip K; Ridings, Daisy M; Ringwood, Amy H; Sokolova, Inna M

    2006-04-01

    In order to understand the role of metabolic regulation in environmental stress tolerance, a comprehensive analysis of demand-side effects (i.e. changes in energy demands for basal maintenance) and supply-side effects (i.e. metabolic capacity to provide ATP to cover the energy demand) of environmental stressors is required. We have studied the effects of temperature (12, 20 and 28 degrees C) and exposure to a trace metal, cadmium (50 microg l(-1)), on the cellular energy budget of a model marine poikilotherm, Crassostrea virginica (eastern oysters), using oxygen demand for ATP turnover, protein synthesis, mitochondrial proton leak and non-mitochondrial respiration in isolated gill and hepatopancreas cells as demand-side endpoints and mitochondrial oxidation capacity, abundance and fractional volume as supply-side endpoints. Cadmium exposure and high acclimation temperatures resulted in a strong increase of oxygen demand in gill and hepatopancreas cells of oysters. Cd-induced increases in cellular energy demand were significant at 12 and 20 degrees C but not at 28 degrees C, possibly indicating a metabolic capacity limitation at the highest temperature. Elevated cellular demand in cells from Cd-exposed oysters was associated with a 2-6-fold increase in protein synthesis and, at cold acclimation temperatures, with a 1.5-fold elevated mitochondrial proton leak. Cellular aerobic capacity, as indicated by mitochondrial oxidation capacity, abundance and volume, did not increase in parallel to compensate for the elevated energy demand. Mitochondrial oxidation capacity was reduced in 28 degrees C-acclimated oysters, and mitochondrial abundance decreased in Cd-exposed oysters, with a stronger decrease (by 20-24%) in warm-acclimated oysters compared with cold-acclimated ones (by 8-13%). These data provide a mechanistic basis for synergism between temperature and cadmium stress on metabolism of marine poikilotherms. Exposure to combined temperature and cadmium stress may

  8. Transgenerational acclimation of fishes to climate change and ocean acidification

    PubMed Central

    2014-01-01

    There is growing concern about the impacts of climate change and ocean acidification on marine organisms and ecosystems, yet the potential for acclimation and adaptation to these threats is poorly understood. Whereas many short-term experiments report negative biological effects of ocean warming and acidification, new studies show that some marine species have the capacity to acclimate to warmer and more acidic environments across generations. Consequently, transgenerational plasticity may be a powerful mechanism by which populations of some species will be able to adjust to projected climate change. Here, I review recent advances in understanding transgenerational acclimation in fishes. Research over the past 2 to 3 years shows that transgenerational acclimation can partially or fully ameliorate negative effects of warming, acidification, and hypoxia in a range of different species. The molecular and cellular pathways underpinning transgenerational acclimation are currently unknown, but modern genetic methods provide the tools to explore these mechanisms. Despite the potential benefits of transgenerational acclimation, there could be limitations to the phenotypic traits that respond transgenerationally, and trade-offs between life stages, that need to be investigated. Future studies should also test the potential interactions between transgenerational plasticity and genetic evolution to determine how these two processes will shape adaptive responses to environmental change over coming decades. PMID:25580253

  9. Transgenerational acclimation of fishes to climate change and ocean acidification.

    PubMed

    Munday, Philip L

    2014-01-01

    There is growing concern about the impacts of climate change and ocean acidification on marine organisms and ecosystems, yet the potential for acclimation and adaptation to these threats is poorly understood. Whereas many short-term experiments report negative biological effects of ocean warming and acidification, new studies show that some marine species have the capacity to acclimate to warmer and more acidic environments across generations. Consequently, transgenerational plasticity may be a powerful mechanism by which populations of some species will be able to adjust to projected climate change. Here, I review recent advances in understanding transgenerational acclimation in fishes. Research over the past 2 to 3 years shows that transgenerational acclimation can partially or fully ameliorate negative effects of warming, acidification, and hypoxia in a range of different species. The molecular and cellular pathways underpinning transgenerational acclimation are currently unknown, but modern genetic methods provide the tools to explore these mechanisms. Despite the potential benefits of transgenerational acclimation, there could be limitations to the phenotypic traits that respond transgenerationally, and trade-offs between life stages, that need to be investigated. Future studies should also test the potential interactions between transgenerational plasticity and genetic evolution to determine how these two processes will shape adaptive responses to environmental change over coming decades. PMID:25580253

  10. RNA-Seq Analysis of Sulfur-Deprived Chlamydomonas Cells Reveals Aspects of Acclimation Critical for Cell Survival[W

    PubMed Central

    González-Ballester, David; Casero, David; Cokus, Shawn; Pellegrini, Matteo; Merchant, Sabeeha S.; Grossman, Arthur R.

    2010-01-01

    The Chlamydomonas reinhardtii transcriptome was characterized from nutrient-replete and sulfur-depleted wild-type and snrk2.1 mutant cells. This mutant is null for the regulatory Ser-Thr kinase SNRK2.1, which is required for acclimation of the alga to sulfur deprivation. The transcriptome analyses used microarray hybridization and RNA-seq technology. Quantitative RT-PCR evaluation of the results obtained by these techniques showed that RNA-seq reports a larger dynamic range of expression levels than do microarray hybridizations. Transcripts responsive to sulfur deprivation included those encoding proteins involved in sulfur acquisition and assimilation, synthesis of sulfur-containing metabolites, Cys degradation, and sulfur recycling. Furthermore, we noted potential modifications of cellular structures during sulfur deprivation, including the cell wall and complexes associated with the photosynthetic apparatus. Moreover, the data suggest that sulfur-deprived cells accumulate proteins with fewer sulfur-containing amino acids. Most of the sulfur deprivation responses are controlled by the SNRK2.1 protein kinase. The snrk2.1 mutant exhibits a set of unique responses during both sulfur-replete and sulfur-depleted conditions that are not observed in wild-type cells; the inability of this mutant to acclimate to S deprivation probably leads to elevated levels of singlet oxygen and severe oxidative stress, which ultimately causes cell death. The transcriptome results for wild-type and mutant cells strongly suggest the occurrence of massive changes in cellular physiology and metabolism as cells become depleted for sulfur and reveal aspects of acclimation that are likely critical for cell survival. PMID:20587772

  11. Remotely estimating photosynthetic capacity, and its response to temperature, in vegetation canopies using imaging spectroscopy

    SciTech Connect

    Serbin, Shawn P.; Singh, Aditya; Desai, Ankur R.; Dubois, Sean G.; Jablonski, Andrew D.; Kingdon, Clayton C.; Kruger, Eric L.; Townsend, Philip A.

    2015-06-11

    temporal variation in key drivers of photosynthetic metabolism in terrestrial vegetation.

  12. Remotely estimating photosynthetic capacity, and its response to temperature, in vegetation canopies using imaging spectroscopy

    DOE PAGESBeta

    Serbin, Shawn P.; Singh, Aditya; Desai, Ankur R.; Dubois, Sean G.; Jablonski, Andrew D.; Kingdon, Clayton C.; Kruger, Eric L.; Townsend, Philip A.

    2015-06-11

    To date, the utility of ecosystem and Earth system models (EESMs) has been limited by poor spatial and temporal representation of critical input parameters. For example, EESMs often rely on leaf-scale or literature-derived estimates for a key determinant of canopy photosynthesis, the maximum velocity of RuBP carboxylation (Vcmax, μmol m–2 s–1). Our recent work (Ainsworth et al., 2014; Serbin et al., 2012) showed that reflectance spectroscopy could be used to estimate Vcmax at the leaf level. Here, we present evidence that imaging spectroscopy data can be used to simultaneously predict Vcmax and its sensitivity to temperature (EV) at the canopymore » scale. In 2013 and 2014, high-altitude Airborne Visible/Infrared Imaging Spectroscopy (AVIRIS) imagery and contemporaneous ground-based assessments of canopy structure and leaf photosynthesis were acquired across an array of monospecific agroecosystems in central and southern California, USA. A partial least-squares regression (PLSR) modeling approach was employed to characterize the pixel-level variation in canopy Vcmax (at a standardized canopy temperature of 30 °C) and EV, based on visible and shortwave infrared AVIRIS spectra (414–2447 nm). Our approach yielded parsimonious models with strong predictive capability for Vcmax (at 30 °C) and EV (R2 of withheld data = 0.94 and 0.92, respectively), both of which varied substantially in the field (≥ 1.7 fold) across the sampled crop types. The models were applied to additional AVIRIS imagery to generate maps of Vcmax and EV, as well as their uncertainties, for agricultural landscapes in California. The spatial patterns exhibited in the maps were consistent with our in-situ observations. As a result, these findings highlight the considerable promise of airborne and, by implication, space-borne imaging spectroscopy, such as the proposed HyspIRI mission, to map spatial and temporal variation in key drivers of photosynthetic metabolism in terrestrial vegetation.« less

  13. Drought Stress Acclimation Imparts Tolerance to Sclerotinia sclerotiorum and Pseudomonas syringae in Nicotiana benthamiana

    PubMed Central

    Ramegowda, Venkategowda; Senthil-Kumar, Muthappa; Ishiga, Yasuhiro; Kaundal, Amita; Udayakumar, Makarla; Mysore, Kirankumar S.

    2013-01-01

    Acclimation of plants with an abiotic stress can impart tolerance to some biotic stresses. Such a priming response has not been widely studied. In particular, little is known about enhanced defense capacity of drought stress acclimated plants to fungal and bacterial pathogens. Here we show that prior drought acclimation in Nicotiana benthamiana plants imparts tolerance to necrotrophic fungus, Sclerotinia sclerotiorum, and also to hemi-biotrophic bacterial pathogen, Pseudomonas syringae pv. tabaci. S. sclerotiorum inoculation on N. benthamiana plants acclimated with drought stress lead to less disease-induced cell death compared to non-acclimated plants. Furthermore, inoculation of P. syringae pv. tabaci on N. benthamiana plants acclimated to moderate drought stress showed reduced disease symptoms. The levels of reactive oxygen species (ROS) in drought acclimated plants were highly correlated with disease resistance. Further, in planta growth of GFPuv expressing P. syringae pv. tabaci on plants pre-treated with methyl viologen showed complete inhibition of bacterial growth. Taken together, these experimental results suggested a role for ROS generated during drought acclimation in imparting tolerance against S. sclerotiorum and P. syringae pv. tabaci. We speculate that the generation of ROS during drought acclimation primed a defense response in plants that subsequently caused the tolerance against the pathogens tested. PMID:23644883

  14. Comparison of Different Cells of Haematococcus pluvialis Reveals an Extensive Acclimation Mechanism during its Aging Process: From a Perspective of Photosynthesis

    PubMed Central

    Gu, Wenhui; Xie, Xiujun; Gao, Shan; Zhou, Wei; Pan, Guanghua; Wang, Guangce

    2013-01-01

    Both biomass dominated green vegetative cells (GV) and astaxanthin-dominated orange resting cells (OR) affect the final astaxanthin yield in industry. Examination of Haematococcus pluvialis revealed that the OR cells greatly varied from the GV cells at both cellular and subcellular levels. In particular, the thylakoid membranes in the OR were disassembled and fragmented. Furthermore, the OR conserved most of the photosynthetic pigments, with elevated concentrations of violaxanthin, antheraxanthin, and neoxanthin. Notably, moderate photosynthesis was detected in OR, even though most of the thylakoid membranes were disassembled, when compared with those in the GV. However, the energy distribution pattern between photosystem I and II (PSI and PSII) in the OR favored PSI, which was also confirmed by 77-K fluorescence. As zeaxanthin was not detected in the OR, we attribute the acclimation role to astaxanthin, instead of xanthophyll cycle. Additionally, proteomic-scale comparison analysis of thylakoids of the OR and GV indicated no photosynthetically remarkable variations. However, an extensive acclimation mechanism of H. pluvialis was proposed, in which proteins in thylakoid of GV were noted to be involved in biomass accumulation and those in OR were involved in stress response. Conclusions of the comparative analysis might provide some physiological background of OR for astaxanthin production by using H. pluvialis. PMID:23922648

  15. Comparison of different cells of Haematococcus pluvialis reveals an extensive acclimation mechanism during its aging process: from a perspective of photosynthesis.

    PubMed

    Gu, Wenhui; Xie, Xiujun; Gao, Shan; Zhou, Wei; Pan, Guanghua; Wang, Guangce

    2013-01-01

    Both biomass dominated green vegetative cells (GV) and astaxanthin-dominated orange resting cells (OR) affect the final astaxanthin yield in industry. Examination of Haematococcus pluvialis revealed that the OR cells greatly varied from the GV cells at both cellular and subcellular levels. In particular, the thylakoid membranes in the OR were disassembled and fragmented. Furthermore, the OR conserved most of the photosynthetic pigments, with elevated concentrations of violaxanthin, antheraxanthin, and neoxanthin. Notably, moderate photosynthesis was detected in OR, even though most of the thylakoid membranes were disassembled, when compared with those in the GV. However, the energy distribution pattern between photosystem I and II (PSI and PSII) in the OR favored PSI, which was also confirmed by 77-K fluorescence. As zeaxanthin was not detected in the OR, we attribute the acclimation role to astaxanthin, instead of xanthophyll cycle. Additionally, proteomic-scale comparison analysis of thylakoids of the OR and GV indicated no photosynthetically remarkable variations. However, an extensive acclimation mechanism of H. pluvialis was proposed, in which proteins in thylakoid of GV were noted to be involved in biomass accumulation and those in OR were involved in stress response. Conclusions of the comparative analysis might provide some physiological background of OR for astaxanthin production by using H. pluvialis. PMID:23922648

  16. Thermoregulation in hypergravity-acclimated rats

    NASA Technical Reports Server (NTRS)

    Monson, Conrad B.; Patterson, Susan L.; Horowitz, John M.; Oyama, Jiro

    1989-01-01

    The effect of acclimation to hypergravity on thermoregulatory responses of rats was determined by comparing data on core temperature, T(c), tail temperature, and O2 consumption in rats raised at 1 G (C) and at 2.1 G. It was found that, when C rats were exposed to an ambient temperature of 9 C concurrently with exposure to 2.1 G, the T(c) fell by about 6 C, while in rats acclimated to 2.1 G, the T(c) fell only by 1 C. Results of O2 consumption measurements showed that C rats exposed simultaneously to cold and hypergravity were not activating their thermogenic mechanism sufficiently to prevent a fall in T(c). In other experiments, rats acclimated to either 1 or 2.1 G were found to lack the ability to maintain their T(c) when exposed to a 5.8-G field or when cold-stressed at 1 G for extended times.

  17. Nitrogen Starvation Acclimation in Synechococcus elongatus: Redox-Control and the Role of Nitrate Reduction as an Electron Sink

    PubMed Central

    Klotz, Alexander; Reinhold, Edgar; Doello, Sofía; Forchhammer, Karl

    2015-01-01

    Nitrogen starvation acclimation in non-diazotrophic cyanobacteria is characterized by a process termed chlorosis, where the light harvesting pigments are degraded and the cells gradually tune down photosynthetic and metabolic activities. The chlorosis response is governed by a complex and poorly understood regulatory network, which converges at the expression of the nblA gene, the triggering factor for phycobiliprotein degradation. This study established a method that allows uncoupling metabolic and redox-signals involved in nitrogen-starvation acclimation. Inhibition of glutamine synthetase (GS) by a precise dosage of l-methionine-sulfoximine (MSX) mimics the metabolic situation of nitrogen starvation. Addition of nitrate to such MSX-inhibited cells eliminates the associated redox-stress by enabling electron flow towards nitrate/nitrite reduction and thereby, prevents the induction of nblA expression and the associated chlorosis response. This study demonstrates that nitrogen starvation is perceived not only through metabolic signals, but requires a redox signal indicating over-reduction of PSI-reduced electron acceptors. It further establishes a cryptic role of nitrate/nitrite reductases as electron sinks to balance conditions of over-reduction. PMID:25780959

  18. Nitrogen Starvation Acclimation in Synechococcus elongatus: Redox-Control and the Role of Nitrate Reduction as an Electron Sink.

    PubMed

    Klotz, Alexander; Reinhold, Edgar; Doello, Sofía; Forchhammer, Karl

    2015-01-01

    Nitrogen starvation acclimation in non-diazotrophic cyanobacteria is characterized by a process termed chlorosis, where the light harvesting pigments are degraded and the cells gradually tune down photosynthetic and metabolic activities. The chlorosis response is governed by a complex and poorly understood regulatory network, which converges at the expression of the nblA gene, the triggering factor for phycobiliprotein degradation. This study established a method that allows uncoupling metabolic and redox-signals involved in nitrogen-starvation acclimation. Inhibition of glutamine synthetase (GS) by a precise dosage of l-methionine-sulfoximine (MSX) mimics the metabolic situation of nitrogen starvation. Addition of nitrate to such MSX-inhibited cells eliminates the associated redox-stress by enabling electron flow towards nitrate/nitrite reduction and thereby, prevents the induction of nblA expression and the associated chlorosis response. This study demonstrates that nitrogen starvation is perceived not only through metabolic signals, but requires a redox signal indicating over-reduction of PSI-reduced electron acceptors. It further establishes a cryptic role of nitrate/nitrite reductases as electron sinks to balance conditions of over-reduction. PMID:25780959

  19. Effect of short-term exercise-heat acclimation on ventilatory and cerebral blood flow responses to passive heating at rest in humans.

    PubMed

    Fujii, Naoto; Tsuji, Bun; Honda, Yasushi; Kondo, Narihiko; Nishiyasu, Takeshi

    2015-09-01

    Hyperthermia induces hyperventilation and cerebral hypoperfusion in resting humans. We tested the hypothesis that short-term exercise-heat acclimation would alleviate those effects. Twenty healthy male subjects were divided into two groups that performed exercise training in the heat (TR-HEAT, n = 10) or cold (TR-COLD, n = 10). Before and after the training, the subjects in both groups participated in passive-heat tests at rest. Training was performed at 37°C (TR-HEAT) or 10°C (TR-COLD) and entailed four 20-min bouts of cycling at 50% peak oxygen uptake separated by 10-min recoveries daily for 6 consecutive days. After TR-HEAT, esophageal temperature was lowered when measured before and during passive heating, as was the esophageal temperature threshold for cutaneous active vasodilation, whereas plasma volume was increased (all P < 0.05). These traditional indices of successful heat acclimation were not all induced by TR-COLD (all P > 0.05). TR-HEAT had no significant effect on passive heating-induced increases in minute ventilation, even when evaluated as the esophageal temperature threshold for increases in minute ventilation and the slope relating minute ventilation to esophageal temperature (all P > 0.05). By contrast, TR-HEAT attenuated the passive heating-induced reduction in the cerebral vascular conductance index (middle cerebral artery mean blood velocity/mean arterial pressure) (all P < 0.05). TR-COLD did not attenuate the increase in minute ventilation or the decrease in the cerebral vascular conductance index observed during passive heating (all P > 0.05). These data suggest that in resting heated humans, short-term heat acclimation achieved through moderate-intensity exercise training (i.e., 50% peak oxygen uptake) in the heat does not influence hyperthermia-induced hyperventilation, but it does potentially attenuate cerebral hypoperfusion. PMID:26159763

  20. In vitro growth and single-leaf photosynthetic response of Cymbidium plantlets to super-elevated CO2 under cold cathode fluorescent lamps.

    PubMed

    Norikane, Atsushi; Takamura, Takejiro; Morokuma, Masahiro; Tanaka, Michio

    2010-03-01

    To examine the effectiveness of super-elevated (10,000 micromol mol(-1)) CO(2) enrichment under cold cathode fluorescent lamps (CCFL) for the clonal propagation of Cymbidium, plantlets were cultured on modified Vacin and Went (VW) medium under 0, 3,000 and 10,000 micromol mol(-1) CO(2) enrichment and two levels of photosynthetic photon flux density (PPFD, 45 and 75 micromol m(-2) s(-1)). Under high PPFD, 10,000 micromol mol(-1) CO(2) increased root dry weight and promoted shoot growth. In addition, a decrease in photosynthetic capacity and chlorosis at leaf tips were observed. Rubisco activity and stomatal conductance of these plantlets were lower than those of plantlets at 3,000 micromol mol(-1) CO(2) under high PPFD, which had a higher photosynthetic capacity. On the other hand, plantlets on Kyoto medium grown in 10,000 micromol mol(-1) CO(2) under high PPFD had a higher photosynthetic rate than those on modified VW medium; no chlorosis was observed. Furthermore, growth of plantlets, in particular the roots, was remarkably enhanced. This result indicates that a negative response to super-elevated CO(2) under high PPFD could be improved by altering medium components. Super-elevated CO(2) enrichment of in vitro-cultured Cymbidium could positively affect the efficiency and quality of commercial production of clonal orchid plantlets. PMID:20094885

  1. Seasonal time-course of gradients of photosynthetic capacity and mesophyll conductance to CO2 across a beech (Fagus sylvatica L.) canopy.

    PubMed

    Montpied, Pierre; Granier, André; Dreyer, Erwin

    2009-01-01

    Leaf photosynthesis is known to acclimate to the actual irradiance received by the different layers of a canopy. This acclimation is usually described in terms of changes in leaf structure, and in photosynthetic capacity. Photosynthetic capacity is likely to be affected by mesophyll conductance to CO(2) which has seldom been assessed in tree species, and whose plasticity in response to local irradiance is still poorly known. Structural [N and chlorophyll content, leaf mass to area ratio (LMA)] and functional leaf traits [maximum carboxylation rate (V(cmax)), maximum light-driven electron flux (J(max)), and mesophyll conductance (g(i))] were assessed by measuring leaf response curves of net CO(2) assimilation versus intercellular CO(2) partial pressure, along a vertical profile across a beech canopy, and by fitting a version of the Farquhar model including g(i). The measurements were repeated five times during a growth season to catch potential seasonal variation. Irradiance gradients resulted in large decreasing gradients of LMA, g(i), V(cmax), and J(max). Relative allocation of leaf N to the different photosynthetic processes was only slightly affected by local irradiance. Seasonal changes after leaf expansion and before induction of leaf senescence were only minor. Structural equation modelling confirmed that LMA was the main driving force for changes in photosynthetic traits, with only a minor contribution of leaf Nitrogen content. In conclusion, mesophyll conductance to CO(2) displays a large plasticity that scales with photosynthetic capacity across a tree canopy, and that it is only moderately (if at all) affected by seasonal changes in the absence of significant soil water depletion. PMID:19457983

  2. Photosynthetic and water relations responses to elevated CO{sub 2} in the C{sub 4} grass Andropogon gerardii

    SciTech Connect

    Knapp, A.K.; Hamerlynck, E.P.; Owensby, C.E.

    1993-12-01

    Undisturbed tallgrass prairie, dominated by the C{sub 4} grass Andropogon gerardii, was exposed to ambient and elevated (double ambient) levels of atmospheric CO{sub 2} in large open-top chambers throughout the 1991 and 1992 growing seasons. Responses in leaf xylem pressure potential ({psi}), net photosynthesis (A), and stomatal conductance (g) were measured for A. gerardii grown within chambers and from adjacent field plots. In 1992, maximum photosynthetic capacity (A{sub max}), apparent quantum requirement (Q{sub r}), the photosynthetic light compensation point (LCP), and dark respiration (R{sub d}) were also measured. Midday {psi} was significantly higher in plants grown at elevated CO{sub 2} in both years; seasonally averaged {psi} was 0.48-0.70 MPa lower in 1991 (a dry year) than 1992 (a wet year). In 1991, A and g were significantly higher in plants grown at elevated vs. ambient CO{sub 2}. Increased A at elevated CO{sub 2} occurred (as much as 7.1 {mu}mol m{sup {minus}2} s{sup {minus}1}) over a broad range of temperatures (17-35 C), but the temperature optimum for A was similar at both 350 and 700 {mu}L L{sup {minus}1} CO{sub 2}. In 1992, no differences in A, A{sub max}, Q{sub r}, LCP, or R{sub d} were detected when ambient and elevated CO{sub 2} plants were compared. In plants collected from field plots, R{sub d}, LCP, and leaf N were significantly higher than in plants within the chambers indicating that a chamber effect exists for these parameters. In both years, g was significantly reduced (21%-51%) when measured at 700 vs. 350 {mu}L L{sup {minus}1} CO{sub 2}. Peak aboveground biomass was increased at elevated CO{sub 2} in 1991 but not in 1992. These data indicate that for C{sub 4} grasses, effects of elevated CO{sub 2} may only be detectable in years with significant water stress, a common occurrence in the central North American tallgrass prairies. 27 refs., 5 figs., 1 tab.

  3. Interactive response of photosynthetic characteristics in Haloxylon ammodendron and Hedysarum scoparium exposed to soil water and air vapor pressure deficits.

    PubMed

    Gong, Chunmei; Wang, Jiajia; Hu, Congxia; Wang, Junhui; Ning, Pengbo; Bai, Juan

    2015-08-01

    C4 plants possess better drought tolerance than C3 plants. However, Hedysarum scoparium, a C3 species, is dominant and widely distributed in the desert areas of northwestern China due to its strong drought tolerance. This study compared it with Haloxylon ammodendron, a C4 species, regarding the interactive effects of drought stress and different leaf-air vapor pressure deficits. Variables of interest included gas exchange, the activity levels of key C4 photosynthetic enzymes, and cellular anatomy. In both species, gas exchange parameters were more sensitive to high vapor pressure deficit than to strong water stress, and the net CO2 assimilation rate (An) was enhanced as vapor pressure deficits increased. A close relationship between An and stomatal conductance (gs) suggested that the species shared a similar response mechanism. In H. ammodendron, the activity levels of key C4 enzymes were higher, including those of phosphoenolpyruvate carboxylase (PEPC) and nicotinamide adenine dinucleotide phosphate-malate enzyme (NADP-ME), whereas in H. scoparium, the activity level of nicotinamide adenine dinucleotide-malate enzyme (NAD-ME) was higher. Meanwhile, H. scoparium utilized adaptive structural features, including a larger relative vessel area and a shorter distance from vein to stomata, which facilitated the movement of water. These findings implied that some C4 biochemical pathways were present in H. scoparium to respond to environmental challenges. PMID:26257361

  4. Seasonal course of photosynthetic efficiency in Larix decidua Mill. in response to temperature and change in pigment composition during senescence.

    PubMed

    Galvagno, M; Rossini, M; Migliavacca, M; Cremonese, E; Colombo, R; Morra di Cella, U

    2013-11-01

    This manuscript presents a study aimed at characterizing the seasonal course of photosynthetic capacity of an alpine deciduous conifer, European larch (Larix decidua Mill.), based on chlorophyll fluorescence measurements and photosynthetic pigment analysis. The study focused on the characterization of autumn senescence events which (contrary to bud-burst) are still scarcely investigated. The study was conducted on two natural European larch stands in the northwestern Italian Alps during two consecutive years. The results show that photosynthetic efficiency as assessed by fluorescence measurements was controlled by variations in air and soil temperature. Photosynthesis responded to variations in maximum air and soil temperature in a delayed way, with a varying lag depending on the seasonal period considered. The analysis of photosynthetic efficiency and pigment decline at the end of the growing season identified two senescence phases. During early senescence, plants manifested only the beginning of needle decolouration, while during late senescence pigment degradation led to a loss in photosynthetic efficiency. This behavior indicates that the beginning of needle yellowing and the decline in photosynthetic efficiency can occur at different times-a finding that should be considered in order to improve models of ecosystem processes. PMID:23263743

  5. The Yin-Yang of Cytokinin Homeostasis and Drought Acclimation/Adaptation.

    PubMed

    Li, Weiqiang; Herrera-Estrella, Luis; Tran, Lam-Son Phan

    2016-07-01

    Increasing evidence has shown that cytokinins (CKs) regulate plant drought acclimation/adaptation through a multistep phosphorelay pathway. Recent progress has allowed us to suggest a yin-and-yang-type relationship between CK homeostasis and acclimation/adaptation responses that modulates plant fitness and yields stability under drought through a complex network involving crosstalk with abscisic acid (ABA). PMID:27270336

  6. The effects of phenotypic plasticity on photosynthetic performance in winter rye, winter wheat and Brassica napus.

    PubMed

    Dahal, Keshav; Kane, Khalil; Gadapati, Winona; Webb, Elizabeth; Savitch, Leonid V; Singh, Jasbir; Sharma, Pooja; Sarhan, Fathey; Longstaffe, Fred J; Grodzinski, Bernard; Hüner, Norman P A

    2012-02-01

    The contributions of phenotypic plasticity to photosynthetic performance in winter (cv Musketeer, cv Norstar) and spring (cv SR4A, cv Katepwa) rye (Secale cereale) and wheat (Triticum aestivum) cultivars grown at either 20°C [non-acclimated (NA)] or 5°C [cold acclimated (CA)] were assessed. The 22-40% increase in light-saturated rates of CO₂ assimilation in CA vs NA winter cereals were accounted for by phenotypic plasticity as indicated by the dwarf phenotype and increased specific leaf weight. However, phenotypic plasticity could not account for (1) the differential temperature sensitivity of CO₂ assimilation and photosynthetic electron transport, (2) the increased efficiency and light-saturated rates of photosynthetic electron transport or (3) the decreased light sensitivity of excitation pressure and non-photochemical quenching between NA and NA winter cultivars. Cold acclimation decreased photosynthetic performance of spring relative to winter cultivars. However, the differences in photosynthetic performances between CA winter and spring cultivars were dependent upon the basis on which photosynthetic performance was expressed. Overexpression of BNCBF17 in Brassica napus generally decreased the low temperature sensitivity (Q₁₀) of CO₂ assimilation and photosynthetic electron transport even though the latter had not been exposed to low temperature. Photosynthetic performance in wild type compared to the BNCBF17-overexpressing transgenic B. napus indicated that CBFs/DREBs regulate not only freezing tolerance but also govern plant architecture, leaf anatomy and photosynthetic performance. The apparent positive and negative effects of cold acclimation on photosynthetic performance are discussed in terms of the apparent costs and benefits of phenotypic plasticity, winter survival and reproductive fitness. PMID:21883254

  7. The role of acclimation in scaling GPP from the leaf to the canopy for crops in a changing climate

    NASA Astrophysics Data System (ADS)

    Bernacchi, C.; Bagley, J. E.; Ort, D. R.; Kumar, P.; Ruiz Vera, U. M.

    2013-12-01

    Multi-faceted challenges from global climate change and increased demands on agriculture for food, fiber and, increasingly fuel is driving a need to understand how major climate change factors, particularly increasing atmospheric concentrations of CO2 and rising temperature, will influence leaf photosynthesis (A) and ecosystem gross primary productivity (GPP). Eight of the ten major crops grown globally utilize the C3 photosynthetic pathway and based on mechanistic understanding of C3 photosynthesis, a synergism exists with rising CO2 and increasing temperature that is predicted to increase A beyond that of an increase in [CO2] alone. However, considerable uncertainty surrounds the acclimation response of photosynthesis to global change and, as a result, the influence of physiological adjustments of photosynthesis is currently not represented in leaf, canopy, ecosystem or general circulation models that are used to predict ecosystem-scale responses to global change scenarios. Here, we incorporate into mechanistic leaf and canopy photosynthesis models the acclimation responses of the two key parameters required for modeling A and GPP, the maximum velocity for carboxylation (Vc,max) and maximum rate of electron transport (Jmax), determined from in-field experimentation for soybean and poplar, which vary in regards to what limits A in elevated CO2. Measurements of Vc,max and Jmax from the Soybean Temperature by Free Air CO2 Enrichment (Soy-T-FACE) experiment and of poplar at the Poplar FACE experiment were used to model the response of net carbon uptake to [CO2] and/or temperature. The modeling was conducted using the mechanistic leaf photosynthesis model (Farquhar, von Caemmerer, & Berry Model) and the latest generation canopy photosynthesis model with an integrated mechanistic representation of physiology and biophysical components, the Multi-Layer Canopy (MLCan) model. While the theory behind the interactions of [CO2] and temperature on photosynthesis are well

  8. Sublethal toxicity of chlorpyrifos to salmonid olfaction after hypersaline acclimation.

    PubMed

    Maryoung, Lindley A; Blunt, Brian; Tierney, Keith B; Schlenk, Daniel

    2015-04-01

    Salmonid habitats can be impacted by several environmental factors, such as salinization, which can also affect salmonid tolerance to anthropogenic stressors, such as pesticides. Previous studies have shown that hypersaline acclimation enhances the acute toxicity of certain organophosphate and carbamate pesticides to euryhaline fish; however, sublethal impacts have been far less studied. The current study aims to determine how hypersaline acclimation and exposure to the organophosphate chlorpyrifos (CPF) impact salmonid olfaction. Combined acclimation and exposure to CPF was shown to impact rainbow trout olfaction at the molecular, physiological, and behavioral levels. Concurrent exposure to hypersalinity and 0.5μg/L CPF upregulated four genes (chloride intracellular channel 4, G protein zgc:101761, calcium calmodulin dependent protein kinase II delta, and adrenergic alpha 2C receptor) that inhibit olfactory signal transduction. At the physiological level, hypersalinity and chlorpyrifos caused a decrease in sensory response to the amino acid l-serine and the bile salt taurocholic acid. Combined acclimation and exposure also negatively impacted behavior and reduced the avoidance of a predator cue (l-serine). Thus, acclimation to hypersaline conditions and exposure to environmentally relevant concentrations of chlorpyrifos caused an inhibition of olfactory signal transduction leading to a decreased response to odorants and impairment of olfactory mediated behaviors. PMID:25697678

  9. Investigating genotype specific response in photosynthetic behavior under drought stress and nitrogen limitation in Brassica rapa.

    NASA Astrophysics Data System (ADS)

    Pleban, J. R.; Mackay, D. S.; Ewers, B. E.; Weinig, C.; Aston, T.

    2015-12-01

    Challenges in terrestrial ecosystem modeling include characterizing the impact of stress on vegetation and the heterogeneous behavior of different species within the environment. In an effort to address these challenges the impacts of drought and nutrient limitation on the CO2 assimilation of multiple genotypes of Brassica rapa was investigated using the Farquhar Model (FM) of photosynthesis following a Bayesian parameterization and updating scheme. Leaf gas exchange and chlorophyll fluorescence measurements from an unstressed group (well-watered/well-fertilized) and two stressed groups (drought/well-fertilized and well-watered/nutrient limited) were used to estimate FM model parameters. Unstressed individuals were used to initialize Bayesian parameter estimation. Posterior mean estimates yielded a close fit with data as observed assimilation (An) closely matched predicted (Ap) with mean standard error for all individuals ranging from 0.8 to 3.1 μmol CO2 m-2 s-1. Posterior parameter distributions of the unstressed individuals were combined and fit to distributions to establish species level Bayesian priors of FM parameters for testing stress responses. Species level distributions of unstressed group identified mean maximum rates of carboxylation standardized to 25° (Vcmax25) as 101.8 μmol m-2 s-1 (± 29.0) and mean maximum rates of electron transport standardized to 25° (Jmax25) as 319.7 μmol m-2 s-1 (± 64.4). These updated priors were used to test the response of drought and nutrient limitations on assimilation. In the well-watered/nutrient limited group a decrease of 28.0 μmol m-2 s-1 was observed in mean estimate of Vcmax25, a decrease of 27.9 μmol m-2 s-1 in Jmax25 and a decrease in quantum yield from 0.40 mol photon/mol e- in unstressed individuals to 0.14 in the nutrient limited group. In the drought/well-fertilized group a decrease was also observed in Vcmax25 and Jmax25. The genotype specific unstressed and stressed responses were then used to

  10. Acclimation of photosynthesis to low leaf water potentials

    SciTech Connect

    Matthews, M.A.; Boyer, J.S.

    1984-01-01

    Photosynthesis is reduced at low leaf water potentials (PSI/sub l/) but repeated water deficits can decrease this reduction, resulting in photosynthetic acclimation. The contribution of the stomata and the chloroplasts to this acclimation is unknown. The authors evaluated stomatal and chloroplast contributions when soil-grown sunflower (Helianthus annuus L.) plants were subjected to water deficit pretreatments for 2 weeks. The relationship between photosynthesis and PSI/sub l/, determined from gas-exchange and isopiestic thermocouple psychometry, was shifted 3 to 4 bars towards lower PSI/sub l/ in pretreated plants. Leaf diffusive resistance was similarly affected. Chloroplast activity, demonstrated in situ with measurements of quantum yield and the capacity to fix CO/sub 2/ at all partial pressures of CO/sub 2/, and in vitro by photosystem II activity of isolated organelles, was inhibited at low PSI/sub l/ but less in pretreated plants than in control plants. The magnitude of this inhibition indicated that decreases in chloroplast activity contributed more than closure of stomata both to losses in photosynthesis and to the acclimation of photosynthesis to low PSI/sub l/. 32 references, 8 figures.

  11. Photosynthetic responses to chilling in a chilling-tolerant and chilling-sensitive Miscanthus hybrid.

    PubMed

    Friesen, P C; Sage, R F

    2016-07-01

    Miscanthus is a C4 perennial grass being developed for bioenergy production in temperate regions where chilling events are common. To evaluate chilling effects on Miscanthus, we assessed the processes controlling net CO2 assimilation rate (A) in Miscanthus x giganteus (M161) and a chilling-sensitive Miscanthus hybrid (M115) before and after a chilling treatment of 12/5 °C. The temperature response of A and maximum Rubisco activity in vitro were identical below 20 °C in chilled and unchilled M161, demonstrating Rubisco capacity limits or co-limits A at cooler temperatures. By contrast, A in M115 decreased at all measurement temperatures after growth at 12/5 °C. Rubisco activity in vitro declined in proportion to the reduction in A in chilled M115 plants, indicating Rubisco capacity is responsible in part for the decline in A. Pyruvate orthophosphate dikinase activities were also reduced by the chilling treatment when assayed at 28 °C, indicating this enzyme may also contribute to the reduction in A in M115. The maximum extractable activities of PEPCase and NADP-ME remained largely unchanged after chilling. The carboxylation efficiency of the C4 cycle was depressed in both genotypes to a similar extent after chilling. ΦP :ΦCO2 remained unchanged in both genotypes indicating the C3 and C4 cycles decline equivalently upon chilling. PMID:26714623

  12. Acclimation to ultraviolet irradiation affects UV-B sensitivity of Daphnia magna to several environmental toxicants.

    PubMed

    Kim, Jungkon; Lee, Minjung; Oh, Sorin; Ku, Ja-Lok; Kim, Kyung-Hee; Choi, Kyungho

    2009-12-01

    Phototoxicity of several environmental contaminants by UV light has been reported in many studies. Nevertheless, field observations suggest the presence of certain defense mechanisms that would protect aquatic organisms against phototoxic damages. The current study was conducted to understand the responses of aquatic receptors to phototoxic chemicals in a natural environment where low dose UV light is present and long-term acclimation to UV might have been taken place. For this purpose, the water flea Daphnia magna was acclimated to a non-lethal, environmentally relevant level of UV-B light for >20 successive generations. The differences in toxicity response were evaluated between the UV-B acclimated and the non-acclimated daphnids when they were exposed to phototoxic compounds such as polynuclear aromatic hydrocarbons (fluoranthene and pyrene), a pharmaceutical (sulfathiazole), or metals (Cd and Cu) under UV-B light. Following the UV-B acclimation, toxicity of metals under UV-B light significantly decreased (P<0.1) suggesting the defense/repair system which might be developed through acclimation. For PAHs and sulfathiazole, however the acclimation rendered organisms more susceptible (P<0.05). The metabolic cost incurred during the acclimation to UV-B stress may in part explain the organisms' reduced capacity to deal with other stressors. Addition of vitamin C significantly increased the resistance of UV-B acclimated individuals against Cu, while no change was observed for the other chemicals, suggesting that the mode of Cu phototoxicity is different from those of the other phototoxicants under UV-B light. Two-dimensional gel electrophoresis analyses showed that long-term acclimation to UV-B lead to notable changes in protein expression, which may be further evaluated to explain varying susceptibilities of the acclimated daphnids to different phototoxicants. PMID:19836821

  13. Photosynthetic characteristics of sinking microalgae under the sea ice

    NASA Astrophysics Data System (ADS)

    Yamamoto, Shinya; Michel, Christine; Gosselin, Michel; Demers, Serge; Fukuchi, Mitsuo; Taguchi, Satoru

    2014-12-01

    The photosynthetic characteristics of sinking a microalgal community were studied to compare with the ice algal community in the sea ice and the phytoplankton community in the water column under the sea ice at the beginning of the light season in the first-year sea ice ecosystem on the Mackenzie Shelf, in the western Canadian Arctic. The phytoplankton community was collected using a water bottle, whereas the sinking algal community was collected using particle collectors, and the ice algal community was obtained by using an ice-core sampler from the bottom portion of ice core. Photosynthesis versus irradiance (P-E) incubation experiments were conducted on deck to obtain the initial slope (αB) and the maximum photosynthetic rate (PmB) of the three algal communities. The αB and the PmB of the light saturation curve, and chlorophyll a (Chl a) specific absorption coefficient (āph*) between the sinking microalgal community and the ice algal community were similar and were distinctly different from the phytoplankton community. The significant linear relationship between αB and PmB, which was obtained among the three groups, may suggest that a photo-acclimation strategy is common for all algal communities under the low light regime of the early season. Although the sinking algal community could be held for the entire duration of deployment at maximum, this community remained photosynthetically active once exposed to light. This response suggests that sinking algal communities can be the seed population, which results in a subsequent phytoplankton bloom under the sea ice or in a surface layer, as well as representing food for the higher trophic level consumers in the Arctic Ocean even before the receding of the sea ice.

  14. The molecular dimension of microbial species: 2. Synechococcus strains representative of putative ecotypes inhabiting different depths in the Mushroom Spring microbial mat exhibit different adaptive and acclimative responses to light.

    PubMed

    Nowack, Shane; Olsen, Millie T; Schaible, George A; Becraft, Eric D; Shen, Gaozhong; Klapper, Isaac; Bryant, Donald A; Ward, David M

    2015-01-01

    Closely related strains of thermophilic Synechococcus were cultivated from the microbial mats found in the effluent channels of Mushroom Spring, Yellowstone National Park (YNP). These strains have identical or nearly identical 16S rRNA sequences but are representative of separate, predicted putative ecotype (PE) populations, which were identified by using the more highly resolving psaA locus and which predominate at different vertical positions within the 1-mm-thick upper-green layer of the mat. Pyrosequencing confirmed that each strain contained a single, predominant psaA genotype. Strains differed in growth rate as a function of irradiance. A strain with a psaA genotype corresponding to a predicted PE that predominates near the mat surface grew fastest at high irradiances, whereas strains with psaA genotypes representative of predominant subsurface populations grew faster at low irradiance and exhibited greater sensitivity to abrupt shifts to high light. The high-light-adapted and low-light-adapted strains also exhibited differences in pigment content and the composition of the photosynthetic apparatus (photosystem ratio) when grown under different light intensities. Cells representative of the different strains had similar morphologies under low-light conditions, but under high-light conditions, cells of low-light-adapted strains became elongated and formed short chains of cells. Collectively, the results presented here are consistent with the hypothesis that closely related, but distinct, ecological species of Synechococcus occupy different light niches in the Mushroom Spring microbial mat and acclimate differently to changing light environments. PMID:26175719

  15. The molecular dimension of microbial species: 2. Synechococcus strains representative of putative ecotypes inhabiting different depths in the Mushroom Spring microbial mat exhibit different adaptive and acclimative responses to light

    PubMed Central

    Nowack, Shane; Olsen, Millie T.; Schaible, George A.; Becraft, Eric D.; Shen, Gaozhong; Klapper, Isaac; Bryant, Donald A.; Ward, David M.

    2015-01-01

    Closely related strains of thermophilic Synechococcus were cultivated from the microbial mats found in the effluent channels of Mushroom Spring, Yellowstone National Park (YNP). These strains have identical or nearly identical 16S rRNA sequences but are representative of separate, predicted putative ecotype (PE) populations, which were identified by using the more highly resolving psaA locus and which predominate at different vertical positions within the 1-mm-thick upper-green layer of the mat. Pyrosequencing confirmed that each strain contained a single, predominant psaA genotype. Strains differed in growth rate as a function of irradiance. A strain with a psaA genotype corresponding to a predicted PE that predominates near the mat surface grew fastest at high irradiances, whereas strains with psaA genotypes representative of predominant subsurface populations grew faster at low irradiance and exhibited greater sensitivity to abrupt shifts to high light. The high-light-adapted and low-light-adapted strains also exhibited differences in pigment content and the composition of the photosynthetic apparatus (photosystem ratio) when grown under different light intensities. Cells representative of the different strains had similar morphologies under low-light conditions, but under high-light conditions, cells of low-light-adapted strains became elongated and formed short chains of cells. Collectively, the results presented here are consistent with the hypothesis that closely related, but distinct, ecological species of Synechococcus occupy different light niches in the Mushroom Spring microbial mat and acclimate differently to changing light environments. PMID:26175719

  16. Photosynthetic response of Cannabis sativa L., an important medicinal plant, to elevated levels of CO2.

    PubMed

    Chandra, Suman; Lata, Hemant; Khan, Ikhlas A; Elsohly, Mahmoud A

    2011-07-01

    The effect of elevated CO2 concentrations (545 and 700 μmol mol(-1)) on gas exchange and stomatal response of four high Δ(9)-THC yielding varieties of Cannabis sativa (HPM, K2, MX and W1) was studied to assess their response to the rising atmospheric CO2 concentration. In general, elevated CO2 concentration (700 μmol mol(-1)) significantly (p < 0.05) stimulated net photosynthesis (P N), water use efficiency (WUE) and internal CO2 concentration (C i), and suppressed transpiration (E) and stomatal conductance (g s) as compared to the ambient CO2 concentration (390 μmol mol(-1)) in all the varieties whereas, the effect of 545 μmol mol(-1) CO2 concentration was found insignificant (p < 0.05) on these parameters in most of the cases. No significant changes (p < 0.05) in the ratio of internal to the ambient CO2 concentration (C i/C a) was observed in these varieties under both the elevated CO2 concentrations (545 and 700 μmol mol(-1)). An average increase of about 48 %, 45 %, 44 % and 38 % in P N and, about 177 %, 157 %, 191 % and 182 % in WUE was observed due to elevated CO2 (700 μmol mol(-1)) as compared to ambient CO2 concentration in HPM, K2, MX and W1 varieties, respectively. The higher WUE under elevated CO2 conditions in Cannabis sativa, primarily because of decreased stomatal conductance and subsequently the transpiration rate, may enable this species to survive under expected harsh greenhouse effects including elevated CO2 concentration and drought conditions. The higher P N, WUE and nearly constant C i/C a ratio under elevated CO2 concentrations in this species reflect a close coordination between its stomatal and mesophyll functions. PMID:23573021

  17. Light acclimation in Porphyridium purpureum (Rhodophyta): Growth, photosynthesis, and phycobilisomes

    SciTech Connect

    Levy, I.; Gantt, E. )

    1988-12-01

    Acclimation to three photon flux densities 10, 35, 180 {mu}E{center dot}m{sup {minus}2}{center dot}s{sup {minus}1} was determined in laboratory cultures of Porphyridium purpureum Bory, Drew and Ross. Cultures grown at low, medium, and high PPFDs had compensation points of <3, 6, and 20 {mu}E{center dot}m{sup {minus}2}{center dot}s{sup {minus}1}, respectively, and saturating irradiances in the initial log phase of 90, 115, 175 {mu}E{center dot}m{sup {minus}2}{center dot}s{sup {minus}1} and up to 240 {mu}E{center dot}m{sup {minus}2}{center dot}s{sup {minus}1} in late log phase. High light cells had the smallest photosynthetic unit size (phycobiliproteins plus chlorophyll), the highest photosynthetic capacity, and the highest growth rates. Photosystem I reaction centers (P700) per cell remained proportional to chlorophyll at ca. 110 chl/P700. However, phycobiliprotein content decreased as did the phycobilisome number (ca. 50%) in high light cells, whereas the phycobilisome size remained the same as in medium and low light cells. We concluded that acclimation of this red alga to varied PPFDs was manifested by the plasticity of the photosystem II antennae with little, if any, affect noted on photosystem I.

  18. Responses of photosynthetic properties and chloroplast ultrastructure of two moss crusts from a desert biological soil crust to supplementary UV-B radiation

    NASA Astrophysics Data System (ADS)

    Hui, Rong; Li, Xinrong; Zhao, Yang; Pan, Yanxia

    2016-04-01

    Our understanding of plant responses to supplementary ultraviolet-B (UV-B) radiation due to stratospheric ozone depletion has improved over recent decades. However, research on biological soil crusts (BSCs) is scarce and it remains controversial. Laboratory studies were conducted to investigate the influence of UV-B radiation on the Bryum argenteum and Didymodon vinealis isolated from BSCs, which are both dominant species in moss crusts found within patches of shrubs and herbs in the Tengger Desert of northern China. The aim of the current work was to evaluate whether supplementary UV-B radiation affected photosynthetic properties and chloroplast ultrastructure of two moss crusts and whether response differences were observed between the crusts. Four levels of UV-B radiation of 2.75 (control), 3.08, 3.25, and 3.41 W m-2 was achieved using fluorescence tube systems for 10 days, simulating 0, 6, 9, and 12% of stratospheric ozone at the latitude of Shapotou, respectively. We measured photosynthetic apparatus as assessed by chlorophyll a fluorescence parameters, photosynthetic pigment contents, and observations of chloroplast ultrastructure. Additionally, soluble proteins and UV-B absorbing compounds were simultaneously investigated. The results of this study showed that chlorophyll a fluorescence parameters (i.e., the maximal quantum yield of PSII photochemistry, the effective quantum yield of PSII photochemistry, and photochemical quenching coefficient), photosynthetic pigment contents, soluble protein contents, total flavonoid contents and the ultrastructure were negatively influenced by elevated UV-B radiation and the degree of detrimental effects significantly increased with the intensity of UV-B radiation. Moreover, results demonstrated that the negative effects on photosynthesis and chloroplast ultrastructure were more serious in B. argenteum than that in D. vinealis. These results may not only provide a potential mechanism for supplemental UV-B effects on

  19. Constraints, independence, and evolution of thermal plasticity: Probing genetic architecture of long- and short-term thermal acclimation

    PubMed Central

    Gerken, Alison R.; Eller, Olivia C.; Hahn, Daniel A.; Morgan, Theodore J.

    2015-01-01

    Seasonal and daily thermal variation can limit species distributions because of physiological tolerances. Low temperatures are particularly challenging for ectotherms, which use both basal thermotolerance and acclimation, an adaptive plastic response, to mitigate thermal stress. Both basal thermotolerance and acclimation are thought to be important for local adaptation and persistence in the face of climate change. However, the evolutionary independence of basal and plastic tolerances remains unclear. Acclimation can occur over longer (seasonal) or shorter (hours to days) time scales, and the degree of mechanistic overlap is unresolved. Using a midlatitude population of Drosophila melanogaster, we show substantial heritable variation in both short- and long-term acclimation. Rapid cold hardening (short-term plasticity) and developmental acclimation (long-term plasticity) are positively correlated, suggesting shared mechanisms. However, there are independent components of these traits, because developmentally acclimated flies respond positively to short-term acclimation. A strong negative correlation between basal cold tolerance and developmental acclimation suggests that basal cold tolerance may constrain developmental acclimation, whereas a weaker negative correlation between basal cold tolerance and short-term acclimation suggests less constraint. Using genome-wide association mapping, we show the genetic architecture of rapid cold hardening and developmental acclimation responses are nonoverlapping at the SNP and corresponding gene level. However, genes associated with each trait share functional similarities, including genes involved in apoptosis and autophagy, cytoskeletal and membrane structural components, and ion binding and transport. These results indicate substantial opportunity for short-term and long-term acclimation responses to evolve separately from each other and for short-term acclimation to evolve separately from basal thermotolerance. PMID

  20. Constraints, independence, and evolution of thermal plasticity: probing genetic architecture of long- and short-term thermal acclimation.

    PubMed

    Gerken, Alison R; Eller, Olivia C; Hahn, Daniel A; Morgan, Theodore J

    2015-04-01

    Seasonal and daily thermal variation can limit species distributions because of physiological tolerances. Low temperatures are particularly challenging for ectotherms, which use both basal thermotolerance and acclimation, an adaptive plastic response, to mitigate thermal stress. Both basal thermotolerance and acclimation are thought to be important for local adaptation and persistence in the face of climate change. However, the evolutionary independence of basal and plastic tolerances remains unclear. Acclimation can occur over longer (seasonal) or shorter (hours to days) time scales, and the degree of mechanistic overlap is unresolved. Using a midlatitude population of Drosophila melanogaster, we show substantial heritable variation in both short- and long-term acclimation. Rapid cold hardening (short-term plasticity) and developmental acclimation (long-term plasticity) are positively correlated, suggesting shared mechanisms. However, there are independent components of these traits, because developmentally acclimated flies respond positively to short-term acclimation. A strong negative correlation between basal cold tolerance and developmental acclimation suggests that basal cold tolerance may constrain developmental acclimation, whereas a weaker negative correlation between basal cold tolerance and short-term acclimation suggests less constraint. Using genome-wide association mapping, we show the genetic architecture of rapid cold hardening and developmental acclimation responses are nonoverlapping at the SNP and corresponding gene level. However, genes associated with each trait share functional similarities, including genes involved in apoptosis and autophagy, cytoskeletal and membrane structural components, and ion binding and transport. These results indicate substantial opportunity for short-term and long-term acclimation responses to evolve separately from each other and for short-term acclimation to evolve separately from basal thermotolerance. PMID

  1. Photosynthetic response to elevated temperature in the symbiotic dinoflagellate Symbiodinium microadriaticum in culture.

    PubMed Central

    Iglesias-Prieto, R; Matta, J L; Robins, W A; Trench, R K

    1992-01-01

    Elevated temperature (28-34 degrees C) has been hypothesized as the primary cause of the loss of algal endosymbionts in coral reef-associated invertebrates, a phenomenon observed on a world-wide scale over the last decade. In past studies of this "bleaching" phenomenon, there has been an underlying assumption that temperature adversely affects the animal hosts, the algae thereby being relegated to a more passive role. Because photosynthesis is a sensitive indicator of thermal stress in plants and has a central role in the nutrition of symbiotic invertebrates, we have tested the hypothesis that elevated temperature adversely affects photosynthesis in the symbiotic dinoflagellate Symbiodinium microadriaticum. The results, based on analyses of light-mediated O2 evolution and in vivo fluorescence, indicate that photosynthesis is impaired at temperatures above 30 degrees C and ceases completely at 34-36 degrees C. These observations are discussed in the context of possible mechanisms that may function in the disassociation of algal-invertebrate symbioses in response to elevated temperature. PMID:11607337

  2. Metabolic responses to sulfur dioxide in grapevine (Vitis vinifera L.): photosynthetic tissues and berries.

    PubMed

    Considine, Michael J; Foyer, Christine H

    2015-01-01

    Research on sulfur metabolism in plants has historically been undertaken within the context of industrial pollution. Resolution of the problem of sulfur pollution has led to sulfur deficiency in many soils. Key questions remain concerning how different plant organs deal with reactive and potentially toxic sulfur metabolites. In this review, we discuss sulfur dioxide/sulfite assimilation in grape berries in relation to gene expression and quality traits, features that remain significant to the food industry. We consider the intrinsic metabolism of sulfite and its consequences for fruit biology and postharvest physiology, comparing the different responses in fruit and leaves. We also highlight inconsistencies in what is considered the "ambient" environmental or industrial exposures to SO2. We discuss these findings in relation to the persistent threat to the table grape industry that intergovernmental agencies will revoke the industry's exemption to the worldwide ban on the use of SO2 for preservation of fresh foods. Transcriptome profiling studies on fruit suggest that added value may accrue from effects of SO2 fumigation on the expression of genes encoding components involved in processes that underpin traits related to customer satisfaction, particularly in table grapes, where SO2 fumigation may extend for several months. PMID:25750643

  3. Metabolic responses to sulfur dioxide in grapevine (Vitis vinifera L.): photosynthetic tissues and berries

    PubMed Central

    Considine, Michael J.; Foyer, Christine H.

    2015-01-01

    Research on sulfur metabolism in plants has historically been undertaken within the context of industrial pollution. Resolution of the problem of sulfur pollution has led to sulfur deficiency in many soils. Key questions remain concerning how different plant organs deal with reactive and potentially toxic sulfur metabolites. In this review, we discuss sulfur dioxide/sulfite assimilation in grape berries in relation to gene expression and quality traits, features that remain significant to the food industry. We consider the intrinsic metabolism of sulfite and its consequences for fruit biology and postharvest physiology, comparing the different responses in fruit and leaves. We also highlight inconsistencies in what is considered the “ambient” environmental or industrial exposures to SO2. We discuss these findings in relation to the persistent threat to the table grape industry that intergovernmental agencies will revoke the industry’s exemption to the worldwide ban on the use of SO2 for preservation of fresh foods. Transcriptome profiling studies on fruit suggest that added value may accrue from effects of SO2 fumigation on the expression of genes encoding components involved in processes that underpin traits related to customer satisfaction, particularly in table grapes, where SO2 fumigation may extend for several months. PMID:25750643

  4. Growth and photosynthetic performance of five tree seedlings species in response to natural light regimes from the Central Pacific of Costa Rica.

    PubMed

    Guzmán, J Antonio; Cordero, Roberto A

    2013-09-01

    Environmental heterogeneity mostly dominated by differing light regimes affects the expression of phenotypic plasticity, which is important for plant growth and survival, especially in the forest understory. The knowledge about these responses to this heterogeneity is a key factor for forest restoration initiatives. In this study, we determine several phenotypic responses to contrasting light conditions in five native tree seedling species of La Cangreja National Park, Central Pacific of Costa Rica, four of them with threatened or relict populations. After 14 weeks at a medium gap condition (24% of full sun), seedlings were transferred and acclimated for 11 weeks to three different natural light regimes: large gap (LG), medium gap (MG) and small gap (SG), corresponding to 52%, 24%, 9% of the mean direct and indirect radiation at each site from full sun. Growth, biomass allocation and leaf gas exchange were measured after the acclimation period. Four species strongly reduced relative growth rate (RGR) in the lower light condition. Total biomass (TB) and RGR were different in Hymenaea courbaril and Platymiscium curiense. H. courbaril and Astronium graveolens had significant changes in the maximum assimilation rate, with a mean value in the LG of 11.02 and 7.70 micromolCO2/m2s, respectively. P. curuense showed the same trend and significant changes in RGR and biomass allocation. Aspidosperma myristicifolium and Plinia puriscalensis showed no adjustments to the light regimes in any of the measured variables. This study remarks the importance of determining the growth and physiological performance of these tree native species. It also demonstrates that the most threatened species are those with the less plastic responses to the light regimes, which stresses the difficult situation of their natural populations. This study highlights an urgent definition of the conservation and restoration needs of the degraded forests of the Costa Rican Central Pacific area, where these

  5. Photosynthetic and growth responses of Schima superba seedlings to sulfuric and nitric acid depositions.

    PubMed

    Yao, Fang-Fang; Ding, Hui-Ming; Feng, Li-Li; Chen, Jing-Jing; Yang, Song-Yu; Wang, Xi-Hua

    2016-05-01

    A continuing rise in acid deposition can cause forest degradation. In China, acid deposition has converted gradually from sulfuric acid deposition (SAD) to nitric acid deposition (NAD). However, the differing responses of photosynthesis and growth to depositions of sulfuric vs. nitric acid have not been well studied. In this study, 1-year-old seedlings of Schima superba, a dominant species in subtropical forests, were treated with two types of acid deposition SO4 (2-)/NO3 (-) ratios (8:1 and 0.7:1) with two applications (foliar spraying and soil drenching) at two pH levels (pH 3.5 and pH 2.5) over a period of 18 months. The results showed that the intensity, acid deposition type, and spraying method had significant effects on the physiological characteristics and growth performance of seedlings. Acid deposition at pH 2.5 via foliar application reduced photosynthesis and growth of S. superba, especially in the first year. Unlike SAD, NAD with high acidity potentially alleviated the negative effects of acidity on physiological properties and growth, probably due to a fertilization effect that improved foliar nitrogen and chlorophyll contents. Our results suggest that trees were damaged mainly by direct acid stress in the short term, whereas in the long term, soil acidification was also likely to be a major risk to forest ecosystems. Our data suggest that the shift in acid deposition type may complicate the ongoing challenge of anthropogenic acid deposition to ecosystem stability. PMID:26797956

  6. Photosynthetic response of two seaweed species along an urban pollution gradient: evidence of selection of pollution-tolerant species.

    PubMed

    Scherner, F; Bonomi Barufi, J; Horta, P A

    2012-11-01

    Urbanization leads to the expansion of ephemeral seaweed species and the decline of important perennial, canopy-forming seaweed species. Understanding the mechanisms that lead to these changes is a current challenge. In the present study, laboratory assays and field transplantations were performed with two seaweed species: the perennial, canopy-forming seaweed Sargassum stenophyllum and the ephemeral seaweed Ulva lactuca. Photosynthetic efficiency was assessed using modulated chlorophyll fluorometry. Brief exposure to urban waters does not appear to be a major stressor to the photosynthetic efficiency of either species. However, after 26 days of transplantation in urban waters, S. stenophyllum declined, whereas U. lactuca had enhanced photosynthetic efficiency. This difference reflects their divergent abilities to regulate the energy distribution at the PSII and shows that urban stressors alter these mechanisms. Our results provide evidence of the physiological causes for the decline of Sargassum species and the expansion of Ulva species in impacted urban areas. PMID:23010654

  7. Dynamic Balancing of Isoprene Carbon Sources Reflects Photosynthetic and Photorespiratory Responses to Temperature Stress1[W][OPEN

    PubMed Central

    Chambers, Jeffrey; Alves, Eliane G.; Teixeira, Andrea; Garcia, Sabrina; Holm, Jennifer; Higuchi, Niro; Manzi, Antonio; Abrell, Leif; Fuentes, Jose D.; Nielsen, Lars K.; Torn, Margaret S.; Vickers, Claudia E.

    2014-01-01

    The volatile gas isoprene is emitted in teragrams per annum quantities from the terrestrial biosphere and exerts a large effect on atmospheric chemistry. Isoprene is made primarily from recently fixed photosynthate; however, alternate carbon sources play an important role, particularly when photosynthate is limiting. We examined the relative contribution of these alternate carbon sources under changes in light and temperature, the two environmental conditions that have the strongest influence over isoprene emission. Using a novel real-time analytical approach that allowed us to examine dynamic changes in carbon sources, we observed that relative contributions do not change as a function of light intensity. We found that the classical uncoupling of isoprene emission from net photosynthesis at elevated leaf temperatures is associated with an increased contribution of alternate carbon. We also observed a rapid compensatory response where alternate carbon sources compensated for transient decreases in recently fixed carbon during thermal ramping, thereby maintaining overall increases in isoprene production rates at high temperatures. Photorespiration is known to contribute to the decline in net photosynthesis at high leaf temperatures. A reduction in the temperature at which the contribution of alternate carbon sources increased was observed under photorespiratory conditions, while photosynthetic conditions increased this temperature. Feeding [2-13C]glycine (a photorespiratory intermediate) stimulated emissions of [13C1–5]isoprene and 13CO2, supporting the possibility that photorespiration can provide an alternate source of carbon for isoprene synthesis. Our observations have important implications for establishing improved mechanistic predictions of isoprene emissions and primary carbon metabolism, particularly under the predicted increases in future global temperatures. PMID:25318937

  8. System Responses to Equal Doses of Photosynthetically Usable Radiation of Blue, Green, and Red Light in the Marine Diatom Phaeodactylum tricornutum

    PubMed Central

    Valle, Kristin Collier; Nymark, Marianne; Aamot, Inga; Hancke, Kasper; Winge, Per; Andresen, Kjersti; Johnsen, Geir; Brembu, Tore; Bones, Atle M.

    2014-01-01

    Due to the selective attenuation of solar light and the absorption properties of seawater and seawater constituents, free-floating photosynthetic organisms have to cope with rapid and unpredictable changes in both intensity and spectral quality. We have studied the transcriptional, metabolic and photo-physiological responses to light of different spectral quality in the marine diatom Phaeodactylum tricornutum through time-series studies of cultures exposed to equal doses of photosynthetically usable radiation of blue, green and red light. The experiments showed that short-term differences in gene expression and profiles are mainly light quality-dependent. Transcription of photosynthesis-associated nuclear genes was activated mainly through a light quality-independent mechanism likely to rely on chloroplast-to-nucleus signaling. In contrast, genes encoding proteins important for photoprotection and PSII repair were highly dependent on a blue light receptor-mediated signal. Changes in energy transfer efficiency by light-harvesting pigments were spectrally dependent; furthermore, a declining trend in photosynthetic efficiency was observed in red light. The combined results suggest that diatoms possess a light quality-dependent ability to activate photoprotection and efficient repair of photodamaged PSII. In spite of approximately equal numbers of PSII-absorbed quanta in blue, green and red light, the spectral quality of light is important for diatom responses to ambient light conditions. PMID:25470731

  9. System responses to equal doses of photosynthetically usable radiation of blue, green, and red light in the marine diatom Phaeodactylum tricornutum.

    PubMed

    Valle, Kristin Collier; Nymark, Marianne; Aamot, Inga; Hancke, Kasper; Winge, Per; Andresen, Kjersti; Johnsen, Geir; Brembu, Tore; Bones, Atle M

    2014-01-01

    Due to the selective attenuation of solar light and the absorption properties of seawater and seawater constituents, free-floating photosynthetic organisms have to cope with rapid and unpredictable changes in both intensity and spectral quality. We have studied the transcriptional, metabolic and photo-physiological responses to light of different spectral quality in the marine diatom Phaeodactylum tricornutum through time-series studies of cultures exposed to equal doses of photosynthetically usable radiation of blue, green and red light. The experiments showed that short-term differences in gene expression and profiles are mainly light quality-dependent. Transcription of photosynthesis-associated nuclear genes was activated mainly through a light quality-independent mechanism likely to rely on chloroplast-to-nucleus signaling. In contrast, genes encoding proteins important for photoprotection and PSII repair were highly dependent on a blue light receptor-mediated signal. Changes in energy transfer efficiency by light-harvesting pigments were spectrally dependent; furthermore, a declining trend in photosynthetic efficiency was observed in red light. The combined results suggest that diatoms possess a light quality-dependent ability to activate photoprotection and efficient repair of photodamaged PSII. In spite of approximately equal numbers of PSII-absorbed quanta in blue, green and red light, the spectral quality of light is important for diatom responses to ambient light conditions. PMID:25470731

  10. A Light Switch Based on Protein S-Nitrosylation Fine-Tunes Photosynthetic Light Harvesting in Chlamydomonas.

    PubMed

    Berger, Hanna; De Mia, Marcello; Morisse, Samuel; Marchand, Christophe H; Lemaire, Stéphane D; Wobbe, Lutz; Kruse, Olaf

    2016-06-01

    Photosynthetic eukaryotes are challenged by a fluctuating light supply, demanding for a modulated expression of nucleus-encoded light-harvesting proteins associated with photosystem II (LHCII) to adjust light-harvesting capacity to the prevailing light conditions. Here, we provide clear evidence for a regulatory circuit that controls cytosolic LHCII translation in response to light quantity changes. In the green unicellular alga Chlamydomonas reinhardtii, the cytosolic RNA-binding protein NAB1 represses translation of certain LHCII isoform mRNAs. Specific nitrosylation of Cys-226 decreases NAB1 activity and could be demonstrated in vitro and in vivo. The less active, nitrosylated form of NAB1 is found in cells acclimated to limiting light supply, which permits accumulation of light-harvesting proteins and efficient light capture. In contrast, elevated light supply causes its denitrosylation, thereby activating the repression of light-harvesting protein synthesis, which is needed to control excitation pressure at photosystem II. Denitrosylation of recombinant NAB1 is efficiently performed by the cytosolic thioredoxin system in vitro. To our knowledge, NAB1 is the first example of stimulus-induced denitrosylation in the context of photosynthetic acclimation. By identifying this novel redox cross-talk pathway between chloroplast and cytosol, we add a new key element required for drawing a precise blue print of the regulatory network of light harvesting. PMID:27208221

  11. A Variable Cluster of Ethylene Response Factor–Like Genes Regulates Metabolic and Developmental Acclimation Responses to Submergence in Rice[W

    PubMed Central

    Fukao, Takeshi; Xu, Kenong; Ronald, Pamela C.; Bailey-Serres, Julia

    2006-01-01

    Submergence-1 (Sub1), a major quantitative trait locus affecting tolerance to complete submergence in lowland rice (Oryza sativa), contains two or three ethylene response factor (ERF)–like genes whose transcripts are regulated by submergence. In the submergence-intolerant japonica cultivar M202, this locus encodes two ERF genes, Sub1B and Sub1C. In the tolerant near-isogenic line containing the Sub1 locus from the indica FR13A, M202(Sub1), the locus additionally encodes the ERF gene Sub1A. During submergence, the tolerant M202(Sub1) displayed restrained leaf and internode elongation, chlorophyll degradation, and carbohydrate consumption, whereas the enzymatic activities of pyruvate decarboxylase and alcohol dehydrogenase were increased significantly compared with the intolerant M202. Transcript levels of genes associated with carbohydrate consumption, ethanolic fermentation, and cell expansion were distinctly regulated in the two lines. Sub1A and Sub1C transcript levels were shown to be upregulated by submergence and ethylene, with the Sub1C allele in M202 also upregulated by treatment with gibberellic acid (GA). These findings demonstrate that the Sub1 region haplotype determines ethylene- and GA-mediated metabolic and developmental responses to submergence through differential expression of Sub1A and Sub1C. Submergence tolerance in lowland rice is conferred by a specific allele variant of Sub1A that dampens ethylene production and GA responsiveness, causing quiescence in growth that correlates with the capacity for regrowth upon desubmergence. PMID:16816135

  12. Excitation energy partitioning and quenching during cold acclimation in Scots pine.

    PubMed

    Sveshnikov, Dmitry; Ensminger, Ingo; Ivanov, Alexander G; Campbell, Douglas; Lloyd, Jon; Funk, Christiane; Hüner, Norman P A; Oquist, Gunnar

    2006-03-01

    We studied the influence of two irradiances on cold acclimation and recovery of photosynthesis in Scots pine (Pinus sylvestris L.) seedlings to assess mechanisms for quenching the excess energy captured by the photosynthetic apparatus. A shift in temperature from 20 to 5 degrees C caused a greater decrease in photosynthetic activity, measured by chlorophyll fluorescence and oxygen evolution, in plants exposed to moderate light (350 micromol m(-2) s(-1)) than in shaded plants (50 micromol m(-2) s(-1)). In response to the temperature shift, maximal photochemical efficiency of photosystem II (PSII), measured as the ratio of variable to maximal chlorophyll fluorescence (Fv/Fm) of dark-adapted samples, decreased to 70% in exposed seedlings, whereas shaded seedlings maintained Fv/Fm close to initial values. After a further temperature decrease to -5 degrees C, only 8% of initial Fv/Fm remained in exposed plants, whereas shaded plants retained 40% of initial Fv/Fm. Seven days after transfer from -5 to 20 degrees C, recovery of photochemical efficiency was more complete in the shaded plants than in the exposed plants (87 and 65% of the initial Fv/Fm value, respectively). In response to cold stress, the estimated functional absorption cross section per remaining PSII reaction center increased at both irradiances, but the increase was more pronounced in exposed seedlings. Estimates of energy partitioning in the needles showed a much higher dissipative component in the exposed seedlings at low temperatures, pointing to stronger development of non-photochemical quenching at moderate irradiances. The de-epoxidation state of the xanthophyll cycle pigments increased in exposed seedlings at 5 degrees C, contributing to the quenching capacity, whereas significant de-epoxidation in the shaded plants was observed only when temperatures decreased to -5 degrees C. Thermoluminescence (TL) measurements of PSII revealed that charge recombinations between the second oxidation state of Mn

  13. Short Duration Heat Acclimation in Australian Football Players

    PubMed Central

    Kelly, Monica; Gastin, Paul B.; Dwyer, Daniel B; Sostaric, Simon; Snow, Rodney J.

    2016-01-01

    This study examined if five sessions of short duration (27 min), high intensity, interval training (HIIT) in the heat over a nine day period would induce heat acclimation in Australian football (AF) players. Fourteen professional AF players were matched for VO2peak (mL·kg-1·min-1) and randomly allocated into either a heat acclimation (Acc) (n = 7) or Control (Con) group (n = 7). The Acc completed five cycle ergometer HIIT sessions within a nine day period on a cycle ergometer in the heat (38.7 ± 0.5 °C; 34.4 ± 1.3 % RH), whereas Con trained in thermo-neutral conditions (22.3 ± 0.2 °C; 35.8 ± 0. % RH). Four days prior and two days post HIIT participants undertook a 30 min constant load cycling test at 60% V̇O2peak in the heat (37.9 ± 0.1 °C; 28.5 ± 0.7 % RH) during which VO2, blood lactate concentration ([Lac-]), heart rate (HR), rating of perceived exertion (RPE), thermal comfort, core and skin temperatures were measured. Heat acclimation resulted in reduced RPE, thermal comfort and [Lac-] (all p < 0.05) during the submaximal exercise test in the heat. Heart rate was lower (p = 0.007) after HIIT, in both groups. Heat acclimation did not influence any other measured variables. In conclusion, five short duration HIIT sessions in hot dry conditions induced limited heat acclimation responses in AF players during the in-season competition phase. In practice, the heat acclimation protocol can be implemented in a professional team environment; however the physiological adaptations resulting from such a protocol were limited. Key points Some minor heat acclimation adaptations can be induced in professional AF players with five 27 min non-consecutive, short duration HIIT sessions in the heat. The heat acclimation protocol employed in this study was able to be implemented in a professional team sport environment during an actual competitive season. Elevating and maintaining a high core temperature sufficient for heat acclimation likely requires a longer heat

  14. Short Duration Heat Acclimation in Australian Football Players.

    PubMed

    Kelly, Monica; Gastin, Paul B; Dwyer, Daniel B; Sostaric, Simon; Snow, Rodney J

    2016-03-01

    This study examined if five sessions of short duration (27 min), high intensity, interval training (HIIT) in the heat over a nine day period would induce heat acclimation in Australian football (AF) players. Fourteen professional AF players were matched for VO2peak (mL·kg(-1)·min(-1)) and randomly allocated into either a heat acclimation (Acc) (n = 7) or Control (Con) group (n = 7). The Acc completed five cycle ergometer HIIT sessions within a nine day period on a cycle ergometer in the heat (38.7 ± 0.5 °C; 34.4 ± 1.3 % RH), whereas Con trained in thermo-neutral conditions (22.3 ± 0.2 °C; 35.8 ± 0. % RH). Four days prior and two days post HIIT participants undertook a 30 min constant load cycling test at 60% V̇O2peak in the heat (37.9 ± 0.1 °C; 28.5 ± 0.7 % RH) during which VO2, blood lactate concentration ([Lac(-)]), heart rate (HR), rating of perceived exertion (RPE), thermal comfort, core and skin temperatures were measured. Heat acclimation resulted in reduced RPE, thermal comfort and [Lac(-)] (all p < 0.05) during the submaximal exercise test in the heat. Heart rate was lower (p = 0.007) after HIIT, in both groups. Heat acclimation did not influence any other measured variables. In conclusion, five short duration HIIT sessions in hot dry conditions induced limited heat acclimation responses in AF players during the in-season competition phase. In practice, the heat acclimation protocol can be implemented in a professional team environment; however the physiological adaptations resulting from such a protocol were limited. Key pointsSome minor heat acclimation adaptations can be induced in professional AF players with five 27 min non-consecutive, short duration HIIT sessions in the heat.The heat acclimation protocol employed in this study was able to be implemented in a professional team sport environment during an actual competitive season.Elevating and maintaining a high core temperature sufficient for heat acclimation likely requires a longer heat

  15. Drinking and water balance during exercise and heat acclimation

    NASA Technical Reports Server (NTRS)

    Greenleaf, J. E.; Brock, P. J.; Keil, L. C.; Morse, J. T.

    1983-01-01

    The interactions between fluid intake and balance, and plasma ion, osmotic, and endocrine responses during dehydration produced by exercise in cool and warm environments during acclimation are explored. Two groups of five male subjects performed 8 days of ergometer exercise in hot and thermoneutral conditions, respectively. The exercise trials lasted 2 hr each. Monitoring was carried out on the PV, osmotic, sodium, and endocrine concentrations, voluntary fluid intake, fluid balances, and fluid deficits. A negative correlation was observed between the plasma sodium and osmolality during acclimation. The presence of hypervolemia during acclimation is suggested as a cause of drinking, while the vasopressin concentration was not found to be a significant factor stimulating drinking. Finally, the predominant mechanism in fluid intake during exercise and heat exposure is concluded to be the renin-angiotensin II system in the presence of reductions in total body water and extracellular plasma volumes.

  16. Chlorophyll a fluorescence and photosynthetic and growth responses of Pinus radiata to phosphorus deficiency, drought stress, and high CO/sub 2/

    SciTech Connect

    Conroy, J.P.; Smillie, R.M.; Kueppers, M.; Bevege, D.I.; Barlow, E.W.

    1986-06-01

    Needles from phosphorus deficient seedlings of Pinus radiata D. Don grown for 8 weeks at either 330 or 660 microliters CO/sub 2/ per liter displayed chlorophyll a fluorescence induction kinetics characteristic of structural changes within the thylakoid chloroplast membrane, i.e. constant yield fluorescence (F/sub O/) was increased and induced fluorescence ((F/sub P/-F/sub I/)/F /sub O/) was reduced. The effect was greatest in the undroughted plants grown at 660 ..mu..l CO/sub 2/ L/sup -1/. By week 22 at 330 ..mu..lCO/sub 2/L/sup -1/ acclimation to P deficiency had occurred as shown by the similarity in the fluorescence characteristics and maximum rates of photosynthesis of the needles from the two P treatments. However, acclimation did not occur in the plants grown at 660 ..mu..l CO/sub 2/ L/sup -1/. The light saturated rate of photosynthesis of needles with adequate P was higher at 660 ..mu..l CO/sub 2/ L/sup -1/ than at 330 ..mu..l CO/sub 2/ L/sup -1/, whereas photosynthesis of P deficient plants showed no increase when grown at the higher CO/sub 2/ concentration. The average growth increase due to CO/sub 2/ enrichment was 14% in P deficient plants and 32% when P was adequate. In drought stressed plants grown at 330 ..mu..l CO/sub 2/ L/sup -1/, there was a reduction in the maximal rate of quenching of fluorescence (R/sub Q/) after the major peak. Constant yield fluorescence was unaffected but induced fluorescence was lower. These results indicate that electron flow subsequent to photosystem II was affected by drought stress. At 660 ..mu..l CO/sub 2/L/sup -1/ this response was eliminated showing that CO/sub 2/ enrichment improved the ability of the seedlings to acclimate to drought stress. The average growth increase with CO/sub 2/ enrichment was 37% in drought stressed plants and 19% in unstressed plants.

  17. Supramaximal heat production induced by aminophylline in temperature-acclimated rats

    NASA Astrophysics Data System (ADS)

    Wang, L. C. H.

    1985-03-01

    Previous studies have shown that aminophylline, a phosphodiesterase inhibitor (thereby increasing intracellular cyclic AMP concentration) elicits supramaximal heat production and improves cold tolerance in rats acclimated to 22°C. To test whether aminophylline-stimulated supramaximal thermogenesis is independent of both the thermogenic capacity (i.e. aerobic fitness) and the mode of thermogenesis (shivering vs. non-shivering), rats (adult male Sprague-Dawley, approximately 400 g) of two different ages (4 11 month and 9 17 month, n=12 for each) were acclimated to 5, 15, and 25°C in succession and their thermogenic responses to aminophylline subsequently assessed. Aminophylline elicited supramaximal thermogenesis and improved cold tolerance regardless of age or acclimating temperatures. Further, the absolute net increase in heat production stimulated by aminophylline was also similar for all acclimating temperatures. After acclimating to 15°C, a single injection of aminophylline in the older rats elicited thermogenesis greater than that of the controls acclimated to 5°C; in the younger rats, aminophylline duplicated 46% of the increase in thermogenesis observed after acclimating to 5°C. These results indicated that the aminophylline-stimulated extra heat production is independent of both the thermogenic capacity and the mode of thermogenesis. It is possible that an enhanced substrate mobilization consequent to increased intracellular cyclic AMP concentration by aminophylline underlies the common mechanism via which supramaximal thermogenesis is elicited in temperature-acclimated rats.

  18. Cold resistance depends on acclimation and behavioral caste in a temperate ant

    NASA Astrophysics Data System (ADS)

    Modlmeier, Andreas P.; Pamminger, Tobias; Foitzik, Susanne; Scharf, Inon

    2012-10-01

    Adjusting to low temperatures is important for animals living in cold environments. We studied the chill-coma recovery time in temperate ant workers ( Temnothorax nylanderi) from colonies collected in autumn and spring in Germany. We experimentally acclimated these ant colonies to cold temperatures followed by warm temperatures. As expected, cold-acclimated workers recovered faster from freezing temperatures, but subsequent heat acclimation did not change the short recovery times observed after cold acclimation. Hence, either heat acclimation improves cold tolerance, possibly as a general response to stress, or at least it does not negate enhanced cold tolerance following cold acclimation. Colonies collected in spring showed similar cold tolerance levels to cold-acclimated colonies in the laboratory. Next, we compared the chill-coma recovery time of different worker castes and found that exterior workers recovered faster than interior workers. This difference may be related to their more frequent exposure to cold, higher activity level, or distinct physiology. Interior workers were also heavier and showed a higher gaster-to-head ratio and thorax ratio compared to exterior workers. An obvious difference between exterior and interior workers is activity level, but we found no link between activity and cold tolerance. This suggests that physiology rather than behavioral differences could cause the increased cold tolerance of exterior workers. Our study reveals the importance of acclimation for cold tolerance under natural and standardized conditions and demonstrates differences in cold tolerance and body dimensions in monomorphic behavioral castes of an ant.

  19. Temperature acclimation in the Mongolian gerbil (Meriones unguiculatus): biochemical and organ weight changes.

    PubMed

    Steffen, J M; Roberts, J C

    1977-01-01

    1. Adult Mongolian gerbils (Meriones unguiculatus) were acclimated to 5 +/- 1, 24 +/- 1 and 34 +/- 1 degrees C for 6-8 weeks. 2. Body weights of temperature acclimated gerbils did not differ significantly from controls. Organ wt/body wt ratios of liver, kidney and heart increased in cold-acclimated and decreased in heat-acclimated gerbils. Adrenal wt/body wt ratio increased in the cold and was unchanged in the heat. Relative weights of brain, spleen, lungs, brown fat and ovaries + uterus did not change with temperature acclimation. 3. Cold acclimation produced significant increases in specific and total activity of brown fat alpha GPO and liver SO and AAO and in total activity of kidney SO; a significant decrease in liver mitochondrial ADP/O ratio with succinate as substrate; and no change in brown fat SO or liver alpha KGO. 4. Heat acclimation produced significant decreases in specific and total activity of liver and kidney SO, and in total activity of brown fat SO and alpha GPO, and liver AAO and alpha KGO. 5. The combined biochemical and organ wt changes seen in temperature-acclimated gerbils suggest that this species is capable of altering its metabolic thermogenic potential in response to a wide range of ambient temperatures. PMID:318267

  20. Waterlogging and submergence stress: affects and acclimation.

    PubMed

    Phukan, Ujjal J; Mishra, Sonal; Shukla, Rakesh Kumar

    2016-10-01

    Submergence, whether partial or complete, imparts some serious consequences on plants grown in flood prone ecosystems. Some plants can endure these conditions by embracing various survival strategies, including morphological adaptations and physiological adjustments. This review summarizes recent progress made in understanding of the stress and the acclimation responses of plants under waterlogged or submerged conditions. Waterlogging and submergence are often associated with hypoxia development, which may trigger various morphological traits and cellular acclimation responses. Ethylene, abscisic acid, gibberellic acid and other hormones play a crucial role in the survival process which is controlled genetically. Effects at the cellular level, including ATP management, starch metabolism, elemental toxicity, role of transporters and redox status have been explained. Transcriptional and hormonal interplay during this stress may provide some key aspects in understanding waterlogging and submergence tolerance. The level and degree of tolerance may vary depending on species or climatic variations which need to be studied for a proper understanding of waterlogging stress at the global level. The exploration of regulatory pathways and interplay in model organisms such as Arabidopsis and rice would provide valuable resources for improvement of economically and agriculturally important plants in waterlogging affected areas. PMID:26177332

  1. Acclimation of Photosynthesis to Elevated CO2 in Five C3 Species 1

    PubMed Central

    Sage, Rowan F.; Sharkey, Thomas D.; Seemann, Jeffrey R.

    1989-01-01

    The effect of long-term (weeks to months) CO2 enhancement on (a) the gas-exchange characteristics, (b) the content and activation state of ribulose-1,5-bisphosphate carboxylase (rubisco), and (c) leaf nitrogen, chlorophyll, and dry weight per area were studied in five C3 species (Chenopodium album, Phaseolus vulgaris, Solanum tuberosum, Solanum melongena, and Brassica oleracea) grown at CO2 partial pressures of 300 or 900 to 1000 microbars. Long-term exposure to elevated CO2 affected the CO2 response of photosynthesis in one of three ways: (a) the initial slope of the CO2 response was unaffected, but the photosynthetic rate at high CO2 increased (S. tuberosum); (b) the initial slope decreased but the CO2-saturated rate of photosynthesis was little affected (C. album, P. vulgaris); (c) both the initial slope and the CO2-saturated rate of photosynthesis decreased (B. oleracea, S. melongena). In all five species, growth at high CO2 increased the extent to which photosynthesis was stimulated following a decrease in the partial pressure of O2 or an increase in measurement CO2 above 600 microbars. This stimulation indicates that a limitation on photosynthesis by the capacity to regenerate orthophosphate was reduced or absent after acclimation to high CO2. Leaf nitrogen per area either increased (S. tuberosum, S. melongena) or was little changed by CO2 enhancement. The content of rubisco was lower in only two of the five species, yet its activation state was 19% to 48% lower in all five species following long-term exposure to high CO2. These results indicate that during growth in CO2-enriched air, leaf rubisco content remains in excess of that required to support the observed photosynthetic rates. PMID:16666587

  2. Heat stress in grapevine: the pros and cons of acclimation.

    PubMed

    Carvalho, Luísa C; Coito, João L; Colaço, Silvana; Sangiogo, Maurício; Amâncio, Sara

    2015-04-01

    Heat stress is a major limiting factor of grapevine production and quality. Acclimation and recovery are essential to ensure plant survival, and the recovery mechanisms can be independent of the heat response mechanisms. An experimental set up with and without acclimation to heat followed by recovery [stepwise acclimation and recovery (SAR) and stepwise recovery (SR), respectively] was applied to two grapevine varieties, Touriga Nacional (TN), and Trincadeira (TR), with different tolerance to abiotic stress. Major differences were found between leaves of SAR and SR, especially after recovery; in SAR, almost all parameters returned to basal levels while in SR they remained altered. Acclimation led to a swifter and short-term antioxidative response, affecting the plant to a lesser extent than SR. Significant differences were found among varieties: upon stress, TN significantly increased ascorbate and glutathione reduction levels, boosting the cell's redox-buffering capacity, while TR needed to synthesize both metabolites, its response being insufficient to keep the redox state at working levels. TR was affected by stress for a longer period and the up-regulation pattern of antioxidative stress genes was more obvious. In TN, heat shock proteins were significantly induced, but the canonical heat-stress gene signature was not evident probably because no shutdown of the housekeeping metabolism was needed. PMID:25211707

  3. Light acclimation of photosynthesis in two closely related firs (Abies pinsapo Boiss. and Abies alba Mill.): the role of leaf anatomy and mesophyll conductance to CO2.

    PubMed

    Peguero-Pina, José Javier; Sancho-Knapik, Domingo; Flexas, Jaume; Galmés, Jeroni; Niinemets, Ülo; Gil-Pelegrín, Eustaquio

    2016-03-01

    Leaves growing in the forest understory usually present a decreased mesophyll conductance (gm) and photosynthetic capacity. The role of leaf anatomy in determining the variability in gm among species is known, but there is a lack of information on how the acclimation of gm to shade conditions is driven by changes in leaf anatomy. Within this context, we demonstrated that Abies pinsapo Boiss. experienced profound modifications in needle anatomy to drastic changes in light availability that ultimately led to differential photosynthetic performance between trees grown in the open field and in the forest understory. In contrast to A. pinsapo, its congeneric Abies alba Mill. did not show differences either in needle anatomy or in photosynthetic parameters between trees grown in the open field and in the forest understory. The increased gm values found in trees of A. pinsapo grown in the open field can be explained by occurrence of stomata at both needle sides (amphistomatous needles), increased chloroplast surface area exposed to intercellular airspace, decreased cell wall thickness and, especially, decreased chloroplast thickness. To the best of our knowledge, the role of such drastic changes in ultrastructural needle anatomy in explaining the response of gm to the light environment has not been demonstrated in field conditions. PMID:26543153

  4. Early induced protein 1 (PrELIP1) and other photosynthetic, stress and epigenetic regulation genes are involved in Pinus radiata D. don UV-B radiation response.

    PubMed

    Valledor, Luis; Cañal, María Jesús; Pascual, Jesús; Rodríguez, Roberto; Meijón, Mónica

    2012-11-01

    The continuous atmospheric and environmental deterioration is likely to increase, among others, the influx of ultraviolet B (UV-B) radiation. The plants have photoprotective responses, which are complex mechanisms involving different physiological responses, to avoid the damages caused by this radiation that may lead to plant death. We have studied the adaptive responses to UV-B in Pinus radiata, given the importance of this species in conifer forests and reforestation programs. We analyzed the photosynthetic activity, pigments content, and gene expression of candidate genes related to photosynthesis, stress and gene regulation in needles exposed to UV-B during a 96 h time course. The results reveal a clear increase of pigments under UV-B stress while photosynthetic activity decreased. The expression levels of the studied genes drastically changed after UV-B exposure, were stress related genes were upregulated while photosynthesis (RBCA and RBCS) and epigenetic regulation were downregulated (MSI1, CSDP2, SHM4). The novel gene PrELIP1, fully sequenced for this work, was upregulated and expressed mainly in the palisade parenchyma of needles. This gene has conserved domains related to the dissipation of the UV-B radiation that give to this protein a key role during photoprotection response of the needles in Pinus radiata. PMID:22471584

  5. Growth response and toxic effects of three antibiotics on Selenastrum capricornutum evaluated by photosynthetic rate and chlorophyll biosynthesis.

    PubMed

    Liu, Binyang; Liu, Weiqiu; Nie, Xiangping; Guan, Chao; Yang, Yufeng; Wang, Zhaohui; Liao, Wei

    2011-01-01

    The effects of three types of antibiotics (erythromycin, ciprofloxacin and sulfamethoxazole) on the photosynthesis of freshwater algae, Selenastrum capricornutum Printz, were investigated by determining the growth rate, chloroplast pigments content, seven main precursors (including delta-aminolevulinic acid, porphobilinogen, uroporphyrinogen III, coproporphyrinogen III, protoporphyrin IX, Mg-proporphyrin IX and protochlorophyllide), and photosynthetic rate during chlorophyll biosynthesis. The antibiotics significantly decreased the growth rate, chlorophyll content, and photosynthetic rate. Erythromycin induced a decreasing effect at a concentration of 0.06 mg/L, while ciprofloxacin and sulfamethoxazole achieved the same results at concentrations higher than 1.5 mg/L. Only erythromycin significantly inhibited chlorophyll biosynthesis, which indicated that it was considerably more toxic to S. capricornutum than ciprofloxacin and sulfamethoxazole, and may pose a high potential risk to aquatic ecosystems. PMID:22432294

  6. Are Bryophytes Shade Plants? Photosynthetic Light Responses and Proportions of Chlorophyll a, Chlorophyll b and Total Carotenoids

    PubMed Central

    MARSCHALL, MARIANN; PROCTOR, MICHAEL C. F.

    2004-01-01

    • Background and Aims Data are presented from 39 species of mosses and 16 liverworts for ratios of chlorophylls and total carotenoids, and light saturation of photosynthetic electron flow or photosynthetic CO2 uptake, in relation to the postulate that bryophyte cells in general show shade-plant characteristics. • Methods Pigment concentrations were measured by spectrophotometer in 80 % acetone extracts. Light-saturation curves were constructed by (modulated) chlorophyll florescence and for some species by infra-red gas analysis. • Key Results The pigment measurements were widely variable but broadly in line with the findings of previous authors. Median values (mosses/liverworts) were: total chlorophyll, 1·64/3·76 mg g−1; chlorophyll a : b, 2·29/1·99; chlorophylls : carotenoids, 4·74/6·75). The PPFD values at 95 % saturation (estimated from fitted curves) also ranged widely, but were almost all <1000 µmol m−2 s−1; the median for mosses was 583 and for liverworts 214 µmol m−2 s−1. The two highest PPFD95% values were from Polytrichum species with lamella systems forming a ventilated photosynthetic tissue. Total chlorophyll, chlorophyll a : b and chlorophylls : carotenoids all correlated significantly with PPFD95%. • Conclusions Bryophytes include but are not inherently shade plants. Light-saturation levels for species of open sun-exposed habitats are lower than for vascular sun plants and are probably limited by CO2 diffusion into unistratose leaves; this limit can only be exceeded by bryophytes with ventilated photosynthetic tissues which provide increased area for CO2 uptake. PMID:15319230

  7. Thermal acclimation, mitochondrial capacities and organ metabolic profiles in a reptile (Alligator mississippiensis).

    PubMed

    Guderley, Helga; Seebacher, Frank

    2011-01-01

    Reptiles thermoregulate behaviourally, but change their preferred temperature and the optimal temperature for performance seasonally. We evaluated whether the digestive and locomotor systems of the alligator show parallel metabolic adjustments during thermal acclimation. To this end, we allowed juvenile alligators to grow under thermal conditions typical of winter and summer, providing them with seasonally appropriate basking opportunities. Although mean body temperatures of alligators in these groups differed by approximately 10°C, their growth and final anatomic status was equivalent. While hepatic mitochondria isolated from cold-acclimated alligators had higher oxidative capacities at 30°C than those from warm-acclimated alligators, the capacities did not differ at 20°C. Cold acclimation decreased maximal oxidative capacities of muscle mitochondria. For mitochondria from both organs and acclimation groups, palmitate increased oligomycin-inhibited respiration. GDP addition reduced palmitate-uncoupled rates more in liver mitochondria from warm- than cold-acclimated alligators. In muscle mitochondria, carboxyatractyloside significantly reduced palmitate-uncoupled rates. This effect was not changed by thermal acclimation. The aerobic capacity of liver, skeletal muscle and duodenum, as estimated by activities of cytochrome c oxidase (COX), increased with cold acclimation. At acclimation temperatures, the activities of COX and citrate synthase (CS) in these organs were equivalent. By measuring COX and CS in isolated mitochondria and tissue extracts, we estimated that cold acclimation did not change the mitochondrial content in liver, but increased that of muscle. The thermal compensation of growth rates and of the aerobic capacity of the locomotor and digestive systems suggests that alligators optimised metabolic processes for the seasonally altered, preferred body temperature. The precision of this compensatory response exceeds that typically shown by aquatic

  8. Thermal acclimation effects differ between voluntary, maximum, and critical swimming velocities in two cyprinid fishes.

    PubMed

    O'Steen, Shyril; Bennett, Albert F

    2003-01-01

    Temperature acclimation may be a critical component of the locomotor physiology and ecology of ectothermic animals, particularly those living in eurythermal environments. Several studies of fish report striking acclimation of biochemical and kinetic properties in isolated muscle. However, the relatively few studies of whole-animal performance report variable acclimation responses. We test the hypothesis that different types of whole-animal locomotion will respond differently to temperature acclimation, probably due to divergent physiological bases of locomotion. We studied two cyprinid fishes, tinfoil barbs (Puntius schwanenfeldii) and river barbels (Barbus barbus). Study fish were acclimated to either cold or warm temperatures for at least 6 wk and then assayed at four test temperatures for three types of swimming performance. We measured voluntary swimming velocity to estimate routine locomotor behavior, maximum fast start velocity to estimate anaerobic capacity, and critical swimming velocity to estimate primarily aerobic capacity. All three performance measures showed some acute thermal dependence, generally a positive correlation between swimming speed and test temperature. However, each performance measure responded quite differently to acclimation. Critical speeds acclimated strongly, maximum speeds not at all, and voluntary speeds uniquely in each species. Thus we conclude that long-term temperature exposure can have very different consequences for different types of locomotion, consistent with our hypothesis. The data also address previous hypotheses that predict that polyploid and eurythermal fish will have greater acclimation abilities than other fish, due to increased genetic flexibility and ecological selection, respectively. Our results conflict with these predictions. River barbels are eurythermal polyploids and tinfoil barbs stenothermal diploids, yet voluntary swimming acclimated strongly in tinfoil barbs and minimally in river barbels, and

  9. Does a Low Nitrogen Supply Necessarily Lead to Acclimation of Photosynthesis to Elevated CO2?1

    PubMed Central

    Farage, Peter K.; McKee, Ian F.; Long, Steve P.

    1998-01-01

    Long-term exposure of plants to elevated partial pressures of CO2 (pCO2) often depresses photosynthetic capacity. The mechanistic basis for this photosynthetic acclimation may involve accumulation of carbohydrate and may be promoted by nutrient limitation. However, our current knowledge is inadequate for making reliable predictions concerning the onset and extent of acclimation. Many studies have sought to investigate the effects of N supply but the methodologies used generally do not allow separation of the direct effects of limited N availability from those caused by a N dilution effect due to accelerated growth at elevated pCO2. To dissociate these interactions, wheat (Triticum aestivum L.) was grown hydroponically and N was added in direct proportion to plant growth. Photosynthesis did not acclimate to elevated pCO2 even when growth was restricted by a low-N relative addition rate. Ribulose-1, 5-bisphosphate carboxylase/oxygenase activity and quantity were maintained, there was no evidence for triose phosphate limitation of photosynthesis, and tissue N content remained within the range recorded for healthy wheat plants. In contrast, wheat grown in sand culture with N supplied at a fixed concentration suffered photosynthetic acclimation at elevated pCO2 in a low-N treatment. This was accompanied by a significant reduction in the quantity of active ribulose-1, 5-bisphosphate carboxylase/oxygenase and leaf N content. PMID:9765543

  10. Photosynthetic Response of an Alpine Plant, Rhododendron delavayi Franch, to Water Stress and Recovery: The Role of Mesophyll Conductance

    PubMed Central

    Cai, Yanfei; Wang, Jihua; Li, Shifeng; Zhang, Lu; Peng, Lvchun; Xie, Weijia; Liu, Feihu

    2015-01-01

    Rhododendron delavayi Franch is an evergreen shrub or small tree with large scarlet flowers that makes it highly attractive as an ornamental species. The species is native to southwest China and southeast Asia, especially the Himalayan region, showing good adaptability, and tolerance to drought. To understand the water stress coping mechanisms of R. delavayi, we analyzed the plant's photosynthetic performance during water stress and recovery. In particular, we looked at the regulation of stomatal (gs) and mesophyll conductance (gm), and maximum rate of carboxylation (Vcmax). After 4 days of water stress treatment, the net CO2 assimilation rate (AN) declined slightly while gs and gm were not affected and stomatal limitation (SL) was therefore negligible. At this stage mesophyll conductance limitation (MCL) and biochemical limitation (BL) constituted the main limitation factors. After 8 days of water stress treatment, AN, gs, and gm had decreased notably. At this stage SL increased markedly and MCL even more so, while BL remained relatively constant. After re-watering, the recovery of AN, gs, and gm was rapid, although remaining below the levels of the control plants, while Vcmax fully regained control levels after 3 days of re-watering. MCL remained the main limitation factor irrespective of the degree of photosynthetic recovery. In conclusion, in our experiment MCL was the main photosynthetic limitation factor of R. delavayi under water stress and during the recovery phase, with the regulation of gm probably being the result of interactions between the environment and leaf anatomical features. PMID:26697043

  11. Synthesis and Photophysical Characterization of an Artificial Photosynthetic Reaction Center Exhibiting Acid-Responsive Regulation of Charge Separation

    NASA Astrophysics Data System (ADS)

    Pahk, Ian

    Non-photochemical quenching (NPQ) is a photoprotective regulatory mechanism essential to the robustness of the photosynthetic apparatus of green plants. Energy flow within the low-light adapted reaction centers is dynamically optimized to match the continuously fluctuating light conditions found in nature. Activated by compartmentalized decreases in pH resulting from photosynthetic activity during periods of elevated photon flux, NPQ induces rapid thermal dissipation of excess excitation energy that would otherwise overwhelm the apparatus's ability to consume it. Consequently, the frequency of charge separation decreases and the formation of potentially deleterious, high-energy intermediates slows, thereby reducing the threat of photodamage by disallowing their accumulation. Herein is described the synthesis and photophysical analysis of a molecular triad that mimics the effects of NPQ on charge separation within the photosynthetic reaction centers. Steady-state absorption and emission, time-resolved fluorescence, and transient absorption spectroscopies were used to demonstrate reversible quenching of the first singlet excited state affecting the quantum yield of charge separation by approximately one order of magnitude. As in the natural system, the populations of unquenched and quenched states and, therefore, the overall yields of charge separation were found to be dependent upon acid concentration.

  12. Molecular processes of transgenerational acclimation to a warming ocean

    NASA Astrophysics Data System (ADS)

    Veilleux, Heather D.; Ryu, Taewoo; Donelson, Jennifer M.; van Herwerden, Lynne; Seridi, Loqmane; Ghosheh, Yanal; Berumen, Michael L.; Leggat, William; Ravasi, Timothy; Munday, Philip L.

    2015-12-01

    Some animals have the remarkable capacity to acclimate across generations to projected future climate change; however, the underlying molecular processes are unknown. We sequenced and assembled de novo transcriptomes of adult tropical reef fish exposed developmentally or transgenerationally to projected future ocean temperatures and correlated the resulting expression profiles with acclimated metabolic traits from the same fish. We identified 69 contigs representing 53 key genes involved in thermal acclimation of aerobic capacity. Metabolic genes were among the most upregulated transgenerationally, suggesting shifts in energy production for maintaining performance at elevated temperatures. Furthermore, immune- and stress-responsive genes were upregulated transgenerationally, indicating a new complement of genes allowing the second generation of fish to better cope with elevated temperatures. Other differentially expressed genes were involved with tissue development and transcriptional regulation. Overall, we found a similar suite of differentially expressed genes among developmental and transgenerational treatments. Heat-shock protein genes were surprisingly unresponsive, indicating that short-term heat-stress responses may not be a good indicator of long-term acclimation capacity. Our results are the first to reveal the molecular processes that may enable marine fishes to adjust to a future warmer environment over multiple generations.

  13. Natural Variation of Cold Deacclimation Correlates with Variation of Cold-Acclimation of the Plastid Antioxidant System in Arabidopsis thaliana Accessions.

    PubMed

    Juszczak, Ilona; Cvetkovic, Jelena; Zuther, Ellen; Hincha, Dirk K; Baier, Margarete

    2016-01-01

    Temperature variations impact on the balance between photosynthetic electron transport and electron-consuming assimilation reactions and transiently increase generation of reactive oxygen species (ROS). Previous studies demonstrated that the expression of C-repeat binding factors (CBFs), which activate cold acclimation reactions, respond to chloroplast ROS signals and that cold deacclimation is partly halted for days after the transfer of acclimated plants to optimal growth conditions in four Arabidopsis accessions from cold-continental habitats. We hypothesized that these accessions differ from others in the regulation of the plastid antioxidant system (PAS). In the present study, we compared the expression intensity of the 12 most prominent PAS genes for peroxidases, superoxide dismutase and low molecular weight antioxidant regenerating enzymes in 10 Arabidopsis accessions with regulation of CBF and COR (cold regulated genes) transcript levels and cold-regulated metabolite levels prior to cold, after 2 week long cold acclimation and during the first 3 days of deacclimation. In the accessions with prolonged activation of cold responses, by trend, weaker induction of various cold-inducible PAS genes and stronger decreases in the expression of negatively cold-regulated PAS genes were observed. Low PAS gene expression delayed the post-cold decrease in H2O2 levels after transfer of the plants from cold to optimal growth conditions. We conclude that weaker expression of various PAS genes in the cold is an adapted strategy of the Arabidopsis accessions N14, N13, Ms-0, and Kas-1 to avoid full inactivation of cold-responses in the first days after the end of the cold period. PMID:27014325

  14. Natural Variation of Cold Deacclimation Correlates with Variation of Cold-Acclimation of the Plastid Antioxidant System in Arabidopsis thaliana Accessions

    PubMed Central

    Juszczak, Ilona; Cvetkovic, Jelena; Zuther, Ellen; Hincha, Dirk K.; Baier, Margarete

    2016-01-01

    Temperature variations impact on the balance between photosynthetic electron transport and electron-consuming assimilation reactions and transiently increase generation of reactive oxygen species (ROS). Previous studies demonstrated that the expression of C-repeat binding factors (CBFs), which activate cold acclimation reactions, respond to chloroplast ROS signals and that cold deacclimation is partly halted for days after the transfer of acclimated plants to optimal growth conditions in four Arabidopsis accessions from cold-continental habitats. We hypothesized that these accessions differ from others in the regulation of the plastid antioxidant system (PAS). In the present study, we compared the expression intensity of the 12 most prominent PAS genes for peroxidases, superoxide dismutase and low molecular weight antioxidant regenerating enzymes in 10 Arabidopsis accessions with regulation of CBF and COR (cold regulated genes) transcript levels and cold-regulated metabolite levels prior to cold, after 2 week long cold acclimation and during the first 3 days of deacclimation. In the accessions with prolonged activation of cold responses, by trend, weaker induction of various cold-inducible PAS genes and stronger decreases in the expression of negatively cold-regulated PAS genes were observed. Low PAS gene expression delayed the post-cold decrease in H2O2 levels after transfer of the plants from cold to optimal growth conditions. We conclude that weaker expression of various PAS genes in the cold is an adapted strategy of the Arabidopsis accessions N14, N13, Ms-0, and Kas-1 to avoid full inactivation of cold-responses in the first days after the end of the cold period. PMID:27014325

  15. Understanding and quantifying foliar temperature acclimation for Earth System Models

    NASA Astrophysics Data System (ADS)

    Smith, N. G.; Dukes, J.

    2015-12-01

    Photosynthesis and respiration on land are the two largest carbon fluxes between the atmosphere and Earth's surface. The parameterization of these processes represent major uncertainties in the terrestrial component of the Earth System Models used to project future climate change. Research has shown that much of this uncertainty is due to the parameterization of the temperature responses of leaf photosynthesis and autotrophic respiration, which are typically based on short-term empirical responses. Here, we show that including longer-term responses to temperature, such as temperature acclimation, can help to reduce this uncertainty and improve model performance, leading to drastic changes in future land-atmosphere carbon feedbacks across multiple models. However, these acclimation formulations have many flaws, including an underrepresentation of many important global flora. In addition, these parameterizations were done using multiple studies that employed differing methodology. As such, we used a consistent methodology to quantify the short- and long-term temperature responses of maximum Rubisco carboxylation (Vcmax), maximum rate of Ribulos-1,5-bisphosphate regeneration (Jmax), and dark respiration (Rd) in multiple species representing each of the plant functional types used in global-scale land surface models. Short-term temperature responses of each process were measured in individuals acclimated for 7 days at one of 5 temperatures (15-35°C). The comparison of short-term curves in plants acclimated to different temperatures were used to evaluate long-term responses. Our analyses indicated that the instantaneous response of each parameter was highly sensitive to the temperature at which they were acclimated. However, we found that this sensitivity was larger in species whose leaves typically experience a greater range of temperatures over the course of their lifespan. These data indicate that models using previous acclimation formulations are likely incorrectly

  16. Photosynthetic responses to water deficit in six Mediterranean sclerophyll species: possible factors explaining the declining distribution of Rhamnus ludovici-salvatoris, an endemic Balearic species.

    PubMed

    Gulías, J; Flexas, J; Abadía, A; Madrano, H

    2002-07-01

    We sought to explain the declining distribution in the Balearic Islands of the endemic shrub Rhamnus ludovici-salvatoris R. Chodat, by comparing its photosynthetic response to drought with that of several widely distributed, competing Mediterranean species (R. alaternus L., Quercus ilex L., Pistacia lentiscus L., Q. humilis Mill. and P. terebinthus L.). All of the study species, except for the two Rhamnus species, avoided desiccation by rapidly adjusting their stomatal conductance at the onset of drought, and maintaining constant leaf relative water content. The two Rhamnus species showed desiccation-tolerant behavior; i.e., as drought progressed, their predawn leaf relative water content decreased simultaneously with stomatal closure. All four desiccation-avoiding species showed a significant positive correlation between leaf thermal dissipation (estimated by the fluorescence parameter NPQ (non-photochemical quenching)) and the de-epoxidation state of the xanthophyll cycle (DPS). The two Rhamnus species exhibited maximum DPS regardless of treatment, but only R. alaternus increased NPQ in response to drought. Rhamnus ludovici-salvatoris had a high ratio of photorespiration to photosynthesis and a low intrinsic water-use efficiency; traits that are likely to be unfavorable for plant productivity under arid conditions. It also had the lowest DPS and thermal dissipation among the six species. We conclude that the photosynthetic traits of R. ludovici-salvatoris account for its limited ability to compete with other species in the Mediterranean region. PMID:12091150

  17. Optimising the acquisition and retention of heat acclimation.

    PubMed

    Daanen, H A M; Jonkman, A G; Layden, J D; Linnane, D M; Weller, A S

    2011-11-01

    Heat acclimation (HA) often starts in a moderately hot environment to prevent thermal overload and stops immediately prior to athletic activities. The aims of this study were (1) to establish whether acclimation to a moderately hot climate is sufficient to provide full acclimation for extreme heat and (2) to investigate the physiological responses to heat stress during the HA decay period. 15 male subjects exercised for 9 consecutive days at 26° C Wet Bulb Globe Temperature (WBGT) and 3 days at 32° C WBGT on a cycle ergometer for up to 2 h per day and repeated the exercise 3, 7 and 18 days later in 26° C WBGT. Rectal temperature (T (re)) and heart rate (HR) were measured during 60 min of steady state exercise (∼45% of maximum oxygen uptake). During days 1-9, end-exercise T (re) was reduced from 38.7±0.1 to a plateau of 38.2±0.1° C (p<0.05), HR was reduced from 156±10 to 131±11 bpm (p<0.05). No changes in HR and T (re) occurred during the 3 days in the very hot environment. However, T (re) during rest and exercise were significantly lower by 0.4-0.5° C after HA compared with day 9, suggesting that heat acclimation did not decay but resulted in further favourable adaptations. PMID:22052034

  18. Interference of heavy metals on the photosynthetic response from a Cr(VI)-resistant Dictyosphaerium chlorelloides strain.

    PubMed

    D'ors, A; Cortés, A A; Sánchez-Fortún, A; Bartolomé, M C; Sánchez-Fortún, S

    2016-01-01

    The successful selection of a particular type of bioelement and its association to the appropriate transducer determines the specificity of a biosensor. Therefore, from a strain of chloroficea Dictyosphaerium chlorelloides, modified in laboratory to tolerate high Cr(VI) concentrations, the possible interferences of other heavy metals on photosynthetic activity were studied. After exposing wild type and Cr(VI)-resistant cells to increasing Ag(+1), Co(+2), Hg(+2), Cr(+3), Cu(+2), Zn(+2), Fe(+3) and Cd(+2) concentrations, both photosynthetic quantum yields was compared. Photosynthetic electron transport rates were measured with a TOXY-PAM chlorophyll fluorometer, non-linear regression analysis of each of the toxicity tests was done, and means of both groups were compared using unpaired t test. The results show no significant differences between both cell types when they were exposed to Ag(+1), Co(+2), Hg(+2), Cr(+3), Cu(+2), Fe(+3) and Cd(+2) metal ions, and extremely significant differences (p < 0.0001) to Zn(+2) exposures. These results demonstrate the suitability of this Cr(VI)-resistant type D. chlorelloides strain as a suitable bioelement to be coupled to a biosensor based on dual-head microalgae strategy to detect and quantify Cr(VI) in water courses and waste water treatment plants. However, some disturbance may be expected, especially when certain analyte species such as zinc are present in water samples tested. The analysis of binary mixtures between Zn(+2) and other heavy metals showed a slight antagonistic phenomenon in all cases, which should not alter the potential Zn(+2) interference in the Cr(+6) detection process. PMID:26458928

  19. Growth and photosynthetic responses of Lemna minor L. exposed to cadmium in combination with zinc or copper.

    PubMed

    Vidaković-Cifrek, Željka; Tkalec, Mirta; Šikić, Sandra; Tolić, Sonja; Lepeduš, Hrvoje; Pevalek-Kozlina, Branka

    2015-06-01

    Metals have a variety of negative outcomes on plants, essential components of any ecosystem. The effects of CdCl2 (5 μmol L-1), ZnCl2 (25 or 50 μmol L-1), and CuCl2 (2.5 or 5 μmol L-1) and combinations of CdCl2 with either ZnCl2 or CuCl2 on the growth, photosynthetic pigments, and photosystem II (PSII) efficiency of duckweed (Lemna minor L.) were investigated. All of the treatments caused growth inhibition and remarkable metal accumulation in plant tissue after 4 and 7 days. In the combined treatments, the accumulation of each metal applied was lesser in comparison to treatments with single metals. After 4 days, all of the treatments generally diminished chlorophyll a content and decreased the maximum quantum yield (Fv/Fm) and effective quantum yield (ΔF/F'm) of PSII. However, after 7 days of exposure to a combination of Cd and Zn, pigment content and PSII activity recovered to control levels. A higher concentration of Cu (5 μmol L-1) as well as Cd in combination with Cu had a prolonged inhibitory effect on photosynthetic features. Our results suggest that growth inhibition was due to the toxic effect of absolute metal quantity in plant tissue. Zn counteracted Cd uptake, as seen from the recovery of pigment content and PSII efficiency in plants exposed for 7 days to the Cd and Zn combination. Cu-induced oxidative stress led to a prolonged inhibitory effect in plants treated both with a higher concentration of Cu (5 μmol L-1) and simultaneously with Cd and Cu. Our findings could contribute to general knowledge on anthropogenic and environmental contaminants that endanger plant communities and significantly disrupt the sensitive balance of an ecosystem by influencing photosynthetic mechanisms. PMID:26110476

  20. Synergic effect of salinity and zinc stress on growth and photosynthetic responses of the cordgrass, Spartina densiflora.

    PubMed

    Redondo-Gómez, Susana; Andrades-Moreno, Luis; Mateos-Naranjo, Enrique; Parra, Raquel; Valera-Burgos, Javier; Aroca, Ricardo

    2011-11-01

    Spartina densiflora is a C(4) halophytic species that has proved to have a high invasive potential which derives from its physiological plasticity to environmental factors, such as salinity. It is found in coastal marshes of south-west Spain, growing over sediments with between 1 mmol l(-1) and 70 mmol l(-1) zinc. A glasshouse experiment was designed to investigate the synergic effect of zinc from 0 mmol l(-1) to 60 mmol l(-1) at 0, 1, and 3% NaCl on the growth and the photosynthetic apparatus of S. densiflora by measuring chlorophyll fluorescence parameters and gas exchange, and its recovery after removing zinc. Antioxidant enzyme activities and total zinc, sodium, calcium, iron, magnesium, manganese, phosphorus, potassium, and nitrogen concentrations were also determined. Spartina densiflora showed the highest growth at 1 mmol l(-1) zinc and 1% NaCl after 90 d of treatment; this enhanced growth was supported by the measurements of net photosynthetic rate (A). Furthermore, there was a stimulatory effect of salinity on accumulation of zinc in tillers of this species. Zinc concentrations >1 mmol l(-1) reduced growth of S. densiflora, regardless of salinity treatments. This declining growth may be attributed to a decrease in A caused by diffusional limitation of photosynthesis, owing to the modification of the potassium/calcium ratio. Also, zinc and salinity had a marked overall effect on the photochemical (photosystem II) apparatus, partially mediated by the accumulation of H(2)O(2) and subsequent oxidative damage. However, salinity favoured the recovery of the photosynthetic apparatus to the toxic action of zinc, and enhanced the nutrient uptake. PMID:21841175

  1. Physiological acclimation to elevated temperature in a reef-building coral from an upwelling environment

    NASA Astrophysics Data System (ADS)

    Mayfield, A. B.; Fan, T.-Y.; Chen, C.-S.

    2013-12-01

    Recent work has found that pocilloporid corals from regions characterized by unstable temperatures, such as those exposed to periodic upwelling, display a remarkable degree of phenotypic plasticity. In order to understand whether important reef builders from these upwelling reefs remain physiologically uncompromised at temperatures they will experience in the coming decades as a result of global climate change, a long-term elevated temperature experiment was conducted with Pocillopora damicornis specimens collected from Houbihu, a small embayment within Nanwan Bay, southern Taiwan that is characterized by 8-9 °C temperature changes during upwelling events. Upon nine months of exposure to nearly 30 °C, all colony (mortality and surface area), polyp ( Symbiodinium density and chlorophyll a content), tissue (total thickness), and molecular (gene expression and molecular composition)-level parameters were documented at similar levels between experimental corals and controls incubated at 26.5 °C, suggesting that this species can readily acclimate to elevated temperatures that cause significant degrees of stress, or even bleaching and mortality, in conspecifics of other regions of the Indo-Pacific. However, the gastrodermal tissue layer was relatively thicker in corals of the high temperature treatment sampled after nine months, possibly as an adaptive response to shade Symbiodinium from the higher photosynthetically active radiation levels that they were experiencing at that sampling time. Such shading may have prevented high light and high temperature-induced photoinhibition, and consequent bleaching, in these samples.

  2. Photosynthetic response to temperature of marine phytoplankton along a latitudinal gradient (16°N to 74°N)

    NASA Astrophysics Data System (ADS)

    Li, W. K. W.

    1985-11-01

    Photosynthesis-temperature relationships for natural phytoplankton assemblages were established by measuring the uptake of H 14CO 3 in freshly collected seawater samples incubated for 2 h across a shipboard laboratory temperature gradient. The minimum, optimum and maximum temperatures for photosynthesis, as well as the extent of photosynthetic change per unit temperature change in the suboptimal range, all decreased from low to high latitude. The empirical mathematical model of RATKOWSKYet al. (1983, Journal of Bacteriology, 154, 1222-1226) provided a good fit to the data.

  3. The photosynthetic and stomatal response of Medicago sativa cv. saranac to free-air CO{sub 2} enrichment (F.A.C.E.) and nitrogen

    SciTech Connect

    Bridson, N.P.

    1996-08-01

    Plots of Medicago sativa cv. saranac were grown in the field at ambient (355 {mu}mol CO{sub 2} mol{sup -1} air) or elevated (600{mu}mol CO{sub 2} mol{sup -1} air) CO{sub 2} concentrations. High (200kg yr{sup -1}) or low (20kg yr{sup -1}) nitrogen levels were applied to two isogeneic lines, one able and one unable to use nitrogen fixing bacteria. Plants were in the second year of field growth. Exposure to elevated CO{sub 2} was via a Free-Air CO{sub 2} Enrichment System (FACE). Elevated CO{sub 2} increased diurnal assimilation by between 12% and 92%. Analysis of A/C{sub i} responses showed that effective nitrogen fertilisation was more important to rubisCO and RuBP activity than elevated CO{sub 2}. No acclimation was consistently observed. Leaves lower down the canopy were found to have lower Vc{sub max} and J{sub max} values, though age may be the cause of the latter effect. FACE conditions have only a small effect on these responses. There was some evidence found for the down-regulation of photosynthesis in the late afternoon. The FACE conditions had no affect on stomatal density but did increase epidermal cell density.

  4. Responses of the photosynthetic apparatus to winter conditions in broadleaved evergreen trees growing in warm temperate regions of Japan.

    PubMed

    Tanaka, Chizuru; Nakano, Takashi; Yamazaki, Jun-Ya; Maruta, Emiko

    2015-01-01

    Photosynthetic characteristics of two broadleaved evergreen trees, Quercus myrsinaefolia and Machilus thunbergii, were compared in autumn and winter. The irradiance was similar in both seasons, but the air temperature was lower in winter. Under the winter conditions, net photosynthesis under natural sunlight (Anet) in both species dropped to 4 μmol CO2 m(-2) s(-1), and the quantum yield of photosystem II (PSII) photochemistry in dark-adapted leaves (Fv/Fm) also dropped to 0.60. In both species the maximum carboxylation rates of Rubisco (V(cmax)) decreased, and the amount of Rubisco increased in winter. A decline in chlorophyll (Chl) concentration and an increase in the Chl a/b ratio in winter resulted in a reduction in the size of the light-harvesting antennae. From measurements of Chl a fluorescence parameters, both the relative fraction and the energy flux rates of thermal dissipation through other non-photochemical processes were markedly elevated in winter. The results indicate that the photosynthetic apparatus in broadleaved evergreen species in warm temperate regions responds to winter through regulatory mechanisms involving the downregulation of light-harvesting and photosynthesis coupled with increased photoprotective thermal energy dissipation to minimize photodamage in winter. These mechanisms aid a quick restart of photosynthesis without the development of new leaves in the following spring. PMID:25500451

  5. Changes in pools of depsidones and melanins, and their function, during growth and acclimation under contrasting natural light in the lichen Lobaria pulmonaria.

    PubMed

    McEvoy, Maria; Gauslaa, Yngvar; Solhaug, Knut Asbjørn

    2007-01-01

    This study analysed relationships between secondary chemistry, lichen growth rates and external habitat factors for two groups of UV-B-absorbing secondary compounds in the lichen Lobaria pulmonaria in order to test some hypotheses on their formation and function. Medullary depsidones and cortical melanins were quantified in thalli transplanted to three successional forest stands (shaded young forest, open old forest, sun-exposed clear-cut area) and subjected to different watering regimes (spraying with water, water + nitrogen, no spraying). Growth rates were already known. The total concentration of all seven depsidones was constant across the entire range of growth rates and sun exposures, showing that these depsidones serve functions other than photoprotection. Thalli from the well-lit transplantation sites had the highest synthesis of melanins. Within each forest type there was a trade-off between growth and melanin synthesis. Melanins and photosynthetic acclimation enhanced survival on a subsequent exposure to high light intensity, despite excessive temperatures resulting from higher absorption of solar energy in melanic thalli relative to pale thalli. In conclusion, the highly responsive melanic pigments play a photoprotective role in light acclimation, whereas the constant amount of depsidones across a wide spectrum of growth ranges and irradiances is consistent with herbivore defence functions. PMID:17587375

  6. Thermal acclimation, growth, and burst swimming of threespine stickleback: enzymatic correlates and influence of photoperiod.

    PubMed

    Guderley, H; Leroy, P H; Gagné, A

    2001-01-01

    Threespine sticklebacks (Gasterosteus aculeatus) that had been reared in the laboratory under natural photoperiods were acclimated to 23 degrees and 8 degrees C in late spring under increasing day lengths and again in late fall under decreasing day lengths. The parents of these fish were from the anadromous Isle Verte population. In the spring, cold- and warm-acclimated fish grew at the same rates and attained similar condition factors (mass L(-3)), although food intake was considerably higher at 23 degrees C. As both groups had similar increases in mass and condition, the higher axial muscle activities of citrate synthase and phosphofructokinase (measured at 20 degrees C) after cold acclimation were likely a direct response to temperature. Multiple regression analysis showed that axial muscle levels of cytochrome C oxidase and citrate synthase were correlated with the burst swimming speeds of the spring sticklebacks, while growth rates were positively correlated with lactate dehydrogenase levels in pectoral and axial muscles and creatine kinase levels in the axial muscle. In the fall, the fish in both acclimation groups grew little, although they fed at similar rates as in the spring experiment. Overall, the sticklebacks showed lower burst swimming speeds in the fall. In both spring and fall, the burst speeds of cold- and warm-acclimated sticklebacks only differed at warm temperatures. In the spring experiment, the cold-acclimated fish swam faster, whereas in the fall experiment the warm-acclimated fish swam faster despite their lower percentage of axial muscle. Swimming speeds were measured both at a fish's acclimation temperature and after 12 h at the other temperature. Cold-acclimated sticklebacks seem to have more facility in rapidly adjusting to warm temperatures when they have experienced increasing rather than decreasing day lengths, perhaps as a result of the requirements of the spring migration to the intertidal breeding grounds. PMID:11226015

  7. General patterns of acclimation of leaf respiration to elevated temperatures across biomes and plant types.

    PubMed

    Slot, Martijn; Kitajima, Kaoru

    2015-03-01

    Respiration is instrumental for survival and growth of plants, but increasing costs of maintenance processes with warming have the potential to change the balance between photosynthetic carbon uptake and respiratory carbon release from leaves. Climate warming may cause substantial increases of leaf respiratory carbon fluxes, which would further impact the carbon balance of terrestrial vegetation. However, downregulation of respiratory physiology via thermal acclimation may mitigate this impact. We have conducted a meta-analysis with data collected from 43 independent studies to assess quantitatively the thermal acclimation capacity of leaf dark respiration to warming of terrestrial plant species from across the globe. In total, 282 temperature contrasts were included in the meta-analysis, representing 103 species of forbs, graminoids, shrubs, trees and lianas native to arctic, boreal, temperate and tropical ecosystems. Acclimation to warming was found to decrease respiration at a set temperature in the majority of the observations, regardless of the biome of origin and growth form, but respiration was not completely homeostatic across temperatures in the majority of cases. Leaves that developed at a new temperature had a greater capacity for acclimation than those transferred to a new temperature. We conclude that leaf respiration of most terrestrial plants can acclimate to gradual warming, potentially reducing the magnitude of the positive feedback between climate and the carbon cycle in a warming world. More empirical data are, however, needed to improve our understanding of interspecific variation in thermal acclimation capacity, and to better predict patterns in respiratory carbon fluxes both within and across biomes in the face of ongoing global warming. PMID:25481817

  8. Photosynthetic traits of Siebold's beech seedlings in changing light conditions by removal of shading trees under elevated CO₂.

    PubMed

    Watanabe, M; Kitaoka, S; Eguchi, N; Watanabe, Y; Satomura, T; Takagi, K; Satoh, F; Koike, T

    2016-01-01

    The purpose of this study was to obtain basic information on acclimation capacity of photosynthesis in Siebold's beech seedlings to increasing light intensity under future elevated CO2 conditions. We monitored leaf photosynthetic traits of these seedlings in changing light conditions (before removal of shade trees, the year after removal of shade trees and after acclimation to open conditions) in a 10-year free air CO2 enrichment experiment in northern Japan. Elevated CO2 did not affect photosynthetic traits such as leaf mass per area, nitrogen content and biochemical photosynthetic capacity of chloroplasts (i.e. maximum rate of carboxylation and maximum rate of electron transport) before removal of the shade trees and after acclimation to open conditions; in fact, a higher net photosynthetic rate was maintained under elevated CO2 . However, in the year after removal of the shade trees, there was no increase in photosynthesis rate under elevated CO2 conditions. This was not due to photoinhibition. In ambient CO2 conditions, leaf mass per area and nitrogen content were higher in the year after removal of shade trees than before, whereas there was no increase under elevated CO2 conditions. These results indicate that elevated CO2 delays the acclimation of photosynthetic traits of Siebold's beech seedlings to increasing light intensity. PMID:26307372

  9. Response of Lemna minor L. to short-term cobalt exposure: The effect on photosynthetic electron transport chain and induction of oxidative damage.

    PubMed

    Begović, Lidija; Mlinarić, Selma; Antunović Dunić, Jasenka; Katanić, Zorana; Lončarić, Zdenko; Lepeduš, Hrvoje; Cesar, Vera

    2016-06-01

    The effect of two concentrations of cobalt (Co(2+)) on photosynthetic activity and antioxidative response in Lemna minor L. were assessed 24, 48 and 72h after the start of the exposure. Higher concentration of cobalt (1mM) induced growth inhibition while lower concentration (0.01mM) increased photosynthetic pigments content. Analysis of chlorophyll a fluorescence transients revealed high sensitivity of photosystem II primary photochemistry to excess of Co(2+) especially at the higher concentration where decreased electron transport beyond primary quinone acceptor QA(-) and impaired function of oxygen evolving complex (OEC) was observed. Due to impairment of OEC, oxygen production was decreased at higher Co(2+) concentration. Activity of superoxide dismutase was mainly inhibited while lipid peroxidation increased, at both concentrations, indicating that cobalt-induced oxidative damage after short exposure and moreover, susceptibility of the membranes in the cell to cobalt toxicity. Results obtained in this study suggest possible application of used parameters as tools in assessment of early damage caused by metals. PMID:27015565

  10. Nano-TiO2 Is Not Phytotoxic As Revealed by the Oilseed Rape Growth and Photosynthetic Apparatus Ultra-Structural Response.

    PubMed

    Li, Jun; Naeem, Muhammad Shahbaz; Wang, Xiuping; Liu, Lixin; Chen, Chang; Ma, Ni; Zhang, Chunlei

    2015-01-01

    Recently nano-materials are widely used but they have shown contrasting effects on human and plant life. Keeping in view the contrasting results, the present study has evaluated plant growth response, antioxidant system activity and photosynthetic apparatus physiological and ultrastructural changes in Brassica napus L. plants grown under a wide range (0, 500, 2500, 4000 mg/l) of nano-TiO2 in a pot experiment. Nano-TiO2 has significantly improved the morphological and physiological indices of oilseed rape plants under our experimental conditions. All the parameters i-e morphological (root length, plant height, fresh biomass), physiological (photosynthetic gas exchange, chlorophyll content, nitrate reductase activity) and antioxidant system (Superoxide dismutase, SOD; Guaiacol peroxidase, POD; Catalase, CAT) recorded have shown improvement in their performance by following nano-TiO2 dose-dependent manner. No significant chloroplast ultra-structural changes were observed. Transmission electron microscopic images have shown that intact & typical grana and stroma thylakoid membranes were in the chloroplast, which suggest that nano-TiO2 has not induced the stressful environment within chloroplast. Finally, it is suggested that, nano-TiO2 have growth promoting effect on oilseed rape plants. PMID:26624621

  11. The photosynthetic response of tobacco plants overexpressing ice plant aquaporin McMIPB to a soil water deficit and high vapor pressure deficit.

    PubMed

    Kawase, Miki; Hanba, Yuko T; Katsuhara, Maki

    2013-07-01

    We investigated the photosynthetic capacity and plant growth of tobacco plants overexpressing ice plant (Mesembryanthemum crystallinum L.) aquaporin McMIPB under (1) a well-watered growth condition, (2) a well-watered and temporal higher vapor pressure deficit (VPD) condition, and (3) a soil water deficit growth condition to investigate the effect of McMIPB on photosynthetic responses under moderate soil and atmospheric humidity and water deficit conditions. Transgenic plants showed a significantly higher photosynthesis rate (by 48 %), higher mesophyll conductance (by 52 %), and enhanced growth under the well-watered growth condition than those of control plants. Decreases in the photosynthesis rate and stomatal conductance from ambient to higher VPD were slightly higher in transgenic plants than those in control plants. When plants were grown under the soil water deficit condition, decreases in the photosynthesis rate and stomatal conductance were less significant in transgenic plants than those in control plants. McMIPB is likely to work as a CO2 transporter, as well as control the regulation of stomata to water deficits. PMID:23371744

  12. Nano-TiO2 Is Not Phytotoxic As Revealed by the Oilseed Rape Growth and Photosynthetic Apparatus Ultra-Structural Response

    PubMed Central

    Wang, Xiuping; Liu, Lixin; Chen, Chang; Ma, Ni; Zhang, Chunlei

    2015-01-01

    Recently nano-materials are widely used but they have shown contrasting effects on human and plant life. Keeping in view the contrasting results, the present study has evaluated plant growth response, antioxidant system activity and photosynthetic apparatus physiological and ultrastructural changes in Brassica napus L. plants grown under a wide range (0, 500, 2500, 4000 mg/l) of nano-TiO2 in a pot experiment. Nano-TiO2 has significantly improved the morphological and physiological indices of oilseed rape plants under our experimental conditions. All the parameters i-e morphological (root length, plant height, fresh biomass), physiological (photosynthetic gas exchange, chlorophyll content, nitrate reductase activity) and antioxidant system (Superoxide dismutase, SOD; Guaiacol peroxidase, POD; Catalase, CAT) recorded have shown improvement in their performance by following nano-TiO2 dose-dependent manner. No significant chloroplast ultra-structural changes were observed. Transmission electron microscopic images have shown that intact & typical grana and stroma thylakoid membranes were in the chloroplast, which suggest that nano-TiO2 has not induced the stressful environment within chloroplast. Finally, it is suggested that, nano-TiO2 have growth promoting effect on oilseed rape plants. PMID:26624621

  13. Ozone Exposure Response for U.S. Soybean Cultivars: Linear Reductions in Photosynthetic Potential, Biomass, and Yield1[W][OA

    PubMed Central

    Betzelberger, Amy M.; Yendrek, Craig R.; Sun, Jindong; Leisner, Courtney P.; Nelson, Randall L.; Ort, Donald R.; Ainsworth, Elizabeth A.

    2012-01-01

    Current background ozone (O3) concentrations over the northern hemisphere’s midlatitudes are high enough to damage crops and are projected to increase. Soybean (Glycine max) is particularly sensitive to O3; therefore, establishing an O3 exposure threshold for damage is critical to understanding the current and future impact of this pollutant. This study aims to determine the exposure response of soybean to elevated tropospheric O3 by measuring the agronomic, biochemical, and physiological responses of seven soybean genotypes to nine O3 concentrations (38–120 nL L−1) within a fully open-air agricultural field location across 2 years. All genotypes responded similarly, with season-long exposure to O3 causing a linear increase in antioxidant capacity while reducing leaf area, light absorption, specific leaf mass, primary metabolites, seed yield, and harvest index. Across two seasons with different temperature and rainfall patterns, there was a robust linear yield decrease of 37 to 39 kg ha−1 per nL L−1 cumulative O3 exposure over 40 nL L−1. The existence of immediate effects of O3 on photosynthesis, stomatal conductance, and photosynthetic transcript abundance before and after the initiation and termination of O3 fumigation were concurrently assessed, and there was no evidence to support an instantaneous photosynthetic response. The ability of the soybean canopy to intercept radiation, the efficiency of photosynthesis, and the harvest index were all negatively impacted by O3, suggesting that there are multiple targets for improving soybean responses to this damaging air pollutant. PMID:23037504

  14. Growth, biomass allocation and photosynthetic responses are related to intensity of root severance and soil moisture conditions in the plantation tree Cunninghamia lanceolata.

    PubMed

    Dong, Tingfa; Duan, Baoli; Zhang, Sheng; Korpelainen, Helena; Niinemets, Ülo; Li, Chunyang

    2016-07-01

    We employed the warm temperate conifer Cunninghamia lanceolata (Lamb.) Hook. as a model of plantation forest species to investigate ecophysiological responses to root treatments (control (0%), and ∼25, 50 or 75% of the initial root mass) under well-watered and water-limited conditions. Our results indicated that total root dry mass accumulation was negatively associated with the severity of root pruning, but there was evidence of multiple compensatory responses. The plants exhibited higher instantaneous and long-term (assessed by carbon isotope composition, δ(13)C) water-use efficiency in pruning treatments, especially under low water availability. Root pruning also increased the fine root/total root mass ratio, specific root length and fine root vitality in both water availability treatments. As a result of the compensatory responses, under well-watered conditions, height, stem dry mass accumulation, leaf/fine root biomass ratio (L/FR), transpiration rate, photosynthetic capacity and photosynthetic nitrogen-use efficiency (EN) were the highest under 25% pruning. Yet, all these traits except L/FR and foliage nitrogen content were severely reduced under 75% pruning. Drought negatively affected growth and leaf gas exchange rates, and there was a greater negative effect on growth, water potential, gas exchange and EN when >25% of total root biomass was removed. The stem/aboveground mass ratio was the highest under 25% pruning in both watering conditions. These results indicate that the responses to root severance are related to the excision intensity and soil moisture content. A moderate root pruning proved to be an effective means to improve stem dry mass accumulation. PMID:27122365

  15. Photosynthetic light reactions: integral to chloroplast retrograde signalling.

    PubMed

    Gollan, Peter J; Tikkanen, Mikko; Aro, Eva-Mari

    2015-10-01

    Chloroplast retrograde signalling is ultimately dependent on the function of the photosynthetic light reactions and not only guides the acclimation of the photosynthetic apparatus to changing environmental and metabolic cues, but has a much wider influence on the growth and development of plants. New information generated during the past few years about regulation of photosynthetic light reactions and identification of the underlying regulatory proteins has paved the way towards better understanding of the signalling molecules produced in chloroplasts upon changes in the environment. Likewise, the availability of various mutants lacking regulatory functions has made it possible to address the role of excitation energy distribution and electron flow in the thylakoid membrane in inducing the retrograde signals from chloroplasts to the nucleus. Such signalling molecules also induce and interact with hormonal signalling cascades to provide comprehensive information from chloroplasts to the nucleus. PMID:26318477

  16. Changes in photosynthetic yield (Fv/Fm) responses of salt-marsh microalgal communities along an osmotic gradient (Mont-Saint-Michel Bay, France)

    NASA Astrophysics Data System (ADS)

    Le Rouzic, Bertrand

    2012-12-01

    The response of salt-marsh microphytobenthic communities to daily changes is characterized by high microalgal growth rates. In comparison, the irregular tidal submersions that prevail in the extreme macrotidal system of "La Baie du Mont-Saint-Michel" (France) could be considered as a large-scale disturbance. The physiological capacities of microphytobenthic communities along a salinity gradient were assessed for rapid response to osmotic stress, salinity tolerance and changes in response to short-time submersion. The photosynthetic system response (Fv/Fm) of microphytobenthic communities sampled at different levels of the saltmarsh along a conductivity gradient was studied during spring-tide and neap-tide periods. All samples demonstrated a dominant adaptation of the microalgal community to coastal seawater salinity, but response heterogeneity ruled out euryhaline adaptation as the global response of microphytobenthic taxa. The higher and lower salinity tolerances at the seaward and uppermost stations, respectively, were probably due to the occurrence of oversalted or undersalted habitats during the neap tide period. Moreover, the seaward communities were characterized by successive stimulation and inhibition of Fv/Fm during the spring tide period. Such a phenomenon could result from the opposing influences of sea submersion, which supplies resources on the one hand and destabilizes the biofilm on the other hand. Despite the singular response of these saltmarsh microphytobenthic communities to a conductivity gradient, the rapid and irregular salinity changes due to seawater submersion cannot be considered as a stressor for the dominant taxa.

  17. Phosphoprotein SAK1 is a regulator of acclimation to singlet oxygen in Chlamydomonas reinhardtii

    PubMed Central

    Wakao, Setsuko; Chin, Brian L; Ledford, Heidi K; Dent, Rachel M; Casero, David; Pellegrini, Matteo; Merchant, Sabeeha S; Niyogi, Krishna K

    2014-01-01

    Singlet oxygen is a highly toxic and inevitable byproduct of oxygenic photosynthesis. The unicellular green alga Chlamydomonas reinhardtii is capable of acclimating specifically to singlet oxygen stress, but the retrograde signaling pathway from the chloroplast to the nucleus mediating this response is unknown. Here we describe a mutant, singlet oxygen acclimation knocked-out 1 (sak1), that lacks the acclimation response to singlet oxygen. Analysis of genome-wide changes in RNA abundance during acclimation to singlet oxygen revealed that SAK1 is a key regulator of the gene expression response during acclimation. The SAK1 gene encodes an uncharacterized protein with a domain conserved among chlorophytes and present in some bZIP transcription factors. The SAK1 protein is located in the cytosol, and it is induced and phosphorylated upon exposure to singlet oxygen, suggesting that it is a critical intermediate component of the retrograde signal transduction pathway leading to singlet oxygen acclimation. DOI: http://dx.doi.org/10.7554/eLife.02286.001 PMID:24859755

  18. Contrasting behavior of higher plant photosystem I and II antenna systems during acclimation.

    PubMed

    Ballottari, Matteo; Dall'Osto, Luca; Morosinotto, Tomas; Bassi, Roberto

    2007-03-23

    In this work we analyzed the photosynthetic apparatus in Arabidopsis thaliana plants acclimated to different light intensity and temperature conditions. Plants showed the ability to acclimate into different environments and avoid photoinhibition. When grown in high light, plants had a faster activation rate for energy dissipation (qE). This ability was correlated to higher accumulation levels of a specific photosystem II subunit, PsbS. The photosystem II antenna size was also regulated according to light exposure; smaller antenna size was observed in high light-acclimated plants with respect to low light plants. Different antenna polypeptides did not behave similarly, and Lhcb1, Lchb2, and Lhcb6 (CP24) are shown to undergo major levels of regulation, whereas Lhcb4 and Lhcb5 (CP29 and CP26) maintained their stoichiometry with respect to the reaction center in all growth conditions. The effect of acclimation on photosystem I antenna was different; in fact, the stoichiometry of any Lhca antenna proteins with respect to photosystem I core complex was not affected by growth conditions. Despite this stability in antenna stoichiometry, photosystem I light harvesting function was shown to be regulated through different mechanisms like the control of photosystem I to photosystem II ratio and the association or dissociation of Lhcb polypeptides to photosystem I. PMID:17229724

  19. Species-specific and seasonal differences in chlorophyll fluorescence and photosynthetic light response among three evergreen species in a Madrean sky island mixed conifer forest

    NASA Astrophysics Data System (ADS)

    Potts, D. L.; Minor, R. L.; Braun, Z.; Barron-Gafford, G. A.

    2012-12-01

    Unlike the snowmelt-dominated hydroclimate of more northern mountainous regions, the hydroclimate of the Madrean sky islands is characterized by snowmelt and convective storms associated with the North American Monsoon. These mid-summer storms trigger biological activity and are important drivers of primary productivity. For example, at the highest elevations where mixed conifer forests occur, ecosystem carbon balance is influenced by monsoon rains. Whereas these storms' significance is increasingly recognized at the ecosystem scale, species-specific physiological responses to the monsoon are poorly known. Prior to and following monsoon onset, we measured pre-dawn and light-adapted chlorophyll fluorescence as well as photosynthetic light response in southwestern white pine (Pinus strobiformis), ponderosa pine (Pinus ponderosa), and Douglas fir (Pseudotsuga menziesii) in a Madrean sky island mixed conifer forest near Tucson, Arizona. Photochemical quenching (qp), an indicator of the proportion of open PSII reaction centers, was greatest in P. strobiformis and least in P. menziesii and increased in response to monsoon rains (repeated-measures ANOVA; species, F2,14 = 6.17, P = 0.012; time, F2,14= 8.17, P = 0.013). In contrast, non-photochemical quenching (qN), an indicator of heat dissipation ability, was greatest in P. ponderosa and least in P. menziesii, but was not influenced by monsoon onset (repeated-measures ANOVA; species, F2,12 = 4.18, P = 0.042). Estimated from leaf area-adjusted photosynthetic light response curves, maximum photosynthetic rate (Amax) was greatest in P. ponderosa and least in P. menziesii (repeated-measures ANOVA; species, F2,8= 40.8, P = 0.001). Surprisingly, while the monsoon positively influenced Amax among P. ponderosa and P. strobiformis, Amax of P. menziesii declined with monsoon onset (repeated-measures ANOVA; species x time, F2,8 = 13.8, P = 0.002). Calculated as the initial slope of the photosynthetic light response curve, light

  20. Living in a coastal lagoon environment: photosynthetic and biochemical mechanisms of key marine macroalgae.

    PubMed

    García-Sánchez, Marta; Korbee, Nathalie; Pérez-Ruzafa, Isabel María; Marcos, Concepción; Figueroa, Félix L; Pérez-Ruzafa, Angel

    2014-10-01

    The physiological status of Cystoseira compressa, Padina pavonica and Palisada tenerrima was studied by in vivo chlorophyll fluorescence, pigment content, stoichiometry (C:N), accumulation of UV photoprotectors and antioxidant activity; comparing their photosynthetic response in a coastal lagoon (Mar Menor) and in Mediterranean coastal waters. In general, the specimens reached their highest ETRmax in spring in the Lagoon, but in summer in the Mediterranean, coinciding with their maximum biomass peak. The species exhibited a dynamic photoinhibition. Except C. compressa, they showed a lower decrease in Fv/Fm and higher recovery rates in the Mediterranean populations when exposed to high irradiance. The higher salinity and temperature of the lagoon could impair the photoprotection mechanisms. The acclimation to lagoon environments is species-specific and involves complex regulatory mechanisms. The results underline the importance of N in repair, avoidance, quenching and scavenging mechanisms. In general, Lagoon specimens showed higher pigment concentration. Although xanthophylls play important photo-protective and antioxidant roles, the observed trend is more likely to be explained by the higher temperatures reached in the lagoon compared to Mediterranean. Therefore the studied photosynthetic and biochemical mechanisms can be effective not only for high irradiance, but also for higher temperatures in a climate change scenario, but are highly dependent on nutrient availability. PMID:25164017

  1. Photosynthetic Pigments in Diatoms.

    PubMed

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

    2015-09-01

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

  2. Photosynthetic Pigments in Diatoms

    PubMed Central

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

    2015-01-01

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

  3. Photosynthetic responses of the tropical spiny shrub Lycium nodosum (Solanaceae) to drought, soil salinity and saline spray.

    PubMed

    Tezara, Wilmer; Martínez, Dayag; Rengifo, Elizabeth; Herrera, Ana

    2003-12-01

    Water relations and photosynthetic characteristics of plants of Lycium nodosum grown under increasing water deficit (WD), saline spray (SS) or saline irrigation (SI) were studied. Plants of this perennial, deciduous shrub growing in the coastal thorn scrubs of Venezuela show succulent leaves which persist for approx. 1 month after the beginning of the dry season; leaf succulence is higher in populations closer to the sea. These observations suggested that L. nodosum is tolerant both to WD and salinity. In the glasshouse, WD caused a marked decrease in the xylem water potential (psi), leaf osmotic potential (psi(s)) and relative water content (RWC) after 21 d; additionally, photosynthetic rate (A), carboxylation efficiency (CE) and stomatal conductance (gs) decreased by more than 90 %. In contrast, in plants treated for 21 d with a foliar spray with 35 per thousand NaCl or irrigation with a 10 % NaCl solution, psi and RWC remained nearly constant, while psi(s) decreased by 30 %, and A, CE and gs decreased by more than 80 %. An osmotic adjustment of 0.60 (SS) and 0.94 MPa (SI) was measured. Relative stomatal and mesophyll limitations to A increased with both WD and SS, but were not determined for SI-treated plants. No evidence of chronic photoinhibition due to any treatment was observed, since maximum quantum yield of PSII, Fv/Fm, did not change with either drought in the field or water or salinity stress in the glasshouse. Nevertheless, WD and SI treatments caused a decrease in the photochemical (qP) and an increase in the non-photochemical (qN) quenching coefficients relative to controls; qN was unaffected by the SS treatment. The occurrence of co-limitation of A by stomatal and non-stomatal factors in plants of L. nodosum may be associated with the extended leaf duration under water or saline stress. Additionally, osmotic adjustment may partly explain the relative maintenance of A and gs in the SS and SI treatments and the tolerance to salinity of plants of this

  4. The interaction among age, thermal acclimation and growth rate in determining muscle metabolic capacities and tissue masses in the threespine stickleback, Gasterosteus aculeatus.

    PubMed

    Guderley, H; Lavoie, B A; Dubois, N

    1994-11-01

    Thermal acclimation may directly modify muscle metabolic capacities, or may modify them indirectly via effects upon physiological processes such as growth, reproduction or senescence. To evaluate these interacting effects, we examined the influence of thermal acclimation and acclimatization upon muscle metabolic capacities and tissue masses in 1 + stickleback, Gasterosteus aculeatus, in which confounding interactions between temperature and senescense should be absent. Furthermore, we examined the influence of thermal acclimation upon individual growth rate, muscle enzyme levels and tissue masses in 2 + stickleback sampled at the beginning of their final reproductive season. For 1 + stickleback, cold acclimation more than doubles mitochondrial enzyme levels in the axial muscle. Thermal acclimation did not change the condition of 1 + stickleback at feeding levels which could not maintain the condition of 2+ stickleback. Compensatory metabolic responses to temperature were not apparent in field acclimatized 1 + stickleback. The growth rate of 2 + stickleback was markedly affected by temperature: warm-acclimated fish generally lost mass even at very high levels of feeding (up to 78 enchytraid worms per day) while cold-acclimated fish gained mass. This suggests that warm temperatures accelerate the senescence of 2 + stickleback. Generally, muscle enzyme activities increased with growth rate. In axial muscle, the relationships between CS activity and growth rate differed with acclimation temperature. Independent of the influence of growth rate, CS activities were consistently higher in cold- than warm-acclimated 2 + stickleback, suggesting compensatory increases of CS activity with cold acclimation. PMID:24197078

  5. The Limits of Acclimation of land plants in a Terrestrial Ecosystems Model

    NASA Astrophysics Data System (ADS)

    Kothavala, Zavareh

    2014-05-01

    In this study, we examine the role of the terrestrial carbon cycle and the ability of different plant types to acclimate to a changing climate at the centennial scale using a global ecosystems model with updated biogeochemical processes related to moisture, carbon, and nitrogen. Elevated level of atmospheric carbon dioxide (CO2) increases CO2 fertilization, resulting in more CO2 uptake by vegetation, whereas the concomitant warming increases autotrophic and heterotrophic respiration, releasing CO2 to the atmosphere. Additionally, warming will enhance photosynthesis if current temperatures are below the optimal temperature for plant growth, while it will reduce photosynthesis if current temperatures are above the optimal temperature for plant growth. We present a series of ensemble simulations to evaluate the ability of plants to acclimate to changing conditions over the last century and how this affects the terrestrial carbon sink. A set of experiments related to (a) the varying relationship between CO2 fertilization and the half saturation constant, (b) the factors related to gross primary productivity and maintenance respiration, and (c) the variables related to heterotrophic respiration, were conducted with thirteen plant functional types. The experiments were performed using the Terrestrial Ecosystem Model (TEM) with a present-day vegetation distribution without the effects of natural or human disturbance, and a closed Nitrogen cycle, at a half-degree resolution over the globe. The experiment design consisted of eight scenarios that are consistent with past and future ecosystem conditions, presented in other scientific studies. The significance of model trends related to runoff, soil moisture, soil carbon, Net Primary Productivity (NPP), crop yield, and Net Ecosystem Productivity (NEP) for different seasons, as well as surface temperature, precipitation, vapor pressure, and photosynthetically active radiation are analyzed for various ecosystems at the global

  6. From ecophysiology to phenomics: some implications of photoprotection and shade-sun acclimation in situ for dynamics of thylakoids in vitro.

    PubMed

    Matsubara, Shizue; Förster, Britta; Waterman, Melinda; Robinson, Sharon A; Pogson, Barry J; Gunning, Brian; Osmond, Barry

    2012-12-19

    Half a century of research into the physiology and biochemistry of sun-shade acclimation in diverse plants has provided reality checks for contemporary understanding of thylakoid membrane dynamics. This paper reviews recent insights into photosynthetic efficiency and photoprotection from studies of two xanthophyll cycles in old shade leaves from the inner canopy of the tropical trees Inga sapindoides and Persea americana (avocado). It then presents new physiological data from avocado on the time frames of the slow coordinated photosynthetic development of sink leaves in sunlight and on the slow renovation of photosynthetic properties in old leaves during sun to shade and shade to sun acclimation. In so doing, it grapples with issues in vivo that seem relevant to our increasingly sophisticated understanding of ΔpH-dependent, xanthophyll-pigment-stabilized non-photochemical quenching in the antenna of PSII in thylakoid membranes in vitro. PMID:23148277

  7. Photosynthetic flexibility in maize exposed to salinity and shade

    PubMed Central

    Sharwood, Robert E.; Sonawane, Balasaheb V.; Ghannoum, Oula

    2014-01-01

    C4 photosynthesis involves a close collaboration of the C3 and C4 metabolic cycles across the mesophyll and bundle-sheath cells. This study investigated the coordination of C4 photosynthesis in maize plants subjected to two salinity (50 and 100mM NaCl) treatments and one shade (20% of full sunlight) treatment. Photosynthetic efficiency was probed by combining leaf gas-exchange measurements with carbon isotope discrimination and assaying the key carboxylases [ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) and phosphoenolpyruvate carboxylase (PEPC)] and decarboxylases [nicotinamide adenine dinucleotide phosphate malic enzyme (NADP-ME) and phosphoenolpyruvate carboxykinase (PEP-CK)] operating in maize leaves. Generally, salinity inhibited plant growth and photosynthesis to a lesser extent than shade. Salinity reduced photosynthesis primarily by reducing stomatal conductance and secondarily by equally reducing Rubisco and PEPC activities; the decarboxylases were inhibited more than the carboxylases. Salinity increased photosynthetic carbon isotope discrimination (Δp) and reduced leaf dry-matter carbon isotope composition (13δ) due to changes in p i/p a (intercellular to ambient CO2 partial pressure), while CO2 leakiness out of the bundle sheath (ϕ) was similar to that in control plants. Acclimation to shade was underpinned by a greater downregulation of PEPC relative to Rubisco activity, and a lesser inhibition of NADP-ME (primary decarboxylase) relative to PEP-CK (secondary decarboxylase). Shade reduced Δp and ɸ without significantly affecting leaf 13δ or p i/p a relative to control plants. Accordingly, shade perturbed the balance between the C3 and C4 cycles during photosynthesis in maize, and demonstrated the flexible partitioning of C4 acid decarboxylation activity between NADP-ME and PEP-CK in response to the environment. This study highlights the need to improve our understanding of the links between leaf 13δ and photosynthetic Δp, and the role

  8. Growth Parameters, Photosynthetic Performance, and Biochemical Characterization of Newly Isolated Green Microalgae in Response to Culture Condition Variations.

    PubMed

    Jazzar, Souhir; Berrejeb, Nadia; Messaoud, Chokri; Marzouki, Mohamed Néjib; Smaali, Issam

    2016-08-01

    This work aimed to characterize two native microalgal strains newly isolated from South Mediterranean areas and identified as Chlorella sorokiniana ES3 and Neochloris sp. AM2. The growth properties and biochemical composition of these microalgae were evaluated in different culture media (Algal, BG-11, f/2, and Conway). Among the tested media, nitrate- and phosphate-rich Algal medium provided the maximum biomass productivities (85.5 and 111.5 mg l(-1) day(-1) for C. sorokiniana and Neochloris sp., respectively), while the nitrate- and phosphate-deficient f/2 medium resulted in the highest lipid productivities (24.1 and 35.8 mg l(-1) day(-1) for C. sorokiniana and Neochloris sp., respectively). The physiological state of both microalgae was investigated under different light and temperature levels using the pulse amplitude-modulated fluorometry. The better photosynthetic efficiency of C. sorokiniana was obtained at 23 °C with a light saturation of 156 μE m(-2) s(-1), while that of Neochloris sp. was achieved at 15 °C with a light saturation of 151 μE m(-2) s(-1). The analysis of fatty acid profile and biodiesel parameters revealed that C. sorokiniana, cultivated in Algal and f/2 media, can be considered as a suitable candidate for high-quality biodiesel production. PMID:27052210

  9. Photosynthetic and leaf water potential responses of Alnus glutinosa saplings to stem-base inoculaton with Phytophthora alni subsp. alni.

    PubMed

    Clemenz, Christian; Fleischmann, Frank; Häberle, Karl-Heinz; Matyssek, Rainer; Osswald, Wolfgang

    2008-11-01

    Three-year-old Alnus glutinosa (L.) Gaertn. (alder) saplings were single or double inoculated at the stem base with Phytophthora alni subsp. alni Brasier & S.A. Kirk under natural climatic conditions. Lesion formation on the bark showed a biphasic pattern of development, with extension occurring at a moderate rate in spring, and more rapidly during late summer. However, large variability was encountered in pathogen development within the population of infected saplings, ranging from high susceptibility to almost complete resistance. Infection resulted in severe growth retardation, and death within two years of inoculation in 75% of the saplings. During disease development, rates of transpiration and CO(2) uptake were significantly reduced. Consequently, minimum leaf water potentials were less negative in infected saplings than in control saplings. Surviving saplings matched control trees in photosynthetic capacity, transpiration rate and water potential during the second year of infection. Leaf starch concentration of infected saplings was significantly higher than in control saplings, possibly indicating that the destruction of bark tissue by the pathogen impaired phloem transport from leaves to roots. PMID:18765375

  10. Metabolic acclimation to low temperature anoxia in cereals

    SciTech Connect

    Andrews, C.J.; Hope, H.J. )

    1989-04-01

    Cold hardened seedlings of winter wheat, but not winter barley show an anaerobic acclimation response in which low temperature flooding increases the survival of plants in subsequent ice encasement at {minus}1{degrees}C. Previous flooding increases the level of total adenylates by about 40%, but the level declines throughout the ice exposure whether the plants are flooded or not. Barley shows a faster decline particularly in those plants previously flooded. ATP:ADP ratios increase, or are maintained in wheat plants briefly ice encased after flooding, but not in barley plants so treated. Activity of alcohol dehydrogenase and phosphofructokinase is higher in plants briefly ice encased after flooding indicating an increase in glycolytic rate. Winter wheat administered {sup 35}S methionine shows a change in radioactive proteins synthesized in 4 days of low temperature flooding, supporting the physiological evidence of acclimation.

  11. Interactive effects of vertical mixing, nutrients and ultraviolet radiation: in situ photosynthetic responses of phytoplankton from high mountain lakes in Southern Europe

    NASA Astrophysics Data System (ADS)

    Helbling, E. W.; Carrillo, P.; Medina-Sánchez, J. M.; Durán, C.; Herrera, G.; Villar-Argaiz, M.; Villafañe, V. E.

    2013-02-01

    Global change, together with human activities, has resulted in increasing amounts of organic material (including nutrients) that water bodies receive. This input further attenuates the penetration of solar radiation, leading to the view that opaque lakes are more "protected" from solar ultraviolet radiation (UVR) than clear ones. Vertical mixing, however, complicates this view as cells are exposed to fluctuating radiation regimes, for which the effects have, in general, been neglected. Furthermore, the combined impacts of mixing, together with those of UVR and nutrient inputs are virtually unknown. In this study, we carried out complex in situ experiments in three high mountain lakes of Spain (Lake Enol in the National Park Picos de Europa, Asturias, and lakes Las Yeguas and La Caldera in the National Park Sierra Nevada, Granada), used as model ecosystems to evaluate the joint impact of these climate change variables. The main goal of this study was to address the question of how short-term pulses of nutrient inputs, together with vertical mixing and increased UVR fluxes modify the photosynthetic responses of phytoplankton. The experimentation consisted in all possible combinations of the following treatments: (a) solar radiation: UVR + PAR (280-700 nm) versus PAR (photosynthetically active radiation) alone (400-700 nm); (b) nutrient addition (phosphorus (P) and nitrogen (N)): ambient versus addition (P to reach to a final concentration of 30 μg P L-1, and N to reach N:P molar ratio of 31); and (c) mixing: mixed (one rotation from surface to 3 m depth (speed of 1 m 4 min-1, total of 10 cycles)) versus static. Our findings suggest that under ambient nutrient conditions there is a synergistic effect between vertical mixing and UVR, increasing phytoplankton photosynthetic inhibition and excretion of organic carbon (EOC) from opaque lakes as compared to algae that received constant mean irradiance within the epilimnion. The opposite occurs in clear lakes where

  12. Cold acclimation induces distinctive changes in the chromatin state and transcript levels of COR genes in Cannabis sativa varieties with contrasting cold acclimation capacities.

    PubMed

    Mayer, Boris F; Ali-Benali, Mohamed Ali; Demone, Jordan; Bertrand, Annick; Charron, Jean-Benoit

    2015-11-01

    Little is known about the capacity of Cannabis sativa to cold-acclimate and develop freezing tolerance. This study investigates the cold acclimation (CA) capacity of nine C. sativa varieties and the underlying genetic and epigenetic responses. The varieties were divided into three groups based on their contrasting CA capacities by comparing the survival of non-acclimated and cold-acclimated plants in whole-plant freeze tests. In response to the CA treatment, all varieties accumulated soluble sugars but only the varieties with superior capacity for CA could maintain higher levels throughout the treatment. In addition, the varieties that acclimated most efficiently accumulated higher transcript levels of cold-regulated (COR) genes and genes involved in de novo DNA methylation while displaying locus- and variety-specific changes in the levels of H3K9ac, H3K27me3 and methylcytosine (MeC) during CA. Furthermore, these hardy C. sativa varieties displayed significant increases in MeC levels at COR gene loci when deacclimated, suggesting a role for locus-specific DNA methylation in deacclimation. This study uncovers the molecular mechanisms underlying CA in C. sativa and reveals higher levels of complexity regarding how genetic, epigenetic and environmental factors intertwine. PMID:25534661

  13. Cardiovascular adaptations supporting human exercise-heat acclimation.

    PubMed

    Périard, Julien D; Travers, Gavin J S; Racinais, Sébastien; Sawka, Michael N

    2016-04-01

    This review examines the cardiovascular adaptations along with total body water and plasma volume adjustments that occur in parallel with improved heat loss responses during exercise-heat acclimation. The cardiovascular system is well recognized as an important contributor to exercise-heat acclimation that acts to minimize physiological strain, reduce the risk of serious heat illness and better sustain exercise capacity. The upright posture adopted by humans during most physical activities and the large skin surface area contribute to the circulatory and blood pressure regulation challenge of simultaneously supporting skeletal muscle blood flow and dissipating heat via increased skin blood flow and sweat secretion during exercise-heat stress. Although it was traditionally held that cardiac output increased during exercise-heat stress to primarily support elevated skin blood flow requirements, recent evidence suggests that temperature-sensitive mechanisms may also mediate an elevation in skeletal muscle blood flow. The cardiovascular adaptations supporting this challenge include an increase in total body water, plasma volume expansion, better sustainment and/or elevation of stroke volume, reduction in heart rate, improvement in ventricular filling and myocardial efficiency, and enhanced skin blood flow and sweating responses. The magnitude of these adaptations is variable and dependent on several factors such as exercise intensity, duration of exposure, frequency and total number of exposures, as well as the environmental conditions (i.e. dry or humid heat) in which acclimation occurs. PMID:26905458

  14. Both Free Indole-3-Acetic Acid and Photosynthetic Performance are Important Players in the Response of Medicago truncatula to Urea and Ammonium Nutrition Under Axenic Conditions.

    PubMed

    Esteban, Raquel; Royo, Beatriz; Urarte, Estibaliz; Zamarreño, Ángel M; Garcia-Mina, José M; Moran, Jose F

    2016-01-01

    We aimed to identify the early stress response and plant performance of Medicago truncatula growing in axenic medium with ammonium or urea as the sole source of nitrogen, with respect to nitrate-based nutrition. Biomass measurements, auxin content analyses, root system architecture (RSA) response analyses, and physiological parameters were determined. Both ammonium and ureic nutrition severely affected the RSA, resulting in changes in the main elongation rate, lateral root development, and insert position from the root base. The auxin content decreased in both urea- and ammonium-treated roots; however, only the ammonium-treated plants were affected at the shoot level. The analysis of chlorophyll a fluorescence transients showed that ammonium affected photosystem II, but urea did not impair photosynthetic activity. Superoxide dismutase isoenzymes in the plastids were moderately affected by urea and ammonium in the roots. Overall, our results showed that low N doses from different sources had no remarkable effects on M. truncatula, with the exception of the differential phenotypic root response. High doses of both ammonium and urea caused great changes in plant length, auxin contents and physiological measurements. Interesting correlations were found between the shoot auxin pool and both plant length and the "performance index" parameter, which is obtained from measurements of the kinetics of chlorophyll a fluorescence. Taken together, these data demonstrate that both the indole-3-acetic acid pool and performance index are important components of the response of M. truncatula under ammonium or urea as the sole N source. PMID:26909089

  15. Both Free Indole-3-Acetic Acid and Photosynthetic Performance are Important Players in the Response of Medicago truncatula to Urea and Ammonium Nutrition Under Axenic Conditions

    PubMed Central

    Esteban, Raquel; Royo, Beatriz; Urarte, Estibaliz; Zamarreño, Ángel M.; Garcia-Mina, José M.; Moran, Jose F.

    2016-01-01

    We aimed to identify the early stress response and plant performance of Medicago truncatula growing in axenic medium with ammonium or urea as the sole source of nitrogen, with respect to nitrate-based nutrition. Biomass measurements, auxin content analyses, root system architecture (RSA) response analyses, and physiological parameters were determined. Both ammonium and ureic nutrition severely affected the RSA, resulting in changes in the main elongation rate, lateral root development, and insert position from the root base. The auxin content decreased in both urea- and ammonium-treated roots; however, only the ammonium-treated plants were affected at the shoot level. The analysis of chlorophyll a fluorescence transients showed that ammonium affected photosystem II, but urea did not impair photosynthetic activity. Superoxide dismutase isoenzymes in the plastids were moderately affected by urea and ammonium in the roots. Overall, our results showed that low N doses from different sources had no remarkable effects on M. truncatula, with the exception of the differential phenotypic root response. High doses of both ammonium and urea caused great changes in plant length, auxin contents and physiological measurements. Interesting correlations were found between the shoot auxin pool and both plant length and the “performance index” parameter, which is obtained from measurements of the kinetics of chlorophyll a fluorescence. Taken together, these data demonstrate that both the indole-3-acetic acid pool and performance index are important components of the response of M. truncatula under ammonium or urea as the sole N source. PMID:26909089

  16. Physiological and biochemical abilities of robusta coffee leaves for acclimation to cope with temporal changes in light availability.

    PubMed

    Rodríguez-López, Nelson F; Cavatte, Paulo C; Silva, Paulo E M; Martins, Samuel C V; Morais, Leandro E; Medina, Eduardo F; Damatta, Fábio M

    2013-09-01

    The effects of varying intensities of light on plants depend on when they occur, even if the total amount of light received is kept constant. We designed an experiment using two clones of robusta coffee (Coffea canephora) intercropped with shelter trees in such a way that allowed us to compare coffee bushes shaded in the morning (SM) with those shaded in the afternoon (SA), and then confronting both with bushes receiving full sunlight over the course of the day (FS). The SM bushes displayed better gas-exchange performance than their SA and FS counterparts, in which the capacity for CO2 fixation was mainly constrained by stomatal (SA bushes) and biochemical (FS bushes) factors. Physiological traits associated with light capture were more responsive to temporal fluctuations of light rather than to the amount of light received, although this behavior could be a clone-specific response. The activity of key antioxidant enzymes differed minimally when comparing the SM and SA clones, but was much larger in FS clones. No signs of photoinhibition or cell damage were found regardless of the light treatments. Acclimations to varying light supplies had no apparent additional cost for constructing and maintaining the leaves regardless of the light supply. Both the SM and SA individuals displayed higher return in terms of revenue streams (e.g. higher mass-based light-saturated photosynthetic rates, photosynthetic nitrogen use efficiencies and long-term water use efficiencies) than their FS counterparts. In conclusion, shading may improve the physiological performance of coffee bushes growing in harsh, tropical environments. PMID:23189943

  17. Boreal and temperate trees show strong acclimation of respiration to warming.

    PubMed

    Reich, Peter B; Sendall, Kerrie M; Stefanski, Artur; Wei, Xiaorong; Rich, Roy L; Montgomery, Rebecca A

    2016-03-31

    Plant respiration results in an annual flux of carbon dioxide (CO2) to the atmosphere that is six times as large as that due to the emissions from fossil fuel burning, so changes in either will impact future climate. As plant respiration responds positively to temperature, a warming world may result in additional respiratory CO2 release, and hence further atmospheric warming. Plant respiration can acclimate to altered temperatures, however, weakening the positive feedback of plant respiration to rising global air temperature, but a lack of evidence on long-term (weeks to years) acclimation to climate warming in field settings currently hinders realistic predictions of respiratory release of CO2 under future climatic conditions. Here we demonstrate strong acclimation of leaf respiration to both experimental warming and seasonal temperature variation for juveniles of ten North American tree species growing for several years in forest conditions. Plants grown and measured at 3.4 °C above ambient temperature increased leaf respiration by an average of 5% compared to plants grown and measured at ambient temperature; without acclimation, these increases would have been 23%. Thus, acclimation eliminated 80% of the expected increase in leaf respiration of non-acclimated plants. Acclimation of leaf respiration per degree temperature change was similar for experimental warming and seasonal temperature variation. Moreover, the observed increase in leaf respiration per degree increase in temperature was less than half as large as the average reported for previous studies, which were conducted largely over shorter time scales in laboratory settings. If such dampening effects of leaf thermal acclimation occur generally, the increase in respiration rates of terrestrial plants in response to climate warming may be less than predicted, and thus may not raise atmospheric CO2 concentrations as much as anticipated. PMID:26982730

  18. Short-term Cold Acclimation Recruits Brown Adipose Tissue in Obese Humans.

    PubMed

    Hanssen, Mark J W; van der Lans, Anouk A J J; Brans, Boudewijn; Hoeks, Joris; Jardon, Kelly M C; Schaart, Gert; Mottaghy, Felix M; Schrauwen, Patrick; van Marken Lichtenbelt, Wouter D

    2016-05-01

    Recruitment of brown adipose tissue (BAT) has emerged as a potential tool to combat obesity and associated metabolic complications. Short-term cold acclimation has been shown not only to enhance the presence and activity of BAT in lean humans but also to improve the metabolic profile of skeletal muscle to benefit glucose uptake in patients with type 2 diabetes. Here we examined whether short-term cold acclimation also induced such adaptations in 10 metabolically healthy obese male subjects. A 10-day cold acclimation period resulted in increased cold-induced glucose uptake in BAT, as assessed by [(18)F]fluorodeoxyglucose positron emission tomography/computed tomography. BAT activity was negatively related to age, with a similar trend for body fat percentage. In addition, cold-induced glucose uptake in BAT was positively related to glucose uptake in visceral white adipose tissue, although glucose uptake in visceral and subcutaneous white adipose tissue depots was unchanged upon cold acclimation. Cold-induced skeletal muscle glucose uptake tended to increase upon cold acclimation, which was paralleled by increased basal GLUT4 localization in the sarcolemma, as assessed through muscle biopsies. Proximal skin temperature was increased and subjective responses to cold were slightly improved at the end of the acclimation period. These metabolic adaptations to prolonged exposure to mild cold may lead to improved glucose metabolism or prevent the development of obesity-associated insulin resistance and hyperglycemia. PMID:26718499

  19. Cold acclimation alters the connective tissue content of the zebrafish (Danio rerio) heart.

    PubMed

    Johnson, Amy C; Turko, Andy J; Klaiman, Jordan M; Johnston, Elizabeth F; Gillis, Todd E

    2014-06-01

    Thermal acclimation can alter cardiac function and morphology in a number of fish species, but little is known about the regulation of these changes. The purpose of the present study was to determine how cold acclimation affects zebrafish (Danio rerio) cardiac morphology, collagen composition and connective tissue regulation. Heart volume, the thickness of the compact myocardium, collagen content and collagen fiber composition were compared between control (27°C) and cold-acclimated (20°C) zebrafish using serially sectioned hearts stained with Picrosirius Red. Collagen content and fiber composition of the pericardial membrane were also examined. Cold acclimation did not affect the volume of the contracted heart; however, there was a significant decrease in the thickness of the compact myocardium. There was also a decrease in the collagen content of the compact myocardium and in the amount of thick collagen fibers throughout the heart. Cold-acclimated zebrafish also increased expression of the gene transcript for matrix metalloproteinase 2, matrix metalloproteinase 9, tissue inhibitor of metalloproteinase 2 and collagen Type I α1. We propose that the reduction in the thickness of the compact myocardium as well as the change in collagen content may help to maintain the compliance of the ventricle as temperatures decrease. Together, these results clearly demonstrate that the zebrafish heart undergoes significant remodeling in response to cold acclimation. PMID:24577447

  20. Benefit of heat acclimation is limited by the evaporative potential when wearing chemical protective clothing.

    PubMed

    Chang, S K; Gonzalez, R R

    1999-08-01

    Heat acclimation-induced sweating responses have the potential of reducing heat strain for chemical protective garment wearers. However, this potential benefit is strongly affected by the properties of the garment. If the clothing ensemble permits sufficient evaporative heat dissipation, then heat acclimation becomes helpful in reducing heat strain. On the other hand, if the garment creates an impenetrable barrier to moisture, no benefit can be gained from heat acclimation as the additional sweating cannot be evaporated. Ten subjects were studied exercising on a treadmill while wearing two different chemical protective ensembles. Skin heat flux, skin temperature, core temperature, metabolic heat production and heart rate were measured. It was found that the benefit of heat acclimation is strongly dependent on the ability of the body to dissipate an adequate amount of heat evaporatively. The evaporative potential (EP), a measure of thermal insulation modified by moisture permeability, of the clothing ensemble offers a quantitative index useful to determine, a priori, whether heat acclimation would be helpful when wearing protective clothing system. The data show that when EP is < 15%, heat acclimation affords no benefit. An evaporative potential graph is created to aid in this determination. PMID:10504888

  1. Nitrogen assimilation and transpiration: key processes conditioning responsiveness of wheat to elevated [CO2] and temperature.

    PubMed

    Jauregui, Iván; Aroca, Ricardo; Garnica, María; Zamarreño, Ángel M; García-Mina, José M; Serret, Maria D; Parry, Martin; Irigoyen, Juan J; Aranjuelo, Iker

    2015-11-01

    Although climate scenarios have predicted an increase in [CO(2)] and temperature conditions, to date few experiments have focused on the interaction of [CO(2)] and temperature effects in wheat development. Recent evidence suggests that photosynthetic acclimation is linked to the photorespiration and N assimilation inhibition of plants exposed to elevated CO(2). The main goal of this study was to analyze the effect of interacting [CO(2)] and temperature on leaf photorespiration, C/N metabolism and N transport in wheat plants exposed to elevated [CO(2)] and temperature conditions. For this purpose, wheat plants were exposed to elevated [CO(2)] (400 vs 700 µmol mol(-1)) and temperature (ambient vs ambient + 4°C) in CO(2) gradient greenhouses during the entire life cycle. Although at the agronomic level, elevated temperature had no effect on plant biomass, physiological analyses revealed that combined elevated [CO(2)] and temperature negatively affected photosynthetic performance. The limited energy levels resulting from the reduced respiratory and photorespiration rates of such plants were apparently inadequate to sustain nitrate reductase activity. Inhibited N assimilation was associated with a strong reduction in amino acid content, conditioned leaf soluble protein content and constrained leaf N status. Therefore, the plant response to elevated [CO(2)] and elevated temperature resulted in photosynthetic acclimation. The reduction in transpiration rates induced limitations in nutrient transport in leaves of plants exposed to elevated [CO(2)] and temperature, led to mineral depletion and therefore contributed to the inhibition of photosynthetic activity. PMID:25958969

  2. Differential responses of stress proteins, antioxidant enzymes, and photosynthetic efficiency to physiological stresses in the Florida red tide dinoflagellate, Karenia brevis.

    PubMed

    Miller-Morey, Jeanine S; Van Dolah, Frances M

    2004-08-01

    This study identifies stress proteins and antioxidant enzymes that may play a role in the survival strategies of the Florida red tide dinoflagellate, Karenia brevis. Heat shock protein 60 (Hsp 60), mitochondrial small heat shock protein (mitosHsp), chloroplastic small heat shock protein (chlsHsp), Mn superoxide dismutase (SOD), and Fe SOD were first identified by Western blotting. The induction of these proteins in laboratory cultures in response to elevated temperatures, hydrogen peroxide, lead, or elevated light intensities was next assessed. In parallel, F(V)/F(M), a measurement of photosynthetic efficiency and common proxy of cellular stress, was determined. Hsp 60, Fe SOD, and Mn SOD were induced following exposure to elevated temperatures, hydrogen peroxide, or lead. MitosHsp responded only to heat, whereas chlsHsp responded only to H(2)O(2)-induced stress. The expression of stress proteins and antioxidant enzymes appears to be a more sensitive indicator of heat or chemically induced stresses than F(V)/F(M). However, F(V)/F(M) decreased significantly in response to elevated light intensities that did not induce the expression of stress proteins. These results identify for the first time stress proteins and antioxidant enzymes in K. brevis, provide evidence for differential sensitivity of cellular organelles to various sources of stress, and confirm the presence of conserved stress responses observed across phyla in a dinoflagellate. PMID:15536057

  3. Acclimation of Plant Populations to Shade: Photosynthesis, Respiration, and Carbon Use Efficiency

    NASA Technical Reports Server (NTRS)

    Frantz, Jonathan M.; Bugbee, Bruce

    2005-01-01

    Cloudy days cause an abrupt reduction in daily photosynthetic photon flux (PPF), but we have a poor understanding of how plants acclimate to this change. We used a unique lo-chamber, steady-state, gas-exchange system to continuously measure daily photosynthesis and night respiration of populations of a starch accumulator [tomato (Lycopersicone scukntum Mill. cv. Micro-Tina)] and a sucrose accumulator [lettuce (Latuca sativa L ev. Grand Rapids)] over 42 days. AI1 measurements were done at elevated CO2, (1200micr-/mol) avoid any CO2 limitations and included both shoots and roots. We integrated photosynthesis and respiration measurements separately to determine daily net carbon gain and carbon use efficiency (CUE) as the ratio of daily net C gain to total day-time C fixed over the 42-day period. After 16 to 20 days of growth in constant PPF, plants in some chambers were subjected to an abrupt PPF reduction to simulate shade or a series of cloudy days. The immediate effect and the long term acclimation rate w'ere assessed from canopy quantum yield and carbon use efficiency. The effect of shade on carbon use efficiency and acclimation was much slower than predicted by widely used growth models. It took 12 days for tomato populations to recover their original CUE and lettuce CUE never completely acclimated. Tomatoes, the starch accumulator, acclimated to low light more rapidly than lettuce, the sucrose accumulator. Plant growth models should be modified to include the photosynthesis/respiration imbalance and resulting inefficiency of carbon gain associated with changing PIT conditions on cloudy days.

  4. Zn2+-induced changes at the root level account for the increased tolerance of acclimated tobacco plants

    PubMed Central

    Bazihizina, Nadia; Taiti, Cosimo; Marti, Lucia; Rodrigo-Moreno, Ana; Spinelli, Francesco; Giordano, Cristiana; Caparrotta, Stefania; Gori, Massimo; Azzarello, Elisa; Mancuso, Stefano

    2014-01-01

    Evidence suggests that heavy-metal tolerance can be induced in plants following pre-treatment with non-toxic metal concentrations, but the results are still controversial. In the present study, tobacco plants were exposed to increasing Zn2+ concentrations (up to 250 and/or 500 μM ZnSO4) with or without a 1-week acclimation period with 30 μM ZnSO4. Elevated Zn2+ was highly toxic for plants, and after 3 weeks of treatments there was a marked (≥50%) decline in plant growth in non-acclimated plants. Plant acclimation, on the other hand, increased plant dry mass and leaf area up to 1.6-fold compared with non-acclimated ones. In non-acclimated plants, the addition of 250 μM ZnSO4 led to transient membrane depolarization and stomatal closure within 24h from the addition of the stress; by contrast, the acclimation process was associated with an improved stomatal regulation and a superior ability to maintain a negative root membrane potential, with values on average 37% more negative compared with non-acclimated plants. The different response at the plasma-membrane level between acclimated and non-acclimated plants was associated with an enhanced vacuolar Zn2+ sequestration and up to 2-fold higher expression of the tobacco orthologue of the Arabidopsis thaliana MTP1 gene. Thus, the acclimation process elicited specific detoxification mechanisms in roots that enhanced Zn2+ compartmentalization in vacuoles, thereby improving root membrane functionality and stomatal regulation in leaves following elevated Zn2+ stress. PMID:24928985

  5. Branchial ionocyte organization and ion-transport protein expression in juvenile alewives acclimated to freshwater or seawater.

    PubMed

    Christensen, A K; Hiroi, J; Schultz, E T; McCormick, S D

    2012-02-15

    The alewife (Alosa pseudoharengus) is a clupeid that undergoes larval and juvenile development in freshwater preceding marine habitation. The purpose of this study was to investigate osmoregulatory mechanisms in alewives that permit homeostasis in different salinities. To this end, we measured physiological, branchial biochemical and cellular responses in juvenile alewives acclimated to freshwater (0.5 p.p.t.) or seawater (35.0 p.p.t.). Plasma chloride concentration was higher in seawater-acclimated than freshwater-acclimated individuals (141 mmol l(-1) vs 134 mmol l(-1)), but the hematocrit remained unchanged. In seawater-acclimated individuals, branchial Na(+)/K(+)-ATPase (NKA) activity was higher by 75%. Western blot analysis indicated that the abundance of the NKA α-subunit and a Na(+)/K(+)/2Cl(-) cotransporter (NKCC1) were greater in seawater-acclimated individuals by 40% and 200%, respectively. NKA and NKCC1 were localized on the basolateral surface and tubular network of ionocytes in both acclimation groups. Immunohistochemical labeling for the cystic fibrosis transmembrane conductance regulator (CFTR) was restricted to the apical crypt of ionocytes in seawater-acclimated individuals, whereas sodium/hydrogen exchanger 3 (NHE3) labeling was present on the apical surface of ionocytes in both acclimation groups. Ionocytes were concentrated on the trailing edge of the gill filament, evenly distributed along the proximal 7