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Sample records for photosynthates

  1. Photosynthate partitioning during flowering in relation to senescence of spinach

    SciTech Connect

    Sklensky, D.; Davies, P.J. )

    1990-05-01

    Male spinach plants are frequently cited as a counter-example to the nutrient drain hypothesis. Photosynthate partitioning in both male and female plants was examined. Leaves just below the inflorescences in plants at various stages of flowering were labelled with {sup 14}CO{sub 2} and the photosynthate allowed to partition for three hours. The leaves, flowers and stems of the inflorescence, and the other above ground vegetative tissue were harvested. These parts were combusted in a sample oxidizer for the collection of the {sup 14}CO{sub 2}. Allocation to the male and female flowers at very early stages are similar. As the flowers develop further, male flowers receive more photosynthate than do female flowers in early fruit production. Thus it is possible that nutrient drain to the flowers in male spinach plants is sufficient to account for senescence.

  2. Photosynthate partitioning and nitrogen fixation of alfalfa and birdsfoot trefoil. [Lotus corniculatus L. ; Medicago sativa L

    SciTech Connect

    Shieh, W.J.

    1985-01-01

    Nodule mass and number are usually correlated with rates of nitrogen fixation in legumes. Birdsfoot trefoil (Lotus corniculatus L.) with more than twice the nodule number and mass, however, fixes far less nitrogen than alfalfa (Medicago sativa L.) at the same age. In this research, photosynthesis and photosynthate partitioning and utilization in relation to nitrogen fixation of alfalfa and birdsfoot trefoil were examined in order to determine their relationship to nitrogen fixation potential. Photosynthate to nodules was studied using /sup 14/CO/sub 2/ labeling techniques. Partitioning patterns were altered by shading and dark depletion treatments. Efficiency of photosynthate utilization was examined by determining turnover of /sup 14/C photosynthate in nodule metabolites and by studying rates of cyanide-resistant and cyanide-sensitive O/sub 2/ uptake. Alfalfa nodule activity was greater than trefoil expressed on a hole pot or nodule dry weight basis. Both shading and dark treatments significantly reduced nodule activity as estimated by the acetylene reduction assay. Shoots of both species were found to be the dominant sinks for photosynthate. Percentage /sup 14/C recovered in alfalfa roots was more than twice that of trefoil at 1,2,3,4 and 24 h after labeling. Greater relative specific radioactivity (RSA) in nodules of both species suggests that they were stronger sinks for current photosynthate than roots.

  3. Pathway and sink activity for photosynthate translocation in Pisolithus extraradical mycelium of ectomycorrhizal Pinus thunbergii seedlings.

    PubMed

    Teramoto, Munemasa; Wu, Bingyun; Hogetsu, Taizo

    2016-07-01

    The purpose of this study was to identify the pathway and sink activity of photosynthate translocation in the extraradical mycelium (ERM) of a Pisolithus isolate. We labelled ectomycorrhizal (ECM) Pinus thunbergii seedlings with (14)CO2 and followed (14)C distribution within the ERM by autoradiography. (14)C photosynthate translocation in the ERM resulted in (14)C distribution in rhizomorphs throughout the ERM, with (14)C accumulation at the front. When most radial mycelial connections between ECM root tips and the ERM front were cut, the whole allocation of (14)C photosynthates to the ERM was reduced. However, the overall pattern of (14)C distribution in the ERM was maintained even in regions immediately above and below the cut, with no local (14)C depletion or accumulation. We inferred from this result that every portion in the ERM has a significant sink activity and a definite sink capacity for photosynthates and that photosynthates detour the cut and reach throughout the ERM by translocation in every direction. Next, we prepared paired ECM seedlings, ERMs of which had been connected with each other by hyphal fusion, alongside, labelled the left seedling with (14)CO2, and shaded none, one or both of them. (14)C photosynthates were acropetally and basipetally translocated from the left ERM to ECM root tips of the right seedling through rhizomorphs in the left and right ERMs, respectively. With the left seedling illuminated, (14)C translocation from the left to the right ERM increased by shading the right seedling. This result suggests that reduced photosynthate transfer from the host to its ERM increased sink activity of the ERM. PMID:26861479

  4. Optimizing rice plant photosynthate allocation reduces N2O emissions from paddy fields.

    PubMed

    Jiang, Yu; Huang, Xiaomin; Zhang, Xin; Zhang, Xingyue; Zhang, Yi; Zheng, Chengyan; Deng, Aixing; Zhang, Jun; Wu, Lianhai; Hu, Shuijin; Zhang, Weijian

    2016-01-01

    Rice paddies are a major source of anthropogenic nitrous oxide (N2O) emissions, especially under alternate wetting-drying irrigation and high N input. Increasing photosynthate allocation to the grain in rice (Oryza sativa L.) has been identified as an effective strategy of genetic and agronomic innovation for yield enhancement; however, its impacts on N2O emissions are still unknown. We conducted three independent but complementary experiments (variety, mutant study, and spikelet clipping) to examine the impacts of rice plant photosynthate allocation on paddy N2O emissions. The three experiments showed that N2O fluxes were significantly and negatively correlated with the ratio of grain yield to total aboveground biomass, known as the harvest index (HI) in agronomy (P < 0.01). Biomass accumulation and N uptake after anthesis were significantly and positively correlated with HI (P < 0.05). Reducing photosynthate allocation to the grain by spikelet clipping significantly increased white root biomass and soil dissolved organic C and reduced plant N uptake, resulting in high soil denitrification potential (P < 0.05). Our findings demonstrate that optimizing photosynthate allocation to the grain can reduce paddy N2O emissions through decreasing belowground C input and increasing plant N uptake, suggesting the potential for genetic and agronomic efforts to produce more rice with less N2O emissions. PMID:27378420

  5. Optimizing rice plant photosynthate allocation reduces N2O emissions from paddy fields

    PubMed Central

    Jiang, Yu; Huang, Xiaomin; Zhang, Xin; Zhang, Xingyue; Zhang, Yi; Zheng, Chengyan; Deng, Aixing; Zhang, Jun; Wu, Lianhai; Hu, Shuijin; Zhang, Weijian

    2016-01-01

    Rice paddies are a major source of anthropogenic nitrous oxide (N2O) emissions, especially under alternate wetting-drying irrigation and high N input. Increasing photosynthate allocation to the grain in rice (Oryza sativa L.) has been identified as an effective strategy of genetic and agronomic innovation for yield enhancement; however, its impacts on N2O emissions are still unknown. We conducted three independent but complementary experiments (variety, mutant study, and spikelet clipping) to examine the impacts of rice plant photosynthate allocation on paddy N2O emissions. The three experiments showed that N2O fluxes were significantly and negatively correlated with the ratio of grain yield to total aboveground biomass, known as the harvest index (HI) in agronomy (P < 0.01). Biomass accumulation and N uptake after anthesis were significantly and positively correlated with HI (P < 0.05). Reducing photosynthate allocation to the grain by spikelet clipping significantly increased white root biomass and soil dissolved organic C and reduced plant N uptake, resulting in high soil denitrification potential (P < 0.05). Our findings demonstrate that optimizing photosynthate allocation to the grain can reduce paddy N2O emissions through decreasing belowground C input and increasing plant N uptake, suggesting the potential for genetic and agronomic efforts to produce more rice with less N2O emissions. PMID:27378420

  6. Optimizing rice plant photosynthate allocation reduces N2O emissions from paddy fields

    NASA Astrophysics Data System (ADS)

    Jiang, Yu; Huang, Xiaomin; Zhang, Xin; Zhang, Xingyue; Zhang, Yi; Zheng, Chengyan; Deng, Aixing; Zhang, Jun; Wu, Lianhai; Hu, Shuijin; Zhang, Weijian

    2016-07-01

    Rice paddies are a major source of anthropogenic nitrous oxide (N2O) emissions, especially under alternate wetting-drying irrigation and high N input. Increasing photosynthate allocation to the grain in rice (Oryza sativa L.) has been identified as an effective strategy of genetic and agronomic innovation for yield enhancement; however, its impacts on N2O emissions are still unknown. We conducted three independent but complementary experiments (variety, mutant study, and spikelet clipping) to examine the impacts of rice plant photosynthate allocation on paddy N2O emissions. The three experiments showed that N2O fluxes were significantly and negatively correlated with the ratio of grain yield to total aboveground biomass, known as the harvest index (HI) in agronomy (P < 0.01). Biomass accumulation and N uptake after anthesis were significantly and positively correlated with HI (P < 0.05). Reducing photosynthate allocation to the grain by spikelet clipping significantly increased white root biomass and soil dissolved organic C and reduced plant N uptake, resulting in high soil denitrification potential (P < 0.05). Our findings demonstrate that optimizing photosynthate allocation to the grain can reduce paddy N2O emissions through decreasing belowground C input and increasing plant N uptake, suggesting the potential for genetic and agronomic efforts to produce more rice with less N2O emissions.

  7. Extraction of /sup 14/C-labeled photosynthate from aquatic plants with dimethyl sulfoxide (DMSO)

    SciTech Connect

    Filbin, G.J.; Hough, R.A.

    1984-03-01

    DMSO was tested as a solvent to extract /sup 14/C-labeled photosynthate from three species of aquatic plants in photosynthesis measurements and compared with the dry oxidation method for plant radioassay. Extraction efficiency was in the range of 96-99% of fixed /sup 14/C, and precision was comparable to, or better than, that obtained with dry oxidation. The method is simple and inexpensive, and for fresh tissue the same sample extracts can be used for chlorophyll analyses.

  8. Measuring chlorophyll. cap alpha. and /sup 14/C-labeled photosynthate in aquatic angiosperms by the use of a tissue solubilizer. [/sup 14/C-labelled photosynthate

    SciTech Connect

    Beer, S.; Stewart, A.J.; Wetzel, R.G.

    1982-01-01

    A compound that quantitatively correlated with chlorophyll ..cap alpha.. could be measured fluorometrically in the extracts of leaves of three aquatic angiosperms (Myriophyllum heterophyllum Michx., Potamogeton crispus L., Elodea canadensis Michx.) treated with the tissue solubilizer BTS-450. Fluorescent characteristics of the solubilized plant tissues were stable for several weeks in the dark at temperatures up to 60/sup 0/C but rapidly degraded in sunlight or when acidified. /sup 14/C-Labeled photosynthate, which had been fixed by leaf discs during 1- to 10-hour exposure to H/sup 14/CO/sub 3/, was also readily extracted by the tissue solubilizer. Solubilizer extraction can, therefore, be used to determine both chlorophyll ..cap alpha.. content and /sup 14/C incorporation rates in the same leaf sample. The method is practical, because no grinding is required, the fluorescent characteristics of the extracts are stable, and analyses can be performed with very little plant material (about 3 milligrams).

  9. Seasonal photosynthate allocation and leaf chemistry in relation to herbivory in the coast live oak, Quercus agrifolia

    SciTech Connect

    Mauffette, Y.

    1987-01-01

    The coast live oak (Quercus agrifolia Nee) is an evergreen tree species distributed along the coastal range of California. The seasonal photosynthate allocation and leaf chemistry were studied on fifteen oak trees from spring 1982 to spring 1984. Branches of Q. agrifolia were labeled with /sup 14/CO/sub 2/ at monthly intervals, to determine photosynthate allocation to growth and to defensive compounds throughout the year. Labeled leaves were chemically analyzed to determine the activity present in various metabolic fractions (sugar, lipid, starch, phenolic, tannin, protein, organic and amino acid, and cell wall material). The utilization of photosynthate for the different chemical fractions varied during the seasons. New leaves allocated a significant proportion of carbon to phenolics early in the growing season, whereas later in the season more carbon was allocated to cell wall material. Old leaves maintained more consistent allocation patterns throughout seasons, and a large proportion of carbon was devoted to storage products.

  10. Exploring the transfer of recent plant photosynthates to soil microbes: mycorrhizal pathway vs direct root exudation

    PubMed Central

    Kaiser, Christina; Kilburn, Matt R; Clode, Peta L; Fuchslueger, Lucia; Koranda, Marianne; Cliff, John B; Solaiman, Zakaria M; Murphy, Daniel V

    2015-01-01

    Plants rapidly release photoassimilated carbon (C) to the soil via direct root exudation and associated mycorrhizal fungi, with both pathways promoting plant nutrient availability. This study aimed to explore these pathways from the root's vascular bundle to soil microbial communities. Using nanoscale secondary ion mass spectrometry (NanoSIMS) imaging and 13C-phospho- and neutral lipid fatty acids, we traced in-situ flows of recently photoassimilated C of 13CO2-exposed wheat (Triticum aestivum) through arbuscular mycorrhiza (AM) into root- and hyphae-associated soil microbial communities. Intraradical hyphae of AM fungi were significantly 13C-enriched compared to other root-cortex areas after 8 h of labelling. Immature fine root areas close to the root tip, where AM features were absent, showed signs of passive C loss and co-location of photoassimilates with nitrogen taken up from the soil solution. A significant and exclusively fresh proportion of 13C-photosynthates was delivered through the AM pathway and was utilised by different microbial groups compared to C directly released by roots. Our results indicate that a major release of recent photosynthates into soil leave plant roots via AM intraradical hyphae already upstream of passive root exudations. AM fungi may act as a rapid hub for translocating fresh plant C to soil microbes. PMID:25382456

  11. Extraction of /sup 14/C-labeled photosynthate from aquatic plants with dimethyl sulfoxide (DMSO)

    SciTech Connect

    Filbin, G.J.; Hough, R.A.

    1984-03-01

    DMSO was tested as a solvent to extract /sup 14/C-labeled photosynthate from three species of aquatic plants in photosynthesis measurements and compared with the dry oxidation method for plant radioassay. Extraction of ca. 300 mg of fresh or rehydrated dry plant tissue samples in 10 ml of reagent-grade DMSO for 8h at 65/sup 0/C resulted in a stable, nonviscous solution with excellent liquid scintillation counting characteristics. Extraction efficiency was in the range of 96-99% of fixed /sup 14/C, and precision was comparable to, or better than, that obtained with dry oxidation. The method is simple and inexpensive, and for fresh tissue the same sample extracts can be used for chlorophyll analyses.

  12. Reduced translocation of current photosynthate precedes changes in gas exchange for Quercus rubra seedlings under flooding stress.

    PubMed

    Sloan, Joshua L; Islam, M Anisul; Jacobs, Douglass F

    2016-01-01

    Northern red oak (Quercus rubra L.) seedlings are frequently planted on suboptimal sites in their native range in North America, subjecting them to environmental stresses, such as flooding, for which they may not be well adapted. Members of the genus Quercus exhibit a wide range of responses to flooding, and responses of northern red oak to flooding remain inadequately described. To better understand the physiological effects of root system inundation in post-transplant northern red oak seedlings and the effects of flooding on endogenous patterns of resource allocation within the plant, we observed the effects of short-term flooding initiated at the linear shoot growth stage on net photosynthetic rates, dark respiration, chlorophyll fluorescence (Fv/Fm) and translocation of (13)C-labeled current photosynthate. Downward translocation of current photosynthate declined after 4 days of flooding and was the first measured physiological response to flooding; net photosynthetic rates decreased and dark respiration rates increased after 7 days of flooding. Short-term flooding did not affect maximal potential efficiency of photosystem II (Fv/Fm). The finding that decreased downward translocation of (13)C-labeled current photosynthate preceded reduced net photosynthesis and increased dark respiration during flooding suggests the occurrence of sink-limited photosynthesis under these conditions. PMID:26655380

  13. Photosynthate Regulation of the Root System Architecture Mediated by the Heterotrimeric G Protein Complex in Arabidopsis

    PubMed Central

    Mudgil, Yashwanti; Karve, Abhijit; Teixeira, Paulo J. P. L.; Jiang, Kun; Tunc-Ozdemir, Meral; Jones, Alan M.

    2016-01-01

    Assimilate partitioning to the root system is a desirable developmental trait to control but little is known of the signaling pathway underlying partitioning. A null mutation in the gene encoding the Gβ subunit of the heterotrimeric G protein complex, a nexus for a variety of signaling pathways, confers altered sugar partitioning in roots. While fixed carbon rapidly reached the roots of wild type and agb1-2 mutant seedlings, agb1 roots had more of this fixed carbon in the form of glucose, fructose, and sucrose which manifested as a higher lateral root density. Upon glucose treatment, the agb1-2 mutant had abnormal gene expression in the root tip validated by transcriptome analysis. In addition, PIN2 membrane localization was altered in the agb1-2 mutant. The heterotrimeric G protein complex integrates photosynthesis-derived sugar signaling incorporating both membrane-and transcriptional-based mechanisms. The time constants for these signaling mechanisms are in the same range as photosynthate delivery to the root, raising the possibility that root cells are able to use changes in carbon fixation in real time to adjust growth behavior. PMID:27610112

  14. Distribution of current photosynthate in two Guinea grass (Panicum maximum Jacq.) cultivars.

    PubMed

    Carvalho, D D; Irving, L J; Carnevalli, R A; Hodgson, J; Matthew, C

    2006-01-01

    In a glasshouse experiment, different tiller categories (main, young primary, and old primary) of two Guinea grass cultivars, Mombaça and Tanzânia, were (14)C-labelled to investigate C translocation between tillers. In both cultivars, young primary tillers retained less radiocarbon (79%) than main (86%) and old primary (87%) labelled tillers, suggesting that the photosynthetic capacity of the young tillers exceeds their capacity either to store or use that photosynthate for growth and maintenance. In cv. Tanzânia the old primary tillers translocated more photoassimilate to their daughter tillers and to the rest of the plant than cv. Mombaça, suggesting either higher vascular connectivity between tillers or stronger diurnal fluctuations in sink-source balance in Tanzânia than Mombaça. For unlabelled tillers, specific activities were almost always higher in roots than in shoots, although total radiocarbon uptake by roots was reduced in younger tillers with low root mass. Where young primary tillers were labelled, the largest single repository of exported photoassimilate was the main tiller roots, indicating that daughter tillers may make an important contribution to the maintenance of older roots on mature tillers. PMID:16687437

  15. Photosynthate Regulation of the Root System Architecture Mediated by the Heterotrimeric G Protein Complex in Arabidopsis.

    PubMed

    Mudgil, Yashwanti; Karve, Abhijit; Teixeira, Paulo J P L; Jiang, Kun; Tunc-Ozdemir, Meral; Jones, Alan M

    2016-01-01

    Assimilate partitioning to the root system is a desirable developmental trait to control but little is known of the signaling pathway underlying partitioning. A null mutation in the gene encoding the Gβ subunit of the heterotrimeric G protein complex, a nexus for a variety of signaling pathways, confers altered sugar partitioning in roots. While fixed carbon rapidly reached the roots of wild type and agb1-2 mutant seedlings, agb1 roots had more of this fixed carbon in the form of glucose, fructose, and sucrose which manifested as a higher lateral root density. Upon glucose treatment, the agb1-2 mutant had abnormal gene expression in the root tip validated by transcriptome analysis. In addition, PIN2 membrane localization was altered in the agb1-2 mutant. The heterotrimeric G protein complex integrates photosynthesis-derived sugar signaling incorporating both membrane-and transcriptional-based mechanisms. The time constants for these signaling mechanisms are in the same range as photosynthate delivery to the root, raising the possibility that root cells are able to use changes in carbon fixation in real time to adjust growth behavior. PMID:27610112

  16. Multi-scale Geological Outcrop Visualisation: Using Gigapan and Photosynth in Fieldwork-related Geology Teaching

    NASA Astrophysics Data System (ADS)

    Stimpson, Ian; Gertisser, Ralf; Montenari, Michael; O'Driscoll, Brian

    2010-05-01

    An increasing proportion of geology (and other fieldwork-related discipline) students are mobility impaired. This is partially due to the widening access agenda and the acceptance of increased numbers of students with severe medical disabilities. In the UK, the expectation of "The Special Educational Needs and Disabilities Act (2001)" (SENDA) and "The Higher Education Quality Assurance Agency" (QAA) is that institutions should, wherever possible, provide alternative experiences where comparable opportunities are available which satisfy the learning outcomes. In order to provide this alternative experience, the ways in which students observe and learn from geology in the field need to be resembled closely by, for example, viewing outcrops at different scales and from different perspectives. Whilst a series of still images at different distances could be taken, students need to be able to decide where to look in detail and 'move around' the outcrop. The Gigapan project is a website and supporting software that allows high-resolution megapixel photographic images to be combined to make gigapixel panoramas which can then be explored at many scales by zooming and panning. Photosynth is a similar project where a number of different digital photographs are combined into a 3D model in which the user can move around. Here, we show examples of both projects, which have been successfully implemented in geology teaching related to a residential undergraduate field course to classic geological areas in Pembrokeshire, South Wales. In addition to providing an alternative learning experience for mobility-impaired students on the fieldtrip, these resources could also be used for non-impaired students where circumstances such as bad weather prevents the whole cohort from visiting a key exposure on a field course. They would also allow a 'virtual' visit of exposures that are inaccessible and may be a useful learning tool for preparing students for a forthcoming field course.

  17. Ocean acidification increases photosynthate translocation in a coral-dinoflagellates symbiosis

    NASA Astrophysics Data System (ADS)

    Tremblay, P.; Fine, M.; Maguer, J. F.; Grover, R.; Ferrier-Pagès, C.

    2013-01-01

    This study has examined the effect of an increased seawater pCO2 on the rates of photosynthesis and carbon translocation in the scleractinian coral species Stylophora pistillata using a new model based on 13C-labelling of the photosynthetic products. Symbiont photosynthesis contributes for a large part of the carbon acquisition in tropical coral species and is therefore an important process that may determine their survival under climate change scenarios. Nubbins of S. pistillata were maintained for six months under two pHs (8.1 and 7.2). Rates of photosynthesis and respiration of the symbiotic association and of isolated symbionts were assessed at each pH. The fate of 13C-photosynthates was then followed in the symbionts and the coral host for 48 h. Nubbins maintained at pH 7.2 presented a lower areal symbiont concentration, lower areal rates of gross photosynthesis, and lower carbon incorporation rates compared to nubbins maintained at pH 8.1, therefore suggesting that the total carbon acquisition was lower in this first set of nubbins. However, the total percentage of carbon translocated to the host, as well as the amount of carbon translocated per symbiont cell was significantly higher under pH 7.2 than under pH 8.1 (70% at pH 7.2 versus 60% at pH 8.1), so that the total amount of photosynthetic carbon received by the coral host was equivalent under both pHs (5.5 to 6.1 μg C cm-2 h-1). Although the carbon budget of the host was unchanged, symbionts acquired less carbon for their own needs (0.6 against 1.8 μg C cm-2 h-1), explaining the overall decrease in symbiont concentration at low pH. In the long-term, this decrease might have important consequences for the survival of corals under an acidification stress.

  18. Measuring chlorophyll a and /sup 14/C-labeled photosynthate in aquatic angiosperms by the use of a tissue solubilizer

    SciTech Connect

    Beer, S.; Stewart, A.J.; Wetzel, R.G.

    1982-01-01

    A compound that quantitatively correlated with chlorophyll a could be measured fluorometrically in the extracts of leaves of three aquatic angiosperms (Myriophyllum heterophyllum Michx., Potamogeton crispus L., Elodea canadensis Michx.) treated with the tissue solubilizer BTS-450. Fluorescent characteristics of the solubilized plant tissues were stable for several weeks in the dark at temperatures up to 60/sup 0/C but rapidly degraded in sunlight or when acidified. /sup 14/C-Labeled photosynthate, which had been fixed by leaf discs during 1- to 10-hour exposure to H/sup 14/CO/sub 3/, was also readily extracted by the tissue solubilizer. Solubilizer extraction can, therefore, be use to determine both chlorophyll a content and /sup 14/C incorporation rates in the same leaf sample. The method is practical, because no grinding is required, the fluorescent characteristics of the extracts are stable, and analyses can be performed with very little plant material (about 3 milligrams).

  19. Powerful fermentative hydrogen evolution of photosynthate in the cyanobacterium Lyngbya aestuarii BL J mediated by a bidirectional hydrogenase

    PubMed Central

    Kothari, Ankita; Parameswaran, Prathap; Garcia-Pichel, Ferran

    2014-01-01

    Cyanobacteria are considered good models for biohydrogen production because they are relatively simple organisms with a demonstrable ability to generate H2 under certain physiological conditions. However, most produce only little H2, revert readily to H2 consumption, and suffer from hydrogenase sensitivity to O2. Strains of the cyanobacteria Lyngbya aestuarii and Microcoleus chthonoplastes obtained from marine intertidal cyanobacterial mats were recently found to display much better H2 production potential. Because of their ecological origin in environments that become quickly anoxic in the dark, we hypothesized that this differential ability may have evolved to serve a role in the fermentation of the photosynthate. Here we show that, when forced to ferment internal substrate, these cyanobacteria display desirable characteristics of physiological H2 production. Among them, the strain L. aestuarii BL J had the fastest specific rates and attained the highest H2 concentrations during fermentation of photosynthate, which proceeded via a mixed acid fermentation pathway to yield acetate, ethanol, lactate, H2, CO2, and pyruvate. Contrary to expectations, the H2 yield per mole of glucose was only average compared to that of other cyanobacteria. Thermodynamic analyses point to the use of electron donors more electronegative than NAD(P)H in Lyngbya hydrogenases as the basis for its strong H2 production ability. In any event, the high specific rates and H2 concentrations coupled with the lack of reversibility of the enzyme, at the expense of internal, photosynthetically generated reductants, makes L. aestuarii BL J and/or its enzymes, a potentially feasible platform for large-scale H2 production. PMID:25540642

  20. Visualization of Uptake of Mineral Elements and the Dynamics of Photosynthates in Arabidopsis by a Newly Developed Real-Time Radioisotope Imaging System (RRIS).

    PubMed

    Sugita, Ryohei; Kobayashi, Natsuko I; Hirose, Atsushi; Saito, Takayuki; Iwata, Ren; Tanoi, Keitaro; Nakanishi, Tomoko M

    2016-04-01

    Minerals and photosynthates are essential for many plant processes, but their imaging in live plants is difficult. We have developed a method for their live imaging in Arabidopsis using a real-time radioisotope imaging system. When each radioisotope,(22)Na,(28)Mg,(32)P-phosphate,(35)S-sulfate,(42)K,(45)Ca,(54)Mn and(137)Cs, was employed as an ion tracer, ion movement from root to shoot over 24 h was clearly observed. The movements of(22)Na,(42)K,(32)P,(35)S and(137)Cs were fast so that they spread to the tip of stems. In contrast, high accumulation of(28)Mg,(45)Ca and(54)Mn was found in the basal part of the main stem. Based on this time-course analysis, the velocity of ion movement in the main stem was calculated, and found to be fastest for S and K among the ions we tested in this study. Furthermore, application of a heat-girdling treatment allowed determination of individual ion movement via xylem flow alone, excluding phloem flow, within the main stem of 43-day-old Arabidopsis inflorescences. We also successfully developed a new system for visualizing photosynthates using labeled carbon dioxide,(14)CO2 Using this system, the switching of source/sink organs and phloem flow direction could be monitored in parts of whole shoots and over time. In roots,(14)C photosynthates accumulated intensively in the growing root tip area, 200-800 µm behind the meristem. These results show that this real-time radioisotope imaging system allows visualization of many nuclides over a long time-course and thus constitutes a powerful tool for the analysis of various physiological phenomena. PMID:27016100

  1. Visualization of Uptake of Mineral Elements and the Dynamics of Photosynthates in Arabidopsis by a Newly Developed Real-Time Radioisotope Imaging System (RRIS)

    PubMed Central

    Sugita, Ryohei; Kobayashi, Natsuko I.; Hirose, Atsushi; Saito, Takayuki; Iwata, Ren; Tanoi, Keitaro; Nakanishi, Tomoko M.

    2016-01-01

    Minerals and photosynthates are essential for many plant processes, but their imaging in live plants is difficult. We have developed a method for their live imaging in Arabidopsis using a real-time radioisotope imaging system. When each radioisotope, 22Na, 28Mg, 32P-phosphate, 35S-sulfate, 42K, 45Ca, 54Mn and 137Cs, was employed as an ion tracer, ion movement from root to shoot over 24 h was clearly observed. The movements of 22Na, 42K, 32P, 35S and 137Cs were fast so that they spread to the tip of stems. In contrast, high accumulation of 28Mg, 45Ca and 54Mn was found in the basal part of the main stem. Based on this time-course analysis, the velocity of ion movement in the main stem was calculated, and found to be fastest for S and K among the ions we tested in this study. Furthermore, application of a heat-girdling treatment allowed determination of individual ion movement via xylem flow alone, excluding phloem flow, within the main stem of 43-day-old Arabidopsis inflorescences. We also successfully developed a new system for visualizing photosynthates using labeled carbon dioxide, 14CO2. Using this system, the switching of source/sink organs and phloem flow direction could be monitored in parts of whole shoots and over time. In roots, 14C photosynthates accumulated intensively in the growing root tip area, 200–800 µm behind the meristem. These results show that this real-time radioisotope imaging system allows visualization of many nuclides over a long time-course and thus constitutes a powerful tool for the analysis of various physiological phenomena. PMID:27016100

  2. Photosynthate translocation increases in response to low seawater pH in a coral-dinoflagellate symbiosis

    NASA Astrophysics Data System (ADS)

    Tremblay, P.; Fine, M.; Maguer, J. F.; Grover, R.; Ferrier-Pagès, C.

    2013-06-01

    This study has examined the effect of low seawater pH values (induced by an increased CO2 partial pressure) on the rates of photosynthesis, as well as on the carbon budget and carbon translocation in the scleractinian coral species Stylophora pistillata, using a new model based on 13C labelling of the photosynthetic products. Symbiont photosynthesis contributes to a large part of the carbon acquisition in tropical coral species, and it is thus important to know how environmental changes affect this carbon acquisition and allocation. For this purpose, nubbins of S. pistillata were maintained for six months at two pHTs (8.1 and 7.2, by bubbling seawater with CO2). The lowest pH value was used to tackle how seawater pH impacts the carbon budget of a scleractinian coral. Rates of photosynthesis and respiration of the symbiotic association and of isolated symbionts were assessed at each pH. The fate of 13C photosynthates was then followed in the symbionts and the coral host for 48 h. Nubbins maintained at pHT 7.2 presented a lower areal symbiont concentration, and lower areal rates of gross photosynthesis and carbon incorporation compared to nubbins maintained at pHT 8.1. The total carbon acquisition was thus lower under low pH. However, the total percentage of carbon translocated to the host as well as the amount of carbon translocated per symbiont cell were significantly higher under pHT 7.2 than under pHT 8.1 (70% at pHT 7.2 vs. 60% at pHT 8.1), such that the total amount of photosynthetic carbon received by the coral host was equivalent under both pHs (5.5 to 6.1 μg C cm-2 h-1). Although the carbon budget of the host was unchanged, symbionts acquired less carbon for their own needs (0.6 compared to 1.8 μg C cm-2 h-1), explaining the overall decrease in symbiont concentration at low pH. In the long term, such decrease in symbiont concentration might severely affect the carbon budget of the symbiotic association.

  3. Net assimilation and photosynthate allocation of Populus clones grown under short-rotation intensive culture: Physiological and genetic responses regulating yield

    SciTech Connect

    Dickmann, D.I.; Pregitzer, K.S.; Nguyen, P.V.

    1996-08-01

    The overall objective of this project was to determine the differential responses of poplar clones from sections Tacamahaca and Aigeiros of the genus Populus to varying levels of applied water and nitrogen. Above- and below-ground phenology and morphology, photosynthate allocation, and physiological processes were examined. By manipulating the availability of soil resources, we have been able to separate inherent clonal differences from plastic responses, and to determine genotype-environment interactions. We also have been able to make some contrasts between trees grown from hardwood cuttings and coppice sprouts. Our overall hypothesis was that carbon allocation during growth is greatly influenced by interactions among moisture, nitrogen, and genotype, and that these interactions greatly influence yield in short-rotation plantations. As is true of any project, some of our original expectations were not realized, whereas other initially unforeseen results were obtained. The reduced funding from the Biofuels Feedstock Development Program (BFDP) during the last few years of the project slowed us down to some extent, so progress was not been as rapid as we might have hoped. The major problem associated with this funding shortfall was the inability to employ skilled and unskilled student labor. Nonetheless, we were able to accomplish most of our original goals. All of the principal investigators on this project feel that we have made progress in advancing the scientific underpinning of short-rotation woody biomass production.

  4. Carbon and oxygen isotope working standards from C3 and C4 photosynthates.

    PubMed

    Spangenberg, Jorge E

    2006-09-01

    A preparation of organic working standards for the online measurement of 13C/12C and 18O/16O ratios in biological material is presented. The organic working standards are simple and inexpensive C3 and C4 carbohydrates (sugars or cellulose) from distinct geographic origin, including white sugar, toilet and XEROX papers from Switzerland, maize from Ivory Coast, cane sugar from Brazil, papyrus from Egypt, and the core of the stem of a Cyperus papyrus plant from Kenya. These photosynthetic products were compared with International Atomic Energy standards CH-3 and CH-6 and other calibration materials. The presented working standards cover a 15% range of 13C/12C ratios and 9% for 18O/16O, with a precision<+/-0.2% for n>10. PMID:16870558

  5. Autotrophic carbon budget in coral tissue: a new 13C-based model of photosynthate translocation.

    PubMed

    Tremblay, Pascale; Grover, Renaud; Maguer, Jean François; Legendre, Louis; Ferrier-Pagès, Christine

    2012-04-15

    Corals live in symbiosis with dinoflagellates of the genus Symbiodinum. These dinoflagellates translocate a large part of the photosynthetically fixed carbon to the host, which in turn uses it for its own needs. Assessing the carbon budget in coral tissue is a central question in reef studies that still vexes ecophysiologists. The amount of carbon fixed by the symbiotic association can be determined by measuring the rate of photosynthesis, but the amount of carbon translocated by the symbionts to the host and the fate of this carbon are more difficult to assess. In the present study, we propose a novel approach to calculate the budget of autotrophic carbon in the tissue of scleractinian corals, based on a new model and measurements made with the stable isotope (13)C. Colonies of the scleractinian coral Stylophora pistillata were incubated in H(13)CO (-)(3)-enriched seawater, after which the fate of (13)C was followed in the symbionts, the coral tissue and the released particulate organic carbon (i.e. mucus). Results obtained showed that after 15 min, ca. 60% of the carbon fixed was already translocated to the host, and after 48 h, this value reached 78%. However, ca. 48% of the photosynthetically fixed carbon was respired by the symbiotic association, and 28% was released as dissolved organic carbon. This is different from other coral species, where <1% of the total organic carbon released is from newly fixed carbon. Only 23% of the initially fixed carbon was retained in the symbionts and coral tissue after 48 h. Results show that our (13)C-based model could successfully trace the carbon flow from the symbionts to the host, and the photosynthetically acquired carbon lost from the symbiotic association. PMID:22442377

  6. Nodule activity and allocation of photosynthate of soybean during recovery from water stress

    NASA Technical Reports Server (NTRS)

    Fellows, R. J.; Patterson, R. P.; Raper, C. D. Jr; Harris, D.; Raper CD, J. r. (Principal Investigator)

    1987-01-01

    Nodulated soybean plants (Glycine max [L.] Merr. cv Ransom) in a growth-chamber study were subjected to a leaf water potential (psi w) of -2.0 megapascal during vegetative growth. Changes in nonstructural carbohydrate contents of leaves, stems, roots, and nodules, allocation of dry matter among plant parts, in situ specific nodule activity, and in situ canopy apparent photosynthetic rate were measured in stressed and nonstressed plants during a 7-day period following rewatering. Leaf and nodule psi w also were determined. At the time of maximum stress, concentration of nonstructural carbohydrates had declined in leaves of stressed, relative to nonstressed, plants, and the concentration of nonstructural carbohydrates had increased in stems, roots, and nodules. Sucrose concentrations in roots and nodules of stressed plants were 1.5 and 3 times greater, respectively, than those of nonstressed plants. Within 12 hours after rewatering, leaf and nodule psi w of stressed plants had returned to values of nonstressed plants. Canopy apparent photosynthesis and specific nodule activity of stressed plants recovered to levels for nonstressed plants within 2 days after rewatering. The elevated sucrose concentrations in roots and nodules of stressed plants also declined rapidly upon rehydration. The increase in sucrose concentration in nodules, as well as the increase of carbohydrates in roots and stems, during water stress and the rapid disappearance upon rewatering indicates that inhibition of carbohydrate utilization within the nodule may be associated with loss of nodule activity. Availability of carbohydrates within the nodules and from photosynthetic activity following rehydration of nodules may mediate the rate of recovery of N2-fixation activity.

  7. Photosynthate Metabolism in the Source Leaves of N2-Fixing Soybean Plants

    PubMed Central

    de Veau, Edward J. I.; Robinson, J. Michael; Warmbrodt, Robert D.; Kremer, Diane F.

    1992-01-01

    Soybean plants (Glycine max [L.] Merr. cv Williams), which were symbiotic with Bradyrhizobium japonicum, and which grew well upon reduced nitrogen supplied solely through N2 fixation processes, often exhibited excess accumulation of starch and sucrose and diminished soluble protein in their source leaves. Nitrate and ammonia, when supplied to the nodulated roots of N2-fixing plants, mediated a reduction of foliar starch accumulation and a corresponding increase in soluble protein in the source leaves. This provided an opportunity to examine the potential metabolic adjustments by which NO3− and NH4+ (N) sufficiency or deficiency exerted an influence upon soybean leaf starch synthesis. When compared with soybean plants supplied with N, elevated starch accumulation was focused in leaf palisade parenchyma tissue of N2-fixing plants. Foliar activities of starch synthesis pathway enzymes including fructose-1,6-bisphosphate phosphatase, phosphohexoisomerase, phosphoglucomutase (PGM), as well as adenosine diphosphate glucose pyrophosphorylase (in some leaves) exhibited highest activities in leaf extracts of N2-fixing plants when expressed on a leaf protein basis. This was interpreted to mean that there was an adaptation of these enzyme activities in the leaves of N2-fixing plants, and this contributed to an increase in starch accumulation. Another major causal factor associated with increased starch accumulation was the elevation in foliar levels of fructose-6-phosphate, glucose-6-phosphate, and glucose-1-phosphate (G1P), which had risen to chloroplast concentrations considerably in excess of the Km values for their respective target enzymes associated with starch synthesis, e.g. elevated G1P with respect to adenosine diphosphate glucose pyrophosphorylase (ADPG-PPiase) binding sites. The cofactor glucose-1,6-bisphosphate (G1,6BP) was found to be obligate for maximal PGM activity in soybean leaf extracts of N2-fixing as well as N-supplemented plants, and G1,6BP levels in N2-fixing plant leaves was twice that of levels in N-supplied treatments. However the concentration of chloroplastic G1,6BP in illuminated leaves was computed to be saturating with respect to PGM in both N2-fixing and N-supplemented plants. This suggested that the higher level of this cofactor in N2-fixing plant leaves did not confer any higher PGM activation and was not a factor in higher starch synthesis rates. Relative to plants supplied with NO3− and NH4+, the source leaf glycerate-3-phosphate (3-PGA) and orthophosphate (Pi) concentrations in leaves of N2-fixing plants were two to four times higher. Although Pi is a physiological competitive inhibitor of leaf chloroplast ADPG-PPiase, and hence, starch synthesis, elevated chloroplast 3-PGA levels in N2-fixing plant leaves apparently prevented interference of Pi with ADPG-PPiase catalysis and starch synthesis. ImagesFigure 2 PMID:16668977

  8. COMPARISON OF SEASONAL PATTERNS OF PHOTOSYNTHATE PRODUCTION AND USE IN BRANCHES OF RED SPRUCE AT TWO ELEVATIONS

    EPA Science Inventory

    Seasonal patterns of carbon transport from 14C-labeled foliage were examined in red spruce (Picea rubens Sarg.) branches at 1935 and 1720m elevations in the Great Smoky Mountains National Park to characterize possible physiological mechanisms underlying the observed reductions in...

  9. Interactions Between Ring Nematodes (Mesocriconema xenoplax) and Arbuscular Mycorrhizal Fungi (AMF) in Grape Roots: Competition for Photosynthate?

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A reduction of arbuscules in roots of grapevines (Vitis vinifera) observed when ring nematodes were added to field microplots led to the hypothesis that nematode feeding suppresses AMF by competing for root carbohydrates. This hypothesis was tested by growing 'Pinot noir' grapevines in a factorial e...

  10. Systemic Signaling and Local Sensing of Phosphate in Common Bean: Cross-Talk Between Photosynthate and MicroRNA399

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Shoot-to-root communication is crucial for plant adaptation to phosphorus (P) deficiency. Both sugars and miRNAs have been implicated as potential signal molecules transported through phloem from shoot to root for the regulation of gene expression and Pi uptake in the root. By studying the expressio...

  11. Low phosphorus tolerance mechanisms: phosphorus recycling and photosynthate partitioning in the tropical forage grass, Brachiaria hybrid cultivar Mulato compared with rice.

    PubMed

    Nanamori, Masahito; Shinano, Takuro; Wasaki, Jun; Yamamura, Takuya; Rao, Idupulapati M; Osaki, Mitsuru

    2004-04-01

    The Brachiaria hybrid cv. Mulato is well adapted to low-fertility acid soils deficient in phosphorus (P). To study the grassy forage's mechanisms for tolerating low P supply, we compared it with rice (Oryza sativa L. cv. Kitaake). We tested by using nutrient solution cultures, and quantified the effects of P deficiency on the enzymatic activities of phosphohydrolases and on carbon metabolism in P-deficient leaves. While P deficiency markedly induced activity of phosphohydrolases in both crops, the ratio of inorganic phosphorus to total P in leaves was greater in Brachiaria hybrid. Phosphorus deficiency in leaves also markedly influenced the partitioning of carbon in both crops. In the Brachiaria hybrid, compared with rice, the smaller proportion of (14)C partitioned into sugars and the larger proportion into amino acids and organic acids in leaves coincided with decreased levels of sucrose and starch. Hence, in P-deficient leaves of the Brachiaria hybrid, triose-P was metabolized into amino acids or organic acids. Results thus indicate that the Brachiaria hybrid, compared with rice, tolerates low P supply to leaves by enhancing sugar catabolism and by inducing the activity of several phosphohydrolases. This apparently causes rapid P turnover and enables the Brachiaria hybrid to use P more efficiently. PMID:15111721

  12. Arabidopsis Type I Proton-Pumping Pyrophosphatase Expresses Strongly in Phloem, Where It Is Required for Pyrophosphate Metabolism and Photosynthate Partitioning1[OPEN

    PubMed Central

    Pizzio, Gaston A.; Paez-Valencia, Julio; Khadilkar, Aswad S.; Regmi, Kamesh; Patron-Soberano, Araceli; Zhang, Shangji; Sanchez-Lares, Jonathan; Furstenau, Tara; Li, Jisheng; Sanchez-Gomez, Concepcion; Valencia-Mayoral, Pedro; Yadav, Umesh P.; Ayre, Brian G.; Gaxiola, Roberto A.

    2015-01-01

    Phloem loading is a critical process in plant physiology. The potential of regulating the translocation of photoassimilates from source to sink tissues represents an opportunity to increase crop yield. Pyrophosphate homeostasis is crucial for normal phloem function in apoplasmic loaders. The involvement of Arabidopsis (Arabidopsis thaliana) type I proton-pumping pyrophosphatase (AVP1) in phloem loading was analyzed at genetic, histochemical, and physiological levels. A transcriptional AVP1 promoter::GUS fusion revealed phloem activity in source leaves. Ubiquitous AVP1 overexpression (35S::AVP1 cassette) enhanced shoot biomass, photoassimilate production and transport, rhizosphere acidification, and expression of sugar-induced root ion transporter genes (POTASSIUM TRANSPORTER2 [KUP2], NITRATE TRANSPORTER2.1 [NRT2.1], NRT2.4, and PHOSPHATE TRANSPORTER1.4 [PHT1.4]). Phloem-specific AVP1 overexpression (Commelina Yellow Mottle Virus promoter [pCOYMV]::AVP1) elicited similar phenotypes. By contrast, phloem-specific AVP1 knockdown (pCoYMV::RNAiAVP1) resulted in stunted seedlings in sucrose-deprived medium. We also present a promoter mutant avp1-2 (SALK046492) with a 70% reduction of expression that did not show severe growth impairment. Interestingly, AVP1 protein in this mutant is prominent in the phloem. Moreover, expression of an Escherichia coli-soluble pyrophosphatase in the phloem (pCoYMV::pyrophosphatase) of avp1-2 plants resulted in severe dwarf phenotype and abnormal leaf morphology. We conclude that the Proton-Pumping Pyrophosphatase AVP1 localized at the plasma membrane of the sieve element-companion cell complexes functions as a synthase, and that this activity is critical for the maintenance of pyrophosphate homeostasis required for phloem function. PMID:25681328

  13. Short-term natural δ13C variations in pools and fluxes in a beech forest: the transfer of isotopic signal from recent photosynthates to soil respired CO2

    NASA Astrophysics Data System (ADS)

    Gavrichkova, O.; Proietti, S.; Moscatello, S.; Portarena, S.; Battistelli, A.; Matteucci, G.; Brugnoli, E.

    2011-03-01

    The fate of photosynthetic products within the plant-soil continuum determines how long the reduced carbon resides within the ecosystem and when it returns back to the atmosphere in the form of respiratory CO2. We have tested the possibility of measuring natural variation in δ13C to disentangle potential times needed to transfer carbohydrates produced by photosynthesis down to roots and, in general, to belowground up to its further release in the form of soil respiration into the atmosphere in a beech (Fagus sylvatica) forest. For these purposes we have measured the variation in stable carbon and oxygen isotope compositions in plant material and in soil respired CO2 every three hours for three consequent days. Possible steps and different signs of post-photosynthetic fractionation during carbon translocation were also identified. A 12 h-periodicity was observed for variation in δ13C in soluble sugars in the top crown leaves and it can be explained by starch day/night dynamics in synthesis and breakdown and by stomatal limitations under elevated vapour pressure deficits. Photosynthetic products were transported down the trunk and mixed with older carbon pools, therefore causing the dampening of the δ13C signal variation. The strongest periodicity of 24 h was found in δ13C in soil respiration indicating changes in root contribution to the total CO2 efflux. Nevertheless, it was possible to identify the speed of carbon translocation through the plant-soil continuum. A period of 24 h was needed to transfer the C assimilated by photosynthesis from the top crown leaves to the tree trunk at breast height and additional 3 h for further respiration of that C by roots and soil microorganisms and its to subsequent diffusion back to the atmosphere.

  14. Short-term natural δ13C and δ18O variations in pools and fluxes in a beech forest: the transfer of isotopic signal from recent photosynthates to soil respired CO2

    NASA Astrophysics Data System (ADS)

    Gavrichkova, O.; Proietti, S.; Moscatello, S.; Portarena, S.; Battistelli, A.; Matteucci, G.; Brugnoli, E.

    2011-10-01

    The fate of photosynthetic products within the plant-soil continuum determines how long the reduced carbon resides within the ecosystem and when it returns back to the atmosphere in the form of respiratory CO2. We have tested the possibility of measuring natural variation in δ13C and δ18O to disentangle the potential times needed to transfer carbohydrates produced by photosynthesis down to trunk, roots and, in general, to belowground up to its further release in the form of soil respiration into the atmosphere in a beech (Fagus sylvatica) forest. We have measured the variation in stable carbon and oxygen isotope compositions in plant material and in soil respired CO2 every three hours for three consecutive days. Possible steps and different signs of post-photosynthetic fractionation during carbon translocation were also identified. A 12 h-periodicity was observed for variation in δ13C in soluble sugars in the top crown leaves and it can be explained by starch day/night dynamics in synthesis and breakdown and by stomatal limitations under elevated vapour pressure deficits. Photosynthetic products were transported down the trunk and mixed with older carbon pools, therefore causing the dampening of the δ13C signal variation. The strongest periodicity of 24 h was found in δ13C in soil respiration indicating changes in root contribution to the total CO2 efflux. Other non-biological causes like diffusion fractionation and advection induced by gas withdrawn from the measurement chamber complicate data interpretation on this step of C transfer path. Nevertheless, it was possible to identify the speed of carbohydrates' translocation from the point of assimilation to the trunk breast height because leaf-imprinted enrichment of δ18O in soluble sugars was less modified along the downward transport and was well related to environmental parameters potentially linked to stomatal conductance. The speed of carbohydrates translocation from the site of assimilation to the trunk at breast height was estimated to be in the range of 0.3-0.4 m h-1.

  15. Girdling and summer pruning in apple increase soil respiration

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The root system of plants derives all its energy from photosynthate translocated from the canopy to the root system. Canopy manipulations that alter either the rate of canopy photosynthesis or the translocation of photosynthate are expected to alter dry matter partitioning to the root system. Fiel...

  16. Canopy sink-source partitioning influences root/soil respiration in apple

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The root system of plants derives all its energy from photosynthate translocated from the canopy to the root system. Canopy manipulations that alter either the rate of canopy photosynthesis or the translocation of photosynthate are expected to alter dry matter partitioning to the root system. Fiel...

  17. Increasing tomato fruit quality by enhancing fruit chloroplast function. A double-edged sword?

    PubMed

    Cocaliadis, Maria Florencia; Fernández-Muñoz, Rafael; Pons, Clara; Orzaez, Diego; Granell, Antonio

    2014-08-01

    Fruits are generally regarded as photosynthate sinks as they rely on energy provided by sugars transported from leaves to carry out the highly demanding processes of development and ripening; eventually these imported photosynthates also contribute to the fruit organoleptic properties. Three recent reports have revealed, however, that transcriptional factors enhancing chloroplast development in fruit may result in higher contents not only of tomato fruit-specialized metabolites but also of sugars. In addition to suggesting new ways to improve fruit quality by fortifying fruit chloroplasts and plastids, these results prompted us to re-evaluate the importance of the contribution of chloroplasts/photosynthesis to fruit development and ripening. PMID:24723405

  18. Differential Growth and Carbohydrate Usage in Switchgrass Ecotypes under Suboptimal Temperatures

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Switchgrass (Panicum virgatum L.), a warm-season C4 grass, shows good potential as a bioenergy feedstock and is widely adapted throughout North America, but its productivity tends to decline with increasing latitude. Little is known about whether genetic potential exists in switchgrass to photosynth...

  19. Examining the Role of Multiple Carbon Sources in Isoprene Synthesis in Plants Using Stable Isotope Techniques

    NASA Astrophysics Data System (ADS)

    Funk, J. L.; Mak, J. E.; Lerdau, M. T.

    2001-12-01

    The carbon source for phytogenc isoprene is an issue with important ramifications for both atmospheric and biological science because of its impact on the isotopic signature of isoprene and its oxidation products and because it lends insight into the function that isoprene serves within leaves. Although recently assimilated carbon is believed to be the primary carbon source for isoprene production in plants, variation in diurnal and seasonal isoprene fluxes that cannot be explained by temperature, light, and leaf development have led to the suggestion that alternative carbon sources may contribute. Stable isotopes of carbon can be used to identify changes in carbon partitioning into isoprene synthesis, and mixing models can assess the relative importance of each source. In preliminary studies, we document an additional 8-10 \\permil discrimination in isoprene emitted in the absence of photosynthesis. This change in signature suggests that the carbon source is switched from recently obtained photosynthate to a source more depleted in 13C. We propose that intermediates from carbohydrate degradation and/or re-fixation of CO2 from mitichondrial respiration and photorespiration can contribute to isoprene production. In addition, we expect alternative carbon sources to be most important when photosynthate is limiting (e.g. during water stress events). Photosynthesis, respiration, and isoprene emission measurements are used to calculate the isotopic signatures of the three potential carbon pools: photosynthate derived from ambient CO2, photosynthate derived from respired CO2, and carbohydrate-derived intermediates.

  20. Unraveling the complex trait of harvest index with association mapping in rice (Oryza sativa L.)

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Harvest index is a measure of success in partitioning assimilated photosynthate. An improvement of harvest index means an increase of economic portion of the plants. Our objective was to identify the markers associated with harvest index and its correlated traits using 203 O. sativa accessions. The ...

  1. Modelling C3 photosynthesis from the chloroplast to the ecosystem

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Globally, photosynthesis accounts for the largest flux of CO2 from the atmosphere into ecosystems and is the driving process for terrestrial ecosystem function. The importance of accurate predictions of photosynthesis over a range of plant growth conditions led to the development of a C3 photosynthe...

  2. Seasonal patterns in above ground growth and nut abortion in young eastern black walnut trees in Midwestern United States

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Eastern black walnut (EBW) is an excellent choice for agroforestry practices in the eastern United States because of its value for nuts and timber. There appears to be competing sinks for photosynthate in young trees early in the growing season; however growth data to support such a hypothesis are l...

  3. Seasonal patterns in above ground growth and nut abortion in seedling trees of eastern black walnut (Juglans nigra, L.) in Midwestern United States

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Eastern black walnut (EBW) is an excellent choice for agroforestry practices in the eastern United States, because of its value for nuts and timber. There appears to be competing sinks for photosynthate in young trees early in the growing season; however growth data to support such a hypothesis are ...

  4. Analysis of soybean leaf metabolism and seed coat transcriptome reveal sink strength is maintained under abiotic stress conditions

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The seed coat is a vital tissue for directing the flow of photosynthate from source leaves to the embryo and cotyledons during seed development. By forming a sucrose gradient, the seed coat promotes transport of sugars from source leaves to seeds, thereby establishing sink strength. Understanding th...

  5. How Do Fruits Ripen?

    ERIC Educational Resources Information Center

    Sargent, Steven A.

    2005-01-01

    A fruit is alive, and for it to ripen normally, many biochemical reactions must occur in a proper order. After pollination, proper nutrition, growing conditions, and certain plant hormones cause the fruit to develop and grow to proper size. During this time, fruits store energy in the form of starch and sugars, called photosynthates because they…

  6. Effects of defoliation and shading on the physiological cost of reproduction in silky locoweed Oxytropis sericea

    PubMed Central

    Ida, Takashi Y.; Harder, Lawrence D.; Kudo, Gaku

    2012-01-01

    Background The production of flowers, fruits and seeds demands considerable energy and nutrients, which can limit the allocation of these resources to other plant functions and, thereby, influence survival and future reproduction. The magnitude of the physiological costs of reproduction depends on both the factors limiting seed production (pollen, ovules or resources) and the capacity of plants to compensate for high resource demand. Methods To assess the magnitude and consequences of reproductive costs, we used shading and defoliation to reduce photosynthate production by fully pollinated plants of a perennial legume, Oxytropis sericea (Fabaceae), and examined the resulting impact on photosynthate allocation, and nectar, fruit and seed production. Key Results Although these leaf manipulations reduced photosynthesis and nectar production, they did not alter photosynthate allocation, as revealed by 13C tracing, or fruit or seed production. That photosynthate allocation to reproductive organs increased >190 % and taproot mass declined by 29 % between flowering and fruiting indicates that reproduction was physiologically costly. Conclusions The insensitivity of fruit and seed production to leaf manipulation is consistent with either compensatory mobilization of stored resources or ovule limitation. Seed production differed considerably between the two years of the study in association with contrasting precipitation prior to flowering, perhaps reflecting contrasting limits on reproductive performance. PMID:22021817

  7. 1-methylcyclopropene (1-MCP)-induced alteration in leaf photosynthetic rate, chlorophyll fluorescence, respiration and membrane damage in rice (Oryza sativa L.) under high night temperature

    Technology Transfer Automated Retrieval System (TEKTRAN)

    High night temperature (HNT) can induce ethylene-triggered reactive oxygen species production, which can cause premature leaf senescence and membrane damage, thereby affecting production, consumption and transfer of photosynthates, and yield. The 1-methylcyclopropene (1-MCP) can competitively bind w...

  8. Discoveries in oxygenic photosynthesis (1727-2003): a perspective.

    PubMed

    Govindjee; Krogmann, David

    2004-01-01

    We present historic discoveries and important observations, related to oxygenic photosynthesis, from 1727 to 2003. The decision to include certain discoveries while omitting others has been difficult. We are aware that ours is an incomplete timeline. In part, this is because the function of this list is to complement, not duplicate, the listing of discoveries in the other papers in these history issues of Photosynthesis Research. In addition, no one can know everything that is in the extensive literature in the field. Furthermore, any judgement about significance presupposes a point of view. This history begins with the observation of the English clergyman Stephen Hales (1677-1761) that plants derive nourishment from the air; it includes the definitive experiments in the 1960-1965 period establishing the two-photosystem and two-light reaction scheme of oxygenic photosynthesis; and includes the near-atomic resolution of the structures of the reaction centers of these two Photosystems, I and II, obtained in 2001-2002 by a team in Berlin, Germany, coordinated by Horst Witt and Wolfgang Saenger. Readers are directed to historical papers in Govindjee and Gest [(2002a) Photosynth Res 73: 1-308], in Govindjee, J. Thomas Beatty and Howard Gest [(2003a) Photosynth Res 76: 1-462], and to other papers in this issue for a more complete picture. Several photographs are provided here. Their selection is based partly on their availability to the authors (see Figures 1-15). Readers may view other photographs in Part 1 (Volume 73, Photosynth Res, 2002), Part 2 (Volume 76, Photosynth Res, 2003) and Part 3 (Volume 80 Photosynth Res, 2004) of the history issues of Photosynthesis Research. Photographs of most of the Nobel-laureates are included in Govindjee, Thomas Beatty and John Allen, this issue. For a complementary time line of anoxygenic photosynthesis, see H. Gest and R. Blankenship (this issue). PMID:16328809

  9. Nitrogen fixation in peanut nodules during dark periods and detopped conditions with special reference to lipid bodies

    SciTech Connect

    Siddique, A.M.; Bal, A.K. )

    1991-03-01

    The peanut plant (Arachis hypogaea L.), unlike other known legumes, can sustain nitrogen fixation when prolonged periods of darkness or detopping curtail the supply of photosynthate to the nodule. This ability to withstand photosynthate stress is attributed to the presence of lipid bodies in infected nodule cells. In both dark-treated and detopped plants, the lipid bodies show a gradual decrease in numbers, suggesting their utilization as a source of energy and carbon for nitrogen fixation. Lipolytic activity can be localized in the lipid bodies, and the existence of {beta}-oxidation pathway and glyoxylate cycle is shown by the release of {sup 14}CO{sub 2} from {sup 14}C lineoleoyl coenzyme A by the nodule homogenate.

  10. Anoxic carbon flux in photosynthetic microbial mats as revealed by metatranscriptomics

    PubMed Central

    Burow, Luke C; Woebken, Dagmar; Marshall, Ian PG; Lindquist, Erika A; Bebout, Brad M; Prufert-Bebout, Leslie; Hoehler, Tori M; Tringe, Susannah G; Pett-Ridge, Jennifer; Weber, Peter K; Spormann, Alfred M; Singer, Steven W

    2013-01-01

    Photosynthetic microbial mats possess extraordinary phylogenetic and functional diversity that makes linking specific pathways with individual microbial populations a daunting task. Close metabolic and spatial relationships between Cyanobacteria and Chloroflexi have previously been observed in diverse microbial mats. Here, we report that an expressed metabolic pathway for the anoxic catabolism of photosynthate involving Cyanobacteria and Chloroflexi in microbial mats can be reconstructed through metatranscriptomic sequencing of mats collected at Elkhorn Slough, Monterey Bay, CA, USA. In this reconstruction, Microcoleus spp., the most abundant cyanobacterial group in the mats, ferment photosynthate to organic acids, CO2 and H2 through multiple pathways, and an uncultivated lineage of the Chloroflexi take up these organic acids to store carbon as polyhydroxyalkanoates. The metabolic reconstruction is consistent with metabolite measurements and single cell microbial imaging with fluorescence in situ hybridization and NanoSIMS. PMID:23190731

  11. Anoxic carbon flux in photosynthetic microbial mats as revealed by metatranscriptomics.

    PubMed

    Burow, Luke C; Woebken, Dagmar; Marshall, Ian P G; Lindquist, Erika A; Bebout, Brad M; Prufert-Bebout, Leslie; Hoehler, Tori M; Tringe, Susannah G; Pett-Ridge, Jennifer; Weber, Peter K; Spormann, Alfred M; Singer, Steven W

    2013-04-01

    Photosynthetic microbial mats possess extraordinary phylogenetic and functional diversity that makes linking specific pathways with individual microbial populations a daunting task. Close metabolic and spatial relationships between Cyanobacteria and Chloroflexi have previously been observed in diverse microbial mats. Here, we report that an expressed metabolic pathway for the anoxic catabolism of photosynthate involving Cyanobacteria and Chloroflexi in microbial mats can be reconstructed through metatranscriptomic sequencing of mats collected at Elkhorn Slough, Monterey Bay, CA, USA. In this reconstruction, Microcoleus spp., the most abundant cyanobacterial group in the mats, ferment photosynthate to organic acids, CO2 and H2 through multiple pathways, and an uncultivated lineage of the Chloroflexi take up these organic acids to store carbon as polyhydroxyalkanoates. The metabolic reconstruction is consistent with metabolite measurements and single cell microbial imaging with fluorescence in situ hybridization and NanoSIMS. PMID:23190731

  12. Explorations of mechanisms regulating ectomycorrhizal colonization of boron-fertilized pine

    SciTech Connect

    Garrett, H.E.; Begonia, G.; Sword, M.A.

    1989-01-01

    The present study examined the effects of foliar boron fertilization and inoculation with an ectomycorrhizal fungus (Pisolithus tinctorius) on {sup 14}C-photosynthate partitioning to various tissues of shortleaf pine seedlings, placing special emphasis on the {sup 14}C distribution to the root systems. Specifically, the hypotheses tested are: (a) {sup 14}C allocation to the root systems will increase with inoculation, and (b) {sup 14}C partitioning will be enhanced by foliar boron application. 13 refs., 3 tabs.

  13. Explorations of mechanisms regulating ectomycorrhizal colonization of boron-fertilized pine: Quarterly report, April 1,1989--June 30, 1989

    SciTech Connect

    Garrett, H.E.; Begonia, G.; Sword, M.A.

    1989-01-01

    The present study examines the effects of foliar boron fertilization and inoculation with an ectomycorrhizal fungus (Pisolithus tinctorius) on /sup 14/C-photosynthate partitioning to various tissues of shortleaf pine seedlings, placing special emphasis on the /sup 14/C distribution to the root systems. Specifically, the hypotheses to be tested are: (a) /sup 14/C allocation to the root systems will increase with inoculation, and (b) /sup 14/C partitioning will be enhanced by foliar boron application.

  14. Effects of belowground litter addition, increased precipitation and clipping on soil carbon and nitrogen mineralization in a temperate steppe

    NASA Astrophysics Data System (ADS)

    Ma, L.; Guo, C.; Xin, X.; Yuan, S.; Wang, R.

    2013-11-01

    Soil carbon (C) and nitrogen (N) cycling are sensitive to changes in environmental factors and play critical roles in the responses of terrestrial ecosystems to natural and anthropogenic perturbations. This study was conducted to quantify the effects of belowground particulate litter (BPL) addition, increased precipitation and their interactions on soil C and N mineralization in two adjacent sites where belowground photosynthate allocation was manipulated through vegetation clipping in a temperate steppe of northeastern China from 2010 to 2011. The results show that BPL addition significantly increase soil C mineralization rate (CMR) and net N mineralization rate (NMR). Although increased precipitation-induced enhancement of soil CMR essentially ceased after the first year, stimulation of soil NMR and net nitrification rate continued into the second year. Clipping only marginally decreased soil CMR and NMR during the two years. There were significant synergistic interactions between BPL addition (and increased precipitation) and clipping on soil CMR and NMR, likely to reflect shifts in soil microbial community structure and a decrease in arbuscular mycorrhizal fungi biomass due to the reduction of belowground photosynthate allocation. These results highlight the importance of plants in mediating the responses of soil C and N mineralization to potentially increased BPL and precipitation by controlling belowground photosynthate allocation in the temperate steppe.

  15. Juvenile corals can acquire more carbon from high-performance algal symbionts

    NASA Astrophysics Data System (ADS)

    Cantin, N. E.; van Oppen, M. J. H.; Willis, B. L.; Mieog, J. C.; Negri, A. P.

    2009-06-01

    Algal endosymbionts of the genus Symbiodinium play a key role in the nutrition of reef building corals and strongly affect the thermal tolerance and growth rate of the animal host. This study reports that 14C photosynthate incorporation into juvenile coral tissues was doubled in Acropora millepora harbouring Symbiodinium C1 compared with juveniles from common parentage harbouring Symbiodinium D in a laboratory experiment. Rapid light curves performed on the same corals revealed that the relative electron transport rate of photosystem II (rETRMAX) was 87% greater in Symbiodinium C1 than in Symbiodinium D in hospite. The greater relative electron transport through photosystem II of Symbiodinium C1 is positively correlated with increased carbon delivery to the host under the applied experimental conditions ( r 2 = 0.91). This may translate into a competitive advantage for juveniles harbouring Symbiodinium C1 under certain field conditions, since rapid early growth typically limits mortality. Both symbiont types exhibited severe reductions in 14C incorporation during a 10-h exposure to the electron transport blocking herbicide diuron (DCMU), confirming the link between electron transport through PSII and photosynthate incorporation within the host tissue. These findings advance the current understanding of symbiotic relationships between corals and their symbionts, providing evidence that enhanced growth rates of juvenile corals may result from greater translocation of photosynthates from Symbiodinium C1.

  16. Stored carbon partly fuels fine-root respiration but is not used for production of new fine roots

    SciTech Connect

    Lynch, Douglas J; Matamala-Paradeda, Roser; Iversen, Colleen M; Norby, Richard J; Gonzalez-Meler, Miguel A

    2013-01-01

    The relative use of new photosynthate compared to stored C for the production and maintenance of fine roots, and the rate of C turnover in heterogeneous fine-root populations, are poorly understood. We followed the relaxation of a 13C tracer in fine roots in a Liquidambar styraciflua plantation at the conclusion of a free-air CO2 enrichment experiment. Goals included quantifying the relative fractions of new photosynthate versus stored C used in root growth and root respiration, as well as the turnover rate of fine-root C fixed during [CO2] fumigation. New fine-root growth was largely from recent photosynthate, while nearly one-quarter of respired C was from a storage pool. Changes in the isotopic composition of the fine-root population over two full growing seasons indicated heterogeneous C pools; less than 10% of root C had a residence time < 3 months, while a majority of root C had a residence time > 2 years. Compared to a 1-pool model, a 2-pool model for C turnover in fine roots (with 5 and 0.37 yr-1 turnover times) doubles the fine-root contribution to forest NPP (9-13%) and supports the 50% root-to-soil transfer rate often used in models.

  17. The continuous incorporation of carbon into existing Sassafras albidum fine roots and its implications for estimating root turnover.

    PubMed

    Adams, Thomas S; Eissenstat, David M

    2014-01-01

    Although understanding the timing of the deposition of recent photosynthate into fine roots is critical for determining root lifespan and turnover using isotopic techniques, few studies have directly examined the deposition and subsequent age of root carbon. To gain a better understanding of the timing of the deposition of root carbon, we labeled four individual Sassafras albidum trees with 99% 13C CO2. We then tracked whether the label appeared in roots that were at least two weeks old and no longer elongating, at the time of labeling. We found that not only were the non-structural carbon pools (soluble sugars and starch) of existing first-order tree roots incorporating carbon from current photosynthate, but so were the structural components of the roots, even in roots that were more than one year old at the time of labeling.Our findings imply that carbon used in root structural and nonstructural pools is not derived solely from photosynthate at root initiation and have implications regarding the determination of root age and turnover using isotopic techniques. PMID:24788762

  18. Photosynthesis, respiration and translocation in green fruit of normal and mutant grapefruit. [Citrus paradisi Macf

    SciTech Connect

    Koch, K.E.; Yen, C.R.; Avigne, W.T.

    1986-04-01

    Gas exchange, /sup 14/CO/sub 2/ fixation/and subsequent photosynthate translocation were followed during a 24h light/dark period in green grapefruit (Citrus paradisi Macf.) detached after 2.5 mo. growth. Fruit photosynthesis could account for net fixation of less than 1% of the daily dry weight increase recorded for fruit at this stage of development, but a comparison of light/dark CO/sub 2/ exchange indicated that as much as 27% of this daily gain was maintained by refixation of respiratory CO/sub 2/ during daylight hours. Approximately 10% of photosynthates labeled in the outer peel (flavedo) were translocated to segment epidermis and juice vesicles of normal fruit during 1 + 23h pulse-chase experiments. This process typically continues for 4 to 5 days and refixation products would presumably follow the same path. In a low-acid mutant believed to differ only in acid/sugar ratio of juice vesicles, however, inward translocation of /sup 14/C-photosynthates from flavedo was restricted primarily to the inner peel (albedo).

  19. Carbon cost of the fungal symbiont relative to net leaf P accumulation in a split-root VA mycorrhizal symbiosis. [Poncirus trifoliata L. Raf. x Citrus sinensis L. Osbeck; Glomus intraradices Schenk and Smith

    SciTech Connect

    Douds, D.D. Jr.; Johnson, C.R.; Koch, K.E. )

    1988-02-01

    Translocation of {sup 14}C-photosynthates to mycorrhizal (++), half mycorrhizal (0+), and nonmycorrhizal (00) split-root systems was compared to P accumulation in leaves of the host plant. Carrizo citrange seedlings (Poncirus trifoliata (L.) Raf. {times} Citrus sinensis (L.) Osbeck) were inoculated with the vesicular-arbuscular mycorrhizal fungus Glomus intraradices Schenck and Smith. Plants were exposed to {sup 14}CO{sub 2} for 10 minutes and ambient air for 2 hours. Three to 4% of recently labeled photosynthate was allocated to metabolism of the mycorrhiza in each inoculated root half independent of shoot P concentration, growth response, and whether one or both root halves were colonized. Nonmycorrhizal roots respired more of the label translocated to them than did mycorrhizal roots. Label recovered in the potting medium due to exudation or transport into extraradical hyphae was 5 to 6 times greater for (++) versus (00) plants. In low nutrient media, roots of (0+) and (++) plants transported more P to leaves per root weight than roots of (00) plants. However, when C translocated to roots utilized for respiration, exudation, etc., as well as growth is considered, (00) plant roots were at least as efficient at P uptake (benefit) per C utilized (cost) as (0+) and (++) plants. Root systems of (++) plants did not supply more P to leaves than (0+) plants in higher nutrient media, yet they still allocated twice the {sup 14}C-photosynthate to the mycorrhiza as did (0+) root systems.

  20. The Continuous Incorporation of Carbon into Existing Sassafras albidum Fine Roots and Its Implications for Estimating Root Turnover

    PubMed Central

    Adams, Thomas S.; Eissenstat, David M.

    2014-01-01

    Although understanding the timing of the deposition of recent photosynthate into fine roots is critical for determining root lifespan and turnover using isotopic techniques, few studies have directly examined the deposition and subsequent age of root carbon. To gain a better understanding of the timing of the deposition of root carbon, we labeled four individual Sassafras albidum trees with 99% 13C CO2. We then tracked whether the label appeared in roots that were at least two weeks old and no longer elongating, at the time of labeling. We found that not only were the non-structural carbon pools (soluble sugars and starch) of existing first-order tree roots incorporating carbon from current photosynthate, but so were the structural components of the roots, even in roots that were more than one year old at the time of labeling.Our findings imply that carbon used in root structural and nonstructural pools is not derived solely from photosynthate at root initiation and have implications regarding the determination of root age and turnover using isotopic techniques. PMID:24788762

  1. Algivore or Phototroph? Plakobranchus ocellatus (Gastropoda) Continuously Acquires Kleptoplasts and Nutrition from Multiple Algal Species in Nature

    PubMed Central

    Maeda, Taro; Hirose, Euichi; Chikaraishi, Yoshito; Kawato, Masaru; Takishita, Kiyotaka; Yoshida, Takao; Verbruggen, Heroen; Tanaka, Jiro; Shimamura, Shigeru; Takaki, Yoshihiro; Tsuchiya, Masashi; Iwai, Kenji; Maruyama, Tadashi

    2012-01-01

    The sea slug Plakobranchus ocellatus (Sacoglossa, Gastropoda) retains photosynthetically active chloroplasts from ingested algae (functional kleptoplasts) in the epithelial cells of its digestive gland for up to 10 months. While its feeding behavior has not been observed in natural habitats, two hypotheses have been proposed: 1) adult P. ocellatus uses kleptoplasts to obtain photosynthates and nutritionally behaves as a photoautotroph without replenishing the kleptoplasts; or 2) it behaves as a mixotroph (photoautotroph and herbivorous consumer) and replenishes kleptoplasts continually or periodically. To address the question of which hypothesis is more likely, we examined the source algae for kleptoplasts and temporal changes in kleptoplast composition and nutritional contribution. By characterizing the temporal diversity of P. ocellatus kleptoplasts using rbcL sequences, we found that P. ocellatus harvests kleptoplasts from at least 8 different siphonous green algal species, that kleptoplasts from more than one species are present in each individual sea slug, and that the kleptoplast composition differs temporally. These results suggest that wild P. ocellatus often feed on multiple species of siphonous algae from which they continually obtain fresh chloroplasts. By estimating the trophic position of wild and starved P. ocellatus using the stable nitrogen isotopic composition of amino acids, we showed that despite the abundance of kleptoplasts, their photosynthates do not contribute greatly to the nutrition of wild P. ocellatus, but that kleptoplast photosynthates form a significant source of nutrition for starved sea slugs. The herbivorous nature of wild P. ocellatus is consistent with insights from molecular analyses indicating that kleptoplasts are frequently replenished from ingested algae, leading to the conclusion that natural populations of P. ocellatus do not rely on photosynthesis but mainly on the digestion of ingested algae. PMID:22848693

  2. Carbon and nitrogen dynamics in the rhizosphere of Pinus ponderosa seedlings

    SciTech Connect

    Norton, J.M.

    1991-01-01

    The rhizosphere is a dynamic soil region characterized by dense microbial populations and enhanced rates of microbial processes. The rhizosphere may be especially important in determinign the spatial distribution of carbon and nitrogen cycling in forest soils. The author has investigated the flow of carbon from roots to the soil, the quantity and metabolic status of bacteria and fungi, and the production and consumption of inorganic nitrogen in the rhizosphere of Pinus ponderosa seedlings. The role of plant/microbial competition for inorganic nitrogen in determining the availability of nitrogen to plant assimilation was assessed. The author examined the flow of recently fixed photosynthate from roots to the soil using a [sup 14]C pulse-labelling technique. The highest concentration of recently fixed photosynthate carbon in the soil was adjacent to the young root tip region. Fine mycorrhizal roots had the highest rate of carbon loss to the soil per unit carbon assimilated by the root. Mycorrhizal hyphae played an important role in the redistribution of recently fixed photosynthate throughout the soil. The input of plant carbon to the soil by rhizodeposition was an important energy source for the microbial community even in soil not directly adjacent to the root. In short-term [sup 15]N experiments, the author observed that rates of mineralization and NH[sub 4][sup +] immobilization were higher in soils harvested from adjacent to roots than in soils harvested from greater than 5 mm from any root. Results from intact microcosms suggest that NH[sub 4][sup +] supply and competition between roots, heterotrophs and nitrifiers for NH[sub 4][sup +] were the direct controls on NH[sub 4][sup +] immobilization rates rather than the supply of, recently fixed carbon by rhizodeposition. Plants were more successful competitors for NH[sub 3][sup [minus

  3. Belowground carbon sources and fine root turnover times using 13C tracer at the conclusion of a long-term FACE experiment

    NASA Astrophysics Data System (ADS)

    Lynch, D. J.; Matamala, R.; Norby, R.; Iversen, C.; Gonzalez-Meler, M. A.

    2011-12-01

    Estimates of carbon budgets require accurate approximations of fine root production and turnover. Current published estimates of root carbon turnover vary more than five-fold, with large differences between isotope-derived estimates, minirhizotron studies or other approaches. Variations in residence times between root structural and reserve C, root orders and new photosynthate to support root function have been shown independently, but have not been yet reconciled in a single study. Taking advantage of the conclusion of the long-term FACE experiment at Oak Ridge National Laboratory, we track the whole ecosystem isotope relaxation in fine root pools (<2mm). Carbon assimilated in 2010 and beyond is isotopically unique from carbon incorporated during fumigation (1998-2009). Our objectives were to quantify carbon turnover time in fine roots of Liquidambar styraciflua, and to identify carbon sources for new root growth and for energy metabolism. We sampled intact and in-growth root cores at regular (minimum time was monthly) intervals in 2010 and at several intervals in 2011. Additionally, fine roots and soils were incubated from three sampling periods each from 2010 and 2011 for measurement of the isotopic signature of respired CO2. Our results show a residence time of carbon in fine roots consistent with previous stable isotope reports for this species, with about 20% of structural C replaced after one full growing season. In contrast, all new root growth (evidenced from in-growth cores) was supported by new photosynthate, except for some storage carbon used very early in the growing season. Carbon used for energy metabolism in roots exclusively originated from new photosynthate during all measurement periods. Our results confirm heterogeneity of C pools in existing and new roots and the relatively long residence time of structural C in existing fine roots.

  4. Temporal dynamics of carbon partitioning and rhizodeposition in wheat.

    PubMed

    Dilkes, Nigel B; Jones, David L; Farrar, John

    2004-02-01

    The temporal dynamics of partitioning and rhizodeposition of recent photosynthate in wheat (Triticum aestivum) roots were quantified in situ in solution culture. After a 30-min pulse of (14)CO(2) to a single intact leaf, (14)C activities of individual carbon fluxes in the root, including exudation, respiration, and root content, were measured continuously over the next 20 h concurrently with (14)C efflux from the leaf. Immediately after the end of the (14)CO(2) pulse, (14)C activity was detected in the root, the hydroponic solution, and in root respiration. The rate of (14)C exudation from the root was maximal after 2 to 3 h, and declined to one-third of maximum after a further 5 h. Completion of the rapid phase of (14)C efflux from the leaf coincided with peak (14)C exudation rate. Thus, exudation flux is much more rapidly and dynamically coupled to current photosynthesis than has been appreciated. Careful cross-calibration of (14)C counting methods allowed a dynamic (14)C budget to be constructed for the root. Cumulative (14)C exudation after 20 h was around 3% of (14)C fixed in photosynthesis. Partitioning of photosynthate between shoot and root was manipulated by partial defoliation before applying the (14)CO(2) pulse to the remaining intact leaf. Although the rate of photosynthesis was largely unaffected by partial defoliation, the proportion of new photosynthate subsequently partitioned to and exuded from the root was substantially reduced. This clearly indicates that exudation depends more on the rate of carbon import into the root than on the rate of photosynthesis. PMID:14764904

  5. Interactive effects of belowground organic matter input, increased precipitation and clipping on soil carbon and nitrogen mineralization in a temperate steppe

    NASA Astrophysics Data System (ADS)

    Ma, L. N.; Guo, C. Y.; Xin, X. P.; Yuan, S.; Wang, R. Z.

    2013-06-01

    Soil organic matter (SOM) inputs, increased precipitation and clipping (reducing belowground photosynthates allocation) are predicted to affect soil C and N cycling in temperate grassland ecosystems. However, the interactive effects between SOM inputs (or increased precipitation) and clipping on soil C and N mineralization in temperate steppes are still poorly understood. A field manipulation experiment was conducted to quantify the effects of SOM inputs, increased precipitation, clipping and their interactions on soil C and N mineralization in a temperate steppe of northeastern China from 2010 to 2011. The results showed that SOM inputs significantly increased soil C mineralization rate (CMR) and net N mineralization rate (NMR). Increased precipitation-induced enhancement of soil CMR essentially ceased after the first year, stimulation of soil NMR and NNR continued into the second year. However, clipping only marginally decreased soil CMR and NMR during the two years. There were significant synergistic interactions between SOM inputs (or increased precipitation) and clipping on soil CMR and NMR, as SOM inputs (or increased precipitation) showed greater effects on soil CMR and NMR under clipped plots than under unclipped plots, which could be explained by the relative shifts in soil microbial community structure because of bacterial biomass increases, and by the relative decreases in arbuscular mycorrhizal fungi biomass due to the reduction of belowground photosynthates allocation. These results highlight the importance of plants in mediating the responses of soil C and N mineralization to potentially increased SOM and precipitation by controlling belowground photosynthates allocation in the temperate steppe. Thus, the findings have important implications for improving prediction of C and N sequestration potential and its feedbacks to climate change in temperate steppe ecosystems.

  6. Energy flow in an arctic aquatic ecosystem

    SciTech Connect

    Schell, D.M.

    1983-12-31

    This component of the terrestrial-aquatic interaction group seeks to use the natural stable carbon isotope ratios and radiocarbon abundances to trace the movement of photosynthate from the terrestrial environment to the stream system at MS-117. In addition to estimating the total flux, we will also attempt to describe the relative fractions derived from modern primary production and that derived from delayed inputs of eroded peat. We will also seek to determine the coupling efficiency of these energy sources to the invertebrate faunal populations in the tundra soils and streams.

  7. Energy flow in an arctic aquatic ecosystem

    SciTech Connect

    Schell, D.M.

    1983-01-01

    This component of the terrestrial-aquatic interaction group seeks to use the natural stable carbon isotope ratios and radiocarbon abundances to trace the movement of photosynthate from the terrestrial environment to the stream system at MS-117. In addition to estimating the total flux, we will also attempt to describe the relative fractions derived from modern primary production and that derived from delayed inputs of eroded peat. We will also seek to determine the coupling efficiency of these energy sources to the invertebrate faunal populations in the tundra soils and streams.

  8. Effect of Potassium Deficiency Upon Translocation of 14C in Attached Blades and Entire Plants of Sugarcane 1

    PubMed Central

    Hartt, Constance E.

    1969-01-01

    A deficiency in potassium decreased the translocation of labeled photosynthate from the leaf to the rest of the plant. Translocation was inhibited in blades which exhibited no visible symptoms of potassium deficiency and in which no decrease in photosynthesis was detected. In more severe deficiency both the rate of photosynthesis and the conversion of intermediates to end products decreased. The rate of respiration in deficient blades increased. The decrease in translocation caused by potassium deficiency is considered to be a primary effect and not secondary to the development of the well-known symptoms of potassium deficiency. PMID:16657226

  9. Transformation of carrots with mutant acetolactate synthase for Orobanche (broomrape) control.

    PubMed

    Aviv, Dvora; Amsellem, Ziva; Gressel, Jonathan

    2002-12-01

    Parasitic Orobanche spp are major constraints to vegetable crop production in the Mediterranean basin (to eastern Europe) and in localized places in India, China and the USA. Transgenic target-site herbicide resistance (eg, to acetolactate synthase inhibitors) allows for movement of unmetabolized herbicide through the crop to the photosynthate sink in the parasite, as well as through the soil. We report the successful engineering of a mutant acetolactate synthase (ALS) gene into carrot, allowing control of broomrape already in heterozygotes of the first back-crossed generation, by imazapyr, an imidazolinone ALS inhibitor. It is expected that homozygotes will have higher levels of resistance. PMID:12476991

  10. Ectomycorrhizae influences on CO/sub 2/ exchange and carbon allocation in Pinus

    SciTech Connect

    Kidd, F.A.

    1983-01-01

    Although the importance of mycorrhizal fungi in nutrient ion absorption is relatively well documented, little is known concerning the energy cost required of the host plant for the maintenance of the nurient-absorbing area provided by the mycorrhizae. The objective of this research was to gain further knowledge on how the basic physiological processes of photosynthesis and respiration, as well as allocation of carbon compounds, may be stimulated in host Pinus seedlings through source-sink relationships resulting from mycorrhizae. Seedlings of four Pinus species with 50-75% short root infection by three mycorrhizae species had a rate of net photosynthesis 3X as great as that of noninfected plants. The increase in CO/sub 2/ fixation appeared linear with respect to fungal infection as percentage short root infection increased from zero to 75%. When other parameters of seedling growth and morphology, i.e. shoot and root dry weight, dark respiration rates, and foliar concentration of nitrogen, were correlated with net photosynthetic rate, only mycorrhizae infection demonstrated a statistically significant (P < 0.05) influence on increasing host CO/sub 2/ exchange. Partitioning of current photosynthate was examined by pulse-labeling Pinus taeda L. with /sup 14/CO/sub 2/ at each of six time intervals. Although the stimulation of photosynthesis and allocation of current photosynthate to the root system by mycorrhizae formation was consistent with the source-sink concept of sink demand, foliar N and P concentrations were also greater in mycorrhizal plants.

  11. Ectomycorrhizal fungi and past high CO2 atmospheres enhance mineral weathering through increased below-ground carbon-energy fluxes

    PubMed Central

    Quirk, Joe; Andrews, Megan Y.; Leake, Jonathan R.; Banwart, Steve A.; Beerling, David J.

    2014-01-01

    Field studies indicate an intensification of mineral weathering with advancement from arbuscular mycorrhizal (AM) to later-evolving ectomycorrhizal (EM) fungal partners of gymnosperm and angiosperm trees. We test the hypothesis that this intensification is driven by increasing photosynthate carbon allocation to mycorrhizal mycelial networks using 14CO2-tracer experiments with representative tree–fungus mycorrhizal partnerships. Trees were grown in either a simulated past CO2 atmosphere (1500 ppm)—under which EM fungi evolved—or near-current CO2 (450 ppm). We report a direct linkage between photosynthate-energy fluxes from trees to EM and AM mycorrhizal mycelium and rates of calcium silicate weathering. Calcium dissolution rates halved for both AM and EM trees as CO2 fell from 1500 to 450 ppm, but silicate weathering by AM trees at high CO2 approached rates for EM trees at near-current CO2. Our findings provide mechanistic insights into the involvement of EM-associating forest trees in strengthening biological feedbacks on the geochemical carbon cycle that regulate atmospheric CO2 over millions of years. PMID:25115032

  12. Release of Sucrose from Vicia faba L. Leaf Discs 1

    PubMed Central

    Anderson, James Michael

    1983-01-01

    The release of sucrose from leaf discs of Vicia faba L. to a bathing medium was studied for evidence of a relationship between this release and mesophyll export of photosynthate in vivo. Sucrose was released specifically over hexoses and represented over 85% of total photosynthate released. The sucrose appeared to be derived from the mesophyll tissue directly and release did not require concurrent photosynthesis. The data indicated two separate channels for sucrose release. The first was sensitive to inhibition by 1 millimolar p-chloromercuribenzenesulfonic acid and the second was promoted by lowering the Ca2+ concentration below 0.1 millimolar. Flow through both channels was about equal when tissue that had been actively photosynthesizing for several hours was used. The rate of release was not dependent on the extracellular pH, but was inhibited by 10 micromolar carbonylcyanide p-trifluromethoxyphenylhydrazone. Lowering the Ca2+ concentration below 0.1 millimolar or raising the K+ concentration above 100 millimolar stimulated sucrose release. The stimulation by high K+ was not reversed by adding Ca2+. The data supported the postulate that Ca2+ removal or K+ addition changed the permeability of the mesophyll plasma membrane to sucrose. PMID:16662827

  13. Tomato GOLDEN2-LIKE Transcription Factors Reveal Molecular Gradients That Function during Fruit Development and Ripening[W][OPEN

    PubMed Central

    Nguyen, Cuong V.; Vrebalov, Julia T.; Gapper, Nigel E.; Zheng, Yi; Zhong, Silin; Fei, Zhangjun; Giovannoni, James J.

    2014-01-01

    Fruit ripening is the summation of changes rendering fleshy fruit tissues attractive and palatable to seed dispersing organisms. For example, sugar content is influenced by plastid numbers and photosynthetic activity in unripe fruit and later by starch and sugar catabolism during ripening. Tomato fruit are sinks of photosynthate, yet unripe green fruit contribute significantly to the sugars that ultimately accumulate in the ripe fruit. Plastid numbers and chlorophyll content are influenced by numerous environmental and genetic factors and are positively correlated with photosynthesis and photosynthate accumulation. GOLDEN2-LIKE (GLK) transcription factors regulate plastid and chlorophyll levels. Tomato (Solanum lycopersicum), like most plants, contains two GLKs (i.e., GLK1 and GLK2/UNIFORM). Mutant and transgene analysis demonstrated that these genes encode functionally similar peptides, though differential expression renders GLK1 more important in leaves, while GLK2 is predominant in fruit. A latitudinal gradient of GLK2 expression influences the typical uneven coloration of green and ripe wild-type fruit. Transcriptome profiling revealed a broader fruit gene expression gradient throughout development. The gradient influenced general ripening activities beyond plastid development and was consistent with the easily observed yet poorly studied ripening gradient present in tomato and many fleshy fruits. PMID:24510723

  14. Plasmadesmatal frequency, apoplast-symplast ratio, and photosynthetic transfer in grapefruit juice vesicles. [Citrus paradisi Macf

    SciTech Connect

    Koch, K.E.; Lowell, C.A.; Avigne, W.T.

    1986-04-01

    Structure and function were examined in phloem-free vesicles and vesicle stalks of grapefruit (Citrus paradisi Macf.) by light and electron microscopy and /sup 14/C-photosynthate transport in intact and dissected tissues. Plasmodesmatal frequencies were approximately 0.3 to 0.5 ..mu..m/sup -1/ cell wall interface (3 to 5 ..mu..m/sup -2/), less than that of known secretory structures but similar to root parenchyma. Cell wall or apoplast comprised 18 to 24% of the total cross-sectional area of the vesicle stalk. The mass of total photosynthate transfer through individual vesicle stalks was ca. 0.5 ..mu..g C h/sup -1/ and rate of /sup 14/C-movement 0.1 to 0.4 mm h/sup -1/. Transport continued in rows of vesicles dissected in association with a vascular bundle. If isolated from fully-expanded fruit, translocation was similar for systems with frozen vs. non-frozen vesicle stalks. Similar freezing treatment decreased transport in vesicles from younger fruit. Symplastic and apoplastic pathways may therefore both operate in this system.

  15. Subcellular Investigation of Photosynthesis-Driven Carbon Assimilation in the Symbiotic Reef Coral Pocillopora damicornis

    PubMed Central

    Domart-Coulon, Isabelle; Escrig, Stephane; Humbel, Bruno M.; Hignette, Michel

    2015-01-01

    ABSTRACT  Reef-building corals form essential, mutualistic endosymbiotic associations with photosynthetic Symbiodinium dinoflagellates, providing their animal host partner with photosynthetically derived nutrients that allow the coral to thrive in oligotrophic waters. However, little is known about the dynamics of these nutritional interactions at the (sub)cellular level. Here, we visualize with submicrometer spatial resolution the carbon and nitrogen fluxes in the intact coral-dinoflagellate association from the reef coral Pocillopora damicornis by combining nanoscale secondary ion mass spectrometry (NanoSIMS) and transmission electron microscopy with pulse-chase isotopic labeling using [13C]bicarbonate and [15N]nitrate. This allows us to observe that (i) through light-driven photosynthesis, dinoflagellates rapidly assimilate inorganic bicarbonate and nitrate, temporarily storing carbon within lipid droplets and starch granules for remobilization in nighttime, along with carbon and nitrogen incorporation into other subcellular compartments for dinoflagellate growth and maintenance, (ii) carbon-containing photosynthates are translocated to all four coral tissue layers, where they accumulate after only 15 min in coral lipid droplets from the oral gastroderm and within 6 h in glycogen granules from the oral epiderm, and (iii) the translocation of nitrogen-containing photosynthates is delayed by 3 h. PMID:25670779

  16. Adaptation to endosymbiosis in the green Hydra, Hydra viridissima

    SciTech Connect

    Dunn, K.W.

    1986-01-01

    Previous work has shown that the growth advantage conferred by algae on green hydra disappears when they are amply fed. From this observation an hypothesis has been advanced that the association may have evolved such that the rate of algal photosynthate translocation is adjusted according to the host's nutritional need. Evidence presented here contradicts this hypothesis. In controlled feeding studies, green hydra grow more rapidly than do aposymbionts at all feeding levels in a way that suggests that the per capita algal contribution to host growth is independent of host feeding rate. The rate of /sup 14/C translocation appears to vary in response to the algae's needs for photosynthate to support their own growth and within a range that suggests that dramatic differences in the algal effect on hydra growth are not likely to be caused by variation in algal carbon translocation. A correspondence in the timing of host and algal mitotic activity has been interpreted to suggest that algal density in hydra is accomplished through closely coordinated host and algal cell division. Similar rates of algal mitosis in growing and in shrinking endosymbiont populations show that some additional mechanism is required. Finally, host digestion of endosymbionts is considered to be rare except in unnatural associations. The absence of algal digestion in the hydra symbiosis has been considered to reflect coevolution between the symbionts, and yet the hydra in this study routinely lost significant numbers of endosymbionts apparently to intracellular digestion.

  17. P-proteins in Arabidopsis are heteromeric structures involved in rapid sieve tube sealing

    PubMed Central

    Jekat, Stephan B.; Ernst, Antonia M.; von Bohl, Andreas; Zielonka, Sascia; Twyman, Richard M.; Noll, Gundula A.; Prüfer, Dirk

    2013-01-01

    Structural phloem proteins (P-proteins) are characteristic components of the sieve elements in all dicotyledonous and many monocotyledonous angiosperms. Tobacco P-proteins were recently confirmed to be encoded by the widespread sieve element occlusion (SEO) gene family, and tobacco SEO proteins were shown to be directly involved in sieve tube sealing thus preventing the loss of photosynthate. Analysis of the two Arabidopsis SEO proteins (AtSEOa and AtSEOb) indicated that the corresponding P-protein subunits do not act in a redundant manner. However, there are still pending questions regarding the interaction properties and specific functions of AtSEOa and AtSEOb as well as the general function of structural P-proteins in Arabidopsis. In this study, we characterized the Arabidopsis P-proteins in more detail. We used in planta bimolecular fluorescence complementation assays to confirm the predicted heteromeric interactions between AtSEOa and AtSEOb. Arabidopsis mutants depleted for one or both AtSEO proteins lacked the typical P-protein structures normally found in sieve elements, underlining the identity of AtSEO proteins as P-proteins and furthermore providing the means to determine the role of Arabidopsis P-proteins in sieve tube sealing. We therefore developed an assay based on phloem exudation. Mutants with reduced AtSEO expression levels lost twice as much photosynthate following injury as comparable wild-type plants, confirming that Arabidopsis P-proteins are indeed involved in sieve tube sealing. PMID:23840197

  18. Functional Relationship between a Dinoflagellate Host and Its Diatom Endosymbiont.

    PubMed

    Hehenberger, Elisabeth; Burki, Fabien; Kolisko, Martin; Keeling, Patrick J

    2016-09-01

    While we know much about the evolutionary patterns of endosymbiotic organelle origins, we know less about how the actual process unfolded within each system. This is partly due to the massive changes endosymbiosis appears to trigger, and partly because most organelles evolved in the distant past. The dinotoms are dinoflagellates with diatom endosymbionts, and they represent a relatively recent but nevertheless obligate endosymbiotic association. We have carried out deep sequencing of both the host and endosymbiont transcriptomes from two dinotoms, Durinskia baltica and Glenodinium foliaceum, to examine how the nucleocytosolic compartments have functionally integrated. This analysis showed little or no functional reduction in either the endosymbiont or host, and no evidence for genetic integration. Rather, host and endosymbiont seem to be bound to each other via metabolites, such as photosynthate exported from the endosymbiont to the host as indicated by the presence of plastidic phosphate translocators in the host transcriptome. The host is able to synthesize starch, using plant-specific starch synthases, as a way to store imported photosynthate. PMID:27297471

  19. Phloem loading in Coleus blumei in the absence of carrier-mediated uptake of export sugar from the apoplast. [Coleus blumei Benth

    SciTech Connect

    Turgeon, R.; Gowan, E. )

    1990-11-01

    Phloem loading in Coleus blumei Benth. leaves cannot be explained by carrier-mediated transport of export sugar from the apoplast into the sieve element-companion cell complex, the mechanism by which sucrose is thought to load in other species that have been studied in detail. Uptake profiles of the export sugars sucrose, raffinose, and stachyose into leaf discs were composed of two components, one saturable and other other not. Saturable (carrier-mediated) uptake of all three sugars was almost completely eliminated by the inhibitor p-chloromercuribenzenesulfonic acid (PCMBS). However, when PCMBS was introduced by transpiration into mature leaves it did not prevent accumulation of {sup 14}C-photosynthate in minor veins or translocation of labeled photosynthate from green to nonchlorophyllous regions of the leaf following exposure to {sup 14}CO{sub 2}. The efficacy of introducing inhibitor solutions in the transpiration stream was proven by observing saffranin O and calcofluor white movement in the minor veins and leaf apoplast. PCMBS introduced by transpiration completely inhibited phloem loading in tobacco leaves. Phloem loading in C. blumei was also studied in plasmolysis experiments. The carbohydrate content of leaves was lowered by keeping plants in the dark and then increased by exposing them to light. The solute level of intermediary cells increased in the light (phloem loading) in both PCMBS-treated and control tissues. A mechanism of symplastic phloem loading is proposed for species that translocate the raffinose series of oligosaccharides.

  20. Assessment of the impact of photosystem I chlorophyll fluorescence on the pulse-amplitude modulated quenching analysis in leaves of Arabidopsis thaliana.

    PubMed

    Giovagnetti, Vasco; Ware, Maxwell A; Ruban, Alexander V

    2015-08-01

    In their natural environment, plants are exposed to varying light conditions, which can lead to a build-up of excitation energy in photosystem (PS) II. Non-photochemical quenching (NPQ) is the primary defence mechanism employed to dissipate this excess energy. Recently, we developed a fluorescence-quenching analysis procedure that enables the protective effectiveness of NPQ in intact Arabidopsis leaves to be determined. However, pulse-amplitude modulation measurements do not currently allow distinguishing between PSII and PSI fluorescence levels. Failure to account for PSI contribution is suggested to lead to inaccurate measurements of NPQ and, particularly, maximum PSII yield (F v/F m). Recently, Pfündel et al. (Photosynth Res 114:189-206, 2013) proposed a method that takes into account PSI contribution in the measurements of F o fluorescence level. However, when PSI contribution was assumed to be constant throughout the induction of NPQ, we observed lower values of the measured minimum fluorescence level ([Formula: see text]) than those calculated according to the formula of Oxborough and Baker (Photosynth Res 54:135-142 1997) ([Formula: see text]), regardless of the light intensity. Therefore, in this work, we propose a refined model to correct for the presence of PSI fluorescence, which takes into account the previously observed NPQ in PSI. This method efficiently resolves the discrepancies between measured and calculated F o' produced by assuming a constant PSI fluorescence contribution, whilst allowing for the correction of the maximum PSII yield. PMID:25613087

  1. Ecological role of algobacterial cenosis links (chlorella - associated microflora or associated bacteria)

    NASA Astrophysics Data System (ADS)

    Pechurkin, N. S.

    The problems of interrelation of microalgae and bacteria in the "autotroph - heterotroph" aquatic biotic cycle are discussed. The cause and mechanisms of algobacterial cenosis formation still have been explained contradictorily. This work views the results of experimental and theoretical study of algobacterial cenosis functioning by the example of microalga Chlorella vulgaris and associated microflora. The representatives of Pseudomonas mainly predominate in the Chlorella microbial complex. The experiment at non-sterile batch cultivation of Chlorella on Tamya medium showed that the biomass of microorganisms increases simultaneously with the increase of microalgal biomass. Microflora of Chlorella can use organic materials evolved by Chlorella after photosynthesis for reproduction. Moreover, microorganisms can use dying cells of Chlorella, i.e. form the "producer - reducer" biocycle. To understand the cenosis-forming role of microalgae the mathematical model of the "autotroph - heterotroph" aquatic biotic cycle was constructed taking into consideration the opportunities for microorganisms of using Chlorella photosynthates, dying cells and contribution of links to the nitrogen cycle. The theoretical investigation showed that the biomass of associated bacteria growing on glucose and detritus exceeds the biomass of bacteria using only microalgal photosynthates, which is comparable with experimental data.

  2. Population dynamics of an algal bacterial cenosis in closed ecological system

    NASA Astrophysics Data System (ADS)

    Pisman, T. I.; Galayda, Ya. V.; Loginova, N. S.

    The paper deals with microalgae-bacteria interrelationships in the "autotroph-heterotroph" aquatic biotic cycle. Explanations of why and how algal-bacterial ecosystems are formed still remain controversial. The paper presents results of experimental and theoretical investigations of the functioning of the algal-bacterial cenosis (the microalga Chlorella vulgaris and concomitant microflora). The Chlorella microbial community is dominated by representatives of the genus Pseudomonas. Experiments with non-sterile batch cultures of Chlorella on Tamiya medium showed that the biomass of microorganisms increases simultaneously with the increase in microalgal biomass. The microflora of Chlorella can grow on organic substances released by photosynthesizing Chlorella. Microorganisms can also use dying Chlorella cells, i.e. form a "producer-reducer" biocycle. To get a better insight into the cenosis-forming role of microalgae, a mathematical model of the "autotroph-heterotroph" aquatic biotic cycle has been constructed, taking into account the utilization of Chlorella photosynthates and dead cells by microorganisms and the contribution of the components to the nitrogen cycle. A theoretical study showed that the biomass of concomitant bacteria grown on glucose and detritus is larger than the biomass of bacteria utilizing only microalgal photosynthates, which agrees well with the experimental data.

  3. Photo- and heterotrophic nitrogenase activity by the cyano-bacterium Nostoc in symbiosis with the bryophyte Anthoceros

    SciTech Connect

    Steinberg, N.A.; Meeks, J.C.

    1987-04-01

    In symbiosis with Anthoceros, Nostoc is thought to do little or no photosynthesis. However, light-dependent /sup 14/CO/sub 2/ fixation by symbiotic Nostoc, freshly isolated from pure cultures of the reconstituted Anthoceros-Nostoc association, was 16% of that by free-living Nostoc. A DCMU-resistant mutant of Nostoc was isolated that fixed CO/sub 2/ at rates comparable to wild-type in both symbiotic and free-living growth states. To determine if symbiotic Nostoc can use its photosynthate directly to fix nitrogen, acetylene reduction by Anthoceros associations reconstituted with wild-type Nostoc was compared to associations with the DCMU-resistant mutant. In wild-type Anthoceros-Nostoc acetylene reduction was inhibited 97% by 5 ..mu..M DCMU, while inhibition of the DCMU-resistant Nostoc association was only 63%. Additions of glucose, fructose, maltose or sucrose to wild-type associations completely restored DCMU-inhibited acetylene reduction in the light. Acetylene reduction in the dark was stimulated by glucose, attaining 84% of the uninhibited light-dependent value. The authors conclude that symbiotic Nostoc maintains a pool of photosynthate which supports nitrogenase activity. The pool can also be supplemented from plant sources.

  4. The beginnings of research on biophysics of photosynthesis and initial contributions made by Russian scientists to its development.

    PubMed

    Borisov, Alexander

    2003-06-01

    In contrast to the classical sciences, biophysics is difficult to define. For example, Roderick Clayton suggested that biophysics requires 'solid grounding in physics, chemistry and mathematics together with enough biology and biochemistry' [Clayton RK (1988) Photosynth Res 19: 207-224]. One may see from the proceedings of the recent biophysical congresses that their materials and ideas in a very wide sense are biological, including global geographic and ecological problems. To be recognized as biophysical, either physico-chemical methods or at least some mathematical and computer programs are usually involved in such work. One exception is the biophysics of photosynthesis, which deals with fundamental photophysical processes: the absorption of solar radiation by chlorophylls (Chls) and accessory pigments. The subsequent intermolecular transfer of singlet electronic excitation results in a primary energy conversion manifested as pairs of opposite electric charges separated in the pigment-protein complexes called reaction centers [see Clayton RK (2002) Photosynth Res 73: 63-71]. I review the initial, basic contributions in this field, and the most important accomplishments of Russian scientists in the 20th century. PMID:16228597

  5. Carbon flux to woody tissues in a beech/spruce forest during summer and in response to chronic O3 exposure

    NASA Astrophysics Data System (ADS)

    Ritter, W.; Andersen, C. P.; Matyssek, R.; Grams, T. E. E.

    2011-11-01

    The present study compares the dynamics in carbon (C) allocation of adult deciduous beech (Fagus sylvatica) and evergreen spruce (Picea abies) during summer and in response to seven-year-long exposure with twice-ambient ozone (O3) concentrations (2 × O3). Focus was on the respiratory turn-over and translocation of recent photosynthates at various positions along the stems, coarse roots and soils. The hypotheses tested were that (1) 2 × O3 decreases the allocation of recent photosynthates to CO2 efflux of stems and coarse roots of adult trees, and that (2) according to their different O3 sensitivities this effect is stronger in beech than in spruce. Labeling of whole tree canopies was applied by releasing 13C depleted CO2 (δ13C of -46.9‰) using a free-air stable carbon isotope approach. Canopy air δ13C was reduced for about 2.5 weeks by ca. 8‰ in beech and 6‰ in spruce while the increase in CO2 concentration was limited to about 110 μl l-1 and 80 μl l-1, respectively. At the end of the labeling period, δ13C of stem CO2 efflux and phloem sugars was reduced to a similar extend by ca. 3-4‰ (beech) and ca. 2-3‰ (spruce). The fraction of labeled C (fE,new) in stem CO2 efflux amounted to 0.3 to 0.4, indicating slow C turnover of the respiratory supply system in both species. Elevated O3 slightly stimulated the allocation of recently fixed photosynthates to stem and coarse root respiration in spruce (rejection of hypothesis I for spruce), but resulted in a significant reduction in C flux in beech (acceptance of hypotheses I and II). The distinct decrease in C allocation to beech stems indicates the potential of chronic O3 stress to substantially mitigate the C sink strength of trees on the long-term scale.

  6. Carbon flux to woody tissues in a beech/spruce forest during summer and in response to chronic elevated O3 exposure

    NASA Astrophysics Data System (ADS)

    Ritter, W.; Andersen, C. P.; Matyssek, R.; Grams, T. E. E.

    2011-04-01

    The present study compares the dynamics in carbon (C) allocation of adult deciduous beech (Fagus sylvatica) and evergreen spruce (Picea abies) during summer and in response to seven-year-long exposure with twice-ambient ozone (O3) concentrations (2 × O3). Focus was on the respiratory turn-over and translocation of recent photosynthates at various positions along the stems, coarse roots and soils. The hypotheses tested were that (1) 2 × O3 decreases the allocation of recent photosynthates to CO2 efflux of stems and coarse roots of adult trees, and that (2) according to their different O3 sensitivities this effect is stronger in beech than in spruce. Labeling of whole tree canopies was applied by releasing 13C depleted CO2 (δ13C of -46.9‰) using a free-air stable carbon isotope approach. Canopy air δ13C was reduced for about 2.5 weeks by ca. 8‰ in beech and 6‰ in spruce while the increase in CO2 concentration was limited to about 110 μL L-1 and 80 μL L-1, respectively. At the end of the labeling period, δ13C of stem CO2 efflux and phloem sugars was reduced to a similar extend by ca. 3-4‰ (beech) and ca. 2-3‰ (spruce). The fraction of labeled C (fE,new) in stem CO2 efflux amounted to 0.3 to 0.4, indicating slow C turnover of the respiratory supply system in both species. Elevated O3 slightly stimulated the allocation of recently fixed photosynthates to stem and coarse root respiration in spruce (rejection of hypothesis I for spruce), but resulted in a significant reduction in C flux in beech (acceptance of hypotheses I and II). The distinct decreased in C allocation to beech stems indicates the potential of chronic O3 stress to substantially mitigate the C sink strength of trees on the long-term scale.

  7. Possible Role of Nutritional Priming for Early Salt and Drought Stress Responses in Medicago truncatula

    PubMed Central

    Staudinger, Christiana; Mehmeti, Vlora; Turetschek, Reinhard; Lyon, David; Egelhofer, Volker; Wienkoop, Stefanie

    2012-01-01

    Most legume species establish a symbiotic association with soil bacteria. The plant accommodates the differentiated rhizobia in specialized organs, the root nodules. In this environment, the microsymbiont reduces atmospheric nitrogen (N) making it available for plant metabolism. Symbiotic N-fixation is driven by the respiration of the host photosynthates and thus constitutes an additional carbon sink for the plant. Molecular phenotypes of symbiotic and non-symbiotic Medicago truncatula are identified. The implication of nodule symbiosis on plant abiotic stress response mechanisms is not well understood. In this study, we exposed nodulated and non-symbiotic N-fertilized plants to salt and drought conditions. We assessed the stress effects with proteomic and metabolomic methods and found a nutritionally regulated phenotypic plasticity pivotal for a differential stress adjustment strategy. PMID:23267362

  8. [Enhancement of photoassimilate utilization by manipulation of the ADPglucose pyrophosphorylase gene]. Progress report, [March 15, 1989--April 14, 1990

    SciTech Connect

    Okita, T.W.

    1990-12-31

    The long term aim of this project is to assess the feasibility of increasing the conversion of photosynthate into starch via manipulation of the gene that encodes for ADPglucose pyrophosphorylase, a key regulatory enzyme of starch biosynthesis. In developing storage tissues such as cereal seeds and tubers, starch biosynthesis is regulated by the gene activation and expression of ADPglucose pyrophosphorylase, starch synthase, branching enzyme and other ancillary starch modifying enzymes, as well as the allosteric-controlled behavior of ADPglucose pyrophosphorylase activity. During the last two years we have obtained information on the structure of this enzyme from both potato tuber and rice endosperm, using a combination of biochemical and molecular biological approaches. Moreover, we present evidence that this enzyme may be localized at discrete regions of the starch grain within the amyloplast, and plays a role in controlling overall starch biosynthesis in potato tubers.

  9. An Experimental Comparison of Two Methods on Photosynthesis Driving Soil Respiration: Girdling and Defoliation

    PubMed Central

    Jing, Yanli; Guan, Dexin; Wu, Jiabing; Wang, Anzhi; Jin, Changjie; Yuan, Fenghui

    2015-01-01

    Previous studies with different experimental methods have demonstrated that photosynthesis significantly influences soil respiration (RS). To compare the experimental results of different methods, RS after girdling and defoliation was measured in five-year-old seedlings of Fraxinus mandshurica from June to September. Girdling and defoliation significantly reduced RS by 33% and 25% within 4 days, and 40% and 32% within the entire treatment period, respectively. The differential response of RS to girdling and defoliation was a result of the over-compensation for RS after girdling and redistribution of stored carbon after defoliation. No significant effect on RS was observed between girdling and defoliation treatment, while the soluble sugar content in fine roots was higher in defoliation than in girdling treatment, indicating that defoliation had less compensation effect for RS after interrupting photosynthates supply. We confirm the close coupling of RS with photosynthesis and recommend defoliation for further studies to estimate the effect of photosynthesis on RS. PMID:26177498

  10. Arabidopsis thaliana—Aphid Interaction

    PubMed Central

    Louis, Joe; Singh, Vijay; Shah, Jyoti

    2012-01-01

    Aphids are important pests of plants that use their stylets to tap into the sieve elements to consume phloem sap. Besides the removal of photosynthates, aphid infestation also alters source-sink patterns. Most aphids also vector viral diseases. In this chapter, we will summarize on recent significant findings in plant-aphid interaction, and how studies involving Arabidopsis thaliana and Myzus persicae (Sülzer), more commonly known as the green peach aphid (GPA), are beginning to provide important insights into the molecular basis of plant defense and susceptibility to aphids. The recent demonstration that expression of dsRNA in Arabidopsis can be used to silence expression of genes in GPA has further expanded the utility of Arabidopsis for evaluating the contribution of the aphid genome-encoded proteins to this interaction. PMID:22666177

  11. The long-distance signaling of mineral macronutrients.

    PubMed

    Liu, Tzu-Yin; Chang, Chiung-Yun; Chiou, Tzyy-Jen

    2009-06-01

    In response to varying nutrient availability in soil, plants display a high degree of physiological and developmental plasticity that relies on both local and systemic signaling pathways to coordinate the expression of genes involved in adaptive responses. The integration of these responses at the whole-plant level requires long-distance signaling mechanisms communicating the information between the two indispensable organs, the shoot and the root, which respectively provide photosynthates and mineral nutrients. Although such long-distance signaling is not well understood at the molecular level, several molecules, including hormones, sugars, and nutrients themselves or their metabolites, have been suggested to function as the systemic signals. Moreover, recent discoveries of the phloem-mobile microRNA399s as key components mediating the plant responses to phosphorus stress reveal a novel biological role of small RNA in the long-distance signaling of nutrient status. PMID:19481493

  12. Etude des relations entre photosynthese respiration, transpiration et nutrition minerale chez le ble

    NASA Astrophysics Data System (ADS)

    André, M.; Ducloux, H.; Richaud, C.; Massimino, D.; Daguenet, A.; Massimino, J.; Gerbaud, A.

    La croissance du Blé Triticum aestivum a été étudiée en environnement contrôlé et fermé pendant une période de 70 jours. Les échanges gazeux (Photosynthèse, Respiration) hydriques (Transpiration) et la consommation en éléments minéraux (Azote, Phosphore, Potassium) ont été mesurés en continu. On présentera les relations dynamiques observées entre les différentes fonctions physiologiques, d'une part sous l'influence de la croissance et d'autre part en réponse à des modifications de l'environnement. L'influence de la teneur en CO2 pendant la croissance (teneur normale ou doublée) sera mise en évidence.

  13. Enhancement of photoassimilate utilization by manipulation of the ADPglucose pyrophosphorylase genes. Progress report, [April 15, 1990--April 14, 1991

    SciTech Connect

    Okita, T.W.

    1990-12-31

    The long term goal of this project is to assess the feasibility of increasing the conversion of photosynthate a key regulatory enzyme in starch biosynthesis. In developing storage tissues such as cereal seeds and tubers, starch biosynthesis is primarily regulated by the gene activation, expression, and allosteric regulation of ADPglucose pyrophosphorylase, as well as starch synthase, and branching enzyme. During the last year we have elucidated the structure of both subunits which compose this tetrameric enzyme and determined the temporal and spatial expression of the genes encoding each subunit as well as their correlation to starch biosynthesis. Genomic clones to both subunits have also been isolated and the gene structure of the small subunit determined. Transgenic potato plants have been produced containing deletions of the small subunit promoter. Currently, cis acting elements and their involvement in spatial and temporal expression are under investigation.

  14. Wheat Grain Filling Is Limited by Grain Filling Capacity rather than the Duration of Flag Leaf Photosynthesis: A Case Study Using NAM RNAi Plants

    PubMed Central

    Borrill, Philippa; Fahy, Brendan; Smith, Alison M.; Uauy, Cristobal

    2015-01-01

    It has been proposed that delayed leaf senescence can extend grain filling duration and thus increase yields in cereal crops. We found that wheat (Triticum aestivum) NAM RNAi plants with delayed senescence carried out 40% more flag leaf photosynthesis after anthesis than control plants, but had the same rate and duration of starch accumulation during grain filling and the same final grain weight. The additional photosynthate available in NAM RNAi plants was in part stored as fructans in the stems, whereas stem fructans were remobilised during grain filling in control plants. In both genotypes, activity of starch synthase was limiting for starch synthesis in the later stages of grain filling. We suggest that in order to realise the potential yield gains offered by delayed leaf senescence, this trait should be combined with increased grain filling capacity. PMID:26241955

  15. The post-Paleozoic chronology and mechanism of 13C depletion in primary marine organic matter

    NASA Technical Reports Server (NTRS)

    Popp, B. N.; Takigiku, R.; Hayes, J. M.; Louda, J. W.; Baker, E. W.

    1989-01-01

    Carbon-isotopic compositions of geoporphyrins have been measured from marine sediments of Mesozoic and Cenozoic age in order to elucidate the timing and extent of depletion of 13C in marine primary producers. These results indicate that the difference in isotopic composition of coeval marine carbonates and marine primary photosynthate was approximately 5 to 7 permil greater during the Mesozoic and early Cenozoic than at present. In contrast to the isotopic record of marine primary producers, isotopic compositions of terrestrial organic materials have remained approximately constant for this same interval of time. This difference in the isotopic records of marine and terrestrial organic matter is considered in terms of the mechanisms controlling the isotopic fractionation associated with photosynthetic fixation of carbon. We show that the decreased isotopic fractionation between marine carbonates and organic matter from the Early to mid-Cenozoic may record variations in the abundance of atmospheric CO2.

  16. Origin and Evolution of Plastids and Photosynthesis in Eukaryotes

    PubMed Central

    McFadden, Geoffrey I.

    2014-01-01

    Recent progress in understanding the origins of plastids from endosymbiotic cyanobacteria is reviewed. Establishing when during geological time the endosymbiosis occurred remains elusive, but progress has been made in defining the cyanobacterial lineage most closely related to plastids, and some mechanistic insight into the possible existence of cryptic endosymbioses perhaps involving Chlamydia-like infections of the host have also been presented. The phylogenetic affinities of the host remain obscure. The existence of a second lineage of primary plastids in euglyphid amoebae has now been confirmed, but the quasipermanent acquisition of plastids by animals has been shown to be more ephemeral than initially suspected. A new understanding of how plastids have been integrated into their hosts by transfer of photosynthate, by endosymbiotic gene transfer and repatriation of gene products back to the endosymbiont, and by regulation of endosymbiont division is presented in context. PMID:24691960

  17. Slow-growth phenotype of transgenic tomato expressing apoplastic invertase

    SciTech Connect

    Dickinson, C.D.; Altabella, T.; Chrispeels, M.J. )

    1991-02-01

    The growth of transgenic tomato (Lycopersicon esculentum) plants that express in their apoplast yeast invertase under the control of the cauliflower mosaic virus 35S promoter is severely inhibited. The higher the level of invertase, the greater the inhibition of growth. A second phenotypic characteristic of these transgenic plants is the development of yellow and necrotic spots on the leaves, and leaf curling. Again the severity of the symptoms is correlated with the level of invertase. These symptoms do not develop in shaded leaves indicating the need for photosynthesis. Keeping the plants in the dark for a prolonged period (24 hours) results in the disappearance of leaf starch from the control plants, but not from the plants with apoplastic invertase. These results are consistent with the interpretation that apoplastic invertase prevents photosynthate export from source leaves and that phloem loading includes an apoplastic step.

  18. 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.

  19. Sucrose synthesizing enzymes and /sup 14/C-assimilation in the chlorophyllous layer of developing grapefruit. [Citrus paradisi Macf

    SciTech Connect

    Tomlinson, P.T.; Lowell, C.A.; Koch, K.E.

    1986-04-01

    Fixation of /sup 14/CO/sub 2/ and activities of sucrose-synthesizing enzymes, sucrose phosphate synthetase (SPS) and sucrose synthase (SS), were assayed in tissues of developing fruit and source leaves from Citrus paradisi Macf. SPS activity of both the outer, chlorophyllous layer of the fruit (flavedo) and source leaves was 10-fold greater than that of the inner, largely non-chlorophyllous layer of the fruit peel (albedo). In contrast, SS activity of the flavedo was 2-fold greater than that of the albedo and 10-fold greater than that of leaves. Fixation of /sup 14/C-photosynthates in isolated tissues (flavedo 2x > albedo) and their redistribution in intact fruit indicated that flavedo functions as both source and sink. Activities of sucrose-synthesizing enzymes were consistent with this dual function.

  20. Forest Soil Respiration: Identifying Sources and Controls

    NASA Astrophysics Data System (ADS)

    Högberg, P.

    2008-12-01

    Most of the respiration in forests comes from the soil. This flux is composed of two components, autotrophic and heterotrophic respiration. In a strict sense the former should be plant belowground respiration only, but the term is used here to denote respiration by roots, their mycorrhizal fungal symbionts and other closely associated organisms dependent on recent photosynthate. Heterotrophs are organisms using organic matter, chiefly above- and belowground litters, as substrate (i.e. substrates of in general much higher ecosystem age). Because of the complexity of the plant-soil system, the component fluxes are difficult to study. I will discuss results of different approaches to partition soil respiratory components and to study their controls. The focus will be on northern boreal forests. In these generally strongly nitrogen-limited forests, the autotrophic respiration equals or exceeds the heterotrophic component. The large autotrophic component reflects high plant allocation of C to roots and mycorrhizal fungi in response to the low N supply. A physiological manipulation, girdling, which stops the flow of photosynthates to roots, showed that autotrophic respiration could account for as much as 70% in N-limited forests, but only 40% in fertilized forests. Also using girdling, we could show that a shift to lower summertime temperature leads to a decrease in heterotrophic but not in autotrophic activity, suggesting substrate (photosynthate) limitation of the latter. Physiological manipulations like girdling and trenching cannot be used to reveal the finer details of soil C dynamics. Natural abundance stable isotope (13C) and 14C approaches also have their limitations if a high resolution in terms of time, space and organism is required. A very high resolution can, of course, be obtained in studies of laboratory micro- or mesocosms, but the possibility to extend the interpretation of their results to the field may be questioned. In the CANIFLEX (CArbon NItrogen

  1. [Application of stable carbon isotope technique in the research of carbon cycling in soil-plant system].

    PubMed

    Liu, Wei; Lü, Hao-Hao; Chen, Ying-Xu; Wu, Wei-Xiang

    2008-03-01

    As a main life element, carbon plays important role in the matter cycling in soil-plant system. Stable carbon isotope 13C has been widely used in the study of carbon cycling in soil-plant system, due to its safe, no pollution, and easy to be handled. Through the analysis of both natural and labeled 13C organic matter in soil-plant system, a better understanding of the mechanisms of photosynthesis, the distribution of photosynthates in plant-soil system, the fate of plant litter, and the source of new carbon in soil could be achieved. In this paper, the applications of stable carbon isotope technique in the researches of photosynthesis, reconstruction of paleoclimate, turnover of soil organic matter, and interactions between plants and rhizosphere microorganisms were briefly summarized, and the perspectives of the application of stable carbon isotope technique were also discussed, based on the issues existed in current researches. PMID:18533543

  2. Possible Role of Nutritional Priming for Early Salt and Drought Stress Responses in Medicago truncatula.

    PubMed

    Staudinger, Christiana; Mehmeti, Vlora; Turetschek, Reinhard; Lyon, David; Egelhofer, Volker; Wienkoop, Stefanie

    2012-01-01

    Most legume species establish a symbiotic association with soil bacteria. The plant accommodates the differentiated rhizobia in specialized organs, the root nodules. In this environment, the microsymbiont reduces atmospheric nitrogen (N) making it available for plant metabolism. Symbiotic N-fixation is driven by the respiration of the host photosynthates and thus constitutes an additional carbon sink for the plant. Molecular phenotypes of symbiotic and non-symbiotic Medicago truncatula are identified. The implication of nodule symbiosis on plant abiotic stress response mechanisms is not well understood. In this study, we exposed nodulated and non-symbiotic N-fertilized plants to salt and drought conditions. We assessed the stress effects with proteomic and metabolomic methods and found a nutritionally regulated phenotypic plasticity pivotal for a differential stress adjustment strategy. PMID:23267362

  3. Diel patterns of autotrophic and heterotrophic respiration among phenological stages

    SciTech Connect

    Savage, Kathleen; Davidson, Eric; Tang, Jianwu

    2013-01-01

    Improved understanding of the links between aboveground production and allocation of photosynthate to belowground processes and the temporal variation in those links is needed to interpret observations of belowground carbon cycling processes. Here, we show that combining a trenching manipulation with high-frequency soil respiration measurements in a temperate hardwood forest permitted identification of the temporally variable influence of roots on diel and seasonal patterns of soil respiration. The presence of roots in an untrenched plot caused larger daily amplitude and a 2–3 h delay in peak soil CO2 efflux relative to a root-free trenched plot. These effects cannot be explained by differences in soil temperature, and they were significant only when a canopy was present during the growing season. This experiment demonstrated that canopy processes affect soil CO2 efflux rates and patterns at hourly and seasonal time scales, and it provides evidence that root and microbial processes respond differently to environmental factors.

  4. Vascular Sap Proteomics: Providing Insight into Long-Distance Signaling during Stress

    PubMed Central

    Carella, Philip; Wilson, Daniel C.; Kempthorne, Christine J.; Cameron, Robin K.

    2016-01-01

    The plant vascular system, composed of the xylem and phloem, is important for the transport of water, mineral nutrients, and photosynthate throughout the plant body. The vasculature is also the primary means by which developmental and stress signals move from one organ to another. Due to practical and technological limitations, proteomics analysis of xylem and phloem sap has been understudied in comparison to accessible sample types such as leaves and roots. However, recent advances in sample collection techniques and mass spectrometry technology are making it possible to comprehensively analyze vascular sap proteomes. In this mini-review, we discuss the emerging field of vascular sap proteomics, with a focus on recent comparative studies to identify vascular proteins that may play roles in long-distance signaling and other processes during stress responses in plants. PMID:27242852

  5. Vascular Sap Proteomics: Providing Insight into Long-Distance Signaling during Stress.

    PubMed

    Carella, Philip; Wilson, Daniel C; Kempthorne, Christine J; Cameron, Robin K

    2016-01-01

    The plant vascular system, composed of the xylem and phloem, is important for the transport of water, mineral nutrients, and photosynthate throughout the plant body. The vasculature is also the primary means by which developmental and stress signals move from one organ to another. Due to practical and technological limitations, proteomics analysis of xylem and phloem sap has been understudied in comparison to accessible sample types such as leaves and roots. However, recent advances in sample collection techniques and mass spectrometry technology are making it possible to comprehensively analyze vascular sap proteomes. In this mini-review, we discuss the emerging field of vascular sap proteomics, with a focus on recent comparative studies to identify vascular proteins that may play roles in long-distance signaling and other processes during stress responses in plants. PMID:27242852

  6. SOYCHMBR.I - A model designed for the study of plant growth in a closed chamber

    NASA Technical Reports Server (NTRS)

    Reinhold, C.

    1982-01-01

    The analytical model SOYCHMBER.I, an update and alteration of the SOYMOD/OARDC model, for describing the total processes experienced by a plant in a controlled mass environment is outlined. The model is intended for use with growth chambers for examining plant growth in a completely controlled environment, leading toward a data base for the design of spacecraft food supply systems. SOYCHMBER.I accounts for the assimilation, respiration, and partitioning of photosynthate and nitrogen compounds among leaves, stems, roots, and potentially, flowers of the soybean plant. The derivation of the governing equations is traced, and the results of the prediction of CO2 dynamics for a seven day experiment with rice in a closed chamber are reported, together with data from three model runs for soybean. It is concluded that the model needs expansion to account for factors such as relative humidity.

  7. Tight coupling of root-associated nitrogen fixation and plant photosynthesis in the salt marsh Spartina alterniflora and carbon dioxide enhancement of Nitrogenase activity

    SciTech Connect

    Whiting, G.J.; Gandy, E.L.; Yoch, D.C.

    1986-07-01

    The coupling of root-associated nitrogen fixation and plant photosynthesis was examined in the salt marsh grass Spartina alterniflora. In both field experiments and hydroponic assay chambers, nitrogen fixation associated with the roots was rapidly enhanced by stimulating plant photosynthesis. A kinetic analysis of acetylene reduction activity (ARA) showed that a five-to-sixfold stimulation occurred within 10 to 60 min after the plant leaves were exposed to light or increase CO/sub 2/ concentrations (with the light held constant). In field experiments, CO/sub 2/ enrichment increased plant-associated ARA by 27%. Further evidence of the dependence of ARA on plant photosynthate was obtained when activity in excised roots was shown to decrease after young greenhouse plants were placed in the dark. Seasonal variation in the ARA of excised plant roots from field cores appears to be related to the annual cycle of net photosynthesis in S. alterniflora.

  8. Assimilation of ammonium and nitrate nitrogen by bean plants

    SciTech Connect

    Volk, R.J. ); Chaillou, S.; Morot-Gaudry, J.F. ); Mariotti, A. )

    1989-04-01

    Enhanced growth is often observed in plants growing on combined ammonium and nitrate nutrition. The physiological basis for such enhancement was examined by exposing non-nodulated bean (Phaseolus vulgaris L.) plants to {sup 15}N-labeled, 1.0 mM N solutions containing 0, 33, 67 or 100% of the N as ammonium, the balance being nitrate. Maximal total N uptake and biomass production were attained by plants receiving 33% ammonium. A higher proportion of incoming ammonium than nitrate was incorporated into root protein. This was accompanied by increased partitioning of plant biomass to roots. It was concluded that as a consequence of greater N metabolism in the root under mixed ammonium and nitrate nutrition, the root became a more active sink for photosynthate. Concurrently, the augmented supply of N to the shoot enhanced net photosynthesis as reflected in increased plant biomass.

  9. [Effects of water and nitrogen management modes on the leaf photosynthetic characters and yield formation of cotton with under-mulch drip irrigation].

    PubMed

    Luo, Hong-Hai; Zhang, Hong-Zhi; Tao, Xian-Ping; Zhang, Ya-Li; Zhang, Wang-feng

    2013-02-01

    Taking different genotype cotton varieties as test materials, a soil column culture experiment was conducted to study the effects of water and nitrogen management modes on the photosynthetic characters and yield formation of cotton with under-mulch drip irrigation in Xinjiang, Northwest China. Under the management mode W4N2, i.e., pre-sowing irrigation + limited drip irrigation before full-flowering + abundant drip irrigation after full-flowering in combining with basal 20% N + topdressing 80% N, the chlorophyll content, net photosynthetic rate (Pn), stomatal conductance (gs) , actual photochemical efficiency of photosystem II (Psi PSII), and photochemical quenching coefficient (qp) at full-flowering stage all decreased significantly, the non-photochemical quenching (NPQ) increased, and the aboveground dry matter accumulation was inhibited, as compared with those under common drip irrigation. From full-flowering stage to boll-opening stage, the chlorophyll content, gs, Pn, Psi PSII, and qp increased with increasing water and nitrogen supply, and the aboveground dry matter accumulation was enhanced by compensation, which benefited the translocation and distribution of photosynthates to seed cotton. Under the fertilization mode of basal 20% N + topdressing 80% N, the seed cotton yield of Xinluzaol3 was the highest in treatment pre-sowing irrigation + common drip irrigation (W3), but that of Xinluzao43 was the highest in treatment pre-sowing irrigation + limited drip irrigation before full-flowering + abundant drip irrigation after full-flowering (W4). It was concluded that under the condition of pre-sowing irrigation, to appropriately decrease the water and nitrogen supply before full-flowering stage and increase the water and nitrogen supply at middle and late growth stages could extend the active photosynthesis duration and promote the photosynthates allocation to reproductive organ, which would fully exploit the yield-increasing potential of cotton with under

  10. 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

  11. Carbon isotope composition of latex does not reflect temporal variations of photosynthetic carbon isotope discrimination in rubber trees (Hevea brasiliensis).

    PubMed

    Kanpanon, Nicha; Kasemsap, Poonpipope; Thaler, Philippe; Kositsup, Boonthida; Gay, Frédéric; Lacote, Régis; Epron, Daniel

    2015-11-01

    Latex, the cytoplasm of laticiferous cells localized in the inner bark of rubber trees (Hevea brasiliensis Müll. Arg.), is collected by tapping the bark. Following tapping, latex flows out of the trunk and is regenerated, whereas in untapped trees, there is no natural exudation. It is still unknown whether the carbohydrates used for latex regeneration in tapped trees is coming from recent photosynthates or from stored carbohydrates, and in the former case, it is expected that latex carbon isotope composition of tapped trees will vary seasonally, whereas latex isotope composition of untapped trees will be more stable. Temporal variations of carbon isotope composition of trunk latex (δ(13)C-L), leaf soluble compounds (δ(13)C-S) and bulk leaf material (δ(13)C-B) collected from tapped and untapped 20-year-old trees were compared. A marked difference in δ(13)C-L was observed between tapped and untapped trees whatever the season. Trunk latex from tapped trees was more depleted (1.6‰ on average) with more variable δ(13)C values than those of untapped trees. δ(13)C-L was higher and more stable across seasons than δ(13)C-S and δ(13)C-B, with a maximum seasonal difference of 0.7‰ for tapped trees and 0.3‰ for untapped trees. δ(13)C-B was lower in tapped than in untapped trees, increasing from August (middle of the rainy season) to April (end of the dry season). Differences in δ(13)C-L and δ(13)C-B between tapped and untapped trees indicated that tapping affects the metabolism of both laticiferous cells and leaves. The lack of correlation between δ(13)C-L and δ(13)C-S suggests that recent photosynthates are mixed in the large pool of stored carbohydrates that are involved in latex regeneration after tapping. PMID:26358051

  12. Regulatory Properties of ADP Glucose Pyrophosphorylase Are Required for Adjustment of Leaf Starch Synthesis in Different Photoperiods1[W][OPEN

    PubMed Central

    Mugford, Sam T.; Fernandez, Olivier; Brinton, Jemima; Flis, Anna; Krohn, Nicole; Encke, Beatrice; Feil, Regina; Sulpice, Ronan; Lunn, John E.; Stitt, Mark; Smith, Alison M.

    2014-01-01

    Arabidopsis (Arabidopsis thaliana) leaves synthesize starch faster in short days than in long days, but the mechanism that adjusts the rate of starch synthesis to daylength is unknown. To understand this mechanism, we first investigated whether adjustment occurs in mutants lacking components of the circadian clock or clock output pathways. Most mutants adjusted starch synthesis to daylength, but adjustment was compromised in plants lacking the GIGANTEA or FLAVIN-BINDING, KELCH REPEAT, F BOX1 components of the photoperiod-signaling pathway involved in flowering. We then examined whether the properties of the starch synthesis enzyme adenosine 5′-diphosphate-glucose pyrophosphorylase (AGPase) are important for adjustment of starch synthesis to daylength. Modulation of AGPase activity is known to bring about short-term adjustments of photosynthate partitioning between starch and sucrose (Suc) synthesis. We found that adjustment of starch synthesis to daylength was compromised in plants expressing a deregulated bacterial AGPase in place of the endogenous AGPase and in plants containing mutant forms of the endogenous AGPase with altered allosteric regulatory properties. We suggest that the rate of starch synthesis is in part determined by growth rate at the end of the preceding night. If growth at night is low, as in short days, there is a delay before growth recovers during the next day, leading to accumulation of Suc and stimulation of starch synthesis via activation of AGPase. If growth at night is fast, photosynthate is used for growth at the start of the day, Suc does not accumulate, and starch synthesis is not up-regulated. PMID:25293961

  13. Regulatory properties of ADP glucose pyrophosphorylase are required for adjustment of leaf starch synthesis in different photoperiods.

    PubMed

    Mugford, Sam T; Fernandez, Olivier; Brinton, Jemima; Flis, Anna; Krohn, Nicole; Encke, Beatrice; Feil, Regina; Sulpice, Ronan; Lunn, John E; Stitt, Mark; Smith, Alison M

    2014-12-01

    Arabidopsis (Arabidopsis thaliana) leaves synthesize starch faster in short days than in long days, but the mechanism that adjusts the rate of starch synthesis to daylength is unknown. To understand this mechanism, we first investigated whether adjustment occurs in mutants lacking components of the circadian clock or clock output pathways. Most mutants adjusted starch synthesis to daylength, but adjustment was compromised in plants lacking the GIGANTEA or FLAVIN-BINDING, KELCH REPEAT, F BOX1 components of the photoperiod-signaling pathway involved in flowering. We then examined whether the properties of the starch synthesis enzyme adenosine 5'-diphosphate-glucose pyrophosphorylase (AGPase) are important for adjustment of starch synthesis to daylength. Modulation of AGPase activity is known to bring about short-term adjustments of photosynthate partitioning between starch and sucrose (Suc) synthesis. We found that adjustment of starch synthesis to daylength was compromised in plants expressing a deregulated bacterial AGPase in place of the endogenous AGPase and in plants containing mutant forms of the endogenous AGPase with altered allosteric regulatory properties. We suggest that the rate of starch synthesis is in part determined by growth rate at the end of the preceding night. If growth at night is low, as in short days, there is a delay before growth recovers during the next day, leading to accumulation of Suc and stimulation of starch synthesis via activation of AGPase. If growth at night is fast, photosynthate is used for growth at the start of the day, Suc does not accumulate, and starch synthesis is not up-regulated. PMID:25293961

  14. Effect of CO sub 2 enriched air on the kinetics of leaf expansion. [Pisum sativa; Glycine max

    SciTech Connect

    Potter, J.R. )

    1991-05-01

    Vegetative plants of Pisum sativum (pea) and Glycine max (soybean) were transferred from 350 to 1,200 ppm CO{sub 2} when they had one (pea) or two (soybean) mature leaves and several developing leaves. Controls were kept at 350 ppm. For pea, high CO{sub 2} for 8 days increased dry mass of root, stem, and leaf fractions by 30-50%. Leaf dry mass increase was due primarily to carbohydrate, particularly starch. Dawn levels of starch increased 10-fold within 1 day at high CO{sub 2} and 20-fold at 2 days. At 2 days after transfer leaf starch levels were 1.0 mg cm{sup {minus}2} of leaf area or nearly 30% of leaf dry weight. Soybean data are less complete, but 10 days at high CO{sub 2} increased leaf + stem dry mass by 50% and leaf weight per unit area increased by 14 and 48% at dawn within 1 and 2 days, respectively, at high CO{sub 2}. However 8-10 days at high CO{sub 2} increased total leaf area only slightly (about 15%) for both species, with all the leaf area increase occurring at nodes that were nearly microscopic at the time of transfer. For soybean, most of the increased leaf area due to high CO{sub 2} was from lateral bud break despite a high CO{sub 2} did not stimulated more leaves per plant. Apparently, extra photosynthate had a delayed effect on leaf expansion and did not increase nodes along the main axis. Leaf expansion under high CO{sub 2} was not limited by photosynthate.

  15. Photophysiology and cellular composition of sea ice algae

    SciTech Connect

    Lizotte, M.P.

    1989-01-01

    The productivity of sea ice algae depends on their physiological capabilities and the environmental conditions within various microhabitats. Pack ice is the dominant form of sea ice, but the photosynthetic activity of associated algae has rarely been studied. Biomass and photosynthetic rates of ice algae of the Weddell-Scotia Sea were investigated during autumn and winter, the period when ice cover grows from its minimum to maximum. Biomass-specific photosynthetic rates typically ranged from 0.3 to 3.0 {mu}g C {center dot} {mu}g chl{sup {minus}1} {center dot} h{sup {minus}1} higher than land-fast ice algae but similar to Antarctic phytoplankton. Primary production in the pack ice during winter may be minor compared to annual phytoplankton production, but could represent a vital seasonal contribution to the Antarctic ecosystem. Nutrient supply may limit the productivity of ice algae. In McMurdo Sound, congelation ice algae appeared to be more nutrient deficient than underlying platelet ice algae based on: lower nitrogen:carbon, chlorophyll:carbon, and protein:carbohydrate; and {sup 14}C-photosynthate distribution to proteins and phospholipids was lower, while distribution to polysaccharides and neutral lipids was higher. Depletion of nitrate led to decreased nitrogen:carbon, chlorophyll:carbon, protein:carbohydrate, and {sup 14}C-photosynthate to proteins. Studied were conducted during the spring bloom; therefore, nutrient limitation may only apply to dense ice algal communities. Growth limiting conditions may be alleviated when algae are released into seawater during the seasonal recession of the ice cover. To continue growth, algae must adapt to the variable light field encountered in a mixed water column. Photoadaptation was studied in surface ice communities and in bottom ice communities.

  16. Expanding leaves of mature deciduous forest trees rapidly become autotrophic.

    PubMed

    Keel, Sonja G; Schädel, Christina

    2010-10-01

    Emerging leaves in evergreen tree species are supplied with carbon (C) from the previous year's foliage. In deciduous trees, no older leaves are present, and the early phase of leaf development must rely on C reserves from other tissues. How soon developing leaves become autotrophic and switch from being C sinks to sources has rarely been studied in mature forest trees, and simultaneous comparisons of species are scarce. Using a canopy crane and a simple (13)CO(2)-pulse-labelling technique, we demonstrate that young leaves of mature trees in three European deciduous species (Fagus sylvatica L., Quercus petraea (Matt.) Liebl., Tilia platyphyllos Scop.) start assimilating CO(2) at a very early stage of development (10-50% expanded). One month after labelling, all leaves were still strongly (13)C enriched, suggesting that recent photosynthates had been incorporated into slow turnover pools such as cellulose or lignin and thus had contributed to leaf growth. In line with previous studies performed at the same site, we found stronger incorporation of recent photosynthates into growing tissues of T. platyphyllos compared with F. sylvatica and Q. petraea. Non-structural carbohydrate (NSC) concentrations analysed for one of the three study species (F. sylvatica) showed that sugar and starch pools rapidly increased during leaf development, suggesting that newly developed leaves soon produce more NSC than can be used for growth. In conclusion, our findings indicate that expanding leaves of mature deciduous trees become C autonomous at an early stage of development despite the presence of vast amounts of mobile carbohydrate reserves. PMID:20688879

  17. Point cloud generation from aerial image data acquired by a quadrocopter type micro unmanned aerial vehicle and a digital still camera.

    PubMed

    Rosnell, Tomi; Honkavaara, Eija

    2012-01-01

    The objective of this investigation was to develop and investigate methods for point cloud generation by image matching using aerial image data collected by quadrocopter type micro unmanned aerial vehicle (UAV) imaging systems. Automatic generation of high-quality, dense point clouds from digital images by image matching is a recent, cutting-edge step forward in digital photogrammetric technology. The major components of the system for point cloud generation are a UAV imaging system, an image data collection process using high image overlaps, and post-processing with image orientation and point cloud generation. Two post-processing approaches were developed: one of the methods is based on Bae Systems' SOCET SET classical commercial photogrammetric software and another is built using Microsoft(®)'s Photosynth™ service available in the Internet. Empirical testing was carried out in two test areas. Photosynth processing showed that it is possible to orient the images and generate point clouds fully automatically without any a priori orientation information or interactive work. The photogrammetric processing line provided dense and accurate point clouds that followed the theoretical principles of photogrammetry, but also some artifacts were detected. The point clouds from the Photosynth processing were sparser and noisier, which is to a large extent due to the fact that the method is not optimized for dense point cloud generation. Careful photogrammetric processing with self-calibration is required to achieve the highest accuracy. Our results demonstrate the high performance potential of the approach and that with rigorous processing it is possible to reach results that are consistent with theory. We also point out several further research topics. Based on theoretical and empirical results, we give recommendations for properties of imaging sensor, data collection and processing of UAV image data to ensure accurate point cloud generation. PMID:22368479

  18. A Role for Programmed Cell Death in the Microbial Loop

    PubMed Central

    Durand, Pierre M.; Whitehead, Kenia; Baliga, Nitin S.

    2013-01-01

    The microbial loop is the conventional model by which nutrients and minerals are recycled in aquatic eco-systems. Biochemical pathways in different organisms become metabolically inter-connected such that nutrients are utilized, processed, released and re-utilized by others. The result is that unrelated individuals end up impacting each others' fitness directly through their metabolic activities. This study focused on the impact of programmed cell death (PCD) on a population's growth as well as its role in the exchange of carbon between two naturally co-occurring halophilic organisms. Flow cytometric, biochemical, 14C radioisotope tracing assays, and global transcriptomic analyses show that organic algal photosynthate released by Dunalliela salina cells undergoing PCD complements the nutritional needs of other non-PCD D. salina cells. This occurs in vitro in a carbon limited environment and enhances the growth of the population. In addition, a co-occurring heterotroph Halobacterium salinarum re-mineralizes the carbon providing elemental nutrients for the mixoheterotrophic chlorophyte. The significance of this is uncertain and the archaeon can also subsist entirely on the lysate of apoptotic algae. PCD is now well established in unicellular organisms; however its ecological relevance has been difficult to decipher. In this study we found that PCD in D. salina causes the release of organic nutrients such as glycerol, which can be used by others in the population as well as a co-occurring halophilic archaeon. H. salinarum also re-mineralizes the dissolved material promoting algal growth. PCD in D. salina was the mechanism for the flow of dissolved photosynthate between unrelated organisms. Ironically, programmed death plays a central role in an organism's own population growth and in the exchange of nutrients in the microbial loop. PMID:23667496

  19. Point Cloud Generation from Aerial Image Data Acquired by a Quadrocopter Type Micro Unmanned Aerial Vehicle and a Digital Still Camera

    PubMed Central

    Rosnell, Tomi; Honkavaara, Eija

    2012-01-01

    The objective of this investigation was to develop and investigate methods for point cloud generation by image matching using aerial image data collected by quadrocopter type micro unmanned aerial vehicle (UAV) imaging systems. Automatic generation of high-quality, dense point clouds from digital images by image matching is a recent, cutting-edge step forward in digital photogrammetric technology. The major components of the system for point cloud generation are a UAV imaging system, an image data collection process using high image overlaps, and post-processing with image orientation and point cloud generation. Two post-processing approaches were developed: one of the methods is based on Bae Systems’ SOCET SET classical commercial photogrammetric software and another is built using Microsoft®’s Photosynth™ service available in the Internet. Empirical testing was carried out in two test areas. Photosynth processing showed that it is possible to orient the images and generate point clouds fully automatically without any a priori orientation information or interactive work. The photogrammetric processing line provided dense and accurate point clouds that followed the theoretical principles of photogrammetry, but also some artifacts were detected. The point clouds from the Photosynth processing were sparser and noisier, which is to a large extent due to the fact that the method is not optimized for dense point cloud generation. Careful photogrammetric processing with self-calibration is required to achieve the highest accuracy. Our results demonstrate the high performance potential of the approach and that with rigorous processing it is possible to reach results that are consistent with theory. We also point out several further research topics. Based on theoretical and empirical results, we give recommendations for properties of imaging sensor, data collection and processing of UAV image data to ensure accurate point cloud generation. PMID:22368479

  20. 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

  1. Simulating Energy, Water and Carbon Fluxes at the Shortgrass Steppe Long Term Ecological Research (LTER) Site

    NASA Astrophysics Data System (ADS)

    Beltran-Przekurat, A. B.; Pielke, R. A.; Morgan, J. A.; Burke, I. C.

    2005-12-01

    Coupled atmospheric-biospheric models are a particularly valuable tool for studying the potential effects of land-use and land-cover changes on the near-surface atmosphere since the atmosphere and biosphere are allowed to dynamically interact through the surface and canopy energy balance. GEMRAMS is a coupled atmospheric-biospheric model comprised of an atmospheric model, RAMS, and an ecophysiological process-based model, GEMTM. In the first part of this study, the soil-vegetation-atmosphere-transfer (SVAT) scheme, LEAF2, from RAMS, coupled with GEMTM, are used to simulate energy, water and carbon fluxes over different cropping systems (winter wheat and irrigated corn) and over a mixed C3/C4 shortgrass prairie located at the USDA-ARS Central Plains Experimental Range near Nunn, Colorado, the LTER Shortgrass Steppe site. The new SVAT scheme, GEMLEAF, is forced with air temperature and humidity, wind speed and photosynthetic active radiation (PAR). Calculated canopy temperature and relative humidity, soil moisture and temperature and PAR are used to compute sunlit/shaded leaf photosynthesis (for C3 and C4 plant types) and respiration. Photosynthate is allocated to leaves, shoots, roots and reproductive organs with variable partition coefficients, which are functions of soil water conditions. As water stress increases, the fraction of photosynthate allocated to root growth increases. Leaf area index (LAI) is estimated from daily leaf biomass growth, using the vegetation-prescribed specific leaf area. Canopy conductance, computed and based on photosynthesis and relative humidity, is used to calculate latent heat flux. Simulated energy and CO2 fluxes are compared to observations collected using Bowen ratio flux towers during two growing seasons. Seasonality of the fluxes reflecting different plant phenologies agrees well with the observed patterns. In the second part of this study, simulations for two clear days are performed with GEMRAMS over a model domain centered at

  2. Clonal integration ameliorates the carbon accumulation capacity of a stoloniferous herb, Glechoma longituba, growing in heterogenous light conditions by facilitating nitrogen assimilation in the rhizosphere

    PubMed Central

    Chen, Jin-Song; Li, Jun; Zhang, Yun; Zong, Hao; Lei, Ning-Fei

    2015-01-01

    Background and Aims Enhanced availability of photosynthates increases nitrogen (N) mineralization and nitrification in the rhizosphere via rhizodeposition from plant roots. Under heterogeneous light conditions, photosynthates supplied by exposed ramets may promote N assimilation in the rhizosphere of shaded, connected ramets. This study was conducted to test this hypothesis. Methods Clonal fragments of the stoloniferous herb Glechoma longituba with two successive ramets were selected. Mother ramets were subjected to full sunlight and offspring ramets were subjected to 80 % shading, and the stolon between the two successive ramets was either severed or left intact. Measurements were taken of photosynthetic and growth parameters. The turnover of available soil N was determined together with the compostion of the rhizosphere microbial community. Key Results The microbial community composition in the rhizosphere of shaded offspring ramets was significantly altered by clonal integration. Positive effects of clonal integration were observed on NAGase activity, net soil N mineralization rate and net soil N nitrification rate. Increased leaf N and chlorophyll content as well as leaf N allocation to the photosynthetic machinery improved the photosynthetic capability of shaded offspring ramets when the stolon was left intact. Clonal integration improved the growth performance of shaded, connected offspring ramets and whole clonal fragments without any cost to the exposed mother ramets. Conclusions Considerable differences in microbial community composition caused by clonal integration may facilitate N assimilation in the rhizosphere of shaded offspring ramets. Increased N content in the photosynthetic machinery may allow pre-acclimation to high light conditions for shaded offspring ramets, thus promoting opportunistic light capture. In accordance with the theory of the division of labour, it is suggested that clonal integration may ameliorate the carbon assimilation

  3. Tracking the influence of global change on soil organic C: opportunities and challenges

    NASA Astrophysics Data System (ADS)

    Billings, S. A.; Ziegler, S. E.; Li, J.

    2009-12-01

    Anthropogenic global changes such as rising atmospheric CO2 and temperatures likely will enhance multiple flows of carbon (C) between terrestrial ecosystems and the atmosphere. Understanding the changes these perturbations exert on soil organic C (SOC) pools and fluxes is critical for predicting climate, yet approaches for quantifying changes in SOC cycling suffer from deficiencies. We outline opportunities and challenges of employing stable isotopes in short- and longer-term studies to track soil change, using two forests as case studies. Relatively short-term lab studies employing isotopically labeled compounds can help us elucidate mechanisms of SOC stabilization and loss, but added substrate represents a small fraction of the complex suite of compounds in situ and can induce priming effects. By replacing inputs to a soil profile with labeled photosynthate, we can trace realistic substrates through the soil profile, but the time required for the substrate to become incorporated into all soil organic matter (SOM) fractions is longer than most study periods. These pros and cons are exemplified by two studies. First, tracing 13C-labeled photosynthate applied to temperate pine forest soils for ~10 y demonstrated unequal distribution of 13C label among SOC components, but we discerned likely enhanced activity of microorganisms that turnover recalcitrant SOC compounds in forests exposed to elevated CO2. Here, we describe data consistent with this, emanating from laboratory incubations in which 13C labeled, individual compounds were applied to elevated CO2 and control soils. We demonstrate increased fungal and actinomycete activity with elevated CO2. Here, short-term, lab experiments with simple 13C compounds strengthen longer-term in situ studies. We also employed knowledge gained from these studies to assess how warming will alter flows of SOC. Along a climate transect in boreal forests with similar vegetation and soil types, we applied 13C-labeled photosynthate to

  4. Sources of Below-Ground Respired Carbon in a Northern Minnesota Ombrotrophic Spruce Bog and the Influence of Heating Manipulations.

    NASA Astrophysics Data System (ADS)

    Guilderson, T. P.; McFarlane, K. J.; McNicol, G.; Hanson, P. J.; Chanton, J.; Wilson, R.; Bosworth, R.; Singleton, M. J.

    2015-12-01

    A significant uncertainty in future land-surface carbon budgets is the response of wetlands to climate change. A related question is the future net climate (radiative) forcing impact due to ecosystem and environmental change in wetlands. Active wetlands emit both CO2 and CH4 to the atmosphere. CH4 is, over a few decades, a much more potent greenhouse gas than CO2 whereas as a consequence of a much longer atmospheric lifetime, CO2 has a longer 'tail' to its influence. Whether wetlands are a net source or sink of atmospheric carbon under future climate change will depend on the response of the ecosystem to rising temperatures and elevated CO2. The largest uncertainty in future wetland budgets, and its climate forcing, is the stability of the large belowground carbon stocks, often in the form of peat, and the partitioning of CO2 and CH4released via ecosystem respiration. We have characterized the isotopic signatures (14,13C of CO2 and CH4, D-CH4) of the respired carbon used for the production of CO2 and CH4 from the DOE Spruce and Peatland Responses Under Climatic and Environmental Change (SPRUCE) site in the Marcell Experimental Forest, which contains replicated mesocosm manipulations including above/below ground warming and elevated CO2. Deep warming (1-2 m) was initiated in July of 2014 and above ground heating will be initiated in July 2015. Comparison of the respired CO2 and CH4with recently fixed photosynthate, below-ground peat (up to 11,000 years old), and dissolved organic carbon allow us to determine the primary substrates used by the microbial community. Control and pre-perturbed plots are characterized by the consumption and respiration of recently fixed photosynthate and recent (few years to 15 yr) carbon. Although CH4 fluxes have begun to respond to deep-heating, the source of carbon remains similar in the control and perturbed plots. Respired CO2 remains consistent with being sourced from carbon only a few years old. We will present additional data

  5. How important is root-derived CO2 transport via the transpiration stream when assessing belowground carbon allocation?

    NASA Astrophysics Data System (ADS)

    Bloemen, J.; Agneessens, L.; Vanhaecke, L.; Steppe, K.

    2012-12-01

    Non-isotopic approaches for studying the impact of belowground carbon allocation on soil respiration are based on soil CO2 efflux measurements after interrupting the flux of photosynthates to belowground tissues (e.g. Högberg et al., 2001). However, recent research has shown that one-half of root-respired CO2 may follow an internal flux pathway via the transpiration stream which cannot be accounted for by soil CO2 efflux measurements (Aubrey & Teskey, 2009). Consequently, given the magnitude of this internally transported CO2 via the stem, established soil CO2 efflux-based approaches might routinely underestimate autotrophic respiration and the carbon needed to sustain belowground tissues. In this study, we measured simultaneously and at a high temporal resolution sap flow and internal xylem CO2 concentration at the stem base of field-grown oak trees as well as soil CO2 efflux near each tree to determine the relative importance of internal transport of root-respired CO2 when assessing belowground carbon allocation. One subgroup of trees was girdled to interrupt the flux of photosynthates to belowground tissues, while a group of non-girdled trees from the same site was used as a control. Results showed, within 5 days after girdling, decreases up to 21.8 ± 3.7% and 21.4 ± 1.1% for soil CO2 efflux and internal CO2 transport, respectively, relative to the measurements in the control plots. Moreover, we found with this new approach that efflux-based methods may substantially underestimate autotrophic respiration, as up to 44.9 ± 0.7% of root-respired CO2 can be transported upwards via the transpiration stream at periods of high sap flow. The results from this study provide the first experimental evidence that CO2 transported via the transpiration stream is strongly dependent on the current assimilate flux to belowground tissues. Therefore approaches for quantifying the impact of belowground carbon allocation on processes at root level should account for this

  6. [Effectiveness of symbiotic n2-fixation in leguminous plants, as affected by inoculation with rhizobia, by substrate, n-fertilizing, and 14c-sucrose application (author's transl)].

    PubMed

    Merbach, W; Schilling, G

    1980-01-01

    Cultivation experiments (Mitscherlich-vessels, quartz sand, 15N-labelled soil, 15N-fertilizer) showed, that various strains of Rhizobium lupini (white and yellow lupines) and of Rhizobium leguminosarum (field beans and peas) induced a different N2-fixation of the inoculated plants, the most effective Rhizobium strains being 367a, Cz, T3, 271 (Rh. lupini), and Azotogen (Rh, leguminosarum). Yellow lupines and field bean plants were supplied with N2 from the air considerably better than white lupines and peas after inoculation with the most effective Rhizobium strains. Application of mineral N to the white lupines and peas not only substituted the inhibited N2-fixation, but increased N amounts in the plants. White lupines fixed more N2 under soil conditions than in quartz sand. An experiment with steam-sterilized and 15-labelled soil as a comparative substrate showed, that this finding was mainly caused by an additional Rhizobium infection from the soil. Contrary to field beans and yellow lupines which fix N2 up to ripeness, white lupines and peas finished N2-fixation in the time of flowering. Mineral-N applied at that time was an additional source of N for last-named plants and they utilized it for production of higher protein yields. Continual spraying of white lupine plants with 14C-labelled sucrose solution after the time of flowering caused continuance of N2-fixation up to the stage of ripeness. It is assumed that the cause of this effect was the competition of growing seeds and nodules for the photosynthates. The supply of nodules was inadequate without external sucrose application. Mineral N inhibited the sucrose-induced N2-fixation of white lupine nodules and their consumption of photosynthates. Consequently, the applied 14C was transported into seeds to a larger extent. The investigations allow the following conclusion: Effective N2-fixation requires nodules being a powerful sink for assimilates on the basis of a highly efficient photosynthetic system of the

  7. Coupling aboveground and belowground activities using short term fluctuations in 13C composition of soil respiration

    NASA Astrophysics Data System (ADS)

    Epron, D.; Parent, F.; Grossiord, C.; Plain, C.; Longdoz, B.; Granier, A.

    2011-12-01

    There is a growing amount of evidence that belowground processes in forest ecosystems are tightly coupled to aboveground activities. Soil CO2 efflux, the largest flux of CO2 to the atmosphere, is dominated by root respiration and by respiration of microorganisms that find the carbohydrates required to fulfil their energetic costs in the rhizosphere. A close coupling between aboveground photosynthetic activity and soil CO2 efflux is therefore expected. The isotopic signature of photosynthates varies with time because photosynthetic carbon isotope discrimination is dynamically controlled by environmental factors. This temporal variation of δ13C of photosynthate is thought to be transferred along the tree-soil continuum and it will be retrieved in soil CO2 efflux after a time lag that reflects the velocity of carbon transport from canopy to belowground. However, isotopic signature of soil CO2 efflux is not solely affected by photosynthetic carbon discrimination, bur also by post photosynthetic fractionation, and especially by fractionation processes affecting CO2 during the transport from soil layers to surface. Tunable diode laser spectrometry is a useful tool to quantify short-term variation in δ13C of soil CO2 efflux and of CO2 in the soil atmosphere. We set up hydrophobic tubes to measure the vertical profile of soil CO2 concentration and its δ13C composition in a temperate beech forest, and we monitored simultaneously δ13C of trunk and soil CO2 efflux, δ13C of phloem exudate and δ13C of leaf sugars. We evidenced that temporal changes in δ13C of soil CO2 and soil CO2 efflux reflected changes in environmental conditions that affect photosynthetic discrimination and that soil CO2 was 4.4% enriched compared to soil CO2 efflux according to diffusion fractionation. However, this close coupling can be disrupted when advective transport of CO2 took place. We also reported evidences that temporal variations in the isotopic composition of soil CO2 efflux reflect

  8. The age of root and soil respired CO2 in a Pacific Northwest old-growth forest: Implications of seasonality and drought effects on carbon source use

    NASA Astrophysics Data System (ADS)

    Taylor, A.; Hopkins, F. M.; Lai, C.; Xu, X.; Randerson, J. T.; Bush, S.; Ehleringer, J. R.

    2013-12-01

    Abstract Climate change has the potential to impact the carbon (C) cycle in unknown ways. Factors such as temperature, light, and moisture can strongly influence whether forest ecosystems are net sources or sinks of CO2. In this study, we used radiocarbon (14C) to determine the age and source of soil- and root-respired CO2 using a combination of soil chamber and biomass incubation measurements in an old-growth forest at the Wind River Field Station, WA. We had two main goals for this study. The first was to determine if the contribution of recent photosynthate to root respiration changed between spring and summer seasons. 14C measurements were used to determine the average age of respired CO2, since respired CO2 fueled by recent photosynthates have Δ14C values similar to that of the current atmosphere (~ 25‰ in 2012), whereas C stored by trees from prior years would be 30‰ or higher. This study occurred over two growing seasons, examining the effects of seasonality and water stress on root/soil respiration. Because of the summer drought conditions consistently experienced by this old-growth forest, this study provides a new dataset to test the hypothesis that plants allocate their C resources in response to stress. Initial results showed soil organic matter components had Δ14C values 80-120‰ greater than that of the background atmosphere, suggesting turnover times on the order of years to decades. In contrast, root respiration was much lower in Δ14C (~40‰), but still elevated with respect to current atmospheric Δ14C values, suggesting that root respiration was at least partially composed of C stored for > 1 year. The second goal was to partition the contribution of autotrophic to heterotrophic respiration and to determine how this ratio differs on diurnal and seasonal timescales. We used the difference between autotrophic and heterotrophic Δ14C values to partition total soil respiration. Preliminary results for April 2013 showed that ~1/3 of soil

  9. Biologically-Mediated Weathering of Minerals From Nanometre Scale to Environmental Systems

    NASA Astrophysics Data System (ADS)

    Brown, D. J.; Banwart, S. A.; Smits, M. M.; Leake, J. R.; Bonneville, S.; Benning, L. G.; Haward, S. J.; Ragnarsdottir, K.

    2007-12-01

    The Weathering Science Consortium is a multi-disciplinary project that aims to create a step change in understanding how biota control mineral weathering and soil formation (http://www.wun.ac.uk/wsc). Our hypothesis is that rates of biotic weathering are driven by the energy supply from plants to the organisms, controlling their biomass, surface area of contact with minerals and their capacity to interact chemically with minerals. Symbiotic fungal mycorrhiza of 90% of plant species are empowered with an available carbohydrate supply from plants that is unparalleled amongst soil microbes. They develop extensive mycelial networks that intimately contact minerals, which they weather aggressively. We hypothesise that mycorrhiza play a critical role through their focussing of photosynthate energy from plants into sub-surface weathering environments. Our work identifies how these fungal cells, and their secretions, interact with mineral surfaces and affect the rates of nutrient transfer from minerals to the organism. Investigating these living systems allows us to create new concepts and mathematical models that can describe biological weathering and be used in computer simulations of soil weathering dynamics. We are studying these biochemical interactions at 3 levels of observation: 1. At the molecular scale to understand interactions between living cells and minerals and to quantify the chemistry that breaks down the mineral structure; 2. At the soil grain scale to quantify the activity and spatial distribution of the fungi, roots and other organisms (e.g. bacteria) and their effects on the rates at which minerals are dissolved to release nutrients; 3. At soil profile scale to test models for the spatial distribution of active fungi and carbon energy and their seasonal variability and impact on mineral dissolution rates. Here we present early results from molecular and soil grain scale experiments. We have grown pure culture (Suillus bovinus, Paxillus involutus

  10. Patterns of Storage, Synthesis and Changing Light Levels Revealed by Carbon Isotope Microsampling within Eocene Metasequoia Tree Rings

    NASA Astrophysics Data System (ADS)

    Jahren, H.; Sternberg, L.

    2005-12-01

    Fossil tree rings from Axel Heiberg Island were microanalyzed for δ13C value in order to assess patterns of tree growth and carbon storage within the Middle Eocene (~45 Ma) Arctic paleoenvironment. Wood from four Metasequoia-type individuals was subsampled for analysis: each individual fossil consisted of between 4 and 10 large (~1 cm thick) consecutive tree rings. One of the fossils displayed an obvious concentric pattern, allowing for the determination of the direction of growth with isotopic pattern. Each ring was divided into ~1 mm thick subsamples, resulting in 5-10 δ13C value determinations per period of ring growth (i.e., growing season). All rings revealed a distinct pattern that was characteristic across growing seasons and across individual fossils. Early in the season, δ13C was at its highest value but descended systematically and sharply to its lowest value at the end of the growing season. Total decrease ranged between 3 and 5 ‰ over the course of each growing season. Identical patterns were observed in the δ13C value of alpha-cellulose isolated from each subsample, indicating that the trends observed did not represent changing levels of secondary metabolites, but rather a seasonal adjustment in the bulk source of carbon used during biosynthesis. Our results are consistent with the following annual pattern of wood synthesis 1.) complete dependence on the mobilization of stored carbon compounds early in the growing season; 2.) systematically increasing use of actively-acquired photosynthate during the growing season; 3.) complete reliance on active photosynthate by the end of the growing season. An additional and significant source of 13C discrimination is declining light levels late in the growing season, and likely contributes to the extreme pattern of δ13C decrease seen across each ring. Our results mimic those seen from modern broadleaf deciduous trees (Helle & Schlesser 2004), but differ from those seen in modern conifers (Barbour et al 2002

  11. Investigating methods of stream planform identification

    NASA Astrophysics Data System (ADS)

    Lohberg, M. M.; Lusk, K.; Miller, D.; Stonedahl, F.; Stonedahl, S. H.

    2013-12-01

    Stream planforms are used to map scientific measurements, estimate volumetric discharge, and model stream flow. Changes in these planforms can be used to quantify erosion and water level fluctuations. This research investigated five cost-effective methods of identifying stream planforms: (1) consumer-grade digital camera GPS (2) multi-view stereo 3D scene reconstruction (using Microsoft Photosynth (TM)) (3) a cross-sectional measurement approach (4) a triangulation-based measurement approach and (5) the 'square method' - a novel photogrammetric procedure which involved floating a large wooden square in the stream, photographing the square and banks from numerous angles and then using the square to correct for perspective and extract the outline (using custom post-processing software). Data for each of the five methods was collected at Blackhawk Creek in Davenport, Iowa. Additionally we placed 30 control points near the banks of the stream and measured 88 lengths between these control points. We measured or calculated the locations of these control points with each of our five methods and calculated the average percent error associated with each method using the predicted control point locations. The effectiveness of each method was evaluated in terms of accuracy, affordability, environmental intrusiveness, and ease of use. The camera equipped with GPS proved to be a very ineffective method due to an extremely high level of error, 289%. The 3D point cloud extracted from Photosynth was missing markers for many of the control points, so the error calculation (which yielded 11.7%) could only be based on five of the 88 lengths and is thus highly uncertain. The two non-camera methods (cross-sectional and triangulation measurements) resulted in low percent error (2.04% and 1.31% respectively) relative to the control point lengths, but these methods were very time consuming, exhausting, and only provided low resolution outlines. High resolution data collection would

  12. The Control of Apical Bud Growth and Senescence by Auxin and Gibberellin in Genetic Lines of Peas.

    PubMed Central

    Zhu, Y. X.; Davies, P. J.

    1997-01-01

    Pea (Pisum sativum L.) lines G2 (dwarf) and NGB1769 (tall) (Sn Hr) produce flowers and fruit under long (LD) or short (SD) days, but senesce only under LD. Endogenous gibberellin (GA) levels were inversely correlated with photoperiod (over 9-18 h) and senescence: GA20 was 3-fold and GA1 was 10- to 11-fold higher in flowering SD G2 shoots, and the vegetative tissues within the SD apical bud contained 4-fold higher levels of GA20, as compared with the LD tissues. Prefloral G2 plants under both photoperiods had GA1 and GA20 levels similar to the flowering plants under LD. Levels of indole-3-acetic acid (IAA) were similar in G2 shoots in LD or SD; SD apical bud vegetative tissues had a slightly higher IAA content. Young floral buds from LD plants had twice as much IAA as under SD. In NGB1769 shoots GA1 decreased after flower initiation only under LD, which correlated with the decreased growth potential. We suggest that the higher GA1 content of G2 and NGB1769 plants under SD conditions is responsible for the extended vegetative growth and continued meristematic activity in the shoot apex. This and the increased IAA level of LD floral buds may play a role in the regulation of nutrient partitioning, since more photosynthate partitions of reproductive tissue under LD conditions, and the rate of reproductive development in LD peas is faster than under SD. PMID:12223631

  13. Seasonal dynamics and age of stemwood nonstructural carbohydrates in temperate forest trees.

    PubMed

    Richardson, Andrew D; Carbone, Mariah S; Keenan, Trevor F; Czimczik, Claudia I; Hollinger, David Y; Murakami, Paula; Schaberg, Paul G; Xu, Xiaomei

    2013-02-01

    Nonstructural carbohydrate reserves support tree metabolism and growth when current photosynthates are insufficient, offering resilience in times of stress. We monitored stemwood nonstructural carbohydrate (starch and sugars) concentrations of the dominant tree species at three sites in the northeastern United States. We estimated the mean age of the starch and sugars in a subset of trees using the radiocarbon ((14) C) bomb spike. With these data, we then tested different carbon (C) allocation schemes in a process-based model of forest C cycling. We found that the nonstructural carbohydrates are both highly dynamic and about a decade old. Seasonal dynamics in starch (two to four times higher in the growing season, lower in the dormant season) mirrored those of sugars. Radiocarbon-based estimates indicated that the mean age of the starch and sugars in red maple (Acer rubrum) was 7-14 yr. A two-pool (fast and slow cycling reserves) model structure gave reasonable estimates of the size and mean residence time of the total NSC pool, and greatly improved model predictions of interannual variability in woody biomass increment, compared with zero- or one-pool structures used in the majority of existing models. This highlights the importance of nonstructural carbohydrates in the context of forest ecosystem carbon cycling. PMID:23190200

  14. A dynamic model of plant growth with interactions between development and functional mechanisms to study plant structural plasticity related to trophic competition

    PubMed Central

    Mathieu, A.; Cournède, P. H.; Letort, V.; Barthélémy, D.; de Reffye, P.

    2009-01-01

    Background and Aims The strong influence of environment and functioning on plant organogenesis has been well documented by botanists but is poorly reproduced in most functional–structural models. In this context, a model of interactions is proposed between plant organogenesis and plant functional mechanisms. Methods The GreenLab model derived from AMAP models was used. Organogenetic rules give the plant architecture, which defines an interconnected network of organs. The plant is considered as a collection of interacting ‘sinks’ that compete for the allocation of photosynthates coming from ‘sources’. A single variable characteristic of the balance between sources and sinks during plant growth controls different events in plant development, such as the number of branches or the fruit load. Key Results Variations in the environmental parameters related to light and density induce changes in plant morphogenesis. Architecture appears as the dynamic result of this balance, and plant plasticity expresses itself very simply at different levels: appearance of branches and reiteration, number of organs, fructification and adaptation of ecophysiological characteristics. Conclusions The modelling framework serves as a tool for theoretical botany to explore the emergence of specific morphological and architectural patterns and can help to understand plant phenotypic plasticity and its strategy in response to environmental changes. PMID:19297366

  15. Nitrogen-fixing Rhizobium-legume symbiosis: are polyploidy and host peptide-governed symbiont differentiation general principles of endosymbiosis?

    PubMed Central

    Maróti, Gergely; Kondorosi, Éva

    2014-01-01

    The symbiosis between rhizobia soil bacteria and legumes is facultative and initiated by nitrogen starvation of the host plant. Exchange of signal molecules between the partners leads to the formation of root nodules where bacteria are converted to nitrogen-fixing bacteroids. In this mutualistic symbiosis, the bacteria provide nitrogen sources for plant growth in return for photosynthates from the host. Depending on the host plant the symbiotic fate of bacteria can either be reversible or irreversible. In Medicago plants the bacteria undergo a host-directed multistep differentiation process culminating in the formation of elongated and branched polyploid bacteria with definitive loss of cell division ability. The plant factors are nodule-specific symbiotic peptides. About 500 of them are cysteine-rich NCR peptides produced in the infected plant cells. NCRs are targeted to the endosymbionts and the concerted action of different sets of peptides governs different stages of endosymbiont maturation. This review focuses on symbiotic plant cell development and terminal bacteroid differentiation and demonstrates the crucial roles of symbiotic peptides by showing an example of multi-target mechanism exerted by one of these symbiotic peptides. PMID:25071739

  16. How succulent leaves of Aizoaceae avoid mesophyll conductance limitations of photosynthesis and survive drought

    PubMed Central

    Ripley, Brad S.

    2013-01-01

    In several taxa, increasing leaf succulence has been associated with decreasing mesophyll conductance (g M) and an increasing dependence on Crassulacean acid metabolism (CAM). However, in succulent Aizoaceae, the photosynthetic tissues are adjacent to the leaf surfaces with an internal achlorophyllous hydrenchyma. It was hypothesized that this arrangement increases g M, obviating a strong dependence on CAM, while the hydrenchyma stores water and nutrients, both of which would only be sporadically available in highly episodic environments. These predictions were tested with species from the Aizoaceae with a 5-fold variation in leaf succulence. It was shown that g M values, derived from the response of photosynthesis to intercellular CO2 concentration (A:C i), were independent of succulence, and that foliar photosynthate δ13C values were typical of C3, but not CAM photosynthesis. Under water stress, the degree of leaf succulence was positively correlated with an increasing ability to buffer photosynthetic capacity over several hours and to maintain light reaction integrity over several days. This was associated with decreased rates of water loss, rather than tolerance of lower leaf water contents. Additionally, the hydrenchyma contained ~26% of the leaf nitrogen content, possibly providing a nutrient reservoir. Thus the intermittent use of C3 photosynthesis interspersed with periods of no positive carbon assimilation is an alternative strategy to CAM for succulent taxa (Crassulaceae and Aizoaceae) which occur sympatrically in the Cape Floristic Region of South Africa. PMID:24127513

  17. Minimal genomes of mycoplasma-related endobacteria are plastic and contain host-derived genes for sustained life within Glomeromycota

    PubMed Central

    Naito, Mizue; Morton, Joseph B.; Pawlowska, Teresa E.

    2015-01-01

    Arbuscular mycorrhizal fungi (AMF, Glomeromycota) colonize roots of the majority of terrestrial plants. They provide essential minerals to their plant hosts and receive photosynthates in return. All major lineages of AMF harbor endobacteria classified as Mollicutes, and known as mycoplasma-related endobacteria (MRE). Except for their substantial intrahost genetic diversity and ability to transmit vertically, virtually nothing is known about the life history of these endobacteria. To understand MRE biology, we sequenced metagenomes of three MRE populations, each associated with divergent AMF hosts. We found that each AMF species harbored a genetically distinct group of MRE. Despite vertical transmission, all MRE populations showed extensive chromosomal rearrangements, which we attributed to genetic recombination, activity of mobile elements, and a history of plectroviral invasion. The MRE genomes are characterized by a highly reduced gene content, indicating metabolic dependence on the fungal host, with the mechanism of energy production remaining unclear. Several MRE genes encode proteins with domains involved in protein–protein interactions with eukaryotic hosts. In addition, the MRE genomes harbor genes horizontally acquired from AMF. Some of these genes encode small ubiquitin-like modifier (SUMO) proteases specific to the SUMOylation systems of eukaryotes, which MRE likely use to manipulate their fungal host. The extent of MRE genome plasticity and reduction, along with the large number of horizontally acquired host genes, suggests a high degree of adaptation to the fungal host. These features, together with the ubiquity of the MRE–Glomeromycota associations, emphasize the significance of MRE in the biology of Glomeromycota. PMID:25964324

  18. Oxalate secretion by ectomycorrhizal Paxillus involutus is mineral-specific and controls calcium weathering from minerals

    NASA Astrophysics Data System (ADS)

    Schmalenberger, A.; Duran, A. L.; Bray, A. W.; Bridge, J.; Bonneville, S.; Benning, L. G.; Romero-Gonzalez, M. E.; Leake, J. R.; Banwart, S. A.

    2015-07-01

    Trees and their associated rhizosphere organisms play a major role in mineral weathering driving calcium fluxes from the continents to the oceans that ultimately control long-term atmospheric CO2 and climate through the geochemical carbon cycle. Photosynthate allocation to tree roots and their mycorrhizal fungi is hypothesized to fuel the active secretion of protons and organic chelators that enhance calcium dissolution at fungal-mineral interfaces. This was tested using 14CO2 supplied to shoots of Pinus sylvestris ectomycorrhizal with the widespread fungus Paxillus involutus in monoxenic microcosms, revealing preferential allocation by the fungus of plant photoassimilate to weather grains of limestone and silicates each with a combined calcium and magnesium content of over 10 wt.%. Hyphae had acidic surfaces and linear accumulation of weathered calcium with secreted oxalate, increasing significantly in sequence: quartz, granite < basalt, olivine, limestone < gabbro. These findings confirmed the role of mineral-specific oxalate exudation in ectomycorrhizal weathering to dissolve calcium bearing minerals, thus contributing to the geochemical carbon cycle.

  19. In situ stable isotope probing of phosphate-solubilizing bacteria in the hyphosphere

    PubMed Central

    Wang, Fei; Shi, Ning; Jiang, Rongfeng; Zhang, Fusuo; Feng, Gu

    2016-01-01

    This study used a [13C]DNA stable isotope probing (SIP) technique to elucidate a direct pathway for the translocation of 13C-labeled photoassimilate from maize plants to extraradical mycelium-associated phosphate-solubilizing bacteria (PSB) that mediate the mineralization and turnover of soil organic phosphorus (P) in the hyphosphere. Inoculation with PSB alone did not provide any benefit to maize plants but utilized the added phytate-P to their own advantage, while inoculation with Rhizophagus irregularis alone significantly promoted shoot biomass and P content compared with the control. However, compared with both sole inoculation treatments, combined inoculation with PSB and R. irregularis in the hyphosphere enhanced organic P mineralization and increased microbial biomass P in the soil. There was no extra benefit to plant P uptake but the hyphal growth of R. irregularis was reduced, suggesting that PSB benefited from the arbuscular mycorrhizal (AM) fungal mycelium and competed for soil P with the fungus. The combination of T-RFLP (terminal restriction fragment length polymorphism) analysis with a clone library revealed that one of the bacteria that actively assimilated carbon derived from pulse-labeled maize plants was Pseudomonas alcaligenes (Pseudomonadaceae) that was initially inoculated into the hyphosphere soil. These results provide the first in situ demonstration of the pathway underlying the carbon flux from plants to the AM mycelium-associated PSB, and the PSB assimilated the photosynthates exuded by the fungus and promoted mineralization and turnover of organic P in the soil. PMID:26802172

  20. Differential CO2 effect on primary carbon metabolism of flag leaves in durum wheat (Triticum durum Desf.).

    PubMed

    Aranjuelo, Iker; Erice, Gorka; Sanz-Sáez, Alvaro; Abadie, Cyril; Gilard, Françoise; Gil-Quintana, Erena; Avice, Jean-Christophe; Staudinger, Christiana; Wienkoop, Stefanie; Araus, Jose L; Bourguignon, Jacques; Irigoyen, Juan J; Tcherkez, Guillaume

    2015-12-01

    C sink/source balance and N assimilation have been identified as target processes conditioning crop responsiveness to elevated CO2 . However, little is known about phenology-driven modifications of C and N primary metabolism at elevated CO2 in cereals such as wheat. Here, we examined the differential effect of elevated CO2 at two development stages (onset of flowering, onset of grain filling) in durum wheat (Triticum durum, var. Sula) using physiological measurements (photosynthesis, isotopes), metabolomics, proteomics and (15) N labelling. Our results show that growth at elevated CO2 was accompanied by photosynthetic acclimation through a lower internal (mesophyll) conductance but no significant effect on Rubisco content, maximal carboxylation or electron transfer. Growth at elevated CO2 altered photosynthate export and tended to accelerate leaf N remobilization, which was visible for several proteins and amino acids, as well as lysine degradation metabolism. However, grain biomass produced at elevated CO2 was larger and less N rich, suggesting that nitrogen use efficiency rather than photosynthesis is an important target for improvement, even in good CO2 -responsive cultivars. PMID:26081746

  1. Independent recruitment of saprotrophic fungi as mycorrhizal partners by tropical achlorophyllous orchids.

    PubMed

    Martos, Florent; Dulormne, Maguy; Pailler, Thierry; Bonfante, Paola; Faccio, Antonella; Fournel, Jacques; Dubois, Marie-Pierre; Selosse, Marc-André

    2009-11-01

    Mycoheterotrophic orchids have adapted to shaded forest understory by shifting to achlorophylly and receiving carbon from their mycorrhizal fungi. In temperate forests, they associate in a highly specific way with fungi forming ectomycorrhizas on nearby trees, and exploiting tree photosynthates. However, many rainforests lack ectomycorrhizal fungi, and there is evidence that some tropical Asiatic species associate with saprotrophic fungi. To investigate this in different geographic and phylogenetic contexts, we identified the mycorrhizal fungi supporting two tropical mycoheterotrophic orchids from Mascarene (Indian Ocean) and Caribbean islands. We tested their possible carbon sources by measuring natural nitrogen ((15)N) and carbon ((13)C) abundances. Saprotrophic basidiomycetes were found: Gastrodia similis associates with a wood-decaying Resinicium (Hymenochaetales); Wullschlaegelia aphylla associates with both litter-decaying Gymnopus and Mycena species, whose rhizomorphs link orchid roots to leaf litter. The (15)N and (13)C abundances make plausible food chains from dead wood to G. similis and from dead leaves to W. aphylla. We propose that temperature and moisture in rainforests, but not in most temperate forests, may favour sufficient saprotrophic activity to support development of mycoheterotrophs. By enlarging the spectrum of mycorrhizal fungi and the level of specificity in mycoheterotrophic orchids, this study provides new insights on orchid and mycorrhizal biology in the tropics. PMID:19694964

  2. Low Carbon Costs of Nitrogen Fixation in Tropical Dry Forests

    NASA Astrophysics Data System (ADS)

    Gei, M. G.; Powers, J. S.

    2015-12-01

    Legume tree species with the ability to fix nitrogen (N) are highly diverse and widespread across tropical forests but in particular in the dry tropics. Their ecological success in lower latitudes has been called a "paradox": soil N in the tropics is thought to be high, while acquiring N through fixation incurs high energetic costs. However, the long held assumptions that N fixation is limited by photosynthate and that N fixation penalizes plant productivity have rarely been tested, particularly in legume tree species. We show results from three different experiments where we grew eleven species of tropical dry forest legumes. We quantified plant biomass and N fixation using nodulation and the 15N natural isotope abundance (Ndfa or nitrogen derived from fixation). These data show little evidence for costs of N fixation in seedlings grown under different soil fertility, light regimes, and with different microbial communities. Seedling productivity did not incur major costs because of N fixation: indeed, the average slope between Ndfa and biomass was positive (range in slopes: -0.03 to 0.3). Moreover, foliar N, which varied among species, was tightly constrained and not correlated with Ndfa. This finding implies that legume species have a target N that does not change depending on N acquisition strategies. The process of N fixation in tropical legumes may be more carbon efficient than previously thought. This view is more consistent with the hyperabundance of members of this family in tropical ecosystems.

  3. Effects of Heavy Metals and Arbuscular Mycorrhiza on the Leaf Proteome of a Selected Poplar Clone: A Time Course Analysis

    PubMed Central

    Lingua, Guido; Bona, Elisa; Todeschini, Valeria; Cattaneo, Chiara; Marsano, Francesco; Berta, Graziella; Cavaletto, Maria

    2012-01-01

    Arbuscular mycorrhizal (AM) fungi establish a mutualistic symbiosis with the roots of most plant species. While receiving photosynthates, they improve the mineral nutrition of the plant and can also increase its tolerance towards some pollutants, like heavy metals. Although the fungal symbionts exclusively colonize the plant roots, some plant responses can be systemic. Therefore, in this work a clone of Populus alba L., previously selected for its tolerance to copper and zinc, was used to investigate the effects of the symbiosis with the AM fungus Glomus intraradices on the leaf protein expression. Poplar leaf samples were collected from plants maintained in a glasshouse on polluted (copper and zinc contaminated) or unpolluted soil, after four, six and sixteen months of growth. For each harvest, about 450 proteins were reproducibly separated on 2DE maps. At the first harvest the most relevant effect on protein modulation was exerted by the AM fungi, at the second one by the metals, and at the last one by both treatments. This work demonstrates how importantly the time of sampling affects the proteome responses in perennial plants. In addition, it underlines the ability of a proteomic approach, targeted on protein identification, to depict changes in a specific pattern of protein expression, while being still far from elucidating the biological function of each protein. PMID:22761694

  4. Seasonal changes in photosynthesis of trees in the flooded forest of the Mapire River.

    PubMed

    Fernandez, M. D.; Pieters, A.; Donoso, C.; Herrera, C.; Tezara, W.; Rengifo, E.; Herrera, A.

    1999-02-01

    We studied the flood tolerance of five tree species growing in the flooded forest adjacent to the Mapire river, in SW Venezuela. Mean photosynthetic rate and leaf conductance were 11 &mgr;mol m(-2) s(-1) and 700 mmol m(-2) s(-1), respectively. Xylem water potential ranged from -0.08 to -1.15 MPa. Based on leaf gas exchange as a criterion of tolerance to flooding, two response patterns were identified: (1) decreasing photosynthetic rate with increasing flooding and leaf conductance (Psidium ovatifolium Berg. ex Desc., Campsiandra laurifolia Benth., Symmeria paniculata Benth. and Acosmium nitens (Vog.) Benth); and (2) independence of photosynthesis and leaf conductance from flooding (Eschweilera tenuifolia (Berg.) Miers.). In the first response pattern, declining photosynthetic rate with flooding may be interpreted as a sign of reduced flood tolerance, whereas the second response pattern may indicate increased flood tolerance. An increase in xylem water potential with depth of water column was found for all species (with the possible exception of P. ovatifolium), indicating that flooding does not cause water stress in these trees. Submerged leaves that had been under water for between four days and four months generally had photosynthetic rates and leaf conductances similar to those of aerial leaves, indicating maintenance of photosynthetic capacity under water. Daily positive oscillations in glucan content in submerged leaves of P. ovatifolium and C. laurifolia suggest that submerged leaves do not represent a sink for photosynthates produced by aerial leaves. PMID:12651586

  5. Endosymbiotic copepods may feed on zooxanthellae from their coral host, Pocillopora damicornis

    NASA Astrophysics Data System (ADS)

    Cheng, Y.-R.; Dai, C.-F.

    2010-03-01

    The Xarifiidae is one of the most common families of endosymbiotic copepods that live in close association with scleractinian corals. Previous studies on xarifiids primarily focused on their taxonomy and morphology, while their influence on corals is still unknown. In this study, we collected a total of 1,579 individuals belonging to 6 species of xarifiids from 360 colonies of Pocillopora damicornis at Nanwan Bay, southern Taiwan from July 2007 to May 2008. Furthermore, using optical and electron microscopic observations, we examined the gut contents of Xarifia fissilis, the most abundant species of the Xarifiidae that we collected. We found that the gut of X. fissilis was characterized by a reddish-brown color due to the presence of numerous unicellular algae with diameters of 5-10 μm. TEM observations indicated that the unicellular algae possessed typical characteristics of Symbiodinium including a peripheral chloroplast, stalked pyrenoids, starch sheaths, mesokaryotic nuclei, amphiesmas, an accumulation body, and mitochondria. After starving the isolated X. fissilis in the light and dark (light intensity: 140 μmol photon m-2 s-1; photoperiod: 12 h light/12 h dark) for 2 weeks, fluorescence was clearly visible in its gut and fecal pellets under fluorescent microscopic observations. The cultivation experiment supports the hypothesis that the unicellular algae were beneficial to the survival of X. fissilis under light conditions, possibly through transferring photosynthates to the hosts. These results suggest that X. fissilis may consume and retain unicellular algae for further photosynthesis.

  6. Fungi with multifunctional lifestyles: endophytic insect pathogenic fungi.

    PubMed

    Barelli, Larissa; Moonjely, Soumya; Behie, Scott W; Bidochka, Michael J

    2016-04-01

    This review examines the symbiotic, evolutionary, proteomic and genetic basis for a group of fungi that occupy a specialized niche as insect pathogens as well as endophytes. We focus primarily on species in the genera Metarhizium and Beauveria, traditionally recognized as insect pathogenic fungi but are also found as plant symbionts. Phylogenetic evidence suggests that these fungi are more closely related to grass endophytes and diverged from that lineage ca. 100 MYA. We explore how the dual life cycles of these fungi as insect pathogens and endophytes are coupled. We discuss the evolution of insect pathogenesis while maintaining an endophytic lifestyle and provide examples of genes that may be involved in the transition toward insect pathogenicity. That is, some genes for insect pathogenesis may have been co-opted from genes involved in endophytic colonization. Other genes may be multifunctional and serve in both lifestyle capacities. We suggest that their evolution as insect pathogens allowed them to effectively barter a specialized nitrogen source (i.e. insects) with host plants for photosynthate. These ubiquitous fungi may play an important role as plant growth promoters and have a potential reservoir of secondary metabolites. PMID:26644135

  7. Air pollution induced alterations in assimilate partitioning in Anagallis arvensis L

    SciTech Connect

    Khan, F.A.; Iqbal, M.; Ahmad, Z.; Saquib, M.; Ghouse, A.K.M. )

    1989-04-01

    The Thermal Power Plant Complex of Kasimpur (Aligarh, UP, India) emits enormous amounts of oxides of sulfur, nitrogen, and carbon as well as particulate matters on consuming 3192 MT of coal/day. These effluents induce significant alterations in carbon allocation in Anagallis arvensis populations. Monthly samples of 10 plants each were collected on random basis at seedling to mature stage from 0.5, 2, 6, 12 and 20 km leeward from the power plant. In oven dried samples, assimilate partitioning was noted to be more severely altered by the air pollutants in the seedling stage. In 2 and 3 months old populations, photosynthate allocation to root and shoot was not altered noticeably. Considerable changes in carbon allocation were noted in 4 mo old mature stage. The carbon allocation to fruit was 3 fold and to seed was about 4 fold greater in the population thriving 20 km away from the source than in those growing in the vicinity of the source. Assimilate partitioning was linearly related to the distance from power plant and the productivity of the populations.

  8. 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

  9. Bacterial quorum sensing and nitrogen cycling in rhizosphere soil

    SciTech Connect

    DeAngelis, K.M.; Lindow, S.E.; Firestone, M.K.

    2008-10-01

    Plant photosynthate fuels carbon-limited microbial growth and activity, resulting in increased rhizosphere nitrogen (N)-mineralization. Most soil organic N is macromolecular (chitin, protein, nucleotides); enzymatic depolymerization is likely rate-limiting for plant N accumulation. Analyzing Avena (wild oat) planted in microcosms containing sieved field soil, we observed increased rhizosphere chitinase and protease specific activities, bacterial cell densities, and dissolved organic nitrogen (DON) compared to bulk soil. Low-molecular weight DON (<3000 Da) was undetectable in bulk soil but comprised 15% of rhizosphere DON. Extracellular enzyme production in many bacteria requires quorum sensing (QS), cell-density dependent group behavior. Because proteobacteria are considered major rhizosphere colonizers, we assayed the proteobacterial QS signals acyl-homoserine lactones (AHLs), which were significantly increased in the rhizosphere. To investigate the linkage between soil signaling and N cycling, we characterized 533 bacterial isolates from Avena rhizosphere: 24% had chitinase or protease activity and AHL production; disruption of QS in 7 of 8 eight isolates disrupted enzyme activity. Many {alpha}-Proteobacteria were newly found with QS-controlled extracellular enzyme activity. Enhanced specific activities of N-cycling enzymes accompanied by bacterial density-dependent behaviors in rhizosphere soil gives rise to the hypothesis that QS could be a control point in the complex process of rhizosphere N-mineralization.

  10. Increasing Leaf Vein Density by Mutagenesis: Laying the Foundations for C4 Rice

    PubMed Central

    Feldman, Aryo B.; Murchie, Erik H.; Leung, Hei; Baraoidan, Marietta; Coe, Robert; Yu, Su-May; Lo, Shuen-Fang; Quick, William P.

    2014-01-01

    A high leaf vein density is both an essential feature of C4 photosynthesis and a foundation trait to C4 evolution, ensuring the optimal proportion and proximity of mesophyll and bundle sheath cells for permitting the rapid exchange of photosynthates. Two rice mutant populations, a deletion mutant library with a cv. IR64 background (12,470 lines) and a T-DNA insertion mutant library with a cv. Tainung 67 background (10,830 lines), were screened for increases in vein density. A high throughput method with handheld microscopes was developed and its accuracy was supported by more rigorous microscopy analysis. Eight lines with significantly increased leaf vein densities were identified to be used as genetic stock for the global C4 Rice Consortium. The candidate population was shown to include both shared and independent mutations and so more than one gene controlled the high vein density phenotype. The high vein density trait was found to be linked to a narrow leaf width trait but the linkage was incomplete. The more genetically robust narrow leaf width trait was proposed to be used as a reliable phenotypic marker for finding high vein density variants in rice in future screens. PMID:24760084

  11. How succulent leaves of Aizoaceae avoid mesophyll conductance limitations of photosynthesis and survive drought.

    PubMed

    Ripley, Brad S; Abraham, Trevor; Klak, Cornelia; Cramer, Michael D

    2013-12-01

    In several taxa, increasing leaf succulence has been associated with decreasing mesophyll conductance (g M) and an increasing dependence on Crassulacean acid metabolism (CAM). However, in succulent Aizoaceae, the photosynthetic tissues are adjacent to the leaf surfaces with an internal achlorophyllous hydrenchyma. It was hypothesized that this arrangement increases g M, obviating a strong dependence on CAM, while the hydrenchyma stores water and nutrients, both of which would only be sporadically available in highly episodic environments. These predictions were tested with species from the Aizoaceae with a 5-fold variation in leaf succulence. It was shown that g M values, derived from the response of photosynthesis to intercellular CO2 concentration (A:C i), were independent of succulence, and that foliar photosynthate δ(13)C values were typical of C3, but not CAM photosynthesis. Under water stress, the degree of leaf succulence was positively correlated with an increasing ability to buffer photosynthetic capacity over several hours and to maintain light reaction integrity over several days. This was associated with decreased rates of water loss, rather than tolerance of lower leaf water contents. Additionally, the hydrenchyma contained ~26% of the leaf nitrogen content, possibly providing a nutrient reservoir. Thus the intermittent use of C3 photosynthesis interspersed with periods of no positive carbon assimilation is an alternative strategy to CAM for succulent taxa (Crassulaceae and Aizoaceae) which occur sympatrically in the Cape Floristic Region of South Africa. PMID:24127513

  12. Effect of high CO/sub 2/ on growth and carbohydrate partitioning in pea (Pisum sativum L. ) plants

    SciTech Connect

    Potter, J.R.

    1986-04-01

    Beginning at 10 days of age, pea plants were exposed to air with normal (350 ppm) or high (1200 ppm) CO/sub 2/ levels until the plants were 20 days old. Growth was exponential between 10 and 20 days regardless of CO/sub 2/ treatment, and relative growth rates (RGR) under normal and high CO/sub 2/ were 0.20 and 0.24 g x g/sup -1/ x day/sup -1/ respectively. Also high CO/sub 2/ stimulated net assimilation rates (NAR) about 34%. While high CO/sub 2/ did not affect partitioning of dry matter into root, stem, or leaf mass, it decreased the partitioning of new dry matter into new leaf area by 12%, hence the failure of high CO/sub 2/ to stimulate RGR as much as it stimulated NAR. This decrease in partitioning into new leaf area elicited by high CO/sub 2/ was due mainly to the continuous accumulation of leaf starch which reached nearly 3.0 mg x cm/sup -2/. However, this accumulation of starch was not associated with a decline in NAR or photosynthesis. Even for high CO/sub 2/ treatments, transport of photosynthate during photoperiods greatly exceeded the rate necessary to deplete leaf starch during the dark period, indicating that there is unused transport capacity.

  13. George Feher: a pioneer in reaction center research.

    PubMed

    Okamura, Melvin

    2014-05-01

    Our understanding of photosynthesis has been greatly advanced by the elucidation of the structure and function of the reaction center (RC), the membrane protein responsible for the initial light-induced charge separation in photosynthetic bacteria and green plants. Although today we know a great deal about the details of the primary processes in photosynthesis, little was known in the early days. George Feher made pioneering contributions to photosynthesis research in characterizing RCs from photosynthetic bacteria following the ground-breaking work of Lou Duysens and Rod Clayton (see articles in this issue by van Gorkom and Wraight). The work in his laboratory at the University of California, San Diego, started in the late 1960s and continued for over 30 years. He isolated a pure RC protein and used magnetic resonance spectroscopy to study the primary reactants. Following this pioneering work, Feher studied the detailed structure of the RC and the basic electron and proton transfer functions that it performs using a wide variety of biophysical and biochemical techniques. These studies, together with work from many other researchers, have led to our present detailed understanding of these proteins and their function in photosynthesis. The present article is a brief historical account of his pioneering contributions to photosynthesis research. A more detailed description of his work can be found in an earlier biographical paper (Feher in Photosynth Res 55:1-40, 1998a). PMID:24104959

  14. Low Water Potential Disrupts Carbohydrate Metabolism in Maize (Zea mays L.) Ovaries.

    PubMed Central

    Zinselmeier, C.; Westgate, M. E.; Schussler, J. R.; Jones, R. J.

    1995-01-01

    Water deficit during pollination increases the frequency of kernel abortion in maize (Zea mays L.). Much of the kernel loss is attributable to lack of current photosynthate, but a large number of kernels fail to develop on water-deficient plants even when assimilate supply is increased. We examined the possibility that assimilate utilization by developing ovaries might be impaired at low water potential ([Psi]w). Plants were grown in the greenhouse in 20-L pots containing 22 kg of amended soil. Water was withheld on the first day silks emerged, and plants were hand-pollinated 4 d later when leaf [Psi]w decreased to approximately - 1.8 MPa and silk [Psi]w was approximately -1.0 MPa. Plants were rehydrated 2 d after pollination. The brief water deficit inhibited ovary growth (dry matter accumulation) and decreased kernel number per ear by 60%, compared to controls. Inhibition of ovary growth was associated with a decrease in the level of reducing sugars, depletion of starch, a 75-fold increase in sucrose concentration (dry weight basis), and inhibition of acid invertase (EC 3.2.1.26) activity. These results indicate that water deficits during pollination disrupt carbohydrate metabolism in maize ovaries. They suggest that acid invertase activity is important for establishing and maintaining reproductive sink strength during pollination and early kernel development. PMID:12228365

  15. Winter wheat: A model for the simulation of growth and yield in winter wheat

    NASA Technical Reports Server (NTRS)

    Baker, D. N.; Smika, D. E.; Black, A. L.; Willis, W. O.; Bauer, A. (Principal Investigator)

    1981-01-01

    The basic ideas and constructs for a general physical/physiological process level winter wheat simulation model are documented. It is a materials balance model which calculates daily increments of photosynthate production and respiratory losses in the crop canopy. The partitioning of the resulting dry matter to the active growing tissues in the plant each day, transpiration and the uptake of nitrogen from the soil profile are simulated. It incorporates the RHIZOS model which simulates, in two dimensions, the movement of water, roots, and soluble nutrients through the soil profile. It records the time of initiation of each of the plant organs. These phenological events are calculated from temperature functions with delays resulting from physiological stress. Stress is defined mathematically as an imbalance in the metabolite supply; demand ratio. Physiological stress is also the basis for the calculation of rates of tiller and floret abortion. Thus, tillering and head differentiation are modeled as the resulants of the two processes, morphogenesis and abortion, which may be occurring simulaneously.

  16. Summer drought alters carbon allocation to roots and root respiration in mountain grassland

    PubMed Central

    Hasibeder, Roland; Fuchslueger, Lucia; Richter, Andreas; Bahn, Michael

    2015-01-01

    Drought affects the carbon (C) source and sink activities of plant organs, with potential consequences for belowground C allocation, a key process of the terrestrial C cycle. The responses of belowground C allocation dynamics to drought are so far poorly understood. We combined experimental rain exclusion with 13C pulse labelling in a mountain meadow to analyse the effects of summer drought on the dynamics of belowground allocation of recently assimilated C and how it is partitioned among different carbohydrate pools and root respiration. Severe soil moisture deficit decreased the ecosystem C uptake and the amounts and velocity of C allocated from shoots to roots. However, the proportion of recently assimilated C translocated belowground remained unaffected by drought. Reduced root respiration, reflecting reduced C demand under drought, was increasingly sustained by C reserves, whilst recent assimilates were preferentially allocated to root storage and an enlarged pool of osmotically active compounds. Our results indicate that under drought conditions the usage of recent photosynthates is shifted from metabolic activity to osmotic adjustment and storage compounds. PMID:25385284

  17. Beech carbon productivity as driver of ectomycorrhizal abundance and diversity.

    PubMed

    Druebert, Christine; Lang, Christa; Valtanen, Kerttu; Polle, Andrea

    2009-08-01

    We tested the hypothesis that carbon productivity of beech (Fagus sylvatica) controls ectomycorrhizal colonization, diversity and community structures. Carbon productivity was limited by long-term shading or by girdling. The trees were grown in compost soil to avoid nutrient deficiencies. Despite severe limitation in photosynthesis and biomass production by shading, the concentrations of carbohydrates in roots were unaffected by the light level. Shade-acclimated plants were only 10% and sun-acclimated plants were 74% colonized by ectomycorrhiza. EM diversity was higher on roots with high than at roots with low mycorrhizal colonization. Evenness was unaffected by any treatment. Low mycorrhizal colonization had no negative effects on plant mineral nutrition. In girdled plants mycorrhizal colonization and diversity were retained although (14)C-leaf feeding showed almost complete disruption of carbon transport from leaves to roots. Carbohydrate storage pools in roots decreased upon girdling. Our results show that plant carbon productivity was the reason for and not the result of high ectomycorrhizal diversity. We suggest that ectomycorrhiza can be supplied by two carbon routes: recent photosynthate and stored carbohydrates. Storage pools may be important for ectomycorrhizal survival when photoassimilates were unavailable, probably feeding preferentially less carbon demanding EM species as shifts in community composition were found. PMID:19344334

  18. Masting in oaks: Disentangling the effect of flowering phenology, airborne pollen load and drought

    NASA Astrophysics Data System (ADS)

    Fernández-Martínez, Marcos; Belmonte, Jordina; Maria Espelta, Josep

    2012-08-01

    Quercus species exhibit an extreme inter-annual variability in seed production often synchronized over large geographical areas (masting). Since this reproductive behavior is mostly observed in anemophilous plants, pollination efficiency is suggested as one hypothesis to explain it, although resource-based hypotheses are also suggested as alternatives. We analyzed the effect of flowering phenology, airborne pollen presence and meteorological conditions in the pattern of acorn production in mixed evergreen-deciduous oak forests (Quercus ilex and Quercus pubescens) in NE Spain for twelve years (1998-2009). In both oaks, higher temperatures advanced the onset of flowering and increased the amount of airborne pollen. Nevertheless, inter-annual differences in pollen production did not influence acorn crop size. Acorn production was enhanced by a delay in flowering onset in Q. ilex but not in Q. pubescens. This suggests that in perennial oaks a larger number of photosynthates produced before flowering could benefit reproduction while the lack of effects on deciduous oaks could be because these species flush new leaves and flowers at the same time. Notwithstanding this effect, spring water deficit was the most relevant factor in explaining inter-annual variability in acorn production in both species. Considering that future climate scenarios predict progressive warmer and dryer spring seasons in the Mediterranean Basin, this might result in earlier onsets of flowering and higher water deficits that would constrain acorn production.

  19. Mechanism of inhibition and decoupling of oxygen evolution from electron transfer in photosystem II by fluoride, ammonia and acetate.

    PubMed

    Lovyagina, E R; Semin, B K

    2016-05-01

    Ca(2+) extraction from oxygen-evolving complex (OEC) of photosystem II (PSII) is accompanied by decoupling of oxygen evolution/electron transfer processes [Semin et al. Photosynth. Res. 98 (2008) 235] and appearance of a broad EPR signal at g=2 (split "S3" signal) what can imply the relationship between these effects. Split signal have been observed not only in Ca-depleted PSII but also in PSII membranes treated by fluoride anions, sodium acetate, and NH4Cl. Here we investigated the question: can such compounds induce the decoupling effect during treatment of PSII like Ca(2+) extraction does? We found that F(-), sodium acetate, and NH4Cl inhibit O2 evolution in PSII membranes more effectively than the reduction of artificial electron acceptor 2,6-dichlorophenolindophenol, i.e. the action of these compounds is accompanied by decoupling of these processes in OEC. Similarity of effects observed after Ca(2+) extraction and F(-), CH3COO(-) or NH4Cl treatments suggests that these compounds can inactivate function of Ca(2+). Such inactivation could originate from disturbance of the network of functionally active hydrogen bonds around OEC formed with participation of Ca(2+). This inhibition effect is observed in the region of low concentration of inhibitors. Increasing of inhibitor concentration is accompanied by appearance of other sites of inhibition. PMID:26971280

  20. The two last overviews by Colin Allen Wraight (1945-2014) on energy conversion in photosynthetic bacteria.

    PubMed

    Maróti, Péter; Govindjee

    2016-02-01

    Colin Allen Wraight (1945-2014) was a well-known biophysicist and biochemist of our times-formerly Professor of Biochemistry, Biophysics and Plant Biology, and Head of the Department of Biochemistry, University of Illinois at Urbana-Champaign, Urbana, IL, USA. (See a detailed Tribute to him by Govindjee et al., Photosynth Res, 2015.) During the latter part of his life, Colin had (1) given an excellent lecture in 2008 on the overall topic of the molecular mechanisms in biological energy conversion, focusing on how an ubiquinone is reduced to ubiquinol at the so-called "two electron gate", and (2) presented a review poster on the design features of long distance proton transport in biological systems, with focus on photosynthetic bacteria (a pdf file of the original is available from one of us, Govindjee). We present here for historical purpose, a complete transcript of his 2008 lecture and his 2013 poster, which have been annotated and expanded by the authors of this paper. The major theme is: electron and proton transfer in biological systems, with emphasis on bacterial reaction centers. The figures, some of which were prepared by us, are presented in sequence for both the lecture and the poster. A common bibliography is provided at the end of the paper, which is divided into two parts: (I) The Lecture; and (II) The Poster. PMID:26216496

  1. Use of 13C labeling to assess carbon partitioning in transgenic and nontransgenic (parental) rice and their rhizosphere soil microbial communities.

    PubMed

    Wu, Wei Xiang; Liu, Wei; Lu, Hao Hao; Chen, Ying Xu; Medha, Devare; Janice, Thies

    2009-01-01

    Photosynthetic assimilation of CO2 is a primary source of carbon in soil and root exudates and can influence the community dynamics of rhizosphere organisms. Thus, if carbon partitioning is affected in transgenic crops, rhizosphere microbial communities may also be affected. In this study, the temporal effects of gene transformation on carbon partitioning in rice and rhizosphere microbial communities were investigated under greenhouse conditions using the 13C pulse-chase labeling method and phospholipid fatty acid (PLFA) analysis. The 13C contents in leaves of transgenic (Bt) and nontransgenic (Ck) rice were significantly different at the seedling, booting and heading stages. There were no detectable differences in 13C distribution in rice roots and rhizosphere microorganisms at any point during rice development. Although a significantly lower amount of Gram-positive bacterial PLFAs and a higher amount of Gram-negative bacterial PLFAs were observed in Bt rice rhizosphere as compared with Ck at all plant development stages, there were no significant differences in the amount of individual 13C-PLFA between Bt and Ck rhizospheres at any growing stage. These findings indicate that the insertion of cry1Ab and marker genes into rice had no persistent or adverse effect on the photosynthate distribution in rice or the microbial community composition in its rhizosphere. PMID:19049503

  2. Rapid mixing between old and new C pools in the canopy of mature forest trees.

    PubMed

    Keel, Sonja G; Siegwolf, Rolf T W; Jäggi, Maya; Körner, Christian

    2007-08-01

    Stable C isotope signals in plant tissues became a key tool in explaining growth responses to the environment. The technique is based on the fundamental assumption that the isotopic composition of a given unit of tissue (e.g. a tree ring) reflects the specific C uptake conditions in the leaf at a given time. Beyond the methodological implications of any deviation from this assumption, it is of physiological interest whether new C is transferred directly from sources (a photosynthesizing leaf) to structural sinks (e.g. adjacent stem tissue), or inherently passes through existing (mobile) C pools, which may be of variable (older) age. Here, we explore the fate of (13)C-labelled photosynthates in the crowns of a 30-35 m tall, mixed forest using a canopy crane. In all nine study species labelled C reached woody tissue within 2-9 h after labelling. Four months later, very small signals were left in branch wood of Tilia suggesting that low mixing of new, labelled C with old C had taken place. In contrast, signals in Fagus and Quercus had increased, indicating more intense mixing. This species-specific mixing of new with old C pools is likely to mask year- or season-specific linkages between tree ring formation and climate and has considerable implications for climate reconstruction using stable isotopes as proxies for past climatic conditions. PMID:17617824

  3. Summer drought alters dynamics of carbon allocation to roots and root respiration in mountain grassland

    NASA Astrophysics Data System (ADS)

    Hasibeder, Roland; Fuchslueger, Lucia; Fritz, Karina; Richter, Andreas; Bahn, Michael

    2014-05-01

    Meteorological extreme events like summer droughts are expected to occur more frequently in a future climate and exert a major impact on the carbon (C) balance of terrestrial ecosystems. Drought impairs the activity of C source (photosynthesis) and sinks (growth, respiration, storage) as well as C partitioning between aboveground and belowground plant organs. To date, little is known about effects of drought on the allocation dynamics of recently assimilated C in intact ecosystems. Combining experimental rain exclusion with 13CO2 pulse labelling in a mountain meadow in the Austrian Central Alps, we investigated how summer drought impacts the translocation of fresh photosynthates to roots and the partitioning of this C input among root carbohydrate pools and respiration. Severe soil drying slowed down and decreased the amount of recent C allocated to the root system by ca. 50%, reflecting similar reductions in C uptake. However, interestingly, the proportion of 13C translocated belowground (relative to the amount of 13C assimilated by the plants) increased under drought, reflecting a change in C allocation patterns. Overall, relatively more C was allocated to root starch and to osmotically active compounds (sugars), whose concentrations were doubled under drought. In contrast, drought reduced the proportional allocation of recent assimilates to root respiration, whose rates were diminished by ca. 26%. These results suggest that while summer drought reduced the supply of recently assimilated C to roots, it increased its proportional allocation to osmotically active sugars and to storage while decreasing its allocation to root respiration.

  4. Oxalate secretion by ectomycorrhizal Paxillus involutus is mineral-specific and controls calcium weathering from minerals

    PubMed Central

    Schmalenberger, A.; Duran, A. L.; Bray, A. W.; Bridge, J.; Bonneville, S.; Benning, L. G.; Romero-Gonzalez, M. E.; Leake, J. R.; Banwart, S. A.

    2015-01-01

    Trees and their associated rhizosphere organisms play a major role in mineral weathering driving calcium fluxes from the continents to the oceans that ultimately control long-term atmospheric CO2 and climate through the geochemical carbon cycle. Photosynthate allocation to tree roots and their mycorrhizal fungi is hypothesized to fuel the active secretion of protons and organic chelators that enhance calcium dissolution at fungal-mineral interfaces. This was tested using 14CO2 supplied to shoots of Pinus sylvestris ectomycorrhizal with the widespread fungus Paxillus involutus in monoxenic microcosms, revealing preferential allocation by the fungus of plant photoassimilate to weather grains of limestone and silicates each with a combined calcium and magnesium content of over 10 wt.%. Hyphae had acidic surfaces and linear accumulation of weathered calcium with secreted oxalate, increasing significantly in sequence: quartz, granite < basalt, olivine, limestone < gabbro. These findings confirmed the role of mineral-specific oxalate exudation in ectomycorrhizal weathering to dissolve calcium bearing minerals, thus contributing to the geochemical carbon cycle. PMID:26197714

  5. Oxalate secretion by ectomycorrhizal Paxillus involutus is mineral-specific and controls calcium weathering from minerals.

    PubMed

    Schmalenberger, A; Duran, A L; Bray, A W; Bridge, J; Bonneville, S; Benning, L G; Romero-Gonzalez, M E; Leake, J R; Banwart, S A

    2015-01-01

    Trees and their associated rhizosphere organisms play a major role in mineral weathering driving calcium fluxes from the continents to the oceans that ultimately control long-term atmospheric CO2 and climate through the geochemical carbon cycle. Photosynthate allocation to tree roots and their mycorrhizal fungi is hypothesized to fuel the active secretion of protons and organic chelators that enhance calcium dissolution at fungal-mineral interfaces. This was tested using (14)CO2 supplied to shoots of Pinus sylvestris ectomycorrhizal with the widespread fungus Paxillus involutus in monoxenic microcosms, revealing preferential allocation by the fungus of plant photoassimilate to weather grains of limestone and silicates each with a combined calcium and magnesium content of over 10 wt.%. Hyphae had acidic surfaces and linear accumulation of weathered calcium with secreted oxalate, increasing significantly in sequence: quartz, granite < basalt, olivine, limestone < gabbro. These findings confirmed the role of mineral-specific oxalate exudation in ectomycorrhizal weathering to dissolve calcium bearing minerals, thus contributing to the geochemical carbon cycle. PMID:26197714

  6. Qualitative Distinction of Autotrophic and Heterotrophic Processes at the Leaf Level by Means of Triple Stable Isotope (C–O–H) Patterns

    PubMed Central

    Kimak, Adam; Kern, Zoltan; Leuenberger, Markus

    2015-01-01

    Foliar samples were harvested from two oaks, a beech, and a yew at the same site in order to trace the development of the leaves over an entire vegetation season. Cellulose yield and stable isotopic compositions (δ13C, δ18O, and δD) were analyzed on leaf cellulose. All parameters unequivocally define a juvenile and a mature period in the foliar expansion of each species. The accompanying shifts of the δ13C-values are in agreement with the transition from remobilized carbohydrates (juvenile period), to current photosynthates (mature phase). While the opponent seasonal trends of δ18O of blade and vein cellulose are in perfect agreement with the state-of-art mechanistic understanding, the lack of this discrepancy for δD, documented for the first time, is unexpected. For example, the offset range of 18 permil (oak veins) to 57 permil (oak blades) in δD may represent a process driven shift from autotrophic to heterotrophic processes. The shared pattern between blade and vein found for both oak and beech suggests an overwhelming metabolic isotope effect on δD that might be accompanied by proton transfer linked to the Calvin-cycle. These results provide strong evidence that hydrogen and oxygen are under different biochemical controls even at the leaf level. PMID:26635835

  7. Photoperiodic flowering regulation in Arabidopsis thaliana

    PubMed Central

    Golembeski, Greg S.; Kinmonth-Schultz, Hannah A.; Song, Young Hun; Imaizumi, Takato

    2015-01-01

    Photoperiod, or the duration of light in a given day, is a critical cue that flowering plants utilize to effectively assess seasonal information and coordinate their reproductive development in synchrony with the external environment. The use of the model plant, Arabidopsis thaliana, has greatly improved our understanding of the molecular mechanisms that determine how plants process and utilize photoperiodic information to coordinate a flowering response. This mechanism is typified by the transcriptional activation of FLOWERING LOCUS T (FT) gene by the transcription factor CONSTANS (CO) under inductive long-day conditions in Arabidopsis. FT protein then moves from the leaves to the shoot apex, where floral meristem development can be initiated. As a point of integration from a variety of environmental factors in the context of a larger system of regulatory pathways that affect flowering, the importance of photoreceptors and the circadian clock in CO regulation throughout the day has been a key feature of the photoperiodic flowering pathway. In addition to these established mechanisms, the recent discovery of a photosynthate derivative trehalose-6-phosphate as an activator of FT in leaves has interesting implications for the involvement of photosynthesis in the photoperiodic flowering response that were suggested from previous physiological experiments in flowering induction. PMID:25684830

  8. Changes in the metabolome and histopathology of Amaranthus hypochondriacus L. in response to Ageratum enation virus infection.

    PubMed

    Srivastava, Shatakshi; Bisht, Hema; Sidhu, O P; Srivastava, Ashish; Singh, P C; Pandey, R M; Raj, S K; Roy, Raja; Nautiyal, C S

    2012-08-01

    Amaranthus hypochondriacus L. infected with Ageratum enation virus (AEV) was investigated for identifying alteration in the anatomical structures, sap translocation and metabolomic variations using light microscopy, magnetic resonance imaging, NMR spectroscopy and GC-MS, respectively. Combination of GC-MS and NMR spectroscopy identified 68 polar and non-polar metabolites that were present in different levels in healthy and virus-infected A. hypochondriacus. Contrast of T₁ and T₂ weighted MR images showed significant differences in the spatial distribution of water, lipids and macromolecules indicating alterations in the cortical region and disruption of vascular bundles in virus-infected stem tissues. MRI observations are supported by light microscopic examination. Microscopic examination of AEV infected stem revealed severe hyperplasia with a considerable reduction in size of stem cells. The NMR spectroscopy and GC-MS analysis indicated that viral infection significantly affected the plant primary and secondary metabolism resulting in decreased glucose and sucrose content and increase in the concentration of β-sitosterol and stigmasterol. Higher accumulation of TCA cycle intermediates such as citric acid and malic acid in AEV infected plants indicated enhanced rate of respiratory metabolism. The viral stress significantly increases the concentration of erythritol and myo-inositol as compared to healthy ones. Lower concentration of glucose and sucrose in viral-infected stem tissues suggests decreased translocation of photosynthates in the plants. The results demonstrated potential of MRI, NMR spectroscopy and GC-MS for studying anatomical and metabolic variations in virus-infected plants. PMID:22683210

  9. In Metabolic Engineering of Eukaryotic Microalgae: Potential and Challenges Come with Great Diversity

    PubMed Central

    Gimpel, Javier A.; Henríquez, Vitalia; Mayfield, Stephen P.

    2015-01-01

    The great phylogenetic diversity of microalgae is corresponded by a wide arrange of interesting and useful metabolites. Nonetheless metabolic engineering in microalgae has been limited, since specific transformation tools must be developed for each species for either the nuclear or chloroplast genomes. Microalgae as production platforms for metabolites offer several advantages over plants and other microorganisms, like the ability of GMO containment and reduced costs in culture media, respectively. Currently, microalgae have proved particularly well suited for the commercial production of omega-3 fatty acids and carotenoids. Therefore most metabolic engineering strategies have been developed for these metabolites. Microalgal biofuels have also drawn great attention recently, resulting in efforts for improving the production of hydrogen and photosynthates, particularly triacylglycerides. Metabolic pathways of microalgae have also been manipulated in order to improve photosynthetic growth under specific conditions and for achieving trophic conversion. Although these pathways are not strictly related to secondary metabolites, the synthetic biology approaches could potentially be translated to this field and will also be discussed. PMID:26696985

  10. [Trophic chains in soil].

    PubMed

    2013-01-01

    Trophic links of soil animals are extensively diverse but also flexible. Moreover, feeding activity of large soil saprotrophs often cascades into a range of ecosystem-level consequences via the ecological engineering. Better knowledge on the main sources of energy utilized by soil animals is needed for understanding functional structure of soil animal communities and their participation in the global carbon cycling. Using published and original data, we consider the relative importance of dead organic matter and saprotrophic microorganisms as a basal energy source in the detritus-based food chains, the feeding of endogeic macrofauna on the stabilized soil organic matter, and the role of recent photosynthate in the energy budget of soil communities. Soil food webs are spatially and functionally compartmentalized, though the separation of food chains into bacteria- and fungi-based channels seems to be an over-simplification. The regulation of the litter decomposition rates via top-down trophic interactions across more than one trophic level is only partly supported by experimental data, but mobile litter-dwelling predators play a crucial role in integrating local food webs within and across neighboring ecosystems. PMID:25508107

  11. [Trophic chains in soil].

    PubMed

    Goncharov, A A; Tiunov, A V

    2013-01-01

    Trophic links of soil animals are extensively diverse but also flexible. Moreover, feeding activity of large soil saprotrophs often cascades into a range of ecosystem-level consequences via the ecological engineering. Better knowledge on the main sources of energy utilized by soil animals is needed for understanding functional structure of soil animal communities and their participation in the global carbon cycling. Using published and original data, we consider the relative importance of dead organic matter and saprotrophic microorganisms as a basal energy source in the detritus-based food chains, the feeding of endogeic macrofauna on the stabilized soil organic matter, and the role of recent photosynthate in the energy budget of soil communities. Soil food webs are spatially and functionally compartmentalized, though the separation of food chains into bacteria- and fungi-based channels seems to be an over-simplification. The regulation of the litter decomposition rates via top-down trophic interactions across more than one trophic level is only partly supported by experimental data, but mobile litter-dwelling predators play a crucial role in integrating local food webs within and across neighboring ecosystems. PMID:25438576

  12. Phloem Transport of Fructans in the Crassulacean Acid Metabolism Species Agave deserti1

    PubMed Central

    Wang, Ning; Nobel, Park S.

    1998-01-01

    Four oligofructans (neokestose, 1-kestose, nystose, and an un-identified pentofructan) occurred in the vascular tissues and phloem sap of mature leaves of Agave deserti. Fructosyltransferases (responsible for fructan biosynthesis) also occurred in the vascular tissues. In contrast, oligofructans and fructosyltransferases were virtually absent from the chlorenchyma, suggesting that fructan biosynthesis was restricted to the vascular tissues. On a molar basis, these oligofructans accounted for 46% of the total soluble sugars in the vascular tissues (sucrose [Suc] for 26%) and for 19% in the phloem sap (fructose for 24% and Suc for 53%). The Suc concentration was 1.8 times higher in the cytosol of the chlorenchyma cells than in the phloem sap; the nystose concentration was 4.9 times higher and that of pentofructan was 3.2 times higher in the vascular tissues than in the phloem sap. To our knowledge, these results provide the first evidence that oligofructans are synthesized and transported in the phloem of higher plants. The polymer-trapping mechanism proposed for dicotyledonous C3 species may also be valid for oligofructan transport in monocotyledonous species, such as A. deserti, which may use a symplastic pathway for phloem loading of photosynthates in its mature leaves. PMID:9490769

  13. Regulation of assimilate partitioning by daylength and spectral quality

    NASA Technical Reports Server (NTRS)

    Britz, Steve J.

    1994-01-01

    The effects of daylength and spectral quality on assimilate partitioning and leaf carbohydrate content should be considered when conducting controlled environment experiments or comparing results between studies obtained under different lighting conditions. Changes in partitioning may indicate alterations to photoregulatory processes within the source leaf rather than disruptions in sink strength. Moreover, it may be possible to use photoregulatory responses of assimilate partitioning to probe mechanisms of growth and development involving translocation of carbon or adaptation to environmental factors such as elevated CO2. It may also be possible to steer assimilate partitioning for the benefit of controlled environment agriculture using energy-efficient manipulations such as daylength extensions with dim irradiances, end-of-day alterations in light quality, or shifting plants between different spectral qualities as a part of phasic control of growth and development. Note that high starch levels measured on a one-time basis provide little information, since it is the proportion of photosynthate stored as starch that is meaningful. Large differences in starch content can result from small changes in partitioning integrated over several days. Rate information is required.

  14. How plants manage food reserves at night: quantitative models and open questions

    PubMed Central

    Scialdone, Antonio; Howard, Martin

    2015-01-01

    In order to cope with night-time darkness, plants during the day allocate part of their photosynthate for storage, often as starch. This stored reserve is then degraded at night to sustain metabolism and growth. However, night-time starch degradation must be tightly controlled, as over-rapid turnover results in premature depletion of starch before dawn, leading to starvation. Recent experiments in Arabidopsis have shown that starch degradation proceeds at a constant rate during the night and is set such that starch reserves are exhausted almost precisely at dawn. Intriguingly, this pattern is robust with the degradation rate being adjusted to compensate for unexpected changes in the time of darkness onset. While a fundamental role for the circadian clock is well-established, the underlying mechanisms controlling starch degradation remain poorly characterized. Here, we discuss recent quantitative models that have been proposed to explain how plants can compute the appropriate starch degradation rate, a process that requires an effective arithmetic division calculation. We review experimental confirmation of the models, and describe aspects that require further investigation. Overall, the process of night-time starch degradation necessitates a fundamental metabolic role for the circadian clock and, more generally, highlights how cells process information in order to optimally manage their resources. PMID:25873925

  15. [Enhancement of photoassimilate utilization by manipulation of the ADPglucose pyrophosphorylase gene]. Summary of progress, [April 15, 1991--April 14, 1992

    SciTech Connect

    Okita, T.W.

    1992-12-31

    The long term aim of this project is to assess the feasibility of increasing the conversion of photosynthate into starch via manipulation of genes encoding enzymes that may be rate-limiting in starch biosynthesis. In developing storage tissues such as tubers, starch biosynthesis is regulated by the gene activation and expression of ADPglucose pyrophosphorylase, starch synthase, branching enzyme and other ancillary starch modifying enzymes, as well as the allosteric-controlled behavior of ADPglucose pyrophosphorylase activity. In view of the regulatory role of ADPglucose pyrophosphorylase in starch biosynthesis at both the genetic and biochemical level, we have focused our attention on the genes that encode for this enzyme in potato tubers. The proposed objectives of the grant were to (1) analyze the structure of the tuber enzyme, (2) isolate and characterize the structure of its genes, and (3) identify the regulatory elements controlling ADPglucose pyrophosphorylase during plant development. During the last two and 1/2 years we have met or have made considerable progress in achieving these objectives as discussed in more detail below.

  16. The Frankia alni symbiotic transcriptome.

    PubMed

    Alloisio, Nicole; Queiroux, Clothilde; Fournier, Pascale; Pujic, Petar; Normand, Philippe; Vallenet, David; Médigue, Claudine; Yamaura, Masatoshi; Kakoi, Kentaro; Kucho, Ken-ichi

    2010-05-01

    The actinobacteria Frankia spp. are able to induce the formation of nodules on the roots of a large spectrum of actinorhizal plants, where they convert dinitrogen to ammonia in exchange for plant photosynthates. In the present study, transcriptional analyses were performed on nitrogen-replete free-living Frankia alni cells and on Alnus glutinosa nodule bacteria, using whole-genome microarrays. Distribution of nodule-induced genes on the genome was found to be mostly over regions with high synteny between three Frankia spp. genomes, while nodule-repressed genes, which were mostly hypothetical and not conserved, were spread around the genome. Genes known to be related to nitrogen fixation were highly induced, nif (nitrogenase), hup2 (hydrogenase uptake), suf (sulfur-iron cluster), and shc (hopanoids synthesis). The expression of genes involved in ammonium assimilation and transport was strongly modified, suggesting that bacteria ammonium assimilation was limited. Genes involved in particular in transcriptional regulation, signaling processes, protein drug export, protein secretion, lipopolysaccharide, and peptidoglycan biosynthesis that may play a role in symbiosis were also identified. We also showed that this Frankia symbiotic transcriptome was highly similar among phylogenetically distant plant families Betulaceae and Myricaceae. Finally, comparison with rhizobia transcriptome suggested that F. alni is metabolically more active in symbiosis than rhizobia. PMID:20367468

  17. Complete Turgor Maintenance at Low Water Potentials in the Elongating Region of Maize Leaves 1

    PubMed Central

    Michelena, V. Arturo; Boyer, John S.

    1982-01-01

    Leaf elongation rate, water potential, and osmotic potential were measured in the fifth leaf of maize (Zea mays L.) plants growing in soil from which water was withheld for varying times. Elongation occurred in the basal region, which was enclosed by other leaf sheaths. When water was withheld from the soil, leaf elongation decreased and eventually ceased even though enough solutes accumulated in the elongating region to maintain turgor virtually constant. In the exposed blade, however, turgor was lost and wilt symptoms developed. If the night was prolonged, the elongating region lost much of its ability to accumulate solute, which suggests that the accumulating solutes were of recent photosynthetic origin. Under these conditions, leaf elongation was restricted to higher water potentials than under the usual photoperiodic regime. The solute accumulation and turgor maintenance of the elongating region at low water potentials indicate that differences in water status and physiological behavior exist along grass leaves and that the water status of the elongating region cannot be inferred from measurements on the exposed blade. The increased sensitivity of leaf elongation to low water potentials in prolonged darkness indicates that accumulation of solute and maintenance of turgor play a role in maintaining leaf growth. However, the inhibition of elongation that occurred even when solute accumulation was sufficient to completely maintain turgor indicates that some factor other than photosynthate supply and turgor also affected growth and caused most of the losses in growth under dry conditions. Images PMID:16662360

  18. An empirical test of partner choice mechanisms in a wild legume–rhizobium interaction

    PubMed Central

    Simms, Ellen L; Taylor, D. Lee; Povich, Joshua; Shefferson, Richard P; Sachs, J.L; Urbina, M; Tausczik, Y

    2005-01-01

    Mutualisms can be viewed as biological markets in which partners of different species exchange goods and services to their mutual benefit. Trade between partners with conflicting interests requires mechanisms to prevent exploitation. Partner choice theory proposes that individuals might foil exploiters by preferentially directing benefits to cooperative partners. Here, we test this theory in a wild legume–rhizobium symbiosis. Rhizobial bacteria inhabit legume root nodules and convert atmospheric dinitrogen (N2) to a plant available form in exchange for photosynthates. Biological market theory suits this interaction because individual plants exchange resources with multiple rhizobia. Several authors have argued that microbial cooperation could be maintained if plants preferentially allocated resources to nodules harbouring cooperative rhizobial strains. It is well known that crop legumes nodulate non-fixing rhizobia, but allocate few resources to those nodules. However, this hypothesis has not been tested in wild legumes which encounter partners exhibiting natural, continuous variation in symbiotic benefit. Our greenhouse experiment with a wild legume, Lupinus arboreus, showed that although plants frequently hosted less cooperative strains, the nodules occupied by these strains were smaller. Our survey of wild-grown plants showed that larger nodules house more Bradyrhizobia, indicating that plants may prevent the spread of exploitation by favouring better cooperators. PMID:16519238

  19. Modeling the effects of ozone on soybean growth and yield.

    PubMed

    Kobayashi, K; Miller, J E; Flagler, R B; Heck, W W

    1990-01-01

    A simple mechanistic model was developed based on an existing growth model in order to address the mechanisms of the effects of ozone on growth and yield of soybean [Glycine max. (L.) Merr. 'Davis'] and interacting effects of other environmental stresses. The model simulates daily growth of soybean plants using environmental data including shortwave radiation, temperature, precipitation, irrigation and ozone concentration. Leaf growth, dry matter accumulation, water budget, nitrogen input and seed growth linked to senescence and abscission of leaves are described in the model. The effects of ozone are modeled as reduced photosynthate production and accelerated senescence. The model was applied to the open-top chamber experiments in which soybean plants were exposed to ozone under two levels of soil moisture regimes. After calibrating the model to the growth data and seed yield, goodness-of-fit of the model was tested. The model fitted well for top dry weight in the vegetative growth phase and also at maturity. The effect of ozone on seen yield was also described satisfactorily by the model. The simulation showed apparent interaction between the effect of ozone and soil moisture stress on the seed yield. The model revealed that further work is needed concerning the effect of ozone on the senescence process and the consequences of alteration of canopy microclimate by the open-top chambers. PMID:15092277

  20. In Metabolic Engineering of Eukaryotic Microalgae: Potential and Challenges Come with Great Diversity.

    PubMed

    Gimpel, Javier A; Henríquez, Vitalia; Mayfield, Stephen P

    2015-01-01

    The great phylogenetic diversity of microalgae is corresponded by a wide arrange of interesting and useful metabolites. Nonetheless metabolic engineering in microalgae has been limited, since specific transformation tools must be developed for each species for either the nuclear or chloroplast genomes. Microalgae as production platforms for metabolites offer several advantages over plants and other microorganisms, like the ability of GMO containment and reduced costs in culture media, respectively. Currently, microalgae have proved particularly well suited for the commercial production of omega-3 fatty acids and carotenoids. Therefore most metabolic engineering strategies have been developed for these metabolites. Microalgal biofuels have also drawn great attention recently, resulting in efforts for improving the production of hydrogen and photosynthates, particularly triacylglycerides. Metabolic pathways of microalgae have also been manipulated in order to improve photosynthetic growth under specific conditions and for achieving trophic conversion. Although these pathways are not strictly related to secondary metabolites, the synthetic biology approaches could potentially be translated to this field and will also be discussed. PMID:26696985

  1. Sucrose transport into stalk tissue of sugarcane

    SciTech Connect

    Thom, M.; Maretzki, A. )

    1990-05-01

    The productivity of higher plants is, in part, dependent on transport of photosynthate from source to sink (in sugarcane, stalk) and upon its assimilation in cells of the sink tissue. In sugarcane, sucrose has been reported to undergo hydrolysis in the apoplast before uptake into the storage parenchyma, whereas recently, sucrose was reported to be taken up intact. This work was based on lack of randomization of ({sup 14}C)fructosyl sucrose accumulated after feeding tissue slices with this sugar. In this report, we present evidence from slices of stalk tissue that sucrose is taken up intact via a carrier-mediated, energy-dependent process. The evidence includes: (1) uptake of fluorosucrose, an analog of sucrose not subject to hydrolysis by invertase; (2) little or no randomization of ({sup 14}C) fructosyl sucrose taken up; (3) the presence of a saturable as well as a linear component of sucrose uptake; and (4) inhibition of both the saturable and linear components of sucrose uptake by protonophore and sulhydryl agents. Hexoses can also be taken up, and at a greater efficiency than sucrose. It is probable that both hexose and sucrose can be transported across the plasma membrane, depending on the physiological status of the plant.

  2. Subcellular localization and vacuolar targeting of sorbitol dehydrogenase in apple seed.

    PubMed

    Wang, Xiu-Ling; Hu, Zi-Ying; You, Chun-Xiang; Kong, Xiu-Zhen; Shi, Xiao-Pu

    2013-09-01

    Sorbitol is the primary photosynthate and translocated carbohydrate in fruit trees of the Rosaceae family. NAD(+)-dependent sorbitol dehydrogenase (NAD-SDH, EC 1.1.1.14), which mainly catalyzes the oxidation of sorbitol to fructose, plays a key role in regulating sink strength in apple. In this study, we found that apple NAD-SDH was ubiquitously distributed in epidermis, parenchyma, and vascular bundle in developing cotyledon. NAD-SDH was localized in the cytosol, the membranes of endoplasmic reticulum and vesicles, and the vacuolar lumen in the cotyledon at the middle stage of seed development. In contrast, NAD-SDH was mainly distributed in the protein storage vacuoles in cotyledon at the late stage of seed development. Sequence analysis revealed there is a putative signal peptide (SP), also being predicated to be a transmembrane domain, in the middle of proteins of apple NAD-SDH isoforms. To investigate whether the putative internal SP functions in the vacuolar targeting of NAD-SDH, we analyzed the localization of the SP-deletion mutants of MdSDH5 and MdSDH6 (two NAD-SDH isoforms in apple) by the transient expression system in Arabidopsis protoplasts. MdSDH5 and MdSDH6 were not localized in the vacuoles after their SPs were deleted, suggesting the internal SP functions in the vacuolar targeting of apple NAD-SDH. PMID:23849111

  3. Rapid Degradation of the Tetrameric Mn Cluster in Illuminated, PsbO-Depleted Photosystem II Preparations

    SciTech Connect

    Semin, B. K.; Davletshina, L. N.; Ivanov, I. I.; Seibert, M.; Rubin, A. B.

    2012-01-01

    A 'decoupling effect' (light-induced electron transport without O{sub 2} evolution) was observed in Ca-depleted photosystem II (PSII(-Ca)) membranes, which lack PsbP and PsbQ (Semin et al. (2008) Photosynth. Res., 98, 235-249). Here PsbO-depleted PSII (PSII(-PsbO)) membranes (which also lack PsbP and PsbQ) were used to examine effects of PsbO on the decoupling. PSII(-PsbO) membranes do not reduce the acceptor 2,6-dichlorophenolindophenol (DCIP), in contrast to PSII(-Ca) membranes. To understand why DCIP reduction is lost, we studied light effects on the Mn content of PSII(-PsbO) samples and found that when they are first illuminated, Mn cations are rapidly released from the Mn cluster. Addition of an electron acceptor to PSII(-PsbO) samples accelerates the process. No effect of light was found on the Mn cluster in PSII(-Ca) membranes. Our results demonstrate that: (a) the oxidant, which directly oxidizes an as yet undefined substrate in PSII(-Ca) membranes, is the Mn cluster (not the Y{sub Z} radical or P680{sup +}); (b) light causes rapid release of Mn cations from the Mn cluster in PSII(-PsbO) membranes, and the mechanism is discussed; and (c) rapid degradation of the Mn cluster under illumination is significant for understanding the lack of functional activity in some PSII(-PsbO) samples reported by others.

  4. In situ stable isotope probing of phosphate-solubilizing bacteria in the hyphosphere.

    PubMed

    Wang, Fei; Shi, Ning; Jiang, Rongfeng; Zhang, Fusuo; Feng, Gu

    2016-03-01

    This study used a [(13)C]DNA stable isotope probing (SIP) technique to elucidate a direct pathway for the translocation of (13)C-labeled photoassimilate from maize plants to extraradical mycelium-associated phosphate-solubilizing bacteria (PSB) that mediate the mineralization and turnover of soil organic phosphorus (P) in the hyphosphere. Inoculation with PSB alone did not provide any benefit to maize plants but utilized the added phytate-P to their own advantage, while inoculation with Rhizophagus irregularis alone significantly promoted shoot biomass and P content compared with the control. However, compared with both sole inoculation treatments, combined inoculation with PSB and R. irregularis in the hyphosphere enhanced organic P mineralization and increased microbial biomass P in the soil. There was no extra benefit to plant P uptake but the hyphal growth of R. irregularis was reduced, suggesting that PSB benefited from the arbuscular mycorrhizal (AM) fungal mycelium and competed for soil P with the fungus. The combination of T-RFLP (terminal restriction fragment length polymorphism) analysis with a clone library revealed that one of the bacteria that actively assimilated carbon derived from pulse-labeled maize plants was Pseudomonas alcaligenes (Pseudomonadaceae) that was initially inoculated into the hyphosphere soil. These results provide the first in situ demonstration of the pathway underlying the carbon flux from plants to the AM mycelium-associated PSB, and the PSB assimilated the photosynthates exuded by the fungus and promoted mineralization and turnover of organic P in the soil. PMID:26802172

  5. Dominant negative RPW8.2 fusion proteins reveal the importance of haustorium-oriented protein trafficking for resistance against powdery mildew in Arabidopsis.

    PubMed

    Zhang, Qiong; Berkey, Robert; Pan, Zhiyong; Wang, Wenming; Zhang, Yi; Ma, Xianfeng; King, Harlan; Xiao, Shunyuan

    2015-01-01

    Powdery mildew fungi form feeding structures called haustoria inside epidermal cells of host plants to extract photosynthates for their epiphytic growth and reproduction. The haustorium is encased by an interfacial membrane termed the extrahaustorial membrane (EHM). The atypical resistance protein RPW8.2 from Arabidopsis is specifically targeted to the EHM where RPW8.2 activates haustorium-targeted (thus broad-spectrum) resistance against powdery mildew fungi. EHM-specific localization of RPW8.2 suggests the existence of an EHM-oriented protein/membrane trafficking pathway during EHM biogenesis. However, the importance of this specific trafficking pathway for host defense has not been evaluated via a genetic approach without affecting other trafficking pathways. Here, we report that expression of EHM-oriented, nonfunctional RPW8.2 chimeric proteins exerts dominant negative effect over functional RPW8.2 and potentially over other EHM-localized defense proteins, thereby compromising both RPW8.2-mediated and basal resistance to powdery mildew. Thus, our results highlight the importance of the EHM-oriented protein/membrane trafficking pathway for host resistance against haustorium-forming pathogens such as powdery mildew fungi. PMID:25830634

  6. Gas Exchange Characteristics of the Sorghum-Striga Host-Parasite Association

    PubMed Central

    Press, Malcolm C.; Tuohy, Janet M.; Stewart, George R.

    1987-01-01

    Gas exchange characteristics are reported for both members of the sorghum-Striga host-parasite association. Both Striga hermonthica (Del.) Benth and Striga asiatica (L.) Kuntze had transpiration rates considerably in excess of those of sorghum (Sorghum bicolor (L.) Moench, cv CSH1). Stomatal conductance in both Striga spp. showed little response to periods of darkness and moderate water stress. Low rates of net CO2 fixation and high rates of dark respiration led to no net daily (24 hours) C gain, and Striga would appear to be reliant on its host for photosynthate. Infection of sorghum plants with either S. hermonthica or S. asiatica reduced host photosynthetic capacity. Infected sorghum plants were also more prone to water stress, but reduced rates of CO2 fixation could not be accounted for in terms of lower stomatal conductance. Lower stomatal conductances were associated with an increase in water use efficiency (WUE) in uninfected sorghum; however, Striga-infected sorghum plants had lower WUE than those of uninfected plants. We suggest that Striga exerts a specific effect on processes affecting C acquisition in sorghum leaves. The water relations of S. hermonthica and S. asiatica are not characteristic of plants growing in semiarid environments and are more likely to reflect the nature of the parasitic life-style. Despite transfer of water and solutes from host to parasite, the reduction in C fixation observed in infected sorghum plants appears to be the major determinant of growth reductions observed in sorghum supporting Striga. PMID:16665527

  7. Nitrogen control of chloroplast differentiation. Final report

    SciTech Connect

    Schmidt, G.W.

    1998-05-01

    This project was directed toward understanding at the physiological, biochemical and molecular levels of how photosynthetic organisms adapt to long-term nitrogen-deficiency conditions is quite incomplete even though limitation of this nutrient is the most commonly restricts plant growth and development. For our work on this problem, the unicellular green alga, Chlamydomonas reinhardtii, was grown in continuous cultures in which steady-state levels of nitrogen can be precisely controlled. N-limited cells exhibit the classical symptoms of deficiency of this nutrient, chlorosis and slow growth rates, and respond to nitrogen provision by rapid greening and chloroplast differentiation. We have addressed three aspects of this problem: (1) the regulation of pigment synthesis; (2) control of expression of nuclear genes encoding photosynthetic proteins; (3) changes in metabolic and electron transport pathways that enable sustained CO{sub 2} fixation even though they cannot be readily converted into amino and nucleic acids. For the last, principle components are: (a) enhanced mitochondrial respiratory activity intimately associated with photosynthates, and (b) the occurrence in thylakoids of a supplemental electron transport pathway that facilitates reduction of the plastoquinone pool. Together, these distinguishing features of N-limited cells are likely to enable cell survival, especially under conditions of high irradiance stress.

  8. A kinetic and microautoradiographic study of sup 14 C-sucrose translocation into developing wheat grains

    SciTech Connect

    Ning Wang; Fisher, D.B. )

    1991-05-01

    The kinetics of {sup 14}C-photosynthate import by developing wheat grains was followed after pulse-labeling the flag leaf with {sup 14}CO{sub 2}. Samples were collected from four successive points along the transport pathway to and within the grain: exuding aphid stylets on the peduncle, exuding grain pedicels, the grain crease tissues, and the liquid contents of the endosperm cavity. In addition, microautoradiographs were prepared of the grain crease tissues during movement of the {sup 14}C pulse into the grain. At all times, sucrose accounted for 93 to 97% of the total {sup 14}C present at all four sampling sites. The main features of the {sup 14}C kinetics could be accounted for by a simple compartmental model consisting of sucrose pools in series. Microautoradiographs of the crease tissues showed fairly uniform labeling of vascular parenchyma at all times, with a sharp gradient in labeling across the chalaza to the nucellus. Thus the principal resistance to post-phloem solute transport through the maternal tissues appears to be in the symplastic pathway across the chalaza.

  9. Seasonal dynamics of fungal communities in a temperate oak forest soil.

    PubMed

    Voříšková, Jana; Brabcová, Vendula; Cajthaml, Tomáš; Baldrian, Petr

    2014-01-01

    Fungi are the agents primarily responsible for the transformation of plant-derived carbon in terrestrial ecosystems. However, little is known of their responses to the seasonal changes in resource availability in deciduous forests, including photosynthate allocation below ground and seasonal inputs of fresh litter. Vertical stratification of and seasonal changes in fungal abundance, activity and community composition were investigated in the litter, organic and upper mineral soils of a temperate Quercus petraea forest using ergosterol and extracellular enzyme assays and amplicon 454-pyrosequencing of the rDNA-ITS region. Fungal activity, biomass and diversity decreased substantially with soil depth. The highest enzyme activities were detected in winter, especially in litter, where these activities were followed by a peak in fungal biomass during spring. The litter community exhibited more profound seasonal changes than did the community in the deeper horizons. In the litter, saprotrophic genera reached their seasonal maxima in autumn, but summer typically saw the highest abundance of ectomycorrhizal taxa. Although the composition of the litter community changes over the course of the year, the mineral soil shows changes in biomass. The fungal community is affected by season. Litter decomposition and phytosynthate allocation represent important factors contributing to the observed variations. PMID:24010995

  10. Investigating energy partitioning during photosynthesis using an expanded quantum yield convention

    NASA Astrophysics Data System (ADS)

    Ahn, Tae Kyu; Avenson, Thomas J.; Peers, Graham; Li, Zhirong; Dall'Osto, Luca; Bassi, Roberto; Niyogi, Krishna K.; Fleming, Graham R.

    2009-02-01

    In higher plants, regulation of excess absorbed light is essential for their survival and fitness, as it enables avoidance of a build up of singlet oxygen and other reactive oxygen species. Regulation processes (known as non-photochemical quenching; NPQ) can be monitored by steady-state fluorescence on intact plant leaves. Pulse amplitude modulated (PAM) measurements of chlorophyll a fluorescence have been used for over 20 years to evaluate the amount of NPQ and photochemistry (PC). Recently, a quantum yield representation of NPQ ( ΦNPQ), which incorporates a variable fraction of open reaction centers, was proposed by Hendrickson et al. [L. Hendrickson, R.T. Furbank, W.S. Chow, Photosynth. Res. 82 (2004) 73]. In this work we extend the quantum yield approach to describe the yields of reversible energy-dependent quenching ( ΦqE), state transitions to balance PC between photosystems II and I ( ΦqT), and photoinhibition quenching associated with damaged reaction centers ( ΦqI). We showed the additivity of the various quantum yield components of NPQ through experiments on wild-type and npq1 strains of Arabidopsis thaliana. The quantum yield approach enables comparison of ΦqE with data from a variety of techniques used to investigate the mechanism of qE. We showed that ΦqE for a series of A. thaliana genotypes scales linearly with the magnitude of zeaxanthin cation formation, suggesting that charge-transfer quenching is largely responsible for qE in plants.

  11. How switches and lags in biophysical regulators affect spatial-temporal variation of soil respiration in an oak-grass savanna

    NASA Astrophysics Data System (ADS)

    Baldocchi, Dennis; Tang, Jianwu; Xu, Liukang

    2006-06-01

    Complex behavior, associated with soil respiration of an oak-grass savanna ecosystem in California, was quantified with continuous measurements of CO2 exchange at two scales (soil and canopy) and with three methods (overstory and understory eddy covariance systems, soil respiration chambers, and a below-ground CO2 flux gradient system). To partition soil respiration into its autotrophic and heterotrophic components, we exploited spatial gradients in the landscape and seasonal variations in rainfall. During the dry summer, heterotrophic respiration was dominant in the senesced grassland area, whereas autotrophic respiration by roots and the feeding of microbes by root exudates was dominant under the trees. A temporal switch in soil respiration occurred in the spring. But the stimulation of root respiration lagged the timing of leaf-out by the trees. Another temporal switch in soil respiration occurred at the start of autumn rains. This switch was induced by the rapid germination of grass seed and new grass growth. Isolated summer rain storms caused a pulse in soil respiration. Such rain events stimulated microbial respiration only; the rain was not sufficient to replenish soil moisture in the root zone or to germinate grass seed. Soil respiration lagged photosynthetic activity on hourly scales. The likely mechanism is the slow translocation of photosynthate to the roots and associated microbes. Another lag occurred on daily scales because of modulations in photosynthesis and stomatal conductance by the passage of dry and humid air masses.

  12. Experimental geobiology links evolutionary intensification of rooting systems and weathering

    NASA Astrophysics Data System (ADS)

    Quirk, Joe; Beerling, David; Leake, Jonathan

    2016-04-01

    The evolution of mycorrhizal fungi in partnership with early land plants over 440 million years ago led to the greening of the continents by plants of increasing biomass, rooting depth, nutrient demand and capacity to alter soil minerals, culminating in modern forested ecosystems. The later co-evolution of trees and rooting systems with arbuscular mycorrhizal (AM) fungi, together driving the biogeochemical cycling of elements and weathering of minerals in soil to meet subsequent increased phosphorus demands is thought to constitute one the most important biotic feedbacks on the geochemical carbon cycle to emerge during the Phanerozoic, and fundamentally rests on the intensifying effect of trees and their root-associating mycorrhizal fungal partners on mineral weathering. Here I present experimental and field evidence linking these evolutionary events to a mechanistic framework whereby: (1) as plants evolved in stature, biomass, and rooting depth, their mycorrhizal fungal partnerships received increasing amounts of plant photosynthate; (2) this enabled intensification of plant-driven fungal weathering of rocks to release growth-limiting nutrients; (3) in turn, this increased land-to-ocean export of Ca and P and enhanced ocean carbonate precipitation impacting the global carbon cycle and biosphere-geosphere-ocean-atmosphere interactions over the past 410 Ma. Our findings support an over-arching hypothesis that evolution has selected plant and mycorrhizal partnerships that have intensified mineral weathering and altered global biogeochemical cycles.

  13. Nanoscale channels on ectomycorrhizal-colonized chlorite: Evidence for plant-driven fungal dissolution

    NASA Astrophysics Data System (ADS)

    Gazzè, Salvatore A.; Saccone, Loredana; Vala Ragnarsdottir, K.; Smits, Mark M.; Duran, Adele L.; Leake, Jonathan R.; Banwart, Steven A.; McMaster, Terence J.

    2012-09-01

    The roots of many trees in temperate and boreal forests are sheathed with ectomycorrhizal fungi (EMF) that extend into the soil, forming intimate contact with soil minerals, from which they absorb nutrient elements required by the plants and, in return, are supported by the organic carbon photosynthesized by the trees. While EMF are strongly implicated in mineral weathering, their effects on mineral surfaces at the nanoscale are less documented. In the present study, we investigated the effects of symbiotic EMF on the topography of a chlorite mineral using atomic force microscopy. A cleaning protocol was successfully applied to remove fungal hyphae without altering the underlying mineral structure and topography. Examination of the exposed chlorite surface showed the presence of primary channels, of the order of a micron in width and up to 50 nm in depth, the morphology of which strongly indicates a fungal-induced origin. Smaller secondary channels were observed extending from the primary channels and would appear to be involved in their enlargement. The presence of channels is the first nanoscale demonstration of the effects of fungal interaction, fuelled by plant photosynthate, on the topography of a chlorite mineral, and it provides clear evidence of the ability of EMF to enhance mineral dissolution.

  14. The LysR-type transcription factor PacR is a global regulator of photosynthetic carbon assimilation in Anabaena.

    PubMed

    Picossi, Silvia; Flores, Enrique; Herrero, Antonia

    2015-09-01

    Cyanobacteria perform water-splitting photosynthesis and are important primary producers impacting the carbon and nitrogen cycles at global scale. They fix CO2 through ribulose-bisphosphate carboxylase/oxygenase (RuBisCo) and have evolved a distinct CO2 concentrating mechanism (CCM) that builds high CO2 concentrations in the vicinity of RuBisCo favouring its carboxylase activity. Filamentous cyanobacteria such as Anabaena fix CO2 in photosynthetic vegetative cells, which donate photosynthate to heterocysts that rely on a heterotrophic metabolism to fix N2 . CCM elements are induced in response to inorganic carbon limitation, a cue that exposes the photosynthetic apparatus to photodamage by over-reduction. An Anabaena mutant lacking the LysR-type transcription factor All3953 grew poorly and dies under high light. The rbcL operon encoding RuBisCo was induced upon carbon limitation in the wild type but not in the mutant. ChIP-Seq analysis was used to globally identify All3953 targets under carbon limitation. Targets include, besides rbcL, genes encoding CCM elements, photorespiratory pathway- photosystem- and electron transport-related components, and factors, including flavodiiron proteins, with a demonstrated or putative function in photoprotection. Quantitative reverse transcription polymerase chain reaction analysis of selected All3953 targets showed regulation in the wild type but not in the mutant. All3953 (PacR) is a global regulator of carbon assimilation in an oxygenic photoautotroph. PMID:25684321

  15. Effect of increased CO sub 2 and decreased O sub 2 on photosynthesis, and carbon allocation in source leaves

    SciTech Connect

    Fondy, B.R. ); Geiger, D.R.; Shieh, W.-J. )

    1990-05-01

    The effect of raising the rate of photosynthesis on the allocation of carbon between sucrose and starch was studied by means of steady-state radiolabeling. Sugar beet source leaves on intact plants were exposed to ambient levels of CO{sub 2} and O{sub 2} for 3 hrs. Next CO{sub 2} was raised to 600 {mu}LL{sup {minus}3} for 3 hrs then O{sub 2} was decreased to 2% for 3 hrs. Rates of net carbon exchange (NCE), export, and starch and sucrose synthesis were measured. NCER increased by 30% under the combined treatments and the proportion of photosynthate allocated to starch and to sucrose did not change. When O{sub 2} concentration was lowered, NCER increased but export did not and sucrose accumulated. This observation, and our earlier conclusion that export rate usually equals sucrose synthesis rate, lead us to conclude that low O{sub 2} directly inhibited export. Low O{sub 2} treatment causes sucrose to accumulate in a sugar beet leaf which usually accumulates little sucrose.

  16. Management and fertility control ecosystem carbon allocation to biomass production

    NASA Astrophysics Data System (ADS)

    Campioli, Matteo; Vicca, Sara; Janssens, Ivan

    2015-04-01

    Carbon (C) allocation within the ecosystem is one of the least understood processes in plant- and geo-sciences. The proportion of the C assimilated through photosynthesis (gross primary production, GPP) that is used for biomass production (BP) is a key variable of the C allocation process and it has been termed as biomass production efficiency (BPE). We investigated the potential drivers of BPE using a global dataset of BP, GPP, BPE and ancillary ecosystem characteristics (vegetation properties, climatic and environmental variables, anthropogenic impacts) for 131 sites comprising six major ecosystem types: forests, grasslands, croplands, tundra, boreal peatlands and marshes. We obtained two major findings. First, site fertility is the key driver of BPE across forests, with nutrient-rich forests allocating 58% of their photosynthates to BP, whereas this fraction is only 42% for nutrient-poor forests. Second, by disentangling the effect of management from the effect of fertility and by integrating all ecosystem types, we observed that BPE is globally not driven by the 'natural' site fertility, but by the positive effect brought by management on the nutrient availability. This resulted in managed ecosystems having substantially larger BPE than natural ecosystems. These findings will crucially improve our elucidation of the human impact on ecosystem functioning and our predictions of the global C cycle.

  17. Effect of Removing Superior Spikelets on Grain Filling of Inferior Spikelets in Rice.

    PubMed

    You, Cuicui; Zhu, Honglei; Xu, Beibei; Huang, Wenxiao; Wang, Shaohua; Ding, Yanfeng; Liu, Zhenghui; Li, Ganghua; Chen, Lin; Ding, Chengqiang; Tang, She

    2016-01-01

    Large-panicle rice cultivars often fail to reach their yield potential due to the poor grain filling of inferior spikelets (IS). Thus, it is important to determine the causes of poor IS grain filling. In this study, we attempted to identify whether inferior grain filling of large panicles is restricted by superior spikelets (SS) and their physiological mechanism. SS were removed from two homozygous japonica rice strains (W1844 and WJ165) during flowering in an attempt to force photosynthate transport to the IS. We measured the effects of SS removal on seed setting rate, grain weight, grain filling rate, sucrose content, as well as hormone levels, activities of key enzymes, and expression of genes involved in sucrose to starch metabolism in rice IS during grain filling. The results showed that SS removal improved IS grain filling by increasing the seed setting rate, grain weight, sucrose content, and hormone levels. SS removal also enhanced the activities of key enzymes and the expression levels of genes involved in sucrose to starch metabolism. These results suggest that sucrose and several hormones act as signal substances and play a vital role in grain filling by regulating enzyme activities and gene expression. Therefore, IS grain filling is restricted by SS, which limit assimilate supply and plant hormones, leading to poor grain filling of IS. PMID:27547210

  18. Defence strategies adopted by the medicinal plant Coleus forskohlii against supplemental ultraviolet-B radiation: Augmentation of secondary metabolites and antioxidants.

    PubMed

    Takshak, Swabha; Agrawal, S B

    2015-12-01

    Supplementary ultraviolet-B (ambient+3.6  kJ m(-2) day(-1)) induced changes on morphological, physiological, and biochemical characteristics (specifically the defence strategies: UV-B protective compounds and antioxidants) of Coleus forskohlii were investigated under field conditions at 30, 60, and 90 days after transplantation. Levels of secondary metabolites increased under s-UV-B stress; flavonoids and phenolics (primary UV-B screening agents) were recorded to be higher in leaves which are directly exposed to s-UV-B. This was also verified by enhanced activities of phenylpropanoid pathway enzymes: phenylalanine ammonia lyase (PAL), cinnamyl alcohol dehydrogenase (CAD), 4-coumarate-CoA ligase (4CL), chalcone-flavanone isomerase (CHI), and dihydroflavonol reductase (DFR). Antioxidants, both enzymatic (ascorbate peroxidase, catalase, glutathione reductase, peroxidase, polyphenol oxidase, and superoxide dismutase) and non-enzymatic (ascorbic acid and α-tocopherol) also increased in the treated organs of the test plant, higher contents being recorded in roots except for ascorbic acid. On the contrary, protein and chlorophyll content (directly implicated in regulating plant growth and development) declined under s-UV-B. These alterations in plant biochemistry led the plant to compromise on its photosynthate allocation towards growth and biomass production as evidenced by a reduction in its height and biomass. The study concludes that s-UV-B is a potent stimulating factor in increasing the concentrations of defense compounds and antioxidants in C. forskohlii to optimize its performance under stress. PMID:26461242

  19. Plastid RNA polymerases: orchestration of enzymes with different evolutionary origins controls chloroplast biogenesis during the plant life cycle.

    PubMed

    Pfannschmidt, Thomas; Blanvillain, Robert; Merendino, Livia; Courtois, Florence; Chevalier, Fabien; Liebers, Monique; Grübler, Björn; Hommel, Elisabeth; Lerbs-Mache, Silva

    2015-12-01

    Chloroplasts are the sunlight-collecting organelles of photosynthetic eukaryotes that energetically drive the biosphere of our planet. They are the base for all major food webs by providing essential photosynthates to all heterotrophic organisms including humans. Recent research has focused largely on an understanding of the function of these organelles, but knowledge about the biogenesis of chloroplasts is rather limited. It is known that chloroplasts develop from undifferentiated precursor plastids, the proplastids, in meristematic cells. This review focuses on the activation and action of plastid RNA polymerases, which play a key role in the development of new chloroplasts from proplastids. Evolutionarily, plastids emerged from the endosymbiosis of a cyanobacterium-like ancestor into a heterotrophic eukaryote. As an evolutionary remnant of this process, they possess their own genome, which is expressed by two types of plastid RNA polymerase, phage-type and prokaryotic-type RNA polymerase. The protein subunits of these polymerases are encoded in both the nuclear and plastid genomes. Their activation and action therefore require a highly sophisticated regulation that controls and coordinates the expression of the components encoded in the plastid and nucleus. Stoichiometric expression and correct assembly of RNA polymerase complexes is achieved by a combination of developmental and environmentally induced programmes. This review highlights the current knowledge about the functional coordination between the different types of plastid RNA polymerases and provides working models of their sequential expression and function for future investigations. PMID:26355147

  20. Hydrogen export from intertidal cyanobacterial mats: sources, fluxes and the influence of community composition.

    PubMed

    Hoffmann, Dörte; Maldonado, Juan; Wojciechowski, Martin F; Garcia-Pichel, Ferran

    2015-10-01

    Microbial mats from marine intertidal settings have been reported to release significant quantities of H2 , in a unique trait among other mats and microbial communities. However, the H2 source and ecophysiological mechanisms that enable its export are not well understood. We examined H2 accumulation and export in three types of greenhouse-reared mats, from the intertidal region of Guerrero Negro, Mexico, and kept under natural light-dark conditions and wetting and drying cycles simulating low-, mid- and high-tidal height periodicity. All mats released H2 reproducibly and sustainably for 1.5 years. Net H2 export took place in a pulsed daily manner, starting after dusk, and waning in the morning, as photosynthesis resumed. Mid- and low-tidal mats developed high concentrations, capable of sustaining export fluxes that represented 2-4% of the water split through primary productivity. Neither N2 fixation nor direct photolytic hydrogenogenesis was significant to this H2 export, which was fermentative in origin, variable among mats, originating from cyanobacterial photosynthate. Analyses of community composition by pyrosequencing of 16S rRNA and hoxH genes indicate that filamentous non-heterocystous cyanobacteria (e.g. Lyngbya, Microcoleus) were important in the process of H2 export, as was the relatively low abundance and activity of methanogens and sulfate reducers. PMID:25580666

  1. Methane Production by Microbial Mats Under Low Sulfate Concentrations

    NASA Technical Reports Server (NTRS)

    Bebout, Brad M.; Hoehler, Tori M.; Thamdrup, Bo; Albert, Dan; Carpenter, Steven P.; Hogan, Mary; Turk, Kendra; DesMarais, David J.

    2003-01-01

    Cyanobacterial mats collected in hypersaline salterns were incubated in a greenhouse under low sulfate concentrations ([SO4]) and examined for their primary productivity and emissions of methane and other major carbon species. Atmospheric greenhouse warming by gases such as carbon dioxide and methane must have been greater during the Archean than today in order to account for a record of moderate to warm paleoclemates, despite a less luminous early sun. It has been suggested that decreased levels of oxygen and sulfate in Archean oceans could have significantly stimulated microbial methanogenesis relative to present marine rates, with a resultant increase in the relative importance of methane in maintaining the early greenhouse. We maintained modern microbial mats, models of ancient coastal marine communities, in artificial brine mixtures containing both modern [SO4=] (ca. 70 mM) and "Archean" [SO4] (less than 0.2 mM). At low [SO4], primary production in the mats was essentially unaffected, while rates of sulfate reduction decreased by a factor of three, and methane fluxes increased by up to ten-fold. However, remineralization by methanogenesis still amounted to less than 0.4 % of the total carbon released by the mats. The relatively low efficiency of conversion of photosynthate to methane is suggested to reflect the particular geometry and chemical microenvironment of hypersaline cyanobacterial mats. Therefore, such mats w-ere probably relatively weak net sources of methane throughout their 3.5 Ga history, even during periods of low- environmental levels oxygen and sulfate.

  2. Effect of Removing Superior Spikelets on Grain Filling of Inferior Spikelets in Rice

    PubMed Central

    You, Cuicui; Zhu, Honglei; Xu, Beibei; Huang, Wenxiao; Wang, Shaohua; Ding, Yanfeng; Liu, Zhenghui; Li, Ganghua; Chen, Lin; Ding, Chengqiang; Tang, She

    2016-01-01

    Large-panicle rice cultivars often fail to reach their yield potential due to the poor grain filling of inferior spikelets (IS). Thus, it is important to determine the causes of poor IS grain filling. In this study, we attempted to identify whether inferior grain filling of large panicles is restricted by superior spikelets (SS) and their physiological mechanism. SS were removed from two homozygous japonica rice strains (W1844 and WJ165) during flowering in an attempt to force photosynthate transport to the IS. We measured the effects of SS removal on seed setting rate, grain weight, grain filling rate, sucrose content, as well as hormone levels, activities of key enzymes, and expression of genes involved in sucrose to starch metabolism in rice IS during grain filling. The results showed that SS removal improved IS grain filling by increasing the seed setting rate, grain weight, sucrose content, and hormone levels. SS removal also enhanced the activities of key enzymes and the expression levels of genes involved in sucrose to starch metabolism. These results suggest that sucrose and several hormones act as signal substances and play a vital role in grain filling by regulating enzyme activities and gene expression. Therefore, IS grain filling is restricted by SS, which limit assimilate supply and plant hormones, leading to poor grain filling of IS. PMID:27547210

  3. Molecular assessment of the effect of light and heterotrophy in the scleractinian coral Stylophora pistillata.

    PubMed

    Levy, Oren; Karako-Lampert, Sarit; Waldman Ben-Asher, Hiba; Zoccola, Didier; Pagès, Gilles; Ferrier-Pagès, Christine

    2016-04-27

    Corals acquire nutrients via the transfer of photosynthates by their endosymbionts (autotrophy), or via zooplankton predation by the animal (heterotrophy). During stress events, corals lose their endosymbionts, and undergo starvation, unless they increase their heterotrophic capacities. Molecular mechanisms by which heterotrophy sustains metabolism in stressed corals remain elusive. Here for the first time, to the best of our knowledge, we identified specific genes expressed in heterotrophically fed and unfed colonies of the scleractinian coral Stylophora pistillata, maintained under normal and light-stress conditions. Physiological parameters and gene expression profiling demonstrated that fed corals better resisted stress than unfed ones by exhibiting less oxidative damage and protein degradation. Processes affected in light-stressed unfed corals (HLU), were related to energy and metabolite supply, carbohydrate biosynthesis, ion and nutrient transport, oxidative stress, Ca(2+) homeostasis, metabolism and calcification (carbonic anhydrases, calcium-transporting ATPase, bone morphogenetic proteins). Two genes (cp2u1 and cp1a2), which belong to the cytochrome P450 superfamily, were also upregulated 249 and 10 times, respectively, in HLU corals. In contrast, few of these processes were affected in light-stressed fed corals (HLF) because feeding supplied antioxidants and energetic molecules, which help repair oxidative damage. Altogether, these results show that heterotrophy helps prevent the cascade of metabolic problems downstream of oxidative stress. PMID:27122555

  4. Seasonal branch and fine root growth of juvenile loblolly pine five growing seasons after fertilization.

    PubMed

    Sword, M. A.; Gravatt, D. A.; Faulkner, P. L.; Chambers, J. L.

    1996-01-01

    In 1989, we established two replications of two fertilization treatments in a 10-year-old loblolly pine (Pinus taeda L.) plantation. Between March and September 1993, branch internode and needle fascicle expansion in the upper and lower third of crowns were measured weekly on three south-facing branches of each of four trees, and new root initiation and elongation were measured at 10-day intervals in three vertical rhizotrons per plot. In one replication, soil water content was measured daily. Fertilization significantly increased the expansion of first flush internodes in the upper crown and first flush needle fascicles in the upper and lower crown. New root growth was stimulated by fertilization in the second half of the growing season. The timing of root growth responses to fertilization corresponded to branch phenologies in the upper and lower crown that were conducive to increased basipetal transport of photosynthate. We conclude, therefore, that new root growth was linked to source-sink activities in the crown. Root initiation was greater in the upper than in the lower part of the soil profile; however, as the growing season progressed and water deficit increased, this relationship was reversed. The effect of soil depth on seasonal root growth was closely associated with water availability, suggesting that root initiation deep in the soil profile is critical for the continued production of new roots in environments subjected to short-term, but relatively severe, water deficits. PMID:14871782

  5. Carbohydrate Content and Enzyme Metabolism in Developing Canola Siliques.

    PubMed Central

    King, S. P.; Lunn, J. E.; Furbank, R. T.

    1997-01-01

    Little biochemical information is available on carbohydrate metabolism in developing canola (Brassica napus L.) silique (pod) wall and seed tissues. This research examines the carbohydrate contents and sucrose (Suc) metabolic enzyme activities in different aged silique wall and seed tissues during oil filling. The silique wall partitioned photosynthate into Suc over starch and predominantly accumulated hexose. The silique wall hexose content and soluble acid invertase activity rapidly fell as embryos progressed from the early- to late-cotyledon developmental stages. A similar trend was not evident for alkaline invertase, Suc synthase (SuSy), and Suc-phosphate synthase. Silique wall SuSy activities were much higher than source leaves at all times and may serve to supply the substrate for secondary cell wall thickening. In young seeds starch was the predominant accumulated carbohydrate over the sampled developmental range. Seed hexose levels dropped as embryos developed from the early- to midcotyledon stage. Hexose and starch were localized to the testa or liquid endosperm, whereas Suc was evenly distributed among seed components. With the switch to oil accumulation, seed SuSy activity increased by 3.6-fold and soluble acid invertase activity decreased by 76%. These data provide valuable baseline knowledge for the genetic manipulation of canola seed carbon partitioning. PMID:12223695

  6. Kinetics of C-14 Translocation in Soybean

    PubMed Central

    Fisher, Donald B.

    1970-01-01

    The kinetics of 14C-assimilates in the soybean leaf were studied in pulse labeling and steady state labeling experiments. 14C-Sucrose apparently served as the ultimate source, at least, of translocated 14C-sucrose. However, since the specific activity of leaf sucrose reached a maximum within 5 minutes after pulse labeling, whereas that of exported sucrose did not reach a maximum until at least 20 minutes, it appeared that there were two sucrose compartments in the leaf. A possible physical basis for the two compartments may be the mesophyll (a photosynthetic compartment) and a specialized “paraveinal mesophyll” (a nonphotosynthetic compartment), through which photosynthate must pass on its way to the veins. The 14C kinetics of sterol glucoside, and probably esterified sterol glucoside, were similar to those for 14C-sucrose export. Sterol glucoside was labeled only in its glucose moiety and was the only stem lipid which became strongly labeled during 14C-sucrose translocation. These sterol derivatives may act as membrane carriers of sucrose between the translocation stream and surrounding cells. The kinetics of 14C-sucrose and its movement to the veins are discussed with reference to compartmentation within the leaf and metabolic exchange with other compounds, particularly with starch. Although a simple compartmental model gave a fairly accurate description of 14C-sucrose kinetics, an entirely accurate model could not be provided, primarily because of loss of 14C from sucrose, at an unknown rate, to starch. PMID:16657287

  7. Transcripts for genes encoding soluble acid invertase and sucrose synthase accumulate in root tip and cortical cells containing mycorrhizal arbuscules.

    PubMed

    Blee, Kristopher A; Anderson, Anne J

    2002-09-01

    Arbuscule formation by the arbuscular mycorrhizal fungus Glomus intraradices (Schenck & Smith) was limited to cortical cells immediately adjacent to the endodermis. Because these cortical cells are the first to intercept photosynthate exiting the vascular cylinder, transcript levels for sucrose metabolizing-enzymes were compared between mycorrhizal and non-mycorrhizal roots. The probes corresponded to genes encoding a soluble acid invertase with potential vacuolar targeting, which we generated from Phaseolus vulgaris roots, a Rhizobium-responsive sucrose synthase of soybean and a cell wall acid invertase of carrot. Transcripts in non-mycorrhizal roots were developmentally regulated and abundant in the root tips for all three probes but in differentiated roots of P. vulgaris they were predominantly located in phloem tissues for sucrose synthase or the endodermis and phloem for soluble acid invertase. In mycorrhizal roots increased accumulations of transcripts for sucrose synthase and vacuolar invertase were both observed in the same cortical cells bearing arbuscules that fluoresce. There was no effect on the expression of the cell wall invertase gene in fluorescent carrot cells containing arbuscules. Thus, it appears that presence of the fungal hyphae in the fluorescent arbusculated cell stimulates discrete alterations in expression of sucrose metabolizing enzymes to increase the sink potential of the cell. PMID:12175013

  8. A Versatile Monosaccharide Transporter That Operates in the Arbuscular Mycorrhizal Fungus Glomus sp Is Crucial for the Symbiotic Relationship with Plants[C][W

    PubMed Central

    Helber, Nicole; Wippel, Kathrin; Sauer, Norbert; Schaarschmidt, Sara; Hause, Bettina; Requena, Natalia

    2011-01-01

    For more than 400 million years, plants have maintained a mutualistic symbiosis with arbuscular mycorrhizal (AM) fungi. This evolutionary success can be traced to the role of these fungi in providing plants with mineral nutrients, particularly phosphate. In return, photosynthates are given to the fungus, which support its obligate biotrophic lifestyle. Although the mechanisms involved in phosphate transfer have been extensively studied, less is known about the reciprocal transfer of carbon. Here, we present the high-affinity Monosaccharide Transporter2 (MST2) from Glomus sp with a broad substrate spectrum that functions at several symbiotic root locations. Plant cell wall sugars can efficiently outcompete the Glc uptake capacity of MST2, suggesting they can serve as alternative carbon sources. MST2 expression closely correlates with that of the mycorrhiza-specific Phosphate Transporter4 (PT4). Furthermore, reduction of MST2 expression using host-induced gene silencing resulted in impaired mycorrhiza formation, malformed arbuscules, and reduced PT4 expression. These findings highlight the symbiotic role of MST2 and support the hypothesis that the exchange of carbon for phosphate is tightly linked. Unexpectedly, we found that the external mycelium of AM fungi is able to take up sugars in a proton-dependent manner. These results imply that the sugar uptake system operating in this symbiosis is more complex than previously anticipated. PMID:21972259

  9. Qualitative Distinction of Autotrophic and Heterotrophic Processes at the Leaf Level by Means of Triple Stable Isotope (C-O-H) Patterns.

    PubMed

    Kimak, Adam; Kern, Zoltan; Leuenberger, Markus

    2015-01-01

    Foliar samples were harvested from two oaks, a beech, and a yew at the same site in order to trace the development of the leaves over an entire vegetation season. Cellulose yield and stable isotopic compositions (δ(13)C, δ(18)O, and δD) were analyzed on leaf cellulose. All parameters unequivocally define a juvenile and a mature period in the foliar expansion of each species. The accompanying shifts of the δ(13)C-values are in agreement with the transition from remobilized carbohydrates (juvenile period), to current photosynthates (mature phase). While the opponent seasonal trends of δ(18)O of blade and vein cellulose are in perfect agreement with the state-of-art mechanistic understanding, the lack of this discrepancy for δD, documented for the first time, is unexpected. For example, the offset range of 18 permil (oak veins) to 57 permil (oak blades) in δD may represent a process driven shift from autotrophic to heterotrophic processes. The shared pattern between blade and vein found for both oak and beech suggests an overwhelming metabolic isotope effect on δD that might be accompanied by proton transfer linked to the Calvin-cycle. These results provide strong evidence that hydrogen and oxygen are under different biochemical controls even at the leaf level. PMID:26635835

  10. Algal biomass and primary production within a temperate zone sandstone

    SciTech Connect

    Bell, R.A.; Sommerfeld, M.R. )

    1987-02-01

    The use of dimethyl sulfoxide (DMSO) to extract chlorophyll a and {sup 14}C-labelled photosynthate from endolithic algae of sparsely vegetated, cold temperate grasslands on the Colorado Plateau in Arizona has yielded the first estimates of biomass and photosynthesis for this unusual community. These subsurface microorganisms are found widespread in exposed Coconino Sandstone, a predominant formation in this cold temperate region. The endolithic community in Coconino Sandstone, composed primarily of coccoid blue-green and coccoid/sarcinoid green algae, yielded a biomass value (as chlorophyll a content) of 87 mg m{sup {minus}2} rock surface area and a photosynthetic rate of 0.37 mg CO{sub 2} dm{sup {minus}2} hr{sup {minus}1} or 0.48 mg CO{sub 2} mg{sup {minus}1} chl a hr{sup {minus}1}. The endolithic algal community contributes moderate biomass (5-10%) and substantial photosynthesis (20-80%) to the sparse grassland ecosystem.

  11. Soluble carbohydrates and relative growth rates in chloro-, cyano- and cephalolichens: effects of temperature and nocturnal hydration.

    PubMed

    Alam, Md Azharul; Gauslaa, Yngvar; Solhaug, Knut Asbjørn

    2015-11-01

    This growth chamber experiment evaluates how temperature and humidity regimes shape soluble carbohydrate pools and growth rates in lichens with different photobionts. We assessed soluble carbohydrates, relative growth rates (RGRs) and relative thallus area growth rates (RTA GRs) in Parmelia sulcata (chlorolichen), Peltigera canina (cyanolichen) and Peltigera aphthosa (cephalolichen) cultivated for 14 d (150 μmol m(-2) s(-1) ; 12-h photoperiod) at four day : night temperatures (28 : 23°C, 20 : 15°C, 13 : 8°C, 6 : 1°C) and two hydration regimes (hydration during the day, dry at night; hydration day : night). The major carbohydrates were mannitol (cephalolichen), glucose (cyanolichen) and arabitol (chlorolichen). Mannitol occurred in all species. During cultivation, total carbohydrate pools decreased in cephalo-/cyanolichens, but increased in the chlorolichen. Carbohydrates varied less than growth with temperature and humidity. All lichens grew rapidly, particularly at 13 : 8°C. RGRs and RTA GRs were significantly higher in lichens hydrated for 24 h than for 12 h. Strong photoinhibition occurred in cephalo- and cyanolichens kept in cool dry nights, resulting in positive relationships between RGR and dark-adapted photosystem II (PSII) efficiency (Fv /Fm ). RGR increased significantly with the photobiont-specific carbohydrate pools within all species. Average RGR peaked in the chlorolichen lowest in total and photobiont carbohydrates. Nocturnal hydration improved recovery from photoinhibition and/or enhanced conversion rates of photosynthates into growth. PMID:26017819

  12. Quantification of Rubisco activase content in leaf extracts.

    PubMed

    Yamori, Wataru; von Caemmerer, Susanne

    2011-01-01

    Rubisco activase functions to promote and maintain the catalytic activity of Rubisco. Studies with the activase-lacking Arabidopsis rca mutant (Salvucci et al. Photosynth Res 7:193-201, 1985; Salvucci et al. Plant Physiol 80:655-659, 1986), antisense activase tobacco, Arabidopsis and Flaveria bidentis plants (Mate et al. Plant Physiol 102:1119-1128, 1993; Eckardt et al. Plant Physiol 113:575-586, 1997; von Caemmerer et al. Plant Physiol 137:747-755, 2005) have shown that photosynthesis at atmospheric levels of CO2 is severely impaired when plants lack activase because Rubisco becomes sequestered in an inactive form. Activase protein has been detected in all plant species, including C3 and C4 plants and green algae (Salvucci et al. Plant Physiol 84:930-936, 1987). Rubisco activase is essential in all these photosynthetic organisms for photosynthesis and plant growth. The physiological importance of Rubisco activase is reinforced by recent studies indicating that it plays a role in the response of photosynthesis to temperature. In this chapter, we describe how to extract and quantify Rubisco activase content in leaf. PMID:20960145

  13. Regulation of cell-specific inositol metabolism and transport in plant salinity tolerance.

    PubMed Central

    Nelson, D E; Rammesmayer, G; Bohnert, H J

    1998-01-01

    myo-Inositol and its derivatives are commonly studied with respect to cell signaling and membrane biogenesis, but they also participate in responses to salinity in animals and plants. In this study, we focused on L-myo-inositol 1-phosphate synthase (INPS), which commits carbon to de novo synthesis, and myo-inositol O-methyltransferase (IMT), which uses myo-inositol for stress-induced accumulation of a methylinositol, D-ononitol. The Imt and Inps promoters are transcriptionally controlled. We determined that the transcription rates, transcript levels, and protein abundance are correlated. During normal growth, INPS is present in all cells, but IMT is repressed. After salinity stress, the amount of INPS was enhanced in leaves but repressed in roots. IMT was induced in all cell types. The absence of myo-inositol synthesis in roots is compensated by inositol/ononitol transport in the phloem. The mobilization of photosynthate through myo-inositol translocation links root metabolism to photosynthesis. Our model integrates the transcriptional control of a specialized metabolic pathway with physiological reactions in different tissues. The tissue-specific differential regulation of INPS, which leads to a gradient of myo-inositol synthesis, supports root growth and sodium uptake. By inducing expression of IMT and increasing myo-inositol synthesis, metabolic end products accumulate, facilitating sodium sequestration and protecting photosynthesis. PMID:9596634

  14. Strategy of nitrogen acquisition and utilization by carnivorous Dionaea muscipula.

    PubMed

    Kruse, Jörg; Gao, Peng; Honsel, Anne; Kreuzwieser, Jürgen; Burzlaff, Tim; Alfarraj, Saleh; Hedrich, Rainer; Rennenberg, Heinz

    2014-03-01

    Plant carnivory represents an exceptional means to acquire N. Snap traps of Dionaea muscipula serve two functions, and provide both N and photosynthate. Using (13)C/(15)N-labelled insect powder, we performed feeding experiments with Dionaea plants that differed in physiological state and N status (spring vs. autumn plants). We measured the effects of (15)N uptake on light-saturated photosynthesis (A(max)), dark respiration (R(D)) and growth. Depending on N status, insect capture briefly altered the dynamics of R(D)/A(max), reflecting high energy demand during insect digestion and nutrient uptake, followed by enhanced photosynthesis and growth. Organic N acquired from insect prey was immediately redistributed, in order to support swift renewal of traps and thereby enhance probability of prey capture. Respiratory costs associated with permanent maintenance of the photosynthetic machinery were thereby minimized. Dionaea's strategy of N utilization is commensurate with the random capture of large prey, occasionally transferring a high load of organic nutrients to the plant. Our results suggest that physiological adaptations to unpredictable resource availability are essential for Dionaea's success with regards to a carnivorous life style. PMID:24141381

  15. Insights into secondary growth in perennial plants: its unequal spatial and temporal dynamics in the apple (Malus domestica) is driven by architectural position and fruit load

    PubMed Central

    Lauri, P. É.; Kelner, J. J.; Trottier, C.; Costes, E.

    2010-01-01

    Background and Aims Secondary growth is a main physiological sink. However, the hierarchy between the processes which compete with secondary growth is still a matter of debate, especially on fruit trees where fruit weight dramatically increases with time. It was hypothesized that tree architecture, here mediated by branch age, is likely to have a major effect on the dynamics of secondary growth within a growing season. Methods Three variables were monitored on 6-year-old ‘Golden Delicious’ apple trees from flowering time to harvest: primary shoot growth, fruit volume, and cross-section area of branch portions of consecutive ages. Analyses were done through an ANOVA-type analysis in a linear mixed model framework. Key Results Secondary growth exhibited three consecutive phases characterized by unequal relative area increment over the season. The age of the branch had the strongest effect, with the highest and lowest relative area increment for the current-year shoots and the trunk, respectively. The growth phase had a lower effect, with a shift of secondary growth through the season from leafy shoots towards older branch portions. Eventually, fruit load had an effect on secondary growth mainly after primary growth had ceased. Conclusions The results support the idea that relationships between production of photosynthates and allocation depend on both primary growth and branch architectural position. Fruit load mainly interacted with secondary growth later in the season, especially on old branch portions. PMID:20228088

  16. N Photo-CIDNP MAS NMR To Reveal Functional Heterogeneity in Electron Donor of Different Plant Organisms.

    PubMed

    Janssen, Geertje J; Roy, Esha; Matysik, Jörg; Alia, A

    2012-02-01

    In plants and cyanobacteria, two light-driven electron pumps, photosystems I and II (PSI, PSII), facilitate electron transfer from water to carbon dioxide with quantum efficiency close to unity. While similar in structure and function, the reaction centers of PSI and PSII operate at widely different potentials with PSI being the strongest reducing agent known in living nature. Photochemically induced dynamic nuclear polarization (photo-CIDNP) in magic-angle spinning (MAS) nuclear magnetic resonance (NMR) measurements provides direct excess to the heart of large photosynthetic complexes (A. Diller, Alia, E. Roy, P. Gast, H.J. van Gorkom, J. Zaanen, H.J.M. de Groot, C. Glaubitz, J. Matysik, Photosynth. Res. 84, 303-308, 2005; Alia, E. Roy, P. Gast, H.J. van Gorkom, H.J.M. de Groot, G. Jeschke, J. Matysik, J. Am. Chem. Soc. 126, 12819-12826, 2004). By combining the dramatic signal increase obtained from the solid-state photo-CIDNP effect with (15)N isotope labeling of PSI, we were able to map the electron spin density in the active cofactors of PSI and study primary charge separation at atomic level. We compare data obtained from two different PSI proteins, one from spinach (Spinacia oleracea) and other from the aquatic plant duckweed (Spirodella oligorrhiza). Results demonstrate a large flexibility of the PSI in terms of its electronic architecture while their electronic ground states are strictly conserved. PMID:22303078

  17. Carbon and phosphorus exchange may enable cooperation between an arbuscular mycorrhizal fungus and a phosphate-solubilizing bacterium.

    PubMed

    Zhang, Lin; Xu, Minggang; Liu, Yu; Zhang, Fusuo; Hodge, Angela; Feng, Gu

    2016-05-01

    Arbuscular mycorrhizal fungi (AMF) transfer plant photosynthate underground which can stimulate soil microbial growth. In this study, we examined whether there was a potential link between carbon (C) release from an AMF and phosphorus (P) availability via a phosphate-solubilizing bacterium (PSB). We investigated the outcome of the interaction between the AMF and the PSB by conducting a microcosm and two Petri plate experiments. An in vitro culture experiment was also conducted to determine the direct impact of AMF hyphal exudates on growth of the PSB. The AMF released substantial C to the environment, triggering PSB growth and activity. In return, the PSB enhanced mineralization of organic P, increasing P availability for the AMF. When soil available P was low, the PSB competed with the AMF for P, and its activity was not stimulated by the fungus. When additional P was added to increase soil available P, the PSB enhanced AMF hyphal growth, and PSB activity was also stimulated by the fungus. Our results suggest that an AMF and a free-living PSB interacted to the benefit of each other by providing the C or P that the other microorganism required, but these interactions depended upon background P availability. PMID:27074400

  18. Mycorrhizal Controls on Nitrogen Uptake Drive Carbon Cycling at the Global Scale

    NASA Astrophysics Data System (ADS)

    Shi, M.; Fisher, J. B.; Brzostek, E. R.; Phillips, R.

    2015-12-01

    Nearly all plants form symbiotic relationships with one of two types of mycorrhizal fungi—arbuscular mycorrhizae (AM) and ectomycorrhizal (ECM) fungi, which are essential to global biogeochemical cycling of nutrient elements. In soils with higher rates of nitrogen and phosphorus mineralization from organic matter, AM-associated plants can be better adapted than ECM-associated plants. Importantly, the photosynthate costs of nutrient uptake for AM-associated plants are usually lower than that for ECM-associated plants. Thus, the global carbon cycle is closely coupled with mycorrhizal controls on N uptake. To investigate the potential climate dependence of terrestrial environments from AM- and ECM-associated plants, this study uses the Community Atmosphere Model (CAM) with a plant productivity-optimized N acquisition model—the Fixation and Uptake of Nitrogen (FUN) model—integrated into its land model—the Community Land Model (CLM). This latest version of CLM coupled with FUN allows for the assessment of mycorrhizal controls on global biogeochemical cycling. Here, we show how the historical evolution of AM- and ECM-associations altered regional and global biogeochemical cycling and climate, and future projections over the next century.

  19. Microbial activity in forest soil reflects the changes in ecosystem properties between summer and winter.

    PubMed

    Žifčáková, Lucia; Větrovský, Tomáš; Howe, Adina; Baldrian, Petr

    2016-01-01

    Understanding the ecology of coniferous forests is very important because these environments represent globally largest carbon sinks. Metatranscriptomics, microbial community and enzyme analyses were combined to describe the detailed role of microbial taxa in the functioning of the Picea abies-dominated coniferous forest soil in two contrasting seasons. These seasons were the summer, representing the peak of plant photosynthetic activity, and late winter, after an extended period with no photosynthate input. The results show that microbial communities were characterized by a high activity of fungi especially in litter where their contribution to microbial transcription was over 50%. Differences in abundance between summer and winter were recorded for 26-33% of bacterial genera and < 15% of fungal genera, but the transcript profiles of fungi, archaea and most bacterial phyla were significantly different among seasons. Further, the seasonal differences were larger in soil than in litter. Most importantly, fungal contribution to total microbial transcription in soil decreased from 33% in summer to 16% in winter. In particular, the activity of the abundant ectomycorrhizal fungi was reduced in winter, which indicates that plant photosynthetic production was likely one of the major drivers of changes in the functioning of microbial communities in this coniferous forest. PMID:26286355

  20. Acclimation of mechanical and hydraulic functions in trees: impact of the thigmomorphogenetic process

    PubMed Central

    Badel, Eric; Ewers, Frank W.; Cochard, Hervé; Telewski, Frank W.

    2015-01-01

    The secondary xylem (wood) of trees mediates several functions including water transport and storage, mechanical support and storage of photosynthates. The optimal structures for each of these functions will most likely differ. The complex structure and function of xylem could lead to trade-offs between conductive efficiency, resistance to embolism, and mechanical strength needed to count for mechanical loading due to gravity and wind. This has been referred to as the trade-off triangle, with the different optimal solutions to the structure/function problems depending on the environmental constraints as well as taxonomic histories. Thus, the optimisation of each function will lead to drastically different anatomical structures. Trees are able to acclimate the internal structure of their trunk and branches according to the stress they experience. These acclimations lead to specific structures that favor the efficiency or the safety of one function but can be antagonistic with other functions. Currently, there are no means to predict the way a tree will acclimate or optimize its internal structure in support of its various functions under differing environmental conditions. In this review, we will focus on the acclimation of xylem anatomy and its resulting mechanical and hydraulic functions to recurrent mechanical strain that usually result from wind-induced thigmomorphogenesis with a special focus on the construction cost and the possible trade-off between wood functions. PMID:25954292

  1. Coral reef invertebrate microbiomes correlate with the presence of photosymbionts

    PubMed Central

    Bourne, David G; Dennis, Paul G; Uthicke, Sven; Soo, Rochelle M; Tyson, Gene W; Webster, Nicole

    2013-01-01

    Coral reefs provide habitat for an array of marine invertebrates that host symbiotic microbiomes. Photosynthetic symbionts including Symbiodinium dinoflagellates and diatoms potentially influence the diversity of their host-associated microbiomes by releasing carbon-containing photosynthates and other organic compounds that fuel microbial metabolism. Here we used 16S ribosomal RNA (rRNA) gene amplicon pyrosequencing to characterise the microbiomes of 11 common Great Barrier Reef marine invertebrate species that host photosynthetic symbionts and five taxa in which they are absent. The presence of photosynthetic symbionts influenced the composition but not the species richness, evenness and phylogenetic diversity of invertebrate-associated microbiomes. Invertebrates without photosynthetic symbionts were dominated by Alphaproteobacteria, whereas those hosting photosynthetic symbionts were dominated by Gammaproteobacteria. Interestingly, many microbial species from photosymbiont-bearing invertebrates, including Oceanospirillales spp., Alteromonas spp., Pseudomonas spp., Halomonas spp., are implicated in the metabolism of dimethylsulfoniopropionate (DMSP). DMSP is produced in high concentrations by photosynthetic dinoflagellates and is involved in climate regulation by facilitating cloud formation. Microbiomes correlated with host taxa and replicate individuals from most sampled species grouped in distance-based redundancy analysis of retrieved 16S rRNA gene sequences. This study highlights the complex nature of invertebrate holobionts and confirms the importance of photosynthetic symbionts in structuring marine invertebrate bacterial communities. PMID:23303372

  2. Annual Growth Bands in Hymenaea courbaril

    SciTech Connect

    Westbrook, J A; Guilderson, T P; Colinvaux, P A

    2004-02-09

    One significant source of annual temperature and precipitation data arises from the regular annual secondary growth rings of trees. Several tropical tree species are observed to form regular growth bands that may or may not form annually. Such growth was observed in one stem disk of the tropical legume Hymenaea courbaril near the area of David, Panama. In comparison to annual reference {Delta}{sup 14}C values from wood and air, the {Delta}{sup 14}C values from the secondary growth rings formed by H. courbaril were determined to be annual in nature in this one stem disk specimen. During this study, H. courbaril was also observed to translocate recently produced photosynthate into older growth rings as sapwood is converted to heartwood. This process alters the overall {Delta}{sup 14}C values of these transitional growth rings as cellulose with a higher {Delta}{sup 14}C content is translocated into growth rings with a relatively lower {Delta}{sup 14}C content. Once the annual nature of these growth rings is established, further stable isotope analyses on H. courbaril material in other studies may help to complete gaps in the understanding of short and of long term global climate patterns.

  3. Co[sub 2] exchange, environmental productivity indices, and productivity of opuntia ficus-indica under current and elevated CO[sub 2] concentrations

    SciTech Connect

    Nobel, P.S.

    1992-01-01

    This project involved placing mature cladodes (flattened stem segments) of Opuntia ficus-indica in growth chambers containing 360 or 720 ppM CO[sub 2]. After nine weeks, the new daughter cladodes initiated on the planted cladodes averaged 7% higher in biomass but 8% less is area, leading to a specific stem mass for this Crassulacean acid metabolism (CAM) species that was 16% higher under the elevated CO[sub 2] condition. This is similar to be less dramatic than the increase in specific leaf mass for C[sub 3] and C[sub 4] plants under elevated CO[sub 2], which generally ranges from 28% to 40%. Another contrast with C[sub 3] and C[sub 4] Plants was the reliance of the new organs of the CAM plant on biomass translocated from existing organs instead of derived directly from current photosynthate. In this regard, 18% less dry weight was translocated from basal cladodes into daughter cladodes of Q. ficus-indica at 720 ppM CO[sub 2] compared with 360 ppM.

  4. Co{sub 2} exchange, environmental productivity indices, and productivity of opuntia ficus-indica under current and elevated CO{sub 2} concentrations. Carbon Dioxide Research Program

    SciTech Connect

    Nobel, P.S.

    1992-12-31

    This project involved placing mature cladodes (flattened stem segments) of Opuntia ficus-indica in growth chambers containing 360 or 720 ppM CO{sub 2}. After nine weeks, the new daughter cladodes initiated on the planted cladodes averaged 7% higher in biomass but 8% less is area, leading to a specific stem mass for this Crassulacean acid metabolism (CAM) species that was 16% higher under the elevated CO{sub 2} condition. This is similar to be less dramatic than the increase in specific leaf mass for C{sub 3} and C{sub 4} plants under elevated CO{sub 2}, which generally ranges from 28% to 40%. Another contrast with C{sub 3} and C{sub 4} Plants was the reliance of the new organs of the CAM plant on biomass translocated from existing organs instead of derived directly from current photosynthate. In this regard, 18% less dry weight was translocated from basal cladodes into daughter cladodes of Q. ficus-indica at 720 ppM CO{sub 2} compared with 360 ppM.

  5. Association between photosynthesis and contrasting features of minor veins in leaves of summer annuals loading phloem via symplastic versus apoplastic routes.

    PubMed

    Muller, Onno; Cohu, Christopher M; Stewart, Jared J; Protheroe, Johanna A; Demmig-Adams, Barbara; Adams, William W

    2014-09-01

    Foliar vascular anatomy and photosynthesis were evaluated for a number of summer annual species that either load sugars into the phloem via a symplastic route (Cucumis sativus L. cv. Straight Eight; Cucurbita pepo L. cv. Italian Zucchini Romanesco; Citrullus lanatus L. cv. Faerie Hybrid; Cucurbita pepo L. cv. Autumn Gold) or an apoplastic route (Nicotiana tabacum L.; Solanum lycopersicum L. cv. Brandywine; Gossypium hirsutum L.; Helianthus annuus L. cv. Soraya), as well as winter annual apoplastic loaders (Spinacia oleracea L. cv. Giant Nobel; Arabidopsis thaliana (L.) Heynhold Col-0, Swedish and Italian ecotypes). For all summer annuals, minor vein cross-sectional xylem area and tracheid number as well as the ratio of phloem loading cells to phloem sieve elements, each when normalized for foliar vein density (VD), was correlated with photosynthesis. These links presumably reflect (1) the xylem's role in providing water to meet foliar transpirational demand supporting photosynthesis and (2) the importance of the driving force of phloem loading as well as the cross-sectional area for phloem sap flux to match foliar photosynthate production. While photosynthesis correlated with the product of VD and cross-sectional phloem cell area among symplastic loaders, photosynthesis correlated with the product of VD and phloem cell number per vein among summer annual apoplastic loaders. Phloem cell size has thus apparently been a target of selection among symplastic loaders (where loading depends on enzyme concentration within loading cells) versus phloem cell number among apoplastic loaders (where loading depends on membrane transporter numbers). PMID:24450755

  6. Seasonal dynamics in the stable carbon isotope composition δ¹³C from non-leafy branch, trunk and coarse root CO₂ efflux of adult deciduous (Fagus sylvatica) and evergreen (Picea abies) trees.

    PubMed

    Kuptz, Daniel; Matyssek, Rainer; Grams, Thorsten E E

    2011-03-01

    Respiration is a substantial driver of carbon (C) flux in forest ecosystems and stable C isotopes provide an excellent tool for its investigation. We studied seasonal dynamics in δ¹³C of CO₂ efflux (δ¹³C(E)) from non-leafy branches, upper and lower trunks and coarse roots of adult trees, comparing deciduous Fagus sylvatica (European beech) with evergreen Picea abies (Norway spruce). In both species, we observed strong and similar seasonal dynamics in the δ¹³C(E) of above-ground plant components, whereas δ¹³C(E) of coarse roots was rather stable. During summer, δ¹³C(E) of trunks was about -28.2‰ (Beech) and -26.8‰ (Spruce). During winter dormancy, δ¹³C(E) increased by 5.6-9.1‰. The observed dynamics are likely related to a switch from growth to starch accumulation during fall and remobilization of starch, low TCA cycle activity and accumulation of malate by PEPc during winter. The seasonal δ¹³C(E) pattern of branches of Beech and upper trunks of Spruce was less variable, probably because these organs were additionally supplied by winter photosynthesis. In view of our results and pervious studies, we conclude that the pronounced increases in δ¹³C(E) of trunks during the winter results from interrupted access to recent photosynthates. PMID:21054435

  7. Bark thickness across the angiosperms: more than just fire.

    PubMed

    Rosell, Julieta A

    2016-07-01

    Global variation in total bark thickness (TBT) is traditionally attributed to fire. However, bark is multifunctional, as reflected by its inner living and outer dead regions, meaning that, in addition to fire protection, other factors probably contribute to TBT variation. To address how fire, climate, and plant size contribute to variation in TBT, inner bark thickness (IBT) and outer bark thickness (OBT), I sampled 640 species spanning all major angiosperm clades and 18 sites with contrasting precipitation, temperature, and fire regime. Stem size was by far the main driver of variation in thickness, with environment being less important. IBT was closely correlated with stem diameter, probably for metabolic reasons, and, controlling for size, was thicker in drier and hotter environments, even fire-free ones, probably reflecting its water and photosynthate storage role. OBT was less closely correlated with size, and was thicker in drier, seasonal sites experiencing frequent fires. IBT and OBT covaried loosely and both contributed to overall TBT variation. Thickness variation was higher within than across sites and was evolutionarily labile. Given high within-site diversity and the multiple selective factors acting on TBT, continued study of the different drivers of variation in bark thickness is crucial to understand bark ecology. PMID:26890029

  8. Louis Nico Marie Duysens (March 15, 1921-September 8, 2015): a leading biophysicist of the 20th century.

    PubMed

    Govindjee; Pulles, M P J

    2016-06-01

    Louis Nico Marie (L. N. M.) Duijsens (Duysens) was one of the giants in the biophysics of photosynthesis. His PhD thesis "Transfer of Excitation Energy in Photosynthesis" (Duysens, 1952) is a classic; he introduced light-induced absorption difference spectroscopy to photosynthesis research and proved the existence of reaction centers, introducing advanced methods from physics to understand biological processes. Further, it is his 1959-1961 seminal work, with Jan Amesz, that provided evidence for the existence of the series scheme for the two light reactions in oxygenic photosynthesis. In one word, he was one of the master biophysicists of the 20th century-who provided direct measurements on many key intermediates, and made us understand the intricacies of photosynthesis with a simplicity that no one else ever did. We present here our personal perspective of the scientist that Lou Duysens was. For an earlier perspective, see van Grondelle and van Gorkom (Photosynth Res 120: 3-7, 2014). PMID:27039907

  9. Dynamic energy budgets in syntrophic symbiotic relationships between heterotrophic hosts and photoautotrophic symbionts.

    PubMed

    Muller, Erik B; Kooijman, Sebastiaan A L M; Edmunds, Peter J; Doyle, Francis J; Nisbet, Roger M

    2009-07-01

    In this paper we develop and investigate a dynamic energy budget (DEB) model describing the syntrophic symbiotic relationship between a heterotrophic host and an internal photoautotrophic symbiont. The model specifies the flows of matter and energy among host, symbiont and environment with minimal complexity and uses the concept of synthesizing units to describe smoothly the assimilation of multiple limiting factors, in particular inorganic carbon and nitrogen, and irradiance. The model has two passive regulation mechanisms: the symbiont shares only photosynthate that it cannot use itself, and the host delivers only excess nutrients to the symbiont. With parameter values plausible for scleractinian corals, we show that these two regulation mechanisms suffice to obtain a stable symbiotic relationship under constant ambient conditions, provided those conditions support sustenance of host and symbiont. Furthermore, the symbiont density in the host varies relatively little as a function of ambient food density, inorganic nitrogen and irradiance. This symbiont density tends to increase with light deprivation or nitrogen enrichment, either directly or via food. We also investigate the relative benefit each partner derives from the relationship and conclude that this relationship may shift from mutualism to parasitism as environmental conditions change. PMID:19285512

  10. Functional Characterization of a Hexose Transporter from Root Endophyte Piriformospora indica

    PubMed Central

    Rani, Mamta; Raj, Sumit; Dayaman, Vikram; Kumar, Manoj; Dua, Meenakshi; Johri, Atul K.

    2016-01-01

    Understanding the mechanism of photosynthate transfer at symbiotic interface by fungal monosaccharide transporter is of substantial importance. The carbohydrate uptake at the apoplast by the fungus is facilitated by PiHXT5 hexose transporter in root endophytic fungus Piriformospora indica. The putative PiHXT5 belongs to MFS superfamily with 12 predicted transmembrane helices. It possess sugar transporter PFAM motif (PF0083) and MFS superfamily domain (PS50850). It contains the signature tags related to glucose transporter GLUT1 of human erythrocyte. PiHXT5 is regulated in response to mutualism as well as glucose concentration. We have functionally characterized PiHXT5 by complementation of hxt-null mutant of Saccharomyces cerevisiae EBY.VW4000. It is involved in transport of multiple sugars ranging from D-glucose, D-fructose, D-xylose, D-mannose, D-galactose with decreasing affinity. The uncoupling experiments indicate that it functions as H+/glucose co-transporter. Further, pH dependence analysis suggests that it functions maximum between pH 5 and 6. The expression of PiHXT5 is dependent on glucose concentration and was found to be expressed at low glucose levels (1 mM) which indicate its role as a high affinity glucose transporter. Our study on this sugar transporter will help in better understanding of carbon metabolism and flow in this agro-friendly fungus. PMID:27499747

  11. Modification of a Specific Class of Plasmodesmata and Loss of Sucrose Export Ability in the sucrose export defective1 Maize Mutant.

    PubMed Central

    Russin, W. A.; Evert, R. F.; Vanderveer, P. J.; Sharkey, T. D.; Briggs, S. P.

    1996-01-01

    We report on the export capability and structural and ultrastructural characteristics of leaves of the sucrose export defective1 (sed1; formerly called sut1) maize mutant. Whole-leaf autoradiography was combined with light and transmission electron microscopy to correlate leaf structure with differences in export capacity in both wild-type and sed1 plants. Tips of sed1 blades had abnormal accumulations of starch and anthocyanin and distorted vascular tissues in the minor veins, and they did not export sucrose. Bases of sed1 blades were structurally identical to those of the wild type and did export sucrose. Electron microscopy revealed that only the plasmodesmata at the bundle sheath-vascular parenchyma cell interface in sed1 minor veins were structurally modified. Aberrant plasmodesmal structure at this critical interface results in a symplastic interruption and a lack of phloem-loading capability. These results clarify the pathway followed by photosynthates, the pivotal role of the plasmodesmata at the bundle sheath-vascular parenchyma cell interface, and the role of the vascular parenchyma cells in phloem loading. PMID:12239395

  12. Biology and control of swamp dodder (Cuscuta gronovii)

    SciTech Connect

    Bewick, T.A.

    1987-01-01

    A simple model predicting swamp dodder (Cuscuta gronovii Willd.) emergence was developed. The model states that 0.1% of the cranberry seedlings will emerge after 150 to 170 GDD have accumulated after the winter ice has melted on the cranberry beds, using 0 C as the low temperature threshold. Experiments in cranberry showed that pronamide (3,5-dichloro-(N-1,1-dimethyl-2-propynyl)benzamide) was effective in controlling swamp dodder when applied preemergence. Rates below 2.4 kg ai/ha appeared to be safe for cranberry plants and fruit. Experiments with /sup 14/C glyphosate showed that the herbicide moved out of carrot leaves to the physiological sinks in the plant. In carrots parasitized by swamp dodder the dodder acted as one of the strongest sinks for photosynthates from the host. In cranberry glyphosate moved out of the leaves, but most remained in the stem to which the treated leaves were attached. The only physiological sinks that accumulated significant amounts of label were the stem apices. The concentration of the herbicide in this sink decreased with time. Swamp dodder stems were able to absorb glyphosate directly from solution.

  13. Caterpillar mimicry by plant galls as a visual defense against herbivores.

    PubMed

    Yamazaki, Kazuo

    2016-09-01

    Plant galls, induced by arthropods and various other organisms have an intimate relationship with host plants, and gall-inducers have limited mobility. In addition to their own photosynthesis, galls are resource sinks rich with nutrients, with neighboring plant organs commonly serving as external photosynthate sources. Galls, if not well defended, may therefore be attractive food sources for herbivores. Galls produced by some aphids, jumping plant lice, thrips, and gall midges in Japan, Palearctic region and in the Middle East visually resemble lepidopteran caterpillars. I propose that such visual resemblance may reduce herbivory of galls and surrounding plant tissues, resulting in an increase in galler survival due to reduced gall damage and in enhanced galler growth due to improved nutrient inflow to the galls, when herbivores avoid colonizing or consuming plant parts that look as if they have been occupied by other herbivores. Potential predators and parasitoids of caterpillars may be attracted to the caterpillar-like galls and then attack real caterpillars and other invertebrate herbivores, which would also be beneficial for both gallers and their hosts. PMID:27220745

  14. An isotopomer strategy to detect plant acclimation to increasing atmospheric CO2

    NASA Astrophysics Data System (ADS)

    Augusti, A.; Betson, T. R.; Schleucher, J.

    2009-04-01

    Abundances of deuterium (D) and 18O in precipitation carry climate signals. Both isotopes are incorporated into leaf photosynthate, and in a second step into tree rings. Strikingly, while D and 18O climate signals in precipitation are related, tree-ring records of both isotopes do not generally go in parallel. This contribution investigates this discrepancy, based on a comparison of the fractionation mechanisms for both isotopes. We present a strategy to detect plant acclimation on time scales of centuries from intramolecular deuterium distributions (D isotopomers). We showed recently that specific C-H groups of glucose units exchange with water during cellulose synthesis in tree trunks, in agreement with the biochemistry of cellulose formation. Most importantly, this result allows separating influences of source water and of D fractionations in the plant, and hence to isolate climate signals and physiological signals. NMR measurements of intramolecular D distributions of glucose demonstrate that each C-H group has a distinct abundance (each D isotopomer), corresponding to its unique biochemical history, and can serve as independent information channel. Therefore, isotopomers increase the information content of isotopes several-fold. Thus, using D isotopomers, a situation may be achieved where experimental quantities overdetermine the number of variables to be reconstructed. This increased information content can be retrieved along the following strategies. Similar to C-O groups that exchange during cellulose synthesis, D isotopomers of C-H groups which heavily exchange should adopt the D abundance of source water and associated climate signals. We will present tree-ring results that support the feasibility of this approach. C-H groups that are not affected by isotope exchange are passed from leaves to the trunk, and can therefore transmit leaf-level information to tree rings. On the leaf level, overall D abundance of photosynthate is influenced by transpiration

  15. Root and Shoot Phenology May Respond Differently to Warming

    NASA Astrophysics Data System (ADS)

    Radville, L.; Eissenstat, D. M.; Post, E.

    2015-12-01

    Climate change is increasing temperatures and extending the growing season for many organisms. Shifts in phenology have been widely reported in response to global warming and have strong effects on ecosystem processes and greenhouse gas emissions. It is well understood that warming generally advances aboveground plant phenology, but the influence of temperature on root phenology is unclear. Most terrestrial biosphere models assume that root and shoot growth occur at the same time and are influenced by warming in the same way, but recent studies suggest that this may not be the case. Testing this assumption is particularly important in the Arctic where over 70% of plant biomass can be belowground and warming is happening faster than in other ecosystems. In 2013 and 2014 we examined the timing of root growth in the Arctic in plots that had been warmed or unwarmed for 10 years. We found that peak root growth occurred about one month before leaf growth, suggesting that spring root phenology is not controlled by carbon produced during spring photosynthesis. If root phenology is not controlled by photosynthate early in the season, earlier spring leaf growth may not cause earlier spring root growth. In support of this, we found that warming advanced spring leaf cover but did not significantly affect root phenology. Root growth was not significantly correlated with soil temperature and did not appear to be limited by near-freezing temperatures above the permafrost. These results suggest that although shoots are influenced by temperature, roots in this system may be more influenced by photosynthesis and carbon storage. Aboveground phenology, one of the most widely measured aspects of climate change, may not represent whole-plant phenology and may be a poor indicator of the timing of whole-plant carbon fluxes. Additionally, climate model assumptions that roots and shoots grow at the same time may need to be revised.

  16. Expression of barley SUSIBA2 transcription factor yields high-starch low-methane rice

    SciTech Connect

    Su, J.; Hu, C.; Yan, X.; Jin, Y.; Chen, Z.; Guan, Q.; Wang, Y.; Zhong, D.; Jansson, Georg C.; Wang, F.; Schnrer, Anna; Sun, Chuanxin

    2015-07-22

    Atmospheric methane is the second most important greenhouse gas after carbon dioxide, and is responsible for about 20% of the global warming effect since pre-industrial times. Rice paddies are the largest anthropogenic methane source and produce 7–17% of atmospheric methane. Warm waterlogged soil and exuded nutrients from rice roots provide ideal conditions for methanogenesis in paddies with annual methane emissions of 25–100-million tonnes. This scenario will be exacerbated by an expansion in rice cultivation needed to meet the escalating demand for food in the coming decades4. There is an urgent need to establish sustainable technologies for increasing rice production while reducing methane fluxes from rice paddies. However, ongoing efforts for methane mitigation in rice paddies are mainly based on farming practices and measures that are difficult to implement5. Despite proposed strategies to increase rice productivity and reduce methane emissions4,6, no high-starch low-methane-emission rice has been developed. Here we show that the addition of a single transcription factor gene, barley SUSIBA2, conferred a shift of carbon flux to SUSIBA2 rice, favouring the allocation of photosynthates to aboveground biomass over allocation to roots. The altered allocation resulted in an increased biomass and starch content in the seeds and stems, and suppressed methanogenesis, possibly through a reduction in root exudates. Three-year field trials in China demonstrated that the cultivation of SUSIBA2 rice was associated with a significant reduction in methane emissions and a decrease in rhizospheric methanogen levels. SUSIBA2 rice offers a sustainable means of providing increased starch content for food production while reducing greenhouse gas emissions from rice cultivation. Approaches to increase rice productivity and reduce methane emissions as seen in SUSIBA2 rice may be particularly beneficial in a future climate with rising temperatures resulting in increased methane

  17. The relationship between isoprene emission, CO(2) assimilation and water use efficiency across a range of poplar genotypes.

    PubMed

    Guidolotti, Gabriele; Calfapietra, Carlo; Loreto, Francesco

    2011-07-01

    Poplars (Populus sp.) are among the strongest isoprene (Iso)-emitting plants. Ten poplar genotypes belonging to four different species were grown under the same environmental conditions in a common garden experiment, to study the influence of the genetic variability on Iso emission and on the relationship between Iso and photosynthesis. Photosynthesis ranged from 13 to 20 µmol CO(2) m(-2) s(-1) , whereas Iso emission ranged from 18.2 to 45.2 nmol m(-2) s(-1) . There was no clear association between Iso emission and photosynthesis. In most genotypes, photosynthetic capacity developed earlier than Iso emission capacity. The emission of Iso was inversely correlated with the intercellular CO(2) concentration (C(i) ) and positively correlated with instantaneous water use efficiency. It is speculated that, by regulating C(i) , stomatal opening also indirectly controls Iso emission in poplars. A positive linear correlation between the fraction of recently assimilated carbon emitted as Iso and Iso emission rate was found. The slope of this relationship indicated that each nanomole of Iso emitted requires a fixed fraction of photosynthetic carbon regardless of the intra- and interspecific variability in the Populus genus, and of leaf ontogeny. A comparison with data from recent studies showed that the slope of this relationship increases in drought-stressed leaves. However, this might be explained by an increasing contribution of carbon sources for Iso biosynthesis from stored photosynthates. If this is true, then the amount of carbon directly shunted from photosynthesis into Iso is constant in all poplars and is not influenced by abiotic stresses. PMID:21361963

  18. [Ghd7, a pleiotropic gene controlling flag leaf area in rice].

    PubMed

    Tan, Cong; Weng, Xiao-Yu; Yan, Wen-Hao; Bai, Xu-Feng; Xing, Yong-Zhong

    2012-07-01

    Photosynthesis is the unique source of energy for plant. Flag leaf contributed the majority of photosynthate after rice flowering. Ghd7 is a pleiotropic gene, which can significantly increase rice production. In order to study the genetic effects of Ghd7 on the flag leaf morphology, we made quantitative trait locus (QTL) analysis for flag leaf length (FLL), flag leaf width (FLW), and flag leaf area (FLA) using a Ghd7-BC2F2 population of 190 plants. In the BC2F2 population, the frequency distribution of FLL, FLW, and FLA were bimodal and in agreement with single Mendelian segregation ratio (3:1). FLL, FLW, and FLA were positively correlated with grains per panicle in the population. One QTL was mapped to the in-terval between markers RM3859 and C39 on chromosome 7, which explained 73.3%, 62.3%, and 71.8% of the variations for FLL, FLW, and FLA, and co-segregated with Ghd7. Two near-isogenic lines of NIL (mh7) and NIL (tq7) were devel-oped using Zhenshan 97 as the recurrent parent and Minghui 63 and Teqing as the donor parent, respectively. Both NILs significantly increased the phenotypic values of FLL, FLW, and FLA as compared with Zhenshan 97. FLL, The values of FLW and FLA for Ghd7 over-expression transgenic plants were 8.9 cm, 0.5 cm, and 17.8 cm2 larger than its recipient Heji-ang 19. These results demonstrated that Ghd7 plays an important role in controlling the flag leaf area in rice. PMID:22805217

  19. Effect of carbohydrates and night temperature on night respiration in rice.

    PubMed

    Peraudeau, Sébastien; Lafarge, Tanguy; Roques, Sandrine; Quiñones, Cherryl O; Clement-Vidal, Anne; Ouwerkerk, Pieter B F; Van Rie, Jeroen; Fabre, Denis; Jagadish, Krishna S V; Dingkuhn, Michael

    2015-07-01

    Global warming causes night temperature (NT) to increase faster than day temperature in the tropics. According to crop growth models, respiration incurs a loss of 40-60% of photosynthate. The thermal sensitivity of night respiration (R(n)) will thus reduce biomass. Instantaneous and acclimated effects of NT on R(n) of leaves and seedlings of two rice cultivars having a variable level of carbohydrates, induced by exposure to different light intensity on the previous day, were investigated. Experiments were conducted in a greenhouse and growth chambers, with R(n) measured on the youngest fully expanded leaves or whole seedlings. Dry weight-based R(n) was 2.6-fold greater for seedlings than for leaves. Leaf R(n) was linearly related to starch (positive intercept) and soluble sugar concentration (zero intercept). Increased NT caused higher R(n) at a given carbohydrate concentration. The change of R(n) at NT increasing from 21 °C to 31 °C was 2.4-fold for the instantaneous response but 1.2- to 1.7-fold after acclimation. The maintenance component of R(n) (R(m)'), estimated by assimilate starvation, averaged 28% in seedlings and 34% in leaves, with no significant thermal effect on this ratio. The acclimated effect of increased NT on R(m)' across experiments was 1.5-fold for a 10 °C increase in NT. No cultivar differences were observed in R(n) or R(m)' responses. The results suggest that the commonly used Q10=2 rule overestimates thermal response of respiration, and R(n) largely depends on assimilate resources. PMID:25954047

  20. How drought severity constrains GPP and its partitioning among carbon pools in a Quercus ilex coppice?

    NASA Astrophysics Data System (ADS)

    Rambal, S.; Lempereur, M.; Limousin, J. M.; Martin-StPaul, N. K.; Ourcival, J. M.; Rodríguez-Calcerrada, J.

    2014-06-01

    The partitioning of photosynthates toward biomass compartments has a crucial role in the carbon sink function of forests. Few studies have examined how carbon is allocated toward plant compartments in drought prone forests. We analyzed the fate of GPP in relation to yearly water deficit in an old evergreen Mediterranean Quercus ilex coppice severely affected by water limitations. Gross and net carbon fluxes between the ecosystem and the atmosphere were measured with an eddy-covariance flux tower running continuously since 2001. Discrete measurements of litterfall, stem growth and fAPAR allowed us to derive annual productions of leaves, wood, flowers and acorns and an isometric relationship between stem and belowground biomass has been used to estimate perennial belowground growth. By combining eddy-covariance fluxes with annual productions we managed to close a C budget and derive values of autotrophic and heterotrophic respirations, NPP and carbon use efficiency (CUE, the ratio between NPP and GPP). Average values of yearly NEP, GPP and Reco were 282, 1259 and 977 g C m-2. The corresponding ANPP components were 142.5, 26.4 and 69.6 g C m-2 for leaves, reproductive effort (flowers and fruits) and stems. Gross and net carbon exchange between the ecosystem and the atmosphere were affected by annual water deficit. Partitioning to the different plant compartments was also impacted by drought, with a hierarchy of responses going from the most affected, the stem growth, to the least affected, the leaf production. The average CUE was 0.40, which is well in the range for Mediterranean-type forest ecosystems. CUE tended to decrease more slightly in response to drought than GPP and NPP, probably due to drought-acclimation of autotrophic respiration. Overall, our results provide a baseline for modeling the inter-annual variations of carbon fluxes and allocation in this widespread Mediterranean ecosystem and highlight the value of maintaining continuous experimental

  1. The age of CO2 emitted from stems and roots of Norway spruce and beech forests in Germany

    NASA Astrophysics Data System (ADS)

    Muhr, J.; Borken, W.; Trumbore, S.

    2012-12-01

    Although pulse-labeling studies follow the fate of recent photosynthetic products over days to months, much less is known about the use of C that was assimilated more than 1 year previously in trees. Trees have the capacity to store C in nonstructural reserves for later use, e.g. when the supply of recent assimilates is insufficient to meet metabolic demands. Comparison of the radiocarbon (14C) signature of CO2 emitted by trees with the observed rate of decline in atmospheric 14C-CO2 provides a measure of the time elapsed between fixation by the plant and return to the atmosphere, thus allowing detection of contribution of older (>1 year-old) C to CO2 efflux. We report radiocarbon data of CO2 that was emitted from tree stems and roots from a Norway spruce (6 dates in 2010/11 for stem CO2, 3 dates in 2011 for root CO2) and from a beech forest (measured in April 2011 just before leaf flush and again in September 2011) in Germany. With the exception of stem CO2 in the spring of 2011, CO2 emitted from tree stems and roots of Norway spruce was always significantly elevated in 14C compared to contemporary atmospheric CO2. The estimated average time elapsed between fixation and emission as CO2 was 1-2 years. For beech, we found seasonal differences. CO2 from tree stems and roots was elevated in 14C in spring, with an estimated average time elapsed since fixation of 4-5 years, whereas we found no differences in 14C to the contemporary atmosphere in autumn, i.e. emitted CO2 predominantly originated from recent (younger than 1 year) photosynthates. Our results imply that C from older, stored C pools contributes to respiration in Norway spruce on a regular basis, while the data for beech suggest a stronger seasonality of the relative contribution of C from older pools to respiration.

  2. Microbial Community Dynamics Associated with Rhizosphere Carbon Flow

    PubMed Central

    Butler, Jessica L.; Williams, Mark A.; Bottomley, Peter J.; Myrold, David D.

    2003-01-01

    Root-deposited photosynthate (rhizodeposition) is an important source of readily available carbon (C) for microbes in the vicinity of growing roots. Plant nutrient availability is controlled, to a large extent, by the cycling of this and other organic materials through the soil microbial community. Currently, our understanding of microbial community dynamics associated with rhizodeposition is limited. We used a 13C pulse-chase labeling procedure to examine the incorporation of rhizodeposition into individual phospholipid fatty acids (PLFAs) in the bulk and rhizosphere soils of greenhouse-grown annual ryegrass (Lolium multiflorum Lam. var. Gulf). Labeling took place during a growth stage in transition between active root growth and rapid shoot growth on one set of plants (labeling period 1) and 9 days later during the rapid shoot growth stage on another set of plants (labeling period 2). Temporal differences in microbial community composition were more apparent than spatial differences, with a greater relative abundance of PLFAs from gram-positive organisms (i15:0 and a15:0) in the second labeling period. Although more abundant, gram-positive organisms appeared to be less actively utilizing rhizodeposited C in labeling period 2 than in labeling period 1. Gram-negative bacteria associated with the 16:1ω5 PLFA were more active in utilizing 13C-labeled rhizodeposits in the second labeling period than in the first labeling period. In both labeling periods, however, the fungal PLFA 18:2ω6,9 was the most highly labeled. These results demonstrate the effectiveness of using 13C labeling and PLFA analysis to examine the microbial dynamics associated with rhizosphere C cycling by focusing on the members actively involved. PMID:14602642

  3. Light intensity alters the extent of arsenic toxicity in Helianthus annuus L. seedlings.

    PubMed

    Yadav, Geeta; Srivastava, Prabhat Kumar; Singh, Vijay Pratap; Prasad, Sheo Mohan

    2014-06-01

    The present study is aimed at assessing the extent of arsenic (As) toxicity under three different light intensities-optimum (400 μmole photon m(-2) s(-1)), sub-optimum (225 μmole photon m(-2) s(-1)), and low (75 μmole photon m(-2) s(-1))-exposed to Helianthus annuus L. var. DRSF-113 seedlings by examining various physiological and biochemical parameters. Irrespective of the light intensities under which H. annuus L. seedlings were grown, there was an As dose (low, i.e., 6 mg kg(-1) soil, As1; and high, i.e., 12 mg kg(-1) soil, As2)-dependent decrease in all the growth parameters, viz., fresh mass, shoot length, and root length. Optimum light-grown seedlings exhibited better growth performance than the sub-optimum and low light-grown seedlings; however, low light-grown plants had maximum root and shoot lengths. Accumulation of As in the plant tissues depended upon its concentration used, proximity of the plant tissue, and intensity of the light. Greater intensity of light allowed greater assimilation of photosynthates accompanied by more uptake of nutrients along with As from the medium. The levels of chlorophyll a, b, and carotenoids declined with increasing concentrations of As. Seedlings acquired maximum Chl a and b under optimum light which were more compatible to face As1 and As2 doses of As, also evident from the overall status of enzymatic (SOD, POD, CAT, and GST) and non-enzymatic antioxidant (Pro). PMID:24699829

  4. Peripheral Light-Harvesting LH2 Complex Can Be Assembled in Cells of Nonsulfur Purple Bacterium Rhodoblastus acidophilus without Carotenoids.

    PubMed

    Bol'shakov, M A; Ashikhmin, A A; Makhneva, Z K; Moskalenko, A A

    2015-09-01

    The effect of carotenoids on the assembly of LH2 complex in cells of the purple nonsulfur bacterium Rhodoblastus acidophilus was investigated. For this purpose, the bacterial culture was cultivated with an inhibitor of carotenoid biosynthesis - 71 µM diphenylamine (DPA). The inhibitor decreased the level of biosynthesis of the colored carotenoids in membranes by ~58%. It was found that a large amount of phytoene was accumulated in them. This carotenoid precursor was bound nonspecifically to LH2 complex and did not stabilize its structure. Thermostability testing of the isolated LH2 complex together with analysis of carotenoid composition revealed that the population of this complex was heterogeneous with respect to carotenoid composition. One fraction of the LH2 complex with carotenoid content around 90% remains stable and was not destroyed under heating for 15 min at 50°C. The other fraction of LH2 complex containing on average less than one molecule of carotenoid per complex was destroyed under heating, forming a zone of free pigments (and polypeptides). The data suggest that a certain part of the LH2 complexes is assembled without carotenoids in cells of the nonsulfur bacterium Rbl. acidophilus grown with DPA. These data contradict the fact that the LH2 complex from nonsulfur bacteria cannot be assembled without carotenoids, but on the other hand, they are in good agreement with the results demonstrated in our earlier studies of the sulfur bacteria Allochromatium minutissimum and Ectothiorhodospira haloalkaliphila. Carotenoidless LH2 complex was obtained from these bacteria with the use of DPA (Moskalenko, A. A., and Makhneva, Z. K. (2012) J. Photochem. Photobiol., 108, 1-7; Ashikhmin, A., et al. (2014) Photosynth. Res., 119, 291-303). PMID:26555469

  5. The Metabolite Transporters of the Plastid Envelope: An Update

    PubMed Central

    Facchinelli, Fabio; Weber, Andreas P. M.

    2011-01-01

    The engulfment of a photoautotrophic cyanobacterium by a primitive mitochondria-bearing eukaryote traces back to more than 1.2 billion years ago. This single endosymbiotic event not only provided the early petroalgae with the metabolic capacity to perform oxygenic photosynthesis, but also introduced a plethora of other metabolic routes ranging from fatty acids and amino acids biosynthesis, nitrogen and sulfur assimilation to secondary compounds synthesis. This implicated the integration and coordination of the newly acquired metabolic entity with the host metabolism. The interface between the host cytosol and the plastidic stroma became of crucial importance in sorting precursors and products between the plastid and other cellular compartments. The plastid envelope membranes fulfill different tasks: they perform important metabolic functions, as they are involved in the synthesis of carotenoids, chlorophylls, and galactolipids. In addition, since most genes of cyanobacterial origin have been transferred to the nucleus, plastidial proteins encoded by nuclear genes are post-translationally transported across the envelopes through the TIC–TOC import machinery. Most importantly, chloroplasts supply the photoautotrophic cell with photosynthates in form of reduced carbon. The innermost bilayer of the plastidic envelope represents the permeability barrier for the metabolites involved in the carbon cycle and is literally stuffed with transporter proteins facilitating their transfer. The intracellular metabolite transporters consist of polytopic proteins containing membrane spans usually in the number of four or more α-helices. Phylogenetic analyses revealed that connecting the plastid with the host metabolism was mainly a process driven by the host cell. In Arabidopsis, 58% of the metabolite transporters are of host origin, whereas only 12% are attributable to the cyanobacterial endosymbiont. This review focuses on the metabolite transporters of the inner envelope

  6. Toward using delta13C of ecosystem respiration to monitor canopy physiology in complex terrain.

    PubMed

    Pypker, T G; Hauck, M; Sulzman, E W; Unsworth, M H; Mix, A C; Kayler, Z; Conklin, D; Kennedy, A M; Barnard, H R; Phillips, C; Bond, B J

    2008-12-01

    In 2005 and 2006, air samples were collected at the base of a Douglas-fir watershed to monitor seasonal changes in the delta13CO2 of ecosystem respiration (delta13C(ER)). The goals of this study were to determine whether variations in delta13C(ER) correlated with environmental variables and could be used to predict expected variations in canopy-average stomatal conductance (Gs). Changes in delta13C(ER) correlated weakly with changes in vapor pressure deficit (VPD) measured 0 and 3-7 days earlier and significantly with soil matric potential (psi(m)) (P value <0.02) measured on the same day. Midday G (s) was estimated using sapflow measurements (heat-dissipation method) at four plots located at different elevations within the watershed. Values of midday Gs from 0 and 3-7 days earlier were correlated with delta13C(ER), with the 5-day lag being significant (P value <0.05). To examine direct relationships between delta13C(ER) and recent Gs, we used models relating isotope discrimination to stomatal conductance and photosynthetic capacity at the leaf level to estimate values of stomatal conductance ("Gs-I") that would be expected if respired CO2 were derived entirely from recent photosynthate. We compared these values with estimates of Gs using direct measurement of transpiration at multiple locations in the watershed. Considering that the approach based on isotopes considers only the effect of photosynthetic discrimination on delta13C(ER), the magnitude and range in the two values were surprisingly similar. We conclude that: (1) delta13C(ER) is sensitive to variations in weather, and (2) delta13C(ER) potentially could be used to directly monitor average, basin-wide variations in Gs in complex terrain if further research improves understanding of how delta13C(ER) is influenced by post-assimilation fractionation processes. PMID:18839214

  7. Mapping nutrient resorption efficiencies of subarctic cryptogams and seed plants onto the Tree of Life

    PubMed Central

    Lang, Simone I; Aerts, Rien; van Logtestijn, Richard S P; Schweikert, Wenka; Klahn, Thorsten; Quested, Helen M; van Hal, Jurgen R; Cornelissen, Johannes H C

    2014-01-01

    Nutrient resorption from senescing photosynthetic organs is a powerful mechanism for conserving nitrogen (N) and phosphorus (P) in infertile environments. Evolution has resulted in enhanced differentiation of conducting tissues to facilitate transport of photosynthate to other plant parts, ultimately leading to phloem. Such tissues may also serve to translocate N and P to other plant parts upon their senescence. Therefore, we hypothesize that nutrient resorption efficiency (RE, % of nutrient pool exported) should correspond with the degree of specialization of these conducting tissues across the autotrophic branches of the Tree of Life. To test this hypothesis, we had to compare members of different plant clades and lichens within a climatic region, to minimize confounding effects of climatic drivers on nutrient resorption. Thus, we compared RE among wide-ranging basal clades from the principally N-limited subarctic region, employing a novel method to correct for mass loss during senescence. Even with the limited numbers of species available for certain clades in this region, we found some consistent patterns. Mosses, lichens, and lycophytes generally showed low REN (<20%), liverworts and conifers intermediate (40%) and monilophytes, eudicots, and monocots high (>70%). REP appeared higher in eudicots and liverworts than in mosses. Within mosses, taxa with more efficient conductance also showed higher REN. The differences in REN among clades broadly matched the degree of specialization of conducting tissues. This novel mapping of a physiological process onto the Tree of Life broadly supports the idea that the evolution of conducting tissues toward specialized phloem has aided land plants to optimize their internal nitrogen recycling. The generality of evolutionary lines in conducting tissues and nutrient resorption efficiency needs to be tested across different floras in different climatic regions with different levels of N versus P availability. PMID:25360262

  8. Hybrid mimics and hybrid vigor in Arabidopsis

    PubMed Central

    Wang, Li; Greaves, Ian K.; Groszmann, Michael; Wu, Li Min; Dennis, Elizabeth S.; Peacock, W. James

    2015-01-01

    F1 hybrids can outperform their parents in yield and vegetative biomass, features of hybrid vigor that form the basis of the hybrid seed industry. The yield advantage of the F1 is lost in the F2 and subsequent generations. In Arabidopsis, from F2 plants that have a F1-like phenotype, we have by recurrent selection produced pure breeding F5/F6 lines, hybrid mimics, in which the characteristics of the F1 hybrid are stabilized. These hybrid mimic lines, like the F1 hybrid, have larger leaves than the parent plant, and the leaves have increased photosynthetic cell numbers, and in some lines, increased size of cells, suggesting an increased supply of photosynthate. A comparison of the differentially expressed genes in the F1 hybrid with those of eight hybrid mimic lines identified metabolic pathways altered in both; these pathways include down-regulation of defense response pathways and altered abiotic response pathways. F6 hybrid mimic lines are mostly homozygous at each locus in the genome and yet retain the large F1-like phenotype. Many alleles in the F6 plants, when they are homozygous, have expression levels different to the level in the parent. We consider this altered expression to be a consequence of transregulation of genes from one parent by genes from the other parent. Transregulation could also arise from epigenetic modifications in the F1. The pure breeding hybrid mimics have been valuable in probing the mechanisms of hybrid vigor and may also prove to be useful hybrid vigor equivalents in agriculture. PMID:26283378

  9. Belowground fungal associations and water interact to influence the compensatory response of Ipomopsis aggregata.

    PubMed

    Allsup, Cassandra M; Paige, Ken N

    2016-02-01

    Although the concept that some plants benefit from being eaten is counterintuitive, there is now considerable evidence demonstrating enhanced fitness following herbivory. It has been assumed that plants growing in high resource conditions are the ones best able to compensate for herbivory. However, just the opposite has been found for dicotyledonous plants exhibiting patterns of overcompensation, with most occurring in resource-poor conditions. Long-term studies of the monocarpic biennial, scarlet gilia, Ipomopsis aggregata growing in resource-poor conditions have shown that ungulate herbivory by mule deer and elk can result in a threefold increase in plant fitness over uneaten controls. These observations led us to hypothesize that fungal associations would facilitate the compensatory response most commonly observed in this Arizona population of scarlet gilia; perhaps mutualistic associations with fungi, such as arbuscular mycorrhizal fungi, would explain the phenomenon of overcompensation altogether. Fungal removal experiments, using Captan®, a commercially available fungicide, showed that a reduction in fungal abundance altered the compensatory response following ungulate herbivory, particularly in years in which water was limited, increasing fitness compensation from equal compensation to overcompensation. A multifactorial experiment revealed that the interactive effects of water and fungicide maximized fruit production following herbivory. Our results are counter to the “modification of tolerance hypothesis” in which plants associating with mycorrhizal fungi will have higher tolerance to herbivory. It is likely that arbuscular mycorrhizal fungi and dark septate endophytes compete with plants for photosynthates following herbivory, thereby limiting the magnitude of compensation. Thus, fungi appear to be parasitic on scarlet gilia following ungulate herbivory. PMID:26497124

  10. Seed coat-associated invertases of fava bean control both unloading and storage functions: cloning of cDNAs and cell type-specific expression.

    PubMed

    Weber, H; Borisjuk, L; Heim, U; Buchner, P; Wobus, U

    1995-11-01

    We have studied the molecular physiology of photosynthate unloading and partitioning during seed development of fava bean (Vicia faba). During the prestorage phase, high levels of hexoses in the cotyledons and the apoplastic endospermal space are correlated with activity of cell wall-bound invertase in the seed coat. Three cDNAs were cloned. Sequence comparison revealed genes putatively encoding one soluble and two cell wall-bound isoforms of invertase. Expression was studied in different organs and tissues of developing seeds by RNA gel analysis, in situ hybridization, enzyme assay, and enzyme activity staining. One extracellular invertase gene is expressed during the prestorage phase in the thin-walled parenchyma of the seed coat, a region known to be the site of photoassimilate unloading. We propose a model for an invertase-mediated unloading process during early seed development and the regulation of cotyledonary sucrose metabolism. After unloading from the seed coat, sucrose is hydrolyzed by cell wall-bound invertases. Thus, invertase contributes to establish sink strength in young seeds. The resultant hexoses are loaded into the cotyledons and control carbohydrate partitioning via an influence on the sucrose synthase/sucrose-phosphate synthase pathway. The developmentally regulated degradation of the thin-walled parenchyma expressing the invertase apparently initiates the storage phase. This is characterized by a switch to a low sucrose/hexoses ratio. Feeding hexoses to storage-phase cotyledons in vitro increases the sucrose-phosphate synthase/sucrose synthase ratio and changes carbohydrate partitioning in favor of sucrose. Concomitantly, the transcript level of the major storage product legumin B is downregulated. PMID:8535137

  11. Impact of Heterobasidion root-rot on fine root morphology and associated fungi in Picea abies stands on peat soils.

    PubMed

    Gaitnieks, Talis; Klavina, Darta; Muiznieks, Indrikis; Pennanen, Taina; Velmala, Sannakajsa; Vasaitis, Rimvydas; Menkis, Audrius

    2016-07-01

    We examined differences in fine root morphology, mycorrhizal colonisation and root-inhabiting fungal communities between Picea abies individuals infected by Heterobasidion root-rot compared with healthy individuals in four stands on peat soils in Latvia. We hypothesised that decreased tree vitality and alteration in supply of photosynthates belowground due to root-rot infection might lead to changes in fungal communities of tree roots. Plots were established in places where trees were infected and in places where they were healthy. Within each stand, five replicate soil cores with roots were taken to 20 cm depth in each root-rot infected and uninfected plot. Root morphological parameters, mycorrhizal colonisation and associated fungal communities, and soil chemical properties were analysed. In three stands root morphological parameters and in all stands root mycorrhizal colonisation were similar between root-rot infected and uninfected plots. In one stand, there were significant differences in root morphological parameters between root-rot infected versus uninfected plots, but these were likely due to significant differences in soil chemical properties between the plots. Sequencing of the internal transcribed spacer of fungal nuclear rDNA from ectomycorrhizal (ECM) root morphotypes of P. abies revealed the presence of 42 fungal species, among which ECM basidiomycetes Tylospora asterophora (24.6 % of fine roots examined), Amphinema byssoides (14.5 %) and Russula sapinea (9.7 %) were most common. Within each stand, the richness of fungal species and the composition of fungal communities in root-rot infected versus uninfected plots were similar. In conclusion, Heterobasidion root-rot had little or no effect on fine root morphology, mycorrhizal colonisation and composition of fungal communities in fine roots of P. abies growing on peat soils. PMID:26861482

  12. Are above and belowground phenology in sync?

    NASA Astrophysics Data System (ADS)

    Abramoff, R. Z.; Finzi, A.

    2014-12-01

    Globally, root production accounts for 30-70% of terrestrial net primary productivity and influences decomposition via root production and turnover, carbon (C) allocation to mycorrhizal fungi and root exudation. As recognized aboveground, the timing of phenological events affects terrestrial C balance, yet there is no parallel understanding for belowground phenology. The objective of this study is to use meta-analysis to identify broad patterns in the phenology of root production and its relationship to temperature, soil moisture, and aboveground phenology. Synthesizing 87 observations of whole plant phenology from 40 studies, we found that on average root growth occurs 25±8 days after shoot growth but that the offset between the peak in root and shoot growth varies >200 days across biomes (boreal, temperate, Mediterranean, and subtropical). Growth form also affected phenology, with deciduous trees more synchronous than evergreen trees. This and the temperature differential between air and soil in spring may explain the relatively early shoot compared to root growth in boreal biomes. Root and shoot growth are positively correlated with median monthly temperature and mean monthly precipitation in boreal, temperate, and subtropical biomes. However, a temperature hysteresis in these biomes leads to the hypothesis that internal controls over C allocation to roots are an equally, if not more, important driver of phenology. In addition, a lack of correlation with temperature or precipitation in the Mediterranean biome implies that other mechanisms are driving phenology. The specific mechanism(s) are as yet unclear but are likely mediated by some combination of photosynthate supply, hormonal signaling, and growth form.

  13. Phytoplankton excretion revisited: Healthy cells may not do it, but how many cells are healthy?. Continuation progress report, May 1, 1993--April 30, 1994

    SciTech Connect

    Wood, A.M.

    1994-05-01

    The primary purpose of the proposed research is to develop molecular tools for determining the health of marine phytoplankton on an individual cell basis. Since the definition of {open_quotes}healthy{close_quotes} in phytoplankton cells is elusive, we propose to develop markers for several different metabolic processes indicative of physiological state: photosynthetic activity, esterase activity, membrane permeability, and mitochondrial activity. One underlying motivation is to develop methods which will allow us to evaluate the hypothesis that, while healthy cells release very little DOC, many phytoplankton communities are comprised of {open_quotes}unhealthy{close_quotes} or physiologically stressed cells which release a large proportion of total photosynthate directly into the pool of labile DOC. This is proposed to be especially true in continental shelf and coastal environments where zones of productivity are patchy and phytoplankton populations adapted to one regime can be easily transported into waters which differ in salinity, nutrient supply, and/or turbidity. The significance of the work, however, extends beyond this immediate goal since there are presently relatively few methods which allow us to estimate the physiological state of phytoplankton cells. When we evaluate population sizes of phytoplankton in the water column or examine fecal pellets, particulate aggregates, or other material, we generally work in ignorance of the activity of the cells except as the average cell-specific activity is estimated from bulk measurements. This approach effectively hides any differences in the relative contribution of different taxa or individuals to overall productivity even though most flux processes are sensitive to physiological and taxonomically determined differences among members of the community.

  14. High Latitude Forest Dynamics - CO2 EXCHANGE Measurements and Forest Growth at the Altitudinal Forest Line in High Subarctic Finnish Lapland

    NASA Astrophysics Data System (ADS)

    Dengel, S.; Siivola, E.; Aakala, T.; Kolari, P.; Hari, P.; Back, J. K.; Grace, J.; Vesala, T.

    2015-12-01

    Forests in high subarctic fell regions of Fennoscandia belong to the most northern forests in the world, a dynamic ecosystem vulnerable under a changing climate with treelines moving further north and also higher up slopes. An ecosystem is characterised by the interaction between micrometeorology, macroecology and the underlying terrain and topography. The current study is carried out at 68° North (Värriö strict nature reserve), the most sensitive zone of the high subarctic in Finnish Lapland. As the treeline is climbing up the slopes trees and eventually forests establish along the slopes leading to a greening of the area ("Greening of the Arctic" effect) and to an increase in CO2 uptake, also as a result of rising air temperatures and Nitrogen fertilization effects. Such developments and the little grazing (in this area) are leading to an increase in photosynthesising biomass. In order to fully understand the atmosphere - forest interaction in the fell region of Finnish Lapland, several important aspects are taken in consideration: its high latitudinal location, on-going climate change, polar day, its topographic characteristic and the dynamic of the progressing tree line. All these physiognomies cumulate in the capacity and efficiency of high latitude biomes in converting energy into photosynthate and contributing to removal of CO2 from the atmosphere. Carrying out CO2 and energy exchange measurements at ecosystem level in such extreme environments are challenging in particular when trying to follow and fulfil established assumptions set out by the application of the eddy covariance technique. Results from the first four consecutive snow free growing seasons show this site to act as a sink for atmospheric CO2. We are investigating the orographic effect on the observed fluxes and evaluate the performance of the flux setup determining if the topography has any systematic effects on fluxes or whether its external properties bias the carbon balance.

  15. Modulation of the multilamellar membrane organization and of the chiral macrodomains in the diatom Phaeodactylum tricornutum revealed by small-angle neutron scattering and circular dichroism spectroscopy.

    PubMed

    Nagy, Gergely; Szabó, Milán; Unnep, Renáta; Káli, György; Miloslavina, Yuliya; Lambrev, Petar H; Zsiros, Ottó; Porcar, Lionel; Timmins, Peter; Rosta, László; Garab, Győző

    2012-03-01

    Diatoms possess effective photoprotection mechanisms, which may involve reorganizations in the photosynthetic machinery. We have shown earlier, by using circular dichroism (CD) spectroscopy, that in Phaeodactylum tricornutum the pigment-protein complexes are arranged into chiral macrodomains, which have been proposed to be associated with the multilamellar organization of the thylakoid membranes and shown to be capable of undergoing light-induced reversible reorganizations (Szabó et al. Photosynth Res 95:237, 2008). Recently, by using small-angle neutron scattering (SANS) on the same algal cells we have determined the repeat distances and revealed reversible light-induced reorganizations in the lamellar order of thylakoids (Nagy et al. Biochem J 436:225, 2011). In this study, we show that in moderately heat-treated samples, the weakening of the lamellar order is accompanied by the diminishment of the psi-type CD signal associated with the long-range chiral order of the chromophores (psi, polymer or salt-induced). Further, we show that the light-induced reversible increase in the psi-type CD is associated with swelling in the membrane system, with magnitudes larger in high light than in low light. In contrast, shrinkage of the membrane system, induced by sorbitol, brings about a decrease in the psi-type CD signal; this shrinkage also diminishes the non-photochemical quenching capability of the cells. These data shed light on the origin of the psi-type CD signal, and confirm that both CD spectroscopy and SANS provide valuable information on the macro-organization of the thylakoid membranes and their dynamic properties; these parameters are evidently of interest with regard to the photoprotection in whole algal cells. PMID:21986933

  16. Modification of carbon partitioning, photosynthetic capacity, and O{sub 2} sensitivity in Arabidopsis plants with low ADP-glucose pyrophosphorylase activity

    SciTech Connect

    Sun, J.; Okita, T.W.; Edwards, G.E.

    1999-01-01

    Wild-type Arabidopsis plants, the starch-deficient mutant TL46, and the near-starchless mutant TL25 were evaluated by noninvasive in situ methods for their capacity for net CO{sub 2} assimilation, true rates of photosynthetic O{sub 2} evolution (determined from chlorophyll fluorescence measurements of photosystem II), partitioning of photosynthate into sucrose and starch, and plant growth. Compared with wild-type plants, the starch mutants showed reduced photosynthetic capacity, with the largest reduction occurring in mutant TL25 subjected to high light and increased CO{sub 2} partial pressure. The extent of stimulation of CO{sub 2} assimilation by increasing CO{sub 2} or by reducing O{sub 2} partial pressure was significantly less for the starch mutants than for wild-type plants. Under high light and moderate to high levels of CO{sub 2}, the rates of CO{sub 2} assimilation and O{sub 2} evolution and the percentage inhibition of photosynthesis by low O{sub 2} were higher for the wild type than for the mutants. The relative rates of {sup 14}CO{sub 2} incorporation into starch under high light and high CO{sub 2} followed the patterns of photosynthetic capacity, with TL46 showing 31% to 40% of the starch-labeling rates of the wild type and TL25 showing less than 14% incorporation. Overall, there were significant correlations between the rates of starch synthesis and CO{sub 2} assimilation and between the rates of starch synthesis and cumulative leaf area. These results indicate that leaf starch plays an important role as a transient reserve, the synthesis of which can ameliorate any potential reduction in photosynthesis caused by feedback regulation.

  17. The ectomycorrhizal fungus Paxillus involutus converts organic matter in plant litter using a trimmed brown-rot mechanism involving Fenton chemistry

    PubMed Central

    Rineau, Francois; Roth, Doris; Shah, Firoz; Smits, Mark; Johansson, Tomas; Canbäck, Björn; Olsen, Peter Bjarke; Persson, Per; Grell, Morten Nedergaard; Lindquist, Erika; Grigoriev, Igor V; Lange, Lene; Tunlid, Anders

    2012-01-01

    Soils in boreal forests contain large stocks of carbon. Plants are the main source of this carbon through tissue residues and root exudates. A major part of the exudates are allocated to symbiotic ectomycorrhizal fungi. In return, the plant receives nutrients, in particular nitrogen from the mycorrhizal fungi. To capture the nitrogen, the fungi must at least partly disrupt the recalcitrant organic matter–protein complexes within which the nitrogen is embedded. This disruption process is poorly characterized. We used spectroscopic analyses and transcriptome profiling to examine the mechanism by which the ectomycorrhizal fungus Paxillus involutus degrades organic matter when acquiring nitrogen from plant litter. The fungus partially degraded polysaccharides and modified the structure of polyphenols. The observed chemical changes were consistent with a hydroxyl radical attack, involving Fenton chemistry similar to that of brown-rot fungi. The set of enzymes expressed by Pa. involutus during the degradation of the organic matter was similar to the set of enzymes involved in the oxidative degradation of wood by brown-rot fungi. However, Pa. involutus lacked transcripts encoding extracellular enzymes needed for metabolizing the released carbon. The saprotrophic activity has been reduced to a radical-based biodegradation system that can efficiently disrupt the organic matter–protein complexes and thereby mobilize the entrapped nutrients. We suggest that the released carbon then becomes available for further degradation and assimilation by commensal microbes, and that these activities have been lost in ectomycorrhizal fungi as an adaptation to symbiotic growth on host photosynthate. The interdependence of ectomycorrhizal symbionts and saprophytic microbes would provide a key link in the turnover of nutrients and carbon in forest ecosystems. PMID:22469289

  18. Terrestrial orchids in a tropical forest: best sites for abundance differ from those for reproduction.

    PubMed

    Whitman, Melissa; Ackerman, James D

    2015-03-01

    Suitable habitat for a species is often modeled by linking its distribution patterns with landscape characteristics. However, modeling the relationship between fitness and landscape characteristics is less common. In this study we take a novel approach towards species distribution modeling (SDM) by investigating factors important not only for species occurrence, but also abundance and physical size, as well as fitness measures. We used the Neotropical terrestrial orchid Prescottia stachyodes as our focal species, and compiled geospatial information on habitat and neighboring plants for use in a two-part conditional SDM that accounted for zero inflation and reduced spatial autocorrelation bias. First, we modeled orchid occurrence, and then within suitable sites we contrasted habitat characteristics important for orchid abundance as compared to plant size. We then tested possible fitness implications, informed by analyses of allometric scaling of reproductive effort and lamina area, as well as size-density relationships in areas of P. stachyodes co-occurrence. We determined that orchid presence was based on a combination of biotic and abiotic factors (indicator species, diffuse solar radiation). Within these sites, P. stachyodes abundance was higher on flat terrain, with fine, moderately well-drained soil, and areas without other native orchids, whereas plant size was greater in less rocky areas. In turn, plant size determined reproductive effort, with floral display height proportionate to lamina area (more photosynthates); however, allometric scaling of flower quantity suggests a higher energy cost for production, or maintenance, of flowers. Overall, habitat factors most important for abundance differed from those for size (and thus reproductive effort), suggesting that sites optimal for either recruitment or survival may not be the primary source of seeds. For plots with multiple P. stachyodes plants, size-density relationships differed depending on the size class

  19. Prolonging the hydration and active metabolism from light periods into nights substantially enhances lichen growth.

    PubMed

    Bidussi, Massimo; Gauslaa, Yngvar; Solhaug, Knut Asbjørn

    2013-05-01

    This study investigates how hydration during light and dark periods influences growth in two epiphytic old forest lichens, the green algal Lobaria pulmonaria and the cyanobacterial L. scrobiculata. The lichens were cultivated in growth chambers for 14 days (200 μmol m(-1) s(-2); 12 h photoperiod) at four temperature regimes (25/20 °C, 21/16 °C, 13/8 °C, and 6/1 °C; day/night temperatures) and two hydration regimes (12 h day-time hydration; 12 h day-time + 12 h night-time hydration). Growth was highly dynamic, showing that short-term growth experiments in growth cabinets have a high, but largely unexplored potential in functional lichen studies. The highest measured growth rates were not far from the maximal dry matter gain estimated from published net photosynthetic CO2 uptake data. For the entire data set, photobiont type, temperature, hydration regime and specific thallus mass accounted for 46.6 % of the variation in relative growth rate (RGR). Both species showed substantially higher relative growth rates based on both biomass (RGR) and thallus area (RTAGR) when they were hydrated day and night compared to hydration in light only. Chronic photoinhibition was substantial in thalli hydrated only during the day time and kept at the highest and lowest temperature regimes, resulting in exponential increases in RGR with increasing maximal PSII efficiency (F v/F m) in both species. However, the depression in F v/F m was stronger for the cyanolichen than for the cephalolichen at extreme temperatures. The growth-stimulating effect of night-time hydration suggests that nocturnal metabolic activity improves recovery of photoinhibition and/or enhances the conversion rate of photosynthates into thallus extension. PMID:23389675

  20. Stover Composition in Maize and Sorghum Reveals Remarkable Genetic Variation and Plasticity for Carbohydrate Accumulation

    PubMed Central

    Sekhon, Rajandeep S.; Breitzman, Matthew W.; Silva, Renato R.; Santoro, Nicholas; Rooney, William L.; de Leon, Natalia; Kaeppler, Shawn M.

    2016-01-01

    Carbohydrates stored in vegetative organs, particularly stems, of grasses are a very important source of energy. We examined carbohydrate accumulation in adult sorghum and maize hybrids with distinct phenology and different end uses (grain, silage, sucrose or sweetness in stalk juice, and biomass). Remarkable variation was observed for non-structural carbohydrates and structural polysaccharides during three key developmental stages both between and within hybrids developed for distinct end use in both species. At the onset of the reproductive phase (average 65 days after planting, DAP), a wide range for accumulation of non-structural carbohydrates (free glucose and sucrose combined), was observed in internodes of maize (11–24%) and sorghum (7–36%) indicating substantial variation for transient storage of excess photosynthate during periods of low grain or vegetative sink strength. Remobilization of these reserves for supporting grain fill or vegetative growth was evident from lower amounts in maize (8–19%) and sorghum (9–27%) near the end of the reproductive period (average 95 DAP). At physiological maturity of grain hybrids (average 120 DAP), amounts of these carbohydrates were generally unchanged in maize (9–21%) and sorghum (16–27%) suggesting a loss of photosynthetic assimilation due to weakening sink demand. Nonetheless, high amounts of non-structural carbohydrates at maturity even in grain maize and sorghum (15–18%) highlight the potential for developing dual-purpose (grain/stover) crops. For both species, the amounts of structural polysaccharides in the cell wall, measured as monomeric components (glucose and pentose), decreased during grain fill but remained unchanged thereafter with maize biomass possessing slightly higher amounts than sorghum. Availability of carbohydrates in maize and sorghum highlights the potential for developing energy-rich dedicated biofuel or dual-purpose (grain/stover) crops. PMID:27375668

  1. Nitrogen control of 13C enrichment in heterotrophic organs relative to leaves in a landscape-building desert plant species

    SciTech Connect

    Zhang, J.; Gu, L.; Bao, F.; Cao, Y.; Hao, Y.; He, J.; Li, J.; Li, Y.; Ren, Y.; Wang, F.; Wu, R.; Yao, B.; Zhao, Y.; Lin, G.; Wu, B.; Lu, Q.; Meng, P.

    2014-09-10

    A longstanding puzzle in isotope studies of C3 plant species is that heterotrophic plant organs (e.g., stems, roots, seeds, and fruits) tend to be enriched in 13C compared to the autotrophic organ (leaves) that provides them with photosynthate. Our inability to explain this puzzle suggests key deficiencies in understanding post-photosynthetic metabolic processes. It also limits the effectiveness of applications of stable carbon isotope analyses in a variety of scientific disciplines ranging from plant physiology to global carbon cycle studies. To gain insight into this puzzle, we excavated whole plant architectures of Nitraria tangutorum Bobrov, a C3 species that has an exceptional capability of fixing sands and building sand dunes, in two deserts in northwestern China. We systematically and simultaneously measured carbon isotope ratios and nitrogen and phosphorous contents of different parts of the excavated plants. We also determined the seasonal variations in leaf carbon isotope ratios on nearby intact plants of N. tangutorum. We found, for the first time, that higher nitrogen contents in heterotrophic organs were significantly correlated with increased heterotrophic 13C enrichment compared to leaves. However, phosphorous contents had no effect on the enrichment. In addition, new leaves had carbon isotope ratios similar to roots but were progressively depleted in 13C as they matured. We concluded that a nitrogen-mediated process, probably the refixation of respiratory CO2 by phosphoenolpyruvate (PEP) carboxylase, was responsible for the differences in 13C enrichment among different heterotrophic organs while processes within leaves or during phloem loading may contribute to the overall autotrophic – heterotrophic difference in carbon isotope compositions.

  2. Nitrogen control of 13C enrichment in heterotrophic organs relative to leaves in a landscape-building desert plant species

    DOE PAGESBeta

    Zhang, J.; Gu, L.; Bao, F.; Cao, Y.; Hao, Y.; He, J.; Li, J.; Li, Y.; Ren, Y.; Wang, F.; et al

    2014-09-10

    A longstanding puzzle in isotope studies of C3 plant species is that heterotrophic plant organs (e.g., stems, roots, seeds, and fruits) tend to be enriched in 13C compared to the autotrophic organ (leaves) that provides them with photosynthate. Our inability to explain this puzzle suggests key deficiencies in understanding post-photosynthetic metabolic processes. It also limits the effectiveness of applications of stable carbon isotope analyses in a variety of scientific disciplines ranging from plant physiology to global carbon cycle studies. To gain insight into this puzzle, we excavated whole plant architectures of Nitraria tangutorum Bobrov, a C3 species that has anmore » exceptional capability of fixing sands and building sand dunes, in two deserts in northwestern China. We systematically and simultaneously measured carbon isotope ratios and nitrogen and phosphorous contents of different parts of the excavated plants. We also determined the seasonal variations in leaf carbon isotope ratios on nearby intact plants of N. tangutorum. We found, for the first time, that higher nitrogen contents in heterotrophic organs were significantly correlated with increased heterotrophic 13C enrichment compared to leaves. However, phosphorous contents had no effect on the enrichment. In addition, new leaves had carbon isotope ratios similar to roots but were progressively depleted in 13C as they matured. We concluded that a nitrogen-mediated process, probably the refixation of respiratory CO2 by phosphoenolpyruvate (PEP) carboxylase, was responsible for the differences in 13C enrichment among different heterotrophic organs while processes within leaves or during phloem loading may contribute to the overall autotrophic – heterotrophic difference in carbon isotope compositions.« less

  3. Stover composition in maize and sorghum reveals remarkable genetic variation and plasticity for carbohydrate accumulation

    DOE PAGESBeta

    Sekhon, Rajandeep S.; Breitzman, Matthew W.; Silva, Renato R.; Santoro, Nicholas; Rooney, William L.; de Leon, Natalia; Kaeppler, Shawn M.

    2016-06-08

    Carbohydrates stored in vegetative organs, particularly stems, of grasses are a very important source of energy. We examined carbohydrate accumulation in adult sorghum and maize hybrids with distinct phenology and different end uses (grain, silage, sucrose or sweetness in stalk juice, and biomass). Remarkable variation was observed for nonstructural carbohydrates and structural polysaccharides during three key developmental stages both between and within hybrids developed for distinct end use in both species. At the onset of the reproductive phase (average 65 days after planting, DAP), a wide range for accumulation of non-structural carbohydrates (free glucose and sucrose combined), was observed inmore » internodes of maize (11-24%) and sorghum (7-36%) indicating substantial variation for transient storage of excess photosynthate during periods of low grain or vegetative sink strength. Remobilization of these reserves for supporting grain fill or vegetative growth was evident from lower amounts in maize (8-19%) and sorghum (9-27%) near the end of the reproductive period (average 95 DAP). At physiological maturity of grain hybrids (average 120 DAP), amounts of these carbohydrates were generally unchanged in maize (9-21%) and sorghum (16-27%) suggesting a loss of photosynthetic assimilation due to weakening sink demand. Nonetheless, high amounts of non-structural carbohydrates at maturity even in grain maize and sorghum (15-18%) highlight the potential for developing dual-purpose (grain/stover) crops. For both species, the amounts of structural polysaccharides in the cell wall, measured as monomeric components (glucose and pentose), decreased during grain fill but remained unchanged thereafter with maize biomass possessing slightly higher amounts than sorghum. In conclusion, availability of carbohydrates in maize and sorghum highlights the potential for developing energy-rich dedicated biofuel or dual-purpose (grain/stover) crops.« less

  4. Do High Dynamic Range threatments improve the results of Structure from Motion approaches in Geomorphology?

    NASA Astrophysics Data System (ADS)

    Gómez-Gutiérrez, Álvaro; Juan de Sanjosé-Blasco, José; Schnabel, Susanne; de Matías-Bejarano, Javier; Pulido-Fernández, Manuel; Berenguer-Sempere, Fernando

    2015-04-01

    In this work, the hypothesis of improving 3D models obtained with Structure from Motion (SfM) approaches using images pre-processed by High Dynamic Range (HDR) techniques is tested. Photographs of the Veleta Rock Glacier in Spain were captured with different exposure values (EV0, EV+1 and EV-1), two focal lengths (35 and 100 mm) and under different weather conditions for the years 2008, 2009, 2011, 2012 and 2014. HDR images were produced using the different EV steps within Fusion F.1 software. Point clouds were generated using commercial and free available SfM software: Agisoft Photoscan and 123D Catch. Models Obtained using pre-processed images and non-preprocessed images were compared in a 3D environment with a benchmark 3D model obtained by means of a Terrestrial Laser Scanner (TLS). A total of 40 point clouds were produced, georeferenced and compared. Results indicated that for Agisoft Photoscan software differences in the accuracy between models obtained with pre-processed and non-preprocessed images were not significant from a statistical viewpoint. However, in the case of the free available software 123D Catch, models obtained using images pre-processed by HDR techniques presented a higher point density and were more accurate. This tendency was observed along the 5 studied years and under different capture conditions. More work should be done in the near future to corroborate whether the results of similar software packages can be improved by HDR techniques (e.g. ARC3D, Bundler and PMVS2, CMP SfM, Photosynth and VisualSFM).

  5. Nutrient availability affects pigment production but not growth in lichens of biological soil crusts

    USGS Publications Warehouse

    Bowker, M.A.; Koch, G.W.; Belnap, J.; Johnson, N.C.

    2008-01-01

    Recent research suggests that micronutrients such as Mn may limit growth of slow-growing biological soil crusts (BSCs) in some of the drylands of the world. These soil surface communities contribute strongly to arid ecosystem function and are easily degraded, creating a need for new restoration tools. The possibility that Mn fertilization could be used as a restoration tool for BSCs has not been tested previously. We used microcosms in a controlled greenhouse setting to investigate the hypothesis that Mn may limit photosynthesis and consequently growth in Collema tenax, a dominant N-fixing lichen found in BSCs worldwide. We found no evidence to support our hypothesis; furthermore, addition of other nutrients (primarily P, K, and Zn) had a suppressive effect on gross photosynthesis (P = 0.05). We also monitored the growth and physiological status of our microcosms and found that other nutrients increased the production of scytonemin, an important sunscreen pigment, but only when not added with Mn (P = 0.01). A structural equation model indicated that this effect was independent of any photosynthesis-related variable. We propose two alternative hypotheses to account for this pattern: (1) Mn suppresses processes needed to produce scytonemin; and (2) Mn is required to suppress scytonemin production at low light, when it is an unnecessary photosynthate sink. Although Mn fertilization does not appear likely to increase photosynthesis or growth of Collema, it could have a role in survivorship during environmentally stressful periods due to modification of scytonemin production. Thus, Mn enrichment should be studied further for its potential to facilitate BSC rehabilitation. ?? 2008 Elsevier Ltd.

  6. Molecular mapping across three populations reveals a QTL hotspot region on chromosome 3 for secondary traits associated with drought tolerance in tropical maize.

    PubMed

    Almeida, Gustavo Dias; Nair, Sudha; Borém, Aluízio; Cairns, Jill; Trachsel, Samuel; Ribaut, Jean-Marcel; Bänziger, Marianne; Prasanna, Boddupalli M; Crossa, Jose; Babu, Raman

    2014-01-01

    Identifying quantitative trait loci (QTL) of sizeable effects that are expressed in diverse genetic backgrounds across contrasting water regimes particularly for secondary traits can significantly complement the conventional drought tolerance breeding efforts. We evaluated three tropical maize biparental populations under water-stressed and well-watered regimes for drought-related morpho-physiological traits, such as anthesis-silking interval (ASI), ears per plant (EPP), stay-green (SG) and plant-to-ear height ratio (PEH). In general, drought stress reduced the genetic variance of grain yield (GY), while that of morpho-physiological traits remained stable or even increased under drought conditions. We detected consistent genomic regions across different genetic backgrounds that could be target regions for marker-assisted introgression for drought tolerance in maize. A total of 203 QTL for ASI, EPP, SG and PEH were identified under both the water regimes. Meta-QTL analysis across the three populations identified six constitutive genomic regions with a minimum of two overlapping traits. Clusters of QTL were observed on chromosomes 1.06, 3.06, 4.09, 5.05, 7.03 and 10.04/06. Interestingly, a ~8-Mb region delimited in 3.06 harboured QTL for most of the morpho-physiological traits considered in the current study. This region contained two important candidate genes viz., zmm16 (MADS-domain transcription factor) and psbs1 (photosystem II unit) that are responsible for reproductive organ development and photosynthate accumulation, respectively. The genomic regions identified in this study partially explained the association of secondary traits with GY. Flanking single nucleotide polymorphism markers reported herein may be useful in marker-assisted introgression of drought tolerance in tropical maize. PMID:25076840

  7. Production of reactive oxygen species in decoupled, Ca(2+)-depleted PSII and their use in assigning a function to chloride on both sides of PSII.

    PubMed

    Semin, Boris K; Davletshina, Lira N; Timofeev, Kirill N; Ivanov, Il'ya I; Rubin, Andrei B; Seibert, Michael

    2013-11-01

    Extraction of Ca(2+) from the oxygen-evolving complex of photosystem II (PSII) in the absence of a chelator inhibits O2 evolution without significant inhibition of the light-dependent reduction of the exogenous electron acceptor, 2,6-dichlorophenolindophenol (DCPIP) on the reducing side of PSII. The phenomenon is known as "the decoupling effect" (Semin et al. Photosynth Res 98:235-249, 2008). Extraction of Cl(-) from Ca(2+)-depleted membranes (PSII[-Ca]) suppresses the reduction of DCPIP. In the current study we investigated the nature of the oxidized substrate and the nature of the product(s) of the substrate oxidation. After elimination of all other possible donors, water was identified as the substrate. Generation of reactive oxygen species HO, H2O2, and O 2 (·-) , as possible products of water oxidation in PSII(-Ca) membranes was examined. During the investigation of O 2 (·-) production in PSII(-Ca) samples, we found that (i) O 2 (·-) is formed on the acceptor side of PSII due to the reduction of O2; (ii) depletion of Cl(-) does not inhibit water oxidation, but (iii) Cl(-) depletion does decrease the efficiency of the reduction of exogenous electron acceptors. In the absence of Cl(-) under aerobic conditions, electron transport is diverted from reducing exogenous acceptors to reducing O2, thereby increasing the rate of O 2 (·-) generation. From these observations we conclude that the product of water oxidation is H2O2 and that Cl(-) anions are not involved in the oxidation of water to H2O2 in decoupled PSII(-Ca) membranes. These results also indicate that Cl(-) anions are not directly involved in water oxidation by the Mn cluster in the native PSII membranes, but possibly provide access for H2O molecules to the Mn4CaO5 cluster and/or facilitate the release of H(+) ions into the lumenal space. PMID:23794169

  8. Potassium deficiency affects water status and photosynthetic rate of the vegetative sink in green house tomato prior to its effects on source activity.

    PubMed

    Kanai, Synsuke; Moghaieb, Reda E; El-Shemy, Hany A; Panigrahi, R; Mohapatra, Pravat K; Ito, J; Nguyen, Nguyen T; Saneoka, Hirofumi; Fujita, Kounosuke

    2011-02-01

    The potassium requirement of green house tomatoes is very high for vegetative growth and fruit production. Potassium deficiency in plants takes long time for expression of visible symptoms. The objective of this study is to detect the deficiency early during the vegetative growth and define the roles of aquaporin and K-channel transporters in the process of regulation of water status and source-sink relationship. The tomato plants were grown hydroponically inside green house of Hiroshima University, Japan and subjected to different levels of K in the rooting medium. Potassium deficiency stress decreased photosynthesis, expansion and transport of ¹⁴C assimilates of the source leaf, but the effects became evident only after diameter expansion of the growing stem (sink) was down-regulated. The depression of stem diameter expansion is assumed to be associated with the suppression of water supply more than photosynthate supply to the organ. The stem diameter expansion is parameterized by root water uptake and leaf transpiration rates. The application of aquaporin inhibitor (AgNO₃) decreased leaf water potential, stem expansion and root hydraulic conductance within minutes of application. Similar results were obtained for application of the K-channel inhibitors. These observations suggested a close relationship between stem diameter expansion and activities of aquaporins and K-channel transporters in roots. The deficiency of potassium might have reduced aquaporin activity, consequently suppressing root hydraulic conductance and water supply to the growing stem for diameter expansion and leaf for transpiration. We conclude that close coupling between aquaporins and K-channel transporters in water uptake of roots is responsible for regulation of stem diameter dynamics of green house tomato plants. PMID:21421382

  9. Flexible resource allocation during plant defense responses

    PubMed Central

    Schultz, Jack C.; Appel, Heidi M.; Ferrieri, Abigail P.; Arnold, Thomas M.

    2013-01-01

    Plants are organisms composed of modules connected by xylem and phloem transport streams. Attack by both insects and pathogens elicits sometimes rapid defense responses in the attacked module. We have also known for some time that proteins are often reallocated away from pathogen-infected tissues, while the same infection sites may draw carbohydrates to them. This has been interpreted as a tug of war in which the plant withdraws critical resources to block microbial growth while the microbes attempt to acquire more resources. Sink-source regulated transport among modules of critical resources, particularly carbon and nitrogen, is also altered in response to attack. Insects and jasmonate can increase local sink strength, drawing carbohydrates that support defense production. Shortly after attack, carbohydrates may also be drawn to the root. The rate and direction of movement of photosynthate or signals in phloem in response to attack is subject to constraints that include branching, degree of connection among tissues, distance between sources and sinks, proximity, strength, and number of competing sinks, and phloem loading/unloading regulators. Movement of materials (e.g., amino acids, signals) to or from attack sites in xylem is less well understood but is partly driven by transpiration. The root is an influential sink and may regulate sink-source interactions and transport above and below ground as well as between the plant and the rhizosphere and nearby, connected plants. Research on resource translocation in response to pathogens or herbivores has focused on biochemical mechanisms; whole-plant research is needed to determine which, if any, of these plant behaviors actually influence plant fitness. PMID:23986767

  10. Autotrophy of green non-sulphur bacteria in hot spring microbial mats: biological explanations for isotopically heavy organic carbon in the geological record

    NASA Technical Reports Server (NTRS)

    van der Meer, M. T.; Schouten, S.; de Leeuw, J. W.; Ward, D. M.

    2000-01-01

    Inferences about the evidence of life recorded in organic compounds within the Earth's ancient rocks have depended on 13C contents low enough to be characteristic of biological debris produced by the well-known CO2 fixation pathway, the Calvin cycle. 'Atypically' high values have been attributed to isotopic alteration of sedimentary organic carbon by thermal metamorphism. We examined the possibility that organic carbon characterized by a relatively high 13C content could have arisen biologically from recently discovered autotrophic pathways. We focused on the green non-sulphur bacterium Chloroflexus aurantiacus that uses the 3-hydroxypropionate pathway for inorganic carbon fixation and is geologically significant as it forms modern mat communities analogous to stromatolites. Organic matter in mats constructed by Chloroflexus spp. alone had relatively high 13C contents (-14.9%) and lipids diagnostic of Chloroflexus that were also isotopically heavy (-8.9% to -18.5%). Organic matter in mats constructed by Chloroflexus in conjunction with cyanobacteria had a more typical Calvin cycle signature (-23.5%). However, lipids diagnostic of Chloroflexus were isotopically enriched (-15.1% to -24.1%) relative to lipids typical of cyanobacteria (-33.9% to -36.3%). This suggests that, in mats formed by both cyanobacteria and Chloroflexus, autotrophy must have a greater effect on Chloroflexus carbon metabolism than the photoheterotrophic consumption of cyanobacterial photosynthate. Chloroflexus cell components were also selectively preserved. Hence, Chloroflexus autotrophy and selective preservation of its products constitute one purely biological mechanism by which isotopically heavy organic carbon could have been introduced into important Precambrian geological features.

  11. Production possibility frontiers in phototroph:heterotroph symbioses: trade-offs in allocating fixed carbon pools and the challenges these alternatives present for understanding the acquisition of intracellular habitats

    PubMed Central

    Hill, Malcolm S.

    2014-01-01

    Intracellular habitats have been invaded by a remarkable diversity of organisms, and strategies employed to successfully reside in another species' cellular space are varied. Common selective pressures may be experienced in symbioses involving phototrophic symbionts and heterotrophic hosts. Here I refine and elaborate the Arrested Phagosome Hypothesis that proposes a mechanism that phototrophs use to gain access to their host's intracellular habitat. I employ the economic concept of production possibility frontiers (PPF) as a useful heuristic to clearly define the trade-offs that an intracellular phototroph is likely to face as it allocates photosynthetically-derived pools of energy. Fixed carbon can fuel basic metabolism/respiration, it can support mitotic division, or it can be translocated to the host. Excess photosynthate can be stored for future use. Thus, gross photosynthetic productivity can be divided among these four general categories, and natural selection will favor phenotypes that best match the demands presented to the symbiont by the host cellular habitat. The PPF highlights trade-offs that exist between investment in growth (i.e., mitosis) or residency (i.e., translocating material to the host). Insights gained from this perspective might help explain phenomena such as coral bleaching because deficits in photosynthetic production are likely to diminish a symbiont's ability to “afford” the costs of intracellular residency. I highlight deficits in our current understanding of host:symbiont interactions at the molecular, genetic, and cellular level, and I also discuss how semantic differences among scientists working with different symbiont systems may diminish the rate of increase in our understanding of phototrophic-based associations. I argue that adopting interdisciplinary (in this case, inter-symbiont-system) perspectives will lead to advances in our general understanding of the phototrophic symbiont's intracellular niche. PMID:25101064

  12. Colonization of rice roots with methanogenic archaea controls photosynthesis-derived methane emission.

    PubMed

    Pump, Judith; Pratscher, Jennifer; Conrad, Ralf

    2015-07-01

    The methane emitted from rice fields originates to a large part (up to 60%) from plant photosynthesis and is formed on the rice roots by methanogenic archaea. To investigate to which extent root colonization controls methane (CH4 ) emission, we pulse-labeled rice microcosms with (13) CO2 to determine the rates of (13) CH4 emission exclusively derived from photosynthates. We also measured emission of total CH4 ((12+13) CH4 ), which was largely produced in the soil. The total abundances of archaea and methanogens on the roots and in the soil were analysed by quantitative polymerase chain reaction of the archaeal 16S rRNA gene and the mcrA gene coding for a subunit of the methyl coenzyme M reductase respectively. The composition of archaeal and methanogenic communities was determined with terminal restriction fragment length polymorphism (T-RFLP). During the vegetative growth stages, emission rates of (13) CH4 linearly increased with the abundance of methanogenic archaea on the roots and then decreased during the last plant growth stage. Rates of (13) CH4 emission and the abundance of methanogenic archaea were lower when the rice was grown in quartz-vermiculite with only 10% rice soil. Rates of total CH4 emission were not systematically related to the abundance of methanogenic archaea in soil plus roots. The composition of the archaeal communities was similar under all conditions; however, the analysis of mcrA genes indicated that the methanogens differed between the soil and root. Our results support the hypothesis that rates of photosynthesis-driven CH4 emission are limited by the abundance of methanogens on the roots. PMID:25367104

  13. The use of photothermal radiometry in assessing leaf photosynthesis: II. Correlation of energy storage to Photosystem II fluorescence parameters.

    PubMed

    Driesenaar, A R; Schreiber, U; Malkin, S

    1994-04-01

    Following the first part of this work (Malkin et al. (1991) Photosynth Res 29: 87-96), where modulated photothermal radiometry (PTR) was used to measure energy storage (ES) in intact leaves as a function of P700 redox state, we report here on simultaneous ES and fluorescence measurements, which characterize the state of PS II. PTR monitors the conversion of modulated light into heat by measuring the modulated infra-red radiation emitted from the sample. The ratio [PTR+-PTR-]/PTR+, where PTR indicates the PTR signal and the subscripts +,- indicate the presence or absence of saturating background light, is used to quantitate ES. We searched carefully for the right conditions where the background light does not introduce a significant rise in the leaf temperature, which influences the PTR signal as such, otherwise the above ratio deviates from the true ES. Under such conditions, ES and the fluorescence parameters, F (momentary fluorescence level) Fm' (fluorescence of fully reduced PS II reaction centers) were measured during the induction phase of photosynthesis and in the steady state. ES and the parameter γ=(Fm'-F)/Fm', considered by Genty et al. ((1989) Biochim Biophys Acta 990: 87-92) to reflect the yield of PS II, had similar kinetics during the induction phase. Both reached a final maximum plateau after about 4-5 min. of illumination. In different experiments, where the measuring light intensities varied, γ was approximately linearly related to ES. This linear relationship was found in the same way also in steady-state measurements, where these parameters varied by using different background light intensities. Extrapolation to an ES value of zero indicates a finite non-zero value of γ. A possible explanation for this may be found in the existence an electron transport cycle around PS II which does not store energy in the range corresponding to the modulation frequency used (ca. 3.6 Hz). PMID:24311213

  14. Warming and Nitrogen Addition Alter Photosynthetic Pigments, Sugars and Nutrients in a Temperate Meadow Ecosystem

    PubMed Central

    Zhang, Tao; Yang, Shaobo; Guo, Rui; Guo, Jixun

    2016-01-01

    Global warming and nitrogen (N) deposition have an important influence on terrestrial ecosystems; however, the influence of warming and N deposition on plant photosynthetic products and nutrient cycling in plants is not well understood. We examined the effects of 3 years of warming and N addition on the plant photosynthetic products, foliar chemistry and stoichiometric ratios of two dominant species, i.e., Leymus chinensis and Phragmites communis, in a temperate meadow in northeastern China. Warming significantly increased the chlorophyll content and soluble sugars in L. chinensis but had no impact on the carotenoid and fructose contents. N addition caused a significant increase in the carotenoid and fructose contents. Warming and N addition had little impact on the photosynthetic products of P. communis. Warming caused significant decreases in the N and phosphorus (P) concentrations and significantly increased the carbon (C):P and N:P ratios of L. chinensis, but not the C concentration or the C:N ratio. N addition significantly increased the N concentration, C:P and N:P ratios, but significantly reduced the C:N ratio of L. chinensis. Warming significantly increased P. communis C and P concentrations, and the C:N and C:P ratios, whereas N addition increased the C, N and P concentrations but had no impact on the stoichiometric variables. This study suggests that both warming and N addition have direct impacts on plant photosynthates and elemental stoichiometry, which may play a vital role in plant-mediated biogeochemical cycling in temperate meadow ecosystems. PMID:27171176

  15. The spatial and temporal relationships between CO2 and CH4 exchange in a temperate ombrotrophic bog

    NASA Astrophysics Data System (ADS)

    Lai, Derrick Y. F.; Roulet, Nigel T.; Moore, Tim R.

    2014-06-01

    We investigate the relationships between CO2 and CH4 fluxes across space and time at a temperate ombrotrophic bog in Canada to assess the coupling between plant production and CH4 emissions. Based on periodic manual chamber measurements, we show that maximum net ecosystem CO2 exchange (NEEmax) was a good predictor of the spatial variations in CH4 flux among the wetter Eriophorum and lawn sites (r2 = 0.61-0.88), but not the drier hummock sites (r2 = 0.04-0.49). Also, we observed large interannual variability in the NEEmax-CH4 relationship at the Eriophorum and lawn sites, with a smaller regression slope in 2010 that had a seasonal mean water table 8 cm lower than in 2009. Results of cross-correlation of instantaneous gross ecosystem production (GEP) and CH4 flux from autochambers show a moderate relationship (σ = -0.31) in the Eriophorum community at a lag of 9-12 h, suggesting a rapid turnover of recent photosynthate for methanogenesis. On the other hand, we found in two Maianthemum-dominated chambers that the temperature-independent residuals of daily mean CH4 flux lagged behind GEP by 18-26 days at the seasonal scale. The lagged correlations between GEP and CH4 flux by month were particularly strong in the late growing season in the Eriophorum and Maianthemum/Ledum communities. Our results suggest the presence of spatial and temporal coupling of plant production and CH4 emissions in this bog, whose strength varies with species composition, water table position, and plant phenology.

  16. Mapping of sugar and amino acid availability in soil around roots with bacterial sensors of sucrose and tryptophan

    PubMed

    Jaeger; Lindow; Miller; Clark; Firestone

    1999-06-01

    We developed a technique to map the availability of sugars and amino acids along live roots in an intact soil-root matrix with native microbial soil flora and fauna present. It will allow us to study interactions between root exudates and soil microorganisms at the fine spatial scale necessary to evaluate mechanisms of nitrogen cycling in the rhizosphere. Erwinia herbicola 299R harboring a promoterless ice nucleation reporter gene, driven by either of two nutrient-responsive promoters, was used as a biosensor. Strain 299RTice exhibits tryptophan-dependent ice nucleation activity, while strain 299R(p61RYice) expresses ice nucleation activity proportional to sucrose concentration in its environment. Both biosensors exhibited up to 100-fold differences in ice nucleation activity in response to varying substrate abundance in culture. The biosensors were introduced into the rhizosphere of the annual grass Avena barbata and, as a control, into bulk soil. Neither strain exhibited significant ice nucleation activity in the bulk soil. Both tryptophan and sucrose were detected in the rhizosphere, but they showed different spatial patterns. Tryptophan was apparently most abundant in soil around roots 12 to 16 cm from the tip, while sucrose was most abundant in soil near the root tip. The largest numbers of bacteria (determined by acridine orange staining and direct microscopy) occurred near root sections with the highest apparent sucrose or tryptophan exudation. High sucrose availability at the root tip is consistent with leakage of photosynthate from immature, rapidly growing root tissues, while tryptophan loss from older root sections may result from lateral root perforation of the root epidermis. PMID:10347061

  17. Processes leading to increased soil organic carbon in a Mojave Desert ecosystem under elevated CO2

    NASA Astrophysics Data System (ADS)

    Koyama, A.; Evans, R. D.

    2011-12-01

    We observed increased soil organic carbon (SOC) following ten years of elevated atmospheric CO2 treatment at the Nevada Desert FACE Facility in the Mojave Desert. Physical and chemical fractions of surface soils collected under the dominant shrub, Larrea tridentata (Larrea), and plant interspace were analyzed for particle size, plant-derived n-alkanes, microbial phospholipid fatty acids (PLFA) and neutral lipid fatty acids (NLFA) to explore potential mechanisms causing the observed increase in SOC. SOC concentrations under Larrea in bulk soils, coarse particulate organic matter (POM), fine POM and mineral-bound soil organic matter (SOM) under elevated CO2 were greater than those under ambient CO2 by 34%, 45%, 26% and 20%, respectively. Under Larrea, n-alkane concentrations were 52% greater under elevated compared to ambient CO2. Such increases in coarse POM and n-alkane concentrations suggest litter input from Larrea was at least one source for increased SOC under elevated CO2. While there was no significant difference in PLFA abundance between the CO2 treatments, elevated CO2 significantly increased the fungi to bacterial PLFA ratio. In addition, fungal and bacterial NLFA and NLFA 16:1ω5, a biomarker of arbuscular mycorrhizal fungi, were significantly higher under elevated than ambient CO2. These observations plus others suggest that Larrea allocated more photosynthate belowground to increased root exudation rather than increased fine root growth under elevated CO2. Thus, increased root exudates and microbial residues as well as episodic increases in litter input from Larrea are mechanisms behind the increased SOC under elevated CO2. Elevated CO2 did not increase SOC in surface soils in plant interspace despite incorporation of CO2 labeled with 13C under elevated CO2.

  18. The relationship between needle sugar carbon isotope ratios and tree rings of larch in Siberia.

    PubMed

    Rinne, K T; Saurer, M; Kirdyanov, A V; Loader, N J; Bryukhanova, M V; Werner, R A; Siegwolf, R T W

    2015-11-01

    Significant gaps still exist in our knowledge about post-photosynthetic leaf level and downstream metabolic processes and isotopic fractionations. This includes their impact on the isotopic climate signal stored in the carbon isotope composition (δ(13)C) of leaf assimilates and tree rings. For the first time, we compared the seasonal δ(13)C variability of leaf sucrose with intra-annual, high-resolution δ(13)C signature of tree rings from larch (Larix gmelinii Rupr.). The trees were growing at two sites in the continuous permafrost zone of Siberia with different growth conditions. Our results indicate very similar low-frequency intra-seasonal trends of the sucrose and tree ring δ(13)C records with little or no indication for the use of 'old' photosynthates formed during the previous year(s). The comparison of leaf sucrose δ(13)C values with that in other leaf sugars and in tree rings elucidates the cause for the reported (13)C-enrichment of sink organs compared with leaves. We observed that while the average δ(13)C of all needle sugars was 1.2‰ more negative than δ(13)C value of wood, the δ(13)C value of the transport sugar sucrose was on an average 1.0‰ more positive than that of wood. Our study shows a high potential of the combined use of compound-specific isotope analysis of sugars (leaf and phloem) with intra-annual tree ring δ(13)C measurements for deepening our understanding about the mechanisms controlling the isotope variability in tree rings under different environmental conditions. PMID:26433019

  19. Environmental effects on photorespiration of C sub 3 -C sub 4 species. I. Influence of CO sub 2 and O sub 2 during growth on photorespiratory characteristics and leaf anatomy. [Flaveria pringlei; Flaveria flroidana; Flaveria trinervia; Panicum milloides; Panicum laxum

    SciTech Connect

    Byrd, G.T.; Brown, R.H. )

    1989-07-01

    The possibility of altering CO{sub 2} exchange of C{sub 3}-C{sub 4} species by growing them under various CO{sub 2} and O{sub 2} concentrations was examined. Growth under CO{sub 2} concentrations of 100, 350, and 750 micromoles per mole had no significant effect on CO{sub 2} exchange characteristics or leaf anatomy of Flaveria pringlei (C{sub 3}), Flaveria floridana (C{sub 3}-C{sub 4}), or Flaveria trinervia (C{sub 4}). Carboxylation efficiency and CO{sub 2} compensation concentrations in leaves of F. floridana developed under the different CO{sub 2} concentrations were intermediate to F. pringlei and F. trinervia. When grown for 12 days at an O{sub 2} concentration of 20 millimoles per mole, apparent photosynthesis was strongly inhibited in Panicum milioides (C{sub 3}-C{sub 4}) and to a lesser degree in Panicum laxum (C{sub 3}). In P. milioides, acute starch buildup was observed microscopically in both mesophyll and bundle sheath cells. Even after only 4 days exposure to 20 millimoles per mole O{sub 2}, the presence of starch was more pronounced in leaf cross-sections of P. milioides compared to those at 100 and 210 millimoles per mole. Even though this observation suggests that P. milioides has a different response to low O{sub 2} with respect to translocation of photosynthate or sink activity than C{sub 3} species, the concentration of total available carbohydrate increased in shoots of all species by 33% or more when grown at low O{sub 2}. This accumulation occurred even though relative growth rates of Festuca arundinacea (C{sub 3}) and P. milioides grown for 4 days at 210 millimoles per mole O{sub 2}, were inhibited 83 and 37%, respectively, when compared to plants grown at 20 millimoles per mole O{sub 2}.

  20. Effects of photoperiod on wheat growth, development and yield in CELSS

    NASA Astrophysics Data System (ADS)

    Yunze, Shen; Shuangsheng, Guo

    2014-12-01

    A Controlled Ecological Life Support System (CELSS) is a sealed system used in spaceflight in order to provide astronauts with food and O2 by plants. It is of great significance to increase the energy-using efficiency because energy is extremely deficient in the space. Therefore, the objective of this research was to increase the energy-using efficiency of wheat by regulating the photoperiod. Sixteen treatments were set in total: four photoperiods before flowering (PBF) combined with four photoperiods after flowering (PAF) of 12 h, 16 h, 20 h and 24 h. The light source was red-blue LED (90% red+10% blue). As a result, the growth period of wheat was largely extended by shorter PBF, particularly the number of days from tillering to jointing and from jointing to heading. The period from flowering to maturity was extended by shorter PAF. Shorter PBF and longer PAF could increase not only the yield but also the energy-using efficiency of wheat. As for the nutritional quality, longer photoperiod (both PBF and PAF) increased starch concentration as well as decreased protein concentration of seeds. The effects of PBF and PAF were interactional. The lighting strategy with PBF of 12 h and PAF of 24 h was proved to be the optimum photoperiod for wheat cultivation in CELSS. The mechanisms of photoperiod effect contain two aspects. Firstly, photoperiod is a signal for many processes in plant growth, particularly the process of ear differentiation. Shorter PBF promoted the ear differentiation of wheat, increasing the spikelet number, floret number and seed number and thus enhancing the yield. Secondly, longer photoperiod leads to more light energy input and longer time of photosynthesis, so that longer PAF provided more photosynthate and increased seed yield.

  1. Mapping nutrient resorption efficiencies of subarctic cryptogams and seed plants onto the Tree of Life.

    PubMed

    Lang, Simone I; Aerts, Rien; van Logtestijn, Richard S P; Schweikert, Wenka; Klahn, Thorsten; Quested, Helen M; van Hal, Jurgen R; Cornelissen, Johannes H C

    2014-06-01

    Nutrient resorption from senescing photosynthetic organs is a powerful mechanism for conserving nitrogen (N) and phosphorus (P) in infertile environments. Evolution has resulted in enhanced differentiation of conducting tissues to facilitate transport of photosynthate to other plant parts, ultimately leading to phloem. Such tissues may also serve to translocate N and P to other plant parts upon their senescence. Therefore, we hypothesize that nutrient resorption efficiency (RE, % of nutrient pool exported) should correspond with the degree of specialization of these conducting tissues across the autotrophic branches of the Tree of Life. To test this hypothesis, we had to compare members of different plant clades and lichens within a climatic region, to minimize confounding effects of climatic drivers on nutrient resorption. Thus, we compared RE among wide-ranging basal clades from the principally N-limited subarctic region, employing a novel method to correct for mass loss during senescence. Even with the limited numbers of species available for certain clades in this region, we found some consistent patterns. Mosses, lichens, and lycophytes generally showed low REN (<20%), liverworts and conifers intermediate (40%) and monilophytes, eudicots, and monocots high (>70%). REP appeared higher in eudicots and liverworts than in mosses. Within mosses, taxa with more efficient conductance also showed higher REN. The differences in REN among clades broadly matched the degree of specialization of conducting tissues. This novel mapping of a physiological process onto the Tree of Life broadly supports the idea that the evolution of conducting tissues toward specialized phloem has aided land plants to optimize their internal nitrogen recycling. The generality of evolutionary lines in conducting tissues and nutrient resorption efficiency needs to be tested across different floras in different climatic regions with different levels of N versus P availability. PMID:25360262

  2. VOC emissions of Grey poplar leaves as affected by salt stress and different N sources.

    PubMed

    Teuber, M; Zimmer, I; Kreuzwieser, J; Ache, P; Polle, A; Rennenberg, H; Schnitzler, J-P

    2008-01-01

    Nitrogen nutrition and salt stress experiments were performed in a greenhouse with hydroponic-cultured, salt-sensitive Grey poplar (Populus x canescens) plants to study the combined influence of different N sources (either 1 mm NO(3) (-) or NH(4)(+)) and salt (up to 75 mm NaCl) on leaf gas exchange, isoprene biosynthesis and VOC emissions. Net assimilation and transpiration proved to be highly sensitive to salt stress and were reduced by approximately 90% at leaf sodium concentrations higher than 1,800 microg Na g dry weight (dw)(-1). In contrast, emissions of isoprene and oxygenated VOC (i.e. acetaldehyde, formaldehyde and acetone) were unaffected. There was no significant effect of combinations of salt stress and N source, and neither NO(3)(-) or NH(4)(+) influenced the salt stress response in the Grey poplar leaves. Also, transcript levels of 1-deoxy-d-xylulose 5-phosphate reductoisomerase (PcDXR) and isoprene synthase (PcISPS) did not respond to the different N sources and only responded slightly to salt application, although isoprene synthase (PcISPS) activity was negatively affected at least in one of two experiments, despite high isoprene emission rates. A significant salt effect was the strong reduction of leaf dimethylallyl diphosphate (DMADP) content, probably due to restricted availability of photosynthates for DMADP biosynthesis. Further consequences of reduced photosynthetic gas exchange and maintaining VOC emissions are a very high C loss, up to 50%, from VOC emissions related to net CO(2) uptake and a strong increase in leaf internal isoprene concentrations, with maximum mean values up to 6.6 microl x l(-1). Why poplar leaves maintain VOC biosynthesis and emission under salt stress conditions, despite impaired photosynthetic CO(2) fixation, is discussed. PMID:18211549

  3. Dynamic carbon allocation significantly changed land carbon sink and carbon pool sizes

    NASA Astrophysics Data System (ADS)

    Xia, J.; Yuan, W.

    2015-12-01

    The allocation of photosynthate among the plant components (e.g., leaves, stems, and roots) plays an important role in regulating plant growth, competition, and terrestrial carbon cycle. However, the carbon allocation process is still a weak part in the earth system models (ESMs). In this study, the Integrated BIosphere Simulator (IBIS) model coupled with a dynamic carbon allocation model (IBISAL) is used to explore the impact of carbon allocation on the terrestrial carbon cycle. This dynamic carbon allocation model suggests that plants should allocate the largest part of carbon to the plant components which need to capture the most limiting resources, such as light, water and nitrogen. In comparison to the results of original IBIS model using fixed allocation ratios, the net ecosystem productivity, global biomass and soil organic carbon simulated by IBISAL model decreased by13.4% , 9.9% and 20.8%, respectively . The dynamic allocation scheme tends to benefit roots allocation. Because roots had short turnover times, high roots allocation led to the decreases of global carbon sink and carbon pool sizes. The observations showed that the carbon allocation ratios changed with temperature and precipitation. The dynamic carbon allocation model could reproduce this phenomenon correctly. The results show that the dynamic carbon allocation ratios of boreal evergreen forests and C3 grasses are consistent well with the observations. However, the IBISAL, and another three ESMs (i.e., CESM1-BGC, IPSL-CM5A-MR and NorESM1-ME models) adopting dynamic allocation scheme overestimated the stems allocation of tropical forests. This study shows the substantial influences of carbon allocation on the carbon sink and carbon pool sizes. Therefore, improving estimations of carbon allocation by ESMs are an important and effective path to reduce uncertainties in the global carbon cycle simulation and climate change prediction.

  4. Multi-Scale Characean Experimental System: From Electrophysiology of Membrane Transporters to Cell-to-Cell Connectivity, Cytoplasmic Streaming and Auxin Metabolism.

    PubMed

    Beilby, Mary J

    2016-01-01

    The morphology of characean algae could be mistaken for a higher plant: stem-like axes with leaf-like branchlets anchored in the soil by root-like rhizoids. However, all of these structures are made up of giant multinucleate cells separated by multicellular nodal complexes. The excised internodal cells survive long enough for the nodes to give rise to new thallus. The size of the internodes and their thick cytoplasmic layer minimize impalement injury and allow specific micro-electrode placement. The cell structure can be manipulated by centrifugation, perfusion of cell contents or creation of cytoplasmic droplets, allowing access to both vacuolar and cytoplasmic compartments and both sides of the cell membranes. Thousands of electrical measurements on intact or altered cells and cytoplasmic droplets laid down basis to modern plant electrophysiology. Furthermore, the giant internodal cells and whole thalli facilitate research into many other plant properties. As nutrients have to be transported from rhizoids to growing parts of the thallus and hormonal signals need to pass from cell to cell, Characeae possess very fast cytoplasmic streaming. The mechanism was resolved in the characean model. Plasmodesmata between the internodal cells and nodal complexes facilitate transport of ions, nutrients and photosynthates across the nodes. The internal structure was found to be similar to those of higher plants. Recent experiments suggest a strong circadian influence on metabolic pathways producing indole-3-acetic acid (IAA) and serotonin/melatonin. The review will discuss the impact of the characean models arising from fragments of cells, single cells, cell-to-cell transport or whole thalli on understanding of plant evolution and physiology. PMID:27504112

  5. Evidence for a Role for NAD(P)H Dehydrogenase in Concentration of CO2 in the Bundle Sheath Cell of Zea mays1[OPEN

    PubMed Central

    Schultes, Neil P.; McHale, Neil A.; Zelitch, Israel

    2016-01-01

    Prior studies with Nicotiana and Arabidopsis described failed assembly of the chloroplastic NDH [NAD(P)H dehydrogenase] supercomplex by serial mutation of several subunit genes. We examined the properties of Zea mays leaves containing Mu and Ds insertions into nuclear gene exons encoding the critical o- and n-subunits of NDH, respectively. In vivo reduction of plastoquinone in the dark was sharply diminished in maize homozygous mutant compared to normal leaves but not to the extreme degree observed for the corresponding lesions in Arabidopsis. The net carbon assimilation rate (A) at high irradiance and saturating CO2 levels was reduced by one-half due to NDH mutation in maize although no genotypic effect was evident at very low CO2 levels. Simultaneous assessment of chlorophyll fluorescence and A in maize at low (2% by volume) and high (21%) O2 levels indicated the presence of a small, yet detectable, O2-dependent component of total linear photosynthetic electron transport in 21% O2. This O2-dependent component decreased with increasing CO2 level indicative of photorespiration. Photorespiration was generally elevated in maize mutant compared to normal leaves. Quantification of the proportion of total electron transport supporting photorespiration enabled estimation of the bundle sheath cell CO2 concentration (Cb) using a simple kinetic model of ribulose bisphosphate carboxylase/oxygenase function. The A versus Cb relationships overlapped for normal and mutant lines consistent with occurrence of strictly CO2-limited photosynthesis in the mutant bundle sheath cell. The results are discussed in terms of a previously reported CO2 concentration model [Laisk A, Edwards GE (2000) Photosynth Res 66: 199–224]. PMID:27002061

  6. Evaluating the Community Land Model in a pine stand with shading manipulations and 13CO2 labeling

    NASA Astrophysics Data System (ADS)

    Mao, J.; Ricciuto, D. M.; Thornton, P. E.; Warren, J. M.; King, A. W.; Shi, X.; Iversen, C. M.; Norby, R. J.

    2016-02-01

    Carbon allocation and flow through ecosystems regulates land surface-atmosphere CO2 exchange and thus is a key, albeit uncertain, component of mechanistic models. The Partitioning in Trees and Soil (PiTS) experiment-model project tracked carbon allocation through a young Pinus taeda stand following pulse labeling with 13CO2 and two levels of shading. The field component of this project provided process-oriented data that were used to evaluate terrestrial biosphere model simulations of rapid shifts in carbon allocation and hydrological dynamics under varying environmental conditions. Here we tested the performance of the Community Land Model version 4 (CLM4) in capturing short-term carbon and water dynamics in relation to manipulative shading treatments and the timing and magnitude of carbon fluxes through various compartments of the ecosystem. When calibrated with pretreatment observations, CLM4 was capable of closely simulating stand-level biomass, transpiration, leaf-level photosynthesis, and pre-labeling 13C values. Over the 3-week treatment period, CLM4 generally reproduced the impacts of shading on soil moisture changes, relative change in stem carbon, and soil CO2 efflux rate. Transpiration under moderate shading was also simulated well by the model, but even with optimization we were not able to simulate the high levels of transpiration observed in the heavy shading treatment, suggesting that the Ball-Berry conductance model is inadequate for these conditions. The calibrated version of CLM4 gave reasonable estimates of label concentration in phloem and in soil surface CO2 after 3 weeks of shade treatment, but it lacks the mechanisms needed to track the labeling pulse through plant tissues on shorter timescales. We developed a conceptual model for photosynthate transport based on the experimental observations, and we discussed conditions under which the hypothesized mechanisms could have an important influence on model behavior in larger-scale applications

  7. Stem tilting in the inter-tropical cactus Echinocactus platyacanthus: an adaptive solution to the trade-off between radiation acquisition and temperature control.

    PubMed

    Herce, M F; Martorell, C; Alonso-Fernandez, C; Boullosa, L F V V; Meave, J A

    2014-05-01

    While plants require radiation for photosynthesis, radiation in warm deserts can have detrimental effects from high temperatures. This dilemma may be solved through plant morphological attributes. In cold deserts, stem tilting keeps reproductive organs warm by increasing radiation interception at the cost of decreased annual light interception. Conversely, little is known about stem tilting in warm deserts. We hypothesised that stem tilting in Echinocactus platyacanthus prevents high temperatures near the apex, where reproduction occurs. The study was conducted in the warm, inter-tropical portion of the Chihuahuan Desert, Mexico. We found that cacti preferentially tilted towards the south, which reduced temperatures of reproductive organs during the hot season, but increased total annual near-apex PAR interception. Tilting also maximised reproduction, a likely consequence of temperature control but perhaps also of the difficulty in translocating photosynthates in cacti; therefore, annual energy acquisition near floral meristems may be largely allocated to reproduction. Unlike plants of higher latitudes, in inter-tropical deserts sunlight at noon comes either from the north or the south, depending on the season, and thus stem tilting may more strongly affect total annual radiation received in different portions of the stem. Inter-tropical cacti can synchronise reproduction with irradiance peaks if flowering occurs in a specific (north or south) portion of the stem; also, they effectively solve the conflict between maximising annual PAR interception and minimising temperature at the hottest time of day. Notably, the two inter-tropical cacti in which stem tilting has been studied successfully solve this conflict. PMID:23992581

  8. [Quantifying rice (Oryza sativa L.) photo-assimilated carbon input into soil organic carbon pools following continuous 14C labeling].

    PubMed

    Nie, San-An; Zhou, Ping; Ge, Ti-Da; Tong, Cheng-Li; Xiao, He-Ai; Wu, Jin-Shui; Zhang, Yang-Zhu

    2012-04-01

    The microcosm experiment was carried out to quantify the input and distribution of photo-assimilated C into soil C pools by using a 14C continuous labeling technique. Destructive samplings of rice (Oryza sativa) were conducted after labeling for 80 days. The allocation of 14C-labeled photosynthates in plants and soil C pools such as dissolved organic C (DOC) and microbial biomass C (MBC) in rice-planted soil were examined over the 14C labeling span. The amounts of rice shoot and root biomass C was ranged from 1.86 to 5.60 g x pot(-1), 0.46 to 0.78 g x pot(-1) in different tested paddy soils after labeling for 80 days, respectively. The amount of 14C in the soil organic C (14C-SOC) was also dependent on the soils, ranged from 114.3 to 348.2 mg x kg(-1), accounting for 5.09% to 6.62% of the rice biomass 14C, respectively. The amounts of 14C in the dissolved organic C (14C-DOC) and in the microbial biomass C(14C-MBC), as proportions of 14C-SOC, were 2.21%-3.54% and 9.72% -17.2%, respectively. The 14C-DOC, 14C-MBC, and 14C-SOC as proportions of total DOC, MBC, and SOC, respectively, were 6.72% -14.64%, 1.70% -7.67%, and 0.73% -1.99%, respectively. Moreover, the distribution and transformation of root-derived C had a greater influence on the dynamics of DOC and MBC than on the dynamics of SOC. Further studies are required to ascertain the functional significance of soil microorganisms (such as C-sequestering bacteria and photosynthetic bacteria) in the paddy system. PMID:22720588

  9. SEORious business: structural proteins in sieve tubes and their involvement in sieve element occlusion.

    PubMed

    Knoblauch, Michael; Froelich, Daniel R; Pickard, William F; Peters, Winfried S

    2014-04-01

    The phloem provides a network of sieve tubes for long-distance translocation of photosynthates. For over a century, structural proteins in sieve tubes have presented a conundrum since they presumably increase the hydraulic resistance of the tubes while no potential function other than sieve tube or wound sealing in the case of injury has been suggested. Here we summarize and critically evaluate current speculations regarding the roles of these proteins. Our understanding suffers from the suggestive power of images; what looks like a sieve tube plug on micrographs may not actually impede translocation very much. Recent reports of an involvement of SEOR (sieve element occlusion-related) proteins, a class of P-proteins, in the sealing of injured sieve tubes are inconclusive; various lines of evidence suggest that, in neither intact nor injured plants, are SEORs determinative of translocation stoppage. Similarly, the popular notion that P-proteins serve in the defence against phloem sap-feeding insects is unsupported by empirical facts; it is conceivable that in functional sieve tubes, aphids actually could benefit from inducing a plug. The idea that rising cytosolic Ca(2+) generally triggers sieve tube blockage by P-proteins appears widely accepted, despite lacking experimental support. Even in forisomes, P-protein assemblages restricted to one single plant family and the only Ca(2+)-responsive P-proteins known, the available evidence does not unequivocally suggest that plug formation is the cause rather than a consequence of translocation stoppage. We conclude that the physiological roles of structural P-proteins remain elusive, and that in vivo studies of their dynamics in continuous sieve tube networks combined with flow velocity measurements will be required to (hopefully) resolve this scientific roadblock. PMID:24591057

  10. Regulation of Phosphoenolpyruvate Carboxylase Phosphorylation by Metabolites and Abscisic Acid during the Development and Germination of Barley Seeds1[C][W

    PubMed Central

    Feria, Ana-Belén; Alvarez, Rosario; Cochereau, Ludivine; Vidal, Jean; García-Mauriño, Sofía; Echevarría, Cristina

    2008-01-01

    During barley (Hordeum vulgare) seed development, phosphoenolpyruvate carboxylase (PEPC) activity increased and PEPC-specific antibodies revealed housekeeping (103-kD) and inducible (108-kD) subunits. Bacterial-type PEPC fragments were immunologically detected in denatured protein extracts from dry and imbibed conditions; however, on nondenaturing gels, the activity of the recently reported octameric PEPC (in castor [Ricinus communis] oil seeds) was not detected. The phosphorylation state of the PEPC, as judged by l-malate 50% inhibition of initial activity values, phosphoprotein chromatography, and immunodetection of the phosphorylated N terminus, was found to be high between 8 and 18 d postanthesis (DPA) and during imbibition. In contrast, the enzyme appeared to be in a low phosphorylation state from 20 DPA up to dry seed. The time course of 32/36-kD, Ca2+-independent PEPC kinase activity exhibited a substantial increase after 30 DPA that did not coincide with the PEPC phosphorylation profile. This kinase was found to be inhibited by l-malate and not by putative protein inhibitors, and the PEPC phosphorylation status correlated with high glucose-6-phosphate to malate ratios, thereby suggesting an in vivo metabolic control of the kinase. PEPC phosphorylation was also regulated by photosynthate supply at 11 DPA. In addition, when fed exogenously to imbibing seeds, abscisic acid significantly increased PEPC kinase activity. This was further enhanced by the cytosolic protein synthesis inhibitor cycloheximide but blocked by protease inhibitors, thereby suggesting that the phytohormone acts on the stability of the kinase. We propose that a similar abscisic acid-dependent effect may contribute to produce the increase in PEPC kinase activity during desiccation stages. PMID:18753284

  11. The ectomycorrhizal fungus Paxillus involutus converts organic matter in plant litter using a trimmed brown-rot mechanism involving Fenton chemistry.

    PubMed

    Rineau, Francois; Roth, Doris; Shah, Firoz; Smits, Mark; Johansson, Tomas; Canbäck, Björn; Olsen, Peter Bjarke; Persson, Per; Grell, Morten Nedergaard; Lindquist, Erika; Grigoriev, Igor V; Lange, Lene; Tunlid, Anders

    2012-06-01

    Soils in boreal forests contain large stocks of carbon. Plants are the main source of this carbon through tissue residues and root exudates. A major part of the exudates are allocated to symbiotic ectomycorrhizal fungi. In return, the plant receives nutrients, in particular nitrogen from the mycorrhizal fungi. To capture the nitrogen, the fungi must at least partly disrupt the recalcitrant organic matter-protein complexes within which the nitrogen is embedded. This disruption process is poorly characterized. We used spectroscopic analyses and transcriptome profiling to examine the mechanism by which the ectomycorrhizal fungus Paxillus involutus degrades organic matter when acquiring nitrogen from plant litter. The fungus partially degraded polysaccharides and modified the structure of polyphenols. The observed chemical changes were consistent with a hydroxyl radical attack, involving Fenton chemistry similar to that of brown-rot fungi. The set of enzymes expressed by Pa. involutus during the degradation of the organic matter was similar to the set of enzymes involved in the oxidative degradation of wood by brown-rot fungi. However, Pa. involutus lacked transcripts encoding extracellular enzymes needed for metabolizing the released carbon. The saprotrophic activity has been reduced to a radical-based biodegradation system that can efficiently disrupt the organic matter-protein complexes and thereby mobilize the entrapped nutrients. We suggest that the released carbon then becomes available for further degradation and assimilation by commensal microbes, and that these activities have been lost in ectomycorrhizal fungi as an adaptation to symbiotic growth on host photosynthate. The interdependence of ectomycorrhizal symbionts and saprophytic microbes would provide a key link in the turnover of nutrients and carbon in forest ecosystems. PMID:22469289

  12. Nonphotosynthetic CO2 Fixation by Alfalfa (Medicago sativa L.) Roots and Nodules 1

    PubMed Central

    Anderson, Michael P.; Heichel, Gary H.; Vance, Carroll P.

    1987-01-01

    The dependence of alfalfa (Medicago sativa L.) root and nodule nonphotosynthetic CO2 fixation on the supply of currently produced photosynthate and nodule nitrogenase activity was examined at various times after phloem-girdling and exposure of nodules to Ar:O2. Phloemgirdling was effected 20 hours and exposure to Ar:O2 was effected 2 to 3 hours before initiation of experiments. Nodule and root CO2 fixation rates of phloem-girdled plants were reduced to 38 and 50%, respectively, of those of control plants. Exposure to Ar:O2 decreased nodule CO2 fixation rates to 45%, respiration rates to 55%, and nitrogenase activities to 51% of those of the controls. The products of nodule CO2 fixation were exported through the xylem to the shoot mainly as amino acids within 30 to 60 minutes after exposure to 14CO2. In contrast to nodules, roots exported very little radioactivity, and most of the 14C was exported as organic acids. The nonphotosynthetic CO2 fixation rate of roots and nodules averaged 26% of the gross respiration rate, i.e. the sum of net respiration and nonphotosynthetic CO2 assimilation. Nodules fixed CO2 at a rate 5.6 times that of roots, but since nodules comprised a small portion of root system mass, roots accounted for 76% of the nodulated root system CO2 fixation. The results of this study showed that exposure of nodules to Ar:O2 reduced nodule-specific respiration and nitrogenase activity by similar amounts, and that phloem-girdling significantly reduced nodule CO2 fixation, nitrogenase activity, nodule-specific respiration, and transport of 14C photoassimilate to nodules. These results indicate that nodule CO2 fixation in alfalfa is associated with N assimilation. PMID:16665671

  13. Short-term carbon cycling responses of a mature eucalypt woodland to gradual stepwise enrichment of atmospheric CO2 concentration.

    PubMed

    Drake, John E; Macdonald, Catriona A; Tjoelker, Mark G; Crous, Kristine Y; Gimeno, Teresa E; Singh, Brajesh K; Reich, Peter B; Anderson, Ian C; Ellsworth, David S

    2016-01-01

    Projections of future climate are highly sensitive to uncertainties regarding carbon (C) uptake and storage by terrestrial ecosystems. The Eucalyptus Free-Air CO2 Enrichment (EucFACE) experiment was established to study the effects of elevated atmospheric CO2 concentrations (eCO2 ) on a native mature eucalypt woodland with low fertility soils in southeast Australia. In contrast to other FACE experiments, the concentration of CO2 at EucFACE was increased gradually in steps above ambient (+0, 30, 60, 90, 120, and 150 ppm CO2 above ambient of ~400 ppm), with each step lasting approximately 5 weeks. This provided a unique opportunity to study the short-term (weeks to months) response of C cycle flux components to eCO2 across a range of CO2 concentrations in an intact ecosystem. Soil CO2 efflux (i.e., soil respiration or Rsoil ) increased in response to initial enrichment (e.g., +30 and +60 ppm CO2 ) but did not continue to increase as the CO2 enrichment was stepped up to higher concentrations. Light-saturated photosynthesis of canopy leaves (Asat ) also showed similar stimulation by elevated CO2 at +60 ppm as at +150 ppm CO2 . The lack of significant effects of eCO2 on soil moisture, microbial biomass, or activity suggests that the increase in Rsoil likely reflected increased root and rhizosphere respiration rather than increased microbial decomposition of soil organic matter. This rapid increase in Rsoil suggests that under eCO2, additional photosynthate was produced, transported belowground, and respired. The consequences of this increased belowground activity and whether it is sustained through time in mature ecosystems under eCO2 are a priority for future research. PMID:26426394

  14. Multi-Scale Characean Experimental System: From Electrophysiology of Membrane Transporters to Cell-to-Cell Connectivity, Cytoplasmic Streaming and Auxin Metabolism

    PubMed Central

    Beilby, Mary J.

    2016-01-01

    The morphology of characean algae could be mistaken for a higher plant: stem-like axes with leaf-like branchlets anchored in the soil by root-like rhizoids. However, all of these structures are made up of giant multinucleate cells separated by multicellular nodal complexes. The excised internodal cells survive long enough for the nodes to give rise to new thallus. The size of the internodes and their thick cytoplasmic layer minimize impalement injury and allow specific micro-electrode placement. The cell structure can be manipulated by centrifugation, perfusion of cell contents or creation of cytoplasmic droplets, allowing access to both vacuolar and cytoplasmic compartments and both sides of the cell membranes. Thousands of electrical measurements on intact or altered cells and cytoplasmic droplets laid down basis to modern plant electrophysiology. Furthermore, the giant internodal cells and whole thalli facilitate research into many other plant properties. As nutrients have to be transported from rhizoids to growing parts of the thallus and hormonal signals need to pass from cell to cell, Characeae possess very fast cytoplasmic streaming. The mechanism was resolved in the characean model. Plasmodesmata between the internodal cells and nodal complexes facilitate transport of ions, nutrients and photosynthates across the nodes. The internal structure was found to be similar to those of higher plants. Recent experiments suggest a strong circadian influence on metabolic pathways producing indole-3-acetic acid (IAA) and serotonin/melatonin. The review will discuss the impact of the characean models arising from fragments of cells, single cells, cell-to-cell transport or whole thalli on understanding of plant evolution and physiology. PMID:27504112

  15. Mechanism of energy transfer from carotenoids to bacteriochlorophyll : light-harvesting by carotenoids having different extents of {pi}-electron conjugation incorporated into the B850 antenna complex from the carotenoidless bacterium Rhodobacter sphaeroides R-26.1.

    SciTech Connect

    Desamero, R. Z. B.; Chynwat, V.; van der Hoef, I.; Jansen, F. J.; Lugtenburg, J.; Gosztola, D.; Wasielewski, M. R.; Cua, A.; Bocian, D. F.; Frank, H. A.; Univ. of Connecticut; Leiden Univ.; Northwestern Univ.; Univ. of California; Univ. of connecticut

    1998-10-15

    Spheroidene and a series of spheroidene analogues with extents of p-electron conjugation ranging from 7 to 13 carbon-carbon double bonds were incorporated into the B850 light-harvesting complex of Rhodobacter sphaeroides R-26.1. The structures and spectroscopic properties of the carotenoids and the dynamics of energy transfer from the carotenoid to bacteriochlorophyll (BChl) in the B850 complex were studied by using steady-state absorption, fluorescence, fluorescence excitation, resonance Raman, and time-resolved absorption spectroscopy. The spheroidene analogues used in this study were 5',6'-dihydro-7',8'-didehydrospheroidene, 7',8'-didehydrospheroidene, and 1',2'-dihydro-3',4',7',8'-tetradehydrospheroidene. These data, taken together with results from 3,4,7,8-tetrahydrospheroidene, 3,4,5,6-tetrahydrospheroidene, 3,4-dihydrospheroidene, and spheroidene already published (Frank, H. A.; Farhoosh, R.; Aldema, M. L.; DeCoster, B.; Christensen, R. L.; Gebhard, R.; Lugtenburg, J. Photochem. Photobiol. 1993, 57, 49. Farhoosh, R.; Chynwat, V.; Gebhard, R.; Lugtenburg, J.; Frank, H. A. Photosynth. Res. 1994, 42, 157), provide a systematic series of molecules for understanding the molecular features that determine the mechanism of energy transfer from carotenoids to BChl in photosynthetic bacterial light-harvesting complexes. The data support the hypothesis that only carotenoids having 10 or less carbon-carbon double bonds transfer energy via their 21Ag (S1) states to BChl to any significant degree. Energy transfer via the 11Bu (S2) state of the carotenoid becomes more important than the S1 route as the number of conjugated carbon-carbon double bonds increases. The results also suggest that the S2 state associated with the Qx transition of the B850 BChl is the most likely acceptor state for energy transfer originating from both the 2{sup 1}A{sub g} (S{sub 1}) and 1{sup 1}B{sub u} (S{sub 2}) states of all carotenoids.

  16. Not just who, but how many: the importance of partner abundance in reef coral symbioses

    PubMed Central

    Cunning, Ross; Baker, Andrew C.

    2014-01-01

    The performance and function of reef corals depends on the genetic identity of their symbiotic algal partners, with some symbionts providing greater benefits (e.g., photosynthate, thermotolerance) than others. However, these interaction outcomes may also depend on partner abundance, with differences in the total number of symbionts changing the net benefit to the coral host, depending on the particular environmental conditions. We suggest that symbiont abundance is a fundamental aspect of the dynamic interface between reef corals and the abiotic environment that ultimately determines the benefits, costs, and functional responses of these symbioses. This density-dependent framework suggests that corals may regulate the size of their symbiont pool to match microhabitat-specific optima, which may contribute to the high spatiotemporal variability in symbiont abundance observed within and among colonies and reefs. Differences in symbiont standing stock may subsequently explain variation in energetics, growth, reproduction, and stress susceptibility, and may mediate the impacts of environmental change on these outcomes. However, the importance of symbiont abundance has received relatively little recognition, possibly because commonly-used metrics based on surface area (e.g., symbiont cells cm-2) may be only weakly linked to biological phenomena and are difficult to compare across studies. We suggest that normalizing symbionts to biological host parameters, such as units of protein or numbers of host cells, will more clearly elucidate the functional role of symbiont abundance in reef coral symbioses. In this article, we generate testable hypotheses regarding the importance of symbiont abundance by first discussing different metrics and their potential links to symbiosis performance and breakdown, and then describing how natural variability and dynamics of symbiont communities may help explain ecological patterns on coral reefs and predict responses to environmental change

  17. Revisiting "You are what you eat, +1‰": Bacterial Trophic Structure and the Sedimentary Record

    NASA Astrophysics Data System (ADS)

    Pearson, A.; Tang, T.; Mohr, W.; Sattin, S.

    2015-12-01

    "You are what you eat, +1‰" is a central principle of carbon stable isotope (δ13C) distributions and is widely applied to understand the structure and ordering of macrobiotic ecosystems. Although based on observations from multicellular organisms that are able to ingest "food", this idea also has been applied to Precambrian ecosystems dominated by unicellular, microbial life, with the suggestion that such systems could sustain ordered trophic structures observable in their isotopes. However, using a new approach to community profiling known as protein stable isotope fingerprinting (P-SIF), we find that the carbon isotope ratios of whole proteins separated from environmental samples show differences only between metabolically-distinct autotrophs; heterotrophs are not 13C-enriched. In parallel, a survey of the relative distribution of 13C between biochemical classes - specifically acetogenic lipids, isoprenoid lipids, amino acids, and nucleic acids/sugars - across a variety of bacterial species appears to be a function of the main carbon metabolite, not an indicator of heterotrophy vs. autotrophy. Indeed, autotrophy, heterotrophy, and mixotrophy all are indistinguishable when the primary food source is fresh photosynthate, i.e., sugar. Significant assimilation of acetate is diagnosed by acetogenic lipids that are relatively 13C-enriched vs. isoprenoid lipids. Mixed-substrate heterotrophy, in contrast, satisfies the classic "…+1‰" rule for bulk biomass, yet simultaneously it collapses the biochemical patterns of 13C almost completely. Together these observations point to a paradigm shift for understanding the preservation of bulk organic and lipid δ13C signatures in the rock record, suggesting that patterns of δ13Corg must primarily reflect changing carbon inputs, not the extent or intensity of heterotrophy.

  18. Spatial patterning and floral synchrony among trillium populations with contrasting histories of herbivory

    PubMed Central

    Jenkins, Michael A.; Poznanovic, Aaron J.

    2015-01-01

    We investigated the spatial patterning and floral synchrony within and among populations of a non-clonal, forest understory herb, Trillium catesbaei. Two populations of T. catesbaei within Great Smoky Mountains National Park were monitored for five years: Cades Cove (high deer abundance) and Whiteoak Sink (low deer abundance). All individuals within each population were mapped during year one and five. Only flowering and single-leaf juveniles were mapped during intervening years. Greater distances between flowering plants (plants currently in flower) and substantially lower population densities and smaller patch sizes were observed at Cades Cove versus Whiteoak Sink. However, with the exception of flowering plants, contrasting histories of herbivory did not appear to fundamentally alter the spatial patterning of the T. catesbaei population at Cades Cove, an area with a long and well-documented history of deer overabundance. Regardless of browse history, non-flowering life stages were significantly clustered at all spatial scales examined. Flowering plants were clustered in all years at Whiteoak Sink, but more often randomly distributed at Cades Cove, possibly as a result of their lower abundance. Between years, however, there was a positive spatial association between the locations of flowering plants at both sites. Flowering rate was synchronous between sites, but lagged a year behind favorable spring growing conditions, which likely allowed plants to allocate photosynthate from a favorable year towards flowering the subsequent year. Collectively, our results suggest that chronically high levels of herbivory may be associated with spatial patterning of flowering within populations of a non-clonal plant. They also highlight the persistence of underlying spatial patterns, as evidenced by high levels of spatial clustering among non-flowering individuals, and the pervasive, although muted in a population subjected to chronic herbivory, influence of precipitation and

  19. Autotrophy of green non-sulphur bacteria in hot spring microbial mats: biological explanations for isotopically heavy organic carbon in the geological record.

    PubMed

    van der Meer, M T; Schouten, S; de Leeuw, J W; Ward, D M

    2000-08-01

    Inferences about the evidence of life recorded in organic compounds within the Earth's ancient rocks have depended on 13C contents low enough to be characteristic of biological debris produced by the well-known CO2 fixation pathway, the Calvin cycle. 'Atypically' high values have been attributed to isotopic alteration of sedimentary organic carbon by thermal metamorphism. We examined the possibility that organic carbon characterized by a relatively high 13C content could have arisen biologically from recently discovered autotrophic pathways. We focused on the green non-sulphur bacterium Chloroflexus aurantiacus that uses the 3-hydroxypropionate pathway for inorganic carbon fixation and is geologically significant as it forms modern mat communities analogous to stromatolites. Organic matter in mats constructed by Chloroflexus spp. alone had relatively high 13C contents (-14.9%) and lipids diagnostic of Chloroflexus that were also isotopically heavy (-8.9% to -18.5%). Organic matter in mats constructed by Chloroflexus in conjunction with cyanobacteria had a more typical Calvin cycle signature (-23.5%). However, lipids diagnostic of Chloroflexus were isotopically enriched (-15.1% to -24.1%) relative to lipids typical of cyanobacteria (-33.9% to -36.3%). This suggests that, in mats formed by both cyanobacteria and Chloroflexus, autotrophy must have a greater effect on Chloroflexus carbon metabolism than the photoheterotrophic consumption of cyanobacterial photosynthate. Chloroflexus cell components were also selectively preserved. Hence, Chloroflexus autotrophy and selective preservation of its products constitute one purely biological mechanism by which isotopically heavy organic carbon could have been introduced into important Precambrian geological features. PMID:11234931

  20. Light, temperature and nutrients as factors in photosynthetic adjustment to elevated carbon dioxide

    SciTech Connect

    Bunce, J.; Lee, D. )

    1991-05-01

    It has been noted many times that the short-term stimulation of photosynthesis by elevated carbon dioxide usually observed in C3 plants may not persist in the long-term. Experiments were designed to test the hypotheses that photosynthetic adjustment to elevated carbon dioxide is due to (a) feedback inhibition resulting from excess photosynthate production relative to use, and (b) nutrient deficiency resulting from more rapid growth. Soybeans and sugarbeets were grown in controlled environment chambers at 350 and 700 ppm carbon dioxide, at two temperatures, two levels of photosynthetically active radiation, and with three nutrient regimes in a factorial design. Net carbon dioxide uptake rates of individual leaves from all growth conditions were measured at both 350 and 700 ppm carbon dioxide to assay photosynthetic adjustment to the elevated carbon dioxide. Growth at elevated carbon dioxide reduced rates of photosynthesis measured at standard carbon dioxide levels in both species. Photosynthetic rates measured at 350 ppm were lower on average by 33% in sugarbeet and 23% in soybean after growth at elevated carbon dioxide. Photosynthetic adjustment to elevated carbon dioxide was not greater after growth at 1.0 than 0.5 mmol m{sup {minus}2}s{sup {minus}1} PPFD, was not greater at 20 than 25C growth temperature, and could not be overcome by high rates of nutrient application. These results do not support either the feedback inhibition nor nutrient deficiency hypotheses of photosynthetic adjustment to elevated carbon dioxide. In soybeans, complete photosynthetic adjustment could be induced by a single night at elevated carbon dioxide.

  1. Potassium in agriculture--status and perspectives.

    PubMed

    Zörb, Christian; Senbayram, Mehmet; Peiter, Edgar

    2014-05-15

    In this review we summarize factors determining the plant availability of soil potassium (K), the role of K in crop yield formation and product quality, and the dependence of crop stress resistance on K nutrition. Average soil reserves of K are generally large, but most of it is not plant-available. Therefore, crops need to be supplied with soluble K fertilizers, the demand of which is expected to increase significantly, particularly in developing regions of the world. Recent investigations have shown that organic exudates of some bacteria and plant roots play a key role in releasing otherwise unavailable K from K-bearing minerals. Thus, breeding for genotypes that have improved mechanisms to gain access to this fixed K will contribute toward more sustainable agriculture, particularly in cropping systems that do not have access to fertilizer K. In K-deficient crops, the supply of sink organs with photosynthates is impaired, and sugars accumulate in source leaves. This not only affects yield formation, but also quality parameters, for example in wheat, potato and grape. As K has beneficial effects on human health, its concentration in the harvest product is a quality parameter in itself. Owing to its fundamental roles in turgor generation, primary metabolism, and long-distance transport, K plays a prominent role in crop resistance to drought, salinity, high light, or cold as well as resistance to pests and pathogens. Despite the abundance of vital roles of K in crop production, an improvement of K uptake and use efficiency has not been a major focus of conventional or transgenic breeding in the past. In addition, current soil analysis methods for K are insufficient for some common soils, posing the risk of imbalanced fertilization. A stronger prioritization of these areas of research is needed to counter declines in soil fertility and to improve food security. PMID:24140002

  2. Zooxanthellae harvested by ciliates associated with brown band syndrome of corals remain photosynthetically competent.

    PubMed

    Ulstrup, Karin E; Kühl, Michael; Bourne, David G

    2007-03-01

    Brown band syndrome is a new coral affliction characterized by a local accumulation of yet-unidentified ciliates migrating as a band along the branches of coral colonies. In the current study, morphologically intact zooxanthellae (= Symbiodinium) were observed in great numbers inside the ciliates (>50 dinoflagellates per ciliate). Microscale oxygen measurements and variable chlorophyll a fluorescence analysis along with microscopic observations demonstrated that zooxanthellae within the ciliates are photosynthetically competent and do not become compromised during the progression of the brown band zone. Zooxanthellae showed similar trends in light acclimation in a comparison of rapid light curve and steady-state light curve measures of variable chlorophyll a fluorescence. Extended light exposure of steady-state light curves resulted in higher quantum yields of photosystem II. The brown band tissue exhibited higher photosynthetically active radiation absorptivity, indicating more efficient light absorption due to a higher density of zooxanthellae in the ciliate-dominated zone. This caused relatively higher gross photosynthesis rates in the zone with zooxanthella-containing ciliates compared to healthy coral tissue. The observation of photosynthetically active intracellular zooxanthellae in the ciliates suggests that the latter can benefit from photosynthates produced by ingested zooxanthellae and from photosynthetic oxygen production that alleviates diffusion limitation of oxic respiration in the densely populated brown band tissue. It remains to be shown whether the zooxanthellae form a stable symbiotic association with the ciliate or are engulfed incidentally during grazing on coral tissue and then maintained as active inside the ciliate for a period before being digested and replaced by new zooxanthellae. PMID:17259357

  3. Stover Composition in Maize and Sorghum Reveals Remarkable Genetic Variation and Plasticity for Carbohydrate Accumulation.

    PubMed

    Sekhon, Rajandeep S; Breitzman, Matthew W; Silva, Renato R; Santoro, Nicholas; Rooney, William L; de Leon, Natalia; Kaeppler, Shawn M

    2016-01-01

    Carbohydrates stored in vegetative organs, particularly stems, of grasses are a very important source of energy. We examined carbohydrate accumulation in adult sorghum and maize hybrids with distinct phenology and different end uses (grain, silage, sucrose or sweetness in stalk juice, and biomass). Remarkable variation was observed for non-structural carbohydrates and structural polysaccharides during three key developmental stages both between and within hybrids developed for distinct end use in both species. At the onset of the reproductive phase (average 65 days after planting, DAP), a wide range for accumulation of non-structural carbohydrates (free glucose and sucrose combined), was observed in internodes of maize (11-24%) and sorghum (7-36%) indicating substantial variation for transient storage of excess photosynthate during periods of low grain or vegetative sink strength. Remobilization of these reserves for supporting grain fill or vegetative growth was evident from lower amounts in maize (8-19%) and sorghum (9-27%) near the end of the reproductive period (average 95 DAP). At physiological maturity of grain hybrids (average 120 DAP), amounts of these carbohydrates were generally unchanged in maize (9-21%) and sorghum (16-27%) suggesting a loss of photosynthetic assimilation due to weakening sink demand. Nonetheless, high amounts of non-structural carbohydrates at maturity even in grain maize and sorghum (15-18%) highlight the potential for developing dual-purpose (grain/stover) crops. For both species, the amounts of structural polysaccharides in the cell wall, measured as monomeric components (glucose and pentose), decreased during grain fill but remained unchanged thereafter with maize biomass possessing slightly higher amounts than sorghum. Availability of carbohydrates in maize and sorghum highlights the potential for developing energy-rich dedicated biofuel or dual-purpose (grain/stover) crops. PMID:27375668

  4. Evidence for a Role for NAD(P)H Dehydrogenase in Concentration of CO2 in the Bundle Sheath Cell of Zea mays.

    PubMed

    Peterson, Richard B; Schultes, Neil P; McHale, Neil A; Zelitch, Israel

    2016-05-01

    Prior studies with Nicotiana and Arabidopsis described failed assembly of the chloroplastic NDH [NAD(P)H dehydrogenase] supercomplex by serial mutation of several subunit genes. We examined the properties of Zea mays leaves containing Mu and Ds insertions into nuclear gene exons encoding the critical o- and n-subunits of NDH, respectively. In vivo reduction of plastoquinone in the dark was sharply diminished in maize homozygous mutant compared to normal leaves but not to the extreme degree observed for the corresponding lesions in Arabidopsis. The net carbon assimilation rate (A) at high irradiance and saturating CO2 levels was reduced by one-half due to NDH mutation in maize although no genotypic effect was evident at very low CO2 levels. Simultaneous assessment of chlorophyll fluorescence and A in maize at low (2% by volume) and high (21%) O2 levels indicated the presence of a small, yet detectable, O2-dependent component of total linear photosynthetic electron transport in 21% O2 This O2-dependent component decreased with increasing CO2 level indicative of photorespiration. Photorespiration was generally elevated in maize mutant compared to normal leaves. Quantification of the proportion of total electron transport supporting photorespiration enabled estimation of the bundle sheath cell CO2 concentration (Cb) using a simple kinetic model of ribulose bisphosphate carboxylase/oxygenase function. The A versus Cb relationships overlapped for normal and mutant lines consistent with occurrence of strictly CO2-limited photosynthesis in the mutant bundle sheath cell. The results are discussed in terms of a previously reported CO2 concentration model [Laisk A, Edwards GE (2000) Photosynth Res 66: 199-224]. PMID:27002061

  5. Mineral nutrition and plant responses to elevated levels of atmospheric CO{sub 2}

    SciTech Connect

    Ahluwalia, A.

    1996-08-01

    The atmospheric concentration of CO{sub 2}, a radiatively-active ({open_quotes}green-house{close_quotes}) gas, is increasing. This increase is considered a post-industrial phenomenon attributable to increasing rates of fossil fuel combustion and changing land use practices, particularly deforestation. Climate changes resulting from such elevated atmospheric CO{sub 2} levels, in addition to the direct effects of increased CO{sub 2}, are expected to modify the productivity of forests and alter species distributions. Elevated levels of CO{sub 2} have been shown, in some cases, to lead to enhanced growth rates in plants, particularly those with C{sub 3} metabolism - indicating that plant growth is CO{sub 2}-limited in these situations. Since the major process underlying growth is CO{sub 2} assimilation via photosynthesis in leaves, plant growth represents a potential for sequestering atmospheric carbon into biomass, but this potential could be hampered by plant carbon sink size. Carbon sinks are utilization sites for assimilated carbon, enabling carbon assimilation to proceed without potential inhibition from the accumulation of assimilate (photosynthate). Plant growth provides new sinks for assimilated carbon which permits greater uptake of atmospheric carbon dioxide. However, sinks are, on the whole, reduced in size by stress events due to the adverse effects of stress on photosynthetic rates and therefore growth. This document reviews some of the literature on plant responses to increasing levels of atmospheric carbon dioxide and to inadequate nutrient supply rates, and with this background, the potential for nutrient-limited plants to respond to increasing carbon dioxide is addressed. Conclusions from the literature review are then tested experimentally by means of a case study exploring carbon-nitrogen interactions in seedlings of loblolly pine.

  6. Expression of barley SUSIBA2 transcription factor yields high-starch low-methane rice.

    PubMed

    Su, J; Hu, C; Yan, X; Jin, Y; Chen, Z; Guan, Q; Wang, Y; Zhong, D; Jansson, C; Wang, F; Schnürer, A; Sun, C

    2015-07-30

    Atmospheric methane is the second most important greenhouse gas after carbon dioxide, and is responsible for about 20% of the global warming effect since pre-industrial times. Rice paddies are the largest anthropogenic methane source and produce 7-17% of atmospheric methane. Warm waterlogged soil and exuded nutrients from rice roots provide ideal conditions for methanogenesis in paddies with annual methane emissions of 25-100-million tonnes. This scenario will be exacerbated by an expansion in rice cultivation needed to meet the escalating demand for food in the coming decades. There is an urgent need to establish sustainable technologies for increasing rice production while reducing methane fluxes from rice paddies. However, ongoing efforts for methane mitigation in rice paddies are mainly based on farming practices and measures that are difficult to implement. Despite proposed strategies to increase rice productivity and reduce methane emissions, no high-starch low-methane-emission rice has been developed. Here we show that the addition of a single transcription factor gene, barley SUSIBA2 (refs 7, 8), conferred a shift of carbon flux to SUSIBA2 rice, favouring the allocation of photosynthates to aboveground biomass over allocation to roots. The altered allocation resulted in an increased biomass and starch content in the seeds and stems, and suppressed methanogenesis, possibly through a reduction in root exudates. Three-year field trials in China demonstrated that the cultivation of SUSIBA2 rice was associated with a significant reduction in methane emissions and a decrease in rhizospheric methanogen levels. SUSIBA2 rice offers a sustainable means of providing increased starch content for food production while reducing greenhouse gas emissions from rice cultivation. Approaches to increase rice productivity and reduce methane emissions as seen in SUSIBA2 rice may be particularly beneficial in a future climate with rising temperatures resulting in increased

  7. Differential characteristics of photochemical acclimation to cold in two contrasting sweet sorghum hybrids.

    PubMed

    Zegada-Lizarazu, Walter; Fernando Luna, Dario; Monti, Andrea

    2016-08-01

    Sweet sorghum has a photosynthetic system which is highly sensitive to cold stress and hence strongly limits its development in temperate environments; therefore, the identification of key exploitable cold tolerance traits is imperative. From a preliminary field trial, two dissimilar sweet sorghum hybrids (ICSSH31 and Bulldozer), in terms of early vigor and productivity, were selected for a controlled-environment trial aiming at identifying useful traits related to acclimation mechanisms to cold stress. The higher cold tolerance of Bulldozer was partially related to a more efficient photochemical regulation mechanism of the incoming light energy: the higher tolerance of photosystem II (PSII) to photo-inactivation was because of a more effective dissipation capacity of the excess of energy and to a more balanced diversion of the absorbed energy into alternative energy sinks. ICSSH31 increased the dissipation and accumulation of a large amount of xanthophylls, as in Bulldozer, but, at the same time, inactivated the oxygen evolving complex and the re-synthesis of chlorophyll (Chl) a and b, thus, leading to an overproduction of CO2 fixation enzymes after re-warming. In summary, in Bulldozer, the acclimation adjustments of the photosynthetic apparatus occurred through an efficient control of energy transfer toward the reaction centers, and this likely allowed a more successful seedling establishment; ICSSH31, conversely, exhibited a fast re-synthesis of Chl pigments, which appears to divert photosynthates from dry matter accumulation. Such broad acclimation traits may constitute a source for selecting higher genetic gain traits relevant for enlarging the growing season of promising biomass sorghum ideotypes in temperate climates. PMID:26867791

  8. Expression of barley SUSIBA2 transcription factor yields high-starch low-methane rice

    NASA Astrophysics Data System (ADS)

    Su, J.; Hu, C.; Yan, X.; Jin, Y.; Chen, Z.; Guan, Q.; Wang, Y.; Zhong, D.; Jansson, C.; Wang, F.; Schnürer, A.; Sun, C.

    2015-07-01

    Atmospheric methane is the second most important greenhouse gas after carbon dioxide, and is responsible for about 20% of the global warming effect since pre-industrial times. Rice paddies are the largest anthropogenic methane source and produce 7-17% of atmospheric methane. Warm waterlogged soil and exuded nutrients from rice roots provide ideal conditions for methanogenesis in paddies with annual methane emissions of 25-100-million tonnes. This scenario will be exacerbated by an expansion in rice cultivation needed to meet the escalating demand for food in the coming decades. There is an urgent need to establish sustainable technologies for increasing rice production while reducing methane fluxes from rice paddies. However, ongoing efforts for methane mitigation in rice paddies are mainly based on farming practices and measures that are difficult to implement. Despite proposed strategies to increase rice productivity and reduce methane emissions, no high-starch low-methane-emission rice has been developed. Here we show that the addition of a single transcription factor gene, barley SUSIBA2 (refs 7, 8), conferred a shift of carbon flux to SUSIBA2 rice, favouring the allocation of photosynthates to aboveground biomass over allocation to roots. The altered allocation resulted in an increased biomass and starch content in the seeds and stems, and suppressed methanogenesis, possibly through a reduction in root exudates. Three-year field trials in China demonstrated that the cultivation of SUSIBA2 rice was associated with a significant reduction in methane emissions and a decrease in rhizospheric methanogen levels. SUSIBA2 rice offers a sustainable means of providing increased starch content for food production while reducing greenhouse gas emissions from rice cultivation. Approaches to increase rice productivity and reduce methane emissions as seen in SUSIBA2 rice may be particularly beneficial in a future climate with rising temperatures resulting in increased

  9. Warming and Nitrogen Addition Alter Photosynthetic Pigments, Sugars and Nutrients in a Temperate Meadow Ecosystem.

    PubMed

    Zhang, Tao; Yang, Shaobo; Guo, Rui; Guo, Jixun

    2016-01-01

    Global warming and nitrogen (N) deposition have an important influence on terrestrial ecosystems; however, the influence of warming and N deposition on plant photosynthetic products and nutrient cycling in plants is not well understood. We examined the effects of 3 years of warming and N addition on the plant photosynthetic products, foliar chemistry and stoichiometric ratios of two dominant species, i.e., Leymus chinensis and Phragmites communis, in a temperate meadow in northeastern China. Warming significantly increased the chlorophyll content and soluble sugars in L. chinensis but had no impact on the carotenoid and fructose contents. N addition caused a significant increase in the carotenoid and fructose contents. Warming and N addition had little impact on the photosynthetic products of P. communis. Warming caused significant decreases in the N and phosphorus (P) concentrations and significantly increased the carbon (C):P and N:P ratios of L. chinensis, but not the C concentration or the C:N ratio. N addition significantly increased the N concentration, C:P and N:P ratios, but significantly reduced the C:N ratio of L. chinensis. Warming significantly increased P. communis C and P concentrations, and the C:N and C:P ratios, whereas N addition increased the C, N and P concentrations but had no impact on the stoichiometric variables. This study suggests that both warming and N addition have direct impacts on plant photosynthates and elemental stoichiometry, which may play a vital role in plant-mediated biogeochemical cycling in temperate meadow ecosystems. PMID:27171176

  10. How drought severity constrains gross primary production(GPP) and its partitioning among carbon pools in a Quercus ilex coppice?

    NASA Astrophysics Data System (ADS)

    Rambal, S.; Lempereur, M.; Limousin, J. M.; Martin-StPaul, N. K.; Ourcival, J. M.; Rodríguez-Calcerrada, J.

    2014-12-01

    The partitioning of photosynthates toward biomass compartments plays a crucial role in the carbon (C) sink function of forests. Few studies have examined how carbon is allocated toward plant compartments in drought-prone forests. We analyzed the fate of gross primary production (GPP) in relation to yearly water deficit in an old evergreen Mediterranean Quercus ilex coppice severely affected by water limitations. Carbon fluxes between the ecosystem and the atmosphere were measured with an eddy covariance flux tower running continuously since 2001. Discrete measurements of litterfall, stem growth and fAPAR allowed us to derive annual productions of leaves, wood, flowers and acorns, and an isometric relationship between stem and belowground biomass has been used to estimate perennial belowground growth. By combining eddy covariance fluxes with annual net primary productions (NPP), we managed to close a C budget and derive values of autotrophic, heterotrophic respirations and carbon-use efficiency (CUE; the ratio between NPP and GPP). Average values of yearly net ecosystem production (NEP), GPP and Reco were 282, 1259 and 977 g C m-2. The corresponding aboveground net primary production (ANPP) components were 142.5, 26.4 and 69.6 g C m-2 for leaves, reproductive effort (flowers and fruits) and stems, respectively. NEP, GPP and Reco were affected by annual water deficit. Partitioning to the different plant compartments was also impacted by drought, with a hierarchy of responses going from the most affected - the stem growth - to the least affected - the leaf production. The average CUE was 0.40, which is well in the range for Mediterranean-type forest ecosystems. CUE tended to decrease less drastically in response to drought than GPP and NPP did, probably due to drought acclimation of autotrophic respiration. Overall, our results provide a baseline for modeling the inter-annual variations of carbon fluxes and allocation in this widespread Mediterranean ecosystem, and

  11. Expression of major photosynthetic and salt-resistance genes in invasive reed lineages grown under elevated CO2 and temperature

    PubMed Central

    Eller, Franziska; Lambertini, Carla; Nielsen, Mette W; Radutoiu, Simona; Brix, Hans

    2014-01-01

    It is important to investigate the molecular causes of the variation in ecologically important traits to fully understand phenotypic responses to climate change. In the Mississippi River Delta, two distinct, sympatric invasive lineages of common reed (Phragmites australis) are known to differ in several ecophysiological characteristics and are expected to become more salt resistant due to increasing atmospheric CO2 and temperature. We investigated whether different patterns of gene expression can explain their ecophysiological differences and increased vigor under future climatic conditions. We compared the transcript abundance of photosynthetic genes of the Calvin cycle (Rubisco small subunit, RbcS; Phosphoglycerate kinase, PGK; Phosphoribulokinase, PRK), genes related with salt transport (Na+/H+ antiporter, PhaNHA) and oxidative stress response genes (Manganese Superoxide dismutase, MnSOD; Glutathione peroxidase, GPX), and the total aboveground biomass production between two genotypes representing the two lineages. The two genotypes (Delta-type, Mediterranean lineage, and EU-type, Eurasian lineage) were grown under an ambient and a future climate scenario with simultaneously elevated CO2 and temperature, and under two different soil salinities (0‰ or 20‰). We found neither differences in the aboveground biomass production nor the transcript abundances of the two genotypes, but soil salinity significantly affected all the investigated parameters, often interacting with the climatic conditions. At 20‰ salinity, most genes were higher expressed in the future than in the ambient climatic conditions. Higher transcription of the genes suggests higher abundance of the protein they code for, and consequently increased photosynthate production, improved stress responses, and salt exclusion. Therefore, the higher expression of these genes most likely contributed to the significantly ameliorated salinity impact on the aboveground biomass production of both P

  12. Verbesina alternifolia Tolerance to the Holoparasite Cuscuta gronovii and the Impact of Drought

    PubMed Central

    Evans, Bethany; Borowicz, Victoria

    2013-01-01

    Holoparasites are nonphotosynthetic plants that acquire all resources from hosts. The holoparasite Cuscuta gronovii is native to much of the US with a broad host range including Verbesina alternifolia, an understory perennial. Both species grow in moderate to moist soils and occur in habitats that may experience prolonged or episodic drought. We applied the Wise-Abrahamson Limiting Resource Model (LRM) developed for plant-herbivore relations to examine the effects of pattern of drought stress on tolerance of V. alternifolia to parasitism by C. gronovii. Individual plants were assigned one of six treatments that were combinations of parasite (none or addition of parasite) and drought stress (well-watered, continuously-stressed, or pulse-stressed). After pulse-stressed plants had experienced two wet-dry cycles all plants were harvested. Parasitism strongly reduced both shoot and root mass and well-watered hosts exhibited the greatest decline, indicating reduced tolerance to parasitism when water was readily available. This is consistent with the LRM if parasitism limits photosynthates available to the host. However, parasitism increased allocation to shoot and this effect did not differ between well-watered and drought-stressed plants, indicating equal tolerance. This outcome is in accord with an alternative prediction of the LRM if hosts are not carbon limited. Total pot productivity was reduced by parasitism and drought stress, and this effect was greater for pulse-stressed than for continuously-stressed hosts. We discuss the applicability of the LRM for understanding the effects of drought on tolerance to parasitism. PMID:27137396

  13. Nitrogen control of 13C enrichment in heterotrophic organs relative to leaves in a landscape-building desert plant species

    NASA Astrophysics Data System (ADS)

    Zhang, J.; Gu, L.; Bao, F.; Cao, Y.; Hao, Y.; He, J.; Li, J.; Li, Y.; Ren, Y.; Wang, F.; Wu, R.; Yao, B.; Zhao, Y.; Lin, G.; Wu, B.; Lu, Q.; Meng, P.

    2015-01-01

    A longstanding puzzle in isotope studies of C3 plant species is that heterotrophic plant organs (e.g., stems, roots, seeds, and fruits) tend to be enriched in 13C compared to the autotrophic organ (leaves) that provides them with photosynthate. Our inability to explain this puzzle suggests key deficiencies in understanding post-photosynthetic metabolic processes. It also limits the effectiveness of applications of stable carbon isotope analyses in a variety of scientific disciplines ranging from plant physiology to global carbon cycle studies. To gain insight into this puzzle, we excavated whole plant architectures of Nitraria tangutorum Bobrov, a C3 species that has an exceptional capability of fixing sands and building sand dunes, in two deserts in northwestern China. We systematically and simultaneously measured carbon isotope ratios and nitrogen and phosphorous contents of different parts of the excavated plants. We also determined the seasonal variations in leaf carbon isotope ratios on nearby intact plants of N. tangutorum. We found, for the first time, that higher nitrogen contents in heterotrophic organs were significantly correlated with increased heterotrophic 13C enrichment compared to leaves. However, phosphorous contents had no effect on the enrichment. In addition, new leaves had carbon isotope ratios similar to roots but were progressively depleted in 13C as they matured. We concluded that a nitrogen-mediated process, hypothesized to be the refixation of respiratory CO2 by phosphoenolpyruvate (PEP) carboxylase, was responsible for the differences in 13C enrichment among different heterotrophic organs, while processes such as fractionating foliar metabolism and preferentially loading into phloem of 13C-enriched sugars may contribute to the overall autotrophic-heterotrophic difference in carbon isotope compositions.

  14. Nitrogen control of 13C enrichment in heterotrophic organs relative to leaves in a landscape-building desert plant species

    NASA Astrophysics Data System (ADS)

    Zhang, J.; Gu, L.; Bao, F.; Cao, Y.; Hao, Y.; He, J.; Li, J.; Li, Y.; Ren, Y.; Wang, F.; Wu, R.; Yao, B.; Zhao, Y.; Lin, G.; Wu, B.; Lu, Q.; Meng, P.

    2014-09-01

    A longstanding puzzle in isotope studies of C3 plant species is that heterotrophic plant organs (e.g., stems, roots, seeds, and fruits) tend to be enriched in 13C compared to the autotrophic organ (leaves) that provides them with photosynthate. Our inability to explain this puzzle suggests key deficiencies in understanding post-photosynthetic metabolic processes. It also limits the effectiveness of applications of stable carbon isotope analyses in a variety of scientific disciplines ranging from plant physiology to global carbon cycle studies. To gain insight into this puzzle, we excavated whole plant architectures of Nitraria tangutorum Bobrov, a C3 species that has an exceptional capability of fixing sands and building sand dunes, in two deserts in northwestern China. We systematically and simultaneously measured carbon isotope ratios and nitrogen and phosphorous contents of different parts of the excavated plants. We also determined the seasonal variations in leaf carbon isotope ratios on nearby intact plants of N. tangutorum. We found, for the first time, that higher nitrogen contents in heterotrophic organs were significantly correlated with increased heterotrophic 13C enrichment compared to leaves. However, phosphorous contents had no effect on the enrichment. In addition, new leaves had carbon isotope ratios similar to roots but were progressively depleted in 13C as they matured. We concluded that a nitrogen-mediated process, probably the refixation of respiratory CO2 by phosphoenolpyruvate (PEP) carboxylase, was responsible for the differences in 13C enrichment among different heterotrophic organs while processes within leaves or during phloem loading may contribute to the overall autotrophic - heterotrophic difference in carbon isotope compositions.

  15. Seasonal changes in D/H fractionation accompanying lipid biosynthesis in Spartina alterniflora

    NASA Astrophysics Data System (ADS)

    Sessions, Alex L.

    2006-05-01

    To investigate potential variability in the biosynthetic fractionation of hydrogen isotopes between environmental water and plant lipids, the cord grass Spartina alterniflora was sampled from a single location in a coastal marsh over a period of 16 months. Values of δD for a variety of lipids were measured by gas chromatography/pyrolysis/isotope ratio mass spectrometry. S. alterniflora grows partially submerged in seawater, so it has a virtually unlimited supply of water with nearly unvarying isotopic composition. Temporal changes in the δD values of lipids can thus be interpreted as representing mainly variations in biosynthetic fractionation. Fatty acids, n-alkanes, and phytol extracted from S. alterniflora have nearly constant δD values from ˜October through May, but exhibit marked decreases of up to 40‰ during summer months. These shifts in lipid δD values are interpreted as representing a change in the source of organic substrates, principally acetate, used for their biosynthesis. Lower summertime δD values for lipids are consistent with an increasing reliance on current photosynthate as feedstock for biosynthesis, whereas stored carbohydrate reserves are utilized more extensively during other times of the year. Regardless of the specific mechanism, the data emphasize that overall fractionations between water and plant lipids depend on biological as well as environmental variables, and that the biosynthetic fractionation is not necessarily constant even for a single plant. Because lipids such as fatty acids are present in all cells and turn over on timescales of weeks to months, measurements of δD values in fatty acids may also provide useful constraints for distinguishing biologic versus environmental controls on cellulose δD values in trees.

  16. Impact of feeding and short-term temperature stress on the content and isotopic signature of fatty acids, sterols, and alcohols in the scleractinian coral Turbinaria reniformis

    NASA Astrophysics Data System (ADS)

    Tolosa, I.; Treignier, C.; Grover, R.; Ferrier-Pagès, C.

    2011-09-01

    This study assesses the combined effect of feeding and short-term thermal stress on various physiological parameters and on the fatty acid, sterol, and alcohol composition of the scleractinian coral Turbinaria reniformis. The compound-specific carbon isotope composition of the lipids was also measured. Under control conditions (26°C), feeding with Artemia salina significantly increased the symbiont density and chlorophyll content and the growth rates of the corals. It also doubled the concentrations of almost all fatty acid (FA) compounds and increased the n-alcohol and sterol contents. δ13C results showed that the feeding enhancement of FA concentrations occurred either via a direct pathway, for one of the major polyunsaturated fatty acid (PUFA) compounds of the food (18:3n-3 FA), or via an enhancement of photosynthate transfer (indirect pathway), for the other coral FAs. Cholesterol (C27Δ5) was also directly acquired from the food. Thermal stress (31°C) affected corals, but differently according to their feeding status. Chlorophyll, protein content, and maximal photosynthetic efficiency of photosystem II (PSII) decreased to a greater extent in starved corals. In such corals, FA concentrations were reduced by 33%, (especially C16, C18 FAs, and n-3 PUFA) and the sterol content by 27% (especially the C28∆5,22 and C28∆5). The enrichment in the δ13C signature of the storage and structural FAs suggests that they were the main compounds respired during the stress to maintain the coral metabolism. Thermal stress had less effect on the lipid concentrations of fed corals, as only FA levels were reduced by 13%, with no major changes in their isotope carbon signatures. In conclusion, feeding plays an essential role in sustaining T. reniformis metabolism during the thermal stress.

  17. Zooxanthellae Harvested by Ciliates Associated with Brown Band Syndrome of Corals Remain Photosynthetically Competent▿

    PubMed Central

    Ulstrup, Karin E.; Kühl, Michael; Bourne, David G.

    2007-01-01

    Brown band syndrome is a new coral affliction characterized by a local accumulation of yet-unidentified ciliates migrating as a band along the branches of coral colonies. In the current study, morphologically intact zooxanthellae (= Symbiodinium) were observed in great numbers inside the ciliates (>50 dinoflagellates per ciliate). Microscale oxygen measurements and variable chlorophyll a fluorescence analysis along with microscopic observations demonstrated that zooxanthellae within the ciliates are photosynthetically competent and do not become compromised during the progression of the brown band zone. Zooxanthellae showed similar trends in light acclimation in a comparison of rapid light curve and steady-state light curve measures of variable chlorophyll a fluorescence. Extended light exposure of steady-state light curves resulted in higher quantum yields of photosystem II. The brown band tissue exhibited higher photosynthetically active radiation absorptivity, indicating more efficient light absorption due to a higher density of zooxanthellae in the ciliate-dominated zone. This caused relatively higher gross photosynthesis rates in the zone with zooxanthella-containing ciliates compared to healthy coral tissue. The observation of photosynthetically active intracellular zooxanthellae in the ciliates suggests that the latter can benefit from photosynthates produced by ingested zooxanthellae and from photosynthetic oxygen production that alleviates diffusion limitation of oxic respiration in the densely populated brown band tissue. It remains to be shown whether the zooxanthellae form a stable symbiotic association with the ciliate or are engulfed incidentally during grazing on coral tissue and then maintained as active inside the ciliate for a period before being digested and replaced by new zooxanthellae. PMID:17259357

  18. Modelling Wheat Growth and Yield Losses from Late Epidemics of Foliar Diseases using Loss of Green Leaf Area per Layer and Pre-anthesis Reserves

    PubMed Central

    Bancal, Marie-Odile; Robert, Corinne; Ney, Bertrand

    2007-01-01

    Background and Aims Crop protection strategies, based on preventing quantitative crop losses rather than pest outbreaks, are being developed as a promising way to reduce fungicide use. The Bastiaans' model was applied to winter wheat crops (Triticum aestivum) affected by leaf rust (Puccinia triticina) and Septoria tritici blotch (STB; Mycosphaerella graminicola) under a range of crop management conditions. This study examined (a) whether green leaf area per layer accurately accounts for growth loss; and (b) whether from growth loss it is possible to derive yield loss accurately and simply. Methods Over 5 years of field experiments, numerous green leaf area dynamics were analysed during the post-anthesis period on wheat crops using natural aerial epidemics of leaf rust and STB. Key Results When radiation use efficiency (RUE) was derived from bulk green leaf area index (GLAI), RUEbulk was hardly accurate and exhibited large variations among diseased wheat crops, thus extending outside the biological range. In contrast, when RUE was derived from GLAI loss per layer, RUElayer was a more accurate calculation and fell within the biological range. In one situation out of 13, no significant shift in the RUElayer of diseased crops vs. healthy crops was observed. A single linear relationship linked yield to post-anthesis accumulated growth for all treatments. Its slope, not different from 1, suggests that the allocation of post-anthesis photosynthates to grains was not affected by the late occurring diseases under study. The mobilization of pre-anthesis reserves completely accounted for the intercept value. Conclusions The results strongly suggest that a simple model based on green leaf area per layer and pre-anthesis reserves can predict both growth and yield of wheat suffering from late epidemics of foliar diseases over a range of crop practices. It could help in better understanding how crop structure and reserve management contribute to tolerance of wheat genotypes to

  19. Metabolic and photosynthetic consequences of blocking starch biosynthesis in the green alga Chlamydomonas reinhardtii sta6 mutant.

    PubMed

    Krishnan, Anagha; Kumaraswamy, G Kenchappa; Vinyard, David J; Gu, Huiya; Ananyev, Gennady; Posewitz, Matthew C; Dismukes, G Charles

    2015-03-01

    Upon nutrient deprivation, microalgae partition photosynthate into starch and lipids at the expense of protein synthesis and growth. We investigated the role of starch biosynthesis with respect to photosynthetic growth and carbon partitioning in the Chlamydomonas reinhardtii starchless mutant, sta6, which lacks ADP-glucose pyrophosphorylase. This mutant is unable to convert glucose-1-phosphate to ADP-glucose, the precursor of starch biosynthesis. During nutrient-replete culturing, sta6 does not re-direct metabolism to make more proteins or lipids, and accumulates 20% less biomass. The underlying molecular basis for the decreased biomass phenotype was identified using LC-MS metabolomics studies and flux methods. Above a threshold light intensity, photosynthetic electron transport rates (water → CO2) decrease in sta6 due to attenuated rates of NADPH re-oxidation, without affecting photosystems I or II (no change in isolated photosynthetic electron transport). We observed large accumulations of carbon metabolites that are precursors for the biosynthesis of lipids, amino acids and sugars/starch, indicating system-wide consequences of slower NADPH re-oxidation. Attenuated carbon fixation resulted in imbalances in both redox and adenylate energy. The pool sizes of both pyridine and adenylate nucleotides in sta6 increased substantially to compensate for the slower rate of turnover. Mitochondrial respiration partially relieved the reductant stress; however, prolonged high-light exposure caused accelerated photoinhibition. Thus, starch biosynthesis in Chlamydomonas plays a critical role as a principal carbon sink influencing cellular energy balance however, disrupting starch biosynthesis does not redirect resources to other bioproducts (lipids or proteins) during nutrient-replete culturing, resulting in cells that are susceptible to photochemical damage caused by redox stress. PMID:25645872

  20. Relationship between Shoot-rooting and Root-sprouting Abilities and the Carbohydrate and Nitrogen Reserves of Mediterranean Dwarf Shrubs

    PubMed Central

    Palacio, Sara; Maestro, Melchor; Montserrat-Martí, Gabriel

    2007-01-01

    Background and Aims This study analysed the differences in nitrogen (N), non-structural carbohydrates (NSC) and biomass allocation to the roots and shoots of 18 species of Mediterranean dwarf shrubs with different shoot-rooting and resprouting abilities. Root N and NSC concentrations of strict root-sprouters and species resprouting from the base of the stems were also compared. Methods Soluble sugars (SS), starch and N concentrations were assessed in roots and shoots. The root : shoot ratio of each species was obtained by thorough root excavations. Cross-species analyses were complemented by phylogenetically independent contrasts (PICs). Key Results Shoot-rooting species showed a preferential allocation of starch to shoots rather than roots as compared with non-shoot-rooting species. Resprouters displayed greater starch concentrations than non-sprouters in both shoots and roots. Trends were maintained after PICs analyses, but differences became weak when root-sprouters versus non-root-sprouters were compared. Within resprouters, strict root-sprouters showed greater root concentrations and a preferential allocation of starch to the roots than stem-sprouters. No differences were found in the root : shoot ratio of species with different rooting and resprouting abilities. Conclusions The shoot-rooting ability of Mediterranean dwarf shrubs seems to depend on the preferential allocation of starch and SS to shoots, though alternative C-sources such as current photosynthates may also be involved. In contrast to plants from other mediterranean areas of the world, the resprouting ability of Mediterranean dwarf shrubs is not related to a preferential allocation of N, NSC and biomass to roots. PMID:17728338

  1. Adaptation of carbon allocation under light and nutrient reduction

    NASA Astrophysics Data System (ADS)

    Wegener, Frederik; Werner, Christiane

    2015-04-01

    The allocation of recently assimilated carbon (C) by plants depends on developmental stage and on environmental factors, but the underlying mechanisms are still a matter of debate. Whereas shifts in the allocation of photosynthates induced by reduced water availability, enhanced temperature and CO2 concentration were recently investigated in various studies, less is known about the response to light and nutrient reduction. We induced different allocation patterns in the Mediterranean shrub Halimium halimifolium L. by a reduction of light (Low L treatment) and nutrient availability (Low N treatment) and analysed allocation parameters as well as morphological and physiological traits for 15 months. Finally, we conducted a 13CO2 pulse-labelling and followed the fate of recently assimilated carbon to eight different classes of plant tissues and respiration for 13 days. The results revealed a high intraspecific variability in C distribution to tissues and in respiration. Allocation changes even varied within leaf and stem tissue classes (e.g. more C in main stems, less in lateral stems). These results show that the common separation of plant tissues in only three classes, i.e. root, shoot and leaf tissues, can result in missing information about allocation changes. The nutrient reduction enhanced the transport of recently assimilated C from leaves to roots in terms of quantity (c. 200%) and velocity compared to control plants. Interestingly, a 57% light reduction enhanced photosynthetic capacity and caused no change in final biomass after 15 months. Therefore, our results support the recently discussed sink regulation of photosynthesis. Finally, our results indicate that growing heterotrophic tissues strongly reduce the C loss from storage and structural C pools and therefore enhance the fraction of recent assimilates used for respiration. We propose that this interruption of the C reflux from storage and structural C pools could be a control mechanism for C

  2. Legume adaptation to sulfur deficiency revealed by comparing nutrient allocation and seed traits in Medicago truncatula.

    PubMed

    Zuber, Hélène; Poignavent, Germain; Le Signor, Christine; Aimé, Delphine; Vieren, Eric; Tadla, Charlène; Lugan, Raphaël; Belghazi, Maya; Labas, Valérie; Santoni, Anne-Lise; Wipf, Daniel; Buitink, Julia; Avice, Jean-Christophe; Salon, Christophe; Gallardo, Karine

    2013-12-01

    Reductions in sulfur dioxide emissions and the use of sulfur-free mineral fertilizers are decreasing soil sulfur levels and threaten the adequate fertilization of most crops. To provide knowledge regarding legume adaptation to sulfur restriction, we subjected Medicago truncatula, a model legume species, to sulfur deficiency at various developmental stages, and compared the yield, nutrient allocation and seed traits. This comparative analysis revealed that sulfur deficiency at the mid-vegetative stage decreased yield and altered the allocation of nitrogen and carbon to seeds, leading to reduced levels of major oligosaccharides in mature seeds, whose germination was dramatically affected. In contrast, during the reproductive period, sulfur deficiency had little influence on yield and nutrient allocation, but the seeds germinated slowly and were characterized by low levels of a biotinylated protein, a putative indicator of germination vigor that has not been previously related to sulfur nutrition. Significantly, plants deprived of sulfur at an intermediary stage (flowering) adapted well by remobilizing nutrients from source organs to seeds, ensuring adequate quantities of carbon and nitrogen in seeds. This efficient remobilization of photosynthates may be explained by vacuolar sulfate efflux to maintain leaf metabolism throughout reproductive growth, as suggested by transcript and metabolite profiling. The seeds from these plants, deprived of sulfur at the floral transition, contained normal levels of major oligosaccharides but their germination was delayed, consistent with low levels of sucrose and the glycolytic enzymes required to restart seed metabolism during imbibition. Overall, our findings provide an integrative view of the legume response to sulfur deficiency. PMID:24118112

  3. Nitrogen Fertilization Modifies the Phenology of Ground CO2 Efflux in a Boreal Scots Pine Forest

    NASA Astrophysics Data System (ADS)

    Marshall, J. D.; Näsholm, T.; Linder, S.; Tarvainen, L.; Peichl, M.; Lundmark, T.

    2015-12-01

    Problems with the extraction of ecosystem respiration rates from eddy covariance data have led to renewed interest in chamber-based estimates of CO2 efflux from near the ground surface. However, chamber measurements frequently have their own issues. Here we describe the results of a study using large (≈2 m radius), transparent chambers over intact ground vegetation to describe the net efflux of CO2 and its environmental controls during the growing season at Rosinedal, a research site in northern Sweden. Measurements were made at thirty-minute intervals over the course of three growing seasons in a heavily fertilized and an unfertilized Scots pine stand. Ammonium nitrate was added at rates of 100 kg N ha-1 for the first five years, after which the rate was halved but the additions continued. The CO2 efflux results were simultaneously fitted to a nonlinear model describing the exponential increase in dark efflux with temperature, the Michaelis-Menten saturation of light-driven CO2 uptake in photosynthesis, the reduction in efflux due to soil drying, and a residual term that we ascribe to weekly shifts in the photosynthate partitioning of canopy trees to belowground processes. We found the expected exponential increase in dark efflux with temperature, however the net efflux in daytime was often negative, reflecting the high GPP of the ground vegetation, especially in dense canopies of bilberry (Vaccinium myrtillus L.). There was a clear reduction in dark efflux under dry conditions. The empirical phenology parameters increased sharply in early July, around the time that leaf expansion and rapid cambial growth were completed. This increase was more pronounced on the control plot than on the fertilized plot, consistent with expectations based on the notion that N fertilization should favor aboveground partitioning. The empirical "partitioning coefficient" shifted net efflux by nearly as much as the seasonal temperature range. Dark efflux of CO2 was nearly halved as a

  4. Transfer from long to short photoperiods affects production efficiency of day-neutral rice

    NASA Technical Reports Server (NTRS)

    Goldman, K. R.; Mitchell, C. A.

    1999-01-01

    The day-neutral, semidwarf rice (Oryza sativa L.) cultivar Ai-Nan-Tsao was grown in a greenhouse under summer conditions using high-pressure sodium lamps to extend the natural photoperiod. After allowing 2 weeks for germination, stand establishment, and thinning to a consistent planting density of 212 plants/m2, stands were maintained under continuous lighting for 35 or 49 days before shifting to 8- or 12-h photoperiods until harvest 76 days after planting. Non-shifted control treatments consisting of 8-, 12-, or 24-h photoperiods also were maintained throughout production. Tiller number increased as duration of exposure to continuous light increased before shifting to shorter photoperiods. However, shoot harvest index and yield efficiency rate were lower for all plants receiving continuous light than for those under the 8- or 12-h photoperiods. Stands receiving 12-h photoperiods throughout production had the highest grain yield per plant and equaled the 8-h-photoperiod control plants for the lowest tiller number per plant. As long as stands were exposed to continuous light, tiller formation continued. Shifting to shorter photoperiods late in the cropping cycle resulted in newly formed tillers that were either sterile or unable to mature grain before harvest. Late-forming tillers also suppressed yield of grain in early-forming tillers, presumably by competing for photosynthate or for remobilized assimilate during senescence. Stands receiving 12-h photoperiods throughout production not only produced the highest grain yield at harvest but had the highest shoot harvest index, which is important for resource-recovery strategies in advanced life-support systems proposed for space.

  5. The Antarctic psychrophile, Chlamydomonas subcaudata, is deficient in state I-state II transitions.

    PubMed

    Morgan-Kiss, Rachael M; Ivanov, Alexander G; Huner, Norman P A

    2002-01-01

    State I-State II transitions were monitored in vivo and in vitro in the Antarctic, psychrophillic, green alga, Chlamydomonas subcaudata, as changes in the low-temperature (77 K) chlorophyll fluorescence emission maxima at 722 nm (F722) relative to 699 nm (F699). As expected, the control mesophillic species, Chlamydomonas reinhardtii, was able to modulate the light energy distribution between photosystem II and photosystem I in response to exposure to four different conditions: (i) dark/anaerobic conditions, (ii) a change in Mg2+ concentration, (iii) red light, and (iv) increased incubation temperature. This was correlated with the ability to phosphorylate both of its major light-harvesting polypeptides. In contrast, exposure of C. subcaudata to the same four conditions induced minimum alterations in the 77 K fluorescence emission spectra, which was correlated with the ability to phosphorylate only one of its major light-harvesting polypeptides. Thus, C. subcaudata appears to be deficient in the ability to undergo a State I-State II transition. Functionally, this is associated with alterations in the apparent redox status of the intersystem electron transport chain and with higher rates of photosystem I cyclic electron transport in the psychrophile than in the mesophile, based on in vivo P700 measurements. Structurally, this deficiency is associated with reduced levels of Psa A/B relative to D1, the absence of specific photosystem I light-harvesting polypeptides [R.M. Morgan et al. (1998) Photosynth Res 56:303-314] and a cytochrome b6/f complex that exhibits a form of cytochrome f that is approximately 7 kDa smaller than that observed in C. reinhardtii. We conclude that the Antarctic psychrophile, C. subcaudata, is an example of a natural variant deficient in State I-State II transitions. PMID:11859846

  6. An In Vivo Analysis of the Effect of Season-Long Open-Air Elevation of Ozone to Anticipated 2050 Levels on Photosynthesis in Soybean1

    PubMed Central

    Morgan, Patrick B.; Bernacchi, Carl J.; Ort, Donald R.; Long, Stephen P.

    2004-01-01

    Rising atmospheric carbon dioxide concentration ([CO2]) is widely recognized, but less appreciated is a concomitant rise in tropospheric ozone concentration ([O3]). In industrialized countries, [O3] has risen by 0.5% to 2.5% per year. Tropospheric [O3] is predicted to reach a global mean of >60 nL L−1 by 2050 with greater averages locally. Previous studies in enclosures suggest that this level of [O3] will decrease leaf photosynthesis, thereby limiting growth and yield of Glycine max L. Merr. SoyFACE (Soybean Free Air gas Concentration Enrichment) is the first facility to elevate atmospheric [O3] (approximately 1.2× current) in replicated plots under completely open-air conditions within an agricultural field. Measurements of gas exchange (assimilation versus light and assimilation versus intercellular [CO2]) were made on excised leaves from control and treatment plots (n = 4). In contrast to expectations from previous chamber studies, elevated [O3] did not alter light-saturated photosynthesis (Asat, P = 0.09), carboxylation capacity (Vc,max, P = 0.82), or maximum electron transport (Jmax, P = 0.66) for the topmost most recently fully expanded leaf at any stage of crop development. Leaves formed during the vegetative growth stage did not show a significant ozone-induced loss of photosynthetic capacity as they aged. Leaves formed during flowering did show a more rapid loss of photosynthetic capacity as they aged in elevated [O3]. Asat, Vc,max, and Jmax (P = 0.04, 0.004, and 0.002, respectively) were decreased 20% to 30% by treatment with ozone. This is noteworthy since these leaves provide photosynthate to the developing grain. In conclusion, a small (approximately 20%) increase in tropospheric [O3] did not significantly alter photosynthetic capacity of newly expanded leaves, but as these leaves aged, losses in photosynthetic carbon assimilation occurred. PMID:15299126

  7. The growth of soybean under free air [CO(2)] enrichment (FACE) stimulates photosynthesis while decreasing in vivo Rubisco capacity.

    PubMed

    Bernacchi, Carl J; Morgan, Patrick B; Ort, Donald R; Long, Stephen P

    2005-01-01

    Down-regulation of light-saturated photosynthesis (A(sat)) at elevated atmospheric CO(2) concentration, [CO(2)], has been demonstrated for many C(3) species and is often associated with inability to utilize additional photosynthate and/or nitrogen limitation. In soybean, a nitrogen-fixing species, both limitations are less likely than in crops lacking an N-fixing symbiont. Prior studies have used controlled environment or field enclosures where the artificial environment can modify responses to [CO(2)]. A soybean free air [CO(2)] enrichment (FACE) facility has provided the first opportunity to analyze the effects of elevated [CO(2)] on photosynthesis under fully open-air conditions. Potential ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) carboxylation (V(c,max)) and electron transport through photosystem II (J(max)) were determined from the responses of A(sat) to intercellular [CO(2)] (C(i)) throughout two growing seasons. Mesophyll conductance to CO(2) (g(m)) was determined from the responses of A(sat) and whole chain electron transport (J) to light. Elevated [CO(2)] increased A(sat) by 15-20% even though there was a small, statistically significant, decrease in V(c,max). This differs from previous studies in that V(c,max)/J(max) decreased, inferring a shift in resource investment away from Rubisco. This raised the C(i) at which the transition from Rubisco-limited to ribulose-1,5-bisphosphate regeneration-limited photosynthesis occurred. The decrease in V(c,max) was not the result of a change in g(m), which was unchanged by elevated [CO(2)]. This first analysis of limitations to soybean photosynthesis under fully open-air conditions reveals important differences to prior studies that have used enclosures to elevate [CO(2)], most significantly a smaller response of A(sat) and an apparent shift in resources away from Rubisco relative to capacity for electron transport. PMID:15252734

  8. An in vivo analysis of the effect of season-long open-air elevation of ozone to anticipated 2050 levels on photosynthesis in soybean.

    PubMed

    Morgan, Patrick B; Bernacchi, Carl J; Ort, Donald R; Long, Stephen P

    2004-08-01

    Rising atmospheric carbon dioxide concentration ([CO(2)]) is widely recognized, but less appreciated is a concomitant rise in tropospheric ozone concentration ([O(3)]). In industrialized countries, [O(3)] has risen by 0.5% to 2.5% per year. Tropospheric [O(3)] is predicted to reach a global mean of >60 nL L(-1) by 2050 with greater averages locally. Previous studies in enclosures suggest that this level of [O(3)] will decrease leaf photosynthesis, thereby limiting growth and yield of Glycine max L. Merr. SoyFACE (Soybean Free Air gas Concentration Enrichment) is the first facility to elevate atmospheric [O(3)] (approximately 1.2x current) in replicated plots under completely open-air conditions within an agricultural field. Measurements of gas exchange (assimilation versus light and assimilation versus intercellular [CO(2)]) were made on excised leaves from control and treatment plots (n = 4). In contrast to expectations from previous chamber studies, elevated [O(3)] did not alter light-saturated photosynthesis (A(sat), P = 0.09), carboxylation capacity (V(c,max), P = 0.82), or maximum electron transport (J(max), P = 0.66) for the topmost most recently fully expanded leaf at any stage of crop development. Leaves formed during the vegetative growth stage did not show a significant ozone-induced loss of photosynthetic capacity as they aged. Leaves formed during flowering did show a more rapid loss of photosynthetic capacity as they aged in elevated [O(3)]. A(sat), V(c,max), and J(max) (P = 0.04, 0.004, and 0.002, respectively) were decreased 20% to 30% by treatment with ozone. This is noteworthy since these leaves provide photosynthate to the developing grain. In conclusion, a small (approximately 20%) increase in tropospheric [O(3)] did not significantly alter photosynthetic capacity of newly expanded leaves, but as these leaves aged, losses in photosynthetic carbon assimilation occurred. PMID:15299126

  9. Increased C availability at elevated carbon dioxide concentration improves N assimilation in a legume.

    PubMed

    Rogers, Alistair; Gibon, Yves; Stitt, Mark; Morgan, Patrick B; Bernacchi, Carl J; Ort, Donald R; Long, Stephen P

    2006-08-01

    Plant growth is typically stimulated at elevated carbon dioxide concentration ([CO2]), but a sustained and maximal stimulation of growth requires acquisition of additional N in proportion to the additional C fixed at elevated [CO2]. We hypothesized that legumes would be able to avoid N limitation at elevated [CO2]. Soybean was grown without N fertilizer from germination to final senescence at elevated [CO2] over two growing seasons under fully open-air conditions, providing a model legume system. Measurements of photosynthesis and foliar carbohydrate content showed that plants growing at elevated [CO2] had a c. 25% increase in the daily integral of photosynthesis and c. 58% increase in foliar carbohydrate content, suggesting that plants at elevated [CO2] had a surplus of photosynthate. Soybeans had a low leaf N content at the beginning of the season, which was a further c. 17% lower at elevated [CO2]. In the middle of the season, ureide, total amino acid and N content increased markedly, and the effect of elevated [CO2] on leaf N content disappeared. Analysis of individual amino acid levels supported the conclusion that plants at elevated [CO2] overcame an early-season N limitation. These soybean plants showed a c. 16% increase in dry mass at final harvest and showed no significant effect of elevated [CO2] on leaf N, protein or total amino acid content in the latter part of the season. One possible explanation for these findings is that N fixation had increased, and that these plants had acclimated to the increased N demand at elevated [CO2]. PMID:16898025

  10. Action spectra of photosystems II and I and quantum yield of photosynthesis in leaves in State 1.

    PubMed

    Laisk, Agu; Oja, Vello; Eichelmann, Hillar; Dall'Osto, Luca

    2014-02-01

    The spectral global quantum yield (YII, electrons/photons absorbed) of photosystem II (PSII) was measured in sunflower leaves in State 1 using monochromatic light. The global quantum yield of PSI (YI) was measured using low-intensity monochromatic light flashes and the associated transmittance change at 810nm. The 810-nm signal change was calibrated based on the number of electrons generated by PSII during the flash (4·O2 evolution) which arrived at the PSI donor side after a delay of 2ms. The intrinsic quantum yield of PSI (yI, electrons per photon absorbed by PSI) was measured at 712nm, where photon absorption by PSII was small. The results were used to resolve the individual spectra of the excitation partitioning coefficients between PSI (aI) and PSII (aII) in leaves. For comparison, pigment-protein complexes for PSII and PSI were isolated, separated by sucrose density ultracentrifugation, and their optical density was measured. A good correlation was obtained for the spectral excitation partitioning coefficients measured by these different methods. The intrinsic yield of PSI was high (yI=0.88), but it absorbed only about 1/3 of quanta; consequently, about 2/3 of quanta were absorbed by PSII, but processed with the low intrinsic yield yII=0.63. In PSII, the quantum yield of charge separation was 0.89 as detected by variable fluorescence Fv/Fm, but 29% of separated charges recombined (Laisk A, Eichelmann H and Oja V, Photosynth. Res. 113, 145-155). At wavelengths less than 580nm about 30% of excitation is absorbed by pigments poorly connected to either photosystem, most likely carotenoids bound in pigment-protein complexes. PMID:24333386

  11. The influence of fruit load on the tomato pericarp metabolome in a Solanum chmielewskii introgression line population.

    PubMed

    Do, Phuc Thi; Prudent, Marion; Sulpice, Ronan; Causse, Mathilde; Fernie, Alisdair R

    2010-11-01

    It has been recently demonstrated, utilizing interspecific introgression lines of tomato, generated from the cross between Solanum lycopersicum and the wild species Solanum pennellii, that the efficiency of photosynthate partitioning exerts a considerable influence on the metabolic composition of tomato fruit pericarp. In order to further evaluate the influence of source-sink interaction, metabolite composition was determined by gas chromatography-mass spectrometry in a different population. For this purpose, we used 23 introgression lines resulting from an interspecific cross between S. lycopersicum and the wild species Solanum chmielewskii under high (unpruned trusses) and low (trusses pruned to one fruit) fruit load conditions. Following this strategy, we were able to contrast the metabolite composition of fruits from plants cultivated at both fruit loads as well as to compare the network behavior of primary metabolism in the introgression line population. The study revealed that while a greater number of metabolic quantitative trait loci were observed under high fruit load (240) than under low fruit load (128) cultivations, the levels of metabolites were more highly correlated under low fruit load cultivation. Finally, an analysis of genotype × fruit load interactions indicated a greater influence of development and cultivation than genotype on fruit composition. Comparison with previously documented transcript profiles from a subset of these lines revealed that changes in metabolite levels did not correlate with changes in the levels of genes associated with their metabolism. These findings are discussed in the context of our current understanding of the genetic and environmental influence on metabolic source-sink interactions in tomato, with particular emphasis given to fruit amino acid content. PMID:20841452

  12. Symbiosome-like intracellular colonization of cereals and other crop plants by nitrogen-fixing bacteria for reduced inputs of synthetic nitrogen fertilizers.

    PubMed

    Cocking, Edward C; Stone, Philip J; Davey, Michael R

    2005-09-01

    It has been forecast that the challenge of meeting increased food demand and protecting environmental quality will be won or lost in maize, rice and wheat cropping systems, and that the problem of environmental nitrogen enrichment is most likely to be solved by substituting synthetic nitrogen fertilizers by the creation of cereal crops that are able to fix nitrogen symbiotically as legumes do. In legumes, rhizobia present intracellularly in membrane-bound vesicular compartments in the cytoplasm of nodule cells fix nitrogen endosymbiotically. Within these symbiosomes, membrane-bound vesicular compartments, rhizobia are supplied with energy derived from plant photosynthates and in return supply the plant with biologically fixed nitrogen, usually as ammonia. This minimizes or eliminates the need for inputs of synthetic nitrogen fertilizers. Recently we have demonstrated, using novel inoculation conditions with very low numbers of bacteria, that cells of root meristems of maize, rice, wheat and other major non-legume crops, such as oilseed rape and tomato, can be intracellularly colonized by the non-rhizobial, non-nodulating, nitrogen fixing bacterium,Gluconacetobacter diazotrophicus that naturally occurs in sugarcane.G. diazotrophicus expressing nitrogen fixing (nifH) genes is present in symbiosome-like compartments in the cytoplasm of cells of the root meristems of the target cereals and non-legume crop species, somewhat similar to the intracellular symbiosome colonization of legume nodule cells by rhizobia. To obtain an indication of the likelihood of adequate growth and yield, of maize for example, with reduced inputs of synthetic nitrogen fertilizers, we are currently determining the extent to which nitrogen fixation, as assessed using various methods, is correlated with the extent of systemic intracellular colonization byG. diazotrophicus, with minimal or zero inputs. PMID:20549443

  13. Symbiosome-like intracellular colonization of cereals and other crop plants by nitrogen-fixing bacteria for reduced inputs of synthetic nitrogen fertilizers.

    PubMed

    Cocking, Edward C; Stone, Philip J; Davey, Michael R

    2005-12-01

    It has been forecast that the challenge of meeting increased food demand and protecting environmental quality will be won or lost in maize, rice and wheat cropping systems, and that the problem of environmental nitrogen enrichment is most likely to be solved by substituting synthetic nitrogen fertilizers by the creation of cereal crops that are able to fix nitrogen symbiotically as legumes do. In legumes, rhizobia present intracellularly in membrane-bound vesicular compartments in the cytoplasm of nodule cells fix nitrogen endosymbiotically. Within these symbiosomes, membrane-bound vesicular compartments, rhizobia are supplied with energy derived from plant photosynthates and in return supply the plant with biologically fixed nitrogen, usually as ammonia. This minimizes or eliminates the need for inputs of synthetic nitrogen fertilizers. Recently we have demonstrated, using novel inoculation conditions with very low numbers of bacteria, that cells of root meristems of maize, rice, wheat and other major non-legume crops, such as oilseed rape and tomato, can be intracellularly colonized by the non-rhizobial, non-nodulating, nitrogen fixing bacterium, Gluconacetobacter diazotrophicus that naturally occurs in sugarcane. G. diazotrophicus expressing nitrogen fixing (nifH) genes is present in symbiosome-like compartments in the cytoplasm of cells of the root meristems of the target cereals and non-legume crop species, somewhat similar to the intracellular symbiosome colonization of legume nodule cells by rhizobia. To obtain an indication of the likelihood of adequate growth and yield, of maize for example, with reduced inputs of synthetic nitrogen fertilizers, we are currently determining the extent to which nitrogen fixation, as assessed using various methods, is correlated with the extent of systemic intracellular colonization by G. diazotrophicus, with minimal or zero inputs. PMID:16512210

  14. Benefits of photosynthesis for insects in galls.

    PubMed

    Haiden, S A; Hoffmann, J H; Cramer, M D

    2012-12-01

    Insect-induced plant galls are predominantly reputed to act as strong carbon sinks, although many types of galls contain chlorophyll and have the potential to photosynthesize. We investigated whether the photosynthetic capacity of bud galls induced by a Pteromalid wasp, Trichilogaster acaciaelongifoliae, in Acacia longifolia subsidises carbon budgets or provides O(2) to the larvae while concurrently consuming CO(2) in the dense gall tissue, thereby maintaining (O(2)) and (CO(2)) within the range of larval tolerance. Low (O(2)) (<5 % v/v) were found within the internal tissues of galls, and these concentrations responded only marginally to light, suggesting that the photosynthetic activity within the gall is inconsequential in the provision of O(2) to the larvae. The metabolic response of larvae to reduced (O(2)) and elevated (CO(2)) indicated that larvae were tolerant of hypoxia/hypercarbia and also capable of reducing their respiratory rates to cope with hypercarbia. The low mortality of larvae in galls shaded with Al-foil for 20 days showed that photosynthesis was not vital for the survival of the larvae, although growth of shaded galls was substantially reduced. Gas exchange measurements confirmed that, while photosynthesis never fully compensated for the respiratory costs of galls, it contributed substantially to the maintenance and growth, especially of young galls, reducing their impact as carbon sinks on the host. We conclude that, although photosynthesis may contribute to O(2) provision, its main role is to reduce the dependence of the insect-induced gall on the host plant for photosynthates, thereby reducing intra-plant, inter-gall competition and enhancing the probability that each gall will reach maturity. PMID:22622876

  15. Pigment organization and their interactions in reaction centers of photosystem II: optical spectroscopy at 6 K of reaction centers with modified pheophytin composition.

    PubMed

    Germano, M; Shkuropatov, A Y; Permentier, H; de Wijn, R; Hoff, A J; Shuvalov, V A; van Gorkom, H J

    2001-09-25

    Photosystem II reaction centers (RC) with selectively exchanged pheophytin (Pheo) molecules as described in [Germano, M., Shkuropatov, A. Ya., Permentier, H., Khatypov, R. A., Shuvalov, V. A., Hoff, A. J., and van Gorkom, H. J. (2000) Photosynth. Res. 64, 189-198] were studied by low-temperature absorption, linear and circular dichroism, and triplet-minus-singlet absorption-difference spectroscopy. The ratio of extinction coefficients epsilon(Pheo)/epsilon(Chl) for Q(Y) absorption in the RC is approximately 0.40 at 6 K and approximately 0.45 at room temperature. The presence of 2 beta-carotenes, one parallel and one perpendicular to the membrane plane, is confirmed. Absorption at 670 nm is due to the perpendicular Q(Y) transitions of the two peripheral chlorophylls (Chl) and not to either Pheo. The "core" pigments, two Pheo and four Chl absorb in the 676-685 nm range. Delocalized excited states as predicted by the "multimer model" are seen in the active branch. The inactive Pheo and the nearby Chl, however, mainly contribute localized transitions at 676 and 680 nm, respectively, although large CD changes indicate that exciton interactions are present on both branches. Replacement of the active Pheo prevents triplet formation, causes an LD increase at 676 and 681 nm, a blue-shift of 680 nm absorbance, and a bleach of the 685 nm exciton band. The triplet state is mainly localized on the Chl corresponding to B(A) in purple bacteria. Both Pheo Q(Y) transitions are oriented out of the membrane plane. Their Q(X) transitions are parallel to that plane, so that the Pheos in PSII are structurally similar to their homologues in purple bacteria. PMID:11560495

  16. [Tools for determining health of phytoplankton cells

    SciTech Connect

    Not Available

    1992-12-31

    The primary purpose of the proposed research is to develop molecular tools for determining the health of marine phytoplankton on an individual cell basis. Since the definition of healthy in phytoplankton cells is elusive, we propose to develop markers for several different metabolic processes indicative of physiological state: photosynthetic activity, esterase activity, membrane permeability, and mitochondrial activity. One underlying motivation is to develop methods which will allow us to evaluate the hypothesis that, while healthy cells release very little dissolved organic carbon (DOC), many phytoplankton communities are comprised of unhealthy or physiologically stressed cells which release a large proportion of total photosynthate directly into the pool of labile DOC. This is proposed to be especially true in continental shelf and coastal environments where zones of productivity are patchy and phytoplankton populations adapted to one regime can be easily transported into waters which differ in salinity, nutrient supply, and/or turbidity. The significance of the work, however, extends beyond this immediate goal since there are presently relatively few methods which allow us to estimate the physiological state of phytoplankton cells.When we evaluate population sizes of phytoplankton in the water column or examine fecal pellets, particulate aggregates, or other material, we generally work in ignorance of the activity of the cells except as the average cell-specific activity is estimated from bulk measurements. This approach effectively hides any differences in the relative contribution of different taxa or individuals to overall productivity eventhough most flux processes are sensitive to physiological and taxonomically determined differences among members of the community.

  17. [Tools for determining health of phytoplankton cells

    SciTech Connect

    Not Available

    1992-01-01

    The primary purpose of the proposed research is to develop molecular tools for determining the health of marine phytoplankton on an individual cell basis. Since the definition of healthy in phytoplankton cells is elusive, we propose to develop markers for several different metabolic processes indicative of physiological state: photosynthetic activity, esterase activity, membrane permeability, and mitochondrial activity. One underlying motivation is to develop methods which will allow us to evaluate the hypothesis that, while healthy cells release very little dissolved organic carbon (DOC), many phytoplankton communities are comprised of unhealthy or physiologically stressed cells which release a large proportion of total photosynthate directly into the pool of labile DOC. This is proposed to be especially true in continental shelf and coastal environments where zones of productivity are patchy and phytoplankton populations adapted to one regime can be easily transported into waters which differ in salinity, nutrient supply, and/or turbidity. The significance of the work, however, extends beyond this immediate goal since there are presently relatively few methods which allow us to estimate the physiological state of phytoplankton cells.When we evaluate population sizes of phytoplankton in the water column or examine fecal pellets, particulate aggregates, or other material, we generally work in ignorance of the activity of the cells except as the average cell-specific activity is estimated from bulk measurements. This approach effectively hides any differences in the relative contribution of different taxa or individuals to overall productivity eventhough most flux processes are sensitive to physiological and taxonomically determined differences among members of the community.

  18. Coral photobiology: new light on old views.

    PubMed

    Iluz, David; Dubinsky, Zvy

    2015-04-01

    The relationship between reef-building corals and light-harvesting pigments of zooxanthellae (Symbiodinium sp.) has been acknowledged for decades. The photosynthetic activity of the algal endocellular symbionts may provide up to 90% of the energy needed for the coral holobiont. This relationship limits the bathymetric distribution of coral reefs to the upper 100 m of tropical shorelines. However, even corals growing under high light intensities have to supplement the photosynthates translocated from the algae by predation on nutrient-rich zooplankton. New information has revealed how the fate of carbon acquired through photosynthesis differs from that secured by predation, whose rates are controlled by light-induced tentacular extension. The Goreau paradigm of "light-enhanced calcification" is being reevaluated, based on evidence that blue light stimulates coral calcification independently from photosynthesis rates. Furthermore, under dim light, calcification rates were stoichiometrically uncoupled from photosynthesis. The rates of photosynthesis of the zooxanthellae exhibit a clear endogenous rhythmicity maintained by light patterns. This daily pattern is concomitant with a periodicity of all the antioxidant protective mechanisms that wax and wane to meet the concomitant fluctuation in oxygen evolution. The phases of the moon are involved in the triggering of coral reproduction and control the spectacular annual mass-spawning events taking place in several reefs. The intensity and directionality of the underwater light field affect the architecture of coral colonies, leading to an optimization of the exposure of the zooxanthellae to light. We present a summary of major gaps in our understanding of the relationship between light and corals as a roadmap for future research. PMID:25467066

  19. Mistletoes and mutant albino shoots on woody plants as mineral nutrient traps

    PubMed Central

    Lo Gullo, M. A.; Glatzel, G.; Devkota, M.; Raimondo, F.; Trifilò, P.; Richter, H.

    2012-01-01

    Background and Aims Potassium, sulphur and zinc contents of mistletoe leaves are generally higher than in their hosts. This is attributed to the fact that chemical elements which are cycled between xylem and phloem in the process of phloem loading of sugars are trapped in the mistletoe, because these parasites do not feed their hosts. Here it is hypothesized that mutant albino shoots on otherwise green plants should behave similarly, because they lack photosynthesis and thus cannot recycle elements involved in sugar loading. Methods The mineral nutrition of the mistletoe Scurrula elata was compared with that of albino shoots on Citrus sinensis and Nerium oleander. The potential for selective nutrient uptake by the mistletoe was studied by comparing element contents of host leaves on infected and uninfected branches and by manipulation of the haustorium–shoot ratio in mistletoes. Phloem anatomy of albino leaves was compared with that of green leaves. Key Results Both mistletoes and albino leaves had higher contents of potassium, sulphur and zinc than hosts or green leaves, respectively. Hypothetical discrimination of nutrient elements during the uptake by the haustorium is not supported by our data. Anatomical studies of albino leaves showed characteristics of release phloem. Conclusions Both albino shoots and mistletoes are traps for elements normally recycled between xylem and phloem, because retranslocation of phloem mobile elements into the mother plant or the host is low or absent. It can be assumed that the lack of photosynthetic activity in albino shoots and thus of sugars needed in phloem loading is responsible for the accumulation of elements. The absence of phloem loading is reflected in phloem anatomy of these abnormal shoots. In mistletoes the evolution of a parasitic lifestyle has obviously eliminated substantial feeding of the host with photosynthates produced by the mistletoe. PMID:22442343

  20. Contribution of Various Carbon Sources Toward Isoprene Biosynthesis in Poplar Leaves Mediated by Altered Atmospheric CO2 Concentrations

    PubMed Central

    Trowbridge, Amy M.; Asensio, Dolores; Eller, Allyson S. D.; Way, Danielle A.; Wilkinson, Michael J.; Schnitzler, Jörg-Peter; Jackson, Robert B.; Monson, Russell K.

    2012-01-01

    Biogenically released isoprene plays important roles in both tropospheric photochemistry and plant metabolism. We performed a 13CO2-labeling study using proton-transfer-reaction mass spectrometry (PTR-MS) to examine the kinetics of recently assimilated photosynthate into isoprene emitted from poplar (Populus × canescens) trees grown and measured at different atmospheric CO2 concentrations. This is the first study to explicitly consider the effects of altered atmospheric CO2 concentration on carbon partitioning to isoprene biosynthesis. We studied changes in the proportion of labeled carbon as a function of time in two mass fragments, M41+, which represents, in part, substrate derived from pyruvate, and M69+, which represents the whole unlabeled isoprene molecule. We observed a trend of slower 13C incorporation into isoprene carbon derived from pyruvate, consistent with the previously hypothesized origin of chloroplastic pyruvate from cytosolic phosphenolpyruvate (PEP). Trees grown under sub-ambient CO2 (190 ppmv) had rates of isoprene emission and rates of labeling of M41+ and M69+ that were nearly twice those observed in trees grown under elevated CO2 (590 ppmv). However, they also demonstrated the lowest proportion of completely labeled isoprene molecules. These results suggest that under reduced atmospheric CO2 availability, more carbon from stored/older carbon sources is involved in isoprene biosynthesis, and this carbon most likely enters the isoprene biosynthesis pathway through the pyruvate substrate. We offer direct evidence that extra-chloroplastic rather than chloroplastic carbon sources are mobilized to increase the availability of pyruvate required to up-regulate the isoprene biosynthesis pathway when trees are grown under sub-ambient CO2. PMID:22384238

  1. Impact of drought on C forms and fluxes in the soil - plant continuum

    NASA Astrophysics Data System (ADS)

    Rumpel, Cornelia; Sanaullah, Muhammad; Chabbi, Abad

    2016-04-01

    Global change is likely to increase the drought periods, which may have significant consequences for the turnover of SOM, in particular through their effect on plants. The aim of the study was to assess different compartments of the soil - plant continuum for their response to drought stress by combining field and laboratory experiments. We focused on three common grassland species (Lolium perenne, Festuca arundinacea and Dactylis glomerata) found to constitute grasslands of the temperate climate. We investigated drought impact on (1) plant biochemistry and potential mineralization of this material in soil, (2) decomposition of aboveground plant leaf litter of different quality, (3) plant-mediated soil C fluxes including (4) soil microbial biomass and their enzyme activities in the rhizosphere. Plant elemental and biochemical composition showed contrasting changes depending on the species in response to drought stress. The changes in elemental and biochemical composition of leaf litter, ultimately influenced its mineralization in soil. Drought stress highly modified the decomposition dynamics of litter from the three grassland species as a function of litter quality. Moreover, drought stress resulted in significant decrease in both shoot and root biomass in monocultures, while root biomass did not change when they were grown in mixture. Under drought stress, we observed higher belowground allocation of photosynthates and the drought had reduced root-derived respiration. This resulted in significant changes of soil enzyme activities. Our results suggested that plant species and community composition strongly influenced the drought effects in the rhizosphere. Thus, plant community composition and in particular the introduction of legumes might be used as a tool to attenuate drought stress not only because of different water use efficiency by plants, but also by their indirect effects on soil microbial activities affecting C and N cycles.

  2. In situ 13CO2 pulse labelling of field-grown eucalypt trees revealed the effects of potassium nutrition and throughfall exclusion on phloem transport of photosynthetic carbon.

    PubMed

    Epron, Daniel; Cabral, Osvaldo Machado Rodrigues; Laclau, Jean-Paul; Dannoura, Masako; Packer, Ana Paula; Plain, Caroline; Battie-Laclau, Patricia; Moreira, Marcelo Zacharias; Trivelin, Paulo Cesar Ocheuze; Bouillet, Jean-Pierre; Gérant, Dominique; Nouvellon, Yann

    2016-01-01

    Potassium (K) is an important limiting factor of tree growth, but little is known of the effects of K supply on the long-distance transport of photosynthetic carbon (C) in the phloem and of the interaction between K fertilization and drought. We pulse-labelled 2-year-old Eucalyptus grandis L. trees grown in a field trial combining K fertilization (+K and -K) and throughfall exclusion (+W and -W), and we estimated the velocity of C transfer by comparing time lags between the uptake of (13)CO2 and its recovery in trunk CO2 efflux recorded at different heights. We also analysed the dynamics of the labelled photosynthates recovered in the foliage and in the phloem sap (inner bark extract). The mean residence time of labelled C in the foliage was short (21-31 h). The time series of (13)C in excess in the foliage was affected by the level of fertilization, whereas the effect of throughfall exclusion was not significant. The velocity of C transfer in the trunk (0.20-0.82 m h(-1)) was twice as high in +K trees than in -K trees, with no significant effect of throughfall exclusion except for one +K -W tree labelled in the middle of the drought season that was exposed to a more pronounced water stress (midday leaf water potential of -2.2 MPa). Our results suggest that besides reductions in photosynthetic C supply and in C demand by sink organs, the lower velocity under K deficiency is due to a lower cross-sectional area of the sieve tubes, whereas an increase in phloem sap viscosity is more likely limiting phloem transport under drought. In all treatments, 10 times less (13)C was recovered in inner bark extracts at the bottom of the trunk when compared with the base of the crown, suggesting that a large part of the labelled assimilates has been exported out of the phloem and replaced by unlabelled C. This supports the 'leakage-retrieval mechanism' that may play a role in maintaining the pressure gradient between source and sink organs required to sustain high

  3. Ethylene, a Hormone at the Center-Stage of Nodulation.

    PubMed

    Guinel, Frédérique C

    2015-01-01

    Nodulation is the result of a beneficial interaction between legumes and rhizobia. It is a sophisticated process leading to nutrient exchange between the two types of symbionts. In this association, within a nodule, the rhizobia, using energy provided as photosynthates, fix atmospheric nitrogen and convert it to ammonium which is available to the plant. Nodulation is recognized as an essential process in nitrogen cycling and legume crops are known to enrich agricultural soils in nitrogenous compounds. Furthermore, as they are rich in nitrogen, legumes are considered important as staple foods for humans and fodder for animals. To tightly control this association and keep it mutualistic, the plant uses several means, including hormones. The hormone ethylene has been known as a negative regulator of nodulation for almost four decades. Since then, much progress has been made in the understanding of both the ethylene signaling pathway and the nodulation process. Here I have taken a large view, using recently obtained knowledge, to describe in some detail the major stages of the process. I have not only reviewed the steps most commonly covered (the common signaling transduction pathway, and the epidermal and cortical programs), but I have also looked into steps less understood (the pre-infection step with the plant defense response, the bacterial release and the formation of the symbiosome, and nodule functioning and senescence). After a succinct review of the ethylene signaling pathway, I have used the knowledge obtained from nodulation- and ethylene-related mutants to paint a more complete picture of the role played by the hormone in nodule organogenesis, functioning, and senescence. It transpires that ethylene is at the center of this effective symbiosis. It has not only been involved in most of the steps leading to a mature nodule, but it has also been implicated in host immunity and nodule senescence. It is likely responsible for the activation of other hormonal

  4. Carbon allocation belowground in Pinus pinaster using stable carbon isotope pulse labeling technique

    NASA Astrophysics Data System (ADS)

    Dannoura, M.; Bosc, A.; Chipeaux, C.; Sartore, M.; Lambrot, C.; Trichet, P.; Bakker, M.; Loustau, D.; Epron, D.

    2010-12-01

    Carbon allocation belowground competes with aboveground growth and biomass production. In the other hand, it contributes to resource acquisition such as nutrient, water and carbon sequestration in soil. Thus, a better characterization of carbon flow from plant to soil and its residence time within each compartment is an important issue for understanding and modeling forest ecosystem carbon budget. 13C pulse labeling of whole crown was conducted at 4 seasons to study the fate of assimilated carbon by photosynthesis into the root on 12 year old Pinus pinaster planted in the INRA domain of Pierroton. Maritime pine is the most widely planted species in South-West Europe. Stem, root and soil CO2 effluxes and their isotope composition were measured continuously by tunable diode laser absorption spectroscopy with a trace gas analyzer (TGA 100A; Campbell Scientific) coupled to flow-through chambers. 13CO2 recovery and peak were observed in respiration of each compartment after labeling. It appeared sequentially from top of stem to bottom, and to coarse root. The maximum velocity of carbon transfer was calculated as the difference in time lag of recovery between two positions on the trunk or on the root. It ranged between 0.08-0.2 m h-1 in stem and between 0.04-0.12 m h-1 in coarse root. This velocity was higher in warmer season, and the difference between time lag of recovery and peak increased after first frost. Photosynthates arrived underground 1.5 to 5 days after labeling, at similar time in soil CO2 effluxes and coarse root respiration. 0.08-1.4 g of carbon was respired per tree during first 20 days following labeling. It presented 0.6 -10% of 13C used for labeling and it is strongly related to seasons. The isotope signal was detected in fine root organs and microbial biomass by periodical core sampling. The peak was observed 6 days after labeling in early summer while it was delayed more than 10 days in autumn and winter with less amount of carbon allocated

  5. Modeling of the redox state dynamics in photosystem II of Chlorella pyrenoidosa Chick cells and leaves of spinach and Arabidopsis thaliana from single flash-induced fluorescence quantum yield changes on the 100 ns-10 s time scale.

    PubMed

    Belyaeva, N E; Schmitt, F-J; Paschenko, V Z; Riznichenko, G Yu; Rubin, A B

    2015-08-01

    The time courses of the photosystem II (PSII) redox states were analyzed with a model scheme supposing a fraction of 11-25 % semiquinone (with reduced [Formula: see text]) RCs in the dark. Patterns of single flash-induced transient fluorescence yield (SFITFY) measured for leaves (spinach and Arabidopsis (A.) thaliana) and the thermophilic alga Chlorella (C.) pyrenoidosa Chick (Steffen et al. Biochemistry 44:3123-3132, 2005; Belyaeva et al. Photosynth Res 98:105-119, 2008, Plant Physiol Biochem 77:49-59, 2014) were fitted with the PSII model. The simulations show that at high-light conditions the flash generated triplet carotenoid (3)Car(t) population is the main NPQ regulator decaying in the time interval of 6-8 μs. So the SFITFY increase up to the maximum level [Formula: see text]/F 0 (at ~50 μs) depends mainly on the flash energy. Transient electron redistributions on the RC redox cofactors were displayed to explain the SFITFY measured by weak light pulses during the PSII relaxation by electron transfer (ET) steps and coupled proton transfer on both the donor and the acceptor side of the PSII. The contribution of non-radiative charge recombination was taken into account. Analytical expressions for the laser flash, the (3)Car(t) decay and the work of the water-oxidizing complex (WOC) were used to improve the modeled P680(+) reduction by YZ in the state S 1 of the WOC. All parameter values were compared between spinach, A. thaliana leaves and C. pyrenoidosa alga cells and at different laser flash energies. ET from [Formula: see text] slower in alga as compared to leaf samples was elucidated by the dynamics of [Formula: see text] fractions to fit SFITFY data. Low membrane energization after the 10 ns single turnover flash was modeled: the ∆Ψ(t) amplitude (20 mV) is found to be about 5-fold smaller than under the continuous light induction; the time-independent lumen pHL, stroma pHS are fitted close to dark estimates. Depending on the flash energy used at 1

  6. Partitioning Soil Respiration Between Autotrophic and Heterotrophic Components in a Mature Boreal Black Spruce Stand

    NASA Astrophysics Data System (ADS)

    Gaumont-Guay, D.; Black, T. A.; Barr, A. G.; Jassal, R. S.; Morgenstern, K.; Nesic, Z.

    2005-12-01

    the seasonal variation in soil temperature, it was found to be strongly correlated with tree photosynthesis. Analysis showed a lagged response with a maximum correlation for 15-25 days Tree photosynthesis also exerted a strong control on autotrophic respiration at the diurnal time scale with a lagged response of approximately 12 hours. These results suggest that the characterization of the soil temperature and water regimes is not sufficient to describe accurately the seasonal and diurnal variations in soil respiration and its components. Models need to incorporate the controls of aboveground photosynthetic production, photosynthate allocation and phloem transport on soil respiration.

  7. A quantitative and qualitative comparison of aquatic and terrestrial plant lignin phenols: Critical information for paleoecological reconstructions

    NASA Astrophysics Data System (ADS)

    Thomas, E. K.; Gao, L.; Huang, Y.

    2009-12-01

    Currently, lignin phenols are used in marine and lacustrine ecosystems as proxies for terrestrial vegetation inputs. Lignins are found in all vascular plants, where they play a crucial role in conduction of water, nutrients and photosynthates through the vascular system, and where they provide structural support. Furthermore, different types of lignin phenols are found in specific types of vegetation (e.g., both syringyl and vanillyl phenols are in angiosperm wood, but only vanillyl phenols are in gymnosperm wood). The ratio of lignin phenols (e.g. syringyl:vanillyl) is indicative of the type of plant from which the lignin phenols were derived. Studies that examine lignin phenols in sedimentary archives assume that lignin phenols are derived solely from terrestrial plants, and changes in the types of lignin phenols are therefore assumed to mark changes in terrestrial vegetation. These assumptions may be flawed, however, because many aquatic plants, including those that are submerged, are vascular, yet little is known about the type and concentration of lignin phenols present in aquatic vascular plants. This knowledge is imperative to the success of paleoecological studies that utilize lignin phenols as a geochemical proxy for terrestrial vegetation. Furthermore, lignin phenols may be important targets for compound-specific radiocarbon dating, which is useful when suitable macrofossils are unavailable. Knowing the origin of the molecules used for radiocarbon dating, however, (i.e. whether they are terrestrial or aquatic) is critical to obtaining meaningful chronologies. We isolated and analyzed lignin phenol monomers from different types of aquatic vascular plants. All plants analyzed are angiosperms, but they occupy different niches in aquatic plant communities: floating, emergent and submergent. We also analyzed different parts of aquatic plants (i.e., stems and leaves). We found lignin phenols in all aquatic species that we analyzed, which highlights the need for

  8. Functional feedbacks by dwarf mistletoe of pine into global climate change in a Yellowstone forest ecosystem

    NASA Astrophysics Data System (ADS)

    Cullings, K.; Hanely, J.

    2009-12-01

    Dwarf mistletoe is a defoliating, carbon-sink pathogen that significantly affects host physiology, and nutrient and water relations. This pathogen is forecast to increase in range and severity in response to global climate change due to effects on host tree physiology. Via impacts on host tree photosynthetic capacity, dwarf mistletoe could directly influence soil processes that that are responsible for the release one of the world’s greatest sources of atmospheric CO2. Despite the obvious ramifications for global climate change (GCC) and potential for feedbacks into the process, no studies have been put forth measuring effects on terrestrial ecology and carbon relations. In this study we investigated effects of dwarf mistletoe infection of pines in Yellowstone on soil fungal species and functional diversity, activities of soil enzymes actively involved in woody breakdown (hence having direct impact on carbon sequestration), and soil CO2 efflux. Despite the wealth of knowledge regarding primary effects of dwarf mistletoe on host physiological process, there is virtually no information regarding secondary effects, for example on the organisms that rely upon host photosynthate, and that in turn play pivotal roles in carbon cycling and terrestrial ecology. In this study we provide the first look at these impacts. Results: 1) direct genetic tests indicate significant decreases in soil fungal species diversity and richness; 2) culture-based methods (Fungilogs) indicate a significant increase in the number of carbon substrates utilized by soil fungi (see table); 3) direct measures of soil enzyme activity indicate significant increases in woody substrate breakdown (see table); 4) direct in situ measures of soil CO2 efflux indicate a doubling of CO2 flux from soils (P<0.02) in infected blocks. Together, these results indicate that there are tertiary and quaternary-level feedbacks into the GCC process that result from primary and secondary effects on disease distribution

  9. Potassium nutrition and water availability affect phloem transport of photosynthetic carbon in eucalypt trees

    NASA Astrophysics Data System (ADS)

    Epron, Daniel; Cabral, Osvaldo; Laclau, Jean-Paul; Dannoura, Masako; Packer, Ana Paula; Plain, Caroline; Battie-Laclau, Patricia; Moreira, Marcelo; Trivelin, Paulo; Bouillet, Jean-Pierre; Gérant, Dominique; Nouvellon, Yann

    2015-04-01

    Potassium fertilisation strongly affects growth and carbon partitioning of eucalypt on tropical soil that are strongly weathered. In addition, potassium fertilization could be of great interest in mitigating the adverse consequences of drought in planted forests, as foliar K concentrations influence osmotic adjustment, stomatal regulation and phloem loading. Phloem is the main pathway for transferring photosynthate from source leaves to sink organs, thus controlling growth partitioning among the different tree compartments. But little is known about the effect of potassium nutrition on phloem transport of photosynthetic carbon and on the interaction between K nutrition and water availability. In situ 13C pulse labelling was conducted on tropical eucalypt trees (Eucalyptus grandis L.) grown in a trial plantation with plots in which 37% of throughfall were excluded (about 500 mm/yr) using home-made transparent gutters (-W) or not (+W) and plots that received 0.45 mol K m-2 applied as KCl three months after planting (+K) or not (-K). Three trees were labelled in each of the four treatments (+K+W, +K-W, -K+W and -K-W). Trees were labelled for one hour by injecting pure 13CO2 in a 27 m3 whole crown chamber. We estimated the velocity of carbon transfer in the trunk by comparing time lags between the uptake of 13CO2 and its recovery in trunk CO2 efflux recorded by off axis integrated cavity output spectroscopy (Los Gatos Research) in two chambers per tree, one just under the crown and one at the base of the trunk. We analyzed the dynamics of the label recovered in the foliage and in the phloem sap by analysing carbon isotope composition of bulk leaf organic matter and phloem extracts using an isotope ratio mass spectrometer. The velocity of carbon transfer in the trunk and the initial rate 13C disappearance from the foliage were much higher in +K trees than in -K trees with no significant effect of rainfall. The volumetric flow of phloem, roughly estimated by multiplying

  10. Effects of Drought Stress and Ozone Exposure on Isoprene Emissions from Oak Seedlings in Texas

    NASA Astrophysics Data System (ADS)

    Madronich, M. B.; Harte, A.; Schade, G. W.

    2014-12-01

    Isoprene is the dominant hydrocarbon emitted by plants to the atmosphere with an approximate global emission of 550 Tg C yr-1. Isoprene emission studies have elucidated plants' isoprene production capacity, and the controlling factors of instantaneous emissions. However, it is not yet well understood how long-term climatic factors such as drought and increasing ozone concentrations affect isoprene emission rates. Drought reduces photosynthetic activity and is thus expected to reduce isoprene emission rate, since isoprene production relies on photosynthates. On the other hand, ozone is also known to negatively affect photosynthesis rates, but can instead increase isoprene emissions. These apparent inconsistencies and a lack of experimental data make it difficult to accurately parameterize isoprene emission responses to changing environmental conditions. The objective of this work is to reduce some of these uncertainties, using oak seedlings as a study system. Our project focuses on isoprene emission responses of oak trees to typical summer drought and high ozone conditions in Texas. We report on experiments conducted using a laboratory whole-plant chamber and leaf-level data obtained from greenhouse-grown seedlings. The chamber experiment studied the effects of ozone and drought on isoprene emissions from >3 year old oak seedlings under controlled conditions of photosynthetically active radiation (PAR), temperature, soil-moisture and the chamber's air composition. Stress in plants was induced by manipulating potted soil-moisture and ozone concentration in the chamber. The greenhouse study focused on understanding the effects of drought under Texas climatic conditions. For this study we used two year old seedlings of water oak (Quercus nigra) and post oak (Quercus stellata). Temperature, humidity and light in the greenhouse followed local conditions. Leaf-level conductance, photosynthesis measurements and isoprene sampling were carried out under controlled leaf

  11. Whole-plant allocation to storage and defense in juveniles of related evergreen and deciduous shrub species.

    PubMed

    Wyka, T P; Karolewski, P; Żytkowiak, R; Chmielarz, P; Oleksyn, J

    2016-05-01

    In evergreen plants, old leaves may contribute photosynthate to initiation of shoot growth in the spring. They might also function as storage sites for carbohydrates and nitrogen (N). We hence hypothesized that whole-plant allocation of carbohydrates and N to storage in stems and roots may be lower in evergreen than in deciduous species. We selected three species pairs consisting of an evergreen and a related deciduous species: Mahonia aquifolium (Pursh) Nutt. and Berberis vulgaris L. (Berberidaceae), Prunus laurocerasus L. and Prunus serotina Ehrh. (Rosaceae), and Viburnum rhytidophyllum Hemsl. and Viburnum lantana L. (Adoxaceae). Seedlings were grown outdoors in pots and harvested on two dates during the growing season for the determination of biomass, carbohydrate and N allocation ratios. Plant size-adjusted pools of nonstructural carbohydrates in stems and roots were lower in the evergreen species of Berberidaceae and Adoxaceae, and the slope of the carbohydrate pool vs plant biomass relationship was lower in the evergreen species of Rosaceae compared with the respective deciduous species, consistent with the leading hypothesis. Pools of N in stems and roots, however, did not vary with leaf habit. In all species, foliage contained more than half of the plant's nonstructural carbohydrate pool and, in late summer, also more than half of the plant's N pool, suggesting that in juvenile individuals of evergreen species, leaves may be a major storage site. Additionally, we hypothesized that concentration of defensive phenolic compounds in leaves should be higher in evergreen than in deciduous species, because the lower carbohydrate pool in stems and roots of the former restricts their capacity for regrowth following herbivory and also because of the need to protect their longer-living foliage. Our results did not support this hypothesis, suggesting that evergreen plants may rely predominantly on structural defenses. In summary, our study indicates that leaf habit has

  12. Plant communities as drivers of soil respiration: pathways, mechanisms, and significance for global change

    NASA Astrophysics Data System (ADS)

    Metcalfe, D. B.; Fisher, R. A.; Wardle, D. A.

    2011-08-01

    produce large quantities of nutrient rich litter. Where this community shift occurs, it could drive an increase in R beyond that expected from direct climate impacts on soil microbial activity alone. We identify key gaps in knowledge and recommend them as priorities for future work. These include the patterns of photosynthate partitioning amongst belowground components, ecosystem level effects of individual plant traits, and the importance of trophic interactions and species invasions or extinctions for ecosystem processes. A final, overarching challenge is how to link these observations and drivers across spatio-temporal scales to predict regional or global changes in R over long time periods. A more unified approach to understanding R, which integrates information about plant traits and community dynamics, will be essential for better understanding, simulating and predicting patterns of R across terrestrial ecosystems and its role within the earth-climate system.

  13. Plant communities as drivers of soil respiration: pathways, mechanisms, and significance for global change

    NASA Astrophysics Data System (ADS)

    Metcalfe, D. B.; Fisher, R. A.; Wardle, D. A.

    2011-03-01

    Understanding the impacts of plant community characteristics on soil carbon dioxide efflux (R) is a key prerequisite for accurate prediction of the future carbon balance of terrestrial ecosystems under climate change. In this review, we synthesize relevant information from a wide spectrum of sources to evaluate the current state of knowledge about plant community effects on R, examine how this information is incorporated into global climate models, and highlight priorities for future research. Plant species consistently exhibit cohesive suites of traits, linked to contrasting life history strategies, which exert a variety of impacts on R. As such, we propose that plant community shifts towards dominance by fast growing plants with nutrient rich litter could provide a major, though often neglected, positive feedback to climate change. Within vegetation types, belowground carbon flux will mainly be controlled by photosynthesis, while amongst vegetation types this flux will be more dependent upon the specific characteristics of the plant life form. We also make the case that community composition, rather than diversity, is usually the dominant control on ecosystem processes in natural systems. Individual species impacts on R may be largest where the species accounts for most of the biomass in the ecosystem, has very distinct traits to the rest of the community, or modulates the occurrence of major natural disturbances. We show that climate-vegetation models incorporate a number of pathways whereby plants can affect R, but that simplifications regarding allocation schemes and drivers of litter decomposition may limit model accuracy. This situation could, however, be relatively easily improved with targeted experimental and field studies. Finally, we identify key gaps in knowledge and recommend them as priorities for future work. These include the patterns of photosynthate partitioning amongst belowground components, ecosystem level effects of individual plant traits

  14. Assessment of growth and yield losses in two Zea mays L. cultivars (quality protein maize and nonquality protein maize) under projected levels of ozone.

    PubMed

    Singh, Aditya Abha; Agrawal, S B; Shahi, J P; Agrawal, Madhoolika

    2014-02-01

    Rapid industrialization and economic developments have increased the tropospheric ozone (O3) budget since preindustrial times, and presently, it is supposed to be a major threat to crop productivity. Maize (Zea mays L.), a C4 plant is the third most important staple crop at global level with a great deal of economic importance. The present study was conducted to evaluate the performance of two maize cultivars [HQPM1: quality protein maize (QPM)] and [DHM117: nonquality protein maize (NQPM)] to variable O3 doses. Experimental setup included filtered chambers, nonfiltered chambers (NFC), and two elevated doses of O3 viz. NFC+15 ppb O3 (NFC+15) and NFC+30 ppb O3 (NFC+30). During initial growth period, both QPM and NQPM plants showed hormetic effect that is beneficial due to exposure of low doses of a toxicant (NFC and NFC+15 ppb O3), but at later stages, growth attributes were negatively affected by O3. Growth indices showed the variable pattern of photosynthate translocation under O3 stress. Foliar injury in the form of interveinal chlorosis and reddening of leaves due to increased production of anthocyanin pigments was observed at higher concentrations of O3. One-dimensional gel electrophoresis of leaves taken from NFC+30 showed reductions of major photosynthetic proteins, and differential response was observed between the two test cultivars. Decline in the number of male flowers at elevated O3 doses suggested damaging effect of O3 on reproductive structures which might be a cause of productivity losses. Variable carbon allocation pattern particularly to husk leaves, foliar injury, and damage of photosynthetic proteins led to significant reductions in economic yield at higher O3 doses. PCA showed that both the cultivars responded more or less similarly to O3 stress in their respective groupings of growth and yield parameters, but magnitude of their response was variable. It is further supported by difference in the significance of correlations between variables of

  15. Carbon dioxide and temperature effects on pima cotton development

    SciTech Connect

    Reddy, K.R.; Hodges, H.F.; McKinion, J.M.

    1995-09-01

    Predicting plant responses to changing atmospheric CO{sub 2} and to the possible global warming are important concerns. Effects of CO{sub 2} on developmental events are poorly documented, as is the interaction of CO{sub 2} and other major climate variables on crop development. This experiment examines the effects of an altered CO{sub 2} environment and interactions of CO{sub 2} and temperature on pima cotton developmental rates. Pima cotton was grown from seed in sun-lit plant growth chambers. Air temperatures were controlled form 20/12 to 40/32{degrees}C (day/night) in 5-degree increments. Daytime CO{sub 2} was maintained at 350 or 700 {mu}L L{sup {minus}1}. In a second experiment, the temperature was maintained at 30/22{degrees}C day/night and the plants were grown in 350, 450, or 700 {mu}L L{sup {minus}1} CO{sub 2}. Rates of mainstem node formation and the time required to produce the first square and first flower were not sensitive to atmospheric CO{sub 2}, but were very sensitive to temperature. Prefruiting branch nodal positions required longer to develop than nodes with fruiting branches. Carbon dioxide levels did not affect the time required to produce nodes. Number of branches produced was sensitive to both temperature and CO{sub 2}. The larger number of bolls set on the lower branches of plants grown at high CO{sub 2} provided a larger sink for photosynthate than plants grown at low CO{sub 2} (possibly explaining reduction in number of fruit at the upper nodes of high-CO{sub 2}-grown plants). More bolls and squares were produced and retained on plants grown in high-CO{sub 2} environments, except that none were produced at 40/32{degrees}C. Results indicate high-temperature-tolerant cotton cultivars would be more productive in the present-day CO{sub 2} world, and they would be essential in the future if global temperature increases. 30 refs., 8 figs.

  16. Reactions to cadmium stress in a cadmium-tolerant variety of cabbage (Brassica oleracea L.): is cadmium tolerance necessarily desirable in food crops?

    PubMed

    Jinadasa, Neel; Collins, Damian; Holford, Paul; Milham, Paul J; Conroy, Jann P

    2016-03-01

    Cadmium is a cumulative, chronic toxicant in humans for which the main exposure pathway is via plant foods. Cadmium-tolerant plants may be used to create healthier food products, provided that the tolerance is associated with the exclusion of Cd from the edible portion of the plant. An earlier study identified the cabbage (Brassica oleracea L.) variety, Pluto, as relatively Cd tolerant. We exposed the roots of intact, 4-week-old seedlings of Pluto to Cd (control ∼1 mg L(-1) treatment 500 μg L(-1)) for 4 weeks in flowing nutrient solutions and observed plant responses. Exposure began when leaf 3 started to emerge, plants were harvested after 4 weeks of Cd exposure and the high Cd treatment affected all measured parameters. The elongation rate of leaves 4-8, but not the duration of elongation was reduced; consequently, individual leaf area was also reduced (P < 0.001) and total leaf area and dry weight were approximately halved. A/C i curves immediately before harvest showed that Cd depressed the photosynthetic capacity of the last fully expanded leaf (leaf 5). Despite such large impairments of the source and sink capacities, specific leaf weight and the partitioning of photosynthate between roots, stems and leaves were unaffected (P > 0.1). Phytochelatins (PCs) and glutathione (GSH) were present in the roots even at the lowest Cd concentration in the nutrient medium, i.e. ∼1 μg Cd L(-1), which would not be considered contaminated if it were a soil solution. The Cd concentration in these roots was unexpectedly high (5 mg kg(-1) DW) and the molar ratio of -SH (in PCs plus GSH) to Cd was large (>100:1). In these control plants, the Cd concentration in the leaves was 1.1 mg kg(-1) DW, and PCs were undetectable. For the high Cd treatment, the concentration of Cd in roots exceeded 680 mg kg(-1) DW and the molar -SH to Cd ratio fell to ∼1.5:1. For these plants, Cd flooded into the leaves (107 mg kg(-1) DW) where it probably induced synthesis of PCs, and the

  17. The carbon isotopic composition of soil respiration in the decade following disturbance by bark beetle or stem girdling

    NASA Astrophysics Data System (ADS)

    Chan, A.; Maurer, G. E.; Bowling, D. R.

    2013-12-01

    Recent outbreaks of mountain pine beetle have caused large-scale tree mortality in western North America, which can lead to fundamental changes in carbon cycling. When a tree is infested, the flow of photosynthate is disrupted. This causes the roots and their symbionts to die, eliminating the autotrophic component of soil respiration. Mycorrhizal fungi are enriched in 13C compared to plant tissues. As the dead fungal biomass is consumed by soil heterotrophs, the δ13C of CO2 in heterotrophic soil respiration may become more enriched as the fungal biomass is consumed. We investigated this response by measuring soil respiration in chronosequences of stem-girdled plots at the Niwot Ridge AmeriFlux site, and beetle-killed plots at the Fraser Experimental Forest, both in Colorado. Stem girdling was used to simulate beetle attack because it kills trees by a similar mechanism. Plots at Niwot Ridge included live trees and 7 years of girdled plots extending back to 2002. Plots at Fraser included live trees and three age classes of beetle-killed trees, within a similar chronosequence. We used manual soil-gas sampling at three depths, during the summers of 2011 and 2012, to determine if there is an isotopic effect associated with disturbance. Consistent with our expectations, in 2011, we found an enrichment in δ13C of approximately 1‰ in the two years following girdling which was absent in subsequent years. Although this pattern was also evident in 2012, the enrichment in δ13C during the same time period was about half that in 2011. At both Niwot and Fraser, in 2011, seasonal mean δ13C decreased by about 1‰ at all depths 3-4 years after disturbance, but returned to values close to control plots in the following 4-6 years. While we found a similar pattern at Fraser in 2012, we measured an enrichment of 1-1.5‰ at the OA interface at Niwot 8-10 years after disturbance, which was not found in 2011. It is possible this is due to the decomposition of woody biomass. At both

  18. Effects of the 100-year most severe El Niño driven drought on above and below ground CO2 exchanges in a seasonal tropical forest

    NASA Astrophysics Data System (ADS)

    Detto, M.; Muller-Landau, H. C.; Davies, S. J.; Rubio Ramos, V. E.

    2015-12-01

    The role of environmental drivers in regulating carbon exchanges, such as the combined effects of different meteorological and hydrological factors, are still poorly understood in many tropical forests. For example, Central American tropical forests are characterized by a distinct dry season with large atmospheric evaporative demand, driven by solar radiations and sustained winds. In contrast, during the wet seasons, cloudiness results in lower radiation inputs but higher diffuse fraction, and higher water availability. Our site, Barro Colorado Island, located in Gatun Lake, Central Panama, averages 2800 mm of annual precipitation, with a pronounced dry season in Jan-Apr. Forest age varies between 100 and >400 yr. In July 2012, an eddy covariance system was installed on a 41 m tower on the top plateau of the island. In the current year (2015) the island is experiencing the most severe El Niño driven drought on record (precipitation is measured since 1921). The eddy covariance measurements show that carbon and water fluxes are strongly influenced by hydrological conditions. Prolonged dry spells during the dry season limit both above ground fluxes (ET and GPP) and below ground processes (root and microbial activities). Light use efficiency is about 30% lower during the dry season and evapotranspiration can be as 40% below potential. These decreases in ecosystem functions are driven primarily by a combination of structural (reduction in leaf area) and physiological (stomata regulation) adaptation. Similarly, soil effluxes respond strongly to hydrological conditions. In the dry season, lower soil respiration rates are spaced out by rare rain events generating large pulses. In contrast, during the wet season, frequent rain events suppress soil CO2effluxes, because of reduced diffusivity and oxygen depletion. Diurnal variation of soil respiration also suggested a potential translocation of photosynthates from leaf to roots to increase nutrient uptake during the dry

  19. Seasonal variations of belowground carbon transfer assessed by in situ 13CO2 pulse labelling of trees

    NASA Astrophysics Data System (ADS)

    Epron, D.; Ngao, J.; Dannoura, M.; Bakker, M. R.; Zeller, B.; Bazot, S.; Bosc, A.; Plain, C.; Lata, J. C.; Priault, P.; Barthes, L.; Loustau, D.

    2011-05-01

    Soil CO2 efflux is the main source of CO2 from forest ecosystems and it is tightly coupled to the transfer of recent photosynthetic assimilates belowground and their metabolism in roots, mycorrhiza and rhizosphere microorganisms feeding on root-derived exudates. The objective of our study was to assess patterns of belowground carbon allocation among tree species and along seasons. Pure 13CO2 pulse labelling of the entire crown of three different tree species (beech, oak and pine) was carried out at distinct phenological stages. Excess 13C in soil CO2 efflux was tracked using tuneable diode laser absorption spectrometry to determine time lags between the start of the labelling and the appearance of 13C in soil CO2 efflux and the amount of 13C allocated to soil CO2 efflux. Isotope composition (δ13C) of CO2 respired by fine roots and soil microbes was measured at several occasions after labelling, together with δ13C of bulk root tissue and microbial carbon. Time lags ranged from 0.5 to 1.3 days in beech and oak and were longer in pine (1.6-2.7 days during the active growing season, more than 4 days during the resting season), and the transfer of C to the microbial biomass was as fast as to the fine roots. The amount of 13C allocated to soil CO2 efflux was estimated from a compartment model. It varied between 1 and 21 % of the amount of 13CO2 taken up by the crown, depending on the species and the season. While rainfall exclusion that moderately decreased soil water content did not affect the pattern of carbon allocation to soil CO2 efflux in beech, seasonal patterns of carbon allocation belowground differed markedly between species, with pronounced seasonal variations in pine and beech. In beech, it may reflect competition with the strength of other sinks (aboveground growth in late spring and storage in late summer) that were not observed in oak. We report a fast transfer of recent photosynthates to the mycorhizosphere and we conclude that the patterns of carbon

  20. Plants determine diversity and function of soil microbial and mesofaunal communities - results from a girdling experiments in a temperate coniferous forest

    NASA Astrophysics Data System (ADS)

    Subke, J.; Voke, N.; Leronni, V.; Briones, M. J. I.; Ineson, P.

    2009-04-01

    The potential for carbon (C) sequestration in soils depends on the rate of humification of C inputs to soils in relation to the decomposition of old soil organic matter. Recent results indicate a close connection between the input of fresh organic matter and the decomposition of old organic matter through soil priming. We conducted a tree girdling experiment in order to better understand the interdependence of soil microbial communities and plant belowground C allocation. A girdling experiment in a mature Western Hemlock (Tsuga heterophylla) stand near York (NE England) confirms the pattern observed in other girdling studies, with a reduction in total soil CO2 efflux (RS) to about 60% of control plots following a delay of about 2 weeks. High frequency measurements of RS immediately after girdling show a short-lived significant increase in RS in girdled plots between 3 and 8 hours after tree girdling, which have not been observed previously. The autotrophic flux contribution (calculated as the difference in RS between the control and girdled plots) declined throughout autumn, but in contrast to most girdling studies, remained significantly greater than zero throughout during December and January. This result indicates that tree belowground allocation continues throughout winter, despite regular night-time frosts in the period measurement were taken. Dominant mesofauna invertebrates (Enchytraeid worms) showed a positive response to girdling and higher abundances were recorded in the girdled plots when compared to the control ones, although differences were only significant on one sampling occasion. These results suggest that, in contrast to other components of the soil food-web, these organisms appear to be underpinned by detrital decomposition rather than by recent photosynthate-C deposition. Litterbag incubations showed no significant short-term treatment effect over the 4 months period following girdling, indicating no measurable interaction of decomposition and

  1. Tree ring isotopes of beech and spruce in response to short-term climate variability across Central European sites: Common and contrasting physiological mechanisms

    NASA Astrophysics Data System (ADS)

    Weigt, Rosemarie; Klesse, Stefan; Treydte, Kerstin; Frank, David; Saurer, Matthias; Siegwolf, Rolf T. W.

    2016-04-01

    The combined study of tree-ring width and stable C and O isotopes provides insight in the coherences between carbon allocation during stem growth and the preceding conditions of gas exchange and formation of photosynthates as all influenced by environmental variation. In this large-scale study comprising 10 sites across a range of climate gradients (temperature, precipitation) throughout Central Europe, we investigated tree-rings in European beech (Fagus sylvatica) and Norway spruce (Picea abies) trees. The sampling design included larger and smaller trees. The short-term, i.e. year-to-year, variability in the isotope time series over 100 yrs was analyzed in relation to tree-ring growth and climate variation. The generally strong correlation between the year-to-year differences in δ13C (corrected for the atmospheric shift due to 13C-depleted CO2 from fossil combustion) and δ18O across most sites emphasized the role of stomatal conductance in controlling leaf gas exchange. However, the correlation between both isotopes decreased during some periods. At several sites this reduction in correlation was particularly pronounced during recent decades. This suggests a decoupling between stomatal and photosynthetic responses to environmental conditions on the one hand, and carbon allocation to stem tissue on the other hand. Variability in the isotopic ratio largely responded to summer climate, but was weakly correlated to annual stem growth. In contrast, climate sensitivity of radial growth in both species was rather site-dependent, and was strongest at the driest (in terms of soil water capacity) site. We will also present results of isotope responses with respect to extreme climate events. Understanding the underlying physiological mechanisms controlling the short-term variation in tree-ring signals will help to assess and more precisely constrain the possible range of growth performance of these ecologically and economically important tree species under future climate

  2. Forest soil respiration rate and delta13C is regulated by recent above ground weather conditions.

    PubMed

    Ekblad, Alf; Boström, Björn; Holm, Anders; Comstedt, Daniel

    2005-03-01

    Soil respiration, a key component of the global carbon cycle, is a major source of uncertainty when estimating terrestrial carbon budgets at ecosystem and higher levels. Rates of soil and root respiration are assumed to be dependent on soil temperature and soil moisture yet these factors often barely explain half the seasonal variation in soil respiration. We here found that soil moisture (range 16.5-27.6% of dry weight) and soil temperature (range 8-17.5 degrees C) together explained 55% of the variance (cross-validated explained variance; Q2) in soil respiration rate (range 1.0-3.4 micromol C m(-2) s(-1)) in a Norway spruce (Picea abies) forest. We hypothesised that this was due to that the two components of soil respiration, root respiration and decomposition, are governed by different factors. We therefore applied PLS (partial least squares regression) multivariate modelling in which we, together with below ground temperature and soil moisture, used the recent above ground air temperature and air humidity (vapour pressure deficit, VPD) conditions as x-variables. We found that air temperature and VPD data collected 1-4 days before respiration measurements explained 86% of the seasonal variation in the rate of soil respiration. The addition of soil moisture and soil temperature to the PLS-models increased the Q2 to 93%. delta13C analysis of soil respiration supported the hypotheses that there was a fast flux of photosynthates to root respiration and a dependence on recent above ground weather conditions. Taken together, our results suggest that shoot activities the preceding 1-6 days influence, to a large degree, the rate of root and soil respiration. We propose this above ground influence on soil respiration to be proportionally largest in the middle of the growing season and in situations when there is large day-to-day shifts in the above ground weather conditions. During such conditions soil temperature may not exert the major control on root respiration. PMID

  3. Friend or foe? Evolutionary history of glycoside hydrolase family 32 genes encoding for sucrolytic activity in fungi and its implications for plant-fungal symbioses

    PubMed Central

    Parrent, Jeri Lynn; James, Timothy Y; Vasaitis, Rimvydas; Taylor, Andrew FS

    2009-01-01

    Background Many fungi are obligate biotrophs of plants, growing in live plant tissues, gaining direct access to recently photosynthesized carbon. Photosynthate within plants is transported from source to sink tissues as sucrose, which is hydrolyzed by plant glycosyl hydrolase family 32 enzymes (GH32) into its constituent monosaccharides to meet plant cellular demands. A number of plant pathogenic fungi also use GH32 enzymes to access plant-derived sucrose, but less is known about the sucrose utilization ability of mutualistic and commensal plant biotrophic fungi, such as mycorrhizal and endophytic fungi. The aim of this study was to explore the distribution and abundance of GH32 genes in fungi to understand how sucrose utilization is structured within and among major ecological guilds and evolutionary lineages. Using bioinformatic and PCR-based analyses, we tested for GH32 gene presence in all available fungal genomes and an additional 149 species representing a broad phylogenetic and ecological range of biotrophic fungi. Results We detected 9 lineages of GH32 genes in fungi, 4 of which we describe for the first time. GH32 gene number in fungal genomes ranged from 0–12. Ancestral state reconstruction of GH32 gene abundance showed a strong correlation with nutritional mode, and gene family expansion was observed in several clades of pathogenic filamentous Ascomycota species. GH32 gene number was negatively correlated with animal pathogenicity and positively correlated with plant biotrophy, with the notable exception of mycorrhizal taxa. Few mycorrhizal species were found to have GH32 genes as compared to other guilds of plant-associated fungi, such as pathogens, endophytes and lichen-forming fungi. GH32 genes were also more prevalent in the Ascomycota than in the Basidiomycota. Conclusion We found a strong signature of both ecological strategy and phylogeny on GH32 gene number in fungi. These data suggest that plant biotrophic fungi exhibit a wide range of ability

  4. Seasonal variations of the amount of carbon allocated to respiration after in situ 13CO2 pulse labelling of trees (Invited)

    NASA Astrophysics Data System (ADS)

    Epron, D.; Dannoura, M.; Ngao, J.; Plain, C.; Berveller, D.; Chipeaux, C.; Gerant, D.; Bosc, A.; Maillard, P.; Loustau, D.; Damesin, C.; Cats Project (Anr-07-Blan-0109)

    2010-12-01

    Soil and trunk respiration are the major sources of carbon from forest ecosystems to the atmosphere and they account for a large fraction of total ecosystem respiration. The amount of photosynthate allocated to respiration affects the growth of the tree and the potential for carbon sequestration of forest ecosystems. This study, aiming at understanding patterns of carbon allocation to respiration among species and seasons, consisted in pure 13CO2 labelling of the entire crown of three different tree species (beech, oak and pine) at distinct phenological stages between Sept 2008 and Feb 2010. 13C was then tracked for several weeks in soil and trunk CO2 efflux at high temporal resolution using tuneable diode laser absorption spectrometry (Plain et al. 2009). Recovery of 13C in trunk and soil CO2 efflux was observed a few couple of hours after the beginning of the labelling in oak and beech. There is a rapid transfer of 13C belowground with a maximum occurring within 2 to 4 days after labelling. Label was recovered at the same time in the respiration and in the biomass of both fine roots and microbes. Maximum recovery occurred earlier in beech and oak, while it happened later in Pine. Indeed, the velocity of phloem transport, calculated as the difference of time lags in 13C recovery in trunk respiration at different height, was around 0.10-0.2m/h in pine and around 0.2-1.2 m/h in oak and beech, reflecting difference in phloem anatomy between angiosperm and gymnosperm. The cumulated amount of label recovered in soil CO2 efflux 20 days after labelling varied among the seasons in all species, from 1 to 16% in beech, 2 to 11% in oak and 1 to 11% in pine. For all species, allocation to soil respiration was greater in early summer compared to spring, late summer and autumn. A compartmental analysis is further conducted to characterise functional pools of labelled substrates and storage compounds that contribute to both trunk and soil respiration. [Plain C, Gérant D

  5. Mesocosm-Scale Experimental Quantification of Plant-Fungi Associations on Carbon Fluxes and Mineral Weathering

    NASA Astrophysics Data System (ADS)

    Andrews, M. Y.; Palmer, B.; Leake, J. R.; Banwart, S. A.; Beerling, D. J.

    2009-12-01

    H, conductivity, and geochemistry) are very different from each other, and from the plant-free controls. 14C labelling of the above-ground shoots indicates preferential allocation of photosynthate to fungal partners associated with basalt as compared to granite. Ongoing measurements will characterize the effects of fungal colonization on basalt and granite weathering in these systems. The novel ability to simultaneously measure biological and geochemical processes with depth allows us to better understand the role of plant and fungal evolution in the shaping Earth’s CO2 history.

  6. Topographic Structure from Motion

    NASA Astrophysics Data System (ADS)

    Fonstad, M. A.; Dietrich, J. T.; Courville, B. C.; Jensen, J.; Carbonneau, P.

    2011-12-01

    The production of high-resolution topographic datasets is of increasing concern and application throughout the geomorphic sciences, and river science is no exception. Consequently, a wide range of topographic measurement methods have evolved. Despite the range of available methods, the production of high resolution, high quality digital elevation models (DEMs) generally requires a significant investment in personnel time, hardware and/or software. However, image-based methods such as digital photogrammetry have steadily been decreasing in costs. Initially developed for the purpose of rapid, inexpensive and easy three dimensional surveys of buildings or small objects, the "structure from motion" photogrammetric approach (SfM) is a purely image based method which could deliver a step-change if transferred to river remote sensing, and requires very little training and is extremely inexpensive. Using the online SfM program Microsoft Photosynth, we have created high-resolution digital elevation models (DEM) of rivers from ordinary photographs produced from a multi-step workflow that takes advantage of free and open source software. This process reconstructs real world scenes from SfM algorithms based on the derived positions of the photographs in three-dimensional space. One of the products of the SfM process is a three-dimensional point cloud of features present in the input photographs. This point cloud can be georeferenced from a small number of ground control points collected via GPS in the field. The georeferenced point cloud can then be used to create a variety of digital elevation model products. Among several study sites, we examine the applicability of SfM in the Pedernales River in Texas (USA), where several hundred images taken from a hand-held helikite are used to produce DEMs of the fluvial topographic environment. This test shows that SfM and low-altitude platforms can produce point clouds with point densities considerably better than airborne LiDAR, with

  7. Seasonality in a boreal forest ecosystem affects the use of soil temperature and moisture as predictors of soil CO2 efflux

    NASA Astrophysics Data System (ADS)

    Niinistö, S. M.; Kellomäki, S.; Silvola, J.

    2011-03-01

    Our objectives were to identify factors related to temporal variation of soil CO2 efflux in a boreal pine forest and to evaluate simple predictive models of temporal variation of soil CO2 efflux. Soil CO2 efflux was measured with a portable chamber in a Finnish Scots pine forest for three years, with a fourth year for model evaluation. Plot averages for soil CO2 efflux ranged from 0.04 to 0.90 g CO2 m-2 h-1 during the snow-free period, i.e. May-October, and from 0.04 to 0.13 g CO2 m-2 h-1 in winter. Soil temperature was a good predictor of soil CO2 efflux. A quadratic model of ln-transformed efflux explained 76-82% of the variation over the snow-free period. The results revealed strong seasonality: at a given soil temperature, soil CO2 efflux was higher later in the snow-free period than in spring and early summer. Regression coefficients for temperature (approximations of a Q10 value) of month-specific models decreased with increasing average soil temperatures. Efflux in July, the month of peak photosynthesis, showed no clear response to temperature or moisture. Inclusion of a seasonality index, degree days, improved the accuracy of temperature response models to predict efflux for the fourth year of measurements, which was not used in building of regression models. Underestimation during peak efflux (mid-July to late-August) remained uncorrected. The strong influence of the flux of photosynthates belowground and the importance of root respiration could explain the relative temperature insensitivity observed in July and together with seasonality of growth of root and root-associated mycorrhizal fungi could explain partial failure of models to predict magnitude of efflux in the peak season from mid-July to August. The effect of moisture early in the season was confounded by simultaneous advancement of the growing season and increase in temperature. In a dry year, however, the effect of drought was evident as soil CO2 efflux was some 30% smaller in September than in

  8. Diel patterns of soil respiration in a moist subtropical forest: key drivers and future research needs

    NASA Astrophysics Data System (ADS)

    Gutiérrez del Arroyo, O.; Wood, T. E.

    2014-12-01

    Moist tropical forests have the highest soil respiration rates (Rs) of any terrestrial ecosystem and account for approximately one third of the world's soil carbon (C) pool. Small increases in the magnitude of Rs in these ecosystems can result in high rates of soil C loss, with significant consequences for global climate change. Identifying the climatic controls of Rs in moist subtropical forests will improve our ability to predict how this large C flux will respond to climate change. Our objectives were (1) to determine whether Rs varies on diel timescales, (2) whether diel Rs patterns vary seasonally, and (3) identify biophysical drivers of this temporal variation. We measured hourly Rs in a secondary, moist subtropical forest in Puerto Rico for a 3-year period using an automated soil respiration system (LI-COR 8100/8150 with six chambers). Concomitant with Rs we measured hourly variation in several climatic drivers (air/soil temperature, soil moisture, relative humidity, and photosynthetically active radiation). Soil respiration showed significant diel variation, with the magnitude, amplitude, and shape of these curves varying throughout the year. Overall, diel Rs peaked in the late afternoon and reached a minimum in the early morning. Diel amplitudes ranged from 1 to 7 μmol CO2 m-2 s-1, with larger amplitudes occurring in warmer months that also have higher rates of Rs. In warmer months Rs exhibited a strong bimodal pattern, and a narrower diel range with a single peak in cooler and drier months. Diel Rs was positively correlated with soil temperature, but this relationship was non-linear during the day and linear at night (i.e., hysteresis). The bimodal pattern of Rs may be due to a mid-day depression of photosynthesis when humidity is low and air temperature is high, thereby reducing transport of photosynthate to the roots and decreasing rhizospheric respiration. The hysteresis between Rs and temperature suggests multiple controls on Rs on diel time

  9. Temperature-driven seasonal and diel variation in soil respiration in a moist subtropical forest in Puerto Rico

    NASA Astrophysics Data System (ADS)

    Gutiérrez del Arroyo, O.; Wood, T. E.; Lugo, A. E.

    2013-12-01

    Tropical forest soils are the largest natural source of carbon dioxide (CO2) to the atmosphere and have the highest soil respiration rates, globally. Currently, we have little understanding of how this large carbon (C) flux will respond to ongoing changes in climate. Identifying climatic controls and natural variability of soil respiration (Rs) in these ecosystems could improve our ability to predict feedbacks to future climate change. We measured hourly Rs in a secondary, moist subtropical forest in Puerto Rico for a 2-year period using an automated soil respiration system (LI-COR 8100) to determine at what time-scale Rs varies and whether this variability can be explained by abiotic factors such as temperature and moisture. Soil respiration varied significantly at both seasonal and diel time-scales. Mean monthly Rs ranged from 4 to 12 μmol CO2 m-2 s-1 and the seasonal variation was positively correlated with air temperature (p<0.0001, R2=0.69). In addition, Rs was notably reduced immediately following large precipitation events, possibly due to reduced diffusion rates out of the soil or low oxygen availability; however, precipitation was not related to Rs on a seasonal time-scale. Soil respiration also demonstrated significant diel variation, changing from 1.5 to 3.5 μmol CO2 m-2 s-1 throughout the day. As with seasonal variation, Rs was positively correlated to soil temperature (p<0.0001, R2=0.61) on a diel time-scale. Diel Rs was decoupled with soil temperature at midday possibly responding to a depression in photosynthesis, which may pause the transport of photosynthate to the roots. The shape of the temperature-Rs hysteresis effect changed seasonally in concert with air temperature. The significant positive effect of temperature on Rs in this forest, despite low intra-annual variability (<4°C), suggests that soil C loss from moist subtropical forests could increase as global temperatures rise. Diel hysteresis effects of Rs suggest that temperature has both

  10. The role of growth rate, redox-state of the plastoquinone pool and the trans-thylakoid deltapH in photoacclimation of Chlorella vulgaris to growth irradiance and temperature.

    PubMed

    Wilson, K E; Huner, N P

    2000-12-01

    The long-term photoacclimation of Chlorella vulgaris Beijer (UTEX 265) to growth irradiance and growth temperature under ambient CO2 conditions was examined. While cultures grew at a faster rate at 27 than at 5 degrees C, growth rates appeared to be independent of irradiance. Decreases in light-harvesting polypeptide accumulation, increases in xanthophyll pool size and changes in the epoxidation state of the xanthophyll cycle pigments were correlated linearly with increases in the relative reduction state of QA, the primary quinone receptor of photosystem II, when estimated as 1-qP under steady-state growth conditions. However, we show that there is also a specific temperature-dependent component, in addition to the redox-state of the QA, involved in regulating the content and composition of light-harvesting complex II of C. vulgaris. In contrast, modulation of the epoxidation state of the xanthophyll pool in response to increased 1-qP in cells grown at 5 degrees C was indistinguishable from that of cells grown at 27 degrees C, indicating that light and temperature interact in a similar way to regulate xanthophyll cycle activity in C. vulgaris. Because C. vulgaris exhibited a low-light phenotype in the presence of 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU), but a high-light phenotype upon addition of 2,5-dibromo-6-isopropyl-3-methyl-1,4-benzoquinone, we conclude that the plastoquinone pool acts as a sensor regulating the accumulation of light-harvesting polypeptides in C. vulgaris. However, concomitant measurements of non-photochemical fluorescence quenching (qN) and the epoxidation state of the xanthophyll pool appear to indicate that, in addition to the redox-state of the plastoquinone pool, the trans-thylakoid deltapH may also contribute to sensing changes in irradiance and temperature that would lead to over-excitation of the photosynthetic apparatus. We suggest that sink capacity as reflected in photosynthate utilization and cell growth ultimately regulate

  11. Secretions from the ventral eversible gland of Spodoptera exigua caterpillars activate defense-related genes and induce emission of volatile organic compounds in tomato, Solanum lycopersicum

    PubMed Central

    2014-01-01

    Background Plant induced defense against herbivory are generally associated with metabolic costs that result in the allocation of photosynthates from growth and reproduction to the synthesis of defense compounds. Therefore, it is essential that plants are capable of sensing and differentiating mechanical injury from herbivore injury. Studies have shown that oral secretions (OS) from caterpillars contain elicitors of induced plant responses. However, studies that shows whether these elicitors originated from salivary glands or from other organs associated with feeding, such as the ventral eversible gland (VEG) are limited. Here, we tested the hypothesis that the secretions from the VEG gland of Spodoptera exigua caterpillars contain elicitors that induce plant defenses by regulating the expression of genes involved in the biosynthesis of volatile organic compounds (VOCs) and other defense-related genes. To test this hypothesis, we quantified and compared the activity of defense-related enzymes, transcript levels of defense-related genes and VOC emission in tomato plants damaged by S. exigua caterpillars with the VEG intact (VEGI) versus plants damaged by caterpillars with the VEG ablated (VEGA). Results The quantified defense-related enzymes (i.e. peroxidase, polyphenol oxidase, and lipoxigenase) were expressed in significantly higher amounts in plants damaged by VEGI caterpillars than in plants damaged by VEGA caterpillars. Similarly, the genes that encode for the key enzymes involved in the biosynthesis of jasmonic acid and terpene synthase genes that regulate production of terpene VOCs, were up-regulated in plants damaged by VEGI caterpillars. Moreover, the OS of VEGA caterpillars were less active in inducing the expression of defense genes in tomato plants. Increased emissions of VOCs were detected in the headspace of plants damaged by VEGI caterpillars compared to plants damaged by VEGA caterpillars. Conclusion These results suggest that the VEG of S. exigua

  12. Ethylene, a Hormone at the Center-Stage of Nodulation

    PubMed Central

    Guinel, Frédérique C.

    2015-01-01

    Nodulation is the result of a beneficial interaction between legumes and rhizobia. It is a sophisticated process leading to nutrient exchange between the two types of symbionts. In this association, within a nodule, the rhizobia, using energy provided as photosynthates, fix atmospheric nitrogen and convert it to ammonium which is available to the plant. Nodulation is recognized as an essential process in nitrogen cycling and legume crops are known to enrich agricultural soils in nitrogenous compounds. Furthermore, as they are rich in nitrogen, legumes are considered important as staple foods for humans and fodder for animals. To tightly control this association and keep it mutualistic, the plant uses several means, including hormones. The hormone ethylene has been known as a negative regulator of nodulation for almost four decades. Since then, much progress has been made in the understanding of both the ethylene signaling pathway and the nodulation process. Here I have taken a large view, using recently obtained knowledge, to describe in some detail the major stages of the process. I have not only reviewed the steps most commonly covered (the common signaling transduction pathway, and the epidermal and cortical programs), but I have also looked into steps less understood (the pre-infection step with the plant defense response, the bacterial release and the formation of the symbiosome, and nodule functioning and senescence). After a succinct review of the ethylene signaling pathway, I have used the knowledge obtained from nodulation- and ethylene-related mutants to paint a more complete picture of the role played by the hormone in nodule organogenesis, functioning, and senescence. It transpires that ethylene is at the center of this effective symbiosis. It has not only been involved in most of the steps leading to a mature nodule, but it has also been implicated in host immunity and nodule senescence. It is likely responsible for the activation of other hormonal

  13. Soil CO2, N2O and Nox Flux Responses to Biofuel Crop Plantation

    NASA Astrophysics Data System (ADS)

    Liang, L.; Eberwein, J.; Allsman, L.; Grantz, D. A.; Jenerette, D.

    2014-12-01

    Biofuel crops in high temperature environments, e.g, sorghum in southern California, USA, have a high capacity to assimilate atmospheric CO2. Photosynthates from the canopy may provide extra labile carbon source to feed soil microorganisms and influence trace gas fluxes, including CO2, N2O and NOx. Understanding how soil microorganisms balance the carbon (energy) and nitrogen (nutrients) allocation between growing microbial biomass and respiration is critical for evaluating the GHG emissions and emissions of regional air quality pollutants. We conducted experiments in a high temperature agroecosystem both in fallow and sorghum production fields with an experimental nitrogen gradient (0,50 and 100 kg/ha, marked as control, low and high with triplicate repeat) to investigate the CO2, N2O and NOx flux responses. All gas fluxes were measured simultaneously from three replicate locations for each treatment in the field biweekly. Measurements were performed 2-5 days after irrigation. We found that planting sorghum has significant effects on soil CO2 (p<0.0001), N2O (p<0.0001) and NOx (p=0.04) fluxes, but nitrogen amendments only have marginally significant effects on CO2 flux (p=0.07). Surprisingly, no significant response of N2O (p=0.27) and NOx (p=0.61) were observed in responses to N amendments. Compared to the fallow field, the CO2 flux in sorghum field increased 77%, 134% and 202% in control, low and high N level amendments, respectively. N2O flux from the sorghum field are consistently higher than from fallow field, with 207%, 174% and 1064% increase in control, low and high N level amendments, respectively. For the NOx flux, no significant difference was found between fallow and sorghum field. Although nitrogen amendments did not show significant effects on CO2, N2O and NOx flux, the high N treatment in sorghum field continuously gains the highest flux rates. Our results suggested additional C inputs may be an important factor regulating CO2, N2O and NOx fluxes in

  14. Allocation of atmospheric CO2 into labile sub-surface carbon pools: a stable isotope labelling approach in a tundra wetland

    NASA Astrophysics Data System (ADS)

    Rüggen, Norman; Knoblauch, Christian; Pfeiffer, Eva-Maria

    2015-04-01

    Greenhouse gas emissions from permafrost-affected wetlands are intensively studied due to their important role in the global carbon cycle. There are concerns of increasing methane and carbon dioxide fluxes from tundra wetlands due to permafrost degradation and hydrology changes in a warming Arctic. Understanding the sub-surface carbon pool interactions will improve the prediction on how trace gas fluxes from these ecosystems will respond to changing environmental conditions. Partitioning the sources of greenhouse gas fluxes will help to evaluate the quantitative role of recently produced plant photosynthates. Furthermore, partitioning allows separating respiration of long-term stored organic matter and freshly produced plant products. This knowledge is crucial for understanding the response of greenhouse gas fluxes in such wetlands to environmental changes. An in situ 13CO2 pulse-labelling experiment has been conducted in the northeast Siberian tundra (Samoylov island, Lena river delta) in August 2013 to quantify interactions among sub-surface carbon pools (DIC, DOC, CH4) in three depths (6, 16 and 36 cm) of the active layer. The experimental site was a low-centred polygon centre in a polygonal tundra landscape, with a sedge-moss (Carex-Scorpidium) plant association. The water table was at the soils' surface and the permafrost table in a depth of 50 cm. After the system has been 13CO2 pulse labelled, all three studied subsurface carbon pools (CH4, DIC and DOC) were clearly 13C-enriched, which accounts for atmospheric C incorporated into these pools. One day after the labelling, in 6 cm depth 1.5 percent of DIC and 0.1 percent of CH4were replaced by label C, which then steadily declined over a ten days period. The label C content of DOC increased gradually over the same period. In 16 cm depth, the label C increased gradually after labelling in both DIC and CH4. Label C was found in DIC and CH4 even in a depth of 36 cm, although in less pronounced concentrations

  15. Influence of plant productivity over variability of soil respiration: a multi-scale approach

    NASA Astrophysics Data System (ADS)

    Curiel Yuste, J.

    2009-04-01

    To investigate the role of plant photosynthetic activity on the variations in soil respiration (SR), SR data obtained from manual sampling and automatic soil respiration chambers placed on eddy flux towers sites were used. Plant photosynthetic activity was represented as Gross Primary Production (GPP), calculated from the half hourly continuous measurements of Net Ecosystem Exchange (NEE). The role of plant photosynthetic activity over the variation in SR was investigated at different time-scales: data averaged hourly, daily and weekly were used to study the photosynthetic effect on SR dial variations (Hourly data), 15 days variations (Daily averages), monthly variations (daily and weekly averages) and seasonal variations (weekly data). Our results confirm the important role of plant photosynthetic activity on the variations of SR at each of the mentioned time-scales. The effect of photosynthetic activity on SR was high on hourly time-scale (dial variations of SR). At half of the studied ecosystems GPP was the best single predictor of dial variations of SR. However at most of the studied sites the combination of soil temperature and GPP was the best predictor of dial variations in SR. The effect of aboveground productivity over dial variations of SR lagged on the range of 5 to 15 hours, depending on the ecosystem. At daily to monthly time scale variations of SR were in general better explained with the combination of temperature and moisture variations. However, ‘jumps' in average weekly SR during the growing season yielded anomaly high values of Q10, in some cases above 1000, which probably reflects synoptic changes in photosynthates translocation from plant activity. Finally, although seasonal changes of SR were in general very well explained by temperature and soil moisture, seasonality of SR was better correlated to seasonality of GPP than to seasonality of soil temperature and/or soil moisture. Therefore the magnitude of the seasonal variation in SR was in

  16. Changes in Arbuscular Mycorrhizal Fungal Abundance and Community Structure in Response to the Long-Term Manipulation of Inorganic Nutrients in a Lowland Tropical Forest

    NASA Astrophysics Data System (ADS)

    Sheldrake, Merlin; Rosenstock, Nicholas; Tanner, Ed

    2014-05-01

    The arbuscular mycorrhizal (AM) symbiosis is considered primarily mutualistic. In exchange for up to 30% of plants' total photosynthate, AM provide improved access to mineral nutrients. While there is evidence that AM fungi provide nitrogen, potassium and other nutrients to their host plants, most research has focused on their effect on plant phosphorus uptake. Pot experiments have shown, and field experiments have provided further support, that nutrient availability (primarily P, but also N) is inversely correlated with mycorrhizal colonization, indicating plant control over carbon losses to AM fungi. Yet pot experiments have also shown that some fungal species are more mutualistic than others and that AM colonization may cause decreased plant growth, suggesting that plant control is not absolute. AMF communities are diverse, and it is poorly understood how factors such as adaptation to local soil environment, fungal-plant compatibility, and plant nutrient status combine to shape AMF community structure. We conducted a study to examine the relative effects of N, P, and K addition on the AMF community in a plant species rich tropical forest, given the long-held belief that AMF are primarily involved in plant P uptake, particularly on weathered tropical soils. Our study site is the Barro Colorado Nature Monument in Panama. It is a 13 year-old factorial N, P, and K addition experiment (40 m x 40m plots; n=4) in an AMF dominated, old (>200 yr), secondary, tropical forest. Previous research has shown co-limitation by N, P, and K, but the strongest plant growth responses were obtained with K additions. We analyzed the AMF community using 454 pyrosequencing of the ribosomal small subunit (SSU) on both soils and the roots of the 6 dominant AMF tree species. Additionally, we used the AMF-specific neutral lipid fatty acid (NLFA) biomarker as a measure of AMF biomass. Both AMF biomass and community structure were altered by nutrient additions. AMF biomass in soil was reduced

  17. Diurnal and Seasonal Variation in the Carbon Isotope Composition of Leaf- and Root- respired CO2 in C3 and C4 Species

    NASA Astrophysics Data System (ADS)

    Sun, W.; Resco, V.; Chen, S.; Williams, D. G.

    2008-12-01

    The carbon isotope signature of leaf (δ13Cl) and root (δ13Cr) dark- respired CO2 records and integrates short-term metabolic changes. Plants with C3 and C4 photosynthetic metabolism are expected to differ in diurnal and seasonal patterns in δ13Cl and δ13Cr because of differences in photorespiration, isotopic fractionation at metabolic branch points and allocation patterns. A thorough understanding of the environmental and metabolic controls on δ13Cl and δ13Cr is necessary to interpret the δ13C of ecosystem respired CO2 and partition the CO2 efflux into autotrophic and heterotrophic respiration sources. We measured δ13Cl in two C3 tree species (Prosopis velutina and Celtis reticulata), a C3 herb (Viguiera dentata) and a C4 grass (Sporobolus wrightii), and δ13Cr in P. velutina and S. wrightii in a semiarid savanna in southeastern Arizona, USA. δ13Cl during the dry pre-monsoon period was relatively enriched in 13C during daytime periods and became depleted in 13C at night relative to daytime values for all species with the exception of S. wrightii, the C4 grass. δ13Cl in S. wrightii was strongly influenced by seasonal differences in water availability with a larger diurnal amplitude in δ13Cl (8.2 +/- 0.6‰) during the wet monsoon period compared to that in the dry pre-monsoon period (4.4 +/- 0.4‰). The δ13C values of starch and lipid fractions remained constant over diurnal periods within the pre-monsoon and monsoon seasons. For C3 species, δ13Cl and δ13C of the cumulative, flux-weighted photosynthate pool estimated from gas exchange were strongly positively correlated, suggesting that progressive 13C-enrichment of leaf-respired CO2 during the daytime period resulted from changes in the δ13C signature of respiratory substrates associated with short-term changes in photosynthetic 13C discrimination. Rapid decreases in δ13Cl following the daytime period was likely caused by decreases in the ratio of PDH:acetyl-CoA oxidation rather than by a shift in

  18. Contribution of various carbon sources toward isoprene synthesis mediated by altered atmospheric CO2 concentrations

    NASA Astrophysics Data System (ADS)

    Trowbridge, A. M.; Asensio, D.; Eller, A. S.; Wilkinson, M. J.; Schnitzler, J.; Jackson, R. B.; Monson, R. K.

    2010-12-01

    Biogenically released isoprene is abundant in the troposphere, and has an essential function in determining atmospheric chemistry and important implications for plant metabolism. As a result, considerable effort has been made to understand the underlying mechanisms driving isoprene synthesis, particularly in the context of a rapidly changing environment. Recently, a number of studies have focused on the contribution of recently assimilated carbon as opposed to stored/alternative intracellular or extracellular carbon sources in the context of environmental stress. Results from these studies can offer clues about the importance of various carbon pools for isoprene production and elucidate the corresponding physiological changes that are responsible for these dynamic shifts in carbon allocation. We performed a 13CO2-labeling study using proton-transfer-reaction mass spectrometry (PTR-MS) to examine the kinetics of the incorporation of recently assimilated photosynthate into isoprene emitted from poplar (Poplar x canescens) under sub-ambient, ambient, and elevated CO2 growth conditions. We also monitored the importance of pyruvate-derived carbon for isoprene biosynthesis and obtained a detailed account of where individual carbons are derived from by analyzing the ratio of the 3C subunit of isoprene (M41+) (a fragment which contains two carbons from pyruvate) to the ratio of the parent isoprene molecule (M69+). Dynamics in the M41+:M69+ ratio indicate that recently assimilated carbon is incorporated into the pyruvate carbon pool slowly across all CO2 treatments and is therefore accessible for isoprene synthesis at a slower rate when compared to substrates derived directly from photosynthesis. Analysis of the rates of change for individual masses indicated that the carbon pools in trees grown in sub-ambient CO2 (200 ppm) are labeled ~2 times faster than those of trees grown in ambient or elevated CO2. Analysis of the total isoprene emission rates between treatments

  19. Variation in the concentration and age of nonstructural carbon stored in different tree tissues

    NASA Astrophysics Data System (ADS)

    Richardson, Andrew; Carbone, Mariah; Huggett, Brett; Furze, Morgan; Czimczik, Claudia I.; Xu, Xiaomei

    2014-05-01

    depth profile. In oak, fine root concentrations of sugar and starch were similar (40 mg/g), and coarse roots had very high concentrations of starch (140 mg/g) compared to sugar (50 mg/g). In pine, fine root concentrations of both sugar and starch (60 mg/g) were higher than in coarse roots (10 mg/g). Coarse root NSC concentrations did not vary substantially along a radial gradient into the root. Even assuming a 1:5 root:shoot ratio, these data indicate that a large portion of the whole-tree NSC budget is stored belowground. For both sugars and starch, the 14C data indicated substantial mixing of new and older carbon across the youngest stemwood rings (up to 5 y), beyond which NSC age increased linearly with ring age. Coarse root NSC age also increased with radial depth and wood tissue age, and root NSC was consistently younger in pine than oak. The fact that NSC age is not constant with radial depth in the aboveground samples demonstrates that NSC reserves cannot be treated as a single, well-mixed pool. Rather, these results are consistent with previous observation suggesting last-in/first-out dynamics. From a modeling standpoint, these results support a simple two-pool structure where new photosynthate not used for current growth or metabolism enters a well-mixed and young "fast" pool, but over time storage in older rings is transferred to a distinct and older "slow" pool with which mixing no longer occurs.

  20. Why Seedlings Die: Linking Carbon and Water Limitations to Mechanisms of Mortality During Establishment in Conifer Seedlings

    NASA Astrophysics Data System (ADS)

    Reinhardt, K.; Germino, M. J.; Kueppers, L. M.; Mitton, J.; Castanha, C.

    2012-12-01

    BACKGROUND Recent ecophysiological studies aimed at explaining adult tree mortality during drought have examined the carbon (C)-exhaustion compared to the hydraulic-failure hypotheses for death. Prolonged drought leads to durations of stomatal closure (and thus limited C gain), which could result in long periods of negative C balance and fatal reductions in whole-plant C reserves (i.e., available non-structural carbohydrates ["NSC"]). Alternatively, C reserves may not decrease much but could become increasingly inaccessible to sink tissues in long dry-periods due to impediments to translocation of photosynthate (e.g., through disruption of hydrostatic pressure flow in phloem). As C reserves decline or become inaccessible, continued maintenance respiration has been hypothesized to lead to exhaustion of NSC after extended durations of drought, especially in isohydric plant species. On the other hand, hydraulic failure (e.g., catastrophic xylem embolisms) during drought may be the proximate cause of death, occurring before true C starvation occurs. Few studies have investigated specifically the mechanism(s) of tree death, and no published studies that we know of have quantified changes in NSC during mortality. EXPERIMENTAL DESIGN AND HYPOTHESES We conducted two studies that investigated whole-tree and tissue-specific C relations (photosynthetic C gain, respiration, dry-mass gain, and NSC pools) in Pinus flexilis seedlings during the initial establishment phase, which is characterized by progressive drought during summer. We measured survival, growth and biomass allocation, and C-balance physiology (photosynthetic C-gain and chlorophyll fluorescence, respiration C-use, and NSC concentrations) from germination to mortality. We hypothesized that 1) stomatal and biochemical limitations to C gain would constrain seedling survival (through inadequate seasonal C-balance), as has been shown for conifer seedlings near alpine treeline; 2) hydraulic constraints (embolisms and

  1. Partitioning soil CO2 fluxes by tree-girdling in a Mediterranean (Pinus pinaster) ecosystem reveals a different response of autotrophic and heterotrophic components to environmental variables and photosynthesis under drought conditions

    NASA Astrophysics Data System (ADS)

    Matteucci, M.; Cescatti, A.; Gruening, C.; Ballarin, I. G.; Guenther, S.; Magnani, F.; Nali, C.; Lorenzini, G.

    2012-04-01

    The response of ecosystems to environmental factors, such as temperature and rainfall, is crucial to understand the impact of climate change on the terrestrial C cycle. Forest soil respiration represents the main pathway by which photosynthetically assimilated C is released to atmosphere; its intensity depends not only on soil environmental conditions, but also on the availability of organic substrates respired by roots and microorganisms. Several techniques have been applied to partition the autotrophic and heterotrophic components of soil respiration in boreal and temperate forests; there is a general lack of information, on the contrary, on the dynamics of soil CO2 efflux in Mediterranean ecosystems. The IPCC A1B scenario highlighted the importance of the Mediterranean area since it is expected to experience a temperature increase (from 2.2 °C to 5.1 °C) and a rainfall reduction ranging from -4 to -27% on annual basis. We used the tree-girdling technique together with periodic chamber-based measurements to study the partitioning of total soil respiration (Rs) into its autotrophic (Ra) and heterotrophic (Rh) components in a 60-year old forest in Central Italy (San Rossore) dominated by Pinus pinaster. This technique has been extensively used to block the flux of photosynthates from leaves to roots, thus stopping the autotrophic root respiration in the soil. We found that two weeks after the treatment soil respiration in the girdled plots decreased by 29% and remained stable over the period of analysis, suggesting that Rh dominates total soil respiration. The anomalous low rainfall regimen of May to October 2011 (102 mm cumulated rain) associated with average air temperatures (with a mean value of 19,6 °C over the period) gave us the opportunity to investigate the decoupled response of soil respiration to water and temperature. Time series analysis performed under this severe drought conditions showed overall low values of soil respiration with three clear

  2. Soluble ferric iron as an effective protective agent against UV radiation: Implications for early life

    NASA Astrophysics Data System (ADS)

    Gómez, Felipe; Aguilera, Angeles; Amils, Ricardo

    2007-11-01

    Some recent MER Rover Opportunity results on ancient sedimentary rocks from Mars describe sandstones originated from the chemical weathering of olivine basalts by acidic waters [Squyres, S.W., Knoll, A.H., 2005. Earth Planet. Sci. Lett. 240, 1-10]. The absence of protective components in early Mars atmosphere forced any possible primordial life forms to deal with high doses of UV radiation. A similar situation occurred on the primitive Earth during the development of early life in the Archean [Berkner, L.V., Marshall, L.C., 1965. J. Atmos. Sci. 22 (3), 225-261; Kasting, J.F., 1993. Science 259, 920-926]. It is known that some cellular and/or external components can shield organisms from damaging UV radiation or quench its toxic effects [Olson, J.M., Pierson, B.K., 1986. Photosynth. Res. 9, 251-259; García-Pichel, F., 1998. Origins Life Evol. B 28, 321-347; Cockell, C., Rettberg, P., Horneck, G., Scherer, K., Stokes, M.D., 2003. Polar Biol. 26, 62-69]. The effectiveness of iron minerals for UV protection has also been reported [Phoenix, V.R., Konhauser, K.O., Adams, D.G., Bottrell, S.H., 2001. Geology 29 (9), 823-826], but nothing is known about the effect of iron in solution. Here we demonstrate the protective effect of soluble ferric iron against UV radiation on acidophilic photosynthetic microorganisms. These results offer an interesting alternative means of protection for life on the surface of early Mars and Earth, especially in light of the geochemical conditions in which the sedimentary minerals, jarosite and goethite, recently reported by the MER missions, were formed [Squyres, S.W., Arvidson, R.E., Bell III, J.F., Brückner, J., Cabrol, N.A., Calvin, W., Carr, M.H., Christensen, P.R., Clark, B.C., Crumpler, L., Des Marais, D.J., d'Uston, C., Economou, T., Farmer, J., Farrand, W., Folkner, W., Golombek, M., Gorevan, S., Grant, J.A., Greeley, R., Grotzinger, J., Haskin, L., Herkenhoff, K.E., Hviid, S., Johnson, J., Klingelhöfer, G., Knoll, A.H., Landis, G

  3. Carbon Isotopes and the Diverging Growth Response of Treeline Trees to Changing Climate in Alaska

    NASA Astrophysics Data System (ADS)

    Barber, V. A.; Wilmking, M.; Juday, G. P.

    2007-12-01

    ) trees in the Alaska Range at a site which contains all three responder types. Ring width was measured to confirm to which responder type each tree belongs. Carbon-13 isotopic content of the annual wood of the rings of these 3 response types (for the past 100 years) is being measured to determine if drought stress can explain the differences. Results are still in the preliminary stage but show promise. The premise is that stomatal conductance is reduced under low moisture conditions as leaf pores shut down to conserve water, resulting in a more limited pool of intercellular carbon dioxide for photosynthesis. The hypothesis is that the resulting photosynthate should therefore be heavier as less discrimination of heavier carbon-13 occurs, resulting in a higher ratio of 13C/12C (del13C) incorporated into the wood. While the stomates are open, the energetically more efficient carbon-12 is preferentially incorporated and this ratio is lower. We hope to begin to identify the processes controlling treeline growth, as no intra-site differences (soil moisture and temperature, depth of the A horizon, tree density, slope, aspect, elevation) were documented on any scale which could explain the 3 different growth responses. Isotopes could provide some of the answers.

  4. Visualizing carbon and nitrogen transfer in the tripartite symbiosis of Fagus sylvatica, ectomycorrhizal fungi and soil microorganisms using NanoSIMS

    NASA Astrophysics Data System (ADS)

    Mayerhofer, Werner; Dietrich, Marlies; Schintlmeister, Arno; Gabriel, Raphael; Gorka, Stefan; Wiesenbauer, Julia; Martin, Victoria; Schweiger, Peter; Reipert, Siegfried; Weidinger, Marieluise; Richter, Andreas; Woebken, Dagmar; Kaiser, Christina

    2016-04-01

    Translocation of recently photoassimilated plant carbon (C) into soil via root exudates or mycorrhizal fungi is key to understand global carbon cycling. Plants support symbiotic fungi and soil microorganisms with recent photosynthates to get access to essential elements, such as nitrogen (N) and phosphorus. While a 'reciprocal reward strategy' (plants trade C in exchange for nutrients from the fungus) has been shown for certain types of mycorrhizal associations, only little is known about the mechanisms of C and N exchange between mycorrhizal fungal hyphae and soil bacteria. Our understanding of the underlying mechanisms is hampered by the fact that C and N transfer between plants, mycorrhizal fungi and soil bacteria takes place at the micrometer scale, which makes it difficult to explore at the macro scale. In this project we intended to analyse carbon and nitrogen flows between roots of beech trees (Fagus sylvatica), their associated ectomycorrhizal fungi and bacterial community. In order to visualize this nutrient flow at a single cell level, we used a stable isotope double labelling (13C and 15N) approach. Young mycorrhizal beech trees were transferred from a forest to split-root boxes, consisting of two compartments separated by a membrane (35 μm mesh size) which was penetrable for hyphae but not for plant roots. After trees and mycorrhizal fungi were allowed to grow for one year in these boxes, 15N-labelled nitrogen solution was added only to the root-free compartment to allow labelled nitrogen supply only through the fungal network. 13C- labelled carbon was applied by exposing the plants to a 13CO2 gas atmosphere for 8 hours. Spatial distribution of the isotopic label was visualised at the microscale in cross sections of mycorrhizal root-tips (the plant/mycorrhizal fungi interface) and within and on the surface of external mycorrhizal hyphae (the fungi/soil bacteria interface) using nanoscale secondary ion mass spectrometry (NanoSIMS). Corresponding

  5. Detecting plant-climate interactions over decades-millennia using NMR isotopomer analysis

    NASA Astrophysics Data System (ADS)

    Ehlers, Ina; Augusti, Angela; Köhler, Iris; Wieloch, Thomas; Zuidema, Pieter; Robertson, Iain; Nilsson, Mats; Marshall, John; Schleucher, Jürgen

    2016-04-01

    Increasing CO2 and climate change affect photosynthesis, which creates a critical influence on the global C cycle and on the future productivity of crops and forests. Manipulative experiments (e.g. FACE) impose step increases in [CO2], and are limited to few locations and to time spans of years, while responses over decades and centuries are critical for Earth system models. To overcome these limitations, we have developed a new method - isotopomer analysis - that allows deducing plant C metabolism by analysis of primary plant photosynthates (Ehlers et al., PNAS 2015, 15585) or tree rings. We apply the method to material from manipulation (CO2, T) experiments, and to remnant - including subfossil - plant material. Thus, metabolic responses can be identified in FACE experiments, and it can be tested to what degree these responses are maintained during gradual environmental changes over decades-millennia. Isotopomer proxies developed using FACE experiments can then be used to reconstruct physiological and climatic changes by retrospective analysis, thus bridging a gap between experimental plant sciences and paleo research. In experiments on annual plants, we have found that specific deuterium isotopomers in photosynthetic glucose reflect the ratio of oxygenation to carboxylation at Rubisco, a central metabolic branching that is the origin of the photorespiration flux in all C3 plants. We found that increasing atmospheric [CO2] over the 20th century has reduced the photorespiration / photosynthesis ratio in all investigated C3 species, with no evidence for acclimatory reactions by the plants. Results on the peat moss Spagnum fuscum suggest a mechanism for increasing peat accumulation rates, a major global C sink. For 12 tree species from five continents, we observe that the CO2 increase since industrialization has reduced the photorespiration / photosynthesis ratio. However, the observed reduction is ca. 50 % smaller than expected from CO2 manipulation experiments

  6. Use of Rhizosphere Metabolomics to Investigate Exudation of Phenolics by Arabidopsis Roots

    NASA Astrophysics Data System (ADS)

    Lee, Yong Jian; Rai, Amit; Reuben, Sheela; Nesati, Victor; Almeida, Reinaldo; Swarup, Sanjay

    2013-04-01

    The rhizosphere is a specialised micro-niche for bacteria that have an active exchange of signals and nutrients with the host plant. Nearly 20% of photosynthates are released as root exudates, which consist of primary metabolites and products of secondary metabolism which are largely phenolic in nature. Previously, using rhizosphere metabolomics, we showed that nearly 50% of organic carbon in the exudates is in the form of phenolic compounds, of which the largest fraction is from the phenylpropanoid synthesis pathway. Using Arabidopsis as a model, we have demonstrated that a biased rhizosphere can be created using plants with varying levels of phenylpropanoids due to mutations in the biosynthetic or regulatory genes. These phenylpropanoids levels are reflected in the exudates, and exudates from lines with regulatory gene mutations, tt8 and ttg, have higher levels of phenylpropanoids, whereas biosynthetic mutant line, tt4, has very low and undetectable levels of phenylpropanoids. The biased rhizosphere of tt8 and ttg lines provides a nutritional advantage to rhizobacteria that can utilize these phenylpropanoids such as quercetin. With such a strategy to increase the competitiveness of plant growth-promoting rhizobacteria (PGPR) such as Pseudomonas putida, this system can be applied to improve plant performance. In order to better understand the metabolic basis of the nutritional advantage behind the competitiveness of the favoured P. putida, we elucidated its quercetin utilization pathway. We have recently cloned the gene for quercetin oxidoreductase (QuoA) and expressed it in transgenic Arabidopsis lines to alter the plant phenylpropanoid metabolism, using a gain of function approach. Since phenylpropanoid biosynthesis in plants involve formation of quercetin from naringenin, we envisaged that QuoA expression in plants will provide us with a genetic tool to "reverse" this biosynthetic step. This perturbation led to a decrease in flavonoids and an increase in lignin

  7. Estimating national forest carbon stocks and dynamics: combining models and remotely sensed information

    NASA Astrophysics Data System (ADS)

    Smallman, Luke; Williams, Mathew

    2016-04-01

    ecological expectations. Moreover, the retrieved LCA is positively correlated with leaf-life span and negatively correlated with allocation of photosynthate to foliage, supported by field observations. This emergence of key plant traits and correlations between traits increases our confidence in the robustness of this analysis. Furthermore, this framework also allows us to search for additional emergent properties from the analysis such as spatial variation of retrieved drought tolerance. Finally our analysis is able to identify components of the carbon cycle with the largest uncertainty providing targets for future observations (e.g. remotely sensed biomass). Our Bayesian analysis system is ideally suited for assimilation of multiple biomass estimates and their associated uncertainties to reduce both uncertainty in the state of the system but also process parameters (e.g. wood residence time).

  8. Seasonality in a boreal forest ecosystem affects the use of soil temperature and moisture as predictors of soil CO2 efflux

    NASA Astrophysics Data System (ADS)

    Niinistö, S. M.; Kellomäki, S.; Silvola, J.

    2011-11-01

    Our objectives were to identify factors related to temporal variation of soil CO2 efflux in a boreal pine forest and to evaluate simple predictive models of temporal variation of soil CO2 efflux. Soil CO2 efflux was measured with a portable chamber in a Finnish Scots pine forest for three years, with a fourth year for model evaluation. Plot averages for soil CO2 efflux ranged from 0.04 to 0.90 g CO2 m-2 h-1 during the snow-free period, i.e. May-October, and from 0.04 to 0.13 g CO2 m-2 h-1 in winter. Soil temperature was a good predictor of soil CO2 efflux. A quadratic model of ln-transformed efflux explained 76-82 % of the variation over the snow-free period. The results revealed an effect of season: at a given temperature of the organic layer, soil CO2 efflux was higher later in the snow-free period (in August and September) than in spring and early summer (in May and June). Regression coefficients for temperature (approximations of a Q10 value) of month-specific models decreased with increasing average soil temperatures. Efflux in July, the month of peak photosynthesis, showed no clear response to temperature or moisture. Inclusion of a seasonality index, degree days, improved the accuracy of temperature response models to predict efflux for the fourth year of measurements, which was not used in building of regression models. During peak efflux from mid-July to late-August, efflux was underestimated with the models that included degree days as well as with the models that did not. The strong influence of the flux of photosynthates belowground and the importance of root respiration could explain the relative temperature insensitivity observed in July and together with seasonality of growth of root and root-associated mycorrhizal fungi could explain partial failure of models to predict magnitude of efflux in the peak season from mid-July to August. The effect of moisture early in the season was confounded by simultaneous advancement of the growing season and

  9. The Contribution of the Long-term Carbon Pool to Nighttime Foliage Respiration as Revealed by a Year-long C-13 Labeling Experiment

    NASA Astrophysics Data System (ADS)

    Smith, M.; Mortazavi, B.; Chanton, J.

    2005-12-01

    Slash pine (Pinus elliottii) saplings were placed in a CO2 enrichment (~500 ppm above ambient) facility for an entire year, starting in June of 2004. The CO2 used for the enrichment, with an isotopic signature of -48‰, allowed us to track the fate of the labeled photosynthate during nighttime respiration experiments once the saplings were removed from the enrichment facility. A set of saplings subject to similar environmental conditions, but not subject to CO2 enrichment, served as controls. Nighttime respiration experiments for the labeled saplings were measured by two methods. The first procedure consisted in determining the isotopic signature of nighttime integrated (sunset to sunrise) foliage respired CO2, while the second procedure consisted in determining the pre-dawn signal. The nighttime integrated signal was determined by enclosing the entire foliage of four labeled saplings in a non-destructive manner in a 300-liter airtight chamber. Initial and final samples were collected at sunset and sunrise for CO2 concentration and 13C determination and a mass balance equation was used to determine the 13C of respired CO2. In the second procedure foliage from four labeled saplings were collected just prior to dawn and placed in a leaf-chamber. Sequential CO2 samples evolved in darkness over a 15 min period were collected for CO2 concentration and 13C determination from which a Keeling plot was constructed to determine the isotopic signature of foliage respired CO2. The isotopic signature of pre-dawn foliage respired CO2 for the control plants was also determined with an identical leaf-chamber system. Immediately after removal from the enrichment facility, the 13C of foliage respired CO2 had a pre-dawn signature of -40.2‰ and a nighttime integrated signal of -44.1‰, while the control plants had a dCf value of -25.8‰ signature. Monitoring of dCf during a 35-day period revealed a non-linear approach in dCf of the labeled plants towards the control dCf values