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Sample records for leaf elongation zone

  1. Growth Rates and Assimilate Partitioning in the Elongation Zone of Tall Fescue Leaf Blades at High and Low Irradiance 1

    PubMed Central

    Schnyder, Hans; Nelson, Curtis J.

    1989-01-01

    Tall fescue (Festuca arundinacea Schreb.) leaf blades elongated 33% faster at continuous low than at continuous high irradiance (60 versus 300 micromoles per second per square meter photosynthetic photon flux density) when temperature of the leaf elongation zone was held constant at 21°C. Increased rate of elongation was associated with a near proportional increase in length of the elongation zone (+38%). In contrast, growth in width and thickness was decreased at low irradiance, resulting in only a 12% increase in leaf area production and 5% less total growth-associated water deposition than at high irradiance. At low irradiance dry matter (DM) import into the elongation zone was 28% less, and 55% less DM was used per unit leaf area produced. DM use in synthesis of structural components (i.e. DM less water-soluble carbohydrates) was only 13% less at low irradiance, whereas water-soluble carbohydrates (WSC) deposition was 43% less. The lower rate of WSC deposition at low irradiance was associated with a higher net rate of monosaccharide deposition (+39%), whereas net deposition rates for sucrose (−27%) and fructan (−56%) were less than at high irradiance. Still, at low irradiance, net fructan accumulation accounted for 64% of WSC deposition, i.e. 25% of DM import, demonstrating the high sink strength of the leaf elongation zone. PMID:16666873

  2. Light interacts with auxin during leaf elongation and leaf angle development in young corn seedlings.

    PubMed

    Fellner, Martin; Horton, Lindsey A; Cocke, Allison E; Stephens, Nicholas R; Ford, E David; Van Volkenburgh, Elizabeth

    2003-01-01

    Modern corn ( Zea mays L.) varieties have been selected for their ability to maintain productivity in dense plantings. We have tested the possibility that the physiological consequence of the selection of the modern hybrid, 3394, for increased crop yield includes changes in responsiveness to auxin and light. Etiolated seedlings in the modern line are shorter than in an older hybrid, 307, since they produce shorter coleoptile, mesocotyl, and leaves (blade as well as sheath). Etiolated 3394 seedlings, as well as isolated mesocotyl and sheath segments, were less responsive to auxin and an inhibitor of polar auxin transport, N-1-naphthylphthalamic acid (NPA). Reduced response of 3394 to auxin was associated with less reduction of elongation growth by light (white, red, far-red, blue) than in 307, whereas the activity of polar auxin transport (PAT) and its reduction by red or far-red light was similar in both genotypes. NPA reduced PAT in etiolated 3394 seedlings much less than in 307. A characteristic feature of 3394 plants is more erect leaves. In both hybrids, light (white, red, blue) increases leaf declination from the vertical, whereas NPA reduces leaf declination in 307, but not in 3394. Our results support findings that auxin and PAT are involved in elongation growth of corn seedlings, and we show that light interacts with auxin or PAT in regulation of leaf declination. We hypothesize that, relative to 307, more erect leaves in the modern hybrid may be primarily a consequence of a reduced amount of auxin receptor(s) and reduced responsiveness to light in etiolated 3394 plants. The more erect leaves in 3394 may contribute to the tolerance of the modern corn hybrid to dense planting. PMID:12520327

  3. Epicuticular Wax Accumulation and Fatty Acid Elongation Activities Are Induced during Leaf Development of Leeks1

    PubMed Central

    Rhee, Yoon; Hlousek-Radojcic, Alenka; Ponsamuel, Jayakumar; Liu, Dehua; Post-Beittenmiller, Dusty

    1998-01-01

    Epicuticular wax production was evaluated along the length of expanding leek (Allium porrum L.) leaves to gain insight into the regulation of wax production. Leaf segments from the bottom to the top were analyzed for (a) wax composition and load; (b) microsomal fatty acid elongase, plastidial fatty acid synthase, and acyl-acyl carrier protein (ACP) thioesterase activities; and (c) tissue and cellular morphological changes. The level of total wax, which was low at the bottom, increased 23-fold along the length of the leaf, whereas accumulation of the hentriacontan-16-one increased more than 1000-fold. The onset of wax accumulation was not linked to cell elongation but, rather, occurred several centimeters above the leaf base. Peak microsomal fatty acid elongation activity preceded the onset of wax accumulation, and the maximum fatty acid synthase activity was coincident with the onset. The C16:0- and C18:0-ACP-hydrolyzing activities changed relatively little along the leaf, whereas C18:1-ACP-hydrolyzing activity increased slightly prior to the peak elongase activity. Electron micrographic analyses revealed that wax crystal formation was asynchronous among cells in the initial stages of wax deposition, and morphological changes in the cuticle and cell wall preceded the appearance of wax crystals. These studies demonstrated that wax production and microsomal fatty acid elongation activities were induced within a defined and identifiable region of the expanding leek leaf and provide the foundation for future molecular studies. PMID:9501123

  4. Leaf Length Tracker: a novel approach to analyse leaf elongation close to the thermal limit of growth in the field

    PubMed Central

    Kirchgessner, Norbert; Yates, Steven; Hiltpold, Maya; Walter, Achim

    2016-01-01

    Leaf growth in monocot crops such as wheat and barley largely follows the daily temperature course, particularly under cold but humid springtime field conditions. Knowledge of the temperature response of leaf extension, particularly variations close to the thermal limit of growth, helps define physiological growth constraints and breeding-related genotypic differences among cultivars. Here, we present a novel method, called ‘Leaf Length Tracker’ (LLT), suitable for measuring leaf elongation rates (LERs) of cereals and other grasses with high precision and high temporal resolution under field conditions. The method is based on image sequence analysis, using a marker tracking approach to calculate LERs. We applied the LLT to several varieties of winter wheat (Triticum aestivum), summer barley (Hordeum vulgare), and ryegrass (Lolium perenne), grown in the field and in growth cabinets under controlled conditions. LLT is easy to use and we demonstrate its reliability and precision under changing weather conditions that include temperature, wind, and rain. We found that leaf growth stopped at a base temperature of 0°C for all studied species and we detected significant genotype-specific differences in LER with rising temperature. The data obtained were statistically robust and were reproducible in the tested environments. Using LLT, we were able to detect subtle differences (sub-millimeter) in leaf growth patterns. This method will allow the collection of leaf growth data in a wide range of future field experiments on different graminoid species or varieties under varying environmental or treatment conditions. PMID:26818912

  5. Leaf Length Tracker: a novel approach to analyse leaf elongation close to the thermal limit of growth in the field.

    PubMed

    Nagelmüller, Sebastian; Kirchgessner, Norbert; Yates, Steven; Hiltpold, Maya; Walter, Achim

    2016-04-01

    Leaf growth in monocot crops such as wheat and barley largely follows the daily temperature course, particularly under cold but humid springtime field conditions. Knowledge of the temperature response of leaf extension, particularly variations close to the thermal limit of growth, helps define physiological growth constraints and breeding-related genotypic differences among cultivars. Here, we present a novel method, called 'Leaf Length Tracker' (LLT), suitable for measuring leaf elongation rates (LERs) of cereals and other grasses with high precision and high temporal resolution under field conditions. The method is based on image sequence analysis, using a marker tracking approach to calculate LERs. We applied the LLT to several varieties of winter wheat (Triticum aestivum), summer barley (Hordeum vulgare), and ryegrass (Lolium perenne), grown in the field and in growth cabinets under controlled conditions. LLT is easy to use and we demonstrate its reliability and precision under changing weather conditions that include temperature, wind, and rain. We found that leaf growth stopped at a base temperature of 0°C for all studied species and we detected significant genotype-specific differences in LER with rising temperature. The data obtained were statistically robust and were reproducible in the tested environments. Using LLT, we were able to detect subtle differences (sub-millimeter) in leaf growth patterns. This method will allow the collection of leaf growth data in a wide range of future field experiments on different graminoid species or varieties under varying environmental or treatment conditions. PMID:26818912

  6. Do pH changes in the leaf apoplast contribute to rapid inhibition of leaf elongation rate by water stress? Comparison of stress responses induced by polyethylene glycol and down-regulation of root hydraulic conductivity.

    PubMed

    Ehlert, Christina; Plassard, Claude; Cookson, Sarah Jane; Tardieu, François; Simonneau, Thierry

    2011-08-01

    We have dissected the influences of apoplastic pH and cell turgor on short-term responses of leaf growth to plant water status, by using a combination of a double-barrelled pH-selective microelectrodes and a cell pressure probe. These techniques were used, together with continuous measurements of leaf elongation rate (LER), in the (hidden) elongating zone of the leaves of intact maize plants while exposing roots to various treatments. Polyethylene glycol (PEG) reduced water availability to roots, while acid load and anoxia decreased root hydraulic conductivity. During the first 30 min, acid load and anoxia induced moderate reductions in leaf growth and turgor, with no effect on leaf apoplastic pH. PEG stopped leaf growth, while turgor was only partially reduced. Rapid alkalinization of the apoplast, from pH 4.9 ± 0.3 to pH 5.8 ± 0.2 within 30 min, may have participated to this rapid growth reduction. After 60 min, leaf growth inhibition correlated well with turgor reduction across all treatments, supporting a growth limitation by hydraulics. We conclude that apoplastic alkalinization may transiently impair the control of leaf growth by cell turgor upon abrupt water stress, whereas direct hydraulic control of growth predominates under moderate conditions and after a 30-60 min delay following imposition of water stress. PMID:21477119

  7. Movement of endogenous calcium in the elongating zone of graviresponding roots of Zea mays

    NASA Technical Reports Server (NTRS)

    Moore, R.; Cameron, I. L.; Smith, N. K.

    1989-01-01

    Endogenous calcium (Ca) accumulates along the lower side of the elongating zone of horizontally oriented roots of Zea mays cv. Yellow Dent. This accumulation of Ca correlates positively with the onset of gravicurvature, and occurs in the cytoplasm, cell walls and mucilage of epidermal cells. Corresponding changes in endogenous Ca do not occur in cortical cells of the elongating zone of intact roots. These results indicate that the calcium asymmetries associated with root gravicurvature occur in the outermost layers of the root.

  8. Polar transport of 45Ca2+ across the elongation zone of gravistimulated roots

    NASA Technical Reports Server (NTRS)

    Lee, J. S.; Evans, M. L.

    1985-01-01

    The movement of calcium across the elongation zone of gravistimulated primary roots of maize (Zea mays L.) was measured using 45Ca2+. Radioactive calcium was applied to one side of the elongation zone about 4 mm back from the root tip and the distribution of radioactivity across the root in the region of application was determined using scintillation spectrometry. The movement of 45Ca2+ across the elongation zone was non-polar in vertically oriented roots. In gravistimulated roots the movement of label was polarized with about twice as much label moving from top to bottom as from bottom to top. A variety of treatments which interfere with gravitropism was found to eliminate the polar movement of 45Ca2+ across the elongation zone. In maize cultivars which require light for gravitropic competency, dark grown roots exhibited neither gravitropism nor polar movement of 45Ca2+ across the elongation zone. Upon illumination the roots developed but gravitropic competency and gravity-induced polar movement of 45Ca2+ across the elongation zone. Similarly, roots of light-grown seedlings lost both gravitropic competency and 45Ca2+ transport polarity upon transfer to the dark. The results indicate a close correlation between calcium movement and gravitropism in primary roots in maize.

  9. Polar transport of 45Ca2+ across the elongation zone of gravistimulated roots.

    PubMed

    Lee, J S; Evans, M L

    1985-01-01

    The movement of calcium across the elongation zone of gravistimulated primary roots of maize (Zea mays L.) was measured using 45Ca2+. Radioactive calcium was applied to one side of the elongation zone about 4 mm back from the root tip and the distribution of radioactivity across the root in the region of application was determined using scintillation spectrometry. The movement of 45Ca2+ across the elongation zone was non-polar in vertically oriented roots. In gravistimulated roots the movement of label was polarized with about twice as much label moving from top to bottom as from bottom to top. A variety of treatments which interfere with gravitropism was found to eliminate the polar movement of 45Ca2+ across the elongation zone. In maize cultivars which require light for gravitropic competency, dark grown roots exhibited neither gravitropism nor polar movement of 45Ca2+ across the elongation zone. Upon illumination the roots developed but gravitropic competency and gravity-induced polar movement of 45Ca2+ across the elongation zone. Similarly, roots of light-grown seedlings lost both gravitropic competency and 45Ca2+ transport polarity upon transfer to the dark. The results indicate a close correlation between calcium movement and gravitropism in primary roots in maize. PMID:11539697

  10. Aquaporin-Mediated Reduction in Maize Root Hydraulic Conductivity Impacts Cell Turgor and Leaf Elongation Even without Changing Transpiration1[W

    PubMed Central

    Ehlert, Christina; Maurel, Christophe; Tardieu, François; Simonneau, Thierry

    2009-01-01

    Root hydraulic conductivity in plants (Lpr) exhibits large variations in response to abiotic stimuli. In this study, we investigated the impact of dynamic, aquaporin-mediated changes of Lpr on leaf growth, water potential, and water flux throughout the plant. For this, we manipulated Lpr by subjecting roots to four independent treatments, with aquaporin inhibitors applied either to transpiring maize (Zea mays) plants grown in hydroponics or to detopped root systems for estimation of Lpr. The treatments were acid load at pH 6.0 and 5.0 and hydrogen peroxide and anoxia applied for 1 to 2 h and subsequently reversed. First, we established that acid load affected cell hydraulic conductivity in maize root cortex. Lpr was reduced by all treatments by 31% to 63%, with half-times of about 15 min, and partly recovered when treatments were reversed. Cell turgor measured in the elongating zone of leaves decreased synchronously with Lpr, and leaf elongation rate closely followed these changes across all treatments in a dose-dependent manner. Leaf and xylem water potentials also followed changes in Lpr. Stomatal conductance and rates of transpiration and water uptake were not affected by Lpr reduction under low evaporative demand. Increased evaporative demand, when combined with acid load at pH 6.0, induced stomatal closure and amplified all other responses without altering their synchrony. Root pressurization reversed the impact of acid load or anoxia on leaf elongation rate and water potential, further indicating that changes in turgor mediated the response of leaf growth to reductions in Lpr. PMID:19369594

  11. The role of the distal elongation zone in the response of maize roots to auxin and gravity.

    PubMed Central

    Ishikawa, H; Evans, M L

    1993-01-01

    We used a video digitizer system to (a) measure changes in the pattern of longitudinal surface extension in primary roots of maize (Zea mays L.) upon application and withdrawal of auxin and (b) compare these patterns during gravitropism in control roots and roots pretreated with auxin. Special attention was paid to the distal elongation zone (DEZ), arbitrarily defined as the region between the meristem and the point within the elongation zone at which the rate of elongation reaches 0.3 of the peak rate. For roots in aqueous solution, the basal limit of the DEZ is about 2.5 mm behind the tip of the root cap. Auxin suppressed elongation throughout the elongation zone, but, after 1 to 3 h, elongation resumed, primarily as a result of induction of rapid elongation in the DEZ. Withdrawal of auxin during the period of strong inhibition resulted in exceptionally rapid elongation attributable to the initiation of rapid elongation in the DEZ plus recovery in the main elongation zone. Gravistimulation of auxin-inhibited roots induced rapid elongation in the DEZ along the top of the root. This resulted in rapid gravitropism even though the elongation rate of the root was zero before gravistimulation. The results indicate that cells of the DEZ differ from cells in the bulk of the elongation zone with respect to auxin sensitivity and that DEZ cells play an important role in gravitropism. PMID:11536543

  12. The role of the distal elongation zone in the response of maize roots to auxin and gravity

    NASA Technical Reports Server (NTRS)

    Ishikawa, H.; Evans, M. L.

    1993-01-01

    We used a video digitizer system to (a) measure changes in the pattern of longitudinal surface extension in primary roots of maize (Zea mays L.) upon application and withdrawal of auxin and (b) compare these patterns during gravitropism in control roots and roots pretreated with auxin. Special attention was paid to the distal elongation zone (DEZ), arbitrarily defined as the region between the meristem and the point within the elongation zone at which the rate of elongation reaches 0.3 of the peak rate. For roots in aqueous solution, the basal limit of the DEZ is about 2.5 mm behind the tip of the root cap. Auxin suppressed elongation throughout the elongation zone, but, after 1 to 3 h, elongation resumed, primarily as a result of induction of rapid elongation in the DEZ. Withdrawal of auxin during the period of strong inhibition resulted in exceptionally rapid elongation attributable to the initiation of rapid elongation in the DEZ plus recovery in the main elongation zone. Gravistimulation of auxin-inhibited roots induced rapid elongation in the DEZ along the top of the root. This resulted in rapid gravitropism even though the elongation rate of the root was zero before gravistimulation. The results indicate that cells of the DEZ differ from cells in the bulk of the elongation zone with respect to auxin sensitivity and that DEZ cells play an important role in gravitropism.

  13. The role of the distal elongation zone in the response of maize roots to auxin and gravity.

    PubMed

    Ishikawa, H; Evans, M L

    1993-08-01

    We used a video digitizer system to (a) measure changes in the pattern of longitudinal surface extension in primary roots of maize (Zea mays L.) upon application and withdrawal of auxin and (b) compare these patterns during gravitropism in control roots and roots pretreated with auxin. Special attention was paid to the distal elongation zone (DEZ), arbitrarily defined as the region between the meristem and the point within the elongation zone at which the rate of elongation reaches 0.3 of the peak rate. For roots in aqueous solution, the basal limit of the DEZ is about 2.5 mm behind the tip of the root cap. Auxin suppressed elongation throughout the elongation zone, but, after 1 to 3 h, elongation resumed, primarily as a result of induction of rapid elongation in the DEZ. Withdrawal of auxin during the period of strong inhibition resulted in exceptionally rapid elongation attributable to the initiation of rapid elongation in the DEZ plus recovery in the main elongation zone. Gravistimulation of auxin-inhibited roots induced rapid elongation in the DEZ along the top of the root. This resulted in rapid gravitropism even though the elongation rate of the root was zero before gravistimulation. The results indicate that cells of the DEZ differ from cells in the bulk of the elongation zone with respect to auxin sensitivity and that DEZ cells play an important role in gravitropism. PMID:11536543

  14. Effects of Nitrogen on Mesophyll Cell Division and Epidermal Cell Elongation in Tall Fescue Leaf Blades 1

    PubMed Central

    MacAdam, Jennifer W.; Volenec, Jeffrey J.; Nelson, Curtis J.

    1989-01-01

    Leaf elongation rate (LER) in grasses is dependent on epidermal cell supply (number) and on rate and duration of epidermal cell elongation. Nitrogen (N) fertilization increases LER. Longitudinal sections from two genotypes of tall fescue (Festuca arundinacea Schreb.), which differ by 50% in LER, were used to quantify the effects of N on the components of epidermal cell elongation and on mesophyll cell division. Rate and duration of epidermal cell elongation were determined by using a relationship between cell length and displacement velocity derived from the continuity equation. Rate of epidermal cell elongation was exponential. Relative rates of epidermal cell elongation increased by 9% with high N, even though high N increased LER by 89%. Duration of cell elongation was approximately 20 h longer in the high- than in the low-LER genotype regardless of N treatment. The percentage of mesophyll cells in division was greater in the high- than in the low-LER genotype. This increased with high N in both genotypes, indicating that LER increased with cell supply. Division of mesophyll cells adjacent to abaxial epidermal cells continued after epidermal cell division stopped, until epidermal cells had elongated to a mean length of 40 micrometers in the high-LER and a mean length of 50 micrometers in the low-LER genotype. The cell cycle length for mesophyll cells was calculated to be 12 to 13 hours. Nitrogen increased mesophyll cell number more than epidermal cell number: in both genotypes, the final number of mesophyll cells adjacent to each abaxial epidermal cell was 10 with low N and 14 with high N. A spatial model is used to describe three cell development processes relevant to leaf growth. It illustrates the overlap of mesophyll cell division and epidermal cell elongation, and the transition from epidermal cell elongation to secondary cell wall deposition. PMID:16666581

  15. Short-term leaf elongation kinetics of maize in response to salinity are independent of the root.

    PubMed

    Cramer, G R; Bowman, D C

    1991-03-01

    The essentiality of roots to the short-term responses of leaf elongation to salinity was tested by removing the roots of maize (Zea mays L.) from the shoots and comparing the initial short-term response of leaf elongation to that with intact plants. Eightday-old seedlings growing in solution culture were treated with 80 millimolar NaCl and their leaf elongation rate (LER) was monitored with a linear variable differential transformer connected to a computerized data aquisition system. Initially, LER of intact plants was sharply reduced by salinity, then rose rapidly to reach a new steady-state rate about 1.5 hours after salinization. The new steady-state rate of salinized intact plants was about 80% of the control rate. When the roots of nonsalinized plants were excised under the surface of the nutrient solution, excision did not disturb the steady-state LER. When these shoots were salinized, they responded in a manner nearly identical to that of intact plants, indicating that roots are not essential for the modulation of short-term LER of salt-stressed plants. PMID:16668080

  16. Organelle sedimentation in gravitropic roots of Limnobium is restricted to the elongation zone

    NASA Technical Reports Server (NTRS)

    Sack, F. D.; Kim, D.; Stein, B.

    1994-01-01

    Roots of the aquatic angiosperm Limnobium spongia (Bosc) Steud. were evaluated by light and electron microscopy to determine the distribution of organelle sedimentation towards gravity. Roots of Limnobium are strongly gravitropic. The rootcap consists of only two layers of cells. Although small amyloplasts are present in the central cap cells, no sedimentation of any organelle, including amyloplasts, was found. In contrast, both amyloplasts and nuclei sediment consistently and completely in cells of the elongation zone. Sedimentation occurs in one cell layer of the cortex just outside the endodermis. Sedimentation of both amyloplasts and nuclei begins in cells that are in their initial stages of elongation and persists at least to the level of the root where root hairs emerge. This is the first modern report of the presence of sedimentation away from, but not in, the rootcap. It shows that sedimentation in the rootcap is not necessary for gravitropic sensing in at least one angiosperm. If amyloplast sedimentation is responsible for gravitropic sensing, then the site of sensing in Limnobium roots is the elongation zone and not the rootcap. These data do not necessarily conflict with the hypothesis that sensing occurs in the cap in other roots, since Limnobium roots are exceptional in rootcap origin and structure, as well as in the distribution of organelle sedimentation. Similarly, if nuclear sedimentation is involved in gravitropic sensing, then nuclear mass would function in addition to, not instead of, that of amyloplasts.

  17. The Regulation of Growth in the Distal Elongation Zone of Maize Roots

    NASA Technical Reports Server (NTRS)

    Evans, Michael L.

    1998-01-01

    The major goals of the proposed research were 1. To develop specialized software for automated whole surface root expansion analysis and to develop technology for controlled placement of surface electrodes for analysis of relationships between root growth and root pH and electrophysiological properties. 2. To measure surface pH patterns and determine the possible role of proton flux in gravitropic sensing or response, and 3. To determine the role of auxin transport in establishment of patterns of proton flux and electrical gradients during the gravitropic response of roots with special emphasis on the role of the distal elongation zone in the early phases of the gravitropic response.

  18. Gibberellin-Regulation and Genetic Variations in Leaf Elongation for Tall Fescue in Association with Differential Gene Expression Controlling Cell Expansion

    PubMed Central

    Xu, Qian; Krishnan, Sanalkumar; Merewitz, Emily; Xu, Jichen; Huang, Bingru

    2016-01-01

    Leaf elongation rate (LER) is an important factor controlling plant growth and productivity. The objective of this study was to determine whether genetic variation in LER for a fast-growing (‘K-31’), and a dwarf cultivar (‘Bonsai’) of tall fescue (Festuca arundinacea) and gibberellic acid (GA) regulation of LER were associated with differential expression of cell-expansion genes. Plants were treated with GA3, trinexapac-ethyl (TE) (GA inhibitor), or water (untreated control) in a hydroponic system. LER of ‘K-31’ was 63% greater than that of ‘Bonsai’, which corresponded with 32% higher endogenous GA4 content in leaf and greater cell elongation and production rates under the untreated control condition. Exogenous application of GA3 significantly enhanced LER while TE treatment inhibited leaf elongation due to GA3-stimulation or TE-inhibition of cell elongation and production rate in leaves for both cultivars. Real-time quantitative polymerase chain reaction analysis revealed that three α-expansins, one β-expansin, and three xyloglucan endotransglycosylase (XET) genes were associated with GA-stimulation of leaf elongation, of which, the differential expression of EXPA4 and EXPA7 was related to the genotypic variation in LER of two cultivars. Those differentially-expressed expansin and XET genes could play major roles in genetic variation and GA-regulated leaf elongation in tall fescue. PMID:27457585

  19. Gibberellin-Regulation and Genetic Variations in Leaf Elongation for Tall Fescue in Association with Differential Gene Expression Controlling Cell Expansion.

    PubMed

    Xu, Qian; Krishnan, Sanalkumar; Merewitz, Emily; Xu, Jichen; Huang, Bingru

    2016-01-01

    Leaf elongation rate (LER) is an important factor controlling plant growth and productivity. The objective of this study was to determine whether genetic variation in LER for a fast-growing ('K-31'), and a dwarf cultivar ('Bonsai') of tall fescue (Festuca arundinacea) and gibberellic acid (GA) regulation of LER were associated with differential expression of cell-expansion genes. Plants were treated with GA3, trinexapac-ethyl (TE) (GA inhibitor), or water (untreated control) in a hydroponic system. LER of 'K-31' was 63% greater than that of 'Bonsai', which corresponded with 32% higher endogenous GA4 content in leaf and greater cell elongation and production rates under the untreated control condition. Exogenous application of GA3 significantly enhanced LER while TE treatment inhibited leaf elongation due to GA3-stimulation or TE-inhibition of cell elongation and production rate in leaves for both cultivars. Real-time quantitative polymerase chain reaction analysis revealed that three α-expansins, one β-expansin, and three xyloglucan endotransglycosylase (XET) genes were associated with GA-stimulation of leaf elongation, of which, the differential expression of EXPA4 and EXPA7 was related to the genotypic variation in LER of two cultivars. Those differentially-expressed expansin and XET genes could play major roles in genetic variation and GA-regulated leaf elongation in tall fescue. PMID:27457585

  20. Strigolactones contribute to shoot elongation and to the formation of leaf margin serrations in Medicago truncatula R108.

    PubMed

    Lauressergues, Dominique; André, Olivier; Peng, Jianling; Wen, Jiangqi; Chen, Rujin; Ratet, Pascal; Tadege, Million; Mysore, Kirankumar S; Rochange, Soizic F

    2015-03-01

    Strigolactones were recently identified as a new class of plant hormones involved in the control of shoot branching. The characterization of strigolactone mutants in several species has progressively revealed their contribution to several other aspects of development in roots and shoots. In this article, we characterize strigolactone-deficient and strigolactone-insensitive mutants of the model legume Medicago truncatula for aerial developmental traits. The most striking mutant phenotype observed was compact shoot architecture. In contrast with what was reported in other species, this could not be attributed to enhanced shoot branching, but was instead due to reduced shoot elongation. Another notable feature was the modified leaf shape in strigolactone mutants: serrations at the leaf margin were smaller in the mutants than in wild-type plants. This phenotype could be rescued in a dose-dependent manner by exogenous strigolactone treatments of strigolactone-deficient mutants, but not of strigolactone-insensitive mutants. Treatment with the auxin transport inhibitor N-1-naphthylphtalamic acid resulted in smooth leaf margins, opposite to the effect of strigolactone treatment. The contribution of strigolactones to the formation of leaf serrations in M. truncatula R108 line represents a novel function of these hormones, which has not been revealed by the analysis of strigolactone mutants in other species. PMID:25472976

  1. Strigolactones contribute to shoot elongation and to the formation of leaf margin serrations in Medicago truncatula R108

    PubMed Central

    Lauressergues, Dominique; André, Olivier; Peng, Jianling; Wen, Jiangqi; Chen, Rujin; Ratet, Pascal; Tadege, Million; Mysore, Kirankumar S.; Rochange, Soizic F.

    2015-01-01

    Strigolactones were recently identified as a new class of plant hormones involved in the control of shoot branching. The characterization of strigolactone mutants in several species has progressively revealed their contribution to several other aspects of development in roots and shoots. In this article, we characterize strigolactone-deficient and strigolactone-insensitive mutants of the model legume Medicago truncatula for aerial developmental traits. The most striking mutant phenotype observed was compact shoot architecture. In contrast with what was reported in other species, this could not be attributed to enhanced shoot branching, but was instead due to reduced shoot elongation. Another notable feature was the modified leaf shape in strigolactone mutants: serrations at the leaf margin were smaller in the mutants than in wild-type plants. This phenotype could be rescued in a dose-dependent manner by exogenous strigolactone treatments of strigolactone-deficient mutants, but not of strigolactone-insensitive mutants. Treatment with the auxin transport inhibitor N-1-naphthylphtalamic acid resulted in smooth leaf margins, opposite to the effect of strigolactone treatment. The contribution of strigolactones to the formation of leaf serrations in M. truncatula R108 line represents a novel function of these hormones, which has not been revealed by the analysis of strigolactone mutants in other species. PMID:25472976

  2. Analysis of changes in relative elemental growth rate patterns in the elongation zone of Arabidopsis roots upon gravistimulation

    NASA Technical Reports Server (NTRS)

    Mullen, J. L.; Ishikawa, H.; Evans, M. L.

    1998-01-01

    Although Arabidopsis is an important system for studying root physiology, the localized growth patterns of its roots have not been well defined, particularly during tropic responses. In order to characterize growth rate profiles along the apex of primary roots of Arabidopsis thaliana (L.) Heynh (ecotype Columbia) we applied small charcoal particles to the root surface and analyzed their displacement during growth using an automated video digitizer system with custom software for tracking the markers. When growing vertically, the maximum elongation rate occurred 481 +/- 50 microns back from the extreme tip of the root (tip of root cap), and the elongation zone extended back to 912 +/- 137 microns. The distal elongation zone (DEZ) has previously been described as the apical region of the elongation zone in which the relative elemental growth rate (REGR) is < or = 30% of the peak rate in the central elongation zone. By this definition, our data indicate that the basal limit of the DEZ was located 248 +/- 30 microns from the root tip. However, after gravistimulation, the growth patterns of the root changed. Within the first hour of graviresponse, the basal limit of the DEZ and the position of peak REGR shifted apically on the upper flank of the root. This was due to a combination of increased growth in the DEZ and growth inhibition in the central elongation zone. On the lower flank, the basal limit of the DEZ shifted basipetally as the REGR decreased. These factors set up the gradient of growth rate across the root, which drives curvature.

  3. Cytoplasmic calcium levels in protoplasts from the cap and elongation zone of maize roots

    NASA Technical Reports Server (NTRS)

    Kiss, H. G.; Evans, M. L.; Johnson, J. D.

    1991-01-01

    Calcium has been implicated as a key component in the signal transduction process of root gravitropism. We measured cytoplasmic free calcium in protoplasts isolated from the elongation zone and cap of primary roots of light-grown, vertically oriented seedlings of Zea mays L. Protoplasts were loaded with the penta-potassium salts of fura-2 and indo-1 by incubation in acidic solutions of these calcium indicators. Loading increased with decreasing pH but the pH dependence was stronger for indo-1 than for fura-2. In the case of fura-2, loading was enhanced only at the lowest pH (4.5) tested. Dyes loaded in this manner were distributed predominantly in the cytoplasm as indicated by fluorescence patterns. As an alternative method of loading, protoplasts were incubated with the acetoxymethylesters of fura-2 and indo-1. Protoplasts loaded by this method exhibited fluorescence both in the cytoplasm and in association with various organelles. Cytoplasmic calcium levels measured using spectrofluorometry, were found to be 160 +/- 40 nM and 257 +/- 27 nM, respectively, in populations of protoplasts from the root cap and elongation zone. Cytoplasmic free calcium did not increase upon addition of calcium to the incubation medium, indicating that the passive permeability to calcium was low.

  4. Distinct bacterial communities dominate tropical and temperate zone leaf litter.

    PubMed

    Kim, Mincheol; Kim, Woo-Sung; Tripathi, Binu M; Adams, Jonathan

    2014-05-01

    Little is known of the bacterial community of tropical rainforest leaf litter and how it might differ from temperate forest leaf litter and from the soils underneath. We sampled leaf litter in a similarly advanced stage of decay, and for comparison, we also sampled the surface layer of soil, at three tropical forest sites in Malaysia and four temperate forest sites in South Korea. Illumina sequencing targeting partial bacterial 16S ribosomal ribonucleic acid (rRNA) gene revealed that the bacterial community composition of both temperate and tropical litter is quite distinct from the soils underneath. Litter in both temperate and tropical forest was dominated by Proteobacteria and Actinobacteria, while soil is dominated by Acidobacteria and, to a lesser extent, Proteobacteria. However, bacterial communities of temperate and tropical litter clustered separately from one another on an ordination. The soil bacterial community structures were also distinctive to each climatic zone, suggesting that there must be a climate-specific biogeographical pattern in bacterial community composition. The differences were also found in the level of diversity. The temperate litter has a higher operational taxonomic unit (OTU) diversity than the tropical litter, paralleling the trend in soil diversity. Overall, it is striking that the difference in community composition between the leaf litter and the soil a few centimeters underneath is about the same as that between leaf litter in tropical and temperate climates, thousands of kilometers apart. However, one substantial difference was that the leaf litter of two tropical forest sites, Meranti and Forest Research Institute Malaysia (FRIM), was overwhelmingly dominated by the single genus Burkholderia, at 37 and 23 % of reads, respectively. The 454 sequencing result showed that most Burkholderia species in tropical leaf litter belong to nonpathogenic "plant beneficial" lineages. The differences from the temperate zone in the bacterial

  5. Elongation growth of the leaf sheath base of Avena sativa seedlings: regulation by hormones and sucrose

    NASA Technical Reports Server (NTRS)

    Brock, T. G.; Kaufman, P. B.

    1991-01-01

    The leaf sheath base of the seedling of Avena sativa was characterized for growth response to hormones and sucrose. Six day old plants, raised under a 10:14 hr light:dark cycle, were excised at the coleoptilar node and 1 cm above the node for treatment. The growth of the leaf sheath base was promoted by gibberellic acid (GA3) and this response was dose dependent. The lag to response initiation was approximately 4 hr. Growth with or without GA3 (10 micromoles) was transient, diminishing appreciably after 48 hr. The addition of 10 mM sucrose greatly prolonged growth; the effect of GA3 and sucrose was additive. Neither indole-3-acetic acid (IAA) nor the cytokinin N6-benzyladenine (BA), alone or in combination, promoted the growth of leaf sheath bases. However, both significantly inhibited the action of GA3. The inhibitory effect of IAA was dose dependent and was not affected by the addition of BA or sucrose. These results indicate that the growth of leaf sheath bases of Avena sativa is promoted specifically by gibberellin, that this action depends on the availability of carbohydrates from outside of the leaf sheath base, and that the promotional effect of GA3 can be modified by either auxins or cytokinins.

  6. Distribution of electrolytes in cells of the tomato root elongation zone during a gravitropic response

    NASA Astrophysics Data System (ADS)

    Klymchuk, Dmytro

    It is known that gravitropic response of etiolated seedlings is accompanied with asymmetrical distribution of auxins. The higher amount of auxins in the tissues of the lower sides of gravistimulated organs induces cell elongation in shoots and inhibits cell elongation in roots. In spite on the progress in understanding of the auxin-mediated effects on plant growth and development, there is no a complete conception concerning of gravitropic response mechanism. This investigation aims to determine whether the growth response of tomato seedlings on reorientation to the horizontal induces alterations in distribution of electrolytes in cells of the main root elongation zone, the site where induction of the curvature takes place. Tomato (Lycopersicon esculentum, Rio Grande) seedlings were grown on agar surface in 10 cm Petri dishes. The gravitropic response of seedlings was evaluated by the angle of gravitropic curvature after the roots were reoriented 90° from the vertical. Root segments of several mm basipetal to the root tip were fixed in liquid nitrogen, freeze-substituted with Lowicril K11M at -35° C. Sections 100 and 1000 nm thick were cut using LKB Ultrotome V, collected by dry method and analyzed in the 6060 LA SEM at accelerating voltage 15 kV. Using different modes of X-ray microanalysis (X-ray map, - line and -point analysis), distribution of the physiologically relevant ions (Na, P, K, Ca) in cells of surface layers of the upper and lower root sides were investigated. The peculiarities in localization of the electrolytes in different subcellular compartments as well as distribution in the direction between upper and lower sides of the root curvature are discussed.

  7. Drought Induces Distinct Growth Response, Protection, and Recovery Mechanisms in the Maize Leaf Growth Zone1[OPEN

    PubMed Central

    Avramova, Viktoriya; AbdElgawad, Hamada; Zhang, Zhengfeng; Fotschki, Bartosz; Casadevall, Romina; Vergauwen, Lucia; Knapen, Dries; Taleisnik, Edith; Guisez, Yves; Asard, Han; Beemster, Gerrit T.S.

    2015-01-01

    Drought is the most important crop yield-limiting factor, and detailed knowledge of its impact on plant growth regulation is crucial. The maize (Zea mays) leaf growth zone offers unique possibilities for studying the spatiotemporal regulation of developmental processes by transcriptional analyses and methods that require more material, such as metabolite and enzyme activity measurements. By means of a kinematic analysis, we show that drought inhibits maize leaf growth by inhibiting cell division in the meristem and cell expansion in the elongation zone. Through a microarray study, we observed the down-regulation of 32 of the 54 cell cycle genes, providing a basis for the inhibited cell division. We also found evidence for an up-regulation of the photosynthetic machinery and the antioxidant and redox systems. This was confirmed by increased chlorophyll content in mature cells and increased activity of antioxidant enzymes and metabolite levels across the growth zone, respectively. We demonstrate the functional significance of the identified transcriptional reprogramming by showing that increasing the antioxidant capacity in the proliferation zone, by overexpression of the Arabidopsis (Arabidopsis thaliana) iron-superoxide dismutase gene, increases leaf growth rate by stimulating cell division. We also show that the increased photosynthetic capacity leads to enhanced photosynthesis upon rewatering, facilitating the often-observed growth compensation. PMID:26297138

  8. A hydraulic model is compatible with rapid changes in leaf elongation under fluctuating evaporative demand and soil water status.

    PubMed

    Caldeira, Cecilio F; Bosio, Mickael; Parent, Boris; Jeanguenin, Linda; Chaumont, François; Tardieu, François

    2014-04-01

    Plants are constantly facing rapid changes in evaporative demand and soil water content, which affect their water status and growth. In apparent contradiction to a hydraulic hypothesis, leaf elongation rate (LER) declined in the morning and recovered upon soil rehydration considerably quicker than transpiration rate and leaf water potential (typical half-times of 30 min versus 1-2 h). The morning decline of LER began at very low light and transpiration and closely followed the stomatal opening of leaves receiving direct light, which represent a small fraction of leaf area. A simulation model in maize (Zea mays) suggests that these findings are still compatible with a hydraulic hypothesis. The small water flux linked to stomatal aperture would be sufficient to decrease water potentials of the xylem and growing tissues, thereby causing a rapid decline of simulated LER, while the simulated water potential of mature tissues declines more slowly due to a high hydraulic capacitance. The model also captured growth patterns in the evening or upon soil rehydration. Changes in plant hydraulic conductance partly counteracted those of transpiration. Root hydraulic conductivity increased continuously in the morning, consistent with the transcript abundance of Zea maize Plasma Membrane Intrinsic Protein aquaporins. Transgenic lines underproducing abscisic acid, with lower hydraulic conductivity and higher stomatal conductance, had a LER declining more rapidly than wild-type plants. Whole-genome transcriptome and phosphoproteome analyses suggested that the hydraulic processes proposed here might be associated with other rapidly occurring mechanisms. Overall, the mechanisms and model presented here may be an essential component of drought tolerance in naturally fluctuating evaporative demand and soil moisture. PMID:24420931

  9. Lyme disease and relapsing fever Borrelia elongate through zones of peptidoglycan synthesis that mark division sites of daughter cells.

    PubMed

    Jutras, Brandon Lyon; Scott, Molly; Parry, Bradley; Biboy, Jacob; Gray, Joe; Vollmer, Waldemar; Jacobs-Wagner, Christine

    2016-08-16

    Agents that cause Lyme disease, relapsing fever, leptospirosis, and syphilis belong to the phylum Spirochaetae-a unique lineage of bacteria most known for their long, spiral morphology. Despite the relevance to human health, little is known about the most fundamental aspects of spirochete growth. Here, using quantitative microscopy to track peptidoglycan cell-wall synthesis, we found that the Lyme disease spirochete Borrelia burgdorferi displays a complex pattern of growth. B. burgdorferi elongates from discrete zones that are both spatially and temporally regulated. In addition, some peptidoglycan incorporation occurs along the cell body, with the notable exception of a large region at the poles. Newborn cells inherit a highly active zone of peptidoglycan synthesis at midcell that contributes to elongation for most of the cell cycle. Concomitant with the initiation of nucleoid separation and cell constriction, second and third zones of elongation are established at the 1/4 and 3/4 cellular positions, marking future sites of division for the subsequent generation. Positioning of elongation zones along the cell is robust to cell length variations and is relatively precise over long distances (>30 µm), suggesting that cells ‟sense" relative, as opposed to absolute, cell length to establish zones of peptidoglycan synthesis. The transition from one to three zones of peptidoglycan growth during the cell cycle is also observed in relapsing fever Borrelia. However, this mode of growth does not extend to representative species from other spirochetal genera, suggesting that this distinctive growth mode represents an evolutionary divide in the spirochete phylum. PMID:27506799

  10. Pinot noir wine volatile and anthocyanin composition under different levels of vine fruit zone leaf removal.

    PubMed

    Feng, Hui; Skinkis, Patricia A; Qian, Michael C

    2017-01-01

    The impacts of fruit zone leaf removal on volatile and anthocyanin compositions of Pinot noir wine were investigated over two growing seasons. Wine volatiles were analyzed by multiple techniques, including headspace solid phase microextraction-GC-MS (HS-SPME-GC-MS), headspace-GC-FID (HS-GC-FID) and stir bar sorptive extraction-GC-MS (SBSE-GC-MS). Fruit zone leaf removal affected the concentration of many grape-derived volatile compounds such as terpene alcohols and C13-norisoprenoids in wine, although the degree of impact depended on the vintage year and severity of leaf removal. Fruit zone leaf removal resulted in greater concentrations of linalool, α-terpineol and β-damascenone but had no impact on other terpene alcohols or β-ionone. Fruit zone leaf removal had no consistent impact on C6 alcohols, volatile phenols, lactones, fermentation-derived alcohols, acids, or most esters. Fruit zone leaf removal increased anthocyanins in final wine. PMID:27507532

  11. Transcriptome Analysis of Short Fiber Mutant Ligon lintless-1 (Li1) Reveals Critical Genes and Key Pathways in Cotton Fiber Elongation and Leaf Development

    PubMed Central

    Liang, Wenhua; Fang, Lei; Xiang, Dan; Hu, Yan; Feng, Hao; Chang, Lijing; Zhang, Tianzhen

    2015-01-01

    For efficient spinning and superior fabric production, long fiber length is a desired trait for cotton production. To unveil the molecular basis of the cotton fiber length regulation, a short fiber mutant, Ligon lintless-1 (Li1), is selected to compare with its corresponding wild type (WT). Li1 is a monogenic dominant cotton mutant causing extremely short fibers (<6mm) on mature seeds with visible pleiotropic effects on vegetative growth and development. In this research, we compared the transcriptome of fiber bearing ovules at 1 DPA, 3 DPA, 8 DPA and leaf between Li1 mutant and WT. A total of 7,852 differentially expressed genes (DEGs) were detected in ovules and leaves, which mainly participated in sugar, secondary metabolite and lipid metabolism pathways based on KEGG analysis. The common DEGs at 1 DPA and 3 DPA were involved in the responses to endogenous stimulus, signal transduction and long-chain fatty acid biosynthesis. For 3 DPA, 8 DPA and leaf, the common DEGs were involved in the responses to auxin and receptor kinases related pathway. Further analysis showed that 37 genes involved in very-long-chain fatty acid biosynthesis were suppressed in Li1 mutant during fiber fast elongation development. Most of the DEGs involved in cell wall metabolism, such cellulose synthase, expansin family, and glycosyl hydrolase were differentially expressed at 3 DPA and 8 DPA. Our results provide new insights into the mechanisms of fiber elongation, and offer novel genes as potential objects for fiber length improvement. PMID:26600249

  12. Xyloglucan endotransglucosylase action is high in the root elongation zone and in the trichoblasts of all vascular plants from Selaginella to Zea mays.

    PubMed

    Vissenberg, K; Van Sandt, V; Fry, S C; Verbelen, J-P

    2003-01-01

    The endotransglucosylase action of the enzyme xyloglucan endotransglucosylase/hydrolase (XTH) was localized in the roots of diverse vascular plants: club-mosses (lycopodiophytes), ferns, gymnosperms, monocots, and dicots. High action was always found in the epidermis cell wall of the elongation zone and in trichoblasts in the differentiation zone. Clearly XTH and its action in root development evolved before the evolutionary divergence of ferns and seed plants and also of the lycopodiophytes and euphyllophytes. PMID:12493861

  13. Differential expression profiles and pathways of genes in sugarcane leaf at elongation stage in response to drought stress.

    PubMed

    Li, Changning; Nong, Qian; Solanki, Manoj Kumar; Liang, Qiang; Xie, Jinlan; Liu, Xiaoyan; Li, Yijie; Wang, Weizan; Yang, Litao; Li, Yangrui

    2016-01-01

    Water stress causes considerable yield losses in sugarcane. To investigate differentially expressed genes under water stress, a pot experiment was performed with the sugarcane variety GT21 at three water-deficit levels (mild, moderate, and severe) during the elongation stage and gene expression was analyzed using microarray technology. Physiological parameters of sugarcane showed significant alterations in response to drought stress. Based on the expression profile of 15,593 sugarcane genes, 1,501 (9.6%) genes were differentially expressed under different water-level treatments; 821 genes were upregulated and 680 genes were downregulated. A gene similarity analysis showed that approximately 62.6% of the differentially expressed genes shared homology with functional proteins. In a Gene Ontology (GO) analysis, 901 differentially expressed genes were assigned to 36 GO categories. Moreover, 325 differentially expressed genes were classified into 101 pathway categories involved in various processes, such as the biosynthesis of secondary metabolites, ribosomes, carbon metabolism, etc. In addition, some unannotated genes were detected; these may provide a basis for studies of water-deficit tolerance. The reliability of the observed expression patterns was confirmed by RT-PCR. The results of this study may help identify useful genes for improving drought tolerance in sugarcane. PMID:27170459

  14. Differential expression profiles and pathways of genes in sugarcane leaf at elongation stage in response to drought stress

    PubMed Central

    Li, Changning; Nong, Qian; Solanki, Manoj Kumar; Liang, Qiang; Xie, Jinlan; Liu, Xiaoyan; Li, Yijie; Wang, Weizan; Yang, Litao; Li, Yangrui

    2016-01-01

    Water stress causes considerable yield losses in sugarcane. To investigate differentially expressed genes under water stress, a pot experiment was performed with the sugarcane variety GT21 at three water-deficit levels (mild, moderate, and severe) during the elongation stage and gene expression was analyzed using microarray technology. Physiological parameters of sugarcane showed significant alterations in response to drought stress. Based on the expression profile of 15,593 sugarcane genes, 1,501 (9.6%) genes were differentially expressed under different water-level treatments; 821 genes were upregulated and 680 genes were downregulated. A gene similarity analysis showed that approximately 62.6% of the differentially expressed genes shared homology with functional proteins. In a Gene Ontology (GO) analysis, 901 differentially expressed genes were assigned to 36 GO categories. Moreover, 325 differentially expressed genes were classified into 101 pathway categories involved in various processes, such as the biosynthesis of secondary metabolites, ribosomes, carbon metabolism, etc. In addition, some unannotated genes were detected; these may provide a basis for studies of water-deficit tolerance. The reliability of the observed expression patterns was confirmed by RT-PCR. The results of this study may help identify useful genes for improving drought tolerance in sugarcane. PMID:27170459

  15. Control of climate and litter quality on leaf litter decomposition in different climatic zones.

    PubMed

    Zhang, Xinyue; Wang, Wei

    2015-09-01

    Climate and initial litter quality are the major factors influencing decomposition rates on large scales. We established a comprehensive database of terrestrial leaf litter decomposition, including 785 datasets, to examine the relationship between climate and litter quality and evaluate the factors controlling decomposition on a global scale, the arid and semi-arid (AS) zone, the humid middle and humid low (HL) latitude zones. Initial litter nitrogen (N) and phosphorus (P) concentration only increased with mean annual temperature (MAT) in the AS zone and decreased with mean annual precipitation (MAP) in the HL zone. Compared with nutrient content, MAT imposed less effect on initial litter lignin content than MAP. MAT were the most important decomposition driving factors on a global scale as well as in different climatic zones. MAP only significantly affected decomposition constants in AS zone. Although litter quality parameters also showed significant influence on decomposition, their importance was less than the climatic factors. Besides, different litter quality parameters exerted significant influence on decomposition in different climatic zones. Our results emphasized that climate consistently exerted important effects on decomposition constants across different climatic zones. PMID:26135888

  16. Effects of radionuclide contamination on leaf litter decomposition in the Chernobyl exclusion zone.

    PubMed

    Bonzom, Jean-Marc; Hättenschwiler, Stephan; Lecomte-Pradines, Catherine; Chauvet, Eric; Gaschak, Sergey; Beaugelin-Seiller, Karine; Della-Vedova, Claire; Dubourg, Nicolas; Maksimenko, Andrey; Garnier-Laplace, Jacqueline; Adam-Guillermin, Christelle

    2016-08-15

    The effects of radioactive contamination on ecosystem processes such as litter decomposition remain largely unknown. Because radionuclides accumulated in soil and plant biomass can be harmful for organisms, the functioning of ecosystems may be altered by radioactive contamination. Here, we tested the hypothesis that decomposition is impaired by increasing levels of radioactivity in the environment by exposing uncontaminated leaf litter from silver birch and black alder at (i) eleven distant forest sites differing in ambient radiation levels (0.22-15μGyh(-1)) and (ii) along a short distance gradient of radioactive contamination (1.2-29μGyh(-1)) within a single forest in the Chernobyl exclusion zone. In addition to measuring ambient external dose rates, we estimated the average total dose rates (ATDRs) absorbed by decomposers for an accurate estimate of dose-induced ecological consequences of radioactive pollution. Taking into account potential confounding factors (soil pH, moisture, texture, and organic carbon content), the results from the eleven distant forest sites, and from the single forest, showed increased litter mass loss with increasing ATDRs from 0.3 to 150μGyh(-1). This unexpected result may be due to (i) overcompensation of decomposer organisms exposed to radionuclides leading to a higher decomposer abundance (hormetic effect), and/or (ii) from preferred feeding by decomposers on the uncontaminated leaf litter used for our experiment compared to locally produced, contaminated leaf litter. Our data indicate that radio-contamination of forest ecosystems over more than two decades does not necessarily have detrimental effects on organic matter decay. However, further studies are needed to unravel the underlying mechanisms of the results reported here, in order to draw firmer conclusions on how radio-contamination affects decomposition and associated ecosystem processes. PMID:27110974

  17. The locations and amounts of endogenous ions and elements in the cap and elongating zone of horizontally oriented roots of Zea mays L.: an electron-probe EDS study

    NASA Technical Reports Server (NTRS)

    Moore, R.; Cameron, I. L.; Hunter, K. E.; Olmos, D.; Smith, N. K.

    1987-01-01

    We used quantitative electron-probe energy-dispersive x-ray microanalysis to localize endogenous Na, Cl, K, P, S, Mg and Ca in cryofixed and freeze-dried cryosections of the cap (i.e. the putative site of graviperception) and elongating zone (i.e. site of gravicurvature) of horizontally oriented roots of Zea mays. Ca, Na, Cl, K and Mg accumulate along the lower side of caps of horizontally oriented roots. The most dramatic asymmetries of these ions occur in the apoplast, especially the mucilage. We could not detect any significant differences in the concentrations of these ions in the central cytoplasm of columella cells along the upper and lower sides of caps of horizontally-oriented roots. However, the increased amounts of Na, Cl, K and Mg in the longitudinal walls of columella cells along the lower side of the cap suggest that these ions may move down through the columella tissue of horizontally-oriented roots. Ca also accumulates (largely in the mucilage) along the lower side of the elongating zone of horizontally-oriented roots, while Na, P, Cl and K tend to accumulate along the upper side of the elongating zone. Of these ions, only K increases in concentration in the cytoplasm and longitudinal walls of cortical cells in the upper vs lower sides of the elongating zone. These results indicate that (1) gravity-induced asymmetries of ions differ significantly in the cap and elongating zone of graviresponding roots, (2) Ca accumulates along the lower side of the cap and elongating zone of graviresponding roots, (3) increased growth of the upper side of the elongating zone of horizontally-oriented roots correlates positively with increased amounts of K in the cytoplasm and longitudinal walls of cortical cells, and (4) the apoplast (especially the mucilage) may be an important component of the pathway via which ions move in graviresponding rots of Zea mays. These results are discussed relative to mechanisms for graviperception and gravicurvature of roots.

  18. Functional traits drive the contribution of solar radiation to leaf litter decomposition among multiple arid-zone species

    PubMed Central

    Pan, Xu; Song, Yao-Bin; Liu, Guo-Fang; Hu, Yu-Kun; Ye, Xue-Hua; Cornwell, William K.; Prinzing, Andreas; Dong, Ming; Cornelissen, Johannes H.C.

    2015-01-01

    In arid zones, strong solar radiation has important consequences for ecosystem processes. To better understand carbon and nutrient dynamics, it is important to know the contribution of solar radiation to leaf litter decomposition of different arid-zone species. Here we investigated: (1) whether such contribution varies among plant species at given irradiance regime, (2) whether interspecific variation in such contribution correlates with interspecific variation in the decomposition rate under shade; and (3) whether this correlation can be explained by leaf traits. We conducted a factorial experiment to determine the effects of solar radiation and environmental moisture for the mass loss and the decomposition constant k-values of 13 species litters collected in Northern China. The contribution of solar radiation to leaf litter decomposition varied significantly among species. Solar radiation accelerated decomposition in particular in the species that already decompose quickly under shade. Functional traits, notably specific leaf area, might predict the interspecific variation in that contribution. Our results provide the first empirical evidence for how the effect of solar radiation on decomposition varies among multiple species. Thus, the effect of solar radiation on the carbon flux between biosphere and atmosphere may depend on the species composition of the vegetation. PMID:26282711

  19. Functional traits drive the contribution of solar radiation to leaf litter decomposition among multiple arid-zone species.

    PubMed

    Pan, Xu; Song, Yao-Bin; Liu, Guo-Fang; Hu, Yu-Kun; Ye, Xue-Hua; Cornwell, William K; Prinzing, Andreas; Dong, Ming; Cornelissen, Johannes H C

    2015-01-01

    In arid zones, strong solar radiation has important consequences for ecosystem processes. To better understand carbon and nutrient dynamics, it is important to know the contribution of solar radiation to leaf litter decomposition of different arid-zone species. Here we investigated: (1) whether such contribution varies among plant species at given irradiance regime, (2) whether interspecific variation in such contribution correlates with interspecific variation in the decomposition rate under shade; and (3) whether this correlation can be explained by leaf traits. We conducted a factorial experiment to determine the effects of solar radiation and environmental moisture for the mass loss and the decomposition constant k-values of 13 species litters collected in Northern China. The contribution of solar radiation to leaf litter decomposition varied significantly among species. Solar radiation accelerated decomposition in particular in the species that already decompose quickly under shade. Functional traits, notably specific leaf area, might predict the interspecific variation in that contribution. Our results provide the first empirical evidence for how the effect of solar radiation on decomposition varies among multiple species. Thus, the effect of solar radiation on the carbon flux between biosphere and atmosphere may depend on the species composition of the vegetation. PMID:26282711

  20. Responses of Leaf-level Carbon Assimilation and Transpiration to Root-zone Water Potential Changes in a Subtropical Tree Species

    NASA Astrophysics Data System (ADS)

    Cicheng, Z.; Guan, H.; Han, G.; Zhang, X.

    2013-12-01

    Photosynthetic carbon assimilation in terrestrial ecosystems significantly contributes to global carbon balance in the atmosphere. While vegetation photosynthesizes to fix CO2, it simultaneously transpires H2O. These two interdependent processes are regulated by leaf stomata which are sensitive to environmental conditions (such as root zone soil moisture). Knowledge of the responses of leaf-level transpiration and carbon assimilation to a change of root-zone soil moisture condition is important to understand how these processes influence water balance and carbon sequestration in terrestrial ecosystems, and to understand the capacity of trees to cope with future climate changes.We will present the results of a one-year observational study on a subtropical evergreen broadleaf tree species (Osmanthus fragrans) in the central south China. The observations were carried out on two 8-year Osmanthus fragrans trees in a plantation site from 1 Sep, 2012 to 31 Aug, 2013. A portable infrared gas exchange analyzer (Li-6400, Li-COR, Inc., Lincoln, Nebraska, USA) was used to measure leaf photosynthesis and leaf transpiration on clear days. Root zone soil water potential was estimated from predawn stem water potential using stem psychrometers (ICT, Australia). Sap flow and micrometeorological data were also collected. The results show that the average leaf carbon assimilation rate at light saturation decreases quickly with the root zone water potential from 0 to -1 MPa, and slowly after the root zone water potential falls below -1 MPa. The average leaf transpiration at light saturation shows a similar pattern. Leaf-level water use efficiency increases slowly with a decrease of root-zone water potential from 0 to -1 MPa, and keeps constant when the root zone gets drier. This relationship provides a potential to estimate whole-tree carbon assimilation from sap flow measurements. Leaf assimilation rates at light saturation in early morning vs. root-zone water potential for Osmanthus

  1. Genotypical Differences in Aluminum Resistance of Maize Are Expressed in the Distal Part of the Transition Zone. Is Reduced Basipetal Auxin Flow Involved in Inhibition of Root Elongation by Aluminum?1

    PubMed Central

    Kollmeier, Malte; Felle, Hubert H.; Horst, Walter J.

    2000-01-01

    Short-term Al treatment (90 μm Al at pH 4.5 for 1 h) of the distal transition zone (DTZ; 1–2 mm from the root tip), which does not contribute significantly to root elongation, inhibited root elongation in the main elongation zone (EZ; 2.5–5 mm from the root tip) to the same extent as treatment of the entire maize (Zea mays) root apex. Application of Al to the EZ had no effect on root elongation. Higher genotypical resistance to Al applied to the entire root apex, and specifically to the DTZ, was expressed by less inhibition of root elongation, Al accumulation, and Al-induced callose formation, primarily in the DTZ. A characteristic pH profile along the surface of the root apex with a maximum of pH 5.3 in the DTZ was demonstrated. Al application induced a substantial flattening of the pH profile moreso in the Al-sensitive than in the Al-resistant cultivar. Application of indole-3-acetic acid to the EZ but not to the meristematic zone significantly alleviated the inhibition of root elongation induced by the application of Al to the DTZ. Basipetal transport of exogenously applied [3H]indole-3-acetic acid to the meristematic zone was significantly inhibited by Al application to the DTZ in the Al-sensitive maize cv Lixis. Our results provide evidence that the primary mechanisms of genotypical differences in Al resistance are located within the DTZ, and suggest a signaling pathway in the root apex mediating the Al signal between the DTZ and the EZ through basipetal auxin transport. PMID:10712559

  2. Genotypical differences in aluminum resistance of maize are expressed in the distal part of the transition zone. Is reduced basipetal auxin flow involved in inhibition of root elongation by aluminum?

    PubMed

    Kollmeier, M; Felle, H H; Horst, W J

    2000-03-01

    Short-term Al treatment (90 microM Al at pH 4.5 for 1 h) of the distal transition zone (DTZ; 1-2 mm from the root tip), which does not contribute significantly to root elongation, inhibited root elongation in the main elongation zone (EZ; 2.5-5 mm from the root tip) to the same extent as treatment of the entire maize (Zea mays) root apex. Application of Al to the EZ had no effect on root elongation. Higher genotypical resistance to Al applied to the entire root apex, and specifically to the DTZ, was expressed by less inhibition of root elongation, Al accumulation, and Al-induced callose formation, primarily in the DTZ. A characteristic pH profile along the surface of the root apex with a maximum of pH 5.3 in the DTZ was demonstrated. Al application induced a substantial flattening of the pH profile moreso in the Al-sensitive than in the Al-resistant cultivar. Application of indole-3-acetic acid to the EZ but not to the meristematic zone significantly alleviated the inhibition of root elongation induced by the application of Al to the DTZ. Basipetal transport of exogenously applied [(3)H]indole-3-acetic acid to the meristematic zone was significantly inhibited by Al application to the DTZ in the Al-sensitive maize cv Lixis. Our results provide evidence that the primary mechanisms of genotypical differences in Al resistance are located within the DTZ, and suggest a signaling pathway in the root apex mediating the Al signal between the DTZ and the EZ through basipetal auxin transport. PMID:10712559

  3. Elongated beamlets: a simple technique for segment and MU reduction for sMLC IMRT delivery on accelerators utilizing 5 mm leaf widths.

    PubMed

    Price, R A; Paskalev, K; McNeeley, S; Ma, C-M

    2005-10-01

    The focus of this work is to demonstrate the effects of using an elongated beamlet to achieve similar dose conformity as achieved with a square beamlet while reducing the number of segments and subsequent MU required. A series of 10 patients were planned for IMRT delivery to the prostate using minimum beamlet sizes of 5x5 mm2 (default scheme), 10x5 mm2 with the short axis parallel to the prostate-rectum interface (scheme 1), and 10x5 mm2 with the short axis perpendicular to the prostate-rectum interface (scheme 2). All other parameters between plans were left unchanged. Plans were appropriately normalized and evaluated for R65, R40, conformity index, total number of segments and MU. All plans were generated using the Corvus inverse planning system. The average number of segments in this study decreased by approximately 49% for both schemes 1 and 2. The subsequent number of MU required decreased by approximately 34.6%. The resultant modified modulation scaling factor (MSFmod) decreased by approximately 34.3%. Additionally, we found that each isodose distribution using scheme 2 would still meet our clinical acceptance criteria with no visible degradation in the dose distribution as compared with the default scheme. In conclusion, we have demonstrated that it is possible to achieve similar results as those obtained using a 5x5 mm2 beamlet with respect to target coverage and critical structure sparing by using strategically oriented elongated beamlets. This technique directly translates to a decreased MSF(mod) allowing for decreased leakage dose to the patient, a decreased risk of exceeding secondary shielding limits in pre-existing vaults, and shorter treatment times. PMID:16177479

  4. NOTE: Elongated beamlets: a simple technique for segment and MU reduction for sMLC IMRT delivery on accelerators utilizing 5 mm leaf widths

    NASA Astrophysics Data System (ADS)

    Price, R. A., Jr.; Paskalev, K.; McNeeley, S.; Ma, C.-M.

    2005-10-01

    The focus of this work is to demonstrate the effects of using an elongated beamlet to achieve similar dose conformity as achieved with a square beamlet while reducing the number of segments and subsequent MU required. A series of 10 patients were planned for IMRT delivery to the prostate using minimum beamlet sizes of 5 × 5 mm2 (default scheme), 10 × 5 mm2 with the short axis parallel to the prostate rectum interface (scheme 1), and 10 × 5 mm2 with the short axis perpendicular to the prostate rectum interface (scheme 2). All other parameters between plans were left unchanged. Plans were appropriately normalized and evaluated for R65, R40, conformity index, total number of segments and MU. All plans were generated using the Corvus inverse planning system. The average number of segments in this study decreased by approximately 49% for both schemes 1 and 2. The subsequent number of MU required decreased by approximately 34.6%. The resultant modified modulation scaling factor (MSFmod) decreased by approximately 34.3%. Additionally, we found that each isodose distribution using scheme 2 would still meet our clinical acceptance criteria with no visible degradation in the dose distribution as compared with the default scheme. In conclusion, we have demonstrated that it is possible to achieve similar results as those obtained using a 5 × 5 mm2 beamlet with respect to target coverage and critical structure sparing by using strategically oriented elongated beamlets. This technique directly translates to a decreased MSFmod allowing for decreased leakage dose to the patient, a decreased risk of exceeding secondary shielding limits in pre-existing vaults, and shorter treatment times.

  5. Core cell cycle regulatory genes in rice and their expression profiles across the growth zone of the leaf.

    PubMed

    Pettkó-Szandtner, A; Cserháti, M; Barrôco, R M; Hariharan, S; Dudits, D; Beemster, G T S

    2015-11-01

    Rice (Oryza sativa L.) as a model and crop plant with a sequenced genome offers an outstanding experimental system for discovering and functionally analyzing the major cell cycle control elements in a cereal species. In this study, we identified the core cell cycle genes in the rice genome through a hidden Markov model search and multiple alignments supported with the use of short protein sequence probes. In total we present 55 rice putative cell cycle genes with locus identity, chromosomal location, approximate chromosome position and EST accession number. These cell cycle genes include nine cyclin dependent-kinase (CDK) genes, 27 cyclin genes, one CKS gene, two RBR genes, nine E2F/DP/DEL genes, six KRP genes, and one WEE gene. We also provide characteristic protein sequence signatures encoded by CDK and cyclin gene variants. Promoter analysis by the FootPrinter program discovered several motifs in the regulatory region of the core cell cycle genes. As a first step towards functional characterization we performed transcript analysis by RT-PCR to determine gene specific variation in transcript levels along the rice leaves. The meristematic zone of the leaves where cells are actively dividing was identified based on kinematic analysis and flow cytometry. As expected, expression of the majority of cell cycle genes was exclusively associated with the meristematic region. However genes such as different D-type cyclins, DEL1, KRP1/3, and RBR2 were also expressed in leaf segments representing the transition zone in which cells start differentiation. PMID:26459328

  6. Reactive oxygen species regulate leaf pulvinus abscission zone cell separation in response to water-deficit stress in cassava

    PubMed Central

    Liao, Wenbin; Wang, Gan; Li, Yayun; Wang, Bin; Zhang, Peng; Peng, Ming

    2016-01-01

    Cassava (Manihot esculenta Crantz) plant resists water-deficit stress by shedding leaves leading to adaptive water-deficit condition. Transcriptomic, physiological, cellular, molecular, metabolic, and transgenic methods were used to study the mechanism of cassava abscission zone (AZ) cell separation under water-deficit stress. Microscopic observation indicated that AZ cell separation initiated at the later stages during water-deficit stress. Transcriptome profiling of AZ suggested that differential expression genes of AZ under stress mainly participate in reactive oxygen species (ROS) pathway. The key genes involved in hydrogen peroxide biosynthesis and metabolism showed significantly higher expression levels in AZ than non-separating tissues adjacent to the AZ under stress. Significantly higher levels of hydrogen peroxide correlated with hydrogen peroxide biosynthesis related genes and AZ cell separation was detected by microscopic observation, colorimetric detection and GC-MS analyses under stress. Co-overexpression of the ROS-scavenging proteins SOD and CAT1 in cassava decreased the levels of hydrogen peroxide in AZ under water-deficit stress. The cell separation of the pulvinus AZ also delayed in co-overexpression of the ROS-scavenging proteins SOD and CAT1 plants both in vitro and at the plant level. Together, the results indicated that ROS play an important regulatory role in the process of cassava leaf abscission under water-deficit stress. PMID:26899473

  7. Reactive oxygen species regulate leaf pulvinus abscission zone cell separation in response to water-deficit stress in cassava.

    PubMed

    Liao, Wenbin; Wang, Gan; Li, Yayun; Wang, Bin; Zhang, Peng; Peng, Ming

    2016-01-01

    Cassava (Manihot esculenta Crantz) plant resists water-deficit stress by shedding leaves leading to adaptive water-deficit condition. Transcriptomic, physiological, cellular, molecular, metabolic, and transgenic methods were used to study the mechanism of cassava abscission zone (AZ) cell separation under water-deficit stress. Microscopic observation indicated that AZ cell separation initiated at the later stages during water-deficit stress. Transcriptome profiling of AZ suggested that differential expression genes of AZ under stress mainly participate in reactive oxygen species (ROS) pathway. The key genes involved in hydrogen peroxide biosynthesis and metabolism showed significantly higher expression levels in AZ than non-separating tissues adjacent to the AZ under stress. Significantly higher levels of hydrogen peroxide correlated with hydrogen peroxide biosynthesis related genes and AZ cell separation was detected by microscopic observation, colorimetric detection and GC-MS analyses under stress. Co-overexpression of the ROS-scavenging proteins SOD and CAT1 in cassava decreased the levels of hydrogen peroxide in AZ under water-deficit stress. The cell separation of the pulvinus AZ also delayed in co-overexpression of the ROS-scavenging proteins SOD and CAT1 plants both in vitro and at the plant level. Together, the results indicated that ROS play an important regulatory role in the process of cassava leaf abscission under water-deficit stress. PMID:26899473

  8. Testing Earth System Model Assumptions of Photosynthetic Parameters with in situ Leaf Measurements from a Temperate Zone Forest.

    NASA Astrophysics Data System (ADS)

    Cheng, S. J.; Thomas, R. Q.; Wilkening, J. V.; Curtis, P.; Sharkey, T. D.; Nadelhoffer, K. J.

    2015-12-01

    Estimates of global land CO2 uptake vary widely across Earth system models. This uncertainty around model estimates of land-atmosphere CO2 fluxes may result from differences in how models parameterize and scale photosynthesis from the leaf-to-global level. To test model assumptions about photosynthesis, we derive rates of maximum carboxylation (Vc,max), electron transport (J), and triose phosphate utilization (TPU) from in situ leaf measurements from a forest representative of the Great Lakes region. Leaf-level gas exchange measurements were collected across a temperature range from sun and shade leaves of canopy-dominant tree species typically grouped into the same plant functional type. We evaluate the influence of short-term increases in leaf temperature, nitrogen per leaf area (Narea), species, and leaf light environment on Vc,max, J, and TPU by testing contrasting model equations that isolate the influence of these factors on these rate-limiting steps in leaf photosynthesis. Results indicate that patterns in Vc,max are best explained by a model that includes temperature and Narea. However, J varied with species and leaf light environment in addition to temperature. TPU also varied with leaf light environment and possibly with temperature. These variations in J and TPU with species or between sun and shade leaves suggest that plant traits outside of Narea are needed to explain patterns in J and TPU. This study provides in situ evidence on how Vc,max, J, and TPU vary within a forest canopy and highlight how leaf responses to changes in climate, forest species composition, and canopy structure may alter forest CO2 uptake.

  9. 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

  10. Kinetic analysis of mitotic spindle elongation in vitro.

    PubMed

    Baskin, T I; Cande, W Z

    1990-09-01

    Studies of mitotic spindle elongation in vitro using populations of diatom spindles visualized with immunofluorescence microscopy have shown that the two interdigitating half-spindles are driven apart by an ATP-dependent process that generates force in the zone of overlap between half-spindles. To characterize further the system responsible for spindle elongation, we observed spindle elongation directly with polarized light or phase-contrast video-microscopy. We report that the kinetics of spindle elongation versus time are linear. A constant rate of spindle elongation occurs despite the continuous decrease in length of the zone of overlap between half-spindles. The average rate of spindle elongation varies as a function of treatment, and rates measured match spindle elongation rates measured in vivo. When spindles elongated in the presence of polymerizing tubulin (from bovine brain), the extent of elongation was greater than the original zone of half-spindle overlap, but the rate of elongation was constant. No component of force due to tubulin polymerization was found. The total elongation observed in the presence of added tubulin could exceed a doubling of original spindle length, matching the elongation in the intact diatom. The linear rate of spindle elongation in vitro suggests that the force transducer for anaphase B is a mechanochemical ATPase, analogous to dynein or myosin, and that the force for spindle elongation does not arise from stored energy, e.g. in an elastic matrix in the midzone. Additionally, on the basis of observations described here, we conclude that the force-transduction system for spindle elongation must be able to remain in the zone of microtubule overlap during the sliding apart of half-spindles, and that the transducer can generate force between microtubules that are not strictly antiparallel. PMID:2258393

  11. An analogue-sensitive approach identifies basal body rotation and flagellum attachment zone elongation as key functions of PLK in Trypanosoma brucei

    PubMed Central

    Lozano-Núñez, Ana; Ikeda, Kyojiro N.; Sauer, Thomas; de Graffenried, Christopher L.

    2013-01-01

    Polo-like kinases are important regulators of cell division, playing diverse roles in mitosis and cytoskeletal inheritance. In the parasite Trypanosoma brucei, the single PLK homologue TbPLK is necessary for the assembly of a series of essential organelles that position and adhere the flagellum to the cell surface. Previous work relied on RNA interference or inhibitors of undefined specificity to inhibit TbPLK, both of which have significant experimental limitations. Here we use an analogue-sensitive approach to selectively and acutely inhibit TbPLK. T. brucei cells expressing only analogue-sensitive TbPLK (TbPLKas) grow normally, but upon treatment with inhibitor develop defects in flagellar attachment and cytokinesis. TbPLK cannot migrate effectively when inhibited and remains trapped in the posterior of the cell throughout the cell cycle. Using synchronized cells, we show that active TbPLK is a direct requirement for the assembly and extension of the flagellum attachment zone, which adheres the flagellum to the cell surface, and for the rotation of the duplicated basal bodies, which positions the new flagellum so that it can extend without impinging on the old flagellum. This approach should be applicable to the many kinases found in the T. brucei genome that lack an ascribed function. PMID:23447704

  12. Carbon Isotope Composition of Nighttime Leaf-Respired CO2 in the Agricultural-Pastoral Zone of the Songnen Plain, Northeast China

    PubMed Central

    Cui, Haiying; Wang, Yunbo; Jiang, Qi; Chen, Shiping; Ma, Jian-Ying; Sun, Wei

    2015-01-01

    Variations in the carbon isotope signature of leaf dark-respired CO2 (δ13CR) within a single night is a widely observed phenomenon. However, it is unclear whether there are plant functional type differences with regard to the amplitude of the nighttime variation in δ13CR. These differences, if present, would be important for interpreting the short-term variations in the stable carbon signature of ecosystem respiration and the partitioning of carbon fluxes. To assess the plant functional type differences relating to the magnitude of the nighttime variation in δ13CR and the respiratory apparent fractionation, we measured the δ13CR, the leaf gas exchange, and the δ13C of the respiratory substrates of 22 species present in the agricultural-pastoral zone of the Songnen Plain, northeast China. The species studied were grouped into C3 and C4 plants, trees, grasses, and herbs. A significant nocturnal shift in δ13CR was detected in 20 of the studied species, with the magnitude of the shift ranging from 1‰ to 5.8‰. The magnitude of the nighttime variation in δ13CR was strongly correlated with the daytime cumulative carbon assimilation, which suggests that variation in δ13CR were influenced, to some extent, by changes in the contribution of malate decarboxylation to total respiratory CO2 flux. There were no differences in the magnitude of the nighttime variation in δ13CR between the C3 and C4 plants, as well as among the woody plants, herbs and graminoids. Leaf respired CO2 was enriched in 13C compared to biomass, soluble carbohydrates and lipids; however the magnitude of enrichment differed between 8 pm and 4 am, which were mainly caused by the changes in δ13CR. We also detected the plant functional type differences in respiratory apparent fractionation relative to biomass at 4 am, which suggests that caution should be exercised when using the δ13C of bulk leaf material as a proxy for the δ13C of leaf-respired CO2. PMID:26356083

  13. Synthesis of Elongated Microcapsules

    NASA Technical Reports Server (NTRS)

    Li, Wenyan; Buhrow, Jerry; Calle, Luz M.

    2011-01-01

    One of the factors that influence the effectiveness of self-healing in functional materials is the amount of liquid healing agents that can be delivered to the damaged area. The use of hollow tubes or fibers and the more sophisticated micro-vascular networks has been proposed as a way to increase the amount of healing agents that can be released when damage is inflicted. Although these systems might be effective in some specific applications, they are not practical for coatings applications. One possible practical way to increase the healing efficiency is to use microcapsules with high-aspect-ratios, or elongated microcapsules. It is understood that elongated microcapsules will be more efficient because they can release more healing agent than a spherical microcapsule when a crack is initiated in the coating. Although the potential advantage of using elongated microcapsules for self healing applications is clear, it is very difficult to make elongated microcapsules from an emulsion system because spherical microcapsules are normally formed due to the interfacial tension between the dispersed phase and the continuous phase. This paper describes the two methods that have been developed by the authors to synthesize elongated microcapsules. The first method involves the use of an emulsion with intermediate stability and the second involves the application of mechanical shear conditions to the emulsion.

  14. Regulation of Growth Response to Water Stress in the Soybean Primary Root. I. Proteomic Analysis Reveals Region-Specific Regulation of Phenylpropanoid Metabolism and Control of Free Iron in the Elongation Zone.

    Technology Transfer Automated Retrieval System (TEKTRAN)

    In water-stressed soybean primary roots, elongation was maintained at well-watered rates in the apical 4 mm (region 1) but was progressively inhibited in the 4-8 mm region (region 2), which exhibits maximum elongation in well-watered roots. These responses are similar to previous results for the mai...

  15. Elongated Microcapsules and Their Formation

    NASA Technical Reports Server (NTRS)

    Calle, Luz M. (Inventor); Li, Wenyan N. (Inventor); Buhrow, Jerry W. (Inventor); Perusich, Stephen A. (Inventor); Jolley, Scott T. (Inventor); Gibson, Tracy L. (Inventor); Williams, Martha K. (Inventor)

    2015-01-01

    Elongated microcapsules, such as elongated hydrophobic-core and hydrophilic-core microcapsules, may be formed by pulse stirring an emulsion or shearing an emulsion between two surfaces moving at different velocities. The elongated microcapsules may be dispersed in a coating formulation, such as paint.

  16. Single Molecule Transcription Elongation

    PubMed Central

    Galburt, Eric A.; Grill, Stephan W.; Bustamante, Carlos

    2009-01-01

    Single molecule optical trapping assays have now been applied to a great number of macromolecular systems including DNA, RNA, cargo motors, restriction enzymes, DNA helicases, chromosome remodelers, DNA polymerases and both viral and bacterial RNA polymerases. The advantages of the technique are the ability to observe dynamic, unsynchronized molecular processes, to determine the distributions of experimental quantities and to apply force to the system while monitoring the response over time. Here, we describe the application of these powerful techniques to study the dynamics of transcription elongation by RNA polymerase II from Saccharomyces cerevisiae. PMID:19426807

  17. Gibberellin biosynthesis and signal transduction is essential for internode elongation in deepwater rice

    PubMed Central

    Ayano, Madoka; Kani, Takahiro; Kojima, Mikiko; Sakakibara, Hitoshi; Kitaoka, Takuya; Kuroha, Takeshi; Angeles-Shim, Rosalyn B; Kitano, Hidemi; Nagai, Keisuke; Ashikari, Motoyuki

    2014-01-01

    Under flooded conditions, the leaves and internodes of deepwater rice can elongate above the water surface to capture oxygen and prevent drowning. Our previous studies showed that three major quantitative trait loci (QTL) regulate deepwater-dependent internode elongation in deepwater rice. In this study, we investigated the age-dependent internode elongation in deepwater rice. We also investigated the relationship between deepwater-dependent internode elongation and the phytohormone gibberellin (GA) by physiological and genetic approach using a QTL pyramiding line (NIL-1 + 3 + 12). Deepwater rice did not show internode elongation before the sixth leaf stage under deepwater condition. Additionally, deepwater-dependent internode elongation occurred on the sixth and seventh internodes during the sixth leaf stage. These results indicate that deepwater rice could not start internode elongation until the sixth leaf stage. Ultra-performance liquid chromatography tandem mass-spectrometry (UPLC-MS/MS) method for the phytohormone contents showed a deepwater-dependent GA1 and GA4 accumulation in deepwater rice. Additionally, a GA inhibitor abolished deepwater-dependent internode elongation in deepwater rice. On the contrary, GA feeding mimicked internode elongation under ordinary growth conditions. However, mutations in GA biosynthesis and signal transduction genes blocked deepwater-dependent internode elongation. These data suggested that GA biosynthesis and signal transduction are essential for deepwater-dependent internode elongation in deepwater rice. Deepwater rice obtained the ability for rapid internode elongation to avoid drowning and adapt to flooded condition. How does it regulate internode elongation? Using both physiological and genetic approach, this paper shows that the plant hormone, gibberellin (GA) regulates internode elongation. PMID:24891164

  18. Auxin and Cellular Elongation.

    PubMed

    Velasquez, Silvia Melina; Barbez, Elke; Kleine-Vehn, Jürgen; Estevez, José M

    2016-03-01

    Auxin is a crucial growth regulator in plants. However, a comprehensive understanding of how auxin induces cell expansion is perplexing, because auxin acts in a concentration- and cell type-dependent manner. Consequently, it is desirable to focus on certain cell types to exemplify the underlying growth mechanisms. On the other hand, plant tissues display supracellular growth (beyond the level of single cells); hence, other cell types might compromise the growth of a certain tissue. Tip-growing cells do not display neighbor-induced growth constraints and, therefore, are a valuable source of information for growth-controlling mechanisms. Here, we focus on auxin-induced cellular elongation in root hairs, exposing a mechanistic view of plant growth regulation. We highlight a complex interplay between auxin metabolism and transport, steering root hair development in response to internal and external triggers. Auxin signaling modules and downstream cascades of transcription factors define a developmental program that appears rate limiting for cellular growth. With this knowledge in mind, the root hair cell is a very suitable model system in which to dissect cellular effectors required for cellular expansion. PMID:26787325

  19. Root cooling strongly affects diel leaf growth dynamics, water and carbohydrate relations in Ricinus communis.

    PubMed

    Poiré, Richard; Schneider, Heike; Thorpe, Michael R; Kuhn, Arnd J; Schurr, Ulrich; Walter, Achim

    2010-03-01

    In laboratory and greenhouse experiments with potted plants, shoots and roots are exposed to temperature regimes throughout a 24 h (diel) cycle that can differ strongly from the regime under which these plants have evolved. In the field, roots are often exposed to lower temperatures than shoots. When the root-zone temperature in Ricinus communis was decreased below a threshold value, leaf growth occurred preferentially at night and was strongly inhibited during the day. Overall, leaf expansion, shoot biomass growth, root elongation and ramification decreased rapidly, carbon fluxes from shoot to root were diminished and carbohydrate contents of both root and shoot increased. Further, transpiration rate was not affected, yet hydrostatic tensions in shoot xylem increased. When root temperature was increased again, xylem tension reduced, leaf growth recovered rapidly, carbon fluxes from shoot to root increased, and carbohydrate pools were depleted. We hypothesize that the decreased uptake of water in cool roots diminishes the growth potential of the entire plant - especially diurnally, when the growing leaf loses water via transpiration. As a consequence, leaf growth and metabolite concentrations can vary enormously, depending on root-zone temperature and its heterogeneity inside pots. PMID:19968824

  20. Halogenated auxins affect microtubules and root elongation in Lactuca sativa

    NASA Technical Reports Server (NTRS)

    Zhang, N.; Hasenstein, K. H.

    2000-01-01

    We studied the effect of 4,4,4-trifluoro-3-(indole-3-)butyric acid (TFIBA), a recently described root growth stimulator, and 5,6-dichloro-indole-3-acetic acid (DCIAA) on growth and microtubule (MT) organization in roots of Lactuca sativa L. DCIAA and indole-3-butyric acid (IBA) inhibited root elongation and depolymerized MTs in the cortex of the elongation zone, inhibited the elongation of stele cells, and promoted xylem maturation. Both auxins caused the plane of cell division to shift from anticlinal to periclinal. In contrast, TFIBA (100 micromolar) promoted elongation of primary roots by 40% and stimulated the elongation of lateral roots, even in the presence of IBA, the microtubular inhibitors oryzalin and taxol, or the auxin transport inhibitor naphthylphthalamic acid. However, TFIBA inhibited the formation of lateral root primordia. Immunostaining showed that TFIBA stabilized MTs orientation perpendicular to the root axis, doubled the cortical cell length, but delayed xylem maturation. The data indicate that the auxin-induced inhibition of elongation and swelling of roots results from reoriented phragmoplasts, the destabilization of MTs in elongating cells, and promotion of vessel formation. In contrast, TFIBA induced promotion of root elongation by enhancing cell length, prolonging transverse MT orientation, delaying cell and xylem maturation.

  1. Halogenated auxins affect microtubules and root elongation in Lactuca sativa.

    PubMed

    Zhang, N; Hasenstein, K H

    2000-12-01

    We studied the effect of 4,4,4-trifluoro-3-(indole-3-)butyric acid (TFIBA), a recently described root growth stimulator, and 5,6-dichloro-indole-3-acetic acid (DCIAA) on growth and microtubule (MT) organization in roots of Lactuca sativa L. DCIAA and indole-3-butyric acid (IBA) inhibited root elongation and depolymerized MTs in the cortex of the elongation zone, inhibited the elongation of stele cells, and promoted xylem maturation. Both auxins caused the plane of cell division to shift from anticlinal to periclinal. In contrast, TFIBA (100 micromolar) promoted elongation of primary roots by 40% and stimulated the elongation of lateral roots, even in the presence of IBA, the microtubular inhibitors oryzalin and taxol, or the auxin transport inhibitor naphthylphthalamic acid. However, TFIBA inhibited the formation of lateral root primordia. Immunostaining showed that TFIBA stabilized MTs orientation perpendicular to the root axis, doubled the cortical cell length, but delayed xylem maturation. The data indicate that the auxin-induced inhibition of elongation and swelling of roots results from reoriented phragmoplasts, the destabilization of MTs in elongating cells, and promotion of vessel formation. In contrast, TFIBA induced promotion of root elongation by enhancing cell length, prolonging transverse MT orientation, delaying cell and xylem maturation. PMID:11762379

  2. Differential Methylation during Maize Leaf Growth Targets Developmentally Regulated Genes1[C][W][OPEN

    PubMed Central

    Candaele, Jasper; Demuynck, Kirin; Mosoti, Douglas; Beemster, Gerrit T.S.; Inzé, Dirk; Nelissen, Hilde

    2014-01-01

    DNA methylation is an important and widespread epigenetic modification in plant genomes, mediated by DNA methyltransferases (DMTs). DNA methylation is known to play a role in genome protection, regulation of gene expression, and splicing and was previously associated with major developmental reprogramming in plants, such as vernalization and transition to flowering. Here, we show that DNA methylation also controls the growth processes of cell division and cell expansion within a growing organ. The maize (Zea mays) leaf offers a great tool to study growth processes, as the cells progressively move through the spatial gradient encompassing the division zone, transition zone, elongation zone, and mature zone. Opposite to de novo DMTs, the maintenance DMTs were transcriptionally regulated throughout the growth zone of the maize leaf, concomitant with differential CCGG methylation levels in the four zones. Surprisingly, the majority of differentially methylated sequences mapped on or close to gene bodies and not to repeat-rich loci. Moreover, especially the 5′ and 3′ regions of genes, which show overall low methylation levels, underwent differential methylation in a developmental context. Genes involved in processes such as chromatin remodeling, cell cycle progression, and growth regulation, were differentially methylated. The presence of differential methylation located upstream of the gene anticorrelated with transcript expression, while gene body differential methylation was unrelated to the expression level. These data indicate that DNA methylation is correlated with the decision to exit mitotic cell division and to enter cell expansion, which adds a new epigenetic level to the regulation of growth processes. PMID:24488968

  3. Elongational rheology of polyethylene melts

    NASA Astrophysics Data System (ADS)

    Seyfzadeh, Bijan

    Elongational melt flow behavior is an important and fundamental concept underlying many industrial plastics operations which involve a rapid change of shape as for example fiber spinning and stretching, bottle blow molding, and film blowing and stretching. Under high process loads polymeric materials experience enormous stresses causing the molecular structure to gain considerable orientation. This event has significant effects on the melt flow behavior and can be measured in terms of elongational viscosity and changes in enthalpy and entropy. Different polymeric materials with unique molecular characteristics are expected to respond uniquely to the elongational deformation; hence, molecular parameters such as molecular weight and degree of branching were related to the measurable elongational flow variables. Elongational viscosities were measured for high and low density polyethylenes using an advanced capillary extrusion rheometer fitted with semi-hyperbolic dies. Said dies establish a purely elongational. flow field at constant elongational strain rate. The elongational viscosities were evaluated under influence of process strain rate, Hencky strain (natural logarithm of area reduction of the extrusion die), and temperature. Enthalpy and entropy changes associated with the orientation development of semi-hyperbolic processed melts were also determined. Results showed that elongational viscosities were primarily affected by differences in weight average molecular weight rather than degree of branching. This effect was process strain rate as well as temperature dependent. An investigation of melt relaxation and the associated first decay time constants revealed that with increasing strain rate the molecular field of the melt asymptotically gained orientation in approaching a limit. As a result of this behavior molecular uniqueness vanished at high process strain rates, yielding to orientation development and the associated restructuring of the melt's molecular

  4. LeafJ: an ImageJ plugin for semi-automated leaf shape measurement.

    PubMed

    Maloof, Julin N; Nozue, Kazunari; Mumbach, Maxwell R; Palmer, Christine M

    2013-01-01

    High throughput phenotyping (phenomics) is a powerful tool for linking genes to their functions (see review and recent examples). Leaves are the primary photosynthetic organ, and their size and shape vary developmentally and environmentally within a plant. For these reasons studies on leaf morphology require measurement of multiple parameters from numerous leaves, which is best done by semi-automated phenomics tools. Canopy shade is an important environmental cue that affects plant architecture and life history; the suite of responses is collectively called the shade avoidance syndrome (SAS). Among SAS responses, shade induced leaf petiole elongation and changes in blade area are particularly useful as indices. To date, leaf shape programs (e.g. SHAPE, LAMINA, LeafAnalyzer, LEAFPROCESSOR) can measure leaf outlines and categorize leaf shapes, but can not output petiole length. Lack of large-scale measurement systems of leaf petioles has inhibited phenomics approaches to SAS research. In this paper, we describe a newly developed ImageJ plugin, called LeafJ, which can rapidly measure petiole length and leaf blade parameters of the model plant Arabidopsis thaliana. For the occasional leaf that required manual correction of the petiole/leaf blade boundary we used a touch-screen tablet. Further, leaf cell shape and leaf cell numbers are important determinants of leaf size. Separate from LeafJ we also present a protocol for using a touch-screen tablet for measuring cell shape, area, and size. Our leaf trait measurement system is not limited to shade-avoidance research and will accelerate leaf phenotyping of many mutants and screening plants by leaf phenotyping. PMID:23380664

  5. Controlled laser production of elongated articles from particulates

    DOEpatents

    Dixon, Raymond D.; Lewis, Gary K.; Milewski, John O.

    2002-01-01

    It has been discovered that wires and small diameter rods can be produced using laser deposition technology in a novel way. An elongated article such as a wire or rod is constructed by melting and depositing particulate material into a deposition zone which has been designed to yield the desired article shape and dimensions. The article is withdrawn from the deposition zone as it is formed, thus enabling formation of the article in a continuous process. Alternatively, the deposition zone is moved along any of numerous deposition paths away from the article being formed.

  6. Leaf physiognomy and climate: A multivariate analysis

    NASA Astrophysics Data System (ADS)

    Davis, J. M.; Taylor, S. E.

    1980-11-01

    Research has demonstrated that leaf physiognomy is representative of the local or microclimate conditions under which plants grow. The physiognomy of leaf samples from Oregon, Michigan, Missouri, Tennessee, and the Panama Canal Zone has been related to the microclimate using Walter diagrams and Thornthwaite water-budget data. A technique to aid paleoclimatologists in identifying the nature of the microclimate from leaf physiognomy utilizes statistical procedures to classify leaf samples into one of six microclimate regimes based on leaf physiognomy information available from fossilized samples.

  7. Elongation Transducer For Tensile Tests

    NASA Technical Reports Server (NTRS)

    Roberts, Paul W.; Stokes, Thomas R.

    1994-01-01

    Extensometer transducer measures elongation of tensile-test specimen with negligible distortion of test results. Used in stress-versus-strain tests of small specimens of composite materials. Clamping stress distributed more evenly. Specimen clamped gently between jaw and facing surface of housing. Friction force of load points on conical tips onto specimen depends on compression of spring, adjusted by turning cover on housing. Limp, light nylon-insulated electrical leads impose minimal extraneous loads on measuring elements.

  8. Key Proliferative Activity in the Junction between the Leaf Blade and Leaf Petiole of Arabidopsis1[W][OA

    PubMed Central

    Ichihashi, Yasunori; Kawade, Kensuke; Usami, Takeshi; Horiguchi, Gorou; Takahashi, Taku; Tsukaya, Hirokazu

    2011-01-01

    Leaves are the most important, fundamental units of organogenesis in plants. Although the basic form of a leaf is clearly divided into the leaf blade and leaf petiole, no study has yet revealed how these are differentiated from a leaf primordium. We analyzed the spatiotemporal pattern of mitotic activity in leaf primordia of Arabidopsis (Arabidopsis thaliana) in detail using molecular markers in combination with clonal analysis. We found that the proliferative zone is established after a short interval following the occurrence of a rod-shaped early leaf primordium; it is separated spatially from the shoot apical meristem and seen at the junction region between the leaf blade and leaf petiole and produces both leaf-blade and leaf-petiole cells. This proliferative region in leaf primordia is marked by activity of the ANGUSTIFOLIA3 (AN3) promoter as a whole and seems to be differentiated into several spatial compartments: activities of the CYCLIN D4;2 promoter and SPATULA enhancer mark parts of it specifically. Detailed analyses of the an3 and blade-on-petiole mutations further support the idea that organogenesis of the leaf blade and leaf petiole is critically dependent on the correct spatial regulation of the proliferative region of leaf primordia. Thus, the proliferative zone of leaf primordia is spatially differentiated and supplies both the leaf-blade and leaf-petiole cells. PMID:21880932

  9. Deepwater rice: A model plant to study stem elongation

    SciTech Connect

    Kende, H.; Knaap, E. van der; Cho, H.T.

    1998-12-01

    Semiaquatic plants grow mostly in flood plains and along river beds and are adapted to survive partial submergence during periods of flooding. Among their adaptive features are the development of internal air channels (aerenchyma) that facilitate aeration of submerged organs and the capacity for rapid elongation when the plants become partially covered by floodwaters. In addition to its importance as a crop plant, deepwater rice is also excellent for studying basic aspects of plant growth. The growth response is induced by an environmental signal and is mediated by at least three interacting hormones, namely ethylene, ABA, and GA. Internodal elongation is based on increased cell-division activity and enhanced cell elongation in well-delineated zones of the internode. This allows one to study both processes of growth in an integrated manner. Also, the unusually high growth rates magnify growth-related cellular, physiological, biochemical, and molecular processes, thereby facilitating their analysis. In addition to yielding fundamental insights into the growth process, studies of internodal elongation in deepwater rice may ultimately help to identify genes that could confer at least limited elongation capacity onto modern, high-yielding cultivars.

  10. Vegetative growth and cluster development in Shiraz grapevines subjected to partial root-zone cooling

    PubMed Central

    Rogiers, Suzy Y.; Clarke, Simon J.

    2013-01-01

    Heterogeneity in root-zone temperature both vertically and horizontally may contribute to the uneven vegetative and reproductive growth often observed across vineyards. An experiment was designed to assess whether the warmed half of a grapevine root zone could compensate for the cooled half in terms of vegetative growth and reproductive development. We divided the root system of potted Shiraz grapevines bilaterally and applied either a cool or a warm treatment to each half from budburst to fruit set. Shoot growth and inflorescence development were monitored over the season. Simultaneous cooling and warming of parts of the root system decreased shoot elongation, leaf emergence and leaf expansion below that of plants with a fully warmed root zone, but not to the same extent as those with a fully cooled root zone. Inflorescence rachis length, flower number and berry number after fertilization were smaller only in those vines exposed to fully cooled root zones. After terminating the treatments, berry enlargement and the onset of veraison were slowed in those vines that had been exposed to complete or partial root-zone cooling. Grapevines exposed to partial root-zone cooling were thus delayed in vegetative and reproductive development, but the inhibition was greater in those plants whose entire root system had been cooled. PMID:24244839

  11. Limitation of Cell Elongation in Barley (Hordeum vulgare L.) Leaves Through Mechanical and Tissue-Hydraulic Properties.

    PubMed

    Touati, Mostefa; Knipfer, Thorsten; Visnovitz, Tamás; Kameli, Abdelkrim; Fricke, Wieland

    2015-07-01

    The aim of the present study was to assess the mechanical and hydraulic limitation of growth in leaf epidermal cells of barley (Hordeum vulgare L.) in response to agents which affect cellular water (mercuric chloride, HgCl(2)) and potassium (cesium chloride, CsCl; tetraethylammonium, TEA) transport, pump activity of plasma membrane H(+)-ATPase and wall acidification (fusicoccin, FC). Cell turgor (P) was measured with the cell pressure probe, and cell osmotic pressure (π) was analyzed through picoliter osmometry of single-cell extracts. A wall extensibility coefficient (M) and tissue hydraulic conductance coefficient (L) were derived using the Lockhart equation. There was a significant positive linear relationship between relative elemental growth rate and P, which fit all treatments, with an overall apparent yield threshold of 0.368 MPa. Differences in growth between treatments could be explained through differences in P. A comparison of L and M showed that growth in all except the FC treatment was co-limited through hydraulic and mechanical properties, though to various extents. This was accompanied by significant (0.17-0.24 MPa) differences in water potential (ΔΨ) between xylem and epidermal cells in the leaf elongation zone. In contrast, FC-treated leaves showed ΔΨ close to zero and a 10-fold increase in L. PMID:25907571

  12. METHOD OF FORMING ELONGATED COMPACTS

    DOEpatents

    Larson, H.F.

    1959-05-01

    A powder compacting procedure and apparatus which produces elongated compacts of Be is described. The powdered metal is placed in a thin metal tube which is chemically compatible to lubricant, powder, atmosphere, and die material and will undergo a high degree of plastic deformation and have intermediate hardness. The tube is capped and placed in the die, and punches are applied to the ends. During the compacting stroke the powder seizes the tube and a thickening and shortening of the tube occurs. The tube is easily removed from the die, split, and peeled from the compact. (T.R.H.)

  13. Effects of elevated CO₂ and temperature on photosynthesis and leaf traits of an understory dwarf bamboo in subalpine forest zone, China.

    PubMed

    Li, Yongping; Zhang, Yuanbin; Zhang, Xiaolu; Korpelainen, Helena; Berninger, Frank; Li, Chunyang

    2013-06-01

    The dwarf bamboo (Fargesia rufa Yi), growing understory in subalpine dark coniferous forest, is one of the main foods for giant panda, and it influences the regeneration of subalpine coniferous forests in southwestern China. To investigate the effects of elevated CO₂, temperature and their combination, the dwarf bamboo plantlets were exposed to two CO₂ regimes (ambient and double ambient CO₂ concentration) and two temperatures (ambient and +2.2°C) in growth chambers. Gas exchange, leaf traits and carbohydrates concentration were measured after the 150-day experiment. Elevated CO₂ significantly increased the net photosynthetic rate (Anet ), intrinsic water-use efficiency (WUEi ) and carbon isotope composition (δ¹³C) and decreased stomatal conductance (g(s)) and total chlorophyll concentration based on mass (Chl(m)) and area (Chl(a)). On the other hand, elevated CO₂ decreased specific leaf area (SLA), which was increased by elevated temperature. Elevated CO₂ also increased foliar carbon concentration based on mass (C(m)) and area (C(a)), nitrogen concentration based on area (N(a)), carbohydrates concentration (i.e. sucrose, sugar, starch and non-structural carbohydrates) and the slope of the A(net)-N(a) relationship. However, elevated temperature decreased C(m), C(a) and N(a). The combination of elevated CO₂ and temperature hardly affected SLA, C(m), C(a), N(m), N(a), Chl(m) and Chl(a). Variables Anet and Na had positive linear relationships in all treatments. Our results showed that photosynthetic acclimation did not occur in dwarf bamboo at elevated CO₂ and it could adjust physiology and morphology to enable the capture of more light, to increase WUE and improve nutritional conditions. PMID:23025819

  14. Leaf Development

    PubMed Central

    2013-01-01

    Leaves are the most important organs for plants. Without leaves, plants cannot capture light energy or synthesize organic compounds via photosynthesis. Without leaves, plants would be unable perceive diverse environmental conditions, particularly those relating to light quality/quantity. Without leaves, plants would not be able to flower because all floral organs are modified leaves. Arabidopsis thaliana is a good model system for analyzing mechanisms of eudicotyledonous, simple-leaf development. The first section of this review provides a brief history of studies on development in Arabidopsis leaves. This history largely coincides with a general history of advancement in understanding of the genetic mechanisms operating during simple-leaf development in angiosperms. In the second section, I outline events in Arabidopsis leaf development, with emphasis on genetic controls. Current knowledge of six important components in these developmental events is summarized in detail, followed by concluding remarks and perspectives. PMID:23864837

  15. Structure and Elongation of fine Ladies’ Hosiery

    NASA Astrophysics Data System (ADS)

    Lozo, M.; Vrljicak, Z.

    2016-07-01

    On a sock-knitting machine with diameter of cylindrical needle bed 100 mm (4e") that knitted with 400 needles, samples of fine women's hosiery were made from four PA filament yarns in counts 20 dtex f 20, 30 dtex f 34, 40 dtex f 40 and 60 dtex f 60. Each type of yarns was used to make hosiery samples with four loop sinking depths of unit values in a computer program 400, 550, 700 and 850. For all the samples, parameters of yarn structure were analyzed and elongation properties of knitted fabric were measured. During the elongation of knitted fabric, areas of knitted fabric elasticity, beginning of permanent deformation and elongation at break were measured. Elongation of knitted fabric in the wale direction, i.e. transverse hosiery elongation and elongation of knitted fabric in the course direction, or longitudinal direction of hosiery were measured. Yarn fineness and loop sinking depth significantly influence the elongation properties of hosiery.

  16. Specialized zones of development in roots

    NASA Technical Reports Server (NTRS)

    Ishikawa, H.; Evans, M. L.

    1995-01-01

    The authors propose using the term "distal elongation zone" (DEZ) rather than "postmitotic isodiametric growth zone" to refer to the group of cells between the apical meristem and the elongation zone in plant roots. Reasons presented for the change are that the proposed DEZ includes many cells that are still dividing, most cells in the region are not isodiametric, and the pattern of cell expansion in this region varies with position in the region. Cells in the DEZ respond to gravistimulation, mechanical impedance, electrotropic stimulation, water stress, and auxin. Differences in gene expression patterns between DEZ cells and cells in the main elongation zone are noted.

  17. Stimulation of root elongation and curvature by calcium

    NASA Technical Reports Server (NTRS)

    Takahashi, H.; Scott, T. K.; Suge, H.

    1992-01-01

    Ca2+ has been proposed to mediate inhibition of root elongation. However, exogenous Ca2+ at 10 or 20 millimolar, applied directly to the root cap, significantly stimulated root elongation in pea (Pisum sativum L.) and corn (Zea mays L.) seedlings. Furthermore, Ca2+ at 1 to 20 millimolar, applied unilaterally to the caps of Alaska pea roots, caused root curvature away from the Ca2+ source, which was caused by an acceleration of elongation growth on the convex side (Ca2+ side) of the roots. Roots of an agravitropic pea mutant, ageotropum, responded to a greater extent. Roots of Merit and Silver Queen corn also responded to Ca2+ in similar ways but required a higher Ca2+ concentration than that of pea roots. Roots of all other cultivars tested (additional four cultivars of pea and one of corn) curved away from the unilateral Ca2+ source as well. The Ca(2+)-stimulated curvature was substantially enhanced by light. A Ca2+ ionophore, A23187, at 20 micromolar or abscisic acid at 0.1 to 100 micromolar partially substituted for the light effect and enhanced the Ca(2+)-stimulated curvature in the dark. Unilateral application of Ca2+ to the elongation zone of intact roots or to the cut end of detipped roots caused either no curvature or very slight curvature toward the Ca2+. Thus, Ca2+ action on root elongation differs depending on its site of application. The stimulatory action of Ca2+ may involve an elevation of cytoplasmic Ca2+ in root cap cells and may partipate in root tropisms.

  18. The blue light receptor Phototropin 1 suppresses lateral root growth by controlling cell elongation.

    PubMed

    Moni, A; Lee, A-Y; Briggs, W R; Han, I-S

    2015-01-01

    We investigated the relationship between the blue light receptor phototropin 1 (phot1) and lateral root growth in Arabidopsis thaliana seedlings. Fluorescence and confocal microscopy images, as well as PHOT1 mRNA expression studies provide evidence that it is highly expressed in the elongation zone of lateral roots where auxin is accumulating. However, treatment with the auxin transport inhibitor N-1-naphthylphthalamic acid significantly reduced PHOT1 expression in this zone. In addition, PHOT1 expression was higher in darkness than in light. The total number of lateral roots was higher in the phot1 mutant than in wild-type Arabidopsis. Cells in the elongation zone of lateral roots of the phot1 mutant were longer than those of wild-type lateral roots. These findings suggest that PHOT1 plays a role(s) in elongation of lateral roots through the control of an auxin-related signalling pathway. PMID:24803136

  19. Correlations between changes in electrical parameters and changes in cell elongation rates in gavistimulated roots

    NASA Astrophysics Data System (ADS)

    Ishikawa, H.; Evans, M. L.

    1994-08-01

    The earliest changes in growth rate following the gravistimulation of roots occur in a special group of cells between the meristem and the elongating region of the root. This zone is called the postomitotic isodiametric growth (PIG) zone and consists of cells which have ceased dividing and are expanding isodiametrically. Upon gravistimulation cells along the upper side of the PIG zone begin elongating rapidly and this accounts for much of the early growth asymmetry. There is rapid (< 30 s) hyperpolarization of cells on the upper side of the PIG zone as well as rapid uptake of potassium from the stele. We propose that there is a relationship between the rate of hydrogen ion efflux and the extent of membrane hyperpolarization in the PIG zone and that such changes in potential are an early indication of impending changes in growth performance. Although the development of auxin asymmetry in the cap and its transmission to the elongating region is considered to be the controlling factor in root gravitropism, auxin asymmetry in the cap develops only after 30 min, about the same as the lag before initiation of curvature. Although this dilemma may be partly resolved by the location of the PIG zone close to the cap, alternative explanations such as gravi-detection by the PIG zone or very rapid (electrical?) signal transmission from the cap to the PIG zone need to be considered.

  20. The Effects of High Steady State Auxin Levels on Root Cell Elongation in Brachypodium.

    PubMed

    Pacheco-Villalobos, David; Díaz-Moreno, Sara M; van der Schuren, Alja; Tamaki, Takayuki; Kang, Yeon Hee; Gujas, Bojan; Novak, Ondrej; Jaspert, Nina; Li, Zhenni; Wolf, Sebastian; Oecking, Claudia; Ljung, Karin; Bulone, Vincent; Hardtke, Christian S

    2016-05-01

    The long-standing Acid Growth Theory of plant cell elongation posits that auxin promotes cell elongation by stimulating cell wall acidification and thus expansin action. To date, the paucity of pertinent genetic materials has precluded thorough analysis of the importance of this concept in roots. The recent isolation of mutants of the model grass species Brachypodium distachyon with dramatically enhanced root cell elongation due to increased cellular auxin levels has allowed us to address this question. We found that the primary transcriptomic effect associated with elevated steady state auxin concentration in elongating root cells is upregulation of cell wall remodeling factors, notably expansins, while plant hormone signaling pathways maintain remarkable homeostasis. These changes are specifically accompanied by reduced cell wall arabinogalactan complexity but not by increased proton excretion. On the contrary, we observed a tendency for decreased rather than increased proton extrusion from root elongation zones with higher cellular auxin levels. Moreover, similar to Brachypodium, root cell elongation is, in general, robustly buffered against external pH fluctuation in Arabidopsis thaliana However, forced acidification through artificial proton pump activation inhibits root cell elongation. Thus, the interplay between auxin, proton pump activation, and expansin action may be more flexible in roots than in shoots. PMID:27169463

  1. The Effects of High Steady State Auxin Levels on Root Cell Elongation in Brachypodium[OPEN

    PubMed Central

    Pacheco-Villalobos, David; Tamaki, Takayuki; Gujas, Bojan; Jaspert, Nina; Oecking, Claudia; Bulone, Vincent; Hardtke, Christian S.

    2016-01-01

    The long-standing Acid Growth Theory of plant cell elongation posits that auxin promotes cell elongation by stimulating cell wall acidification and thus expansin action. To date, the paucity of pertinent genetic materials has precluded thorough analysis of the importance of this concept in roots. The recent isolation of mutants of the model grass species Brachypodium distachyon with dramatically enhanced root cell elongation due to increased cellular auxin levels has allowed us to address this question. We found that the primary transcriptomic effect associated with elevated steady state auxin concentration in elongating root cells is upregulation of cell wall remodeling factors, notably expansins, while plant hormone signaling pathways maintain remarkable homeostasis. These changes are specifically accompanied by reduced cell wall arabinogalactan complexity but not by increased proton excretion. On the contrary, we observed a tendency for decreased rather than increased proton extrusion from root elongation zones with higher cellular auxin levels. Moreover, similar to Brachypodium, root cell elongation is, in general, robustly buffered against external pH fluctuation in Arabidopsis thaliana. However, forced acidification through artificial proton pump activation inhibits root cell elongation. Thus, the interplay between auxin, proton pump activation, and expansin action may be more flexible in roots than in shoots. PMID:27169463

  2. Elongated Deposits in Southern Elysium Planitia, Mars

    NASA Astrophysics Data System (ADS)

    Nussbaumer, J. W.

    2012-03-01

    In the Elysium Planitia region, deposits have elongated elevations that resemble terrestrial drumlins or yardangs. Drumlins and drumlin clusters are glacial landforms that have been extensively studied. In contrast, Yardangs are formed by wind.

  3. Effects of elongation delay in transcription dynamics.

    PubMed

    Zhang, Xuan; Jin, Huiqin; Yang, Zhuoqin; Lei, Jinzhi

    2014-12-01

    In the transcription process, elongation delay is induced by the movement of RNA polymerases (RNAP) along the DNA sequence, and can result in changes in the transcription dynamics. This paper studies the transcription dynamics that involved the elongation delay and effects of cell division and DNA replication. The stochastic process of gene expression is modeled with delay chemical master equation with periodic coefficients, and is studied numerically through the stochastic simulation algorithm with delay. We show that the average transcription level approaches to a periodic dynamics over cell cycles at homeostasis, and the elongation delay can reduce the transcription level and increase the transcription noise. Moreover, the transcription elongation can induce bimodal distribution of mRNA levels that can be measured by the techniques of flow cytometry. PMID:25365608

  4. [Influence of perennial flooding and drought on growth restoration of Acorus calamus in water-level-fluctuation zone of the Three Gorges Reservoir].

    PubMed

    Li, Qiang; Gao, Xiang; Ding, Wu-quan; Zhu, Qi-hong; Ou, Yuan; Liu, Yu

    2012-08-01

    Acorus calamus L. is a common kind of wetland plant species in the Three Gorges Reservoir. In this study, we investigated the influence of perennial flooding on growth restoration of A. calamus in the lightless conditions and the drought stress on this plant species' growth after flooding. Our research provided the scientific basis for the selection of candidate species for vegetations restoration in water-level-fluctuation zone of the Three Gorges Reservoir. A. calamus plants were exposed to waters in the lightless conditions in September 2009 and September 2010 respectively and taken away from the waters and grew in natural conditions in the following March, April and May (named as S1, S2, S3). All plants in the control, S1 and S2 groups were challenged with drought stress in May for 20 days. During the experiment, the plant number and leaf number were recorded regularly, as well as leaf length and leaf width. The results showed that flooding restrained the germination of the plants with much less plant in flooding groups than the control, and the plant germination rate had inverse relation to the flooding time. Flooding promoted formation and elongation of the leaves in S1 and S2 groups, which showed higher leaf growth parameters, such as leaf length, leaf number, total leaf length of one plant and total leaf length of all plants than the control. However, all of these growth parameters in S3 group had significantly lower values compared to the control. The survival rate of the plants after flooding decreased significantly with longer flooding time. Besides, the leaf length and leaf width in S1 and S2 groups increased significantly but with decreased leaf number. Additionally, all growth parameters (leaf length, leaf width, leaf number, total leaf number, total leaf length of one plant, total leaf length of all plants) in S3 group decreased remarkably. Furthermore, drought decreased the values of all growth parameters and the plant number in the control, S1 and

  5. Synergistic action of auxin and ethylene on root elongation inhibition is caused by a reduction of epidermal cell length.

    PubMed

    Alarcón, M Victoria; Lloret, Pedro G; Salguero, Julio

    2014-01-01

    Auxin and ethylene have been largely reported to reduce root elongation in maize primary root. However the effects of auxin are greater than those caused by ethylene. Although auxin stimulates ethylene biosynthesis through the specific increase of ACC synthase, the auxin inhibitory effect on root elongation is not mediated by the auxin-induced increase of ethylene production. Recently it has been demonstrated that root inhibition by the application of the synthetic auxin NAA (1-naphtalenacetic acid) is increased if combined with the ethylene precursor ACC (1-aminocyclopropane-1-carboxilic acid) when both compounds are applied at very low concentrations.   Root elongation is basically the result of two processes: a) cell divisions in the meristem where meristematic cells continuously generate new cells and b) subsequently polarized growth by elongation along the root axis as cells leave the meristem and enter the root elongation zone. Our results indicate that exogenous auxin reduced both root elongation and epidermal cell length. In a different way, ethylene at very low concentrations only inhibited root elongation without affecting significantly epidermal cell length. However, these concentrations of ethylene increased the inhibitory effect of auxin on root elongation and cell length. Consequently the results support the hypothesis that ethylene acts synergistically with auxin in the regulation of root elongation and that inhibition by both hormones is due, at least partially, to the reduction of cell length in the epidermal layer. PMID:24598313

  6. The structure of elongated viral capsids.

    PubMed

    Luque, Antoni; Reguera, David

    2010-06-16

    There are many viruses whose genetic material is protected by a closed elongated protein shell. Unlike spherical viruses, the structure and construction principles of these elongated capsids are not fully known. In this article, we have developed a general geometrical model to describe the structure of prolate or bacilliform capsids. We show that only a limited set of tubular architectures can be built closed by hemispherical icosahedral caps. In particular, the length and number of proteins adopt a very special set of discrete values dictated by the axial symmetry (fivefold, threefold, or twofold) and the triangulation number of the caps. The results are supported by experimental observations and simulations of simplified physical models. This work brings about a general classification of elongated viruses that will help to predict their structure, and to design viral cages with tailored geometrical properties for biomedical and nanotechnological applications. PMID:20550912

  7. Bacterial Cellulose-Binding Domain Modulates in Vitro Elongation of Different Plant Cells1

    PubMed Central

    Shpigel, Etai; Roiz, Levava; Goren, Raphael; Shoseyov, Oded

    1998-01-01

    Recombinant cellulose-binding domain (CBD) derived from the cellulolytic bacterium Clostridium cellulovorans was found to modulate the elongation of different plant cells in vitro. In peach (Prunus persica L.) pollen tubes, maximum elongation was observed at 50 μg mL−1 CBD. Pollen tube staining with calcofluor showed a loss of crystallinity in the tip zone of CBD-treated pollen tubes. At low concentrations CBD enhanced elongation of Arabidopsis roots. At high concentrations CBD dramatically inhibited root elongation in a dose-responsive manner. Maximum effect on root hair elongation was at 100 μg mL−1, whereas root elongation was inhibited at that concentration. CBD was found to compete with xyloglucan for binding to cellulose when CBD was added first to the cellulose, before the addition of xyloglucan. When Acetobacter xylinum L. was used as a model system, CBD was found to increase the rate of cellulose synthase in a dose-responsive manner, up to 5-fold compared with the control. Electron microscopy examination of the cellulose ribbons produced by A. xylinum showed that CBD treatment resulted in a splayed ribbon composed of separate fibrillar subunits, compared with a thin, uniform ribbon in the control. PMID:9701575

  8. Oregon 'Pinot noir' grape anthocyanin enhancement by early leaf removal

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Complete cluster zone leaf removal of ‘Pinot noir’ was initiated at three separate pre-véraison growth stages (bloom, grain-pea size, and bunch closure) and maintained leaf free until harvest for four growing seasons (2008-2011). Fruit anthocyanin composition was examined at harvest for the last tw...

  9. Defoliation by introduced Diorhabda elongata leaf beetles (Coleoptera: Chrysomelidae) reduces carbohydrate reserves and regrowth of Tamarix (Tamaricacceae)

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Diorhabda elongate (Brulle) sensu lato leaf beetles have been released in the United States for the classical biological control of invasive Tamarix L. species, which are exotic trees that are causing deterioration of riparian ecosystems in western North America. The impact of D. elongate defoliat...

  10. Electrorheological fluid under elongation, compression, and shearing

    NASA Astrophysics Data System (ADS)

    Tian, Y.; Meng, Y.; Mao, H.; Wen, S.

    2002-03-01

    Electrorheological (ER) fluid based on zeolite and silicone oil under elongation, compression, and shearing was investigated at room temperature. Dc electric fields were applied on the ER fluid when elongation and compression were carried out on a self-constructed test system. The shear yield stress, presenting the macroscopic interactions of particles in the ER fluid along the direction of shearing and perpendicular to the direction of the electric field, was also obtained by a HAAKE RV20 rheometer. The tensile yield stress, presenting the macroscopic interactions of particles in the ER fluid along the direction of the electric field, was achieved as the peak value in the elongating curve with an elongating yield strain of 0.15-0.20. A shear yield angle of about 15°-18.5° reasonably connected tensile yield stress with shear yield stress, agreeing with the shear yield angle tested well by other researchers. The compressing tests showed that the ER fluid has a high compressive modulus under a small compressive strain lower than 0.1. The compressive stress has an exponential relationship with the compressive strain when it is higher than 0.1, and it is much higher than shear yield stress.

  11. Reorientation of elongated particles at density interfaces.

    PubMed

    Doostmohammadi, A; Ardekani, A M

    2014-09-01

    Density interfaces in the water column are ubiquitously found in oceans and lakes. Interaction of settling particles with pycnoclines plays a pivotal function in nutrient transport between ocean layers and settling rates of marine particles. We perform direct numerical simulations of an elongated particle settling through a density interface and scrutinize the role of stratification on the settling dynamics. It is found that the presence of the density interface tends to turn the long axis of an elongated particle parallel to the settling direction, which is dramatically different from its counterpart in a homogeneous fluid. Although broadside-on settling of the elongated particle is enhanced upon approaching the interface, the long axis rotates toward the settling direction as the particle passes through the interface. We quantify turning couples due to stratification effects, which counteract the pressure-induced torques due to the fluid inertia. A similar behavior is observed for different initial orientations of the particle. It is shown that the reorientation of an elongated particle occurs in both sharp and linear density stratifications. PMID:25314535

  12. Antimicrobial effect of Pistacia atlantica leaf extract

    PubMed Central

    Ali Roozegar, Mohamad; Azizi Jalilian, Farid; Reza Havasian, Mohamad; Panahi, Jafar; Pakzad, Iraj

    2016-01-01

    The antimicrobial effect of the mastic tree (Pistacia atlantica) under in vitro conditions has been reported. Therefore, it is of interest to evaluate the effect of the plant leaf extract (aqueous) on bacterial load in mouth and saliva. The leaf of the Pistacia atlantica plant was collected and cleaned, dried at 40⁰c and then powdered. The extraction was carried out using the maceration method in vacuum with the rotary evaporator device. Bacterial inhibition (Streptococcus species) by the leaf extract was studied using the disc diffusion and embedding sink diffusion methods. The values of MIC and MBC were determined. The collected data was further analyzed using t-test and repeated measure statistical tests. The disc diffusion technique showed a significant inhibitory effect for Pistacia atlantica leaf extract on S. mutans (ATCC 35668) and S. mitis (ATCC 49456) with inhibition zones of 19 and 25 millimeters, respectively. This is for the highest leaf extract concentration used in this study (p<0.01). The values of MIC and MBC for S.mutans was 60, 90 μg/ml and for S. mitis was 75, 110 μg/ml (p<0.01 significance). The leaf extract has no significant effect on S. salivarius (ATCC 13419). Thus, the antimicrobial properties of the aqueous leaf extract from Pistacia atlantica is demonstrated in this study. PMID:27212840

  13. Antimicrobial effect of Pistacia atlantica leaf extract.

    PubMed

    Ali Roozegar, Mohamad; Azizi Jalilian, Farid; Reza Havasian, Mohamad; Panahi, Jafar; Pakzad, Iraj

    2016-01-01

    The antimicrobial effect of the mastic tree (Pistacia atlantica) under in vitro conditions has been reported. Therefore, it is of interest to evaluate the effect of the plant leaf extract (aqueous) on bacterial load in mouth and saliva. The leaf of the Pistacia atlantica plant was collected and cleaned, dried at 40⁰c and then powdered. The extraction was carried out using the maceration method in vacuum with the rotary evaporator device. Bacterial inhibition (Streptococcus species) by the leaf extract was studied using the disc diffusion and embedding sink diffusion methods. The values of MIC and MBC were determined. The collected data was further analyzed using t-test and repeated measure statistical tests. The disc diffusion technique showed a significant inhibitory effect for Pistacia atlantica leaf extract on S. mutans (ATCC 35668) and S. mitis (ATCC 49456) with inhibition zones of 19 and 25 millimeters, respectively. This is for the highest leaf extract concentration used in this study (p<0.01). The values of MIC and MBC for S.mutans was 60, 90 μg/ml and for S. mitis was 75, 110 μg/ml (p<0.01 significance). The leaf extract has no significant effect on S. salivarius (ATCC 13419). Thus, the antimicrobial properties of the aqueous leaf extract from Pistacia atlantica is demonstrated in this study. PMID:27212840

  14. Gibberellins accumulate in the elongating endodermal cells of Arabidopsis root

    PubMed Central

    Shani, Eilon; Weinstain, Roy; Zhang, Yi; Castillejo, Cristina; Kaiserli, Eirini; Chory, Joanne; Tsien, Roger Y.; Estelle, Mark

    2013-01-01

    Plant hormones are small-molecule signaling compounds that are collectively involved in all aspects of plant growth and development. Unlike animals, plants actively regulate the spatial distribution of several of their hormones. For example, auxin transport results in the formation of auxin maxima that have a key role in developmental patterning. However, the spatial distribution of the other plant hormones, including gibberellic acid (GA), is largely unknown. To address this, we generated two bioactive fluorescent GA compounds and studied their distribution in Arabidopsis thaliana roots. The labeled GAs specifically accumulated in the endodermal cells of the root elongation zone. Pharmacological studies, along with examination of mutants affected in endodermal specification, indicate that GA accumulation is an active and highly regulated process. Our results strongly suggest the presence of an active GA transport mechanism that would represent an additional level of GA regulation. PMID:23382232

  15. Radiation Guiding In a Dense, Elongated Cold-Atom Cloud

    NASA Astrophysics Data System (ADS)

    Ramos, Andira; Chen, Yun-Jhih; Maclennan, Jamie; Raithel, Georg

    2016-05-01

    Radiation guiding through a dense, elongated cold-atom cloud in a deep optical lattice created by an in-vacuum cavity has been experimentally observed. When atoms are loaded into the optical lattice, a cylindrically symmetric depletion zone surrounding the lattice location is created. This variation in atomic density gives rise to a position-dependent index of refraction which allows for a probe beam properly coupled into the atomic cloud to be guided through it. For a Hermite-Gaussian mode (HG00) , this mini fiber exhibits a transmission pattern consisting of a central feature and multiple concentric rings around it, with higher cavity modes also being accessible in the current experimental setup. Simulations that look to properly model these features are presented. This form of radiation guiding can be useful for Rydberg polariton and EIT experiments, where the atomic fiber would guide one or more trains of single-photon pulses, depending on the cavity mode.

  16. The short-term growth response to salt of the developing barley leaf.

    PubMed

    Fricke, Wieland; Akhiyarova, Gulya; Wei, Wenxue; Alexandersson, Erik; Miller, Anthony; Kjellbom, Per Ola; Richardson, Andrew; Wojciechowski, Tobias; Schreiber, Lukas; Veselov, Dima; Kudoyarova, Guzel; Volkov, Vadim

    2006-01-01

    Recent results concerning the short-term growth response to salinity of the developing barley leaf are reviewed. Plants were grown hydroponically and the growth response of leaf 3 was studied between 10 min and 5 d following addition of 100 mM NaCl to the root medium. The aim of the experiments was to relate changes in variables that are likely to affect cell elongation to changes in leaf growth. Changes in hormone content (ABA, cytokinins), water and solute relationships (osmolality, turgor, water potential, solute concentrations), gene expression (water channel), cuticle deposition, membrane potential, and transpiration were followed, while leaf elongation velocity was monitored. Leaf elongation decreased close to zero within seconds following addition of NaCl. Between 20 and 30 min after exposure to salt, elongation velocity recovered rather abruptly, to about 46% of the pre-stress level, and remained at the reduced rate for the following 5 d, when it reached about 70% of the level in non-stressed plants. Biophysical and physiological analyses led to three major conclusions. (i) The immediate reduction and sudden recovery in elongation velocity is due to changes in the water potential gradient between leaf xylem and peripheral elongating cells. Changes in transpiration, ABA and cytokinin content, water channel expression, and plasma membrane potential are involved in this response. (ii) Significant solute accumulation, which aids growth recovery, is detectable from 1 h onwards; growing and non-growing leaf regions and mesophyll and epidermis differ in their solute response. (iii) Cuticular wax density is not affected by short-term exposure to salt; transpirational changes are due to stomatal control. PMID:16513814

  17. Leaf seal for gas turbine stator shrouds and a nozzle band

    DOEpatents

    Burdgick, Steven Sebastian; Sexton, Brendan Francis

    2002-01-01

    A leaf seal assembly is secured to the trailing edge of a shroud segment for sealing between the shroud segment and the leading edge side wall of a nozzle outer band. The leaf seal includes a circumferentially elongated seal plate biased by a pair of spring clips disposed in a groove along the trailing edge of the shroud segment to maintain the seal plate in engagement with the flange on the leading edge side wall of the nozzle outer band. The leaf seal plate and spring clips receive pins tack-welded to the shroud segment to secure the leaf seal assembly in place.

  18. Cell elongation is an adaptive response for clearing long chromatid arms from the cleavage plane

    PubMed Central

    Kotadia, Shaila; Montembault, Emilie; Sullivan, William

    2012-01-01

    Chromosome segregation must be coordinated with cell cleavage to ensure correct transmission of the genome to daughter cells. Here we identify a novel mechanism by which Drosophila melanogaster neuronal stem cells coordinate sister chromatid segregation with cleavage furrow ingression. Cells adapted to a dramatic increase in chromatid arm length by transiently elongating during anaphase/telophase. The degree of cell elongation correlated with the length of the trailing chromatid arms and was concomitant with a slight increase in spindle length and an enlargement of the zone of cortical myosin distribution. Rho guanine-nucleotide exchange factor (Pebble)–depleted cells failed to elongate during segregation of long chromatids. As a result, Pebble-depleted adult flies exhibited morphological defects likely caused by cell death during development. These studies reveal a novel pathway linking trailing chromatid arms and cortical myosin that ensures the clearance of chromatids from the cleavage plane at the appropriate time during cytokinesis, thus preserving genome integrity. PMID:23185030

  19. Vertically stabilized elongated cross-section tokamak

    DOEpatents

    Sheffield, George V.

    1977-01-01

    This invention provides a vertically stabilized, non-circular (minor) cross-section, toroidal plasma column characterized by an external separatrix. To this end, a specific poloidal coil means is added outside a toroidal plasma column containing an endless plasma current in a tokamak to produce a rectangular cross-section plasma column along the equilibrium axis of the plasma column. By elongating the spacing between the poloidal coil means the plasma cross-section is vertically elongated, while maintaining vertical stability, efficiently to increase the poloidal flux in linear proportion to the plasma cross-section height to achieve a much greater plasma volume than could be achieved with the heretofore known round cross-section plasma columns. Also, vertical stability is enhanced over an elliptical cross-section plasma column, and poloidal magnetic divertors are achieved.

  20. Elongational viscosity of photo-oxidated LDPE

    SciTech Connect

    Rolón-Garrido, Víctor H. E-mail: manfred.wagner@tu-berlin.de; Wagner, Manfred H. E-mail: manfred.wagner@tu-berlin.de

    2014-05-15

    Sheets of low-density polyethylene (LDPE) were photo-oxidatively treated at room temperature, and subsequently characterized rheologically in the melt state by shear and uniaxial extensional experiments. For photo-oxidation, a xenon lamp was used to irradiate the samples for times between 1 day and 6 weeks. Linear-viscoelastic characterization was performed in a temperature range of 130 to 220°C to obtain the master curve at 170°C, the reference temperature at which the elongational viscosities were measured. Linear viscoelasticity is increasingly affected by increasing photo-oxidation due to crosslinking of LDPE, as corroborated by an increasing gel fraction as determined by a solvent extraction method. The elongational measurements reveal a strong enhancement of strain hardening until a saturation level is achieved. The elongational data are analyzed in the frame work of two constitutive equations, the rubber-like liquid and the molecular stress function models. Within the experimental window, timedeformation separability is confirmed for all samples, independent of the degree of photo-oxidation.

  1. Species-specific contribution of volumetric growth and tissue convergence to posterior body elongation in vertebrates.

    PubMed

    Steventon, Ben; Duarte, Fernando; Lagadec, Ronan; Mazan, Sylvie; Nicolas, Jean-François; Hirsinger, Estelle

    2016-05-15

    Posterior body elongation is a widespread mechanism propelling the generation of the metazoan body plan. The posterior growth model predicts that a posterior growth zone generates sufficient tissue volume to elongate the posterior body. However, there are energy supply-related differences between vertebrates in the degree to which growth occurs concomitantly with embryogenesis. By applying a multi-scalar morphometric analysis in zebrafish embryos, we show that posterior body elongation is generated by an influx of cells from lateral regions, by convergence-extension of cells as they exit the tailbud, and finally by a late volumetric growth in the spinal cord and notochord. Importantly, the unsegmented region does not generate additional tissue volume. Fibroblast growth factor inhibition blocks tissue convergence rather than volumetric growth, showing that a conserved molecular mechanism can control convergent morphogenesis through different cell behaviours. Finally, via a comparative morphometric analysis in lamprey, dogfish, zebrafish and mouse, we propose that elongation via posterior volumetric growth is linked to increased energy supply and is associated with an overall increase in volumetric growth and elongation. PMID:26989170

  2. The INDETERMINATE DOMAIN Protein BROAD LEAF1 Limits Barley Leaf Width by Restricting Lateral Proliferation.

    PubMed

    Jöst, Moritz; Hensel, Götz; Kappel, Christian; Druka, Arnis; Sicard, Adrien; Hohmann, Uwe; Beier, Sebastian; Himmelbach, Axel; Waugh, Robbie; Kumlehn, Jochen; Stein, Nils; Lenhard, Michael

    2016-04-01

    Variation in the size, shape, and positioning of leaves as the major photosynthetic organs strongly impacts crop yield, and optimizing these aspects is a central aim of cereal breeding [1, 2]. Leaf growth in grasses is driven by cell proliferation and cell expansion in a basal growth zone [3]. Although several factors influencing final leaf size and shape have been identified from rice and maize [4-14], what limits grass leaf growth in the longitudinal or transverse directions during leaf development remains poorly understood. To identify factors involved in this process, we characterized the barley mutant broad leaf1 (blf1). Mutants form wider but slightly shorter leaves due to changes in the numbers of longitudinal cell files and of cells along the leaf length. These differences arise during primordia outgrowth because of more cell divisions in the width direction increasing the number of cell files. Positional cloning, analysis of independent alleles, and transgenic complementation confirm that BLF1 encodes a presumed transcriptional regulator of the INDETERMINATE DOMAIN family. In contrast to loss-of-function mutants, moderate overexpression of BLF1 decreases leaf width below wild-type levels. A functional BLF1-vYFP fusion protein expressed from the endogenous promoter shows a dynamic expression pattern in the shoot apical meristem and young leaf primordia. Thus, we propose that the BLF1 gene regulates barley leaf size by restricting cell proliferation in the leaf-width direction. Given the agronomic importance of canopy traits in cereals, identifying functionally different BLF1 alleles promises to allow for the generation of optimized cereal ideotypes. PMID:26996502

  3. Dimerization of elongator protein 1 is essential for Elongator complex assembly

    PubMed Central

    Xu, Huisha; Lin, Zhijie; Li, Fengzhi; Diao, Wentao; Dong, Chunming; Zhou, Hao; Xie, Xingqiao; Wang, Zheng; Shen, Yuequan; Long, Jiafu

    2015-01-01

    The evolutionarily conserved Elongator complex, which is composed of six subunits elongator protein 1 (Elp1 to -6), plays vital roles in gene regulation. The molecular hallmark of familial dysautonomia (FD) is the splicing mutation of Elp1 [also known as IκB kinase complex-associated protein (IKAP)] in the nervous system that is believed to be the primary cause of the devastating symptoms of this disease. Here, we demonstrate that disease-related mutations in Elp1 affect Elongator assembly, and we have determined the structure of the C-terminal portion of human Elp1 (Elp1-CT), which is sufficient for full-length Elp1 dimerization, as well as the structure of the cognate dimerization domain of yeast Elp1 (yElp1-DD). Our study reveals that the formation of the Elp1 dimer contributes to its stability in vitro and in vivo and is required for the assembly of both the human and yeast Elongator complexes. Functional studies suggest that Elp1 dimerization is essential for yeast viability. Collectively, our results identify the evolutionarily conserved dimerization domain of Elp1 and suggest that the pathological mechanisms underlying the onset and progression of Elp1 mutation-related disease may result from impaired Elongator activities. PMID:26261306

  4. Assessing soybean leaf area and leaf biomass by spectral measurements

    NASA Technical Reports Server (NTRS)

    Holben, B. N.; Tucker, C. J.; Fan, C. J.

    1979-01-01

    Red and photographic infrared spectral radiances were correlated with soybean total leaf area index, green leaf area index, chlorotic leaf area index, green leaf biomass, chlorotic leaf biomass, and total biomass. The most significant correlations were found to exist between the IR/red radiance ratio data and green leaf area index and/or green leaf biomass (r squared equals 0.85 and 0.86, respectively). These findings demonstrate that remote sensing data can supply information basic to soybean canopy growth, development, and status by nondestructive determination of the green leaf area or green leaf biomass.

  5. Growth-limiting proteins in maize coleoptiles and the auxin-brassinosteroid hypothesis of mesocotyl elongation.

    PubMed

    Kutschera, Ulrich; Wang, Zhi-Yong

    2016-01-01

    The shoot of grass coleoptiles consists of the mesocotyl, the node, and the coleoptile (with enclosed primary leaf). Since the 1930s, it is known that auxin (indole-3-acetic acid, IAA), produced in the tip of the coleoptile, is the central regulator of turgor-driven organ growth. Fifty years ago, it was discovered that antibiotics that suppress protein biosynthesis, such as cycloheximide, inhibit auxin (IAA)-induced cell elongation in excised sections of coleoptiles and stems. Based on such inhibitor studies, the concept of "growth-limiting proteins (GLPs)" emerged that was subsequently elaborated and modified. Here, we summarize the history of this idea with reference to IAA-mediated shoot elongation in maize (Zea mays) seedlings and recent studies on the molecular mechanism underlying auxin action in Arabidopsis thaliana. In addition, the analysis of light-induced inhibition of shoot elongation in intact corn seedlings is discussed. We propose a concept to account for the GLP-mediated epidermal wall-loosening process in coleoptile segments and present a more general model of growth regulation in intact maize seedlings. Quantitative proteomic and genomic studies led to a refinement of the classic "GLP concept" to explain phytohormone-mediated cell elongation at the molecular level (i.e., the recently proposed theory of a "central growth regulation network," CGRN). Novel data show that mesocotyl elongation not only depends on auxin but also on brassinosteroids (BRs). However, the biochemical key processes that regulate the IAA/BR-mediated loosening of the expansion-limiting epidermal wall(s) have not yet been elucidated. PMID:25772679

  6. A multiprotein complex that interacts with RNA polymerase II elongator.

    PubMed

    Li, Y; Takagi, Y; Jiang, Y; Tokunaga, M; Erdjument-Bromage, H; Tempst, P; Kornberg, R D

    2001-08-10

    A three-subunit Hap complex that interacts with the RNA polymerase II Elongator was isolated from yeast. Deletions of genes for two Hap subunits, HAP1 and HAP3, confer pGKL killer-insensitive and weak Elongator phenotypes. Preferential interaction of the Hap complex with free rather than RNA polymerase II-associated Elongator suggests a role in the regulation of Elongator activity. PMID:11390369

  7. An ATP-binding cassette subfamily G full transporter is essential for the retention of leaf water in both wild barley and rice

    PubMed Central

    Chen, Guoxiong; Komatsuda, Takao; Ma, Jian Feng; Nawrath, Christiane; Pourkheirandish, Mohammad; Tagiri, Akemi; Hu, Yin-Gang; Sameri, Mohammad; Li, Xinrong; Zhao, Xin; Liu, Yubing; Li, Chao; Ma, Xiaoying; Wang, Aidong; Nair, Sudha; Wang, Ning; Miyao, Akio; Sakuma, Shun; Yamaji, Naoki; Zheng, Xiuting; Nevo, Eviatar

    2011-01-01

    Land plants have developed a cuticle preventing uncontrolled water loss. Here we report that an ATP-binding cassette (ABC) subfamily G (ABCG) full transporter is required for leaf water conservation in both wild barley and rice. A spontaneous mutation, eibi1.b, in wild barley has a low capacity to retain leaf water, a phenotype associated with reduced cutin deposition and a thin cuticle. Map-based cloning revealed that Eibi1 encodes an HvABCG31 full transporter. The gene was highly expressed in the elongation zone of a growing leaf (the site of cutin synthesis), and its gene product also was localized in developing, but not in mature tissue. A de novo wild barley mutant named “eibi1.c,” along with two transposon insertion lines of rice mutated in the ortholog of HvABCG31 also were unable to restrict water loss from detached leaves. HvABCG31 is hypothesized to function as a transporter involved in cutin formation. Homologs of HvABCG31 were found in green algae, moss, and lycopods, indicating that this full transporter is highly conserved in the evolution of land plants. PMID:21737747

  8. An ATP-binding cassette subfamily G full transporter is essential for the retention of leaf water in both wild barley and rice.

    PubMed

    Chen, Guoxiong; Komatsuda, Takao; Ma, Jian Feng; Nawrath, Christiane; Pourkheirandish, Mohammad; Tagiri, Akemi; Hu, Yin-Gang; Sameri, Mohammad; Li, Xinrong; Zhao, Xin; Liu, Yubing; Li, Chao; Ma, Xiaoying; Wang, Aidong; Nair, Sudha; Wang, Ning; Miyao, Akio; Sakuma, Shun; Yamaji, Naoki; Zheng, Xiuting; Nevo, Eviatar

    2011-07-26

    Land plants have developed a cuticle preventing uncontrolled water loss. Here we report that an ATP-binding cassette (ABC) subfamily G (ABCG) full transporter is required for leaf water conservation in both wild barley and rice. A spontaneous mutation, eibi1.b, in wild barley has a low capacity to retain leaf water, a phenotype associated with reduced cutin deposition and a thin cuticle. Map-based cloning revealed that Eibi1 encodes an HvABCG31 full transporter. The gene was highly expressed in the elongation zone of a growing leaf (the site of cutin synthesis), and its gene product also was localized in developing, but not in mature tissue. A de novo wild barley mutant named "eibi1.c," along with two transposon insertion lines of rice mutated in the ortholog of HvABCG31 also were unable to restrict water loss from detached leaves. HvABCG31 is hypothesized to function as a transporter involved in cutin formation. Homologs of HvABCG31 were found in green algae, moss, and lycopods, indicating that this full transporter is highly conserved in the evolution of land plants. PMID:21737747

  9. Elongated nanostructures for radial junction solar cells.

    PubMed

    Kuang, Yinghuan; Vece, Marcel Di; Rath, Jatindra K; Dijk, Lourens van; Schropp, Ruud E I

    2013-10-01

    In solar cell technology, the current trend is to thin down the active absorber layer. The main advantage of a thinner absorber is primarily the reduced consumption of material and energy during production. For thin film silicon (Si) technology, thinning down the absorber layer is of particular interest since both the device throughput of vacuum deposition systems and the stability of the devices are significantly enhanced. These features lead to lower cost per installed watt peak for solar cells, provided that the (stabilized) efficiency is the same as for thicker devices. However, merely thinning down inevitably leads to a reduced light absorption. Therefore, advanced light trapping schemes are crucial to increase the light path length. The use of elongated nanostructures is a promising method for advanced light trapping. The enhanced optical performance originates from orthogonalization of the light's travel path with respect to the direction of carrier collection due to the radial junction, an improved anti-reflection effect thanks to the three-dimensional geometric configuration and the multiple scattering between individual nanostructures. These advantages potentially allow for high efficiency at a significantly reduced quantity and even at a reduced material quality, of the semiconductor material. In this article, several types of elongated nanostructures with the high potential to improve the device performance are reviewed. First, we briefly introduce the conventional solar cells with emphasis on thin film technology, following the most commonly used fabrication techniques for creating nanostructures with a high aspect ratio. Subsequently, several representative applications of elongated nanostructures, such as Si nanowires in realistic photovoltaic (PV) devices, are reviewed. Finally, the scientific challenges and an outlook for nanostructured PV devices are presented. PMID:24088584

  10. Faraday waves in elongated superfluid fermionic clouds

    NASA Astrophysics Data System (ADS)

    Capuzzi, P.; Vignolo, P.

    2008-10-01

    We use hydrodynamic equations to study the formation of Faraday waves in a superfluid Fermi gas at zero temperature confined in a strongly elongated cigar-shaped trap. First, we treat the role of the radial density profile in the limit of an infinite cylindrical geometry and analytically evaluate the wavelength of the Faraday pattern. The effect of the axial confinement is fully taken into account in the numerical solution of hydrodynamic equations, and shows that the infinite cylinder geometry provides a very good description of the phenomena.

  11. Cell division versus cell elongation: the control of radicle elongation during thermoinhibition of Tagetes minuta achenes.

    PubMed

    Taylor, Nicky J; Hills, Paul N; van Staden, Johannes

    2007-12-01

    Endogenous embryo factors, which act mainly in the radicle, prevent germination in Tagetes minuta at high temperatures. These factors act to prevent cell elongation, which is critical for radicle protrusion under optimal conditions. Once the radicle has emerged both cell elongation and cell division are required for post-germination growth. Germination can be induced at high temperatures by fusicoccin, which rapidly stimulates cell elongation. In addition, priming seeds at 25 degrees C on polyethylene glycol (PEG) 6000 and mannitol could also induce germination on water at 36 degrees C, indicating that priming prevents radicle protrusion at a point subsequent to the point of control in thermoinhibited achenes. Flow cytometry studies revealed that DNA synthesis occurs during thermoinhibition and the inhibition of DNA synthesis during this process inhibits subsequent germination on water under optimal conditions, suggesting a protective role for DNA synthesis in thermoinhibited achenes of T. minuta. PMID:17360069

  12. Dynamic enhancer–gene body contacts during transcription elongation

    PubMed Central

    Lee, Kiwon; Hsiung, Chris C.-S.; Huang, Peng; Raj, Arjun; Blobel, Gerd A.

    2015-01-01

    Enhancers govern transcription through multiple mechanisms, including the regulation of elongation by RNA polymerase II (RNAPII). We characterized the dynamics of looped enhancer contacts during synchronous transcription elongation. We found that many distal enhancers form stable contacts with their target promoters during the entire interval of elongation. Notably, we detected additional dynamic enhancer contacts throughout the gene bodies that track with elongating RNAPII and the leading edge of RNA synthesis. These results support a model in which the gene body changes its position relative to a stable enhancer–promoter complex, which has broad ramifications for enhancer function and architectural models of transcriptional elongation. PMID:26443845

  13. Genetic variability of oxalate oxidase activity and elongation in water-stressed primary roots of diverse maize and rice lines

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Previous work on maize primary roots under water stress showed that cell elongation is maintained in the apical region of the growth zone but progressively inhibited further from the apex. In association with these responses, several proteins related to reactive oxygen species (ROS) production, part...

  14. Differentially phased leaf growth and movements in Arabidopsis depend on coordinated circadian and light regulation.

    PubMed

    Dornbusch, Tino; Michaud, Olivier; Xenarios, Ioannis; Fankhauser, Christian

    2014-10-01

    In contrast to vastly studied hypocotyl growth, little is known about diel regulation of leaf growth and its coordination with movements such as changes in leaf elevation angle (hyponasty). We developed a 3D live-leaf growth analysis system enabling simultaneous monitoring of growth and movements. Leaf growth is maximal several hours after dawn, requires light, and is regulated by daylength, suggesting coupling between growth and metabolism. We identify both blade and petiole positioning as important components of leaf movements in Arabidopsis thaliana and reveal a temporal delay between growth and movements. In hypocotyls, the combination of circadian expression of PHYTOCHROME INTERACTING FACTOR4 (PIF4) and PIF5 and their light-regulated protein stability drives rhythmic hypocotyl elongation with peak growth at dawn. We find that PIF4 and PIF5 are not essential to sustain rhythmic leaf growth but influence their amplitude. Furthermore, EARLY FLOWERING3, a member of the evening complex (EC), is required to maintain the correct phase between growth and movement. Our study shows that the mechanisms underlying rhythmic hypocotyl and leaf growth differ. Moreover, we reveal the temporal relationship between leaf elongation and movements and demonstrate the importance of the EC for the coordination of these phenotypic traits. PMID:25281688

  15. Mechanical elongation of the centromere in the barley metaphase chromosome.

    PubMed

    Otobe, Kazunori; Shichiri, Motoharu; Fukushi, Daisuke; Yoshino, Tomoyuki; Nakao, Hidenobu; Sugiyama, Shigeru; Ohtani, Toshio

    2002-12-01

    The present study investigated the mechanical elongation of the centromere in the barley chromosomes by a microneedle manipulation method for the structural analysis of the chromosomes. Chromosomes were extracted from barley root cells, affixed on a cover slip by a standard preparation method, and elongated in either distilled water, phosphate buffered saline (PBS), or 2 x sodium saline citrate (SSC). The mechanical property of the chromosome elongation was assessed by the measurement of the force required for the elongation of chromosomes. This assessment has shown that the chromosomes in distilled water were much firmer than those in the PBS or 2 x SSC. To confirm the elongation of the centromere, the elongated chromosomes were investigated by fluorescence in situ hybridization with a centromere probe. The fluorescence information indicated that the extent of the loosening of the centromere during elongation differed depending on the buffers used; the centromere elongated in 2 x SSC was more loosened than that in the PBS. Atomic force microscopy also revealed the structure of the unpacked centromere after the mechanical elongation, when rows of fibrous structures about 30 to 50 nm thick were clearly observed in the centromere elongated in 2 x SSC. The investigation of elongated chromosomes should prove useful for an understanding of the structural analysis of chromosomes. PMID:12680461

  16. Impact of plant shoot architecture on leaf cooling: a coupled heat and mass transfer model

    PubMed Central

    Bridge, L. J.; Franklin, K. A.; Homer, M. E.

    2013-01-01

    Plants display a range of striking architectural adaptations when grown at elevated temperatures. In the model plant Arabidopsis thaliana, these include elongation of petioles, and increased petiole and leaf angles from the soil surface. The potential physiological significance of these architectural changes remains speculative. We address this issue computationally by formulating a mathematical model and performing numerical simulations, testing the hypothesis that elongated and elevated plant configurations may reflect a leaf-cooling strategy. This sets in place a new basic model of plant water use and interaction with the surrounding air, which couples heat and mass transfer within a plant to water vapour diffusion in the air, using a transpiration term that depends on saturation, temperature and vapour concentration. A two-dimensional, multi-petiole shoot geometry is considered, with added leaf-blade shape detail. Our simulations show that increased petiole length and angle generally result in enhanced transpiration rates and reduced leaf temperatures in well-watered conditions. Furthermore, our computations also reveal plant configurations for which elongation may result in decreased transpiration rate owing to decreased leaf liquid saturation. We offer further qualitative and quantitative insights into the role of architectural parameters as key determinants of leaf-cooling capacity. PMID:23720538

  17. Yellow leaf blotch

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Yellow leaf blotch occurs worldwide in temperate climates. The disease is reported from countries in Asia, Australasia, Oceania, Europe, North America, Central America, the West Indies, and South America. In the northern Great Plains of North America, it is often the major leaf disease on alfalfa....

  18. Low temperature viscosity in elongated ferrofluids

    NASA Astrophysics Data System (ADS)

    Alarcón, T.; Pérez-Madrid, A.; Rubí, J. M.

    1997-12-01

    We have studied the relaxation and transport properties of a ferrofluid in an elongational flow. These properties are influenced by the bistable nature of the potential energy. Bistability comes from the irrotational character of the flow together with the symmetry of the dipoles. Additionally, the presence of a constant magnetic field destroys the symmetry of the potential energy magnetizing the system. We have shown that at a moderate temperature, compared to the height of the energy barrier, the viscosity decreases with respect to the value it would have if the potential were stable. This phenomenon is known as the "negative viscosity" effect. Thermal motion induces jumps of the magnetic moment between the two stable states of the system leading to the aforementioned lowered dissipation effect.

  19. Potential flow about elongated bodies of revolution

    NASA Technical Reports Server (NTRS)

    Kaplan, Carl

    1936-01-01

    This report presents a method of solving the problem of axial and transverse potential flows around arbitrary elongated bodies of revolution. The solutions of Laplace's equation for the velocity potentials of the axial and transverse flows, the system of coordinates being an elliptic one in a meridian plane, are given. The theory is applied to a body of revolution obtained from a symmetrical Joukowsky profile, a shape resembling an airship hull. The pressure distribution and the transverse-force distribution are calculated and serve as examples of the procedure to be followed in the case of an actual airship. A section on the determination of inertia coefficients is also included in which the validity of some earlier work is questioned.

  20. Very elongated nuclei near A = 194

    SciTech Connect

    Becker, J.A.; Henry, E.A.; Yates, S.W.; Wang, T.F.; Kuhnert, A. ); Brinkman, M.J.; Cizewski, J.A. ); Deleplanque, M.A.; Diamond, R.M.; Stephens, F.S.; Azaiez, F.; Korten, W.; Draper, J.E. )

    1990-10-01

    A {gamma}-ray cascade in {sup 191}Hg of 12 members with average energy spacing 37 keV and Q{sub t} {equals} 18(3)eb was reported by Moore, and coworkers in 1989. This was the first report of very elongated nuclei (superdeformation) in this mass region. Since then, some 25 {gamma}-ray cascades have been observed in 11 (slightly neutron deficient) Hg, Pb and Tl nuclei. The bands have similar dynamic moments-of-inertia. Some nuclei exhibit multiple bands, and the backbending phenomena has been observed. Level spins can be obtained from comparison of transition energies to rotational model formulas. Selected bands (in different nuclei) have equal transition energies (within 0.1%). Alignment in integer multiples of {h bar} has been observed. Properties of these bands will be described. 27 refs., 3 figs.

  1. Mechanical modelling quantifies the functional importance of outer tissue layers during root elongation and bending.

    PubMed

    Dyson, Rosemary J; Vizcay-Barrena, Gema; Band, Leah R; Fernandes, Anwesha N; French, Andrew P; Fozard, John A; Hodgman, T Charlie; Kenobi, Kim; Pridmore, Tony P; Stout, Michael; Wells, Darren M; Wilson, Michael H; Bennett, Malcolm J; Jensen, Oliver E

    2014-06-01

    Root elongation and bending require the coordinated expansion of multiple cells of different types. These processes are regulated by the action of hormones that can target distinct cell layers. We use a mathematical model to characterise the influence of the biomechanical properties of individual cell walls on the properties of the whole tissue. Taking a simple constitutive model at the cell scale which characterises cell walls via yield and extensibility parameters, we derive the analogous tissue-level model to describe elongation and bending. To accurately parameterise the model, we take detailed measurements of cell turgor, cell geometries and wall thicknesses. The model demonstrates how cell properties and shapes contribute to tissue-level extensibility and yield. Exploiting the highly organised structure of the elongation zone (EZ) of the Arabidopsis root, we quantify the contributions of different cell layers, using the measured parameters. We show how distributions of material and geometric properties across the root cross-section contribute to the generation of curvature, and relate the angle of a gravitropic bend to the magnitude and duration of asymmetric wall softening. We quantify the geometric factors which lead to the predominant contribution of the outer cell files in driving root elongation and bending. PMID:24641449

  2. Fatty Acid-Elongating Activity in Rapidly Expanding Leek Epidermis.

    PubMed Central

    Evenson, K. J.; Post-Beittenmiller, D.

    1995-01-01

    A microsomal fatty acid elongase activity measured in epidermis of rapidly expanding leek (Allium porrum L.) was 10-fold higher in specific activity than preparations from store-bought leek. These preparations elongated acyl chains effectively using endogenous or supplied primers. Elongation of C20:0 was specifically inhibited by 2 [mu]M cerulenin, and labeling experiments with [3H]cerulenin labeled two polypeptides (65 and 88 kD). ATP was required for maximal elongase activity in expanding leaves but was lost in nonexpanding tissues. Both [14C]stearoyl-coenzyme A (CoA) and [14C]stearate were maximally elongated in the presence of ATP. Addition of fully reduced CoA, however, inhibited [14C]stearate elongation, suggesting that stearoyl-CoA synthesis was not a prerequisite for elongation. Furthermore, microsomes preincubated with [14C]stearoyl-CoA plus ATP resulted in loss of radiolabel from the acyl-CoA pool without a corresponding loss in elongating activity. The lack of correlation between elongating activity and the label retained in the putative acyl-CoA substrate pool suggests that acyl-CoAs may not be the immediate precursors for elongation and that ATP plays a critical, yet undefined, role in the elongation process. We propose that an ATP-dependent elongating activity may generate the long-chain fatty acids required for wax biosynthesis. PMID:12228624

  3. Elongate and Radial Hummocky Tracts in Southern Sweden - Evidence for Extensive Subglacial Drainage?

    NASA Astrophysics Data System (ADS)

    Peterson, Gustaf; Johnson, Mark D.

    2016-04-01

    Complete understanding of glacial melt-water processes is crucial for a profound view on former and contemporary ice sheets. Investigating sediments and landforms below ice sheets is complicated; however, formerly glaciated regions are easily accessible. For over a century, the hummocky characteristics of the South Swedish Uplands (SSU) have been recognized, and several explanations have been proposed since. Most of these studies describe hummocks shown to be products of a stagnant ice environment. The arrival of detailed elevation models (LiDAR) has revealed this landscape in an unprecedented detail. We have made an inventory of glacial landforms on detailed DEMs covering SSU, and can present a more diverse view of the hummocky tracts. In the field we have investigated the sedimentology and stratigraphy in machine dug sections. It is possible to manually distinguish at least four different hummocky tracts: I) Ribbed moraine, II) Dead ice moraine, III) An enigmatic landform type with a fish scale pattern, and IV) Hummocky tracts in elongate zones. This abstract will focus on the last type (IV). The four most striking morphological characteristics are: First, there are distinct elongate zones of hummocks with a radial pattern with distinct borders to the surrounding lineated till plains. Second, the hummocky zones in some places show an anastamosing pattern. Third, in analyzing these elongate zones, it is clear that they do not follow regional lows but instead runs over highlands. Fourth, in these zones there are localities with eskers superposed on hummocks. Sedimentological excavations yield a compact sandy silty till. Fabric measurements are not very strong; however, they are sub-parallel to lineations on nearby upland till surfaces. Taken together, these observations can possibly explain the elongate hummocky zones invoking processes of subglacial meltwater eroding hummocks in the bottom of tunnel valleys. A large amount of subglacial meltwater is controversial

  4. Control of cell proliferation and elongation by miR396.

    PubMed

    Ercoli, María Florencia; Rojas, Arantxa M L; Debernardi, Juan Manuel; Palatnik, Javier F; Rodriguez, Ramiro E

    2016-06-01

    The combinatory effects of cell proliferation and cell elongation determines the rate at which organs growth. In the root meristematic zone cells both divide and expand, while post-mitotic cells in the elongation zone only expands until they reach their final size. The transcription factors of the GROWTH-REGULATING FACTOR (GRF) class promote cell proliferation in various plant organs. Their expression is restricted to cells with a high proliferative capacity, yet strong downregulation of the GRF activity compromise the plant survival. Part of expression pattern of the GRFs is ensured by the post-transcriptional repression mediated by the conserved microRNA miR396. Here we show the quantitative effects in root growth caused by GRF depletion in a series of transgenic lines with different miR396 levels. We show that high miRNA levels affect cell elongation and proliferation in roots. Detailed analysis suggests that cell proliferation is restricted due to a reduction in cell cycle speed that might result from defects in the accumulation of mitotic cyclins. The results provide insights into the participation of the miRNA-GRF regulatory network in root development. PMID:27172373

  5. Auxin depletion from leaf primordia contributes to organ patterning.

    PubMed

    Qi, Jiyan; Wang, Ying; Yu, Ting; Cunha, Alexandre; Wu, Binbin; Vernoux, Teva; Meyerowitz, Elliot; Jiao, Yuling

    2014-12-30

    Stem cells are responsible for organogenesis, but it is largely unknown whether and how information from stem cells acts to direct organ patterning after organ primordia are formed. It has long been proposed that the stem cells at the plant shoot apex produce a signal, which promotes leaf adaxial-abaxial (dorsoventral) patterning. Here we show the existence of a transient low auxin zone in the adaxial domain of early leaf primordia. We also demonstrate that this adaxial low auxin domain contributes to leaf adaxial-abaxial patterning. The auxin signal is mediated by the auxin-responsive transcription factor MONOPTEROS (MP), whose constitutive activation in the adaxial domain promotes abaxial cell fate. Furthermore, we show that auxin flow from emerging leaf primordia to the shoot apical meristem establishes the low auxin zone, and that this auxin flow contributes to leaf polarity. Our results provide an explanation for the hypothetical meristem-derived leaf polarity signal. Opposite to the original proposal, instead of a signal derived from the meristem, we show that a signaling molecule is departing from the primordium to the meristem to promote robustness in leaf patterning. PMID:25512543

  6. Auxin depletion from leaf primordia contributes to organ patterning

    PubMed Central

    Qi, Jiyan; Wang, Ying; Yu, Ting; Cunha, Alexandre; Wu, Binbin; Vernoux, Teva; Meyerowitz, Elliot; Jiao, Yuling

    2014-01-01

    Stem cells are responsible for organogenesis, but it is largely unknown whether and how information from stem cells acts to direct organ patterning after organ primordia are formed. It has long been proposed that the stem cells at the plant shoot apex produce a signal, which promotes leaf adaxial-abaxial (dorsoventral) patterning. Here we show the existence of a transient low auxin zone in the adaxial domain of early leaf primordia. We also demonstrate that this adaxial low auxin domain contributes to leaf adaxial-abaxial patterning. The auxin signal is mediated by the auxin-responsive transcription factor MONOPTEROS (MP), whose constitutive activation in the adaxial domain promotes abaxial cell fate. Furthermore, we show that auxin flow from emerging leaf primordia to the shoot apical meristem establishes the low auxin zone, and that this auxin flow contributes to leaf polarity. Our results provide an explanation for the hypothetical meristem-derived leaf polarity signal. Opposite to the original proposal, instead of a signal derived from the meristem, we show that a signaling molecule is departing from the primordium to the meristem to promote robustness in leaf patterning. PMID:25512543

  7. The effect of glyphosate on import into a sink leaf of sugar beet

    SciTech Connect

    Shieh, Wenjang; Geiger, D.R. )

    1990-05-01

    The basis for glyphosate inducted limitation of carbon import into developing leaves was studied in sugar beet. To separate the effects of the herbicide on export from those on import, glyphosate was supplied to a developing leaf from two exporting source leaves which fed the sink leaf. Carbon import into the sink leaf was determined by supplying {sup 14}CO{sub 2} to a third source leaf which also supplies carbon to the monitored sink leaf. Import into the sink leaf decreased within 2 to 3 h after glyphosate application, even though photosynthesis and export in the source leaf supplying {sup 14}C were unaffected. Reduced import into the sink leaf was accompanied by increased import by the tap root. Elongation of the sink leaf was only slightly decreased following arrival of glyphosate. Photosynthesis by the sink leaf was not inhibited. The results to data support the view that import is slowed by the inhibition of synthesis of structural or storage compounds in the developing leaves.

  8. Gravity-induced changes in intracellular potentials in elongating cortical cells of mung bean roots.

    PubMed

    Ishikawa, H; Evans, M L

    1990-06-01

    Gravity-induced changes in intracellular potentials in primary roots of 2-day-old mung bean (Vigna mungo L. cv. black matpe) seedlings were investigated using glass microelectrodes held by 3-dimensional hydraulic micro-drives. The electrodes were inserted into outer cortical cells within the elongation zone. Intracellular potentials, angle of root orientation with respect to gravity, and position within the root of the impaled cortical cell were measured simultaneously. Gravistimulation caused intracellular potential changes in cortical cells of the elongation zone. When the roots were oriented vertically, the intracellular potentials of the outer cortical cells (2 mm behind the root apex) were approximately - 115 mV. When the roots were placed horizontally cortical cells on the upper side hyperpolarized to - 154 mV within 30 s while cortical cells on the lower side depolarized to about - 62 mV. This electrical asymmetry did not occur in cells of the maturation zone. Because attempts to insert the electrode into cells of the root cap were unsuccessful, these cells were not measured. The hyperpolarization of cortical cells on the upper side was greatly reduced upon application of N,N'-dicyclohexylcarbodiimide (DCCD), an inhibitor of respiratory energy coupling. When stimulated roots were returned to the vertical, the degree of hyperpolarization of cortical cells on the previous upper side decreased within 30 s and approached that of cortical cells in non-stimulated roots. This cycle of hyperpolarization/loss of hyperpolarization was repeatable at least ten times by alternately turning the root from the vertical to the horizontal and back again. The very short (<30 s) lag period of these electrical changes indicates that they may result from stimulus-perception and transduction within the elongation zone rather than from transmission of a signal from the root cap. PMID:11537168

  9. Gravity-induced changes in intracellular potentials in elongating cortical cells of mung bean roots

    NASA Technical Reports Server (NTRS)

    Ishikawa, H.; Evans, M. L.

    1990-01-01

    Gravity-induced changes in intracellular potentials in primary roots of 2-day-old mung bean (Vigna mungo L. cv. black matpe) seedlings were investigated using glass microelectrodes held by 3-dimensional hydraulic micro-drives. The electrodes were inserted into outer cortical cells within the elongation zone. Intracellular potentials, angle of root orientation with respect to gravity, and position within the root of the impaled cortical cell were measured simultaneously. Gravistimulation caused intracellular potential changes in cortical cells of the elongation zone. When the roots were oriented vertically, the intracellular potentials of the outer cortical cells (2 mm behind the root apex) were approximately - 115 mV. When the roots were placed horizontally cortical cells on the upper side hyperpolarized to - 154 mV within 30 s while cortical cells on the lower side depolarized to about - 62 mV. This electrical asymmetry did not occur in cells of the maturation zone. Because attempts to insert the electrode into cells of the root cap were unsuccessful, these cells were not measured. The hyperpolarization of cortical cells on the upper side was greatly reduced upon application of N,N'-dicyclohexylcarbodiimide (DCCD), an inhibitor of respiratory energy coupling. When stimulated roots were returned to the vertical, the degree of hyperpolarization of cortical cells on the previous upper side decreased within 30 s and approached that of cortical cells in non-stimulated roots. This cycle of hyperpolarization/loss of hyperpolarization was repeatable at least ten times by alternately turning the root from the vertical to the horizontal and back again. The very short (<30 s) lag period of these electrical changes indicates that they may result from stimulus-perception and transduction within the elongation zone rather than from transmission of a signal from the root cap.

  10. Leaf growth is conformal.

    PubMed

    Alim, Karen; Armon, Shahaf; Shraiman, Boris I; Boudaoud, Arezki

    2016-01-01

    Growth pattern dynamics lie at the heart of morphogenesis. Here, we investigate the growth of plant leaves. We compute the conformal transformation that maps the contour of a leaf at a given stage onto the contour of the same leaf at a later stage. Based on the mapping we predict the local displacement field in the leaf blade and find it to agree with the experimentally measured displacement field to 92%. This approach is applicable to any two-dimensional system with locally isotropic growth, enabling the deduction of the whole growth field just from observation of the tissue contour. PMID:27597439

  11. The little elongation complex functions at initiation and elongation phases of snRNA gene transcription.

    PubMed

    Hu, Deqing; Smith, Edwin R; Garruss, Alexander S; Mohaghegh, Nima; Varberg, Joseph M; Lin, Chengqi; Jackson, Jessica; Gao, Xin; Saraf, Anita; Florens, Laurence; Washburn, Michael P; Eissenberg, Joel C; Shilatifard, Ali

    2013-08-22

    The small nuclear RNA (snRNA) genes have been widely used as a model system for understanding transcriptional regulation due to the unique aspects of their promoter structure, selectivity for either RNA polymerase (Pol) II or III, and because of their unique mechanism of termination that is tightly linked with the promoter. Recently, we identified the little elongation complex (LEC) in Drosophila that is required for the expression of Pol II-transcribed snRNA genes. Here, using Drosophila and mammalian systems, we provide genetic and molecular evidence that LEC functions in at least two phases of snRNA transcription: an initiation step requiring the ICE1 subunit, and an elongation step requiring ELL. PMID:23932780

  12. The Little Elongation Complex functions at initiation and elongation phases of snRNA gene transcription

    PubMed Central

    Hu, Deqing; Smith, Edwin R.; Garruss, Alexander S.; Mohaghegh, Nima; Varberg, Joseph M.; Lin, Chengqi; Jackson, Jessica; Gao, Xin; Saraf, Anita; Florens, Laurence; Washburn, Michael P.; Eissenberg, Joel C.; Shilatifard, Ali

    2014-01-01

    SUMMARY The small nuclear RNA (snRNA) genes have been widely used as a model system for understanding transcriptional regulation due to the unique aspects of their promoter structure, selectivity for either RNA Polymerase (Pol) II or III, and because of their unique mechanism of termination that is tightly linked with the promoter. Recently, we identified the Little Elongation Complex (LEC) in Drosophila that is required for the expression of Pol II-transcribed snRNA genes. Here, using Drosophila and mammalian systems, we provide genetic and molecular evidence that LEC functions in at least two phases of snRNA transcription: an initiation step requiring the ICE1 subunit, and an elongation step requiring ELL. PMID:23932780

  13. Light-Induced Indeterminacy Alters Shade-Avoiding Tomato Leaf Morphology1[OPEN

    PubMed Central

    Chitwood, Daniel H.; Kumar, Ravi; Ranjan, Aashish; Pelletier, Julie M.; Townsley, Brad T.; Ichihashi, Yasunori; Martinez, Ciera C.; Zumstein, Kristina; Harada, John J.; Maloof, Julin N.; Sinha, Neelima R.

    2015-01-01

    Plants sense the foliar shade of competitors and alter their developmental programs through the shade-avoidance response. Internode and petiole elongation, and changes in overall leaf area and leaf mass per area, are the stereotypical architectural responses to foliar shade in the shoot. However, changes in leaf shape and complexity in response to shade remain incompletely, and qualitatively, described. Using a meta-analysis of more than 18,000 previously published leaflet outlines, we demonstrate that shade avoidance alters leaf shape in domesticated tomato (Solanum lycopersicum) and wild relatives. The effects of shade avoidance on leaf shape are subtle with respect to individual traits but are combinatorially strong. We then seek to describe the developmental origins of shade-induced changes in leaf shape by swapping plants between light treatments. Leaf size is light responsive late into development, but patterning events, such as stomatal index, are irrevocably specified earlier. Observing that shade induces increases in shoot apical meristem size, we then describe gene expression changes in early leaf primordia and the meristem using laser microdissection. We find that in leaf primordia, shade avoidance is not mediated through canonical pathways described in mature organs but rather through the expression of KNOTTED1-LIKE HOMEOBOX and other indeterminacy genes, altering known developmental pathways responsible for patterning leaf shape. We also demonstrate that shade-induced changes in leaf primordium gene expression largely do not overlap with those found in successively initiated leaf primordia, providing evidence against classic hypotheses that shaded leaf morphology results from the prolonged production of juvenile leaf types. PMID:26381315

  14. Light-Induced Indeterminacy Alters Shade-Avoiding Tomato Leaf Morphology.

    PubMed

    Chitwood, Daniel H; Kumar, Ravi; Ranjan, Aashish; Pelletier, Julie M; Townsley, Brad T; Ichihashi, Yasunori; Martinez, Ciera C; Zumstein, Kristina; Harada, John J; Maloof, Julin N; Sinha, Neelima R

    2015-11-01

    Plants sense the foliar shade of competitors and alter their developmental programs through the shade-avoidance response. Internode and petiole elongation, and changes in overall leaf area and leaf mass per area, are the stereotypical architectural responses to foliar shade in the shoot. However, changes in leaf shape and complexity in response to shade remain incompletely, and qualitatively, described. Using a meta-analysis of more than 18,000 previously published leaflet outlines, we demonstrate that shade avoidance alters leaf shape in domesticated tomato (Solanum lycopersicum) and wild relatives. The effects of shade avoidance on leaf shape are subtle with respect to individual traits but are combinatorially strong. We then seek to describe the developmental origins of shade-induced changes in leaf shape by swapping plants between light treatments. Leaf size is light responsive late into development, but patterning events, such as stomatal index, are irrevocably specified earlier. Observing that shade induces increases in shoot apical meristem size, we then describe gene expression changes in early leaf primordia and the meristem using laser microdissection. We find that in leaf primordia, shade avoidance is not mediated through canonical pathways described in mature organs but rather through the expression of KNOTTED1-LIKE HOMEOBOX and other indeterminacy genes, altering known developmental pathways responsible for patterning leaf shape. We also demonstrate that shade-induced changes in leaf primordium gene expression largely do not overlap with those found in successively initiated leaf primordia, providing evidence against classic hypotheses that shaded leaf morphology results from the prolonged production of juvenile leaf types. PMID:26381315

  15. Molecular phylogenetic relationships of the brown leaf rust fungi on wheat, rye and other grasses

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Phylogenetic analyses were conducted with DNA sequence data from the rDNA internal transcribed spacer region and elongation factor 1–alpha to elucidate the species complex of brown leaf rust fungi infecting wheat, rye and other grasses. Three phylogenetic lineages were recovered within the complex o...

  16. Boron deficiency inhibits root cell elongation via an ethylene/auxin/ROS-dependent pathway in Arabidopsis seedlings

    PubMed Central

    Camacho-Cristóbal, Juan J.; Martín-Rejano, Esperanza M.; Herrera-Rodríguez, M. Begoña; Navarro-Gochicoa, M. Teresa; Rexach, Jesús; González-Fontes, Agustín

    2015-01-01

    One of the earliest symptoms of boron (B) deficiency is the inhibition of root elongation which can reasonably be attributed to the damaging effects of B deprivation on cell wall integrity. It is shown here that exposure of wild-type Arabidopsis thaliana seedlings to B deficiency for 4h led to a drastic inhibition of root cell length in the transition between the elongation and differentiation zones. To investigate the possible mediation of ethylene, auxin, and reactive oxygen species (ROS) in the effect of B deficiency on root cell elongation, B deficiency was applied together with aminoethoxyvinylglycine (AVG, a chemical inhibitor of ethylene biosynthesis), silver ions (Ag+, an antagonist of ethylene perception), α-(phenylethyl-2‐oxo)‐indoleacetic acid (PEO-IAA, a synthetic antagonist of TIR1 receptor function), and diphenylene iodonium (DPI, an inhibitor of ROS production). Interestingly, all these chemicals partially or fully restored cell elongation in B-deficient roots. To further explore the possible role of ethylene and auxin in the inhibition of root cell elongation under B deficiency, a genetic approach was performed by using Arabidopsis mutants defective in the ethylene (ein2‐1) or auxin (eir1-4 and aux1-22) response. Root cell elongation in these mutants was less sensitive to B-deficient treatment than that in wild-type plants. Altogether, these results demonstrated that a signalling pathway involving ethylene, auxin, and ROS participates in the reduction of root cell elongation when Arabidopsis seedlings are subjected to B deficiency. A similar signalling process has been described to reduce root elongation rapidly under various types of cell wall stress which supports the idea that this signalling pathway is triggered by the impaired cell wall integrity caused by B deficiency. PMID:25922480

  17. Ethylene Upregulates Auxin Biosynthesis in Arabidopsis Seedlings to Enhance Inhibition of Root Cell Elongation[W

    PubMed Central

    Swarup, Ranjan; Perry, Paula; Hagenbeek, Dik; Van Der Straeten, Dominique; Beemster, Gerrit T.S.; Sandberg, Göran; Bhalerao, Rishikesh; Ljung, Karin; Bennett, Malcolm J.

    2007-01-01

    Ethylene represents an important regulatory signal for root development. Genetic studies in Arabidopsis thaliana have demonstrated that ethylene inhibition of root growth involves another hormone signal, auxin. This study investigated why auxin was required by ethylene to regulate root growth. We initially observed that ethylene positively controls auxin biosynthesis in the root apex. We subsequently demonstrated that ethylene-regulated root growth is dependent on (1) the transport of auxin from the root apex via the lateral root cap and (2) auxin responses occurring in multiple elongation zone tissues. Detailed growth studies revealed that the ability of the ethylene precursor 1-aminocyclopropane-1-carboxylic acid to inhibit root cell elongation was significantly enhanced in the presence of auxin. We conclude that by upregulating auxin biosynthesis, ethylene facilitates its ability to inhibit root cell expansion. PMID:17630275

  18. Conditions for bubble elongation in cold ice-sheet ice

    USGS Publications Warehouse

    Alley, R.B.; Fitzpatrick, J.J.

    1999-01-01

    Highly elongated bubbles are sometimes observed in ice-sheet ice. Elongation is favored by rapid ice deformation, and opposed by diffusive processes. We use simple models to show that vapor transport dominates diffusion except possibly very close to the melting point, and that latent-heat effects are insignificant. Elongation is favored by larger bubbles at pore close-off, but is nearly independent of bubble compression below close-off. The simple presence of highly elongated bubbles indicates only that a critical ice-strain rate has been exceeded for significant time, and provides no information on possible disruption of stratigraphic continuity by ice deformation.

  19. Super elongation complex contains a TFIIF-related subcomplex.

    PubMed

    Knutson, Bruce A; Smith, Marissa L; Walker-Kopp, Nancy; Xu, Xia

    2016-08-01

    Super elongation complex (SEC) belongs to a family of RNA polymerase II (Pol II) elongation factors that has similar properties as TFIIF, a general transcription factor that increases the transcription elongation rate by reducing pausing. Although SEC has TFIIF-like functional properties, it apparently lacks sequence and structural homology. Using HHpred, we find that SEC contains an evolutionarily related TFIIF-like subcomplex. We show that the SEC subunit ELL interacts with the Pol II Rbp2 subunit, as expected for a TFIIF-like factor. These findings suggest a new model for how SEC functions as a Pol II elongation factor and how it suppresses Pol II pausing. PMID:27223670

  20. Leaf Tissue Senescence

    PubMed Central

    Manos, Peter J.; Goldthwaite, Jonathan

    1975-01-01

    During winter, excised leaf tissue from Rumex obtusifolius degrades chlorophyll at twice the summer rate but the plant hormones, gibberellic acid and zeatin, inhibit the senescence rate by a constant percentage, regardless of season. PMID:16659225

  1. Ethylene Inhibits Root Elongation during Alkaline Stress through AUXIN1 and Associated Changes in Auxin Accumulation.

    PubMed

    Li, Juan; Xu, Heng-Hao; Liu, Wen-Cheng; Zhang, Xiao-Wei; Lu, Ying-Tang

    2015-08-01

    Soil alkalinity causes major reductions in yield and quality of crops worldwide. The plant root is the first organ sensing soil alkalinity, which results in shorter primary roots. However, the mechanism underlying alkaline stress-mediated inhibition of root elongation remains to be further elucidated. Here, we report that alkaline conditions inhibit primary root elongation of Arabidopsis (Arabidopsis thaliana) seedlings by reducing cell division potential in the meristem zones and that ethylene signaling affects this process. The ethylene perception antagonist silver (Ag(+)) alleviated the inhibition of root elongation by alkaline stress. Moreover, the ethylene signaling mutants ethylene response1-3 (etr1-3), ethylene insensitive2 (ein2), and ein3-1 showed less reduction in root length under alkaline conditions, indicating a reduced sensitivity to alkalinity. Ethylene biosynthesis also was found to play a role in alkaline stress-mediated root inhibition; the ethylene overproducer1-1 mutant, which overproduces ethylene because of increased stability of 1-AMINOCYCLOPROPANE-1-CARBOXYLIC ACID SYNTHASE5, was hypersensitive to alkaline stress. In addition, the ethylene biosynthesis inhibitor cobalt (Co(2+)) suppressed alkaline stress-mediated inhibition of root elongation. We further found that alkaline stress caused an increase in auxin levels by promoting expression of auxin biosynthesis-related genes, but the increase in auxin levels was reduced in the roots of the etr1-3 and ein3-1 mutants and in Ag(+)/Co(2+)-treated wild-type plants. Additional genetic and physiological data showed that AUXIN1 (AUX1) was involved in alkaline stress-mediated inhibition of root elongation. Taken together, our results reveal that ethylene modulates alkaline stress-mediated inhibition of root growth by increasing auxin accumulation by stimulating the expression of AUX1 and auxin biosynthesis-related genes. PMID:26109425

  2. Shaping organs by a wingless-int/Notch/nonmuscle myosin module which orients feather bud elongation.

    PubMed

    Li, Ang; Chen, Meng; Jiang, Ting-Xin; Wu, Ping; Nie, Qing; Widelitz, Randall; Chuong, Cheng-Ming

    2013-04-16

    How organs are shaped to specific forms is a fundamental issue in developmental biology. To address this question, we used the repetitive, periodic pattern of feather morphogenesis on chicken skin as a model. Avian feathers within a single tract extend from dome-shaped primordia to thin conical structures with a common axis of orientation. From a systems biology perspective, the process is precise and robust. Using tissue transplantation assays, we demonstrate that a "zone of polarizing activity," localized in the posterior feather bud, is necessary and sufficient to mediate the directional elongation. This region contains a spatially well-defined nuclear β-catenin zone, which is induced by wingless-int (Wnt)7a protein diffusing in from posterior bud epithelium. Misexpressing nuclear β-catenin randomizes feather polarity. This dermal nuclear β-catenin zone, surrounded by Notch1 positive dermal cells, induces Jagged1. Inhibition of Notch signaling disrupts the spatial configuration of the nuclear β-catenin zone and leads to randomized feather polarity. Mathematical modeling predicts that lateral inhibition, mediated by Notch signaling, functions to reduce Wnt7a gradient variations and fluctuations to form the sharp boundary observed for the dermal β-catenin zone. This zone is also enriched for nonmuscle myosin IIB. Suppressing nonmuscle myosin IIB disrupts directional cell rearrangements and abolishes feather bud elongation. These data suggest that a unique molecular module involving chemical-mechanical coupling converts a pliable chemical gradient to a precise domain, ready for subsequent mechanical action, thus defining the position, boundary, and duration of localized morphogenetic activity that molds the shape of growing organs. PMID:23576731

  3. Shaping organs by a wingless-int/Notch/nonmuscle myosin module which orients feather bud elongation

    PubMed Central

    Li, Ang; Chen, Meng; Jiang, Ting-Xin; Wu, Ping; Nie, Qing; Widelitz, Randall; Chuong, Cheng-Ming

    2013-01-01

    How organs are shaped to specific forms is a fundamental issue in developmental biology. To address this question, we used the repetitive, periodic pattern of feather morphogenesis on chicken skin as a model. Avian feathers within a single tract extend from dome-shaped primordia to thin conical structures with a common axis of orientation. From a systems biology perspective, the process is precise and robust. Using tissue transplantation assays, we demonstrate that a “zone of polarizing activity,” localized in the posterior feather bud, is necessary and sufficient to mediate the directional elongation. This region contains a spatially well-defined nuclear β-catenin zone, which is induced by wingless-int (Wnt)7a protein diffusing in from posterior bud epithelium. Misexpressing nuclear β-catenin randomizes feather polarity. This dermal nuclear β-catenin zone, surrounded by Notch1 positive dermal cells, induces Jagged1. Inhibition of Notch signaling disrupts the spatial configuration of the nuclear β-catenin zone and leads to randomized feather polarity. Mathematical modeling predicts that lateral inhibition, mediated by Notch signaling, functions to reduce Wnt7a gradient variations and fluctuations to form the sharp boundary observed for the dermal β-catenin zone. This zone is also enriched for nonmuscle myosin IIB. Suppressing nonmuscle myosin IIB disrupts directional cell rearrangements and abolishes feather bud elongation. These data suggest that a unique molecular module involving chemical–mechanical coupling converts a pliable chemical gradient to a precise domain, ready for subsequent mechanical action, thus defining the position, boundary, and duration of localized morphogenetic activity that molds the shape of growing organs. PMID:23576731

  4. Calcineurin Links Mitochondrial Elongation with Energy Metabolism.

    PubMed

    Pfluger, Paul T; Kabra, Dhiraj G; Aichler, Michaela; Schriever, Sonja C; Pfuhlmann, Katrin; García, Verónica Casquero; Lehti, Maarit; Weber, Jon; Kutschke, Maria; Rozman, Jan; Elrod, John W; Hevener, Andrea L; Feuchtinger, Annette; Hrabě de Angelis, Martin; Walch, Axel; Rollmann, Stephanie M; Aronow, Bruce J; Müller, Timo D; Perez-Tilve, Diego; Jastroch, Martin; De Luca, Maria; Molkentin, Jeffery D; Tschöp, Matthias H

    2015-11-01

    Canonical protein phosphatase 3/calcineurin signaling is central to numerous physiological processes. Here we provide evidence that calcineurin plays a pivotal role in controlling systemic energy and body weight homeostasis. Knockdown of calcineurin in Drosophila melanogaster led to a decrease in body weight and energy stores, and increased energy expenditure. In mice, global deficiency of catalytic subunit Ppp3cb, and tissue-specific ablation of regulatory subunit Ppp3r1 from skeletal muscle, but not adipose tissue or liver, led to protection from high-fat-diet-induced obesity and comorbid sequelæ. Ser637 hyperphosphorylation of dynamin-related protein 1 (Drp1) in skeletal muscle of calcineurin-deficient mice was associated with mitochondrial elongation into power-cable-shaped filaments and increased mitochondrial respiration, but also with attenuated exercise performance. Our data suggest that calcineurin acts as highly conserved pivot for the adaptive metabolic responses to environmental changes such as high-fat, high-sugar diets or exercise. PMID:26411342

  5. Emerging brain morphologies from axonal elongation

    PubMed Central

    Holland, Maria A.; Miller, Kyle E.; Kuhl, Ellen

    2015-01-01

    Understanding the characteristic morphology of our brain remains a challenging, yet important task in human evolution, developmental biology, and neurosciences. Mathematical modeling shapes our understanding of cortical folding and provides functional relations between cortical wavelength, thickness, and stiffness. Yet, current mathematical models are phenomenologically isotropic and typically predict non-physiological, periodic folding patterns. Here we establish a mechanistic model for cortical folding, in which macroscopic changes in white matter volume are a natural consequence of microscopic axonal growth. To calibrate our model, we consult axon elongation experiments in chick sensory neurons. We demonstrate that a single parameter, the axonal growth rate, explains a wide variety of in vitro conditions including immediate axonal thinning and gradual thickness restoration. We embed our axonal growth model into a continuum model for brain development using axonal orientation distributions motivated by diffusion spectrum imaging. Our simulations suggest that white matter anisotropy - as an emergent property from directional axonal growth - intrinsically induces symmetry breaking, and predicts more physiological, less regular morphologies with regionally varying gyral wavelengths and sulcal depths. Mechanistic modeling of brain development could establish valuable relationships between brain connectivity, brain anatomy, and brain function. PMID:25824370

  6. Glycoproteome of Elongating Cotton Fiber Cells*

    PubMed Central

    Kumar, Saravanan; Kumar, Krishan; Pandey, Pankaj; Rajamani, Vijayalakshmi; Padmalatha, Kethireddy Venkata; Dhandapani, Gurusamy; Kanakachari, Mogilicherla; Leelavathi, Sadhu; Kumar, Polumetla Ananda; Reddy, Vanga Siva

    2013-01-01

    Cotton ovule epidermal cell differentiation into long fibers primarily depends on wall-oriented processes such as loosening, elongation, remodeling, and maturation. Such processes are governed by cell wall bound structural proteins and interacting carbohydrate active enzymes. Glycosylation plays a major role in the structural, functional, and localization aspects of the cell wall and extracellular destined proteins. Elucidating the glycoproteome of fiber cells would reflect its wall composition as well as compartmental requirement, which must be system specific. Following complementary proteomic approaches, we have identified 334 unique proteins comprising structural and regulatory families. Glycopeptide-based enrichment followed by deglycosylation with PNGase F and A revealed 92 unique peptides containing 106 formerly N-linked glycosylated sites from 67 unique proteins. Our results showed that structural proteins like arabinogalactans and carbohydrate active enzymes were relatively more abundant and showed stage- and isoform-specific expression patterns in the differentiating fiber cell. Furthermore, our data also revealed the presence of heterogeneous and novel forms of structural and regulatory glycoproteins. Comparative analysis with other plant glycoproteomes highlighted the unique composition of the fiber glycoproteome. The present study provides the first insight into the identity, abundance, diversity, and composition of the glycoproteome within single celled cotton fibers. The elucidated composition also indirectly provides clues about unicellular compartmental requirements underlying single cell differentiation. PMID:24019148

  7. Regulated tissue fluidity steers zebrafish body elongation

    PubMed Central

    Lawton, Andrew K.; Nandi, Amitabha; Stulberg, Michael J.; Dray, Nicolas; Sneddon, Michael W.; Pontius, William; Emonet, Thierry; Holley, Scott A.

    2013-01-01

    The tailbud is the posterior leading edge of the growing vertebrate embryo and consists of motile progenitors of the axial skeleton, musculature and spinal cord. We measure the 3D cell flow field of the zebrafish tailbud and identify changes in tissue fluidity revealed by reductions in the coherence of cell motion without alteration of cell velocities. We find a directed posterior flow wherein the polarization between individual cell motion is high, reflecting ordered collective migration. At the posterior tip of the tailbud, this flow makes sharp bilateral turns facilitated by extensive cell mixing due to increased directional variability of individual cell motions. Inhibition of Wnt or Fgf signaling or cadherin 2 function reduces the coherence of the flow but has different consequences for trunk and tail extension. Modeling and additional data analyses suggest that the balance between the coherence and rate of cell flow determines whether body elongation is linear or whether congestion forms within the flow and the body axis becomes contorted. PMID:23293289

  8. The mycorrhiza fungus Piriformospora indica induces fast root-surface pH signaling and primes systemic alkalinization of the leaf apoplast upon powdery mildew infection.

    PubMed

    Felle, Hubert H; Waller, Frank; Molitor, Alexandra; Kogel, Karl-Heinz

    2009-09-01

    We analyze here, by noninvasive electrophysiology, local and systemic plant responses in the interaction of barley (Hordeum vulgare L.) with the root-colonizing basidiomycete Piriformospora indica. In the short term (seconds, minutes), a constant flow of P. indica chlamydospores along primary roots altered surface pH characteristics; whereas the root-hair zone transiently alkalized-a typical elicitor response-the elongation zone acidified, indicative of enhanced H(+) extrusion and plasma membrane H(+) ATPase stimulation. Eight to 10 min after treating roots with chlamydospores, the apoplastic pH of leaves began to acidify, which contrasts with observations of an alkalinization response to various stressors and microbe-associated molecular patterns (MAMPs). In the long term (days), plants with P. indica-colonized roots responded to inoculation with the leaf-pathogenic powdery mildew fungus Blumeria graminis f. sp. hordei with a leaf apoplastic pH increase of about 2, while the leaf apoplast of noncolonized barley responded to B. graminis f. sp. hordei merely with a pH increase of 0.8. The strong apoplastic pH response is reminiscent of B. graminis f. sp. hordei-triggered pH shifts in resistance gene-mediated resistant barley leaves or upon treatment with a chemical resistance inducer. In contrast, the MAMP N-acetylchito-octaose did not induce resistance to B. graminis f. sp. hordei and did not trigger the primed apoplastic pH shift. We speculate that the primed pH increase is indicative of and supports the potentiated systemic response to B. graminis f. sp. hordei-induced by P. indica in barley. PMID:19656052

  9. Deer predation on leaf miners via leaf abscission

    NASA Astrophysics Data System (ADS)

    Yamazaki, Kazuo; Sugiura, Shinji

    2008-03-01

    The evergreen oak Quercus gilva Blume sheds leaves containing mines of the leaf miner Stigmella sp. (Lepidoptera: Nepticulidae) earlier than leaves with no mines in early spring in Nara, central Japan. The eclosion rates of the leaf miner in abscised and retained leaves were compared in the laboratory to clarify the effects of leaf abscission on leaf miner survival in the absence of deer. The leaf miner eclosed successfully from both fallen leaves and leaves retained on trees. However, sika deer ( Cervus nippon centralis Kishida) feed on the fallen mined leaves. Field observations showed that deer consume many fallen leaves under Q. gilva trees, suggesting considerable mortality of leaf miners due to deer predation via leaf abscission. This is a previously unreported relationship between a leaf miner and a mammalian herbivore via leaf abscission.

  10. Calorimetric studies of the elongation of Avena coleoptile segments.

    PubMed

    Bogie, H E; Kresheck, G C; Harmet, K H

    1976-06-01

    Elongation rate and heat produced by Avena coleoptile segments suspended in sucrose buffer solutions were measured at pH values from 3.5 to 8.5. The caloric efficiency of elongation (CEE) was defined as the ratio of the rate of elongation to the rate of heat production. Elongation and CEE were greatest at intermediate pH values, but heat production (about 1 cal/g.hr) was insensitive to pH within the limits of experimental error (+/-20%). Quantitative agreement was found between the results of previous respiration studies and the rate of heat production in an aerobic atmosphere, which indicates that oxidative metabolism accounts for essentially all energy changes in the cell, so matter flow is a significant component of the bioenergetics of cell function. Indole-3-acetic acid up to 1 mm, produced about a 10-fold increase in elongation rate, a 5-fold increase of the CEE, and a 25% increase in heat production. Above this concentration, sharp drops in both elongation and heat production occurred, without altering the CEE at pH 6.5, but greatly decreasing the CEE at pH 4.5. Elongation and CEE showed marked decreases after 4 hours in an anaerobic atmosphere, but heat production did not exhibit a proportional decrease. These studies indicate that rate of cell elongation in the presence and absence of auxin is not directly proportional to the overall metabolism of the cell. PMID:16659582

  11. Blastocyst Elongation, Trophoblastic Differentiation and Embryonic Pattern Formation

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The molecular basis behind elongation and concomitant gastrulation in ungulates that occurs during pre-implantation is still poorly understood. In-depth transcriptome analysis of the elongating porcine conceptus at specific stages has demonstrated that protein synthesis, protein trafficking, cell g...

  12. Formation of Elongated Starch Granules in High-amylose Maize

    Technology Transfer Automated Retrieval System (TEKTRAN)

    GEMS-0067 maize starch contains up to 32% elongated starch granules much higher than amylose-extender (ae) single-mutant maize starch (~7%) and normal (non-mutant) maize starch (0%). These elongated granules are highly resistant to enzymatic hydrolysis at 95-100 C, which function as resistant starc...

  13. Formation of elongated galaxies with low masses at high redshift

    NASA Astrophysics Data System (ADS)

    Ceverino, Daniel; Primack, Joel; Dekel, Avishai

    2015-10-01

    We report the identification of elongated (triaxial or prolate) galaxies in cosmological simulations at z ≃ 2. These are preferentially low-mass galaxies (M* ≤ 109.5 M⊙), residing in dark matter (DM) haloes with strongly elongated inner parts, a common feature of high-redshift DM haloes in the Λ cold dark matter cosmology. Feedback slows formation of stars at the centres of these haloes, so that a dominant and prolate DM distribution gives rise to galaxies elongated along the DM major axis. As galaxies grow in stellar mass, stars dominate the total mass within the galaxy half-mass radius, making stars and DM rounder and more oblate. A large population of elongated galaxies produces a very asymmetric distribution of projected axis ratios, as observed in high-z galaxy surveys. This indicates that the majority of the galaxies at high redshifts are not discs or spheroids but rather galaxies with elongated morphologies.

  14. Leaf removal in cool seasons enhances ‘Pinot noir’ anthocyanins

    Technology Transfer Automated Retrieval System (TEKTRAN)

    ‘Pinot noir’ grapes were harvested from a control (no leaf removal) and three complete leaf removed cluster zone treatments, which were initiated at three separate pre-véraison growth stages (bloom, grain-pea size, and bunch closure). Control and leaf–removed treatments were monitored and maintained...

  15. Nanosecond plasma-mediated electrosurgery with elongated electrodes

    NASA Astrophysics Data System (ADS)

    Vankov, Alexander; Palanker, Daniel

    2007-06-01

    Progress in interventional medicine is associated with the development of more delicate and less invasive surgical procedures, which requires more precise and less traumatic, yet affordable, surgical instruments. Previously we reported on the development of the pulsed electron avalanche knife for dissection of soft tissue in liquid media using the 100 ns plasma-mediated electric discharges applied via a 25 μm disk microelectrode. Cavitation bubbles accompanying explosive vaporization of the liquid medium in front of such a pointed electrode produced a series of craters that did not always merge into a continuous cut. In addition, this approach of surface ablation provided a limited depth of cutting. Application of an elongated electrode capable of cutting with its edge rather than just with its pointed apex faces a problem of nonuniformity of the electric field on a nonspherical electrode. In this article we explore dynamics of the plasma-mediated nanosecond discharges in liquid medium in positive and negative polarities and describe the geometry of an electrode that provides a sufficiently uniform electric field along an extended edge of a surgical probe. A highly enhanced and uniform electric field was obtained on very sharp (2.5 μm) exposed edges of a planar electrode insulated on its flat sides. Uniform ionization and simultaneous vaporization was obtained along the whole edge of such a blade with 100 ns pulses at 4-6 kV. A continuous cutting rate of 1 mm/s in the retina and in soft membranes was achieved at a pulse repetition rate of 100 Hz. The collateral damage zone at the edges of incision did not exceed 80 μm. Negative polarity was found advantageous due to the lower rate of electrode erosion and due to better spatial confinement of the plasma-mediated discharge in liquid.

  16. Damped leaf flexure hinge

    NASA Astrophysics Data System (ADS)

    Chen, Zhong; Chen, Guisheng; Zhang, Xianmin

    2015-05-01

    Flexure-based mechanism like compliant actuation system embeds complex dynamics that will reduce the control bandwidth and limits their dynamic positioning precision. This paper presents a theoretical model of a leaf flexure hinge with damping layers using strain energy method and Kelvin damping model. The modified loss factor of the damped leaf flexure hinge is derived, and the equivalent viscous damping coefficient of the damped leaf hinge is obtained, which could be used to improve the pseudo-rigid-model. The free vibration signals of the hinge in three different damping configurations are measured. The experimental modal analysis also is performed on the three kinds of damped leaf flexure hinges in order to evaluate their 1st order bending natural frequency and vibration-suppressing effects. The evaluation of modified loss factor model also is performed. The experimental results indicate that the constrained layer damping can enhance the structure damping of the hinge even if only single damping layer each side, the modified loss factor model can get good predicts of a damped leaf flexure hinge in the frequency range below 1st order natural frequency, and it is necessary that the dimensional parameters of the damping layers and basic layer of the hinge should be optimized for simplification at the mechanism's design stage.

  17. Damped leaf flexure hinge.

    PubMed

    Chen, Zhong; Chen, Guisheng; Zhang, Xianmin

    2015-05-01

    Flexure-based mechanism like compliant actuation system embeds complex dynamics that will reduce the control bandwidth and limits their dynamic positioning precision. This paper presents a theoretical model of a leaf flexure hinge with damping layers using strain energy method and Kelvin damping model. The modified loss factor of the damped leaf flexure hinge is derived, and the equivalent viscous damping coefficient of the damped leaf hinge is obtained, which could be used to improve the pseudo-rigid-model. The free vibration signals of the hinge in three different damping configurations are measured. The experimental modal analysis also is performed on the three kinds of damped leaf flexure hinges in order to evaluate their 1st order bending natural frequency and vibration-suppressing effects. The evaluation of modified loss factor model also is performed. The experimental results indicate that the constrained layer damping can enhance the structure damping of the hinge even if only single damping layer each side, the modified loss factor model can get good predicts of a damped leaf flexure hinge in the frequency range below 1st order natural frequency, and it is necessary that the dimensional parameters of the damping layers and basic layer of the hinge should be optimized for simplification at the mechanism's design stage. PMID:26026549

  18. Analysis of Cell Division and Elongation Underlying the Developmental Acceleration of Root Growth in Arabidopsis thaliana1

    PubMed Central

    Beemster, Gerrit T.S.; Baskin, Tobias I.

    1998-01-01

    To investigate the relation between cell division and expansion in the regulation of organ growth rate, we used Arabidopsis thaliana primary roots grown vertically at 20°C with an elongation rate that increased steadily during the first 14 d after germination. We measured spatial profiles of longitudinal velocity and cell length and calculated parameters of cell expansion and division, including rates of local cell production (cells mm−1 h−1) and cell division (cells cell−1 h−1). Data were obtained for the root cortex and also for the two types of epidermal cell, trichoblasts and atrichoblasts. Accelerating root elongation was caused by an increasingly longer growth zone, while maximal strain rates remained unchanged. The enlargement of the growth zone and, hence, the accelerating root elongation rate, were accompanied by a nearly proportionally increased cell production. This increased production was caused by increasingly numerous dividing cells, whereas their rates of division remained approximately constant. Additionally, the spatial profile of cell division rate was essentially constant. The meristem was longer than generally assumed, extending well into the region where cells elongated rapidly. In the two epidermal cell types, meristem length and cell division rate were both very similar to that of cortical cells, and differences in cell length between the two epidermal cell types originated at the apex of the meristem. These results highlight the importance of controlling the number of dividing cells, both to generate tissues with different cell lengths and to regulate the rate of organ enlargement. PMID:9536070

  19. Differentially Phased Leaf Growth and Movements in Arabidopsis Depend on Coordinated Circadian and Light Regulation[W

    PubMed Central

    Dornbusch, Tino; Michaud, Olivier; Xenarios, Ioannis; Fankhauser, Christian

    2014-01-01

    In contrast to vastly studied hypocotyl growth, little is known about diel regulation of leaf growth and its coordination with movements such as changes in leaf elevation angle (hyponasty). We developed a 3D live-leaf growth analysis system enabling simultaneous monitoring of growth and movements. Leaf growth is maximal several hours after dawn, requires light, and is regulated by daylength, suggesting coupling between growth and metabolism. We identify both blade and petiole positioning as important components of leaf movements in Arabidopsis thaliana and reveal a temporal delay between growth and movements. In hypocotyls, the combination of circadian expression of PHYTOCHROME INTERACTING FACTOR4 (PIF4) and PIF5 and their light-regulated protein stability drives rhythmic hypocotyl elongation with peak growth at dawn. We find that PIF4 and PIF5 are not essential to sustain rhythmic leaf growth but influence their amplitude. Furthermore, EARLY FLOWERING3, a member of the evening complex (EC), is required to maintain the correct phase between growth and movement. Our study shows that the mechanisms underlying rhythmic hypocotyl and leaf growth differ. Moreover, we reveal the temporal relationship between leaf elongation and movements and demonstrate the importance of the EC for the coordination of these phenotypic traits. PMID:25281688

  20. Nanoscale segregation of actin nucleation and elongation factors determines dendritic spine protrusion

    PubMed Central

    Chazeau, Anaël; Mehidi, Amine; Nair, Deepak; Gautier, Jérémie J; Leduc, Cécile; Chamma, Ingrid; Kage, Frieda; Kechkar, Adel; Thoumine, Olivier; Rottner, Klemens; Choquet, Daniel; Gautreau, Alexis; Sibarita, Jean-Baptiste; Giannone, Grégory

    2014-01-01

    Actin dynamics drive morphological remodeling of neuronal dendritic spines and changes in synaptic transmission. Yet, the spatiotemporal coordination of actin regulators in spines is unknown. Using single protein tracking and super-resolution imaging, we revealed the nanoscale organization and dynamics of branched F-actin regulators in spines. Branched F-actin nucleation occurs at the PSD vicinity, while elongation occurs at the tip of finger-like protrusions. This spatial segregation differs from lamellipodia where both branched F-actin nucleation and elongation occur at protrusion tips. The PSD is a persistent confinement zone for IRSp53 and the WAVE complex, an activator of the Arp2/3 complex. In contrast, filament elongators like VASP and formin-like protein-2 move outwards from the PSD with protrusion tips. Accordingly, Arp2/3 complexes associated with F-actin are immobile and surround the PSD. Arp2/3 and Rac1 GTPase converge to the PSD, respectively, by cytosolic and free-diffusion on the membrane. Enhanced Rac1 activation and Shank3 over-expression, both associated with spine enlargement, induce delocalization of the WAVE complex from the PSD. Thus, the specific localization of branched F-actin regulators in spines might be reorganized during spine morphological remodeling often associated with synaptic plasticity. PMID:25293574

  1. Elastocaloric effect dependence on pre-elongation in natural rubber

    NASA Astrophysics Data System (ADS)

    Xie, Zhongjian; Sebald, Gael; Guyomar, Daniel

    2015-08-01

    In the context of solid-state-cooling, the elastocaloric effect offers a very large controlled entropy change based in low-cost polymers, especially natural rubber which is environmentally friendly. However, large elastocaloric activity requires large elongation (>5), which makes this material impractical for cooling systems due to the large change in sample's area. By performing a pre-elongation, area change is limited, and β = - ∂ γ / ∂ λ (where γ is the specific entropy and λ is the elongation) is larger. The highest β value is obtained when pre-elongation is right before (at the "eve") the onset of the strain-induced crystallization, which is also interpreted in the view of molecular conformation. Experimental results obtained on a natural rubber sample showed an adiabatic temperature change of 4.3 °C for pre-elongation of 4 with further elongation of 4 (true strain change of 69%). Furthermore, the entropy exhibits a quasi-linear dependence on elongation, and the β value is found to be 6400 J K-1 m-3.

  2. Rice HOX12 Regulates Panicle Exsertion by Directly Modulating the Expression of ELONGATED UPPERMOST INTERNODE1.

    PubMed

    Gao, Shaopei; Fang, Jun; Xu, Fan; Wang, Wei; Chu, Chengcai

    2016-03-01

    Bioactive gibberellins (GAs) are key endogenous regulators of plant growth. Previous work identified ELONGATED UPPERMOST INTERNODE1 (EUI1) as aGA-deactivating enzyme that plays an important role in panicle exsertion from the flag leaf sheath in rice (Oryza sativa). However, the mechanism that regulates EUI1 activity during development is still largely unexplored. In this study, we identified the dominant panicle enclosure mutantregulator of eui1(ree1-D), whose phenotype is caused by the activation of the homeodomain-leucine zipper transcription factor HOX12. DiminishedHOX12expression by RNA interference enhanced panicle exsertion, mimicking theeui1phenotype.HOX12knockdown plants contain higher levels of the major biologically activeGAs(such as GA1and GA4) than the wild type. The expression ofEUI1is elevated in theree1-Dmutant but reduced inHOX12knockdown plants. Interestingly, bothHOX12andEUI1are predominantly expressed in panicles, where GA4is highly accumulated. Yeast one-hybrid, electrophoretic mobility shift assay, and chromatin immunoprecipitation analyses showed that HOX12 physically interacts with theEUI1promoter both in vitro and in vivo. Furthermore, plants overexpressingHOX12in theeui1mutant background retained the elongated uppermost internode phenotype. These results indicate that HOX12 acts directly throughEUI1to regulate panicle exsertion in rice. PMID:26977084

  3. The shape of a long leaf

    PubMed Central

    Liang, Haiyi; Mahadevan, L.

    2009-01-01

    Long leaves in terrestrial plants and their submarine counterparts, algal blades, have a typical, saddle-like midsurface and rippled edges. To understand the origin of these morphologies, we dissect leaves and differentially stretch foam ribbons to show that these shapes arise from a simple cause, the elastic relaxation via bending that follows either differential growth (in leaves) or differential stretching past the yield point (in ribbons). We quantify these different modalities in terms of a mathematical model for the shape of an initially flat elastic sheet with lateral gradients in longitudinal growth. By using a combination of scaling concepts, stability analysis, and numerical simulations, we map out the shape space for these growing ribbons and find that as the relative growth strain is increased, a long flat lamina deforms to a saddle shape and/or develops undulations that may lead to strongly localized ripples as the growth strain is localized to the edge of the leaf. Our theory delineates the geometric and growth control parameters that determine the shape space of finite laminae and thus allows for a comparative study of elongated leaf morphology. PMID:19966215

  4. Elongation dynamics of amyloid fibrils: A rugged energy landscape picture

    NASA Astrophysics Data System (ADS)

    Lee, Chiu Fan; Loken, James; Jean, Létitia; Vaux, David J.

    2009-10-01

    Protein amyloid fibrils are a form of linear protein aggregates that are implicated in many neurodegenerative diseases. Here, we study the dynamics of amyloid fibril elongation by performing Langevin dynamic simulations on a coarse-grained model of peptides. Our simulation results suggest that the elongation process is dominated by a series of local minimum due to frustration in monomer-fibril interactions. This rugged energy landscape picture indicates that the amount of recycling of monomers at the fibrils’ ends before being fibrilized is substantially reduced in comparison to the conventional two-step elongation model. This picture, along with other predictions discussed, can be tested with current experimental techniques.

  5. Maple Leaf Outdoor Centre.

    ERIC Educational Resources Information Center

    Maguire, Molly; Gunton, Ric

    2000-01-01

    Maple Leaf Outdoor Centre (Ontario) has added year-round outdoor education facilities and programs to help support its summer camp for disadvantaged children. Schools, youth centers, religious groups, and athletic teams conduct their own programs, collaborate with staff, or use staff-developed programs emphasizing adventure education and personal…

  6. Raspberry leaf curl virus

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Raspberry leaf curl virus (RLCV) is limited to hosts in the genus Rubus and is transmitted persistently by the small raspberry aphid, Aphis rubicola Oestlund. It is found only in North America, principally in the northeastern United States and southeastern Canada and in the Rocky Mountain regions of...

  7. Bacterial leaf spot

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Bacterial leaf spot has been reported in Australia (Queensland), Egypt, El Salvador, India, Japan, Nicaragua, Sudan, and the United States (Florida, Iowa, Kansas, Maryland, and Wisconsin). It occasionally causes locally severe defoliation and post-emergence damping-off and stunting. The disease is...

  8. Salt stress response triggers activation of the jasmonate signaling pathway leading to inhibition of cell elongation in Arabidopsis primary root.

    PubMed

    Valenzuela, Camilo E; Acevedo-Acevedo, Orlando; Miranda, Giovanna S; Vergara-Barros, Pablo; Holuigue, Loreto; Figueroa, Carlos R; Figueroa, Pablo M

    2016-07-01

    Salinity is a severe abiotic stress that affects irrigated croplands. Jasmonate (JA) is an essential hormone involved in plant defense against herbivory and in responses to abiotic stress. However, the relationship between the salt stress response and the JA pathway in Arabidopsis thaliana is not well understood at molecular and cellular levels. In this work we investigated the activation of JA signaling by NaCl and its effect on primary root growth. We found that JA-responsive JAZ genes were up-regulated by salt stress in a COI1-dependent manner in the roots. Using a JA-Ile sensor we demonstrated that activation of JA signaling by salt stress occurs in the meristematic zone and stele of the differentiation zone and that this activation was dependent on JAR1 and proteasome functions. Another finding is that the elongation zone (EZ) and its cortical cells were significantly longer in JA-related mutants (AOS, COI1, JAZ3 and MYC2/3/4 genes) compared with wild-type plants under salt stress, revealing the participation of the canonical JA signaling pathway. Noteworthy, osmotic stress - a component of salt stress - inhibited cell elongation in the EZ in a COI1-dependent manner. We propose that salt stress triggers activation of the JA signaling pathway followed by inhibition of cell elongation in the EZ. We have shown that salt-inhibited root growth partially involves the jasmonate signaling pathway in Arabidopsis. PMID:27217545

  9. Direct Characterization of Transcription Elongation by RNA Polymerase I.

    PubMed

    Ucuncuoglu, Suleyman; Engel, Krysta L; Purohit, Prashant K; Dunlap, David D; Schneider, David A; Finzi, Laura

    2016-01-01

    RNA polymerase I (Pol I) transcribes ribosomal DNA and is responsible for more than 60% of transcription in a growing cell. Despite this fundamental role that directly impacts cell growth and proliferation, the kinetics of transcription by Pol I are poorly understood. This study provides direct characterization of S. Cerevisiae Pol I transcription elongation using tethered particle microscopy (TPM). Pol I was shown to elongate at an average rate of approximately 20 nt/s. However, the maximum speed observed was, in average, about 60 nt/s, comparable to the rate calculated based on the in vivo number of active genes, the cell division rate and the number of engaged polymerases observed in EM images. Addition of RNA endonucleases to the TPM elongation assays enhanced processivity. Together, these data suggest that additional transcription factors contribute to efficient and processive transcription elongation by RNA polymerase I in vivo. PMID:27455049

  10. Morphological and Chemical Mechanisms of Elongated Mineral Particle Toxicities

    EPA Science Inventory

    Much of our understanding regarding the mechanisms for induction of disease following inhalation of respirable elongated mineral particles (REMPs) is based on studies involving the biological effects of asbestos fibers. The factors governing the disease potential of an exposure i...

  11. The Emerging Role of Forces in Axonal Elongation

    PubMed Central

    Suter, Daniel M.; Miller, Kyle E.

    2011-01-01

    An understanding of how axons elongate is needed to develop rational strategies to treat neurological diseases and nerve injury. Growth cone-mediated neuronal elongation is currently viewed as occurring through cytoskeletal dynamics involving the polymerization of actin and tubulin subunits at the tip of the axon. However, recent work suggests that axons and growth cones also generate forces (through cytoskeletal dynamics, kinesin, dynein, and myosin), forces induce axonal elongation, and axons lengthen by stretching. This review highlights results from various model systems (Drosophila, Aplysia, Xenopus, chicken, mouse, rat, and PC12 cells), supporting a role for forces, bulk microtubule movements, and intercalated mass addition in the process of axonal elongation. We think that a satisfying answer to the question, “How do axons grow?” will come by integrating the best aspects of biophysics, genetics, and cell biology. PMID:21527310

  12. Power losses in bent and elongated polymer optical fibers.

    PubMed

    Chen, Yung-Chuan

    2007-07-20

    This study performs experimental and numerical investigations into the power losses induced in bent, elongated polymer optical fibers (POFs). The theoretical analysis is based on a three-dimensional elastic-plastic finite-element model and makes the assumption of a planar waveguide. The finite-element model is used to calculate the deformation of the elongated POFs such that the power loss can be analytically derived. The effect of bending on the power loss is examined by considering seven different bend radii ranging from 10 to 50 mm. The results show that bending and elongation have a significant effect on the power loss in POFs. The contribution of skew rays to the overall power loss in bent, elongated POFs is not obvious at large radii of curvature but becomes more significant as the radius is reduced. PMID:17609702

  13. Direct Characterization of Transcription Elongation by RNA Polymerase I

    PubMed Central

    Ucuncuoglu, Suleyman; Engel, Krysta L.; Purohit, Prashant K.; Dunlap, David D.; Schneider, David A.

    2016-01-01

    RNA polymerase I (Pol I) transcribes ribosomal DNA and is responsible for more than 60% of transcription in a growing cell. Despite this fundamental role that directly impacts cell growth and proliferation, the kinetics of transcription by Pol I are poorly understood. This study provides direct characterization of S. Cerevisiae Pol I transcription elongation using tethered particle microscopy (TPM). Pol I was shown to elongate at an average rate of approximately 20 nt/s. However, the maximum speed observed was, in average, about 60 nt/s, comparable to the rate calculated based on the in vivo number of active genes, the cell division rate and the number of engaged polymerases observed in EM images. Addition of RNA endonucleases to the TPM elongation assays enhanced processivity. Together, these data suggest that additional transcription factors contribute to efficient and processive transcription elongation by RNA polymerase I in vivo. PMID:27455049

  14. Root-to-shoot signalling when soil moisture is heterogeneous: increasing the proportion of root biomass in drying soil inhibits leaf growth and increases leaf abscisic acid concentration.

    PubMed

    Martin-Vertedor, Ana Isabel; Dodd, Ian C

    2011-07-01

    To determine whether root-to-shoot signalling of soil moisture heterogeneity depended on root distribution, wild-type (WT) and abscisic acid (ABA)-deficient (Az34) barley (Hordeum vulgare) plants were grown in split pots into which different numbers of seminal roots were inserted. After establishment, all plants received the same irrigation volumes, with one pot watered (w) and the other allowed to dry the soil (d), imposing three treatments (1 d: 3 w, 2 d: 2 w, 3 d: 1 w) that differed in the number of seminal roots exposed to drying soil. Root distribution did not affect leaf water relations and had no sustained effect on plant evapotranspiration (ET). In both genotypes, leaf elongation was less and leaf ABA concentrations were higher in plants with more roots in drying soil, with leaf ABA concentrations and water potentials 30% and 0.2 MPa higher, respectively, in WT plants. Whole-pot soil drying increased xylem ABA concentrations, but maximum values obtained when leaf growth had virtually ceased (100 nm in Az34, 330 nm in WT) had minimal effects (<40% leaf growth inhibition) when xylem supplied to detached shoots. Although ABA may not regulate leaf growth in vivo, genetic variation in foliar ABA concentration in the field may indicate different root distributions between upper (drier) and lower (wetter) soil layers. PMID:21410712

  15. Shear and effective elongational rheology and polymer molecular characteristics

    NASA Astrophysics Data System (ADS)

    Wei, Xiaoling

    Extensional deformations play a significant role in many processing operations which involve a rapid change of shape such as fiber spinning, film blowing, blow molding, and nonwoven melt processing. To develop real time, on-line process and quality control analysis in these operations, knowledge of the molecular weight (MW) and molecular weight distribution (MWD), effects of molecular characteristics and processing conditions on the elongational rheology, and orientation of polymeric materials in these operations is essential. In this work, shear rheology of six polyethylenes (PE), one polyisobutylene (PIB), and five cellulose solutions was measured at different temperatures using a rotational rheometer. Effective elongational viscosity of polyethylenes and polyisobutylene was also measured at different Hencky strains and temperatures using a capillary rheometer by replacing the capillary cylindrical die with a hyperbolic converging die. The hyperbolic shape of the dies establishes a purely elongational flow field at a constant elongational strain rate throughout the die. The effect of molecular characteristics such as MW, MWD, and long chain branches and the processing conditions such as temperature and Hencky strain on the elongational rheology of PE and PIB samples was studied. The results from the hyperbolic dies were compared with results from other techniques, namely Rheometrics Extensional Rheometer (RER) and Elongational Rheometer for Melts (RME). Good master curves were generated for the temperature and Hencky strain shifting, and simultaneous shifting with respect to both temperature and Hencky strain. The enthalpy and entropy changes were calculated from the effective elongational and shear viscosities to investigate flow induced orientation of the polymer melts in hyperbolic dies. The enthalpy and entropy changes increase in magnitude with higher elongational strain rate and higher Hencky strain. The storage and loss moduli were used to determine and

  16. Prevalence of Elongated Styloid Process in a Central Brazilian Population

    PubMed Central

    Vieira, Evanice Menezes Marçal; Morais, Sylvania De; Musis, Carlo Ralph De; Albuquerque, Paulo Artur Andrade De; Borges, Álvaro Henrique

    2015-01-01

    Background Eagle’s syndrome comprises a rare disorder caused by compression of an elongated or deformed styloid process or ossified/calcified stylohyoid ligament on neural and vascular structures. It is characterized by facial and neck pain and can be confused with a wide variety of facial neuralgias, oral and dental diseases and temporomandibular disorders. An imaging evaluation associated with a careful clinical examination, are mandatory in structuring a correct differential diagnosis and in the establishment of a proper therapeutic protocol. Aim To investigate the prevalence of the elongated styloid process in a Central Brazilian population and its relation to gender, age and side. Materials and Methods Digital panoramic radiographs of 736 patients (412 female and 324 male, with a mean age of 35.03 years) were consecutively selected from a private radiology clinic’s secondary database. The apparent length of the styloid process was measured from the point where the styloid left the tympanic plate to the tip of the process by two specialists in dental radiology, with the help of the measuring tools on the accompanying software. Styloid process measuring more than 30 mm was considered elongated. The statistical analysis included frequency distribution and cross tabulation. The data were analysed by using Chi-squared tests. The level of significance was set at 5% for all analyses. Results A total of 323 (43.89%) radiographic images were suggestive of elongated styloid process. No statistically significant difference was found between the genders, although a higher prevalence was noticed in female participants. Approximately, 31% of the elongated styloid process was observed in 18-53-year-old participants (p < 0.05). Two hundred and sixty seven styloid processes (36.28%) were elongated on both right and left sides. Conclusion The prevalence of elongated styloid process was high and no statistically significant correlation was found between the presence of

  17. Antibacterial and antioxidant activities of Vaccinium corymbosum L. leaf extract

    PubMed Central

    Pervin, Mehnaz; Hasnat, Md Abul; Lim, Beong Ou

    2013-01-01

    Objective To investigate antibacterial and antioxidant activity of the leaf extract of tropical medicinal herb and food plant Vaccinium corymbosum L. (V. corymbosum). Methods Free radical scavenging activity on DPPH, ABTS, and nitrites were used to analyse phenoic and flavonoid contents of leaf extract. Other focuses included the determination of antioxidant enzymatic activity (SOD, CAT and GPx), metal chelating activity, reduction power, lipid peroxidation inhibition and the prevention of oxidative DNA damage. Antibacterial activity was determined by using disc diffusion for seven strains of bacteria. Results Results found that V. corymbosum leaf extract had significant antibacterial activity. The tested extract displayed the highest activity (about 23.18 mm inhibition zone) against Salmonella typhymurium and the lowest antibacterial activity was observed against Enterococcus faecalis (about 14.08 mm inhibition zone) at 10 mg/ disc. The IC50 values for DPPH, ABTS and radical scavenging activity were 0.120, 0.049 and 1.160 mg/mL, respectively. V. corymbosum leaf extract also showed dose dependent reduction power, lipid peroxidation, DNA damage prevention and significant antioxidant enzymatic activity. Conclusions These findings demonstrate that leaf extract of V. corymbosum could be used as an alternative therapy for antibiotic-resistant bacteria and help prevent various free radical related diseases.

  18. Insights on the development, kinetics, and variation of photoinhibition using chlorophyll fluorescence imaging of a chilled, variegated leaf.

    PubMed

    Hogewoning, Sander W; Harbinson, Jeremy

    2007-01-01

    The effect of chilling on photosystem II (PSII) efficiency was studied in the variegated leaves of Calathea makoyana, in order to gain insight into the causes of chilling-induced photoinhibition. Additionally, a relationship was revealed between (chilling) stress and variation in photosynthesis. Chilling treatments (5 degrees C and 10 degrees C) were performed for different durations (1-7 d) under a moderate irradiance (120 micromol m-2 s-1). The individual leaves were divided into a shaded zone and two illuminated, chilled zones. The leaf tip and sometimes the leaf base were not chilled. Measurements of the dark-adapted Fv/Fm were made on the different leaf zones at the end of the chilling treatment, and then for several days thereafter to monitor recovery. Chilling up to 7 d in the dark did not affect PSII efficiency and visual appearance, whereas chilling in the light caused severe photoinhibition, sometimes followed by leaf necrosis. Photoinhibition increased with the duration of the chilling period, whereas, remarkably, chilling temperature had no effect. In the unchilled leaf tip, photoinhibition also occurred, whereas in the unchilled leaf base it did not. Whatever the leaf zone, photoinhibition became permanent if the mean value dropped below 0.4, although chlorosis and necrosis were associated solely with chilled illuminated tissue. Starch accumulated in the unchilled leaf tip, in contrast to the adjacent chilled irradiated zone. This suggests that photoinhibition was due to a secondary effect in the unchilled leaf tip (sink limitation), whereas it was a direct effect of chilling and irradiance in the chilled illuminated zones. The PSII efficiency and its coefficient of variation showed a unique negative linearity across all leaf zones and different tissue types. The slope of this curve was steeper for chilled leaves than it was for healthy, non-stressed leaves, suggesting that the coefficient of variation may be an important tool for assessing stress in

  19. Characterizing natural cellulose fibers from velvet leaf (Abutilon theophrasti) stems.

    PubMed

    Reddy, Narendra; Yang, Yiqi

    2008-05-01

    Velvet leaf (Abutilon theophrasti) that is currently considered a weed and an agricultural problem could be used as a source for high quality natural cellulose fibers. The fibers obtained from the velvet leaf stems are mainly composed of approximately 69% cellulose and 17% lignin. The single cells in the fiber have lengths of approximately 0.9 mm, shorter than those in common bast fibers, hemp and kenaf. However, the widths of single cells in velvet leaf fibers are similar to the single cells in hemp and kenaf. The fibers exhibited breaking tenacity from 2.4 to 3.9 g/denier (325-500 MPa), breaking elongation of 1.6-2.4% and Young's modulus of 140-294 g/denier (18-38 GPa). Overall, velvet leaf fibers have properties similar to that of common bast fibers such as hemp and kenaf. Velvet leaves fibers could be processed on the current kenaf processing machineries for textile, composite, automotive and other fibrous applications. PMID:17583497

  20. Comparison of flooding-tolerance in four mangrove species in a diurnal tidal zone in the Beibu Gulf

    NASA Astrophysics Data System (ADS)

    He, Binyuan; Lai, Tinghe; Fan, Hangqing; Wang, Wenqing; Zheng, Hailei

    2007-08-01

    The flood tolerance of four mangrove species, Aegiceras corniculatum (L.) Blanco (AC), Avicennia marina (Forsk.) Vierh. (Am), Bruguiera gymnorrhiza (L.) Savigny (Bg) and Rhizophora stylosa Griff. (Rs) was examined in a field trial conducted from August 2004 until August 2005 in a diurnal tidal zone in Yingluo Bay, Guangxi province, China. In a section of tidal flat, three replicate artificial platforms were constructed for seedling cultivation. Eight different tidal flat elevation (TFE) treatments were created on each platform. After one year of cultivation under the TFE treatments, the survival rate and growth parameters of seedlings were measured. Seedlings of A. corniculatum and A. marina seedlings survived all treatments. The survival rate of B. gymnorrhiza and R. stylosa seedlings, however, decreased sharply as the TFE fell; in any treatment, fewer B. gymnorrhiza seedlings survived than R. stylosa seedlings. Stem elongation in A. corniculatum and A. marina seedlings was significantly increased by lower TFEs. Lower TFE treatments also increased stem heights in B. gymnorrhiza and R. stylosa seedlings; however, growth was significantly higher as TFE increased. Leaf number, leaf conservation rate and leaf area per seedling changed relatively little among treatments in A. corniculatum and A. marina seedlings, while these three indexes in B. gymnorrhiza and R. stylosa seedlings all decreased dramatically with decreasing TFE. A. marina seedlings reached a higher neonatal biomass at lower TFE treatments, whereas A. corniculatum seedlings attained a higher biomass under moderate TFEs. In contrast, B. gymnorrhiza and R. stylosa seedlings accumulated more biomass in the higher TFEs habitats. Biomass partitioning among the components of both A. corniculatum and A. marina seedlings changed evenly; however, A. corniculatum accumulated more biomass in the leaf while A. marina accumulated more in the stem. The TFE treatments greatly influenced biomass partitioning in B

  1. Leaf absorbance and photosynthesis

    NASA Technical Reports Server (NTRS)

    Schurer, Kees

    1994-01-01

    The absorption spectrum of a leaf is often thought to contain some clues to the photosynthetic action spectrum of chlorophyll. Of course, absorption of photons is needed for photosynthesis, but the reverse, photosynthesis when there is absorption, is not necessarily true. As a check on the existence of absorption limits we measured spectra for a few different leaves. Two techniques for measuring absorption have been used, viz. the separate determination of the diffuse reflectance and the diffuse transmittance with the leaf at a port of an integrating sphere and the direct determination of the non-absorbed fraction with the leaf in the sphere. In a cross-check both methods yielded the same results for the absorption spectrum. The spectrum of a Fuchsia leaf, covering the short-wave region from 350 to 2500 nm, shows a high absorption in UV, blue and red, the well known dip in the green and a steep fall-off at 700 nm. Absorption drops to virtually zero in the near infrared, with subsequent absorptions, corresponding to the water absorption bands. In more detailed spectra, taken at 5 nm intervals with a 5 nm bandwidth, differences in chlorophyll content show in the different depths of the dip around 550 nm and in a small shift of the absorption edge at 700 nm. Spectra for Geranium (Pelargonium zonale) and Hibiscus (with a higher chlorophyll content) show that the upper limit for photosynthesis can not be much above 700 nm. No evidence, however, is to be seen of a lower limit for photosynthesis and, in fact, some experiments down to 300 nm still did not show a decrease of the absorption although it is well recognized that no photosynthesis results with 300 nm wavelengths.

  2. Correlation Between NDE Measurements and Elongation of Aluminum

    SciTech Connect

    Thompson, R. Bruce; Margetan, Frank J.; Nakagawa, Norio; Haldipur, Pranaam

    2007-03-21

    Complex aluminum forgings can have engineering properties which vary with position due to changes in the underlying local metal microstructure. Consequently, the material properties may be in compliance with production requirements in some regions of the forging, but out of compliance in others. One conical Al-7050 forging of interest was found to have elongation properties which failed required tests in certain regions. NDE measurements sensitive to microstructural changes were carried out to search for correlations with elongation properties. The results of a set of initial feasibility experiments will be reported. Both ultrasonic and eddy current NDE methods were used, with the goal being to determine which properties were sensitive to the elongation. Ultrasonic testing included the measurement of longitudinal and shear-wave velocity, longitudinal wave attenuation, and longitudinal and shear-wave backscattered grain noise. All tests were performed with the sonic beam entering through the coupon face that would be adjacent to the outer surface of the forging. Only modest differences in wave speed and attenuation values were seen among the suite of coupons, but significant differences were seen in backscattered noise levels. These appeared to indicate changes in grain structure but only exhibited partial correlation with elongation. The eddy current measurements were designed to be sensitive to the electrical resistivity. Included were a number of measurement configurations and frequencies. The signals exhibited a significant correlation with elongation.

  3. Using the conservative nature of fresh leaf surface density to measure foliar area

    NASA Astrophysics Data System (ADS)

    Castillo, Omar S.; Zaragoza, Esther M.; Alvarado, Carlos J.; Barrera, Maria G.; Dasgupta-Schubert, Nabanita

    2014-10-01

    For a herbaceous species, the inverse of the fresh leaf surface density, the Hughes constant, is nearly conserved. We apply the Hughes constant to develop an absolute method of leafarea measurement that requires no regression fits, prior calibrations or oven-drying. The Hughes constant was determined in situ using a known geometry and weights of a sub-set obtained from the fresh leaves whose areas are desired. Subsequently, the leaf-areas (at any desired stratification level), were derived by utilizing the Hughes constant and the masses of the fresh leaves. The proof of concept was established for leaf-discs of the plants Mandevilla splendens and Spathiphyllum wallisii. The conservativeness of the Hughes constant over individual leaf-zones and different leaftypes from the leaves of each species was quantitatively validated. Using the globally averaged Hughes constant for each species, the leaf-area of these and additional co-species plants, were obtained. The leaf-area-measurement-by-mass was cross-checked with standard digital image analysis. There were no statistically significant differences between the leaf-area-measurement-by-mass and the digital image analysis measured leaf-areas and the linear correlation between the two methods was very good. Leaf-areameasurement- by-mass was found to be rapid and simple with accuracies comparable to the digital image analysis method. The greatly reduced cost of leaf-area-measurement-by-mass could be beneficial for small agri-businesses in developing countries.

  4. Rapid effects of nitrogen form on leaf morphogenesis in tobacco.

    PubMed

    Walch-Liu, P; Neumann, G; Bangerth, F; Engels, C

    2000-02-01

    Ammonium (NH4+) instead of nitrate (NO3-) as the nitrogen (N) source for tobacco (Nicotiana tabacum L.) cultivated in a pH-buffered nutrient solution resulted in decreased shoot and root biomass. Reduction of shoot fresh weight was mainly related to inhibition of leaf growth, which was already detectable after short-term NH4+ treatments of 24 h, and even at a moderate concentration level of 2 mM. Microscopic analysis of the epidermis of fully expanded leaves revealed a decrease in cell number (50%) and in cell size (30%) indicating that both cell division and cell elongation were affected by NH4+ application. Changes in various physiological parameters known to be associated with NH4(+)-induced growth depression were examined both in long-term and short-term experiments: the concentrations of total N, soluble sugars and starch as well as the osmotic potential, the apparent hydraulic conductivity and the rate of water uptake were not reduced by NH4+ treatments (duration 1-12 d), suggesting that leaf growth was neither limited by the availability of N and carbohydrates, nor by a lack of osmotica or water supply. Although the concentration of K+ in leaf press sap declined in expanding leaves by approximately 15% in response to NH4+ nutrition, limitation of mineral nutrients seems to be unlikely in view of the fast response of leaf growth at 24 h after the start of the NH4+ treatment. No inhibitory effects were observed when NH4+ and NO3- were applied simultaneously (each 1 mM) resulting in a NO3-/NH4+ net uptake ratio of 6:4. These findings suggest that the rapid inhibition of leaf growth was not primarily related to NH4+ toxicity, but to the lack of NO3(-)-supply. Growth inhibition of plants fed solely with NH4+ was associated with a 60% reduction of the zeatine + zeatine riboside (Z + ZR) cytokinin fraction in the xylem sap after 24 h. Furthermore Z + ZR levels declined to almost zero within the next 4 d after start of the NH4+ treatment. In contrast, the

  5. Leaf gas films, underwater photosynthesis and plant species distributions in a flood gradient.

    PubMed

    Winkel, Anders; Visser, Eric J W; Colmer, Timothy D; Brodersen, Klaus P; Voesenek, Laurentius A C J; Sand-Jensen, Kaj; Pedersen, Ole

    2016-07-01

    Traits for survival during flooding of terrestrial plants include stimulation or inhibition of shoot elongation, aerenchyma formation and efficient gas exchange. Leaf gas films form on superhydrophobic cuticles during submergence and enhance underwater gas exchange. The main hypothesis tested was that the presence of leaf gas films influences the distribution of plant species along a natural flood gradient. We conducted laboratory experiments and field observations on species distributed along a natural flood gradient. We measured presence or absence of leaf gas films and specific leaf area of 95 species. We also measured, gas film retention time during submergence and underwater net photosynthesis and dark respiration of 25 target species. The presence of a leaf gas film was inversely correlated to flood frequency and duration and reached a maximum value of 80% of the species in the rarely flooded locations. This relationship was primarily driven by grasses that all, independently of their field location along the flood gradient, possess gas films when submerged. Although the present study and earlier experiments have shown that leaf gas films enhance gas exchange of submerged plants, the ability of species to form leaf gas films did not show the hypothesized relationship with species composition along the flood gradient. PMID:26846194

  6. A New Model Incorporating Variably Saturated Flow That Accounts for Capillary-Fringe Elongation in Unconfined-Aquifer Tests

    NASA Astrophysics Data System (ADS)

    Moench, A. F.

    2006-12-01

    A seven-day, constant-rate aquifer test conducted by University of Waterloo researchers at Canadian Forces Base Borden in Ontario, Canada is useful for advancing understanding of fluid flow processes in response to pumping from an unconfined aquifer. Measured data included detailed water content in the unsaturated zone through time and space and drawdown in the saturated zone. The water content data reveal downward translation of the soil-moisture profiles and simultaneous elongations of the capillary fringe. Estimates of capillary-fringe thicknesses made use of use of model-calculated water-table elevations. Using drawdown data only, parameter estimation with a numerical model that solves Richards' equation for fluid flow and uses Brooks and Corey functional relations to represent unsaturated-zone characteristics yielded simulated drawdowns in the saturated zone that compared favorably with measured drawdowns. However, the modeled soil-moisture profile bore no resemblance to measured soil- moisture profiles and the model did not accurately simulate capillary-fringe elongation. I propose a modified model that largely decouples the Brooks and Corey soil-moisture and relative hydraulic conductivity functions by using two pore-size distribution functions, one for each functional relation. With the proposed model the general shape of the measured soil-moisture profiles was reproduced, there were time-varying vertical extensions of the capillary fringe consistent with observations, and there was satisfactory agreement between simulated and measured drawdowns in the saturated zone. The model does not account for appreciable radial variations in the thickness of the capillary fringe. For example, in seven days of pumping the capillary fringe grew from 35 to 58 cm at a distance of 1 m and 41 to 50 cm at a distance of 20 m. The analysis shows that drawdown measurements in the saturated zone by themselves without supporting soil-moisture measurements are not sufficient to

  7. Elongate summit calderas as Neogene paleostress indicators in Antarctica

    USGS Publications Warehouse

    Paulsen, T.S.; Wilson, T.J.

    2007-01-01

    The orientations and ages of elongate summit calderas on major polygenetic volcanoes were compiled to document Miocene to Pleistocene Sh (minimum horizontal stress) directions on the western and northern flanks of the West Antarctic rift system. Miocene to Pleistocene summit calderas along the western Ross Sea show relatively consistent ENE long axis trends, which are at a high angle to the Transantarctic Mountain Front and parallel to the N77ºE Sh direction at Cape Roberts. The elongation directions of many Miocene to Pleistocene summit calderas in Marie Byrd Land parallel the alignment of polygenetic volcanoes in which they occur, except several Pleistocene calderas with consistent NNE to NE trends. The overall pattern of elongate calderas in Marie Byrd Land is probably due to a combination of structurally controlled orientations and regional stress fields in which Sh is oriented NNE to NE at a moderate to high angle to the trace of the West Antarctic rift system.

  8. An Elongated Tetrakaidecahedron Model for Open-Celled Foams

    NASA Technical Reports Server (NTRS)

    Sullivan, Roy M.; Ghosn, Louis J.; Lerch, Bradley A.

    2007-01-01

    A micro-mechanics model for non-isotropic, open-celled foams is developed using an elongated tetrakaidecahedron (Kelvin model) as the repeating unit cell. The micro-mechanics model employs an elongated Kelvin model geometry which is more general than that employed by previous authors. Assuming the cell edges possess axial and bending rigidity, the mechanics of deformation of the elongated tetrakaidecahedron lead to a set of equations for the Young's modulus, Poisson's ratio and strength of the foam in the principal material directions. These equations are written as a function of the cell edge lengths and cross-section properties, the inclination angle and the strength and stiffness of the solid material. The model is applied to predict the strength and stiffness of several polymeric foams. Good agreement is observed between the model results and the experimental measurements.

  9. Wnt5a is essential for intestinal elongation in mice

    PubMed Central

    Cervantes, Sara; Yamaguchi, Terry P.; Hebrok, Matthias

    2009-01-01

    Summary Morphogenesis of the mammalian small intestine entails extensive elongation and folding of the primitive gut into a tightly coiled digestive tube. Surprisingly, little is known about the cellular and molecular mechanisms that mediate the morphological aspects of small intestine formation. Here, we demonstrate that Wnt5a, a member of the Wnt family of secreted proteins, is essential for the development and elongation of the small intestine from the midgut region. We found that the small intestine in mice lacking Wnt5a was dramatically shortened and duplicated, forming a bifurcated lumen instead of a single tube. In addition, cell proliferation was reduced and re-intercalation of post-mitotic cells into the elongating gut tube epithelium was disrupted. Thus, our study demonstrates that Wnt5a functions as a critical regulator of midgut formation and morphogenesis in mammals. PMID:19100728

  10. Protein Elongation, Co-translational Folding and Targeting.

    PubMed

    Rodnina, Marina V; Wintermeyer, Wolfgang

    2016-05-22

    The elongation phase of protein synthesis defines the overall speed and fidelity of protein synthesis and affects protein folding and targeting. The mechanisms of reactions taking place during translation elongation remain important questions in understanding ribosome function. The ribosome-guided by signals in the mRNA-can recode the genetic information, resulting in alternative protein products. Co-translational protein folding and interaction of ribosomes and emerging polypeptides with associated protein biogenesis factors determine the quality and localization of proteins. In this review, we summarize recent findings on mechanisms of translation elongation in bacteria, including decoding and recoding, peptide bond formation, tRNA-mRNA translocation, co-translational protein folding, interaction with protein biogenesis factors and targeting of ribosomes synthesizing membrane proteins to the plasma membrane. The data provide insights into how the ribosome shapes composition and quality of the cellular proteome. PMID:27038507

  11. Progressive cis-inhibition of telomerase upon telomere elongation.

    PubMed Central

    Marcand, S; Brevet, V; Gilson, E

    1999-01-01

    In yeast, the constant length of telomeric DNA results from a negative regulation of telomerase by the telomere itself. Here we follow the return to equilibrium of an abnormally shortened telomere. We observe that telomere elongation is restricted to a few base pairs per generation and that its rate decreases progressively with increasing telomere length. In contrast, in the absence of telomerase or in the presence of an over-elongated telomere, the degradation rate linked to the succession of generations appears to be constant, i.e. independent of telomere length. Together, these results indicate that telomerase is gradually inhibited at its site of action by the elongating telomere. The implications of this finding for the dynamics of telomere length regulation are discussed in this study. PMID:10369690

  12. Electrical conductivity and rheology of carbon black composites under elongation

    NASA Astrophysics Data System (ADS)

    Starý, Zdeněk

    2015-04-01

    Electrical properties of conductive polymer composites are governed by filler particle structures which are formed in the material during the mixing. Therefore, knowledge of the behavior of conductive particle structures under defined conditions of deformation is necessary to produce materials with balanced electrical and rheological properties. Whereas the electrical conductivity evolution under shear can be nowadays studied even with the commercial rheometers, the investigations under elongation were not performed up to now. In this work simultaneous electrical and rheological measurements in elongation on polystyrene/carbon black composites are introduced. Such kind of experiment can help in understanding the relationships between processing conditions and properties of conductive polymer composites.

  13. Leaf development: a cellular perspective

    PubMed Central

    Kalve, Shweta; De Vos, Dirk; Beemster, Gerrit T. S.

    2014-01-01

    Through its photosynthetic capacity the leaf provides the basis for growth of the whole plant. In order to improve crops for higher productivity and resistance for future climate scenarios, it is important to obtain a mechanistic understanding of leaf growth and development and the effect of genetic and environmental factors on the process. Cells are both the basic building blocks of the leaf and the regulatory units that integrate genetic and environmental information into the developmental program. Therefore, to fundamentally understand leaf development, one needs to be able to reconstruct the developmental pathway of individual cells (and their progeny) from the stem cell niche to their final position in the mature leaf. To build the basis for such understanding, we review current knowledge on the spatial and temporal regulation mechanisms operating on cells, contributing to the formation of a leaf. We focus on the molecular networks that control exit from stem cell fate, leaf initiation, polarity, cytoplasmic growth, cell division, endoreduplication, transition between division and expansion, expansion and differentiation and their regulation by intercellular signaling molecules, including plant hormones, sugars, peptides, proteins, and microRNAs. We discuss to what extent the knowledge available in the literature is suitable to be applied in systems biology approaches to model the process of leaf growth, in order to better understand and predict leaf growth starting with the model species Arabidopsis thaliana. PMID:25132838

  14. 7 CFR 29.2528 - Leaf.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ...-Cured Tobacco (u.s. Types 22, 23, and Foreign Type 96) § 29.2528 Leaf. Whole, unstemmed leaf. Leaf, when applied to tobacco in strip form, shall describe the divided unit of a whole leaf. ... 7 Agriculture 2 2010-01-01 2010-01-01 false Leaf. 29.2528 Section 29.2528 Agriculture...

  15. Leaf Dynamics of Panicum maximum under Future Climatic Changes.

    PubMed

    Britto de Assis Prado, Carlos Henrique; Haik Guedes de Camargo-Bortolin, Lívia; Castro, Érique; Martinez, Carlos Alberto

    2016-01-01

    Panicum maximum Jacq. 'Mombaça' (C4) was grown in field conditions with sufficient water and nutrients to examine the effects of warming and elevated CO2 concentrations during the winter. Plants were exposed to either the ambient temperature and regular atmospheric CO2 (Control); elevated CO2 (600 ppm, eC); canopy warming (+2°C above regular canopy temperature, eT); or elevated CO2 and canopy warming (eC+eT). The temperatures and CO2 in the field were controlled by temperature free-air controlled enhancement (T-FACE) and mini free-air CO2 enrichment (miniFACE) facilities. The most green, expanding, and expanded leaves and the highest leaf appearance rate (LAR, leaves day(-1)) and leaf elongation rate (LER, cm day(-1)) were observed under eT. Leaf area and leaf biomass were higher in the eT and eC+eT treatments. The higher LER and LAR without significant differences in the number of senescent leaves could explain why tillers had higher foliage area and leaf biomass in the eT treatment. The eC treatment had the lowest LER and the fewest expanded and green leaves, similar to Control. The inhibitory effect of eC on foliage development in winter was indicated by the fewer green, expanded, and expanding leaves under eC+eT than eT. The stimulatory and inhibitory effects of the eT and eC treatments, respectively, on foliage raised and lowered, respectively, the foliar nitrogen concentration. The inhibition of foliage by eC was confirmed by the eC treatment having the lowest leaf/stem biomass ratio and by the change in leaf biomass-area relationships from linear or exponential growth to rectangular hyperbolic growth under eC. Besides, eC+eT had a synergist effect, speeding up leaf maturation. Therefore, with sufficient water and nutrients in winter, the inhibitory effect of elevated CO2 on foliage could be partially offset by elevated temperatures and relatively high P. maximum foliage production could be achieved under future climatic change. PMID:26894932

  16. Leaf Dynamics of Panicum maximum under Future Climatic Changes

    PubMed Central

    Britto de Assis Prado, Carlos Henrique; Haik Guedes de Camargo-Bortolin, Lívia; Castro, Érique; Martinez, Carlos Alberto

    2016-01-01

    Panicum maximum Jacq. ‘Mombaça’ (C4) was grown in field conditions with sufficient water and nutrients to examine the effects of warming and elevated CO2 concentrations during the winter. Plants were exposed to either the ambient temperature and regular atmospheric CO2 (Control); elevated CO2 (600 ppm, eC); canopy warming (+2°C above regular canopy temperature, eT); or elevated CO2 and canopy warming (eC+eT). The temperatures and CO2 in the field were controlled by temperature free-air controlled enhancement (T-FACE) and mini free-air CO2 enrichment (miniFACE) facilities. The most green, expanding, and expanded leaves and the highest leaf appearance rate (LAR, leaves day-1) and leaf elongation rate (LER, cm day-1) were observed under eT. Leaf area and leaf biomass were higher in the eT and eC+eT treatments. The higher LER and LAR without significant differences in the number of senescent leaves could explain why tillers had higher foliage area and leaf biomass in the eT treatment. The eC treatment had the lowest LER and the fewest expanded and green leaves, similar to Control. The inhibitory effect of eC on foliage development in winter was indicated by the fewer green, expanded, and expanding leaves under eC+eT than eT. The stimulatory and inhibitory effects of the eT and eC treatments, respectively, on foliage raised and lowered, respectively, the foliar nitrogen concentration. The inhibition of foliage by eC was confirmed by the eC treatment having the lowest leaf/stem biomass ratio and by the change in leaf biomass-area relationships from linear or exponential growth to rectangular hyperbolic growth under eC. Besides, eC+eT had a synergist effect, speeding up leaf maturation. Therefore, with sufficient water and nutrients in winter, the inhibitory effect of elevated CO2 on foliage could be partially offset by elevated temperatures and relatively high P. maximum foliage production could be achieved under future climatic change. PMID:26894932

  17. Posterior elongation in the annelid Platynereis dumerilii involves stem cells molecularly related to primordial germ cells.

    PubMed

    Gazave, Eve; Béhague, Julien; Laplane, Lucie; Guillou, Aurélien; Préau, Laetitia; Demilly, Adrien; Balavoine, Guillaume; Vervoort, Michel

    2013-10-01

    Like most bilaterian animals, the annelid Platynereis dumerilii generates the majority of its body axis in an anterior to posterior temporal progression with new segments added sequentially. This process relies on a posterior subterminal proliferative body region, known as the "segment addition zone" (SAZ). We explored some of the molecular and cellular aspects of posterior elongation in Platynereis, in particular to test the hypothesis that the SAZ contains a specific set of stem cells dedicated to posterior elongation. We cloned and characterized the developmental expression patterns of orthologs of 17 genes known to be involved in the formation, behavior, or maintenance of stem cells in other metazoan models. These genes encode RNA-binding proteins (e.g., tudor, musashi, pumilio) or transcription factors (e.g., myc, id, runx) widely conserved in eumetazoans. Most of these genes are expressed both in the migrating primordial germ cells and in overlapping ring-like patterns in the SAZ, similar to some previously analyzed genes (piwi, vasa). The SAZ patterns are coincident with the expression of proliferation markers cyclin B and PCNA. EdU pulse and chase experiments suggest that new segments are produced through many rounds of divisions from small populations of teloblast-like posterior stem cells. The shared molecular signature between primordial germ cells and posterior stem cells in Platynereis thus corresponds to an ancestral "stemness" program. PMID:23891818

  18. Vertex-element models for anisotropic growth of elongated plant organs

    PubMed Central

    Fozard, John A.; Lucas, Mikaël; King, John R.; Jensen, Oliver E.

    2013-01-01

    New tools are required to address the challenge of relating plant hormone levels, hormone responses, wall biochemistry and wall mechanical properties to organ-scale growth. Current vertex-based models (applied in other contexts) can be unsuitable for simulating the growth of elongated organs such as roots because of the large aspect ratio of the cells, and these models fail to capture the mechanical properties of cell walls in sufficient detail. We describe a vertex-element model which resolves individual cells and includes anisotropic non-linear viscoelastic mechanical properties of cell walls and cell division whilst still being computationally efficient. We show that detailed consideration of the cell walls in the plane of a 2D simulation is necessary when cells have large aspect ratio, such as those in the root elongation zone of Arabidopsis thaliana, in order to avoid anomalous transverse swelling. We explore how differences in the mechanical properties of cells across an organ can result in bending and how cellulose microfibril orientation affects macroscale growth. We also demonstrate that the model can be used to simulate growth on realistic geometries, for example that of the primary root apex, using moderate computational resources. The model shows how macroscopic root shape can be sensitive to fine-scale cellular geometries. PMID:23847638

  19. Quadratic elongation: A quantitative measure of distortion in coordination polyhedra

    USGS Publications Warehouse

    Robinson, Kelly F.; Gibbs, G.V.; Ribbe, P.H.

    1971-01-01

    Quadratic elongation and the variance of bond angles are linearly correlated for distorted octahedral and tetrahedral coordination complexes, both of which show variations in bond length and bond angle. The quadratic elonga tion is dimensionless, giving a quantitative measure of polyhedral distortion which is independent of the effective size of the polyhedron.

  20. Osteogenetic changes in elongated styloid processes of Eagle syndrome patients.

    PubMed

    Kim, Soung Min; Seo, Mi Hyun; Myoung, Hoon; Choi, Jin Young; Kim, Yeon Sook; Lee, Suk Keun

    2014-07-01

    Abnormal elongation of the styloid process, or Eagle syndrome, can be painful, and is associated with differential diagnoses including cranio-facial malformations and vasculo-neurological disturbances. The precise molecular mechanism leading to styloid process elongation is unknown. In this study, elongated styloid processes with periosteal fibrous ligament tissue were obtained from three patients with Eagle syndrome and examined by immunohistochemical methods using different antisera. In all cases, marked bony deposition was found at the apex of the styloid process. The osteogenetic proteins, such as osteonectin, osteocalcin, BMP-2, BMP-4, and RANKL were strongly positive by immunohistochemistry in both the ligament fibers and the periosteal membrane attached to the styloid process apex. Staining for protective proteins, HO-1, HSP-70, and HSP-90 was also positive. These results suggest that styloid process elongation is related to increased expression of osteogenetic and protective proteins. Therefore, we propose that Eagle syndrome results from a protective response to increased tensile stress in the ligament attached to the styloid process, which could also signal osteogenetic protein expression in the periosteal fibrous tissue. PMID:24161467

  1. Quantitative regulation of FLC via coordinated transcriptional initiation and elongation

    PubMed Central

    Wu, Zhe; Ietswaart, Robert; Liu, Fuquan; Yang, Hongchun; Howard, Martin; Dean, Caroline

    2016-01-01

    The basis of quantitative regulation of gene expression is still poorly understood. In Arabidopsis thaliana, quantitative variation in expression of FLOWERING LOCUS C (FLC) influences the timing of flowering. In ambient temperatures, FLC expression is quantitatively modulated by a chromatin silencing mechanism involving alternative polyadenylation of antisense transcripts. Investigation of this mechanism unexpectedly showed that RNA polymerase II (Pol II) occupancy changes at FLC did not reflect RNA fold changes. Mathematical modeling of these transcriptional dynamics predicted a tight coordination of transcriptional initiation and elongation. This prediction was validated by detailed measurements of total and chromatin-bound FLC intronic RNA, a methodology appropriate for analyzing elongation rate changes in a range of organisms. Transcription initiation was found to vary ∼25-fold with elongation rate varying ∼8- to 12-fold. Premature sense transcript termination contributed very little to expression differences. This quantitative variation in transcription was coincident with variation in H3K36me3 and H3K4me2 over the FLC gene body. We propose different chromatin states coordinately influence transcriptional initiation and elongation rates and that this coordination is likely to be a general feature of quantitative gene regulation in a chromatin context. PMID:26699513

  2. Molecular development of the mid-stage elongating cotton fiber

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Cotton fiber is one of the leading natural textile fibers and is the leading value added crop in the USA. The annual business revenue from the cotton industry exceeds $120 billion. The growth of the cotton fiber is divided into four unique, yet overlapping stages; initiation, elongation, secondary w...

  3. THE BRASSICA RAPA ELONGATED INTERNODE (EIN) GENE ENCODES PHYTOCHROME B

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The elongated internode (ein) mutation of Brassica rapa leads to a deficiency in immunochemically detectable phytochrome B. Molecular analysis of the PHYB gene from ein indicates a deletion in the flanking DNA 5' of the ATG start codon, which could interfere either with PHYB transcription or process...

  4. Molecular landscape of cotton fiber in early elongation

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Cotton fibers are the dominant source of natural fibers used in the textile industry and contribute significantly to the world economy. Adverse environmental conditions negatively affect fiber characteristics, especially when the fibers are in the elongation phase of development. Improvement in the...

  5. Effect of aglycon structure on saccharide elongation by cells.

    PubMed

    Kimura, Tamami; Kasuya, Maria Carmelita Z; Hatanaka, Kenichi; Matsuoka, Koji

    2015-02-01

    Alkyl N-acetyl-β-D-glucosaminide (GlcNAc primers) with different aglycon moieties were synthesized and used to determine the effect of the aglycon structure on cellular saccharide elongation. Dodecyl N-acetyl-β-D-glucosaminide (GlcNAc-C12), tridecan-7-yl N-acetyl-β-D-glucosaminide (GlcNAc-2C6), and pentacosan-13-yl N-acetyl-β-D-glucosaminide (GlcNAc-2C12) primers were synthesized by glycosylation of dodecan-1-ol, tridecan-7-ol, and pentacosan-13-ol, respectively, with peracetylglucosamine. These primers were introduced to mouse B16 melanoma cells to prepare glycolipids. After 48 h incubation, results showed that GlcNAc-C12 was elongated to give NeuAc-Gal-GlcNAc-C12. GlcNAc-2C6 was also elongated to afford Gal-GlcNAc-2C6 and NeuAc-Gal-GlcNAc-2C6. On the other hand, GlcNAc-2C12 primer was not elongated. Significantly, the results demonstrated that the amount of glycosylated product increased 1.5-times by modifying the aglycon structure of GlcNAc from C12 to 2 C6 despite having almost the same number of C-units. PMID:25676505

  6. Collisional diffusion in toroidal plasmas with elongation and triangularity

    SciTech Connect

    Martin, P.; Castro, E.; Haines, M. G.

    2007-05-15

    Collisional diffusion is analyzed for plasma tokamaks with different ellipticities and triangularities. Improved nonlinear equations for the families of magnetic surfaces are used here. Dimensionless average velocities are calculated as a function of the inductive electric field, elongation, triangularity, and Shafranov shift. Confinement has been found to depend significantly on triangularity.

  7. The artificial leaf.

    PubMed

    Nocera, Daniel G

    2012-05-15

    To convert the energy of sunlight into chemical energy, the leaf splits water via the photosynthetic process to produce molecular oxygen and hydrogen, which is in a form of separated protons and electrons. The primary steps of natural photosynthesis involve the absorption of sunlight and its conversion into spatially separated electron-hole pairs. The holes of this wireless current are captured by the oxygen evolving complex (OEC) of photosystem II (PSII) to oxidize water to oxygen. The electrons and protons produced as a byproduct of the OEC reaction are captured by ferrodoxin of photosystem I. With the aid of ferrodoxin-NADP(+) reductase, they are used to produce hydrogen in the form of NADPH. For a synthetic material to realize the solar energy conversion function of the leaf, the light-absorbing material must capture a solar photon to generate a wireless current that is harnessed by catalysts, which drive the four electron/hole fuel-forming water-splitting reaction under benign conditions and under 1 sun (100 mW/cm(2)) illumination. This Account describes the construction of an artificial leaf comprising earth-abundant elements by interfacing a triple junction, amorphous silicon photovoltaic with hydrogen- and oxygen-evolving catalysts made from a ternary alloy (NiMoZn) and a cobalt-phosphate cluster (Co-OEC), respectively. The latter captures the structural and functional attributes of the PSII-OEC. Similar to the PSII-OEC, the Co-OEC self-assembles upon oxidation of an earth-abundant metal ion from 2+ to 3+, may operate in natural water at room temperature, and is self-healing. The Co-OEC also activates H(2)O by a proton-coupled electron transfer mechanism in which the Co-OEC is increased by four hole equivalents akin to the S-state pumping of the Kok cycle of PSII. X-ray absorption spectroscopy studies have established that the Co-OEC is a structural relative of Mn(3)CaO(4)-Mn cubane of the PSII-OEC, where Co replaces Mn and the cubane is extended in a

  8. Binary asteroid population. 3. Secondary rotations and elongations

    NASA Astrophysics Data System (ADS)

    Pravec, P.; Scheirich, P.; Kušnirák, P.; Hornoch, K.; Galád, A.; Naidu, S. P.; Pray, D. P.; Világi, J.; Gajdoš, Š.; Kornoš, L.; Krugly, Yu. N.; Cooney, W. R.; Gross, J.; Terrell, D.; Gaftonyuk, N.; Pollock, J.; Husárik, M.; Chiorny, V.; Stephens, R. D.; Durkee, R.; Reddy, V.; Dyvig, R.; Vraštil, J.; Žižka, J.; Mottola, S.; Hellmich, S.; Oey, J.; Benishek, V.; Kryszczyńska, A.; Higgins, D.; Ries, J.; Marchis, F.; Baek, M.; Macomber, B.; Inasaridze, R.; Kvaratskhelia, O.; Ayvazian, V.; Rumyantsev, V.; Masi, G.; Colas, F.; Lecacheux, J.; Montaigut, R.; Leroy, A.; Brown, P.; Krzeminski, Z.; Molotov, I.; Reichart, D.; Haislip, J.; LaCluyze, A.

    2016-03-01

    We collected data on rotations and elongations of 46 secondaries of binary and triple systems among near-Earth, Mars-crossing and small main belt asteroids. 24 were found or are strongly suspected to be synchronous (in 1:1 spin-orbit resonance), and the other 22, generally on more distant and/or eccentric orbits, were found or are suggested to have asynchronous rotations. For 18 of the synchronous secondaries, we constrained their librational angles, finding that their long axes pointed to within 20° of the primary on most epochs. The observed anti-correlation of secondary synchroneity with orbital eccentricity and the limited librational angles agree with the theories by Ćuk and Nesvorný (Ćuk, M., Nesvorný, D. [2010]. Icarus 207, 732-743) and Naidu and Margot (Naidu, S.P., Margot, J.-L. [2015]. Astron. J. 149, 80). A reason for the asynchronous secondaries being on wider orbits than synchronous ones may be longer tidal circularization time scales at larger semi-major axes. The asynchronous secondaries show relatively fast spins; their rotation periods are typically < 10 h. An intriguing observation is a paucity of chaotic secondary rotations; with an exception of (35107) 1991 VH, the secondary rotations are single-periodic with no signs of chaotic rotation and their periods are constant on timescales from weeks to years. The secondary equatorial elongations show an upper limit of a2 /b2 ∼ 1.5 . The lack of synchronous secondaries with greater elongations appears consistent, considering uncertainties of the axis ratio estimates, with the theory by Ćuk and Nesvorný that predicts large regions of chaotic rotation in the phase space for a2 /b2 ≳√{ 2 } . Alternatively, secondaries may not form or stay very elongated in gravitational (tidal) field of the primary. It could be due to the secondary fission mechanism suggested by Jacobson and Scheeres (Jacobson, S.A., Scheeres, D.J. [2011]. Icarus 214, 161-178), as its efficiency is correlated with the

  9. Ethylene Inhibits Root Elongation during Alkaline Stress through AUXIN1 and Associated Changes in Auxin Accumulation1

    PubMed Central

    Li, Juan; Xu, Heng-Hao; Liu, Wen-Cheng; Zhang, Xiao-Wei; Lu, Ying-Tang

    2015-01-01

    Soil alkalinity causes major reductions in yield and quality of crops worldwide. The plant root is the first organ sensing soil alkalinity, which results in shorter primary roots. However, the mechanism underlying alkaline stress-mediated inhibition of root elongation remains to be further elucidated. Here, we report that alkaline conditions inhibit primary root elongation of Arabidopsis (Arabidopsis thaliana) seedlings by reducing cell division potential in the meristem zones and that ethylene signaling affects this process. The ethylene perception antagonist silver (Ag+) alleviated the inhibition of root elongation by alkaline stress. Moreover, the ethylene signaling mutants ethylene response1-3 (etr1-3), ethylene insensitive2 (ein2), and ein3-1 showed less reduction in root length under alkaline conditions, indicating a reduced sensitivity to alkalinity. Ethylene biosynthesis also was found to play a role in alkaline stress-mediated root inhibition; the ethylene overproducer1-1 mutant, which overproduces ethylene because of increased stability of 1-AMINOCYCLOPROPANE-1-CARBOXYLIC ACID SYNTHASE5, was hypersensitive to alkaline stress. In addition, the ethylene biosynthesis inhibitor cobalt (Co2+) suppressed alkaline stress-mediated inhibition of root elongation. We further found that alkaline stress caused an increase in auxin levels by promoting expression of auxin biosynthesis-related genes, but the increase in auxin levels was reduced in the roots of the etr1-3 and ein3-1 mutants and in Ag+/Co2+-treated wild-type plants. Additional genetic and physiological data showed that AUXIN1 (AUX1) was involved in alkaline stress-mediated inhibition of root elongation. Taken together, our results reveal that ethylene modulates alkaline stress-mediated inhibition of root growth by increasing auxin accumulation by stimulating the expression of AUX1 and auxin biosynthesis-related genes. PMID:26109425

  10. Transcriptome Sequencing and Analysis for Culm Elongation of the World's Largest Bamboo (Dendrocalamus sinicus).

    PubMed

    Cui, Kai; Wang, Haiying; Liao, Shengxi; Tang, Qi; Li, Li; Cui, Yongzhong; He, Yuan

    2016-01-01

    proteins that regarded as the main tool for capturing light of plants, implying stem photosynthesis plays a key role during culm elongation due to the unavailability of its leaf. By real-time quantitative PCR, the expression level of 6 unigenes was detected. The results showed the expression level of all genes accorded with the transcriptome data, which confirm the reliability of the transcriptome data. As we know, this is the first study underline the D. sinicus transcriptome, which will deepen the understanding of the molecular mechanisms of culm development. The results may help variety improvement and resource utilization of bamboos. PMID:27304219

  11. Transcriptome Sequencing and Analysis for Culm Elongation of the World’s Largest Bamboo (Dendrocalamus sinicus)

    PubMed Central

    Cui, Kai; Wang, Haiying; Liao, Shengxi; Tang, Qi; Li, Li; Cui, Yongzhong; He, Yuan

    2016-01-01

    proteins that regarded as the main tool for capturing light of plants, implying stem photosynthesis plays a key role during culm elongation due to the unavailability of its leaf. By real-time quantitative PCR, the expression level of 6 unigenes was detected. The results showed the expression level of all genes accorded with the transcriptome data, which confirm the reliability of the transcriptome data. As we know, this is the first study underline the D. sinicus transcriptome, which will deepen the understanding of the molecular mechanisms of culm development. The results may help variety improvement and resource utilization of bamboos. PMID:27304219

  12. Individual Leaf Development in Arabidopsis thaliana: a Stable Thermal‐time‐based Programme

    PubMed Central

    GRANIER, CHRISTINE; MASSONNET, CATHERINE; TURC, OLIVIER; MULLER, BERTRAND; CHENU, KARINE; TARDIEU, FRANÇOIS

    2002-01-01

    In crop species, the impact of temperature on plant development is classically modelled using thermal time. We examined whether this method could be used in a non‐crop species, Arabidopsis thaliana, to analyse the response to temperature of leaf initiation rate and of the development of two leaves of the rosette. The results confirmed the large plant‐to‐plant variability in the studied isogenic line of the Columbia ecotype: 100‐fold differences in leaf area among plants sown on the same date were commonly observed at a given date. These differences disappeared in mature leaves, suggesting that they were due to a variability in plant developmental stage. The whole population could therefore be represented by any group of synchronous plants labelled at the two‐leaf stage and followed during their development. Leaf initiation rate, duration of leaf expansion and maximal relative leaf expansion rate varied considerably among experiments performed at different temperatures (from 6 to 26 °C) but they were linearly related to temperature in the range 6–26 °C, with a common x‐intercept of 3 °C. Expressing time in thermal time with a threshold temperature of 3 °C unified the time courses of leaf initiation and of individual leaf development for plants grown at different temperatures and experimental conditions. The two leaves studied (leaf 2 and leaf 6) had a two‐phase development, with an exponential phase followed by a phase with decreasing relative elongation rate. Both phases had constant durations for a given leaf position if expressed in thermal time. Changes in temperature caused changes in both the rate of development and in the expansion rate which mutually compensated such that they had no consequence on leaf area at a given thermal time. The resulting model of leaf development was applied to ten experiments carried out in a glasshouse or in a growth chamber, with plants grown in soil or hydroponically. Because it predicts accurately the stage

  13. ADENYLATE CYCLASE REGULATES ELONGATION OF MAMMALIAN PRIMARY CILIA

    PubMed Central

    Ou, Young; Ruan, Yibing; Cheng, Min; Moser, Joanna J.; Rattner, Jerome B.; van der Hoorn, Frans A.

    2011-01-01

    The primary cilium is a non-motile microtubule-based structure that shares many similarities with the structures of flagella and motile cilia. It is well known that the length of flagella is under stringent control, but it is not known whether this is true for primary cilia. In this study, we found that the length of primary cilia in fibroblast-like synoviocytes, either in log phase culture or in quiescent state, was confined within a range. However, when lithium was added to the culture to a final concentration of 100 mM, primary cilia of synoviocytes grew beyond this range, elongating to a length that was on average approximately 3 times the length of untreated cilia. Lithium is a drug approved for treating bipolar disorder. We dissected the molecular targets of this drug, and observed that inhibition of adenylate cyclase III (ACIII) by specific inhibitors mimicked the effects of lithium on primary cilium elongation. Inhibition of GSK-3β by four different inhibitors did not induce primary cilia elongation. ACIII was found in primary cilia of a variety of cell types, and lithium treatment of these cell types led to their cilium elongation. Further, we demonstrate that different cell types displayed distinct sensitivities to the lithium treatment. However, in all cases examined primary cilia elongated as a result of lithium treatment. In particular, two neuronal cell types, rat PC-12 adrenal medulla cells and human astrocytes, developed long primary cilia when lithium was used at or close to the therapeutic relevant concentration (1–2 mM). These results suggest that the length of primary cilia is controlled, at least in part, by the ACIII-cAMP signaling pathway. PMID:19576885

  14. Adenylate cyclase regulates elongation of mammalian primary cilia

    SciTech Connect

    Ou, Young; Ruan, Yibing; Cheng, Min; Moser, Joanna J.; Rattner, Jerome B.; Hoorn, Frans A. van der

    2009-10-01

    The primary cilium is a non-motile microtubule-based structure that shares many similarities with the structures of flagella and motile cilia. It is well known that the length of flagella is under stringent control, but it is not known whether this is true for primary cilia. In this study, we found that the length of primary cilia in fibroblast-like synoviocytes, either in log phase culture or in quiescent state, was confined within a range. However, when lithium was added to the culture to a final concentration of 100 mM, primary cilia of synoviocytes grew beyond this range, elongating to a length that was on average approximately 3 times the length of untreated cilia. Lithium is a drug approved for treating bipolar disorder. We dissected the molecular targets of this drug, and observed that inhibition of adenylate cyclase III (ACIII) by specific inhibitors mimicked the effects of lithium on primary cilium elongation. Inhibition of GSK-3{beta} by four different inhibitors did not induce primary cilia elongation. ACIII was found in primary cilia of a variety of cell types, and lithium treatment of these cell types led to their cilium elongation. Further, we demonstrate that different cell types displayed distinct sensitivities to the lithium treatment. However, in all cases examined primary cilia elongated as a result of lithium treatment. In particular, two neuronal cell types, rat PC-12 adrenal medulla cells and human astrocytes, developed long primary cilia when lithium was used at or close to the therapeutic relevant concentration (1-2 mM). These results suggest that the length of primary cilia is controlled, at least in part, by the ACIII-cAMP signaling pathway.

  15. Exserohilum Leaf Spot on Tigergrass

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Tigergrass (Thysanolaena maxima (Roxb.) Kuntze ) is a popular ornamental grass grown throughout landscapes in South Florida. In the summer of 2006, a leaf spot was observed on tigergrass in the landscape and a commercial nursery in Homestead, FL. The causal agent of the leaf spot was isolated, cha...

  16. How to pattern a leaf

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Leaf development presents a tremendous resource for tackling the question of patterning in biology. Leaves can be simple or highly dissected. They may have elaborated parts such as the tendrils of a pea leaf or the rolled blade of a carnivorous pitcher plant. Despite the variation in size, shape, an...

  17. Leaf Epicuticular Waxes of the Eceriferum Mutants in Arabidopsis.

    PubMed Central

    Jenks, M. A.; Tuttle, H. A.; Eigenbrode, S. D.; Feldmann, K. A.

    1995-01-01

    Wild-type Arabidopsis leaf epicuticular wax (EW) occurs as a smooth layer over the epidermal surface, whereas stem EW has a crystalline microstructure. Wild-type EW load was more than 10-fold lower on leaves than on stems. Compared with the EW on wild-type stems, EW on wild-type leaves had a much higher proportion of their total EW load in the form of alkanes and 1-alcohols; a large reduction in secondary alcohols, ketones, and esters; and a chain-length distribution for major EW classes that was skewed toward longer lengths. The eceriferum (cer) mutations often differentially affected leaf and stem EW chemical compositions. For example, the cer2 mutant EW phenotype was expressed on the stem but not on the leaf. Compared to wild type, the amount of primary alcohols on cer9 mutants was reduced on leaves but elevated on stems, whereas an opposite differential effect for primary alcohols was observed on cer16 leaves and stems. Putative functions for CER gene products are discussed. The CER4 and CER6 gene products may be involved in fatty aldehyde reduction and C26 fatty acylcoenzyme A elongation, respectively. CER1, CER8, CER9, and CER16 gene products may be involved in EW substrate transfer. The CER3 gene product may be involved in release of fatty acids from elongase complexes. CER2 gene product may have regulatory functions. PMID:12228482

  18. Leaf-inhabiting genera of the Gnomoniaceae, Diaporthales

    PubMed Central

    Sogonov, M.V.; Castlebury, L.A.; Rossman, A.Y.; Mejía, L.C.; White, J.F.

    2008-01-01

    The Gnomoniaceae are characterised by ascomata that are generally immersed, solitary, without a stroma, or aggregated with a rudimentary stroma, in herbaceous plant material especially in leaves, twigs or stems, but also in bark or wood. The ascomata are black, soft-textured, thin-walled, and pseudoparenchymatous with one or more central or eccentric necks. The asci usually have a distinct apical ring. The Gnomoniaceae includes species having ascospores that are small, mostly less than 25 μm long, although some are longer, and range in septation from non-septate to one-septate, rarely multi-septate. Molecular studies of the Gnomoniaceae suggest that the traditional classification of genera based on characteristics of the ascomata such as position of the neck and ascospores such as septation have resulted in genera that are not monophyletic. In this paper the concepts of the leaf-inhabiting genera in the Gnomoniaceae are reevaluated using multiple genes, specifically nrLSU, translation elongation factor 1-alpha (tef1-α), and RNA polymerase II second largest subunit (rpb2) for 64 isolates. ITS sequences were generated for 322 isolates. Six genera of leaf-inhabiting Gnomoniaceae are defined based on placement of their type species within the multigene phylogeny. The new monotypic genus Ambarignomonia is established for an unusual species, A. petiolorum. A key to 59 species of leaf-inhabiting Gnomoniaceae is presented and 22 species of Gnomoniaceae are described and illustrated. PMID:19287541

  19. The control of tomato fruit elongation orchestrated by sun, ovate and fs8.1 in a wild relative of tomato.

    PubMed

    Wu, Shan; Clevenger, Josh P; Sun, Liang; Visa, Sofia; Kamiya, Yuji; Jikumaru, Yusuke; Blakeslee, Joshua; van der Knaap, Esther

    2015-09-01

    Within the cultivated tomato germplasm, sun, ovate and fs8.1 are the three predominant QTLs controlling fruit elongation. Although SUN and OVATE have been cloned, their role in plant growth and development are not well understood. To compare and contrast the effects of the three QTLs in a homogeneous background, we developed near isogenic lines (NILs) in the wild species Solanum pimpinellifolium LA1589 background. We carried out detailed morphological characterization of reproductive and vegetative organs in the single, double and triple NILs and determined the epistatic interactions of the three loci affecting fruit shape. The phenotypic evaluations demonstrated that the three loci regulate unique aspects of ovary and fruit elongation and in different temporal manners. The strongest effect on organ shape was caused by sun. In addition to fruit shape, sun also affected leaf and sepal elongation and stem thickness. The synergistic interaction between sun and ovate or fs8.1 suggested that the pathways involving SUN, OVATE and the gene(s) underlying fs8.1 may converge at a common node. The results of an extensive profiling analysis suggested that the degree of fruit elongation was not related to the accumulation of any of the classical hormones. PMID:26259178

  20. Modelling changes in leaf shape prior to phyllode acquisition in Acacia mangium Willd. seedlings.

    PubMed

    Leroy, Céline; Heuret, Patrick

    2008-02-01

    The aim of this study was to characterise changes in leaf shape prior to phyllode acquisition along the axes of Acacia mangium seedlings. The study area was located in North Lampung (South Sumatra, Indonesia), where these trees belong to a naturally regenerated stand. A total of 173 seedlings, less than three months old, were described node by node. Leaf shape and leaf length were recorded and the way in which one leaf type succeeded another was modelled using a hidden semi-Markov chain composed of seven states. The phyllotactical pattern was studied using another sample of forty 6-month-old seedlings. The results indicate (i) the existence of successive zones characterised by one or a combination of leaf types, and (ii) that phyllode acquisition seems to be accompanied by a change in the phyllotactical pattern. The concepts of juvenility and heteroblasty, as well as potential applications for taxonomy are discussed. PMID:18241805

  1. Mutations in the gene for the red/far-red light receptor phytochrome B alter cell elongation and physiological responses throughout Arabidopsis development.

    PubMed Central

    Reed, J W; Nagpal, P; Poole, D S; Furuya, M; Chory, J

    1993-01-01

    Phytochromes are a family of plant photoreceptors that mediate physiological and developmental responses to changes in red and far-red light conditions. In Arabidopsis, there are genes for at least five phytochrome proteins. These photoreceptors control such responses as germination, stem elongation, flowering, gene expression, and chloroplast and leaf development. However, it is not known which red light responses are controlled by which phytochrome species, or whether the different phytochromes have overlapping functions. We report here that previously described hy3 mutants have mutations in the gene coding for phytochrome B (PhyB). These are the first mutations shown to lie in a plant photoreceptor gene. A number of tissues are abnormally elongated in the hy3(phyB) mutants, including hypocotyls, stems, petioles, and root hairs. In addition, the mutants flower earlier than the wild type, and they accumulate less chlorophyll. PhyB thus controls Arabidopsis development at numerous stages and in multiple tissues. PMID:8453299

  2. Proteomic Analysis Reveals the Leaf Color Regulation Mechanism in Chimera Hosta "Gold Standard" Leaves.

    PubMed

    Yu, Juanjuan; Zhang, Jinzheng; Zhao, Qi; Liu, Yuelu; Chen, Sixue; Guo, Hongliang; Shi, Lei; Dai, Shaojun

    2016-01-01

    Leaf color change of variegated leaves from chimera species is regulated by fine-tuned molecular mechanisms. Hosta "Gold Standard" is a typical chimera Hosta species with golden-green variegated leaves, which is an ideal material to investigate the molecular mechanisms of leaf variegation. In this study, the margin and center regions of young and mature leaves from Hosta "Gold Standard", as well as the leaves from plants after excess nitrogen fertilization were studied using physiological and comparative proteomic approaches. We identified 31 differentially expressed proteins in various regions and development stages of variegated leaves. Some of them may be related to the leaf color regulation in Hosta "Gold Standard". For example, cytosolic glutamine synthetase (GS1), heat shock protein 70 (Hsp70), and chloroplastic elongation factor G (cpEF-G) were involved in pigment-related nitrogen synthesis as well as protein synthesis and processing. By integrating the proteomics data with physiological results, we revealed the metabolic patterns of nitrogen metabolism, photosynthesis, energy supply, as well as chloroplast protein synthesis, import and processing in various leaf regions at different development stages. Additionally, chloroplast-localized proteoforms involved in nitrogen metabolism, photosynthesis and protein processing implied that post-translational modifications were crucial for leaf color regulation. These results provide new clues toward understanding the mechanisms of leaf color regulation in variegated leaves. PMID:27005614

  3. Proteomic Analysis Reveals the Leaf Color Regulation Mechanism in Chimera Hosta “Gold Standard” Leaves

    PubMed Central

    Yu, Juanjuan; Zhang, Jinzheng; Zhao, Qi; Liu, Yuelu; Chen, Sixue; Guo, Hongliang; Shi, Lei; Dai, Shaojun

    2016-01-01

    Leaf color change of variegated leaves from chimera species is regulated by fine-tuned molecular mechanisms. Hosta “Gold Standard” is a typical chimera Hosta species with golden-green variegated leaves, which is an ideal material to investigate the molecular mechanisms of leaf variegation. In this study, the margin and center regions of young and mature leaves from Hosta “Gold Standard”, as well as the leaves from plants after excess nitrogen fertilization were studied using physiological and comparative proteomic approaches. We identified 31 differentially expressed proteins in various regions and development stages of variegated leaves. Some of them may be related to the leaf color regulation in Hosta “Gold Standard”. For example, cytosolic glutamine synthetase (GS1), heat shock protein 70 (Hsp70), and chloroplastic elongation factor G (cpEF-G) were involved in pigment-related nitrogen synthesis as well as protein synthesis and processing. By integrating the proteomics data with physiological results, we revealed the metabolic patterns of nitrogen metabolism, photosynthesis, energy supply, as well as chloroplast protein synthesis, import and processing in various leaf regions at different development stages. Additionally, chloroplast-localized proteoforms involved in nitrogen metabolism, photosynthesis and protein processing implied that post-translational modifications were crucial for leaf color regulation. These results provide new clues toward understanding the mechanisms of leaf color regulation in variegated leaves. PMID:27005614

  4. Leaf hydraulics II: vascularized tissues.

    PubMed

    Rockwell, Fulton E; Holbrook, N Michele; Stroock, Abraham D

    2014-01-01

    Current models of leaf hydration employ an Ohm's law analogy of the leaf as an ideal capacitor, neglecting the resistance to flow between cells, or treat the leaf as a plane sheet with a source of water at fixed potential filling the mid-plane, neglecting the discrete placement of veins as well as their resistance. We develop a model of leaf hydration that considers the average conductance of the vascular network to a representative areole (region bounded by the vascular network), and represent the volume of tissue within the areole as a poroelastic composite of cells and air spaces. Solutions to the 3D flow problem are found by numerical simulation, and these results are then compared to 1D models with exact solutions for a range of leaf geometries, based on a survey of temperate woody plants. We then show that the hydration times given by these solutions are well approximated by a sum of the ideal capacitor and plane sheet times, representing the time for transport through the vasculature and tissue respectively. We then develop scaling factors relating this approximate solution to the 3D model, and examine the dependence of these scaling factors on leaf geometry. Finally, we apply a similar strategy to reduce the dimensions of the steady state problem, in the context of peristomatal transpiration, and consider the relation of transpirational gradients to equilibrium leaf water potential measurements. PMID:24012489

  5. Accumulation of motile elongated micro-organisms in turbulence

    NASA Astrophysics Data System (ADS)

    Zhan, Caijuan; Sardina, Gaetano; Lushi, Enkeleida; Brandt, Luca

    2014-01-01

    We study the effect of turbulence on marine life by performing numerical simulations of motile microorganisms, modelled as prolate spheroids, in isotropic homogeneous turbulence. We show that the clustering and patchiness observed in laminar flows, linear shear and vortex flows, are significantly reduced in a three-dimensional turbulent flow mainly because of the complex topology; elongated micro-orgamisms show some level of clustering in the case of swimmers without any preferential alignment whereas spherical swimmers remain uniformly distributed. Micro-organisms with one preferential swimming direction (e.g. gyrotaxis) still show significant clustering if spherical in shape, whereas prolate swimmers remain more uniformly distributed. Due to their large sensitivity to the local shear, these elongated swimmers react slower to the action of vorticity and gravity and therefore do not have time to accumulate in a turbulent flow. These results show how purely hydrodynamic effects can alter the ecology of microorganisms that can vary their shape and their preferential orientation.

  6. Enhanced delivery of nano- and submicron particles using elongated microparticles.

    PubMed

    Raphael, Anthony P; Sisney, John P; Liu, David C; Prow, Tarl W

    2015-01-01

    Nanodermatology is a rapidly emerging field of study receiving significant interest because of its potential application in the prevention and treatment of skin diseases. However, nanoparticulate penetration into and through the skin is not feasible through topical application alone. Many physical and chemical approaches have been developed to enhance particulate penetration into skin. The most successful have been physical penetration enhancers. We have found that elongated microparticles can significantly improve topical nano- and microsphere delivery in an in vivo porcine model. The delivery efficiency was inversely related to the diameter of the payload. These data support a role for elongated microparticle enhanced delivery of nano- and submicron particulate cosmeceutical or therapeutic applications. PMID:25176162

  7. Quantifying elongation rhythm during full-length protein synthesis.

    PubMed

    Rosenblum, Gabriel; Chen, Chunlai; Kaur, Jaskiran; Cui, Xiaonan; Zhang, Haibo; Asahara, Haruichi; Chong, Shaorong; Smilansky, Zeev; Goldman, Yale E; Cooperman, Barry S

    2013-07-31

    Pauses regulate the rhythm of ribosomal protein synthesis. Mutations disrupting even minor pauses can give rise to improperly formed proteins and human disease. Such minor pauses are difficult to characterize by ensemble methods, but can be readily examined by single-molecule (sm) approaches. Here we use smFRET to carry out real-time monitoring of the expression of a full-length protein, the green fluorescent protein variant Emerald GFP. We demonstrate significant correlations between measured elongation rates and codon and isoacceptor tRNA usage, and provide a quantitative estimate of the effect on elongation rate of replacing a codon recognizing an abundant tRNA with a synonymous codon cognate to a rarer tRNA. Our results suggest that tRNA selection plays an important general role in modulating the rates and rhythms of protein synthesis, potentially influencing simultaneous co-translational processes such as folding and chemical modification. PMID:23822614

  8. Kinetics of protein fibrillation controlled by fibril elongation.

    PubMed

    Kashchiev, Dimo

    2014-09-01

    Numerous proteins have the ability to assemble into fibrillar aggregates which are of great interest, because they feature in scores of human diseases and many technological products. In the present work, we analyze the kinetics of protein fibrillation when the process is governed solely by elongation of initially appeared fibrils in the protein solution. We derive exact expressions for the time dependences of the fibrillation degree, the concentration of monomeric protein in the solution, and the average fibril size. Furthermore, we present formulas for the initial fibrillation rate and the half-fibrillation time in terms of experimentally controllable quantities. The results obtained provide a mechanistic insight into the kinetics of protein fibrillation mediated by fibril elongation. We confront theory with experiment and find that it allows a good description of available experimental data for fibrillation of the Alzheimer's disease-associated protein Aβ(1-40) and the yeast prion protein Sup35. PMID:24753319

  9. TERRA promotes telomerase-mediated telomere elongation in Schizosaccharomyces pombe.

    PubMed

    Moravec, Martin; Wischnewski, Harry; Bah, Amadou; Hu, Yan; Liu, Na; Lafranchi, Lorenzo; King, Megan C; Azzalin, Claus M

    2016-07-01

    Telomerase-mediated telomere elongation provides cell populations with the ability to proliferate indefinitely. Telomerase is capable of recognizing and extending the shortest telomeres in cells; nevertheless, how this mechanism is executed remains unclear. Here, we show that, in the fission yeast Schizosaccharomyces pombe, shortened telomeres are highly transcribed into the evolutionarily conserved long noncoding RNA TERRA A fraction of TERRA produced upon telomere shortening is polyadenylated and largely devoid of telomeric repeats, and furthermore, telomerase physically interacts with this polyadenylated TERRA in vivo We also show that experimentally enhanced transcription of a manipulated telomere promotes its association with telomerase and concomitant elongation. Our data represent the first direct evidence that TERRA stimulates telomerase recruitment and activity at chromosome ends in an organism with human-like telomeres. PMID:27154402

  10. Elongated solid electrolyte cell configurations and flexible connections therefor

    DOEpatents

    Reichner, Philip

    1989-01-01

    A flexible, high temperature, solid oxide electrolyte electrochemical cell stack configuration is made, comprising a plurality of flattened, elongated, connected cell combinations 1, each cell combination containing an interior electrode 2 having a top surface and a plurality of interior gas feed conduits 3, through its axial length, electrolyte 5 contacting the interior electrode and exterior electrode 8 contacting electrolyte, where a major portion of the air electrode top surface 7 is covered by interconnection material 6, and where each cell has at least one axially elongated, electronically conductive, flexible, porous, metal fiber felt material 9 in electronic connection with the air electrode 2 through contact with a major portion of the interconnection material 6, the metal fiber felt being effective as a shock absorbent body between the cells.

  11. Noise regulation and symmetry breaking during vertebrate body elongation

    NASA Astrophysics Data System (ADS)

    Emonet, Thierry; Das, Dipjyoti; Holley, Scott A.

    Elongation of the vertebrate body axis is driven by collective cell migration and cell proliferation at the posteriorly advancing embryonic tailbud. Within the Zebrafish tailbud an ordered stream of cells symmetrically bifurcates to form the left and right halves of the presomitic mesoderm. Maintaining bilateral symmetry during this process is critical to avoid catastrophic spine deformation. Using direct comparison between experimental data and a simple model of cell migration we identified the dynamic regulation of the noise in the direction of motion of individual cells as a critical factor in maintaining symmetric cell flow. Genetic perturbations that reduced noise led to body axis deformation whereas an increase in noise led to retarded elongation as predicted by our model.

  12. Elongated solid electrolyte cell configurations and flexible connections therefor

    DOEpatents

    Reichner, P.

    1989-10-17

    A flexible, high temperature, solid oxide electrolyte electrochemical cell stack configuration is made, comprising a plurality of flattened, elongated, connected cell combinations, each cell combination containing an interior electrode having a top surface and a plurality of interior gas feed conduits, through its axial length, electrolyte contacting the interior electrode and exterior electrode contacting electrolyte, where a major portion of the air electrode top surface is covered by interconnection material, and where each cell has at least one axially elongated, electronically conductive, flexible, porous, metal fiber felt material in electronic connection with the air electrode through contact with a major portion of the interconnection material, the metal fiber felt being effective as a shock absorbent body between the cells. 4 figs.

  13. Visualizing the elongated vortices in γ -Ga nanostrips

    NASA Astrophysics Data System (ADS)

    Zhang, Hui-Min; Li, Zi-Xiang; Peng, Jun-Ping; Song, Can-Li; Guan, Jia-Qi; Li, Zhi; Wang, Lili; He, Ke; Ji, Shuai-Hua; Chen, Xi; Yao, Hong; Ma, Xu-Cun; Xue, Qi-Kun

    2016-01-01

    We study the magnetic response of superconducting γ -Ga via low temperature scanning tunneling microscopy and spectroscopy. The magnetic vortex cores rely substantially on the Ga geometry, and exhibit an unexpectedly large axial elongation with aspect ratio up to 40 in rectangular Ga nanostrips (width l <100 nm). This is in stark contrast with the isotropic circular vortex core in a larger round-shaped Ga island. We suggest that the unusual elongated vortices in Ga nanostrips originate from geometric confinement effect probably via the strong repulsive interaction between the vortices and Meissner screening currents at the sample edge. Our finding provides novel conceptual insights into the geometrical confinement effect on magnetic vortices and forms the basis for the technological applications of superconductors.

  14. Mapping the Escherichia coli transcription elongation complex with exonuclease III

    PubMed Central

    Liu, Zhaokun; Artsimovitch, Irina

    2014-01-01

    Summary RNA polymerase interactions with the nucleic acids control every step of the transcription cycle. These contacts mediate RNA polymerase recruitment to promoters; induce pausing during RNA chain synthesis, and control transcription termination. These interactions are dissected using footprinting assays, in which a bound protein protects nucleic acids from the digestion by nucleases or modification by chemical probes. Exonuclease III is frequently employed to study protein-DNA interactions owing to relatively simple procedures and low background. Exonuclease III has been used to determine RNA polymerase position in transcription initiation and elongation complexes and to infer the translocation register of the enzyme. In this chapter, we describe probing the location and the conformation of transcription elongation complexes formed by walking of the RNA polymerase along an immobilized template. PMID:25665555

  15. New Insights on Plant Cell Elongation: A Role for Acetylcholine

    PubMed Central

    Di Sansebastiano, Gian-Pietro; Fornaciari, Silvia; Barozzi, Fabrizio; Piro, Gabriella; Arru, Laura

    2014-01-01

    We investigated the effect of auxin and acetylcholine on the expression of the tomato expansin gene LeEXPA2, a specific expansin gene expressed in elongating tomato hypocotyl segments. Since auxin interferes with clathrin-mediated endocytosis, in order to regulate cellular and developmental responses we produced protoplasts from tomato elongating hypocotyls and followed the endocytotic marker, FM4-64, internalization in response to treatments. Tomato protoplasts were observed during auxin and acetylcholine treatments after transient expression of chimerical markers of volume-control related compartments such as vacuoles. Here we describe the contribution of auxin and acetylcholine to LeEXPA2 expression regulation and we support the hypothesis that a possible subcellular target of acetylcholine signal is the vesicular transport, shedding some light on the characterization of this small molecule as local mediator in the plant physiological response. PMID:24642879

  16. New insights on plant cell elongation: a role for acetylcholine.

    PubMed

    Di Sansebastiano, Gian-Pietro; Fornaciari, Silvia; Barozzi, Fabrizio; Piro, Gabriella; Arru, Laura

    2014-01-01

    We investigated the effect of auxin and acetylcholine on the expression of the tomato expansin gene LeEXPA2, a specific expansin gene expressed in elongating tomato hypocotyl segments. Since auxin interferes with clathrin-mediated endocytosis, in order to regulate cellular and developmental responses we produced protoplasts from tomato elongating hypocotyls and followed the endocytotic marker, FM4-64, internalization in response to treatments. Tomato protoplasts were observed during auxin and acetylcholine treatments after transient expression of chimerical markers of volume-control related compartments such as vacuoles. Here we describe the contribution of auxin and acetylcholine to LeEXPA2 expression regulation and we support the hypothesis that a possible subcellular target of acetylcholine signal is the vesicular transport, shedding some light on the characterization of this small molecule as local mediator in the plant physiological response. PMID:24642879

  17. Role of tooth elongation in promoting fracture resistance.

    PubMed

    Barani, Amir; Keown, Amanda J; Bush, Mark B; Lee, James J-W; Lawn, Brian R

    2012-04-01

    A study is made of the role of tooth height on the resistance to side-wall longitudinal fracture under axial occlusal loading, building on earlier analyses for molar teeth with low dome-like ('bunodont') crown structures characteristic of primates and several other omnivorous mammals. The present study extends the analysis by considering molar teeth with an elongate columnar structure below the crown, more characteristic of grazing mammals. Extended finite element modeling is used to determine the evolution of longitudinal cracking, from initial growth to final failure. Experimental tests on sheep teeth confirm the predicted behavior of the longitudinal fracture mode, at least in its early stages. It is demonstrated that elongate tooth structures have a substantially increased resistance to longitudinal fracture, by restricting crack growth along the extended side walls. Biological implications concerning the adaptation of tooth structure to meet changes in the dietary habits of herbivores, and of some carnivores, are considered. PMID:22402152

  18. A Note on Elongations of Summable QTAG-Modules

    PubMed Central

    Mehdi, Alveera; Naji, Sabah A. R. K.

    2013-01-01

    A right module M over an associative ring with unity is a QTAG-module if every finitely generated submodule of any homomorphic image of M is a direct sum of uniserial modules. In this paper we find a suitable condition under which a special ω-elongation of a summable QTAG-module by a (ω+k)-projective QTAG-module is also a summable QTAG-module. PMID:24459429

  19. Neuroprotective copper bis(thiosemicarbazonato) complexes promote neurite elongation.

    PubMed

    Bica, Laura; Liddell, Jeffrey R; Donnelly, Paul S; Duncan, Clare; Caragounis, Aphrodite; Volitakis, Irene; Paterson, Brett M; Cappai, Roberto; Grubman, Alexandra; Camakaris, James; Crouch, Peter J; White, Anthony R

    2014-01-01

    Abnormal biometal homeostasis is a central feature of many neurodegenerative disorders including Alzheimer's disease (AD), Parkinson's disease (PD), and motor neuron disease. Recent studies have shown that metal complexing compounds behaving as ionophores such as clioquinol and PBT2 have robust therapeutic activity in animal models of neurodegenerative disease; however, the mechanism of neuroprotective action remains unclear. These neuroprotective or neurogenerative processes may be related to the delivery or redistribution of biometals, such as copper and zinc, by metal ionophores. To investigate this further, we examined the effect of the bis(thiosemicarbazonato)-copper complex, Cu(II)(gtsm) on neuritogenesis and neurite elongation (neurogenerative outcomes) in PC12 neuronal-related cultures. We found that Cu(II)(gtsm) induced robust neurite elongation in PC12 cells when delivered at concentrations of 25 or 50 nM overnight. Analogous effects were observed with an alternative copper bis(thiosemicarbazonato) complex, Cu(II)(atsm), but at a higher concentration. Induction of neurite elongation by Cu(II)(gtsm) was restricted to neurites within the length range of 75-99 µm with a 2.3-fold increase in numbers of neurites in this length range with 50 nM Cu(II)(gtsm) treatment. The mechanism of neurogenerative action was investigated and revealed that Cu(II)(gtsm) inhibited cellular phosphatase activity. Treatment of cultures with 5 nM FK506 (calcineurin phosphatase inhibitor) resulted in analogous elongation of neurites compared to 50 nM Cu(II)(gtsm), suggesting a potential link between Cu(II)(gtsm)-mediated phosphatase inhibition and neurogenerative outcomes. PMID:24587210

  20. Solitary waves in elongated clouds of strongly interacting bosons

    SciTech Connect

    Oegren, M.; Kavoulakis, G.M.; Jackson, A.D.

    2005-08-15

    We examine the propagation of solitary waves in elongated clouds of trapped bosonic atoms as the confinement, the strength of the interatomic interaction, and the atom density are varied. We identify three different physical regimes and develop a general formalism that allows us to interpolate between them. Finally we pay special attention to the transition to the Tonks-Girardeau limit of strongly interacting bosons.

  1. Toll Genes Have an Ancestral Role in Axis Elongation.

    PubMed

    Benton, Matthew A; Pechmann, Matthias; Frey, Nadine; Stappert, Dominik; Conrads, Kai H; Chen, Yen-Ta; Stamataki, Evangelia; Pavlopoulos, Anastasios; Roth, Siegfried

    2016-06-20

    One of the key morphogenetic processes used during development is the controlled intercalation of cells between their neighbors. This process has been co-opted into a range of developmental events, and it also underlies an event that occurs in each major group of bilaterians: elongation of the embryo along the anterior-posterior axis [1]. In Drosophila, a novel component of this process was recently discovered by Paré et al., who showed that three Toll genes function together to drive cell intercalation during germband extension [2]. This finding raises the question of whether this role of Toll genes is an evolutionary novelty of flies or a general mechanism of embryonic morphogenesis. Here we show that the Toll gene function in axis elongation is, in fact, widely conserved among arthropods. First, we functionally demonstrate that two Toll genes are required for cell intercalation in the beetle Tribolium castaneum. We then show that these genes belong to a previously undescribed Toll subfamily and that members of this subfamily exhibit striped expression (as seen in Tribolium and previously reported in Drosophila [3-5]) in embryos of six other arthropod species spanning the entire phylum. Last, we show that two of these Toll genes are required for normal morphogenesis during anterior-posterior embryo elongation in the spider Parasteatoda tepidariorum, a member of the most basally branching arthropod lineage. From our findings, we hypothesize that Toll genes had a morphogenetic function in embryo elongation in the last common ancestor of all arthropods, which existed over 550 million years ago. PMID:27212406

  2. Origins of improved carrier multiplication efficiency in elongated semiconductor nanostructures.

    PubMed

    Sills, Andrew; Califano, Marco

    2015-01-28

    Nanorod solar cells have been attracting a lot of attention recently, as they have been shown to exhibit a lower carrier multiplication onset and a higher quantum efficiency than quantum dots with similar bandgaps. The underpinning theory for this phenomenon is not yet completely understood, and is still the subject of ongoing study. Here we conduct a theoretical investigation into CM efficiency in elongated semiconductor nanostructures with square cross section made of different materials (GaAs, GaSb, InAs, InP, InSb, CdSe, Ge, Si and PbSe), using a single-band effective mass model. Following Luo, Franceschetti and Zunger we adopt the CM figure of merit (the ratio between biexciton and single-exciton density of states) as a measure of CM efficiency and investigate its dependence on the aspect ratio for both (a) constant cross section (i.e. varying the volume) and (b) constant volume (i.e., varying the cross section), by decoupling electronic structure effects from surface-related effects, increased absorption and Coulomb coupling effects. The results show that in both (a) and (b) cases elongation causes an increase in both single- and bi-exciton density of states, with the latter, however, growing much faster with increasing energy. This leads to the availability of more bi-exciton states than single-exciton states for photon energies just above the bi-exciton ground state and therefore suggests a higher probability of CM at these energies for elongated structures. Our results therefore show that the origin of the observed decrease of the CM threshold in elongated structures can be attributed purely to electronic structure effects, paving the way to the implementation of CM-efficiency-boosting strategies in nanostructures based on the lowering of the CM onset. PMID:25493662

  3. Leaf Relative Water Content Estimated from Leaf Reflectance and Transmittance

    NASA Technical Reports Server (NTRS)

    Vanderbilt, Vern; Daughtry, Craig; Dahlgren, Robert

    2016-01-01

    Remotely sensing the water status of plants and the water content of canopies remain long term goals of remote sensing research. In the research we report here, we used optical polarization techniques to monitor the light reflected from the leaf interior, R, as well as the leaf transmittance, T, as the relative water content (RWC) of corn (Zea mays) leaves decreased. Our results show that R and T both change nonlinearly. The result show that the nonlinearities cancel in the ratio R/T, which appears linearly related to RWC for RWC less than 90%. The results suggest that potentially leaf water status and perhaps even canopy water status could be monitored starting from leaf and canopy optical measurements.

  4. Differential Responsiveness of Cortical Microtubule Orientation to Suppression of Cell Expansion among the Developmental Zones of Arabidopsis thaliana Root Apex

    PubMed Central

    Panteris, Emmanuel; Adamakis, Ioannis-Dimosthenis S.; Daras, Gerasimos; Hatzopoulos, Polydefkis; Rigas, Stamatis

    2013-01-01

    Τhe bidirectional relationship between cortical microtubule orientation and cell wall structure has been extensively studied in elongating cells. Nevertheless, the possible interplay between microtubules and cell wall elements in meristematic cells still remains elusive. Herein, the impact of cellulose synthesis inhibition and suppressed cell elongation on cortical microtubule orientation was assessed throughout the developmental zones of Arabidopsis thaliana root apex by whole-mount tubulin immunolabeling and confocal microscopy. Apart from the wild-type, thanatos and pom2-4 mutants of Cellulose SynthaseA3 and Cellulose Synthase Interacting1, respectively, were studied. Pharmacological and mechanical approaches inhibiting cell expansion were also applied. Cortical microtubules of untreated wild-type roots were predominantly transverse in the meristematic, transition and elongation root zones. Cellulose-deficient mutants, chemical inhibition of cell expansion, or growth in soil resulted in microtubule reorientation in the elongation zone, wherein cell length was significantly decreased. Combinatorial genetic and chemical suppression of cell expansion extended microtubule reorientation to the transition zone. According to the results, transverse cortical microtubule orientation is established in the meristematic root zone, persisting upon inhibition of cell expansion. Microtubule reorientation in the elongation zone could be attributed to conditional suppression of cell elongation. The differential responsiveness of microtubule orientation to genetic and environmental cues is most likely associated with distinct biophysical traits of the cells among each developmental root zone. PMID:24324790

  5. Differential responsiveness of cortical microtubule orientation to suppression of cell expansion among the developmental zones of Arabidopsis thaliana root apex.

    PubMed

    Panteris, Emmanuel; Adamakis, Ioannis-Dimosthenis S; Daras, Gerasimos; Hatzopoulos, Polydefkis; Rigas, Stamatis

    2013-01-01

    Τhe bidirectional relationship between cortical microtubule orientation and cell wall structure has been extensively studied in elongating cells. Nevertheless, the possible interplay between microtubules and cell wall elements in meristematic cells still remains elusive. Herein, the impact of cellulose synthesis inhibition and suppressed cell elongation on cortical microtubule orientation was assessed throughout the developmental zones of Arabidopsis thaliana root apex by whole-mount tubulin immunolabeling and confocal microscopy. Apart from the wild-type, thanatos and pom2-4 mutants of Cellulose SynthaseA3 and Cellulose Synthase Interacting1, respectively, were studied. Pharmacological and mechanical approaches inhibiting cell expansion were also applied. Cortical microtubules of untreated wild-type roots were predominantly transverse in the meristematic, transition and elongation root zones. Cellulose-deficient mutants, chemical inhibition of cell expansion, or growth in soil resulted in microtubule reorientation in the elongation zone, wherein cell length was significantly decreased. Combinatorial genetic and chemical suppression of cell expansion extended microtubule reorientation to the transition zone. According to the results, transverse cortical microtubule orientation is established in the meristematic root zone, persisting upon inhibition of cell expansion. Microtubule reorientation in the elongation zone could be attributed to conditional suppression of cell elongation. The differential responsiveness of microtubule orientation to genetic and environmental cues is most likely associated with distinct biophysical traits of the cells among each developmental root zone. PMID:24324790

  6. Regulation of Compound Leaf Development

    PubMed Central

    Wang, Yuan; Chen, Rujin

    2013-01-01

    Leaf morphology is one of the most variable, yet inheritable, traits in the plant kingdom. How plants develop a variety of forms and shapes is a major biological question. Here, we discuss some recent progress in understanding the development of compound or dissected leaves in model species, such as tomato (Solanum lycopersicum), Cardamine hirsuta and Medicago truncatula, with an emphasis on recent discoveries in legumes. We also discuss progress in gene regulations and hormonal actions in compound leaf development. These studies facilitate our understanding of the underlying regulatory mechanisms and put forward a prospective in compound leaf studies. PMID:27135488

  7. Canopy shade causes a rapid and transient arrest in leaf development through auxin-induced cytokinin oxidase activity.

    PubMed

    Carabelli, Monica; Possenti, Marco; Sessa, Giovanna; Ciolfi, Andrea; Sassi, Massimiliano; Morelli, Giorgio; Ruberti, Ida

    2007-08-01

    A plant grown under canopies perceives the reduction in the ratio of red (R) to far-red (FR) light as a warning of competition, and enhances elongation growth in an attempt to overgrow its neighbors. Here, we report that the same low R/FR signal that induces hypocotyl elongation also triggers a rapid arrest of leaf primordium growth, ensuring that plant resources are redirected into extension growth. The growth arrest induced by low R/FR depends on auxin-induced cytokinin breakdown in incipient vein cells of developing primordia, thus demonstrating the existence of a previously unrecognized regulatory circuit underlying plant response to canopy shade. PMID:17671088

  8. Canopy shade causes a rapid and transient arrest in leaf development through auxin-induced cytokinin oxidase activity

    PubMed Central

    Carabelli, Monica; Possenti, Marco; Sessa, Giovanna; Ciolfi, Andrea; Sassi, Massimiliano; Morelli, Giorgio; Ruberti, Ida

    2007-01-01

    A plant grown under canopies perceives the reduction in the ratio of red (R) to far-red (FR) light as a warning of competition, and enhances elongation growth in an attempt to overgrow its neighbors. Here, we report that the same low R/FR signal that induces hypocotyl elongation also triggers a rapid arrest of leaf primordium growth, ensuring that plant resources are redirected into extension growth. The growth arrest induced by low R/FR depends on auxin-induced cytokinin breakdown in incipient vein cells of developing primordia, thus demonstrating the existence of a previously unrecognized regulatory circuit underlying plant response to canopy shade. PMID:17671088

  9. Telomerase Efficiently Elongates Highly Transcribing Telomeres in Human Cancer Cells

    PubMed Central

    Arora, Rajika; Lorenzi, Luca E.; Azzalin, Claus M.

    2012-01-01

    RNA polymerase II transcribes the physical ends of linear eukaryotic chromosomes into a variety of long non-coding RNA molecules including telomeric repeat-containing RNA (TERRA). Since TERRA discovery, advances have been made in the characterization of TERRA biogenesis and regulation; on the contrary its associated functions remain elusive. Most of the biological roles so far proposed for TERRA are indeed based on in vitro experiments carried out using short TERRA-like RNA oligonucleotides. In particular, it has been suggested that TERRA inhibits telomerase activity. We have exploited two alternative cellular systems to test whether TERRA and/or telomere transcription influence telomerase-mediated telomere elongation in human cancer cells. In cells lacking the two DNA methyltransferases DNMT1 and DNMT3b, TERRA transcription and steady-state levels are greatly increased while telomerase is able to elongate telomeres normally. Similarly, telomerase can efficiently elongate transgenic inducible telomeres whose transcription has been experimentally augmented. Our data challenge the current hypothesis that TERRA functions as a general inhibitor of telomerase and suggest that telomere length homeostasis is maintained independently of TERRA and telomere transcription. PMID:22558207

  10. Mechanism of gibberellin-dependent stem elongation in peas

    NASA Technical Reports Server (NTRS)

    Cosgrove, D. J.; Sovonick-Dunford, S. A.

    1989-01-01

    Stem elongation in peas (Pisum sativum L.) is under partial control by gibberellins, yet the mechanism of such control is uncertain. In this study, we examined the cellular and physical properties that govern stem elongation, to determine how gibberellins influence pea stem growth. Stem elongation of etiolated seedlings was retarded with uniconozol, a gibberellin synthesis inhibitor, and the growth retardation was reversed by exogenous gibberellin. Using the pressure probe and vapor pressure osmometry, we found little effect of uniconozol and gibberellin on cell turgor pressure or osmotic pressure. In contrast, these treatments had major effects on in vivo stress relaxation, measured by turgor relaxation and pressure-block techniques. Uniconozol-treated plants exhibited reduced wall relaxation (both initial rate and total amount). The results show that growth retardation is effected via a reduction in the wall yield coefficient and an increase in the yield threshold. These effects were largely reversed by exogenous gibberellin. When we measured the mechanical characteristics of the wall by stress/strain (Instron) analysis, we found only minor effects of uniconozol and gibberellin on the plastic compliance. This observation indicates that these agents did not alter wall expansion through effects on the mechanical (viscoelastic) properties of the wall. Our results suggest that wall expansion in peas is better viewed as a chemorheological, rather than a viscoelastic, process.