Sample records for relative root elongation

  1. 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.

  2. 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.

  3. Inhibition of root elongation in microgravity by an applied electric field

    NASA Technical Reports Server (NTRS)

    Wolverton, C.; Mullen, J. L.; Aizawa, S.; Yoshizaki, I.; Kamigaichi, S.; Mukai, C.; Shimazu, T.; Fukui, K.; Evans, M. L.; Ishikawa, H.

    1999-01-01

    Roots grown in an applied electric field demonstrate a bidirectional curvature. To further understand the nature of this response and its implications for the regulation of differential growth, we applied an electric field to roots growing in microgravity. We found that growth rates of roots in microgravity were higher than growth rates of ground controls. Immediately upon application of the electric field, root elongation was inhibited. We interpret this result as an indication that, in the absence of a gravity stimulus, the sensitivity of the root to an applied electric stimulus is increased. Further space experiments are required to determine the extent to which this sensitivity is shifted. The implications of this result are discussed in relation to gravitropic signaling and the regulation of differential cell elongation in the root.

  4. Effects of daylength and temperature on root elongation in tundra graminoids

    Microsoft Academic Search

    G. R. Shaver; W. D. Billings

    1977-01-01

    Effects of soil temperature and daylength on root elongation of Carex aquatilis, Dupontia fischeri, and Eriophorum angustifolium were studied under both field and phytotron conditions. Late season decrease in root elongation rate and cessation of root elongation in Dupontia and Eriophorum are shown to be controlled by decreasing daylength. During the growing season, low temperature is not a direct factor

  5. Effects of abscisic acid and xanthoxin on elongation and gravitropism in primary roots of Zea mays

    NASA Technical Reports Server (NTRS)

    Lee, J. S.; Hasenstein, K. H.; Mulkey, T. J.; Yang, R. L.; Evans, M. L.

    1990-01-01

    We examined the involvement of abscisic acid (ABA) and xanthoxin (Xan) in maize root gravitropism by (1) testing the ability of ABA to allow positive gravitropism in dark-grown seedlings of the maize cultivar LG11, a cultivar known to require light for positive gravitropism of the primary root, (2) comparing curvature in roots in which half of the cap had been excised and replaced with agar containing either ABA or indole-3-acetic acid (IAA), (3) measuring gravitropism in roots of seedlings submerged in oxygenated solutions of ABA or IAA and (4) testing the effect of Xan on root elongation. Using a variety of methods of applying ABA to the root, we found that ABA did not cause horizontally-oriented primary roots of dark-grown seedlings to become positively gravitropic. Replacing half of the root cap of vertically oriented roots with an agar block containing ABA had little or no effect on curvature relative to that of controls in which the half cap was replaced by a plain agar block. Replacement of the removed half cap with IAA either canceled or reversed the curvature displayed by controls. When light-grown seedlings were submerged in ABA they responded strongly to gravistimulation while those in IAA did not. Xan (up to 0.1 mM) did not affect root elongation. The results indicate that ABA is not a likely mediator of root gravitropism and that the putative ABA precursor, Xan, lacks the appropriate growth-inhibiting properties to serve as a mediator of root gravitropism.

  6. Progressive inhibition by water deficit of cell wall extensibility and growth along the elongation zone of maize roots is related to increased lignin metabolism and progressive stelar accumulation of wall phenolics.

    PubMed

    Fan, Ling; Linker, Raphael; Gepstein, Shimon; Tanimoto, Eiichi; Yamamoto, Ryoichi; Neumann, Peter M

    2006-02-01

    Water deficit caused by addition of polyethylene glycol 6000 at -0.5 MPa water potential to well-aerated nutrient solution for 48 h inhibited the elongation of maize (Zea mays) seedling primary roots. Segmental growth rates in the root elongation zone were maintained 0 to 3 mm behind the tip, but in comparison with well-watered control roots, progressive growth inhibition was initiated by water deficit as expanding cells crossed the region 3 to 9 mm behind the tip. The mechanical extensibility of the cell walls was also progressively inhibited. We investigated the possible involvement in root growth inhibition by water deficit of alterations in metabolism and accumulation of wall-linked phenolic substances. Water deficit increased expression in the root elongation zone of transcripts of two genes involved in lignin biosynthesis, cinnamoyl-CoA reductase 1 and 2, after only 1 h, i.e. before decreases in wall extensibility. Further increases in transcript expression and increased lignin staining were detected after 48 h. Progressive stress-induced increases in wall-linked phenolics at 3 to 6 and 6 to 9 mm behind the root tip were detected by comparing Fourier transform infrared spectra and UV-fluorescence images of isolated cell walls from water deficit and control roots. Increased UV fluorescence and lignin staining colocated to vascular tissues in the stele. Longitudinal bisection of the elongation zone resulted in inward curvature, suggesting that inner, stelar tissues were also rate limiting for root growth. We suggest that spatially localized changes in wall-phenolic metabolism are involved in the progressive inhibition of wall extensibility and root growth and may facilitate root acclimation to drying environments. PMID:16384904

  7. Progressive Inhibition by Water Deficit of Cell Wall Extensibility and Growth along the Elongation Zone of Maize Roots Is Related to Increased Lignin Metabolism and Progressive Stelar Accumulation of Wall Phenolics1

    PubMed Central

    Fan, Ling; Linker, Raphael; Gepstein, Shimon; Tanimoto, Eiichi; Yamamoto, Ryoichi; Neumann, Peter M.

    2006-01-01

    Water deficit caused by addition of polyethylene glycol 6000 at ?0.5 MPa water potential to well-aerated nutrient solution for 48 h inhibited the elongation of maize (Zea mays) seedling primary roots. Segmental growth rates in the root elongation zone were maintained 0 to 3 mm behind the tip, but in comparison with well-watered control roots, progressive growth inhibition was initiated by water deficit as expanding cells crossed the region 3 to 9 mm behind the tip. The mechanical extensibility of the cell walls was also progressively inhibited. We investigated the possible involvement in root growth inhibition by water deficit of alterations in metabolism and accumulation of wall-linked phenolic substances. Water deficit increased expression in the root elongation zone of transcripts of two genes involved in lignin biosynthesis, cinnamoyl-CoA reductase 1 and 2, after only 1 h, i.e. before decreases in wall extensibility. Further increases in transcript expression and increased lignin staining were detected after 48 h. Progressive stress-induced increases in wall-linked phenolics at 3 to 6 and 6 to 9 mm behind the root tip were detected by comparing Fourier transform infrared spectra and UV-fluorescence images of isolated cell walls from water deficit and control roots. Increased UV fluorescence and lignin staining colocated to vascular tissues in the stele. Longitudinal bisection of the elongation zone resulted in inward curvature, suggesting that inner, stelar tissues were also rate limiting for root growth. We suggest that spatially localized changes in wall-phenolic metabolism are involved in the progressive inhibition of wall extensibility and root growth and may facilitate root acclimation to drying environments. PMID:16384904

  8. Inhibitory Action of Auxin on Root Elongation Not Mediated by Ethylene

    PubMed Central

    Eliasson, Lennart; Bertell, Gertrud; Bolander, Eva

    1989-01-01

    The inhibitory effects of indole-3-acetic acid (IAA) and 1-aminocyclopropane-1-carboxylic acid (ACC) on elongation growth of pea (Pisum sativum L.) seedling roots were investigated in relation to the effects of these compounds on ethylene production by the root tips. When added to the growth solution both compounds caused a progressively increasing inhibition of growth within the concentration range of 0.01 to 1 micromolar. However, only ACC increased ethylene production in root tips excised from the treated seedlings after 24 hours. High auxin concentrations caused a transitory increase of ethylene production during a few hours in the beginning of the treatment period, but even in 1 micromolar IAA this increase was too low to have any appreciable effect on growth. ACC, but not IAA, caused growth curvatures, typical of ethylene treatment, in the root tips. IAA caused conspicuous swelling of the root tips while ACC did not. Cobalt and silver ions reversed the growth inhibitory effects induced by ACC but did not counteract the inhibition of elongation or swelling caused by IAA. The growth effects caused by the ACC treatments were obviously due to ethylene production. We found no evidence to indicate that the growth inhibition or swelling caused by IAA is mediated by ethylene. It is concluded that the inhibitory action of IAA on root growth is caused by this auxin per se. PMID:16667017

  9. 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.

  10. Phosphorus and magnesium interactively modulate the elongation and directional growth of primary roots in Arabidopsis thaliana (L.) Heynh.

    PubMed

    Niu, Yaofang; Jin, Gulei; Li, Xin; Tang, Caixian; Zhang, Yongsong; Liang, Yongchao; Yu, Jingquan

    2015-07-01

    A balanced supply of essential nutrients is an important factor influencing root architecture in many plants, yet data related to the interactive effects of two nutrients on root growth are limited. Here, we investigated the interactive effect between phosphorus (P) and magnesium (Mg) on root growth of Arabidopsis grown in pH-buffered agar medium at different P and Mg levels. The results showed that elongation and deviation of primary roots were directly correlated with the amount of P added to the medium but could be modified by the Mg level, which was related to the root meristem activity and stem-cell division. High P enhanced while low P decreased the tip-focused fluorescence signal of auxin biosynthesis, transport, and redistribution during elongation of primary roots; these effects were greater under low Mg than under high Mg. The altered root growth in response to P and Mg supply was correlated with AUX1, PIN2, and PIN3 mRNA abundance and expression and the accumulation of the protein. Application of either auxin influx inhibitor or efflux inhibitor inhibited the elongation and increased the deviation angle of primary roots, and decreased auxin level in root tips. Furthermore, the auxin-transport mutants aux1-22 and eir1-1 displayed reduced root growth and increased the deviation angle. Our data suggest a profound effect of the combined supply of P and Mg on the development of root morphology in Arabidopsis through auxin signals that modulate the elongation and directional growth of primary root and the expression of root differentiation and development genes. PMID:25922494

  11. Phosphorus and magnesium interactively modulate the elongation and directional growth of primary roots in Arabidopsis thaliana (L.) Heynh

    PubMed Central

    Niu, Yaofang; Jin, Gulei; Li, Xin; Tang, Caixian; Zhang, Yongsong; Liang, Yongchao; Yu, Jingquan

    2015-01-01

    A balanced supply of essential nutrients is an important factor influencing root architecture in many plants, yet data related to the interactive effects of two nutrients on root growth are limited. Here, we investigated the interactive effect between phosphorus (P) and magnesium (Mg) on root growth of Arabidopsis grown in pH-buffered agar medium at different P and Mg levels. The results showed that elongation and deviation of primary roots were directly correlated with the amount of P added to the medium but could be modified by the Mg level, which was related to the root meristem activity and stem-cell division. High P enhanced while low P decreased the tip-focused fluorescence signal of auxin biosynthesis, transport, and redistribution during elongation of primary roots; these effects were greater under low Mg than under high Mg. The altered root growth in response to P and Mg supply was correlated with AUX1, PIN2, and PIN3 mRNA abundance and expression and the accumulation of the protein. Application of either auxin influx inhibitor or efflux inhibitor inhibited the elongation and increased the deviation angle of primary roots, and decreased auxin level in root tips. Furthermore, the auxin-transport mutants aux1-22 and eir1-1 displayed reduced root growth and increased the deviation angle. Our data suggest a profound effect of the combined supply of P and Mg on the development of root morphology in Arabidopsis through auxin signals that modulate the elongation and directional growth of primary root and the expression of root differentiation and development genes. PMID:25922494

  12. Germination and root elongation bioassays in six different plant species for testing Ni contamination in soil.

    PubMed

    Visioli, Giovanna; Conti, Federica D; Gardi, Ciro; Menta, Cristina

    2014-04-01

    In vitro short-term chronic phytotoxicity germination and root elongation test were applied to test the effects of nickel (Ni) in seed germination and root elongation in six plants species: Cucumis sativus (Cucurbitaceae), Lepidium sativum and Brassica nigra (Brassicaceae), Trifolium alexandrinum and Medicago sativa (Fabaceae), Phacelia tanacetifolia (Boraginaceae). A naturally Ni rich soil was used to compare the results obtained. Unlike root elongation, germination was not affected by Ni in any of the six species tested. EC50 values, calculated on the root elongation, showed that Ni toxicity decreases in the following order: P. tanacetifolia > B. nigra > C. sativus > L. sativum > M. sativa > T. alexandrinum. The test conducted using soil elutriate revealed a significantly lower effect in both seed germination and root elongation when compared to the results obtained using untreated soil. Conversely, the test performed on soil confirmed the high sensitivity of C. sativus, P. tanacetifolia and L. sativum to Ni. PMID:24288040

  13. Abscisic acid regulates root elongation through the activities of auxin and ethylene in Arabidopsis thaliana.

    PubMed

    Thole, Julie M; Beisner, Erin R; Liu, James; Venkova, Savina V; Strader, Lucia C

    2014-07-01

    Abscisic acid (ABA) regulates many aspects of plant growth and development, including inhibition of root elongation and seed germination. We performed an ABA resistance screen to identify factors required for ABA response in root elongation inhibition. We identified two classes of Arabidopsis thaliana AR mutants that displayed ABA-resistant root elongation: those that displayed resistance to ABA in both root elongation and seed germination and those that displayed resistance to ABA in root elongation but not in seed germination. We used PCR-based genotyping to identify a mutation in ABA INSENSITIVE2 (ABI2), positional information to identify mutations in AUXIN RESISTANT1 (AUX1) and ETHYLENE INSENSITIVE2 (EIN2), and whole genome sequencing to identify mutations in AUX1, AUXIN RESISTANT4 (AXR4), and ETHYLENE INSENSITIVE ROOT1/PIN-FORMED2 (EIR1/PIN2). Identification of auxin and ethylene response mutants among our isolates suggested that auxin and ethylene responsiveness were required for ABA inhibition of root elongation. To further our understanding of auxin/ethylene/ABA crosstalk, we examined ABA responsiveness of double mutants of ethylene overproducer1 (eto1) or ein2 combined with auxin-resistant mutants and found that auxin and ethylene likely operate in a linear pathway to affect ABA-responsive inhibition of root elongation, whereas these two hormones likely act independently to affect ABA-responsive inhibition of seed germination. PMID:24836325

  14. Abscisic Acid Regulates Root Elongation Through the Activities of Auxin and Ethylene in Arabidopsis thaliana

    PubMed Central

    Thole, Julie M.; Beisner, Erin R.; Liu, James; Venkova, Savina V.; Strader, Lucia C.

    2014-01-01

    Abscisic acid (ABA) regulates many aspects of plant growth and development, including inhibition of root elongation and seed germination. We performed an ABA resistance screen to identify factors required for ABA response in root elongation inhibition. We identified two classes of Arabidopsis thaliana AR mutants that displayed ABA-resistant root elongation: those that displayed resistance to ABA in both root elongation and seed germination and those that displayed resistance to ABA in root elongation but not in seed germination. We used PCR-based genotyping to identify a mutation in ABA INSENSITIVE2 (ABI2), positional information to identify mutations in AUXIN RESISTANT1 (AUX1) and ETHYLENE INSENSITIVE2 (EIN2), and whole genome sequencing to identify mutations in AUX1, AUXIN RESISTANT4 (AXR4), and ETHYLENE INSENSITIVE ROOT1/PIN-FORMED2 (EIR1/PIN2). Identification of auxin and ethylene response mutants among our isolates suggested that auxin and ethylene responsiveness were required for ABA inhibition of root elongation. To further our understanding of auxin/ethylene/ABA crosstalk, we examined ABA responsiveness of double mutants of ethylene overproducer1 (eto1) or ein2 combined with auxin-resistant mutants and found that auxin and ethylene likely operate in a linear pathway to affect ABA-responsive inhibition of root elongation, whereas these two hormones likely act independently to affect ABA-responsive inhibition of seed germination. PMID:24836325

  15. Effect of auxins and plant oligosaccharides on root formation and elongation growth of mung bean hypocotyls

    Microsoft Academic Search

    Karin Kollárová; Mária Henselová; Desana Lišková

    2005-01-01

    The interaction of auxins – IAA, IBA or NAA – with galactoglucomannan oligosaccharides (GGMOs) on adventitious root formation and elongation growth of mung bean hypocotyl cuttings was studied. GGMOs induced adventitious roots in the absence of auxins; however, their effect was lower compared with IBA or NAA. On the other hand, in the presence of auxins, GGMOs inhibited adventitious root

  16. The Arabidopsis thaliana elongator complex subunit 2 epigenetically affects root development.

    PubMed

    Jia, Yuebin; Tian, Huiyu; Li, Hongjiang; Yu, Qianqian; Wang, Lei; Friml, Jiri; Ding, Zhaojun

    2015-08-01

    The elongator complex subunit 2 (ELP2) protein, one subunit of an evolutionarily conserved histone acetyltransferase complex, has been shown to participate in leaf patterning, plant immune and abiotic stress responses in Arabidopsis thaliana. Here, its role in root development was explored. Compared to the wild type, the elp2 mutant exhibited an accelerated differentiation of its root stem cells and cell division was more active in its quiescent centre (QC). The key transcription factors responsible for maintaining root stem cell and QC identity, such as AP2 transcription factors PLT1 (PLETHORA1) and PLT2 (PLETHORA2), GRAS transcription factors such as SCR (SCARECROW) and SHR (SHORT ROOT) and WUSCHEL-RELATED HOMEOBOX5 transcription factor WOX5, were all strongly down-regulated in the mutant. On the other hand, expression of the G2/M transition activator CYCB1 was substantially induced in elp2. The auxin efflux transporters PIN1 and PIN2 showed decreased protein levels and PIN1 also displayed mild polarity alterations in elp2, which resulted in a reduced auxin content in the root tip. Either the acetylation or methylation level of each of these genes differed between the mutant and the wild type, suggesting that the ELP2 regulation of root development involves the epigenetic modification of a range of transcription factors and other developmental regulators. PMID:25998905

  17. Food reserves in mountain longleaf pine roots during shoot elongation.

    SciTech Connect

    Walkinshaw, C.H.; W.J. Otrosina

    2001-03-20

    Roots of saplings appear to be models for healthy tissues in longleaf pines. Results show that roots of mountain longleaf pine have a normal anatomy, but also have unusual amounts of starch when compared to loblolly pine roots growing during phenologiexecy equal time periods. Roots appear large in diameter and grow much nearer the soil surface than roots observed from Coastal Plain longleaf pine. Starch grains are large in size and uniformly filled root cells. These results yield methodology potentially useful in assessment of health and productivity of longleaf pine.

  18. Aluminum targets elongating cells by reducing cell wall extensibility in wheat roots.

    PubMed

    Ma, Jian Feng; Shen, Renfang; Nagao, Sakiko; Tanimoto, Eiichi

    2004-05-01

    Phytotoxicity of aluminum is characterized by a rapid inhibition of root elongation at micromolar concentrations, however, the mechanisms primarily responsible for this response are not well understood. We investigated the effect of Al on the viscosity and elasticity parameters of root cell wall by a creep-extension analysis in two cultivars of wheat (Triticum aestivum L.) differing in Al resistance. The root elongation and both viscous and elastic extensibility of cell wall of the root apices were hardly affected by the exposure to 10 microM Al in an Al-resistant cultivar, Atlas 66. However, similar exposure rapidly inhibited root elongation in an Al-sensitive cultivar, Scout 66 and this was associated with a time-dependent accumulation of Al in the root tissues with more than 77% residing in the cell wall. Al caused a significant decrease in both the viscous and elastic extensibility of cell wall of the root apices of Scout 66. The "break load" of the root apex of Scout 66 was also decreased by Al. However, neither the viscosity nor elasticity of the cell wall was affected by in vitro Al treatment. Furthermore, pre-treatment of seedlings with Al in conditions where root elongation was slow (i.e. low temperature) did not affect the subsequent elongation of roots in a 0 Al treatment at room temperature. These results suggest that the Al-dependent changes in the cell wall viscosity and elasticity are involved in the inhibition of root growth. Furthermore, for Al to reduce cell wall extensibility it must interact with the cell walls of actively elongating cells. PMID:15169940

  19. 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.

  20. SWP1 negatively regulates lateral root initiation and elongation in Arabidopsis

    PubMed Central

    Singh, Sharmila; Singh, Archita; Roy, Shradha; Sarkar, Ananda K.

    2012-01-01

    The main root and continuously emerging lateral roots constitute the root architecture of an adult plant during its postembryonic development. Epigenetic modifications like methylation or deacetylation of histones have been suggested to regulate root development. SWP1/LDL1, a component of plant specific corepressor complex, has been implicated in the induction of flowers and root through histone modifications in Arabidopsis. However, molecular role of SWP1 in regulating the lateral root development remained unexplored. Here we show that SWP1 regulates lateral root initiation and elongation in Arabidopsis. Mutation in SWP1 increases both the density and length of lateral roots. SWP1 negatively regulates lateral root initiation through direct/indirect transcriptional repression of lateral root promoting factors, such as AUXIN RESPONSE FACTORS (ARFs) and GATA23. PMID:23073020

  1. Exposure of iron nanoparticles to Arabidopsis thaliana enhances root elongation by triggering cell wall loosening.

    PubMed

    Kim, Jae-Hwan; Lee, Yongjik; Kim, Eun-Ju; Gu, Sungmin; Sohn, Eun Ju; Seo, Young Sook; An, Hyun Joo; Chang, Yoon-Seok

    2014-03-18

    In this study, we investigated the effect of nZVI on plant root elongation in Arabidopsis thaliana and showed, for the first time, that nZVI enhanced root elongation by inducing OH radical-induced cell wall loosening. Exposure of plants to 0.5 g/L nZVI enhanced root elongation by 150-200% over that in the control, and further mechanistic studies showed that this occurred via nZVI-mediated OH radical-induced cell wall loosening. The oxidation capacity of nZVI, leading to release of H2O2, allowed it to cause OH radical-induced cell wall loosening in roots. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometers (MALDI-TOFMS)-based analysis clearly revealed that pectin-polysaccharides in roots were degraded; they are one of the main matrix-polysaccharide-connecting and load-bearing polymers in cell walls. Rapid root elongation led to structural changes in root cell walls: reduction of cell wall thickness and a bias on the orientation of cellulose microfibrils. Additionally, the asymmetrical distribution of tensional strength resulted from the OH radical-induced cell wall loosening enhanced endocytosis. These findings emphasize that OH radical-induced cell wall loosening is important for mechanical regulation of the cell wall and provide new insights into the cellular responses of plants exposed to reactive metal nanoparticles. PMID:24579868

  2. Acetylcholine promotes the emergence and elongation of lateral roots of Raphanus sativus.

    PubMed

    Sugiyama, Kou-ichi; Tezuka, Takafumi

    2011-10-01

    Radish (Raphanus sativus L.) was grown on four layers of paper towel moistened with distilled water with and without acetylcholine (ACh) for five days in the dark after sowing. ACh at 1 nM promoted the growth (emergence and elongation) of lateral roots of radish plants, but had no effect on the stems and main roots. Moreover, ACh enhanced the dry weight of roots [main (primary) + lateral roots]. Neostigmine, an inhibitor of acetylcholinesterase (AChE) also promoted the emergence and elongation of lateral roots, and atropine, a competitive inhibitor of ACh receptor, suppressed the emergence and elongation. ACh suppressed the activity of AChE and increased the amount of proteins and pyridine nucleotides (NAD and NADH) in the roots of the seedlings. It also increased the activities of NAD-forming enzymes [NAD synthetase and ATP-nicotinamide mononucleotide (ATP-NMN) adenyltransferase], and enhanced the amount of DNA in the roots of the seedlings. The relationship between ACh and the emergence and growth of lateral roots was discussed from a biochemical viewpoint. PMID:21900743

  3. Acetylcholine promotes the emergence and elongation of lateral roots of Raphanus sativus

    PubMed Central

    Sugiyama, Kou-ichi

    2011-01-01

    Radish (Raphanus sativus L.) was grown on four layers of paper towel moistened with distilled water with and without acetylcholine (ACh) for five days in the dark after sowing. ACh at 1 nM promoted the growth (emergence and elongation) of lateral roots of radish plants, but had no effect on the stems and main roots. Moreover, ACh enhanced the dry weight of roots [main (primary) + lateral roots]. Neostigmine, an inhibitor of acetylcholinesterase (AChE) also promoted the emergence and elongation of lateral roots, and atropine, a competitive inhibitor of ACh receptor, suppressed the emergence and elongation. ACh promoted the activities of glyceraldehyde-3-phosephate dehydrogenase (G-3-PD), nicotinamide adenine dinucleotide-specific isocitrate dehydrogenase (NAD-ICDH), succinate dehydrogenase (SDH) and cytochrome-c oxidase (Cyt-c OD) in seedlings. Moreover, ACh suppressed the activity of AChE and increased the amount of proteins and pyridine nucleotides (NAD and NADH) in the roots of the seedlings. It also increased the activities of NAD-forming enzymes [NAD synthetase and ATP-nicotinamide mononucleotide (ATP-NMN) adenyltransferase], and enhanced the amount of DNA in the roots of the seedlings. The relationship between ACh and the emergence and growth of lateral roots was discussed from a biochemical viewpoint. PMID:21900743

  4. Soybean Root Elongation Response to Magnesium Additions to Acid Subsoil

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Additions of micromolar concentrations of Mg2+ to hydroponic solutions enhance Al tolerance of soybean [Glycine max (L.) Merr.] by increasing citrate secretion from roots and external complexation of toxic Al species in solution. The objective of this study was to assess the ameliorative effect of M...

  5. Sulfur nutrient availability regulates root elongation by affecting root indole-3-acetic acid levels and the stem cell niche.

    PubMed

    Zhao, Qing; Wu, Yu; Gao, Lei; Ma, Jun; Li, Chuan-You; Xiang, Cheng-Bin

    2014-12-01

    Sulfur is an essential macronutrient for plants with numerous biological functions. However, the influence of sulfur nutrient availability on the regulation of root development remains largely unknown. Here, we report the response of Arabidopsis thaliana L. root development and growth to different levels of sulfate, demonstrating that low sulfate levels promote the primary root elongation. By using various reporter lines, we examined in vivo IAA level and distribution, cell division, and root meristem in response to different sulfate levels. Meanwhile the dynamic changes of in vivo cysteine, glutathione, and IAA levels were measured. Root cysteine, glutathione, and IAA levels are positively correlated with external sulfate levels in the physiological range, which eventually affect root system architecture. Low sulfate levels also downregulate the genes involved in auxin biosynthesis and transport, and elevate the accumulation of PLT1 and PLT2. This study suggests that sulfate level affects the primary root elongation by regulating the endogenous auxin level and root stem cell niche maintenance. PMID:24831283

  6. Normal root elongation requires arginine produced by argininosuccinate lyase in rice.

    PubMed

    Xia, Jixing; Yamaji, Naoki; Che, Jing; Shen, Ren Fang; Ma, Jian Feng

    2014-04-01

    Plant roots play an important role in the uptake of water and nutrients, structural support and environmental sensing, but the molecular mechanisms involved in root development are poorly understood in rice (Oryza sativa), which is characterized by a dense fibrous root system. Here we report a rice mutant (red1 for root elongation defect 1) with short roots. Morphological and physiological analyses showed that the mutant had a shorter length from the quiescent center (QC) to the starting point of the elongation zone but a similar cell size and number of lateral and crown roots compared with the wild type. Furthermore, the mutant had similar radial structure and nutrient uptake patterns to the wild type. Map-based cloning revealed that the mutant phenotype was caused by a point mutation of a gene encoding an argininosuccinate lyase (ASL), catalyzing the last step of arginine biosynthesis. The OsASL1 gene has two distinct transcripts, OsASL1.1 and OsASL1.2, which result from different transcription start sites, but only OsASL1.1 was able to complement the mutant phenotype. OsASL1.1 was expressed in both the roots and shoots. The protein encoded by OsASL1.1 showed ASL activity in yeast. OsALS1.1 was localized to the plastid. The short root of the mutant was rescued by exogenous addition of arginine, but not by other amino acids. These results indicate that arginine produced by ASL is required for normal root elongation in rice. PMID:24528386

  7. Rare earth elements and plant growth: I. Effects of lanthanum and cerium on root elongation of corn and mungbean

    Microsoft Academic Search

    E. Diatloff; F. W. Smith; C. J. Asher

    1995-01-01

    Root elongation of corn (Zea mays cv. Hycorn 82) and mungbean (Vigna radiata cv. Berken) seedlings was measured in dilute complete nutrient solutions to which varying amounts of lanthanum (La) or cerium (Ce) had been added. The nutrient solutions were aged for 9 d prior to conducting the root elongation experiments and solution samples ultra?filtered to 0.025 ?m before chemical

  8. Effects of rare earth oxide nanoparticles on root elongation of plants.

    PubMed

    Ma, Yuhui; Kuang, Linglin; He, Xiao; Bai, Wei; Ding, Yayun; Zhang, Zhiyong; Zhao, Yuliang; Chai, Zhifang

    2010-01-01

    The phytotoxicity of four rare earth oxide nanoparticles, nano-CeO(2), nano-La(2)O(3), nano-Gd(2)O(3) and nano-Yb(2)O(3) on seven higher plant species (radish, rape, tomato, lettuce, wheat, cabbage, and cucumber) were investigated in the present study by means of root elongation experiments. Their effects on root growth varied greatly between different nanoparticles and plant species. A suspension of 2000 mg L(-1) nano-CeO(2) had no effect on the root elongation of six plants, except lettuce. On the contrary, 2000 mg L(-1) suspensions of nano-La(2)O(3), nano-Gd(2)O(3) and nano-Yb(2)O(3) severely inhibited the root elongation of all the seven species. Inhibitory effects of nano-La(2)O(3), nano-Gd(2)O(3), and nano-Yb(2)O(3) also differed in the different growth process of plants. For wheat, the inhibition mainly took place during the seed incubation process, while lettuce and rape were inhibited on both seed soaking and incubation process. The fifty percent inhibitory concentrations (IC(50)) for rape were about 40 mg L(-1) of nano-La(2)O(3), 20mg L(-1) of nano-Gd(2)O(3), and 70 mg L(-1) of nano-Yb(2)O(3), respectively. In the concentration ranges used in this study, the RE(3+) ion released from the nanoparticles had negligible effects on the root elongation. These results are helpful in understanding phytotoxicity of rare earth oxide nanoparticles. PMID:19897228

  9. Abscisic Acid and LATERAL ROOT ORGAN DEFECTIVE/NUMEROUS INFECTIONS AND POLYPHENOLICS Modulate Root Elongation via Reactive Oxygen Species in Medicago truncatula1[W][OPEN

    PubMed Central

    Zhang, Chang; Bousquet, Amanda; Harris, Jeanne M.

    2014-01-01

    Abscisic acid (ABA) modulates root growth in plants grown under normal and stress conditions and can rescue the root growth defects of the Medicago truncatula lateral root-organ defective (latd) mutant. Here, we demonstrate that reactive oxygen species (ROS) function downstream of ABA in the regulation of root growth by controlling cell elongation. We also show that the MtLATD/NUMEROUS INFECTIONS AND POLYPHENOLICS (NIP) nitrate transporter is required for ROS homeostasis and cell elongation in roots and that this balance is perturbed in latd mutants, leading to an excess of superoxide and hydrogen peroxide and a corresponding decrease in cell elongation. We found that expression of the superoxide-generating NADPH oxidase genes, MtRbohA and MtRbohC (for respiratory burst oxidase homologs), is increased in latd roots and that inhibition of NADPH oxidase activity pharmacologically can both reduce latd root ROS levels and increase cell length, implicating NADPH oxidase function in latd root growth defects. Finally, we demonstrate that ABA treatment alleviates ectopic ROS accumulation in latd roots, restores MtRbohC expression to wild-type levels, and promotes an increase in cell length. Reducing the expression of MtRbohC using RNA interference leads to increased root elongation in both wild-type and latd roots. These results reveal a mechanism by which the MtLATD/NIP nitrate transporter and ABA modulate root elongation via superoxide generation by the MtRbohC NADPH oxidase. PMID:25192698

  10. NO homeostasis is a key regulator of early nitrate perception and root elongation in maize*

    PubMed Central

    Quaggiotti, Silvia

    2014-01-01

    Crop plant development is strongly dependent on nitrogen availability in the soil and on the efficiency of its recruitment by roots. For this reason, the understanding of the molecular events underlying root adaptation to nitrogen fluctuations is a primary goal to develop biotechnological tools for sustainable agriculture. However, knowledge about molecular responses to nitrogen availability is derived mainly from the study of model species. Nitric oxide (NO) has been recently proposed to be implicated in plant responses to environmental stresses, but its exact role in the response of plants to nutritional stress is still under evaluation. In this work, the role of NO production by maize roots after nitrate perception was investigated by focusing on the regulation of transcription of genes involved in NO homeostasis and by measuring NO production in roots. Moreover, its involvement in the root growth response to nitrate was also investigated. The results provide evidence that NO is produced by nitrate reductase as an early response to nitrate supply and that the coordinated induction of non-symbiotic haemoglobins (nsHbs) could finely regulate the NO steady state. This mechanism seems to be implicated on the modulation of the root elongation in response to nitrate perception. Moreover, an improved agar-plate system for growing maize seedlings was developed. This system, which allows localized treatments to be performed on specific root portions, gave the opportunity to discern between localized and systemic effects of nitrate supply to roots. PMID:24220653

  11. Seed germination and root elongation as indicators of exposure of wetland seedlings to metals

    SciTech Connect

    Sutton, H.D.; Stokes, S.L.; Hook, D.D.; Klaine, S.J. [Clemson Univ., Pendleton, SC (United States)

    1995-12-31

    Wetland ecosystems have often been impacted by the addition of hazardous waste materials. Methods are needed to evaluate the effect of these substances on wetland ecosystems and the organisms within them. This study evaluates the response of various wetland plant species to representative contaminants (cadmium, nickel, atrazine, anthracene, and tetrachloroethylene). Species tested include Caphalanthus occidentalis (buttonbush), Saururus cernuus (lizard`s tail), Liquidambar styraciflua (sweetgum), Sparganium americanum (bur-reed), and Fraxinus pennsylvanica (green ash). To the authors` knowledge these species have rarely if ever been used in toxicological assays. The endpoints used are germination and root elongation. Preliminary studies using a petri dish system have shown decreased germination at the highest metal concentration (50mg/L) and decreased root elongation in the higher metal concentrations (10, 25, and 50mg/L). Interference from the carrier was observed in the organic tests. Root elongation studies using the metals are being continued using tubes with various sand and vermiculite mixes into which freshly germinated seeds are placed. Species with the best responses will be tested in the field at the Savannah River Site, SC, and also with fuel oil. Lettuce (Lactuca saliva) and radish (Raphanus sativus) are being tested alongside the wetland species as reference organisms for which tests are well established.

  12. Development of a biotic ligand model for acute zinc toxicity to barley root elongation.

    PubMed

    Wang, Xuedong; Li, Bo; Ma, Yibing; Hua, Luo

    2010-09-01

    The effects of pH and some cations on the acute toxicity of zinc (Zn) to barley (Hordeum vulgare) root elongation were investigated to aid the development of an appropriate biotic ligand model (BLM). The results showed that Zn toxicity decreased with increased activity of Mg2+, K+ and Ca2+ but not Na+. The effect of pH on Zn toxicity to barley root elongation could be explained by H+ competition with Zn2+ bound to a biotic ligand (BL) at pHor=6. Stability constants were obtained for the binding of Zn2+, ZnHCO3+, Mg2+, K+, Ca2+ and H+ with BL: logKZnBL 4.06, logKZnHCO3BL+ 5.15, logKMgBL 3.72, logKKBL 2.62, logKCaBL 1.99 and logKHBL 4.27. On the basis of these estimated parameters, a BLM was successfully developed to predict Zn toxicity to barley root elongation as a function of solution characteristics. PMID:20570355

  13. Abscisic Acid Accumulation Maintains Maize Primary Root Elongation at Low Water Potentials by Restricting Ethylene Production1

    PubMed Central

    Spollen, William G.; LeNoble, Mary E.; Samuels, Timmy D.; Bernstein, Nirit; Sharp, Robert E.

    2000-01-01

    Previous work showed that primary root elongation in maize (Zea mays L.) seedlings at low water potentials (?w) requires the accumulation of abscisic acid (ABA) (R.E. Sharp, Y. Wu, G.S. Voetberg, I.N. Saab, M.E. LeNoble [1994] J Exp Bot 45: 1743–1751). The objective of the present study was to determine whether the inhibition of elongation in ABA-deficient roots is attributable to ethylene. At a ?w of ?1.6 MPa, inhibition of root elongation in dark-grown seedlings treated with fluridone to impose ABA deficiency was largely prevented with two inhibitors of ethylene synthesis (aminooxyacetic acid and aminoethoxyvinylglycine) and one inhibitor of ethylene action (silver thiosulfate). The fluridone treatment caused an increase in the rate of ethylene evolution from intact seedlings. This effect was completely prevented with aminooxyacetic acid and also when ABA was supplied at a concentration that restored the ABA content of the root elongation zone and the root elongation rate. Consistent results were obtained when ABA deficiency was imposed using the vp5 mutant. Both fluridone-treated and vp5 roots exhibited additional morphological symptoms of excess ethylene. The results demonstrate that an important role of ABA accumulation in the maintenance of root elongation at low ?w is to restrict ethylene production. PMID:10712561

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

    PubMed

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

    2015-07-01

    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), ?-(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

  15. 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), ?-(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

  16. Root Hair-Specific EXPANSIN A7 Is Required for Root Hair Elongation in Arabidopsis

    PubMed Central

    Lin, Changfa; Choi, Hee-Seung; Cho, Hyung-Taeg

    2011-01-01

    Expansins are non-hydrolytic cell wall-loosening proteins that are involved in the cell wall modifications that underlie many plant developmental processes. Root hair growth requires the accumulation of cell wall materials and dynamic cell wall modification at the tip region. Although several lines of indirect evidence support the idea that expansin-mediated wall modification occurs during root hair growth, the involvement of these proteins remains to be demonstrated in vivo. In this study, we used RNA interference (RNAi) to examine the biological function of Arabidopsis thaliana EXPANSIN A7 (AtEXPA7), which is expressed specifically in the root hair cell. The root hairspecific AtEXPA7 promoter was used to drive RNAi expression, which targeted two independent regions in the AtEXPA7 transcript. Quantitative reverse transcriptase- PCR analyses were used to examine AtEXPA7 transcript levels. In four independent RNAi transformant lines, RNAi expression reduced AtEXPA7 transcript levels by 25-58% compared to controls. Accordingly, the root hairs of RNAi transformant lines were 25-48% shorter than control plants and exhibited a broader range of lengths than the controls. Our results provide in vivo evidence that expansins are required for root hair tip growth. PMID:21359675

  17. Tall or short? Slender or thick? A plant strategy for regulating elongation growth of roots by low concentrations of gibberellin

    PubMed Central

    Tanimoto, Eiichi

    2012-01-01

    Background Since the plant hormone gibberellin (GA) was discovered as a fungal toxin that caused abnormal elongation of rice shoots, the physiological function of GA has mainly been investigated in relation to the regulation of plant height. However, an indispensable role for GA in root growth has been elucidated by using severely GA-depleted plants, either with a gene mutation in GA biosynthesis or which have been treated by an inhibitor of GA biosynthesis. The molecular sequence of GA signalling has also been studied to understand GA functions in root growth. Scope This review addresses research progress on the physiological functions of GA in root growth. Concentration-dependent stimulation of elongation growth by GA is important for the regulation of plant height and root length. Thus the endogenous level of GA and/or the GA sensitivity of shoots and roots plays a role in determining the shoot-to-root ratio of the plant body. Since the shoot-to-root ratio is an important parameter for agricultural production, control of GA production and GA sensitivity may provide a strategy for improving agricultural productivity. The sequence of GA signal transduction has recently been unveiled, and some component molecules are suggested as candidate in planta regulatory sites and as points for the artificial manipulation of GA-mediated growth control. Conclusions This paper reviews: (1) the breakthrough dose–response experiments that show that root growth is regulated by GA in a lower concentration range than is required for shoot growth; (2) research on the regulation of GA biosynthesis pathways that are known predominantly to control shoot growth; and (3) recent research on GA signalling pathways, including GA receptors, which have been suggested to participate in GA-mediated growth regulation. This provides useful information to suggest a possible strategy for the selective control of shoot and root growth, and to explain how GA plays a role in rosette and liana plants with tall or short, and slender or thick axial organs. PMID:22437663

  18. 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.

  19. Non-hydraulic signals from maize roots in drying soil: inhibition of leaf elongation but not stomatal conductance.

    PubMed

    Saab, I N; Sharp, R E

    1989-11-01

    Conditions of soil drying and plant growth that lead to non-hydraulic inhibition of leaf elongation and stomatal conductance in maize (Zea mays L.) were investigated using plants grown with their root systems divided between two containers. The soil in one container was allowed to dry while the other container was kept well-watered. Soil drying resulted in a maximum 35% inhibition of leaf elongation rate which occurred during the light hours, with no measurable decline in leaf water potential (?w). Leaf area was 15% less than in control plants after 18 d of soil drying. The inhibition of elongation was observed only when the soil ?w declined to below that of the leaves and, thus, the drying soil no longer contributed to transpiration. However, midday root ?w in the dry container (-0.29 MPa) remained much higher than that of the surrounding soil (-1.0 MPa) after 15 d of drying, indicating that the roots in drying soil were rehydrated in the dark.To prove that the inhibition of leaf elongation was not caused by undetectable changes in leaf water status as a result of loss of half the watergathering capacity, one-half of the root system of control plants was excised. This treatment had no effect on leaf elongation or stomatal conductance. The inhibition of leaf elongation was also not explained by reductions in nutrient supply.Soil drying had no effect on stomatal conductance despite variations in the rate or extent of soild drying, light, humidity or nutrition. The results indicate that non-hydraulic inhibition of leaf elongation may act to conserve water as the soil dries before the occurrence of shoot water deficits. PMID:24201770

  20. 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.

  1. The Effect of Iron on the Primary Root Elongation of Arabidopsis during Phosphate Deficiency1[W][OA

    PubMed Central

    Ward, James T.; Lahner, Brett; Yakubova, Elena; Salt, David E.; Raghothama, Kashchandra G.

    2008-01-01

    Root architecture differences have been linked to the survival of plants on phosphate (P)-deficient soils, as well as to the improved yields of P-efficient crop cultivars. To understand how these differences arise, we have studied the root architectures of P-deficient Arabidopsis (Arabidopsis thaliana Columbia-0) plants. A striking aspect of the root architecture of these plants is that their primary root elongation is inhibited when grown on P-deficient medium. Here, we present evidence suggesting that this inhibition is a result of iron (Fe) toxicity. When the Fe concentration in P-deficient medium is reduced, we observe elongation of the primary root without an increase in P availability or a corresponding change in the expression of P deficiency-regulated genes. Recovery of the primary root elongation is associated with larger plant weights, improved ability to take up P from the medium, and increased tissue P content. This suggests that manipulating Fe availability to a plant could be a valuable strategy for improving a plant's ability to tolerate P deficiency. PMID:18467463

  2. Assessment of heavy metals phytotoxicity using seed germination and root elongation tests: A comparison of two growth substrates

    Microsoft Academic Search

    M. Di Salvatore; A. M. Carafa; G. Carratù

    2008-01-01

    Seed germination and root elongation test is used to evaluate hazardous waste sites and to assess toxicity of organic and inorganic compounds. Paper substrate, especially circular filter paper placed inside a Petri dish has long been used for this test. Same reports indicate that filter paper might interfere with the toxicity of inorganic substances, especially metal cations.This study evaluate toxicity

  3. Ammonium Inhibits Primary Root Growth by Reducing the Length of Meristem and Elongation Zone and Decreasing Elemental Expansion Rate in the Root Apex in Arabidopsis thaliana

    PubMed Central

    Gao, Kun; Chen, Fanjun; Yuan, Lixing; Mi, Guohua

    2013-01-01

    The inhibitory effect of ammonium on primary root growth has been well documented; however the underlying physiological and molecular mechanisms are still controversial. To avoid ammonium toxicity to shoot growth, we used a vertical two-layer split plate system, in which the upper layer contained nitrate and the lower layer contained ammonium. In this way, nitrogen status was maintained and only the apical part of the root system was exposed to ammonium. Using a kinematic approach, we show here that 1 mM ammonium reduces primary root growth, decreasing both elemental expansion and cell production. Ammonium inhibits the length of elongation zone and the maximum elemental expansion rate. Ammonium also decreases the apparent length of the meristem as well as the number of dividing cells without affecting cell division rate. Moreover, ammonium reduces the number of root cap cells but appears to affect neither the status of root stem cell niche nor the distal auxin maximum at the quiescent center. Ammonium also inhibits root gravitropism and concomitantly down-regulates the expression of two pivotal auxin transporters, AUX1 and PIN2. Insofar as ammonium inhibits root growth rate in AUX1 and PIN2 loss-of-function mutants almost as strongly as in wild type, we conclude that ammonium inhibits root growth and gravitropism by largely distinct pathways. PMID:23577185

  4. The role of the root apoplast in aluminium-induced inhibition of root elongation and in aluminium resistance of plants: a review

    PubMed Central

    Horst, Walter J.; Wang, Yunxia; Eticha, Dejene

    2010-01-01

    Background Aluminium (Al) toxicity is the most important soil constraint for plant growth and development in acid soils. The mechanism of Al-induced inhibition of root elongation is still not well understood, and it is a matter of debate whether the primary lesions of Al toxicity are apoplastic or symplastic. Scope The present review focuses on the role of the apoplast in Al toxicity and resistance, summarizing evidence from our own experimental work and other evidence published since 1995. Conclusions The binding of Al in the cell wall particularly to the pectic matrix and to the apoplastic face of the plasma membrane in the most Al-sensitive root zone of the root apex thus impairing apoplastic and symplastic cell functions is a major factor leading to Al-induced inhibition of root elongation. Although symplastic lesions of Al toxicity cannot be excluded, the protection of the root apoplast appears to be a prerequisite for Al resistance in both Al-tolerant and Al-accumulating plant species. In many plant species the release of organic acid anions complexing Al, thus protecting the root apoplast from Al binding, is a most important Al resistance mechanism. However, there is increasing physiological, biochemical and, most recently also, molecular evidence showing that the modification of the binding properties of the root apoplast contributes to Al resistance. A further in-depth characterization of the Al-induced apoplastic reaction in the most Al-sensitive zone of the root apex is urgently required, particularly to understand the Al resistance of the most Al-resistant plant species. PMID:20237112

  5. Transcription coactivator Arabidopsis?ANGUSTIFOLIA3 modulates anthocyanin accumulation and light-induced root elongation through transrepression of Constitutive?Photomorphogenic1.

    PubMed

    Meng, Lai-Sheng

    2015-04-01

    ANGUSTIFOLIA3 (AN3), a transcription coactivator, is implicated in modulating cell proliferation. In this study, I found that AN3 is a novel regulator of anthocyanin biosynthesis and light-induced root elongation. Seedlings and seeds lacking AN3 activity presented significantly reduced anthocyanin accumulation and light-induced root elongation, whereas those of transgenic plants harbouring the 35S:AN3 construct exhibited increased anthocyanin accumulation. AN3 is required for the proper expression of other genes that affect anthocyanin accumulation and light-induced root elongation, Constitutive?Photomorphogenic1 (COP1), encoding a RING motif - containing E3 ubiquitin ligase. AN3 was associated with COP1 promoter in vivo. Thus, AN3 may act with other proteins that bind to COP1 promoter to promote anthocyanin accumulation and inhibit light-induced root elongation. PMID:25256341

  6. Root hair elongation is inhibited by hypaphorine, the indole alkaloid from the ectomycorrhizal fungus Pisolithus tinctorius , and restored by indole-3-acetic acid

    Microsoft Academic Search

    Franck Anicet Ditengou; Thierry Béguiristain; Frédéric Lapeyrie

    2000-01-01

    .   Hypaphorine, the major indolic compound isolated from the ectomycorrhizal fungus Pisolithus tinctorius, controls the elongation rate of root hairs. At inhibitory concentrations (100??M), hypaphorine induced a transitory swelling\\u000a of root hair tips of Eucalyptus globulus Labill. ssp. bicostata. When the polar tip growth resumed, a characteristic deformation was still visible on elongating hairs. At higher hypaphorine\\u000a concentrations (500??M and

  7. Nitric Oxide is Involved in Nitrate-induced Inhibition of Root Elongation in Zea mays

    Microsoft Academic Search

    DONG-YAN ZHAO; QIU-YING TIAN; L.-H. Li; W.-H. Zhang

    2007-01-01

    †Background and Aims Root growth and development are closely dependent upon nitrate supply in the growth medium. To unravel the mechanism underlying dependence of root growth on nitrate, an examination was made of whether endogenous nitric oxide (NO) is involved in nitrate-dependent growth of primary roots in maize. †Methods Maize seedlings grown in varying concentrations of nitrate for 7 d

  8. Natural genetic variation in Arabidopsis identifies BREVIS RADIX, a novel regulator of cell proliferation and elongation in the root

    PubMed Central

    Mouchel, Céline F.; Briggs, Georgette C.; Hardtke, Christian S.

    2004-01-01

    Mutant analysis has been tremendously successful in deciphering the genetics of plant development. However, less is known about the molecular basis of morphological variation within species, which is caused by naturally occurring alleles. In this study, we succeeded in isolating a novel regulator of root growth by exploiting natural genetic variation in the model plant Arabidopsis. Quantitative trait locus analysis of a cross between isogenized accessions revealed that a single locus is responsible for ?80% of the variance of the observed difference in root length. This gene, named BREVIS RADIX (BRX), controls the extent of cell proliferation and elongation in the growth zone of the root tip. We isolated BRX by positional cloning. BRX is a member of a small group of highly conserved genes, the BRX gene family, which is only found in multicellular plants. Analyses of Arabidopsis single and double mutants suggest that BRX is the only gene of this family with a role in root development. The BRX protein is nuclear localized and activates transcription in a heterologous yeast system, indicating that BRX family proteins represent a novel class of transcription factors. Thus, we have identified a novel regulatory factor controlling quantitative aspects of root growth. PMID:15031265

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

    Microsoft Academic Search

    K. Vissenberg; V. Van Sandt; S. C. Fry

    2003-01-01

    The endotransglucosylase action of the enzyme xylo- glucan 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

  10. Rapid bioassessment methods for assessing vegetation toxicity at the Savannah River Site - germination tests and root elongation trials

    SciTech Connect

    Specht, W.L.; Klaine, S.J.; Hook, D.D. [and others

    1996-01-01

    Plants form the basis of all ecosystems including wetlands. Although they are the most abundant life form and are the primary producers for all other organisms, they have received the least attention when it comes to environmental matters. Higher plants have rarely been used in ecotoxicity testing and may not respond in the same manner as algae, which have been used more frequently. The introduction of hazardous waste materials into wetland areas has the potential to alter and damage the ecological processes in these ecosystems. Measuring the impact of these contaminants on higher plants is therefore important and needs further research. Higher plants are useful for detecting both herbicidal toxicity and heavy metal toxicity. For phytotoxicity tests to be practical they must be simple, inexpensive, yet sensitive to a variety of contaminants. A difference between seed germination and root elongation tests is that seed germination tests measure toxicity associated with soils directly, while root elongation tests consider the indirect effects of water-soluble constituents that may be present in site samples.

  11. Selenium inhibits root elongation by repressing the generation of endogenous hydrogen sulfide in Brassica rapa.

    PubMed

    Chen, Yi; Mo, Hai-Zhen; Zheng, Mei-Yu; Xian, Ming; Qi, Zhong-Qiang; Li, You-Qin; Hu, Liang-Bin; Chen, Jian; Yang, Li-Fei

    2014-01-01

    Selenium (Se) has been becoming an emerging pollutant causing severe phytotoxicity, which the biochemical mechanism is rarely known. Although hydrogen sulfide (H2S) has been suggested as an important exogenous regulator modulating plant physiological adaptions in response to heavy metal stress, whether and how the endogenous H2S regulates Se-induce phytotoxicity remains unclear. In this work, a self-developed specific fluorescent probe (WSP-1) was applied to track endogenous H2S in situ in the roots of Brassica rapa under Se(IV) stress. Se(IV)-induced root growth stunt was closely correlated with the inhibition of endogenous H2S generation in root tips. Se(IV) stress dampened the expression of most LCD and DCD homologues in the roots of B. rapa. By using various specific fluorescent probes for bio-imaging root tips in situ, we found that the increase in endogenous H2S by the application of H2S donor NaHS could significantly alleviate Se(IV)-induced reactive oxygen species (ROS) over-accumulation, oxidative impairment, and cell death in root tips, which further resulted in the recovery of root growth under Se(IV) stress. However, dampening the endogenous H2S could block the alleviated effect of NaHS on Se(IV)-induced phytotoxicity. Finally, the increase in endogenous H2S resulted in the enhancement of glutathione (GSH) in Se(IV)-treated roots, which may share the similar molecular mechanism for the dominant role of H2S in removing ROS by activating GSH biosynthesis in mammals. Altogether, these data provide the first direct evidences confirming the pivotal role of endogenous H2S in modulating Se(IV)-induced phytotoxicity in roots. PMID:25333279

  12. Hyper, a hydrogen peroxide sensor, indicates the sensitivity of the Arabidopsis root elongation zone to aluminum treatment.

    PubMed

    Hernández-Barrera, Alejandra; Velarde-Buendía, Ana; Zepeda, Isaac; Sanchez, Federico; Quinto, Carmen; Sánchez-Lopez, Rosana; Cheung, Alice Y; Wu, Hen-Ming; Cardenas, Luis

    2015-01-01

    Emerging evidence indicates that some reactive oxygen species (ROS), such as the superoxide anion radical and hydrogen peroxide (H2O2), are central regulators of plant responses to biotic and abiotic stresses. Thus, the cellular levels of ROS are thought to be tightly regulated by an efficient and elaborate pro- and antioxidant system that modulates the production and scavenging of ROS. Until recently, studies of ROS in plant cells have been limited to biochemical assays and the use of fluorescent probes; however, the irreversible oxidation of these fluorescent probes makes it impossible to visualize dynamic changes in ROS levels. In this work, we describe the use of Hyper, a recently developed live cell probe for H2O2 measurements in living cells, to monitor oxidative stress in Arabidopsis roots subjected to aluminum treatment. Hyper consists of a circularly permuted YFP (cpYFP) inserted into the regulatory domain of the Escherichia coli hydrogen peroxide-binding protein (OxyR), and is a H2O2-specific ratiometric, and therefore quantitative, probe that can be expressed in plant and animal cells. Now we demonstrate that H2O2 levels drop sharply in the elongation zone of roots treated with aluminum. This response could contribute to root growth arrest and provides evidence that H2O2 is involved in early Al sensing. PMID:25569758

  13. Hyper, a Hydrogen Peroxide Sensor, Indicates the Sensitivity of the Arabidopsis Root Elongation Zone to Aluminum Treatment

    PubMed Central

    Hernández-Barrera, Alejandra; Velarde-Buendía, Ana; Zepeda, Isaac; Sanchez, Federico; Quinto, Carmen; Sánchez-Lopez, Rosana; Cheung, Alice Y.; Wu, Hen-Ming; Cardenas, Luis

    2015-01-01

    Emerging evidence indicates that some reactive oxygen species (ROS), such as the superoxide anion radical and hydrogen peroxide (H2O2), are central regulators of plant responses to biotic and abiotic stresses. Thus, the cellular levels of ROS are thought to be tightly regulated by an efficient and elaborate pro- and antioxidant system that modulates the production and scavenging of ROS. Until recently, studies of ROS in plant cells have been limited to biochemical assays and the use of fluorescent probes; however, the irreversible oxidation of these fluorescent probes makes it impossible to visualize dynamic changes in ROS levels. In this work, we describe the use of Hyper, a recently developed live cell probe for H2O2 measurements in living cells, to monitor oxidative stress in Arabidopsis roots subjected to aluminum treatment. Hyper consists of a circularly permuted YFP (cpYFP) inserted into the regulatory domain of the Escherichia coli hydrogen peroxide-binding protein (OxyR), and is a H2O2-specific ratiometric, and therefore quantitative, probe that can be expressed in plant and animal cells. Now we demonstrate that H2O2 levels drop sharply in the elongation zone of roots treated with aluminum. This response could contribute to root growth arrest and provides evidence that H2O2 is involved in early Al sensing. PMID:25569758

  14. Seed germination, root elongation, root-tip mitosis, and micronucleus induction of five crop plants exposed to chromium in fluvo-aquic soil.

    PubMed

    Hou, Jing-; Liu, Guan-Nan; Xue, Wei; Fu, Wen-Jun; Liang, Bao-Cui; Liu, Xin-Hui

    2014-03-01

    The present study aimed to determine the toxic effects of chromium (Cr) on cabbage (Brassica oleracea), cucumber (Cucumis sativus), lettuce (Lactuca sativa), wheat (Triticum aestivum), and corn (Zea mays), and identify the sensitive plant species and appropriate bioassays for potential use in phytotoxicity assessment of Cr in soil. Results showed that seed germination might not be a sensitive assay for assessing Cr toxicity because at most of the Cr levels there were no toxic effects. Root elongation was more sensitive to Cr than seed germination. The lowest concentration of adverse effect (LOAEC) of lettuce was 20 mg Cr/kg(-1) soil, and that of the other 4 species was 50 mg Cr/kg(-1) soil. The mitotic index fluctuated with increasing Cr concentration, thus it was insufficient to assess toxicity of Cr in soil. However, micronucleus assay showed that 5 mg Cr/kg(-1) soil caused a significant increase in micronucleus frequency in cabbage, cucumber, and lettuce. For wheat and corn, however, the LOAEC was 20 and 50 mg/Cr/kg(-1) soil, respectively. Furthermore, the analysis of Cr accumulation showed that lettuce significantly accumulated Cr for all the tested concentrations. However, corn and wheat significantly accumulated Cr only with the highest tested dose. This may explain the higher inhibitory effects of Cr on root growth. It can be concluded that root elongation and micronucleus assay are good indicators to assess the phytotoxicity of Cr in soil. Lettuce is the most sensitive species for indicating the toxicity of Cr in soil. PMID:24318542

  15. ROOT ELONGATION OF BLACK WILLOW STAKES IN RESPONSE TO CUTTING SIZE AND SOIL MOISTURE REGIME (TENNESSEE).

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Woody plants such as black willow are often used for riparian zone erosion control and restoration because they may be established from cuttings. Rapid root development is important for bank stabilization and plant survival. Restoration handbooks advocate use of a wide range of willow cutting sizes,...

  16. Effect of heavy metals on inhibition of root elongation in 23 cultivars of flax (Linum usitatissimum L.).

    PubMed

    Soudek, Petr; Katrusáková, Adéla; Sedlácek, Lukás; Petrová, Sárka; Kocí, Vladimír; Marsík, Petr; Griga, Miroslav; Vanek, Tomás

    2010-08-01

    The effect of toxic metals on seed germination was studied in 23 cultivars of flax (Linum usitatissimum L.). Toxicity of cadmium, cobalt, copper, zinc, nickel, lead, chromium, and arsenic at five different concentrations (0.01-1 mM) was tested by standard ecotoxicity test. Root length was measured after 72 h of incubation. Elongation inhibition, EC50 value, slope, and NOEC values were calculated. Results were evaluated by principal component analysis, a multidimensional statistical method. The results showed that heavy-metal toxicity decreased in the following order: As3+>or=As5+>Cu2+>Cd2+>Co2+>Cr6+>Ni2+>Pb2+>Cr3+>Zn2+. PMID:20174789

  17. Mechanism-based quantitative structure-phytotoxicity relationships comparative inhibition of substituted phenols on root elongation of Cucumis sativus.

    PubMed

    Wang, X; Wang, Y; Chunsheng, Y; Wang, L; Han, S

    2002-01-01

    Phytotoxicity of selected substituted phenols to Cucumis sativus (log1/RC50, root elongation half inhibition concentration [mol/L] in logarithmic form) was determined by using a root elongation inhibition method and quantitative structure-activity relationships (QSARs) were developed. Hydrophobicity, described by 1-octanol/water partition coefficient in logarithmic form (log Kow) and electronic effect (characterized by the energy of the lowest unoccupied orbital, Elumo) proved to contribute mainly to the phytotoxicity of phenols in this study. Log Kow was used as a probe to classify the tested chemicals into subsets according to the modes of toxic action. The result indicated that the substituted phenols fell into two classes in general: narcotic phenols and bioreactive phenols. Most phenols elicited their toxic response via a polar narcosis mechanism and an excellent log Kow-dependent QSAR was developed (log1/RC50 = 0.94 log Kow + 2.04, n = 22, r2adj = 0.89). Selected phenols with bioreactive substructures exhibited elevated bioreactive toxicity and a strong Elumo-dependent correlation was achieved (log1/RC50 = -0.91 Elumo + 2.73, n = 6, r2adj = 0.81). This implied that their reactive toxicity involved mainly their in vivo electrophilic reactions. In an effort to model all chemicals without regard to their mechanisms, a highly predictive response-surface was developed with the phytotoxicity, hydrophobicity, and electrophilic reactivity (log1/RC50 = 0.66 log Kow - 0.57 Elumo + 2.31, n = 28, r2adj = 0.88). PMID:11706365

  18. 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

  19. Control of root meristem size by DA1-RELATED PROTEIN2 in Arabidopsis.

    PubMed

    Peng, Yuancheng; Ma, Wenying; Chen, Liangliang; Yang, Lei; Li, Shengjun; Zhao, Hongtao; Zhao, Yankun; Jin, Weihuan; Li, Na; Bevan, Michael W; Li, Xia; Tong, Yiping; Li, Yunhai

    2013-03-01

    The control of organ growth by coordinating cell proliferation and differentiation is a fundamental developmental process. In plants, postembryonic root growth is sustained by the root meristem. For maintenance of root meristem size, the rate of cell differentiation must equal the rate of cell division. Cytokinin and auxin interact to affect the cell proliferation and differentiation balance and thus control root meristem size. However, the genetic and molecular mechanisms that determine root meristem size still remain largely unknown. Here, we report that da1-related protein2 (dar2) mutants produce small root meristems due to decreased cell division and early cell differentiation in the root meristem of Arabidopsis (Arabidopsis thaliana). dar2 mutants also exhibit reduced stem cell niche activity in the root meristem. DAR2 encodes a Lin-11, Isl-1, and Mec-3 domain-containing protein and shows an expression peak in the border between the transition zone and the elongation zone. Genetic analyses show that DAR2 functions downstream of cytokinin and SHORT HYPOCOTYL2 to maintain normal auxin distribution by influencing auxin transport. Further results indicate that DAR2 acts through the PLETHORA pathway to influence root stem cell niche activity and therefore control root meristem size. Collectively, our findings identify the role of DAR2 in root meristem size control and provide a novel link between several key regulators influencing root meristem size. PMID:23296689

  20. Roles of BOR2, a Boron Exporter, in Cross Linking of Rhamnogalacturonan II and Root Elongation under Boron Limitation in Arabidopsis1[W

    PubMed Central

    Miwa, Kyoko; Wakuta, Shinji; Takada, Shigeki; Ide, Koji; Takano, Junpei; Naito, Satoshi; Omori, Hiroyuki; Matsunaga, Toshiro; Fujiwara, Toru

    2013-01-01

    Boron (B) is required for cross linking of the pectic polysaccharide rhamnogalacturonan II (RG-II) and is consequently essential for the maintenance of cell wall structure. Arabidopsis (Arabidopsis thaliana) BOR1 is an efflux B transporter for xylem loading of B. Here, we describe the roles of BOR2, the most similar paralog of BOR1. BOR2 encodes an efflux B transporter localized in plasma membrane and is strongly expressed in lateral root caps and epidermis of elongation zones of roots. Transfer DNA insertion of BOR2 reduced root elongation by 68%, whereas the mutation in BOR1 reduced it by 32% under low B availability (0.1 µm), but the reduction in shoot growth was not as obvious as that in the BOR1 mutant. A double mutant of BOR1 and BOR2 exhibited much more severe growth defects in both roots and shoots under B-limited conditions than the corresponding single mutants. All single and double mutants grew normally under B-sufficient conditions. These results suggest that both BOR1 and BOR2 are required under B limitation and that their roles are, at least in part, different. The total B concentrations in roots of BOR2 mutants were not significantly different from those in wild-type plants, but the proportion of cross-linked RG-II was reduced under low B availability. Such a reduction in RG-II cross linking was not evident in roots of the BOR1 mutant. Thus, we propose that under B-limited conditions, transport of boric acid/borate by BOR2 from symplast to apoplast is required for effective cross linking of RG-II in cell wall and root cell elongation. PMID:24114060

  1. GABA Accumulation Causes Cell Elongation Defects and a Decrease in Expression of Genes Encoding Secreted and Cell Wall-Related Proteins in Arabidopsis thaliana

    PubMed Central

    Renault, Hugues; El Amrani, Abdelhak; Palanivelu, Ravishankar; Updegraff, Emily P.; Yu, Agnès; Renou, Jean-Pierre; Preuss, Daphne; Bouchereau, Alain; Deleu, Carole

    2011-01-01

    GABA (?-aminobutyric acid), a non-protein amino acid, is a signaling factor in many organisms. In plants, GABA is known to accumulate under a variety of stresses. However, the consequence of GABA accumulation, especially in vegetative tissues, remains poorly understood. Moreover, gene expression changes as a consequence of GABA accumulation in plants are largely unknown. The pop2 mutant, which is defective in GABA catabolism and accumulates GABA, is a good model to examine the effects of GABA accumulation on plant development. Here, we show that the pop2 mutants have pollen tube elongation defects in the transmitting tract of pistils. Additionally, we observed growth inhibition of primary root and dark-grown hypocotyl, at least in part due to cell elongation defects, upon exposure to exogenous GABA. Microarray analysis of pop2-1 seedlings grown in GABA-supplemented medium revealed that 60% of genes whose expression decreased encode secreted proteins. Besides, functional classification of genes with decreased expression in the pop2-1 mutant showed that cell wall-related genes were significantly enriched in the microarray data set, consistent with the cell elongation defects observed in pop2 mutants. Our study identifies cell elongation defects caused by GABA accumulation in both reproductive and vegetative tissues. Additionally, our results show that genes that encode secreted and cell wall-related proteins may mediate some of the effects of GABA accumulation. The potential function of GABA as a growth control factor under stressful conditions is discussed. PMID:21471118

  2. Osmotic Sensitivity of Ca 2+ and H + Transporters in Corn Roots: Effect on Fluxes and Their Oscillations in the Elongation Region

    Microsoft Academic Search

    S. N. Shabala; I. A. Newman

    1998-01-01

    .   Seedling roots of corn were treated with different concentrations of mannitol-containing solution for 1 to 1.5 hr, and net\\u000a fluxes of Ca2+ and H+ were measured in the elongation region. H+ fluxes were much more sensitive to osmotic pressure than were Ca2+ fluxes. Oscillations of 7-min period in H+ flux, normally observed in the control, were almost fully suppressed

  3. Development of a Multi-Species Biotic Ligand Model Predicting the Toxicity of Trivalent Chromium to Barley Root Elongation in Solution Culture

    PubMed Central

    Song, Ningning; Zhong, Xu; Li, Bo; Li, Jumei; Wei, Dongpu; Ma, Yibing

    2014-01-01

    Little knowledge is available about the influence of cation competition and metal speciation on trivalent chromium (Cr(III)) toxicity. In the present study, the effects of pH and selected cations on the toxicity of trivalent chromium (Cr(III)) to barley (Hordeum vulgare) root elongation were investigated to develop an appropriate biotic ligand model (BLM). Results showed that the toxicity of Cr(III) decreased with increasing activity of Ca2+ and Mg2+ but not with K+ and Na+. The effect of pH on Cr(III) toxicity to barley root elongation could be explained by H+ competition with Cr3+ bound to a biotic ligand (BL) as well as by the concomitant toxicity of CrOH2+ in solution culture. Stability constants were obtained for the binding of Cr3+, CrOH2+, Ca2+, Mg2+ and H+ with binding ligand: log KCrBL 7.34, log KCrOHBL 5.35, log KCaBL 2.64, log KMgBL 2.98, and log KHBL 4.74. On the basis of those estimated parameters, a BLM was successfully developed to predict Cr(III) toxicity to barley root elongation as a function of solution characteristics. PMID:25119269

  4. Chemical root pruning and its effects on water relations and root morphology of photinia 

    E-print Network

    Vartak, Diptish Ramesh

    1993-01-01

    -treated containers. The effects of chemical root pruning on water relations and root morphology were studied. A model was developed to predict transpiration in greenhouse grown photinia. A separate experiment was conducted to test accuracy of stem gauges...

  5. Relative Mesothelioma Potencies for Unregulated Respirable Elongated Mineral and Synthetic Particles

    EPA Science Inventory

    For decades uncertainties and contradictions have surrounded the issue of whether exposures to respirable elongated mineral and synthetic particles (REMPs and RESPs) present health risks such as those recognized for exposures to elongated asbestiform mineral particles from the fi...

  6. Multiple functions of Kip-related protein5 connect endoreduplication and cell elongation.

    PubMed

    Jégu, Teddy; Latrasse, David; Delarue, Marianne; Mazubert, Christelle; Bourge, Mickaël; Hudik, Elodie; Blanchet, Sophie; Soler, Marie-Noëlle; Charon, Céline; De Veylder, Lieven; Raynaud, Cécile; Bergounioux, Catherine; Benhamed, Moussa

    2013-04-01

    Despite considerable progress in our knowledge regarding the cell cycle inhibitor of the Kip-related protein (KRP) family in plants, less is known about the coordination of endoreduplication and cell differentiation. In animals, the role of cyclin-dependent kinase (CDK) inhibitors as multifunctional factors coordinating cell cycle regulation and cell differentiation is well documented and involves not only the inhibition of CDK/cyclin complexes but also other mechanisms, among them the regulation of transcription. Interestingly, several plant KRPs have a punctuated distribution in the nucleus, suggesting that they are associated with heterochromatin. Here, one of these chromatin-bound KRPs, KRP5, has been studied in Arabidopsis (Arabidopsis thaliana). KRP5 is expressed in endoreduplicating cells, and loss of KRP5 function decreases endoreduplication, indicating that KRP5 is a positive regulator of endoreduplication. This regulation relies on several mechanisms: in addition to its role in cyclin/CDK kinase inhibition previously described, chromatin immunoprecipitation sequencing data combined with transcript quantification provide evidence that KRP5 regulates the transcription of genes involved in cell wall organization. Furthermore, KRP5 overexpression increases chromocenter decondensation and endoreduplication in the Arabidopsis trithorax-related protein5 (atxr5) atxr6 double mutant, which is deficient for the deposition of heterochromatin marks. Hence, KRP5 could bind chromatin to coordinately control endoreduplication and chromatin structure and allow the expression of genes required for cell elongation. PMID:23426196

  7. RICE SALT SENSITIVE3 Forms a Ternary Complex with JAZ and Class-C bHLH Factors and Regulates Jasmonate-Induced Gene Expression and Root Cell Elongation[C][W

    PubMed Central

    Toda, Yosuke; Tanaka, Maiko; Ogawa, Daisuke; Kurata, Kyo; Kurotani, Ken-ichi; Habu, Yoshiki; Ando, Tsuyu; Sugimoto, Kazuhiko; Mitsuda, Nobutaka; Katoh, Etsuko; Abe, Kiyomi; Miyao, Akio; Hirochika, Hirohiko; Hattori, Tsukaho; Takeda, Shin

    2013-01-01

    Plasticity of root growth in response to environmental cues and stresses is a fundamental characteristic of land plants. However, the molecular basis underlying the regulation of root growth under stressful conditions is poorly understood. Here, we report that a rice nuclear factor, RICE SALT SENSITIVE3 (RSS3), regulates root cell elongation during adaptation to salinity. Loss of function of RSS3 only moderately inhibits cell elongation under normal conditions, but it provokes spontaneous root cell swelling, accompanied by severe root growth inhibition, under saline conditions. RSS3 is preferentially expressed in the root tip and forms a ternary complex with class-C basic helix-loop-helix (bHLH) transcription factors and JASMONATE ZIM-DOMAIN proteins, the latter of which are the key regulators of jasmonate (JA) signaling. The mutated protein arising from the rss3 allele fails to interact with bHLH factors, and the expression of a significant portion of JA-responsive genes is upregulated in rss3. These results, together with the known roles of JAs in root growth regulation, suggest that RSS3 modulates the expression of JA-responsive genes and plays a crucial role in a mechanism that sustains root cell elongation at appropriate rates under stressful conditions. PMID:23715469

  8. RICE SALT SENSITIVE3 forms a ternary complex with JAZ and class-C bHLH factors and regulates jasmonate-induced gene expression and root cell elongation.

    PubMed

    Toda, Yosuke; Tanaka, Maiko; Ogawa, Daisuke; Kurata, Kyo; Kurotani, Ken-Ichi; Habu, Yoshiki; Ando, Tsuyu; Sugimoto, Kazuhiko; Mitsuda, Nobutaka; Katoh, Etsuko; Abe, Kiyomi; Miyao, Akio; Hirochika, Hirohiko; Hattori, Tsukaho; Takeda, Shin

    2013-05-01

    Plasticity of root growth in response to environmental cues and stresses is a fundamental characteristic of land plants. However, the molecular basis underlying the regulation of root growth under stressful conditions is poorly understood. Here, we report that a rice nuclear factor, RICE SALT SENSITIVE3 (RSS3), regulates root cell elongation during adaptation to salinity. Loss of function of RSS3 only moderately inhibits cell elongation under normal conditions, but it provokes spontaneous root cell swelling, accompanied by severe root growth inhibition, under saline conditions. RSS3 is preferentially expressed in the root tip and forms a ternary complex with class-C basic helix-loop-helix (bHLH) transcription factors and JASMONATE ZIM-DOMAIN proteins, the latter of which are the key regulators of jasmonate (JA) signaling. The mutated protein arising from the rss3 allele fails to interact with bHLH factors, and the expression of a significant portion of JA-responsive genes is upregulated in rss3. These results, together with the known roles of JAs in root growth regulation, suggest that RSS3 modulates the expression of JA-responsive genes and plays a crucial role in a mechanism that sustains root cell elongation at appropriate rates under stressful conditions. PMID:23715469

  9. Armadillo-related proteins promote lateral root development in Arabidopsis

    E-print Network

    Haseloff, Jim

    Armadillo-related proteins promote lateral root development in Arabidopsis Juliet C. Coates) Armadillo -catenin and related proteins have important func- tions during animal and Dictyostelium development, regulating cell differentiation, proliferation, and adhesion. Armadillo-repeat- containing

  10. Tomato BRASSINOSTEROID INSENSITIVE1 is required for systemin-induced root elongation in Solanum pimpinellifolium but is not essential for wound signaling.

    PubMed

    Holton, Nicholas; Caño-Delgado, Ana; Harrison, Kate; Montoya, Teresa; Chory, Joanne; Bishop, Gerard J

    2007-05-01

    The tomato Leu-rich repeat receptor kinase BRASSINOSTEROID INSENSITIVE1 (BRI1) has been implicated in both peptide (systemin) and steroid (brassinosteroid [BR]) hormone perception. In an attempt to dissect these signaling pathways, we show that transgenic expression of BRI1 can restore the dwarf phenotype of the tomato curl3 (cu3) mutation. Confirmation that BRI1 is involved in BR signaling is highlighted by the lack of BR binding to microsomal fractions made from cu3 mutants and the restoration of BR responsiveness following transformation with BRI1. In addition, wound and systemin responses in the cu3 mutants are functional, as assayed by proteinase inhibitor gene induction and rapid alkalinization of culture medium. However, we observed BRI1-dependent root elongation in response to systemin in Solanum pimpinellifolium. In addition, ethylene perception is required for normal systemin responses in roots. These data taken together suggest that cu3 is not defective in systemin-induced wound signaling and that systemin perception can occur via a non-BRI1 mechanism. PMID:17513502

  11. Aluminum tolerance of two wheat cultivars (Brevor and Atlas66) in relation to their rhizosphere pH and organic acids exuded from roots.

    PubMed

    Wang, Ping; Bi, Shuping; Ma, Liping; Han, Weiying

    2006-12-27

    Phytotoxicity of aluminum (Al) has become a serious problem in inhibiting plant growth on acid soils. Under Al stress, the changes of rhizosphere pH, root elongation, absorption of Al by wheat roots, organic acids exuded from roots, and some main factors related to Al-tolerant mechanisms have been studied using hydroponics, fluorescence spectrophotometry, and high performance liquid chromatography (HPLC). Two wheat cultivars, Brevor and Atlas66, differing in Al tolerance are chosen in the study. Accordingly, the rhizosphere pH has a positive effect on Al tolerance. Atlas66 (Al-tolerant) has higher capability to maintain high rhizosphere pH than Brevor (Al-sensitive) does. High pH can reduce Al3+ activity and toxicity, and increase the efficiency of exuding organic acids from the roots. More inhibition of root elongation has been found in Brevor because of the exposure of roots to Al3+ solution at low pH. Brevor accumulate more Al in roots than Atlas66 even at higher pH. Al-induced exudation of malic and citric acids has been found in Atlas66 roots, while no Al-induced organic acids have been found in Brevor. These results indicate that the Al-induced secretion of organic acids from Atlas66 roots has a positive correlation with Al tolerance. Comprehensive treatment of Al3+ and H+ indicates that wheat is adversely influenced by excess Al3+, rather than low pH. PMID:17177538

  12. Structure comparison and evolutionary relations between elongation factors EFTu (EF1?) and SUP 2 proteins

    Microsoft Academic Search

    M. G. Samsonova; S. G. Inge-Vechtomov; P. Taylor

    1991-01-01

    On the basis of high homology and structural similarity, three genes, SUP2 Saccharomyces cerevisiae, SUP2 Pichia pinus and GST1 Homo sapiens, might be considered as members of one family named SUP2. Comparison of the primary structure of SUP2 proteins and elongation factors EF-Tu(EF-1a) from 19 different species was performed. It was found that SUP2 proteins bear more homology to eukaryotic

  13. The transcript elongation factor SPT4/SPT5 is involved in auxin-related gene expression in Arabidopsis

    PubMed Central

    Dürr, Julius; Lolas, Ihab B.; Sørensen, Brian B.; Schubert, Veit; Houben, Andreas; Melzer, Michael; Deutzmann, Rainer; Grasser, Marion; Grasser, Klaus D.

    2014-01-01

    The heterodimeric complex SPT4/SPT5 is a transcript elongation factor (TEF) that directly interacts with RNA polymerase II (RNAPII) to regulate messenger RNA synthesis in the chromatin context. We provide biochemical evidence that in Arabidopsis, SPT4 occurs in a complex with SPT5, demonstrating that the SPT4/SPT5 complex is conserved in plants. Each subunit is encoded by two genes SPT4-1/2 and SPT5-1/2. A mutant affected in the tissue-specifically expressed SPT5-1 is viable, whereas inactivation of the generally expressed SPT5-2 is homozygous lethal. RNAi-mediated downregulation of SPT4 decreases cell proliferation and causes growth reduction and developmental defects. These plants display especially auxin signalling phenotypes. Consistently, auxin-related genes, most strikingly AUX/IAA genes, are downregulated in SPT4–RNAi plants that exhibit an enhanced auxin response. In Arabidopsis nuclei, SPT5 clearly localizes to the transcriptionally active euchromatin, and essentially co-localizes with transcribing RNAPII. Typical for TEFs, SPT5 is found over the entire transcription unit of RNAPII-transcribed genes. In SPT4–RNAi plants, elevated levels of RNAPII and SPT5 are detected within transcribed regions (including those of downregulated genes), indicating transcript elongation defects in these plants. Therefore, SPT4/SPT5 acts as a TEF in Arabidopsis, regulating transcription during the elongation stage with particular impact on the expression of certain auxin-related genes. PMID:24497194

  14. Why fine tree roots are stronger than thicker roots: The role of cellulose and lignin in relation to slope stability

    NASA Astrophysics Data System (ADS)

    Zhang, Chao-Bo; Chen, Li-Hua; Jiang, Jing

    2014-02-01

    Plant roots help to reinforce the soil, increase slope stability and decrease water erosion. Root tensile strength plays an important role in soil reinforcement and slope stabilization. The relationship between tensile strength and internal chemical composition of roots is unknown due to limited studies. Thus, it is difficult to determine why root tensile strength tends to decrease with increasing root diameter. In this study, biomechanical and biochemical tests were performed on the roots of Chinese pine (Pinus tabulaeformis) to determine the relationships among tensile strength and the contents of the main chemical composition: cellulose, alpha-cellulose and lignin in the roots with different diameters. Our results confirmed that the tensile strength of Chinese pine roots decreased with increasing root diameter, and this relationship might be a power function. The chemical contents of the roots and root diameter were also related to each other with significant power regression. With increasing root diameter, the cellulose content and alpha-cellulose content increased, but the lignin content decreased. In addition, the lignin content exhibited a significantly positive relationship with tensile strength. Furthermore, the ratios of lignin/cellulose and lignin/alpha-cellulose decreased with increasing root diameter following significant power regressions, and they also demonstrated a positive relationship with tensile strength. Taken together, these results may be useful for studies on root tensile strength, soil reinforcement and slope stability.

  15. Ubiquitin-Related Modifiers of Arabidopsis thaliana Influence Root Development

    PubMed Central

    John, Florian; Philipp, Matthias; Leiber, Ruth-Maria; Errafi, Sanae; Ringli, Christoph

    2014-01-01

    Ubiquitins are small peptides that allow for posttranslational modification of proteins. Ubiquitin-related modifier (URM) proteins belong to the class of ubiquitin-like proteins. A primary function of URM proteins has been shown to be the sulfur transfer reaction leading to thiolation of tRNAs, a process that is important for accurate and effective protein translation. Recent analyses revealed that the Arabidopsis genome codes for two URM proteins, URM11 and URM12, which both are active in the tRNA thiolation process. Here, we show that URM11 and URM12 have overlapping expression patterns and are required for tRNA thiolation. The characterization of urm11 and urm12 mutants reveals that the lack of tRNA thiolation induces changes in general root architecture by influencing the rate of lateral root formation. In addition, they synergistically influence root hair cell growth. During the sulfur transfer reaction, URM proteins of different organisms interact with a thiouridylase, a protein-protein interaction that also takes place in Arabidopsis, since URM11 and URM12 interact with the Arabidopsis thiouridylase ROL5. Hence, the sulfur transfer reaction is conserved between distantly related species such as yeast, humans, and plants, and in Arabidopsis has an impact on root development. PMID:24466270

  16. Species differences in ligand specificity of auxin-controlled elongation and auxin transport: comparing Zea and Vigna

    NASA Technical Reports Server (NTRS)

    Zhao, Hu; Hertel, Rainer; Ishikawa, Hideo; Evans, Michael L.

    2002-01-01

    The plant hormone auxin affects cell elongation in both roots and shoots. In roots, the predominant action of auxin is to inhibit cell elongation while in shoots auxin, at normal physiological levels, stimulates elongation. The question of whether the primary receptor for auxin is the same in roots and shoots has not been resolved. In addition to its action on cell elongation in roots and shoots, auxin is transported in a polar fashion in both organs. Although auxin transport is well characterized in both roots and shoots, there is relatively little information on the connection, if any, between auxin transport and its action on elongation. In particular, it is not clear whether the protein mediating polar auxin movement is separate from the protein mediating auxin action on cell elongation or whether these two processes might be mediated by one and the same receptor. We examined the identity of the auxin growth receptor in roots and shoots by comparing the response of roots and shoots of the grass Zea mays L. and the legume Vigna mungo L. to indole-3-acetic acid, 2-naphthoxyacetic acid, 4,6-dichloroindoleacetic acid, and 4,7-dichloroindoleacetic acid. We also studied whether or not a single protein might mediate both auxin transport and auxin action by comparing the polar transport of indole-3-acetic acid and 2-naphthoxyacetic acid through segments from Vigna hypocotyls and maize coleoptiles. For all of the assays performed (root elongation, shoot elongation, and polar transport) the action and transport of the auxin derivatives was much greater in the dicots than in the grass species. The preservation of ligand specificity between roots and shoots and the parallels in ligand specificity between auxin transport and auxin action on growth are consistent with the hypothesis that the auxin receptor is the same in roots and shoots and that this protein may mediate auxin efflux as well as auxin action in both organ types.

  17. Shoot regeneration capacity from roots and transgenic hairy roots of tomato cultivars and wild related species

    Microsoft Academic Search

    Lázaro E. P. Peres; Patrícia G. Morgante; Cláudia Vecchi; Jane E. Kraus; Marie-Anne van Sluys

    2001-01-01

    The organogenetic competence of roots and Agrobacterium rhizogenes-induced hairy roots of twelve Lycopersicon genotypes was investigated. Both roots and hairy roots of L. peruvianum, L. chilense, L. hirsutum and two L. peruvianum-derived genotypes regenerated shoots after 2–4 weeks of incubation on zeatin-contained medium. Anatomical analysis showed\\u000a that shoot regeneration in roots could be direct or indirect, depending on the genotype

  18. Involvement of root ABA and hydraulic conductivity in the control of water relations in wheat plants exposed to increased evaporative demand.

    PubMed

    Kudoyarova, Guzel; Veselova, Svetlana; Hartung, Wolfram; Farhutdinov, Rashit; Veselov, Dmitry; Sharipova, Guzyal

    2011-01-01

    We studied the possible involvement of ABA in the control of water relations under conditions of increased evaporative demand. Warming the air by 3°C increased stomatal conductance and raised transpiration rates of hydroponically grown Triticum durum plants while bringing about a temporary loss of relative water content (RWC) and immediate cessation of leaf extension. However, both RWC and extension growth recovered within 30 min although transpiration remained high. The restoration of leaf hydration and growth were enabled by increased root hydraulic conductivity after increasing the air temperature. The use of mercuric chloride (an inhibitor of water channels) to interfere with the rise on root hydraulic conductivity hindered the restoration of extension growth. Air warming increased ABA content in roots and decreased it in shoots. We propose this redistribution of ABA in favour of the roots which increased the root hydraulic conductivity sufficiently to permit rapid recovery of shoot hydration and leaf elongation rates without the involvement of stomatal closure. This proposal is based on known ability of ABA to increase hydraulic conductivity confirmed in these experiments by measuring the effect of exogenous ABA on osmotically driven flow of xylem sap from the roots. Accumulation of root ABA was mainly the outcome of increased export from the shoots. When phloem transport in air-warmed plants was inhibited by cooling the shoot base this prevented ABA enrichment of the roots and favoured an accumulation of ABA in the shoot. As a consequence, stomata closed. PMID:20924765

  19. Asymmetric growth of root epidermal cells is related to the differentiation of root hair cells in Hordeum vulgare (L.).

    PubMed

    Marzec, Marek; Melzer, Michael; Szarejko, Iwona

    2013-11-01

    The root epidermis of most vascular plants harbours two cell types, namely trichoblasts (capable of producing a root hair) and atrichoblasts. Here, in vivo analysis, confocal laser-scanning microscopy, transmission electron microscopy, histological analysis, and three-dimensional reconstruction were used to characterize the cell types present in the barley root epidermis and their distribution in the tissue. Both trichoblasts and atrichoblasts were present in the wild-type cultivars and could be distinguished from one another at an early stage. Trichoblast/atrichoblast differentiation depended on asymmetric cell expansion after a period of symmetrical cell division. After asymmetric growth, only the shorter epidermal cells could produce root hairs, whereas the longer cells became atrichoblasts. Moreover, the root epidermis did not develop root hairs at all if the epidermal cells did not differentiate into two asymmetric cell types. The root hairless phenotype of bald root barley (brb) and root hairless 1.b (rhl1.b) mutants was caused by a mutation in a gene related to the asymmetric expansion of the root epidermal cells. Additionally, the results showed that the mechanism of trichoblast/atrichoblast differentiation is not evolutionally conserved across the subfamilies of the Poaceae; in the Pooideae subfamily, both asymmetric division and asymmetric cell expansion have been observed. PMID:24043851

  20. Asymmetric growth of root epidermal cells is related to the differentiation of root hair cells in Hordeum vulgare (L.)

    PubMed Central

    Marzec, Marek

    2013-01-01

    The root epidermis of most vascular plants harbours two cell types, namely trichoblasts (capable of producing a root hair) and atrichoblasts. Here, in vivo analysis, confocal laser-scanning microscopy, transmission electron microscopy, histological analysis, and three-dimensional reconstruction were used to characterize the cell types present in the barley root epidermis and their distribution in the tissue. Both trichoblasts and atrichoblasts were present in the wild-type cultivars and could be distinguished from one another at an early stage. Trichoblast/atrichoblast differentiation depended on asymmetric cell expansion after a period of symmetrical cell division. After asymmetric growth, only the shorter epidermal cells could produce root hairs, whereas the longer cells became atrichoblasts. Moreover, the root epidermis did not develop root hairs at all if the epidermal cells did not differentiate into two asymmetric cell types. The root hairless phenotype of bald root barley (brb) and root hairless 1.b (rhl1.b) mutants was caused by a mutation in a gene related to the asymmetric expansion of the root epidermal cells. Additionally, the results showed that the mechanism of trichoblast/atrichoblast differentiation is not evolutionally conserved across the subfamilies of the Poaceae; in the Pooideae subfamily, both asymmetric division and asymmetric cell expansion have been observed. PMID:24043851

  1. Plasticity in relative growth rate after a reduction in nitrogen availability is related to root morphological and physiological responses

    PubMed Central

    Useche, Antonio; Shipley, Bill

    2010-01-01

    Background and Aims To maximize growth and fitness a plant must adjust its phenotype by an amount and speed that matches changes in nitrogen availability. To determine how plastic ontogenetic changes in root physiological and morphological traits interact and whether or not these responses are likely to maximize growth, ontogenetic changes in relative growth rate (RGR, proportional rate of change of plant dry mass), unit root rate (URR, rate of change of plant dry mass per unit root length or area), specific root length (SRL, root length per dry root mass), specific root area (SRA, root area per dry root mass), and other root traits before and after a decrease in nitrogen supply, were studied in ten herbaceous species. Methods Plants of each species were grown in hydroponic culture under controlled conditions in a control treatment where the supply of nitrogen remained constant at 1 mm, and in a stress treatment where the nitrogen supply was abruptly reduced from 1 to 0·01 mm during the growth period. Key Results and Conclusions In the treatment series the number of bifurcations per root area and per root length, specific root area (SRA) and length (SRL), areal (URRarea) and length-based (URRmass) unit root rate and RGR decreased, and root tissue density increased relative to the control. Species having greater plasticity in the percentage decrease in SRA at the end of the experiment also had smaller reductions in RGR; plasticity in SRA is therefore adaptive. In contrast, species which showed a greater reduction in URRarea and in the number of bifurcations per root area and per root length, showed stronger reductions in RGR; plasticity in URRarea and in the number of bifurcations per root area and per root length is therefore not adaptive. The plastic responses observed in SRA, SRL and in root tissue density constitute a set of plastic adjustments that would lead to resource conservation in response nutrient stress. PMID:20639301

  2. Lipids in Grape Roots in Relation to Chloride Transport 1

    PubMed Central

    Kuiper, Pieter J. C.

    1968-01-01

    A comparison was made between the lipids of the roots of 5 grape rootstocks which differ markedly in the extent to which they permit chloride accumulation in leaves. Monogalactose diglyceride concentration was directly related to chloride accumulation in the leaves of the 5 rootstocks. Phosphatidylcholine and phosphatidylethanolamine were inversely related to chloride accumulation. The variety with the highest chloride accumulation contained an unusually small amount of sterols. A striking negative correlation between content of lignoceric acid and chloride accumulation was observed. The lignoceric acid concentration ranged from 11.9% in the rootstock with the lowest chloride accumulation to 0.8% in the rootstock with the highest chloride accumulation. This fatty acid was found mainly in the phosphatidylcholine and the phosphatidylethanolamine lipid fractions. PMID:16656921

  3. Measurement of Elongated Particle Dissolution Rates and Consequent Size/Shape Distribution Alterations in Support of Relative Potency Determinations and Human Dosimetry Model Development

    EPA Science Inventory

    Clearance of inhaled bio-persistent elongated particles (EPs) from the lungs and their associated translocation to pleural and other extra-pulmonary tissues involves a number of inter-related and coincidental physicochemical and physiological processes. These can result in EP dis...

  4. ORIGINAL PAPER Root growth dynamics of Aleppo pine (Pinus halepensis Mill.)

    E-print Network

    Villar-Salvador, Pedro

    ORIGINAL PAPER Root growth dynamics of Aleppo pine (Pinus halepensis Mill.) seedlings in relation seedlings with the opposite traits, which has been linked to the production of deeper and larger root concentration on root growth dynamics and its relation to shoot elongation in Aleppo pine (Pinus halep- ensis

  5. Effect of calmodulin antagonists on the growth and graviresponsiveness of primary roots of maize

    NASA Technical Reports Server (NTRS)

    Stinemetz, C. L.; Hasenstein, K. H.; Young, L. M.; Evans, M. L.

    1992-01-01

    We examined the effect of calmodulin (CaM) antagonists applied at the root tip on root growth, gravity-induced root curvature, and the movement of calcium across the root tip and auxin (IAA) across the elongation zone of gravistimulated roots. All of the CaM antagonists used in these studies delayed gravity-induced curvature at a concentration (1 micromole) that did not affect root growth. Calmodulin antagonists (> or = 1 micromole) inhibited downward transport of label from 45Ca2+ across the caps of gravistimulated roots relative to the downward transport of 45Ca2+ in gravistimulated roots which were not treated with CaM antagonists. Application of CaM antagonists at the root tip (> or = 1 micromole) also decreased the relative downward movement of label from 3H-IAA applied to the upper side of the elongation zone of gravistimulated roots. In general, tip application of antagonists inhibited neither the upward transport of 45Ca2+ in the root tip nor the upward movement of label from 3H-IAA in the elongation zone of gravistimulated roots. Thus, roots treated with CaM antagonists > or = 1 micromole become less graviresponsive and exhibit reduced or even a reversal of downward polarity of calcium transport across the root tip and IAA transport across the elongation zone. The results indicate that calmodulin-regulated events play a role in root gravitropism.

  6. Relation of Soil Acidity to Cotton Root Rot.

    E-print Network

    Taubenhaus, J. J. (Jacob Joseph); Ezekiel, Walter N. (Walter Naphtali); Fudge, J. F. (Joseph Franklin)

    1937-01-01

    soil. The Ochlockonee clay loam, which varied from pH 6.3 to 5.9, supported root rot for only three %ears, and none occurred after 1930. In the next three soils, varying from about neutrality to slight alkalinity, root rot survived for the period... TO COTTON ROOT ROT AGRICLZTURAL AND BECHANICAL COLLEGE OF TEXAS T. 0. \\VALTON, President Cotton plants grown in containers of soils varying naturally in hydrogen-ion concentration (a measure of soil acidity) were inocu- lated with cotton root rot...

  7. TEF-7A, a transcript elongation factor gene, influences yield-related traits in bread wheat (Triticum aestivum L.)

    PubMed Central

    Zheng, Jun; Liu, Hong; Wang, Yuquan; Wang, Lanfen; Chang, Xiaoping; Jing, Ruilian; Hao, Chenyang; Zhang, Xueyong

    2014-01-01

    In this study, TaTEF-7A, a member of the transcript elongation factor gene family, and its ?anking sequences were isolated. TaTEF-7A was located on chromosome 7A and was ?anked by markers Xwmc83 and XP3156.3. Subcellular localization revealed that TaTEF-7A protein was localized in the nucleus. This gene was expressed in all organs, but the highest expression occurred in young spikes and developing seeds. Overexpression of TaTEF-7A in Arabidopsis thaliana produced pleiotropic effects on vegetative and reproductive development that enhanced grain length, silique number, and silique length. No diversity was found in the coding region of TaTEF-7A, but 16 single nucleotide polymorphisms and Indels were detected in the promoter regions of different cultivars. Markers based on sequence variations in the promoter regions (InDel-629 and InDel-604) were developed, and three haplotypes were identified based on those markers. Haplotype–trait association analysis of the Chinese wheat mini core collection revealed that TaTEF-7A was significantly associated with grain number per spike. Phenotyping of near-isogenic lines (NILs) confirmed that TaTEF-7A increases potential grain yield and yield-related traits. Frequency changes in favoured haplotypes gradually increased in cultivars released in China from the 1940s. Geographic distributions of favoured haplotypes were characterized in six major wheat production regions worldwide. The presence of Hap-7A-3, the favoured haplotype, showed a positive correlation with yield in a global set of breeding lines. These results suggest that TaTEF-7A is a functional regulatory factor for grain number per spike and provide a basis for marker-assisted selection. PMID:25056774

  8. Auxin increases the hydrogen peroxide (H2O2) concentration in tomato (Solanum lycopersicum) root tips while inhibiting root growth

    PubMed Central

    Ivanchenko, Maria G.; den Os, Désirée; Monshausen, Gabriele B.; Dubrovsky, Joseph G.; Bedná?ová, Andrea; Krishnan, Natraj

    2013-01-01

    Background and Aims The hormone auxin and reactive oxygen species (ROS) regulate root elongation, but the interactions between the two pathways are not well understood. The aim of this study was to investigate how auxin interacts with ROS in regulating root elongation in tomato, Solanum lycopersicum. Methods Wild-type and auxin-resistant mutant, diageotropica (dgt), of tomato (S. lycopersicum ‘Ailsa Craig’) were characterized in terms of root apical meristem and elongation zone histology, expression of the cell-cycle marker gene Sl-CycB1;1, accumulation of ROS, response to auxin and hydrogen peroxide (H2O2), and expression of ROS-related mRNAs. Key Results The dgt mutant exhibited histological defects in the root apical meristem and elongation zone and displayed a constitutively increased level of hydrogen peroxide (H2O2) in the root tip, part of which was detected in the apoplast. Treatments of wild-type with auxin increased the H2O2 concentration in the root tip in a dose-dependent manner. Auxin and H2O2 elicited similar inhibition of cell elongation while bringing forth differential responses in terms of meristem length and number of cells in the elongation zone. Auxin treatments affected the expression of mRNAs of ROS-scavenging enzymes and less significantly mRNAs related to antioxidant level. The dgt mutation resulted in resistance to both auxin and H2O2 and affected profoundly the expression of mRNAs related to antioxidant level. Conclusions The results indicate that auxin regulates the level of H2O2 in the root tip, so increasing the auxin level triggers accumulation of H2O2 leading to inhibition of root cell elongation and root growth. The dgt mutation affects this pathway by reducing the auxin responsiveness of tissues and by disrupting the H2O2 homeostasis in the root tip. PMID:23965615

  9. Role of adventitious roots in water relations of tamarack (Larix laricina) seedlings exposed to flooding

    PubMed Central

    2012-01-01

    Background Flooding reduces supply of oxygen to the roots affecting plant water uptake. Some flooding-tolerant tree species including tamarack (Larix laricina (Du Roi) K. Koch) produce adventitious roots in response to flooding. These roots were reported to have higher hydraulic conductivity under flooding conditions compared with non-adventitious roots. In the present study, we examined structural and functional modifications in adventitious roots of tamarack seedlings to explain their flooding tolerance. Results Seedlings were subjected to the flooding treatment for six months, which resulted in an almost complete disintegration of the existing root system and its replacement with adventitious roots. We compared gas exchange parameters and water relations of flooded plants with the plants growing in well-drained soil and examined the root structures and root water transport properties. Although flooded seedlings had lower needle chlorophyll concentrations, their stomatal conductance, net photosynthesis rates and shoot water potentials were similar to non-flooded plants, indicative of flooding tolerance. Flooded adventitious roots had higher activation energy and a higher ratio of apoplastic to cell-to-cell water flow compared with non-flooded control roots as determined with the 1-hydroxypirene 3,6,8-trisulfonic acid apoplastic tracer dye. The adventitious roots in flooded plants also exhibited retarded xylem and endodermal development and accumulated numerous starch grains in the cortex. Microscopic examination of root sections treated with the PIP1 and PIP2 antibodies revealed high immunoreactivity in the cortex of non-flooded roots, as compared with flooded roots. Conclusions Structural modifications of adventitious roots suggest increased contribution of apoplastic bypass to water flow. The reduced dependence of roots on the hypoxia-sensitive aquaporin-mediated water transport is likely among the main mechanisms allowing tamarack seedlings to maintain water balance and gas exchange under flooding conditions. PMID:22738296

  10. Effects of applying stem-shortening plant growth regulators to leaves on root elongation by seedlings of wheat, oat and barley: mediation by ethylene

    Microsoft Academic Search

    Ari Rajala; Pirjo Peltonen-Sainio; Marko Onnela; Michael Jackson

    2002-01-01

    Several plant growth regulators (PGRs) commonly used in practicalfarming to restrict shoot height and control lodging were examined for theirimpact on root growth in naturally short or tall cultivars of barley (cvs.Kymppi and Saana), oat (cvs. Veli and Pal), and wheat (cvs. Mahti and Tjalve).The possible involvement of ethylene in the responses was also examined. Shootswere sprayed at the two-leaf

  11. Intraspecific variation in the magnitude and pattern of flooding-induced shoot elongation in Rumex palustris

    PubMed Central

    Chen, Xin; Huber, Heidrun; de Kroon, Hans; Peeters, Anton J. M.; Poorter, Hendrik; Voesenek, Laurentius A. C. J.; Visser, Eric J. W.

    2009-01-01

    Background and Aims Intraspecific variation in flooding tolerance is the basic pre-condition for adaptive flooding tolerance to evolve, and flooding-induced shoot elongation is an important trait that enables plants to survive shallow, prolonged flooding. Here an investigation was conducted to determine to what extent variation in flooding-induced leaf elongation exists among and within populations of the wetland species Rumex palustris, and whether the magnitude of elongation can be linked to habitat characteristics. Methods Offspring of eight genotypes collected in each of 12 populations from different sites (ranging from river mudflats with dynamic flooding regimes to areas with stagnant water) were submerged, and petioles, laminas and roots were harvested separately to measure traits related to elongation and plant growth. Key Results We found strong elongation of petioles upon submergence, and both among- and within-population variation in this trait, not only in final length, but also in the timing of the elongation response. However, the variation in elongation responses could not be linked to habitat type. Conclusions Spatio-temporal variation in the duration and depth of flooding in combination with a presumably weak selection against flooding-induced elongation may have contributed to the maintenance of large genetic variation in flooding-related traits among and within populations. PMID:19687030

  12. Soil sheaths, photosynthate distribution to roots, and rhizosphere water relations for Opuntia ficus-indica

    SciTech Connect

    Huang, B.; North, G.B.; Nobel, P.S. (Univ. of California, Los Angeles, CA (United States))

    1993-09-01

    Soil sheaths incorporating aggregated soil particles surround young roots of many species, but the effects of such sheaths on water movement between roots and the soil are largely unknown. The quantity and location of root exudates associated with soil sheath along the entire length of its young roots, except within 1.4 cm of the tip. The soil sheaths, which average 0.7 mm in thickness, were composed of soil particles and root hairs, both of which were covered with exuded mucilaginous material. As determined with a [sup 14]C pulse-labeling technique, 2% of newly fixed [sup 14]C-photosynthate was translocated into the roots at 3d, 6% at 9 d, and 8% at 15 d after labeling. The fraction of insoluble [sup 14]C in the roots increased twofold from 3 d to 15 d. Over the same time period, 6%-9% of the [sup 14]C translocated to the roots was exuded into the soil. The soluble [sup 14]C compounds exuded into the soil were greater in the 3-cm segment at the root tip than elsewhere along the root, whereas mucilage was exuded relatively uniformly along roots 15 cm in length. The volumetric efflux of water increase for both sheathed and unsheathed roots as the soil water potential decreased form -0.1 MPa to -1.0 MPa. The efflux rate was greater for unsheathed roots than for sheathed roots, which were more turgid and had a higher water potential, especially at lower soil water potentials. During drying, soil particles in the sheaths aggregate more tightly, making the sheaths less permeable to water and possibly creating air gaps. The soil sheaths of O. ficus-indica thus reduce water loss from the roots to a drying soil. 34 refs., 6 figs., 1 tab.

  13. Relation of Soil Acidity to Cotton Root Rot. 

    E-print Network

    Taubenhaus, J. J. (Jacob Joseph); Ezekiel, Walter N. (Walter Naphtali); Fudge, J. F. (Joseph Franklin)

    1937-01-01

    No . 1 2 7 8 9 10 15 16 17 18 -- 19 20 21 22 23 24 29 30 31 32 33 34 39 40 41 42 43 44 45 46 47 48 63 51 52 53 54 various soils, adjusted by additions of lime or csf acid. -- pH 0-2 feet 1931 5.7 5.8 7.7 7...- Sufficient acid to change the soil to approximately pH 5.2-5.5 (boxes 15 and 16), however, eradicated root rot by the end of the first year following inoculation; that is, root rot overwintered once but not a second time. Greater acidification, changing...

  14. Relation between maize ( Zea mays L.) leaf area and root density observed with minirhizotrons

    Microsoft Academic Search

    Markus Liedgens; Walter Richner

    2001-01-01

    The shoot and the root system are functionally closely related. This study describes the correlation between leaf area and root density of maize over the entire crop season to contribute to the understanding of shoot-to-root relationships. The crop was planted for three years in drainage lysimeters in repacked soil. Leaf area was estimated from non-destructive, morphometric measurements of individual leaves.

  15. Changes in fructooligosaccaride composition and related enzyme activities of burdock root during low-temperature storage

    Microsoft Academic Search

    Yoshihiro Imahori; Naoki Kitamura; Shizuka Kobayashi; Takanobu Takihara; Kimiko Ose; Yoshinori Ueda

    2010-01-01

    Changes in the composition of fructooligosaccarides (FOSs) and related enzyme activities of burdock root during low-temperature storage (1°C) were measured. Burdock root is composed of monosaccharides, such as glucose and fructose, disaccharides, such as sucrose, and FOS in the extracted carbohydrates. The composition was the highest in fructose, followed by sucrose, FOS, and glucose. The FOS composition was the highest

  16. Automated Root Tracking with "Root System Analyzer"

    NASA Astrophysics Data System (ADS)

    Schnepf, Andrea; Jin, Meina; Ockert, Charlotte; Bol, Roland; Leitner, Daniel

    2015-04-01

    Crucial factors for plant development are water and nutrient availability in soils. Thus, root architecture is a main aspect of plant productivity and needs to be accurately considered when describing root processes. Images of root architecture contain a huge amount of information, and image analysis helps to recover parameters describing certain root architectural and morphological traits. The majority of imaging systems for root systems are designed for two-dimensional images, such as RootReader2, GiA Roots, SmartRoot, EZ-Rhizo, and Growscreen, but most of them are semi-automated and involve mouse-clicks in each root by the user. "Root System Analyzer" is a new, fully automated approach for recovering root architectural parameters from two-dimensional images of root systems. Individual roots can still be corrected manually in a user interface if required. The algorithm starts with a sequence of segmented two-dimensional images showing the dynamic development of a root system. For each image, morphological operators are used for skeletonization. Based on this, a graph representation of the root system is created. A dynamic root architecture model helps to determine which edges of the graph belong to an individual root. The algorithm elongates each root at the root tip and simulates growth confined within the already existing graph representation. The increment of root elongation is calculated assuming constant growth. For each root, the algorithm finds all possible paths and elongates the root in the direction of the optimal path. In this way, each edge of the graph is assigned to one or more coherent roots. Image sequences of root systems are handled in such a way that the previous image is used as a starting point for the current image. The algorithm is implemented in a set of Matlab m-files. Output of Root System Analyzer is a data structure that includes for each root an identification number, the branching order, the time of emergence, the parent identification number, the distance between branching point to the parent root base, the root length, the root radius and the nodes that belong to each individual root path. This information is relevant for the analysis of dynamic root system development as well as the parameterisation of root architecture models. Here, we show results of Root System Analyzer applied to analyse the root systems of wheat plants grown in rhizotrons. Different treatments with respect to soil moisture and apatite concentrations were used to test the effects of those conditions on root system development. Photographs of the root systems were taken at high spatial and temporal resolution and root systems are automatically tracked.

  17. Expression of Root-Related Transcription Factors Associated with Flooding Tolerance of Soybean (Glycine max)

    PubMed Central

    Valliyodan, Babu; Van Toai, Tara T.; Alves, Jose Donizeti; de Fátima P. Goulart, Patricia; Lee, Jeong Dong; Fritschi, Felix B.; Rahman, Mohammed Atiqur; Islam, Rafiq; Shannon, J. Grover; Nguyen, Henry T.

    2014-01-01

    Much research has been conducted on the changes in gene expression of the model plant Arabidopsis to low-oxygen stress. Flooding results in a low oxygen environment in the root zone. However, there is ample evidence that tolerance to soil flooding is more than tolerance to low oxygen alone. In this study, we investigated the physiological response and differential expression of root-related transcription factors (TFs) associated with the tolerance of soybean plants to soil flooding. Differential responses of PI408105A and S99-2281 plants to ten days of soil flooding were evaluated at physiological, morphological and anatomical levels. Gene expression underlying the tolerance response was investigated using qRT-PCR of root-related TFs, known anaerobic genes, and housekeeping genes. Biomass of flood-sensitive S99-2281 roots remained unchanged during the entire 10 days of flooding. Flood-tolerant PI408105A plants exhibited recovery of root growth after 3 days of flooding. Flooding induced the development of aerenchyma and adventitious roots more rapidly in the flood-tolerant than the flood-sensitive genotype. Roots of tolerant plants also contained more ATP than roots of sensitive plants at the 7th and 10th days of flooding. Quantitative transcript analysis identified 132 genes differentially expressed between the two genotypes at one or more time points of flooding. Expression of genes related to the ethylene biosynthesis pathway and formation of adventitious roots was induced earlier and to higher levels in roots of the flood-tolerant genotype. Three potential flood-tolerance TFs which were differentially expressed between the two genotypes during the entire 10-day flooding duration were identified. This study confirmed the expression of anaerobic genes in response to soil flooding. Additionally, the differential expression of TFs associated with soil flooding tolerance was not qualitative but quantitative and temporal. Functional analyses of these genes will be necessary to reveal their potential to enhance flooding tolerance of soybean cultivars. PMID:25268626

  18. Expression of root-related transcription factors associated with flooding tolerance of soybean (Glycine max).

    PubMed

    Valliyodan, Babu; Van Toai, Tara T; Alves, Jose Donizeti; de Fátima P Goulart, Patricia; Lee, Jeong Dong; Fritschi, Felix B; Rahman, Mohammed Atiqur; Islam, Rafiq; Shannon, J Grover; Nguyen, Henry T

    2014-01-01

    Much research has been conducted on the changes in gene expression of the model plant Arabidopsis to low-oxygen stress. Flooding results in a low oxygen environment in the root zone. However, there is ample evidence that tolerance to soil flooding is more than tolerance to low oxygen alone. In this study, we investigated the physiological response and differential expression of root-related transcription factors (TFs) associated with the tolerance of soybean plants to soil flooding. Differential responses of PI408105A and S99-2281 plants to ten days of soil flooding were evaluated at physiological, morphological and anatomical levels. Gene expression underlying the tolerance response was investigated using qRT-PCR of root-related TFs, known anaerobic genes, and housekeeping genes. Biomass of flood-sensitive S99-2281 roots remained unchanged during the entire 10 days of flooding. Flood-tolerant PI408105A plants exhibited recovery of root growth after 3 days of flooding. Flooding induced the development of aerenchyma and adventitious roots more rapidly in the flood-tolerant than the flood-sensitive genotype. Roots of tolerant plants also contained more ATP than roots of sensitive plants at the 7th and 10th days of flooding. Quantitative transcript analysis identified 132 genes differentially expressed between the two genotypes at one or more time points of flooding. Expression of genes related to the ethylene biosynthesis pathway and formation of adventitious roots was induced earlier and to higher levels in roots of the flood-tolerant genotype. Three potential flood-tolerance TFs which were differentially expressed between the two genotypes during the entire 10-day flooding duration were identified. This study confirmed the expression of anaerobic genes in response to soil flooding. Additionally, the differential expression of TFs associated with soil flooding tolerance was not qualitative but quantitative and temporal. Functional analyses of these genes will be necessary to reveal their potential to enhance flooding tolerance of soybean cultivars. PMID:25268626

  19. Histone acetylation associated up-regulation of the cell wall related genes is involved in salt stress induced maize root swelling

    PubMed Central

    2014-01-01

    Background Salt stress usually causes crop growth inhibition and yield decrease. Epigenetic regulation is involved in plant responses to environmental stimuli. The epigenetic regulation of the cell wall related genes associated with the salt-induced cellular response is still little known. This study aimed to analyze cell morphological alterations in maize roots as a consequence of excess salinity in relation to the transcriptional and epigenetic regulation of the cell wall related protein genes. Results In this study, maize seedling roots got shorter and displayed swelling after exposure to 200 mM NaCl for 48 h and 96 h. Cytological observation showed that the growth inhibition of maize roots was due to the reduction in meristematic zone cell division activity and elongation zone cell production. The enlargement of the stele tissue and cortex cells contributed to root swelling in the elongation zone. The cell wall is thought to be the major control point for cell enlargement. Cell wall related proteins include xyloglucan endotransglucosylase (XET), expansins (EXP), and the plasma membrane proton pump (MHA). RT-PCR results displayed an up-regulation of cell wall related ZmEXPA1, ZmEXPA3, ZmEXPA5, ZmEXPB1, ZmEXPB2 and ZmXET1 genes and the down-regulation of cell wall related ZmEXPB4 and ZmMHA genes as the duration of exposure was increased. Histone acetylation is regulated by HATs, which are often correlated with gene activation. The expression of histone acetyltransferase genes ZmHATB and ZmGCN5 was increased after 200 mM NaCl treatment, accompanied by an increase in the global acetylation levels of histones H3K9 and H4K5. ChIP experiment showed that the up-regulation of the ZmEXPB2 and ZmXET1 genes was associated with the elevated H3K9 acetylation levels on the promoter regions and coding regions of these two genes. Conclusions These data suggested that the up-regulation of some cell wall related genes mediated cell enlargement to possibly mitigate the salinity-induced ionic toxicity, and different genes had specific function in response to salt stress. Histone modification as a mediator may contribute to rapid regulation of cell wall related gene expression, which reduces the damage of excess salinity to plants. PMID:24758373

  20. Metals (Fe, Mn, Zn) in the root plaque of submerged aquatic plants collected in situ : Relations with metal concentrations in the adjacent sediments and in the root tissue

    Microsoft Academic Search

    Louise St-Cyr; Peter G. C. Campbell

    1996-01-01

    We have investigated the extent of iron oxyhydroxide deposition on the roots of two common freshwater species, Vallisneria americana Michx. and Heteranthera dubia (Jacq.) MacM., collected from different sites in the St. Lawrence River, Québec, Canada, and have related metal concentrations in the root plaques both to the geochemical conditions prevailing in the host sediments (pH; metal partitioning) and to

  1. Computer based imaging and analysis of root gravitropism

    NASA Technical Reports Server (NTRS)

    Evans, M. L.; Ishikawa, H.

    1997-01-01

    Two key issues in studies of the nature of the gravitropic response in roots have been the determination of the precise pattern of differential elongation responsible for downward bending and the identification of the cells that show the initial motor response. The main approach for examining patterns of differential growth during root gravitropic curvature has been to apply markers to the root surface and photograph the root at regular intervals during gravitropic curvature. Although these studies have provided valuable information on the characteristics of the gravitropic motor response in roots, their labor intensive nature limits sample size and discourages both high frequency of sampling and depth of analysis of surface expansion data. In this brief review we describe the development of computer-based video analysis systems for automated measurement of root growth and shape change and discuss some key features of the root gravitropic response that have been revealed using this methodology. We summarize the capabilities of several new pieces of software designed to measure growth and shape changes in graviresponding roots and describe recent progress in developing analysis systems for studying the small, but experimentally popular, primary roots of Arabidopsis. A key finding revealed by such studies is that the initial gravitropic response of roots of maize and Arabidopsis occurs in the distal elongation zone (DEZ) near the root apical meristem, not in the main elongation zone. Another finding is that the initiation of rapid elongation in the DEZ following gravistimulation appears to be related to rapid membrane potential changes in this region of the root. These observations have provided the incentive for ongoing studies examining possible links between potential growth modifying factors (auxin, calcium, protons) and gravistimulated changes in membrane potential and growth patterns in the DEZ.

  2. Relation of Cotton Root Rot and Fusarium Wilt to the Acidity and Alkalinity of the Soil. 

    E-print Network

    Taubenhaus, J. J. (Jacob Joseph); Ezekiel, Walter N. (Walter Naphtali); Killough, D. T. (David Thornton)

    1928-01-01

    HOME RESEARCH: JESSIE WHITACRE Ph. D Chief MAMIE GRIMES, M. S., ~eztile and Clothing S~ecralrst 5. SUMNER. M. S., Nutrition Specialist - - - - - - - - . - - - **W T. CARTER B. S. Chief E. 'H. TEMPLI~; B S' Soil Sutvegor T. C. REITCH. B. s.. $oil... examined, and the acidity or alkalinity of the soil studied in relation to the pres- ence of cotton root rot and also of Fusarium wilt. Root rot was found in acid soils (pH 5.5-6.4) as well as in neutral (pH 6.5-7.4) and alkaline soils (pH 7.5...

  3. Control of transcriptional elongation.

    PubMed

    Kwak, Hojoong; Lis, John T

    2013-01-01

    Elongation is becoming increasingly recognized as a critical step in eukaryotic transcriptional regulation. Although traditional genetic and biochemical studies have identified major players of transcriptional elongation, our understanding of the importance and roles of these factors is evolving rapidly through the recent advances in genome-wide and single-molecule technologies. Here, we focus on how elongation can modulate the transcriptional outcome through the rate-liming step of RNA polymerase II (Pol II) pausing near promoters and how the participating factors were identified. Among the factors we describe are the pausing factors--NELF (negative elongation factor) and DSIF (DRB sensitivity-inducing factor)--and P-TEFb (positive elongation factor b), which is the key player in pause release. We also describe the high-resolution view of Pol II pausing and propose nonexclusive models for how pausing is achieved. We then discuss Pol II elongation through the bodies of genes and the roles of FACT and SPT6, factors that allow Pol II to move through nucleosomes. PMID:24050178

  4. SNF1-related kinases allow plants to tolerate herbivory by allocating carbon to roots

    PubMed Central

    Schwachtje, Jens; Minchin, Peter E. H.; Jahnke, Sigfried; van Dongen, Joost T.; Schittko, Ursula; Baldwin, Ian T.

    2006-01-01

    Herbivore attack elicits costly defenses that are known to decrease plant fitness by using resources that are normally slated for growth and reproduction. Additionally, plants have evolved mechanisms for tolerating attack, which are not understood on a molecular level. Using 11C-photosynthate labeling as well as sugar and enzyme measurements, we found rapid changes in sink–source relations in the annual Nicotiana attenuata after simulated herbivore attacks, which increased the allocation of sugars to roots. This herbivore-induced response is regulated by the ?-subunit of an SnRK1 (SNF1-related kinase) protein kinase, GAL83, transcripts of which are rapidly down-regulated in source leaves after herbivore attack and, when silenced, increase assimilate transport to roots. This C diversion response is activated by herbivore-specific elicitors and is independent of jasmonate signaling, which regulates most of the plant's defense responses. Herbivore attack during early stages of development increases root reserves, which, in turn, delays senescence and prolongs flowering. That attacked GAL83-silenced plants use their enhanced root reserves to prolong reproduction demonstrates that SnRK1 alters resource allocation so that plants better tolerate herbivory. This tolerance mechanism complements the likely defensive value of diverting resources to a less vulnerable location within the plant. PMID:16912118

  5. 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.

  6. Soil water relations, crop production and root pruning of a belt of trees

    Microsoft Academic Search

    G. S. Woodall; B. H. Ward

    2002-01-01

    In southwestern Australia extensive revegetation with perennial plants is required to reverse hydrological imbalance and associated secondary salinity. The effect of a Pinus radiata\\/Schinus areira belt on soil water relations and crop production on a duplex soil in a medium rainfall area (480mm) was studied. Root pruning was used to manage tree–crop competition for resources. The tree belt altered the

  7. Root gravitropism

    NASA Technical Reports Server (NTRS)

    Masson, P. H.

    1995-01-01

    When a plant root is reoriented within the gravity field, it responds by initiating a curvature which eventually results in vertical growth. Gravity sensing occurs primarily in the root tip. It may involve amyloplast sedimentation in the columella cells of the root cap, or the detection of forces exerted by the mass of the protoplast on opposite sides of its cell wall. Gravisensing activates a signal transduction cascade which results in the asymmetric redistribution of auxin and apoplastic Ca2+ across the root tip, with accumulation at the bottom side. The resulting lateral asymmetry in Ca2+ and auxin concentration is probably transmitted to the elongation zone where differential cellular elongation occurs until the tip resumes vertical growth. The Cholodny-Went theory proposes that gravity-induced auxin redistribution across a gravistimulated plant organ is responsible for the gravitropic response. However, recent data indicate that the gravity-induced reorientation is more complex, involving both auxin gradient-dependent and auxin gradient-independent events.

  8. Relating foliar dehydration tolerance of mycorrhizal Phaseolus vulgaris to soil and root colonization by hyphae.

    PubMed

    Augé, Robert M; Moore, Jennifer L; Cho, Keunho; Stutz, Jean C; Sylvia, David M; al-Agely, Abid K; Saxton, Arnold M

    2003-10-01

    Mycorrhizal symbiosis can modify plant response to drying soil, but little is known about the relative contribution of soil vs. root hyphal colonization to drought resistance of mycorrhizal plants. Foliar dehydration tolerance, characterized as leaf and soil water potential at the end of a lethal drying episode, was measured in bean plants (Phaseolus vulgaris) colonized by Glomus intraradices or by a mix of arbuscular mycorrhizal fungi collected from a semi-arid grassland. Path analysis modeling was used to evaluate how colonization rates and other variables affected these lethal values. Of several plant and soil characteristics tested, variation in dehydration tolerance was best explained by soil hyphal density. Soil hyphal colonization had larger direct and total effects on both lethal leaf water potential and soil water potential than did root hyphal colonization, root density, soil aggregation, soil glomalin concentration, leaf phosphorus concentration or leaf osmotic potential. Plants colonized by the semi-arid mix of mycorrhizal fungi had lower lethal leaf water potential and soil water potential than plants colonized by G. intraradices. Our findings support the assertion that external, soil hyphae may play an important role in mycorrhizal influence on the water relations of host plants. PMID:14610883

  9. Measurement of Libby Amphibole (LA) Elongated Particle Dissolution Rates and Alteration of Size/Shape Distributions in Support of Human Dosimetry Model Development and Relative Potency Determinations

    EPA Science Inventory

    To maximize the value of toxicological data in development of human health risk assessment models of inhaled elongated mineral particles, improvements in human dosimetry modeling are needed. In order to extend the dosimetry model of deposited fibers (Asgharian et aI., Johnson 201...

  10. Induction of branch roots by cutting method in t Hyoscyamus niger root culture

    Microsoft Academic Search

    Seung Han Woo; Jong Moon Park; Ji-Won Yang

    1997-01-01

    Root tips of Hyoscyamus niger were cultivated on agar or in liquid medium, and patterns of elongation and branching were investigated.\\u000a The elongation of roots compared to branching, particularly tertiary root branching, was more effective in liquid medium than\\u000a on agar medium. The number (0.06 per cm) of tertiary roots which branched out from secondary roots was far less than

  11. Pain-related mediators underlie incision-induced mechanical nociception in the dorsal root ganglia

    PubMed Central

    Yuan, Xiuhong; Liu, Xiangyan; Tang, Qiuping; Deng, Yunlong

    2013-01-01

    Approximately 50–70% of patients experience incision-induced mechanical nociception after surgery. However, the mechanism underlying incision-induced mechanical nociception is still unclear. Interleukin-10 and brain-derived neurotrophic factor are important pain mediators, but whether interleukin-10 and brain-derived neurotrophic factor are involved in incision-induced mechanical nociception remains uncertain. In this study, forty rats were divided randomly into the incision surgery (n = 32) and sham surgery (n = 8) groups. Plantar incision on the central part of left hind paw was performed under anesthesia in rats from the surgery group. Rats in the sham surgery group received anesthesia, but not an incision. Von Frey test results showed that, compared with the sham surgery group, incision surgery decreased the withdrawal threshold of rats at 0.5, 3, 6 and 24 hours after incision. Immunofluorescence staining in the dorsal root ganglia of the spinal cord (L3–5) showed that interleukin-10 and brain-derived neurotrophic factor were expressed mainly on small- and medium-sized neurons (diameter < 20 ?m and 20–40 ?m) and satellite cells in the dorsal root ganglia of the spinal cord (L3–5) in the sham surgery group. By contrast, in the surgery group, high expression of interleukin-10 and brain-derived neurotrophic factor appeared in large-sized neurons (diameter > 40 ?m) at 6 and 24 hours after incision surgery, which corresponded to the decreased mechanical withdrawal threshold of rats in the surgery group. These experimental findings suggest that expression pattern shift of interleukin-10 and brain-derived neurotrophic factor induced by incision surgery in dorsal root ganglia of rats was closely involved in lowering the threshold to mechanical stimulus in the hind paw following incision surgery. Pain-related mediators induced by incision surgery in dorsal root ganglia of rats possibly underlie mechanical nociception in ipsilateral hind paws. PMID:25206654

  12. Thiophene accumulation in relation to morphology in roots of Tagetes patula

    Microsoft Academic Search

    A. F. Croes; A. J. R. Berg; M. Bosveld; H. Breteler; G. J. Wullems

    1989-01-01

    Roots of marigold (Tagetes patula L.) accumulate thiophenes, heterocyclic sulfurous compounds with strong biocidal activity. In detached roots cultured in vitro, the thiophene content was 5 µmol·(g fresh weight)-1 which is 25-times higher than in roots attached to the plant. In roots derived from tissues transformed by Agrobacterium tumefaciens and A. rhizogenes, the morphology and thiophene content varied with the

  13. Soil sheaths, photosynthate distribution to roots, and rhizosphere water relations for Opuntia ficus-indica

    Microsoft Academic Search

    Bingru Huang; Gretchen B. North; Park S. Nobel

    1993-01-01

    Soil sheaths incorporating aggregated soil particles surround young roots of many species, but the effects of such sheaths on water movement between roots and the soil are largely unknown. The quantity and location of root exudates associated with soil sheath along the entire length of its young roots, except within 1.4 cm of the tip. The soil sheaths, which average

  14. Plant iodine-131 uptake in relation to root concentration as measured in minirhizotron by video camera:

    SciTech Connect

    Moss, K.J.

    1990-09-01

    Glass viewing tubes (minirhizotrons) were placed in the soil beneath native perennial bunchgrass (Agropyron spicatum). The tubes provided access for observing and quantifying plant roots with a miniature video camera and soil moisture estimates by neutron hydroprobe. The radiotracer I-131 was delivered to the root zone at three depths with differing root concentrations. The plant was subsequently sampled and analyzed for I-131. Plant uptake was greater when I-131 was applied at soil depths with higher root concentrations. When I-131 was applied at soil depths with lower root concentrations, plant uptake was less. However, the relationship between root concentration and plant uptake was not a direct one. When I-131 was delivered to deeper soil depths with low root concentrations, the quantity of roots there appeared to be less effective in uptake than the same quantity of roots at shallow soil depths with high root concentration. 29 refs., 6 figs., 11 tabs.

  15. Root signals and stomatal closure in relation to photosynthesis, chlorophyll a fluorescence and adventitious rooting of flooded tomato plants

    Microsoft Academic Search

    Mark A. Else; Franciszek Janowiak; Christopher J. Atkinson; Michael B. Jackson

    2008-01-01

    †Background and Aims An investigation was carried out to determine whether stomatal closure in flooded tomato plants (Solanum lycopersicum) results from decreased leaf water potentials (cL), decreased photosynthetic capacity and attendant increases in internal CO2 (Ci) or from losses of root function such as cytokinin and gibber- ellin export. †Methods Pot-grown plants were flooded when 1 month old. Leaf conductance

  16. Etanercept attenuates pain-related behavior following compression of the dorsal root ganglion in the rat

    Microsoft Academic Search

    Kazuyuki Watanabe; Shoji Yabuki; Miho Sekiguchi; Shin-ichi Kikuchi; Shin-ichi Konno

    Purpose  TNF? is an inflammatory mediator related to neuropathic pain including sciatica. Much basic research suggests that anti-TNF?\\u000a therapy may be useful for the treatment of sciatica. The purpose of this study was to clarify the effects of etanercept in\\u000a a dorsal root ganglion (DRG) compression model.\\u000a \\u000a \\u000a \\u000a \\u000a Methods  Adult male Sprague-Dawley rats (200–250 g, n = 60) were used. An L-shaped stainless rod was used

  17. 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

  18. Fine root biomass in relation to site and stand characteristics in Norway spruce and Scots pine stands.

    PubMed

    Helmisaari, Heljä-Sisko; Derome, John; Nöjd, Pekka; Kukkola, Mikko

    2007-10-01

    Variations in fine root biomass of trees and understory in 16 stands throughout Finland were examined and relationships to site and stand characteristics determined. Norway spruce fine root biomass varied between 184 and 370 g m(-2), and that of Scots pine ranged between 149 and 386 g m(-2). In northern Finland, understory roots and rhizomes (< 2 mm diameter) accounted for up to 50% of the stand total fine root biomass. Therefore, the fine root biomass of trees plus understory was larger in northern Finland in stands of both tree species, resulting in a negative relationship between fine root biomass and the temperature sum and a positive relationship between fine root biomass and the carbon:nitrogen ratio of the soil organic layer. The foliage:fine root ratio varied between 2.1 and 6.4 for Norway spruce and between 0.8 and 2.2 for Scots pine. The ratio decreased for both Norway spruce and Scots pine from south to north, as well as from fertile to more infertile site types. The foliage:fine root ratio of Norway spruce was related to basal area and stem surface area. The strong positive correlations of these three parameters with fine root nitrogen concentration implies that more fine roots are needed to maintain a certain amount of foliage when nutrient availability is low. No significant relationships were found between stand parameters and fine root biomass at the stand level, but the relationships considerably improved when both fine root biomass and stand parameters were calculated for the mean tree in the stand. When the northern and southern sites were analyzed separately, fine root biomass per tree of both species was significantly correlated with basal area and stem surface area per tree. Basal area, stem surface area and stand density can be estimated accurately and easily. Thus, our results may have value in predicting fine root biomass at the tree and stand level in boreal Norway spruce and Scots pine forests. PMID:17669739

  19. Sites and Regulation of Auxin Biosynthesis in Arabidopsis Roots

    Microsoft Academic Search

    Karin Ljung; Anna K. Hull; John Celenza; Masashi Yamada; Mark Estelle; Jennifer Normanly; Goran Sandberga

    2005-01-01

    Auxin has been shown to be important for many aspects of root development, including initiation and emergence of lateral roots, patterning of the root apical meristem, gravitropism, and root elongation. Auxin biosynthesis occurs in both aerial portions of the plant and in roots; thus, the auxin required for root development could come from either source, or both. To monitor putative

  20. Comparative assessment of the polypeptide profiles from lateral and primary roots of Phaseolus vulgaris L

    NASA Technical Reports Server (NTRS)

    Westberg, J.; Odom, W. R.; Guikema, J. A.; Spooner, B. S. (Principal Investigator)

    1994-01-01

    In Phaseolus vulgaris, primary roots show gravitational sensitivity soon after emerging from the seed. In contrast, lateral roots are agravitropic during early development, and become gravitropic after several cm growth. Primary and lateral root tissues were examined by polyacrylamide gel electrophoresis, coupled with western blotting techniques, to compare proteins which may contribute to the acquisition of gravitational sensitivity. Root tips and zones of cell elongation were compared for each root type, using immunological probes for calmodulin, alpha-actin, alpha-tubulin, and proteins of the plastid envelope. Lateral roots contained qualitatively less calmodulin, and showed a slightly different pattern of actin-related epitope proteins, than did primary root tissues, suggesting that polypeptide differences may contribute to the gravitational sensitivity which these root types express.

  1. Chromatin elongation factors.

    PubMed

    Svejstrup, Jesper Q

    2002-04-01

    As RNA polymerase II leaves a gene promoter to transcribe the coding region, it faces a major obstacle - nucleosomes tightly wrapped into chromatin. Mechanisms to deal with this obstacle clearly exist in cells, as transcription through chromatin is very efficient in vivo, whereas nucleosomal templates pose a considerable problem for polymerase progression in reconstituted in vitro systems. Advances in our understanding of transcriptional elongation through chromatin have been made possible recently by the identification of several accessory factors that assist polymerase in the process. Insights into the function of these factors have been gained by a combination of yeast genetics and biochemical studies in mammalian systems. PMID:11893488

  2. Foliage, fine-root, woody-tissue and stand respiration in Pinus radiata in relation to nitrogen status.

    PubMed

    Ryan, M G; Hubbard, R M; Pongracic, S; Raison, R J; McMurtrie, R E

    1996-03-01

    We measured respiration of 20-year-old Pinus radiata D. Don trees growing in control (C), irrigated (I), and irrigated + fertilized (IL) stands in the Biology of Forest Growth experimental plantation near Canberra, Australia. Respiration was measured on fully expanded foliage, live branches, boles, and fine and coarse roots to determine the relationship between CO(2) efflux, tissue temperature, and biomass or nitrogen (N) content of individual tissues. Efflux of CO(2) from foliage (dark respiration at night) and fine roots was linearly related to biomass and N content, but N was a better predictor of CO(2) efflux than biomass. Respiration (assumed to be maintenance) per unit N at 15 degrees C and a CO(2) concentration of 400 micro mol mol(-1) was 1.71 micro mol s(-1) mol(-1) N for foliage and 11.2 micro mol s(-1) mol(-1) N for fine roots. Efflux of CO(2) from stems, coarse roots and branches was linearly related to sapwood volume (stems) or total volume (branches + coarse roots) and growth, with rates for maintenance respiration at 15 degrees C ranging from 18 to 104 micro mol m(-3) s(-1). Among woody components, branches in the upper canopy and small diameter coarse roots had the highest respiration rates. Stem maintenance respiration per unit sapwood volume did not differ among treatments. Annual C flux was estimated by summing (1) dry matter production and respiration of aboveground components, (2) annual soil CO(2) efflux minus aboveground litterfall, and (3) the annual increment in coarse root biomass. Annual C flux was 24.4, 25.3 and 34.4 Mg ha(-1) year(-1) for the C, I and IL treatments, respectively. Total belowground C allocation, estimated as the sum of (2) and (3) above, was equal to the sum of root respiration and estimated root production in the IL treatment, whereas in the nutrient-limited C and I treatments, total belowground C allocation was greater than the sum of root respiration and estimated root production, suggesting higher fine root turnover or increased allocation to mycorrhizae and root exudation. Carbon use efficiency, the ratio of net primary production to assimilation, was similar among treatments for aboveground tissues (0.43-0.50). Therefore, the proportion of assimilation used for construction and maintenance respiration on an annual basis was also similar among treatments. PMID:14871734

  3. lnduction of Defense-Related Ultrastructural Modifications in Pea Root Tissues lnoculated with Endophytic Bacteria

    Microsoft Academic Search

    Nicole Benhamou; Joseph W. Kloepper; Andrea Quadt-Hallman; Sadik Tuzun

    The stimulation exerted by the endophytic bacterium Bacillus pumilus strain SE34 in plant defense reactions was investigated at the ultrastructural leve1 using an in vitro system in which root- inducing T-DNA pea (Pisum sativum 1.) roots were infected with the pea root-rotting fungus Fusarium oxysporum f. sp. pisi. In nonbac- terized roots, the pathogen multiplied abundantly through much of the

  4. Plant iodine-131 uptake in relation to root concentration as measured in minirhizotron by video camera

    Microsoft Academic Search

    1990-01-01

    Glass viewing tubes (minirhizotrons) were placed in the soil beneath native perennial bunchgrass (Agropyron spicatum). The tubes provided access for observing and quantifying plant roots with a miniature video camera and soil moisture estimates by neutron hydroprobe. The radiotracer I-131 was delivered to the root zone at three depths with differing root concentrations. The plant was subsequently sampled and analyzed

  5. The distribution and strength of riparian tree roots in relation to riverbank reinforcement

    Microsoft Academic Search

    Bruce Abernethy; Ian D. Rutherfurd

    2001-01-01

    The main influences of plants on the mass stability of riverbanks are those that affect the strength of bank sediments. Plants enhance bank strength by reducing pore-water pressures and by directly reinforcing bank material with their roots. In this paper we do not consider bank hydrology but focus on quantifying increases in sediment strength due to root reinforcement. Root reinforcement

  6. Wounding Response in Relation to Polar Transport of Radiocalcium in Isolated Root Segments of Zea mays

    PubMed Central

    Evans, Evan C.; Vaughan, Burton E.

    1966-01-01

    A perfusion bridge technique is described which permits the continuous collection of exudations from both ends of corn root segments. By exposing the central portion of the segments to radiocalcium, the amounts and rates of tracer movement in either direction may be determined. Typically, a peak in both acropetal and basipetal transport occurs at about 90 minutes after exposure to tracer. This transport peak is followed by a sharp decline to relatively low transport rates. Thereafter the 2 perfusates from opposite ends of a segment pair show significant differences. The acropetal increments decrease somewhat erratically to 0 at 10 to 12 hours, while the basipetal increments steadily increase to a steady-state value which remains constant from 8 to 24 hours. After a segment pair has reached steady-state polar transport, a fresh cut on the apical ends causes the resumption of acropetal transport. Such response suggests that polar transport in these root segments is at least partially a wound response. A possible explanation of the complex transport behavior is advanced. PMID:16656377

  7. The Electromagnetic Conception of Nature at the Root of the Special and General Relativity Theories and Its Revolutionary Meaning

    ERIC Educational Resources Information Center

    Giannetto, Enrico R. A.

    2009-01-01

    The revolution in XX century physics, induced by relativity theories, had its roots within the electromagnetic conception of Nature. It was developed through a tradition related to Brunian and Leibnizian physics, to the German "Naturphilosophie" and English XIXth physics. The electromagnetic conception of Nature was in some way realized by the…

  8. Computer-based video digitizer analysis of surface extension in maize roots: kinetics of growth rate changes during gravitropism

    NASA Technical Reports Server (NTRS)

    Ishikawa, H.; Hasenstein, K. H.; Evans, M. L.

    1991-01-01

    We used a video digitizer system to measure surface extension and curvature in gravistimulated primary roots of maize (Zea mays L.). Downward curvature began about 25 +/- 7 min after gravistimulation and resulted from a combination of enhanced growth along the upper surface and reduced growth along the lower surface relative to growth in vertically oriented controls. The roots curved at a rate of 1.4 +/- 0.5 degrees min-1 but the pattern of curvature varied somewhat. In about 35% of the samples the roots curved steadily downward and the rate of curvature slowed as the root neared 90 degrees. A final angle of about 90 degrees was reached 110 +/- 35 min after the start of gravistimulation. In about 65% of the samples there was a period of backward curvature (partial reversal of curvature) during the response. In some cases (about 15% of those showing a period of reverse bending) this period of backward curvature occurred before the root reached 90 degrees. Following transient backward curvature, downward curvature resumed and the root approached a final angle of about 90 degrees. In about 65% of the roots showing a period of reverse curvature, the roots curved steadily past the vertical, reaching maximum curvature about 205 +/- 65 min after gravistimulation. The direction of curvature then reversed back toward the vertical. After one or two oscillations about the vertical the roots obtained a vertical orientation and the distribution of growth within the root tip became the same as that prior to gravistimulation. The period of transient backward curvature coincided with and was evidently caused by enhancement of growth along the concave and inhibition of growth along the convex side of the curve, a pattern opposite to that prevailing in the earlier stages of downward curvature. There were periods during the gravitropic response when the normally unimodal growth-rate distribution within the elongation zone became bimodal with two peaks of rapid elongation separated by a region of reduced elongation rate. This occurred at different times on the convex and concave sides of the graviresponding root. During the period of steady downward curvature the elongation zone along the convex side extended farther toward the tip than in the vertical control. During the period of reduced rate of curvature, the zone of elongation extended farther toward the tip along the concave side of the root. The data show that the gravitropic response pattern varies with time and involves changes in localized elongation rates as well as changes in the length and position of the elongation zone. Models of root gravitropic curvature based on simple unimodal inhibition of growth along the lower side cannot account for these complex growth patterns.

  9. Sex-Related Responses of Populus cathayana Shoots and Roots to AM Fungi and Drought Stress.

    PubMed

    Li, Zhen; Wu, Na; Liu, Ting; Chen, Hui; Tang, Ming

    2015-01-01

    We investigated the impact of drought and arbuscular mycorrhizal (AM) fungi on the morphological structure and physiological function of shoots and roots of male and female seedlings of the dioecious plant Populus cathayana Rehder. Pot-grown seedlings were subjected to well watered or water-limiting conditions (drought) and were grown in soil that was either inoculated or not inoculated with the AM fungus Rhizophagus intraradices. No significant differences were found in the infection rates between the two sexes. Drought decreased root and shoot growth, biomass and root morphological characteristics, whereas superoxide radical (O2-) and hydrogen peroxide content, peroxidase (POD) activity, malondialdehyde (MDA) concentration and proline content were significantly enhanced in both sexes. Male plants that formed an AM fungal symbiosis showed a significant increase in shoot and root morphological growth, increased proline content of leaves and roots, and increased POD activity in roots under both watering regimes; however, MDA concentration in the roots decreased. By contrast, AM fungi either had no effect or a slight negative effect on the shoot and root growth of female plants, with lower root biomass, total biomass and root/shoot ration under drought. In females, MDA concentration increased in leaves and roots under both watering regimes, and the proline content and POD activity of roots increased under drought conditions; however, POD activity significantly decreased under well-watered conditions. These findings suggest that AM fungi enhanced the tolerance of male plants to drought by improving shoot and root growth, biomass and the antioxidant system. Further investigation is needed to unravel the complex effects of AM fungi on the growth and antioxidant system of female plants. PMID:26102587

  10. Sex-Related Responses of Populus cathayana Shoots and Roots to AM Fungi and Drought Stress

    PubMed Central

    Li, Zhen; Wu, Na; Liu, Ting; Chen, Hui; Tang, Ming

    2015-01-01

    We investigated the impact of drought and arbuscular mycorrhizal (AM) fungi on the morphological structure and physiological function of shoots and roots of male and female seedlings of the dioecious plant Populus cathayana Rehder. Pot-grown seedlings were subjected to well watered or water-limiting conditions (drought) and were grown in soil that was either inoculated or not inoculated with the AM fungus Rhizophagus intraradices. No significant differences were found in the infection rates between the two sexes. Drought decreased root and shoot growth, biomass and root morphological characteristics, whereas superoxide radical (O2–) and hydrogen peroxide content, peroxidase (POD) activity, malondialdehyde (MDA) concentration and proline content were significantly enhanced in both sexes. Male plants that formed an AM fungal symbiosis showed a significant increase in shoot and root morphological growth, increased proline content of leaves and roots, and increased POD activity in roots under both watering regimes; however, MDA concentration in the roots decreased. By contrast, AM fungi either had no effect or a slight negative effect on the shoot and root growth of female plants, with lower root biomass, total biomass and root/shoot ration under drought. In females, MDA concentration increased in leaves and roots under both watering regimes, and the proline content and POD activity of roots increased under drought conditions; however, POD activity significantly decreased under well-watered conditions. These findings suggest that AM fungi enhanced the tolerance of male plants to drought by improving shoot and root growth, biomass and the antioxidant system. Further investigation is needed to unravel the complex effects of AM fungi on the growth and antioxidant system of female plants. PMID:26102587

  11. Magnetic study of elongated polypropylene fibres

    Microsoft Academic Search

    M. Rákos; R. Šimo; Z. Varga

    1966-01-01

    A study is made of the magnetic properties of polypropylene fibres (PP) subjected to permanent unidirectional deformation at room and higher temperatures of the medium (120°C). It follows from the results that the values of the magnetic susceptibility, measured perpendicular to the axis of the fibres, change as a function of the relative elongation while they express the changes in

  12. Isolation and expression analysis of tuberous root development related genes in Rehmannia glutinosa

    Microsoft Academic Search

    Peng Sun; Yuhai Guo; Jianjun Qi; Lili Zhou; Xianen Li

    2010-01-01

    As one kind of important modified storage organs, tuberous roots are attractive for their economic and biological values.\\u000a Although considerable progresses have been made in the past, molecular information regarding the tuberous root development\\u000a is still limited. In this study, we focused on the molecular profiling of the tuberous root development of Rehmannia glutinosa. Suppression subtractive hybridization technology was employed

  13. Transpiration rate in relation to root and leaf growth in cuttings of Begonia X hiemalis Fotsch

    Microsoft Academic Search

    B. Ottosson; N. T. Welander

    1997-01-01

    Cuttings of Begonia X hiemalis Fotsch. cv. ‘Schwabenland Red’ were rooted in an aeroponics system at 21 °C and 2.9 mol m?2 day?1 photosynthetic photon flux density (PPFD) for 18 h day?1. Leaf length increase rate was higher in leaves appearing at time of root formation compared with leaves starting to expand before roots were formed. Transpiration rate per unit

  14. Midday depression of tree root respiration in relation to leaf transpiration

    Microsoft Academic Search

    Yukiko Sakata Bekku; Tsuyoshi Sakata; Tadashi Tanaka; Takashi Nakano

    The root respiration rate often shows an exponential or a linear relationship with temperature under laboratory conditions.\\u000a However, under intact conditions in the field, the root respiration rates of some tree species decreased around midday despite\\u000a an increment of the root temperature (Bekku et al. 2009). To clarify the cause of midday depression, we examined the relationships between the intact

  15. Ecophysiology of wetland plant roots: A modelling comparison of aeration in relation to species distribution

    USGS Publications Warehouse

    Sorrell, B.K.; Mendelssohn, I.A.; McKee, K.L.; Woods, R.A.

    2000-01-01

    This study examined the potential for inter-specific differences in root aeration to determine wetland plant distribution in nature. We compared aeration in species that differ in the type of sediment and depth of water they colonize. Differences in root anatomy, structure and physiology were applied to aeration models that predicted the maximum possible aerobic lengths and development of anoxic zones in primary adventitious roots. Differences in anatomy and metabolism that provided higher axial fluxes of oxygen allowed deeper root growth in species that favour more reducing sediments and deeper water. Modelling identified factors that affected growth in anoxic soils through their effects on aeration. These included lateral root formation, which occurred at the expense of extension of the primary root because of the additional respiratory demand they imposed, reducing oxygen fluxes to the tip and stele, and the development of stelar anoxia. However, changes in sediment oxygen demand had little detectable effect on aeration in the primary roots due to their low wall permeability and high surface impedance, but appeared to reduce internal oxygen availability by accelerating loss from laterals. The development of pressurized convective gas flow in shoots and rhizomes was also found to be important in assisting root aeration, as it maintained higher basal oxygen concentrations at the rhizome-root junctions in species growing into deep water. (C) 2000 Annals of Botany Company.

  16. Quantitative divergence of the bacterial root microbiota in Arabidopsis thaliana relatives

    PubMed Central

    Schlaeppi, Klaus; Dombrowski, Nina; Oter, Ruben Garrido; Ver Loren van Themaat, Emiel; Schulze-Lefert, Paul

    2014-01-01

    Plants host at the contact zone with soil a distinctive root-associated bacterial microbiota believed to function in plant nutrition and health. We investigated the diversity of the root microbiota within a phylogenetic framework of hosts: three Arabidopsis thaliana ecotypes along with its sister species Arabidopsis halleri and Arabidopsis lyrata, as well as Cardamine hirsuta, which diverged from the former ?35 Mya. We surveyed their microbiota under controlled environmental conditions and of A. thaliana and C. hirsuta in two natural habitats. Deep 16S rRNA gene profiling of root and corresponding soil samples identified a total of 237 quantifiable bacterial ribotypes, of which an average of 73 community members were enriched in roots. The composition of this root microbiota depends more on interactions with the environment than with host species. Interhost species microbiota diversity is largely quantitative and is greater between the three Arabidopsis species than the three A. thaliana ecotypes. Host species-specific microbiota were identified at the levels of individual community members, taxonomic groups, and whole root communities. Most of these signatures were observed in the phylogenetically distant C. hirsuta. However, the branching order of host phylogeny is incongruent with interspecies root microbiota diversity, indicating that host phylogenetic distance alone cannot explain root microbiota diversification. Our work reveals within 35 My of host divergence a largely conserved and taxonomically narrow root microbiota, which comprises stable community members belonging to the Actinomycetales, Burkholderiales, and Flavobacteriales. PMID:24379374

  17. Quantitative divergence of the bacterial root microbiota in Arabidopsis thaliana relatives.

    PubMed

    Schlaeppi, Klaus; Dombrowski, Nina; Oter, Ruben Garrido; Ver Loren van Themaat, Emiel; Schulze-Lefert, Paul

    2014-01-14

    Plants host at the contact zone with soil a distinctive root-associated bacterial microbiota believed to function in plant nutrition and health. We investigated the diversity of the root microbiota within a phylogenetic framework of hosts: three Arabidopsis thaliana ecotypes along with its sister species Arabidopsis halleri and Arabidopsis lyrata, as well as Cardamine hirsuta, which diverged from the former ? 35 Mya. We surveyed their microbiota under controlled environmental conditions and of A. thaliana and C. hirsuta in two natural habitats. Deep 16S rRNA gene profiling of root and corresponding soil samples identified a total of 237 quantifiable bacterial ribotypes, of which an average of 73 community members were enriched in roots. The composition of this root microbiota depends more on interactions with the environment than with host species. Interhost species microbiota diversity is largely quantitative and is greater between the three Arabidopsis species than the three A. thaliana ecotypes. Host species-specific microbiota were identified at the levels of individual community members, taxonomic groups, and whole root communities. Most of these signatures were observed in the phylogenetically distant C. hirsuta. However, the branching order of host phylogeny is incongruent with interspecies root microbiota diversity, indicating that host phylogenetic distance alone cannot explain root microbiota diversification. Our work reveals within 35 My of host divergence a largely conserved and taxonomically narrow root microbiota, which comprises stable community members belonging to the Actinomycetales, Burkholderiales, and Flavobacteriales. PMID:24379374

  18. Tungsten disrupts root growth in Arabidopsis thaliana by PIN targeting.

    PubMed

    Adamakis, Ioannis-Dimosthenis S; Panteris, Emmanuel; Eleftheriou, Eleftherios P

    2014-08-15

    Tungsten is a heavy metal with increasing concern over its environmental impact. In plants it is extensively used to deplete nitric oxide by inhibiting nitrate reductase, but its presumed toxicity as a heavy metal has been less explored. Accordingly, its effects on Arabidopsis thaliana primary root were assessed. The effects on root growth, mitotic cell percentage, nitric oxide and hydrogen peroxide levels, the cytoskeleton, cell ultrastructure, auxin and cytokinin activity, and auxin carrier distribution were investigated. It was found that tungsten reduced root growth, particularly by inhibiting cell expansion in the elongation zone, so that root hairs emerged closer to the root tip than in the control. Although extensive vacuolation was observed, even in meristematic cells, cell organelles were almost unaffected and microtubules were not depolymerized but reoriented. Tungsten affected auxin and cytokinin activity, as visualized by the DR5-GFP and TCS-GFP expressing lines, respectively. Cytokinin fluctuations were similar to those of the mitotic cell percentage. DR5-GFP signal appeared ectopically expressed, while the signals of PIN2-GFP and PIN3-GFP were diminished even after relatively short exposures. The observed effects were not reminiscent of those of any nitric oxide scavengers. Taken together, inhibition of root growth by tungsten might rather be related to a presumed interference with the basipetal flow of auxin, specifically affecting cell expansion in the elongation zone. PMID:24973590

  19. De novo assembly of Euphorbia fischeriana root transcriptome identifies prostratin pathway related genes

    PubMed Central

    2011-01-01

    Background Euphorbia fischeriana is an important medicinal plant found in Northeast China. The plant roots contain many medicinal compounds including 12-deoxyphorbol-13-acetate, commonly known as prostratin that is a phorbol ester from the tigliane diterpene series. Prostratin is a protein kinase C activator and is effective in the treatment of Human Immunodeficiency Virus (HIV) by acting as a latent HIV activator. Latent HIV is currently the biggest limitation for viral eradication. The aim of this study was to sequence, assemble and annotate the E. fischeriana transcriptome to better understand the potential biochemical pathways leading to the synthesis of prostratin and other related diterpene compounds. Results In this study we conducted a high throughput RNA-seq approach to sequence the root transcriptome of E. fischeriana. We assembled 18,180 transcripts, of these the majority encoded protein-coding genes and only 17 transcripts corresponded to known RNA genes. Interestingly, we identified 5,956 protein-coding transcripts with high similarity (> = 75%) to Ricinus communis, a close relative to E. fischeriana. We also evaluated the conservation of E. fischeriana genes against EST datasets from the Euphorbeacea family, which included R. communis, Hevea brasiliensis and Euphorbia esula. We identified a core set of 1,145 gene clusters conserved in all four species and 1,487 E. fischeriana paralogous genes. Furthermore, we screened E. fischeriana transcripts against an in-house reference database for genes implicated in the biosynthesis of upstream precursors to prostratin. This identified 24 and 9 candidate transcripts involved in the terpenoid and diterpenoid biosyntehsis pathways, respectively. The majority of the candidate genes in these pathways presented relatively low expression levels except for 1-hydroxy-2-methyl-2-(E)-butenyl 4-diphosphate synthase (HDS) and isopentenyl diphosphate/dimethylallyl diphosphate synthase (IDS), which are required for multiple downstream pathways including synthesis of casbene, a proposed precursor to prostratin. Conclusion The resources generated in this study provide new insights into the upstream pathways to the synthesis of prostratin and will likely facilitate functional studies aiming to produce larger quantities of this compound for HIV research and/or treatment of patients. PMID:22151917

  20. Induction of Defense-Related Ultrastructural Modifications in Pea Root Tissues Inoculated with Endophytic Bacteria.

    PubMed Central

    Benhamou, N.; Kloepper, J. W.; Quadt-Hallman, A.; Tuzun, S.

    1996-01-01

    The stimulation exerted by the endophytic bacterium Bacillus pumilus strain SE34 in plant defense reactions was investigated at the ultrastructural level using an in vitro system in which root-inducing T-DNA pea (Pisum sativum L.) roots were infected with the pea root-rotting fungus Fusarium oxysporum f. sp. pisi. In nonbacterized roots, the pathogen multiplied abundantly through much of the tissue including the vascular stele, whereas in prebacterized roots, pathogen growth was restricted to the epidermis and the outer cortex In these prebacterized roots, typical host reactions included strengthening the epidermal and cortical cell walls and deposition of newly formed barriers beyond the infection sites. Wall appositions were found to contain large amounts of callose in addition to being infiltrated with phenolic compounds. The labeling pattern obtained with the gold-complexed laccase showed that phenolics were widely distributed in Fusarium-challenged, bacterized roots. Such compounds accumulated in the host cell walls and the intercellular spaces as well as at the surface or even inside of the invading hyphae of the pathogen. The wall-bound chitin component in Fusarium hyphae colonizing bacterized roots was preserved even when hyphae had undergone substantial degradation. These observations confirm that endophytic bacteria may function as potential inducers of plant disease resistance. PMID:12226427

  1. Root Suberin Forms an Extracellular Barrier That Affects Water Relations and Mineral Nutrition in Arabidopsis

    Microsoft Academic Search

    Ivan Baxter; Prashant S. Hosmani; Ana Rus; Brett Lahner; Justin O. Borevitz; Balasubramaniam Muthukumar; Michael V. Mickelbart; Lukas Schreiber; Rochus B. Franke; David E. Salt

    2009-01-01

    Though central to our understanding of how roots perform their vital function of scavenging water and solutes from the soil, no direct genetic evidence currently exists to support the foundational model that suberin acts to form a chemical barrier limiting the extracellular, or apoplastic, transport of water and solutes in plant roots. Using the newly characterized enhanced suberin1 (esb1) mutant,

  2. Variation, co-ordination and compensation in root systems in relation to soil variability

    Microsoft Academic Search

    David Robinson

    1996-01-01

    In soil, the distributions of nutrients, water, pores, and microbes vary in time and space. These, in turn, contribute to the variations in root form and function that we see when we grow plants in soil and other non-uniform media. This paper addresses three questions about the consequences of non-uniform distributions of nutrients: how do roots respond to variations in

  3. Distribution of Rhizoctonia Bare Patch and Root Rot in Eastern Washington and Relation to Climatic Variables

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Rhizoctonia is a fungus that attacks the roots of wheat and barley, causing a root rot and bare patch in the dryland wheat cropping area of the inland Pacific Northwest. Over the last 7 years, we have been investigating the distribution of this pathogen, using molecular methods based on extracting a...

  4. Changes in fine root production and longevity in relation to water and nutrient availability in a Norway spruce stand in northern Sweden.

    PubMed

    Majdi, H

    2001-09-01

    Effects of irrigation and liquid fertilization on fine root (< 1 mm) production and longevity, and fine root (< 0.5-2 mm) biomass were studied in a Norway spruce (Picea abies (L.) Karst.) stand in northern Sweden. Fine root length production and longevity were measured by the minirhizotron technique at 0-10 cm depth in the following treatments: irrigation (I), liquid fertilization (IL) and control (C). Standing root biomass and root length density (RLD) were studied in the litter-fermented humus (LFH) layer and at depths of 0-10, 10-20 and 20-30 cm using soil cores in solid fertilized (F) and C plots. Minirhizotrons were installed in October 1994 and measurements recorded monthly from July to September 1995 and during the growing season in 1996. Soil cores were sampled in 1996. Fine root production increased significantly in IL plots compared with C plots, but the I treatment did not increase root production. Root mortality increased significantly in IL plots compared with C plots. Fine root longevity in IL plots was significantly lower compared with C and I plots. No significant difference was found between longevity of fine roots in I and C plots. Compared with C, F treatment increased fine root biomass in the LFH and mineral soil layers, and increased the amount of fine roots in mineral soil layers relative to the LFH layer. Furthermore, F increased RLD and the number of mycorrhizal root tips significantly. PMID:11560819

  5. Temperature Interactions with Growth Regulators and Endogenous Gibberellin-like Activity during Seedstalk Elongation in Carrots.

    PubMed

    Hiller, L K; Kelly, W C; Powell, L E

    1979-06-01

    Stecklings (roots) of three cultivars of carrots (Daucus carota L.) were vernalized 10 weeks at 5 C and subsequently grown at each of three greenhouse night/day temperature regimes: high (27/32 C), medium (21/27 C), and low (15/21 C). Floral differentiation occurred first in the easy bolting cv. Scarlet Nantes, intermediate in cv. Danvers 126, and last in cv. Royal Chantenay. Stem elongation arising from the subapical meristematic region always preceded floral differentiation. Extractable gibberellin-like activity in carrot stem apices increased from harvest during the 10-week vernalization period, then remained constant even though floral differentiation and stem elongation occurred during an additional 20-week cold storage period. Low temperature had both an inductive and a direct effect on reproductive development depending on length of low temperature exposure.After 10 weeks vernalization at 5 C, high greenhouse temperature severely reduced ultimate seedstalk height and the endogenous gibberellinlike activity decreased rapidly during the first 3 weeks in the greenhouse. At the low greenhouse temperature, activity remained fairly constant during the 10-week sampling period. Changes in endogenous gibberellinlike activity were related with stem elongation, but not with floral initiation. Exogenous gibberellic acid (GA(3)) applied following vernalization prevented the inhibitory effect of high greenhouse temperature on seedstalk elongation and resulted in seedstalk heights comparable to untreated controls grown at the low greenhouse temperature. Exogenous applications of succinic acid-2,2-dimethylhydrazide and chlormequat reduced seedstalk height of carrot plants grown at the medium and low greenhouse temperatures to that of untreated controls grown at high temperature. Exogenous growth regulators and greenhouse temperature affected seedstalk elongation, but did not affect the number of plants that flowered. PMID:16660856

  6. ? 2Adrenergic receptor activation inhibits calcitonin gene-related peptide expression in cultured dorsal root ganglia neurons

    Microsoft Academic Search

    Scott C Supowit; Diane M Hallman; Huawei Zhao; Donald J DiPette

    1998-01-01

    Calcitonin gene-related peptide (CGRP), a potent vasodilator, is produced in dorsal root ganglia (DRG) neurons which extend nerves peripherally to blood vessels and centrally to the spinal cord. We previously reported that neuronal CGRP expression is significantly reduced in the spontaneously hypertensive rat (SHR) which could contribute to the elevated BP. Other studies suggest that the enhanced activity of the

  7. On the use of the multivariate autoregressive and relative power contribution models for determination of transient root cause

    Microsoft Academic Search

    Rogelio Castillo-Durán; Javier Ortiz-Villafuerte; Javier C. Palacios

    2008-01-01

    The multivariate autoregressive (MAR) model and the relative power contribution (RPC) ratio are used in this work to determine the root causes of a power oscillation event and an apparent positive reactivity insertion transient occurred at the at the BWR\\/5 Units of the Laguna Verde Nuclear Power Plant (LVNPP) of México. The application of the MAR and PRC models leads

  8. Hairy roots are more sensitive to auxin than normal roots

    PubMed Central

    Shen, Wen Hui; Petit, Annik; Guern, Jean; Tempé, Jacques

    1988-01-01

    Responses to auxin of Lotus corniculatus root tips or protoplasts transformed by Agrobacterium rhizogenes strains 15834 and 8196 were compared to those of their normal counterparts. Three different types of experiments were performed, involving long-term, medium-term, or short-term responses to a synthetic auxin, 1-naphthaleneacetic acid. Root tip elongation, proton excretion by root tips, and transmembrane electrical potential difference of root protoplasts were measured as a function of exogenous auxin concentration. The sensitivity of hairy root tips or protoplasts to exogenous auxin was found to be 100-1000 times higher than that of untransformed material. PMID:16593928

  9. The novel expression of Oct3/4 and Bmi1 in the root development of mouse molars.

    PubMed

    Nakagawa, Eizo; Zhang, Li; Shin, Jeong-Oh; Kim, Eun-Jung; Cho, Sung-Won; Ohshima, Hayato; Chen, Zhi; Jung, Han-Sung

    2012-02-01

    The root apex of the tooth elongates until the completion of root development. Although the signaling molecules inducing root elongation have been studied, the characteristic of the cells having the ability to maintain the root elongation remains unclear. This study aimed to investigate the characteristics of the cells involved in the root elongation. Octamer-binding factor 3/4 (Oct3/4) is known as one of the key regulators in maintaining the pluripotency and self-renewal properties of embryonic stem cells. Bmi1, the polycomb-group transcriptional repressor, has emerged as a key regulator in several cellular processes including stem cell self-renewal and cancer cell proliferation. At the beginning of root formation, ameloblasts expressed Oct3/4 in the nucleus, except in the apex of the cervical loop, in which Bmi1and cyclinD were expressed. At PN6, the expression of Oct3/4 in the ameloblasts shifted from the nucleus to the cytoplasm, whereas ameloblastin-negative Hertwig's epithelial root sheath (HERS) cells expressed Bmi1 and cyclinD. By PN10, the cells in the apex of HERS began to express Oct3/4 in their nucleus, whereas Bmi1 and cyclinD began to decrease in their expressions. The odontoblasts consistently expressed Oct3/4 in their cytoplasm. Our results suggest that (1) Oct3/4 creates the border between the ameloblasts from the proliferative region of HERS, (2) Bmi1-positive cells would be one of the candidates resulting in root elongation and (3) the Oct3/4 expression in the cytoplasm of odontoblasts may be related to maintain the odontoblastic characteristics. PMID:22287043

  10. Agrobacterium rhizogenes rol genes induce productivity-related phenotypical modifications in "creeping-rooted" alfalfa types.

    PubMed

    Frugis, G; Caretto, S; Santini, L; Mariotti, D

    1995-05-01

    Agrobacterium rhizogenes rol genes were transferred individually or in combination into the forage legume Medicago sativa L. (alfalfa). Kanamycin resistant, neomycin phosphotransferase II positive plants showed the presence of the rol inserts in their genome. Phenotypical evaluation of transgenic populations indicated significant morphological alterations of the root system, stem number per plant and plant structure. A possible utilization of these transgenics in breeding programs of the so-called "creeping-rooted" alfalfa strains is discussed. PMID:24185517

  11. Effects of a novel pathogenesis-related class 10 (PR-10) protein from Crotalaria pallida Roots with papain inhibitory activity against root-knot nematode Meloidogyne incognita.

    PubMed

    Andrade, Lúcia Betânia da S; Oliveira, Adeliana S; Ribeiro, Jannison K C; Kiyota, Sumika; Vasconcelos, Ilka Maria; de Oliveira, José Tadeu Abreu; de Sales, Maurício P

    2010-04-14

    A novel pathogenesis-related class 10 (PR-10) protein with papain inhibitory activity, named CpPRI, was purified from Crotalaria pallida roots by ammonium sulfate precipitation followed by three reverse-phase high-performance liquid chromatographies (HPLCs). CpPRI is made up of a single polypeptide chain with a M(r) of 15 kDa, as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). This protein exhibited a K(i) value of 1.8 x 10(-9) M and operates via a noncompetitive inhibition mechanism. The alignment of the N-terminal amino acid sequence of CpPRI with other proteins revealed its identity with PR-10 proteins. CpPRI acts against digestive proteinase from root-knot nematode Meloidogyne incognita and demonstrated nematostatic and nematicide effects on this parasite in bioassays. In a localization study, fluorescein-5-isothiocyanate (FITC)-CpPRI was observed to internalize and diffuse over the entire J2 body after 6 h of incubation. This fact could explain the natural tolerance of this plant species to nematodes. PMID:20199085

  12. Effects of root medium pH on water transport in paper birch (Betula papyrifera) seedlings in relation to root temperature and abscisic acid treatments.

    PubMed

    Kamaluddin, M; Zwiazek, Janusz J

    2004-10-01

    We investigated the effects of root medium pH on water transport in whole-plant and detached roots of paper birch (Betula papyrifera Marsh.). Exposure of seedling roots to pH 4 and 8 significantly decreased root hydraulic conductivity (Lp) and stomatal conductance (gs), compared with pH 6. When roots of solution-culture-grown (pH 6) seedlings were transferred to pH 4 or 8, their steady-state water flow (Qv) declined within minutes, followed by a decline in gs. The root oxygen uptake rates were not significantly affected by the pH treatments. Treatment of roots with mercuric chloride resulted in a large decrease in Qv at pH 6; the extent of this decrease was similar to that brought about by pH 4 and 8. Lowering root temperature from 21 to 4 degrees C decreased Qv irrespective of medium pH. Low root temperatures did not offset the effects of medium pH 4 on Qv and the roots in this treatment had a high activation energy for water flow. Conversely, roots exposed to pH 8 had a low activation energy, similar to that at pH 6. When 2 micro M abscisic acid, (+/-)-cis-trans-ABA, was added to the root medium, Qv increased in roots that were incubated at pH 6. It also increased slightly in roots incubated at pH 4, but not at pH 8. The increase at pH 4 and 6 was temperature-dependent, occurring at 21 degrees C, but not 4 degrees C. We suggest that the pH treatments are responsible for altering root water flow properties through their effects on the activity of water channels. These results support the concept that ABA effects on water channels are modulated by other, possibly metabolic- and pH-dependent factors. PMID:15294764

  13. Reciprocation, Square Root, Inverse Square Root, and Some Elementary Functions

    E-print Network

    Muller, Jean-Michel

    Reciprocation, Square Root, Inverse Square Root, and Some Elementary Functions Using Small with the computation of reciprocals, square roots, inverse square roots, and some elementary functions using small/number of multipliers and compare with other related methods. Index TermsÐReciprocal, square root, inverse square root

  14. Clustering, haplotype diversity and locations of MIC-3: a unique root-specific defense-related gene family in upland cotton (Gossypium hirsutum L.)

    Technology Transfer Automated Retrieval System (TEKTRAN)

    MIC-3-related genes of cotton (Gossypium spp.) were identified and shown to have root-specific expression, associated with pathogen defense-related function and specifically increased expression in root-knot nematode (RKN) resistant plants after nematode infection. Here we cloned and sequenced MIC-...

  15. Cluster-root formation and carboxylate release in three Lupinus species as dependent on phosphorus supply, internal phosphorus concentration and relative growth rate

    PubMed Central

    Wang, Xing; Pearse, Stuart J.; Lambers, Hans

    2013-01-01

    Background and Aims Some Lupinus species produce cluster roots in response to low plant phosphorus (P) status. The cause of variation in cluster-root formation among cluster-root-forming Lupinus species is unknown. The aim of this study was to investigate if cluster-root formation is, in part, dependent on different relative growth rates (RGRs) among Lupinus species when they show similar shoot P status. Methods Three cluster-root-forming Lupinus species, L. albus, L. pilosus and L. atlanticus, were grown in washed river sand at 0, 7·5, 15 or 40 mg P kg?1 dry sand. Plants were harvested at 34, 42 or 62 d after sowing, and fresh and dry weight of leaves, stems, cluster roots and non-cluster roots of different ages were measured. The percentage of cluster roots, tissue P concentrations, root exudates and plant RGR were determined. Key Results Phosphorus treatments had major effects on cluster-root allocation, with a significant but incomplete suppression in L. albus and L. pilosus when P supply exceeded 15 mg P kg?1 sand. Complete suppression was found in L. atlanticus at the highest P supply; this species never invested more than 20 % of its root weight in cluster roots. For L. pilosus and L. atlanticus, cluster-root formation was decreased at high internal P concentration, irrespective of RGR. For L. albus, there was a trend in the same direction, but this was not significant. Conclusions Cluster-root formation in all three Lupinus species was suppressed at high leaf P concentration, irrespective of RGR. Variation in cluster-root formation among the three species cannot be explained by species-specific variation in RGR or leaf P concentration. PMID:24061491

  16. The relative importance of allelopathy in interference: the effects of an invasive weed on a native bunchgrass

    Microsoft Academic Search

    Wendy M. Ridenour; Ragan M. Callaway

    2001-01-01

    The relative importance of allelopathy and re- source competition in plant-plant interactions has been vigorously debated but seldom tested. We used activated carbon to manipulate the effects of root exudates of Centaurea maculosa, a noxious weed in much of western North America, on root elongation rates and growth of the native bunchgrass Festuca idahoensis in order to in- vestigate the

  17. Ion Transport Characteristics of Grape Root Lipids in Relation to Chloride Transport 1

    PubMed Central

    Kuiper, Pieter J. C.

    1968-01-01

    Ion transport properties of grape root lipids were measured as liquid-membrane permeability. Phosphatidylcholine exchanged chloride very slowly against carbonate and bicarbonate but more rapidly against nitrate, phosphate, and sulfate. Exchange of chloride against nitrate was rather low for the phosphatidylcholine and phosphatidylethanolamine lipid fractions; monogalactose diglyceride was by far the most effective chloride transporter studied. Comparison between the lipid composition of the roots of the 5 grape rootstocks and the chloride transport capacity of the specific membranes strongly suggests that, indeed, the chloride transport capacity of the lipids present in the membranes of the root cells accounts for the observed differences in chloride transport to the leaves. Whereas monogalactose diglyceride had a high chloride transport capacity, compared with phosphatidylcholine, the reverse was true for exchange of sodium against potassium. Thus, phosphatidylcholine has more the properties of a cation exchanger, and monogalactose diglyceride those of an anion transporter. PMID:16656922

  18. Water relations and root activities of Buchloe dactyloides and Zoysia japonica in response to localized soil drying

    Microsoft Academic Search

    Bingru Huang

    1999-01-01

    Effects of localized soil drought stress on water relations, root growth, and nutrient uptake were examined in drought tolerant\\u000a ‘Prairie’ buffalograss [Buchloe dactyloides (Nutt.) Engelm.] and sensitive ‘Meyer’ zoysiagrass (Zoysia japonica Steud.). Grasses\\u000a were grown in small rhizotrons in a greenhouse and subjected to three soil moisture regimes: (1) watering the entire 80-cm\\u000a soil profile (well-watered control); (2) drying 0–40

  19. The structure of barley roots in relation to the transport of ions into the stele

    Microsoft Academic Search

    A. W. Robards; S. Margaret Jackson; D. T. Clarkson; J. Sanderson

    1973-01-01

    Summary Three successive states are recognized in the development of endodermal cells in seminal and nodal axes and primary lateral roots of barley: 1. Casparian bands in the anticlinal walls; 2. suberin lamella around the whole inner face of the wall; 3. unevenly deposited cellulosic wall thickening. These states develop asynchronously, the cells adjacent to the protoxylem pole cells always

  20. Cation fluxes in excised and intact roots in relation to specific and varietal differences

    Microsoft Academic Search

    W. D. Jeschke

    1983-01-01

    Summary In this short survey differences between species and varieties in the four major mechanisms that affect selective uptake of potassium and sodium to the plant within the root are considered. These include influx selectivity, K+\\/Na+ exchange at the plasmalemma, and selectivity at the tonoplast as well as at the symplasm-xylem boundary. The affinity of various plants for potassium influx

  1. Soybean root growth in acid subsoils in relation to magnesium additions and soil solution ionic strength

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Hydroponic studies with soybean [Glycine max (L.) Merr.] have shown that µM additions of Mg2+ were as effective in ameliorating Al rhizotoxicity as additions of Ca2+ in the mM concentration range. The objectives of this study were to assess ameliorative effects of Mg on soybean root growth in acidic...

  2. Abscisic acid root and leaf concentration in relation to biomass partitioning in salinized tomato plants

    Microsoft Academic Search

    Stella Lovelli; Antonio Scopa; Michele Perniola; Teodoro Di Tommaso; Adriano Sofo

    Salinization is one of the most important causes of crop productivity reduction in many areas of the world. Mechanisms that control leaf growth and shoot development under the osmotic phase of salinity are still obscure, and opinions differ regarding the Abscisic acid (ABA) role in regulation of biomass allocation under salt stress. ABA concentration in roots and leaves was analyzed

  3. Growth and shoot: root ratio of seedlings in relation to nutrient availability

    Microsoft Academic Search

    Tom Ericsson

    1995-01-01

    The influence of mineral nutrient availability, light intensity and CO2 on growth and shoot:root ratio in young plants is reviewed. Special emphasis in this evaluation is given to data from laboratory experiments with small Betula pendula plants, in which the concept of steady-state nutrition has been applied.

  4. SOYBEAN ROOT DISTRIBUTION RELATED TO CLAYPAN SOIL PROPERTIES AND APPARENT SOIL ELECTRICAL CONDUCTIVITY

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Soybean [Glycine max (L.)] yield in claypan soils varies as a result of systematic relationships with soil properties and landscape position. This variability is likely caused by soil-landscape interactions with soybean roots. While much data exists on the landscape variability of yield, field obser...

  5. Genetic diversity for root-knot nematode resistance in white clover and related species

    Microsoft Academic Search

    Christophe N. Kouamé; Kenneth H. Quesenberry; David S. Wofford; Robert A. Dunn

    1998-01-01

    A total of 237 Plant Introduction in eleven Trifolium species were evaluated for resistance to Meloidogyne arenaria (Neal) Chitwood race 1, M. hapla Chitwood, M. incognita (Kofoid & White) Chitwood race 3, and M. javanica (Treub) Chitwood. Plants were infected with 1500 nematode eggs collected from 'Rutgers' tomato (Lycoperiscon esculentum Mill.) roots with 0.5% NaOCl. Ratings of galling severity and

  6. Effects of anaerobic conditions on water and solute relations, and on active transport in roots of maize ( Zea mays L.)

    Microsoft Academic Search

    Thomas P. Birner; Ernst Steudle

    1993-01-01

    The effects of anoxia on water and solute transport across excised roots of young maize plants (Zea mays L. cv. Tanker) grown hydroponically have been studied. With the aid of the root pressure probe, root pressure (Pr), root hydraulic conductivity (Lpr), and root permeability (Psr), and reflection (ssr) coefficients were measured using potassium nitrate (a typical nutrient salt) and sodium

  7. Differential Two-Dimensional Protein Patterns as Related to Tissue Specificity and Water Conditions in Brassica napus var oleifera Root System

    PubMed Central

    Damerval, Catherine; Vartanian, Nicole; de Vienne, Dominique

    1988-01-01

    Differential two-dimensional protein patterns as related to tissue specificity and water conditions were investigated within Brassica napus var oleifera root system. The different parts of the root system (tap root, lateral roots, and drought-induced short roots) were analyzed under various moisture regimes (regular watering at field capacity, progressive drought stress, and rewatering). Tissue specificity was evident from 25 differences in protein patterns (qualitative and quantitative) between well-watered lateral and tap roots. Twice as many polypeptides (52) were drought-affected and the response to the water stress was shown to be similar in both root types. In addition, more than half of the polypeptides detected as organ-specific were affected by drought. Based upon the trend of variation observed under drought and rehydration, three categories of polypeptides could be defined that might be differently involved in drought susceptibility or tolerance. A highly differentiated protein pattern characterized the drought-induced short roots. This pattern appeared as far from the watered as from the water-stressed normal roots. In particular, 13 unique polypeptides were detected which could be relevant to their adaptive morphogenesis and/or their specific drought tolerance induction. Upon rehydration, their polypeptide pattern and their specific morphology returned to a normal well-watered lateral root type. Images Fig. 2 Fig. 3 PMID:16666071

  8. Gibberellin Biosynthesis Mutations and Root Development in Pea

    PubMed Central

    Yaxley, Julian R.; Ross, John J.; Sherriff, Leanne J.; Reid, James B.

    2001-01-01

    Dwarf mutants of pea (Pisum sativum), with impaired gibberellin (GA) biosynthesis in the shoot, were studied to determine whether the roots of these genotypes had altered elongation and GA levels. Mutations na, lh-2, and ls-1 reduced GA levels in root tips and taproot elongation, although in lh-2 and ls-1 roots the reduction in elongation was small (less than 15%). The na mutation reduced taproot length by about 50%. The roots of na plants elongated in response to applied GA1 and recombining na with mutation sln (which blocks GA catabolism) increased GA1 levels in root tips and completely restored normal root development. In shoots, Mendel's le-1 mutation impairs the 3?-hydroxylation of GA20 to the bioactive GA1, resulting in dwarfism. However, GA1 and GA20 levels were normal in le-1 roots, as was root development. The null mutation le-2 also did not reduce root GA levels or elongation. The results support the theory that GAs are important for normal root elongation in pea, and indicate that a 3?-hydroxylase gene other than LE operates in pea roots. PMID:11161020

  9. Quantitative Assessment of Ultrastructural Changes in Primary Roots of Corn (Zea mays L.) after Geotropic Stimulation: II. Curving and Noncurving Zones of the Root Proper.

    PubMed

    Shen-Miller, J; McNitt, R E

    1978-04-01

    In outer cortical cells of corn (Zea mays L.) roots we made ultrastructural comparisons between the geotropically responding (661 nm irradiated) and nonresponding (dark control) roots in both the curving and noncurving regions of the root. In the control treatment, Golgi apparatus (dictyosomes) and mitochondria exhibited centrifugal distribution (taking the stele as the center) in both regions of the roots (the organelles localized in the top of the cells in the upper tissues, and in the bottom of the cells in the lower tissues). In the geotropically responding roots, the distribution patterns were the same as those of the controls. However, in the zone of curvature the dictyosomes (but not the mitochondria) were randomly distributed in the cells of the upper tissues. This change in pattern of dictyosome distribution could be related to the change in cell elongation of upper cells. PMID:16660355

  10. Inhibitory effect of parthenium ( Parthenium hysterophorus L.) residue on growth of water hyacinth ( Eichhornia crassipes Mart Solms.) II. Relative effect of flower, leaf, stem, and root residue

    Microsoft Academic Search

    D. K. Pandey; L. P. Kauraw; V. M. Bhan

    1993-01-01

    The relative effect of residue of leaf, flower, stem, and root of parthenium (Parthenium hysterophorus L.) on growth of water hyacinth was studied. The inhibitory activity of the residue as shown by its effect on biomass and healthy leaf number (HLN) of treated plants was in the order: leaf and flower >stem >root. Total phenolic acids in the medium after

  11. Development and function of Azospirillum -inoculated roots

    Microsoft Academic Search

    Y. Okon; Y. Kapulnik

    1986-01-01

    Summary  The surface distribution ofAzospirillum on inoculated roots of maize and wheat is generally similar to that of other members of the rhizoplane microflora. During the first three days, colonization takes place mainly on the root elongation zone, on the base of root hairs and, to a lesser extent, on the surface of young root hairs.Azospirillum has been found in cortical

  12. Transient Responses of Cell Turgor and Growth of Maize Roots as Affected by Changes in Water Potential.

    PubMed Central

    Frensch, J.; Hsiao, T. C.

    1994-01-01

    Transient responses of cell turgor (P) and root elongation to changes in water potential were measured in maize (Zea mays L.) to evaluate mechanisms of adaptation to water stress. Changes of water potential were induced by exposing roots to solutions of KCl and mannitol (osmotic pressure about 0.3 MPa). Prior to a treatment, root elongation was about 1.2 mm h-1 and P was about 0.67 MPa across the cortex of the expansion zone (3-10 mm behind the root tip). Upon addition of an osmoticum, P decreased rapidly and growth stopped completely at pressure below approximately 0.6 MPa, which indicated that the yield threshold (Ytrans,1) was just below the initial turgor. Turgor recovered partly within the next 30 min and reached a new steady value at about 0.53 MPa. The root continued to elongate as soon as P rose above a new threshold (Ytrans,2) of about 0.45 MPa. The time between Ytrans,1 and Ytrans,2 was about 10 min. During this transition turgor gradients of as much as 0.15 MPa were measured across the cortex. They resulted from a faster rate of turgor recovery of cells deeper inside the tissue compared with cells near the root periphery. Presumably, the phloem was the source of the compounds for the osmotic adjustment. Turgor recovery was restricted to the expansion zone, as was confirmed by measurements of pressure kinetics in mature root tissue. Withdrawal of the osmoticum caused an enormous transient increase of elongation, which was related to only a small initial increase of P. Throughout the experiment, the relationship between root elongation rate and turgor was nonlinear. Consequently, when Y were calculated from steady-state conditions of P and root elongation before and after the osmotic treatment, Yss was only 0.21 MPa and significantly smaller compared with the values obtained from direct measurements (0.42-0.64 MPa). Thus, we strongly emphasize the need for measurements of short-term responses of elongation and turgor to determine cell wall mechanics appropriately. Our results indicate that the rate of solute flow into the growth zone could become rate-limiting for cell expansion under conditions of mild water stress. PMID:12232076

  13. Agrobacterium rhizogenes rol genes induce productivity-related phenotypical modifications in “creeping-rooted” alfalfa types

    Microsoft Academic Search

    Giovanna Frugis; Sofia Caretto; Luigi Santini; Domenico Mariotti

    1995-01-01

    Summary  \\u000aAgrobacterium rhizogenes rol genes were transferred individually or in combination into the forage legume Medicago sativa L. (alfalfa). Kanamycin resistant, neomycin phosphotransferase II positive plants showed the presence of the rol inserts in their genome. Phenotypical evaluation of transgenic populations indicated significant morphological alterations of the root system, stem number per plant and plant structure. A possible utilization of

  14. Elongator, a Multisubunit Component of a Novel RNA Polymerase II Holoenzyme for Transcriptional Elongation

    Microsoft Academic Search

    Gabriel Otero; Jane Fellows; Yang Li; Therese de Bizemont; Annette M. G Dirac; Claes M Gustafsson; Hediye Erdjument-Bromage; Paul Tempst; Jesper Q Svejstrup

    1999-01-01

    The form of RNA polymerase II (RNAPII) engaged in transcriptional elongation was isolated. Elongating RNAPII was associated with a novel multisubunit complex, termed elongator, whose stable interaction was dependent on a hyperphosphorylated state of the RNAPII carboxy-terminal domain (CTD). A free form of elongator was also isolated, demonstrating the discrete nature of the complex, and free elongator could bind directly

  15. Short sampling intervals reveal very rapid root turnover in a temperate grassland.

    PubMed

    Stewart, Anna M; Frank, Douglas A

    2008-09-01

    Although root growth and mortality play critical regulatory roles in terrestrial ecosystems, little is known about the temporal scale of these dynamics. In temperate grasslands, root dynamics may be particularly rapid because of the high proportion of production allocated to very fine root biomass. In this study, we used minirhizotron tubes to estimate root growth and mortality in an upland grassland in Yellowstone National Park that was grazed by migratory herds of ungulates. Monthly rates of root growth and mortality were estimated from May to September 2005, by measuring the elongation (growth) and disappearance (mortality) of roots at 3-day intervals. Average daily growth (millimeters of root length) was approximately 5 times greater in May and June than in July, August, and September. Average daily mortality (millimeters of root length) did not differ among months. A comparison of the June-September rates of root growth and mortality derived from sampling at short (3-day) and long (1-month) time intervals indicated that the long sampling intervals underestimated both growth and mortality by approximately 60% relative to the short intervals. These results suggest that estimates of grassland root dynamics from minirhizotrons are influenced significantly by sampling interval length, and that rapid root turnover may play a more critical role in regulating energy and nutrient fluxes in temperate grasslands than has previously been recognized. PMID:18566834

  16. Root-zone acidity affects relative uptake of nitrate and ammonium from mixed nitrogen sources

    NASA Technical Reports Server (NTRS)

    Vessey, J. K.; Henry, L. T.; Chaillou, S.; Raper, C. D. Jr; Raper CD, J. r. (Principal Investigator)

    1990-01-01

    Soybean plants (Glycine max [L.] Merr. cv Ransom) were grown for 21 days on 4 sources of N (1.0 mM NO3-, 0.67 mM NO3- plus 0.33 mM NH4+, 0.33 mM NO3- plus 0.67 mM NH4+, and 1.0 mM NH4+) in hydroponic culture with the acidity of the nutrient solution controlled at pH 6.0, 5.5, 5.0, and 4.5. Dry matter and total N accumulation of the plants was not significantly affected by N-source at any of the pH levels except for decreases in these parameters in plants supplied solely with NH4+ at pH 4.5. Shoot-to-root ratios increased in plants which had an increased proportion [correction of proporiton] of NH4(+)-N in their nutrient solutions at all levels of root-zone pH. Uptake of NO3- and NH4+ was monitored daily by ion chromatography as depletion of these ions from the replenished hydroponic solutions. At all pH levels the proportion of either ion that was absorbed increased as the ratio of that ion increased in the nutrient solution. In plants which were supplied with sources of NO3- plus NH4+, NH4+ was absorbed at a ratio of 2:1 over NO3- at pH 6.0. As the pH of the root-zone declined, however, NH4+ uptake decreased and NO3- uptake increased. Thus, the NH4+ to NO3- uptake ratio declined with decreases in root-zone pH. The data indicate a negative effect of declining root-zone pH on NH4+ uptake and supports a hypothesis that the inhibition of growth of plants dependent on NH4(+)-N at low pH is due to a decline in NH4+ uptake and a consequential limitation of growth by N stress.

  17. Elongational rheology of polyethylene melts

    Microsoft Academic Search

    Bijan Seyfzadeh

    1999-01-01

    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

  18. Soil aggregation and slope stability related to soil density, root length, and mycorrhiza

    NASA Astrophysics Data System (ADS)

    Graf, Frank; Frei, Martin

    2013-04-01

    Eco-engineering measures combine the use of living plants and inert mechanical constructions to protect slopes against erosion and shallow mass movement. Whereas in geotechnical engineering several performance standards and guidelines for structural safety and serviceability of construction exist, there is a lack of comparable tools in the field of ecological restoration. Various indicators have been proposed, including the fractal dimension of soil particle size distribution, microbiological parameters, and soil aggregate stability. We present results of an soil aggregate stability investigation and compare them with literature data of the angle of internal friction ?' which is conventionally used in slope stability analysis and soil failure calculation. Aggregate stability tests were performed with samples of differently treated moraine, including soil at low (~15.5 kN/m³) and high (~19.0 kN/m³) dry unit weight, soil planted with Alnus incana (White Alder) as well as the combination of soil planted with alder and inoculated with the mycorrhizal fungus Melanogaster variegatus s.l. After a 20 weeks growth period in a greenhouse, a total of 100 samples was tested and evaluated. Positive correlations were found between the soil aggregate stability and the three variables dry unit weight, root length per soil volume, and degree of mycorrhization. Based on robust statistics it turned out that dry unit weight and mycorrhization degree were strongest correlated with soil aggregate stability. Compared to the non-inoculated control plants, mycorrhized White Alder produced significantly more roots and higher soil aggregate stability. Furthermore, the combined biological effect of plant roots and mycorrhizal mycelia on aggregate stability on soil with low density (~15.5 kN/m³) was comparable to the compaction effect of the pure soil from 15.5 to ~19.0 kN/m³. Literature data on the effect of vegetation on the angle of internal friction ?' of the same moraine showed similar correlations, i.e. that ?' of low density soil material (~15.5 kN/m³) increased by the same amount whether by planting with White Alder or by compaction to ~19.0 kN/m³. Based on this coincidence the method to quantify soil aggregate produced satisfying results which indicate that soil aggregate stability is a potential proxy for ?' and the joint impact of mycorrhizal fungi and plant roots increase the resistance against superficial soil failure. It is concluded that soil aggregate stability mirrors biological effects on soil stability reasonably well and may be used as an indicator to quantify the effectiveness of ecological restoration and stabilisation measures.

  19. Quantitative Assessment of Ultrastructural Changes in Primary Roots of Corn (Zea mays L.) after Geotropic Stimulation

    PubMed Central

    Shen-Miller, Jane; McNitt, Rand E.

    1978-01-01

    In outer cortical cells of corn (Zea mays L.) roots we made ultrastructural comparisons between the geotropically responding (661 nm irradiated) and nonresponding (dark control) roots in both the curving and noncurving regions of the root. In the control treatment, Golgi apparatus (dictyosomes) and mitochondria exhibited centrifugal distribution (taking the stele as the center) in both regions of the roots (the organelles localized in the top of the cells in the upper tissues, and in the bottom of the cells in the lower tissues). In the geotropically responding roots, the distribution patterns were the same as those of the controls. However, in the zone of curvature the dictyosomes (but not the mitochondria) were randomly distributed in the cells of the upper tissues. This change in pattern of dictyosome distribution could be related to the change in cell elongation of upper cells. ImagesFig. 1Fig. 2 PMID:16660355

  20. Root canal obturation: experimental study on the thermafil system related to different irrigation protocols

    PubMed Central

    Migliau, Guido; Sofan, Afrah Ali Abdullah; Sofan, Eshrak Ali Abdullah; Cosma, Salvatore; Eramo, Stefano; Gallottini, Livio

    2014-01-01

    Summary Aim The aim of this study was to stress the ability of a specific obturation technique (thermafil technique) to seal root canal system in presence or absence of smear layer. Methodology Sixteen monoradicular teeth, extracted for periodontal reasons, were collected for this study. All specimens were prepared with nickel-titanium rotary files, and then divided into two groups: for each group was applied a different kind of irrigation method, verifying the effectiveness in removing the smear layer, thus rendering the dentinal tubules more permeable for penetration of softened gutta-percha. Thermafil system was used to fill the root canals, and then all the specimens were observed under scanning electron microscope (SEM). Results The results showed that the Group which followed irrigation only with sodium hypochlorite exhibited significantly less gutta-percha tags when compared to the second Group, which was irrigated with sodium hypochlorite and EDTA. Conclusion The thermafil systems have a very good quality of compression and fluency that permit to gain a good seal of endodontic space; furthermore it allows the penetration of gutta-percha with the formation of numerous of gutta-percha tags inside the dentinal tubules above all when smear layer is reduced or eliminated. PMID:25506413

  1. Molecular characterization of coprophilous fungal communities reveals sequences related to root-associated fungal endophytes.

    PubMed

    Herrera, José; Poudel, Ravin; Khidir, Hana H

    2011-02-01

    This paper reports the use of molecular methods to characterize the coprophilous fungal communities (CFC) that inhabit the dung of four species of mammalian herbivores at two sites, Sevilleta National Wildlife Refuge (SNWR) in New Mexico and Wind Cave National Park (WCNP) in South Dakota. Results reveal that CFC from domesticated cattle (Bos taurus) at SNWR, and bison (Bison bison) and black-tailed prairie dogs (Cynomys ludovicianus) at WCNP were diverse but dominated primarily by members within eight taxonomic orders, including the rarely cultured and anaerobic order Neocallimastigales. In addition, 7.7% (138 of 1,788) of the sequences obtained from all dung samples were at least 97% similar to root-associated fungal (RAF) sequences previously described from blue grama (Bouteloua gracilis), a common forage grass found throughout North America and growing at both study sites. In contrast, 95.8% (295 of 308) of the sequences and four of the total seven operational taxonomic units obtained from pronghorn antelope (Antilocapra americana) dung belonged to the Pleosporalean order. We hypothesize that some herbivore vectors disperse non-systemic (non-clavicipitaceous) fungal endophytes. These dispersal events, it is argued, are most likely to occur via herbivores that occasionally forage and masticate root tissue, especially in arid regions where aboveground vegetation is sparse. The results of this study suggest that some (possibly many) members of the RAF community can expand their ecological role to include colonizing dung. PMID:20842497

  2. Temperature Interactions with Growth Regulators and Endogenous Gibberellin-like Activity during Seedstalk Elongation in Carrots 1

    PubMed Central

    Hiller, Larry K.; Kelly, William C.; Powell, Loyd E.

    1979-01-01

    Stecklings (roots) of three cultivars of carrots (Daucus carota L.) were vernalized 10 weeks at 5 C and subsequently grown at each of three greenhouse night/day temperature regimes: high (27/32 C), medium (21/27 C), and low (15/21 C). Floral differentiation occurred first in the easy bolting cv. Scarlet Nantes, intermediate in cv. Danvers 126, and last in cv. Royal Chantenay. Stem elongation arising from the subapical meristematic region always preceded floral differentiation. Extractable gibberellin-like activity in carrot stem apices increased from harvest during the 10-week vernalization period, then remained constant even though floral differentiation and stem elongation occurred during an additional 20-week cold storage period. Low temperature had both an inductive and a direct effect on reproductive development depending on length of low temperature exposure. After 10 weeks vernalization at 5 C, high greenhouse temperature severely reduced ultimate seedstalk height and the endogenous gibberellinlike activity decreased rapidly during the first 3 weeks in the greenhouse. At the low greenhouse temperature, activity remained fairly constant during the 10-week sampling period. Changes in endogenous gibberellinlike activity were related with stem elongation, but not with floral initiation. Exogenous gibberellic acid (GA3) applied following vernalization prevented the inhibitory effect of high greenhouse temperature on seedstalk elongation and resulted in seedstalk heights comparable to untreated controls grown at the low greenhouse temperature. Exogenous applications of succinic acid-2,2-dimethylhydrazide and chlormequat reduced seedstalk height of carrot plants grown at the medium and low greenhouse temperatures to that of untreated controls grown at high temperature. Exogenous growth regulators and greenhouse temperature affected seedstalk elongation, but did not affect the number of plants that flowered. Images PMID:16660856

  3. Identification of the primary lesion of toxic aluminum in plant roots.

    PubMed

    Kopittke, Peter M; Moore, Katie L; Lombi, Enzo; Gianoncelli, Alessandra; Ferguson, Brett J; Blamey, F Pax C; Menzies, Neal W; Nicholson, Timothy M; McKenna, Brigid A; Wang, Peng; Gresshoff, Peter M; Kourousias, George; Webb, Richard I; Green, Kathryn; Tollenaere, Alina

    2015-04-01

    Despite the rhizotoxicity of aluminum (Al) being identified over 100 years ago, there is still no consensus regarding the mechanisms whereby root elongation rate is initially reduced in the approximately 40% of arable soils worldwide that are acidic. We used high-resolution kinematic analyses, molecular biology, rheology, and advanced imaging techniques to examine soybean (Glycine max) roots exposed to Al. Using this multidisciplinary approach, we have conclusively shown that the primary lesion of Al is apoplastic. In particular, it was found that 75 µm Al reduced root growth after only 5 min (or 30 min at 30 µm Al), with Al being toxic by binding to the walls of outer cells, which directly inhibited their loosening in the elongation zone. An alteration in the biosynthesis and distribution of ethylene and auxin was a second, slower effect, causing both a transient decrease in the rate of cell elongation after 1.5 h but also a longer term gradual reduction in the length of the elongation zone. These findings show the importance of focusing on traits related to cell wall composition as well as mechanisms involved in wall loosening to overcome the deleterious effects of soluble Al. PMID:25670815

  4. Identification of the Primary Lesion of Toxic Aluminum in Plant Roots1[OPEN

    PubMed Central

    Kopittke, Peter M.; Moore, Katie L.; Lombi, Enzo; Gianoncelli, Alessandra; Ferguson, Brett J.; Blamey, F. Pax C.; Menzies, Neal W.; Nicholson, Timothy M.; McKenna, Brigid A.; Wang, Peng; Gresshoff, Peter M.; Kourousias, George; Webb, Richard I.; Green, Kathryn; Tollenaere, Alina

    2015-01-01

    Despite the rhizotoxicity of aluminum (Al) being identified over 100 years ago, there is still no consensus regarding the mechanisms whereby root elongation rate is initially reduced in the approximately 40% of arable soils worldwide that are acidic. We used high-resolution kinematic analyses, molecular biology, rheology, and advanced imaging techniques to examine soybean (Glycine max) roots exposed to Al. Using this multidisciplinary approach, we have conclusively shown that the primary lesion of Al is apoplastic. In particular, it was found that 75 µm Al reduced root growth after only 5 min (or 30 min at 30 µm Al), with Al being toxic by binding to the walls of outer cells, which directly inhibited their loosening in the elongation zone. An alteration in the biosynthesis and distribution of ethylene and auxin was a second, slower effect, causing both a transient decrease in the rate of cell elongation after 1.5 h but also a longer term gradual reduction in the length of the elongation zone. These findings show the importance of focusing on traits related to cell wall composition as well as mechanisms involved in wall loosening to overcome the deleterious effects of soluble Al. PMID:25670815

  5. 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.

  6. Modulation of ethylene biosynthesis by ACC and AIB reveals a structural and functional relationship between the K15NO3 uptake rate and root absorbing surfaces.

    PubMed

    Lemaire, Lucile; Deleu, Carole; Le Deunff, Erwan

    2013-07-01

    The modification of root traits in relation to nitrate uptake represents a source for improvement of nitrogen uptake efficiency. Because ethylene signalling modulates growth of exploratory and root hair systems more rapidly (minutes to hours) than nitrate signalling (days to weeks), a pharmacological approach was used to decipher the relationships between root elongation and N uptake. Rape seedlings were grown on agar plates supplied with 1mM K(15)NO3 and treated with different concentrations of either the ethylene precursor, ACC (0.1, 1, and 10 ?M) or an inhibitor of ethylene biosynthesis, AIB (0.5 and 1 ?M). The results showed that rapid modulation of root elongation (up to 8-fold) is more dependent on the ethylene than the nitrate signal. Indeed, ACC treatment induced a partial compensatory increase in (15)N uptake associated with overexpression of the BnNRT2.1 and BnNRT1.1 genes. Likewise, daily root elongation between treatments was not associated with daily nitrate uptake but was correlated with N status. This suggested that a part of the daily root response was modulated by cross talks between ethylene signalling and N and C metabolisms. This was confirmed by the reduction in C allocation to the roots induced by ACC treatment and the correlations of changes in the root length and shoot surface area with the aspartate content. The observed effects of ethylene signalling in the root elongation and NRT gene expression are discussed in the context of the putative role of NRT2.1 and NRT1.1 transporters as nitrate sensors. PMID:23811694

  7. The effect of ethylene on root growth of Zea mays seedlings

    NASA Technical Reports Server (NTRS)

    Whalen, M. C.; Feldman, L. J.

    1988-01-01

    The control of primary root growth in Zea mays cv. Merit by ethylene was examined. At applied concentrations of ethylene equal to or greater than 0.1 microliter L-1, root elongation during 24 h was inhibited. The half-maximal response occurred at 0.6 microliter L-1 and the response saturated at 6 microliters L-1. Inhibition of elongation took place within 20 min. However, after ethylene was removed, elongation recovered to control values within 15 min. Root elongation was also inhibited by green light. The inhibition caused by a 24-h exposure to ethylene was restricted to the elongating region just behind the apex, with inhibition of cortical cell elongation being the primary contributor to the effect. Based on use of 2,5-norbornadiene, a gaseous competitive inhibitor of ethylene, it was concluded that endogenous ethylene normally inhibits root elongation.

  8. The effect of ethylene on root growth of Zea mays seedlings.

    PubMed

    Whalen, M C; Feldman, L J

    1988-04-01

    The control of primary root growth in Zea mays cv. Merit by ethylene was examined. At applied concentrations of ethylene equal to or greater than 0.1 microliter L-1, root elongation during 24 h was inhibited. The half-maximal response occurred at 0.6 microliter L-1 and the response saturated at 6 microliters L-1. Inhibition of elongation took place within 20 min. However, after ethylene was removed, elongation recovered to control values within 15 min. Root elongation was also inhibited by green light. The inhibition caused by a 24-h exposure to ethylene was restricted to the elongating region just behind the apex, with inhibition of cortical cell elongation being the primary contributor to the effect. Based on use of 2,5-norbornadiene, a gaseous competitive inhibitor of ethylene, it was concluded that endogenous ethylene normally inhibits root elongation. PMID:11537849

  9. 4sUDRB-seq: measuring genomewide transcriptional elongation rates and initiation frequencies within cells

    PubMed Central

    2014-01-01

    Although transcriptional elongation by RNA polymerase II is coupled with many RNA-related processes, genomewide elongation rates remain unknown. We describe a method, called 4sUDRB-seq, based on reversible inhibition of transcription elongation coupled with tagging newly transcribed RNA with 4-thiouridine and high throughput sequencing to measure simultaneously with high confidence genome-wide transcription elongation rates in cells. We find that most genes are transcribed at about 3.5 Kb/min, with elongation rates varying between 2 Kb/min and 6 Kb/min. 4sUDRB-seq can facilitate genomewide exploration of the involvement of specific elongation factors in transcription and the contribution of deregulated transcription elongation to various pathologies. PMID:24887486

  10. Root Apex Transition Zone As Oscillatory Zone

    PubMed Central

    Baluška, František; Mancuso, Stefano

    2013-01-01

    Root apex of higher plants shows very high sensitivity to environmental stimuli. The root cap acts as the most prominent plant sensory organ; sensing diverse physical parameters such as gravity, light, humidity, oxygen, and critical inorganic nutrients. However, the motoric responses to these stimuli are accomplished in the elongation region. This spatial discrepancy was solved when we have discovered and characterized the transition zone which is interpolated between the apical meristem and the subapical elongation zone. Cells of this zone are very active in the cytoskeletal rearrangements, endocytosis and endocytic vesicle recycling, as well as in electric activities. Here we discuss the oscillatory nature of the transition zone which, together with several other features of this zone, suggest that it acts as some kind of command center. In accordance with the early proposal of Charles and Francis Darwin, cells of this root zone receive sensory information from the root cap and instruct the motoric responses of cells in the elongation zone. PMID:24106493

  11. Factors controlling decomposition in arctic tundra and related root mycorrhizal processes

    SciTech Connect

    Linkins, A.E.

    1990-01-01

    Work proposed for the final year of Phase 1 of the R D Program will focus on three areas: (1) acquire soil and root-mycorrhizal process data which will incorporate baseline enzymatic and soil respiration data, as has been collected during the duration of the project, into the manipulations in the project initiated by Drs. Chapin and Schimmel. Additional enzymatic data on a broader range of organic nitrogen compound decomposition will be collected to better integrate existing decomposition data and modeling structure with the expanded information to be collected on nitrogen dynamics in soils and plant compartments. This activity will principally be done in the new dust disturbance experiment the overall project has planned. (2) Finalize data sets on the complete mineralization of cellulose, and cellulose like plant structural material, and cellulose intermediate hydrolysis products into CO2 and CH4 from soils from water track and non-water track soils and soils from riparian sedge moss meadow vegetation areas. Gas efflux from these soils will be measured in closed microcosms in which the soils will be manipulated to alter their redox state. (3) Continue developing and testing the GAS models on decomposition and plant growth and nutrient acquisition. The primary activity of this project will be on this latter task. 22 refs.

  12. CORN-RESIDUE TRANSFORMATIONS INTO ROOT AND SOIL CARBON AS RELATED TO NITROGEN, TILLAGE, AND STOVER MANAGEMENT

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Soil organic carbon (SOC) is sensitive to management schemes of tillage, residue (stover) harvest, and N fertilization. Most of these estimates use long term field trials but a major problem is to estimate SOC responses to the unharvestable root, root exudates, and crown. Most often a shoot-to-root-...

  13. Lead, zinc and iron (Fe 2+) tolerances in wetland plants and relation to root anatomy and spatial pattern of ROL

    Microsoft Academic Search

    H. Deng; Z. H. Ye; M. H. Wong

    2009-01-01

    Metal (Pb, Zn and Fe2+) tolerances, root anatomy and profile of radial oxygen loss (ROL) along the root (i.e., spatial pattern of ROL) were studied in 10 emergent wetland plants. The species studied could be classified into three groups. Group I included Alternanthera philoxeroides, Beckmannia syzigachne, Oenanthe javanica and Polypogon fugax, with high ROL along the whole length of root

  14. Ionic and pH signalling from roots to shoots of flooded tomato plants in relation to stomatal closure

    Microsoft Academic Search

    Michael B. Jackson; Leslie R. Saker; Carol M. Crisp; Mark A. Else; Franciszek Janowiak

    2003-01-01

    Soil flooding damages shoot systems by inhibiting root functioning. An example is the inhibition of water uptake brought about by decreased root hydraulic conductance. The extent of any resulting foliar dehydration this causes is limited by partial stomatal closure that begins within 4 h and is maintained for several days. Root to shoot signals that promote closure in flooded tomato

  15. SSD1, which encodes a plant-specific novel protein, controls plant elongation by regulating cell division in rice

    PubMed Central

    Asano, Kenji; Miyao, Akio; Hirochika, Hirohiko; Kitano, Hidemi; Matsuoka, Makoto; Ashikari, Motoyuki

    2010-01-01

    Plant height is one of the most important traits in crop improvement. Therefore revealing the mechanism of plant elongation and controlling plant height in accordance with breeding object is important. In this study we analyzed a novel dwarf mutant, ssd1, of which phenotype is different from typical GA- or BR-related dwarf phenotype. ssd1 exhibits pleiotropic defects in elongation of various organs such as stems, roots, leaves, and flowers. ssd1 also shows abnormal cell files and shapes, which suggests defects of normal cell division in the mutant. Map-based cloning and complementation test demonstrated that the dwarf phenotype in ssd1 mutant was caused by insertion of retrotransposon in a gene, which encodes plant-specific protein with unknown biochemical function. A BLAST search revealed that SSD1-like genes exist in diverse plant species, including monocots and dicots, but not fern and moss. Our results demonstrate that SSD1 controls plant elongation by controlling cell division in higher plants. PMID:20228626

  16. Temperature sensing by primary roots of maize

    NASA Technical Reports Server (NTRS)

    Poff, K. L.

    1990-01-01

    Zea mays L. seedlings, grown on agar plates at 26 degrees C, reoriented the original vertical direction of their primary root when exposed to a thermal gradient applied perpendicular to the gravity vector. The magnitude and direction of curvature can not be explained simply by either a temperature or a humidity effect on root elongation. It is concluded that primary roots of maize sense temperature gradients in addition to sensing the gravitational force.

  17. Original article Effects of sodium chloride salinity on root growth

    E-print Network

    Paris-Sud XI, Université de

    Original article Effects of sodium chloride salinity on root growth and respiration in oak either 50 or 250 mM NaCl. Both moderate and high salinity treatment strongly altered root elongation. In contrast, specific respiration of roots was unaffected by the moderate salinity treatment while

  18. Oxidative stress triggered by aluminum in plant roots

    Microsoft Academic Search

    Yoko Yamamoto; Yukiko Kobayashi; Saddikuti Rama Devi; Sanae Rikiishi; Hideaki Matsumoto

    2003-01-01

    Aluminum (Al) is a major growth-limiting factor for plants in acid soils. The primary site of Al accumulation and toxicity is the root meristem, and the inhibition of root elongation is the most sensitive response to Al. Al cannot catalyze redox reactions but triggers lipid peroxidation and reactive oxygen species (ROS) production in roots. Furthermore, Al causes respiration inhibition and

  19. More on the elongational viscosity of an oriented fiber assembly

    NASA Technical Reports Server (NTRS)

    Pipes, R. Byron, Jr.; Beaussart, A. J.; Okine, R. K.

    1990-01-01

    The effective elongational viscosity for an oriented fiber assembly of discontinuous fibers suspended in a viscous matrix fluid is developed for a fiber array with variable overlap length of both symmetric and asymmetric geometries. Further, the relation is developed for a power-law matrix fluid with finite yield stress. The developed relations for a Newtonian fluid reveal that the influence of overlap length upon elongational viscosity may be expressed as a polynomial of second order. The results for symmetric and asymmetric geometries are shown to be equivalent. Finally, for the power-law fluid the influence of fiber aspect ratio on elongational viscosity was shown to be of order m + 1, where m is greater than 0 and less than 1, as compared to 2 for the Newtonian fluid, while the effective yield stress was found to be proportional to the fiber aspect ratio and volume fraction.

  20. Relative susceptibility of two sweetpotato varieties to storage root damage by sweetpotato flea beetle (Coleoptera: Chrysomelidae) and wireworm (Coleoptera: Elateridae).

    PubMed

    Abney, Mark R; Kennedy, George G

    2011-02-01

    The feeding of soil dwelling insects on storage roots is one of the most serious management issues faced by sweetpotato, Ipomoea batatas (L.) Lam. (Convolvulaceae), growers in the southern United States. Field studies were conducted to evaluate the relative susceptibility of two commonly grown sweetpotato varieties to sweetpotato flea beetle, Chaetocnema confinis Crotch (Coleoptera: Chrysomelidae), and wireworms (Coleoptera: Elateridae, various species). The incidence and severity of sweetpotato flea beetle damage was significantly lower in the variety Covington than Beauregard in two small plot replicated studies. Surveys conducted in commercial sweetpotato fields also showed significantly less sweetpotato flea beetle damage in fields planted to Covington compared with those planted to Beauregard. There was no clear evidence of varietal effect on the incidence of wireworm damage in the study. Results indicate that the severity of wireworm damage as measured by the size of feeding scars may be less in Covington than Beauregard. PMID:21404851

  1. The delayed initiation and slow elongation of fuzz-like short fibre cells in relation to altered patterns of sucrose synthase expression and plasmodesmata gating in a lintless mutant of cotton

    Microsoft Academic Search

    Yong-Ling Ruan; Danny J. Llewellyn; Robert T. Furbank; Prem S. Chourey

    2005-01-01

    Cotton (Gossypium hirsutum L.) seed develops single- celled long fibres (lint) from the seed-coat epidermis at anthesis. Previous studies have shown that the initi- ation and rapid elongation of these fibres requires the expression of sucrose synthase (Sus) and, potentially, a transient closure of plasmodesmata. This study extends the previous work to examine the patterns of Sus expression and plasmodesmata

  2. A Simple Symmetry Generating Operads Related to Rooted Planar m-ary Trees and Polygonal Numbers

    Microsoft Academic Search

    Philippe Leroux

    2007-01-01

    The aim of this paper is to further explore an idea from J.-L. Loday and extend some of his results. We impose a natural and simple symmetry on a unit action over the most general quadratic relation which can be written. This leads us to two families of binary, quadratic and regular operads whose free objects are computed, as much

  3. A simple symmetry generating operads related to rooted planar $m$-ary trees and polygonal numbers

    Microsoft Academic Search

    Leroux Philippe

    2005-01-01

    The aim of this paper is to further explore an idea from J.-L. Loday briefly exposed in [5]. We impose a natural and simple symmetry on a unit action over the most general quadratic relation which can be written. This leads us to two families of binary, quadratic and regular operads whose free objects, as well as their duals in

  4. Fertilizer-induced changes in rhizosphere electrical conductivity: relation to forest tree seedling root

    E-print Network

    -1 Fertilizer-induced changes in rhizosphere electrical conductivity: relation to forest tree-765-494-3608/9461) Received 1 July 2004; accepted in revised form 19 April 2005 Key words: Controlled-release fertilizer, Ion toxicity, Mineral nutrition, Reforestation, Salinity, Soil osmotic potential Abstract. Fertilization

  5. Capturing Arabidopsis Root Architecture Dynamics with root-fit Reveals Diversity in Responses to Salinity1[W][OPEN

    PubMed Central

    Julkowska, Magdalena M.; Hoefsloot, Huub C.J.; Mol, Selena; Feron, Richard; de Boer, Gert-Jan; Haring, Michel A.; Testerink, Christa

    2014-01-01

    The plant root is the first organ to encounter salinity stress, but the effect of salinity on root system architecture (RSA) remains elusive. Both the reduction in main root (MR) elongation and the redistribution of the root mass between MRs and lateral roots (LRs) are likely to play crucial roles in water extraction efficiency and ion exclusion. To establish which RSA parameters are responsive to salt stress, we performed a detailed time course experiment in which Arabidopsis (Arabidopsis thaliana) seedlings were grown on agar plates under different salt stress conditions. We captured RSA dynamics with quadratic growth functions (root-fit) and summarized the salt-induced differences in RSA dynamics in three growth parameters: MR elongation, average LR elongation, and increase in number of LRs. In the ecotype Columbia-0 accession of Arabidopsis, salt stress affected MR elongation more severely than LR elongation and an increase in LRs, leading to a significantly altered RSA. By quantifying RSA dynamics of 31 different Arabidopsis accessions in control and mild salt stress conditions, different strategies for regulation of MR and LR meristems and root branching were revealed. Different RSA strategies partially correlated with natural variation in abscisic acid sensitivity and different Na+/K+ ratios in shoots of seedlings grown under mild salt stress. Applying root-fit to describe the dynamics of RSA allowed us to uncover the natural diversity in root morphology and cluster it into four response types that otherwise would have been overlooked. PMID:25271266

  6. Elongation cutoff technique: low-order scaling SCF method.

    PubMed

    Korchowiec, Jacek; Lewandowski, Jakub

    2008-08-01

    The elongation cutoff technique at restricted Hartree-Fock (HF) level of theory in conventional type of calculations, i.e., with two electron integrals (TEI) stored on a disc, is presented for two model systems. It is demonstrated that the number of TEI in the elongation cutoff calculations increases linearly with the system size thus, allowing to extend the conventional type of calculations to bigger systems. The step CPU (central processing unit) time in the elongation cutoff calculations is much lower than in the HF reference calculations. Such behavior reduces significantly the prefactor in the quadratic scaling relation. The total CPU time in the elongation calculation is about 40% lower than in the conventional HF calculations or comparable to direct type of calculations with the quantum fast multipoles method employed. It is shown that by introducing the interaction radius one can obtain linear scaling in the SCF calculations. Figure: The structure of density matrix and total CPU timings for polyglycine clusters in the elongation cutoff calculations. PMID:18386083

  7. Continued fraction TBA and functional relations in XXZ model at root of unity

    Microsoft Academic Search

    Atsuo Kuniba; Kazumitsu Sakai; Junji Suzuki

    1998-01-01

    Thermodynamics of the spin 12 XXZ model is studied in the critical regime using the quantum transfer matrix (QTM) approach. We find functional relations indexed by the Takahashi-Suzuki numbers among the fusion hierarchy of the QTM's (T-system) and their certain combinations (Y-system). By investigating analyticity of the latter, we derive a closed set of nonlinear integral equations which characterize the

  8. Inhibitors of Fatty Acid Synthesis and Elongation

    NSDL National Science Digital Library

    Fatty acid synthesis and fatty acid elongation are two parts of a critically important pathway in plants. The endproducts are essential components of cell membranes, waxes, and suberin. Two chemical families of herbicide (groups that share similar chemical structures) inhibit fatty acid synthesis, while fatty acid elongation is inhibited by two other families. This lesson will provide an overview of fatty acid synthesis and elongation, and explain where herbicides inhibit the pathway. Mechanisms of resistance to these herbicides will be described.

  9. Multilayered Organization of Jasmonate Signalling in the Regulation of Root Growth

    PubMed Central

    Gasperini, Debora; Chételat, Aurore; Acosta, Ivan F.; Goossens, Jonas; Pauwels, Laurens; Goossens, Alain; Dreos, René; Alfonso, Esteban; Farmer, Edward E.

    2015-01-01

    Physical damage can strongly affect plant growth, reducing the biomass of developing organs situated at a distance from wounds. These effects, previously studied in leaves, require the activation of jasmonate (JA) signalling. Using a novel assay involving repetitive cotyledon wounding in Arabidopsis seedlings, we uncovered a function of JA in suppressing cell division and elongation in roots. Regulatory JA signalling components were then manipulated to delineate their relative impacts on root growth. The new transcription factor mutant myc2-322B was isolated. In vitro transcription assays and whole-plant approaches revealed that myc2-322B is a dosage-dependent gain-of-function mutant that can amplify JA growth responses. Moreover, myc2-322B displayed extreme hypersensitivity to JA that totally suppressed root elongation. The mutation weakly reduced root growth in undamaged plants but, when the upstream negative regulator NINJA was genetically removed, myc2-322B powerfully repressed root growth through its effects on cell division and cell elongation. Furthermore, in a JA-deficient mutant background, ninja1 myc2-322B still repressed root elongation, indicating that it is possible to generate JA-responses in the absence of JA. We show that NINJA forms a broadly expressed regulatory layer that is required to inhibit JA signalling in the apex of roots grown under basal conditions. By contrast, MYC2, MYC3 and MYC4 displayed cell layer-specific localisations and MYC3 and MYC4 were expressed in mutually exclusive regions. In nature, growing roots are likely subjected to constant mechanical stress during soil penetration that could lead to JA production and subsequent detrimental effects on growth. Our data reveal how distinct negative regulatory layers, including both NINJA-dependent and -independent mechanisms, restrain JA responses to allow normal root growth. Mechanistic insights from this work underline the importance of mapping JA signalling components to specific cell types in order to understand and potentially engineer the growth reduction that follows physical damage. PMID:26070206

  10. Multilayered Organization of Jasmonate Signalling in the Regulation of Root Growth.

    PubMed

    Gasperini, Debora; Chételat, Aurore; Acosta, Ivan F; Goossens, Jonas; Pauwels, Laurens; Goossens, Alain; Dreos, René; Alfonso, Esteban; Farmer, Edward E

    2015-06-01

    Physical damage can strongly affect plant growth, reducing the biomass of developing organs situated at a distance from wounds. These effects, previously studied in leaves, require the activation of jasmonate (JA) signalling. Using a novel assay involving repetitive cotyledon wounding in Arabidopsis seedlings, we uncovered a function of JA in suppressing cell division and elongation in roots. Regulatory JA signalling components were then manipulated to delineate their relative impacts on root growth. The new transcription factor mutant myc2-322B was isolated. In vitro transcription assays and whole-plant approaches revealed that myc2-322B is a dosage-dependent gain-of-function mutant that can amplify JA growth responses. Moreover, myc2-322B displayed extreme hypersensitivity to JA that totally suppressed root elongation. The mutation weakly reduced root growth in undamaged plants but, when the upstream negative regulator NINJA was genetically removed, myc2-322B powerfully repressed root growth through its effects on cell division and cell elongation. Furthermore, in a JA-deficient mutant background, ninja1 myc2-322B still repressed root elongation, indicating that it is possible to generate JA-responses in the absence of JA. We show that NINJA forms a broadly expressed regulatory layer that is required to inhibit JA signalling in the apex of roots grown under basal conditions. By contrast, MYC2, MYC3 and MYC4 displayed cell layer-specific localisations and MYC3 and MYC4 were expressed in mutually exclusive regions. In nature, growing roots are likely subjected to constant mechanical stress during soil penetration that could lead to JA production and subsequent detrimental effects on growth. Our data reveal how distinct negative regulatory layers, including both NINJA-dependent and -independent mechanisms, restrain JA responses to allow normal root growth. Mechanistic insights from this work underline the importance of mapping JA signalling components to specific cell types in order to understand and potentially engineer the growth reduction that follows physical damage. PMID:26070206

  11. 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.

  12. Root canal

    MedlinePLUS

    A root canal is a dental procedure to remove dead or dying nerve tissue and bacteria from inside a tooth. ... A root canal is done if you have an infection that affects the nerve in the root of a tooth. ...

  13. Root systems

    NSDL National Science Digital Library

    N/A N/A (U.S. Government; )

    2004-10-30

    One purpose that roots serve is that of anchoring the plant in the ground. Roots also take up water and nutrients for the plant. Plants all have different root system types to fit their individual needs and locations.

  14. Elongator and its epigenetic role in plant development and responses to abiotic and biotic stresses

    PubMed Central

    Ding, Yezhang; Mou, Zhonglin

    2015-01-01

    Elongator, a six-subunit protein complex, was initially isolated as an interactor of hyperphosphorylated RNA polymerase II in yeast, and was subsequently identified in animals and plants. Elongator has been implicated in multiple cellular activities or biological processes including tRNA modification, histone modification, DNA demethylation or methylation, tubulin acetylation, and exocytosis. Studies in the model plant Arabidopsis thaliana suggest that the structure of Elongator and its functions are highly conserved between plants and yeast. Disruption of the Elongator complex in plants leads to aberrant growth and development, resistance to abiotic stresses, and susceptibility to plant pathogens. The morphological and physiological phenotypes of Arabidopsis Elongator mutants are associated with decreased histone acetylation and/or altered DNA methylation. This review summarizes recent findings related to the epigenetic function of Elongator in plant development and responses to abiotic and biotic stresses. PMID:25972888

  15. The Compact Root Architecture1 Gene Regulates Lignification, Flavonoid Production, and Polar Auxin Transport in Medicago truncatula1[W

    PubMed Central

    Laffont, Carole; Blanchet, Sandrine; Lapierre, Catherine; Brocard, Lysiane; Ratet, Pascal; Crespi, Martin; Mathesius, Ulrike; Frugier, Florian

    2010-01-01

    The root system architecture is crucial to adapt plant growth to changing soil environmental conditions and consequently to maintain crop yield. In addition to root branching through lateral roots, legumes can develop another organ, the nitrogen-fixing nodule, upon a symbiotic bacterial interaction. A mutant, cra1, showing compact root architecture was identified in the model legume Medicago truncatula. cra1 roots were short and thick due to defects in cell elongation, whereas densities of lateral roots and symbiotic nodules were similar to the wild type. Grafting experiments showed that a lengthened life cycle in cra1 was due to the smaller root system and not to the pleiotropic shoot phenotypes observed in the mutant. Analysis of the cra1 transcriptome at a similar early developmental stage revealed few significant changes, mainly related to cell wall metabolism. The most down-regulated gene in the cra1 mutant encodes a Caffeic Acid O-Methyl Transferase, an enzyme involved in lignin biosynthesis; accordingly, whole lignin content was decreased in cra1 roots. This correlated with differential accumulation of specific flavonoids and decreased polar auxin transport in cra1 mutants. Exogenous application of the isoflavone formononetin to wild-type plants mimicked the cra1 root phenotype, whereas decreasing flavonoid content through silencing chalcone synthases restored the polar auxin transport capacity of the cra1 mutant. The CRA1 gene, therefore, may control legume root growth through the regulation of lignin and flavonoid profiles, leading to changes in polar auxin transport. PMID:20522723

  16. Rooting characteristics of slash pine (Pinus elliottii Engelm.) in relation to soil fragipans in the flatwoods section of southeast Texas

    E-print Network

    Batte, Charles David

    1975-01-01

    on plant growth. Most of the research included observations of few or no roots within the pan except in the cleavage planes. The roots of mature scarlet oak (guercus Coccinea Muenchh. ) were found to be restricted to the cleavage planes of the fragipan...

  17. River Elongation as a Proxy for Lateral Channel Activity

    NASA Astrophysics Data System (ADS)

    Lauer, J. W.

    2009-12-01

    Lateral channel movement is a process that is tightly linked to both channel hydraulics and sediment transport, strongly influences floodplain ecology, and also has great relevance for banktop property owners. The correlation between channel migration rate and channel curvature usually causes meandering river channels to elongate as they migrate laterally. Over the long term, the increase in sinuosity is compensated by a rapid decrease in sinuosity where and when river bends shorten through cutoff processes. However, the elongation for most meander bends in systems free to migrate across wide floodplains often occurs relatively uniformly throughout the system. Consequently, the rate of elongation of individual river bends, integrated across a river reach, offers a simple mechanism for characterizing the reach’s lateral activity. Spatial series of accumulated elongation can also be used to delineate reaches with similar properties. We use aerial imagery pairs to compare rates of lateral channel centerline shifting with channel centerline elongation for reaches many bends long along eight different rivers with widths ranging from 12 to 584 m. Except where bends translate downstream without changing form, elongation rates are closely linked to lateral shifting. In several cases, a change in elongation rate corresponds closely with a change in channel width, discharge, and/or bed material. For reaches free to migrate across a wide, unconfined floodplain and where lateral migration measurements are likely of high quality, the average ratio between the reach average migration rate normalized by channel width and the rate of sinuosity increase (excluding bends that experienced a cutoff between imagery dates) is approximately 5.6. Since elongation rate measurements can be made accurately even from photos that are poorly aligned, the relationship between sinuosity increase and lateral migration potentially provides a means of bypassing time-consuming georeferencing, allowing immediate use of any set of adequately scaled historical photography for estimating lateral channel activity. It may also allow measurements of lateral activity over very short time periods of several years, rather than the typical decadal timescale, or from relatively low resolution imagery.

  18. On the Arnold cat map and periodic boundary conditions for planar elongational flow

    E-print Network

    On the Arnold cat map and periodic boundary conditions for planar elongational flow THOMAS A. HUNT) In this paper we show that the periodic boundary conditions used to simulate planar elongational flow are closely related to the Arnold cat map. In particular the relationship between the Arnold cat map

  19. Light-activation of teleost rod photoreceptor elongation.

    PubMed

    Liepe, B A; Burnside, B

    1993-07-01

    Rod photoreceptors in the retinas of teleost fish undergo changes in cell length in response to changing ambient light intensities. In the dark rods shorten and in the light rods elongate. These movements are mediated by actin-dependent processes which occur in the ellipsoid and myoid of the inner segment. As an approach to examining the underlying intracellular signaling pathways that link light absorption to actin-dependent motility in the inner segment, we have investigated the quantitative aspects of the light stimulus required to activate elongation in isolated rod inner/outer segments (RIS-ROS) of the green sunfish (Lepomis cyanellus). The intensity thresholds and strength-duration characteristics of the light stimulus required to activate teleost rod elongation were found to differ from those reported to activate vertebrate rod membrane hyperpolarization. In response to brief pulses of light, RIS-ROS elongated in a graded manner, both as a function of increasing light pulse intensity and light pulse duration. Half maximal activation of light-induced RIS-ROS elongation was produced by a stimulus of roughly 6 x 10(15) photons cm-2, which is calculated to bleach approximately 20% of the photopigment molecules in green sunfish rod outer segments. This degree of photopigment bleach is approximately 6-7 orders of magnitude greater than that required to elicit half maximal changes in membrane potential in other vertebrate rod preparations. Furthermore, the reciprocal relationship between light pulse intensity and duration in eliciting an equal elongation response held for relatively long light pulse durations.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:8405167

  20. Elongation and cell division in Bdellovibrio bacteriovorus

    Microsoft Academic Search

    Marta Eksztejn; Mazal Varon

    1977-01-01

    Elongation and division of Bdellovibrio bacteriovorus were studied in axenic synchronous cultures. The cells elongate unidirectionally from one end attaining a length of several “unit cells”, and then divide into the corresponding number of cells. The length of the filament and, consequently, the progeny number, vary within the range of two to several dozen cells, according to the conditions used.

  1. Characteristics of a root hair-less line of Arabidopsis thaliana under physiological stresses

    PubMed Central

    Maeshima, Masayoshi

    2014-01-01

    The plasma membrane-associated Ca2+-binding protein-2 of Arabidopsis thaliana is involved in the growth of root hair tips. Several transgenic lines that overexpress the 23 residue N-terminal domain of this protein under the control of the root hair-specific EXPANSIN A7 promoter lack root hairs completely. The role of root hairs under normal and stress conditions was examined in one of these root hair-less lines (NR23). Compared with the wild type, NR23 showed a 47% reduction in water absorption, decreased drought tolerance, and a lower ability to adapt to heat. Growth of NR23 was suppressed in media deficient in phosphorus, iron, calcium, zinc, copper, or potassium. Also, the content of an individual mineral in NR23 grown in normal medium, or in medium lacking a specific mineral, was relatively low. In wild-type plants, the primary and lateral roots produce numerous root hairs that become elongated under phosphate-deficient conditions; NR23 did not produce root hairs. Although several isoforms of the plasma membrane phosphate transporters including PHT1;1–PHT1;6 were markedly induced after growth in phosphate-deficient medium, the levels induced in NR23 were less than half those observed in the wild type. In phosphate-deficient medium, the amounts of acid phosphatase, malate, and citrate secreted from NR23 roots were 38, 9, and 16% of the levels secreted from wild-type roots. The present results suggest that root hairs play significant roles in the absorption of water and several minerals, secretion of acid phosphatase(s) and organic acids, and in penetration of the primary roots into gels. PMID:24501179

  2. Production of transgenic Aralia elata regenerated from Agrobacterium rhizogenes -mediated transformed roots

    Microsoft Academic Search

    H. J. Kang; V. R. Anbazhagan; X. L. You; H. K. Moon; J. S. Yi; Y. E. Choi

    2006-01-01

    Transgenic hairy roots were induced from petiole and root segments of in vitro plant Aralia elata, a medicinal woody shrub, after co-cultivation with A. rhizogenes ATCC 15834. The percentage of putative hairy root induction from root segments was higher (26.7%) than petiole explants (10.0%). Hairy roots showed active production of lateral roots with vigorous elongation. Transgenic plants were regenerated from

  3. Genotype-Specific Variation in the Structure of Root Fungal Communities Is Related to Chickpea Plant Productivity

    PubMed Central

    Hamel, Chantal; Gan, Yantai; Tar'an, Bunyamin; Knight, Joan Diane

    2015-01-01

    Increasing evidence supports the existence of variations in the association of plant roots with symbiotic fungi that can improve plant growth and inhibit pathogens. However, it is unclear whether intraspecific variations in the symbiosis exist among plant cultivars and if they can be used to improve crop productivity. In this study, we determined genotype-specific variations in the association of chickpea roots with soil fungal communities and evaluated the effect of root mycota on crop productivity. A 2-year field experiment was conducted in southwestern Saskatchewan, the central zone of the chickpea growing region of the Canadian prairie. The effects of 13 cultivars of chickpea, comprising a wide range of phenotypes and genotypes, were tested on the structure of root-associated fungal communities based on internal transcribed spacer (ITS) and 18S rRNA gene markers using 454 amplicon pyrosequencing. Chickpea cultivar significantly influenced the structure of the root fungal community. The magnitude of the effect varied with the genotypes evaluated, and effects were consistent across years. For example, the roots of CDC Corrine, CDC Cory, and CDC Anna hosted the highest fungal diversity and CDC Alma and CDC Xena the lowest. Fusarium sp. was dominant in chickpea roots but was less abundant in CDC Corrine than the other cultivars. A bioassay showed that certain of these fungal taxa, including Fusarium species, can reduce the productivity of chickpea, whereas Trichoderma harzianum can increase chickpea productivity. The large variation in the profile of chickpea root mycota, which included growth-promoting and -inhibiting species, supports the possibility of improving the productivity of chickpea by improving its root mycota in chickpea genetic improvement programs using traditional breeding techniques. PMID:25616789

  4. Genotype-specific variation in the structure of root fungal communities is related to chickpea plant productivity.

    PubMed

    Bazghaleh, Navid; Hamel, Chantal; Gan, Yantai; Tar'an, Bunyamin; Knight, Joan Diane

    2015-04-01

    Increasing evidence supports the existence of variations in the association of plant roots with symbiotic fungi that can improve plant growth and inhibit pathogens. However, it is unclear whether intraspecific variations in the symbiosis exist among plant cultivars and if they can be used to improve crop productivity. In this study, we determined genotype-specific variations in the association of chickpea roots with soil fungal communities and evaluated the effect of root mycota on crop productivity. A 2-year field experiment was conducted in southwestern Saskatchewan, the central zone of the chickpea growing region of the Canadian prairie. The effects of 13 cultivars of chickpea, comprising a wide range of phenotypes and genotypes, were tested on the structure of root-associated fungal communities based on internal transcribed spacer (ITS) and 18S rRNA gene markers using 454 amplicon pyrosequencing. Chickpea cultivar significantly influenced the structure of the root fungal community. The magnitude of the effect varied with the genotypes evaluated, and effects were consistent across years. For example, the roots of CDC Corrine, CDC Cory, and CDC Anna hosted the highest fungal diversity and CDC Alma and CDC Xena the lowest. Fusarium sp. was dominant in chickpea roots but was less abundant in CDC Corrine than the other cultivars. A bioassay showed that certain of these fungal taxa, including Fusarium species, can reduce the productivity of chickpea, whereas Trichoderma harzianum can increase chickpea productivity. The large variation in the profile of chickpea root mycota, which included growth-promoting and -inhibiting species, supports the possibility of improving the productivity of chickpea by improving its root mycota in chickpea genetic improvement programs using traditional breeding techniques. PMID:25616789

  5. Profilin Plays a Role in Cell Elongation, Cell Shape Maintenance, and Flowering in Arabidopsis1

    PubMed Central

    Ramachandran, Srinivasan; Christensen, Hans E.M.; Ishimaru, Yasuko; Dong, Chun-Hai; Chao-Ming, Wen; Cleary, Ann L.; Chua, Nam-Hai

    2000-01-01

    Profilin (PFN) is an ubiquitous, low-Mr, actin-binding protein involved in the organization of the cytoskeleton of eukaryotes including higher plants. PFNs are encoded by a multigene family in Arabidopsis. We have analyzed in vivo functions of Arabidopsis PFN by generating transgenic plants carrying a 35S-PFN-1 or 35S-antisense PFN-1 transgene. Etiolated seedlings underexpressing PFN (PFN-U) displayed an overall dwarf phenotype with short hypocotyls whose lengths were 20% to 25% that of wild type (WT) at low temperatures. Light-grown PFN-U plants were smaller in stature and flowered early. Compared with equivalent cells in WT, most cells in PFN-U hypocotyls and roots were shorter, but more isodiametric, and microscopic observations of etiolated PFN-U hypocotyls revealed a rough epidermal surface. In contrast, light-grown seedlings overexpressing PFN had longer roots and root hair although etiolated seedlings overexpressing PFN were either the same size or slightly longer than WT seedlings. Transgenic seedlings harboring a PFN-1-GUS transgene directed expression in root and root hair and in a ring of cells at the elongating zone of the root tip. As the seedlings matured PFN-1-GUS was mainly expressed in the vascular bundles of cotyledons and leaves. Our results show that Arabidopsis PFNs play a role in cell elongation, cell shape maintenance, polarized growth of root hair, and unexpectedly, in determination of flowering time. PMID:11115881

  6. TRICOT encodes an AMP1-related carboxypeptidase that regulates root nodule development and shoot apical meristem maintenance in Lotus japonicus.

    PubMed

    Suzaki, Takuya; Kim, Chong Sung; Takeda, Naoya; Szczyglowski, Krzysztof; Kawaguchi, Masayoshi

    2013-01-15

    During the course of evolution, mainly leguminous plants have acquired the ability to form de novo structures called root nodules. Recent studies on the autoregulation and hormonal controls of nodulation have identified key mechanisms and also indicated a possible link to other developmental processes, such as the formation of the shoot apical meristem (SAM). However, our understanding of nodulation is still limited by the low number of nodulation-related genes that have been identified. Here, we show that the induced mutation tricot (tco) can suppress the activity of spontaneous nodule formation 2, a gain-of-function mutation of the cytokinin receptor in Lotus japonicus. Our analyses of tco mutant plants demonstrate that TCO positively regulates rhizobial infection and nodule organogenesis. Defects in auxin regulation are also observed during nodule development in tco mutants. In addition to its role in nodulation, TCO is involved in the maintenance of the SAM. The TCO gene was isolated by a map-based cloning approach and found to encode a putative glutamate carboxypeptidase with greatest similarity to Arabidopsis ALTERED MERISTEM PROGRAM 1, which is involved in cell proliferation in the SAM. Taken together, our analyses have not only identified a novel gene for regulation of nodule organogenesis but also provide significant additional evidence for a common genetic regulatory mechanism in nodulation and SAM formation. These new data will contribute further to our understanding of the evolution and genetic basis of nodulation. PMID:23250209

  7. Impact of copper oxide nanoparticles exposure on Arabidopsis thaliana growth, root system development, root lignificaion, and molecular level changes.

    PubMed

    Nair, Prakash M Gopalakrishnan; Chung, Ill Min

    2014-11-01

    The effect of copper oxide nanoparticles (CuONPs) on physiological and molecular level responses were studied in Arabidopsis thaliana. The seedlings were exposed to different concentrations of CuONPs (0, 0.5, 1, 2, 5, 10, 20, 50, and 100 mg/L) for 21 days in half strength Murashige and Skoog medium. The plant biomass significantly reduced under different concentrations (2, 5, 10, 20, 50, and 100 mg/L) of CuONPs stress. Exposure to 2, 5, 10, 20, 50, and 100 mg/L of CuONPs has resulted in significant reduction of total chlorophyll content. The anthocyanin content significantly increased upon exposure to 10, 20, 50, and 100 mg/L of CuONPs. Increased lipid peroxidation was observed upon exposure to 5, 10, and 20 mg/L of CuONPs and amino acid proline content was significantly high in plants exposed to 10 and 20 mg/L of CuONPs. Significant reduction in root elongation was observed upon exposure to 0.5-100 mg/L of CuONPs for 21 days. Exposure to CuONPs has resulted in retardation of primary root growth, enhanced lateral root formation, and also resulted in loss of root gravitropism. Staining with phloroglucionol detected the deposition of lignin in CuONPs-treated roots. Histochemical staining of leaves and roots of CuONPs-exposed plants with nitroblue tetrazolium and 3'3'-diaminobenzidine showed a concentration-dependant increase in superoxide and hydrogen peroxide formation in leaves and roots of CuONPs-exposed plants. Cytotoxicity was observed in root tips of CuONPs-exposed plants as evidenced by increased propidium iodide staining. Real-time PCR analysis showed significant induction of genes related to oxidative stress responses, sulfur assimilation, glutathione, and proline biosynthesis under CuONPs stress. PMID:24965006

  8. Root architecture impacts on root decomposition rates in switchgrass

    NASA Astrophysics Data System (ADS)

    de Graaff, M.; Schadt, C.; Garten, C. T.; Jastrow, J. D.; Phillips, J.; Wullschleger, S. D.

    2010-12-01

    Roots strongly contribute to soil organic carbon accrual, but the rate of soil carbon input via root litter decomposition is still uncertain. Root systems are built up of roots with a variety of different diameter size classes, ranging from very fine to very coarse roots. Since fine roots have low C:N ratios and coarse roots have high C:N ratios, root systems are heterogeneous in quality, spanning a range of different C:N ratios. Litter decomposition rates are generally well predicted by litter C:N ratios, thus decomposition of roots may be controlled by the relative abundance of fine versus coarse roots. With this study we asked how root architecture (i.e. the relative abundance of fine versus coarse roots) affects the decomposition of roots systems in the biofuels crop switchgrass (Panicum virgatum L.). To understand how root architecture affects root decomposition rates, we collected roots from eight switchgrass cultivars (Alamo, Kanlow, Carthage, Cave-in-Rock, Forestburg, Southlow, Sunburst, Blackwell), grown at FermiLab (IL), by taking 4.8-cm diameter soil cores from on top of the crown and directly next to the crown of individual plants. Roots were carefully excised from the cores by washing and analyzed for root diameter size class distribution using WinRhizo. Subsequently, root systems of each of the plants (4 replicates per cultivar) were separated in 'fine' (0-0.5 mm), 'medium' (0.5-1 mm) and 'coarse' roots (1-2.5 mm), dried, cut into 0.5 cm (medium and coarse roots) and 2 mm pieces (fine roots), and incubated for 90 days. For each of the cultivars we established five root-treatments: 20g of soil was amended with 0.2g of (1) fine roots, (2) medium roots, (3) coarse roots, (4) a 1:1:1 mixture of fine, medium and coarse roots, and (5) a mixture combining fine, medium and coarse roots in realistic proportions. We measured CO2 respiration at days 1, 3, 7, 15, 30, 60 and 90 during the experiment. The 13C signature of the soil was -26‰, and the 13C signature of plants was -12‰, enabling us to differentiate between root-derived C and native SOM-C respiration. We found that the relative abundance of fine, medium and coarse roots were significantly different among cultivars. Root systems of Alamo, Kanlow and Cave-in-Rock were characterized by a large abundance of coarse-, relative to fine roots, whereas Carthage, Forestburg and Blackwell had a large abundance of fine, relative to coarse roots. Fine roots had a 28% lower C:N ratio than medium and coarse roots. These differences led to different root decomposition rates. We conclude that root architecture should be taken into account when predicting root decomposition rates; enhanced understanding of the mechanisms of root decomposition will improve model predictions of C input to soil organic matter.

  9. Correlations between polyamine ratios and growth patterns in seedling roots

    NASA Technical Reports Server (NTRS)

    Shen, H. J.; Galston, A. W.

    1985-01-01

    The levels of putrescine, cadaverine, spermidine and spermine were determined in seedling roots of pea, tomato, millet and corn, as well as in corn coleoptiles and pea internodes. In all roots, putrescine content increased as elongation progressed, and the putrescine/spermine ratio closely paralleled the sigmoid growth curve up until the time of lateral root initiation. Spermidine and spermine were most abundant near the apices and declined progressively with increasing age of the cells. In the zone of differentiation of root hairs in pea roots, putrescine rose progressively with increasing age, while cadaverine declined. In both pea internodes and corn coleoptiles, the putrescine/spermidine ratio rises with increasing age and elongation. Thus, a block in the conversion of the diamine putrescine to the triamine spermidine may be an important step in the change from cell division to cell elongation.

  10. A Cotton Annexin Protein AnxGb6 Regulates Fiber Elongation through Its Interaction with Actin 1

    PubMed Central

    Huang, Yiqun; Wang, Jin; Zhang, Lida; Zuo, Kaijing

    2013-01-01

    Annexins are assumed to be involved in regulating cotton fiber elongation, but direct evidence remains to be presented. Here we cloned six Annexin genes (AnxGb) abundantly expressed in fiber from sea-island cotton (G. barbadense). qRT-PCR results indicated that all six G. barbadense annexin genes were expressed in elongating cotton fibers, while only the expression of AnxGb6 was cotton fiber-specific. Yeast two hybridization and BiFC analysis revealed that AnxGb6 homodimer interacted with a cotton fiber specific actin GbAct1. Ectopic-expressed AnxGb6 in Arabidopsis enhanced its root elongation without increasing the root cell number. Ectopic AnxGb6 expression resulted in more F-actin accumulation in the basal part of the root cell elongation zone. Analysis of AnxGb6 expression in three cotton genotypes with different fiber length confirmed that AnxGb6 expression was correlated to cotton fiber length, especially fiber elongation rate. Our results demonstrated that AnxGb6 was important for fiber elongation by potentially providing a domain for F-actin organization. PMID:23750279

  11. Redox-related peroxidative responses evoked by methyl-jasmonate in axenically cultured aeroponic sunflower (Helianthus annuus L.) seedling roots.

    PubMed

    Garrido, I; Espinosa, F; Córdoba-Pedregosa, M C; González-Reyes, J A; Alvarez-Tinaut, M C

    2003-05-01

    Methyl-jasmonate (MeJA) has been proposed to be involved in the evocation of defense reactions, as the oxidative burst in plants, substituting the elicitors or enhancing their effect. 48 h dark- and sterilely cultured (axenic) aeroponic sunflower seedling roots excised and treated with different concentrations of MeJA showed a strong and quick depression of the H(+) efflux rate, 1.80 microM MeJA totally stopping it for approximately 90 min and then reinitiating it again at a lower rate than controls. These results were wholly similar to those obtained with nonsterilely cultured roots and have been interpreted as mainly based on H(+) consumption for O(2)(*-) dismutation to H(2)O(2). Also K(+) influx was strongly depressed by MeJA, even transitorily reverting to K(+) efflux. These results were consistent with those associated to the oxidative burst in plants. MeJA induced massive H(2)O(2) accumulation in the middle lamella and intercellular spaces of both the root cap cells and the inside tissues of the roots. The native acidic extracellular peroxidase activity of the intact (nonexcised) seedling roots showed a sudden enhancement (by about 52%) after 5 min of MeJA addition, maintained for approximately 15 min and then decaying again to control rates. O(2) uptake by roots gave similar results. These and other results for additions of H(2)O(2) or horseradish peroxidase, diphenylene iodonium, and sodium diethyldithiocarbamate trihydrate to the reaction mixture with roots were all consistent with the hypothesis that MeJA induced an oxidative burst, with the generation of H(2)O(2) being necessary for peroxidase activity. Results with peroxidase activity of the apoplastic fluid were in accordance with those of the whole root. Finally, MeJA enhanced NADH oxidation and inhibited hexacyanoferrate(III) reduction by axenic roots, and diphenylene iodonium cancelled out these effects. Redox activities by CN(-)- preincubated roots were also studied. All these results are consistent with the hypothesis that MeJA enhanced the NAD(P)H oxidase of a redox chain linked to the oxidative burst, so enhancing the generation of O(2)(*-) and H(2)O(2), O(2) uptake, and peroxidase activity by roots. PMID:12768345

  12. Root morphology, hydraulic conductivity and plant water relations of high-yielding rice grown under aerobic conditions

    PubMed Central

    Kato, Yoichiro; Okami, Midori

    2011-01-01

    Background and Aims Increasing physical water scarcity is a major constraint for irrigated rice (Oryza sativa) production. ‘Aerobic rice culture’ aims to maximize yield per unit water input by growing plants in aerobic soil without flooding or puddling. The objective was to determine (a) the effect of water management on root morphology and hydraulic conductance, and (b) their roles in plant–water relationships and stomatal conductance in aerobic culture. Methods Root system development, stomatal conductance (gs) and leaf water potential (?leaf) were monitored in a high-yielding rice cultivar (‘Takanari’) under flooded and aerobic conditions at two soil moisture levels [nearly saturated (> –10 kPa) and mildly dry (> –30 kPa)] over 2 years. In an ancillary pot experiment, whole-plant hydraulic conductivity (soil-leaf hydraulic conductance; Kpa) was measured under flooded and aerobic conditions. Key Results Adventitious root emergence and lateral root proliferation were restricted even under nearly saturated conditions, resulting in a 72–85 % reduction in total root length under aerobic culture conditions. Because of their reduced rooting size, plants grown under aerobic conditions tended to have lower Kpa than plants grown under flooded conditions. ?leaf was always significantly lower in aerobic culture than in flooded culture, while gs was unchanged when the soil moisture was at around field capacity. gs was inevitably reduced when the soil water potential at 20-cm depth reached –20 kPa. Conclusions Unstable performance of rice in water-saving cultivations is often associated with reduction in ?leaf. ?leaf may reduce even if Kpa is not significantly changed, but the lower ?leaf would certainly occur in case Kpa reduces as a result of lower water-uptake capacity under aerobic conditions. Rice performance in aerobic culture might be improved through genetic manipulation that promotes lateral root branching and rhizogenesis as well as deep rooting. PMID:21807692

  13. Pursuing the identification of O2 deprivation survival mechanisms in plants related to selective mRNA translation, hormone-independent cellular elongation and preparation for the arrival of oxygen

    PubMed Central

    Shingaki-Wells, Rachel N; Huang, Shaobai; Taylor, Nicolas L

    2011-01-01

    Anoxia can occur in crop fields when flooding forms a physical barrier that reduces oxygen availability. Rice, but not wheat, can germinate and elongate its coleoptile under anoxia, providing an excellent model for understanding mechanisms of anoxia tolerance. We have shown differential molecular responses of rice and wheat coleoptiles to anoxia and discovered novel metabolic adaptations in amino acid metabolism for tissue tolerance.1 In this addendum, we elaborate on our discussion to speculate on the functions of differentially regulated proteins and their possible roles in selective transcription and translation, alternative elongation strategies and preparedness for exposure to air. In addition, it is thought that rapid growth is a stress avoidance strategy; if adequate coleoptile growth occurs then plants can outgrow floodwaters to resume or begin aerobic respiration. An innate response mechanism to the arrival of air, and the oxidative stress inherent to this, would therefore be necessary in survival beyond the alleviation of anoxia. Thus, we emphasize the importance of recognizing anoxia as a multi-stage stress where responses otherwise considered counter-intuitive may have evolved as preparative defenses for when exposure to air occurs. PMID:21921695

  14. The role of defoliation and root rot pathogen infection in driving the mode of drought-related physiological decline in Scots pine (Pinus sylvestris L.).

    PubMed

    Aguadé, D; Poyatos, R; Gómez, M; Oliva, J; Martínez-Vilalta, J

    2015-03-01

    Drought-related tree die-off episodes have been observed in all vegetated continents. Despite much research effort, however, the multiple interactions between carbon starvation, hydraulic failure and biotic agents in driving tree mortality under field conditions are still not well understood. We analysed the seasonal variability of non-structural carbohydrates (NSCs) in four organs (leaves, branches, trunk and roots), the vulnerability to embolism in roots and branches, native embolism (percentage loss of hydraulic conductivity (PLC)) in branches and the presence of root rot pathogens in defoliated and non-defoliated individuals in a declining Scots pine (Pinus sylvestris L.) population in the NE Iberian Peninsula in 2012, which included a particularly dry and warm summer. No differences were observed between defoliated and non-defoliated pines in hydraulic parameters, except for a higher vulnerability to embolism at pressures below -2?MPa in roots of defoliated pines. No differences were found between defoliation classes in branch PLC. Total NSC (TNSC, soluble sugars plus starch) values decreased during drought, particularly in leaves. Defoliation reduced TNSC levels across tree organs, especially just before (June) and during (August) drought. Root rot infection by the fungal pathogen Onnia P. Karst spp. was detected but it did not appear to be associated to tree defoliation. However, Onnia infection was associated with reduced leaf-specific hydraulic conductivity and sapwood depth, and thus contributed to hydraulic impairment, especially in defoliated pines. Infection was also associated with virtually depleted root starch reserves during and after drought in defoliated pines. Moreover, defoliated and infected trees tended to show lower basal area increment. Overall, our results show the intertwined nature of physiological mechanisms leading to drought-induced mortality and the inherent difficulty of isolating their contribution under field conditions. PMID:25724949

  15. Root contact responses and the positive relationship between intraspecific diversity and ecosystem productivity

    PubMed Central

    Yang, Lixue; Callaway, Ragan M.; Atwater, Daniel Z.

    2015-01-01

    High species and functional group richness often has positive effects on ecosystem function including increasing productivity. Recently, intraspecific diversity has been found to have similar effects, but because traits vary far less within a species than among species we have a much poorer understanding of the mechanisms by which intraspecific diversity affects ecosystem function. We explored the potential for identity recognition among the roots of different Pseudoroegneria spicata accessions to contribute to previously demonstrated overyielding in plots with high intraspecific richness of this species relative to monocultures. First, we found that when plants from different populations were planted together in pots the total biomass yield was 30 % more than in pots with two plants from the same population. Second, we found that the elongation rates of roots of Pseudoroegneria plants decreased more after contact with roots from another plant from the same population than after contact with roots from a plant from a different population. These results suggest the possibility of some form of detection and avoidance mechanism among more closely related Pseudoroegneria plants. If decreased growth after contact results in reduced root overlap, and reduced root overlap corresponds with reduced growth and productivity, then variation in detection and avoidance among related and unrelated accessions may contribute to how ecotypic diversity in Pseudoroegneria increases productivity. PMID:25990363

  16. Root contact responses and the positive relationship between intraspecific diversity and ecosystem productivity.

    PubMed

    Yang, Lixue; Callaway, Ragan M; Atwater, Daniel Z

    2015-01-01

    High species and functional group richness often has positive effects on ecosystem function including increasing productivity. Recently, intraspecific diversity has been found to have similar effects, but because traits vary far less within a species than among species we have a much poorer understanding of the mechanisms by which intraspecific diversity affects ecosystem function. We explored the potential for identity recognition among the roots of different Pseudoroegneria spicata accessions to contribute to previously demonstrated overyielding in plots with high intraspecific richness of this species relative to monocultures. First, we found that when plants from different populations were planted together in pots the total biomass yield was 30 % more than in pots with two plants from the same population. Second, we found that the elongation rates of roots of Pseudoroegneria plants decreased more after contact with roots from another plant from the same population than after contact with roots from a plant from a different population. These results suggest the possibility of some form of detection and avoidance mechanism among more closely related Pseudoroegneria plants. If decreased growth after contact results in reduced root overlap, and reduced root overlap corresponds with reduced growth and productivity, then variation in detection and avoidance among related and unrelated accessions may contribute to how ecotypic diversity in Pseudoroegneria increases productivity. PMID:25990363

  17. Disturbances during minirhizotron installation can affect root observation data

    SciTech Connect

    Joslin, J.D.; Wolfe, M.H. [Tennessee Valley Authority, Norris, TN (United States)

    1999-01-01

    Use of minirhizotrons in forested ecosystems has produced considerable information on production, mortality, distribution, and the phenology of root growth. But installation of minirhizotrons severs roots and disturbs soil, which can cause root proliferation in perennial plants. The authors compared the magnitude and vertical distribution of root growth observations in a mature hardwood forest during the growing season immediately after minirhizotron installation with observations more than two years later. They also compared the vertical root growth distribution during these two different years with the preinstallation distribution of fine root biomass. Before minirhizotron installation and again two years later, about 74% of fine root biomass was in the upper 30 cm of soil, but immediately after installation, 98% of the root elongation was in the upper 30 cm. Large differences in the quantity of root elongation were observed across different slope positions in the minirhizotron data from the first growing season (approximately four times greater on the upper slope as the lower slope). Such differences with slope position were not sen in the later minirhizotron data, nor in the preinstallation fine root biomass data. The evidence suggests that the minirhizotron data collected immediately after installation can be biased by disturbance of roots and soil during installation, which result in excessive root proliferation, particularly near the soil surface. Root proliferation appears to be the result of a response to both root pruning and to nutrient release in microsites near the newly installed minirhizotron.

  18. Kinetics of actin elongation and depolymerization at the pointed end.

    PubMed

    Weber, A; Northrop, J; Bishop, M F; Ferrone, F A; Mooseker, M S

    1987-05-01

    We measured the rate of elongation at the pointed filament end with increasing concentrations of G-actin [J(c) function] using villin-capped actin filaments of very small (actin/villin = 3, VA3) and relatively large size (actin/villin = 18, VA18) as nuclei for elongation. The measurements were made under physiological conditions in the presence of both Mg2+ and K+. In both cases the J(c) function was nonlinear. In contrast to the barbed filament end, however, the slope of the J(c) function sharply decreased rather than increased when the monomer concentration was lowered to concentrations near and below the critical concentration c infinity. At zero monomer concentration, depolymerization at the pointed end was very slow with a rate constant of 0.02 s-1 for VA18. When VA3 was used, the nonlinearity of the J(c) function was greatly exaggerated, and the nuclei elongated at actin concentrations below the independently measured critical concentration for the pointed end. This is consistent with and confirms our previous finding [Weber, A., Northrop, J., Bishop, M. F., Ferrone, F. A., & Mooseker, M. S. (1987) Biochemistry (preceding paper in the issue)] that at an actin-villin ratio of 3 a significant fraction of the villin is free and that a series of steady states exist between villin-actin complexes of increasing size and G-actin. The rate constant of elongation seems to increase with increasing G-actin concentrations because of increasing conversion of free villin into villin-actin oligomers during the period of the measurement of the initial elongation rate. The villin-actin oligomers have a much higher rate constant of actin binding than does free villin.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:3607031

  19. Transcription elongation regulator 1 (TCERG1) regulates competent RNA polymerase II-mediated elongation of HIV-1 transcription and facilitates efficient viral replication

    PubMed Central

    2013-01-01

    Background Control of RNA polymerase II (RNAPII) release from pausing has been proposed as a checkpoint mechanism to ensure optimal RNAPII activity, especially in large, highly regulated genes. HIV-1 gene expression is highly regulated at the level of elongation, which includes transcriptional pausing that is mediated by both viral and cellular factors. Here, we present evidence for a specific role of the elongation-related factor TCERG1 in regulating the extent of HIV-1 elongation and viral replication in vivo. Results We show that TCERG1 depletion diminishes the basal and viral Tat-activated transcription from the HIV-1 LTR. In support of a role for an elongation mechanism in the transcriptional control of HIV-1, we found that TCERG1 modifies the levels of pre-mRNAs generated at distal regions of HIV-1. Most importantly, TCERG1 directly affects the elongation rate of RNAPII transcription in vivo. Furthermore, our data demonstrate that TCERG1 regulates HIV-1 transcription by increasing the rate of RNAPII elongation through the phosphorylation of serine 2 within the carboxyl-terminal domain (CTD) of RNAPII and suggest a mechanism for the involvement of TCERG1 in relieving pausing. Finally, we show that TCERG1 is required for HIV-1 replication. Conclusions Our study reveals that TCERG1 regulates HIV-1 transcriptional elongation by increasing the elongation rate of RNAPII and phosphorylation of Ser 2 within the CTD. Based on our data, we propose a general mechanism for TCERG1 acting on genes that are regulated at the level of elongation by increasing the rate of RNAPII transcription through the phosphorylation of Ser2. In the case of HIV-1, our evidence provides the basis for further investigation of TCERG1 as a potential therapeutic target for the inhibition of HIV-1 replication PMID:24165037

  20. Roles of proteome dynamics and cytokinin signaling in root to hypocotyl ratio changes induced by shading roots of Arabidopsis seedlings.

    PubMed

    Novák, Jan; ?erný, Martin; Pavl?, Jaroslav; Zemánková, Jana; Skalák, Jan; Pla?ková, Lenka; Brzobohatý, B?etislav

    2015-05-01

    In nature, root systems of most terrestrial plants are protected from light exposure by growing in a dark soil environment. Hence, in vitro cultivation in transparent Petri dishes leads to physiological perturbations, but the mechanisms underlying root-mediated light perception and responses have not been fully elucidated. Thus, we compared Arabidopsis thaliana seedling development in transparent and darkened Petri dishes at low light intensity (20 µmol m(-2) s(-1)), allowing us to follow (inter alia) hypocotyl elongation, which is an excellent process for studying interactions of signals involved in the regulation of growth and developmental responses. To obtain insights into molecular events underlying differences in seedling growth under these two conditions, we employed liquid chromatography-mass spectrometry (LC-MS) shotgun proteomics (available via the PRIDE deposit PXD001612). In total, we quantified the relative abundances of peptides representing 1,209 proteins detected in all sample replicates of LC-MS analyses. Comparison of MS spectra after manual validation revealed 48 differentially expressed proteins. Functional classification, analysis of available gene expression data and literature searches revealed alterations associated with root illumination (inter alia) in autotrophic CO2 fixation, C compound and carbohydrate metabolism, and nitrogen metabolism. The results also indicate a previously unreported role for cytokinin plant hormones in the escape-tropism response to root illumination. We complemented these results with reverse transcription followed by quantitative PCR (RT-qPCR), chlorophyll fluorescence and detailed cytokinin signaling analyses, detecting in the latter a significant increase in the activity of the cytokinin two-component signaling cascade in roots and implicating the cytokinin receptor AHK3 as the major mediator of root to hypocotyl signaling in responses to root illumination. PMID:25700275

  1. Simultaneous quantification of six major phenolic acids in the roots of Salvia miltiorrhiza and four related traditional Chinese medicinal preparations by HPLC–DAD method

    Microsoft Academic Search

    Ai-Hua Liu; Lie Li; Man Xu; Yan-Hua Lin; Hong-Zhu Guo; De-An Guo

    2006-01-01

    A high-performance liquid chromatographic method was applied to the determination of danshensu, protocatechuic aldehyde, rosmarinic acid, lithospermic acid, salvianolic acid B and salvianolic acid A in the roots of Salvia miltiorrhiza and four related traditional Chinese medicinal preparations. The six phenolic acids were simultaneously analyzed with a Zorbax Extend C18 column by gradient elution using 0.026% (v\\/v) phosphoric acid and

  2. The tertiary endodermis in barley roots: Fine structure in relation to radial transport of ions and water

    Microsoft Academic Search

    D. T. Clarkson; A. W. Robards; J. Sanderson

    1971-01-01

    The presence of numerous pits containing plasmodesmata in the inner tangential wall of the tertiary endodermis in barley roots is demonstrated by electron microscopy. The pit floor is covered by a thin layer of material which is continuous with and resembles the tertiary wall. The plasmodesmatal pore is constricted at its ends so that the plasmalemma lining the pore is

  3. Effects of water deficit stress and recovery on the root water relations of trembling aspen ( Populus tremuloides) seedlings

    Microsoft Academic Search

    J. Aurea Siemens; Janusz J. Zwaizek

    2003-01-01

    Aspen (Populus tremuloides Michx.) seedlings were grown in sand culture and subjected to mild and severe water deficit stress by withholding watering. Severely-stressed seedlings were also rewatered for 24 h to determine the effects of water deficit stress and stress recovery on root water flow properties. Both stress levels and stress recovery treatment reduced leaf stomatal conductance and shoot water

  4. Root Growth and Enzymes Related to the Lignification of Maize Seedlings Exposed to the Allelochemical L-DOPA

    PubMed Central

    Siqueira-Soares, Rita de Cássia; Parizotto, Angela Valderrama; Ferrarese, Maria de Lourdes Lucio

    2013-01-01

    L-3,4-Dihydroxyphenylalanine (L-DOPA) is a known allelochemical exuded from the roots of velvet bean (Mucuna pruriens L. Fabaceae). In the current work, we analyzed the effects of L-DOPA on the growth, the activities of phenylalanine ammonia-lyase (PAL), tyrosine ammonia-lyase (TAL), and peroxidase (POD), and the contents of phenylalanine, tyrosine, and lignin in maize (Zea mays) roots. Three-day-old seedlings were cultivated in nutrient solution with or without 0.1 to 2.0?mM L-DOPA in a growth chamber (25°C, light/dark photoperiod of 12/12, and photon flux density of 280??mol?m?2?s?1) for 24?h. The results revealed that the growth (length and weight) of the roots, the PAL, TAL, and soluble and cell wall-bound POD activities decreased, while phenylalanine, tyrosine, and lignin contents increased after L-DOPA exposure. Together, these findings showed the susceptibility of maize to L-DOPA. In brief, these results suggest that the inhibition of PAL and TAL can accumulate phenylalanine and tyrosine, which contribute to enhanced lignin deposition in the cell wall followed by a reduction of maize root growth. PMID:24348138

  5. [Evaluation of root and bud cold hardiness of wine grape varieties based on temperature-injury relation].

    PubMed

    2014-04-01

    A system for differential thermal analysis (DTA) was applied for low temperature exotherms (LTE) analysis of roots and buds of eight wine grape varieties, and the temperature-injury (LT-I) regression functions of buds, phloem and xylem of roots were established to evaluate the cold hardiness of roots and buds of the different varieties. The order of phloem 50% lethal temperature of the eight grapevines was Marselan > Cabernet Franc > Cabernet Sauvignon > Petit Manseng > Chardonnay > Cabernet Gernischt > Italian Riesling > Xiongyuebai. The xylem 50% lethal temperature of the different cultivars was in the order of Marselan > Chardonnay > Cabernet Sauvignon > Petit Manseng > Cabernet Franc > Cabernet Gernischt > Italian Riesling > Xiongyuebai. The order of bud 50% lethal temperature was Cabernet Sauvignon > Petit Manseng > Cabernet Gernischt > Cabernet Franc > Chardonnay > Italian Riesling > Marselan > Xiongyuebai. A comprehensive evaluation on cold hardiness of the different varieties was conducted by fuzzy membership function. For roots, Marselan was the poorest, and Xiongyuebai was the best. For buds, Cabernet Sauvignon, Cabernet Franc, Petit Manseng and Cabernet Gernischt were poorer, while Italian Riesling and Xiongyuebai were better. PMID:25011289

  6. Water-table depth and oxygen content of deep peat in relation to root growth of Pinus contorta

    Microsoft Academic Search

    Robert Boggie

    1977-01-01

    Summary Oxygen concentrations were measured at monthly intervals in deep peat in plots in which the water-tables are maintained artificially at levels ranging in depth from 11 cm to 33 cm below the surface. Good correlation was observed between weight of roots of 11 year oldPinus contorta in these plots and oxygen concentrations in different horizons at all times of

  7. Effect of Potassium on Ultrastructure of Maize Stalk Pith and Young Root and Their Relation to Stalk Rot Resistance

    Microsoft Academic Search

    Wen-juan LI; Ping HE; Ji-yun JIN

    2010-01-01

    To study the mechanism of potassium (K) application on improvement of maize resistance to stalk rot at cellular level, scanning electron microscope and transmission electron microscope were used to observe the effect of K on the ultrastructure of maize stalk pith tissue and young root tip cell influenced by K and pathogen. In K deficient treatment, parenchyma cells of stalk

  8. Geostatistical Modeling of the Spatial Variability and Risk Areas of Southern Root-knot Nematodes in Relation to Soil Properties

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Site-specific management (SSM) of cotton (Gossypium hirsutum L.) fields at risk for southern root-knot nematode [Meloidogine Incognita (Kofoid & White) Chitwood] (RKN) infection may offer producers better management of on-farm resources and optimization of profitability. However, it requires the st...

  9. NITRIC OXIDE-ASSOCIATED PROTEIN1 (AtNOA1) is essential for salicylic acid-induced root waving in Arabidopsis thaliana.

    PubMed

    Zhao, Xiang; Wang, Jin; Yuan, Jing; Wang, Xi-Li; Zhao, Qing-Ping; Kong, Pei-Tao; Zhang, Xiao

    2015-07-01

    Root waving responses have been attributed to both environmental and genetics factors, but the potential inducers and transducers of root waving remain elusive. Thus, the identification of novel signal elements related to root waving is an intriguing field of research. Genetic, physiological, cytological, live cell imaging, and pharmacological approaches provide strong evidence for the involvement of Arabidopsis thaliana NITRIC OXIDE-ASSOCIATED PROTEIN1 (AtNOA1) in salicylic acid (SA)-induced root waving. SA specially induced root waving, with an overall decrease in root elongation in A. thaliana, and this SA-induced response was disrupted in the Atnoa1 mutant, as well as in nonexpresser of pathogenesis-related genes 1 (npr1), which is defective in SA-mediated plant defense signal transduction, but not in npr3/4 single and double mutants. The expression assays revealed that the abundance of AtNOA1 was significantly increased by application of SA. Genetic and pharmacological analyses showed that SA-induced root waving involved an AtNOA1-dependent Ca(2+) signal transduction pathway, and PIN-FORMED2 (PIN2) -based polar auxin transport possibly plays a crucial role in this process. Our work suggests that SA signaling through NPR1 and AtNOA1 is involved in the control of root waving, which provides new insights into the mechanisms that control root growth behavior on a hard agar surface. PMID:25690466

  10. Response to non-uniform salinity in the root zone of the halophyte Atriplex nummularia: growth, photosynthesis, water relations and tissue ion concentrations

    PubMed Central

    Bazihizina, Nadia; Colmer, Timothy D.; Barrett-Lennard, Edward G.

    2009-01-01

    Background and Aims Soil salinity is often heterogeneous, yet the physiology of halophytes has typically been studied with uniform salinity treatments. An evaluation was made of the growth, net photosynthesis, water use, water relations and tissue ions in the halophytic shrub Atriplex nummularia in response to non-uniform NaCl concentrations in a split-root system. Methods Atriplex nummularia was grown in a split-root system for 21 d, with either the same or two different NaCl concentrations (ranging from 10 to 670 mm), in aerated nutrient solution bathing each root half. Key Results Non-uniform salinity, with high NaCl in one root half (up to 670 mm) and 10 mm in the other half, had no effect on shoot ethanol-insoluble dry mass, net photosynthesis or shoot pre-dawn water potential. In contrast, a modest effect occurred for leaf osmotic potential (up to 30 % more solutes compared with uniform 10 mm NaCl treatment). With non-uniform NaCl concentrations (10/670 mm), 90 % of water was absorbed from the low salinity side, and the reduction in water use from the high salinity side caused whole-plant water use to decrease by about 30 %; there was no compensatory water uptake from the low salinity side. Leaf Na+ and Cl? concentrations were 1·9- to 2·3-fold higher in the uniform 670 mm treatment than in the 10/670 mm treatment, whereas leaf K+ concentrations were 1·2- to 2·0-fold higher in the non-uniform treatment. Conclusions Atriplex nummularia with one root half in 10 mm NaCl maintained net photosynthesis, shoot growth and shoot water potential even when the other root half was exposed to 670 mm NaCl, a concentration that inhibits growth by 65 % when uniform in the root zone. Given the likelihood of non-uniform salinity in many field situations, this situation would presumably benefit halophyte growth and physiology in saline environments. PMID:19556265

  11. Molecular characterization and temporal expression analyses indicate the MIC (Meloidogyne Induced Cotton) gene family represents a novel group of root-specific defense-related genes in Upland cotton (Gossypium hirsutum L.)

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The molecular events underlying the resistance of Upland cotton to the root-knot nematode (RKN) are largely unknown. In this report, we further characterize the previously identified MIC3 gene including the identification of fourteen related MIC cDNAs in nematode-infected roots of allotetraploid co...

  12. Phylogenetic relationships among Armillaria species inferred from partial elongation factor 1-alpha DNA sequence data

    Microsoft Academic Search

    L. Maphosa; B. D. Wingfield; M. P. A. Coetzee; E. Mwenje; M. J. Wingfield

    2006-01-01

    Armillaria species are important root rot pathogens with a wide host range and a worldwide distribution. The taxonomy of these fungi\\u000a has been problematic for many years but the understanding of the relationships between them has been substantially improved\\u000a through the application of DNA sequence comparisons. In this study, relationships between different Armillaria species were determined using elongation factor 1-alpha

  13. 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

  14. Neuroprotective Copper Bis(thiosemicarbazonato) Complexes Promote Neurite Elongation

    PubMed Central

    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, CuII(gtsm) on neuritogenesis and neurite elongation (neurogenerative outcomes) in PC12 neuronal-related cultures. We found that CuII(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, CuII(atsm), but at a higher concentration. Induction of neurite elongation by CuII(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 CuII(gtsm) treatment. The mechanism of neurogenerative action was investigated and revealed that CuII(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 CuII(gtsm), suggesting a potential link between CuII(gtsm)-mediated phosphatase inhibition and neurogenerative outcomes. PMID:24587210

  15. Amythiamicin?D and related thiopeptides as inhibitors of the bacterial elongation factor EF-Tu: modification of the amino acid at carbon atom C2 of ring?C dramatically influences activity.

    PubMed

    Gross, Stefan; Nguyen, Fabian; Bierschenk, Matthias; Sohmen, Daniel; Menzel, Thomas; Antes, Iris; Wilson, Daniel N; Bach, Thorsten

    2013-12-01

    Three analogues of amythiamicin?D, which differ in the substitution pattern at the methine group adjacent to C2 of the thiazole ring?C, were prepared by de?novo total synthesis. In amythiamicin?D, this carbon atom is (S)-isopropyl substituted. Two of the new analogues carry a hydroxymethyl in place of the isopropyl group, one at an S- (compound 3?a) and the other at an R-configured stereogenic center (3?b). The third analogue, 3?c, contains a benzyloxymethyl group at an S-configured stereogenic center. Compounds 3?b and 3?c showed no inhibitory effect toward various bacterial strains, nor did they influence the translation of firefly luciferase. In stark contrast, compound 3?a inhibited the growth of Gram-positive bacteria Staphylococcus aureus (strains NCTC and Mu50) and Listeria monocytogenes EGD. In the firefly luciferase assay it proved more potent than amythiamicin?D, and rescue experiments provided evidence that translation inhibition is due to binding to the bacterial elongation factor Tu (EF-Tu). The results were rationalized by structural investigations and by molecular dynamics simulations of the free compounds in solution and bound to the EF-Tu binding site. The low affinity of compound 3?b was attributed to the absence of a critical hydrogen bond, which stabilizes the conformation required for binding to EF-Tu. Compound 3?c was shown not to comply with the binding properties of the binding site. PMID:24106106

  16. Fine Structure of the Early Interaction of Lily Roots with Fusarium oxysporum f.sp. lilii

    Microsoft Academic Search

    R. P. Baayen; F. H. J. Rijkenberg

    1999-01-01

    The early interaction of lily roots with the cortical rot pathogen Fusarium oxysporum f.sp. lilii was studied using roots of lily bulblets grown in Hoagland's solution, inoculated with the pathogen, and sampled up to 48?h later. Conidia produced germ tubes within 6?h, which extended towards and into the mucilage covering the root elongation zone, and along and into the anticlinal

  17. The increase in conductance of a gold single atom chain during elastic elongation

    NASA Astrophysics Data System (ADS)

    Tavazza, F.; Barzilai, S.; Smith, D. T.; Levine, L. E.

    2013-02-01

    The conductance of monoatomic gold wires has been studied using ab initio calculations and the transmission was found to vary with the elastic strain. Counter-intuitively, the conductance was found to increase for the initial stages of the elongation, where the structure has a zigzag shape and the bond angles increase from ?140° toward ?160°. After a certain elongation limit, where the angles are relatively high, the bond length elongation associated with a Peierls distortion reverses this trend and the conductance decreases. These simulations are in good agreement with previously unexplained experimental results.

  18. Stimulation of peptide elongation by thyroxine.

    PubMed Central

    Carter, W J; Faas, F H; Wynn, J O

    1976-01-01

    This study suggests that thyroxine stimulates peptide elongation in a cell-free rat liver polyribosome system. The thyroxine effect persists in the presence of sufficient aurintricarboxylic acid to prevent polyuridylic acid-stimulated peptide initiation. In addition, thyroxine stimulates elongation of pre-existing polyphenylalanine chains providing conclusive evidence that the effect does not depend on peptide initiation. Thyroxine does not stimulate release of nascent peptides from ribosomes into the supernatant phase of the reaction mixture. Therefore in this protein-synthesis system the thyroxine effect is expected to occur at one or more of the reactions of peptide chain elongation, which include aminoacyl-tRNA binding, peptide bond synthesis and translocation. PMID:949351

  19. Evaporating momentum force and shear force on meniscuses of elongated bubble in microchannel flow boiling

    NASA Astrophysics Data System (ADS)

    Yin, Liaofei; Jia, Li; Guan, Peng; Liu, Fuhao

    2014-04-01

    The evaporating momentum force and the shear force acting on the meniscus of an evaporating and elongating bubble in flow boiling in microchannel have been investigated theoretically and numerically. The concept of the effective evaporation region and the theory of the liquid layer supplement between elongated bubble and microchannel are proposed, and the analytical expressions of the evaporating momentum force and shear force have been obtained. The relative importance of both forces has been determined by the method of magnitude analysis and numerical simulation. It has been found that the evaporating momentum force can always be neglected in analyzing the bubble elongation process and the motion law of meniscus of elongated bubble in microchannel flow boiling, but whether the shear force should be considered or not is determined by its relative order of magnitude and the particular conditions such as channel dimension and the operating conditions.

  20. Characterizing pathways by which gravitropic effectors could move from the root cap to the root of primary roots of Zea mays

    NASA Technical Reports Server (NTRS)

    Moore, R.; McClelen, C. E.

    1989-01-01

    Plasmodesmata linking the root cap and root in primary roots Zea mays are restricted to approx. 400 protodermal cells bordering approx. 110000 microns2 of the calyptrogen of the root cap. This area is less than 10% of the cross-sectional area of the root-tip at the cap junction. Therefore, gravitropic effectors moving from the root cap to the root can move symplastically only through a relatively small area in the centre of the root. Decapped roots are non-responsive to gravity. However, decapped roots whose caps are replaced immediately after decapping are strongly graviresponsive. Thus, gravicurvature occurs only when the root cap contacts the root, and symplastic continuity between the cap and root is not required for gravicurvature. Completely removing mucilage from the root tip renders the root non-responsive to gravity. Taken together, these data suggest that gravitropic effectors move apoplastically through mucilage from the cap to the root.

  1. Pre-mRNA splicing is facilitated by an optimal RNA polymerase II elongation rate

    PubMed Central

    Fong, Nova; Kim, Hyunmin; Zhou, Yu; Ji, Xiong; Qiu, Jinsong; Saldi, Tassa; Diener, Katrina; Jones, Ken; Fu, Xiang-Dong

    2014-01-01

    Alternative splicing modulates expression of most human genes. The kinetic model of cotranscriptional splicing suggests that slow elongation expands and that fast elongation compresses the “window of opportunity” for recognition of upstream splice sites, thereby increasing or decreasing inclusion of alternative exons. We tested the model using RNA polymerase II mutants that change average elongation rates genome-wide. Slow and fast elongation affected constitutive and alternative splicing, frequently altering exon inclusion and intron retention in ways not predicted by the model. Cassette exons included by slow and excluded by fast elongation (type I) have weaker splice sites, shorter flanking introns, and distinct sequence motifs relative to “slow-excluded” and “fast-included” exons (type II). Many rate-sensitive exons are misspliced in tumors. Unexpectedly, slow and fast elongation often both increased or both decreased inclusion of a particular exon or retained intron. These results suggest that an optimal rate of transcriptional elongation is required for normal cotranscriptional pre-mRNA splicing. PMID:25452276

  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. Shear Modulus for Nonisotropic, Open-Celled Foams Using a General Elongated Kelvin Foam Model

    NASA Technical Reports Server (NTRS)

    Sullivan, Roy M.; Ghosn, Louis J.

    2008-01-01

    An equation for the shear modulus for nonisotropic, open-celled foams in the plane transverse to the elongation (rise) direction is derived using an elongated Kelvin foam model with the most general geometric description. The shear modulus was found to be a function of the unit cell dimensions, the solid material properties, and the cell edge cross-section properties. The shear modulus equation reduces to the relation derived by others for isotropic foams when the unit cell is equiaxed.

  4. The effect of post-hypoxia on roots in Senecio and Myosotis species related to the glutathione system

    Microsoft Academic Search

    Sophia Biemelt; Gerd Albrecht; Ernst-Manfred Wiedenroth

    1996-01-01

    This paper shows the effect of re-aeration following hypoxic pretreatment on the glutathione system in plants with different\\u000a flooding tolerance. Re-aeration of hypoxically pretreated roots led to an increase of TBA-rm content indicating an accelerated\\u000a lipid peroxidation (post-anoxic injury). Re-admission of oxygen resulted in a clear increase in the content of total glutathione\\u000a in both flooding-intolerant speciesMyosotis arvensis andSenecio jacobaea.

  5. Structural Basis of the Translational Elongation

    E-print Network

    Ramakrishnan, Venki

    Medical Research Council Keywords translation, ribosome, protein synthesis, decoding, translocation, protein synthesis is car- ried out by the large macromolecular machine known as the ribosome. Both out by the ribosome in a complicated multistep process called the elongation cycle. It involves

  6. Water relations and leaf expansion: importance of time scale.

    PubMed

    Munns, R; Passioura, J B; Guo, J; Chazen, O; Cramer, G R

    2000-09-01

    The role of leaf water relations in controlling cell expansion in leaves of water-stressed maize and barley depends on time scale. Sudden changes in leaf water status, induced by sudden changes in humidity, light and soil salinity, greatly affect leaf elongation rate, but often only transiently. With sufficiently large changes in salinity, leaf elongation rates are persistently reduced. When plants are kept fully turgid throughout such sudden environmental changes, by placing their roots in a pressure chamber and raising the pressure so that the leaf xylem sap is maintained at atmospheric pressure, both the transient and persistent changes in leaf elongation rate disappear. All these responses show that water relations are responsible for the sudden changes in leaf elongation rate resulting from sudden changes in water stress and putative root signals play no part. However, at a time scale of days, pressurization fails to maintain high rates of leaf elongation of plants in either saline or drying soil, indicating that root signals are overriding water relations effects. In both saline and drying soil, pressurization does raise the growth rate during the light period, but a subsequent decrease during the dark results in no net effect on leaf growth over a 24 h period. When transpirational demand is very high, however, growth-promoting effects of pressurization during the light period outweigh any reductions in the dark, resulting in a net increase in growth of pressurized plants over 24 h. Thus leaf water status can limit leaf expansion rates during periods of high transpiration despite the control exercised by hormonal effects on a 24 h basis. PMID:11006301

  7. Lead-induced genotoxicity to Vicia faba L. roots in relation with metal cell uptake and initial speciation.

    PubMed

    Shahid, M; Pinelli, E; Pourrut, B; Silvestre, J; Dumat, C

    2011-01-01

    Formation of organometallic complexes in soil solution strongly influence metals phytoavailability. However, only few studies deal with the influence of metal speciation both on plant uptake and genotoxicity. In the present study, Vicia faba seedlings were exposed for 6h in controlled hydroponic conditions to 5 ?M of lead nitrate alone and chelated to varying degrees by different organic ligands. Ethylenediaminetetraacetic acid and citric acid were, respectively, chosen as models of humic substances and low weight organic acids present in natural soil solutions. Visual Minteq software was used to estimate free lead cations concentration and ultimately to design the experimental layout. For all experimental conditions, both micronucleus test and measure of lead uptake by plants were finally performed. Chelation of Pb by EDTA, a strong chelator, dose-dependently increased the uptake in V. faba roots while its genotoxicity was significantly reduced, suggesting a protective role of EDTA. A weak correlation was observed between total lead concentration absorbed by roots and genotoxicity (r(2)=0.65). In contrast, a strong relationship (r(2)=0.93) exists between Pb(2+) concentration in exposure media and genotoxicity in the experiment performed with EDTA. Citric acid induced labile organometallic complexes did not demonstrate any significant changes in lead genotoxicity or uptake. These results demonstrate that metal speciation knowledge could improve the interpretation of V. faba genotoxicity test performed to test soil quality. PMID:20851467

  8. Misguided transcriptional elongation causes mixed lineage leukemia.

    PubMed

    Mueller, Dorothee; García-Cuéllar, María-Paz; Bach, Christian; Buhl, Sebastian; Maethner, Emanuel; Slany, Robert K

    2009-11-01

    Fusion proteins composed of the histone methyltransferase mixed-lineage leukemia (MLL) and a variety of unrelated fusion partners are highly leukemogenic. Despite their prevalence, particularly in pediatric acute leukemia, many molecular details of their transforming mechanism are unknown. Here, we provide mechanistic insight into the function of MLL fusions, demonstrating that they capture a transcriptional elongation complex that has been previously found associated with the eleven-nineteen leukemia protein (ENL). We show that this complex consists of a tight core stabilized by recursive protein-protein interactions. This central part integrates histone H3 lysine 79 methylation, RNA Polymerase II (RNA Pol II) phosphorylation, and MLL fusion partners to stimulate transcriptional elongation as evidenced by RNA tethering assays. Coimmunoprecipitations indicated that MLL fusions are incorporated into this complex, causing a constitutive recruitment of elongation activity to MLL target loci. Chromatin immunoprecipitations (ChIP) of the homeobox gene A cluster confirmed a close relationship between binding of MLL fusions and transcript levels. A time-resolved ChIP utilizing a conditional MLL fusion singled out H3K79 methylation as the primary parameter correlated with target expression. The presence of MLL fusion proteins also kept RNA Pol II in an actively elongating state and prevented accumulation of inhibitory histone methylation on target chromatin. Hox loci remained open and productive in the presence of MLL fusion activity even under conditions of forced differentiation. Finally, MLL-transformed cells were particularly sensitive to pharmacological inhibition of RNA Pol II phosphorylation, pointing to a potential treatment for MLL. In summary, we show aberrant transcriptional elongation as a novel mechanism for oncogenic transformation. PMID:19956800

  9. Misguided Transcriptional Elongation Causes Mixed Lineage Leukemia

    PubMed Central

    Mueller, Dorothee; García-Cuéllar, María-Paz; Bach, Christian; Buhl, Sebastian; Maethner, Emanuel; Slany, Robert K.

    2009-01-01

    Fusion proteins composed of the histone methyltransferase mixed-lineage leukemia (MLL) and a variety of unrelated fusion partners are highly leukemogenic. Despite their prevalence, particularly in pediatric acute leukemia, many molecular details of their transforming mechanism are unknown. Here, we provide mechanistic insight into the function of MLL fusions, demonstrating that they capture a transcriptional elongation complex that has been previously found associated with the eleven-nineteen leukemia protein (ENL). We show that this complex consists of a tight core stabilized by recursive protein–protein interactions. This central part integrates histone H3 lysine 79 methylation, RNA Polymerase II (RNA Pol II) phosphorylation, and MLL fusion partners to stimulate transcriptional elongation as evidenced by RNA tethering assays. Coimmunoprecipitations indicated that MLL fusions are incorporated into this complex, causing a constitutive recruitment of elongation activity to MLL target loci. Chromatin immunoprecipitations (ChIP) of the homeobox gene A cluster confirmed a close relationship between binding of MLL fusions and transcript levels. A time-resolved ChIP utilizing a conditional MLL fusion singled out H3K79 methylation as the primary parameter correlated with target expression. The presence of MLL fusion proteins also kept RNA Pol II in an actively elongating state and prevented accumulation of inhibitory histone methylation on target chromatin. Hox loci remained open and productive in the presence of MLL fusion activity even under conditions of forced differentiation. Finally, MLL-transformed cells were particularly sensitive to pharmacological inhibition of RNA Pol II phosphorylation, pointing to a potential treatment for MLL. In summary, we show aberrant transcriptional elongation as a novel mechanism for oncogenic transformation. PMID:19956800

  10. Suppression of vertical instability in elongated current-carrying plasmas by applying stellarator rotational transform

    SciTech Connect

    ArchMiller, M. C.; Cianciosa, M. R.; Ennis, D. A.; Hanson, J. D.; Hartwell, G. J.; Hebert, J. D.; Herfindal, J. L.; Knowlton, S. F.; Ma, X.; Maurer, D. A.; Pandya, M. D.; Traverso, P. [Physics Department, Auburn University, Auburn, Alabama 36849 (United States)

    2014-05-15

    The passive stability of vertically elongated current-carrying toroidal plasmas has been investigated in the Compact Toroidal Hybrid, a stellarator/tokamak hybrid device. In this experiment, the fractional transform f, defined as the ratio of the imposed external rotational transform from stellarator coils to the total rotational transform, was varied from 0.04 to 0.50, and the elongation ? was varied from 1.4 to 2.2. Plasmas that were vertically unstable were evidenced by motion of the plasma in the vertical direction. Vertical drifts are measured with a set of poloidal field pickup coils. A three chord horizontally viewing interferometer and a soft X-ray diode array confirmed the drifts. Plasmas with low fractional transform and high elongation are the most susceptible to vertical instability, consistent with analytic predictions that the vertical mode in elongated plasmas can be stabilized by the poloidal field of a relatively weak stellarator equilibrium.

  11. Elongational viscosities from nonequilibrium molecular dynamics simulations of oscillatory elongational flow

    E-print Network

    of interest, such as the diagonal elements of the pressure tensor, and hence elongational viscosities in the processing of polymer melts, for example, where manufac- turing techniques such as sheet casting, blow

  12. Patterns in hydraulic architecture from roots to branches in six tropical tree species from cacao agroforestry and their relation to wood density and stem growth

    PubMed Central

    Kotowska, Martyna M.; Hertel, Dietrich; Rajab, Yasmin Abou; Barus, Henry; Schuldt, Bernhard

    2015-01-01

    For decades it has been assumed that the largest vessels are generally found in roots and that vessel size and corresponding sapwood area-specific hydraulic conductivity are acropetally decreasing toward the distal twigs. However, recent studies from the perhumid tropics revealed a hump-shaped vessel size distribution. Worldwide tropical perhumid forests are extensively replaced by agroforestry systems often using introduced species of various biogeographical and climatic origins. Nonetheless, it is unknown so far what kind of hydraulic architectural patterns are developed in those agroforestry tree species and which impact this exerts regarding important tree functional traits, such as stem growth, hydraulic efficiency and wood density (WD). We investigated wood anatomical and hydraulic properties of the root, stem and branch wood in Theobroma cacao and five common shade tree species in agroforestry systems on Sulawesi (Indonesia); three of these were strictly perhumid tree species, and the other three tree species are tolerating seasonal drought. The overall goal of our study was to relate these properties to stem growth and other tree functional traits such as foliar nitrogen content and sapwood to leaf area ratio. Our results confirmed a hump-shaped vessel size distribution in nearly all species. Drought-adapted species showed divergent patterns of hydraulic conductivity, vessel density, and relative vessel lumen area between root, stem and branch wood compared to wet forest species. Confirming findings from natural old-growth forests in the same region, WD showed no relationship to specific conductivity. Overall, aboveground growth performance was better predicted by specific hydraulic conductivity than by foliar traits and WD. Our study results suggest that future research on conceptual trade-offs of tree hydraulic architecture should consider biogeographical patterns underlining the importance of anatomical adaptation mechanisms to environment. PMID:25873922

  13. Metabolic and Physical Control of Cell Elongation Rate

    PubMed Central

    Green, P. B.; Erickson, R. O.; Buggy, J.

    1971-01-01

    Several levels of control of elongation rate are revealed through the detailed study of responses of the Nitella internode to abrupt shifts in turgor. The immediate response, which apparently reflects the physical state of the cell, is approximately described by the equation r = (P — Y)m where r is rate, P is pressure, Y is the wall's yielding threshold, and m is related to the wall's apparent fluidity (reciprocal viscosity). Because P and Y are in the range 5 to 6 atmospheres, and (P — Y) is roughly 0.2 atmosphere, elongation rate is initially extremely sensitive to changes in P. A small step-down in turgor (0.7 atmosphere) stops growth, and a similar rise greatly accelerates it. These initial responses are, however, soon (15 minutes) compensated by changes in Y. An apparent metabolism-dependent reaction (azide-sensitive) lowers Y; strain hardening (azide-insensitive) raises it. These two opposing processes, acting on Y, serve as a governor on (P — Y), tending to maintain it at a given value despite changes in P. This ability to compensate is itself a function of turgor. Turgor step-downs are less and less well compensated, leading to lower rate, as turgor falls from 5 atmospheres to about 2 atmospheres where growth appears not to resume. This is the lowest attainable yield value, Y1. The turgor dependency of compensation reflects a turgor requirement of the Y-lowering (“wall-softening”) process. Thus the relation between steady state, rs, and turgor is an indirect one, derived from time-dependent alterations of the cell wall. This relationship superficially resembles the instantaneously valid one in that, roughly, rs = (P — Y1)ms. Y1 and ms, however, have much lower values than Y and m. The duality of the elongation rate versus turgor relation and the prominent role of Y in regulating rate are the major features of growth control in Nitella. PMID:16657635

  14. The importance of codon-anticodon interactions in translation elongation.

    PubMed

    Saint-Léger, Adélaïde; Ribas de Pouplana, Lluís

    2015-07-01

    Translation is the process by which genetic information is turned into amino acid sequence, following the instructions of the genetic code. The formation of a correct codon-anticodon pair is essential to ensure efficiency and fidelity during translation. Here we review the influence that codon-anticodon interactions play over the elongation phase of translation; including the role of this interaction in cognate tRNA selection by ribosomes, the importance of relative codon frequencies in the cell, and the roles of tRNA modifications in the process of codon-anticodon recognition. PMID:25921436

  15. Proteomic responses to lead-induced oxidative stress in Talinum triangulare Jacq. (Willd.) roots: identification of key biomarkers related to glutathione metabolisms.

    PubMed

    Kumar, Abhay; Majeti, Narasimha Vara Prasad

    2014-01-01

    In this study, Talinum triangulare Jacq. (Willd.) treated with different lead (Pb) concentrations for 7 days has been investigated to understand the mechanisms of ascorbate-glutathione metabolisms in response to Pb-induced oxidative stress. Proteomic study was performed for control and 1.25 mM Pb-treated plants to examine the root protein dynamics in the presence of Pb. Results of our analysis showed that Pb treatment caused a decrease in non-protein thiols, reduced glutathione (GSH), total ascorbate, total glutathione, GSH/oxidized glutathione (GSSG) ratio, and activities of glutathione reductase and ?-glutamylcysteine synthetase. Conversely, cysteine and GSSG contents and glutathione-S-transferase activity was increased after Pb treatment. Fourier transform infrared spectroscopy confirmed our metabolic and proteomic studies and showed that amino, phenolic, and carboxylic acids as well as alcoholic, amide, and ester-containing biomolecules had key roles in detoxification of Pb/Pb-induced toxic metabolites. Proteomic analysis revealed an increase in relative abundance of 20 major proteins and 3 new proteins (appeared only in 1.25 mM Pb). Abundant proteins during 1.25 mM Pb stress conditions have given a very clear indication about their involvement in root architecture, energy metabolism, reactive oxygen species (ROS) detoxification, cell signaling, primary and secondary metabolisms, and molecular transport systems. Relative accumulation patterns of both common and newly identified proteins are highly correlated with our other morphological, physiological, and biochemical parameters. PMID:24705950

  16. Application of Natural Blends of Phytochemicals Derived from the Root Exudates of Arabidopsis to the Soil Reveal That Phenolic-related Compounds Predominantly Modulate the Soil Microbiome*

    PubMed Central

    Badri, Dayakar V.; Chaparro, Jacqueline M.; Zhang, Ruifu; Shen, Qirong; Vivanco, Jorge M.

    2013-01-01

    The roots of plants have the ability to influence its surrounding microbiology, the so-called rhizosphere microbiome, through the creation of specific chemical niches in the soil mediated by the release of phytochemicals. Here we report how these phytochemicals could modulate the microbial composition of a soil in the absence of the plant. For this purpose, root exudates of Arabidopsis were collected and fractionated to obtain natural blends of phytochemicals at various relative concentrations that were characterized by GC-MS and applied repeatedly to a soil. Soil bacterial changes were monitored by amplifying and pyrosequencing the 16 S ribosomal small subunit region. Our analyses reveal that one phytochemical can culture different operational taxonomic units (OTUs), mixtures of phytochemicals synergistically culture groups of OTUs, and the same phytochemical can act as a stimulator or deterrent to different groups of OTUs. Furthermore, phenolic-related compounds showed positive correlation with a higher number of unique OTUs compared with other groups of compounds (i.e. sugars, sugar alcohols, and amino acids). For instance, salicylic acid showed positive correlations with species of Corynebacterineae, Pseudonocardineae and Streptomycineae, and GABA correlated with species of Sphingomonas, Methylobacterium, Frankineae, Variovorax, Micromonosporineae, and Skermanella. These results imply that phenolic compounds act as specific substrates or signaling molecules for a large group of microbial species in the soil. PMID:23293028

  17. Application of natural blends of phytochemicals derived from the root exudates of Arabidopsis to the soil reveal that phenolic-related compounds predominantly modulate the soil microbiome.

    PubMed

    Badri, Dayakar V; Chaparro, Jacqueline M; Zhang, Ruifu; Shen, Qirong; Vivanco, Jorge M

    2013-02-15

    The roots of plants have the ability to influence its surrounding microbiology, the so-called rhizosphere microbiome, through the creation of specific chemical niches in the soil mediated by the release of phytochemicals. Here we report how these phytochemicals could modulate the microbial composition of a soil in the absence of the plant. For this purpose, root exudates of Arabidopsis were collected and fractionated to obtain natural blends of phytochemicals at various relative concentrations that were characterized by GC-MS and applied repeatedly to a soil. Soil bacterial changes were monitored by amplifying and pyrosequencing the 16 S ribosomal small subunit region. Our analyses reveal that one phytochemical can culture different operational taxonomic units (OTUs), mixtures of phytochemicals synergistically culture groups of OTUs, and the same phytochemical can act as a stimulator or deterrent to different groups of OTUs. Furthermore, phenolic-related compounds showed positive correlation with a higher number of unique OTUs compared with other groups of compounds (i.e. sugars, sugar alcohols, and amino acids). For instance, salicylic acid showed positive correlations with species of Corynebacterineae, Pseudonocardineae and Streptomycineae, and GABA correlated with species of Sphingomonas, Methylobacterium, Frankineae, Variovorax, Micromonosporineae, and Skermanella. These results imply that phenolic compounds act as specific substrates or signaling molecules for a large group of microbial species in the soil. PMID:23293028

  18. Licorice Root

    MedlinePLUS

    ... sweet root, gan zao (Chinese licorice) Latin Name: Glycyrrhiza glabra, Glycyrrhiza uralensis (Chinese licorice) licorice_foster.jpg © Steven Foster ... Sources Armanini D, Fiore C, Bielenberg J. Licorice ( Glycyrrhiza glabra ). In: Coates P, Blackman M, Cragg G, ...

  19. Licorice Root

    MedlinePLUS

    ... sweet root, gan zao (Chinese licorice) Latin Name: Glycyrrhiza glabra, Glycyrrhiza uralensis (Chinese licorice) licorice_foster.jpg © Steven Foster ... References Armanini D, Fiore C, Bielenberg J. Licorice ( Glycyrrhiza glabra ). In: Coates P, Blackman M, Cragg G, ...

  20. Alteration of root growth by lettuce, wheat, and soybean in response to wear debris from automotive brake pads.

    PubMed

    Dodd, Misty D; Ebbs, Stephen D; Gibson, David J; Filip, Peter

    2014-11-01

    Brakes from motor vehicles release brake pad wear debris (BPWD) with increased concentrations of heavy metals. Germination and root-elongation assays with lettuce, wheat, and soybean were used to provide an initial evaluation of the phytotoxicity of either a water extract of BPWD or BPWD particulates. In terms of germination, the only effect observed was that lettuce germination decreased significantly in the BPWD particulate treatment. Lettuce and wheat showed decreased root length and root-elongation rate in the presence of the BPWD particulates, whereas lettuce produced a significantly greater number of lateral roots in response to BPWD extract. There was no significant effect of either BPWD treatment on soybean root elongation or lateral roots. Treatment with BPWD extracts or particulates caused significant alterations in the bending pattern of the plant roots. These initial results suggest that BPWD may have effects on the early growth and development of plants. PMID:24957180

  1. Elongational viscosity of photo-oxidated LDPE

    SciTech Connect

    Rolón-Garrido, Víctor H., E-mail: victor.h.rolongarrido@tu-berlin.de, E-mail: manfred.wagner@tu-berlin.de; Wagner, Manfred H., E-mail: victor.h.rolongarrido@tu-berlin.de, E-mail: manfred.wagner@tu-berlin.de [Chair of Polymer Engineering and Polymer Physics, Berlin Institute of Technology-TU Berlin. Fasanenstr. 90. 10623 Berlin (Germany)

    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.

  2. Referred Visual Sensations: Rapid Perceptual Elongation after Visual Cortical Deprivation

    E-print Network

    Baker, Chris I.

    Visual perceptual distortion (i.e., elongation) has been demonstrated in a single case study after several months of cortical deprivation after a stroke. Here we asked whether similar perceptual elongation can be observed ...

  3. The kinetics of root gravitropism in PIN mutants suggest redundancy in the signal transduction pathway

    NASA Astrophysics Data System (ADS)

    Wolverton, Chris

    As nonmotile organisms, plants rely on differential growth responses to maximize exposure to the resources necessary for growth and reproduction. One of the primary environmental cues causing differential growth in roots is gravity, which is thought to be sensed predominately in the root cap. This gravity perception event is thought to be transduced into information in the form of an auxin gradient across the cap and propagating basipetally toward the elongation zone. The discovery of several families of auxin efflux and influx carriers has provided significant insight into the mechanisms of directional auxin transport, and the identification of mutants in the genes encoding these carriers provides the opportunity to test the roles of these transporters in plant gravitropism. In this study, we report the results of a systematic, high-resolution study of the kinetics of root gravitropism of mutants in the PIN family of auxin efflux carriers. Based on reported expression and localization patterns, we predicted mutations in PIN2, PIN3, PIN4, and PIN7 to cause the greatest reduction in root gravitropism. While pin2 mutants showed severe gravitropic deficiencies in roots as reported previously, several alleles of pin3, pin4 and pin7 remained strongly gravitropic. PIN3 has been localized to the central columella cells, the purported gravisensing cells in the root, and shown to rapidly relocate to the lower flank of the columella cells upon gravistimulation, suggesting an early role in auxin gradient formation. Mutant alleles of PIN3 showed an early delay in response, with just 7 deg of curvature in the first hour compared to approximately 15 deg h-1 in wild-type, but their rate of curvature recovered to near wild-type levels over the ensuing 3 h. Pin3 mutants also showed a slower overall growth rate (124 µm h-1 ), elongating at approximately half the rate of wild-type roots (240 µm h-1 ). PIN4 has been localized to the quiescent center in the root, where it presumably plays a role in efflux to the columella. Pin4 mutants showed no deficiencies in gravitropism, in fact responding at a greater rate than wild-type roots over the first hour (22 deg h-1 ). PIN7 has been localized to the vascular tissue of the elongation zone and to the central columella. Like pin4 mutants, pin7 mutants did not show a significantly reduced gravitropic response relative to wild-type roots. Interestingly, roots of pin3pin7 double mutants showed curvature and growth rates similar to pin7 single mutants and wild-type roots, suggesting a genetic interaction between PIN3 and PIN7 in this pathway. These results suggest a significant degree of redundancy in the regulation of directional auxin transport and perhaps in the gravity signaling pathway in roots in general.

  4. Relation Between the Arc-Root Fluctuations, the Cold Boundary Layer Thickness and the Particle Thermal Treatment

    NASA Astrophysics Data System (ADS)

    Noguès, E.; Fauchais, P.; Vardelle, M.; Granger, P.

    2007-12-01

    In plasma spraying, the arc-root fluctuations, modifying the length and characteristics of the plasma jet, have an important influence on particle thermal treatment. These voltage fluctuations are strongly linked to the thickness of the cold boundary layer (CBL), surrounding the arc column. This thickness depends on the plasma spray parameters (composition and plasma forming gas mass flow rate, arc current, etc.) and the plasma torch design (anode-nozzle internal diameter and shape, etc.). In order to determine the influence of these different spray parameters on the CBL properties and voltage fluctuations, experiments were performed with two different plasma torches from Sulzer Metco. The first one is a PTF4 torch with a cylindrical anode-nozzle, working with Ar-H2 plasma gas mixtures and the second one is a 3MB torch with either a conical or a cylindrical anode-nozzle, working with N2-H2 plasma gas mixtures. Moreover, arc voltage fluctuations influence on particle thermal treatment was studied through the measurements of transient temperature and velocity of particles, issued from an yttria partially stabilized zirconia powder with a size distribution between 5 and 25 ?m.

  5. [Reduction in oxaliplatin-related neurotoxicity by the administration of Keishikajutsubuto(TJ-18)and powdered processed aconite root].

    PubMed

    Yamada, Takeshi; Kan, Hayato; Matsumoto, Satoshi; Koizumi, Michihiro; Sasaki, Junpei; Tani, Aya; Yokoi, Kimiyoshi; Uchida, Eiji

    2012-11-01

    Oxaliplatin (L-OHP)is an important chemotherapeutic drug for the treatment of colorectal cancer. Peripheral neuropathy was observed in 90% of patients who received L-OHP.Neuropathy often results in the discontinuation of treatment or a decrease the quality of life(QOL). The most effective method for reducing neuropathy is the discontinuation of L-OHP. To reduce neuropathy, we administered Keishikajutsubutou(TJ-18)with powdered processed aconite root(TJ-3023), and we report the effect of these compounds. The subjects comprised 11 patients with metastatic colorectal cancer. L-OHP(85mg/m2)was administered as part of the FOLFOX6(10 patients)or FOLFOX7(1 patient)regimen. All patients had experienced neuropathy. We administered TJ-18(7.5 g)and T-3023(1 g). After 2 weeks, the TJ-3023 dose was increased to 2 g for nonresponders. The response was evaluated according to the Neurotoxicity Criteria of DEBIOPHARM. Reduction in neuropathy was observed in 5 cases(45.5% ). Among 6 patients whose feet and hands felt warm, reduction in neuropathy was observed in 5(83.3% ). PMID:23152020

  6. Plant Movement. Submergence-Induced Petiole Elongation in Rumex palustris Depends on Hyponastic Growth1

    PubMed Central

    Cox, Marjolein C.H.; Millenaar, Frank F.; van Berkel, Yvonne E.M. de Jong; Peeters, Anton J.M.; Voesenek, Laurentius A.C.J.

    2003-01-01

    The submergence-tolerant species Rumex palustris (Sm.) responds to complete submergence by an increase in petiole angle with the horizontal. This hyponastic growth, in combination with stimulated elongation of the petiole, can bring the leaf tips above the water surface, thus restoring gas exchange and enabling survival. Using a computerized digital camera set-up the kinetics of this hyponastic petiole movement and stimulated petiole elongation were studied. The hyponastic growth is a relatively rapid process that starts after a lag phase of 1.5 to 3 h and is completed after 6 to 7 h. The kinetics of hyponastic growth depend on the initial angle of the petiole at the time of submergence, a factor showing considerable seasonal variation. For example, lower petiole angles at the time of submergence result in a shorter lag phase for hyponastic growth. This dependency of the hyponastic growth kinetics can be mimicked by experimentally manipulating the petiole angle at the time of submergence. Stimulated petiole elongation in response to complete submergence also shows kinetics that are dependent on the petiole angle at the time of submergence, with lower initial petiole angles resulting in a longer lag phase for petiole elongation. Angle manipulation experiments show that stimulated petiole elongation can only start when the petiole has reached an angle of 40° to 50°. The petiole can reach this “critical angle” for stimulated petiole elongation by the process of hyponastic growth. This research shows a functional dependency of one response to submergence in R. palustris (stimulated petiole elongation) on another response (hyponastic petiole growth), because petiole elongation can only contribute to the leaf reaching the water surface when the petiole has a more or less upright position. PMID:12746533

  7. Functional Diversity of Culturable Bacterial Communities in the Rhizosphere in Relation to Fine-root and Soil Parameters in Alder Stands on Forest, Abandoned Agricultural, and Oil-shale Mining Areas

    Microsoft Academic Search

    K. Lõhmus; M. Truu; J. Truu; I. Ostonen; E. Kaar; A. Vares; V. Uri; S. Alama; A. Kanal

    2006-01-01

    Grey alder (Alnus incana) and black alder (Alnus glutinosa) stands on forest land, abandoned agricultural, and reclaimed oil-shale mining areas were investigated with the aim of analysing\\u000a the functional diversity and activity of microbial communities in the soil–root interface and in the bulk soil in relation\\u000a to fine-root parameters, alder species, and soil type. Biolog Ecoplates were used to determine

  8. Temporal and soil depth-related variation in soil enzyme activities and in root growth of red clover ( Trifolium pratense) and timothy ( Phleum pratense) in the field

    Microsoft Academic Search

    R. M. Niemi; M. Vepsäläinen; K. Wallenius; S. Simpanen; L. Alakukku; L. Pietola

    2005-01-01

    Activities of 12 different enzymes in soil and growth of timothy (Phleum pratense) and red clover (Trifolium pratense) roots were monitored on fine sand soil (Aquic Haplocryoll) throughout the third growing season of the plants. Both root biomass and enzyme activities decreased with increasing soil depth. The root biomass depended on the plant, the soil depth and the date within

  9. Root gravitropism: a complex response to a simple stimulus?

    NASA Technical Reports Server (NTRS)

    Rosen, E.; Chen, R.; Masson, P. H.

    1999-01-01

    Roots avoid depleting their immediate environment of essential nutrients by continuous growth. Root growth is directed by environmental cues, including gravity. Gravity sensing occurs mainly in the columella cells of the root cap. Upon reorientation within the gravity field, the root-cap amyloplasts sediment, generating a physiological signal that promotes the development of a curvature at the root elongation zones. Recent molecular genetic studies in Arabidopsis have allowed the identification of genes that play important roles in root gravitropism. Among them, the ARG1 gene encodes a DnaJ-like protein involved in gravity signal transduction, whereas the AUX1 and AGR1 genes encode proteins involved in polar auxin transport. These studies have important implications for understanding the intra- and inter-cellular signaling processes that underlie root gravitropism.

  10. Soil conditions and cereal root system architecture: review and considerations for linking Darwin and Weaver.

    PubMed

    Rich, Sarah M; Watt, Michelle

    2013-03-01

    Charles Darwin founded root system architecture research in 1880 when he described a root bending with gravity. Curving, elongating, and branching are the three cellular processes in roots that underlie root architecture. Together they determine the distribution of roots through soil and time, and hence the plants' access to water and nutrients, and anchorage. Most knowledge of these cellular processes comes from seedlings of the model dicotyledon, Arabidopsis, grown in soil-less conditions with single treatments. Root systems in the field, however, face multiple stimuli that interact with the plant genetics to result in the root system architecture. Here we review how soil conditions influence root system architecture; focusing on cereals. Cereals provide half of human calories, and their root systems differ from those of dicotyledons. We find that few controlled-environment studies combine more than one soil stimulus and, those that do, highlight the complexity of responses. Most studies are conducted on seedling roots; those on adult roots generally show low correlations to seedling studies. Few field studies report root and soil conditions. Until technologies are available to track root architecture in the field, soil analyses combined with knowledge of the effects of factors on elongation and gravitropism could be ranked to better predict the interaction between genetics and environment (G×E) for a given crop. Understanding how soil conditions regulate root architecture can be effectively used to design soil management and plant genetics that best exploit synergies from G×E of roots. PMID:23505309

  11. Root fortification.

    PubMed

    Seghi, Robert R; Nasrin, Sadia; Draney, Jonathan; Katsube, Noriko

    2013-03-01

    An incompletely formed tooth is left with thin dentin walls and experiences a higher incidence of cervical root fracture that reduces the long-term overall prognosis of the tooth. Faced with these situations, clinicians have attempted to use various restorative methods to reinforce the remaining root. Various techniques have been reported, and the scientific evidence for each has been reviewed. The biomechanical considerations of reinforcing a weakened root are also reviewed, and the most current information about failure analysis, fracture characteristics of natural dentin, and in vitro test configurations used have been considered. In light of these additional considerations, some recommendations for future understanding of this complex problem have been proposed. PMID:23439045

  12. Gravity Signal Transduction in Primary Roots

    PubMed Central

    PERRIN, ROBYN M.; YOUNG, LI-SEN; NARAYANA MURTHY, U.M.; HARRISON, BENJAMIN R.; WANG, YAN; WILL, JESSICA L.; MASSON, PATRICK H.

    2005-01-01

    • Aims The molecular mechanisms that correlate with gravity perception and signal transduction in the tip of angiosperm primary roots are discussed. • Scope Gravity provides a cue for downward orientation of plant roots, allowing anchorage of the plant and uptake of the water and nutrients needed for growth and development. Root gravitropism involves a succession of physiological steps: gravity perception and signal transduction (mainly mediated by the columella cells of the root cap); signal transmission to the elongation zone; and curvature response. Interesting new insights into gravity perception and signal transduction within the root tip have accumulated recently by use of a wide range of experimental approaches in physiology, biochemistry, genetics, genomics, proteomics and cell biology. The data suggest a network of signal transduction pathways leading to a lateral redistribution of auxin across the root cap and a possible involvement of cytokinin in initial phases of gravicurvature. • Conclusion These new discoveries illustrate the complexity of a highly redundant gravity-signalling process in roots, and help to elucidate the global mechanisms that govern auxin transport and morphogenetic regulation in roots. PMID:16033778

  13. The cotton transcription factor TCP14 functions in auxin-mediated epidermal cell differentiation and elongation.

    PubMed

    Wang, Miao-Ying; Zhao, Pi-Ming; Cheng, Huan-Qing; Han, Li-Bo; Wu, Xiao-Min; Gao, Peng; Wang, Hai-Yun; Yang, Chun-Lin; Zhong, Nai-Qin; Zuo, Jian-Ru; Xia, Gui-Xian

    2013-07-01

    Plant-specific TEOSINTE-BRANCHED1/CYCLOIDEA/PCF (TCP) transcription factors play crucial roles in development, but their functional mechanisms remain largely unknown. Here, we characterized the cellular functions of the class I TCP transcription factor GhTCP14 from upland cotton (Gossypium hirsutum). GhTCP14 is expressed predominantly in fiber cells, especially at the initiation and elongation stages of development, and its expression increased in response to exogenous auxin. Induced heterologous overexpression of GhTCP14 in Arabidopsis (Arabidopsis thaliana) enhanced initiation and elongation of trichomes and root hairs. In addition, root gravitropism was severely affected, similar to mutant of the auxin efflux carrier PIN-FORMED2 (PIN2) gene. Examination of auxin distribution in GhTCP14-expressing Arabidopsis by observation of auxin-responsive reporters revealed substantial alterations in auxin distribution in sepal trichomes and root cortical regions. Consistent with these changes, expression of the auxin uptake carrier AUXIN1 (AUX1) was up-regulated and PIN2 expression was down-regulated in the GhTCP14-expressing plants. The association of GhTCP14 with auxin responses was also evidenced by the enhanced expression of auxin response gene IAA3, a gene in the AUXIN/INDOLE-3-ACETIC ACID (Aux/IAA) family. Electrophoretic mobility shift assays showed that GhTCP14 bound the promoters of PIN2, IAA3, and AUX1, and transactivation assays indicated that GhTCP14 had transcription activation activity. Taken together, these results demonstrate that GhTCP14 is a dual-function transcription factor able to positively or negatively regulate expression of auxin response and transporter genes, thus potentially acting as a crucial regulator in auxin-mediated differentiation and elongation of cotton fiber cells. PMID:23715527

  14. Molecular Mobility of Soft Segment of Polyurethane Elastomers under Elongation

    NASA Astrophysics Data System (ADS)

    Kojio, Ken; Shimada, Makoto; Motokucho, Suguru; Furukawa, Mutsuhisa

    2008-07-01

    In this study, we investigated molecular mobility of a soft segment in the poly(oxypropylene) glycol (PPG), 4,4'-diphenylmethane diisocyanate (MDI) and 1,4-butane diol (BD)-based polyurethane elastomers (PUE) with and without elongation by dynamic viscoelastic property measurement and pulse nuclear magnetic resonance (NMR) measurement. The peak position of the loss tangent (tand) curves shifted to the lower temperature region with increasing elongation. In the pulse NMR measurement, the long spin-spin relaxation time (T2) component appeared at -18.0(? = 0) and -26.0 °C(? = 1.5), respectively, with increasing temperature. Since this temperature seems to be related to the glass transition temperature (Tg) of the soft segment in the PUE, it is likely to consider that the Tg decreased with increasing strain. These results might be attributed that the size of cooperative motion during the glass transition decrease due to the orientation of the soft segment, and the soft segment phase approach to a pure phase on account of the extraction of the hard segment from the soft segment phase.

  15. Chromosome end elongation by recombination in the mosquito Anopheles gambiae.

    PubMed Central

    Roth, C W; Kobeski, F; Walter, M F; Biessmann, H

    1997-01-01

    One of the functions of telomeres is to counteract the terminal nucleotide loss associated with DNA replication. While the vast majority of eukaryotic organisms maintain their chromosome ends via telomerase, an enzyme system that generates short, tandem repeats on the ends of chromosomes, other mechanisms such as the transposition of retrotransposons or recombination can also be used in some species. Chromosome end regression and extension were studied in a medically important mosquito, the malaria vector Anopheles gambiae, to determine how this dipteran insect maintains its chromosome ends. The insertion of a transgenic pUChsneo plasmid at the left end of chromosome 2 provided a unique marker for measuring the dynamics of the 2L telomere over a period of about 3 years. The terminal length was relatively uniform in the 1993 population with the chromosomes ending within the white gene sequence of the inserted transgene. Cloned terminal chromosome fragments did not end in short repeat sequences that could have been synthesized by telomerase. By late 1995, the chromosome ends had become heterogeneous: some had further shortened while other chromosomes had been elongated by regenerating part of the integrated pUChsneo plasmid. A model is presented for extension of the 2L chromosome by recombination between homologous 2L chromosome ends by using the partial plasmid duplication generated during its original integration. It is postulated that this mechanism is also important in wild-type telomere elongation. PMID:9271395

  16. An attempt to estimate out-of-plane lung nodule elongation in tomosynthesis images

    NASA Astrophysics Data System (ADS)

    Chodorowski, Artur; Arvidsson, Jonathan; Söderman, Christina; Svalkvist, Angelica; Johnsson, Šse A.; Bâth, Magnus

    2015-03-01

    In chest tomosynthesis (TS) the most commonly used reconstruction methods are based on Filtered Back Projection (FBP) algorithms. Due to the limited angular range of x-ray projections, FBP reconstructed data is typically associated with a low spatial resolution in the out-of-plane dimension. Lung nodule measures that depend on depth information such as 3D shape and volume are therefore difficult to estimate. In this paper the relation between features from FBP reconstructed lung nodules and the true out-of-plane nodule elongation is investigated and a method for estimating the out-of-plane nodule elongation is proposed. In order to study these relations a number of steps that include simulation of spheroidal-shaped nodules, insertion into synthetic data volumes, construction of TS-projections and FBP-reconstruction were performed. In addition, the same procedure was used to simulate nodules and insert them into clinical chest TS projection data. The reconstructed nodule data was then investigated with respect to in-plane diameter, out-of-plane elongation, and attenuation coefficient. It was found that the voxel value in each nodule increased linearly with nodule elongation, for nodules with a constant attenuation coefficient. Similarly, the voxel value increased linearly with in-plane diameter. These observations indicate the possibility to predict the nodule elongation from the reconstructed voxel intensity values. Such a method would represent a quantitative approach to chest tomosynthesis that may be useful in future work on volume and growth rate estimation of lung nodules.

  17. Effect of phorbol derivatives and staurosporine on growth of primary root of maize

    SciTech Connect

    Kim, S.Y.; Mulkey, T.J. (Indiana State Univ., Terre Haute (United States)); Lee, J.S. (Ewha Womans Univ., Seoul (Korea))

    1991-05-01

    A computer-based auxanometer system was used to examine the effects of phorbol derivatives (phorbol 12-myristate 13-acetate, TPA; phorbol 12-myristate 13-acetate 4-O-methyl ether, mTPA) and staurosporine on elongation of the primary roots of maize (Zea mays L., Pioneer 3343 and Golden Cross Bantam). TPA induces a biphasic promotion of elongation maize roots. Initially, TPA (1{mu}M) promotes elongation by 60% within 30 min. The increase in the rate of elongation is maintained for 30 min prior to a decline in rate to the initial rate over a 10 min period. A second increase in elongation rate begins 1.25 hours after the initial application of TPA with a maximal elongation rate of 210% observed 2.75 hrs after treatment. mTPA, the inactive analog of TPA, promotes elongation by < 10% during the initial phase and < 20% during the second phase elongation. Staurosporine (10{sup {minus}8}M), a microbial alkaloid which has been reported to have antifungal activity and to inhibit phospholipid/Ca{sup ++} dependent protein kinase, completely inhibits TPS-induced elongation. DAG (1-oleoyl-2-acetyl-rac-glycerol), a synthetic diglyceride activator of protein kinase C, exhibits similar activity to TPA. TPA-induced alterations in tissue response to calcium will be presented.

  18. Distinct modes of adventitious rooting in Arabidopsis thaliana.

    PubMed

    Correa, L da Rocha; Troleis, J; Mastroberti, A A; Mariath, J E A; Fett-Neto, A G

    2012-01-01

    The literature describes different rooting protocols for Arabidopsis thaliana as models to study adventitious rooting, and results are generally perceived as comparable. However, there is a lack of investigations focusing on the distinct features, advantages and limitations of each method in the study of adventitious rooting with both wild-type (WT) ecotypes and their respective mutants. This investigation was undertaken to evaluate the adventitious rooting process in three different experimental systems, all using A. thaliana, analysing the same rooting parameters after transient exposure to auxin (indole-3-acetic acid) and control conditions: excised leaves, de-rooted plants and etiolated seedlings. The founding tissues and sites of origin of roots differed depending on the system used, whereas all rooting patterns were of the direct type (i.e., without callus formation). None of the systems had an absolute requirement for exogenous auxin, although rooting was enhanced by this phytohormone, with the exception of de-rooted plants, which had adventitious rooting strongly inhibited by exogenous auxin. Root elongation was much favoured in isolated leaves. Auxin-overproducing mutants could not be used in the detached leaf system due to precocious senescence; in the de-rooted plant system, these mutants had a WT-like rooting response, whereas the expression of the 'rooty' phenotype was only evident in the etiolated seedling system. Adventitious rooting of etiolated WT seedlings in the presence of exogenous auxin was inhibited by exogenous flavonoids, which act as auxin transport inhibitors; surprisingly, the flavonoid-deficient mutant chs had a lower rooting response compared to WT. Although Arabidopsis is an excellent model system to study adventitious rooting, physiological and developmental responses differed significantly, underlining the importance of avoiding data generalisation on rooting responses derived from different experimental systems with this species. PMID:21974782

  19. A screening method to identify genetic variation in root growth response to a salinity gradient.

    PubMed

    Rahnama, Afrasyab; Munns, Rana; Poustini, Kazem; Watt, Michelle

    2011-01-01

    Salinity as well as drought are increasing problems in agriculture. Durum wheat (Triticum turgidum L. ssp. durum Desf.) is relatively salt sensitive compared with bread wheat (Triticum aestivum L.), and yields poorly on saline soil. Field studies indicate that roots of durum wheat do not proliferate as extensively as bread wheat in saline soil. In order to look for genetic diversity in root growth within durum wheat, a screening method was developed to identify genetic variation in rates of root growth in a saline solution gradient similar to that found in many saline fields. Seedlings were grown in rolls of germination paper in plastic tubes 37 cm tall, with a gradient of salt concentration increasing towards the bottom of the tubes which contained from 50-200 mM NaCl with complete nutrients. Seedlings were grown in the light to the two leaf stage, and transpiration and evaporation were minimized so that the salinity gradient was maintained. An NaCl concentration of 150 mM at the bottom was found suitable to identify genetic variation. This corresponds to a level of salinity in the field that reduces shoot growth by 50% or more. The screen inhibited seminal axile root length more than branch root length in three out of four genotypes, highlighting changes in root system architecture caused by a saline gradient that is genotype dependent. This method can be extended to other species to identify variation in root elongation in response to gradients in salt, nutrients, or toxic elements. PMID:21118825

  20. ETIOLATION AND AVOCADO BUD ELONGATION IN VITRO

    Microsoft Academic Search

    C. A. Schroeder

    Several lines of investigation on the behavior of specific tissue pieces of avocado plant axis, flower, and fruit indicate that the species can be maintained for long periods of time as a continuously growing callus mass from which well developed roots can be induced occasionally (4). Likewise the generation of callus tissue from pericarp cells, while not a unique characteristic,

  1. Adventitious rooting bioassay for auxin-like activity in extracts of Salix (Salicaceae) and Ascophyllum (Phaeophyceae)

    Microsoft Academic Search

    Brian Basor

    Auxins are a constant source of study by plant physiologists because of their involvement in many aspects of cellular function: cell elongation, phototropism, apical dominance, and root initiation. The project objective was to test this null hypothesis: H0 = Extracts of kelp and willow will have no effect on adventitious root formation of cuttings. For both the bean hypocotyl cuttings

  2. Dynamics of heterorhizic root systems: protoxylem groups within the fine-root system of Chamaecyparis obtusa.

    PubMed

    Hishi, Takuo; Takeda, Hiroshi

    2005-08-01

    To understand the physiology of fine-root functions in relation to soil organic sources, the heterogeneity of individual root functions within a fine-root system requires investigation. Here the heterogeneous dynamics within fine-root systems are reported. The fine roots of Chamaecyparis obtusa were sampled using a sequential ingrowth core method over 2 yr. After color categorization, roots were classified into protoxylem groups from anatomical observations. The root lengths with diarch and triarch groups fluctuated seasonally, whereas the tetrarch root length increased. The percentage of secondary root mortality to total mortality increased with increasing amounts of protoxylem. The carbon : nitrogen ratio indicated that the decomposability of primary roots might be greater than that of secondary roots. The position of diarch roots was mostly apical, whereas tetrarch roots tended to be distributed in basal positions within the root architecture. We demonstrate the heterogeneous dynamics within a fine-root system of C. obtusa. Fine-root heterogeneity should affect soil C dynamics. This heterogeneity is determined by the branching position within the root architecture. PMID:15998402

  3. Root tensile strength of grey alder and mountain maple grown on a coarse grained eco-engineered slope in the Swiss Alps related to wood anatomical features

    NASA Astrophysics Data System (ADS)

    Kink, Dimitri; Bast, Alexander; Meyer, Christine; Meier, Wolfgang; Egli, Markus; Gärtner, Holger

    2014-05-01

    Steep, vegetation free slopes are a common feature in alpine areas. The material covering these slopes is prone to all kind of erosional processes, resulting in a high risk potential for population and infrastructure. This risk potential is likely to increase with the predicted change in the spatiotemporal distribution of precipitation events. A potential increase in extreme precipitation events will also result in a higher magnitude and frequency of erosional processes. In the Swiss Alps as in many other mountainous areas, there is a need to stabilize these slopes to reduce their direct or indirect hazard potential. In this regard, eco-engineering is a very promising and sustainable approach for slope stabilization. Planting trees and shrubs is a central task in eco-engineering. A developing vegetation cover will on one hand reduce the mechanical effects of rainfall by an increased interception, on the other hand, the root systems cause modifications of soil properties. Roots not only provide anchorage for the plants, they also promote soil aggregation and are able to penetrate possible shear horizons. Overall, anchorage of plants is at the same extend also stabilizing the near subsurface. When rainfall occurs, the saturated soil exerts downhill pressure to a tree or shrub. As long as the root distribution supports anchorage, the respective slope area remains stable. At this point, the tensile strength of the roots is a critical measure, because it is more likely that the supporting roots break than the entire root system being pulled out of the soil completely. As a consequence, root tensile strength is an important parameter in characterizing the soil stabilization potential of trees and shrubs. It is known that tree roots show a high variability in their anatomical structure depending on their depth below soil surface as well as their distance to the main stem. Therefore, we assume that these structural changes affect the tensile strength of every single root. In order to confirm this assumption and possibly find more important root properties which have an influence on soil stabilization, the root systems of seven trees (three grey alder, four mountain maple) were excavated and analyzed. The study site is a catchment, where shallow landslides are common. It is located in the Prättigau valley in the Eastern Swiss Alps and was eco-engineered in 1997. The substrate is coarse-grained morainic material, mean annual air temperature reaches 4.64°C, average precipitation is 1170 mm, and the altitude is about 1000 m a.s.l.. The root system of each tree was uncovered carefully by hand to keep the roots undamaged, before removal it was photographed in situ to document the root distribution. The root systems were then cut into single root pieces of about 20 cm length and the position of each sample was documented. The root samples were then hierarchically classified in several root classes. The tensile strength of more than 500 samples was determined. In addition, the values for age, diameter, and root moisture were ascertained. Since it was assumed, that the cellular structure of the roots has an influence on the tensile strength, two microscopic thin-sections were prepared from all successfully tested root samples. The microscopic analysis focused on anatomical parameters such as the size and number of vessels, their distribution as well as their conductivity. The results for the final correlation between the anatomical characteristics and the root's tensile strength are presented for both tree species.

  4. Root Formation in Ethylene-Insensitive Plants1

    PubMed Central

    Clark, David G.; Gubrium, Erika K.; Barrett, James E.; Nell, Terril A.; Klee, Harry J.

    1999-01-01

    Experiments with ethylene-insensitive tomato (Lycopersicon esculentum) and petunia (Petunia × hybrida) plants were conducted to determine if normal or adventitious root formation is affected by ethylene insensitivity. Ethylene-insensitive Never ripe (NR) tomato plants produced more belowground root mass but fewer aboveground adventitious roots than wild-type Pearson plants. Applied auxin (indole-3-butyric acid) increased adventitious root formation on vegetative stem cuttings of wild-type plants but had little or no effect on rooting of NR plants. Reduced adventitious root formation was also observed in ethylene-insensitive transgenic petunia plants. Applied 1-aminocyclopropane-1-carboxylic acid increased adventitious root formation on vegetative stem cuttings from NR and wild-type plants, but NR cuttings produced fewer adventitious roots than wild-type cuttings. These data suggest that the promotive effect of auxin on adventitious rooting is influenced by ethylene responsiveness. Seedling root growth of tomato in response to mechanical impedance was also influenced by ethylene sensitivity. Ninety-six percent of wild-type seedlings germinated and grown on sand for 7 d grew normal roots into the medium, whereas 47% of NR seedlings displayed elongated taproots, shortened hypocotyls, and did not penetrate the medium. These data indicate that ethylene has a critical role in various responses of roots to environmental stimuli. PMID:10482660

  5. [Ultrastructure of statocytes and cells of distal elongation zone of Arabidopsis thaliana under clinorotation].

    PubMed

    Romanchuk, S M

    2010-01-01

    Results of the electron-microscopic investigation of root apices of Arabidopsis thaliana 3-, 5- and 7-days-old seedlings grown in the stationary conditions and under clinorotation are presented. It was shown the similarity in the root apex cell ultrastructure in control and under clinorotation. At the same time there were some differences in the ultrastructure of statocytes and the distal elongation zone under clinorotation. For the first time the sensitivity of ER-bodies, which are derivatives of GER and contain beta-glucosidase, to the influence of simulated microgravity was demonstrated by increased quantity and area of ER-bodies at the cell section as well as by higher variability of their form under clinorotation. A degree of these changes correlated with the duration of clinorotation. On the basis of experimental data a protective role of ER-bodies in adaptation of plants to microgravity is supposed. PMID:21254615

  6. Proteome of Soybean Seed Exudates Contains Plant Defense-Related Proteins Active against the Root-Knot Nematode Meloidogyne incognita.

    PubMed

    Rocha, Raquel O; Morais, Janne K S; Oliveira, Jose T A; Oliveira, Hermogenes D; Sousa, Daniele O B; Souza, Carlos Eduardo A; Moreno, Frederico B; Monteiro-Moreira, Ana Cristina O; Antonino de Souza Júnior, José Dijair; Grossi de Sá, Maria F; Vasconcelos, Ilka M

    2015-06-10

    Several studies have described the effects of seed exudates against microorganisms, but only few of them have investigated the proteins that have defensive activity particularly against nematode parasites. This study focused on the proteins released in the exudates of soybean seeds and evaluated their nematicidal properties against Meloidogyne incognita. A proteomic approach indicated the existence of 63 exuded proteins, including ?-1,3-glucanase, chitinase, lectin, trypsin inhibitor, and lipoxygenase, all of which are related to plant defense. The presence of some of these proteins was confirmed by their in vitro activity. The soybean exudates were able to reduce the hatching of nematode eggs and to cause 100% mortality of second-stage juveniles (J2). The pretreatment of J2 with these exudates resulted in a 90% reduction of the gall number in tobacco plants. These findings suggest that the exuded proteins are directly involved in plant defense against soil pathogens, including nematodes, during seed germination. PMID:26034922

  7. Copper compounds influence in vitro rooting of birch microcuttings

    SciTech Connect

    Arnold, M.A.; Lineberger, R.D.; Struve, D.K. (Ohio State Univ., Columbus, OH (United States). Dept. of Horticulture)

    1994-01-01

    The effects of woody plant medium (WPM) with various formulations and concentrations of Cu[sup 2+] on in vitro rooting and subsequent shoot growth of microcuttings of a Betula pubescens x papyrifera clone were monitored for 28 days. Adventitious root initiation and elongation were reduced in magnitude and slowed in development by moderate to high Cu concentrations, with near zero root regeneration occurring at 157 [mu]M Cu. Shoot growth was also inhibited by 157 [mu]m Cu as cupric sulfate. Copper-toxicity symptoms were significantly increased by moderate to high levels of Cu as cuptric sulfate. Microcuttings responded differently to Cu[sup 2+] applied as cupric chloride. Root imitation, root elongation, and root branching were increased by moderate concentrations of Cu as cupric chloride. Shoot growth was slightly stimulated by cuptric chloride at moderate levels. No significant increase in Cu-toxicity symptoms was observed at concentrations up to 157 [mu]M Cu as cupric chloride. Cupric acetate and cupric carbonate produced more severe Cu-toxicity symptoms than cupric sulfate. Root regeneration and shoot growth were inhibited and increased Cu-toxicity symptoms were apparent even with low concentrations of Cu as cupric acetate or cupric carbonate. There was little or no effect on root regeneration when the Cu[sup 2+] in cupric sulfate was replaced by different cations, i.e., magnesium sulfate, calcium sulfate, and sulfuric acid.

  8. A Chemical Kinetic Model of Transcriptional Elongation

    E-print Network

    Yujiro Richard Yamada; Charles S. Peskin

    2006-05-23

    A chemical kinetic model of the elongation dynamics of RNA polymerase along a DNA sequence is introduced. The proposed model governs the discrete movement of the RNA polymerase along a DNA template, with no consideration given to elastic effects. The model's novel concept is a ``look-ahead'' feature, in which nucleotides bind reversibly to the DNA prior to being incorporated covalently into the nascent RNA chain. Results are presented for specific DNA sequences that have been used in single-molecule experiments of the random walk of RNA polymerase along DNA. By replicating the data analysis algorithm from the experimental procedure, the model produces velocity histograms, enabling direct comparison with these published results.

  9. Immiscible blend morphology after shear and elongation

    NASA Astrophysics Data System (ADS)

    Batch, Gibson L.; Trifkovic, Milana; Hedegaard, Aaron; Macosko, Christopher W.

    2015-05-01

    This work examines the role of shear and extensional strain on immiscible blend morphology, namely domain size, orientation, and co-continuity. The domain size reduces with surface tension similar to what is observed with isolated droplets. The domain size is shown to increase with shear strain due to coalescence. Hence the best mixing is found with low shear strains, i.e. low rates of shear and short durations of time. Extensional strain (extrusion draw ratio DR) reduces phase width and thickness with a DR-0.5 dependence, suggesting the transformation to a fibrilar morphology. The critical draw ratio for morphology transformation is approximately 7, in agreement with observations by Grace for droplet breakup in elongation. Fibrilar morphology is also consistent with a large increase in strain-to-break in the drawn film and with observed creep and optical scattering behavior.

  10. Genetic improvement for root growth angle to enhance crop production

    PubMed Central

    Uga, Yusaku; Kitomi, Yuka; Ishikawa, Satoru; Yano, Masahiro

    2015-01-01

    The root system is an essential organ for taking up water and nutrients and anchoring shoots to the ground. On the other hand, the root system has rarely been regarded as breeding target, possibly because it is more laborious and time-consuming to evaluate roots (which require excavation) in a large number of plants than aboveground tissues. The root growth angle (RGA), which determines the direction of root elongation in the soil, affects the area in which roots capture water and nutrients. In this review, we describe the significance of RGA as a potential trait to improve crop production, and the physiological and molecular mechanisms that regulate RGA. We discuss the prospects for breeding to improve RGA based on current knowledge of quantitative trait loci for RGA in rice.

  11. The social vagina: labia elongation and social capital among women in Rwanda.

    PubMed

    Larsen, Josefine

    2010-10-01

    Far from being an individual concern, vaginas are located within complex socio-cultural settings. The acceptability of policies that focus on health-promoting behavioural change is influenced by values regarding normative gender and sexual roles. In Rwanda, the elongation of the labia minora through manual manipulation is not an individual act but takes place in social groups and thus cannot be fully understood by focusing one's attention solely on the individual-related behavioural components but, rather, on the social environment in which it exists. This paper aims to increase knowledge about labia elongation and assesses whether this vaginal practice produce social capital. PMID:20665297

  12. Comparative investigation of primary and tertiary endodermal cell walls isolated from the roots of five monocotyledoneous species: chemical composition in relation to fine structure

    Microsoft Academic Search

    Jürgen Zeier; Lukas Schreiber

    1998-01-01

    .   The chemical composition of isolated endodermal cell walls from the roots of the five monocotyledoneous species Monstera deliciosa Liebm., Iris germanica L., Allium cepa L., Aspidistra elatior Bl. and Agapanthus africanus (L.) Hoffmgg. was determined. Endodermal cell walls isolated from aerial roots of M. deliciosa were in their primary developmental state (Casparian bands). They contained large amounts of lignin

  13. Transcriptome profiling of leaf elongation zone under drought in contrasting rice cultivars.

    PubMed

    Cal, Andrew J; Liu, Dongcheng; Mauleon, Ramil; Hsing, Yue-Ie Caroline; Serraj, Rachid

    2013-01-01

    Inhibition of leaf elongation and expansion is one of the earliest responses of rice to water deficit. Despite this sensitivity, a great deal of genetic variation exists in the extant of leaf elongation rate (LER) reduction in response to declining soil moisture. We analyzed global gene expression in the leaf elongation zone under drought in two rice cultivars with disparate LER sensitivities to water stress. We found little overlap in gene regulation between the two varieties under moderate drought; however, the transcriptional response to severe drought was more conserved. In response to moderate drought, we found several genes related to secondary cell wall deposition that were down regulated in Moroberekan, an LER tolerant variety, but up-regulated in LER sensitive variety IR64. PMID:23372737

  14. Crystal structure of elongation factor 4 bound to a clockwise ratcheted ribosome.

    PubMed

    Gagnon, Matthieu G; Lin, Jinzhong; Bulkley, David; Steitz, Thomas A

    2014-08-01

    Elongation factor 4 (EF4/LepA) is a highly conserved guanosine triphosphatase translation factor. It was shown to promote back-translocation of tRNAs on posttranslocational ribosome complexes and to compete with elongation factor G for interaction with pretranslocational ribosomes, inhibiting the elongation phase of protein synthesis. Here, we report a crystal structure of EF4-guanosine diphosphate bound to the Thermus thermophilus ribosome with a P-site tRNA at 2.9 angstroms resolution. The C-terminal domain of EF4 reaches into the peptidyl transferase center and interacts with the acceptor stem of the peptidyl-tRNA in the P site. The ribosome is in an unusual state of ratcheting with the 30S subunit rotated clockwise relative to the 50S subunit, resulting in a remodeled decoding center. The structure is consistent with EF4 functioning either as a back-translocase or a ribosome sequester. PMID:25104389

  15. Spinal Elongation and its Effects on Seated Height in a Microgravity Environment

    NASA Technical Reports Server (NTRS)

    Rajulu, Sudhakar; Young, Karen

    2009-01-01

    Objectives: 1. To collect spinal elongation induced seated height data for subjects exposed to microgravity environments. 2. To provide information relating to the seated height rate of change over time for astronauts subjected to microgravity. We will collect: Seated Height measurement (ground & flight) and digital still photograph (ground and flight).

  16. Comparative Elongated Mineral Particle Toxicology & Erionite?s Apparent  High Potency for Inducing Mesothelioma

    EPA Science Inventory

    Recent NHEERL research under EPA's Libby Action Plan has determined that elongated particle relative potency for rat pleural mesothelioma is best predicted on the basis of total external surface area (TSA) of slightly acid leached test samples which simulate particle bio-durabili...

  17. Analysis of harmonics for an elongated FTMS cell with multiple electrode detection

    Microsoft Academic Search

    E. N. Nikolaev; V. S. Rakov; J. H. Futrell

    1996-01-01

    The form of FTMS signals is analyzed for the general case of multiple electrode ICR cells with detailed results for two, eight and sixteen electrodes. The analysis is based on an elongated cylindrical cell to reduce the problem of treating the electric field distribution to two dimensions. The relative contributions of cyclotron and magnetron motion to the detected signal are

  18. CIRCADIAN CLOCK ASSOCIATED1 and LATE ELONGATED HYPOCOTYL Function Synergistically in

    E-print Network

    Tobin, Elaine

    ASSOCIATED1 (CCA1) and LATE ELONGATED HYPOCOTYL (LHY) are Myb-related proteins that function in or close and molecular processes in organisms ranging from cyanobacteria to humans. In plants, leaf movements, stomata also been suggested to function in or close to the central oscillator (Doyle et al., 2002; Hazen et al

  19. Hormonal interactions during cluster-root development in phosphate-deficient white lupin (Lupinus albus L.).

    PubMed

    Wang, Zhengrui; Rahman, A B M Moshiur; Wang, Guoying; Ludewig, Uwe; Shen, Jianbo; Neumann, Günter

    2015-04-01

    This study addresses hormonal interactions involved in cluster-root (CR) development of phosphate (Pi)-deficient white lupin (Lupinus albus), which represents the most efficient plant strategy for root-induced mobilisation of sparingly soluble soil phosphorus (P) sources. Shoot-to-root translocation of auxin was unaffected by P-limitation, while strong stimulatory effects of external sucrose on CR formation, even in P-sufficient plants, suggest sucrose, rather than auxins, acts as a shoot-borne signal, triggering the induction of CR primordia. Ethylene may act as mediator of the sucrose signal, as indicated by moderately increased expression of genes involved in ethylene biosynthesis in pre-emergent clusters and by strong inhibitory effects of the ethylene antagonist CoCl2 on CR formation induced by sucrose amendments or P-limitation. As reported in other plants, moderately increased production of brassinosteroids (BRs) and cytokinin, in pre-emergent clusters, may be required for the formation of auxin gradients necessary for induction of CR primordia via interference with auxin biosynthesis and transport. The well-documented inhibition of root elongation by high doses of ethylene may be involved in the growth inhibition of lateral rootlets during CR maturation, indicated by a massive increased expression of gene involved in ethylene production, associated with a declined expression of transcripts with stimulatory effects (BR and auxin-related genes). PMID:25668414

  20. Root Communication: The Role of Root Exudates

    Microsoft Academic Search

    B. Prithiviraj; Mark W. Paschke; Jorge M. Vivanco

    Plants communicate with neighboring plants and other organisms surrounding them. Aboveground communication isarticulatedthroughstems,leaves,orflowerswhilebelow-groundcommunication ismedi- ated by roots. The plant root is capable of secreting chemicals into the rhizosphere through root exudates. Thechemicalconstituentsoftherootexudatesarecharacteristicofaparticularplantspeciesandalsodepend on the surrounding biotic and abiotic environment. Recent research suggests that the root exudates act as a sort of chemical 'language' between the secreting plant and other organisms

  1. Jasmonate-dependent alkaloid biosynthesis in Catharanthus Roseus hairy root cultures is correlated with the relative expression of Orca and Zct transcription factors.

    PubMed

    Goklany, Sheba; Rizvi, Noreen F; Loring, Ralph H; Cram, Erin J; Lee-Parsons, Carolyn W T

    2013-01-01

    The effects of methyl jasmonate (MJ) dosage on terpenoid indole alkaloid (TIA) biosynthesis in Catharanthus roseus are correlated with the relative levels of specific MJ-responsive transcription factors. In this study, the expression of transcription factors (Orca, Zct, Gbf, Myc2, At-hook, and Wrky1), TIA pathway genes (G10h, Tdc, Str, and Sgd), and TIA metabolites (secologanin, strictosidine, and tabersonine) were investigated in C. roseus hairy root cultures elicited with a range of MJ dosages (0-1,000 µM) during mid-exponential growth. The highest production of TIA metabolites occurs at 250 ?M MJ, increasing by 150-370% compared with untreated controls. At this MJ dosage, the expression of the transcriptional activators (Orca) is dramatically increased (29-40 fold) while the levels of the transcriptional repressors (Zct) remain low (2-7 fold). Simultaneously, the expression of genes coding for key enzymes involved in TIA biosynthesis increases by 8-15 fold. In contrast, high MJ dosages (1,000 µM) inhibit the production of TIA metabolites. This dosage is correlated with elevated expression levels of Zct (up to 40-fold) relative to Orca (13-19-fold) and minimal induction of the TIA biosynthetic genes (0-6 fold). The significant changes in the expression of Orca and Zct with MJ dosage do not correspond to changes in the expression of the early-response transcription factors (AT-hook, Myc2, and Wrky1) believed to regulate Orca and Zct. In summary, these observations suggest that the dependence of alkaloid production on MJ dosage in C. roseus may be partly mediated through the relative levels of Orca and Zct family transcription factors. PMID:23970483

  2. A comprehensive analysis of root morphological changes and nitrogen allocation in maize in response to low nitrogen stress.

    PubMed

    Gao, Kun; Chen, Fanjun; Yuan, Lixing; Zhang, Fusuo; Mi, Guohua

    2015-04-01

    The plasticity of root architecture is crucial for plants to acclimate to unfavourable environments including low nitrogen (LN) stress. How maize roots coordinate the growth of axile roots and lateral roots (LRs), as well as longitudinal and radial cell behaviours in response to LN stress, remains unclear. Maize plants were cultivated hydroponically under control (4?mm nitrate) and LN (40??m) conditions. Temporal and spatial samples were taken to analyse changes in the morphology, anatomical structure and carbon/nitrogen (C/N) ratio in the axile root and LRs. LN stress increased axile root elongation, reduced the number of crown roots and decreased LR density and length. LN stress extended cell elongation zones and increased the mature cell length in the roots. LN stress reduced the cell diameter and total area of vessels and increased the amount of aerenchyma, but the number of cell layers in the crown root cortex was unchanged. The C/N ratio was higher in the axile roots than in the LRs. Maize roots acclimate to LN stress by optimizing the anatomical structure and N allocation. As a result, axile root elongation is favoured to efficiently find available N in the soil. PMID:25159094

  3. Effects of defoliating Stipa tenuis and Piptochaetium napostaense at different phenological stages: root growth

    Microsoft Academic Search

    G. F. Becker; C. A. Busso; T. Montani; M. A. Burgos; A. C. Flemmer; M. B. Toribio

    1997-01-01

    During 1991–1993, root growth after a single annual defoliation at different phenological stages (vegetative or during early, late or post-internode elongation) to 5–7 cm stubble height was determined on field-grown plants ofStipa tenuisandPiptochaetium napostaense, two important forage grasses in the semi-arid, temperate rangelands of Central Argentina. Nondefoliated plants served as controls. Root growth was estimated by root length density measurements

  4. Elongation as a factor in artefacts of humans and other animals: an Acheulean example in comparative context

    PubMed Central

    Gowlett, J. A. J.

    2013-01-01

    Elongation is a commonly found feature in artefacts made and used by humans and other animals and can be analysed in comparative study. Whether made for use in hand or beak, the artefacts have some common properties of length, breadth, thickness and balance point, and elongation can be studied as a factor relating to construction or use of a long axis. In human artefacts, elongation can be traced through the archaeological record, for example in stone blades of the Upper Palaeolithic (traditionally regarded as more sophisticated than earlier artefacts), and in earlier blades of the Middle Palaeolithic. It is now recognized that elongation extends to earlier Palaeolithic artefacts, being found in the repertoire of both Neanderthals and more archaic humans. Artefacts used by non-human animals, including chimpanzees, capuchin monkeys and New Caledonian crows show selection for diameter and length, and consistent interventions of modification. Both chimpanzees and capuchins trim side branches from stems, and appropriate lengths of stave are selected or cut. In human artefacts, occasional organic finds show elongation back to about 0.5 million years. A record of elongation achieved in stone tools survives to at least 1.75 Ma (million years ago) in the Acheulean tradition. Throughout this tradition, some Acheulean handaxes are highly elongated, usually found with others that are less elongated. Finds from the million-year-old site of Kilombe and Kenya are given as an example. These findings argue that the elongation need not be integral to a design, but that artefacts may be the outcome of adjustments to individual variables. Such individual adjustments are seen in animal artefacts. In the case of a handaxe, the maker must balance the adjustments to achieve a satisfactory outcome in the artefact as a whole. It is argued that the need to make decisions about individual variables within multivariate objects provides an essential continuity across artefacts made by different species. PMID:24101633

  5. Original article Variation in the phenology of shoot elongation

    E-print Network

    Paris-Sud XI, Université de

    Original article Variation in the phenology of shoot elongation between geographic provenances of maritime pine (Pinus pinaster) - implications for the synchrony with the phenology of the twisting rust December 1993) Summary — The phenology of shoot elongation was monitored for 2 or 3 years at 4 sites

  6. Quadratic Elongation: A Quantitative Measure of Distortion in Coordination Polyhedra

    Microsoft Academic Search

    Keith Robinson; G. V. Gibbs; P. H. Ribbe

    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 elongation is dimensionless, giving a quantitative measure of polyhedral distortion which is independent of the effective size of the polyhedron.

  7. New insights into root gravitropic signalling.

    PubMed

    Sato, Ethel Mendocilla; Hijazi, Hussein; Bennett, Malcolm J; Vissenberg, Kris; Swarup, Ranjan

    2015-04-01

    An important feature of plants is the ability to adapt their growth towards or away from external stimuli such as light, water, temperature, and gravity. These responsive plant growth movements are called tropisms and they contribute to the plant's survival and reproduction. Roots modulate their growth towards gravity to exploit the soil for water and nutrient uptake, and to provide anchorage. The physiological process of root gravitropism comprises gravity perception, signal transmission, growth response, and the re-establishment of normal growth. Gravity perception is best explained by the starch-statolith hypothesis that states that dense starch-filled amyloplasts or statoliths within columella cells sediment in the direction of gravity, resulting in the generation of a signal that causes asymmetric growth. Though little is known about the gravity receptor(s), the role of auxin linking gravity sensing to the response is well established. Auxin influx and efflux carriers facilitate creation of a differential auxin gradient between the upper and lower side of gravistimulated roots. This asymmetric auxin gradient causes differential growth responses in the graviresponding tissue of the elongation zone, leading to root curvature. Cell biological and mathematical modelling approaches suggest that the root gravitropic response begins within minutes of a gravity stimulus, triggering genomic and non-genomic responses. This review discusses recent advances in our understanding of root gravitropism in Arabidopsis thaliana and identifies current challenges and future perspectives. PMID:25547917

  8. Germination and elongation of flax in microgravity

    NASA Astrophysics Data System (ADS)

    Levine, H.; Anderson, K.; Boody, A.; Cox, D.; Kuznetsov, O.; Hasenstein, K.

    This experiment was conducted as part of a risk mitigation BIOTUBE Precursor hardware demonstration payload aboard the Space Shuttle Atlantis on STS-101. The objectives were to provide a demonstration and test of the newly developed BIOTUBE water delivery subsystem, and to determine the optimal water volume and germination paper combination for the automated imbibition and germination of flax (Linum usitatissimum) seeds in space. Two different substrate treatments of standard laboratory germination paper were tested for their ability to absorb, distribute, and retain water in microgravity. The first consisted of one layer of thick germination paper (designated "heavy"), and the second consisted of one layer of standard germination paper (designated "normal") under one layer of heavy germination paper. The germination paper strips were cut (4 X 1.6 cm) to fit snugly into seed cassettes. The seeds were attached to them by applying guar glue (1.25% w/v) drops to 8 premarked spots and the seeds orientated with the micropyle ends pointing outward. Water was delivered in 50 ?L boluses which slowly traveled down the paper via capillary action (eliminating the complications caused by excess water pooling around the seed's surface). The data indicated that the 480 ?L water delivery volume provided the best wetness level treatment for both percent germination (90.6%) and overall root growth (mean = 4.1 mm) during the 34 hour spaceflight experiment. The ground control experiment experienced similar results, but with slightly lower rates of germination (84.4%) and significantly shorter root lengths (2.8 mm). It is not clear if the roots emerged more quickly in microgravity and/or grew faster than the ground controls. The single layer of "Heavy" germination paper generally exhibited better overall growth than the two layered option. This in conjunction with the simplicity of using a single strip per seed cassette argues in favor of its selection. Significant seed position effects were observed in both the flight and ground control experiments. Overall, the design of the water delivery subsystem, seed cassettes and the germination paper strip concept was validated under microgravity conditions as an effective method of maintaining seed position and allowing adequate room for root growth. This work was supported under NASA Contract NAS10-002001.

  9. Cell wall-bound cationic and anionic class III isoperoxidases of pea root: biochemical characterization and function in root growth

    PubMed Central

    Lüthje, Sabine

    2012-01-01

    Cell wall isolated from pea roots was used to separate and characterize two fractions possessing class III peroxidase activity: (i) ionically bound proteins and (ii) covalently bound proteins. Modified SDS–PAGE separated peroxidase isoforms by their apparent molecular weights: four bands of 56, 46, 44, and 41kDa were found in the ionically bound fraction (iPOD) and one band (70kDa) was resolved after treatment of the cell wall with cellulase and pectinase (cPOD). Isoelectric focusing (IEF) patterns for iPODs and cPODs were significantly different: five iPODs with highly cationic pI (9.5–9.2) were detected, whereas the nine cPODs were anionic with pI values between pH 3.7 and 5. iPODs and cPODs showed rather specific substrate affinity and different sensitivity to inhibitors, heat, and deglycosylation treatments. Peroxidase and oxidase activities and their IEF patterns for both fractions were determined in different zones along the root and in roots of different ages. New iPODs with pI 9.34 and 9.5 were induced with root growth, while the activity of cPODs was more related to the formation of the cell wall in non-elongating tissue. Treatment with auxin that inhibits root growth led to suppression of iPOD and induction of cPOD. A similar effect was obtained with the widely used elicitor, chitosan, which also induced cPODs with pI 5.3 and 5.7, which may be specifically related to pathogen defence. The differences reported here between biochemical properties of cPOD and iPOD and their differential induction during development and under specific treatments implicate that they are involved in specific and different physiological processes. Abbreviations:cPODcovalently bound peroxidaseDAB3,3'-diaminobenzidineDEPMPOspin-trap (5-diethoxy-phosphoryl-5-methyl-1-pyrroline-n-oxide)EPRelectron paramagnetic resonanceHRPhorseradish peroxidaseIAAindole-3-acetic acidHRPhorseradish peroxidaseIEFisoelectric focusingiPODionically bound peroxidaseNAAnaphthalene acetic acidPNGase Fpeptide N-glycosidase FPRpathogen-relatedSDS–PAGEsodium dodecyl sulphate–polyacrylamide gel electrophoresisSHAMsalicylhydroxamic acidTMBtetramethyl benzidineWGAwheat germ agglutinin PMID:22760472

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

    E-print Network

    Ceverino, Daniel; Dekel, Avishai

    2015-01-01

    We report the identification of elongated (triaxial or prolate) galaxies in cosmological simulations at $z\\simeq2$. These are preferentially low-mass galaxies ($M_s \\le 10^{9.5} \\ M_\\odot$), residing in dark-matter (DM) haloes with strongly elongated inner parts, a common feature of high-redshift DM haloes in the $\\Lambda$CDM cosmology. Feedback slows formation of stars at the centres of these halos, 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.

  11. Sequence-dependent elongation dynamics on macrolide-bound ribosomes

    PubMed Central

    Johansson, Magnus; Chen, Jin; Tsai, Albert; Kornberg, Guy; Puglisi, Joseph D.

    2015-01-01

    SUMMARY The traditional view of macrolide antibiotics as plugs inside the ribosomal nascent peptide exit tunnel (NPET) has lately been challenged in favor of a more complex, heterogeneous mechanism, where drug-peptide interactions determine the fate of a translating ribosome. To investigate these highly dynamic processes, we applied single-molecule tracking of elongating ribosomes during inhibition of elongation by erythromycin of several nascent chains, including ErmCL and H-NS, which were shown to be respectively sensitive and resistant to erythromycin. Peptide sequence-specific changes were observed in translation elongation dynamics in the presence of a macrolide-obstructed NPET. Elongation rates were not severely inhibited in general by the presence of the drug; instead, stalls or pauses were observed as abrupt events. The dynamic pathways of nascent-chain dependent elongation pausing in the presence of macrolides determine the fate of the translating ribosome - stalling or read-through. PMID:24836000

  12. Phenotypic expression of wild-type tomato and three wilty mutants in relation to abscisic acid accumulation in roots and leaflets of reciprocal grafts

    SciTech Connect

    Cornish, K.; Zeevaart, J.A.D. (Michigan State Univ., East Lansing (USA))

    1988-05-01

    Lycopersicon esculentum Mill. cv Rheinlands Ruhm (RR) and cv Moneymaker and the three wilty mutants flacca (flc), sitiens (sit), and sitiens{sup w} (sit{sup w}), together with the most reciprocal grafts, were grown in pots and in solution culture. Detached leaflets, and control and stem-girdled intact plants, were left turgid or were wilted in air. Detached leaflets and the leaflets and roots of the intact plants were analyzed for their abscisic acid (ABA) content. Turgid RR leaflets contained about 2.9 ng ABA per miligram dry weight. On average, the flc and sit leaflets contained 33 and 11% of this amount, respectively. The lack of ABA approximately correlated with the severity of the mutant phenotype. Mutant roots also contained less ABA than wild-type roots. Wild-type scions on mutant stocks (wild type/mutant) maintained the normal phenotype of ungrafted plants. Mutant scions grafted onto wild-type stocks reverted to a near wild-type phenotype. After the wild-type leaves were excised from solution culture-grown mutant/wild-type plants, the revertive morphology of the mutant scions was maintained, although endogenous ABA levels in the leaflets fell to typical mutant levels and the leaflets became wilty again. When stressed in air, both leaflets and roots of RR plants produced stress-induced ABA, but the mutant leaflets and roots did not. The roots and leaflets of the grafted plants behaved according to their own genotype, with the notable exception of mutant roots grown with wild-type scions. Roots of flc and sit{sup w} recovered the ability to accumulate stress-induced ABA when grafted with RR scions before the stress was imposed.

  13. Enhancement of transpiration by ethylene is responsible for absence of internodal elongation in floating rice at low humidity.

    PubMed

    Azuma, Tetsushi; Hatanaka, Tomoko; Uchida, Naotsugu; Yasuda, Takeshi

    2003-09-01

    Internodal elongation in floating rice (Oryza sativa) is known to be enhanced by treatment with ethylene or gibberellic acid (GA3) at high relative humidity (RH). However, ethylene-induced internodal elongation is inhibited at low RH, while GA3-induced internodal elongation is hardly affected by humidity. We examined the effects of ethylene and GA3 on the rate of transpiration in stem segments incubated at 30% or 100% RH. Ethylene promoted the transpiration of stem segments at 30% RH, but not at 100% RH, while GA3 had little effect on transpiration at either 30% or 100% RH. We propose that the absence of ethylene-induced internodal elongation at low RH is due, at least in part, to ethylene-induced transpiration. PMID:14593815

  14. Estimating age-dependent costs and benefits of roots with contrasting life span: comparing apples and oranges

    Microsoft Academic Search

    Tjeerd J. Bouma; Ruth D. Yanai; Adrienne D. Elkin; Ulrich Hartmond; Dora E. Flores-Alva; David M. Eissenstat

    2001-01-01

    The relation between root age and root function is poorly understood, despite its importance to root longevity. The effect of root age on respiration rates and P-32-uptake kinetics was determined for roots excavated from mature apple and citrus trees (median root life spans of 30 vs 300 d). To evaluate whether root longevity maximizes the efficiency of nutrient capture, daily

  15. Gravity-dependent differentiation and root coils in Arabidopsis thaliana wild type and phospholipase-A-I knockdown mutant grown on the International Space Station.

    PubMed

    Scherer, G F E; Pietrzyk, P

    2014-01-01

    Arabidopsis roots on 45° tilted agar in 1-g grow in wave-like figures. In addition to waves, formation of root coils is observed in several mutants compromised in gravitropism and/or auxin transport. The knockdown mutant ppla-I-1 of patatin-related phospholipase-A-I is delayed in root gravitropism and forms increased numbers of root coils. Three known factors contribute to waving: circumnutation, gravisensing and negative thigmotropism. In microgravity, deprivation of wild type (WT) and mutant roots of gravisensing and thigmotropism and circumnutation (known to slow down in microgravity, and could potentially lead to fewer waves or increased coiling in both WT and mutant). To resolve this, mutant ppla-I-1 and WT were grown in the BIOLAB facility in the International Space Station. In 1-g, roots of both types only showed waving. In the first experiment in microgravity, the mutant after 9 days formed far more coils than in 1-g but the WT also formed several coils. After 24 days in microgravity, in both types the coils were numerous with slightly more in the mutant. In the second experiment, after 9 days in microgravity only the mutant formed coils and the WT grew arcuated roots. Cell file rotation (CFR) on the mutant root surface in microgravity decreased in comparison to WT, and thus was not important for coiling. Several additional developmental responses (hypocotyl elongation, lateral root formation, cotyledon expansion) were found to be gravity-influenced. We tentatively discuss these in the context of disturbances in auxin transport, which are known to decrease through lack of gravity. PMID:24373011

  16. Instability of dusty plasma waves in the presence of elongated and rotating charged particulates

    Microsoft Academic Search

    D. D. Tshkhakaya; P. K. Shukla; N. L. Tsintsadze; J. Mahmoodi

    2001-01-01

    A new dispersion relation for low-frequency waves in an unmagnetized dusty plasma is obtained when the plasma contains electrons, ions and non-spherical (elongated) rotating charged dust grains. Since the dipole moments of the latter are non-zero, significant modifications of the dusty plasma wave spectra emerge. Analyses of the newly found dispersion relation reveals instabilities of both the electromagnetic and electrostatic

  17. Instability of Dusty Plasma Waves in the Presence of Elongated and Rotating Charged Particulates

    Microsoft Academic Search

    D. D. Tshkhakaya; P. K. Shukla; N. L. Tsintsadze; J. Mahmoodi

    2001-01-01

    A new dispersion relation for low-frequency waves in an unmagnetized dusty plasma is obtained when the plasma contains electrons, ions and non-spherical (elongated) rotating charged dust grains. Since the dipole moments of the latter are non-zero, significant modifications of the dusty plasma wave spectra emerge. Analyses of the newly found dispersion relation reveals instabilities of both the electromagnetic and electrostatic

  18. Nerve and Nerve Root Biomechanics

    Microsoft Academic Search

    Kristen J. Nicholson; Beth A. Winkelstein

    \\u000a Together, the relationship between the mechanical response of neural tissues and the related mechanisms of injury provide\\u000a a foundation for defining relevant thresholds for injury. The nerves and nerve roots are biologic structures with specific\\u000a and important functions, and whose response to mechanical loading can have immediate, long-lasting and widespread consequences.\\u000a In particular, when nerves or nerve roots are mechanically

  19. Influence of root structure on root survivorship: an analysis of 18 tree species using a minirhizotron method

    Microsoft Academic Search

    Jiacun GuShuiqiang; Shuiqiang Yu; Yue Sun; Zhengquan Wang; Dali Guo

    Fine root survivorship is an important aspect of root ecology and is known to be influenced by a suite of covariates. However,\\u000a the relative importance of each covariate on root survivorship is not clear. Here, we used minirhizotron-based data from 18\\u000a woody species to evaluate the relative strength of influence on root survivorship by root diameter, branch order, soil depth,

  20. Human Root Caries: Microbiota in Plaque Covering Sound, Carious and Arrested Carious Root Surfaces

    Microsoft Academic Search

    P. Schüpbach; V. Osterwalder; B. Guggenheim

    1995-01-01

    The plaque microbiota covering sound or carious root surfaces were studied and compared with that covering arrested root caries lesions. From each of these categories five extracted teeth were examined. The experimental design of the study allowed us to relate the qualitative and quantitative microbial composition to the degree of integrity of the root surface. Plaque was sampled by a

  1. Role of NINJA in root jasmonate signaling.

    PubMed

    Acosta, Iván F; Gasperini, Debora; Chételat, Aurore; Stolz, Stéphanie; Santuari, Luca; Farmer, Edward E

    2013-09-17

    Wound responses in plants have to be coordinated between organs so that locally reduced growth in a wounded tissue is balanced by appropriate growth elsewhere in the body. We used a JASMONATE ZIM DOMAIN 10 (JAZ10) reporter to screen for mutants affected in the organ-specific activation of jasmonate (JA) signaling in Arabidopsis thaliana seedlings. Wounding one cotyledon activated the reporter in both aerial and root tissues, and this was either disrupted or restricted to certain organs in mutant alleles of core components of the JA pathway including COI1, OPR3, and JAR1. In contrast, three other mutants showed constitutive activation of the reporter in the roots and hypocotyls of unwounded seedlings. All three lines harbored mutations in Novel Interactor of JAZ (NINJA), which encodes part of a repressor complex that negatively regulates JA signaling. These ninja mutants displayed shorter roots mimicking JA-mediated growth inhibition, and this was due to reduced cell elongation. Remarkably, this phenotype and the constitutive JAZ10 expression were still observed in backgrounds lacking the ability to synthesize JA or the key transcriptional activator MYC2. Therefore, JA-like responses can be recapitulated in specific tissues without changing a plant's ability to make or perceive JA, and MYC2 either has no role or is not the only derepressed transcription factor in ninja mutants. Our results show that the role of NINJA in the root is to repress JA signaling and allow normal cell elongation. Furthermore, the regulation of the JA pathway differs between roots and aerial tissues at all levels, from JA biosynthesis to transcriptional activation. PMID:24003128

  2. Auxin Transport Is Required for Hypocotyl Elongation in Light-Grown but Not Dark-Grown Arabidopsis1

    PubMed Central

    Jensen, Philip J.; Hangarter, Roger P.; Estelle, Mark

    1998-01-01

    Many auxin responses are dependent on redistribution and/or polar transport of indoleacetic acid. Polar transport of auxin can be inhibited through the application of phytotropins such as 1-naphthylphthalamic acid (NPA). When Arabidopsis thaliana seedlings were grown in the light on medium containing 1.0 ?m NPA, hypocotyl and root elongation and gravitropism were strongly inhibited. When grown in darkness, however, NPA disrupted the gravity response but did not affect elongation. The extent of inhibition of hypocotyl elongation by NPA increased in a fluence-rate-dependent manner to a maximum of about 75% inhibition at 50 ?mol m?2 s?1 of white light. Plants grown under continuous blue or far-red light showed NPA-induced hypocotyl inhibition similar to that of white-light-grown plants. Plants grown under continuous red light showed less NPA-induced inhibition. Analysis of photoreceptor mutants indicates the involvement of phytochrome and cryptochrome in mediating this NPA response. Hypocotyls of some auxin-resistant mutants had decreased sensitivity to NPA in the light, but etiolated seedlings of these mutants were similar in length to the wild type. These results indicate that light has a significant effect on NPA-induced inhibition in Arabidopsis, and suggest that auxin has a more important role in elongation responses in light-grown than in dark-grown seedlings. PMID:9489005

  3. Chromatin modification by the RNA Polymerase II elongation complex.

    PubMed

    Tanny, Jason C

    2014-01-01

    Transcription elongation by RNA polymerase II (RNAP II) involves the coordinated action of numerous regulatory factors. Among these are chromatin-modifying enzymes, which generate a stereotypic and conserved pattern of histone modifications along transcribed genes. This pattern implies a precise coordination between regulators of histone modification and the RNAP II elongation complex. Here I review the pathways and molecular events that regulate co-transcriptional histone modifications. Insight into these events will illuminate the assembly of functional RNAP II elongation complexes and how the chromatin landscape influences their composition and function. PMID:25494544

  4. Study on the connection between the rotating mass dipole and natural elongated bodies

    NASA Astrophysics Data System (ADS)

    Zeng, Xiangyuan; Jiang, Fanghua; Li, Junfeng; Baoyin, Hexi

    2015-03-01

    The focus of this paper is to connect the rotating mass dipole with natural elongated bodies. The dipole system is consisted with two point masses connected with a massless rod in a constant characteristic distance. A brief introduction on the dynamics near the rotating mass dipole is given with the distribution of its equilibrium points and zero-velocity curves. Five parameters of the dipole model are required to approximate the potential distribution of an elongated body out of the body's surface, including the mass ratio, system mass, spinning period, characteristic distance and the ratio between the gravitational and centrifugal forces. The method to obtain the five parameters is presented along with its application to the asteroid 1620 Geographos in detail. The accuracy of the dipole model is quantified with the relative tolerance of locations of the equilibrium points. Six more elongated asteroids and comets, such as 25143 Itokawa and 103P/Hartley-2, are illustrated to provide a reference for further studies. Model justification is evaluated through comparison between sample elongated bodies and their corresponding dipole models with regard to the external potential distribution, the stability and topological manifold structure of the equilibrium points.

  5. Distribution of Calcium Ions in Cells of the Root Distal Elongation Zone Under Clinorotation

    Microsoft Academic Search

    Margarita Sobol; Elizabeth Kordyum

    2009-01-01

    Currently, calcium ions are known to play a crucial role in the vital activity of plant cells and in stimulus–response coupling\\u000a for many environmental signals, altered gravity included. The available data on changes in Ca2?+? distribution and concentration in the cells of different organisms influenced by altered gravity allow to suggest that microgravity\\u000a affects the calcium messenger system, and provide

  6. Developmental Distribution of the Plasma Membrane-Enriched Proteome in the Maize Primary Root Growth Zone

    PubMed Central

    Zhang, Zhe; Voothuluru, Priyamvada; Yamaguchi, Mineo; Sharp, Robert E.; Peck, Scott C.

    2013-01-01

    Within the growth zone of the maize primary root, there are well-defined patterns of spatial and temporal organization of cell division and elongation. However, the processes underlying this organization remain poorly understood. To gain additional insights into the differences amongst the defined regions, we performed a proteomic analysis focusing on fractions enriched for plasma membrane (PM) proteins. The PM is the interface between the plant cell and the apoplast and/or extracellular space. As such, it is a key structure involved in the exchange of nutrients and other molecules as well as in the integration of signals that regulate growth and development. Despite the important functions of PM-localized proteins in mediating these processes, a full understanding of dynamic changes in PM proteomes is often impeded by low relative concentrations relative to total proteins. Using a relatively simple strategy of treating microsomal fractions with Brij-58 detergent to enrich for PM proteins, we compared the developmental distribution of proteins within the root growth zone which revealed a number of previously known as well as novel proteins with interesting patterns of abundance. For instance, the quantitative proteomic analysis detected a gradient of PM aquaporin proteins similar to that previously reported using immunoblot analyses, confirming the veracity of this strategy. Cellulose synthases increased in abundance with increasing distance from the root apex, consistent with expected locations of cell wall deposition. The similar distribution pattern for Brittle-stalk-2-like protein implicates that this protein may also have cell wall related functions. These results show that the simplified PM enrichment method previously demonstrated in Arabidopsis can be successfully applied to completely unrelated plant tissues and provide insights into differences in the PM proteome throughout growth and development zones of the maize primary root. PMID:23508561

  7. Reconstructing the Root System Development of Barley in an Undisturbed Soil using Minirhizotron Data

    NASA Astrophysics Data System (ADS)

    Garre, S.; Pagès, L.; Javaux, M.; Vanderborght, J.; Vereecken, H.

    2010-12-01

    Increasing computer power favors the use of complex mesoscopic models to predict root water uptake. Those models explicitly consider the 3-D root architecture and root growth of a plant and may have variable hydraulic potentials in both soil and root. However, a lack of high-quality data to calibrate and validate these models remains, especially for non-woody plant growth in undisturbed, layered soils and for situations with more than one plant. We tried to reconstruct the root system architecture for growing barley in an undisturbed lysimeter using minirhizotron data at four depths. The evolution of the number of roots in a minirhizotron image with time was used to optimize the root architecture model RootTyp. We adjusted a simple architecture to the data, which contained only long primary roots starting from the seed and small, regularly spaced secondary roots. However, the result was not satisfying since the simple model could not reproduce an increasing root number with depth. The model could be improved making the branching and root elongation more horizon-dependent and by making reiteration of root tips possible. Reiteration is an alternative form of branching, where secondary roots can become as long and thick as primary roots. However, minirhizotron data do not contain enough information to restrain the parameters governing these processes. Therefore, different experimental techniques should be combined to achieve a better model result.

  8. Dichotomization of mycorrhizal and NPA-treated short roots in Pinus sylvestris

    PubMed Central

    Salo, Vanamo

    2008-01-01

    Conifers like Scots pine (Pinus sylvestris) have a complicated root system consisting of morphologically and anatomically different root types, of which the short roots have a very limited ability to elongate. Short roots have an important role in nature since they are able to establish ectomycorrhizal symbiosis, in which the growth of fungal mycelium between the epidermal cells and in the intercellular space between cortical cells leads to formation of dichotomous short roots, which may, through further splitting of the meristem, form coralloid root structures. Dichotomous short roots have been suggested to result from changes in either auxin or ethylene concentrations due to the fungal growth inside the root. NPA, the inhibitor of polar auxin transport, enhances the dichotomization of P. sylvestris short root tips similarly to the fungal growth in the root, thus confirming that auxin plays a role in short root morphogenesis. Ethylene is also known to have an important role in the regulation of root morphogenesis. In future the research dealing with the root system and ectomycorrhiza development in P. sylvestris must take into account that both auxin and ethylene are involved and that there is no contradiction in obtaining the same phenotype with both hormones. The expression analysis of PIN proteins, auxin efflux carriers, could give valuable information about the role of auxin transport in regulating the root growth and morphogenesis of coniferous root system and mycorrhiza. PMID:19704726

  9. Distribution of expansins in graviresponding maize roots

    NASA Technical Reports Server (NTRS)

    Zhang, N.; Hasenstein, K. H.

    2000-01-01

    To test if expansins, wall loosening proteins that disrupt binding between microfibrils and cell wall matrix, participate in the differential elongation of graviresponding roots, Zea mays L. cv. Merit roots were gravistimulated and used for immunolocalization with anti-expansin. Western blots showed cross-reaction with two proteins of maize, one of the same mass as cucumber expansin (29 kDa), the second slightly larger (32 kDa). Maize roots contained mainly the larger protein, but both were found in coleoptiles. The expansin distribution in cucumber roots and hypocotyls was similar to the distribution in maize. Roots showed stronger expansin signals on the expanding convex side than the concave flank as early as 30 min after gravistimulation. Treatment with brefeldin A, a vesicle transport inhibitor, or the auxin transport inhibitor, naphthylphthalamic acid, showed delayed graviresponse and the appearance of differential staining. Our results indicate that expansins may be transported and secreted to cell walls via vesicles and function in wall expansion.

  10. A Randomised, Double-Blind, Placebo-Controlled, Parallel-Group Study of the Standardised Extract SHR-5 of the Roots of Rhodiola rosea in the Treatment of Subjects with Stress-Related Fatigue

    Microsoft Academic Search

    Erik M. G. Olsson; Bo von Schéele; Alexander G. Panossian

    2009-01-01

    The aim of the study was to assess the efficacy of the standardised extract SHR-5 of roots of Rhodiola rosea L. in the treatment of individuals suffering from stress-related fatigue. The phase III clinical trial took the form of a randomised, double-blind, placebo-controlled study with par- allel groups. Participants, males and females aged between 20 and 55 years, were selected

  11. Flagellar Elongation Induced by Glucose Limitation Is Preadaptive for

    E-print Network

    Engman, David M.

    Flagellar Elongation Induced by Glucose Limitation Is Preadaptive for Trypanosoma cruzi trypanosome, Trypanosoma cruzi, differentiates from the noninfective epimastigote form to the infective Parasites with complex life cycles must interact with multiple environments. Trypanosoma cruzi

  12. Cervical elongation following sacrospinous hysteropexy: a case series.

    PubMed

    Hyakutake, Momoe Tina; Cundiff, Geoffrey William; Geoffrion, Roxana

    2014-06-01

    In recent years, pelvic floor surgeons have increasingly repaired pelvic organ prolapse around an intact uterus. Uterine conservation and hysteropexy have been driven by patient preference, less risk of mesh erosion, shorter operative time, and decreased blood loss and postoperative pain. We present a case series of patients with cervical elongation after vaginal sacrospinous hysteropexy using polypropylene mesh arms, a novel technique developed by the senior author. We defined cervical elongation as greater than or equal to a two-fold increase in cervical length compared with preoperative measurements. Of the 8 patients who underwent this procedure, 5 (62.5 %) had cervical elongation during the first year postoperatively. In the most severe case, the cervix extended to 4 cm beyond the hymenal ring. Most of the patients were mildly symptomatic and chose expectant management. The cases are reviewed in detail. A brief literature review on cervical elongation is presented. PMID:24297063

  13. Transcriptional elongation checkpoint control in development and disease

    PubMed Central

    Smith, Edwin; Shilatifard, Ali

    2013-01-01

    Transcriptional elongation control by RNA polymerase II and its associated factors has taken center stage as a process essential for the regulation of gene expression throughout development. In this review, we analyze recent findings on the identification of factors functioning in the regulation of the transcriptional elongation checkpoint control (TECC) stage of gene expression and how the factors' misregulation is associated with disease pathogenesis, including cancer. PMID:23699407

  14. Hexane extract of Raphanus sativus L. roots inhibits cell proliferation and induces apoptosis in human cancer cells by modulating genes related to apoptotic pathway.

    PubMed

    Beevi, Syed Sultan; Mangamoori, Lakshmi Narasu; Subathra, Murugan; Edula, Jyotheeswara Reddy

    2010-09-01

    Raphanus sativus, a common cruciferous vegetable has been attributed to possess a number of pharmacological and therapeutic properties. It has been used in indigenous system of medicine for the treatment of various human ailments in India. This present study evaluated the chemopreventive efficacy of different parts of R. sativus such as root, stem and leaves, extracted with solvents of varying polarity and investigated the molecular mechanism leading to growth arrest and apoptotic cell death in human cancer cell lines. Of the different parts, significant growth inhibitory effect was observed with hexane extract of R. sativus root. Analysis of hexane extract by GC-MS revealed the presence of several isothiocyanates (ITCs) such as 4-(methylthio)-3-butenyl isothiocyanate (MTBITC), 4-(methylthio)-3-butyl isothiocyanate (erucin), 4-methylpentyl isothiocyanate, 4-pentenyl isothiocyanate and sulforaphene. R. sativus root extract induced cell death both in p53 proficient and p53 deficient cell lines through induction of apoptotic signaling pathway regardless of the p53 status of cells. The molecular mechanisms underlying R. sativus-induced apoptosis may involve interactions among Bcl(2) family genes, as evidenced by up-regulation of pro-apoptotic genes and down-regulation of anti-apoptotic genes along with activation of Caspase-3. Our findings present the first evidence that hexane extract of R. sativus root exerts potential chemopreventive efficacy and induces apoptosis in cancer cell lines through modulation of genes involved in apoptotic signaling pathway. PMID:20652750

  15. Cyst nematode parasitism of Arabidopsis thaliana is inhibited by salicylic acid (SA) and elicits uncoupled SA-independent pathogenesis-related gene expression in roots

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Compatible interactions between plants and sedentary endoparasitic nematodes, including Heterodera and Meloidogyne spp., require the formation of elaborate feeding sites in proximity to the root vasculature. Feeding site development involves a signal exchange between the host and the nematode and i...

  16. Negative feedback on a perennial crop: Fusarium crown and root rot of asparagus is related to changes in soil microbial community structure

    Microsoft Academic Search

    C. Hamel; V. Vujanovic; R. Jeannotte; A. Nakano-Hylander; M. St-Arnaud

    2005-01-01

    The dynamic equilibrium of an ecosystem is driven by mutual feedback interactions between plants and soil microorganisms. Asparagus exerts a particularly strong influence on its soil environment through abundant production of persistent phenolic acids, which impact selectively soil microorganisms and may be involved in Fusarium crown and root rot (FCRR) of asparagus. In a survey of 50 asparagus plantations of

  17. Characterization of stipe elongation of the mushroom Coprinopsis cinerea.

    PubMed

    Zhang, Wenming; Wu, Xiuxiu; Zhou, Yajun; Liu, Zhonghua; Zhang, Wen; Niu, Xin; Zhao, Yan; Pei, Siyu; Zhao, Yang; Yuan, Sheng

    2014-09-01

    Previously, we observed an acid-induced short-term wall extension in Flammulina velutipes apical stipes during a 15 min period after a change from a neutral to an acidic pH. This acid-induced stipe wall extension was eliminated by heating and reconstituted by a snail expansin-like protein, although we failed to isolate any endogenous expansin-like protein from F. velutipes because of its limited 1 mm fast elongation region. In this study, we report that Coprinopsis cinerea stipes possess a 9 mm fast elongation apical region, which is suitable as a model material for wall extension studies. The elongating apical stipe showed two phases of acid-induced wall extension, an initial quick short-term wall extension during the first 15 min and a slower, gradually decaying long-term wall extension over the subsequent 2 h. After heating or protein inactivation pretreatment, apical stipes lost the long-term wall extension, retaining a slower short-term wall extension, which was reconstituted by an expansin-like snail protein. In contrast, the non-elongating basal stipes showed only a weaker short-term wall extension. We propose that the long-term wall extension is a protein-mediated process involved in stipe elongation, whereas the short-term wall extension is a non-protein mediated process not involved in stipe elongation. PMID:24996826

  18. Rapid auxin-induced root growth inhibition requires the TIR and AFB auxin receptors.

    PubMed

    Scheitz, Katharina; Lüthen, Hartwig; Schenck, Daniel

    2013-08-01

    We investigated the relation between auxin-induced gene expression and the rapid auxin-induced growth inhibition in Arabidopsis thaliana roots. The natural auxin indole-3-acetic acid (IAA) induced a strong activation of gene expression as visualized by the DR5rev::GFP reporter gene technique. This effect was specific for active auxins and was abolished in knockout mutants of the F-box auxin receptors. We measured the IAA-induced growth inhibition at high time resolution and show that the F-box auxin receptor mutants failed to display this effect. We conclude that the F-box auxin receptors are needed for the response. In hypocotyls, auxin induces an increase in elongation growth, and this effect has been earlier shown to be independent of the F-box receptors. Based on these findings, we discuss differences in the growth control modes in roots and shoots. We demonstrate that the rapid auxin-induced root growth inhibition, unlike the induction of growth in hypocotyls, requires the presence of the F-box auxin receptors. PMID:23925852

  19. Rapid flooding-induced adventitious root development from preformed primordia in Solanum dulcamara

    PubMed Central

    Dawood, Thikra; Rieu, Ivo; Wolters-Arts, Mieke; Derksen, Emiel B.; Mariani, Celestina; Visser, Eric J. W.

    2014-01-01

    Flooding is a common stress factor in both natural and agricultural systems, and affects plant growth by the slow diffusion rate of gases in water. This results in low oxygen concentrations in submerged tissues, and hence in a decreased respiration rate. Understanding the responses of plants to flooding is essential for the management of wetland ecosystems, and may benefit research to improve the flood tolerance of crop species. This study describes the response to partial submergence of bittersweet (Solanum dulcamara). Bittersweet is a Eurasian species that grows both in dry habitats such as coastal dunes, and in wetlands, and therefore is a suitable model plant for studying responses to a variety of environmental stresses. A further advantage is that the species is closely related to flood-intolerant crops such as tomato and eggplant. The species constitutively develops dormant primordia on the stem, which we show to have a predetermined root identity. We investigated adventitious root growth from these primordia during flooding. The synchronized growth of roots from the primordia was detected after 2–3 days of flooding and was due to a combination of cell division and cell elongation. Gene expression analysis demonstrated that the molecular response to flooding began within 2 h and included activation of hypoxia and ethylene signalling genes. Unexpectedly, these early changes in gene expression were very similar in primordia and adjacent stem tissue, suggesting that there is a dominant general response in tissues during early flooding. PMID:24790121

  20. Can we improve heterosis for root growth of maize by selecting parental inbred lines with different temperature behaviour?

    PubMed Central

    Hund, Andreas; Reimer, Regina; Stamp, Peter; Walter, Achim

    2012-01-01

    Tolerance to high and low temperature is an important breeding aim for Central and Northern Europe, where temperature fluctuations are predicted to increase. However, the extent to which genotypes differ in their response to the whole range of possible temperatures is not well understood. We tested the hypothesis that the combination of maize (Zea mays L.) inbred lines with differing temperature optima for root growth would lead to superior hybrids. This hypothesis is based on the concept of ‘marginal overdominance’ in which the hybrid expresses higher relative fitness than its parents, summed over all situations. The elongation rates of axile and lateral roots of the reciprocal cross between two flint and two dent inbred lines were assessed at temperatures between 15°C and 40°C. Indeed, the cross between UH005 and UH250 with lateral root growth temperature optima at 34°C and 28°C, respectively, resulted in intermediate hybrids. At temperatures below and above 31°C, the hybrids' root growth was comparable to the better parent, respectively, thereby increasing temperature tolerance of the hybrid compared with its parents. The implications of and reasons for this heterosis effect are discussed in the context of breeding for abiotic stress tolerance and of putatively underlying molecular mechanisms. This finding paves the way for more detailed investigations of this phenomenon in future studies. PMID:22527401

  1. Ribosomally synthesized thiopeptide antibiotics targeting elongation factor Tu.

    PubMed

    Morris, Rowan P; Leeds, Jennifer A; Naegeli, Hans Ulrich; Oberer, Lukas; Memmert, Klaus; Weber, Eric; LaMarche, Matthew J; Parker, Christian N; Burrer, Nathalie; Esterow, Stacey; Hein, Andreas E; Schmitt, Esther K; Krastel, Philipp

    2009-04-29

    We identified the thiomuracins, a novel family of thiopeptides produced by a rare-actinomycete bacterium typed as a Nonomuraea species, via a screen for inhibition of growth of the bacterial pathogen Staphylococcus aureus. Thiopeptides are a class of macrocyclic, highly modified peptides that are decorated by thiazoles and defined by a central six-membered heterocyclic ring system. Mining the genomes of thiopeptide-producing strains revealed the elusive biosynthetic route for this class of antibiotics. The thiopeptides are chromosomally encoded, ribosomally synthesized proteins, and isolation of gene clusters for production of thiomuracin and the related thiopeptide GE2270A revealed the post-translational machinery required for maturation. The target of the thiomuracins was identified as bacterial Elongation Factor Tu (EF-Tu). In addition to potently inhibiting a target that is unexploited by marketed human therapeutics, the thiomuracins have a low propensity for selecting for antibiotic resistance and confer no measurable cross-resistance to antibiotics in clinical use. PMID:19338336

  2. Investigation of elongated styloid process prevalence in patients with torus palatinus

    Microsoft Academic Search

    Y. Sisman; C. Gokce; E. Tarim Ertas; M. Sipahioglu; F. Akgunlu

    2009-01-01

    The aim of the current study was to determine the presence of styloid process elongation (SPE) detected on panoramic radiographs\\u000a in patients with torus palatinus (TP). Between December 2005 and November 2007, a total of 149 patients with TP are investigated\\u000a for routine dental examination in the outpatient clinic. Any patient who had disorders related to calcium and phosphorus metabolism

  3. The Arabidopsis NRT1.1 transporter participates in the signaling pathway triggering root colonization of nitrate-rich patches

    Microsoft Academic Search

    Tony Remans; Philippe Nacry; Marjorie Pervent; Sophie Filleur; Eugene Diatloff; Emmanuelle Mounier; Pascal Tillard; B. G. Forde; Alain Gojon

    2006-01-01

    Localized proliferation of lateral roots in NO??-rich patches is a striking example of the nutrient-induced plasticity of root development. In Arabidopsis, NO?? stimulation of lateral root elongation is apparently under the control of a NO??-signaling pathway involving the ANR1 transcription factor. ANR1 is thought to transduce the NO?? signal internally, but the upstream NO?? sensing system is unknown. Here, we

  4. Automated motion estimation of root responses to sucrose in two Arabidopsis thaliana genotypes using confocal microscopy.

    PubMed

    Wuyts, Nathalie; Bengough, A Glyn; Roberts, Timothy J; Du, Chengjin; Bransby, M Fraser; McKenna, Stephen J; Valentine, Tracy A

    2011-10-01

    Root growth is a highly dynamic process influenced by genetic background and environment. This paper reports the development of R scripts that enable root growth kinematic analysis that complements a new motion analysis tool: PlantVis. Root growth of Arabidopsis thaliana expressing a plasma membrane targeted GFP (C24 and Columbia 35S:LTI6b-EGFP) was imaged using time-lapse confocal laser scanning microscopy. Displacement of individual pixels in the time-lapse sequences was estimated automatically by PlantVis, producing dense motion vector fields. R scripts were developed to extract kinematic growth parameters and report displacement to ± 0.1 pixel. In contrast to other currently available tools, Plantvis-R delivered root velocity profiles without interpolation or averaging across the root surface and also estimated the uncertainty associated with tracking each pixel. The PlantVis-R analysis tool has a range of potential applications in root physiology and gene expression studies, including linking motion to specific cell boundaries and analysis of curvature. The potential for quantifying genotype × environment interactions was examined by applying PlantVis-R in a kinematic analysis of root growth of C24 and Columbia, under contrasting carbon supply. Large genotype-dependent effects of sucrose were recorded. C24 exhibited negligible differences in elongation zone length and elongation rate but doubled the density of lateral roots in the presence of sucrose. Columbia, in contrast, increased its elongation zone length and doubled its elongation rate and the density of lateral roots. PMID:21630041

  5. Root and shoot responses of Taxodium distichum seedlings subjected to saline flooding

    USGS Publications Warehouse

    Krauss, K.W.; Chambers, J.L.; Allen, J.A.; Luse, B.P.; DeBosier, A.S.

    1999-01-01

    Variation among progeny of five half-sib family collections of baldcypress (Taxodium distichum) from three freshwater and two brackish-water seed sources subjected to saline flooding was evaluated Mini-rhizotrons (slant tubes) were used to monitor root elongation for a period of 99 days. Salinity level produced significant effects across all baldcypress half-sib families, with root elongation averaging 1594.0, 956.8, and 382.1 mm, respectively, for the 0, 4, and 6 g l-1 treatments. Combined mean root elongation for families from brackish-water seed sources was greater (1236.7 mm) than for families from freshwater seed sources (794.6 mm). Considerable variation occurred at the highest salinity treatment, however, with one freshwater family maintaining more than 28% more root growth than the average of the two brackish-water collections. Hence, results indicate that short-term evaluation of root elongation at these salinity concentrations may not be a reliable method for salt tolerance screening of baldcypress. Species-level effects for height and diameter, which were measured at day 62, were significant for both parameters. Height increment in the control (7.4 cm), for example, was approximately five times greater than height increment in the 6 g l-1 salinity treatment (1.5 cm). Family-level variation was significant only for diameter, which had an incremental range of 0.2 to 1.5 mm across all salinity levels.

  6. Regulation of FATTY ACID ELONGATION1 expression in embryonic and vascular tissues of Brassica napus.

    PubMed

    Chiron, Hélène; Wilmer, Jeroen; Lucas, Marie-Odile; Nesi, Nathalie; Delseny, Michel; Devic, Martine; Roscoe, Thomas J

    2015-05-01

    The expression of the FATTY ACID ELONGATION1 genes was characterised to provide insight into the regulation of very long chain fatty acid (VLCFA) biosynthesis in Brassica napus embryos. Each of the two rapeseed homoeologous genes (Bn-FAE1.1 and Bn-FAE1.2) encoding isozymes of 3-keto-acylCoA synthase, a subunit of the cytoplasmic acyl-CoA elongase complex that controls the production of elongated fatty acids, are expressed predominantly in developing seeds. The proximal regions of the Bn-FAE1.1 and Bn-FAE1.2 promoters possess strong sequence identity suggesting that transcriptional control of expression is mediated by this region which contains putative cis-elements characteristic of those found in the promoters of genes expressed in embryo and endosperm. Histochemical staining of rapeseed lines expressing Bn-FAE1.1 promoter:reporter gene fusions revealed a strong expression in the embryo cotyledon and axis throughout the maturation phase. Quantitative analyses revealed the region, -331 to -149, exerts a major control on cotyledon specific expression and the level of expression. A second region, -640 to -475, acts positively to enhance expression levels and extends expression of Bn-FAE1.1 into the axis and hypocotyl but also acts negatively to repress expression in the root meristem. The expression of the Bn-FAE1.1 gene was not restricted to the seed but was also detected in the vascular tissues of germinating seedlings and mature plants in the fascicular cambium tissue present in roots, stem and leaf petiole. We propose that Bn-FAE1.1 expression in vascular tissue may contribute VLCFA for barrier lipid synthesis and reflects the ancestral function of FAE1 encoded 3-keto-acylCoA synthase. PMID:25795129

  7. Kinetics of Growth Retardant and Hormone Interactions in Affecting Cucumber Hypocotyl Elongation 1

    PubMed Central

    Moore, Thomas C.

    1967-01-01

    The capacities of indole-3-acetic acid (IAA) and gibberellin A3 (GA3) to counteract the inhibitory effects of (2-chloroethyl) trimethylammonium chloride (CCC), 2-isopropyl-4-dimethylamino-5-methylphenyl-1-piperidinecarboxylate methyl chloride (Amo-1618), and N,N-dimethylaminosuccinamic acid (B-995) on hypocotyl elongation in light-grown cucumber (Cucumis sativus L.) seedlings were investigated. One ?g of GA3 applied to the shoot tip was sufficient to completely nullify the effect of 10 ?g of Amo-1618 or 25 ?g of B-995 applied simultaneously to the shoot tip, and 10 ?g of GA3 completely counteracted the effect of 10?3 m CCC added to the root medium. One ?g of IAA counteracted the effect of 10?3 m CCC in the root medium, but IAA did not nullify the action of either Amo-1618 or B-995. Experiments were conducted using 2 growth retardants simultaneously, which indicated that Amo-1618 and CCC inhibit a common process, namely GA biosynthesis, essential to hypocotyl elongation. However, since the effect of CCC was overcome by applications of both GA and IAA, growth retardation resulting from treatment with CCC apparently is not due solely to inhibition of GA biosynthesis. B-995 did not interact additively with either Amo-1618 or CCC, which suggests that B-995 affects a process different from those affected by the other 2 retardants. Thus, while inhibition evoked by B-995 is reversible by applied GA, the action of B-995 does not appear to be inhibition of GA biosynthesis. PMID:16656555

  8. Implant Surface Coating and Bone Quality-Related Survival Outcomes Through 36 Months Post-Placement of Root-Form Endosseous Dental Implants

    Microsoft Academic Search

    Richard S. Truhlar; Harold F. Morris; Shigeru Ochi

    2000-01-01

    Survival rates from placement to 36 months were reported for the ongoing Dental Implant Clinical Research Group studies of root-form endosseous dental implants. Failure rates for all implants were similar in bone qualities 1 and 2 (6.2% and 6.7%, respectively) and slightly higher in bone qualities 3 and 4 (8.5% and 8.7%, respectively). Hydroxyapatite (HA)-coated implants had an overall failure

  9. The timing of grain Cd accumulation in rice plants: the relative importance of remobilisation within the plant and root Cd uptake post-flowering

    Microsoft Academic Search

    Matthew S. Rodda; Gang Li; Robert J. Reid

    The pathways by which Cd is accumulated in rice grain are not well understood, in particular the components attributable to\\u000a direct transfer from the root, and to remobilisation of Cd previously accumulated in other plant parts. In order to observe\\u000a the timing of Cd accumulation in rice plants and determine the major period for accumulation of Cd which can be

  10. Variation of total FOS, total IOS, inulin and their related-metabolizing enzymes in burdock roots ( Arctium lappa L.) stored under different temperatures

    Microsoft Academic Search

    Y. Ishiguro; S. Onodera; N. Benkeblia; N. Shiomi

    2010-01-01

    Burdock roots were stored for six weeks at three temperatures, 0, 15 and 20°C, and activity of sucrose hydrolase (SH), 1-kestose hydrolase (1-KH), inulin hydrolase (InH), sucrose:sucrose 1-fructosyltransferase (1-SST) and fructan:fructan 1-fructoslytransferase (1-FFT) were assessed. Simultaneously, total fructooligosaccharides (FOS), total inulooligosaccharides (IOS) and inulin were also assessed during storage. During storage, SH showed an irregular variation at 15 and 20°C,

  11. Postembryonic control of root meristem growth and development.

    PubMed

    Sozzani, Rosangela; Iyer-Pascuzzi, Anjali

    2014-02-01

    Organ development in multicellular organisms is dependent on the proper balance between cell proliferation and differentiation. In the Arabidopsis root apical meristem, meristem growth is the result of cell divisions in the proximal meristem and cell differentiation in the elongation and differentiation zones. Hormones, transcription factors and small peptides underpin the molecular mechanisms governing these processes. Computer modeling has aided our understanding of the dynamic interactions involved in stem cell maintenance and meristem activity. Here we review recent advances in our understanding of postembryonic root stem cell maintenance and control of meristem size. PMID:24507488

  12. Loquat fruit ripening is associated with root depletion. Nutritional and hormonal control.

    PubMed

    Reig, Carmina; Mesejo, Carlos; Martínez-Fuentes, Amparo; Martínez-Alcántara, Belén; Agustí, Manuel

    2015-04-01

    In woody species, it is known that there is a competition for nutrients, water and carbohydrates between root and fruit-shoot systems, however the influence of root development on fruit quality has received little attention. This research aims to identify the network of mechanisms involved in loquat (Eriobotrya japonica Lindl.) fruit ripening in connection with root activity. The study includes root growth rate measurements paralleling the ongoing fruit developmental stages, photosynthate translocation to the root by using (13)CO2 tracing, and nitrogen fractions (N-NH4(+), N-NO3(-), and N-proteinaceous) as well as their upward translocation to the fruit. The role of hormones (IAA, zeatin and ABA) in regulating the responses is also addressed. The experiment was conducted during two consecutive years on adult and 3-year-old loquat trees from early fruit developmental stage (10% of final size, 701 BBCH scale) to fully developed fruit colour (809 BBCH scale). This approach revealed that root development depends on the growing fruit sink strength, which reduces carbohydrates translocation to the roots and prevents them for further elongation. A nitrate accumulation in roots during the active fruit growth period takes place, which also contributes to slowing elongation and paralleled reduced ammonium and proteinaceous nitrogen concentrations. Concomitantly, the concentration of IAA and zeatin were lowest while that of ABA was highest when root exhibited minimum elongation. The depletion in zeatin and nitrogen supply by the roots paralleling the high ABA transport to the fruit allowed for colour break. These results suggest that loquat fruit changes colour by reducing root growth, as fruit increases sugars and ABA concentrations and reduces nitrogen and zeatin concentrations. PMID:25659335

  13. Root sampling methods - applications and limitations of the minirhizotron technique

    Microsoft Academic Search

    Hooshang Majdi

    1996-01-01

    Applications and limitations of the minirhizotron technique (non-destructive) in relation to two frequently used destructive methods (soil coreing and ingrowth cores) is discussed. Sequential coreing provides data on standing crop but it is difficult to obtain data on root biomass production. Ingrowth cores can provide a quick estimate of relative fine-root growth when root growth is rapid. One limitation of

  14. Circumnutation as an autonomous root movement in plants.

    PubMed

    Migliaccio, Fernando; Tassone, Paola; Fortunati, Alessio

    2013-01-01

    Although publications on circumnutation of the aerial parts of flowering plants are numerous and primarily from the time between Darwin (1880) and the 1950s, reports on circumnutation of roots are scarce. With the introduction of modern molecular biology techniques, many topics in the plant sciences have been revitalized; among these is root circumnutation. The most important research in this area has been done on Arabidopsis thaliana, which has roots that behave differently from those of many other plants; roots grown on inclined agar dishes produce a pattern of half waves slanted to one side. When grown instead on horizontally set dishes, the roots grow in loops or in tight right-handed coils that are characterized by a tight torsion to the left-hand. The roots of the few plants that differ from Arabidopsis and have been similarly tested do not present such patterns, because even if they circumnutate generally in a helical pattern, they subsequently straighten. Research on plants in space or on a clinostat has allowed the testing of these roots in a habitat lacking gravity or simulating the lack. Recently, molecular geneticists have started to connect various root behaviors to specific groups of genes. For example, anomalies in auxin responses caused by some genes can be overcome by complementation with wild-type genes. Such important studies contribute to understanding the mechanisms of growth and elongation, processes that are only superficially understood. PMID:23243099

  15. Ethylene can stimulate Arabidopsis hypocotyl elongation in the?light

    PubMed Central

    Smalle, Jan; Haegman, Mira; Kurepa, Jasmina; Van Montagu, Marc; Straeten, Dominique Van Der

    1997-01-01

    Ethylene inhibits hypocotyl elongation in etiolated Arabidopsis seedlings. However, when Arabidopsis was grown in the light in the presence of ethylene or its precursor 1-aminocyclopropane-1-carboxylic acid (ACC), a marked induction of hypocotyl elongation occurred. This resulted from an increase in cell expansion rather than cell division. The effects of ethylene and ACC were antagonized by the ethylene action inhibitor Ag+. The elongation response was absent or weakened in a set of ethylene-insensitive mutants (etr1-3, ein2-1, ein3-1, ein4, ain1-10, ein7). With the exception of ein4, the degree of inhibition of hypocotyl elongation was correlated with the strength of the ethylene-insensitive phenotype based on the triple response assay. In addition, the constitutive ethylene response mutant ctr1-1, grown in the light, had a longer hypocotyl than the wild type. Exogenous auxin also induced hypocotyl elongation in light-grown Arabidopsis. Again, the response was abolished by treatment with Ag+, suggesting that ethylene might be a mediator. The results showed that, depending on light conditions, ethylene can induce opposite effects on cell expansion in Arabidopsis hypocotyls. PMID:11038610

  16. Macromolecular crowding induced elongation and compaction of single DNA molecules confined in a nanochannel

    PubMed Central

    Zhang, Ce; Shao, Pei Ge; van Kan, Jeroen A.; van der Maarel, Johan R. C.

    2009-01-01

    The effect of dextran nanoparticles on the conformation and compaction of single DNA molecules confined in a nanochannel was investigated with fluorescence microscopy. It was observed that the DNA molecules elongate and eventually condense into a compact form with increasing volume fraction of the crowding agent. Under crowded conditions, the channel diameter is effectively reduced, which is interpreted in terms of depletion in DNA segment density in the interfacial region next to the channel wall. Confinement in a nanochannel also facilitates compaction with a neutral crowding agent at low ionic strength. The threshold volume fraction for condensation is proportional to the size of the nanoparticle, due to depletion induced attraction between DNA segments. We found that the effect of crowding is not only related to the colligative properties of the agent and that confinement is also important. It is the interplay between anisotropic confinement and osmotic pressure which gives the elongated conformation and the possibility for condensation at low ionic strength. PMID:19805352

  17. Auxin Overproduction in Shoots Cannot Rescue Auxin Deficiencies in Arabidopsis Roots

    PubMed Central

    Chen, Qingguo; Dai, Xinhua; De-Paoli, Henrique; Cheng, Youfa; Takebayashi, Yumiko; Kasahara, Hiroyuki; Kamiya, Yuji; Zhao, Yunde

    2014-01-01

    Auxin plays an essential role in root development. It has been a long-held dogma that auxin required for root development is mainly transported from shoots into roots by polarly localized auxin transporters. However, it is known that auxin is also synthesized in roots. Here we demonstrate that a group of YUCCA (YUC) genes, which encode the rate-limiting enzymes for auxin biosynthesis, plays an essential role in Arabidopsis root development. Five YUC genes (YUC3, YUC5, YUC7, YUC8 and YUC9) display distinct expression patterns during root development. Simultaneous inactivation of the five YUC genes (yucQ mutants) leads to the development of very short and agravitropic primary roots. The yucQ phenotypes are rescued by either adding 5 nM of the natural auxin, IAA, in the growth media or by expressing a YUC gene in the roots of yucQ. Interestingly, overexpression of a YUC gene in shoots in yucQ causes the characteristic auxin overproduction phenotypes in shoots; however, the root defects of yucQ are not rescued. Our data demonstrate that localized auxin biosynthesis in roots is required for normal root development and that auxin transported from shoots is not sufficient for supporting root elongation and root gravitropic responses. PMID:24562917

  18. Distribution of sodium channels during nerve elongation in rat peripheral nerve

    Microsoft Academic Search

    Harumitsu Ichimura; Takashi Shiga; Ichiro Abe; Yuki Hara; Naoto Terui; Akihito Tsujino; Naoyuki Ochiai

    2005-01-01

    A number of studies have investigated electrophysiological and morphological changes of peripheral nerves during gradual elongation. There has been, however, no report on the distribution of sodium channels at Ranvier’s nodes during peripheral nerve elongation. We investigated peripheral nerve injury after the gradual elongation of rat sciatic nerves. Indirect nerve elongation was induced by leg lengthening at a rate of

  19. Plant growth-promoting rhizobacterial strain-mediated induced systemic resistance in tea (Camellia sinensis (L.) O. Kuntze) through defense-related enzymes against brown root rot and charcoal stump rot.

    PubMed

    Mishra, A K; Morang, P; Deka, M; Nishanth Kumar, S; Dileep Kumar, B S

    2014-09-01

    Induction of systemic resistance in host plants through microbes and their bioactive metabolites are attaining popularity in modern agricultural practices. In this regard, individual application of two strains of Pseudomonas, RRLJ 134 and RRLJ 04, exhibited development of induced systemic resistance in tea plants against brown root rot and charcoal stump rot under split root experiments. The experimental findings also confirmed that the cuttings treated with fungal test pathogen and plant growth-promoting rhizobacteria (PGPR) strains survived longer as compared with pathogen-alone-treated cuttings. The enzyme level studies revealed that the presence of PGPR strains reduced the viscosity loss of cellulose and pectin by both the pathogens to a significant level. The activity of defense-related enzymes like L-phenylalanine ammonia lyase, peroxidase, and polyphenol oxidase were also recorded higher in tea cuttings treated with PGPR strains in presence of pathogen. Crude bioactive metabolites isolated from these strains also showed in vitro antagonism against the test pathogens besides reducing the number of diseased plants under gnotobiotic conditions. These findings confirm the utilization of these two strains for induction of systemic resistance against two major root diseases in tea plants under plantation conditions. PMID:25082766

  20. Regulation of Intercellular Water Exchange in Various Zones of Maize Root under Stresses

    Microsoft Academic Search

    O. V. Volobueva; G. A. Velikanov; F. Baluška

    2004-01-01

    Apical root meristems and segments of root elongation zone were sampled from 4- to 5-day-old Zea mays L. seedlings. The vacuolar ATPase and pyrophosphatase, the tonoplast marker enzymes, and the tonoplast a-, d-, and ?-aquaporins were visualized by means of indirect immunofluorescent microscopy with the use of the respective antibodies. Following cell plasmolysis (700 mM mannitol, 2.5 h), the vacuolar

  1. Allelopathic Substance Exuded from a Serious Weed, Germinating Barnyard Grass ( Echinochloa crus-galli L.), Roots

    Microsoft Academic Search

    T. Yamamoto; K. Yokotani-Tomita; S. Kosemura; S. Yamamura; K. Yamada; K. Hasegawa

    1999-01-01

    .   The allelopathy of a serious weed, barnyard grass (Echinochloa crus-galli L.), was investigated. Root exudates of young barnyard grass showed allelopathic effects and plant-selective activity and\\u000a inhibited root elongation of all plants tested. With respect to shoot growth, the exudates did not show inhibition of barnyard\\u000a grass only. The allelopathic substance was isolated and identified as p-hydroxymandelic acid by

  2. 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

  3. Facts about FACT and transcript elongation through chromatin.

    PubMed

    Belotserkovskaya, Rimma; Reinberg, Danny

    2004-04-01

    The regulation of transcription elongation within the context of chromatin is a topic of great interest. Even though chromatin presents a barrier to transcription by the PolII machinery in vitro, this process is rather efficient in vivo. Importantly, the chromatin structure of the actively transcribed genes is altered as part of this process. A large number of factors implicated in the control of transcript elongation have been identified through genetics, biochemistry and targeted proteomics approaches. However the precise roles and mechanisms of action of these factors remain obscure. A significant advance came about this past year with the elucidation of the roles of FACT and Spt6 in transcription elongation. These factors facilitate PolII passage through chromatin by destabilizing the nucleosome structure as well as reassemble nucleosomes traversed by PolII. PMID:15196460

  4. A Grass Root Proposal for Carbon Sequestration

    Microsoft Academic Search

    Stephen Salter; Tony Lovell; Bruce Ward

    2010-01-01

    The mass of invisible root material below ground is related to the amount of visible plant material above ground as would have been shown below except for EGU rules. However in many countries modern livestock management methods involve constant grazing which keeps grass short and so leaves very little root mass. This paper will show photographic comparisons, such as the

  5. A statistical approach to root system classification

    PubMed Central

    Bodner, Gernot; Leitner, Daniel; Nakhforoosh, Alireza; Sobotik, Monika; Moder, Karl; Kaul, Hans-Peter

    2013-01-01

    Plant root systems have a key role in ecology and agronomy. In spite of fast increase in root studies, still there is no classification that allows distinguishing among distinctive characteristics within the diversity of rooting strategies. Our hypothesis is that a multivariate approach for “plant functional type” identification in ecology can be applied to the classification of root systems. The classification method presented is based on a data-defined statistical procedure without a priori decision on the classifiers. The study demonstrates that principal component based rooting types provide efficient and meaningful multi-trait classifiers. The classification method is exemplified with simulated root architectures and morphological field data. Simulated root architectures showed that morphological attributes with spatial distribution parameters capture most distinctive features within root system diversity. While developmental type (tap vs. shoot-borne systems) is a strong, but coarse classifier, topological traits provide the most detailed differentiation among distinctive groups. Adequacy of commonly available morphologic traits for classification is supported by field data. Rooting types emerging from measured data, mainly distinguished by diameter/weight and density dominated types. Similarity of root systems within distinctive groups was the joint result of phylogenetic relation and environmental as well as human selection pressure. We concluded that the data-define classification is appropriate for integration of knowledge obtained with different root measurement methods and at various scales. Currently root morphology is the most promising basis for classification due to widely used common measurement protocols. To capture details of root diversity efforts in architectural measurement techniques are essential. PMID:23914200

  6. Inhibition of 2,4-dichlorophenoxyacetic acid-stimulated elongation of pea stem segments by a xyloglucan oligosaccharide

    SciTech Connect

    York, W.S.; Darvill, A.G.; Albersheim, P.

    1984-06-01

    Xyloglucan, isolated from the soluble extracellular polysaccharides of suspension-cultured sycamore (Acer pseudoplatanus) cells, was digested with an endo-..beta..-1,4-glucanase purified from the culture fluid of Trichoderma viride. A nonasaccharide-rich Bio-Gel P-2 fraction of this digest inhibited 2,4-dichlorophenoxyacetic-acid-stimulated elongation of etiolated pea stem segments. The inhibitory activity of this oligosaccharide fraction exhibited a well-define concentraction optimum between 10/sup -2/ and 10/sup -1/ micrograms per milliliter. Another fraction of the same xyloglucan digest, rich in a structurally related heptasaccharide, did not, at similar concentrations, significantly inhibit the elongation. 11 references, 3 figures.

  7. Identification and cloning of two immunogenic Clostridium perfringens proteins, elongation factor Tu and pyruvate:ferredoxin oxidoreductase of C. perfringens

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Clostridium-related poultry diseases such as necrotic enteritis (NE) and gangrenous dermatitis (GD) cause substantial economic losses on a global scale. Two antigenic Clostridium perfringens proteins, elongation factor Tu (EF-Tu) and pyruvate:ferredoxin oxidoreductase (PFO), were identified by react...

  8. Residence-time distribution as a measure of mixing in T-junction and multilaminated\\/elongational flow micromixers

    Microsoft Academic Search

    John T. Adeosun; Adeniyi Lawal

    2010-01-01

    The ineffective mixing in microchannel mixers or reactors, primarily due to the laminar flow behavior in such microfluidic devices, has become an issue of significant interest to many researchers working in the field of microreaction engineering and related disciplines. The present study describes the numerical and experimental investigation of mixing performance in a proposed multilaminated\\/elongational flow micromixer (herein referred to

  9. Role of ethylene signalling in the formation of constitutive aerenchyma in primary roots of rice.

    PubMed

    Yukiyoshi, Kenta; Karahara, Ichirou

    2014-01-01

    Although the extent of aerenchyma (interconnected gas-filled space) formed in the cortex of the roots of some species can be promoted by submergence and ethylene, such roots also form a somewhat less extensive aerenchyma under well-aerated conditions. It has been unclear whether or not ethylene is also involved in promoting this constitutive aerenchyma. To confirm the potential of ethylene to stimulate aerenchyma development and test the possibility that gas regulates constitutive aerenchyma, a novel sandwich method was employed in rice roots. This involved germinating japonica rice (Oryza sativa) caryopses sandwiched between two agar slabs with or without 1-aminocyclopropane-1-carboxylic acid (ACC) at 1 µM. The roots were then grown for 4 days in the dark in the presence or absence of gaseous 1-methylcyclopropene (1-MCP), an inhibitor of ethylene action. Examination of aerenchyma development by light microscopy demonstrated a more extensive aerenchyma in cross-section on the ACC-treated side that also commenced closer to the root tip. In the presence of 1-MCP at 0.1 or 1 ppm, aerenchyma formation was inhibited in the presence or absence of ACC. 1-Methylcyclopropene also overcame ACC-inhibited root elongation. The results indicate that ethylene signalling is involved in aerenchyma development in primary roots of rice and that this may include the regulation of constitutive aerenchyma. In addition, root elongation was slowed in control roots in the presence of 1 ppm 1-MCP, supporting previous studies demonstrating that endogenous levels of ethylene stimulate root elongation. PMID:25063833

  10. Variability of Root Traits in Spring Wheat Germplasm

    PubMed Central

    Narayanan, Sruthi; Mohan, Amita; Gill, Kulvinder S.; Prasad, P. V. Vara

    2014-01-01

    Root traits influence the amount of water and nutrient absorption, and are important for maintaining crop yield under drought conditions. The objectives of this research were to characterize variability of root traits among spring wheat genotypes and determine whether root traits are related to shoot traits (plant height, tiller number per plant, shoot dry weight, and coleoptile length), regions of origin, and market classes. Plants were grown in 150-cm columns for 61 days in a greenhouse under optimal growth conditions. Rooting depth, root dry weight, root: shoot ratio, and shoot traits were determined for 297 genotypes of the germplasm, Cultivated Wheat Collection (CWC). The remaining root traits such as total root length and surface area were measured for a subset of 30 genotypes selected based on rooting depth. Significant genetic variability was observed for root traits among spring wheat genotypes in CWC germplasm or its subset. Genotypes Sonora and Currawa were ranked high, and genotype Vandal was ranked low for most root traits. A positive relationship (R2?0.35) was found between root and shoot dry weights within the CWC germplasm and between total root surface area and tiller number; total root surface area and shoot dry weight; and total root length and coleoptile length within the subset. No correlations were found between plant height and most root traits within the CWC germplasm or its subset. Region of origin had significant impact on rooting depth in the CWC germplasm. Wheat genotypes collected from Australia, Mediterranean, and west Asia had greater rooting depth than those from south Asia, Latin America, Mexico, and Canada. Soft wheat had greater rooting depth than hard wheat in the CWC germplasm. The genetic variability identified in this research for root traits can be exploited to improve drought tolerance and/or resource capture in wheat. PMID:24945438

  11. Growth maintenance of the maize primary root at low water potentials involves increases in cell-wall extension properties, expansin activity, and wall susceptibility to expansins.

    PubMed Central

    Wu, Y; Sharp, R E; Durachko, D M; Cosgrove, D J

    1996-01-01

    Previous work on the growth biophysics of maize (Zea mays L.) primary roots suggested that cell walls in the apical 5 mm of the elongation zone increased their yielding ability as an adaptive response to low turgor and water potential (psi w). To test this hypothesis more directly, we measured the acid-induced extension of isolated walls from roots grown at high (-0.03 MPa) or low (-1.6 MPa) psi w using an extensometer. Acid-induced extension was greatly increased in the apical 5 mm and was largely eliminated in the 5- to 10-mm region of roots grown at low psi w. This pattern is consistent with the maintenance of elongation toward the apex and the shortening of the elongation zone in these roots. Wall proteins extracted from the elongation zone possessed expansin activity, which increased substantially in roots grown at low psi w. Western blots likewise indicated higher expansin abundance in the roots at low psi w. Additionally, the susceptibility of walls to expansin action was higher in the apical 5 mm of roots at low psi w than in roots at high psi w. The basal region of the elongation zone (5-10 mm) did not extend in response to expansins, indicating that loss of susceptibility to expansins was associated with growth cessation in this region. Our results indicate that both the increase in expansin activity and the increase in cell-wall susceptibility to expansins play a role in enhancing cell-wall yielding and, therefore, in maintaining elongation in the apical region of maize primary roots at low psi w. PMID:11536740

  12. The Arabidopsis Elongator Complex Subunit2 Epigenetically Regulates Plant Immune Responses[W][OA

    PubMed Central

    Wang, Yongsheng; An, Chuanfu; Zhang, Xudong; Yao, Jiqiang; Zhang, Yanping; Sun, Yijun; Yu, Fahong; Amador, David Moraga; Mou, Zhonglin

    2013-01-01

    The Arabidopsis thaliana Elongator complex subunit2 (ELP2) genetically interacts with NONEXPRESSOR OF PATHOGENESIS-RELATED GENES1 (NPR1), a key transcription coactivator of plant immunity, and regulates the induction kinetics of defense genes. However, the mechanistic relationship between ELP2 and NPR1 and how ELP2 regulates the kinetics of defense gene induction are unclear. Here, we demonstrate that ELP2 is an epigenetic regulator required for pathogen-induced rapid transcriptome reprogramming. We show that ELP2 functions in a transcriptional feed-forward loop regulating both NPR1 and its target genes. An elp2 mutation increases the total methylcytosine number, reduces the average methylation levels of methylcytosines, and alters (increases or decreases) methylation levels of specific methylcytosines. Interestingly, infection of plants with the avirulent bacterial pathogen Pseudomonas syringae pv tomato DC3000/avrRpt2 induces biphasic changes in DNA methylation levels of NPR1 and PHYTOALEXIN DEFICIENT4 (PAD4), which encodes another key regulator of plant immunity. These dynamic changes are blocked by the elp2 mutation, which is correlated with delayed induction of NPR1 and PAD4. The elp2 mutation also reduces basal histone acetylation levels in the coding regions of several defense genes. Together, our data demonstrate a new role for Elongator in somatic DNA demethylation/methylation and suggest a function for Elongator-mediated chromatin regulation in pathogen-induced transcriptome reprogramming. PMID:23435660

  13. ECHIDNA-mediated post-Golgi trafficking of auxin carriers for differential cell elongation

    PubMed Central

    Boutté, Yohann; Jonsson, Kristoffer; McFarlane, Heather E.; Johnson, Errin; Gendre, Delphine; Swarup, Ranjan; Friml, Ji?í; Samuels, Lacey; Robert, Stéphanie; Bhalerao, Rishikesh P.

    2013-01-01

    The plant hormone indole-acetic acid (auxin) is essential for many aspects of plant development. Auxin-mediated growth regulation typically involves the establishment of an auxin concentration gradient mediated by polarly localized auxin transporters. The localization of auxin carriers and their amount at the plasma membrane are controlled by membrane trafficking processes such as secretion, endocytosis, and recycling. In contrast to endocytosis or recycling, how the secretory pathway mediates the localization of auxin carriers is not well understood. In this study we have used the differential cell elongation process during apical hook development to elucidate the mechanisms underlying the post-Golgi trafficking of auxin carriers in Arabidopsis. We show that differential cell elongation during apical hook development is defective in Arabidopsis mutant echidna (ech). ECH protein is required for the trans-Golgi network (TGN)–mediated trafficking of the auxin influx carrier AUX1 to the plasma membrane. In contrast, ech mutation only marginally perturbs the trafficking of the highly related auxin influx carrier LIKE-AUX1-3 or the auxin efflux carrier PIN-FORMED-3, both also involved in hook development. Electron tomography reveals that the trafficking defects in ech mutant are associated with the perturbation of secretory vesicle genesis from the TGN. Our results identify differential mechanisms for the post-Golgi trafficking of de novo-synthesized auxin carriers to plasma membrane from the TGN and reveal how trafficking of auxin influx carriers mediates the control of differential cell elongation in apical hook development. PMID:24043780

  14. ECHIDNA-mediated post-Golgi trafficking of auxin carriers for differential cell elongation.

    PubMed

    Boutté, Yohann; Jonsson, Kristoffer; McFarlane, Heather E; Johnson, Errin; Gendre, Delphine; Swarup, Ranjan; Friml, Jirí; Samuels, Lacey; Robert, Stéphanie; Bhalerao, Rishikesh P

    2013-10-01

    The plant hormone indole-acetic acid (auxin) is essential for many aspects of plant development. Auxin-mediated growth regulation typically involves the establishment of an auxin concentration gradient mediated by polarly localized auxin transporters. The localization of auxin carriers and their amount at the plasma membrane are controlled by membrane trafficking processes such as secretion, endocytosis, and recycling. In contrast to endocytosis or recycling, how the secretory pathway mediates the localization of auxin carriers is not well understood. In this study we have used the differential cell elongation process during apical hook development to elucidate the mechanisms underlying the post-Golgi trafficking of auxin carriers in Arabidopsis. We show that differential cell elongation during apical hook development is defective in Arabidopsis mutant echidna (ech). ECH protein is required for the trans-Golgi network (TGN)-mediated trafficking of the auxin influx carrier AUX1 to the plasma membrane. In contrast, ech mutation only marginally perturbs the trafficking of the highly related auxin influx carrier LIKE-AUX1-3 or the auxin efflux carrier PIN-FORMED-3, both also involved in hook development. Electron tomography reveals that the trafficking defects in ech mutant are associated with the perturbation of secretory vesicle genesis from the TGN. Our results identify differential mechanisms for the post-Golgi trafficking of de novo-synthesized auxin carriers to plasma membrane from the TGN and reveal how trafficking of auxin influx carriers mediates the control of differential cell elongation in apical hook development. PMID:24043780

  15. Styloid process elongation and calcification in subjects with tmd: clinical and radiographic aspects.

    PubMed

    de Andrade, Kelly Machado; Rodrigues, Carolina Almeida; Watanabe, Plauto C Aranha; Mazzetto, Marcelo Oliveira

    2012-01-01

    Knowledge of the Eagle's syndrome shows that its symptoms can be very easily confused with other types of craniomandibular disorders, especially temporomandibular disorders (TMD). The aim of this study was to find a possible correlation between the presence of TMD and elongation of the styloid process as well relate to presence of calcification of the stilohyoid chain. Fifty patients with TMD, confirmed from the RDC/TMD, were examined clinically and radiographically. Radiographic documentation consisted of digital panoramic radiograph and digital lateral cephalometric radiograph. Radiocef software (Radiomemory) was used for the analysis of radiographs by means of specific cephalometric tracing and linear measurements of the styloid process. Each radiograph was traced and measured three times with intervals of 1 month to spread the error. Statistical analysis was performed by Pearson's test (p=0.001) using Biostat 4.0 statistical software. Result showed an incidence of 76% elongation of the styloid process in the sample. There was a correlation between the bilateral measures taken in panoramic radiographs (?<0.001) and also for measures of styloid process length carried out in different panoramic radiographs and lateral cephalometric radiographs (?<0.001). It was concluded that there is prevalence of elongated styloid process in patients with TMD. However, no relationship was found between measurements on the stylohyoid chain and symptoms of headache, orofacial pain, tinnitus and vertigo. PMID:23207864

  16. Cortical dynein and asymmetric membrane elongation coordinately position the spindle in anaphase.

    PubMed

    Kiyomitsu, Tomomi; Cheeseman, Iain M

    2013-07-18

    Mitotic spindle position defines the cell-cleavage site during cytokinesis. However, the mechanisms that control spindle positioning to generate equal-sized daughter cells remain poorly understood. Here, we demonstrate that two mechanisms act coordinately to center the spindle during anaphase in symmetrically dividing human cells. First, the spindle is positioned directly by the microtubule-based motor dynein, which we demonstrate is targeted to the cell cortex by two distinct pathways: a G?i/LGN/NuMA-dependent pathway and a 4.1G/R and NuMA-dependent, anaphase-specific pathway. Second, we find that asymmetric plasma membrane elongation occurs in response to spindle mispositioning to alter the cellular boundaries relative to the spindle. Asymmetric membrane elongation is promoted by chromosome-derived Ran-GTP signals that locally reduce Anillin at the growing cell cortex. In asymmetrically elongating cells, dynein-dependent spindle anchoring at the stationary cell cortex ensures proper spindle positioning. Our results reveal the anaphase-specific spindle centering systems that achieve equal-sized cell division. PMID:23870127

  17. BLACK ROOT ROT

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Black Root Rot Prepared by G. S. Abawi, Revised by L.E. Hanson Black root rot is caused by Thielaviopsis basicola (syn. Chalara elegans). The pathogen is widely distributed, can infect more than 130 plant species in 15 families, and causes severe black root rot diseases in ornamentals and crops suc...

  18. Centrotemporal sharp wave EEG trait in rolandic epilepsy maps to Elongator Protein Complex 4 (ELP4)

    PubMed Central

    Strug, Lisa J; Clarke, Tara; Chiang, Theodore; Chien, Minchen; Baskurt, Zeynep; Li, Weili; Dorfman, Ruslan; Bali, Bhavna; Wirrell, Elaine; Kugler, Steven L; Mandelbaum, David E; Wolf, Steven M; McGoldrick, Patricia; Hardison, Huntley; Novotny, Edward J; Ju, Jingyue; Greenberg, David A; Russo, James J; Pal, Deb K

    2009-01-01

    Rolandic epilepsy (RE) is the most common human epilepsy, affecting children between 3 and 12 years of age, boys more often than girls (3:2). Focal sharp waves in the centrotemporal area define the electroencephalographic (EEG) trait for the syndrome, are a feature of several related childhood epilepsies and are frequently observed in common developmental disorders (eg, speech dyspraxia, attention deficit hyperactivity disorder and developmental coordination disorder). Here we report the first genome-wide linkage scan in RE for the EEG trait, centrotemporal sharp waves (CTS), with genome-wide linkage of CTS to 11p13 (HLOD 4.30). Pure likelihood statistical analysis refined our linkage peak by fine mapping CTS to variants in Elongator Protein Complex 4 (ELP4) in two independent data sets; the strongest evidence was with rs986527 in intron 9 of ELP4, providing a likelihood ratio of 629:1 (P=0.0002) in favor of an association. Resequencing of ELP4 coding, flanking and promoter regions revealed no significant exonic polymorphisms. This is the first report of a gene implicated in a common focal epilepsy and the first human disease association of ELP4. ELP4 is a component of the Elongator complex, involved in transcription and tRNA modification. Elongator depletion results in the brain-specific downregulation of genes implicated in cell motility and migration. We hypothesize that a non-coding mutation in ELP4 impairs brain-specific Elongator-mediated interaction of genes implicated in brain development, resulting in susceptibility to seizures and neurodevelopmental disorders. PMID:19172991

  19. Mechanical force-driven growth of elongated bending TiO2 -based nanotubular materials for ultrafast rechargeable lithium ion batteries.

    PubMed

    Tang, Yuxin; Zhang, Yanyan; Deng, Jiyang; Wei, Jiaqi; Le Tam, Hong; Chandran, Bevita Kallupalathinkal; Dong, Zhili; Chen, Zhong; Chen, Xiaodong

    2014-09-17

    A stirring hydrothermal process that enables the formation of elongated bending TiO2 -based nanotubes is presented. By making use of its bending nature, the elongated TiO2 (B) nanotubular crosslinked-network anode electrode can cycle over 10 000 times in half cells while retaining a relatively high capacity (114 mA h g(-1)) at an ultra-high rate of 25 C (8.4 A g(-1)). PMID:25043343

  20. Cortical microtubule patterning in roots of Arabidopsis thaliana primary cell wall mutants reveals the bidirectional interplay with cell expansion.

    PubMed

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

    2015-06-01

    Cell elongation requires directional deposition of cellulose microfibrils regulated by transverse cortical microtubules. Microtubules respond differentially to suppression of cell elongation along the developmental zones of Arabidopsis thaliana root apex. Cortical microtubule orientation is particularly affected in the fast elongation zone but not in the meristematic or transition zones of thanatos and pom2-4 cellulose-deficient mutants of Arabidopsis thaliana. Here, we report that a uniform phenotype is established among the primary cell wall mutants, as cortical microtubules of root epidermal cells of rsw1 and prc1 mutants exhibit the same pattern described in thanatos and pom2-4. Whether cortical microtubules assume transverse orientation or not is determined by the demand for cellulose synthesis, according to each root zone's expansion rate. It is suggested that cessation of cell expansion may provide a biophysical signal resulting in microtubule reorientation. PMID:26042727

  1. Phytotoxic Allelochemicals From Roots and Root Exudates of Leafy Spurge (Euphorbia esula L.).

    PubMed

    Qin, Bo; Perry, Laura G; Broeckling, Corey D; Du, Jiang; Stermitz, Frank R; Paschke, Mark W; Vivanco, Jorge M

    2006-11-01

    Invasive plants are a widespread problem but the mechanisms used by these plants to become invasive are often unknown. The production of phytotoxic natural products by invasive weeds is one mechanism by which these species may become successful competitors. Here we conducted a bioactivity-driven fractionation of root extracts and exudates from the invasive plant leafy spurge (Euphorbia esula L.), and structurally characterized jatrophane diterpenes and ellagic acid derivatives. Ellagic acid derivatives and one of the jatrophane diterpenes, esulone A, have been previously reported from leafy spurge, but another of the jatrophane diterpenes, kasuinine B, has not. We show that these compounds are phytotoxic but affect plants in different ways, either inducing overall plant necrosis or reducing root branching and elongation. PMID:19517003

  2. AMELIORATION OF SUBSOIL ACIDITY CONSTRAINTS TO SOYBEAN ROOT GROWTH WITH MAGNESIUM

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Aluminum rhizotoxicity in acid soils inhibits root elongation and limits crop acquisition of water and nutrients from the subsoil layers. Studies with soybean [Glycine max (L.) Merr.] in hydroponic systems have shown that µM additions of Mg2+ were as effective in ameliorating Al rhizotoxicity as add...

  3. Allometry of root branching and its relationship to root morphological and functional traits in three range grasses

    PubMed Central

    Arredondo, J. Tulio; Johnson, Douglas A.

    2011-01-01

    The study of proportional relationships between size, shape, and function of part of or the whole organism is traditionally known as allometry. Examination of correlative changes in the size of interbranch distances (IBDs) at different root orders may help to identify root branching rules. Root morphological and functional characteristics in three range grasses {bluebunch wheatgrass [Pseudoroegneria spicata (Pursh) Löve], crested wheatgrass [Agropyron desertorum (Fisch. ex Link) Schult.×A. cristatum (L.) Gaert.], and cheatgrass (Bromus tectorum L.)} were examined in response to a soil nutrient gradient. Interbranch distances along the main root axis and the first-order laterals as well as other morphological and allocation root traits were determined. A model of nutrient diffusivity parameterized with root length and root diameter for the three grasses was used to estimate root functional properties (exploitation efficiency and exploitation potential). The results showed a significant negative allometric relationship between the main root axis and first-order lateral IBD (P ?0.05), but only for bluebunch wheatgrass. The main root axis IBD was positively related to the number and length of roots, estimated exploitation efficiency of second-order roots, and specific root length, and was negatively related to estimated exploitation potential of first-order roots. Conversely, crested wheatgrass and cheatgrass, which rely mainly on root proliferation responses, exhibited fewer allometric relationships. Thus, the results suggested that species such as bluebunch wheatgrass, which display slow root growth and architectural root plasticity rather than opportunistic root proliferation and rapid growth, exhibit correlative allometry between the main axis IBD and morphological, allocation, and functional traits of roots. PMID:21868398

  4. Allometry of root branching and its relationship to root morphological and functional traits in three range grasses.

    PubMed

    Arredondo, J Tulio; Johnson, Douglas A

    2011-11-01

    The study of proportional relationships between size, shape, and function of part of or the whole organism is traditionally known as allometry. Examination of correlative changes in the size of interbranch distances (IBDs) at different root orders may help to identify root branching rules. Root morphological and functional characteristics in three range grasses {bluebunch wheatgrass [Pseudoroegneria spicata (Pursh) Löve], crested wheatgrass [Agropyron desertorum (Fisch. ex Link) Schult.×A. cristatum (L.) Gaert.], and cheatgrass (Bromus tectorum L.)} were examined in response to a soil nutrient gradient. Interbranch distances along the main root axis and the first-order laterals as well as other morphological and allocation root traits were determined. A model of nutrient diffusivity parameterized with root length and root diameter for the three grasses was used to estimate root functional properties (exploitation efficiency and exploitation potential). The results showed a significant negative allometric relationship between the main root axis and first-order lateral IBD (P ? 0.05), but only for bluebunch wheatgrass. The main root axis IBD was positively related to the number and length of roots, estimated exploitation efficiency of second-order roots, and specific root length, and was negatively related to estimated exploitation potential of first-order roots. Conversely, crested wheatgrass and cheatgrass, which rely mainly on root proliferation responses, exhibited fewer allometric relationships. Thus, the results suggested that species such as bluebunch wheatgrass, which display slow root growth and architectural root plasticity rather than opportunistic root proliferation and rapid growth, exhibit correlative allometry between the main axis IBD and morphological, allocation, and functional traits of roots. PMID:21868398

  5. DNA content and differentiation of root apical cells of Brassica rapa plants grown in microgravity.

    PubMed

    Kordyum, E L; Martin, G I; Zaslavsky, V A; Jiao, S; Hilaire, E; Guikema, J A

    1999-07-01

    Root cap is proposed to be a graviperceptive tissue in the plant root, and it is composed of several cell types. One such cell type, the columella cells, are thought to initiate the gravity-induced signal transduction cascade, and these cells arise from the activity of the meristematic zone of the root cap. There is, in fact, a continuum of cells in the central column of the root cap representing the meristematic cells, developing columella cells, mature cells, and those that will soon be sloughed off into the soil. In order to study the functional roles of the root cap cells in gravity-sensing, we compared the ultrastructural organization, differentiation, and DNA content in the meristematic, elongating, and differentiating cells of root tips in Brassica rapa plants grown in space microgravity and at 1g. The experiments were also designed to determine the reactions of root cap cells in both main roots (in which the original root cap was present in an embryonic form within the seed) and lateral roots (in which the root cap formed completely in space after seed germination on orbit) to the space microgravity. This study (ROOTS) was performed in collaboration with the B-PAC experiment on the Space shuttle "Columbia" mission STS-87 (Collaborative US/Ukrainian Experiment (CUE) during November 19-December 5, 1997. PMID:11542985

  6. 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...

  7. An elongation model of left ventricle deformation in diastole

    PubMed Central

    Hu, Yingying; Shi, Liang; Du, Dongxing; Parameswaran, Siva; He, Zhaoming

    2011-01-01

    A numerical method of the left ventricle (LV) deformation, an elongation model, was put forth for the study of LV fluid mechanics in diastole. The LV elongated only along the apical axis, and the motion was controlled by the intraventricular flow rate. Two other LV models, a fixed control volume model and a dilation model, were also used for model comparison and the study of LV fluid mechanics. For clinical sphere indices (SIs, between 1.0 and 2.0), the three models showed little difference in pressure and velocity distributions along the apical axis at E-peak. The energy dissipation was lower at a larger SI in that the jet and vortex development was less limited by the LV cavity in the apical direction. LV deformation of apical elongation may represent the primary feature of LV deformation in comparison with the secondary radial expansion. The elongation model of the LV deformation with an appropriate SI is a reasonable, simple method to study LV fluid mechanics in diastole. PMID:21916674

  8. Elongated solid electrolyte cell configurations and flexible connections therefor

    Microsoft Academic Search

    Reichner

    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,

  9. Elongated solid electrolyte cell configurations and flexible connections therefor

    Microsoft Academic Search

    Reichner

    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, 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

  10. Light scattering by an elongated particle: spheroid versus infinite cylinder

    Microsoft Academic Search

    N. V. Voshchinnikov; V. G. Farafonov

    2002-01-01

    Using the method of separation of variables and a new approach to calculations of the prolate spheroidal wave functions, we study the optical properties of very elongated (cigar-like) spheroidal particles. A comparison of extinction efficiency factors of prolate spheroids and infinitely long circular cylinders is made. For the normal and oblique incidence of radiation, the efficiency factors for spheroids converge

  11. Geographical Database Watermarking by Polygon Elongation (Technical Report)

    E-print Network

    Paris-Sud XI, Université de

    , spatial accuracy is not crucial for tourist city maps designers who apply strong transformations to roadGeographical Database Watermarking by Polygon Elongation (Technical Report) Julien Lafaye1 , Jean B geographical databases, with the focus on the buildings layer. Embedded watermarks survive common geographical

  12. HYPOCREA/TRICHODERMA: SPECIES WITH CONIDIOPHORE ELONGATIONS AND GREEN CONIDIA

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The species of Trichoderma and Hypocrea that have green conidia and sterile or fertile elongations of their conidiophores are described or redescribed and their phylogenetic position is explored. Five new species of Hypocrea are described, viz. H. cremea, H. cuneispora, H. estonica, H. strictipilis,...

  13. Photoinhibition of Stem Elongation by Blue and Red Light 1

    PubMed Central

    Kigel, Jaime; Cosgrove, Daniel J.

    1991-01-01

    The underlying mechanism of photoinhibition of stem elongation by blue (BL) and red light (RL) was studied in etiolated seedlings of pea (Pisum sativum L. cv Alaska). Brief BL irradiations resulted in fast transient inhibition of elongation, while a delayed (lag approximately 60 minutes) but prolonged inhibition was observed after brief RL. Possible changes in the hydraulic and wall properties of the growing cells during photoinhibition were examined. Cell sap osmotic pressure was unaffected by BL and RL, but both irradiations increased turgor pressure by approximately 0.05 megapascal (pressure-probe technique). Cell wall yielding was analyzed by in vivo stress relaxation (pressure-block technique). BL and RL reduced the initial rate of relaxation by 38 and 54%, while the final amount of relaxation was decreased by 48 and 10%, respectively. These results indicate that RL inhibits elongation mainly by lowering the wall yield coefficient, while most of the inhibitory effect of BL was due to an increase of the yield threshold. Mechanical extensibility of cell walls (Instron technique) was decreased by BL and RL, mainly due to a reduction in the plastic component of extensibility. Thus, photoinhibitions of elongation by both BL and RL are achieved through changes in cell wall properties, and are not due to effects on the hydraulic properties of the cell. PMID:11537486

  14. Viral-host interactions that control HIV-1 transcriptional elongation

    PubMed Central

    Lu, Huasong; Li, Zichong; Xue, Yuhua; Zhou, Qiang

    2015-01-01

    1. Summary Regulation of the pause and elongation by RNA polymerase (Pol) II is used widely by metazoans to attain the pattern of gene expression that is essential for optimal cell growth/renewal, differentiation and stress response. Currently, much of what we know about Pol II elongation control comes from pioneering studies of the HIV-1-encoded Tat protein and its host cellular co-factors. The interaction between the two fuels a powerful feedback circuit that activates HIV transcription and prevents the virus from entering latency. One of the key Tat cofactors is the human positive transcription elongation factor b (P-TEFb), which exists in a family of complexes with distinct functions during Tat transactivation. This article reviews recent progresses in HIV transcription research with an emphasis on the intricate control of the various P-TEFb complexes, structural and functional insights into their interactions with Tat, the multifaceted roles of post-translational modifications of Tat and epigenetic control of HIV chromatin in modulating Tat activity and HIV latency. The knowledge from these studies will not only help design better strategies to fight HIV infection and transcriptional latency, but also advance the overall understanding of the mechanism controlling transcriptional elongation in general. PMID:23795863

  15. 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...

  16. River Elongation as a Proxy for Lateral Channel Activity

    Microsoft Academic Search

    J. W. Lauer

    2009-01-01

    Lateral channel movement is a process that is tightly linked to both channel hydraulics and sediment transport, strongly influences floodplain ecology, and also has great relevance for banktop property owners. The correlation between channel migration rate and channel curvature usually causes meandering river channels to elongate as they migrate laterally. Over the long term, the increase in sinuosity is compensated

  17. Model Calculations for Io's Atmosphere at Eastern and Western Elongations

    Microsoft Academic Search

    Mau C. Wong; William H. Smyth

    2000-01-01

    Numerical calculations are performed for Io's sublimation atmosphere at eastern and western elongations using an improved version of the multispecies hydrodynamic model first developed by Wong and Johnson (1996). Subsolar SO2 frost temperatures of 113 and 120 K are adopted to cover a range of plausible atmospheric abundances that are consistent with recent observations. In the model, the incoming plasma

  18. Mitigation of Spot Elongation Effects ErezN Ribak1

    E-print Network

    Ribak, Erez

    to their elongation7,4 . · Height imaging, relaying each section along the beam on a different pixel of the detector, if the laser creating the artificial beacon is broken up into many weak independent lasers, sent from scattered locations up to the periphery of a large telescope. Keywords : adaptive optics, laser guide stars

  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. Kinetic analysis of beta-amyloid fibril elongation

    Microsoft Academic Search

    Michelle J Cannon; Angela D Williams; Ronald Wetzel; David G Myszka

    2004-01-01

    We used surface plasmon resonance biosensors to evaluate the kinetics associated with the initial events of beta-amyloid (A?) fibril elongation. Fibrils were immobilized on the sensor chip surface and extended by exposure to soluble A?(1–40) peptide. The fibril surfaces bound Congo red, a marker for ? sheet structures, and exhibited a slow linear background decay that is consistent with fibril

  1. 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-?-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-?-D-glucosaminide (GlcNAc-C12), tridecan-7-yl N-acetyl-?-D-glucosaminide (GlcNAc-2C6), and pentacosan-13-yl N-acetyl-?-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

  2. The critical temperature of steel columns with restrained thermal elongation

    Microsoft Academic Search

    I. Cabrita Neves

    1995-01-01

    The influence of restraint of their thermal elongation on the fire resistance of steel columns is studied. The restraining forces are calculated as a function of steel temperature. The influence of several parameters on the fire resistance is analyzed: stiffness of the structure to which the column belongs; slenderness of the column; and eccentricity of the restraining forces.

  3. Transposon tagging and the study of root development in Arabidopsis

    NASA Technical Reports Server (NTRS)

    Tsugeki, R.; Olson, M. L.; Fedoroff, N. V.

    1998-01-01

    The maize Ac-Ds transposable element family has been used as the basis of transposon mutagenesis systems that function in a variety of plants, including Arabidopsis. We have developed modified transposons and methods which simplify the detection, cloning and analysis of insertion mutations. We have identified and are analyzing two plant lines in which genes expressed either in the root cap cells or in the quiescent cells, cortex/endodermal initial cells and columella cells of the root cap have been tagged with a transposon carrying a reporter gene. A gene expressed in root cap cells tagged with an enhancer-trap Ds was isolated and its corresponding EST cDNA was identified. Nucleotide and deduced amino acid sequences of the gene show no significant similarity to other genes in the database. Genetic ablation experiments have been done by fusing a root cap-specific promoter to the diphtheria toxin A-chain gene and introducing the fusion construct into Arabidopsis plants. We find that in addition to eliminating gravitropism, root cap ablation inhibits elongation of roots by lowering root meristematic activities.

  4. An estimate of the error caused by the elongation of the wavelength in a focused beam in free-space electromagnetic parameters measurement.

    PubMed

    Zhang, Yunpeng; Li, En; Guo, Gaofeng; Xu, Jiadi; Wang, Chao

    2014-09-01

    A pair of spot-focusing horn lens antenna is the key component in a free-space measurement system. The electromagnetic constitutive parameters of a planar sample are determined using transmitted and reflected electromagnetic beams. These parameters are obtained from the measured scattering parameters by the microwave network analyzer, thickness of the sample, and wavelength of a focused beam on the sample. Free-space techniques introduced by most papers consider the focused wavelength as the free-space wavelength. But in fact, the incident wave projected by a lens into the sample approximates a Gaussian beam, thus, there has an elongation of the wavelength in the focused beam and this elongation should be taken into consideration in dielectric and magnetic measurement. In this paper, elongation of the wavelength has been analyzed and measured. Measurement results show that the focused wavelength in the vicinity of the focus has an elongation of 1%-5% relative to the free-space wavelength. Elongation's influence on the measurement result of the permittivity and permeability has been investigated. Numerical analyses show that the elongation of the focused wavelength can cause the increase of the measured value of the permeability relative to traditionally measured value, but for the permittivity, it is affected by several parameters and may increase or decrease relative to traditionally measured value. PMID:25273749

  5. Europium Uptake and Partitioning in Oat (Avena sativa) Roots as studied By Laser-Induced Fluorescence Spectroscopy and Confocal Microscopy Profiling Technique

    SciTech Connect

    Fellows, Robert J.; Wang, Zheming; Ainsworth, Calvin C.

    2003-11-15

    The uptake of Eu3+ by elongating oat plant roots was studied by fluorescence spectroscopy, fluorescence lifetime measurement, as well as laser excitation time-resolved confocal fluorescence profiling technique. The results of this work indicated that the initial uptake of Eu(III) by oat root was most evident within the apical meristem of the root just proximal to the root cap. Distribution of assimilated Eu(III) within the roots differentiation and elongation zone was non-uniform. Higher concentrations were observed within the vascular cylinder, specifically in the phloem and developing xylem parenchyma. Elevated levels of the metal were also observed in the root hairs of the mature root. The concentration of assimilated Eu3+ dropped sharply from the apical meristem to the differentiation and elongation zone and then gradually decreased as the distance from the root cap increased. Fluorescence spectroscopic characteristics of the assimilated Eu3+ suggested that the Eu3+ exists a s inner-sphere mononuclear complexes inside the root. This work has also demonstrated the effectiveness of a time-resolved Eu3+ fluorescence spectroscopy and confocal fluorescence profiling techniques for the in vivo, real-time study of metal[Eu3+] accumulation by a functioning intact plant root. This approach can prove valuable for basic and applied studies in plant nutrition and environmental uptake of actinide radionuclides.

  6. Growth efficiency increases as relative growth rate increases in shoots and roots of Eucalyptus globulus deprived of nitrogen or treated with salt.

    PubMed

    Macfarlane, Craig; Hansen, Lee D; Edwards, Justine; White, Donald A; Adams, Mark A

    2005-05-01

    We used calorimetry to test whether there is a single general relationship between growth and respiration in shoots and roots of Eucalyptus globulus Labill. seedlings when stressed, irrespective of the type or severity of stress. We found that nitrogen (N) deprivation and salt treatment had no effect on the relationship between growth and respiration and little effect on absolute rates of respiration. Carbon-conversion efficiency (epsilonC) ranged from 0.7 to 0.9 for specific growth rates (R(SG)) greater than 0.3 day(-1). Above an R(SG) of 0.1 day(-1), epsilonC decreased gradually with decreasing R(SG) and between an R(SG) of 0- 0.1 day(-1), epsilonC decreased rapidly. We conclude that the relationship between epsilonC and R(SG) is not greatly affected by salt or N-deprivation stresses. Relationships between gross productivity and epsilonC may be generally applicable, in which case they could improve on the "flat-tax" approach to modeling net primary productivity from gross productivity while avoiding the complexity of more explicit models of plant respiration. However, the relationship between gross productivity and epsilonC was sensitive to temperature and the effect of temperature on epsilonC thus requires further investigation. Nitrogen deprivation caused large decreases in leaf area and shoot to root ratio, and mature leaves of N-deprived plants had lower intrinsic water-use efficiencies than leaves of plants well supplied with nutrients. Nitrogen deprivation increased apical dominance and most of the reduction in leaf area was the result of fewer secondary branches, although leaf size was also reduced. Our results suggest that N deprivation reduces productivity primarily by reducing sink size, rather than sink activity, and that apical dominance may be an important mechanism for maintaining adequate epsilonC in resource-limited conditions. PMID:15741150

  7. Bacteria isolated from roots and rhizosphere of Vitis vinifera retard water losses, induce abscisic acid accumulation and synthesis of defense-related terpenes in in vitro cultured grapevine.

    PubMed

    Salomon, María Victoria; Bottini, Rubén; de Souza Filho, Gonçalo Apolinário; Cohen, Ana Carmen; Moreno, Daniela; Gil, Mariana; Piccoli, Patricia

    2014-08-01

    Eleven bacterial strains were isolated at different soil depths from roots and rhizosphere of grapevines from a commercial vineyard. By 16S rRNA gene sequencing 10 different genera and 8 possible at species level were identified. From them, Bacillus licheniformis Rt4M10 and Pseudomonas fluorescens Rt6M10 were selected according to their characteristics as plant growth promoting rhizobacteria (PGPR). Both produced abscisic acid (ABA), indole-3-acetic acid (IAA) and the gibberellins A1 and A3 in chemically-defined medium. They also colonized roots of in vitro grown Vitis vinifera cv. Malbec plants. As result of bacterization ABA levels in 45 days-old in vitro plants were increased 76-fold by B. licheniformis and 40-fold by P. fluorescens as compared to controls. Both bacteria diminished plant water loss rate in correlation with increments of ABA. Twenty and 30 days post bacterization the plants incremented terpenes. The monoterpenes ?-pinene, terpinolene, 4-carene, limonene, eucalyptol and lilac aldehyde A, and the sesquiterpenes ?-bergamotene, ?-farnesene, nerolidol and farnesol were assessed by gas chromatography-electron impact mass spectrometry analysis. ?-Pinene and nerolidol were the most abundant (µg per g of tissue in plants bacterized with P. fluorescens). Only ?-pinene, eucalyptol and farnesol were identified at low concentration in non-bacterized plants treated with ABA, while no terpenes were detected in controls. The results obtained along with others from literature suggest that B. licheniformis and P. fluorescens act as stress alleviators by inducing ABA synthesis so diminishing water losses. These bacteria also elicit synthesis of compounds of plant defense via an ABA independent mechanism. PMID:24118032

  8. Conditioning lesions enhance growth state only in sensory neurons lacking calcitonin gene-related peptide and isolectin B4-binding.

    PubMed

    Kalous, A; Keast, J R

    2010-03-10

    A conditioning lesion improves regeneration of central and peripheral axons of dorsal root ganglion (DRG) neurons after a subsequent injury by enhancing intrinsic growth capacity. This enhanced growth state is also observed in cultured DRG neurons, which support a more sparsely and rapidly elongating mode of growth after a prior conditioning lesion in vivo. Here we examined differences in the capacity or requirements of specific types of sensory neurons for regenerative growth, which has important consequences for development of strategies to improve recovery after injury. We showed that after partial or complete injury of the sciatic nerve in mice, an elongating mode of growth in vitro was activated only in DRG neurons that did not express calcitonin gene-related peptide (CGRP) or bind Bandeiraea simplicifolia I-isolectin B4 (IB4). We also directly examined the response of conditioned sensory neurons to nerve growth factor (NGF), which does not enhance growth in injured peripheral nerves in vivo. We showed that after partial injury, NGF stimulated a highly branched and linearly restricted rather than elongating mode of growth. After complete injury, the function of NGF was impaired, which immunohistochemical studies of DRG indicated was at least partly due to downregulation of the NGF receptor, tropomyosin-related kinase A (TrkA). These results suggest that, regardless of the type of conditioning lesion, each type of DRG neuron has a distinct intrinsic capacity or requirement for the activation of rapidly elongating growth, which does not appear to be influenced by NGF. PMID:20006678

  9. The calcium sensor GhCaM7 promotes cotton fiber elongation by modulating reactive oxygen species (ROS) production.

    PubMed

    Tang, Wenxin; Tu, Lili; Yang, Xiyan; Tan, Jiafu; Deng, Fenglin; Hao, Juan; Guo, Kai; Lindsey, Keith; Zhang, Xianlong

    2014-04-01

    Fiber elongation is the key determinant of fiber quality and output in cotton (Gossypium hirsutum). Although expression profiling and functional genomics provide some data, the mechanism of fiber development is still not well understood. Here, a gene encoding a calcium sensor, GhCaM7, was isolated based on its high expression level relative to other GhCaMs in fiber cells at the fast elongation stage. The level of expression of GhCaM7 in the wild-type and the fuzzless/lintless mutant correspond to the presence and absence, respectively, of fiber initials. Overexpressing GhCaM7 promotes early fiber elongation, whereas GhCaM7 suppression by RNAi delays fiber initiation and inhibits fiber elongation. Reactive oxygen species (ROS) play important roles in early fiber development. ROS induced by exogenous hydrogen peroxide (H2 O2 ) and Ca(2+) starvation promotes early fiber elongation. GhCaM7 overexpression fiber cells show increased ROS concentrations compared with the wild-type, while GhCaM7 RNAi fiber cells have reduced concentrations. Furthermore, we show that H2 O2 enhances Ca(2+) influx into the fiber and feedback-regulates the expression of GhCaM7. We conclude that GhCaM7, Ca(2+) and ROS are three important regulators involved in early fiber elongation. GhCaM7 might modulate ROS production and act as a molecular link between Ca(2+) and ROS signal pathways in early fiber development. PMID:24443839

  10. Interaction between hydrotropism and gravitropism in seedling roots

    NASA Astrophysics Data System (ADS)

    Kobayashi, A.; Takahashi, A.; Yamazaki, Y.; Kakimoto, Y.; Higashitani, A.; Fujii, N.; Takahashi, H.

    Roots display positive hydrotropism in response to a moisture gradient, which could play a role in avoiding drought stress. Because roots also respond to other stimuli such as gravity, touch and light and exhibit gravitropism, thigmotropism and phototropism, respectively, their growth orientation is determined by interaction among those tropisms. We have demonstrated the interaction between hydrotropism and gravitropism. For example, 1) agravitropic roots of pea mutant strongly respond to a moisture gradient and show positive hydrotropism by overcoming gravitropism, 2) in wild type pea roots hydrotropism is weak but pronounced when rotated on clinostat, 3) cucumber roots are positively gravitropic on the ground but become hydrotropic in microgravity, and 4) maize roots change their growth direction depending on the intensities of both gravistimulation and hydrostimulation. Here we found that Arabidopsis roots could display strong hydrotropism by overcoming gravitropism. It was discovered that amyloplasts in the columella cells are rapidly degraded upon exposure to a moisture gradient. Thus, degradation of amyloplasts could reduce the responsiveness to gravity, which could pronounce the hydrotropic response. In hydrotropically stimulated roots of pea seedlings, however, we could not observe a rapid degradation of amyloplasts in the columella cells. These results suggest that mechanism underlying the interaction between hydrotropism and gravitropism differs among plant species. To further study the molecular mechanism of hydrotropism and its interaction with gravitropism, we isolated unique mutants of Arabidopsis of which roots showed either ahydrotropism, reduced hydrotropism or negative hydrotropic response and examined their gravitropism, phototropism, waving response, amyloplast degradation and elongation growth. Based on the characterization of hydrotropic mutants, we will attempt to compare the mechanisms of the two tropisms and to clarify their cross talk for controlling the directional growth of seedling roots.

  11. Myosin XIK of Arabidopsis thaliana Accumulates at the Root Hair Tip and Is Required for Fast Root Hair Growth

    PubMed Central

    Park, Eunsook; Nebenführ, Andreas

    2013-01-01

    Myosin motor proteins are thought to carry out important functions in the establishment and maintenance of cell polarity by moving cellular components such as organelles, vesicles, or protein complexes along the actin cytoskeleton. In Arabidopsis thaliana, disruption of the myosin XIK gene leads to reduced elongation of the highly polar root hairs, suggesting that the encoded motor protein is involved in this cell growth. Detailed live-cell observations in this study revealed that xik root hairs elongated more slowly and stopped growth sooner than those in wild type. Overall cellular organization including the actin cytoskeleton appeared normal, but actin filament dynamics were reduced in the mutant. Accumulation of RabA4b-containing vesicles, on the other hand, was not significantly different from wild type. A functional YFP-XIK fusion protein that could complement the mutant phenotype accumulated at the tip of growing root hairs in an actin-dependent manner. The distribution of YFP-XIK at the tip, however, did not match that of the ER or several tip-enriched markers including CFP-RabA4b. We conclude that the myosin XIK is required for normal actin dynamics and plays a role in the subapical region of growing root hairs to facilitate optimal growth. PMID:24116145

  12. Touch modulates gravity sensing to regulate the growth of primary roots of Arabidopsis thaliana.

    PubMed

    Massa, Gioia D; Gilroy, Simon

    2003-02-01

    Plants must sense and respond to diverse stimuli to optimize the architecture of their root system for water and nutrient scavenging and anchorage. We have therefore analyzed how information from two of these stimuli, touch and gravity, are integrated to direct root growth. In Arabidopsis thaliana, touch stimulation provided by a glass barrier placed across the direction of growth caused the root to form a step-like growth habit with bends forming in the central and later the distal elongation zones. This response led to the main root axis growing parallel to, but not touching the obstacle, whilst the root cap maintained contact with the barrier. Removal of the graviperceptive columella cells of the root cap using laser ablation reduced the bending response of the distal elongation zone. Similarly, although the roots of the gravisensing impaired pgm1-1 mutant grew along the barrier at the same average angle as wild-type, this angle became more variable with time. These observations imply a constant gravitropic re-setting of the root tip response to touch stimulation from the barrier. In wild-type plants, transient touch stimulation of root cap cells, but not other regions of the root, inhibited both subsequent gravitropic growth and amyloplast sedimentation in the columella. Taken together, these results suggest that the cells of the root cap sense touch stimuli and their subsequent signaling acts on the columella cells to modulate their graviresponse. This interaction of touch and gravity signaling would then direct root growth to avoid obstacles in the soil while generally maintaining downward growth. PMID:12581302

  13. Long-distance abscisic acid signalling under different vertical soil moisture gradients depends on bulk root water potential and average soil water content in the root zone.

    PubMed

    Puértolas, Jaime; Alcobendas, Rosalía; Alarcón, Juan J; Dodd, Ian C

    2013-08-01

    To determine how root-to-shoot abscisic acid (ABA) signalling is regulated by vertical soil moisture gradients, root ABA concentration ([ABA](root)), the fraction of root water uptake from, and root water potential of different parts of the root zone, along with bulk root water potential, were measured to test various predictive models of root xylem ABA concentration [RX-ABA](sap). Beans (Phaseolus vulgaris?L. cv. Nassau) were grown in soil columns and received different irrigation treatments (top and basal watering, and withholding water for varying lengths of time) to induce different vertical soil moisture gradients. Root water uptake was measured at four positions within the column by continuously recording volumetric soil water content (?v). Average ?v was inversely related to bulk root water potential (?(root)). In turn, ?(root) was correlated with both average [ABA](root) and [RX-ABA](sap). Despite large gradients in ?v, [ABA](root) and root water potential was homogenous within the root zone. Consequently, unlike some split-root studies, root water uptake fraction from layers with different soil moisture did not influence xylem sap (ABA). This suggests two different patterns of ABA signalling, depending on how soil moisture heterogeneity is distributed within the root zone, which might have implications for implementing water-saving irrigation techniques. PMID:23387513

  14. Calculated activity of Mn2+ at the outer surface of the root cell plasma membrane governs Mn nutrition of cowpea seedlings

    PubMed Central

    Kopittke, Peter M.; Blamey, F. Pax C.; Wang, Peng; Menzies, Neal W.

    2011-01-01

    Manganese (Mn) is an essential micronutrient for plant growth but is often toxic in acid or waterlogged soils. Using cowpea (Vigna unguiculata L. Walp.) grown with 0.05–1500 ?M Mn in solution, two short-term (48 h) solution culture experiments examined if the effects of cations (Ca, Mg, Na, Al, or H) on Mn nutrition are related to the root cells’ plasma membrane (PM) surface potential, ?00. When grown in solutions containing levels of Mn that were toxic, both relative root elongation rate (RRER) and root tissue Mn concentration were more closely related to the activity of Mn2+ at the outer surface of the PM, {Mn2+}00 (R2=0.812 and 0.871) than to its activity in the bulk solution, {Mn2+}b (R2=0.673 and 0.769). This was also evident at lower levels of Mn (0.05–10 ?M) relevant to studies investigating Mn as an essential micronutrient (R2=0.791 versus 0.590). In addition, changes in the electrical driving force for ion transport across the PM influenced both RRER and the Mn concentration in roots. The {Mn2+}b causing a 50% reduction in root growth was found to be c. 500 to >1000 ?M (depending upon solution composition), whilst the corresponding value was 3300 ?M when related to {Mn2+}00. Although specific effects such as competition are not precluded, the data emphasize the importance of non-specific electrostatic effects in the Mn nutrition of cowpea seedlings over a 1×105-fold range of Mn concentration in solution. PMID:21511910

  15. Graviresponsiveness and columella cell structure in primary and secondary roots of Ricinus communis

    Microsoft Academic Search

    Randy Moore; John Pasieniuk

    1984-01-01

    In order to determine what structural changes are associated with the onset of graviresponsiveness by plant roots, we have monitored the quantitative ultrastructures of columella (i.e., graviperceptive) cells in primary and secondary roots of Ricinus communis. The relative volumes of cellular components in lateral (i.e., minimally graviresponsive) roots were not significantly different from those of primary roots. The relative volumes

  16. CO/sub 2/ speeds root growth of cuttings

    SciTech Connect

    Yarris, L.

    1984-06-01

    Researchers have determined that CO/sub 2/ enrichment accelerates cutting root growth on foliage plants and flowering shrubs. For horticultural crops, including most woody ornamentals, apples, pears, and small fruit trees, roots consistently emerged 1 or 2 days earlier in the enriched atmosphere. These tests were conducted as part of a broad, ongoing study to determine how photosynthesis is related to rooting and whether rooting can be stimulated by stimulating photosynthesis.

  17. Variability in root production, phenology, and turnover rate among 12 temperate tree species.

    PubMed

    McCormack, M Luke; Adams, Thomas S; Smithwick, Erica A H; Eissenstat, David M

    2014-08-01

    The timing of fine root production and turnover strongly influences both the seasonal potential for soil resource acquisition among competing root systems and the plant fluxes of root carbon into soil pools. However, basic patterns and variability in the rates and timing or fine root production and turnover are generally unknown among perennial plants species. We address this shortfall using a heuristic model relating root phenology to turnover together with three years of minirhizotron observations of root dynamics in 12 temperate tree species grown in a common garden. We specifically investigated how the amount and the timing of root production differ among species and how they impact estimates of fine root turnover. Across the 12 species, there was wide variation in the timing of root production with some species producing a single root flush in early summer and others producing roots either more uniformly over the growing season or in multiple pulses. Additionally, the pattern and timing of root production appeared to be consistent across years for some species but varied in others. Root turnover rate was related to total root production (P < 0.001) as species with greater root production typically had faster root turnover rates. We also found that, within species, annual root production varied up to a threefold increase between years, which led to large interannual differences in turnover rate. Results from the heuristic model indicated that shifting the pattern or timing of root production can impact estimates of root turnover rates for root populations with life spans less than one year while estimates of root turnover rate for longer lived roots were unaffected by changes in root phenology. Overall, we suggest that more detailed observations of root phenology and production will improve fidelity of root turnover estimates. Future efforts should link patterns of root phenology and production with whole-plant life history traits and variation in annual and seasonal climate. PMID:25230473

  18. Light as stress factor to plant roots – case of root halotropism

    PubMed Central

    Yokawa, Ken; Fasano, Rossella; Kagenishi, Tomoko; Baluška, František

    2014-01-01

    Despite growing underground, largely in darkness, roots emerge to be very sensitive to light. Recently, several important papers have been published which reveal that plant roots not only express all known light receptors but also that their growth, physiology and adaptive stress responses are light-sensitive. In Arabidopsis, illumination of roots speeds-up root growth via reactive oxygen species-mediated and F-actin dependent process. On the other hand, keeping Arabidopsis roots in darkness alters F-actin distribution, polar localization of PIN proteins as well as polar transport of auxin. Several signaling components activated by phytohormones are overlapping with light-related signaling cascade. We demonstrated that the sensitivity of roots to salinity is altered in the light-grown Arabidopsis roots. Particularly, light-exposed roots are less effective in their salt-avoidance behavior known as root halotropism. Here we discuss these new aspects of light-mediated root behavior from cellular, physiological and evolutionary perspectives. PMID:25566292

  19. Root canal preparation with Endo-Eze AET: changes in root canal shape assessed by micro-computed tomography

    Microsoft Academic Search

    F. Paque ´; F. Barbakow; O. A. Peters

    2005-01-01

    PaqueF, Barbakow F, Peters OA. Root canal preparation with Endo-Eze AET: changes in root canal shape assessed by micro-computed tomography. International Endodontic Journal, 38, 456-464, 2005. Aim To evaluate the relative performance of Endo-Eze Anatomic Endodontic Technology (AET) stainless steel instruments when shaping maxillary molar root canals in vitro. Methodology Extracted human maxillary molars were scanned, before and after root

  20. Ecology of Root Colonizing Massilia (Oxalobacteraceae)

    PubMed Central

    Ofek, Maya; Hadar, Yitzhak; Minz, Dror

    2012-01-01

    Background Ecologically meaningful classification of bacterial populations is essential for understanding the structure and function of bacterial communities. As in soils, the ecological strategy of the majority of root-colonizing bacteria is mostly unknown. Among those are Massilia (Oxalobacteraceae), a major group of rhizosphere and root colonizing bacteria of many plant species. Methodology/Principal Findings The ecology of Massilia was explored in cucumber root and seed, and compared to that of Agrobacterium population, using culture-independent tools, including DNA-based pyrosequencing, fluorescence in situ hybridization and quantitative real-time PCR. Seed- and root-colonizing Massilia were primarily affiliated with other members of the genus described in soil and rhizosphere. Massilia colonized and proliferated on the seed coat, radicle, roots, and also on hyphae of phytopathogenic Pythium aphanidermatum infecting seeds. High variation in Massilia abundance was found in relation to plant developmental stage, along with sensitivity to plant growth medium modification (amendment with organic matter) and potential competitors. Massilia absolute abundance and relative abundance (dominance) were positively related, and peaked (up to 85%) at early stages of succession of the root microbiome. In comparison, variation in abundance of Agrobacterium was moderate and their dominance increased at later stages of succession. Conclusions In accordance with contemporary models for microbial ecology classification, copiotrophic and competition-sensitive root colonization by Massilia is suggested. These bacteria exploit, in a transient way, a window of opportunity within the succession of communities within this niche. PMID:22808103

  1. Tobacco leaves and roots differ in the expression of proline metabolism-related genes in the course of drought stress and subsequent recovery.

    PubMed

    Dobrá, Jana; Vanková, Radomira; Havlová, Marie; Burman, Adlai J; Libus, Ji?i; Storchová, Helena

    2011-09-01

    In plants, members of gene families differ in function and mode of regulation. Fine-tuning of the expression of individual genes helps plants to cope with a variable environment. Genes encoding proline dehydrogenase (PDH), the key enzyme in proline degradation, and the proline biosynthetic enzyme, ?(1)-pyrroline-5-carboxylate synthetase (P5CS), play an important role in responses to osmotic and drought stresses. We compared the expression patterns of three PDH and two putative P5CS genes during drought stress progression and subsequent recovery. Whereas the NtPDH1 gene was affected little by dehydration or rehydration, the NtPDH2 gene responded rapidly to both conditions, and was down-regulated under drought. The CIG1 gene, encoding cytokinin-inducible PDH, exhibited an intermediate transcription pattern. Whereas P5CS B was not affected by the stress conditions, the P5CS A gene was highly up-regulated during drought stress. CIG1 and NtPDH1 transcription was not activated, and P5CS A was only partially reduced in leaves within 24-h after rehydration, a re-watering period sufficient for large physiological changes to occur. The lack of activation of tobacco PDH genes and incomplete reduction of the P5CS A gene in leaves within 24-h of rehydration may reflect the need for the protection of plants to potential subsequent stresses. The data indicate that recovery is a specific physiological process following different patterns in leaves and roots. PMID:21481968

  2. Deficits in foot skin sensation are related to alterations in balance control in chronic low back patients experiencing clinical signs of lumbar nerve root impingement.

    PubMed

    Frost, Lydia R; Bijman, Marc; Strzalkowski, Nicholas D J; Bent, Leah R; Brown, Stephen H M

    2015-05-01

    Chronic low back pain (LBP) patients with radiculopathy, or sciatica, experience pain, tingling or numbness radiating down their leg due to compression of the lumbar nerve root. The resulting reduction in somatosensory information from the foot sole may contribute to deficits in standing balance control. This work was designed to investigate the relationship between foot skin sensitivity and standing balance control in chronic LBP patients with associated radiculopathy. Patients (n=9) and matched healthy controls (n=9) were recruited to the study, and were tested for balance control in both quiet standing as well as during rapid arm raise perturbation trials on a force plate. Foot skin sensitivity was tested bilaterally for vibratory threshold (3, 40 and 250 Hz) and touch (monofilament) threshold. Results demonstrate that patients had reduced sensitivity to 250 Hz vibration in their affected compared to unaffected foot (at the great toe and heel), as well as compared to controls (at the great toe), but there were no differences with lower frequency vibratory testing or with monofilament testing. While there were no significant between-group differences in balance measures, moderate statistically significant correlations between 250 Hz sensitivity and quiet standing balance parameters were uncovered. Thus, patients demonstrate reduced high-frequency vibratory sensitivity at the foot sole, and correlations with quiet standing balance measures indicate a connection between these foot skin sensitivity deficits and alterations in balance control. Clinically, this identifies high frequency vibration testing as an important measure of skin sensitivity in patients with radiculopathy. PMID:25887249

  3. Prokaryotic translation initiation factor IF3 is an elongated protein consisting of two crystallizable domains

    SciTech Connect

    Kycia, J.H.; Biou, V.; Shu, F. [Brookhaven National Lab., Upton, New York, NY (United States)

    1995-05-09

    We show that translation initiation factor IF3 can be split into two fragments of nearly equal size by the Escherichia coli outer membrane protease omptin. Circular dichroism and small-angle neutron scattering show that the two fragments are structured as domains. Each domain is relatively compact, and they are separated by about 45 {Angstrom} in intact IF3. Thus IF3 is an elongated protein that consists of two well-separated domains. We suggest that these two domains are involved in ribosome binding across the cleft of the 30S ribosome. We also report the crystallization of each domain of IF3. 26 refs., 3 figs., 1 tab.

  4. Root canal irrigants

    PubMed Central

    Kandaswamy, Deivanayagam; Venkateshbabu, Nagendrababu

    2010-01-01

    Successful root canal therapy relies on the combination of proper instrumentation, irrigation, and obturation of the root canal. Of these three essential steps of root canal therapy, irrigation of the root canal is the most important determinant in the healing of the periapical tissues. The primary endodontic treatment goal must thus be to optimize root canal disinfection and to prevent reinfection. In this review of the literature, various irrigants and the interactions between irrigants are discussed. We performed a Medline search for English-language papers published untill July 2010. The keywords used were ‘root canal irrigants’ and ‘endodontic irrigants.’ The reference lists of each article were manually checked for additional articles of relevance. PMID:21217955

  5. Elongated solid electrolyte cell configurations and flexible connections therefor

    DOEpatents

    Reichner, Philip (Plum Boro, PA)

    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.

  6. Elongational Flow-induced Crystallization in Polypropylene/Talc Nanocomposites

    NASA Astrophysics Data System (ADS)

    khalil, Mouhamad; hébraud, Pascal; Mcheik, Ali; Mortada, Houssein; Lakis, Hassan; Hamieh, Tayssir

    During the processing of the polymers, macromolecules undergo a significant flow just before or during cooling. For semi-crystalline materials, the flow widely influences both the crystallization kinetics and the resulting crystalline orientation. Moreover, in the presence of nucleating filler, even more with a high aspect ratio, these phenomena of crystallization under elongational conditions can be disrupted. In this study, melt blended nanocomposites of PP /Talc were processed using an internal mixer. An elongational rheometer was used to generate well controlled different extensional flow conditions. Samples were then characterized by WAXS to reveal and quantify the fillers and PP crystalline phase orientation. Crystalline orientation of polypropylene was found to be strongly affected by the addition of Talc under extensional flow and the Talc orientation.

  7. 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.

  8. Influence of Multiplicative Stochastic Variation on Translational Elongation Rates

    E-print Network

    Sandip Datta; Brian Seed

    2014-09-15

    Recent experiments have shown that stochastic effects exerted at the level of translation contribute a substantial portion of the variation in abundance of proteins expressed at moderate to high levels. This study analyzes translational noise arising from fluctuations in residue-specific elongation rates. The resulting variation has multiplicative components that lead individual protein abundances in a population to exhibit approximately log-normal behavior. The high variability inherent in the process leads to parameter variation that has the features of a type of noise in biological systems that has been characterized as extrinsic. Elongation rate variation offers an accounting for a major component of extrinsic noise, and the analysis provided here highlights a probability distribution that is a natural extension of the Poisson and has broad applicability to many types of multiplicative noise processes.

  9. Priciples of rehabilitation in cases of lower limbs; elongation.

    PubMed

    Lisi?ski, Przemys?aw; Stry?a, Wanda

    2002-08-30

    That to received positive results of lower limbs; elongation is necessary to accommodate rehabilitation to stages of orthopedic treatment. Rehabilitation in each case is divided into five periods. Main goals are improvement of nutritive status of all tissues and restoration of full range movement. Beside of this rehabilitation is concentrated on improvement of power and efficiency of muscles. The last step is reconstruction of the normal gait. PMID:17679888

  10. Elongated mouse chromosomes suitable for enhanced molecular cytogenetics

    Microsoft Academic Search

    Sherif Louis; Katalin Benedek; Michael Mowat; George Klein; Sabine Mai

    2004-01-01

    Characterization of genetic disorders in humans and animal models requires identification of chromosomal aberrations. However, identifying fine deletions or insertion in metaphase chromosomes has been always a challenge due to limitations of resolution. In this study we developed a rapid method for chromosome elongation using two different intercalating agents: ethidium bromide and 5-bromo-2?-deoxyuridine (BrdU), together with a short-term mitotic block

  11. Dynamics of an elongated magnetic droplet in a rotating field.

    PubMed

    C?bers, A

    2002-12-01

    A model is proposed for the dynamics of an elongated droplet under the action of a low frequency rotating magnetic field. This model determines a set of critical frequencies at which the transitions to more complex bent shapes take place. These transitions occur through propagation of jumps of the droplet's axial tangent angle described by a nonlinear singularly perturbed partial differential equation with the intrinsic viscosity of the droplet playing the regularizing role. PMID:12513280

  12. Novel domains and orthologues of eukaryotic transcription elongation factors

    Microsoft Academic Search

    Chris P. Ponting

    2002-01-01

    The passage of RNA polymerase II across eukary- otic genes is impeded by the nucleosome, an octamer of histones H2A, H2B, H3 and H4 dimers. More than a dozen factors in the yeast Saccharomyces cerevisiae are known to facilitate transcription elongation through chromatin. In order to better understand the evolution and func- tion of these factors, their sequences have been

  13. The solar elongation distribution of low-frequency radio bursts

    Microsoft Academic Search

    M. L. Kaiser

    1975-01-01

    Over 500 days of low-frequency (less than 1 MHz) radio observations from the IMP-6 spacecraft have been accumulated to produce a two-dimensional map (frequency vs elongation) of solar type III burst occurrences. This map indicates that most solar bursts in this frequency range are observed at the second harmonic of the plasma frequency, rather than the fundamental. The map also

  14. Microleakage of root restorations.

    PubMed

    Wenner, K K; Fairhurst, C W; Morris, C F; Hawkins, I K; Ringle, R D

    1988-12-01

    This study evaluated the microleakage of various restorative materials placed in root surfaces. A minimum of 20 freshly extracted single-rooted teeth were used for each combination of restorative materials. Four preparations were made on the root surface and each restored with a different material. After thermocycling in dye, the root was cut transversely in several sections through the restoration, and microscopically examined to record the microleakage at the interface between restorative materials and tooth. Results indicated that fewer composite resin specimens allowed microleakage into dentin as compared with either amalgam or glass ionomer materials. PMID:3060508

  15. JIP3 Activates Kinesin-1 Motility to Promote Axon Elongation.

    PubMed

    Watt, Dana; Dixit, Ram; Cavalli, Valeria

    2015-06-19

    Kinesin-1 is a molecular motor responsible for cargo transport along microtubules and plays critical roles in polarized cells, such as neurons. Kinesin-1 can function as a dimer of two kinesin heavy chains (KHC), which harbor the motor domain, or as a tetramer in combination with two accessory light chains (KLC). To ensure proper cargo distribution, kinesin-1 activity is precisely regulated. Both KLC and KHC subunits bind cargoes or regulatory proteins to engage the motor for movement along microtubules. We previously showed that the scaffolding protein JIP3 interacts directly with KHC in addition to its interaction with KLC and positively regulates dimeric KHC motility. Here we determined the stoichiometry of JIP3-KHC complexes and observed approximately four JIP3 molecules binding per KHC dimer. We then determined whether JIP3 activates tetrameric kinesin-1 motility. Using an in vitro motility assay, we show that JIP3 binding to KLC engages kinesin-1 with microtubules and that JIP3 binding to KHC promotes kinesin-1 motility along microtubules. We tested the in vivo relevance of these findings using axon elongation as a model for kinesin-1-dependent cellular function. We demonstrate that JIP3 binding to KHC, but not KLC, is essential for axon elongation in hippocampal neurons as well as axon regeneration in sensory neurons. These findings reveal that JIP3 regulation of kinesin-1 motility is critical for axon elongation and regeneration. PMID:25944905

  16. Ethylene-promoted Elongation: an Adaptation to Submergence Stress

    PubMed Central

    Jackson, Michael B.

    2008-01-01

    Background A sizeable minority of taxa is successful in areas prone to submergence. Many such plants elongate with increased vigour when underwater. This helps to restore contact with the aerial environment by shortening the duration of inundation. Poorly adapted species are usually incapable of this underwater escape. Scope Evidence implicating ethylene as the principal factor initiating fast underwater elongation by leaves or stems is evaluated comprehensively along with its interactions with other hormones and gases. These interactions make up a sequence of events that link the perception of submergence to a prompt acceleration of extension. The review encompasses whole plant physiology, cell biology and molecular genetics. It includes assessments of how submergence threatens plant life and of the extent to which the submergence escape demonstrably improves the likelihood of survival. Conclusions Experimental testing over many years establishes ethylene-promoted underwater extension as one of the most convincing examples of hormone-mediated stress adaptation by plants. The research has utilized a wide range of species that includes numerous angiosperms, a fern and a liverwort. It has also benefited from detailed physiological and molecular studies of underwater elongation by rice (Oryza sativa) and the marsh dock (Rumex palustris). Despite complexities and interactions, the work reveals that the signal transduction pathway is initiated by the simple expediency of physical entrapment of ethylene within growing cells by a covering of water. PMID:17956854

  17. Novel domains and orthologues of eukaryotic transcription elongation factors.

    PubMed

    Ponting, Chris P

    2002-09-01

    The passage of RNA polymerase II across eukaryotic genes is impeded by the nucleosome, an octamer of histones H2A, H2B, H3 and H4 dimers. More than a dozen factors in the yeast Saccharomyces cerevisiae are known to facilitate transcription elongation through chromatin. In order to better understand the evolution and function of these factors, their sequences have been compared with known protein, EST and DNA sequences. Elongator subcomplex components Elp4p and Elp6p are shown to be homologues of ATPases, yet with substitutions of amino acids critical for ATP hydrolysis, and novel orthologues of Elp5p are detectable in human, and other animal, sequences. The yeast CP complex is shown to contain a likely inactive homologue of M24 family metalloproteases in Spt16p/Cdc68p and a 2-fold repeat in Pob3p, the orthologue of mammalian SSRP1. Archaeal DNA-directed RNA polymerase subunit E" is shown to be the orthologue of eukaryotic Spt4p, and Spt5p and prokaryotic NusG are shown to contain a novel 'NGN' domain. Spt6p is found to contain a domain homologous to the YqgF family of RNases, although this domain may also lack catalytic activity. These findings imply that much of the transcription elongation machinery of eukaryotes has been acquired subsequent to their divergence from prokaryotes. PMID:12202748

  18. Stem elongation and gibberellins in alpine and prairie ecotypes of Stellaria longipes

    Microsoft Academic Search

    R. J. N. Emery; D. W. Pearce; R. P. Pharis; D. M. Reid; C. C. Chinnappa

    2001-01-01

    The potential for gibberellins (GAs) to control stem elongation and itsplasticity (range of phenotypic expression) was investigated inStellaria longipes grown in long warm days. Gibberellinmetabolism and sensitivity was compared between a slow-growing alpine dwarfwithlow stem elongation plasticity and a rapidly elongating, highly plastic prairieecotype. Both ecotypes elongated in response to exogenous GA1,GA4 or GA9, but surprisingly, the alpine dwarf wasrelatively

  19. Peroxisome elongation and constriction but not fission can occur independently of dynamin-like protein 1

    Microsoft Academic Search

    Annett Koch; Gabriele Schneider; Georg H. Lüers; Michael Schrader; Robert Koch; Robert Koch Strasse

    2004-01-01

    elongation and network formation of the peroxisomal compartment. Time-lapse microscopy of living cells silenced for DLP1 revealed that the elongated peroxisomes moved in a microtubule-dependent manner and emanated tubular projections. DLP1-silencing in COS-7 cells also resulted in a pronounced elongation of mitochondria, and in more dispersed, elongated Golgi structures, whereas morphological changes of the rER, lysosomes and the cytoskeleton were

  20. X-ray computed tomography uncovers root-root interactions: quantifying spatial relationships between interacting root systems in three dimensions.

    PubMed

    Paya, Alexander M; Silverberg, Jesse L; Padgett, Jennifer; Bauerle, Taryn L

    2015-01-01

    Research in the field of plant biology has recently demonstrated that inter- and intra-specific interactions belowground can dramatically alter root growth. Our aim was to answer questions related to the effect of inter- vs. intra-specific interactions on the growth and utilization of undisturbed space by fine roots within three dimensions (3D) using micro X-ray computed tomography. To achieve this, Populus tremuloides (quaking aspen) and Picea mariana (black spruce) seedlings were planted into containers as either solitary individuals, or inter-/intra-specific pairs, allowed to grow for 2 months, and 3D metrics developed in order to quantify their use of belowground space. In both aspen and spruce, inter-specific root interactions produced a shift in the vertical distribution of the root system volume, and deepened the average position of root tips when compared to intra-specifically growing seedlings. Inter-specific interactions also increased the minimum distance between root tips belonging to the same root system. There was no effect of belowground interactions on the radial distribution of roots, or the directionality of lateral root growth for either species. In conclusion, we found that significant differences were observed more often when comparing controls (solitary individuals) and paired seedlings (inter- or intra-specific), than when comparing inter- and intra-specifically growing seedlings. This would indicate that competition between neighboring seedlings was more responsible for shifting fine root growth in both species than was neighbor identity. However, significant inter- vs. intra-specific differences were observed, which further emphasizes the importance of biological interactions in competition studies. PMID:25972880

  1. X-ray computed tomography uncovers root–root interactions: quantifying spatial relationships between interacting root systems in three dimensions

    PubMed Central

    Paya, Alexander M.; Silverberg, Jesse L.; Padgett, Jennifer; Bauerle, Taryn L.

    2015-01-01

    Research in the field of plant biology has recently demonstrated that inter- and intra-specific interactions belowground can dramatically alter root growth. Our aim was to answer questions related to the effect of inter- vs. intra-specific interactions on the growth and utilization of undisturbed space by fine roots within three dimensions (3D) using micro X-ray computed tomography. To achieve this, Populus tremuloides (quaking aspen) and Picea mariana (black spruce) seedlings were planted into containers as either solitary individuals, or inter-/intra-specific pairs, allowed to grow for 2 months, and 3D metrics developed in order to quantify their use of belowground space. In both aspen and spruce, inter-specific root interactions produced a shift in the vertical distribution of the root system volume, and deepened the average position of root tips when compared to intra-specifically growing seedlings. Inter-specific interactions also increased the minimum distance between root tips belonging to the same root system. There was no effect of belowground interactions on the radial distribution of roots, or the directionality of lateral root growth for either species. In conclusion, we found that significant differences were observed more often when comparing controls (solitary individuals) and paired seedlings (inter- or intra-specific), than when comparing inter- and intra-specifically growing seedlings. This would indicate that competition between neighboring seedlings was more responsible for shifting fine root growth in both species than was neighbor identity. However, significant inter- vs. intra-specific differences were observed, which further emphasizes the importance of biological interactions in competition studies. PMID:25972880

  2. Interaction of galactoglucomannan oligosaccharides with auxin in mung bean primary root.

    PubMed

    Kollárová, Karin; Vatehová, Zuzana; Slováková, L'udmila; Lisková, Desana

    2010-06-01

    In the present paper timing of galactoglucomannan oligosaccharides (GGMOs) with exogenously added indole-3-butyric acid (IBA) action on early germination stage (24 h) and primary root elongation of mung bean (Vigna radiata (L.) Wilczek) has been studied. GGMOs inhibited primary root elongation induced by low concentration (10(-8) M) of IBA. This inhibition was considerably higher after preincubation with GGMOs compared with other timing experiments. The most intensive inhibition of elongation has been ascertained at the 10(-8) M concentration of GGMOs. On the other hand GGMOs stimulated this elongation inhibited by high IBA concentration (10(-4) M). This stimulation was the most intensive by simultaneous addition of IBA and GGMOs at the beginning of the experiment and subsequent seeds incubation in distilled water. Our results indicate competition between GGMOs and auxin. The root growth inhibition, induced by GGMOs and/or IBA, was accompanied by the increase of cell wall-associated peroxidase activity and by a higher number of peroxidase isoenzymes. The presence of different peroxidase isoenzymes in experiments with distinct treatment of GGMOs and IBA could indicate variations in the mechanism of interaction between GGMOs and IBA. PMID:20400322

  3. Root traits contributing to plant productivity under drought

    PubMed Central

    Comas, Louise H.; Becker, Steven R.; Cruz, Von Mark V.; Byrne, Patrick F.; Dierig, David A.

    2013-01-01

    Geneticists and breeders are positioned to breed plants with root traits that improve productivity under drought. However, a better understanding of root functional traits and how traits are related to whole plant strategies to increase crop productivity under different drought conditions is needed. Root traits associated with maintaining plant productivity under drought include small fine root diameters, long specific root length, and considerable root length density, especially at depths in soil with available water. In environments with late season water deficits, small xylem diameters in targeted seminal roots save soil water deep in the soil profile for use during crop maturation and result in improved yields. Capacity for deep root growth and large xylem diameters in deep roots may also improve root acquisition of water when ample water at depth is available. Xylem pit anatomy that makes xylem less “leaky” and prone to cavitation warrants further exploration holding promise that such traits may improve plant productivity in water-limited environments without negatively impacting yield under adequate water conditions. Rapid resumption of root growth following soil rewetting may improve plant productivity under episodic drought. Genetic control of many of these traits through breeding appears feasible. Several recent reviews have covered methods for screening root traits but an appreciation for the complexity of root systems (e.g., functional differences between fine and coarse roots) needs to be paired with these methods to successfully identify relevant traits for crop improvement. Screening of root traits at early stages in plant development can proxy traits at mature stages but verification is needed on a case by case basis that traits are linked to increased crop productivity under drought. Examples in lesquerella (Physaria) and rice (Oryza) show approaches to phenotyping of root traits and current understanding of root trait genetics for breeding. PMID:24204374

  4. NELF, a Multisubunit Complex Containing RD, Cooperates with DSIF to Repress RNA Polymerase II Elongation

    Microsoft Academic Search

    Yuki Yamaguchi; Toshiyuki Takagi; Tadashi Wada; Keiichi Yano; Akiko Furuya; Seiji Sugimoto; Jun Hasegawa; Hiroshi Handa

    1999-01-01

    DRB is a classic inhibitor of transcription elongation by RNA polymerase II (pol II). Since DRB generally affects class II genes, factors involved in this process must play fundamental roles in pol II elongation. Recently, two elongation factors essential for DRB action were identified, namely DSIF and P-TEFb. Here we describe the identification and purification from HeLa nuclear extract of

  5. Microtubule configuration and membranous vesicle transport in elongating fiber cells of the rat lens

    Microsoft Academic Search

    Woo-Kuen Lo; Xiao-Jun Wen; Cheng-Jing Zhou

    2003-01-01

    This study examines the microtubule configuration and its close association with the Golgi complex and Golgi-derived membranous vesicles in elongating fiber cells of the rat lens. Since fiber cells elongate tremendously during lens differentiation, we hypothesize that a microtubule-based motor system exists in the elongating fiber cells for transporting important membrane proteins and organelles to the target regions for cell

  6. Stimulation of glycolysis in anaerobic elongation of pondweed (Potamogeton distinctus) turions

    Microsoft Academic Search

    Tatsuhisa Sato; Taro Harada; Kimiharu Ishizawa

    2002-01-01

    Stem segments prepared from pondweed (Potamo- geton distinctus A. Benn.) turions (overwintering buds) elongate in anaerobic conditions, whereas there is almost no elongation in air. The anaerobic elongation was accompanied by a decrease in dry weights of stem segments, mainly due to consump- tion of storage starch in the amyloplasts of stem cells. On the other hand, total contents of

  7. A High-Resolution Tissue-Specific Proteome and Phosphoproteome Atlas of Maize Primary Roots Reveals Functional Gradients along the Root Axes1[OPEN

    PubMed Central

    Malik, Waqas Ahmed; Shen, Zhouxin; Paschold, Anja

    2015-01-01

    A high-resolution proteome and phosphoproteome atlas of four maize (Zea mays) primary root tissues, the cortex, stele, meristematic zone, and elongation zone, was generated. High-performance liquid chromatography coupled with tandem mass spectrometry identified 11,552 distinct nonmodified and 2,852 phosphorylated proteins across the four root tissues. Two gradients reflecting the abundance of functional protein classes along the longitudinal root axis were observed. While the classes RNA, DNA, and protein peaked in the meristematic zone, cell wall, lipid metabolism, stress, transport, and secondary metabolism culminated in the differentiation zone. Functional specialization of tissues is underscored by six of 10 cortex-specific proteins involved in flavonoid biosynthesis. Comparison of this data set with high-resolution seed and leaf proteome studies revealed 13% (1,504/11,552) root-specific proteins. While only 23% of the 1,504 root-specific proteins accumulated in all four root tissues, 61% of all 11,552 identified proteins accumulated in all four root tissues. This suggests a much higher degree of tissue-specific functionalization of root-specific proteins. In summary, these data illustrate the remarkable plasticity of the proteomic landscape of maize primary roots and thus provide a starting point for gaining a better understanding of their tissue-specific functions. PMID:25780097

  8. Selenium Absorption by Excised Astragalus Roots 1

    PubMed Central

    Ulrich, Jane M.; Shrift, Alex

    1968-01-01

    Absorption of selenate and selenite by excised roots of Astragalus Crotalariae, a selenium accumulator, and of A. lentiginosus, a non-accumulator, was favored by CaCl2 and a pH of 4.0. The uptake of selenate and possibly selenite, is metabolically linked. Roots of a number of Astragalus species were examined, and in all cases selenate entered the roots much faster than selenite. In these short-term experiments there was no relation between uptake of the 2 ions and classification of a species as selenium-accumulator or non-accumulator. PMID:5638040

  9. Selenium absorption by excised Astragalus roots.

    PubMed

    Ulrich, J M; Shrift, A

    1968-01-01

    Absorption of selenate and selenite by excised roots of Astragalus Crotalariae, a selenium accumulator, and of A. lentiginosus, a non-accumulator, was favored by CaCl(2) and a pH of 4.0. The uptake of selenate and possibly selenite, is metabolically linked. Roots of a number of Astragalus species were examined, and in all cases selenate entered the roots much faster than selenite. In these short-term experiments there was no relation between uptake of the 2 ions and classification of a species as selenium-accumulator or non-accumulator. PMID:5638040

  10. Coexpression of preprotachykinin-A, ?-calcitonin gene-related peptide, somatostatin, and neurotrophin receptor family messenger RNAs in rat dorsal root ganglion neurons

    Microsoft Academic Search

    H. Kashiba; Y. Ueda; E. Senba

    1996-01-01

    Syntheses of substance P, somatostatin, and calcitonin gene-related peptide in sensory neurons have been suggested to be regulated by neurotrophic factors retrogradely transported from target tissues. In this study, we re-examined this idea by investigating the coexpression of neurotrophin receptor (trk family proto-oncogene) messenger RNAs, and preprotachykinin-A (a precursor peptide of substance P), ?-calcitonin gene-related peptide and somatostatin messenger RNAs

  11. Irrational Square Roots

    ERIC Educational Resources Information Center

    Misiurewicz, Michal

    2013-01-01

    If students are presented the standard proof of irrationality of [square root]2, can they generalize it to a proof of the irrationality of "[square root]p", "p" a prime if, instead of considering divisibility by "p", they cling to the notions of even and odd used in the standard proof?

  12. Root numbers of curves

    Microsoft Academic Search

    MARIA SABITOVA

    2004-01-01

    We generalize a theorem of D. Rohrlich concerning root numbers of elliptic curves over the field of rational numbers. Our result applies to curves of all higher genera over number fields. Namely, under certain conditions which naturally extend the conditions used by D. Rohrlich, we show that the root number associated to a smooth projective curve over a number field

  13. Plant root distributions and nitrogen uptake predicted by a hypothesis of optimal root foraging

    PubMed Central

    McMurtrie, Ross E; Iversen, Colleen M; Dewar, Roderick C; Medlyn, Belinda E; Näsholm, Torgny; Pepper, David A; Norby, Richard J

    2012-01-01

    CO2-enrichment experiments consistently show that rooting depth increases when trees are grown at elevated CO2 (eCO2), leading in some experiments to increased capture of available soil nitrogen (N) from deeper soil. However, the link between N uptake and root distributions remains poorly represented in forest ecosystem and global land-surface models. Here, this link is modeled and analyzed using a new optimization hypothesis (MaxNup) for root foraging in relation to the spatial variability of soil N, according to which a given total root mass is distributed vertically in order to maximize annual N uptake. MaxNup leads to analytical predictions for the optimal vertical profile of root biomass, maximum rooting depth, and N-uptake fraction (i.e., the proportion of plant-available soil N taken up annually by roots). We use these predictions to gain new insight into the behavior of the N-uptake fraction in trees growing at the Oak Ridge National Laboratory free-air CO2-enrichment experiment. We also compare MaxNup with empirical equations previously fitted to root-distribution data from all the world's plant biomes, and find that the empirical equations underestimate the capacity of root systems to take up N. PMID:22833797

  14. Reduced frequency of lateral root branching improves N capture from low-N soils in maize

    PubMed Central

    Zhan, Ai; Lynch, Jonathan P.

    2015-01-01

    Suboptimal nitrogen (N) availability is a primary constraint for crop production in developing countries, while in developed countries, intensive N fertilization is a primary economic, energy, and environmental cost for crop production. We tested the hypothesis that under low-N conditions, maize (Zea mays) lines with few but long (FL) lateral roots would have greater axial root elongation, deeper rooting, and greater N acquisition than lines with many but short (MS) lateral roots. Maize recombinant inbred lines contrasting in lateral root number and length were grown with adequate and suboptimal N in greenhouse mesocosms and in the field in the USA and South Africa (SA). In low-N mesocosms, the FL phenotype had substantially reduced root respiration and greater rooting depth than the MS phenotype. In low-N fields in the USA and SA, the FL phenotype had greater rooting depth, shoot N content, leaf photosynthesis, and shoot biomass than the MS phenotype. The FL phenotype yielded 31.5% more than the MS phenotype under low N in the USA. Our results are consistent with the hypothesis that sparse but long lateral roots improve N capture from low-N soils. These results with maize probably pertain to other species. The FL lateral root phenotype merits consideration as a selection target for greater crop N efficiency. PMID:25680794

  15. Association between border cell responses and localized root infection by pathogenic Aphanomyces euteiches

    PubMed Central

    Cannesan, Marc Antoine; Gangneux, Christophe; Lanoue, Arnaud; Giron, David; Laval, Karine; Hawes, Martha; Driouich, Azeddine; Vicré-Gibouin, Maïté

    2011-01-01

    Background and Aims The oomycete Aphanomyces euteiches causes up to 80 % crop loss in pea (Pisum sativum). Aphanomyces euteiches invades the root system leading to a complete arrest of root growth and ultimately to plant death. To date, disease control measures are limited to crop rotation and no resistant pea lines are available. The present study aims to get a deeper understanding of the early oomycete–plant interaction at the tissue and cellular levels. Methods Here, the process of root infection by A. euteiches on pea is investigated using flow cytometry and microscopic techniques. Dynamic changes in secondary metabolism are analysed with high-performance liquid chromatography with diode-array detection. Key Results Root infection is initiated in the elongation zone but not in the root cap and border cells. Border-cell production is significantly enhanced in response to root inoculation with changes in their size and morphology. The stimulatory effect of A. euteiches on border-cell production is dependent on the number of oospores inoculated. Interestingly, border cells respond to pathogen challenge by increasing the synthesis of the phytoalexin pisatin. Conclusions Distinctive responses to A. euteiches inoculation occur at the root tissue level. The findings suggest that root border cells in pea are involved in local defence of the root tip against A. euteiches. Root border cells constitute a convenient quantitative model to measure the molecular and cellular basis of plant–microbe interactions. PMID:21807690

  16. Electrophysiological and histological investigation on the gradual elongation of rabbit sciatic nerve.

    PubMed

    Kodera, Norie; Aoki, Takafumi; Ito, Hiromoto

    2011-01-01

    A basic study using animal models was performed to investigate whether the sciatic nerve retains physiological functions and normal morphology after the gradual elongation associated with adjacent bone elongation. Electrophysiological and histological studies were performed on the elongated sciatic nerve of rabbit accompanied by the femur bone elongation. Compound action potentials evoked by electrical stimulation of the sciatic nerve were recorded and histological specimens of elongated nerve fibers were obtained immediately after final bone elongation from 4 rabbits (immediate group). Three rabbits were allowed to recover for 8 weeks after the bone elongation (maintained group). Three rabbits without bone elongation were used as controls of the immediate and maintained groups (control group). In the immediate group, the average amplitude of evoked nerve potentials were 30.38 ± 1.58 mV before elongation and diminished significantly to 18.35 ± 1.25 mV immediately after elongation (P<0.01). The amplitude of evoked potentials was not significantly different between before (30.30 ± 0.61 mV) elongation and after elongation (27.47 ± 1.63 mV) in the maintained group. The axonal area of the myelinated nerve fibers of the proximal region of the sciatic nerve in the immediate group was significantly decreased after elongation (P<0.01). The decrease in the area of the distal region was greatest in the control group and was followed by that in the maintained group and the immediate group (P<0.05, 0.01). These results suggest that the sciatic nerve shows dysfunction immediately after elongation, but can recover electrophysiologically and histologically several weeks after elongation. PMID:21720090

  17. Spinal Elongation and its Effects on Seated Height in a Microgravity Environment (Spinal)

    NASA Technical Reports Server (NTRS)

    Rajulu, Sudhakar; Young, Karen

    2009-01-01

    The primary objective of this project is to provide information pertaining to changes in seated height due to spinal elongation in a microgravity environment. The proposed experiment aims to collect seated height data for subjects exposed to microgravity environments, provide information relating to seated height rate of change over time, and feed new information regarding the elongation of the spine forward into the design of Constellation systems. Historical data indicates that spinal elongation occurs when crewmembers are subjected to microgravity. In as little as two days, the typical crewmember will exhibit increases in stature of up to 3 percent. However, data has been collected only for crewmembers in standing postures, and a limited pool of subjects was available. Due to the criticality of seated height in the design of the Crew Exploration Vehicle (CEV), a better understanding of the effects of microgravity on seated height is necessary. Small changes in seated height that may not have impacted crew accommodation in previous programs will have significant effects on crew accommodation due to the layout of seats in the CEV. The proposed study will directly measure changes in seated height for crewmembers in the Shuttle cockpit. An anthropometer will be used to record measurements to the top of the head of a seated subject, and an orthogonal photograph will be taken in order to measure seated height based on scaling references of known sizes as well as verify the posture and positioning remained consistent throughout the study. Data gained from this study will provide better information to CEV designers. Accurate measurements of crew seated height will be valuable for vehicle and habitation designers for future programs as well.

  18. Down-regulation of the IbEXP1 gene enhanced storage root development in sweetpotato

    PubMed Central

    Bae, Jung Myung

    2013-01-01

    The role of an expansin gene (IbEXP1) in the formation of the storage root (SR) was investigated by expression pattern analysis and characterization of IbEXP1-antisense sweetpotato (Ipomoea batatas cv. Yulmi) plants in an attempt to elucidate the molecular mechanism underlying SR development in sweetpotato. The transcript level of IbEXP1 was high in the fibrous root (FR) and petiole at the FR stage, but decreased significantly at the young storage root (YSR) stage. IbEXP1-antisense plants cultured in vitro produced FRs which were both thicker and shorter than those of wild-type (WT) plants. Elongation growth of the epidermal cells was significantly reduced, and metaxylem and cambium cell proliferation was markedly enhanced in the FRs of IbEXP1-antisense plants, resulting in an earlier thickening growth in these plants relative to WT plants. There was a marked reduction in the lignification of the central stele of the FRs of the IbEXP1-antisense plants, suggesting that the FRs of the mutant plants possessed a higher potential than those of WT plants to develop into SRs. IbEXP1-antisense plants cultured in soil produced a larger number of SRs and, consequently, total SR weight per IbEXP1-antisense plant was greater than that per WT plant. These results demonstrate that SR development was accelerated in IbEXP1-antisense plants and suggest that IbEXP1 plays a negative role in the formation of SR by suppressing the proliferation of metaxylem and cambium cells to inhibit the initial thickening growth of SRs. IbEXP1 is the first sweetpotato gene whose role in SR development has been directly identified in soil-grown transgenic sweetpotato plants. PMID:22945944

  19. Kinesin-4 Functions in Vesicular Transport on Cortical Microtubules and Regulates Cell Wall Mechanics during Cell Elongation in Plants.

    PubMed

    Kong, Zhaosheng; Ioki, Motohide; Braybrook, Siobhan; Li, Shundai; Ye, Zheng-Hua; Julie Lee, Yuh-Ru; Hotta, Takashi; Chang, Anny; Tian, Juan; Wang, Guangda; Liu, Bo

    2015-07-01

    In plants, anisotropic cell expansion depends on cortical microtubules that serve as tracks along which macromolecules and vesicles are transported by the motor kinesins of unknown identities. We used cotton (Gossypium hirsutum) fibers that underwent robust elongation to discover kinesins that are involved in cell elongation and found Gh KINESIN-4A expressed abundantly. The motor was detected by immunofluorescence on vesicle-like structures that were associated with cortical microtubules. In Arabidopsis thaliana, the orthologous motor At KINESIN-4A/FRA1, previously implicated in cellulose deposition during secondary growth in fiber cells, was examined by live-cell imaging in cells expressing the fluorescently tagged functional protein. The motor decorated vesicle-like particles that exhibit a linear movement along cortical microtubules with an average velocity of 0.89 ?m/min, which was significantly different from those linked to cellulose biosynthesis. We also discovered that At KINESIN-4A/FRA1 and the related At KINESIN-4C play redundant roles in cell wall mechanics, cell elongation, and the axial growth of various vegetative and reproductive organs, as the loss of At KINESIN-4C greatly enhanced the defects caused by a null mutation at the KINESIN-4A/FRA1 locus. The double mutant displayed a lack of cell wall softening at normal stages of rapid cell elongation. Furthermore, enhanced deposition of arabinose-containing carbohydrate was detected in the kinesin-4 mutants. Our findings established a connection between the Kinesin-4-based transport of cargoes containing non-cellulosic components along cortical microtubules and cell wall mechanics and cell elongation in flowering plants. PMID:25600279

  20. Competition between Plant-Populations with Different Rooting Depths. 3. Field Experiments

    Microsoft Academic Search

    F. Berendse

    1982-01-01

    The model proposed in the first paper in this series predicts that in mixtures of plant species with different rooting depths there will be an inverse correlation between the relative crowding coefficient of the deep rooting species with respect to the shallow rooting one and the frequency of the deep rooting plants. Two field experiments are reported in which this

  1. Numerical Algorithms (2005) 39: 349378 Springer 2005 Algorithms for the matrix pth root

    E-print Network

    Higham, Nicholas J.

    2005-01-01

    Numerical Algorithms (2005) 39: 349­378 Springer 2005 Algorithms for the matrix pth root Dario A the principal matrix pth root. In particular, we show that the pth root is related to the matrix sign function of the pth root. We also analyze the convergence and numerical stability properties of Newton's method

  2. In vitro propagation of olive (Olea europaea L.) by nodal segmentation of elongated shoots.

    PubMed

    Lambardi, Maurizio; Ozudogru, Elif Aylin; Roncasaglia, Romano

    2013-01-01

    Olive (Olea europaea L.), long-living, ever-green fruit tree of the Old World, has been part of a traditional landscape in the Mediterranean area for centuries. Both the fruits consumed after processing and the oil extracted from the fruits are among the main components of the Mediterranean diet, widely used for salads and cooking, as well as for preserving other food. Documentations show that the ancient use of this beautiful tree also includes lamp fuel production, wool treatment, soap production, medicine, and cosmetics. However, unlike the majority of the fruit species, olive propagation is still a laborious practice. As regards traditional propagation, rooting of cuttings and grafting stem segments onto rootstocks are possible, former being achieved only when the cuttings are collected in specific periods (spring or beginning of autumn), and latter only when skilled grafters are available. In both the cases, performance of the cultivars varies considerably. The regeneration of whole plants from ovules, on the other hand, is used only occasionally. Micropropagation of olive is not easy mainly due to explant oxidation, difficulties in explant disinfection, and labor-oriented establishment of in vitro shoot cultures. However today, the progress in micropropagation technology has made available the complete protocols for several Mediterranean cultivars. This chapter describes a micropropagation protocol based on the segmentation of nodal segments obtained from elongated shoots. PMID:23179688

  3. Gibberellin deficiency and response mutations suppress the stem elongation phenotype of phytochrome-deficient mutants of Arabidopsis.

    PubMed Central

    Peng, J; Harberd, N P

    1997-01-01

    Plant growth and development are regulated by numerous internal and external factors. Among these, gibberellin (GA) (an endogenous plant growth regulator) and phytochrome (a photoreceptor) often influence the same processes. For example, in plants grown in the light Arabidopsis thaliana hypocotyl elongation is reduced by GA deficiency and increased by phytochrome deficiency. Here we describe experiments in which the phenotypes of Arabidopsis plants doubly homozygous for GA-related and phytochrome-related mutations were examined. The double mutants were studied at various stages in the plant life cycle, including the seed germination, young seedling, adult, and reproductive phases of development. The results of these experiments are complex, but indicate that a fully functional GA system is necessary for full expression of the elongated phenotypes conferred by phytochrome deficiency. PMID:9112768

  4. Simulations of nucleation and elongation of amyloid fibrils

    PubMed Central

    Zhang, Jianing; Muthukumar, M.

    2009-01-01

    We present a coarse-grained model for the growth kinetics of amyloid fibrils from solutions of peptides and address the fundamental mechanism of nucleation and elongation by using a lattice Monte Carlo procedure. We reproduce the three main characteristics of nucleation of amyloid fibrils: (1) existence of lag time, (2) occurrence of a critical concentration, and (3) seeding. We find the nucleation of amyloid fibrils to require a quasi-two-dimensional configuration, where a second layer of ? sheet must be formed adjunct to a first layer, which in turn leads to a highly cooperative nucleation barrier. The elongation stage is found to involve the Ostwald ripening (evaporation-condensation) mechanism, whereby bigger fibrils grow at the expense of smaller ones. This new mechanism reconciles the debate as to whether protofibrils are precursors or monomer reservoirs. We have systematically investigated the roles of time, peptide concentration, temperature, and seed size. In general, we find that there are two kinds of lag time arising from two different mechanisms. For higher temperatures or low enough concentrations close to the disassembly boundary, the fibrillization follows the nucleation mechanism. However, for low temperatures, where the nucleation time is sufficiently short, there still exists an apparent lag time due to slow Ostwald ripening mechanism. Consequently, the lag time is nonmonotonic with temperature, with the shortest lag time occurring at intermediate temperatures, which in turn depend on the peptide concentration. While the nucleation dominated regime can be controlled by seeding, the Ostwald ripening regime is insensitive to seeding. Simulation results from our coarse-grained model on the fibril size, lag time, elongation rate, and solubility are consistent with available experimental observations on many specific amyloid systems. PMID:19173542

  5. Single-Plane Magnetically Focused Elongated Small Field Proton Beams.

    PubMed

    McAuley, Grant A; Slater, James M; Wroe, Andrew J

    2014-11-19

    We previously performed Monte Carlo simulations of magnetically focused proton beams shaped by a single quadrapole magnet and thereby created narrow elongated beams with superior dose delivery characteristics (compared to collimated beams) suitable for targets of similar geometry. The present study seeks to experimentally validate these simulations using a focusing magnet consisting of 24 segments of samarium cobalt permanent magnetic material adhered into a hollow cylinder. Proton beams with properties relevant to clinical radiosurgery applications were delivered through the magnet to a water tank containing a diode detector or radiochromic film. Dose profiles were analyzed and compared with analogous Monte Carlo simulations. The focused beams produced elongated beam spots with high elliptical symmetry, indicative of magnet quality. Experimental data showed good agreement with simulations, affirming the utility of Monte Carlo simulations as a tool to model the inherent complexity of a magnetic focusing system. Compared to target-matched unfocused simulations, focused beams showed larger peak to entrance ratios (26% to 38%) and focused simulations showed a two-fold increase in beam delivery efficiency. These advantages can be attributed to the magnetic acceleration of protons in the transverse plane that tends to counteract the particle outscatter that leads to degradation of peak to entrance performance in small field proton beams. Our results have important clinical implications and suggest rare earth focusing magnet assemblies are feasible and could reduce skin dose and beam number while delivering enhanced dose to narrow elongated targets (eg, in and around the spinal cord) in less time compared to collimated beams. PMID:25414143

  6. Morphological and Chemical Mechanisms of Elongated Mineral Particle Toxicities

    PubMed Central

    Aust, Ann E.; Cook, Philip M.; Dodson, Ronald F.

    2011-01-01

    Much of our understanding regarding the mechanisms for induction of disease following inhalation of respirable elongated mineral particles (REMP) is based on studies involving the biological effects of asbestos fibers. The factors governing the disease potential of an exposure include duration and frequency of exposures; tissue-specific dose over time; impacts on dose persistence from in vivo REMP dissolution, comminution, and clearance; individual susceptibility; and the mineral type and surface characteristics. The mechanisms associated with asbestos particle toxicity involve two facets for each particle's contribution: (1) the physical features of the inhaled REMP, which include width, length, aspect ratio, and effective surface area available for cell contact; and (2) the surface chemical composition and reactivity of the individual fiber/elongated particle. Studies in cell-free systems and with cultured cells suggest an important way in which REMP from asbestos damage cellular molecules or influence cellular processes. This may involve an unfortunate combination of the ability of REMP to chemically generate potentially damaging reactive oxygen species, through surface iron, and the interaction of the unique surfaces with cell membranes to trigger membrane receptor activation. Together these events appear to lead to a cascade of cellular events, including the production of damaging reactive nitrogen species, which may contribute to the disease process. Thus, there is a need to be more cognizant of the potential impact that the total surface area of REMP contributes to the generation of events resulting in pathological changes in biological systems. The information presented has applicability to inhaled dusts, in general, and specifically to respirable elongated mineral particles. PMID:21534085

  7. How to study deep roots—and why it matters

    PubMed Central

    Maeght, Jean-Luc; Rewald, Boris; Pierret, Alain

    2013-01-01

    The drivers underlying the development of deep root systems, whether genetic or environmental, are poorly understood but evidence has accumulated that deep rooting could be a more widespread and important trait among plants than commonly anticipated from their share of root biomass. Even though a distinct classification of “deep roots” is missing to date, deep roots provide important functions for individual plants such as nutrient and water uptake but can also shape plant communities by hydraulic lift (HL). Subterranean fauna and microbial communities are highly influenced by resources provided in the deep rhizosphere and deep roots can influence soil pedogenesis and carbon storage.Despite recent technological advances, the study of deep roots and their rhizosphere remains inherently time-consuming, technically demanding and costly, which explains why deep roots have yet to be given the attention they deserve. While state-of-the-art technologies are promising for laboratory studies involving relatively small soil volumes, they remain of limited use for the in situ observation of deep roots. Thus, basic techniques such as destructive sampling or observations at transparent interfaces with the soil (e.g., root windows) which have been known and used for decades to observe roots near the soil surface, must be adapted to the specific requirements of deep root observation. In this review, we successively address major physical, biogeochemical and ecological functions of deep roots to emphasize the significance of deep roots and to illustrate the yet limited knowledge. In the second part we describe the main methodological options to observe and measure deep roots, providing researchers interested in the field of deep root/rhizosphere studies with a comprehensive overview. Addressed methodologies are: excavations, trenches and soil coring approaches, minirhizotrons (MR), access shafts, caves and mines, and indirect approaches such as tracer-based techniques. PMID:23964281

  8. Reduction of laser spot elongation in adaptive optics.

    PubMed

    Ribak, Erez N; Ragazzoni, Roberto

    2004-06-15

    Adaptive optics systems measure the wave front to be corrected by use of a reference source, a star, or a laser beacon. Such laser guide stars are a few kilometers long, and when observed near the edges of large telescopes they appear elongated. This limits their utility significantly. However, with more sophisticated launch optics their shape and length can be controlled. We propose to string around the rim of a telescope a number of small telescopes that will add laser beams in the scattering medium to create a compact spot. The method could also be adapted for ocular adaptive optics. PMID:15233432

  9. Controlled laser production of elongated articles from particulates

    DOEpatents

    Dixon, Raymond D. (Los Alamos, NM); Lewis, Gary K. (Los Alamos, NM); Milewski, John O. (Santa Fe, NM)

    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.

  10. Vesicle dynamics in elongation flow: Wrinkling instability and bud formation

    E-print Network

    Vasiliy Kantsler; Enrico Segre; Victor Steinberg

    2007-04-30

    We present experimental results on the relaxation dynamics of vesicles subjected to a time-dependent elongation flow. We observed and characterized a new instability, which results in the formation of higher order modes of the vesicle shape (wrinkles), after a switch in the direction of the gradient of the velocity. This surprising generation of membrane wrinkles can be explained by the appearance of a negative surface tension during the vesicle deflation, due to compression in a sign-switching transient. Moreover, the formation of buds in the vesicle membrane has been observed in the vicinity of the dynamical transition point.

  11. Vesicle dynamics in elongation flow: Wrinkling instability and bud formation

    E-print Network

    Kantsler, Vasiliy; Steinberg, Victor; 10.1103/PhysRevLett.99.178102

    2011-01-01

    We present experimental results on the relaxation dynamics of vesicles subjected to a time-dependent elongation flow. We observed and characterized a new instability, which results in the formation of higher order modes of the vesicle shape (wrinkles), after a switch in the direction of the gradient of the velocity. This surprising generation of membrane wrinkles can be explained by the appearance of a negative surface tension during the vesicle deflation, due to compression in a sign-switching transient. Moreover, the formation of buds in the vesicle membrane has been observed in the vicinity of the dynamical transition point.

  12. Amorphous Zr-Based Foams with Aligned, Elongated Pores

    Microsoft Academic Search

    Marie E. Cox; Suveen N. Mathaudhu; K. Ted Hartwig; David C. Dunand

    2010-01-01

    Interpenetrating phase composites are created by warm equal channel angular extrusion (ECAE) of blended powders of amorphous\\u000a Zr58.5Nb2.8Cu15.6Ni12.8Al10.3 (Vit106a) and a crystalline ductile metal (Cu, Ni, or W). Subsequent dissolution of the continuous metallic phase results\\u000a in amorphous Vit106a foams with ~40 pct aligned, elongated pores. The extent of Vit106a powder densification in the composites\\u000a improves with the strength of the

  13. Amorphous Zr-Based Foams with Aligned, Elongated Pores

    Microsoft Academic Search

    Marie E. Cox; Suveen N. Mathaudhu; K. Ted Hartwig; David C. Dunand

    2010-01-01

    Interpenetrating phase composites are created by warm equal channel angular extrusion (ECAE) of blended powders of amorphous Zr58.5Nb2.8Cu15.6Ni12.8Al10.3 (Vit106a) and a crystalline ductile metal (Cu, Ni, or W). Subsequent dissolution of the continuous metallic phase results in amorphous Vit106a foams with ~40 pct aligned, elongated pores. The extent of Vit106a powder densification in the composites improves with the strength of

  14. Amorphous Zr-Based Foams with Aligned, Elongated Pores

    NASA Astrophysics Data System (ADS)

    Cox, Marie E.; Mathaudhu, Suveen N.; Hartwig, K. Ted; Dunand, David C.

    2010-07-01

    Interpenetrating phase composites are created by warm equal channel angular extrusion (ECAE) of blended powders of amorphous Zr58.5Nb2.8Cu15.6Ni12.8Al10.3 (Vit106a) and a crystalline ductile metal (Cu, Ni, or W). Subsequent dissolution of the continuous metallic phase results in amorphous Vit106a foams with ~40 pct aligned, elongated pores. The extent of Vit106a powder densification in the composites improves with the strength of the crystalline metallic powder, from low for Cu to high for W, with a concomitant improvement in foam compressive strength, ductility, and energy absorption.

  15. The solar elongation distribution of low-frequency radio bursts

    NASA Technical Reports Server (NTRS)

    Kaiser, M. L.

    1975-01-01

    Over 500 days of low-frequency (less than 1 MHz) radio observations from the IMP-6 spacecraft have been accumulated to produce a two-dimensional map (frequency vs elongation) of solar type III burst occurrences. This map indicates that most solar bursts in this frequency range are observed at the second harmonic of the plasma frequency, rather than the fundamental. The map also shows that the solar wind electron density varies as an inverse power of heliocentric distance, with the exponent somewhat less than 2 to perhaps 3 or higher.

  16. Growth and Movement of Spot Inoculated Rhizobium meliloti on the Root Surface of Alfalfa 1

    PubMed Central

    Caetano-Anollés, Gustavo; Wrobel-Boerner, Elizabeth; Bauer, Wolfgang D.

    1992-01-01

    Inoculum droplets of approximately 10 nanoliter volume and containing about 10 Rhizobium meliloti cells were placed onto the root surface of alfalfa seedlings in plastic growth pouches at either the root tip, the position of the smallest emergent root hairs, or at a site midway between these points. The droplets were initially confined to an area of about 0.2 square millimeter at the point of application. By 48 and 96 hours after inoculation, the inoculum bacteria and their progeny were distributed over several centimeters of the root between the initial site of deposition and the growing root tip, reaching densities of 103 to 104 bacteria per centimeter near the site of initial deposition and decreasing exponentially from that point toward the root tip. Graphite particles deposited on the root surface close to the growing tip were similarly distributed along the root length by 48 and 96 hours, suggesting that passive displacement by root cell elongation was primarily responsible for the spread of bacteria. A nonmotile mutant of R. meliloti colonized alfalfa roots to the same extent as the wild type and was usually distributed in the same manner, indicating that bacterial motility contributed little under these conditions to long distance spread of the bacteria. However, when applied in low numbers, R. meliloti mutants defective in motility or chemotaxis were considerably less efficient in initiating nodules near the point of inoculation than the wild type. This implies that motility and/or chemotaxis contribute significantly to local exploration for suitable infection sites. Almost all nodules on the primary root formed within a few millimeters of the spot-inoculation site, indicating that, under our experimental conditions, movement and multiplication of R. meliloti on the root surface were not sufficient to maintain an adequate population in the infectible region of the root during root growth. PMID:16668744

  17. Intraspecific variation in root and leaf traits and leaf-root trait linkages in eight aspen demes (Populus tremula and P. tremuloides).

    PubMed

    Hajek, Peter; Hertel, Dietrich; Leuschner, Christoph

    2013-01-01

    Leaf and fine root morphology and physiology have been found to vary considerably among tree species, but not much is known about intraspecific variation in root traits and their relatedness to leaf traits. Various aspen progenies (Populus tremula and P. tremuloides) with different growth performance are used in short-rotation forestry. Hence, a better understanding of the link between root trait syndromes and the adaptation of a deme to a particular environment is essential in order to improve the match between planted varieties and their growth conditions. We examined the between-deme (genetic) and within-deme (mostly environmental) variation in important fine root traits [mean root diameter, specific root area (SRA) and specific root length (SRL), root tissue density (RTD), root tip abundance, root N concentration] and their co-variation with leaf traits [specific leaf area (SLA), leaf size, leaf N concentration] in eight genetically distinct P. tremula and P. tremuloides demes. Five of the six root traits varied significantly between the demes with largest genotypic variation in root tip abundance and lowest in mean root diameter and RTD (no significant difference). Within-deme variation in root morphology was as large as between-deme variation suggesting a relatively low genetic control. Significant relationships existed neither between SLA and SRA nor between leaf N and root N concentration in a plant. Contrary to expectation, high aboveground relative growth rates (RGR) were associated with large, and not small, fine root diameters with low SRA and SRL. Compared to leaf traits, the influence of root traits on RGR was generally low. We conclude that aspen exhibits large intraspecific variation in leaf and also in root morphological traits which is only partly explained by genetic distances. A root order-related analysis might give deeper insights into intraspecific root trait variation. PMID:24155751

  18. Cavitation behavior of coarse-grained Al4.5 Mg alloy exhibiting superplastic-like elongation

    Microsoft Academic Search

    H. Iwasaki; T. Mori; H. Hosokawa; T. Tagata; M. Mabuchi; K. Higashi

    2000-01-01

    Cavitation behaviors related to ferrous primary crystals have been investigated at a temperature of 653 K and a strain rate of 10³\\/s for Al-4.5% Mg-0.05%FE and Al-4.5% Mg-0.2%Fe alloys which have a grain size of 50 m. The alloys constantly exhibited a large elongation-to-failure above 300% at the temperature of 653 K and strain rate of 10³\\/s. Cavitation was increased

  19. Enhanced root system C-sink activity, water relations and aspects of nutrient acquisition in mycotrophic Bouteloua gracilis subjected to CO 2 enrichment

    Microsoft Academic Search

    J. A. Morgan; W. G. Knight; L. M. Dudley; H. W. Hunt

    1994-01-01

    In order to better elucidate fixed-C partitioning, nutrient acquisition and water relations of prairie grasses under elevated\\u000a [CO2], we grew the C4 grass Bouteloua gracilis (H.B.K.) lag ex Steud. from seed in soil-packed, column-lysimeters in two growth chambers maintained at current ambient [CO2] (350 ?L L?1) and twice enriched [CO2] (700 ?L L?1). Once established, plants were deficit irrigated; growth

  20. Spatial distribution of glomalin-related soil protein and its relationships with root mycorrhization, soil aggregates, carbohydrates, activity of protease and ?-glucosidase in the rhizosphere of Citrus unshiu

    Microsoft Academic Search

    Qiang-Sheng Wu; Xin-Hua He; Ying-Ning Zou; Kai-Ping He; Ya-Hong Sun; Ming-Qin Cao

    Relationships between the spatial distributions of glomalin-related soil protein (GRSP) and soil aggregates, carbohydrates or relevant enzymes are poorly studied. We found that two categories of GRSP, the easily extractable Bradford-reactive soil protein (EE-BRSP) and total BRSP (T-BRSP), respectively ranged between 0.3–0.6 and 0.5–0.8 mg\\/g DW soil, and these two BRSPs decreased with the increase of soil depth (0–40 cm)