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1

Differential expression of cell wall related genes in the elongation zone of rice roots under water deficit  

Microsoft Academic Search

Growth in the apical elongation zone of plant roots is central to the development of functional root systems. It has been\\u000a known that rice seminal root elongation could be enhanced by water stress. In the present study, 17 cell-wall related genes\\u000a were identified by cDNA-amplified fragment length polymorphism (cDNA-AFLP) technique. Five genes encoded cell-wall loosening\\u000a enzymes and six genes were

L. Yang; C. C. Wang; W. D. Guo; X. B. Li; M. Lu; C. L. Yu

2006-01-01

2

Soil strength and macropore volume limit root elongation rates in many UK agricultural soils  

PubMed Central

Background and Aims Simple indicators of crop and cultivar performance across a range of soil types and management are needed for designing and testing sustainable cropping practices. This paper determined the extent to which soil chemical and physical properties, particularly soil strength and pore-size distribution influences root elongation in a wide range of agricultural top soils, using a seedling-based indicator. Methods Intact soil cores were sampled from the topsoil of 59 agricultural fields in Scotland, representing a wide geographic spread, range of textures and management practices. Water release characteristics, dry bulk density and needle penetrometer resistance were measured on three cores from each field. Soil samples from the same locations were sieved, analysed for chemical characteristics, and packed to dry bulk density of 1·0 g cm?3 to minimize physical constraints. Root elongation rates were determined for barley seedlings planted in both intact field and packed soil cores at a water content close to field capacity (–20 kPa matric potential). Key Results Root elongation in field soil was typically less than half of that in packed soils. Penetrometer resistance was typically between 1 and 3 MPa for field soils, indicating the soils were relatively hard, despite their moderately wet condition (compared with <0·2 MPa for packed soil). Root elongation was strongly linked to differences in physical rather than chemical properties. In field soil root elongation was related most closely to the volume of soil pores between 60 µm and 300 µm equivalent diameter, as estimated from water-release characteristics, accounting for 65·7 % of the variation in the elongation rates. Conclusions Root elongation rate in the majority of field soils was slower than half of the unimpeded (packed) rate. Such major reductions in root elongation rates will decrease rooting volumes and limit crop growth in soils where nutrients and water are scarce.

Valentine, Tracy A.; Hallett, Paul D.; Binnie, Kirsty; Young, Mark W.; Squire, Geoffrey R.; Hawes, Cathy; Bengough, A. Glyn

2012-01-01

3

Inhibition of root elongation in microgravity by an applied electric field  

NASA Technical Reports Server (NTRS)

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.

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

4

ALFIN-LIKE 6 is involved in root hair elongation during phosphate deficiency in Arabidopsis.  

PubMed

Phosphate (Pi) starvation in plants induces dense and elongated root hairs, which increase the absorptive surface area of the roots and play a critical role in Pi uptake. The molecular mechanism underlying these changes remains unclear. Forward and reverse genetic approaches were employed to identify novel genes involved in root hair formation on Pi starvation. The mutant per2, with defects in root hair elongation specifically under low Pi conditions, was identified in a large-scale genetic screen of T-DNA insertion lines. The phenotype was caused by a mutation in the homeodomain protein ALFIN-LIKE 6 (AL6). From a screen of mutants defective in genes that showed lower transcript abundance in per2 relative to wild-type roots on low Pi medium, we identified four putative downstream targets of AL6, namely ETC1, NPC4, SQD2 and PS2, all of which were critical in root hair elongation of Pi-deficient plants. The results further indicate that AL6 is involved in the control of growth and several key responses to Pi starvation. Our findings demonstrate that AL6 controls the transcription of a suite of genes critical for root hair elongation under low Pi conditions, suggesting a novel physiological function for an Alfin gene in Arabidopsis. PMID:23432399

Chandrika, Nulu Naga Prafulla; Sundaravelpandian, Kalaipandian; Yu, Su-May; Schmidt, Wolfgang

2013-05-01

5

Analysis of Cell Division and Elongation Underlying the Developmental Acceleration of Root Growth in Arabidopsis thaliana  

Microsoft Academic Search

To investigate the relation between cell division and expansion in the regulation of organ growth rate, we used Arabidopsis thaliana primary roots grown vertically at 20°C with an elongation rate that increased steadily during the first 14 d after germination. We mea- sured spatial profiles of longitudinal velocity and cell length and calculated parameters of cell expansion and division, including

Gerrit T. S. Beemster; Tobias I. Baskin

1998-01-01

6

Gibberellins accumulate in the elongating endodermal cells of Arabidopsis root  

PubMed Central

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

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

2013-01-01

7

HDG11 upregulates cell-wall-loosening protein genes to promote root elongation in Arabidopsis  

PubMed Central

The gain-of-function mutant edt1 shows significantly enhanced drought tolerance and a well-developed root system including deeper primary roots and more lateral roots. To explore the molecular mechanisms underlying the improved root system of edt1, we performed transcriptome comparison between the wild-type and edt1 roots. One of the interesting findings from the analysis was that several gene families of cell-wall-loosening proteins were upregulated in the mutant roots, including expansins, extensins, xyloglucan endotransglucosylase/hydrolases (XTHs), pectin-related enzymes, and cellulases. Most of these genes contain HD-binding cis-elements in their promoters predominantly with the TTTAATTT sequence, which can be bound by HDG11 in vitro and in vivo. The coordinated expression of these gene families overlaps fast root elongation. Furthermore, overexpression of AtEXPA5, which was dramatically upregulated in edt1, resulted in longer primary roots because cells were more extended longitudinally. When combined by crossing the AtEXPA5-overexpression lines with one pectin methylesterase inhibitor family protein (PMEI) gene (At5g62360)- or one cellulase (CEL) gene (At2g32990)-overexpression lines, the primary roots of the progeny even exceeded both parents in length. Our results demonstrate that HDG11 directly upregulates cell-wall-loosening protein genes, which is correlated with altered root system architecture, and confirm that cell-wall-loosening proteins play important roles in coordinating cell-wall extensibility with root development. The results of transgene experiments showed that expansin works together with PMEI and CEL to generate synergistic effects on primary root elongation, suggesting that different cell-wall-loosening protein families may function in combination to generate optimal effects on root extensibility.

Xu, Ping; Cai, Xiao-Teng; Wang, Yao; Xing, Lu; Chen, Qiong; Xiang, Cheng-Bin

2014-01-01

8

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

PubMed

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

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

2014-06-01

9

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

NASA Technical Reports Server (NTRS)

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.

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

1990-01-01

10

Effects of antagonists and inhibitors of ethylene biosynthesis on maize root elongation.  

PubMed

During the first days of development, maize roots showed considerable variation in the production of ethylene and the rate of elongation. As endogenous ethylene increases, root elongation decreases. When these roots are treated with the precursor of ethylene aminocyclopropane- 1-carboxylic acid (ACC), or inhibitors of ethylene biosynthesis 2-aminoethoxyvinyl glycine (AVG) or cobalt ions, the root elongation is also inhibited. Because of root growth diminishes at high or reduced endogenous ethylene concentrations, it appears that this phytohormone must be maintained in a range of concentrations to support normal root growth. In spite of its known role as inhibitor of ethylene action, silver thiosulphate (STS) does not change significantly the root elongation rate. This suggests that the action of ethylene on root elongation should occur, at least partially, by interaction with other growth regulators. PMID:20514233

Alarcón, María Victoria; Lloret-Salamanca, Alberto; Lloret, Pedro Gaspar; Iglesias, Domingo José; Talón, Manuel; Salguero, Julio

2009-12-01

11

Strigolactones affect lateral root formation and root-hair elongation in Arabidopsis.  

PubMed

Strigolactones (SLs) have been proposed as a new group of plant hormones, inhibiting shoot branching, and as signaling molecules for plant interactions. Here, we present evidence for effects of SLs on root development. The analysis of mutants flawed in SLs synthesis or signaling suggested that the absence of SLs enhances lateral root formation. In accordance, roots grown in the presence of GR24, a synthetic bioactive SL, showed reduced number of lateral roots in WT and in max3-11 and max4-1 mutants, deficient in SL synthesis. The GR24-induced reduction in lateral roots was not apparent in the SL signaling mutant max2-1. Moreover, GR24 led to increased root-hair length in WT and in max3-11 and max4-1 mutants, but not in max2-1. SLs effect on lateral root formation and root-hair elongation may suggest a role for SLs in the regulation of root development; perhaps, as a response to growth conditions. PMID:21080198

Kapulnik, Yoram; Delaux, Pierre-Marc; Resnick, Natalie; Mayzlish-Gati, Einav; Wininger, Smadar; Bhattacharya, Chaitali; Séjalon-Delmas, Nathalie; Combier, Jean-Philippe; Bécard, Guillaume; Belausov, Eduard; Beeckman, Tom; Dor, Evgenia; Hershenhorn, Joseph; Koltai, Hinanit

2011-01-01

12

Localized Iron Supply Triggers Lateral Root Elongation in Arabidopsis by Altering the AUX1-Mediated Auxin Distribution[C][W][OA  

PubMed Central

Root system architecture depends on nutrient availability, which shapes primary and lateral root development in a nutrient-specific manner. To better understand how nutrient signals are integrated into root developmental programs, we investigated the morphological response of Arabidopsis thaliana roots to iron (Fe). Relative to a homogeneous supply, localized Fe supply in horizontally separated agar plates doubled lateral root length without having a differential effect on lateral root number. In the Fe uptake-defective mutant iron-regulated transporter1 (irt1), lateral root development was severely repressed, but a requirement for IRT1 could be circumvented by Fe application to shoots, indicating that symplastic Fe triggered the local elongation of lateral roots. The Fe-stimulated emergence of lateral root primordia and root cell elongation depended on the rootward auxin stream and was accompanied by a higher activity of the auxin reporter DR5-?-glucuronidase in lateral root apices. A crucial role of the auxin transporter AUXIN RESISTANT1 (AUX1) in Fe-triggered lateral root elongation was indicated by Fe-responsive AUX1 promoter activities in lateral root apices and by the failure of the aux1-T mutant to elongate lateral roots into Fe-enriched agar patches. We conclude that a local symplastic Fe gradient in lateral roots upregulates AUX1 to accumulate auxin in lateral root apices as a prerequisite for lateral root elongation.

Giehl, Ricardo F.H.; Lima, Joni E.; von Wiren, Nicolaus

2012-01-01

13

Multiple signaling pathways control nitrogen-mediated root elongation in maize.  

PubMed

Response of root system architecture to nutrient availability is an essential way for plants to adapt to soil environments. Nitrogen can affect root development either as a result of changes in the external concentration, or through changes in the internal nutrient status of the plant. Low soil N stimulates root elongation in maize. Recent evidence suggests that plant hormones auxin and cytokinin, as well as NO signaling pathway, are involved in the regulation of root elongation by low nitrogen nutrition. PMID:19704443

Mi, Guohua; Chen, Fanjun; Zhang, Fusuo

2008-11-01

14

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

NASA Technical Reports Server (NTRS)

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.

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

1989-01-01

15

Occlusion regulates tooth-root elongation during root development in rat molars.  

PubMed

Occlusion is commenced by contact of a tooth with an opposing tooth and is the mechanical force working against the periodontal ligament (PDL). However, the influences of occlusion during root development remain uncertain. By extracting the unerupted counterpart molars of rats, we established a non-occlusal model that directly examined the effects of the absence of occlusion in developing molars using micro-computed tomography (?-CT) and histological procedures. The ?-CT data for experimental molars confirmed no attrition and hypogenesis of the alveolar bone. Root lengths in experimental groups increased more than in control groups. Histological findings of experimental molars showed a wide crown pulp, a long and narrow root, immature Sharpey's fibers, and hypogenesis of cementum. Proliferating cells localized in Hertwig's epithelial root sheath (HERS), the apical pulp, and the PDL of experimental teeth. Furthermore, cell-proliferative activity in experimental roots exceeded that in normal roots. These data indicate that cell proliferation is decreased by occlusion during root formation. Thus, occlusion is one factor that regulates root elongation. PMID:22112026

Nakasone, Naohiro; Yoshie, Hiromasa

2011-12-01

16

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

PubMed

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

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

2014-04-01

17

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

NASA Technical Reports Server (NTRS)

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

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

1985-01-01

18

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

Microsoft Academic Search

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

Karin Kollárová; Mária Henselová; Desana Lišková

2005-01-01

19

Arabidopsis thaliana RALF1 opposes brassinosteroid effects on root cell elongation and lateral root formation.  

PubMed

Rapid alkalinization factor (RALF) is a peptide signal that plays a basic role in cell biology and most likely regulates cell expansion. In this study, transgenic Arabidopsis thaliana lines with high and low levels of AtRALF1 transcripts were used to investigate this peptide's mechanism of action. Overexpression of the root-specific isoform AtRALF1 resulted in reduced cell size. Conversely, AtRALF1 silencing increased root length by increasing the size of root cells. AtRALF1-silenced plants also showed an increase in the number of lateral roots, whereas AtRALF1 overexpression produced the opposite effect. In addition, four AtRALF1-inducible genes were identified: two genes encoding proline-rich proteins (AtPRP1 and AtPRP3), one encoding a hydroxyproline-rich glycoprotein (AtHRPG2), and one encoding a xyloglucan endotransglucosylase (TCH4). These genes were expressed in roots and involved in cell-wall rearrangement, and their induction was concentration dependent. Furthermore, AtRALF1-overexpressing plants were less sensitive to exogenous brassinolide (BL); upon BL treatment, the plants showed no increase in root length and a compromised increase in hypocotyl elongation. In addition, the treatment had no effect on the number of emerged lateral roots. AtRALF1 also induces two brassinosteroid (BR)-downregulated genes involved in the BR biosynthetic pathway: the cytochrome P450 monooxygenases CONSTITUTIVE PHOTOMORPHISM AND DWARFISM (CPD) and DWARF4 (DWF4). Simultaneous treatment with both AtRALF1 and BL caused a reduction in AtRALF1-inducible gene expression levels, suggesting that these signals may compete for components shared by both pathways. Taken together, these results indicate an opposing effect of AtRALF1 and BL, and suggest that RALF's mechanism of action could be to interfere with the BR signalling pathway. PMID:24620000

Bergonci, Tábata; Ribeiro, Bianca; Ceciliato, Paulo H O; Guerrero-Abad, Juan Carlos; Silva-Filho, Marcio C; Moura, Daniel S

2014-05-01

20

Arabidopsis thaliana RALF1 opposes brassinosteroid effects on root cell elongation and lateral root formation  

PubMed Central

Rapid alkalinization factor (RALF) is a peptide signal that plays a basic role in cell biology and most likely regulates cell expansion. In this study, transgenic Arabidopsis thaliana lines with high and low levels of AtRALF1 transcripts were used to investigate this peptide’s mechanism of action. Overexpression of the root-specific isoform AtRALF1 resulted in reduced cell size. Conversely, AtRALF1 silencing increased root length by increasing the size of root cells. AtRALF1-silenced plants also showed an increase in the number of lateral roots, whereas AtRALF1 overexpression produced the opposite effect. In addition, four AtRALF1-inducible genes were identified: two genes encoding proline-rich proteins (AtPRP1 and AtPRP3), one encoding a hydroxyproline-rich glycoprotein (AtHRPG2), and one encoding a xyloglucan endotransglucosylase (TCH4). These genes were expressed in roots and involved in cell-wall rearrangement, and their induction was concentration dependent. Furthermore, AtRALF1-overexpressing plants were less sensitive to exogenous brassinolide (BL); upon BL treatment, the plants showed no increase in root length and a compromised increase in hypocotyl elongation. In addition, the treatment had no effect on the number of emerged lateral roots. AtRALF1 also induces two brassinosteroid (BR)-downregulated genes involved in the BR biosynthetic pathway: the cytochrome P450 monooxygenases CONSTITUTIVE PHOTOMORPHISM AND DWARFISM (CPD) and DWARF4 (DWF4). Simultaneous treatment with both AtRALF1 and BL caused a reduction in AtRALF1-inducible gene expression levels, suggesting that these signals may compete for components shared by both pathways. Taken together, these results indicate an opposing effect of AtRALF1 and BL, and suggest that RALF’s mechanism of action could be to interfere with the BR signalling pathway.

Moura, Daniel S.

2014-01-01

21

Food reserves in mountain longleaf pine roots during shoot elongation.  

SciTech Connect

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.

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

2001-03-20

22

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

PubMed

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

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

23

Formin homology 1 (OsFH1) regulates root-hair elongation in rice (Oryza sativa).  

PubMed

The outgrowth of root hairs from the epidermal cell layer is regulated by a strict genetic regulatory system and external growth conditions. Rice plants cultivated in water-logged paddy land are exposed to a soil ecology that differs from the environment surrounding upland plants, such as Arabidopsis and maize. To identify genes that play important roles in root-hair growth, a forward genetics approach was used to screen for short-root-hair mutants. A short-root-hair mutant was identified, and the gene was isolated using map-based cloning and sequencing. The mutant harbored a point mutation at a splicing acceptor site, which led to truncation of OsFH1 (rice formin homology 1). Subsequent analysis of two additional T-DNA mutants verified that OsFH1 is important for root-hair elongation. Further studies revealed that the action of OsFH1 on root-hair growth is dependent on growth conditions. The mutant Osfh1 exhibited root-hair defects when roots were grown submerged in solution, and mutant roots produced normal root hairs in the air. However, root-hair phenotypes of mutants were not influenced by the external supply of hormones or carbohydrates, a deficiency of nutrients, such as Fe or P i , or aeration. This study shows that OsFH1 plays a significant role in root-hair elongation in a growth condition-dependent manner. PMID:23334469

Huang, Jin; Kim, Chul Min; Xuan, Yuan-hu; Liu, Jingmiao; Kim, Tae Ho; Kim, Bo-Kyeong; Han, Chang-deok

2013-05-01

24

Root elongation against a constant force: experiment with a computerized feedback-controlled device  

NASA Technical Reports Server (NTRS)

Axial force was applied to the root tip of corn (Zea mays L. cv. Merit) seedlings using a computerized, feedback-controlled mechanical device. The system's feedback capability allowed continuous control of a constant tip load, and the attached displacement transducer provided the time course of root elongation. Loads up to 7.5 g decreased the root elongation rate by 0.13 mm h-1 g-1, but loads 7.5 to 17.5 g decreased the growth rate by only 0.04 mm h-1 g-1. Loads higher than 18 g stopped root elongation completely. Measurement of the cross-sectional areas of the root tips indicated that the 18 g load had applied about 0.98 MPa of axial pressure to the root, thereby exceeding the root's ability to respond with increased turgor pressure. Recorded time-lapse images of loaded roots showed that radial thickening (swelling) occurred behind the root cap, whose cross-sectional area increased with tip load.

Kuzeja, P. S.; Lintilhac, P. M.; Wei, C.

2001-01-01

25

The boundary of the meristematic and elongation zones in roots: endoreduplication precedes rapid cell expansion  

PubMed Central

Plant roots consist of a meristematic zone of mitotic cells and an elongation zone of rapidly expanding cells, in which DNA replication often occurs without cell division, a process known as endoreduplication. The duration of the cell cycle and DNA replication, as measured by 5-ethynyl-2?-deoxy-uridine (EdU) incorporation, differed between the two regions (17?h in the meristematic zone, 30?h in the elongation zone). Two distinct subnuclear patterns of EdU signals, whole and speckled, marked nuclei undergoing DNA replication at early and late S phase, respectively. The boundary region between the meristematic and elongation zones was analysed by a combination of DNA replication imaging and optical estimation of the amount of DNA in each nucleus (C-value). We found a boundary cell with 4C nuclei exhibiting the whole pattern of EdU signals. Analyses of cells in the boundary region revealed that endoreduplication precedes rapid cell elongation in roots.

Hayashi, Kohma; Hasegawa, Junko; Matsunaga, Sachihiro

2013-01-01

26

Elongation, rooting and acclimatization of micropropagated shoots from mature material of hybrid larch  

Microsoft Academic Search

Factors were defined for elongation, rooting and acclimatization of micropropagated shoots ofLarix x eurolepis Henry initiated from short shoot buds of plagiotropic stecklings serially propagated for 9 years from an 8-year-old tree. Initiation and multiplication were on Schenk and Hildebrandt (SH) medium supplemented with 5 µM 6-benzyladenine (BA) and 1 µM indole-butyric acid (IBA). Stem elongation was obtained in 36%

Nicole Brassard; Line Brissette; Daniel Lord; Sylvie Laliberté

1996-01-01

27

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

NASA Technical Reports Server (NTRS)

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

Evans, Michael L.

1998-01-01

28

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

NASA Technical Reports Server (NTRS)

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

Ishikawa, H.; Evans, M. L.

1990-01-01

29

COMPARATIVE TOXICITY OF SIX TEST CHEMICALS TO LETTUCE USING TWO ROOT ELONGATION TEST METHODS (JOURNAL VERSION)  

EPA Science Inventory

Lettuce (Lactuca sativa L., cv buttercrunch) was used to evaluate and compare the results from two different root elongation phytotoxicity test methods with the same six test substances. Seeds were either germinated in the dark on an inclined filter paper substrate with one end i...

30

Root-Localized Phytochrome Chromophore Synthesis Is Required for Photoregulation of Root Elongation and Impacts Root Sensitivity to Jasmonic Acid in Arabidopsis1[W][OA  

PubMed Central

Plants exhibit organ- and tissue-specific light responses. To explore the molecular basis of spatial-specific phytochrome-regulated responses, a transgenic approach for regulating the synthesis and accumulation of the phytochrome chromophore phytochromobilin (P?B) was employed. In prior experiments, transgenic expression of the BILIVERDIN REDUCTASE (BVR) gene was used to metabolically inactivate biliverdin IX?, a key precursor in the biosynthesis of P?B, and thereby render cells accumulating BVR phytochrome deficient. Here, we report analyses of transgenic Arabidopsis (Arabidopsis thaliana) lines with distinct patterns of BVR accumulation dependent upon constitutive or tissue-specific, promoter-driven BVR expression that have resulted in insights on a correlation between root-localized BVR accumulation and photoregulation of root elongation. Plants with BVR accumulation in roots and a P?B-deficient elongated hypocotyl2 (hy2-1) mutant exhibit roots that are longer than those of wild-type plants under white illumination. Additional analyses of a line with root-specific BVR accumulation generated using a GAL4-dependent bipartite enhancer-trap system confirmed that P?B or phytochromes localized in roots directly impact light-dependent root elongation under white, blue, and red illumination. Additionally, roots of plants with constitutive plastid-localized or root-specific cytosolic BVR accumulation, as well as phytochrome chromophore-deficient hy1-1 and hy2-1 mutants, exhibit reduced sensitivity to the plant hormone jasmonic acid (JA) in JA-dependent root inhibition assays, similar to the response observed for the JA-insensitive mutants jar1 and myc2. Our analyses of lines with root-localized phytochrome deficiency or root-specific phytochrome depletion have provided novel insights into the roles of root-specific P?B, or phytochromes themselves, in the photoregulation of root development and root sensitivity to JA.

Costigan, Stephanie E.; Warnasooriya, Sankalpi N.; Humphries, Brock A.; Montgomery, Beronda L.

2011-01-01

31

The Control of Cell Size and Rate of Elongation in the Arabidopsis Root  

Microsoft Academic Search

The control of cell elongation is studied in the root of Arabidopsis\\u000a by focusing on reduction of cell size. Reduced organ size is a common response of a plant to\\u000a different exogenous and endogenous signals. There is not a single specific event\\/actor that is solely\\u000a responsible for the fast inhibition of cell elongation, but a battery of different actors at different\\u000a levels work together

Tinne De Cnodder; Jean-Pierre Verbelen; Kris Vissenberg

32

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

NASA Astrophysics Data System (ADS)

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

Klymchuk, Dmytro

33

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

PubMed

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

Manoli, Alessandro; Begheldo, Maura; Genre, Andrea; Lanfranco, Luisa; Trevisan, Sara; Quaggiotti, Silvia

2014-01-01

34

Strigolactones affect lateral root formation and root-hair elongation in Arabidopsis  

Microsoft Academic Search

Strigolactones (SLs) have been proposed as a new group of plant hormones, inhibiting shoot branching, and as signaling molecules\\u000a for plant interactions. Here, we present evidence for effects of SLs on root development. The analysis of mutants flawed in\\u000a SLs synthesis or signaling suggested that the absence of SLs enhances lateral root formation. In accordance, roots grown in\\u000a the presence

Yoram Kapulnik; Pierre-Marc Delaux; Natalie Resnick; Einav Mayzlish-Gati; Smadar Wininger; Chaitali Bhattacharya; Nathalie Séjalon-Delmas; Jean-Philippe Combier; Guillaume Bécard; Eduard Belausov; Tom Beeckman; Evgenia Dor; Joseph Hershenhorn; Hinanit Koltai

2011-01-01

35

Melatonin promotes seminal root elongation and root growth in transgenic rice after germination.  

PubMed

The effect of melatonin on root growth after germination was examined in transgenic rice seedlings expressing sheep serotonin N-acetyltransferase (NAT). Enhanced melatonin levels were found in T(3) homozygous seedlings because of the ectopic overexpression of sheep NAT, which is believed to be the rate-limiting enzyme in melatonin biosynthesis in animals. Compared with wild-type rice seeds, the transgenic rice seeds showed enhanced seminal root growth and an analogous number of adventitious roots 4 and 10 days after seeding on half-strength Murashige and Skoog medium. The enhanced initial seminal root growth in the transgenic seedlings matched their increased root biomass well. We also found that treatment with 0.5 and 1 ?M melatonin promoted seminal root growth of the wild type under continuous light. These results indicate that melatonin plays an important role in regulating both seminal root length and root growth after germination in monocotyledonous rice plants. This is the first report on the effects of melatonin on root growth in gain-of-function mutant plants that produce high levels of melatonin. PMID:22640001

Park, Sangkyu; Back, Kyoungwhan

2012-11-01

36

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

PubMed

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

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

2010-09-01

37

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

NASA Technical Reports Server (NTRS)

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.

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

1991-01-01

38

Arabidopsis thaliana root elongation growth is sensitive to lunisolar tidal acceleration and may also be weakly correlated with geomagnetic variations  

PubMed Central

Background Correlative evidence suggests a relationship between the lunisolar tidal acceleration and the elongation rate of arabidopsis roots grown under free-running conditions of constant low light. Methods Seedlings of Arabidopsis thaliana were grown in a controlled-climate chamber maintained at a constant temperature and subjected to continuous low-level illumination from fluorescent tubes, conditions that approximate to a ‘free-running’ state in which most of the abiotic factors that entrain root growth rates are excluded. Elongation of evenly spaced, vertical primary roots was recorded continuously over periods of up to 14 d using high temporal- and spatial-resolution video imaging and were analysed in conjunction with geophysical variables. Key Results and Conclusions The results confirm the lunisolar tidal/root elongation relationship. Also presented are relationships between the hourly elongation rates and the contemporaneous variations in geomagnetic activity, as evaluated from the disturbance storm time and ap indices. On the basis of time series of root elongation rates that extend over ?4 d and recorded at different seasons of the year, a provisional conclusion is that root elongation responds to variation in the lunisolar force and also appears to adjust in accordance with variations in the geomagnetic field. Thus, both lunisolar tidal acceleration and the geomagnetic field should be considered as modulators of root growth rate, alongside other, stronger and more well-known abiotic environmental regulators, and perhaps unexplored factors such as air ions. Major changes in atmospheric pressure are not considered to be a factor contributing to oscillations of root elongation rate.

Barlow, Peter W.; Fisahn, Joachim; Yazdanbakhsh, Nima; Moraes, Thiago A.; Khabarova, Olga V.; Gallep, Cristiano M.

2013-01-01

39

Effects of functionalized and nonfunctionalized single-walled carbon nanotubes on root elongation of select crop species.  

PubMed

Single-walled carbon nanotubes have many potential beneficial uses, with additional applications constantly being investigated. Their unique properties, however, create a potential concern regarding toxicity, not only in humans and animals but also in plants. To help develop protocols to determine the effects of nanotubes on plants, we conducted a pilot study on the effects of functionalized and nonfunctionalized single-walled carbon nanotubes on root elongation of six crop species (cabbage, carrot, cucumber, lettuce, onion, and tomato) routinely used in phytotoxicity testing. Nanotubes were functionalized with poly-3-aminobenzenesulfonic acid. Root growth was measured at 0, 24, and 48 h following exposure. Scanning-electron microscopy was used to evaluate potential uptake of carbon nanotubes and to observe the interaction of nanotubes with the root surface. In general, nonfunctionalized carbon nanotubes affected root length more than functionalized nanotubes. Nonfunctionalized nanotubes inhibited root elongation in tomato and enhanced root elongation in onion and cucumber. Functionalized nanotubes inhibited root elongation in lettuce. Cabbage and carrots were not affected by either form of nanotubes. Effects observed following exposure to carbon nanotubes tended to be more pronounced at 24 h than at 48 h. Microscopy images showed the presence of nanotube sheets on the root surfaces, but no visible uptake of nanotubes was observed. PMID:19086209

Cańas, Jaclyn E; Long, Monique; Nations, Shawna; Vadan, Rodica; Dai, Lenore; Luo, Mingxiang; Ambikapathi, Ramya; Lee, E Henry; Olszyk, David

2008-09-01

40

Reductions in Maize Root-tip Elongation by Salt and Osmotic Stress do not Correlate with Apoplastic O2•? Levels  

PubMed Central

Background and Aims Experimental evidence in the literature suggests that O2•? produced in the elongation zone of roots and leaves by plasma membrane NADPH oxidase activity is required for growth. This study explores whether growth changes along the root tip induced by hyperosmotic treatments in Zea mays are associated with the distribution of apoplastic O2•?. Methods Stress treatments were imposed using 150 mm NaCl or 300 mm sorbitol. Root elongation rates and the spatial distribution of growth rates in the root tip were measured. Apoplastic O2•? was determined using nitro blue tetrazolium, and H2O2 was determined using 2?, 7?-dichlorofluorescin. Key Results In non-stressed plants, the distribution of accelerating growth and highest O2•? levels coincided along the root tip. Salt and osmotic stress of the same intensity had similar inhibitory effects on root elongation, but O2•? levels increased in sorbitol-treated roots and decreased in NaCl-treated roots. Conclusions The lack of association between apoplastic O2•? levels and root growth inhibition under hyper-osmotic stress leads us to hypothesize that under those conditions the role of apoplastic O2•? may be to participate in signalling processes, that convey information on the nature of the substrate that the growing root is exploring.

Bustos, Dolores; Lascano, Ramiro; Villasuso, Ana Laura; Machado, Estela; Senn, Maria Eugenia; Cordoba, Alicia; Taleisnik, Edith

2008-01-01

41

Spatial distribution of transcript changes in the maize primary root elongation zone at low water potential  

PubMed Central

Background Previous work showed that the maize primary root adapts to low ?w (-1.6 MPa) by maintaining longitudinal expansion in the apical 3 mm (region 1), whereas in the adjacent 4 mm (region 2) longitudinal expansion reaches a maximum in well-watered roots but is progressively inhibited at low ?w. To identify mechanisms that determine these responses to low ?w, transcript expression was profiled in these regions of water-stressed and well-watered roots. In addition, comparison between region 2 of water-stressed roots and the zone of growth deceleration in well-watered roots (region 3) distinguished stress-responsive genes in region 2 from those involved in cell maturation. Results Responses of gene expression to water stress in regions 1 and 2 were largely distinct. The largest functional categories of differentially expressed transcripts were reactive oxygen species and carbon metabolism in region 1, and membrane transport in region 2. Transcripts controlling sucrose hydrolysis distinguished well-watered and water-stressed states (invertase vs. sucrose synthase), and changes in expression of transcripts for starch synthesis indicated further alteration in carbon metabolism under water deficit. A role for inositols in the stress response was suggested, as was control of proline metabolism. Increased expression of transcripts for wall-loosening proteins in region 1, and for elements of ABA and ethylene signaling were also indicated in the response to water deficit. Conclusion The analysis indicates that fundamentally different signaling and metabolic response mechanisms are involved in the response to water stress in different regions of the maize primary root elongation zone.

Spollen, William G; Tao, Wenjing; Valliyodan, Babu; Chen, Kegui; Hejlek, Lindsey G; Kim, Jong-Joo; LeNoble, Mary E; Zhu, Jinming; Bohnert, Hans J; Henderson, David; Schachtman, Daniel P; Davis, Georgia E; Springer, Gordon K; Sharp, Robert E; Nguyen, Henry T

2008-01-01

42

Identification of genes involved in the ACC-mediated control of root cell elongation in Arabidopsis thaliana  

PubMed Central

Background Along the root axis of Arabidopsis thaliana, cells pass through different developmental stages. In the apical meristem repeated cycles of division increase the numbers of cells. Upon leaving the meristem, these cells pass the transition zone where they are physiologically and mechanically prepared to undergo subsequent rapid elongation. During the process of elongation epidermal cells increase their length by 300% in a couple of hours. When elongation ceases, the cells acquire their final size, shape and functions (in the differentiation zone). Ethylene administered as its precursor 1-aminocyclopropane-1-carboxylic acid (ACC) is capable of inhibiting elongation in a concentration-dependent way. Using a microarray analysis, genes and/or processes involved in this elongation arrest are identified. Results Using a CATMA-microarray analysis performed on control and 3h ACC-treated roots, 240 differentially expressed genes were identified. Quantitative Real-Time RT-PCR analysis of the 10 most up and down regulated genes combined with literature search confirmed the accurateness of the analysis. This revealed that inhibition of cell elongation is, at least partly, caused by restricting the events that under normal growth conditions initiate elongation and by increasing the processes that normally stop cellular elongation at the end of the elongation/onset of differentiation zone. Conclusions ACC interferes with cell elongation in the Arabidopsis thaliana roots by inhibiting cells from entering the elongation process and by immediately stimulating the formation of cross-links in cell wall components, diminishing the remaining elongation capacity. From the analysis of the differentially expressed genes, it becomes clear that many genes identified in this response, are also involved in several other kind of stress responses. This suggests that many responses originate from individual elicitors, but that somewhere in the downstream signaling cascade, these are converged to a ’common pathway’. Furthermore, several potential keyplayers, such as transcription factors and auxin-responsive genes, were identified by the microarray analysis. They await further analysis to reveal their exact role in the control of cell elongation.

2012-01-01

43

Hydrogen-rich water alleviates aluminum-induced inhibition of root elongation in alfalfa via decreasing nitric oxide production.  

PubMed

One of the earliest and distinct symptoms of aluminum (Al) toxicity is the inhibition of root elongation. Although hydrogen gas (H2) is recently described as an important bio-regulator in plants, whether and how H2 regulates Al-induced inhibition of root elongation is largely unknown. To address these gaps, hydrogen-rich water (HRW) was used to investigate a physiological role of H2 and its possible molecular mechanism. Individual or simultaneous (in particular) exposure of alfalfa seedlings to Al, or a fresh but not old nitric oxide (NO)-releasing compound sodium nitroprusside (SNP), not only increased NO production, but also led to a significant inhibition of root elongation. Above responses were differentially alleviated by pretreatment with 50% saturation of HRW. The addition of HRW also alleviated the appearance of Al toxicity symptoms, including the improvement of seedling growth and less accumulation of Al. Subsequent results revealed that the removal of NO by the NO scavenger, similar to HRW, could decrease NO production and alleviate Al- or SNP-induced inhibition of root growth. Thus, we proposed that HRW alleviated Al-induced inhibition of alfalfa root elongation by decreasing NO production. Such findings may be applicable to enhance crop yield and improve stress tolerance. PMID:24413050

Chen, Meng; Cui, Weiti; Zhu, Kaikai; Xie, Yanjie; Zhang, Chunhua; Shen, Wenbiao

2014-02-28

44

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

PubMed Central

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.

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

2008-01-01

45

A new algorithm for computational image analysis of deformable motion at high spatial and temporal resolution applied to root growth. Roughly uniform elongation in the meristem and also, after an abrupt acceleration, in the elongation zone.  

PubMed

A requirement for understanding morphogenesis is being able to quantify expansion at the cellular scale. Here, we present new software (RootflowRT) for measuring the expansion profile of a growing root at high spatial and temporal resolution. The software implements an image processing algorithm using a novel combination of optical flow methods for deformable motion. The algorithm operates on a stack of nine images with a given time interval between each (usually 10 s) and quantifies velocity confidently at most pixels of the image. The root does not need to be marked. The software calculates components of motion parallel and perpendicular to the local tangent of the root's midline. A variation of the software has been developed that reports the overall root growth rate versus time. Using this software, we find that the growth zone of the root can be divided into two distinct regions, an apical region where the rate of motion, i.e. velocity, rises gradually with position and a subapical region where velocity rises steeply with position. In both zones, velocity increases almost linearly with position, and the transition between zones is abrupt. We observed this pattern for roots of Arabidopsis, tomato (Lycopersicon lycopersicum), lettuce (Lactuca sativa), alyssum (Aurinia saxatilis), and timothy (Phleum pratense). These velocity profiles imply that relative elongation rate is regulated in a step-wise fashion, being low but roughly uniform within the meristem and then becoming high, but again roughly uniform, within the zone of elongation. The executable code for RootflowRT is available from the corresponding author on request. PMID:12857796

van der Weele, Corine M; Jiang, Hai S; Palaniappan, Krishnan K; Ivanov, Viktor B; Palaniappan, Kannapan; Baskin, Tobias I

2003-07-01

46

Assessment of chromium efficacy on germination, root elongation, and coleoptile growth of wheat (Triticum aestivum L.) at different growth periods.  

PubMed

The tannery effluents contain a high concentration of chromium (Cr). It drastically reduces the crop yield when used for irrigation purpose. A huge volume of tannery effluents is available as irrigation for crop production. It is negatively affecting germination as well as yield of the crop. The wheat seeds were exposed to five different concentrations of Cr (0, 20, 40, 80, and 100 ppm). In Petri plates, 100 seeds were placed and the germination percent was recorded after 72 hour (h). Root elongation and coleoptile growth were measured at 72, 120, 168, and 240 h. Results showed that the germination percent of the test crop decreased with increasing Cr levels. It decreased by 6, 14, 30, and 37 % under the Cr concentration of 20, 40, 80, and 100 ppm, respectively. The root elongation was more sensitive than the coleoptile growth. The negative correlation was found between Cr levels and root elongation as well as coleoptile growth. These growth parameters were significantly affected up to 80 ppm of Cr level. The wheat growers using tannery effluent as irrigation should be well treated prior to application. PMID:24415062

Dotaniya, M L; Das, H; Meena, V D

2014-05-01

47

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

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.

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

2013-01-01

48

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

PubMed Central

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.

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

2010-01-01

49

Apoplastic Alkalinization Is Instrumental for the Inhibition of Cell Elongation in the Arabidopsis Root by the Ethylene Precursor 1-Aminocyclopropane-1-Carboxylic Acid1[W][OA  

PubMed Central

In Arabidopsis (Arabidopsis thaliana; Columbia-0) roots, the so-called zone of cell elongation comprises two clearly different domains: the transition zone, a postmeristematic region (approximately 200–450 ?m proximal of the root tip) with a low rate of elongation, and a fast elongation zone, the adjacent proximal region (450 ?m away from the root tip up to the first root hair) with a high rate of elongation. In this study, the surface pH was measured in both zones using the microelectrode ion flux estimation technique. The surface pH is highest in the apical part of the transition zone and is lowest at the basal part of the fast elongation zone. Fast cell elongation is inhibited within minutes by the ethylene precursor 1-aminocyclopropane-1-carboxylic acid; concomitantly, apoplastic alkalinization occurs in the affected root zone. Fusicoccin, an activator of the plasma membrane H+-ATPase, can partially rescue this inhibition of cell elongation, whereas the inhibitor N,N?-dicyclohexylcarbodiimide does not further reduce the maximal cell length. Microelectrode ion flux estimation experiments with auxin mutants lead to the final conclusion that control of the activity state of plasma membrane H+-ATPases is one of the mechanisms by which ethylene, via auxin, affects the final cell length in the root.

Staal, Marten; De Cnodder, Tinne; Simon, Damien; Vandenbussche, Filip; Van Der Straeten, Dominique; Verbelen, Jean-Pierre; Elzenga, Theo; Vissenberg, Kris

2011-01-01

50

GbTCP, a cotton TCP transcription factor, confers fibre elongation and root hair development by a complex regulating system  

PubMed Central

As the most important natural raw material for textile industry, cotton fibres are an excellent model for studying single-cell development. Although expression profiling and functional genomics have provided some data, the mechanism of fibre development is still not well known. A class I TCP transcription factor (designated GbTCP), encoding 344 amino acids, was isolated from the normalized cDNA library of sea-island cotton fibre (from –2 to 25 days post anthesis). GbTCP was preferentially expressed in the elongating cotton fibre from 5 to 15 days post anthesis. Some expression was also observed in stems, apical buds, and petals. RNAi silencing of GbTCP produced shorter fibre, a reduced lint percentage, and a lower fibre quality than the wild-type plants. Overexpression of GbTCP enhanced root hair initiation and elongation in Arabidopsis and regulated branching. Solexa sequencing and Affymetrix GeneChip analysis indicated that GbTCP positively regulates the level of jasmonic acid (JA) and, as a result, activates downstream genes (reactive oxygen species, calcium signalling, ethylene biosynthesis and response, and several NAC and WRKY transcription factors) necessary for elongation of fibres and root hairs. JA content analysis in cotton also confirmed that GbTCP has a profound effect on JA biosynthesis. In vitro ovule culture showed that an appropriate concentration of JA promoted fibre elongation. The results suggest that GbTCP is an important transcription factor for fibre and root hair development by regulating JA biosynthesis and response and other pathways, including reactive oxygen species, calcium channel and ethylene signalling.

Zhang, Xianlong

2012-01-01

51

GbTCP, a cotton TCP transcription factor, confers fibre elongation and root hair development by a complex regulating system.  

PubMed

As the most important natural raw material for textile industry, cotton fibres are an excellent model for studying single-cell development. Although expression profiling and functional genomics have provided some data, the mechanism of fibre development is still not well known. A class I TCP transcription factor (designated GbTCP), encoding 344 amino acids, was isolated from the normalized cDNA library of sea-island cotton fibre (from -2 to 25 days post anthesis). GbTCP was preferentially expressed in the elongating cotton fibre from 5 to 15 days post anthesis. Some expression was also observed in stems, apical buds, and petals. RNAi silencing of GbTCP produced shorter fibre, a reduced lint percentage, and a lower fibre quality than the wild-type plants. Overexpression of GbTCP enhanced root hair initiation and elongation in Arabidopsis and regulated branching. Solexa sequencing and Affymetrix GeneChip analysis indicated that GbTCP positively regulates the level of jasmonic acid (JA) and, as a result, activates downstream genes (reactive oxygen species, calcium signalling, ethylene biosynthesis and response, and several NAC and WRKY transcription factors) necessary for elongation of fibres and root hairs. JA content analysis in cotton also confirmed that GbTCP has a profound effect on JA biosynthesis. In vitro ovule culture showed that an appropriate concentration of JA promoted fibre elongation. The results suggest that GbTCP is an important transcription factor for fibre and root hair development by regulating JA biosynthesis and response and other pathways, including reactive oxygen species, calcium channel and ethylene signalling. PMID:23105133

Hao, Juan; Tu, Lili; Hu, Haiyan; Tan, Jiafu; Deng, Fenglin; Tang, Wenxin; Nie, Yichun; Zhang, Xianlong

2012-10-01

52

OsSNDP1, a Sec14-nodulin domain-containing protein, plays a critical role in root hair elongation in rice.  

PubMed

Rice is cultivated in water-logged paddy lands. Thus, rice root hairs on the epidermal layers are exposed to a different redox status of nitrogen species, organic acids, and metal ions than root hairs growing in drained soil. To identify genes that play an important role in root hair growth, a forward genetics approach was used to screen for short-root-hair mutants. A short-root-hair mutant was identified and isolated by using map-based cloning and sequencing. The mutation arose from a single amino acid substitution of OsSNDP1 (Oryza sativa Sec14-nodulin domain protein), which shows high sequence homology with Arabidopsis COW1/AtSFH1 and encodes a phosphatidylinositol transfer protein (PITP). By performing complementation assays with Atsfh1 mutants, we demonstrated that OsSNDP1 is involved in growth of root hairs. Cryo-scanning electron microscopy was utilized to further characterize the effect of the Ossndp1 mutation on root hair morphology. Aberrant morphogenesis was detected in root hair elongation and maturation zones. Many root hairs were branched and showed irregular shapes due to bulged nodes. Many epidermal cells also produced dome-shaped root hairs, which indicated that root hair elongation ceased at an early stage. These studies showed that PITP-mediated phospholipid signaling and metabolism is critical for root hair elongation in rice. PMID:23456248

Huang, Jin; Kim, Chul Min; Xuan, Yuan-hu; Park, Soon Ju; Piao, Hai Long; Je, Byoung Il; Liu, Jingmiao; Kim, Tae Ho; Kim, Bo-Kyeong; Han, Chang-Deok

2013-05-01

53

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

PubMed Central

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.

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

2004-01-01

54

Skeletal Ultramicrostructure of Some Elongate-Chambered Planktonic Foraminifera and Related Species.  

National Technical Information Service (NTIS)

Nine species of Cenozoic planktonic foraminifera having axially or radially elongate adult chambers and six related species are examined by the scanning electron microscope to determine their generic and family classification. These species can be grouped...

T. Saito P. R. Thompson D. Breger

1976-01-01

55

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

SciTech Connect

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.

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

1996-01-01

56

Intracellular Organization: A Prerequisite for Root Hair Elongation and Cell Wall Deposition  

Microsoft Academic Search

\\u000a Cell growth requires not only production of matter, but in addition, the targeting, transport, and delivery of this matter\\u000a to the site of cell expansion. Thus, a proper organization of cell structure, the cytoarchitecture, is a necessity for cell\\u000a elongation. The actual process of cell growth in a cell under turgor pressure is Golgi vesicle membrane insertion into the\\u000a plasma

A. M. C. Emons; T. Ketelaar

2009-01-01

57

Yeast alpha-tubulin suppressor Ats1/Kti13 relates to the Elongator complex and interacts with Elongator partner protein Kti11.  

PubMed

The alpha-tubulin suppressor 1 (ATS1) gene and the killer toxin-insensitive 13 (KTI13) locus from Saccharomyces cerevisiae are allelic. The Ats1/Kti13 gene product interacts with the cell polarity factor Nap1 and promotes growth inhibition of S. cerevisiae by zymocin, a tRNAse toxin complex from Kluyveromyces lactis. Kti13 removal causes zymocin resistance, a trait that is typical of defects in the Elongator complex. Here, we show that Kti13 co-purifies with the Elongator partner protein Kti11 and that the Kti11 interaction, not the Nap1 partnership, requires the C-terminus of Kti13. Moreover, Kti13 functionally relates to roles of the Elongator complex in tRNA wobble uridine modification, tRNA suppression of nonsense (SUP4) and missense (SOE1) mutations and tRNA restriction by zymocin. Also, inactivation of Kti13 or Elongator rescues the thermosensitive growth defect of secretory mutants (sec2-59(ts), sec12-4(ts)), suggesting that Kti13 and Elongator affect secretion processes that depend on the GTP exchange factors Sec2 and Sec12 respectively. Distinct from tandem deletions in KTI13 and Elongator genes, a kti13Delta kti11Delta double deletion induces synthetic sickness or lethality. In sum, our data suggest that Kti13 and Kti11 support Elongator functions and that they both share Elongator-independent role(s) that are important for cell viability. PMID:18466297

Zabel, René; Bär, Christian; Mehlgarten, Constance; Schaffrath, Raffael

2008-07-01

58

The GCR1 and GPA1 participate in promotion of Arabidopsis primary root elongation induced by N-acyl-homoserine lactones, the bacterial quorum-sensing signals.  

PubMed

Many gram-negative bacteria use N-acyl-homoserine lactones (AHL) as quorum-sensing signals to coordinate their collective behaviors. Accumulating evidence indicates that plants can respond to AHL. However, little is known about the molecular mechanism of plants reacting to these bacterial signals. In this study, we show that the treatment of Arabidopsis roots with N-3-oxo-hexanoyl-homoserine lactone (3OC6-HSL) and N-3-oxo-octanoyl-homoserine lactone (3OC8-HSL) resulted in significant root elongation. The genetic analysis revealed that the T-DNA insertional mutants of gcr1, encoding a G-protein-coupled receptor GCR1, were insensitive to 3OC6-HSL or 3OC8-HSL in assays of root growth. The loss-of-function mutants of the sole canonical G? subunit GPA1 showed no response to AHL promotion of root elongation whereas G? gain-of-function plants overexpressing either the wild type or a constitutively active version of Arabidopsis G? exhibited the exaggerated effect on root elongation caused by AHL. Furthermore, the expression of GCR1 and GPA1 were significantly upregulated after plants were contacted with both AHL. Taken together, our results suggest that GCR1 and GPA1 are involved in AHL-mediated elongation of Arabidopsis roots. This provides insight into the mechanism of plant responses to bacterial quorum-sensing signals. PMID:22250582

Liu, Fang; Bian, Ziriu; Jia, Zhenhua; Zhao, Qian; Song, Shuishan

2012-05-01

59

Transient Proliferation of Proanthocyanidin-Accumulating Cells on the Epidermal Apex Contributes to Highly Aluminum-Resistant Root Elongation in Camphor Tree1[W  

PubMed Central

Aluminum (Al) is a harmful element that rapidly inhibits the elongation of plant roots in acidic soils. The release of organic anions explains Al resistance in annual crops, but the mechanisms that are responsible for superior Al resistance in some woody plants remain unclear. We examined cell properties at the surface layer of the root apex in the camphor tree (Cinnamomum camphora) to understand its high Al resistance mechanism. Exposure to 500 ?m Al for 8 d, more than 20-fold higher concentration and longer duration than what soybean (Glycine max) can tolerate, only reduced root elongation in the camphor tree to 64% of the control despite the slight induction of citrate release. In addition, Al content in the root apices was maintained at low levels. Histochemical profiling revealed that proanthocyanidin (PA)-accumulating cells were present at the adjacent outer layer of epidermis cells at the root apex, having distinctive zones for cell division and the early phase of cell expansion. Then the PA cells were gradually detached off the root, leaving thin debris behind, and the root surface was replaced with the elongating epidermis cells at the 3- to 4-mm region behind the tip. Al did not affect the proliferation of PA cells or epidermis cells, except for the delay in the start of expansion and the accelerated detachment of the former. In soybean roots, the innermost lateral root cap cells were absent in both PA accumulation and active cell division and failed to protect the epidermal cell expansion at 25 ?m Al. These results suggest that transient proliferation and detachment of PA cells may facilitate the expansion of epidermis cells away from Al during root elongation in camphor tree.

Osawa, Hiroki; Endo, Izuki; Hara, Yukari; Matsushima, Yuki; Tange, Takeshi

2011-01-01

60

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

PubMed

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

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

2010-08-01

61

Cytokinin action is coupled to ethylene in its effects on the inhibition of root and hypocotyl elongation in Arabidopsis thaliana seedlings.  

PubMed Central

Cytokinins have profound effects on seedling development in Arabidopsis thaliana. Benzyladenine (BA) inhibits root elongation in light- or dark-grown seedlings, and in dark-grown seedlings BA inhibits hypocotyl elongation and exaggerates the curvature of apical hooks. The latter are characteristic ethylene responses and, therefore, the possible involvement of ethylene in BA responses was examined in seedlings. It was found that the inhibitory effects of BA on root and hypocotyl elongation were partially blocked by the action of ethylene inhibitors or ethylene-resistant mutations (ein1-1 and ein2-1). Ethylene production was stimulated by submicromolar concentrations of BA and could account, in part, for the inhibition of root and hypocotyl elongation. It was demonstrated further that BA did not affect the sensitivity of seedlings to ethylene. Thus, the effect of cytokinin on root and hypocotyl elongation in Arabidopsis appears to be mediated largely by the production of ethylene. The coupling between cytokinin and ethylene responses is further supported by the discovery that the cytokinin-resistant mutant ckr1 is resistant to ethylene and is allelic to the ethylene-resistant mutant ein2.

Cary, A J; Liu, W; Howell, S H

1995-01-01

62

Comparative Proteomics Indicates That Biosynthesis of Pectic Precursors Is Important for Cotton Fiber and Arabidopsis Root Hair Elongation*  

PubMed Central

The quality of cotton fiber is determined by its final length and strength, which is a function of primary and secondary cell wall deposition. Using a comparative proteomics approach, we identified 104 proteins from cotton ovules 10 days postanthesis with 93 preferentially accumulated in the wild type and 11 accumulated in the fuzzless-lintless mutant. Bioinformatics analysis indicated that nucleotide sugar metabolism was the most significantly up-regulated biochemical process during fiber elongation. Seven protein spots potentially involved in pectic cell wall polysaccharide biosynthesis were specifically accumulated in wild-type samples at both the protein and transcript levels. Protein and mRNA expression of these genes increased when either ethylene or lignoceric acid (C24:0) was added to the culture medium, suggesting that these compounds may promote fiber elongation by modulating the production of cell wall polymers. Quantitative analysis revealed that fiber primary cell walls contained significantly higher amounts of pectin, whereas more hemicellulose was found in ovule samples. Significant fiber growth was observed when UDP-l-rhamnose, UDP-d-galacturonic acid, or UDP-d-glucuronic acid, all of which were readily incorporated into the pectin fraction of cell wall preparations, was added to the ovule culture medium. The short root hairs of Arabidopsis uer1-1 and gae6-1 mutants were complemented either by genetic transformation of the respective cotton cDNA or by adding a specific pectin precursor to the growth medium. When two pectin precursors, produced by either UDP-4-keto-6-deoxy-d-glucose 3,5-epimerase 4-reductase or by UDP-d-glucose dehydrogenase and UDP-d-glucuronic acid 4-epimerase successively, were used in the chemical complementation assay, wild-type root hair lengths were observed in both cut1 and ein2-5 Arabidopsis seedlings, which showed defects in C24:0 biosynthesis or ethylene signaling, respectively. Our results suggest that ethylene and C24:0 may promote cotton fiber and Arabidopsis root hair growth by activating the pectin biosynthesis network, especially UDP-l-rhamnose and UDP-d-galacturonic acid synthesis.

Pang, Chao-You; Wang, Hui; Pang, Yu; Xu, Chao; Jiao, Yue; Qin, Yong-Mei; Western, Tamara L.; Yu, Shu-Xun; Zhu, Yu-Xian

2010-01-01

63

Genome-wide analysis of small RNAs reveals eight fiber elongation-related and 257 novel microRNAs in elongating cotton fiber cells  

PubMed Central

Background MicroRNAs (miRNAs) and other types of small regulatory RNAs play critical roles in the regulation of gene expression at the post-transcriptional level in plants. Cotton is one of the most economically important crops, but little is known about the roles of miRNAs during cotton fiber elongation. Results Here, we combined high-throughput sequencing with computational analysis to identify small RNAs (sRNAs) related to cotton fiber elongation in Gossypium hirsutum L. (G. hirsutum). The sequence analysis confirmed the expression of 79 known miRNA families in elongating fiber cells and identified 257 novel miRNAs, primarily derived from corresponding specific loci in the Gossypium raimondii Ulbr. (G. raimondii) genome. Furthermore, a comparison of the miRNAomes revealed that 46 miRNA families were differentially expressed throughout the elongation period. Importantly, the predicted and experimentally validated targets of eight miRNAs were associated with fiber elongation, with obvious functional relationships with calcium and auxin signal transduction, fatty acid metabolism, anthocyanin synthesis and the xylem tissue differentiation. Moreover, one tasiRNA was also identified, and its target, ARF4, was experimentally validated in vivo. Conclusion This study not only facilitated the discovery of 257 novel low-abundance miRNAs in elongating cotton fiber cells but also revealed a potential regulatory network of nine sRNAs important for fiber elongation. The identification and characterization of miRNAs in elongating cotton fiber cells might promote the further study of fiber miRNA regulation mechanisms and provide insight into the importance of miRNAs in cotton.

2013-01-01

64

Rooting depths of plants relative to biological and environmental factors  

SciTech Connect

In 1981 to 1982 an extensive bibliographic study was completed to document rooting depths of native plants in the United States. The data base presently contains 1034 citations with approximately 12,000 data elements. In this paper the data were analyzed for rooting depths as related to life form, soil type, geographical region, root type, family, root depth to shoot height ratios, and root depth to root lateral ratios. Average rooting depth and rooting frequencies were determined and related to present low-level waste site maintenance.

Foxx, T S; Tierney, G D; Williams, J M

1984-11-01

65

Roles of BOR2, a boron exporter, in cross linking of rhamnogalacturonan II and root elongation under boron limitation in Arabidopsis.  

PubMed

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

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

2013-12-01

66

Transcription of DWARF4 Plays a Crucial Role in Auxin-Regulated Root Elongation in Addition to Brassinosteroid Homeostasis in Arabidopsis thaliana  

PubMed Central

The expression of DWARF4 (DWF4), which encodes a C-22 hydroxylase, is crucial for brassinosteroid (BR) biosynthesis and for the feedback control of endogenous BR levels. To advance our knowledge of BRs, we examined the effects of different plant hormones on DWF4 transcription in Arabidopsis thaliana. Semi-quantitative reverse-transcriptase PCR showed that the amount of the DWF4 mRNA precursor either decreased or increased, similarly with its mature form, in response to an exogenously applied bioactive BR, brassinolide (BL), and a BR biosynthesis inhibitor, brassinazole (Brz), respectively. The response to these chemicals in the levels of ?-glucuronidase (GUS) mRNA and its enzymatic activity is similar to the response of native DWF4 mRNA in DWF4::GUS plants. Contrary to the effects of BL, exogenous auxin induced GUS activity, but this enhancement was suppressed by anti-auxins, such as ?-(phenylethyl-2-one)-IAA and ?-tert-butoxycarbonylaminohexyl-IAA, suggesting the involvement of SCFTIR1-mediated auxin signaling in auxin-induced DWF4 transcription. Auxin-enhanced GUS activity was observed exclusively in roots; it was the most prominent in the elongation zones of both primary and lateral roots. Furthermore, auxin-induced lateral root elongation was suppressed by both Brz application and the dwf4 mutation, and this suppression was rescued by BL, suggesting that BRs act positively on root elongation under the control of auxin. Altogether, our results indicate that DWF4 transcription plays a novel role in the BR-auxin crosstalk associated with root elongation, in addition to its role in BR homeostasis.

Yoshimitsu, Yuya; Tanaka, Kiwamu; Fukuda, Wataru; Asami, Tadao; Yoshida, Shigeo; Hayashi, Ken-ichiro; Kamiya, Yuji; Jikumaru, Yusuke; Shigeta, Tomoaki; Nakamura, Yasushi; Matsuo, Tomoaki; Okamoto, Shigehisa

2011-01-01

67

PROCUSTE1 Encodes a Cellulose Synthase Required for Normal Cell Elongation Specifically in Roots and Dark-Grown Hypocotyls of Arabidopsis  

PubMed Central

Mutants at the PROCUSTE1 (PRC1) locus show decreased cell elongation, specifically in roots and dark-grown hypocotyls. Cell elongation defects are correlated with a cellulose deficiency and the presence of gapped walls. Map-based cloning of PRC1 reveals that it encodes a member (CesA6) of the cellulose synthase catalytic subunit family, of which at least nine other members exist in Arabidopsis. Mutations in another family member, RSW1 (CesA1), cause similar cell wall defects in all cell types, including those in hypocotyls and roots, suggesting that cellulose synthesis in these organs requires the coordinated expression of at least two distinct cellulose synthase isoforms.

Fagard, Mathilde; Desnos, Thierry; Desprez, Thierry; Goubet, Florence; Refregier, Guislaine; Mouille, Gregory; McCann, Maureen; Rayon, Catherine; Vernhettes, Samantha; Hofte, Herman

2000-01-01

68

Effects of aluminium on tap-root elongation of soybean ( Glycine max ), cowpea ( Vigna unguiculata ) and green gram ( Vigna radiata ) grown in the presence of organic acids  

Microsoft Academic Search

The role of fulvic, malic, and oxalic acids in alleviating the toxic effects of aluminium (Al) on tap-root elongation of soybean cv. Fitzroy, cowpea cv. Vita 4, and green gram cv. Berken was studied. Treatments consisted of a factorial combination of four Al concentrations (0, 12.5, 25 and 50 µM as Al(NO3)3·9H2O) and two concentrations either of malic or oxalic

S. Suthipradit; D. G. Edwards; C. J. Asher

1990-01-01

69

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

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.

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

2011-01-01

70

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...

71

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

PubMed Central

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

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

2000-01-01

72

Succinate dehydrogenase assembly factor 2 is needed for assembly and activity of mitochondrial complex II and for normal root elongation in Arabidopsis.  

PubMed

Mitochondria complex II (succinate dehydrogenase, SDH) plays a central role in respiratory metabolism as a component of both the electron transport chain and the tricarboxylic acid cycle. We report the identification of an SDH assembly factor by analysis of T-DNA insertions in At5g51040, a protein with unknown function that was identified by mass spectrometry analysis as a low abundance mitochondrial protein. This gene is co-expressed with a number of genes encoding mitochondrial proteins, including SDH1-1, and has low partial sequence similarity to human SDHAF2, a protein required for flavin-adenine dinucleotide (FAD) insertion into SDH. In contrast to observations of other SDH deficient lines in Arabidopsis, the sdhaf2 line did not affect photosynthetic rate or stomatal conductance, but instead showed inhibition of primary root elongation with early lateral root emergence, presumably due to the low SDH activity caused by the reduced abundance of SDHAF2. Both roots and leaves showed succinate accumulation but different responses in the abundance of other organic acids and amino acids assayed. Isolated mitochondria showed lowered SDH1 protein abundance, lowered maximal SDH activity and less protein-bound flavin-adenine dinucleotide (FAD) at the molecular mass of SDH1 in the gel separation. The short root phenotype and SDH function of sdhaf2 was fully complemented by transformation with SDHAF2. Application of the SDH inhibitor, malonate, phenocopied the sdhaf2 root architecture in WT. Whole root respiratory assays showed no difference between WT and sdhaf2, but micro-respirometry of the tips of roots clearly showed low oxygen consumption in sdhaf2 which could explain a metabolic deficit responsible for root tip growth. PMID:23036115

Huang, Shaobai; Taylor, Nicolas L; Ströher, Elke; Fenske, Ricarda; Millar, A Harvey

2013-02-01

73

Control of Root Meristem Size by DA1-RELATED PROTEIN2 in Arabidopsis1[C][W  

PubMed Central

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.

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

2013-01-01

74

Thiophene accumulation in relation to morphology in roots of Tagetes patula : Effects of auxin and transformation by Agrobacterium.  

PubMed

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 ?mol·(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 bacterial strain used. Transformation stimulated the elongation of the root tips and the formation of lateral roots but lowered the thiophene level to 20-50% relative to the concentration in untransformed detached roots. A negative correlation was found between the number of laterals in a root system and the thiophene content. Extensive branching and a decrease in thiophene accumulation was evoked in untransformed roots by indole-3-acetic acid (1-10 ?mol·l(-1)) added to the medium. Within the roots, the highest thiophene concentrations were found in the tips. The results indicate that auxin directly or indirectly plays a role in the regulation of the thiophene level in root tips. PMID:24201420

Croes, A F; van den Berg, A J; Bosveld, M; Breteler, H; Wullems, G J

1989-08-01

75

Zonal Changes in Ascorbate and Hydrogen Peroxide Contents, Peroxidase, and Ascorbate-Related Enzyme Activities in Onion Roots1  

PubMed Central

Onion (Allium cepa) roots growing hydroponically show differential zonal values for intra- (symplastic) and extra- (apoplastic) cellular ascorbate (ASC) and dehydroascorbate (DHA) contents and for related enzyme activities. In whole roots, ASC and DHA concentrations were higher in root apex and meristem and gradually decreased toward the root base. Guaiacol peroxidase, ASC peroxidase, monodehydroascorbate oxidoreductase, DHA reductase, catalase, and glutathione reductase activities showed differential activity patterns depending on the zone of the root and their apoplastic or symplastic origin. An in vivo staining of peroxidase activity also revealed a specific distribution pattern along the root axis. Using electron microscopy, hydrogen peroxide was found at different locations depending on the root zone but was mainly located in cell walls from epidermal and meristematic cells and in cells undergoing lignification. A balanced control of all of these molecules seems to exist along the root axis and may be directly related to the mechanisms in which the ASC system is involved, as cell division and elongation. The role of ASC on growth and development in relation to its presence at the different zones of the root is discussed.

del Carmen Cordoba-Pedregosa, Maria; Cordoba, Francisco; Villalba, Jose Manuel; Gonzalez-Reyes, Jose Antonio

2003-01-01

76

Multiple Functions of Kip-Related Protein5 Connect Endoreduplication and Cell Elongation[C][W  

PubMed Central

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.

Jegu, Teddy; Latrasse, David; Delarue, Marianne; Mazubert, Christelle; Bourge, Mickael; Hudik, Elodie; Blanchet, Sophie; Soler, Marie-Noelle; Charon, Celine; De Veylder, Lieven; Raynaud, Cecile; Bergounioux, Catherine; Benhamed, Moussa

2013-01-01

77

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

PubMed

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

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

78

Involvement of S. cerevisiae Rpb4 in subset of pathways related to transcription elongation.  

PubMed

Yeast Rpb4, a subunit of RNA pol II is not essential for viability but is involved in multiple cellular phenotypes such as temperature sensitivity, enhanced pseudohyphal morphology, and decreased sporulation. Both in vivo and in vitro studies strongly support involvement of Rpb4 in transcription initiation, while its role in transcription elongation is not entirely consistent. Here we show that Rpb4 is not required for recruitment of RNA pol II on the coding region of YLR454w, a representative long gene. Yet we find strong genetic interaction of rpb4? with mutants in many transcription elongation factors such as Paf1, Spt4, Dst1, Elp3 and Rpb9. We demonstrate that, Rpb4 interacts functionally with Paf1 to affect the transcription elongation of the FKS1 gene. Our results suggest that while Rpb4 is not required for general transcription elongation, it could support transcription elongation for specific of class of genes by interaction with other elongation factors. PMID:24780862

Deshpande, Swati M; Sadhale, Parag P; Vijayraghavan, Usha

2014-07-15

79

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

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.

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

80

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

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

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

81

Cessation of reproduction-related spine elongation after multiple breeding cycles in female naked mole-rats.  

PubMed

The breeding female or "queen" naked mole-rat has a uniquely elongated body morphology attributed to the lengthening of the lumbar vertebral column that occurs during pregnancy. It is unknown whether this vertebral growth is a continuous process, or associated only with early reproductive experience. We compared pregnancy-related bone elongation in nascent primiparous queens and established queens to determine if this vertebral expansion was a lifelong process in these females. We also investigated the impact of lactation on vertebral elongation in these mole-rats because it is known to be a time of significant bone loss in other mammals. Our data show that after eight or more pregnancies, established queens no longer experienced a net gain in lumbar spine length over the reproductive cycle, whereas the nascent breeders demonstrated significant spine lengthening over this time. Despite the lack of net spine lengthening in established breeders, our results indicated that these queens still experienced some pregnancy-specific vertebral elongation. In naked mole-rats, pregnancy-induced bone elongation may serve the dual purposes of first lengthening the spine, and then once optimal spine size is achieved, serving as a homeostatic mechanism that prepares the spine for the mineral demands of lactation. Anat Rec, 2009. (c) 2008 Wiley-Liss, Inc. PMID:18951517

Dengler-Crish, Christine M; Catania, Kenneth C

2009-01-01

82

The Arabidopsis CDK inhibitor ICK3/KRP5 is rate limiting for primary root growth and promotes growth through cell elongation and endoreduplication  

PubMed Central

The coordination of plant cell division and expansion controls plant morphogenesis, development, and growth. Cyclin-dependent kinases (CDKs) are not only key regulators of cell division but also play an important role in cell differentiation. In plants, CDK activity is modulated by the binding of INHIBITOR OF CDK/KIP-RELATED PROTEIN (ICK/KRP). Previously, ICK2/KRP2 has been shown to mediate auxin responses in lateral root initiation. Here are analysed the roles of all ICK/KRP genes in root growth. Analysis of ick/krp null-mutants revealed that only ick3/krp5 was affected in primary root growth. ICK3/KRP5 is strongly expressed in the root apical meristem (RAM), with lower expression in the expansion zone. ick3/krp5 roots grow more slowly than wildtype controls, and this results not from reduction of division in the proliferative region of the RAM but rather reduced expansion as cells exit the meristem. This leads to shorter final cell lengths in different tissues of the ick3/krp5 mutant root, particularly the epidermal non-hair cells, and this reduction in cell size correlates with reduced endoreduplication. Loss of ICK3/KRP5 also leads to delayed germination and in the mature embryo ICK3/KRP5 is specifically expressed in the transition zone between root and hypocotyl. Cells in the transition zone were smaller in the ick3/krp5 mutant, despite the absence of endoreduplication in the embryo suggesting a direct effect of ICK3/KRP5 on cell growth. It is concluded that ICK3/KRP5 is a positive regulator of both cell growth and endoreduplication.

Wen, Bo; Nieuwland, Jeroen; Murray, James A. H.

2013-01-01

83

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

PubMed

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

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

2014-04-01

84

Acremonium with catenate elongate conidia: phylogeny of Acremonium fusidioides and related species.  

PubMed

Acremonium is one of the largest and most complex genera of hyphomycetes. Its taxonomy is not yet resolved and the phylogenetic value of the most distinctive morphological features is unknown. The species of this genus produce conidia in chains or form slimy heads or both. We have studied a set of clinical and environmental Acremonium strains morphologically characterized by producing mostly catenate, elongate, more or less fusiform conidia. Based on phenotypic data and in the analysis of the sequences of the ITS region, the D1/D2 domains of the 28S rRNA gene and a fragment of the ?-tubulin gene, three new species morphologically similar to Acremonium fusidioides and belonging to the family Bionectriaceae (Hypocreales) are described and illustrated; they are Acremonium pilosum, Acremonium parvum and Acremonium citrinum. The first species produces two kinds of conidia: clavate with smooth walls and globose with abundant filiform projections. Acremonium parvum is characterized by slow growth and pyriform or slightly lanceolate conidia with an elongate and truncate base. Acremonium citrinum produces a diffusible yellow pigment and obovoid conidia. PMID:24782500

Giraldo, Alejandra; Gené, Josepa; Cano, Josep; de Hoog, Sybren; Decock, Cony; Guarro, Josep

2014-01-01

85

Ubiquitin-related modifiers of Arabidopsis thaliana influence root development.  

PubMed

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

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

2014-01-01

86

The relative effect of citral on mitotic microtubules in wheat roots and BY2 cells.  

PubMed

The plant volatile monoterpene citral is a highly active compound with suggested allelopathic traits. Seed germination and seedling development are inhibited in the presence of citral, and it disrupts microtubules in both plant and animal cells in interphase. We addressed the following additional questions: can citral interfere with cell division; what is the relative effect of citral on mitotic microtubules compared to interphase cortical microtubules; what is its effect on newly formed cell plates; and how does it affect the association of microtubules with ?-tubulin? In wheat seedlings, citral led to inhibition of root elongation, curvature of newly formed cell walls and deformation of microtubule arrays. Citral's effect on microtubules was both dose- and time-dependent, with mitotic microtubules appearing to be more sensitive to citral than cortical microtubules. Association of ?-tubulin with microtubules was more sensitive to citral than were the microtubules themselves. To reveal the role of disrupted mitotic microtubules in dictating aberrations in cell plates in the presence of citral, we used tobacco BY2 cells expressing GFP-Tua6. Citral disrupted mitotic microtubules, inhibited the cell cycle and increased the frequency of asymmetric cell plates in these cells. The time scale of citral's effect in BY2 cells suggested a direct influence on cell plates during their formation. Taken together, we suggest that at lower concentrations, citral interferes with cell division by disrupting mitotic microtubules and cell plates, and at higher concentrations it inhibits cell elongation by disrupting cortical microtubules. PMID:22039835

Chaimovitsh, D; Rogovoy Stelmakh, O; Altshuler, O; Belausov, E; Abu-Abied, M; Rubin, B; Sadot, E; Dudai, N

2012-03-01

87

Ultrastructure of xylem parenchyma cells of barley roots in relation to ion transport to the xylem  

Microsoft Academic Search

The structure of xylem parenchyma cells is examined in relation to transport of ions through the root. Measurement of uptake of 86Rb+ and its transport through the root at different distances from the apex show that this is a general activity along the length of the root and not confined to a limited region. Thus transport through the root is

A. Läuchli; D. Kramer; M. G. Pitman; U. Lüttge

1974-01-01

88

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

PubMed

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

Marzec, Marek; Melzer, Michael; Szarejko, Iwona

2013-11-01

89

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

NASA Technical Reports Server (NTRS)

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.

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

2002-01-01

90

Inactivation of plasma membrane-localized CDPK-RELATED KINASE5 decelerates PIN2 exocytosis and root gravitropic response in Arabidopsis.  

PubMed

CRK5 is a member of the Arabidopsis thaliana Ca(2+)/calmodulin-dependent kinase-related kinase family. Here, we show that inactivation of CRK5 inhibits primary root elongation and delays gravitropic bending of shoots and roots. Reduced activity of the auxin-induced DR5-green fluorescent protein reporter suggests that auxin is depleted from crk5 root tips. However, no tip collapse is observed and the transcription of genes for auxin biosynthesis, AUXIN TRANSPORTER/AUXIN TRANSPORTER-LIKE PROTEIN (AUX/LAX) auxin influx, and PIN-FORMED (PIN) efflux carriers is unaffected by the crk5 mutation. Whereas AUX1, PIN1, PIN3, PIN4, and PIN7 display normal localization, PIN2 is depleted from apical membranes of epidermal cells and shows basal to apical relocalization in the cortex of the crk5 root transition zone. This, together with an increase in the number of crk5 lateral root primordia, suggests facilitated auxin efflux through the cortex toward the elongation zone. CRK5 is a plasma membrane-associated kinase that forms U-shaped patterns facing outer lateral walls of epidermis and cortex cells. Brefeldin inhibition of exocytosis stimulates CRK5 internalization into brefeldin bodies. CRK5 phosphorylates the hydrophilic loop of PIN2 in vitro, and PIN2 shows accelerated accumulation in brefeldin bodies in the crk5 mutant. Delayed gravitropic response of the crk5 mutant thus likely reflects defective phosphorylation of PIN2 and deceleration of its brefeldin-sensitive membrane recycling. PMID:23673979

Rigó, Gábor; Ayaydin, Ferhan; Tietz, Olaf; Zsigmond, Laura; Kovács, Hajnalka; Páy, Anikó; Salchert, Klaus; Darula, Zsuzsanna; Medzihradszky, Katalin F; Szabados, László; Palme, Klaus; Koncz, Csaba; Cséplo, Agnes

2013-05-01

91

The Angiospermous Root Parasite Orobanche L. (Orobanchaceae) Induces Expression of a Pathogenesis Related (PR) Gene in Susceptible Tobacco Roots  

Microsoft Academic Search

Parasitic plants develop a haustorium that intrudes host tissues. In roots of transgenic PRb-1b-GUS tobacco the expression of the chimeric gene was prominent nearOrobancheinfection. The expression of the pathogenesis related (PR) protein gene inOrobanche-infected roots indicates thatOrobanchereleases appropriate elicitors, and that the susceptible plant does senseOrobancheinvasion. TheOrobanche-responsive promoter may be a useful tool in engineering resistances to this parasitic weed.

DANIEL M JOEL; VITALY H PORTNOY

1998-01-01

92

Molecular Cloning and Characterization of ?-Expansin Gene Related to Root Hair Formation in Barley1  

PubMed Central

Root hairs are specialized epidermal cells that play a role in the uptake of water and nutrients from the rhizosphere and serve as a site of interaction with soil microorganisms. The process of root hair formation is well characterized in Arabidopsis (Arabidopsis thaliana); however, there is a very little information about the genetic and molecular basis of root hair development in monocots. Here, we report on isolation and cloning of the ?-expansin (EXPB) gene HvEXPB1, tightly related to root hair initiation in barley (Hordeum vulgare). Using root transcriptome differentiation in the wild-type/root-hairless mutant system, a cDNA fragment present in roots of wild-type plants only was identified. After cloning of full-length cDNA and genomic sequences flanking the identified fragment, the subsequent bioinformatics analyses revealed homology of the protein coded by the identified gene to the EXPB family. Reverse transcription-PCR showed that expression of HvEXPB1 cosegregated with the root hair phenotype in F2 progeny of the cross between the hairless mutant rhl1.a and the wild-type Karat parent variety. Expression of the HvEXPB1 gene was root specific; it was expressed in roots of wild-type forms, but not in coleoptiles, leaves, tillers, and spikes. The identified gene was active in roots of two other analyzed root hair mutants: rhp1.a developing root hair primordia only and rhs1.a with very short root hairs. Contrary to this, a complete lack of HvEXPB1 expression was observed in roots of the spontaneous root-hairless mutant bald root barley. All these observations suggest a role of the HvEXPB1 gene in the process of root hair formation in barley.

Kwasniewski, Miroslaw; Szarejko, Iwona

2006-01-01

93

Control of root system architecture by DEEPER ROOTING 1 increases rice yield under drought conditions.  

PubMed

The genetic improvement of drought resistance is essential for stable and adequate crop production in drought-prone areas. Here we demonstrate that alteration of root system architecture improves drought avoidance through the cloning and characterization of DEEPER ROOTING 1 (DRO1), a rice quantitative trait locus controlling root growth angle. DRO1 is negatively regulated by auxin and is involved in cell elongation in the root tip that causes asymmetric root growth and downward bending of the root in response to gravity. Higher expression of DRO1 increases the root growth angle, whereby roots grow in a more downward direction. Introducing DRO1 into a shallow-rooting rice cultivar by backcrossing enabled the resulting line to avoid drought by increasing deep rooting, which maintained high yield performance under drought conditions relative to the recipient cultivar. Our experiments suggest that control of root system architecture will contribute to drought avoidance in crops. PMID:23913002

Uga, Yusaku; Sugimoto, Kazuhiko; Ogawa, Satoshi; Rane, Jagadish; Ishitani, Manabu; Hara, Naho; Kitomi, Yuka; Inukai, Yoshiaki; Ono, Kazuko; Kanno, Noriko; Inoue, Haruhiko; Takehisa, Hinako; Motoyama, Ritsuko; Nagamura, Yoshiaki; Wu, Jianzhong; Matsumoto, Takashi; Takai, Toshiyuki; Okuno, Kazutoshi; Yano, Masahiro

2013-09-01

94

Roots.  

PubMed

Many unicellular eukaryotic organisms possess complex fiber systems that organize and anchor the flagellar basal apparatus in the cell [20, 24]. In 1978 we first published the observation that one of these fiber systems, the striated flagellar root of the quadriflagellate green alga Tetraselmis subcordiformis (= Platymonas subcordiformis), is a contractile organelle [31]. We subsequently found that striated flagellar roots are composed, in part, of the Ca(2+)-binding protein centrin [30]. Since that time, centrin has been found to be a ubiquitous component of the flagellar basal apparatus, basal bodies and centrioles, and centrosomes and mitotic spindle poles of eukaryotic cells (for general reviews see [28, 34]). While we have learned a great deal about centrin from other organisms, our earliest success in understanding the biology of centrin was in large part due to the extraordinary extent to which Tetraselmis cells have elaborated their centrin-based organelles. In this paper, I will return attention to several unanswered questions concerning Tetraselmis striated flagellar root behavior and I will suggest several new directions that students may wish to pursue in order to tease fresh insights from this fascinating organism. PMID:9495031

Salisbury, J L

1998-01-01

95

Adventitious root formation in relation to irradiance and auxin supply  

Microsoft Academic Search

High irradiance during treatment of mung bean cuttings favours root formation in response to supplied auxin, whether the latter\\u000a is IAA or IBA. On the other hand it is inhibitory towards root formation in the absence of supplied auxin. Light promotes\\u000a the uptake of14C-IAA into cuttings and its upward movement into the leaves. When14C-IAA is applied to leaves of cuttings

B. C. Jarvis; A. I. SlYAHEED

1987-01-01

96

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

NASA Technical Reports Server (NTRS)

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.

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

1992-01-01

97

Bioactive components of the roots of Salvia miltiorrhizae: Changes related to harvest time and germplasm line  

Microsoft Academic Search

Field-grown Danshen (Salvia miltiorrhizae) has been used for the preparation of phytopharmaceutical products. The changes in bioactive components in the roots of S. miltiorrhizae related to harvest time and germplasm were investigated in trials during 2008 and 2009. The content of bioactive components in the roots was closely related to germplasm and harvest time, resulting in different optimum harvest dates

Chun-e He; Jianhe Wei; Yue Jin; Shilin Chen

2010-01-01

98

Oxidative damage and antioxidant response of Allium cepa meristematic and elongation cells exposed to metronidazole.  

PubMed

The toxicity of metronidazole (MTZ) in meristematic and elongation zones of Allium cepa roots was analyzed for 30?h of exposition. Toxic effects were evaluated by lipid peroxidation (content of thiobarbituric-reactive substances [TBARS]), reduced glutathione (GSH) levels, ascorbate acid and dehydroascorbate acid content, and enzymatic activities of superoxide dismutase and catalase. The root zones showed differentiated susceptibility to MTZ. In the elongation zone, MTZ induced an increase of TBARS content and a significant rise in GSH levels, whereas in the meristematic zone, lipid peroxidation was not observed and all antioxidant defense parameters analyzed were significantly increased. These results indicate that MTZ exposure induced oxidative stress in A. cepa roots, and that the antioxidant defenses in the meristematic zone are more efficient compared with the elongation zone, which is probably related to higher oxidative metabolism of meristematic tissue. PMID:22411046

Andrioli, Nancy; Sabatini, Sebastián E; Mudry, Marta D; Ríos de Molina, María Del Carmen

2012-05-01

99

Root hairs improve root penetration, root-soil contact, and phosphorus acquisition in soils of different strength.  

PubMed

Root hairs are a key trait for improving the acquisition of phosphorus (P) by plants. However, it is not known whether root hairs provide significant advantage for plant growth under combined soil stresses, particularly under conditions that are known to restrict root hair initiation or elongation (e.g. compacted or high-strength soils). To investigate this, the root growth and P uptake of root hair genotypes of barley, Hordeum vulgare L. (i.e. genotypes with and without root hairs), were assessed under combinations of P deficiency and high soil strength. Genotypes with root hairs were found to have an advantage for root penetration into high-strength layers relative to root hairless genotypes. In P-deficient soils, despite a 20% reduction in root hair length under high-strength conditions, genotypes with root hairs were also found to have an advantage for P uptake. However, in fertilized soils, root hairs conferred an advantage for P uptake in low-strength soil but not in high-strength soil. Improved root-soil contact, coupled with an increased supply of P to the root, may decrease the value of root hairs for P acquisition in high-strength, high-P soils. Nevertheless, this work demonstrates that root hairs are a valuable trait for plant growth and nutrient acquisition under combined soil stresses. Selecting plants with superior root hair traits is important for improving P uptake efficiency and hence the sustainability of agricultural systems. PMID:23861547

Haling, Rebecca E; Brown, Lawrie K; Bengough, A Glyn; Young, Iain M; Hallett, Paul D; White, Philip J; George, Timothy S

2013-09-01

100

Interactive Effects of Al3+, H+, and Other Cations on Root Elongation Considered in Terms of Cell-Surface Electrical Potential 1  

PubMed Central

The rhizotoxicities of Al3+ and of La3+ to wheat (Triticum aestivum L.) were similarly ameliorated by cations in the following order of effectiveness: H+ ? C3+ > C2+ > C1+. Among tested cations of a given charge, ameliorative effectiveness was similar except that Ca2+ was slightly more effective than other divalent cations and H+ was much more effective than other monovalent cations. H+ rhizotoxicity was also ameliorated by cations in the order C3+ > C2+ > C1+. These results suggest a role for cell-surface electrical potential in the rhizotoxicity of Al3+, La3+, H+, and other toxic cations: negatively charged cell surfaces of the root accumulate the toxic cations, and amelioration is effected by treatments that reduce the negativity of the cell-surface electrical potential by charge screening or cation binding. Membrane-surface activities of free Al3+ or La3+ computed according to a Gouy-Chapman-Stern model correlated well with growth inhibition, which correlated only poorly with Al3+ or La3+ activities in the external medium. The similar responses of Al-intoxicated and La-intoxicated roots to ameliorative treatments provide evidence that Al3+, rather than AlOH2+ or Al(OH)2+, is the principal toxic species of mononuclear Al. Comparisons of the responses of Al-sensitive and Al-tolerant wheats to Al3+ and to La3+ did not support the hypothesis that varietal sensitivity to Al3+ is based upon differences in cell-surface electrical potential.

Kinraide, Thomas B.; Ryan, Peter R.; Kochian, Leon V.

1992-01-01

101

Topology, scaling relations and Leonardo's rule in root systems from African tree species.  

PubMed

Aspects of root architecture, including topology, link length, diameter and scaling relations, were analyzed in excavated coarse root systems of three field-grown fruit tree species (Strychnos cocculoides Bak., Strychnos spinosa Lam. and Vangueria infausta Burch) and the fruit-bearing shrub Grewia flava DC. We investigated the root systems using semi-automatic digitizing and computer-based 3-D reconstruction techniques. Topological analysis was carried out to investigate branching patterns as basic determinants of root architecture. New topological indices were developed and revealed significant differences among the species. The different architectural strategies can be explained in terms of cost-benefit relations and efficiency in soil resource exploration and exploitation. In addition, some well-known hypotheses about geometry and scaling, most of them previously unverified by empirical observations on root systems, were tested. For practical applications, the main emphasis is on the relationship between proximal root diameter, an easily determined parameter, and several parameters describing the size of the whole root system. We also tested the "pipe stem" theory, essentially dating back to Leonardo da Vinci, which underlies many models and which we found conformed to our measurement data with reasonable accuracy. A physiological consequence of the "constant cross-sectional area rule" may be a certain homogeneity of hydraulic architecture throughout root systems. PMID:11303642

Oppelt, A L; Kurth, W; Godbold, D L

2001-02-01

102

Distribution of superoxide and hydrogen peroxide in Arabidopsis root and their influence on root development: possible interaction with peroxidases.  

PubMed

The respective distribution of superoxide (O(2) (.-)) and hydrogen peroxide (H(2)O(2)), two reactive oxygen species (ROS) involved in root growth and differentiation, was determined within the Arabidopsis root tip. We investigated the effect of changing the levels of these ROS on root development and the possible interactions with peroxidases. H(2)O(2) was detected by confocal laser-scanning microscopy using hydroxyphenyl fluorescein (HPF). Both O(2) (.-) accumulation and peroxidase distribution were assessed by light microscopy, using nitroblue tetrazolium (NBT) and o-dianisidine, respectively. Root length and root hair length and density were also quantified following ROS scavenging. O(2) (.-) was predominantly located in the apoplast of cell elongation zone, whereas H(2)O(2) accumulated in the differentiation zone and the cell wall of root hairs in formation. Treatments that decrease O(2) (.-) concentration reduced root elongation and root hair formation, while scavenging H(2)O(2) promoted root elongation and suppressed root hair formation. The results allow to precise the respective role of O(2) (.-) and H(2)O(2) in root growth and development. The consequences of their distinct accumulation sites within the root tip are discussed, especially in relation to peroxidases. PMID:17388896

Dunand, Christophe; Crčvecoeur, Michčle; Penel, Claude

2007-01-01

103

Diurnal Regulation of Leaf Blade Elongation in Rice by CO2 (Is it Related to Sucrose-Phosphate Synthase Activity?).  

PubMed Central

The relationship between leaf blade elongation rates (LER) and sucrose-phosphate synthase (SPS) activity was investigated at different times during ontogeny of rice (Oryza sativa L. cv Jarrah) grown in flooded soil at either 350 or 700 [mu]L CO2 L-1. High CO2 concentrations increased LER of expanding blades and in vivo activity (Vlimiting) SPS activity of expanded blades during the early vegetative stage (21 d after planting [DAP]), when tiller number was small and growing blades were strong carbohydrate sinks. Despite a constant light environment, there was a distinct diurnal pattern in LER, Vlimiting SPS activity, and concentration of soluble sugars, with an increase in the early part of the light period and a decrease later in the light period. The strong correlation (r = 0.65) between LER and Vlimiting SPS activity over the diurnal cycle indicated that SPS activity played an important role in controlling blade growth. The higher Vlimiting SPS activity at elevated CO2 at 21 DAP was caused by an increase in the activation state of the enzyme rather than an increase in Vmax. Fructose and glucose accumulated to a greater extent than sucrose at high CO2 and may have been utilized for synthesis of cell-wall components, contributing to higher specific leaf weight. By the mid-tillering stage (42 DAP), CO2 enrichment enhanced Vlimiting and Vmax activities of source blades. Nevertheless, LER was depressed by high CO2, probably because tillers were stronger carbohydrate sinks than growing blades.

Seneweera, S. P.; Basra, A. S.; Barlow, E. W.; Conroy, J. P.

1995-01-01

104

Root Hairs  

PubMed Central

Roots hairs are cylindrical extensions of root epidermal cells that are important for acquisition of nutrients, microbe interactions, and plant anchorage. The molecular mechanisms involved in the specification, differentiation, and physiology of root hairs in Arabidopsis are reviewed here. Root hair specification in Arabidopsis is determined by position-dependent signaling and molecular feedback loops causing differential accumulation of a WD-bHLH-Myb transcriptional complex. The initiation of root hairs is dependent on the RHD6 bHLH gene family and auxin to define the site of outgrowth. Root hair elongation relies on polarized cell expansion at the growing tip, which involves multiple integrated processes including cell secretion, endomembrane trafficking, cytoskeletal organization, and cell wall modifications. The study of root hair biology in Arabidopsis has provided a model cell type for insights into many aspects of plant development and cell biology.

Grierson, Claire; Nielsen, Erik; Ketelaarc, Tijs; Schiefelbein, John

2014-01-01

105

The Elongation of Ovococci  

PubMed Central

The morphogenesis of ovococci has been reviewed extensively. Recent results have provided new insights concerning the mechanisms of elongation in ovoid bacteria. We present here the proteins involved in the elongation (firmly established and more or less hypothetical) and discuss the relationship between elongation and division of ovococci.

Philippe, Jules; Vernet, Thierry

2014-01-01

106

An approximate technique to determine elongation stresses in stagnation flow  

Microsoft Academic Search

A technique is presented in which approximate values of the elongation stress can be measured at large elongation rates by using opposed orifices to generate a stagnation flow similar to uniaxial elongation. The elongation rate is related to the volumetric flow rate of fluid into the orifices and the apparatus geometry. The first law of thermodynamics is simplified to relate

M. E. Mackaya; A. M. Dajan; H. Wippel; H. Janeschitz-Kriegl; M. Lipp

107

The effects of temperature and relative humidity on ochratoxin A formation in fresh liquorice root.  

PubMed

In this study, the effects of temperature and relative humidity (RH) on ochratoxin A (OTA) formation during liquorice root storage were investigated. For this purpose, a real storage procedure in which fresh root was dried in the open air was simulated. Four RH-temperature combinations corresponding to average climate conditions (RH-temperature) of each season in an important liquorice growing and processing region were simulated as follows: A, autumn (T = 15°C, RH = 49%); B, winter (T = 9°C, RH = 51%); C, spring (T = 22°C, RH = 35%); and D, summer (T = 29°C, RH = 27%). The crushed fresh roots were incubated for 60 days, and the OTA content of the roots was determined at 20-day intervals by using inverse ion mobility spectrometry. The results showed that the maximum levels of OTA occurred after 40 days and were 4.3 ± 1.1, 0.9 ± 0.2, 7.3 ± 0.0 and 24.2 ± 2.5 ngg(-1) in roots stored under simulated conditions A, B, C and D, respectively. After 40 days, the amount of OTA started to decline in all samples but at different rates. The results seem to indicate that temperature plays a more significant role than RH in producing OTA by moulds in liquorice root. It appears that 22°C could be considered as the critical temperature for OTA formation in liquorice root stored under experimental conditions. It could be concluded that liquorice-processing plants should obtain, dry and store fresh moist root when the temperature is below the critical point. Moreover, the roots stored in the open shade condition should not be covered by plastic films even when it is raining as this increases the root temperature. PMID:23116224

Khalesi, Mohammadreza; Tabrizchi, Mahmoud; Sheikh-Zeinoddin, Mahmoud

2013-01-01

108

Relative susceptibility of peach rootstocks to crown gall and Phytophthora root and crown rot in Chile  

Microsoft Academic Search

G. Guzmán, B.A. Latorre, R. Torres, and W.F. Wilcox. 2007. Relative susceptibility of peach rootstocks to crown gall and Phytophthora root and crown rot in Chile. Cien. Inv. Agr. 34(1):31-40. Crown gall (Agrobacterium tumefaciens) and Phytophthora root and crown rot (PRCR), caused by P. cryptogea, are two major limiting factors affecting peach (Prunus persica) production in Chile. At present, Nemaguard

Gonzalo Guzman; Bernardo A. Latorre; Rene Torres; Wayne F. Wilcox

2007-01-01

109

Root Growth and Oxygen Relations at Low Water Potentials. Impact of Oxygen Availability in Polyethylene Glycol Solutions1  

Microsoft Academic Search

Polyethylene glycol (PEG), which is often used to impose low water potentials (cw) in solution culture, decreases O2 movement by increasing solution viscosity. We investigated whether this prop- erty causes O2 deficiency that affects the elongation or metabolism of maize (Zea mays L.) primary roots. Seedlings grown in vigorously aerated PEG solutions at ambient solution O2 partial pressure (pO2) had

Paul E. Verslues; Eric S. Ober; Robert E. Sharp

1998-01-01

110

Induction of H2O2 and related enzymes in tomato roots infected with root knot nematode (M.javanica) by several chemical and microbial elicitors  

Microsoft Academic Search

The effects of chemical and microbial elicitors such as ?-aminobutyric acid (BABA), Salicylic acid (SA), and Pseudomonasfluorecens CHAO on hydrogen peroxide generation and activity of the enzymes related to its metabolism, i.e., superoxide dismutase (SOD), guaiacol peroxidase (GPOX), and catalase (CAT) were investigated in tomato roots infected with root-knot nematode (Meloidogynejavanica). Results of this study show that treating the tomato

N. Sahebani; N. Hadavi

2009-01-01

111

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

PubMed Central

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.

2014-01-01

112

Investigation of multiple roots of the resistive wall mode dispersion relation, including kinetic effects  

SciTech Connect

The resistive wall mode instability in tokamak plasmas has a complex frequency which can be determined by a dispersion relation that is cubic, in general, leading to three distinct roots. A simplified model of the dispersion relation, including kinetic effects, is presented and used to explore the behavior of these roots. By changing the plasma rotation frequency, it is shown that one root has a slow mode rotation frequency (less than the inverse wall time) while the other two rotate more quickly, one leading and one lagging the plasma rotation frequency. When realistic experimental parameters from the National Spherical Torus Experiment [M. Ono et al., Nucl. Fusion 40, 557 (2000)] are used, however, only one slow rotating, near-marginal stability root is found, consistent with present experiments and more detailed calculations with the MISK code [B. Hu et al., Phys. Plasmas 12, 057301 (2005)]. Electron collisionality acts to stabilize one of the rotating roots, while ion collisionality can stabilize the other. In devices with low rotation and low collisionality, these two rotating roots may manifest themselves, but they are likely to remain stable.

Berkery, J. W.; Sabbagh, S. A. [Department of Applied Physics and Applied Mathematics, Columbia University, New York, New York 10027 (United States); Betti, R. [Princeton Plasma Physics Laboratory, Princeton University, Princeton, New Jersey 08543 (United States)

2011-07-15

113

Root Respiration in White Spruce (Picea glauca [Moench] Voss) Seedlings in Relation to Morphology and Environment 1  

PubMed Central

Roots of white spruce seedlings (Picea glauca [Moench] Voss) undergo respiratory changes during the year that are related to changing metabolic requirements. An alternative pathway is always present, functions during most of the year, and operates maximally during periods of root and shoot growth. Although some differences in respiration and the apportioning of respiration can be correlated to root morphology, the environment and the stage of shoot development are also important controls. Differences in respiration related to root morphology are not manifest in mitochondrial structure, but overall rates were found to correlate with the number of mitochondria present. Root respiration in seedlings grown under root growth capacity conditions reflects root and shoot growth at that time rather than root growth capacity.

Johnson-Flanagan, Anne M.; Owens, John N.

1986-01-01

114

Arabidopsis ELONGATED MITOCHONDRIA1 Is Required for Localization of DYNAMIN-RELATED PROTEIN3A to Mitochondrial Fission Sites  

Microsoft Academic Search

Mitochondrial fission is achieved partially by the activity of self-assembling dynamin-related proteins (DRPs) in diverse organisms. Mitochondrial fission in Arabidopsis thaliana is mediated by DRP3A and DRP3B, but the other genes and molecular mechanisms involved have yet to be elucidated. To identify these genes, we screened and analyzed Arabidopsis mutants with longer and fewer mitochondria than those of the wild

Shin-ichi Arimura; Masaru Fujimoto; Yoko Doniwa; Naoki Kadoya; Mikio Nakazono; Wataru Sakamoto; Nobuhiro Tsutsumi

2008-01-01

115

Root respiration and its relation to nutrient contents in soil and root and EVI among 8 ecosystems, northern China  

Microsoft Academic Search

Root respiration is a critical and uncertain component of ecosystem carbon budgets. We assessed whether variation in root\\u000a respiration at a reference temperature were associated with that of root and soil nutrient contents and enhanced vegetation\\u000a index (EVI) among 8 ecosystems, including three forests, two shrublands, two meadow grasslands, and one meadow in a forest-steppe\\u000a ecotone in northern China. Mass

Wei Wang; Shushi Peng; Jingyun Fang

2010-01-01

116

Price's Square Root Law: Empirical Validity and Relation to Lotka's Law.  

ERIC Educational Resources Information Center

Presents Price's law, which states that half of the literature on a subject will be contributed by the square root of total number of authors publishing in that area, and assesses it against empirical evidence and simulated productivity distributions. The discussion covers this law's relation to Lotka's law and its empirical validity. (Author/CLB)

Nicholls, Paul Travis

1988-01-01

117

Computer based imaging and analysis of root gravitropism  

NASA Technical Reports Server (NTRS)

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.

Evans, M. L.; Ishikawa, H.

1997-01-01

118

Diffuse age-related lumbar mri changes confound diagnosis of single (L5) root lesions.  

PubMed

Introduction: L5 radiculopathy has characteristic clinical and electrodiagnostic features including: radicular pain; weakness or denervation of hip abductors, ankle dorsiflexors, and inverters; and pre-ganglionic dorsal foot sensory loss. It is unknown how often patients with this distinctive clinical-electrodiagnostic presentation have isolated L5-root compression on neuroimaging or more widespread, possibly age-related, lumbar neuroforaminal or spinal stenosis. Methods: A study-blinded neuroradiologist quantitated lumbosacral neuroforaminal, lateral recess, and spinal stenosis in 26 consecutive patients with unilateral, clinically and EMG-ascertained L5 monoradiculopathy, and quantitated a global neuroforaminal and spinal stenosis score (SSS). Results: Only 9 patients (35%) had isolated L5-root compression, 14 (54%) had multi-root compression, and 3 (12%) had normal neuroimaging. Increasing age correlated with SSS, and the 9 patients with isolated L5-root compression were significantly younger than patients with multi-root involvement. Conclusions: This study underscores the role of clinical and electrodiagnostic data when interpreting lumbosacral neuroimaging, particularly in older patients. Muscle Nerve 50: 135-137, 2014. PMID:24402913

Botez, Stephan A; Zynda-Weiss, Andrea M; Logigian, Eric L

2014-07-01

119

The Relation Between Rotation Deformity and Nerve Root Stress in Lumbar Scoliosis  

NASA Astrophysics Data System (ADS)

Even though several finite element models of lumbar spine were introduced, there has been no model including the neural structure. Therefore, the authors made the novel lumbar spine finite element model including neural structure. Using this model, we investigated the relation between the deformity pattern and nerve root stress. Two lumbar models with different types of curve pattern (lateral bending and lateral bending with rotation curve) were made. In the model of lateral bending curves without rotation, the principal compressive nerve root stress on the concave side was greater than the principal tensile stress on the convex side at the apex vertebra. Contrarily, in the lateral bending curve with rotational deformity, the nerve stress on the convex side was higher than that on the concave side. Therefore, this study elicit that deformity pattern could have significantly influence on the nerve root stress in the lumbar spine.

Kim, Ho-Joong; Lee, Hwan-Mo; Moon, Seong-Hwan; Chun, Heoung-Jae; Kang, Kyoung-Tak

120

Respiration rate in maize roots is related to concentration of reduced nitrogen and proliferation of lateral roots  

NASA Technical Reports Server (NTRS)

The relationship between specific rate of respiration (respiration rate per unit root dry weight) and concentration of reduced nitrogen was examined for maize (Zea mays L.) roots. Plants with 2 primary nodal root axes were grown for 8 days in a split-root hydroponic system in which NO3- was supplied to both axes at 1.0 mol m-3, to one axis at 1.0 mol m-3 and the other axis at 0.0 mol m-3, or to both axes at 0.0 mol m-3. Respiration rates and root characteristics were measured at 2-day intervals. Specific rate of respiration was positively correlated in a nonlinear relationship with concentration of reduced nitrogen. The lowest specific rates of respiration occurred when neither axis received exogenous NO3- and the concentration of reduced nitrogen in the axes was less than 9 mg g-1. The greatest rates occurred in axes that were actively absorbing NO3- and contained more than 35 mg g-1 of reduced nitrogen. At 23 mg g-1 of reduced nitrogen, below which initiation of lateral branches was decreased by 30-50%, specific rate of respiration was 17% greater for roots actively absorbing NO3- than for roots not absorbing NO3-. Increases in specific rate of respiration associated with concentrations of reduced nitrogen greater than 23 mg g-1 were concluded to be attributable primarily to proliferation of lateral branches.

Granato, T. C.; Raper, C. D. Jr; Wilkerson, G. G.; Raper CD, J. r. (Principal Investigator)

1989-01-01

121

Length and Elongation Sensor.  

National Technical Information Service (NTIS)

A length and elongation sensor includes an elastomeric optical wave guide and a time domain reflectometer. The elastomeric optical wave guide consists of a urethane outer cladding and an optical gel core. A transparent window is hermetically sealed to the...

L. E. Sansone

1996-01-01

122

Tetraponera ants have gut symbionts related to nitrogen-fixing root-nodule bacteria.  

PubMed Central

Some Tetraponera ants (Formicidae, Pseudomyrmecinae) subsist almost entirely on amino acid deficient honeydew secretions of pseudococcids and harbour a dense aggregation of bacterial symbionts in a unique pouch-shaped organ at the junction of the midgut and the intestine. The organ is surrounded by a network of intruding tracheae and Malpighian tubules, suggesting that these bacteria are involved in the oxidative recycling of nitrogen-rich metabolic waste. We have examined the ultrastructure of these bacteria and have amplified, cloned and sequenced ribosomal RNA-encoding genes, showing that the ant pouch contains a series of close relatives of Flavobacteria and Rhizobium, Methylobacterium, Burkholderia and Pseudomonas nitrogen-fixing root-nodule bacteria. We argue that pouch bacteria have been repeatedly 'domesticated' by the ants as nitrogen-recycling endosymbionts. This ant-associated community of mutualists is, to our knowledge, the first finding of symbionts related to root-nodule bacteria in animals.

van Borm, Steven; Buschinger, Alfred; Boomsma, Jacobus J; Billen, Johan

2002-01-01

123

Abscisic Acid Accumulation by Roots of Xanthium strumarium L. and Lycopersicon esculentum Mill. in Relation to Water Stress 1  

PubMed Central

Plants of Xanthium strumarium L. and Lycopersicon esculentum Mill. cv `Rheinlands Ruhm' were grown in solution culture, and control and steam-girdled intact plants were stressed. Detached roots of both species were stressed to different extents in two ways: (a) either in warm air or, (b) in the osmoticum Aquacide III. The roots of both species produced and accumulated progressively more abscisic acid (ABA), the greater the stress inflicted by either method. ABA-glucose ester levels in Xanthium roots were not affected by water stress and were too low to be the source of the stress-induced ABA. The fact that ABA accumulated in detached roots and in roots of girdled plants proves that ABA was synthesized in the roots and not merely transported from the shoots. Maximum ABA accumulation in detached roots occurred after 60 to 70% loss of fresh weight. In Xanthium roots, ABA levels continued to increase for at least 11 hours, and no catabolism was apparent when stressed roots were immersed in water, although the roots did stop accumulating ABA. When osmotically stressed, Xanthium roots reached a maximum ABA level after 2 hours, but ABA continued to rise in the medium. Under optimal stress conditions, endogenous ABA levels increased 100 times over their prestress values in detached roots of Xanthium, and 15 times in Lycopersicon under nonoptimal stress, when endogenous ABA was expressed as concentrations based on tissue water content. These are much greater relative increases than observed in the leaves (15 times in Xanthium, 3 times in Lycopersicon), although the roots contain substantially less ABA than the leaves in all circumstances. The results suggest that the endogenous level of ABA in roots could rise appreciably prior to leaf wilt, and could modify the plant's water economy before the leaves become stressed.

Cornish, Katrina; Zeevaart, Jan A. D.

1985-01-01

124

Root architecture in relation to tree-soil-crop interactions and shoot pruning in agroforestry  

Microsoft Academic Search

Desirable root architecture for trees differs between sequential and simultaneous agroforestry systems. In sequential systems extensive tree root development may enhance nutrient capture and transfer to subsequent crops via organic pools. In simultaneous systems tree root development in the crop root zone leads to competition for resources.Fractal branching models provide relationships between proximal root diameter, close to the tree stem,

M. Van Noordwijk; P. Purnomosidhi

1995-01-01

125

Synthesis of Elongated Microcapsules  

NASA Technical Reports Server (NTRS)

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.

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

2011-01-01

126

Extensometer automatically measures elongation in elastomers  

NASA Technical Reports Server (NTRS)

Extensometer, with a calibrated shaft, measures the elongation of elastomers and automatically records this distance on a chart. It is adaptable to almost any tensile testing machine and is fabricated at a relatively low cost.

Hooper, C. D.

1966-01-01

127

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

PubMed

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

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

2003-10-01

128

Rice WUSCHEL-related homeobox 3A (OsWOX3A) modulates auxin-transport gene expression in lateral root and root hair development.  

PubMed

Coordinated regulation of the many genes controlling leaf, flower, and root development determines the phenotypes of plants; this regulation requires exquisite control of many transcription factors, including the WUSCHEL-related homeobox (WOX) family. We recently reported that rice (Oryza sativa) WUSCHEL-related homeobox 3A (OsWOX3A) plays important roles in organ development, including lateral-axis outgrowth and vasculature patterning in leaves, lemma and palea morphogenesis in spikelets, and the numbers of tillers and lateral roots. OsWOX3A is encoded by NARROW LEAF2 (NAL2) and NAL3, a pair of duplicated genes. In this study, further analysis of nal2 nal3 (hereafter nal2/3) double mutants revealed that, in addition to its role in lateral root development, OsWOX3A also acts in the control of root hair formation. Based on this new finding, we describe a possible mechanism by which OsWOX3A regulation of auxin transport genes acts in root development. PMID:24002214

Yoo, Soo-Cheul; Cho, Sung-Hwan; Paek, Nam-Chon

2013-10-01

129

Role of arbuscular mycorrhizal symbiosis in root mineral uptake under CaCO 3 stress  

Microsoft Academic Search

This study investigated the effects of increasing CaCO3 concentrations (0, 5, 10, 20 mM) on arbuscular mycorrhizal (AM) symbiosis establishment as well as on chicory root growth\\u000a and mineral nutrient uptake in a monoxenic system. Although CaCO3 treatments significantly decreased root growth and altered the symbiosis-related development steps of the AM fungus Rhizophagus irregularis (germination, germination hypha elongation, root colonization rate,

Sonia Labidi; Fayçal Ben Jeddi; Benoit Tisserant; Djouher Debiane; Salah Rezgui; Anne Grandmougin-Ferjani; Anissa Lounčs-Hadj Sahraoui

130

Nitrate and phosphate availability and distribution have different effects on root system architecture of Arabidopsis.  

PubMed

Plant root systems can respond to nutrient availability and distribution by changing the three-dimensional deployment of their roots: their root system architecture (RSA). We have compared RSA in homogeneous and heterogeneous nitrate and phosphate supply in Arabidopsis. Changes in nitrate and phosphate availability were found to have contrasting effects on primary root length and lateral root density, but similar effects on lateral root length. Relative to shoot dry weight (DW), primary root length decreased with increasing nitrate availability, while it increased with increasing phosphate supply. Lateral root density remained constant across a range of nitrate supplies, but decreased with increasing phosphate supply. In contrast, lateral root elongation was suppressed both by high nitrate and high phosphate supplies. Local supplies of high nitrate or phosphate in a patch also had different effects. Primary root growth was not affected by a high nitrate patch, but growth through a high phosphate patch reduced primary root growth after the root left the patch. A high nitrate patch induced an increase in lateral root density in the patch, whereas lateral root density was unaffected by a high phosphate patch. However, both phosphate- and nitrate-rich patches induced lateral root elongation in the patch and suppressed it outside the patch. This co-ordinated response of lateral roots also occurs in soil-grown plants exposed to a nutrient-rich patch. The auxin-resistant mutants axrl, axr4 and aux1 all showed the wild-type lateral root elongation responses to a nitrate-rich patch, suggesting that auxin is not required for this response. PMID:12148533

Linkohr, Birgit I; Williamson, Lisa C; Fitter, Alastair H; Leyser, H M Ottoline

2002-03-01

131

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...

132

The elongation rate at the base of a maize leaf shows an invariant pattern during both the steady-state elongation and the establishment of the elongation zone.  

PubMed

Spatial and temporal analyses of elongation and cell length of monocotyledon leaves have most often been performed during the period when leaves are visible and elongate at a constant rate (steady-state). In the present study, the focus was on the earlier stages, during the establishment of the elongation zone. Regardless of leaf development stage, the segment located between 0 and 35 mm from the leaf insertion point had a relative elongation rate that increased with distance from insertion point ('accelerating zone') while the segment located further than 35 mm had a relative elongation rate that decreased ('decelerating zone'). This stable pattern held for both young, non-emerged leaves, where it was restricted to the portion corresponding to the length of the blade, and for leaves during steady-state elongation. In the same way, the profile of cell length was essentially the same during early development and during steady-state elongation. The results of a temporal analysis of whole-leaf elongation rate, carried out in the field and in the greenhouse at different light intensities were consistent with a time-invariant pattern of elongation. Whole-leaf relative elongation rate increased with time until the leaf reached 30-40 mm length (although at different leaf ages depending on conditions), and declined afterwards. These results suggest that the patterns governing the elongation rate of a sector of a maize leaf are independent of the leaf developmental stage but depend on sector position only. PMID:11432944

Muller, B; Reymond, M; Tardieu, F

2001-06-01

133

Brassinosteroids promote root growth in Arabidopsis.  

PubMed

Although brassinosteroids (BRs) are known to regulate shoot growth, their role in the regulation of root growth is less clear. We show that low concentrations of BRs such as 24-epicastasterone and 24-epibrassinolide promote root elongation in Arabidopsis wild-type plants up to 50% and in BR-deficient mutants such as dwf1-6 (cbb1) and cbb3 (which is allelic to cpd) up to 150%. The growth-stimulating effect of exogenous BRs is not reduced by the auxin transport inhibitor 2,3,5-triidobenzoic acid. BR-deficient mutants show normal gravitropism, and 2,3,5-triidobenzoic acid or higher concentrations of 2,4-dichlorophenoxyacetic acid and naphtaleneacetic acid inhibit root growth in the mutants to the same extent as in wild-type plants. Simultaneous administration of 24-epibrassinolide and 2,4-dichlorophenoxyacetic acid results in largely additive effects. Exogenous gibberellins do not promote root elongation in the BR-deficient mutants, and the sensitivity to the ethylene precursor 1-aminocyclopropane-1-carboxylic acid is not altered. Thus, the root growth-stimulating effect of BRs appears to be largely independent of auxin and gibberellin action. Furthermore, we analyzed BR interactions with other phytohormones on the gene expression level. Only a limited set of auxin- and ethylene-related genes showed altered expression levels. Genes related to other phytohormones barely showed changes, providing further evidence for an autonomous stimulatory effect of BR on root growth. PMID:14526105

Müssig, Carsten; Shin, Ga-Hee; Altmann, Thomas

2003-11-01

134

Brassinosteroids Promote Root Growth in Arabidopsis  

PubMed Central

Although brassinosteroids (BRs) are known to regulate shoot growth, their role in the regulation of root growth is less clear. We show that low concentrations of BRs such as 24-epicastasterone and 24-epibrassinolide promote root elongation in Arabidopsis wild-type plants up to 50% and in BR-deficient mutants such as dwf1-6 (cbb1) and cbb3 (which is allelic to cpd) up to 150%. The growth-stimulating effect of exogenous BRs is not reduced by the auxin transport inhibitor 2,3,5-triidobenzoic acid. BR-deficient mutants show normal gravitropism, and 2,3,5-triidobenzoic acid or higher concentrations of 2,4-dichlorophenoxyacetic acid and naphtaleneacetic acid inhibit root growth in the mutants to the same extent as in wild-type plants. Simultaneous administration of 24-epibrassinolide and 2,4-dichlorophenoxyacetic acid results in largely additive effects. Exogenous gibberellins do not promote root elongation in the BR-deficient mutants, and the sensitivity to the ethylene precursor 1-aminocyclopropane-1-carboxylic acid is not altered. Thus, the root growth-stimulating effect of BRs appears to be largely independent of auxin and gibberellin action. Furthermore, we analyzed BR interactions with other phytohormones on the gene expression level. Only a limited set of auxin- and ethylene-related genes showed altered expression levels. Genes related to other phytohormones barely showed changes, providing further evidence for an autonomous stimulatory effect of BR on root growth.

Mussig, Carsten; Shin, Ga-Hee; Altmann, Thomas

2003-01-01

135

Pectin methyl esterase activity of root exudates of legumes in relation to Rhizobia  

Microsoft Academic Search

Summary Seven different legumes were grown aseptically and in the presence of homologous and heterologous rhizobia in the root region. Samples of root exudates were tested for pectin methyl esterse activity. Root exudates of aspetically grown legumes possesed demonstrable pectin methyl esterase activity. In six legumes, the presence of homologous rhizobia in the root region stimulated the enzyme activity of

N. S. Subba-rao; K. S. B. Sarma

1968-01-01

136

Soybean Root Distribution Related to Claypan Soil Properties and Apparent Soil Electrical Conductivity  

Microsoft Academic Search

Soybean (Glycine max (L.) Merr.) yield in claypan soils varies systematically with soil properties and landscape position. This is likely caused by soil interactions with soybean roots. Field obser- vations of soybean root distribution are needed to reveal its effect on yield variability. This study examined profi le distributions of soybean root length density (RLD) and average root diameter (ARD)

D. Brenton Myers; Newell R. Kitchen; Kenneth A. Sudduth; Robert E. Sharp; Randall J. Miles

2007-01-01

137

Prevalence of elongation and calcification patterns of elongated styloid process in south India  

PubMed Central

Objective: Very few studies have been reported in the literature classifying the elongation and calcification patterns of styloid process. The present study was done to investigate the prevalence of elongation and calcification patterns of styloid process in patients attending a dental institution in south India. Study design: 600 digital panoramic radiographs of patients with dental problems were obtained from the outpatient department of the Dental institution. The apparent length of the styloid process was measured by a single experienced oral radiologist, with the help of the measuring tools on the accompanying software. The type of elongation and calcification patterns of each elongated styloid process was classified as per Langlai’s classification with few modifications. Finally the data was subjected to statistical analysis. Results: Out of 520 measurable styloid processes (260 panoramic radiographs), 154 styloid processes had length greater than 3cm. The mean average length of elongated styloid process was 3.67±0.62 cm. No significant association was obtained between age and length of styloid process. In present study, the type of elongation pattern has no effect on the calcification pattern. Our results suggested that Type I elongated styloid processes were most likely to be completely calcified (type D), but statistically not significant. Conclusion: Type I pattern of elongation was found to be more prevalent in elder age group and was completely calcified in most of the cases. Interestingly, only three patients (out of 260) showed symptomatic elongation of styloid process. A relatively high prevalence of type IV elongation pattern (9 /154) was obtained in the present study, when compared to type III styloid process. Further large scale imaging studies are required to evaluate the presence of type IV elongation pattern in various population groups. Key words:Eagle’s syndrome, Elongated styloid process, Stylopharyngeous muscle, Tonsillectomy.

Sai Kiran, Ch; Sai Madhavi, N.; Raghavendra, M N.; Satish, A.

2013-01-01

138

PLASMA ELONGATION STUDIES FOR ITER-LIKE TOKAMAKS  

SciTech Connect

Trade studies are performed to determine the optimum plasma elongation for a next-step tokamak such as the International Thermonuclear Experimental Reactor (ITER). Degradations of the plasma beta limit for high elongations and poloidal field coil scaling with elongation are included in the analysis. When plasma ignition is required using confinement scalings that include direct plasma current or power degradation terms, the optimum elongation is between 2.5 and 2.9, but generally the minimum-cost curve is relatively flat for elongations over 2.3. When confinement scalings that depend only on size are used or when only current drive performance is required, the optimum elongation is near 2.3. Also, when only a plasma current and neutron wall load are used as plasma performance limits, the optimum elongation is between 2.6 and 2.8, but with small cost benefits above elongations of 2.3.

Galambos, John D [ORNL; Peng, Yueng Kay Martin [ORNL

1989-01-01

139

FACT, the Bur Kinase Pathway, and the Histone Co-Repressor HirC Have Overlapping Nucleosome-Related Roles in Yeast Transcription Elongation  

PubMed Central

Gene transcription is constrained by the nucleosomal nature of chromosomal DNA. This nucleosomal barrier is modulated by FACT, a conserved histone-binding heterodimer. FACT mediates transcription-linked nucleosome disassembly and also nucleosome reassembly in the wake of the RNA polymerase II transcription complex, and in this way maintains the repression of ‘cryptic’ promoters found within some genes. Here we focus on a novel mutant version of the yeast FACT subunit Spt16 that supplies essential Spt16 activities but impairs transcription-linked nucleosome reassembly in dominant fashion. This Spt16 mutant protein also has genetic effects that are recessive, which we used to show that certain Spt16 activities collaborate with histone acetylation and the activities of a Bur-kinase/Spt4–Spt5/Paf1C pathway that facilitate transcription elongation. These collaborating activities were opposed by the actions of Rpd3S, a histone deacetylase that restores a repressive chromatin environment in a transcription-linked manner. Spt16 activity paralleling that of HirC, a co-repressor of histone gene expression, was also found to be opposed by Rpd3S. Our findings suggest that Spt16, the Bur/Spt4–Spt5/Paf1C pathway, and normal histone abundance and/or stoichiometry, in mutually cooperative fashion, facilitate nucleosome disassembly during transcription elongation. The recessive nature of these effects of the mutant Spt16 protein on transcription-linked nucleosome disassembly, contrasted to its dominant negative effect on transcription-linked nucleosome reassembly, indicate that mutant FACT harbouring the mutant Spt16 protein competes poorly with normal FACT at the stage of transcription-linked nucleosome disassembly, but effectively with normal FACT for transcription-linked nucleosome reassembly. This functional difference is consistent with the idea that FACT association with the transcription elongation complex depends on nucleosome disassembly, and that the same FACT molecule that associates with an elongation complex through nucleosome disassembly is retained for reassembly of the same nucleosome.

Stevens, Jennifer R.; O'Donnell, Allyson F.; Perry, Troy E.; Benjamin, Jeremy J. R.; Barnes, Christine A.; Johnston, Gerald C.; Singer, Richard A.

2011-01-01

140

Biosynthesis of defense-related proteins in transformed root cultures of Trichosanthes kirilowii Maxim. var japonicum (Kitam.).  

PubMed Central

We have established transformed ("hairy") root cultures from Trichosanthes kirilowii Maxim. var japonicum Kitam. (Cucurbitaceae) and four related species to study the biosynthesis of the ribosome-inactivating protein trichosanthin (TCN) and other root-specific defense-related plant proteins. Stable, fast-growing root clones were obtained for each species by infecting in vitro grown plantlets with Agrobacterium rhizogenes American Type Culture Collection strain 15834. Each species accumulated reproducibly a discrete protein pattern in the culture medium. Analysis of the extracellular proteins from T. kirilowii var japonicum root cultures showed differential protein accumulation in the medium during the time course of growth in batch cultures. Maximum protein accumulation, approaching 20 micrograms/mL, was observed at mid-exponential phase, followed by a degradation of a specific protein subset that coincided with the onset of stationary phase. Two major extracellular proteins and one intracellular protein, purified by ion-exchange and reverse-phase high-performance liquid chromatography, were identified as class III chitinases (EC 3.2.1.14) based on N-terminal amino acid sequence and amino acid composition homologies with other class III chitinases. The Trichosanthes chitinases also showed reactivity with a cucumber class III chitinase antiserum and chitinolytic activity in a glycol chitin gel assay. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis and western blot analysis of intracellular proteins showed that normal and transformed T. kirilowii var japonicum roots accumulated only low levels of TCN (approximately 0.5% total soluble protein). Storage roots from the plant displayed protein and antigen patterns different from root cultures and produced TCN as the dominant protein. Roots undergoing secondary growth and differentiation exhibited patterns similar to those of storage roots, including increased TCN levels, indicating that high production of TCN is associated with induction of secondary growth in roots.

Savary, B J; Flores, H E

1994-01-01

141

Auxin and Cell Elongation  

Microsoft Academic Search

\\u000a One of the most dramatic and rapid hormone responses in plants is the induction by auxin of rapid cell elongation in isolated\\u000a stem and coleoptile sections. The response begins within 10 minutes after the addition of auxin, results in a 5-10 fold increase\\u000a in the growth rate, and persists for hours or even days (22). It is hardly surprising that

Robert E. Cleland

142

Ectopic expression of Kip-related proteins restrains root-knot nematode-feeding site expansion.  

PubMed

The development of nematode feeding sites induced by root-knot nematodes involves the synchronized activation of cell cycle processes such as acytokinetic mitoses and DNA amplification. A number of key cell cycle genes are reported to be critical for nematode feeding site development. However, it remains unknown whether plant cyclin-dependent kinase (CDK) inhibitors such as the Arabidopsis interactor/inhibitor of CDK (ICK)/Kip-related protein (KRP) family are involved in nematode feeding site development. This study demonstrates the involvement of Arabidopsis ICK2/KRP2 and ICK1/KRP1 in the control of mitosis to endoreduplication in galls induced by the root-knot nematode Meloidogyne incognita. Using ICK/KRP promoter-GUS fusions and mRNA in situ hybridizations, we showed that ICK2/KRP2, ICK3/KRP5 and ICK4/KRP6 are expressed in galls after nematode infection. Loss-of-function mutants have minor effects on gall development and nematode reproduction. Conversely, overexpression of both ICK1/KRP1 and ICK2/KRP2 impaired mitosis in giant cells and blocked neighboring cell proliferation, resulting in a drastic reduction of gall size. Studying the dynamics of protein expression demonstrated that protein levels of ICK2/KRP2 are tightly regulated during giant cell development and reliant on the presence of the nematode. This work demonstrates that impeding cell cycle progression by means of ICK1/KRP1 and ICK2/KRP2 overexpression severely restricts gall development, leading to a marked limitation of root-knot nematode development and reduced numbers of offspring. PMID:23574394

Vieira, Paulo; Escudero, Carmen; Rodiuc, Natalia; Boruc, Joanna; Russinova, Eugenia; Glab, Nathalie; Mota, Manuel; De Veylder, Lieven; Abad, Pierre; Engler, Gilbert; de Almeida Engler, Janice

2013-07-01

143

Host-related metabolic cues affect colonization strategies of a root endophyte  

PubMed Central

The mechanisms underpinning broad compatibility in root symbiosis are largely unexplored. The generalist root endophyte Piriformospora indica establishes long-lasting interactions with morphologically and biochemically different hosts, stimulating their growth, alleviating salt stress, and inducing local and systemic resistance to pathogens. Cytological studies and global investigations of fungal transcriptional responses to colonization of barley and Arabidopsis at different symbiotic stages identified host-dependent colonization strategies and host-specifically induced effector candidates. Here, we show that in Arabidopsis, P. indica establishes and maintains biotrophic nutrition within living epidermal cells, whereas in barley the symbiont undergoes a nutritional switch to saprotrophy that is associated with the production of secondary thinner hyphae in dead cortex cells. Consistent with a diversified trophic behavior and with the occurrence of nitrogen deficiency at the onset of saprotrophy in barley, fungal genes encoding hydrolytic enzymes and nutrient transporters were highly induced in this host but not in Arabidopsis. Silencing of the high-affinity ammonium transporter PiAMT1 gene, whose transcripts are accumulating during nitrogen starvation and in barley, resulted in enhanced colonization of this host, whereas it had no effect on the colonization of Arabidopsis. Increased levels of free amino acids and reduced enzymatic activity for the cell-death marker VPE (vacuolar-processing enzyme) in colonized barley roots coincided with an extended biotrophic lifestyle of P. indica upon silencing of PiAMT1. This suggests that PiAmt1 functions as a nitrogen sensor mediating the signal that triggers the in planta activation of the saprotrophic program. Thus, host-related metabolic cues affect the expression of P. indica’s alternative lifestyles.

Lahrmann, Urs; Ding, Yi; Banhara, Aline; Rath, Magnus; Hajirezaei, Mohammad R.; Dohlemann, Stefanie; von Wiren, Nicolaus; Parniske, Martin; Zuccaro, Alga

2013-01-01

144

Host-related metabolic cues affect colonization strategies of a root endophyte.  

PubMed

The mechanisms underpinning broad compatibility in root symbiosis are largely unexplored. The generalist root endophyte Piriformospora indica establishes long-lasting interactions with morphologically and biochemically different hosts, stimulating their growth, alleviating salt stress, and inducing local and systemic resistance to pathogens. Cytological studies and global investigations of fungal transcriptional responses to colonization of barley and Arabidopsis at different symbiotic stages identified host-dependent colonization strategies and host-specifically induced effector candidates. Here, we show that in Arabidopsis, P. indica establishes and maintains biotrophic nutrition within living epidermal cells, whereas in barley the symbiont undergoes a nutritional switch to saprotrophy that is associated with the production of secondary thinner hyphae in dead cortex cells. Consistent with a diversified trophic behavior and with the occurrence of nitrogen deficiency at the onset of saprotrophy in barley, fungal genes encoding hydrolytic enzymes and nutrient transporters were highly induced in this host but not in Arabidopsis. Silencing of the high-affinity ammonium transporter PiAMT1 gene, whose transcripts are accumulating during nitrogen starvation and in barley, resulted in enhanced colonization of this host, whereas it had no effect on the colonization of Arabidopsis. Increased levels of free amino acids and reduced enzymatic activity for the cell-death marker VPE (vacuolar-processing enzyme) in colonized barley roots coincided with an extended biotrophic lifestyle of P. indica upon silencing of PiAMT1. This suggests that PiAmt1 functions as a nitrogen sensor mediating the signal that triggers the in planta activation of the saprotrophic program. Thus, host-related metabolic cues affect the expression of P. indica's alternative lifestyles. PMID:23918389

Lahrmann, Urs; Ding, Yi; Banhara, Aline; Rath, Magnus; Hajirezaei, Mohammad R; Döhlemann, Stefanie; von Wirén, Nicolaus; Parniske, Martin; Zuccaro, Alga

2013-08-20

145

Strigolactones stimulate internode elongation independently of gibberellins.  

PubMed

Strigolactone (SL) mutants in diverse species show reduced stature in addition to their extensive branching. Here, we show that this dwarfism in pea (Pisum sativum) is not attributable to the strong branching of the mutants. The continuous supply of the synthetic SL GR24 via the root system using hydroponics can restore internode length of the SL-deficient rms1 mutant but not of the SL-response rms4 mutant, indicating that SLs stimulate internode elongation via RMS4. Cytological analysis of internode epidermal cells indicates that SLs control cell number but not cell length, suggesting that SL may affect stem elongation by stimulating cell division. Consequently, SLs can repress (in axillary buds) or promote (in the stem) cell division in a tissue-dependent manner. Because gibberellins (GAs) increase internode length by affecting both cell division and cell length, we tested if SLs stimulate internode elongation by affecting GA metabolism or signaling. Genetic analyses using SL-deficient and GA-deficient or DELLA-deficient double mutants, together with molecular and physiological approaches, suggest that SLs act independently from GAs to stimulate internode elongation. PMID:23943865

de Saint Germain, Alexandre; Ligerot, Yasmine; Dun, Elizabeth A; Pillot, Jean-Paul; Ross, John J; Beveridge, Christine A; Rameau, Catherine

2013-10-01

146

Alkamides Isolated from Plants Promote Growth and Alter Root Development in Arabidopsis1  

PubMed Central

To date, several classes of hormones have been described that influence plant development, including auxins, cytokinins, ethylene, and, more recently, brassinosteroids. However, it is known that many fungal and bacterial species produce substances that alter plant growth that, if naturally present in plants, might represent novel classes of plant growth regulators. Alkamides are metabolites widely distributed in plants with a broad range of biological activities. In this work, we investigated the effects of affinin, an alkamide naturally occurring in plants, and its derivates, N-isobutyl-2E-decenamide and N-isobutyl-decanamide, on plant growth and early root development in Arabidopsis. We found that treatments with affinin in the range of 10-6 to 10-4 m alter shoot and root biomass production. This effect correlated with alteration on primary root growth, lateral root formation, and root hair elongation. Low concentrations of affinin (7 × 10-6–2.8 × 10-5 m) enhanced primary root growth and root hair elongation, whereas higher concentrations inhibited primary root growth that related with a reduction in cell proliferating activity and cell elongation. N-isobutyl-2E-decenamide and N-isobutyl-decanamide were found to stimulate root hair elongation at concentrations between 10-8 to 10-7 m. Although the effects of alkamides were similar to those produced by auxins on root growth and cell parameters, the ability of the root system to respond to affinin was found to be independent of auxin signaling. Our results suggest that alkamides may represent a new group of plant growth promoting substances with significant impact on root development and opens the possibility of using these compounds for improved plant production.

Ramirez-Chavez, Enrique; Lopez-Bucio, Jose; Herrera-Estrella, Luis; Molina-Torres, Jorge

2004-01-01

147

Root gravitropism in maize and Arabidopsis  

NASA Technical Reports Server (NTRS)

Research during the period 1 March 1992 to 30 November 1993 focused on improvements in a video digitizer system designed to automate the recording of surface extension in plants responding to gravistimulation. The improvements included modification of software to allow detailed analysis of localized extension patterns in roots of Arabidopsis. We used the system to analyze the role of the postmitotic isodiametric growth zone (a region between the meristem and the elongation zone) in the response of maize roots to auxin, calcium, touch and gravity. We also used the system to analyze short-term auxin and gravitropic responses in mutants of Arabidopsis with reduced auxin sensitivity. In a related project, we studied the relationship between growth rate and surface electrical currents in roots by examining the effects of gravity and thigmostimulation on surface potentials in maize roots.

Evans, Michael L.

1993-01-01

148

Sites and Regulation of Auxin Biosynthesis in Arabidopsis Roots  

Microsoft Academic Search

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

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

2005-01-01

149

Vertex-element models for anisotropic growth of elongated plant organs  

PubMed Central

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.

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

2013-01-01

150

Chemical composition fluctuations in roots of Plumbago scandens L. in relation to floral development.  

PubMed

Plumbago scandens L. is a Brazilian tropical/subtropical species that occurs along the coast. Chemically it is mainly represented by naphthoquinones, flavonoids, terpenoids and steroids. The aim of the present work is to study quantitative changes in the root metabolic production of Plumbago scandens during different physiologic developmental stages relative to floration. The results indicated the presence of four substances in the extracts: plumbagin, epi-isoshinanolone, palmitic acid and sitosterol, independent on developmental stage. The naphthoquinone plumbagin has always showed to be the major component of all extracts. Naphthoquinones exhibited their highest content during floration, while the content of the two others components decreased during this stage, revealing an inverse profile. The chemical composition changed depending on the plant requirements. PMID:22146952

Paiva, Selma R; Lima, Lucilene A; Figueiredo, Maria Raquel; Kaplan, Maria Auxiliadora C

2011-12-01

151

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

NASA Technical Reports Server (NTRS)

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.

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

1994-01-01

152

[Annual developmental cycle of roots and shoots in Symphytum officinale L. in relation to storage and consumption of carbohydrates].  

PubMed

The development of the root and shoot system of Symphytum officinale always begins with the formation of a rape with 6-8 leaves on its epicotyl. After this stage development is determined by the length of the day. If the day is shorter than 15 hours, the subterraneous organs grow thicker. Flower formation needs a day length of at least 12 hours, shoot growth a day length of 14 hours. The shorter the day length the more leaves are formed.Starch is always stored until 6-8 leaves are formed by the young plant. After this stage it is only stored when the days are longer than 14 hours. When the days are shorter the amount of starch is reduced, partly during the thickening of the subterraneous organs. Fructosans are stored and reduced independent of day length. They are consumed during shoot elongation and flowering.A hydrolysis of starch and fructosans is also caused by low temperatures during the winter.Starch and fructosans are stored to a different degree in the various subterraneous organs: the most is stored in the shoot-born roots and the least in the subterraneous shoot parts. In the latter organs the carbohydrate content is influenced the most by the growth processes. PMID:24554049

Staesche, K

1966-09-01

153

Plant growth regulators and adventitious root development in relation to auxin  

Microsoft Academic Search

Adventitious root formation in stem cuttings of mung bean was enhanced by ethrel, which had an additive effect when employed\\u000a simultaneously with indolebutyric acid (IBA). Abscisic acid (ABA) did not influence the number of roots per cutting whereas\\u000a gibberellic acid (GA3) and kinetin were without effect on rooting at lower concentrations but were inhibitory at higher concentrations. Nevertheless,\\u000a all three

B. C. Jarvis; S. Yasmin

1987-01-01

154

Influence of cultural practices on edaphic factors related to root disease in Pinus nursery seedlings  

Microsoft Academic Search

Conifer seedlings grown in bare-root nurseries are frequently damaged and destroyed by soil-borne pathogenic fungi that cause\\u000a root rot. Relationships between nursery cultural practices, soil characteristics, and populations of potential pathogens in\\u000a the soil were examined in three bare-root tree nurseries in the Midwestern USA. Soil-borne populations of Fusarium spp. and\\u000a Pythium spp. were enumerated as a function of soil

J. Juzwik; K. M. Gust; R. R. Allmaras

1999-01-01

155

Development and persistence of sandsheaths of Lyginia barbata (Restionaceae): relation to root structural development and longevity  

PubMed Central

Background and Aims Strongly coherent sandsheaths that envelop perennial roots of many monocotyledonous species of arid environments have been described for over a century. This study, for the first time, details the roles played by the structural development of the subtending roots in the formation and persistence of the sheaths. Methods The structural development of root tissues associated with persistent sandsheaths was studied in Lyginia barbata, native to the Western Australian sand plains. Cryo-scanning electron microscopy CSEM, optical microscopy and specific staining methods were applied to fresh, field material. The role of root hairs was clarified by monitoring sheath development in roots separated from the sand profile by fine mesh. Key Results and Conclusions The formation of the sheaths depends entirely on the numerous living root hairs which extend into the sand and track closely around individual grains enmeshing, by approx. 12 cm from the root tip, a volume of sand more than 14 times that of the subtending root. The longevity of the perennial sheaths depends on the subsequent development of the root hairs and of the epidermis and cortex. Before dying, the root hairs develop cellulosic walls approx. 3 µm thick, incrusted with ferulic acid and lignin, which persist for the life of the sheath. The dead hairs remain in place fused to a persistent platform of sclerified epidermis and outer cortex. The mature cortex comprises this platform, a wide, sclerified inner rim and a lysigenous central region – all dead tissue. We propose that the sandsheath/root hair/epidermis/cortex complex is a structural unit facilitating water and nutrient uptake while the tissues are alive, recycling scarce phosphorus during senescence, and forming, when dead, a persistent essential structure for maintenance of a functional stele in the perennial Lyginia roots.

Shane, Michael W.; McCully, Margaret E.; Canny, Martin J.; Pate, John S.; Lambers, Hans

2011-01-01

156

[Water cultured propagation of Polygonum multiflorum and dynamic changes of physiological and biochemical characteristics during adventitious roots formation].  

PubMed

Water cultured propagation technology of Polygonum multiflorum was investigated with Rooting Powder No. 2 (ABT 2) comparison experiments, and the dynamic changes of endogenous hormones including indole acetic acid (IAA), abscisic acid (ABA), zeatin riboside (ZRs) contents and activities of indoleacetic acid oxidase (IAAO), polyphenol oxidase (PPO) were analyzed during rooting period. The results showed that rooting percentage of softwood cutting with 50 mg x L(-1) ABT2 and 10 mg x L(-1) ABT2 + 0.2% Urea + 0.2% KH2PO4 treatments was 94%, rooting percentage of softwood cuttings of control was 46% only. The adventitious rooting displayed three distinct phases i. e. root-inducing, root formation and root-elongating phases. The dynamic changes of contents of endogenous plant hormones (IAA, ABA, ZRs) and activities of IAAO, PPO tested were tightly related to the rooting process of soft-wood cuttings in P. multiflorum. During root-inducing phase the contents of IAA, ABA and ZRs decreased sharply, whereas ZRs content and IAAO activity kept higher level. IAA content reached the peak and PPO activity increased obviously during root formation phase, while IAAO activities and ABA, ZRs contents declined to minimum. During root-elongating phase PPO, IAAO activities were higher and IAA, ABA, ZRs contents kept steady. During rooting ABT2 (50 mg x L(-1)) treatment increased the content of IAA and PPO activity in cuttings, while the opposite result occurred in contents of ZRs, ABA and IAAO activity. PMID:21585047

Gao, Jie; Liu, Xiaohui; Yuan, Yike

2011-02-01

157

Evaluation of a simple technique for characterizing rice root systems in relation to drought resistance  

Microsoft Academic Search

Drought is a constraint to rice yields in much of Asia's rainfed rice crop. Although genotypic variation for root system characteristics is well documented in this semiaquatic species, little improvement of rice for drought resistance has been attempted. No simple method to evaluate root systems exists. In this paper we report the development and testing of a simple device to

J. C. O'Toole; Soemartono

1981-01-01

158

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

PubMed Central

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.

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

1996-01-01

159

Success rate of miniscrews relative to their position to adjacent roots  

Microsoft Academic Search

SUMMARY The purpose of this study was to evaluate, histologically, root contact, proximity to a root, and proximity to marginal bone level as possible risk factors for the failure of mini-screws when inserted between neighbouring teeth. Twenty mini-screws were inserted into the mandible of fi ve beagle dogs. Each dog received two bracket screw bone anchors in each lower quadrant,

K. Asscherickx; B. Vande Vannet; H. Wehrbein; M. M. Sabzevar

2008-01-01

160

[Studies on the Nepalese crude drugs. XVII. On the naphthalene related compounds from the root bark of Oroxylum indicum VENT].  

PubMed

Nine new naphthalene related compounds (I, IV, V, VII-XII) together with four known compounds (II, III, VI, XIII) were isolated from the root bark of Oroxylum indicum Vent. (Bignoniaceae), one of the Nepalese crude drugs. Their structures were determined based on chemical and physiocochemical evidence. PMID:7932095

Kizu, H; Habe, S; Ishida, M; Tomimori, T

1994-07-01

161

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

NASA Technical Reports Server (NTRS)

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.

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

1991-01-01

162

QTL analysis of root traits as related to phosphorus efficiency in soybean  

PubMed Central

Background and Aims Low phosphorus (P) availability is a major constraint to soybean growth and production, especially in tropical and subtropical areas. Root traits have been shown to play critical roles in P efficiency in crops. Identification of the quantitative trait loci (QTLs) conferring superior root systems could significantly enhance genetic improvement in soybean P efficiency. Methods A population of 106 F9 recombinant inbred lines (RILs) derived from a cross between BD2 and BX10, which contrast in both P efficiency and root architecture, was used for mapping and QTL analysis. Twelve traits were examined in acid soils. A linkage map was constructed using 296 simple sequence repeat (SSR) markers with the Kosambi function, and the QTLs associated with these traits were detected by composite interval mapping and multiple-QTL mapping. Key Results The first soybean genetic map based on field data from parental genotypes contrasting both in P efficiency and root architecture was constructed. Thirty-one putative QTLs were detected on five linkage groups, with corresponding contribution ratios of 9·1–31·1 %. Thirteen putative QTLs were found for root traits, five for P content, five for biomass and five for yield traits. Three clusters of QTLs associated with the traits for root and P efficiency at low P were located on the B1 linkage group close to SSR markers Satt519 and Satt519-Sat_128, and on the D2 group close to Satt458; and one cluster was on the B1 linkage group close to Satt519 at high P. Conclusions Most root traits in soybean were conditioned by more than two minor QTLs. The region closer to Satt519 on the B1 linkage group might have great potential for future genetic improvement for soybean P efficiency through root selection.

Liang, Quan; Cheng, Xiaohui; Mei, Mantong; Yan, Xiaolong; Liao, Hong

2010-01-01

163

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

PubMed Central

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, we established a connection in Arabidopsis thaliana between suberin in the root and both water movement through the plant and solute accumulation in the shoot. Esb1 mutants, characterized by increased root suberin, were found to have reduced day time transpiration rates and increased water-use efficiency during their vegetative growth period. Furthermore, these changes in suberin and water transport were associated with decreases in the accumulation of Ca, Mn, and Zn and increases in the accumulation of Na, S, K, As, Se, and Mo in the shoot. Here, we present direct genetic evidence establishing that suberin in the roots plays a critical role in controlling both water and mineral ion uptake and transport to the leaves. The changes observed in the elemental accumulation in leaves are also interpreted as evidence that a significant component of the radial root transport of Ca, Mn, and Zn occurs in the apoplast.

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

2009-01-01

164

Biointeractivity-related versus chemi/physisorption-related apatite precursor-forming ability of current root end filling materials.  

PubMed

Commercial root end filling materials, namely two zinc oxide eugenol-based cements [intermediate restorative material (IRM), Superseal], a glass ionomer cement (Vitrebond) and three calcium-silicate mineral trioxide aggregate (MTA)-based cements (ProRoot MTA, MTA Angelus, and Tech Biosealer root end), were examined for their ability to: (a) release calcium (Ca(2+) ) and hydroxyl (OH(-) ) ions (biointeractivity) and (b) form apatite (Ap) and/or calcium phosphate (CaP) precursors. Materials were immersed in Hank's balanced salt solution (HBSS) for 1-28 days. Ca(2+) and OH(-) release were measured by ion selective probes, surface analysis was performed by environmental scanning electron microscopy/energy dispersive X-ray analysis, micro-Raman, and Fourier transform infrared spectroscopy. IRM and Superseal released small quantities of Ca(2+) and no OH(-) ions. Uneven sparse nonapatitic Ca-poor amorphous CaP (ACP) deposits were observed after 24 h soaking. Vitrebond did not release either Ca(2+) or OH(-) ions, but uneven nonapatitic Ca-poor CaP deposits were detected after 7 days soaking. ProRoot MTA, MTA Angelus, and Tech Biosealer root end released significant amounts of Ca(2+) and OH(-) ions throughout the experiment. After 1 day soaking, nanospherulites of CaP deposits formed by amorphous calcium/magnesium phosphate (ACP) Ap precursors were detected. A more mature ACP phase was present on ProRoot MTA and on Tech Biosealer root end at all times. In conclusion, zinc oxide and glass ionomer cements had little or no ability to release mineralizing ions: they simply act as substrates for the possible chemical bonding/adsorption of environmental ions and precipitation of nonapatitic Ca-poor ACP deposits. On the contrary, calcium-silicate cements showed a high calcium release and basifying effect and generally a pronounced formation of more mature ACP apatitic precursors correlated with their higher ion-releasing ability. PMID:23559495

Gandolfi, Maria Giovanna; Taddei, Paola; Modena, Enrico; Siboni, Francesco; Prati, Carlo

2013-10-01

165

Tungsten disrupts root growth in Arabidopsis thaliana by PIN targeting.  

PubMed

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

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

2014-08-15

166

Analysis of periodontal attachment loss in relation to root form abnormalities  

PubMed Central

Purpose The aim of this study was to explore root shape abnormalities, to investigate the influence of root form abnormalities on periodontal attachment loss, and to gather basic data to assist in the diagnosis and treatment of aggressive periodontitis. Methods From January 2010 to June 2012, a survey was conducted of all 3,284 periodontitis patients who visited the Department of Periodontology, Daejeon Dental Hospital, Wonkwang University School of Dentistry. Clinical parameters (probing depth, periodontal attachment loss, missing teeth) were measured and a radiographic examination was performed at the baseline. We classified the root shape abnormality of bicuspids and molars based on Meng classification. Results The periodontal attachment loss was the highest at the maxillary first molar (6.03 mm). The loss of the second molar was prominent. Type V deformity was shown to be the most common in the second maxillary and mandibular molars (P<0.05). Type V root shape was associated with the highest attachment loss (P=0.01). Conclusions Considering the small population and limited design of this study, definitive conclusions cannot be drawn. We suggest larger scale, methodologically more sophisticated studies that include normal controls and chronic periodontitis patients to clarify whether root form abnormalities are a potential risk factor for aggressive periodontitis.

Chung, Young-Mi

2013-01-01

167

Extreme cervical elongation after sacrohysteropexy.  

PubMed

We present a case of extreme cervical elongation with a cervix of 12 cm after an unusual operation in which the uterine corpus was directly fixed to the promontory, and which became symptomatic after 8 years. The possible pathophysiology of cervical elongation is discussed. Diagnosing a case of severe cervical elongation can be important in the pre-operative evaluation. It can alter the operative plan to a uterus-sparing technique or it can alert the surgeon to a difficult entry in the abdominal cavity during vaginal hysterectomy. PMID:23052629

Vierhout, Mark E; Fütterer, Jurgen J

2013-09-01

168

Accumulation of essential oils in relation to root differentiation in Angelica archangelica L.  

PubMed

The accumulation of essential oils in Angelica archangelica subsp. archangelica roots at different developmental stages was investigated through histochemical and chemical analyses. Roots less than 1 mm in diameter showed a primary diarch structure and two primary secretory ducts in the pericycle. These ducts were ephemeral and probably became dysfunctional early on. Oil accumulation was observed only in the secondary secretory ducts formed by cambium activity and located in the secondary phloem. Gas chromatographic analyses revealed that only taproots exceeding 5 mm in diameter contained a high concentration of alpha- and beta-phellandrene, which appreciably influence the oil's aroma. PMID:12685562

Pasqua, G; Monacelli, B; Silvestrini, A

2003-01-01

169

ECONOMIC ANALYSIS, ROOT CONTROL, AND BACKWATER FLOW CONTROL AS RELATED TO INFILTRATION/INFLOW CONTROL. APPENDICES  

EPA Science Inventory

A study was conducted to identify and analyze present practices for determining and controlling infiltration and inflow (I/I) and investigate the role of roots and tide or backwater gates in the I/I problem. It was found through on-site investigations and questionnaires that loca...

170

ECONOMIC ANALYSIS, ROOT CONTROL, AND BACKWATER FLOW CONTROL AS RELATED TO INFILTRATION/INFLOW CONTROL  

EPA Science Inventory

A study was conducted to identify and analyze present practices for determining and controlling infiltration and inflow (I/I) and investigate the role of roots and tide or backwater gates in the I/I problem. It was found through on-site investigations and questionnaires that loca...

171

Relating Hybrid Poplar Fine Root Production, Soil Nutrients, and Hydrocarbon Contamination  

Microsoft Academic Search

Quantifying the effects of hydrocarbon contamination on hybrid poplar fine root dynamics provides information about how well these trees tolerate the adverse conditions imposed by the presence of petroleum in the soil. The objective of this research was to investigate the relationship between the varying concentrations of total petroleum hydrocarbons (TPH) and nutrients across a hydrocarbon-contaminated site, and quantify the

J. J. Gunderson; J. D. Knight; K. C. J. Van Rees

2008-01-01

172

The Mutual Adaptation Concept: Its Roots and Relatives. Documentation and Technical Assistance in Urban Schools.  

ERIC Educational Resources Information Center

This paper explores the roots of the concept of mutual adaptation in the literature of cognitive psychology, anthropology, biology, organizational behavior, and policy analysis. It is said that while educational researchers use the concept, their neglect of the literature on it is due, in part, to contradictory definitions of mutual adaptation as…

Meara, Hannah

173

Advocacy: Building Influence at the Grass Roots Level: Closing the School Year with Positive Public Relations.  

ERIC Educational Resources Information Center

Presents suggestions for library media center advocacy at the grass roots level. Discusses spring ordering and inclusion of staff, new materials, Internet resources, bookmarks, networking, establishing rapport with students, encouraging return of materials, media center as study area during final exams, graduation, attending Board of Education…

Seewald, Jacqueline

1999-01-01

174

Use of the root contact concept, an empirical leaf conductance model and pressure-volume curves in simulating crop water relations  

Microsoft Academic Search

A simulation model “DanStress” was developed for studying the integrated effects of soil, crop and climatic conditions on\\u000a water relations and water use of field grown cereal crops. The root zone was separated into 0.1 m deep layers of topsoil and\\u000a subsoil. For each layer the water potential at the root surface was calculated by a single root model, and

C. R. Jensen; H. Svendsen; M. N. Andersen; R. Lösch

1993-01-01

175

High-performance liquid chromatographic determination of tanshinones in the roots of Salvia miltiorrhiza and related traditional Chinese medicinal preparations  

Microsoft Academic Search

Purpose: This paper describes a validated high-performance liquid chromatographic method to quantitate four tanshinones as markers; dihydrotanshinone I, cryptotanshinone, tanshinone I and tanshinone IIA for use in the quality control of the roots of Salvia miltiorrhiza and its related traditional Chinese medicinal preparations. Methods: Separation was achieved using a Zorbax Extend C18 reserved-phase column (5µm, 250×4.6mm) at 20 °C with

Ai-Hua Liu; Yan-Hua Lin; Min Yang; Hui Guo; De-An Guo

176

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

Microsoft Academic Search

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

Thomas P. Birner; Ernst Steudle

1993-01-01

177

Rosmarinic acid and related phenolics in hairy root cultures of Ocimum basilicum  

Microsoft Academic Search

Five clones of Ocimum basilicum hairy roots, A-1 and A-2 (included by Agrobacterium rhizogenes ATCC 15834), and J-1, J-2 and J-3 (induced by A. rhizogenes MAFF 03-01724), grew well in hormone-free Murashige-Skoog, Gamborg B5 and Woody Plant liquid media. In these cultures, a large amount of rosmarinic acid was produced (maximum: 14.1% dry wt, by J-1 in MS medium) together

Hiromi Tada; Yoshie Murakami; Toshio Omoto; Koichiro Shimomura; Kanji Ishimaru

1996-01-01

178

Photomorphogenesis and pigment induction in lentil seedling roots exposed to low light conditions.  

PubMed

Although roots are normally hidden in soil, they may inadvertently be exposed to low light levels in experiments or in natural conditions through cracks or light transmittance through the soil. Light has been implicated in root morphogenesis. Thus, effects of low light conditions on lentil (Lens culinaris L. cv. Verte du Puy) root morphology and root pigmentation were studied. Lentil seedlings were grown in peat or transparent, nutrient-fortified agar at a 12-h light (PAR 240 ?mol · m(-2) · s(-1)), 12-h dark cycle. Roots were exposed to low levels (? 1-10 ?mol · m(-2) · s(-1)) of broadband white light, either directly or indirectly by aboveground light penetrating the growth medium. Control roots were grown in darkness. In situ spectroscopy was used to measure transmittance and reflectance spectra of intact root tissue by mounting the upper part of the primary root directly in a spectrophotometer equipped with an integrating sphere attachment. The transmittance and reflectance spectra were used to calculate the in situ root absorbance spectrum. Absorbance bands were found in the regions 480-500 nm and 650-680 nm, possibly due to low levels of root-localised carotenoids and chlorophylls, respectively. Low light levels (? 1-10 ?mol · m(-2) · s(-1) ) transmitted through the growth medium significantly increased root pigment concentration and root biomass, and altered root morphology by enhancing lateral root formation and inhibiting root elongation relative to roots grown in complete darkness. The light-induced changes in root morphogenesis and pigmentation appear to be primarily due to upper root light perception. PMID:22117590

Vollsnes, A V; Melř, T B; Futsaether, C M

2012-05-01

179

Elongation studies of the human agouti-related protein (AGRP) core decapeptide (Yc[CRFFNAFC]Y) results in antagonism at the mouse melanocortin-3 receptor  

Microsoft Academic Search

The agouti-related protein (AGRP) is an endogenous antagonist of the brain melanocortin receptors (MC3R and MC4R) and is believed to be involved in feeding behavior and energy homeostasis. Previous results identified that the human AGRP decapeptide Yc[CRFFNAFC]Y binds to the MC3R and MC4R and acts as an antagonist at the MC4R but not at the MC3R. We have synthesized the

Christine G Joseph; Rayna M Bauzo; Zhimin Xiang; Amanda M Shaw; William J Millard; Carrie Haskell-Luevano

2003-01-01

180

Alteration in expression of hormone-related genes in wild emmer wheat roots associated with drought adaptation mechanisms.  

PubMed

Transcriptomic and metabolomic profiles were used to unravel drought adaptation mechanisms in wild emmer wheat (Triticum turgidum ssp. dicoccoides), the progenitor of cultivated wheat, by comparing the response to drought stress in roots of genotypes contrasting in drought tolerance. The differences between the drought resistant (R) and drought susceptible (S) genotypes were characterized mainly by shifts in expression of hormone-related genes (e.g., gibberellins, abscisic acid (ABA) and auxin), including biosynthesis, signalling and response; RNA binding; calcium (calmodulin, caleosin and annexin) and phosphatidylinositol signalling, in the R genotype. ABA content in the roots of the R genotype was higher in the well-watered treatment and increased in response to drought, while in the S genotype ABA was invariant. The metabolomic profiling revealed in the R genotype a higher accumulation of tricarboxylic acid cycle intermediates and drought-related metabolites, including glucose, trehalose, proline and glycine. The integration of transcriptomics and metabolomics results indicated that adaptation to drought included efficient regulation and signalling pathways leading to effective bio-energetic processes, carbon metabolism and cell homeostasis. In conclusion, mechanisms of drought tolerance were identified in roots of wild emmer wheat, supporting our previous studies on the potential of this genepool as a valuable source for novel candidate genes to improve drought tolerance in cultivated wheat. PMID:21656015

Krugman, Tamar; Peleg, Zvi; Quansah, Lydia; Chagué, Véronique; Korol, Abraham B; Nevo, Eviatar; Saranga, Yehoshua; Fait, Aaron; Chalhoub, Boulos; Fahima, Tzion

2011-12-01

181

Microfilaments and microtubules in elongating parenchyma cells of Nymphoides indica  

Microsoft Academic Search

Observations on microfilaments and microtubules in elongating parenchyma cells of the central vascular bundle of Nymphoides indica (L.) O. Kuntze petiole are reported and discussed in relation to current concepts of the involvement of cellular organelles in cell wall synthesis.

A. Freundlich

1974-01-01

182

Electrical potential differences in cells of barley roots and their relation to ion uptake.  

PubMed

Single cell electropotentials of barley (Hordeum vulgare L., cv. ;Compana') root cortex were measured at different external concentrations of KCl in the presence of Ca(2+). The roots were low in salt from seedlings grown on 0.5 mm aerated CaSO(4) solution. Thus, the conditions were equivalent to those used to define the dual mechanisms found with radioactive tracer-labeled ion uptake. In 0.5 mm CaSO(4) alone, there is an increase with time of cell negativity from about -65 millivolts 15 minutes after cutting segments to about -185 millivolts in 6 to 8 hours. Two possible hypotheses, not mutually exclusive, are offered to explain this aging effect: that cutting exposes plasmodesmata which are leaky initially but which seal in time, and that some internal factors, e.g., hormones diffusing from the apex, have a regulatory effect on the cell potential, an influence which becomes dissipated in isolated segments and permits the development of a higher potential difference. In any case changes in selective ion transport must be involved. The cell potentials at KCl concentrations above 2.0 mm are more negative than would be expected for a passive diffusion potential. It is suggested that this discrepancy may be due to an electrogenic pump or to a higher K(+) concentration in the cytoplasm than in the remainder of the cell, or perhaps to both. Whether there is a clear relationship between cell potential and mechanisms 1 and 2 of cation transport depends upon whether the cell potentials of freshly cut or of aged tissue represent the values relevant to intact roots. PMID:16657583

Pitman, M G; Mertz, S M; Graves, J S; Pierce, W S; Higinbotham, N

1971-01-01

183

ROP (Rho-Related Protein from Plants) GTPases for Spatial Control of Root Hair Morphogenesis  

Microsoft Academic Search

\\u000a Cell polarity control is inherently a complex process based on the feedback loops where it is difficult to distinguish cause–effect\\u000a relationships and identify “master regulators.” However, small GTPases from the Rac\\/Rho family are certainly an important\\u000a part of polar growth core regulatory circuit\\/network also in plants. ROPs (Rac\\/Rho of plant) involvement in root hair polar\\u000a tip-growth is best documented by

V. Žárský; J. Fowler

184

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

NASA Astrophysics Data System (ADS)

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/mł) and high (~19.0 kN/mł) 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/mł) was comparable to the compaction effect of the pure soil from 15.5 to ~19.0 kN/mł. 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/mł) increased by the same amount whether by planting with White Alder or by compaction to ~19.0 kN/mł. 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.

Graf, Frank; Frei, Martin

2013-04-01

185

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

Microsoft Academic Search

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

Wendy M. Ridenour; Ragan M. Callaway

2001-01-01

186

A novel function for a redox-related LEA protein (SAG21/AtLEA5) in root development and biotic stress responses.  

PubMed

SAG21/AtLEA5 belongs to the late embryogenesis-associated (LEA) protein family. Although it has been implicated in growth and redox responses, its precise roles remain obscure. To address this problem, we characterized root and shoot development and response to biotic stress in SAG21/AtLEA5 over-expressor (OEX) and antisense (AS) lines. AS lines exhibited earlier flowering and senescence and reduced shoot biomass. Primary root length was reduced in AS lines, as was the number of laterals relative to the primary root. Root hair number was unchanged but root hair length was proportional to SAG21/AtLEA5 expression level, with longer root hairs in OEX lines and shorter root hairs in AS, relative to wild type. Growth of the fungal nectroph, Botrytis cinerea and of a virulent bacterial pathogen (Pseudomonas syringae pv. tomato) was affected by SAG21/AtLEA5 expression; however, growth of an avirulent P.syringae strain was unaffected. A SAG21/AtLEA5-YFP fusion was localized to mitochondria, raising the intriguing possibility that SAG21 interacts with proteins involved in mitochondrial ROS signalling, which in turn, impacts on root development and pathogen responses. PMID:21736589

Salleh, Faezah Mohd; Evans, Karly; Goodall, Benjamin; Machin, Helena; Mowla, Shaheen B; Mur, Luis A J; Runions, John; Theodoulou, Frederica L; Foyer, Christine H; Rogers, Hilary J

2012-02-01

187

Strigolactone Positively Controls Crown Root Elongation in Rice  

Microsoft Academic Search

Strigolactones are recently identified plant hormones that inhibit shoot branching. Pleiotropic defects in strigolactone-deficient\\u000a or -insensitive mutants indicate that strigolactones control various aspects of plant growth and development. However, our\\u000a understanding of the hormonal function of strigolactones in plants is very limited. In this study we demonstrate that rice\\u000a dwarf mutants that are strigolactone-deficient or -insensitive exhibit a short crown

Tomotsugu Arite; Hiromu Kameoka; Junko Kyozuka

188

Plant meristems: CLAVATA3/ESR-related signaling in the shoot apical meristem and the root apical meristem.  

PubMed

The plant meristems, shoot apical meristem (SAM) and root apical meristem (RAM), are unique structures made up of a self-renewing population of undifferentiated pluripotent stem cells. The SAM produces all aerial parts of postembryonic organs, and the RAM promotes the continuous growth of roots. Even though the structures of the SAM and RAM differ, the signaling components required for stem cell maintenance seem to be relatively conserved. Both meristems utilize cell-to-cell communication to maintain proper meristematic activities and meristem organization and to coordinate new organ formation. In SAM, an essential regulatory mechanism for meristem organization is a regulatory loop between WUSCHEL (WUS) and CLAVATA (CLV), which functions in a non-cell-autonomous manner. This intercellular signaling network coordinates the development of the organization center, organ boundaries and distant organs. The CLAVATA3/ESR (CLE)-related genes produce signal peptides, which act non-cell-autonomously in the meristem regulation in SAM. In RAM, it has been suggested that a similar mechanism can regulate meristem maintenance, but these functions are largely unknown. Here, we overview the WUS-CLV signaling network for stem cell maintenance in SAM and a related mechanism in RAM maintenance. We also discuss conservation of the regulatory system for stem cells in various plant species. PMID:19104754

Miwa, Hiroki; Kinoshita, Atsuko; Fukuda, Hiroo; Sawa, Shinichiro

2009-01-01

189

Root tips moving through soil  

PubMed Central

Root elongation occurs by the generation of new cells from meristematic tissue within the apical 1–2 mm region of root tips. Therefore penetration of the soil environment is carried out by newly synthesized plant tissue, whose cells are inherently vulnerable to invasion by pathogens. This conundrum, on its face, would seem to reflect an intolerable risk to the successful establishment of root systems needed for plant life. Yet root tip regions housing the meristematic tissues repeatedly have been found to be free of microbial infection and colonization. Even when spore germination, chemotaxis, and/or growth of pathogens are stimulated by signals from the root tip, the underlying root tissue can escape invasion. Recent insights into the functions of root border cells, and the regulation of their production by transient exposure to external signals, may shed light on long-standing observations.

Curlango-Rivera, Gilberto

2011-01-01

190

Study of Root Uptake and Xylem Translocation of Cinmethylin and Related Compounds in Detopped Soybean Roots Using a Pressure Chamber Technique  

PubMed Central

A pressure chamber technique was used to study the root uptake and xylem translocation of nonradiolabeled cinmethylin and its analogs in detopped soybean (Glycine max) roots. Quantifications of compounds were achieved by gas chromatography analysis using a mass spectrometry detector under selected ion monitoring. The compounds tested, with octanol-water partition coefficients (log Kow values) ranging from 0.96 to 5.3, were all nonionizable under the experimental conditions. Root efflux curves of all compounds exhibited a steady-state kinetic profile. The time required to achieve the steady state efflux concentration in the xylem sap correlated with log Kow values in a manner very similar to the root binding profile reported previously by GG Briggs et al. ([1982] Pestic Sci 13: 495-504). After reaching the steady state efflux, the concentration ratio of each compound in the xylem sap to the final concentration in the pressure chamber was taken as the transpiration stream concentration factor (TSCF). A nonlinear relationship was observed between TSCF and log Kow values. The highest TSCF value was between 0.6 to 0.8 for compounds with log Kow between 2.5 to 3.5. The range of optimal log Kow values was slightly higher than that reported earlier by Briggs et al. ([1982] Pestic Sci 13: 495-504). After taking into account the binding of the compound to soil, the apparent optimal Kow value for best root-to-shoot translocation is lowered to around 1. The relationship of root-to-shoot and phloem translocation was also discussed to promote a better understanding at the whole plant level of the uptake and translocation of a soil-applied xenobiotic.

Hsu, Francis C.; Marxmiller, Ronald L.; Yang, Alex Y. S.

1990-01-01

191

Root responses of flood-tolerant and flood-sensitive tree species to soil redox conditions  

Microsoft Academic Search

Under controlled rhizotron conditions, roots of Taxodium distichum L., Quercus lyrata Walt, and Q. falcata var. pagodaefolia Ell. were subjected to low soil redox potentials. Root elongation was inhibited at low soil redox potentials. In T. distichum, redox potentials below +200 mV resulted in a significant inhibition of root elongation. In Q. falcata var. pagodaefolia and Q. lyrata, redox potentials

S. R. Pezeshki

1991-01-01

192

Relative Abundance of Integral Plasma Membrane Proteins in Arabidopsis Leaf and Root Tissue Determined by Metabolic Labeling and Mass Spectrometry  

PubMed Central

Metabolic labeling of proteins with a stable isotope (15N) in intact Arabidopsis plants was used for accurate determination by mass spectrometry of differences in protein abundance between plasma membranes isolated from leaves and roots. In total, 703 proteins were identified, of which 188 were predicted to be integral membrane proteins. Major classes were transporters, receptors, proteins involved in membrane trafficking and cell wall-related proteins. Forty-one of the integral proteins, including nine of the 13 isoforms of the PIP (plasma membrane intrinsic protein) aquaporin subfamily, could be identified by peptides unique to these proteins, which made it possible to determine their relative abundance in leaf and root tissue. In addition, peptides shared between isoforms gave information on the proportions of these isoforms. A comparison between our data for protein levels and corresponding data for mRNA levels in the widely used database Genevestigator showed an agreement for only about two thirds of the proteins. By contrast, localization data available in the literature for 21 of the 41 proteins show a much better agreement with our data, in particular data based on immunostaining of proteins and GUS-staining of promoter activity. Thus, although mRNA levels may provide a useful approximation for protein levels, detection and quantification of isoform-specific peptides by proteomics should generate the most reliable data for the proteome.

Bernfur, Katja; Larsson, Olaf; Larsson, Christer; Gustavsson, Niklas

2013-01-01

193

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

Microsoft Academic Search

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

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

2009-01-01

194

Pulse pressure is inversely related to aortic root diameter implications for the pathogenesis of systolic hypertension.  

PubMed

Hypertension accelerates the age-associated increase in aortic root diameter (AoD), likely because of chronically elevated distending pressures. However, the pulsatile component of blood pressure may have a different relationship with AoD. We sought to assess the relationship between AoD and pulse pressure (PP) while accounting for left ventricular and central arterial structural and functional properties, which are known to influence PP. The study population was composed of 1256 individuals, aged 30 to 79 years (48% women and 48% hypertensive), none of whom were on antihypertensive medications. Blood pressure was measured in the sitting position with conventional sphygmomanometry. PP was calculated as the difference between systolic and diastolic blood pressures. AoD was measured at end diastole at the level of the sinuses of Valsalva with echocardiography. The relationship between AoD and PP was evaluated with multiple regression analyses. PP was 50+/-14 mm Hg in men and 54+/-18 mm Hg in women, and AoD was 31.9+/-3.5 mm in men and 28.9+/-3.5 mm in women. After adjusting for age, age(2), height, weight, and mean arterial pressure, AoD was independently and inversely associated with PP in both sexes. After further adjustments for central arterial stiffness and wall thickness, reflected waves, and left ventricular geometry, AoD remained inversely associated with PP in both men (coefficient=-0.48; P=0.0003; model R(2)=0.51) and women (coefficient=-0.40; P=0.01; model R(2)=0.61). Thus, AoD is inversely associated with PP, suggesting that a small AoD may contribute to the pathogenesis of systolic hypertension. Longitudinal studies are needed to examine this possibility. PMID:18158348

Farasat, S Morteza; Morrell, Christopher H; Scuteri, Angelo; Ting, Chih-Tai; Yin, Frank C P; Spurgeon, Harold A; Chen, Chen-Huan; Lakatta, Edward G; Najjar, Samer S

2008-02-01

195

Strigolactones Effects on Root Growth  

NASA Astrophysics Data System (ADS)

Strigolactones (SLs) were defined as a new group of plant hormones that suppress lateral shoot branching. Our previous studies suggested SLs to be regulators of root development. SLs were shown to alter root architecture by regulating lateral root formation and to affect root hair elongation in Arabidopsis. Another important effect of SLs on root growth was shown to be associated with root directional growth. Supplementation of SLs to roots led to alterations in root directional growth, whereas associated mutants showed asymmetrical root growth, which was influenced by environmental factors. The regulation by SLs of root development was shown to be conducted via a cross talk of SLs with other plant hormones, including auxin. SLs were shown to regulate auxin transport, and to interfere with the activity of auxin-efflux carriers. Therefore, it might be that SLs are regulators of root directional growth as a result of their ability to regulated auxin transport. However, other evidences suggest a localized effect of SLs on cell division, which may not necessarily be associated with auxin efflux. These and other, recent hypothesis as to the SLs mode of action and the associated root perception and response to environmental factors will be discussed.

Koltai, Hinanit

2012-07-01

196

Root growth, secondary root formation and root gravitropism in carotenoid-deficient seedlings of Zea mays L  

NASA Technical Reports Server (NTRS)

The effect of ABA on root growth, secondary-root formation and root gravitropism in seedlings of Zea mays was investigated by using Fluridone-treated seedlings and a viviparous mutant, both of which lack carotenoids and ABA. Primary roots of seedlings grown in the presence of Fluridone grew significantly slower than those of control (i.e. untreated) roots. Elongation of Fluridone-treated roots was inhibited significantly by the exogenous application of 1 mM ABA. Exogenous application of 1 micromole and 1 nmole ABA had either no effect or only a slight stimulatory effect on root elongation, depending on the method of application. The absence of ABA in Fluridone-treated plants was not an important factor in secondary-root formation in seedlings less than 9-10 d old. However, ABA may suppress secondary-root formation in older seedlings, since 11-d-old control seedlings had significantly fewer secondary roots than Fluridone-treated seedlings. Roots of Fluridone-treated and control seedlings were graviresponsive. Similar data were obtained for vp-9 mutants of Z. mays, which are phenotypically identical to Fluridone-treated seedlings. These results indicate that ABA is necessary for neither secondary-root formation nor for positive gravitropism by primary roots.

Ng, Y. K.; Moore, R.

1985-01-01

197

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

PubMed Central

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

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

1979-01-01

198

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

PubMed

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

Abney, Mark R; Kennedy, George G

2011-02-01

199

F-Box Proteins Elongate Translation During Stress Recovery  

NSDL National Science Digital Library

Protein synthesis is energetically costly and is tightly regulated by evolutionarily conserved mechanisms. Under restrictive growth conditions and in response to various stresses, such as DNA damage, cells inhibit protein synthesis to redirect available adenosine triphosphate to more essential processes. Conversely, proliferating cells, such as cancer cells, increase protein synthetic rates to support growth-related anabolic processes. mRNA translation occurs in three separate phases, consisting of initiation, elongation, and termination. Although all three phases are highly regulated, most of the translational control occurs at the rate-limiting initiation step. New evidence has described a molecular mechanism involved in the regulation of translation elongation. DNA damage initially slowed down elongation rates by activating the eukaryotic elongation factor 2 kinase (eEF2K) through an adenosine monophosphate (AMP)–activated protein kinase (AMPK)–dependent mechanism. However, during checkpoint recovery, the SCF (Skp, Cullin, F-box–containing) βTrCP (β-transducin repeat–containing protein) E3 ubiquitin ligase promoted degradation of eEF2K, thereby allowing the restoration of peptide chain elongation. These findings establish an important link between DNA damage signaling and the regulation of translation elongation.

Sylvain Meloche (Universite de Montreal;Institute for Research in Immunology and Cancer REV); Philippe P. Roux (Universite de Montreal;Institute for Research in Immunology and Cancer REV)

2012-06-05

200

Of spiders and elongated spots  

NASA Astrophysics Data System (ADS)

We present simulation results for various aspects of the 39m E-ELT AO systems. First, we look at the impact of a thick (more than one sub-aperture) spider on Laser Tomography AO performance. Then, what happens when elongated Laser Guide Star spots in the wavefront sensor are truncated, in a Multi-Conjugate AO system. Several sodium layer profiles are investigated. We also look at the performance of an LTAO system for a far infrared system. Finally, different reconstructors (Frim3D, Kaczmarz) are compared in an MCAO system.

Le Louarn, Miska; Béchet, Clémentine; Tallon, Michel

2013-12-01

201

Root Apex Transition Zone As Oscillatory Zone  

PubMed Central

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.

Baluska, Frantisek; Mancuso, Stefano

2013-01-01

202

The Electromagnetic Conception of Nature at the Root of the Special and General Relativity Theories and its Revolutionary Meaning  

NASA Astrophysics Data System (ADS)

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 relativistic dynamics of Poincaré of 1905. Einstein, on the contrary, after some years, linked relativistic dynamics to a semi-mechanist conception of Nature. He developed general relativity theory on the same ground, but Hilbert formulated it starting from the electromagnetic conception of Nature. Here, a comparison between these two conceptions is proposed in order to understand the conceptual foundations of special relativity within the context of the changing world views. The whole history of physics as well as history of science can be considered as a conflict among different worldviews. Every theory, as well as every different formulation of a theory implies a different worldview: a particular image of Nature implies a particular image of God (atheism too has a particular image of God) as well as of mankind and of their relationship. Thus, it is very relevant for scientific education to point out which image of Nature belongs to a particular formulation of a theory, which image comes to dominate and for which ideological reason.

Giannetto, Enrico R. A.

2009-06-01

203

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

PubMed

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

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

2013-07-01

204

Retention of cadmium in roots of maize seedlings. Role of complexation by phytochelatins and related thiol peptides  

Microsoft Academic Search

Cd from roots of maize was partitioned in seedlings exposed to 3 p~ CdSO, for 1 to 7 d. Most of the root Cd (92-94%) was buffer soluble and provided the classical metal-induced cysteine-rich, high-molecular-weight Cd-binding complex. This complex, how- ever, bound only part of the Cd within the roots, from 19% after 1 d of exposure to 59% by

Wilfried E. Rauser; Philippe Meuwly

1995-01-01

205

Histological characterization of root-knot nematode resistance in cowpea and its relation to reactive oxygen species modulation  

Microsoft Academic Search

Root-knot nematodes (Meloidogyne spp.) are seden- tary endoparasites with a broad host range which includes economically important crop species. Cowpea (Vigna unguiculata L. Walp) is an important food and fodder legume grown in many regions where root-knot nematodes are a major problem in production fields. Several sources of resistance to root-knot nematode have been identified in cowpea, including the widely

Sayan Das; Darleen A. DeMason; Jeffrey D. Ehlers; Timothy J. Close; Philip A. Roberts

2008-01-01

206

Temperature sensing by primary roots of maize  

NASA Technical Reports Server (NTRS)

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.

Poff, K. L.

1990-01-01

207

Relativity in Transylvania and Patusan: Finding the roots of Einstein's theories of relativity in "Dracula" and "Lord Jim"  

NASA Astrophysics Data System (ADS)

This thesis investigates the similarities in the study of time and space in literature and science during the modern period. Specifically, it focuses on the portrayal of time and space within Bram Stoker's Dracula (1897) and Joseph Conrad's Lord Jim (1899-1900), and compares the ideas presented with those later scientifically formulated by Albert Einstein in his special and general theories of relativity (1905-1915). Although both novels precede Einstein's theories, they reveal advanced complex ideas of time and space very similar to those later argued by the iconic physicist. These ideas follow a linear progression including a sense of temporal dissonance, the search for a communal sense of the present, the awareness and expansion of the individual's sense of the present, and the effect of mass on surrounding space. This approach enhances readings of Dracula and Lord Jim, illuminating the fascination with highly refined notions of time and space within modern European culture.

Tatum, Brian Shane

208

Space-Time Grains: Roots of Special and Doubly Special Relativity  

NASA Astrophysics Data System (ADS)

We show that the special relativistic dynamics when combined with quantum mechanics and the concept of superstatistics can be interpreted as arising from two interlocked non-relativistic stochastic processes that operate at different energy scales. This interpretation leads to Feynman amplitudes that are in the Euclidean regime identical to transition probability of a Brownian particle propagating through a granular space. Some kind of spacetime granularity could be therefore held responsible for the emergence at larger scales of various symmetries. For illustration we consider also the dynamics and the propagator of a spinless relativistic particle. Implications for doubly special relativity, quantum field theory, quantum gravity and cosmology are discussed.

Jizba, Petr; Scardigli, Fabio

2014-05-01

209

Pyocyanin, a virulence factor produced by Pseudomonas aeruginosa, alters root development through reactive oxygen species and ethylene signaling in Arabidopsis.  

PubMed

Pyocyanin acts as a virulence factor in Pseudomonas aeruginosa, a plant and animal pathogen. In this study, we evaluated the effect of pyocyanin on growth and development of Arabidopsis seedlings. Root inoculation with P. aeruginosa PAO1 strain inhibited primary root growth in wild-type (WT) Arabidopsis seedlings. In contrast, single lasI- and double rhlI-/lasI- mutants of P. aeruginosa defective in pyocyanin production showed decreased root growth inhibition concomitant with an increased phytostimulation. Treatment with pyocyanin modulates root system architecture, inhibiting primary root growth and promoting lateral root and root hair formation without affecting meristem viability or causing cell death. These effects correlated with altered proportions of hydrogen peroxide and superoxide in root tips and with an inhibition of cell division and elongation. Mutant analyses showed that pyocyanin modulation of root growth was likely independent of auxin, cytokinin, and abscisic acid but required ethylene signaling because the Arabidopsis etr1-1, ein2-1, and ein3-1 ethylene-related mutants were less sensitive to pyocyanin-induced root stoppage and reactive oxygen species (ROS) distribution. Our findings suggest that pyocyanin is an important factor modulating the interplay between ROS production and root system architecture by an ethylene-dependent signaling. PMID:24224532

Ortiz-Castro, Randy; Pelagio-Flores, Ramón; Méndez-Bravo, Alfonso; Ruiz-Herrera, León Francisco; Campos-García, Jesús; López-Bucio, José

2014-04-01

210

Relation of soluble RANKL and osteoprotegerin levels in blood and gingival crevicular fluid to the degree of root resorption after orthodontic tooth movement.  

PubMed

The aim of the present study was the determination of the levels of osteoprotegerin and soluble RANKL in blood serum and in gingival crevicular fluid relative to the degree of orthodontic root resorption in a rat model. Blood samples and gingival crevicular fluid were collected from fourteen 6-month-old male Wistar rats weighing 350-500 g. A 25-g closed orthodontic coil spring was inserted between each upper right first molar and the upper incisors. After 21 days of loading, both upper first molars (treated and control) were extracted and studied under microcomputed tomography scanning. Statistical analysis demonstrated a positive linear correlation between the initial concentration of RANKL in blood serum and the degree of root resorption. The ratio of the initial concentrations of osteoprotegerin to RANKL in blood serum proved to be an independent prognostic factor of the degree of root resorption. The initial concentration of RANKL in gingival crevicular fluid showed a negative correlation to the initial concentration of RANKL in blood serum and for a finite range of initial concentrations of osteoprotegerin in gingival crevicular fluid, the dental root seemed protected against extreme external root resorption. Finally, the concentration of osteoprotegerin in blood serum decreased significantly in cases of severe root resorption. PMID:20587957

Tyrovola, Joanna B; Perrea, Despoina; Halazonetis, Dimitrios J; Dontas, Ismene; Vlachos, Ioannis S; Makou, Margarita

2010-06-01

211

Root systems  

NSDL National Science Digital Library

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.

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

2004-10-30

212

Expression of tomato salicylic acid (SA)-responsive pathogenesis-related genes in Mi-1-mediated and SA-induced resistance to root-knot nematodes.  

PubMed

The expression pattern of pathogenesis-related genes PR-1, PR-2 and PR-5, considered as markers for salicylic acid (SA)-dependent systemic acquired resistance (SAR), was examined in the roots and shoots of tomato plants pre-treated with SA and subsequently infected with root-knot nematodes (RKNs) (Meloidogyne incognita). PR-1 was up-regulated in both roots and shoots of SA-treated plants, whereas the expression of PR-5 was enhanced only in roots. The over-expression of PR-1 in the whole plant occurred as soon as 1 day after SA treatment. Up-regulation of the PR-1 gene was considered to be the main marker of SAR elicitation. One day after treatment, plants were inoculated with active juveniles (J2s) of M.?incognita. The number of J2s that entered the roots and started to develop was significantly lower in SA-treated than in untreated plants at 5 and 15 days after inoculation. The expression pattern of PR-1, PR-2 and PR-5 was also examined in the roots and shoots of susceptible and Mi-1-carrying resistant tomato plants infected by RKNs. Nematode infection produced a down-regulation of PR genes in both roots and shoots of SA-treated and untreated plants, and in roots of Mi-carrying resistant plants. Moreover, in resistant infected plants, PR gene expression, in particular PR-1 gene expression, was highly induced in shoots. Thus, nematode infection was demonstrated to elicit SAR in shoots of resistant plants. The data presented in this study show that the repression of host defence SA signalling is associated with the successful development of RKNs, and that SA exogenously added as a soil drench is able to trigger a SAR-like response to RKNs in tomato. PMID:24118790

Molinari, Sergio; Fanelli, Elena; Leonetti, Paola

2014-04-01

213

Strictosidine-related enzymes involved in the alkaloid biosynthesis of Uncaria tomentosa root cultures grown under oxidative stress.  

PubMed

The activity and gene expression of strictosidine-related enzymes in Uncaria tomentosa root cultures exposed to oxidative stress were studied. Elicitation with 0.2 mM hydrogen peroxide (H2 O2 ) or a combination of 0.8 mM buthionine sulfoximine and 0.2 mM jasmonic acid (BSO-JA) increased peroxidase activities by twofold at Day 8 and glutathione reductase by 1.4-fold at Day 5 in H2 O2 elicited cultures respect to the control. Production of monoterpenoid oxindole alkaloids (MOA), 3?-dihydrocadambine, and dolichantoside was stimulated after H2 O2 elicitation, reaching levels of 886.4 ± 23.6, 847.7 ± 25.4, and 87.5 ± 7.2 µg/g DW, at Day 8 which were 1.7-, 2.1-, and 2.3-fold higher relative to control. BSO-JA elicited cultures produced about twice alkaloids than H2 O2 -treated cultures, following a biphasic pattern with maxima at 0.5 and 8 days. Alkaloid production was preceded by increase in strictosidine synthase (STR) and strictosidine glucosidase (SGD) activities. After elicitation with H2 O2 or BSO-JA, the STR activity (pKat/mg protein) increased by 1.9-fold (93.8 ± 17.8 at 24 h) or 2.5-fold (102.4 ± 2.2 at 6 h) and the SGD activity (pKat/mg protein) by 2.8-fold (245.2 ± 14.4 at 6 h) or 4.2-fold (421.2 ± 1.8 at 18 h) relative to control. STR and SGD transcripts were upregulated after elicitation. H2 O2 -treated roots showed higher levels of STR at 48-192 h and SGD at 24-48 h, while BSO-JA treatments showed STR increased at 12 h and SGD at 24 h. Also, LC/ESI-MS confirmed the biosynthesis of dolichantoside from N-?-methyltryptamine and secologanin by U. tomentosa protein extracts. PMID:23606578

Vera-Reyes, Ileana; Huerta-Heredia, Ariana A; Ponce-Noyola, Teresa; Flores-Sanchez, Isvett Josefina; Esparza-García, Fernando; Cerda-García-Rojas, Carlos M; Trejo-Tapia, Gabriela; Ramos-Valdivia, Ana C

2013-01-01

214

Strictosidine-related enzymes involved in the alkaloid biosynthesis of Uncaria tomentosa root cultures grown under oxidative stress.  

PubMed

The activity and gene expression of strictosidine-related enzymes in Uncaria tomentosa root cultures exposed to oxidative stress were studied. Elicitation with 0.2 mM hydrogen peroxide (H2 O2 ) or a combination of 0.8 mM buthionine sulfoximine and 0.2 mM jasmonic acid (BSO-JA) increased peroxidase activities by 2-fold at day 8 and glutathione reductase by 1.4-fold at day 5 in H2 O2 elicited cultures respect to the control. Production of monoterpenoid oxindole alkaloids (MOA), 3?-dihydrocadambine, and dolichantoside was stimulated after H2 O2 elicitation, reaching levels of 886.4 ± 23.6, 847.7 ± 25.4, and 87.5 ± 7.2 µg/g DW, at day 8 which were 1.7-, 2.1- and 2.3-fold higher relative to control. BSO-JA elicited cultures produced ca. twice alkaloids than H2 O2 treated cultures, following a biphasic pattern with maxima at 0.5 and 8 days. Alkaloid production was preceded by increase in strictosidine synthase (STR) and strictosidine glucosidase (SGD) activities. After elicitation with H2 O2 or BSO-JA, the STR activity (pKat/mg protein) increased by 1.9-fold (93.8 ± 17.8 at 24 h) or 2.5-fold (102.4 ± 2.2 at 6 h) and the SGD activity (pKat/mg protein) by 2.8-fold (245.2 ± 14.4 at 6 h) or 4.2-fold (421.2 ± 1.8 at 18 h) relative to control. STR and SGD transcripts were upregulated after elicitation. H2 O2 treated roots showed higher levels of STR at 48-192 h and SGD at 24-48 h, while BSO-JA treatments showed STR increased at 12 h and SGD at 24 h. Also, LC/ESI-MS confirmed the biosynthesis of dolichantoside from N-?-methyltryptamine and secologanin by U. tomentosa protein extracts. © 2013 American Institute of Chemical Engineers Biotechnol. Prog., 2013. PMID:23475777

Vera-Reyes, Ileana; Huerta-Heredia, Ariana A; Ponce-Noyola, Teresa; Flores-Sanchez, Isvett Josefina; Esparza-García, Fernando; Cerda-García-Rojas, Carlos M; Trejo-Tapia, Gabriela; Ramos-Valdivia, Ana C

2013-03-01

215

Root hair length and rhizosheath mass depend on soil porosity, strength and water content in barley genotypes.  

PubMed

Selecting plants with improved root hair growth is a key strategy for improving phosphorus-uptake efficiency in agriculture. While significant inter- and intra-specific variation is reported for root hair length, it is not known whether these phenotypic differences are exhibited under conditions that are known to affect root hair elongation. This work investigates the effect of soil strength, soil water content (SWC) and soil particle size (SPS) on the root hair length of different root hair genotypes of barley. The root hair and rhizosheath development of five root hair genotypes of barley (Hordeum vulgare L.) was compared in soils with penetrometer resistances ranging from 0.03 to 4.45 MPa (dry bulk densities 1.2-1.7 g cm(-3)). A "short" (SRH) and "long" root hair (LRH) genotype was selected to further investigate whether differentiation of these genotypes was related to SWC or SPS when grown in washed graded sand. In low-strength soil (<1.43 MPa), root hairs of the LRH genotype were on average 25 % longer than that of the SRH genotype. In high-strength soil, root hair length of the LRH genotype was shorter than that in low-strength soil and did not differ from that of the SRH genotype. Root hairs were shorter in wetter soils or soils with smaller particles, and again SRH and LRH did not differ in hair length. Longer root hairs were generally, but not always, associated with larger rhizosheaths, suggesting that mucilage adhesion was also important. The root hair growth of barley was found to be highly responsive to soil properties and this impacted on the expression of phenotypic differences in root hair length. While root hairs are an important trait for phosphorus acquisition in dense soils, the results highlight the importance of selecting multiple and potentially robust root traits to improve resource acquisition in agricultural systems. PMID:24318401

Haling, Rebecca E; Brown, Lawrie K; Bengough, A Glyn; Valentine, Tracy A; White, Philip J; Young, Iain M; George, Timothy S

2014-03-01

216

Sensitivity of growth of roots versus leaves to water stress: biophysical analysis and relation to water transport  

Microsoft Academic Search

moisture depletion. The model simulation also showed that roots behave as reversibly leaky cable in water Water transport is an integral part of the process of uptake. Some field data on root water extraction and growth by cell expansion and accounts for most of the vertical profiles of Y in shoots are viewed as mani- increase in cell volume characterizing

Theodore C. Hsiao; Liu-Kang Xu

2000-01-01

217

Response of three root rot fungi to strawberry phenolics and the relation of phenolics to disease resistance  

Microsoft Academic Search

Pythium irregulare, Rhizoctonia solani, and Alternaria alternata, usually associated with strawberry root rot diseases, were sensitive in vitro to several phenolics present in strawberry roots, fruits, and leaves, P. irregulare was the most sensitive. Eighteen strawberry cultivars were divided into two types, based on qualitative phenolic content. Five contained an unidentified xanthone and generally less kaempferol-7-glucoside than the remaining thirteen.

S. Nemec

1976-01-01

218

The effect of root pressurization on water relations, shoot growth, and leaf gas exchange of peach (Prunus persica) trees on rootstocks with differing growth potential and hydraulic conductance.  

PubMed

It is well known that rootstocks can have an effect on the vegetative growth and development of the tree; however, there has been no clear explanation about the physiological mechanism involved in this phenomenon. Evidence indicates that the rootstock effects on tree vegetative growth may be related to hydraulic limitations of the rootstock. The objective of these experiments was to investigate the shoot growth, water potential, and gas exchange of peach trees on different rootstocks in response to manipulations of water relations of trees on rootstocks that differ in root hydraulic conductance. Tree water relations were manipulated by applying different amounts of pneumatic pressure on the root system and then relative shoot extension growth rate, tree transpiration rate, leaf water potential, leaf conductance, leaf transpiration, and net CO(2) exchange rate responses were measured. Root pressurization increased leaf water potential, relative shoot extension growth rate, leaf conductance, leaf transpiration, and net CO(2) exchange rates of trees on both vigorous and dwarfing rootstocks. There was a significant positive linear correlation between applied pneumatic pressure and tree transpiration rate and leaf water potential. Leaf conductance, transpiration rate, and net CO(2) exchange rate as well as relative shoot extension growth rates were also positively correlated with the applied pneumatic pressure on the root system. These relationships were consistent across both vigorous and size-controlling rootstocks, indicating that rootstock hydraulic limitation may be directly involved in the vegetative growth control of peach trees. PMID:16690626

Solari, Luis I; DeJong, Theodore M

2006-01-01

219

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

PubMed Central

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.

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

2010-01-01

220

Transmembrane electropotential in barley roots as related to cell type, cell location, and cutting and aging effects.  

PubMed

Transmembrane electropotential difference (PD) was measured in whole roots of barley (Hordeum vulgare L. cvs. Compana and Himalaya). Seedlings were grown 4 to 5 days in aerated 0.5 mm CaSO(4) or a nutrient solution. Measurements of PD were made with roots bathed in CaSO(4), KCl + CaSO(4), or the nutrient solution. The following results were found. (a) There was a radial PD gradient with epidermal cells being 10 to 58 millivolts less negative than cells in the third layer of the cortex (outside to inside). There was no longitudinal PD gradient in the region 0.5 to 4 cm from the root tip, nor was there any difference between the PD of young root hairs and other epidermal cells. (b) Cell PD in excised whole roots was not detectably different from that found in roots attached to the shoot, and was unchanged for 2 hours from excision. (c) In 1-centimeter sections of root, cell PD at the freshly cut surface was depolarized by 90 millivolts from that in the intact root; cells farther than 1 millimeter from the cut surface were not depolarized. The PD of cells at the cut surface became more negative upon aging the segment in 0.5 mm CaSO(4), eventually becoming greater by -25 millivolts than that in cells of intact roots. Cells in segments to which the root tips were attached had less negative PDs after aging than those in subapical segments, indicating a possible hormonal effect. PDs in aged, excised segments are not equivalent to those in intact roots. (d) Creeping of cytoplasm over electrode tips inserted into the vacuole gave measurements of vacuole-to-cytoplasm PD of + 9 millivolts in 0.5 mm CaSO(4) and + 35 millivolts in 1 mm KCl + 0.5 mm CaSO(4). Most of the cell PD was across the plasmalemma. (e) The reducing sugar content of roots in CaSO(4) solution was greater than that of roots in the nutrient solution in which ion uptake, particularly K(+) occurred. PMID:16659435

Mertz, S M; Higinbotham, N

1976-02-01

221

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.

222

AXR3 and SHY2 interact to regulate root hair development.  

PubMed

Signal transduction of the plant hormone auxin centres on the regulation of the abundance of members of the Aux/IAA family of transcriptional regulators, of which there are 29 in Arabidopsis. Auxin can influence Aux/IAA abundance by promoting the transcription of Aux/IAA genes and by reducing the half-life of Aux/IAA proteins. Stabilising mutations, which render Aux/IAA proteins resistant to auxin-mediated degradation, confer a wide range of phenotypes consistent with disruptions in auxin response. Interestingly, similar mutations in different family members can confer opposite phenotypic effects. To understand the molecular basis for this functional specificity in the Aux/IAA family, we have studied a pair of Aux/IAAs, which have contrasting roles in root hair development. We have found that stabilising mutations in AXR3/IAA17 blocks root hair initiation and elongation, whereas similar mutations in SHY2/IAA3 result in early initiation of root hair development and prolonged hair elongation, giving longer root hairs. The phenotypes resulting from double mutant combinations, the transient induction of expression of the proteins, and the pattern of transcription of the cognate genes suggest that root hair initiation is controlled by the relative abundance of SHY2 and AXR3 in a cell. These results suggest a general model for auxin signalling in which the modulation of the relative abundance of different Aux/IAA proteins can determine which down-stream responses are induced. PMID:14534134

Knox, Kirsten; Grierson, Claire S; Leyser, Ottoline

2003-12-01

223

Quantifying and Comparing the Relative Effects of Riparian Root Networks on the Geotechnical, Hydrologic and Hydraulic Processes Acting on a Streambank  

NASA Astrophysics Data System (ADS)

Riparian vegetation can both positively and negatively affect streambank stability. Previous research has shown that the effect of mechanical root-reinforcement on soil stability can be considerable, and can be successfully quantified and included in streambank stability models. However, root networks contained within a soil-matrix also have effects on the hydrologic and hydraulic processes acting on a streambank. Although these effects are often discussed they have generally been difficult to quantify. The work presented here summarizes the results of fieldwork, laboratory testing and computer simulations carried out to better quantify the effects of riparian vegetation on hydrologic and hydraulic processes occurring along streambanks. First, the evapotranspiration potentials of different riparian species were isolated by setting up an experiment to grow young riparian trees and switch grass in separate soil columns instrumented with tensiometers. The hydrological reinforcement provided to the soil from increased apparent cohesion as a result of enhanced matric suction was estimated to range from 1.0 to 3.1 kPa in spring when bank stability was most critical and up to a maximum of 5.0 kPa in the summer. Second, a vertical jet-test device was used to measure rates and volumes of scour in soils permeated by switch grass roots. Calculation of relative soil detachment rates (RSD) showed that with the highest rooting densities measured in the field jet-tests, eroded soil volume was 10 % of that in the tests with no roots. Third, the effects of enhanced matric suction due to evapotranspiration, and decreased soil erodibility because of the presence of plant roots were modeled using BSTEM 5.1 to quantify their effects on streambank factor of safety (Fs), and to compare with the effects of mechanical root-reinforcement. A sensitivity analysis showed that the change in soil matric suction due to evapotranspiration provided the greatest potential benefit to Fs but only during the summer months. During the winter and spring months, root-reinforcement remained the most important contributor to Fs. The sensitivity analysis conducted here also showed that whilst roots are capable of reducing the volume of hydraulic scour, the resulting effect on streambank geometry did not increase Fs as much as changes in soil matric suction and/or mechanical root-reinforcement.

Bankhead, N. L.; Simon, A.

2009-12-01

224

Characteristics of the electrical oscillations evoked by 4-aminopyridine on dorsal root fibers and their relation to fictive locomotor patterns in the rat spinal cord in vitro.  

PubMed

4-Aminopyridine (4-AP) is suggested to improve symptomatology of spinal injury patients because it may facilitate neuromuscular transmission, spinal impulse flow and the operation of the locomotor central pattern generator (CPG). Since 4-AP can also induce repetitive discharges from dorsal root afferents, this phenomenon might interfere with sensory signals necessary to modulate CPG activity. Using electrophysiological recording from dorsal and ventral roots of the rat isolated spinal cord, we investigated 4-AP-evoked discharges and their relation with fictive locomotor patterns. On dorsal roots 4-AP (5-10 microM) induced sustained synchronous oscillations (3.3+/-0.8 s period) smaller than electrically evoked synaptic potentials, persistent after sectioning off the ventral region and preserved in an isolated dorsal quadrant, indicating their dorsal horn origin. 4-AP oscillations were blocked by tetrodotoxin, or 6-cyano-7-nitroquinoxaline-2,3-dione and d-amino-phosphonovalerate, or strychnine and bicuculline, suggesting they were network mediated via glutamatergic, glycinergic and GABAergic transmission. Isolated ventral horn areas could not generated 4-AP oscillations, although their intrinsic disinhibited bursting was accelerated by 4-AP. Thus, ventral horn areas contained 4-AP sensitive sites, yet lacked the network for 4-AP induced oscillations. Activation of fictive locomotion by either application of N-methyl-D-aspartate and serotonin or stimulus trains to a single dorsal root reversibly suppressed dorsal root oscillations induced by 4-AP. This suppression was due to depression of dorsal network activity rather than simple block of root discharges. Since dorsal root oscillations evoked by 4-AP were turned off when the fictive locomotor program was initiated, these discharges are unlikely to interfere with proprioceptive signals during locomotor training in spinal patients. PMID:15857720

Taccola, G; Nistri, A

2005-01-01

225

Ferroelectric phase transitions in systems of axially symmetric dipolar particles in elongational flow  

Microsoft Academic Search

Effects of steady elongational flow on orientational phase transitions in systems of uniaxial, elongated particles with dipole moments are considered. The Onsager model is used with mean-field dipole–dipole and excluded-volume quadrupole interactions, combined with quadrupole effects introduced by elongational flow. Self-consistent, equilibrium orientation distribution of dipole particles, equilibrium thermodynamic properties and phase transitions are controlled by three dimensionless parameters related

Leszek Jarecki; Andrzej Ziabicki

2001-01-01

226

WUSCHEL-related Homeobox genes in Populus tomentosa: diversified expression patterns and a functional similarity in adventitious root formation  

PubMed Central

Background WUSCHEL (WUS)-related homeobox (WOX) protein family members play important roles in the maintenance and proliferation of the stem cell niche in the shoot apical meristem (SAM), root apical meristem (RAM), and cambium (CAM). Although the roles of some WOXs in meristematic cell regulation have been well studied in annual plants such as Arabidopsis and rice, the expression and function of WOX members in woody plant poplars has not been systematically investigated. Here, we present the identification and comprehensive analysis of the expression and function of WOXs in Populus tomentosa. Results A genome-wide survey identified 18 WOX encoding sequences in the sequenced genome of Populus trichocarpa (PtrWOXs). Phylogenetic and gene structure analysis revealed that these 18 PtrWOXs fall into modern/WUS, intermediate, and ancient clades, but that the WOX genes in P. trichocarpa may have expanded differently from the WOX genes in Arabidopsis. In the P. trichocarpa genome, no WOX members could be closely classified as AtWOX3, AtWOX6, AtWOX7, AtWOX10, and AtWOX14, but there were two copies of WOX genes that could be classified as PtrWUS, PtrWOX2, PtrWOX4, PtrWOX5, PtrWOX8/9, and PtrWOX11/12, and three copies of WOX genes that could be classified as PtrWOX1 and PtrWOX13. The use of primers specific for each PtrWOX gene allowed the identification and cloning of 18 WOX genes from P. tomentosa (PtoWOXs), a poplar species physiologically close to P. trichocarpa. It was found that PtoWOXs and PtrWOXs shared very high amino acid sequence identity, and that PtoWOXs could be classified identically to PtrWOXs. We revealed that the expression patterns of some PtoWOXs were different to their Arabidopsis counterparts. When PtoWOX5a and PtoWOX11/12a, as well as PtoWUSa and PtoWOX4a were ectopically expressed in transgenic hybrid poplars, the regeneration of adventitious root (AR) was promoted, indicating a functional similarity of these four WOXs in AR regeneration. Conclusions This is the first attempt towards a systematical analysis of the function of WOXs in P. tomentosa. A diversified expression, yet functional similarity of PtoWOXs in AR regeneration is revealed. Our findings provide useful information for further elucidation of the functions and mechanisms of WOXs in the development of poplars.

2014-01-01

227

Cytokinin Interplay with Ethylene, Auxin, and Glucose Signaling Controls Arabidopsis Seedling Root Directional Growth1[W][OA  

PubMed Central

Optimal root architecture is established by multiple intrinsic (e.g. hormones) and extrinsic (e.g. gravity and touch) signals and is established, in part, by directed root growth. We show that asymmetrical exposure of cytokinin (CK) at the root tip in Arabidopsis (Arabidopsis thaliana) promotes cell elongation that is potentiated by glucose in a hexokinase-influenced, G protein-independent manner. This mode of CK signaling requires the CK receptor, ARABIDOPSIS HISTIDINE KINASE4 and, at a minimum, its cognate type B ARABIDOPSIS RESPONSE REGULATORS ARR1, ARR10, and ARR11 for full responsiveness, while type A response regulators act redundantly to attenuate this CK response. Ethylene signaling through the ethylene receptor ETHYLENE RESISTANT1 and its downstream signaling element ETHYLENE INSENSITIVE2 are required for CK-induced root cell elongation. Negative and positive feedback loops are reinforced by CK regulation of the expression of the genes encoding these elements in both the CK and ethylene signaling pathways. Auxin transport facilitated by PIN-FORMED2 as well as auxin signaling through control of the steady-state level of transcriptional repressors INDOLE-3-ACETIC ACID7 (IAA7), IAA14, and IAA17 via TRANSPORT INHIBITOR RESPONSE1/AUXIN SIGNALING F-BOX PROTEIN are involved in CK-induced root cell elongation. This action lies downstream of ethylene and CK induction. Intrinsic signaling in this response operates independently of the extrinsic signal touch, although actin filament organization, which is important in the touch response, may be important for this response, since latrunculin B can induce similar growth. This root growth response may have adaptive significance, since CK responsiveness is inversely related to root coiling and waving, two root behaviors known to be important for fitness.

Kushwah, Sunita; Jones, Alan M.; Laxmi, Ashverya

2011-01-01

228

Unit Root Properties of Seasonal Adjustment and Related Filters. Research Report Series (Statistics No. 2010-08).  

National Technical Information Service (NTIS)

Linear filters used in seasonal adjustment (model-based or from the X-11 method) contain unit root factors in the form of differencing operators and seasonal summation operators. The extent to which the various filters (seasonal, seasonal adjustment, tren...

W. R. Bell

2011-01-01

229

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

PubMed Central

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.

Kato, Yoichiro; Okami, Midori

2011-01-01

230

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

PubMed Central

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.

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

2010-01-01

231

Strigolactone signaling in the endodermis is sufficient to restore root responses and involves SHORT HYPOCOTYL 2 (SHY2) activity.  

PubMed

Strigolactones (SLs) are plant hormones and regulators of root development, including lateral root (LR) formation, root hair (RH) elongation and meristem cell number, in a MORE AXILLARY GROWTH 2 (MAX2)-dependent way. However, whether SL signaling is acting cell-autonomously or in a non-cell-autonomous way in roots is unclear. We analyzed root phenotype, hormonal responses and gene expression in multiple lines of Arabidopsis thaliana max2-1 mutants expressing MAX2 under various tissue-specific promoters and shy2 mutants. The results demonstrate for the first time that expression of MAX2 under the SCARECROW (SCR) promoter, expressed mainly in the root endodermis, is sufficient to confer SL sensitivity in the root for RH, LR and meristem cell number. Moreover, loss of function mutation of SHORT HYPOCOTYL 2 (SHY2), a key component in auxin and cytokinin regulation of meristem size, has been found to be insensitive to SLs in relation to LR formation and meristem cell number. Endodermal SL signaling, mediated by MAX2, is sufficient to confer SL sensitivity in root, and SHY2 may participate in SL signaling to regulate meristem size and LR formation. These SL signaling pathways thus may act through modulation of auxin flux in the root tip, and may indicate a root-specific, yet non-cell-autonomous regulatory mode of action. PMID:23425316

Koren, Dikla; Resnick, Nathalie; Mayzlish Gati, Einav; Belausov, Eduard; Weininger, Smadar; Kapulnik, Yoram; Koltai, Hinanit

2013-05-01

232

Root gravitropism and root hair development constitute coupled developmental responses regulated by auxin homeostasis in the Arabidopsis root apex.  

PubMed

Active polar transport establishes directional auxin flow and the generation of local auxin gradients implicated in plant responses and development. Auxin modulates gravitropism at the root tip and root hair morphogenesis at the differentiation zone. Genetic and biochemical analyses provide evidence for defective basipetal auxin transport in trh1 roots. The trh1, pin2, axr2 and aux1 mutants, and transgenic plants overexpressing PIN1, all showing impaired gravity response and root hair development, revealed ectopic PIN1 localization. The auxin antagonist hypaphorine blocked root hair elongation and caused moderate agravitropic root growth, also leading to PIN1 mislocalization. These results suggest that auxin imbalance leads to proximal and distal developmental defects in Arabidopsis root apex, associated with agravitropic root growth and root hair phenotype, respectively, providing evidence that these two auxin-regulated processes are coupled. Cell-specific subcellular localization of TRH1-YFP in stele and epidermis supports TRH1 engagement in auxin transport, and hence impaired function in trh1 causes dual defects of auxin imbalance. The interplay between intrinsic cues determining root epidermal cell fate through the TTG/GL2 pathway and environmental cues including abiotic stresses modulates root hair morphogenesis. As a consequence of auxin imbalance in Arabidopsis root apex, ectopic PIN1 mislocalization could be a risk aversion mechanism to trigger root developmental responses ensuring root growth plasticity. PMID:23252740

Rigas, Stamatis; Ditengou, Franck Anicet; Ljung, Karin; Daras, Gerasimos; Tietz, Olaf; Palme, Klaus; Hatzopoulos, Polydefkis

2013-03-01

233

Electrophysiological responses of maize roots to low water potentials: relationship to growth and ABA accumulation  

Microsoft Academic Search

The maintenance of root elongation is an important adaptive response to low water potentials (yw), but little is known about its regulation. An important component may be changes in root cell electrophy- siology, which both signal and maintain growth main- tenance processes. As a first test of this hypothesis, membrane potentials (Em) were measured within the cell elongation zone of

Eric S. Ober; Robert E. Sharp

2003-01-01

234

Stimulation of adventitious root formation in non-woody stem cuttings by uridine  

Microsoft Academic Search

Uridine strongly stimulated adventitious root formation in stem cuttings of sunflower (Helianthus annuus L.), mung bean (Vigna radiata L.) and common bean (Phaseolus vulgaris L.). A dose response curve of uridine induced rooting showed that the optimum concentration of uridine was 0.1 µM. At all concentrations employed, uridine had no significant effect on root elongation. The rooting response of stem

Samih M. Tamimi

2003-01-01

235

ROLE OF SALICYLIC ACID IN REGULATING CADMIUM INDUCED OXIDATIVE STRESS IN ORYZA SATIVA L. ROOTS  

Microsoft Academic Search

Summary. In the present investigation we studied the role of salicylic acid in cadmium induced physiological and biochemical changes and the pos- sible induction of oxidative stress in developing rice roots. 24h cadmium treatment resulted in the inhibition of root dry biomass, root elongation and increased cadmium accumulation in roots. Salicylic acid presoaking for 16hrs resulted in protection against cadmium,

Shuvasish Choudhury; Sanjib Kumar Panda

236

Elongation and cell division in Bdellovibrio bacteriovorus  

Microsoft Academic Search

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.

Marta Eksztejn; Mazal Varon

1977-01-01

237

Analysis of Arabidopsis thaliana root growth kinetics with high temporal and spatial resolution  

PubMed Central

Background Methods exist to quantify the distribution of growth rate over the root axis. However, non-destructive, high-throughput evaluations of total root elongation in controlled environments and the field are lacking in growth studies. A new imaging approach to analyse total root elongation is described. Scope High pixel resolution of the images enables the study of growth in short time intervals and provides high temporal resolution. Using the method described, total root elongation rates are calculated from the displacement of the root tip. Although the absolute root elongation rate changes in response to growth conditions, this set-up enables root growth of Arabidopsis wild-type seedlings to be followed for more than 1 month after germination. The method provides an easy approach to decipher root extension rate and much simpler calculations compared with other methods that use segmental growth to address this question. Conclusions The high temporal resolution allows small modifications of total root elongation growth to be revealed. Furthermore, with the options to investigate growth of various mutants in diverse growth conditions the present tool allows modulations in root growth kinetics due to different biotic and abiotic stimuli to be unravelled. Measurements performed on Arabidopsis thaliana wild-type (Col0) plants revealed rhythms superimposed on root elongation. Results obtained from the starchless mutant pgm, however, present a clearly modified pattern. As expected, deviation is strongest during the dark period.

Yazdanbakhsh, Nima; Fisahn, Joachim

2010-01-01

238

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

PubMed Central

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.

Maeshima, Masayoshi

2014-01-01

239

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

PubMed

The plasma membrane-associated Ca(2+)-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

Tanaka, Natsuki; Kato, Mariko; Tomioka, Rie; Kurata, Rie; Fukao, Yoichiro; Aoyama, Takashi; Maeshima, Masayoshi

2014-04-01

240

Quantitative and Qualitative Effects of Phosphorus on Extracts and Exudates of Sudangrass Roots in Relation to Vesicular-Arbuscular Mycorrhiza Formation  

PubMed Central

A comparison was made of water-soluble root exudates and extracts of Sorghum vulgare Pers. grown under two levels of P nutrition. An increase in P nutrition significantly decreased the concentration of carbohydrates, carboxylic acids, and amino acids in exudates, and decreased the concentration of carboxylic acids in extracts. Higher P did not affect the relative proportions of specific carboxylic acids and had little effect on proportions of specific amino acids in both extracts and exudates. Phosphorus amendment resulted in an increase in the relative proportion of arabinose and a decrease in the proportion of fructose in exudates, but did not have a large effect on the proportion of individual sugars in extracts. The proportions of specific carbohydrates, carboxylic acids, and amino acids varied between exudates and extracts. Therefore, the quantity and composition of root extracts may not be a reliable predictor of the availability of substrate for symbiotic vesicular-arbuscular mycorrhizal fungi. Comparisons of the rate of leakage of compounds from roots with the growth rate of vesicular-arbuscular mycorrhizal fungi suggest that the fungus must either be capable of using a variety of organic substrates for growth, or be capable of inducing a much higher rate of movement of specific organic compounds across root cell membranes than occurs through passive exudation as measured in this study.

Schwab, Suzanne M.; Menge, John A.; Leonard, Robert T.

1983-01-01

241

Adaptation of plasma membrane H(+)-ATPase of rice roots to low pH as related to ammonium nutrition.  

PubMed

The preference of paddy rice for NH(4)(+) rather than NO(3)(-) is associated with its tolerance to low pH since a rhizosphere acidification occurs during NH(4)(+) absorption. However, the adaptation of rice root to low pH has not been fully elucidated. This study investigated the acclimation of plasma membrane H(+)-ATPase of rice root to low pH. Rice seedlings were grown either with NH(4)(+) or NO(3)(-). For both nitrogen forms, the pH value of nutrient solutions was gradually adjusted to pH 6.5 or 3.0. After 4 d cultivation, hydrolytic H(+)-ATPase activity, V(max), K(m), H(+)-pumping activity, H(+) permeability and pH gradient across the plasma membrane were significantly higher in rice roots grown at pH 3.0 than at 6.5, irrespective of the nitrogen forms supplied. The higher activity of plasma membrane H(+)-ATPase of adapted rice roots was attributed to the increase in expression of OSA1, OSA3, OSA7, OSA8 and OSA9 genes, which resulted in an increase of H(+)-ATPase protein concentration. In conclusion, a high regulation of various plasma membrane H(+)-ATPase genes is responsible for the adaptation of rice roots to low pH. This mechanism may be partly responsible for the preference of rice plants to NH(4)(+) nutrition. PMID:19558410

Zhu, Yiyong; DI, Tingjun; Xu, Guohua; Chen, Xi; Zeng, Houqing; Yan, Feng; Shen, Qirong

2009-10-01

242

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

Microsoft Academic Search

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

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

2006-01-01

243

Pursuing the identification of O(2) deprivation survival mechanisms in plants related to selective mRNA translation, hormone-independent cellular elongation and preparation for the arrival of oxygen.  

PubMed

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. 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

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

2011-10-01

244

Variation in growth and osmotic regulation of roots of water-stressed maritime pine (Pinus pinaster Ait.) provenances.  

PubMed

Hydroponically cultivated Pinus pinaster Ait. seedlings of a drought-sensitive population from France (Landes) and of a more drought-adapted population from Morocco (Tamjoute) were subjected to a progressive increase in water stress by additions of an osmoticum (polyethylene glycol 600) to the nutrient solution. The final osmotic potential (Psi(ms)) of the nutrient solution was achieved over a period of up to 6 days, and ranged from -0.03 (control, no added osmoticum) to -0.8 MPa. In the 6 days during which water stress was imposed, roots elongated faster in the Moroccan provenance than in the French provenance, but the applied water deficits did not inhibit root elongation in either population. Among treatments, root dry weight per unit root length, total root dry weight and root/shoot dry weight ratio increased with decreasing Psi(ms) in both provenances. Both the water potential (Psi(w)) of the roots (apices) and the water potential difference between the roots and the nutrient solution decreased as Psi(ms) decreased. The reduction in Psi(w) was matched by a decrease of comparable magnitude in cell osmotic potential (Psi(pi)) so that root turgor was unaffected by the Psi(ms). Osmotic adjustment was greater, however, in the Moroccan provenance than in the French provenance. Consequently, under the osmotically imposed water stress, the water potential difference between root and nutrient solution was greater in the Moroccan provenance than in the French provenance. Similar changes in plant water relations were observed when seedlings were grown in drying sand. PMID:14973004

Nguyen, A; Lamant, A

1989-03-01

245

Polyamines and Root Formation in Mung Bean Hypocotyl Cuttings 1  

PubMed Central

The incorporation of [14C]arginine and [14C]ornithine into various polyamines was studied in mung bean (Vigna radiata [L.] Wilczek) hypocotyl cuttings with respect to the effect of indole-3-butyric acid on adventitious root formation. Both [14C]arginine and [14C]ornithine are rapidly incorporated into putrescine, spermidine, and spermine, with similar kinetics, during 5- to 24-hour incubation periods. The incorporation of arginine into putrescine is generally higher than that of ornithine. The biosynthesis of putrescine and spermidine from the precursors, in the hypocotyls, is closely related to the pattern of root formation: a first peak at 0 to 24 hours corresponding to the period of root primordia development, and a second peak of putrescine biosynthesis at 48 to 72 hours corresponding to root growth and elongation. Indole-3-butyric acid considerably enhances putrescine biosynthesis in both phases, resulting in an increase of the putrescine/spermidine ratio. It is concluded that the promotive effect of indole-3-butyric acid on putrescine biosynthesis, from both arginine and ornithine, supports the hypothesis that auxin-induced root formation may require the promotion of polyamine biosynthesis.

Friedman, Ra'Anan; Altman, Arie; Bachrach, Uriel

1985-01-01

246

Overexpression of soybean GmCBL1 enhances abiotic stress tolerance and promotes hypocotyl elongation in Arabidopsis.  

PubMed

Although extensive studies and remarkable progress have been made with Arabidopsis calcineurin B-like proteins (CBLs), knowledge of their functions in other plant species is still limited. Here we isolated gene GmCBL1 from soybean, a homolog of AtCBL1 in Arabidopsis. GmCBL1 was differentially induced by multiple abiotic stress and plant hormones, and its transcripts were abundant in seedlings and mature roots. We over-expressed GmCBL1 in Arabidopsis and found that it enhanced tolerances to both high salt and drought stresses in the transgenic plants. Overexpression of GmCBL1 also promoted hypocotyl elongation under light conditions. GmCBL1 may regulate stress tolerance through activation of stress-related genes, and may control hypocotyl development by altering the expression of gibberellin biosynthesis-related genes. This study identifies a putative soybean CBL gene that functions in both stress tolerance and light-dependent hypocotyl development. PMID:23044418

Li, Zhi-Yong; Xu, Zhao-Shi; He, Guang-Yuan; Yang, Guang-Xiao; Chen, Ming; Li, Lian-Cheng; Ma, You-Zhi

2012-11-01

247

Root hair sweet growth  

PubMed Central

Root hairs are single cells specialized in the absorption of water and nutrients from the soil. Growing root hairs require intensive cell-wall changes to accommodate cell expansion at the apical end by a process known as tip or polarized growth. We have recently shown that cell wall glycoproteins such as extensins (EXTs) are essential components of the cell wall during polarized growth. Proline hydroxylation, an early posttranslational modification of cell wall EXTs that is catalyzed by prolyl 4-hydroxylases (P4Hs), defines the subsequent O-glycosylation sites in EXTs. Biochemical inhibition or genetic disruption of specific P4Hs resulted in the blockage of polarized growth in root hairs. Our results demonstrate that correct hydroxylation and also further O-glycosylation on EXTs are essential for cell-wall self-assembly and, hence, root hair elongation. The changes that O-glycosylated cell-wall proteins like EXTs undergo during cell growth represent a starting point to unravel the entire biochemical pathway involved in plant development.

Velasquez, Silvia M; Iusem, Norberto D

2011-01-01

248

Elongational perturbations on nematic liquid crystal polymers under a weak shear  

Microsoft Academic Search

The two-dimensional Smoluchowski equation is employed to study the effect of elongational perturbations on nematic liquid crystal polymers under a weak shear. We use the multiscale asymptotic analysis to show that (1) when the elongational perturbation is small relative to the weak shear, the orientational probability density function (pdf) tumbles periodically only in an intermediate range of polymer concentration; outside

Hong Zhou; Hongyun Wang

2007-01-01

249

Change in Apoplastic Aluminum during the Initial Growth Response to Aluminum by Roots of a Tolerant Maize Variety1  

PubMed Central

Root elongation, hematoxylin staining, and changes in the ultrastructure of root-tip cells of an Al-tolerant maize variety (Zea mays L. C 525 M) exposed to nutrient solutions with 20 ?m Al (2.1 ?m Al3+ activity) for 0, 4, and 24 h were investigated in relation to the subcellular distribution of Al using scanning transmission electron microscopy and energy-dispersive x-ray microanalysis on samples fixed by different methods. Inhibition of root-elongation rates, hematoxylin staining, cell wall thickening, and disturbance of the distribution of pyroantimoniate-stainable cations, mainly Ca, was observed only after 4 and not after 24 h of exposure to Al. The occurrence of these transient, toxic Al effects on root elongation and in cell walls was accompanied by the presence of solid Al-P deposits in the walls. Whereas no Al was detectable in cell walls after 24 h, an increase of vacuolar Al was observed after 4 h of exposure. After 24 h, a higher amount of electron-dense deposits containing Al and P or Si was observed in the vacuoles. These results indicate that in this tropical maize variety, tolerance mechanisms that cause a change in apoplastic Al must be active. Our data support the hypothesis that in Al-tolerant plants, Al can rapidly cross the plasma membrane; these data clearly contradict the former conclusions that Al mainly accumulates in the apoplast and enters the symplast only after severe cell damage has occurred.

Vazquez, Maria Dolores; Poschenrieder, Charlotte; Corrales, Isabel; Barcelo, Juan

1999-01-01

250

Correlations between polyamine ratios and growth patterns in seedling roots  

NASA Technical Reports Server (NTRS)

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.

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

1985-01-01

251

Effect of Second-Phase Precipitates on Local Elongation in Extruded Magnesium Alloys  

NASA Astrophysics Data System (ADS)

The effect of precipitates on room-temperature tensile ductility, specifically post-uniform elongation (local elongation), was investigated in three magnesium alloys. The alloys were prepared by extrusion and had different types of precipitate morphology. Tensile tests revealed an almost total absence of local elongation in an alloy with intergranular precipitate particles (a few hundred nanometers in diameter), in spite of a relatively high total elongation to fracture of 17%. On the other hand, an alloy with densely dispersed fine intragranular precipitates (up to a few tens of nanometers in diameter) showed the highest local elongation at 17% and an alloy with a sparse dispersion showed moderate local elongation. The fracture surfaces of the latter two alloys had a primarily ductile appearance with dimples. For the specimen that showed the highest local elongation, twinning was observed in the necked portion, whereas very few twins were observed in the uniformly elongated portion. It was suggested that fine precipitates in the grain interior inhibit the formation of twins, a feature that can be exploited to enhance local elongation in magnesium alloys.

Watanabe, Hiroyuki

2013-11-01

252

A cotton annexin protein AnxGb6 regulates fiber elongation through its interaction with actin 1.  

PubMed

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

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

2013-01-01

253

Race:cultivar-specific induction of enzymes related to phytoalexin biosynthesis in soybean roots following infection with Phytophthora megasperma f. sp. glycinea.  

PubMed

Primary roots of soybean [Glycine max (L.), cv Harosoy 63] seedlings were inoculated with zoospores from either race 1 (incompatible, host resistant) or race 3 (compatible, host susceptible) of Phytophthora megasperma f. sp. glycinea (Pmg) and the activities of phenylalanine ammonia-lyase (PAL), chalcone synthase (CHS), isoflavone synthase, and dihydroxypterocarpan 6a-hydroxylase related to phytoalexin (glyceollin) biosynthesis, and of glucose-6-phosphate dehydrogenase (Glc-6-PDH) and glutamate dehydrogenase (Glu-DH) were determined at various times after inoculation. About 2-4 h after inoculation with race 1, the activities of PAL, CHS, and pterocarpan 6a-hydroxylase were higher than after inoculation with race 3 and increased considerably thereafter. In contrast, activities of these enzymes in the compatible interaction were equal to or only slightly higher than in the controls over the entire infection period investigated (2-8 h). Isoflavone synthase did not increase until 7 h after inoculation with race 1. There were no significant differences in activities for Glc-6-PDH and Glu-DH between inoculated roots and controls. The results show that infection of soybean roots with zoospores of Pmg race 1 causes a race:cultivar-specific early induction of enzymes involved in glyceollin synthesis, whereas such an induction does not occur with zoospores of race 3. These findings are in agreement with the race:cultivar-specific accumulation of glyceollin in soybean roots reported previously [M. G. Hahn, A. Bonhoff, and H. Grisebach (1985) Plant Physiol. 77, 591-601]. PMID:3963819

Bonhoff, A; Loyal, R; Ebel, J; Grisebach, H

1986-04-01

254

A Chalcone and Two Related Flavonoids Released from Alfalfa Roots Induce nod Genes of Rhizobium meliloti1  

PubMed Central

Flavonoid signals from alfalfa (Medicago sativa L.) induce transcription of nodulation (nod) genes in Rhizobium meliloti. Previous investigations identified the flavone luteolin as an active inducer in alfalfa seed extracts, but the nature of nod inducers released from roots has not been reported. Root exudate from 3-day-old alfalfa seedlings was purified and then assayed for biological activity with a nodABC-lacZ fusion in R. meliloti. Indentities of major nod inducers were established by spectroscopic analyses (ultraviolet/visible, proton nuclear magnetic resonance, and mass spectroscopy) and comparison with authentic standards. Major nod inducers, which were identified as 4?,7-dihydroxyflavone, 4?-7-dihydroxyflavanone, and 4,4?-dihydroxy-2?-methoxychalcone, were released from seedling roots at 54, 22, and 20 picomole·plant?1·day?1, respectively. Luteolin was not found in these root exudates. The 4,4?-dihydroxy-2?-methoxychalcone induced nod genes at a concentration one order of magnitude lower than luteolin and is the first naturally released chalcone reported to have this function. Moderate and weak nod-inducing activity was associated, respectively, with 4?,7-dihydroxyflavone and 4?,7-dihydroxyflavanone.

Maxwell, Carl A.; Hartwig, Ueli A.; Joseph, Cecillia M.; Phillips, Donald A.

1989-01-01

255

FOLIAR LEACHING AND ROOT UPTAKE OF CA, MG, AND K IN RELATION TO ACID FOG EFFECTS ON DOUGLAS-FIR  

EPA Science Inventory

The impact of acid fog on foliar leaching and root uptake of Ca, Mg, and K by Douglas-fir (Pseudotsuga menziesii) seedlings was examined. n a factorial experiment, 1-year old seedlings were grown in solution culture at two levels of nutrient availability (low and moderate) and ex...

256

Foliar Leaching and Root Uptake of Ca, Mg and K in Relation to Acid Fog Effects on Douglas-Fir.  

National Technical Information Service (NTIS)

The impact of acid fog on foliar leaching and root uptake of Ca, Mg, and K by Douglas-fir (Pseudotsuga menziesii) seedlings was examined. In a factorial experiment, 1-year old seedlings were grown in a solution culture at two levels of nutrient availabili...

D. P. Turner D. T. Tingey

1990-01-01

257

Growth, Water Relations, and Accumulation of Organic and Inorganic Solutes in Roots of Maize Seedlings during Salt Stress.  

PubMed

Seedlings of maize (Zea mays L. cv Pioneer 3906), hydroponically grown in the dark, were exposed to NaCl either gradually (salt acclimation) or in one step (salt shock). In the salt-acclimation treatment, root extension was indistinguishable from that of unsalinized controls for at least 6 d at concentrations up to 100 mM NaCl. By contrast, salt shock rapidly inhibited extension, followed by a gradual recovery, so that by 24 h extension rates were the same as for controls, even at 150 mM NaCl. Salt shock caused a rapid decrease in root water and solute potentials for the apical zones, and the estimated turgor potential showed only a small decline; similar but more gradual changes occurred with salt acclimation. The 5-bar decrease in root solute potential with salt shock (150 mM NaCl) during the initial 10 min of exposure could not be accounted for by dehydration, indicating that substantial osmotic adjustment occurred rapidly. Changes in concentration of inorganic solutes (Na+, K+, and Cl-) and organic solutes (proline, sucrose, fructose, and glucose) were measured during salt shock. The contribution of these solutes to changes in root solute potential with salinization was estimated. PMID:12223650

Rodriguez, H. G.; Roberts, JKM.; Jordan, W. R.; Drew, M. C.

1997-03-01

258

Relation Between Ca and Sr Transport Rates, as Determined Simultaneously in Isolated Segments of Vetch, Barley, and Pine Roots.  

National Technical Information Service (NTIS)

Root segments of vetch, barley, and pine were exposed to nutrient containing 85Sr and 45Ca tracers. Transport in both vetch and barley usually declined before an elapsed time of 24 hours unlike corn, which maintains its steady state beyond 24 hours. Pine ...

M. E. Hutchin B. E. Vaughan

1968-01-01

259

Growth, Water Relations, and Accumulation of Organic and Inorganic Solutes in Roots of Maize Seedlings during Salt Stress.  

PubMed Central

Seedlings of maize (Zea mays L. cv Pioneer 3906), hydroponically grown in the dark, were exposed to NaCl either gradually (salt acclimation) or in one step (salt shock). In the salt-acclimation treatment, root extension was indistinguishable from that of unsalinized controls for at least 6 d at concentrations up to 100 mM NaCl. By contrast, salt shock rapidly inhibited extension, followed by a gradual recovery, so that by 24 h extension rates were the same as for controls, even at 150 mM NaCl. Salt shock caused a rapid decrease in root water and solute potentials for the apical zones, and the estimated turgor potential showed only a small decline; similar but more gradual changes occurred with salt acclimation. The 5-bar decrease in root solute potential with salt shock (150 mM NaCl) during the initial 10 min of exposure could not be accounted for by dehydration, indicating that substantial osmotic adjustment occurred rapidly. Changes in concentration of inorganic solutes (Na+, K+, and Cl-) and organic solutes (proline, sucrose, fructose, and glucose) were measured during salt shock. The contribution of these solutes to changes in root solute potential with salinization was estimated.

Rodriguez, H. G.; Roberts, JKM.; Jordan, W. R.; Drew, M. C.

1997-01-01

260

Eckart axis conditions and the minimization of the root-mean-square deviation: two closely related problems.  

PubMed

We highlight the fact that the rotation matrix minimizing the root-mean-square deviation between two molecular conformations [W. Kabsch, Acta Cryst. A32, 922 (1976)] also satisfies the Eckart axis conditions [C. Eckart, Phys. Rev. 47, 552 (1935)]. PMID:15974649

Kudin, Konstantin N; Dymarsky, Anatoly Y

2005-06-01

261

Enzymes of N-methylputrescine biosynthesis in relation to hyoscyamine formation in transformed root cultures of Datura stramonium and Atropa belladonna  

Microsoft Academic Search

The activities of enzymes related to the biosynthesis of N-methylputrescine, a precursor of the alkaloid hyoscyamine, have been measured in root cultures of Datura stramonium L. and Atropa belladonna L. transformed with Agrobacterium rhizogenes. Ornithine d-Nmethyltransferase and d-N-methylornithine decafboxylase were undetectable, indicating that d-N-methylornithine is an unlikely intermediate in the formation of N-methylputrescine. The activity of putrescine-N-methyltransferase (EC 2.1.1.53) was

Nicholas J. Walton; Richard J. Robins; Abigael C. J. Peerless

1990-01-01

262

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

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

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

2006-01-01

263

Development of the fingerprints for the quality of the roots of Salvia miltiorrhiza and its related preparations by HPLC-DAD and LC–MS n  

Microsoft Academic Search

High-performance liquid chromatographic (HPLC) fingerprints were developed for identification of both lipophilic and hydrophilic components of the roots of Salvia miltiorrhiza and four related preparations. These samples were separated with an Agilent Zorbax Extend C18 reserved-phase column (5?m, 250mm×4.6mm) by linear gradient elution using water-phosphoric acid (100:0.026, v\\/v) and acetonitrile as mobile phase. The flow rate was 0.8ml\\/min and the

Ai-Hua Liu; Yan-Hua Lin; Min Yang; Hui Guo; Shu-Hong Guan; Jiang-Hao Sun; De-An Guo

2007-01-01

264

Effect of lowering the root\\/shoot ratio by pruning roots on water use efficiency and grain yield of winter wheat  

Microsoft Academic Search

A pot and a field experiment were conducted to assess the effects of root\\/shoot ratio (R\\/S) on the water use efficiency (WUE) and grain yield of winter wheat. The R\\/S was regulated by pruning the roots during the stem elongation stage, resulting in reduced root systems of the plants. At the heading stage, the root dry weight of root-pruned plants

Shou-Chen Ma; Feng-Min Li; Bing-Cheng Xu; Zhan-Bin Huang

2010-01-01

265

Osteogenetic changes in elongated styloid processes of Eagle syndrome patients.  

PubMed

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

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

2014-07-01

266

Simplicial quantum gravity in the elongated phase  

NASA Astrophysics Data System (ADS)

We discuss the elongated phase of four-dimensional simplicial quantum gravity by exploiting recent analytical results. In particular using Walkup's theorem we prove that the dominating configurations in the elongated phase are treelike structures called ``stacked spheres.'' Such configurations can be mapped into branched polymers and baby universes arguments are used in order to analyze the critical behavior of theory in the weak coupling regime.

Gionti, Gabriele

1998-12-01

267

Ion-Accelerator Grids With Elongated Holes  

NASA Technical Reports Server (NTRS)

Ion-accelerator grids designed and fabricated with elongated holes instead of circular holes. Although grids made of lightweight carbon/carbon composites and conceived for use in ion thrusters for spacecraft, also made of other materials and installed in industrial ion accelerators for material-processing applications. Elongated holes offer advantages of lower costs of fabrication and option to increase open-area fractions of grids, thereby increasing output ion currents extracted through grids.

Mueller, Juergen

1996-01-01

268

Rooting gene trees without outgroups: EP rooting.  

PubMed

Gene sequences are routinely used to determine the topologies of unrooted phylogenetic trees, but many of the most important questions in evolution require knowing both the topologies and the roots of trees. However, general algorithms for calculating rooted trees from gene and genomic sequences in the absence of gene paralogs are few. Using the principles of evolutionary parsimony (EP) (Lake JA. 1987a. A rate-independent technique for analysis of nucleic acid sequences: evolutionary parsimony. Mol Biol Evol. 4:167-181) and its extensions (Cavender, J. 1989. Mechanized derivation of linear invariants. Mol Biol Evol. 6:301-316; Nguyen T, Speed TP. 1992. A derivation of all linear invariants for a nonbalanced transversion model. J Mol Evol. 35:60-76), we explicitly enumerate all linear invariants that solely contain rooting information and derive algorithms for rooting gene trees directly from gene and genomic sequences. These new EP linear rooting invariants allow one to determine rooted trees, even in the complete absence of outgroups and gene paralogs. EP rooting invariants are explicitly derived for three taxon trees, and rules for their extension to four or more taxa are provided. The method is demonstrated using 18S ribosomal DNA to illustrate how the new animal phylogeny (Aguinaldo AMA et al. 1997. Evidence for a clade of nematodes, arthropods, and other moulting animals. Nature 387:489-493; Lake JA. 1990. Origin of the metazoa. Proc Natl Acad Sci USA 87:763-766) may be rooted directly from sequences, even when they are short and paralogs are unavailable. These results are consistent with the current root (Philippe H et al. 2011. Acoelomorph flatworms are deuterostomes related to Xenoturbella. Nature 470:255-260). PMID:22593551

Sinsheimer, Janet S; Little, Roderick J A; Lake, James A

2012-01-01

269

Rooting Gene Trees without Outgroups: EP Rooting  

PubMed Central

Gene sequences are routinely used to determine the topologies of unrooted phylogenetic trees, but many of the most important questions in evolution require knowing both the topologies and the roots of trees. However, general algorithms for calculating rooted trees from gene and genomic sequences in the absence of gene paralogs are few. Using the principles of evolutionary parsimony (EP) (Lake JA. 1987a. A rate-independent technique for analysis of nucleic acid sequences: evolutionary parsimony. Mol Biol Evol. 4:167–181) and its extensions (Cavender, J. 1989. Mechanized derivation of linear invariants. Mol Biol Evol. 6:301–316; Nguyen T, Speed TP. 1992. A derivation of all linear invariants for a nonbalanced transversion model. J Mol Evol. 35:60–76), we explicitly enumerate all linear invariants that solely contain rooting information and derive algorithms for rooting gene trees directly from gene and genomic sequences. These new EP linear rooting invariants allow one to determine rooted trees, even in the complete absence of outgroups and gene paralogs. EP rooting invariants are explicitly derived for three taxon trees, and rules for their extension to four or more taxa are provided. The method is demonstrated using 18S ribosomal DNA to illustrate how the new animal phylogeny (Aguinaldo AMA et al. 1997. Evidence for a clade of nematodes, arthropods, and other moulting animals. Nature 387:489–493; Lake JA. 1990. Origin of the metazoa. Proc Natl Acad Sci USA 87:763–766) may be rooted directly from sequences, even when they are short and paralogs are unavailable. These results are consistent with the current root (Philippe H et al. 2011. Acoelomorph flatworms are deuterostomes related to Xenoturbella. Nature 470:255–260).

Sinsheimer, Janet S.; Little, Roderick J. A.; Lake, James A.

2012-01-01

270

Chromosaponin I Specifically Interacts with AUX1 Protein in Regulating the Gravitropic Response of Arabidopsis Roots  

Microsoft Academic Search

We have found that chromosaponin I (CSI), a g-pyronyl-triterpenoid saponin isolated from pea (Pisum sativum L. cv Alaska), specifically interacts with AUX1 protein in regulating the gravitropic response of Arabidopsis roots. Application of 60 mm CSI disrupts the vertically oriented elongation of wild-type roots grown on agar plates but orients the elongation of agravitropic mutant aux1-7 roots toward the gravity.

Abidur Rahman; Arifa Ahamed; Taisaku Amakawa; Nobuharu Goto; Seiji Tsurumi

2001-01-01

271

SIZ1 regulation of phosphate starvation-induced root architecture remodeling involves the control of auxin accumulation.  

PubMed

Phosphate (Pi) limitation causes plants to modulate the architecture of their root systems to facilitate the acquisition of Pi. Previously, we reported that the Arabidopsis (Arabidopsis thaliana) SUMO E3 ligase SIZ1 regulates root architecture remodeling in response to Pi limitation; namely, the siz1 mutations cause the inhibition of primary root (PR) elongation and the promotion of lateral root (LR) formation. Here, we present evidence that SIZ1 is involved in the negative regulation of auxin patterning to modulate root system architecture in response to Pi starvation. The siz1 mutations caused greater PR growth inhibition and LR development of seedlings in response to Pi limitation. Similar root phenotypes occurred if Pi-deficient wild-type seedlings were supplemented with auxin. N-1-Naphthylphthalamic acid, an inhibitor of auxin efflux activity, reduced the Pi starvation-induced LR root formation of siz1 seedlings to a level equivalent to that seen in the wild type. Monitoring of the auxin-responsive reporter DR5::uidA indicated that auxin accumulates in PR tips at early stages of the Pi starvation response. Subsequently, DR5::uidA expression was observed in the LR primordia, which was associated with LR elongation. The time-sequential patterning of DR5::uidA expression occurred earlier in the roots of siz1 as compared with the wild type. In addition, microarray analysis revealed that several other auxin-responsive genes, including genes involved in cell wall loosening and biosynthesis, were up-regulated in siz1 relative to wild-type seedlings in response to Pi starvation. Together, these results suggest that SIZ1 negatively regulates Pi starvation-induced root architecture remodeling through the control of auxin patterning. PMID:21156857

Miura, Kenji; Lee, Jiyoung; Gong, Qingqiu; Ma, Shisong; Jin, Jing Bo; Yoo, Chan Yul; Miura, Tomoko; Sato, Aiko; Bohnert, Hans J; Hasegawa, Paul M

2011-02-01

272

Glycoproteome of Elongating Cotton Fiber Cells*  

PubMed Central

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

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

2013-01-01

273

Metal (Pb, Zn and Cu) uptake and tolerance by mangroves in relation to root anatomy and lignification/suberization.  

PubMed

Metal pollution has been widely reported in mangrove wetlands; however, the mechanisms involved in metal detoxification by mangroves are still poorly understood. This study aimed to investigate the possible function of root anatomy and lignification/suberization on metal uptake and tolerance in seedlings of six species of mangroves. The results revealed that the three rhizophoraceous species (Bruguiera gymnorrhiza (L.) Poir, Kandelia obovata Sheue, Liu & Yong and Rhizophora stylosa Griff) consistently exhibited higher metal tolerances than the three pioneer species (Aegiceras corniculatum (Linn.) Blanco, Acanthus ilicifolius L. and Avicennia marina (Forsk.) Viern.). Moreover, metal-tolerant species often exhibited a thick exodermis with high lignification and suberization. The tolerance indices of the mangroves were found to be positively correlated with the amounts of lignin and suberin deposition within the exodermal cell walls. The observed metal uptake by the excised roots further illustrated that a lignified/suberized exodermis directly delayed the entry of metals into the roots, and thereby contributed to a higher tolerance to heavy metals. In summary, the present study proposes a barrier property of the lignified/suberized exodermis in dealing with the stresses of heavy metals, such that the mangroves which possessed more extensive lignification/suberization within the exodermis appeared to exhibit higher metal tolerance. PMID:24965807

Cheng, Hao; Jiang, Zhao-Yu; Liu, Yong; Ye, Zhi-Hong; Wu, Mei-Lin; Sun, Cui-Ci; Sun, Fu-Lin; Fei, Jiao; Wang, You-Shao

2014-06-01

274

A test of microtubule translocation during neurite elongation  

PubMed Central

In a previous study using PC-12 cells (Lim, S. S., P. J. Sammak, and G. G. Borisy, 1989. J. Cell Biol. 109:253-263), we presented evidence that the microtubule component of the neuronal cytoskeleton is differentially dynamic but stationary. However, neurites of PC-12 cells grow slowly, hindering a stringent test of slow axonal transport mechanisms under conditions where growth was substantial. We therefore extended our studies to primary cultures of dorsal root ganglion cells where the rate of neurite outgrowth is rapid. Cells were microinjected with X-rhodamine-labeled tubulin 7-16 h after plating. After a further incubation for 6-18 h, the cells were photobleached with an argon ion laser. Using a cooled charged couple device and video microscopy, the cells were monitored for growth of the neurite and movement and recovery of fluorescence in the bleached zone. As for PC-12 cells, all bleached zones in the neurite recovered their fluorescence, indicating that incorporation of tubulin occurred along the neurite. Despite increases in neurite length of up to 70 microns, and periods of observation of up to 5 h, no movement of bleached zones was observed. We conclude that neurite elongation cannot be accounted for by the transport of a microtubule network assembled only at the cell body. Rather, microtubules turn over all along the length of the neurite and neurite elongation occurs by net assembly at the tip.

1990-01-01

275

Auxin redistribution modulates plastic development of root system architecture under salt stress in Arabidopsis thaliana.  

PubMed

Auxin plays an important role in the modulation of root system architecture. The effect of salinity on primary root growth has been extensively studied. However, how salinity affects lateral root development and its underlying molecular mechanisms is still unclear. Here, we report that high salt exposure suppresses lateral root initiation and organogenesis, resulting in the abortion of lateral root development. In contrast, salt stress markedly promotes lateral root elongation. Histochemical staining showed that the quantity of auxin and its patterning in roots were both greatly altered by exposure to high concentrations of salt, as compared with those found in the untreated control. Physiological experiments using transport inhibitors and genetic analysis revealed that the auxin transport pathway is important for salt-induced root development. These results demonstrate that auxin transport activities are required for remodeling lateral root formation and elongation and for adaptive root system development under salt stress. PMID:19457582

Wang, Youning; Li, Kexue; Li, Xia

2009-10-15

276

The influence of calcium and pH on growth in primary roots of Zea mays  

NASA Technical Reports Server (NTRS)

We investigated the interaction of Ca2+ and pH on root elongation in Zea mays L. cv. B73 x Missouri 17 and cv. Merit. Seedlings were raised to contain high levels of Ca2+ (HC, imbibed and raised in 10 mM CaCl2) or low levels of Ca2+ (LC, imbibed and raised in distilled water). In HC roots, lowering the pH (5 mM MES/Tris) from 6.5 to 4.5 resulted in strong, long-lasting growth promotion. Surprisingly, increasing the pH from 6.5 to 8.5 also resulted in strong growth promotion. In LC roots acidification of the medium (pH 6.5 to 4.5) resulted in transient growth stimulation followed by a gradual decline in the growth rate toward zero. Exposure of LC roots to high pH (pH shift from 6.5 to 8.5) also promoted growth. Addition of EGTA resulted in strong growth promotion in both LC and HC roots. The ability of EGTA to stimulate growth appeared not to be related to H+ release from EGTA upon Ca2+ chelation since, 1) LC roots showed a strong and prolonged response to EGTA, but only a transient response to acid pH, and 2) promotion of growth by EGTA was observed in strongly buffered solutions. We also examined the pH dependence of the release of 45Ca2+ from roots of 3-day-old seedlings grown from grains imbibed in 45Ca2+. Release of 45Ca2+ from the root into agar blocks placed on the root surface was greater the more acidic the pH of the blocks. The results indicate that Ca2+ may be necessary for the acid growth response in roots.

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

1988-01-01

277

Natural H+ Currents Traverse Growing Roots and Root Hairs of Barley (Hordeum vulgare L.) 1  

PubMed Central

With the aid of an extracellular vibrating electrode, natural electric fields were detected and measured in the medium near growing roots and root hairs of barley seedlings. An exploration of these fields indicates that both the root as a whole, as well as individual root hairs, drive large steady currents through themselves. Current consistently enters both the main elongation zone of the root as well as the growing tips of elongating root hairs; it leaves the surface of the root beneath the root hairs. These currents enter with a density of about 2 microamperes per square centimeter, leave with a density of about 0.5 to 1 microampere per square centimeter, and total about 30 nanoamperes. Responses of the natural fields to changes in the ionic composition of the medium as well as observations of the pH pattern in the medium near the roots (made with bromocresol purple) together indicate that much of the current consists of hydrogen ions. Altogether, H+ ions seem to leak into growing cells or cell parts and to be pumped out of nongrowing ones. Images

Weisenseel, Manfred H.; Dorn, Alfred; Jaffe, Lionel F.

1979-01-01

278

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

PubMed

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

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

2011-01-01

279

Root traits and microbial community interactions in relation to phosphorus availability and acquisition, with particular reference to Brassica  

PubMed Central

Brassicas are among the most widely grown and important crops worldwide. Phosphorus (P) is a key mineral element in the growth of all plants and is largely supplied as inorganic rock-phosphate, a dwindling resource, which is likely to be an increasingly significant factor in global agriculture. In order to develop crops which can abstract P from the soil, utilize it more efficiently, require less of it or obtain more from other sources such as soil organic P reservoirs, a detailed understanding the factors that influence P metabolism and cycling in plants and associated soil is required. This review focuses on the current state of understanding of root traits, rhizodeposition and rhizosphere community interaction as it applies to P solubilization and acquisition, with particular reference to Brassica species. Physical root characteristics, exudation of organic acids (particularly malate and citrate) and phosphatase enzymes are considered and the potential mechanisms of control of these responses to P deficiency examined. The influence of rhizodeposits on the development of the rhizosphere microbial community is discussed and the specific features of this community in response to P deficiency are considered; specifically production of phosphatases, phytases and phosphonate hydrolases. Finally various potential approaches for improving overall P use efficiency in Brassica production are discussed.

Hunter, Paul J.; Teakle, Grahams R.; Bending, Gary D.

2014-01-01

280

The structure of elongated viral capsids.  

PubMed

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

Luque, Antoni; Reguera, David

2010-06-16

281

MIGRATORY CELL LOCOMOTION VERSUS NERVE AXON ELONGATION  

PubMed Central

The effects of lanthanum ions (La+++) on the locomotion and adhesion of g lial cells and elongating nerve axons are reported. La+++ increases adhesion of both glia and of nerve growth cones to a plastic substratum. La+++ also markedly reduces glia locomotion, but it does not inhibit nerve elongation. Electron-opaque deposits are seen on the cell surface and within cytoplasmic vesicles of glia and nerves cultured in a La+++-containing medium. Possible modes of action for La+++ are discussed, particularly the possibilities that Ca++ fluxes or Ca++ involvement in adhesion are altered by La+++. The results are consistent with the hypothesis that cell migration and nerve axon elongation differ in mechanism, with respect to both adhesive interactions and the activity of microfilament systems.

Letourneau, Paul C.; Wessells, Norman K.

1974-01-01

282

Impact of galactoglucomannan oligosaccharides on elongation growth in intact mung bean plants  

Microsoft Academic Search

The impact of exogenously applied galactoglucomannan oligosaccharides (GGMOs) and their structurally modified forms (GGMOs-r—galactoglucomannosyl alditols, GGMOs-g—with reduced galactose content) on the growth of mung bean (Vigna radiata (L.) Wilczek) intact plants cultured in hydroponics has been determined. GGMOs alone or in combination with exogenously added IBA have influenced (with stimulation and\\/or inhibition effect) hypocotyl and seminal root elongation, adventitious and

Karin Kollárová; Danica Richterová; ?udmila Slováková; Mária Henselová; Peter Capek; Desana Lišková

2009-01-01

283

Phosphate availability regulates root system architecture in Arabidopsis.  

PubMed

Plant root systems are highly plastic in their development and can adapt their architecture in response to the prevailing environmental conditions. One important parameter is the availability of phosphate, which is highly immobile in soil such that the arrangement of roots within the soil will profoundly affect the ability of the plant to acquire this essential nutrient. Consistent with this, the availability of phosphate was found to have a marked effect on the root system architecture of Arabidopsis. Low phosphate availability favored lateral root growth over primary root growth, through increased lateral root density and length, and reduced primary root growth mediated by reduced cell elongation. The ability of the root system to respond to phosphate availability was found to be independent of sucrose supply and auxin signaling. In contrast, shoot phosphate status was found to influence the root system architecture response to phosphate availability. PMID:11402214

Williamson, L C; Ribrioux, S P; Fitter, A H; Leyser, H M

2001-06-01

284

Kinetic analysis of the template effect in ribooligoguanylate elongation  

NASA Technical Reports Server (NTRS)

The paper presents kinetic studies on the reaction of elongation of the 3-prime-5-prime-linked ribooligoguanylates with guanosine 5-prime-phospho-2-methylimidazolide (2-MelmpG) in the presence or absence of a complementary template, the polycytidylic acid. In the absence of poly(C), the reaction leads to three isomeric oligomers that are elongated by one monomer unit: the 3-prime-5-prime linked, the 2-prime-5-prime linked, and the pyrophosphate, formed in a ratio of 1:2:5. In the presence of the template, the reaction is 20-fold faster and yields products (n + 1), (n + 2), (n + 3), etc., as long as 2-MelmpG is available. The formation of the natural, 3-prime-5-prime-linked isomer, is enhanced selectively by 140-fold at 37 C, and its relative yield increases with decreasing temperature.

Kanavarioti, Anastassia; White, David H.

1987-01-01

285

New Insights on Plant Cell Elongation: A Role for Acetylcholine  

PubMed Central

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

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

2014-01-01

286

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

PubMed

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

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

2014-01-01

287

Modulation of development, growth dynamics, wall crystallinity, and infection sites in white clover root hairs by membrane chitolipooligosaccharides from Rhizobium leguminosarum biovar trifolii.  

PubMed Central

We used bright-field, time-lapse video, cross-polarized, phase-contrast, and fluorescence microscopies to examine the influence of isolated chitolipooligosaccharides (CLOSs) from wild-type Rhizobium leguminosarum bv. trifolii on development of white clover root hairs, and the role of these bioactive glycolipids in primary host infection. CLOS action caused a threefold increase in the differentiation of root epidermal cells into root hairs. At maturity, root hairs were significantly longer because of an extended period of active elongation without a change in the elongation rate itself. Time-series image analysis showed that the morphological basis of CLOS-induced root hair deformation is a redirection of tip growth displaced from the medial axis as previously predicted. Further studies showed several newly described infection-related root hair responses to CLOSs, including the localized disruption of the normal crystallinity in cell wall architecture and the induction of new infection sites. The application of CLOS also enabled a NodC- mutant of R. leguminosarum bv. trifolii to progress further in the infection process by inducing bright refractile spot modifications of the deformed root hair walls. However, CLOSs did not rescue the ability of the NodC- mutant to induce marked curlings or infection threads within root hairs. These results indicate that CLOS Nod factors elicit several host responses that modulate the growth dynamics and symbiont infectibility of white clover root hairs but that CLOSs alone are not sufficient to permit successful entry of the bacteria into root hairs during primary host infection in the Rhizobium-clover symbiosis.

Dazzo, F B; Orgambide, G G; Philip-Hollingsworth, S; Hollingsworth, R I; Ninke, K O; Salzwedel, J L

1996-01-01

288

Descendant root volume varies as a function of root type: estimation of root biomass lost during uprooting in Pinus pinaster  

PubMed Central

Root systems of woody plants generally display a strong relationship between the cross-sectional area or cross-sectional diameter (CSD) of a root and the dry weight of biomass (DWd) or root volume (Vd) that has grown (i.e., is descendent) from a point. Specification of this relationship allows one to quantify root architectural patterns and estimate the amount of material lost when root systems are extracted from the soil. However, specifications of this relationship generally do not account for the fact that root systems are comprised of multiple types of roots. We assessed whether the relationship between CSD and Vd varies as a function of root type. Additionally, we sought to identify a more accurate and time-efficient method for estimating missing root volume than is currently available. We used a database that described the 3D root architecture of Pinus pinaster root systems (5, 12, or 19 years) from a stand in southwest France. We determined the relationship between CSD and Vd for 10,000 root segments from intact root branches. Models were specified that did and did not account for root type. The relationships were then applied to the diameters of 11,000 broken root ends to estimate the volume of missing roots. CSD was nearly linearly related to the square root of Vd, but the slope of the curve varied greatly as a function of root type. Sinkers and deep roots tapered rapidly, as they were limited by available soil depth. Distal shallow roots tapered gradually, as they were less limited spatially. We estimated that younger trees lost an average of 17% of root volume when excavated, while older trees lost 4%. Missing volumes were smallest in the central parts of root systems and largest in distal shallow roots. The slopes of the curves for each root type are synthetic parameters that account for differentiation due to genetics, soil properties, or mechanical stimuli. Accounting for this differentiation is critical to estimating root loss accurately.

Danjon, Frederic; Caplan, Joshua S.; Fortin, Mathieu; Meredieu, Celine

2013-01-01

289

Neuroprotective Copper Bis(thiosemicarbazonato) Complexes Promote Neurite Elongation  

PubMed Central

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.

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

290

Neuroprotective copper bis(thiosemicarbazonato) complexes promote neurite elongation.  

PubMed

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

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

291

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

Microsoft Academic Search

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

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

1999-01-01

292

Responses of two closely related oak species, Quercus robur and Q. petraea, to excess manganese concentrations in the rooting medium.  

PubMed

Quercus robur (L.) and Q. petraea (Matt.) Liebl. are European oak species that often grow in forest soils with high soluble manganese (Mn2+) concentrations. We tested the effects of Mn2+ at concentrations of 0.0024 mM (control), 0.24 mM (typical of acidic forest soils) and 1.2 mM (typical of forest soils under strongly reducing conditions) on the growth, tissue anatomy, foliar element concentrations, subcellular element distribution and gas exchange of solution-cultured seedlings. At the highest Mn2+ concentration, seedlings were grown with and without an elevated concentration (1.2 mM) of magnesium (Mg2+). At 0.24 mM Mn2+, foliar Mn concentrations were higher than observed in the field. Vacuoles of the leaf epidermis and mesophyll were the main sites of manganese accumulation. High nutrient solution Mn2+ concentration significantly lowered foliar iron (Fe) and Mg concentrations. Elevated Mg2+ concentration raised the foliar Mg concentrations to control values, but Fe concentrations and gas exchange remained depressed. In seedlings grown in the 1.2 mM Mn2+ treatment without elevated Mg2+ damage to the phloem of the petioles and a reduction in root mass were observed in both species. The effects on shoot and root growth were greatest in Q. petraea. Alleviation of manganese toxicity symptoms by Mg2+ in Q. petraea was less effective than in Q. robur. Our results suggest that the soil solution Mn2+ concentrations that occur in European oak forests are unlikely to affect the distribution and performance of Q. robur and Q. petraea in the field. PMID:18171658

Thomas, Frank M; Sprenger, Susanne

2008-03-01

293

Root-gel interactions and the root waving behavior of Arabidopsis.  

PubMed

Arabidopsis roots grown on inclined agarose gels exhibit a sinusoidal growth pattern known as root waving. While root waving has been attributed to both intrinsic factors (e.g. circumnutation) and growth responses to external signals such as gravity, the potential for physical interactions between the root and its substrate to influence the development of this complex phenotype has been generally ignored. Using a rotating stage microscope and time-lapse digital imaging, we show that (1) root tip mobility is impeded by the gel surface, (2) this impedance causes root tip deflections by amplifying curvature in the elongation zone in a way that is distinctly nontropic, and (3) root tip impedance is augmented by normal gravitropic pressure applied by the root tip against the gel surface. Thus, both lateral corrective bending near the root apex and root tip impedance could be due to different vector components of the same graviresponse. Furthermore, we speculate that coupling between root twisting and bending is a mechanical effect resulting from root tip impedance. PMID:15247406

Thompson, Matthew V; Holbrook, N Michele

2004-07-01

294

Lectin Binding to the Root and Root Hair Tips of the Tropical Legume Macroptilium atropurpureum Urb  

PubMed Central

Ten fluorescein isothiocyanate-labeled lectins were tested on the roots of the tropical legume Macroptilium atropurpureum Urb. Four of these (concanavalin A, peanut agglutinin, Ricinis communis agglutinin I [RCA-I], wheat germ agglutinin) were found to bind to the exterior of root cap cells, the root cap slime, and the channels between epidermal cells in the root elongation zone. One of these lectins, RCA-I, bound to the root hair tips in the mature and emerging hair zones and also to sites at which root hairs were only just emerging. There was no RCA-I binding to immature trichoblasts. Preincubation of these lectins with their hapten sugars eliminated all types of root cell binding. By using a microinoculation technique, preincubation of the root surface with RCA-I lectin was found to inhibit infection and nodulation by Rhizobium spp. Preincubation of the root surface with the RCA-I hapten ?-d-galactose or a mixture of RCA-I lectin and its hapten failed to inhibit nodulation. Application of RCA-I lectin to the root surface caused no apparent detrimental effects to the root hair cells and did not prevent the growth of root hairs. The lectin did not prevent Rhizobium sp. motility or viability even after 24 h of incubation. It was concluded that the RCA-I lectin-specific sugar ?-d-galactose may be involved in the recognition or early infection stages, or both, in the Rhizobium sp. infection of M. atropurpureum. Images

Ridge, R. W.; Rolfe, B. G.

1986-01-01

295

The Snf1-related protein kinases SnRK2.4 and SnRK2.10 are involved in maintenance of root system architecture during salt stress.  

PubMed

The sucrose non-fermenting-1-related protein kinase 2 (SnRK2) family represents a unique family of plant-specific protein kinases implicated in cellular signalling in response to osmotic stress. In our studies, we observed that two class 1 SnRK2 kinases, SnRK2.4 and SnRK2.10, are rapidly and transiently activated in Arabidopsis roots after exposure to salt. Under saline conditions, snrk2.4 knockout mutants had a reduced primary root length, while snrk2.10 mutants exhibited a reduction in the number of lateral roots. The reduced lateral root density was found to be a combinatory effect of a decrease in the number of lateral root primordia and an increase in the number of arrested lateral root primordia. The phenotypes were in agreement with the observed expression patterns of genomic yellow fluorescent protein (YFP) fusions of SnRK2.10 and -2.4, under control of their native promoter sequences. SnRK2.10 was found to be expressed in the vascular tissue at the base of a developing lateral root, whereas SnRK2.4 was expressed throughout the root, with higher expression in the vascular system. Salt stress triggered a rapid re-localization of SnRK2.4-YFP from the cytosol to punctate structures in root epidermal cells. Differential centrifugation experiments of isolated Arabidopsis root proteins confirmed recruitment of endogenous SnRK2.4/2.10 to membranes upon exposure to salt, supporting their observed binding affinity for the phospholipid phosphatidic acid. Together, our results reveal a role for SnRK2.4 and -2.10 in root growth and architecture in saline conditions. PMID:22738204

McLoughlin, Fionn; Galvan-Ampudia, Carlos S; Julkowska, Magdalena M; Caarls, Lotte; van der Does, Dieuwertje; Lauričre, Christiane; Munnik, Teun; Haring, Michel A; Testerink, Christa

2012-11-01

296

Effect of elongation in divertor tokamaks  

Microsoft Academic Search

Method of maps developed by Punjabi and Boozer [A. Punjabi, A. Verma, and A. Boozer, Phys.Rev. Lett. 69, 3322 (1992)] is used to calculate the effects of elongation on stochastic layer and magnetic footprint in divertor tokamaks. The parameters in the map are chosen such that the poloidal magnetic flux chiSEP inside the ideal separatrix, the amplitude delta of magnetic

Morgin Jones; Halima Ali; Alkesh Punjabi

2008-01-01

297

Coordination of Chromatid Separation and Spindle Elongation by Antagonistic Activities of Mitotic and S-Phase CDKs  

PubMed Central

Because cohesion prevents sister-chromatid separation and spindle elongation, cohesion dissolution may trigger these two events simultaneously. However, the relatively normal spindle elongation kinetics in yeast cohesin mutants indicates an additional mechanism for the temporal control of spindle elongation. Here we show evidence indicating that S-phase CDK (cyclin dependent kinase) negatively regulates spindle elongation. In contrast, mitotic CDK promotes spindle elongation by activating Cdc14 phosphatase, which reverses the protein phosphorylation imposed by S-phase CDK. Our data suggest that S-phase CDK negatively regulates spindle elongation partly through its phosphorylation of a spindle pole body (SPB) protein Spc110. We also show that hyperactive S-phase CDK compromises the microtubule localization of Stu2, a processive microtubule polymerase essential for spindle elongation. Strikingly, we found that hyperactive mitotic CDK induces uncoupled spindle elongation and sister-chromatid separation in securin mutants (pds1?), and we speculate that asynchronous chromosome segregation in pds1? cells contributes to this phenotype. Therefore, the tight temporal control of spindle elongation and cohesin cleavage assure orchestrated chromosome separation and spindle elongation.

Liang, Fengshan; Richmond, Daniel; Wang, Yanchang

2013-01-01

298

Analysis of the defence-related mechanism in cucumber seedlings in relation to root colonization by nonpathogenic Fusarium oxysporum CS-20.  

PubMed

A defence response can be induced by nonpathogenic Fusarium oxysporum CS-20 in several crops, but the molecular mechanism has not been clearly demonstrated. In the present study, we analysed the defence mechanism of a susceptible cucumber cultivar (Cucumis sativus L. 9930) against a pathogen (F. oxysporum f. sp. cucumerinum) through the root precolonization of CS-20. A challenge inoculation assay indicated that the disease severity index (DSI) was reduced, ranging from 18.83 to 61.67 in comparison with the pathogen control. Root colonization analysis indicated that CS-20 clearly did not appear to influence the growth of cucumber seedlings. Quantitative reverse-transcriptase polymerase chain reaction (qRT-PCR) revealed that CS-20-mediated defence response was activated by PR3, LOX1 and PAL1 and the pathogen-mediated resistance response was regulated by PR1 and PR3. Moreover, both nonpathogenic and pathogenic F. oxysporum were able to upregulate NPR1 expression. In contrast to a pathogen, CS-20 can activate the Ca(2+) /CaM signal transduction pathway, and the gene expression of both CsCam7 and CsCam12 increased significantly. The gene expression analysis indicated that CS-20 strongly enhanced the expression of PR3, LOX1, PAL1, NPR1, CsCam7 and CsCam12 after inoculation. Overall, the defence response induced by CS-20 can be controlled by multiple genes in the cucumber plant. PMID:24810367

Pu, Xiaoming; Xie, Bingyan; Li, Peiqian; Mao, Zhenchuan; Ling, Jian; Shen, Huifang; Zhang, Jingxin; Huang, Ning; Lin, Birun

2014-06-01

299

Root hydrotropism: an update.  

PubMed

While water shortage remains the single-most important factor influencing world agriculture, there are very few studies on how plants grow in response to water potential, i.e., hydrotropism. Terrestrial plant roots dwell in the soil, and their ability to grow and explore underground requires many sensors for stimuli such as gravity, humidity gradients, light, mechanical stimulations, temperature, and oxygen. To date, extremely limited information is available on the components of such sensors; however, all of these stimuli are sensed in the root cap. Directional growth of roots is controlled by gravity, which is fixed in direction and intensity. However, other environmental factors, such as water potential gradients, which fluctuate in time, space, direction, and intensity, can act as a signal for modifying the direction of root growth accordingly. Hydrotropism may help roots to obtain water from the soil and at the same time may participate in the establishment of the root system. Current genetic analysis of hydrotropism in Arabidopsis has offered new players, mainly AHR1, NHR1, MIZ1, and MIZ2, which seem to modulate how root caps sense and choose to respond hydrotropically as opposed to other tropic responses. Here we review the mechanism(s) by which these genes and the plant hormones abscisic acid and cytokinins coordinate hydrotropism to counteract the tropic responses to gravitational field, light or touch stimuli. The biological consequence of hydrotropism is also discussed in relation to water stress avoidance. PMID:23258371

Cassab, Gladys I; Eapen, Delfeena; Campos, María Eugenia

2013-01-01

300

Evolution and Allometry of Calcaneal Elongation in Living and Extinct Primates  

PubMed Central

Specialized acrobatic leaping has been recognized as a key adaptive trait tied to the origin and subsequent radiation of euprimates based on its observed frequency in extant primates and inferred frequency in extinct early euprimates. Hypothesized skeletal correlates include elongated tarsal elements, which would be expected to aid leaping by allowing for increased rates and durations of propulsive acceleration at takeoff. Alternatively, authors of a recent study argued that pronounced distal calcaneal elongation of euprimates (compared to other mammalian taxa) was related primarily to specialized pedal grasping. Testing for correlations between calcaneal elongation and leaping versus grasping is complicated by body size differences and associated allometric affects. We re-assess allometric constraints on, and the functional significance of, calcaneal elongation using phylogenetic comparative methods, and present an evolutionary hypothesis for the evolution of calcaneal elongation in primates using a Bayesian approach to ancestral state reconstruction (ASR). Results show that among all primates, logged ratios of distal calcaneal length to total calcaneal length are inversely correlated with logged body mass proxies derived from the area of the calcaneal facet for the cuboid. Results from phylogenetic ANOVA on residuals from this allometric line suggest that deviations are explained by degree of leaping specialization in prosimians, but not anthropoids. Results from ASR suggest that non-allometric increases in calcaneal elongation began in the primate stem lineage and continued independently in haplorhines and strepsirrhines. Anthropoid and lorisid lineages show stasis and decreasing elongation, respectively. Initial increases in calcaneal elongation in primate evolution may be related to either development of hallucal-grasping or a combination of grasping and more specialized leaping behaviors. As has been previously suggested, subsequent increases in calcaneal elongation are likely adaptations for more effective acrobatic leaping, highlighting the importance of this behavior in early euprimate evolution.

Boyer, Doug M.; Seiffert, Erik R.; Gladman, Justin T.; Bloch, Jonathan I.

2013-01-01

301

Anatomy of the aortic and pulmonary roots  

Microsoft Academic Search

The use of the pulmonary autograft for aortic root replacement has renewed interest in the morphology of the arterial roots. In this article the basic construction of the roots, their anchorage, and their support from surrounding structures are reviewed. The arterial roots manifest a complex anatomy, with an intricate relation between the anulus and its adjacent structures, which span the

Margot M. Bartelings; Ad J. J. C. Bogers; Mark E. Galantowicz; Adriana C. Gittenberger-de Groot

1998-01-01

302

Sequential rooting media and rooting capacity of Sequoiadendron giganteum in vitro. Peroxidase activity as a marker.  

PubMed

The rooting capacities of tips of seedling, juvenile and mature shoots of Sequoiadendron giganteum were compared on different rooting media (inductive and expressive media) after passage on an elongating medium. None of the cuttings rooted when continuously kept on medium containing the auxin NAA and vitamin D2. Peroxidase activity of all those cuttings on NAA+D2 first increased during the 7-9 first days and decreased in the days after. Rooting was obtained by transfer of the cuttings after periods longer than 7-9 days from the NAA+D2 inductive medium to a basal medium supplemented or not with rutin (expressive medium). The rooting capacity was emphasized by rutin treatment and was in correlation with the peroxidase peak reached on the NAA+D2 medium. Seedlings, characterised by the highest peroxidase activity, were most performing in rooting. PMID:24248840

Berthon, J Y; Boyer, N; Gaspar, T

1987-10-01

303

Thellungiella halophila, a salt-tolerant relative of Arabidopsis thaliana, has specific root ion-channel features supporting K+/Na+ homeostasis under salinity stress.  

PubMed

Thellungiella halophila is a salt-tolerant relative of Arabidopsis thaliana with high genetic and morphological similarity. In a saline environment, T. halophila accumulates less sodium and retains more potassium than A. thaliana. Detailed electrophysiological comparison of ion currents in roots of both species showed that, unlike A. thaliana, T. halophila exhibits high potassium/sodium selectivity of the instantaneous current. This current differs in its pharmacological profile from the current through inward- and outward-rectifying K(+) channels insofar as it is insensitive to Cs(+) and TEA(+), but resembles voltage-independent channels of glycophytes as it is inhibited by external Ca(2+). Addition of Cs(+) and TEA(+) to the growth medium confirmed the key role of the instantaneous current in whole-plant sodium accumulation. A negative shift in the reversal potential of the instantaneous current under high-salt conditions was essential for decreasing sodium influx to twofold lower than the corresponding value in A. thaliana. The lower overall sodium permeability of the T. halophila root plasma membrane resulted in a smaller membrane depolarization during salt exposure, thus allowing the cells to maintain their driving force for potassium uptake. Our data provide quantitative evidence that specific features of ion channels lead to superior sodium/potassium homeostasis in a halophyte compared with a closely related glycophyte. PMID:17052322

Volkov, Vadim; Amtmann, Anna

2006-11-01

304

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

PubMed

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

Kumar, Abhay; Majeti, Narasimha Vara Prasad

2014-07-01

305

A fiber-reinforced-fluid model of anisotropic plant root cell growth  

NASA Astrophysics Data System (ADS)

We present a theoretical model of a single cell in the expansion zone of the primary root of the plant Arabidopsis thaliana. The cell undergoes rapid elongation with approximately constant radius. Growth is driven by high internal turgor pressure causing viscous stretching of the cell wall, with embedded cellulose microfibrils providing the wall with strongly anisotropic properties. We represent the cell as a thin cylindrical fiber-reinforced viscous sheet between rigid end plates. Asymptotic reduction of the governing equations, under simple sets of assumptions about fiber and wall properties, yields variants of the traditional Lockhart equation that relates the axial cell growth rate to the internal pressure. The model provides insights into the geometric and biomechanical parameters underlying bulk quantities such as wall extensibility and shows how either dynamical changes in wall material properties or passive fibre reorientation may suppress cell elongation.

Jensen, Oliver E.; Dyson, Rosemary J.

2009-11-01

306

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

PubMed

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

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

2012-11-01

307

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

NASA Technical Reports Server (NTRS)

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.

Sullivan, Roy M.; Ghosn, Louis J.

2008-01-01

308

Elongational effects in the flow of viscoelastic fluid through a wavy channel  

Microsoft Academic Search

The numerical simulation of the viscoelastic flow through a wavy channel was carried out using the modified Giesekus model.\\u000a It was found that the excess pressure loss relates to the stretch-thickening properties of elongational viscosity and the\\u000a geometry of the wavy channel through a large elongational component of the flow at the winding part of the channel. The profiles\\u000a of

Takashi Koshiba; Noriyasu Mori; Shiro Sugiyama; Kiyoji Nakamura

1999-01-01

309

Vertical distribution of fine roots in relation to soil factors in Pinus tabulaeformis Carr. forest of the Loess Plateau of China  

Microsoft Academic Search

Growth and vertical distribution of fine root closely depend on soil resource availability. Better understanding of relationships\\u000a of root profile with vertical distribution of available soil resource and soil characteristics can allow ecologists to predict\\u000a the fine root distribution on the scales ranging from individual plants to vegetation communities. The objective of the study\\u000a was to understand the fine root

Zhengchao Zhou; Zhouping Shangguan

2007-01-01

310

Arabidopsis thaliana root growth kinetics and lunisolar tidal acceleration.  

PubMed

• All living organisms on Earth are continually exposed to diurnal variations in the gravitational tidal force due to the Sun and Moon. • Elongation of primary roots of Arabidopsis thaliana seedlings maintained at a constant temperature was monitored for periods of up to 14 d using high temporal- and spatial-resolution video imaging. The time-course of the half-hourly elongation rates exhibited an oscillation which was maintained when the roots were placed in the free-running condition of continuous illumination. • Correlation between the root growth kinetics collected from seedlings initially raised under several light protocols but whose roots were subsequently in the free-running condition and the lunisolar tidal profiles enabled us to identify that the latter is the probable exogenous determinant of the rhythmic variation in root elongation rate. Similar observations and correlations using roots of Arabidopsis starch mutants suggest a central function of starch metabolism in the response to the lunisolar tide. The periodicity of the lunisolar tidal signal and the concomitant adjustments in root growth rate indicate that an exogenous timer exists for the modulation of root growth and development. • We propose that, in addition to the sensitivity to Earthly 1G gravity, which is inherent to all animals and plants, there is another type of responsiveness which is attuned to the natural diurnal variations of the lunisolar tidal force. PMID:22583121

Fisahn, Joachim; Yazdanbakhsh, Nima; Klingele, Emile; Barlow, Peter

2012-07-01

311

Sound propagation in elongated superfluid fermionic clouds  

SciTech Connect

We use hydrodynamic equations to study sound propagation in a superfluid Fermi gas at zero temperature inside a strongly elongated cigar-shaped trap, with main attention to the transition from the BCS to the unitary regime. First, we treat the role of the radial density profile in the limit of a cylindrical geometry and then evaluate numerically the effect of the axial confinement in a configuration in which a hole is present in the gas density at the center of the trap. We find that in a strongly elongated trap the speed of sound in both the BCS and the unitary regime differs by a factor {radical}(3/5) from that in a homogeneous three-dimensional superfluid. The predictions of the theory could be tested by measurements of sound-wave propagation in a setup such as that exploited by Andrews et al. [Phys. Rev. Lett. 79, 553 (1997)] for an atomic Bose-Einstein condensate.

Capuzzi, P.; Vignolo, P.; Federici, F.; Tosi, M. P. [NEST-CNR-INFM and Classe di Scienze, Scuola Normale Superiore, I-56126 Pisa (Italy)

2006-02-15

312

Impact of a short-term heat event on C and N relations in shoots vs. roots of the stress-tolerant C4 grass, Andropogon gerardii.  

PubMed

Global warming will increase heat waves, but effects of abrupt heat stress on shoot-root interactions have rarely been studied in heat-tolerant species, and abrupt heat-stress effects on root N uptake and shoot C flux to roots and soil remains uncertain. We investigated effects of a high-temperature event on shoot vs. root growth and function, including transfer of shoot C to roots and soil and uptake and translocation of soil N by roots in the warm-season drought-tolerant C4 prairie grass, Andropogon gerardii. We heated plants in the lab and field (lab=5.5days at daytime of 30+5 or 10°C; field=5days at ambient (up to 32°C daytime) vs. ambient +10°C). Heating had small or no effects on photosynthesis, stomatal conductance, leaf water potential, and shoot mass, but increased root mass and decreased root respiration and exudation per g. (13)C-labeling indicated that heating increased transfer of recently-fixed C from shoot to roots and soil (the latter likely via increased fine-root turnover). Heating decreased efficiency of N uptake by roots (uptake/g root), but did not affect total N uptake or the transfer of labeled soil (15)N to shoots. Though heating increased soil temperature in the lab, it did not do so in the field (10cm depth); yet results were similar for lab and field. Hence, acute heating affected roots more than shoots in this stress-tolerant species, increasing root mass and C loss to soil, but decreasing function per g root, and some of these effects were likely independent of direct effects from soil heating. PMID:24974323

Mainali, Kumar P; Heckathorn, Scott A; Wang, Dan; Weintraub, Michael N; Frantz, Jonathan M; Hamilton, E William

2014-07-15

313

Root growth is modulated by differential hormonal sensitivity in neighboring cells.  

PubMed

Coherent plant growth requires spatial integration of hormonal pathways and cell wall remodeling activities. However, the mechanisms governing sensitivity to hormones and how cell wall structure integrates with hormonal effects are poorly understood. We found that coordination between two types of epidermal root cells, hair and nonhair cells, establishes root sensitivity to the plant hormones brassinosteroids (BRs). While expression of the BR receptor BRASSINOSTEROID-INSENSITIVE1 (BRI1) in hair cells promotes cell elongation in all tissues, its high relative expression in nonhair cells is inhibitory. Elevated ethylene and deposition of crystalline cellulose underlie the inhibitory effect of BRI1. We propose that the relative spatial distribution of BRI1, and not its absolute level, fine-tunes growth. PMID:24736847

Fridman, Yulia; Elkouby, Liron; Holland, Neta; Vragovi?, Kristina; Elbaum, Rivka; Savaldi-Goldstein, Sigal

2014-04-15

314

Elongational viscosity of photo-oxidated LDPE  

NASA Astrophysics Data System (ADS)

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.

Rolón-Garrido, Víctor H.; Wagner, Manfred H.

2014-05-01

315

Effects of aqueous root extracts and hydrophobic root exudates of cucumber ( Cucumis sativus L.) on nuclei DNA content and expression of cell cycle-related genes in cucumber radicles  

Microsoft Academic Search

Allelopathic interactions implicate the inhibition of cell division by allelochemicals. To examine the effects of autotoxic\\u000a agents on cell cycle and plant growth, germinated cucumber seeds (Cucumis sativus L.) were incubated in solutions containing the aqueous root extracts of cucumber at 1:100, 1:50, 1:25 and 1:10 (w:v), or the hydrophobic root exudates of cucumber at 25, 50 and 100 mg·L?1. Aqueous

Yun Zhang; Min Gu; Kai Shi; Yan Hong Zhou; Jing Quan Yu

2010-01-01

316

Suppression of vertical instability in elongated current-carrying plasmas by applying stellarator rotational transforma)  

NASA Astrophysics Data System (ADS)

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.

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.

2014-05-01

317

Experiments at high elongations in DIII-D  

SciTech Connect

In this paper we discuss the limitation to elongation observed in D-shaped plasmas in the DIII-D tokamak. We find that as the triangularity is increased and {ell}{sub i} is decreased that the n = 0 mode takes on an increasingly non-rigid character. Our analysis shows two aspects of the behavior; first, an increasing variation of the m/n = 1/0 component across flux surfaces and second, an increase in the relative amplitude of a m/n = 3/0 component which couples to the m/n = 1/0 component and further destabilizes the mode.

Lazarus, E.A. (Oak Ridge National Lab., TN (USA)); Turnbull, A.D.; Kellman, A.G.; Ferron, J.R.; Helton, F.J.; Lao, L.L.; Leuer, J.A.; Strait, E.J.; Taylor, T.S. (General Atomics, San Diego, CA (USA))

1990-06-01

318

Aflatoxins in ginseng roots.  

PubMed

Ginseng roots can be infected by molds during growth, harvest and storage and result in contamination with mycotoxins. In this study, an analytical method for the determination of aflatoxins B(1), B(2), G(1) and G(2), a group of structurally similar mycotoxins, in ginseng root was developed. Test samples were extracted with methanol-water (8?+?2), diluted and passed through an immunoaffinity column packed with antibodies specific for aflatoxins. The purified extract was then derivatized with a mixture of water, trifluoroacetic acid and acetic acid. Aflatoxins were then separated and quantified by reverse phase liquid chromatography (LC) with fluorescence detection. Recoveries of total aflatoxins at 2, 4, 8 and 16 ng/g added to toxin-free 4 to 5-year old dried sliced Wisconsin ginseng were 92, 77, 91 and 83% respectively; and relative standard deviations were 3.6, 8.0, 6.9 and 2.0% respectively. A total of 11 wild simulated and 12 cultivated ginseng root samples were analysed for aflatoxins. All cultivated roots were found to be free of aflatoxin contamination. Two of the wild simulated roots contained total aflatoxins B(1), B(2), G(1) and G(2) at 15.1 and 15.2 ng/g. One moldy ginseng root purchased from a grocery store was found to be contaminated with aflatoxins at 16 ng/g. PMID:16449060

D'Ovidio, Kathleen; Trucksess, Mary; Weaver, Carol; Horn, Erin; McIntosh, Marla; Bean, George

2006-02-01

319

Changes in rupture formation and zonary region stained with Evans blue during the recovery process from aluminum toxicity in the pea root apex.  

PubMed

We investigated how the pea (Pisum sativum cv. Harunoka) root, upon return to an Al-free condition, recovers from injury caused by exposure to Al. Elongation and re-elongation of the root during the recovery process from Al injury occurred only in the apical 5-mm region of the pea root. With the model system of the pea root for recovery from Al injury, images of the root characterized by zonal staining with Evans blue showed the existence of two regions in the root apex consisting of rupture and zonary stained regions. Ruptures enlarged by increase in their depth but without widening of the intervals among zonary stained regions in the roots treated with Al continuously. On the other hand, intervals of the zonary stained regions were widened due to re-elongation of the root and were narrow in the rupture region in the recovery root. PMID:21258208

Motoda, Hirotoshi; Kano, Yoshio; Hiragami, Fukumi; Kawamura, Kenji; Matsumoto, Hideaki

2011-01-01

320

Saccharomyces cerevisiae transcription elongation mutants are defective in PUR5 induction in response to nucleotide depletion.  

PubMed

IMP dehydrogenase (IMPDH) is the rate-limiting enzyme in the de novo synthesis of guanine nucleotides. It is a target of therapeutically useful drugs and is implicated in the regulation of cell growth rate. In the yeast Saccharomyces cerevisiae, mutations in components of the RNA polymerase II (Pol II) transcription elongation machinery confer increased sensitivity to a drug that inhibits IMPDH, 6-azauracil (6AU), by a mechanism that is poorly understood. This phenotype is thought to reflect the need for an optimally functioning transcription machinery under conditions of lowered intracellular GTP levels. Here we show that in response to the application of IMPDH inhibitors such as 6AU, wild-type yeast strains induce transcription of PUR5, one of four genes encoding IMPDH-related enzymes. Yeast elongation mutants sensitive to 6AU, such as those with a disrupted gene encoding elongation factor SII or those containing amino acid substitutions in Pol II subunits, are defective in PUR5 induction. The inability to fully induce PUR5 correlates with mutations that effect transcription elongation since 6AU-sensitive strains deleted for genes not related to transcription elongation are competent to induce PUR5. DNA encompassing the PUR5 promoter and 5' untranslated region supports 6AU induction of a luciferase reporter gene in wild-type cells. Thus, yeast sense and respond to nucleotide depletion via a mechanism of transcriptional induction that restores nucleotides to levels required for normal growth. An optimally functioning elongation machinery is critical for this response. PMID:11003640

Shaw, R J; Reines, D

2000-10-01

321

Interaction of galactoglucomannan oligosaccharides with auxin in mung bean primary root  

Microsoft Academic Search

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

Karin Kollárová; Zuzana Vatehová; L'udmila Slováková; Desana Lišková

2010-01-01

322

Cadmium-induced oxalate secretion from root apex is associated with cadmium exclusion and resistance in Lycopersicon esulentum.  

PubMed

The mechanisms of heavy metal resistance in plants can be classified into internal tolerance and exclusion mechanisms, but exclusion of heavy metals with the help of organic acids secretion has not been well documented. Here we demonstrated the contribution of oxalate secretion to cadmium (Cd) exclusion and resistance in tomato. Different Cd resistance between two tomato cultivars was evaluated by relative root elongation (RRE) and Cd accumulation. Cultivar 'Micro-Tom' showed better growth and lower Cd content in roots than 'Hezuo903' at different Cd concentrations not only in short-term hydroponic experiment but also in long-term hydroponic and soil experiments, indicating that the genotypic difference in Cd resistance is related to the exclusion of Cd from roots. 'Micro-Tom' had greater ability to secrete oxalate, suggesting that oxalate secretion might contribute to Cd resistance. Cd-induced secretion of oxalate was localized to root apex at which the majority of Cd accumulated. Phenylglyoxal, an anion-channel inhibitor, effectively blocked Cd-induced oxalate secretion and aggravated Cd toxicity while exogenous oxalate supply ameliorated Cd toxicity efficiently. These results indicated that the oxalate secreted from the root apex helps to exclude Cd from entering tomato roots, thus contributes to Cd resistance in the Cd-resistant tomato cultivar. PMID:21388421

Zhu, Xiao Fang; Zheng, Cheng; Hu, Yi Ting; Jiang, Tao; Liu, Yu; Dong, Ning Yu; Yang, Jian Li; Zheng, Shao Jian

2011-07-01

323

N 2 -fixation by ammonium-excreting Azospirillum brasilense in auxine-induced root tumours of wheat ( Triticum aestivum L.)  

Microsoft Academic Search

Wheat seedlings, treated with the auxine 2,4-dichlor-phenoxy acetic acid (2,4-D) during germination developed only a residual root system. Root elongation was extremely restricted and root tips were deformed to thick club-shaped tumours. When 2,4-D was added in a later stage of plant growth the plants developed additional nodule-like knots along primary roots. Root and shoot dry-matter production was slightly repressed

C. Christiansen-Weniger

1992-01-01

324

Evolution and Development of Hertwig's Epithelial Root Sheath  

PubMed Central

Periodontal regeneration and tissue engineering has re-awakened interest in the role of Hertwig’s Epithelial Root Sheath (HERS), an epithelial tissue layer first discovered in amphibians more than a century ago. Using developmental, evolutionary, and cell biological approaches we have therefore performed a careful analysis of the role of HERS in root formation and compared our data with clinical findings. Our developmental studies revealed HERS as a transient structure assembled in the early period of root formation and elongation and subsequently fenestrated and reduced to epithelial rests of Malassez (ERM). Our comparative evolutionary studies indicated that HERS fenestration was closely associated with the presence of a periodontal ligament and a gomphosis-type attachment apparatus in crocodilians and mammals. Based on these studies, we are proposing that HERS plays an important role in the regulation and maintenance of periodontal ligament space and function. Additional support for this hypothesis was rendered by our meta-analysis of recent clinical reports related to HERS function.

Luan, Xianghong; Ito, Yoshihiro; Diekwisch, Thomas G.H.

2009-01-01

325

Spatio-temporal dynamics of expansion growth in roots: automatic quantification of diurnal course and temperature response by digital image sequence processing.  

PubMed

A newly developed technique based on image sequence analysis allows automatic and precise quantification of the dynamics of the growth velocity of the root tip, the distribution of expansion growth rates along the entire growth zone and the oscillation frequencies of the root tip during growth without the need of artificial landmarks. These three major parameters characterizing expansion growth of primary roots can be analysed over several days with high spatial (20 microm) and temporal resolution (several minutes) as the camera follows the growing root by an image-controlled root tracking device. In combination with a rhizotron set up for hydroponic plant cultivation the impact of rapid changes of environmental factors can be assessed. First applications of this new system proved the absence of diurnal variation of root growth in Zea mays under constant temperature conditions. The distribution profile of relative elemental growth rate (REGR) showed two maxima under constant and varying growth conditions. Lateral oscillatory movements of growing root tips were present even under constant environmental conditions. Dynamic changes in velocity- and REGR-distribution within 1 h could be quantified after a step change in temperature from 21 degrees C to 26 degrees C. Most prominent growth responses were found in the zone of maximal root elongation. PMID:11886889

Walter, A; Spies, H; Terjung, S; Küsters, R; Kirchgessner, N; Schurr, U

2002-04-01

326

Relative Content of NO3? and Reduced N in Xylem Exudate as an Indicator of Root Reduction of Concurrently Absorbed 15NO3?1  

PubMed Central

It is unclear if the relative content of NO3? and reduced N in xylem exudate provides an accurate estimate of the percentage reduction of concurrently absorbed NO3? in the root. Experiments were conducted to determine whether NO3? and reduced N in xylem exudate of vegetative, nonnodulated soybean plants (Glycine max [L.] Merr., `Ransom') originated from exogenous recently absorbed 15NO3? or from endogenous 14N pools. Plants either were decapitated and exposed to 15NO3? solutions for 2 hours or were decapitated for the final 20 minutes of a 50-minute exposure to 15NO3? in the dark and in the light. Considerable amounts of 14NO3? and reduced 14N were transported into the xylem, but almost all of the 15N was present as 15NO3?. Dissimilar changes in transport of 14NO3?, reduced 14N and 15NO3? during the 2 hours of sap collection resulted in large variability over time in the percentage of total N in the exudate which was reduced N. Over a 20-minute period the rate of 15N transport into the xylem of decapitated plants was only 21 to 36% of the 15N delivered to the shoot of intact plants. Based on the proportion of total 15N which was found as reduced 15N in exudate and in intact plants in the dark, it was estimated that 5 to 17% of concurrently absorbed 15NO3? was reduced in the root. This was much less than the 38 to 59% which would have been predicted from the relative content of total NO3? and total reduced N in the xylem exudate.

Rufty, Thomas W.; Volk, Richard J.; McClure, Peter R.; Israel, Daniel W.; Raper, C. David

1982-01-01

327

A pollen-specific RALF from tomato that regulates pollen tube elongation.  

PubMed

Rapid Alkalinization Factors (RALFs) are plant peptides that rapidly increase the pH of plant suspension cell culture medium and inhibit root growth. A pollen-specific tomato (Solanum lycopersicum) RALF (SlPRALF) has been identified. The SlPRALF gene encodes a preproprotein that appears to be processed and released from the pollen tube as an active peptide. A synthetic SlPRALF peptide based on the putative active peptide did not affect pollen hydration or viability but inhibited the elongation of normal pollen tubes in an in vitro growth system. Inhibitory effects of SlPRALF were detectable at concentrations as low as 10 nm, and complete inhibition was observed at 1 mum peptide. At least 10-fold higher levels of alkSlPRALF, which lacks disulfide bonds, were required to see similar effects. A greater effect of peptide was observed in low-pH-buffered medium. Inhibition of pollen tube elongation was reversible if peptide was removed within 15 min of exposure. Addition of 100 nm SlPRALF to actively growing pollen tubes inhibited further elongation until tubes were 40 to 60 mum in length, after which pollen tubes became resistant to the peptide. The onset of resistance correlated with the timing of the exit of the male germ unit from the pollen grain into the tube. Thus, exogenous SlPRALF acts as a negative regulator of pollen tube elongation within a specific developmental window. PMID:20388667

Covey, Paul A; Subbaiah, Chalivendra C; Parsons, Ronald L; Pearce, Gregory; Lay, Fung T; Anderson, Marilyn A; Ryan, Clarence A; Bedinger, Patricia A

2010-06-01

328

A Pollen-Specific RALF from Tomato That Regulates Pollen Tube Elongation12[W][OA  

PubMed Central

Rapid Alkalinization Factors (RALFs) are plant peptides that rapidly increase the pH of plant suspension cell culture medium and inhibit root growth. A pollen-specific tomato (Solanum lycopersicum) RALF (SlPRALF) has been identified. The SlPRALF gene encodes a preproprotein that appears to be processed and released from the pollen tube as an active peptide. A synthetic SlPRALF peptide based on the putative active peptide did not affect pollen hydration or viability but inhibited the elongation of normal pollen tubes in an in vitro growth system. Inhibitory effects of SlPRALF were detectable at concentrations as low as 10 nm, and complete inhibition was observed at 1 ?m peptide. At least 10-fold higher levels of alkSlPRALF, which lacks disulfide bonds, were required to see similar effects. A greater effect of peptide was observed in low-pH-buffered medium. Inhibition of pollen tube elongation was reversible if peptide was removed within 15 min of exposure. Addition of 100 nm SlPRALF to actively growing pollen tubes inhibited further elongation until tubes were 40 to 60 ?m in length, after which pollen tubes became resistant to the peptide. The onset of resistance correlated with the timing of the exit of the male germ unit from the pollen grain into the tube. Thus, exogenous SlPRALF acts as a negative regulator of pollen tube elongation within a specific developmental window.

Covey, Paul A.; Subbaiah, Chalivendra C.; Parsons, Ronald L.; Pearce, Gregory; Lay, Fung T.; Anderson, Marilyn A.; Ryan, Clarence A.; Bedinger, Patricia A.

2010-01-01

329

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

NASA Astrophysics Data System (ADS)

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.

Wolverton, Chris

330

Elongated nanostructures for radial junction solar cells  

NASA Astrophysics Data System (ADS)

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

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

2013-10-01

331

Population Dynamics of Fusarium Oxysporum f. Sp. Radicis-lycopersici in Relation to the Onset of Fusarium Crown and Root Rot of Tomato  

Microsoft Academic Search

Fusarium oxysporum f. sp. radicis-lycopersici the causal agent of crown and root rot in tomato comprises two overlapping separate phases: monocyclic and polycyclic. Oversummering inoculum is the source of primary infection (the monocyclic phase) and the spread from plant to plant via root-to-root contact is the source of the secondary infection (the polycyclic phase). In the present work, relationships between

Yael Rekah; D. Shtienberg; J. Katan

2001-01-01

332

Contribution of root growth responses to leaf traits and relative growth rate of Populus alba under different water-table conditions  

Microsoft Academic Search

Water-table depth variations alter root growth response and may affect whole-plant growth in arid and semi-arid regions. We\\u000a examined how root biomass allocation and root morphological traits affect the leaf physiological and morphological traits\\u000a and whole-plant growth of Populus alba growing under different water tables. We exposed 1-year-old P. alba cuttings to contrasting soil–water conditions via water table changes in

Shogo Imada; Norikazu Yamanaka; Shigenobu Tamai

2010-01-01

333

Root gravitropism requires lateral root cap and epidermal cells for transport and response to a mobile auxin signal.  

PubMed

Re-orientation of Arabidopsis seedlings induces a rapid, asymmetric release of the growth regulator auxin from gravity-sensing columella cells at the root apex. The resulting lateral auxin gradient is hypothesized to drive differential cell expansion in elongation-zone tissues. We mapped those root tissues that function to transport or respond to auxin during a gravitropic response. Targeted expression of the auxin influx facilitator AUX1 demonstrated that root gravitropism requires auxin to be transported via the lateral root cap to all elongating epidermal cells. A three-dimensional model of the root elongation zone predicted that AUX1 causes the majority of auxin to accumulate in the epidermis. Selectively disrupting the auxin responsiveness of expanding epidermal cells by expressing a mutant form of the AUX/IAA17 protein, axr3-1, abolished root gravitropism. We conclude that gravitropic curvature in Arabidopsis roots is primarily driven by the differential expansion of epidermal cells in response to an influx-carrier-dependent auxin gradient. PMID:16244669

Swarup, Ranjan; Kramer, Eric M; Perry, Paula; Knox, Kirsten; Leyser, H M Ottoline; Haseloff, Jim; Beemster, Gerrit T S; Bhalerao, Rishikesh; Bennett, Malcolm J

2005-11-01

334

Dispenser for deploying elongated flexible articles  

NASA Astrophysics Data System (ADS)

This document discloses a dispenser for storing an elongated flexible article in a coil coaxially about a deployment axis. The dispenser includes a receptacle with a storage volume about the deployment axis. A partitioning structure in the storage volume includes circumferentially spaced sets of axially extending, deflectable fingers that define portions of storage channels for each turn in a coil. Flexible restraining bands attached to the receptacle overlie the storage volume to retain the turns axially within the storage channels. The structure prevents random turn positioning of individual turns of the coil. Deployment from the dispenser occurs without tangles, kinks or knots and proceeds smoothly and quietly.

Hrycin, Frank M.; Abdow, David A.; Babb, John D.

1995-01-01

335

Hektor - The largest highly elongated asteroid  

NASA Technical Reports Server (NTRS)

New observations of Trojan asteroid 624, Hektor, in April 1979 establish that the high amplitude of the rotational light curve of this object is caused by its elongated shape and not by patches of dark and light albedo on opposing hemispheres. These observations confirm the fact that Hektor is a very unusual object and are consistent with the hypothesis that it may be a compound asteroid formed when two Trojans of comparable size fell together - a rare fossilized example of a planetary accretion process.

Hartmann, W. K.; Cruikshank, D. P.

1980-01-01

336

Hektor - The largest highly elongated asteroid  

NASA Astrophysics Data System (ADS)

New observations of Trojan asteroid 624, Hektor, in April 1979 establish that the high amplitude of the rotational light curve of this object is caused by its elongated shape and not by patches of dark and light albedo on opposing hemispheres. These observations confirm the fact that Hektor is a very unusual object and are consistent with the hypothesis that it may be a compound asteroid formed when two Trojans of comparable size fell together - a rare fossilized example of a planetary accretion process.

Hartmann, W. K.; Cruikshank, D. P.

1980-02-01

337

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

PubMed

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

Rich, Sarah M; Watt, Michelle

2013-03-01

338

Elongation in translation as a dynamic interaction among the ribosome, tRNA, and elongation factors EF-G and EF-Tu  

PubMed Central

The ribosome is a complex macromolecular machine that translates the message encoded in the messenger RNA and synthesizes polypeptides by linking the individual amino acids carried by the cognate transfer RNAs (tRNAs). The protein elongation cycle, during which the tRNAs traverse the ribosome in a coordinated manner along a path of more than 100 Ĺ, is facilitated by large-scale rearrangements of the ribosome. These rearrangements go hand in hand with conformational changes of tRNA as well as elongation factors EF-Tu and EF-G – GTPases that catalyze tRNA delivery and translocation, respectively. This review focuses on the structural data related to the dynamics of the ribosomal machinery, which are the basis, in conjunction with existing biochemical, kinetic, and fluorescence resonance energy transfer data, of our knowledge of the decoding and translocation steps of protein elongation.

Agirrezabala, Xabier; Frank, Joachim

2010-01-01

339

In vivo anterior cruciate ligament elongation in response to axial tibial loads  

PubMed Central

Background The knowledge of in vivo anterior cruciate ligament (ACL) deformation is fundamental for understanding ACL injury mechanisms and for improving surgical reconstruction of the injured ACL. This study investigated the relative elongation of the ACL when the knee is subject to no load (<10 N) and then to full body weight (axial tibial load) at various flexion angles using a combined dual fluoroscopic and magnetic resonance imaging (MRI) technique. Methods Nine healthy subjects were scanned with MRI and imaged when one knee was subject to no load and then to full body weight using a dual fluoroscopic system (0°–45° flexion angles). The ACL was analyzed using three models: a single central bundle; an anteromedial and posterolateral (double functional) bundle; and multiple (eight) surface fiber bundles. Results The anteromedial bundle had a peak relative elongation of 4.4% ± 3.4% at 30° and that of the posterolateral bundle was 5.9% ± 3.4% at 15°. The ACL surface fiber bundles at the posterior portion of the ACL were shorter in length than those at the anterior portion. However, the peak relative elongation of one posterolateral fiber bundle reached more than 13% whereas one anteromedial fiber bundle reached a peak relative elongation of only about 3% at 30° of flexion by increasing the axial tibial load from no load to full body weight. Conclusions The data quantitatively demonstrated that under external loading the ACL experiences nonhomogeneous elongation, with the posterior fiber bundles stretching more than the anterior fiber bundles.

Hosseini, Ali; Gill, Thomas J.; Li, Guoan

2013-01-01

340

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)

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.

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

2014-05-01

341

Validation of Uniaxial Data Beyond Uniform Elongation  

NASA Astrophysics Data System (ADS)

Uniaxial testing is one of the simplest methods used to determining mechanical properties for sheet metals, but the classic test does not determine properties to sufficiently high strain levels for use in models of very large deformations such as forming operations. This limitation is primarily due to the classical test requiring uniform deformation in the gage length. Full-field optical techniques are now being used to extend the applicable strain range of uniaxial testing to strains beyond uniform elongation and well into diffuse necking, but assumptions must be made as to the multi-axial state of stress in this regime. In order to determine if such assumptions are correct, uniaxial experiments are performed combined with a unique combination of digital image correlation to measure plastic strains and stress tensor measurement through X-ray diffraction methods. The combination of metrology permits determination of the true stress-strain response to strains four times uniform elongation and the associated multi-axial stresses at the highest strain levels.

Iadicola, Mark A.

2011-08-01

342

Trade studies of plasma elongation for next-step tokamaks  

SciTech Connect

The effect of elongation on minimum-cost devices is investigated for elongations ranging from 2 to 3. The analysis, carried out with the TETRA tokamak systems code, includes the effects of elongation on both physics (plasma beta limit) and engineering (poloidal field coil currents) issues. When ignition is required, the minimum cost occurs for elongations from 2.3 to 2.9, depending on the plasma energy confinement scaling used. Scalings that include favorable plasma current dependence and/or degradation with fusion power tend to have minimum cost at higher elongation (2.5-2.9); scalings that depend primarily on size result in lower elongation (/approximately/2.3) for minimum cost. For design concepts that include steady-state current-driven operation, minimum cost occurs at an elongation of 2.3. 12 refs., 13 figs.

Galambos, J.D.; Strickler, D.J.; Peng, Y.K.M.; Reid, R.L.

1988-09-01

343

Strigolactones' ability to regulate root development may be executed by induction of the ethylene pathway  

PubMed Central

The newly defined phytohormones strigolactones (SLs) were recently shown to act as regulators of root development. Their positive effect on root-hair (RH) elongation enabled examination of their cross talk with auxin and ethylene. Analysis of wild-type plants and hormone-signaling mutants combined with hormonal treatments suggested that SLs and ethylene regulate RH elongation via a common regulatory pathway, in which ethylene is epistatic to SLs. The SL and auxin hormonal pathways were suggested to converge for regulation of RH elongation; this convergence was suggested to be mediated via the ethylene pathway, and to include regulation of auxin transport.

2011-01-01

344

Using stable isotopes to reconcile differences in nitrogen uptake efficiency relative to late season fertilization of northern red oak seedlings in Wisconsin bare-root nurseries  

NASA Astrophysics Data System (ADS)

Cultural applications (e.g., timing, amount) of nitrogen (N) fertilizer in bareroot tree nurseries have been assessed for some time. However, the use of different metrologies to quantify the efficient use of fertilizer N and its allocation within biomass has confounded comparisons between fertilization regimes. This inconsistency is especially problematic when quantifying N fertilizer uptake efficiency (NFUE) of late season N fertilization in northern red oak (Quercus rubra L.) (NRO) seedlings characterized by episodic flushes in growth and N storage in perennial tissue to support spring growth. The use of isotopic tracers could help elucidate these differences. We therefore hypothesized that: 1) calculations of NFUE using isotopically enriched fertilizer would yield lower, more precise estimates of NFUE relative to traditional methods due to differences in the accounting of mineralized and reabsorbed N, and 2) a significant fraction of leaf N in older leaves (early flushes) would be reabsorbed into root and shoot tissue before abscission relative to leaves produced toward the end of the growing season (late flushes). To test these hypotheses, we conducted an experiment in two-year old NRO seedlings at two bare-root nurseries in Wisconsin. We applied a total of 147 mg N seedling-1 in pulses from early July after the seedlings completed their second leaf flush until late August. The treatments consisted of three replicated plots of 15N enriched (1.000 atom%) ammonium sulfate, three non-enriched plots, and three unfertilized plots (controls) at each nursery. Subsequent changes in plant N uptake and N allocation were quantified from destructively harvested samples taken at 40, 60, and 120 days after the fertilization began. We evaluated three common methods currently used to estimate NFUE (total N without control, total N with control, and isotopic difference). The total N without control method overestimated mean NFUE by 3.2 times relative to the isotope method, because mineralized N uptake and reabsorption of leaf N was unaccounted for. The total N with control method also overestimated mean NFUE, but only by 20% relative to the isotope method; variation associated with the effects of N fertilization on mineralization and immobilization was large enough to preclude significant difference between these methods. The difference of non-labeled N between day 60 and day 120 revealed that the roots and shoots absorbed 95% and 5%, respectively, of initial leaf N. However, isotopic mass balance between day 60 and day 120 indicated that the NRO seedlings did not reabsorb leaf fertilized N from the youngest leaves before abscission. This study shows that using stable isotopes to understand plant-soil interactions in response to fertilization will help elucidate the contribution of additional N fluxes (e.g., N reabsorption) within perennial plants and thus improve fertility management of production systems.

Fujinuma, R.; Balster, N. J.

2009-12-01

345

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

PubMed

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

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

346

Relative strength of lithospheric mantle compared to granulite lower crust in orogenic roots: insight from field laboratory.  

NASA Astrophysics Data System (ADS)

The continental lithosphere is composed by strong lithospheric mantle and weak lower crust for average and hot geotherms. However, some experiments and seismic studies show that the strength contrast between mantle and crust can vary in order of several magnitudes. The internal zone of the European Variscan orogen (Bohemian Massif, Czech Republic) contains large complexes of Ky - K-feldspar granulites with incorporated spinel and garnet peridotites that can respond to question of mantle-lower crust strength contrast from the field perspective. The studied spinel-garnet harzburgite body (the Mohelno peridotite) represents probably a fragment of strongly depleted oceanic lithosphere showing peak conditions of 22,4-27,6 kbar and 1120-1275°C. The peridotite forms large folded sheet with steep hinge and vertical axial plane. It exhibits presence of spinel along the outer arc and the internal part of the fold and garnet along inner arc, both related to coarse-grained orthopyroxene - olivine microstructure. This coarse microstructure is dynamically recrystallized forming fine-grained matrix (~10 - 20 microns) and the EBSD measurements show presence of axial [100] LPO olivine pattern dominantly along the outer arc of the fold and in spinel harzburgite, while the inner arc of the fold and partly also garnet harzburgite reveals presence of axial [010] LPO pattern. Steep foliation and sub-horizontal to moderately plunging lineation determined from olivine EBSD data defines the shape of the megafold. Host rocks exhibit transposed mylonitic fabric S1-2 revealing peak conditions of 18 kbar, 800°C and heterogeneous D3 retrogression at about 10 - 7 kbar, 650°C. The foliation S2-3 is fully concordant with limbs of peridotite megafold, but close to the outer arc it is affected by asymmetrical folds with axial planar leucosomes coherent with the shape of the megafold hinge zone. In contrast, the S2 in the internal part of the megafold is affected by sinistral and dextral melt filled shear zones S3 oriented at high angle to the megafold axial plane. The mineral zoning of coarse-grained peridotite pre-mylonitic microstructure reflects probably metamorphic processes deep in the mantle and is not connected with variations in observed olivine LPO patterns in fine-grained mylonite. The LPO of olivine most likely results from strain partitioning in the intra-mantle transpressive shear zone, along which the mantle sheet was emplaced into orogenic lower crust. At this stage the granulites responded by development of mylonitic fabric S1-2 and the coherency of fabrics may indicate at least partial mechanical coupling and low rheological contrast between lower crust and mantle. The whole sequence was subsequently exhumed, folded and re-deformed at mid-crustal levels during almost orthogonal D3 event. Folding mechanism of peridotite sheet is governed by active amplification, while the flow in retrogressed and partially molten granulites was entirely passive. The folds in front of fold hinge are probably related to propagation of fold head in frontally constrained space, while shear zones in the core of megafold reflect post-buckle flattening. Our observations suggest transient evolution of the rheological contrast between mantle and crust lithologies marked by decrease of competence of partially molten crustal material in mid-crustal levels.

Kusbach, V.; Ulrich, S.; Schulmann, K.

2009-04-01

347

Auxin, ethylene and the regulation of root growth under mechanical impedance  

NASA Astrophysics Data System (ADS)

Among the multitude functions performed by plant roots, little information is available about the mechanisms that allow roots to overcome the soil resistance, in order to grow in the soil to obtain water and nutrient. Tomato (Solanum lycopersicum) seedlings grown on horizontally placed agar plates showed a progressive decline in the root length with the increasing impedance of agar media. The incubation with 1-methylcyclopropane (1-MCP), an inhibitor of ethylene perception, led to aerial growth of roots. In contrast, in absence of 1-MCP control roots grew horizontally anchored to the agar surface. Though 1-MCP-treated and control seedlings showed differential ability to penetrate in the agar, the inhibition of root elongation was nearly similar for both treatments. While increased mechanical impedance also progressively impaired hypocotyl elongation in 1-MCP treated seedlings, it did not affect the hypocotyl length of control seedlings. The decline in root elongation was also associated with increased expression of DR5::GUS activity in the root tip signifying accumulation of auxin at the root tip. The increased expression of DR5::GUS activity in the root tip was also observed in 1-MCP treated seedlings, indicating independence of this response from ethylene signaling. Our results indicate operation of a sensing mechanism in root that likely operates independently of ethylene but involves auxin to determine the degree of impedance of the substratum.

Sharma, Rameshwar; Santisree, Parankusam; Nongmaithem, Sapana; Sreelakshmi, Yellamaraju

2012-07-01

348

Influence of N deficiency and salinity on metal (Pb, Zn and Cu) accumulation and tolerance by Rhizophora stylosa in relation to root anatomy and permeability.  

PubMed

Effects of N deficiency and salinity on root anatomy, permeability and metal (Pb, Zn and Cu) translocation and tolerance were investigated using mangrove seedlings of Rhizophora stylosa. The results showed that salt could directly reduce radial oxygen loss (ROL) by stimulation of lignification within exodermis. N deficiency, oppositely, would reduce lignification. Such an alteration in root permeability may also influence metal tolerance by plants. The data indicated that a moderate salinity could stimulate a lignified exodermis that delayed the entry of metals into the roots and thereby contributed to a higher metal tolerance, while N deficiency would aggravate metal toxicity. The results from sand pot trail further confirmed this issue. This study provides a barrier property of the exodermis in dealing with environments. The plasticity of root anatomy is likely an adaptive strategy to regulate the fluxes of gases, nutrients and toxins at root-soil interface. PMID:22361050

Cheng, Hao; Wang, You-Shao; Ye, Zhi-Hong; Chen, Dan-Ting; Wang, Yu-Tu; Peng, Ya-Lan; Wang, Li-Ying

2012-05-01

349

Lysigenous aerenchyma formation in maize root is confined to cortical cells by regulation of genes related to generation and scavenging of reactive oxygen species  

PubMed Central

To adapt to waterlogging, maize (Zea mays) forms lysigenous aerenchyma in root cortex as a result of ethylene-promoted programmed cell death (PCD). Respiratory burst oxidase homolog (RBOH) gene encodes a homolog of gp91phox in NADPH oxidase, and has a role in the generation of reactive oxygen species (ROS). Recently, we found that during aerenchyma formation, RBOH was upregulated in all maize root tissues examined, whereas an ROS scavengingrelated metallothionein (MT) gene was downregulated specifically in cortical cells. Together these changes should lead to high accumulations of ROS in root cortex, thereby inducing PCD for aerenchyma formation. As further evidence of the involvement of ROS in root aerenchyma formation, the PCD was inhibited by diphenyleneiodonium (DPI), an NADPH oxidase inhibitor. Based on these results, we propose a model of cortical cell-specific PCD for root aerenchyma formation.

Yamauchi, Takaki; Rajhi, Imene

2011-01-01

350

Phosphorus deficiency enhances aluminum tolerance of rice (Oryza sativa) by changing the physicochemical characteristics of root plasma membranes and cell walls.  

PubMed

The negative charge at the root surface is mainly derived from the phosphate group of phospholipids in plasma membranes (PMs) and the carboxyl group of pectins in cell walls, which are usually neutralized by calcium (Ca) ions contributing to maintain the root integrity. The major toxic effect of aluminum (Al) in plants is the inhibition of root elongation due to Al binding tightly to these negative sites in exchange for Ca. Because phospholipid and pectin concentrations decrease in roots of some plant species under phosphorus (P)-limiting conditions, we hypothesized that rice (Oryza sativa L.) seedlings grown under P-limiting conditions would demonstrate enhanced Al tolerance because of their fewer sites on their roots. For pretreatment, rice seedlings were grown in a culture solution with (+P) or without (-P) P. Thereafter, the seedlings were transferred to a solution with or without Al, and the lipid, pectin, hemicellulose, and mineral concentrations as well as Al tolerance were then determined. Furthermore, the low-Ca tolerance of P-pretreated seedlings was investigated under different pH conditions. The concentrations of phospholipids and pectins in the roots of rice receiving -P pretreatment were lower than those receiving +P pretreatment. As expected, seedlings receiving the -P pretreatment showed enhanced Al tolerance, accompanied by the decrease in Al accumulation in their roots and shoots. This low P-induced enhanced Al tolerance was not explained by enhanced antioxidant activities or organic acid secretion from roots but by the decrease in phospholipid and pectin concentrations in the roots. In addition, low-Ca tolerance of the roots was enhanced by the -P pretreatment under low pH conditions. This low P-induced enhancement of low-Ca tolerance may be related to the lower Ca requirement to maintain PM and cell wall structures in roots of rice with fewer phospholipids and pectins. PMID:24331414

Maejima, Eriko; Watanabe, Toshihiro; Osaki, Mitsuru; Wagatsuma, Tadao

2014-01-15

351

Actin filament nucleation and elongation factors - structure-function relationships  

PubMed Central

The spontaneous and unregulated polymerization of actin filaments is inhibited in cells by actin monomer-binding proteins such as profilin and T?4. Eukaryotic cells and certain pathogens use filament nucleators to stabilize actin polymerization nuclei, whose formation is rate-limiting. Known filament nucleators include the Arp2/3 complex and its large family of Nucleation Promoting Factors (NPFs), formins, Spire, Cobl, VopL/VopF, TARP and Lmod. These molecules control the time and location for polymerization, and additionally influence the structures of the actin networks that they generate. Filament nucleators are generally unrelated, but with the exception of formins they all use the WASP-Homology 2 domain (WH2 or W), a small and versatile actin-binding motif, for interaction with actin. A common architecture, found in Spire, Cobl and VopL/VopF, consists of tandem W domains that bind three to four actin subunits to form a nucleus. Structural considerations suggest that NPFs-Arp2/3 complex can also be viewed as a specialized form of tandem W-based nucleator. Formins are unique in that they use the formin-homology 2 (FH2) domain for interaction with actin and promote not only nucleation, but also processive barbed end elongation. In contrast, the elongation function among W-based nucleators has been “outsourced” to a dedicated family of proteins, Eva/VASP, which are related to WASP-family NPFs.

Dominguez, Roberto

2009-01-01

352

Molecular Mobility of Soft Segment of Polyurethane Elastomers under Elongation  

NASA Astrophysics Data System (ADS)

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(V = 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.

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

2008-07-01

353

Root gravitropism requires lateral root cap and epidermal cells for transport and response to a mobile auxin signal  

Microsoft Academic Search

Re-orientation of Arabidopsis seedlings induces a rapid, asymmetric release of the growth regulator auxin from gravity-sensing columella cells at the root apex. The resulting lateral auxin gradient is hypothesized to drive differential cell expansion in elongation-zone tissues. We mapped those root tissues that function to transport or respond to auxin during a gravitropic response. Targeted expression of the auxin influx

Ranjan Swarup; Eric M. Kramer; Paula Perry; Kirsten Knox; H. M. Ottoline Leyser; Jim Haseloff; Gerrit T. S. Beemster; Rishikesh Bhalerao; Malcolm J. Bennett

2005-01-01

354

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

PubMed

The molecular events underlying the resistance of Upland cotton (Gossypium hirsutum L.) to the root-knot nematode (RKN) are largely unknown. In this report, we further characterize the previously identified MIC3 gene including the identification of 14 related MIC cDNAs in nematode-infected roots of allotetraploid cotton that show >85% identity with MIC3. A time-course analysis of RKN infection in resistant and susceptible cotton lines showed that maximum MIC transcript accumulation occurred immediately prior to the phenotypic manifestation of resistance. MIC expression was not induced by mechanical wounding or by virulent reniform nematode infection. MIC expression was undetectable in cotton leaves undergoing a hypersensitive response to Xanthomonas campestris. A time-course analysis of defense gene expression (PR10, ERF5, CDNS, LOX1, POD4, POD8) in resistant and susceptible cotton roots showed that RKN infection specifically elicits the induction of MIC in resistant roots and not other common defense-signaling pathways. These results suggest that cotton resistance to RKN involves novel defense-signaling pathways and further supports the idea that the MIC genes are intimately involved in this resistance response and represent a group of root-specific defense-related genes in cotton. PMID:18357465

Wubben, Martin J; Callahan, Franklin E; Hayes, Russel W; Jenkins, Johnie N

2008-06-01

355

Fatty Acid-Elongating Activity in Rapidly Expanding Leek Epidermis.  

PubMed Central

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

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

1995-01-01

356

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

PubMed

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

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

2011-01-01

357

Intermediate electrostatic field for the elongation method.  

PubMed

A simple way to improve the accuracy of the fragmentation methods is proposed. The formalism was applied to the elongation (ELG) method at restricted open-shell Hartree-Fock (ROHF) level of theory. The ?-helix conformer of polyglycine was taken as a model system. The modified ELG method includes a simplified electrostatic field resulting from point-charge distribution of the system's environment. In this way the long-distance polarization is approximately taken into account. The field attenuates during the ELG process to eventually disappear when the final structure is reached. The point-charge distributions for each ELG step are obtained from charge sensitivity analysis (CSA) in force-field atoms resolution. The presence of the intermediate field improves the accuracy of ELG calculations. The errors in total energy and its kinetic and potential contributions are reduced by at least one-order of magnitude. In addition the SCF convergence of ROHF scheme is improved. PMID:24878802

Ku?niarowicz, Piotr; Liu, Kai; Aoki, Yuriko; Gu, Feng Long; Stachowicz, Anna; Korchowiec, Jacek

2014-06-01

358

Cotton AnnGh3 encoding an annexin protein is preferentially expressed in fibers and promotes initiation and elongation of leaf trichomes in transgenic Arabidopsis.  

PubMed

The annexins are a multifamily of calcium-regulated phospholipid-binding proteins. To investigate the roles of annexins in fiber development, four genes encoding putative annexin proteins were isolated from cotton (Gossypium hirsutum) and designated AnnGh3, AnnGh4, AnnGh5, and AnnGh6. Quantitative reverse transcription-polymerase chain reaction (qRT-PCR) results indicated that AnnGh3, AnnGh4, and AnnGh5 were preferentially expressed in fibers, while the transcripts of AnnGh6 were predominantly accumulated in roots. During fiber development, the transcripts of AnnGh3/4/5 genes were mainly accumulated in rapidly elongating fibers. With fiber cells further developed, their expression activity was dramatically declined to a relatively low level. In situ hybridization results indicated that AnnGh3 and AnnGh5 were expressed in initiating fiber cells (0-2 DPA). Additionally, their expression in fibers was also regulated by phytohormones and [Ca(2+)]. Subcellular localization analysis discovered that AnnGh3 protein was localized in the cytoplasm. Overexpression of AnnGh3 in Arabidopsis resulted in a significant increase in trichome density and length on leaves of the transgenic plants, suggesting that AnnGh3 may be involved in fiber cell initiation and elongation of cotton. PMID:23651035

Li, Bing; Li, Deng-Di; Zhang, Jie; Xia, Hui; Wang, Xiu-Lan; Li, Ying; Li, Xue-Bao

2013-10-01

359

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

PubMed

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

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

2013-01-01

360

Quantitative Localization of the Phytoalexin Glyceollin I in Relation to Fungal Hyphae in Soybean Roots Infected with Phytophthora megasperma f. sp. glycinea 1  

PubMed Central

A radioimmunoassay specific for glyceollin I was used to quantitate this phytoalexin in roots of soybean (Glycine max [L.] Merr. cv Harosoy 63) after infection with zoospores of either race 1 (incompatible) or race 3 (compatible) of Phytophthora megasperma Drechs. f. sp. glycinea Kuan and Erwin. The sensitivity of the radioimmunoassay and an inmmunofluorescent stain for hyphae permitted quantitation of phytoalexin and localization of the fungus in alternate serial cryotome sections from the same root. The incompatible interaction was characterized by extensive fungal colonization of the root cortex which was limited to the immediate vicinity of the inoculation site. Glyceollin I was first detected in extracts of whole roots 2 hours after infection, and phytoalexin content rose rapidly thereafter. Significant concentrations of glyceollin I were present at the infection site in cross-sections (42 micrometers thick) of such roots by 5 hours, and exceeded 0.6 micromoles per milliliter (EC90in vitro for glyceollin I) by 8 hours after infection. Longitudinal sectioning (14 micrometers thick) showed that glyceollin I accumulated particularly in the epidermal cell layers, but also was present in the root cortex at inhibitory concentrations. No hyphae were observed in advance of detectable levels of the phytoalexin and, in most roots, glyceollin I concentrations dropped sharply at the leading edge of the infection. In contrast, the compatible interaction was characterized by extensive unchecked fungal colonization of the root stele, with lesser growth in the rest of the root. Only small amounts of glyceollin I were detected in whole root extracts during the first 14 hours after infection. Measurable amounts of glyceollin I were detected only in occasional cross-sections of such roots 11 and 14 hours after infection. The phytoalexin was present at inhibitory concentrations in the epidermal cell layers, but the inhibitory zone did not extend appreciably into the cortex. Altogether, these data support the hypothesis that the accumulation of glyceollin I is an important early response of soybean roots to infection by P. megasperma, but may not be solely responsible for inhibition of fungal growth in the resistant response. Images Fig. 5 Fig. 6 Fig. 2

Hahn, Michael G.; Bonhoff, Anne; Grisebach, Hans

1985-01-01

361

In vitro Micropropagation of Datura metel L. through Somatic Embryos from Root Explants  

Microsoft Academic Search

A simple reproducible protocol has been reported from root explants for in vitro micropropagation of Datura metel through somatic embryos. A large number of somatic embryos were developed from these explants on MS supplemented with BAP 4.0 mg\\/l 15 days after inoculation. Subsequently all embryos developed into plants while they were attached to the explants. Fast shoot elongation and root

P. Nithiya; D. I. Arockiasamy

2007-01-01

362

The possible involvement of root-cap mucilage in gravitropism and calcium movement across root tips of Allium cepa L  

NASA Technical Reports Server (NTRS)

Roots of Allium cepa L. grown in aerated water elongate rapidly, but are not graviresponsive. These roots (1) possess extensive columella tissues comprised of cells containing numerous sedimented amyloplasts, (2) lack mucilage on their tips, and (3) are characterized by a weakly polar movement of calcium (Ca) across their tips. Placing roots in humid air correlates positively with the (1) onset of gravicurvature, (2) appearance of mucilage on tips of the roots, and (3) onset of the ability to transport Ca polarly to the lower side of the root tip. Gravicurvature of roots previously submerged in aerated water is more rapid when roots are oriented vertically for 1-2 h in humid air prior to being oriented horizontally. The more rapid gravicurvature of these roots correlates positively with the accumulation of mucilage at the tips of roots during the time the roots are oriented vertically. Therefore, the onset of gravicurvature and the ability of roots to transport Ca to the lower sides of their tips correlate positively with the presence of mucilage at their tips. These results suggest that mucilage may be important for the transport of Ca across root caps.

Moore, R.; Fondren, W. M.

1986-01-01

363

Correlation between Root-Generated Ionic Currents, pH, Fusicoccin, Indoleacetic Acid, and Growth of the Primary Root of Zea mays1  

PubMed Central

Correlations between root-generated ionic currents, extracellular pH, indoleacetic acid, fusicoccin, and growth were investigated. Current consistently entered the meristematic and elongating tissues of intact growing roots of Zea mays cv Golden Bantam. Mature root regions generated the outward limb of the current loop. Ion-substitution and pH-profile experiments suggested that the bulk of the ionic current was carried by H+. Calcium ions did not carry current, but calcium may regulate the proton circulation since the proton current density was slightly larger in calcium-depleted media. Increased root elongation at low pH was associated with increased current density and an extended zone of inward current. Conversely decreased elongation at high pH was associated with a reduced current density and a more restricted zone of inward current. The effect of the fungal toxin fusicoccin was to increase the current density of the inward limb of the ion current and to increase root extension. Concentrations of indoleacetic acid that reduced root growth, also reduced the density of the inward current and shortened the inward current zone. The results emphasize the point that roots are electrically contiguous over many millimeters and that the electrophysiology of root growth is best studied in intact root systems.

Miller, Andrew L.; Gow, Neil A. R.

1989-01-01

364

Phosphorus Deficiency Decreases Cell Division and Elongation in Grass Leaves1  

PubMed Central

Leaf growth in monocotyledons results from the flux of newly born cells out of the division zone and into the adjacent elongation-only zone, where cells reach their final length. We used a kinematic method to analyze the effect of phosphorus nutrition status on cell division and elongation parameters in the epidermis of Lolium perenne. Phosphorus deficiency reduced the leaf elongation rate by 39% due to decreases in the cell production rate (?19%) and final cell length (?20%). The former was solely due to a lower average cell division rate (0.028 versus 0.046 cell cell?1 h?1) and, thus, a lengthened average cell cycle duration (25 versus 15 h). The number of division cycles of the initial cell progeny (five to six) and, as a result, the number of meristematic cells (32–64) and division zone length were independent of phosphorus status. Accordingly, low-phosphorus cells maintained meristematic activity longer. Lack of effect of phosphorus deficiency on meristematic cell length implies that a lower division rate was matched to a lower elongation rate. Phosphorus deficiency did not affect the elongation-only zone length, thus leading to longer cell elongation duration (99 versus 75 h). However, the substantially reduced postmitotic average relative elongation rate (0.045 versus 0.064 mm mm?1 h?1) resulted in shorter mature cells. In summary, phosphorus deficiency did not affect the general controls of cell morphogenesis, but, by slowing down the rates of cell division and expansion, it slowed down its pace.

Kavanova, Monika; Lattanzi, Fernando Alfredo; Grimoldi, Agustin Alberto; Schnyder, Hans

2006-01-01

365

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

PubMed

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

Romanchuk, S M

2010-01-01

366

Elongated styloid process associated with nevoid basal cell carcinoma syndrome.  

PubMed

This article presents a case with nevoid basal cell carcinoma syndrome (NBCCS) and an elongated styloid process. Basal cell carcinoma syndrome, also known as Gorlin-Goltz syndrome, is an autosomal dominant inherited syndrome manifested by multiple defects involving the skin, nervous system, eyes, endocrine system, and bones. Elongated styloid process or calcified stylohyoid ligament cause craniofacial or cervical pain. The actual cause of elongation of the styloid process or the calcification of the stylohyoid ligament is unclear. The cause of elongation of styloid process in this case may be the calcification induced by NBCCS. This report is the first case presentation of NBCCS with elongated styloid process. Elongated styloid process might be described as an anomaly of an NBCCS. PMID:22067864

Uysal, Ismail Önder; Atalar, Mehmet H; Ko?ar, Mehmet Ilkay; Durmu?, Kasim

2011-11-01

367

Fatty Acid Elongation Is Independent of Acyl-Coenzyme A Synthetase Activities in Leek and Brassica napus1  

PubMed Central

In both animal and plant acyl elongation systems, it has been proposed that fatty acids are first activated to acyl-coenzyme A (CoA) before their elongation, and that the ATP dependence of fatty acid elongation is evidence of acyl-CoA synthetase involvement. However, because CoA is not supplied in standard fatty acid elongation assays, it is not clear if CoA-dependent acyl-CoA synthetase activity can provide levels of acyl-CoAs necessary to support typical rates of fatty acid elongation. Therefore, we examined the role of acyl-CoA synthetase in providing the primer for acyl elongation in leek (Allium porrum L.) epidermal microsomes and Brassica napus L. cv Reston oil bodies. As presented here, fatty acid elongation was independent of CoA and proceeded at maximum rates with CoA-free preparations of malonyl-CoA. We also showed that stearic acid ([1-14C]18:0)-CoA was synthesized from [1-14C]18:0 in the presence of CoA-free malonyl-CoA or acetyl-CoA, and that [1-14C]18:0-CoA synthesis under these conditions was ATP dependent. Furthermore, the appearance of [1-14C]18:0 in the acyl-CoA fraction was simultaneous with its appearance in phosphatidylcholine. These data, together with the s of a previous study (A. Hlousek-Radojcic, H. Imai, J.G. Jaworski [1995] Plant J 8: 803–809) showing that exogenous [14C]acyl-CoAs are diluted by a relatively large endogenous pool before they are elongated, strongly indicated that acyl-CoA synthetase did not play a direct role in fatty acid elongation, and that phosphatidylcholine or another glycerolipid was a more likely source of elongation primers than acyl-CoAs.

Hlousek-Radojcic, Alenka; Evenson, Kimberly J.; Jaworski, Jan G.; Post-Beittenmiller, Dusty

1998-01-01

368

Internode and petiole elongation of soybean in response to photoperiod and end-of-day light quality  

NASA Technical Reports Server (NTRS)

Elongation of main stem internodes and petioles of soybeans, Glycine max 'Ransom,' was examined in response to various photoperiod/temperature combinations and to end-of-day (EOD) light quality. Photoperiod treatments consisted of 10, 14, and 16 h in combination with day/night temperatures of 18/14, 22/18, 26/22, 30/26, and 34/30 C. The EOD treatments consisted of exposing plants to illumination from either incandescent (high far-red component, FR) or fluorescent (high red component, R) lamps during the final 0.5 h of a 10-h photoperiod. Internode elongation was not significantly promoted by the photoperiod treatments, and, in fact, under the two highest temperature regimes, internode elongation was suppressed under the longer photoperiods. Petiole elongation, however, was enhanced under the longer photoperiods at all temperatures. In the EOD light study, internode and petiole elongation was significantly greater on plants exposed to 0.5 h EOD from incandescent lamps than from fluorescent. Under the incandescent EOD treatment, plants increased dry matter production by 41% and exhibited greater partitioning of assimilates in stem and root portions than under fluorescent EOD.

Thomas, J. F.; Raper, C. D. Jr; Raper CD, J. r. (Principal Investigator)

1985-01-01

369

Effects of co-inoculation with arbuscular mycorrhizal fungi and rhizobia on soybean growth as related to root architecture and availability of N and P  

Microsoft Academic Search

Soybean plants can form tripartite symbiotic associations with rhizobia and arbuscular mycorrhizal (AM) fungi, but little\\u000a is known about effects of co-inoculation with rhizobia and AM fungi on plant growth, or their relationships to root architecture\\u000a as well as nitrogen (N) and phosphorus (P) availability. In the present study, two soybean genotypes contrasting in root architecture\\u000a were grown in a

Xiurong Wang; Qiang Pan; Fengxian Chen; Xiaolong Yan; Hong Liao

2011-01-01

370

RNA polymerase II subunit Rpb9 regulates transcription elongation in vivo.  

PubMed

RNA polymerase II lacking the Rpb9 subunit uses alternate transcription initiation sites in vitro and in vivo and is unable to respond to the transcription elongation factor TFIIS in vitro. Here, we show that RPB9 has a synthetic phenotype with the TFIIS gene. Disruption of RPB9 in yeast also resulted in sensitivity to 6-azauracil, which is a phenotype linked to defects in transcription elongation. Expression of the TFIIS gene on a high-copy plasmid partially suppressed the 6-azauracil sensitivity of Deltarpb9 cells. We set out to determine the relevant cellular role of yeast Rpb9 by assessing the ability of 20 different site-directed and deletion mutants of RPB9 to complement the initiation and elongation defects of Deltarpb9 cells in vivo. Rpb9 is composed of two zinc ribbons. The N-terminal zinc ribbon restored the wild-type pattern of initiation start sites, but was unable to complement the growth defects associated with defects in elongation. Most of the site-directed mutants complemented the elongation-specific growth phenotypes and reconstituted the normal pattern of transcription initiation sites. The anti-correlation between the growth defects of cells disrupted for RPB9 and the selection of transcription start sites suggests that this is not the primary cellular role for Rpb9. Genome-wide transcription profiling of Deltarpb9 cells revealed only a few changes, predominantly in genes related to metabolism. PMID:10938084

Hemming, S A; Jansma, D B; Macgregor, P F; Goryachev, A; Friesen, J D; Edwards, A M

2000-11-10

371

Fine structure of elongate polyhedral bodies (carboxysomes) in two Oscillatoria (Cyanophyceae) isolates.  

PubMed

Polyhedral bodies (carboxysomes) in two Oscillatoria isolates were of two morphological forms. Some were typical polygonal bodies with many straight sides and were approximately 0.2 micron in diameter. Most of the bodies in these isolates were elongate being up to 2.6 microns in length, 33 nm in width and approximately 0.1 micron in depth. Some of the bodies were polygonal with an elongate extension. All of the bodies were limited by a membrane monolayer of approximately 20 A. The function of polyhedral bodies (carboxysomes) is discussed in relation to their observed morphology. PMID:7837992

Jensen, T E

1994-01-01

372

Transcriptome Profiling of Leaf Elongation Zone under Drought in Contrasting Rice Cultivars  

PubMed Central

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.

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

2013-01-01

373

Erosion of root epidermal cell walls by Rhizobium polysaccharide-degrading enzymes as related to primary host infection in the Rhizobium-legume symbiosis.  

PubMed

A central event of the infection process in the Rhizobium-legume symbiosis is the modification of the host cell wall barrier to form a portal of entry large enough for bacterial penetration. Transmission electron microscopy (TEM) indicates that rhizobia enter the legume root hair through a completely eroded hole that is slightly larger than the bacterial cell and is presumably created by localized enzymatic hydrolysis of the host cell wall. In this study, we have used microscopy and enzymology to further clarify how rhizobia modify root epidermal cell walls to shed new light on the mechanism of primary host infection in the Rhizobium-legume symbiosis. Quantitative scanning electron microscopy indicated that the incidence of highly localized, partially eroded pits on legume root epidermal walls that follow the contour of the rhizobial cell was higher in host than in nonhost legume combinations, was inhibited by high nitrate supply, and was not induced by immobilized wild-type chitolipooligosaccharide Nod factors reversibly adsorbed to latex beads. TEM examination of these partially eroded, epidermal pits indicated that the amorphous, noncrystalline portions of the wall were disrupted, whereas the crystalline portions remained ultrastructurally intact. Further studies using phase-contrast and polarized light microscopy indicated that (i) the structural integrity of clover root hair walls is dependent on wall polymers that are valid substrates for cell-bound polysaccharide-degrading enzymes from rhizobia, (ii) the major site where these rhizobial enzymes can completely erode the root hair wall is highly localized at the isotropic, noncrystalline apex of the root hair tip, and (iii) the degradability of clover root hair walls by rhizobial polysaccharide-degrading enzymes is enhanced by modifications induced during growth in the presence of chitolipooligosaccharide Nod factors from wild-type clover rhizobia. The results suggest a complementary role of rhizobial cell-bound glycanases and chitolipooligosaccharides in creating the localized portals of entry for successful primary host infection. PMID:11467723

Mateos, P F; Baker, D L; Petersen, M; Velázquez, E; Jiménez-Zurdo, J I; Martínez-Molina, E; Squartini, A; Orgambide, G; Hubbell, D H; Dazzo, F B

2001-06-01

374

Molecular Phylogeny and Evolution of Parabasalia with Improved Taxon Sampling and New Protein Markers of Actin and Elongation Factor-1?  

PubMed Central

Background Inferring the evolutionary history of phylogenetically isolated, deep-branching groups of taxa—in particular determining the root—is often extraordinarily difficult because their close relatives are unavailable as suitable outgroups. One of these taxonomic groups is the phylum Parabasalia, which comprises morphologically diverse species of flagellated protists of ecological, medical, and evolutionary significance. Indeed, previous molecular phylogenetic analyses of members of this phylum have yielded conflicting and possibly erroneous inferences. Furthermore, many species of Parabasalia are symbionts in the gut of termites and cockroaches or parasites and therefore formidably difficult to cultivate, rendering available data insufficient. Increasing the numbers of examined taxa and informative characters (e.g., genes) is likely to produce more reliable inferences. Principal Findings Actin and elongation factor-1? genes were identified newly from 22 species of termite-gut symbionts through careful manipulations and seven cultured species, which covered major lineages of Parabasalia. Their protein sequences were concatenated and analyzed with sequences of previously and newly identified glyceraldehyde-3-phosphate dehydrogenase and the small-subunit rRNA gene. This concatenated dataset provided more robust phylogenetic relationships among major groups of Parabasalia and a more plausible new root position than those previously reported. Conclusions/Significance We conclude that increasing the number of sampled taxa as well as the addition of new sequences greatly improves the accuracy and robustness of the phylogenetic inference. A morphologically simple cell is likely the ancient form in Parabasalia as opposed to a cell with elaborate flagellar and cytoskeletal structures, which was defined as most basal in previous inferences. Nevertheless, the evolution of Parabasalia is complex owing to several independent multiplication and simplification events in these structures. Therefore, systematics based solely on morphology does not reflect the evolutionary history of parabasalids.

Noda, Satoko; Mantini, Clea; Meloni, Dionigia; Inoue, Jun-Ichi; Kitade, Osamu; Viscogliosi, Eric; Ohkuma, Moriya

2012-01-01

375

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

NASA Technical Reports Server (NTRS)

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).

Rajulu, Sudhakar; Young, Karen

2009-01-01

376

Elongated Styloid Process and Cervical Spondylosis  

PubMed Central

SUMMARY Background Dysphagia, is a significant sign of many different lesions in upper digestive system especially in proximal esophagus. Tumors, gastroesophageal reflux, achalasia and extrinsic compressions are the most common causes that may lead to dysphagia in geriatric population. Cervical osteophyte induced dysphagia, is one of the uncommon reasons of dysphagia, therefore other causes of dysphagia must be excluded to establish the exact diagnosis. Eagle syndrome is one of the considerable reason which may lead to misdiagnosis in patients with cervical osteophytes. In this case report, we represent four patients who had dysphagia due to anteriorly located cervical osteophytes and evaluate the patients with special reference to Eagle syndrome. Material and methods After a detailed anamnesis and ENT examination, cervical plain radiographs in four projections and Towne radiographs were obtained for every patient. After that, magnetic resonance imaging (MRI) of cervical spine and barium swallowing studies were performed to evaluate the presence of esophageal compression. Results Eagle syndrome was excluded due to absence of other symptoms and physical signs, eventhough unilateral or bilateral elongation of styloid processes was found in all of the patients. Conclusion Cervical osteophytes induced dysphagia is a rare clinical entity, diagnosis should be done by a careful examination, intensive radiologic evaluation. Moreover, all the other causes like Eagle syndrome should be excluded during the diagnosis of cervical osteophyte induced dysphagia.

Unlu, Zeliha; Orguc, Sebnem; Eskiizmir, Gorkem; Aslan, Asim; Bayindir, Petek

2008-01-01

377

Regulated tissue fluidity steers zebrafish body elongation  

PubMed Central

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

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

2013-01-01

378

Nonlocal order in elongated dipolar gases  

NASA Astrophysics Data System (ADS)

Dipolar particles in an elongated trap are expected to undergo a quantum phase transition from a linear to a zigzag structure with decreasing transverse confinement. We derive the low-energy effective theory of the transition showing that in the presence of quantum fluctuations the zigzag phase can be characterized by a long-ranged string order, while the local Ising correlations decay as a power law. This is also confirmed using density matrix renormalization group calculations on a microscopic model. The nonlocal order in the bulk gives rise to zero energy states localized at the interface between the ordered and disordered phases. Such an interface naturally arises when the particles are subject to a weak harmonic confinement along the tube axis. We compute the signature of the edge states in the single-particle tunneling spectra pointing to differences between a system with bosonic versus fermionic particles. Finally we assess the magnitude of the relevant quantum fluctuations in realistic systems of dipolar particles, including ultracold polar molecules as well as alkali atoms weakly dressed by a Rydberg excitation.

Ruhman, J.; Dalla Torre, E. G.; Huber, S. D.; Altman, E.

2012-03-01

379

Extended Ane Root Systems  

Microsoft Academic Search

There are two notions of the extended ane root systems in the literature which both are introduced axiomatically. One, extended ane root system (SAERS for short), consists only of nonisotropic roots, while the other, extended ane root system (EARS for short), contains certain isotropic roots too. We show that there is a one to one correspondence between (reduced) SEARSs and

Saeid Azam

2002-01-01

380

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

PubMed Central

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

Adams, Thomas S.; Eissenstat, David M.

2014-01-01