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1

Genetic analysis of root elongation induced by phosphorus deficiency in rice ( Oryza sativa L.): fine QTL mapping and multivariate analysis of related traits  

Microsoft Academic Search

Root elongation induced by phosphorus deficiency has been reported as one of the adaptive mechanisms in plants. Genetic differences\\u000a were found in rice for the root elongation under phosphorus deficiency (REP), for which a distinct quantitative trait locus\\u000a (QTL) was detected on the long arm of chromosome 6. Subsequently, the effect and position of the QTL, designated as qREP-6, were

Akifumi Shimizu; Kenji Kato; Akiko Komatsu; Keiji Motomura; Hiroshi Ikehashi

2008-01-01

2

"GROWTH-PROMOTING SUBSTANCE" AND ELONGATION OF ROOTS.  

PubMed

The vertical elongation of normal roots of Lupinus seedlings proceeds at constant rate over periods of 4 to 5 hours. The decapitation of a root stops its elongation for a variable length of time, followed by a period of renewed elongation at a rate lower than that of the normal root. The tipping of the decapitated root with a tip of a coleoptile of Zea induces a decrease in the rate of elongation of the root. The same effect can be obtained with the diffusate from tips of coleoptile of Avena and to a lesser extent with diffusate of root tips. The reduction in the rate of elongation of the root determined by diffusate from the lower half of the tip of a coleoptile placed horizontally is more pronounced than the inhibition elicited by the diffusate of the upper half of the same tip. Various experiments with the diffusate of tips support the idea that under the conditions used the growth-promoting substance of the coleoptile tip or root tip inhibits the elongation of the decapitated root. PMID:19872734

Navez, A E

1933-05-20

3

Promotion of root elongation by phosphorus deficiency  

Microsoft Academic Search

Decrease of culture solution pH and increase in cation\\/anion ratio in the plant were observed when horsegram (Macrotyloma uniflorum (Lam.) Verdc.) was grown in solution culture deficient in phosphorus. The effux of H+ from the roots of ?P plants was observed in bromocresol purple agar. The length of root cells was considerably increased by ?P treatment. Thus a close correlation

M. Anuradha; A. Narayanan

1991-01-01

4

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

5

Root growth dynamics of Aleppo pine ( Pinus halepensis Mill.) seedlings in relation to shoot elongation, plant size and tissue nitrogen concentration  

Microsoft Academic Search

Large and high nitrogen (N) concentration seedlings frequently have higher survival and growth in Mediterranean forest plantations\\u000a than seedlings with the opposite traits, which has been linked to the production of deeper and larger root systems in the\\u000a former type of seedlings. This study assessed the influence of seedling size and N concentration on root growth dynamics and\\u000a its relation

Bárbara Cuesta; Jesús Vega; Pedro Villar-Salvador

2010-01-01

6

Root hair-specific expansins modulate root hair elongation in rice.  

PubMed

Root hair growth requires intensive cell-wall modification. This study demonstrates that root hair-specific expansin?As, a sub-clade of the cell wall-loosening expansin proteins, are required for root hair elongation in rice (Oryza sativa L.). We identified a gene encoding EXPA17 (OsEXPA17) from a rice mutant with short root hairs. Promoter::reporter transgenic lines exhibited exclusive OsEXPA17 expression in root hair cells. The OsEXPA17 mutant protein (OsexpA17) contained a point mutation, causing a change in the amino acid sequence (Gly104?Arg). This amino acid alteration is predicted to disrupt a highly conserved disulfide bond in the mutant. Suppression of OsEXPA17 by RNA interference further confirmed requirement for the gene in root hair elongation. Complementation of the OsEXPA17 mutant with other root hair EXPAs (OsEXPA30 and Arabidopsis EXPA7) can restore root hair elongation, indicating functional conservation of these root hair EXPAs in monocots and dicots. These results demonstrate that members of the root hair EXPA sub-clade play a crucial role in root hair cell elongation in Graminaceae. PMID:21309868

ZhiMing, Yu; Bo, Kang; XiaoWei, He; ShaoLei, Lv; YouHuang, Bai; WoNa, Ding; Ming, Chen; Hyung-Taeg, Cho; Ping, Wu

2011-03-21

7

Rooting for the root of elongation factor-like protein phylogeny.  

PubMed

Lateral gene transfer (LGT) may play a pivotal role in the evolution of elongation factor-like (EFL) genes in eukaryotes. To date, numbers of putative cases for lateral transfer of EFL genes have been postulated based on unrooted EFL phylogenies. Nevertheless, the root position in EFL phylogeny is important to validate lateral EFL gene transfer: for instance, a clade of two EFL homologs from distantly related organisms in an unrooted EFL tree does not necessarily confirm the LGT, since the possibility that the root may locate in this clade cannot be excluded. Cocquyt et al. (2009, p. 39) recently demonstrated that a putative case of lateral EFL gene transfer, which was originally proposed based on an unrooted phylogeny, could not be endorsed by the corresponding rooted analysis. Although rooting EFL phylogeny is indispensable to elucidate various aspects in EFL gene evolution, we suspected that the outgroup clade comprised of EF-1alpha and eukaryote-specific EF-1alpha paralogs erroneously attached to long EFL branches in Cocquyt et al. (2009) - a typical long branch attraction (LBA) artifact. Here, we systematically assessed the putative LBA artifact between the branch leading to the outgroup clade and long ingroup branches by analyzing the original dataset used in Cocquyt et al. (2009) with and without modifying ingroup-sequence sampling. A series of the rooted EFL analyses indicated that the root inference was highly susceptible to presence and absence of long-branched ingroup-sequences, suggesting that the rooted EFL phylogenies cannot be free from severe LBA artifact. We also discussed a new aspect in EFL gene evolution in stramenopiles identified in the course of the EFL analyses described above. Finally, the relative timing of the first emergence of EFL gene in eukaryotes was contemplated based on the current EF-1alpha/EFL distribution. PMID:20450979

Kamikawa, Ryoma; Sakaguchi, Miako; Matsumoto, Takuya; Hashimoto, Tetsuo; Inagaki, Yuji

2010-05-05

8

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

9

Gibberellins accumulate in the elongating endodermal cells of Arabidopsis root.  

PubMed

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

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

2013-02-04

10

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

11

[Toxic effect of musk ketone based on the determinations of wheat (Triticum aestivum) seed germination and root elongation].  

PubMed

Through the determinations of wheat (Triticum aestivum) seed germination and seedling growth, the toxic effect of emerging pollutant musk ketone was investigated. The results showed that 10 mg x kg(-1) of musk ketone could significantly inhibit the seed germination rate (P < 0. 05) and the seedling's root- and shoot elongation of wheat (P <0.01), and there existed a significant (P < 0.01) dose-effect relationship between musk ketone and root- and shoot elongation, suggesting that the seedling's root- and shoot elongation of wheat could indicate the pollution extent of musk ketone in soil. The correlation analysis revealed that under soil musk ketone pollution, there was a significant (P < 0.01) positive correlation between root- and shoot elongation, and a significant (P < 0.01) negative correlation between seed germination and biomass. Besides the solubility in water, the toxicity of organic pollutant was related to its chemical characters, and its action mechanisms to the target organism. PMID:18808038

Fan, Fei; Zhou, Qi-Xing; Wang, Mei-E

2008-06-01

12

Factors controlling the timing of root elongation intensity in a mature upland oak stand  

Microsoft Academic Search

We examined the timing of root elongation intensity (REI) – the production of newly elongating roots measured in length per unit soil volume per unit time – in a mature white oak-chestnut oak forest in Tennessee, USA, over a 4-year period. We used a network of minirhizotrons to (1) examine environmental control of soil moisture and temperature over REI, (2)

J. D. Joslin; M. H. Wolfe; P. J. Hanson

2001-01-01

13

Aluminium-induced inhibition of root elongation in Arabidopsis is mediated by ethylene and auxin  

PubMed Central

Aluminium (Al) is phytotoxic when solubilized into Al3+ in acidic soils. One of the earliest and distinct symptoms of Al3+ toxicity is inhibition of root elongation. To decipher the mechanism by which Al3+ inhibits root elongation, the role of ethylene and auxin in Al3+-induced inhibition of root elongation in Arabidopsis thaliana was investigated using the wild type and mutants defective in ethylene signalling (etr1-3 and ein2-1) and auxin polar transport (aux1-7 and pin2). Exposure of wild-type Arabidopsis to AlCl3 led to a marked inhibition of root elongation, and elicited a rapid ethylene evolution and enhanced activity of the ethylene reporter EBS:GUS in root apices. Root elongation in etr1-3 and ein2-1 mutants was less inhibited by Al3+ than that in wild-type plants. Ethylene synthesis inhibitors, Co2+ and aminoethoxyvinylglycine (AVG), and an antagonist of ethylene perception (Ag+) abolished the Al3+-induced inhibition of root elongation. There was less inhibition of root elongation by Al3+ in aux1-7 and pin2 mutants than in the wild type. The auxin polar transport inhibitor, naphthylphthalamic acid (NPA), substantially alleviated the Al3+-induced inhibition of root elongation. The Al3+ and ethylene synthesis precursor aminocyclopropane carboxylic acid (ACC) increased auxin reporter DR5:GUS activity in roots. The Al3+-induced increase in DR5:GUS activity was reduced by AVG, while the Al3+-induced increase in EBS:GUS activity was not altered by NPA. Al3+ and ACC increased transcripts of AUX1 and PIN2, and this effect was no longer observed in the presence of AVG and Co2+. These findings indicate that Al3+-induced ethylene production is likely to act as a signal to alter auxin distribution in roots by disrupting AUX1- and PIN2-mediated auxin polar transport, leading to arrest of root elongation.

Sun, Pei; Tian, Qiu-Ying; Chen, Jie; Zhang, Wen-Hao

2010-01-01

14

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

PubMed

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

Lee, J S; Evans, M L

1985-01-01

15

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

PubMed Central

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

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

2007-01-01

16

Aluminium-induced inhibition of root elongation in Arabidopsis is mediated by ethylene and auxin.  

PubMed

Aluminium (Al) is phytotoxic when solubilized into Al(3+) in acidic soils. One of the earliest and distinct symptoms of Al(3+) toxicity is inhibition of root elongation. To decipher the mechanism by which Al(3+) inhibits root elongation, the role of ethylene and auxin in Al(3+)-induced inhibition of root elongation in Arabidopsis thaliana was investigated using the wild type and mutants defective in ethylene signalling (etr1-3 and ein2-1) and auxin polar transport (aux1-7 and pin2). Exposure of wild-type Arabidopsis to AlCl(3) led to a marked inhibition of root elongation, and elicited a rapid ethylene evolution and enhanced activity of the ethylene reporter EBS:GUS in root apices. Root elongation in etr1-3 and ein2-1 mutants was less inhibited by Al(3+) than that in wild-type plants. Ethylene synthesis inhibitors, Co(2+) and aminoethoxyvinylglycine (AVG), and an antagonist of ethylene perception (Ag(+)) abolished the Al(3+)-induced inhibition of root elongation. There was less inhibition of root elongation by Al(3+) in aux1-7 and pin2 mutants than in the wild type. The auxin polar transport inhibitor, naphthylphthalamic acid (NPA), substantially alleviated the Al(3+)-induced inhibition of root elongation. The Al(3+) and ethylene synthesis precursor aminocyclopropane carboxylic acid (ACC) increased auxin reporter DR5:GUS activity in roots. The Al(3+)-induced increase in DR5:GUS activity was reduced by AVG, while the Al(3+)-induced increase in EBS:GUS activity was not altered by NPA. Al(3+) and ACC increased transcripts of AUX1 and PIN2, and this effect was no longer observed in the presence of AVG and Co(2+). These findings indicate that Al(3+)-induced ethylene production is likely to act as a signal to alter auxin distribution in roots by disrupting AUX1- and PIN2-mediated auxin polar transport, leading to arrest of root elongation. PMID:19858117

Sun, Pei; Tian, Qiu-Ying; Chen, Jie; Zhang, Wen-Hao

2009-10-25

17

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

18

Regions of differential cell elongation and mitosis, and root meristem morphology in different tissues of geotropically stimulated maize root apices.  

PubMed

We examined cell length, mitosis, and root meristem "cuticle" in different tissues of geostimulated, red light-exposed primary roots of corn (Zea Mays, Wisconsin hybrid 64A x 22R). The examination was done at 15-minute intervals for a period of 240 minutes. Differences in cell elongation between the upper and lower sides were most prominent between 1.5 and 2.5 mm from the root meristem; the outer cortex had the greatest elongation growth, and the upper cells showed a significant increase in length compared to the lower. A differential mitosis was also found, with the lower tissue being greater. We infer that the mitotic activity is indicative of cell division, and this division occurs strictly in the first 1.5 mm of the root meristem. The combined effect of differential cell elongation and cell division results in the localization of the geotropic curvature in the 1.5- to 2.5-mm region from the root meristem. Mitosis that occurs primarily in the cortex and stele were asynchronous; the peak of cortical division preceded that of the stele. Both peaks occurred before the peak of geotropism. A densely stained layer separates the cap from the root meristem. This layer is thinner at the apex of the root meristem. The area of the thin region increased with time and peaked at 180 minutes after geostimulation, which was coincidental with the peak of the geotropic response. PMID:16660240

Shen-Miller, J; McNitt, R E; Wojciechowski, M

1978-01-01

19

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

20

SCAR Mediates Light-Induced Root Elongation in Arabidopsis through Photoreceptors and Proteasomes[W][OA  

PubMed Central

The ARP2/3 complex, a highly conserved nucleator of F-actin, and its activator, the SCAR complex, are essential for growth in plants and animals. In this article, we present a pathway through which roots of Arabidopsis thaliana directly perceive light to promote their elongation. The ARP2/3-SCAR complex and the maintenance of longitudinally aligned F-actin arrays are crucial components of this pathway. The involvement of the ARP2/3-SCAR complex in light-regulated root growth is supported by our finding that mutants of the SCAR complex subunit BRK1/HSPC300, or other individual subunits of the ARP2/3-SCAR complex, showed a dramatic inhibition of root elongation in the light, which mirrored reduced growth of wild-type roots in the dark. SCAR1 degradation in dark-grown wild-type roots by constitutive photomorphogenic 1 (COP1) E3 ligase and 26S proteasome accompanied the loss of longitudinal F-actin and reduced root growth. Light perceived by the root photoreceptors, cryptochrome and phytochrome, suppressed COP1-mediated SCAR1 degradation. Taken together, our data provide a biochemical explanation for light-induced promotion of root elongation by the ARP2/3-SCAR complex.

Dyachok, Julia; Zhu, Ling; Liao, Fuqi; He, Ji; Huq, Enamul; Blancaflor, Elison B.

2011-01-01

21

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

PubMed

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

Sugiyama, Kou-ichi; Tezuka, Takafumi

2011-10-01

22

Evidence that high activity of vacuolar invertase is required for cotton fiber and Arabidopsis root elongation through osmotic dependent and independent pathways, respectively.  

PubMed

Vacuolar invertase (VIN) has long been considered as a major player in cell expansion. However, direct evidence for this view is lacking due, in part, to the complexity of multicellular plant tissues. Here, we used cotton (Gossypium spp.) fibers, fast-growing single-celled seed trichomes, to address this issue. VIN activity in elongating fibers was approximately 4-6-fold higher than that in leaves, stems, and roots. It was undetectable in fiberless cotton seed epidermis but became evident in initiating fibers and remained high during their fast elongation and dropped when elongation slowed. Furthermore, a genotype with faster fiber elongation had significantly higher fiber VIN activity and hexose levels than a slow-elongating genotype. By contrast, cell wall or cytoplasmic invertase activities did not show correlation with fiber elongation. To unravel the molecular basis of VIN-mediated fiber elongation, we cloned GhVIN1, which displayed VIN sequence features and localized to the vacuole. Once introduced to Arabidopsis (Arabidopsis thaliana), GhVIN1 complemented the short-root phenotype of a VIN T-DNA mutant and enhanced the elongation of root cells in the wild type. This demonstrates that GhVIN1 functions as VIN in vivo. In cotton fiber, GhVIN1 expression level matched closely with VIN activity and fiber elongation rate. Indeed, transformation of cotton fiber with GhVIN1 RNA interference or overexpression constructs reduced or enhanced fiber elongation, respectively. Together, these analyses provide evidence on the role of VIN in cotton fiber elongation mediated by GhVIN1. Based on the relative contributions of sugars to sap osmolality in cotton fiber and Arabidopsis root, we conclude that VIN regulates their elongation in an osmotic dependent and independent manner, respectively. PMID:20699399

Wang, Lu; Li, Xiao-Rong; Lian, Heng; Ni, Di-An; He, Yu-ke; Chen, Xiao-Ya; Ruan, Yong-Ling

2010-08-10

23

The ethylene pathway contributes to root hair elongation induced by the beneficial bacteria Phyllobacterium brassicacearum STM196.  

PubMed

In Arabidopsis roots, some epidermal cells differentiate into root hair cells. Auxin regulates root hair positioning, while ethylene controls cell elongation. Phyllobacterium brassicacearum STM196, a beneficial strain of plant growth promoting rhizobacteria (PGPR) isolated from the roots of field-grown oilseed rape, stimulates root hair elongation in Arabidopsis thaliana seedlings. We investigated the role of ethylene in the response of root hair cells to STM196 inoculation. While we could not detect a significant increase in ethylene biosynthesis, we could detect a slight activation of the ethylene signalling pathway. Consistent with this, an exhaustive survey of the root hair elongation response of mutants and transgenic lines affected in the ethylene pathway showed contrasting root hair sensitivities to STM196. We propose that local ethylene emission contributes to STM196-induceed root hair elongation. PMID:22608521

Galland, Marc; Gamet, Lydia; Varoquaux, Fabrice; Touraine, Brigitte; Touraine, Bruno; Desbrosses, Guilhem

2012-04-01

24

SEED GERMINATION AND ROOT ELONGATION TOXICITY TESTS IN HAZARDOUS WASTE SITE EVALUATION: METHODS DEVELOPMENT AND APPLICATIONS  

EPA Science Inventory

Seed germination tests measure soil toxicity directly, while root elongation tests consider the indirect effects of water-soluble constituents which may be present in site-samples. n the seed germination toxicity test, site-soil is mixed with a reference soil to yield exposure co...

25

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

26

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

Microsoft Academic Search

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

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

1995-01-01

27

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

28

Length of the apical unbranched zone of maize axile roots: Its relationship to root elongation rate  

Microsoft Academic Search

The length of the apical unbranched zone was studied in maize axile roots. Plants were grown in an aeroponic growth chamber allowing direct measurements on individual axile roots. The total length of the roots and the length of the apical unbranched zone were measured regularly. A commonly accepted hypothesis, according to which laterals emerge at a constant distance behind the

Sylvain Pellerin; Florence Tabourel

1995-01-01

29

Effects of rare earth oxide nanoparticles on root elongation of plants  

Microsoft Academic Search

The phytotoxicity of four rare earth oxide nanoparticles, nano-CeO2, nano-La2O3, nano-Gd2O3 and nano-Yb2O3 on seven higher plant species (radish, rape, tomato, lettuce, wheat, cabbage, and cucumber) were investigated in the present study by means of root elongation experiments. Their effects on root growth varied greatly between different nanoparticles and plant species. A suspension of 2000mg L?1 nano-CeO2 had no effect

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

2010-01-01

30

Kinematic study of root elongation in Arabidopsis thaliana with a novel image-analysis program.  

PubMed

The measurement of the spatial profile of root elongation needs to determine matching points between time-lapse images and calculate their displacement. These data have been obtained by laborious manual methods in the past. Some computer-based programs have been developed to improve the measurement, but they require many time-series digital images or sprinkling graphite particles on the root prior to image capture. Here, we have developed GrowthTracer, a new image-analysis program for the kinematic study of root elongation. GrowthTracer employs a multiresolution image matching method with a nonlinear filter called the critical point filter (CPF), which extracts critical points from images at each resolution and can determine precise matching points by analysis of only two intact images, without pre-marking by graphite particles. This program calculates the displacement of each matching point and determines the displacement velocity profile along the medial axis of the root. In addition, a manual input of distinct matching points increases the matching accuracy. We show a successful application of this novel program for the kinematic analysis of root growth in Arabidopsis thaliana. PMID:23076437

Iwamoto, Akitoshi; Kondo, Eri; Fujihashi, Hirotomo; Sugiyama, Munetaka

2012-10-18

31

Response of the plant root to aluminum stress: Analysis of the inhibition of the root elongation and changes in membrane function  

Microsoft Academic Search

Pea root elongation was strongly inhibited in the presence of a low concentration of Al (5 ?M). In Al-treated root, the epidermis\\u000a was markedly injured and characterized by an irregular layer of cells of the root surface. Approximately 30% of total absorbed\\u000a Al accumulated in the root tip and Al therein was found to cause the inhibition of whole root

Hideaki Matsumoto; Yasushi Senoo; Minobu Kasai; Masayoshi Maeshima

1996-01-01

32

Phenotypic analysis of Arabidopsis mutants: root elongation under salt/hormone-induced stress.  

PubMed

Abiotic stress, such as high salt or low temperature, adversely affects plant growth and development. Salt stress inhibits seed germination, retards plant growth, and accelerates senescence. Freezing or drought stress can cause cell damage and plant death. The following parameters can be used to evaluate plant tolerance to salt, drought, or freezing stress: root elongation (described here), fresh weight gain, seed germination, electrolyte leakage, or water loss measurement. Several stress mutants have been characterized using these tests, including hos1 and hos2, which show higher expression of some stress-regulated genes when exposed to low-temperature stress; hos5, which shows higher expression of some stress-regulated genes under abscisic acid (ABA) and salt treatments; sfr mutants, which are deficient in freezing tolerance; and eskimo1, which is constitutively freezing-tolerant. To determine whether a mutant shows altered response to osmotic stress or to specific ions, various concentrations of salts can be used. Mannitol can also be used to impose osmotic stress, and ABA can be used to impose hormone stress. Among the salts used in this protocol, Li(+) is considered a toxic analog of Na(+), whereas Cs(+) is a toxic cation related to K(+). The levels of stress suggested in this protocol may need to be adjusted, depending on the ecotype and growth conditions used. PMID:20150051

Lee, Byeong-ha; Zhu, Jian-Kang

2009-11-01

33

Root hair-specific EXPANSIN A7 is required for root hair elongation in Arabidopsis.  

PubMed

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

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

2011-02-22

34

Elongation Changes of Exploratory and Root Hair Systems Induced by Aminocyclopropane Carboxylic Acid and Aminoethoxyvinylglycine Affect Nitrate Uptake and BnNrt2.1 and BnNrt1.1 Transporter Gene Expression in Oilseed Rape[W  

PubMed Central

Ethylene is a plant hormone that plays a major role in the elongation of both exploratory and root hair systems. Here, we demonstrate in Brassica napus seedlings that treatments with the ethylene precursor, aminocyclopropane carboxylic acid (ACC) and the ethylene biosynthesis inhibitor, aminoethoxyvinylglycine (AVG), cause modification of the dynamic processes of primary root and root hair elongation in a dose-dependent way. Moreover, restoration of root elongation in AVG-treated seedlings by 1 mm l-glutamate suggested that high concentrations of AVG affect root elongation through nonoverlapping ethylene metabolic pathway involving pyridoxal 5?-P-dependent enzymes of nitrate (N) metabolism. In this respect, treatments with high concentrations of ACC and AVG (10 ?m) over 5 d revealed significant differences in relationships between root growth architecture and N uptake capacities. Indeed, if these treatments decreased severely the elongation of the exploratory root system (primary root and lateral roots) they had opposing effects on the root hair system. Although ACC increased the length and number of root hairs, the rate of N uptake and the transcript level of the N transporter BnNrt2.1 were markedly reduced. In contrast, the decrease in root hair length and number in AVG-treated seedlings was overcompensated by an increase of N uptake and BnNrt2.1 gene expression. These root architectural changes demonstrated that BnNrt2.1 expression levels were more correlated to the changes of the exploratory root system than the changes of the root hair system. The difference between treatments in N transporters BnNrt1.1 and BnNrt2.1 gene expression is discussed with regard to presumed transport functions of BnNrt1.1 in relation to root elongation.

Leblanc, Antonin; Renault, Hugues; Lecourt, Julien; Etienne, Philippe; Deleu, Carole; Le Deunff, Erwan

2008-01-01

35

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

36

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

37

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

PubMed Central

A previous study of maize primary roots under water stress showed pronounced increases in oxalate oxidase activity and apoplastic hydrogen peroxide in the apical region of the growth zone where cell elongation is maintained. We examined whether increased oxalate oxidase activity in water-stressed roots is conserved across diverse lines of maize and rice. The maize lines exhibited varied patterns of activity, with some lines lacking activity in the apical region. Moreover, none of the rice lines showed activity in the apical region. Also, although the genotypic response of root elongation to water stress was variable in both maize and rice, this was not correlated with the pattern of oxalate oxidase activity. Implications of these findings for root growth regulation under water stress are discussed.

Voothuluru, Priyamvada; Thompson, Hallie J.; Flint-Garcia, Sherry A.; Sharp, Robert E.

2013-01-01

38

THE EFFECTS OF FUNCTIONALIZED AND NON-FUNCTIONALIZED CARBON NANOTUBES ON ROOT ELONGATION OF SELECTED CROP SPECIES  

EPA Science Inventory

Single-walled carbon nanotubes (SWNT) have many potential beneficial uses with additional applications constantly being investigated. However, these unique properties create a potential cause for concern of toxicity, not only in humans and animals, but also in plants. Root elong...

39

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

Microsoft Academic Search

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

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

2008-01-01

40

Cell Wall Proteome in the Maize Primary Root Elongation Zone. I. Extraction and Identification of Water-Soluble and Lightly Ionically Bound Proteins1  

PubMed Central

Cell wall proteins (CWPs) play important roles in various processes, including cell elongation. However, relatively little is known about the composition of CWPs in growing regions. We are using a proteomics approach to gain a comprehensive understanding of the identity of CWPs in the maize (Zea mays) primary root elongation zone. As the first step, we examined the effectiveness of a vacuum infiltration-centrifugation technique for extracting water-soluble and loosely ionically bound (fraction 1) CWPs from the root elongation zone. The purity of the CWP extract was evaluated by comparing with total soluble proteins extracted from homogenized tissue. Several lines of evidence indicated that the vacuum infiltration-centrifugation technique effectively enriched for CWPs. Protein identification revealed that 84% of the CWPs were different from the total soluble proteins. About 40% of the fraction 1 CWPs had traditional signal peptides and 33% were predicted to be nonclassical secretory proteins, whereas only 3% and 11%, respectively, of the total soluble proteins were in these categories. Many of the CWPs have previously been shown to be involved in cell wall metabolism and cell elongation. In addition, maize has type II cell walls, and several of the CWPs identified in this study have not been identified in previous cell wall proteomics studies that have focused only on type I walls. These proteins include endo-1,3;1,4-?-d-glucanase and ?-l-arabinofuranosidase, which act on the major polysaccharides only or mainly present in type II cell walls.

Zhu, Jinming; Chen, Sixue; Alvarez, Sophie; Asirvatham, Victor S.; Schachtman, Daniel P.; Wu, Yajun; Sharp, Robert E.

2006-01-01

41

Promotion of root elongation and ion uptake in rice seedlings by 4,4,4-trifluoro-3-(indole-3-)butyric acid  

Microsoft Academic Search

We examined the mode of action of 4,4,4-trifluoro-3-(indole-3-)butyric acid (TFIBA) on rice seminal root elongation, the most effective application method of TFIBA to plants and the effect of TFIBA on ion uptake by rice seedlings. Elongation of the seminal root of rice was promoted approximately 80% by a continuous supply of 10 mol L TFIBA, whereas elongation was inhibited approximately 40% by

Xiuping Li; Tomoko Suzuki; Hideo Sasakawa

2009-01-01

42

Toxic effects of wastewater from various phases of monosodium glutamate production on seed germination and root elongation of crops  

Microsoft Academic Search

To make a comprehensive assessment on monosodium glutamate (MSG) wastewater pollution, a pollution exposure experiment was\\u000a carried out on the seed germination and root elongation of wheat, Chinese cabbage and tomato by using the wastewater discharged\\u000a from different processing phases of MSG production. The results showed that there were significantly positive linear relationships\\u000a between the inhibitory rates of wheat seed

Rui Liu; Qixing Zhou; Lanying Zhang; Hao Guo

2007-01-01

43

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

44

Apoplastic alkalinization is instrumental for the inhibition of cell elongation in the Arabidopsis root by the ethylene precursor 1-aminocyclopropane-1-carboxylic acid.  

PubMed

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. PMID:21282405

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

2011-01-31

45

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

46

A Mathematical Model for BRASSINOSTEROID INSENSITIVE1-Mediated Signaling in Root Growth and Hypocotyl Elongation1[W  

PubMed Central

Brassinosteroid (BR) signaling is essential for plant growth and development. In Arabidopsis (Arabidopsis thaliana), BRs are perceived by the BRASSINOSTEROID INSENSITIVE1 (BRI1) receptor. Root growth and hypocotyl elongation are convenient downstream physiological outputs of BR signaling. A computational approach was employed to predict root growth solely on the basis of BRI1 receptor activity. The developed mathematical model predicts that during normal root growth, few receptors are occupied with ligand. The model faithfully predicts root growth, as observed in bri1 loss-of-function mutants. For roots, it incorporates one stimulatory and two inhibitory modules, while for hypocotyls, a single inhibitory module is sufficient. Root growth as observed when BRI1 is overexpressed can only be predicted assuming that a decrease occurred in the BRI1 half-maximum response values. Root growth appears highly sensitive to variation in BR concentration and much less to reduction in BRI1 receptor level, suggesting that regulation occurs primarily by ligand availability and biochemical activity.

van Esse, G. Wilma; van Mourik, Simon; Stigter, Hans; ten Hove, Colette A.; Molenaar, Jaap; de Vries, Sacco C.

2012-01-01

47

Root elongation in tropical Eucalyptus plantations: effect of soil water content  

Microsoft Academic Search

– \\u000a \\u000a • Sustainability of Eucalyptus plantations is often questioned in resource-limited environments, especially in areas characterized by soils with poor nutrient\\u000a and water holding capacities. Yet, field-based observations of fine root dynamics in relation with the seasonality of rainfall\\u000a are lacking.\\u000a \\u000a \\u000a \\u000a \\u000a – \\u000a \\u000a • This study was undertaken on two Eucalyptus stands planted in the Kouilou Region (south-western Congo), which is

Armel Thongo M’bou; Christophe Jourdan; Philippe Deleporte; Yann Nouvellon; Laurent Saint-André; Jean-Pierre Bouillet; Fidèle Mialoundama; André Mabiala; Daniel Epron

2008-01-01

48

Differences in the frequency and disposition of plasmodesmata resulting from root cell elongation  

Microsoft Academic Search

Differences in plasmodesmatal organization and frequency between cells which have and have not undergone wall expansion, were studied in four plant species (Trifolium repens L., Raphanus sativus L., Zea mays L., Sorghum vulgare L.). Plasmodesmatal disposition ranged from single dispersed to clustered into primary pit-fields. As the result of wall expansion (i.e. by comparing meristematic and elongate cells) there is

Robert W. Seagull

1983-01-01

49

Overlapping functions of the four class XI myosins in Arabidopsis growth, root hair elongation, and organelle motility  

PubMed Central

Flowering plants have evolved multigene families of the class XI myosin motors, the functions of which remain poorly understood. Here, we investigated functional profiles of the Arabidopsis myosins that belong to two paralogous pairs, XI-K/XI-1 and XI-2/XI-B, using single and double gene-knockout mutants. It was found that the myosins XI-K, XI-2, and XI-B, but not XI-1 have overlapping and additive roles in the root hair elongation. A nonidentical set of the three myosins, XI-K, XI-1, and XI-2, exhibited partially redundant and additive roles in the transport of Golgi stacks, peroxisomes, and mitochondria. Conspicuously, the double xi-k/1 knockout plants that showed the largest cumulative reduction of the organelle velocities also exhibited a stunted plant growth and reduced fecundity phenotype. Collectively, these results suggest that the rapid, myosin-powered organelle trafficking is required for the optimal plant growth, whereas a distinct myosin function, presumably the vesicular transport, is involved in elongation of the root hairs. In addition, our data imply that the myosin gene duplication in plants has been followed by a gradual functional specialization of the resulting pairs of myosin paralogs.

Prokhnevsky, Alexey I.; Peremyslov, Valera V.; Dolja, Valerian V.

2008-01-01

50

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

51

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

PubMed Central

Polyethylene glycol (PEG), which is often used to impose low water potentials (?w) in solution culture, decreases O2 movement by increasing solution viscosity. We investigated whether this property 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 decreased steady-state root elongation rates, increased root-tip alanine concentrations, and decreased root-tip proline concentrations relative to seedlings grown in PEG solutions of above-ambient pO2 (alanine and proline accumulation are responses to hypoxia and low ?w, respectively). Measurements of root pO2 were made using an O2 microsensor to ensure that increased solution pO2 did not increase root pO2 above physiological levels. In oxygenated PEG solutions that gave maximal root elongation rates, root pO2 was similar to or less than (depending on depth in the tissue) pO2 of roots growing in vermiculite at the same ?w. Even without PEG, high solution pO2 was necessary to raise root pO2 to the levels found in vermiculite-grown roots. Vermiculite was used for comparison because it has large air spaces that allow free movement of O2 to the root surface. The results show that supplemental oxygenation is required to avoid hypoxia in PEG solutions. Also, the data suggest that the O2 demand of the root elongation zone may be greater at low relative to high ?w, compounding the effect of PEG on O2 supply. Under O2-sufficient conditions root elongation was substantially less sensitive to the low ?w imposed by PEG than that imposed by dry vermiculite.

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

1998-01-01

52

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

Technology Transfer Automated Retrieval System (TEKTRAN)

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

53

Lettuce seed germination and root elongation toxicity evaluation of the F-Area seepline soils  

SciTech Connect

This study is a continuation of similar studies conducted by Easton and Murphy (1993) and Loehle (1990). The objectives of these studies are to: (1) assess the toxicity of the water-soluble constituents of soil in a seepline adjacent to the F-Area Seepage Basins and (2) evaluate the effectiveness of rainwater movements in reducing the toxicity of the soil. Soils from the F-Area seepline that were found to inhibit lettuce seed germination and radical elongation in 1990 were not found to be significantly different from soils from an uncontaminated control site in this test. After six washings of the soil, the toxicity of the leachate was comparable to that of de-ionized water. This indicates that natural water movements may have rendered the F-Area seepline soils less toxic to lettuce seedlings than in previous tests.

Nelson, E.A.; Westbury, H.M. Jr.

1994-09-01

54

Comparative proteomics indicates that biosynthesis of pectic precursors is important for cotton fiber and Arabidopsis root hair elongation.  

PubMed

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. PMID:20525998

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

2010-06-06

55

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

56

Dynamics of aquaporins and water relations during hypocotyl elongation in Ricinus communis L. seedlings.  

PubMed

The rate of water flow across biological membranes can be modulated by aquaporins which are expressed in many cells and tissues. The biological functions of these water channels in cellular processes have often been anticipated from the expression pattern, although the participation in the underlying process is not known in many cases. Ten putative aquaporin transcripts were identified in castor bean (Ricinus communis L.) seedlings and the water channel activity of three selected genes was analysed by heterologous expression in Xenopus oocytes, as well as the spatial and temporal expression by in situ hybridization/immunolocalization along the hypocotyl's axis. Water relations parameters were studied in elongating and non-elongating tissues using the cell pressure probe technique. These results indicate that (i) the amount of the RcPIP2-1 aquaporin correlated best with the elongation activity of the etiolated hypocotyl and (ii) the hydraulic conductivity of cortex cells is significantly higher in the elongating region of the hypocotyl compared with the non-elongating, mature region. PMID:15897227

Eisenbarth, Daniel A; Weig, Alfons R

2005-05-16

57

Elongational flow behavior of viscoelastic liquids: Modelling bubble dynamics with viscoelastic constitutive relations  

Microsoft Academic Search

Summary Earlier parts of this series have described a technique based on the collapse of single bubbles in the fluids for studying the elongational rheology of viscoelastic solutions and melts of moderate viscosities (?0 > 102p) at relatively high strain rates\\u000a

G. Pearson; S. Middleman

1978-01-01

58

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

Technology Transfer Automated Retrieval System (TEKTRAN)

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

59

Three related receptor-like kinases are required for optimal cell elongation in Arabidopsis thaliana.  

PubMed

Cell elongation in plants is controlled by environmental cues such as light and internal growth regulators including plant steroid hormones, brassinosteroids (BRs). In this study, we found that 3 related receptor-like kinases (RLKs), HERCULES1, THESEUS1, and FERONIA, are transcriptionally induced by BRs and are down-regulated in the loss-of-function BR mutant bri1 and up-regulated in the constitutive BR-response mutant bes1-D. These RLKs belong to the CrRLK family that has 17 members in Arabidopsis. We hypothesize that these RLKs are involved in BR-regulated processes. Although 2 of the RLKs were recently found to mediate male-female interaction during pollen tube reception (FERONIA) and to sense cell wall integrity (THESEUS1), our genetic studies demonstrated that they are required for cell elongation during vegetative growth as herk1 the1 double and fer RNAi mutants displayed striking dwarf phenotypes. The herk1 the1 double mutant enhances the dwarf phenotype of bri1 and partially suppresses bes1-D phenotype, supporting a role of HERK1/THE1 in BR-mediated cell elongation. Microarray experiments demonstrated that these RLKs control the expression of a unique set of genes including those implicated in cell elongation and 16% of the genes affected in herk1 the1 are regulated by BRs. Our results, therefore, identify a previously unknown pathway that functions cooperatively with, but largely independent of the BR pathway to regulate cell elongation. The work establishes a platform to identify other signaling components in this important pathway for plant growth and provides a paradigm to study the coordination of independent pathways in the regulation of a common biological process. PMID:19383785

Guo, Hongqing; Li, Lei; Ye, Huaxun; Yu, Xiaofei; Algreen, Alexandria; Yin, Yanhai

2009-04-21

60

Three related receptor-like kinases are required for optimal cell elongation in Arabidopsis thaliana  

Microsoft Academic Search

Cell elongation in plants is controlled by environmental cues such as light and internal growth regulators including plant steroid hormones, brassinosteroids (BRs). In this study, we found that 3 related receptor-like kinases (RLKs), HERCULES1, THESEUS1, and FERONIA, are transcriptionally induced by BRs and are down-regulated in the loss-of-function BR mutant bri1 and up-regulated in the constitutive BR-response mutant bes1-D. These

Hongqing Guo; Lei Li; Huaxun Ye; Xiaofei Yu; Alexandria Algreen; Yanhai Yin

2009-01-01

61

Cooperative Action of SLR1 and SLR2 Is Required for Lateral Root-Specific Cell Elongation in Maize  

Microsoft Academic Search

Lateral roots play an important role in water and nutrient uptake largely by increasing the root surface area. In an effort to characterize lateral root development in maize (Zea mays), we have isolated from Mutator (Mu) transposon stocks and characterized two nonallelic monogenic recessive mutants: slr1 and slr2 (short lateral roots1 and 2), which display short lateral roots as a

Frank Hochholdinger; Woong June Park; Gunter H. Feix

2001-01-01

62

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

63

GABA accumulation causes cell elongation defects and a decrease in expression of genes encoding secreted and cell wall-related proteins in Arabidopsis thaliana.  

PubMed

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

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

2011-04-06

64

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

65

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

66

Relations between Roots and Coefficients of Cubic Equations with One Root Negative the Reciprocal of Another  

ERIC Educational Resources Information Center

|Under predetermined conditions on the roots and coefficients, necessary and sufficient conditions relating the coefficients of a given cubic equation x[cubed] + ax[squared] + bx + c = 0 can be established so that the roots possess desired properties. In this note, the condition for one root of a cubic equation to be "the negative reciprocal of…

Asiru, M. A.

2007-01-01

67

Production of Reactive Oxygen Intermediates (O2??, H2O2, and ?OH) by Maize Roots and Their Role in Wall Loosening and Elongation Growth  

PubMed Central

Cell extension in the growing zone of plant roots typically takes place with a maximum local growth rate of 50% length increase per hour. The biochemical mechanism of this dramatic growth process is still poorly understood. Here we test the hypothesis that the wall-loosening reaction controlling root elongation is effected by the production of reactive oxygen intermediates, initiated by a NAD(P)H oxidase-catalyzed formation of superoxide radicals (O2??) at the plasma membrane and culminating in the generation of polysaccharide-cleaving hydroxyl radicals (?OH) by cell wall peroxidase. The following results were obtained using primary roots of maize (Zea mays) seedlings as experimental material. (1) Production of O2??, H2O2, and ?OH can be demonstrated in the growing zone using specific histochemical assays and electron paramagnetic resonance spectroscopy. (2) Auxin-induced inhibition of growth is accompanied by a reduction of O2?? production. (3) Experimental generation of ?OH in the cell walls with the Fenton reaction causes wall loosening (cell wall creep), specifically in the growing zone. Alternatively, wall loosening can be induced by ?OH produced by endogenous cell wall peroxidase in the presence of NADH and H2O2. (4) Inhibition of endogenous ?OH formation by O2?? or ?OH scavengers, or inhibitors of NAD(P)H oxidase or peroxidase activity, suppress elongation growth. These results show that juvenile root cells transiently express the ability to generate ?OH, and to respond to ?OH by wall loosening, in passing through the growing zone. Moreover, inhibitor studies indicate that ?OH formation is essential for normal root growth.

Liszkay, Anja; van der Zalm, Esther; Schopfer, Peter

2004-01-01

68

Very long-chain fatty acids: elongation, physiology and related disorders.  

PubMed

Very long-chain fatty acids (VLCFAs) are fatty acids (FAs) with a chain-length of ?22 carbons. Mammals have a variety of VLCFAs differing in chain-length and the number of double bonds. Each VLCFA exhibits certain functions, for example in skin barrier formation, liver homeostasis, myelin maintenance, spermatogenesis, retinal function and anti-inflammation. These functions are elicited not by free VLCFAs themselves, but through their influences as components of membrane lipids (sphingolipids and glycerophospholipids) or precursors of inflammation-resolving lipid mediators. VLCFAs are synthesized by endoplasmic reticulum membrane-embedded enzymes through a four-step cycle. The most important enzymes determining the tissue distribution of VLCFAs are FA elongases, which catalyze the first, rate-limiting step of the FA elongation cycle. Mammals have seven elongases (ELOVL1-7), each exhibiting a characteristic substrate specificity. Several inherited disorders are caused by mutations in genes involved in VLCFA synthesis or degradation. In this review, I describe the molecular mechanism of FA elongation and the responsible enzymes in mammals and yeast, as well as VLCFA-related disorders in human. PMID:22984005

Kihara, Akio

2012-09-14

69

Primary Site of Action of Amitrole in Arabidopsis thaliana Involves Inhibition of Root Elongation but Not of Histidine or Pigment Biosynthesis  

PubMed Central

Interference with histidine metabolism, inhibition of pigment biosynthesis, or both have been the principal candidates for the primary site of action of 3-amino 1,2,4-triazole (amitrole). Arabidopsis thaliana is sensitive to 1,2,4-triazole-3-alanine, a feedback inhibitor of histidine biosynthesis, and this effect is reversed by histidine. The combination of triazolealanine and histidine, however, does not reverse the herbicidal effect of amitrole. This indicates that amitrole toxicity is not caused by histidine starvation, nor is it caused by the accumulation of a toxic intermediate of the histidine pathway. Amitrole inhibits root elongation at lower concentrations than it causes pigment bleaching in the leaves. In contrast, fluridone, a known inhibitor of the carotenoid biosynthetic pathway does not block root elongation. Fluridone also inhibits carotenoid accumulation in etiolated seedlings in the dark, but amitrole does not. Last, gabaculine and acifluorfen, but not amitrole, prevent chlorophyll accumulation in greening etiolated seedlings of Arabidopsis. These experiments cast doubt on pigment biosynthesis as the primary site of action of amitrole.

Heim, Dale R.; Larrinua, Ignacio M.

1989-01-01

70

Patatin-Related Phospholipase pPLAIII?-Induced Changes in Lipid Metabolism Alter Cellulose Content and Cell Elongation in Arabidopsis[C][W  

PubMed Central

The release of fatty acids from membrane lipids has been implicated in various plant processes, and the patatin-related phospholipases (pPLAs) constitute a major enzyme family that catalyzes fatty acid release. The Arabidopsis thaliana pPLA family has 10 members that are classified into three groups. Group 3 pPLAIII has four members but lacks the canonical lipase/esterase consensus catalytic sequences, and their enzymatic activity and cellular functions have not been delineated. Here, we show that pPLAIII? hydrolyzes phospholipids and galactolipids and additionally has acyl-CoA thioesterase activity. Alterations of pPLAIII? result in changes in lipid levels and composition. pPLAIII?-KO plants have longer leaves, petioles, hypocotyls, primary roots, and root hairs than wild-type plants, whereas pPLAIII?-OE plants exhibit the opposite phenotype. In addition, pPLAIII?-OE plants have significantly lower cellulose content and mechanical strength than wild-type plants. Root growth of pPLAIII?-KO plants is less sensitive to treatment with free fatty acids, the enzymatic products of pPLAIII?, than wild-type plants; root growth of pPLAIII?-OE plants is more sensitive. These data suggest that alteration of pPLAIII? expression and the resulting lipid changes alter cellulose content and cell elongation in Arabidopsis.

Li, Maoyin; Bahn, Sung Chul; Guo, Liang; Musgrave, William; Berg, Howard; Welti, Ruth; Wang, Xuemin

2011-01-01

71

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

72

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

Microsoft Academic Search

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

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

2004-01-01

73

DSK1, a novel kinesin-related protein from the diatom Cylindrotheca fusiformis that is involved in anaphase spindle elongation  

PubMed Central

We have identified an 80-kD protein that is involved in mitotic spindle elongation in the diatom Cylindrotheca fusiformis. DSK1 (Diatom Spindle Kinesin 1) was isolated using a peptide antibody raised against a conserved region in the motor domain of the kinesin superfamily. By sequence homology, DSK1 belongs to the central motor family of kinesin- related proteins. Immunoblots using an antibody raised against a non- conserved region of DSK1 show that DSK1 is greatly enriched in mitotic spindle preparations. Anti-DSK1 stains in diatom central spindle with a bias toward the midzone, and staining is retained in the spindle midzone during spindle elongation in vitro. Furthermore, preincubation with anti-DSK1 blocks function in an in vitro spindle elongation assay. This inhibition of spindle elongation can be rescued by preincubating concurrently with the fusion protein against which anti-DSK1 was raised. We conclude that DSK1 is involved in spindle elongation and is likely to be responsible for pushing hal-spindles apart in the spindle midzone.

1996-01-01

74

Seasonal water relations of Lyginia barbata (Southern rush) in relation to root xylem development and summer dormancy of root apices.  

PubMed

*Periods of dormancy in shallow roots allow perennial monocotyledons to establish deep root systems, but we know little about patterns of xylem maturation, water-transport capacities and associated economies in water use of growing and dormant roots. *Xylem development, anatomy, conductance and in situ cellular [K] and [Cl] were investigated in roots of field-grown Lyginia barbata (Restionaceae) in Mediterranean southwestern Australia. Parallel studies of gas exchange, culm relative water loss and soil water content were conducted. *Stomatal conductance and photosynthesis decreased during summer drought as soil profiles dried, but rates recovered when dormant roots became active with the onset of wetter conditions. Anatomical studies identified sites of close juxtaposition of phloem and xylem in dormant and growing roots. Ion data and dye tracing showed mature late metaxylem of growing roots was located >or= 100 mm from the tip, but at only roots. Dormant roots remained hydrated in dry soils (0.001-0.005 g g(-1)). *Effective regulation of growth and water-conserving/obtaining properties permits the survival of shallow roots of L. barbata during summer drought and may represent important strategies for establishing deeper perennial root systems in other monocotyledonous plants adapted to seasonally dry habitats. PMID:20085620

Shane, Michael W; McCully, Margaret E; Canny, Martin J; Pate, John S; Huang, Cheng; Ngo, Hai; Lambers, Hans

2010-01-18

75

Tomato BRASSINOSTEROID INSENSITIVE1 Is Required for Systemin-Induced Root Elongation in Solanum pimpinellifolium but Is Not Essential for Wound Signaling[W  

PubMed Central

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

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

2007-01-01

76

Gibberellins in Relation to Flowering and Stem Elongation in the Long Day Plant Silene armeria1  

PubMed Central

Two long days induced some flowering and 4 or more long days caused 100% flowering in Silene armeria. On long days microscopically detectable flower primordia were first seen after 6 days, which is at least 1 day before the start of stem elongation. Both gibberellin A3 and A7 caused flowering on short days, but the results were variable and flowering was never 100%. Three different gibberellins were detected in Silene extracts. The pattern of gibberellins extracted from plants on short and long days was qualitatively the same, but on long days gibberellin content was up to 100% higher than on short days. Only small amounts of diffusible gibberellins were obtained from Silene shoot tips (including very young leaves) on short days. However, on long days the diffusible gibberellins increased by as much as 10-fold after 4 to 6 long days but then declined somewhat after 10 long days. The gibberellins extracted from the shoot tips at the completion of the diffusion period also increased under long days, although the increase was not as large as for the diffusible gibberellins. An A5-like gibberellin present in extracts was not detected in diffusates. Treatment with AMO 1618 (2-isopropyl-4-dimethylamino-5-methylphenyl-1-piperidine-carboxylate methyl chloride) completely inhibited stem elongation on long days but had no effect on flowering. In addition, treatment with AMO 1618 caused at least an 80% decrease in the level of extractable gibberellin, while the diffusible gibberellin was reduced below the limits of detection in the d5 corn bioassay. When endogenous gibberellin levels were suppressed by pretreatment with AMO 1618 on short days, gibberellin A3 caused more stem elongation in plants moved to long days than in plants left on short days. Thus the sensitivity of Silene plants to gibberellin with respect to stem growth is affected by photoperiod. It is concluded that in Silene endogenous gibberellins are a controlling factor for stem elongation but apparently are not required for flower formation.

Cleland, Charles F.; Zeevaart, Jan A. D.

1970-01-01

77

Drosophila egg chamber elongation  

PubMed Central

As tissues and organs are formed, they acquire a specific shape that plays an integral role in their ability to function properly. A relatively simple system that has been used to examine how tissues and organs are shaped is the formation of an elongated Drosophila egg. While it has been known for some time that Drosophila egg elongation requires interactions between a polarized intracellular basal actin network and a polarized extracellular network of basal lamina proteins, how these interactions contribute to egg elongation remained unclear. Recent studies using live imaging have revealed two novel processes, global tissue rotation and oscillating basal actomyosin contractions, which have provided significant insight into how the two polarized protein networks cooperate to produce an elongated egg. This review summarizes the proteins involved in Drosophila egg elongation and how this recent work has contributed to our current understanding of how egg elongation is achieved.

2012-01-01

78

Relation between elongation factor and angle of friction from various outcrops  

NASA Astrophysics Data System (ADS)

The study of granular materials, and more particularly their mechanical behaviour, has made it possible to highlight, the influence of the grains shape on their mechanical behaviour. Recently when being concerned with till formations (glacial deposits) that cover mountain slopes and govern natural hazards, Lebourg (2000) has shown that there exists a simple linear regression of the internal angle of friction (phi) on a shape parameter (elongation factor IA ) based on the analysis of six tills formations coming from a paleoglacial valley (Vallée d Aspe, Pyrénées Occidentales : IGN map 1547 OT, 1/25 000 ; geological map URDOS 1/80 000). These results are in agreement with previous works where relation between shape and mechanical properties is assumed. Till-forming materials look like a heap of unsorted very heterogeneous material characterised by rock debris of all sizes from angular blocks of metric size to very fine rock. In addition to the block sizes, lithology, petrography and the spatial distribution of the blocks are also heterogeneous. Then it is hard, if not impossible, to collect a large sample of mechanical and physical data from the till in order to execute good simulations while running numerical programs. The validation of such a relation would be very interesting for other till formations and in any case of natural hazards such as landslides. So we propose new results based on the analysis of a set of samples collected on the site of La Clapière, a rocky landslide. The landslide at La Clapière, in south-eastern France, is located on the east side of the steep La Tinée river valley upstream of the village of Saint Etienne de Tinée. On the one hand, triaxial compression (test with simultaneous compression of a cylindrical sample and application of axisymetric confining pressure) has been performed on four sets of samples collected at La Clapière, then mechanical properties (E : Young modulus, phi: angle of internal friction, C : cohesion) were estimated. Sample forming materials are coarse to fine particles (gouge and weathered and crushed gneiss). On the other side samples were screened with a set of 10 from 0.08 mm up to 25 mm, then grey level images of a series of individual particles belonging to each granulometric interval have been acquired (particles lie on a stage in a natural way) for 2D parameters measurements. Two dimensional size and shape parameters (A: area, P, perimeter, RI, RC : radii of the largest inner respectively the smallest outer circle of each particle and the ratio IA= RI/RC) have been measured by the mean of an image analyser and computed and statiscally analysed (statistical parameters, normality evaluation, …). This paper is an attempt to show how the simple linear regression inferred for various tills can be extended to weathered, crushed materials.

Martins-Campina, B.; Lebourg, T.; Riss, J.; Benabderrazik, A.; Fabre, R.

2003-04-01

79

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

PubMed

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

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

2013-07-25

80

Occurrence of osmiophilic particles is correlated to elongation growth of higher plants  

Microsoft Academic Search

Summary The occurrence of elongation growth-related osmiophilic particles (OPs) was investigated in hypocotyls of sunflower, bean, and spruce as well as in pea epicotyls and in cress roots of intact seedlings. In all analyzed species, OPs were found to occur specifically within the periplasmic space between plasma membrane and the outer epidermal cell walls of elongating parts of hypocotyls, epicotyls,

O. Šamajová; J. Šamaj; D. Volkmann; H. G. Edelmann

1998-01-01

81

Vegetation roots and fluvial ecomorphodynamics: processes and related timescales  

NASA Astrophysics Data System (ADS)

The biological dynamics of riparian and riverbed vegetation has been recognized to play a fundamental role in fluvial ecomorphodynamics. Contrarily to terrain slopes, the role of vegetation roots in alluvial (non-cohesive) sediment is quite unexplored both at the field and laboratory scales. Hydrologic and biologic growth processes can interact at certain timescales and be determinant to the colonization and successive stabilization of alluvial bedforms. This influences the reworking return period (i.e., the magnitude of impacting floods) of islands and bars in the absence of vegetation and may lead to specific riverbed morphological features. In this paper we first discuss how river hydrology may influence root tropisms and the related growing architecture at the field scale (Pasquale et al., 2012). Different root density vertical distributions can thus be determinant to uprooting and transport processes (Edmaier et al., 2011). Results from a number of laboratory experiments aimed at relating floods intertime and root growth timescales to uprooting statistics are then presented (Perona et al., 2012). We show the biomass selection mechanism operated by flow disturbances on riverbed vegetation, and discuss :i) the related impact that this process may have to select young vegetation in and among species (Crouzy and Perona, 2012; ii) two exemplary vegetation patterns that have been observed in rivers with converging boundaries and ephemeral streams. This study is a first step to better understand and model the sediment stabilization mechanism by vegetation roots in the equations of morphodynamics.

Perona, P.

2012-04-01

82

Hydroxyproline Formation and Its Relation to Auxin-induced Cell Elongation in the Avena Coleoptile.  

PubMed

A study has been made of the effects on hydroxyproline formation of 4 factors that influence the rate of cell elongation in the Avena coleoptile; auxin, sugars, an external osmoticum, and actinomycin D. Hydroxyproline formation is increased by a combination of auxin and sucrose, but is affected to a much lesser extent by either factor alone. Its formation is inhibited by an external osmoticum but is scarcely affected by actinomycin D. The lack of correlation between the amount of hydroxyproline synthesis and the growth rate suggests that hydroxyproline formation is not involved in the actual process of wall loosening. It is suggested, instead, that if the wall is to retain its capacity for rapid extension, those hemicelluloses which are incorporated into it by intussusception rather than by apposition must be attached to a hydroxyproline-protein. PMID:16656947

Cleland, R

1968-10-01

83

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

Microsoft Academic Search

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

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

2001-01-01

84

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

PubMed

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

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

2011-05-16

85

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

PubMed

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

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

2010-10-06

86

A Model Relating Root Permeability to Flux and Potentials  

PubMed Central

A model that relates hydraulic permeability to water flux and to gradients in pressure potential and solute potential was tested using soybean (Glycine max) plants. Water flux was varied by additions of polyethylene glycol 6,000 around one portion of a divided root system and by changing the light intensity and CO2 concentration around the plants. The data are compatible with the model only if the hydraulic permeability varies with flux; however, the data were insufficient for rigorous testing. Three sets of published data fit the model only if hydraulic permeability varies. Evidence originally presented as involving constant hydraulic permeability is shown, rather, to require variable hydraulic permeability.

Michel, Burlyn E.

1977-01-01

87

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

PubMed Central

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

Useche, Antonio; Shipley, Bill

2010-01-01

88

Lipids in Grape Roots in Relation to Chloride Transport 1  

PubMed Central

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

Kuiper, Pieter J. C.

1968-01-01

89

Physiological evidence for involvement of a kinesin-related protein during anaphase spindle elongation in diatom central spindles  

Microsoft Academic Search

We have developed a new model system for studying spindle elongation in vitro using the pennate, marine diatom Cylindrotheca fusiformis. C. fusiformis can be grown in bulk to high densities while in log phase growth and synchronized by a simple light\\/dark regime. Isolated spindles can be attained in quantities sufficient for biochemical analysis and spindle tubulin is ,x,5 % of

Christopher J. Hogan; Lanie Stephens; Takashi Shimizu; W. Zacheus Cande

1992-01-01

90

The mechanical behavior of isolated Avena coleoptile walls subjected to constant stress: properties and relation to cell elongation.  

PubMed

In order to assess the role of the mechanical properties of the wall in auxin-induced cell elongation, a study has been made of the ability of isolated Avena coleoptile walls to extend (creep) when subjected to a constant applied stress. Creep occurs as a viscoelastic extension which has the following characteristics: the extension is proportional to log time and is partly reversible, and the extension rate has a Q(10) of about 1.05 and is markedly greater in auxin-pretreated walls. In nonconditioned walls the extension rate is proportional to applied stress, but pre-extension causes the appearance of an apparent yield strain. The similarity of creep and instantaneous plastic deformation in response to temperature or to pretreatment with auxin or KCN suggests that the instantaneous deformation is simply the viscoelastic extension which occurs at very short times. A comparison of these viscoelastic properties with the properties of auxin-induced cell elongation indicates that cell elongation requires more than just a physical extension of the wall. It is suggested that elongation occurs as a series of extension steps, each of which involves a viscoelastic extension preceded or accompanied by an auxin-dependent biochemical change in the wall properties. PMID:16657709

Cleland, R

1971-06-01

91

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

92

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

PubMed

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. PMID:11537498

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

1992-11-01

93

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

PubMed Central

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

2012-01-01

94

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

Microsoft Academic Search

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

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

2002-01-01

95

Water Relations of Pine Seedlings in Relation to Root and Shoot Growth 1  

PubMed Central

The effects of water stress on growth and water relations of loblolly and white pine seedlings were studied during series of drying cycles. As mean soil water potential decreased, growth of roots, needles, and buds decreased. Growth of roots during successive severe drying cycles was not uniform, however. A study of needle and root extension showed that of the total growth of roots for 3 7-day drying cycles, only 6% occurred during the third cycle, while needle extension was uniform for the 3 cycles. The difference in response of needles and roots to drying cycles may be attributed primarily to the effect of water stress on the growing region. When subjected to a severe stress, roots matured toward the tip and became dormant, resulting in less growth during subsequent drying cycles. The intercalary growing region of needles, however, was not altered seriously enough by the stress to cause a difference in amount of growth during each drying cycle. Transpiration of loblolly pine was lower in the second drying cycle than in the first. Needle water potential after rewatering was as high as that of control plants watered daily; root resistance was apparently not important in restricting transpiration during a second drying cycle. Needle diffusion resistance of loblolly pine, measured with a low-resistance diffusion porometer, was slightly higher during the second drying cycle than during the first. In addition, many primary needles were killed during the first period of stress. These factors contributed to the reduction of transpiration during the second drying cycle. Diffusion resistance of Coleus increased and transpiration ceased during the first drying cycle while water potential remained relatively high. After rewatering, both leaf resistance and transpiration returned to the control level, presumably because the stress during the first period of drying was not severe. The diffusion resistances observed for well-watered plants were 30 to 50 sec·cm?1 for loblolly pine, 3 to 5 sec·cm?1 for Coleus, and 4 to 6 sec·cm?1 for tomato. These values agree closely with those reported by other workers.

Kaufmann, Merrill R.

1968-01-01

96

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

PubMed

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

Ivanchenko, Maria G; den Os, Désirée; Monshausen, Gabriele B; Dubrovsky, Joseph G; Bednárová, Andrea; Krishnan, Natraj

2013-08-21

97

Changes in onion root development induced by the inhibition of peptidyl-prolyl hydroxylase and influence of the ascorbate system on cell division and elongation  

Microsoft Academic Search

.   Post-translational hydroxylation of peptide-bound proline residues, catalyzed by peptidyl-prolyl-4 hydroxylase (EC 1.14.11.2)\\u000a using ascorbate as co-substrate, is a key event in the maturation of a number of cell wall-associated hydroxyproline-rich\\u000a glycoproteins (HRGPs), including extensins and arabinogalactan-proteins, which are involved in the processes of wall stiffening,\\u000a signalling and cell proliferation. Allium cepa L. roots treated with 3,4-DL-dehydroproline (DP), a specific

Mario C. De Tullio; Costantino Paciolla; Francesca Dalla Vecchia; Nicoletta Rascio; Saverio D'Emerico; Laura De Gara; Rosalia Liso; Oreste Arrigoni

1999-01-01

98

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

SciTech Connect

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

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

1993-09-01

99

Relative contribution of initial root and shoot morphology in predicting field performance of hardwood seedlings  

Microsoft Academic Search

Single and multiple linear regression techniques were used to explain the capacity of initial seedling root volume (Rv) and first-order lateral roots (FOLR) relative to shoot height, diameter, and fresh mass to serve as important indicators of stock quality and predictors of first- and second-year height and diameter on an afforestation site in southern Indiana, USA. This was accomplished for

D. F. Jacobs; K. F. Salifu; J. R. Seifert

2005-01-01

100

Episodic Growth and Relative Shoot:Root Balance in Loblolly Pine Seedlings  

Microsoft Academic Search

Leaf, root and stem systems of loblolfy pine seedlings are characterized by a seasonal periodicity in growth, during which they alternate in spurts of activity. Despite this periodicity, the aflometric co- efficient describing the ratio of the relative growth rates of leaf to root remains constant for at last the first two years of development. In part, constancy results from

A. P. DREW; F. T. LEDIGt

101

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; Crèvecoeur, Michèle; Penel, Claude

2007-01-01

102

Root Secretion of Defense-related Proteins Is Development-dependent and Correlated with Flowering Time*  

PubMed Central

Proteins found in the root exudates are thought to play a role in the interactions between plants and soil organisms. To gain a better understanding of protein secretion by roots, we conducted a systematic proteomic analysis of the root exudates of Arabidopsis thaliana at different plant developmental stages. In total, we identified 111 proteins secreted by roots, the majority of which were exuded constitutively during all stages of development. However, defense-related proteins such as chitinases, glucanases, myrosinases, and others showed enhanced secretion during flowering. Defense-impaired mutants npr1-1 and NahG showed lower levels of secretion of defense proteins at flowering compared with the wild type. The flowering-defective mutants fca-1, stm-4, and co-1 showed almost undetectable levels of defense proteins in their root exudates at similar time points. In contrast, root secretions of defense-enhanced cpr5-2 mutants showed higher levels of defense proteins. The proteomics data were positively correlated with enzymatic activity assays for defense proteins and with in silico gene expression analysis of genes specifically expressed in roots of Arabidopsis. In conclusion, our results show a clear correlation between defense-related proteins secreted by roots and flowering time.

De-la-Pena, Clelia; Badri, Dayakar V.; Lei, Zhentian; Watson, Bonnie S.; Brandao, Marcelo M.; Silva-Filho, Marcio C.; Sumner, Lloyd W.; Vivanco, Jorge M.

2010-01-01

103

In vitro rooting of genetically related Eucalyptus urophylla  ×  Eucalyptus grandis clones in relation to the time spent in culture  

Microsoft Academic Search

In vitro responsiveness of microshoots derived from three genetically related and different age Eucalyptus urophylla × Eucalyptus grandis clones kept cultivated by monthly subcultures was assessed on two rooting media in relation to the time spent in culture.\\u000a Significant differences of rooting capacity were found between the two 22-year-old half sibling genotypes 147 and 149 according\\u000a to the concentration of BA added

François Mankessi; Aubin Saya; Christelle Baptiste; Sophie Nourissier; Olivier Monteuuis

2009-01-01

104

Cell elongation and branching are regulated by differential phosphorylation states of the nuclear Dbf2-related kinase COT1 in Neurospora crassa.  

PubMed

Dysfunction of the Neurospora crassa nuclear Dbf2-related kinase COT1 leads to cessation of tip extension and massive induction of new sites of growth. To determine the role phosphorylation plays in COT1 function, we mutated COT1 residues corresponding to positions of highly conserved nuclear Dbf2-related phosphorylation sites. Analyses of the point-mutation cot-1 strains (mimicking non- and constitutively phosphorylated states) indicate the involvement of COT1 phosphorylation in the regulation of hyphal elongation and branching as well as asexual development by altering cell wall integrity and actin organization. Phosphorylation of COT1's activation segment (at Ser417) is required for proper in vitro kinase activity, but has only a limited effect on hyphal growth. In marked contrast, even though phosphorylation of the C-terminal hydrophobic motif (at Thr589) is crucial for all COT1 functions in vivo, the lack of Thr589 phosphorylation did not significantly affect in vitro COT1 kinase activity. Nevertheless, its regulatory role has been made evident by the significant increase observed in COT1 kinase activity when this residue was substituted in a manner mimicking constitutive phosphorylation. We conclude that COT1 regulates elongation and branching in an independent manner, which is determined by its phosphorylation state. PMID:19818014

Ziv, Carmit; Kra-Oz, Galia; Gorovits, Rena; März, Sabine; Seiler, Stephan; Yarden, Oded

2009-10-08

105

Kernel elongation in rice.  

PubMed

Kernel elongation after cooking is an important character of fine rice and most rice consumers prefer length-wise elongation. Although improvement of aromatic rice began early in the 1970s, until now the mechanisms and genetics of kernel elongation has remained unrevealed. Kernel elongation is considered as a physical phenomenon and is influenced by several physicochemical and genetic factors, including genotypes, aging temperature, aging time, water uptake, amylose content and gelatinization temperature. Recently the complete genetic map of fine rice has been created and the gene responsible for kernel length identified; moreover, this gene is tightly linked with the cooked kernel elongation trait. Several molecular markers linked with cooked kernel elongation have been developed. These tools will be helpful for the improvement of this important trait. For the proper study of cooked kernel elongation of rice, this review paper will provide the basis and directional materials for further studies. PMID:23238771

Golam, Faruq; Prodhan, Zakaria H

2012-12-12

106

Auxin-induced inhibition of lateral root initiation contributes to root system shaping in Arabidopsis thaliana.  

PubMed

The hormone auxin is known to inhibit root elongation and to promote initiation of lateral roots. Here we report complex effects of auxin on lateral root initiation in roots showing reduced cell elongation after auxin treatment. In Arabidopsis thaliana, the promotion of lateral root initiation by indole-3-acetic acid (IAA) was reduced as the IAA concentration was increased in the nanomolar range, and IAA became inhibitory at 25 nM. Detection of this unexpected inhibitory effect required evaluation of root portions that had newly formed during treatment, separately from root portions that existed prior to treatment. Lateral root initiation was also reduced in the iaaM-OX Arabidopsis line, which has an endogenously increased IAA level. The ethylene signaling mutants ein2-5 and etr1-3, the auxin transport mutants aux1-7 and eir1/pin2, and the auxin perception/response mutant tir1-1 were resistant to the inhibitory effect of IAA on lateral root initiation, consistent with a requirement for intact ethylene signaling, auxin transport and auxin perception/response for this effect. The pericycle cell length was less dramatically reduced than cortical cell length, suggesting that a reduction in the pericycle cell number relative to the cortex could occur with the increase of the IAA level. Expression of the DR5:GUS auxin reporter was also less effectively induced, and the AXR3 auxin repressor protein was less effectively eliminated in such root portions, suggesting that decreased auxin responsiveness may accompany the inhibition. Our study highlights a connection between auxin-regulated inhibition of parent root elongation and a decrease in lateral root initiation. This may be required to regulate the spacing of lateral roots and optimize root architecture to environmental demands. PMID:21105922

Ivanchenko, Maria G; Napsucialy-Mendivil, Selene; Dubrovsky, Joseph G

2010-10-15

107

Bacteroides buccae and related taxa in necrotic root canal infections.  

PubMed Central

Fifty-seven adults with apical periodontitis were examined for the presence of nonpigmented Bacteroides species in 62 infected root canals. Nonpigmented Bacteroides species were found in 35 canals. In four cases two nonpigmented Bacteroides species and in one case three nonpigmented Bacteroides species were found. Species belonging to the B. fragilis group were not isolated. The most frequently isolated species were B. buccae (15 strains), B. oris (12 strains), and B. oralis (7 strains). alpha-Fucosidase, beta-N-acetylglucosaminidase, and beta-xylosidase appeared to be useful in the identification of B. buccae and B. oris. Corroding Bacteroides species were not found; all corroding strains were identified as Wolinella recta. The occurrence of nonpigmented Bacteroides species was compared with the severity of the periapical infection. A total of 13 B. buccae strains were found in acute infections and only 2 strains were found in asymptomatic infections, whereas other nonpigmented Bacteroides species were present in acutely infected and asymptomatic teeth with nearly equal frequency. Ultrastructural study of 13 B. buccae strains showed that 8 strains had a crystalline proteinaceous surface layer (S-layer) outside the outer membrane, but all 13 strains had areas of crystalline protein throughout in the outer membrane. The results suggest that B. buccae may have a specific role in the development of an acute opportunistic infection. Images

Haapasalo, M

1986-01-01

108

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

2012-11-01

109

Cytohistological analysis of roots whose growth is affected by a 60-Hz electric field  

SciTech Connect

Roots of Pisum sativum were exposed for 48 h to 60-Hz electric fields of 430 V/m in an aqueous inorganic growth medium. The growth in length of the exposed roots was 44% of that for control roots. Root tips were analyzed for mitotic index and cell cycle duration. Mature, differentiated root sections from tissue produced after electrode energization were analyzed for cell lengths and number of files. The major reason for the observation that exposed roots are shorter than control roots is that cell elongation in the former is greatly diminished relative to controls. 15 references, 1 figures, 4 tables.

Brulfert, A.; Miller, M.W.; Robertson, D.; Dooley, D.A.; Economou, P.

1985-01-01

110

Accumulation of peroxidase-related reactive oxygen species in trichoblasts correlates with root hair initiation in barley.  

PubMed

Root hairs are an important model in studies of cell differentiation and development in higher plants. The function of NADPH oxidase-related reactive oxygen species (ROS) in root hair development has been reported extensively in studies on Arabidopsis. In this study, we investigated the mechanism of the initiation of root hair formation, mediated by the peroxidase-dependent production of the highly reactive hydroxyl radical in barley (Hordeum vulgare L.). The distribution of ROS, including the hydroxyl radical (OH) and superoxide (O(2)(-)) was assessed using hydroxyphenyl fluorescein and nitroblue tetrazolium chloride, respectively, in the roots of wild-type plants and two root-hair mutants: root-hairless (rhl1.a) and with root hair growth blocked at the primordium stage (rhp1.b). Peroxidase-dependent OH accumulation was linked to root hair initiation and growth in plants where root hair formation was at least initiated, whereas OH was not detectable in the epidermis of the root-hairless mutant rhl1.a. O(2)(-) distribution in the roots of rhl1.a and rhp1.b mutants was not impaired and did not influence the root hair phenotype. Peroxidase inhibitor treatments of wild-type roots dramatically reduced the ability of growing roots to form root hairs and thus phenocopied the root-hairless phenotype. Expression of two candidate peroxidase genes, HvPRX45 and HvPRX2, was analyzed and their possible role in root hair-specific production of hydroxyl radicals was discussed. We propose a model of a two-step, coordinated ROS formation process in root hair cells that involves root hair-specific peroxidase(s) and root hair-specific NADPH oxidase necessary for a proper root hair formation in barley. PMID:23218546

Kwasniewski, Miroslaw; Chwialkowska, Karolina; Kwasniewska, Jolanta; Kusak, Julia; Siwinski, Kamil; Szarejko, Iwona

2012-12-04

111

Rhizosphere Microbial Community Structure in Relation to Root Location and Plant Iron Nutritional Status  

Microsoft Academic Search

Root exudate composition and quantity vary in relation to plant nutritional status, but the impact of the differences on rhizosphere microbial communities is not known. To examine this question, we performed an experiment with barley (Hordeum vulgare) plants under iron-limiting and iron-sufficient growth conditions. Plants were grown in an iron-limiting soil in root box microcosms. One-half of the plants were

CHING-HONG YANG; DAVID E. CROWLEY

2000-01-01

112

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

113

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

114

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

NASA Astrophysics Data System (ADS)

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.; Betti, R.; Sabbagh, S. A.

2011-07-01

115

Phosphorus relations of roots and mycorrhizas of Rhododendron maximum L. in the southern Appalachians, North Carolina  

Microsoft Academic Search

The mycorrhizal associations of Rhododendron maximum in the southern Appalachian mountains were studied in relation to the supply and demand of phosphate at three altitudes. A variety of mycorrhizal associations are described together with the ability of the differing mycorrhizal types to produce phosphatase enzyme, which was inversely related to the availability of inorganic phosphate determined by a root bioassay,

John Dighton; David C. Coleman

1992-01-01

116

RNA Polymerase Elongation Factors  

PubMed Central

The elongation phase of transcription by RNA polymerase is highly regulated and modulated. Both general and operon-specific elongation factors determine the local rate and extent of transcription to coordinate the appearance of transcript with its use as a messenger or functional ribonucleoprotein or regulatory element, as well as to provide operonspecific gene regulation.

Roberts, Jeffrey W.; Shankar, Smita; Filter, Joshua J.

2010-01-01

117

Contribution of relative growth rate to root foraging by annual and perennial grasses from California oak woodlands  

Microsoft Academic Search

Plants forage for nutrients by increasing their root length density (RLD) in nutrient-rich soil microsites through root morphological changes resulting in increased root biomass density (RBD), specific root length (SRL), or branching frequency (BF). It is commonly accepted that fast-growing species will forage more than slow-growing species. However, foraging responses may be due solely to differences in relative growth rates

Zachary T. Aanderud; Caroline S. Bledsoe; James H. Richards

2003-01-01

118

Genetic Dissection of the Relative Roles of Auxin and Gibberellin in the Regulation of Stem Elongation in Intact Light-Grown Peas.  

PubMed Central

Exogenous gibberellin (GA) and auxin (indoleacetic acid [IAA]) strongly stimulated stem elongation in dwarf GA1-deficient le mutants of light-grown pea (Pisum sativum L.): IAA elicited a sharp increase in growth rate after 20 min followed by a slow decline; the GA response had a longer lag (3 h) and growth increased gradually with time. These responses were additive. The effect of GA was mainly in internodes less than 25% expanded, whereas that of IAA was in the older, elongating internodes. IAA stimulated growth by cell extension; GA stimulated growth by an increase in cell length and cell number. Dwarf lkb GA-response-mutant plants elongated poorly in response to GA (accounted for by an increase in cell number) but were very responsive to IAA. GA produced a substantial elongation in lkb plants only in the presence of IAA. Because lkb plants contain low levels of IAA, growth suppression in dwarf lkb mutants seems to be due to a deficiency in endogenous auxin. GA may enhance the auxin induction of cell elongation but cannot promote elongation in the absence of auxin. The effect of GA may, in part, be mediated by auxin. Auxin and GA control separate processes that together contribute to stem elongation. A deficiency in either leads to a dwarfed phenotype.

Yang, T.; Davies, P. J.; Reid, J. B.

1996-01-01

119

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

120

Water relations and root growth of two populations of Gutierrezia sarothrae  

Microsoft Academic Search

We hypothesise that genotypic differences in transpiration and root growth in the southern and northern populations of Gutierrezia sarothrae are driven by growing season vapour pressure deficit (VPD) and that ecotypic differentiations are linked to corresponding variations in tissue and leaf water relations. Seedlings from an Idaho (ID) and a Texas (TX) seed source were grown either in an open

Changgui Wan; Ronald E Sosebee; Bobby L McMichael

1998-01-01

121

CULTURE PARAMETERS INFLUENCING THE PRODUCTION OF GOSSYPOL AND RELATED COMPOUNDS IN COTTON HAIRY ROOTS  

Technology Transfer Automated Retrieval System (TEKTRAN)

Previously, we established conditions for culturing hairy roots from Rhizobium rhizogenes-transformed Gossypium hirsutum and Gossypium barbadense. Significant levels of gossypol and related derivatives were produced in culture. Gossypol is a di-sesquiterpene that has antiviral activity against env...

122

PIN2 is required for the adaptation of Arabidopsis roots to alkaline stress by modulating proton secretion  

PubMed Central

Soil alkalinity is a widespread environmental problem that limits agricultural productivity. The hypothesis that an auxin-regulated proton secretion by plasma membrane H+-ATPase plays an important role in root adaption to alkaline stress was studied. It was found that alkaline stress increased auxin transport and PIN2 (an auxin efflux transporter) abundance in the root tip of wild-type Arabidopsis plants (WT). Compared with WT roots, the pin2 mutant roots exhibited much reduced plasma membrane H+-ATPase activity, root elongation, auxin transport, and proton secretion under alkaline stress. More importantly, roots of the pks5 mutant (PKS5, a protein kinase) lacking PIN2 (a pks5/pin2 double mutant) lost the previous higher proton-secretion capacity and higher elongation rate of primary roots under alkaline stress. By using Arabidopsis natural accessions with a high proton-secretion capacity, it was found that their PIN2 transcription abundance is positively related to the elongation rate of the primary root and proton-secretion capacity under alkaline stress. Taken together, our results confirm that PIN2 is involved in the PKS5-mediated signalling cascade under alkaline-stress and suggest that PIN2 is required for the adaptation of roots to alkaline stress by modulating proton secretion in the root tip to maintain primary root elongation.

Xu, Weifeng; Jia, Liguo; Shi, Weiming; Zhang, Jianhua

2012-01-01

123

Geotropism in corn roots: evidence for its mediation by differential Acid efflux.  

PubMed

The elongation zone in intact growing corn roots secretes acid leading to a reduced pH along the surface of the root and in the adjacent medium. This can be detected by placing the root on an agar medium containing the pH indicator dye bromocresol purple. When the root is treated with a growth inhibitory concentration of the hormone indole-3-acetic acid, the acid efflux is reversed and growth is greatly retarded. When the root is mounted vertically, acid secretion is uniform along the elongation zone, and the root grows straight downward. When the root is placed horizontally, there is enhanced acid efflux along the upper surface of the elongation zone and reduced acid efflux along the lower surface. An increased rate of elongation of the upper cells relative to the lower cells then results in downward curvature of the root. The correlation between acid efflux patterns and growth patterns indicates that proton efflux is important in the control of root growth. PMID:17747632

Mulkey, T J; Evans, M L

1981-04-01

124

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

PubMed

Salinization is one of the most important causes of crop productivity reduction in many areas of the world. Mechanisms that control leaf growth and shoot development under the osmotic phase of salinity are still obscure, and opinions differ regarding the Abscisic acid (ABA) role in regulation of biomass allocation under salt stress. ABA concentration in roots and leaves was analyzed in a genotype of processing tomato under two increasing levels of salinity stress for five weeks: 100 mM NaCl (S10) and 150 mM NaCl (S15), to study the effect of ABA changes on leaf gas exchange and dry matter partitioning of this crop under salinity conditions. In S15, salinization decreased dry matter by 78% and induced significant increases of Na(+) and Cl(-) in both leaves and roots. Dry matter allocated in different parts of plant was significantly different in salt-stressed treatments, as salinization increased root/shoot ratio 2-fold in S15 and 3-fold in S15 compared to the control. Total leaf water potential (?(w)) decreased from an average value of approximately -1.0 MPa, measured on control plants and S10, to -1.17 MPa in S15. In S15, photosynthesis was reduced by 23% and stomatal conductance decreased by 61%. Moreover, salinity induced ABA accumulation both in tomato leaves and roots of the more stressed treatment (S15), where ABA level was higher in roots than in leaves (550 and 312 ng g(-1) fresh weight, respectively). Our results suggest that the dynamics of ABA and ion accumulation in tomato leaves significantly affected both growth and gas exchange-related parameters in tomato. In particular, ABA appeared to be involved in the tomato salinity response and could play an important role in dry matter partitioning between roots and shoots of tomato plants subjected to salt stress. PMID:22070973

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

2011-11-08

125

Silicon alleviates cadmium toxicity in Avicennia marina (Forsk.) Vierh. seedlings in relation to root anatomy and radial oxygen loss.  

PubMed

The effects of Si on growth, the anatomy of the roots, radial oxygen loss (ROL) and Fe/Mn plaque on the root surface were investigated in Avicennia marina (Forsk.) Vierh. seedlings under Cd stress. Si prompted the growth of seedlings and reduced the Cd concentration in the root, stem and leaf of A. marina. Si prompted the development of the apoplastic barrier in the roots, which may be related to the reduction of Cd uptake. The higher amount of ROL and Mn plaque on the root surface due to Si were also related to the promotion of Cd tolerance in A. marina seedlings. Therefore, it is concluded that the alteration of the anatomy of the roots, the increase of ROL and Mn plaque of A. marina seedlings play an important role in alleviation of Cd toxicity due to Si. PMID:24095049

Zhang, Qiong; Yan, Chongling; Liu, Jingchun; Lu, Haoliang; Wang, Wenyun; Du, Jingna; Duan, Hanhui

2013-10-04

126

Biophoton Emission Induced by Osmotic Stress in Adzuki Bean Root  

NASA Astrophysics Data System (ADS)

In order to evaluate the physiological damage to plants caused by osmotic stress, we have investigated the relationship between the inhibition of root elongation and spontaneous photon emission from the root. Adzuki bean roots were soaked in polyethylene glycol (PEG) solutions for short periods in their early growth stage, and their root length and photon emission were measured afterwards. Consequently, it became clear that the root elongation decreased with the increase of PEG concentration. Moreover, there was a clear correlation between the emission intensity of the cell division area in the root and the inhibition of elongation, though the elongation of individual roots varied to some degree.

Ohya, Tomoyuki; Oikawa, Noriko; Kawabata, Ryuzou; Okabe, Hirotaka; Kai, Shoichi

2003-12-01

127

Amelin: an enamel-related protein, transcribed in the cells of epithelial root sheath.  

PubMed

Since 1974, when Slavkin and his collaborators proposed the epithelial origin of cementum, many experiments have been carried out to provide evidence for deposition of enamel-related proteins along the root surface. However, neither amelogenin nor other proteins have fully satisfied expectations. In previous studies, we have identified a novel mRNA coding for an extracellular-like protein which we called amelin. It was expressed at high levels in secretory and postsecretory ameloblasts in rat molars and incisors. In situ hybridization experiments described in the present study also localized the amelin message to epithelial cells adjacent to the peripheral surface of newly deposited dentin in the root end and to cells embedded in cellular cementum in molars. In incisors, the amelin RNA positive cells were detected in the area where cementum formation had been initiated. No amelogenin RNA signal was found in the cells at the root surface. We postulate that the epithelial cells of the root sheath as well as the ameloblasts are synthesizing amelin which might be one of the key proteins coupled to the process of cementogenesis. PMID:8797108

Fong, C D; Slaby, I; Hammarström, L

1996-07-01

128

Chemical composition of apoplastic transport barriers in relation to radial hydraulic conductivity of corn roots ( Zea mays L.)  

Microsoft Academic Search

.   The hydraulic conductivity of roots (Lpr) of 6- to 8-d-old maize seedlings has been related to the chemical composition of apoplastic transport barriers in the endodermis\\u000a and hypodermis (exodermis), and to the hydraulic conductivity of root cortical cells. Roots were cultivated in two different\\u000a ways. When grown in aeroponic culture, they developed an exodermis (Casparian band in the hypodermal

Hilde Monika Zimmermann; Klaus Hartmann; Lukas Schreiber; Ernst Steudle

2000-01-01

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 Lounès-Hadj Sahraoui

130

Surgical Treatment of Aortic Root Aneurysm Related to Marfan Syndrome in Early Childhood  

Microsoft Academic Search

.   The prognosis of Marfan syndrome in both adult and pediatric patients is primarily related to the cardiovascular complications.\\u000a In infantile Marfan syndrome, although involvement of the mitral valve is the most frequently encountered cardiovascular lesion,\\u000a the aortic root can be more worrisome because of its excessive dilatation, leading to aortic insufficiency or dissection.\\u000a If the role of elective surgery

P. Dervanian; L. Mace ´; T. A. Folliguet; A. di Virgilio; J. M. Grinda; J. F. Fuzellier; B. De Geeter; P. Morville; J. Y. Neveux

1998-01-01

131

Comparison of the Levels of Six Endogenous Gibberellins in Roots and Shoots of Spinach in Relation to Photoperiod 1  

PubMed Central

This communication describes the distribution of gibberellins (GAs) in roots and shoots of spinach in relation to photoperiod. From previous work (Metzger, Zeevaart 1980 Plant Physiol 65: 623-626) shoots were known to contain GA53, GA44, GA19, GA17, GA20, and GA29. We now show by combined gas chromatography—mass spectrometry that roots contain GA44, GA19, and GA29. Trace amounts of GA53 were detected by combined gas chromatography—selected ion current monitoring. Neither GA17 nor GA20 were detected in root extracts. Analysis by the d-5 corn bioassay also showed no effect of photoperiodic treatment on the levels of GA-like substances in root extracts. Both phloem and xylem exudates had patterns of GA-like activity similar to those found in shoots and roots, respectively. Moreover, foliar application of [3H]GA20 resulted in the transport of label from the shoot to the roots. Over half of the label in the roots represented unmetabolized [3H]GA20, indicating that part of the GA20 in the phloem is transported to the roots. Consequently, if GA20 is made in, or transported to the roots, it is rapidly metabolized in that organ. This is a clear indication that regulation of GA metabolism is greatly different in roots and shoots.

Metzger, James D.; Zeevaart, Jan A. D.

1980-01-01

132

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...

133

Cortical Aerenchyma Formation in Hypocotyl and Adventitious Roots of Luffa cylindrica Subjected to Soil Flooding  

PubMed Central

Background and Aims Aerenchyma formation is thought to be one of the important morphological adaptations to hypoxic stress. Although sponge gourd is an annual vegetable upland crop, in response to flooding the hypocotyl and newly formed adventitious roots create aerenchyma that is neither schizogenous nor lysigenous, but is produced by radial elongation of cortical cells. The aim of this study is to characterize the morphological changes in flooded tissues and the pattern of cortical aerenchyma formation, and to analyse the relative amount of aerenchyma formed. Method Plants were harvested at 16 d after the flooding treatment was initiated. The root system was observed, and sections of fresh materials (hypocotyl, tap root and adventitious root) were viewed with a light or fluorescence microscope. Distributions of porosity along adventitious roots were estimated by a pycnometer method. Key Results Under flooded conditions, a considerable part of the root system consisted of new adventitious roots which soon emerged and grew quickly over the soil surface. The outer cortical cells of these roots and those of the hypocotyl elongated radially and contributed to the development of large intercellular spaces. The elongated cortical cells of adventitious roots were clearly T-shaped, and occurred regularly in mesh-like lacunate structures. In these positions, slits were formed in the epidermis. In the roots, the enlargement of the gas space system began close to the apex in the cortical cell layers immediately beneath the epidermis. The porosity along these roots was 11–45 %. In non-flooded plants, adventitious roots were not formed and no aerenchyma developed in the hypocotyl or tap root. Conclusions Sponge gourd aerenchyma is produced by the unique radial elongation of cells that make the expansigeny. These morphological changes seem to enhance flooding tolerance by promoting tissue gas exchange, and sponge gourd might thereby adapt to flooding stress.

Shimamura, Satoshi; Yoshida, Satoshi; Mochizuki, Toshihiro

2007-01-01

134

Spatial and temporal effects of soil temperature and moisture and the relation to fine root density on root and soil respiration in a mature apple orchard  

Microsoft Academic Search

We identified the role of various soil parameters and root density as drivers of soil respiration (Rs) in an apple orchard, measured during different periods of the year and at a range of distances from trees, in plots with\\u000a a different history of nutrient supply. Rs was measured in April, May, August and December and studied in relation to soil

Christian Ceccon; Pietro Panzacchi; Francesca Scandellari; Luca Prandi; Maurizio Ventura; Barbara Russo; Peter Millard; Massimo Tagliavini

2011-01-01

135

Optic Nerve Elongation  

PubMed Central

The length of the optic nerves is a reflection of normal postnatal cranio-orbital development. Unilateral elongation of an optic nerve has been observed in two patients with orbital and skull base neoplasms. In the first case as compared to the patient's opposite, normal optic nerve, an elongated length of the involved optic nerve of 45 mm was present. The involved optic nerve in the second patient was 10 mm longer than the normal opposite optic nerve. The visual and extraocular function was preserved in the second patient. The first patient had only light perception in the affected eye. In this paper, the embryology, anatomy, and physiology of the optic nerve and its mechanisms of stretch and repair are discussed. ImagesFigure 1Figure 2Figure 3Figure 4Figure 5Figure 6Figure 7Figure 8Figure 9Figure 10Figure 11Figure 13

Alvi, Aijaz; Janecka, Ivo P.; Kapadia, Silloo; Johnson, Bruce L.; McVay, William

1996-01-01

136

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

137

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

Microsoft Academic Search

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

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

1993-01-01

138

Root features related to plant growth and nutrient removal of 35 wetland plants.  

PubMed

Morphological, structural, and eco-physiological features of roots, nutrient removal, and correlation between the indices were comparatively studied for 35 emergent wetland plants in small-scale wetlands for further investigation into the hypothesis of two types of wetland plant roots (Chen et al., 2004). Significant differences in root morphological, structural, and eco-physiological features were found among the 35 species. They were divided into two types: fibrous-root plants and thick-root plants. The fibrous-root plants had most or all roots of diameter (D) ? 1 mm. Roots of D > 1 mm also had many fine and long lateral roots of D ? 1 mm. The roots of these plants were long and had a thin epidermis and a low degree of lignification. The roots of the thick-root plants were almost all thicker than 1 mm, and generally had no further fine lateral roots. The roots were short, smooth, and fleshy, and had a thick epidermis. Root porosity of the fibrous-root plants was higher than that of the thick-root plants (p = 0.001). The aerenchyma of the fibrous-root plants was composed of large cavities which were formed from many small cavities, and distributed radially between the exodermis and vascular tissues. The aerenchyma of the thick-root plants had a large number of small cavities which were distributed in the mediopellis. The fibrous-root plants had a significantly larger root biomass of D ? 1 mm, of 1 mm < D < 3 mm, above-ground biomass, total biomass, and longer root system, but shorter root longevity than those of the thick-root plants (p = 0.003, 0.018, 0.020, 0.032, 0.042, 0.001). The fibrous-root plants also had significantly higher radial oxygen loss (ROL), root activity, photosynthetic rate, transpiration rate, and removal rates of total nitrogen and total phosphorus than the thick-root plants (p = 0.001, 0.008, 0.010, 0.004, 0.020, 0.002). The results indicate that significantly different root morphological and structural features existed among different wetland plants, and these features had a close relationship to nutrient removal capacity. PMID:21640369

Lai, Wen-Ling; Wang, Shu-Qiang; Peng, Chang-Lian; Chen, Zhang-He

2011-05-11

139

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

Microsoft Academic Search

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

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

2008-01-01

140

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

2013-08-13

141

Exogenous proline effects on water relations and ions contents in leaves and roots of young olive.  

PubMed

The ability of exogenous compatible solutes, such as proline, to counteract salt inhibitory effects was investigated in 2-year-old olive trees (Olea europaea L. cv. Chemlali) subjected to different saline water irrigation levels supplied or not with exogenous proline. Leaf water relations [relative water content (RWC), water potential], photosynthetic activity, leaf chlorophyll content, and starch contents were measured in young and old leaves. Salt ions (Na(+), K(+), and Ca(2+)), proline and soluble sugars contents were determined in leaf and root tissues. Supplementary proline significantly mitigated the adverse effects of salinity via the improvement of photosynthetic activity (Pn), RWC, chlorophyll and carotenoid, and starch contents. Pn of young leaves in the presence of 25 mM proline was at 1.18 and 1.38 times higher than the values recorded under moderate (SS1) and high salinity (SS2) treatments, respectively. Further, the proline supply seems to have a more important relaxing effect on the photosynthetic chain in young than in old leaves of salt-stressed olive plants. The differential pattern of proline content between young and old leaves suggests that there would be a difference between these tissues in distinguishing between the proline taken from the growing media and that produced as a result of salinity stress. Besides, the large reduction in Na(+) accumulation in leaves and roots in the presence of proline could be due to its interference in osmotic adjustment process and/or its dilution by proline supply. Moreover, the lower accumulation of Na(+) in proline-treated plants, compared to their corresponding salinity treatment, displayed the improved effect of proline on the ability of roots to exclude the salt ions from the xylem sap flowing to the shoot, and thus better growth rates. PMID:20617349

Ben Ahmed, Ch; Magdich, S; Ben Rouina, B; Sensoy, S; Boukhris, M; Ben Abdullah, F

2010-07-09

142

In the long term root-related priming can lead to carbon loss and chemical alterations in the deep subsoil  

NASA Astrophysics Data System (ADS)

Recent publications and reviews concern the major importance of the deep subsoil for carbon (C) storage and cycling in terrestrial environments. However, the subsoil (below A horizon) and especially the deep subsoil (> 1m) is a target not easy to study and especially the relevant processes therein. Therefore, in the current study we focussed on recent and ancient root systems extending in terrestrial sediments until 9 m depth below the present surface and more than 7 m below the present soil. We sampled rhizosphere in the direct vicinity of the roots and with increasing distance (up to 10 cm) from visible root remains, and determined the root frequency in different depths. Additionally, sedimentary material without visible root remains was sampled for each of these depth intervals, and all samples were analysed for C contents and lipid composition. Main aim of the study was to obtain information of root effects on C content and composition in the deep subsoil. The loess-paleosol sequence of Nussloch (SW Germany) with a Cambisol on its top was chosen as a key site as recent and ancient roots were easy to assess and to differentiate. Furthermore, two sites near Sopron (NW Hungary) were sampled for recent tree roots rooting deeply (at least 4 m) into loess sediment. All samples were investigated for Corg, Ccarb and extractable lipid contents and the lipid composition. The frequency of recent roots strongly decreased with depth in the Nussloch profile until zero at 2 m depth below the present soil surface as recent tree vegetation was rather young (<7 years). In comparison to this, ancient tree root remains, frequently visible as carbonate precipitates surrounding the former roots, could be observed continuously until 9 m depth with the largest frequency (~200 roots m-2) at 2-3 m depth. However, only root remains of a diameter larger than 1 mm were counted, thus highly underestimating fine root remains, which were not counted throughout the profile due to their high frequency (>>10,000 m-2). In the rhizosphere of former and recent roots, Corg tended to slightly decrease compared to reference sediment. Ccarb contents revealed in some depths slight changes in the rhizosphere. Especially the precipitates surrounding the former roots were strongly enriched in Ccarb although the investigated sediments were rich in carbonate (20-40 mass-%). Taking into account the rhizolith frequency (only of the carbonate precipitates >1 mm), the bulk density, the carbon concentrations and the estimated extension of the rhizosphere, a decrease of more than 1 kg C m-2 was determined in the rhizosphere by comparison to root-free loess. The C loss was mainly related to the more depth intervals with densely occurring large root remains (>20 m-2) at a depth of less than 5 m, whereas in larger depth intervals with a lower frequency of root remains C contents slightly increased in the rhizosphere. Despite the high C storage in deep subsoil, root related processes might alter the chemical composition in the subsoil and can result in C loss in the long term.

Wiesenberg, Guido; Gocke, Martina

2013-04-01

143

Single Molecule Transcription Elongation  

PubMed Central

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

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

2009-01-01

144

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

145

A plausible mechanism for auxin patterning along the developing root  

Microsoft Academic Search

BACKGROUND: In plant roots, auxin is critical for patterning and morphogenesis. It regulates cell elongation and division, the development and maintenance of root apical meristems, and other processes. In Arabidopsis, auxin distribution along the central root axis has several maxima: in the root tip, in the basal meristem and at the shoot\\/root junction. The distal maximum in the root tip

Victoria V Mironova; Nadezda A Omelyanchuk; Guy Yosiphon; Stanislav I Fadeev; Nikolai A Kolchanov; Eric Mjolsness; Vitaly A Likhoshvai

2010-01-01

146

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

147

Use of nuclear magnetic resonance microscopy for noninvasive observations of root-soil water relations  

Microsoft Academic Search

As part of our strategy to study root-soil water relationships, it was necessary to develop a nondestructive technique to detect small changes in water distribution in and near the root. Nuclear magnetic resonance imaging (MRI), clinically used to nondestructively and noninvasively acquire anatomical information, can also be used to observe water distribution in roots, soils and other plant tissues. In

J. M. Brown; P. J. Kramer; G. P. Cofer; G. A. Johnson

1990-01-01

148

MAPKs regulate root growth by influencing auxin signaling and cell cycle-related gene expression in cadmium-stressed rice.  

PubMed

This work aims to analyze the relationship between root growth, mitogen-activated protein kinase (MAPK), auxin signaling, and cell cycle-related gene expression in cadmium (Cd)-stressed rice. The role of MAPKs in auxin signal modification and cell cycle-related gene expression during root growth was investigated by disrupting MAPK signaling using the MAPKK inhibitor PD98059 (PD). Treatment with Cd caused a significant accumulation of Cd in the roots. A Cd-specific probe showed that Cd is mainly localized in the meristematic zone and vascular tissues. Perturbation of MAPK signaling using PD significantly suppressed root system growth under Cd stress. The transcription of six MAPK genes was inhibited by Cd compared to the control. Detection using DR5-GUS transgenic rice showed that the intensity and distribution pattern of GUS staining was similar in roots treated with PD or Cd, whereas in Cd plus PD-treated roots, the GUS staining pattern was similar to that of the control, which indicates a close association of MAPK signaling with auxin homeostasis under control and Cd stress conditions. The expression of most key genes of auxin signaling, including OsYUCCA, OsPIN, OsARF, and OsIAA, and of most cell cycle-related genes, was negatively regulated by MAPKs under Cd stress. These results suggest that the MAPK pathway plays specific roles in auxin signal transduction and in the control of the cell cycle in response to Cd stress. Altogether, MAPKs take part in the regulation of root growth via auxin signal variation and the modified expression of cell cycle-related genes in Cd-stressed rice. A working model for the function of MAPKs in rice root systems grown under Cd stress is proposed. PMID:23430734

Zhao, Feng Yun; Hu, Fan; Zhang, Shi Yong; Wang, Kai; Zhang, Cheng Ren; Liu, Tao

2013-02-21

149

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

PubMed Central

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

Evans, Evan C.; Vaughan, Burton E.

1966-01-01

150

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

NASA Astrophysics Data System (ADS)

The main influences of plants on the mass stability of riverbanks are those that affect the strength of bank sediments. Plants enhance bank strength by reducing pore-water pressures and by directly reinforcing bank material with their roots. In this paper we do not consider bank hydrology but focus on quantifying increases in sediment strength due to root reinforcement. Root reinforcement is a function of root strength, interface friction between the roots and the soil, and the distribution of roots within the soil. Field and laboratory studies of Australian riparian trees, river red gum (Eucalyptus camaldulensis) and swamp paperbark (Melaleuca ericifolia), indicate that bank reinforcement, due to the roots of these species, decreases exponentially with depth below the soil surface and distance away from the trees. Differences in the spatial distribution of root reinforcement are illustrated by a comparison of the apparent cohesion due to roots (cr) with the effective cohesion of the saturated bank material (15 kPa). Directly below the river red gum, root reinforcement is equal to effective cohesion at 1·7 m depth. At the dripline (17 m from the trunk), root reinforcement is equal to material strength at 0·4 m depth. For the swamp paperbark, cr=15 kPa at 1·1 m depth beneath surface, at the trunks, and at 0·4 m depth at the dripline (2·5 m from the trunk). A description of the spatial distribution of root reinforcement is important in the riverbank context. We find that interspecies differences in the strength of living roots have less significance for bank reinforcement than interspecies differences in root distribution.

Abernethy, Bruce; Rutherfurd, Ian D.

2001-01-01

151

Auxin Induced Lateral Root Formation in Chicory  

Microsoft Academic Search

The supply of auxins [2,4-dichlorophenoxy acetic acid (2,4D), indole-3 acetic acid (1AA) and ?-naphthaleneacetic acid (NAA)] to excised chicory roots induced the formation of lateral root meristems mainly located close to the pre-existing apical root meristem. Lateral root growth induced in non-excised roots required higher auxin concentrations. Inhibition of root elongation and concomittant enlargement of the apices was also observed.

CHRISTOPHE VUYLSTEKER; ERIC DEWAELE; SERGE RAMBOUR

1998-01-01

152

Relation of uric acid levels to aortic root dilatation in hypertensive patients with and without metabolic syndrome*  

PubMed Central

Objective: Uric acid (UA) is considered to be a powerful predictor of cardiovascular risk and hyperuricemia might be involved in the metabolic syndrome (MS). This study aims to investigate the relation between UA levels and aortic root dilatation. Methods: A total of 348 hypertensive patients [age (67.5±9.8) years] with or without MS were included in the study. The aortic root diameters at the aortic annulus, the sinuses of Valsalva, the sinotubular junction, and the proximal part of the ascending aorta were measured using a two-dimensional (2D) echocardiography. Serum UA levels were also measured for all patients. Results: A high UA level is independently associated with aortic root diameters at the sinuses of Valsalva (P=0.001) and the proximal ascending aorta (P<0.0001) in the hypertensive patients without MS. In contrast, aortic root diameters were not significantly related to UA levels in the hypertensive patients with MS. Furthermore, increased UA levels were associated with an increased risk for aortic root dilatation in the patients without MS (sex-adjusted hazard ratio 1.75, 95% confidence intervals (CI) 1.27–2.41), but not in those with MS. Conclusions: This study demonstrated an independent relationship between the aortic root dimensions and increased levels of serum UA in the hypertensive patients without MS. Further understanding of the mechanisms underlying these associations may allow a clearer interpretation of the potential value of specific urate-lowering treatment on cardiovascular disease.

Tang, Li-jiang; Jiang, Jian-jun; Chen, Xiao-feng; Wang, Jian-an; Lin, Xian-fang; Du, Yu-xi; Fang, Cong-feng; Pu, Zhao-xia

2010-01-01

153

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

ERIC Educational Resources Information Center

|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…

Giannetto, Enrico R. A.

2009-01-01

154

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

ERIC Educational Resources Information Center

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…

Giannetto, Enrico R. A.

2009-01-01

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

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

157

The effect of root temperature on rose plants in relation to air temperature  

Microsoft Academic Search

Rose plants (Rosa hybrida ‘Sonia’=‘Sweet Promise’) were grown in heated (minimum night temperature 17C), and unheated greenhouses with or without\\u000a root heating to 21C. These trials covered 6 growth cycles extending over two winter seasons. In the heated greenhouse, root\\u000a heating did not increase yield, flower quality or plant development. In the unheated greenhouse, root-heated plants grew as\\u000a well as

M. Zeroni; J. Gale

1987-01-01

158

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

USGS Publications Warehouse

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

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

2000-01-01

159

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

PubMed Central

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

2011-01-01

160

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

161

Hypoglycaemic and other related actions of Tinospora cordifolia roots in alloxan-induced diabetic rats  

Microsoft Academic Search

Tinospora cordifolia is widely used in Indian Ayurvedic medicine for treating diabetes mellitus. Oral administration of an aqueous T. cordifolia root extract (TCREt) to alloxan diabetic rats caused a significant reduction in blood glucose and brain lipids. The extract caused an increase in body weight, total haemoglobin and hepatic hexokinase. The root extract also lowers hepatic glucose-6-phosphatase and serum acid

P. Stanely; Mainzen Prince; Venugopal P. Menon

2000-01-01

162

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

163

RELATING FINE ROOT BIOMASS TO SOIL AND CLIMATE CONDITIONS IN THE PACIFIC NORTHWEST  

EPA Science Inventory

The additive contribution of fine root biomass for Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco var. menziesii) and western hemlock (Tsuga heterophylla (Raf.) Sarg.) to the stand average fine root biomass were estimated for eight conifer stands in the Pacific Northwest. Base...

164

Light-induced transpiration alters cell water relations in figleaf gourd (Cucurbita ficifolia) seedlings exposed to low root temperatures.  

PubMed

Water relation parameters including elastic modulus (epsilon), half-times of water exchange (T(w)(1/2)), hydraulic conductivity and turgor pressure (P) were measured in individual root cortical and cotyledon midrib cells in intact figleaf gourd (Cucurbita ficifolia) seedlings, using a cell pressure probe. Transpiration rates (E) of cotyledons were also measured using a steady-state porometer. The seedlings were exposed to low ambient (approximately 10 micromol m(-2) s(-1)) or high supplemental irradiance (approximately 300 micromol m(-2) s(-1) PPF density) at low (8 degrees C) or warm (22 degrees C) root temperatures. When exposed to low irradiance, all the water relation parameters of cortical cells remained similar at both root temperatures. The exposure of cotyledons to supplemental light at warm root temperatures, however, resulted in a two- to three-fold increase in T(w)(1/2) values accompanied with the reduced hydraulic conductivity in both root cortical (Lp) and cotyledon midrib cells (Lp(c)). Low root temperature (LRT) further reduced Lp(c) and E, whether it was measured under low or high irradiance levels. The reductions of Lp as the result of respective light and LRT treatments were prevented by the application of 1 microM ABA. Midrib cells required higher concentrations of ABA (2 microM) in order to prevent the reduction in Lp(c). When the exposure of cotyledons to light was accompanied by LRT, however, ABA proved ineffective in reversing the inhibition of Lp. LRT combined with high irradiance triggered a drastic 10-fold reduction in water permeability of cortical and midrib cells and increased epsilon and T(w)(1/2) values. Measurement of E indicated that the increased water demand by the transpiring plants was fulfilled by an increase in the apoplastic pathway as principal water flow route. The importance of water transport regulation by transpiration affecting the hydraulic conductivity of the roots is discussed. PMID:18346079

Lee, Seong Hee; Zwiazek, Janusz J; Chung, Gap Chae

2008-03-11

165

Root porosity and radial oxygen loss related to arsenic tolerance and uptake in wetland plants.  

PubMed

The rates of radial oxygen loss (ROL), root porosity, concentrations of arsenic (As), iron (Fe) and manganese (Mn) in shoot and root tissues and on root surfaces, As tolerances, and their relationships in different wetland plants were investigated based on a hydroponic experiment (control, 0.8, 1.6 mg As L(-1)) and a soil pot trail (control, 60 mg As kg(-1)). The results revealed that wetland plants showed great differences in root porosity (9-64%), rates of ROL (55-1750 mmo1 O2 kg(-1) root d.w.d(-1)), As uptake (e.g., 8.8-151 mg kg(-1) in shoots in 0.8 mg As L(-1) treatment), translocation factor (2.1-47% in 0.8 mg As L(-1)) and tolerance (29-106% in 0.8 mg As L(-1)). Wetland plants with higher rates of ROL and root porosity tended to form more Fe/Mn plaque, possess higher As tolerance, higher concentrations of As on root surfaces and a lower As translocation factor so decreasing As toxicity. PMID:20970900

Li, H; Ye, Z H; Wei, Z J; Wong, M H

2011-01-01

166

Modelling Rooting Depth and Soil Strength in a Drying Soil Profile  

Microsoft Academic Search

A combined root growth and water extraction model is described that simulates the affects of mechanical impedance on root elongation in soil. The model simulates the vertical redistribution of water in the soil profile, water uptake by plant roots, and the effects of decreasing water content on increasing soil strength and decreasing the root elongation rate. The modelling approach is

A. G. Bengough

1997-01-01

167

Adventitious root induction in Arabidopsis thaliana as a model for in vitro root organogenesis.  

PubMed

Adventitious root formation, the development of roots on non-root tissue (e.g. leaves, hypocotyls and stems) is a critical step during micropropagation. Although root induction treatments are routinely used for a large number of species micropropagated in vitro as well as for in vivo cuttings, the mechanisms controlling adventitious rooting are still poorly understood. Researchers attempt to gain better insight into the molecular aspects by studying adventitious rooting in Arabidopsis thaliana. The existing assay involves etiolation of seedlings and measurements of de novo formed roots on the elongated hypocotyl. The etiolated hypocotyls express a novel auxin-controlled signal transduction pathway in which auxin response factors (ARFs), microRNAs and environmental conditions that drive adventitious rooting are integrated. An alternative assay makes use of so-called thin cell layers (TCL), excised strips of cells from the inflorescence stem of Arabidopsis thaliana. However, both the etiolated seedling system and the TCL assay are only distantly related to industrial rooting processes in which roots are induced on adult stem tissue. Here, we describe an adventitious root induction system that uses segments of the inflorescence stems of Arabidopsis thaliana, which have a histological structure similar to cuttings or in vitro micropropagated shoots. The system allows multiple treatments with chemicals as well as the evaluation of different environmental conditions on a large number of explants. It is therefore suitable for high throughput chemical screenings and experiments that require numerous data points for statistical analysis. Using this assay, the adventitious root induction capacity of classical auxins was evaluated and a differential response to the different auxins could be demonstrated. NAA, IBA and IAA stimulated adventitious rooting on the stem segment, whereas 2,4-D and picloram did not. Light conditions profoundly influenced the root induction capacity of the auxins. Additionally to the environmental control of adventitious root formation, we also investigated the spatial and temporal aspects of stem-based adventitious root organogenesis. To determine the cells involved in de novo root initiation on the adult stems, we adopted scanning electron microscopy, which allows the visualization of the auxin responsive stem tissue. Using this technique, direct (without callus interface) and indirect (with intermediate callus phase) organogenesis was readily distinguished. The described micro-stem segment system is also suitable for other non-woody species and it is a valuable tool to perform fast evaluations of different treatments to study adventitious root induction. PMID:23299674

Verstraeten, Inge; Beeckman, Tom; Geelen, Danny

2013-01-01

168

Aquaporin functionality in relation to H+-ATPase activity in root cells of Capsicum annuum grown under salinity.  

PubMed

As water and nutrient uptake should be related in the response of plants to salinity, the aim of this paper is to establish whether or not aquaporin functionality is related to H+-ATPase activity in root cells of pepper (Capsicum annuum L.) plants. Thus, H+-ATPase activity was measured in plasma membrane vesicles isolated from roots and aquaporin functionality was measured using a cell pressure probe in intact roots. Salinity was applied as 60 mM NaCl or 60 mM KCl, to determine which ion (Na+, K+ or Cl-) is producing the effects. We also investigated whether the effects of both salts were ameliorated by Ca2+. Similar results were obtained for cell hydraulic conductivity, Lpc, and H+-ATPase activity, large reductions in the presence at NaCl or KCl and an ameliorative effect of Ca2+. However, fusicoccin (an activator of H+-ATPase) did not alter osmotic water permeability of protoplasts isolated from roots. Addition of Hg2+ inhibited both ATPase and aquaporins, but ATPase also contains Hg-binding sites. Therefore, the results indicate that H+-ATPase and aquaporin activities may not be related in pepper plants. PMID:12654042

Martínez-Ballesta, M. Carmen; Martínez, Vicente; Carvajal, Micaela

2003-03-01

169

Thermodynamic Model of Transcription Elongation  

NASA Astrophysics Data System (ADS)

We present a statistical mechanics approach to the prediction of backtracked pauses in prokaryotic transcription elongation derived from structural models of the transcription elongation complex (TEC). Our algorithm is based on the thermodynamic stability of TEC along the DNA template calculated from the sequence dependent free-energy of DNA-DNA, DNA-RNA and RNA-RNA base pairing associated with (a) the translocation and size fluctuations of the transcription bubble; (b) the changes in the DNA-RNA hybrid; and (c) the changes in the RNA folding free-energy. The calculations involve no adjustable parameters apart from a cutoff used to discriminate paused from non-paused complexes. When applied to 100 experimental pauses in transcription elongation by E. coli RNA polymerase on ten DNA templates the approach produces highly statistically significant results. Transcription elongation is an inherently kinetic process and a simplified kinetic model with the same predictive power is presented separately.

Tadigotla, Vasisht; O'Maoileidigh, Daibhid; Sengupta, Anirvan; Epshtein, Vitaly; Ebright, Richard; Nudler, Evgeny; Ruckenstein, Andrei

2006-03-01

170

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

Microsoft Academic Search

The revolution in XX century physics, induced by relativity theories, had its roots within the electromagnetic conception\\u000a 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\\u000a of Poincaré of 1905. Einstein, on the

Enrico R. A. Giannetto

2009-01-01

171

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

Microsoft Academic Search

The revolution in XX century physics, induced by relativity theories, had its roots within the electromagnetic conception\\u000a 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\\u000a of Poincaré of 1905. Einstein, on the

Enrico R. A. Giannetto

172

A Rab-related small GTP binding protein is predominantly expressed in root nodules of Medicago sativa  

Microsoft Academic Search

Rab-related small GTP-binding proteins are known to be involved in the regulation of the vesicular transport system in eucaryotic cells. In this paper we report the isolation of the cDNA clone MS- rab11f from Medicago sativa (alfalfa) root nodules using a combination of RT-PCR and SSCP analysis. MS- rab11f shows high homology to the Rab-related cDNA clone LJ- rab11f from

K. Schiene; S. Donath; M. Brecht; A. Pühler; K. Niehaus

2004-01-01

173

Use of nuclear magnetic resonance microscopy for noninvasive observations of root-soil water relations  

NASA Astrophysics Data System (ADS)

As part of our strategy to study root-soil water relationships, it was necessary to develop a nondestructive technique to detect small changes in water distribution in and near the root. Nuclear magnetic resonance imaging (MRI), clinically used to nondestructively and noninvasively acquire anatomical information, can also be used to observe water distribution in roots, soils and other plant tissues. In MRI, a sample is placed in a strong magnetic field and a sequence of radio frequency (rf) pulses and magnetic field gradients is used to measure the concentration and relaxation properties of protons, chiefly those associated with water. This information is then reconstructed into a digital image representing the spatial distribution of water in plant tissues and soil. Today, intact roots less than 1 mm in diameter growing in soil or synthetic media can be clearly imaged in less than 4 minutes at resolutions typically less than 30µm. This permits rapid production of images that simultaneously distinguish temporal changes in water distribution in root tissue, the rhizosphere and the adjacent soil at microscopic levels. Applications of this technique for investigating plant-soil water relationships will be discussed.

Brown, J. M.; Kramer, P. J.; Cofer, G. P.; Johnson, G. A.

1990-12-01

174

Investigation of Plant Water Relations with Divided Root Systems of Soybean 1  

PubMed Central

Soybean (Glycine max) was grown with root systems divided between adjacent cartons containing nutrient solution or soil. By adding polyethylene glycol (Carbowax 6000) to reduce solute potential or withholding water to reduce soil matric potential until water absorption from that side stopped, the root xylem water potential could be ascertained. Carbowax appeared to increase root resistance. An imbalance technique is described with which soil moisture contents of adjacent containers were followed individually. The patterns of water absorption obtained following repeated additions of water or addition of CaCl2 solutions to one side indicated soil hydraulic conductivity became limiting at a soil water potential of ?2 bars. A high concentration of CaCl2 added to one side greatly reduced transpiration and produced severe plant injury. With part of the root system developing in nutrient solution, growth of roots into and water absorption from soil were slow; however, reduction of solute potential in the solution side greatly increased water absorption from the soil side. Images

Michel, B. E.; Elsharkawi, H. M.

1970-01-01

175

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

PubMed

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

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

2013-09-22

176

On the relative roles of hydrology, salinity, temperature, and root productivity in controlling soil respiration from coastal swamps (freshwater)  

USGS Publications Warehouse

Background and aims Soil CO2 emissions can dominate gaseous carbon losses from forested wetlands (swamps), especially those positioned in coastal environments. Understanding the varied roles of hydroperiod, salinity, temperature, and root productivity on soil respiration is important in discerning how carbon balances may shift as freshwater swamps retreat inland with sea-level rise and salinity incursion, and convert to mixed communities with marsh plants. Methods We exposed soil mesocosms to combinations of permanent flooding, tide, and salinity, and tracked soil respiration over 2 1/2 growing seasons. We also related these measurements to rates from field sites along the lower Savannah River, Georgia, USA. Soil temperature and root productivity were assessed simultaneously for both experiments. Results Soil respiration from mesocosms (22.7-1678.2 mg CO2 m-2 h-1) differed significantly among treatments during four of the seven sampling intervals, where permanently flooded treatments contributed to low rates of soil respiration and tidally flooded treatments sometimes contributed to higher rates. Permanent flooding reduced the overall capacity for soil respiration as soils warmed. Salinity did reduce soil respiration at times in tidal treatments, indicating that salinity may affect the amount of CO2 respired with tide more strongly than under permanent flooding. However, soil respiration related greatest to root biomass (mesocosm) and standing root length (field); any stress reducing root productivity (incl. salinity and permanent flooding) therefore reduces soil respiration. Conclusions Overall, we hypothesized a stronger, direct role for salinity on soil respiration, and found that salinity effects were being masked by varied capacities for increases in respiration with soil warming as dictated by hydrology, and the indirect influence that salinity can have on plant productivity.

Krauss, Ken W.; Whitbeck, Julie L.; Howard, Rebecca J.

2012-01-01

177

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. © 2013 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 101B: 1107-1123, 2013. PMID:23559495

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

2013-04-04

178

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

179

Spatial Variability of Root Knot Nematodes in Relation to within Field Variability of Soil Properties  

Technology Transfer Automated Retrieval System (TEKTRAN)

Site-specific management (SSM) of cotton (Gossypium hirsutum L.) fields under risk of southern root-knot nematode [M. incognita] (RKN) infection may offer producers better management of on-farm resources and optimization of profitability. However, it requires the study of RKN spatio-temporal variabi...

180

Root development and earthworm movement in relation to soil strength and structure  

Microsoft Academic Search

Factors which influence the ability of plant roots and earthworms to penetrate soil are reviewed. Plant factors include the hydraulic conductivity, yield stress and extensibility of the cell walls and the osmotic potential of the cell contents. Earthworm factors include the tensions than can be generated by the longitudinal and circular muscles. Soil factors include the penetration resistance and water

W. R. Whalley; A. R. Dexter

1994-01-01

181

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

Technology Transfer Automated Retrieval System (TEKTRAN)

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

182

Gel observation chamber for rapid screening of root traits in cereal seedlings  

Microsoft Academic Search

A simple gel chamber is described for measurement of seedling root traits. Seedlings are located between two closely spaced flat layers of transparent gel, on plastic plates (at least one of which is transparent). Root system traits can be non-destructively recorded in two-dimensions using a flatbed scanner. Easily measured rooting traits include root length, elongation rate, longest root, deepest root,

A. G. Bengough; D. C. Gordon; H. Al-Menaie; R. P. Ellis; D. Allan; R. Keith; W. T. B. Thomas; B. P. Forster

2004-01-01

183

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

Microsoft Academic Search

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

Giovanna Frugis; Sofia Caretto; Luigi Santini; Domenico Mariotti

1995-01-01

184

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

2011-06-08

185

How does undergraduate college biology students' level of understanding, in regard to the role of the seed plant root system, relate to their level of understanding of photosynthesis?  

Microsoft Academic Search

This research study investigated how undergraduate college biology students' level of understanding of the role of the seed plant root system relates to their level of understanding of photosynthesis. This research was conducted with 65 undergraduate non-majors biology who had completed 1 year of biology at Louisiana State University in Baton Rouge and Southeastern Louisiana University in Hammond. A root

James Gicheha Njeng'ere

1999-01-01

186

Dual Mechanisms of Ion Uptake in Relation to Vacuolation in Corn Roots  

PubMed Central

Absorption isotherms for chloride and rubidium ions have been determined through a wide concentration range for nonvacuolate root tips, and for vacuolate subapical sections of corn root. In the range 0 to 0.5 mm, chloride absorption is hyperbolic with concentration in both tips and proximal sections. At high concentrations, 1 to 50 mm, a second multiple-hyperbolic isotherm for chloride is noted in vacuolate tissue, while the isotherm for nonvacuolate tips rises exponentially. A linear to exponentially rising isotherm is taken to signify diffusive permeation. The same distinction between tip and subapical tissue characterizes Rb absorption. Rb uptake is indifferent to the nature of the counterion at all concentrations in the tip, while the counterion exerts a predictable influence on Rb absorption in proximal tissue. The effect of a poorly absorbable anion on Rb uptake is greater in the high concentration range. Evidence is presented for the metabolic nature of ion transport into nonvacuolate root tips. Verification is offered that ion uptake is mediated by dual mechanisms, and the thesis is developed that the high-affinity (low Ks) system mediates ion passage through the plasma membrane while the low-affinity (high Ks) system implements transport through the tonoplast.

Torii, Kenji; Laties, George G.

1966-01-01

187

Boron deficiency increases the levels of cytosolic Ca(2+) and expression of Ca(2+)-related genes in Arabidopsis thaliana roots.  

PubMed

Boron (B) deficiency affects the expressions of genes involved in major physiological processes. However, signal transduction pathway through which plants are able to sense and transmit B-deprivation signal to the nucleus is unknown. The aim of this work was to research in Arabidopsis thaliana roots whether the short-term B deficiency affects cytosolic Ca(2+) levels ([Ca(2+)]cyt) as well as expression of genes involved in Ca(2+) signaling. To visualize in vivo changes in root [Ca(2+)]cyt, Arabidopsis seedlings expressing Yellow Cameleon (YC) 3.6 were grown in a nutrient solution supplemented with 2 ?M B and then transferred to a B-free medium for 24 h. Root [Ca(2+)]cyt was clearly higher in B-deficient seedlings upon 6 and 24 h of B treatments when compared to controls. Transcriptome analyses showed that transcript levels of Ca(2+) signaling-related genes were affected by B deprivation. Interestingly, Ca(2+) channel (CNGC19, cyclic nucleotide-gated ion channel) gene was strongly upregulated as early as 6 h after B deficiency. Expression levels of Ca(2+) transporter (ACA, autoinhibited Ca(2+)-ATPase; CAX, cation exchanger) genes increased when seedlings were subjected to B deficiency. Gene expressions of calmodulin-like proteins (CMLs) and Ca(2+)-dependent protein kinases (CPKs) were also overexpressed upon exposure to B starvation. Our results suggest that B deficiency causes early responses in the expression of CNGC19 Ca(2+)-influx channel, ACA- and CAX-efflux, and Ca(2+) sensor genes to regulate Ca(2+) homeostasis. It is the first time that changes in the levels of in vivo cytosolic Ca(2+) and expression of Ca(2+) channel/transporter genes are related with short-term B deficiency in Arabidopsis roots. PMID:23416496

Quiles-Pando, Carlos; Rexach, Jesús; Navarro-Gochicoa, M Teresa; Camacho-Cristóbal, Juan J; Herrera-Rodríguez, M Begoña; González-Fontes, Agustín

2013-01-29

188

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

Microsoft Academic Search

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

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

1999-01-01

189

Change in XET activities, cell wall extensibility and hypocotyl elongation of soybean seedlings at low water potential  

Microsoft Academic Search

In dark-grown soybean ( Glycine max [L.] Merr.) seedlings, exposing the roots to water-deficient vermiculite (? w=?0.36 MPa) inhibited hypocotyl (stem) elongation. The inhibition was associated with decreased extensibility of the cell walls in the elongation zone. A detailed spatial analysis showed xyloglucan endotransglucosylase (XET; EC 2.4.1.207) activity on the basis of unit cell wall dry weight was decreased in the elongation

Yajun Wu; Beong-Reong Jeong; Stephen C. Fry; John S. Boyer

2005-01-01

190

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

PubMed Central

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

Frensch, J.; Hsiao, T. C.

1994-01-01

191

Vibrational, 1H-NMR spectroscopic, and thermal characterization of gladiolus root exudates in relation to Fusarium oxysporum f. sp. gladioli resistance.  

PubMed

Fourier transform Raman (FT Raman) and IR (FTIR) and (1)H-NMR spectroscopies coupled with differential scanning calorimetry (DSC) were applied to the characterization of root exudates from two cultivars of gladiolus (Spic Span and White Prosperity) with different degrees of resistance and susceptibility to Fusarium oxysporum gladioli, the main pathogen of gladiolus. This work was aimed at correlating the composition of root exudates with the varietal resistance to the pathogen. Spectroscopic analysis showed that White Prosperity root exudate differs from Spic Span root exudate by a higher relative amount of the aromatic-phenolic and sugarlike components and a lower relative amount of carbonylic and aliphatic compounds. DSC analysis confirmed the spectroscopic results and showed that White Prosperity root exudate is characterized by an aromatic component that is present in a higher amount than in the Spic Span root exudate. The results are discussed in relation to the spore germination tests showing that White Prosperity, which is characterized by a remarkable resistance toward F. oxysporum gladioli, exudes substances having a negative influence on microconidial germination of the pathogen; root exudates from Spic Span, one of the most susceptible cultivars to F. oxysporum gladioli, proved to have no effect. White Prosperity's ability to inhibit conidial germination of F. oxysporum gladioli can be mainly related to the presence of a higher relative amount of aromatic-phenolic compounds. PMID:12209451

Taddei, P; Tugnoli, V; Bottura, G; Dallavalle, E; Zechini D'Aulerio, A

2002-01-01

192

Supertraces on the algebras of observables of the rational calogero models related to classical root systems  

NASA Astrophysics Data System (ADS)

A complete set of supertraces on the algebras of observables of the rational Calogero models with harmonic interaction based on the classical root systems of B_N, C_N and D_N types is found. These results extend the results known for the case A_N. It is shown that there exist Q independent supertraces where Q(B_N)=Q(C_N) is a number of partitions of N into a sum of positive integers and Q(D_N) is a number of partitions of N into a sum of positive integers with even number of even integers.

Konstein, S. E.

1997-05-01

193

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

194

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

PubMed

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

Stewart, Anna M; Frank, Douglas A

2008-06-20

195

Decalepis hamiltonii root extract attenuates the age-related decline in the cognitive function in Drosophila melanogaster.  

PubMed

Age-associated accumulation of oxidative damage linked to decline of antioxidant defense mechanism, leads to impairment of cognitive function in many organisms. These damages can pass through generations and affect the cognitive quality of progenies. In Drosophila, classical olfactory conditioning results in the formation of different types of memory. Age-related memory impairment (AMI) causes reduction in middle term memory (MTM) and parental senescence causes decline in short-term memory (STM) of the offspring. We have further examined the neuromodulatory effect of Decalepis hamiltonii (Dh) root extract, which is a cocktail of novel antioxidant molecules, on the biochemical oxidative defenses in relation to cognitive ability of the aged flies and their offspring. There is a strong correlation between the age-related decline in the activity of the antioxidant enzymes and the lower cognitive ability of the aged flies and their offspring. Feeding of aged flies in the diet containing 0.1% Dh, markedly enhances the cognitive ability of both aged flies and their offspring which is associated with enhanced antioxidant defenses as evident for the activity of superoxide dismutase (SOD) and catalase. Our findings, for the first time, show that the antioxidant-rich Dh root extract attenuates the age-related decline in cognitive ability of Drosophila, and also shows ameliorative effect on the memory of the offspring. PMID:23608486

Haddadi, Mohammad; Jahromi, Samaneh Reiszadeh; Shivanandappa, T; Ramesh, S R

2013-04-19

196

Waterlogging-induced increase in sugar mobilization, fermentation, and related gene expression in the roots of mung bean (Vigna radiata).  

PubMed

The objective of this study was to examine the role of root carbohydrate levels and metabolism in the waterlogging tolerance of contrasting mung bean genotypes. An experiment was conducted with two cultivated mung bean (Vigna radiata) genotypes viz., T44 (tolerant) and Pusa Baisakhi (PB) (susceptible), and a wild Vigna species Vigna luteola under pot-culture to study the physiological and molecular mechanism of waterlogging tolerance. Waterlogging resulted in decrease in relative water content (RWC), membrane stability index (MSI) in root and leaf tissues, and chlorophyll (Chl) content in leaves, while the Chl a/b ratio increased. Waterlogging-induced decline in RWC, MSI, Chl and increase in Chl a/b ratio was greater in PB than V. luteola and T44. Waterlogging caused decline in total and non-reducing sugars in all the genotypes and reducing sugars in PB, while the content of reducing sugar increased in V. luteola and T44. The pattern of variation in reducing sugar content in the 3 genotypes was parallel to sucrose synthase (SS) activity. V. luteola and T44 also showed fewer declines in total and non-reducing sugars and greater increase in reducing sugar and SS activity than PB. Activity of alcohol dehydrogenase (ADH) increased up to 8d of waterlogging in V. luteola and T44, while in PB a marginal increase was observed only up to 4d of treatment. Gene expression studies done by RT-PCR in 24h waterlogged plants showed enhanced expression of ADH and SS in the roots of V. luteola and T44, while in PB there was no change in expression level in control or treated plants. PCR band products were cloned and sequenced, and partial cDNAs of 531, 626, and 667; 702, 736, and 744bp of SS and ADH, respectively were obtained. The partial cDNA sequences of cloned SS genes showed 93-100 homologies among different genotypes and with D10266, while in case of ADH the similarity was in the range of 97-100% amongst each other and with Z23170. The results suggest that the availability of sufficient sugar reserve in the roots, activity of SS to provide reducing sugars for glycolytic activity and ADH for the recycling of NADH, and for the continuation of glycolysis, could be one of the important mechanisms of waterlogging tolerance of V. radiata genotype T44 and wild species V. luteola. This was reflected in better RWC and Chl content in leaves, and membrane stability of leaf and root tissue in V. luteola and T44. PMID:18947901

Sairam, Raj K; Dharmar, Kumutha; Chinnusamy, Viswanathan; Meena, Ramesh C

2008-10-22

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 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

199

Cytokinin interplay with ethylene, auxin, and glucose signaling controls Arabidopsis seedling root directional growth.  

PubMed

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. PMID:21666052

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

2011-06-10

200

Differential gene expression during elongation in the preimplantation pig embryo.  

PubMed

On day 12-13 of gestation, the preimplantation pig conceptus undergoes a dramatic morphologic change from an approximately 1-cm sphere to a nearly 1-m long thread. This transformation, referred to as elongation, occurs in just 12-24 h. Elongation is primarily the result of trophectodermal cell shape changes, as there is relatively little mitosis during this stage of development. Thus far, descriptions of elongation have been limited to histologic and immunofluorescent studies of cell morphology and gross biochemical evaluations. We hypothesized that the changes in trophectoderm morphology likely involves significant changes in gene expression. Therefore, we used RNA arbitrarily primed-PCR (RAP-PCR) to characterize potential differential gene expression by trophectodermal cells during pig conceptus elongation. We found that the porcine heterogeneous nuclear ribonucleoprotein (hnRNP) A2/B1 was shown to be differentially expressed by trophectodermal cells during elongation. We suggest that regulated alternative splicing may contribute to the morphogenetic process of elongation. genesis 26:9-14, 2000. Published 2000 Wiley-Liss, Inc. PMID:10660669

Wilson, M E; Sonstegard, T S; Smith, T P; Fahrenkrug, S C; Ford, S P

2000-01-01

201

Factors controlling decomposition in arctic tundra and related root mycorrhizal processes  

SciTech Connect

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

Linkins, A.E.

1990-01-01

202

METHOD OF FORMING ELONGATED COMPACTS  

DOEpatents

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

Larson, H.F.

1959-05-01

203

AtrbohD and AtrbohF positively regulate abscisic acid-inhibited primary root growth by affecting Ca2+ signalling and auxin response of roots in Arabidopsis.  

PubMed

Reactive oxygen species (ROS) originating from the NADPH oxidases AtrbohD and AtrbohF play an important role in abscisic acid (ABA)-inhibited primary root growth in Arabidopsis. However, the mechanisms underlying this process remain elusive. In this study, the double mutant atrbohD1/F1 and atrbohD2/F2, in which both AtrbohD and AtrbohF were disrupted, were less sensitive to ABA suppression of root cell elongation than wild-type (WT) plants. Furthermore, the double mutants showed impaired ABA responses in roots, including ROS generation, cytosolic Ca(2+) increases, and activation of plasma membrane Ca(2+)-permeable channels compared with WT. Exogenous H2O2 can activate the Ca(2+) currents in roots of atrbohD1/F1. In addition, exogenous application of the auxin transport inhibitor naphthylphthalamic acid effectively promoted ABA inhibition of root growth of the mutants relative to that of WT. The ABA-induced decreases in auxin sensitivity of the root tips were more pronounced in WT than in atrbohD1/F1. These findings suggest that both AtrbohD and AtrbohF are essential for ABA-promoted ROS production in roots. ROS activate Ca(2+) signalling and reduce auxin sensitivity of roots, thus positively regulating ABA-inhibited primary root growth in Arabidopsis. PMID:23963673

Jiao, Yiheng; Sun, Lirong; Song, Yalin; Wang, Limin; Liu, Liping; Zhang, Liyue; Liu, Bo; Li, Ning; Miao, Chen; Hao, Fushun

2013-08-20

204

Comparative effects of partial root drying (PRD) and regulated deficit irrigation (RDI) on water relations and water use efficiency in common bean ( Phaseolus vulgaris L.)  

Microsoft Academic Search

In order to investigate the hypothesis that plant responses to altered water relations was related to hormonal signals in water-restricted plants, the comparative effects of partial root drying (PRD) and regulated deficit irrigation (RDI) were investigated by measuring plant growth, water relations, leaf abscissic acid (ABA) concentrations and xylem sap pH in common bean (Phaseolus vulgaris L.). In a first

R. Wakrim; S. Wahbi; H. Tahi; B. Aganchich; R. Serraj

2005-01-01

205

The effect of phosphate nutrition of young rape plants on nitrate reductase activity and xylem exudation, and their relation to H ion efflux from the roots  

Microsoft Academic Search

Levels of nitrate reductase activity (N.R.A.) were measured in shoots and roots of P sufficient and P deficient rape plants\\u000a and changes in N.R.A. examined in relation to the onset of H ion efflux from the roots. Rates of xylem exudation were measured\\u000a and the sap analysed for nitrate, amino-N and phosphate content.\\u000a \\u000a The optimum concentration of phosphate in the

H. Moorby; P. H. Nye; R. E. White

1988-01-01

206

Growth-inhibiting effects of Paeonia lactiflora root steam distillate constituents and structurally related compounds on human intestinal bacteria.  

PubMed

The growth-inhibiting activities of Paeonia lactiflora (Paeoniaceae) root steam distillate constituents and structurally related compounds against nine harmful intestinal bacteria and eight lactic acid-producing bacteria were compared with those of two antibiotics, amoxicillin and tetracycline. Thymol, ?-terpinolene, (-)-perilla alcohol and (1R)-(-)-myrtenol exhibited high to extremely high levels of growth inhibition of all the harmful bacteria, whereas thymol and ?-terpinolene (except for Lactobacillus casei ATCC 393) inhibited the growth of all the beneficial bacteria (MIC, both 0.08-0.62 mg mL(-1)). Tetracycline and amoxicillin exhibited extremely high level of growth inhibition of all the test bacteria (MIC, <0.00002-0.001 mg mL(-1)). 1,8-Cineole, geraniol, (-)-borneol, (1S,2S,5S)-(-)-myrtanol, nerol, (S)-(-)-?-citronellol and (±)-lavandulol also exhibited inhibitory activity but with differing specificity and levels of activity. Structure-activity relationship indicates that structural characteristics, such as geometric isomerism, degrees of saturation, types of functional groups and types of carbon skeleton, appear to play a role in determining the growth-inhibiting activity of monoterpenoids. Global efforts to reduce the level of antibiotics justify further studies on naturally occurring P. lactiflora root-derived materials as potential preventive agents against various diseases caused by harmful intestinal bacteria such as clostridia. PMID:22805939

Ngan, Luong Thi My; Moon, Joon-Kwan; Kim, Jeong-Han; Shibamoto, Takayuki; Ahn, Young-Joon

2011-11-26

207

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

208

Root apex transition zone as oscillatory zone.  

PubMed

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

Baluška, František; Mancuso, Stefano

2013-10-02

209

Ammonium affects cell viability to inhibit root growth in Arabidopsis * #  

PubMed Central

Ammonium (NH4 +) is an important form of nitrogen nutrient for most plants, yet is also a stressor for many of them. However, the primary events of NH4 + toxicity at the cellular level are still unclear. Here, we showed that NH4 + toxicity can induce the root cell death in a temporal pattern which primarily occurs in the cells of root maturation and elongation zones, and then spreads to the cells in the meristem and root cap. The results from the NH4 +-hypersensitive mutant hsn1 further confirmed our findings. Taken together, NH4 + toxicity inhibits primary root growth by inhibiting cell elongation and division and inducing root cell death.

Qin, Cheng; Yi, Ke-ke; Wu, Ping

2011-01-01

210

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

211

Antisense expression of a cell wall-associated protein kinase, WAK4, inhibits cell elongation and alters morphology.  

PubMed

The Arabidopsis cell wall-associated receptor-like kinase (WAK) gene family contains five highly related members whose products are suited for exchanging signals between the intracellular and extracellular compartments. WAK members are expressed in specific organs and regulated differentially by various biotic and abiotic factors. To gain further insight into how WAKs function during development, we used a glucocorticoid-inducible system to express ectopically the WAK4 antisense gene. The induced expression of the WAK4 antisense gene resulted in a significant decrease of WAK proteins. Ninety-six hours after the induction of WAK4 antisense expression, WAK proteins became undetectable. Cell elongation was impaired, and lateral root development was blocked. The level of WAK protein could be controlled by the concentration of the applied inducer, dexamethasone, and was correlated with the severity of the cell elongation inhibition phenotype. These results suggest that the WAKs serve a vital role in cell elongation and are required for plant development. PMID:11402163

Lally, D; Ingmire, P; Tong, H Y; He, Z H

2001-06-01

212

The IRE gene encodes a protein kinase homologue and modulates root hair growth in Arabidopsis.  

PubMed

We identified an Arabidopsis mutant, incomplete root hair elongation (ire), whose root hairs are about 40% shorter than the wild type owing to the early cessation of their growth. In contrast, the hy5 mutant has root hairs about twice as long as the wild type, possibly because of delayed cessation of growth. Thus IRE and HY5 are likely to modify the duration of growth of root hairs. We cloned the IRE locus using the T-DNA tagged line. The IRE locus encodes a protein that includes a serine/threonine protein kinase domain. The primary structure of this kinase domain shows significant similarity to a group of protein kinases among various eukaryotes. In the Arabidopsis genome there are at least three genes that are closely related to IRE. The IRE transcript was detected in every organ examined. However, the IRE promoter-GUS fusion gene was strongly expressed in the elongating root hair cells, suggesting the cell-autonomous function of IRE in root hairs. GUS activity was also detected in pollen grains, which develop by tip growth, suggesting that IRE has a common role in the tip growth of plant cells. PMID:12000677

Oyama, Tokitaka; Shimura, Yoshiro; Okada, Kiyotaka

2002-05-01

213

Aortic valve-sparing procedure with cusp elongation and free edge reinforcement for bicuspid aortic valve.  

PubMed

Aortic valve-sparing procedures demonstrate excellent valvular function at midterm. Recently authors have reported acceptable early results with aortic valve-sparing procedures on patients with regurgitant bicuspid valves. We report the case of a novel procedure to preserve bicuspid valves with a calcified raphe and root dilatation. This procedure includes raphe excision, pericardial patch elongation, free edge leaflet reinforcement, and a root reimplantation valve-sparing procedure. PMID:15797089

Dagenais, Francois; Bauset, Richard; Mathieu, Patrick

2005-04-01

214

Ectopic ferredoxin I protein promotes root hair growth through induction of reactive oxygen species in Arabidopsis thaliana.  

PubMed

Ferredoxin I (Fd-1) is a protein existing in green tissues as an electron carrier for photosynthesis. Reactive oxygen species (ROS) are generated from an over-accumulation of electrons in photosynthetic electron chains. In previous studies, plant ferredoxin-like protein (PFLP) transgenic plants could be made resistant to virulent pathogens, by inducing the generation of ROS. The generation of ROS is closely associated with root hair development, increasing with the elongation of root hairs. We propose that an ectopic expression of pflp may alter root hair development through the enhanced generation of ROS. In this report, Arabidopsis transformed with pflp was generated to determine the potential role of PFLP in root development. Transgenic Arabidopsis exhibited longer root hairs with a significant increase in endogenous H(2)O(2) compared with wild type. The growth of transgenic lines in root hairs was inhibited when treated with NADPH oxidase inhibitor. Results suggest that an over-expression of pflp had enhanced the accumulation of H(2)O(2) in the roots and further promoted the growth of root hairs. Transcriptional activities of root hair development-related and redox-regulated genes were mediated through increased levels of ROS, to alter the growth of transgenic lines in root hairs. In summary, we propose that an ectopic expression of pflp promotes root hair growth, resulting from an enhancement of ROS production. PMID:20828872

Shin, Lung-Jiun; Huang, Hsiang-En; Chang, Hsiang; Lin, Yi-Hsien; Feng, Teng-Yung; Ger, Mang-Jye

2010-09-09

215

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

216

Hydraulic Conductance and Mercury-Sensitive Water Transport for Roots of Opuntia acanthocarpa in Relation to Soil Drying and Rewetting  

Microsoft Academic Search

Drought-induced changes in root hydraulic conductance (LP) and mercury-sensitive water transport were examined for distal (immature) and mid-root (mature) regions of Opuntia acanthocarpa. During 45 d of soil drying, LP decreased by about 67% for distal and mid-root regions. Afte r8di nrewetted soil, LP recovered to 60% of its initial value for both regions. Axial xylem hydraulic conductivity was only

Pierre Martre; Gretchen B. North; Park S. Nobel

2001-01-01

217

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.

218

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

219

Olpidium brassicae, tobacco necrosis virus, and Pythium spp. in relation to rusty root of carrots in Ontario and Quebec  

Microsoft Academic Search

Olpidum brassicae, Pythium sulcatum, and Pythium irregulare were frequently isolated from roots of carrots grown in soils from Ontario and Quebec carrot fields regardless of the presence of carrot rusty root. Although there were physiological strains of these fungi, there were no apparent differences in morphology or pathogenicity of isolates collected from the Holland-Bradford and Keswick marshes in Ontario, where

D. J. S. Barr; W. G. Kemp

220

Water Transport Properties of Roots and Root Cortical Cells in Proton- and Al-Stressed Maize Varieties.  

PubMed Central

Root and root cell pressure-probe techniques were used to investigate the possible relationship between Al- or H+-induced alterations of the hydraulic conductivity of root cells (LPc) and whole-root water conductivity (LPr) in maize (Zea mays L.) plants. To distinguish between H+ and Al effects two varieties that differ in H+ and Al tolerance were assayed. Based on root elongation rates after 24 h in nutrient solution of pH 6.0, pH 4.5, or pH 4.5 plus 50 [mu]M Al, the variety Adour 250 was found to be H+-sensitive and Al-tolerant, whereas the variety BR 201 F was found to be H+-tolerant but Al-sensitive. No Al-induced decrease of root pressure and root cell turgor was observed in Al-sensitive BR 201 F, indicating that Al toxicity did not cause a general breakdown of membrane integrity and that ion pumping to the stele was maintained. Al reduced LPc more than LPr in Al-sensitive BR 201 F. Proton toxicity in Adour 250 affected LPr more than LPc. In this Al-tolerant variety LPc was increased by Al. Nevertheless, this positive effect on LPc did not render higher LPr values. In conclusion, there were no direct relationships between Al- or H+-induced decreases of LPr and the effects on LPc. To our knowledge, this is the first time that the influence of H+ and Al on root and root cell water relations has been directly measured by pressure-probe techniques.

Gunse, B.; Poschenrieder, C.; Barcelo, J.

1997-01-01

221

Phytochemical analysis of mature tree root exudates in situ and their role in shaping soil microbial communities in relation to tree N-acquisition strategy.  

PubMed

Eperua falcata (Aublet), a late-successional species in tropical rainforest and one of the most abundant tree in French Guiana, has developed an original strategy concerning N-acquisition by largely preferring nitrate, rather than ammonium (H. Schimann, S. Ponton, S. Hättenschwiler, B. Ferry, R. Lensi, A.M. Domenach, J.C. Roggy, Differing nitrogen use strategies of two tropical rainforest tree species in French Guiana: evidence from (15)N natural abundance and microbial activities, Soil Biol. Biochem. 40 (2008) 487-494). Given the preference of this species for nitrate, we hypothesized that root exudates would promote nitrate availability by (a) enhancing nitrate production by stimulating ammonium oxidation or (b) minimizing nitrate losses by inhibiting denitrification. Root exudates were collected in situ in monospecific planted plots. The phytochemical analysis of these exudates and of several of their corresponding root extracts was achieved using UHPLC/DAD/ESI-QTOF and allowed the identification of diverse secondary metabolites belonging to the flavonoid family. Our results show that (i) the distinct exudation patterns observed are related to distinct root morphologies, and this was associated with a shift in the root flavonoid content, (ii) a root extract representative of the diverse compounds detected in roots showed a significant and selective metabolic inhibition of isolated denitrifiers in vitro, and (iii) in soil plots the abundance of nirK-type denitrifiers was negatively affected in rhizosphere soil compared to bulk. Altogether this led us to formulate hypothesis concerning the ecological role of the identified compounds in relation to N-acquisition strategy of this species. PMID:23727287

Michalet, Serge; Rohr, Julien; Warshan, Denis; Bardon, Clément; Roggy, Jean-Christophe; Domenach, Anne-Marie; Czarnes, Sonia; Pommier, Thomas; Combourieu, Bruno; Guillaumaud, Nadine; Bellvert, Floriant; Comte, Gilles; Poly, Franck

2013-05-16

222

Modelling Root Systems Using Oriented Density Distributions  

NASA Astrophysics Data System (ADS)

Root architectural models are essential tools to understand how plants access and utilize soil resources during their development. However, root architectural models use complex geometrical descriptions of the root system and this has limitations to model interactions with the soil. This paper presents the development of continuous models based on the concept of oriented density distribution function. The growth of the root system is built as a hierarchical system of partial differential equations (PDEs) that incorporate single root growth parameters such as elongation rate, gravitropism and branching rate which appear explicitly as coefficients of the PDE. Acquisition and transport of nutrients are then modelled by extending Darcy's law to oriented density distribution functions. This framework was applied to build a model of the growth and water uptake of barley root system. This study shows that simplified and computer effective continuous models of the root system development can be constructed. Such models will allow application of root growth models at field scale.

Dupuy, Lionel X.

2011-09-01

223

Roles of phosphatidylinositol 3-kinase in root hair growth.  

PubMed

The root hair is a model system for understanding plant cell tip growth. As phosphatidylinositol 3-phosphate [PtdIns(3)P] has been shown in other plant cell types to regulate factors that affect root hair growth, including reactive oxygen species (ROS) levels, cytoskeleton, and endosomal movement, we hypothesized that PtdIns(3)P is also important for root hair elongation. The enzyme that generates PtdIns(3)P, phosphatidylinositol 3-kinase (PI3K), was expressed in root hair cells of transgenic plants containing the PI3K promoter:beta-glucuronidase reporter construct. To obtain genetic evidence for the role of PtdIns(3)P in root hair elongation, we attempted to isolate Arabidopsis (Arabidopsis thaliana) mutant plants that did not express the gene VPS34 encoding the PI3K enzyme. However, the homozygous mutant was lethal due to gametophytic defects, and heterozygous plants were not discernibly different from wild-type plants. Alternatively, we made transgenic plants expressing the PtdIns(3)P-binding FYVE domain in the root hair cell to block signal transduction downstream of PtdIns(3)P. These transgenic plants had shorter root hairs and a reduced hair growth rate compared with wild-type plants. In addition, LY294002, a PI3K-specific inhibitor, inhibited root hair elongation but not initiation. In LY294002-treated root hair cells, endocytosis at the stage of final fusion of the late endosomes to the tonoplast was inhibited and ROS level decreased in a dose-dependent manner. Surprisingly, the LY294002 effects on ROS and root hair elongation were similar in rhd2 mutant plants, suggesting that RHD2 was not the major ROS generator in the PtdIns(3)P-mediated root hair elongation process. Collectively, these results suggest that PtdIns(3)P is required for maintenance of the processes essential for root hair cell elongation. PMID:18408046

Lee, Yuree; Bak, Gwangbae; Choi, Yunjung; Chuang, Wen-I; Cho, Hyung-Taeg; Lee, Youngsook

2008-04-11

224

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

225

Induction of coleoptile elongation by carbon dioxide.  

PubMed

The ability of CO(2) to induce elongation of Avena sativa coleoptile segments was examined with the use of a high resolution growth-recording device. CO(2)-saturated water causes an 8- to 16-fold promotion in the rate of elongation within 1 minute. This elongation is insensitive to a variety of metabolic inhibitors that suppress auxin-induced elongation, and the CO(2) effect cannot be prevented by pretreatment with these inhibitors. Buffers of pH 3 to 4 also stimulate elongation quickly, and it seems that at least a major part of the action of CO(2) depends upon its ability to reduce pH. The rate of elongation of auxin-promoted segments can be further enhanced by treatment with CO(2) but not vice versa.The response to CO(2) can be inhibited by mannitol at osmotic concentrations that inhibit normal growth, by calcium, and by brief pretreatment with heavy water (D(2)O). The elongation rate that results from CO(2) treatment is sensitive to temperature, but the induction by CO(2) itself appears to be almost temperature-independent.Elongation following treatment with CO(2) may be a physical flow phenomenon, essentially independent of immediate biochemical participation, which occurs when wall polymer interactions that normally restrict strain in the cell wall are weakened or broken by CO(2) in a manner that in effect substitutes for the role of metabolism in normal auxin-inducible cell enlargement. PMID:16657618

Evans, M L; Ray, P M; Reinhold, L

1971-03-01

226

Avena coleoptile elongation: stimulation by fluorophenylalanine  

Microsoft Academic Search

A 100 to 150% stimulation of Avena coleoptile segment elongation by the amino acid analogue p-fluorophenylalanine (FPA) has been observed. The effect is reversed by phenylalanine and is not seen with comparable concentrations of sodium fluoride. FPA does not alter elongation of red-irradiated segments. Stimulation by FPA occurs only when the apex is intact and the segments are incubated in

W. G. Hopkins; K. F. Bonnell

1969-01-01

227

Role of calcium in gravity perception of plant roots.  

PubMed

Calcium ions may play a key role in linking graviperception by the root cap to the asymmetric growth which occurs in the elongation zone of gravistimulated roots. Application of calcium-chelating agents to the root cap inhibits gravitropic curvature without affecting growth. Asymmetric application of calcium to one side of the root cap induces curvature toward the calcium source, and gravistimulation induces polar movement of applied 45Ca2+ across the root cap toward the lower side. The action of calcium may be linked to auxin movement in roots since 1) auxin transport inhibitors interfere both with gravitropic curvature and gravi-induced polar calcium movement and 2) asymmetric application of calcium enhances auxin movement across the elongation zone of gravistimulated roots. Indirect evidence indicates that the calcium-modulated regulator protein, calmodulin, may be involved in either the transport or action of calcium in the gravitropic response mechanism of roots. PMID:11537844

Evans, M L

1986-01-01

228

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

229

Effects of Oxazepam and an Extract of Kava Roots (Piper methysticum) on Event-Related Potentials in a Word Recognition Task  

Microsoft Academic Search

Twelve healthy volunteers were tested in a double-blind crossover study to assess the effects of oxazepam and an extract of kava roots (Piper methysticum) on behavior and event-related potentials (ERPs) in a recognition memory task. The subjects’ task was to identify within a list of visually presented words those that were shown for the first time and those that were

T. F. Münte; H. J. Heinze; M. Matzke; J. Steitz

1993-01-01

230

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

2012-12-18

231

Novel natural genetic variation controlling the competence to form adventitious roots and shoots from the tomato wild relative Solanum pennellii.  

PubMed

Tomato (Solanum lycopersicum L.) is an attractive model to study the genetic basis of adventitious organ formation capacity, since there is considerable natural genetic variation among wild relatives. Using a set of 46 introgression lines (ILs), each containing a small chromosomal segment of Solanum pennellii LA716 introgressed and mapped into the tomato cultivar M82, we characterized a high shoot-regeneration capacity for ILs 3-2, 6-1, 7-1, 7-2, 8-2, 8-3, 9-1, 9-2, 10-2 and 10-3, when cotyledon explants were cultivated on medium containing 5.0?M BAP. F1 seedlings from the crosses 'Micro-Tom×ILs' and 'ILs×ILs' demonstrated that the shoot regeneration capacity of most ILs was dominant and that the regeneration ability of IL8-3 enhanced that of the other ILs in an additive manner. The ILs 3-2, 7-1, 8-3, and 10-2 also exhibited enhanced root formation on MS medium containing 0.4?M NAA, indicating that these chromosomal segments may contain genes controlling the competence to assume distinct cell fates, rather than the induction of a specific organ. We also performed the introgression of the genes controlling competence into the model system 'Micro-Tom'. The further isolation of such genes will improve our understanding of the molecular basis of organogenic capacity. PMID:23265325

Arikita, Fernanda Namie; Azevedo, Mariana Silva; Scotton, Danielle Camargo; Pinto, Maísa de Siqueira; Figueira, Antonio; Peres, Lázaro Eustáquio Pereira

2012-11-23

232

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

233

Rooting phylogenies using gene duplications: an empirical example from the bees (Apoidea).  

PubMed

The placement of the root node in a phylogeny is fundamental to characterizing evolutionary relationships. The root node of bee phylogeny remains unclear despite considerable previous attention. In order to test alternative hypotheses for the location of the root node in bees, we used the F1 and F2 paralogs of elongation factor 1-alpha (EF-1?) to compare the tree topologies that result when using outgroup versus paralogous rooting. Fifty-two taxa representing each of the seven bee families were sequenced for both copies of EF-1?. Two datasets were analyzed. In the first (the "concatenated" dataset), the F1 and F2 copies for each species were concatenated and the tree was rooted using appropriate outgroups (sphecid and crabronid wasps). In the second dataset (the "duplicated" dataset), the F1 and F2 copies were aligned to each another and each copy for all taxa were treated as separate terminals. In this dataset, the root was placed between the F1 and F2 copies (e.g., paralog rooting). Bayesian analyses demonstrate that the outgroup rooting approach outperforms paralog rooting, recovering deeper clades and showing stronger support for groups well established by both morphological and other molecular data. Sequence characteristics of the two copies were compared at the amino acid level, but little evidence was found to suggest that one copy is more functionally conserved. Although neither approach yields an unambiguous root to the tree, both approaches strongly indicate that the root of bee phylogeny does not fall near Colletidae, as has been previously proposed. We discuss paralog rooting as a general strategy and why this approach performs relatively poorly with our particular dataset. PMID:21600997

Brady, Seán G; Litman, Jessica R; Danforth, Bryan N

2011-05-12

234

Upregulation of ginsenoside and gene expression related to triterpene biosynthesis in ginseng hairy root cultures elicited by methyl jasmonate  

Microsoft Academic Search

In this study, methyl jasmonate (MJ)-induced changes of triterpene saponins in ginseng (Panax ginseng C.A. Meyer) hairy roots and expression profiling of relevant responsive genes were analyzed. The transcription of PgSS (squalene synthase), PgSE (squalene epoxidase), and PNA (dammarenediol synthase-II) genes in hairy root cultures elicited by MJ treatment increased as compared with the controls,\\u000a whereas that of PNX (cycloartenol

Ok Tae Kim; Kyong Hwan Bang; Young Chang Kim; Dong Yun Hyun; Min Young Kim; Seon Woo Cha

2009-01-01

235

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

Microsoft Academic Search

The plant meristems, shoot apical meristem (SAM) and root apical meristem (RAM), are unique structures made up of a self-renewing\\u000a population of undifferentiated pluripotent stem cells. The SAM produces all aerial parts of postembryonic organs, and the\\u000a RAM promotes the continuous growth of roots. Even though the structures of the SAM and RAM differ, the signaling components\\u000a required for stem

Hiroki Miwa; Atsuko Kinoshita; Hiroo Fukuda; Shinichiro Sawa

2009-01-01

236

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

237

Root architecture impacts on root decomposition rates in switchgrass  

NASA Astrophysics Data System (ADS)

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

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

2010-12-01

238

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

PubMed Central

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

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

2011-01-01

239

Modulation of root branching by a coumarin derivative  

PubMed Central

A healthy root system is crucial to plant growth and survival. To maintain efficiency of root function, plants have to dynamically modulate root system architecture through various adaptive mechanisms such as lateral root formation to respond to a changing and diversified soil environment. Exogenous application of a coumarin derivative, 4-methylumbelliferone (4-MU), in Arabidopsis thaliana inhibits seed germination by mainly reducing primary root growth. UDP-glycosyltransferases play an integral role in the biochemical mechanism of 4-MU detoxification in plant roots.1 However, 4-MU treatment also dramatically led to increased lateral root initiation, elongation and density. Moreover, marked root bending at the root-hypocotyl junction and auxin redistribution appeared to contribute to the 4-MU-mediated lateral root formation. We propose that 4-MU would serve as a useful chemical tool to study auxin-mediated root branching.

Li, Xiang; Gao, Ming-Jun

2011-01-01

240

Growth and anatomical parameters of adventitious roots formed on mung bean hypocotyls are correlated with galactoglucomannan oligosaccharides structure.  

PubMed

The effect of galactoglucomannan oligosaccharides (GGMOs) compared with chemically modified oligosaccharides, GGMOs-g (with reduced number of D-galactose side chains) and GGMOs-r (with reduced reducing ends) on mung bean (Vigna radiata (L.) Wilczek) adventitious roots formation, elongation, and anatomical structure have been studied. All types of oligosaccharides influenced adventitious root formation in the same way: stimulation in the absence of exogenous auxin and inhibition in the presence of exogenous auxin. Both reactions are probably related with the presence/content of endogenous auxin in plant cuttings. However, the adventitious root length was inhibited by GGMOs both in the absence as well as in the presence of auxin (IBA or NAA), while GGMOs-g inhibition was significantly weaker compared with GGMOs. GGMOs-r were without significant difference on both processes, compared with GGMOs. GGMOs affected not only the adventitious root length but also their anatomy in dependence on the combination with certain type of auxin. The oligosaccharides influenced cortical cells division, which was reflected in the cortex area and in the root diameter. All processes followed were dependent on oligosaccharides chemical structure. The results suggest also that GGM-derived oligosaccharides may play an important role in adventitious roots elongation but not in their formation. PMID:22666154

Kollárová, K; Zelko, I; Henselová, M; Capek, P; Lišková, D

2012-05-22

241

Reinnervation of hind limb extremity after lumbar dorsal root ganglion injury.  

PubMed

Loss of dorsal root ganglion neuron, or injury to dorsal roots, induces permanent somatosensory defect without therapeutic option. We explored an approach to restoring hind limb somatosensory innervation after elimination of L4, L5 and L6 dorsal root ganglion neurons in rats. Somatosensory pathways were reconstructed by connecting L4, L5 and L6 lumbar dorsal roots to T10, T11 and T12 intercostal nerves, respectively, thus allowing elongation of thoracic ganglion neuron peripheral axons into the sciatic nerve. Connection of thoracic dorsal root ganglion neurons to peripheral tissues was documented 4 and 7 months after injury. Myelinated and unmyelinated fibers regrew in the sciatic nerve. Nerve terminations expressing calcitonin-gene-related-peptide colonized the footpad skin. Retrograde tracing showed that T10, T11 and T12 dorsal root ganglion neurons expressing calcitonin-gene-related-peptide or the neurofilament RT97 projected axons to the sciatic nerve and the footpad skin. Recording of somatosensory evoked potentials in the upper spinal cord indicated connection between the sciatic nerve and the central nervous system. Hind limb retraction in response to nociceptive stimulation of the reinnervated footpads and reversion of skin lesions suggested partial recovery of sensory function. Proprioceptive defects persisted. Delayed somatosensory reinnervation of the hind limb after destruction of lumbar dorsal root neurons in rats indicates potential approaches to reduce chronic disability after severe injury to somatosensory pathways. PMID:16202409

Liu, Song; Bréjot, Thomas; Cressant, Arnaud; Bacci, Josette; Saïd, Gérard; Tadié, Marc; Heard, Jean Michel

2005-10-03

242

The model of root graviresponse with retarded arguments  

NASA Astrophysics Data System (ADS)

The graviperception mechanism (GPM) of the roots of higher plants localized in the cap region of a root and supposedly related to statoliths sedimentation produces the signals in response to the change of the root axis orientation relative to the gravity vector G. Meanwhile, the regions (Distal Elongation Zone -DEZ and Central Elongation Zone-CEZ), where the signals initiate the changes of the growth rates of the upper and lower flanks of the root, are located at the significant distances from the cap (thousands microns for some plants). It causes the time delays between the relocation of statoliths in statocytes and the change of the growth rates in elongation zones. It is suggested that the signal targeting the CEZ modulates the initially uniform lateral distribution of some specific substances (S) in the cap region. Then already nonhomogeneous lateral distribution of S is transferred to the CEZ to initiate the change of the growth rates of the opposite flanks. It results in the bending of the root in the line of G and thus in the change of the GPM signal in the cap region. In the present model the kinetics of a root apex bending (angle A) in response to the time (t)-dependent change of the G orientation is described by the integro-differential equation in A(t). The main peculiarity of this model is the presence of retarded (time-delayed) arguments t-TCEZ and t-TDEZ . In this case the solutions of this equation depend on the preceding kinetics of A(t) during the time delays TCEZ and TDEZ . It is suggested that the signals activating the CEZ and DEZ are of different nature. The work is focused on two problems concerning the modeling of the effects of time-delay(s) on the root bending. The first problem supposes the existence of one zone (CEZ) and one time-delay TCEZ . This equation was studied and solved using analytical and numerical methods. We analyzed the model as to whether it can be used to describe the kinetics of root graviresponse in the case of different orientations of the root apex relative to the G vector during the time interval equal to TCEZ (TCEZ > TDEZ ) that precedes the beginning of gravistimultion. Also we explored the conditions of the overshooting (the vertical) and non-overshooting regimes of gravistimulated root bending. Good correlation between the results of the modeling and known experimental data (Barlow et al, 1993, Stochkus, 1994, Mullen, 1998) was found. This allowed us to estimate and analyze the parameters of the model. The second problem supposed the existence of two zones of growth (CEZ and DEZ) and two corresponding time-delays. The effects of the second time-delay connected with the presence of the DEZ on the behavior of the model equation of the root graviresponse kinetics were analyzed and discussed.

Kondrachuk, Alexander

243

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

244

Elongation of Fatty Acids in Mycobacterium tuberculosis  

PubMed Central

Cell-free extracts of the H37Ra strain of Mycobacterium tuberculosis contain a soluble enzyme system which catalyzes an elongation reaction of long-chain fatty acids. The predominant reaction involves the addition of a single C2 unit to the acceptor fatty acid; the elongation takes place exclusively at the carboxyl end of the acceptor molecule. The endogenous acceptor lipid can be removed by solvent extraction of the enzyme system. The lipid-depleted enzyme can be fully reactivated with external acyl coenzyme A, after which elongation with acetyl coenzyme A takes place. The elongation reaction is avidin-insensitive and does not require adenosine triphosphate. Reduced nicotinamide adenine dinucleotide is the source of reducing equivalent, whereas reduced nicotinamide adenine dinucleotide phosphate is without effect.

Wang, Lynn; Kusaka, Takashi; Goldman, Dexter S.

1970-01-01

245

Elongate Hemlock Scale - Treesearch - USDA Forest Service  

Treesearch

Jul 21, 2013 ... Description: The elongate hemlock scale, Fiorinia externa Ferris, native to ... and in nine states from Virginia to southern New England and west to Ohio. ... (Marlatt ), and the hemlock woolly adelgid, Adelges tsugae Annand.

246

Elongated supramolecular assemblies in drug delivery.  

PubMed

This review presents different lipid-based elongated microstructures: tubules, cochleate cylinders and ribbons. Their composition, process of preparation and the mechanism behind their formation is discussed as well as their use as a drug delivery system. PMID:11992674

Zarif, Leila

2002-05-17

247

Retention of transcription initiation factor sigma70 in transcription elongation: single-molecule analysis.  

PubMed

We report a single-molecule assay that defines, simultaneously, the translocational position of a protein complex relative to DNA and the subunit stoichiometry of the complex. We applied the assay to define translocational positions and sigma70 contents of bacterial transcription elongation complexes in vitro. The results confirm ensemble results indicating that a large fraction, approximately 70%-90%, of early elongation complexes retain sigma70 and that a determinant for sigma70 recognition in the initial transcribed region increases sigma70 retention in early elongation complexes. The results establish that a significant fraction, approximately 50%-60%, of mature elongation complexes retain sigma70 and that a determinant for sigma70 recognition in the initial transcribed region does not appreciably affect sigma70 retention in mature elongation complexes. The results further establish that, in mature elongation complexes that retain sigma70, the half-life of sigma70 retention is long relative to the time-scale of elongation, suggesting that some complexes may retain sigma70 throughout elongation. PMID:16285917

Kapanidis, Achillefs N; Margeat, Emmanuel; Laurence, Ted A; Doose, Sören; Ho, Sam On; Mukhopadhyay, Jayanta; Kortkhonjia, Ekaterine; Mekler, Vladimir; Ebright, Richard H; Weiss, Shimon

2005-11-11

248

Evolution of axial patterning in elongate fishes  

Microsoft Academic Search

Within the ray-finned fishes, eel-like (extremely elongate) body forms have evolved multiple times from deeper-bod- ied forms. Previous studies have shown that elongation of the vertebral column may be associated with an increase in the number of vertebrae, an increase in the length of the vertebral centra, or a combination of both. Because the vertebral column of fishes has at

ANDREA B. WARD; ELIZABETH L. BRAINERD

249

Water and solute permeabilities of Arabidopsis roots in relation to the amount and composition of aliphatic suberin.  

PubMed

Although it is implied that suberized apoplastic barriers of roots negatively correlate with water and solute permeabilities, direct transport measurements across roots with altered amounts and compositions of aliphatic suberin are scarce. In the present study, hydroponically grown Arabidopsis wild types (Col8 and Col0) and different suberin mutants with altered amounts and/or compositions (horst, esb1-1, and esb1-2) were used to test this hypothesis. Detailed histochemical studies revealed late development of Casparian bands and suberin lamellae in the horst mutant compared with wild types and esb mutants. Suberin analysis with gas chromatography and mass spectrometry (GC-MS) showed that the horst mutant had ?33% lower amounts of aliphatic monomers than Col8 and Col0. In contrast, enhanced suberin mutants (esb1-1 and esb1-2) had twice the amount of suberin as the wild types. Correlative permeability measurements, which were carried out for the first time with a root pressure probe for Arabidopsis, revealed that the hydraulic conductivity (Lp(r)) and NaCl permeability (P(sr)) of the whole root system of the horst mutant were markedly greater than in the respective wild types. This was reflected by the total amounts of aliphatic suberin determined in the roots. However, increased levels of aliphatic suberin in esb mutants failed to reduce either water or NaCl permeabilities below those of the wild types. It was concluded that the simple view and the conventional assumption that the amount of root suberin negatively correlates with permeability may not always be true. The aliphatic monomer arrangement in the suberin biopolymer and its microstructure also play a role in apoplastic barrier formation. PMID:21421706

Ranathunge, Kosala; Schreiber, Lukas

2011-03-01

250

The role of graded nerve root compression on axonal damage, neuropeptide changes, and pain-related behaviors.  

PubMed

Rapid neck motions can load cervical nerve roots and produce persistent pain. This study investigated the cellular basis of radicular pain and mechanical implications of tissue loading rate. A range of peak loads was applied in an in vivo rat model of dorsal root compression, and mechanical allodynia (i.e. pain) was measured. Axonal damage and nociceptive mediators were assessed in the axons and cell bodies of compressed dorsal roots in separate groups of rats at days 1 and 7 after injury. In the day 7 group, damage in the compressed axons, evaluated by decreased heavy chain neurofilament immunoreactivity, was increased for compressions above a load of 34.08 mN, which is similar to the load-threshold for producing persistent pain in that model. Also, the neuropeptide substance P and glial cell line-derived neurotrophic factor and its receptor significantly decreased (p < 0.02) with increasing load in the small nociceptive neurons of the dorsal root ganglion, suggesting that axonal damage may also decrease neurotrophic support in injured nociceptive afferent fibers. In a separate study, roots were compressed at 2mm/s, and held, to develop a quasi-linear viscoelastic model that was validated through comparisons to quasistatic loading. The model demonstrated that nearly 23% less displacement was required to reach the axonal injury load threshold during dynamic loading than for quasistatic rates. Together, these studies demonstrate that nerve root compressions that produce pain symptoms are sufficient to mediate nociceptive cellular changes, and that thresholds for pain and nociceptive pathophysiology may be lower for dynamic loading scenarios. PMID:19085157

Hubbard, Raymond D; Quinn, Kyle P; Martínez, Joan J; Winkelstein, Beth A

2008-11-01

251

The Cytoskeleton and Root Growth Behavior  

Microsoft Academic Search

\\u000a The roots of many plant species develop complex growth behaviors when germinated on hard surfaces, and scientists have learned\\u000a to use this experimental set-up to study the structure and dynamics of cytoskeletal arrays. Our knowledge of the elements\\u000a that lead to anisotropic cell expansion in rapidly elongating cells has increased by finding mutants with altered root growth\\u000a behavior as well

Laura M. Vaughn; Katherine L. Baldwin; Gengxiang Jia; Julian C. Verdonk; Allison K. Strohm; Patrick H. Masson

252

Mass Spectrometric Quantification of Indole-3-Acetic Acid in Rhizobium Culture Supernatants: Relation to Root Hair Curling and Nodule Initiation  

PubMed Central

Indole-3-acetic acid (IAA) has been unequivocally identified in culture supernatants of Rhizobium strains by gas chromatography-mass spectrometry. A method for accurately quantitating IAA in bacterial culture supernatants, employing deuterium-labeled IAA as an internal standard, has been developed. Similar IAA concentrations were found in culture supernatants of chosen Rhizobium mutants (defective in nodule formation) and their corresponding parent strains. Since some of the mutants are known to adhere to root hairs, it can be concluded that root hair curling is not simply a consequence of IAA production by rhizobia.

Badenoch-Jones, Jane; Summons, R. E.; Djordjevic, M. A.; Shine, J.; Letham, D. S.; Rolfe, B. G.

1982-01-01

253

Normal Limits in Relation to Age, Body Size and Gender of Two-Dimensional Echocardiographic Aortic Root Dimensions in Persons >=15 Years of Age  

PubMed Central

Nomograms to predict normal aortic root diameter for body surface area (BSA) in broad ranges of age have been widely used, but are limited by lack of consideration of gender effects, jumps in upper limits of aortic diameter between age strata, and data from older teenagers. Sinuses of Valsalva diameter was measured by American Society of Echocardiography convention in normal-weight, non-hypertensive, non-diabetic individuals ?15 years old without aortic valve disease from clinical or population-based samples. Analyses of covariance and linear regression with assessment of residuals identified determinants and developed predictive models for normal aortic root diameter. Among 1,207 apparently normal individuals ?15 years old (54% female), aortic root diameter was 2.1 to 4.3 cm. Aortic root diameter was strongly related to BSA and height (both r=0.48), age (r=0.36) and male gender (+2.7 mm adjusted for BSA and age) (all p<0.001). Multivariable equations using age, gender, and either BSA or height predicted aortic diameter strongly (both R=0.674, p <0.001) with minimal relation of residuals to age or body size: for BSA: 2.423+(age [yrs]*0.009) + (bsa [m2]*0.461) -(sex [1=M, 2=F]*.267) SEE = 0.261 cmfor height: 1.519+(age [yrs]*0.010) + (ht [cm]*.010)-(sex [1=M, 2=F]*.247) SEE = 0.215 cm. In conclusion, aortic root diameter is larger in men and increases with body size and age. Regression models incorporating body size, age and gender are applicable to adolescents and adults without limitations of previous nomograms.

Devereux, Richard B.; de Simone, Giovanni; Arnett, Donna K.; Best, Lyle G.; Boerwinkle, Eric; Howard, Barbara V.; Kitzman, Dalane; Lee, Elisa T.; Mosley, Thomas H.; Weder, Alan; Roman, Mary J.

2012-01-01

254

Local treatment with indole-3-acetic acid induces differential growth responses in Zea mays L. roots  

Microsoft Academic Search

Differential growth responses of primary Zea mays L. roots were induced after asymmetrical applications of IAA-loaded beads along their elongating zone (1.0–4.0 mm from tip) and were modulated according to the initial growth rates of the roots. The amplitude and location (midpoint) of curvature, the elongation of the roots and the uptake of IAA were measured after 4 h. The

Philippe Meuwly; Paul-Emile Pilet

1991-01-01

255

The Spatially Variable Inhibition by Water Deficit of Maize Root Growth Correlates with Altered Profiles of Proton Flux and Cell Wall pH  

Microsoft Academic Search

pH indicator gel. Profiles of root segmental elongation correlated qualitatively and quantitatively (r2 5 0.74) with proton flux along the surface of the elongation zone from water-deficit and control treatments. Proton flux and segmental elongation in roots under water deficit were remarkably well maintained in the region 0 to 3 mm behind the root tip and were inhibited from 3

Ling Fan; Peter M. Neumann

2004-01-01

256

Fertilizer-induced Changes in Rhizosphere Electrical Conductivity: Relation to Forest Tree Seedling Root System Growth and Function  

Microsoft Academic Search

Fertilization is standard practice in forest tree seedling nursery culture. Additionally, fertilization at outplanting has potential to facilitate nutrient uptake and reduce transplant shock. Fertilization, however, may dramatically alter rhizosphere chemical properties such as pH, ion availability, and electrical conductivity (EC). These changes may inhibit root system growth and function by reducing soil osmotic potential and creating specific ion toxicities.

Douglass F. Jacobs; Vic R. Timmer

2005-01-01

257

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

258

Identification of novel drought-related mRNAs in common bean roots by differential display RT-PCR  

Microsoft Academic Search

Drought is a major constraint for the production of common bean (Phaseolus vulgaris L.). To identify molecular responses to water deficit, we performed a differential display RT-PCR (DDRT) analysis using roots of bean plants grown aeroponically and submitted to dehydration. This allowed us to visualise 1200 DDRT bands, 8.7% of which showed a clear regulation by dehydration, and to clone

Gisele A. M. Torres; Stephanie Pflieger; Fabienne Corre-Menguy; Christelle Mazubert; Caroline Hartmann; Christine Lelandais-Brière

2006-01-01

259

Aberrant cell expansion in the elongation mutants of barley.  

PubMed

The elongation (elo) mutants of barley (Hordeum vulgare cv 'Himalaya') are a class of dwarf plants with defects affecting cell expansion. The phenotypes of mutants in three of the elo loci (elo1, elo2 and elo3) are recessive to the wild-type allele, and the mutations at elo-4 and elo-5 are semi-dominant. Allelism tests showed that elo1, elo2 and elo3 were at separate loci, and mapping data indicated that elo-5 was possibly allelic to either elo1 or elo2. A phenotype common to all elo mutants was the presence of short, radially swollen cells on the leaf epidermis, indicating a defect in longitudinal cell expansion. In three of the mutants, elo1, elo3 and elo5, this was accompanied by a twisting growth habit. Two of the mutations, elo2 and elo-5, affected cell division, with aberrant periclinal cell division resulting in the formation of increased cell layers in the leaf epidermis of elo2 and elo-5 homozygotes and in the aleurone layer of elo2 grains. Misplaced anticlinal divisions also occurred in the elo-5 leaf epidermis. Leaf cell walls of all elo lines contained less cellulose than the wild- type, and the cortical microtubules in elongating root epidermal cells in some elo lines were more randomly oriented than in the wild-type, consistent with the presence of radially swollen cells. We discuss possible functions for the Elo genes in primary cell wall synthesis. PMID:19181700

Lewis, Dyani; Bacic, Antony; Chandler, Peter M; Newbigin, Edward J

2009-01-30

260

Plant growth promoting rhizobacterial (PGPR) bioconsortia mediates induction of defense-related proteins against infection of root rot pathogen in mulberry plants  

Microsoft Academic Search

The mixture of Pseudomonas fluorescens isolate Pf1 and Py15 and Bacillus subtilis isolate 16 (Bs16) was found to protect mulberry plants from root rot disease caused by Macrophomina phaseolina. Induction of defense-related proteins and chemicals by the mixture of Pf1, Py15 and Bs16 against challenge inoculation with M. phaseolina in mulberry were studied. The activity of defense enzymes peroxidase (PO),

P. Ganeshamoorthi; T. Anand; V. Prakasam; M. Bharani; N. Ragupathi; R. Samiyappan

2008-01-01

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

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

263

Age-related changes in dorsal root ganglia, circulating and vascular calcitonin gene-related peptide (CGRP) concentrations in female rats: Effect of female sex steroid hormones  

PubMed Central

The aim of the present study is to investigate whether immunoreactive (I) calcitonin gene-related peptide (CGRP) content is decreased in plasma and mesenteric arteries (resistance arteries) in middle-aged rats and if so, whether sex steroid hormones enhance I-CGRP in middle-aged female rats. We also examined whether vascular CGRP receptor components, calcitonin receptor like receptor (CRLR) and receptor activity modifying protein 1 (RAMP1) are elevated by sex steroid hormones treatment in middle-aged female rats. Young adult (3 months old) and middle-aged (10–12 months old) ovariectomized rats were treated subcutaneously with estradiol-17? (E2; 2 mg), progesterone (P4; 5 mg), E2 +P4 (2 mg + 20 mg) or placebo (control). Radioimmunoassay and Western blot analysis were performed to measure I-CGRP content and CGRP receptor components in dorsal root ganglia (DRG), in resistance arteries and in plasma. Immunofluorescent staining methods were employed to determine cellular localization of CRLR, RAMP1 in resistance arteries. Our data demonstrated that I-CGRP content was significantly (p < 0.05) lower in the plasma and resistance arteries of middle-aged female rats compared to young controls. Both RAMP1 and CRLR were concentrated in vascular endothelium and the underlying smooth muscle cells. RAMP1 but not CRLR appeared to be decreased in middle-aged rat vasculature. Chronic perfusion of sex steroid hormones to ovariectomized rats: (1) significantly (p < 0.05) elevated I-CGRP in the DRG and in the plasma, and (2) significantly elevated RAMP1 (p < 0.05) but did not alter CRLR in resistance arteries. These data suggest that female sex steroid treatment enhances I-CGRP and its receptors, and thus regulate the blood pressure in aged female rats.

Gangula, Pandu R.R.; Chauhan, Madhu; Reed, Luckey; Yallampalli, Chandra

2009-01-01

264

Pericycle Cell Proliferation and Lateral Root Initiation in Arabidopsis  

Microsoft Academic Search

In contrast with other cells generated by the root apical meristem in Arabidopsis, pericycle cells adjacent to the protoxylem poles of the vascular cylinder continue to cycle without interruption during passage through the elongation and differen- tiation zones. However, only some of the dividing pericycle cells are committed to the asymmetric, formative divisions that give rise to lateral root primordia

Joseph G. Dubrovsky; Peter W. Doerner; Adan Colon-Carmona; Thomas L. Rost

2000-01-01

265

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

PubMed Central

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

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

2009-01-01

266

Ethylene modifies architecture of root system in response to stomatal opening and water allocation changes between root and shoot  

PubMed Central

Ethylene plays a key role in the elongation of exploratory and root hair systems in plants, as demonstrated by pharmacological modulation of the activity of ethylene biosynthesis enzymes: ACC synthase (ACS) and ACC oxidase (ACO). Thus, treatments with high concentrations (10 µM) of aminoethoxyvinylglycine (AVG, inhibitor of ACS) and 1-aminocyclopropane carboxylic acid (ACC, ethylene precursor, ACO activator) severely decrease the elongation of the exploratory root system but induce opposite effects on the root hair system: root hair length and numbers were increased in seedlings treated with ACC, whereas they were reduced in seedlings treated with AVG. Until now, such elongation changes of root architecture had not been questioned in terms of nitrate uptake. In the march issue of Plant Physiology we report that N uptake and nitrate transporter BnNrt2.1 transcript level were markedly reduced in ACC treated seedlings, but were increased in AVG treated seedlings compared to the control.1 Because recent studies have revealed that ethylene can also modulate stomatal opening as well as root hair cell elongation, we have examined whether pharmacological modulation of ethylene biosynthesis could affect, in an integrated manner, and at a whole-plant level, the exploratory and root hair systems, through changes of stomatal conductance and water allocation between the root and shoot.

Patrick, Beauclair; Antonin, Leblanc; Servane, Lemauviel-Lavenant; Deleu, Carole

2009-01-01

267

Analysis of root meristem size development.  

PubMed

Plant post-embryonic development takes place in the meristems. In the root of the model plant Arabidopsis thaliana, stem cells organized in a stem-cell niche in the apex of the root meristem generate transit-amplifying cells, which undergo additional division in the proximal meristem and differentiate in the elongation/differentiation zone. For meristem maintenance, and therefore continuous root growth, the rate of cell differentiation must equal the rate of generation of new cells: how this balance is achieved is a central question in plant development. We have shown that maintenance of the Arabidopsis root meristem size is established by a balance between the antagonistic effects of cytokinin, which promotes cell differentiation, and auxin, which promotes cell division. Cytokinin antagonizes auxin in a specific developmental domain (the vascular tissue transition zone) from where it controls the differentiation rate of all the other root tissues. Here, we describe protocols to analyze development of root meristems. PMID:20734261

Perilli, Serena; Sabatini, Sabrina

2010-01-01

268

Investigation of Elongation and Its Relationship to Residual Stresses in Boron Filaments.  

National Technical Information Service (NTIS)

Elongation in boron filament during fabrication was investigated and found to be as great as 16% under certain conditions. It was also found to obey a relatively simple empirical relationship which yielded effective activation energies. A model for the el...

F. E. Wawner J. W. Eason R. A. Johnson

1979-01-01

269

Localization of superoxide in the root apex of Arabidopsis.  

PubMed

Reactive oxygen species (ROS) fulfil many functions in plants. They have a signaling role in several physiological mechanisms, but they are also directly involved as substrates in important reactions, especially in the apoplast. Two ROS, superoxide and hydrogen peroxide, were shown to exhibit a typical accumulation pattern in the Arabidopsis root apex. While hydrogen peroxide is mainly present in the cell wall of fully elongated cells in the region of root hair formation, superoxide accumulation roughly coincides with the transition zone, between the meristem and the fast elongating zone. Developing lateral roots also exhibit a strong superoxide labeling with the same localization. PMID:19704760

Dunand, Christophe; Penel, Claude

2007-03-01

270

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

Microsoft Academic Search

Summary.  ?Methyl-jasmonate (MeJA) has been proposed to be involved in the evocation of defense reactions, as the oxidative burst in\\u000a plants, substituting the elicitors or enhancing their effect. 48?h dark- and sterilely cultured (axenic) aeroponic sunflower\\u000a seedling roots excised and treated with different concentrations of MeJA showed a strong and quick depression of the H+ efflux rate, 1.80??M MeJA totally stopping

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

2003-01-01

271

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

Technology Transfer Automated Retrieval System (TEKTRAN)

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

272

Avena coleoptile elongation: stimulation by fluorophenylalanine.  

PubMed

A 100 to 150% stimulation of Avena coleoptile segment elongation by the amino acid analogue p-fluorophenylalanine (FPA) has been observed. The effect is reversed by phenylalanine and is not seen with comparable concentrations of sodium fluoride. FPA does not alter elongation of red-irradiated segments. Stimulation by FPA occurs only when the apex is intact and the segments are incubated in the absence of exogenous auxin. In the presence of FPA, (14)C-leucine uptake by coleoptile segments is reduced by 34% and protein synthesis by 42%. When pre-incubated on labeled media and subsequently transferred to unlabeled media, segments fail to incorporate into the protein fraction any of the previously absorbed label. It is therefore difficult to ascertain whether FPA results in a genuine inhibition of protein synthesis in apical coleoptile segments. Possible mechanisms for the action of FPA and its relationship to light dependent elongation are considered. PMID:16657057

Hopkins, W G; Bonnell, K F

1969-02-01

273

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

PubMed

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. PMID:11537850

Hasenstein, K H; Evans, M L

1988-01-01

274

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

275

Helical growth of stage-IVb sporangiophores of Phycomyces blakesleeanus : the relationship between rotation and elongation growth rates  

Microsoft Academic Search

An understanding of the relationship between the two components of helical growth (rotation rate and elongation rate) is fundamental to understanding the biophysical and molecular mechanism(s) of cell wall extension in algal cells, fungal cells, and plant stems and roots. Helical growth occurs throughout development of the sporangiophores of Phycomyces blakesleeanus. Previous studies within the growth zone of stage-IVb sporangiophores

Joseph K. E. Ortega; Georgia E. Lesh-Laurie; Mark A. Espinosa; Elena L. Ortega; Steve M. Manos; Melissa D. Cunning; Jessica E. Olson

2003-01-01

276

Magnetic field affects meristem activity and cell differentiation in Zea mays roots  

Microsoft Academic Search

Exposure of Zea mays seedlings to a continuous electromagnetic field (EMF) for 30 h induced a 30% stimulation in the rate of root elongation compared with the controls. It also resulted in a significant increase of cell expansion, in both the acropetal (metaxylem cell lineage) and basipetal (root cap cells) direction. In addition, in EMF-exposed roots a precocious structural disorder was

M. B. Bitonti; S. Mazzuca; T. Ting; A. M. Innocenti

2006-01-01

277

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

NASA Astrophysics Data System (ADS)

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

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

2013-02-01

278

Actin and the elongation of plant cells  

Microsoft Academic Search

Summary We have investigated in parallel the effects of different types of inhibitors on elongation of oat coleoptile cells in IAA and on the integrity of the longitudinally oriented actin-containing microfilaments present in control cells as detected by rhodamine phalloidin (RP) staining. Where growth was 50% inhibited by cytochalasin D (CD), we observed extensive to complete breakdown of the microfilaments

K. V. Thimann; K. Reese; V. T. Nachmias

1992-01-01

279

Elongated 3D FDTD modeling using PML  

Microsoft Academic Search

The method of perfectly matched layers (PML) has been proposed by Berenger (1994) for the finite-difference time-domain (FDTD) method. The new method aroused an enthusiastic response in the electromagnetics community. Many papers have been published on the subject, but the PML has never been tested for modeling a large elongated region which is often the case when we are interested

Y. H. Chen; W. C. Chew; M. Oristaglio

1996-01-01

280

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

281

Dependence of Plasma Properties on Elongation Ratio in Non-Circular Tokamak TNT-A  

Microsoft Academic Search

The relation between the plasma properties and elongation ratio is studied in a non-circular tokamak in the case of the safety factor qa˜2. With the increase of elongation ratio kappa (1.3-->1.5), the plasma current increases from 19.5 to 25 kA, the loop voltage decreases from 4 to 3 V, the mean current density and the electron temperature increase slightly (˜10%),

Shunjiro Shinohara; Isao Ochiai; Shunji Tsuji; Hiroshi Toyama

1982-01-01

282

Elongated uvula and diagnostic utility of spirometry in upper airway obstruction  

PubMed Central

Elongated uvula is relatively an uncommon condition. Upper airway obstruction is often a missed complication of such a rare condition. Clinical presentations of upper airway obstruction often mimic asthma. Hence it is very easily mis-diagnosed as asthma. Spirometry offers a very simple test to diagnose upper airway obstruction very early and easily. Once diagnosed, the management of elongated uvula, almost exclusively, is surgical excision leading to total cure. Here is a case report of such a rare condition.

Paliwal, Rajiv; Patel, Satish; Patel, Purvesh; Soni, Hiren

2010-01-01

283

Magnetic-field amplification in metal shaped-charge jets during their inertial elongation  

Microsoft Academic Search

This paper considers magnetic-field amplification in inertially elongating metal shaped-charge jets formed by explosion of a shaped charge with an axial field previously produced in the charge liner. The amplification is related to the effect of magnetic-field freezing in a conducting material and is due to the deformation of the jet material with particle elongation along the magnetic lines. The

S. V. Fedorov

2005-01-01

284

Spatial aluminium sensitivity of root apices of two common bean (Phaseolus vulgaris L.) genotypes with contrasting aluminium resistance  

Microsoft Academic Search

The initial response of plants to aluminium (Al) is an inhibition of root elongation. In the present study, short and medium-term effects of Al treatment (20 mM) on root growth and Al accumulation of two common bean (Phaseolus vulgaris L.) genotypes, VAX-1 (Al- sensitive) and Quimbaya (Al-resistant), were studied. Root elongation of both genotypes was severely inhibited during the first

Andres F. Rangel; Idupulapati M. Rao; Walter J. Horst

2007-01-01

285

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; Laurière, Christiane; Munnik, Teun; Haring, Michel A; Testerink, Christa

2012-08-20

286

Comparison between gradient-dependent hydraulic conductivities of roots using the root pressure probe: the role of pressure propagations and implications for the relative roles of parallel radial pathways.  

PubMed

Hydrostatic pressure relaxations with the root pressure probe are commonly used for measuring the hydraulic conductivity (Lp(r)) of roots. We compared the Lp(r) of roots from species with different root hydraulic properties (Lupinus angustifolius L. 'Merrit', Lupinus luteus L. 'Wodjil', Triticum aestivum L. 'Kulin' and Zea mays L. 'Pacific DK 477') using pressure relaxations, a pressure clamp and osmotic gradients to induce water flow across the root. Only the pressure clamp measures water flow under steady-state conditions. Lp(r) determined by pressure relaxations was two- to threefold greater than Lp(r) from pressure clamps and was independent of the direction of water flow. Lp(r) (pressure clamp) was two- to fourfold higher than for Lp(r) (osmotic) for all species except Triticum aestivum where Lp(r) (pressure clamp) and Lp(r) (osmotic) were not significantly different. A novel technique was developed to measure the propagation of pressure through roots to investigate the cause of the differences in Lp(r). Root segments were connected between two pressure probes so that when root pressure (P(r)) was manipulated by one probe, the other probe recorded changes in P(r). Pressure relaxations did not induce the expected kinetics in pressure in the probe at the other end of the root when axial hydraulic conductance, and probe and root capacitances were accounted for. An electric circuit model of the root was constructed that included an additional capacitance in the root loaded by a series of resistances. This accounted for the double exponential kinetics for intact roots in pressure relaxation experiments as well as the reduced response observed with the double probe experiments. Although there were potential errors with all the techniques, we considered that the measurement of Lp(r) using the pressure clamp was the most unambiguous for small pressure changes, and provided that sufficient time was allowed for pressure propagation through the root. The differences in Lp(r) from different methods of measurement have implications for the models describing water transport through roots and the potential role of aquaporins. PMID:17547657

Bramley, Helen; Turner, Neil C; Turner, David W; Tyerman, Stephen D

2007-07-01

287

SIZ1 Regulation of Phosphate Starvation-Induced Root Architecture Remodeling Involves the Control of Auxin Accumulation1[C][W][OA  

PubMed Central

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.

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

2011-01-01

288

Relations between Root-zone Soil Moisture and MODIS-derived Vegetation Indices in Oak savanna and Open Grassland in California  

NASA Astrophysics Data System (ADS)

Optical remote sensing cannot provide direct quantification of soil moisture, but here we test the idea that plant available soil moisture can be inferred through calibration of images that quantify plant-leaf water and photosynthetic relationships. We measured relationships between volumetric soil water content in the rooting zone of annual grasslands and oak savanna and six vegetation indices (VIs) derived from MODIS data (NDVI, EVI, ARVI, SAVI,VARI and NDWI). The measured sites were part of the AmeriFlux network in California: Tonzi Ranch (oak savanna)and Vaira Ranch(open grassland). To reduce the empirical effect of linking vegetation indices to soil moisture directly, measured gross primary production (GPP) was used to bridge them. The results showed that (1) VARI was most sensitive to soil moisture variations; (2) in open grassland GPP is significantly controlled by the available water in the soil but the relationship is not linear----- GPP continues to increase in the growing season as long as soil moisture is sufficient. In oak savanna, the relationship is less obvious because oak trees can exploit water in deep soil layers. The results also demonstrated a strong linear relationship between GPP and vegetation indices for both oak savanna and open grassland. Therefore, based on the relation between GPP and root-zone soil moisture and the relation between GPP and VI, we estimated soil moisture as a function of a VI. Likely, the functional parameters are dependent on vegetation types, soil texture and topography. In order to explore the sensitivity of this relationship in areas where soil moisture and vegetation production data are not available, we will use DayCENTURY and ISOLSM models to simulate soil moisture and primary production at instrumented sites with meteorological data and soil properties data. The simulation tested in Tonzi Ranch and Vaira Ranch suggest that we can estimate root-zone soil moisture with optical remotely sensed data at large scale.

Liu, S.; Chadwick, O.; Roberts, D.

2008-12-01

289

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

2012-12-20

290

Ethylene directs auxin to control root cell expansion  

PubMed Central

SUMMARY Root morphogenesis is controlled by the regulation of cell division and expansion. We isolated an allele of the eto1 ethylene overproducer as a suppressor of the auxin-resistant mutant ibr5, prompting an examination of crosstalk between the phytohormones auxin and ethylene in control of root epidermal cell elongation and root hair elongation. We examined the interaction of eto1 with mutants that have reduced auxin response or transport and found that ethylene overproduction partially restored auxin responsiveness to these mutants. In addition, we found that the effects of endogenous ethylene on root cell expansion in eto1 seedlings were partially impeded by dampening auxin signaling, and were fully suppressed by blocking auxin influx. These data provide insight into the interaction between these two key plant hormones, and suggest that endogenous ethylene directs auxin to control root cell expansion.

Strader, Lucia C.; Chen, Grace L.; Bartel, Bonnie

2013-01-01

291

A proteomic approach to analyzing responses of Arabidopsis thaliana root cells to different gravitational conditions using an agravitropic mutant, pin2 and its wild type  

PubMed Central

Background Root gravitropsim has been proposed to require the coordinated, redistribution of the plant signaling molecule auxin within the root meristem, but the underlying molecular mechanisms are still unknown. PIN proteins are membrane transporters that mediate the efflux of auxin from cells. The PIN2 is important for the basipetal transport of auxin in roots and plays a critical role in the transmission of gravity signals perceived in the root cap to the root elongation zone. The loss of function pin2 mutant exhibits a gravity-insensitive root growth phenotype. By comparing the proteomes of wild type and the pin2 mutant root tips under different gravitational conditions, we hope to identify proteins involved in the gravity-related signal transduction. Results To identify novel proteins involved in the gravity signal transduction pathway we have carried out a comparative proteomic analysis of Arabidopsis pin2 mutant and wild type (WT) roots subjected to different gravitational conditions. These conditions included horizontal (H) and vertical (V) clinorotation, hypergravity (G) and the stationary control (S). Analysis of silver-stained two-dimensional SDS-PAGE gels revealed 28 protein spots that showed significant expression changes in altered gravity (H or G) compared to control roots (V and S). Whereas the majority of these proteins exhibited similar expression patterns in WT and pin2 roots, a significant number displayed different patterns of response between WT and pin2 roots. The latter group included 11 protein spots in the H samples and two protein spots in the G samples that exhibited an altered expression exclusively in WT but not in pin2 roots. One of these proteins was identified as annexin2, which was induced in the root cap columella cells under altered gravitational conditions. Conclusions The most interesting observation in this study is that distinctly different patterns of protein expression were found in WT and pin2 mutant roots subjected to altered gravity conditions. The data also demonstrate that PIN2 mutation not only affects the basipetal transport of auxin to the elongation zone, but also results in an altered expression of proteins in the root columella.

2011-01-01

292

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

2012-05-14

293

Vibrational modes of elongated sessile liquid droplets.  

PubMed

Vibrations of small (microliter) sessile liquid droplets were studied using a simple optical deflection technique. The droplets were made to elongate in one direction by taking advantage of the anisotropic wetting of the liquids on structured diffraction grating surfaces. They were vibrated by applying a puff of nitrogen gas. Motion of the droplets was monitored by scattering laser light from their surfaces. The scattered light was collected using a photodiode, and the resulting time-dependent intensity signals were Fourier-transformed to obtain the vibrational response of the drops. The vibrational spectra of elongated sessile drops were observed to contain two closely spaced peaks. A simple model that considers the frequency of capillary wave fluctuations on the surfaces of the drops was used to show that the vibrational frequencies of these peaks correspond to standing wave states that exist along the major and minor profile lengths of the droplets. PMID:23517045

Temperton, Robert H; Sharp, James S

2013-04-04

294

Vertically stabilized elongated cross-section tokamak  

DOEpatents

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

Sheffield, George V. (Hopewell, NJ)

1977-01-01

295

RNA chain elongation on a chromatin template.  

PubMed Central

The rate of RNA chain elongation has been measured with DNA and chromatin as template. RNA propagation on chromatin is about 50% of the rate found with DNA. Kinetic experiments demonstrate that the inhibition is not due to interference with the addition of the nucleoside triphosphates. Analysis of the dependence of propagation on the Tm of DNA shows that the chromatin proteins interfere with the translocation of the RNA polymerase along the DNA template.

Solage, A; Cedar, H

1976-01-01

296

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

PubMed

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

Kukavica, Biljana M; Veljovicc-Jovanovicc, Sonja D; Menckhoff, Ljiljana; Lüthje, Sabine

2012-07-03

297

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

PubMed

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

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

2013-01-04

298

The Distal Part of the Transition Zone Is the Most Aluminum-Sensitive Apical Root Zone of Maize1  

PubMed Central

For a better understanding of Al inhibition of root elongation, knowledge of the morphological and functional organization of the root apex is a prerequisite. We developed a polyvinyl chloride-block technique to supply Al (90 ?m monomeric Al) in a medium containing agarose to individual 1-mm root zones of intact seedlings of maize (Zea mays L. cv Lixis). Root elongation was measured during a period of 5 h. After Al treatment, callose (5 h) and Al (1 h) contents of individual 1-mm apical root segments were determined. For comparison, callose and Al levels were also measured in root segments after uniform Al supply in agarose blocks to the 10-mm root apex. Only applying Al to the three apical 1-mm root zones inhibited root elongation after 1 h. The order of sensitivity was 1 to 2 > 0 to 1 > 2 to 3 mm. In the 1- to 2-mm root zone high levels of Al-induced callose formation and accumulation of Al was found, independently of whether Al was applied to individual apical root zones or uniformly to the whole-root apex. We conclude from these results that the distal part of the transition zone of the root apex, where the cells are undergoing a preparatory phase for rapid elongation (F. Baluška, D. Volkmann, P.W. Barlow [1996] Plant Physiol 112: 3–4), is the primary target of Al in this Al-sensitive maize cultivar.

Sivaguru, Mayandi; Horst, Walter J.

1998-01-01

299

Disturbed local auxin homeostasis enhances cellular anisotropy and reveals alternative wiring of auxin-ethylene crosstalk in Brachypodium distachyon seminal roots.  

PubMed

Observations gained from model organisms are essential, yet it remains unclear to which degree they are applicable to distant relatives. For example, in the dicotyledon Arabidopsis thaliana (Arabidopsis), auxin biosynthesis via indole-3-pyruvic acid (IPA) is essential for root development and requires redundant TRYPTOPHAN AMINOTRANSFERASE OF ARABIDOPSIS 1 (TAA1) and TAA1-RELATED (TAR) genes. A promoter T-DNA insertion in the monocotyledon Brachypodium distachyon (Brachypodium) TAR2-LIKE gene (BdTAR2L) severely down-regulates expression, suggesting reduced tryptophan aminotransferase activity in this mutant, which thus represents a hypomorphic Bdtar2l allele (Bdtar2l(hypo) ). Counterintuitive however, Bdtar2l(hypo) mutants display dramatically elongated seminal roots because of enhanced cell elongation. This phenotype is also observed in another, stronger Bdtar2l allele and can be mimicked by treating wild type with L-kynerunine, a specific TAA1/TAR inhibitor. Surprisingly, L-kynerunine-treated as well as Bdtar2l roots display elevated rather than reduced auxin levels. This does not appear to result from compensation by alternative auxin biosynthesis pathways. Rather, expression of YUCCA genes, which are rate-limiting for conversion of IPA to auxin, is increased in Bdtar2l mutants. Consistent with suppression of Bdtar2l(hypo) root phenotypes upon application of the ethylene precursor 1-aminocyclopropane-1-carboxylic-acid (ACC), BdYUCCA genes are down-regulated upon ACC treatment. Moreover, they are up-regulated in a downstream ethylene-signaling component homolog mutant, Bd ethylene insensitive 2-like 1, which also displays a Bdtar2l root phenotype. In summary, Bdtar2l phenotypes contrast with gradually reduced root growth and auxin levels described for Arabidopsis taa1/tar mutants. This could be explained if in Brachypodium, ethylene inhibits the rate-limiting step of auxin biosynthesis in an IPA-dependent manner to confer auxin levels that are sub-optimal for root cell elongation, as suggested by our observations. Thus, our results reveal a delicate homeostasis of local auxin and ethylene activity to control cell elongation in Brachypodium roots and suggest alternative wiring of auxin-ethylene crosstalk as compared to Arabidopsis. PMID:23840182

Pacheco-Villalobos, David; Sankar, Martial; Ljung, Karin; Hardtke, Christian S

2013-06-20

300

Disturbed Local Auxin Homeostasis Enhances Cellular Anisotropy and Reveals Alternative Wiring of Auxin-ethylene Crosstalk in Brachypodium distachyon Seminal Roots  

PubMed Central

Observations gained from model organisms are essential, yet it remains unclear to which degree they are applicable to distant relatives. For example, in the dicotyledon Arabidopsis thaliana (Arabidopsis), auxin biosynthesis via indole-3-pyruvic acid (IPA) is essential for root development and requires redundant TRYPTOPHAN AMINOTRANSFERASE OF ARABIDOPSIS 1 (TAA1) and TAA1-RELATED (TAR) genes. A promoter T-DNA insertion in the monocotyledon Brachypodium distachyon (Brachypodium) TAR2-LIKE gene (BdTAR2L) severely down-regulates expression, suggesting reduced tryptophan aminotransferase activity in this mutant, which thus represents a hypomorphic Bdtar2l allele (Bdtar2lhypo). Counterintuitive however, Bdtar2lhypo mutants display dramatically elongated seminal roots because of enhanced cell elongation. This phenotype is also observed in another, stronger Bdtar2l allele and can be mimicked by treating wild type with L-kynerunine, a specific TAA1/TAR inhibitor. Surprisingly, L-kynerunine-treated as well as Bdtar2l roots display elevated rather than reduced auxin levels. This does not appear to result from compensation by alternative auxin biosynthesis pathways. Rather, expression of YUCCA genes, which are rate-limiting for conversion of IPA to auxin, is increased in Bdtar2l mutants. Consistent with suppression of Bdtar2lhypo root phenotypes upon application of the ethylene precursor 1-aminocyclopropane-1-carboxylic-acid (ACC), BdYUCCA genes are down-regulated upon ACC treatment. Moreover, they are up-regulated in a downstream ethylene-signaling component homolog mutant, Bd ethylene insensitive 2-like 1, which also displays a Bdtar2l root phenotype. In summary, Bdtar2l phenotypes contrast with gradually reduced root growth and auxin levels described for Arabidopsis taa1/tar mutants. This could be explained if in Brachypodium, ethylene inhibits the rate-limiting step of auxin biosynthesis in an IPA-dependent manner to confer auxin levels that are sub-optimal for root cell elongation, as suggested by our observations. Thus, our results reveal a delicate homeostasis of local auxin and ethylene activity to control cell elongation in Brachypodium roots and suggest alternative wiring of auxin-ethylene crosstalk as compared to Arabidopsis.

Pacheco-Villalobos, David; Sankar, Martial; Ljung, Karin; Hardtke, Christian S.

2013-01-01

301

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

302

Fine Root Biomass, Production, Turnover Rates, and Nutrient Contents in Boreal Forest Ecosystems in Relation to Species, Climate, Fertility, and Stand Age: Literature Review and Meta-Analyses  

Microsoft Academic Search

Fine roots <2 mm in diameter play a key role in regulating the biogeochemical cycles of ecosystems and are important to our understanding of ecosystem responses to global climate changes. Given the sensitivity of fine roots, especially in boreal region, to climate changes, it is important to assess whether and to what extent fine roots in this region change with

Z. Y. Yuan

2010-01-01

303

Gramicidin-D-stimulated influx of monovalent cations into plant roots  

Microsoft Academic Search

Gramicidin D and nigericin were found to stimulate K+ influx into oat roots. Valinomycin and nonactin had little effect on K+ influx. The region of the root most sensitive to gramicidin was the elongation zone. Monocot roots were more sensitive to gramicidin than dicot roots. At 0.2 mM KCl, gramicidin stimulated K+ influx by 4- to 8fold over a 30-min

T. K. Hodges; R. L. Darding; T. Weidner

1971-01-01

304

Reactive oxygen species localization in roots of Arabidopsis thaliana seedlings grown under phosphate deficiency  

Microsoft Academic Search

Arabidopsis plants responding to phosphorus (P) deficiency increase lateral root formation and reduce primary root elongation. In addition\\u000a the number and length of root hairs increases in response to P deficiency. Here we studied the patterns of radical oxygen\\u000a species (ROS) in the roots of Arabidopsis seedlings cultured on media supplemented with high or low P concentration. We found that

Jaros?aw Tyburski; Kamila Dunajska; Andrzej Tretyn

2009-01-01

305

Oversynthesis of elongation factors G and Tu in Escherichia coli.  

PubMed Central

We induced the oversynthesis of elongation factors Tu and G by using multicopy plasmids carrying the structural genes for these proteins under the control of the lac operator-promoter. We found no evidence that accumulation of excess elongation factor Tu or G affects the expression of genes for ribosomal proteins or elongation factors. Images

Zengel, J M; Lindahl, L

1982-01-01

306

Elongation and Isotope Scaling in Tokamak Transport Simulations  

Microsoft Academic Search

The elongation and isotope scaling of confinement in tokamaks is investigated using the Multi-Mode Transport Model in the BALDUR code. At high elongation kappa, the empirical energy confinement time scales like kappa to the fourth power at constant beta and magnetic q. However, we find that the elongation scaling of the drift wave contribution to the transport model has a

Arnold H. Kritz; Glenn Bateman; Aaron J. Redd; Jon E. Kinsey

1997-01-01

307

Novel temporal, fine-scale and growth variation phenotypes in roots of adult-stage maize (Zea mays L.) in response to low nitrogen stress.  

PubMed

There is interest in discovering root traits associated with acclimation to nutrient stress. Large root systems, such as in adult maize, have proven difficult to be phenotyped comprehensively and over time, causing target traits to be missed. These challenges were overcome here using aeroponics, a system where roots grow in the air misted with a nutrient solution. Applying an agriculturally relevant degree of low nitrogen (LN) stress, 30-day-old plants responded by increasing lengths of individual crown roots (CRs) by 63%, compensated by a 40% decline in CR number. LN increased the CR elongation rate rather than lengthening the duration of CR growth. Only younger CR were significantly responsive to LN stress, a novel finding. LN shifted the root system architectural balance, increasing the lateral root (LR)-to-CR ratio, adding ?70 m to LR length. LN caused a dramatic increase in second-order LR density, not previously reported in adult maize. Despite the near-uniform aeroponics environment, LN induced increased variation in the relative lengths of opposing LR pairs. Large-scale analysis of root hairs (RHs) showed that LN decreased RH length and density. Time-course experiments suggested the RH responses may be indirect consequences of decreased biomass/demand under LN. These results identify novel root traits for genetic dissection. PMID:21848860

Gaudin, Amelie C M; McClymont, Sarah A; Holmes, Bridget M; Lyons, Eric; Raizada, Manish N

2011-09-12

308

Agravitropic mutant for the study of hydrotropism in seedling roots  

NASA Astrophysics Data System (ADS)

Roots have been shown to respond to a moisture gradient by positive hydrotropism. Agravitropic mutant plants are useful for the study of the hydrotropism in roots because on Earth hydrotropism is obviously altered by the gravity response in the roots of normally gravitropic plants. The roots are able to sense water potential gradient as small as 0.5 MPa mm-1. The root cap includes the sensing apparatus that causes a differential growth at the elongation region of roots. A gradient in apoplastic calcium and calcium influx through plasmamembrane in the root cap is somehow involved in the signal transduction mechanism in hydrotropism, which may cause a differential change in cell wall extensibility at the elongation region. We have isolated an endoxy loglucan transferase (EXGT) gene that is strongly expressed in pea roots and appears to be involved in the differential growth in hydrotropically responding roots. Thus, it is now possible to study hydrotropism in roots by comparing with or separate from gravitropism. These results also imply that microgravity conditions in space are useful for the study of hydrotropism and its interaction with gravitropism.

Takahashi, H.; Takano, M.; Fujii, N.; Higashitani, A.; Yamashita, M.; Hirasawa, T.; Nishitani, K.

1999-01-01

309

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

Microsoft Academic Search

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

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

2006-01-01

310

Relationship among photosynthesis, ribulose-1,5-bisphosphate carboxylase (Rubisco) and water relations of the subtropical vegetable Chinese broccoli grown in the tropics by manipulation of root-zone temperature  

Microsoft Academic Search

Photosynthesis, initial Rubisco activity, Rubisco protein, total soluble protein and water relations were studied in subtropical Chinese broccoli (Brassica alboglabra) grown aeroponically in a tropical (Singapore) greenhouse. Aerial parts of the plant were maintained at hot ambient (A) temperature, but with their roots exposed to two different root-zone temperatures (RZTs): a constant 25°C-RZT and a diurnally fluctuating ambient temperature (25–40°C).

Jie He; Sing Kong Lee

2001-01-01

311

Co-ordinated Growth between Aerial and Root Systems in Young Apple Plants Issued from in vitro Culture  

PubMed Central

• Background and Aims In several species exhibiting a rhythmic aerial growth, the existence of an alternation between root and shoot growth has been demonstrated. The present study aims to investigate the respective involvement of the emergence of new organs and their elongation in relation to this phenomenon and its possible genotypic variation in young apple plants. • Methods Two apple varieties, X6407 (recently named ‘Ariane’) and X3305 (‘Chantecler’ × ‘Baujade’), were compared. Five plants per variety, issued from in vitro culture, were observed in minirhizotrons over 4 months. For each plant, root emergence and growth were observed twice per week. Growth rates were calculated for all roots with more than two segments and the branching density was calculated on primary roots. On the aerial part, the number of leaves, leaf area and total shoot length were observed weekly. • Key Results No significant difference was observed between varieties in any of the final characteristics of aerial growth. Increase in leaf area and shoot length exhibited a 3-week rhythm in X3305 while a weaker signal was observed in Ariane. The primary root growth rate was homogeneous between the plants and likewise between the varieties, while their branching density differed significantly. Secondary roots emerged rhythmically, with a 3-week and a 2-week rhythm, respectively, in X3305 and ‘Ariane’. Despite a high intra-variety variability, significant differences were observed between varieties in the secondary root life span and mean length. A synchronism between leaf emergence and primary root growth was highlighted in both varieties, while an opposition phase was observed between leaf area increments and secondary root emergence in X3305 only. • Conclusion A biological model of dynamics that summarizes the interactions between processes and includes the assumption of a feedback effect of lateral root emergence on leaf emergence is proposed.

COSTES, E.; GARCIA-VILLANUEVA, E.; JOURDAN, C.; REGNARD, J. L.; GUEDON, Y.

2006-01-01

312

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

313

Ethylene Modulates Flavonoid Accumulation and Gravitropic Responses in Roots of Arabidopsis1[W  

PubMed Central

Plant organs change their growth direction in response to reorientation relative to the gravity vector. We explored the role of ethylene in Arabidopsis (Arabidopsis thaliana) root gravitropism. Treatment of wild-type Columbia seedlings with the ethylene precursor 1-aminocyclopropane carboxylic acid (ACC) reduced root elongation and gravitropic curvature. The ethylene-insensitive mutants ein2-5 and etr1-3 had wild-type root gravity responses, but lacked the growth and gravity inhibition by ACC found in the wild type. We examined the effect of ACC on tt4(2YY6) seedlings, which have a null mutation in the gene encoding chalcone synthase, the first enzyme in flavonoid synthesis. The tt4(2YY6) mutant makes no flavonoids, has elevated indole-3-acetic acid transport, and exhibits a delayed gravity response. Roots of tt4(2YY6), the backcrossed line tt4-2, and two other tt4 alleles had wild-type sensitivity to growth inhibition by ACC, whereas the root gravitropic curvature of these tt4 alleles was much less inhibited by ACC than wild-type roots, suggesting that ACC may reduce gravitropic curvature by altering flavonoid synthesis. ACC treatment induced flavonoid accumulation in root tips, as judged by a dye that becomes fluorescent upon binding flavonoids in wild type, but not in ein2-5 and etr1-3. ACC also prevented a transient peak in flavonoid synthesis in response to gravity. Together, these experiments suggest that elevated ethylene levels negatively regulate root gravitropism, using EIN2- and ETR1-dependent pathways, and that ACC inhibition of gravity response occurs through altering flavonoid synthesis.

Buer, Charles S.; Sukumar, Poornima; Muday, Gloria K.

2006-01-01

314

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

PubMed

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

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

2007-03-13

315

Elongated nanostructures for radial junction solar cells.  

PubMed

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

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

2013-10-03

316

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

317

Transcription Elongation and Tissue-Specific Somatic CAG Instability  

PubMed Central

The expansion of CAG/CTG repeats is responsible for many diseases, including Huntington's disease (HD) and myotonic dystrophy 1. CAG/CTG expansions are unstable in selective somatic tissues, which accelerates disease progression. The mechanisms underlying repeat instability are complex, and it remains unclear whether chromatin structure and/or transcription contribute to somatic CAG/CTG instability in vivo. To address these issues, we investigated the relationship between CAG instability, chromatin structure, and transcription at the HD locus using the R6/1 and R6/2 HD transgenic mouse lines. These mice express a similar transgene, albeit integrated at a different site, and recapitulate HD tissue-specific instability. We show that instability rates are increased in R6/2 tissues as compared to R6/1 matched-samples. High transgene expression levels and chromatin accessibility correlated with the increased CAG instability of R6/2 mice. Transgene mRNA and H3K4 trimethylation at the HD locus were increased, whereas H3K9 dimethylation was reduced in R6/2 tissues relative to R6/1 matched-tissues. However, the levels of transgene expression and these specific histone marks were similar in the striatum and cerebellum, two tissues showing very different CAG instability levels, irrespective of mouse line. Interestingly, the levels of elongating RNA Pol II at the HD locus, but not the initiating form of RNA Pol II, were tissue-specific and correlated with CAG instability levels. Similarly, H3K36 trimethylation, a mark associated with transcription elongation, was specifically increased at the HD locus in the striatum and not in the cerebellum. Together, our data support the view that transcription modulates somatic CAG instability in vivo. More specifically, our results suggest for the first time that transcription elongation is regulated in a tissue-dependent manner, contributing to tissue-selective CAG instability.

Goula, Agathi-Vasiliki; Stys, Agnieszka; Chan, Jackson P. K.; Trottier, Yvon; Festenstein, Richard; Merienne, Karine

2012-01-01

318

Hypocrea/Trichoderma: species with conidiophore elongations and green conidia.  

PubMed

Species of Trichoderma and Hypocrea that have green conidia and sterile or fertile elongations of their conidiophores are described or redescribed and their phylogenetic position explored. The described species include T. crassum, T. fasciculatum, T. fertile, T. hamatum, T. longipile, T. oblongisporum, T. pubescens, T. spirale, T. strictipile, T. strigosum, T. stromaticum, T. tomentosum, Hypocrea aureoviridis f. macrospora, H. ceramica. and H. semiorbis. Trichoderma fasciculatum originally was described from cultures from ascospores of an unidentified Hypocrea specimen; it is considered to be a synonym of T. strictipile. The remaining species of Trichoderma considered here have not been linked to teleomorphs, and the Trichoderma anamorphs of H. aureoviridis f. macrospora and H. semiorbis have not been named. Five new species of Hypocrea are described, viz. H. cremea, H. cuneispora, H. estonica, H. strictipilosa and H. surrotunda. The phylogenetic relationships of these species were inferred based on partial RPB2 and EF-1? DNA sequence data and phenotypic characteristics, including teleomorph, anamorph, colony and growth rates. Trichoderma crassum was found to be a sister species to T. virens, based on molecular sequences and phenotypic data. Hypocrea surrotunda and H. cremea, H. cuneispora and T. longipile, T. fertile and T. oblongisporum, T. tomentosum and H. atrogelatinosa, and T. hamatum and T. pubescens, respectively, were found to be closely related phylogenetically, based on RPB2 and EF-1? gene genealogies. Anamorph and teleomorph phenotype, including conidiophore elongations, phialide morphology, conidial morphology, stroma anatomy and ascospore morphology are not useful predictors of relationships. Despite the shared phenotypic characters of these Trichoderma and Hypocrea species, they are distributed between two major clades of Trichoderma/Hypocrea. Redescriptions and a key to species of Hypocrea/Trichoderma with green conidia and conidiophore elongations are presented. PMID:21149016

Chaverri, Priscila; Castlebury, Lisa A; Overton, Barrie E; Samuels, Gary J

319

Dynamic strength tests for low elongation lanyards.  

PubMed

Lanyards are still important and common components of personal systems protecting against falls from a height. Experience with dynamic strength tests of lanyards indicates that test methods based on EN and ISO standards do not make objective assessment possible. This paper presents the results of theoretical and laboratory investigations of the performance of adjustable lanyards during fall arrest. The obtained results indicate that methods of testing and assessment based on those standards demonstrate considerable shortcomings when applied to low elongation lanyards. The assumptions for improved requirements and test methods of lanyards made of, e.g., steel wire and aramid ropes are also presented. PMID:17362657

Baszczy?ski, Krzysztof

2007-01-01

320

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

321

Cell elongation via intrinsic antipodal stretching forces  

NASA Astrophysics Data System (ADS)

To probe the mechanical properties of cells, we investigate a technique to perform deformability-based cytometry that inherently induces normal antipodal surface forces using a single line-shaped optical trap. We show theoretically that these opposing forces are generated simultaneously over curved microscopic object surfaces with optimal magnitude at low numerical apertures, allowing the directed stretching of elastic cells with a single, weakly focused laser source. Matching these findings with concomitant experimental observations, we elongate red blood cells, effectively stretching them within the narrow confines of a steep, optically induced potential well.

Sawetzki, T.; Eggleton, C. D.; Marr, D. W. M.

2012-12-01

322

The transition from transcriptional initiation to elongation  

PubMed Central

Transcription is the first step in gene expression, and its regulation underlies multicellular development and the response to environmental changes. Most studies of transcriptional regulation have focused on the recruitment of RNA polymerase to promoters. However, recent work has shown that, for many promoters, post-recruitment steps in transcriptional initiation are likely to be rate-limiting. The rate at which RNA polymerase transitions from transcriptional initiation to elongation varies dramatically between promoters and between organisms, and is the target of multiple regulatory proteins that can function to both repress and activate transcription.

Wade, Joseph T.; Struhl, Kevin

2008-01-01

323

Faraday waves in elongated superfluid fermionic clouds  

NASA Astrophysics Data System (ADS)

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

Capuzzi, P.; Vignolo, P.

2008-10-01

324

Regeneration of dorsal root axons is related to specific non-neuronal cells lining NGF-treated intraspinal nitrocellulose implants.  

PubMed

The regeneration of sensory axons from severed dorsal roots can be enhanced by the presence of nerve growth factor (NGF)-treated nitrocellulose strips implanted into an intraspinal lesion cavity. Rather than being directly apposed to the transplant, most regenerating axons are separated from the nitrocellulose by several layers of non-neuronal cells, suggesting that these cells may have a role in the promotion of axonal regrowth. The cellular layers associated with untreated nitrocellulose strips or NGF-treated implants were examined in this study to determine if there were differences in their arrangement or orientation along the implant which might explain some of the possible effects of substrate-bound NGF on axonal regrowth. Into a hemisection lesion cavity created in the adult rat lumbar spinal cord NGF-treated or untreated strips of nitrocellulose were placed vertically, with intact pieces of fetal spinal cord (FSC) tissue transplanted along each side. The distal ends of cut dorsal rootlets were apposed to the fetal tissue. Immunocytochemical and electron microscopic examination 30-60 days post-transplantation revealed a distinct layering of cell types along the NGF-treated strips. Closest to the nitrocellulose was a single layer of macrophages, followed by a separate layer of fibroblasts with dense collagen bundles, then a layer of astroglial cells, before reaching the neuropil of the fetal spinal cord tissue. A thickened basal lamina formed between the fibroblast and astrocytic cell layers and bundles of regenerated sensory axons extended along the interface between these two layers. In contrast, non-neuronal cells along untreated nitrocellulose strips were not as well organized, with an intermixing of fibroblasts and astroglial cells and only scattered macrophage-like cells. Axons rarely were found in conjunction with this mixed population of cells and, overall, fewer regenerated axons extended into transplants with untreated nitrocellulose. The results demonstrate consistent differences in the composition and organization of non-neuronal cells adjacent to NGF-treated nitrocellulose implants, compared to untreated implants. This suggests that the presence of bound NGF influences the recruitment of various cells from the surrounding transplant tissue as well as from the previously injured dorsal rootlets. The capacity for NGF to promote the regeneration of sensory axons may be an indirect effect that is mediated or potentiated by the non-neuronal cell population that gathers in response to the presence of bound NGF. PMID:1426123

Houle, J D

1992-11-01

325

Family Roots of Empathy-Related Characteristics: The Role of Perceived Maternal and Paternal Need Support in Adolescence  

ERIC Educational Resources Information Center

Theories on empathy development have stressed the role of socialization in general and the role of parental support in particular. This 3-wave longitudinal study of middle adolescents (N = 678) aimed to contribute to the extant research on the socialization of empathy (a) by examining the relative contribution of perceived maternal and paternal…

Miklikowska, Marta; Duriez, Bart; Soenens, Bart

2011-01-01

326

The fall and bounce of pencils and other elongated objects  

NASA Astrophysics Data System (ADS)

If an inclined pencil is released from rest with its bottom end resting on a table, the bottom end will slide forward or backward or it will remain at rest at the start of the fall, then slide backward for a short period before sliding forward. The magnitude and direction of the displacement of the bottom end of the pencil depends on the initial angle of inclination, the coefficient of friction, and on the length and mass distribution of the pencil. The same ground reaction forces play a similar role in the fall of trees and chimneys, the bounce of a football and any other elongated object, and in activities such as walking and running. When an elongated object is thrown obliquely to the ground, the object can bounce either forward or backward depending on the angle of inclination at impact. Spherical objects bounce away from the thrower. The difference arises because the horizontal friction force is determined not only by the normal reaction force, but also by the line of action of the normal reaction force relative to the center of mass.

Cross, Rod

2006-01-01

327

Chloroplast development in isolated roots of Convolvulus arvensis (L.)  

Microsoft Academic Search

The fine structure of chloroplast development is described for isolated roots of Convolvulus arvensis. Stages in the transition from the leucoplast, characteristic of dark-grown roots, to the chloroplast, found in light-grown roots, are defined and related to chlorophyll content of the root tissue. The interdependence of tissue type and organellogenesis has been investigated for three tissues in the primary root:

Jane Heltne; Howard T. Bonnett

1970-01-01

328

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

329

Growth and terpenoid indole alkaloid production in Catharanthus roseus hairy root clones in relation to left- and right-termini-linked Ri T-DNA gene integration  

Microsoft Academic Search

Hairy root cultures of Catharanthus roseus var. Prabal were established by infecting the leaves with Agrobacterium rhizogenes agropine-type A4 strain. Two hundred and fifty independent root clones were evaluated for growth, morphology, number of integration of Ri T-DNA genes and alkaloid contents. On the basis of growth pattern, type of branching and number of lateral roots we were able to separate

Jyoti Batra; Ajaswrata Dutta; Digvijay Singh; Sushil Kumar; Jayanti Sen

2004-01-01

330

"Roots": Medium and Message.  

ERIC Educational Resources Information Center

A national telephone survey indicated that audiences rated the television production of "Roots" positively in terms of the following: realistic portrayal of the people and the times; relevance for contemporary race relations; perceived emotional effect; and increased understanding of the psychology of black people. However, a comparison of the…

Kinnamon, Keneth

331

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

2013-07-29

332

Improved tolerance of Acacia nilotica to salt stress by Arbuscular mycorrhiza, Glomus fasciculatum may be partly related to elevated K/Na ratios in root and shoot tissues.  

PubMed

A pot experiment was conducted to examine the effect of arbuscular mycorrhizal fungus, Glomus fasciculatum, and salinity on the growth of Acacia nilotica. Plants were grown in soil under different salinity levels (1.2, 4.0, 6.5, and 9.5 dS m(-1)). In saline soil, mycorrhizal colonization was higher at 1.2, 4.0, and 6.5 dS m(-1) salinity levels in AM-inoculated plants, which decreased as salinity levels further increased (9.5 dS m(-1)). Mycorrhizal plants maintained greater root and shoot biomass at all salinity levels compared to nonmycorrhizal plants. AM-inoculated plants had higher P, Zn, and Cu concentrations than uninoculated plants. In mycorrhizal plants, nutrient concentrations decreased with the increasing levels of salinity, but were higher than those of the nonmycorrhizal plants. Mycorrhizal plants had greater Na concentration at low salinity levels (1.2, 4.0 dS m(-1)), which lowered as salinity levels increased (6.5, 9.5 dS m(-1)), whereas Na concentration increased in control plants. Mycorrhizal plants accumulated a higher concentration of K at all salinity levels. Unlike Na, the uptake of K increased in shoot tissues of mycorrhizal plants with the increasing levels of salinity. Our results indicate that mycorrhizal fungus alleviates deleterious effects of saline soils on plant growth that could be primarily related to improved P nutrition. The improved K/Na ratios in root and shoot tissues of mycorrhizal plants may help in protecting disruption of K-mediated enzymatic processes under salt stress conditions. PMID:17372663

Giri, Bhoopander; Kapoor, Rupam; Mukerji, K G

2007-03-20

333

Growth-inhibiting, bactericidal, and urease inhibitory effects of Paeonia lactiflora root constituents and related compounds on antibiotic-susceptible and -resistant strains of Helicobacter pylori.  

PubMed

An assessment was made of the growth-inhibiting, bactericidal, and urease inhibitory activities of paeonol (PA), benzoic acid (BA), methyl gallate (MG), and 1,2,3,4,6-penta-O-galloyl-?-d-glucopyranose (PGG) identified in Paeonia lactiflora root, structurally related compounds, and four antibiotics toward three reference strains and four clinical isolates of Helicobacter pylori using broth dilution bioassay and Western blot. BA and PA showed strong bactericidal effect at pH 4, while MG and PGG were effective at pH 7. These constituents exhibited strong growth-inhibiting and bactericidal activity toward the five strains resistant to amoxicillin (minimal inhibitory concentration (MIC) 12.5 mg/L), clarithromycin (64 mg/L), metronidazole (64 mg/L), or tetracycline (15 mg/L), indicating that these constituents and the antibiotics do not share a common mode of action. Structural characteristics, such as types of functional groups and carbon skeleton, and hydrophobicity appear to play a role in determining the anti- H. pylori activity. H. pylori urease inhibitory activity of PGG was comparable to that of acetohydroxamic acid, while MG was less potent at inhibiting urease than thiourea. The UreB band disappeared at 250 mg/L PGG on Western blot, while the UreA bands were faintly visible at 1000 mg/L PGG. These constituents showed no significant cytotoxicity. Global efforts to reduce the level of antibiotics justify further studies on P. lactiflora root-derived materials containing MG, PA, and PGG as potential antibacterial products or lead molecules for the prevention or eradication from humans from diseases caused by H. pylori . PMID:22891951

Ngan, Luong Thi My; Moon, Joon-Kwan; Shibamoto, Takayuki; Ahn, Young-Joon

2012-08-31

334

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

335

Composite Cucurbita pepo plants with transgenic roots as a tool to study root development  

PubMed Central

Background and Aims In most plant species, initiation of lateral root primordia occurs above the elongation zone. However, in cucurbits and some other species, lateral root primordia initiation and development takes place in the apical meristem of the parental root. Composite transgenic plants obtained by Agrobacterium rhizogenes-mediated transformation are known as a suitable model to study root development. The aim of the present study was to establish this transformation technique for squash. Methods The auxin-responsive promoter DR5 was cloned into the binary vectors pKGW-RR-MGW and pMDC162-GFP. Incorporation of 5-ethynyl-2?-deoxyuridine (EdU) was used to evaluate the presence of DNA-synthesizing cells in the hypocotyl of squash seedlings to find out whether they were suitable for infection. Two A. rhizogenes strains, R1000 and MSU440, were used. Roots containing the respective constructs were selected based on DsRED1 or green fluorescent protein (GFP) fluorescence, and DR5::Egfp-gusA or DR5::gusA insertion, respectively, was verified by PCR. Distribution of the response to auxin was visualized by GFP fluorescence or ?-glucuronidase (GUS) activity staining and confirmed by immunolocalization of GFP and GUS proteins, respectively. Key Results Based on the distribution of EdU-labelled cells, it was determined that 6-day-old squash seedlings were suited for inoculation by A. rhizogenes since their root pericycle and the adjacent layers contain enough proliferating cells. Agrobacterium rhizogenes R1000 proved to be the most virulent strain on squash seedlings. Squash roots containing the respective constructs did not exhibit the hairy root phenotype and were morphologically and structurally similar to wild-type roots. Conclusions The auxin response pattern in the root apex of squash resembled that in arabidopsis roots. Composite squash plants obtained by A. rhizogenes-mediated transformation are a good tool for the investigation of root apical meristem development and root branching.

Ilina, Elena L.; Logachov, Anton A.; Laplaze, Laurent; Demchenko, Nikolay P.; Pawlowski, Katharina; Demchenko, Kirill N.

2012-01-01

336

Elongation of 20-carbon polyunsaturated fatty acids by human skin fibroblasts  

SciTech Connect

Human skin fibroblasts readily incorporate exogenous arachidonate (20:4(n-6)) and eicosapentaenoate (20:5(n-3)) into cellular phospholipids and triacylglycerol. The extent of incorporation of 1.25 ..mu..M (/sup 14/C)20:4(n-6) and (/sup 14/C)20:5(n-3) from culture medium with delipidized serum protein is similar, 20% in 1 hr increasing to 60-70% within 8 hr. Elongation of incorporated (/sup 14/C)20:5(n-3) to (/sup 14/C)22:5(n-3) is extensive, 40% by 8 hr and 85% by 48 hr. Elongation of (/sup 14/C)20:4(n-6) to (/sup 14/C)22:4(n-6) is <1/2 that of (/sup 1/$C)20:5(n-3) and plateaus at approx.20% of incorporated /sup 14/C-fatty acid. Although incorporated, exogenous 22:4(n-6) is not an effective inhibitor of the elongation of (/sup 14/C)arachidonate; however, exogenous 20:5(n-3) is inhibitory, with an ID/sub 50/ of 5 ..mu..M. With exogenous concentrations of (/sup 14/C)arachidonate from 0.4 - 10 ..mu..M, the percentage incorporated in 24 hr remains relatively constant. By contrast, the extent of elongation of incorporated (/sup 14/C)arachidonate increases from 12% at 0.4 ..mu..M to 43% at 10 ..mu..M. Under these conditions, elongation of incorporated (/sup 14/C)20:5(n-3) is approx.75%. Thus, in these cells, selectivity of the elongation system results in differential metabolism of 20-carbon n-6 and n-3 fatty acids. Furthermore, arachidonate appears to act as a positive modulator of its own elongation.

Banerjee, N.; Rosenthal, M.D.

1986-05-01

337

Calculation of relative thermal elongation of structural steels  

Microsoft Academic Search

In the recent past, there have been a number of studies toward predicting the thermal and structural behavior of components\\u000a subjected to elevated temperature due to an exposure to fire. Numerical modeling has been applied quite extensively toward\\u000a this end. An accurate numerical model requires the use of appropriate thermophysical properties of the materials such as steels,\\u000a concretes etc. Recent

Dilip K. Banerjee; Ursula R. Kattner

2009-01-01

338

Decoupling the influence of leaf and root hydraulic conductances on stomatal conductance and its sensitivity to vapour pressure deficit as soil dries in a drained loblolly pine plantation.  

PubMed

The study examined the relationships between whole tree hydraulic conductance (K(tree)) and the conductance in roots (K(root)) and leaves (K(leaf)) in loblolly pine trees. In addition, the role of seasonal variations in K(root) and K(leaf) in mediating stomatal control of transpiration and its response to vapour pressure deficit (D) as soil-dried was studied. Compared to trunk and branches, roots and leaves had the highest loss of conductivity and contributed to more than 75% of the total tree hydraulic resistance. Drought altered the partitioning of the resistance between roots and leaves. As soil moisture dropped below 50%, relative extractable water (REW), K(root) declined faster than K(leaf). Although K(tree) depended on soil moisture, its dynamics was tempered by the elongation of current-year needles that significantly increased K(leaf) when REW was below 50%. After accounting for the effect of D on g(s), the seasonal decline in K(tree) caused a 35% decrease in g(s) and in its sensitivity to D, responses that were mainly driven by K(leaf) under high REW and by K(root) under low REW. We conclude that not only water stress but also leaf phenology affects the coordination between K(tree) and g(s) and the acclimation of trees to changing environmental conditions. PMID:19344336

Domec, Jean-Christophe; Noormets, Asko; King, John S; Sun, Ge; McNulty, Steven G; Gavazzi, Michael J; Boggs, Johnny L; Treasure, Emrys A

2009-04-02

339

Linking root morphology, longevity and function to root branch order: a case study in three shrubs  

Microsoft Academic Search

Root branching order supports a powerful approach to understanding complex root systems; however, how the pattern of root\\u000a morphological characteristics, tissue carbon (C) and nitrogen (N) concentrations, and root lifespan are related to anatomical\\u000a features of variable root orders for mature shrubs (?19 years old) in sandy habitats is still unclear. In this study, these\\u000a relationships were investigated for three typical

Gang Huang; Xue-yong Zhao; Ha-lin Zhao; Ying-xin Huang; Xiao-an Zuo

2010-01-01

340

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

341

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

342

Immobilization of Aluminum with Phosphorus in Roots Is Associated with High Aluminum Resistance in Buckwheat1  

PubMed Central

Oxalic acid secretion from roots is considered to be an important mechanism for aluminum (Al) resistance in buckwheat (Fygopyrum esculentum Moench). Nonetheless, only a single Al-resistant buckwheat cultivar was used to investigate the significance of oxalic acid in detoxifying Al. In this study, we investigated two buckwheat cultivars, Jiangxi (Al resistant) and Shanxi (Al sensitive), which showed significant variation in their resistance to Al stress. In the presence of 0 to 100 ?m Al, the inhibition of root elongation was greater in Shanxi than that in Jiangxi, and the Al content of root apices (0–10 mm) was much lower in Jiangxi. However, the dependence of oxalic acid secretion on external Al concentration and the time course for secretion were similar in both cultivars. Furthermore, the variation in Al-induced oxalic acid efflux along the root was similar, showing a 10-fold greater efflux from the apical 0- to 5-mm region than from the 5- to 10-mm region. These results suggest that both Shanxi and Jiangxi possess an equal capacity for Al-dependent oxalic acid secretion. Another two potential Al resistance mechanisms, i.e. Al-induced alkalinization of rhizosphere pH and root inorganic phosphate release, were also not involved in their differential Al resistance. However, after longer treatments in Al (10 d), the concentrations of phosphorus and Al in the roots of the Al-resistant cultivar Jiangxi were significantly higher than those in Shanxi. Furthermore, more Al was localized in the cell walls of the resistant cultivar. All these results suggest that while Al-dependent oxalic acid secretion might contribute to the overall high resistance to Al stress of buckwheat, this response cannot explain the variation in tolerance between these two cultivars. We present evidence suggesting the greater Al resistance in buckwheat is further related to the immobilization and detoxification of Al by phosphorus in the root tissues.

Zheng, Shao Jian; Yang, Jian Li; He, Yun Feng; Yu, Xue Hui; Zhang, Lei; You, Jiang Feng; Shen, Ren Fang; Matsumoto, Hideaki

2005-01-01

343

[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

344

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

Microsoft Academic Search

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

N. L. Bankhead; A. Simon

2009-01-01

345

Regeneration of Lasiurus sindicus in relation to grazing pressure and root-zone soil moisture in arid rangelands of western Rajasthan (India)  

Microsoft Academic Search

This study conducted in arid rangelands of Jaisalmer district in western Rajasthan, India, assessed the effect of root-zone soil moisture and grazing pressure on regenerative potential and fodder yields of Lasiurus sindicus (Sewan) grass. Uncontrolled grazing sig- nifi cantly reduced stand density of grass tussocks and their regeneration compared with sites subjected to controlled grazing or no grazing. The root-zone

R. S. MERTIA; R. PRASAD; B. K. KANDPAL

346

New population of odontoblasts responsible for tooth root formation.  

PubMed

Root formation is initiated with the extension of Hertwig's epithelial root sheath (HERS) after crown morphogenesis. To date, little is known about the molecular and cellular mechanisms controlling root formation. Recently we found rootless molars are formed in the dental mesenchyme-specific ?-catenin conditional knockout mice. The striking root phenotypes of these mutant mice result from the disrupted differentiation of differentiating odontoblasts, caused by ablation of ?-catenin during initiation of root formation. Here we show the cellular and molecular characteristics of differentiating odontoblasts using histochemistry and immunohistochemistry. These cells were not found in crown formation, but appeared only in the apical end of developing tooth, thus we have named these cells "apical odontoblasts" (AOds). AOds appeared immediately after HERS formation and were always present on the apical side of developing roots until root formation was complete. These findings indicate that AOds are closely associated with the transition from crown to root and with root elongation. In AOds, several transcription factors, including Nfic, Creb3l1, and Osx, as well as ?-catenin and alkaline phosphatase were expressed but Phex and Dspp were not expressed. Taken together, our results indicate that AOds are the principal cells responsible for tooth root formation. These findings may contribute to the further understanding of the mechanisms underlying tooth root formation and root regeneration. PMID:23603379

Bae, Cheol-Hyeon; Kim, Tak-Heun; Chu, Jung-Yob; Cho, Eui-Sic

2013-04-18

347

Root Formation in Ethylene-Insensitive Plants1  

PubMed Central

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

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

1999-01-01

348

Helical growth of stage-IVb sporangiophores of Phycomyces blakesleeanus: the relationship between rotation and elongation growth rates.  

PubMed

An understanding of the relationship between the two components of helical growth (rotation rate and elongation rate) is fundamental to understanding the biophysical and molecular mechanism(s) of cell wall extension in algal cells, fungal cells, and plant stems and roots. Helical growth occurs throughout development of the sporangiophores of Phycomyces blakesleeanus. Previous studies within the growth zone of stage-IVb sporangiophores have reported conflicting conclusions. An implicit assumption in the previous studies [E.S. Castle (1937) J Cell Comp Physiol 9:477-489; R. Cohen and M. Delbruck (1958) J Cell Comp Physiol 52:361-388; J.K.E. Ortega et al. (1974) Plant Physiol 53:485-490] was that the relationship between rotation rate and elongation rate was independent of the magnitude of the elongation rate. In the present study, for stage-IVb sporangiophores growing at a steady rate, it is shown that the ratio of rotation rate and elongation rate decreases as the elongation rate increases. Previously proposed biophysical and molecular mechanisms cannot account for the observed behavior. The previously postulated fibril-reorientation mechanism [J.K.E. Ortega and R.I. Gamow (1974) J Theor Biol 47:317-332; J.K.E. Ortega et al. (1974) Plant Physiol 53:485-490] is modified to accommodate this new finding. Other experiments were conducted to determine how the ratio of rotation rate and elongation rate behaves during a pressure response (a transient decrease in elongation rate produced by a large step-up in turgor pressure using the pressure probe). Results of these experiments indicate that this ratio increases during the pressure response. PMID:12569415

Ortega, Joseph E; Lesh-Laurie, Georgia E; Espinosa, Mark A; Ortega, Elena L; Manos, Steve M; Cunning, Melissa D; Olson, Jessica C

2002-11-22

349

Elongational behaviour of a low density polyethylene melt  

Microsoft Academic Search

Summary The steady-state elongational viscosityµs of melts of the low density polyethylene IUPAC A was investigated over six decades of strain rate. At low elongation rates the melt behaves as a linear viscoelastic liquid. TheTrouton relationµ0=3?0 is valid. The tensile compliance is one third of the shear compliance. With increasing strain rate the elongational viscosity goes through a pronounced maximum

H. M. Laun; H. Münstedt

1978-01-01

350

Efficient algorithm for computing orbital energies within elongation method  

NASA Astrophysics Data System (ADS)

We developed a new approach for solving eigenvalue problem for the oligomer chain systems based on localized molecular orbitals (LMO) of the separated fragments within elongation method. The method performed in this work and implemented in elongation scheme yields excellent agreement with the conventional results. It has been demonstrated that the proposed algorithm for computing orbital energies and eigenvectors in elongation method reduces the CPU time usage up to 50%.

Loboda, Oleksandr; Gu, Feng Long; Pomogaeva, Anna V.; Makowski, Marcin; Aoki, Yuriko

2012-12-01

351

Copper compounds influence in vitro rooting of birch microcuttings  

SciTech Connect

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

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

1994-01-01

352

Cytoplasmic free calcium distributions during the development of root hairs of Arabidopsis thaliana.  

PubMed

In this study, confocal ratio analysis was used to image the relationship between cytoplasmic free calcium concentration ([Ca2+]c) and the development of root hairs of Arabidopsis thaliana. Although a localized change in [Ca2+]c that preceded or predicted the site of root hair initiation could not be detected, once initiated the majority of emerging root hairs showed an elevated [Ca2+]c (> 1 microM) in their apical cytoplasm, compared with 100-200 nM in the rest of the cell. These emerging root hairs then moved into a 3-5 h phase of sustained elongation during which they showed variable growth rates. Root hairs that were rapidly elongating exhibited a highly localized, elevated [Ca2+]c at the tip. Non-growing root hairs did not exhibit the [Ca2+]c gradient. The rhd-2 mutant, which is defective in sustained root hair growth, showed an altered [Ca2+]c distribution compared with wild-type. These results implicate [Ca2+]c in regulating the tip growth process. Treatment of elongating wild-type root hairs with the Ca2+ channel blocker verapamil (50 microM) caused dissipation of the elevated [Ca2+]c at the tip and cessation of growth, suggesting a requirement for Ca2+ channel activity at the root hair tip to maintain growth. Manganese treatment also preferentially quenched Indo-1 fluorescence in the apical cytoplasm of the root hair. As manganese is thought to enter cells through Ca(2+)-permeable channels, this result also suggests increased Ca2+ channel activity at the tip of the growing hair. Taken together, these data suggest that although Ca2+ does not trigger the initiation of root hairs, Ca2+ influx at the tip of the root hair leads to an elevated [Ca2+]c that may be required to sustain root hair elongation. PMID:9301093

Wymer, C L; Bibikova, T N; Gilroy, S

1997-08-01

353

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

2008-03-21

354

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

PubMed

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

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

2013-08-08

355

Dynamic tracking of tendon elongation in ultrasound imaging  

NASA Astrophysics Data System (ADS)

The aim of this study was to evaluate the elongation of the Achilles tendon by looking at the changing position of Myo-Tendenious Junction (MTJ) using ultrasound during isometric contraction on an Isometric dynamometer. A sequence of ultrasound images in the form of movie, obtained from a unit operating at a frequency of 12MHz during isometric contraction, was analyzed offline using MATLAB to track the MTJ. This investigation has implemented important techniques for in vivo feature extraction of Achilles tendon. Prior to feature extraction, the images were filtered by anisotropic diffusion method and morphological enhancements. The cross correlation search algorithm with an adaptive mask was utilized to track MTJ by comparing adjacent segmented frames. The present method was studied on seventeen subjects, where it was able to measure the related movement accurately.

Karimpoor, Mahta; Screen, Hazel; Morrissey, Dylan

2010-03-01

356

Inhibition of primary roots and stimulation of lateral root development in Arabidopsis thaliana by the rhizobacterium Serratia marcescens 90–166 is through both auxin-dependent and -independent signaling pathways  

Microsoft Academic Search

The rhizobacterium Serratia marcescens strain 90–166 was previously reported to promote plant growth and induce resistance in Arabidopsis thaliana. In this study, the influence of strain 90-166 on root development was studied in vitro. We observed inhibition of primary root elongation, enhanced lateral root emergence, and early emergence of second order\\u000a lateral roots after inoculation with strain 90–166 at a

Chun-Lin Shi; Hyo-Bee Park; Jong Suk Lee; Sangryeol Ryu; Choong-Min Ryu

2010-01-01

357

The crystal structure of elongation factor G complexed with GDP, at 2.7 A resolution.  

PubMed Central

Elongation factor G (EF-G) catalyzes the translocation step of protein synthesis in bacteria, and like the other bacterial elongation factor, EF-Tu--whose structure is already known--it is a member of the GTPase superfamily. We have determined the crystal structure of EF-G--GDP from Thermus thermophilus. It is an elongated molecule whose large, N-terminal domain resembles the G domain of EF-Tu, except for a 90 residue insert, which covers a surface that is involved in nucleotide exchange in EF-Tu and other G proteins. The tertiary structures of the second domains of EF-G and EF-Tu are nearly identical, but the relative placement of the first two domains in EF-G--GDP resembles that seen in EF-Tu--GTP, not EF-Tu--GDP. The remaining three domains of EF-G look like RNA binding domains, and have no counterparts in EF-Tu. Images

Czworkowski, J; Wang, J; Steitz, T A; Moore, P B

1994-01-01

358

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

PubMed

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

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

2013-01-23

359

A New Anatomically Based Nomenclature for the Roots and Root Canals--Part 1: Maxillary Molars  

PubMed Central

Numerous terminologies have been employed in the dental literature to describe the roots and root canal systems of maxillary molars. This multiplicity in naming of roots and canals makes the reader susceptible to misinterpretation and confusion. No consensus thus far has been arrived at for defining the names of roots and root canals in maxillary molars, including their various morphological aberrations. The anatomical relation of roots and their root canals were identified and were subsequently named based on definite sets of criteria. A new method for identification and naming of roots and root canal anatomy in maxillary molars, based on their root and canal relationship, was formulated and is presented in this paper. The nomenclature makes certain essential modifications to the traditional approach to accommodate naming of the various aberrations presented in the maxillary molars. A simple, yet extensive, nomenclature system has been proposed that appropriately names the internal and external morphology of maxillary molars.

Kottoor, Jojo; Albuquerque, Denzil Valerian; Velmurugan, Natanasabapathy

2012-01-01

360

Power and Roots by Recursion.  

ERIC Educational Resources Information Center

|This article illustrates how questions from elementary finance can serve as motivation for studying high order powers, roots, and exponential functions using Logo procedures. A second discussion addresses a relatively unknown algorithm for the trigonometric exponential and hyperbolic functions. (PK)|

Aieta, Joseph F.

1987-01-01

361

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

PubMed

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. PMID:24167506

Danjon, Frédéric; Caplan, Joshua S; Fortin, Mathieu; Meredieu, Céline

2013-10-23

362

SPATIAL VARIATION OF THE DEPTH OF THE ROOT-RESTRICTING LAYER IN AN UPLAND SOIL OF NORTHERN MISSISSIPPI  

Microsoft Academic Search

The root-restricting layers present in most Southeastern soils prevent adequate root growth into the soil profile. Reduced root elongation contributes to temporal drought stress which annually limits yield potential in this region. Many farmers combat this layer of soil by annually subsoiling, usually to a depth of 25-40 cm. However, the depth of this root-restricting layer varies greatly from field

S. M. Dabney

363

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

EPA Science Inventory

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

364

Bottoms Up! The Influence of Elongation on Pouring and Consumption Volume  

Microsoft Academic Search

Although the effects of shapes on area perceptions have been widely investigated, we replicate, extend, and generalize one of the few studies to relate the effects of shapes to consumption volumes (Raghubir and Krishna 1999). While Raghubir and Krishna demonstrate the effect of the elongation of prepoured drinks on consumption volume, we have people pour their own drinks in a

Brian Wansink; Koert van Ittersum

2003-01-01

365

Germination and elongation of flax in microgravity  

NASA Astrophysics Data System (ADS)

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

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

366

Relative biological effectiveness of fission neutrons for producing micronuclei in the root-tip cells of onion seedlings after irradiation as dry seeds.  

PubMed

The relative biological effectiveness (RBE) of mixed neutron and gamma-ray radiation emitted at a 252Cf source at the Research Institute for Radiation Biology and Medicine, Hiroshima University, compared with 60Co gamma-ray radiation was determined. The tissue-absorbed dose contribution of the accompanying gamma radiation was about 35.7% to the total tissue-absorbed dose from the 252Cf mixed radiation. The 252Cf mixed radiation and 60Co gamma rays produced approximate linear changes in the frequency of micronuclei induced in root-tip cells of Allium cepa L. onion seedlings after irradiation as dry dormant seeds with varying absorbed doses in onion seeds. Therefore, the RBE for radiation-induced micronuclei was calculated as the ratio of the slopes for the 252Cf mixed radiation and the 60Co gamma rays. The deduced RBE value of 252Cf mixed radiation to 60Co gamma rays to induce micronuclei in dry dormant onion seed cells was about 90.5 +/- 3.6 (+/- 1sigma); the RBE of neutrons from the 252Cf mixed radiation was about 150 +/- 6 (+/- 1sigma). Furthermore, the sensitivity ratio of the induction rate of micronuclei in dry dormant seeds to that in seedlings by neutrons from 252Cf mixed radiation was significantly different from that by 60Co gamma rays. From these results, we concluded that the repair efficiency of DNA damage induced by neutrons may be different from that by gamma rays. PMID:12674204

Zhang, Wenyi; Endo, Satoru; Ishikawa, Masayori; Ikeda, Hideo; Hoshi, Masaharu

2002-12-01

367

Effect of Agar, MS Medium Strength, Sucrose and Polyamines on in vitro Rooting of Syzygium Alternifolium  

Microsoft Academic Search

This paper describes the effect of agar, MS basal medium strength, sucrose and polyamines on the in vitro rooting of Syzygium\\u000a alternifolium realized by a two step procedure involving root initiation (RI) and root elongation (RE). RI was carried out\\u000a on solidified MS medium supplemented with 1.0 mg dm?3 indole-3-butyric acid (IBA) for 3 weeks, and RE following transfer to

P. S. Sha Valli Khan; J. F. Hausman; K. R. Rao

1999-01-01

368

The contractility of elongated microvilli in early sea urchin embryos  

Microsoft Academic Search

Summary Elongated microvilli attach the early sea urchin embryo to the fertilization envelope and support it in a concentric position within the perivitelline space. The contractility of the elongated microvilli was demonstrated in several ways. (1) During normal cleavage, these microvilli change their length to adapt to the change in shape and numbers of blastomeres. (2) When treated with calcium-free

Evelyn Spiegel; Louisa Howard; Melvin Spiegel

1990-01-01

369

A study of the performance of elongated scintillation detectors  

Microsoft Academic Search

The performance of scintillation detectors of varied length and design was investigated in order to work out an optimum variant, of elongated shape, in the development of a total-absorption scintillation spectrometer. The degree of nonuniformity of the detector is isolated and defined as the most important characteristic. Excellent uniformity in light collection was attained in large-area scintillation detectors of elongated

V. G. Abulova; V. M. Mialkovskii; A. D. Nurkhodzhaev; T. S. Iuldashbaev

1976-01-01

370

The Initiation and Elongation of Rhizoid Clusters in Caulerpa Prolifera.  

National Technical Information Service (NTIS)

Under improved environmental conditions the average rate of elongation of the rhizoid cluster was 5.2 mm/day in the first 3 days. The rate decreases thereafter and is close to zero around 5-6 days after initiation. The elongation, like that of the rhizome...

J. C. W. Chen W. P. Jacobs

1968-01-01

371

Induction of Coleoptile Elongation by Carbon Dioxide 1  

PubMed Central

The ability of CO2 to induce elongation of Avena sativa coleoptile segments was examined with the use of a high resolution growth-recording device. CO2-saturated water causes an 8- to 16-fold promotion in the rate of elongation within 1 minute. This elongation is insensitive to a variety of metabolic inhibitors that suppress auxin-induced elongation, and the CO2 effect cannot be prevented by pretreatment with these inhibitors. Buffers of pH 3 to 4 also stimulate elongation quickly, and it seems that at least a major part of the action of CO2 depends upon its ability to reduce pH. The rate of elongation of auxin-promoted segments can be further enhanced by treatment with CO2 but not vice versa. The response to CO2 can be inhibited by mannitol at osmotic concentrations that inhibit normal growth, by calcium, and by brief pretreatment with heavy water (D2O). The elongation rate that results from CO2 treatment is sensitive to temperature, but the induction by CO2 itself appears to be almost temperature-independent. Elongation following treatment with CO2 may be a physical flow phenomenon, essentially independent of immediate biochemical participation, which occurs when wall polymer interactions that normally restrict strain in the cell wall are weakened or broken by CO2 in a manner that in effect substitutes for the role of metabolism in normal auxin-inducible cell enlargement.

Evans, Michael L.; Ray, Peter M.; Reinhold, Leonora

1971-01-01

372

TRANSORAL SURGICAL RESECTION OF BILATERAL STYLOID PROCESSES ELONGATION (EAGLE'S SYNDROME)  

PubMed Central

Eagle’s syndrome represents a symptomatic styloid process elongation or calcification of stylohyoid or stylomandibular ligament. The symptoms include the throat pain radiating to ipsilateral ear or foreign body sensation in the pharynx causing odynophagia and dysphagia. It is commonly unilateral and bilateral cases are rare. We report a case of bilateral elongation of styloid processes treated surgically by transoral approach.

Baharudin, Abdullah; Rohaida, Ibrahim; Khairudin, Abdullah

2012-01-01

373

Resin Elongation Phenomenon of Polystyrene Nanopillars in Nanoimprint Lithography  

Microsoft Academic Search

We investigated the elongation of polystyrene nanopillars formed by thermal nanoimprint lithography. Silicone and perfluoropolyether were used as mold release agents to obtain molds with different adhesion forces against polystyrene to be imprinted. The adhesion force between the resin and release layers was evaluated as a force curve by atomic force microscope with a polystyrene colloid probe. Elongation depended on

Kosuke Kuwabara; Akihiro Miyauchi; Hiroyuki Sugimura

2010-01-01

374

Calorimetric studies of the elongation of Avena coleoptile segments.  

PubMed

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

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

1976-06-01

375

moonshine illuminates a developmental role for regulated transcription elongation  

PubMed Central

Mutations in the zebrafish gene moonshine, encoding the ortholog of tif1?, cause profound anemia and embryonic lethality. In a recent issue of Cell, Bai et al. (2010) provide evidence that these defects arise from inefficient transcription elongation, implicating elongation as an important point of regulation during cell differentiation and development.

Gilchrist, Daniel A.; Adelman, Karen

2010-01-01

376

Moonshine illuminates a developmental role for regulated transcription elongation.  

PubMed

Mutations in the zebrafish gene moonshine, encoding the ortholog of TIF1 gamma, cause profound anemia and embryonic lethality. In a recent issue of Cell, Bai et al. provide evidence that these defects arise from inefficient transcription elongation, implicating elongation as an important point of regulation during cell differentiation and development. PMID:20643345

Gilchrist, Daniel A; Adelman, Karen

2010-07-20

377

Ethylene can Stimulate Arabidopsis Hypocotyl Elongation in the Light  

Microsoft Academic Search

Ethylene inhibits hypocotyl elongation in etiolated Arabidopsis seedlings. However, when Arabidopsis was grown in the light in the presence of ethylene or its precursor 1-aminocyclopropane-1-carboxylic acid (ACC), a marked induction of hypocotyl elongation occurred. This resulted from an increase in cell expansion rather than cell division. The effects of ethylene and ACC were antagonized by the ethylene action inhibitor Ag+.

Jan Smalle; Mira Haegman; Jasmina Kurepa; Marc van Montagu; Dominique van der Straeten

1997-01-01

378

Plant iodine-131 uptake in relation to root concentration as measured in minirhizotron by video camera:. Status report for FY 1989.  

National Technical Information Service (NTIS)

Glass viewing tubes (minirhizotrons) were placed in the soil beneath native perennial bunchgrass (Agropyron spicatum). The tubes provided access for observing and quantifying plant roots with a miniature video camera and soil moisture estimates by neutron...

K. J. Moss

1990-01-01

379

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

SciTech Connect

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

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

1988-05-01

380

Regulon-Specific Control of Transcription Elongation across the Yeast Genome  

PubMed Central

Transcription elongation by RNA polymerase II was often considered an invariant non-regulated process. However, genome-wide studies have shown that transcriptional pausing during elongation is a frequent phenomenon in tightly-regulated metazoan genes. Using a combination of ChIP-on-chip and genomic run-on approaches, we found that the proportion of transcriptionally active RNA polymerase II (active versus total) present throughout the yeast genome is characteristic of some functional gene classes, like those related to ribosomes and mitochondria. This proportion also responds to regulatory stimuli mediated by protein kinase A and, in relation to cytosolic ribosomal-protein genes, it is mediated by the silencing domain of Rap1. We found that this inactive form of RNA polymerase II, which accumulates along the full length of ribosomal protein genes, is phosphorylated in the Ser5 residue of the CTD, but is hypophosphorylated in Ser2. Using the same experimental approach, we show that the in vivo–depletion of FACT, a chromatin-related elongation factor, also produces a regulon-specific effect on the expression of the yeast genome. This work demonstrates that the regulation of transcription elongation is a widespread, gene class–dependent phenomenon that also affects housekeeping genes.

Pelechano, Vicent; Jimeno-Gonzalez, Silvia; Rodriguez-Gil, Alfonso; Garcia-Martinez, Jose; Perez-Ortin, Jose E.; Chavez, Sebastian

2009-01-01

381

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

PubMed

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

Gowlett, J A J

2013-10-07

382

Proteomic changes in different growth periods of ginseng roots.  

PubMed

For the first time, proteomics and biochemical variables have been employed to unravel the growth strategies for the different root growth periods of ginseng (Panax ginseng CA May., Araliaceae). Enzymatic activities and cellular contents, except for starch, related to defence and metabolism were significantly increased in the slow-growth period but decreased in the fast-growth period. Proteomic characterisation by two-dimensional gel electrophoresis (2DE) showed 83 differentially expressed spots; 62 spots were up-regulated and 21 spots were down-regulated in the slow-growth period when compared to the fast-growth period. The identification of these spots indicated that the major groups of differential proteins were associated with energy metabolism (37%) and defence (17%), which was consistent with the changes observed in the biochemical measurements. These results clearly demonstrate that ginseng stores energy during its fast-growth period to promote root elongation, whereas it expends energy to improve the synthesis of secondary metabolites and stress resistance during its slow-growth period. The levels of many proteins were changed during the conversion period from fast to slow growth, providing new insights into ginseng proteome evolution. The proposed hypothetical model explains the interaction of metabolic proteins associated with the growth strategies of ginseng. PMID:23537955

Ma, Rui; Sun, Liwei; Chen, Xuenan; Jiang, Rui; Sun, Hang; Zhao, Daqing

2013-03-13

383

Calcium dependence of rapid auxin action in maize roots.  

PubMed

We investigated the interaction of Ca2+ and auxin on root elongation in seedlings of Zea mays L. The seedlings were raised either in the presence of Ca2+ (high calcium; HC = imbibed and raised in 10 millimolar CaCl2), in the absence of additional Ca2+ (intermediate calcium; IC = imbibed and raised in distilled H2O, calcium supply from seed only), or without additional Ca2+ and subsequently depleting them of Ca2+ (low calcium; LC = imbibed and raised in distilled H2O and subsequently treated with 1 millimolar ethyleneglycol-bis-[beta-aminoethylether]-N,N,N',N'-tetraacetic acid [EGTA]). Exposure of roots of either HC or IC seedlings to auxin concentrations from 0.1 to 10 micromolar resulted in strong inhibition of elongation. In roots of LC seedlings, on the other hand, auxin concentrations as high as 10 micromolar caused only slight inhibition of elongation. Adding 0.5 millimolar Ca2+ to LC roots in the presence of IAA allowed normal expression of the inhibitory action of the hormone. Inhibition of elongation in IC roots by indoleacetic acid was reversible upon treatment of the roots with 1 millimolar EGTA. The inhibitory action of auxin could then be re-established by supplying 0.5 millimolar Ca2+. The data indicate that Ca2+ may be necessary to the growth-regulating action of auxin. The significance of this finding is discussed with respect to the potential role of Ca2+ as a second messenger of auxin action and the relevance of this model to recent evidence for gravi-induced redistribution of Ca2+ and its role in establishing gravitropic curvature. PMID:11538659

Hasenstein, K H; Evans, M L

1986-01-01

384

The identification of a domain in Escherichia coli elongation factor Tu that interacts with elongation factor Ts.  

PubMed

A method has been developed to search for the elongation factor Tu (EF-Tu) domain(s) that interact with elongation factor Ts (EF-Ts). This method is based on the suppression of Escherichia coli EF-Tu-dominant negative mutation K136E, a mutation that exerts its effect by sequestering EF-Ts. We have identified nine single-amino acid- substituted suppression mutations in the region 146-199 of EF-Tu. These mutations are R154C, P168L, A174V, K176E, D181G, E190K, D196G, S197F, and I199V. All suppression mutations but one (R154C) significantly affect EF-Tu's ability to interact with EF-Ts under equilibrium conditions. Moreover, with the exception of mutation A174V, the GDP affinity of EF-Tu appears to be relatively unaffected by these mutations. These results suggest that the domain of residues 154 to 199 on EF-Tu is involved in interacting with EF-Ts. These suppression mutations are also capable of suppressing dominant negative mutants N135D and N135I to various degrees. This suggests that dominant negative mutants N135D and N135I are likely to have the same molecular basis as the K136E mutation. The method we have developed in this study is versatile and can be readily adapted to map other regions of EF-Tu. A model of EF-Ts-catalyzed guanine-nucleotide exchange is discussed. PMID:1429571

Hwang, Y W; Carter, M; Miller, D L

1992-11-01

385

Elongator Protein 3b Negatively Regulates Ribosomal DNA Transcription in African Trypanosomes ? †  

PubMed Central

Eukaryotic cells limit ribosomal DNA (rDNA) transcription by RNA polymerase I (RNAP-I) to maintain genome integrity. African trypanosomes present an excellent model for studies on RNAP-I regulation because they possess a bifunctional RNAP-I and because RNAP-II transcription appears unregulated. Since Elp3, the catalytic component of Elongator, controls RNAP-II transcription in yeast and human cells, we predicted a role for a trypanosome Elp3-related protein, ELP3a or ELP3b, in RNAP-I regulation. elp3b null and conditional strains specifically exhibited resistance to a transcription elongation inhibitor, suggesting that ELP3b negatively impacts elongation. Nascent RNA analysis and expression of integrated reporter cassettes supported this interpretation and revealed negative control of rDNA transcription. ELP3b specifically localized to the nucleolus, and ELP3b loss rendered cells hypersensitive to DNA damage and to translation inhibition, suggesting that anti-Elongator function was important to maintain genome integrity rather than to modulate ribosome production. Finally, ELP3b displayed discrimination between RNAP-I compartments in the same cell. Our results establish ELP3b as a major negative regulator of rDNA transcription and extend the roles of the Elp3-related proteins to RNAP-I transcription units. ELP3b is also the first trypanosome protein shown to distinguish between rDNA and variant surface glycoprotein transcription within different RNAP-I compartments.

Alsford, Sam; Horn, David

2011-01-01

386

Histone chaperones Nap1 and Vps75 regulate histone acetylation during transcription elongation.  

PubMed

Histone chaperones function in chromatin assembly and disassembly, suggesting they have important regulatory roles in transcription elongation. The Saccharomyces cerevisiae proteins Nap1 and Vps75 are structurally related, evolutionarily conserved histone chaperones. We showed that Nap1 genetically interacts with several transcription elongation factors and that both Nap1 and Vps75 interact with the RNA polymerase II kinase, CTK1. Loss of NAP1 or VPS75 suppressed cryptic transcription within the open reading frame (ORF) observed when strains are deleted for the kinase CTK1. Loss of the histone acetyltransferase Rtt109 also suppressed ctk1-dependent cryptic transcription. Vps75 regulates Rtt109 function, suggesting that they function together in this process. Histone H3 K9 was found to be the important lysine that is acetylated by Rtt109 during ctk1-dependent cryptic transcription. We showed that both Vps75 and Nap1 regulate the relative level of H3 K9 acetylation in the STE11 ORF. This supports a model in which Nap1, like Vps75, directly regulates Rtt109 activity or regulates the assembly of acetylated chromatin. Although Nap1 and Vps75 share many similarities, due to their distinct interactions with SET2, Nap1 and Vps75 may also play separate roles during transcription elongation. This work sheds further light on the importance of histone chaperones as general regulators of transcription elongation. PMID:23401858

Xue, Yu-Ming; Kowalska, Anna K; Grabowska, Kamila; Przybyt, Katarzyna; Cichewicz, Magda A; Del Rosario, Brian C; Pemberton, Lucy F

2013-02-11

387

Histone Chaperones Nap1 and Vps75 Regulate Histone Acetylation during Transcription Elongation  

PubMed Central

Histone chaperones function in chromatin assembly and disassembly, suggesting they have important regulatory roles in transcription elongation. The Saccharomyces cerevisiae proteins Nap1 and Vps75 are structurally related, evolutionarily conserved histone chaperones. We showed that Nap1 genetically interacts with several transcription elongation factors and that both Nap1 and Vps75 interact with the RNA polymerase II kinase, CTK1. Loss of NAP1 or VPS75 suppressed cryptic transcription within the open reading frame (ORF) observed when strains are deleted for the kinase CTK1. Loss of the histone acetyltransferase Rtt109 also suppressed ctk1-dependent cryptic transcription. Vps75 regulates Rtt109 function, suggesting that they function together in this process. Histone H3 K9 was found to be the important lysine that is acetylated by Rtt109 during ctk1-dependent cryptic transcription. We showed that both Vps75 and Nap1 regulate the relative level of H3 K9 acetylation in the STE11 ORF. This supports a model in which Nap1, like Vps75, directly regulates Rtt109 activity or regulates the assembly of acetylated chromatin. Although Nap1 and Vps75 share many similarities, due to their distinct interactions with SET2, Nap1 and Vps75 may also play separate roles during transcription elongation. This work sheds further light on the importance of histone chaperones as general regulators of transcription elongation.

Xue, Yu-Ming; Kowalska, Anna K.; Grabowska, Kamila; Przybyt, Katarzyna; Cichewicz, Magda A.; Del Rosario, Brian C.

2013-01-01

388

FINE ROOT (< 0.5 MM DIAMETER) ADAPTATION TO NUTRIENT STRESS  

Technology Transfer Automated Retrieval System (TEKTRAN)

Few attempts at in-situ assessment of root function exist, but many studies have attempted to relate observable and measurable root morphologies and anatomies to root function. One of the most successful has been Specific Root Length (SRL - meters of root per gram of root biomass). SRL requires a ...

389

Root canal medicaments.  

PubMed

The ultimate goals of endodontic treatment are complete removal of bacteria, their byproducts and pulpal remnants from infected root canals and the complete seal of disinfected root canals. Intracanal medicaments have been thought an essential step in killing the bacteria in root canals; however, in modern endodontics, shaping and cleaning may be assuming greater importance than intracanal medicaments as a means of disinfecting root canals. Until recently, formocresol and its relatives were frequently used as intracanal medicaments, but it was pointed out that such bactericidal chemicals dressed in the canal distributed to the whole body from the root apex and so might induce various harmful effects including allergies. Furthermore, as these medicaments are potent carcinogenic agents, there is no indication for these chemicals in modern endodontic treatment. Today, biocompatibility and stability are essential properties for intracanal medicaments. The more modern meaning of intracanal dressing is for a blockade against coronal leakage from the gap between filling materials and cavity wall. Calcium hydroxide has been determined as suitable for use as an intracanal medicament as it is stable for long periods, harmless to the body, and bactericidal in a limited area. It also induces hard tissue formation and is effective for stopping inflammatory exudates. Single-visit endodontics, where intracanal medicaments are not used, is generally not now contraindicated and various reports have shown that the clinical outcomes between single- and multiple- visit endodontics are similar. There is no reason to counsel against single-visit endodontics: however, if multiple-visit endodontics is chosen, calcium hydroxide is recommended to be used as an intracanal medicament. PMID:19323305

Kawashima, Nobuyuki; Wadachi, Reiko; Suda, Hideaki; Yeng, Thai; Parashos, Peter

2009-02-01

390

Protease-activated receptor 4 activation increases the expression of calcitonin gene-related peptide mRNA and protein in dorsal root ganglion neurons.  

PubMed

Accumulating evidence demonstrates that nociceptor activation evokes a rapid change in mRNA and protein levels of calcitonin gene-related peptide (CGRP) in dorsal root ganglion (DRG) neurons. Although the colocalization of CGRP and protease-activated receptor-4 (PAR4), a potent modulator of pain processing and inflammation, was detected in DRG neurons, the role of PAR4 activation in the expression of CGRP has not been investigated. In the present study, the expression of CGRP and activation (phosphorylation) of extracellular signal-regulated kinases 1 and 2 (ERK1/2) in rat DRG neurons were measured by immunofluorescence, real-time PCR, and Western blotting after AYPGKF-NH2 (selective PAR4-activating peptide; PAR4-AP) intraplantar injection or treatment of cultured DRG neurons. The expression of CGRP in cultured DRG neurons was also assessed after treatment with AYPGKF-NH2 with preaddition of PD98059 (an inhibitor for ERK1/2 pathway). Results showed that PAR4-AP intraplantar injection or treatment of cultured DRG neurons evoked significant increases in DRG cells displaying CGRP immunoreactivity and cytoplasmic and nuclear staining for phospho-ERK1/2 (p-ERK1/2). Percentages of total DRG neurons expressing both CGRP and PAR4 or p-ERK1/2 also increased significantly at 2 hr after PAR4-AP treatment. Real-time PCR and Western blotting showed that PAR4-AP treatment significantly increased expression of CGRP mRNA and protein levels in DRG neurons. The PAR4 activation-evoked CGRP expression both at mRNA and at protein levels was significantly inhibited after p-ERK1/2 was inhibited by PD98059. These results provide evidence that activation of PAR4 upregulates the expression of CGRP mRNA and protein levels in DRG neurons via the p-ERK1/2 signal pathway. © 2013 Wiley Periodicals, Inc. PMID:24105611

Wang, Zhaojin; Chen, Dan; Zhang, Zaifeng; Zhang, Rui; An, Shuhong; Yu, Lianfeng

2013-09-16

391

Succinoglycan Is Required for Initiation and Elongation of Infection Threads during Nodulation of Alfalfa by Rhizobium meliloti  

PubMed Central

Rhizobium meliloti Rm1021 must be able to synthesize succinoglycan in order to invade successfully the nodules which it elicits on alfalfa and to establish an effective nitrogen-fixing symbiosis. Using R. meliloti cells that express green fluorescent protein (GFP), we have examined the nature of the symbiotic deficiency of exo mutants that are defective or altered in succinoglycan production. Our observations indicate that an exoY mutant, which does not produce succinoglycan, is symbiotically defective because it cannot initiate the formation of infection threads. An exoZ mutant, which produces succinoglycan without the acetyl modification, forms nitrogen-fixing nodules on plants, but it exhibits a reduced efficiency in the initiation and elongation of infection threads. An exoH mutant, which produces symbiotically nonfunctional high-molecular-weight succinoglycan that lacks the succinyl modification, cannot form extended infection threads. Infection threads initiate at a reduced rate and then abort before they reach the base of the root hairs. Overproduction of succinoglycan by the exoS96::Tn5 mutant does not reduce the efficiency of infection thread initiation and elongation, but it does significantly reduce the ability of this mutant to colonize the curled root hairs, which is the first step of the invasion process. The exoR95::Tn5 mutant, which overproduces succinoglycan to an even greater extent than the exoS96::Tn5 mutant, has completely lost its ability to colonize the curled root hairs. These new observations lead us to propose that succinoglycan is required for both the initiation and elongation of infection threads during nodule invasion and that excess production of succinoglycan interferes with the ability of the rhizobia to colonize curled root hairs.

Cheng, Hai-Ping; Walker, Graham C.

1998-01-01

392

Unraveling root developmental programs initiated by beneficial Pseudomonas spp. bacteria.  

PubMed

Plant roots are colonized by an immense number of microbes, referred to as the root microbiome. Selected strains of beneficial soil-borne bacteria can protect against abiotic stress and prime the plant immune system against a broad range of pathogens. Pseudomonas spp. rhizobacteria represent one of the most abundant genera of the root microbiome. Here, by employing a germ-free experimental system, we demonstrate the ability of selected Pseudomonas spp. strains to promote plant growth and drive developmental plasticity in the roots of Arabidopsis (Arabidopsis thaliana) by inhibiting primary root elongation and promoting lateral root and root hair formation. By studying cell type-specific developmental markers and employing genetic and pharmacological approaches, we demonstrate the crucial role of auxin signaling and transport in rhizobacteria-stimulated changes in the root system architecture of Arabidopsis. We further show that Pseudomonas spp.-elicited alterations in root morphology and rhizobacteria-mediated systemic immunity are mediated by distinct signaling pathways. This study sheds new light on the ability of soil-borne beneficial bacteria to interfere with postembryonic root developmental programs. PMID:23542149

Zamioudis, Christos; Mastranesti, Parthena; Dhonukshe, Pankaj; Blilou, Ikram; Pieterse, Corné M J

2013-03-29

393

Effect of pectin methylesterase gene expression on pea root development.  

PubMed Central

Expression of an inducible gene with sequences common to genes encoding pectin methylesterase (PME) was found to be tightly correlated, both spatially and temporally, with border cell separation in pea root caps. Partial inhibition of the gene's expression by antisense mRNA in transgenic pea hairy roots prevented the normal separation of root border cells from the root tip into the external environment. This phenotype was correlated with an increase in extracellular pH, reduced root elongation, and altered cellular morphology. The translation product of the gene exhibited PME activity in vitro. These results are consistent with the long-standing hypothesis that the demethylation of pectin by PME plays a key role in cell wall metabolism.

Wen, F; Zhu, Y; Hawes, M C

1999-01-01

394

Lettuce seed germination and root elongation toxicity evaluation of the F-Area seepline soils.  

National Technical Information Service (NTIS)

This study is a continuation of similar studies conducted by Easton and Murphy (1993) and Loehle (1990). The objectives of these studies are to: (1) assess the toxicity of the water-soluble constituents of soil in a seepline adjacent to the F-Area Seepage...

E. A. Nelson H. M. Westbury

1994-01-01

395

INTERLABORATORY ROOT ELONGATION TESTING OF TOXIC SUBSTANCES ON SELECTED PLANT SPECIES  

EPA Science Inventory

Four contract laboratories and three EPA laboratories participated in the inter-laboratory testing of 10 toxic substances on a representative plant species from five families. Seeds were germinated on filter paper saturated in a solution of the toxic substance and incubated for 1...

396

Nerve and Nerve Root Biomechanics  

Microsoft Academic Search

\\u000a Together, the relationship between the mechanical response of neural tissues and the related mechanisms of injury provide\\u000a a foundation for defining relevant thresholds for injury. The nerves and nerve roots are biologic structures with specific\\u000a and important functions, and whose response to mechanical loading can have immediate, long-lasting and widespread consequences.\\u000a In particular, when nerves or nerve roots are mechanically

Kristen J. Nicholson; Beth A. Winkelstein

397

[Study of elongation complexes for T7 RNA polymerase].  

PubMed

Complexes of bacteriophage T7 RNA polymerase with a DNA template for transcription elongation were visualized by atomic force microscopy. Images for complexes of T7 RNA polymerase with terminal fragments of DNA template were obtained for single molecules. Complexes of a single DNA template molecule with several T7 RNA polymerase molecules corresponding to stages of initiation, elongation and termination of transcription were visualized under the elimination of unspecific DNA-protein binding. Immobilized on the amino mica RNA transcripts form rod-like condensed structures. Detailes of specific and unspecific complex formation for the T7 RNA polymerase-DNA system during initiation and transcription elongation are discussed. PMID:23035523

Limanskaia, O Iu; Limanski?, A P

398

Mapping the messenger RNA within the elongating ribosome  

NASA Astrophysics Data System (ADS)

The method of proton-spin contrast-variation was applied for determining the position of the messenger RNA within the elongating ribosome. Using an artificial mRNA fragment the mass center of the mRNA sequence covered by the ribosome could be localized for the pre- and the post-translocational elongation states. The mass center moves about 12 +/- 5 Å upon translocation. The radius of gyration was 12 +/- 3 Å. The data give an independent contribution for refining a structural model including the RNA ligands of the elongating ribosome.

Jünemann, R.; Wadzack, J.; Burkhardt, N.; Schmitt, M.; Zhao, J.; Stuhrmann, H. B.; Nierhaus, K. H.

1997-02-01

399

Resin Elongation Phenomenon of Polystyrene Nanopillars in Nanoimprint Lithography  

NASA Astrophysics Data System (ADS)

We investigated the elongation of polystyrene nanopillars formed by thermal nanoimprint lithography. Silicone and perfluoropolyether were used as mold release agents to obtain molds with different adhesion forces against polystyrene to be imprinted. The adhesion force between the resin and release layers was evaluated as a force curve by atomic force microscope with a polystyrene colloid probe. Elongation depended on the aspect ratio of the corresponding microholes on the mold and